tracing: Use seq_buf for building dynevent_cmd string

[linux.git] / kernel / trace / trace_events_hist.c

// SPDX-License-Identifier: GPL-2.0
/*
 * trace_events_hist - trace event hist triggers
 *
 * Copyright (C) 2015 Tom Zanussi <tom.zanussi@linux.intel.com>
 */

#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/security.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/stacktrace.h>
#include <linux/rculist.h>
#include <linux/tracefs.h>

/* for gfp flag names */
#include <linux/trace_events.h>
#include <trace/events/mmflags.h>

#include "tracing_map.h"
#include "trace.h"
#include "trace_dynevent.h"

#define SYNTH_SYSTEM            "synthetic"
#define SYNTH_FIELDS_MAX        32

#define STR_VAR_LEN_MAX         32 /* must be multiple of sizeof(u64) */

#define ERRORS                                                          \
        C(NONE,                 "No error"),                            \
        C(DUPLICATE_VAR,        "Variable already defined"),            \
        C(VAR_NOT_UNIQUE,       "Variable name not unique, need to use fully qualified name (subsys.event.var) for variable"), \
        C(TOO_MANY_VARS,        "Too many variables defined"),          \
        C(MALFORMED_ASSIGNMENT, "Malformed assignment"),                \
        C(NAMED_MISMATCH,       "Named hist trigger doesn't match existing named trigger (includes variables)"), \
        C(TRIGGER_EEXIST,       "Hist trigger already exists"),         \
        C(TRIGGER_ENOENT_CLEAR, "Can't clear or continue a nonexistent hist trigger"), \
        C(SET_CLOCK_FAIL,       "Couldn't set trace_clock"),            \
        C(BAD_FIELD_MODIFIER,   "Invalid field modifier"),              \
        C(TOO_MANY_SUBEXPR,     "Too many subexpressions (3 max)"),     \
        C(TIMESTAMP_MISMATCH,   "Timestamp units in expression don't match"), \
        C(TOO_MANY_FIELD_VARS,  "Too many field variables defined"),    \
        C(EVENT_FILE_NOT_FOUND, "Event file not found"),                \
        C(HIST_NOT_FOUND,       "Matching event histogram not found"),  \
        C(HIST_CREATE_FAIL,     "Couldn't create histogram for field"), \
        C(SYNTH_VAR_NOT_FOUND,  "Couldn't find synthetic variable"),    \
        C(SYNTH_EVENT_NOT_FOUND,"Couldn't find synthetic event"),       \
        C(SYNTH_TYPE_MISMATCH,  "Param type doesn't match synthetic event field type"), \
        C(SYNTH_COUNT_MISMATCH, "Param count doesn't match synthetic event field count"), \
        C(FIELD_VAR_PARSE_FAIL, "Couldn't parse field variable"),       \
        C(VAR_CREATE_FIND_FAIL, "Couldn't create or find variable"),    \
        C(ONX_NOT_VAR,          "For onmax(x) or onchange(x), x must be a variable"), \
        C(ONX_VAR_NOT_FOUND,    "Couldn't find onmax or onchange variable"), \
        C(ONX_VAR_CREATE_FAIL,  "Couldn't create onmax or onchange variable"), \
        C(FIELD_VAR_CREATE_FAIL,"Couldn't create field variable"),      \
        C(TOO_MANY_PARAMS,      "Too many action params"),              \
        C(PARAM_NOT_FOUND,      "Couldn't find param"),                 \
        C(INVALID_PARAM,        "Invalid action param"),                \
        C(ACTION_NOT_FOUND,     "No action found"),                     \
        C(NO_SAVE_PARAMS,       "No params found for save()"),          \
        C(TOO_MANY_SAVE_ACTIONS,"Can't have more than one save() action per hist"), \
        C(ACTION_MISMATCH,      "Handler doesn't support action"),      \
        C(NO_CLOSING_PAREN,     "No closing paren found"),              \
        C(SUBSYS_NOT_FOUND,     "Missing subsystem"),                   \
        C(INVALID_SUBSYS_EVENT, "Invalid subsystem or event name"),     \
        C(INVALID_REF_KEY,      "Using variable references in keys not supported"), \
        C(VAR_NOT_FOUND,        "Couldn't find variable"),              \
        C(FIELD_NOT_FOUND,      "Couldn't find field"),                 \
        C(EMPTY_ASSIGNMENT,     "Empty assignment"),                    \
        C(INVALID_SORT_MODIFIER,"Invalid sort modifier"),               \
        C(EMPTY_SORT_FIELD,     "Empty sort field"),                    \
        C(TOO_MANY_SORT_FIELDS, "Too many sort fields (Max = 2)"),      \
        C(INVALID_SORT_FIELD,   "Sort field must be a key or a val"),

#undef C
#define C(a, b)         HIST_ERR_##a

enum { ERRORS };

#undef C
#define C(a, b)         b

static const char *err_text[] = { ERRORS };

struct hist_field;

typedef u64 (*hist_field_fn_t) (struct hist_field *field,
                                struct tracing_map_elt *elt,
                                struct ring_buffer_event *rbe,
                                void *event);

#define HIST_FIELD_OPERANDS_MAX 2
#define HIST_FIELDS_MAX         (TRACING_MAP_FIELDS_MAX + TRACING_MAP_VARS_MAX)
#define HIST_ACTIONS_MAX        8

enum field_op_id {
        FIELD_OP_NONE,
        FIELD_OP_PLUS,
        FIELD_OP_MINUS,
        FIELD_OP_UNARY_MINUS,
};

/*
 * A hist_var (histogram variable) contains variable information for
 * hist_fields having the HIST_FIELD_FL_VAR or HIST_FIELD_FL_VAR_REF
 * flag set.  A hist_var has a variable name e.g. ts0, and is
 * associated with a given histogram trigger, as specified by
 * hist_data.  The hist_var idx is the unique index assigned to the
 * variable by the hist trigger's tracing_map.  The idx is what is
 * used to set a variable's value and, by a variable reference, to
 * retrieve it.
 */
struct hist_var {
        char                            *name;
        struct hist_trigger_data        *hist_data;
        unsigned int                    idx;
};

struct hist_field {
        struct ftrace_event_field       *field;
        unsigned long                   flags;
        hist_field_fn_t                 fn;
        unsigned int                    size;
        unsigned int                    offset;
        unsigned int                    is_signed;
        const char                      *type;
        struct hist_field               *operands[HIST_FIELD_OPERANDS_MAX];
        struct hist_trigger_data        *hist_data;

        /*
         * Variable fields contain variable-specific info in var.
         */
        struct hist_var                 var;
        enum field_op_id                operator;
        char                            *system;
        char                            *event_name;

        /*
         * The name field is used for EXPR and VAR_REF fields.  VAR
         * fields contain the variable name in var.name.
         */
        char                            *name;

        /*
         * When a histogram trigger is hit, if it has any references
         * to variables, the values of those variables are collected
         * into a var_ref_vals array by resolve_var_refs().  The
         * current value of each variable is read from the tracing_map
         * using the hist field's hist_var.idx and entered into the
         * var_ref_idx entry i.e. var_ref_vals[var_ref_idx].
         */
        unsigned int                    var_ref_idx;
        bool                            read_once;
};

static u64 hist_field_none(struct hist_field *field,
                           struct tracing_map_elt *elt,
                           struct ring_buffer_event *rbe,
                           void *event)
{
        return 0;
}

static u64 hist_field_counter(struct hist_field *field,
                              struct tracing_map_elt *elt,
                              struct ring_buffer_event *rbe,
                              void *event)
{
        return 1;
}

static u64 hist_field_string(struct hist_field *hist_field,
                             struct tracing_map_elt *elt,
                             struct ring_buffer_event *rbe,
                             void *event)
{
        char *addr = (char *)(event + hist_field->field->offset);

        return (u64)(unsigned long)addr;
}

static u64 hist_field_dynstring(struct hist_field *hist_field,
                                struct tracing_map_elt *elt,
                                struct ring_buffer_event *rbe,
                                void *event)
{
        u32 str_item = *(u32 *)(event + hist_field->field->offset);
        int str_loc = str_item & 0xffff;
        char *addr = (char *)(event + str_loc);

        return (u64)(unsigned long)addr;
}

static u64 hist_field_pstring(struct hist_field *hist_field,
                              struct tracing_map_elt *elt,
                              struct ring_buffer_event *rbe,
                              void *event)
{
        char **addr = (char **)(event + hist_field->field->offset);

        return (u64)(unsigned long)*addr;
}

static u64 hist_field_log2(struct hist_field *hist_field,
                           struct tracing_map_elt *elt,
                           struct ring_buffer_event *rbe,
                           void *event)
{
        struct hist_field *operand = hist_field->operands[0];

        u64 val = operand->fn(operand, elt, rbe, event);

        return (u64) ilog2(roundup_pow_of_two(val));
}

static u64 hist_field_plus(struct hist_field *hist_field,
                           struct tracing_map_elt *elt,
                           struct ring_buffer_event *rbe,
                           void *event)
{
        struct hist_field *operand1 = hist_field->operands[0];
        struct hist_field *operand2 = hist_field->operands[1];

        u64 val1 = operand1->fn(operand1, elt, rbe, event);
        u64 val2 = operand2->fn(operand2, elt, rbe, event);

        return val1 + val2;
}

static u64 hist_field_minus(struct hist_field *hist_field,
                            struct tracing_map_elt *elt,
                            struct ring_buffer_event *rbe,
                            void *event)
{
        struct hist_field *operand1 = hist_field->operands[0];
        struct hist_field *operand2 = hist_field->operands[1];

        u64 val1 = operand1->fn(operand1, elt, rbe, event);
        u64 val2 = operand2->fn(operand2, elt, rbe, event);

        return val1 - val2;
}

static u64 hist_field_unary_minus(struct hist_field *hist_field,
                                  struct tracing_map_elt *elt,
                                  struct ring_buffer_event *rbe,
                                  void *event)
{
        struct hist_field *operand = hist_field->operands[0];

        s64 sval = (s64)operand->fn(operand, elt, rbe, event);
        u64 val = (u64)-sval;

        return val;
}

#define DEFINE_HIST_FIELD_FN(type)                                      \
        static u64 hist_field_##type(struct hist_field *hist_field,     \
                                     struct tracing_map_elt *elt,       \
                                     struct ring_buffer_event *rbe,     \
                                     void *event)                       \
{                                                                       \
        type *addr = (type *)(event + hist_field->field->offset);       \
                                                                        \
        return (u64)(unsigned long)*addr;                               \
}

DEFINE_HIST_FIELD_FN(s64);
DEFINE_HIST_FIELD_FN(u64);
DEFINE_HIST_FIELD_FN(s32);
DEFINE_HIST_FIELD_FN(u32);
DEFINE_HIST_FIELD_FN(s16);
DEFINE_HIST_FIELD_FN(u16);
DEFINE_HIST_FIELD_FN(s8);
DEFINE_HIST_FIELD_FN(u8);

#define for_each_hist_field(i, hist_data)       \
        for ((i) = 0; (i) < (hist_data)->n_fields; (i)++)

#define for_each_hist_val_field(i, hist_data)   \
        for ((i) = 0; (i) < (hist_data)->n_vals; (i)++)

#define for_each_hist_key_field(i, hist_data)   \
        for ((i) = (hist_data)->n_vals; (i) < (hist_data)->n_fields; (i)++)

#define HIST_STACKTRACE_DEPTH   16
#define HIST_STACKTRACE_SIZE    (HIST_STACKTRACE_DEPTH * sizeof(unsigned long))
#define HIST_STACKTRACE_SKIP    5

#define HITCOUNT_IDX            0
#define HIST_KEY_SIZE_MAX       (MAX_FILTER_STR_VAL + HIST_STACKTRACE_SIZE)

enum hist_field_flags {
        HIST_FIELD_FL_HITCOUNT          = 1 << 0,
        HIST_FIELD_FL_KEY               = 1 << 1,
        HIST_FIELD_FL_STRING            = 1 << 2,
        HIST_FIELD_FL_HEX               = 1 << 3,
        HIST_FIELD_FL_SYM               = 1 << 4,
        HIST_FIELD_FL_SYM_OFFSET        = 1 << 5,
        HIST_FIELD_FL_EXECNAME          = 1 << 6,
        HIST_FIELD_FL_SYSCALL           = 1 << 7,
        HIST_FIELD_FL_STACKTRACE        = 1 << 8,
        HIST_FIELD_FL_LOG2              = 1 << 9,
        HIST_FIELD_FL_TIMESTAMP         = 1 << 10,
        HIST_FIELD_FL_TIMESTAMP_USECS   = 1 << 11,
        HIST_FIELD_FL_VAR               = 1 << 12,
        HIST_FIELD_FL_EXPR              = 1 << 13,
        HIST_FIELD_FL_VAR_REF           = 1 << 14,
        HIST_FIELD_FL_CPU               = 1 << 15,
        HIST_FIELD_FL_ALIAS             = 1 << 16,
};

struct var_defs {
        unsigned int    n_vars;
        char            *name[TRACING_MAP_VARS_MAX];
        char            *expr[TRACING_MAP_VARS_MAX];
};

struct hist_trigger_attrs {
        char            *keys_str;
        char            *vals_str;
        char            *sort_key_str;
        char            *name;
        char            *clock;
        bool            pause;
        bool            cont;
        bool            clear;
        bool            ts_in_usecs;
        unsigned int    map_bits;

        char            *assignment_str[TRACING_MAP_VARS_MAX];
        unsigned int    n_assignments;

        char            *action_str[HIST_ACTIONS_MAX];
        unsigned int    n_actions;

        struct var_defs var_defs;
};

struct field_var {
        struct hist_field       *var;
        struct hist_field       *val;
};

struct field_var_hist {
        struct hist_trigger_data        *hist_data;
        char                            *cmd;
};

struct hist_trigger_data {
        struct hist_field               *fields[HIST_FIELDS_MAX];
        unsigned int                    n_vals;
        unsigned int                    n_keys;
        unsigned int                    n_fields;
        unsigned int                    n_vars;
        unsigned int                    key_size;
        struct tracing_map_sort_key     sort_keys[TRACING_MAP_SORT_KEYS_MAX];
        unsigned int                    n_sort_keys;
        struct trace_event_file         *event_file;
        struct hist_trigger_attrs       *attrs;
        struct tracing_map              *map;
        bool                            enable_timestamps;
        bool                            remove;
        struct hist_field               *var_refs[TRACING_MAP_VARS_MAX];
        unsigned int                    n_var_refs;

        struct action_data              *actions[HIST_ACTIONS_MAX];
        unsigned int                    n_actions;

        struct field_var                *field_vars[SYNTH_FIELDS_MAX];
        unsigned int                    n_field_vars;
        unsigned int                    n_field_var_str;
        struct field_var_hist           *field_var_hists[SYNTH_FIELDS_MAX];
        unsigned int                    n_field_var_hists;

        struct field_var                *save_vars[SYNTH_FIELDS_MAX];
        unsigned int                    n_save_vars;
        unsigned int                    n_save_var_str;
};

static int create_synth_event(int argc, const char **argv);
static int synth_event_show(struct seq_file *m, struct dyn_event *ev);
static int synth_event_release(struct dyn_event *ev);
static bool synth_event_is_busy(struct dyn_event *ev);
static bool synth_event_match(const char *system, const char *event,
                        int argc, const char **argv, struct dyn_event *ev);

static struct dyn_event_operations synth_event_ops = {
        .create = create_synth_event,
        .show = synth_event_show,
        .is_busy = synth_event_is_busy,
        .free = synth_event_release,
        .match = synth_event_match,
};

struct synth_field {
        char *type;
        char *name;
        size_t size;
        unsigned int offset;
        bool is_signed;
        bool is_string;
};

struct synth_event {
        struct dyn_event                        devent;
        int                                     ref;
        char                                    *name;
        struct synth_field                      **fields;
        unsigned int                            n_fields;
        unsigned int                            n_u64;
        struct trace_event_class                class;
        struct trace_event_call                 call;
        struct tracepoint                       *tp;
        struct module                           *mod;
};

static bool is_synth_event(struct dyn_event *ev)
{
        return ev->ops == &synth_event_ops;
}

static struct synth_event *to_synth_event(struct dyn_event *ev)
{
        return container_of(ev, struct synth_event, devent);
}

static bool synth_event_is_busy(struct dyn_event *ev)
{
        struct synth_event *event = to_synth_event(ev);

        return event->ref != 0;
}

static bool synth_event_match(const char *system, const char *event,
                        int argc, const char **argv, struct dyn_event *ev)
{
        struct synth_event *sev = to_synth_event(ev);

        return strcmp(sev->name, event) == 0 &&
                (!system || strcmp(system, SYNTH_SYSTEM) == 0);
}

struct action_data;

typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
                             struct tracing_map_elt *elt, void *rec,
                             struct ring_buffer_event *rbe, void *key,
                             struct action_data *data, u64 *var_ref_vals);

typedef bool (*check_track_val_fn_t) (u64 track_val, u64 var_val);

enum handler_id {
        HANDLER_ONMATCH = 1,
        HANDLER_ONMAX,
        HANDLER_ONCHANGE,
};

enum action_id {
        ACTION_SAVE = 1,
        ACTION_TRACE,
        ACTION_SNAPSHOT,
};

struct action_data {
        enum handler_id         handler;
        enum action_id          action;
        char                    *action_name;
        action_fn_t             fn;

        unsigned int            n_params;
        char                    *params[SYNTH_FIELDS_MAX];

        /*
         * When a histogram trigger is hit, the values of any
         * references to variables, including variables being passed
         * as parameters to synthetic events, are collected into a
         * var_ref_vals array.  This var_ref_idx array is an array of
         * indices into the var_ref_vals array, one for each synthetic
         * event param, and is passed to the synthetic event
         * invocation.
         */
        unsigned int            var_ref_idx[TRACING_MAP_VARS_MAX];
        struct synth_event      *synth_event;
        bool                    use_trace_keyword;
        char                    *synth_event_name;

        union {
                struct {
                        char                    *event;
                        char                    *event_system;
                } match_data;

                struct {
                        /*
                         * var_str contains the $-unstripped variable
                         * name referenced by var_ref, and used when
                         * printing the action.  Because var_ref
                         * creation is deferred to create_actions(),
                         * we need a per-action way to save it until
                         * then, thus var_str.
                         */
                        char                    *var_str;

                        /*
                         * var_ref refers to the variable being
                         * tracked e.g onmax($var).
                         */
                        struct hist_field       *var_ref;

                        /*
                         * track_var contains the 'invisible' tracking
                         * variable created to keep the current
                         * e.g. max value.
                         */
                        struct hist_field       *track_var;

                        check_track_val_fn_t    check_val;
                        action_fn_t             save_data;
                } track_data;
        };
};

struct track_data {
        u64                             track_val;
        bool                            updated;

        unsigned int                    key_len;
        void                            *key;
        struct tracing_map_elt          elt;

        struct action_data              *action_data;
        struct hist_trigger_data        *hist_data;
};

struct hist_elt_data {
        char *comm;
        u64 *var_ref_vals;
        char *field_var_str[SYNTH_FIELDS_MAX];
};

struct snapshot_context {
        struct tracing_map_elt  *elt;
        void                    *key;
};

static void track_data_free(struct track_data *track_data)
{
        struct hist_elt_data *elt_data;

        if (!track_data)
                return;

        kfree(track_data->key);

        elt_data = track_data->elt.private_data;
        if (elt_data) {
                kfree(elt_data->comm);
                kfree(elt_data);
        }

        kfree(track_data);
}

static struct track_data *track_data_alloc(unsigned int key_len,
                                           struct action_data *action_data,
                                           struct hist_trigger_data *hist_data)
{
        struct track_data *data = kzalloc(sizeof(*data), GFP_KERNEL);
        struct hist_elt_data *elt_data;

        if (!data)
                return ERR_PTR(-ENOMEM);

        data->key = kzalloc(key_len, GFP_KERNEL);
        if (!data->key) {
                track_data_free(data);
                return ERR_PTR(-ENOMEM);
        }

        data->key_len = key_len;
        data->action_data = action_data;
        data->hist_data = hist_data;

        elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
        if (!elt_data) {
                track_data_free(data);
                return ERR_PTR(-ENOMEM);
        }
        data->elt.private_data = elt_data;

        elt_data->comm = kzalloc(TASK_COMM_LEN, GFP_KERNEL);
        if (!elt_data->comm) {
                track_data_free(data);
                return ERR_PTR(-ENOMEM);
        }

        return data;
}

static char last_cmd[MAX_FILTER_STR_VAL];
static char last_cmd_loc[MAX_FILTER_STR_VAL];

static int errpos(char *str)
{
        return err_pos(last_cmd, str);
}

static void last_cmd_set(struct trace_event_file *file, char *str)
{
        const char *system = NULL, *name = NULL;
        struct trace_event_call *call;

        if (!str)
                return;

        strcpy(last_cmd, "hist:");
        strncat(last_cmd, str, MAX_FILTER_STR_VAL - 1 - sizeof("hist:"));

        if (file) {
                call = file->event_call;

                system = call->class->system;
                if (system) {
                        name = trace_event_name(call);
                        if (!name)
                                system = NULL;
                }
        }

        if (system)
                snprintf(last_cmd_loc, MAX_FILTER_STR_VAL, "hist:%s:%s", system, name);
}

static void hist_err(struct trace_array *tr, u8 err_type, u8 err_pos)
{
        tracing_log_err(tr, last_cmd_loc, last_cmd, err_text,
                        err_type, err_pos);
}

static void hist_err_clear(void)
{
        last_cmd[0] = '\0';
        last_cmd_loc[0] = '\0';
}

struct synth_trace_event {
        struct trace_entry      ent;
        u64                     fields[];
};

static int synth_event_define_fields(struct trace_event_call *call)
{
        struct synth_trace_event trace;
        int offset = offsetof(typeof(trace), fields);
        struct synth_event *event = call->data;
        unsigned int i, size, n_u64;
        char *name, *type;
        bool is_signed;
        int ret = 0;

        for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
                size = event->fields[i]->size;
                is_signed = event->fields[i]->is_signed;
                type = event->fields[i]->type;
                name = event->fields[i]->name;
                ret = trace_define_field(call, type, name, offset, size,
                                         is_signed, FILTER_OTHER);
                if (ret)
                        break;

                event->fields[i]->offset = n_u64;

                if (event->fields[i]->is_string) {
                        offset += STR_VAR_LEN_MAX;
                        n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
                } else {
                        offset += sizeof(u64);
                        n_u64++;
                }
        }

        event->n_u64 = n_u64;

        return ret;
}

static bool synth_field_signed(char *type)
{
        if (str_has_prefix(type, "u"))
                return false;
        if (strcmp(type, "gfp_t") == 0)
                return false;

        return true;
}

static int synth_field_is_string(char *type)
{
        if (strstr(type, "char[") != NULL)
                return true;

        return false;
}

static int synth_field_string_size(char *type)
{
        char buf[4], *end, *start;
        unsigned int len;
        int size, err;

        start = strstr(type, "char[");
        if (start == NULL)
                return -EINVAL;
        start += sizeof("char[") - 1;

        end = strchr(type, ']');
        if (!end || end < start)
                return -EINVAL;

        len = end - start;
        if (len > 3)
                return -EINVAL;

        strncpy(buf, start, len);
        buf[len] = '\0';

        err = kstrtouint(buf, 0, &size);
        if (err)
                return err;

        if (size > STR_VAR_LEN_MAX)
                return -EINVAL;

        return size;
}

static int synth_field_size(char *type)
{
        int size = 0;

        if (strcmp(type, "s64") == 0)
                size = sizeof(s64);
        else if (strcmp(type, "u64") == 0)
                size = sizeof(u64);
        else if (strcmp(type, "s32") == 0)
                size = sizeof(s32);
        else if (strcmp(type, "u32") == 0)
                size = sizeof(u32);
        else if (strcmp(type, "s16") == 0)
                size = sizeof(s16);
        else if (strcmp(type, "u16") == 0)
                size = sizeof(u16);
        else if (strcmp(type, "s8") == 0)
                size = sizeof(s8);
        else if (strcmp(type, "u8") == 0)
                size = sizeof(u8);
        else if (strcmp(type, "char") == 0)
                size = sizeof(char);
        else if (strcmp(type, "unsigned char") == 0)
                size = sizeof(unsigned char);
        else if (strcmp(type, "int") == 0)
                size = sizeof(int);
        else if (strcmp(type, "unsigned int") == 0)
                size = sizeof(unsigned int);
        else if (strcmp(type, "long") == 0)
                size = sizeof(long);
        else if (strcmp(type, "unsigned long") == 0)
                size = sizeof(unsigned long);
        else if (strcmp(type, "pid_t") == 0)
                size = sizeof(pid_t);
        else if (strcmp(type, "gfp_t") == 0)
                size = sizeof(gfp_t);
        else if (synth_field_is_string(type))
                size = synth_field_string_size(type);

        return size;
}

static const char *synth_field_fmt(char *type)
{
        const char *fmt = "%llu";

        if (strcmp(type, "s64") == 0)
                fmt = "%lld";
        else if (strcmp(type, "u64") == 0)
                fmt = "%llu";
        else if (strcmp(type, "s32") == 0)
                fmt = "%d";
        else if (strcmp(type, "u32") == 0)
                fmt = "%u";
        else if (strcmp(type, "s16") == 0)
                fmt = "%d";
        else if (strcmp(type, "u16") == 0)
                fmt = "%u";
        else if (strcmp(type, "s8") == 0)
                fmt = "%d";
        else if (strcmp(type, "u8") == 0)
                fmt = "%u";
        else if (strcmp(type, "char") == 0)
                fmt = "%d";
        else if (strcmp(type, "unsigned char") == 0)
                fmt = "%u";
        else if (strcmp(type, "int") == 0)
                fmt = "%d";
        else if (strcmp(type, "unsigned int") == 0)
                fmt = "%u";
        else if (strcmp(type, "long") == 0)
                fmt = "%ld";
        else if (strcmp(type, "unsigned long") == 0)
                fmt = "%lu";
        else if (strcmp(type, "pid_t") == 0)
                fmt = "%d";
        else if (strcmp(type, "gfp_t") == 0)
                fmt = "%x";
        else if (synth_field_is_string(type))
                fmt = "%s";

        return fmt;
}

static enum print_line_t print_synth_event(struct trace_iterator *iter,
                                           int flags,
                                           struct trace_event *event)
{
        struct trace_array *tr = iter->tr;
        struct trace_seq *s = &iter->seq;
        struct synth_trace_event *entry;
        struct synth_event *se;
        unsigned int i, n_u64;
        char print_fmt[32];
        const char *fmt;

        entry = (struct synth_trace_event *)iter->ent;
        se = container_of(event, struct synth_event, call.event);

        trace_seq_printf(s, "%s: ", se->name);

        for (i = 0, n_u64 = 0; i < se->n_fields; i++) {
                if (trace_seq_has_overflowed(s))
                        goto end;

                fmt = synth_field_fmt(se->fields[i]->type);

