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"
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 */
239 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
240 * within the scheduler's rq lock. It must be released before calling
241 * console_unlock() or anything else that might wake up a process.
243 static DEFINE_RAW_SPINLOCK(logbuf_lock
);
246 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
247 /* the next printk record to read by syslog(READ) or /proc/kmsg */
248 static u64 syslog_seq
;
249 static u32 syslog_idx
;
250 static enum log_flags syslog_prev
;
251 static size_t syslog_partial
;
253 /* index and sequence number of the first record stored in the buffer */
254 static u64 log_first_seq
;
255 static u32 log_first_idx
;
257 /* index and sequence number of the next record to store in the buffer */
258 static u64 log_next_seq
;
259 static u32 log_next_idx
;
261 /* the next printk record to write to the console */
262 static u64 console_seq
;
263 static u32 console_idx
;
264 static enum log_flags console_prev
;
266 /* the next printk record to read after the last 'clear' command */
267 static u64 clear_seq
;
268 static u32 clear_idx
;
270 #define PREFIX_MAX 32
271 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
273 #define LOG_LEVEL(v) ((v) & 0x07)
274 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
277 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
280 #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 if (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 /* sequence numbers are equal, so the log buffer is empty */
379 if (logbuf_has_space(msg_size
, true))
385 /* compute the message size including the padding bytes */
386 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
390 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
391 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
398 * Define how much of the log buffer we could take at maximum. The value
399 * must be greater than two. Note that only half of the buffer is available
400 * when the index points to the middle.
402 #define MAX_LOG_TAKE_PART 4
403 static const char trunc_msg
[] = "<truncated>";
405 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
406 u16
*dict_len
, u32
*pad_len
)
409 * The message should not take the whole buffer. Otherwise, it might
410 * get removed too soon.
412 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
413 if (*text_len
> max_text_len
)
414 *text_len
= max_text_len
;
415 /* enable the warning message */
416 *trunc_msg_len
= strlen(trunc_msg
);
417 /* disable the "dict" completely */
419 /* compute the size again, count also the warning message */
420 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
423 /* insert record into the buffer, discard old ones, update heads */
424 static int log_store(int facility
, int level
,
425 enum log_flags flags
, u64 ts_nsec
,
426 const char *dict
, u16 dict_len
,
427 const char *text
, u16 text_len
)
429 struct printk_log
*msg
;
431 u16 trunc_msg_len
= 0;
433 /* number of '\0' padding bytes to next message */
434 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
436 if (log_make_free_space(size
)) {
437 /* truncate the message if it is too long for empty buffer */
438 size
= truncate_msg(&text_len
, &trunc_msg_len
,
439 &dict_len
, &pad_len
);
440 /* survive when the log buffer is too small for trunc_msg */
441 if (log_make_free_space(size
))
445 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
447 * This message + an additional empty header does not fit
448 * at the end of the buffer. Add an empty header with len == 0
449 * to signify a wrap around.
451 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
456 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
457 memcpy(log_text(msg
), text
, text_len
);
458 msg
->text_len
= text_len
;
460 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
461 msg
->text_len
+= trunc_msg_len
;
463 memcpy(log_dict(msg
), dict
, dict_len
);
464 msg
->dict_len
= dict_len
;
465 msg
->facility
= facility
;
466 msg
->level
= level
& 7;
467 msg
->flags
= flags
& 0x1f;
469 msg
->ts_nsec
= ts_nsec
;
471 msg
->ts_nsec
= local_clock();
472 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
476 log_next_idx
+= msg
->len
;
479 return msg
->text_len
;
482 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
484 static int syslog_action_restricted(int type
)
489 * Unless restricted, we allow "read all" and "get buffer size"
492 return type
!= SYSLOG_ACTION_READ_ALL
&&
493 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
496 int check_syslog_permissions(int type
, int source
)
499 * If this is from /proc/kmsg and we've already opened it, then we've
500 * already done the capabilities checks at open time.
502 if (source
== SYSLOG_FROM_PROC
&& type
!= SYSLOG_ACTION_OPEN
)
505 if (syslog_action_restricted(type
)) {
506 if (capable(CAP_SYSLOG
))
509 * For historical reasons, accept CAP_SYS_ADMIN too, with
512 if (capable(CAP_SYS_ADMIN
)) {
513 pr_warn_once("%s (%d): Attempt to access syslog with "
514 "CAP_SYS_ADMIN but no CAP_SYSLOG "
516 current
->comm
, task_pid_nr(current
));
522 return security_syslog(type
);
524 EXPORT_SYMBOL_GPL(check_syslog_permissions
);
526 static void append_char(char **pp
, char *e
, char c
)
532 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
533 struct printk_log
*msg
, u64 seq
,
534 enum log_flags prev_flags
)
536 u64 ts_usec
= msg
->ts_nsec
;
539 do_div(ts_usec
, 1000);
542 * If we couldn't merge continuation line fragments during the print,
543 * export the stored flags to allow an optional external merge of the
544 * records. Merging the records isn't always neccessarily correct, like
545 * when we hit a race during printing. In most cases though, it produces
546 * better readable output. 'c' in the record flags mark the first
547 * fragment of a line, '+' the following.
549 if (msg
->flags
& LOG_CONT
&& !(prev_flags
& LOG_CONT
))
551 else if ((msg
->flags
& LOG_CONT
) ||
552 ((prev_flags
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
)))
555 return scnprintf(buf
, size
, "%u,%llu,%llu,%c;",
556 (msg
->facility
<< 3) | msg
->level
, seq
, ts_usec
, cont
);
559 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
560 char *dict
, size_t dict_len
,
561 char *text
, size_t text_len
)
563 char *p
= buf
, *e
= buf
+ size
;
566 /* escape non-printable characters */
567 for (i
= 0; i
< text_len
; i
++) {
568 unsigned char c
= text
[i
];
570 if (c
< ' ' || c
>= 127 || c
== '\\')
571 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
573 append_char(&p
, e
, c
);
575 append_char(&p
, e
, '\n');
580 for (i
= 0; i
< dict_len
; i
++) {
581 unsigned char c
= dict
[i
];
584 append_char(&p
, e
, ' ');
589 append_char(&p
, e
, '\n');
594 if (c
< ' ' || c
>= 127 || c
== '\\') {
595 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
599 append_char(&p
, e
, c
);
601 append_char(&p
, e
, '\n');
607 /* /dev/kmsg - userspace message inject/listen interface */
608 struct devkmsg_user
{
613 char buf
[CONSOLE_EXT_LOG_MAX
];
616 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
619 int level
= default_message_loglevel
;
620 int facility
= 1; /* LOG_USER */
621 size_t len
= iov_iter_count(from
);
624 if (len
> LOG_LINE_MAX
)
626 buf
= kmalloc(len
+1, GFP_KERNEL
);
631 if (copy_from_iter(buf
, len
, from
) != len
) {
637 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
638 * the decimal value represents 32bit, the lower 3 bit are the log
639 * level, the rest are the log facility.
641 * If no prefix or no userspace facility is specified, we
642 * enforce LOG_USER, to be able to reliably distinguish
643 * kernel-generated messages from userspace-injected ones.
