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 <asm/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
)
216 if (down_trylock(&console_sem
))
218 mutex_acquire(&console_lock_dep_map
, 0, 1, ip
);
221 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
223 #define up_console_sem() do { \
224 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
229 * This is used for debugging the mess that is the VT code by
230 * keeping track if we have the console semaphore held. It's
231 * definitely not the perfect debug tool (we don't know if _WE_
232 * hold it and are racing, but it helps tracking those weird code
233 * paths in the console code where we end up in places I want
234 * locked without the console sempahore held).
236 static int console_locked
, console_suspended
;
239 * If exclusive_console is non-NULL then only this console is to be printed to.
241 static struct console
*exclusive_console
;
244 * Array of consoles built from command line options (console=)
247 #define MAX_CMDLINECONSOLES 8
249 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
251 static int selected_console
= -1;
252 static int preferred_console
= -1;
253 int console_set_on_cmdline
;
254 EXPORT_SYMBOL(console_set_on_cmdline
);
256 /* Flag: console code may call schedule() */
257 static int console_may_schedule
;
260 * The printk log buffer consists of a chain of concatenated variable
261 * length records. Every record starts with a record header, containing
262 * the overall length of the record.
264 * The heads to the first and last entry in the buffer, as well as the
265 * sequence numbers of these entries are maintained when messages are
268 * If the heads indicate available messages, the length in the header
269 * tells the start next message. A length == 0 for the next message
270 * indicates a wrap-around to the beginning of the buffer.
272 * Every record carries the monotonic timestamp in microseconds, as well as
273 * the standard userspace syslog level and syslog facility. The usual
274 * kernel messages use LOG_KERN; userspace-injected messages always carry
275 * a matching syslog facility, by default LOG_USER. The origin of every
276 * message can be reliably determined that way.
278 * The human readable log message directly follows the message header. The
279 * length of the message text is stored in the header, the stored message
282 * Optionally, a message can carry a dictionary of properties (key/value pairs),
283 * to provide userspace with a machine-readable message context.
285 * Examples for well-defined, commonly used property names are:
286 * DEVICE=b12:8 device identifier
290 * +sound:card0 subsystem:devname
291 * SUBSYSTEM=pci driver-core subsystem name
293 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
294 * follows directly after a '=' character. Every property is terminated by
295 * a '\0' character. The last property is not terminated.
297 * Example of a message structure:
298 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
299 * 0008 34 00 record is 52 bytes long
300 * 000a 0b 00 text is 11 bytes long
301 * 000c 1f 00 dictionary is 23 bytes long
302 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
303 * 0010 69 74 27 73 20 61 20 6c "it's a l"
305 * 001b 44 45 56 49 43 "DEVIC"
306 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
307 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
309 * 0032 00 00 00 padding to next message header
311 * The 'struct printk_log' buffer header must never be directly exported to
312 * userspace, it is a kernel-private implementation detail that might
313 * need to be changed in the future, when the requirements change.
315 * /dev/kmsg exports the structured data in the following line format:
316 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
318 * Users of the export format should ignore possible additional values
319 * separated by ',', and find the message after the ';' character.
321 * The optional key/value pairs are attached as continuation lines starting
322 * with a space character and terminated by a newline. All possible
323 * non-prinatable characters are escaped in the "\xff" notation.
327 LOG_NOCONS
= 1, /* already flushed, do not print to console */
328 LOG_NEWLINE
= 2, /* text ended with a newline */
329 LOG_PREFIX
= 4, /* text started with a prefix */
330 LOG_CONT
= 8, /* text is a fragment of a continuation line */
334 u64 ts_nsec
; /* timestamp in nanoseconds */
335 u16 len
; /* length of entire record */
336 u16 text_len
; /* length of text buffer */
337 u16 dict_len
; /* length of dictionary buffer */
338 u8 facility
; /* syslog facility */
339 u8 flags
:5; /* internal record flags */
340 u8 level
:3; /* syslog level */
342 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
343 __packed
__aligned(4)
348 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
349 * within the scheduler's rq lock. It must be released before calling
350 * console_unlock() or anything else that might wake up a process.
352 DEFINE_RAW_SPINLOCK(logbuf_lock
);
355 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
356 /* the next printk record to read by syslog(READ) or /proc/kmsg */
357 static u64 syslog_seq
;
358 static u32 syslog_idx
;
359 static enum log_flags syslog_prev
;
360 static size_t syslog_partial
;
362 /* index and sequence number of the first record stored in the buffer */
363 static u64 log_first_seq
;
364 static u32 log_first_idx
;
366 /* index and sequence number of the next record to store in the buffer */
367 static u64 log_next_seq
;
368 static u32 log_next_idx
;
370 /* the next printk record to write to the console */
371 static u64 console_seq
;
372 static u32 console_idx
;
373 static enum log_flags console_prev
;
375 /* the next printk record to read after the last 'clear' command */
376 static u64 clear_seq
;
377 static u32 clear_idx
;
379 #define PREFIX_MAX 32
380 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
382 #define LOG_LEVEL(v) ((v) & 0x07)
383 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
386 #define LOG_ALIGN __alignof__(struct printk_log)
387 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
388 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
389 static char *log_buf
= __log_buf
;
390 static u32 log_buf_len
= __LOG_BUF_LEN
;
392 /* Return log buffer address */
393 char *log_buf_addr_get(void)
398 /* Return log buffer size */
399 u32
log_buf_len_get(void)
404 /* human readable text of the record */
405 static char *log_text(const struct printk_log
*msg
)
407 return (char *)msg
+ sizeof(struct printk_log
);
410 /* optional key/value pair dictionary attached to the record */
411 static char *log_dict(const struct printk_log
*msg
)
413 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
416 /* get record by index; idx must point to valid msg */
417 static struct printk_log
*log_from_idx(u32 idx
)
419 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
422 * A length == 0 record is the end of buffer marker. Wrap around and
423 * read the message at the start of the buffer.
426 return (struct printk_log
*)log_buf
;
430 /* get next record; idx must point to valid msg */
431 static u32
log_next(u32 idx
)
433 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
435 /* length == 0 indicates the end of the buffer; wrap */
437 * A length == 0 record is the end of buffer marker. Wrap around and
438 * read the message at the start of the buffer as *this* one, and
439 * return the one after that.
442 msg
= (struct printk_log
*)log_buf
;
445 return idx
+ msg
->len
;
449 * Check whether there is enough free space for the given message.
451 * The same values of first_idx and next_idx mean that the buffer
452 * is either empty or full.
454 * If the buffer is empty, we must respect the position of the indexes.
455 * They cannot be reset to the beginning of the buffer.
457 static int logbuf_has_space(u32 msg_size
, bool empty
)
461 if (log_next_idx
> log_first_idx
|| empty
)
462 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
464 free
= log_first_idx
- log_next_idx
;
467 * We need space also for an empty header that signalizes wrapping
470 return free
>= msg_size
+ sizeof(struct printk_log
);
473 static int log_make_free_space(u32 msg_size
)
475 while (log_first_seq
< log_next_seq
&&
476 !logbuf_has_space(msg_size
, false)) {
477 /* drop old messages until we have enough contiguous space */
478 log_first_idx
= log_next(log_first_idx
);
482 if (clear_seq
< log_first_seq
) {
483 clear_seq
= log_first_seq
;
484 clear_idx
= log_first_idx
;
487 /* sequence numbers are equal, so the log buffer is empty */
488 if (logbuf_has_space(msg_size
, log_first_seq
== log_next_seq
))
494 /* compute the message size including the padding bytes */
495 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
499 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
500 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
507 * Define how much of the log buffer we could take at maximum. The value
508 * must be greater than two. Note that only half of the buffer is available
509 * when the index points to the middle.
511 #define MAX_LOG_TAKE_PART 4
512 static const char trunc_msg
[] = "<truncated>";
514 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
515 u16
*dict_len
, u32
*pad_len
)
518 * The message should not take the whole buffer. Otherwise, it might
519 * get removed too soon.
521 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
522 if (*text_len
> max_text_len
)
523 *text_len
= max_text_len
;
524 /* enable the warning message */
525 *trunc_msg_len
= strlen(trunc_msg
);
526 /* disable the "dict" completely */
528 /* compute the size again, count also the warning message */
529 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
532 /* insert record into the buffer, discard old ones, update heads */
533 static int log_store(int facility
, int level
,
534 enum log_flags flags
, u64 ts_nsec
,
535 const char *dict
, u16 dict_len
,
536 const char *text
, u16 text_len
)
538 struct printk_log
*msg
;
540 u16 trunc_msg_len
= 0;
542 /* number of '\0' padding bytes to next message */
543 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
545 if (log_make_free_space(size
)) {
546 /* truncate the message if it is too long for empty buffer */
547 size
= truncate_msg(&text_len
, &trunc_msg_len
,
548 &dict_len
, &pad_len
);
549 /* survive when the log buffer is too small for trunc_msg */
550 if (log_make_free_space(size
))
554 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
556 * This message + an additional empty header does not fit
557 * at the end of the buffer. Add an empty header with len == 0
558 * to signify a wrap around.
