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"
89 * Number of registered extended console drivers.
91 * If extended consoles are present, in-kernel cont reassembly is disabled
92 * and each fragment is stored as a separate log entry with proper
93 * continuation flag so that every emitted message has full metadata. This
94 * doesn't change the result for regular consoles or /proc/kmsg. For
95 * /dev/kmsg, as long as the reader concatenates messages according to
96 * consecutive continuation flags, the end result should be the same too.
98 static int nr_ext_console_drivers
;
101 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
102 * macros instead of functions so that _RET_IP_ contains useful information.
104 #define down_console_sem() do { \
106 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
109 static int __down_trylock_console_sem(unsigned long ip
)
111 if (down_trylock(&console_sem
))
113 mutex_acquire(&console_lock_dep_map
, 0, 1, ip
);
116 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
118 #define up_console_sem() do { \
119 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
124 * This is used for debugging the mess that is the VT code by
125 * keeping track if we have the console semaphore held. It's
126 * definitely not the perfect debug tool (we don't know if _WE_
127 * hold it and are racing, but it helps tracking those weird code
128 * paths in the console code where we end up in places I want
129 * locked without the console sempahore held).
131 static int console_locked
, console_suspended
;
134 * If exclusive_console is non-NULL then only this console is to be printed to.
136 static struct console
*exclusive_console
;
139 * Array of consoles built from command line options (console=)
142 #define MAX_CMDLINECONSOLES 8
144 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
146 static int selected_console
= -1;
147 static int preferred_console
= -1;
148 int console_set_on_cmdline
;
149 EXPORT_SYMBOL(console_set_on_cmdline
);
151 /* Flag: console code may call schedule() */
152 static int console_may_schedule
;
155 * The printk log buffer consists of a chain of concatenated variable
156 * length records. Every record starts with a record header, containing
157 * the overall length of the record.
159 * The heads to the first and last entry in the buffer, as well as the
160 * sequence numbers of these entries are maintained when messages are
163 * If the heads indicate available messages, the length in the header
164 * tells the start next message. A length == 0 for the next message
165 * indicates a wrap-around to the beginning of the buffer.
167 * Every record carries the monotonic timestamp in microseconds, as well as
168 * the standard userspace syslog level and syslog facility. The usual
169 * kernel messages use LOG_KERN; userspace-injected messages always carry
170 * a matching syslog facility, by default LOG_USER. The origin of every
171 * message can be reliably determined that way.
173 * The human readable log message directly follows the message header. The
174 * length of the message text is stored in the header, the stored message
177 * Optionally, a message can carry a dictionary of properties (key/value pairs),
178 * to provide userspace with a machine-readable message context.
180 * Examples for well-defined, commonly used property names are:
181 * DEVICE=b12:8 device identifier
185 * +sound:card0 subsystem:devname
186 * SUBSYSTEM=pci driver-core subsystem name
188 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
189 * follows directly after a '=' character. Every property is terminated by
190 * a '\0' character. The last property is not terminated.
192 * Example of a message structure:
193 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
194 * 0008 34 00 record is 52 bytes long
195 * 000a 0b 00 text is 11 bytes long
196 * 000c 1f 00 dictionary is 23 bytes long
197 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
198 * 0010 69 74 27 73 20 61 20 6c "it's a l"
200 * 001b 44 45 56 49 43 "DEVIC"
201 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
202 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
204 * 0032 00 00 00 padding to next message header
206 * The 'struct printk_log' buffer header must never be directly exported to
207 * userspace, it is a kernel-private implementation detail that might
208 * need to be changed in the future, when the requirements change.
210 * /dev/kmsg exports the structured data in the following line format:
211 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
213 * Users of the export format should ignore possible additional values
214 * separated by ',', and find the message after the ';' character.
216 * The optional key/value pairs are attached as continuation lines starting
217 * with a space character and terminated by a newline. All possible
218 * non-prinatable characters are escaped in the "\xff" notation.
222 LOG_NOCONS
= 1, /* already flushed, do not print to console */
223 LOG_NEWLINE
= 2, /* text ended with a newline */
224 LOG_PREFIX
= 4, /* text started with a prefix */
225 LOG_CONT
= 8, /* text is a fragment of a continuation line */
229 u64 ts_nsec
; /* timestamp in nanoseconds */
230 u16 len
; /* length of entire record */
231 u16 text_len
; /* length of text buffer */
232 u16 dict_len
; /* length of dictionary buffer */
233 u8 facility
; /* syslog facility */
234 u8 flags
:5; /* internal record flags */
235 u8 level
:3; /* syslog level */
237 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
238 __packed
__aligned(4)
243 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
244 * within the scheduler's rq lock. It must be released before calling
245 * console_unlock() or anything else that might wake up a process.
247 DEFINE_RAW_SPINLOCK(logbuf_lock
);
250 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
251 /* the next printk record to read by syslog(READ) or /proc/kmsg */
252 static u64 syslog_seq
;
253 static u32 syslog_idx
;
254 static enum log_flags syslog_prev
;
255 static size_t syslog_partial
;
257 /* index and sequence number of the first record stored in the buffer */
258 static u64 log_first_seq
;
259 static u32 log_first_idx
;
261 /* index and sequence number of the next record to store in the buffer */
262 static u64 log_next_seq
;
263 static u32 log_next_idx
;
265 /* the next printk record to write to the console */
266 static u64 console_seq
;
267 static u32 console_idx
;
268 static enum log_flags console_prev
;
270 /* the next printk record to read after the last 'clear' command */
271 static u64 clear_seq
;
272 static u32 clear_idx
;
274 #define PREFIX_MAX 32
275 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
277 #define LOG_LEVEL(v) ((v) & 0x07)
278 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
281 #define LOG_ALIGN __alignof__(struct printk_log)
282 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
283 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
284 static char *log_buf
= __log_buf
;
285 static u32 log_buf_len
= __LOG_BUF_LEN
;
287 /* Return log buffer address */
288 char *log_buf_addr_get(void)
293 /* Return log buffer size */
294 u32
log_buf_len_get(void)
299 /* human readable text of the record */
300 static char *log_text(const struct printk_log
*msg
)
302 return (char *)msg
+ sizeof(struct printk_log
);
305 /* optional key/value pair dictionary attached to the record */
306 static char *log_dict(const struct printk_log
*msg
)
308 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
311 /* get record by index; idx must point to valid msg */
312 static struct printk_log
*log_from_idx(u32 idx
)
314 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
317 * A length == 0 record is the end of buffer marker. Wrap around and
318 * read the message at the start of the buffer.
321 return (struct printk_log
*)log_buf
;
325 /* get next record; idx must point to valid msg */
326 static u32
log_next(u32 idx
)
328 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
330 /* length == 0 indicates the end of the buffer; wrap */
332 * A length == 0 record is the end of buffer marker. Wrap around and
333 * read the message at the start of the buffer as *this* one, and
334 * return the one after that.
337 msg
= (struct printk_log
*)log_buf
;
340 return idx
+ msg
->len
;
344 * Check whether there is enough free space for the given message.
346 * The same values of first_idx and next_idx mean that the buffer
347 * is either empty or full.
349 * If the buffer is empty, we must respect the position of the indexes.
350 * They cannot be reset to the beginning of the buffer.
352 static int logbuf_has_space(u32 msg_size
, bool empty
)
356 if (log_next_idx
> log_first_idx
|| empty
)
357 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
359 free
= log_first_idx
- log_next_idx
;
362 * We need space also for an empty header that signalizes wrapping
365 return free
>= msg_size
+ sizeof(struct printk_log
);
368 static int log_make_free_space(u32 msg_size
)
370 while (log_first_seq
< log_next_seq
&&
371 !logbuf_has_space(msg_size
, false)) {
372 /* drop old messages until we have enough contiguous space */
373 log_first_idx
= log_next(log_first_idx
);
377 if (clear_seq
< log_first_seq
) {
378 clear_seq
= log_first_seq
;
379 clear_idx
= log_first_idx
;
382 /* sequence numbers are equal, so the log buffer is empty */
383 if (logbuf_has_space(msg_size
, log_first_seq
== log_next_seq
))
389 /* compute the message size including the padding bytes */
390 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
394 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
395 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
402 * Define how much of the log buffer we could take at maximum. The value
403 * must be greater than two. Note that only half of the buffer is available
404 * when the index points to the middle.
406 #define MAX_LOG_TAKE_PART 4
407 static const char trunc_msg
[] = "<truncated>";
409 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
410 u16
*dict_len
, u32
*pad_len
)
413 * The message should not take the whole buffer. Otherwise, it might
414 * get removed too soon.
416 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
417 if (*text_len
> max_text_len
)
418 *text_len
= max_text_len
;
419 /* enable the warning message */
420 *trunc_msg_len
= strlen(trunc_msg
);
421 /* disable the "dict" completely */
423 /* compute the size again, count also the warning message */
424 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
427 /* insert record into the buffer, discard old ones, update heads */
428 static int log_store(int facility
, int level
,
429 enum log_flags flags
, u64 ts_nsec
,
430 const char *dict
, u16 dict_len
,
431 const char *text
, u16 text_len
)
433 struct printk_log
*msg
;
435 u16 trunc_msg_len
= 0;
437 /* number of '\0' padding bytes to next message */
438 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
440 if (log_make_free_space(size
)) {
441 /* truncate the message if it is too long for empty buffer */
442 size
= truncate_msg(&text_len
, &trunc_msg_len
,
443 &dict_len
, &pad_len
);
444 /* survive when the log buffer is too small for trunc_msg */
445 if (log_make_free_space(size
))
449 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
451 * This message + an additional empty header does not fit
452 * at the end of the buffer. Add an empty header with len == 0
453 * to signify a wrap around.