                /* parameter types */
                if (tr && tr->trace_flags & TRACE_ITER_VERBOSE)
                        trace_seq_printf(s, "%s ", fmt);

                snprintf(print_fmt, sizeof(print_fmt), "%%s=%s%%s", fmt);

                /* parameter values */
                if (se->fields[i]->is_string) {
                        trace_seq_printf(s, print_fmt, se->fields[i]->name,
                                         (char *)&entry->fields[n_u64],
                                         i == se->n_fields - 1 ? "" : " ");
                        n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
                } else {
                        struct trace_print_flags __flags[] = {
                            __def_gfpflag_names, {-1, NULL} };

                        trace_seq_printf(s, print_fmt, se->fields[i]->name,
                                         entry->fields[n_u64],
                                         i == se->n_fields - 1 ? "" : " ");

                        if (strcmp(se->fields[i]->type, "gfp_t") == 0) {
                                trace_seq_puts(s, " (");
                                trace_print_flags_seq(s, "|",
                                                      entry->fields[n_u64],
                                                      __flags);
                                trace_seq_putc(s, ')');
                        }
                        n_u64++;
                }
        }
end:
        trace_seq_putc(s, '\n');

        return trace_handle_return(s);
}

static struct trace_event_functions synth_event_funcs = {
        .trace          = print_synth_event
};

static notrace void trace_event_raw_event_synth(void *__data,
                                                u64 *var_ref_vals,
                                                unsigned int *var_ref_idx)
{
        struct trace_event_file *trace_file = __data;
        struct synth_trace_event *entry;
        struct trace_event_buffer fbuffer;
        struct trace_buffer *buffer;
        struct synth_event *event;
        unsigned int i, n_u64, val_idx;
        int fields_size = 0;

        event = trace_file->event_call->data;

        if (trace_trigger_soft_disabled(trace_file))
                return;

        fields_size = event->n_u64 * sizeof(u64);

        /*
         * Avoid ring buffer recursion detection, as this event
         * is being performed within another event.
         */
        buffer = trace_file->tr->array_buffer.buffer;
        ring_buffer_nest_start(buffer);

        entry = trace_event_buffer_reserve(&fbuffer, trace_file,
                                           sizeof(*entry) + fields_size);
        if (!entry)
                goto out;

        for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
                val_idx = var_ref_idx[i];
                if (event->fields[i]->is_string) {
                        char *str_val = (char *)(long)var_ref_vals[val_idx];
                        char *str_field = (char *)&entry->fields[n_u64];

                        strscpy(str_field, str_val, STR_VAR_LEN_MAX);
                        n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
                } else {
                        struct synth_field *field = event->fields[i];
                        u64 val = var_ref_vals[val_idx];

                        switch (field->size) {
                        case 1:
                                *(u8 *)&entry->fields[n_u64] = (u8)val;
                                break;

                        case 2:
                                *(u16 *)&entry->fields[n_u64] = (u16)val;
                                break;

                        case 4:
                                *(u32 *)&entry->fields[n_u64] = (u32)val;
                                break;

                        default:
                                entry->fields[n_u64] = val;
                                break;
                        }
                        n_u64++;
                }
        }

        trace_event_buffer_commit(&fbuffer);
out:
        ring_buffer_nest_end(buffer);
}

static void free_synth_event_print_fmt(struct trace_event_call *call)
{
        if (call) {
                kfree(call->print_fmt);
                call->print_fmt = NULL;
        }
}

static int __set_synth_event_print_fmt(struct synth_event *event,
                                       char *buf, int len)
{
        const char *fmt;
        int pos = 0;
        int i;

        /* When len=0, we just calculate the needed length */
#define LEN_OR_ZERO (len ? len - pos : 0)

        pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
        for (i = 0; i < event->n_fields; i++) {
                fmt = synth_field_fmt(event->fields[i]->type);
                pos += snprintf(buf + pos, LEN_OR_ZERO, "%s=%s%s",
                                event->fields[i]->name, fmt,
                                i == event->n_fields - 1 ? "" : ", ");
        }
        pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");

        for (i = 0; i < event->n_fields; i++) {
                pos += snprintf(buf + pos, LEN_OR_ZERO,
                                ", REC->%s", event->fields[i]->name);
        }

#undef LEN_OR_ZERO

        /* return the length of print_fmt */
        return pos;
}

static int set_synth_event_print_fmt(struct trace_event_call *call)
{
        struct synth_event *event = call->data;
        char *print_fmt;
        int len;

        /* First: called with 0 length to calculate the needed length */
        len = __set_synth_event_print_fmt(event, NULL, 0);

        print_fmt = kmalloc(len + 1, GFP_KERNEL);
        if (!print_fmt)
                return -ENOMEM;

        /* Second: actually write the @print_fmt */
        __set_synth_event_print_fmt(event, print_fmt, len + 1);
        call->print_fmt = print_fmt;

        return 0;
}

static void free_synth_field(struct synth_field *field)
{
        kfree(field->type);
        kfree(field->name);
        kfree(field);
}

static struct synth_field *parse_synth_field(int argc, const char **argv,
                                             int *consumed)
{
        struct synth_field *field;
        const char *prefix = NULL, *field_type = argv[0], *field_name, *array;
        int len, ret = 0;

        if (field_type[0] == ';')
                field_type++;

        if (!strcmp(field_type, "unsigned")) {
                if (argc < 3)
                        return ERR_PTR(-EINVAL);
                prefix = "unsigned ";
                field_type = argv[1];
                field_name = argv[2];
                *consumed = 3;
        } else {
                field_name = argv[1];
                *consumed = 2;
        }

        field = kzalloc(sizeof(*field), GFP_KERNEL);
        if (!field)
                return ERR_PTR(-ENOMEM);

        len = strlen(field_name);
        array = strchr(field_name, '[');
        if (array)
                len -= strlen(array);
        else if (field_name[len - 1] == ';')
                len--;

        field->name = kmemdup_nul(field_name, len, GFP_KERNEL);
        if (!field->name) {
                ret = -ENOMEM;
                goto free;
        }

        if (field_type[0] == ';')
                field_type++;
        len = strlen(field_type) + 1;
        if (array)
                len += strlen(array);
        if (prefix)
                len += strlen(prefix);

        field->type = kzalloc(len, GFP_KERNEL);
        if (!field->type) {
                ret = -ENOMEM;
                goto free;
        }
        if (prefix)
                strcat(field->type, prefix);
        strcat(field->type, field_type);
        if (array) {
                strcat(field->type, array);
                if (field->type[len - 1] == ';')
                        field->type[len - 1] = '\0';
        }

        field->size = synth_field_size(field->type);
        if (!field->size) {
                ret = -EINVAL;
                goto free;
        }

        if (synth_field_is_string(field->type))
                field->is_string = true;

        field->is_signed = synth_field_signed(field->type);

 out:
        return field;
 free:
        free_synth_field(field);
        field = ERR_PTR(ret);
        goto out;
}

static void free_synth_tracepoint(struct tracepoint *tp)
{
        if (!tp)
                return;

        kfree(tp->name);
        kfree(tp);
}

static struct tracepoint *alloc_synth_tracepoint(char *name)
{
        struct tracepoint *tp;

        tp = kzalloc(sizeof(*tp), GFP_KERNEL);
        if (!tp)
                return ERR_PTR(-ENOMEM);

        tp->name = kstrdup(name, GFP_KERNEL);
        if (!tp->name) {
                kfree(tp);
                return ERR_PTR(-ENOMEM);
        }

        return tp;
}

typedef void (*synth_probe_func_t) (void *__data, u64 *var_ref_vals,
                                    unsigned int *var_ref_idx);

static inline void trace_synth(struct synth_event *event, u64 *var_ref_vals,
                               unsigned int *var_ref_idx)
{
        struct tracepoint *tp = event->tp;

        if (unlikely(atomic_read(&tp->key.enabled) > 0)) {
                struct tracepoint_func *probe_func_ptr;
                synth_probe_func_t probe_func;
                void *__data;

                if (!(cpu_online(raw_smp_processor_id())))
                        return;

                probe_func_ptr = rcu_dereference_sched((tp)->funcs);
                if (probe_func_ptr) {
                        do {
                                probe_func = probe_func_ptr->func;
                                __data = probe_func_ptr->data;
                                probe_func(__data, var_ref_vals, var_ref_idx);
                        } while ((++probe_func_ptr)->func);
                }
        }
}

static struct synth_event *find_synth_event(const char *name)
{
        struct dyn_event *pos;
        struct synth_event *event;

        for_each_dyn_event(pos) {
                if (!is_synth_event(pos))
                        continue;
                event = to_synth_event(pos);
                if (strcmp(event->name, name) == 0)
                        return event;
        }

        return NULL;
}

static int register_synth_event(struct synth_event *event)
{
        struct trace_event_call *call = &event->call;
        int ret = 0;

        event->call.class = &event->class;
        event->class.system = kstrdup(SYNTH_SYSTEM, GFP_KERNEL);
        if (!event->class.system) {
                ret = -ENOMEM;
                goto out;
        }

        event->tp = alloc_synth_tracepoint(event->name);
        if (IS_ERR(event->tp)) {
                ret = PTR_ERR(event->tp);
                event->tp = NULL;
                goto out;
        }

        INIT_LIST_HEAD(&call->class->fields);
        call->event.funcs = &synth_event_funcs;
        call->class->define_fields = synth_event_define_fields;

        ret = register_trace_event(&call->event);
        if (!ret) {
                ret = -ENODEV;
                goto out;
        }
        call->flags = TRACE_EVENT_FL_TRACEPOINT;
        call->class->reg = trace_event_reg;
        call->class->probe = trace_event_raw_event_synth;
        call->data = event;
        call->tp = event->tp;

        ret = trace_add_event_call(call);
        if (ret) {
                pr_warn("Failed to register synthetic event: %s\n",
                        trace_event_name(call));
                goto err;
        }

        ret = set_synth_event_print_fmt(call);
        if (ret < 0) {
                trace_remove_event_call(call);
                goto err;
        }
 out:
        return ret;
 err:
        unregister_trace_event(&call->event);
        goto out;
}

static int unregister_synth_event(struct synth_event *event)
{
        struct trace_event_call *call = &event->call;
        int ret;

        ret = trace_remove_event_call(call);

        return ret;
}

static void free_synth_event(struct synth_event *event)
{
        unsigned int i;

        if (!event)
                return;

        for (i = 0; i < event->n_fields; i++)
                free_synth_field(event->fields[i]);

        kfree(event->fields);
        kfree(event->name);
        kfree(event->class.system);
        free_synth_tracepoint(event->tp);
        free_synth_event_print_fmt(&event->call);
        kfree(event);
}

static struct synth_event *alloc_synth_event(const char *name, int n_fields,
                                             struct synth_field **fields)
{
        struct synth_event *event;
        unsigned int i;

        event = kzalloc(sizeof(*event), GFP_KERNEL);
        if (!event) {
                event = ERR_PTR(-ENOMEM);
                goto out;
        }

        event->name = kstrdup(name, GFP_KERNEL);
        if (!event->name) {
                kfree(event);
                event = ERR_PTR(-ENOMEM);
                goto out;
        }

        event->fields = kcalloc(n_fields, sizeof(*event->fields), GFP_KERNEL);
        if (!event->fields) {
                free_synth_event(event);
                event = ERR_PTR(-ENOMEM);
                goto out;
        }

        dyn_event_init(&event->devent, &synth_event_ops);

        for (i = 0; i < n_fields; i++)
                event->fields[i] = fields[i];

        event->n_fields = n_fields;
 out:
        return event;
}

static void action_trace(struct hist_trigger_data *hist_data,
                         struct tracing_map_elt *elt, void *rec,
                         struct ring_buffer_event *rbe, void *key,
                         struct action_data *data, u64 *var_ref_vals)
{
        struct synth_event *event = data->synth_event;

        trace_synth(event, var_ref_vals, data->var_ref_idx);
}

struct hist_var_data {
        struct list_head list;
        struct hist_trigger_data *hist_data;
};

static int synth_event_check_arg_fn(void *data)
{
        struct dynevent_arg_pair *arg_pair = data;
        int size;

        size = synth_field_size((char *)arg_pair->lhs);

        return size ? 0 : -EINVAL;
}

/**
 * synth_event_add_field - Add a new field to a synthetic event cmd
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @type: The type of the new field to add
 * @name: The name of the new field to add
 *
 * Add a new field to a synthetic event cmd object.  Field ordering is in
 * the same order the fields are added.
 *
 * See synth_field_size() for available types. If field_name contains
 * [n] the field is considered to be an array.
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_add_field(struct dynevent_cmd *cmd, const char *type,
                          const char *name)
{
        struct dynevent_arg_pair arg_pair;
        int ret;

        if (cmd->type != DYNEVENT_TYPE_SYNTH)
                return -EINVAL;

        if (!type || !name)
                return -EINVAL;

        dynevent_arg_pair_init(&arg_pair, 0, ';');

        arg_pair.lhs = type;
        arg_pair.rhs = name;

        ret = dynevent_arg_pair_add(cmd, &arg_pair, synth_event_check_arg_fn);
        if (ret)
                return ret;

        if (++cmd->n_fields > SYNTH_FIELDS_MAX)
                ret = -EINVAL;

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_add_field);

/**
 * synth_event_add_field_str - Add a new field to a synthetic event cmd
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @type_name: The type and name of the new field to add, as a single string
 *
 * Add a new field to a synthetic event cmd object, as a single
 * string.  The @type_name string is expected to be of the form 'type
 * name', which will be appended by ';'.  No sanity checking is done -
 * what's passed in is assumed to already be well-formed.  Field
 * ordering is in the same order the fields are added.
 *
 * See synth_field_size() for available types. If field_name contains
 * [n] the field is considered to be an array.
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_add_field_str(struct dynevent_cmd *cmd, const char *type_name)
{
        struct dynevent_arg arg;
        int ret;

        if (cmd->type != DYNEVENT_TYPE_SYNTH)
                return -EINVAL;

        if (!type_name)
                return -EINVAL;

        dynevent_arg_init(&arg, ';');

        arg.str = type_name;

        ret = dynevent_arg_add(cmd, &arg, NULL);
        if (ret)
                return ret;

        if (++cmd->n_fields > SYNTH_FIELDS_MAX)
                ret = -EINVAL;

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_add_field_str);

/**
 * synth_event_add_fields - Add multiple fields to a synthetic event cmd
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @fields: An array of type/name field descriptions
 * @n_fields: The number of field descriptions contained in the fields array
 *
 * Add a new set of fields to a synthetic event cmd object.  The event
 * fields that will be defined for the event should be passed in as an
 * array of struct synth_field_desc, and the number of elements in the
 * array passed in as n_fields.  Field ordering will retain the
 * ordering given in the fields array.
 *
 * See synth_field_size() for available types. If field_name contains
 * [n] the field is considered to be an array.
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_add_fields(struct dynevent_cmd *cmd,
                           struct synth_field_desc *fields,
                           unsigned int n_fields)
{
        unsigned int i;
        int ret = 0;

        for (i = 0; i < n_fields; i++) {
                if (fields[i].type == NULL || fields[i].name == NULL) {
                        ret = -EINVAL;
                        break;
                }

                ret = synth_event_add_field(cmd, fields[i].type, fields[i].name);
                if (ret)
                        break;
        }

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_add_fields);

/**
 * __synth_event_gen_cmd_start - Start a synthetic event command from arg list
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @name: The name of the synthetic event
 * @mod: The module creating the event, NULL if not created from a module
 * @args: Variable number of arg (pairs), one pair for each field
 *
 * NOTE: Users normally won't want to call this function directly, but
 * rather use the synth_event_gen_cmd_start() wrapper, which
 * automatically adds a NULL to the end of the arg list.  If this
 * function is used directly, make sure the last arg in the variable
 * arg list is NULL.
 *
 * Generate a synthetic event command to be executed by
 * synth_event_gen_cmd_end().  This function can be used to generate
 * the complete command or only the first part of it; in the latter
 * case, synth_event_add_field(), synth_event_add_field_str(), or
 * synth_event_add_fields() can be used to add more fields following
 * this.
 *
 * There should be an even number variable args, each pair consisting
 * of a type followed by a field name.
 *
 * See synth_field_size() for available types. If field_name contains
 * [n] the field is considered to be an array.
 *
 * Return: 0 if successful, error otherwise.
 */
int __synth_event_gen_cmd_start(struct dynevent_cmd *cmd, const char *name,
                                struct module *mod, ...)
{
        struct dynevent_arg arg;
        va_list args;
        int ret;

        cmd->event_name = name;
        cmd->private_data = mod;

        if (cmd->type != DYNEVENT_TYPE_SYNTH)
                return -EINVAL;

        dynevent_arg_init(&arg, 0);
        arg.str = name;
        ret = dynevent_arg_add(cmd, &arg, NULL);
        if (ret)
                return ret;

        va_start(args, mod);
        for (;;) {
                const char *type, *name;

                type = va_arg(args, const char *);
                if (!type)
                        break;
                name = va_arg(args, const char *);
                if (!name)
                        break;

                if (++cmd->n_fields > SYNTH_FIELDS_MAX) {
                        ret = -EINVAL;
                        break;
                }

                ret = synth_event_add_field(cmd, type, name);
                if (ret)
                        break;
        }
        va_end(args);

        return ret;
}
EXPORT_SYMBOL_GPL(__synth_event_gen_cmd_start);

/**
 * synth_event_gen_cmd_array_start - Start synthetic event command from an array
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @name: The name of the synthetic event
 * @fields: An array of type/name field descriptions
 * @n_fields: The number of field descriptions contained in the fields array
 *
 * Generate a synthetic event command to be executed by
 * synth_event_gen_cmd_end().  This function can be used to generate
 * the complete command or only the first part of it; in the latter
 * case, synth_event_add_field(), synth_event_add_field_str(), or
 * synth_event_add_fields() can be used to add more fields following
 * this.
 *
 * The event fields that will be defined for the event should be
 * passed in as an array of struct synth_field_desc, and the number of
 * elements in the array passed in as n_fields.  Field ordering will
 * retain the ordering given in the fields array.
 *
 * See synth_field_size() for available types. If field_name contains
 * [n] the field is considered to be an array.
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_gen_cmd_array_start(struct dynevent_cmd *cmd, const char *name,
                                    struct module *mod,
                                    struct synth_field_desc *fields,
                                    unsigned int n_fields)
{
        struct dynevent_arg arg;
        unsigned int i;
        int ret = 0;

        cmd->event_name = name;
        cmd->private_data = mod;

        if (cmd->type != DYNEVENT_TYPE_SYNTH)
                return -EINVAL;

        if (n_fields > SYNTH_FIELDS_MAX)
                return -EINVAL;

        dynevent_arg_init(&arg, 0);
        arg.str = name;
        ret = dynevent_arg_add(cmd, &arg, NULL);
        if (ret)
                return ret;

        for (i = 0; i < n_fields; i++) {
                if (fields[i].type == NULL || fields[i].name == NULL)
                        return -EINVAL;

                ret = synth_event_add_field(cmd, fields[i].type, fields[i].name);
                if (ret)
                        break;
        }

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_gen_cmd_array_start);

static int __create_synth_event(int argc, const char *name, const char **argv)
{
        struct synth_field *field, *fields[SYNTH_FIELDS_MAX];
        struct synth_event *event = NULL;
        int i, consumed = 0, n_fields = 0, ret = 0;

        /*
         * Argument syntax:
         *  - Add synthetic event: <event_name> field[;field] ...
         *  - Remove synthetic event: !<event_name> field[;field] ...
         *      where 'field' = type field_name
         */

        if (name[0] == '\0' || argc < 1)
                return -EINVAL;

        mutex_lock(&event_mutex);

        event = find_synth_event(name);
        if (event) {
                ret = -EEXIST;
                goto out;
        }

        for (i = 0; i < argc - 1; i++) {
                if (strcmp(argv[i], ";") == 0)
                        continue;
                if (n_fields == SYNTH_FIELDS_MAX) {
                        ret = -EINVAL;
                        goto err;
                }

                field = parse_synth_field(argc - i, &argv[i], &consumed);
                if (IS_ERR(field)) {
                        ret = PTR_ERR(field);
                        goto err;
                }
                fields[n_fields++] = field;
                i += consumed - 1;
        }

        if (i < argc && strcmp(argv[i], ";") != 0) {
                ret = -EINVAL;
                goto err;
        }

        event = alloc_synth_event(name, n_fields, fields);
        if (IS_ERR(event)) {
                ret = PTR_ERR(event);
                event = NULL;
                goto err;
        }
        ret = register_synth_event(event);
        if (!ret)
                dyn_event_add(&event->devent);
        else
                free_synth_event(event);
 out:
        mutex_unlock(&event_mutex);

        return ret;
 err:
        for (i = 0; i < n_fields; i++)
                free_synth_field(fields[i]);

        goto out;
}

/**
 * synth_event_create - Create a new synthetic event
 * @name: The name of the new sythetic event
 * @fields: An array of type/name field descriptions
 * @n_fields: The number of field descriptions contained in the fields array
 * @mod: The module creating the event, NULL if not created from a module
 *
 * Create a new synthetic event with the given name under the
 * trace/events/synthetic/ directory.  The event fields that will be
 * defined for the event should be passed in as an array of struct
 * synth_field_desc, and the number elements in the array passed in as
 * n_fields. Field ordering will retain the ordering given in the
 * fields array.
 *
 * If the new synthetic event is being created from a module, the mod
 * param must be non-NULL.  This will ensure that the trace buffer
 * won't contain unreadable events.
 *
 * The new synth event should be deleted using synth_event_delete()
 * function.  The new synthetic event can be generated from modules or
 * other kernel code using trace_synth_event() and related functions.
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_create(const char *name, struct synth_field_desc *fields,
                       unsigned int n_fields, struct module *mod)
{
        struct dynevent_cmd cmd;
        char *buf;
        int ret;

        buf = kzalloc(MAX_DYNEVENT_CMD_LEN, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        synth_event_cmd_init(&cmd, buf, MAX_DYNEVENT_CMD_LEN);

        ret = synth_event_gen_cmd_array_start(&cmd, name, mod,
                                              fields, n_fields);
        if (ret)
                goto out;

        ret = synth_event_gen_cmd_end(&cmd);
 out:
        kfree(buf);

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_create);

static int destroy_synth_event(struct synth_event *se)
{
        int ret;

        if (se->ref)
                ret = -EBUSY;
        else {
                ret = unregister_synth_event(se);
                if (!ret) {
                        dyn_event_remove(&se->devent);
                        free_synth_event(se);
                }
        }

        return ret;
}

/**
 * synth_event_delete - Delete a synthetic event
 * @event_name: The name of the new sythetic event
 *
 * Delete a synthetic event that was created with synth_event_create().
 *
 * Return: 0 if successful, error otherwise.
 */
int synth_event_delete(const char *event_name)
{
        struct synth_event *se = NULL;
        struct module *mod = NULL;
        int ret = -ENOENT;

        mutex_lock(&event_mutex);
        se = find_synth_event(event_name);
        if (se) {
                mod = se->mod;
                ret = destroy_synth_event(se);
        }
        mutex_unlock(&event_mutex);

        if (mod) {
                mutex_lock(&trace_types_lock);
                /*
                 * It is safest to reset the ring buffer if the module
                 * being unloaded registered any events that were
                 * used. The only worry is if a new module gets
                 * loaded, and takes on the same id as the events of
                 * this module. When printing out the buffer, traced
                 * events left over from this module may be passed to
                 * the new module events and unexpected results may
                 * occur.
                 */
                tracing_reset_all_online_cpus();
                mutex_unlock(&trace_types_lock);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_delete);

static int create_or_delete_synth_event(int argc, char **argv)
{
        const char *name = argv[0];
        int ret;

        /* trace_run_command() ensures argc != 0 */
        if (name[0] == '!') {
                ret = synth_event_delete(name + 1);
                return ret;
        }

        ret = __create_synth_event(argc - 1, name, (const char **)argv + 1);
        return ret == -ECANCELED ? -EINVAL : ret;
}

static int synth_event_run_command(struct dynevent_cmd *cmd)
{
        struct synth_event *se;
        int ret;

        ret = trace_run_command(cmd->seq.buffer, create_or_delete_synth_event);
        if (ret)
                return ret;

        se = find_synth_event(cmd->event_name);
        if (WARN_ON(!se))
                return -ENOENT;

        se->mod = cmd->private_data;

        return ret;
}

/**
 * synth_event_cmd_init - Initialize a synthetic event command object
 * @cmd: A pointer to the dynevent_cmd struct representing the new event
 * @buf: A pointer to the buffer used to build the command
 * @maxlen: The length of the buffer passed in @buf
 *
 * Initialize a synthetic event command object.  Use this before
 * calling any of the other dyenvent_cmd functions.
 */
void synth_event_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen)
{
        dynevent_cmd_init(cmd, buf, maxlen, DYNEVENT_TYPE_SYNTH,
                          synth_event_run_command);
}
EXPORT_SYMBOL_GPL(synth_event_cmd_init);

