2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/delay.h>
30 #include <linux/smp.h>
31 #include <linux/security.h>
32 #include <linux/bootmem.h>
33 #include <linux/memblock.h>
34 #include <linux/syscalls.h>
35 #include <linux/crash_core.h>
36 #include <linux/kdb.h>
37 #include <linux/ratelimit.h>
38 #include <linux/kmsg_dump.h>
39 #include <linux/syslog.h>
40 #include <linux/cpu.h>
41 #include <linux/notifier.h>
42 #include <linux/rculist.h>
43 #include <linux/poll.h>
44 #include <linux/irq_work.h>
45 #include <linux/utsname.h>
46 #include <linux/ctype.h>
47 #include <linux/uio.h>
48 #include <linux/sched/clock.h>
49 #include <linux/sched/debug.h>
50 #include <linux/sched/task_stack.h>
52 #include <linux/uaccess.h>
53 #include <asm/sections.h>
55 #define CREATE_TRACE_POINTS
56 #include <trace/events/printk.h>
58 #include "console_cmdline.h"
62 int console_printk[4] = {
63 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
64 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
65 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
66 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
70 * Low level drivers may need that to know if they can schedule in
71 * their unblank() callback or not. So let's export it.
74 EXPORT_SYMBOL(oops_in_progress);
77 * console_sem protects the console_drivers list, and also
78 * provides serialisation for access to the entire console
81 static DEFINE_SEMAPHORE(console_sem);
82 struct console *console_drivers;
83 EXPORT_SYMBOL_GPL(console_drivers);
86 static struct lockdep_map console_lock_dep_map = {
87 .name = "console_lock"
91 enum devkmsg_log_bits {
92 __DEVKMSG_LOG_BIT_ON = 0,
93 __DEVKMSG_LOG_BIT_OFF,
94 __DEVKMSG_LOG_BIT_LOCK,
97 enum devkmsg_log_masks {
98 DEVKMSG_LOG_MASK_ON = BIT(__DEVKMSG_LOG_BIT_ON),
99 DEVKMSG_LOG_MASK_OFF = BIT(__DEVKMSG_LOG_BIT_OFF),
100 DEVKMSG_LOG_MASK_LOCK = BIT(__DEVKMSG_LOG_BIT_LOCK),
103 /* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
104 #define DEVKMSG_LOG_MASK_DEFAULT 0
106 static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
108 static int __control_devkmsg(char *str)
113 if (!strncmp(str, "on", 2)) {
114 devkmsg_log = DEVKMSG_LOG_MASK_ON;
116 } else if (!strncmp(str, "off", 3)) {
117 devkmsg_log = DEVKMSG_LOG_MASK_OFF;
119 } else if (!strncmp(str, "ratelimit", 9)) {
120 devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
126 static int __init control_devkmsg(char *str)
128 if (__control_devkmsg(str) < 0)
132 * Set sysctl string accordingly:
134 if (devkmsg_log == DEVKMSG_LOG_MASK_ON) {
135 memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE);
136 strncpy(devkmsg_log_str, "on", 2);
137 } else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF) {
138 memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE);
139 strncpy(devkmsg_log_str, "off", 3);
141 /* else "ratelimit" which is set by default. */
144 * Sysctl cannot change it anymore. The kernel command line setting of
145 * this parameter is to force the setting to be permanent throughout the
146 * runtime of the system. This is a precation measure against userspace
147 * trying to be a smarta** and attempting to change it up on us.
149 devkmsg_log |= DEVKMSG_LOG_MASK_LOCK;
153 __setup("printk.devkmsg=", control_devkmsg);
155 char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit";
157 int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
158 void __user *buffer, size_t *lenp, loff_t *ppos)
160 char old_str[DEVKMSG_STR_MAX_SIZE];
165 if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK)
169 strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE);
172 err = proc_dostring(table, write, buffer, lenp, ppos);
177 err = __control_devkmsg(devkmsg_log_str);
180 * Do not accept an unknown string OR a known string with
183 if (err < 0 || (err + 1 != *lenp)) {
185 /* ... and restore old setting. */
187 strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE);
197 * Number of registered extended console drivers.
199 * If extended consoles are present, in-kernel cont reassembly is disabled
200 * and each fragment is stored as a separate log entry with proper
201 * continuation flag so that every emitted message has full metadata. This
202 * doesn't change the result for regular consoles or /proc/kmsg. For
203 * /dev/kmsg, as long as the reader concatenates messages according to
204 * consecutive continuation flags, the end result should be the same too.
206 static int nr_ext_console_drivers;
209 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
210 * macros instead of functions so that _RET_IP_ contains useful information.
212 #define down_console_sem() do { \
214 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
217 static int __down_trylock_console_sem(unsigned long ip)
223 * Here and in __up_console_sem() we need to be in safe mode,
224 * because spindump/WARN/etc from under console ->lock will
225 * deadlock in printk()->down_trylock_console_sem() otherwise.
227 printk_safe_enter_irqsave(flags);
228 lock_failed = down_trylock(&console_sem);
229 printk_safe_exit_irqrestore(flags);
233 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
236 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
238 static void __up_console_sem(unsigned long ip)
242 mutex_release(&console_lock_dep_map, 1, ip);
244 printk_safe_enter_irqsave(flags);
246 printk_safe_exit_irqrestore(flags);
248 #define up_console_sem() __up_console_sem(_RET_IP_)
251 * This is used for debugging the mess that is the VT code by
252 * keeping track if we have the console semaphore held. It's
253 * definitely not the perfect debug tool (we don't know if _WE_
254 * hold it and are racing, but it helps tracking those weird code
255 * paths in the console code where we end up in places I want
256 * locked without the console sempahore held).
258 static int console_locked, console_suspended;
261 * If exclusive_console is non-NULL then only this console is to be printed to.
263 static struct console *exclusive_console;
266 * Array of consoles built from command line options (console=)
269 #define MAX_CMDLINECONSOLES 8
271 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
273 static int preferred_console = -1;
274 int console_set_on_cmdline;
275 EXPORT_SYMBOL(console_set_on_cmdline);
277 /* Flag: console code may call schedule() */
278 static int console_may_schedule;
281 * The printk log buffer consists of a chain of concatenated variable
282 * length records. Every record starts with a record header, containing
283 * the overall length of the record.
285 * The heads to the first and last entry in the buffer, as well as the
286 * sequence numbers of these entries are maintained when messages are
289 * If the heads indicate available messages, the length in the header
290 * tells the start next message. A length == 0 for the next message
291 * indicates a wrap-around to the beginning of the buffer.
293 * Every record carries the monotonic timestamp in microseconds, as well as
294 * the standard userspace syslog level and syslog facility. The usual
295 * kernel messages use LOG_KERN; userspace-injected messages always carry
296 * a matching syslog facility, by default LOG_USER. The origin of every
297 * message can be reliably determined that way.
299 * The human readable log message directly follows the message header. The
300 * length of the message text is stored in the header, the stored message
303 * Optionally, a message can carry a dictionary of properties (key/value pairs),
304 * to provide userspace with a machine-readable message context.
306 * Examples for well-defined, commonly used property names are:
307 * DEVICE=b12:8 device identifier
311 * +sound:card0 subsystem:devname
312 * SUBSYSTEM=pci driver-core subsystem name
314 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
315 * follows directly after a '=' character. Every property is terminated by
316 * a '\0' character. The last property is not terminated.
318 * Example of a message structure:
319 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
320 * 0008 34 00 record is 52 bytes long
321 * 000a 0b 00 text is 11 bytes long
322 * 000c 1f 00 dictionary is 23 bytes long
323 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
324 * 0010 69 74 27 73 20 61 20 6c "it's a l"
326 * 001b 44 45 56 49 43 "DEVIC"
327 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
328 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
330 * 0032 00 00 00 padding to next message header
332 * The 'struct printk_log' buffer header must never be directly exported to
333 * userspace, it is a kernel-private implementation detail that might
334 * need to be changed in the future, when the requirements change.
336 * /dev/kmsg exports the structured data in the following line format:
337 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
339 * Users of the export format should ignore possible additional values
340 * separated by ',', and find the message after the ';' character.
342 * The optional key/value pairs are attached as continuation lines starting
343 * with a space character and terminated by a newline. All possible
344 * non-prinatable characters are escaped in the "\xff" notation.
348 LOG_NOCONS = 1, /* already flushed, do not print to console */
349 LOG_NEWLINE = 2, /* text ended with a newline */
350 LOG_PREFIX = 4, /* text started with a prefix */
351 LOG_CONT = 8, /* text is a fragment of a continuation line */
355 u64 ts_nsec; /* timestamp in nanoseconds */
356 u16 len; /* length of entire record */
357 u16 text_len; /* length of text buffer */
358 u16 dict_len; /* length of dictionary buffer */
359 u8 facility; /* syslog facility */
360 u8 flags:5; /* internal record flags */
361 u8 level:3; /* syslog level */
363 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
364 __packed __aligned(4)
369 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
370 * within the scheduler's rq lock. It must be released before calling
371 * console_unlock() or anything else that might wake up a process.
