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
&& !(prev_flags
& LOG_CONT
))
660 else if ((msg
->flags
& LOG_CONT
) ||
661 ((prev_flags
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
)))
664 return scnprintf(buf
, size
, "%u,%llu,%llu,%c;",
665 (msg
->facility
<< 3) | msg
->level
, seq
, ts_usec
, cont
);
668 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
669 char *dict
, size_t dict_len
,
670 char *text
, size_t text_len
)
672 char *p
= buf
, *e
= buf
+ size
;
675 /* escape non-printable characters */
676 for (i
= 0; i
< text_len
; i
++) {
677 unsigned char c
= text
[i
];
679 if (c
< ' ' || c
>= 127 || c
== '\\')
680 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
682 append_char(&p
, e
, c
);
684 append_char(&p
, e
, '\n');
689 for (i
= 0; i
< dict_len
; i
++) {
690 unsigned char c
= dict
[i
];
693 append_char(&p
, e
, ' ');
698 append_char(&p
, e
, '\n');
703 if (c
< ' ' || c
>= 127 || c
== '\\') {
704 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
708 append_char(&p
, e
, c
);
710 append_char(&p
, e
, '\n');
716 /* /dev/kmsg - userspace message inject/listen interface */
717 struct devkmsg_user
{
721 struct ratelimit_state rs
;
723 char buf
[CONSOLE_EXT_LOG_MAX
];
726 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
729 int level
= default_message_loglevel
;
730 int facility
= 1; /* LOG_USER */
731 struct file
*file
= iocb
->ki_filp
;
732 struct devkmsg_user
*user
= file
->private_data
;
733 size_t len
= iov_iter_count(from
);
736 if (!user
|| len
> LOG_LINE_MAX
)
739 /* Ignore when user logging is disabled. */
740 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
743 /* Ratelimit when not explicitly enabled. */
744 if (!(devkmsg_log
& DEVKMSG_LOG_MASK_ON
)) {
745 if (!___ratelimit(&user
->rs
, current
->comm
))
749 buf
= kmalloc(len
+1, GFP_KERNEL
);
754 if (copy_from_iter(buf
, len
, from
) != len
) {
760 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
761 * the decimal value represents 32bit, the lower 3 bit are the log
762 * level, the rest are the log facility.
764 * If no prefix or no userspace facility is specified, we
765 * enforce LOG_USER, to be able to reliably distinguish
766 * kernel-generated messages from userspace-injected ones.
769 if (line
[0] == '<') {
773 u
= simple_strtoul(line
+ 1, &endp
, 10);
774 if (endp
&& endp
[0] == '>') {
775 level
= LOG_LEVEL(u
);
776 if (LOG_FACILITY(u
) != 0)
777 facility
= LOG_FACILITY(u
);
784 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
789 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
790 size_t count
, loff_t
*ppos
)
792 struct devkmsg_user
*user
= file
->private_data
;
793 struct printk_log
*msg
;
800 ret
= mutex_lock_interruptible(&user
->lock
);
803 raw_spin_lock_irq(&logbuf_lock
);
804 while (user
->seq
== log_next_seq
) {
805 if (file
->f_flags
& O_NONBLOCK
) {
807 raw_spin_unlock_irq(&logbuf_lock
);
811 raw_spin_unlock_irq(&logbuf_lock
);
812 ret
= wait_event_interruptible(log_wait
,
813 user
->seq
!= log_next_seq
);
816 raw_spin_lock_irq(&logbuf_lock
);
819 if (user
->seq
< log_first_seq
) {
820 /* our last seen message is gone, return error and reset */
821 user
->idx
= log_first_idx
;
822 user
->seq
= log_first_seq
;
824 raw_spin_unlock_irq(&logbuf_lock
);
828 msg
= log_from_idx(user
->idx
);
829 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
830 msg
, user
->seq
, user
->prev
);
831 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
832 log_dict(msg
), msg
->dict_len
,
833 log_text(msg
), msg
->text_len
);
835 user
->prev
= msg
->flags
;
836 user
->idx
= log_next(user
->idx
);
838 raw_spin_unlock_irq(&logbuf_lock
);
845 if (copy_to_user(buf
, user
->buf
, len
)) {
851 mutex_unlock(&user
->lock
);
855 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
857 struct devkmsg_user
*user
= file
->private_data
;
865 raw_spin_lock_irq(&logbuf_lock
);
868 /* the first record */
869 user
->idx
= log_first_idx
;
870 user
->seq
= log_first_seq
;
874 * The first record after the last SYSLOG_ACTION_CLEAR,
875 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
876 * changes no global state, and does not clear anything.
878 user
->idx
= clear_idx
;
879 user
->seq
= clear_seq
;
882 /* after the last record */
883 user
->idx
= log_next_idx
;
884 user
->seq
= log_next_seq
;
889 raw_spin_unlock_irq(&logbuf_lock
);
893 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
895 struct devkmsg_user
*user
= file
->private_data
;
899 return POLLERR
|POLLNVAL
;
901 poll_wait(file
, &log_wait
, wait
);
903 raw_spin_lock_irq(&logbuf_lock
);
904 if (user
->seq
< log_next_seq
) {
905 /* return error when data has vanished underneath us */
906 if (user
->seq
< log_first_seq
)
907 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
909 ret
= POLLIN
|POLLRDNORM
;
911 raw_spin_unlock_irq(&logbuf_lock
);
916 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
918 struct devkmsg_user
*user
;
921 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
924 /* write-only does not need any file context */
925 if ((file
->f_flags
& O_ACCMODE
) != O_WRONLY
) {
926 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
932 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
936 ratelimit_default_init(&user
->rs
);
937 ratelimit_set_flags(&user
->rs
, RATELIMIT_MSG_ON_RELEASE
);
939 mutex_init(&user
->lock
);
941 raw_spin_lock_irq(&logbuf_lock
);
942 user
->idx
= log_first_idx
;
943 user
->seq
= log_first_seq
;
944 raw_spin_unlock_irq(&logbuf_lock
);
946 file
->private_data
= user
;
950 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
952 struct devkmsg_user
*user
= file
->private_data
;
957 ratelimit_state_exit(&user
->rs
);
959 mutex_destroy(&user
->lock
);
964 const struct file_operations kmsg_fops
= {
965 .open
= devkmsg_open
,
966 .read
= devkmsg_read
,
967 .write_iter
= devkmsg_write
,
968 .llseek
= devkmsg_llseek
,
969 .poll
= devkmsg_poll
,
970 .release
= devkmsg_release
,
973 #ifdef CONFIG_KEXEC_CORE
975 * This appends the listed symbols to /proc/vmcore
977 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
978 * obtain access to symbols that are otherwise very difficult to locate. These
979 * symbols are specifically used so that utilities can access and extract the
980 * dmesg log from a vmcore file after a crash.
982 void log_buf_kexec_setup(void)
984 VMCOREINFO_SYMBOL(log_buf
);
985 VMCOREINFO_SYMBOL(log_buf_len
);
986 VMCOREINFO_SYMBOL(log_first_idx
);
987 VMCOREINFO_SYMBOL(clear_idx
);
988 VMCOREINFO_SYMBOL(log_next_idx
);
990 * Export struct printk_log size and field offsets. User space tools can
991 * parse it and detect any changes to structure down the line.