455 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
460 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
461 memcpy(log_text(msg
), text
, text_len
);
462 msg
->text_len
= text_len
;
464 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
465 msg
->text_len
+= trunc_msg_len
;
467 memcpy(log_dict(msg
), dict
, dict_len
);
468 msg
->dict_len
= dict_len
;
469 msg
->facility
= facility
;
470 msg
->level
= level
& 7;
471 msg
->flags
= flags
& 0x1f;
473 msg
->ts_nsec
= ts_nsec
;
475 msg
->ts_nsec
= local_clock();
476 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
480 log_next_idx
+= msg
->len
;
483 return msg
->text_len
;
486 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
488 static int syslog_action_restricted(int type
)
493 * Unless restricted, we allow "read all" and "get buffer size"
496 return type
!= SYSLOG_ACTION_READ_ALL
&&
497 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
500 int check_syslog_permissions(int type
, int source
)
503 * If this is from /proc/kmsg and we've already opened it, then we've
504 * already done the capabilities checks at open time.
506 if (source
== SYSLOG_FROM_PROC
&& type
!= SYSLOG_ACTION_OPEN
)
509 if (syslog_action_restricted(type
)) {
510 if (capable(CAP_SYSLOG
))
513 * For historical reasons, accept CAP_SYS_ADMIN too, with
516 if (capable(CAP_SYS_ADMIN
)) {
517 pr_warn_once("%s (%d): Attempt to access syslog with "
518 "CAP_SYS_ADMIN but no CAP_SYSLOG "
520 current
->comm
, task_pid_nr(current
));
526 return security_syslog(type
);
528 EXPORT_SYMBOL_GPL(check_syslog_permissions
);
530 static void append_char(char **pp
, char *e
, char c
)
536 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
537 struct printk_log
*msg
, u64 seq
,
538 enum log_flags prev_flags
)
540 u64 ts_usec
= msg
->ts_nsec
;
543 do_div(ts_usec
, 1000);
546 * If we couldn't merge continuation line fragments during the print,
547 * export the stored flags to allow an optional external merge of the
548 * records. Merging the records isn't always neccessarily correct, like
549 * when we hit a race during printing. In most cases though, it produces
550 * better readable output. 'c' in the record flags mark the first
551 * fragment of a line, '+' the following.
553 if (msg
->flags
& LOG_CONT
&& !(prev_flags
& LOG_CONT
))
555 else if ((msg
->flags
& LOG_CONT
) ||
556 ((prev_flags
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
)))
559 return scnprintf(buf
, size
, "%u,%llu,%llu,%c;",
560 (msg
->facility
<< 3) | msg
->level
, seq
, ts_usec
, cont
);
563 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
564 char *dict
, size_t dict_len
,
565 char *text
, size_t text_len
)
567 char *p
= buf
, *e
= buf
+ size
;
570 /* escape non-printable characters */
571 for (i
= 0; i
< text_len
; i
++) {
572 unsigned char c
= text
[i
];
574 if (c
< ' ' || c
>= 127 || c
== '\\')
575 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
577 append_char(&p
, e
, c
);
579 append_char(&p
, e
, '\n');
584 for (i
= 0; i
< dict_len
; i
++) {
585 unsigned char c
= dict
[i
];
588 append_char(&p
, e
, ' ');
593 append_char(&p
, e
, '\n');
598 if (c
< ' ' || c
>= 127 || c
== '\\') {
599 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
603 append_char(&p
, e
, c
);
605 append_char(&p
, e
, '\n');
611 /* /dev/kmsg - userspace message inject/listen interface */
612 struct devkmsg_user
{
617 char buf
[CONSOLE_EXT_LOG_MAX
];
620 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
623 int level
= default_message_loglevel
;
624 int facility
= 1; /* LOG_USER */
625 size_t len
= iov_iter_count(from
);
628 if (len
> LOG_LINE_MAX
)
630 buf
= kmalloc(len
+1, GFP_KERNEL
);
635 if (copy_from_iter(buf
, len
, from
) != len
) {
641 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
642 * the decimal value represents 32bit, the lower 3 bit are the log
643 * level, the rest are the log facility.
645 * If no prefix or no userspace facility is specified, we
646 * enforce LOG_USER, to be able to reliably distinguish
647 * kernel-generated messages from userspace-injected ones.
650 if (line
[0] == '<') {
654 u
= simple_strtoul(line
+ 1, &endp
, 10);
655 if (endp
&& endp
[0] == '>') {
656 level
= LOG_LEVEL(u
);
657 if (LOG_FACILITY(u
) != 0)
658 facility
= LOG_FACILITY(u
);
665 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
670 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
671 size_t count
, loff_t
*ppos
)
673 struct devkmsg_user
*user
= file
->private_data
;
674 struct printk_log
*msg
;
681 ret
= mutex_lock_interruptible(&user
->lock
);
684 raw_spin_lock_irq(&logbuf_lock
);
685 while (user
->seq
== log_next_seq
) {
686 if (file
->f_flags
& O_NONBLOCK
) {
688 raw_spin_unlock_irq(&logbuf_lock
);
692 raw_spin_unlock_irq(&logbuf_lock
);
693 ret
= wait_event_interruptible(log_wait
,
694 user
->seq
!= log_next_seq
);
697 raw_spin_lock_irq(&logbuf_lock
);
700 if (user
->seq
< log_first_seq
) {
701 /* our last seen message is gone, return error and reset */
702 user
->idx
= log_first_idx
;
703 user
->seq
= log_first_seq
;
705 raw_spin_unlock_irq(&logbuf_lock
);
709 msg
= log_from_idx(user
->idx
);
710 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
711 msg
, user
->seq
, user
->prev
);
712 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
713 log_dict(msg
), msg
->dict_len
,
714 log_text(msg
), msg
->text_len
);
716 user
->prev
= msg
->flags
;
717 user
->idx
= log_next(user
->idx
);
719 raw_spin_unlock_irq(&logbuf_lock
);
726 if (copy_to_user(buf
, user
->buf
, len
)) {
732 mutex_unlock(&user
->lock
);
736 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
738 struct devkmsg_user
*user
= file
->private_data
;
746 raw_spin_lock_irq(&logbuf_lock
);
749 /* the first record */
750 user
->idx
= log_first_idx
;
751 user
->seq
= log_first_seq
;
755 * The first record after the last SYSLOG_ACTION_CLEAR,
756 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
757 * changes no global state, and does not clear anything.
759 user
->idx
= clear_idx
;
760 user
->seq
= clear_seq
;
763 /* after the last record */
764 user
->idx
= log_next_idx
;
765 user
->seq
= log_next_seq
;
770 raw_spin_unlock_irq(&logbuf_lock
);
774 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
776 struct devkmsg_user
*user
= file
->private_data
;
780 return POLLERR
|POLLNVAL
;
782 poll_wait(file
, &log_wait
, wait
);
784 raw_spin_lock_irq(&logbuf_lock
);
785 if (user
->seq
< log_next_seq
) {
786 /* return error when data has vanished underneath us */
787 if (user
->seq
< log_first_seq
)
788 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
790 ret
= POLLIN
|POLLRDNORM
;
792 raw_spin_unlock_irq(&logbuf_lock
);
797 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
799 struct devkmsg_user
*user
;
802 /* write-only does not need any file context */
803 if ((file
->f_flags
& O_ACCMODE
) == O_WRONLY
)
806 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
811 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
815 mutex_init(&user
->lock
);
817 raw_spin_lock_irq(&logbuf_lock
);
818 user
->idx
= log_first_idx
;
819 user
->seq
= log_first_seq
;
820 raw_spin_unlock_irq(&logbuf_lock
);
822 file
->private_data
= user
;
826 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
828 struct devkmsg_user
*user
= file
->private_data
;
833 mutex_destroy(&user
->lock
);
838 const struct file_operations kmsg_fops
= {
839 .open
= devkmsg_open
,
840 .read
= devkmsg_read
,
841 .write_iter
= devkmsg_write
,
842 .llseek
= devkmsg_llseek
,
843 .poll
= devkmsg_poll
,
844 .release
= devkmsg_release
,
847 #ifdef CONFIG_KEXEC_CORE
849 * This appends the listed symbols to /proc/vmcore
851 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
852 * obtain access to symbols that are otherwise very difficult to locate. These
853 * symbols are specifically used so that utilities can access and extract the
854 * dmesg log from a vmcore file after a crash.
856 void log_buf_kexec_setup(void)
858 VMCOREINFO_SYMBOL(log_buf
);
859 VMCOREINFO_SYMBOL(log_buf_len
);
860 VMCOREINFO_SYMBOL(log_first_idx
);
861 VMCOREINFO_SYMBOL(clear_idx
);
862 VMCOREINFO_SYMBOL(log_next_idx
);
864 * Export struct printk_log size and field offsets. User space tools can
865 * parse it and detect any changes to structure down the line.