646 if (line
[0] == '<') {
650 u
= simple_strtoul(line
+ 1, &endp
, 10);
651 if (endp
&& endp
[0] == '>') {
652 level
= LOG_LEVEL(u
);
653 if (LOG_FACILITY(u
) != 0)
654 facility
= LOG_FACILITY(u
);
661 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
666 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
667 size_t count
, loff_t
*ppos
)
669 struct devkmsg_user
*user
= file
->private_data
;
670 struct printk_log
*msg
;
677 ret
= mutex_lock_interruptible(&user
->lock
);
680 raw_spin_lock_irq(&logbuf_lock
);
681 while (user
->seq
== log_next_seq
) {
682 if (file
->f_flags
& O_NONBLOCK
) {
684 raw_spin_unlock_irq(&logbuf_lock
);
688 raw_spin_unlock_irq(&logbuf_lock
);
689 ret
= wait_event_interruptible(log_wait
,
690 user
->seq
!= log_next_seq
);
693 raw_spin_lock_irq(&logbuf_lock
);
696 if (user
->seq
< log_first_seq
) {
697 /* our last seen message is gone, return error and reset */
698 user
->idx
= log_first_idx
;
699 user
->seq
= log_first_seq
;
701 raw_spin_unlock_irq(&logbuf_lock
);
705 msg
= log_from_idx(user
->idx
);
706 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
707 msg
, user
->seq
, user
->prev
);
708 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
709 log_dict(msg
), msg
->dict_len
,
710 log_text(msg
), msg
->text_len
);
712 user
->prev
= msg
->flags
;
713 user
->idx
= log_next(user
->idx
);
715 raw_spin_unlock_irq(&logbuf_lock
);
722 if (copy_to_user(buf
, user
->buf
, len
)) {
728 mutex_unlock(&user
->lock
);
732 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
734 struct devkmsg_user
*user
= file
->private_data
;
742 raw_spin_lock_irq(&logbuf_lock
);
745 /* the first record */
746 user
->idx
= log_first_idx
;
747 user
->seq
= log_first_seq
;
751 * The first record after the last SYSLOG_ACTION_CLEAR,
752 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
753 * changes no global state, and does not clear anything.
755 user
->idx
= clear_idx
;
756 user
->seq
= clear_seq
;
759 /* after the last record */
760 user
->idx
= log_next_idx
;
761 user
->seq
= log_next_seq
;
766 raw_spin_unlock_irq(&logbuf_lock
);
770 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
772 struct devkmsg_user
*user
= file
->private_data
;
776 return POLLERR
|POLLNVAL
;
778 poll_wait(file
, &log_wait
, wait
);
780 raw_spin_lock_irq(&logbuf_lock
);
781 if (user
->seq
< log_next_seq
) {
782 /* return error when data has vanished underneath us */
783 if (user
->seq
< log_first_seq
)
784 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
786 ret
= POLLIN
|POLLRDNORM
;
788 raw_spin_unlock_irq(&logbuf_lock
);
793 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
795 struct devkmsg_user
*user
;
798 /* write-only does not need any file context */
799 if ((file
->f_flags
& O_ACCMODE
) == O_WRONLY
)
802 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
807 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
811 mutex_init(&user
->lock
);
813 raw_spin_lock_irq(&logbuf_lock
);
814 user
->idx
= log_first_idx
;
815 user
->seq
= log_first_seq
;
816 raw_spin_unlock_irq(&logbuf_lock
);
818 file
->private_data
= user
;
822 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
824 struct devkmsg_user
*user
= file
->private_data
;
829 mutex_destroy(&user
->lock
);
834 const struct file_operations kmsg_fops
= {
835 .open
= devkmsg_open
,
836 .read
= devkmsg_read
,
837 .write_iter
= devkmsg_write
,
838 .llseek
= devkmsg_llseek
,
839 .poll
= devkmsg_poll
,
840 .release
= devkmsg_release
,
843 #ifdef CONFIG_KEXEC_CORE
845 * This appends the listed symbols to /proc/vmcore
847 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
848 * obtain access to symbols that are otherwise very difficult to locate. These
849 * symbols are specifically used so that utilities can access and extract the
850 * dmesg log from a vmcore file after a crash.
852 void log_buf_kexec_setup(void)
854 VMCOREINFO_SYMBOL(log_buf
);
855 VMCOREINFO_SYMBOL(log_buf_len
);
856 VMCOREINFO_SYMBOL(log_first_idx
);
857 VMCOREINFO_SYMBOL(log_next_idx
);
859 * Export struct printk_log size and field offsets. User space tools can
860 * parse it and detect any changes to structure down the line.
862 VMCOREINFO_STRUCT_SIZE(printk_log
);
863 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
864 VMCOREINFO_OFFSET(printk_log
, len
);
865 VMCOREINFO_OFFSET(printk_log
, text_len
);
866 VMCOREINFO_OFFSET(printk_log
, dict_len
);
870 /* requested log_buf_len from kernel cmdline */
871 static unsigned long __initdata new_log_buf_len
;
873 /* we practice scaling the ring buffer by powers of 2 */
874 static void __init
log_buf_len_update(unsigned size
)
877 size
= roundup_pow_of_two(size
);
878 if (size
> log_buf_len
)
879 new_log_buf_len
= size
;
882 /* save requested log_buf_len since it's too early to process it */
883 static int __init
log_buf_len_setup(char *str
)
885 unsigned size
= memparse(str
, &str
);
887 log_buf_len_update(size
);
891 early_param("log_buf_len", log_buf_len_setup
);
894 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
896 static void __init
log_buf_add_cpu(void)
898 unsigned int cpu_extra
;
901 * archs should set up cpu_possible_bits properly with
902 * set_cpu_possible() after setup_arch() but just in
903 * case lets ensure this is valid.
905 if (num_possible_cpus() == 1)
908 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
910 /* by default this will only continue through for large > 64 CPUs */
911 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
914 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
915 __LOG_CPU_MAX_BUF_LEN
);
916 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
918 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
920 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
922 #else /* !CONFIG_SMP */
923 static inline void log_buf_add_cpu(void) {}
924 #endif /* CONFIG_SMP */
926 void __init
setup_log_buf(int early
)
932 if (log_buf
!= __log_buf
)
935 if (!early
&& !new_log_buf_len
)
938 if (!new_log_buf_len
)
943 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
945 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
949 if (unlikely(!new_log_buf
)) {
950 pr_err("log_buf_len: %ld bytes not available\n",
955 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
956 log_buf_len
= new_log_buf_len
;
957 log_buf
= new_log_buf
;
959 free
= __LOG_BUF_LEN
- log_next_idx
;
960 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
961 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
963 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
964 pr_info("early log buf free: %d(%d%%)\n",
965 free
, (free
* 100) / __LOG_BUF_LEN
);
968 static bool __read_mostly ignore_loglevel
;
970 static int __init
ignore_loglevel_setup(char *str
)
972 ignore_loglevel
= true;
973 pr_info("debug: ignoring loglevel setting.\n");
978 early_param("ignore_loglevel", ignore_loglevel_setup
);
979 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
980 MODULE_PARM_DESC(ignore_loglevel
,
981 "ignore loglevel setting (prints all kernel messages to the console)");
983 #ifdef CONFIG_BOOT_PRINTK_DELAY
985 static int boot_delay
; /* msecs delay after each printk during bootup */
986 static unsigned long long loops_per_msec
; /* based on boot_delay */
988 static int __init
boot_delay_setup(char *str
)
992 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
993 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
995 get_option(&str
, &boot_delay
);
996 if (boot_delay
> 10 * 1000)
999 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1000 "HZ: %d, loops_per_msec: %llu\n",
1001 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
1004 early_param("boot_delay", boot_delay_setup
);
1006 static void boot_delay_msec(int level
)
1008 unsigned long long k
;
1009 unsigned long timeout
;
1011 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
1012 || (level
>= console_loglevel
&& !ignore_loglevel
)) {
1016 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1018 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1023 * use (volatile) jiffies to prevent
1024 * compiler reduction; loop termination via jiffies
1025 * is secondary and may or may not happen.
