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/kexec.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>
49 #include <linux/uaccess.h>
50 #include <asm/sections.h>
52 #define CREATE_TRACE_POINTS
53 #include <trace/events/printk.h>
55 #include "console_cmdline.h"
59 int console_printk
[4] = {
60 CONSOLE_LOGLEVEL_DEFAULT
, /* console_loglevel */
61 MESSAGE_LOGLEVEL_DEFAULT
, /* default_message_loglevel */
62 CONSOLE_LOGLEVEL_MIN
, /* minimum_console_loglevel */
63 CONSOLE_LOGLEVEL_DEFAULT
, /* default_console_loglevel */
67 * Low level drivers may need that to know if they can schedule in
68 * their unblank() callback or not. So let's export it.
71 EXPORT_SYMBOL(oops_in_progress
);
74 * console_sem protects the console_drivers list, and also
75 * provides serialisation for access to the entire console
78 static DEFINE_SEMAPHORE(console_sem
);
79 struct console
*console_drivers
;
80 EXPORT_SYMBOL_GPL(console_drivers
);
83 static struct lockdep_map console_lock_dep_map
= {
84 .name
= "console_lock"
88 enum devkmsg_log_bits
{
89 __DEVKMSG_LOG_BIT_ON
= 0,
90 __DEVKMSG_LOG_BIT_OFF
,
91 __DEVKMSG_LOG_BIT_LOCK
,
94 enum devkmsg_log_masks
{
95 DEVKMSG_LOG_MASK_ON
= BIT(__DEVKMSG_LOG_BIT_ON
),
96 DEVKMSG_LOG_MASK_OFF
= BIT(__DEVKMSG_LOG_BIT_OFF
),
97 DEVKMSG_LOG_MASK_LOCK
= BIT(__DEVKMSG_LOG_BIT_LOCK
),
100 /* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
101 #define DEVKMSG_LOG_MASK_DEFAULT 0
103 static unsigned int __read_mostly devkmsg_log
= DEVKMSG_LOG_MASK_DEFAULT
;
105 static int __control_devkmsg(char *str
)
110 if (!strncmp(str
, "on", 2)) {
111 devkmsg_log
= DEVKMSG_LOG_MASK_ON
;
113 } else if (!strncmp(str
, "off", 3)) {
114 devkmsg_log
= DEVKMSG_LOG_MASK_OFF
;
116 } else if (!strncmp(str
, "ratelimit", 9)) {
117 devkmsg_log
= DEVKMSG_LOG_MASK_DEFAULT
;
123 static int __init
control_devkmsg(char *str
)
125 if (__control_devkmsg(str
) < 0)
129 * Set sysctl string accordingly:
131 if (devkmsg_log
== DEVKMSG_LOG_MASK_ON
) {
132 memset(devkmsg_log_str
, 0, DEVKMSG_STR_MAX_SIZE
);
133 strncpy(devkmsg_log_str
, "on", 2);
134 } else if (devkmsg_log
== DEVKMSG_LOG_MASK_OFF
) {
135 memset(devkmsg_log_str
, 0, DEVKMSG_STR_MAX_SIZE
);
136 strncpy(devkmsg_log_str
, "off", 3);
138 /* else "ratelimit" which is set by default. */
141 * Sysctl cannot change it anymore. The kernel command line setting of
142 * this parameter is to force the setting to be permanent throughout the
143 * runtime of the system. This is a precation measure against userspace
144 * trying to be a smarta** and attempting to change it up on us.
146 devkmsg_log
|= DEVKMSG_LOG_MASK_LOCK
;
150 __setup("printk.devkmsg=", control_devkmsg
);
152 char devkmsg_log_str
[DEVKMSG_STR_MAX_SIZE
] = "ratelimit";
154 int devkmsg_sysctl_set_loglvl(struct ctl_table
*table
, int write
,
155 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
157 char old_str
[DEVKMSG_STR_MAX_SIZE
];
162 if (devkmsg_log
& DEVKMSG_LOG_MASK_LOCK
)
166 strncpy(old_str
, devkmsg_log_str
, DEVKMSG_STR_MAX_SIZE
);
169 err
= proc_dostring(table
, write
, buffer
, lenp
, ppos
);
174 err
= __control_devkmsg(devkmsg_log_str
);
177 * Do not accept an unknown string OR a known string with
180 if (err
< 0 || (err
+ 1 != *lenp
)) {
182 /* ... and restore old setting. */
184 strncpy(devkmsg_log_str
, old_str
, DEVKMSG_STR_MAX_SIZE
);
194 * Number of registered extended console drivers.
196 * If extended consoles are present, in-kernel cont reassembly is disabled
197 * and each fragment is stored as a separate log entry with proper
198 * continuation flag so that every emitted message has full metadata. This
199 * doesn't change the result for regular consoles or /proc/kmsg. For
200 * /dev/kmsg, as long as the reader concatenates messages according to
201 * consecutive continuation flags, the end result should be the same too.
203 static int nr_ext_console_drivers
;
206 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
207 * macros instead of functions so that _RET_IP_ contains useful information.
209 #define down_console_sem() do { \
211 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
214 static int __down_trylock_console_sem(unsigned long ip
)
220 * Here and in __up_console_sem() we need to be in safe mode,
221 * because spindump/WARN/etc from under console ->lock will
222 * deadlock in printk()->down_trylock_console_sem() otherwise.
224 printk_safe_enter_irqsave(flags
);
225 lock_failed
= down_trylock(&console_sem
);
226 printk_safe_exit_irqrestore(flags
);
230 mutex_acquire(&console_lock_dep_map
, 0, 1, ip
);
233 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
235 static void __up_console_sem(unsigned long ip
)
239 mutex_release(&console_lock_dep_map
, 1, ip
);
241 printk_safe_enter_irqsave(flags
);
243 printk_safe_exit_irqrestore(flags
);
245 #define up_console_sem() __up_console_sem(_RET_IP_)
248 * This is used for debugging the mess that is the VT code by
249 * keeping track if we have the console semaphore held. It's
250 * definitely not the perfect debug tool (we don't know if _WE_
251 * hold it and are racing, but it helps tracking those weird code
252 * paths in the console code where we end up in places I want
253 * locked without the console sempahore held).
255 static int console_locked
, console_suspended
;
258 * If exclusive_console is non-NULL then only this console is to be printed to.
260 static struct console
*exclusive_console
;
263 * Array of consoles built from command line options (console=)
266 #define MAX_CMDLINECONSOLES 8
268 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
270 static int selected_console
= -1;
271 static int preferred_console
= -1;
272 int console_set_on_cmdline
;
273 EXPORT_SYMBOL(console_set_on_cmdline
);
275 /* Flag: console code may call schedule() */
276 static int console_may_schedule
;
279 * The printk log buffer consists of a chain of concatenated variable
280 * length records. Every record starts with a record header, containing
281 * the overall length of the record.
283 * The heads to the first and last entry in the buffer, as well as the
284 * sequence numbers of these entries are maintained when messages are
287 * If the heads indicate available messages, the length in the header
288 * tells the start next message. A length == 0 for the next message
289 * indicates a wrap-around to the beginning of the buffer.
291 * Every record carries the monotonic timestamp in microseconds, as well as
292 * the standard userspace syslog level and syslog facility. The usual
293 * kernel messages use LOG_KERN; userspace-injected messages always carry
294 * a matching syslog facility, by default LOG_USER. The origin of every
295 * message can be reliably determined that way.
297 * The human readable log message directly follows the message header. The
298 * length of the message text is stored in the header, the stored message
301 * Optionally, a message can carry a dictionary of properties (key/value pairs),
302 * to provide userspace with a machine-readable message context.
304 * Examples for well-defined, commonly used property names are:
305 * DEVICE=b12:8 device identifier
309 * +sound:card0 subsystem:devname
310 * SUBSYSTEM=pci driver-core subsystem name
312 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
313 * follows directly after a '=' character. Every property is terminated by
314 * a '\0' character. The last property is not terminated.
316 * Example of a message structure:
317 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
318 * 0008 34 00 record is 52 bytes long
319 * 000a 0b 00 text is 11 bytes long
320 * 000c 1f 00 dictionary is 23 bytes long
321 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
322 * 0010 69 74 27 73 20 61 20 6c "it's a l"
324 * 001b 44 45 56 49 43 "DEVIC"
325 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
326 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
328 * 0032 00 00 00 padding to next message header
330 * The 'struct printk_log' buffer header must never be directly exported to
331 * userspace, it is a kernel-private implementation detail that might
332 * need to be changed in the future, when the requirements change.
334 * /dev/kmsg exports the structured data in the following line format:
335 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
337 * Users of the export format should ignore possible additional values
338 * separated by ',', and find the message after the ';' character.
340 * The optional key/value pairs are attached as continuation lines starting
341 * with a space character and terminated by a newline. All possible
342 * non-prinatable characters are escaped in the "\xff" notation.
