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/aio.h>
36 #include <linux/syscalls.h>
37 #include <linux/kexec.h>
38 #include <linux/kdb.h>
39 #include <linux/ratelimit.h>
40 #include <linux/kmsg_dump.h>
41 #include <linux/syslog.h>
42 #include <linux/cpu.h>
43 #include <linux/notifier.h>
44 #include <linux/rculist.h>
45 #include <linux/poll.h>
46 #include <linux/irq_work.h>
47 #include <linux/utsname.h>
48 #include <linux/ctype.h>
50 #include <asm/uaccess.h>
52 #define CREATE_TRACE_POINTS
53 #include <trace/events/printk.h>
55 #include "console_cmdline.h"
58 int console_printk
[4] = {
59 CONSOLE_LOGLEVEL_DEFAULT
, /* console_loglevel */
60 MESSAGE_LOGLEVEL_DEFAULT
, /* default_message_loglevel */
61 CONSOLE_LOGLEVEL_MIN
, /* minimum_console_loglevel */
62 CONSOLE_LOGLEVEL_DEFAULT
, /* default_console_loglevel */
66 * Low level drivers may need that to know if they can schedule in
67 * their unblank() callback or not. So let's export it.
70 EXPORT_SYMBOL(oops_in_progress
);
73 * console_sem protects the console_drivers list, and also
74 * provides serialisation for access to the entire console
77 static DEFINE_SEMAPHORE(console_sem
);
78 struct console
*console_drivers
;
79 EXPORT_SYMBOL_GPL(console_drivers
);
82 static struct lockdep_map console_lock_dep_map
= {
83 .name
= "console_lock"
88 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
89 * macros instead of functions so that _RET_IP_ contains useful information.
91 #define down_console_sem() do { \
93 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
96 static int __down_trylock_console_sem(unsigned long ip
)
98 if (down_trylock(&console_sem
))
100 mutex_acquire(&console_lock_dep_map
, 0, 1, ip
);
103 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
105 #define up_console_sem() do { \
106 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
111 * This is used for debugging the mess that is the VT code by
112 * keeping track if we have the console semaphore held. It's
113 * definitely not the perfect debug tool (we don't know if _WE_
114 * hold it and are racing, but it helps tracking those weird code
115 * paths in the console code where we end up in places I want
116 * locked without the console sempahore held).
118 static int console_locked
, console_suspended
;
121 * If exclusive_console is non-NULL then only this console is to be printed to.
123 static struct console
*exclusive_console
;
126 * Array of consoles built from command line options (console=)
129 #define MAX_CMDLINECONSOLES 8
131 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
133 static int selected_console
= -1;
134 static int preferred_console
= -1;
135 int console_set_on_cmdline
;
136 EXPORT_SYMBOL(console_set_on_cmdline
);
138 /* Flag: console code may call schedule() */
139 static int console_may_schedule
;
142 * The printk log buffer consists of a chain of concatenated variable
143 * length records. Every record starts with a record header, containing
144 * the overall length of the record.
146 * The heads to the first and last entry in the buffer, as well as the
147 * sequence numbers of these entries are maintained when messages are
150 * If the heads indicate available messages, the length in the header
151 * tells the start next message. A length == 0 for the next message
152 * indicates a wrap-around to the beginning of the buffer.
154 * Every record carries the monotonic timestamp in microseconds, as well as
155 * the standard userspace syslog level and syslog facility. The usual
156 * kernel messages use LOG_KERN; userspace-injected messages always carry
157 * a matching syslog facility, by default LOG_USER. The origin of every
158 * message can be reliably determined that way.
160 * The human readable log message directly follows the message header. The
161 * length of the message text is stored in the header, the stored message
164 * Optionally, a message can carry a dictionary of properties (key/value pairs),
165 * to provide userspace with a machine-readable message context.
167 * Examples for well-defined, commonly used property names are:
168 * DEVICE=b12:8 device identifier
172 * +sound:card0 subsystem:devname
173 * SUBSYSTEM=pci driver-core subsystem name
175 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
176 * follows directly after a '=' character. Every property is terminated by
177 * a '\0' character. The last property is not terminated.
179 * Example of a message structure:
180 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
181 * 0008 34 00 record is 52 bytes long
182 * 000a 0b 00 text is 11 bytes long
183 * 000c 1f 00 dictionary is 23 bytes long
184 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
185 * 0010 69 74 27 73 20 61 20 6c "it's a l"
187 * 001b 44 45 56 49 43 "DEVIC"
188 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
189 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
191 * 0032 00 00 00 padding to next message header
193 * The 'struct printk_log' buffer header must never be directly exported to
194 * userspace, it is a kernel-private implementation detail that might
195 * need to be changed in the future, when the requirements change.
197 * /dev/kmsg exports the structured data in the following line format:
198 * "level,sequnum,timestamp;<message text>\n"
200 * The optional key/value pairs are attached as continuation lines starting
201 * with a space character and terminated by a newline. All possible
202 * non-prinatable characters are escaped in the "\xff" notation.
204 * Users of the export format should ignore possible additional values
205 * separated by ',', and find the message after the ';' character.
209 LOG_NOCONS
= 1, /* already flushed, do not print to console */
210 LOG_NEWLINE
= 2, /* text ended with a newline */
211 LOG_PREFIX
= 4, /* text started with a prefix */
212 LOG_CONT
= 8, /* text is a fragment of a continuation line */
216 u64 ts_nsec
; /* timestamp in nanoseconds */
217 u16 len
; /* length of entire record */
218 u16 text_len
; /* length of text buffer */
219 u16 dict_len
; /* length of dictionary buffer */
220 u8 facility
; /* syslog facility */
221 u8 flags
:5; /* internal record flags */
222 u8 level
:3; /* syslog level */
226 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
227 * within the scheduler's rq lock. It must be released before calling
228 * console_unlock() or anything else that might wake up a process.
230 static DEFINE_RAW_SPINLOCK(logbuf_lock
);
233 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
234 /* the next printk record to read by syslog(READ) or /proc/kmsg */
235 static u64 syslog_seq
;
236 static u32 syslog_idx
;
237 static enum log_flags syslog_prev
;
238 static size_t syslog_partial
;
240 /* index and sequence number of the first record stored in the buffer */
241 static u64 log_first_seq
;
242 static u32 log_first_idx
;
244 /* index and sequence number of the next record to store in the buffer */
245 static u64 log_next_seq
;
246 static u32 log_next_idx
;
248 /* the next printk record to write to the console */
249 static u64 console_seq
;
250 static u32 console_idx
;
251 static enum log_flags console_prev
;
253 /* the next printk record to read after the last 'clear' command */
254 static u64 clear_seq
;
255 static u32 clear_idx
;
257 #define PREFIX_MAX 32
258 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
261 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
264 #define LOG_ALIGN __alignof__(struct printk_log)
266 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
267 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
268 static char *log_buf
= __log_buf
;
269 static u32 log_buf_len
= __LOG_BUF_LEN
;
271 /* Return log buffer address */
272 char *log_buf_addr_get(void)
277 /* Return log buffer size */
278 u32
log_buf_len_get(void)
283 /* human readable text of the record */
284 static char *log_text(const struct printk_log
*msg
)
286 return (char *)msg
+ sizeof(struct printk_log
);
289 /* optional key/value pair dictionary attached to the record */
290 static char *log_dict(const struct printk_log
*msg
)
292 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
295 /* get record by index; idx must point to valid msg */
296 static struct printk_log
*log_from_idx(u32 idx
)
298 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
301 * A length == 0 record is the end of buffer marker. Wrap around and
302 * read the message at the start of the buffer.
305 return (struct printk_log
*)log_buf
;
309 /* get next record; idx must point to valid msg */
310 static u32
log_next(u32 idx
)
312 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
314 /* length == 0 indicates the end of the buffer; wrap */
316 * A length == 0 record is the end of buffer marker. Wrap around and
317 * read the message at the start of the buffer as *this* one, and
318 * return the one after that.
321 msg
= (struct printk_log
*)log_buf
;
324 return idx
+ msg
->len
;
328 * Check whether there is enough free space for the given message.
330 * The same values of first_idx and next_idx mean that the buffer
331 * is either empty or full.
333 * If the buffer is empty, we must respect the position of the indexes.
334 * They cannot be reset to the beginning of the buffer.