1027 if (time_after(jiffies
, timeout
))
1029 touch_nmi_watchdog();
1033 static inline void boot_delay_msec(int level
)
1038 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1039 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1041 static size_t print_time(u64 ts
, char *buf
)
1043 unsigned long rem_nsec
;
1048 rem_nsec
= do_div(ts
, 1000000000);
1051 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1053 return sprintf(buf
, "[%5lu.%06lu] ",
1054 (unsigned long)ts
, rem_nsec
/ 1000);
1057 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1060 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1064 len
+= sprintf(buf
, "<%u>", prefix
);
1069 else if (prefix
> 99)
1071 else if (prefix
> 9)
1076 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1080 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1081 bool syslog
, char *buf
, size_t size
)
1083 const char *text
= log_text(msg
);
1084 size_t text_size
= msg
->text_len
;
1086 bool newline
= true;
1089 if ((prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
))
1092 if (msg
->flags
& LOG_CONT
) {
1093 if ((prev
& LOG_CONT
) && !(prev
& LOG_NEWLINE
))
1096 if (!(msg
->flags
& LOG_NEWLINE
))
1101 const char *next
= memchr(text
, '\n', text_size
);
1105 text_len
= next
- text
;
1107 text_size
-= next
- text
;
1109 text_len
= text_size
;
1113 if (print_prefix(msg
, syslog
, NULL
) +
1114 text_len
+ 1 >= size
- len
)
1118 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1119 memcpy(buf
+ len
, text
, text_len
);
1121 if (next
|| newline
)
1124 /* SYSLOG_ACTION_* buffer size only calculation */
1126 len
+= print_prefix(msg
, syslog
, NULL
);
1128 if (next
|| newline
)
1139 static int syslog_print(char __user
*buf
, int size
)
1142 struct printk_log
*msg
;
1145 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1153 raw_spin_lock_irq(&logbuf_lock
);
1154 if (syslog_seq
< log_first_seq
) {
1155 /* messages are gone, move to first one */
1156 syslog_seq
= log_first_seq
;
1157 syslog_idx
= log_first_idx
;
1161 if (syslog_seq
== log_next_seq
) {
1162 raw_spin_unlock_irq(&logbuf_lock
);
1166 skip
= syslog_partial
;
1167 msg
= log_from_idx(syslog_idx
);
1168 n
= msg_print_text(msg
, syslog_prev
, true, text
,
1169 LOG_LINE_MAX
+ PREFIX_MAX
);
1170 if (n
- syslog_partial
<= size
) {
1171 /* message fits into buffer, move forward */
1172 syslog_idx
= log_next(syslog_idx
);
1174 syslog_prev
= msg
->flags
;
1175 n
-= syslog_partial
;
1178 /* partial read(), remember position */
1180 syslog_partial
+= n
;
1183 raw_spin_unlock_irq(&logbuf_lock
);
1188 if (copy_to_user(buf
, text
+ skip
, n
)) {
1203 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1208 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1212 raw_spin_lock_irq(&logbuf_lock
);
1217 enum log_flags prev
;
1219 if (clear_seq
< log_first_seq
) {
1220 /* messages are gone, move to first available one */
1221 clear_seq
= log_first_seq
;
1222 clear_idx
= log_first_idx
;
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);
1487 * Check if we have any console that is capable of printing while cpu is
1488 * booting or shutting down. Requires console_sem.
1490 static int have_callable_console(void)
1492 struct console
*con
;
1494 for_each_console(con
)
1495 if (con
->flags
& CON_ANYTIME
)
1502 * Can we actually use the console at this time on this cpu?
1504 * Console drivers may assume that per-cpu resources have been allocated. So
1505 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1506 * call them until this CPU is officially up.
1508 static inline int can_use_console(unsigned int cpu
)
1510 return cpu_online(cpu
) || have_callable_console();
1514 * Try to get console ownership to actually show the kernel
1515 * messages from a 'printk'. Return true (and with the
1516 * console_lock held, and 'console_locked' set) if it
1517 * is successful, false otherwise.
1519 static int console_trylock_for_printk(void)
1521 unsigned int cpu
= smp_processor_id();
1523 if (!console_trylock())
1526 * If we can't use the console, we need to release the console
1527 * semaphore by hand to avoid flushing the buffer. We need to hold the
1528 * console semaphore in order to do this test safely.
1530 if (!can_use_console(cpu
)) {
1538 int printk_delay_msec __read_mostly
;
1540 static inline void printk_delay(void)
1542 if (unlikely(printk_delay_msec
)) {
1543 int m
= printk_delay_msec
;
1547 touch_nmi_watchdog();
1553 * Continuation lines are buffered, and not committed to the record buffer
1554 * until the line is complete, or a race forces it. The line fragments
1555 * though, are printed immediately to the consoles to ensure everything has
1556 * reached the console in case of a kernel crash.
1558 static struct cont
{
1559 char buf
[LOG_LINE_MAX
];
1560 size_t len
; /* length == 0 means unused buffer */
1561 size_t cons
; /* bytes written to console */
1562 struct task_struct
*owner
; /* task of first print*/
1563 u64 ts_nsec
; /* time of first print */
1564 u8 level
; /* log level of first message */
1565 u8 facility
; /* log facility of first message */
1566 enum log_flags flags
; /* prefix, newline flags */
1567 bool flushed
:1; /* buffer sealed and committed */
1570 static void cont_flush(enum log_flags flags
)
1579 * If a fragment of this line was directly flushed to the
1580 * console; wait for the console to pick up the rest of the
1581 * line. LOG_NOCONS suppresses a duplicated output.
1583 log_store(cont
.facility
, cont
.level
, flags
| LOG_NOCONS
,
1584 cont
.ts_nsec
, NULL
, 0, cont
.buf
, cont
.len
);
1586 cont
.flushed
= true;
1589 * If no fragment of this line ever reached the console,
1590 * just submit it to the store and free the buffer.
1592 log_store(cont
.facility
, cont
.level
, flags
, 0,
1593 NULL
, 0, cont
.buf
, cont
.len
);
1598 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1600 if (cont
.len
&& cont
.flushed
)
1604 * If ext consoles are present, flush and skip in-kernel
1605 * continuation. See nr_ext_console_drivers definition. Also, if
1606 * the line gets too long, split it up in separate records.
1608 if (nr_ext_console_drivers
|| cont
.len
+ len
> sizeof(cont
.buf
)) {
1609 cont_flush(LOG_CONT
);
1614 cont
.facility
= facility
;
1616 cont
.owner
= current
;
1617 cont
.ts_nsec
= local_clock();
1620 cont
.flushed
= false;
1623 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1626 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1627 cont_flush(LOG_CONT
);
1632 static size_t cont_print_text(char *text
, size_t size
)
1637 if (cont
.cons
== 0 && (console_prev
& LOG_NEWLINE
)) {
1638 textlen
+= print_time(cont
.ts_nsec
, text
);
1642 len
= cont
.len
- cont
.cons
;
1646 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1648 cont
.cons
= cont
.len
;
1652 if (cont
.flags
& LOG_NEWLINE
)
1653 text
[textlen
++] = '\n';
1654 /* got everything, release buffer */
1660 asmlinkage
int vprintk_emit(int facility
, int level
,
1661 const char *dict
, size_t dictlen
,
1662 const char *fmt
, va_list args
)
1664 static bool recursion_bug
;
1665 static char textbuf
[LOG_LINE_MAX
];
1666 char *text
= textbuf
;
1667 size_t text_len
= 0;
1668 enum log_flags lflags
= 0;
1669 unsigned long flags
;
1671 int printed_len
= 0;
1672 bool in_sched
= false;
1673 /* cpu currently holding logbuf_lock in this function */
1674 static unsigned int logbuf_cpu
= UINT_MAX
;
1676 if (level
== LOGLEVEL_SCHED
) {
1677 level
= LOGLEVEL_DEFAULT
;
1681 boot_delay_msec(level
);
1684 /* This stops the holder of console_sem just where we want him */
1685 local_irq_save(flags
);
1686 this_cpu
= smp_processor_id();
1689 * Ouch, printk recursed into itself!