993 VMCOREINFO_STRUCT_SIZE(printk_log
);
994 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
995 VMCOREINFO_OFFSET(printk_log
, len
);
996 VMCOREINFO_OFFSET(printk_log
, text_len
);
997 VMCOREINFO_OFFSET(printk_log
, dict_len
);
1001 /* requested log_buf_len from kernel cmdline */
1002 static unsigned long __initdata new_log_buf_len
;
1004 /* we practice scaling the ring buffer by powers of 2 */
1005 static void __init
log_buf_len_update(unsigned size
)
1008 size
= roundup_pow_of_two(size
);
1009 if (size
> log_buf_len
)
1010 new_log_buf_len
= size
;
1013 /* save requested log_buf_len since it's too early to process it */
1014 static int __init
log_buf_len_setup(char *str
)
1016 unsigned size
= memparse(str
, &str
);
1018 log_buf_len_update(size
);
1022 early_param("log_buf_len", log_buf_len_setup
);
1025 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1027 static void __init
log_buf_add_cpu(void)
1029 unsigned int cpu_extra
;
1032 * archs should set up cpu_possible_bits properly with
1033 * set_cpu_possible() after setup_arch() but just in
1034 * case lets ensure this is valid.
1036 if (num_possible_cpus() == 1)
1039 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
1041 /* by default this will only continue through for large > 64 CPUs */
1042 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
1045 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1046 __LOG_CPU_MAX_BUF_LEN
);
1047 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1049 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
1051 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
1053 #else /* !CONFIG_SMP */
1054 static inline void log_buf_add_cpu(void) {}
1055 #endif /* CONFIG_SMP */
1057 void __init
setup_log_buf(int early
)
1059 unsigned long flags
;
1063 if (log_buf
!= __log_buf
)
1066 if (!early
&& !new_log_buf_len
)
1069 if (!new_log_buf_len
)
1074 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
1076 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
1080 if (unlikely(!new_log_buf
)) {
1081 pr_err("log_buf_len: %ld bytes not available\n",
1086 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
1087 log_buf_len
= new_log_buf_len
;
1088 log_buf
= new_log_buf
;
1089 new_log_buf_len
= 0;
1090 free
= __LOG_BUF_LEN
- log_next_idx
;
1091 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
1092 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
1094 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
1095 pr_info("early log buf free: %d(%d%%)\n",
1096 free
, (free
* 100) / __LOG_BUF_LEN
);
1099 static bool __read_mostly ignore_loglevel
;
1101 static int __init
ignore_loglevel_setup(char *str
)
1103 ignore_loglevel
= true;
1104 pr_info("debug: ignoring loglevel setting.\n");
1109 early_param("ignore_loglevel", ignore_loglevel_setup
);
1110 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1111 MODULE_PARM_DESC(ignore_loglevel
,
1112 "ignore loglevel setting (prints all kernel messages to the console)");
1114 static bool suppress_message_printing(int level
)
1116 return (level
>= console_loglevel
&& !ignore_loglevel
);
1119 #ifdef CONFIG_BOOT_PRINTK_DELAY
1121 static int boot_delay
; /* msecs delay after each printk during bootup */
1122 static unsigned long long loops_per_msec
; /* based on boot_delay */
1124 static int __init
boot_delay_setup(char *str
)
1128 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
1129 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
1131 get_option(&str
, &boot_delay
);
1132 if (boot_delay
> 10 * 1000)
1135 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1136 "HZ: %d, loops_per_msec: %llu\n",
1137 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
1140 early_param("boot_delay", boot_delay_setup
);
1142 static void boot_delay_msec(int level
)
1144 unsigned long long k
;
1145 unsigned long timeout
;
1147 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
1148 || suppress_message_printing(level
)) {
1152 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1154 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1159 * use (volatile) jiffies to prevent
1160 * compiler reduction; loop termination via jiffies
1161 * is secondary and may or may not happen.
1163 if (time_after(jiffies
, timeout
))
1165 touch_nmi_watchdog();
1169 static inline void boot_delay_msec(int level
)
1174 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1175 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1177 static size_t print_time(u64 ts
, char *buf
)
1179 unsigned long rem_nsec
;
1184 rem_nsec
= do_div(ts
, 1000000000);
1187 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1189 return sprintf(buf
, "[%5lu.%06lu] ",
1190 (unsigned long)ts
, rem_nsec
/ 1000);
1193 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1196 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1200 len
+= sprintf(buf
, "<%u>", prefix
);
1205 else if (prefix
> 99)
1207 else if (prefix
> 9)
1212 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1216 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1217 bool syslog
, char *buf
, size_t size
)
1219 const char *text
= log_text(msg
);
1220 size_t text_size
= msg
->text_len
;
1222 bool newline
= true;
1225 if ((prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
))
1228 if (msg
->flags
& LOG_CONT
) {
1229 if ((prev
& LOG_CONT
) && !(prev
& LOG_NEWLINE
))
1232 if (!(msg
->flags
& LOG_NEWLINE
))
1237 const char *next
= memchr(text
, '\n', text_size
);
1241 text_len
= next
- text
;
1243 text_size
-= next
- text
;
1245 text_len
= text_size
;
1249 if (print_prefix(msg
, syslog
, NULL
) +
1250 text_len
+ 1 >= size
- len
)
1254 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1255 memcpy(buf
+ len
, text
, text_len
);
1257 if (next
|| newline
)
1260 /* SYSLOG_ACTION_* buffer size only calculation */
1262 len
+= print_prefix(msg
, syslog
, NULL
);
1264 if (next
|| newline
)
1275 static int syslog_print(char __user
*buf
, int size
)
1278 struct printk_log
*msg
;
1281 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1289 raw_spin_lock_irq(&logbuf_lock
);
1290 if (syslog_seq
< log_first_seq
) {
1291 /* messages are gone, move to first one */
1292 syslog_seq
= log_first_seq
;
1293 syslog_idx
= log_first_idx
;
1297 if (syslog_seq
== log_next_seq
) {
1298 raw_spin_unlock_irq(&logbuf_lock
);
1302 skip
= syslog_partial
;
1303 msg
= log_from_idx(syslog_idx
);
1304 n
= msg_print_text(msg
, syslog_prev
, true, text
,
1305 LOG_LINE_MAX
+ PREFIX_MAX
);
1306 if (n
- syslog_partial
<= size
) {
1307 /* message fits into buffer, move forward */
1308 syslog_idx
= log_next(syslog_idx
);
1310 syslog_prev
= msg
->flags
;
1311 n
-= syslog_partial
;
1314 /* partial read(), remember position */
1316 syslog_partial
+= n
;
1319 raw_spin_unlock_irq(&logbuf_lock
);
1324 if (copy_to_user(buf
, text
+ skip
, n
)) {
1339 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1344 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1348 raw_spin_lock_irq(&logbuf_lock
);
1353 enum log_flags prev
;
1356 * Find first record that fits, including all following records,
1357 * into the user-provided buffer for this dump.
