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/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/memblock.h>
35 #include <linux/syscalls.h>
36 #include <linux/kexec.h>
37 #include <linux/kdb.h>
38 #include <linux/ratelimit.h>
39 #include <linux/kmsg_dump.h>
40 #include <linux/syslog.h>
41 #include <linux/cpu.h>
42 #include <linux/notifier.h>
43 #include <linux/rculist.h>
44 #include <linux/poll.h>
45 #include <linux/irq_work.h>
46 #include <linux/utsname.h>
47 #include <linux/ctype.h>
48 #include <linux/uio.h>
50 #include <asm/uaccess.h>
51 #include <asm-generic/sections.h>
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/printk.h>
56 #include "console_cmdline.h"
60 int console_printk
[4] = {
61 CONSOLE_LOGLEVEL_DEFAULT
, /* console_loglevel */
62 MESSAGE_LOGLEVEL_DEFAULT
, /* default_message_loglevel */
63 CONSOLE_LOGLEVEL_MIN
, /* minimum_console_loglevel */
64 CONSOLE_LOGLEVEL_DEFAULT
, /* default_console_loglevel */
68 * Low level drivers may need that to know if they can schedule in
69 * their unblank() callback or not. So let's export it.
72 EXPORT_SYMBOL(oops_in_progress
);
75 * console_sem protects the console_drivers list, and also
76 * provides serialisation for access to the entire console
79 static DEFINE_SEMAPHORE(console_sem
);
80 struct console
*console_drivers
;
81 EXPORT_SYMBOL_GPL(console_drivers
);
84 static struct lockdep_map console_lock_dep_map
= {
85 .name
= "console_lock"
90 * Number of registered extended console drivers.
92 * If extended consoles are present, in-kernel cont reassembly is disabled
93 * and each fragment is stored as a separate log entry with proper
94 * continuation flag so that every emitted message has full metadata. This
95 * doesn't change the result for regular consoles or /proc/kmsg. For
96 * /dev/kmsg, as long as the reader concatenates messages according to
97 * consecutive continuation flags, the end result should be the same too.
99 static int nr_ext_console_drivers
;
102 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
103 * macros instead of functions so that _RET_IP_ contains useful information.
105 #define down_console_sem() do { \
107 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
110 static int __down_trylock_console_sem(unsigned long ip
)
112 if (down_trylock(&console_sem
))
114 mutex_acquire(&console_lock_dep_map
, 0, 1, ip
);
117 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
119 #define up_console_sem() do { \
120 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
125 * This is used for debugging the mess that is the VT code by
126 * keeping track if we have the console semaphore held. It's
127 * definitely not the perfect debug tool (we don't know if _WE_
128 * hold it and are racing, but it helps tracking those weird code
129 * paths in the console code where we end up in places I want
130 * locked without the console sempahore held).
132 static int console_locked
, console_suspended
;
135 * If exclusive_console is non-NULL then only this console is to be printed to.
137 static struct console
*exclusive_console
;
140 * Array of consoles built from command line options (console=)
143 #define MAX_CMDLINECONSOLES 8
145 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
147 static int selected_console
= -1;
148 static int preferred_console
= -1;
149 int console_set_on_cmdline
;
150 EXPORT_SYMBOL(console_set_on_cmdline
);
152 /* Flag: console code may call schedule() */
153 static int console_may_schedule
;
156 * The printk log buffer consists of a chain of concatenated variable
157 * length records. Every record starts with a record header, containing
158 * the overall length of the record.
160 * The heads to the first and last entry in the buffer, as well as the
161 * sequence numbers of these entries are maintained when messages are
164 * If the heads indicate available messages, the length in the header
165 * tells the start next message. A length == 0 for the next message
166 * indicates a wrap-around to the beginning of the buffer.
168 * Every record carries the monotonic timestamp in microseconds, as well as
169 * the standard userspace syslog level and syslog facility. The usual
170 * kernel messages use LOG_KERN; userspace-injected messages always carry
171 * a matching syslog facility, by default LOG_USER. The origin of every
172 * message can be reliably determined that way.
174 * The human readable log message directly follows the message header. The
175 * length of the message text is stored in the header, the stored message
178 * Optionally, a message can carry a dictionary of properties (key/value pairs),
179 * to provide userspace with a machine-readable message context.
181 * Examples for well-defined, commonly used property names are:
182 * DEVICE=b12:8 device identifier
186 * +sound:card0 subsystem:devname
187 * SUBSYSTEM=pci driver-core subsystem name
189 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
190 * follows directly after a '=' character. Every property is terminated by
191 * a '\0' character. The last property is not terminated.
193 * Example of a message structure:
194 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
195 * 0008 34 00 record is 52 bytes long
196 * 000a 0b 00 text is 11 bytes long
197 * 000c 1f 00 dictionary is 23 bytes long
198 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
199 * 0010 69 74 27 73 20 61 20 6c "it's a l"
201 * 001b 44 45 56 49 43 "DEVIC"
202 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
203 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
205 * 0032 00 00 00 padding to next message header
207 * The 'struct printk_log' buffer header must never be directly exported to
208 * userspace, it is a kernel-private implementation detail that might
209 * need to be changed in the future, when the requirements change.
211 * /dev/kmsg exports the structured data in the following line format:
212 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
214 * Users of the export format should ignore possible additional values
215 * separated by ',', and find the message after the ';' character.
217 * The optional key/value pairs are attached as continuation lines starting
218 * with a space character and terminated by a newline. All possible
219 * non-prinatable characters are escaped in the "\xff" notation.
223 LOG_NOCONS
= 1, /* already flushed, do not print to console */
224 LOG_NEWLINE
= 2, /* text ended with a newline */
225 LOG_PREFIX
= 4, /* text started with a prefix */
226 LOG_CONT
= 8, /* text is a fragment of a continuation line */
230 u64 ts_nsec
; /* timestamp in nanoseconds */
231 u16 len
; /* length of entire record */
232 u16 text_len
; /* length of text buffer */
233 u16 dict_len
; /* length of dictionary buffer */
234 u8 facility
; /* syslog facility */
235 u8 flags
:5; /* internal record flags */
236 u8 level
:3; /* syslog level */
238 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
239 __packed
__aligned(4)
244 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
245 * within the scheduler's rq lock. It must be released before calling
246 * console_unlock() or anything else that might wake up a process.
248 DEFINE_RAW_SPINLOCK(logbuf_lock
);
251 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
252 /* the next printk record to read by syslog(READ) or /proc/kmsg */
253 static u64 syslog_seq
;
254 static u32 syslog_idx
;
255 static enum log_flags syslog_prev
;
256 static size_t syslog_partial
;
258 /* index and sequence number of the first record stored in the buffer */
259 static u64 log_first_seq
;
260 static u32 log_first_idx
;
262 /* index and sequence number of the next record to store in the buffer */
263 static u64 log_next_seq
;
264 static u32 log_next_idx
;
266 /* the next printk record to write to the console */
267 static u64 console_seq
;
268 static u32 console_idx
;
269 static enum log_flags console_prev
;
271 /* the next printk record to read after the last 'clear' command */
272 static u64 clear_seq
;
273 static u32 clear_idx
;
275 #define PREFIX_MAX 32
276 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
278 #define LOG_LEVEL(v) ((v) & 0x07)
279 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
282 #define LOG_ALIGN __alignof__(struct printk_log)
283 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
284 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
285 static char *log_buf
= __log_buf
;
286 static u32 log_buf_len
= __LOG_BUF_LEN
;
288 /* Return log buffer address */
289 char *log_buf_addr_get(void)
294 /* Return log buffer size */
295 u32
log_buf_len_get(void)
300 /* human readable text of the record */
301 static char *log_text(const struct printk_log
*msg
)
303 return (char *)msg
+ sizeof(struct printk_log
);
306 /* optional key/value pair dictionary attached to the record */
307 static char *log_dict(const struct printk_log
*msg
)
309 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
312 /* get record by index; idx must point to valid msg */
313 static struct printk_log
*log_from_idx(u32 idx
)
315 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
318 * A length == 0 record is the end of buffer marker. Wrap around and
319 * read the message at the start of the buffer.
322 return (struct printk_log
*)log_buf
;
326 /* get next record; idx must point to valid msg */
327 static u32
log_next(u32 idx
)
329 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
331 /* length == 0 indicates the end of the buffer; wrap */
333 * A length == 0 record is the end of buffer marker. Wrap around and
334 * read the message at the start of the buffer as *this* one, and
335 * return the one after that.
338 msg
= (struct printk_log
*)log_buf
;
341 return idx
+ msg
->len
;
345 * Check whether there is enough free space for the given message.
347 * The same values of first_idx and next_idx mean that the buffer
348 * is either empty or full.
350 * If the buffer is empty, we must respect the position of the indexes.
351 * They cannot be reset to the beginning of the buffer.
