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>
46 #include <asm/uaccess.h>
48 #define CREATE_TRACE_POINTS
49 #include <trace/events/printk.h>
52 * Architectures can override it:
54 void asmlinkage
__attribute__((weak
)) early_printk(const char *fmt
, ...)
58 /* printk's without a loglevel use this.. */
59 #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
61 /* We show everything that is MORE important than this.. */
62 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
63 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
65 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
67 int console_printk
[4] = {
68 DEFAULT_CONSOLE_LOGLEVEL
, /* console_loglevel */
69 DEFAULT_MESSAGE_LOGLEVEL
, /* default_message_loglevel */
70 MINIMUM_CONSOLE_LOGLEVEL
, /* minimum_console_loglevel */
71 DEFAULT_CONSOLE_LOGLEVEL
, /* default_console_loglevel */
75 * Low level drivers may need that to know if they can schedule in
76 * their unblank() callback or not. So let's export it.
79 EXPORT_SYMBOL(oops_in_progress
);
82 * console_sem protects the console_drivers list, and also
83 * provides serialisation for access to the entire console
86 static DEFINE_SEMAPHORE(console_sem
);
87 struct console
*console_drivers
;
88 EXPORT_SYMBOL_GPL(console_drivers
);
91 * This is used for debugging the mess that is the VT code by
92 * keeping track if we have the console semaphore held. It's
93 * definitely not the perfect debug tool (we don't know if _WE_
94 * hold it are racing, but it helps tracking those weird code
95 * path in the console code where we end up in places I want
96 * locked without the console sempahore held
98 static int console_locked
, console_suspended
;
101 * If exclusive_console is non-NULL then only this console is to be printed to.
103 static struct console
*exclusive_console
;
106 * Array of consoles built from command line options (console=)
108 struct console_cmdline
110 char name
[8]; /* Name of the driver */
111 int index
; /* Minor dev. to use */
112 char *options
; /* Options for the driver */
113 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
114 char *brl_options
; /* Options for braille driver */
118 #define MAX_CMDLINECONSOLES 8
120 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
121 static int selected_console
= -1;
122 static int preferred_console
= -1;
123 int console_set_on_cmdline
;
124 EXPORT_SYMBOL(console_set_on_cmdline
);
126 /* Flag: console code may call schedule() */
127 static int console_may_schedule
;
130 * The printk log buffer consists of a chain of concatenated variable
131 * length records. Every record starts with a record header, containing
132 * the overall length of the record.
134 * The heads to the first and last entry in the buffer, as well as the
135 * sequence numbers of these both entries are maintained when messages
138 * If the heads indicate available messages, the length in the header
139 * tells the start next message. A length == 0 for the next message
140 * indicates a wrap-around to the beginning of the buffer.
142 * Every record carries the monotonic timestamp in microseconds, as well as
143 * the standard userspace syslog level and syslog facility. The usual
144 * kernel messages use LOG_KERN; userspace-injected messages always carry
145 * a matching syslog facility, by default LOG_USER. The origin of every
146 * message can be reliably determined that way.
148 * The human readable log message directly follows the message header. The
149 * length of the message text is stored in the header, the stored message
152 * Optionally, a message can carry a dictionary of properties (key/value pairs),
153 * to provide userspace with a machine-readable message context.
155 * Examples for well-defined, commonly used property names are:
156 * DEVICE=b12:8 device identifier
160 * +sound:card0 subsystem:devname
161 * SUBSYSTEM=pci driver-core subsystem name
163 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
164 * follows directly after a '=' character. Every property is terminated by
165 * a '\0' character. The last property is not terminated.
167 * Example of a message structure:
168 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
169 * 0008 34 00 record is 52 bytes long
170 * 000a 0b 00 text is 11 bytes long
171 * 000c 1f 00 dictionary is 23 bytes long
172 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
173 * 0010 69 74 27 73 20 61 20 6c "it's a l"
175 * 001b 44 45 56 49 43 "DEVIC"
176 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
177 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
179 * 0032 00 00 00 padding to next message header
181 * The 'struct log' buffer header must never be directly exported to
182 * userspace, it is a kernel-private implementation detail that might
183 * need to be changed in the future, when the requirements change.
185 * /dev/kmsg exports the structured data in the following line format:
186 * "level,sequnum,timestamp;<message text>\n"
188 * The optional key/value pairs are attached as continuation lines starting
189 * with a space character and terminated by a newline. All possible
190 * non-prinatable characters are escaped in the "\xff" notation.
192 * Users of the export format should ignore possible additional values
193 * separated by ',', and find the message after the ';' character.
197 u64 ts_nsec
; /* timestamp in nanoseconds */
198 u16 len
; /* length of entire record */
199 u16 text_len
; /* length of text buffer */
200 u16 dict_len
; /* length of dictionary buffer */
201 u16 level
; /* syslog level + facility */
205 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
206 * used in interesting ways to provide interlocking in console_unlock();
208 static DEFINE_RAW_SPINLOCK(logbuf_lock
);
210 /* the next printk record to read by syslog(READ) or /proc/kmsg */
211 static u64 syslog_seq
;
212 static u32 syslog_idx
;
214 /* index and sequence number of the first record stored in the buffer */
215 static u64 log_first_seq
;
216 static u32 log_first_idx
;
218 /* index and sequence number of the next record to store in the buffer */
219 static u64 log_next_seq
;
221 static u32 log_next_idx
;
223 /* the next printk record to read after the last 'clear' command */
224 static u64 clear_seq
;
225 static u32 clear_idx
;
227 #define LOG_LINE_MAX 1024
230 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
231 static char __log_buf
[__LOG_BUF_LEN
];
232 static char *log_buf
= __log_buf
;
233 static u32 log_buf_len
= __LOG_BUF_LEN
;
235 /* cpu currently holding logbuf_lock */
236 static volatile unsigned int logbuf_cpu
= UINT_MAX
;
238 /* human readable text of the record */
239 static char *log_text(const struct log
*msg
)
241 return (char *)msg
+ sizeof(struct log
);
244 /* optional key/value pair dictionary attached to the record */
245 static char *log_dict(const struct log
*msg
)
247 return (char *)msg
+ sizeof(struct log
) + msg
->text_len
;
250 /* get record by index; idx must point to valid msg */
251 static struct log
*log_from_idx(u32 idx
)
253 struct log
*msg
= (struct log
*)(log_buf
+ idx
);
256 * A length == 0 record is the end of buffer marker. Wrap around and
257 * read the message at the start of the buffer.
260 return (struct log
*)log_buf
;
264 /* get next record; idx must point to valid msg */
265 static u32
log_next(u32 idx
)
267 struct log
*msg
= (struct log
*)(log_buf
+ idx
);
269 /* length == 0 indicates the end of the buffer; wrap */
271 * A length == 0 record is the end of buffer marker. Wrap around and
272 * read the message at the start of the buffer as *this* one, and
273 * return the one after that.