867 VMCOREINFO_STRUCT_SIZE(printk_log
);
868 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
869 VMCOREINFO_OFFSET(printk_log
, len
);
870 VMCOREINFO_OFFSET(printk_log
, text_len
);
871 VMCOREINFO_OFFSET(printk_log
, dict_len
);
875 /* requested log_buf_len from kernel cmdline */
876 static unsigned long __initdata new_log_buf_len
;
878 /* we practice scaling the ring buffer by powers of 2 */
879 static void __init
log_buf_len_update(unsigned size
)
882 size
= roundup_pow_of_two(size
);
883 if (size
> log_buf_len
)
884 new_log_buf_len
= size
;
887 /* save requested log_buf_len since it's too early to process it */
888 static int __init
log_buf_len_setup(char *str
)
890 unsigned size
= memparse(str
, &str
);
892 log_buf_len_update(size
);
896 early_param("log_buf_len", log_buf_len_setup
);
899 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
901 static void __init
log_buf_add_cpu(void)
903 unsigned int cpu_extra
;
906 * archs should set up cpu_possible_bits properly with
907 * set_cpu_possible() after setup_arch() but just in
908 * case lets ensure this is valid.
910 if (num_possible_cpus() == 1)
913 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
915 /* by default this will only continue through for large > 64 CPUs */
916 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
919 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
920 __LOG_CPU_MAX_BUF_LEN
);
921 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
923 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
925 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
927 #else /* !CONFIG_SMP */
928 static inline void log_buf_add_cpu(void) {}
929 #endif /* CONFIG_SMP */
931 void __init
setup_log_buf(int early
)
937 if (log_buf
!= __log_buf
)
940 if (!early
&& !new_log_buf_len
)
943 if (!new_log_buf_len
)
948 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
950 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
954 if (unlikely(!new_log_buf
)) {
955 pr_err("log_buf_len: %ld bytes not available\n",
960 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
961 log_buf_len
= new_log_buf_len
;
962 log_buf
= new_log_buf
;
964 free
= __LOG_BUF_LEN
- log_next_idx
;
965 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
966 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
968 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
969 pr_info("early log buf free: %d(%d%%)\n",
970 free
, (free
* 100) / __LOG_BUF_LEN
);
973 static bool __read_mostly ignore_loglevel
;
975 static int __init
ignore_loglevel_setup(char *str
)
977 ignore_loglevel
= true;
978 pr_info("debug: ignoring loglevel setting.\n");
983 early_param("ignore_loglevel", ignore_loglevel_setup
);
984 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
985 MODULE_PARM_DESC(ignore_loglevel
,
986 "ignore loglevel setting (prints all kernel messages to the console)");
988 static bool suppress_message_printing(int level
)
990 return (level
>= console_loglevel
&& !ignore_loglevel
);
993 #ifdef CONFIG_BOOT_PRINTK_DELAY
995 static int boot_delay
; /* msecs delay after each printk during bootup */
996 static unsigned long long loops_per_msec
; /* based on boot_delay */
998 static int __init
boot_delay_setup(char *str
)
1002 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
1003 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
1005 get_option(&str
, &boot_delay
);
1006 if (boot_delay
> 10 * 1000)
1009 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1010 "HZ: %d, loops_per_msec: %llu\n",
1011 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
1014 early_param("boot_delay", boot_delay_setup
);
1016 static void boot_delay_msec(int level
)
1018 unsigned long long k
;
1019 unsigned long timeout
;
1021 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
1022 || suppress_message_printing(level
)) {
1026 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1028 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1033 * use (volatile) jiffies to prevent
1034 * compiler reduction; loop termination via jiffies
1035 * is secondary and may or may not happen.
1037 if (time_after(jiffies
, timeout
))
1039 touch_nmi_watchdog();
1043 static inline void boot_delay_msec(int level
)
1048 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1049 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1051 static size_t print_time(u64 ts
, char *buf
)
1053 unsigned long rem_nsec
;
1058 rem_nsec
= do_div(ts
, 1000000000);
1061 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1063 return sprintf(buf
, "[%5lu.%06lu] ",
1064 (unsigned long)ts
, rem_nsec
/ 1000);
1067 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1070 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1074 len
+= sprintf(buf
, "<%u>", prefix
);
1079 else if (prefix
> 99)
1081 else if (prefix
> 9)
1086 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1090 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1091 bool syslog
, char *buf
, size_t size
)
1093 const char *text
= log_text(msg
);
1094 size_t text_size
= msg
->text_len
;
1096 bool newline
= true;
1099 if ((prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
))
1102 if (msg
->flags
& LOG_CONT
) {
1103 if ((prev
& LOG_CONT
) && !(prev
& LOG_NEWLINE
))
1106 if (!(msg
->flags
& LOG_NEWLINE
))
1111 const char *next
= memchr(text
, '\n', text_size
);
1115 text_len
= next
- text
;
1117 text_size
-= next
- text
;
1119 text_len
= text_size
;
1123 if (print_prefix(msg
, syslog
, NULL
) +
1124 text_len
+ 1 >= size
- len
)
1128 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1129 memcpy(buf
+ len
, text
, text_len
);
1131 if (next
|| newline
)
1134 /* SYSLOG_ACTION_* buffer size only calculation */
1136 len
+= print_prefix(msg
, syslog
, NULL
);
1138 if (next
|| newline
)
1149 static int syslog_print(char __user
*buf
, int size
)
1152 struct printk_log
*msg
;
1155 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1163 raw_spin_lock_irq(&logbuf_lock
);
1164 if (syslog_seq
< log_first_seq
) {
1165 /* messages are gone, move to first one */
1166 syslog_seq
= log_first_seq
;
1167 syslog_idx
= log_first_idx
;
1171 if (syslog_seq
== log_next_seq
) {
1172 raw_spin_unlock_irq(&logbuf_lock
);
1176 skip
= syslog_partial
;
1177 msg
= log_from_idx(syslog_idx
);
1178 n
= msg_print_text(msg
, syslog_prev
, true, text
,
1179 LOG_LINE_MAX
+ PREFIX_MAX
);
1180 if (n
- syslog_partial
<= size
) {
1181 /* message fits into buffer, move forward */
1182 syslog_idx
= log_next(syslog_idx
);
1184 syslog_prev
= msg
->flags
;
1185 n
-= syslog_partial
;
1188 /* partial read(), remember position */
1190 syslog_partial
+= n
;
1193 raw_spin_unlock_irq(&logbuf_lock
);
1198 if (copy_to_user(buf
, text
+ skip
, n
)) {
1213 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1218 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1222 raw_spin_lock_irq(&logbuf_lock
);
1227 enum log_flags prev
;
1230 * Find first record that fits, including all following records,
1231 * into the user-provided buffer for this dump.
1236 while (seq
< log_next_seq
) {
1237 struct printk_log
*msg
= log_from_idx(idx
);
1239 len
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1241 idx
= log_next(idx
);
1245 /* move first record forward until length fits into the buffer */
1249 while (len
> size
&& seq
< log_next_seq
) {
1250 struct printk_log
*msg
= log_from_idx(idx
);
1252 len
-= msg_print_text(msg
, prev
, true, NULL
, 0);
1254 idx
= log_next(idx
);
1258 /* last message fitting into this dump */
1259 next_seq
= log_next_seq
;
1262 while (len
>= 0 && seq
< next_seq
) {
1263 struct printk_log
*msg
= log_from_idx(idx
);
1266 textlen
= msg_print_text(msg
, prev
, true, text
,
1267 LOG_LINE_MAX
+ PREFIX_MAX
);
1272 idx
= log_next(idx
);
1276 raw_spin_unlock_irq(&logbuf_lock
);
1277 if (copy_to_user(buf
+ len
, text
, textlen
))
1281 raw_spin_lock_irq(&logbuf_lock
);
1283 if (seq
< log_first_seq
) {
1284 /* messages are gone, move to next one */
1285 seq
= log_first_seq
;
1286 idx
= log_first_idx
;
1293 clear_seq
= log_next_seq
;
1294 clear_idx
= log_next_idx
;
1296 raw_spin_unlock_irq(&logbuf_lock
);
1302 int do_syslog(int type
, char __user
*buf
, int len
, int source
)
1305 static int saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1308 error
= check_syslog_permissions(type
, source
);
1313 case SYSLOG_ACTION_CLOSE
: /* Close log */
1315 case SYSLOG_ACTION_OPEN
: /* Open log */
1317 case SYSLOG_ACTION_READ
: /* Read from log */
1319 if (!buf
|| len
< 0)
1324 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1328 error
= wait_event_interruptible(log_wait
,
1329 syslog_seq
!= log_next_seq
);
1332 error
= syslog_print(buf
, len
);
1334 /* Read/clear last kernel messages */
1335 case SYSLOG_ACTION_READ_CLEAR
:
1338 /* Read last kernel messages */
1339 case SYSLOG_ACTION_READ_ALL
:
1341 if (!buf
|| len
< 0)
1346 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1350 error
= syslog_print_all(buf
, len
, clear
);
1352 /* Clear ring buffer */
1353 case SYSLOG_ACTION_CLEAR
:
1354 syslog_print_all(NULL
, 0, true);
1356 /* Disable logging to console */
1357 case SYSLOG_ACTION_CONSOLE_OFF
:
1358 if (saved_console_loglevel
== LOGLEVEL_DEFAULT
)
1359 saved_console_loglevel
= console_loglevel
;
1360 console_loglevel
= minimum_console_loglevel
;
1362 /* Enable logging to console */
1363 case SYSLOG_ACTION_CONSOLE_ON
:
1364 if (saved_console_loglevel
!= LOGLEVEL_DEFAULT
) {
1365 console_loglevel
= saved_console_loglevel
;
1366 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1369 /* Set level of messages printed to console */
1370 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1372 if (len
< 1 || len
> 8)
1374 if (len
< minimum_console_loglevel
)
1375 len
= minimum_console_loglevel
;
1376 console_loglevel
= len
;
1377 /* Implicitly re-enable logging to console */
1378 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1381 /* Number of chars in the log buffer */
1382 case SYSLOG_ACTION_SIZE_UNREAD
:
1383 raw_spin_lock_irq(&logbuf_lock
);
1384 if (syslog_seq
< log_first_seq
) {
1385 /* messages are gone, move to first one */
1386 syslog_seq
= log_first_seq
;
1387 syslog_idx
= log_first_idx
;
1391 if (source
== SYSLOG_FROM_PROC
) {
1393 * Short-cut for poll(/"proc/kmsg") which simply checks
1394 * for pending data, not the size; return the count of
1395 * records, not the length.