353 static int logbuf_has_space(u32 msg_size
, bool empty
)
357 if (log_next_idx
> log_first_idx
|| empty
)
358 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
360 free
= log_first_idx
- log_next_idx
;
363 * We need space also for an empty header that signalizes wrapping
366 return free
>= msg_size
+ sizeof(struct printk_log
);
369 static int log_make_free_space(u32 msg_size
)
371 while (log_first_seq
< log_next_seq
&&
372 !logbuf_has_space(msg_size
, false)) {
373 /* drop old messages until we have enough contiguous space */
374 log_first_idx
= log_next(log_first_idx
);
378 if (clear_seq
< log_first_seq
) {
379 clear_seq
= log_first_seq
;
380 clear_idx
= log_first_idx
;
383 /* sequence numbers are equal, so the log buffer is empty */
384 if (logbuf_has_space(msg_size
, log_first_seq
== log_next_seq
))
390 /* compute the message size including the padding bytes */
391 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
395 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
396 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
403 * Define how much of the log buffer we could take at maximum. The value
404 * must be greater than two. Note that only half of the buffer is available
405 * when the index points to the middle.
407 #define MAX_LOG_TAKE_PART 4
408 static const char trunc_msg
[] = "<truncated>";
410 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
411 u16
*dict_len
, u32
*pad_len
)
414 * The message should not take the whole buffer. Otherwise, it might
415 * get removed too soon.
417 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
418 if (*text_len
> max_text_len
)
419 *text_len
= max_text_len
;
420 /* enable the warning message */
421 *trunc_msg_len
= strlen(trunc_msg
);
422 /* disable the "dict" completely */
424 /* compute the size again, count also the warning message */
425 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
428 /* insert record into the buffer, discard old ones, update heads */
429 static int log_store(int facility
, int level
,
430 enum log_flags flags
, u64 ts_nsec
,
431 const char *dict
, u16 dict_len
,
432 const char *text
, u16 text_len
)
434 struct printk_log
*msg
;
436 u16 trunc_msg_len
= 0;
438 /* number of '\0' padding bytes to next message */
439 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
441 if (log_make_free_space(size
)) {
442 /* truncate the message if it is too long for empty buffer */
443 size
= truncate_msg(&text_len
, &trunc_msg_len
,
444 &dict_len
, &pad_len
);
445 /* survive when the log buffer is too small for trunc_msg */
446 if (log_make_free_space(size
))
450 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
452 * This message + an additional empty header does not fit
453 * at the end of the buffer. Add an empty header with len == 0
454 * to signify a wrap around.
456 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
461 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
462 memcpy(log_text(msg
), text
, text_len
);
463 msg
->text_len
= text_len
;
465 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
466 msg
->text_len
+= trunc_msg_len
;
468 memcpy(log_dict(msg
), dict
, dict_len
);
469 msg
->dict_len
= dict_len
;
470 msg
->facility
= facility
;
471 msg
->level
= level
& 7;
472 msg
->flags
= flags
& 0x1f;
474 msg
->ts_nsec
= ts_nsec
;
476 msg
->ts_nsec
= local_clock();
477 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
481 log_next_idx
+= msg
->len
;
484 return msg
->text_len
;
487 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
489 static int syslog_action_restricted(int type
)
494 * Unless restricted, we allow "read all" and "get buffer size"
497 return type
!= SYSLOG_ACTION_READ_ALL
&&
498 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
501 int check_syslog_permissions(int type
, int source
)
504 * If this is from /proc/kmsg and we've already opened it, then we've
505 * already done the capabilities checks at open time.
507 if (source
== SYSLOG_FROM_PROC
&& type
!= SYSLOG_ACTION_OPEN
)
510 if (syslog_action_restricted(type
)) {
511 if (capable(CAP_SYSLOG
))
514 * For historical reasons, accept CAP_SYS_ADMIN too, with
517 if (capable(CAP_SYS_ADMIN
)) {
518 pr_warn_once("%s (%d): Attempt to access syslog with "
519 "CAP_SYS_ADMIN but no CAP_SYSLOG "
521 current
->comm
, task_pid_nr(current
));
527 return security_syslog(type
);
529 EXPORT_SYMBOL_GPL(check_syslog_permissions
);
531 static void append_char(char **pp
, char *e
, char c
)
537 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
538 struct printk_log
*msg
, u64 seq
,
539 enum log_flags prev_flags
)
541 u64 ts_usec
= msg
->ts_nsec
;
544 do_div(ts_usec
, 1000);
547 * If we couldn't merge continuation line fragments during the print,
548 * export the stored flags to allow an optional external merge of the
549 * records. Merging the records isn't always neccessarily correct, like
550 * when we hit a race during printing. In most cases though, it produces
551 * better readable output. 'c' in the record flags mark the first
552 * fragment of a line, '+' the following.
554 if (msg
->flags
& LOG_CONT
&& !(prev_flags
& LOG_CONT
))
556 else if ((msg
->flags
& LOG_CONT
) ||
557 ((prev_flags
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
)))
560 return scnprintf(buf
, size
, "%u,%llu,%llu,%c;",
561 (msg
->facility
<< 3) | msg
->level
, seq
, ts_usec
, cont
);
564 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
565 char *dict
, size_t dict_len
,
566 char *text
, size_t text_len
)
568 char *p
= buf
, *e
= buf
+ size
;
571 /* escape non-printable characters */
572 for (i
= 0; i
< text_len
; i
++) {
573 unsigned char c
= text
[i
];
575 if (c
< ' ' || c
>= 127 || c
== '\\')
576 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
578 append_char(&p
, e
, c
);
580 append_char(&p
, e
, '\n');
585 for (i
= 0; i
< dict_len
; i
++) {
586 unsigned char c
= dict
[i
];
589 append_char(&p
, e
, ' ');
594 append_char(&p
, e
, '\n');
599 if (c
< ' ' || c
>= 127 || c
== '\\') {
600 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
604 append_char(&p
, e
, c
);
606 append_char(&p
, e
, '\n');
612 /* /dev/kmsg - userspace message inject/listen interface */
613 struct devkmsg_user
{
618 char buf
[CONSOLE_EXT_LOG_MAX
];
621 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
624 int level
= default_message_loglevel
;
625 int facility
= 1; /* LOG_USER */
626 size_t len
= iov_iter_count(from
);
629 if (len
> LOG_LINE_MAX
)
631 buf
= kmalloc(len
+1, GFP_KERNEL
);
636 if (copy_from_iter(buf
, len
, from
) != len
) {
642 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
643 * the decimal value represents 32bit, the lower 3 bit are the log
644 * level, the rest are the log facility.
646 * If no prefix or no userspace facility is specified, we
647 * enforce LOG_USER, to be able to reliably distinguish
648 * kernel-generated messages from userspace-injected ones.
651 if (line
[0] == '<') {
655 u
= simple_strtoul(line
+ 1, &endp
, 10);
656 if (endp
&& endp
[0] == '>') {
657 level
= LOG_LEVEL(u
);
658 if (LOG_FACILITY(u
) != 0)
659 facility
= LOG_FACILITY(u
);
666 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
671 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
672 size_t count
, loff_t
*ppos
)
674 struct devkmsg_user
*user
= file
->private_data
;
675 struct printk_log
*msg
;
682 ret
= mutex_lock_interruptible(&user
->lock
);
685 raw_spin_lock_irq(&logbuf_lock
);
686 while (user
->seq
== log_next_seq
) {
687 if (file
->f_flags
& O_NONBLOCK
) {
689 raw_spin_unlock_irq(&logbuf_lock
);
693 raw_spin_unlock_irq(&logbuf_lock
);
694 ret
= wait_event_interruptible(log_wait
,
695 user
->seq
!= log_next_seq
);
698 raw_spin_lock_irq(&logbuf_lock
);
701 if (user
->seq
< log_first_seq
) {
702 /* our last seen message is gone, return error and reset */
703 user
->idx
= log_first_idx
;
704 user
->seq
= log_first_seq
;
706 raw_spin_unlock_irq(&logbuf_lock
);
710 msg
= log_from_idx(user
->idx
);
711 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
712 msg
, user
->seq
, user
->prev
);
713 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
714 log_dict(msg
), msg
->dict_len
,
715 log_text(msg
), msg
->text_len
);
717 user
->prev
= msg
->flags
;
718 user
->idx
= log_next(user
->idx
);
720 raw_spin_unlock_irq(&logbuf_lock
);
727 if (copy_to_user(buf
, user
->buf
, len
)) {
733 mutex_unlock(&user
->lock
);
737 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
739 struct devkmsg_user
*user
= file
->private_data
;
747 raw_spin_lock_irq(&logbuf_lock
);
750 /* the first record */
751 user
->idx
= log_first_idx
;
752 user
->seq
= log_first_seq
;
756 * The first record after the last SYSLOG_ACTION_CLEAR,
757 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
758 * changes no global state, and does not clear anything.