336 static int logbuf_has_space(u32 msg_size
, bool empty
)
340 if (log_next_idx
> log_first_idx
|| empty
)
341 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
343 free
= log_first_idx
- log_next_idx
;
346 * We need space also for an empty header that signalizes wrapping
349 return free
>= msg_size
+ sizeof(struct printk_log
);
352 static int log_make_free_space(u32 msg_size
)
354 while (log_first_seq
< log_next_seq
) {
355 if (logbuf_has_space(msg_size
, false))
357 /* drop old messages until we have enough contiguous space */
358 log_first_idx
= log_next(log_first_idx
);
362 /* sequence numbers are equal, so the log buffer is empty */
363 if (logbuf_has_space(msg_size
, true))
369 /* compute the message size including the padding bytes */
370 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
374 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
375 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
382 * Define how much of the log buffer we could take at maximum. The value
383 * must be greater than two. Note that only half of the buffer is available
384 * when the index points to the middle.
386 #define MAX_LOG_TAKE_PART 4
387 static const char trunc_msg
[] = "<truncated>";
389 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
390 u16
*dict_len
, u32
*pad_len
)
393 * The message should not take the whole buffer. Otherwise, it might
394 * get removed too soon.
396 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
397 if (*text_len
> max_text_len
)
398 *text_len
= max_text_len
;
399 /* enable the warning message */
400 *trunc_msg_len
= strlen(trunc_msg
);
401 /* disable the "dict" completely */
403 /* compute the size again, count also the warning message */
404 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
407 /* insert record into the buffer, discard old ones, update heads */
408 static int log_store(int facility
, int level
,
409 enum log_flags flags
, u64 ts_nsec
,
410 const char *dict
, u16 dict_len
,
411 const char *text
, u16 text_len
)
413 struct printk_log
*msg
;
415 u16 trunc_msg_len
= 0;
417 /* number of '\0' padding bytes to next message */
418 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
420 if (log_make_free_space(size
)) {
421 /* truncate the message if it is too long for empty buffer */
422 size
= truncate_msg(&text_len
, &trunc_msg_len
,
423 &dict_len
, &pad_len
);
424 /* survive when the log buffer is too small for trunc_msg */
425 if (log_make_free_space(size
))
429 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
431 * This message + an additional empty header does not fit
432 * at the end of the buffer. Add an empty header with len == 0
433 * to signify a wrap around.
435 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
440 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
441 memcpy(log_text(msg
), text
, text_len
);
442 msg
->text_len
= text_len
;
444 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
445 msg
->text_len
+= trunc_msg_len
;
447 memcpy(log_dict(msg
), dict
, dict_len
);
448 msg
->dict_len
= dict_len
;
449 msg
->facility
= facility
;
450 msg
->level
= level
& 7;
451 msg
->flags
= flags
& 0x1f;
453 msg
->ts_nsec
= ts_nsec
;
455 msg
->ts_nsec
= local_clock();
456 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
460 log_next_idx
+= msg
->len
;
463 return msg
->text_len
;
466 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
468 static int syslog_action_restricted(int type
)
473 * Unless restricted, we allow "read all" and "get buffer size"
476 return type
!= SYSLOG_ACTION_READ_ALL
&&
477 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
480 int check_syslog_permissions(int type
, bool from_file
)
483 * If this is from /proc/kmsg and we've already opened it, then we've
484 * already done the capabilities checks at open time.
486 if (from_file
&& type
!= SYSLOG_ACTION_OPEN
)
489 if (syslog_action_restricted(type
)) {
490 if (capable(CAP_SYSLOG
))
493 * For historical reasons, accept CAP_SYS_ADMIN too, with
496 if (capable(CAP_SYS_ADMIN
)) {
497 pr_warn_once("%s (%d): Attempt to access syslog with "
498 "CAP_SYS_ADMIN but no CAP_SYSLOG "
500 current
->comm
, task_pid_nr(current
));
505 return security_syslog(type
);
509 /* /dev/kmsg - userspace message inject/listen interface */
510 struct devkmsg_user
{
518 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
522 int level
= default_message_loglevel
;
523 int facility
= 1; /* LOG_USER */
524 size_t len
= iocb
->ki_nbytes
;
527 if (len
> LOG_LINE_MAX
)
529 buf
= kmalloc(len
+1, GFP_KERNEL
);
534 if (copy_from_iter(buf
, len
, from
) != len
) {
540 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
541 * the decimal value represents 32bit, the lower 3 bit are the log
542 * level, the rest are the log facility.
544 * If no prefix or no userspace facility is specified, we
545 * enforce LOG_USER, to be able to reliably distinguish
546 * kernel-generated messages from userspace-injected ones.
549 if (line
[0] == '<') {
552 i
= simple_strtoul(line
+1, &endp
, 10);
553 if (endp
&& endp
[0] == '>') {
563 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
568 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
569 size_t count
, loff_t
*ppos
)
571 struct devkmsg_user
*user
= file
->private_data
;
572 struct printk_log
*msg
;
582 ret
= mutex_lock_interruptible(&user
->lock
);
585 raw_spin_lock_irq(&logbuf_lock
);
586 while (user
->seq
== log_next_seq
) {
587 if (file
->f_flags
& O_NONBLOCK
) {
589 raw_spin_unlock_irq(&logbuf_lock
);
593 raw_spin_unlock_irq(&logbuf_lock
);
594 ret
= wait_event_interruptible(log_wait
,
595 user
->seq
!= log_next_seq
);
598 raw_spin_lock_irq(&logbuf_lock
);
601 if (user
->seq
< log_first_seq
) {
602 /* our last seen message is gone, return error and reset */
603 user
->idx
= log_first_idx
;
604 user
->seq
= log_first_seq
;
606 raw_spin_unlock_irq(&logbuf_lock
);
610 msg
= log_from_idx(user
->idx
);
611 ts_usec
= msg
->ts_nsec
;
612 do_div(ts_usec
, 1000);
615 * If we couldn't merge continuation line fragments during the print,
616 * export the stored flags to allow an optional external merge of the
617 * records. Merging the records isn't always neccessarily correct, like
618 * when we hit a race during printing. In most cases though, it produces
619 * better readable output. 'c' in the record flags mark the first
620 * fragment of a line, '+' the following.
622 if (msg
->flags
& LOG_CONT
&& !(user
->prev
& LOG_CONT
))
624 else if ((msg
->flags
& LOG_CONT
) ||
625 ((user
->prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
)))
628 len
= sprintf(user
->buf
, "%u,%llu,%llu,%c;",
629 (msg
->facility
<< 3) | msg
->level
,
630 user
->seq
, ts_usec
, cont
);
631 user
->prev
= msg
->flags
;
633 /* escape non-printable characters */
634 for (i
= 0; i
< msg
->text_len
; i
++) {
635 unsigned char c
= log_text(msg
)[i
];
637 if (c
< ' ' || c
>= 127 || c
== '\\')
638 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
640 user
->buf
[len
++] = c
;
642 user
->buf
[len
++] = '\n';
647 for (i
= 0; i
< msg
->dict_len
; i
++) {
648 unsigned char c
= log_dict(msg
)[i
];
651 user
->buf
[len
++] = ' ';
656 user
->buf
[len
++] = '\n';
661 if (c
< ' ' || c
>= 127 || c
== '\\') {
662 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
666 user
->buf
[len
++] = c
;
668 user
->buf
[len
++] = '\n';
671 user
->idx
= log_next(user
->idx
);
673 raw_spin_unlock_irq(&logbuf_lock
);
680 if (copy_to_user(buf
, user
->buf
, len
)) {
686 mutex_unlock(&user
->lock
);
690 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
692 struct devkmsg_user
*user
= file
->private_data
;
700 raw_spin_lock_irq(&logbuf_lock
);
703 /* the first record */
704 user
->idx
= log_first_idx
;
705 user
->seq
= log_first_seq
;
709 * The first record after the last SYSLOG_ACTION_CLEAR,
710 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
711 * changes no global state, and does not clear anything.
713 user
->idx
= clear_idx
;
714 user
->seq
= clear_seq
;
717 /* after the last record */
718 user
->idx
= log_next_idx
;
719 user
->seq
= log_next_seq
;
724 raw_spin_unlock_irq(&logbuf_lock
);
728 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
730 struct devkmsg_user
*user
= file
->private_data
;
734 return POLLERR
|POLLNVAL
;
736 poll_wait(file
, &log_wait
, wait
);
738 raw_spin_lock_irq(&logbuf_lock
);
739 if (user
->seq
< log_next_seq
) {
740 /* return error when data has vanished underneath us */
741 if (user
->seq
< log_first_seq
)
742 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
744 ret
= POLLIN
|POLLRDNORM
;
746 raw_spin_unlock_irq(&logbuf_lock
);
751 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
753 struct devkmsg_user
*user
;
756 /* write-only does not need any file context */
757 if ((file
->f_flags
& O_ACCMODE
) == O_WRONLY
)
760 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
765 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
769 mutex_init(&user
->lock
);
771 raw_spin_lock_irq(&logbuf_lock
);
772 user
->idx
= log_first_idx
;
773 user
->seq
= log_first_seq
;
774 raw_spin_unlock_irq(&logbuf_lock
);
776 file
->private_data
= user
;
780 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
782 struct devkmsg_user
*user
= file
->private_data
;
787 mutex_destroy(&user
->lock
);
792 const struct file_operations kmsg_fops
= {
793 .open
= devkmsg_open
,
794 .read
= devkmsg_read
,
795 .write_iter
= devkmsg_write
,
796 .llseek
= devkmsg_llseek
,
797 .poll
= devkmsg_poll
,
798 .release
= devkmsg_release
,
803 * This appends the listed symbols to /proc/vmcore
805 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
806 * obtain access to symbols that are otherwise very difficult to locate. These
807 * symbols are specifically used so that utilities can access and extract the
808 * dmesg log from a vmcore file after a crash.