1362 while (seq
< log_next_seq
) {
1363 struct printk_log
*msg
= log_from_idx(idx
);
1365 len
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1367 idx
= log_next(idx
);
1371 /* move first record forward until length fits into the buffer */
1375 while (len
> size
&& seq
< log_next_seq
) {
1376 struct printk_log
*msg
= log_from_idx(idx
);
1378 len
-= msg_print_text(msg
, prev
, true, NULL
, 0);
1380 idx
= log_next(idx
);
1384 /* last message fitting into this dump */
1385 next_seq
= log_next_seq
;
1388 while (len
>= 0 && seq
< next_seq
) {
1389 struct printk_log
*msg
= log_from_idx(idx
);
1392 textlen
= msg_print_text(msg
, prev
, true, text
,
1393 LOG_LINE_MAX
+ PREFIX_MAX
);
1398 idx
= log_next(idx
);
1402 raw_spin_unlock_irq(&logbuf_lock
);
1403 if (copy_to_user(buf
+ len
, text
, textlen
))
1407 raw_spin_lock_irq(&logbuf_lock
);
1409 if (seq
< log_first_seq
) {
1410 /* messages are gone, move to next one */
1411 seq
= log_first_seq
;
1412 idx
= log_first_idx
;
1419 clear_seq
= log_next_seq
;
1420 clear_idx
= log_next_idx
;
1422 raw_spin_unlock_irq(&logbuf_lock
);
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
:
1509 raw_spin_lock_irq(&logbuf_lock
);
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
;
1517 if (source
== SYSLOG_FROM_PROC
) {
1519 * Short-cut for poll(/"proc/kmsg") which simply checks
1520 * for pending data, not the size; return the count of
1521 * records, not the length.
1523 error
= log_next_seq
- syslog_seq
;
1525 u64 seq
= syslog_seq
;
1526 u32 idx
= syslog_idx
;
1527 enum log_flags prev
= syslog_prev
;
1530 while (seq
< log_next_seq
) {
1531 struct printk_log
*msg
= log_from_idx(idx
);
1533 error
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1534 idx
= log_next(idx
);
1538 error
-= syslog_partial
;
1540 raw_spin_unlock_irq(&logbuf_lock
);
1542 /* Size of the log buffer */
1543 case SYSLOG_ACTION_SIZE_BUFFER
:
1544 error
= log_buf_len
;
1554 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1556 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1560 * Call the console drivers, asking them to write out
1561 * log_buf[start] to log_buf[end - 1].
1562 * The console_lock must be held.
1564 static void call_console_drivers(int level
,
1565 const char *ext_text
, size_t ext_len
,
1566 const char *text
, size_t len
)
1568 struct console
*con
;
1570 trace_console(text
, len
);
1572 if (!console_drivers
)
1575 for_each_console(con
) {
1576 if (exclusive_console
&& con
!= exclusive_console
)
1578 if (!(con
->flags
& CON_ENABLED
))
1582 if (!cpu_online(smp_processor_id()) &&
1583 !(con
->flags
& CON_ANYTIME
))
1585 if (con
->flags
& CON_EXTENDED
)
1586 con
->write(con
, ext_text
, ext_len
);
1588 con
->write(con
, text
, len
);
1593 * Zap console related locks when oopsing.
1594 * To leave time for slow consoles to print a full oops,
1595 * only zap at most once every 30 seconds.
1597 static void zap_locks(void)
1599 static unsigned long oops_timestamp
;
1601 if (time_after_eq(jiffies
, oops_timestamp
) &&
1602 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1605 oops_timestamp
= jiffies
;
1608 /* If a crash is occurring, make sure we can't deadlock */
1609 raw_spin_lock_init(&logbuf_lock
);
1610 /* And make sure that we print immediately */
1611 sema_init(&console_sem
, 1);
1614 int printk_delay_msec __read_mostly
;
1616 static inline void printk_delay(void)
1618 if (unlikely(printk_delay_msec
)) {
1619 int m
= printk_delay_msec
;
1623 touch_nmi_watchdog();
1629 * Continuation lines are buffered, and not committed to the record buffer
1630 * until the line is complete, or a race forces it. The line fragments
1631 * though, are printed immediately to the consoles to ensure everything has
1632 * reached the console in case of a kernel crash.
1634 static struct cont
{
1635 char buf
[LOG_LINE_MAX
];
1636 size_t len
; /* length == 0 means unused buffer */
1637 size_t cons
; /* bytes written to console */
1638 struct task_struct
*owner
; /* task of first print*/
1639 u64 ts_nsec
; /* time of first print */
1640 u8 level
; /* log level of first message */
1641 u8 facility
; /* log facility of first message */
1642 enum log_flags flags
; /* prefix, newline flags */
1643 bool flushed
:1; /* buffer sealed and committed */
1646 static void cont_flush(enum log_flags flags
)
1655 * If a fragment of this line was directly flushed to the
1656 * console; wait for the console to pick up the rest of the
1657 * line. LOG_NOCONS suppresses a duplicated output.
1659 log_store(cont
.facility
, cont
.level
, flags
| LOG_NOCONS
,
1660 cont
.ts_nsec
, NULL
, 0, cont
.buf
, cont
.len
);
1662 cont
.flushed
= true;
1665 * If no fragment of this line ever reached the console,
1666 * just submit it to the store and free the buffer.
1668 log_store(cont
.facility
, cont
.level
, flags
, 0,
1669 NULL
, 0, cont
.buf
, cont
.len
);
1674 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1676 if (cont
.len
&& cont
.flushed
)
1680 * If ext consoles are present, flush and skip in-kernel
1681 * continuation. See nr_ext_console_drivers definition. Also, if
1682 * the line gets too long, split it up in separate records.
1684 if (nr_ext_console_drivers
|| cont
.len
+ len
> sizeof(cont
.buf
)) {
1685 cont_flush(LOG_CONT
);
1690 cont
.facility
= facility
;
1692 cont
.owner
= current
;
1693 cont
.ts_nsec
= local_clock();
1696 cont
.flushed
= false;
1699 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1702 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1703 cont_flush(LOG_CONT
);
1708 static size_t cont_print_text(char *text
, size_t size
)
1713 if (cont
.cons
== 0 && (console_prev
& LOG_NEWLINE
)) {
1714 textlen
+= print_time(cont
.ts_nsec
, text
);
1718 len
= cont
.len
- cont
.cons
;
1722 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1724 cont
.cons
= cont
.len
;
1728 if (cont
.flags
& LOG_NEWLINE
)
1729 text
[textlen
++] = '\n';
1730 /* got everything, release buffer */
1736 asmlinkage
int vprintk_emit(int facility
, int level
,
1737 const char *dict
, size_t dictlen
,
1738 const char *fmt
, va_list args
)
1740 static bool recursion_bug
;
1741 static char textbuf
[LOG_LINE_MAX
];
1742 char *text
= textbuf
;
1743 size_t text_len
= 0;
1744 enum log_flags lflags
= 0;
1745 unsigned long flags
;
1747 int printed_len
= 0;
1748 int nmi_message_lost
;
1749 bool in_sched
= false;
1750 /* cpu currently holding logbuf_lock in this function */
1751 static unsigned int logbuf_cpu
= UINT_MAX
;
1753 if (level
== LOGLEVEL_SCHED
) {
1754 level
= LOGLEVEL_DEFAULT
;
1758 boot_delay_msec(level
);
1761 local_irq_save(flags
);
1762 this_cpu
= smp_processor_id();
1765 * Ouch, printk recursed into itself!