760 user
->idx
= clear_idx
;
761 user
->seq
= clear_seq
;
764 /* after the last record */
765 user
->idx
= log_next_idx
;
766 user
->seq
= log_next_seq
;
771 raw_spin_unlock_irq(&logbuf_lock
);
775 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
777 struct devkmsg_user
*user
= file
->private_data
;
781 return POLLERR
|POLLNVAL
;
783 poll_wait(file
, &log_wait
, wait
);
785 raw_spin_lock_irq(&logbuf_lock
);
786 if (user
->seq
< log_next_seq
) {
787 /* return error when data has vanished underneath us */
788 if (user
->seq
< log_first_seq
)
789 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
791 ret
= POLLIN
|POLLRDNORM
;
793 raw_spin_unlock_irq(&logbuf_lock
);
798 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
800 struct devkmsg_user
*user
;
803 /* write-only does not need any file context */
804 if ((file
->f_flags
& O_ACCMODE
) == O_WRONLY
)
807 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
812 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
816 mutex_init(&user
->lock
);
818 raw_spin_lock_irq(&logbuf_lock
);
819 user
->idx
= log_first_idx
;
820 user
->seq
= log_first_seq
;
821 raw_spin_unlock_irq(&logbuf_lock
);
823 file
->private_data
= user
;
827 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
829 struct devkmsg_user
*user
= file
->private_data
;
834 mutex_destroy(&user
->lock
);
839 const struct file_operations kmsg_fops
= {
840 .open
= devkmsg_open
,
841 .read
= devkmsg_read
,
842 .write_iter
= devkmsg_write
,
843 .llseek
= devkmsg_llseek
,
844 .poll
= devkmsg_poll
,
845 .release
= devkmsg_release
,
848 #ifdef CONFIG_KEXEC_CORE
850 * This appends the listed symbols to /proc/vmcore
852 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
853 * obtain access to symbols that are otherwise very difficult to locate. These
854 * symbols are specifically used so that utilities can access and extract the
855 * dmesg log from a vmcore file after a crash.
857 void log_buf_kexec_setup(void)
859 VMCOREINFO_SYMBOL(log_buf
);
860 VMCOREINFO_SYMBOL(log_buf_len
);
861 VMCOREINFO_SYMBOL(log_first_idx
);
862 VMCOREINFO_SYMBOL(clear_idx
);
863 VMCOREINFO_SYMBOL(log_next_idx
);
865 * Export struct printk_log size and field offsets. User space tools can
866 * parse it and detect any changes to structure down the line.
868 VMCOREINFO_STRUCT_SIZE(printk_log
);
869 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
870 VMCOREINFO_OFFSET(printk_log
, len
);
871 VMCOREINFO_OFFSET(printk_log
, text_len
);
872 VMCOREINFO_OFFSET(printk_log
, dict_len
);
876 /* requested log_buf_len from kernel cmdline */
877 static unsigned long __initdata new_log_buf_len
;
879 /* we practice scaling the ring buffer by powers of 2 */
880 static void __init
log_buf_len_update(unsigned size
)
883 size
= roundup_pow_of_two(size
);
884 if (size
> log_buf_len
)
885 new_log_buf_len
= size
;
888 /* save requested log_buf_len since it's too early to process it */
889 static int __init
log_buf_len_setup(char *str
)
891 unsigned size
= memparse(str
, &str
);
893 log_buf_len_update(size
);
897 early_param("log_buf_len", log_buf_len_setup
);
900 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
902 static void __init
log_buf_add_cpu(void)
904 unsigned int cpu_extra
;
907 * archs should set up cpu_possible_bits properly with
908 * set_cpu_possible() after setup_arch() but just in
909 * case lets ensure this is valid.
911 if (num_possible_cpus() == 1)
914 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
916 /* by default this will only continue through for large > 64 CPUs */
917 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
920 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
921 __LOG_CPU_MAX_BUF_LEN
);
922 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
924 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
926 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
928 #else /* !CONFIG_SMP */
929 static inline void log_buf_add_cpu(void) {}
930 #endif /* CONFIG_SMP */
932 void __init
setup_log_buf(int early
)
938 if (log_buf
!= __log_buf
)
941 if (!early
&& !new_log_buf_len
)
944 if (!new_log_buf_len
)
949 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
951 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
955 if (unlikely(!new_log_buf
)) {
956 pr_err("log_buf_len: %ld bytes not available\n",
961 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
962 log_buf_len
= new_log_buf_len
;
963 log_buf
= new_log_buf
;
965 free
= __LOG_BUF_LEN
- log_next_idx
;
966 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
967 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
969 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
970 pr_info("early log buf free: %d(%d%%)\n",
971 free
, (free
* 100) / __LOG_BUF_LEN
);
974 static bool __read_mostly ignore_loglevel
;
976 static int __init
ignore_loglevel_setup(char *str
)
978 ignore_loglevel
= true;
979 pr_info("debug: ignoring loglevel setting.\n");
984 early_param("ignore_loglevel", ignore_loglevel_setup
);
985 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
986 MODULE_PARM_DESC(ignore_loglevel
,
987 "ignore loglevel setting (prints all kernel messages to the console)");
989 #ifdef CONFIG_BOOT_PRINTK_DELAY
991 static int boot_delay
; /* msecs delay after each printk during bootup */
992 static unsigned long long loops_per_msec
; /* based on boot_delay */
994 static int __init
boot_delay_setup(char *str
)
998 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
999 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
1001 get_option(&str
, &boot_delay
);
1002 if (boot_delay
> 10 * 1000)
1005 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1006 "HZ: %d, loops_per_msec: %llu\n",
1007 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
1010 early_param("boot_delay", boot_delay_setup
);
1012 static void boot_delay_msec(int level
)
1014 unsigned long long k
;
1015 unsigned long timeout
;
1017 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
1018 || (level
>= console_loglevel
&& !ignore_loglevel
)) {
1022 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1024 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1029 * use (volatile) jiffies to prevent
1030 * compiler reduction; loop termination via jiffies
1031 * is secondary and may or may not happen.
1033 if (time_after(jiffies
, timeout
))
1035 touch_nmi_watchdog();
1039 static inline void boot_delay_msec(int level
)
1044 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1045 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1047 static size_t print_time(u64 ts
, char *buf
)
1049 unsigned long rem_nsec
;
1054 rem_nsec
= do_div(ts
, 1000000000);
1057 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1059 return sprintf(buf
, "[%5lu.%06lu] ",
1060 (unsigned long)ts
, rem_nsec
/ 1000);
1063 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1066 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1070 len
+= sprintf(buf
, "<%u>", prefix
);
1075 else if (prefix
> 99)
1077 else if (prefix
> 9)
1082 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1086 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1087 bool syslog
, char *buf
, size_t size
)
1089 const char *text
= log_text(msg
);
1090 size_t text_size
= msg
->text_len
;
1092 bool newline
= true;
1095 if ((prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
))
1098 if (msg
->flags
& LOG_CONT
) {
1099 if ((prev
& LOG_CONT
) && !(prev
& LOG_NEWLINE
))
1102 if (!(msg
->flags
& LOG_NEWLINE
))
1107 const char *next
= memchr(text
, '\n', text_size
);
1111 text_len
= next
- text
;
1113 text_size
-= next
- text
;
1115 text_len
= text_size
;
1119 if (print_prefix(msg
, syslog
, NULL
) +
1120 text_len
+ 1 >= size
- len
)
1124 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1125 memcpy(buf
+ len
, text
, text_len
);
1127 if (next
|| newline
)
1130 /* SYSLOG_ACTION_* buffer size only calculation */
1132 len
+= print_prefix(msg
, syslog
, NULL
);
1134 if (next
|| newline
)
1145 static int syslog_print(char __user
*buf
, int size
)
1148 struct printk_log
*msg
;
1151 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1159 raw_spin_lock_irq(&logbuf_lock
);
1160 if (syslog_seq
< log_first_seq
) {
1161 /* messages are gone, move to first one */
1162 syslog_seq
= log_first_seq
;
1163 syslog_idx
= log_first_idx
;
1167 if (syslog_seq
== log_next_seq
) {
1168 raw_spin_unlock_irq(&logbuf_lock
);
1172 skip
= syslog_partial
;
1173 msg
= log_from_idx(syslog_idx
);
1174 n
= msg_print_text(msg
, syslog_prev
, true, text
,
1175 LOG_LINE_MAX
+ PREFIX_MAX
);
1176 if (n
- syslog_partial
<= size
) {
1177 /* message fits into buffer, move forward */
1178 syslog_idx
= log_next(syslog_idx
);
1180 syslog_prev
= msg
->flags
;
1181 n
-= syslog_partial
;
1184 /* partial read(), remember position */
1186 syslog_partial
+= n
;
1189 raw_spin_unlock_irq(&logbuf_lock
);
1194 if (copy_to_user(buf
, text
+ skip
, n
)) {
1209 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1214 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1218 raw_spin_lock_irq(&logbuf_lock
);
1223 enum log_flags prev
;
1226 * Find first record that fits, including all following records,
1227 * into the user-provided buffer for this dump.
