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
);
257 static bool of_specified_console
;
259 void console_set_by_of(void)
261 of_specified_console
= true;
264 # define of_specified_console false
267 /* Flag: console code may call schedule() */
268 static int console_may_schedule
;
271 * The printk log buffer consists of a chain of concatenated variable
272 * length records. Every record starts with a record header, containing
273 * the overall length of the record.
275 * The heads to the first and last entry in the buffer, as well as the
276 * sequence numbers of these entries are maintained when messages are
279 * If the heads indicate available messages, the length in the header
280 * tells the start next message. A length == 0 for the next message
281 * indicates a wrap-around to the beginning of the buffer.
283 * Every record carries the monotonic timestamp in microseconds, as well as
284 * the standard userspace syslog level and syslog facility. The usual
285 * kernel messages use LOG_KERN; userspace-injected messages always carry
286 * a matching syslog facility, by default LOG_USER. The origin of every
287 * message can be reliably determined that way.
289 * The human readable log message directly follows the message header. The
290 * length of the message text is stored in the header, the stored message
293 * Optionally, a message can carry a dictionary of properties (key/value pairs),
294 * to provide userspace with a machine-readable message context.
296 * Examples for well-defined, commonly used property names are:
297 * DEVICE=b12:8 device identifier
301 * +sound:card0 subsystem:devname
302 * SUBSYSTEM=pci driver-core subsystem name
304 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
305 * follows directly after a '=' character. Every property is terminated by
306 * a '\0' character. The last property is not terminated.
308 * Example of a message structure:
309 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
310 * 0008 34 00 record is 52 bytes long
311 * 000a 0b 00 text is 11 bytes long
312 * 000c 1f 00 dictionary is 23 bytes long
313 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
314 * 0010 69 74 27 73 20 61 20 6c "it's a l"
316 * 001b 44 45 56 49 43 "DEVIC"
317 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
318 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
320 * 0032 00 00 00 padding to next message header
322 * The 'struct printk_log' buffer header must never be directly exported to
323 * userspace, it is a kernel-private implementation detail that might
324 * need to be changed in the future, when the requirements change.
326 * /dev/kmsg exports the structured data in the following line format:
327 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
329 * Users of the export format should ignore possible additional values
330 * separated by ',', and find the message after the ';' character.
332 * The optional key/value pairs are attached as continuation lines starting
333 * with a space character and terminated by a newline. All possible
334 * non-prinatable characters are escaped in the "\xff" notation.
338 LOG_NOCONS
= 1, /* already flushed, do not print to console */
339 LOG_NEWLINE
= 2, /* text ended with a newline */
340 LOG_PREFIX
= 4, /* text started with a prefix */
341 LOG_CONT
= 8, /* text is a fragment of a continuation line */
345 u64 ts_nsec
; /* timestamp in nanoseconds */
346 u16 len
; /* length of entire record */
347 u16 text_len
; /* length of text buffer */
348 u16 dict_len
; /* length of dictionary buffer */
349 u8 facility
; /* syslog facility */
350 u8 flags
:5; /* internal record flags */
351 u8 level
:3; /* syslog level */
353 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
354 __packed
__aligned(4)
359 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
360 * within the scheduler's rq lock. It must be released before calling
361 * console_unlock() or anything else that might wake up a process.
363 DEFINE_RAW_SPINLOCK(logbuf_lock
);
366 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
367 /* the next printk record to read by syslog(READ) or /proc/kmsg */
368 static u64 syslog_seq
;
369 static u32 syslog_idx
;
370 static enum log_flags syslog_prev
;
371 static size_t syslog_partial
;
373 /* index and sequence number of the first record stored in the buffer */
374 static u64 log_first_seq
;
375 static u32 log_first_idx
;
377 /* index and sequence number of the next record to store in the buffer */
378 static u64 log_next_seq
;
379 static u32 log_next_idx
;
381 /* the next printk record to write to the console */
382 static u64 console_seq
;
383 static u32 console_idx
;
384 static enum log_flags console_prev
;
386 /* the next printk record to read after the last 'clear' command */
387 static u64 clear_seq
;
388 static u32 clear_idx
;
390 #define PREFIX_MAX 32
391 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
393 #define LOG_LEVEL(v) ((v) & 0x07)
394 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
397 #define LOG_ALIGN __alignof__(struct printk_log)
398 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
399 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
400 static char *log_buf
= __log_buf
;
401 static u32 log_buf_len
= __LOG_BUF_LEN
;
403 /* Return log buffer address */
404 char *log_buf_addr_get(void)
409 /* Return log buffer size */
410 u32
log_buf_len_get(void)
415 /* human readable text of the record */
416 static char *log_text(const struct printk_log
*msg
)
418 return (char *)msg
+ sizeof(struct printk_log
);
421 /* optional key/value pair dictionary attached to the record */
422 static char *log_dict(const struct printk_log
*msg
)
424 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
427 /* get record by index; idx must point to valid msg */
428 static struct printk_log
*log_from_idx(u32 idx
)
430 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
433 * A length == 0 record is the end of buffer marker. Wrap around and
434 * read the message at the start of the buffer.
437 return (struct printk_log
*)log_buf
;
441 /* get next record; idx must point to valid msg */
442 static u32
log_next(u32 idx
)
444 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
446 /* length == 0 indicates the end of the buffer; wrap */
448 * A length == 0 record is the end of buffer marker. Wrap around and
449 * read the message at the start of the buffer as *this* one, and
450 * return the one after that.
453 msg
= (struct printk_log
*)log_buf
;
456 return idx
+ msg
->len
;
460 * Check whether there is enough free space for the given message.
462 * The same values of first_idx and next_idx mean that the buffer
463 * is either empty or full.
465 * If the buffer is empty, we must respect the position of the indexes.
466 * They cannot be reset to the beginning of the buffer.
468 static int logbuf_has_space(u32 msg_size
, bool empty
)
472 if (log_next_idx
> log_first_idx
|| empty
)
473 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
475 free
= log_first_idx
- log_next_idx
;
478 * We need space also for an empty header that signalizes wrapping
481 return free
>= msg_size
+ sizeof(struct printk_log
);
484 static int log_make_free_space(u32 msg_size
)
486 while (log_first_seq
< log_next_seq
&&
487 !logbuf_has_space(msg_size
, false)) {
488 /* drop old messages until we have enough contiguous space */
489 log_first_idx
= log_next(log_first_idx
);
493 if (clear_seq
< log_first_seq
) {
494 clear_seq
= log_first_seq
;
495 clear_idx
= log_first_idx
;
498 /* sequence numbers are equal, so the log buffer is empty */
499 if (logbuf_has_space(msg_size
, log_first_seq
== log_next_seq
))
505 /* compute the message size including the padding bytes */
506 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
510 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
511 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
518 * Define how much of the log buffer we could take at maximum. The value
519 * must be greater than two. Note that only half of the buffer is available
520 * when the index points to the middle.
522 #define MAX_LOG_TAKE_PART 4
523 static const char trunc_msg
[] = "<truncated>";
525 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
526 u16
*dict_len
, u32
*pad_len
)
529 * The message should not take the whole buffer. Otherwise, it might
530 * get removed too soon.
532 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
533 if (*text_len
> max_text_len
)
534 *text_len
= max_text_len
;
535 /* enable the warning message */
536 *trunc_msg_len
= strlen(trunc_msg
);
537 /* disable the "dict" completely */
539 /* compute the size again, count also the warning message */
540 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
543 /* insert record into the buffer, discard old ones, update heads */
544 static int log_store(int facility
, int level
,
545 enum log_flags flags
, u64 ts_nsec
,
546 const char *dict
, u16 dict_len
,
547 const char *text
, u16 text_len
)
549 struct printk_log
*msg
;
551 u16 trunc_msg_len
= 0;
553 /* number of '\0' padding bytes to next message */
554 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
556 if (log_make_free_space(size
)) {
557 /* truncate the message if it is too long for empty buffer */
558 size
= truncate_msg(&text_len
, &trunc_msg_len
,
559 &dict_len
, &pad_len
);
560 /* survive when the log buffer is too small for trunc_msg */
561 if (log_make_free_space(size
))
565 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
567 * This message + an additional empty header does not fit
568 * at the end of the buffer. Add an empty header with len == 0
569 * to signify a wrap around.
571 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
576 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
577 memcpy(log_text(msg
), text
, text_len
);
578 msg
->text_len
= text_len
;
580 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
581 msg
->text_len
+= trunc_msg_len
;
583 memcpy(log_dict(msg
), dict
, dict_len
);
584 msg
->dict_len
= dict_len
;
585 msg
->facility
= facility
;
586 msg
->level
= level
& 7;
587 msg
->flags
= flags
& 0x1f;
589 msg
->ts_nsec
= ts_nsec
;
591 msg
->ts_nsec
= local_clock();
592 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
596 log_next_idx
+= msg
->len
;
599 return msg
->text_len
;
602 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
604 static int syslog_action_restricted(int type
)
609 * Unless restricted, we allow "read all" and "get buffer size"
612 return type
!= SYSLOG_ACTION_READ_ALL
&&
613 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
616 int check_syslog_permissions(int type
, int source
)
619 * If this is from /proc/kmsg and we've already opened it, then we've
620 * already done the capabilities checks at open time.