/**
 * synth_event_trace - Trace a synthetic event
 * @file: The trace_event_file representing the synthetic event
 * @n_vals: The number of values in vals
 * @args: Variable number of args containing the event values
 *
 * Trace a synthetic event using the values passed in the variable
 * argument list.
 *
 * The argument list should be a list 'n_vals' u64 values.  The number
 * of vals must match the number of field in the synthetic event, and
 * must be in the same order as the synthetic event fields.
 *
 * All vals should be cast to u64, and string vals are just pointers
 * to strings, cast to u64.  Strings will be copied into space
 * reserved in the event for the string, using these pointers.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_trace(struct trace_event_file *file, unsigned int n_vals, ...)
{
        struct trace_event_buffer fbuffer;
        struct synth_trace_event *entry;
        struct trace_buffer *buffer;
        struct synth_event *event;
        unsigned int i, n_u64;
        int fields_size = 0;
        va_list args;
        int ret = 0;

        /*
         * Normal event generation doesn't get called at all unless
         * the ENABLED bit is set (which attaches the probe thus
         * allowing this code to be called, etc).  Because this is
         * called directly by the user, we don't have that but we
         * still need to honor not logging when disabled.
         */
        if (!(file->flags & EVENT_FILE_FL_ENABLED))
                return 0;

        event = file->event_call->data;

        if (n_vals != event->n_fields)
                return -EINVAL;

        if (trace_trigger_soft_disabled(file))
                return -EINVAL;

        fields_size = event->n_u64 * sizeof(u64);

        /*
         * Avoid ring buffer recursion detection, as this event
         * is being performed within another event.
         */
        buffer = file->tr->array_buffer.buffer;
        ring_buffer_nest_start(buffer);

        entry = trace_event_buffer_reserve(&fbuffer, file,
                                           sizeof(*entry) + fields_size);
        if (!entry) {
                ret = -EINVAL;
                goto out;
        }

        va_start(args, n_vals);
        for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
                u64 val;

                val = va_arg(args, u64);

                if (event->fields[i]->is_string) {
                        char *str_val = (char *)(long)val;
                        char *str_field = (char *)&entry->fields[n_u64];

                        strscpy(str_field, str_val, STR_VAR_LEN_MAX);
                        n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
                } else {
                        entry->fields[n_u64] = val;
                        n_u64++;
                }
        }
        va_end(args);

        trace_event_buffer_commit(&fbuffer);
out:
        ring_buffer_nest_end(buffer);

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_trace);

/**
 * synth_event_trace_array - Trace a synthetic event from an array
 * @file: The trace_event_file representing the synthetic event
 * @vals: Array of values
 * @n_vals: The number of values in vals
 *
 * Trace a synthetic event using the values passed in as 'vals'.
 *
 * The 'vals' array is just an array of 'n_vals' u64.  The number of
 * vals must match the number of field in the synthetic event, and
 * must be in the same order as the synthetic event fields.
 *
 * All vals should be cast to u64, and string vals are just pointers
 * to strings, cast to u64.  Strings will be copied into space
 * reserved in the event for the string, using these pointers.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_trace_array(struct trace_event_file *file, u64 *vals,
                            unsigned int n_vals)
{
        struct trace_event_buffer fbuffer;
        struct synth_trace_event *entry;
        struct trace_buffer *buffer;
        struct synth_event *event;
        unsigned int i, n_u64;
        int fields_size = 0;
        int ret = 0;

        /*
         * Normal event generation doesn't get called at all unless
         * the ENABLED bit is set (which attaches the probe thus
         * allowing this code to be called, etc).  Because this is
         * called directly by the user, we don't have that but we
         * still need to honor not logging when disabled.
         */
        if (!(file->flags & EVENT_FILE_FL_ENABLED))
                return 0;

        event = file->event_call->data;

        if (n_vals != event->n_fields)
                return -EINVAL;

        if (trace_trigger_soft_disabled(file))
                return -EINVAL;

        fields_size = event->n_u64 * sizeof(u64);

        /*
         * Avoid ring buffer recursion detection, as this event
         * is being performed within another event.
         */
        buffer = file->tr->array_buffer.buffer;
        ring_buffer_nest_start(buffer);

        entry = trace_event_buffer_reserve(&fbuffer, file,
                                           sizeof(*entry) + fields_size);
        if (!entry) {
                ret = -EINVAL;
                goto out;
        }

        for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
                if (event->fields[i]->is_string) {
                        char *str_val = (char *)(long)vals[i];
                        char *str_field = (char *)&entry->fields[n_u64];

                        strscpy(str_field, str_val, STR_VAR_LEN_MAX);
                        n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
                } else {
                        entry->fields[n_u64] = vals[i];
                        n_u64++;
                }
        }

        trace_event_buffer_commit(&fbuffer);
out:
        ring_buffer_nest_end(buffer);

        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_trace_array);

/**
 * synth_event_trace_start - Start piecewise synthetic event trace
 * @file: The trace_event_file representing the synthetic event
 * @trace_state: A pointer to object tracking the piecewise trace state
 *
 * Start the trace of a synthetic event field-by-field rather than all
 * at once.
 *
 * This function 'opens' an event trace, which means space is reserved
 * for the event in the trace buffer, after which the event's
 * individual field values can be set through either
 * synth_event_add_next_val() or synth_event_add_val().
 *
 * A pointer to a trace_state object is passed in, which will keep
 * track of the current event trace state until the event trace is
 * closed (and the event finally traced) using
 * synth_event_trace_end().
 *
 * Note that synth_event_trace_end() must be called after all values
 * have been added for each event trace, regardless of whether adding
 * all field values succeeded or not.
 *
 * Note also that for a given event trace, all fields must be added
 * using either synth_event_add_next_val() or synth_event_add_val()
 * but not both together or interleaved.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_trace_start(struct trace_event_file *file,
                            struct synth_event_trace_state *trace_state)
{
        struct synth_trace_event *entry;
        int fields_size = 0;
        int ret = 0;

        if (!trace_state) {
                ret = -EINVAL;
                goto out;
        }

        memset(trace_state, '\0', sizeof(*trace_state));

        /*
         * Normal event tracing doesn't get called at all unless the
         * ENABLED bit is set (which attaches the probe thus allowing
         * this code to be called, etc).  Because this is called
         * directly by the user, we don't have that but we still need
         * to honor not logging when disabled.  For the the iterated
         * trace case, we save the enabed state upon start and just
         * ignore the following data calls.
         */
        if (!(file->flags & EVENT_FILE_FL_ENABLED)) {
                trace_state->enabled = false;
                goto out;
        }

        trace_state->enabled = true;

        trace_state->event = file->event_call->data;

        if (trace_trigger_soft_disabled(file)) {
                ret = -EINVAL;
                goto out;
        }

        fields_size = trace_state->event->n_u64 * sizeof(u64);

        /*
         * Avoid ring buffer recursion detection, as this event
         * is being performed within another event.
         */
        trace_state->buffer = file->tr->array_buffer.buffer;
        ring_buffer_nest_start(trace_state->buffer);

        entry = trace_event_buffer_reserve(&trace_state->fbuffer, file,
                                           sizeof(*entry) + fields_size);
        if (!entry) {
                ret = -EINVAL;
                goto out;
        }

        trace_state->entry = entry;
out:
        return ret;
}
EXPORT_SYMBOL_GPL(synth_event_trace_start);

static int __synth_event_add_val(const char *field_name, u64 val,
                                 struct synth_event_trace_state *trace_state)
{
        struct synth_field *field = NULL;
        struct synth_trace_event *entry;
        struct synth_event *event;
        int i, ret = 0;

        if (!trace_state) {
                ret = -EINVAL;
                goto out;
        }

        /* can't mix add_next_synth_val() with add_synth_val() */
        if (field_name) {
                if (trace_state->add_next) {
                        ret = -EINVAL;
                        goto out;
                }
                trace_state->add_name = true;
        } else {
                if (trace_state->add_name) {
                        ret = -EINVAL;
                        goto out;
                }
                trace_state->add_next = true;
        }

        if (!trace_state->enabled)
                goto out;

        event = trace_state->event;
        if (trace_state->add_name) {
                for (i = 0; i < event->n_fields; i++) {
                        field = event->fields[i];
                        if (strcmp(field->name, field_name) == 0)
                                break;
                }
                if (!field) {
                        ret = -EINVAL;
                        goto out;
                }
        } else {
                if (trace_state->cur_field >= event->n_fields) {
                        ret = -EINVAL;
                        goto out;
                }
                field = event->fields[trace_state->cur_field++];
        }

        entry = trace_state->entry;
        if (field->is_string) {
                char *str_val = (char *)(long)val;
                char *str_field;

                if (!str_val) {
                        ret = -EINVAL;
                        goto out;
                }

                str_field = (char *)&entry->fields[field->offset];
                strscpy(str_field, str_val, STR_VAR_LEN_MAX);
        } else
                entry->fields[field->offset] = val;
 out:
        return ret;
}

/**
 * synth_event_add_next_val - Add the next field's value to an open synth trace
 * @val: The value to set the next field to
 * @trace_state: A pointer to object tracking the piecewise trace state
 *
 * Set the value of the next field in an event that's been opened by
 * synth_event_trace_start().
 *
 * The val param should be the value cast to u64.  If the value points
 * to a string, the val param should be a char * cast to u64.
 *
 * This function assumes all the fields in an event are to be set one
 * after another - successive calls to this function are made, one for
 * each field, in the order of the fields in the event, until all
 * fields have been set.  If you'd rather set each field individually
 * without regard to ordering, synth_event_add_val() can be used
 * instead.
 *
 * Note however that synth_event_add_next_val() and
 * synth_event_add_val() can't be intermixed for a given event trace -
 * one or the other but not both can be used at the same time.
 *
 * Note also that synth_event_trace_end() must be called after all
 * values have been added for each event trace, regardless of whether
 * adding all field values succeeded or not.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_add_next_val(u64 val,
                             struct synth_event_trace_state *trace_state)
{
        return __synth_event_add_val(NULL, val, trace_state);
}
EXPORT_SYMBOL_GPL(synth_event_add_next_val);

/**
 * synth_event_add_val - Add a named field's value to an open synth trace
 * @field_name: The name of the synthetic event field value to set
 * @val: The value to set the next field to
 * @trace_state: A pointer to object tracking the piecewise trace state
 *
 * Set the value of the named field in an event that's been opened by
 * synth_event_trace_start().
 *
 * The val param should be the value cast to u64.  If the value points
 * to a string, the val param should be a char * cast to u64.
 *
 * This function looks up the field name, and if found, sets the field
 * to the specified value.  This lookup makes this function more
 * expensive than synth_event_add_next_val(), so use that or the
 * none-piecewise synth_event_trace() instead if efficiency is more
 * important.
 *
 * Note however that synth_event_add_next_val() and
 * synth_event_add_val() can't be intermixed for a given event trace -
 * one or the other but not both can be used at the same time.
 *
 * Note also that synth_event_trace_end() must be called after all
 * values have been added for each event trace, regardless of whether
 * adding all field values succeeded or not.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_add_val(const char *field_name, u64 val,
                        struct synth_event_trace_state *trace_state)
{
        return __synth_event_add_val(field_name, val, trace_state);
}
EXPORT_SYMBOL_GPL(synth_event_add_val);

/**
 * synth_event_trace_end - End piecewise synthetic event trace
 * @trace_state: A pointer to object tracking the piecewise trace state
 *
 * End the trace of a synthetic event opened by
 * synth_event_trace__start().
 *
 * This function 'closes' an event trace, which basically means that
 * it commits the reserved event and cleans up other loose ends.
 *
 * A pointer to a trace_state object is passed in, which will keep
 * track of the current event trace state opened with
 * synth_event_trace_start().
 *
 * Note that this function must be called after all values have been
 * added for each event trace, regardless of whether adding all field
 * values succeeded or not.
 *
 * Return: 0 on success, err otherwise.
 */
int synth_event_trace_end(struct synth_event_trace_state *trace_state)
{
        if (!trace_state)
                return -EINVAL;

        trace_event_buffer_commit(&trace_state->fbuffer);

        ring_buffer_nest_end(trace_state->buffer);

        return 0;
}
EXPORT_SYMBOL_GPL(synth_event_trace_end);

static int create_synth_event(int argc, const char **argv)
{
        const char *name = argv[0];
        int len;

        if (name[0] != 's' || name[1] != ':')
                return -ECANCELED;
        name += 2;

        /* This interface accepts group name prefix */
        if (strchr(name, '/')) {
                len = str_has_prefix(name, SYNTH_SYSTEM "/");
                if (len == 0)
                        return -EINVAL;
                name += len;
        }
        return __create_synth_event(argc - 1, name, argv + 1);
}

static int synth_event_release(struct dyn_event *ev)
{
        struct synth_event *event = to_synth_event(ev);
        int ret;

        if (event->ref)
                return -EBUSY;

        ret = unregister_synth_event(event);
        if (ret)
                return ret;

        dyn_event_remove(ev);
        free_synth_event(event);
        return 0;
}

static int __synth_event_show(struct seq_file *m, struct synth_event *event)
{
        struct synth_field *field;
        unsigned int i;

        seq_printf(m, "%s\t", event->name);

        for (i = 0; i < event->n_fields; i++) {
                field = event->fields[i];

                /* parameter values */
                seq_printf(m, "%s %s%s", field->type, field->name,
                           i == event->n_fields - 1 ? "" : "; ");
        }

        seq_putc(m, '\n');

        return 0;
}

static int synth_event_show(struct seq_file *m, struct dyn_event *ev)
{
        struct synth_event *event = to_synth_event(ev);

        seq_printf(m, "s:%s/", event->class.system);

        return __synth_event_show(m, event);
}

static int synth_events_seq_show(struct seq_file *m, void *v)
{
        struct dyn_event *ev = v;

        if (!is_synth_event(ev))
                return 0;

        return __synth_event_show(m, to_synth_event(ev));
}

static const struct seq_operations synth_events_seq_op = {
        .start  = dyn_event_seq_start,
        .next   = dyn_event_seq_next,
        .stop   = dyn_event_seq_stop,
        .show   = synth_events_seq_show,
};

static int synth_events_open(struct inode *inode, struct file *file)
{
        int ret;

        ret = security_locked_down(LOCKDOWN_TRACEFS);
        if (ret)
                return ret;

        if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
                ret = dyn_events_release_all(&synth_event_ops);
                if (ret < 0)
                        return ret;
        }

        return seq_open(file, &synth_events_seq_op);
}

static ssize_t synth_events_write(struct file *file,
                                  const char __user *buffer,
                                  size_t count, loff_t *ppos)
{
        return trace_parse_run_command(file, buffer, count, ppos,
                                       create_or_delete_synth_event);
}

static const struct file_operations synth_events_fops = {
        .open           = synth_events_open,
        .write          = synth_events_write,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release,
};

static u64 hist_field_timestamp(struct hist_field *hist_field,
                                struct tracing_map_elt *elt,
                                struct ring_buffer_event *rbe,
                                void *event)
{
        struct hist_trigger_data *hist_data = hist_field->hist_data;
        struct trace_array *tr = hist_data->event_file->tr;

        u64 ts = ring_buffer_event_time_stamp(rbe);

        if (hist_data->attrs->ts_in_usecs && trace_clock_in_ns(tr))
                ts = ns2usecs(ts);

        return ts;
}

static u64 hist_field_cpu(struct hist_field *hist_field,
                          struct tracing_map_elt *elt,
                          struct ring_buffer_event *rbe,
                          void *event)
{
        int cpu = smp_processor_id();

        return cpu;
}

/**
 * check_field_for_var_ref - Check if a VAR_REF field references a variable
 * @hist_field: The VAR_REF field to check
 * @var_data: The hist trigger that owns the variable
 * @var_idx: The trigger variable identifier
 *
 * Check the given VAR_REF field to see whether or not it references
 * the given variable associated with the given trigger.
 *
 * Return: The VAR_REF field if it does reference the variable, NULL if not
 */
static struct hist_field *
check_field_for_var_ref(struct hist_field *hist_field,
                        struct hist_trigger_data *var_data,
                        unsigned int var_idx)
{
        WARN_ON(!(hist_field && hist_field->flags & HIST_FIELD_FL_VAR_REF));

        if (hist_field && hist_field->var.idx == var_idx &&
            hist_field->var.hist_data == var_data)
                return hist_field;

        return NULL;
}

/**
 * find_var_ref - Check if a trigger has a reference to a trigger variable
 * @hist_data: The hist trigger that might have a reference to the variable
 * @var_data: The hist trigger that owns the variable
 * @var_idx: The trigger variable identifier
 *
 * Check the list of var_refs[] on the first hist trigger to see
 * whether any of them are references to the variable on the second
 * trigger.
 *
 * Return: The VAR_REF field referencing the variable if so, NULL if not
 */
static struct hist_field *find_var_ref(struct hist_trigger_data *hist_data,
                                       struct hist_trigger_data *var_data,
                                       unsigned int var_idx)
{
        struct hist_field *hist_field;
        unsigned int i;

        for (i = 0; i < hist_data->n_var_refs; i++) {
                hist_field = hist_data->var_refs[i];
                if (check_field_for_var_ref(hist_field, var_data, var_idx))
                        return hist_field;
        }

        return NULL;
}

/**
 * find_any_var_ref - Check if there is a reference to a given trigger variable
 * @hist_data: The hist trigger
 * @var_idx: The trigger variable identifier
 *
 * Check to see whether the given variable is currently referenced by
 * any other trigger.
 *
 * The trigger the variable is defined on is explicitly excluded - the
 * assumption being that a self-reference doesn't prevent a trigger
 * from being removed.
 *
 * Return: The VAR_REF field referencing the variable if so, NULL if not
 */
static struct hist_field *find_any_var_ref(struct hist_trigger_data *hist_data,
                                           unsigned int var_idx)
{
        struct trace_array *tr = hist_data->event_file->tr;
        struct hist_field *found = NULL;
        struct hist_var_data *var_data;

        list_for_each_entry(var_data, &tr->hist_vars, list) {
                if (var_data->hist_data == hist_data)
                        continue;
                found = find_var_ref(var_data->hist_data, hist_data, var_idx);
                if (found)
                        break;
        }

        return found;
}

/**
 * check_var_refs - Check if there is a reference to any of trigger's variables
 * @hist_data: The hist trigger
 *
 * A trigger can define one or more variables.  If any one of them is
 * currently referenced by any other trigger, this function will
 * determine that.

 * Typically used to determine whether or not a trigger can be removed
 * - if there are any references to a trigger's variables, it cannot.
 *
 * Return: True if there is a reference to any of trigger's variables
 */
static bool check_var_refs(struct hist_trigger_data *hist_data)
{
        struct hist_field *field;
        bool found = false;
        int i;

        for_each_hist_field(i, hist_data) {
                field = hist_data->fields[i];
                if (field && field->flags & HIST_FIELD_FL_VAR) {
                        if (find_any_var_ref(hist_data, field->var.idx)) {
                                found = true;
                                break;
                        }
                }
        }

        return found;
}

static struct hist_var_data *find_hist_vars(struct hist_trigger_data *hist_data)
{
        struct trace_array *tr = hist_data->event_file->tr;
        struct hist_var_data *var_data, *found = NULL;

        list_for_each_entry(var_data, &tr->hist_vars, list) {
                if (var_data->hist_data == hist_data) {
                        found = var_data;
                        break;
                }
        }

        return found;
}

static bool field_has_hist_vars(struct hist_field *hist_field,
                                unsigned int level)
{
        int i;

        if (level > 3)
                return false;

        if (!hist_field)
                return false;

        if (hist_field->flags & HIST_FIELD_FL_VAR ||
            hist_field->flags & HIST_FIELD_FL_VAR_REF)
                return true;

        for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++) {
                struct hist_field *operand;

                operand = hist_field->operands[i];
                if (field_has_hist_vars(operand, level + 1))
                        return true;
        }

        return false;
}

static bool has_hist_vars(struct hist_trigger_data *hist_data)
{
        struct hist_field *hist_field;
        int i;

        for_each_hist_field(i, hist_data) {
                hist_field = hist_data->fields[i];
                if (field_has_hist_vars(hist_field, 0))
                        return true;
        }

        return false;
}

static int save_hist_vars(struct hist_trigger_data *hist_data)
{
        struct trace_array *tr = hist_data->event_file->tr;
        struct hist_var_data *var_data;

        var_data = find_hist_vars(hist_data);
        if (var_data)
                return 0;

        if (tracing_check_open_get_tr(tr))
                return -ENODEV;

        var_data = kzalloc(sizeof(*var_data), GFP_KERNEL);
        if (!var_data) {
                trace_array_put(tr);
                return -ENOMEM;
        }

        var_data->hist_data = hist_data;
        list_add(&var_data->list, &tr->hist_vars);

        return 0;
}

static void remove_hist_vars(struct hist_trigger_data *hist_data)
{
        struct trace_array *tr = hist_data->event_file->tr;
        struct hist_var_data *var_data;

        var_data = find_hist_vars(hist_data);
        if (!var_data)
                return;

        if (WARN_ON(check_var_refs(hist_data)))
                return;

        list_del(&var_data->list);

        kfree(var_data);

        trace_array_put(tr);
}

static struct hist_field *find_var_field(struct hist_trigger_data *hist_data,
                                         const char *var_name)
{
        struct hist_field *hist_field, *found = NULL;
        int i;

        for_each_hist_field(i, hist_data) {
                hist_field = hist_data->fields[i];
                if (hist_field && hist_field->flags & HIST_FIELD_FL_VAR &&
                    strcmp(hist_field->var.name, var_name) == 0) {
                        found = hist_field;
                        break;
                }
        }

        return found;
}

static struct hist_field *find_var(struct hist_trigger_data *hist_data,
                                   struct trace_event_file *file,
                                   const char *var_name)
{
        struct hist_trigger_data *test_data;
        struct event_trigger_data *test;
        struct hist_field *hist_field;

        lockdep_assert_held(&event_mutex);

        hist_field = find_var_field(hist_data, var_name);
        if (hist_field)
                return hist_field;

        list_for_each_entry(test, &file->triggers, list) {
                if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
                        test_data = test->private_data;
                        hist_field = find_var_field(test_data, var_name);
                        if (hist_field)
                                return hist_field;
                }
        }

        return NULL;
}

static struct trace_event_file *find_var_file(struct trace_array *tr,
                                              char *system,
                                              char *event_name,
                                              char *var_name)
{
        struct hist_trigger_data *var_hist_data;
        struct hist_var_data *var_data;
        struct trace_event_file *file, *found = NULL;

        if (system)
                return find_event_file(tr, system, event_name);

        list_for_each_entry(var_data, &tr->hist_vars, list) {
                var_hist_data = var_data->hist_data;
                file = var_hist_data->event_file;
                if (file == found)
                        continue;

                if (find_var_field(var_hist_data, var_name)) {
                        if (found) {
                                hist_err(tr, HIST_ERR_VAR_NOT_UNIQUE, errpos(var_name));
                                return NULL;
                        }

                        found = file;
                }
        }

        return found;
}

static struct hist_field *find_file_var(struct trace_event_file *file,
                                        const char *var_name)
{
        struct hist_trigger_data *test_data;
        struct event_trigger_data *test;
        struct hist_field *hist_field;

        lockdep_assert_held(&event_mutex);

        list_for_each_entry(test, &file->triggers, list) {
                if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
                        test_data = test->private_data;
                        hist_field = find_var_field(test_data, var_name);
                        if (hist_field)
                                return hist_field;
                }
        }

        return NULL;
}

static struct hist_field *
find_match_var(struct hist_trigger_data *hist_data, char *var_name)
{
        struct trace_array *tr = hist_data->event_file->tr;
        struct hist_field *hist_field, *found = NULL;
        struct trace_event_file *file;
        unsigned int i;

        for (i = 0; i < hist_data->n_actions; i++) {
                struct action_data *data = hist_data->actions[i];

                if (data->handler == HANDLER_ONMATCH) {
                        char *system = data->match_data.event_system;
                        char *event_name = data->match_data.event;

                        file = find_var_file(tr, system, event_name, var_name);
                        if (!file)
                                continue;
                        hist_field = find_file_var(file, var_name);
                        if (hist_field) {
                                if (found) {
                                        hist_err(tr, HIST_ERR_VAR_NOT_UNIQUE,
                                                 errpos(var_name));
                                        return ERR_PTR(-EINVAL);
                                }