1232 while (seq
< log_next_seq
) {
1233 struct printk_log
*msg
= log_from_idx(idx
);
1235 len
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1237 idx
= log_next(idx
);
1241 /* move first record forward until length fits into the buffer */
1245 while (len
> size
&& seq
< log_next_seq
) {
1246 struct printk_log
*msg
= log_from_idx(idx
);
1248 len
-= msg_print_text(msg
, prev
, true, NULL
, 0);
1250 idx
= log_next(idx
);
1254 /* last message fitting into this dump */
1255 next_seq
= log_next_seq
;
1258 while (len
>= 0 && seq
< next_seq
) {
1259 struct printk_log
*msg
= log_from_idx(idx
);
1262 textlen
= msg_print_text(msg
, prev
, true, text
,
1263 LOG_LINE_MAX
+ PREFIX_MAX
);
1268 idx
= log_next(idx
);
1272 raw_spin_unlock_irq(&logbuf_lock
);
1273 if (copy_to_user(buf
+ len
, text
, textlen
))
1277 raw_spin_lock_irq(&logbuf_lock
);
1279 if (seq
< log_first_seq
) {
1280 /* messages are gone, move to next one */
1281 seq
= log_first_seq
;
1282 idx
= log_first_idx
;
1289 clear_seq
= log_next_seq
;
1290 clear_idx
= log_next_idx
;
1292 raw_spin_unlock_irq(&logbuf_lock
);
1298 int do_syslog(int type
, char __user
*buf
, int len
, int source
)
1301 static int saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1304 error
= check_syslog_permissions(type
, source
);
1309 case SYSLOG_ACTION_CLOSE
: /* Close log */
1311 case SYSLOG_ACTION_OPEN
: /* Open log */
1313 case SYSLOG_ACTION_READ
: /* Read from log */
1315 if (!buf
|| len
< 0)
1320 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1324 error
= wait_event_interruptible(log_wait
,
1325 syslog_seq
!= log_next_seq
);
1328 error
= syslog_print(buf
, len
);
1330 /* Read/clear last kernel messages */
1331 case SYSLOG_ACTION_READ_CLEAR
:
1334 /* Read last kernel messages */
1335 case SYSLOG_ACTION_READ_ALL
:
1337 if (!buf
|| len
< 0)
1342 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1346 error
= syslog_print_all(buf
, len
, clear
);
1348 /* Clear ring buffer */
1349 case SYSLOG_ACTION_CLEAR
:
1350 syslog_print_all(NULL
, 0, true);
1352 /* Disable logging to console */
1353 case SYSLOG_ACTION_CONSOLE_OFF
:
1354 if (saved_console_loglevel
== LOGLEVEL_DEFAULT
)
1355 saved_console_loglevel
= console_loglevel
;
1356 console_loglevel
= minimum_console_loglevel
;
1358 /* Enable logging to console */
1359 case SYSLOG_ACTION_CONSOLE_ON
:
1360 if (saved_console_loglevel
!= LOGLEVEL_DEFAULT
) {
1361 console_loglevel
= saved_console_loglevel
;
1362 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1365 /* Set level of messages printed to console */
1366 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1368 if (len
< 1 || len
> 8)
1370 if (len
< minimum_console_loglevel
)
1371 len
= minimum_console_loglevel
;
1372 console_loglevel
= len
;
1373 /* Implicitly re-enable logging to console */
1374 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1377 /* Number of chars in the log buffer */
1378 case SYSLOG_ACTION_SIZE_UNREAD
:
1379 raw_spin_lock_irq(&logbuf_lock
);
1380 if (syslog_seq
< log_first_seq
) {
1381 /* messages are gone, move to first one */
1382 syslog_seq
= log_first_seq
;
1383 syslog_idx
= log_first_idx
;
1387 if (source
== SYSLOG_FROM_PROC
) {
1389 * Short-cut for poll(/"proc/kmsg") which simply checks
1390 * for pending data, not the size; return the count of
1391 * records, not the length.
1393 error
= log_next_seq
- syslog_seq
;
1395 u64 seq
= syslog_seq
;
1396 u32 idx
= syslog_idx
;
1397 enum log_flags prev
= syslog_prev
;
1400 while (seq
< log_next_seq
) {
1401 struct printk_log
*msg
= log_from_idx(idx
);
1403 error
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1404 idx
= log_next(idx
);
1408 error
-= syslog_partial
;
1410 raw_spin_unlock_irq(&logbuf_lock
);
1412 /* Size of the log buffer */
1413 case SYSLOG_ACTION_SIZE_BUFFER
:
1414 error
= log_buf_len
;
1424 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1426 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1430 * Call the console drivers, asking them to write out
1431 * log_buf[start] to log_buf[end - 1].
1432 * The console_lock must be held.
1434 static void call_console_drivers(int level
,
1435 const char *ext_text
, size_t ext_len
,
1436 const char *text
, size_t len
)
1438 struct console
*con
;
1440 trace_console(text
, len
);
1442 if (level
>= console_loglevel
&& !ignore_loglevel
)
1444 if (!console_drivers
)
1447 for_each_console(con
) {
1448 if (exclusive_console
&& con
!= exclusive_console
)
1450 if (!(con
->flags
& CON_ENABLED
))
1454 if (!cpu_online(smp_processor_id()) &&
1455 !(con
->flags
& CON_ANYTIME
))
1457 if (con
->flags
& CON_EXTENDED
)
1458 con
->write(con
, ext_text
, ext_len
);
1460 con
->write(con
, text
, len
);
1465 * Zap console related locks when oopsing.
1466 * To leave time for slow consoles to print a full oops,
1467 * only zap at most once every 30 seconds.
1469 static void zap_locks(void)
1471 static unsigned long oops_timestamp
;
1473 if (time_after_eq(jiffies
, oops_timestamp
) &&
1474 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1477 oops_timestamp
= jiffies
;
1480 /* If a crash is occurring, make sure we can't deadlock */
1481 raw_spin_lock_init(&logbuf_lock
);
1482 /* And make sure that we print immediately */
1483 sema_init(&console_sem
, 1);
1486 int printk_delay_msec __read_mostly
;
1488 static inline void printk_delay(void)
1490 if (unlikely(printk_delay_msec
)) {
1491 int m
= printk_delay_msec
;
1495 touch_nmi_watchdog();
1501 * Continuation lines are buffered, and not committed to the record buffer
1502 * until the line is complete, or a race forces it. The line fragments
1503 * though, are printed immediately to the consoles to ensure everything has
1504 * reached the console in case of a kernel crash.
1506 static struct cont
{
1507 char buf
[LOG_LINE_MAX
];
1508 size_t len
; /* length == 0 means unused buffer */
1509 size_t cons
; /* bytes written to console */
1510 struct task_struct
*owner
; /* task of first print*/
1511 u64 ts_nsec
; /* time of first print */
1512 u8 level
; /* log level of first message */
1513 u8 facility
; /* log facility of first message */
1514 enum log_flags flags
; /* prefix, newline flags */
1515 bool flushed
:1; /* buffer sealed and committed */
1518 static void cont_flush(enum log_flags flags
)
1527 * If a fragment of this line was directly flushed to the
1528 * console; wait for the console to pick up the rest of the
1529 * line. LOG_NOCONS suppresses a duplicated output.
1531 log_store(cont
.facility
, cont
.level
, flags
| LOG_NOCONS
,
1532 cont
.ts_nsec
, NULL
, 0, cont
.buf
, cont
.len
);
1534 cont
.flushed
= true;
1537 * If no fragment of this line ever reached the console,
1538 * just submit it to the store and free the buffer.
1540 log_store(cont
.facility
, cont
.level
, flags
, 0,
1541 NULL
, 0, cont
.buf
, cont
.len
);
1546 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1548 if (cont
.len
&& cont
.flushed
)
1552 * If ext consoles are present, flush and skip in-kernel
1553 * continuation. See nr_ext_console_drivers definition. Also, if
1554 * the line gets too long, split it up in separate records.
1556 if (nr_ext_console_drivers
|| cont
.len
+ len
> sizeof(cont
.buf
)) {
1557 cont_flush(LOG_CONT
);
1562 cont
.facility
= facility
;
1564 cont
.owner
= current
;
1565 cont
.ts_nsec
= local_clock();
1568 cont
.flushed
= false;
1571 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1574 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1575 cont_flush(LOG_CONT
);
1580 static size_t cont_print_text(char *text
, size_t size
)
1585 if (cont
.cons
== 0 && (console_prev
& LOG_NEWLINE
)) {
1586 textlen
+= print_time(cont
.ts_nsec
, text
);
1590 len
= cont
.len
- cont
.cons
;
1594 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1596 cont
.cons
= cont
.len
;
1600 if (cont
.flags
& LOG_NEWLINE
)
1601 text
[textlen
++] = '\n';
1602 /* got everything, release buffer */
1608 asmlinkage
int vprintk_emit(int facility
, int level
,
1609 const char *dict
, size_t dictlen
,
1610 const char *fmt
, va_list args
)
1612 static bool recursion_bug
;
1613 static char textbuf
[LOG_LINE_MAX
];
1614 char *text
= textbuf
;
1615 size_t text_len
= 0;
1616 enum log_flags lflags
= 0;
1617 unsigned long flags
;
1619 int printed_len
= 0;
1620 int nmi_message_lost
;
1621 bool in_sched
= false;
1622 /* cpu currently holding logbuf_lock in this function */
1623 static unsigned int logbuf_cpu
= UINT_MAX
;
1625 if (level
== LOGLEVEL_SCHED
) {
1626 level
= LOGLEVEL_DEFAULT
;
1630 boot_delay_msec(level
);
1633 local_irq_save(flags
);
1634 this_cpu
= smp_processor_id();
1637 * Ouch, printk recursed into itself!