346 LOG_NOCONS
= 1, /* already flushed, do not print to console */
347 LOG_NEWLINE
= 2, /* text ended with a newline */
348 LOG_PREFIX
= 4, /* text started with a prefix */
349 LOG_CONT
= 8, /* text is a fragment of a continuation line */
353 u64 ts_nsec
; /* timestamp in nanoseconds */
354 u16 len
; /* length of entire record */
355 u16 text_len
; /* length of text buffer */
356 u16 dict_len
; /* length of dictionary buffer */
357 u8 facility
; /* syslog facility */
358 u8 flags
:5; /* internal record flags */
359 u8 level
:3; /* syslog level */
361 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
362 __packed
__aligned(4)
367 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
368 * within the scheduler's rq lock. It must be released before calling
369 * console_unlock() or anything else that might wake up a process.
371 DEFINE_RAW_SPINLOCK(logbuf_lock
);
374 * Helper macros to lock/unlock logbuf_lock and switch between
375 * printk-safe/unsafe modes.
377 #define logbuf_lock_irq() \
379 printk_safe_enter_irq(); \
380 raw_spin_lock(&logbuf_lock); \
383 #define logbuf_unlock_irq() \
385 raw_spin_unlock(&logbuf_lock); \
386 printk_safe_exit_irq(); \
389 #define logbuf_lock_irqsave(flags) \
391 printk_safe_enter_irqsave(flags); \
392 raw_spin_lock(&logbuf_lock); \
395 #define logbuf_unlock_irqrestore(flags) \
397 raw_spin_unlock(&logbuf_lock); \
398 printk_safe_exit_irqrestore(flags); \
402 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
403 /* the next printk record to read by syslog(READ) or /proc/kmsg */
404 static u64 syslog_seq
;
405 static u32 syslog_idx
;
406 static size_t syslog_partial
;
408 /* index and sequence number of the first record stored in the buffer */
409 static u64 log_first_seq
;
410 static u32 log_first_idx
;
412 /* index and sequence number of the next record to store in the buffer */
413 static u64 log_next_seq
;
414 static u32 log_next_idx
;
416 /* the next printk record to write to the console */
417 static u64 console_seq
;
418 static u32 console_idx
;
420 /* the next printk record to read after the last 'clear' command */
421 static u64 clear_seq
;
422 static u32 clear_idx
;
424 #define PREFIX_MAX 32
425 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
427 #define LOG_LEVEL(v) ((v) & 0x07)
428 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
431 #define LOG_ALIGN __alignof__(struct printk_log)
432 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
433 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
434 static char *log_buf
= __log_buf
;
435 static u32 log_buf_len
= __LOG_BUF_LEN
;
437 /* Return log buffer address */
438 char *log_buf_addr_get(void)
443 /* Return log buffer size */
444 u32
log_buf_len_get(void)
449 /* human readable text of the record */
450 static char *log_text(const struct printk_log
*msg
)
452 return (char *)msg
+ sizeof(struct printk_log
);
455 /* optional key/value pair dictionary attached to the record */
456 static char *log_dict(const struct printk_log
*msg
)
458 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
461 /* get record by index; idx must point to valid msg */
462 static struct printk_log
*log_from_idx(u32 idx
)
464 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
467 * A length == 0 record is the end of buffer marker. Wrap around and
468 * read the message at the start of the buffer.
471 return (struct printk_log
*)log_buf
;
475 /* get next record; idx must point to valid msg */
476 static u32
log_next(u32 idx
)
478 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
480 /* length == 0 indicates the end of the buffer; wrap */
482 * A length == 0 record is the end of buffer marker. Wrap around and
483 * read the message at the start of the buffer as *this* one, and
484 * return the one after that.
487 msg
= (struct printk_log
*)log_buf
;
490 return idx
+ msg
->len
;
494 * Check whether there is enough free space for the given message.
496 * The same values of first_idx and next_idx mean that the buffer
497 * is either empty or full.
499 * If the buffer is empty, we must respect the position of the indexes.
500 * They cannot be reset to the beginning of the buffer.
502 static int logbuf_has_space(u32 msg_size
, bool empty
)
506 if (log_next_idx
> log_first_idx
|| empty
)
507 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
509 free
= log_first_idx
- log_next_idx
;
512 * We need space also for an empty header that signalizes wrapping
515 return free
>= msg_size
+ sizeof(struct printk_log
);
518 static int log_make_free_space(u32 msg_size
)
520 while (log_first_seq
< log_next_seq
&&
521 !logbuf_has_space(msg_size
, false)) {
522 /* drop old messages until we have enough contiguous space */
523 log_first_idx
= log_next(log_first_idx
);
527 if (clear_seq
< log_first_seq
) {
528 clear_seq
= log_first_seq
;
529 clear_idx
= log_first_idx
;
532 /* sequence numbers are equal, so the log buffer is empty */
533 if (logbuf_has_space(msg_size
, log_first_seq
== log_next_seq
))
539 /* compute the message size including the padding bytes */
540 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
544 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
545 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
552 * Define how much of the log buffer we could take at maximum. The value
553 * must be greater than two. Note that only half of the buffer is available
554 * when the index points to the middle.
556 #define MAX_LOG_TAKE_PART 4
557 static const char trunc_msg
[] = "<truncated>";
559 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
560 u16
*dict_len
, u32
*pad_len
)
563 * The message should not take the whole buffer. Otherwise, it might
564 * get removed too soon.
566 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
567 if (*text_len
> max_text_len
)
568 *text_len
= max_text_len
;
569 /* enable the warning message */
570 *trunc_msg_len
= strlen(trunc_msg
);
571 /* disable the "dict" completely */
573 /* compute the size again, count also the warning message */
574 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
577 /* insert record into the buffer, discard old ones, update heads */
578 static int log_store(int facility
, int level
,
579 enum log_flags flags
, u64 ts_nsec
,
580 const char *dict
, u16 dict_len
,
581 const char *text
, u16 text_len
)
583 struct printk_log
*msg
;
585 u16 trunc_msg_len
= 0;
587 /* number of '\0' padding bytes to next message */
588 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
590 if (log_make_free_space(size
)) {
591 /* truncate the message if it is too long for empty buffer */
592 size
= truncate_msg(&text_len
, &trunc_msg_len
,
593 &dict_len
, &pad_len
);
594 /* survive when the log buffer is too small for trunc_msg */
595 if (log_make_free_space(size
))
599 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
601 * This message + an additional empty header does not fit
602 * at the end of the buffer. Add an empty header with len == 0
603 * to signify a wrap around.
605 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
610 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
611 memcpy(log_text(msg
), text
, text_len
);
612 msg
->text_len
= text_len
;
614 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
615 msg
->text_len
+= trunc_msg_len
;
617 memcpy(log_dict(msg
), dict
, dict_len
);
618 msg
->dict_len
= dict_len
;
619 msg
->facility
= facility
;
620 msg
->level
= level
& 7;
621 msg
->flags
= flags
& 0x1f;
623 msg
->ts_nsec
= ts_nsec
;
625 msg
->ts_nsec
= local_clock();
626 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
630 log_next_idx
+= msg
->len
;
633 return msg
->text_len
;
636 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
638 static int syslog_action_restricted(int type
)
643 * Unless restricted, we allow "read all" and "get buffer size"
646 return type
!= SYSLOG_ACTION_READ_ALL
&&
647 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
650 int check_syslog_permissions(int type
, int source
)
653 * If this is from /proc/kmsg and we've already opened it, then we've
654 * already done the capabilities checks at open time.
656 if (source
== SYSLOG_FROM_PROC
&& type
!= SYSLOG_ACTION_OPEN
)
659 if (syslog_action_restricted(type
)) {
660 if (capable(CAP_SYSLOG
))
663 * For historical reasons, accept CAP_SYS_ADMIN too, with
666 if (capable(CAP_SYS_ADMIN
)) {
667 pr_warn_once("%s (%d): Attempt to access syslog with "
668 "CAP_SYS_ADMIN but no CAP_SYSLOG "
670 current
->comm
, task_pid_nr(current
));
676 return security_syslog(type
);
678 EXPORT_SYMBOL_GPL(check_syslog_permissions
);
680 static void append_char(char **pp
, char *e
, char c
)
686 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
687 struct printk_log
*msg
, u64 seq
)
689 u64 ts_usec
= msg
->ts_nsec
;
691 do_div(ts_usec
, 1000);
693 return scnprintf(buf
, size
, "%u,%llu,%llu,%c;",
694 (msg
->facility
<< 3) | msg
->level
, seq
, ts_usec
,
695 msg
->flags
& LOG_CONT
? 'c' : '-');
698 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
699 char *dict
, size_t dict_len
,
700 char *text
, size_t text_len
)
702 char *p
= buf
, *e
= buf
+ size
;
705 /* escape non-printable characters */
706 for (i
= 0; i
< text_len
; i
++) {
707 unsigned char c
= text
[i
];
709 if (c
< ' ' || c
>= 127 || c
== '\\')
710 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
712 append_char(&p
, e
, c
);
714 append_char(&p
, e
, '\n');
719 for (i
= 0; i
< dict_len
; i
++) {
720 unsigned char c
= dict
[i
];
723 append_char(&p
, e
, ' ');
728 append_char(&p
, e
, '\n');
733 if (c
< ' ' || c
>= 127 || c
== '\\') {
734 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
738 append_char(&p
, e
, c
);
740 append_char(&p
, e
, '\n');
746 /* /dev/kmsg - userspace message inject/listen interface */
747 struct devkmsg_user
{
750 struct ratelimit_state rs
;
752 char buf
[CONSOLE_EXT_LOG_MAX
];
755 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
758 int level
= default_message_loglevel
;
759 int facility
= 1; /* LOG_USER */
760 struct file
*file
= iocb
->ki_filp
;
761 struct devkmsg_user
*user
= file
->private_data
;
762 size_t len
= iov_iter_count(from
);
765 if (!user
|| len
> LOG_LINE_MAX
)
768 /* Ignore when user logging is disabled. */
769 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
772 /* Ratelimit when not explicitly enabled. */
773 if (!(devkmsg_log
& DEVKMSG_LOG_MASK_ON
)) {
774 if (!___ratelimit(&user
->rs
, current
->comm
))
778 buf
= kmalloc(len
+1, GFP_KERNEL
);
783 if (!copy_from_iter_full(buf
, len
, from
)) {
789 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
790 * the decimal value represents 32bit, the lower 3 bit are the log
791 * level, the rest are the log facility.