560 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
565 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
566 memcpy(log_text(msg
), text
, text_len
);
567 msg
->text_len
= text_len
;
569 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
570 msg
->text_len
+= trunc_msg_len
;
572 memcpy(log_dict(msg
), dict
, dict_len
);
573 msg
->dict_len
= dict_len
;
574 msg
->facility
= facility
;
575 msg
->level
= level
& 7;
576 msg
->flags
= flags
& 0x1f;
578 msg
->ts_nsec
= ts_nsec
;
580 msg
->ts_nsec
= local_clock();
581 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
585 log_next_idx
+= msg
->len
;
588 return msg
->text_len
;
591 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
593 static int syslog_action_restricted(int type
)
598 * Unless restricted, we allow "read all" and "get buffer size"
601 return type
!= SYSLOG_ACTION_READ_ALL
&&
602 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
605 int check_syslog_permissions(int type
, int source
)
608 * If this is from /proc/kmsg and we've already opened it, then we've
609 * already done the capabilities checks at open time.
611 if (source
== SYSLOG_FROM_PROC
&& type
!= SYSLOG_ACTION_OPEN
)
614 if (syslog_action_restricted(type
)) {
615 if (capable(CAP_SYSLOG
))
618 * For historical reasons, accept CAP_SYS_ADMIN too, with
621 if (capable(CAP_SYS_ADMIN
)) {
622 pr_warn_once("%s (%d): Attempt to access syslog with "
623 "CAP_SYS_ADMIN but no CAP_SYSLOG "
625 current
->comm
, task_pid_nr(current
));
631 return security_syslog(type
);
633 EXPORT_SYMBOL_GPL(check_syslog_permissions
);
635 static void append_char(char **pp
, char *e
, char c
)
641 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
642 struct printk_log
*msg
, u64 seq
,
643 enum log_flags prev_flags
)
645 u64 ts_usec
= msg
->ts_nsec
;
648 do_div(ts_usec
, 1000);
651 * If we couldn't merge continuation line fragments during the print,
652 * export the stored flags to allow an optional external merge of the
653 * records. Merging the records isn't always neccessarily correct, like
654 * when we hit a race during printing. In most cases though, it produces
655 * better readable output. 'c' in the record flags mark the first
656 * fragment of a line, '+' the following.
658 if (msg
->flags
& LOG_CONT
)
659 cont
= (prev_flags
& LOG_CONT
) ? '+' : 'c';
661 return scnprintf(buf
, size
, "%u,%llu,%llu,%c;",
662 (msg
->facility
<< 3) | msg
->level
, seq
, ts_usec
, cont
);
665 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
666 char *dict
, size_t dict_len
,
667 char *text
, size_t text_len
)
669 char *p
= buf
, *e
= buf
+ size
;
672 /* escape non-printable characters */
673 for (i
= 0; i
< text_len
; i
++) {
674 unsigned char c
= text
[i
];
676 if (c
< ' ' || c
>= 127 || c
== '\\')
677 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
679 append_char(&p
, e
, c
);
681 append_char(&p
, e
, '\n');
686 for (i
= 0; i
< dict_len
; i
++) {
687 unsigned char c
= dict
[i
];
690 append_char(&p
, e
, ' ');
695 append_char(&p
, e
, '\n');
700 if (c
< ' ' || c
>= 127 || c
== '\\') {
701 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
705 append_char(&p
, e
, c
);
707 append_char(&p
, e
, '\n');
713 /* /dev/kmsg - userspace message inject/listen interface */
714 struct devkmsg_user
{
718 struct ratelimit_state rs
;
720 char buf
[CONSOLE_EXT_LOG_MAX
];
723 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
726 int level
= default_message_loglevel
;
727 int facility
= 1; /* LOG_USER */
728 struct file
*file
= iocb
->ki_filp
;
729 struct devkmsg_user
*user
= file
->private_data
;
730 size_t len
= iov_iter_count(from
);
733 if (!user
|| len
> LOG_LINE_MAX
)
736 /* Ignore when user logging is disabled. */
737 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
740 /* Ratelimit when not explicitly enabled. */
741 if (!(devkmsg_log
& DEVKMSG_LOG_MASK_ON
)) {
742 if (!___ratelimit(&user
->rs
, current
->comm
))
746 buf
= kmalloc(len
+1, GFP_KERNEL
);
751 if (copy_from_iter(buf
, len
, from
) != len
) {
757 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
758 * the decimal value represents 32bit, the lower 3 bit are the log
759 * level, the rest are the log facility.
761 * If no prefix or no userspace facility is specified, we
762 * enforce LOG_USER, to be able to reliably distinguish
763 * kernel-generated messages from userspace-injected ones.
766 if (line
[0] == '<') {
770 u
= simple_strtoul(line
+ 1, &endp
, 10);
771 if (endp
&& endp
[0] == '>') {
772 level
= LOG_LEVEL(u
);
773 if (LOG_FACILITY(u
) != 0)
774 facility
= LOG_FACILITY(u
);
781 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
786 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
787 size_t count
, loff_t
*ppos
)
789 struct devkmsg_user
*user
= file
->private_data
;
790 struct printk_log
*msg
;
797 ret
= mutex_lock_interruptible(&user
->lock
);
800 raw_spin_lock_irq(&logbuf_lock
);
801 while (user
->seq
== log_next_seq
) {
802 if (file
->f_flags
& O_NONBLOCK
) {
804 raw_spin_unlock_irq(&logbuf_lock
);
808 raw_spin_unlock_irq(&logbuf_lock
);
809 ret
= wait_event_interruptible(log_wait
,
810 user
->seq
!= log_next_seq
);
813 raw_spin_lock_irq(&logbuf_lock
);
816 if (user
->seq
< log_first_seq
) {
817 /* our last seen message is gone, return error and reset */
818 user
->idx
= log_first_idx
;
819 user
->seq
= log_first_seq
;
821 raw_spin_unlock_irq(&logbuf_lock
);
825 msg
= log_from_idx(user
->idx
);
826 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
827 msg
, user
->seq
, user
->prev
);
828 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
829 log_dict(msg
), msg
->dict_len
,
830 log_text(msg
), msg
->text_len
);
832 user
->prev
= msg
->flags
;
833 user
->idx
= log_next(user
->idx
);
835 raw_spin_unlock_irq(&logbuf_lock
);
842 if (copy_to_user(buf
, user
->buf
, len
)) {
848 mutex_unlock(&user
->lock
);
852 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
854 struct devkmsg_user
*user
= file
->private_data
;
862 raw_spin_lock_irq(&logbuf_lock
);
865 /* the first record */
866 user
->idx
= log_first_idx
;
867 user
->seq
= log_first_seq
;
871 * The first record after the last SYSLOG_ACTION_CLEAR,
872 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
873 * changes no global state, and does not clear anything.
875 user
->idx
= clear_idx
;
876 user
->seq
= clear_seq
;
879 /* after the last record */
880 user
->idx
= log_next_idx
;
881 user
->seq
= log_next_seq
;
886 raw_spin_unlock_irq(&logbuf_lock
);
890 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
892 struct devkmsg_user
*user
= file
->private_data
;
896 return POLLERR
|POLLNVAL
;
898 poll_wait(file
, &log_wait
, wait
);
900 raw_spin_lock_irq(&logbuf_lock
);
901 if (user
->seq
< log_next_seq
) {
902 /* return error when data has vanished underneath us */
903 if (user
->seq
< log_first_seq
)
904 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
906 ret
= POLLIN
|POLLRDNORM
;
908 raw_spin_unlock_irq(&logbuf_lock
);
913 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
915 struct devkmsg_user
*user
;
918 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
921 /* write-only does not need any file context */
922 if ((file
->f_flags
& O_ACCMODE
) != O_WRONLY
) {
923 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
929 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
933 ratelimit_default_init(&user
->rs
);
934 ratelimit_set_flags(&user
->rs
, RATELIMIT_MSG_ON_RELEASE
);
936 mutex_init(&user
->lock
);
938 raw_spin_lock_irq(&logbuf_lock
);
939 user
->idx
= log_first_idx
;
940 user
->seq
= log_first_seq
;
941 raw_spin_unlock_irq(&logbuf_lock
);
943 file
->private_data
= user
;
947 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
949 struct devkmsg_user
*user
= file
->private_data
;
954 ratelimit_state_exit(&user
->rs
);
956 mutex_destroy(&user
->lock
);
961 const struct file_operations kmsg_fops
= {
962 .open
= devkmsg_open
,
963 .read
= devkmsg_read
,
964 .write_iter
= devkmsg_write
,
965 .llseek
= devkmsg_llseek
,
966 .poll
= devkmsg_poll
,
967 .release
= devkmsg_release
,
970 #ifdef CONFIG_KEXEC_CORE
972 * This appends the listed symbols to /proc/vmcore
974 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
975 * obtain access to symbols that are otherwise very difficult to locate. These
976 * symbols are specifically used so that utilities can access and extract the
977 * dmesg log from a vmcore file after a crash.
