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 int syslog_print_line(u32 idx
, char *text
, size_t size
)
794 msg
= log_from_idx(idx
);
796 /* calculate length only */
807 len
+= msg
->text_len
;
812 len
= sprintf(text
, "<%u>", msg
->level
);
815 unsigned long long t
= msg
->ts_nsec
;
816 unsigned long rem_ns
= do_div(t
, 1000000000);
818 len
+= sprintf(text
+ len
, "[%5lu.%06lu] ",
819 (unsigned long) t
, rem_ns
/ 1000);
822 if (len
+ msg
->text_len
> size
)
824 memcpy(text
+ len
, log_text(msg
), msg
->text_len
);
825 len
+= msg
->text_len
;
830 static int syslog_print(char __user
*buf
, int size
)
835 text
= kmalloc(LOG_LINE_MAX
, GFP_KERNEL
);
839 raw_spin_lock_irq(&logbuf_lock
);
840 if (syslog_seq
< log_first_seq
) {
841 /* messages are gone, move to first one */
842 syslog_seq
= log_first_seq
;
843 syslog_idx
= log_first_idx
;
845 len
= syslog_print_line(syslog_idx
, text
, LOG_LINE_MAX
);
846 syslog_idx
= log_next(syslog_idx
);
848 raw_spin_unlock_irq(&logbuf_lock
);
850 if (len
> 0 && copy_to_user(buf
, text
, len
))
857 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
862 text
= kmalloc(LOG_LINE_MAX
, GFP_KERNEL
);
866 raw_spin_lock_irq(&logbuf_lock
);
872 if (clear_seq
< log_first_seq
) {
873 /* messages are gone, move to first available one */
874 clear_seq
= log_first_seq
;
875 clear_idx
= log_first_idx
;
879 * Find first record that fits, including all following records,
880 * into the user-provided buffer for this dump.
884 while (seq
< log_next_seq
) {
885 len
+= syslog_print_line(idx
, NULL
, 0);
891 while (len
> size
&& seq
< log_next_seq
) {
892 len
-= syslog_print_line(idx
, NULL
, 0);
897 /* last message in this dump */
898 next_seq
= log_next_seq
;
901 while (len
>= 0 && seq
< next_seq
) {
904 textlen
= syslog_print_line(idx
, text
, LOG_LINE_MAX
);
912 raw_spin_unlock_irq(&logbuf_lock
);
913 if (copy_to_user(buf
+ len
, text
, textlen
))
917 raw_spin_lock_irq(&logbuf_lock
);
919 if (seq
< log_first_seq
) {
920 /* messages are gone, move to next one */
928 clear_seq
= log_next_seq
;
929 clear_idx
= log_next_idx
;
931 raw_spin_unlock_irq(&logbuf_lock
);
937 int do_syslog(int type
, char __user
*buf
, int len
, bool from_file
)
940 static int saved_console_loglevel
= -1;
943 error
= check_syslog_permissions(type
, from_file
);
947 error
= security_syslog(type
);
952 case SYSLOG_ACTION_CLOSE
: /* Close log */
954 case SYSLOG_ACTION_OPEN
: /* Open log */
956 case SYSLOG_ACTION_READ
: /* Read from log */
963 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
967 error
= wait_event_interruptible(log_wait
,
968 syslog_seq
!= log_next_seq
);
971 error
= syslog_print(buf
, len
);
973 /* Read/clear last kernel messages */
974 case SYSLOG_ACTION_READ_CLEAR
:
977 /* Read last kernel messages */
978 case SYSLOG_ACTION_READ_ALL
:
985 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
989 error
= syslog_print_all(buf
, len
, clear
);
991 /* Clear ring buffer */
992 case SYSLOG_ACTION_CLEAR
:
993 syslog_print_all(NULL
, 0, true);
994 /* Disable logging to console */
995 case SYSLOG_ACTION_CONSOLE_OFF
:
996 if (saved_console_loglevel
== -1)
997 saved_console_loglevel
= console_loglevel
;
998 console_loglevel
= minimum_console_loglevel
;
1000 /* Enable logging to console */
1001 case SYSLOG_ACTION_CONSOLE_ON
:
1002 if (saved_console_loglevel
!= -1) {
1003 console_loglevel
= saved_console_loglevel
;
1004 saved_console_loglevel
= -1;
1007 /* Set level of messages printed to console */