373 DEFINE_RAW_SPINLOCK(logbuf_lock);
376 * Helper macros to lock/unlock logbuf_lock and switch between
377 * printk-safe/unsafe modes.
379 #define logbuf_lock_irq() \
381 printk_safe_enter_irq(); \
382 raw_spin_lock(&logbuf_lock); \
385 #define logbuf_unlock_irq() \
387 raw_spin_unlock(&logbuf_lock); \
388 printk_safe_exit_irq(); \
391 #define logbuf_lock_irqsave(flags) \
393 printk_safe_enter_irqsave(flags); \
394 raw_spin_lock(&logbuf_lock); \
397 #define logbuf_unlock_irqrestore(flags) \
399 raw_spin_unlock(&logbuf_lock); \
400 printk_safe_exit_irqrestore(flags); \
404 DECLARE_WAIT_QUEUE_HEAD(log_wait);
405 /* the next printk record to read by syslog(READ) or /proc/kmsg */
406 static u64 syslog_seq;
407 static u32 syslog_idx;
408 static size_t syslog_partial;
410 /* index and sequence number of the first record stored in the buffer */
411 static u64 log_first_seq;
412 static u32 log_first_idx;
414 /* index and sequence number of the next record to store in the buffer */
415 static u64 log_next_seq;
416 static u32 log_next_idx;
418 /* the next printk record to write to the console */
419 static u64 console_seq;
420 static u32 console_idx;
422 /* the next printk record to read after the last 'clear' command */
423 static u64 clear_seq;
424 static u32 clear_idx;
426 #define PREFIX_MAX 32
427 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
429 #define LOG_LEVEL(v) ((v) & 0x07)
430 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
433 #define LOG_ALIGN __alignof__(struct printk_log)
434 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
435 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
436 static char *log_buf = __log_buf;
437 static u32 log_buf_len = __LOG_BUF_LEN;
439 /* Return log buffer address */
440 char *log_buf_addr_get(void)
445 /* Return log buffer size */
446 u32 log_buf_len_get(void)
451 /* human readable text of the record */
452 static char *log_text(const struct printk_log *msg)
454 return (char *)msg + sizeof(struct printk_log);
457 /* optional key/value pair dictionary attached to the record */
458 static char *log_dict(const struct printk_log *msg)
460 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
463 /* get record by index; idx must point to valid msg */
464 static struct printk_log *log_from_idx(u32 idx)
466 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
469 * A length == 0 record is the end of buffer marker. Wrap around and
470 * read the message at the start of the buffer.
473 return (struct printk_log *)log_buf;
477 /* get next record; idx must point to valid msg */
478 static u32 log_next(u32 idx)
480 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
482 /* length == 0 indicates the end of the buffer; wrap */
484 * A length == 0 record is the end of buffer marker. Wrap around and
485 * read the message at the start of the buffer as *this* one, and
486 * return the one after that.
489 msg = (struct printk_log *)log_buf;
492 return idx + msg->len;
496 * Check whether there is enough free space for the given message.
498 * The same values of first_idx and next_idx mean that the buffer
499 * is either empty or full.
501 * If the buffer is empty, we must respect the position of the indexes.
502 * They cannot be reset to the beginning of the buffer.
504 static int logbuf_has_space(u32 msg_size, bool empty)
508 if (log_next_idx > log_first_idx || empty)
509 free = max(log_buf_len - log_next_idx, log_first_idx);
511 free = log_first_idx - log_next_idx;
514 * We need space also for an empty header that signalizes wrapping
517 return free >= msg_size + sizeof(struct printk_log);
520 static int log_make_free_space(u32 msg_size)
522 while (log_first_seq < log_next_seq &&
523 !logbuf_has_space(msg_size, false)) {
524 /* drop old messages until we have enough contiguous space */
525 log_first_idx = log_next(log_first_idx);
529 if (clear_seq < log_first_seq) {
530 clear_seq = log_first_seq;
531 clear_idx = log_first_idx;
534 /* sequence numbers are equal, so the log buffer is empty */
535 if (logbuf_has_space(msg_size, log_first_seq == log_next_seq))
541 /* compute the message size including the padding bytes */
542 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
546 size = sizeof(struct printk_log) + text_len + dict_len;
547 *pad_len = (-size) & (LOG_ALIGN - 1);
554 * Define how much of the log buffer we could take at maximum. The value
555 * must be greater than two. Note that only half of the buffer is available
556 * when the index points to the middle.
558 #define MAX_LOG_TAKE_PART 4
559 static const char trunc_msg[] = "<truncated>";
561 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
562 u16 *dict_len, u32 *pad_len)
565 * The message should not take the whole buffer. Otherwise, it might
566 * get removed too soon.
568 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
569 if (*text_len > max_text_len)
570 *text_len = max_text_len;
571 /* enable the warning message */
572 *trunc_msg_len = strlen(trunc_msg);
573 /* disable the "dict" completely */
575 /* compute the size again, count also the warning message */
576 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
579 /* insert record into the buffer, discard old ones, update heads */
580 static int log_store(int facility, int level,
581 enum log_flags flags, u64 ts_nsec,
582 const char *dict, u16 dict_len,
583 const char *text, u16 text_len)
585 struct printk_log *msg;
587 u16 trunc_msg_len = 0;
589 /* number of '\0' padding bytes to next message */
590 size = msg_used_size(text_len, dict_len, &pad_len);
592 if (log_make_free_space(size)) {
593 /* truncate the message if it is too long for empty buffer */
594 size = truncate_msg(&text_len, &trunc_msg_len,
595 &dict_len, &pad_len);
596 /* survive when the log buffer is too small for trunc_msg */
597 if (log_make_free_space(size))
601 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
603 * This message + an additional empty header does not fit
604 * at the end of the buffer. Add an empty header with len == 0
605 * to signify a wrap around.
607 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
612 msg = (struct printk_log *)(log_buf + log_next_idx);
613 memcpy(log_text(msg), text, text_len);
614 msg->text_len = text_len;
616 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
617 msg->text_len += trunc_msg_len;
619 memcpy(log_dict(msg), dict, dict_len);
620 msg->dict_len = dict_len;
621 msg->facility = facility;
622 msg->level = level & 7;
623 msg->flags = flags & 0x1f;
625 msg->ts_nsec = ts_nsec;
627 msg->ts_nsec = local_clock();
628 memset(log_dict(msg) + dict_len, 0, pad_len);
632 log_next_idx += msg->len;
635 return msg->text_len;
638 int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
640 static int syslog_action_restricted(int type)
645 * Unless restricted, we allow "read all" and "get buffer size"
648 return type != SYSLOG_ACTION_READ_ALL &&
649 type != SYSLOG_ACTION_SIZE_BUFFER;
652 static int check_syslog_permissions(int type, int source)
655 * If this is from /proc/kmsg and we've already opened it, then we've
656 * already done the capabilities checks at open time.
658 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
661 if (syslog_action_restricted(type)) {
662 if (capable(CAP_SYSLOG))
665 * For historical reasons, accept CAP_SYS_ADMIN too, with
668 if (capable(CAP_SYS_ADMIN)) {
669 pr_warn_once("%s (%d): Attempt to access syslog with "
670 "CAP_SYS_ADMIN but no CAP_SYSLOG "
672 current->comm, task_pid_nr(current));
678 return security_syslog(type);
681 static void append_char(char **pp, char *e, char c)
687 static ssize_t msg_print_ext_header(char *buf, size_t size,
688 struct printk_log *msg, u64 seq)
690 u64 ts_usec = msg->ts_nsec;
692 do_div(ts_usec, 1000);
694 return scnprintf(buf, size, "%u,%llu,%llu,%c;",
695 (msg->facility << 3) | msg->level, seq, ts_usec,
696 msg->flags & LOG_CONT ? 'c' : '-');
699 static ssize_t msg_print_ext_body(char *buf, size_t size,
700 char *dict, size_t dict_len,
701 char *text, size_t text_len)
703 char *p = buf, *e = buf + size;
706 /* escape non-printable characters */
707 for (i = 0; i < text_len; i++) {
708 unsigned char c = text[i];
710 if (c < ' ' || c >= 127 || c == '\\')
711 p += scnprintf(p, e - p, "\\x%02x", c);
713 append_char(&p, e, c);
715 append_char(&p, e, '\n');
720 for (i = 0; i < dict_len; i++) {
721 unsigned char c = dict[i];
724 append_char(&p, e, ' ');
729 append_char(&p, e, '\n');
734 if (c < ' ' || c >= 127 || c == '\\') {
735 p += scnprintf(p, e - p, "\\x%02x", c);
739 append_char(&p, e, c);
741 append_char(&p, e, '\n');
747 /* /dev/kmsg - userspace message inject/listen interface */
748 struct devkmsg_user {
751 struct ratelimit_state rs;
753 char buf[CONSOLE_EXT_LOG_MAX];
756 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
759 int level = default_message_loglevel;
760 int facility = 1; /* LOG_USER */
761 struct file *file = iocb->ki_filp;
762 struct devkmsg_user *user = file->private_data;
763 size_t len = iov_iter_count(from);
766 if (!user || len > LOG_LINE_MAX)
769 /* Ignore when user logging is disabled. */
770 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
773 /* Ratelimit when not explicitly enabled. */
774 if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) {
775 if (!___ratelimit(&user->rs, current->comm))
779 buf = kmalloc(len+1, GFP_KERNEL);
784 if (!copy_from_iter_full(buf, len, from)) {
790 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
791 * the decimal value represents 32bit, the lower 3 bit are the log
792 * level, the rest are the log facility.