276 msg
= (struct log
*)log_buf
;
279 return idx
+ msg
->len
;
282 #if !defined(CONFIG_64BIT) || defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
288 /* insert record into the buffer, discard old ones, update heads */
289 static void log_store(int facility
, int level
,
290 const char *dict
, u16 dict_len
,
291 const char *text
, u16 text_len
)
296 /* number of '\0' padding bytes to next message */
297 size
= sizeof(struct log
) + text_len
+ dict_len
;
298 pad_len
= (-size
) & (LOG_ALIGN
- 1);
301 while (log_first_seq
< log_next_seq
) {
304 if (log_next_idx
> log_first_idx
)
305 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
307 free
= log_first_idx
- log_next_idx
;
309 if (free
> size
+ sizeof(struct log
))
312 /* drop old messages until we have enough contiuous space */
313 log_first_idx
= log_next(log_first_idx
);
317 if (log_next_idx
+ size
+ sizeof(struct log
) >= log_buf_len
) {
319 * This message + an additional empty header does not fit
320 * at the end of the buffer. Add an empty header with len == 0
321 * to signify a wrap around.
323 memset(log_buf
+ log_next_idx
, 0, sizeof(struct log
));
328 msg
= (struct log
*)(log_buf
+ log_next_idx
);
329 memcpy(log_text(msg
), text
, text_len
);
330 msg
->text_len
= text_len
;
331 memcpy(log_dict(msg
), dict
, dict_len
);
332 msg
->dict_len
= dict_len
;
333 msg
->level
= (facility
<< 3) | (level
& 7);
334 msg
->ts_nsec
= local_clock();
335 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
336 msg
->len
= sizeof(struct log
) + text_len
+ dict_len
+ pad_len
;
339 log_next_idx
+= msg
->len
;
343 /* /dev/kmsg - userspace message inject/listen interface */
344 struct devkmsg_user
{
351 static ssize_t
devkmsg_writev(struct kiocb
*iocb
, const struct iovec
*iv
,
352 unsigned long count
, loff_t pos
)
356 int level
= default_message_loglevel
;
357 int facility
= 1; /* LOG_USER */
358 size_t len
= iov_length(iv
, count
);
361 if (len
> LOG_LINE_MAX
)
363 buf
= kmalloc(len
+1, GFP_KERNEL
);
368 for (i
= 0; i
< count
; i
++) {
369 if (copy_from_user(line
, iv
[i
].iov_base
, iv
[i
].iov_len
))
371 line
+= iv
[i
].iov_len
;
375 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
376 * the decimal value represents 32bit, the lower 3 bit are the log
377 * level, the rest are the log facility.
379 * If no prefix or no userspace facility is specified, we
380 * enforce LOG_USER, to be able to reliably distinguish
381 * kernel-generated messages from userspace-injected ones.
384 if (line
[0] == '<') {
387 i
= simple_strtoul(line
+1, &endp
, 10);
388 if (endp
&& endp
[0] == '>') {
399 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
405 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
406 size_t count
, loff_t
*ppos
)
408 struct devkmsg_user
*user
= file
->private_data
;
418 mutex_lock(&user
->lock
);
419 raw_spin_lock(&logbuf_lock
);
420 while (user
->seq
== log_next_seq
) {
421 if (file
->f_flags
& O_NONBLOCK
) {
423 raw_spin_unlock(&logbuf_lock
);
427 raw_spin_unlock(&logbuf_lock
);
428 ret
= wait_event_interruptible(log_wait
,
429 user
->seq
!= log_next_seq
);
432 raw_spin_lock(&logbuf_lock
);
435 if (user
->seq
< log_first_seq
) {
436 /* our last seen message is gone, return error and reset */
437 user
->idx
= log_first_idx
;
438 user
->seq
= log_first_seq
;
440 raw_spin_unlock(&logbuf_lock
);
444 msg
= log_from_idx(user
->idx
);
445 ts_usec
= msg
->ts_nsec
;
446 do_div(ts_usec
, 1000);
447 len
= sprintf(user
->buf
, "%u,%llu,%llu;",
448 msg
->level
, user
->seq
, ts_usec
);
450 /* escape non-printable characters */
451 for (i
= 0; i
< msg
->text_len
; i
++) {
452 char c
= log_text(msg
)[i
];
454 if (c
< ' ' || c
>= 128)
455 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
457 user
->buf
[len
++] = c
;
459 user
->buf
[len
++] = '\n';
464 for (i
= 0; i
< msg
->dict_len
; i
++) {
465 char c
= log_dict(msg
)[i
];
468 user
->buf
[len
++] = ' ';
473 user
->buf
[len
++] = '\n';
478 if (c
< ' ' || c
>= 128) {
479 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
483 user
->buf
[len
++] = c
;
485 user
->buf
[len
++] = '\n';
488 user
->idx
= log_next(user
->idx
);
490 raw_spin_unlock(&logbuf_lock
);
497 if (copy_to_user(buf
, user
->buf
, len
)) {
503 mutex_unlock(&user
->lock
);
507 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
509 struct devkmsg_user
*user
= file
->private_data
;
517 raw_spin_lock(&logbuf_lock
);
520 /* the first record */
521 user
->idx
= log_first_idx
;
522 user
->seq
= log_first_seq
;
526 * The first record after the last SYSLOG_ACTION_CLEAR,
527 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
528 * changes no global state, and does not clear anything.
530 user
->idx
= clear_idx
;
531 user
->seq
= clear_seq
;
534 /* after the last record */
535 user
->idx
= log_next_idx
;
536 user
->seq
= log_next_seq
;
541 raw_spin_unlock(&logbuf_lock
);
545 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
547 struct devkmsg_user
*user
= file
->private_data
;
551 return POLLERR
|POLLNVAL
;
553 poll_wait(file
, &log_wait
, wait
);
555 raw_spin_lock(&logbuf_lock
);
556 if (user
->seq
< log_next_seq
) {
557 /* return error when data has vanished underneath us */
558 if (user
->seq
< log_first_seq
)
559 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
560 ret
= POLLIN
|POLLRDNORM
;
562 raw_spin_unlock(&logbuf_lock
);
567 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
569 struct devkmsg_user
*user
;
572 /* write-only does not need any file context */
573 if ((file
->f_flags
& O_ACCMODE
) == O_WRONLY
)
576 err
= security_syslog(SYSLOG_ACTION_READ_ALL
);
580 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
584 mutex_init(&user
->lock
);
586 raw_spin_lock(&logbuf_lock
);
587 user
->idx
= log_first_idx
;
588 user
->seq
= log_first_seq
;
589 raw_spin_unlock(&logbuf_lock
);
591 file
->private_data
= user
;
595 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
597 struct devkmsg_user
*user
= file
->private_data
;
602 mutex_destroy(&user
->lock
);
607 const struct file_operations kmsg_fops
= {
608 .open
= devkmsg_open
,
609 .read
= devkmsg_read
,
610 .aio_write
= devkmsg_writev
,
611 .llseek
= devkmsg_llseek
,
612 .poll
= devkmsg_poll
,
613 .release
= devkmsg_release
,
618 * This appends the listed symbols to /proc/vmcoreinfo
620 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
621 * obtain access to symbols that are otherwise very difficult to locate. These
622 * symbols are specifically used so that utilities can access and extract the
623 * dmesg log from a vmcore file after a crash.