793 * If no prefix or no userspace facility is specified, we
794 * enforce LOG_USER, to be able to reliably distinguish
795 * kernel-generated messages from userspace-injected ones.
798 if (line
[0] == '<') {
802 u
= simple_strtoul(line
+ 1, &endp
, 10);
803 if (endp
&& endp
[0] == '>') {
804 level
= LOG_LEVEL(u
);
805 if (LOG_FACILITY(u
) != 0)
806 facility
= LOG_FACILITY(u
);
813 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
818 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
819 size_t count
, loff_t
*ppos
)
821 struct devkmsg_user
*user
= file
->private_data
;
822 struct printk_log
*msg
;
829 ret
= mutex_lock_interruptible(&user
->lock
);
834 while (user
->seq
== log_next_seq
) {
835 if (file
->f_flags
& O_NONBLOCK
) {
842 ret
= wait_event_interruptible(log_wait
,
843 user
->seq
!= log_next_seq
);
849 if (user
->seq
< log_first_seq
) {
850 /* our last seen message is gone, return error and reset */
851 user
->idx
= log_first_idx
;
852 user
->seq
= log_first_seq
;
858 msg
= log_from_idx(user
->idx
);
859 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
861 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
862 log_dict(msg
), msg
->dict_len
,
863 log_text(msg
), msg
->text_len
);
865 user
->idx
= log_next(user
->idx
);
874 if (copy_to_user(buf
, user
->buf
, len
)) {
880 mutex_unlock(&user
->lock
);
884 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
886 struct devkmsg_user
*user
= file
->private_data
;
897 /* the first record */
898 user
->idx
= log_first_idx
;
899 user
->seq
= log_first_seq
;
903 * The first record after the last SYSLOG_ACTION_CLEAR,
904 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
905 * changes no global state, and does not clear anything.
907 user
->idx
= clear_idx
;
908 user
->seq
= clear_seq
;
911 /* after the last record */
912 user
->idx
= log_next_idx
;
913 user
->seq
= log_next_seq
;
922 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
924 struct devkmsg_user
*user
= file
->private_data
;
928 return POLLERR
|POLLNVAL
;
930 poll_wait(file
, &log_wait
, wait
);
933 if (user
->seq
< log_next_seq
) {
934 /* return error when data has vanished underneath us */
935 if (user
->seq
< log_first_seq
)
936 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
938 ret
= POLLIN
|POLLRDNORM
;
945 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
947 struct devkmsg_user
*user
;
950 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
953 /* write-only does not need any file context */
954 if ((file
->f_flags
& O_ACCMODE
) != O_WRONLY
) {
955 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
961 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
965 ratelimit_default_init(&user
->rs
);
966 ratelimit_set_flags(&user
->rs
, RATELIMIT_MSG_ON_RELEASE
);
968 mutex_init(&user
->lock
);
971 user
->idx
= log_first_idx
;
972 user
->seq
= log_first_seq
;
975 file
->private_data
= user
;
979 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
981 struct devkmsg_user
*user
= file
->private_data
;
986 ratelimit_state_exit(&user
->rs
);
988 mutex_destroy(&user
->lock
);
993 const struct file_operations kmsg_fops
= {
994 .open
= devkmsg_open
,
995 .read
= devkmsg_read
,
996 .write_iter
= devkmsg_write
,
997 .llseek
= devkmsg_llseek
,
998 .poll
= devkmsg_poll
,
999 .release
= devkmsg_release
,
1002 #ifdef CONFIG_KEXEC_CORE
1004 * This appends the listed symbols to /proc/vmcore
1006 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
1007 * obtain access to symbols that are otherwise very difficult to locate. These
1008 * symbols are specifically used so that utilities can access and extract the
1009 * dmesg log from a vmcore file after a crash.
1011 void log_buf_kexec_setup(void)
1013 VMCOREINFO_SYMBOL(log_buf
);
1014 VMCOREINFO_SYMBOL(log_buf_len
);
1015 VMCOREINFO_SYMBOL(log_first_idx
);
1016 VMCOREINFO_SYMBOL(clear_idx
);
1017 VMCOREINFO_SYMBOL(log_next_idx
);
1019 * Export struct printk_log size and field offsets. User space tools can
1020 * parse it and detect any changes to structure down the line.
1022 VMCOREINFO_STRUCT_SIZE(printk_log
);
1023 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
1024 VMCOREINFO_OFFSET(printk_log
, len
);
1025 VMCOREINFO_OFFSET(printk_log
, text_len
);
1026 VMCOREINFO_OFFSET(printk_log
, dict_len
);
1030 /* requested log_buf_len from kernel cmdline */
1031 static unsigned long __initdata new_log_buf_len
;
1033 /* we practice scaling the ring buffer by powers of 2 */
1034 static void __init
log_buf_len_update(unsigned size
)
1037 size
= roundup_pow_of_two(size
);
1038 if (size
> log_buf_len
)
1039 new_log_buf_len
= size
;
1042 /* save requested log_buf_len since it's too early to process it */
1043 static int __init
log_buf_len_setup(char *str
)
1045 unsigned size
= memparse(str
, &str
);
1047 log_buf_len_update(size
);
1051 early_param("log_buf_len", log_buf_len_setup
);
1054 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1056 static void __init
log_buf_add_cpu(void)
1058 unsigned int cpu_extra
;
1061 * archs should set up cpu_possible_bits properly with
1062 * set_cpu_possible() after setup_arch() but just in
1063 * case lets ensure this is valid.
1065 if (num_possible_cpus() == 1)
1068 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
1070 /* by default this will only continue through for large > 64 CPUs */
1071 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
1074 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1075 __LOG_CPU_MAX_BUF_LEN
);
1076 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1078 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
1080 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
1082 #else /* !CONFIG_SMP */
1083 static inline void log_buf_add_cpu(void) {}
1084 #endif /* CONFIG_SMP */
1086 void __init
setup_log_buf(int early
)
1088 unsigned long flags
;
1092 if (log_buf
!= __log_buf
)
1095 if (!early
&& !new_log_buf_len
)
1098 if (!new_log_buf_len
)
1103 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
1105 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
1109 if (unlikely(!new_log_buf
)) {
1110 pr_err("log_buf_len: %ld bytes not available\n",
1115 logbuf_lock_irqsave(flags
);
1116 log_buf_len
= new_log_buf_len
;
1117 log_buf
= new_log_buf
;
1118 new_log_buf_len
= 0;
1119 free
= __LOG_BUF_LEN
- log_next_idx
;
1120 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
1121 logbuf_unlock_irqrestore(flags
);
1123 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
1124 pr_info("early log buf free: %d(%d%%)\n",
1125 free
, (free
* 100) / __LOG_BUF_LEN
);
1128 static bool __read_mostly ignore_loglevel
;
1130 static int __init
ignore_loglevel_setup(char *str
)
1132 ignore_loglevel
= true;
1133 pr_info("debug: ignoring loglevel setting.\n");
1138 early_param("ignore_loglevel", ignore_loglevel_setup
);
1139 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1140 MODULE_PARM_DESC(ignore_loglevel
,
1141 "ignore loglevel setting (prints all kernel messages to the console)");
1143 static bool suppress_message_printing(int level
)
1145 return (level
>= console_loglevel
&& !ignore_loglevel
);
1148 #ifdef CONFIG_BOOT_PRINTK_DELAY
1150 static int boot_delay
; /* msecs delay after each printk during bootup */
1151 static unsigned long long loops_per_msec
; /* based on boot_delay */
1153 static int __init
boot_delay_setup(char *str
)
1157 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
1158 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
1160 get_option(&str
, &boot_delay
);
1161 if (boot_delay
> 10 * 1000)
1164 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1165 "HZ: %d, loops_per_msec: %llu\n",
1166 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
1169 early_param("boot_delay", boot_delay_setup
);
1171 static void boot_delay_msec(int level
)
1173 unsigned long long k
;
1174 unsigned long timeout
;
1176 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
1177 || suppress_message_printing(level
)) {
1181 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1183 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1188 * use (volatile) jiffies to prevent
1189 * compiler reduction; loop termination via jiffies
1190 * is secondary and may or may not happen.