1639 if (unlikely(logbuf_cpu
== this_cpu
)) {
1641 * If a crash is occurring during printk() on this CPU,
1642 * then try to get the crash message out but make sure
1643 * we can't deadlock. Otherwise just return to avoid the
1644 * recursion and return - but flag the recursion so that
1645 * it can be printed at the next appropriate moment:
1647 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1648 recursion_bug
= true;
1649 local_irq_restore(flags
);
1656 /* This stops the holder of console_sem just where we want him */
1657 raw_spin_lock(&logbuf_lock
);
1658 logbuf_cpu
= this_cpu
;
1660 if (unlikely(recursion_bug
)) {
1661 static const char recursion_msg
[] =
1662 "BUG: recent printk recursion!";
1664 recursion_bug
= false;
1665 /* emit KERN_CRIT message */
1666 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1667 NULL
, 0, recursion_msg
,
1668 strlen(recursion_msg
));
1671 nmi_message_lost
= get_nmi_message_lost();
1672 if (unlikely(nmi_message_lost
)) {
1673 text_len
= scnprintf(textbuf
, sizeof(textbuf
),
1674 "BAD LUCK: lost %d message(s) from NMI context!",
1676 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1677 NULL
, 0, textbuf
, text_len
);
1681 * The printf needs to come first; we need the syslog
1682 * prefix which might be passed-in as a parameter.
1684 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1686 /* mark and strip a trailing newline */
1687 if (text_len
&& text
[text_len
-1] == '\n') {
1689 lflags
|= LOG_NEWLINE
;
1692 /* strip kernel syslog prefix and extract log level or control flags */
1693 if (facility
== 0) {
1694 int kern_level
= printk_get_level(text
);
1697 const char *end_of_header
= printk_skip_level(text
);
1698 switch (kern_level
) {
1700 if (level
== LOGLEVEL_DEFAULT
)
1701 level
= kern_level
- '0';
1703 case 'd': /* KERN_DEFAULT */
1704 lflags
|= LOG_PREFIX
;
1707 * No need to check length here because vscnprintf
1708 * put '\0' at the end of the string. Only valid and
1709 * newly printed level is detected.
1711 text_len
-= end_of_header
- text
;
1712 text
= (char *)end_of_header
;
1716 if (level
== LOGLEVEL_DEFAULT
)
1717 level
= default_message_loglevel
;
1720 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1722 if (!(lflags
& LOG_NEWLINE
)) {
1724 * Flush the conflicting buffer. An earlier newline was missing,
1725 * or another task also prints continuation lines.
1727 if (cont
.len
&& (lflags
& LOG_PREFIX
|| cont
.owner
!= current
))
1728 cont_flush(LOG_NEWLINE
);
1730 /* buffer line if possible, otherwise store it right away */
1731 if (cont_add(facility
, level
, text
, text_len
))
1732 printed_len
+= text_len
;
1734 printed_len
+= log_store(facility
, level
,
1735 lflags
| LOG_CONT
, 0,
1736 dict
, dictlen
, text
, text_len
);
1738 bool stored
= false;
1741 * If an earlier newline was missing and it was the same task,
1742 * either merge it with the current buffer and flush, or if
1743 * there was a race with interrupts (prefix == true) then just
1744 * flush it out and store this line separately.
1745 * If the preceding printk was from a different task and missed
1746 * a newline, flush and append the newline.
1749 if (cont
.owner
== current
&& !(lflags
& LOG_PREFIX
))
1750 stored
= cont_add(facility
, level
, text
,
1752 cont_flush(LOG_NEWLINE
);
1756 printed_len
+= text_len
;
1758 printed_len
+= log_store(facility
, level
, lflags
, 0,
1759 dict
, dictlen
, text
, text_len
);
1762 logbuf_cpu
= UINT_MAX
;
1763 raw_spin_unlock(&logbuf_lock
);
1765 local_irq_restore(flags
);
1767 /* If called from the scheduler, we can not call up(). */
1771 * Try to acquire and then immediately release the console
1772 * semaphore. The release will print out buffers and wake up
1773 * /dev/kmsg and syslog() users.
1775 if (console_trylock())
1782 EXPORT_SYMBOL(vprintk_emit
);
1784 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1786 return vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1788 EXPORT_SYMBOL(vprintk
);
1790 asmlinkage
int printk_emit(int facility
, int level
,
1791 const char *dict
, size_t dictlen
,
1792 const char *fmt
, ...)
1797 va_start(args
, fmt
);
1798 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1803 EXPORT_SYMBOL(printk_emit
);
1805 int vprintk_default(const char *fmt
, va_list args
)
1809 #ifdef CONFIG_KGDB_KDB
1810 if (unlikely(kdb_trap_printk
)) {
1811 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1815 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1819 EXPORT_SYMBOL_GPL(vprintk_default
);
1822 * printk - print a kernel message
1823 * @fmt: format string
1825 * This is printk(). It can be called from any context. We want it to work.
1827 * We try to grab the console_lock. If we succeed, it's easy - we log the
1828 * output and call the console drivers. If we fail to get the semaphore, we
1829 * place the output into the log buffer and return. The current holder of
1830 * the console_sem will notice the new output in console_unlock(); and will
1831 * send it to the consoles before releasing the lock.
1833 * One effect of this deferred printing is that code which calls printk() and
1834 * then changes console_loglevel may break. This is because console_loglevel
1835 * is inspected when the actual printing occurs.
1840 * See the vsnprintf() documentation for format string extensions over C99.
1842 asmlinkage __visible
int printk(const char *fmt
, ...)
1847 va_start(args
, fmt
);
1848 r
= vprintk_func(fmt
, args
);
1853 EXPORT_SYMBOL(printk
);
1855 #else /* CONFIG_PRINTK */
1857 #define LOG_LINE_MAX 0
1858 #define PREFIX_MAX 0
1860 static u64 syslog_seq
;
1861 static u32 syslog_idx
;
1862 static u64 console_seq
;
1863 static u32 console_idx
;
1864 static enum log_flags syslog_prev
;
1865 static u64 log_first_seq
;
1866 static u32 log_first_idx
;
1867 static u64 log_next_seq
;
1868 static enum log_flags console_prev
;
1869 static struct cont
{
1875 static char *log_text(const struct printk_log
*msg
) { return NULL
; }
1876 static char *log_dict(const struct printk_log
*msg
) { return NULL
; }
1877 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
1878 static u32
log_next(u32 idx
) { return 0; }
1879 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
1880 struct printk_log
*msg
, u64 seq
,
1881 enum log_flags prev_flags
) { return 0; }
1882 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
1883 char *dict
, size_t dict_len
,
1884 char *text
, size_t text_len
) { return 0; }
1885 static void call_console_drivers(int level
,
1886 const char *ext_text
, size_t ext_len
,
1887 const char *text
, size_t len
) {}
1888 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1889 bool syslog
, char *buf
, size_t size
) { return 0; }
1890 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
1892 /* Still needs to be defined for users */
1893 DEFINE_PER_CPU(printk_func_t
, printk_func
);
1895 #endif /* CONFIG_PRINTK */
1897 #ifdef CONFIG_EARLY_PRINTK
1898 struct console
*early_console
;
1900 asmlinkage __visible
void early_printk(const char *fmt
, ...)
1910 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
1913 early_console
->write(early_console
, buf
, n
);
1917 static int __add_preferred_console(char *name
, int idx
, char *options
,
1920 struct console_cmdline
*c
;
1924 * See if this tty is not yet registered, and
1925 * if we have a slot free.
1927 for (i
= 0, c
= console_cmdline
;
1928 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
1930 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
1932 selected_console
= i
;
1936 if (i
== MAX_CMDLINECONSOLES
)
1939 selected_console
= i
;
1940 strlcpy(c
->name
, name
, sizeof(c
->name
));
1941 c
->options
= options
;
1942 braille_set_options(c
, brl_options
);
1948 * Set up a console. Called via do_early_param() in init/main.c
1949 * for each "console=" parameter in the boot command line.
1951 static int __init
console_setup(char *str
)
1953 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
1954 char *s
, *options
, *brl_options
= NULL
;
1957 if (_braille_console_setup(&str
, &brl_options
))
1961 * Decode str into name, index, options.
1963 if (str
[0] >= '0' && str
[0] <= '9') {
1964 strcpy(buf
, "ttyS");
1965 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1967 strncpy(buf
, str
, sizeof(buf
) - 1);
1969 buf
[sizeof(buf
) - 1] = 0;
1970 options
= strchr(str
, ',');
1974 if (!strcmp(str
, "ttya"))
1975 strcpy(buf
, "ttyS0");
1976 if (!strcmp(str
, "ttyb"))
1977 strcpy(buf
, "ttyS1");
1979 for (s
= buf
; *s
; s
++)
1980 if (isdigit(*s
) || *s
== ',')
1982 idx
= simple_strtoul(s
, NULL
, 10);
1985 __add_preferred_console(buf
, idx
, options
, brl_options
);
1986 console_set_on_cmdline
= 1;
1989 __setup("console=", console_setup
);
1992 * add_preferred_console - add a device to the list of preferred consoles.
1993 * @name: device name
1994 * @idx: device index
1995 * @options: options for this console
1997 * The last preferred console added will be used for kernel messages
1998 * and stdin/out/err for init. Normally this is used by console_setup
1999 * above to handle user-supplied console arguments; however it can also
2000 * be used by arch-specific code either to override the user or more
2001 * commonly to provide a default console (ie from PROM variables) when
2002 * the user has not supplied one.