622 if (source
== SYSLOG_FROM_PROC
&& type
!= SYSLOG_ACTION_OPEN
)
625 if (syslog_action_restricted(type
)) {
626 if (capable(CAP_SYSLOG
))
629 * For historical reasons, accept CAP_SYS_ADMIN too, with
632 if (capable(CAP_SYS_ADMIN
)) {
633 pr_warn_once("%s (%d): Attempt to access syslog with "
634 "CAP_SYS_ADMIN but no CAP_SYSLOG "
636 current
->comm
, task_pid_nr(current
));
642 return security_syslog(type
);
644 EXPORT_SYMBOL_GPL(check_syslog_permissions
);
646 static void append_char(char **pp
, char *e
, char c
)
652 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
653 struct printk_log
*msg
, u64 seq
,
654 enum log_flags prev_flags
)
656 u64 ts_usec
= msg
->ts_nsec
;
659 do_div(ts_usec
, 1000);
662 * If we couldn't merge continuation line fragments during the print,
663 * export the stored flags to allow an optional external merge of the
664 * records. Merging the records isn't always neccessarily correct, like
665 * when we hit a race during printing. In most cases though, it produces
666 * better readable output. 'c' in the record flags mark the first
667 * fragment of a line, '+' the following.
669 if (msg
->flags
& LOG_CONT
&& !(prev_flags
& LOG_CONT
))
671 else if ((msg
->flags
& LOG_CONT
) ||
672 ((prev_flags
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
)))
675 return scnprintf(buf
, size
, "%u,%llu,%llu,%c;",
676 (msg
->facility
<< 3) | msg
->level
, seq
, ts_usec
, cont
);
679 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
680 char *dict
, size_t dict_len
,
681 char *text
, size_t text_len
)
683 char *p
= buf
, *e
= buf
+ size
;
686 /* escape non-printable characters */
687 for (i
= 0; i
< text_len
; i
++) {
688 unsigned char c
= text
[i
];
690 if (c
< ' ' || c
>= 127 || c
== '\\')
691 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
693 append_char(&p
, e
, c
);
695 append_char(&p
, e
, '\n');
700 for (i
= 0; i
< dict_len
; i
++) {
701 unsigned char c
= dict
[i
];
704 append_char(&p
, e
, ' ');
709 append_char(&p
, e
, '\n');
714 if (c
< ' ' || c
>= 127 || c
== '\\') {
715 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
719 append_char(&p
, e
, c
);
721 append_char(&p
, e
, '\n');
727 /* /dev/kmsg - userspace message inject/listen interface */
728 struct devkmsg_user
{
732 struct ratelimit_state rs
;
734 char buf
[CONSOLE_EXT_LOG_MAX
];
737 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
740 int level
= default_message_loglevel
;
741 int facility
= 1; /* LOG_USER */
742 struct file
*file
= iocb
->ki_filp
;
743 struct devkmsg_user
*user
= file
->private_data
;
744 size_t len
= iov_iter_count(from
);
747 if (!user
|| len
> LOG_LINE_MAX
)
750 /* Ignore when user logging is disabled. */
751 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
754 /* Ratelimit when not explicitly enabled. */
755 if (!(devkmsg_log
& DEVKMSG_LOG_MASK_ON
)) {
756 if (!___ratelimit(&user
->rs
, current
->comm
))
760 buf
= kmalloc(len
+1, GFP_KERNEL
);
765 if (copy_from_iter(buf
, len
, from
) != len
) {
771 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
772 * the decimal value represents 32bit, the lower 3 bit are the log
773 * level, the rest are the log facility.
775 * If no prefix or no userspace facility is specified, we
776 * enforce LOG_USER, to be able to reliably distinguish
777 * kernel-generated messages from userspace-injected ones.
780 if (line
[0] == '<') {
784 u
= simple_strtoul(line
+ 1, &endp
, 10);
785 if (endp
&& endp
[0] == '>') {
786 level
= LOG_LEVEL(u
);
787 if (LOG_FACILITY(u
) != 0)
788 facility
= LOG_FACILITY(u
);
795 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
800 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
801 size_t count
, loff_t
*ppos
)
803 struct devkmsg_user
*user
= file
->private_data
;
804 struct printk_log
*msg
;
811 ret
= mutex_lock_interruptible(&user
->lock
);
814 raw_spin_lock_irq(&logbuf_lock
);
815 while (user
->seq
== log_next_seq
) {
816 if (file
->f_flags
& O_NONBLOCK
) {
818 raw_spin_unlock_irq(&logbuf_lock
);
822 raw_spin_unlock_irq(&logbuf_lock
);
823 ret
= wait_event_interruptible(log_wait
,
824 user
->seq
!= log_next_seq
);
827 raw_spin_lock_irq(&logbuf_lock
);
830 if (user
->seq
< log_first_seq
) {
831 /* our last seen message is gone, return error and reset */
832 user
->idx
= log_first_idx
;
833 user
->seq
= log_first_seq
;
835 raw_spin_unlock_irq(&logbuf_lock
);
839 msg
= log_from_idx(user
->idx
);
840 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
841 msg
, user
->seq
, user
->prev
);
842 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
843 log_dict(msg
), msg
->dict_len
,
844 log_text(msg
), msg
->text_len
);
846 user
->prev
= msg
->flags
;
847 user
->idx
= log_next(user
->idx
);
849 raw_spin_unlock_irq(&logbuf_lock
);
856 if (copy_to_user(buf
, user
->buf
, len
)) {
862 mutex_unlock(&user
->lock
);
866 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
868 struct devkmsg_user
*user
= file
->private_data
;
876 raw_spin_lock_irq(&logbuf_lock
);
879 /* the first record */
880 user
->idx
= log_first_idx
;
881 user
->seq
= log_first_seq
;
885 * The first record after the last SYSLOG_ACTION_CLEAR,
886 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
887 * changes no global state, and does not clear anything.
889 user
->idx
= clear_idx
;
890 user
->seq
= clear_seq
;
893 /* after the last record */
894 user
->idx
= log_next_idx
;
895 user
->seq
= log_next_seq
;
900 raw_spin_unlock_irq(&logbuf_lock
);
904 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
906 struct devkmsg_user
*user
= file
->private_data
;
910 return POLLERR
|POLLNVAL
;
912 poll_wait(file
, &log_wait
, wait
);
914 raw_spin_lock_irq(&logbuf_lock
);
915 if (user
->seq
< log_next_seq
) {
916 /* return error when data has vanished underneath us */
917 if (user
->seq
< log_first_seq
)
918 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
920 ret
= POLLIN
|POLLRDNORM
;
922 raw_spin_unlock_irq(&logbuf_lock
);
927 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
929 struct devkmsg_user
*user
;
932 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
935 /* write-only does not need any file context */
936 if ((file
->f_flags
& O_ACCMODE
) != O_WRONLY
) {
937 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
943 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
947 ratelimit_default_init(&user
->rs
);
948 ratelimit_set_flags(&user
->rs
, RATELIMIT_MSG_ON_RELEASE
);
950 mutex_init(&user
->lock
);
952 raw_spin_lock_irq(&logbuf_lock
);
953 user
->idx
= log_first_idx
;
954 user
->seq
= log_first_seq
;
955 raw_spin_unlock_irq(&logbuf_lock
);
957 file
->private_data
= user
;
961 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
963 struct devkmsg_user
*user
= file
->private_data
;
968 ratelimit_state_exit(&user
->rs
);
970 mutex_destroy(&user
->lock
);
975 const struct file_operations kmsg_fops
= {
976 .open
= devkmsg_open
,
977 .read
= devkmsg_read
,
978 .write_iter
= devkmsg_write
,
979 .llseek
= devkmsg_llseek
,
980 .poll
= devkmsg_poll
,
981 .release
= devkmsg_release
,
984 #ifdef CONFIG_KEXEC_CORE
986 * This appends the listed symbols to /proc/vmcore
988 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
989 * obtain access to symbols that are otherwise very difficult to locate. These
990 * symbols are specifically used so that utilities can access and extract the
991 * dmesg log from a vmcore file after a crash.
993 void log_buf_kexec_setup(void)
995 VMCOREINFO_SYMBOL(log_buf
);
996 VMCOREINFO_SYMBOL(log_buf_len
);
997 VMCOREINFO_SYMBOL(log_first_idx
);
998 VMCOREINFO_SYMBOL(clear_idx
);
999 VMCOREINFO_SYMBOL(log_next_idx
);
1001 * Export struct printk_log size and field offsets. User space tools can
1002 * parse it and detect any changes to structure down the line.