1192 if (time_after(jiffies
, timeout
))
1194 touch_nmi_watchdog();
1198 static inline void boot_delay_msec(int level
)
1203 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1204 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1206 static size_t print_time(u64 ts
, char *buf
)
1208 unsigned long rem_nsec
;
1213 rem_nsec
= do_div(ts
, 1000000000);
1216 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1218 return sprintf(buf
, "[%5lu.%06lu] ",
1219 (unsigned long)ts
, rem_nsec
/ 1000);
1222 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1225 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1229 len
+= sprintf(buf
, "<%u>", prefix
);
1234 else if (prefix
> 99)
1236 else if (prefix
> 9)
1241 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1245 static size_t msg_print_text(const struct printk_log
*msg
, bool syslog
, char *buf
, size_t size
)
1247 const char *text
= log_text(msg
);
1248 size_t text_size
= msg
->text_len
;
1252 const char *next
= memchr(text
, '\n', text_size
);
1256 text_len
= next
- text
;
1258 text_size
-= next
- text
;
1260 text_len
= text_size
;
1264 if (print_prefix(msg
, syslog
, NULL
) +
1265 text_len
+ 1 >= size
- len
)
1268 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1269 memcpy(buf
+ len
, text
, text_len
);
1273 /* SYSLOG_ACTION_* buffer size only calculation */
1274 len
+= print_prefix(msg
, syslog
, NULL
);
1285 static int syslog_print(char __user
*buf
, int size
)
1288 struct printk_log
*msg
;
1291 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1300 if (syslog_seq
< log_first_seq
) {
1301 /* messages are gone, move to first one */
1302 syslog_seq
= log_first_seq
;
1303 syslog_idx
= log_first_idx
;
1306 if (syslog_seq
== log_next_seq
) {
1307 logbuf_unlock_irq();
1311 skip
= syslog_partial
;
1312 msg
= log_from_idx(syslog_idx
);
1313 n
= msg_print_text(msg
, true, text
, LOG_LINE_MAX
+ PREFIX_MAX
);
1314 if (n
- syslog_partial
<= size
) {
1315 /* message fits into buffer, move forward */
1316 syslog_idx
= log_next(syslog_idx
);
1318 n
-= syslog_partial
;
1321 /* partial read(), remember position */
1323 syslog_partial
+= n
;
1326 logbuf_unlock_irq();
1331 if (copy_to_user(buf
, text
+ skip
, n
)) {
1346 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1351 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1362 * Find first record that fits, including all following records,
1363 * into the user-provided buffer for this dump.
1367 while (seq
< log_next_seq
) {
1368 struct printk_log
*msg
= log_from_idx(idx
);
1370 len
+= msg_print_text(msg
, true, NULL
, 0);
1371 idx
= log_next(idx
);
1375 /* move first record forward until length fits into the buffer */
1378 while (len
> size
&& seq
< log_next_seq
) {
1379 struct printk_log
*msg
= log_from_idx(idx
);
1381 len
-= msg_print_text(msg
, true, NULL
, 0);
1382 idx
= log_next(idx
);
1386 /* last message fitting into this dump */
1387 next_seq
= log_next_seq
;
1390 while (len
>= 0 && seq
< next_seq
) {
1391 struct printk_log
*msg
= log_from_idx(idx
);
1394 textlen
= msg_print_text(msg
, true, text
,
1395 LOG_LINE_MAX
+ PREFIX_MAX
);
1400 idx
= log_next(idx
);
1403 logbuf_unlock_irq();
1404 if (copy_to_user(buf
+ len
, text
, textlen
))
1410 if (seq
< log_first_seq
) {
1411 /* messages are gone, move to next one */
1412 seq
= log_first_seq
;
1413 idx
= log_first_idx
;
1419 clear_seq
= log_next_seq
;
1420 clear_idx
= log_next_idx
;
1422 logbuf_unlock_irq();
1428 int do_syslog(int type
, char __user
*buf
, int len
, int source
)
1431 static int saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1434 error
= check_syslog_permissions(type
, source
);
1439 case SYSLOG_ACTION_CLOSE
: /* Close log */
1441 case SYSLOG_ACTION_OPEN
: /* Open log */
1443 case SYSLOG_ACTION_READ
: /* Read from log */
1445 if (!buf
|| len
< 0)
1450 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1454 error
= wait_event_interruptible(log_wait
,
1455 syslog_seq
!= log_next_seq
);
1458 error
= syslog_print(buf
, len
);
1460 /* Read/clear last kernel messages */
1461 case SYSLOG_ACTION_READ_CLEAR
:
1464 /* Read last kernel messages */
1465 case SYSLOG_ACTION_READ_ALL
:
1467 if (!buf
|| len
< 0)
1472 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1476 error
= syslog_print_all(buf
, len
, clear
);
1478 /* Clear ring buffer */
1479 case SYSLOG_ACTION_CLEAR
:
1480 syslog_print_all(NULL
, 0, true);
1482 /* Disable logging to console */
1483 case SYSLOG_ACTION_CONSOLE_OFF
:
1484 if (saved_console_loglevel
== LOGLEVEL_DEFAULT
)
1485 saved_console_loglevel
= console_loglevel
;
1486 console_loglevel
= minimum_console_loglevel
;
1488 /* Enable logging to console */
1489 case SYSLOG_ACTION_CONSOLE_ON
:
1490 if (saved_console_loglevel
!= LOGLEVEL_DEFAULT
) {
1491 console_loglevel
= saved_console_loglevel
;
1492 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1495 /* Set level of messages printed to console */
1496 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1498 if (len
< 1 || len
> 8)
1500 if (len
< minimum_console_loglevel
)
1501 len
= minimum_console_loglevel
;
1502 console_loglevel
= len
;
1503 /* Implicitly re-enable logging to console */
1504 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1507 /* Number of chars in the log buffer */
1508 case SYSLOG_ACTION_SIZE_UNREAD
:
1510 if (syslog_seq
< log_first_seq
) {
1511 /* messages are gone, move to first one */
1512 syslog_seq
= log_first_seq
;
1513 syslog_idx
= log_first_idx
;
1516 if (source
== SYSLOG_FROM_PROC
) {
1518 * Short-cut for poll(/"proc/kmsg") which simply checks
1519 * for pending data, not the size; return the count of
1520 * records, not the length.
1522 error
= log_next_seq
- syslog_seq
;
1524 u64 seq
= syslog_seq
;
1525 u32 idx
= syslog_idx
;
1528 while (seq
< log_next_seq
) {
1529 struct printk_log
*msg
= log_from_idx(idx
);
1531 error
+= msg_print_text(msg
, true, NULL
, 0);
1532 idx
= log_next(idx
);
1535 error
-= syslog_partial
;
1537 logbuf_unlock_irq();
1539 /* Size of the log buffer */
1540 case SYSLOG_ACTION_SIZE_BUFFER
:
1541 error
= log_buf_len
;
1551 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1553 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1557 * Call the console drivers, asking them to write out
1558 * log_buf[start] to log_buf[end - 1].
1559 * The console_lock must be held.
1561 static void call_console_drivers(const char *ext_text
, size_t ext_len
,
1562 const char *text
, size_t len
)
1564 struct console
*con
;
1566 trace_console_rcuidle(text
, len
);
1568 if (!console_drivers
)
1571 for_each_console(con
) {
1572 if (exclusive_console
&& con
!= exclusive_console
)
1574 if (!(con
->flags
& CON_ENABLED
))
1578 if (!cpu_online(smp_processor_id()) &&
1579 !(con
->flags
& CON_ANYTIME
))
1581 if (con
->flags
& CON_EXTENDED
)
1582 con
->write(con
, ext_text
, ext_len
);
1584 con
->write(con
, text
, len
);
1588 int printk_delay_msec __read_mostly
;
1590 static inline void printk_delay(void)
1592 if (unlikely(printk_delay_msec
)) {
1593 int m
= printk_delay_msec
;
1597 touch_nmi_watchdog();
1603 * Continuation lines are buffered, and not committed to the record buffer
1604 * until the line is complete, or a race forces it. The line fragments
1605 * though, are printed immediately to the consoles to ensure everything has
1606 * reached the console in case of a kernel crash.
1608 static struct cont
{
1609 char buf
[LOG_LINE_MAX
];
1610 size_t len
; /* length == 0 means unused buffer */
1611 struct task_struct
*owner
; /* task of first print*/
1612 u64 ts_nsec
; /* time of first print */
1613 u8 level
; /* log level of first message */
1614 u8 facility
; /* log facility of first message */
1615 enum log_flags flags
; /* prefix, newline flags */
1618 static void cont_flush(void)
1623 log_store(cont
.facility
, cont
.level
, cont
.flags
, cont
.ts_nsec
,
1624 NULL
, 0, cont
.buf
, cont
.len
);
1628 static bool cont_add(int facility
, int level
, enum log_flags flags
, const char *text
, size_t len
)
1631 * If ext consoles are present, flush and skip in-kernel
1632 * continuation. See nr_ext_console_drivers definition. Also, if
1633 * the line gets too long, split it up in separate records.