810 void log_buf_kexec_setup(void)
812 VMCOREINFO_SYMBOL(log_buf
);
813 VMCOREINFO_SYMBOL(log_buf_len
);
814 VMCOREINFO_SYMBOL(log_first_idx
);
815 VMCOREINFO_SYMBOL(log_next_idx
);
817 * Export struct printk_log size and field offsets. User space tools can
818 * parse it and detect any changes to structure down the line.
820 VMCOREINFO_STRUCT_SIZE(printk_log
);
821 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
822 VMCOREINFO_OFFSET(printk_log
, len
);
823 VMCOREINFO_OFFSET(printk_log
, text_len
);
824 VMCOREINFO_OFFSET(printk_log
, dict_len
);
828 /* requested log_buf_len from kernel cmdline */
829 static unsigned long __initdata new_log_buf_len
;
831 /* we practice scaling the ring buffer by powers of 2 */
832 static void __init
log_buf_len_update(unsigned size
)
835 size
= roundup_pow_of_two(size
);
836 if (size
> log_buf_len
)
837 new_log_buf_len
= size
;
840 /* save requested log_buf_len since it's too early to process it */
841 static int __init
log_buf_len_setup(char *str
)
843 unsigned size
= memparse(str
, &str
);
845 log_buf_len_update(size
);
849 early_param("log_buf_len", log_buf_len_setup
);
852 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
854 static void __init
log_buf_add_cpu(void)
856 unsigned int cpu_extra
;
859 * archs should set up cpu_possible_bits properly with
860 * set_cpu_possible() after setup_arch() but just in
861 * case lets ensure this is valid.
863 if (num_possible_cpus() == 1)
866 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
868 /* by default this will only continue through for large > 64 CPUs */
869 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
872 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
873 __LOG_CPU_MAX_BUF_LEN
);
874 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
876 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
878 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
880 #else /* !CONFIG_SMP */
881 static inline void log_buf_add_cpu(void) {}
882 #endif /* CONFIG_SMP */
884 void __init
setup_log_buf(int early
)
890 if (log_buf
!= __log_buf
)
893 if (!early
&& !new_log_buf_len
)
896 if (!new_log_buf_len
)
901 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
903 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
907 if (unlikely(!new_log_buf
)) {
908 pr_err("log_buf_len: %ld bytes not available\n",
913 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
914 log_buf_len
= new_log_buf_len
;
915 log_buf
= new_log_buf
;
917 free
= __LOG_BUF_LEN
- log_next_idx
;
918 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
919 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
921 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
922 pr_info("early log buf free: %d(%d%%)\n",
923 free
, (free
* 100) / __LOG_BUF_LEN
);
926 static bool __read_mostly ignore_loglevel
;
928 static int __init
ignore_loglevel_setup(char *str
)
930 ignore_loglevel
= true;
931 pr_info("debug: ignoring loglevel setting.\n");
936 early_param("ignore_loglevel", ignore_loglevel_setup
);
937 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
938 MODULE_PARM_DESC(ignore_loglevel
,
939 "ignore loglevel setting (prints all kernel messages to the console)");
941 #ifdef CONFIG_BOOT_PRINTK_DELAY
943 static int boot_delay
; /* msecs delay after each printk during bootup */
944 static unsigned long long loops_per_msec
; /* based on boot_delay */
946 static int __init
boot_delay_setup(char *str
)
950 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
951 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
953 get_option(&str
, &boot_delay
);
954 if (boot_delay
> 10 * 1000)
957 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
958 "HZ: %d, loops_per_msec: %llu\n",
959 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
962 early_param("boot_delay", boot_delay_setup
);
964 static void boot_delay_msec(int level
)
966 unsigned long long k
;
967 unsigned long timeout
;
969 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
970 || (level
>= console_loglevel
&& !ignore_loglevel
)) {
974 k
= (unsigned long long)loops_per_msec
* boot_delay
;
976 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
981 * use (volatile) jiffies to prevent
982 * compiler reduction; loop termination via jiffies
983 * is secondary and may or may not happen.
985 if (time_after(jiffies
, timeout
))
987 touch_nmi_watchdog();
991 static inline void boot_delay_msec(int level
)
996 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
997 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
999 static size_t print_time(u64 ts
, char *buf
)
1001 unsigned long rem_nsec
;
1006 rem_nsec
= do_div(ts
, 1000000000);
1009 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1011 return sprintf(buf
, "[%5lu.%06lu] ",
1012 (unsigned long)ts
, rem_nsec
/ 1000);
1015 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1018 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1022 len
+= sprintf(buf
, "<%u>", prefix
);
1027 else if (prefix
> 99)
1029 else if (prefix
> 9)
1034 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1038 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1039 bool syslog
, char *buf
, size_t size
)
1041 const char *text
= log_text(msg
);
1042 size_t text_size
= msg
->text_len
;
1044 bool newline
= true;
1047 if ((prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
))
1050 if (msg
->flags
& LOG_CONT
) {
1051 if ((prev
& LOG_CONT
) && !(prev
& LOG_NEWLINE
))
1054 if (!(msg
->flags
& LOG_NEWLINE
))
1059 const char *next
= memchr(text
, '\n', text_size
);
1063 text_len
= next
- text
;
1065 text_size
-= next
- text
;
1067 text_len
= text_size
;
1071 if (print_prefix(msg
, syslog
, NULL
) +
1072 text_len
+ 1 >= size
- len
)
1076 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1077 memcpy(buf
+ len
, text
, text_len
);
1079 if (next
|| newline
)
1082 /* SYSLOG_ACTION_* buffer size only calculation */
1084 len
+= print_prefix(msg
, syslog
, NULL
);
1086 if (next
|| newline
)
1097 static int syslog_print(char __user
*buf
, int size
)
1100 struct printk_log
*msg
;
1103 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1111 raw_spin_lock_irq(&logbuf_lock
);
1112 if (syslog_seq
< log_first_seq
) {
1113 /* messages are gone, move to first one */
1114 syslog_seq
= log_first_seq
;
1115 syslog_idx
= log_first_idx
;
1119 if (syslog_seq
== log_next_seq
) {
1120 raw_spin_unlock_irq(&logbuf_lock
);
1124 skip
= syslog_partial
;
1125 msg
= log_from_idx(syslog_idx
);
1126 n
= msg_print_text(msg
, syslog_prev
, true, text
,
1127 LOG_LINE_MAX
+ PREFIX_MAX
);
1128 if (n
- syslog_partial
<= size
) {
1129 /* message fits into buffer, move forward */
1130 syslog_idx
= log_next(syslog_idx
);
1132 syslog_prev
= msg
->flags
;
1133 n
-= syslog_partial
;
1136 /* partial read(), remember position */
1138 syslog_partial
+= n
;
1141 raw_spin_unlock_irq(&logbuf_lock
);
1146 if (copy_to_user(buf
, text
+ skip
, n
)) {
1161 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1166 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1170 raw_spin_lock_irq(&logbuf_lock
);
1175 enum log_flags prev
;
1177 if (clear_seq
< log_first_seq
) {
1178 /* messages are gone, move to first available one */
1179 clear_seq
= log_first_seq
;
1180 clear_idx
= log_first_idx
;
1184 * Find first record that fits, including all following records,
1185 * into the user-provided buffer for this dump.