979 void log_buf_kexec_setup(void)
981 VMCOREINFO_SYMBOL(log_buf
);
982 VMCOREINFO_SYMBOL(log_buf_len
);
983 VMCOREINFO_SYMBOL(log_first_idx
);
984 VMCOREINFO_SYMBOL(clear_idx
);
985 VMCOREINFO_SYMBOL(log_next_idx
);
987 * Export struct printk_log size and field offsets. User space tools can
988 * parse it and detect any changes to structure down the line.
990 VMCOREINFO_STRUCT_SIZE(printk_log
);
991 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
992 VMCOREINFO_OFFSET(printk_log
, len
);
993 VMCOREINFO_OFFSET(printk_log
, text_len
);
994 VMCOREINFO_OFFSET(printk_log
, dict_len
);
998 /* requested log_buf_len from kernel cmdline */
999 static unsigned long __initdata new_log_buf_len
;
1001 /* we practice scaling the ring buffer by powers of 2 */
1002 static void __init
log_buf_len_update(unsigned size
)
1005 size
= roundup_pow_of_two(size
);
1006 if (size
> log_buf_len
)
1007 new_log_buf_len
= size
;
1010 /* save requested log_buf_len since it's too early to process it */
1011 static int __init
log_buf_len_setup(char *str
)
1013 unsigned size
= memparse(str
, &str
);
1015 log_buf_len_update(size
);
1019 early_param("log_buf_len", log_buf_len_setup
);
1022 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1024 static void __init
log_buf_add_cpu(void)
1026 unsigned int cpu_extra
;
1029 * archs should set up cpu_possible_bits properly with
1030 * set_cpu_possible() after setup_arch() but just in
1031 * case lets ensure this is valid.
1033 if (num_possible_cpus() == 1)
1036 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
1038 /* by default this will only continue through for large > 64 CPUs */
1039 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
1042 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1043 __LOG_CPU_MAX_BUF_LEN
);
1044 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1046 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
1048 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
1050 #else /* !CONFIG_SMP */
1051 static inline void log_buf_add_cpu(void) {}
1052 #endif /* CONFIG_SMP */
1054 void __init
setup_log_buf(int early
)
1056 unsigned long flags
;
1060 if (log_buf
!= __log_buf
)
1063 if (!early
&& !new_log_buf_len
)
1066 if (!new_log_buf_len
)
1071 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
1073 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
1077 if (unlikely(!new_log_buf
)) {
1078 pr_err("log_buf_len: %ld bytes not available\n",
1083 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
1084 log_buf_len
= new_log_buf_len
;
1085 log_buf
= new_log_buf
;
1086 new_log_buf_len
= 0;
1087 free
= __LOG_BUF_LEN
- log_next_idx
;
1088 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
1089 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
1091 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
1092 pr_info("early log buf free: %d(%d%%)\n",
1093 free
, (free
* 100) / __LOG_BUF_LEN
);
1096 static bool __read_mostly ignore_loglevel
;
1098 static int __init
ignore_loglevel_setup(char *str
)
1100 ignore_loglevel
= true;
1101 pr_info("debug: ignoring loglevel setting.\n");
1106 early_param("ignore_loglevel", ignore_loglevel_setup
);
1107 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1108 MODULE_PARM_DESC(ignore_loglevel
,
1109 "ignore loglevel setting (prints all kernel messages to the console)");
1111 static bool suppress_message_printing(int level
)
1113 return (level
>= console_loglevel
&& !ignore_loglevel
);
1116 #ifdef CONFIG_BOOT_PRINTK_DELAY
1118 static int boot_delay
; /* msecs delay after each printk during bootup */
1119 static unsigned long long loops_per_msec
; /* based on boot_delay */
1121 static int __init
boot_delay_setup(char *str
)
1125 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
1126 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
1128 get_option(&str
, &boot_delay
);
1129 if (boot_delay
> 10 * 1000)
1132 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1133 "HZ: %d, loops_per_msec: %llu\n",
1134 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
1137 early_param("boot_delay", boot_delay_setup
);
1139 static void boot_delay_msec(int level
)
1141 unsigned long long k
;
1142 unsigned long timeout
;
1144 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
1145 || suppress_message_printing(level
)) {
1149 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1151 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1156 * use (volatile) jiffies to prevent
1157 * compiler reduction; loop termination via jiffies
1158 * is secondary and may or may not happen.
1160 if (time_after(jiffies
, timeout
))
1162 touch_nmi_watchdog();
1166 static inline void boot_delay_msec(int level
)
1171 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1172 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1174 static size_t print_time(u64 ts
, char *buf
)
1176 unsigned long rem_nsec
;
1181 rem_nsec
= do_div(ts
, 1000000000);
1184 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1186 return sprintf(buf
, "[%5lu.%06lu] ",
1187 (unsigned long)ts
, rem_nsec
/ 1000);
1190 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1193 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1197 len
+= sprintf(buf
, "<%u>", prefix
);
1202 else if (prefix
> 99)
1204 else if (prefix
> 9)
1209 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1213 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1214 bool syslog
, char *buf
, size_t size
)
1216 const char *text
= log_text(msg
);
1217 size_t text_size
= msg
->text_len
;
1219 bool newline
= true;
1222 if ((prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
))
1225 if (msg
->flags
& LOG_CONT
) {
1226 if ((prev
& LOG_CONT
) && !(prev
& LOG_NEWLINE
))
1229 if (!(msg
->flags
& LOG_NEWLINE
))
1234 const char *next
= memchr(text
, '\n', text_size
);
1238 text_len
= next
- text
;
1240 text_size
-= next
- text
;
1242 text_len
= text_size
;
1246 if (print_prefix(msg
, syslog
, NULL
) +
1247 text_len
+ 1 >= size
- len
)
1251 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1252 memcpy(buf
+ len
, text
, text_len
);
1254 if (next
|| newline
)
1257 /* SYSLOG_ACTION_* buffer size only calculation */
1259 len
+= print_prefix(msg
, syslog
, NULL
);
1261 if (next
|| newline
)
1272 static int syslog_print(char __user
*buf
, int size
)
1275 struct printk_log
*msg
;
1278 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1286 raw_spin_lock_irq(&logbuf_lock
);
1287 if (syslog_seq
< log_first_seq
) {
1288 /* messages are gone, move to first one */
1289 syslog_seq
= log_first_seq
;
1290 syslog_idx
= log_first_idx
;
1294 if (syslog_seq
== log_next_seq
) {
1295 raw_spin_unlock_irq(&logbuf_lock
);
1299 skip
= syslog_partial
;
1300 msg
= log_from_idx(syslog_idx
);
1301 n
= msg_print_text(msg
, syslog_prev
, true, text
,
1302 LOG_LINE_MAX
+ PREFIX_MAX
);
1303 if (n
- syslog_partial
<= size
) {
1304 /* message fits into buffer, move forward */
1305 syslog_idx
= log_next(syslog_idx
);
1307 syslog_prev
= msg
->flags
;
1308 n
-= syslog_partial
;
1311 /* partial read(), remember position */
1313 syslog_partial
+= n
;
1316 raw_spin_unlock_irq(&logbuf_lock
);
1321 if (copy_to_user(buf
, text
+ skip
, n
)) {
1336 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1341 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1345 raw_spin_lock_irq(&logbuf_lock
);
1350 enum log_flags prev
;
1353 * Find first record that fits, including all following records,
1354 * into the user-provided buffer for this dump.