1767 if (unlikely(logbuf_cpu
== this_cpu
)) {
1769 * If a crash is occurring during printk() on this CPU,
1770 * then try to get the crash message out but make sure
1771 * we can't deadlock. Otherwise just return to avoid the
1772 * recursion and return - but flag the recursion so that
1773 * it can be printed at the next appropriate moment:
1775 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1776 recursion_bug
= true;
1777 local_irq_restore(flags
);
1784 /* This stops the holder of console_sem just where we want him */
1785 raw_spin_lock(&logbuf_lock
);
1786 logbuf_cpu
= this_cpu
;
1788 if (unlikely(recursion_bug
)) {
1789 static const char recursion_msg
[] =
1790 "BUG: recent printk recursion!";
1792 recursion_bug
= false;
1793 /* emit KERN_CRIT message */
1794 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1795 NULL
, 0, recursion_msg
,
1796 strlen(recursion_msg
));
1799 nmi_message_lost
= get_nmi_message_lost();
1800 if (unlikely(nmi_message_lost
)) {
1801 text_len
= scnprintf(textbuf
, sizeof(textbuf
),
1802 "BAD LUCK: lost %d message(s) from NMI context!",
1804 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1805 NULL
, 0, textbuf
, text_len
);
1809 * The printf needs to come first; we need the syslog
1810 * prefix which might be passed-in as a parameter.
1812 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1814 /* mark and strip a trailing newline */
1815 if (text_len
&& text
[text_len
-1] == '\n') {
1817 lflags
|= LOG_NEWLINE
;
1820 /* strip kernel syslog prefix and extract log level or control flags */
1821 if (facility
== 0) {
1822 int kern_level
= printk_get_level(text
);
1825 const char *end_of_header
= printk_skip_level(text
);
1826 switch (kern_level
) {
1828 if (level
== LOGLEVEL_DEFAULT
)
1829 level
= kern_level
- '0';
1831 case 'd': /* KERN_DEFAULT */
1832 lflags
|= LOG_PREFIX
;
1835 * No need to check length here because vscnprintf
1836 * put '\0' at the end of the string. Only valid and
1837 * newly printed level is detected.
1839 text_len
-= end_of_header
- text
;
1840 text
= (char *)end_of_header
;
1844 if (level
== LOGLEVEL_DEFAULT
)
1845 level
= default_message_loglevel
;
1848 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1850 if (!(lflags
& LOG_NEWLINE
)) {
1852 * Flush the conflicting buffer. An earlier newline was missing,
1853 * or another task also prints continuation lines.
1855 if (cont
.len
&& (lflags
& LOG_PREFIX
|| cont
.owner
!= current
))
1856 cont_flush(LOG_NEWLINE
);
1858 /* buffer line if possible, otherwise store it right away */
1859 if (cont_add(facility
, level
, text
, text_len
))
1860 printed_len
+= text_len
;
1862 printed_len
+= log_store(facility
, level
,
1863 lflags
| LOG_CONT
, 0,
1864 dict
, dictlen
, text
, text_len
);
1866 bool stored
= false;
1869 * If an earlier newline was missing and it was the same task,
1870 * either merge it with the current buffer and flush, or if
1871 * there was a race with interrupts (prefix == true) then just
1872 * flush it out and store this line separately.
1873 * If the preceding printk was from a different task and missed
1874 * a newline, flush and append the newline.
1877 if (cont
.owner
== current
&& !(lflags
& LOG_PREFIX
))
1878 stored
= cont_add(facility
, level
, text
,
1880 cont_flush(LOG_NEWLINE
);
1884 printed_len
+= text_len
;
1886 printed_len
+= log_store(facility
, level
, lflags
, 0,
1887 dict
, dictlen
, text
, text_len
);
1890 logbuf_cpu
= UINT_MAX
;
1891 raw_spin_unlock(&logbuf_lock
);
1893 local_irq_restore(flags
);
1895 /* If called from the scheduler, we can not call up(). */
1899 * Try to acquire and then immediately release the console
1900 * semaphore. The release will print out buffers and wake up
1901 * /dev/kmsg and syslog() users.
1903 if (console_trylock())
1910 EXPORT_SYMBOL(vprintk_emit
);
1912 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1914 return vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1916 EXPORT_SYMBOL(vprintk
);
1918 asmlinkage
int printk_emit(int facility
, int level
,
1919 const char *dict
, size_t dictlen
,
1920 const char *fmt
, ...)
1925 va_start(args
, fmt
);
1926 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1931 EXPORT_SYMBOL(printk_emit
);
1933 int vprintk_default(const char *fmt
, va_list args
)
1937 #ifdef CONFIG_KGDB_KDB
1938 if (unlikely(kdb_trap_printk
)) {
1939 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1943 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1947 EXPORT_SYMBOL_GPL(vprintk_default
);
1950 * printk - print a kernel message
1951 * @fmt: format string
1953 * This is printk(). It can be called from any context. We want it to work.
1955 * We try to grab the console_lock. If we succeed, it's easy - we log the
1956 * output and call the console drivers. If we fail to get the semaphore, we
1957 * place the output into the log buffer and return. The current holder of
1958 * the console_sem will notice the new output in console_unlock(); and will
1959 * send it to the consoles before releasing the lock.
1961 * One effect of this deferred printing is that code which calls printk() and
1962 * then changes console_loglevel may break. This is because console_loglevel
1963 * is inspected when the actual printing occurs.
1968 * See the vsnprintf() documentation for format string extensions over C99.
1970 asmlinkage __visible
int printk(const char *fmt
, ...)
1975 va_start(args
, fmt
);
1976 r
= vprintk_func(fmt
, args
);
1981 EXPORT_SYMBOL(printk
);
1983 #else /* CONFIG_PRINTK */
1985 #define LOG_LINE_MAX 0
1986 #define PREFIX_MAX 0
1988 static u64 syslog_seq
;
1989 static u32 syslog_idx
;
1990 static u64 console_seq
;
1991 static u32 console_idx
;
1992 static enum log_flags syslog_prev
;
1993 static u64 log_first_seq
;
1994 static u32 log_first_idx
;
1995 static u64 log_next_seq
;
1996 static enum log_flags console_prev
;
1997 static struct cont
{
2003 static char *log_text(const struct printk_log
*msg
) { return NULL
; }
2004 static char *log_dict(const struct printk_log
*msg
) { return NULL
; }
2005 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
2006 static u32
log_next(u32 idx
) { return 0; }
2007 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
2008 struct printk_log
*msg
, u64 seq
,
2009 enum log_flags prev_flags
) { return 0; }
2010 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
2011 char *dict
, size_t dict_len
,
2012 char *text
, size_t text_len
) { return 0; }
2013 static void call_console_drivers(int level
,
2014 const char *ext_text
, size_t ext_len
,
2015 const char *text
, size_t len
) {}
2016 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
2017 bool syslog
, char *buf
, size_t size
) { return 0; }
2018 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
2019 static bool suppress_message_printing(int level
) { return false; }
2021 /* Still needs to be defined for users */
2022 DEFINE_PER_CPU(printk_func_t
, printk_func
);
2024 #endif /* CONFIG_PRINTK */
2026 #ifdef CONFIG_EARLY_PRINTK
2027 struct console
*early_console
;
2029 asmlinkage __visible
void early_printk(const char *fmt
, ...)
2039 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
2042 early_console
->write(early_console
, buf
, n
);
2046 static int __add_preferred_console(char *name
, int idx
, char *options
,
2049 struct console_cmdline
*c
;
2053 * See if this tty is not yet registered, and
2054 * if we have a slot free.
2056 for (i
= 0, c
= console_cmdline
;
2057 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2059 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
2061 selected_console
= i
;
2065 if (i
== MAX_CMDLINECONSOLES
)
2068 selected_console
= i
;
2069 strlcpy(c
->name
, name
, sizeof(c
->name
));
2070 c
->options
= options
;
2071 braille_set_options(c
, brl_options
);
2077 * Set up a console. Called via do_early_param() in init/main.c
2078 * for each "console=" parameter in the boot command line.