                                found = hist_field;
                        }
                }
        }
        return found;
}

static struct hist_field *find_event_var(struct hist_trigger_data *hist_data,
                                         char *system,
                                         char *event_name,
                                         char *var_name)
{
        struct trace_array *tr = hist_data->event_file->tr;
        struct hist_field *hist_field = NULL;
        struct trace_event_file *file;

        if (!system || !event_name) {
                hist_field = find_match_var(hist_data, var_name);
                if (IS_ERR(hist_field))
                        return NULL;
                if (hist_field)
                        return hist_field;
        }

        file = find_var_file(tr, system, event_name, var_name);
        if (!file)
                return NULL;

        hist_field = find_file_var(file, var_name);

        return hist_field;
}

static u64 hist_field_var_ref(struct hist_field *hist_field,
                              struct tracing_map_elt *elt,
                              struct ring_buffer_event *rbe,
                              void *event)
{
        struct hist_elt_data *elt_data;
        u64 var_val = 0;

        if (WARN_ON_ONCE(!elt))
                return var_val;

        elt_data = elt->private_data;
        var_val = elt_data->var_ref_vals[hist_field->var_ref_idx];

        return var_val;
}

static bool resolve_var_refs(struct hist_trigger_data *hist_data, void *key,
                             u64 *var_ref_vals, bool self)
{
        struct hist_trigger_data *var_data;
        struct tracing_map_elt *var_elt;
        struct hist_field *hist_field;
        unsigned int i, var_idx;
        bool resolved = true;
        u64 var_val = 0;

        for (i = 0; i < hist_data->n_var_refs; i++) {
                hist_field = hist_data->var_refs[i];
                var_idx = hist_field->var.idx;
                var_data = hist_field->var.hist_data;

                if (var_data == NULL) {
                        resolved = false;
                        break;
                }

                if ((self && var_data != hist_data) ||
                    (!self && var_data == hist_data))
                        continue;

                var_elt = tracing_map_lookup(var_data->map, key);
                if (!var_elt) {
                        resolved = false;
                        break;
                }

                if (!tracing_map_var_set(var_elt, var_idx)) {
                        resolved = false;
                        break;
                }

                if (self || !hist_field->read_once)
                        var_val = tracing_map_read_var(var_elt, var_idx);
                else
                        var_val = tracing_map_read_var_once(var_elt, var_idx);

                var_ref_vals[i] = var_val;
        }

        return resolved;
}

static const char *hist_field_name(struct hist_field *field,
                                   unsigned int level)
{
        const char *field_name = "";

        if (level > 1)
                return field_name;

        if (field->field)
                field_name = field->field->name;
        else if (field->flags & HIST_FIELD_FL_LOG2 ||
                 field->flags & HIST_FIELD_FL_ALIAS)
                field_name = hist_field_name(field->operands[0], ++level);
        else if (field->flags & HIST_FIELD_FL_CPU)
                field_name = "cpu";
        else if (field->flags & HIST_FIELD_FL_EXPR ||
                 field->flags & HIST_FIELD_FL_VAR_REF) {
                if (field->system) {
                        static char full_name[MAX_FILTER_STR_VAL];

                        strcat(full_name, field->system);
                        strcat(full_name, ".");
                        strcat(full_name, field->event_name);
                        strcat(full_name, ".");
                        strcat(full_name, field->name);
                        field_name = full_name;
                } else
                        field_name = field->name;
        } else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
                field_name = "common_timestamp";

        if (field_name == NULL)
                field_name = "";

        return field_name;
}

static hist_field_fn_t select_value_fn(int field_size, int field_is_signed)
{
        hist_field_fn_t fn = NULL;

        switch (field_size) {
        case 8:
                if (field_is_signed)
                        fn = hist_field_s64;
                else
                        fn = hist_field_u64;
                break;
        case 4:
                if (field_is_signed)
                        fn = hist_field_s32;
                else
                        fn = hist_field_u32;
                break;
        case 2:
                if (field_is_signed)
                        fn = hist_field_s16;
                else
                        fn = hist_field_u16;
                break;
        case 1:
                if (field_is_signed)
                        fn = hist_field_s8;
                else
                        fn = hist_field_u8;
                break;
        }

        return fn;
}

static int parse_map_size(char *str)
{
        unsigned long size, map_bits;
        int ret;

        ret = kstrtoul(str, 0, &size);
        if (ret)
                goto out;

        map_bits = ilog2(roundup_pow_of_two(size));
        if (map_bits < TRACING_MAP_BITS_MIN ||
            map_bits > TRACING_MAP_BITS_MAX)
                ret = -EINVAL;
        else
                ret = map_bits;
 out:
        return ret;
}

static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
{
        unsigned int i;

        if (!attrs)
                return;

        for (i = 0; i < attrs->n_assignments; i++)
                kfree(attrs->assignment_str[i]);

        for (i = 0; i < attrs->n_actions; i++)
                kfree(attrs->action_str[i]);

        kfree(attrs->name);
        kfree(attrs->sort_key_str);
        kfree(attrs->keys_str);
        kfree(attrs->vals_str);
        kfree(attrs->clock);
        kfree(attrs);
}

static int parse_action(char *str, struct hist_trigger_attrs *attrs)
{
        int ret = -EINVAL;

        if (attrs->n_actions >= HIST_ACTIONS_MAX)
                return ret;

        if ((str_has_prefix(str, "onmatch(")) ||
            (str_has_prefix(str, "onmax(")) ||
            (str_has_prefix(str, "onchange("))) {
                attrs->action_str[attrs->n_actions] = kstrdup(str, GFP_KERNEL);
                if (!attrs->action_str[attrs->n_actions]) {
                        ret = -ENOMEM;
                        return ret;
                }
                attrs->n_actions++;
                ret = 0;
        }
        return ret;
}

static int parse_assignment(struct trace_array *tr,
                            char *str, struct hist_trigger_attrs *attrs)
{
        int len, ret = 0;

        if ((len = str_has_prefix(str, "key=")) ||
            (len = str_has_prefix(str, "keys="))) {
                attrs->keys_str = kstrdup(str + len, GFP_KERNEL);
                if (!attrs->keys_str) {
                        ret = -ENOMEM;
                        goto out;
                }
        } else if ((len = str_has_prefix(str, "val=")) ||
                   (len = str_has_prefix(str, "vals=")) ||
                   (len = str_has_prefix(str, "values="))) {
                attrs->vals_str = kstrdup(str + len, GFP_KERNEL);
                if (!attrs->vals_str) {
                        ret = -ENOMEM;
                        goto out;
                }
        } else if ((len = str_has_prefix(str, "sort="))) {
                attrs->sort_key_str = kstrdup(str + len, GFP_KERNEL);
                if (!attrs->sort_key_str) {
                        ret = -ENOMEM;
                        goto out;
                }
        } else if (str_has_prefix(str, "name=")) {
                attrs->name = kstrdup(str, GFP_KERNEL);
                if (!attrs->name) {
                        ret = -ENOMEM;
                        goto out;
                }
        } else if ((len = str_has_prefix(str, "clock="))) {
                str += len;

                str = strstrip(str);
                attrs->clock = kstrdup(str, GFP_KERNEL);
                if (!attrs->clock) {
                        ret = -ENOMEM;
                        goto out;
                }
        } else if ((len = str_has_prefix(str, "size="))) {
                int map_bits = parse_map_size(str + len);

                if (map_bits < 0) {
                        ret = map_bits;
                        goto out;
                }
                attrs->map_bits = map_bits;
        } else {
                char *assignment;

                if (attrs->n_assignments == TRACING_MAP_VARS_MAX) {
                        hist_err(tr, HIST_ERR_TOO_MANY_VARS, errpos(str));
                        ret = -EINVAL;
                        goto out;
                }

                assignment = kstrdup(str, GFP_KERNEL);
                if (!assignment) {
                        ret = -ENOMEM;
                        goto out;
                }

                attrs->assignment_str[attrs->n_assignments++] = assignment;
        }
 out:
        return ret;
}

static struct hist_trigger_attrs *
parse_hist_trigger_attrs(struct trace_array *tr, char *trigger_str)
{
        struct hist_trigger_attrs *attrs;
        int ret = 0;

        attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
        if (!attrs)
                return ERR_PTR(-ENOMEM);

        while (trigger_str) {
                char *str = strsep(&trigger_str, ":");
                char *rhs;

                rhs = strchr(str, '=');
                if (rhs) {
                        if (!strlen(++rhs)) {
                                ret = -EINVAL;
                                hist_err(tr, HIST_ERR_EMPTY_ASSIGNMENT, errpos(str));
                                goto free;
                        }
                        ret = parse_assignment(tr, str, attrs);
                        if (ret)
                                goto free;
                } else if (strcmp(str, "pause") == 0)
                        attrs->pause = true;
                else if ((strcmp(str, "cont") == 0) ||
                         (strcmp(str, "continue") == 0))
                        attrs->cont = true;
                else if (strcmp(str, "clear") == 0)
                        attrs->clear = true;
                else {
                        ret = parse_action(str, attrs);
                        if (ret)
                                goto free;
                }
        }

        if (!attrs->keys_str) {
                ret = -EINVAL;
                goto free;
        }

        if (!attrs->clock) {
                attrs->clock = kstrdup("global", GFP_KERNEL);
                if (!attrs->clock) {
                        ret = -ENOMEM;
                        goto free;
                }
        }

        return attrs;
 free:
        destroy_hist_trigger_attrs(attrs);

        return ERR_PTR(ret);
}

static inline void save_comm(char *comm, struct task_struct *task)
{
        if (!task->pid) {
                strcpy(comm, "<idle>");
                return;
        }

        if (WARN_ON_ONCE(task->pid < 0)) {
                strcpy(comm, "<XXX>");
                return;
        }

        strncpy(comm, task->comm, TASK_COMM_LEN);
}

static void hist_elt_data_free(struct hist_elt_data *elt_data)
{
        unsigned int i;

        for (i = 0; i < SYNTH_FIELDS_MAX; i++)
                kfree(elt_data->field_var_str[i]);

        kfree(elt_data->comm);
        kfree(elt_data);
}

static void hist_trigger_elt_data_free(struct tracing_map_elt *elt)
{
        struct hist_elt_data *elt_data = elt->private_data;

        hist_elt_data_free(elt_data);
}

static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
{
        struct hist_trigger_data *hist_data = elt->map->private_data;
        unsigned int size = TASK_COMM_LEN;
        struct hist_elt_data *elt_data;
        struct hist_field *key_field;
        unsigned int i, n_str;

        elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
        if (!elt_data)
                return -ENOMEM;

        for_each_hist_key_field(i, hist_data) {
                key_field = hist_data->fields[i];

                if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
                        elt_data->comm = kzalloc(size, GFP_KERNEL);
                        if (!elt_data->comm) {
                                kfree(elt_data);
                                return -ENOMEM;
                        }
                        break;
                }
        }

        n_str = hist_data->n_field_var_str + hist_data->n_save_var_str;

        size = STR_VAR_LEN_MAX;

        for (i = 0; i < n_str; i++) {
                elt_data->field_var_str[i] = kzalloc(size, GFP_KERNEL);
                if (!elt_data->field_var_str[i]) {
                        hist_elt_data_free(elt_data);
                        return -ENOMEM;
                }
        }

        elt->private_data = elt_data;

        return 0;
}

static void hist_trigger_elt_data_init(struct tracing_map_elt *elt)
{
        struct hist_elt_data *elt_data = elt->private_data;

        if (elt_data->comm)
                save_comm(elt_data->comm, current);
}

static const struct tracing_map_ops hist_trigger_elt_data_ops = {
        .elt_alloc      = hist_trigger_elt_data_alloc,
        .elt_free       = hist_trigger_elt_data_free,
        .elt_init       = hist_trigger_elt_data_init,
};

static const char *get_hist_field_flags(struct hist_field *hist_field)
{
        const char *flags_str = NULL;

        if (hist_field->flags & HIST_FIELD_FL_HEX)
                flags_str = "hex";
        else if (hist_field->flags & HIST_FIELD_FL_SYM)
                flags_str = "sym";
        else if (hist_field->flags & HIST_FIELD_FL_SYM_OFFSET)
                flags_str = "sym-offset";
        else if (hist_field->flags & HIST_FIELD_FL_EXECNAME)
                flags_str = "execname";
        else if (hist_field->flags & HIST_FIELD_FL_SYSCALL)
                flags_str = "syscall";
        else if (hist_field->flags & HIST_FIELD_FL_LOG2)
                flags_str = "log2";
        else if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP_USECS)
                flags_str = "usecs";

        return flags_str;
}

static void expr_field_str(struct hist_field *field, char *expr)
{
        if (field->flags & HIST_FIELD_FL_VAR_REF)
                strcat(expr, "$");

        strcat(expr, hist_field_name(field, 0));

        if (field->flags && !(field->flags & HIST_FIELD_FL_VAR_REF)) {
                const char *flags_str = get_hist_field_flags(field);

                if (flags_str) {
                        strcat(expr, ".");
                        strcat(expr, flags_str);
                }
        }
}

static char *expr_str(struct hist_field *field, unsigned int level)
{
        char *expr;

        if (level > 1)
                return NULL;

        expr = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
        if (!expr)
                return NULL;

        if (!field->operands[0]) {
                expr_field_str(field, expr);
                return expr;
        }

        if (field->operator == FIELD_OP_UNARY_MINUS) {
                char *subexpr;

                strcat(expr, "-(");
                subexpr = expr_str(field->operands[0], ++level);
                if (!subexpr) {
                        kfree(expr);
                        return NULL;
                }
                strcat(expr, subexpr);
                strcat(expr, ")");

                kfree(subexpr);

                return expr;
        }

        expr_field_str(field->operands[0], expr);

        switch (field->operator) {
        case FIELD_OP_MINUS:
                strcat(expr, "-");
                break;
        case FIELD_OP_PLUS:
                strcat(expr, "+");
                break;
        default:
                kfree(expr);
                return NULL;
        }

        expr_field_str(field->operands[1], expr);

        return expr;
}

static int contains_operator(char *str)
{
        enum field_op_id field_op = FIELD_OP_NONE;
        char *op;

        op = strpbrk(str, "+-");
        if (!op)
                return FIELD_OP_NONE;

        switch (*op) {
        case '-':
                if (*str == '-')
                        field_op = FIELD_OP_UNARY_MINUS;
                else
                        field_op = FIELD_OP_MINUS;
                break;
        case '+':
                field_op = FIELD_OP_PLUS;
                break;
        default:
                break;
        }

        return field_op;
}

static void __destroy_hist_field(struct hist_field *hist_field)
{
        kfree(hist_field->var.name);
        kfree(hist_field->name);
        kfree(hist_field->type);

        kfree(hist_field);
}

static void destroy_hist_field(struct hist_field *hist_field,
                               unsigned int level)
{
        unsigned int i;

        if (level > 3)
                return;

        if (!hist_field)
                return;

        if (hist_field->flags & HIST_FIELD_FL_VAR_REF)
                return; /* var refs will be destroyed separately */

        for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++)
                destroy_hist_field(hist_field->operands[i], level + 1);

        __destroy_hist_field(hist_field);
}

static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
                                            struct ftrace_event_field *field,
                                            unsigned long flags,
                                            char *var_name)
{
        struct hist_field *hist_field;

        if (field && is_function_field(field))
                return NULL;

        hist_field = kzalloc(sizeof(struct hist_field), GFP_KERNEL);
        if (!hist_field)
                return NULL;

        hist_field->hist_data = hist_data;

        if (flags & HIST_FIELD_FL_EXPR || flags & HIST_FIELD_FL_ALIAS)
                goto out; /* caller will populate */

        if (flags & HIST_FIELD_FL_VAR_REF) {
                hist_field->fn = hist_field_var_ref;
                goto out;
        }

        if (flags & HIST_FIELD_FL_HITCOUNT) {
                hist_field->fn = hist_field_counter;
                hist_field->size = sizeof(u64);
                hist_field->type = kstrdup("u64", GFP_KERNEL);
                if (!hist_field->type)
                        goto free;
                goto out;
        }

        if (flags & HIST_FIELD_FL_STACKTRACE) {
                hist_field->fn = hist_field_none;
                goto out;
        }

        if (flags & HIST_FIELD_FL_LOG2) {
                unsigned long fl = flags & ~HIST_FIELD_FL_LOG2;
                hist_field->fn = hist_field_log2;
                hist_field->operands[0] = create_hist_field(hist_data, field, fl, NULL);
                hist_field->size = hist_field->operands[0]->size;
                hist_field->type = kstrdup(hist_field->operands[0]->type, GFP_KERNEL);
                if (!hist_field->type)
                        goto free;
                goto out;
        }

        if (flags & HIST_FIELD_FL_TIMESTAMP) {
                hist_field->fn = hist_field_timestamp;
                hist_field->size = sizeof(u64);
                hist_field->type = kstrdup("u64", GFP_KERNEL);
                if (!hist_field->type)
                        goto free;
                goto out;
        }

        if (flags & HIST_FIELD_FL_CPU) {
                hist_field->fn = hist_field_cpu;
                hist_field->size = sizeof(int);
                hist_field->type = kstrdup("unsigned int", GFP_KERNEL);
                if (!hist_field->type)
                        goto free;
                goto out;
        }

        if (WARN_ON_ONCE(!field))
                goto out;

        if (is_string_field(field)) {
                flags |= HIST_FIELD_FL_STRING;

                hist_field->size = MAX_FILTER_STR_VAL;
                hist_field->type = kstrdup(field->type, GFP_KERNEL);
                if (!hist_field->type)
                        goto free;

                if (field->filter_type == FILTER_STATIC_STRING)
                        hist_field->fn = hist_field_string;
                else if (field->filter_type == FILTER_DYN_STRING)
                        hist_field->fn = hist_field_dynstring;
                else
                        hist_field->fn = hist_field_pstring;
        } else {
                hist_field->size = field->size;
                hist_field->is_signed = field->is_signed;
                hist_field->type = kstrdup(field->type, GFP_KERNEL);
                if (!hist_field->type)
                        goto free;

                hist_field->fn = select_value_fn(field->size,
                                                 field->is_signed);
                if (!hist_field->fn) {
                        destroy_hist_field(hist_field, 0);
                        return NULL;
                }
        }
 out:
        hist_field->field = field;
        hist_field->flags = flags;

        if (var_name) {
                hist_field->var.name = kstrdup(var_name, GFP_KERNEL);
                if (!hist_field->var.name)
                        goto free;
        }

        return hist_field;
 free:
        destroy_hist_field(hist_field, 0);
        return NULL;
}

static void destroy_hist_fields(struct hist_trigger_data *hist_data)
{
        unsigned int i;

        for (i = 0; i < HIST_FIELDS_MAX; i++) {
                if (hist_data->fields[i]) {
                        destroy_hist_field(hist_data->fields[i], 0);
                        hist_data->fields[i] = NULL;
                }
        }

        for (i = 0; i < hist_data->n_var_refs; i++) {
                WARN_ON(!(hist_data->var_refs[i]->flags & HIST_FIELD_FL_VAR_REF));
                __destroy_hist_field(hist_data->var_refs[i]);
                hist_data->var_refs[i] = NULL;
        }
}

static int init_var_ref(struct hist_field *ref_field,
                        struct hist_field *var_field,
                        char *system, char *event_name)
{
        int err = 0;

        ref_field->var.idx = var_field->var.idx;
        ref_field->var.hist_data = var_field->hist_data;
        ref_field->size = var_field->size;
        ref_field->is_signed = var_field->is_signed;
        ref_field->flags |= var_field->flags &
                (HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);

        if (system) {
                ref_field->system = kstrdup(system, GFP_KERNEL);
                if (!ref_field->system)
                        return -ENOMEM;
        }

        if (event_name) {
                ref_field->event_name = kstrdup(event_name, GFP_KERNEL);
                if (!ref_field->event_name) {
                        err = -ENOMEM;
                        goto free;
                }
        }

        if (var_field->var.name) {
                ref_field->name = kstrdup(var_field->var.name, GFP_KERNEL);
                if (!ref_field->name) {
                        err = -ENOMEM;
                        goto free;
                }
        } else if (var_field->name) {
                ref_field->name = kstrdup(var_field->name, GFP_KERNEL);
                if (!ref_field->name) {
                        err = -ENOMEM;
                        goto free;
                }
        }

        ref_field->type = kstrdup(var_field->type, GFP_KERNEL);
        if (!ref_field->type) {
                err = -ENOMEM;
                goto free;
        }
 out:
        return err;
 free:
        kfree(ref_field->system);
        kfree(ref_field->event_name);
        kfree(ref_field->name);

        goto out;
}

static int find_var_ref_idx(struct hist_trigger_data *hist_data,
                            struct hist_field *var_field)
{
        struct hist_field *ref_field;
        int i;

        for (i = 0; i < hist_data->n_var_refs; i++) {
                ref_field = hist_data->var_refs[i];
                if (ref_field->var.idx == var_field->var.idx &&
                    ref_field->var.hist_data == var_field->hist_data)
                        return i;
        }

        return -ENOENT;
}

/**
 * create_var_ref - Create a variable reference and attach it to trigger
 * @hist_data: The trigger that will be referencing the variable
 * @var_field: The VAR field to create a reference to
 * @system: The optional system string
 * @event_name: The optional event_name string
 *
 * Given a variable hist_field, create a VAR_REF hist_field that
 * represents a reference to it.
 *
 * This function also adds the reference to the trigger that
 * now references the variable.
 *
 * Return: The VAR_REF field if successful, NULL if not
 */
static struct hist_field *create_var_ref(struct hist_trigger_data *hist_data,
                                         struct hist_field *var_field,
                                         char *system, char *event_name)
{
        unsigned long flags = HIST_FIELD_FL_VAR_REF;
        struct hist_field *ref_field;

        ref_field = create_hist_field(var_field->hist_data, NULL, flags, NULL);
        if (ref_field) {
                if (init_var_ref(ref_field, var_field, system, event_name)) {
                        destroy_hist_field(ref_field, 0);
                        return NULL;
                }

                hist_data->var_refs[hist_data->n_var_refs] = ref_field;
                ref_field->var_ref_idx = hist_data->n_var_refs++;
        }

        return ref_field;
}

static bool is_var_ref(char *var_name)
{
        if (!var_name || strlen(var_name) < 2 || var_name[0] != '$')
                return false;

        return true;
}

static char *field_name_from_var(struct hist_trigger_data *hist_data,
                                 char *var_name)
{
        char *name, *field;
        unsigned int i;

        for (i = 0; i < hist_data->attrs->var_defs.n_vars; i++) {
                name = hist_data->attrs->var_defs.name[i];

                if (strcmp(var_name, name) == 0) {
                        field = hist_data->attrs->var_defs.expr[i];
                        if (contains_operator(field) || is_var_ref(field))
                                continue;
                        return field;
                }
        }

        return NULL;
}

static char *local_field_var_ref(struct hist_trigger_data *hist_data,
                                 char *system, char *event_name,
                                 char *var_name)
{
        struct trace_event_call *call;

        if (system && event_name) {
                call = hist_data->event_file->event_call;

                if (strcmp(system, call->class->system) != 0)
                        return NULL;

                if (strcmp(event_name, trace_event_name(call)) != 0)
                        return NULL;
        }

        if (!!system != !!event_name)
                return NULL;

        if (!is_var_ref(var_name))
                return NULL;

        var_name++;

        return field_name_from_var(hist_data, var_name);
}

static struct hist_field *parse_var_ref(struct hist_trigger_data *hist_data,
                                        char *system, char *event_name,
                                        char *var_name)
{
        struct hist_field *var_field = NULL, *ref_field = NULL;
        struct trace_array *tr = hist_data->event_file->tr;

        if (!is_var_ref(var_name))
                return NULL;

        var_name++;

        var_field = find_event_var(hist_data, system, event_name, var_name);
        if (var_field)
                ref_field = create_var_ref(hist_data, var_field,
                                           system, event_name);

        if (!ref_field)
                hist_err(tr, HIST_ERR_VAR_NOT_FOUND, errpos(var_name));

        return ref_field;
}

static struct ftrace_event_field *
parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
            char *field_str, unsigned long *flags)
{
        struct ftrace_event_field *field = NULL;
        char *field_name, *modifier, *str;
        struct trace_array *tr = file->tr;

        modifier = str = kstrdup(field_str, GFP_KERNEL);
        if (!modifier)
                return ERR_PTR(-ENOMEM);

        field_name = strsep(&modifier, ".");
        if (modifier) {
                if (strcmp(modifier, "hex") == 0)
                        *flags |= HIST_FIELD_FL_HEX;
                else if (strcmp(modifier, "sym") == 0)
                        *flags |= HIST_FIELD_FL_SYM;
                else if (strcmp(modifier, "sym-offset") == 0)
                        *flags |= HIST_FIELD_FL_SYM_OFFSET;
                else if ((strcmp(modifier, "execname") == 0) &&
                         (strcmp(field_name, "common_pid") == 0))
                        *flags |= HIST_FIELD_FL_EXECNAME;
                else if (strcmp(modifier, "syscall") == 0)
                        *flags |= HIST_FIELD_FL_SYSCALL;
                else if (strcmp(modifier, "log2") == 0)
                        *flags |= HIST_FIELD_FL_LOG2;
                else if (strcmp(modifier, "usecs") == 0)
                        *flags |= HIST_FIELD_FL_TIMESTAMP_USECS;
                else {
                        hist_err(tr, HIST_ERR_BAD_FIELD_MODIFIER, errpos(modifier));
                        field = ERR_PTR(-EINVAL);
                        goto out;
                }
        }

        if (strcmp(field_name, "common_timestamp") == 0) {
                *flags |= HIST_FIELD_FL_TIMESTAMP;
                hist_data->enable_timestamps = true;
                if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS)
                        hist_data->attrs->ts_in_usecs = true;
        } else if (strcmp(field_name, "cpu") == 0)
                *flags |= HIST_FIELD_FL_CPU;
        else {
                field = trace_find_event_field(file->event_call, field_name);
                if (!field || !field->size) {
                        hist_err(tr, HIST_ERR_FIELD_NOT_FOUND, errpos(field_name));
                        field = ERR_PTR(-EINVAL);
                        goto out;
                }
        }
 out:
        kfree(str);

        return field;
}

static struct hist_field *create_alias(struct hist_trigger_data *hist_data,
                                       struct hist_field *var_ref,
                                       char *var_name)
{
        struct hist_field *alias = NULL;
        unsigned long flags = HIST_FIELD_FL_ALIAS | HIST_FIELD_FL_VAR;

        alias = create_hist_field(hist_data, NULL, flags, var_name);
        if (!alias)
                return NULL;

        alias->fn = var_ref->fn;
        alias->operands[0] = var_ref;

        if (init_var_ref(alias, var_ref, var_ref->system, var_ref->event_name)) {
                destroy_hist_field(alias, 0);
                return NULL;
        }

        alias->var_ref_idx = var_ref->var_ref_idx;

        return alias;
}

static struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
                                     struct trace_event_file *file, char *str,
                                     unsigned long *flags, char *var_name)
{
        char *s, *ref_system = NULL, *ref_event = NULL, *ref_var = str;
        struct ftrace_event_field *field = NULL;
        struct hist_field *hist_field = NULL;
        int ret = 0;

        s = strchr(str, '.');
        if (s) {
                s = strchr(++s, '.');
                if (s) {
                        ref_system = strsep(&str, ".");
                        if (!str) {
                                ret = -EINVAL;
                                goto out;
                        }
                        ref_event = strsep(&str, ".");
                        if (!str) {
                                ret = -EINVAL;
                                goto out;
                        }
                        ref_var = str;
                }
        }

        s = local_field_var_ref(hist_data, ref_system, ref_event, ref_var);
        if (!s) {
                hist_field = parse_var_ref(hist_data, ref_system,
                                           ref_event, ref_var);
                if (hist_field) {
                        if (var_name) {
                                hist_field = create_alias(hist_data, hist_field, var_name);
                                if (!hist_field) {
                                        ret = -ENOMEM;
                                        goto out;
                                }
                        }
                        return hist_field;
                }
        } else
                str = s;

        field = parse_field(hist_data, file, str, flags);
        if (IS_ERR(field)) {
                ret = PTR_ERR(field);
                goto out;
        }

        hist_field = create_hist_field(hist_data, field, *flags, var_name);
        if (!hist_field) {
                ret = -ENOMEM;
                goto out;
        }

        return hist_field;
 out:
        return ERR_PTR(ret);
}

static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
                                     struct trace_event_file *file,
                                     char *str, unsigned long flags,
                                     char *var_name, unsigned int level);

static struct hist_field *parse_unary(struct hist_trigger_data *hist_data,
                                      struct trace_event_file *file,
                                      char *str, unsigned long flags,
                                      char *var_name, unsigned int level)
{
        struct hist_field *operand1, *expr = NULL;
        unsigned long operand_flags;
        int ret = 0;
        char *s;