2004 int add_preferred_console(char *name
, int idx
, char *options
)
2006 return __add_preferred_console(name
, idx
, options
, NULL
);
2009 bool console_suspend_enabled
= true;
2010 EXPORT_SYMBOL(console_suspend_enabled
);
2012 static int __init
console_suspend_disable(char *str
)
2014 console_suspend_enabled
= false;
2017 __setup("no_console_suspend", console_suspend_disable
);
2018 module_param_named(console_suspend
, console_suspend_enabled
,
2019 bool, S_IRUGO
| S_IWUSR
);
2020 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2021 " and hibernate operations");
2024 * suspend_console - suspend the console subsystem
2026 * This disables printk() while we go into suspend states
2028 void suspend_console(void)
2030 if (!console_suspend_enabled
)
2032 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2034 console_suspended
= 1;
2038 void resume_console(void)
2040 if (!console_suspend_enabled
)
2043 console_suspended
= 0;
2048 * console_cpu_notify - print deferred console messages after CPU hotplug
2049 * @self: notifier struct
2050 * @action: CPU hotplug event
2053 * If printk() is called from a CPU that is not online yet, the messages
2054 * will be spooled but will not show up on the console. This function is
2055 * called when a new CPU comes online (or fails to come up), and ensures
2056 * that any such output gets printed.
2058 static int console_cpu_notify(struct notifier_block
*self
,
2059 unsigned long action
, void *hcpu
)
2064 case CPU_DOWN_FAILED
:
2065 case CPU_UP_CANCELED
:
2073 * console_lock - lock the console system for exclusive use.
2075 * Acquires a lock which guarantees that the caller has
2076 * exclusive access to the console system and the console_drivers list.
2078 * Can sleep, returns nothing.
2080 void console_lock(void)
2085 if (console_suspended
)
2088 console_may_schedule
= 1;
2090 EXPORT_SYMBOL(console_lock
);
2093 * console_trylock - try to lock the console system for exclusive use.
2095 * Try to acquire a lock which guarantees that the caller has exclusive
2096 * access to the console system and the console_drivers list.
2098 * returns 1 on success, and 0 on failure to acquire the lock.
2100 int console_trylock(void)
2102 if (down_trylock_console_sem())
2104 if (console_suspended
) {
2110 * When PREEMPT_COUNT disabled we can't reliably detect if it's
2111 * safe to schedule (e.g. calling printk while holding a spin_lock),
2112 * because preempt_disable()/preempt_enable() are just barriers there
2113 * and preempt_count() is always 0.
2115 * RCU read sections have a separate preemption counter when
2116 * PREEMPT_RCU enabled thus we must take extra care and check
2117 * rcu_preempt_depth(), otherwise RCU read sections modify
2120 console_may_schedule
= !oops_in_progress
&&
2122 !rcu_preempt_depth();
2125 EXPORT_SYMBOL(console_trylock
);
2127 int is_console_locked(void)
2129 return console_locked
;
2133 * Check if we have any console that is capable of printing while cpu is
2134 * booting or shutting down. Requires console_sem.
2136 static int have_callable_console(void)
2138 struct console
*con
;
2140 for_each_console(con
)
2141 if ((con
->flags
& CON_ENABLED
) &&
2142 (con
->flags
& CON_ANYTIME
))
2149 * Can we actually use the console at this time on this cpu?
2151 * Console drivers may assume that per-cpu resources have been allocated. So
2152 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2153 * call them until this CPU is officially up.
2155 static inline int can_use_console(void)
2157 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2160 static void console_cont_flush(char *text
, size_t size
)
2162 unsigned long flags
;
2165 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2171 * We still queue earlier records, likely because the console was
2172 * busy. The earlier ones need to be printed before this one, we
2173 * did not flush any fragment so far, so just let it queue up.
2175 if (console_seq
< log_next_seq
&& !cont
.cons
)
2178 len
= cont_print_text(text
, size
);
2179 raw_spin_unlock(&logbuf_lock
);
2180 stop_critical_timings();
2181 call_console_drivers(cont
.level
, NULL
, 0, text
, len
);
2182 start_critical_timings();
2183 local_irq_restore(flags
);
2186 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2190 * console_unlock - unlock the console system
2192 * Releases the console_lock which the caller holds on the console system
2193 * and the console driver list.
2195 * While the console_lock was held, console output may have been buffered
2196 * by printk(). If this is the case, console_unlock(); emits
2197 * the output prior to releasing the lock.
2199 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2201 * console_unlock(); may be called from any context.
2203 void console_unlock(void)
2205 static char ext_text
[CONSOLE_EXT_LOG_MAX
];
2206 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2207 static u64 seen_seq
;
2208 unsigned long flags
;
2209 bool wake_klogd
= false;
2210 bool do_cond_resched
, retry
;
2212 if (console_suspended
) {
2218 * Console drivers are called under logbuf_lock, so
2219 * @console_may_schedule should be cleared before; however, we may
2220 * end up dumping a lot of lines, for example, if called from
2221 * console registration path, and should invoke cond_resched()
2222 * between lines if allowable. Not doing so can cause a very long
2223 * scheduling stall on a slow console leading to RCU stall and
2224 * softlockup warnings which exacerbate the issue with more
2225 * messages practically incapacitating the system.
2227 do_cond_resched
= console_may_schedule
;
2228 console_may_schedule
= 0;
2232 * We released the console_sem lock, so we need to recheck if
2233 * cpu is online and (if not) is there at least one CON_ANYTIME
2236 if (!can_use_console()) {
2242 /* flush buffered message fragment immediately to console */
2243 console_cont_flush(text
, sizeof(text
));
2246 struct printk_log
*msg
;
2251 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2252 if (seen_seq
!= log_next_seq
) {
2254 seen_seq
= log_next_seq
;
2257 if (console_seq
< log_first_seq
) {
2258 len
= sprintf(text
, "** %u printk messages dropped ** ",
2259 (unsigned)(log_first_seq
- console_seq
));
2261 /* messages are gone, move to first one */
2262 console_seq
= log_first_seq
;
2263 console_idx
= log_first_idx
;
2269 if (console_seq
== log_next_seq
)
2272 msg
= log_from_idx(console_idx
);
2273 if (msg
->flags
& LOG_NOCONS
) {
2275 * Skip record we have buffered and already printed
2276 * directly to the console when we received it.
2278 console_idx
= log_next(console_idx
);
2281 * We will get here again when we register a new
2282 * CON_PRINTBUFFER console. Clear the flag so we
2283 * will properly dump everything later.
2285 msg
->flags
&= ~LOG_NOCONS
;
2286 console_prev
= msg
->flags
;
2291 len
+= msg_print_text(msg
, console_prev
, false,
2292 text
+ len
, sizeof(text
) - len
);
2293 if (nr_ext_console_drivers
) {
2294 ext_len
= msg_print_ext_header(ext_text
,
2296 msg
, console_seq
, console_prev
);
2297 ext_len
+= msg_print_ext_body(ext_text
+ ext_len
,
2298 sizeof(ext_text
) - ext_len
,
2299 log_dict(msg
), msg
->dict_len
,
2300 log_text(msg
), msg
->text_len
);
2302 console_idx
= log_next(console_idx
);
2304 console_prev
= msg
->flags
;
2305 raw_spin_unlock(&logbuf_lock
);
2307 stop_critical_timings(); /* don't trace print latency */
2308 call_console_drivers(level
, ext_text
, ext_len
, text
, len
);
2309 start_critical_timings();
2310 local_irq_restore(flags
);
2312 if (do_cond_resched
)
2317 /* Release the exclusive_console once it is used */
2318 if (unlikely(exclusive_console
))
2319 exclusive_console
= NULL
;
2321 raw_spin_unlock(&logbuf_lock
);
2326 * Someone could have filled up the buffer again, so re-check if there's
2327 * something to flush. In case we cannot trylock the console_sem again,
2328 * there's a new owner and the console_unlock() from them will do the
2329 * flush, no worries.
2331 raw_spin_lock(&logbuf_lock
);
2332 retry
= console_seq
!= log_next_seq
;
2333 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2335 if (retry
&& console_trylock())
2341 EXPORT_SYMBOL(console_unlock
);
2344 * console_conditional_schedule - yield the CPU if required
2346 * If the console code is currently allowed to sleep, and
2347 * if this CPU should yield the CPU to another task, do
2350 * Must be called within console_lock();.
2352 void __sched
console_conditional_schedule(void)
2354 if (console_may_schedule
)
2357 EXPORT_SYMBOL(console_conditional_schedule
);
2359 void console_unblank(void)
2364 * console_unblank can no longer be called in interrupt context unless
2365 * oops_in_progress is set to 1..
2367 if (oops_in_progress
) {
2368 if (down_trylock_console_sem() != 0)
2374 console_may_schedule
= 0;
2376 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2382 * console_flush_on_panic - flush console content on panic
2384 * Immediately output all pending messages no matter what.
2386 void console_flush_on_panic(void)
2389 * If someone else is holding the console lock, trylock will fail
2390 * and may_schedule may be set. Ignore and proceed to unlock so
2391 * that messages are flushed out. As this can be called from any
2392 * context and we don't want to get preempted while flushing,
2393 * ensure may_schedule is cleared.