1008 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1010 if (len
< 1 || len
> 8)
1012 if (len
< minimum_console_loglevel
)
1013 len
= minimum_console_loglevel
;
1014 console_loglevel
= len
;
1015 /* Implicitly re-enable logging to console */
1016 saved_console_loglevel
= -1;
1019 /* Number of chars in the log buffer */
1020 case SYSLOG_ACTION_SIZE_UNREAD
:
1021 raw_spin_lock_irq(&logbuf_lock
);
1022 if (syslog_seq
< log_first_seq
) {
1023 /* messages are gone, move to first one */
1024 syslog_seq
= log_first_seq
;
1025 syslog_idx
= log_first_idx
;
1029 * Short-cut for poll(/"proc/kmsg") which simply checks
1030 * for pending data, not the size; return the count of
1031 * records, not the length.
1033 error
= log_next_idx
- syslog_idx
;
1041 while (seq
< log_next_seq
) {
1042 error
+= syslog_print_line(idx
, NULL
, 0);
1043 idx
= log_next(idx
);
1047 raw_spin_unlock_irq(&logbuf_lock
);
1049 /* Size of the log buffer */
1050 case SYSLOG_ACTION_SIZE_BUFFER
:
1051 error
= log_buf_len
;
1061 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1063 return do_syslog(type
, buf
, len
, SYSLOG_FROM_CALL
);
1066 #ifdef CONFIG_KGDB_KDB
1067 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
1068 * uses locks so it cannot be used during debugging. Just tell kdb
1069 * where the start and end of the physical and logical logs are. This
1070 * is equivalent to do_syslog(3).
1072 void kdb_syslog_data(char *syslog_data
[4])
1074 syslog_data
[0] = log_buf
;
1075 syslog_data
[1] = log_buf
+ log_buf_len
;
1076 syslog_data
[2] = log_buf
+ log_first_idx
;
1077 syslog_data
[3] = log_buf
+ log_next_idx
;
1079 #endif /* CONFIG_KGDB_KDB */
1081 static bool __read_mostly ignore_loglevel
;
1083 static int __init
ignore_loglevel_setup(char *str
)
1085 ignore_loglevel
= 1;
1086 printk(KERN_INFO
"debug: ignoring loglevel setting.\n");
1091 early_param("ignore_loglevel", ignore_loglevel_setup
);
1092 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1093 MODULE_PARM_DESC(ignore_loglevel
, "ignore loglevel setting, to"
1094 "print all kernel messages to the console.");
1097 * Call the console drivers, asking them to write out
1098 * log_buf[start] to log_buf[end - 1].
1099 * The console_lock must be held.
1101 static void call_console_drivers(int level
, const char *text
, size_t len
)
1103 struct console
*con
;
1105 trace_console(text
, 0, len
, len
);
1107 if (level
>= console_loglevel
&& !ignore_loglevel
)
1109 if (!console_drivers
)
1112 for_each_console(con
) {
1113 if (exclusive_console
&& con
!= exclusive_console
)
1115 if (!(con
->flags
& CON_ENABLED
))
1119 if (!cpu_online(smp_processor_id()) &&
1120 !(con
->flags
& CON_ANYTIME
))
1122 con
->write(con
, text
, len
);
1127 * Zap console related locks when oopsing. Only zap at most once
1128 * every 10 seconds, to leave time for slow consoles to print a
1131 static void zap_locks(void)
1133 static unsigned long oops_timestamp
;
1135 if (time_after_eq(jiffies
, oops_timestamp
) &&
1136 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1139 oops_timestamp
= jiffies
;
1142 /* If a crash is occurring, make sure we can't deadlock */
1143 raw_spin_lock_init(&logbuf_lock
);
1144 /* And make sure that we print immediately */
1145 sema_init(&console_sem
, 1);
1148 /* Check if we have any console registered that can be called early in boot. */
1149 static int have_callable_console(void)
1151 struct console
*con
;
1153 for_each_console(con
)
1154 if (con
->flags
& CON_ANYTIME
)
1161 * Can we actually use the console at this time on this cpu?