1691 if (unlikely(logbuf_cpu
== this_cpu
)) {
1693 * If a crash is occurring during printk() on this CPU,
1694 * then try to get the crash message out but make sure
1695 * we can't deadlock. Otherwise just return to avoid the
1696 * recursion and return - but flag the recursion so that
1697 * it can be printed at the next appropriate moment:
1699 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1700 recursion_bug
= true;
1701 local_irq_restore(flags
);
1708 raw_spin_lock(&logbuf_lock
);
1709 logbuf_cpu
= this_cpu
;
1711 if (unlikely(recursion_bug
)) {
1712 static const char recursion_msg
[] =
1713 "BUG: recent printk recursion!";
1715 recursion_bug
= false;
1716 /* emit KERN_CRIT message */
1717 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1718 NULL
, 0, recursion_msg
,
1719 strlen(recursion_msg
));
1723 * The printf needs to come first; we need the syslog
1724 * prefix which might be passed-in as a parameter.
1726 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1728 /* mark and strip a trailing newline */
1729 if (text_len
&& text
[text_len
-1] == '\n') {
1731 lflags
|= LOG_NEWLINE
;
1734 /* strip kernel syslog prefix and extract log level or control flags */
1735 if (facility
== 0) {
1736 int kern_level
= printk_get_level(text
);
1739 const char *end_of_header
= printk_skip_level(text
);
1740 switch (kern_level
) {
1742 if (level
== LOGLEVEL_DEFAULT
)
1743 level
= kern_level
- '0';
1745 case 'd': /* KERN_DEFAULT */
1746 lflags
|= LOG_PREFIX
;
1749 * No need to check length here because vscnprintf
1750 * put '\0' at the end of the string. Only valid and
1751 * newly printed level is detected.
1753 text_len
-= end_of_header
- text
;
1754 text
= (char *)end_of_header
;
1758 if (level
== LOGLEVEL_DEFAULT
)
1759 level
= default_message_loglevel
;
1762 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1764 if (!(lflags
& LOG_NEWLINE
)) {
1766 * Flush the conflicting buffer. An earlier newline was missing,
1767 * or another task also prints continuation lines.
1769 if (cont
.len
&& (lflags
& LOG_PREFIX
|| cont
.owner
!= current
))
1770 cont_flush(LOG_NEWLINE
);
1772 /* buffer line if possible, otherwise store it right away */
1773 if (cont_add(facility
, level
, text
, text_len
))
1774 printed_len
+= text_len
;
1776 printed_len
+= log_store(facility
, level
,
1777 lflags
| LOG_CONT
, 0,
1778 dict
, dictlen
, text
, text_len
);
1780 bool stored
= false;
1783 * If an earlier newline was missing and it was the same task,
1784 * either merge it with the current buffer and flush, or if
1785 * there was a race with interrupts (prefix == true) then just
1786 * flush it out and store this line separately.
1787 * If the preceding printk was from a different task and missed
1788 * a newline, flush and append the newline.
1791 if (cont
.owner
== current
&& !(lflags
& LOG_PREFIX
))
1792 stored
= cont_add(facility
, level
, text
,
1794 cont_flush(LOG_NEWLINE
);
1798 printed_len
+= text_len
;
1800 printed_len
+= log_store(facility
, level
, lflags
, 0,
1801 dict
, dictlen
, text
, text_len
);
1804 logbuf_cpu
= UINT_MAX
;
1805 raw_spin_unlock(&logbuf_lock
);
1807 local_irq_restore(flags
);
1809 /* If called from the scheduler, we can not call up(). */
1813 * Disable preemption to avoid being preempted while holding
1814 * console_sem which would prevent anyone from printing to
1820 * Try to acquire and then immediately release the console
1821 * semaphore. The release will print out buffers and wake up
1822 * /dev/kmsg and syslog() users.
1824 if (console_trylock_for_printk())
1832 EXPORT_SYMBOL(vprintk_emit
);
1834 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1836 return vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1838 EXPORT_SYMBOL(vprintk
);
1840 asmlinkage
int printk_emit(int facility
, int level
,
1841 const char *dict
, size_t dictlen
,
1842 const char *fmt
, ...)
1847 va_start(args
, fmt
);
1848 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1853 EXPORT_SYMBOL(printk_emit
);
1855 int vprintk_default(const char *fmt
, va_list args
)
1859 #ifdef CONFIG_KGDB_KDB
1860 if (unlikely(kdb_trap_printk
)) {
1861 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1865 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1869 EXPORT_SYMBOL_GPL(vprintk_default
);
1872 * This allows printk to be diverted to another function per cpu.
1873 * This is useful for calling printk functions from within NMI
1874 * without worrying about race conditions that can lock up the
1877 DEFINE_PER_CPU(printk_func_t
, printk_func
) = vprintk_default
;
1880 * printk - print a kernel message
1881 * @fmt: format string
1883 * This is printk(). It can be called from any context. We want it to work.
1885 * We try to grab the console_lock. If we succeed, it's easy - we log the
1886 * output and call the console drivers. If we fail to get the semaphore, we
1887 * place the output into the log buffer and return. The current holder of
1888 * the console_sem will notice the new output in console_unlock(); and will
1889 * send it to the consoles before releasing the lock.
1891 * One effect of this deferred printing is that code which calls printk() and
1892 * then changes console_loglevel may break. This is because console_loglevel
1893 * is inspected when the actual printing occurs.
1898 * See the vsnprintf() documentation for format string extensions over C99.
1900 asmlinkage __visible
int printk(const char *fmt
, ...)
1902 printk_func_t vprintk_func
;
1906 va_start(args
, fmt
);
1909 * If a caller overrides the per_cpu printk_func, then it needs
1910 * to disable preemption when calling printk(). Otherwise
1911 * the printk_func should be set to the default. No need to
1912 * disable preemption here.