1635 if (nr_ext_console_drivers
|| cont
.len
+ len
> sizeof(cont
.buf
)) {
1641 cont
.facility
= facility
;
1643 cont
.owner
= current
;
1644 cont
.ts_nsec
= local_clock();
1648 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1651 // The original flags come from the first line,
1652 // but later continuations can add a newline.
1653 if (flags
& LOG_NEWLINE
) {
1654 cont
.flags
|= LOG_NEWLINE
;
1658 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1664 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
)
1667 * If an earlier line was buffered, and we're a continuation
1668 * write from the same process, try to add it to the buffer.
1671 if (cont
.owner
== current
&& (lflags
& LOG_CONT
)) {
1672 if (cont_add(facility
, level
, lflags
, text
, text_len
))
1675 /* Otherwise, make sure it's flushed */
1679 /* Skip empty continuation lines that couldn't be added - they just flush */
1680 if (!text_len
&& (lflags
& LOG_CONT
))
1683 /* If it doesn't end in a newline, try to buffer the current line */
1684 if (!(lflags
& LOG_NEWLINE
)) {
1685 if (cont_add(facility
, level
, lflags
, text
, text_len
))
1689 /* Store it in the record log */
1690 return log_store(facility
, level
, lflags
, 0, dict
, dictlen
, text
, text_len
);
1693 asmlinkage
int vprintk_emit(int facility
, int level
,
1694 const char *dict
, size_t dictlen
,
1695 const char *fmt
, va_list args
)
1697 static char textbuf
[LOG_LINE_MAX
];
1698 char *text
= textbuf
;
1699 size_t text_len
= 0;
1700 enum log_flags lflags
= 0;
1701 unsigned long flags
;
1702 int printed_len
= 0;
1703 bool in_sched
= false;
1705 if (level
== LOGLEVEL_SCHED
) {
1706 level
= LOGLEVEL_DEFAULT
;
1710 boot_delay_msec(level
);
1713 /* This stops the holder of console_sem just where we want him */
1714 logbuf_lock_irqsave(flags
);
1716 * The printf needs to come first; we need the syslog
1717 * prefix which might be passed-in as a parameter.
1719 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1721 /* mark and strip a trailing newline */
1722 if (text_len
&& text
[text_len
-1] == '\n') {
1724 lflags
|= LOG_NEWLINE
;
1727 /* strip kernel syslog prefix and extract log level or control flags */
1728 if (facility
== 0) {
1731 while ((kern_level
= printk_get_level(text
)) != 0) {
1732 switch (kern_level
) {
1734 if (level
== LOGLEVEL_DEFAULT
)
1735 level
= kern_level
- '0';
1737 case 'd': /* KERN_DEFAULT */
1738 lflags
|= LOG_PREFIX
;
1740 case 'c': /* KERN_CONT */
1749 if (level
== LOGLEVEL_DEFAULT
)
1750 level
= default_message_loglevel
;
1753 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1755 printed_len
+= log_output(facility
, level
, lflags
, dict
, dictlen
, text
, text_len
);
1757 logbuf_unlock_irqrestore(flags
);
1759 /* If called from the scheduler, we can not call up(). */
1762 * Try to acquire and then immediately release the console
1763 * semaphore. The release will print out buffers and wake up
1764 * /dev/kmsg and syslog() users.
1766 if (console_trylock())
1772 EXPORT_SYMBOL(vprintk_emit
);
1774 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1776 return vprintk_func(fmt
, args
);
1778 EXPORT_SYMBOL(vprintk
);
1780 asmlinkage
int printk_emit(int facility
, int level
,
1781 const char *dict
, size_t dictlen
,
1782 const char *fmt
, ...)
1787 va_start(args
, fmt
);
1788 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1793 EXPORT_SYMBOL(printk_emit
);
1795 int vprintk_default(const char *fmt
, va_list args
)
1799 #ifdef CONFIG_KGDB_KDB
1800 /* Allow to pass printk() to kdb but avoid a recursion. */
1801 if (unlikely(kdb_trap_printk
&& kdb_printf_cpu
< 0)) {
1802 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1806 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1810 EXPORT_SYMBOL_GPL(vprintk_default
);
1813 * printk - print a kernel message
1814 * @fmt: format string
1816 * This is printk(). It can be called from any context. We want it to work.
1818 * We try to grab the console_lock. If we succeed, it's easy - we log the
1819 * output and call the console drivers. If we fail to get the semaphore, we
1820 * place the output into the log buffer and return. The current holder of
1821 * the console_sem will notice the new output in console_unlock(); and will
1822 * send it to the consoles before releasing the lock.
1824 * One effect of this deferred printing is that code which calls printk() and
1825 * then changes console_loglevel may break. This is because console_loglevel
1826 * is inspected when the actual printing occurs.
1831 * See the vsnprintf() documentation for format string extensions over C99.
1833 asmlinkage __visible
int printk(const char *fmt
, ...)
1838 va_start(args
, fmt
);
1839 r
= vprintk_func(fmt
, args
);
1844 EXPORT_SYMBOL(printk
);
1846 #else /* CONFIG_PRINTK */
1848 #define LOG_LINE_MAX 0
1849 #define PREFIX_MAX 0
1851 static u64 syslog_seq
;
1852 static u32 syslog_idx
;
1853 static u64 console_seq
;
1854 static u32 console_idx
;
1855 static u64 log_first_seq
;
1856 static u32 log_first_idx
;
1857 static u64 log_next_seq
;
1858 static char *log_text(const struct printk_log
*msg
) { return NULL
; }
1859 static char *log_dict(const struct printk_log
*msg
) { return NULL
; }
1860 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
1861 static u32
log_next(u32 idx
) { return 0; }
1862 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
1863 struct printk_log
*msg
,
1864 u64 seq
) { return 0; }
1865 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
1866 char *dict
, size_t dict_len
,
1867 char *text
, size_t text_len
) { return 0; }
1868 static void call_console_drivers(const char *ext_text
, size_t ext_len
,
1869 const char *text
, size_t len
) {}
1870 static size_t msg_print_text(const struct printk_log
*msg
,
1871 bool syslog
, char *buf
, size_t size
) { return 0; }
1872 static bool suppress_message_printing(int level
) { return false; }
1874 #endif /* CONFIG_PRINTK */
1876 #ifdef CONFIG_EARLY_PRINTK
1877 struct console
*early_console
;
1879 asmlinkage __visible
void early_printk(const char *fmt
, ...)
1889 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
1892 early_console
->write(early_console
, buf
, n
);
1896 static int __add_preferred_console(char *name
, int idx
, char *options
,
1899 struct console_cmdline
*c
;
1903 * See if this tty is not yet registered, and
1904 * if we have a slot free.
1906 for (i
= 0, c
= console_cmdline
;
1907 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
1909 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
1911 selected_console
= i
;
1915 if (i
== MAX_CMDLINECONSOLES
)
1918 selected_console
= i
;
1919 strlcpy(c
->name
, name
, sizeof(c
->name
));
1920 c
->options
= options
;
1921 braille_set_options(c
, brl_options
);
1927 * Set up a console. Called via do_early_param() in init/main.c
1928 * for each "console=" parameter in the boot command line.
1930 static int __init
console_setup(char *str
)
1932 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
1933 char *s
, *options
, *brl_options
= NULL
;
1936 if (_braille_console_setup(&str
, &brl_options
))
1940 * Decode str into name, index, options.
1942 if (str
[0] >= '0' && str
[0] <= '9') {
1943 strcpy(buf
, "ttyS");
1944 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1946 strncpy(buf
, str
, sizeof(buf
) - 1);
1948 buf
[sizeof(buf
) - 1] = 0;
1949 options
= strchr(str
, ',');
1953 if (!strcmp(str
, "ttya"))
1954 strcpy(buf
, "ttyS0");
1955 if (!strcmp(str
, "ttyb"))
1956 strcpy(buf
, "ttyS1");
1958 for (s
= buf
; *s
; s
++)
1959 if (isdigit(*s
) || *s
== ',')
1961 idx
= simple_strtoul(s
, NULL
, 10);
1964 __add_preferred_console(buf
, idx
, options
, brl_options
);
1965 console_set_on_cmdline
= 1;
1968 __setup("console=", console_setup
);
1971 * add_preferred_console - add a device to the list of preferred consoles.
1972 * @name: device name
1973 * @idx: device index
1974 * @options: options for this console
1976 * The last preferred console added will be used for kernel messages
1977 * and stdin/out/err for init. Normally this is used by console_setup
1978 * above to handle user-supplied console arguments; however it can also
1979 * be used by arch-specific code either to override the user or more
1980 * commonly to provide a default console (ie from PROM variables) when
1981 * the user has not supplied one.