1163 * Console drivers may assume that per-cpu resources have
1164 * been allocated. So unless they're explicitly marked as
1165 * being able to cope (CON_ANYTIME) don't call them until
1166 * this CPU is officially up.
1168 static inline int can_use_console(unsigned int cpu
)
1170 return cpu_online(cpu
) || have_callable_console();
1174 * Try to get console ownership to actually show the kernel
1175 * messages from a 'printk'. Return true (and with the
1176 * console_lock held, and 'console_locked' set) if it
1177 * is successful, false otherwise.
1179 * This gets called with the 'logbuf_lock' spinlock held and
1180 * interrupts disabled. It should return with 'lockbuf_lock'
1181 * released but interrupts still disabled.
1183 static int console_trylock_for_printk(unsigned int cpu
)
1184 __releases(&logbuf_lock
)
1186 int retval
= 0, wake
= 0;
1188 if (console_trylock()) {
1192 * If we can't use the console, we need to release
1193 * the console semaphore by hand to avoid flushing
1194 * the buffer. We need to hold the console semaphore
1195 * in order to do this test safely.
1197 if (!can_use_console(cpu
)) {
1203 logbuf_cpu
= UINT_MAX
;
1206 raw_spin_unlock(&logbuf_lock
);
1210 int printk_delay_msec __read_mostly
;
1212 static inline void printk_delay(void)
1214 if (unlikely(printk_delay_msec
)) {
1215 int m
= printk_delay_msec
;
1219 touch_nmi_watchdog();
1224 asmlinkage
int vprintk_emit(int facility
, int level
,
1225 const char *dict
, size_t dictlen
,
1226 const char *fmt
, va_list args
)
1228 static int recursion_bug
;
1229 static char buf
[LOG_LINE_MAX
];
1230 static size_t buflen
;
1231 static int buflevel
;
1232 static char textbuf
[LOG_LINE_MAX
];
1233 char *text
= textbuf
;
1235 unsigned long flags
;
1237 bool newline
= false;
1239 int printed_len
= 0;
1244 /* This stops the holder of console_sem just where we want him */
1245 local_irq_save(flags
);
1246 this_cpu
= smp_processor_id();
1249 * Ouch, printk recursed into itself!
1251 if (unlikely(logbuf_cpu
== this_cpu
)) {
1253 * If a crash is occurring during printk() on this CPU,
1254 * then try to get the crash message out but make sure
1255 * we can't deadlock. Otherwise just return to avoid the
1256 * recursion and return - but flag the recursion so that
1257 * it can be printed at the next appropriate moment:
1259 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1261 goto out_restore_irqs
;
1267 raw_spin_lock(&logbuf_lock
);
1268 logbuf_cpu
= this_cpu
;
1270 if (recursion_bug
) {
1271 static const char recursion_msg
[] =
1272 "BUG: recent printk recursion!";
1275 printed_len
+= strlen(recursion_msg
);
1276 /* emit KERN_CRIT message */
1277 log_store(0, 2, NULL
, 0, recursion_msg
, printed_len
);
1281 * The printf needs to come first; we need the syslog
1282 * prefix which might be passed-in as a parameter.