        /* we support only -(xxx) i.e. explicit parens required */

        if (level > 3) {
                hist_err(file->tr, HIST_ERR_TOO_MANY_SUBEXPR, errpos(str));
                ret = -EINVAL;
                goto free;
        }

        str++; /* skip leading '-' */

        s = strchr(str, '(');
        if (s)
                str++;
        else {
                ret = -EINVAL;
                goto free;
        }

        s = strrchr(str, ')');
        if (s)
                *s = '\0';
        else {
                ret = -EINVAL; /* no closing ')' */
                goto free;
        }

        flags |= HIST_FIELD_FL_EXPR;
        expr = create_hist_field(hist_data, NULL, flags, var_name);
        if (!expr) {
                ret = -ENOMEM;
                goto free;
        }

        operand_flags = 0;
        operand1 = parse_expr(hist_data, file, str, operand_flags, NULL, ++level);
        if (IS_ERR(operand1)) {
                ret = PTR_ERR(operand1);
                goto free;
        }

        expr->flags |= operand1->flags &
                (HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);
        expr->fn = hist_field_unary_minus;
        expr->operands[0] = operand1;
        expr->operator = FIELD_OP_UNARY_MINUS;
        expr->name = expr_str(expr, 0);
        expr->type = kstrdup(operand1->type, GFP_KERNEL);
        if (!expr->type) {
                ret = -ENOMEM;
                goto free;
        }

        return expr;
 free:
        destroy_hist_field(expr, 0);
        return ERR_PTR(ret);
}

static int check_expr_operands(struct trace_array *tr,
                               struct hist_field *operand1,
                               struct hist_field *operand2)
{
        unsigned long operand1_flags = operand1->flags;
        unsigned long operand2_flags = operand2->flags;

        if ((operand1_flags & HIST_FIELD_FL_VAR_REF) ||
            (operand1_flags & HIST_FIELD_FL_ALIAS)) {
                struct hist_field *var;

                var = find_var_field(operand1->var.hist_data, operand1->name);
                if (!var)
                        return -EINVAL;
                operand1_flags = var->flags;
        }

        if ((operand2_flags & HIST_FIELD_FL_VAR_REF) ||
            (operand2_flags & HIST_FIELD_FL_ALIAS)) {
                struct hist_field *var;

                var = find_var_field(operand2->var.hist_data, operand2->name);
                if (!var)
                        return -EINVAL;
                operand2_flags = var->flags;
        }

        if ((operand1_flags & HIST_FIELD_FL_TIMESTAMP_USECS) !=
            (operand2_flags & HIST_FIELD_FL_TIMESTAMP_USECS)) {
                hist_err(tr, HIST_ERR_TIMESTAMP_MISMATCH, 0);
                return -EINVAL;
        }

        return 0;
}

static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
                                     struct trace_event_file *file,
                                     char *str, unsigned long flags,
                                     char *var_name, unsigned int level)
{
        struct hist_field *operand1 = NULL, *operand2 = NULL, *expr = NULL;
        unsigned long operand_flags;
        int field_op, ret = -EINVAL;
        char *sep, *operand1_str;

        if (level > 3) {
                hist_err(file->tr, HIST_ERR_TOO_MANY_SUBEXPR, errpos(str));
                return ERR_PTR(-EINVAL);
        }

        field_op = contains_operator(str);

        if (field_op == FIELD_OP_NONE)
                return parse_atom(hist_data, file, str, &flags, var_name);

        if (field_op == FIELD_OP_UNARY_MINUS)
                return parse_unary(hist_data, file, str, flags, var_name, ++level);

        switch (field_op) {
        case FIELD_OP_MINUS:
                sep = "-";
                break;
        case FIELD_OP_PLUS:
                sep = "+";
                break;
        default:
                goto free;
        }

        operand1_str = strsep(&str, sep);
        if (!operand1_str || !str)
                goto free;

        operand_flags = 0;
        operand1 = parse_atom(hist_data, file, operand1_str,
                              &operand_flags, NULL);
        if (IS_ERR(operand1)) {
                ret = PTR_ERR(operand1);
                operand1 = NULL;
                goto free;
        }

        /* rest of string could be another expression e.g. b+c in a+b+c */
        operand_flags = 0;
        operand2 = parse_expr(hist_data, file, str, operand_flags, NULL, ++level);
        if (IS_ERR(operand2)) {
                ret = PTR_ERR(operand2);
                operand2 = NULL;
                goto free;
        }

        ret = check_expr_operands(file->tr, operand1, operand2);
        if (ret)
                goto free;

        flags |= HIST_FIELD_FL_EXPR;

        flags |= operand1->flags &
                (HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);

        expr = create_hist_field(hist_data, NULL, flags, var_name);
        if (!expr) {
                ret = -ENOMEM;
                goto free;
        }

        operand1->read_once = true;
        operand2->read_once = true;

        expr->operands[0] = operand1;
        expr->operands[1] = operand2;
        expr->operator = field_op;
        expr->name = expr_str(expr, 0);
        expr->type = kstrdup(operand1->type, GFP_KERNEL);
        if (!expr->type) {
                ret = -ENOMEM;
                goto free;
        }

        switch (field_op) {
        case FIELD_OP_MINUS:
                expr->fn = hist_field_minus;
                break;
        case FIELD_OP_PLUS:
                expr->fn = hist_field_plus;
                break;
        default:
                ret = -EINVAL;
                goto free;
        }

        return expr;
 free:
        destroy_hist_field(operand1, 0);
        destroy_hist_field(operand2, 0);
        destroy_hist_field(expr, 0);

        return ERR_PTR(ret);
}

static char *find_trigger_filter(struct hist_trigger_data *hist_data,
                                 struct trace_event_file *file)
{
        struct event_trigger_data *test;

        lockdep_assert_held(&event_mutex);

        list_for_each_entry(test, &file->triggers, list) {
                if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
                        if (test->private_data == hist_data)
                                return test->filter_str;
                }
        }

        return NULL;
}

static struct event_command trigger_hist_cmd;
static int event_hist_trigger_func(struct event_command *cmd_ops,
                                   struct trace_event_file *file,
                                   char *glob, char *cmd, char *param);

static bool compatible_keys(struct hist_trigger_data *target_hist_data,
                            struct hist_trigger_data *hist_data,
                            unsigned int n_keys)
{
        struct hist_field *target_hist_field, *hist_field;
        unsigned int n, i, j;

        if (hist_data->n_fields - hist_data->n_vals != n_keys)
                return false;

        i = hist_data->n_vals;
        j = target_hist_data->n_vals;

        for (n = 0; n < n_keys; n++) {
                hist_field = hist_data->fields[i + n];
                target_hist_field = target_hist_data->fields[j + n];

                if (strcmp(hist_field->type, target_hist_field->type) != 0)
                        return false;
                if (hist_field->size != target_hist_field->size)
                        return false;
                if (hist_field->is_signed != target_hist_field->is_signed)
                        return false;
        }

        return true;
}

static struct hist_trigger_data *
find_compatible_hist(struct hist_trigger_data *target_hist_data,
                     struct trace_event_file *file)
{
        struct hist_trigger_data *hist_data;
        struct event_trigger_data *test;
        unsigned int n_keys;

        lockdep_assert_held(&event_mutex);

        n_keys = target_hist_data->n_fields - target_hist_data->n_vals;

        list_for_each_entry(test, &file->triggers, list) {
                if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
                        hist_data = test->private_data;

                        if (compatible_keys(target_hist_data, hist_data, n_keys))
                                return hist_data;
                }
        }

        return NULL;
}

static struct trace_event_file *event_file(struct trace_array *tr,
                                           char *system, char *event_name)
{
        struct trace_event_file *file;

        file = __find_event_file(tr, system, event_name);
        if (!file)
                return ERR_PTR(-EINVAL);

        return file;
}

static struct hist_field *
find_synthetic_field_var(struct hist_trigger_data *target_hist_data,
                         char *system, char *event_name, char *field_name)
{
        struct hist_field *event_var;
        char *synthetic_name;

        synthetic_name = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
        if (!synthetic_name)
                return ERR_PTR(-ENOMEM);

        strcpy(synthetic_name, "synthetic_");
        strcat(synthetic_name, field_name);

        event_var = find_event_var(target_hist_data, system, event_name, synthetic_name);

        kfree(synthetic_name);

        return event_var;
}

/**
 * create_field_var_hist - Automatically create a histogram and var for a field
 * @target_hist_data: The target hist trigger
 * @subsys_name: Optional subsystem name
 * @event_name: Optional event name
 * @field_name: The name of the field (and the resulting variable)
 *
 * Hist trigger actions fetch data from variables, not directly from
 * events.  However, for convenience, users are allowed to directly
 * specify an event field in an action, which will be automatically
 * converted into a variable on their behalf.

 * If a user specifies a field on an event that isn't the event the
 * histogram currently being defined (the target event histogram), the
 * only way that can be accomplished is if a new hist trigger is
 * created and the field variable defined on that.
 *
 * This function creates a new histogram compatible with the target
 * event (meaning a histogram with the same key as the target
 * histogram), and creates a variable for the specified field, but
 * with 'synthetic_' prepended to the variable name in order to avoid
 * collision with normal field variables.
 *
 * Return: The variable created for the field.
 */
static struct hist_field *
create_field_var_hist(struct hist_trigger_data *target_hist_data,
                      char *subsys_name, char *event_name, char *field_name)
{
        struct trace_array *tr = target_hist_data->event_file->tr;
        struct hist_field *event_var = ERR_PTR(-EINVAL);
        struct hist_trigger_data *hist_data;
        unsigned int i, n, first = true;
        struct field_var_hist *var_hist;
        struct trace_event_file *file;
        struct hist_field *key_field;
        char *saved_filter;
        char *cmd;
        int ret;

        if (target_hist_data->n_field_var_hists >= SYNTH_FIELDS_MAX) {
                hist_err(tr, HIST_ERR_TOO_MANY_FIELD_VARS, errpos(field_name));
                return ERR_PTR(-EINVAL);
        }

        file = event_file(tr, subsys_name, event_name);

        if (IS_ERR(file)) {
                hist_err(tr, HIST_ERR_EVENT_FILE_NOT_FOUND, errpos(field_name));
                ret = PTR_ERR(file);
                return ERR_PTR(ret);
        }

        /*
         * Look for a histogram compatible with target.  We'll use the
         * found histogram specification to create a new matching
         * histogram with our variable on it.  target_hist_data is not
         * yet a registered histogram so we can't use that.
         */
        hist_data = find_compatible_hist(target_hist_data, file);
        if (!hist_data) {
                hist_err(tr, HIST_ERR_HIST_NOT_FOUND, errpos(field_name));
                return ERR_PTR(-EINVAL);
        }

        /* See if a synthetic field variable has already been created */
        event_var = find_synthetic_field_var(target_hist_data, subsys_name,
                                             event_name, field_name);
        if (!IS_ERR_OR_NULL(event_var))
                return event_var;

        var_hist = kzalloc(sizeof(*var_hist), GFP_KERNEL);
        if (!var_hist)
                return ERR_PTR(-ENOMEM);

        cmd = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
        if (!cmd) {
                kfree(var_hist);
                return ERR_PTR(-ENOMEM);
        }

        /* Use the same keys as the compatible histogram */
        strcat(cmd, "keys=");

        for_each_hist_key_field(i, hist_data) {
                key_field = hist_data->fields[i];
                if (!first)
                        strcat(cmd, ",");
                strcat(cmd, key_field->field->name);
                first = false;
        }

        /* Create the synthetic field variable specification */
        strcat(cmd, ":synthetic_");
        strcat(cmd, field_name);
        strcat(cmd, "=");
        strcat(cmd, field_name);

        /* Use the same filter as the compatible histogram */
        saved_filter = find_trigger_filter(hist_data, file);
        if (saved_filter) {
                strcat(cmd, " if ");
                strcat(cmd, saved_filter);
        }

        var_hist->cmd = kstrdup(cmd, GFP_KERNEL);
        if (!var_hist->cmd) {
                kfree(cmd);
                kfree(var_hist);
                return ERR_PTR(-ENOMEM);
        }

        /* Save the compatible histogram information */
        var_hist->hist_data = hist_data;

        /* Create the new histogram with our variable */
        ret = event_hist_trigger_func(&trigger_hist_cmd, file,
                                      "", "hist", cmd);
        if (ret) {
                kfree(cmd);
                kfree(var_hist->cmd);
                kfree(var_hist);
                hist_err(tr, HIST_ERR_HIST_CREATE_FAIL, errpos(field_name));
                return ERR_PTR(ret);
        }

        kfree(cmd);

        /* If we can't find the variable, something went wrong */
        event_var = find_synthetic_field_var(target_hist_data, subsys_name,
                                             event_name, field_name);
        if (IS_ERR_OR_NULL(event_var)) {
                kfree(var_hist->cmd);
                kfree(var_hist);
                hist_err(tr, HIST_ERR_SYNTH_VAR_NOT_FOUND, errpos(field_name));
                return ERR_PTR(-EINVAL);
        }

        n = target_hist_data->n_field_var_hists;
        target_hist_data->field_var_hists[n] = var_hist;
        target_hist_data->n_field_var_hists++;

        return event_var;
}

static struct hist_field *
find_target_event_var(struct hist_trigger_data *hist_data,
                      char *subsys_name, char *event_name, char *var_name)
{
        struct trace_event_file *file = hist_data->event_file;
        struct hist_field *hist_field = NULL;

        if (subsys_name) {
                struct trace_event_call *call;

                if (!event_name)
                        return NULL;

                call = file->event_call;

                if (strcmp(subsys_name, call->class->system) != 0)
                        return NULL;

                if (strcmp(event_name, trace_event_name(call)) != 0)
                        return NULL;
        }

        hist_field = find_var_field(hist_data, var_name);

        return hist_field;
}

static inline void __update_field_vars(struct tracing_map_elt *elt,
                                       struct ring_buffer_event *rbe,
                                       void *rec,
                                       struct field_var **field_vars,
                                       unsigned int n_field_vars,
                                       unsigned int field_var_str_start)
{
        struct hist_elt_data *elt_data = elt->private_data;
        unsigned int i, j, var_idx;
        u64 var_val;

        for (i = 0, j = field_var_str_start; i < n_field_vars; i++) {
                struct field_var *field_var = field_vars[i];
                struct hist_field *var = field_var->var;
                struct hist_field *val = field_var->val;

                var_val = val->fn(val, elt, rbe, rec);
                var_idx = var->var.idx;

                if (val->flags & HIST_FIELD_FL_STRING) {
                        char *str = elt_data->field_var_str[j++];
                        char *val_str = (char *)(uintptr_t)var_val;

                        strscpy(str, val_str, STR_VAR_LEN_MAX);
                        var_val = (u64)(uintptr_t)str;
                }
                tracing_map_set_var(elt, var_idx, var_val);
        }
}

static void update_field_vars(struct hist_trigger_data *hist_data,
                              struct tracing_map_elt *elt,
                              struct ring_buffer_event *rbe,
                              void *rec)
{
        __update_field_vars(elt, rbe, rec, hist_data->field_vars,
                            hist_data->n_field_vars, 0);
}

static void save_track_data_vars(struct hist_trigger_data *hist_data,
                                 struct tracing_map_elt *elt, void *rec,
                                 struct ring_buffer_event *rbe, void *key,
                                 struct action_data *data, u64 *var_ref_vals)
{
        __update_field_vars(elt, rbe, rec, hist_data->save_vars,
                            hist_data->n_save_vars, hist_data->n_field_var_str);
}

static struct hist_field *create_var(struct hist_trigger_data *hist_data,
                                     struct trace_event_file *file,
                                     char *name, int size, const char *type)
{
        struct hist_field *var;
        int idx;

        if (find_var(hist_data, file, name) && !hist_data->remove) {
                var = ERR_PTR(-EINVAL);
                goto out;
        }

        var = kzalloc(sizeof(struct hist_field), GFP_KERNEL);
        if (!var) {
                var = ERR_PTR(-ENOMEM);
                goto out;
        }

        idx = tracing_map_add_var(hist_data->map);
        if (idx < 0) {
                kfree(var);
                var = ERR_PTR(-EINVAL);
                goto out;
        }

        var->flags = HIST_FIELD_FL_VAR;
        var->var.idx = idx;
        var->var.hist_data = var->hist_data = hist_data;
        var->size = size;
        var->var.name = kstrdup(name, GFP_KERNEL);
        var->type = kstrdup(type, GFP_KERNEL);
        if (!var->var.name || !var->type) {
                kfree(var->var.name);
                kfree(var->type);
                kfree(var);
                var = ERR_PTR(-ENOMEM);
        }
 out:
        return var;
}

static struct field_var *create_field_var(struct hist_trigger_data *hist_data,
                                          struct trace_event_file *file,
                                          char *field_name)
{
        struct hist_field *val = NULL, *var = NULL;
        unsigned long flags = HIST_FIELD_FL_VAR;
        struct trace_array *tr = file->tr;
        struct field_var *field_var;
        int ret = 0;

        if (hist_data->n_field_vars >= SYNTH_FIELDS_MAX) {
                hist_err(tr, HIST_ERR_TOO_MANY_FIELD_VARS, errpos(field_name));
                ret = -EINVAL;
                goto err;
        }

        val = parse_atom(hist_data, file, field_name, &flags, NULL);
        if (IS_ERR(val)) {
                hist_err(tr, HIST_ERR_FIELD_VAR_PARSE_FAIL, errpos(field_name));
                ret = PTR_ERR(val);
                goto err;
        }

        var = create_var(hist_data, file, field_name, val->size, val->type);
        if (IS_ERR(var)) {
                hist_err(tr, HIST_ERR_VAR_CREATE_FIND_FAIL, errpos(field_name));
                kfree(val);
                ret = PTR_ERR(var);
                goto err;
        }

        field_var = kzalloc(sizeof(struct field_var), GFP_KERNEL);
        if (!field_var) {
                kfree(val);
                kfree(var);
                ret =  -ENOMEM;
                goto err;
        }

        field_var->var = var;
        field_var->val = val;
 out:
        return field_var;
 err:
        field_var = ERR_PTR(ret);
        goto out;
}

/**
 * create_target_field_var - Automatically create a variable for a field
 * @target_hist_data: The target hist trigger
 * @subsys_name: Optional subsystem name
 * @event_name: Optional event name
 * @var_name: The name of the field (and the resulting variable)
 *
 * Hist trigger actions fetch data from variables, not directly from
 * events.  However, for convenience, users are allowed to directly
 * specify an event field in an action, which will be automatically
 * converted into a variable on their behalf.

 * This function creates a field variable with the name var_name on
 * the hist trigger currently being defined on the target event.  If
 * subsys_name and event_name are specified, this function simply
 * verifies that they do in fact match the target event subsystem and
 * event name.
 *
 * Return: The variable created for the field.
 */
static struct field_var *
create_target_field_var(struct hist_trigger_data *target_hist_data,
                        char *subsys_name, char *event_name, char *var_name)
{
        struct trace_event_file *file = target_hist_data->event_file;

        if (subsys_name) {
                struct trace_event_call *call;

                if (!event_name)
                        return NULL;

                call = file->event_call;

                if (strcmp(subsys_name, call->class->system) != 0)
                        return NULL;

                if (strcmp(event_name, trace_event_name(call)) != 0)
                        return NULL;
        }

        return create_field_var(target_hist_data, file, var_name);
}

static bool check_track_val_max(u64 track_val, u64 var_val)
{
        if (var_val <= track_val)
                return false;

        return true;
}

static bool check_track_val_changed(u64 track_val, u64 var_val)
{
        if (var_val == track_val)
                return false;

        return true;
}

static u64 get_track_val(struct hist_trigger_data *hist_data,
                         struct tracing_map_elt *elt,
                         struct action_data *data)
{
        unsigned int track_var_idx = data->track_data.track_var->var.idx;
        u64 track_val;

        track_val = tracing_map_read_var(elt, track_var_idx);

        return track_val;
}

static void save_track_val(struct hist_trigger_data *hist_data,
                           struct tracing_map_elt *elt,
                           struct action_data *data, u64 var_val)
{
        unsigned int track_var_idx = data->track_data.track_var->var.idx;

        tracing_map_set_var(elt, track_var_idx, var_val);
}

static void save_track_data(struct hist_trigger_data *hist_data,
                            struct tracing_map_elt *elt, void *rec,
                            struct ring_buffer_event *rbe, void *key,
                            struct action_data *data, u64 *var_ref_vals)
{
        if (data->track_data.save_data)
                data->track_data.save_data(hist_data, elt, rec, rbe, key, data, var_ref_vals);
}

static bool check_track_val(struct tracing_map_elt *elt,
                            struct action_data *data,
                            u64 var_val)
{
        struct hist_trigger_data *hist_data;
        u64 track_val;

        hist_data = data->track_data.track_var->hist_data;
        track_val = get_track_val(hist_data, elt, data);

        return data->track_data.check_val(track_val, var_val);
}

#ifdef CONFIG_TRACER_SNAPSHOT
static bool cond_snapshot_update(struct trace_array *tr, void *cond_data)
{
        /* called with tr->max_lock held */
        struct track_data *track_data = tr->cond_snapshot->cond_data;
        struct hist_elt_data *elt_data, *track_elt_data;
        struct snapshot_context *context = cond_data;
        struct action_data *action;
        u64 track_val;

        if (!track_data)
                return false;

        action = track_data->action_data;

        track_val = get_track_val(track_data->hist_data, context->elt,
                                  track_data->action_data);

        if (!action->track_data.check_val(track_data->track_val, track_val))
                return false;

        track_data->track_val = track_val;
        memcpy(track_data->key, context->key, track_data->key_len);

        elt_data = context->elt->private_data;
        track_elt_data = track_data->elt.private_data;
        if (elt_data->comm)
                strncpy(track_elt_data->comm, elt_data->comm, TASK_COMM_LEN);

        track_data->updated = true;

        return true;
}

static void save_track_data_snapshot(struct hist_trigger_data *hist_data,
                                     struct tracing_map_elt *elt, void *rec,
                                     struct ring_buffer_event *rbe, void *key,
                                     struct action_data *data,
                                     u64 *var_ref_vals)
{
        struct trace_event_file *file = hist_data->event_file;
        struct snapshot_context context;

        context.elt = elt;
        context.key = key;

        tracing_snapshot_cond(file->tr, &context);
}

static void hist_trigger_print_key(struct seq_file *m,
                                   struct hist_trigger_data *hist_data,
                                   void *key,
                                   struct tracing_map_elt *elt);

static struct action_data *snapshot_action(struct hist_trigger_data *hist_data)
{
        unsigned int i;

        if (!hist_data->n_actions)
                return NULL;

        for (i = 0; i < hist_data->n_actions; i++) {
                struct action_data *data = hist_data->actions[i];

                if (data->action == ACTION_SNAPSHOT)
                        return data;
        }

        return NULL;
}

static void track_data_snapshot_print(struct seq_file *m,
                                      struct hist_trigger_data *hist_data)
{
        struct trace_event_file *file = hist_data->event_file;
        struct track_data *track_data;
        struct action_data *action;

        track_data = tracing_cond_snapshot_data(file->tr);
        if (!track_data)
                return;

        if (!track_data->updated)
                return;

        action = snapshot_action(hist_data);
        if (!action)
                return;

        seq_puts(m, "\nSnapshot taken (see tracing/snapshot).  Details:\n");
        seq_printf(m, "\ttriggering value { %s(%s) }: %10llu",
                   action->handler == HANDLER_ONMAX ? "onmax" : "onchange",
                   action->track_data.var_str, track_data->track_val);

        seq_puts(m, "\ttriggered by event with key: ");
        hist_trigger_print_key(m, hist_data, track_data->key, &track_data->elt);
        seq_putc(m, '\n');
}
#else
static bool cond_snapshot_update(struct trace_array *tr, void *cond_data)
{
        return false;
}
static void save_track_data_snapshot(struct hist_trigger_data *hist_data,
                                     struct tracing_map_elt *elt, void *rec,
                                     struct ring_buffer_event *rbe, void *key,
                                     struct action_data *data,
                                     u64 *var_ref_vals) {}
static void track_data_snapshot_print(struct seq_file *m,
                                      struct hist_trigger_data *hist_data) {}
#endif /* CONFIG_TRACER_SNAPSHOT */

static void track_data_print(struct seq_file *m,
                             struct hist_trigger_data *hist_data,
                             struct tracing_map_elt *elt,
                             struct action_data *data)
{
        u64 track_val = get_track_val(hist_data, elt, data);
        unsigned int i, save_var_idx;