1004 VMCOREINFO_STRUCT_SIZE(printk_log
);
1005 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
1006 VMCOREINFO_OFFSET(printk_log
, len
);
1007 VMCOREINFO_OFFSET(printk_log
, text_len
);
1008 VMCOREINFO_OFFSET(printk_log
, dict_len
);
1012 /* requested log_buf_len from kernel cmdline */
1013 static unsigned long __initdata new_log_buf_len
;
1015 /* we practice scaling the ring buffer by powers of 2 */
1016 static void __init
log_buf_len_update(unsigned size
)
1019 size
= roundup_pow_of_two(size
);
1020 if (size
> log_buf_len
)
1021 new_log_buf_len
= size
;
1024 /* save requested log_buf_len since it's too early to process it */
1025 static int __init
log_buf_len_setup(char *str
)
1027 unsigned size
= memparse(str
, &str
);
1029 log_buf_len_update(size
);
1033 early_param("log_buf_len", log_buf_len_setup
);
1036 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1038 static void __init
log_buf_add_cpu(void)
1040 unsigned int cpu_extra
;
1043 * archs should set up cpu_possible_bits properly with
1044 * set_cpu_possible() after setup_arch() but just in
1045 * case lets ensure this is valid.
1047 if (num_possible_cpus() == 1)
1050 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
1052 /* by default this will only continue through for large > 64 CPUs */
1053 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
1056 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1057 __LOG_CPU_MAX_BUF_LEN
);
1058 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1060 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
1062 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
1064 #else /* !CONFIG_SMP */
1065 static inline void log_buf_add_cpu(void) {}
1066 #endif /* CONFIG_SMP */
1068 void __init
setup_log_buf(int early
)
1070 unsigned long flags
;
1074 if (log_buf
!= __log_buf
)
1077 if (!early
&& !new_log_buf_len
)
1080 if (!new_log_buf_len
)
1085 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
1087 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
1091 if (unlikely(!new_log_buf
)) {
1092 pr_err("log_buf_len: %ld bytes not available\n",
1097 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
1098 log_buf_len
= new_log_buf_len
;
1099 log_buf
= new_log_buf
;
1100 new_log_buf_len
= 0;
1101 free
= __LOG_BUF_LEN
- log_next_idx
;
1102 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
1103 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
1105 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
1106 pr_info("early log buf free: %d(%d%%)\n",
1107 free
, (free
* 100) / __LOG_BUF_LEN
);
1110 static bool __read_mostly ignore_loglevel
;
1112 static int __init
ignore_loglevel_setup(char *str
)
1114 ignore_loglevel
= true;
1115 pr_info("debug: ignoring loglevel setting.\n");
1120 early_param("ignore_loglevel", ignore_loglevel_setup
);
1121 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1122 MODULE_PARM_DESC(ignore_loglevel
,
1123 "ignore loglevel setting (prints all kernel messages to the console)");
1125 static bool suppress_message_printing(int level
)
1127 return (level
>= console_loglevel
&& !ignore_loglevel
);
1130 #ifdef CONFIG_BOOT_PRINTK_DELAY
1132 static int boot_delay
; /* msecs delay after each printk during bootup */
1133 static unsigned long long loops_per_msec
; /* based on boot_delay */
1135 static int __init
boot_delay_setup(char *str
)
1139 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
1140 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
1142 get_option(&str
, &boot_delay
);
1143 if (boot_delay
> 10 * 1000)
1146 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1147 "HZ: %d, loops_per_msec: %llu\n",
1148 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
1151 early_param("boot_delay", boot_delay_setup
);
1153 static void boot_delay_msec(int level
)
1155 unsigned long long k
;
1156 unsigned long timeout
;
1158 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
1159 || suppress_message_printing(level
)) {
1163 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1165 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1170 * use (volatile) jiffies to prevent
1171 * compiler reduction; loop termination via jiffies
1172 * is secondary and may or may not happen.
1174 if (time_after(jiffies
, timeout
))
1176 touch_nmi_watchdog();
1180 static inline void boot_delay_msec(int level
)
1185 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1186 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1188 static size_t print_time(u64 ts
, char *buf
)
1190 unsigned long rem_nsec
;
1195 rem_nsec
= do_div(ts
, 1000000000);
1198 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1200 return sprintf(buf
, "[%5lu.%06lu] ",
1201 (unsigned long)ts
, rem_nsec
/ 1000);
1204 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1207 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1211 len
+= sprintf(buf
, "<%u>", prefix
);
1216 else if (prefix
> 99)
1218 else if (prefix
> 9)
1223 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1227 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1228 bool syslog
, char *buf
, size_t size
)
1230 const char *text
= log_text(msg
);
1231 size_t text_size
= msg
->text_len
;
1233 bool newline
= true;
1236 if ((prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
))
1239 if (msg
->flags
& LOG_CONT
) {
1240 if ((prev
& LOG_CONT
) && !(prev
& LOG_NEWLINE
))
1243 if (!(msg
->flags
& LOG_NEWLINE
))
1248 const char *next
= memchr(text
, '\n', text_size
);
1252 text_len
= next
- text
;
1254 text_size
-= next
- text
;
1256 text_len
= text_size
;
1260 if (print_prefix(msg
, syslog
, NULL
) +
1261 text_len
+ 1 >= size
- len
)
1265 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1266 memcpy(buf
+ len
, text
, text_len
);
1268 if (next
|| newline
)
1271 /* SYSLOG_ACTION_* buffer size only calculation */
1273 len
+= print_prefix(msg
, syslog
, NULL
);
1275 if (next
|| newline
)
1286 static int syslog_print(char __user
*buf
, int size
)
1289 struct printk_log
*msg
;
1292 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1300 raw_spin_lock_irq(&logbuf_lock
);
1301 if (syslog_seq
< log_first_seq
) {
1302 /* messages are gone, move to first one */
1303 syslog_seq
= log_first_seq
;
1304 syslog_idx
= log_first_idx
;
1308 if (syslog_seq
== log_next_seq
) {
1309 raw_spin_unlock_irq(&logbuf_lock
);
1313 skip
= syslog_partial
;
1314 msg
= log_from_idx(syslog_idx
);
1315 n
= msg_print_text(msg
, syslog_prev
, true, text
,
1316 LOG_LINE_MAX
+ PREFIX_MAX
);
1317 if (n
- syslog_partial
<= size
) {
1318 /* message fits into buffer, move forward */
1319 syslog_idx
= log_next(syslog_idx
);
1321 syslog_prev
= msg
->flags
;
1322 n
-= syslog_partial
;
1325 /* partial read(), remember position */
1327 syslog_partial
+= n
;
1330 raw_spin_unlock_irq(&logbuf_lock
);
1335 if (copy_to_user(buf
, text
+ skip
, n
)) {
1350 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1355 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1359 raw_spin_lock_irq(&logbuf_lock
);
1364 enum log_flags prev
;
1367 * Find first record that fits, including all following records,
1368 * into the user-provided buffer for this dump.
1373 while (seq
< log_next_seq
) {
1374 struct printk_log
*msg
= log_from_idx(idx
);
1376 len
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1378 idx
= log_next(idx
);
1382 /* move first record forward until length fits into the buffer */
1386 while (len
> size
&& seq
< log_next_seq
) {
1387 struct printk_log
*msg
= log_from_idx(idx
);
1389 len
-= msg_print_text(msg
, prev
, true, NULL
, 0);
1391 idx
= log_next(idx
);
1395 /* last message fitting into this dump */
1396 next_seq
= log_next_seq
;
1399 while (len
>= 0 && seq
< next_seq
) {
1400 struct printk_log
*msg
= log_from_idx(idx
);
1403 textlen
= msg_print_text(msg
, prev
, true, text
,
1404 LOG_LINE_MAX
+ PREFIX_MAX
);
1409 idx
= log_next(idx
);
1413 raw_spin_unlock_irq(&logbuf_lock
);
1414 if (copy_to_user(buf
+ len
, text
, textlen
))
1418 raw_spin_lock_irq(&logbuf_lock
);
1420 if (seq
< log_first_seq
) {
1421 /* messages are gone, move to next one */
1422 seq
= log_first_seq
;
1423 idx
= log_first_idx
;
1430 clear_seq
= log_next_seq
;
1431 clear_idx
= log_next_idx
;
1433 raw_spin_unlock_irq(&logbuf_lock
);
1439 int do_syslog(int type
, char __user
*buf
, int len
, int source
)
1442 static int saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1445 error
= check_syslog_permissions(type
, source
);
1450 case SYSLOG_ACTION_CLOSE
: /* Close log */
1452 case SYSLOG_ACTION_OPEN
: /* Open log */
1454 case SYSLOG_ACTION_READ
: /* Read from log */
1456 if (!buf
|| len
< 0)
1461 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1465 error
= wait_event_interruptible(log_wait
,
1466 syslog_seq
!= log_next_seq
);
1469 error
= syslog_print(buf
, len
);
1471 /* Read/clear last kernel messages */
1472 case SYSLOG_ACTION_READ_CLEAR
:
1475 /* Read last kernel messages */
1476 case SYSLOG_ACTION_READ_ALL
:
1478 if (!buf
|| len
< 0)
1483 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1487 error
= syslog_print_all(buf
, len
, clear
);
1489 /* Clear ring buffer */
1490 case SYSLOG_ACTION_CLEAR
:
1491 syslog_print_all(NULL
, 0, true);
1493 /* Disable logging to console */
1494 case SYSLOG_ACTION_CONSOLE_OFF
:
1495 if (saved_console_loglevel
== LOGLEVEL_DEFAULT
)
1496 saved_console_loglevel
= console_loglevel
;
1497 console_loglevel
= minimum_console_loglevel
;
1499 /* Enable logging to console */
1500 case SYSLOG_ACTION_CONSOLE_ON
:
1501 if (saved_console_loglevel
!= LOGLEVEL_DEFAULT
) {
1502 console_loglevel
= saved_console_loglevel
;
1503 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1506 /* Set level of messages printed to console */
1507 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1509 if (len
< 1 || len
> 8)
1511 if (len
< minimum_console_loglevel
)
1512 len
= minimum_console_loglevel
;
1513 console_loglevel
= len
;
1514 /* Implicitly re-enable logging to console */
1515 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1518 /* Number of chars in the log buffer */
1519 case SYSLOG_ACTION_SIZE_UNREAD
:
1520 raw_spin_lock_irq(&logbuf_lock
);
1521 if (syslog_seq
< log_first_seq
) {
1522 /* messages are gone, move to first one */
1523 syslog_seq
= log_first_seq
;
1524 syslog_idx
= log_first_idx
;
1528 if (source
== SYSLOG_FROM_PROC
) {
1530 * Short-cut for poll(/"proc/kmsg") which simply checks
1531 * for pending data, not the size; return the count of
1532 * records, not the length.