1359 while (seq
< log_next_seq
) {
1360 struct printk_log
*msg
= log_from_idx(idx
);
1362 len
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1364 idx
= log_next(idx
);
1368 /* move first record forward until length fits into the buffer */
1372 while (len
> size
&& seq
< log_next_seq
) {
1373 struct printk_log
*msg
= log_from_idx(idx
);
1375 len
-= msg_print_text(msg
, prev
, true, NULL
, 0);
1377 idx
= log_next(idx
);
1381 /* last message fitting into this dump */
1382 next_seq
= log_next_seq
;
1385 while (len
>= 0 && seq
< next_seq
) {
1386 struct printk_log
*msg
= log_from_idx(idx
);
1389 textlen
= msg_print_text(msg
, prev
, true, text
,
1390 LOG_LINE_MAX
+ PREFIX_MAX
);
1395 idx
= log_next(idx
);
1399 raw_spin_unlock_irq(&logbuf_lock
);
1400 if (copy_to_user(buf
+ len
, text
, textlen
))
1404 raw_spin_lock_irq(&logbuf_lock
);
1406 if (seq
< log_first_seq
) {
1407 /* messages are gone, move to next one */
1408 seq
= log_first_seq
;
1409 idx
= log_first_idx
;
1416 clear_seq
= log_next_seq
;
1417 clear_idx
= log_next_idx
;
1419 raw_spin_unlock_irq(&logbuf_lock
);
1425 int do_syslog(int type
, char __user
*buf
, int len
, int source
)
1428 static int saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1431 error
= check_syslog_permissions(type
, source
);
1436 case SYSLOG_ACTION_CLOSE
: /* Close log */
1438 case SYSLOG_ACTION_OPEN
: /* Open log */
1440 case SYSLOG_ACTION_READ
: /* Read from log */
1442 if (!buf
|| len
< 0)
1447 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
:
1464 if (!buf
|| len
< 0)
1469 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1473 error
= syslog_print_all(buf
, len
, clear
);
1475 /* Clear ring buffer */
1476 case SYSLOG_ACTION_CLEAR
:
1477 syslog_print_all(NULL
, 0, true);
1479 /* Disable logging to console */
1480 case SYSLOG_ACTION_CONSOLE_OFF
:
1481 if (saved_console_loglevel
== LOGLEVEL_DEFAULT
)
1482 saved_console_loglevel
= console_loglevel
;
1483 console_loglevel
= minimum_console_loglevel
;
1485 /* Enable logging to console */
1486 case SYSLOG_ACTION_CONSOLE_ON
:
1487 if (saved_console_loglevel
!= LOGLEVEL_DEFAULT
) {
1488 console_loglevel
= saved_console_loglevel
;
1489 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1492 /* Set level of messages printed to console */
1493 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1495 if (len
< 1 || len
> 8)
1497 if (len
< minimum_console_loglevel
)
1498 len
= minimum_console_loglevel
;
1499 console_loglevel
= len
;
1500 /* Implicitly re-enable logging to console */
1501 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1504 /* Number of chars in the log buffer */
1505 case SYSLOG_ACTION_SIZE_UNREAD
:
1506 raw_spin_lock_irq(&logbuf_lock
);
1507 if (syslog_seq
< log_first_seq
) {
1508 /* messages are gone, move to first one */
1509 syslog_seq
= log_first_seq
;
1510 syslog_idx
= log_first_idx
;
1514 if (source
== SYSLOG_FROM_PROC
) {
1516 * Short-cut for poll(/"proc/kmsg") which simply checks
1517 * for pending data, not the size; return the count of
1518 * records, not the length.
1520 error
= log_next_seq
- syslog_seq
;
1522 u64 seq
= syslog_seq
;
1523 u32 idx
= syslog_idx
;
1524 enum log_flags prev
= syslog_prev
;
1527 while (seq
< log_next_seq
) {
1528 struct printk_log
*msg
= log_from_idx(idx
);
1530 error
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1531 idx
= log_next(idx
);
1535 error
-= syslog_partial
;
1537 raw_spin_unlock_irq(&logbuf_lock
);
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(int level
,
1562 const char *ext_text
, size_t ext_len
,
1563 const char *text
, size_t len
)
1565 struct console
*con
;
1567 trace_console(text
, len
);
1569 if (!console_drivers
)
1572 for_each_console(con
) {
1573 if (exclusive_console
&& con
!= exclusive_console
)
1575 if (!(con
->flags
& CON_ENABLED
))
1579 if (!cpu_online(smp_processor_id()) &&
1580 !(con
->flags
& CON_ANYTIME
))
1582 if (con
->flags
& CON_EXTENDED
)
1583 con
->write(con
, ext_text
, ext_len
);
1585 con
->write(con
, text
, len
);
1590 * Zap console related locks when oopsing.
1591 * To leave time for slow consoles to print a full oops,
1592 * only zap at most once every 30 seconds.
1594 static void zap_locks(void)
1596 static unsigned long oops_timestamp
;
1598 if (time_after_eq(jiffies
, oops_timestamp
) &&
1599 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1602 oops_timestamp
= jiffies
;
1605 /* If a crash is occurring, make sure we can't deadlock */
1606 raw_spin_lock_init(&logbuf_lock
);
1607 /* And make sure that we print immediately */
1608 sema_init(&console_sem
, 1);
1611 int printk_delay_msec __read_mostly
;
1613 static inline void printk_delay(void)
1615 if (unlikely(printk_delay_msec
)) {
1616 int m
= printk_delay_msec
;
1620 touch_nmi_watchdog();
1626 * Continuation lines are buffered, and not committed to the record buffer
1627 * until the line is complete, or a race forces it. The line fragments
1628 * though, are printed immediately to the consoles to ensure everything has
1629 * reached the console in case of a kernel crash.
1631 static struct cont
{
1632 char buf
[LOG_LINE_MAX
];
1633 size_t len
; /* length == 0 means unused buffer */
1634 size_t cons
; /* bytes written to console */
1635 struct task_struct
*owner
; /* task of first print*/
1636 u64 ts_nsec
; /* time of first print */
1637 u8 level
; /* log level of first message */
1638 u8 facility
; /* log facility of first message */
1639 enum log_flags flags
; /* prefix, newline flags */
1640 bool flushed
:1; /* buffer sealed and committed */
1643 static void cont_flush(enum log_flags flags
)
1652 * If a fragment of this line was directly flushed to the
1653 * console; wait for the console to pick up the rest of the
1654 * line. LOG_NOCONS suppresses a duplicated output.
1656 log_store(cont
.facility
, cont
.level
, flags
| LOG_NOCONS
,
1657 cont
.ts_nsec
, NULL
, 0, cont
.buf
, cont
.len
);
1659 cont
.flushed
= true;
1662 * If no fragment of this line ever reached the console,
1663 * just submit it to the store and free the buffer.
1665 log_store(cont
.facility
, cont
.level
, flags
, 0,
1666 NULL
, 0, cont
.buf
, cont
.len
);
1671 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1673 if (cont
.len
&& cont
.flushed
)
1677 * If ext consoles are present, flush and skip in-kernel
1678 * continuation. See nr_ext_console_drivers definition. Also, if
1679 * the line gets too long, split it up in separate records.
1681 if (nr_ext_console_drivers
|| cont
.len
+ len
> sizeof(cont
.buf
)) {
1682 cont_flush(LOG_CONT
);
1687 cont
.facility
= facility
;
1689 cont
.owner
= current
;
1690 cont
.ts_nsec
= local_clock();
1693 cont
.flushed
= false;
1696 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1699 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1700 cont_flush(LOG_CONT
);
1705 static size_t cont_print_text(char *text
, size_t size
)
1710 if (cont
.cons
== 0 && (console_prev
& LOG_NEWLINE
)) {
1711 textlen
+= print_time(cont
.ts_nsec
, text
);
1715 len
= cont
.len
- cont
.cons
;
1719 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1721 cont
.cons
= cont
.len
;
1725 if (cont
.flags
& LOG_NEWLINE
)
1726 text
[textlen
++] = '\n';
1727 /* got everything, release buffer */
1733 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
)
1735 if (!(lflags
& LOG_NEWLINE
)) {
1737 * Flush the conflicting buffer. An earlier newline was missing,
1738 * or another task also prints continuation lines.
1740 if (cont
.len
&& (!(lflags
& LOG_CONT
) || cont
.owner
!= current
))
1741 cont_flush(LOG_NEWLINE
);
1743 /* buffer line if possible, otherwise store it right away */
1744 if (cont_add(facility
, level
, text
, text_len
))
1747 return log_store(facility
, level
, lflags
| LOG_CONT
, 0, dict
, dictlen
, text
, text_len
);
1751 * If an earlier newline was missing and it was the same task,
1752 * either merge it with the current buffer and flush, or if
1753 * there was a race with interrupts (prefix == true) then just
1754 * flush it out and store this line separately.
1755 * If the preceding printk was from a different task and missed
1756 * a newline, flush and append the newline.
1759 bool stored
= false;
1761 if (cont
.owner
== current
&& (lflags
& LOG_CONT
))
1762 stored
= cont_add(facility
, level
, text
, text_len
);
1763 cont_flush(LOG_NEWLINE
);
1768 return log_store(facility
, level
, lflags
, 0, dict
, dictlen
, text
, text_len
);
1771 asmlinkage
int vprintk_emit(int facility
, int level
,
1772 const char *dict
, size_t dictlen
,
1773 const char *fmt
, va_list args
)
1775 static bool recursion_bug
;
1776 static char textbuf
[LOG_LINE_MAX
];
1777 char *text
= textbuf
;
1778 size_t text_len
= 0;
1779 enum log_flags lflags
= 0;
1780 unsigned long flags
;
1782 int printed_len
= 0;
1783 int nmi_message_lost
;
1784 bool in_sched
= false;
1785 /* cpu currently holding logbuf_lock in this function */
1786 static unsigned int logbuf_cpu
= UINT_MAX
;
1788 if (level
== LOGLEVEL_SCHED
) {
1789 level
= LOGLEVEL_DEFAULT
;
1793 boot_delay_msec(level
);
1796 local_irq_save(flags
);
1797 this_cpu
= smp_processor_id();
1800 * Ouch, printk recursed into itself!