1190 while (seq
< log_next_seq
) {
1191 struct printk_log
*msg
= log_from_idx(idx
);
1193 len
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1195 idx
= log_next(idx
);
1199 /* move first record forward until length fits into the buffer */
1203 while (len
> size
&& seq
< log_next_seq
) {
1204 struct printk_log
*msg
= log_from_idx(idx
);
1206 len
-= msg_print_text(msg
, prev
, true, NULL
, 0);
1208 idx
= log_next(idx
);
1212 /* last message fitting into this dump */
1213 next_seq
= log_next_seq
;
1216 while (len
>= 0 && seq
< next_seq
) {
1217 struct printk_log
*msg
= log_from_idx(idx
);
1220 textlen
= msg_print_text(msg
, prev
, true, text
,
1221 LOG_LINE_MAX
+ PREFIX_MAX
);
1226 idx
= log_next(idx
);
1230 raw_spin_unlock_irq(&logbuf_lock
);
1231 if (copy_to_user(buf
+ len
, text
, textlen
))
1235 raw_spin_lock_irq(&logbuf_lock
);
1237 if (seq
< log_first_seq
) {
1238 /* messages are gone, move to next one */
1239 seq
= log_first_seq
;
1240 idx
= log_first_idx
;
1247 clear_seq
= log_next_seq
;
1248 clear_idx
= log_next_idx
;
1250 raw_spin_unlock_irq(&logbuf_lock
);
1256 int do_syslog(int type
, char __user
*buf
, int len
, bool from_file
)
1259 static int saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1262 error
= check_syslog_permissions(type
, from_file
);
1266 error
= security_syslog(type
);
1271 case SYSLOG_ACTION_CLOSE
: /* Close log */
1273 case SYSLOG_ACTION_OPEN
: /* Open log */
1275 case SYSLOG_ACTION_READ
: /* Read from log */
1277 if (!buf
|| len
< 0)
1282 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1286 error
= wait_event_interruptible(log_wait
,
1287 syslog_seq
!= log_next_seq
);
1290 error
= syslog_print(buf
, len
);
1292 /* Read/clear last kernel messages */
1293 case SYSLOG_ACTION_READ_CLEAR
:
1296 /* Read last kernel messages */
1297 case SYSLOG_ACTION_READ_ALL
:
1299 if (!buf
|| len
< 0)
1304 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1308 error
= syslog_print_all(buf
, len
, clear
);
1310 /* Clear ring buffer */
1311 case SYSLOG_ACTION_CLEAR
:
1312 syslog_print_all(NULL
, 0, true);
1314 /* Disable logging to console */
1315 case SYSLOG_ACTION_CONSOLE_OFF
:
1316 if (saved_console_loglevel
== LOGLEVEL_DEFAULT
)
1317 saved_console_loglevel
= console_loglevel
;
1318 console_loglevel
= minimum_console_loglevel
;
1320 /* Enable logging to console */
1321 case SYSLOG_ACTION_CONSOLE_ON
:
1322 if (saved_console_loglevel
!= LOGLEVEL_DEFAULT
) {
1323 console_loglevel
= saved_console_loglevel
;
1324 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1327 /* Set level of messages printed to console */
1328 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1330 if (len
< 1 || len
> 8)
1332 if (len
< minimum_console_loglevel
)
1333 len
= minimum_console_loglevel
;
1334 console_loglevel
= len
;
1335 /* Implicitly re-enable logging to console */
1336 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1339 /* Number of chars in the log buffer */
1340 case SYSLOG_ACTION_SIZE_UNREAD
:
1341 raw_spin_lock_irq(&logbuf_lock
);
1342 if (syslog_seq
< log_first_seq
) {
1343 /* messages are gone, move to first one */
1344 syslog_seq
= log_first_seq
;
1345 syslog_idx
= log_first_idx
;
1351 * Short-cut for poll(/"proc/kmsg") which simply checks
1352 * for pending data, not the size; return the count of
1353 * records, not the length.
1355 error
= log_next_seq
- syslog_seq
;
1357 u64 seq
= syslog_seq
;
1358 u32 idx
= syslog_idx
;
1359 enum log_flags prev
= syslog_prev
;
1362 while (seq
< log_next_seq
) {
1363 struct printk_log
*msg
= log_from_idx(idx
);
1365 error
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1366 idx
= log_next(idx
);
1370 error
-= syslog_partial
;
1372 raw_spin_unlock_irq(&logbuf_lock
);
1374 /* Size of the log buffer */
1375 case SYSLOG_ACTION_SIZE_BUFFER
:
1376 error
= log_buf_len
;
1386 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1388 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1392 * Call the console drivers, asking them to write out
1393 * log_buf[start] to log_buf[end - 1].
1394 * The console_lock must be held.
1396 static void call_console_drivers(int level
, const char *text
, size_t len
)
1398 struct console
*con
;
1400 trace_console(text
, len
);
1402 if (level
>= console_loglevel
&& !ignore_loglevel
)
1404 if (!console_drivers
)
1407 for_each_console(con
) {
1408 if (exclusive_console
&& con
!= exclusive_console
)
1410 if (!(con
->flags
& CON_ENABLED
))
1414 if (!cpu_online(smp_processor_id()) &&
1415 !(con
->flags
& CON_ANYTIME
))
1417 con
->write(con
, text
, len
);
1422 * Zap console related locks when oopsing.
1423 * To leave time for slow consoles to print a full oops,
1424 * only zap at most once every 30 seconds.
1426 static void zap_locks(void)
1428 static unsigned long oops_timestamp
;
1430 if (time_after_eq(jiffies
, oops_timestamp
) &&
1431 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1434 oops_timestamp
= jiffies
;
1437 /* If a crash is occurring, make sure we can't deadlock */
1438 raw_spin_lock_init(&logbuf_lock
);
1439 /* And make sure that we print immediately */
1440 sema_init(&console_sem
, 1);
1444 * Check if we have any console that is capable of printing while cpu is
1445 * booting or shutting down. Requires console_sem.
1447 static int have_callable_console(void)
1449 struct console
*con
;
1451 for_each_console(con
)
1452 if (con
->flags
& CON_ANYTIME
)
1459 * Can we actually use the console at this time on this cpu?
1461 * Console drivers may assume that per-cpu resources have been allocated. So
1462 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1463 * call them until this CPU is officially up.
1465 static inline int can_use_console(unsigned int cpu
)
1467 return cpu_online(cpu
) || have_callable_console();
1471 * Try to get console ownership to actually show the kernel
1472 * messages from a 'printk'. Return true (and with the
1473 * console_lock held, and 'console_locked' set) if it
1474 * is successful, false otherwise.
1476 static int console_trylock_for_printk(void)
1478 unsigned int cpu
= smp_processor_id();
1480 if (!console_trylock())
1483 * If we can't use the console, we need to release the console
1484 * semaphore by hand to avoid flushing the buffer. We need to hold the
1485 * console semaphore in order to do this test safely.
1487 if (!can_use_console(cpu
)) {
1495 int printk_delay_msec __read_mostly
;
1497 static inline void printk_delay(void)
1499 if (unlikely(printk_delay_msec
)) {
1500 int m
= printk_delay_msec
;
1504 touch_nmi_watchdog();
1510 * Continuation lines are buffered, and not committed to the record buffer
1511 * until the line is complete, or a race forces it. The line fragments
1512 * though, are printed immediately to the consoles to ensure everything has
1513 * reached the console in case of a kernel crash.
1515 static struct cont
{
1516 char buf
[LOG_LINE_MAX
];
1517 size_t len
; /* length == 0 means unused buffer */
1518 size_t cons
; /* bytes written to console */
1519 struct task_struct
*owner
; /* task of first print*/
1520 u64 ts_nsec
; /* time of first print */
1521 u8 level
; /* log level of first message */
1522 u8 facility
; /* log facility of first message */
1523 enum log_flags flags
; /* prefix, newline flags */
1524 bool flushed
:1; /* buffer sealed and committed */
1527 static void cont_flush(enum log_flags flags
)
1536 * If a fragment of this line was directly flushed to the
1537 * console; wait for the console to pick up the rest of the
1538 * line. LOG_NOCONS suppresses a duplicated output.
1540 log_store(cont
.facility
, cont
.level
, flags
| LOG_NOCONS
,
1541 cont
.ts_nsec
, NULL
, 0, cont
.buf
, cont
.len
);
1543 cont
.flushed
= true;
1546 * If no fragment of this line ever reached the console,
1547 * just submit it to the store and free the buffer.