1534 error
= log_next_seq
- syslog_seq
;
1536 u64 seq
= syslog_seq
;
1537 u32 idx
= syslog_idx
;
1538 enum log_flags prev
= syslog_prev
;
1541 while (seq
< log_next_seq
) {
1542 struct printk_log
*msg
= log_from_idx(idx
);
1544 error
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1545 idx
= log_next(idx
);
1549 error
-= syslog_partial
;
1551 raw_spin_unlock_irq(&logbuf_lock
);
1553 /* Size of the log buffer */
1554 case SYSLOG_ACTION_SIZE_BUFFER
:
1555 error
= log_buf_len
;
1565 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1567 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1571 * Call the console drivers, asking them to write out
1572 * log_buf[start] to log_buf[end - 1].
1573 * The console_lock must be held.
1575 static void call_console_drivers(int level
,
1576 const char *ext_text
, size_t ext_len
,
1577 const char *text
, size_t len
)
1579 struct console
*con
;
1581 trace_console(text
, len
);
1583 if (!console_drivers
)
1586 for_each_console(con
) {
1587 if (exclusive_console
&& con
!= exclusive_console
)
1589 if (!(con
->flags
& CON_ENABLED
))
1593 if (!cpu_online(smp_processor_id()) &&
1594 !(con
->flags
& CON_ANYTIME
))
1596 if (con
->flags
& CON_EXTENDED
)
1597 con
->write(con
, ext_text
, ext_len
);
1599 con
->write(con
, text
, len
);
1604 * Zap console related locks when oopsing.
1605 * To leave time for slow consoles to print a full oops,
1606 * only zap at most once every 30 seconds.
1608 static void zap_locks(void)
1610 static unsigned long oops_timestamp
;
1612 if (time_after_eq(jiffies
, oops_timestamp
) &&
1613 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1616 oops_timestamp
= jiffies
;
1619 /* If a crash is occurring, make sure we can't deadlock */
1620 raw_spin_lock_init(&logbuf_lock
);
1621 /* And make sure that we print immediately */
1622 sema_init(&console_sem
, 1);
1625 int printk_delay_msec __read_mostly
;
1627 static inline void printk_delay(void)
1629 if (unlikely(printk_delay_msec
)) {
1630 int m
= printk_delay_msec
;
1634 touch_nmi_watchdog();
1640 * Continuation lines are buffered, and not committed to the record buffer
1641 * until the line is complete, or a race forces it. The line fragments
1642 * though, are printed immediately to the consoles to ensure everything has
1643 * reached the console in case of a kernel crash.
1645 static struct cont
{
1646 char buf
[LOG_LINE_MAX
];
1647 size_t len
; /* length == 0 means unused buffer */
1648 size_t cons
; /* bytes written to console */
1649 struct task_struct
*owner
; /* task of first print*/
1650 u64 ts_nsec
; /* time of first print */
1651 u8 level
; /* log level of first message */
1652 u8 facility
; /* log facility of first message */
1653 enum log_flags flags
; /* prefix, newline flags */
1654 bool flushed
:1; /* buffer sealed and committed */
1657 static void cont_flush(enum log_flags flags
)
1666 * If a fragment of this line was directly flushed to the
1667 * console; wait for the console to pick up the rest of the
1668 * line. LOG_NOCONS suppresses a duplicated output.
1670 log_store(cont
.facility
, cont
.level
, flags
| LOG_NOCONS
,
1671 cont
.ts_nsec
, NULL
, 0, cont
.buf
, cont
.len
);
1673 cont
.flushed
= true;
1676 * If no fragment of this line ever reached the console,
1677 * just submit it to the store and free the buffer.
1679 log_store(cont
.facility
, cont
.level
, flags
, 0,
1680 NULL
, 0, cont
.buf
, cont
.len
);
1685 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1687 if (cont
.len
&& cont
.flushed
)
1691 * If ext consoles are present, flush and skip in-kernel
1692 * continuation. See nr_ext_console_drivers definition. Also, if
1693 * the line gets too long, split it up in separate records.
1695 if (nr_ext_console_drivers
|| cont
.len
+ len
> sizeof(cont
.buf
)) {
1696 cont_flush(LOG_CONT
);
1701 cont
.facility
= facility
;
1703 cont
.owner
= current
;
1704 cont
.ts_nsec
= local_clock();
1707 cont
.flushed
= false;
1710 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1713 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1714 cont_flush(LOG_CONT
);
1719 static size_t cont_print_text(char *text
, size_t size
)
1724 if (cont
.cons
== 0 && (console_prev
& LOG_NEWLINE
)) {
1725 textlen
+= print_time(cont
.ts_nsec
, text
);
1729 len
= cont
.len
- cont
.cons
;
1733 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1735 cont
.cons
= cont
.len
;
1739 if (cont
.flags
& LOG_NEWLINE
)
1740 text
[textlen
++] = '\n';
1741 /* got everything, release buffer */
1747 asmlinkage
int vprintk_emit(int facility
, int level
,
1748 const char *dict
, size_t dictlen
,
1749 const char *fmt
, va_list args
)
1751 static bool recursion_bug
;
1752 static char textbuf
[LOG_LINE_MAX
];
1753 char *text
= textbuf
;
1754 size_t text_len
= 0;
1755 enum log_flags lflags
= 0;
1756 unsigned long flags
;
1758 int printed_len
= 0;
1759 int nmi_message_lost
;
1760 bool in_sched
= false;
1761 /* cpu currently holding logbuf_lock in this function */
1762 static unsigned int logbuf_cpu
= UINT_MAX
;
1764 if (level
== LOGLEVEL_SCHED
) {
1765 level
= LOGLEVEL_DEFAULT
;
1769 boot_delay_msec(level
);
1772 local_irq_save(flags
);
1773 this_cpu
= smp_processor_id();
1776 * Ouch, printk recursed into itself!
1778 if (unlikely(logbuf_cpu
== this_cpu
)) {
1780 * If a crash is occurring during printk() on this CPU,
1781 * then try to get the crash message out but make sure
1782 * we can't deadlock. Otherwise just return to avoid the
1783 * recursion and return - but flag the recursion so that
1784 * it can be printed at the next appropriate moment:
1786 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1787 recursion_bug
= true;
1788 local_irq_restore(flags
);
1795 /* This stops the holder of console_sem just where we want him */
1796 raw_spin_lock(&logbuf_lock
);
1797 logbuf_cpu
= this_cpu
;
1799 if (unlikely(recursion_bug
)) {
1800 static const char recursion_msg
[] =
1801 "BUG: recent printk recursion!";
1803 recursion_bug
= false;
1804 /* emit KERN_CRIT message */
1805 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1806 NULL
, 0, recursion_msg
,
1807 strlen(recursion_msg
));
1810 nmi_message_lost
= get_nmi_message_lost();
1811 if (unlikely(nmi_message_lost
)) {
1812 text_len
= scnprintf(textbuf
, sizeof(textbuf
),
1813 "BAD LUCK: lost %d message(s) from NMI context!",
1815 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1816 NULL
, 0, textbuf
, text_len
);
1820 * The printf needs to come first; we need the syslog
1821 * prefix which might be passed-in as a parameter.