2396 console_may_schedule
= 0;
2401 * Return the console tty driver structure and its associated index
2403 struct tty_driver
*console_device(int *index
)
2406 struct tty_driver
*driver
= NULL
;
2409 for_each_console(c
) {
2412 driver
= c
->device(c
, index
);
2421 * Prevent further output on the passed console device so that (for example)
2422 * serial drivers can disable console output before suspending a port, and can
2423 * re-enable output afterwards.
2425 void console_stop(struct console
*console
)
2428 console
->flags
&= ~CON_ENABLED
;
2431 EXPORT_SYMBOL(console_stop
);
2433 void console_start(struct console
*console
)
2436 console
->flags
|= CON_ENABLED
;
2439 EXPORT_SYMBOL(console_start
);
2441 static int __read_mostly keep_bootcon
;
2443 static int __init
keep_bootcon_setup(char *str
)
2446 pr_info("debug: skip boot console de-registration.\n");
2451 early_param("keep_bootcon", keep_bootcon_setup
);
2454 * The console driver calls this routine during kernel initialization
2455 * to register the console printing procedure with printk() and to
2456 * print any messages that were printed by the kernel before the
2457 * console driver was initialized.
2459 * This can happen pretty early during the boot process (because of
2460 * early_printk) - sometimes before setup_arch() completes - be careful
2461 * of what kernel features are used - they may not be initialised yet.
2463 * There are two types of consoles - bootconsoles (early_printk) and
2464 * "real" consoles (everything which is not a bootconsole) which are
2465 * handled differently.
2466 * - Any number of bootconsoles can be registered at any time.
2467 * - As soon as a "real" console is registered, all bootconsoles
2468 * will be unregistered automatically.
2469 * - Once a "real" console is registered, any attempt to register a
2470 * bootconsoles will be rejected
2472 void register_console(struct console
*newcon
)
2475 unsigned long flags
;
2476 struct console
*bcon
= NULL
;
2477 struct console_cmdline
*c
;
2479 if (console_drivers
)
2480 for_each_console(bcon
)
2481 if (WARN(bcon
== newcon
,
2482 "console '%s%d' already registered\n",
2483 bcon
->name
, bcon
->index
))
2487 * before we register a new CON_BOOT console, make sure we don't
2488 * already have a valid console
2490 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2491 /* find the last or real console */
2492 for_each_console(bcon
) {
2493 if (!(bcon
->flags
& CON_BOOT
)) {
2494 pr_info("Too late to register bootconsole %s%d\n",
2495 newcon
->name
, newcon
->index
);
2501 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2502 bcon
= console_drivers
;
2504 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2505 preferred_console
= selected_console
;
2508 * See if we want to use this console driver. If we
2509 * didn't select a console we take the first one
2510 * that registers here.
2512 if (preferred_console
< 0) {
2513 if (newcon
->index
< 0)
2515 if (newcon
->setup
== NULL
||
2516 newcon
->setup(newcon
, NULL
) == 0) {
2517 newcon
->flags
|= CON_ENABLED
;
2518 if (newcon
->device
) {
2519 newcon
->flags
|= CON_CONSDEV
;
2520 preferred_console
= 0;
2526 * See if this console matches one we selected on
2529 for (i
= 0, c
= console_cmdline
;
2530 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2532 if (!newcon
->match
||
2533 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2534 /* default matching */
2535 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2536 if (strcmp(c
->name
, newcon
->name
) != 0)
2538 if (newcon
->index
>= 0 &&
2539 newcon
->index
!= c
->index
)
2541 if (newcon
->index
< 0)
2542 newcon
->index
= c
->index
;
2544 if (_braille_register_console(newcon
, c
))
2547 if (newcon
->setup
&&
2548 newcon
->setup(newcon
, c
->options
) != 0)
2552 newcon
->flags
|= CON_ENABLED
;
2553 if (i
== selected_console
) {
2554 newcon
->flags
|= CON_CONSDEV
;
2555 preferred_console
= selected_console
;
2560 if (!(newcon
->flags
& CON_ENABLED
))
2564 * If we have a bootconsole, and are switching to a real console,
2565 * don't print everything out again, since when the boot console, and
2566 * the real console are the same physical device, it's annoying to
2567 * see the beginning boot messages twice
2569 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2570 newcon
->flags
&= ~CON_PRINTBUFFER
;
2573 * Put this console in the list - keep the
2574 * preferred driver at the head of the list.
2577 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2578 newcon
->next
= console_drivers
;
2579 console_drivers
= newcon
;
2581 newcon
->next
->flags
&= ~CON_CONSDEV
;
2583 newcon
->next
= console_drivers
->next
;
2584 console_drivers
->next
= newcon
;
2587 if (newcon
->flags
& CON_EXTENDED
)
2588 if (!nr_ext_console_drivers
++)
2589 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2591 if (newcon
->flags
& CON_PRINTBUFFER
) {
2593 * console_unlock(); will print out the buffered messages
2596 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2597 console_seq
= syslog_seq
;
2598 console_idx
= syslog_idx
;
2599 console_prev
= syslog_prev
;
2600 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2602 * We're about to replay the log buffer. Only do this to the
2603 * just-registered console to avoid excessive message spam to
2604 * the already-registered consoles.
2606 exclusive_console
= newcon
;
2609 console_sysfs_notify();
2612 * By unregistering the bootconsoles after we enable the real console
2613 * we get the "console xxx enabled" message on all the consoles -
2614 * boot consoles, real consoles, etc - this is to ensure that end
2615 * users know there might be something in the kernel's log buffer that
2616 * went to the bootconsole (that they do not see on the real console)
2618 pr_info("%sconsole [%s%d] enabled\n",
2619 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2620 newcon
->name
, newcon
->index
);
2622 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2624 /* We need to iterate through all boot consoles, to make
2625 * sure we print everything out, before we unregister them.
2627 for_each_console(bcon
)
2628 if (bcon
->flags
& CON_BOOT
)
2629 unregister_console(bcon
);
2632 EXPORT_SYMBOL(register_console
);
2634 int unregister_console(struct console
*console
)
2636 struct console
*a
, *b
;
2639 pr_info("%sconsole [%s%d] disabled\n",
2640 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2641 console
->name
, console
->index
);
2643 res
= _braille_unregister_console(console
);
2649 if (console_drivers
== console
) {
2650 console_drivers
=console
->next
;
2652 } else if (console_drivers
) {
2653 for (a
=console_drivers
->next
, b
=console_drivers
;
2654 a
; b
=a
, a
=b
->next
) {
2663 if (!res
&& (console
->flags
& CON_EXTENDED
))
2664 nr_ext_console_drivers
--;
2667 * If this isn't the last console and it has CON_CONSDEV set, we
2668 * need to set it on the next preferred console.
2670 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2671 console_drivers
->flags
|= CON_CONSDEV
;
2673 console
->flags
&= ~CON_ENABLED
;
2675 console_sysfs_notify();
2678 EXPORT_SYMBOL(unregister_console
);
2681 * Some boot consoles access data that is in the init section and which will
2682 * be discarded after the initcalls have been run. To make sure that no code
2683 * will access this data, unregister the boot consoles in a late initcall.
2685 * If for some reason, such as deferred probe or the driver being a loadable
2686 * module, the real console hasn't registered yet at this point, there will
2687 * be a brief interval in which no messages are logged to the console, which
2688 * makes it difficult to diagnose problems that occur during this time.
2690 * To mitigate this problem somewhat, only unregister consoles whose memory
2691 * intersects with the init section. Note that code exists elsewhere to get
2692 * rid of the boot console as soon as the proper console shows up, so there
2693 * won't be side-effects from postponing the removal.
2695 static int __init
printk_late_init(void)
2697 struct console
*con
;
2699 for_each_console(con
) {
2700 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2702 * Make sure to unregister boot consoles whose data
2703 * resides in the init section before the init section
2704 * is discarded. Boot consoles whose data will stick
2705 * around will automatically be unregistered when the
2706 * proper console replaces them.
2708 if (init_section_intersects(con
, sizeof(*con
)))
2709 unregister_console(con
);
2712 hotcpu_notifier(console_cpu_notify
, 0);
2715 late_initcall(printk_late_init
);
2717 #if defined CONFIG_PRINTK
2719 * Delayed printk version, for scheduler-internal messages:
2721 #define PRINTK_PENDING_WAKEUP 0x01
2722 #define PRINTK_PENDING_OUTPUT 0x02
2724 static DEFINE_PER_CPU(int, printk_pending
);
2726 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2728 int pending
= __this_cpu_xchg(printk_pending
, 0);
2730 if (pending
& PRINTK_PENDING_OUTPUT
) {
2731 /* If trylock fails, someone else is doing the printing */
2732 if (console_trylock())
2736 if (pending
& PRINTK_PENDING_WAKEUP
)
2737 wake_up_interruptible(&log_wait
);
2740 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2741 .func
= wake_up_klogd_work_func
,
2742 .flags
= IRQ_WORK_LAZY
,
2745 void wake_up_klogd(void)
2748 if (waitqueue_active(&log_wait
)) {
2749 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2750 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2755 int printk_deferred(const char *fmt
, ...)
2761 va_start(args
, fmt
);
2762 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2765 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2766 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2773 * printk rate limiting, lifted from the networking subsystem.
2775 * This enforces a rate limit: not more than 10 kernel messages
2776 * every 5s to make a denial-of-service attack impossible.