1549 log_store(cont
.facility
, cont
.level
, flags
, 0,
1550 NULL
, 0, cont
.buf
, cont
.len
);
1555 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1557 if (cont
.len
&& cont
.flushed
)
1560 if (cont
.len
+ len
> sizeof(cont
.buf
)) {
1561 /* the line gets too long, split it up in separate records */
1562 cont_flush(LOG_CONT
);
1567 cont
.facility
= facility
;
1569 cont
.owner
= current
;
1570 cont
.ts_nsec
= local_clock();
1573 cont
.flushed
= false;
1576 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1579 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1580 cont_flush(LOG_CONT
);
1585 static size_t cont_print_text(char *text
, size_t size
)
1590 if (cont
.cons
== 0 && (console_prev
& LOG_NEWLINE
)) {
1591 textlen
+= print_time(cont
.ts_nsec
, text
);
1595 len
= cont
.len
- cont
.cons
;
1599 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1601 cont
.cons
= cont
.len
;
1605 if (cont
.flags
& LOG_NEWLINE
)
1606 text
[textlen
++] = '\n';
1607 /* got everything, release buffer */
1613 asmlinkage
int vprintk_emit(int facility
, int level
,
1614 const char *dict
, size_t dictlen
,
1615 const char *fmt
, va_list args
)
1617 static int recursion_bug
;
1618 static char textbuf
[LOG_LINE_MAX
];
1619 char *text
= textbuf
;
1620 size_t text_len
= 0;
1621 enum log_flags lflags
= 0;
1622 unsigned long flags
;
1624 int printed_len
= 0;
1625 bool in_sched
= false;
1626 /* cpu currently holding logbuf_lock in this function */
1627 static unsigned int logbuf_cpu
= UINT_MAX
;
1629 if (level
== LOGLEVEL_SCHED
) {
1630 level
= LOGLEVEL_DEFAULT
;
1634 boot_delay_msec(level
);
1637 /* This stops the holder of console_sem just where we want him */
1638 local_irq_save(flags
);
1639 this_cpu
= smp_processor_id();
1642 * Ouch, printk recursed into itself!
1644 if (unlikely(logbuf_cpu
== this_cpu
)) {
1646 * If a crash is occurring during printk() on this CPU,
1647 * then try to get the crash message out but make sure
1648 * we can't deadlock. Otherwise just return to avoid the
1649 * recursion and return - but flag the recursion so that
1650 * it can be printed at the next appropriate moment:
1652 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1654 local_irq_restore(flags
);
1661 raw_spin_lock(&logbuf_lock
);
1662 logbuf_cpu
= this_cpu
;
1664 if (unlikely(recursion_bug
)) {
1665 static const char recursion_msg
[] =
1666 "BUG: recent printk recursion!";
1669 /* emit KERN_CRIT message */
1670 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1671 NULL
, 0, recursion_msg
,
1672 strlen(recursion_msg
));
1676 * The printf needs to come first; we need the syslog
1677 * prefix which might be passed-in as a parameter.
1679 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1681 /* mark and strip a trailing newline */
1682 if (text_len
&& text
[text_len
-1] == '\n') {
1684 lflags
|= LOG_NEWLINE
;
1687 /* strip kernel syslog prefix and extract log level or control flags */
1688 if (facility
== 0) {
1689 int kern_level
= printk_get_level(text
);
1692 const char *end_of_header
= printk_skip_level(text
);
1693 switch (kern_level
) {
1695 if (level
== LOGLEVEL_DEFAULT
)
1696 level
= kern_level
- '0';
1698 case 'd': /* KERN_DEFAULT */
1699 lflags
|= LOG_PREFIX
;
1702 * No need to check length here because vscnprintf
1703 * put '\0' at the end of the string. Only valid and
1704 * newly printed level is detected.
1706 text_len
-= end_of_header
- text
;
1707 text
= (char *)end_of_header
;
1711 if (level
== LOGLEVEL_DEFAULT
)
1712 level
= default_message_loglevel
;
1715 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1717 if (!(lflags
& LOG_NEWLINE
)) {
1719 * Flush the conflicting buffer. An earlier newline was missing,
1720 * or another task also prints continuation lines.
1722 if (cont
.len
&& (lflags
& LOG_PREFIX
|| cont
.owner
!= current
))
1723 cont_flush(LOG_NEWLINE
);
1725 /* buffer line if possible, otherwise store it right away */
1726 if (cont_add(facility
, level
, text
, text_len
))
1727 printed_len
+= text_len
;
1729 printed_len
+= log_store(facility
, level
,
1730 lflags
| LOG_CONT
, 0,
1731 dict
, dictlen
, text
, text_len
);
1733 bool stored
= false;
1736 * If an earlier newline was missing and it was the same task,
1737 * either merge it with the current buffer and flush, or if
1738 * there was a race with interrupts (prefix == true) then just
1739 * flush it out and store this line separately.
1740 * If the preceding printk was from a different task and missed
1741 * a newline, flush and append the newline.
1744 if (cont
.owner
== current
&& !(lflags
& LOG_PREFIX
))
1745 stored
= cont_add(facility
, level
, text
,
1747 cont_flush(LOG_NEWLINE
);
1751 printed_len
+= text_len
;
1753 printed_len
+= log_store(facility
, level
, lflags
, 0,
1754 dict
, dictlen
, text
, text_len
);
1757 logbuf_cpu
= UINT_MAX
;
1758 raw_spin_unlock(&logbuf_lock
);
1760 local_irq_restore(flags
);
1762 /* If called from the scheduler, we can not call up(). */
1766 * Disable preemption to avoid being preempted while holding
1767 * console_sem which would prevent anyone from printing to
1773 * Try to acquire and then immediately release the console
1774 * semaphore. The release will print out buffers and wake up
1775 * /dev/kmsg and syslog() users.
1777 if (console_trylock_for_printk())
1785 EXPORT_SYMBOL(vprintk_emit
);
1787 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1789 return vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1791 EXPORT_SYMBOL(vprintk
);
1793 asmlinkage
int printk_emit(int facility
, int level
,
1794 const char *dict
, size_t dictlen
,
1795 const char *fmt
, ...)
1800 va_start(args
, fmt
);
1801 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1806 EXPORT_SYMBOL(printk_emit
);
1808 int vprintk_default(const char *fmt
, va_list args
)
1812 #ifdef CONFIG_KGDB_KDB
1813 if (unlikely(kdb_trap_printk
)) {
1814 r
= vkdb_printf(fmt
, args
);
1818 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1822 EXPORT_SYMBOL_GPL(vprintk_default
);
1825 * This allows printk to be diverted to another function per cpu.
1826 * This is useful for calling printk functions from within NMI
1827 * without worrying about race conditions that can lock up the
1830 DEFINE_PER_CPU(printk_func_t
, printk_func
) = vprintk_default
;
1833 * printk - print a kernel message
1834 * @fmt: format string
1836 * This is printk(). It can be called from any context. We want it to work.
1838 * We try to grab the console_lock. If we succeed, it's easy - we log the
1839 * output and call the console drivers. If we fail to get the semaphore, we
1840 * place the output into the log buffer and return. The current holder of
1841 * the console_sem will notice the new output in console_unlock(); and will
1842 * send it to the consoles before releasing the lock.
1844 * One effect of this deferred printing is that code which calls printk() and
1845 * then changes console_loglevel may break. This is because console_loglevel
1846 * is inspected when the actual printing occurs.
1851 * See the vsnprintf() documentation for format string extensions over C99.
1853 asmlinkage __visible
int printk(const char *fmt
, ...)
1855 printk_func_t vprintk_func
;
1859 va_start(args
, fmt
);
1862 * If a caller overrides the per_cpu printk_func, then it needs
1863 * to disable preemption when calling printk(). Otherwise
1864 * the printk_func should be set to the default. No need to
1865 * disable preemption here.
1867 vprintk_func
= this_cpu_read(printk_func
);
1868 r
= vprintk_func(fmt
, args
);
1874 EXPORT_SYMBOL(printk
);
1876 #else /* CONFIG_PRINTK */
1878 #define LOG_LINE_MAX 0
1879 #define PREFIX_MAX 0
1881 static u64 syslog_seq
;
1882 static u32 syslog_idx
;
1883 static u64 console_seq
;
1884 static u32 console_idx
;
1885 static enum log_flags syslog_prev
;
1886 static u64 log_first_seq
;
1887 static u32 log_first_idx
;
1888 static u64 log_next_seq
;
1889 static enum log_flags console_prev
;
1890 static struct cont
{
1896 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
1897 static u32
log_next(u32 idx
) { return 0; }
1898 static void call_console_drivers(int level
, const char *text
, size_t len
) {}
1899 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1900 bool syslog
, char *buf
, size_t size
) { return 0; }
1901 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
1903 /* Still needs to be defined for users */
1904 DEFINE_PER_CPU(printk_func_t
, printk_func
);
1906 #endif /* CONFIG_PRINTK */
1908 #ifdef CONFIG_EARLY_PRINTK
1909 struct console
*early_console
;
1911 asmlinkage __visible
void early_printk(const char *fmt
, ...)
1921 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
1924 early_console
->write(early_console
, buf
, n
);
1928 static int __add_preferred_console(char *name
, int idx
, char *options
,
1931 struct console_cmdline
*c
;
1935 * See if this tty is not yet registered, and
1936 * if we have a slot free.