625 void log_buf_kexec_setup(void)
627 VMCOREINFO_SYMBOL(log_buf
);
628 VMCOREINFO_SYMBOL(log_buf_len
);
629 VMCOREINFO_SYMBOL(log_first_idx
);
630 VMCOREINFO_SYMBOL(log_next_idx
);
634 /* requested log_buf_len from kernel cmdline */
635 static unsigned long __initdata new_log_buf_len
;
637 /* save requested log_buf_len since it's too early to process it */
638 static int __init
log_buf_len_setup(char *str
)
640 unsigned size
= memparse(str
, &str
);
643 size
= roundup_pow_of_two(size
);
644 if (size
> log_buf_len
)
645 new_log_buf_len
= size
;
649 early_param("log_buf_len", log_buf_len_setup
);
651 void __init
setup_log_buf(int early
)
657 if (!new_log_buf_len
)
663 mem
= memblock_alloc(new_log_buf_len
, PAGE_SIZE
);
666 new_log_buf
= __va(mem
);
668 new_log_buf
= alloc_bootmem_nopanic(new_log_buf_len
);
671 if (unlikely(!new_log_buf
)) {
672 pr_err("log_buf_len: %ld bytes not available\n",
677 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
678 log_buf_len
= new_log_buf_len
;
679 log_buf
= new_log_buf
;
681 free
= __LOG_BUF_LEN
- log_next_idx
;
682 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
683 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
685 pr_info("log_buf_len: %d\n", log_buf_len
);
686 pr_info("early log buf free: %d(%d%%)\n",
687 free
, (free
* 100) / __LOG_BUF_LEN
);
690 #ifdef CONFIG_BOOT_PRINTK_DELAY
692 static int boot_delay
; /* msecs delay after each printk during bootup */
693 static unsigned long long loops_per_msec
; /* based on boot_delay */
695 static int __init
boot_delay_setup(char *str
)
699 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
700 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
702 get_option(&str
, &boot_delay
);
703 if (boot_delay
> 10 * 1000)
706 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
707 "HZ: %d, loops_per_msec: %llu\n",
708 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
711 __setup("boot_delay=", boot_delay_setup
);
713 static void boot_delay_msec(void)
715 unsigned long long k
;
716 unsigned long timeout
;
718 if (boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
721 k
= (unsigned long long)loops_per_msec
* boot_delay
;
723 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
728 * use (volatile) jiffies to prevent
729 * compiler reduction; loop termination via jiffies
730 * is secondary and may or may not happen.
732 if (time_after(jiffies
, timeout
))
734 touch_nmi_watchdog();
738 static inline void boot_delay_msec(void)
743 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
744 int dmesg_restrict
= 1;
749 static int syslog_action_restricted(int type
)
753 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
754 return type
!= SYSLOG_ACTION_READ_ALL
&& type
!= SYSLOG_ACTION_SIZE_BUFFER
;
757 static int check_syslog_permissions(int type
, bool from_file
)
760 * If this is from /proc/kmsg and we've already opened it, then we've
761 * already done the capabilities checks at open time.
763 if (from_file
&& type
!= SYSLOG_ACTION_OPEN
)
766 if (syslog_action_restricted(type
)) {
767 if (capable(CAP_SYSLOG
))
769 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
770 if (capable(CAP_SYS_ADMIN
)) {
771 printk_once(KERN_WARNING
"%s (%d): "
772 "Attempt to access syslog with CAP_SYS_ADMIN "
773 "but no CAP_SYSLOG (deprecated).\n",
774 current
->comm
, task_pid_nr(current
));
782 #if defined(CONFIG_PRINTK_TIME)
783 static bool printk_time
= 1;
785 static bool printk_time
;
787 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
789 static size_t prepend_timestamp(unsigned long long t
, char *buf
)
791 unsigned long rem_ns
;
799 rem_ns
= do_div(t
, 1000000000);
801 return sprintf(buf
, "[%5lu.%06lu] ",
802 (unsigned long) t
, rem_ns
/ 1000);
805 static int syslog_print_line(u32 idx
, char *text
, size_t size
)
810 msg
= log_from_idx(idx
);
812 /* calculate length only */
819 len
+= prepend_timestamp(0, NULL
);
821 len
+= msg
->text_len
;
826 len
= sprintf(text
, "<%u>", msg
->level
);
827 len
+= prepend_timestamp(msg
->ts_nsec
, text
+ len
);
828 if (len
+ msg
->text_len
> size
)
830 memcpy(text
+ len
, log_text(msg
), msg
->text_len
);
831 len
+= msg
->text_len
;
836 static int syslog_print(char __user
*buf
, int size
)
841 text
= kmalloc(LOG_LINE_MAX
, GFP_KERNEL
);
845 raw_spin_lock_irq(&logbuf_lock
);
846 if (syslog_seq
< log_first_seq
) {
847 /* messages are gone, move to first one */
848 syslog_seq
= log_first_seq
;
849 syslog_idx
= log_first_idx
;
851 len
= syslog_print_line(syslog_idx
, text
, LOG_LINE_MAX
);
852 syslog_idx
= log_next(syslog_idx
);
854 raw_spin_unlock_irq(&logbuf_lock
);
856 if (len
> 0 && copy_to_user(buf
, text
, len
))
863 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
868 text
= kmalloc(LOG_LINE_MAX
, GFP_KERNEL
);
872 raw_spin_lock_irq(&logbuf_lock
);
878 if (clear_seq
< log_first_seq
) {
879 /* messages are gone, move to first available one */
880 clear_seq
= log_first_seq
;
881 clear_idx
= log_first_idx
;
885 * Find first record that fits, including all following records,
886 * into the user-provided buffer for this dump.