794 * If no prefix or no userspace facility is specified, we
795 * enforce LOG_USER, to be able to reliably distinguish
796 * kernel-generated messages from userspace-injected ones.
799 if (line[0] == '<') {
803 u = simple_strtoul(line + 1, &endp, 10);
804 if (endp && endp[0] == '>') {
805 level = LOG_LEVEL(u);
806 if (LOG_FACILITY(u) != 0)
807 facility = LOG_FACILITY(u);
814 printk_emit(facility, level, NULL, 0, "%s", line);
819 static ssize_t devkmsg_read(struct file *file, char __user *buf,
820 size_t count, loff_t *ppos)
822 struct devkmsg_user *user = file->private_data;
823 struct printk_log *msg;
830 ret = mutex_lock_interruptible(&user->lock);
835 while (user->seq == log_next_seq) {
836 if (file->f_flags & O_NONBLOCK) {
843 ret = wait_event_interruptible(log_wait,
844 user->seq != log_next_seq);
850 if (user->seq < log_first_seq) {
851 /* our last seen message is gone, return error and reset */
852 user->idx = log_first_idx;
853 user->seq = log_first_seq;
859 msg = log_from_idx(user->idx);
860 len = msg_print_ext_header(user->buf, sizeof(user->buf),
862 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
863 log_dict(msg), msg->dict_len,
864 log_text(msg), msg->text_len);
866 user->idx = log_next(user->idx);
875 if (copy_to_user(buf, user->buf, len)) {
881 mutex_unlock(&user->lock);
885 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
887 struct devkmsg_user *user = file->private_data;
898 /* the first record */
899 user->idx = log_first_idx;
900 user->seq = log_first_seq;
904 * The first record after the last SYSLOG_ACTION_CLEAR,
905 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
906 * changes no global state, and does not clear anything.
908 user->idx = clear_idx;
909 user->seq = clear_seq;
912 /* after the last record */
913 user->idx = log_next_idx;
914 user->seq = log_next_seq;
923 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
925 struct devkmsg_user *user = file->private_data;
929 return POLLERR|POLLNVAL;
931 poll_wait(file, &log_wait, wait);
934 if (user->seq < log_next_seq) {
935 /* return error when data has vanished underneath us */
936 if (user->seq < log_first_seq)
937 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
939 ret = POLLIN|POLLRDNORM;
946 static int devkmsg_open(struct inode *inode, struct file *file)
948 struct devkmsg_user *user;
951 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
954 /* write-only does not need any file context */
955 if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
956 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
962 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
966 ratelimit_default_init(&user->rs);
967 ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);
969 mutex_init(&user->lock);
972 user->idx = log_first_idx;
973 user->seq = log_first_seq;
976 file->private_data = user;
980 static int devkmsg_release(struct inode *inode, struct file *file)
982 struct devkmsg_user *user = file->private_data;
987 ratelimit_state_exit(&user->rs);
989 mutex_destroy(&user->lock);
994 const struct file_operations kmsg_fops = {
995 .open = devkmsg_open,
996 .read = devkmsg_read,
997 .write_iter = devkmsg_write,
998 .llseek = devkmsg_llseek,
999 .poll = devkmsg_poll,
1000 .release = devkmsg_release,
1003 #ifdef CONFIG_CRASH_CORE
1005 * This appends the listed symbols to /proc/vmcore
1007 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
1008 * obtain access to symbols that are otherwise very difficult to locate. These
1009 * symbols are specifically used so that utilities can access and extract the
1010 * dmesg log from a vmcore file after a crash.
1012 void log_buf_vmcoreinfo_setup(void)
1014 VMCOREINFO_SYMBOL(log_buf);
1015 VMCOREINFO_SYMBOL(log_buf_len);
1016 VMCOREINFO_SYMBOL(log_first_idx);
1017 VMCOREINFO_SYMBOL(clear_idx);
1018 VMCOREINFO_SYMBOL(log_next_idx);
1020 * Export struct printk_log size and field offsets. User space tools can
1021 * parse it and detect any changes to structure down the line.
1023 VMCOREINFO_STRUCT_SIZE(printk_log);
1024 VMCOREINFO_OFFSET(printk_log, ts_nsec);
1025 VMCOREINFO_OFFSET(printk_log, len);
1026 VMCOREINFO_OFFSET(printk_log, text_len);
1027 VMCOREINFO_OFFSET(printk_log, dict_len);
1031 /* requested log_buf_len from kernel cmdline */
1032 static unsigned long __initdata new_log_buf_len;
1034 /* we practice scaling the ring buffer by powers of 2 */
1035 static void __init log_buf_len_update(unsigned size)
1038 size = roundup_pow_of_two(size);
1039 if (size > log_buf_len)
1040 new_log_buf_len = size;
1043 /* save requested log_buf_len since it's too early to process it */
1044 static int __init log_buf_len_setup(char *str)
1046 unsigned size = memparse(str, &str);
1048 log_buf_len_update(size);
1052 early_param("log_buf_len", log_buf_len_setup);
1055 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1057 static void __init log_buf_add_cpu(void)
1059 unsigned int cpu_extra;
1062 * archs should set up cpu_possible_bits properly with
1063 * set_cpu_possible() after setup_arch() but just in
1064 * case lets ensure this is valid.
1066 if (num_possible_cpus() == 1)
1069 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
1071 /* by default this will only continue through for large > 64 CPUs */
1072 if (cpu_extra <= __LOG_BUF_LEN / 2)
1075 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1076 __LOG_CPU_MAX_BUF_LEN);
1077 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1079 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
1081 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
1083 #else /* !CONFIG_SMP */
1084 static inline void log_buf_add_cpu(void) {}
1085 #endif /* CONFIG_SMP */
1087 void __init setup_log_buf(int early)
1089 unsigned long flags;
1093 if (log_buf != __log_buf)
1096 if (!early && !new_log_buf_len)
1099 if (!new_log_buf_len)
1104 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
1106 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
1110 if (unlikely(!new_log_buf)) {
1111 pr_err("log_buf_len: %ld bytes not available\n",
1116 logbuf_lock_irqsave(flags);
1117 log_buf_len = new_log_buf_len;
1118 log_buf = new_log_buf;
1119 new_log_buf_len = 0;
1120 free = __LOG_BUF_LEN - log_next_idx;
1121 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
1122 logbuf_unlock_irqrestore(flags);
1124 pr_info("log_buf_len: %d bytes\n", log_buf_len);
1125 pr_info("early log buf free: %d(%d%%)\n",
1126 free, (free * 100) / __LOG_BUF_LEN);
1129 static bool __read_mostly ignore_loglevel;
1131 static int __init ignore_loglevel_setup(char *str)
1133 ignore_loglevel = true;
1134 pr_info("debug: ignoring loglevel setting.\n");
1139 early_param("ignore_loglevel", ignore_loglevel_setup);
1140 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1141 MODULE_PARM_DESC(ignore_loglevel,
1142 "ignore loglevel setting (prints all kernel messages to the console)");
1144 static bool suppress_message_printing(int level)
1146 return (level >= console_loglevel && !ignore_loglevel);
1149 #ifdef CONFIG_BOOT_PRINTK_DELAY
1151 static int boot_delay; /* msecs delay after each printk during bootup */
1152 static unsigned long long loops_per_msec; /* based on boot_delay */
1154 static int __init boot_delay_setup(char *str)
1158 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
1159 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
1161 get_option(&str, &boot_delay);
1162 if (boot_delay > 10 * 1000)
1165 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1166 "HZ: %d, loops_per_msec: %llu\n",
1167 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1170 early_param("boot_delay", boot_delay_setup);
1172 static void boot_delay_msec(int level)
1174 unsigned long long k;
1175 unsigned long timeout;
1177 if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING)
1178 || suppress_message_printing(level)) {
1182 k = (unsigned long long)loops_per_msec * boot_delay;
1184 timeout = jiffies + msecs_to_jiffies(boot_delay);
1189 * use (volatile) jiffies to prevent
1190 * compiler reduction; loop termination via jiffies
1191 * is secondary and may or may not happen.