1938 for (i
= 0, c
= console_cmdline
;
1939 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
1941 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
1943 selected_console
= i
;
1947 if (i
== MAX_CMDLINECONSOLES
)
1950 selected_console
= i
;
1951 strlcpy(c
->name
, name
, sizeof(c
->name
));
1952 c
->options
= options
;
1953 braille_set_options(c
, brl_options
);
1959 * Set up a console. Called via do_early_param() in init/main.c
1960 * for each "console=" parameter in the boot command line.
1962 static int __init
console_setup(char *str
)
1964 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
1965 char *s
, *options
, *brl_options
= NULL
;
1968 if (_braille_console_setup(&str
, &brl_options
))
1972 * Decode str into name, index, options.
1974 if (str
[0] >= '0' && str
[0] <= '9') {
1975 strcpy(buf
, "ttyS");
1976 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1978 strncpy(buf
, str
, sizeof(buf
) - 1);
1980 buf
[sizeof(buf
) - 1] = 0;
1981 options
= strchr(str
, ',');
1985 if (!strcmp(str
, "ttya"))
1986 strcpy(buf
, "ttyS0");
1987 if (!strcmp(str
, "ttyb"))
1988 strcpy(buf
, "ttyS1");
1990 for (s
= buf
; *s
; s
++)
1991 if (isdigit(*s
) || *s
== ',')
1993 idx
= simple_strtoul(s
, NULL
, 10);
1996 __add_preferred_console(buf
, idx
, options
, brl_options
);
1997 console_set_on_cmdline
= 1;
2000 __setup("console=", console_setup
);
2003 * add_preferred_console - add a device to the list of preferred consoles.
2004 * @name: device name
2005 * @idx: device index
2006 * @options: options for this console
2008 * The last preferred console added will be used for kernel messages
2009 * and stdin/out/err for init. Normally this is used by console_setup
2010 * above to handle user-supplied console arguments; however it can also
2011 * be used by arch-specific code either to override the user or more
2012 * commonly to provide a default console (ie from PROM variables) when
2013 * the user has not supplied one.
2015 int add_preferred_console(char *name
, int idx
, char *options
)
2017 return __add_preferred_console(name
, idx
, options
, NULL
);
2020 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
2022 struct console_cmdline
*c
;
2025 for (i
= 0, c
= console_cmdline
;
2026 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2028 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
2029 strlcpy(c
->name
, name_new
, sizeof(c
->name
));
2030 c
->options
= options
;
2038 bool console_suspend_enabled
= true;
2039 EXPORT_SYMBOL(console_suspend_enabled
);
2041 static int __init
console_suspend_disable(char *str
)
2043 console_suspend_enabled
= false;
2046 __setup("no_console_suspend", console_suspend_disable
);
2047 module_param_named(console_suspend
, console_suspend_enabled
,
2048 bool, S_IRUGO
| S_IWUSR
);
2049 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2050 " and hibernate operations");
2053 * suspend_console - suspend the console subsystem
2055 * This disables printk() while we go into suspend states
2057 void suspend_console(void)
2059 if (!console_suspend_enabled
)
2061 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2063 console_suspended
= 1;
2067 void resume_console(void)
2069 if (!console_suspend_enabled
)
2072 console_suspended
= 0;
2077 * console_cpu_notify - print deferred console messages after CPU hotplug
2078 * @self: notifier struct
2079 * @action: CPU hotplug event
2082 * If printk() is called from a CPU that is not online yet, the messages
2083 * will be spooled but will not show up on the console. This function is
2084 * called when a new CPU comes online (or fails to come up), and ensures
2085 * that any such output gets printed.
2087 static int console_cpu_notify(struct notifier_block
*self
,
2088 unsigned long action
, void *hcpu
)
2093 case CPU_DOWN_FAILED
:
2094 case CPU_UP_CANCELED
:
2102 * console_lock - lock the console system for exclusive use.
2104 * Acquires a lock which guarantees that the caller has
2105 * exclusive access to the console system and the console_drivers list.
2107 * Can sleep, returns nothing.
2109 void console_lock(void)
2114 if (console_suspended
)
2117 console_may_schedule
= 1;
2119 EXPORT_SYMBOL(console_lock
);
2122 * console_trylock - try to lock the console system for exclusive use.
2124 * Try to acquire a lock which guarantees that the caller has exclusive
2125 * access to the console system and the console_drivers list.
2127 * returns 1 on success, and 0 on failure to acquire the lock.
2129 int console_trylock(void)
2131 if (down_trylock_console_sem())
2133 if (console_suspended
) {
2138 console_may_schedule
= 0;
2141 EXPORT_SYMBOL(console_trylock
);
2143 int is_console_locked(void)
2145 return console_locked
;
2148 static void console_cont_flush(char *text
, size_t size
)
2150 unsigned long flags
;
2153 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2159 * We still queue earlier records, likely because the console was
2160 * busy. The earlier ones need to be printed before this one, we
2161 * did not flush any fragment so far, so just let it queue up.
2163 if (console_seq
< log_next_seq
&& !cont
.cons
)
2166 len
= cont_print_text(text
, size
);
2167 raw_spin_unlock(&logbuf_lock
);
2168 stop_critical_timings();
2169 call_console_drivers(cont
.level
, text
, len
);
2170 start_critical_timings();
2171 local_irq_restore(flags
);
2174 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2178 * console_unlock - unlock the console system
2180 * Releases the console_lock which the caller holds on the console system
2181 * and the console driver list.
2183 * While the console_lock was held, console output may have been buffered
2184 * by printk(). If this is the case, console_unlock(); emits
2185 * the output prior to releasing the lock.
2187 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2189 * console_unlock(); may be called from any context.
2191 void console_unlock(void)
2193 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2194 static u64 seen_seq
;
2195 unsigned long flags
;
2196 bool wake_klogd
= false;
2199 if (console_suspended
) {
2204 console_may_schedule
= 0;
2206 /* flush buffered message fragment immediately to console */
2207 console_cont_flush(text
, sizeof(text
));
2210 struct printk_log
*msg
;
2214 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2215 if (seen_seq
!= log_next_seq
) {
2217 seen_seq
= log_next_seq
;
2220 if (console_seq
< log_first_seq
) {
2221 len
= sprintf(text
, "** %u printk messages dropped ** ",
2222 (unsigned)(log_first_seq
- console_seq
));
2224 /* messages are gone, move to first one */
2225 console_seq
= log_first_seq
;
2226 console_idx
= log_first_idx
;
2232 if (console_seq
== log_next_seq
)
2235 msg
= log_from_idx(console_idx
);
2236 if (msg
->flags
& LOG_NOCONS
) {
2238 * Skip record we have buffered and already printed
2239 * directly to the console when we received it.
2241 console_idx
= log_next(console_idx
);
2244 * We will get here again when we register a new
2245 * CON_PRINTBUFFER console. Clear the flag so we
2246 * will properly dump everything later.
2248 msg
->flags
&= ~LOG_NOCONS
;
2249 console_prev
= msg
->flags
;
2254 len
+= msg_print_text(msg
, console_prev
, false,
2255 text
+ len
, sizeof(text
) - len
);
2256 console_idx
= log_next(console_idx
);
2258 console_prev
= msg
->flags
;
2259 raw_spin_unlock(&logbuf_lock
);
2261 stop_critical_timings(); /* don't trace print latency */
2262 call_console_drivers(level
, text
, len
);
2263 start_critical_timings();
2264 local_irq_restore(flags
);
2268 /* Release the exclusive_console once it is used */
2269 if (unlikely(exclusive_console
))
2270 exclusive_console
= NULL
;
2272 raw_spin_unlock(&logbuf_lock
);
2277 * Someone could have filled up the buffer again, so re-check if there's
2278 * something to flush. In case we cannot trylock the console_sem again,
2279 * there's a new owner and the console_unlock() from them will do the
2280 * flush, no worries.
2282 raw_spin_lock(&logbuf_lock
);
2283 retry
= console_seq
!= log_next_seq
;
2284 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2286 if (retry
&& console_trylock())
2292 EXPORT_SYMBOL(console_unlock
);
2295 * console_conditional_schedule - yield the CPU if required
2297 * If the console code is currently allowed to sleep, and
2298 * if this CPU should yield the CPU to another task, do
2301 * Must be called within console_lock();.
2303 void __sched
console_conditional_schedule(void)
2305 if (console_may_schedule
)
2308 EXPORT_SYMBOL(console_conditional_schedule
);
2310 void console_unblank(void)
2315 * console_unblank can no longer be called in interrupt context unless
2316 * oops_in_progress is set to 1..
2318 if (oops_in_progress
) {
2319 if (down_trylock_console_sem() != 0)
2325 console_may_schedule
= 0;
2327 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2333 * Return the console tty driver structure and its associated index
2335 struct tty_driver
*console_device(int *index
)
2338 struct tty_driver
*driver
= NULL
;
2341 for_each_console(c
) {
2344 driver
= c
->device(c
, index
);
2353 * Prevent further output on the passed console device so that (for example)
2354 * serial drivers can disable console output before suspending a port, and can
2355 * re-enable output afterwards.