1802 if (unlikely(logbuf_cpu
== this_cpu
)) {
1804 * If a crash is occurring during printk() on this CPU,
1805 * then try to get the crash message out but make sure
1806 * we can't deadlock. Otherwise just return to avoid the
1807 * recursion and return - but flag the recursion so that
1808 * it can be printed at the next appropriate moment:
1810 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1811 recursion_bug
= true;
1812 local_irq_restore(flags
);
1819 /* This stops the holder of console_sem just where we want him */
1820 raw_spin_lock(&logbuf_lock
);
1821 logbuf_cpu
= this_cpu
;
1823 if (unlikely(recursion_bug
)) {
1824 static const char recursion_msg
[] =
1825 "BUG: recent printk recursion!";
1827 recursion_bug
= false;
1828 /* emit KERN_CRIT message */
1829 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1830 NULL
, 0, recursion_msg
,
1831 strlen(recursion_msg
));
1834 nmi_message_lost
= get_nmi_message_lost();
1835 if (unlikely(nmi_message_lost
)) {
1836 text_len
= scnprintf(textbuf
, sizeof(textbuf
),
1837 "BAD LUCK: lost %d message(s) from NMI context!",
1839 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1840 NULL
, 0, textbuf
, text_len
);
1844 * The printf needs to come first; we need the syslog
1845 * prefix which might be passed-in as a parameter.
1847 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1849 /* mark and strip a trailing newline */
1850 if (text_len
&& text
[text_len
-1] == '\n') {
1852 lflags
|= LOG_NEWLINE
;
1855 /* strip kernel syslog prefix and extract log level or control flags */
1856 if (facility
== 0) {
1859 while ((kern_level
= printk_get_level(text
)) != 0) {
1860 switch (kern_level
) {
1862 if (level
== LOGLEVEL_DEFAULT
)
1863 level
= kern_level
- '0';
1865 case 'd': /* KERN_DEFAULT */
1866 lflags
|= LOG_PREFIX
;
1868 case 'c': /* KERN_CONT */
1877 if (level
== LOGLEVEL_DEFAULT
)
1878 level
= default_message_loglevel
;
1881 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1883 printed_len
+= log_output(facility
, level
, lflags
, dict
, dictlen
, text
, text_len
);
1885 logbuf_cpu
= UINT_MAX
;
1886 raw_spin_unlock(&logbuf_lock
);
1888 local_irq_restore(flags
);
1890 /* If called from the scheduler, we can not call up(). */
1894 * Try to acquire and then immediately release the console
1895 * semaphore. The release will print out buffers and wake up
1896 * /dev/kmsg and syslog() users.
1898 if (console_trylock())
1905 EXPORT_SYMBOL(vprintk_emit
);
1907 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1909 return vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1911 EXPORT_SYMBOL(vprintk
);
1913 asmlinkage
int printk_emit(int facility
, int level
,
1914 const char *dict
, size_t dictlen
,
1915 const char *fmt
, ...)
1920 va_start(args
, fmt
);
1921 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1926 EXPORT_SYMBOL(printk_emit
);
1928 int vprintk_default(const char *fmt
, va_list args
)
1932 #ifdef CONFIG_KGDB_KDB
1933 if (unlikely(kdb_trap_printk
)) {
1934 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1938 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1942 EXPORT_SYMBOL_GPL(vprintk_default
);
1945 * printk - print a kernel message
1946 * @fmt: format string
1948 * This is printk(). It can be called from any context. We want it to work.
1950 * We try to grab the console_lock. If we succeed, it's easy - we log the
1951 * output and call the console drivers. If we fail to get the semaphore, we
1952 * place the output into the log buffer and return. The current holder of
1953 * the console_sem will notice the new output in console_unlock(); and will
1954 * send it to the consoles before releasing the lock.
1956 * One effect of this deferred printing is that code which calls printk() and
1957 * then changes console_loglevel may break. This is because console_loglevel
1958 * is inspected when the actual printing occurs.
1963 * See the vsnprintf() documentation for format string extensions over C99.
1965 asmlinkage __visible
int printk(const char *fmt
, ...)
1970 va_start(args
, fmt
);
1971 r
= vprintk_func(fmt
, args
);
1976 EXPORT_SYMBOL(printk
);
1978 #else /* CONFIG_PRINTK */
1980 #define LOG_LINE_MAX 0
1981 #define PREFIX_MAX 0
1983 static u64 syslog_seq
;
1984 static u32 syslog_idx
;
1985 static u64 console_seq
;
1986 static u32 console_idx
;
1987 static enum log_flags syslog_prev
;
1988 static u64 log_first_seq
;
1989 static u32 log_first_idx
;
1990 static u64 log_next_seq
;
1991 static enum log_flags console_prev
;
1992 static struct cont
{
1998 static char *log_text(const struct printk_log
*msg
) { return NULL
; }
1999 static char *log_dict(const struct printk_log
*msg
) { return NULL
; }
2000 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
2001 static u32
log_next(u32 idx
) { return 0; }
2002 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
2003 struct printk_log
*msg
, u64 seq
,
2004 enum log_flags prev_flags
) { return 0; }
2005 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
2006 char *dict
, size_t dict_len
,
2007 char *text
, size_t text_len
) { return 0; }
2008 static void call_console_drivers(int level
,
2009 const char *ext_text
, size_t ext_len
,
2010 const char *text
, size_t len
) {}
2011 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
2012 bool syslog
, char *buf
, size_t size
) { return 0; }
2013 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
2014 static bool suppress_message_printing(int level
) { return false; }
2016 /* Still needs to be defined for users */
2017 DEFINE_PER_CPU(printk_func_t
, printk_func
);
2019 #endif /* CONFIG_PRINTK */
2021 #ifdef CONFIG_EARLY_PRINTK
2022 struct console
*early_console
;
2024 asmlinkage __visible
void early_printk(const char *fmt
, ...)
2034 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
2037 early_console
->write(early_console
, buf
, n
);
2041 static int __add_preferred_console(char *name
, int idx
, char *options
,
2044 struct console_cmdline
*c
;
2048 * See if this tty is not yet registered, and
2049 * if we have a slot free.
2051 for (i
= 0, c
= console_cmdline
;
2052 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2054 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
2056 selected_console
= i
;
2060 if (i
== MAX_CMDLINECONSOLES
)
2063 selected_console
= i
;
2064 strlcpy(c
->name
, name
, sizeof(c
->name
));
2065 c
->options
= options
;
2066 braille_set_options(c
, brl_options
);
2072 * Set up a console. Called via do_early_param() in init/main.c
2073 * for each "console=" parameter in the boot command line.
2075 static int __init
console_setup(char *str
)
2077 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
2078 char *s
, *options
, *brl_options
= NULL
;
2081 if (_braille_console_setup(&str
, &brl_options
))
2085 * Decode str into name, index, options.
2087 if (str
[0] >= '0' && str
[0] <= '9') {
2088 strcpy(buf
, "ttyS");
2089 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
2091 strncpy(buf
, str
, sizeof(buf
) - 1);
2093 buf
[sizeof(buf
) - 1] = 0;
2094 options
= strchr(str
, ',');
2098 if (!strcmp(str
, "ttya"))
2099 strcpy(buf
, "ttyS0");
2100 if (!strcmp(str
, "ttyb"))
2101 strcpy(buf
, "ttyS1");
2103 for (s
= buf
; *s
; s
++)
2104 if (isdigit(*s
) || *s
== ',')
2106 idx
= simple_strtoul(s
, NULL
, 10);
2109 __add_preferred_console(buf
, idx
, options
, brl_options
);
2110 console_set_on_cmdline
= 1;
2113 __setup("console=", console_setup
);
2116 * add_preferred_console - add a device to the list of preferred consoles.
2117 * @name: device name
2118 * @idx: device index
2119 * @options: options for this console
2121 * The last preferred console added will be used for kernel messages
2122 * and stdin/out/err for init. Normally this is used by console_setup
2123 * above to handle user-supplied console arguments; however it can also
2124 * be used by arch-specific code either to override the user or more
2125 * commonly to provide a default console (ie from PROM variables) when
2126 * the user has not supplied one.
2128 int add_preferred_console(char *name
, int idx
, char *options
)
2130 return __add_preferred_console(name
, idx
, options
, NULL
);
2133 bool console_suspend_enabled
= true;
2134 EXPORT_SYMBOL(console_suspend_enabled
);
2136 static int __init
console_suspend_disable(char *str
)
2138 console_suspend_enabled
= false;
2141 __setup("no_console_suspend", console_suspend_disable
);
2142 module_param_named(console_suspend
, console_suspend_enabled
,
2143 bool, S_IRUGO
| S_IWUSR
);
2144 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2145 " and hibernate operations");
2148 * suspend_console - suspend the console subsystem
2150 * This disables printk() while we go into suspend states
2152 void suspend_console(void)
2154 if (!console_suspend_enabled
)
2156 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2158 console_suspended
= 1;
2162 void resume_console(void)
2164 if (!console_suspend_enabled
)
2167 console_suspended
= 0;
2172 * console_cpu_notify - print deferred console messages after CPU hotplug
2173 * @self: notifier struct
2174 * @action: CPU hotplug event
2177 * If printk() is called from a CPU that is not online yet, the messages
2178 * will be spooled but will not show up on the console. This function is
2179 * called when a new CPU comes online (or fails to come up), and ensures
2180 * that any such output gets printed.