1397 error
= log_next_seq
- syslog_seq
;
1399 u64 seq
= syslog_seq
;
1400 u32 idx
= syslog_idx
;
1401 enum log_flags prev
= syslog_prev
;
1404 while (seq
< log_next_seq
) {
1405 struct printk_log
*msg
= log_from_idx(idx
);
1407 error
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1408 idx
= log_next(idx
);
1412 error
-= syslog_partial
;
1414 raw_spin_unlock_irq(&logbuf_lock
);
1416 /* Size of the log buffer */
1417 case SYSLOG_ACTION_SIZE_BUFFER
:
1418 error
= log_buf_len
;
1428 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1430 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1434 * Call the console drivers, asking them to write out
1435 * log_buf[start] to log_buf[end - 1].
1436 * The console_lock must be held.
1438 static void call_console_drivers(int level
,
1439 const char *ext_text
, size_t ext_len
,
1440 const char *text
, size_t len
)
1442 struct console
*con
;
1444 trace_console(text
, len
);
1446 if (!console_drivers
)
1449 for_each_console(con
) {
1450 if (exclusive_console
&& con
!= exclusive_console
)
1452 if (!(con
->flags
& CON_ENABLED
))
1456 if (!cpu_online(smp_processor_id()) &&
1457 !(con
->flags
& CON_ANYTIME
))
1459 if (con
->flags
& CON_EXTENDED
)
1460 con
->write(con
, ext_text
, ext_len
);
1462 con
->write(con
, text
, len
);
1467 * Zap console related locks when oopsing.
1468 * To leave time for slow consoles to print a full oops,
1469 * only zap at most once every 30 seconds.
1471 static void zap_locks(void)
1473 static unsigned long oops_timestamp
;
1475 if (time_after_eq(jiffies
, oops_timestamp
) &&
1476 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1479 oops_timestamp
= jiffies
;
1482 /* If a crash is occurring, make sure we can't deadlock */
1483 raw_spin_lock_init(&logbuf_lock
);
1484 /* And make sure that we print immediately */
1485 sema_init(&console_sem
, 1);
1488 int printk_delay_msec __read_mostly
;
1490 static inline void printk_delay(void)
1492 if (unlikely(printk_delay_msec
)) {
1493 int m
= printk_delay_msec
;
1497 touch_nmi_watchdog();
1503 * Continuation lines are buffered, and not committed to the record buffer
1504 * until the line is complete, or a race forces it. The line fragments
1505 * though, are printed immediately to the consoles to ensure everything has
1506 * reached the console in case of a kernel crash.
1508 static struct cont
{
1509 char buf
[LOG_LINE_MAX
];
1510 size_t len
; /* length == 0 means unused buffer */
1511 size_t cons
; /* bytes written to console */
1512 struct task_struct
*owner
; /* task of first print*/
1513 u64 ts_nsec
; /* time of first print */
1514 u8 level
; /* log level of first message */
1515 u8 facility
; /* log facility of first message */
1516 enum log_flags flags
; /* prefix, newline flags */
1517 bool flushed
:1; /* buffer sealed and committed */
1520 static void cont_flush(enum log_flags flags
)
1529 * If a fragment of this line was directly flushed to the
1530 * console; wait for the console to pick up the rest of the
1531 * line. LOG_NOCONS suppresses a duplicated output.
1533 log_store(cont
.facility
, cont
.level
, flags
| LOG_NOCONS
,
1534 cont
.ts_nsec
, NULL
, 0, cont
.buf
, cont
.len
);
1536 cont
.flushed
= true;
1539 * If no fragment of this line ever reached the console,
1540 * just submit it to the store and free the buffer.
1542 log_store(cont
.facility
, cont
.level
, flags
, 0,
1543 NULL
, 0, cont
.buf
, cont
.len
);
1548 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1550 if (cont
.len
&& cont
.flushed
)
1554 * If ext consoles are present, flush and skip in-kernel
1555 * continuation. See nr_ext_console_drivers definition. Also, if
1556 * the line gets too long, split it up in separate records.
1558 if (nr_ext_console_drivers
|| cont
.len
+ len
> sizeof(cont
.buf
)) {
1559 cont_flush(LOG_CONT
);
1564 cont
.facility
= facility
;
1566 cont
.owner
= current
;
1567 cont
.ts_nsec
= local_clock();
1570 cont
.flushed
= false;
1573 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1576 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1577 cont_flush(LOG_CONT
);
1582 static size_t cont_print_text(char *text
, size_t size
)
1587 if (cont
.cons
== 0 && (console_prev
& LOG_NEWLINE
)) {
1588 textlen
+= print_time(cont
.ts_nsec
, text
);
1592 len
= cont
.len
- cont
.cons
;
1596 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1598 cont
.cons
= cont
.len
;
1602 if (cont
.flags
& LOG_NEWLINE
)
1603 text
[textlen
++] = '\n';
1604 /* got everything, release buffer */
1610 asmlinkage
int vprintk_emit(int facility
, int level
,
1611 const char *dict
, size_t dictlen
,
1612 const char *fmt
, va_list args
)
1614 static bool recursion_bug
;
1615 static char textbuf
[LOG_LINE_MAX
];
1616 char *text
= textbuf
;
1617 size_t text_len
= 0;
1618 enum log_flags lflags
= 0;
1619 unsigned long flags
;
1621 int printed_len
= 0;
1622 int nmi_message_lost
;
1623 bool in_sched
= false;
1624 /* cpu currently holding logbuf_lock in this function */
1625 static unsigned int logbuf_cpu
= UINT_MAX
;
1627 if (level
== LOGLEVEL_SCHED
) {
1628 level
= LOGLEVEL_DEFAULT
;
1632 boot_delay_msec(level
);
1635 local_irq_save(flags
);
1636 this_cpu
= smp_processor_id();
1639 * Ouch, printk recursed into itself!
1641 if (unlikely(logbuf_cpu
== this_cpu
)) {
1643 * If a crash is occurring during printk() on this CPU,
1644 * then try to get the crash message out but make sure
1645 * we can't deadlock. Otherwise just return to avoid the
1646 * recursion and return - but flag the recursion so that
1647 * it can be printed at the next appropriate moment:
1649 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1650 recursion_bug
= true;
1651 local_irq_restore(flags
);
1658 /* This stops the holder of console_sem just where we want him */
1659 raw_spin_lock(&logbuf_lock
);
1660 logbuf_cpu
= this_cpu
;
1662 if (unlikely(recursion_bug
)) {
1663 static const char recursion_msg
[] =
1664 "BUG: recent printk recursion!";
1666 recursion_bug
= false;
1667 /* emit KERN_CRIT message */
1668 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1669 NULL
, 0, recursion_msg
,
1670 strlen(recursion_msg
));
1673 nmi_message_lost
= get_nmi_message_lost();
1674 if (unlikely(nmi_message_lost
)) {
1675 text_len
= scnprintf(textbuf
, sizeof(textbuf
),
1676 "BAD LUCK: lost %d message(s) from NMI context!",
1678 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1679 NULL
, 0, textbuf
, text_len
);
1683 * The printf needs to come first; we need the syslog
1684 * prefix which might be passed-in as a parameter.
1686 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1688 /* mark and strip a trailing newline */
1689 if (text_len
&& text
[text_len
-1] == '\n') {
1691 lflags
|= LOG_NEWLINE
;
1694 /* strip kernel syslog prefix and extract log level or control flags */
1695 if (facility
== 0) {
1696 int kern_level
= printk_get_level(text
);
1699 const char *end_of_header
= printk_skip_level(text
);
1700 switch (kern_level
) {
1702 if (level
== LOGLEVEL_DEFAULT
)
1703 level
= kern_level
- '0';
1705 case 'd': /* KERN_DEFAULT */
1706 lflags
|= LOG_PREFIX
;
1709 * No need to check length here because vscnprintf
1710 * put '\0' at the end of the string. Only valid and
1711 * newly printed level is detected.