2080 static int __init
console_setup(char *str
)
2082 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
2083 char *s
, *options
, *brl_options
= NULL
;
2086 if (_braille_console_setup(&str
, &brl_options
))
2090 * Decode str into name, index, options.
2092 if (str
[0] >= '0' && str
[0] <= '9') {
2093 strcpy(buf
, "ttyS");
2094 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
2096 strncpy(buf
, str
, sizeof(buf
) - 1);
2098 buf
[sizeof(buf
) - 1] = 0;
2099 options
= strchr(str
, ',');
2103 if (!strcmp(str
, "ttya"))
2104 strcpy(buf
, "ttyS0");
2105 if (!strcmp(str
, "ttyb"))
2106 strcpy(buf
, "ttyS1");
2108 for (s
= buf
; *s
; s
++)
2109 if (isdigit(*s
) || *s
== ',')
2111 idx
= simple_strtoul(s
, NULL
, 10);
2114 __add_preferred_console(buf
, idx
, options
, brl_options
);
2115 console_set_on_cmdline
= 1;
2118 __setup("console=", console_setup
);
2121 * add_preferred_console - add a device to the list of preferred consoles.
2122 * @name: device name
2123 * @idx: device index
2124 * @options: options for this console
2126 * The last preferred console added will be used for kernel messages
2127 * and stdin/out/err for init. Normally this is used by console_setup
2128 * above to handle user-supplied console arguments; however it can also
2129 * be used by arch-specific code either to override the user or more
2130 * commonly to provide a default console (ie from PROM variables) when
2131 * the user has not supplied one.
2133 int add_preferred_console(char *name
, int idx
, char *options
)
2135 return __add_preferred_console(name
, idx
, options
, NULL
);
2138 bool console_suspend_enabled
= true;
2139 EXPORT_SYMBOL(console_suspend_enabled
);
2141 static int __init
console_suspend_disable(char *str
)
2143 console_suspend_enabled
= false;
2146 __setup("no_console_suspend", console_suspend_disable
);
2147 module_param_named(console_suspend
, console_suspend_enabled
,
2148 bool, S_IRUGO
| S_IWUSR
);
2149 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2150 " and hibernate operations");
2153 * suspend_console - suspend the console subsystem
2155 * This disables printk() while we go into suspend states
2157 void suspend_console(void)
2159 if (!console_suspend_enabled
)
2161 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2163 console_suspended
= 1;
2167 void resume_console(void)
2169 if (!console_suspend_enabled
)
2172 console_suspended
= 0;
2177 * console_cpu_notify - print deferred console messages after CPU hotplug
2178 * @self: notifier struct
2179 * @action: CPU hotplug event
2182 * If printk() is called from a CPU that is not online yet, the messages
2183 * will be spooled but will not show up on the console. This function is
2184 * called when a new CPU comes online (or fails to come up), and ensures
2185 * that any such output gets printed.
2187 static int console_cpu_notify(struct notifier_block
*self
,
2188 unsigned long action
, void *hcpu
)
2193 case CPU_DOWN_FAILED
:
2194 case CPU_UP_CANCELED
:
2202 * console_lock - lock the console system for exclusive use.
2204 * Acquires a lock which guarantees that the caller has
2205 * exclusive access to the console system and the console_drivers list.
2207 * Can sleep, returns nothing.
2209 void console_lock(void)
2214 if (console_suspended
)
2217 console_may_schedule
= 1;
2219 EXPORT_SYMBOL(console_lock
);
2222 * console_trylock - try to lock the console system for exclusive use.
2224 * Try to acquire a lock which guarantees that the caller has exclusive
2225 * access to the console system and the console_drivers list.
2227 * returns 1 on success, and 0 on failure to acquire the lock.
2229 int console_trylock(void)
2231 if (down_trylock_console_sem())
2233 if (console_suspended
) {
2239 * When PREEMPT_COUNT disabled we can't reliably detect if it's
2240 * safe to schedule (e.g. calling printk while holding a spin_lock),
2241 * because preempt_disable()/preempt_enable() are just barriers there
2242 * and preempt_count() is always 0.
2244 * RCU read sections have a separate preemption counter when
2245 * PREEMPT_RCU enabled thus we must take extra care and check
2246 * rcu_preempt_depth(), otherwise RCU read sections modify
2249 console_may_schedule
= !oops_in_progress
&&
2251 !rcu_preempt_depth();
2254 EXPORT_SYMBOL(console_trylock
);
2256 int is_console_locked(void)
2258 return console_locked
;
2262 * Check if we have any console that is capable of printing while cpu is
2263 * booting or shutting down. Requires console_sem.
2265 static int have_callable_console(void)
2267 struct console
*con
;
2269 for_each_console(con
)
2270 if ((con
->flags
& CON_ENABLED
) &&
2271 (con
->flags
& CON_ANYTIME
))
2278 * Can we actually use the console at this time on this cpu?
2280 * Console drivers may assume that per-cpu resources have been allocated. So
2281 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2282 * call them until this CPU is officially up.
2284 static inline int can_use_console(void)
2286 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2289 static void console_cont_flush(char *text
, size_t size
)
2291 unsigned long flags
;
2294 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2299 if (suppress_message_printing(cont
.level
)) {
2300 cont
.cons
= cont
.len
;
2307 * We still queue earlier records, likely because the console was
2308 * busy. The earlier ones need to be printed before this one, we
2309 * did not flush any fragment so far, so just let it queue up.
2311 if (console_seq
< log_next_seq
&& !cont
.cons
)
2314 len
= cont_print_text(text
, size
);
2315 raw_spin_unlock(&logbuf_lock
);
2316 stop_critical_timings();
2317 call_console_drivers(cont
.level
, NULL
, 0, text
, len
);
2318 start_critical_timings();
2319 local_irq_restore(flags
);
2322 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2326 * console_unlock - unlock the console system
2328 * Releases the console_lock which the caller holds on the console system
2329 * and the console driver list.
2331 * While the console_lock was held, console output may have been buffered
2332 * by printk(). If this is the case, console_unlock(); emits
2333 * the output prior to releasing the lock.
2335 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2337 * console_unlock(); may be called from any context.
2339 void console_unlock(void)
2341 static char ext_text
[CONSOLE_EXT_LOG_MAX
];
2342 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2343 static u64 seen_seq
;
2344 unsigned long flags
;
2345 bool wake_klogd
= false;
2346 bool do_cond_resched
, retry
;
2348 if (console_suspended
) {
2354 * Console drivers are called under logbuf_lock, so
2355 * @console_may_schedule should be cleared before; however, we may
2356 * end up dumping a lot of lines, for example, if called from
2357 * console registration path, and should invoke cond_resched()
2358 * between lines if allowable. Not doing so can cause a very long
2359 * scheduling stall on a slow console leading to RCU stall and
2360 * softlockup warnings which exacerbate the issue with more
2361 * messages practically incapacitating the system.