1193 if (time_after(jiffies, timeout))
1195 touch_nmi_watchdog();
1199 static inline void boot_delay_msec(int level)
1204 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1205 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1207 static size_t print_time(u64 ts, char *buf)
1209 unsigned long rem_nsec;
1214 rem_nsec = do_div(ts, 1000000000);
1217 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1219 return sprintf(buf, "[%5lu.%06lu] ",
1220 (unsigned long)ts, rem_nsec / 1000);
1223 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1226 unsigned int prefix = (msg->facility << 3) | msg->level;
1230 len += sprintf(buf, "<%u>", prefix);
1235 else if (prefix > 99)
1237 else if (prefix > 9)
1242 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1246 static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *buf, size_t size)
1248 const char *text = log_text(msg);
1249 size_t text_size = msg->text_len;
1253 const char *next = memchr(text, '\n', text_size);
1257 text_len = next - text;
1259 text_size -= next - text;
1261 text_len = text_size;
1265 if (print_prefix(msg, syslog, NULL) +
1266 text_len + 1 >= size - len)
1269 len += print_prefix(msg, syslog, buf + len);
1270 memcpy(buf + len, text, text_len);
1274 /* SYSLOG_ACTION_* buffer size only calculation */
1275 len += print_prefix(msg, syslog, NULL);
1286 static int syslog_print(char __user *buf, int size)
1289 struct printk_log *msg;
1292 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1301 if (syslog_seq < log_first_seq) {
1302 /* messages are gone, move to first one */
1303 syslog_seq = log_first_seq;
1304 syslog_idx = log_first_idx;
1307 if (syslog_seq == log_next_seq) {
1308 logbuf_unlock_irq();
1312 skip = syslog_partial;
1313 msg = log_from_idx(syslog_idx);
1314 n = msg_print_text(msg, true, text, LOG_LINE_MAX + PREFIX_MAX);
1315 if (n - syslog_partial <= size) {
1316 /* message fits into buffer, move forward */
1317 syslog_idx = log_next(syslog_idx);
1319 n -= syslog_partial;
1322 /* partial read(), remember position */
1324 syslog_partial += n;
1327 logbuf_unlock_irq();
1332 if (copy_to_user(buf, text + skip, n)) {
1347 static int syslog_print_all(char __user *buf, int size, bool clear)
1352 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1363 * Find first record that fits, including all following records,
1364 * into the user-provided buffer for this dump.
1368 while (seq < log_next_seq) {
1369 struct printk_log *msg = log_from_idx(idx);
1371 len += msg_print_text(msg, true, NULL, 0);
1372 idx = log_next(idx);
1376 /* move first record forward until length fits into the buffer */
1379 while (len > size && seq < log_next_seq) {
1380 struct printk_log *msg = log_from_idx(idx);
1382 len -= msg_print_text(msg, true, NULL, 0);
1383 idx = log_next(idx);
1387 /* last message fitting into this dump */
1388 next_seq = log_next_seq;
1391 while (len >= 0 && seq < next_seq) {
1392 struct printk_log *msg = log_from_idx(idx);
1395 textlen = msg_print_text(msg, true, text,
1396 LOG_LINE_MAX + PREFIX_MAX);
1401 idx = log_next(idx);
1404 logbuf_unlock_irq();
1405 if (copy_to_user(buf + len, text, textlen))
1411 if (seq < log_first_seq) {
1412 /* messages are gone, move to next one */
1413 seq = log_first_seq;
1414 idx = log_first_idx;
1420 clear_seq = log_next_seq;
1421 clear_idx = log_next_idx;
1423 logbuf_unlock_irq();
1429 int do_syslog(int type, char __user *buf, int len, int source)
1432 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1435 error = check_syslog_permissions(type, source);
1440 case SYSLOG_ACTION_CLOSE: /* Close log */
1442 case SYSLOG_ACTION_OPEN: /* Open log */
1444 case SYSLOG_ACTION_READ: /* Read from log */
1445 if (!buf || len < 0)
1449 if (!access_ok(VERIFY_WRITE, buf, len))
1451 error = wait_event_interruptible(log_wait,
1452 syslog_seq != log_next_seq);
1455 error = syslog_print(buf, len);
1457 /* Read/clear last kernel messages */
1458 case SYSLOG_ACTION_READ_CLEAR:
1461 /* Read last kernel messages */
1462 case SYSLOG_ACTION_READ_ALL:
1463 if (!buf || len < 0)
1467 if (!access_ok(VERIFY_WRITE, buf, len))
1469 error = syslog_print_all(buf, len, clear);
1471 /* Clear ring buffer */
1472 case SYSLOG_ACTION_CLEAR:
1473 syslog_print_all(NULL, 0, true);
1475 /* Disable logging to console */
1476 case SYSLOG_ACTION_CONSOLE_OFF:
1477 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1478 saved_console_loglevel = console_loglevel;
1479 console_loglevel = minimum_console_loglevel;
1481 /* Enable logging to console */
1482 case SYSLOG_ACTION_CONSOLE_ON:
1483 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1484 console_loglevel = saved_console_loglevel;
1485 saved_console_loglevel = LOGLEVEL_DEFAULT;
1488 /* Set level of messages printed to console */
1489 case SYSLOG_ACTION_CONSOLE_LEVEL:
1490 if (len < 1 || len > 8)
1492 if (len < minimum_console_loglevel)
1493 len = minimum_console_loglevel;
1494 console_loglevel = len;
1495 /* Implicitly re-enable logging to console */
1496 saved_console_loglevel = LOGLEVEL_DEFAULT;
1498 /* Number of chars in the log buffer */
1499 case SYSLOG_ACTION_SIZE_UNREAD:
1501 if (syslog_seq < log_first_seq) {
1502 /* messages are gone, move to first one */
1503 syslog_seq = log_first_seq;
1504 syslog_idx = log_first_idx;
1507 if (source == SYSLOG_FROM_PROC) {
1509 * Short-cut for poll(/"proc/kmsg") which simply checks
1510 * for pending data, not the size; return the count of
1511 * records, not the length.
1513 error = log_next_seq - syslog_seq;
1515 u64 seq = syslog_seq;
1516 u32 idx = syslog_idx;
1518 while (seq < log_next_seq) {
1519 struct printk_log *msg = log_from_idx(idx);
1521 error += msg_print_text(msg, true, NULL, 0);
1522 idx = log_next(idx);
1525 error -= syslog_partial;
1527 logbuf_unlock_irq();
1529 /* Size of the log buffer */
1530 case SYSLOG_ACTION_SIZE_BUFFER:
1531 error = log_buf_len;
1541 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1543 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1547 * Call the console drivers, asking them to write out
1548 * log_buf[start] to log_buf[end - 1].
1549 * The console_lock must be held.
1551 static void call_console_drivers(const char *ext_text, size_t ext_len,
1552 const char *text, size_t len)
1554 struct console *con;
1556 trace_console_rcuidle(text, len);
1558 if (!console_drivers)
1561 for_each_console(con) {
1562 if (exclusive_console && con != exclusive_console)
1564 if (!(con->flags & CON_ENABLED))
1568 if (!cpu_online(smp_processor_id()) &&
1569 !(con->flags & CON_ANYTIME))
1571 if (con->flags & CON_EXTENDED)
1572 con->write(con, ext_text, ext_len);
1574 con->write(con, text, len);
1578 int printk_delay_msec __read_mostly;
1580 static inline void printk_delay(void)
1582 if (unlikely(printk_delay_msec)) {
1583 int m = printk_delay_msec;
1587 touch_nmi_watchdog();
1593 * Continuation lines are buffered, and not committed to the record buffer
1594 * until the line is complete, or a race forces it. The line fragments
1595 * though, are printed immediately to the consoles to ensure everything has
1596 * reached the console in case of a kernel crash.
1598 static struct cont {
1599 char buf[LOG_LINE_MAX];
1600 size_t len; /* length == 0 means unused buffer */
1601 struct task_struct *owner; /* task of first print*/
1602 u64 ts_nsec; /* time of first print */
1603 u8 level; /* log level of first message */
1604 u8 facility; /* log facility of first message */
1605 enum log_flags flags; /* prefix, newline flags */
1608 static void cont_flush(void)
1613 log_store(cont.facility, cont.level, cont.flags, cont.ts_nsec,
1614 NULL, 0, cont.buf, cont.len);
1618 static bool cont_add(int facility, int level, enum log_flags flags, const char *text, size_t len)
1621 * If ext consoles are present, flush and skip in-kernel
1622 * continuation. See nr_ext_console_drivers definition. Also, if
1623 * the line gets too long, split it up in separate records.
1625 if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
1631 cont.facility = facility;
1633 cont.owner = current;
1634 cont.ts_nsec = local_clock();
1638 memcpy(cont.buf + cont.len, text, len);
1641 // The original flags come from the first line,
1642 // but later continuations can add a newline.
1643 if (flags & LOG_NEWLINE) {
1644 cont.flags |= LOG_NEWLINE;
1648 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1654 static size_t log_output(int facility, int level, enum log_flags lflags, const char *dict, size_t dictlen, char *text, size_t text_len)
1657 * If an earlier line was buffered, and we're a continuation
1658 * write from the same process, try to add it to the buffer.