1713 text_len
-= end_of_header
- text
;
1714 text
= (char *)end_of_header
;
1718 if (level
== LOGLEVEL_DEFAULT
)
1719 level
= default_message_loglevel
;
1722 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1724 if (!(lflags
& LOG_NEWLINE
)) {
1726 * Flush the conflicting buffer. An earlier newline was missing,
1727 * or another task also prints continuation lines.
1729 if (cont
.len
&& (lflags
& LOG_PREFIX
|| cont
.owner
!= current
))
1730 cont_flush(LOG_NEWLINE
);
1732 /* buffer line if possible, otherwise store it right away */
1733 if (cont_add(facility
, level
, text
, text_len
))
1734 printed_len
+= text_len
;
1736 printed_len
+= log_store(facility
, level
,
1737 lflags
| LOG_CONT
, 0,
1738 dict
, dictlen
, text
, text_len
);
1740 bool stored
= false;
1743 * If an earlier newline was missing and it was the same task,
1744 * either merge it with the current buffer and flush, or if
1745 * there was a race with interrupts (prefix == true) then just
1746 * flush it out and store this line separately.
1747 * If the preceding printk was from a different task and missed
1748 * a newline, flush and append the newline.
1751 if (cont
.owner
== current
&& !(lflags
& LOG_PREFIX
))
1752 stored
= cont_add(facility
, level
, text
,
1754 cont_flush(LOG_NEWLINE
);
1758 printed_len
+= text_len
;
1760 printed_len
+= log_store(facility
, level
, lflags
, 0,
1761 dict
, dictlen
, text
, text_len
);
1764 logbuf_cpu
= UINT_MAX
;
1765 raw_spin_unlock(&logbuf_lock
);
1767 local_irq_restore(flags
);
1769 /* If called from the scheduler, we can not call up(). */
1773 * Try to acquire and then immediately release the console
1774 * semaphore. The release will print out buffers and wake up
1775 * /dev/kmsg and syslog() users.
1777 if (console_trylock())
1784 EXPORT_SYMBOL(vprintk_emit
);
1786 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1788 return vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1790 EXPORT_SYMBOL(vprintk
);
1792 asmlinkage
int printk_emit(int facility
, int level
,
1793 const char *dict
, size_t dictlen
,
1794 const char *fmt
, ...)
1799 va_start(args
, fmt
);
1800 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1805 EXPORT_SYMBOL(printk_emit
);
1807 #ifdef CONFIG_PRINTK
1808 #define define_pr_level(func, loglevel) \
1809 asmlinkage __visible void func(const char *fmt, ...) \
1813 va_start(args, fmt); \
1814 vprintk_default(loglevel, fmt, args); \
1819 define_pr_level(__pr_emerg
, LOGLEVEL_EMERG
);
1820 define_pr_level(__pr_alert
, LOGLEVEL_ALERT
);
1821 define_pr_level(__pr_crit
, LOGLEVEL_CRIT
);
1822 define_pr_level(__pr_err
, LOGLEVEL_ERR
);
1823 define_pr_level(__pr_warn
, LOGLEVEL_WARNING
);
1824 define_pr_level(__pr_notice
, LOGLEVEL_NOTICE
);
1825 define_pr_level(__pr_info
, LOGLEVEL_INFO
);
1828 int vprintk_default(int level
, const char *fmt
, va_list args
)
1832 #ifdef CONFIG_KGDB_KDB
1833 if (unlikely(kdb_trap_printk
)) {
1834 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1838 r
= vprintk_emit(0, level
, NULL
, 0, fmt
, args
);
1842 EXPORT_SYMBOL_GPL(vprintk_default
);
1845 * printk - print a kernel message
1846 * @fmt: format string
1848 * This is printk(). It can be called from any context. We want it to work.
1850 * We try to grab the console_lock. If we succeed, it's easy - we log the
1851 * output and call the console drivers. If we fail to get the semaphore, we
1852 * place the output into the log buffer and return. The current holder of
1853 * the console_sem will notice the new output in console_unlock(); and will
1854 * send it to the consoles before releasing the lock.
1856 * One effect of this deferred printing is that code which calls printk() and
1857 * then changes console_loglevel may break. This is because console_loglevel
1858 * is inspected when the actual printing occurs.
1863 * See the vsnprintf() documentation for format string extensions over C99.
1865 asmlinkage __visible
int printk(const char *fmt
, ...)
1870 va_start(args
, fmt
);
1871 r
= vprintk_func(LOGLEVEL_DEFAULT
, fmt
, args
);
1876 EXPORT_SYMBOL(printk
);
1878 #else /* CONFIG_PRINTK */
1880 #define LOG_LINE_MAX 0
1881 #define PREFIX_MAX 0
1883 static u64 syslog_seq
;
1884 static u32 syslog_idx
;
1885 static u64 console_seq
;
1886 static u32 console_idx
;
1887 static enum log_flags syslog_prev
;
1888 static u64 log_first_seq
;
1889 static u32 log_first_idx
;
1890 static u64 log_next_seq
;
1891 static enum log_flags console_prev
;
1892 static struct cont
{
1898 static char *log_text(const struct printk_log
*msg
) { return NULL
; }
1899 static char *log_dict(const struct printk_log
*msg
) { return NULL
; }
1900 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
1901 static u32
log_next(u32 idx
) { return 0; }
1902 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
1903 struct printk_log
*msg
, u64 seq
,
1904 enum log_flags prev_flags
) { return 0; }
1905 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
1906 char *dict
, size_t dict_len
,
1907 char *text
, size_t text_len
) { return 0; }
1908 static void call_console_drivers(int level
,
1909 const char *ext_text
, size_t ext_len
,
1910 const char *text
, size_t len
) {}
1911 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1912 bool syslog
, char *buf
, size_t size
) { return 0; }
1913 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
1914 static bool suppress_message_printing(int level
) { return false; }
1916 /* Still needs to be defined for users */
1917 DEFINE_PER_CPU(printk_func_t
, printk_func
);
1919 #endif /* CONFIG_PRINTK */
1921 #ifdef CONFIG_EARLY_PRINTK
1922 struct console
*early_console
;
1924 asmlinkage __visible
void early_printk(const char *fmt
, ...)
1934 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
1937 early_console
->write(early_console
, buf
, n
);
1941 static int __add_preferred_console(char *name
, int idx
, char *options
,
1944 struct console_cmdline
*c
;
1948 * See if this tty is not yet registered, and
1949 * if we have a slot free.
1951 for (i
= 0, c
= console_cmdline
;
1952 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
1954 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
1956 selected_console
= i
;
1960 if (i
== MAX_CMDLINECONSOLES
)
1963 selected_console
= i
;
1964 strlcpy(c
->name
, name
, sizeof(c
->name
));
1965 c
->options
= options
;
1966 braille_set_options(c
, brl_options
);
1972 * Set up a console. Called via do_early_param() in init/main.c
1973 * for each "console=" parameter in the boot command line.
1975 static int __init
console_setup(char *str
)
1977 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
1978 char *s
, *options
, *brl_options
= NULL
;
1981 if (_braille_console_setup(&str
, &brl_options
))
1985 * Decode str into name, index, options.
1987 if (str
[0] >= '0' && str
[0] <= '9') {
1988 strcpy(buf
, "ttyS");
1989 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1991 strncpy(buf
, str
, sizeof(buf
) - 1);
1993 buf
[sizeof(buf
) - 1] = 0;
1994 options
= strchr(str
, ',');
1998 if (!strcmp(str
, "ttya"))
1999 strcpy(buf
, "ttyS0");
2000 if (!strcmp(str
, "ttyb"))
2001 strcpy(buf
, "ttyS1");
2003 for (s
= buf
; *s
; s
++)
2004 if (isdigit(*s
) || *s
== ',')
2006 idx
= simple_strtoul(s
, NULL
, 10);
2009 __add_preferred_console(buf
, idx
, options
, brl_options
);
2010 console_set_on_cmdline
= 1;
2013 __setup("console=", console_setup
);
2016 * add_preferred_console - add a device to the list of preferred consoles.
2017 * @name: device name
2018 * @idx: device index
2019 * @options: options for this console
2021 * The last preferred console added will be used for kernel messages
2022 * and stdin/out/err for init. Normally this is used by console_setup
2023 * above to handle user-supplied console arguments; however it can also
2024 * be used by arch-specific code either to override the user or more
2025 * commonly to provide a default console (ie from PROM variables) when
2026 * the user has not supplied one.