        if (data->handler == HANDLER_ONMAX)
                seq_printf(m, "\n\tmax: %10llu", track_val);
        else if (data->handler == HANDLER_ONCHANGE)
                seq_printf(m, "\n\tchanged: %10llu", track_val);

        if (data->action == ACTION_SNAPSHOT)
                return;

        for (i = 0; i < hist_data->n_save_vars; i++) {
                struct hist_field *save_val = hist_data->save_vars[i]->val;
                struct hist_field *save_var = hist_data->save_vars[i]->var;
                u64 val;

                save_var_idx = save_var->var.idx;

                val = tracing_map_read_var(elt, save_var_idx);

                if (save_val->flags & HIST_FIELD_FL_STRING) {
                        seq_printf(m, "  %s: %-32s", save_var->var.name,
                                   (char *)(uintptr_t)(val));
                } else
                        seq_printf(m, "  %s: %10llu", save_var->var.name, val);
        }
}

static void ontrack_action(struct hist_trigger_data *hist_data,
                           struct tracing_map_elt *elt, void *rec,
                           struct ring_buffer_event *rbe, void *key,
                           struct action_data *data, u64 *var_ref_vals)
{
        u64 var_val = var_ref_vals[data->track_data.var_ref->var_ref_idx];

        if (check_track_val(elt, data, var_val)) {
                save_track_val(hist_data, elt, data, var_val);
                save_track_data(hist_data, elt, rec, rbe, key, data, var_ref_vals);
        }
}

static void action_data_destroy(struct action_data *data)
{
        unsigned int i;

        lockdep_assert_held(&event_mutex);

        kfree(data->action_name);

        for (i = 0; i < data->n_params; i++)
                kfree(data->params[i]);

        if (data->synth_event)
                data->synth_event->ref--;

        kfree(data->synth_event_name);

        kfree(data);
}

static void track_data_destroy(struct hist_trigger_data *hist_data,
                               struct action_data *data)
{
        struct trace_event_file *file = hist_data->event_file;

        destroy_hist_field(data->track_data.track_var, 0);

        if (data->action == ACTION_SNAPSHOT) {
                struct track_data *track_data;

                track_data = tracing_cond_snapshot_data(file->tr);
                if (track_data && track_data->hist_data == hist_data) {
                        tracing_snapshot_cond_disable(file->tr);
                        track_data_free(track_data);
                }
        }

        kfree(data->track_data.var_str);

        action_data_destroy(data);
}

static int action_create(struct hist_trigger_data *hist_data,
                         struct action_data *data);

static int track_data_create(struct hist_trigger_data *hist_data,
                             struct action_data *data)
{
        struct hist_field *var_field, *ref_field, *track_var = NULL;
        struct trace_event_file *file = hist_data->event_file;
        struct trace_array *tr = file->tr;
        char *track_data_var_str;
        int ret = 0;

        track_data_var_str = data->track_data.var_str;
        if (track_data_var_str[0] != '$') {
                hist_err(tr, HIST_ERR_ONX_NOT_VAR, errpos(track_data_var_str));
                return -EINVAL;
        }
        track_data_var_str++;

        var_field = find_target_event_var(hist_data, NULL, NULL, track_data_var_str);
        if (!var_field) {
                hist_err(tr, HIST_ERR_ONX_VAR_NOT_FOUND, errpos(track_data_var_str));
                return -EINVAL;
        }

        ref_field = create_var_ref(hist_data, var_field, NULL, NULL);
        if (!ref_field)
                return -ENOMEM;

        data->track_data.var_ref = ref_field;

        if (data->handler == HANDLER_ONMAX)
                track_var = create_var(hist_data, file, "__max", sizeof(u64), "u64");
        if (IS_ERR(track_var)) {
                hist_err(tr, HIST_ERR_ONX_VAR_CREATE_FAIL, 0);
                ret = PTR_ERR(track_var);
                goto out;
        }

        if (data->handler == HANDLER_ONCHANGE)
                track_var = create_var(hist_data, file, "__change", sizeof(u64), "u64");
        if (IS_ERR(track_var)) {
                hist_err(tr, HIST_ERR_ONX_VAR_CREATE_FAIL, 0);
                ret = PTR_ERR(track_var);
                goto out;
        }
        data->track_data.track_var = track_var;

        ret = action_create(hist_data, data);
 out:
        return ret;
}

static int parse_action_params(struct trace_array *tr, char *params,
                               struct action_data *data)
{
        char *param, *saved_param;
        bool first_param = true;
        int ret = 0;

        while (params) {
                if (data->n_params >= SYNTH_FIELDS_MAX) {
                        hist_err(tr, HIST_ERR_TOO_MANY_PARAMS, 0);
                        goto out;
                }

                param = strsep(&params, ",");
                if (!param) {
                        hist_err(tr, HIST_ERR_PARAM_NOT_FOUND, 0);
                        ret = -EINVAL;
                        goto out;
                }

                param = strstrip(param);
                if (strlen(param) < 2) {
                        hist_err(tr, HIST_ERR_INVALID_PARAM, errpos(param));
                        ret = -EINVAL;
                        goto out;
                }

                saved_param = kstrdup(param, GFP_KERNEL);
                if (!saved_param) {
                        ret = -ENOMEM;
                        goto out;
                }

                if (first_param && data->use_trace_keyword) {
                        data->synth_event_name = saved_param;
                        first_param = false;
                        continue;
                }
                first_param = false;

                data->params[data->n_params++] = saved_param;
        }
 out:
        return ret;
}

static int action_parse(struct trace_array *tr, char *str, struct action_data *data,
                        enum handler_id handler)
{
        char *action_name;
        int ret = 0;

        strsep(&str, ".");
        if (!str) {
                hist_err(tr, HIST_ERR_ACTION_NOT_FOUND, 0);
                ret = -EINVAL;
                goto out;
        }

        action_name = strsep(&str, "(");
        if (!action_name || !str) {
                hist_err(tr, HIST_ERR_ACTION_NOT_FOUND, 0);
                ret = -EINVAL;
                goto out;
        }

        if (str_has_prefix(action_name, "save")) {
                char *params = strsep(&str, ")");

                if (!params) {
                        hist_err(tr, HIST_ERR_NO_SAVE_PARAMS, 0);
                        ret = -EINVAL;
                        goto out;
                }

                ret = parse_action_params(tr, params, data);
                if (ret)
                        goto out;

                if (handler == HANDLER_ONMAX)
                        data->track_data.check_val = check_track_val_max;
                else if (handler == HANDLER_ONCHANGE)
                        data->track_data.check_val = check_track_val_changed;
                else {
                        hist_err(tr, HIST_ERR_ACTION_MISMATCH, errpos(action_name));
                        ret = -EINVAL;
                        goto out;
                }

                data->track_data.save_data = save_track_data_vars;
                data->fn = ontrack_action;
                data->action = ACTION_SAVE;
        } else if (str_has_prefix(action_name, "snapshot")) {
                char *params = strsep(&str, ")");

                if (!str) {
                        hist_err(tr, HIST_ERR_NO_CLOSING_PAREN, errpos(params));
                        ret = -EINVAL;
                        goto out;
                }

                if (handler == HANDLER_ONMAX)
                        data->track_data.check_val = check_track_val_max;
                else if (handler == HANDLER_ONCHANGE)
                        data->track_data.check_val = check_track_val_changed;
                else {
                        hist_err(tr, HIST_ERR_ACTION_MISMATCH, errpos(action_name));
                        ret = -EINVAL;
                        goto out;
                }

                data->track_data.save_data = save_track_data_snapshot;
                data->fn = ontrack_action;
                data->action = ACTION_SNAPSHOT;
        } else {
                char *params = strsep(&str, ")");

                if (str_has_prefix(action_name, "trace"))
                        data->use_trace_keyword = true;

                if (params) {
                        ret = parse_action_params(tr, params, data);
                        if (ret)
                                goto out;
                }

                if (handler == HANDLER_ONMAX)
                        data->track_data.check_val = check_track_val_max;
                else if (handler == HANDLER_ONCHANGE)
                        data->track_data.check_val = check_track_val_changed;

                if (handler != HANDLER_ONMATCH) {
                        data->track_data.save_data = action_trace;
                        data->fn = ontrack_action;
                } else
                        data->fn = action_trace;

                data->action = ACTION_TRACE;
        }

        data->action_name = kstrdup(action_name, GFP_KERNEL);
        if (!data->action_name) {
                ret = -ENOMEM;
                goto out;
        }

        data->handler = handler;
 out:
        return ret;
}

static struct action_data *track_data_parse(struct hist_trigger_data *hist_data,
                                            char *str, enum handler_id handler)
{
        struct action_data *data;
        int ret = -EINVAL;
        char *var_str;

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (!data)
                return ERR_PTR(-ENOMEM);

        var_str = strsep(&str, ")");
        if (!var_str || !str) {
                ret = -EINVAL;
                goto free;
        }

        data->track_data.var_str = kstrdup(var_str, GFP_KERNEL);
        if (!data->track_data.var_str) {
                ret = -ENOMEM;
                goto free;
        }

        ret = action_parse(hist_data->event_file->tr, str, data, handler);
        if (ret)
                goto free;
 out:
        return data;
 free:
        track_data_destroy(hist_data, data);
        data = ERR_PTR(ret);
        goto out;
}

static void onmatch_destroy(struct action_data *data)
{
        kfree(data->match_data.event);
        kfree(data->match_data.event_system);

        action_data_destroy(data);
}

static void destroy_field_var(struct field_var *field_var)
{
        if (!field_var)
                return;

        destroy_hist_field(field_var->var, 0);
        destroy_hist_field(field_var->val, 0);

        kfree(field_var);
}

static void destroy_field_vars(struct hist_trigger_data *hist_data)
{
        unsigned int i;

        for (i = 0; i < hist_data->n_field_vars; i++)
                destroy_field_var(hist_data->field_vars[i]);
}

static void save_field_var(struct hist_trigger_data *hist_data,
                           struct field_var *field_var)
{
        hist_data->field_vars[hist_data->n_field_vars++] = field_var;

        if (field_var->val->flags & HIST_FIELD_FL_STRING)
                hist_data->n_field_var_str++;
}


static int check_synth_field(struct synth_event *event,
                             struct hist_field *hist_field,
                             unsigned int field_pos)
{
        struct synth_field *field;

        if (field_pos >= event->n_fields)
                return -EINVAL;

        field = event->fields[field_pos];

        if (strcmp(field->type, hist_field->type) != 0) {
                if (field->size != hist_field->size ||
                    field->is_signed != hist_field->is_signed)
                        return -EINVAL;
        }

        return 0;
}

static struct hist_field *
trace_action_find_var(struct hist_trigger_data *hist_data,
                      struct action_data *data,
                      char *system, char *event, char *var)
{
        struct trace_array *tr = hist_data->event_file->tr;
        struct hist_field *hist_field;

        var++; /* skip '$' */

        hist_field = find_target_event_var(hist_data, system, event, var);
        if (!hist_field) {
                if (!system && data->handler == HANDLER_ONMATCH) {
                        system = data->match_data.event_system;
                        event = data->match_data.event;
                }

                hist_field = find_event_var(hist_data, system, event, var);
        }

        if (!hist_field)
                hist_err(tr, HIST_ERR_PARAM_NOT_FOUND, errpos(var));

        return hist_field;
}

static struct hist_field *
trace_action_create_field_var(struct hist_trigger_data *hist_data,
                              struct action_data *data, char *system,
                              char *event, char *var)
{
        struct hist_field *hist_field = NULL;
        struct field_var *field_var;

        /*
         * First try to create a field var on the target event (the
         * currently being defined).  This will create a variable for
         * unqualified fields on the target event, or if qualified,
         * target fields that have qualified names matching the target.
         */
        field_var = create_target_field_var(hist_data, system, event, var);

        if (field_var && !IS_ERR(field_var)) {
                save_field_var(hist_data, field_var);
                hist_field = field_var->var;
        } else {
                field_var = NULL;
                /*
                 * If no explicit system.event is specfied, default to
                 * looking for fields on the onmatch(system.event.xxx)
                 * event.
                 */
                if (!system && data->handler == HANDLER_ONMATCH) {
                        system = data->match_data.event_system;
                        event = data->match_data.event;
                }

                /*
                 * At this point, we're looking at a field on another
                 * event.  Because we can't modify a hist trigger on
                 * another event to add a variable for a field, we need
                 * to create a new trigger on that event and create the
                 * variable at the same time.
                 */
                hist_field = create_field_var_hist(hist_data, system, event, var);
                if (IS_ERR(hist_field))
                        goto free;
        }
 out:
        return hist_field;
 free:
        destroy_field_var(field_var);
        hist_field = NULL;
        goto out;
}

static int trace_action_create(struct hist_trigger_data *hist_data,
                               struct action_data *data)
{
        struct trace_array *tr = hist_data->event_file->tr;
        char *event_name, *param, *system = NULL;
        struct hist_field *hist_field, *var_ref;
        unsigned int i;
        unsigned int field_pos = 0;
        struct synth_event *event;
        char *synth_event_name;
        int var_ref_idx, ret = 0;

        lockdep_assert_held(&event_mutex);

        if (data->use_trace_keyword)
                synth_event_name = data->synth_event_name;
        else
                synth_event_name = data->action_name;

        event = find_synth_event(synth_event_name);
        if (!event) {
                hist_err(tr, HIST_ERR_SYNTH_EVENT_NOT_FOUND, errpos(synth_event_name));
                return -EINVAL;
        }

        event->ref++;

        for (i = 0; i < data->n_params; i++) {
                char *p;

                p = param = kstrdup(data->params[i], GFP_KERNEL);
                if (!param) {
                        ret = -ENOMEM;
                        goto err;
                }

                system = strsep(&param, ".");
                if (!param) {
                        param = (char *)system;
                        system = event_name = NULL;
                } else {
                        event_name = strsep(&param, ".");
                        if (!param) {
                                kfree(p);
                                ret = -EINVAL;
                                goto err;
                        }
                }

                if (param[0] == '$')
                        hist_field = trace_action_find_var(hist_data, data,
                                                           system, event_name,
                                                           param);
                else
                        hist_field = trace_action_create_field_var(hist_data,
                                                                   data,
                                                                   system,
                                                                   event_name,
                                                                   param);

                if (!hist_field) {
                        kfree(p);
                        ret = -EINVAL;
                        goto err;
                }

                if (check_synth_field(event, hist_field, field_pos) == 0) {
                        var_ref = create_var_ref(hist_data, hist_field,
                                                 system, event_name);
                        if (!var_ref) {
                                kfree(p);
                                ret = -ENOMEM;
                                goto err;
                        }

                        var_ref_idx = find_var_ref_idx(hist_data, var_ref);
                        if (WARN_ON(var_ref_idx < 0)) {
                                ret = var_ref_idx;
                                goto err;
                        }

                        data->var_ref_idx[i] = var_ref_idx;

                        field_pos++;
                        kfree(p);
                        continue;
                }

                hist_err(tr, HIST_ERR_SYNTH_TYPE_MISMATCH, errpos(param));
                kfree(p);
                ret = -EINVAL;
                goto err;
        }

        if (field_pos != event->n_fields) {
                hist_err(tr, HIST_ERR_SYNTH_COUNT_MISMATCH, errpos(event->name));
                ret = -EINVAL;
                goto err;
        }

        data->synth_event = event;
 out:
        return ret;
 err:
        event->ref--;

        goto out;
}

static int action_create(struct hist_trigger_data *hist_data,
                         struct action_data *data)
{
        struct trace_event_file *file = hist_data->event_file;
        struct trace_array *tr = file->tr;
        struct track_data *track_data;
        struct field_var *field_var;
        unsigned int i;
        char *param;
        int ret = 0;

        if (data->action == ACTION_TRACE)
                return trace_action_create(hist_data, data);

        if (data->action == ACTION_SNAPSHOT) {
                track_data = track_data_alloc(hist_data->key_size, data, hist_data);
                if (IS_ERR(track_data)) {
                        ret = PTR_ERR(track_data);
                        goto out;
                }

                ret = tracing_snapshot_cond_enable(file->tr, track_data,
                                                   cond_snapshot_update);
                if (ret)
                        track_data_free(track_data);

                goto out;
        }

        if (data->action == ACTION_SAVE) {
                if (hist_data->n_save_vars) {
                        ret = -EEXIST;
                        hist_err(tr, HIST_ERR_TOO_MANY_SAVE_ACTIONS, 0);
                        goto out;
                }

                for (i = 0; i < data->n_params; i++) {
                        param = kstrdup(data->params[i], GFP_KERNEL);
                        if (!param) {
                                ret = -ENOMEM;
                                goto out;
                        }

                        field_var = create_target_field_var(hist_data, NULL, NULL, param);
                        if (IS_ERR(field_var)) {
                                hist_err(tr, HIST_ERR_FIELD_VAR_CREATE_FAIL,
                                         errpos(param));
                                ret = PTR_ERR(field_var);
                                kfree(param);
                                goto out;
                        }

                        hist_data->save_vars[hist_data->n_save_vars++] = field_var;
                        if (field_var->val->flags & HIST_FIELD_FL_STRING)
                                hist_data->n_save_var_str++;
                        kfree(param);
                }
        }
 out:
        return ret;
}

static int onmatch_create(struct hist_trigger_data *hist_data,
                          struct action_data *data)
{
        return action_create(hist_data, data);
}

static struct action_data *onmatch_parse(struct trace_array *tr, char *str)
{
        char *match_event, *match_event_system;
        struct action_data *data;
        int ret = -EINVAL;

        data = kzalloc(sizeof(*data), GFP_KERNEL);
        if (!data)
                return ERR_PTR(-ENOMEM);

        match_event = strsep(&str, ")");
        if (!match_event || !str) {
                hist_err(tr, HIST_ERR_NO_CLOSING_PAREN, errpos(match_event));
                goto free;
        }

        match_event_system = strsep(&match_event, ".");
        if (!match_event) {
                hist_err(tr, HIST_ERR_SUBSYS_NOT_FOUND, errpos(match_event_system));
                goto free;
        }

        if (IS_ERR(event_file(tr, match_event_system, match_event))) {
                hist_err(tr, HIST_ERR_INVALID_SUBSYS_EVENT, errpos(match_event));
                goto free;
        }

        data->match_data.event = kstrdup(match_event, GFP_KERNEL);
        if (!data->match_data.event) {
                ret = -ENOMEM;
                goto free;
        }

        data->match_data.event_system = kstrdup(match_event_system, GFP_KERNEL);
        if (!data->match_data.event_system) {
                ret = -ENOMEM;
                goto free;
        }

        ret = action_parse(tr, str, data, HANDLER_ONMATCH);
        if (ret)
                goto free;
 out:
        return data;
 free:
        onmatch_destroy(data);
        data = ERR_PTR(ret);
        goto out;
}

static int create_hitcount_val(struct hist_trigger_data *hist_data)
{
        hist_data->fields[HITCOUNT_IDX] =
                create_hist_field(hist_data, NULL, HIST_FIELD_FL_HITCOUNT, NULL);
        if (!hist_data->fields[HITCOUNT_IDX])
                return -ENOMEM;

        hist_data->n_vals++;
        hist_data->n_fields++;

        if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX))
                return -EINVAL;

        return 0;
}

static int __create_val_field(struct hist_trigger_data *hist_data,
                              unsigned int val_idx,
                              struct trace_event_file *file,
                              char *var_name, char *field_str,
                              unsigned long flags)
{
        struct hist_field *hist_field;
        int ret = 0;

        hist_field = parse_expr(hist_data, file, field_str, flags, var_name, 0);
        if (IS_ERR(hist_field)) {
                ret = PTR_ERR(hist_field);
                goto out;
        }

        hist_data->fields[val_idx] = hist_field;

        ++hist_data->n_vals;
        ++hist_data->n_fields;

        if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX + TRACING_MAP_VARS_MAX))
                ret = -EINVAL;
 out:
        return ret;
}

static int create_val_field(struct hist_trigger_data *hist_data,
                            unsigned int val_idx,
                            struct trace_event_file *file,
                            char *field_str)
{
        if (WARN_ON(val_idx >= TRACING_MAP_VALS_MAX))
                return -EINVAL;

        return __create_val_field(hist_data, val_idx, file, NULL, field_str, 0);
}

static int create_var_field(struct hist_trigger_data *hist_data,
                            unsigned int val_idx,
                            struct trace_event_file *file,
                            char *var_name, char *expr_str)
{
        struct trace_array *tr = hist_data->event_file->tr;
        unsigned long flags = 0;

        if (WARN_ON(val_idx >= TRACING_MAP_VALS_MAX + TRACING_MAP_VARS_MAX))
                return -EINVAL;

        if (find_var(hist_data, file, var_name) && !hist_data->remove) {
                hist_err(tr, HIST_ERR_DUPLICATE_VAR, errpos(var_name));
                return -EINVAL;
        }

        flags |= HIST_FIELD_FL_VAR;
        hist_data->n_vars++;
        if (WARN_ON(hist_data->n_vars > TRACING_MAP_VARS_MAX))
                return -EINVAL;

        return __create_val_field(hist_data, val_idx, file, var_name, expr_str, flags);
}

static int create_val_fields(struct hist_trigger_data *hist_data,
                             struct trace_event_file *file)
{
        char *fields_str, *field_str;
        unsigned int i, j = 1;
        int ret;

        ret = create_hitcount_val(hist_data);
        if (ret)
                goto out;

        fields_str = hist_data->attrs->vals_str;
        if (!fields_str)
                goto out;

        for (i = 0, j = 1; i < TRACING_MAP_VALS_MAX &&
                     j < TRACING_MAP_VALS_MAX; i++) {
                field_str = strsep(&fields_str, ",");
                if (!field_str)
                        break;

                if (strcmp(field_str, "hitcount") == 0)
                        continue;

                ret = create_val_field(hist_data, j++, file, field_str);
                if (ret)
                        goto out;
        }

        if (fields_str && (strcmp(fields_str, "hitcount") != 0))
                ret = -EINVAL;
 out:
        return ret;
}

static int create_key_field(struct hist_trigger_data *hist_data,
                            unsigned int key_idx,
                            unsigned int key_offset,
                            struct trace_event_file *file,
                            char *field_str)
{
        struct trace_array *tr = hist_data->event_file->tr;
        struct hist_field *hist_field = NULL;
        unsigned long flags = 0;
        unsigned int key_size;
        int ret = 0;

        if (WARN_ON(key_idx >= HIST_FIELDS_MAX))
                return -EINVAL;

        flags |= HIST_FIELD_FL_KEY;

        if (strcmp(field_str, "stacktrace") == 0) {
                flags |= HIST_FIELD_FL_STACKTRACE;
                key_size = sizeof(unsigned long) * HIST_STACKTRACE_DEPTH;
                hist_field = create_hist_field(hist_data, NULL, flags, NULL);
        } else {
                hist_field = parse_expr(hist_data, file, field_str, flags,
                                        NULL, 0);
                if (IS_ERR(hist_field)) {
                        ret = PTR_ERR(hist_field);
                        goto out;
                }

                if (field_has_hist_vars(hist_field, 0)) {
                        hist_err(tr, HIST_ERR_INVALID_REF_KEY, errpos(field_str));
                        destroy_hist_field(hist_field, 0);
                        ret = -EINVAL;
                        goto out;
                }

                key_size = hist_field->size;
        }

        hist_data->fields[key_idx] = hist_field;

        key_size = ALIGN(key_size, sizeof(u64));
        hist_data->fields[key_idx]->size = key_size;
        hist_data->fields[key_idx]->offset = key_offset;

        hist_data->key_size += key_size;

        if (hist_data->key_size > HIST_KEY_SIZE_MAX) {
                ret = -EINVAL;
                goto out;
        }

        hist_data->n_keys++;
        hist_data->n_fields++;

        if (WARN_ON(hist_data->n_keys > TRACING_MAP_KEYS_MAX))
                return -EINVAL;

        ret = key_size;
 out:
        return ret;
}

static int create_key_fields(struct hist_trigger_data *hist_data,
                             struct trace_event_file *file)
{
        unsigned int i, key_offset = 0, n_vals = hist_data->n_vals;
        char *fields_str, *field_str;
        int ret = -EINVAL;

        fields_str = hist_data->attrs->keys_str;
        if (!fields_str)
                goto out;

        for (i = n_vals; i < n_vals + TRACING_MAP_KEYS_MAX; i++) {
                field_str = strsep(&fields_str, ",");
                if (!field_str)
                        break;
                ret = create_key_field(hist_data, i, key_offset,
                                       file, field_str);
                if (ret < 0)
                        goto out;
                key_offset += ret;
        }
        if (fields_str) {
                ret = -EINVAL;
                goto out;
        }
        ret = 0;
 out:
        return ret;
}

static int create_var_fields(struct hist_trigger_data *hist_data,
                             struct trace_event_file *file)
{
        unsigned int i, j = hist_data->n_vals;
        int ret = 0;

        unsigned int n_vars = hist_data->attrs->var_defs.n_vars;

        for (i = 0; i < n_vars; i++) {
                char *var_name = hist_data->attrs->var_defs.name[i];
                char *expr = hist_data->attrs->var_defs.expr[i];

                ret = create_var_field(hist_data, j++, file, var_name, expr);
                if (ret)
                        goto out;
        }
 out:
        return ret;
}

static void free_var_defs(struct hist_trigger_data *hist_data)
{
        unsigned int i;

        for (i = 0; i < hist_data->attrs->var_defs.n_vars; i++) {
                kfree(hist_data->attrs->var_defs.name[i]);
                kfree(hist_data->attrs->var_defs.expr[i]);
        }

        hist_data->attrs->var_defs.n_vars = 0;
}

static int parse_var_defs(struct hist_trigger_data *hist_data)
{
        struct trace_array *tr = hist_data->event_file->tr;
        char *s, *str, *var_name, *field_str;
        unsigned int i, j, n_vars = 0;
        int ret = 0;

        for (i = 0; i < hist_data->attrs->n_assignments; i++) {
                str = hist_data->attrs->assignment_str[i];
                for (j = 0; j < TRACING_MAP_VARS_MAX; j++) {
                        field_str = strsep(&str, ",");
                        if (!field_str)
                                break;