1284 textlen
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1286 /* mark and strip a trailing newline */
1287 if (textlen
&& text
[textlen
-1] == '\n') {
1292 /* strip syslog prefix and extract log level or flags */
1293 if (text
[0] == '<' && text
[1] && text
[2] == '>') {
1297 level
= text
[1] - '0';
1301 case 'c': /* KERN_CONT */
1303 case 'd': /* KERN_DEFAULT */
1310 if (buflen
&& (!cont
|| dict
)) {
1311 /* no continuation; flush existing buffer */
1312 log_store(facility
, buflevel
, NULL
, 0, buf
, buflen
);
1313 printed_len
+= buflen
;
1318 /* remember level for first message in the buffer */
1320 buflevel
= default_message_loglevel
;
1325 if (buflen
|| !newline
) {
1326 /* append to existing buffer, or buffer until next message */
1327 if (buflen
+ textlen
> sizeof(buf
))
1328 textlen
= sizeof(buf
) - buflen
;
1329 memcpy(buf
+ buflen
, text
, textlen
);
1334 /* end of line; flush buffer */
1336 log_store(facility
, buflevel
,
1337 dict
, dictlen
, buf
, buflen
);
1338 printed_len
+= buflen
;
1341 log_store(facility
, buflevel
,
1342 dict
, dictlen
, text
, textlen
);
1343 printed_len
+= textlen
;
1348 * Try to acquire and then immediately release the console semaphore.
1349 * The release will print out buffers and wake up /dev/kmsg and syslog()
1352 * The console_trylock_for_printk() function will release 'logbuf_lock'
1353 * regardless of whether it actually gets the console semaphore or not.
1355 if (console_trylock_for_printk(this_cpu
))
1360 local_irq_restore(flags
);
1364 EXPORT_SYMBOL(vprintk_emit
);
1366 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1368 return vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1370 EXPORT_SYMBOL(vprintk
);
1372 asmlinkage
int printk_emit(int facility
, int level
,
1373 const char *dict
, size_t dictlen
,
1374 const char *fmt
, ...)
1379 va_start(args
, fmt
);
1380 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1385 EXPORT_SYMBOL(printk_emit
);
1388 * printk - print a kernel message
1389 * @fmt: format string
1391 * This is printk(). It can be called from any context. We want it to work.
1393 * We try to grab the console_lock. If we succeed, it's easy - we log the
1394 * output and call the console drivers. If we fail to get the semaphore, we
1395 * place the output into the log buffer and return. The current holder of
1396 * the console_sem will notice the new output in console_unlock(); and will
1397 * send it to the consoles before releasing the lock.
1399 * One effect of this deferred printing is that code which calls printk() and
1400 * then changes console_loglevel may break. This is because console_loglevel
1401 * is inspected when the actual printing occurs.
1406 * See the vsnprintf() documentation for format string extensions over C99.
1408 asmlinkage
int printk(const char *fmt
, ...)
1413 #ifdef CONFIG_KGDB_KDB
1414 if (unlikely(kdb_trap_printk
)) {
1415 va_start(args
, fmt
);
1416 r
= vkdb_printf(fmt
, args
);
1421 va_start(args
, fmt
);
1422 r
= vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1427 EXPORT_SYMBOL(printk
);
1431 #define LOG_LINE_MAX 0
1432 static struct log
*log_from_idx(u32 idx
) { return NULL
; }
1433 static u32
log_next(u32 idx
) { return 0; }
1434 static char *log_text(const struct log
*msg
) { return NULL
; }
1435 static void call_console_drivers(int level
, const char *text
, size_t len
) {}
1437 #endif /* CONFIG_PRINTK */
1439 static int __add_preferred_console(char *name
, int idx
, char *options
,
1442 struct console_cmdline
*c
;
1446 * See if this tty is not yet registered, and
1447 * if we have a slot free.