2028 int add_preferred_console(char *name
, int idx
, char *options
)
2030 return __add_preferred_console(name
, idx
, options
, NULL
);
2033 bool console_suspend_enabled
= true;
2034 EXPORT_SYMBOL(console_suspend_enabled
);
2036 static int __init
console_suspend_disable(char *str
)
2038 console_suspend_enabled
= false;
2041 __setup("no_console_suspend", console_suspend_disable
);
2042 module_param_named(console_suspend
, console_suspend_enabled
,
2043 bool, S_IRUGO
| S_IWUSR
);
2044 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2045 " and hibernate operations");
2048 * suspend_console - suspend the console subsystem
2050 * This disables printk() while we go into suspend states
2052 void suspend_console(void)
2054 if (!console_suspend_enabled
)
2056 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2058 console_suspended
= 1;
2062 void resume_console(void)
2064 if (!console_suspend_enabled
)
2067 console_suspended
= 0;
2072 * console_cpu_notify - print deferred console messages after CPU hotplug
2073 * @self: notifier struct
2074 * @action: CPU hotplug event
2077 * If printk() is called from a CPU that is not online yet, the messages
2078 * will be spooled but will not show up on the console. This function is
2079 * called when a new CPU comes online (or fails to come up), and ensures
2080 * that any such output gets printed.
2082 static int console_cpu_notify(struct notifier_block
*self
,
2083 unsigned long action
, void *hcpu
)
2088 case CPU_DOWN_FAILED
:
2089 case CPU_UP_CANCELED
:
2097 * console_lock - lock the console system for exclusive use.
2099 * Acquires a lock which guarantees that the caller has
2100 * exclusive access to the console system and the console_drivers list.
2102 * Can sleep, returns nothing.
2104 void console_lock(void)
2109 if (console_suspended
)
2112 console_may_schedule
= 1;
2114 EXPORT_SYMBOL(console_lock
);
2117 * console_trylock - try to lock the console system for exclusive use.
2119 * Try to acquire a lock which guarantees that the caller has exclusive
2120 * access to the console system and the console_drivers list.
2122 * returns 1 on success, and 0 on failure to acquire the lock.
2124 int console_trylock(void)
2126 if (down_trylock_console_sem())
2128 if (console_suspended
) {
2134 * When PREEMPT_COUNT disabled we can't reliably detect if it's
2135 * safe to schedule (e.g. calling printk while holding a spin_lock),
2136 * because preempt_disable()/preempt_enable() are just barriers there
2137 * and preempt_count() is always 0.
2139 * RCU read sections have a separate preemption counter when
2140 * PREEMPT_RCU enabled thus we must take extra care and check
2141 * rcu_preempt_depth(), otherwise RCU read sections modify
2144 console_may_schedule
= !oops_in_progress
&&
2146 !rcu_preempt_depth();
2149 EXPORT_SYMBOL(console_trylock
);
2151 int is_console_locked(void)
2153 return console_locked
;
2157 * Check if we have any console that is capable of printing while cpu is
2158 * booting or shutting down. Requires console_sem.
2160 static int have_callable_console(void)
2162 struct console
*con
;
2164 for_each_console(con
)
2165 if ((con
->flags
& CON_ENABLED
) &&
2166 (con
->flags
& CON_ANYTIME
))
2173 * Can we actually use the console at this time on this cpu?
2175 * Console drivers may assume that per-cpu resources have been allocated. So
2176 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2177 * call them until this CPU is officially up.
2179 static inline int can_use_console(void)
2181 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2184 static void console_cont_flush(char *text
, size_t size
)
2186 unsigned long flags
;
2189 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2194 if (suppress_message_printing(cont
.level
)) {
2195 cont
.cons
= cont
.len
;
2202 * We still queue earlier records, likely because the console was
2203 * busy. The earlier ones need to be printed before this one, we
2204 * did not flush any fragment so far, so just let it queue up.
2206 if (console_seq
< log_next_seq
&& !cont
.cons
)
2209 len
= cont_print_text(text
, size
);
2210 raw_spin_unlock(&logbuf_lock
);
2211 stop_critical_timings();
2212 call_console_drivers(cont
.level
, NULL
, 0, text
, len
);
2213 start_critical_timings();
2214 local_irq_restore(flags
);
2217 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2221 * console_unlock - unlock the console system
2223 * Releases the console_lock which the caller holds on the console system
2224 * and the console driver list.
2226 * While the console_lock was held, console output may have been buffered
2227 * by printk(). If this is the case, console_unlock(); emits
2228 * the output prior to releasing the lock.
2230 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2232 * console_unlock(); may be called from any context.
2234 void console_unlock(void)
2236 static char ext_text
[CONSOLE_EXT_LOG_MAX
];
2237 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2238 static u64 seen_seq
;
2239 unsigned long flags
;
2240 bool wake_klogd
= false;
2241 bool do_cond_resched
, retry
;
2243 if (console_suspended
) {
2249 * Console drivers are called under logbuf_lock, so
2250 * @console_may_schedule should be cleared before; however, we may
2251 * end up dumping a lot of lines, for example, if called from
2252 * console registration path, and should invoke cond_resched()
2253 * between lines if allowable. Not doing so can cause a very long
2254 * scheduling stall on a slow console leading to RCU stall and
2255 * softlockup warnings which exacerbate the issue with more
2256 * messages practically incapacitating the system.
2258 do_cond_resched
= console_may_schedule
;
2259 console_may_schedule
= 0;
2263 * We released the console_sem lock, so we need to recheck if
2264 * cpu is online and (if not) is there at least one CON_ANYTIME
2267 if (!can_use_console()) {
2273 /* flush buffered message fragment immediately to console */
2274 console_cont_flush(text
, sizeof(text
));
2277 struct printk_log
*msg
;
2282 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2283 if (seen_seq
!= log_next_seq
) {
2285 seen_seq
= log_next_seq
;
2288 if (console_seq
< log_first_seq
) {
2289 len
= sprintf(text
, "** %u printk messages dropped ** ",
2290 (unsigned)(log_first_seq
- console_seq
));
2292 /* messages are gone, move to first one */
2293 console_seq
= log_first_seq
;
2294 console_idx
= log_first_idx
;
2300 if (console_seq
== log_next_seq
)
2303 msg
= log_from_idx(console_idx
);
2305 if ((msg
->flags
& LOG_NOCONS
) ||
2306 suppress_message_printing(level
)) {
2308 * Skip record we have buffered and already printed
2309 * directly to the console when we received it, and
2310 * record that has level above the console loglevel.
2312 console_idx
= log_next(console_idx
);
2315 * We will get here again when we register a new
2316 * CON_PRINTBUFFER console. Clear the flag so we
2317 * will properly dump everything later.
2319 msg
->flags
&= ~LOG_NOCONS
;
2320 console_prev
= msg
->flags
;
2324 len
+= msg_print_text(msg
, console_prev
, false,
2325 text
+ len
, sizeof(text
) - len
);
2326 if (nr_ext_console_drivers
) {
2327 ext_len
= msg_print_ext_header(ext_text
,
2329 msg
, console_seq
, console_prev
);
2330 ext_len
+= msg_print_ext_body(ext_text
+ ext_len
,
2331 sizeof(ext_text
) - ext_len
,
2332 log_dict(msg
), msg
->dict_len
,
2333 log_text(msg
), msg
->text_len
);
2335 console_idx
= log_next(console_idx
);
2337 console_prev
= msg
->flags
;
2338 raw_spin_unlock(&logbuf_lock
);
2340 stop_critical_timings(); /* don't trace print latency */
2341 call_console_drivers(level
, ext_text
, ext_len
, text
, len
);
2342 start_critical_timings();
2343 local_irq_restore(flags
);
2345 if (do_cond_resched
)
2350 /* Release the exclusive_console once it is used */
2351 if (unlikely(exclusive_console
))
2352 exclusive_console
= NULL
;
2354 raw_spin_unlock(&logbuf_lock
);
2359 * Someone could have filled up the buffer again, so re-check if there's
2360 * something to flush. In case we cannot trylock the console_sem again,
2361 * there's a new owner and the console_unlock() from them will do the
2362 * flush, no worries.
2364 raw_spin_lock(&logbuf_lock
);
2365 retry
= console_seq
!= log_next_seq
;
2366 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2368 if (retry
&& console_trylock())
2374 EXPORT_SYMBOL(console_unlock
);
2377 * console_conditional_schedule - yield the CPU if required
2379 * If the console code is currently allowed to sleep, and
2380 * if this CPU should yield the CPU to another task, do
2383 * Must be called within console_lock();.
2385 void __sched
console_conditional_schedule(void)
2387 if (console_may_schedule
)
2390 EXPORT_SYMBOL(console_conditional_schedule
);
2392 void console_unblank(void)
2397 * console_unblank can no longer be called in interrupt context unless
2398 * oops_in_progress is set to 1..
2400 if (oops_in_progress
) {
2401 if (down_trylock_console_sem() != 0)
2407 console_may_schedule
= 0;
2409 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2415 * console_flush_on_panic - flush console content on panic
2417 * Immediately output all pending messages no matter what.
2419 void console_flush_on_panic(void)
2422 * If someone else is holding the console lock, trylock will fail
2423 * and may_schedule may be set. Ignore and proceed to unlock so
2424 * that messages are flushed out. As this can be called from any
2425 * context and we don't want to get preempted while flushing,
2426 * ensure may_schedule is cleared.
2429 console_may_schedule
= 0;
2434 * Return the console tty driver structure and its associated index
2436 struct tty_driver
*console_device(int *index
)
2439 struct tty_driver
*driver
= NULL
;
2442 for_each_console(c
) {
2445 driver
= c
->device(c
, index
);
2454 * Prevent further output on the passed console device so that (for example)
2455 * serial drivers can disable console output before suspending a port, and can
2456 * re-enable output afterwards.