1914 vprintk_func
= this_cpu_read(printk_func
);
1915 r
= vprintk_func(fmt
, args
);
1921 EXPORT_SYMBOL(printk
);
1923 #else /* CONFIG_PRINTK */
1925 #define LOG_LINE_MAX 0
1926 #define PREFIX_MAX 0
1928 static u64 syslog_seq
;
1929 static u32 syslog_idx
;
1930 static u64 console_seq
;
1931 static u32 console_idx
;
1932 static enum log_flags syslog_prev
;
1933 static u64 log_first_seq
;
1934 static u32 log_first_idx
;
1935 static u64 log_next_seq
;
1936 static enum log_flags console_prev
;
1937 static struct cont
{
1943 static char *log_text(const struct printk_log
*msg
) { return NULL
; }
1944 static char *log_dict(const struct printk_log
*msg
) { return NULL
; }
1945 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
1946 static u32
log_next(u32 idx
) { return 0; }
1947 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
1948 struct printk_log
*msg
, u64 seq
,
1949 enum log_flags prev_flags
) { return 0; }
1950 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
1951 char *dict
, size_t dict_len
,
1952 char *text
, size_t text_len
) { return 0; }
1953 static void call_console_drivers(int level
,
1954 const char *ext_text
, size_t ext_len
,
1955 const char *text
, size_t len
) {}
1956 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1957 bool syslog
, char *buf
, size_t size
) { return 0; }
1958 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
1960 /* Still needs to be defined for users */
1961 DEFINE_PER_CPU(printk_func_t
, printk_func
);
1963 #endif /* CONFIG_PRINTK */
1965 #ifdef CONFIG_EARLY_PRINTK
1966 struct console
*early_console
;
1968 asmlinkage __visible
void early_printk(const char *fmt
, ...)
1978 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
1981 early_console
->write(early_console
, buf
, n
);
1985 static int __add_preferred_console(char *name
, int idx
, char *options
,
1988 struct console_cmdline
*c
;
1992 * See if this tty is not yet registered, and
1993 * if we have a slot free.
1995 for (i
= 0, c
= console_cmdline
;
1996 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
1998 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
2000 selected_console
= i
;
2004 if (i
== MAX_CMDLINECONSOLES
)
2007 selected_console
= i
;
2008 strlcpy(c
->name
, name
, sizeof(c
->name
));
2009 c
->options
= options
;
2010 braille_set_options(c
, brl_options
);
2016 * Set up a console. Called via do_early_param() in init/main.c
2017 * for each "console=" parameter in the boot command line.
2019 static int __init
console_setup(char *str
)
2021 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
2022 char *s
, *options
, *brl_options
= NULL
;
2025 if (_braille_console_setup(&str
, &brl_options
))
2029 * Decode str into name, index, options.
2031 if (str
[0] >= '0' && str
[0] <= '9') {
2032 strcpy(buf
, "ttyS");
2033 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
2035 strncpy(buf
, str
, sizeof(buf
) - 1);
2037 buf
[sizeof(buf
) - 1] = 0;
2038 options
= strchr(str
, ',');
2042 if (!strcmp(str
, "ttya"))
2043 strcpy(buf
, "ttyS0");
2044 if (!strcmp(str
, "ttyb"))
2045 strcpy(buf
, "ttyS1");
2047 for (s
= buf
; *s
; s
++)
2048 if (isdigit(*s
) || *s
== ',')
2050 idx
= simple_strtoul(s
, NULL
, 10);
2053 __add_preferred_console(buf
, idx
, options
, brl_options
);
2054 console_set_on_cmdline
= 1;
2057 __setup("console=", console_setup
);
2060 * add_preferred_console - add a device to the list of preferred consoles.
2061 * @name: device name
2062 * @idx: device index
2063 * @options: options for this console
2065 * The last preferred console added will be used for kernel messages
2066 * and stdin/out/err for init. Normally this is used by console_setup
2067 * above to handle user-supplied console arguments; however it can also
2068 * be used by arch-specific code either to override the user or more
2069 * commonly to provide a default console (ie from PROM variables) when
2070 * the user has not supplied one.
2072 int add_preferred_console(char *name
, int idx
, char *options
)
2074 return __add_preferred_console(name
, idx
, options
, NULL
);
2077 bool console_suspend_enabled
= true;
2078 EXPORT_SYMBOL(console_suspend_enabled
);
2080 static int __init
console_suspend_disable(char *str
)
2082 console_suspend_enabled
= false;
2085 __setup("no_console_suspend", console_suspend_disable
);
2086 module_param_named(console_suspend
, console_suspend_enabled
,
2087 bool, S_IRUGO
| S_IWUSR
);
2088 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2089 " and hibernate operations");
2092 * suspend_console - suspend the console subsystem
2094 * This disables printk() while we go into suspend states
2096 void suspend_console(void)
2098 if (!console_suspend_enabled
)
2100 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2102 console_suspended
= 1;
2106 void resume_console(void)
2108 if (!console_suspend_enabled
)
2111 console_suspended
= 0;
2116 * console_cpu_notify - print deferred console messages after CPU hotplug
2117 * @self: notifier struct
2118 * @action: CPU hotplug event
2121 * If printk() is called from a CPU that is not online yet, the messages
2122 * will be spooled but will not show up on the console. This function is
2123 * called when a new CPU comes online (or fails to come up), and ensures
2124 * that any such output gets printed.
2126 static int console_cpu_notify(struct notifier_block
*self
,
2127 unsigned long action
, void *hcpu
)
2132 case CPU_DOWN_FAILED
:
2133 case CPU_UP_CANCELED
:
2141 * console_lock - lock the console system for exclusive use.
2143 * Acquires a lock which guarantees that the caller has
2144 * exclusive access to the console system and the console_drivers list.
2146 * Can sleep, returns nothing.
2148 void console_lock(void)
2153 if (console_suspended
)
2156 console_may_schedule
= 1;
2158 EXPORT_SYMBOL(console_lock
);
2161 * console_trylock - try to lock the console system for exclusive use.
2163 * Try to acquire a lock which guarantees that the caller has exclusive
2164 * access to the console system and the console_drivers list.
2166 * returns 1 on success, and 0 on failure to acquire the lock.
2168 int console_trylock(void)
2170 if (down_trylock_console_sem())
2172 if (console_suspended
) {
2177 console_may_schedule
= 0;
2180 EXPORT_SYMBOL(console_trylock
);
2182 int is_console_locked(void)
2184 return console_locked
;
2187 static void console_cont_flush(char *text
, size_t size
)
2189 unsigned long flags
;
2192 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2198 * We still queue earlier records, likely because the console was
2199 * busy. The earlier ones need to be printed before this one, we
2200 * did not flush any fragment so far, so just let it queue up.
2202 if (console_seq
< log_next_seq
&& !cont
.cons
)
2205 len
= cont_print_text(text
, size
);
2206 raw_spin_unlock(&logbuf_lock
);
2207 stop_critical_timings();
2208 call_console_drivers(cont
.level
, NULL
, 0, text
, len
);
2209 start_critical_timings();
2210 local_irq_restore(flags
);
2213 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2217 * console_unlock - unlock the console system
2219 * Releases the console_lock which the caller holds on the console system
2220 * and the console driver list.
2222 * While the console_lock was held, console output may have been buffered
2223 * by printk(). If this is the case, console_unlock(); emits
2224 * the output prior to releasing the lock.
2226 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2228 * console_unlock(); may be called from any context.
2230 void console_unlock(void)
2232 static char ext_text
[CONSOLE_EXT_LOG_MAX
];
2233 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2234 static u64 seen_seq
;
2235 unsigned long flags
;
2236 bool wake_klogd
= false;
2237 bool do_cond_resched
, retry
;
2239 if (console_suspended
) {
2245 * Console drivers are called under logbuf_lock, so
2246 * @console_may_schedule should be cleared before; however, we may
2247 * end up dumping a lot of lines, for example, if called from
2248 * console registration path, and should invoke cond_resched()
2249 * between lines if allowable. Not doing so can cause a very long
2250 * scheduling stall on a slow console leading to RCU stall and
2251 * softlockup warnings which exacerbate the issue with more
2252 * messages practically incapacitating the system.