2363 do_cond_resched
= console_may_schedule
;
2364 console_may_schedule
= 0;
2368 * We released the console_sem lock, so we need to recheck if
2369 * cpu is online and (if not) is there at least one CON_ANYTIME
2372 if (!can_use_console()) {
2378 /* flush buffered message fragment immediately to console */
2379 console_cont_flush(text
, sizeof(text
));
2382 struct printk_log
*msg
;
2387 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2388 if (seen_seq
!= log_next_seq
) {
2390 seen_seq
= log_next_seq
;
2393 if (console_seq
< log_first_seq
) {
2394 len
= sprintf(text
, "** %u printk messages dropped ** ",
2395 (unsigned)(log_first_seq
- console_seq
));
2397 /* messages are gone, move to first one */
2398 console_seq
= log_first_seq
;
2399 console_idx
= log_first_idx
;
2405 if (console_seq
== log_next_seq
)
2408 msg
= log_from_idx(console_idx
);
2410 if ((msg
->flags
& LOG_NOCONS
) ||
2411 suppress_message_printing(level
)) {
2413 * Skip record we have buffered and already printed
2414 * directly to the console when we received it, and
2415 * record that has level above the console loglevel.
2417 console_idx
= log_next(console_idx
);
2420 * We will get here again when we register a new
2421 * CON_PRINTBUFFER console. Clear the flag so we
2422 * will properly dump everything later.
2424 msg
->flags
&= ~LOG_NOCONS
;
2425 console_prev
= msg
->flags
;
2429 len
+= msg_print_text(msg
, console_prev
, false,
2430 text
+ len
, sizeof(text
) - len
);
2431 if (nr_ext_console_drivers
) {
2432 ext_len
= msg_print_ext_header(ext_text
,
2434 msg
, console_seq
, console_prev
);
2435 ext_len
+= msg_print_ext_body(ext_text
+ ext_len
,
2436 sizeof(ext_text
) - ext_len
,
2437 log_dict(msg
), msg
->dict_len
,
2438 log_text(msg
), msg
->text_len
);
2440 console_idx
= log_next(console_idx
);
2442 console_prev
= msg
->flags
;
2443 raw_spin_unlock(&logbuf_lock
);
2445 stop_critical_timings(); /* don't trace print latency */
2446 call_console_drivers(level
, ext_text
, ext_len
, text
, len
);
2447 start_critical_timings();
2448 local_irq_restore(flags
);
2450 if (do_cond_resched
)
2455 /* Release the exclusive_console once it is used */
2456 if (unlikely(exclusive_console
))
2457 exclusive_console
= NULL
;
2459 raw_spin_unlock(&logbuf_lock
);
2464 * Someone could have filled up the buffer again, so re-check if there's
2465 * something to flush. In case we cannot trylock the console_sem again,
2466 * there's a new owner and the console_unlock() from them will do the
2467 * flush, no worries.
2469 raw_spin_lock(&logbuf_lock
);
2470 retry
= console_seq
!= log_next_seq
;
2471 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2473 if (retry
&& console_trylock())
2479 EXPORT_SYMBOL(console_unlock
);
2482 * console_conditional_schedule - yield the CPU if required
2484 * If the console code is currently allowed to sleep, and
2485 * if this CPU should yield the CPU to another task, do
2488 * Must be called within console_lock();.
2490 void __sched
console_conditional_schedule(void)
2492 if (console_may_schedule
)
2495 EXPORT_SYMBOL(console_conditional_schedule
);
2497 void console_unblank(void)
2502 * console_unblank can no longer be called in interrupt context unless
2503 * oops_in_progress is set to 1..
2505 if (oops_in_progress
) {
2506 if (down_trylock_console_sem() != 0)
2512 console_may_schedule
= 0;
2514 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2520 * console_flush_on_panic - flush console content on panic
2522 * Immediately output all pending messages no matter what.
2524 void console_flush_on_panic(void)
2527 * If someone else is holding the console lock, trylock will fail
2528 * and may_schedule may be set. Ignore and proceed to unlock so
2529 * that messages are flushed out. As this can be called from any
2530 * context and we don't want to get preempted while flushing,
2531 * ensure may_schedule is cleared.
2534 console_may_schedule
= 0;
2539 * Return the console tty driver structure and its associated index
2541 struct tty_driver
*console_device(int *index
)
2544 struct tty_driver
*driver
= NULL
;
2547 for_each_console(c
) {
2550 driver
= c
->device(c
, index
);
2559 * Prevent further output on the passed console device so that (for example)
2560 * serial drivers can disable console output before suspending a port, and can
2561 * re-enable output afterwards.
2563 void console_stop(struct console
*console
)
2566 console
->flags
&= ~CON_ENABLED
;
2569 EXPORT_SYMBOL(console_stop
);
2571 void console_start(struct console
*console
)
2574 console
->flags
|= CON_ENABLED
;
2577 EXPORT_SYMBOL(console_start
);
2579 static int __read_mostly keep_bootcon
;
2581 static int __init
keep_bootcon_setup(char *str
)
2584 pr_info("debug: skip boot console de-registration.\n");
2589 early_param("keep_bootcon", keep_bootcon_setup
);
2592 * The console driver calls this routine during kernel initialization
2593 * to register the console printing procedure with printk() and to
2594 * print any messages that were printed by the kernel before the
2595 * console driver was initialized.
2597 * This can happen pretty early during the boot process (because of
2598 * early_printk) - sometimes before setup_arch() completes - be careful
2599 * of what kernel features are used - they may not be initialised yet.
2601 * There are two types of consoles - bootconsoles (early_printk) and
2602 * "real" consoles (everything which is not a bootconsole) which are
2603 * handled differently.
2604 * - Any number of bootconsoles can be registered at any time.
2605 * - As soon as a "real" console is registered, all bootconsoles
2606 * will be unregistered automatically.
2607 * - Once a "real" console is registered, any attempt to register a
2608 * bootconsoles will be rejected
2610 void register_console(struct console
*newcon
)
2613 unsigned long flags
;
2614 struct console
*bcon
= NULL
;
2615 struct console_cmdline
*c
;
2617 if (console_drivers
)
2618 for_each_console(bcon
)
2619 if (WARN(bcon
== newcon
,
2620 "console '%s%d' already registered\n",
2621 bcon
->name
, bcon
->index
))
2625 * before we register a new CON_BOOT console, make sure we don't
2626 * already have a valid console
2628 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2629 /* find the last or real console */
2630 for_each_console(bcon
) {
2631 if (!(bcon
->flags
& CON_BOOT
)) {
2632 pr_info("Too late to register bootconsole %s%d\n",
2633 newcon
->name
, newcon
->index
);
2639 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2640 bcon
= console_drivers
;
2642 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2643 preferred_console
= selected_console
;
2646 * See if we want to use this console driver. If we
2647 * didn't select a console we take the first one
2648 * that registers here.
2650 if (preferred_console
< 0) {
2651 if (newcon
->index
< 0)
2653 if (newcon
->setup
== NULL
||
2654 newcon
->setup(newcon
, NULL
) == 0) {
2655 newcon
->flags
|= CON_ENABLED
;
2656 if (newcon
->device
) {
2657 newcon
->flags
|= CON_CONSDEV
;
2658 preferred_console
= 0;
2664 * See if this console matches one we selected on
2667 for (i
= 0, c
= console_cmdline
;
2668 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2670 if (!newcon
->match
||
2671 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2672 /* default matching */
2673 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2674 if (strcmp(c
->name
, newcon
->name
) != 0)
2676 if (newcon
->index
>= 0 &&
2677 newcon
->index
!= c
->index
)
2679 if (newcon
->index
< 0)
2680 newcon
->index
= c
->index
;
2682 if (_braille_register_console(newcon
, c
))
2685 if (newcon
->setup
&&
2686 newcon
->setup(newcon
, c
->options
) != 0)
2690 newcon
->flags
|= CON_ENABLED
;
2691 if (i
== selected_console
) {
2692 newcon
->flags
|= CON_CONSDEV
;
2693 preferred_console
= selected_console
;
2698 if (!(newcon
->flags
& CON_ENABLED
))
2702 * If we have a bootconsole, and are switching to a real console,
2703 * don't print everything out again, since when the boot console, and
2704 * the real console are the same physical device, it's annoying to
2705 * see the beginning boot messages twice
2707 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2708 newcon
->flags
&= ~CON_PRINTBUFFER
;
2711 * Put this console in the list - keep the
2712 * preferred driver at the head of the list.