890 while (seq
< log_next_seq
) {
891 len
+= syslog_print_line(idx
, NULL
, 0);
897 while (len
> size
&& seq
< log_next_seq
) {
898 len
-= syslog_print_line(idx
, NULL
, 0);
903 /* last message in this dump */
904 next_seq
= log_next_seq
;
907 while (len
>= 0 && seq
< next_seq
) {
910 textlen
= syslog_print_line(idx
, text
, LOG_LINE_MAX
);
918 raw_spin_unlock_irq(&logbuf_lock
);
919 if (copy_to_user(buf
+ len
, text
, textlen
))
923 raw_spin_lock_irq(&logbuf_lock
);
925 if (seq
< log_first_seq
) {
926 /* messages are gone, move to next one */
934 clear_seq
= log_next_seq
;
935 clear_idx
= log_next_idx
;
937 raw_spin_unlock_irq(&logbuf_lock
);
943 int do_syslog(int type
, char __user
*buf
, int len
, bool from_file
)
946 static int saved_console_loglevel
= -1;
949 error
= check_syslog_permissions(type
, from_file
);
953 error
= security_syslog(type
);
958 case SYSLOG_ACTION_CLOSE
: /* Close log */
960 case SYSLOG_ACTION_OPEN
: /* Open log */
962 case SYSLOG_ACTION_READ
: /* Read from log */
969 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
973 error
= wait_event_interruptible(log_wait
,
974 syslog_seq
!= log_next_seq
);
977 error
= syslog_print(buf
, len
);
979 /* Read/clear last kernel messages */
980 case SYSLOG_ACTION_READ_CLEAR
:
983 /* Read last kernel messages */
984 case SYSLOG_ACTION_READ_ALL
:
991 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
995 error
= syslog_print_all(buf
, len
, clear
);
997 /* Clear ring buffer */
998 case SYSLOG_ACTION_CLEAR
:
999 syslog_print_all(NULL
, 0, true);
1000 /* Disable logging to console */
1001 case SYSLOG_ACTION_CONSOLE_OFF
:
1002 if (saved_console_loglevel
== -1)
1003 saved_console_loglevel
= console_loglevel
;
1004 console_loglevel
= minimum_console_loglevel
;
1006 /* Enable logging to console */
1007 case SYSLOG_ACTION_CONSOLE_ON
:
1008 if (saved_console_loglevel
!= -1) {
1009 console_loglevel
= saved_console_loglevel
;
1010 saved_console_loglevel
= -1;
1013 /* Set level of messages printed to console */
1014 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1016 if (len
< 1 || len
> 8)
1018 if (len
< minimum_console_loglevel
)
1019 len
= minimum_console_loglevel
;
1020 console_loglevel
= len
;
1021 /* Implicitly re-enable logging to console */
1022 saved_console_loglevel
= -1;
1025 /* Number of chars in the log buffer */
1026 case SYSLOG_ACTION_SIZE_UNREAD
:
1027 raw_spin_lock_irq(&logbuf_lock
);
1028 if (syslog_seq
< log_first_seq
) {
1029 /* messages are gone, move to first one */
1030 syslog_seq
= log_first_seq
;
1031 syslog_idx
= log_first_idx
;
1035 * Short-cut for poll(/"proc/kmsg") which simply checks
1036 * for pending data, not the size; return the count of
1037 * records, not the length.
1039 error
= log_next_idx
- syslog_idx
;
1047 while (seq
< log_next_seq
) {
1048 error
+= syslog_print_line(idx
, NULL
, 0);
1049 idx
= log_next(idx
);
1053 raw_spin_unlock_irq(&logbuf_lock
);
1055 /* Size of the log buffer */
1056 case SYSLOG_ACTION_SIZE_BUFFER
:
1057 error
= log_buf_len
;
1067 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1069 return do_syslog(type
, buf
, len
, SYSLOG_FROM_CALL
);
1072 #ifdef CONFIG_KGDB_KDB
1073 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
1074 * uses locks so it cannot be used during debugging. Just tell kdb
1075 * where the start and end of the physical and logical logs are. This
1076 * is equivalent to do_syslog(3).
1078 void kdb_syslog_data(char *syslog_data
[4])
1080 syslog_data
[0] = log_buf
;
1081 syslog_data
[1] = log_buf
+ log_buf_len
;
1082 syslog_data
[2] = log_buf
+ log_first_idx
;
1083 syslog_data
[3] = log_buf
+ log_next_idx
;
1085 #endif /* CONFIG_KGDB_KDB */
1087 static bool __read_mostly ignore_loglevel
;
1089 static int __init
ignore_loglevel_setup(char *str
)
1091 ignore_loglevel
= 1;
1092 printk(KERN_INFO
"debug: ignoring loglevel setting.\n");
1097 early_param("ignore_loglevel", ignore_loglevel_setup
);
1098 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1099 MODULE_PARM_DESC(ignore_loglevel
, "ignore loglevel setting, to"
1100 "print all kernel messages to the console.");
1103 * Call the console drivers, asking them to write out
1104 * log_buf[start] to log_buf[end - 1].
1105 * The console_lock must be held.
1107 static void call_console_drivers(int level
, const char *text
, size_t len
)
1109 struct console
*con
;
1111 trace_console(text
, 0, len
, len
);
1113 if (level
>= console_loglevel
&& !ignore_loglevel
)
1115 if (!console_drivers
)
1118 for_each_console(con
) {
1119 if (exclusive_console
&& con
!= exclusive_console
)
1121 if (!(con
->flags
& CON_ENABLED
))
1125 if (!cpu_online(smp_processor_id()) &&
1126 !(con
->flags
& CON_ANYTIME
))
1128 con
->write(con
, text
, len
);
1133 * Zap console related locks when oopsing. Only zap at most once
1134 * every 10 seconds, to leave time for slow consoles to print a
1137 static void zap_locks(void)
1139 static unsigned long oops_timestamp
;
1141 if (time_after_eq(jiffies
, oops_timestamp
) &&
1142 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1145 oops_timestamp
= jiffies
;
1148 /* If a crash is occurring, make sure we can't deadlock */
1149 raw_spin_lock_init(&logbuf_lock
);
1150 /* And make sure that we print immediately */
1151 sema_init(&console_sem
, 1);
1154 /* Check if we have any console registered that can be called early in boot. */
1155 static int have_callable_console(void)
1157 struct console
*con
;
1159 for_each_console(con
)
1160 if (con
->flags
& CON_ANYTIME
)
1167 * Can we actually use the console at this time on this cpu?
1169 * Console drivers may assume that per-cpu resources have
1170 * been allocated. So unless they're explicitly marked as
1171 * being able to cope (CON_ANYTIME) don't call them until
1172 * this CPU is officially up.
1174 static inline int can_use_console(unsigned int cpu
)
1176 return cpu_online(cpu
) || have_callable_console();
1180 * Try to get console ownership to actually show the kernel
1181 * messages from a 'printk'. Return true (and with the
1182 * console_lock held, and 'console_locked' set) if it
1183 * is successful, false otherwise.
