tracing: Kernel access to Ftrace instances

Ftrace provides the feature “instances” that provides the capability to
create multiple Ftrace ring buffers. However, currently these buffers
are created/accessed via userspace only. The kernel APIs providing these
features are not exported, hence cannot be used by other kernel
components.

This patch aims to extend this infrastructure to provide the
flexibility to create/log/remove/ enable-disable existing trace events
to these buffers from within the kernel.

Link: http://lkml.kernel.org/r/1553106531-3281-2-git-send-email-divya.indi@oracle.com
Signed-off-by: Divya Indi <divya.indi@oracle.com>
Reviewed-by: Joe Jin <joe.jin@oracle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 21153e64bf1c366033213e90272438ba171b2822..4384fcc386c80fa6d97dd3e4691508e44b319b6c 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3053,6 +3053,7 @@ void trace_printk_init_buffers(void)
        if (global_trace.trace_buffer.buffer)
                tracing_start_cmdline_record();
 }
+EXPORT_SYMBOL_GPL(trace_printk_init_buffers);
 
 void trace_printk_start_comm(void)
 {
@@ -3213,6 +3214,7 @@ int trace_array_printk(struct trace_array *tr,
        va_end(ap);
        return ret;
 }
+EXPORT_SYMBOL_GPL(trace_array_printk);
 
 __printf(3, 4)
 int trace_array_printk_buf(struct ring_buffer *buffer,
@@ -8037,7 +8039,7 @@ static void update_tracer_options(struct trace_array *tr)
        mutex_unlock(&trace_types_lock);
 }
 
-static int instance_mkdir(const char *name)
+struct trace_array *trace_array_create(const char *name)
 {
        struct trace_array *tr;
        int ret;
@@ -8101,7 +8103,7 @@ static int instance_mkdir(const char *name)
        mutex_unlock(&trace_types_lock);
        mutex_unlock(&event_mutex);
 
-       return 0;
+       return tr;
 
  out_free_tr:
        free_trace_buffers(tr);
@@ -8113,33 +8115,21 @@ static int instance_mkdir(const char *name)
        mutex_unlock(&trace_types_lock);
        mutex_unlock(&event_mutex);
 
-       return ret;
+       return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(trace_array_create);
 
+static int instance_mkdir(const char *name)
+{
+       return PTR_ERR_OR_ZERO(trace_array_create(name));
 }
 
-static int instance_rmdir(const char *name)
+static int __remove_instance(struct trace_array *tr)
 {
-       struct trace_array *tr;
-       int found = 0;
-       int ret;
        int i;
 
-       mutex_lock(&event_mutex);
-       mutex_lock(&trace_types_lock);
-
-       ret = -ENODEV;
-       list_for_each_entry(tr, &ftrace_trace_arrays, list) {
-               if (tr->name && strcmp(tr->name, name) == 0) {
-                       found = 1;
-                       break;
-               }
-       }
-       if (!found)
-               goto out_unlock;
-
-       ret = -EBUSY;
        if (tr->ref || (tr->current_trace && tr->current_trace->ref))
-               goto out_unlock;
+               return -EBUSY;
 
        list_del(&tr->list);
 
@@ -8165,10 +8155,46 @@ static int instance_rmdir(const char *name)
        free_cpumask_var(tr->tracing_cpumask);
        kfree(tr->name);
        kfree(tr);
+       tr = NULL;
 
-       ret = 0;
+       return 0;
+}
+
+int trace_array_destroy(struct trace_array *tr)
+{
+       int ret;
+
+       if (!tr)
+               return -EINVAL;
+
+       mutex_lock(&event_mutex);
+       mutex_lock(&trace_types_lock);
+
+       ret = __remove_instance(tr);
+
+       mutex_unlock(&trace_types_lock);
+       mutex_unlock(&event_mutex);
+
+       return ret;
+}
+EXPORT_SYMBOL_GPL(trace_array_destroy);
+
+static int instance_rmdir(const char *name)
+{
+       struct trace_array *tr;
+       int ret;
+
+       mutex_lock(&event_mutex);
+       mutex_lock(&trace_types_lock);
+
+       ret = -ENODEV;
+       list_for_each_entry(tr, &ftrace_trace_arrays, list) {
+               if (tr->name && strcmp(tr->name, name) == 0) {
+                       ret = __remove_instance(tr);
+                       break;
+               }
+       }
 
- out_unlock:
        mutex_unlock(&trace_types_lock);
        mutex_unlock(&event_mutex);
 

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 5b3b0c3c8a47e581483818e270af391fd0ef1d57..81c038ed6cee780965e33fe40ec468a6f4fdf004 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -832,6 +832,7 @@ static int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set)
 
        return ret;
 }
+EXPORT_SYMBOL_GPL(ftrace_set_clr_event);
 
 /**
  * trace_set_clr_event - enable or disable an event