1983 int add_preferred_console(char *name
, int idx
, char *options
)
1985 return __add_preferred_console(name
, idx
, options
, NULL
);
1988 bool console_suspend_enabled
= true;
1989 EXPORT_SYMBOL(console_suspend_enabled
);
1991 static int __init
console_suspend_disable(char *str
)
1993 console_suspend_enabled
= false;
1996 __setup("no_console_suspend", console_suspend_disable
);
1997 module_param_named(console_suspend
, console_suspend_enabled
,
1998 bool, S_IRUGO
| S_IWUSR
);
1999 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2000 " and hibernate operations");
2003 * suspend_console - suspend the console subsystem
2005 * This disables printk() while we go into suspend states
2007 void suspend_console(void)
2009 if (!console_suspend_enabled
)
2011 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2013 console_suspended
= 1;
2017 void resume_console(void)
2019 if (!console_suspend_enabled
)
2022 console_suspended
= 0;
2027 * console_cpu_notify - print deferred console messages after CPU hotplug
2030 * If printk() is called from a CPU that is not online yet, the messages
2031 * will be spooled but will not show up on the console. This function is
2032 * called when a new CPU comes online (or fails to come up), and ensures
2033 * that any such output gets printed.
2035 static int console_cpu_notify(unsigned int cpu
)
2037 if (!cpuhp_tasks_frozen
) {
2045 * console_lock - lock the console system for exclusive use.
2047 * Acquires a lock which guarantees that the caller has
2048 * exclusive access to the console system and the console_drivers list.
2050 * Can sleep, returns nothing.
2052 void console_lock(void)
2057 if (console_suspended
)
2060 console_may_schedule
= 1;
2062 EXPORT_SYMBOL(console_lock
);
2065 * console_trylock - try to lock the console system for exclusive use.
2067 * Try to acquire a lock which guarantees that the caller has exclusive
2068 * access to the console system and the console_drivers list.
2070 * returns 1 on success, and 0 on failure to acquire the lock.
2072 int console_trylock(void)
2074 if (down_trylock_console_sem())
2076 if (console_suspended
) {
2082 * When PREEMPT_COUNT disabled we can't reliably detect if it's
2083 * safe to schedule (e.g. calling printk while holding a spin_lock),
2084 * because preempt_disable()/preempt_enable() are just barriers there
2085 * and preempt_count() is always 0.
2087 * RCU read sections have a separate preemption counter when
2088 * PREEMPT_RCU enabled thus we must take extra care and check
2089 * rcu_preempt_depth(), otherwise RCU read sections modify
2092 console_may_schedule
= !oops_in_progress
&&
2094 !rcu_preempt_depth();
2097 EXPORT_SYMBOL(console_trylock
);
2099 int is_console_locked(void)
2101 return console_locked
;
2105 * Check if we have any console that is capable of printing while cpu is
2106 * booting or shutting down. Requires console_sem.
2108 static int have_callable_console(void)
2110 struct console
*con
;
2112 for_each_console(con
)
2113 if ((con
->flags
& CON_ENABLED
) &&
2114 (con
->flags
& CON_ANYTIME
))
2121 * Can we actually use the console at this time on this cpu?
2123 * Console drivers may assume that per-cpu resources have been allocated. So
2124 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2125 * call them until this CPU is officially up.
2127 static inline int can_use_console(void)
2129 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2133 * console_unlock - unlock the console system
2135 * Releases the console_lock which the caller holds on the console system
2136 * and the console driver list.
2138 * While the console_lock was held, console output may have been buffered
2139 * by printk(). If this is the case, console_unlock(); emits
2140 * the output prior to releasing the lock.
2142 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2144 * console_unlock(); may be called from any context.
2146 void console_unlock(void)
2148 static char ext_text
[CONSOLE_EXT_LOG_MAX
];
2149 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2150 static u64 seen_seq
;
2151 unsigned long flags
;
2152 bool wake_klogd
= false;
2153 bool do_cond_resched
, retry
;
2155 if (console_suspended
) {
2161 * Console drivers are called under logbuf_lock, so
2162 * @console_may_schedule should be cleared before; however, we may
2163 * end up dumping a lot of lines, for example, if called from
2164 * console registration path, and should invoke cond_resched()
2165 * between lines if allowable. Not doing so can cause a very long
2166 * scheduling stall on a slow console leading to RCU stall and
2167 * softlockup warnings which exacerbate the issue with more
2168 * messages practically incapacitating the system.
2170 do_cond_resched
= console_may_schedule
;
2171 console_may_schedule
= 0;
2175 * We released the console_sem lock, so we need to recheck if
2176 * cpu is online and (if not) is there at least one CON_ANYTIME
2179 if (!can_use_console()) {
2186 struct printk_log
*msg
;
2190 printk_safe_enter_irqsave(flags
);
2191 raw_spin_lock(&logbuf_lock
);
2192 if (seen_seq
!= log_next_seq
) {
2194 seen_seq
= log_next_seq
;
2197 if (console_seq
< log_first_seq
) {
2198 len
= sprintf(text
, "** %u printk messages dropped ** ",
2199 (unsigned)(log_first_seq
- console_seq
));
2201 /* messages are gone, move to first one */
2202 console_seq
= log_first_seq
;
2203 console_idx
= log_first_idx
;
2208 if (console_seq
== log_next_seq
)
2211 msg
= log_from_idx(console_idx
);
2212 if (suppress_message_printing(msg
->level
)) {
2214 * Skip record we have buffered and already printed
2215 * directly to the console when we received it, and
2216 * record that has level above the console loglevel.
2218 console_idx
= log_next(console_idx
);
2223 len
+= msg_print_text(msg
, false, text
+ len
, sizeof(text
) - len
);
2224 if (nr_ext_console_drivers
) {
2225 ext_len
= msg_print_ext_header(ext_text
,
2228 ext_len
+= msg_print_ext_body(ext_text
+ ext_len
,
2229 sizeof(ext_text
) - ext_len
,
2230 log_dict(msg
), msg
->dict_len
,
2231 log_text(msg
), msg
->text_len
);
2233 console_idx
= log_next(console_idx
);
2235 raw_spin_unlock(&logbuf_lock
);
2237 stop_critical_timings(); /* don't trace print latency */
2238 call_console_drivers(ext_text
, ext_len
, text
, len
);
2239 start_critical_timings();
2240 printk_safe_exit_irqrestore(flags
);
2242 if (do_cond_resched
)
2247 /* Release the exclusive_console once it is used */
2248 if (unlikely(exclusive_console
))
2249 exclusive_console
= NULL
;
2251 raw_spin_unlock(&logbuf_lock
);
2256 * Someone could have filled up the buffer again, so re-check if there's
2257 * something to flush. In case we cannot trylock the console_sem again,
2258 * there's a new owner and the console_unlock() from them will do the
2259 * flush, no worries.
2261 raw_spin_lock(&logbuf_lock
);
2262 retry
= console_seq
!= log_next_seq
;
2263 raw_spin_unlock(&logbuf_lock
);
2264 printk_safe_exit_irqrestore(flags
);
2266 if (retry
&& console_trylock())
2272 EXPORT_SYMBOL(console_unlock
);
2275 * console_conditional_schedule - yield the CPU if required
2277 * If the console code is currently allowed to sleep, and
2278 * if this CPU should yield the CPU to another task, do
2281 * Must be called within console_lock();.
2283 void __sched
console_conditional_schedule(void)
2285 if (console_may_schedule
)
2288 EXPORT_SYMBOL(console_conditional_schedule
);
2290 void console_unblank(void)
2295 * console_unblank can no longer be called in interrupt context unless
2296 * oops_in_progress is set to 1..
2298 if (oops_in_progress
) {
2299 if (down_trylock_console_sem() != 0)
2305 console_may_schedule
= 0;
2307 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2313 * console_flush_on_panic - flush console content on panic
2315 * Immediately output all pending messages no matter what.
2317 void console_flush_on_panic(void)
2320 * If someone else is holding the console lock, trylock will fail
2321 * and may_schedule may be set. Ignore and proceed to unlock so
2322 * that messages are flushed out. As this can be called from any
2323 * context and we don't want to get preempted while flushing,
2324 * ensure may_schedule is cleared.
2327 console_may_schedule
= 0;
2332 * Return the console tty driver structure and its associated index
2334 struct tty_driver
*console_device(int *index
)
2337 struct tty_driver
*driver
= NULL
;
2340 for_each_console(c
) {
2343 driver
= c
->device(c
, index
);
2352 * Prevent further output on the passed console device so that (for example)
2353 * serial drivers can disable console output before suspending a port, and can
2354 * re-enable output afterwards.
2356 void console_stop(struct console
*console
)
2359 console
->flags
&= ~CON_ENABLED
;
2362 EXPORT_SYMBOL(console_stop
);
2364 void console_start(struct console
*console
)
2367 console
->flags
|= CON_ENABLED
;
2370 EXPORT_SYMBOL(console_start
);
2372 static int __read_mostly keep_bootcon
;
2374 static int __init
keep_bootcon_setup(char *str
)
2377 pr_info("debug: skip boot console de-registration.\n");
2382 early_param("keep_bootcon", keep_bootcon_setup
);
2385 * The console driver calls this routine during kernel initialization
2386 * to register the console printing procedure with printk() and to
2387 * print any messages that were printed by the kernel before the
2388 * console driver was initialized.