2357 void console_stop(struct console
*console
)
2360 console
->flags
&= ~CON_ENABLED
;
2363 EXPORT_SYMBOL(console_stop
);
2365 void console_start(struct console
*console
)
2368 console
->flags
|= CON_ENABLED
;
2371 EXPORT_SYMBOL(console_start
);
2373 static int __read_mostly keep_bootcon
;
2375 static int __init
keep_bootcon_setup(char *str
)
2378 pr_info("debug: skip boot console de-registration.\n");
2383 early_param("keep_bootcon", keep_bootcon_setup
);
2386 * The console driver calls this routine during kernel initialization
2387 * to register the console printing procedure with printk() and to
2388 * print any messages that were printed by the kernel before the
2389 * console driver was initialized.
2391 * This can happen pretty early during the boot process (because of
2392 * early_printk) - sometimes before setup_arch() completes - be careful
2393 * of what kernel features are used - they may not be initialised yet.
2395 * There are two types of consoles - bootconsoles (early_printk) and
2396 * "real" consoles (everything which is not a bootconsole) which are
2397 * handled differently.
2398 * - Any number of bootconsoles can be registered at any time.
2399 * - As soon as a "real" console is registered, all bootconsoles
2400 * will be unregistered automatically.
2401 * - Once a "real" console is registered, any attempt to register a
2402 * bootconsoles will be rejected
2404 void register_console(struct console
*newcon
)
2407 unsigned long flags
;
2408 struct console
*bcon
= NULL
;
2409 struct console_cmdline
*c
;
2411 if (console_drivers
)
2412 for_each_console(bcon
)
2413 if (WARN(bcon
== newcon
,
2414 "console '%s%d' already registered\n",
2415 bcon
->name
, bcon
->index
))
2419 * before we register a new CON_BOOT console, make sure we don't
2420 * already have a valid console
2422 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2423 /* find the last or real console */
2424 for_each_console(bcon
) {
2425 if (!(bcon
->flags
& CON_BOOT
)) {
2426 pr_info("Too late to register bootconsole %s%d\n",
2427 newcon
->name
, newcon
->index
);
2433 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2434 bcon
= console_drivers
;
2436 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2437 preferred_console
= selected_console
;
2439 if (newcon
->early_setup
)
2440 newcon
->early_setup();
2443 * See if we want to use this console driver. If we
2444 * didn't select a console we take the first one
2445 * that registers here.
2447 if (preferred_console
< 0) {
2448 if (newcon
->index
< 0)
2450 if (newcon
->setup
== NULL
||
2451 newcon
->setup(newcon
, NULL
) == 0) {
2452 newcon
->flags
|= CON_ENABLED
;
2453 if (newcon
->device
) {
2454 newcon
->flags
|= CON_CONSDEV
;
2455 preferred_console
= 0;
2461 * See if this console matches one we selected on
2464 for (i
= 0, c
= console_cmdline
;
2465 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2467 if (strcmp(c
->name
, newcon
->name
) != 0)
2469 if (newcon
->index
>= 0 &&
2470 newcon
->index
!= c
->index
)
2472 if (newcon
->index
< 0)
2473 newcon
->index
= c
->index
;
2475 if (_braille_register_console(newcon
, c
))
2478 if (newcon
->setup
&&
2479 newcon
->setup(newcon
, console_cmdline
[i
].options
) != 0)
2481 newcon
->flags
|= CON_ENABLED
;
2482 newcon
->index
= c
->index
;
2483 if (i
== selected_console
) {
2484 newcon
->flags
|= CON_CONSDEV
;
2485 preferred_console
= selected_console
;
2490 if (!(newcon
->flags
& CON_ENABLED
))
2494 * If we have a bootconsole, and are switching to a real console,
2495 * don't print everything out again, since when the boot console, and
2496 * the real console are the same physical device, it's annoying to
2497 * see the beginning boot messages twice
2499 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2500 newcon
->flags
&= ~CON_PRINTBUFFER
;
2503 * Put this console in the list - keep the
2504 * preferred driver at the head of the list.
2507 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2508 newcon
->next
= console_drivers
;
2509 console_drivers
= newcon
;
2511 newcon
->next
->flags
&= ~CON_CONSDEV
;
2513 newcon
->next
= console_drivers
->next
;
2514 console_drivers
->next
= newcon
;
2516 if (newcon
->flags
& CON_PRINTBUFFER
) {
2518 * console_unlock(); will print out the buffered messages
2521 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2522 console_seq
= syslog_seq
;
2523 console_idx
= syslog_idx
;
2524 console_prev
= syslog_prev
;
2525 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2527 * We're about to replay the log buffer. Only do this to the
2528 * just-registered console to avoid excessive message spam to
2529 * the already-registered consoles.
2531 exclusive_console
= newcon
;
2534 console_sysfs_notify();
2537 * By unregistering the bootconsoles after we enable the real console
2538 * we get the "console xxx enabled" message on all the consoles -
2539 * boot consoles, real consoles, etc - this is to ensure that end
2540 * users know there might be something in the kernel's log buffer that
2541 * went to the bootconsole (that they do not see on the real console)
2543 pr_info("%sconsole [%s%d] enabled\n",
2544 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2545 newcon
->name
, newcon
->index
);
2547 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2549 /* We need to iterate through all boot consoles, to make
2550 * sure we print everything out, before we unregister them.
2552 for_each_console(bcon
)
2553 if (bcon
->flags
& CON_BOOT
)
2554 unregister_console(bcon
);
2557 EXPORT_SYMBOL(register_console
);
2559 int unregister_console(struct console
*console
)
2561 struct console
*a
, *b
;
2564 pr_info("%sconsole [%s%d] disabled\n",
2565 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2566 console
->name
, console
->index
);
2568 res
= _braille_unregister_console(console
);
2574 if (console_drivers
== console
) {
2575 console_drivers
=console
->next
;
2577 } else if (console_drivers
) {
2578 for (a
=console_drivers
->next
, b
=console_drivers
;
2579 a
; b
=a
, a
=b
->next
) {
2589 * If this isn't the last console and it has CON_CONSDEV set, we
2590 * need to set it on the next preferred console.
2592 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2593 console_drivers
->flags
|= CON_CONSDEV
;
2595 console
->flags
&= ~CON_ENABLED
;
2597 console_sysfs_notify();
2600 EXPORT_SYMBOL(unregister_console
);
2602 static int __init
printk_late_init(void)
2604 struct console
*con
;
2606 for_each_console(con
) {
2607 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2608 unregister_console(con
);
2611 hotcpu_notifier(console_cpu_notify
, 0);
2614 late_initcall(printk_late_init
);
2616 #if defined CONFIG_PRINTK
2618 * Delayed printk version, for scheduler-internal messages:
2620 #define PRINTK_PENDING_WAKEUP 0x01
2621 #define PRINTK_PENDING_OUTPUT 0x02
2623 static DEFINE_PER_CPU(int, printk_pending
);
2625 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2627 int pending
= __this_cpu_xchg(printk_pending
, 0);
2629 if (pending
& PRINTK_PENDING_OUTPUT
) {
2630 /* If trylock fails, someone else is doing the printing */
2631 if (console_trylock())
2635 if (pending
& PRINTK_PENDING_WAKEUP
)
2636 wake_up_interruptible(&log_wait
);
2639 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2640 .func
= wake_up_klogd_work_func
,
2641 .flags
= IRQ_WORK_LAZY
,
2644 void wake_up_klogd(void)
2647 if (waitqueue_active(&log_wait
)) {
2648 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2649 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2654 int printk_deferred(const char *fmt
, ...)
2660 va_start(args
, fmt
);
2661 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2664 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2665 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2672 * printk rate limiting, lifted from the networking subsystem.
2674 * This enforces a rate limit: not more than 10 kernel messages
2675 * every 5s to make a denial-of-service attack impossible.
2677 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2679 int __printk_ratelimit(const char *func
)
2681 return ___ratelimit(&printk_ratelimit_state
, func
);
2683 EXPORT_SYMBOL(__printk_ratelimit
);
2686 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2687 * @caller_jiffies: pointer to caller's state
2688 * @interval_msecs: minimum interval between prints
2690 * printk_timed_ratelimit() returns true if more than @interval_msecs
2691 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2694 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2695 unsigned int interval_msecs
)
2697 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2699 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2702 *caller_jiffies
= jiffies
;
2705 EXPORT_SYMBOL(printk_timed_ratelimit
);
2707 static DEFINE_SPINLOCK(dump_list_lock
);
2708 static LIST_HEAD(dump_list
);
2711 * kmsg_dump_register - register a kernel log dumper.