2715 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2716 newcon
->next
= console_drivers
;
2717 console_drivers
= newcon
;
2719 newcon
->next
->flags
&= ~CON_CONSDEV
;
2721 newcon
->next
= console_drivers
->next
;
2722 console_drivers
->next
= newcon
;
2725 if (newcon
->flags
& CON_EXTENDED
)
2726 if (!nr_ext_console_drivers
++)
2727 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2729 if (newcon
->flags
& CON_PRINTBUFFER
) {
2731 * console_unlock(); will print out the buffered messages
2734 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2735 console_seq
= syslog_seq
;
2736 console_idx
= syslog_idx
;
2737 console_prev
= syslog_prev
;
2738 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2740 * We're about to replay the log buffer. Only do this to the
2741 * just-registered console to avoid excessive message spam to
2742 * the already-registered consoles.
2744 exclusive_console
= newcon
;
2747 console_sysfs_notify();
2750 * By unregistering the bootconsoles after we enable the real console
2751 * we get the "console xxx enabled" message on all the consoles -
2752 * boot consoles, real consoles, etc - this is to ensure that end
2753 * users know there might be something in the kernel's log buffer that
2754 * went to the bootconsole (that they do not see on the real console)
2756 pr_info("%sconsole [%s%d] enabled\n",
2757 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2758 newcon
->name
, newcon
->index
);
2760 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2762 /* We need to iterate through all boot consoles, to make
2763 * sure we print everything out, before we unregister them.
2765 for_each_console(bcon
)
2766 if (bcon
->flags
& CON_BOOT
)
2767 unregister_console(bcon
);
2770 EXPORT_SYMBOL(register_console
);
2772 int unregister_console(struct console
*console
)
2774 struct console
*a
, *b
;
2777 pr_info("%sconsole [%s%d] disabled\n",
2778 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2779 console
->name
, console
->index
);
2781 res
= _braille_unregister_console(console
);
2787 if (console_drivers
== console
) {
2788 console_drivers
=console
->next
;
2790 } else if (console_drivers
) {
2791 for (a
=console_drivers
->next
, b
=console_drivers
;
2792 a
; b
=a
, a
=b
->next
) {
2801 if (!res
&& (console
->flags
& CON_EXTENDED
))
2802 nr_ext_console_drivers
--;
2805 * If this isn't the last console and it has CON_CONSDEV set, we
2806 * need to set it on the next preferred console.
2808 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2809 console_drivers
->flags
|= CON_CONSDEV
;
2811 console
->flags
&= ~CON_ENABLED
;
2813 console_sysfs_notify();
2816 EXPORT_SYMBOL(unregister_console
);
2819 * Some boot consoles access data that is in the init section and which will
2820 * be discarded after the initcalls have been run. To make sure that no code
2821 * will access this data, unregister the boot consoles in a late initcall.
2823 * If for some reason, such as deferred probe or the driver being a loadable
2824 * module, the real console hasn't registered yet at this point, there will
2825 * be a brief interval in which no messages are logged to the console, which
2826 * makes it difficult to diagnose problems that occur during this time.
2828 * To mitigate this problem somewhat, only unregister consoles whose memory
2829 * intersects with the init section. Note that code exists elsewhere to get
2830 * rid of the boot console as soon as the proper console shows up, so there
2831 * won't be side-effects from postponing the removal.
2833 static int __init
printk_late_init(void)
2835 struct console
*con
;
2837 for_each_console(con
) {
2838 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2840 * Make sure to unregister boot consoles whose data
2841 * resides in the init section before the init section
2842 * is discarded. Boot consoles whose data will stick
2843 * around will automatically be unregistered when the
2844 * proper console replaces them.
2846 if (init_section_intersects(con
, sizeof(*con
)))
2847 unregister_console(con
);
2850 hotcpu_notifier(console_cpu_notify
, 0);
2853 late_initcall(printk_late_init
);
2855 #if defined CONFIG_PRINTK
2857 * Delayed printk version, for scheduler-internal messages:
2859 #define PRINTK_PENDING_WAKEUP 0x01
2860 #define PRINTK_PENDING_OUTPUT 0x02
2862 static DEFINE_PER_CPU(int, printk_pending
);
2864 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2866 int pending
= __this_cpu_xchg(printk_pending
, 0);
2868 if (pending
& PRINTK_PENDING_OUTPUT
) {
2869 /* If trylock fails, someone else is doing the printing */
2870 if (console_trylock())
2874 if (pending
& PRINTK_PENDING_WAKEUP
)
2875 wake_up_interruptible(&log_wait
);
2878 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2879 .func
= wake_up_klogd_work_func
,
2880 .flags
= IRQ_WORK_LAZY
,
2883 void wake_up_klogd(void)
2886 if (waitqueue_active(&log_wait
)) {
2887 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2888 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2893 int printk_deferred(const char *fmt
, ...)
2899 va_start(args
, fmt
);
2900 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2903 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2904 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2911 * printk rate limiting, lifted from the networking subsystem.
2913 * This enforces a rate limit: not more than 10 kernel messages
2914 * every 5s to make a denial-of-service attack impossible.
2916 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2918 int __printk_ratelimit(const char *func
)
2920 return ___ratelimit(&printk_ratelimit_state
, func
);
2922 EXPORT_SYMBOL(__printk_ratelimit
);
2925 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2926 * @caller_jiffies: pointer to caller's state
2927 * @interval_msecs: minimum interval between prints
2929 * printk_timed_ratelimit() returns true if more than @interval_msecs
2930 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2933 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2934 unsigned int interval_msecs
)
2936 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2938 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2941 *caller_jiffies
= jiffies
;
2944 EXPORT_SYMBOL(printk_timed_ratelimit
);
2946 static DEFINE_SPINLOCK(dump_list_lock
);
2947 static LIST_HEAD(dump_list
);
2950 * kmsg_dump_register - register a kernel log dumper.
2951 * @dumper: pointer to the kmsg_dumper structure
2953 * Adds a kernel log dumper to the system. The dump callback in the
2954 * structure will be called when the kernel oopses or panics and must be
2955 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2957 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2959 unsigned long flags
;
2962 /* The dump callback needs to be set */
2966 spin_lock_irqsave(&dump_list_lock
, flags
);
2967 /* Don't allow registering multiple times */
2968 if (!dumper
->registered
) {
2969 dumper
->registered
= 1;
2970 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2973 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2977 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2980 * kmsg_dump_unregister - unregister a kmsg dumper.
2981 * @dumper: pointer to the kmsg_dumper structure
2983 * Removes a dump device from the system. Returns zero on success and
2984 * %-EINVAL otherwise.
2986 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2988 unsigned long flags
;
2991 spin_lock_irqsave(&dump_list_lock
, flags
);
2992 if (dumper
->registered
) {
2993 dumper
->registered
= 0;
2994 list_del_rcu(&dumper
->list
);
2997 spin_unlock_irqrestore(&dump_list_lock
, flags
);
3002 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
3004 static bool always_kmsg_dump
;
3005 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
3008 * kmsg_dump - dump kernel log to kernel message dumpers.