                        var_name = strsep(&field_str, "=");
                        if (!var_name || !field_str) {
                                hist_err(tr, HIST_ERR_MALFORMED_ASSIGNMENT,
                                         errpos(var_name));
                                ret = -EINVAL;
                                goto free;
                        }

                        if (n_vars == TRACING_MAP_VARS_MAX) {
                                hist_err(tr, HIST_ERR_TOO_MANY_VARS, errpos(var_name));
                                ret = -EINVAL;
                                goto free;
                        }

                        s = kstrdup(var_name, GFP_KERNEL);
                        if (!s) {
                                ret = -ENOMEM;
                                goto free;
                        }
                        hist_data->attrs->var_defs.name[n_vars] = s;

                        s = kstrdup(field_str, GFP_KERNEL);
                        if (!s) {
                                kfree(hist_data->attrs->var_defs.name[n_vars]);
                                ret = -ENOMEM;
                                goto free;
                        }
                        hist_data->attrs->var_defs.expr[n_vars++] = s;

                        hist_data->attrs->var_defs.n_vars = n_vars;
                }
        }

        return ret;
 free:
        free_var_defs(hist_data);

        return ret;
}

static int create_hist_fields(struct hist_trigger_data *hist_data,
                              struct trace_event_file *file)
{
        int ret;

        ret = parse_var_defs(hist_data);
        if (ret)
                goto out;

        ret = create_val_fields(hist_data, file);
        if (ret)
                goto out;

        ret = create_var_fields(hist_data, file);
        if (ret)
                goto out;

        ret = create_key_fields(hist_data, file);
        if (ret)
                goto out;
 out:
        free_var_defs(hist_data);

        return ret;
}

static int is_descending(struct trace_array *tr, const char *str)
{
        if (!str)
                return 0;

        if (strcmp(str, "descending") == 0)
                return 1;

        if (strcmp(str, "ascending") == 0)
                return 0;

        hist_err(tr, HIST_ERR_INVALID_SORT_MODIFIER, errpos((char *)str));

        return -EINVAL;
}

static int create_sort_keys(struct hist_trigger_data *hist_data)
{
        struct trace_array *tr = hist_data->event_file->tr;
        char *fields_str = hist_data->attrs->sort_key_str;
        struct tracing_map_sort_key *sort_key;
        int descending, ret = 0;
        unsigned int i, j, k;

        hist_data->n_sort_keys = 1; /* we always have at least one, hitcount */

        if (!fields_str)
                goto out;

        for (i = 0; i < TRACING_MAP_SORT_KEYS_MAX; i++) {
                struct hist_field *hist_field;
                char *field_str, *field_name;
                const char *test_name;

                sort_key = &hist_data->sort_keys[i];

                field_str = strsep(&fields_str, ",");
                if (!field_str)
                        break;

                if (!*field_str) {
                        ret = -EINVAL;
                        hist_err(tr, HIST_ERR_EMPTY_SORT_FIELD, errpos("sort="));
                        break;
                }

                if ((i == TRACING_MAP_SORT_KEYS_MAX - 1) && fields_str) {
                        hist_err(tr, HIST_ERR_TOO_MANY_SORT_FIELDS, errpos("sort="));
                        ret = -EINVAL;
                        break;
                }

                field_name = strsep(&field_str, ".");
                if (!field_name || !*field_name) {
                        ret = -EINVAL;
                        hist_err(tr, HIST_ERR_EMPTY_SORT_FIELD, errpos("sort="));
                        break;
                }

                if (strcmp(field_name, "hitcount") == 0) {
                        descending = is_descending(tr, field_str);
                        if (descending < 0) {
                                ret = descending;
                                break;
                        }
                        sort_key->descending = descending;
                        continue;
                }

                for (j = 1, k = 1; j < hist_data->n_fields; j++) {
                        unsigned int idx;

                        hist_field = hist_data->fields[j];
                        if (hist_field->flags & HIST_FIELD_FL_VAR)
                                continue;

                        idx = k++;

                        test_name = hist_field_name(hist_field, 0);

                        if (strcmp(field_name, test_name) == 0) {
                                sort_key->field_idx = idx;
                                descending = is_descending(tr, field_str);
                                if (descending < 0) {
                                        ret = descending;
                                        goto out;
                                }
                                sort_key->descending = descending;
                                break;
                        }
                }
                if (j == hist_data->n_fields) {
                        ret = -EINVAL;
                        hist_err(tr, HIST_ERR_INVALID_SORT_FIELD, errpos(field_name));
                        break;
                }
        }

        hist_data->n_sort_keys = i;
 out:
        return ret;
}

static void destroy_actions(struct hist_trigger_data *hist_data)
{
        unsigned int i;

        for (i = 0; i < hist_data->n_actions; i++) {
                struct action_data *data = hist_data->actions[i];

                if (data->handler == HANDLER_ONMATCH)
                        onmatch_destroy(data);
                else if (data->handler == HANDLER_ONMAX ||
                         data->handler == HANDLER_ONCHANGE)
                        track_data_destroy(hist_data, data);
                else
                        kfree(data);
        }
}

static int parse_actions(struct hist_trigger_data *hist_data)
{
        struct trace_array *tr = hist_data->event_file->tr;
        struct action_data *data;
        unsigned int i;
        int ret = 0;
        char *str;
        int len;

        for (i = 0; i < hist_data->attrs->n_actions; i++) {
                str = hist_data->attrs->action_str[i];

                if ((len = str_has_prefix(str, "onmatch("))) {
                        char *action_str = str + len;

                        data = onmatch_parse(tr, action_str);
                        if (IS_ERR(data)) {
                                ret = PTR_ERR(data);
                                break;
                        }
                } else if ((len = str_has_prefix(str, "onmax("))) {
                        char *action_str = str + len;

                        data = track_data_parse(hist_data, action_str,
                                                HANDLER_ONMAX);
                        if (IS_ERR(data)) {
                                ret = PTR_ERR(data);
                                break;
                        }
                } else if ((len = str_has_prefix(str, "onchange("))) {
                        char *action_str = str + len;

                        data = track_data_parse(hist_data, action_str,
                                                HANDLER_ONCHANGE);
                        if (IS_ERR(data)) {
                                ret = PTR_ERR(data);
                                break;
                        }
                } else {
                        ret = -EINVAL;
                        break;
                }

                hist_data->actions[hist_data->n_actions++] = data;
        }

        return ret;
}

static int create_actions(struct hist_trigger_data *hist_data)
{
        struct action_data *data;
        unsigned int i;
        int ret = 0;

        for (i = 0; i < hist_data->attrs->n_actions; i++) {
                data = hist_data->actions[i];

                if (data->handler == HANDLER_ONMATCH) {
                        ret = onmatch_create(hist_data, data);
                        if (ret)
                                break;
                } else if (data->handler == HANDLER_ONMAX ||
                           data->handler == HANDLER_ONCHANGE) {
                        ret = track_data_create(hist_data, data);
                        if (ret)
                                break;
                } else {
                        ret = -EINVAL;
                        break;
                }
        }

        return ret;
}

static void print_actions(struct seq_file *m,
                          struct hist_trigger_data *hist_data,
                          struct tracing_map_elt *elt)
{
        unsigned int i;

        for (i = 0; i < hist_data->n_actions; i++) {
                struct action_data *data = hist_data->actions[i];

                if (data->action == ACTION_SNAPSHOT)
                        continue;

                if (data->handler == HANDLER_ONMAX ||
                    data->handler == HANDLER_ONCHANGE)
                        track_data_print(m, hist_data, elt, data);
        }
}

static void print_action_spec(struct seq_file *m,
                              struct hist_trigger_data *hist_data,
                              struct action_data *data)
{
        unsigned int i;

        if (data->action == ACTION_SAVE) {
                for (i = 0; i < hist_data->n_save_vars; i++) {
                        seq_printf(m, "%s", hist_data->save_vars[i]->var->var.name);
                        if (i < hist_data->n_save_vars - 1)
                                seq_puts(m, ",");
                }
        } else if (data->action == ACTION_TRACE) {
                if (data->use_trace_keyword)
                        seq_printf(m, "%s", data->synth_event_name);
                for (i = 0; i < data->n_params; i++) {
                        if (i || data->use_trace_keyword)
                                seq_puts(m, ",");
                        seq_printf(m, "%s", data->params[i]);
                }
        }
}

static void print_track_data_spec(struct seq_file *m,
                                  struct hist_trigger_data *hist_data,
                                  struct action_data *data)
{
        if (data->handler == HANDLER_ONMAX)
                seq_puts(m, ":onmax(");
        else if (data->handler == HANDLER_ONCHANGE)
                seq_puts(m, ":onchange(");
        seq_printf(m, "%s", data->track_data.var_str);
        seq_printf(m, ").%s(", data->action_name);

        print_action_spec(m, hist_data, data);

        seq_puts(m, ")");
}

static void print_onmatch_spec(struct seq_file *m,
                               struct hist_trigger_data *hist_data,
                               struct action_data *data)
{
        seq_printf(m, ":onmatch(%s.%s).", data->match_data.event_system,
                   data->match_data.event);

        seq_printf(m, "%s(", data->action_name);

        print_action_spec(m, hist_data, data);

        seq_puts(m, ")");
}

static bool actions_match(struct hist_trigger_data *hist_data,
                          struct hist_trigger_data *hist_data_test)
{
        unsigned int i, j;

        if (hist_data->n_actions != hist_data_test->n_actions)
                return false;

        for (i = 0; i < hist_data->n_actions; i++) {
                struct action_data *data = hist_data->actions[i];
                struct action_data *data_test = hist_data_test->actions[i];
                char *action_name, *action_name_test;

                if (data->handler != data_test->handler)
                        return false;
                if (data->action != data_test->action)
                        return false;

                if (data->n_params != data_test->n_params)
                        return false;

                for (j = 0; j < data->n_params; j++) {
                        if (strcmp(data->params[j], data_test->params[j]) != 0)
                                return false;
                }

                if (data->use_trace_keyword)
                        action_name = data->synth_event_name;
                else
                        action_name = data->action_name;

                if (data_test->use_trace_keyword)
                        action_name_test = data_test->synth_event_name;
                else
                        action_name_test = data_test->action_name;

                if (strcmp(action_name, action_name_test) != 0)
                        return false;

                if (data->handler == HANDLER_ONMATCH) {
                        if (strcmp(data->match_data.event_system,
                                   data_test->match_data.event_system) != 0)
                                return false;
                        if (strcmp(data->match_data.event,
                                   data_test->match_data.event) != 0)
                                return false;
                } else if (data->handler == HANDLER_ONMAX ||
                           data->handler == HANDLER_ONCHANGE) {
                        if (strcmp(data->track_data.var_str,
                                   data_test->track_data.var_str) != 0)
                                return false;
                }
        }

        return true;
}


static void print_actions_spec(struct seq_file *m,
                               struct hist_trigger_data *hist_data)
{
        unsigned int i;

        for (i = 0; i < hist_data->n_actions; i++) {
                struct action_data *data = hist_data->actions[i];

                if (data->handler == HANDLER_ONMATCH)
                        print_onmatch_spec(m, hist_data, data);
                else if (data->handler == HANDLER_ONMAX ||
                         data->handler == HANDLER_ONCHANGE)
                        print_track_data_spec(m, hist_data, data);
        }
}

static void destroy_field_var_hists(struct hist_trigger_data *hist_data)
{
        unsigned int i;

        for (i = 0; i < hist_data->n_field_var_hists; i++) {
                kfree(hist_data->field_var_hists[i]->cmd);
                kfree(hist_data->field_var_hists[i]);
        }
}

static void destroy_hist_data(struct hist_trigger_data *hist_data)
{
        if (!hist_data)
                return;

        destroy_hist_trigger_attrs(hist_data->attrs);
        destroy_hist_fields(hist_data);
        tracing_map_destroy(hist_data->map);

        destroy_actions(hist_data);
        destroy_field_vars(hist_data);
        destroy_field_var_hists(hist_data);

        kfree(hist_data);
}

static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
{
        struct tracing_map *map = hist_data->map;
        struct ftrace_event_field *field;
        struct hist_field *hist_field;
        int i, idx = 0;

        for_each_hist_field(i, hist_data) {
                hist_field = hist_data->fields[i];
                if (hist_field->flags & HIST_FIELD_FL_KEY) {
                        tracing_map_cmp_fn_t cmp_fn;

                        field = hist_field->field;

                        if (hist_field->flags & HIST_FIELD_FL_STACKTRACE)
                                cmp_fn = tracing_map_cmp_none;
                        else if (!field)
                                cmp_fn = tracing_map_cmp_num(hist_field->size,
                                                             hist_field->is_signed);
                        else if (is_string_field(field))
                                cmp_fn = tracing_map_cmp_string;
                        else
                                cmp_fn = tracing_map_cmp_num(field->size,
                                                             field->is_signed);
                        idx = tracing_map_add_key_field(map,
                                                        hist_field->offset,
                                                        cmp_fn);
                } else if (!(hist_field->flags & HIST_FIELD_FL_VAR))
                        idx = tracing_map_add_sum_field(map);

                if (idx < 0)
                        return idx;

                if (hist_field->flags & HIST_FIELD_FL_VAR) {
                        idx = tracing_map_add_var(map);
                        if (idx < 0)
                                return idx;
                        hist_field->var.idx = idx;
                        hist_field->var.hist_data = hist_data;
                }
        }

        return 0;
}

static struct hist_trigger_data *
create_hist_data(unsigned int map_bits,
                 struct hist_trigger_attrs *attrs,
                 struct trace_event_file *file,
                 bool remove)
{
        const struct tracing_map_ops *map_ops = NULL;
        struct hist_trigger_data *hist_data;
        int ret = 0;

        hist_data = kzalloc(sizeof(*hist_data), GFP_KERNEL);
        if (!hist_data)
                return ERR_PTR(-ENOMEM);

        hist_data->attrs = attrs;
        hist_data->remove = remove;
        hist_data->event_file = file;

        ret = parse_actions(hist_data);
        if (ret)
                goto free;

        ret = create_hist_fields(hist_data, file);
        if (ret)
                goto free;

        ret = create_sort_keys(hist_data);
        if (ret)
                goto free;

        map_ops = &hist_trigger_elt_data_ops;

        hist_data->map = tracing_map_create(map_bits, hist_data->key_size,
                                            map_ops, hist_data);
        if (IS_ERR(hist_data->map)) {
                ret = PTR_ERR(hist_data->map);
                hist_data->map = NULL;
                goto free;
        }

        ret = create_tracing_map_fields(hist_data);
        if (ret)
                goto free;
 out:
        return hist_data;
 free:
        hist_data->attrs = NULL;

        destroy_hist_data(hist_data);

        hist_data = ERR_PTR(ret);

        goto out;
}

static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
                                    struct tracing_map_elt *elt, void *rec,
                                    struct ring_buffer_event *rbe,
                                    u64 *var_ref_vals)
{
        struct hist_elt_data *elt_data;
        struct hist_field *hist_field;
        unsigned int i, var_idx;
        u64 hist_val;

        elt_data = elt->private_data;
        elt_data->var_ref_vals = var_ref_vals;

        for_each_hist_val_field(i, hist_data) {
                hist_field = hist_data->fields[i];
                hist_val = hist_field->fn(hist_field, elt, rbe, rec);
                if (hist_field->flags & HIST_FIELD_FL_VAR) {
                        var_idx = hist_field->var.idx;
                        tracing_map_set_var(elt, var_idx, hist_val);
                        continue;
                }
                tracing_map_update_sum(elt, i, hist_val);
        }

        for_each_hist_key_field(i, hist_data) {
                hist_field = hist_data->fields[i];
                if (hist_field->flags & HIST_FIELD_FL_VAR) {
                        hist_val = hist_field->fn(hist_field, elt, rbe, rec);
                        var_idx = hist_field->var.idx;
                        tracing_map_set_var(elt, var_idx, hist_val);
                }
        }

        update_field_vars(hist_data, elt, rbe, rec);
}

static inline void add_to_key(char *compound_key, void *key,
                              struct hist_field *key_field, void *rec)
{
        size_t size = key_field->size;

        if (key_field->flags & HIST_FIELD_FL_STRING) {
                struct ftrace_event_field *field;

                field = key_field->field;
                if (field->filter_type == FILTER_DYN_STRING)
                        size = *(u32 *)(rec + field->offset) >> 16;
                else if (field->filter_type == FILTER_PTR_STRING)
                        size = strlen(key);
                else if (field->filter_type == FILTER_STATIC_STRING)
                        size = field->size;

                /* ensure NULL-termination */
                if (size > key_field->size - 1)
                        size = key_field->size - 1;

                strncpy(compound_key + key_field->offset, (char *)key, size);
        } else
                memcpy(compound_key + key_field->offset, key, size);
}

static void
hist_trigger_actions(struct hist_trigger_data *hist_data,
                     struct tracing_map_elt *elt, void *rec,
                     struct ring_buffer_event *rbe, void *key,
                     u64 *var_ref_vals)
{
        struct action_data *data;
        unsigned int i;

        for (i = 0; i < hist_data->n_actions; i++) {
                data = hist_data->actions[i];
                data->fn(hist_data, elt, rec, rbe, key, data, var_ref_vals);
        }
}

static void event_hist_trigger(struct event_trigger_data *data, void *rec,
                               struct ring_buffer_event *rbe)
{
        struct hist_trigger_data *hist_data = data->private_data;
        bool use_compound_key = (hist_data->n_keys > 1);
        unsigned long entries[HIST_STACKTRACE_DEPTH];
        u64 var_ref_vals[TRACING_MAP_VARS_MAX];
        char compound_key[HIST_KEY_SIZE_MAX];
        struct tracing_map_elt *elt = NULL;
        struct hist_field *key_field;
        u64 field_contents;
        void *key = NULL;
        unsigned int i;

        memset(compound_key, 0, hist_data->key_size);

        for_each_hist_key_field(i, hist_data) {
                key_field = hist_data->fields[i];

                if (key_field->flags & HIST_FIELD_FL_STACKTRACE) {
                        memset(entries, 0, HIST_STACKTRACE_SIZE);
                        stack_trace_save(entries, HIST_STACKTRACE_DEPTH,
                                         HIST_STACKTRACE_SKIP);
                        key = entries;
                } else {
                        field_contents = key_field->fn(key_field, elt, rbe, rec);
                        if (key_field->flags & HIST_FIELD_FL_STRING) {
                                key = (void *)(unsigned long)field_contents;
                                use_compound_key = true;
                        } else
                                key = (void *)&field_contents;
                }

                if (use_compound_key)
                        add_to_key(compound_key, key, key_field, rec);
        }

        if (use_compound_key)
                key = compound_key;

        if (hist_data->n_var_refs &&
            !resolve_var_refs(hist_data, key, var_ref_vals, false))
                return;

        elt = tracing_map_insert(hist_data->map, key);
        if (!elt)
                return;

        hist_trigger_elt_update(hist_data, elt, rec, rbe, var_ref_vals);

        if (resolve_var_refs(hist_data, key, var_ref_vals, true))
                hist_trigger_actions(hist_data, elt, rec, rbe, key, var_ref_vals);
}

static void hist_trigger_stacktrace_print(struct seq_file *m,
                                          unsigned long *stacktrace_entries,
                                          unsigned int max_entries)
{
        char str[KSYM_SYMBOL_LEN];
        unsigned int spaces = 8;
        unsigned int i;

        for (i = 0; i < max_entries; i++) {
                if (!stacktrace_entries[i])
                        return;

                seq_printf(m, "%*c", 1 + spaces, ' ');
                sprint_symbol(str, stacktrace_entries[i]);
                seq_printf(m, "%s\n", str);
        }
}

static void hist_trigger_print_key(struct seq_file *m,
                                   struct hist_trigger_data *hist_data,
                                   void *key,
                                   struct tracing_map_elt *elt)
{
        struct hist_field *key_field;
        char str[KSYM_SYMBOL_LEN];
        bool multiline = false;
        const char *field_name;
        unsigned int i;
        u64 uval;

        seq_puts(m, "{ ");

        for_each_hist_key_field(i, hist_data) {
                key_field = hist_data->fields[i];

                if (i > hist_data->n_vals)
                        seq_puts(m, ", ");

                field_name = hist_field_name(key_field, 0);

                if (key_field->flags & HIST_FIELD_FL_HEX) {
                        uval = *(u64 *)(key + key_field->offset);
                        seq_printf(m, "%s: %llx", field_name, uval);
                } else if (key_field->flags & HIST_FIELD_FL_SYM) {
                        uval = *(u64 *)(key + key_field->offset);
                        sprint_symbol_no_offset(str, uval);
                        seq_printf(m, "%s: [%llx] %-45s", field_name,
                                   uval, str);
                } else if (key_field->flags & HIST_FIELD_FL_SYM_OFFSET) {
                        uval = *(u64 *)(key + key_field->offset);
                        sprint_symbol(str, uval);
                        seq_printf(m, "%s: [%llx] %-55s", field_name,
                                   uval, str);
                } else if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
                        struct hist_elt_data *elt_data = elt->private_data;
                        char *comm;

                        if (WARN_ON_ONCE(!elt_data))
                                return;

                        comm = elt_data->comm;

                        uval = *(u64 *)(key + key_field->offset);
                        seq_printf(m, "%s: %-16s[%10llu]", field_name,
                                   comm, uval);
                } else if (key_field->flags & HIST_FIELD_FL_SYSCALL) {
                        const char *syscall_name;

                        uval = *(u64 *)(key + key_field->offset);
                        syscall_name = get_syscall_name(uval);
                        if (!syscall_name)
                                syscall_name = "unknown_syscall";

                        seq_printf(m, "%s: %-30s[%3llu]", field_name,
                                   syscall_name, uval);
                } else if (key_field->flags & HIST_FIELD_FL_STACKTRACE) {
                        seq_puts(m, "stacktrace:\n");
                        hist_trigger_stacktrace_print(m,
                                                      key + key_field->offset,
                                                      HIST_STACKTRACE_DEPTH);
                        multiline = true;
                } else if (key_field->flags & HIST_FIELD_FL_LOG2) {
                        seq_printf(m, "%s: ~ 2^%-2llu", field_name,
                                   *(u64 *)(key + key_field->offset));
                } else if (key_field->flags & HIST_FIELD_FL_STRING) {
                        seq_printf(m, "%s: %-50s", field_name,
                                   (char *)(key + key_field->offset));
                } else {
                        uval = *(u64 *)(key + key_field->offset);
                        seq_printf(m, "%s: %10llu", field_name, uval);
                }
        }

        if (!multiline)
                seq_puts(m, " ");

        seq_puts(m, "}");
}

static void hist_trigger_entry_print(struct seq_file *m,
                                     struct hist_trigger_data *hist_data,
                                     void *key,
                                     struct tracing_map_elt *elt)
{
        const char *field_name;
        unsigned int i;

        hist_trigger_print_key(m, hist_data, key, elt);

        seq_printf(m, " hitcount: %10llu",
                   tracing_map_read_sum(elt, HITCOUNT_IDX));

        for (i = 1; i < hist_data->n_vals; i++) {
                field_name = hist_field_name(hist_data->fields[i], 0);

                if (hist_data->fields[i]->flags & HIST_FIELD_FL_VAR ||
                    hist_data->fields[i]->flags & HIST_FIELD_FL_EXPR)
                        continue;

                if (hist_data->fields[i]->flags & HIST_FIELD_FL_HEX) {
                        seq_printf(m, "  %s: %10llx", field_name,
                                   tracing_map_read_sum(elt, i));
                } else {
                        seq_printf(m, "  %s: %10llu", field_name,
                                   tracing_map_read_sum(elt, i));
                }
        }

        print_actions(m, hist_data, elt);

        seq_puts(m, "\n");
}

static int print_entries(struct seq_file *m,
                         struct hist_trigger_data *hist_data)
{
        struct tracing_map_sort_entry **sort_entries = NULL;
        struct tracing_map *map = hist_data->map;
        int i, n_entries;

        n_entries = tracing_map_sort_entries(map, hist_data->sort_keys,
                                             hist_data->n_sort_keys,
                                             &sort_entries);
        if (n_entries < 0)
                return n_entries;

        for (i = 0; i < n_entries; i++)
                hist_trigger_entry_print(m, hist_data,
                                         sort_entries[i]->key,
                                         sort_entries[i]->elt);

        tracing_map_destroy_sort_entries(sort_entries, n_entries);

        return n_entries;
}

static void hist_trigger_show(struct seq_file *m,
                              struct event_trigger_data *data, int n)
{
        struct hist_trigger_data *hist_data;
        int n_entries;

        if (n > 0)
                seq_puts(m, "\n\n");

        seq_puts(m, "# event histogram\n#\n# trigger info: ");
        data->ops->print(m, data->ops, data);
        seq_puts(m, "#\n\n");

        hist_data = data->private_data;
        n_entries = print_entries(m, hist_data);
        if (n_entries < 0)
                n_entries = 0;

        track_data_snapshot_print(m, hist_data);

        seq_printf(m, "\nTotals:\n    Hits: %llu\n    Entries: %u\n    Dropped: %llu\n",
                   (u64)atomic64_read(&hist_data->map->hits),
                   n_entries, (u64)atomic64_read(&hist_data->map->drops));
}

static int hist_show(struct seq_file *m, void *v)
{
        struct event_trigger_data *data;
        struct trace_event_file *event_file;
        int n = 0, ret = 0;

        mutex_lock(&event_mutex);

        event_file = event_file_data(m->private);
        if (unlikely(!event_file)) {
                ret = -ENODEV;
                goto out_unlock;
        }

        list_for_each_entry(data, &event_file->triggers, list) {
                if (data->cmd_ops->trigger_type == ETT_EVENT_HIST)
                        hist_trigger_show(m, data, n++);
        }

 out_unlock:
        mutex_unlock(&event_mutex);

        return ret;
}

static int event_hist_open(struct inode *inode, struct file *file)
{
        int ret;

        ret = security_locked_down(LOCKDOWN_TRACEFS);
        if (ret)
                return ret;

        return single_open(file, hist_show, file);
}

const struct file_operations event_hist_fops = {
        .open = event_hist_open,
        .read = seq_read,
        .llseek = seq_lseek,
        .release = single_release,
};

static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
{
        const char *field_name = hist_field_name(hist_field, 0);

        if (hist_field->var.name)
                seq_printf(m, "%s=", hist_field->var.name);

        if (hist_field->flags & HIST_FIELD_FL_CPU)
                seq_puts(m, "cpu");
        else if (field_name) {
                if (hist_field->flags & HIST_FIELD_FL_VAR_REF ||
                    hist_field->flags & HIST_FIELD_FL_ALIAS)
                        seq_putc(m, '$');
                seq_printf(m, "%s", field_name);
        } else if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP)
                seq_puts(m, "common_timestamp");

        if (hist_field->flags) {
                if (!(hist_field->flags & HIST_FIELD_FL_VAR_REF) &&
                    !(hist_field->flags & HIST_FIELD_FL_EXPR)) {
                        const char *flags = get_hist_field_flags(hist_field);