1661 if (cont.owner == current && (lflags & LOG_CONT)) {
1662 if (cont_add(facility, level, lflags, text, text_len))
1665 /* Otherwise, make sure it's flushed */
1669 /* Skip empty continuation lines that couldn't be added - they just flush */
1670 if (!text_len && (lflags & LOG_CONT))
1673 /* If it doesn't end in a newline, try to buffer the current line */
1674 if (!(lflags & LOG_NEWLINE)) {
1675 if (cont_add(facility, level, lflags, text, text_len))
1679 /* Store it in the record log */
1680 return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len);
1683 asmlinkage int vprintk_emit(int facility, int level,
1684 const char *dict, size_t dictlen,
1685 const char *fmt, va_list args)
1687 static char textbuf[LOG_LINE_MAX];
1688 char *text = textbuf;
1690 enum log_flags lflags = 0;
1691 unsigned long flags;
1693 bool in_sched = false;
1695 if (level == LOGLEVEL_SCHED) {
1696 level = LOGLEVEL_DEFAULT;
1700 boot_delay_msec(level);
1703 /* This stops the holder of console_sem just where we want him */
1704 logbuf_lock_irqsave(flags);
1706 * The printf needs to come first; we need the syslog
1707 * prefix which might be passed-in as a parameter.
1709 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1711 /* mark and strip a trailing newline */
1712 if (text_len && text[text_len-1] == '\n') {
1714 lflags |= LOG_NEWLINE;
1717 /* strip kernel syslog prefix and extract log level or control flags */
1718 if (facility == 0) {
1721 while ((kern_level = printk_get_level(text)) != 0) {
1722 switch (kern_level) {
1724 if (level == LOGLEVEL_DEFAULT)
1725 level = kern_level - '0';
1727 case 'd': /* KERN_DEFAULT */
1728 lflags |= LOG_PREFIX;
1730 case 'c': /* KERN_CONT */
1739 if (level == LOGLEVEL_DEFAULT)
1740 level = default_message_loglevel;
1743 lflags |= LOG_PREFIX|LOG_NEWLINE;
1745 printed_len = log_output(facility, level, lflags, dict, dictlen, text, text_len);
1747 logbuf_unlock_irqrestore(flags);
1749 /* If called from the scheduler, we can not call up(). */
1752 * Try to acquire and then immediately release the console
1753 * semaphore. The release will print out buffers and wake up
1754 * /dev/kmsg and syslog() users.
1756 if (console_trylock())
1762 EXPORT_SYMBOL(vprintk_emit);
1764 asmlinkage int vprintk(const char *fmt, va_list args)
1766 return vprintk_func(fmt, args);
1768 EXPORT_SYMBOL(vprintk);
1770 asmlinkage int printk_emit(int facility, int level,
1771 const char *dict, size_t dictlen,
1772 const char *fmt, ...)
1777 va_start(args, fmt);
1778 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1783 EXPORT_SYMBOL(printk_emit);
1785 int vprintk_default(const char *fmt, va_list args)
1789 #ifdef CONFIG_KGDB_KDB
1790 /* Allow to pass printk() to kdb but avoid a recursion. */
1791 if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0)) {
1792 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1796 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1800 EXPORT_SYMBOL_GPL(vprintk_default);
1803 * printk - print a kernel message
1804 * @fmt: format string
1806 * This is printk(). It can be called from any context. We want it to work.
1808 * We try to grab the console_lock. If we succeed, it's easy - we log the
1809 * output and call the console drivers. If we fail to get the semaphore, we
1810 * place the output into the log buffer and return. The current holder of
1811 * the console_sem will notice the new output in console_unlock(); and will
1812 * send it to the consoles before releasing the lock.
1814 * One effect of this deferred printing is that code which calls printk() and
1815 * then changes console_loglevel may break. This is because console_loglevel
1816 * is inspected when the actual printing occurs.
1821 * See the vsnprintf() documentation for format string extensions over C99.
1823 asmlinkage __visible int printk(const char *fmt, ...)
1828 va_start(args, fmt);
1829 r = vprintk_func(fmt, args);
1834 EXPORT_SYMBOL(printk);
1836 #else /* CONFIG_PRINTK */
1838 #define LOG_LINE_MAX 0
1839 #define PREFIX_MAX 0
1841 static u64 syslog_seq;
1842 static u32 syslog_idx;
1843 static u64 console_seq;
1844 static u32 console_idx;
1845 static u64 log_first_seq;
1846 static u32 log_first_idx;
1847 static u64 log_next_seq;
1848 static char *log_text(const struct printk_log *msg) { return NULL; }
1849 static char *log_dict(const struct printk_log *msg) { return NULL; }
1850 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1851 static u32 log_next(u32 idx) { return 0; }
1852 static ssize_t msg_print_ext_header(char *buf, size_t size,
1853 struct printk_log *msg,
1854 u64 seq) { return 0; }
1855 static ssize_t msg_print_ext_body(char *buf, size_t size,
1856 char *dict, size_t dict_len,
1857 char *text, size_t text_len) { return 0; }
1858 static void call_console_drivers(const char *ext_text, size_t ext_len,
1859 const char *text, size_t len) {}
1860 static size_t msg_print_text(const struct printk_log *msg,
1861 bool syslog, char *buf, size_t size) { return 0; }
1862 static bool suppress_message_printing(int level) { return false; }
1864 #endif /* CONFIG_PRINTK */
1866 #ifdef CONFIG_EARLY_PRINTK
1867 struct console *early_console;
1869 asmlinkage __visible void early_printk(const char *fmt, ...)
1879 n = vscnprintf(buf, sizeof(buf), fmt, ap);
1882 early_console->write(early_console, buf, n);
1886 static int __add_preferred_console(char *name, int idx, char *options,
1889 struct console_cmdline *c;
1893 * See if this tty is not yet registered, and
1894 * if we have a slot free.
1896 for (i = 0, c = console_cmdline;
1897 i < MAX_CMDLINECONSOLES && c->name[0];
1899 if (strcmp(c->name, name) == 0 && c->index == idx) {
1901 preferred_console = i;
1905 if (i == MAX_CMDLINECONSOLES)
1908 preferred_console = i;
1909 strlcpy(c->name, name, sizeof(c->name));
1910 c->options = options;
1911 braille_set_options(c, brl_options);
1917 * Set up a console. Called via do_early_param() in init/main.c
1918 * for each "console=" parameter in the boot command line.
1920 static int __init console_setup(char *str)
1922 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
1923 char *s, *options, *brl_options = NULL;
1926 if (_braille_console_setup(&str, &brl_options))
1930 * Decode str into name, index, options.
1932 if (str[0] >= '0' && str[0] <= '9') {
1933 strcpy(buf, "ttyS");
1934 strncpy(buf + 4, str, sizeof(buf) - 5);
1936 strncpy(buf, str, sizeof(buf) - 1);
1938 buf[sizeof(buf) - 1] = 0;
1939 options = strchr(str, ',');
1943 if (!strcmp(str, "ttya"))
1944 strcpy(buf, "ttyS0");
1945 if (!strcmp(str, "ttyb"))
1946 strcpy(buf, "ttyS1");
1948 for (s = buf; *s; s++)
1949 if (isdigit(*s) || *s == ',')
1951 idx = simple_strtoul(s, NULL, 10);
1954 __add_preferred_console(buf, idx, options, brl_options);
1955 console_set_on_cmdline = 1;
1958 __setup("console=", console_setup);
1961 * add_preferred_console - add a device to the list of preferred consoles.
1962 * @name: device name
1963 * @idx: device index
1964 * @options: options for this console
1966 * The last preferred console added will be used for kernel messages
1967 * and stdin/out/err for init. Normally this is used by console_setup
1968 * above to handle user-supplied console arguments; however it can also
1969 * be used by arch-specific code either to override the user or more
1970 * commonly to provide a default console (ie from PROM variables) when
1971 * the user has not supplied one.
1973 int add_preferred_console(char *name, int idx, char *options)
1975 return __add_preferred_console(name, idx, options, NULL);
1978 bool console_suspend_enabled = true;
1979 EXPORT_SYMBOL(console_suspend_enabled);
1981 static int __init console_suspend_disable(char *str)
1983 console_suspend_enabled = false;
1986 __setup("no_console_suspend", console_suspend_disable);
1987 module_param_named(console_suspend, console_suspend_enabled,
1988 bool, S_IRUGO | S_IWUSR);
1989 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1990 " and hibernate operations");
1993 * suspend_console - suspend the console subsystem
1995 * This disables printk() while we go into suspend states
1997 void suspend_console(void)
1999 if (!console_suspend_enabled)
2001 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2003 console_suspended = 1;
2007 void resume_console(void)
2009 if (!console_suspend_enabled)
2012 console_suspended = 0;
2017 * console_cpu_notify - print deferred console messages after CPU hotplug
2020 * If printk() is called from a CPU that is not online yet, the messages
2021 * will be printed on the console only if there are CON_ANYTIME consoles.