3009 * @reason: the reason (oops, panic etc) for dumping
3011 * Call each of the registered dumper's dump() callback, which can
3012 * retrieve the kmsg records with kmsg_dump_get_line() or
3013 * kmsg_dump_get_buffer().
3015 void kmsg_dump(enum kmsg_dump_reason reason
)
3017 struct kmsg_dumper
*dumper
;
3018 unsigned long flags
;
3020 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
3024 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
3025 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
3028 /* initialize iterator with data about the stored records */
3029 dumper
->active
= true;
3031 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3032 dumper
->cur_seq
= clear_seq
;
3033 dumper
->cur_idx
= clear_idx
;
3034 dumper
->next_seq
= log_next_seq
;
3035 dumper
->next_idx
= log_next_idx
;
3036 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3038 /* invoke dumper which will iterate over records */
3039 dumper
->dump(dumper
, reason
);
3041 /* reset iterator */
3042 dumper
->active
= false;
3048 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
3049 * @dumper: registered kmsg dumper
3050 * @syslog: include the "<4>" prefixes
3051 * @line: buffer to copy the line to
3052 * @size: maximum size of the buffer
3053 * @len: length of line placed into buffer
3055 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3056 * record, and copy one record into the provided buffer.
3058 * Consecutive calls will return the next available record moving
3059 * towards the end of the buffer with the youngest messages.
3061 * A return value of FALSE indicates that there are no more records to
3064 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
3066 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
3067 char *line
, size_t size
, size_t *len
)
3069 struct printk_log
*msg
;
3073 if (!dumper
->active
)
3076 if (dumper
->cur_seq
< log_first_seq
) {
3077 /* messages are gone, move to first available one */
3078 dumper
->cur_seq
= log_first_seq
;
3079 dumper
->cur_idx
= log_first_idx
;
3083 if (dumper
->cur_seq
>= log_next_seq
)
3086 msg
= log_from_idx(dumper
->cur_idx
);
3087 l
= msg_print_text(msg
, 0, syslog
, line
, size
);
3089 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
3099 * kmsg_dump_get_line - retrieve one kmsg log line
3100 * @dumper: registered kmsg dumper
3101 * @syslog: include the "<4>" prefixes
3102 * @line: buffer to copy the line to
3103 * @size: maximum size of the buffer
3104 * @len: length of line placed into buffer
3106 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3107 * record, and copy one record into the provided buffer.
3109 * Consecutive calls will return the next available record moving
3110 * towards the end of the buffer with the youngest messages.
3112 * A return value of FALSE indicates that there are no more records to
3115 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
3116 char *line
, size_t size
, size_t *len
)
3118 unsigned long flags
;
3121 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3122 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
3123 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3127 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
3130 * kmsg_dump_get_buffer - copy kmsg log lines
3131 * @dumper: registered kmsg dumper
3132 * @syslog: include the "<4>" prefixes
3133 * @buf: buffer to copy the line to
3134 * @size: maximum size of the buffer
3135 * @len: length of line placed into buffer
3137 * Start at the end of the kmsg buffer and fill the provided buffer
3138 * with as many of the the *youngest* kmsg records that fit into it.
3139 * If the buffer is large enough, all available kmsg records will be
3140 * copied with a single call.
3142 * Consecutive calls will fill the buffer with the next block of
3143 * available older records, not including the earlier retrieved ones.
3145 * A return value of FALSE indicates that there are no more records to
3148 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
3149 char *buf
, size_t size
, size_t *len
)
3151 unsigned long flags
;
3156 enum log_flags prev
;
3160 if (!dumper
->active
)
3163 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3164 if (dumper
->cur_seq
< log_first_seq
) {
3165 /* messages are gone, move to first available one */
3166 dumper
->cur_seq
= log_first_seq
;
3167 dumper
->cur_idx
= log_first_idx
;
3171 if (dumper
->cur_seq
>= dumper
->next_seq
) {
3172 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3176 /* calculate length of entire buffer */
3177 seq
= dumper
->cur_seq
;
3178 idx
= dumper
->cur_idx
;
3180 while (seq
< dumper
->next_seq
) {
3181 struct printk_log
*msg
= log_from_idx(idx
);
3183 l
+= msg_print_text(msg
, prev
, true, NULL
, 0);
3184 idx
= log_next(idx
);
3189 /* move first record forward until length fits into the buffer */
3190 seq
= dumper
->cur_seq
;
3191 idx
= dumper
->cur_idx
;
3193 while (l
> size
&& seq
< dumper
->next_seq
) {
3194 struct printk_log
*msg
= log_from_idx(idx
);
3196 l
-= msg_print_text(msg
, prev
, true, NULL
, 0);
3197 idx
= log_next(idx
);
3202 /* last message in next interation */
3207 while (seq
< dumper
->next_seq
) {
3208 struct printk_log
*msg
= log_from_idx(idx
);
3210 l
+= msg_print_text(msg
, prev
, syslog
, buf
+ l
, size
- l
);
3211 idx
= log_next(idx
);
3216 dumper
->next_seq
= next_seq
;
3217 dumper
->next_idx
= next_idx
;
3219 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3225 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
3228 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3229 * @dumper: registered kmsg dumper
3231 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3232 * kmsg_dump_get_buffer() can be called again and used multiple
3233 * times within the same dumper.dump() callback.
3235 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3237 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3239 dumper
->cur_seq
= clear_seq
;
3240 dumper
->cur_idx
= clear_idx
;
3241 dumper
->next_seq
= log_next_seq
;
3242 dumper
->next_idx
= log_next_idx
;
3246 * kmsg_dump_rewind - reset the interator
3247 * @dumper: registered kmsg dumper
3249 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3250 * kmsg_dump_get_buffer() can be called again and used multiple
3251 * times within the same dumper.dump() callback.
3253 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3255 unsigned long flags
;
3257 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3258 kmsg_dump_rewind_nolock(dumper
);
3259 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3261 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3263 static char dump_stack_arch_desc_str
[128];
3266 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3267 * @fmt: printf-style format string
3268 * @...: arguments for the format string
3270 * The configured string will be printed right after utsname during task
3271 * dumps. Usually used to add arch-specific system identifiers. If an
3272 * arch wants to make use of such an ID string, it should initialize this
3273 * as soon as possible during boot.
3275 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3279 va_start(args
, fmt
);
3280 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3286 * dump_stack_print_info - print generic debug info for dump_stack()
3287 * @log_lvl: log level
3289 * Arch-specific dump_stack() implementations can use this function to
3290 * print out the same debug information as the generic dump_stack().
3292 void dump_stack_print_info(const char *log_lvl
)
3294 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3295 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3296 print_tainted(), init_utsname()->release
,
3297 (int)strcspn(init_utsname()->version
, " "),
3298 init_utsname()->version
);
3300 if (dump_stack_arch_desc_str
[0] != '\0')
3301 printk("%sHardware name: %s\n",
3302 log_lvl
, dump_stack_arch_desc_str
);
3304 print_worker_info(log_lvl
, current
);
3308 * show_regs_print_info - print generic debug info for show_regs()
3309 * @log_lvl: log level
3311 * show_regs() implementations can use this function to print out generic
3312 * debug information.
3314 void show_regs_print_info(const char *log_lvl
)
3316 dump_stack_print_info(log_lvl
);
3318 printk("%stask: %p task.stack: %p\n",
3319 log_lvl
, current
, task_stack_page(current
));