2182 static int console_cpu_notify(struct notifier_block
*self
,
2183 unsigned long action
, void *hcpu
)
2188 case CPU_DOWN_FAILED
:
2189 case CPU_UP_CANCELED
:
2197 * console_lock - lock the console system for exclusive use.
2199 * Acquires a lock which guarantees that the caller has
2200 * exclusive access to the console system and the console_drivers list.
2202 * Can sleep, returns nothing.
2204 void console_lock(void)
2209 if (console_suspended
)
2212 console_may_schedule
= 1;
2214 EXPORT_SYMBOL(console_lock
);
2217 * console_trylock - try to lock the console system for exclusive use.
2219 * Try to acquire a lock which guarantees that the caller has exclusive
2220 * access to the console system and the console_drivers list.
2222 * returns 1 on success, and 0 on failure to acquire the lock.
2224 int console_trylock(void)
2226 if (down_trylock_console_sem())
2228 if (console_suspended
) {
2234 * When PREEMPT_COUNT disabled we can't reliably detect if it's
2235 * safe to schedule (e.g. calling printk while holding a spin_lock),
2236 * because preempt_disable()/preempt_enable() are just barriers there
2237 * and preempt_count() is always 0.
2239 * RCU read sections have a separate preemption counter when
2240 * PREEMPT_RCU enabled thus we must take extra care and check
2241 * rcu_preempt_depth(), otherwise RCU read sections modify
2244 console_may_schedule
= !oops_in_progress
&&
2246 !rcu_preempt_depth();
2249 EXPORT_SYMBOL(console_trylock
);
2251 int is_console_locked(void)
2253 return console_locked
;
2257 * Check if we have any console that is capable of printing while cpu is
2258 * booting or shutting down. Requires console_sem.
2260 static int have_callable_console(void)
2262 struct console
*con
;
2264 for_each_console(con
)
2265 if ((con
->flags
& CON_ENABLED
) &&
2266 (con
->flags
& CON_ANYTIME
))
2273 * Can we actually use the console at this time on this cpu?
2275 * Console drivers may assume that per-cpu resources have been allocated. So
2276 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2277 * call them until this CPU is officially up.
2279 static inline int can_use_console(void)
2281 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2284 static void console_cont_flush(char *text
, size_t size
)
2286 unsigned long flags
;
2289 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2294 if (suppress_message_printing(cont
.level
)) {
2295 cont
.cons
= cont
.len
;
2302 * We still queue earlier records, likely because the console was
2303 * busy. The earlier ones need to be printed before this one, we
2304 * did not flush any fragment so far, so just let it queue up.
2306 if (console_seq
< log_next_seq
&& !cont
.cons
)
2309 len
= cont_print_text(text
, size
);
2310 raw_spin_unlock(&logbuf_lock
);
2311 stop_critical_timings();
2312 call_console_drivers(cont
.level
, NULL
, 0, text
, len
);
2313 start_critical_timings();
2314 local_irq_restore(flags
);
2317 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2321 * console_unlock - unlock the console system
2323 * Releases the console_lock which the caller holds on the console system
2324 * and the console driver list.
2326 * While the console_lock was held, console output may have been buffered
2327 * by printk(). If this is the case, console_unlock(); emits
2328 * the output prior to releasing the lock.
2330 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2332 * console_unlock(); may be called from any context.
2334 void console_unlock(void)
2336 static char ext_text
[CONSOLE_EXT_LOG_MAX
];
2337 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2338 static u64 seen_seq
;
2339 unsigned long flags
;
2340 bool wake_klogd
= false;
2341 bool do_cond_resched
, retry
;
2343 if (console_suspended
) {
2349 * Console drivers are called under logbuf_lock, so
2350 * @console_may_schedule should be cleared before; however, we may
2351 * end up dumping a lot of lines, for example, if called from
2352 * console registration path, and should invoke cond_resched()
2353 * between lines if allowable. Not doing so can cause a very long
2354 * scheduling stall on a slow console leading to RCU stall and
2355 * softlockup warnings which exacerbate the issue with more
2356 * messages practically incapacitating the system.
2358 do_cond_resched
= console_may_schedule
;
2359 console_may_schedule
= 0;
2363 * We released the console_sem lock, so we need to recheck if
2364 * cpu is online and (if not) is there at least one CON_ANYTIME
2367 if (!can_use_console()) {
2373 /* flush buffered message fragment immediately to console */
2374 console_cont_flush(text
, sizeof(text
));
2377 struct printk_log
*msg
;
2382 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2383 if (seen_seq
!= log_next_seq
) {
2385 seen_seq
= log_next_seq
;
2388 if (console_seq
< log_first_seq
) {
2389 len
= sprintf(text
, "** %u printk messages dropped ** ",
2390 (unsigned)(log_first_seq
- console_seq
));
2392 /* messages are gone, move to first one */
2393 console_seq
= log_first_seq
;
2394 console_idx
= log_first_idx
;
2400 if (console_seq
== log_next_seq
)
2403 msg
= log_from_idx(console_idx
);
2405 if ((msg
->flags
& LOG_NOCONS
) ||
2406 suppress_message_printing(level
)) {
2408 * Skip record we have buffered and already printed
2409 * directly to the console when we received it, and
2410 * record that has level above the console loglevel.
2412 console_idx
= log_next(console_idx
);
2415 * We will get here again when we register a new
2416 * CON_PRINTBUFFER console. Clear the flag so we
2417 * will properly dump everything later.
2419 msg
->flags
&= ~LOG_NOCONS
;
2420 console_prev
= msg
->flags
;
2424 len
+= msg_print_text(msg
, console_prev
, false,
2425 text
+ len
, sizeof(text
) - len
);
2426 if (nr_ext_console_drivers
) {
2427 ext_len
= msg_print_ext_header(ext_text
,
2429 msg
, console_seq
, console_prev
);
2430 ext_len
+= msg_print_ext_body(ext_text
+ ext_len
,
2431 sizeof(ext_text
) - ext_len
,
2432 log_dict(msg
), msg
->dict_len
,
2433 log_text(msg
), msg
->text_len
);
2435 console_idx
= log_next(console_idx
);
2437 console_prev
= msg
->flags
;
2438 raw_spin_unlock(&logbuf_lock
);
2440 stop_critical_timings(); /* don't trace print latency */
2441 call_console_drivers(level
, ext_text
, ext_len
, text
, len
);
2442 start_critical_timings();
2443 local_irq_restore(flags
);
2445 if (do_cond_resched
)
2450 /* Release the exclusive_console once it is used */
2451 if (unlikely(exclusive_console
))
2452 exclusive_console
= NULL
;
2454 raw_spin_unlock(&logbuf_lock
);
2459 * Someone could have filled up the buffer again, so re-check if there's
2460 * something to flush. In case we cannot trylock the console_sem again,
2461 * there's a new owner and the console_unlock() from them will do the
2462 * flush, no worries.
2464 raw_spin_lock(&logbuf_lock
);
2465 retry
= console_seq
!= log_next_seq
;
2466 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2468 if (retry
&& console_trylock())
2474 EXPORT_SYMBOL(console_unlock
);
2477 * console_conditional_schedule - yield the CPU if required
2479 * If the console code is currently allowed to sleep, and
2480 * if this CPU should yield the CPU to another task, do
2483 * Must be called within console_lock();.
2485 void __sched
console_conditional_schedule(void)
2487 if (console_may_schedule
)
2490 EXPORT_SYMBOL(console_conditional_schedule
);
2492 void console_unblank(void)
2497 * console_unblank can no longer be called in interrupt context unless
2498 * oops_in_progress is set to 1..
2500 if (oops_in_progress
) {
2501 if (down_trylock_console_sem() != 0)
2507 console_may_schedule
= 0;
2509 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2515 * console_flush_on_panic - flush console content on panic
2517 * Immediately output all pending messages no matter what.
2519 void console_flush_on_panic(void)
2522 * If someone else is holding the console lock, trylock will fail
2523 * and may_schedule may be set. Ignore and proceed to unlock so
2524 * that messages are flushed out. As this can be called from any
2525 * context and we don't want to get preempted while flushing,
2526 * ensure may_schedule is cleared.
2529 console_may_schedule
= 0;
2534 * Return the console tty driver structure and its associated index
2536 struct tty_driver
*console_device(int *index
)
2539 struct tty_driver
*driver
= NULL
;
2542 for_each_console(c
) {
2545 driver
= c
->device(c
, index
);
2554 * Prevent further output on the passed console device so that (for example)
2555 * serial drivers can disable console output before suspending a port, and can
2556 * re-enable output afterwards.