1449 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
1450 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
1451 console_cmdline
[i
].index
== idx
) {
1453 selected_console
= i
;
1456 if (i
== MAX_CMDLINECONSOLES
)
1459 selected_console
= i
;
1460 c
= &console_cmdline
[i
];
1461 strlcpy(c
->name
, name
, sizeof(c
->name
));
1462 c
->options
= options
;
1463 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1464 c
->brl_options
= brl_options
;
1470 * Set up a list of consoles. Called from init/main.c
1472 static int __init
console_setup(char *str
)
1474 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for index */
1475 char *s
, *options
, *brl_options
= NULL
;
1478 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1479 if (!memcmp(str
, "brl,", 4)) {
1482 } else if (!memcmp(str
, "brl=", 4)) {
1483 brl_options
= str
+ 4;
1484 str
= strchr(brl_options
, ',');
1486 printk(KERN_ERR
"need port name after brl=\n");
1494 * Decode str into name, index, options.
1496 if (str
[0] >= '0' && str
[0] <= '9') {
1497 strcpy(buf
, "ttyS");
1498 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1500 strncpy(buf
, str
, sizeof(buf
) - 1);
1502 buf
[sizeof(buf
) - 1] = 0;
1503 if ((options
= strchr(str
, ',')) != NULL
)
1506 if (!strcmp(str
, "ttya"))
1507 strcpy(buf
, "ttyS0");
1508 if (!strcmp(str
, "ttyb"))
1509 strcpy(buf
, "ttyS1");
1511 for (s
= buf
; *s
; s
++)
1512 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
1514 idx
= simple_strtoul(s
, NULL
, 10);
1517 __add_preferred_console(buf
, idx
, options
, brl_options
);
1518 console_set_on_cmdline
= 1;
1521 __setup("console=", console_setup
);
1524 * add_preferred_console - add a device to the list of preferred consoles.
1525 * @name: device name
1526 * @idx: device index
1527 * @options: options for this console
1529 * The last preferred console added will be used for kernel messages
1530 * and stdin/out/err for init. Normally this is used by console_setup
1531 * above to handle user-supplied console arguments; however it can also
1532 * be used by arch-specific code either to override the user or more
1533 * commonly to provide a default console (ie from PROM variables) when
1534 * the user has not supplied one.
1536 int add_preferred_console(char *name
, int idx
, char *options
)
1538 return __add_preferred_console(name
, idx
, options
, NULL
);
1541 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
1543 struct console_cmdline
*c
;
1546 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
1547 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
1548 console_cmdline
[i
].index
== idx
) {
1549 c
= &console_cmdline
[i
];
1550 strlcpy(c
->name
, name_new
, sizeof(c
->name
));
1551 c
->name
[sizeof(c
->name
) - 1] = 0;
1552 c
->options
= options
;
1560 bool console_suspend_enabled
= 1;
1561 EXPORT_SYMBOL(console_suspend_enabled
);
1563 static int __init
console_suspend_disable(char *str
)
1565 console_suspend_enabled
= 0;
1568 __setup("no_console_suspend", console_suspend_disable
);
1569 module_param_named(console_suspend
, console_suspend_enabled
,
1570 bool, S_IRUGO
| S_IWUSR
);
1571 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
1572 " and hibernate operations");
1575 * suspend_console - suspend the console subsystem
1577 * This disables printk() while we go into suspend states
1579 void suspend_console(void)
1581 if (!console_suspend_enabled
)
1583 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1585 console_suspended
= 1;
1589 void resume_console(void)
1591 if (!console_suspend_enabled
)
1594 console_suspended
= 0;
1599 * console_cpu_notify - print deferred console messages after CPU hotplug
1600 * @self: notifier struct
1601 * @action: CPU hotplug event
1604 * If printk() is called from a CPU that is not online yet, the messages
1605 * will be spooled but will not show up on the console. This function is
1606 * called when a new CPU comes online (or fails to come up), and ensures
1607 * that any such output gets printed.
1609 static int __cpuinit
console_cpu_notify(struct notifier_block
*self
,
1610 unsigned long action
, void *hcpu
)
1616 case CPU_DOWN_FAILED
:
1617 case CPU_UP_CANCELED
:
1625 * console_lock - lock the console system for exclusive use.
1627 * Acquires a lock which guarantees that the caller has
1628 * exclusive access to the console system and the console_drivers list.