1185 * This gets called with the 'logbuf_lock' spinlock held and
1186 * interrupts disabled. It should return with 'lockbuf_lock'
1187 * released but interrupts still disabled.
1189 static int console_trylock_for_printk(unsigned int cpu
)
1190 __releases(&logbuf_lock
)
1192 int retval
= 0, wake
= 0;
1194 if (console_trylock()) {
1198 * If we can't use the console, we need to release
1199 * the console semaphore by hand to avoid flushing
1200 * the buffer. We need to hold the console semaphore
1201 * in order to do this test safely.
1203 if (!can_use_console(cpu
)) {
1209 logbuf_cpu
= UINT_MAX
;
1212 raw_spin_unlock(&logbuf_lock
);
1216 int printk_delay_msec __read_mostly
;
1218 static inline void printk_delay(void)
1220 if (unlikely(printk_delay_msec
)) {
1221 int m
= printk_delay_msec
;
1225 touch_nmi_watchdog();
1230 asmlinkage
int vprintk_emit(int facility
, int level
,
1231 const char *dict
, size_t dictlen
,
1232 const char *fmt
, va_list args
)
1234 static int recursion_bug
;
1235 static char buf
[LOG_LINE_MAX
];
1236 static size_t buflen
;
1237 static int buflevel
;
1238 static char textbuf
[LOG_LINE_MAX
];
1239 static struct task_struct
*cont
;
1240 char *text
= textbuf
;
1242 unsigned long flags
;
1244 bool newline
= false;
1245 bool prefix
= false;
1246 int printed_len
= 0;
1251 /* This stops the holder of console_sem just where we want him */
1252 local_irq_save(flags
);
1253 this_cpu
= smp_processor_id();
1256 * Ouch, printk recursed into itself!
1258 if (unlikely(logbuf_cpu
== this_cpu
)) {
1260 * If a crash is occurring during printk() on this CPU,
1261 * then try to get the crash message out but make sure
1262 * we can't deadlock. Otherwise just return to avoid the
1263 * recursion and return - but flag the recursion so that
1264 * it can be printed at the next appropriate moment:
1266 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1268 goto out_restore_irqs
;
1274 raw_spin_lock(&logbuf_lock
);
1275 logbuf_cpu
= this_cpu
;
1277 if (recursion_bug
) {
1278 static const char recursion_msg
[] =
1279 "BUG: recent printk recursion!";
1282 printed_len
+= strlen(recursion_msg
);
1283 /* emit KERN_CRIT message */
1284 log_store(0, 2, NULL
, 0, recursion_msg
, printed_len
);
1288 * The printf needs to come first; we need the syslog
1289 * prefix which might be passed-in as a parameter.
1291 textlen
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1293 /* mark and strip a trailing newline */
1294 if (textlen
&& text
[textlen
-1] == '\n') {
1299 /* strip syslog prefix and extract log level or flags */
1300 if (text
[0] == '<' && text
[1] && text
[2] == '>') {
1304 level
= text
[1] - '0';
1305 case 'd': /* KERN_DEFAULT */
1307 case 'c': /* KERN_CONT */
1313 if (buflen
&& (prefix
|| dict
|| cont
!= current
)) {
1314 /* flush existing buffer */
1315 log_store(facility
, buflevel
, NULL
, 0, buf
, buflen
);
1316 printed_len
+= buflen
;
1321 /* remember level for first message in the buffer */
1323 buflevel
= default_message_loglevel
;
1328 if (buflen
|| !newline
) {
1329 /* append to existing buffer, or buffer until next message */
1330 if (buflen
+ textlen
> sizeof(buf
))
1331 textlen
= sizeof(buf
) - buflen
;
1332 memcpy(buf
+ buflen
, text
, textlen
);
1337 /* end of line; flush buffer */
1339 log_store(facility
, buflevel
,
1340 dict
, dictlen
, buf
, buflen
);
1341 printed_len
+= buflen
;
1344 log_store(facility
, buflevel
,
1345 dict
, dictlen
, text
, textlen
);
1346 printed_len
+= textlen
;
1350 /* remember thread which filled the buffer */
1355 * Try to acquire and then immediately release the console semaphore.
1356 * The release will print out buffers and wake up /dev/kmsg and syslog()
1359 * The console_trylock_for_printk() function will release 'logbuf_lock'
1360 * regardless of whether it actually gets the console semaphore or not.
1362 if (console_trylock_for_printk(this_cpu
))
1367 local_irq_restore(flags
);
1371 EXPORT_SYMBOL(vprintk_emit
);
1373 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1375 return vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1377 EXPORT_SYMBOL(vprintk
);
1379 asmlinkage
int printk_emit(int facility
, int level
,
1380 const char *dict
, size_t dictlen
,
1381 const char *fmt
, ...)
1386 va_start(args
, fmt
);
1387 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1392 EXPORT_SYMBOL(printk_emit
);
1395 * printk - print a kernel message
1396 * @fmt: format string
1398 * This is printk(). It can be called from any context. We want it to work.
1400 * We try to grab the console_lock. If we succeed, it's easy - we log the
1401 * output and call the console drivers. If we fail to get the semaphore, we
1402 * place the output into the log buffer and return. The current holder of
1403 * the console_sem will notice the new output in console_unlock(); and will
1404 * send it to the consoles before releasing the lock.
1406 * One effect of this deferred printing is that code which calls printk() and
1407 * then changes console_loglevel may break. This is because console_loglevel
1408 * is inspected when the actual printing occurs.
1413 * See the vsnprintf() documentation for format string extensions over C99.
1415 asmlinkage
int printk(const char *fmt
, ...)
1420 #ifdef CONFIG_KGDB_KDB
1421 if (unlikely(kdb_trap_printk
)) {
1422 va_start(args
, fmt
);
1423 r
= vkdb_printf(fmt
, args
);
1428 va_start(args
, fmt
);
1429 r
= vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1434 EXPORT_SYMBOL(printk
);
1438 #define LOG_LINE_MAX 0
1439 static struct log
*log_from_idx(u32 idx
) { return NULL
; }
1440 static u32
log_next(u32 idx
) { return 0; }
1441 static char *log_text(const struct log
*msg
) { return NULL
; }
1442 static void call_console_drivers(int level
, const char *text
, size_t len
) {}
1444 #endif /* CONFIG_PRINTK */
1446 static int __add_preferred_console(char *name
, int idx
, char *options
,
1449 struct console_cmdline
*c
;
1453 * See if this tty is not yet registered, and
1454 * if we have a slot free.