2558 void console_stop(struct console
*console
)
2561 console
->flags
&= ~CON_ENABLED
;
2564 EXPORT_SYMBOL(console_stop
);
2566 void console_start(struct console
*console
)
2569 console
->flags
|= CON_ENABLED
;
2572 EXPORT_SYMBOL(console_start
);
2574 static int __read_mostly keep_bootcon
;
2576 static int __init
keep_bootcon_setup(char *str
)
2579 pr_info("debug: skip boot console de-registration.\n");
2584 early_param("keep_bootcon", keep_bootcon_setup
);
2587 * The console driver calls this routine during kernel initialization
2588 * to register the console printing procedure with printk() and to
2589 * print any messages that were printed by the kernel before the
2590 * console driver was initialized.
2592 * This can happen pretty early during the boot process (because of
2593 * early_printk) - sometimes before setup_arch() completes - be careful
2594 * of what kernel features are used - they may not be initialised yet.
2596 * There are two types of consoles - bootconsoles (early_printk) and
2597 * "real" consoles (everything which is not a bootconsole) which are
2598 * handled differently.
2599 * - Any number of bootconsoles can be registered at any time.
2600 * - As soon as a "real" console is registered, all bootconsoles
2601 * will be unregistered automatically.
2602 * - Once a "real" console is registered, any attempt to register a
2603 * bootconsoles will be rejected
2605 void register_console(struct console
*newcon
)
2608 unsigned long flags
;
2609 struct console
*bcon
= NULL
;
2610 struct console_cmdline
*c
;
2612 if (console_drivers
)
2613 for_each_console(bcon
)
2614 if (WARN(bcon
== newcon
,
2615 "console '%s%d' already registered\n",
2616 bcon
->name
, bcon
->index
))
2620 * before we register a new CON_BOOT console, make sure we don't
2621 * already have a valid console
2623 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2624 /* find the last or real console */
2625 for_each_console(bcon
) {
2626 if (!(bcon
->flags
& CON_BOOT
)) {
2627 pr_info("Too late to register bootconsole %s%d\n",
2628 newcon
->name
, newcon
->index
);
2634 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2635 bcon
= console_drivers
;
2637 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2638 preferred_console
= selected_console
;
2641 * See if we want to use this console driver. If we
2642 * didn't select a console we take the first one
2643 * that registers here.
2645 if (preferred_console
< 0) {
2646 if (newcon
->index
< 0)
2648 if (newcon
->setup
== NULL
||
2649 newcon
->setup(newcon
, NULL
) == 0) {
2650 newcon
->flags
|= CON_ENABLED
;
2651 if (newcon
->device
) {
2652 newcon
->flags
|= CON_CONSDEV
;
2653 preferred_console
= 0;
2659 * See if this console matches one we selected on
2662 for (i
= 0, c
= console_cmdline
;
2663 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2665 if (!newcon
->match
||
2666 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2667 /* default matching */
2668 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2669 if (strcmp(c
->name
, newcon
->name
) != 0)
2671 if (newcon
->index
>= 0 &&
2672 newcon
->index
!= c
->index
)
2674 if (newcon
->index
< 0)
2675 newcon
->index
= c
->index
;
2677 if (_braille_register_console(newcon
, c
))
2680 if (newcon
->setup
&&
2681 newcon
->setup(newcon
, c
->options
) != 0)
2685 newcon
->flags
|= CON_ENABLED
;
2686 if (i
== selected_console
) {
2687 newcon
->flags
|= CON_CONSDEV
;
2688 preferred_console
= selected_console
;
2693 if (!(newcon
->flags
& CON_ENABLED
))
2697 * If we have a bootconsole, and are switching to a real console,
2698 * don't print everything out again, since when the boot console, and
2699 * the real console are the same physical device, it's annoying to
2700 * see the beginning boot messages twice
2702 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2703 newcon
->flags
&= ~CON_PRINTBUFFER
;
2706 * Put this console in the list - keep the
2707 * preferred driver at the head of the list.
2710 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2711 newcon
->next
= console_drivers
;
2712 console_drivers
= newcon
;
2714 newcon
->next
->flags
&= ~CON_CONSDEV
;
2716 newcon
->next
= console_drivers
->next
;
2717 console_drivers
->next
= newcon
;
2720 if (newcon
->flags
& CON_EXTENDED
)
2721 if (!nr_ext_console_drivers
++)
2722 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2724 if (newcon
->flags
& CON_PRINTBUFFER
) {
2726 * console_unlock(); will print out the buffered messages
2729 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2730 console_seq
= syslog_seq
;
2731 console_idx
= syslog_idx
;
2732 console_prev
= syslog_prev
;
2733 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2735 * We're about to replay the log buffer. Only do this to the
2736 * just-registered console to avoid excessive message spam to
2737 * the already-registered consoles.
2739 exclusive_console
= newcon
;
2742 console_sysfs_notify();
2745 * By unregistering the bootconsoles after we enable the real console
2746 * we get the "console xxx enabled" message on all the consoles -
2747 * boot consoles, real consoles, etc - this is to ensure that end
2748 * users know there might be something in the kernel's log buffer that
2749 * went to the bootconsole (that they do not see on the real console)
2751 pr_info("%sconsole [%s%d] enabled\n",
2752 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2753 newcon
->name
, newcon
->index
);
2755 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2757 /* We need to iterate through all boot consoles, to make
2758 * sure we print everything out, before we unregister them.
2760 for_each_console(bcon
)
2761 if (bcon
->flags
& CON_BOOT
)
2762 unregister_console(bcon
);
2765 EXPORT_SYMBOL(register_console
);
2767 int unregister_console(struct console
*console
)
2769 struct console
*a
, *b
;
2772 pr_info("%sconsole [%s%d] disabled\n",
2773 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2774 console
->name
, console
->index
);
2776 res
= _braille_unregister_console(console
);
2782 if (console_drivers
== console
) {
2783 console_drivers
=console
->next
;
2785 } else if (console_drivers
) {
2786 for (a
=console_drivers
->next
, b
=console_drivers
;
2787 a
; b
=a
, a
=b
->next
) {
2796 if (!res
&& (console
->flags
& CON_EXTENDED
))
2797 nr_ext_console_drivers
--;
2800 * If this isn't the last console and it has CON_CONSDEV set, we
2801 * need to set it on the next preferred console.
2803 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2804 console_drivers
->flags
|= CON_CONSDEV
;
2806 console
->flags
&= ~CON_ENABLED
;
2808 console_sysfs_notify();
2811 EXPORT_SYMBOL(unregister_console
);
2814 * Some boot consoles access data that is in the init section and which will
2815 * be discarded after the initcalls have been run. To make sure that no code
2816 * will access this data, unregister the boot consoles in a late initcall.
2818 * If for some reason, such as deferred probe or the driver being a loadable
2819 * module, the real console hasn't registered yet at this point, there will
2820 * be a brief interval in which no messages are logged to the console, which
2821 * makes it difficult to diagnose problems that occur during this time.
2823 * To mitigate this problem somewhat, only unregister consoles whose memory
2824 * intersects with the init section. Note that code exists elsewhere to get
2825 * rid of the boot console as soon as the proper console shows up, so there
2826 * won't be side-effects from postponing the removal.
2828 static int __init
printk_late_init(void)
2830 struct console
*con
;
2832 for_each_console(con
) {
2833 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2835 * Make sure to unregister boot consoles whose data
2836 * resides in the init section before the init section
2837 * is discarded. Boot consoles whose data will stick
2838 * around will automatically be unregistered when the
2839 * proper console replaces them.
2841 if (init_section_intersects(con
, sizeof(*con
)))
2842 unregister_console(con
);
2845 hotcpu_notifier(console_cpu_notify
, 0);
2848 late_initcall(printk_late_init
);
2850 #if defined CONFIG_PRINTK
2852 * Delayed printk version, for scheduler-internal messages:
2854 #define PRINTK_PENDING_WAKEUP 0x01
2855 #define PRINTK_PENDING_OUTPUT 0x02
2857 static DEFINE_PER_CPU(int, printk_pending
);
2859 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2861 int pending
= __this_cpu_xchg(printk_pending
, 0);
2863 if (pending
& PRINTK_PENDING_OUTPUT
) {
2864 /* If trylock fails, someone else is doing the printing */
2865 if (console_trylock())
2869 if (pending
& PRINTK_PENDING_WAKEUP
)
2870 wake_up_interruptible(&log_wait
);
2873 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2874 .func
= wake_up_klogd_work_func
,
2875 .flags
= IRQ_WORK_LAZY
,
2878 void wake_up_klogd(void)
2881 if (waitqueue_active(&log_wait
)) {
2882 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2883 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2888 int printk_deferred(const char *fmt
, ...)
2894 va_start(args
, fmt
);
2895 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2898 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2899 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2906 * printk rate limiting, lifted from the networking subsystem.
2908 * This enforces a rate limit: not more than 10 kernel messages
2909 * every 5s to make a denial-of-service attack impossible.