2022 * This function is called when a new CPU comes online (or fails to come
2023 * up) or goes offline.
2025 static int console_cpu_notify(unsigned int cpu)
2027 if (!cpuhp_tasks_frozen) {
2028 /* If trylock fails, someone else is doing the printing */
2029 if (console_trylock())
2036 * console_lock - lock the console system for exclusive use.
2038 * Acquires a lock which guarantees that the caller has
2039 * exclusive access to the console system and the console_drivers list.
2041 * Can sleep, returns nothing.
2043 void console_lock(void)
2048 if (console_suspended)
2051 console_may_schedule = 1;
2053 EXPORT_SYMBOL(console_lock);
2056 * console_trylock - try to lock the console system for exclusive use.
2058 * Try to acquire a lock which guarantees that the caller has exclusive
2059 * access to the console system and the console_drivers list.
2061 * returns 1 on success, and 0 on failure to acquire the lock.
2063 int console_trylock(void)
2065 if (down_trylock_console_sem())
2067 if (console_suspended) {
2073 * When PREEMPT_COUNT disabled we can't reliably detect if it's
2074 * safe to schedule (e.g. calling printk while holding a spin_lock),
2075 * because preempt_disable()/preempt_enable() are just barriers there
2076 * and preempt_count() is always 0.
2078 * RCU read sections have a separate preemption counter when
2079 * PREEMPT_RCU enabled thus we must take extra care and check
2080 * rcu_preempt_depth(), otherwise RCU read sections modify
2083 console_may_schedule = !oops_in_progress &&
2085 !rcu_preempt_depth();
2088 EXPORT_SYMBOL(console_trylock);
2090 int is_console_locked(void)
2092 return console_locked;
2096 * Check if we have any console that is capable of printing while cpu is
2097 * booting or shutting down. Requires console_sem.
2099 static int have_callable_console(void)
2101 struct console *con;
2103 for_each_console(con)
2104 if ((con->flags & CON_ENABLED) &&
2105 (con->flags & CON_ANYTIME))
2112 * Can we actually use the console at this time on this cpu?
2114 * Console drivers may assume that per-cpu resources have been allocated. So
2115 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2116 * call them until this CPU is officially up.
2118 static inline int can_use_console(void)
2120 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2124 * console_unlock - unlock the console system
2126 * Releases the console_lock which the caller holds on the console system
2127 * and the console driver list.
2129 * While the console_lock was held, console output may have been buffered
2130 * by printk(). If this is the case, console_unlock(); emits
2131 * the output prior to releasing the lock.
2133 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2135 * console_unlock(); may be called from any context.
2137 void console_unlock(void)
2139 static char ext_text[CONSOLE_EXT_LOG_MAX];
2140 static char text[LOG_LINE_MAX + PREFIX_MAX];
2141 static u64 seen_seq;
2142 unsigned long flags;
2143 bool wake_klogd = false;
2144 bool do_cond_resched, retry;
2146 if (console_suspended) {
2152 * Console drivers are called with interrupts disabled, so
2153 * @console_may_schedule should be cleared before; however, we may
2154 * end up dumping a lot of lines, for example, if called from
2155 * console registration path, and should invoke cond_resched()
2156 * between lines if allowable. Not doing so can cause a very long
2157 * scheduling stall on a slow console leading to RCU stall and
2158 * softlockup warnings which exacerbate the issue with more
2159 * messages practically incapacitating the system.
2161 * console_trylock() is not able to detect the preemptive
2162 * context reliably. Therefore the value must be stored before
2163 * and cleared after the the "again" goto label.
2165 do_cond_resched = console_may_schedule;
2167 console_may_schedule = 0;
2170 * We released the console_sem lock, so we need to recheck if
2171 * cpu is online and (if not) is there at least one CON_ANYTIME
2174 if (!can_use_console()) {
2181 struct printk_log *msg;
2185 printk_safe_enter_irqsave(flags);
2186 raw_spin_lock(&logbuf_lock);
2187 if (seen_seq != log_next_seq) {
2189 seen_seq = log_next_seq;
2192 if (console_seq < log_first_seq) {
2193 len = sprintf(text, "** %u printk messages dropped ** ",
2194 (unsigned)(log_first_seq - console_seq));
2196 /* messages are gone, move to first one */
2197 console_seq = log_first_seq;
2198 console_idx = log_first_idx;
2203 if (console_seq == log_next_seq)
2206 msg = log_from_idx(console_idx);
2207 if (suppress_message_printing(msg->level)) {
2209 * Skip record we have buffered and already printed
2210 * directly to the console when we received it, and
2211 * record that has level above the console loglevel.
2213 console_idx = log_next(console_idx);
2218 len += msg_print_text(msg, false, text + len, sizeof(text) - len);
2219 if (nr_ext_console_drivers) {
2220 ext_len = msg_print_ext_header(ext_text,
2223 ext_len += msg_print_ext_body(ext_text + ext_len,
2224 sizeof(ext_text) - ext_len,
2225 log_dict(msg), msg->dict_len,
2226 log_text(msg), msg->text_len);
2228 console_idx = log_next(console_idx);
2230 raw_spin_unlock(&logbuf_lock);
2232 stop_critical_timings(); /* don't trace print latency */
2233 call_console_drivers(ext_text, ext_len, text, len);
2234 start_critical_timings();
2235 printk_safe_exit_irqrestore(flags);
2237 if (do_cond_resched)
2242 /* Release the exclusive_console once it is used */
2243 if (unlikely(exclusive_console))
2244 exclusive_console = NULL;
2246 raw_spin_unlock(&logbuf_lock);
2251 * Someone could have filled up the buffer again, so re-check if there's
2252 * something to flush. In case we cannot trylock the console_sem again,
2253 * there's a new owner and the console_unlock() from them will do the
2254 * flush, no worries.
2256 raw_spin_lock(&logbuf_lock);
2257 retry = console_seq != log_next_seq;
2258 raw_spin_unlock(&logbuf_lock);
2259 printk_safe_exit_irqrestore(flags);
2261 if (retry && console_trylock())
2267 EXPORT_SYMBOL(console_unlock);
2270 * console_conditional_schedule - yield the CPU if required
2272 * If the console code is currently allowed to sleep, and
2273 * if this CPU should yield the CPU to another task, do
2276 * Must be called within console_lock();.
2278 void __sched console_conditional_schedule(void)
2280 if (console_may_schedule)
2283 EXPORT_SYMBOL(console_conditional_schedule);
2285 void console_unblank(void)
2290 * console_unblank can no longer be called in interrupt context unless
2291 * oops_in_progress is set to 1..
2293 if (oops_in_progress) {
2294 if (down_trylock_console_sem() != 0)
2300 console_may_schedule = 0;
2302 if ((c->flags & CON_ENABLED) && c->unblank)
2308 * console_flush_on_panic - flush console content on panic
2310 * Immediately output all pending messages no matter what.
2312 void console_flush_on_panic(void)
2315 * If someone else is holding the console lock, trylock will fail
2316 * and may_schedule may be set. Ignore and proceed to unlock so
2317 * that messages are flushed out. As this can be called from any
2318 * context and we don't want to get preempted while flushing,
2319 * ensure may_schedule is cleared.
2322 console_may_schedule = 0;
2327 * Return the console tty driver structure and its associated index
2329 struct tty_driver *console_device(int *index)
2332 struct tty_driver *driver = NULL;
2335 for_each_console(c) {
2338 driver = c->device(c, index);
2347 * Prevent further output on the passed console device so that (for example)
2348 * serial drivers can disable console output before suspending a port, and can
2349 * re-enable output afterwards.
2351 void console_stop(struct console *console)
2354 console->flags &= ~CON_ENABLED;
2357 EXPORT_SYMBOL(console_stop);
2359 void console_start(struct console *console)
2362 console->flags |= CON_ENABLED;
2365 EXPORT_SYMBOL(console_start);
2367 static int __read_mostly keep_bootcon;
2369 static int __init keep_bootcon_setup(char *str)
2372 pr_info("debug: skip boot console de-registration.\n");
2377 early_param("keep_bootcon", keep_bootcon_setup);
2380 * The console driver calls this routine during kernel initialization
2381 * to register the console printing procedure with printk() and to
2382 * print any messages that were printed by the kernel before the
2383 * console driver was initialized.
2385 * This can happen pretty early during the boot process (because of
2386 * early_printk) - sometimes before setup_arch() completes - be careful
2387 * of what kernel features are used - they may not be initialised yet.
2389 * There are two types of consoles - bootconsoles (early_printk) and
2390 * "real" consoles (everything which is not a bootconsole) which are
2391 * handled differently.
2392 * - Any number of bootconsoles can be registered at any time.
2393 * - As soon as a "real" console is registered, all bootconsoles
2394 * will be unregistered automatically.