1823 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1825 /* mark and strip a trailing newline */
1826 if (text_len
&& text
[text_len
-1] == '\n') {
1828 lflags
|= LOG_NEWLINE
;
1831 /* strip kernel syslog prefix and extract log level or control flags */
1832 if (facility
== 0) {
1833 int kern_level
= printk_get_level(text
);
1836 const char *end_of_header
= printk_skip_level(text
);
1837 switch (kern_level
) {
1839 if (level
== LOGLEVEL_DEFAULT
)
1840 level
= kern_level
- '0';
1842 case 'd': /* KERN_DEFAULT */
1843 lflags
|= LOG_PREFIX
;
1846 * No need to check length here because vscnprintf
1847 * put '\0' at the end of the string. Only valid and
1848 * newly printed level is detected.
1850 text_len
-= end_of_header
- text
;
1851 text
= (char *)end_of_header
;
1855 if (level
== LOGLEVEL_DEFAULT
)
1856 level
= default_message_loglevel
;
1859 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1861 if (!(lflags
& LOG_NEWLINE
)) {
1863 * Flush the conflicting buffer. An earlier newline was missing,
1864 * or another task also prints continuation lines.
1866 if (cont
.len
&& (lflags
& LOG_PREFIX
|| cont
.owner
!= current
))
1867 cont_flush(LOG_NEWLINE
);
1869 /* buffer line if possible, otherwise store it right away */
1870 if (cont_add(facility
, level
, text
, text_len
))
1871 printed_len
+= text_len
;
1873 printed_len
+= log_store(facility
, level
,
1874 lflags
| LOG_CONT
, 0,
1875 dict
, dictlen
, text
, text_len
);
1877 bool stored
= false;
1880 * If an earlier newline was missing and it was the same task,
1881 * either merge it with the current buffer and flush, or if
1882 * there was a race with interrupts (prefix == true) then just
1883 * flush it out and store this line separately.
1884 * If the preceding printk was from a different task and missed
1885 * a newline, flush and append the newline.
1888 if (cont
.owner
== current
&& !(lflags
& LOG_PREFIX
))
1889 stored
= cont_add(facility
, level
, text
,
1891 cont_flush(LOG_NEWLINE
);
1895 printed_len
+= text_len
;
1897 printed_len
+= log_store(facility
, level
, lflags
, 0,
1898 dict
, dictlen
, text
, text_len
);
1901 logbuf_cpu
= UINT_MAX
;
1902 raw_spin_unlock(&logbuf_lock
);
1904 local_irq_restore(flags
);
1906 /* If called from the scheduler, we can not call up(). */
1910 * Try to acquire and then immediately release the console
1911 * semaphore. The release will print out buffers and wake up
1912 * /dev/kmsg and syslog() users.
1914 if (console_trylock())
1921 EXPORT_SYMBOL(vprintk_emit
);
1923 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1925 return vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1927 EXPORT_SYMBOL(vprintk
);
1929 asmlinkage
int printk_emit(int facility
, int level
,
1930 const char *dict
, size_t dictlen
,
1931 const char *fmt
, ...)
1936 va_start(args
, fmt
);
1937 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1942 EXPORT_SYMBOL(printk_emit
);
1944 int vprintk_default(const char *fmt
, va_list args
)
1948 #ifdef CONFIG_KGDB_KDB
1949 if (unlikely(kdb_trap_printk
)) {
1950 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1954 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1958 EXPORT_SYMBOL_GPL(vprintk_default
);
1961 * printk - print a kernel message
1962 * @fmt: format string
1964 * This is printk(). It can be called from any context. We want it to work.
1966 * We try to grab the console_lock. If we succeed, it's easy - we log the
1967 * output and call the console drivers. If we fail to get the semaphore, we
1968 * place the output into the log buffer and return. The current holder of
1969 * the console_sem will notice the new output in console_unlock(); and will
1970 * send it to the consoles before releasing the lock.
1972 * One effect of this deferred printing is that code which calls printk() and
1973 * then changes console_loglevel may break. This is because console_loglevel
1974 * is inspected when the actual printing occurs.
1979 * See the vsnprintf() documentation for format string extensions over C99.
1981 asmlinkage __visible
int printk(const char *fmt
, ...)
1986 va_start(args
, fmt
);
1987 r
= vprintk_func(fmt
, args
);
1992 EXPORT_SYMBOL(printk
);
1994 #else /* CONFIG_PRINTK */
1996 #define LOG_LINE_MAX 0
1997 #define PREFIX_MAX 0
1999 static u64 syslog_seq
;
2000 static u32 syslog_idx
;
2001 static u64 console_seq
;
2002 static u32 console_idx
;
2003 static enum log_flags syslog_prev
;
2004 static u64 log_first_seq
;
2005 static u32 log_first_idx
;
2006 static u64 log_next_seq
;
2007 static enum log_flags console_prev
;
2008 static struct cont
{
2014 static char *log_text(const struct printk_log
*msg
) { return NULL
; }
2015 static char *log_dict(const struct printk_log
*msg
) { return NULL
; }
2016 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
2017 static u32
log_next(u32 idx
) { return 0; }
2018 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
2019 struct printk_log
*msg
, u64 seq
,
2020 enum log_flags prev_flags
) { return 0; }
2021 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
2022 char *dict
, size_t dict_len
,
2023 char *text
, size_t text_len
) { return 0; }
2024 static void call_console_drivers(int level
,
2025 const char *ext_text
, size_t ext_len
,
2026 const char *text
, size_t len
) {}
2027 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
2028 bool syslog
, char *buf
, size_t size
) { return 0; }
2029 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
2030 static bool suppress_message_printing(int level
) { return false; }
2032 /* Still needs to be defined for users */
2033 DEFINE_PER_CPU(printk_func_t
, printk_func
);
2035 #endif /* CONFIG_PRINTK */
2037 #ifdef CONFIG_EARLY_PRINTK
2038 struct console
*early_console
;
2040 asmlinkage __visible
void early_printk(const char *fmt
, ...)
2050 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
2053 early_console
->write(early_console
, buf
, n
);
2057 static int __add_preferred_console(char *name
, int idx
, char *options
,
2060 struct console_cmdline
*c
;
2064 * See if this tty is not yet registered, and
2065 * if we have a slot free.
2067 for (i
= 0, c
= console_cmdline
;
2068 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2070 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
2072 selected_console
= i
;
2076 if (i
== MAX_CMDLINECONSOLES
)
2079 selected_console
= i
;
2080 strlcpy(c
->name
, name
, sizeof(c
->name
));
2081 c
->options
= options
;
2082 braille_set_options(c
, brl_options
);
2088 * Set up a console. Called via do_early_param() in init/main.c
2089 * for each "console=" parameter in the boot command line.
2091 static int __init
console_setup(char *str
)
2093 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
2094 char *s
, *options
, *brl_options
= NULL
;
2097 if (_braille_console_setup(&str
, &brl_options
))
2101 * Decode str into name, index, options.
2103 if (str
[0] >= '0' && str
[0] <= '9') {
2104 strcpy(buf
, "ttyS");
2105 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
2107 strncpy(buf
, str
, sizeof(buf
) - 1);
2109 buf
[sizeof(buf
) - 1] = 0;
2110 options
= strchr(str
, ',');
2114 if (!strcmp(str
, "ttya"))
2115 strcpy(buf
, "ttyS0");
2116 if (!strcmp(str
, "ttyb"))
2117 strcpy(buf
, "ttyS1");
2119 for (s
= buf
; *s
; s
++)
2120 if (isdigit(*s
) || *s
== ',')
2122 idx
= simple_strtoul(s
, NULL
, 10);
2125 __add_preferred_console(buf
, idx
, options
, brl_options
);
2126 console_set_on_cmdline
= 1;
2129 __setup("console=", console_setup
);
2132 * add_preferred_console - add a device to the list of preferred consoles.
2133 * @name: device name
2134 * @idx: device index
2135 * @options: options for this console
2137 * The last preferred console added will be used for kernel messages
2138 * and stdin/out/err for init. Normally this is used by console_setup
2139 * above to handle user-supplied console arguments; however it can also
2140 * be used by arch-specific code either to override the user or more
2141 * commonly to provide a default console (ie from PROM variables) when
2142 * the user has not supplied one.
2144 int add_preferred_console(char *name
, int idx
, char *options
)
2146 return __add_preferred_console(name
, idx
, options
, NULL
);
2149 bool console_suspend_enabled
= true;
2150 EXPORT_SYMBOL(console_suspend_enabled
);
2152 static int __init
console_suspend_disable(char *str
)
2154 console_suspend_enabled
= false;
2157 __setup("no_console_suspend", console_suspend_disable
);
2158 module_param_named(console_suspend
, console_suspend_enabled
,
2159 bool, S_IRUGO
| S_IWUSR
);
2160 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2161 " and hibernate operations");
2164 * suspend_console - suspend the console subsystem
2166 * This disables printk() while we go into suspend states
2168 void suspend_console(void)
2170 if (!console_suspend_enabled
)
2172 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2174 console_suspended
= 1;
2178 void resume_console(void)
2180 if (!console_suspend_enabled
)
2183 console_suspended
= 0;
2188 * console_cpu_notify - print deferred console messages after CPU hotplug
2189 * @self: notifier struct
2190 * @action: CPU hotplug event
2193 * If printk() is called from a CPU that is not online yet, the messages
2194 * will be spooled but will not show up on the console. This function is
2195 * called when a new CPU comes online (or fails to come up), and ensures
2196 * that any such output gets printed.