2254 do_cond_resched
= console_may_schedule
;
2255 console_may_schedule
= 0;
2257 /* flush buffered message fragment immediately to console */
2258 console_cont_flush(text
, sizeof(text
));
2261 struct printk_log
*msg
;
2266 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2267 if (seen_seq
!= log_next_seq
) {
2269 seen_seq
= log_next_seq
;
2272 if (console_seq
< log_first_seq
) {
2273 len
= sprintf(text
, "** %u printk messages dropped ** ",
2274 (unsigned)(log_first_seq
- console_seq
));
2276 /* messages are gone, move to first one */
2277 console_seq
= log_first_seq
;
2278 console_idx
= log_first_idx
;
2284 if (console_seq
== log_next_seq
)
2287 msg
= log_from_idx(console_idx
);
2288 if (msg
->flags
& LOG_NOCONS
) {
2290 * Skip record we have buffered and already printed
2291 * directly to the console when we received it.
2293 console_idx
= log_next(console_idx
);
2296 * We will get here again when we register a new
2297 * CON_PRINTBUFFER console. Clear the flag so we
2298 * will properly dump everything later.
2300 msg
->flags
&= ~LOG_NOCONS
;
2301 console_prev
= msg
->flags
;
2306 len
+= msg_print_text(msg
, console_prev
, false,
2307 text
+ len
, sizeof(text
) - len
);
2308 if (nr_ext_console_drivers
) {
2309 ext_len
= msg_print_ext_header(ext_text
,
2311 msg
, console_seq
, console_prev
);
2312 ext_len
+= msg_print_ext_body(ext_text
+ ext_len
,
2313 sizeof(ext_text
) - ext_len
,
2314 log_dict(msg
), msg
->dict_len
,
2315 log_text(msg
), msg
->text_len
);
2317 console_idx
= log_next(console_idx
);
2319 console_prev
= msg
->flags
;
2320 raw_spin_unlock(&logbuf_lock
);
2322 stop_critical_timings(); /* don't trace print latency */
2323 call_console_drivers(level
, ext_text
, ext_len
, text
, len
);
2324 start_critical_timings();
2325 local_irq_restore(flags
);
2327 if (do_cond_resched
)
2332 /* Release the exclusive_console once it is used */
2333 if (unlikely(exclusive_console
))
2334 exclusive_console
= NULL
;
2336 raw_spin_unlock(&logbuf_lock
);
2341 * Someone could have filled up the buffer again, so re-check if there's
2342 * something to flush. In case we cannot trylock the console_sem again,
2343 * there's a new owner and the console_unlock() from them will do the
2344 * flush, no worries.
2346 raw_spin_lock(&logbuf_lock
);
2347 retry
= console_seq
!= log_next_seq
;
2348 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2350 if (retry
&& console_trylock())
2356 EXPORT_SYMBOL(console_unlock
);
2359 * console_conditional_schedule - yield the CPU if required
2361 * If the console code is currently allowed to sleep, and
2362 * if this CPU should yield the CPU to another task, do
2365 * Must be called within console_lock();.
2367 void __sched
console_conditional_schedule(void)
2369 if (console_may_schedule
)
2372 EXPORT_SYMBOL(console_conditional_schedule
);
2374 void console_unblank(void)
2379 * console_unblank can no longer be called in interrupt context unless
2380 * oops_in_progress is set to 1..
2382 if (oops_in_progress
) {
2383 if (down_trylock_console_sem() != 0)
2389 console_may_schedule
= 0;
2391 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2397 * console_flush_on_panic - flush console content on panic
2399 * Immediately output all pending messages no matter what.
2401 void console_flush_on_panic(void)
2404 * If someone else is holding the console lock, trylock will fail
2405 * and may_schedule may be set. Ignore and proceed to unlock so
2406 * that messages are flushed out. As this can be called from any
2407 * context and we don't want to get preempted while flushing,
2408 * ensure may_schedule is cleared.
2411 console_may_schedule
= 0;
2416 * Return the console tty driver structure and its associated index
2418 struct tty_driver
*console_device(int *index
)
2421 struct tty_driver
*driver
= NULL
;
2424 for_each_console(c
) {
2427 driver
= c
->device(c
, index
);
2436 * Prevent further output on the passed console device so that (for example)
2437 * serial drivers can disable console output before suspending a port, and can
2438 * re-enable output afterwards.
2440 void console_stop(struct console
*console
)
2443 console
->flags
&= ~CON_ENABLED
;
2446 EXPORT_SYMBOL(console_stop
);
2448 void console_start(struct console
*console
)
2451 console
->flags
|= CON_ENABLED
;
2454 EXPORT_SYMBOL(console_start
);
2456 static int __read_mostly keep_bootcon
;
2458 static int __init
keep_bootcon_setup(char *str
)
2461 pr_info("debug: skip boot console de-registration.\n");
2466 early_param("keep_bootcon", keep_bootcon_setup
);
2469 * The console driver calls this routine during kernel initialization
2470 * to register the console printing procedure with printk() and to
2471 * print any messages that were printed by the kernel before the
2472 * console driver was initialized.
2474 * This can happen pretty early during the boot process (because of
2475 * early_printk) - sometimes before setup_arch() completes - be careful
2476 * of what kernel features are used - they may not be initialised yet.
2478 * There are two types of consoles - bootconsoles (early_printk) and
2479 * "real" consoles (everything which is not a bootconsole) which are
2480 * handled differently.
2481 * - Any number of bootconsoles can be registered at any time.
2482 * - As soon as a "real" console is registered, all bootconsoles
2483 * will be unregistered automatically.
2484 * - Once a "real" console is registered, any attempt to register a
2485 * bootconsoles will be rejected
2487 void register_console(struct console
*newcon
)
2490 unsigned long flags
;
2491 struct console
*bcon
= NULL
;
2492 struct console_cmdline
*c
;
2494 if (console_drivers
)
2495 for_each_console(bcon
)
2496 if (WARN(bcon
== newcon
,
2497 "console '%s%d' already registered\n",
2498 bcon
->name
, bcon
->index
))
2502 * before we register a new CON_BOOT console, make sure we don't
2503 * already have a valid console
2505 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2506 /* find the last or real console */
2507 for_each_console(bcon
) {
2508 if (!(bcon
->flags
& CON_BOOT
)) {
2509 pr_info("Too late to register bootconsole %s%d\n",
2510 newcon
->name
, newcon
->index
);
2516 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2517 bcon
= console_drivers
;
2519 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2520 preferred_console
= selected_console
;
2523 * See if we want to use this console driver. If we
2524 * didn't select a console we take the first one
2525 * that registers here.
2527 if (preferred_console
< 0) {
2528 if (newcon
->index
< 0)
2530 if (newcon
->setup
== NULL
||
2531 newcon
->setup(newcon
, NULL
) == 0) {
2532 newcon
->flags
|= CON_ENABLED
;
2533 if (newcon
->device
) {
2534 newcon
->flags
|= CON_CONSDEV
;
2535 preferred_console
= 0;
2541 * See if this console matches one we selected on
2544 for (i
= 0, c
= console_cmdline
;
2545 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2547 if (!newcon
->match
||
2548 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2549 /* default matching */
2550 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2551 if (strcmp(c
->name
, newcon
->name
) != 0)
2553 if (newcon
->index
>= 0 &&
2554 newcon
->index
!= c
->index
)
2556 if (newcon
->index
< 0)
2557 newcon
->index
= c
->index
;
2559 if (_braille_register_console(newcon
, c
))
2562 if (newcon
->setup
&&
2563 newcon
->setup(newcon
, c
->options
) != 0)
2567 newcon
->flags
|= CON_ENABLED
;
2568 if (i
== selected_console
) {
2569 newcon
->flags
|= CON_CONSDEV
;
2570 preferred_console
= selected_console
;
2575 if (!(newcon
->flags
& CON_ENABLED
))
2579 * If we have a bootconsole, and are switching to a real console,
2580 * don't print everything out again, since when the boot console, and
2581 * the real console are the same physical device, it's annoying to
2582 * see the beginning boot messages twice
2584 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2585 newcon
->flags
&= ~CON_PRINTBUFFER
;
2588 * Put this console in the list - keep the
2589 * preferred driver at the head of the list.