2911 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2913 int __printk_ratelimit(const char *func
)
2915 return ___ratelimit(&printk_ratelimit_state
, func
);
2917 EXPORT_SYMBOL(__printk_ratelimit
);
2920 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2921 * @caller_jiffies: pointer to caller's state
2922 * @interval_msecs: minimum interval between prints
2924 * printk_timed_ratelimit() returns true if more than @interval_msecs
2925 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2928 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2929 unsigned int interval_msecs
)
2931 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2933 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2936 *caller_jiffies
= jiffies
;
2939 EXPORT_SYMBOL(printk_timed_ratelimit
);
2941 static DEFINE_SPINLOCK(dump_list_lock
);
2942 static LIST_HEAD(dump_list
);
2945 * kmsg_dump_register - register a kernel log dumper.
2946 * @dumper: pointer to the kmsg_dumper structure
2948 * Adds a kernel log dumper to the system. The dump callback in the
2949 * structure will be called when the kernel oopses or panics and must be
2950 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2952 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2954 unsigned long flags
;
2957 /* The dump callback needs to be set */
2961 spin_lock_irqsave(&dump_list_lock
, flags
);
2962 /* Don't allow registering multiple times */
2963 if (!dumper
->registered
) {
2964 dumper
->registered
= 1;
2965 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2968 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2972 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2975 * kmsg_dump_unregister - unregister a kmsg dumper.
2976 * @dumper: pointer to the kmsg_dumper structure
2978 * Removes a dump device from the system. Returns zero on success and
2979 * %-EINVAL otherwise.
2981 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2983 unsigned long flags
;
2986 spin_lock_irqsave(&dump_list_lock
, flags
);
2987 if (dumper
->registered
) {
2988 dumper
->registered
= 0;
2989 list_del_rcu(&dumper
->list
);
2992 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2997 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2999 static bool always_kmsg_dump
;
3000 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
3003 * kmsg_dump - dump kernel log to kernel message dumpers.
3004 * @reason: the reason (oops, panic etc) for dumping
3006 * Call each of the registered dumper's dump() callback, which can
3007 * retrieve the kmsg records with kmsg_dump_get_line() or
3008 * kmsg_dump_get_buffer().
3010 void kmsg_dump(enum kmsg_dump_reason reason
)
3012 struct kmsg_dumper
*dumper
;
3013 unsigned long flags
;
3015 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
3019 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
3020 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
3023 /* initialize iterator with data about the stored records */
3024 dumper
->active
= true;
3026 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3027 dumper
->cur_seq
= clear_seq
;
3028 dumper
->cur_idx
= clear_idx
;
3029 dumper
->next_seq
= log_next_seq
;
3030 dumper
->next_idx
= log_next_idx
;
3031 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3033 /* invoke dumper which will iterate over records */
3034 dumper
->dump(dumper
, reason
);
3036 /* reset iterator */
3037 dumper
->active
= false;
3043 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
3044 * @dumper: registered kmsg dumper
3045 * @syslog: include the "<4>" prefixes
3046 * @line: buffer to copy the line to
3047 * @size: maximum size of the buffer
3048 * @len: length of line placed into buffer
3050 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3051 * record, and copy one record into the provided buffer.
3053 * Consecutive calls will return the next available record moving
3054 * towards the end of the buffer with the youngest messages.
3056 * A return value of FALSE indicates that there are no more records to
3059 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
3061 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
3062 char *line
, size_t size
, size_t *len
)
3064 struct printk_log
*msg
;
3068 if (!dumper
->active
)
3071 if (dumper
->cur_seq
< log_first_seq
) {
3072 /* messages are gone, move to first available one */
3073 dumper
->cur_seq
= log_first_seq
;
3074 dumper
->cur_idx
= log_first_idx
;
3078 if (dumper
->cur_seq
>= log_next_seq
)
3081 msg
= log_from_idx(dumper
->cur_idx
);
3082 l
= msg_print_text(msg
, 0, syslog
, line
, size
);
3084 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
3094 * kmsg_dump_get_line - retrieve one kmsg log line
3095 * @dumper: registered kmsg dumper
3096 * @syslog: include the "<4>" prefixes
3097 * @line: buffer to copy the line to
3098 * @size: maximum size of the buffer
3099 * @len: length of line placed into buffer
3101 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3102 * record, and copy one record into the provided buffer.
3104 * Consecutive calls will return the next available record moving
3105 * towards the end of the buffer with the youngest messages.
3107 * A return value of FALSE indicates that there are no more records to
3110 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
3111 char *line
, size_t size
, size_t *len
)
3113 unsigned long flags
;
3116 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3117 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
3118 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3122 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
3125 * kmsg_dump_get_buffer - copy kmsg log lines
3126 * @dumper: registered kmsg dumper
3127 * @syslog: include the "<4>" prefixes
3128 * @buf: buffer to copy the line to
3129 * @size: maximum size of the buffer
3130 * @len: length of line placed into buffer
3132 * Start at the end of the kmsg buffer and fill the provided buffer
3133 * with as many of the the *youngest* kmsg records that fit into it.
3134 * If the buffer is large enough, all available kmsg records will be
3135 * copied with a single call.
3137 * Consecutive calls will fill the buffer with the next block of
3138 * available older records, not including the earlier retrieved ones.
3140 * A return value of FALSE indicates that there are no more records to
3143 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
3144 char *buf
, size_t size
, size_t *len
)
3146 unsigned long flags
;
3151 enum log_flags prev
;
3155 if (!dumper
->active
)
3158 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3159 if (dumper
->cur_seq
< log_first_seq
) {
3160 /* messages are gone, move to first available one */
3161 dumper
->cur_seq
= log_first_seq
;
3162 dumper
->cur_idx
= log_first_idx
;
3166 if (dumper
->cur_seq
>= dumper
->next_seq
) {
3167 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3171 /* calculate length of entire buffer */
3172 seq
= dumper
->cur_seq
;
3173 idx
= dumper
->cur_idx
;
3175 while (seq
< dumper
->next_seq
) {
3176 struct printk_log
*msg
= log_from_idx(idx
);
3178 l
+= msg_print_text(msg
, prev
, true, NULL
, 0);
3179 idx
= log_next(idx
);
3184 /* move first record forward until length fits into the buffer */
3185 seq
= dumper
->cur_seq
;
3186 idx
= dumper
->cur_idx
;
3188 while (l
> size
&& seq
< dumper
->next_seq
) {
3189 struct printk_log
*msg
= log_from_idx(idx
);
3191 l
-= msg_print_text(msg
, prev
, true, NULL
, 0);
3192 idx
= log_next(idx
);
3197 /* last message in next interation */
3202 while (seq
< dumper
->next_seq
) {
3203 struct printk_log
*msg
= log_from_idx(idx
);
3205 l
+= msg_print_text(msg
, prev
, syslog
, buf
+ l
, size
- l
);
3206 idx
= log_next(idx
);
3211 dumper
->next_seq
= next_seq
;
3212 dumper
->next_idx
= next_idx
;
3214 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3220 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
3223 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3224 * @dumper: registered kmsg dumper
3226 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3227 * kmsg_dump_get_buffer() can be called again and used multiple
3228 * times within the same dumper.dump() callback.
3230 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3232 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3234 dumper
->cur_seq
= clear_seq
;
3235 dumper
->cur_idx
= clear_idx
;
3236 dumper
->next_seq
= log_next_seq
;
3237 dumper
->next_idx
= log_next_idx
;
3241 * kmsg_dump_rewind - reset the interator
3242 * @dumper: registered kmsg dumper
3244 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3245 * kmsg_dump_get_buffer() can be called again and used multiple
3246 * times within the same dumper.dump() callback.
3248 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3250 unsigned long flags
;
3252 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3253 kmsg_dump_rewind_nolock(dumper
);
3254 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3256 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3258 static char dump_stack_arch_desc_str
[128];
3261 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3262 * @fmt: printf-style format string
3263 * @...: arguments for the format string
3265 * The configured string will be printed right after utsname during task
3266 * dumps. Usually used to add arch-specific system identifiers. If an
3267 * arch wants to make use of such an ID string, it should initialize this
3268 * as soon as possible during boot.
3270 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3274 va_start(args
, fmt
);
3275 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3281 * dump_stack_print_info - print generic debug info for dump_stack()
3282 * @log_lvl: log level
3284 * Arch-specific dump_stack() implementations can use this function to
3285 * print out the same debug information as the generic dump_stack().
3287 void dump_stack_print_info(const char *log_lvl
)
3289 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3290 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3291 print_tainted(), init_utsname()->release
,
3292 (int)strcspn(init_utsname()->version
, " "),
3293 init_utsname()->version
);
3295 if (dump_stack_arch_desc_str
[0] != '\0')
3296 printk("%sHardware name: %s\n",
3297 log_lvl
, dump_stack_arch_desc_str
);
3299 print_worker_info(log_lvl
, current
);
3303 * show_regs_print_info - print generic debug info for show_regs()
3304 * @log_lvl: log level
3306 * show_regs() implementations can use this function to print out generic
3307 * debug information.
3309 void show_regs_print_info(const char *log_lvl
)
3311 dump_stack_print_info(log_lvl
);
3313 printk("%stask: %p task.stack: %p\n",
3314 log_lvl
, current
, task_stack_page(current
));