2390 * This can happen pretty early during the boot process (because of
2391 * early_printk) - sometimes before setup_arch() completes - be careful
2392 * of what kernel features are used - they may not be initialised yet.
2394 * There are two types of consoles - bootconsoles (early_printk) and
2395 * "real" consoles (everything which is not a bootconsole) which are
2396 * handled differently.
2397 * - Any number of bootconsoles can be registered at any time.
2398 * - As soon as a "real" console is registered, all bootconsoles
2399 * will be unregistered automatically.
2400 * - Once a "real" console is registered, any attempt to register a
2401 * bootconsoles will be rejected
2403 void register_console(struct console
*newcon
)
2406 unsigned long flags
;
2407 struct console
*bcon
= NULL
;
2408 struct console_cmdline
*c
;
2410 if (console_drivers
)
2411 for_each_console(bcon
)
2412 if (WARN(bcon
== newcon
,
2413 "console '%s%d' already registered\n",
2414 bcon
->name
, bcon
->index
))
2418 * before we register a new CON_BOOT console, make sure we don't
2419 * already have a valid console
2421 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2422 /* find the last or real console */
2423 for_each_console(bcon
) {
2424 if (!(bcon
->flags
& CON_BOOT
)) {
2425 pr_info("Too late to register bootconsole %s%d\n",
2426 newcon
->name
, newcon
->index
);
2432 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2433 bcon
= console_drivers
;
2435 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2436 preferred_console
= selected_console
;
2439 * See if we want to use this console driver. If we
2440 * didn't select a console we take the first one
2441 * that registers here.
2443 if (preferred_console
< 0) {
2444 if (newcon
->index
< 0)
2446 if (newcon
->setup
== NULL
||
2447 newcon
->setup(newcon
, NULL
) == 0) {
2448 newcon
->flags
|= CON_ENABLED
;
2449 if (newcon
->device
) {
2450 newcon
->flags
|= CON_CONSDEV
;
2451 preferred_console
= 0;
2457 * See if this console matches one we selected on
2460 for (i
= 0, c
= console_cmdline
;
2461 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2463 if (!newcon
->match
||
2464 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2465 /* default matching */
2466 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2467 if (strcmp(c
->name
, newcon
->name
) != 0)
2469 if (newcon
->index
>= 0 &&
2470 newcon
->index
!= c
->index
)
2472 if (newcon
->index
< 0)
2473 newcon
->index
= c
->index
;
2475 if (_braille_register_console(newcon
, c
))
2478 if (newcon
->setup
&&
2479 newcon
->setup(newcon
, c
->options
) != 0)
2483 newcon
->flags
|= CON_ENABLED
;
2484 if (i
== selected_console
) {
2485 newcon
->flags
|= CON_CONSDEV
;
2486 preferred_console
= selected_console
;
2491 if (!(newcon
->flags
& CON_ENABLED
))
2495 * If we have a bootconsole, and are switching to a real console,
2496 * don't print everything out again, since when the boot console, and
2497 * the real console are the same physical device, it's annoying to
2498 * see the beginning boot messages twice
2500 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2501 newcon
->flags
&= ~CON_PRINTBUFFER
;
2504 * Put this console in the list - keep the
2505 * preferred driver at the head of the list.
2508 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2509 newcon
->next
= console_drivers
;
2510 console_drivers
= newcon
;
2512 newcon
->next
->flags
&= ~CON_CONSDEV
;
2514 newcon
->next
= console_drivers
->next
;
2515 console_drivers
->next
= newcon
;
2518 if (newcon
->flags
& CON_EXTENDED
)
2519 if (!nr_ext_console_drivers
++)
2520 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2522 if (newcon
->flags
& CON_PRINTBUFFER
) {
2524 * console_unlock(); will print out the buffered messages
2527 logbuf_lock_irqsave(flags
);
2528 console_seq
= syslog_seq
;
2529 console_idx
= syslog_idx
;
2530 logbuf_unlock_irqrestore(flags
);
2532 * We're about to replay the log buffer. Only do this to the
2533 * just-registered console to avoid excessive message spam to
2534 * the already-registered consoles.
2536 exclusive_console
= newcon
;
2539 console_sysfs_notify();
2542 * By unregistering the bootconsoles after we enable the real console
2543 * we get the "console xxx enabled" message on all the consoles -
2544 * boot consoles, real consoles, etc - this is to ensure that end
2545 * users know there might be something in the kernel's log buffer that
2546 * went to the bootconsole (that they do not see on the real console)
2548 pr_info("%sconsole [%s%d] enabled\n",
2549 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2550 newcon
->name
, newcon
->index
);
2552 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2554 /* We need to iterate through all boot consoles, to make
2555 * sure we print everything out, before we unregister them.
2557 for_each_console(bcon
)
2558 if (bcon
->flags
& CON_BOOT
)
2559 unregister_console(bcon
);
2562 EXPORT_SYMBOL(register_console
);
2564 int unregister_console(struct console
*console
)
2566 struct console
*a
, *b
;
2569 pr_info("%sconsole [%s%d] disabled\n",
2570 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2571 console
->name
, console
->index
);
2573 res
= _braille_unregister_console(console
);
2579 if (console_drivers
== console
) {
2580 console_drivers
=console
->next
;
2582 } else if (console_drivers
) {
2583 for (a
=console_drivers
->next
, b
=console_drivers
;
2584 a
; b
=a
, a
=b
->next
) {
2593 if (!res
&& (console
->flags
& CON_EXTENDED
))
2594 nr_ext_console_drivers
--;
2597 * If this isn't the last console and it has CON_CONSDEV set, we
2598 * need to set it on the next preferred console.
2600 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2601 console_drivers
->flags
|= CON_CONSDEV
;
2603 console
->flags
&= ~CON_ENABLED
;
2605 console_sysfs_notify();
2608 EXPORT_SYMBOL(unregister_console
);
2611 * Some boot consoles access data that is in the init section and which will
2612 * be discarded after the initcalls have been run. To make sure that no code
2613 * will access this data, unregister the boot consoles in a late initcall.
2615 * If for some reason, such as deferred probe or the driver being a loadable
2616 * module, the real console hasn't registered yet at this point, there will
2617 * be a brief interval in which no messages are logged to the console, which
2618 * makes it difficult to diagnose problems that occur during this time.
2620 * To mitigate this problem somewhat, only unregister consoles whose memory
2621 * intersects with the init section. Note that code exists elsewhere to get
2622 * rid of the boot console as soon as the proper console shows up, so there
2623 * won't be side-effects from postponing the removal.
2625 static int __init
printk_late_init(void)
2627 struct console
*con
;
2630 for_each_console(con
) {
2631 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2633 * Make sure to unregister boot consoles whose data
2634 * resides in the init section before the init section
2635 * is discarded. Boot consoles whose data will stick
2636 * around will automatically be unregistered when the
2637 * proper console replaces them.
2639 if (init_section_intersects(con
, sizeof(*con
)))
2640 unregister_console(con
);
2643 ret
= cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD
, "printk:dead", NULL
,
2644 console_cpu_notify
);
2646 ret
= cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN
, "printk:online",
2647 console_cpu_notify
, NULL
);
2651 late_initcall(printk_late_init
);
2653 #if defined CONFIG_PRINTK
2655 * Delayed printk version, for scheduler-internal messages:
2657 #define PRINTK_PENDING_WAKEUP 0x01
2658 #define PRINTK_PENDING_OUTPUT 0x02
2660 static DEFINE_PER_CPU(int, printk_pending
);
2662 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2664 int pending
= __this_cpu_xchg(printk_pending
, 0);
2666 if (pending
& PRINTK_PENDING_OUTPUT
) {
2667 /* If trylock fails, someone else is doing the printing */
2668 if (console_trylock())
2672 if (pending
& PRINTK_PENDING_WAKEUP
)
2673 wake_up_interruptible(&log_wait
);
2676 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2677 .func
= wake_up_klogd_work_func
,
2678 .flags
= IRQ_WORK_LAZY
,
2681 void wake_up_klogd(void)
2684 if (waitqueue_active(&log_wait
)) {
2685 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2686 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2691 int printk_deferred(const char *fmt
, ...)
2697 va_start(args
, fmt
);
2698 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2701 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2702 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2709 * printk rate limiting, lifted from the networking subsystem.
2711 * This enforces a rate limit: not more than 10 kernel messages
2712 * every 5s to make a denial-of-service attack impossible.
2714 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2716 int __printk_ratelimit(const char *func
)
2718 return ___ratelimit(&printk_ratelimit_state
, func
);
2720 EXPORT_SYMBOL(__printk_ratelimit
);
2723 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2724 * @caller_jiffies: pointer to caller's state
2725 * @interval_msecs: minimum interval between prints
2727 * printk_timed_ratelimit() returns true if more than @interval_msecs
2728 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2731 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2732 unsigned int interval_msecs
)
2734 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2736 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2739 *caller_jiffies
= jiffies
;
2742 EXPORT_SYMBOL(printk_timed_ratelimit
);
2744 static DEFINE_SPINLOCK(dump_list_lock
);
2745 static LIST_HEAD(dump_list
);
2748 * kmsg_dump_register - register a kernel log dumper.