2712 * @dumper: pointer to the kmsg_dumper structure
2714 * Adds a kernel log dumper to the system. The dump callback in the
2715 * structure will be called when the kernel oopses or panics and must be
2716 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2718 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2720 unsigned long flags
;
2723 /* The dump callback needs to be set */
2727 spin_lock_irqsave(&dump_list_lock
, flags
);
2728 /* Don't allow registering multiple times */
2729 if (!dumper
->registered
) {
2730 dumper
->registered
= 1;
2731 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2734 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2738 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2741 * kmsg_dump_unregister - unregister a kmsg dumper.
2742 * @dumper: pointer to the kmsg_dumper structure
2744 * Removes a dump device from the system. Returns zero on success and
2745 * %-EINVAL otherwise.
2747 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2749 unsigned long flags
;
2752 spin_lock_irqsave(&dump_list_lock
, flags
);
2753 if (dumper
->registered
) {
2754 dumper
->registered
= 0;
2755 list_del_rcu(&dumper
->list
);
2758 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2763 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2765 static bool always_kmsg_dump
;
2766 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2769 * kmsg_dump - dump kernel log to kernel message dumpers.
2770 * @reason: the reason (oops, panic etc) for dumping
2772 * Call each of the registered dumper's dump() callback, which can
2773 * retrieve the kmsg records with kmsg_dump_get_line() or
2774 * kmsg_dump_get_buffer().
2776 void kmsg_dump(enum kmsg_dump_reason reason
)
2778 struct kmsg_dumper
*dumper
;
2779 unsigned long flags
;
2781 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2785 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2786 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2789 /* initialize iterator with data about the stored records */
2790 dumper
->active
= true;
2792 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2793 dumper
->cur_seq
= clear_seq
;
2794 dumper
->cur_idx
= clear_idx
;
2795 dumper
->next_seq
= log_next_seq
;
2796 dumper
->next_idx
= log_next_idx
;
2797 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2799 /* invoke dumper which will iterate over records */
2800 dumper
->dump(dumper
, reason
);
2802 /* reset iterator */
2803 dumper
->active
= false;
2809 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2810 * @dumper: registered kmsg dumper
2811 * @syslog: include the "<4>" prefixes
2812 * @line: buffer to copy the line to
2813 * @size: maximum size of the buffer
2814 * @len: length of line placed into buffer
2816 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2817 * record, and copy one record into the provided buffer.
2819 * Consecutive calls will return the next available record moving
2820 * towards the end of the buffer with the youngest messages.
2822 * A return value of FALSE indicates that there are no more records to
2825 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2827 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
2828 char *line
, size_t size
, size_t *len
)
2830 struct printk_log
*msg
;
2834 if (!dumper
->active
)
2837 if (dumper
->cur_seq
< log_first_seq
) {
2838 /* messages are gone, move to first available one */
2839 dumper
->cur_seq
= log_first_seq
;
2840 dumper
->cur_idx
= log_first_idx
;
2844 if (dumper
->cur_seq
>= log_next_seq
)
2847 msg
= log_from_idx(dumper
->cur_idx
);
2848 l
= msg_print_text(msg
, 0, syslog
, line
, size
);
2850 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2860 * kmsg_dump_get_line - retrieve one kmsg log line
2861 * @dumper: registered kmsg dumper
2862 * @syslog: include the "<4>" prefixes
2863 * @line: buffer to copy the line to
2864 * @size: maximum size of the buffer
2865 * @len: length of line placed into buffer
2867 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2868 * record, and copy one record into the provided buffer.
2870 * Consecutive calls will return the next available record moving
2871 * towards the end of the buffer with the youngest messages.
2873 * A return value of FALSE indicates that there are no more records to
2876 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2877 char *line
, size_t size
, size_t *len
)
2879 unsigned long flags
;
2882 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2883 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
2884 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2888 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
2891 * kmsg_dump_get_buffer - copy kmsg log lines
2892 * @dumper: registered kmsg dumper
2893 * @syslog: include the "<4>" prefixes
2894 * @buf: buffer to copy the line to
2895 * @size: maximum size of the buffer
2896 * @len: length of line placed into buffer
2898 * Start at the end of the kmsg buffer and fill the provided buffer
2899 * with as many of the the *youngest* kmsg records that fit into it.
2900 * If the buffer is large enough, all available kmsg records will be
2901 * copied with a single call.
2903 * Consecutive calls will fill the buffer with the next block of
2904 * available older records, not including the earlier retrieved ones.
2906 * A return value of FALSE indicates that there are no more records to
2909 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
2910 char *buf
, size_t size
, size_t *len
)
2912 unsigned long flags
;
2917 enum log_flags prev
;
2921 if (!dumper
->active
)
2924 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2925 if (dumper
->cur_seq
< log_first_seq
) {
2926 /* messages are gone, move to first available one */
2927 dumper
->cur_seq
= log_first_seq
;
2928 dumper
->cur_idx
= log_first_idx
;
2932 if (dumper
->cur_seq
>= dumper
->next_seq
) {
2933 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2937 /* calculate length of entire buffer */
2938 seq
= dumper
->cur_seq
;
2939 idx
= dumper
->cur_idx
;
2941 while (seq
< dumper
->next_seq
) {
2942 struct printk_log
*msg
= log_from_idx(idx
);
2944 l
+= msg_print_text(msg
, prev
, true, NULL
, 0);
2945 idx
= log_next(idx
);
2950 /* move first record forward until length fits into the buffer */
2951 seq
= dumper
->cur_seq
;
2952 idx
= dumper
->cur_idx
;
2954 while (l
> size
&& seq
< dumper
->next_seq
) {
2955 struct printk_log
*msg
= log_from_idx(idx
);
2957 l
-= msg_print_text(msg
, prev
, true, NULL
, 0);
2958 idx
= log_next(idx
);
2963 /* last message in next interation */
2968 while (seq
< dumper
->next_seq
) {
2969 struct printk_log
*msg
= log_from_idx(idx
);
2971 l
+= msg_print_text(msg
, prev
, syslog
, buf
+ l
, size
- l
);
2972 idx
= log_next(idx
);
2977 dumper
->next_seq
= next_seq
;
2978 dumper
->next_idx
= next_idx
;
2980 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2986 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
2989 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2990 * @dumper: registered kmsg dumper
2992 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2993 * kmsg_dump_get_buffer() can be called again and used multiple
2994 * times within the same dumper.dump() callback.
2996 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2998 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3000 dumper
->cur_seq
= clear_seq
;
3001 dumper
->cur_idx
= clear_idx
;
3002 dumper
->next_seq
= log_next_seq
;
3003 dumper
->next_idx
= log_next_idx
;
3007 * kmsg_dump_rewind - reset the interator
3008 * @dumper: registered kmsg dumper
3010 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3011 * kmsg_dump_get_buffer() can be called again and used multiple
3012 * times within the same dumper.dump() callback.
3014 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3016 unsigned long flags
;
3018 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3019 kmsg_dump_rewind_nolock(dumper
);
3020 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3022 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3024 static char dump_stack_arch_desc_str
[128];
3027 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3028 * @fmt: printf-style format string
3029 * @...: arguments for the format string
3031 * The configured string will be printed right after utsname during task
3032 * dumps. Usually used to add arch-specific system identifiers. If an
3033 * arch wants to make use of such an ID string, it should initialize this
3034 * as soon as possible during boot.
3036 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3040 va_start(args
, fmt
);
3041 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3047 * dump_stack_print_info - print generic debug info for dump_stack()
3048 * @log_lvl: log level
3050 * Arch-specific dump_stack() implementations can use this function to
3051 * print out the same debug information as the generic dump_stack().
3053 void dump_stack_print_info(const char *log_lvl
)
3055 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3056 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3057 print_tainted(), init_utsname()->release
,
3058 (int)strcspn(init_utsname()->version
, " "),
3059 init_utsname()->version
);
3061 if (dump_stack_arch_desc_str
[0] != '\0')
3062 printk("%sHardware name: %s\n",
3063 log_lvl
, dump_stack_arch_desc_str
);
3065 print_worker_info(log_lvl
, current
);
3069 * show_regs_print_info - print generic debug info for show_regs()
3070 * @log_lvl: log level
3072 * show_regs() implementations can use this function to print out generic
3073 * debug information.
3075 void show_regs_print_info(const char *log_lvl
)
3077 dump_stack_print_info(log_lvl
);
3079 printk("%stask: %p ti: %p task.ti: %p\n",
3080 log_lvl
, current
, current_thread_info(),
3081 task_thread_info(current
));