2592 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2593 newcon
->next
= console_drivers
;
2594 console_drivers
= newcon
;
2596 newcon
->next
->flags
&= ~CON_CONSDEV
;
2598 newcon
->next
= console_drivers
->next
;
2599 console_drivers
->next
= newcon
;
2602 if (newcon
->flags
& CON_EXTENDED
)
2603 if (!nr_ext_console_drivers
++)
2604 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2606 if (newcon
->flags
& CON_PRINTBUFFER
) {
2608 * console_unlock(); will print out the buffered messages
2611 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2612 console_seq
= syslog_seq
;
2613 console_idx
= syslog_idx
;
2614 console_prev
= syslog_prev
;
2615 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2617 * We're about to replay the log buffer. Only do this to the
2618 * just-registered console to avoid excessive message spam to
2619 * the already-registered consoles.
2621 exclusive_console
= newcon
;
2624 console_sysfs_notify();
2627 * By unregistering the bootconsoles after we enable the real console
2628 * we get the "console xxx enabled" message on all the consoles -
2629 * boot consoles, real consoles, etc - this is to ensure that end
2630 * users know there might be something in the kernel's log buffer that
2631 * went to the bootconsole (that they do not see on the real console)
2633 pr_info("%sconsole [%s%d] enabled\n",
2634 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2635 newcon
->name
, newcon
->index
);
2637 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2639 /* We need to iterate through all boot consoles, to make
2640 * sure we print everything out, before we unregister them.
2642 for_each_console(bcon
)
2643 if (bcon
->flags
& CON_BOOT
)
2644 unregister_console(bcon
);
2647 EXPORT_SYMBOL(register_console
);
2649 int unregister_console(struct console
*console
)
2651 struct console
*a
, *b
;
2654 pr_info("%sconsole [%s%d] disabled\n",
2655 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2656 console
->name
, console
->index
);
2658 res
= _braille_unregister_console(console
);
2664 if (console_drivers
== console
) {
2665 console_drivers
=console
->next
;
2667 } else if (console_drivers
) {
2668 for (a
=console_drivers
->next
, b
=console_drivers
;
2669 a
; b
=a
, a
=b
->next
) {
2678 if (!res
&& (console
->flags
& CON_EXTENDED
))
2679 nr_ext_console_drivers
--;
2682 * If this isn't the last console and it has CON_CONSDEV set, we
2683 * need to set it on the next preferred console.
2685 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2686 console_drivers
->flags
|= CON_CONSDEV
;
2688 console
->flags
&= ~CON_ENABLED
;
2690 console_sysfs_notify();
2693 EXPORT_SYMBOL(unregister_console
);
2696 * Some boot consoles access data that is in the init section and which will
2697 * be discarded after the initcalls have been run. To make sure that no code
2698 * will access this data, unregister the boot consoles in a late initcall.
2700 * If for some reason, such as deferred probe or the driver being a loadable
2701 * module, the real console hasn't registered yet at this point, there will
2702 * be a brief interval in which no messages are logged to the console, which
2703 * makes it difficult to diagnose problems that occur during this time.
2705 * To mitigate this problem somewhat, only unregister consoles whose memory
2706 * intersects with the init section. Note that code exists elsewhere to get
2707 * rid of the boot console as soon as the proper console shows up, so there
2708 * won't be side-effects from postponing the removal.
2710 static int __init
printk_late_init(void)
2712 struct console
*con
;
2714 for_each_console(con
) {
2715 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2717 * Make sure to unregister boot consoles whose data
2718 * resides in the init section before the init section
2719 * is discarded. Boot consoles whose data will stick
2720 * around will automatically be unregistered when the
2721 * proper console replaces them.
2723 if (init_section_intersects(con
, sizeof(*con
)))
2724 unregister_console(con
);
2727 hotcpu_notifier(console_cpu_notify
, 0);
2730 late_initcall(printk_late_init
);
2732 #if defined CONFIG_PRINTK
2734 * Delayed printk version, for scheduler-internal messages:
2736 #define PRINTK_PENDING_WAKEUP 0x01
2737 #define PRINTK_PENDING_OUTPUT 0x02
2739 static DEFINE_PER_CPU(int, printk_pending
);
2741 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2743 int pending
= __this_cpu_xchg(printk_pending
, 0);
2745 if (pending
& PRINTK_PENDING_OUTPUT
) {
2746 /* If trylock fails, someone else is doing the printing */
2747 if (console_trylock())
2751 if (pending
& PRINTK_PENDING_WAKEUP
)
2752 wake_up_interruptible(&log_wait
);
2755 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2756 .func
= wake_up_klogd_work_func
,
2757 .flags
= IRQ_WORK_LAZY
,
2760 void wake_up_klogd(void)
2763 if (waitqueue_active(&log_wait
)) {
2764 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2765 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2770 int printk_deferred(const char *fmt
, ...)
2776 va_start(args
, fmt
);
2777 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2780 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2781 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2788 * printk rate limiting, lifted from the networking subsystem.
2790 * This enforces a rate limit: not more than 10 kernel messages
2791 * every 5s to make a denial-of-service attack impossible.
2793 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2795 int __printk_ratelimit(const char *func
)
2797 return ___ratelimit(&printk_ratelimit_state
, func
);
2799 EXPORT_SYMBOL(__printk_ratelimit
);
2802 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2803 * @caller_jiffies: pointer to caller's state
2804 * @interval_msecs: minimum interval between prints
2806 * printk_timed_ratelimit() returns true if more than @interval_msecs
2807 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2810 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2811 unsigned int interval_msecs
)
2813 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2815 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2818 *caller_jiffies
= jiffies
;
2821 EXPORT_SYMBOL(printk_timed_ratelimit
);
2823 static DEFINE_SPINLOCK(dump_list_lock
);
2824 static LIST_HEAD(dump_list
);
2827 * kmsg_dump_register - register a kernel log dumper.
2828 * @dumper: pointer to the kmsg_dumper structure
2830 * Adds a kernel log dumper to the system. The dump callback in the
2831 * structure will be called when the kernel oopses or panics and must be
2832 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2834 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2836 unsigned long flags
;
2839 /* The dump callback needs to be set */
2843 spin_lock_irqsave(&dump_list_lock
, flags
);
2844 /* Don't allow registering multiple times */
2845 if (!dumper
->registered
) {
2846 dumper
->registered
= 1;
2847 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2850 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2854 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2857 * kmsg_dump_unregister - unregister a kmsg dumper.
2858 * @dumper: pointer to the kmsg_dumper structure
2860 * Removes a dump device from the system. Returns zero on success and
2861 * %-EINVAL otherwise.