2198 static int console_cpu_notify(struct notifier_block
*self
,
2199 unsigned long action
, void *hcpu
)
2204 case CPU_DOWN_FAILED
:
2205 case CPU_UP_CANCELED
:
2213 * console_lock - lock the console system for exclusive use.
2215 * Acquires a lock which guarantees that the caller has
2216 * exclusive access to the console system and the console_drivers list.
2218 * Can sleep, returns nothing.
2220 void console_lock(void)
2225 if (console_suspended
)
2228 console_may_schedule
= 1;
2230 EXPORT_SYMBOL(console_lock
);
2233 * console_trylock - try to lock the console system for exclusive use.
2235 * Try to acquire a lock which guarantees that the caller has exclusive
2236 * access to the console system and the console_drivers list.
2238 * returns 1 on success, and 0 on failure to acquire the lock.
2240 int console_trylock(void)
2242 if (down_trylock_console_sem())
2244 if (console_suspended
) {
2250 * When PREEMPT_COUNT disabled we can't reliably detect if it's
2251 * safe to schedule (e.g. calling printk while holding a spin_lock),
2252 * because preempt_disable()/preempt_enable() are just barriers there
2253 * and preempt_count() is always 0.
2255 * RCU read sections have a separate preemption counter when
2256 * PREEMPT_RCU enabled thus we must take extra care and check
2257 * rcu_preempt_depth(), otherwise RCU read sections modify
2260 console_may_schedule
= !oops_in_progress
&&
2262 !rcu_preempt_depth();
2265 EXPORT_SYMBOL(console_trylock
);
2267 int is_console_locked(void)
2269 return console_locked
;
2273 * Check if we have any console that is capable of printing while cpu is
2274 * booting or shutting down. Requires console_sem.
2276 static int have_callable_console(void)
2278 struct console
*con
;
2280 for_each_console(con
)
2281 if ((con
->flags
& CON_ENABLED
) &&
2282 (con
->flags
& CON_ANYTIME
))
2289 * Can we actually use the console at this time on this cpu?
2291 * Console drivers may assume that per-cpu resources have been allocated. So
2292 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2293 * call them until this CPU is officially up.
2295 static inline int can_use_console(void)
2297 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2300 static void console_cont_flush(char *text
, size_t size
)
2302 unsigned long flags
;
2305 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2310 if (suppress_message_printing(cont
.level
)) {
2311 cont
.cons
= cont
.len
;
2318 * We still queue earlier records, likely because the console was
2319 * busy. The earlier ones need to be printed before this one, we
2320 * did not flush any fragment so far, so just let it queue up.
2322 if (console_seq
< log_next_seq
&& !cont
.cons
)
2325 len
= cont_print_text(text
, size
);
2326 raw_spin_unlock(&logbuf_lock
);
2327 stop_critical_timings();
2328 call_console_drivers(cont
.level
, NULL
, 0, text
, len
);
2329 start_critical_timings();
2330 local_irq_restore(flags
);
2333 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2337 * console_unlock - unlock the console system
2339 * Releases the console_lock which the caller holds on the console system
2340 * and the console driver list.
2342 * While the console_lock was held, console output may have been buffered
2343 * by printk(). If this is the case, console_unlock(); emits
2344 * the output prior to releasing the lock.
2346 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2348 * console_unlock(); may be called from any context.
2350 void console_unlock(void)
2352 static char ext_text
[CONSOLE_EXT_LOG_MAX
];
2353 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2354 static u64 seen_seq
;
2355 unsigned long flags
;
2356 bool wake_klogd
= false;
2357 bool do_cond_resched
, retry
;
2359 if (console_suspended
) {
2365 * Console drivers are called under logbuf_lock, so
2366 * @console_may_schedule should be cleared before; however, we may
2367 * end up dumping a lot of lines, for example, if called from
2368 * console registration path, and should invoke cond_resched()
2369 * between lines if allowable. Not doing so can cause a very long
2370 * scheduling stall on a slow console leading to RCU stall and
2371 * softlockup warnings which exacerbate the issue with more
2372 * messages practically incapacitating the system.
2374 do_cond_resched
= console_may_schedule
;
2375 console_may_schedule
= 0;
2379 * We released the console_sem lock, so we need to recheck if
2380 * cpu is online and (if not) is there at least one CON_ANYTIME
2383 if (!can_use_console()) {
2389 /* flush buffered message fragment immediately to console */
2390 console_cont_flush(text
, sizeof(text
));
2393 struct printk_log
*msg
;
2398 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2399 if (seen_seq
!= log_next_seq
) {
2401 seen_seq
= log_next_seq
;
2404 if (console_seq
< log_first_seq
) {
2405 len
= sprintf(text
, "** %u printk messages dropped ** ",
2406 (unsigned)(log_first_seq
- console_seq
));
2408 /* messages are gone, move to first one */
2409 console_seq
= log_first_seq
;
2410 console_idx
= log_first_idx
;
2416 if (console_seq
== log_next_seq
)
2419 msg
= log_from_idx(console_idx
);
2421 if ((msg
->flags
& LOG_NOCONS
) ||
2422 suppress_message_printing(level
)) {
2424 * Skip record we have buffered and already printed
2425 * directly to the console when we received it, and
2426 * record that has level above the console loglevel.
2428 console_idx
= log_next(console_idx
);
2431 * We will get here again when we register a new
2432 * CON_PRINTBUFFER console. Clear the flag so we
2433 * will properly dump everything later.
2435 msg
->flags
&= ~LOG_NOCONS
;
2436 console_prev
= msg
->flags
;
2440 len
+= msg_print_text(msg
, console_prev
, false,
2441 text
+ len
, sizeof(text
) - len
);
2442 if (nr_ext_console_drivers
) {
2443 ext_len
= msg_print_ext_header(ext_text
,
2445 msg
, console_seq
, console_prev
);
2446 ext_len
+= msg_print_ext_body(ext_text
+ ext_len
,
2447 sizeof(ext_text
) - ext_len
,
2448 log_dict(msg
), msg
->dict_len
,
2449 log_text(msg
), msg
->text_len
);
2451 console_idx
= log_next(console_idx
);
2453 console_prev
= msg
->flags
;
2454 raw_spin_unlock(&logbuf_lock
);
2456 stop_critical_timings(); /* don't trace print latency */
2457 call_console_drivers(level
, ext_text
, ext_len
, text
, len
);
2458 start_critical_timings();
2459 local_irq_restore(flags
);
2461 if (do_cond_resched
)
2466 /* Release the exclusive_console once it is used */
2467 if (unlikely(exclusive_console
))
2468 exclusive_console
= NULL
;
2470 raw_spin_unlock(&logbuf_lock
);
2475 * Someone could have filled up the buffer again, so re-check if there's
2476 * something to flush. In case we cannot trylock the console_sem again,
2477 * there's a new owner and the console_unlock() from them will do the
2478 * flush, no worries.
2480 raw_spin_lock(&logbuf_lock
);
2481 retry
= console_seq
!= log_next_seq
;
2482 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2484 if (retry
&& console_trylock())
2490 EXPORT_SYMBOL(console_unlock
);
2493 * console_conditional_schedule - yield the CPU if required
2495 * If the console code is currently allowed to sleep, and
2496 * if this CPU should yield the CPU to another task, do
2499 * Must be called within console_lock();.
2501 void __sched
console_conditional_schedule(void)
2503 if (console_may_schedule
)
2506 EXPORT_SYMBOL(console_conditional_schedule
);
2508 void console_unblank(void)
2513 * console_unblank can no longer be called in interrupt context unless
2514 * oops_in_progress is set to 1..
2516 if (oops_in_progress
) {
2517 if (down_trylock_console_sem() != 0)
2523 console_may_schedule
= 0;
2525 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2531 * console_flush_on_panic - flush console content on panic
2533 * Immediately output all pending messages no matter what.
2535 void console_flush_on_panic(void)
2538 * If someone else is holding the console lock, trylock will fail
2539 * and may_schedule may be set. Ignore and proceed to unlock so
2540 * that messages are flushed out. As this can be called from any
2541 * context and we don't want to get preempted while flushing,
2542 * ensure may_schedule is cleared.
2545 console_may_schedule
= 0;
2550 * Return the console tty driver structure and its associated index
2552 struct tty_driver
*console_device(int *index
)
2555 struct tty_driver
*driver
= NULL
;
2558 for_each_console(c
) {
2561 driver
= c
->device(c
, index
);
2570 * Prevent further output on the passed console device so that (for example)
2571 * serial drivers can disable console output before suspending a port, and can
2572 * re-enable output afterwards.