1630 * Can sleep, returns nothing.
1632 void console_lock(void)
1634 BUG_ON(in_interrupt());
1636 if (console_suspended
)
1639 console_may_schedule
= 1;
1641 EXPORT_SYMBOL(console_lock
);
1644 * console_trylock - try to lock the console system for exclusive use.
1646 * Tried to acquire a lock which guarantees that the caller has
1647 * exclusive access to the console system and the console_drivers list.
1649 * returns 1 on success, and 0 on failure to acquire the lock.
1651 int console_trylock(void)
1653 if (down_trylock(&console_sem
))
1655 if (console_suspended
) {
1660 console_may_schedule
= 0;
1663 EXPORT_SYMBOL(console_trylock
);
1665 int is_console_locked(void)
1667 return console_locked
;
1671 * Delayed printk version, for scheduler-internal messages:
1673 #define PRINTK_BUF_SIZE 512
1675 #define PRINTK_PENDING_WAKEUP 0x01
1676 #define PRINTK_PENDING_SCHED 0x02
1678 static DEFINE_PER_CPU(int, printk_pending
);
1679 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE
], printk_sched_buf
);
1681 void printk_tick(void)
1683 if (__this_cpu_read(printk_pending
)) {
1684 int pending
= __this_cpu_xchg(printk_pending
, 0);
1685 if (pending
& PRINTK_PENDING_SCHED
) {
1686 char *buf
= __get_cpu_var(printk_sched_buf
);
1687 printk(KERN_WARNING
"[sched_delayed] %s", buf
);
1689 if (pending
& PRINTK_PENDING_WAKEUP
)
1690 wake_up_interruptible(&log_wait
);
1694 int printk_needs_cpu(int cpu
)
1696 if (cpu_is_offline(cpu
))
1698 return __this_cpu_read(printk_pending
);
1701 void wake_up_klogd(void)
1703 if (waitqueue_active(&log_wait
))
1704 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
1707 /* the next printk record to write to the console */
1708 static u64 console_seq
;
1709 static u32 console_idx
;
1712 * console_unlock - unlock the console system
1714 * Releases the console_lock which the caller holds on the console system
1715 * and the console driver list.
1717 * While the console_lock was held, console output may have been buffered
1718 * by printk(). If this is the case, console_unlock(); emits
1719 * the output prior to releasing the lock.
1721 * If there is output waiting, we wake /dev/kmsg and syslog() users.
1723 * console_unlock(); may be called from any context.
1725 void console_unlock(void)
1727 static u64 seen_seq
;
1728 unsigned long flags
;
1729 bool wake_klogd
= false;
1732 if (console_suspended
) {
1737 console_may_schedule
= 0;
1742 static char text
[LOG_LINE_MAX
];
1746 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
1747 if (seen_seq
!= log_next_seq
) {
1749 seen_seq
= log_next_seq
;
1752 if (console_seq
< log_first_seq
) {
1753 /* messages are gone, move to first one */
1754 console_seq
= log_first_seq
;
1755 console_idx
= log_first_idx
;
1758 if (console_seq
== log_next_seq
)
1761 msg
= log_from_idx(console_idx
);
1762 level
= msg
->level
& 7;
1763 len
= msg
->text_len
;
1764 if (len
+1 >= sizeof(text
))
1765 len
= sizeof(text
)-1;
1766 memcpy(text
, log_text(msg
), len
);
1769 console_idx
= log_next(console_idx
);
1771 raw_spin_unlock(&logbuf_lock
);
1773 stop_critical_timings(); /* don't trace print latency */
1774 call_console_drivers(level
, text
, len
);
1775 start_critical_timings();
1776 local_irq_restore(flags
);
1780 /* Release the exclusive_console once it is used */
1781 if (unlikely(exclusive_console
))
1782 exclusive_console
= NULL
;
1784 raw_spin_unlock(&logbuf_lock
);
1789 * Someone could have filled up the buffer again, so re-check if there's
1790 * something to flush. In case we cannot trylock the console_sem again,
1791 * there's a new owner and the console_unlock() from them will do the
1792 * flush, no worries.