2395 * - Once a "real" console is registered, any attempt to register a
2396 * bootconsoles will be rejected
2398 void register_console(struct console *newcon)
2401 unsigned long flags;
2402 struct console *bcon = NULL;
2403 struct console_cmdline *c;
2404 static bool has_preferred;
2406 if (console_drivers)
2407 for_each_console(bcon)
2408 if (WARN(bcon == newcon,
2409 "console '%s%d' already registered\n",
2410 bcon->name, bcon->index))
2414 * before we register a new CON_BOOT console, make sure we don't
2415 * already have a valid console
2417 if (console_drivers && newcon->flags & CON_BOOT) {
2418 /* find the last or real console */
2419 for_each_console(bcon) {
2420 if (!(bcon->flags & CON_BOOT)) {
2421 pr_info("Too late to register bootconsole %s%d\n",
2422 newcon->name, newcon->index);
2428 if (console_drivers && console_drivers->flags & CON_BOOT)
2429 bcon = console_drivers;
2431 if (!has_preferred || bcon || !console_drivers)
2432 has_preferred = preferred_console >= 0;
2435 * See if we want to use this console driver. If we
2436 * didn't select a console we take the first one
2437 * that registers here.
2439 if (!has_preferred) {
2440 if (newcon->index < 0)
2442 if (newcon->setup == NULL ||
2443 newcon->setup(newcon, NULL) == 0) {
2444 newcon->flags |= CON_ENABLED;
2445 if (newcon->device) {
2446 newcon->flags |= CON_CONSDEV;
2447 has_preferred = true;
2453 * See if this console matches one we selected on
2456 for (i = 0, c = console_cmdline;
2457 i < MAX_CMDLINECONSOLES && c->name[0];
2459 if (!newcon->match ||
2460 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2461 /* default matching */
2462 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2463 if (strcmp(c->name, newcon->name) != 0)
2465 if (newcon->index >= 0 &&
2466 newcon->index != c->index)
2468 if (newcon->index < 0)
2469 newcon->index = c->index;
2471 if (_braille_register_console(newcon, c))
2474 if (newcon->setup &&
2475 newcon->setup(newcon, c->options) != 0)
2479 newcon->flags |= CON_ENABLED;
2480 if (i == preferred_console) {
2481 newcon->flags |= CON_CONSDEV;
2482 has_preferred = true;
2487 if (!(newcon->flags & CON_ENABLED))
2491 * If we have a bootconsole, and are switching to a real console,
2492 * don't print everything out again, since when the boot console, and
2493 * the real console are the same physical device, it's annoying to
2494 * see the beginning boot messages twice
2496 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2497 newcon->flags &= ~CON_PRINTBUFFER;
2500 * Put this console in the list - keep the
2501 * preferred driver at the head of the list.
2504 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2505 newcon->next = console_drivers;
2506 console_drivers = newcon;
2508 newcon->next->flags &= ~CON_CONSDEV;
2510 newcon->next = console_drivers->next;
2511 console_drivers->next = newcon;
2514 if (newcon->flags & CON_EXTENDED)
2515 if (!nr_ext_console_drivers++)
2516 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2518 if (newcon->flags & CON_PRINTBUFFER) {
2520 * console_unlock(); will print out the buffered messages
2523 logbuf_lock_irqsave(flags);
2524 console_seq = syslog_seq;
2525 console_idx = syslog_idx;
2526 logbuf_unlock_irqrestore(flags);
2528 * We're about to replay the log buffer. Only do this to the
2529 * just-registered console to avoid excessive message spam to
2530 * the already-registered consoles.
2532 exclusive_console = newcon;
2535 console_sysfs_notify();
2538 * By unregistering the bootconsoles after we enable the real console
2539 * we get the "console xxx enabled" message on all the consoles -
2540 * boot consoles, real consoles, etc - this is to ensure that end
2541 * users know there might be something in the kernel's log buffer that
2542 * went to the bootconsole (that they do not see on the real console)
2544 pr_info("%sconsole [%s%d] enabled\n",
2545 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2546 newcon->name, newcon->index);
2548 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2550 /* We need to iterate through all boot consoles, to make
2551 * sure we print everything out, before we unregister them.
2553 for_each_console(bcon)
2554 if (bcon->flags & CON_BOOT)
2555 unregister_console(bcon);
2558 EXPORT_SYMBOL(register_console);
2560 int unregister_console(struct console *console)
2562 struct console *a, *b;
2565 pr_info("%sconsole [%s%d] disabled\n",
2566 (console->flags & CON_BOOT) ? "boot" : "" ,
2567 console->name, console->index);
2569 res = _braille_unregister_console(console);
2575 if (console_drivers == console) {
2576 console_drivers=console->next;
2578 } else if (console_drivers) {
2579 for (a=console_drivers->next, b=console_drivers ;
2580 a; b=a, a=b->next) {
2589 if (!res && (console->flags & CON_EXTENDED))
2590 nr_ext_console_drivers--;
2593 * If this isn't the last console and it has CON_CONSDEV set, we
2594 * need to set it on the next preferred console.
2596 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2597 console_drivers->flags |= CON_CONSDEV;
2599 console->flags &= ~CON_ENABLED;
2601 console_sysfs_notify();
2604 EXPORT_SYMBOL(unregister_console);
2607 * Initialize the console device. This is called *early*, so
2608 * we can't necessarily depend on lots of kernel help here.
2609 * Just do some early initializations, and do the complex setup
2612 void __init console_init(void)
2616 /* Setup the default TTY line discipline. */
2620 * set up the console device so that later boot sequences can
2621 * inform about problems etc..
2623 call = __con_initcall_start;
2624 while (call < __con_initcall_end) {
2631 * Some boot consoles access data that is in the init section and which will
2632 * be discarded after the initcalls have been run. To make sure that no code
2633 * will access this data, unregister the boot consoles in a late initcall.
2635 * If for some reason, such as deferred probe or the driver being a loadable
2636 * module, the real console hasn't registered yet at this point, there will
2637 * be a brief interval in which no messages are logged to the console, which
2638 * makes it difficult to diagnose problems that occur during this time.
2640 * To mitigate this problem somewhat, only unregister consoles whose memory
2641 * intersects with the init section. Note that all other boot consoles will
2642 * get unregistred when the real preferred console is registered.
2644 static int __init printk_late_init(void)
2646 struct console *con;
2649 for_each_console(con) {
2650 if (!(con->flags & CON_BOOT))
2653 /* Check addresses that might be used for enabled consoles. */
2654 if (init_section_intersects(con, sizeof(*con)) ||
2655 init_section_contains(con->write, 0) ||
2656 init_section_contains(con->read, 0) ||
2657 init_section_contains(con->device, 0) ||
2658 init_section_contains(con->unblank, 0) ||
2659 init_section_contains(con->data, 0)) {
2661 * Please, consider moving the reported consoles out
2662 * of the init section.
2664 pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n",
2665 con->name, con->index);
2666 unregister_console(con);
2669 ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL,
2670 console_cpu_notify);
2672 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online",
2673 console_cpu_notify, NULL);
2677 late_initcall(printk_late_init);
2679 #if defined CONFIG_PRINTK
2681 * Delayed printk version, for scheduler-internal messages:
2683 #define PRINTK_PENDING_WAKEUP 0x01
2684 #define PRINTK_PENDING_OUTPUT 0x02
2686 static DEFINE_PER_CPU(int, printk_pending);
2688 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2690 int pending = __this_cpu_xchg(printk_pending, 0);
2692 if (pending & PRINTK_PENDING_OUTPUT) {
2693 /* If trylock fails, someone else is doing the printing */
2694 if (console_trylock())
2698 if (pending & PRINTK_PENDING_WAKEUP)
2699 wake_up_interruptible(&log_wait);
2702 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2703 .func = wake_up_klogd_work_func,
2704 .flags = IRQ_WORK_LAZY,
2707 void wake_up_klogd(void)
2710 if (waitqueue_active(&log_wait)) {
2711 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2712 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2717 int vprintk_deferred(const char *fmt, va_list args)
2721 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2724 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2725 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2731 int printk_deferred(const char *fmt, ...)
2736 va_start(args, fmt);
2737 r = vprintk_deferred(fmt, args);
2744 * printk rate limiting, lifted from the networking subsystem.
2746 * This enforces a rate limit: not more than 10 kernel messages
2747 * every 5s to make a denial-of-service attack impossible.
2749 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2751 int __printk_ratelimit(const char *func)
2753 return ___ratelimit(&printk_ratelimit_state, func);
2755 EXPORT_SYMBOL(__printk_ratelimit);
2758 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2759 * @caller_jiffies: pointer to caller's state
2760 * @interval_msecs: minimum interval between prints
2762 * printk_timed_ratelimit() returns true if more than @interval_msecs
2763 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2766 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2767 unsigned int interval_msecs)
2769 unsigned long elapsed = jiffies - *caller_jiffies;
2771 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2774 *caller_jiffies = jiffies;
2777 EXPORT_SYMBOL(printk_timed_ratelimit);
2779 static DEFINE_SPINLOCK(dump_list_lock);
2780 static LIST_HEAD(dump_list);
2783 * kmsg_dump_register - register a kernel log dumper.