2574 void console_stop(struct console
*console
)
2577 console
->flags
&= ~CON_ENABLED
;
2580 EXPORT_SYMBOL(console_stop
);
2582 void console_start(struct console
*console
)
2585 console
->flags
|= CON_ENABLED
;
2588 EXPORT_SYMBOL(console_start
);
2590 static int __read_mostly keep_bootcon
;
2592 static int __init
keep_bootcon_setup(char *str
)
2595 pr_info("debug: skip boot console de-registration.\n");
2600 early_param("keep_bootcon", keep_bootcon_setup
);
2603 * The console driver calls this routine during kernel initialization
2604 * to register the console printing procedure with printk() and to
2605 * print any messages that were printed by the kernel before the
2606 * console driver was initialized.
2608 * This can happen pretty early during the boot process (because of
2609 * early_printk) - sometimes before setup_arch() completes - be careful
2610 * of what kernel features are used - they may not be initialised yet.
2612 * There are two types of consoles - bootconsoles (early_printk) and
2613 * "real" consoles (everything which is not a bootconsole) which are
2614 * handled differently.
2615 * - Any number of bootconsoles can be registered at any time.
2616 * - As soon as a "real" console is registered, all bootconsoles
2617 * will be unregistered automatically.
2618 * - Once a "real" console is registered, any attempt to register a
2619 * bootconsoles will be rejected
2621 void register_console(struct console
*newcon
)
2624 unsigned long flags
;
2625 struct console
*bcon
= NULL
;
2626 struct console_cmdline
*c
;
2628 if (console_drivers
)
2629 for_each_console(bcon
)
2630 if (WARN(bcon
== newcon
,
2631 "console '%s%d' already registered\n",
2632 bcon
->name
, bcon
->index
))
2636 * before we register a new CON_BOOT console, make sure we don't
2637 * already have a valid console
2639 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2640 /* find the last or real console */
2641 for_each_console(bcon
) {
2642 if (!(bcon
->flags
& CON_BOOT
)) {
2643 pr_info("Too late to register bootconsole %s%d\n",
2644 newcon
->name
, newcon
->index
);
2650 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2651 bcon
= console_drivers
;
2653 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2654 preferred_console
= selected_console
;
2657 * See if we want to use this console driver. If we
2658 * didn't select a console we take the first one
2659 * that registers here.
2661 if (preferred_console
< 0 && !of_specified_console
) {
2662 if (newcon
->index
< 0)
2664 if (newcon
->setup
== NULL
||
2665 newcon
->setup(newcon
, NULL
) == 0) {
2666 newcon
->flags
|= CON_ENABLED
;
2667 if (newcon
->device
) {
2668 newcon
->flags
|= CON_CONSDEV
;
2669 preferred_console
= 0;
2675 * See if this console matches one we selected on
2678 for (i
= 0, c
= console_cmdline
;
2679 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2681 if (!newcon
->match
||
2682 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2683 /* default matching */
2684 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2685 if (strcmp(c
->name
, newcon
->name
) != 0)
2687 if (newcon
->index
>= 0 &&
2688 newcon
->index
!= c
->index
)
2690 if (newcon
->index
< 0)
2691 newcon
->index
= c
->index
;
2693 if (_braille_register_console(newcon
, c
))
2696 if (newcon
->setup
&&
2697 newcon
->setup(newcon
, c
->options
) != 0)
2701 newcon
->flags
|= CON_ENABLED
;
2702 if (i
== selected_console
) {
2703 newcon
->flags
|= CON_CONSDEV
;
2704 preferred_console
= selected_console
;
2709 if (!(newcon
->flags
& CON_ENABLED
))
2713 * If we have a bootconsole, and are switching to a real console,
2714 * don't print everything out again, since when the boot console, and
2715 * the real console are the same physical device, it's annoying to
2716 * see the beginning boot messages twice
2718 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2719 newcon
->flags
&= ~CON_PRINTBUFFER
;
2722 * Put this console in the list - keep the
2723 * preferred driver at the head of the list.
2726 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2727 newcon
->next
= console_drivers
;
2728 console_drivers
= newcon
;
2730 newcon
->next
->flags
&= ~CON_CONSDEV
;
2732 newcon
->next
= console_drivers
->next
;
2733 console_drivers
->next
= newcon
;
2736 if (newcon
->flags
& CON_EXTENDED
)
2737 if (!nr_ext_console_drivers
++)
2738 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2740 if (newcon
->flags
& CON_PRINTBUFFER
) {
2742 * console_unlock(); will print out the buffered messages
2745 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2746 console_seq
= syslog_seq
;
2747 console_idx
= syslog_idx
;
2748 console_prev
= syslog_prev
;
2749 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2751 * We're about to replay the log buffer. Only do this to the
2752 * just-registered console to avoid excessive message spam to
2753 * the already-registered consoles.
2755 exclusive_console
= newcon
;
2758 console_sysfs_notify();
2761 * By unregistering the bootconsoles after we enable the real console
2762 * we get the "console xxx enabled" message on all the consoles -
2763 * boot consoles, real consoles, etc - this is to ensure that end
2764 * users know there might be something in the kernel's log buffer that
2765 * went to the bootconsole (that they do not see on the real console)
2767 pr_info("%sconsole [%s%d] enabled\n",
2768 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2769 newcon
->name
, newcon
->index
);
2771 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2773 /* We need to iterate through all boot consoles, to make
2774 * sure we print everything out, before we unregister them.
2776 for_each_console(bcon
)
2777 if (bcon
->flags
& CON_BOOT
)
2778 unregister_console(bcon
);
2781 EXPORT_SYMBOL(register_console
);
2783 int unregister_console(struct console
*console
)
2785 struct console
*a
, *b
;
2788 pr_info("%sconsole [%s%d] disabled\n",
2789 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2790 console
->name
, console
->index
);
2792 res
= _braille_unregister_console(console
);
2798 if (console_drivers
== console
) {
2799 console_drivers
=console
->next
;
2801 } else if (console_drivers
) {
2802 for (a
=console_drivers
->next
, b
=console_drivers
;
2803 a
; b
=a
, a
=b
->next
) {
2812 if (!res
&& (console
->flags
& CON_EXTENDED
))
2813 nr_ext_console_drivers
--;
2816 * If this isn't the last console and it has CON_CONSDEV set, we
2817 * need to set it on the next preferred console.
2819 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2820 console_drivers
->flags
|= CON_CONSDEV
;
2822 console
->flags
&= ~CON_ENABLED
;
2824 console_sysfs_notify();
2827 EXPORT_SYMBOL(unregister_console
);
2830 * Some boot consoles access data that is in the init section and which will
2831 * be discarded after the initcalls have been run. To make sure that no code
2832 * will access this data, unregister the boot consoles in a late initcall.
2834 * If for some reason, such as deferred probe or the driver being a loadable
2835 * module, the real console hasn't registered yet at this point, there will
2836 * be a brief interval in which no messages are logged to the console, which
2837 * makes it difficult to diagnose problems that occur during this time.
2839 * To mitigate this problem somewhat, only unregister consoles whose memory
2840 * intersects with the init section. Note that code exists elsewhere to get
2841 * rid of the boot console as soon as the proper console shows up, so there
2842 * won't be side-effects from postponing the removal.
2844 static int __init
printk_late_init(void)
2846 struct console
*con
;
2848 for_each_console(con
) {
2849 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2851 * Make sure to unregister boot consoles whose data
2852 * resides in the init section before the init section
2853 * is discarded. Boot consoles whose data will stick
2854 * around will automatically be unregistered when the
2855 * proper console replaces them.
2857 if (init_section_intersects(con
, sizeof(*con
)))
2858 unregister_console(con
);
2861 hotcpu_notifier(console_cpu_notify
, 0);
2864 late_initcall(printk_late_init
);
2866 #if defined CONFIG_PRINTK
2868 * Delayed printk version, for scheduler-internal messages:
2870 #define PRINTK_PENDING_WAKEUP 0x01
2871 #define PRINTK_PENDING_OUTPUT 0x02
2873 static DEFINE_PER_CPU(int, printk_pending
);
2875 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2877 int pending
= __this_cpu_xchg(printk_pending
, 0);
2879 if (pending
& PRINTK_PENDING_OUTPUT
) {
2880 /* If trylock fails, someone else is doing the printing */
2881 if (console_trylock())
2885 if (pending
& PRINTK_PENDING_WAKEUP
)
2886 wake_up_interruptible(&log_wait
);
2889 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2890 .func
= wake_up_klogd_work_func
,
2891 .flags
= IRQ_WORK_LAZY
,
2894 void wake_up_klogd(void)
2897 if (waitqueue_active(&log_wait
)) {
2898 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2899 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2904 int printk_deferred(const char *fmt
, ...)
2910 va_start(args
, fmt
);
2911 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2914 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2915 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2922 * printk rate limiting, lifted from the networking subsystem.
2924 * This enforces a rate limit: not more than 10 kernel messages
2925 * every 5s to make a denial-of-service attack impossible.