2749 * @dumper: pointer to the kmsg_dumper structure
2751 * Adds a kernel log dumper to the system. The dump callback in the
2752 * structure will be called when the kernel oopses or panics and must be
2753 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2755 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2757 unsigned long flags
;
2760 /* The dump callback needs to be set */
2764 spin_lock_irqsave(&dump_list_lock
, flags
);
2765 /* Don't allow registering multiple times */
2766 if (!dumper
->registered
) {
2767 dumper
->registered
= 1;
2768 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2771 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2775 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2778 * kmsg_dump_unregister - unregister a kmsg dumper.
2779 * @dumper: pointer to the kmsg_dumper structure
2781 * Removes a dump device from the system. Returns zero on success and
2782 * %-EINVAL otherwise.
2784 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2786 unsigned long flags
;
2789 spin_lock_irqsave(&dump_list_lock
, flags
);
2790 if (dumper
->registered
) {
2791 dumper
->registered
= 0;
2792 list_del_rcu(&dumper
->list
);
2795 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2800 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2802 static bool always_kmsg_dump
;
2803 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2806 * kmsg_dump - dump kernel log to kernel message dumpers.
2807 * @reason: the reason (oops, panic etc) for dumping
2809 * Call each of the registered dumper's dump() callback, which can
2810 * retrieve the kmsg records with kmsg_dump_get_line() or
2811 * kmsg_dump_get_buffer().
2813 void kmsg_dump(enum kmsg_dump_reason reason
)
2815 struct kmsg_dumper
*dumper
;
2816 unsigned long flags
;
2818 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2822 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2823 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2826 /* initialize iterator with data about the stored records */
2827 dumper
->active
= true;
2829 logbuf_lock_irqsave(flags
);
2830 dumper
->cur_seq
= clear_seq
;
2831 dumper
->cur_idx
= clear_idx
;
2832 dumper
->next_seq
= log_next_seq
;
2833 dumper
->next_idx
= log_next_idx
;
2834 logbuf_unlock_irqrestore(flags
);
2836 /* invoke dumper which will iterate over records */
2837 dumper
->dump(dumper
, reason
);
2839 /* reset iterator */
2840 dumper
->active
= false;
2846 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2847 * @dumper: registered kmsg dumper
2848 * @syslog: include the "<4>" prefixes
2849 * @line: buffer to copy the line to
2850 * @size: maximum size of the buffer
2851 * @len: length of line placed into buffer
2853 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2854 * record, and copy one record into the provided buffer.
2856 * Consecutive calls will return the next available record moving
2857 * towards the end of the buffer with the youngest messages.
2859 * A return value of FALSE indicates that there are no more records to
2862 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2864 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
2865 char *line
, size_t size
, size_t *len
)
2867 struct printk_log
*msg
;
2871 if (!dumper
->active
)
2874 if (dumper
->cur_seq
< log_first_seq
) {
2875 /* messages are gone, move to first available one */
2876 dumper
->cur_seq
= log_first_seq
;
2877 dumper
->cur_idx
= log_first_idx
;
2881 if (dumper
->cur_seq
>= log_next_seq
)
2884 msg
= log_from_idx(dumper
->cur_idx
);
2885 l
= msg_print_text(msg
, syslog
, line
, size
);
2887 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2897 * kmsg_dump_get_line - retrieve one kmsg log line
2898 * @dumper: registered kmsg dumper
2899 * @syslog: include the "<4>" prefixes
2900 * @line: buffer to copy the line to
2901 * @size: maximum size of the buffer
2902 * @len: length of line placed into buffer
2904 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2905 * record, and copy one record into the provided buffer.
2907 * Consecutive calls will return the next available record moving
2908 * towards the end of the buffer with the youngest messages.
2910 * A return value of FALSE indicates that there are no more records to
2913 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2914 char *line
, size_t size
, size_t *len
)
2916 unsigned long flags
;
2919 logbuf_lock_irqsave(flags
);
2920 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
2921 logbuf_unlock_irqrestore(flags
);
2925 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
2928 * kmsg_dump_get_buffer - copy kmsg log lines
2929 * @dumper: registered kmsg dumper
2930 * @syslog: include the "<4>" prefixes
2931 * @buf: buffer to copy the line to
2932 * @size: maximum size of the buffer
2933 * @len: length of line placed into buffer
2935 * Start at the end of the kmsg buffer and fill the provided buffer
2936 * with as many of the the *youngest* kmsg records that fit into it.
2937 * If the buffer is large enough, all available kmsg records will be
2938 * copied with a single call.
2940 * Consecutive calls will fill the buffer with the next block of
2941 * available older records, not including the earlier retrieved ones.
2943 * A return value of FALSE indicates that there are no more records to
2946 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
2947 char *buf
, size_t size
, size_t *len
)
2949 unsigned long flags
;
2957 if (!dumper
->active
)
2960 logbuf_lock_irqsave(flags
);
2961 if (dumper
->cur_seq
< log_first_seq
) {
2962 /* messages are gone, move to first available one */
2963 dumper
->cur_seq
= log_first_seq
;
2964 dumper
->cur_idx
= log_first_idx
;
2968 if (dumper
->cur_seq
>= dumper
->next_seq
) {
2969 logbuf_unlock_irqrestore(flags
);
2973 /* calculate length of entire buffer */
2974 seq
= dumper
->cur_seq
;
2975 idx
= dumper
->cur_idx
;
2976 while (seq
< dumper
->next_seq
) {
2977 struct printk_log
*msg
= log_from_idx(idx
);
2979 l
+= msg_print_text(msg
, true, NULL
, 0);
2980 idx
= log_next(idx
);
2984 /* move first record forward until length fits into the buffer */
2985 seq
= dumper
->cur_seq
;
2986 idx
= dumper
->cur_idx
;
2987 while (l
> size
&& seq
< dumper
->next_seq
) {
2988 struct printk_log
*msg
= log_from_idx(idx
);
2990 l
-= msg_print_text(msg
, true, NULL
, 0);
2991 idx
= log_next(idx
);
2995 /* last message in next interation */
3000 while (seq
< dumper
->next_seq
) {
3001 struct printk_log
*msg
= log_from_idx(idx
);
3003 l
+= msg_print_text(msg
, syslog
, buf
+ l
, size
- l
);
3004 idx
= log_next(idx
);
3008 dumper
->next_seq
= next_seq
;
3009 dumper
->next_idx
= next_idx
;
3011 logbuf_unlock_irqrestore(flags
);
3017 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
3020 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3021 * @dumper: registered kmsg dumper
3023 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3024 * kmsg_dump_get_buffer() can be called again and used multiple
3025 * times within the same dumper.dump() callback.
3027 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3029 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3031 dumper
->cur_seq
= clear_seq
;
3032 dumper
->cur_idx
= clear_idx
;
3033 dumper
->next_seq
= log_next_seq
;
3034 dumper
->next_idx
= log_next_idx
;
3038 * kmsg_dump_rewind - reset the interator
3039 * @dumper: registered kmsg dumper
3041 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3042 * kmsg_dump_get_buffer() can be called again and used multiple
3043 * times within the same dumper.dump() callback.
3045 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3047 unsigned long flags
;
3049 logbuf_lock_irqsave(flags
);
3050 kmsg_dump_rewind_nolock(dumper
);
3051 logbuf_unlock_irqrestore(flags
);
3053 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3055 static char dump_stack_arch_desc_str
[128];
3058 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3059 * @fmt: printf-style format string
3060 * @...: arguments for the format string
3062 * The configured string will be printed right after utsname during task
3063 * dumps. Usually used to add arch-specific system identifiers. If an
3064 * arch wants to make use of such an ID string, it should initialize this
3065 * as soon as possible during boot.
3067 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3071 va_start(args
, fmt
);
3072 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3078 * dump_stack_print_info - print generic debug info for dump_stack()
3079 * @log_lvl: log level
3081 * Arch-specific dump_stack() implementations can use this function to
3082 * print out the same debug information as the generic dump_stack().
3084 void dump_stack_print_info(const char *log_lvl
)
3086 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3087 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3088 print_tainted(), init_utsname()->release
,
3089 (int)strcspn(init_utsname()->version
, " "),
3090 init_utsname()->version
);
3092 if (dump_stack_arch_desc_str
[0] != '\0')
3093 printk("%sHardware name: %s\n",
3094 log_lvl
, dump_stack_arch_desc_str
);
3096 print_worker_info(log_lvl
, current
);
3100 * show_regs_print_info - print generic debug info for show_regs()
3101 * @log_lvl: log level
3103 * show_regs() implementations can use this function to print out generic
3104 * debug information.
3106 void show_regs_print_info(const char *log_lvl
)
3108 dump_stack_print_info(log_lvl
);
3110 printk("%stask: %p task.stack: %p\n",
3111 log_lvl
, current
, task_stack_page(current
));