1456 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
1457 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
1458 console_cmdline
[i
].index
== idx
) {
1460 selected_console
= i
;
1463 if (i
== MAX_CMDLINECONSOLES
)
1466 selected_console
= i
;
1467 c
= &console_cmdline
[i
];
1468 strlcpy(c
->name
, name
, sizeof(c
->name
));
1469 c
->options
= options
;
1470 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1471 c
->brl_options
= brl_options
;
1477 * Set up a list of consoles. Called from init/main.c
1479 static int __init
console_setup(char *str
)
1481 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for index */
1482 char *s
, *options
, *brl_options
= NULL
;
1485 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1486 if (!memcmp(str
, "brl,", 4)) {
1489 } else if (!memcmp(str
, "brl=", 4)) {
1490 brl_options
= str
+ 4;
1491 str
= strchr(brl_options
, ',');
1493 printk(KERN_ERR
"need port name after brl=\n");
1501 * Decode str into name, index, options.
1503 if (str
[0] >= '0' && str
[0] <= '9') {
1504 strcpy(buf
, "ttyS");
1505 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1507 strncpy(buf
, str
, sizeof(buf
) - 1);
1509 buf
[sizeof(buf
) - 1] = 0;
1510 if ((options
= strchr(str
, ',')) != NULL
)
1513 if (!strcmp(str
, "ttya"))
1514 strcpy(buf
, "ttyS0");
1515 if (!strcmp(str
, "ttyb"))
1516 strcpy(buf
, "ttyS1");
1518 for (s
= buf
; *s
; s
++)
1519 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
1521 idx
= simple_strtoul(s
, NULL
, 10);
1524 __add_preferred_console(buf
, idx
, options
, brl_options
);
1525 console_set_on_cmdline
= 1;
1528 __setup("console=", console_setup
);
1531 * add_preferred_console - add a device to the list of preferred consoles.
1532 * @name: device name
1533 * @idx: device index
1534 * @options: options for this console
1536 * The last preferred console added will be used for kernel messages
1537 * and stdin/out/err for init. Normally this is used by console_setup
1538 * above to handle user-supplied console arguments; however it can also
1539 * be used by arch-specific code either to override the user or more
1540 * commonly to provide a default console (ie from PROM variables) when
1541 * the user has not supplied one.
1543 int add_preferred_console(char *name
, int idx
, char *options
)
1545 return __add_preferred_console(name
, idx
, options
, NULL
);
1548 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
1550 struct console_cmdline
*c
;
1553 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
1554 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
1555 console_cmdline
[i
].index
== idx
) {
1556 c
= &console_cmdline
[i
];
1557 strlcpy(c
->name
, name_new
, sizeof(c
->name
));
1558 c
->name
[sizeof(c
->name
) - 1] = 0;
1559 c
->options
= options
;
1567 bool console_suspend_enabled
= 1;
1568 EXPORT_SYMBOL(console_suspend_enabled
);
1570 static int __init
console_suspend_disable(char *str
)
1572 console_suspend_enabled
= 0;
1575 __setup("no_console_suspend", console_suspend_disable
);
1576 module_param_named(console_suspend
, console_suspend_enabled
,
1577 bool, S_IRUGO
| S_IWUSR
);
1578 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
1579 " and hibernate operations");
1582 * suspend_console - suspend the console subsystem
1584 * This disables printk() while we go into suspend states
1586 void suspend_console(void)
1588 if (!console_suspend_enabled
)
1590 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1592 console_suspended
= 1;
1596 void resume_console(void)
1598 if (!console_suspend_enabled
)
1601 console_suspended
= 0;
1606 * console_cpu_notify - print deferred console messages after CPU hotplug
1607 * @self: notifier struct
1608 * @action: CPU hotplug event
1611 * If printk() is called from a CPU that is not online yet, the messages
1612 * will be spooled but will not show up on the console. This function is
1613 * called when a new CPU comes online (or fails to come up), and ensures
1614 * that any such output gets printed.
1616 static int __cpuinit
console_cpu_notify(struct notifier_block
*self
,
1617 unsigned long action
, void *hcpu
)
1623 case CPU_DOWN_FAILED
:
1624 case CPU_UP_CANCELED
:
1632 * console_lock - lock the console system for exclusive use.
1634 * Acquires a lock which guarantees that the caller has
1635 * exclusive access to the console system and the console_drivers list.
1637 * Can sleep, returns nothing.
1639 void console_lock(void)
1641 BUG_ON(in_interrupt());
1643 if (console_suspended
)
1646 console_may_schedule
= 1;
1648 EXPORT_SYMBOL(console_lock
);
1651 * console_trylock - try to lock the console system for exclusive use.
1653 * Tried to acquire a lock which guarantees that the caller has
1654 * exclusive access to the console system and the console_drivers list.
1656 * returns 1 on success, and 0 on failure to acquire the lock.
1658 int console_trylock(void)
1660 if (down_trylock(&console_sem
))
1662 if (console_suspended
) {
1667 console_may_schedule
= 0;
1670 EXPORT_SYMBOL(console_trylock
);
1672 int is_console_locked(void)
1674 return console_locked
;
1678 * Delayed printk version, for scheduler-internal messages:
1680 #define PRINTK_BUF_SIZE 512
1682 #define PRINTK_PENDING_WAKEUP 0x01
1683 #define PRINTK_PENDING_SCHED 0x02
1685 static DEFINE_PER_CPU(int, printk_pending
);
1686 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE
], printk_sched_buf
);
1688 void printk_tick(void)
1690 if (__this_cpu_read(printk_pending
)) {
1691 int pending
= __this_cpu_xchg(printk_pending
, 0);
1692 if (pending
& PRINTK_PENDING_SCHED
) {
1693 char *buf
= __get_cpu_var(printk_sched_buf
);
1694 printk(KERN_WARNING
"[sched_delayed] %s", buf
);
1696 if (pending
& PRINTK_PENDING_WAKEUP
)
1697 wake_up_interruptible(&log_wait
);
1701 int printk_needs_cpu(int cpu
)
1703 if (cpu_is_offline(cpu
))
1705 return __this_cpu_read(printk_pending
);
1708 void wake_up_klogd(void)
1710 if (waitqueue_active(&log_wait
))
1711 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
1714 /* the next printk record to write to the console */
1715 static u64 console_seq
;
1716 static u32 console_idx
;
1719 * console_unlock - unlock the console system
1721 * Releases the console_lock which the caller holds on the console system
1722 * and the console driver list.
1724 * While the console_lock was held, console output may have been buffered
1725 * by printk(). If this is the case, console_unlock(); emits
1726 * the output prior to releasing the lock.
1728 * If there is output waiting, we wake /dev/kmsg and syslog() users.
1730 * console_unlock(); may be called from any context.