2458 void console_stop(struct console
*console
)
2461 console
->flags
&= ~CON_ENABLED
;
2464 EXPORT_SYMBOL(console_stop
);
2466 void console_start(struct console
*console
)
2469 console
->flags
|= CON_ENABLED
;
2472 EXPORT_SYMBOL(console_start
);
2474 static int __read_mostly keep_bootcon
;
2476 static int __init
keep_bootcon_setup(char *str
)
2479 pr_info("debug: skip boot console de-registration.\n");
2484 early_param("keep_bootcon", keep_bootcon_setup
);
2487 * The console driver calls this routine during kernel initialization
2488 * to register the console printing procedure with printk() and to
2489 * print any messages that were printed by the kernel before the
2490 * console driver was initialized.
2492 * This can happen pretty early during the boot process (because of
2493 * early_printk) - sometimes before setup_arch() completes - be careful
2494 * of what kernel features are used - they may not be initialised yet.
2496 * There are two types of consoles - bootconsoles (early_printk) and
2497 * "real" consoles (everything which is not a bootconsole) which are
2498 * handled differently.
2499 * - Any number of bootconsoles can be registered at any time.
2500 * - As soon as a "real" console is registered, all bootconsoles
2501 * will be unregistered automatically.
2502 * - Once a "real" console is registered, any attempt to register a
2503 * bootconsoles will be rejected
2505 void register_console(struct console
*newcon
)
2508 unsigned long flags
;
2509 struct console
*bcon
= NULL
;
2510 struct console_cmdline
*c
;
2512 if (console_drivers
)
2513 for_each_console(bcon
)
2514 if (WARN(bcon
== newcon
,
2515 "console '%s%d' already registered\n",
2516 bcon
->name
, bcon
->index
))
2520 * before we register a new CON_BOOT console, make sure we don't
2521 * already have a valid console
2523 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2524 /* find the last or real console */
2525 for_each_console(bcon
) {
2526 if (!(bcon
->flags
& CON_BOOT
)) {
2527 pr_info("Too late to register bootconsole %s%d\n",
2528 newcon
->name
, newcon
->index
);
2534 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2535 bcon
= console_drivers
;
2537 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2538 preferred_console
= selected_console
;
2541 * See if we want to use this console driver. If we
2542 * didn't select a console we take the first one
2543 * that registers here.
2545 if (preferred_console
< 0) {
2546 if (newcon
->index
< 0)
2548 if (newcon
->setup
== NULL
||
2549 newcon
->setup(newcon
, NULL
) == 0) {
2550 newcon
->flags
|= CON_ENABLED
;
2551 if (newcon
->device
) {
2552 newcon
->flags
|= CON_CONSDEV
;
2553 preferred_console
= 0;
2559 * See if this console matches one we selected on
2562 for (i
= 0, c
= console_cmdline
;
2563 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2565 if (!newcon
->match
||
2566 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2567 /* default matching */
2568 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2569 if (strcmp(c
->name
, newcon
->name
) != 0)
2571 if (newcon
->index
>= 0 &&
2572 newcon
->index
!= c
->index
)
2574 if (newcon
->index
< 0)
2575 newcon
->index
= c
->index
;
2577 if (_braille_register_console(newcon
, c
))
2580 if (newcon
->setup
&&
2581 newcon
->setup(newcon
, c
->options
) != 0)
2585 newcon
->flags
|= CON_ENABLED
;
2586 if (i
== selected_console
) {
2587 newcon
->flags
|= CON_CONSDEV
;
2588 preferred_console
= selected_console
;
2593 if (!(newcon
->flags
& CON_ENABLED
))
2597 * If we have a bootconsole, and are switching to a real console,
2598 * don't print everything out again, since when the boot console, and
2599 * the real console are the same physical device, it's annoying to
2600 * see the beginning boot messages twice
2602 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2603 newcon
->flags
&= ~CON_PRINTBUFFER
;
2606 * Put this console in the list - keep the
2607 * preferred driver at the head of the list.
2610 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2611 newcon
->next
= console_drivers
;
2612 console_drivers
= newcon
;
2614 newcon
->next
->flags
&= ~CON_CONSDEV
;
2616 newcon
->next
= console_drivers
->next
;
2617 console_drivers
->next
= newcon
;
2620 if (newcon
->flags
& CON_EXTENDED
)
2621 if (!nr_ext_console_drivers
++)
2622 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2624 if (newcon
->flags
& CON_PRINTBUFFER
) {
2626 * console_unlock(); will print out the buffered messages
2629 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2630 console_seq
= syslog_seq
;
2631 console_idx
= syslog_idx
;
2632 console_prev
= syslog_prev
;
2633 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2635 * We're about to replay the log buffer. Only do this to the
2636 * just-registered console to avoid excessive message spam to
2637 * the already-registered consoles.
2639 exclusive_console
= newcon
;
2642 console_sysfs_notify();
2645 * By unregistering the bootconsoles after we enable the real console
2646 * we get the "console xxx enabled" message on all the consoles -
2647 * boot consoles, real consoles, etc - this is to ensure that end
2648 * users know there might be something in the kernel's log buffer that
2649 * went to the bootconsole (that they do not see on the real console)
2651 pr_info("%sconsole [%s%d] enabled\n",
2652 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2653 newcon
->name
, newcon
->index
);
2655 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2657 /* We need to iterate through all boot consoles, to make
2658 * sure we print everything out, before we unregister them.
2660 for_each_console(bcon
)
2661 if (bcon
->flags
& CON_BOOT
)
2662 unregister_console(bcon
);
2665 EXPORT_SYMBOL(register_console
);
2667 int unregister_console(struct console
*console
)
2669 struct console
*a
, *b
;
2672 pr_info("%sconsole [%s%d] disabled\n",
2673 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2674 console
->name
, console
->index
);
2676 res
= _braille_unregister_console(console
);
2682 if (console_drivers
== console
) {
2683 console_drivers
=console
->next
;
2685 } else if (console_drivers
) {
2686 for (a
=console_drivers
->next
, b
=console_drivers
;
2687 a
; b
=a
, a
=b
->next
) {
2696 if (!res
&& (console
->flags
& CON_EXTENDED
))
2697 nr_ext_console_drivers
--;
2700 * If this isn't the last console and it has CON_CONSDEV set, we
2701 * need to set it on the next preferred console.
2703 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2704 console_drivers
->flags
|= CON_CONSDEV
;
2706 console
->flags
&= ~CON_ENABLED
;
2708 console_sysfs_notify();
2711 EXPORT_SYMBOL(unregister_console
);
2714 * Some boot consoles access data that is in the init section and which will
2715 * be discarded after the initcalls have been run. To make sure that no code
2716 * will access this data, unregister the boot consoles in a late initcall.
2718 * If for some reason, such as deferred probe or the driver being a loadable
2719 * module, the real console hasn't registered yet at this point, there will
2720 * be a brief interval in which no messages are logged to the console, which
2721 * makes it difficult to diagnose problems that occur during this time.
2723 * To mitigate this problem somewhat, only unregister consoles whose memory
2724 * intersects with the init section. Note that code exists elsewhere to get
2725 * rid of the boot console as soon as the proper console shows up, so there
2726 * won't be side-effects from postponing the removal.
2728 static int __init
printk_late_init(void)
2730 struct console
*con
;
2732 for_each_console(con
) {
2733 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2735 * Make sure to unregister boot consoles whose data
2736 * resides in the init section before the init section
2737 * is discarded. Boot consoles whose data will stick
2738 * around will automatically be unregistered when the
2739 * proper console replaces them.
2741 if (init_section_intersects(con
, sizeof(*con
)))
2742 unregister_console(con
);
2745 hotcpu_notifier(console_cpu_notify
, 0);
2748 late_initcall(printk_late_init
);
2750 #if defined CONFIG_PRINTK
2752 * Delayed printk version, for scheduler-internal messages:
2754 #define PRINTK_PENDING_WAKEUP 0x01
2755 #define PRINTK_PENDING_OUTPUT 0x02
2757 static DEFINE_PER_CPU(int, printk_pending
);
2759 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2761 int pending
= __this_cpu_xchg(printk_pending
, 0);
2763 if (pending
& PRINTK_PENDING_OUTPUT
) {
2764 /* If trylock fails, someone else is doing the printing */
2765 if (console_trylock())
2769 if (pending
& PRINTK_PENDING_WAKEUP
)
2770 wake_up_interruptible(&log_wait
);
2773 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2774 .func
= wake_up_klogd_work_func
,
2775 .flags
= IRQ_WORK_LAZY
,
2778 void wake_up_klogd(void)
2781 if (waitqueue_active(&log_wait
)) {
2782 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2783 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2788 int printk_deferred(const char *fmt
, ...)
2794 va_start(args
, fmt
);
2795 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2798 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2799 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2806 * printk rate limiting, lifted from the networking subsystem.
2808 * This enforces a rate limit: not more than 10 kernel messages
2809 * every 5s to make a denial-of-service attack impossible.