2784 * @dumper: pointer to the kmsg_dumper structure
2786 * Adds a kernel log dumper to the system. The dump callback in the
2787 * structure will be called when the kernel oopses or panics and must be
2788 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2790 int kmsg_dump_register(struct kmsg_dumper *dumper)
2792 unsigned long flags;
2795 /* The dump callback needs to be set */
2799 spin_lock_irqsave(&dump_list_lock, flags);
2800 /* Don't allow registering multiple times */
2801 if (!dumper->registered) {
2802 dumper->registered = 1;
2803 list_add_tail_rcu(&dumper->list, &dump_list);
2806 spin_unlock_irqrestore(&dump_list_lock, flags);
2810 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2813 * kmsg_dump_unregister - unregister a kmsg dumper.
2814 * @dumper: pointer to the kmsg_dumper structure
2816 * Removes a dump device from the system. Returns zero on success and
2817 * %-EINVAL otherwise.
2819 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2821 unsigned long flags;
2824 spin_lock_irqsave(&dump_list_lock, flags);
2825 if (dumper->registered) {
2826 dumper->registered = 0;
2827 list_del_rcu(&dumper->list);
2830 spin_unlock_irqrestore(&dump_list_lock, flags);
2835 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2837 static bool always_kmsg_dump;
2838 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2841 * kmsg_dump - dump kernel log to kernel message dumpers.
2842 * @reason: the reason (oops, panic etc) for dumping
2844 * Call each of the registered dumper's dump() callback, which can
2845 * retrieve the kmsg records with kmsg_dump_get_line() or
2846 * kmsg_dump_get_buffer().
2848 void kmsg_dump(enum kmsg_dump_reason reason)
2850 struct kmsg_dumper *dumper;
2851 unsigned long flags;
2853 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2857 list_for_each_entry_rcu(dumper, &dump_list, list) {
2858 if (dumper->max_reason && reason > dumper->max_reason)
2861 /* initialize iterator with data about the stored records */
2862 dumper->active = true;
2864 logbuf_lock_irqsave(flags);
2865 dumper->cur_seq = clear_seq;
2866 dumper->cur_idx = clear_idx;
2867 dumper->next_seq = log_next_seq;
2868 dumper->next_idx = log_next_idx;
2869 logbuf_unlock_irqrestore(flags);
2871 /* invoke dumper which will iterate over records */
2872 dumper->dump(dumper, reason);
2874 /* reset iterator */
2875 dumper->active = false;
2881 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2882 * @dumper: registered kmsg dumper
2883 * @syslog: include the "<4>" prefixes
2884 * @line: buffer to copy the line to
2885 * @size: maximum size of the buffer
2886 * @len: length of line placed into buffer
2888 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2889 * record, and copy one record into the provided buffer.
2891 * Consecutive calls will return the next available record moving
2892 * towards the end of the buffer with the youngest messages.
2894 * A return value of FALSE indicates that there are no more records to
2897 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2899 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2900 char *line, size_t size, size_t *len)
2902 struct printk_log *msg;
2906 if (!dumper->active)
2909 if (dumper->cur_seq < log_first_seq) {
2910 /* messages are gone, move to first available one */
2911 dumper->cur_seq = log_first_seq;
2912 dumper->cur_idx = log_first_idx;
2916 if (dumper->cur_seq >= log_next_seq)
2919 msg = log_from_idx(dumper->cur_idx);
2920 l = msg_print_text(msg, syslog, line, size);
2922 dumper->cur_idx = log_next(dumper->cur_idx);
2932 * kmsg_dump_get_line - retrieve one kmsg log line
2933 * @dumper: registered kmsg dumper
2934 * @syslog: include the "<4>" prefixes
2935 * @line: buffer to copy the line to
2936 * @size: maximum size of the buffer
2937 * @len: length of line placed into buffer
2939 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2940 * record, and copy one record into the provided buffer.
2942 * Consecutive calls will return the next available record moving
2943 * towards the end of the buffer with the youngest messages.
2945 * A return value of FALSE indicates that there are no more records to
2948 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2949 char *line, size_t size, size_t *len)
2951 unsigned long flags;
2954 logbuf_lock_irqsave(flags);
2955 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2956 logbuf_unlock_irqrestore(flags);
2960 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2963 * kmsg_dump_get_buffer - copy kmsg log lines
2964 * @dumper: registered kmsg dumper
2965 * @syslog: include the "<4>" prefixes
2966 * @buf: buffer to copy the line to
2967 * @size: maximum size of the buffer
2968 * @len: length of line placed into buffer
2970 * Start at the end of the kmsg buffer and fill the provided buffer
2971 * with as many of the the *youngest* kmsg records that fit into it.
2972 * If the buffer is large enough, all available kmsg records will be
2973 * copied with a single call.
2975 * Consecutive calls will fill the buffer with the next block of
2976 * available older records, not including the earlier retrieved ones.
2978 * A return value of FALSE indicates that there are no more records to
2981 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2982 char *buf, size_t size, size_t *len)
2984 unsigned long flags;
2992 if (!dumper->active)
2995 logbuf_lock_irqsave(flags);
2996 if (dumper->cur_seq < log_first_seq) {
2997 /* messages are gone, move to first available one */
2998 dumper->cur_seq = log_first_seq;
2999 dumper->cur_idx = log_first_idx;
3003 if (dumper->cur_seq >= dumper->next_seq) {
3004 logbuf_unlock_irqrestore(flags);
3008 /* calculate length of entire buffer */
3009 seq = dumper->cur_seq;
3010 idx = dumper->cur_idx;
3011 while (seq < dumper->next_seq) {
3012 struct printk_log *msg = log_from_idx(idx);
3014 l += msg_print_text(msg, true, NULL, 0);
3015 idx = log_next(idx);
3019 /* move first record forward until length fits into the buffer */
3020 seq = dumper->cur_seq;
3021 idx = dumper->cur_idx;
3022 while (l > size && seq < dumper->next_seq) {
3023 struct printk_log *msg = log_from_idx(idx);
3025 l -= msg_print_text(msg, true, NULL, 0);
3026 idx = log_next(idx);
3030 /* last message in next interation */
3035 while (seq < dumper->next_seq) {
3036 struct printk_log *msg = log_from_idx(idx);
3038 l += msg_print_text(msg, syslog, buf + l, size - l);
3039 idx = log_next(idx);
3043 dumper->next_seq = next_seq;
3044 dumper->next_idx = next_idx;
3046 logbuf_unlock_irqrestore(flags);
3052 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3055 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3056 * @dumper: registered kmsg dumper
3058 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3059 * kmsg_dump_get_buffer() can be called again and used multiple
3060 * times within the same dumper.dump() callback.
3062 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3064 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3066 dumper->cur_seq = clear_seq;
3067 dumper->cur_idx = clear_idx;
3068 dumper->next_seq = log_next_seq;
3069 dumper->next_idx = log_next_idx;
3073 * kmsg_dump_rewind - reset the interator
3074 * @dumper: registered kmsg dumper
3076 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3077 * kmsg_dump_get_buffer() can be called again and used multiple
3078 * times within the same dumper.dump() callback.
3080 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3082 unsigned long flags;
3084 logbuf_lock_irqsave(flags);
3085 kmsg_dump_rewind_nolock(dumper);
3086 logbuf_unlock_irqrestore(flags);
3088 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3090 static char dump_stack_arch_desc_str[128];
3093 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3094 * @fmt: printf-style format string
3095 * @...: arguments for the format string
3097 * The configured string will be printed right after utsname during task
3098 * dumps. Usually used to add arch-specific system identifiers. If an
3099 * arch wants to make use of such an ID string, it should initialize this
3100 * as soon as possible during boot.
3102 void __init dump_stack_set_arch_desc(const char *fmt, ...)
3106 va_start(args, fmt);
3107 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3113 * dump_stack_print_info - print generic debug info for dump_stack()
3114 * @log_lvl: log level
3116 * Arch-specific dump_stack() implementations can use this function to
3117 * print out the same debug information as the generic dump_stack().
3119 void dump_stack_print_info(const char *log_lvl)
3121 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3122 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3123 print_tainted(), init_utsname()->release,
3124 (int)strcspn(init_utsname()->version, " "),
3125 init_utsname()->version);
3127 if (dump_stack_arch_desc_str[0] != '\0')
3128 printk("%sHardware name: %s\n",
3129 log_lvl, dump_stack_arch_desc_str);
3131 print_worker_info(log_lvl, current);
3135 * show_regs_print_info - print generic debug info for show_regs()
3136 * @log_lvl: log level
3138 * show_regs() implementations can use this function to print out generic
3139 * debug information.
3141 void show_regs_print_info(const char *log_lvl)
3143 dump_stack_print_info(log_lvl);
3145 printk("%stask: %p task.stack: %p\n",
3146 log_lvl, current, task_stack_page(current));