                        if (flags)
                                seq_printf(m, ".%s", flags);
                }
        }
}

static int event_hist_trigger_print(struct seq_file *m,
                                    struct event_trigger_ops *ops,
                                    struct event_trigger_data *data)
{
        struct hist_trigger_data *hist_data = data->private_data;
        struct hist_field *field;
        bool have_var = false;
        unsigned int i;

        seq_puts(m, "hist:");

        if (data->name)
                seq_printf(m, "%s:", data->name);

        seq_puts(m, "keys=");

        for_each_hist_key_field(i, hist_data) {
                field = hist_data->fields[i];

                if (i > hist_data->n_vals)
                        seq_puts(m, ",");

                if (field->flags & HIST_FIELD_FL_STACKTRACE)
                        seq_puts(m, "stacktrace");
                else
                        hist_field_print(m, field);
        }

        seq_puts(m, ":vals=");

        for_each_hist_val_field(i, hist_data) {
                field = hist_data->fields[i];
                if (field->flags & HIST_FIELD_FL_VAR) {
                        have_var = true;
                        continue;
                }

                if (i == HITCOUNT_IDX)
                        seq_puts(m, "hitcount");
                else {
                        seq_puts(m, ",");
                        hist_field_print(m, field);
                }
        }

        if (have_var) {
                unsigned int n = 0;

                seq_puts(m, ":");

                for_each_hist_val_field(i, hist_data) {
                        field = hist_data->fields[i];

                        if (field->flags & HIST_FIELD_FL_VAR) {
                                if (n++)
                                        seq_puts(m, ",");
                                hist_field_print(m, field);
                        }
                }
        }

        seq_puts(m, ":sort=");

        for (i = 0; i < hist_data->n_sort_keys; i++) {
                struct tracing_map_sort_key *sort_key;
                unsigned int idx, first_key_idx;

                /* skip VAR vals */
                first_key_idx = hist_data->n_vals - hist_data->n_vars;

                sort_key = &hist_data->sort_keys[i];
                idx = sort_key->field_idx;

                if (WARN_ON(idx >= HIST_FIELDS_MAX))
                        return -EINVAL;

                if (i > 0)
                        seq_puts(m, ",");

                if (idx == HITCOUNT_IDX)
                        seq_puts(m, "hitcount");
                else {
                        if (idx >= first_key_idx)
                                idx += hist_data->n_vars;
                        hist_field_print(m, hist_data->fields[idx]);
                }

                if (sort_key->descending)
                        seq_puts(m, ".descending");
        }
        seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));
        if (hist_data->enable_timestamps)
                seq_printf(m, ":clock=%s", hist_data->attrs->clock);

        print_actions_spec(m, hist_data);

        if (data->filter_str)
                seq_printf(m, " if %s", data->filter_str);

        if (data->paused)
                seq_puts(m, " [paused]");
        else
                seq_puts(m, " [active]");

        seq_putc(m, '\n');

        return 0;
}

static int event_hist_trigger_init(struct event_trigger_ops *ops,
                                   struct event_trigger_data *data)
{
        struct hist_trigger_data *hist_data = data->private_data;

        if (!data->ref && hist_data->attrs->name)
                save_named_trigger(hist_data->attrs->name, data);

        data->ref++;

        return 0;
}

static void unregister_field_var_hists(struct hist_trigger_data *hist_data)
{
        struct trace_event_file *file;
        unsigned int i;
        char *cmd;
        int ret;

        for (i = 0; i < hist_data->n_field_var_hists; i++) {
                file = hist_data->field_var_hists[i]->hist_data->event_file;
                cmd = hist_data->field_var_hists[i]->cmd;
                ret = event_hist_trigger_func(&trigger_hist_cmd, file,
                                              "!hist", "hist", cmd);
        }
}

static void event_hist_trigger_free(struct event_trigger_ops *ops,
                                    struct event_trigger_data *data)
{
        struct hist_trigger_data *hist_data = data->private_data;

        if (WARN_ON_ONCE(data->ref <= 0))
                return;

        data->ref--;
        if (!data->ref) {
                if (data->name)
                        del_named_trigger(data);

                trigger_data_free(data);

                remove_hist_vars(hist_data);

                unregister_field_var_hists(hist_data);

                destroy_hist_data(hist_data);
        }
}

static struct event_trigger_ops event_hist_trigger_ops = {
        .func                   = event_hist_trigger,
        .print                  = event_hist_trigger_print,
        .init                   = event_hist_trigger_init,
        .free                   = event_hist_trigger_free,
};

static int event_hist_trigger_named_init(struct event_trigger_ops *ops,
                                         struct event_trigger_data *data)
{
        data->ref++;

        save_named_trigger(data->named_data->name, data);

        event_hist_trigger_init(ops, data->named_data);

        return 0;
}

static void event_hist_trigger_named_free(struct event_trigger_ops *ops,
                                          struct event_trigger_data *data)
{
        if (WARN_ON_ONCE(data->ref <= 0))
                return;

        event_hist_trigger_free(ops, data->named_data);

        data->ref--;
        if (!data->ref) {
                del_named_trigger(data);
                trigger_data_free(data);
        }
}

static struct event_trigger_ops event_hist_trigger_named_ops = {
        .func                   = event_hist_trigger,
        .print                  = event_hist_trigger_print,
        .init                   = event_hist_trigger_named_init,
        .free                   = event_hist_trigger_named_free,
};

static struct event_trigger_ops *event_hist_get_trigger_ops(char *cmd,
                                                            char *param)
{
        return &event_hist_trigger_ops;
}

static void hist_clear(struct event_trigger_data *data)
{
        struct hist_trigger_data *hist_data = data->private_data;

        if (data->name)
                pause_named_trigger(data);

        tracepoint_synchronize_unregister();

        tracing_map_clear(hist_data->map);

        if (data->name)
                unpause_named_trigger(data);
}

static bool compatible_field(struct ftrace_event_field *field,
                             struct ftrace_event_field *test_field)
{
        if (field == test_field)
                return true;
        if (field == NULL || test_field == NULL)
                return false;
        if (strcmp(field->name, test_field->name) != 0)
                return false;
        if (strcmp(field->type, test_field->type) != 0)
                return false;
        if (field->size != test_field->size)
                return false;
        if (field->is_signed != test_field->is_signed)
                return false;

        return true;
}

static bool hist_trigger_match(struct event_trigger_data *data,
                               struct event_trigger_data *data_test,
                               struct event_trigger_data *named_data,
                               bool ignore_filter)
{
        struct tracing_map_sort_key *sort_key, *sort_key_test;
        struct hist_trigger_data *hist_data, *hist_data_test;
        struct hist_field *key_field, *key_field_test;
        unsigned int i;

        if (named_data && (named_data != data_test) &&
            (named_data != data_test->named_data))
                return false;

        if (!named_data && is_named_trigger(data_test))
                return false;

        hist_data = data->private_data;
        hist_data_test = data_test->private_data;

        if (hist_data->n_vals != hist_data_test->n_vals ||
            hist_data->n_fields != hist_data_test->n_fields ||
            hist_data->n_sort_keys != hist_data_test->n_sort_keys)
                return false;

        if (!ignore_filter) {
                if ((data->filter_str && !data_test->filter_str) ||
                   (!data->filter_str && data_test->filter_str))
                        return false;
        }

        for_each_hist_field(i, hist_data) {
                key_field = hist_data->fields[i];
                key_field_test = hist_data_test->fields[i];

                if (key_field->flags != key_field_test->flags)
                        return false;
                if (!compatible_field(key_field->field, key_field_test->field))
                        return false;
                if (key_field->offset != key_field_test->offset)
                        return false;
                if (key_field->size != key_field_test->size)
                        return false;
                if (key_field->is_signed != key_field_test->is_signed)
                        return false;
                if (!!key_field->var.name != !!key_field_test->var.name)
                        return false;
                if (key_field->var.name &&
                    strcmp(key_field->var.name, key_field_test->var.name) != 0)
                        return false;
        }

        for (i = 0; i < hist_data->n_sort_keys; i++) {
                sort_key = &hist_data->sort_keys[i];
                sort_key_test = &hist_data_test->sort_keys[i];

                if (sort_key->field_idx != sort_key_test->field_idx ||
                    sort_key->descending != sort_key_test->descending)
                        return false;
        }

        if (!ignore_filter && data->filter_str &&
            (strcmp(data->filter_str, data_test->filter_str) != 0))
                return false;

        if (!actions_match(hist_data, hist_data_test))
                return false;

        return true;
}

static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
                                 struct event_trigger_data *data,
                                 struct trace_event_file *file)
{
        struct hist_trigger_data *hist_data = data->private_data;
        struct event_trigger_data *test, *named_data = NULL;
        struct trace_array *tr = file->tr;
        int ret = 0;

        if (hist_data->attrs->name) {
                named_data = find_named_trigger(hist_data->attrs->name);
                if (named_data) {
                        if (!hist_trigger_match(data, named_data, named_data,
                                                true)) {
                                hist_err(tr, HIST_ERR_NAMED_MISMATCH, errpos(hist_data->attrs->name));
                                ret = -EINVAL;
                                goto out;
                        }
                }
        }

        if (hist_data->attrs->name && !named_data)
                goto new;

        lockdep_assert_held(&event_mutex);

        list_for_each_entry(test, &file->triggers, list) {
                if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
                        if (!hist_trigger_match(data, test, named_data, false))
                                continue;
                        if (hist_data->attrs->pause)
                                test->paused = true;
                        else if (hist_data->attrs->cont)
                                test->paused = false;
                        else if (hist_data->attrs->clear)
                                hist_clear(test);
                        else {
                                hist_err(tr, HIST_ERR_TRIGGER_EEXIST, 0);
                                ret = -EEXIST;
                        }
                        goto out;
                }
        }
 new:
        if (hist_data->attrs->cont || hist_data->attrs->clear) {
                hist_err(tr, HIST_ERR_TRIGGER_ENOENT_CLEAR, 0);
                ret = -ENOENT;
                goto out;
        }

        if (hist_data->attrs->pause)
                data->paused = true;

        if (named_data) {
                data->private_data = named_data->private_data;
                set_named_trigger_data(data, named_data);
                data->ops = &event_hist_trigger_named_ops;
        }

        if (data->ops->init) {
                ret = data->ops->init(data->ops, data);
                if (ret < 0)
                        goto out;
        }

        if (hist_data->enable_timestamps) {
                char *clock = hist_data->attrs->clock;

                ret = tracing_set_clock(file->tr, hist_data->attrs->clock);
                if (ret) {
                        hist_err(tr, HIST_ERR_SET_CLOCK_FAIL, errpos(clock));
                        goto out;
                }

                tracing_set_time_stamp_abs(file->tr, true);
        }

        if (named_data)
                destroy_hist_data(hist_data);

        ret++;
 out:
        return ret;
}

static int hist_trigger_enable(struct event_trigger_data *data,
                               struct trace_event_file *file)
{
        int ret = 0;

        list_add_tail_rcu(&data->list, &file->triggers);

        update_cond_flag(file);

        if (trace_event_trigger_enable_disable(file, 1) < 0) {
                list_del_rcu(&data->list);
                update_cond_flag(file);
                ret--;
        }

        return ret;
}

static bool have_hist_trigger_match(struct event_trigger_data *data,
                                    struct trace_event_file *file)
{
        struct hist_trigger_data *hist_data = data->private_data;
        struct event_trigger_data *test, *named_data = NULL;
        bool match = false;

        lockdep_assert_held(&event_mutex);

        if (hist_data->attrs->name)
                named_data = find_named_trigger(hist_data->attrs->name);

        list_for_each_entry(test, &file->triggers, list) {
                if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
                        if (hist_trigger_match(data, test, named_data, false)) {
                                match = true;
                                break;
                        }
                }
        }

        return match;
}

static bool hist_trigger_check_refs(struct event_trigger_data *data,
                                    struct trace_event_file *file)
{
        struct hist_trigger_data *hist_data = data->private_data;
        struct event_trigger_data *test, *named_data = NULL;

        lockdep_assert_held(&event_mutex);

        if (hist_data->attrs->name)
                named_data = find_named_trigger(hist_data->attrs->name);

        list_for_each_entry(test, &file->triggers, list) {
                if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
                        if (!hist_trigger_match(data, test, named_data, false))
                                continue;
                        hist_data = test->private_data;
                        if (check_var_refs(hist_data))
                                return true;
                        break;
                }
        }

        return false;
}

static void hist_unregister_trigger(char *glob, struct event_trigger_ops *ops,
                                    struct event_trigger_data *data,
                                    struct trace_event_file *file)
{
        struct hist_trigger_data *hist_data = data->private_data;
        struct event_trigger_data *test, *named_data = NULL;
        bool unregistered = false;

        lockdep_assert_held(&event_mutex);

        if (hist_data->attrs->name)
                named_data = find_named_trigger(hist_data->attrs->name);

        list_for_each_entry(test, &file->triggers, list) {
                if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
                        if (!hist_trigger_match(data, test, named_data, false))
                                continue;
                        unregistered = true;
                        list_del_rcu(&test->list);
                        trace_event_trigger_enable_disable(file, 0);
                        update_cond_flag(file);
                        break;
                }
        }

        if (unregistered && test->ops->free)
                test->ops->free(test->ops, test);

        if (hist_data->enable_timestamps) {
                if (!hist_data->remove || unregistered)
                        tracing_set_time_stamp_abs(file->tr, false);
        }
}

static bool hist_file_check_refs(struct trace_event_file *file)
{
        struct hist_trigger_data *hist_data;
        struct event_trigger_data *test;

        lockdep_assert_held(&event_mutex);

        list_for_each_entry(test, &file->triggers, list) {
                if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
                        hist_data = test->private_data;
                        if (check_var_refs(hist_data))
                                return true;
                }
        }

        return false;
}

static void hist_unreg_all(struct trace_event_file *file)
{
        struct event_trigger_data *test, *n;
        struct hist_trigger_data *hist_data;
        struct synth_event *se;
        const char *se_name;

        lockdep_assert_held(&event_mutex);

        if (hist_file_check_refs(file))
                return;

        list_for_each_entry_safe(test, n, &file->triggers, list) {
                if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
                        hist_data = test->private_data;
                        list_del_rcu(&test->list);
                        trace_event_trigger_enable_disable(file, 0);

                        se_name = trace_event_name(file->event_call);
                        se = find_synth_event(se_name);
                        if (se)
                                se->ref--;

                        update_cond_flag(file);
                        if (hist_data->enable_timestamps)
                                tracing_set_time_stamp_abs(file->tr, false);
                        if (test->ops->free)
                                test->ops->free(test->ops, test);
                }
        }
}

static int event_hist_trigger_func(struct event_command *cmd_ops,
                                   struct trace_event_file *file,
                                   char *glob, char *cmd, char *param)
{
        unsigned int hist_trigger_bits = TRACING_MAP_BITS_DEFAULT;
        struct event_trigger_data *trigger_data;
        struct hist_trigger_attrs *attrs;
        struct event_trigger_ops *trigger_ops;
        struct hist_trigger_data *hist_data;
        struct synth_event *se;
        const char *se_name;
        bool remove = false;
        char *trigger, *p;
        int ret = 0;

        lockdep_assert_held(&event_mutex);

        if (glob && strlen(glob)) {
                hist_err_clear();
                last_cmd_set(file, param);
        }

        if (!param)
                return -EINVAL;

        if (glob[0] == '!')
                remove = true;

        /*
         * separate the trigger from the filter (k:v [if filter])
         * allowing for whitespace in the trigger
         */
        p = trigger = param;
        do {
                p = strstr(p, "if");
                if (!p)
                        break;
                if (p == param)
                        return -EINVAL;
                if (*(p - 1) != ' ' && *(p - 1) != '\t') {
                        p++;
                        continue;
                }
                if (p >= param + strlen(param) - (sizeof("if") - 1) - 1)
                        return -EINVAL;
                if (*(p + sizeof("if") - 1) != ' ' && *(p + sizeof("if") - 1) != '\t') {
                        p++;
                        continue;
                }
                break;
        } while (p);

        if (!p)
                param = NULL;
        else {
                *(p - 1) = '\0';
                param = strstrip(p);
                trigger = strstrip(trigger);
        }

        attrs = parse_hist_trigger_attrs(file->tr, trigger);
        if (IS_ERR(attrs))
                return PTR_ERR(attrs);

        if (attrs->map_bits)
                hist_trigger_bits = attrs->map_bits;

        hist_data = create_hist_data(hist_trigger_bits, attrs, file, remove);
        if (IS_ERR(hist_data)) {
                destroy_hist_trigger_attrs(attrs);
                return PTR_ERR(hist_data);
        }

        trigger_ops = cmd_ops->get_trigger_ops(cmd, trigger);

        trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
        if (!trigger_data) {
                ret = -ENOMEM;
                goto out_free;
        }

        trigger_data->count = -1;
        trigger_data->ops = trigger_ops;
        trigger_data->cmd_ops = cmd_ops;

        INIT_LIST_HEAD(&trigger_data->list);
        RCU_INIT_POINTER(trigger_data->filter, NULL);

        trigger_data->private_data = hist_data;

        /* if param is non-empty, it's supposed to be a filter */
        if (param && cmd_ops->set_filter) {
                ret = cmd_ops->set_filter(param, trigger_data, file);
                if (ret < 0)
                        goto out_free;
        }

        if (remove) {
                if (!have_hist_trigger_match(trigger_data, file))
                        goto out_free;

                if (hist_trigger_check_refs(trigger_data, file)) {
                        ret = -EBUSY;
                        goto out_free;
                }

                cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
                se_name = trace_event_name(file->event_call);
                se = find_synth_event(se_name);
                if (se)
                        se->ref--;
                ret = 0;
                goto out_free;
        }

        ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file);
        /*
         * The above returns on success the # of triggers registered,
         * but if it didn't register any it returns zero.  Consider no
         * triggers registered a failure too.
         */
        if (!ret) {
                if (!(attrs->pause || attrs->cont || attrs->clear))
                        ret = -ENOENT;
                goto out_free;
        } else if (ret < 0)
                goto out_free;

        if (get_named_trigger_data(trigger_data))
                goto enable;

        if (has_hist_vars(hist_data))
                save_hist_vars(hist_data);

        ret = create_actions(hist_data);
        if (ret)
                goto out_unreg;

        ret = tracing_map_init(hist_data->map);
        if (ret)
                goto out_unreg;
enable:
        ret = hist_trigger_enable(trigger_data, file);
        if (ret)
                goto out_unreg;

        se_name = trace_event_name(file->event_call);
        se = find_synth_event(se_name);
        if (se)
                se->ref++;
        /* Just return zero, not the number of registered triggers */
        ret = 0;
 out:
        if (ret == 0)
                hist_err_clear();

        return ret;
 out_unreg:
        cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
 out_free:
        if (cmd_ops->set_filter)
                cmd_ops->set_filter(NULL, trigger_data, NULL);

        remove_hist_vars(hist_data);

        kfree(trigger_data);

        destroy_hist_data(hist_data);
        goto out;
}

static struct event_command trigger_hist_cmd = {
        .name                   = "hist",
        .trigger_type           = ETT_EVENT_HIST,
        .flags                  = EVENT_CMD_FL_NEEDS_REC,
        .func                   = event_hist_trigger_func,
        .reg                    = hist_register_trigger,
        .unreg                  = hist_unregister_trigger,
        .unreg_all              = hist_unreg_all,
        .get_trigger_ops        = event_hist_get_trigger_ops,
        .set_filter             = set_trigger_filter,
};

__init int register_trigger_hist_cmd(void)
{
        int ret;

        ret = register_event_command(&trigger_hist_cmd);
        WARN_ON(ret < 0);

        return ret;
}

static void
hist_enable_trigger(struct event_trigger_data *data, void *rec,
                    struct ring_buffer_event *event)
{
        struct enable_trigger_data *enable_data = data->private_data;
        struct event_trigger_data *test;

        list_for_each_entry_rcu(test, &enable_data->file->triggers, list,
                                lockdep_is_held(&event_mutex)) {
                if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
                        if (enable_data->enable)
                                test->paused = false;
                        else
                                test->paused = true;
                }
        }
}

static void
hist_enable_count_trigger(struct event_trigger_data *data, void *rec,
                          struct ring_buffer_event *event)
{
        if (!data->count)
                return;

        if (data->count != -1)
                (data->count)--;

        hist_enable_trigger(data, rec, event);
}

static struct event_trigger_ops hist_enable_trigger_ops = {
        .func                   = hist_enable_trigger,
        .print                  = event_enable_trigger_print,
        .init                   = event_trigger_init,
        .free                   = event_enable_trigger_free,
};

static struct event_trigger_ops hist_enable_count_trigger_ops = {
        .func                   = hist_enable_count_trigger,
        .print                  = event_enable_trigger_print,
        .init                   = event_trigger_init,
        .free                   = event_enable_trigger_free,
};

static struct event_trigger_ops hist_disable_trigger_ops = {
        .func                   = hist_enable_trigger,
        .print                  = event_enable_trigger_print,
        .init                   = event_trigger_init,
        .free                   = event_enable_trigger_free,
};

static struct event_trigger_ops hist_disable_count_trigger_ops = {
        .func                   = hist_enable_count_trigger,
        .print                  = event_enable_trigger_print,
        .init                   = event_trigger_init,
        .free                   = event_enable_trigger_free,
};

static struct event_trigger_ops *
hist_enable_get_trigger_ops(char *cmd, char *param)
{
        struct event_trigger_ops *ops;
        bool enable;

        enable = (strcmp(cmd, ENABLE_HIST_STR) == 0);

        if (enable)
                ops = param ? &hist_enable_count_trigger_ops :
                        &hist_enable_trigger_ops;
        else
                ops = param ? &hist_disable_count_trigger_ops :
                        &hist_disable_trigger_ops;

        return ops;
}

static void hist_enable_unreg_all(struct trace_event_file *file)
{
        struct event_trigger_data *test, *n;

        list_for_each_entry_safe(test, n, &file->triggers, list) {
                if (test->cmd_ops->trigger_type == ETT_HIST_ENABLE) {
                        list_del_rcu(&test->list);
                        update_cond_flag(file);
                        trace_event_trigger_enable_disable(file, 0);
                        if (test->ops->free)
                                test->ops->free(test->ops, test);
                }
        }
}

static struct event_command trigger_hist_enable_cmd = {
        .name                   = ENABLE_HIST_STR,
        .trigger_type           = ETT_HIST_ENABLE,
        .func                   = event_enable_trigger_func,
        .reg                    = event_enable_register_trigger,
        .unreg                  = event_enable_unregister_trigger,
        .unreg_all              = hist_enable_unreg_all,
        .get_trigger_ops        = hist_enable_get_trigger_ops,
        .set_filter             = set_trigger_filter,
};

static struct event_command trigger_hist_disable_cmd = {
        .name                   = DISABLE_HIST_STR,
        .trigger_type           = ETT_HIST_ENABLE,
        .func                   = event_enable_trigger_func,
        .reg                    = event_enable_register_trigger,
        .unreg                  = event_enable_unregister_trigger,
        .unreg_all              = hist_enable_unreg_all,
        .get_trigger_ops        = hist_enable_get_trigger_ops,
        .set_filter             = set_trigger_filter,
};

static __init void unregister_trigger_hist_enable_disable_cmds(void)
{
        unregister_event_command(&trigger_hist_enable_cmd);
        unregister_event_command(&trigger_hist_disable_cmd);
}

__init int register_trigger_hist_enable_disable_cmds(void)
{
        int ret;

        ret = register_event_command(&trigger_hist_enable_cmd);
        if (WARN_ON(ret < 0))
                return ret;
        ret = register_event_command(&trigger_hist_disable_cmd);
        if (WARN_ON(ret < 0))
                unregister_trigger_hist_enable_disable_cmds();

        return ret;
}

static __init int trace_events_hist_init(void)
{
        struct dentry *entry = NULL;
        struct dentry *d_tracer;
        int err = 0;

        err = dyn_event_register(&synth_event_ops);
        if (err) {
                pr_warn("Could not register synth_event_ops\n");
                return err;
        }

        d_tracer = tracing_init_dentry();
        if (IS_ERR(d_tracer)) {
                err = PTR_ERR(d_tracer);
                goto err;
        }

        entry = tracefs_create_file("synthetic_events", 0644, d_tracer,
                                    NULL, &synth_events_fops);
        if (!entry) {
                err = -ENODEV;
                goto err;
        }

        return err;
 err:
        pr_warn("Could not create tracefs 'synthetic_events' entry\n");

        return err;
}

fs_initcall(trace_events_hist_init);