1732 void console_unlock(void)
1734 static u64 seen_seq
;
1735 unsigned long flags
;
1736 bool wake_klogd
= false;
1739 if (console_suspended
) {
1744 console_may_schedule
= 0;
1749 static char text
[LOG_LINE_MAX
];
1753 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
1754 if (seen_seq
!= log_next_seq
) {
1756 seen_seq
= log_next_seq
;
1759 if (console_seq
< log_first_seq
) {
1760 /* messages are gone, move to first one */
1761 console_seq
= log_first_seq
;
1762 console_idx
= log_first_idx
;
1765 if (console_seq
== log_next_seq
)
1768 msg
= log_from_idx(console_idx
);
1769 level
= msg
->level
& 7;
1771 len
= prepend_timestamp(msg
->ts_nsec
, text
);
1773 if (len
+ l
+ 1 >= sizeof(text
))
1774 l
= sizeof(text
) - len
- 1;
1775 memcpy(text
+ len
, log_text(msg
), l
);
1779 console_idx
= log_next(console_idx
);
1781 raw_spin_unlock(&logbuf_lock
);
1783 stop_critical_timings(); /* don't trace print latency */
1784 call_console_drivers(level
, text
, len
);
1785 start_critical_timings();
1786 local_irq_restore(flags
);
1790 /* Release the exclusive_console once it is used */
1791 if (unlikely(exclusive_console
))
1792 exclusive_console
= NULL
;
1794 raw_spin_unlock(&logbuf_lock
);
1799 * Someone could have filled up the buffer again, so re-check if there's
1800 * something to flush. In case we cannot trylock the console_sem again,
1801 * there's a new owner and the console_unlock() from them will do the
1802 * flush, no worries.
1804 raw_spin_lock(&logbuf_lock
);
1805 retry
= console_seq
!= log_next_seq
;
1806 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
1808 if (retry
&& console_trylock())
1814 EXPORT_SYMBOL(console_unlock
);
1817 * console_conditional_schedule - yield the CPU if required
1819 * If the console code is currently allowed to sleep, and
1820 * if this CPU should yield the CPU to another task, do
1823 * Must be called within console_lock();.
1825 void __sched
console_conditional_schedule(void)
1827 if (console_may_schedule
)
1830 EXPORT_SYMBOL(console_conditional_schedule
);
1832 void console_unblank(void)
1837 * console_unblank can no longer be called in interrupt context unless
1838 * oops_in_progress is set to 1..
1840 if (oops_in_progress
) {
1841 if (down_trylock(&console_sem
) != 0)
1847 console_may_schedule
= 0;
1849 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
1855 * Return the console tty driver structure and its associated index
1857 struct tty_driver
*console_device(int *index
)
1860 struct tty_driver
*driver
= NULL
;
1863 for_each_console(c
) {
1866 driver
= c
->device(c
, index
);
1875 * Prevent further output on the passed console device so that (for example)
1876 * serial drivers can disable console output before suspending a port, and can
1877 * re-enable output afterwards.
1879 void console_stop(struct console
*console
)
1882 console
->flags
&= ~CON_ENABLED
;
1885 EXPORT_SYMBOL(console_stop
);
1887 void console_start(struct console
*console
)
1890 console
->flags
|= CON_ENABLED
;
1893 EXPORT_SYMBOL(console_start
);
1895 static int __read_mostly keep_bootcon
;
1897 static int __init
keep_bootcon_setup(char *str
)
1900 printk(KERN_INFO
"debug: skip boot console de-registration.\n");
1905 early_param("keep_bootcon", keep_bootcon_setup
);
1908 * The console driver calls this routine during kernel initialization
1909 * to register the console printing procedure with printk() and to
1910 * print any messages that were printed by the kernel before the
1911 * console driver was initialized.
1913 * This can happen pretty early during the boot process (because of
1914 * early_printk) - sometimes before setup_arch() completes - be careful
1915 * of what kernel features are used - they may not be initialised yet.
1917 * There are two types of consoles - bootconsoles (early_printk) and
1918 * "real" consoles (everything which is not a bootconsole) which are
1919 * handled differently.
1920 * - Any number of bootconsoles can be registered at any time.
1921 * - As soon as a "real" console is registered, all bootconsoles
1922 * will be unregistered automatically.
1923 * - Once a "real" console is registered, any attempt to register a
1924 * bootconsoles will be rejected
1926 void register_console(struct console
*newcon
)
1929 unsigned long flags
;
1930 struct console
*bcon
= NULL
;
1933 * before we register a new CON_BOOT console, make sure we don't
1934 * already have a valid console
1936 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
1937 /* find the last or real console */
1938 for_each_console(bcon
) {
1939 if (!(bcon
->flags
& CON_BOOT
)) {
1940 printk(KERN_INFO
"Too late to register bootconsole %s%d\n",
1941 newcon
->name
, newcon
->index
);
1947 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
1948 bcon
= console_drivers
;
1950 if (preferred_console
< 0 || bcon
|| !console_drivers
)
1951 preferred_console
= selected_console
;
1953 if (newcon
->early_setup
)
1954 newcon
->early_setup();
1957 * See if we want to use this console driver. If we
1958 * didn't select a console we take the first one
1959 * that registers here.
1961 if (preferred_console
< 0) {
1962 if (newcon
->index
< 0)
1964 if (newcon
->setup
== NULL
||
1965 newcon
->setup(newcon
, NULL
) == 0) {
1966 newcon
->flags
|= CON_ENABLED
;
1967 if (newcon
->device
) {
1968 newcon
->flags
|= CON_CONSDEV
;
1969 preferred_console
= 0;
1975 * See if this console matches one we selected on
1978 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
1980 if (strcmp(console_cmdline
[i
].name
, newcon
->name
) != 0)
1982 if (newcon
->index
>= 0 &&
1983 newcon
->index
!= console_cmdline
[i
].index
)
1985 if (newcon
->index
< 0)
1986 newcon
->index
= console_cmdline
[i
].index
;
1987 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1988 if (console_cmdline
[i
].brl_options
) {
1989 newcon
->flags
|= CON_BRL
;
1990 braille_register_console(newcon
,
1991 console_cmdline
[i
].index
,
1992 console_cmdline
[i
].options
,
1993 console_cmdline
[i
].brl_options
);
1997 if (newcon
->setup
&&
1998 newcon
->setup(newcon
, console_cmdline
[i
].options
) != 0)
2000 newcon
->flags
|= CON_ENABLED
;
2001 newcon
->index
= console_cmdline
[i
].index
;
2002 if (i
== selected_console
) {
2003 newcon
->flags
|= CON_CONSDEV
;
2004 preferred_console
= selected_console
;
2009 if (!(newcon
->flags
& CON_ENABLED
))
2013 * If we have a bootconsole, and are switching to a real console,
2014 * don't print everything out again, since when the boot console, and
2015 * the real console are the same physical device, it's annoying to
2016 * see the beginning boot messages twice
2018 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2019 newcon
->flags
&= ~CON_PRINTBUFFER
;
2022 * Put this console in the list - keep the
2023 * preferred driver at the head of the list.