2863 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2865 unsigned long flags
;
2868 spin_lock_irqsave(&dump_list_lock
, flags
);
2869 if (dumper
->registered
) {
2870 dumper
->registered
= 0;
2871 list_del_rcu(&dumper
->list
);
2874 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2879 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2881 static bool always_kmsg_dump
;
2882 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2885 * kmsg_dump - dump kernel log to kernel message dumpers.
2886 * @reason: the reason (oops, panic etc) for dumping
2888 * Call each of the registered dumper's dump() callback, which can
2889 * retrieve the kmsg records with kmsg_dump_get_line() or
2890 * kmsg_dump_get_buffer().
2892 void kmsg_dump(enum kmsg_dump_reason reason
)
2894 struct kmsg_dumper
*dumper
;
2895 unsigned long flags
;
2897 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2901 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2902 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2905 /* initialize iterator with data about the stored records */
2906 dumper
->active
= true;
2908 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2909 dumper
->cur_seq
= clear_seq
;
2910 dumper
->cur_idx
= clear_idx
;
2911 dumper
->next_seq
= log_next_seq
;
2912 dumper
->next_idx
= log_next_idx
;
2913 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2915 /* invoke dumper which will iterate over records */
2916 dumper
->dump(dumper
, reason
);
2918 /* reset iterator */
2919 dumper
->active
= false;
2925 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2926 * @dumper: registered kmsg dumper
2927 * @syslog: include the "<4>" prefixes
2928 * @line: buffer to copy the line to
2929 * @size: maximum size of the buffer
2930 * @len: length of line placed into buffer
2932 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2933 * record, and copy one record into the provided buffer.
2935 * Consecutive calls will return the next available record moving
2936 * towards the end of the buffer with the youngest messages.
2938 * A return value of FALSE indicates that there are no more records to
2941 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2943 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
2944 char *line
, size_t size
, size_t *len
)
2946 struct printk_log
*msg
;
2950 if (!dumper
->active
)
2953 if (dumper
->cur_seq
< log_first_seq
) {
2954 /* messages are gone, move to first available one */
2955 dumper
->cur_seq
= log_first_seq
;
2956 dumper
->cur_idx
= log_first_idx
;
2960 if (dumper
->cur_seq
>= log_next_seq
)
2963 msg
= log_from_idx(dumper
->cur_idx
);
2964 l
= msg_print_text(msg
, 0, syslog
, line
, size
);
2966 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2976 * kmsg_dump_get_line - retrieve one kmsg log line
2977 * @dumper: registered kmsg dumper
2978 * @syslog: include the "<4>" prefixes
2979 * @line: buffer to copy the line to
2980 * @size: maximum size of the buffer
2981 * @len: length of line placed into buffer
2983 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2984 * record, and copy one record into the provided buffer.
2986 * Consecutive calls will return the next available record moving
2987 * towards the end of the buffer with the youngest messages.
2989 * A return value of FALSE indicates that there are no more records to
2992 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2993 char *line
, size_t size
, size_t *len
)
2995 unsigned long flags
;
2998 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2999 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
3000 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3004 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
3007 * kmsg_dump_get_buffer - copy kmsg log lines
3008 * @dumper: registered kmsg dumper
3009 * @syslog: include the "<4>" prefixes
3010 * @buf: buffer to copy the line to
3011 * @size: maximum size of the buffer
3012 * @len: length of line placed into buffer
3014 * Start at the end of the kmsg buffer and fill the provided buffer
3015 * with as many of the the *youngest* kmsg records that fit into it.
3016 * If the buffer is large enough, all available kmsg records will be
3017 * copied with a single call.
3019 * Consecutive calls will fill the buffer with the next block of
3020 * available older records, not including the earlier retrieved ones.
3022 * A return value of FALSE indicates that there are no more records to
3025 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
3026 char *buf
, size_t size
, size_t *len
)
3028 unsigned long flags
;
3033 enum log_flags prev
;
3037 if (!dumper
->active
)
3040 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3041 if (dumper
->cur_seq
< log_first_seq
) {
3042 /* messages are gone, move to first available one */
3043 dumper
->cur_seq
= log_first_seq
;
3044 dumper
->cur_idx
= log_first_idx
;
3048 if (dumper
->cur_seq
>= dumper
->next_seq
) {
3049 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3053 /* calculate length of entire buffer */
3054 seq
= dumper
->cur_seq
;
3055 idx
= dumper
->cur_idx
;
3057 while (seq
< dumper
->next_seq
) {
3058 struct printk_log
*msg
= log_from_idx(idx
);
3060 l
+= msg_print_text(msg
, prev
, true, NULL
, 0);
3061 idx
= log_next(idx
);
3066 /* move first record forward until length fits into the buffer */
3067 seq
= dumper
->cur_seq
;
3068 idx
= dumper
->cur_idx
;
3070 while (l
> size
&& seq
< dumper
->next_seq
) {
3071 struct printk_log
*msg
= log_from_idx(idx
);
3073 l
-= msg_print_text(msg
, prev
, true, NULL
, 0);
3074 idx
= log_next(idx
);
3079 /* last message in next interation */
3084 while (seq
< dumper
->next_seq
) {
3085 struct printk_log
*msg
= log_from_idx(idx
);
3087 l
+= msg_print_text(msg
, prev
, syslog
, buf
+ l
, size
- l
);
3088 idx
= log_next(idx
);
3093 dumper
->next_seq
= next_seq
;
3094 dumper
->next_idx
= next_idx
;
3096 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3102 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
3105 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3106 * @dumper: registered kmsg dumper
3108 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3109 * kmsg_dump_get_buffer() can be called again and used multiple
3110 * times within the same dumper.dump() callback.
3112 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3114 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3116 dumper
->cur_seq
= clear_seq
;
3117 dumper
->cur_idx
= clear_idx
;
3118 dumper
->next_seq
= log_next_seq
;
3119 dumper
->next_idx
= log_next_idx
;
3123 * kmsg_dump_rewind - reset the interator
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 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3132 unsigned long flags
;
3134 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3135 kmsg_dump_rewind_nolock(dumper
);
3136 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3138 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3140 static char dump_stack_arch_desc_str
[128];
3143 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3144 * @fmt: printf-style format string
3145 * @...: arguments for the format string
3147 * The configured string will be printed right after utsname during task
3148 * dumps. Usually used to add arch-specific system identifiers. If an
3149 * arch wants to make use of such an ID string, it should initialize this
3150 * as soon as possible during boot.
3152 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3156 va_start(args
, fmt
);
3157 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3163 * dump_stack_print_info - print generic debug info for dump_stack()
3164 * @log_lvl: log level
3166 * Arch-specific dump_stack() implementations can use this function to
3167 * print out the same debug information as the generic dump_stack().
3169 void dump_stack_print_info(const char *log_lvl
)
3171 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3172 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3173 print_tainted(), init_utsname()->release
,
3174 (int)strcspn(init_utsname()->version
, " "),
3175 init_utsname()->version
);
3177 if (dump_stack_arch_desc_str
[0] != '\0')
3178 printk("%sHardware name: %s\n",
3179 log_lvl
, dump_stack_arch_desc_str
);
3181 print_worker_info(log_lvl
, current
);
3185 * show_regs_print_info - print generic debug info for show_regs()
3186 * @log_lvl: log level
3188 * show_regs() implementations can use this function to print out generic
3189 * debug information.
3191 void show_regs_print_info(const char *log_lvl
)
3193 dump_stack_print_info(log_lvl
);
3195 printk("%stask: %p ti: %p task.ti: %p\n",
3196 log_lvl
, current
, current_thread_info(),
3197 task_thread_info(current
));