2927 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2929 int __printk_ratelimit(const char *func
)
2931 return ___ratelimit(&printk_ratelimit_state
, func
);
2933 EXPORT_SYMBOL(__printk_ratelimit
);
2936 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2937 * @caller_jiffies: pointer to caller's state
2938 * @interval_msecs: minimum interval between prints
2940 * printk_timed_ratelimit() returns true if more than @interval_msecs
2941 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2944 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2945 unsigned int interval_msecs
)
2947 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2949 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2952 *caller_jiffies
= jiffies
;
2955 EXPORT_SYMBOL(printk_timed_ratelimit
);
2957 static DEFINE_SPINLOCK(dump_list_lock
);
2958 static LIST_HEAD(dump_list
);
2961 * kmsg_dump_register - register a kernel log dumper.
2962 * @dumper: pointer to the kmsg_dumper structure
2964 * Adds a kernel log dumper to the system. The dump callback in the
2965 * structure will be called when the kernel oopses or panics and must be
2966 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2968 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2970 unsigned long flags
;
2973 /* The dump callback needs to be set */
2977 spin_lock_irqsave(&dump_list_lock
, flags
);
2978 /* Don't allow registering multiple times */
2979 if (!dumper
->registered
) {
2980 dumper
->registered
= 1;
2981 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2984 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2988 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2991 * kmsg_dump_unregister - unregister a kmsg dumper.
2992 * @dumper: pointer to the kmsg_dumper structure
2994 * Removes a dump device from the system. Returns zero on success and
2995 * %-EINVAL otherwise.
2997 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2999 unsigned long flags
;
3002 spin_lock_irqsave(&dump_list_lock
, flags
);
3003 if (dumper
->registered
) {
3004 dumper
->registered
= 0;
3005 list_del_rcu(&dumper
->list
);
3008 spin_unlock_irqrestore(&dump_list_lock
, flags
);
3013 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
3015 static bool always_kmsg_dump
;
3016 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
3019 * kmsg_dump - dump kernel log to kernel message dumpers.
3020 * @reason: the reason (oops, panic etc) for dumping
3022 * Call each of the registered dumper's dump() callback, which can
3023 * retrieve the kmsg records with kmsg_dump_get_line() or
3024 * kmsg_dump_get_buffer().
3026 void kmsg_dump(enum kmsg_dump_reason reason
)
3028 struct kmsg_dumper
*dumper
;
3029 unsigned long flags
;
3031 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
3035 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
3036 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
3039 /* initialize iterator with data about the stored records */
3040 dumper
->active
= true;
3042 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3043 dumper
->cur_seq
= clear_seq
;
3044 dumper
->cur_idx
= clear_idx
;
3045 dumper
->next_seq
= log_next_seq
;
3046 dumper
->next_idx
= log_next_idx
;
3047 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3049 /* invoke dumper which will iterate over records */
3050 dumper
->dump(dumper
, reason
);
3052 /* reset iterator */
3053 dumper
->active
= false;
3059 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
3060 * @dumper: registered kmsg dumper
3061 * @syslog: include the "<4>" prefixes
3062 * @line: buffer to copy the line to
3063 * @size: maximum size of the buffer
3064 * @len: length of line placed into buffer
3066 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3067 * record, and copy one record into the provided buffer.
3069 * Consecutive calls will return the next available record moving
3070 * towards the end of the buffer with the youngest messages.
3072 * A return value of FALSE indicates that there are no more records to
3075 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
3077 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
3078 char *line
, size_t size
, size_t *len
)
3080 struct printk_log
*msg
;
3084 if (!dumper
->active
)
3087 if (dumper
->cur_seq
< log_first_seq
) {
3088 /* messages are gone, move to first available one */
3089 dumper
->cur_seq
= log_first_seq
;
3090 dumper
->cur_idx
= log_first_idx
;
3094 if (dumper
->cur_seq
>= log_next_seq
)
3097 msg
= log_from_idx(dumper
->cur_idx
);
3098 l
= msg_print_text(msg
, 0, syslog
, line
, size
);
3100 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
3110 * kmsg_dump_get_line - retrieve one kmsg log line
3111 * @dumper: registered kmsg dumper
3112 * @syslog: include the "<4>" prefixes
3113 * @line: buffer to copy the line to
3114 * @size: maximum size of the buffer
3115 * @len: length of line placed into buffer
3117 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3118 * record, and copy one record into the provided buffer.
3120 * Consecutive calls will return the next available record moving
3121 * towards the end of the buffer with the youngest messages.
3123 * A return value of FALSE indicates that there are no more records to
3126 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
3127 char *line
, size_t size
, size_t *len
)
3129 unsigned long flags
;
3132 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3133 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
3134 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3138 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
3141 * kmsg_dump_get_buffer - copy kmsg log lines
3142 * @dumper: registered kmsg dumper
3143 * @syslog: include the "<4>" prefixes
3144 * @buf: buffer to copy the line to
3145 * @size: maximum size of the buffer
3146 * @len: length of line placed into buffer
3148 * Start at the end of the kmsg buffer and fill the provided buffer
3149 * with as many of the the *youngest* kmsg records that fit into it.
3150 * If the buffer is large enough, all available kmsg records will be
3151 * copied with a single call.
3153 * Consecutive calls will fill the buffer with the next block of
3154 * available older records, not including the earlier retrieved ones.
3156 * A return value of FALSE indicates that there are no more records to
3159 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
3160 char *buf
, size_t size
, size_t *len
)
3162 unsigned long flags
;
3167 enum log_flags prev
;
3171 if (!dumper
->active
)
3174 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3175 if (dumper
->cur_seq
< log_first_seq
) {
3176 /* messages are gone, move to first available one */
3177 dumper
->cur_seq
= log_first_seq
;
3178 dumper
->cur_idx
= log_first_idx
;
3182 if (dumper
->cur_seq
>= dumper
->next_seq
) {
3183 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3187 /* calculate length of entire buffer */
3188 seq
= dumper
->cur_seq
;
3189 idx
= dumper
->cur_idx
;
3191 while (seq
< dumper
->next_seq
) {
3192 struct printk_log
*msg
= log_from_idx(idx
);
3194 l
+= msg_print_text(msg
, prev
, true, NULL
, 0);
3195 idx
= log_next(idx
);
3200 /* move first record forward until length fits into the buffer */
3201 seq
= dumper
->cur_seq
;
3202 idx
= dumper
->cur_idx
;
3204 while (l
> size
&& seq
< dumper
->next_seq
) {
3205 struct printk_log
*msg
= log_from_idx(idx
);
3207 l
-= msg_print_text(msg
, prev
, true, NULL
, 0);
3208 idx
= log_next(idx
);
3213 /* last message in next interation */
3218 while (seq
< dumper
->next_seq
) {
3219 struct printk_log
*msg
= log_from_idx(idx
);
3221 l
+= msg_print_text(msg
, prev
, syslog
, buf
+ l
, size
- l
);
3222 idx
= log_next(idx
);
3227 dumper
->next_seq
= next_seq
;
3228 dumper
->next_idx
= next_idx
;
3230 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3236 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
3239 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3240 * @dumper: registered kmsg dumper
3242 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3243 * kmsg_dump_get_buffer() can be called again and used multiple
3244 * times within the same dumper.dump() callback.
3246 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3248 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3250 dumper
->cur_seq
= clear_seq
;
3251 dumper
->cur_idx
= clear_idx
;
3252 dumper
->next_seq
= log_next_seq
;
3253 dumper
->next_idx
= log_next_idx
;
3257 * kmsg_dump_rewind - reset the interator
3258 * @dumper: registered kmsg dumper
3260 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3261 * kmsg_dump_get_buffer() can be called again and used multiple
3262 * times within the same dumper.dump() callback.
3264 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3266 unsigned long flags
;
3268 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3269 kmsg_dump_rewind_nolock(dumper
);
3270 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3272 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3274 static char dump_stack_arch_desc_str
[128];
3277 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3278 * @fmt: printf-style format string
3279 * @...: arguments for the format string
3281 * The configured string will be printed right after utsname during task
3282 * dumps. Usually used to add arch-specific system identifiers. If an
3283 * arch wants to make use of such an ID string, it should initialize this
3284 * as soon as possible during boot.
3286 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3290 va_start(args
, fmt
);
3291 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3297 * dump_stack_print_info - print generic debug info for dump_stack()
3298 * @log_lvl: log level
3300 * Arch-specific dump_stack() implementations can use this function to
3301 * print out the same debug information as the generic dump_stack().
3303 void dump_stack_print_info(const char *log_lvl
)
3305 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3306 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3307 print_tainted(), init_utsname()->release
,
3308 (int)strcspn(init_utsname()->version
, " "),
3309 init_utsname()->version
);
3311 if (dump_stack_arch_desc_str
[0] != '\0')
3312 printk("%sHardware name: %s\n",
3313 log_lvl
, dump_stack_arch_desc_str
);
3315 print_worker_info(log_lvl
, current
);
3319 * show_regs_print_info - print generic debug info for show_regs()
3320 * @log_lvl: log level
3322 * show_regs() implementations can use this function to print out generic
3323 * debug information.
3325 void show_regs_print_info(const char *log_lvl
)
3327 dump_stack_print_info(log_lvl
);
3329 printk("%stask: %p task.stack: %p\n",
3330 log_lvl
, current
, task_stack_page(current
));