2026 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2027 newcon
->next
= console_drivers
;
2028 console_drivers
= newcon
;
2030 newcon
->next
->flags
&= ~CON_CONSDEV
;
2032 newcon
->next
= console_drivers
->next
;
2033 console_drivers
->next
= newcon
;
2035 if (newcon
->flags
& CON_PRINTBUFFER
) {
2037 * console_unlock(); will print out the buffered messages
2040 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2041 console_seq
= syslog_seq
;
2042 console_idx
= syslog_idx
;
2043 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2045 * We're about to replay the log buffer. Only do this to the
2046 * just-registered console to avoid excessive message spam to
2047 * the already-registered consoles.
2049 exclusive_console
= newcon
;
2052 console_sysfs_notify();
2055 * By unregistering the bootconsoles after we enable the real console
2056 * we get the "console xxx enabled" message on all the consoles -
2057 * boot consoles, real consoles, etc - this is to ensure that end
2058 * users know there might be something in the kernel's log buffer that
2059 * went to the bootconsole (that they do not see on the real console)
2062 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2064 /* we need to iterate through twice, to make sure we print
2065 * everything out, before we unregister the console(s)
2067 printk(KERN_INFO
"console [%s%d] enabled, bootconsole disabled\n",
2068 newcon
->name
, newcon
->index
);
2069 for_each_console(bcon
)
2070 if (bcon
->flags
& CON_BOOT
)
2071 unregister_console(bcon
);
2073 printk(KERN_INFO
"%sconsole [%s%d] enabled\n",
2074 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2075 newcon
->name
, newcon
->index
);
2078 EXPORT_SYMBOL(register_console
);
2080 int unregister_console(struct console
*console
)
2082 struct console
*a
, *b
;
2085 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2086 if (console
->flags
& CON_BRL
)
2087 return braille_unregister_console(console
);
2091 if (console_drivers
== console
) {
2092 console_drivers
=console
->next
;
2094 } else if (console_drivers
) {
2095 for (a
=console_drivers
->next
, b
=console_drivers
;
2096 a
; b
=a
, a
=b
->next
) {
2106 * If this isn't the last console and it has CON_CONSDEV set, we
2107 * need to set it on the next preferred console.
2109 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2110 console_drivers
->flags
|= CON_CONSDEV
;
2113 console_sysfs_notify();
2116 EXPORT_SYMBOL(unregister_console
);
2118 static int __init
printk_late_init(void)
2120 struct console
*con
;
2122 for_each_console(con
) {
2123 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2124 printk(KERN_INFO
"turn off boot console %s%d\n",
2125 con
->name
, con
->index
);
2126 unregister_console(con
);
2129 hotcpu_notifier(console_cpu_notify
, 0);
2132 late_initcall(printk_late_init
);
2134 #if defined CONFIG_PRINTK
2136 int printk_sched(const char *fmt
, ...)
2138 unsigned long flags
;
2143 local_irq_save(flags
);
2144 buf
= __get_cpu_var(printk_sched_buf
);
2146 va_start(args
, fmt
);
2147 r
= vsnprintf(buf
, PRINTK_BUF_SIZE
, fmt
, args
);
2150 __this_cpu_or(printk_pending
, PRINTK_PENDING_SCHED
);
2151 local_irq_restore(flags
);
2157 * printk rate limiting, lifted from the networking subsystem.
2159 * This enforces a rate limit: not more than 10 kernel messages
2160 * every 5s to make a denial-of-service attack impossible.
2162 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2164 int __printk_ratelimit(const char *func
)
2166 return ___ratelimit(&printk_ratelimit_state
, func
);
2168 EXPORT_SYMBOL(__printk_ratelimit
);
2171 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2172 * @caller_jiffies: pointer to caller's state
2173 * @interval_msecs: minimum interval between prints
2175 * printk_timed_ratelimit() returns true if more than @interval_msecs
2176 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2179 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2180 unsigned int interval_msecs
)
2182 if (*caller_jiffies
== 0
2183 || !time_in_range(jiffies
, *caller_jiffies
,
2185 + msecs_to_jiffies(interval_msecs
))) {
2186 *caller_jiffies
= jiffies
;
2191 EXPORT_SYMBOL(printk_timed_ratelimit
);
2193 static DEFINE_SPINLOCK(dump_list_lock
);
2194 static LIST_HEAD(dump_list
);
2197 * kmsg_dump_register - register a kernel log dumper.
2198 * @dumper: pointer to the kmsg_dumper structure
2200 * Adds a kernel log dumper to the system. The dump callback in the
2201 * structure will be called when the kernel oopses or panics and must be
2202 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2204 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2206 unsigned long flags
;
2209 /* The dump callback needs to be set */
2213 spin_lock_irqsave(&dump_list_lock
, flags
);
2214 /* Don't allow registering multiple times */
2215 if (!dumper
->registered
) {
2216 dumper
->registered
= 1;
2217 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2220 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2224 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2227 * kmsg_dump_unregister - unregister a kmsg dumper.
2228 * @dumper: pointer to the kmsg_dumper structure
2230 * Removes a dump device from the system. Returns zero on success and
2231 * %-EINVAL otherwise.
2233 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2235 unsigned long flags
;
2238 spin_lock_irqsave(&dump_list_lock
, flags
);
2239 if (dumper
->registered
) {
2240 dumper
->registered
= 0;
2241 list_del_rcu(&dumper
->list
);
2244 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2249 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2251 static bool always_kmsg_dump
;
2252 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2255 * kmsg_dump - dump kernel log to kernel message dumpers.
2256 * @reason: the reason (oops, panic etc) for dumping
2258 * Iterate through each of the dump devices and call the oops/panic
2259 * callbacks with the log buffer.
2261 void kmsg_dump(enum kmsg_dump_reason reason
)
2264 struct kmsg_dumper
*dumper
;
2265 const char *s1
, *s2
;
2266 unsigned long l1
, l2
;
2267 unsigned long flags
;
2269 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2272 /* Theoretically, the log could move on after we do this, but
2273 there's not a lot we can do about that. The new messages
2274 will overwrite the start of what we dump. */
2276 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2277 if (syslog_seq
< log_first_seq
)
2280 idx
= log_first_idx
;
2282 if (idx
> log_next_idx
) {
2287 l2
= log_buf_len
- idx
;
2293 l2
= log_next_idx
- idx
;
2295 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2298 list_for_each_entry_rcu(dumper
, &dump_list
, list
)
2299 dumper
->dump(dumper
, reason
, s1
, l1
, s2
, l2
);