2811 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2813 int __printk_ratelimit(const char *func
)
2815 return ___ratelimit(&printk_ratelimit_state
, func
);
2817 EXPORT_SYMBOL(__printk_ratelimit
);
2820 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2821 * @caller_jiffies: pointer to caller's state
2822 * @interval_msecs: minimum interval between prints
2824 * printk_timed_ratelimit() returns true if more than @interval_msecs
2825 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2828 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2829 unsigned int interval_msecs
)
2831 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2833 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2836 *caller_jiffies
= jiffies
;
2839 EXPORT_SYMBOL(printk_timed_ratelimit
);
2841 static DEFINE_SPINLOCK(dump_list_lock
);
2842 static LIST_HEAD(dump_list
);
2845 * kmsg_dump_register - register a kernel log dumper.
2846 * @dumper: pointer to the kmsg_dumper structure
2848 * Adds a kernel log dumper to the system. The dump callback in the
2849 * structure will be called when the kernel oopses or panics and must be
2850 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2852 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2854 unsigned long flags
;
2857 /* The dump callback needs to be set */
2861 spin_lock_irqsave(&dump_list_lock
, flags
);
2862 /* Don't allow registering multiple times */
2863 if (!dumper
->registered
) {
2864 dumper
->registered
= 1;
2865 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2868 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2872 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2875 * kmsg_dump_unregister - unregister a kmsg dumper.
2876 * @dumper: pointer to the kmsg_dumper structure
2878 * Removes a dump device from the system. Returns zero on success and
2879 * %-EINVAL otherwise.
2881 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2883 unsigned long flags
;
2886 spin_lock_irqsave(&dump_list_lock
, flags
);
2887 if (dumper
->registered
) {
2888 dumper
->registered
= 0;
2889 list_del_rcu(&dumper
->list
);
2892 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2897 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2899 static bool always_kmsg_dump
;
2900 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2903 * kmsg_dump - dump kernel log to kernel message dumpers.
2904 * @reason: the reason (oops, panic etc) for dumping
2906 * Call each of the registered dumper's dump() callback, which can
2907 * retrieve the kmsg records with kmsg_dump_get_line() or
2908 * kmsg_dump_get_buffer().
2910 void kmsg_dump(enum kmsg_dump_reason reason
)
2912 struct kmsg_dumper
*dumper
;
2913 unsigned long flags
;
2915 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2919 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2920 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2923 /* initialize iterator with data about the stored records */
2924 dumper
->active
= true;
2926 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2927 dumper
->cur_seq
= clear_seq
;
2928 dumper
->cur_idx
= clear_idx
;
2929 dumper
->next_seq
= log_next_seq
;
2930 dumper
->next_idx
= log_next_idx
;
2931 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2933 /* invoke dumper which will iterate over records */
2934 dumper
->dump(dumper
, reason
);
2936 /* reset iterator */
2937 dumper
->active
= false;
2943 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2944 * @dumper: registered kmsg dumper
2945 * @syslog: include the "<4>" prefixes
2946 * @line: buffer to copy the line to
2947 * @size: maximum size of the buffer
2948 * @len: length of line placed into buffer
2950 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2951 * record, and copy one record into the provided buffer.
2953 * Consecutive calls will return the next available record moving
2954 * towards the end of the buffer with the youngest messages.
2956 * A return value of FALSE indicates that there are no more records to
2959 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2961 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
2962 char *line
, size_t size
, size_t *len
)
2964 struct printk_log
*msg
;
2968 if (!dumper
->active
)
2971 if (dumper
->cur_seq
< log_first_seq
) {
2972 /* messages are gone, move to first available one */
2973 dumper
->cur_seq
= log_first_seq
;
2974 dumper
->cur_idx
= log_first_idx
;
2978 if (dumper
->cur_seq
>= log_next_seq
)
2981 msg
= log_from_idx(dumper
->cur_idx
);
2982 l
= msg_print_text(msg
, 0, syslog
, line
, size
);
2984 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2994 * kmsg_dump_get_line - retrieve one kmsg log line
2995 * @dumper: registered kmsg dumper
2996 * @syslog: include the "<4>" prefixes
2997 * @line: buffer to copy the line to
2998 * @size: maximum size of the buffer
2999 * @len: length of line placed into buffer
3001 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3002 * record, and copy one record into the provided buffer.
3004 * Consecutive calls will return the next available record moving
3005 * towards the end of the buffer with the youngest messages.
3007 * A return value of FALSE indicates that there are no more records to
3010 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
3011 char *line
, size_t size
, size_t *len
)
3013 unsigned long flags
;
3016 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3017 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
3018 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3022 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
3025 * kmsg_dump_get_buffer - copy kmsg log lines
3026 * @dumper: registered kmsg dumper
3027 * @syslog: include the "<4>" prefixes
3028 * @buf: buffer to copy the line to
3029 * @size: maximum size of the buffer
3030 * @len: length of line placed into buffer
3032 * Start at the end of the kmsg buffer and fill the provided buffer
3033 * with as many of the the *youngest* kmsg records that fit into it.
3034 * If the buffer is large enough, all available kmsg records will be
3035 * copied with a single call.
3037 * Consecutive calls will fill the buffer with the next block of
3038 * available older records, not including the earlier retrieved ones.
3040 * A return value of FALSE indicates that there are no more records to
3043 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
3044 char *buf
, size_t size
, size_t *len
)
3046 unsigned long flags
;
3051 enum log_flags prev
;
3055 if (!dumper
->active
)
3058 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3059 if (dumper
->cur_seq
< log_first_seq
) {
3060 /* messages are gone, move to first available one */
3061 dumper
->cur_seq
= log_first_seq
;
3062 dumper
->cur_idx
= log_first_idx
;
3066 if (dumper
->cur_seq
>= dumper
->next_seq
) {
3067 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3071 /* calculate length of entire buffer */
3072 seq
= dumper
->cur_seq
;
3073 idx
= dumper
->cur_idx
;
3075 while (seq
< dumper
->next_seq
) {
3076 struct printk_log
*msg
= log_from_idx(idx
);
3078 l
+= msg_print_text(msg
, prev
, true, NULL
, 0);
3079 idx
= log_next(idx
);
3084 /* move first record forward until length fits into the buffer */
3085 seq
= dumper
->cur_seq
;
3086 idx
= dumper
->cur_idx
;
3088 while (l
> size
&& seq
< dumper
->next_seq
) {
3089 struct printk_log
*msg
= log_from_idx(idx
);
3091 l
-= msg_print_text(msg
, prev
, true, NULL
, 0);
3092 idx
= log_next(idx
);
3097 /* last message in next interation */
3102 while (seq
< dumper
->next_seq
) {
3103 struct printk_log
*msg
= log_from_idx(idx
);
3105 l
+= msg_print_text(msg
, prev
, syslog
, buf
+ l
, size
- l
);
3106 idx
= log_next(idx
);
3111 dumper
->next_seq
= next_seq
;
3112 dumper
->next_idx
= next_idx
;
3114 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3120 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
3123 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3124 * @dumper: registered kmsg dumper
3126 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3127 * kmsg_dump_get_buffer() can be called again and used multiple
3128 * times within the same dumper.dump() callback.
3130 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3132 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3134 dumper
->cur_seq
= clear_seq
;
3135 dumper
->cur_idx
= clear_idx
;
3136 dumper
->next_seq
= log_next_seq
;
3137 dumper
->next_idx
= log_next_idx
;
3141 * kmsg_dump_rewind - reset the interator
3142 * @dumper: registered kmsg dumper
3144 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3145 * kmsg_dump_get_buffer() can be called again and used multiple
3146 * times within the same dumper.dump() callback.
3148 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3150 unsigned long flags
;
3152 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3153 kmsg_dump_rewind_nolock(dumper
);
3154 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3156 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3158 static char dump_stack_arch_desc_str
[128];
3161 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3162 * @fmt: printf-style format string
3163 * @...: arguments for the format string
3165 * The configured string will be printed right after utsname during task
3166 * dumps. Usually used to add arch-specific system identifiers. If an
3167 * arch wants to make use of such an ID string, it should initialize this
3168 * as soon as possible during boot.
3170 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3174 va_start(args
, fmt
);
3175 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3181 * dump_stack_print_info - print generic debug info for dump_stack()
3182 * @log_lvl: log level
3184 * Arch-specific dump_stack() implementations can use this function to
3185 * print out the same debug information as the generic dump_stack().
3187 void dump_stack_print_info(const char *log_lvl
)
3189 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3190 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3191 print_tainted(), init_utsname()->release
,
3192 (int)strcspn(init_utsname()->version
, " "),
3193 init_utsname()->version
);
3195 if (dump_stack_arch_desc_str
[0] != '\0')
3196 printk("%sHardware name: %s\n",
3197 log_lvl
, dump_stack_arch_desc_str
);
3199 print_worker_info(log_lvl
, current
);
3203 * show_regs_print_info - print generic debug info for show_regs()
3204 * @log_lvl: log level
3206 * show_regs() implementations can use this function to print out generic
3207 * debug information.
3209 void show_regs_print_info(const char *log_lvl
)
3211 dump_stack_print_info(log_lvl
);
3213 printk("%stask: %p task.stack: %p\n",
3214 log_lvl
, current
, task_stack_page(current
));