2778 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2780 int __printk_ratelimit(const char *func
)
2782 return ___ratelimit(&printk_ratelimit_state
, func
);
2784 EXPORT_SYMBOL(__printk_ratelimit
);
2787 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2788 * @caller_jiffies: pointer to caller's state
2789 * @interval_msecs: minimum interval between prints
2791 * printk_timed_ratelimit() returns true if more than @interval_msecs
2792 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2795 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2796 unsigned int interval_msecs
)
2798 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2800 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2803 *caller_jiffies
= jiffies
;
2806 EXPORT_SYMBOL(printk_timed_ratelimit
);
2808 static DEFINE_SPINLOCK(dump_list_lock
);
2809 static LIST_HEAD(dump_list
);
2812 * kmsg_dump_register - register a kernel log dumper.
2813 * @dumper: pointer to the kmsg_dumper structure
2815 * Adds a kernel log dumper to the system. The dump callback in the
2816 * structure will be called when the kernel oopses or panics and must be
2817 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2819 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2821 unsigned long flags
;
2824 /* The dump callback needs to be set */
2828 spin_lock_irqsave(&dump_list_lock
, flags
);
2829 /* Don't allow registering multiple times */
2830 if (!dumper
->registered
) {
2831 dumper
->registered
= 1;
2832 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2835 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2839 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2842 * kmsg_dump_unregister - unregister a kmsg dumper.
2843 * @dumper: pointer to the kmsg_dumper structure
2845 * Removes a dump device from the system. Returns zero on success and
2846 * %-EINVAL otherwise.
2848 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2850 unsigned long flags
;
2853 spin_lock_irqsave(&dump_list_lock
, flags
);
2854 if (dumper
->registered
) {
2855 dumper
->registered
= 0;
2856 list_del_rcu(&dumper
->list
);
2859 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2864 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2866 static bool always_kmsg_dump
;
2867 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2870 * kmsg_dump - dump kernel log to kernel message dumpers.
2871 * @reason: the reason (oops, panic etc) for dumping
2873 * Call each of the registered dumper's dump() callback, which can
2874 * retrieve the kmsg records with kmsg_dump_get_line() or
2875 * kmsg_dump_get_buffer().
2877 void kmsg_dump(enum kmsg_dump_reason reason
)
2879 struct kmsg_dumper
*dumper
;
2880 unsigned long flags
;
2882 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2886 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2887 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2890 /* initialize iterator with data about the stored records */
2891 dumper
->active
= true;
2893 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2894 dumper
->cur_seq
= clear_seq
;
2895 dumper
->cur_idx
= clear_idx
;
2896 dumper
->next_seq
= log_next_seq
;
2897 dumper
->next_idx
= log_next_idx
;
2898 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2900 /* invoke dumper which will iterate over records */
2901 dumper
->dump(dumper
, reason
);
2903 /* reset iterator */
2904 dumper
->active
= false;
2910 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2911 * @dumper: registered kmsg dumper
2912 * @syslog: include the "<4>" prefixes
2913 * @line: buffer to copy the line to
2914 * @size: maximum size of the buffer
2915 * @len: length of line placed into buffer
2917 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2918 * record, and copy one record into the provided buffer.
2920 * Consecutive calls will return the next available record moving
2921 * towards the end of the buffer with the youngest messages.
2923 * A return value of FALSE indicates that there are no more records to
2926 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2928 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
2929 char *line
, size_t size
, size_t *len
)
2931 struct printk_log
*msg
;
2935 if (!dumper
->active
)
2938 if (dumper
->cur_seq
< log_first_seq
) {
2939 /* messages are gone, move to first available one */
2940 dumper
->cur_seq
= log_first_seq
;
2941 dumper
->cur_idx
= log_first_idx
;
2945 if (dumper
->cur_seq
>= log_next_seq
)
2948 msg
= log_from_idx(dumper
->cur_idx
);
2949 l
= msg_print_text(msg
, 0, syslog
, line
, size
);
2951 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2961 * kmsg_dump_get_line - retrieve one kmsg log line
2962 * @dumper: registered kmsg dumper
2963 * @syslog: include the "<4>" prefixes
2964 * @line: buffer to copy the line to
2965 * @size: maximum size of the buffer
2966 * @len: length of line placed into buffer
2968 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2969 * record, and copy one record into the provided buffer.
2971 * Consecutive calls will return the next available record moving
2972 * towards the end of the buffer with the youngest messages.
2974 * A return value of FALSE indicates that there are no more records to
2977 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2978 char *line
, size_t size
, size_t *len
)
2980 unsigned long flags
;
2983 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2984 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
2985 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2989 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
2992 * kmsg_dump_get_buffer - copy kmsg log lines
2993 * @dumper: registered kmsg dumper
2994 * @syslog: include the "<4>" prefixes
2995 * @buf: buffer to copy the line to
2996 * @size: maximum size of the buffer
2997 * @len: length of line placed into buffer
2999 * Start at the end of the kmsg buffer and fill the provided buffer
3000 * with as many of the the *youngest* kmsg records that fit into it.
3001 * If the buffer is large enough, all available kmsg records will be
3002 * copied with a single call.
3004 * Consecutive calls will fill the buffer with the next block of
3005 * available older records, not including the earlier retrieved ones.
3007 * A return value of FALSE indicates that there are no more records to
3010 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
3011 char *buf
, size_t size
, size_t *len
)
3013 unsigned long flags
;
3018 enum log_flags prev
;
3022 if (!dumper
->active
)
3025 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3026 if (dumper
->cur_seq
< log_first_seq
) {
3027 /* messages are gone, move to first available one */
3028 dumper
->cur_seq
= log_first_seq
;
3029 dumper
->cur_idx
= log_first_idx
;
3033 if (dumper
->cur_seq
>= dumper
->next_seq
) {
3034 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3038 /* calculate length of entire buffer */
3039 seq
= dumper
->cur_seq
;
3040 idx
= dumper
->cur_idx
;
3042 while (seq
< dumper
->next_seq
) {
3043 struct printk_log
*msg
= log_from_idx(idx
);
3045 l
+= msg_print_text(msg
, prev
, true, NULL
, 0);
3046 idx
= log_next(idx
);
3051 /* move first record forward until length fits into the buffer */
3052 seq
= dumper
->cur_seq
;
3053 idx
= dumper
->cur_idx
;
3055 while (l
> size
&& seq
< dumper
->next_seq
) {
3056 struct printk_log
*msg
= log_from_idx(idx
);
3058 l
-= msg_print_text(msg
, prev
, true, NULL
, 0);
3059 idx
= log_next(idx
);
3064 /* last message in next interation */
3069 while (seq
< dumper
->next_seq
) {
3070 struct printk_log
*msg
= log_from_idx(idx
);
3072 l
+= msg_print_text(msg
, prev
, syslog
, buf
+ l
, size
- l
);
3073 idx
= log_next(idx
);
3078 dumper
->next_seq
= next_seq
;
3079 dumper
->next_idx
= next_idx
;
3081 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3087 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
3090 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3091 * @dumper: registered kmsg dumper
3093 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3094 * kmsg_dump_get_buffer() can be called again and used multiple
3095 * times within the same dumper.dump() callback.
3097 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3099 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3101 dumper
->cur_seq
= clear_seq
;
3102 dumper
->cur_idx
= clear_idx
;
3103 dumper
->next_seq
= log_next_seq
;
3104 dumper
->next_idx
= log_next_idx
;
3108 * kmsg_dump_rewind - reset the interator
3109 * @dumper: registered kmsg dumper
3111 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3112 * kmsg_dump_get_buffer() can be called again and used multiple
3113 * times within the same dumper.dump() callback.
3115 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3117 unsigned long flags
;
3119 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3120 kmsg_dump_rewind_nolock(dumper
);
3121 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3123 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3125 static char dump_stack_arch_desc_str
[128];
3128 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3129 * @fmt: printf-style format string
3130 * @...: arguments for the format string
3132 * The configured string will be printed right after utsname during task
3133 * dumps. Usually used to add arch-specific system identifiers. If an
3134 * arch wants to make use of such an ID string, it should initialize this
3135 * as soon as possible during boot.
3137 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3141 va_start(args
, fmt
);
3142 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3148 * dump_stack_print_info - print generic debug info for dump_stack()
3149 * @log_lvl: log level
3151 * Arch-specific dump_stack() implementations can use this function to
3152 * print out the same debug information as the generic dump_stack().
3154 void dump_stack_print_info(const char *log_lvl
)
3156 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3157 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3158 print_tainted(), init_utsname()->release
,
3159 (int)strcspn(init_utsname()->version
, " "),
3160 init_utsname()->version
);
3162 if (dump_stack_arch_desc_str
[0] != '\0')
3163 printk("%sHardware name: %s\n",
3164 log_lvl
, dump_stack_arch_desc_str
);
3166 print_worker_info(log_lvl
, current
);
3170 * show_regs_print_info - print generic debug info for show_regs()
3171 * @log_lvl: log level
3173 * show_regs() implementations can use this function to print out generic
3174 * debug information.
3176 void show_regs_print_info(const char *log_lvl
)
3178 dump_stack_print_info(log_lvl
);
3180 printk("%stask: %p ti: %p task.ti: %p\n",
3181 log_lvl
, current
, current_thread_info(),
3182 task_thread_info(current
));