1794 raw_spin_lock(&logbuf_lock
);
1795 retry
= console_seq
!= log_next_seq
;
1796 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
1798 if (retry
&& console_trylock())
1804 EXPORT_SYMBOL(console_unlock
);
1807 * console_conditional_schedule - yield the CPU if required
1809 * If the console code is currently allowed to sleep, and
1810 * if this CPU should yield the CPU to another task, do
1813 * Must be called within console_lock();.
1815 void __sched
console_conditional_schedule(void)
1817 if (console_may_schedule
)
1820 EXPORT_SYMBOL(console_conditional_schedule
);
1822 void console_unblank(void)
1827 * console_unblank can no longer be called in interrupt context unless
1828 * oops_in_progress is set to 1..
1830 if (oops_in_progress
) {
1831 if (down_trylock(&console_sem
) != 0)
1837 console_may_schedule
= 0;
1839 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
1845 * Return the console tty driver structure and its associated index
1847 struct tty_driver
*console_device(int *index
)
1850 struct tty_driver
*driver
= NULL
;
1853 for_each_console(c
) {
1856 driver
= c
->device(c
, index
);
1865 * Prevent further output on the passed console device so that (for example)
1866 * serial drivers can disable console output before suspending a port, and can
1867 * re-enable output afterwards.
1869 void console_stop(struct console
*console
)
1872 console
->flags
&= ~CON_ENABLED
;
1875 EXPORT_SYMBOL(console_stop
);
1877 void console_start(struct console
*console
)
1880 console
->flags
|= CON_ENABLED
;
1883 EXPORT_SYMBOL(console_start
);
1885 static int __read_mostly keep_bootcon
;
1887 static int __init
keep_bootcon_setup(char *str
)
1890 printk(KERN_INFO
"debug: skip boot console de-registration.\n");
1895 early_param("keep_bootcon", keep_bootcon_setup
);
1898 * The console driver calls this routine during kernel initialization
1899 * to register the console printing procedure with printk() and to
1900 * print any messages that were printed by the kernel before the
1901 * console driver was initialized.
1903 * This can happen pretty early during the boot process (because of
1904 * early_printk) - sometimes before setup_arch() completes - be careful
1905 * of what kernel features are used - they may not be initialised yet.
1907 * There are two types of consoles - bootconsoles (early_printk) and
1908 * "real" consoles (everything which is not a bootconsole) which are
1909 * handled differently.
1910 * - Any number of bootconsoles can be registered at any time.
1911 * - As soon as a "real" console is registered, all bootconsoles
1912 * will be unregistered automatically.
1913 * - Once a "real" console is registered, any attempt to register a
1914 * bootconsoles will be rejected
1916 void register_console(struct console
*newcon
)
1919 unsigned long flags
;
1920 struct console
*bcon
= NULL
;
1923 * before we register a new CON_BOOT console, make sure we don't
1924 * already have a valid console
1926 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
1927 /* find the last or real console */
1928 for_each_console(bcon
) {
1929 if (!(bcon
->flags
& CON_BOOT
)) {
1930 printk(KERN_INFO
"Too late to register bootconsole %s%d\n",
1931 newcon
->name
, newcon
->index
);
1937 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
1938 bcon
= console_drivers
;
1940 if (preferred_console
< 0 || bcon
|| !console_drivers
)
1941 preferred_console
= selected_console
;
1943 if (newcon
->early_setup
)
1944 newcon
->early_setup();
1947 * See if we want to use this console driver. If we
1948 * didn't select a console we take the first one
1949 * that registers here.
1951 if (preferred_console
< 0) {
1952 if (newcon
->index
< 0)
1954 if (newcon
->setup
== NULL
||
1955 newcon
->setup(newcon
, NULL
) == 0) {
1956 newcon
->flags
|= CON_ENABLED
;
1957 if (newcon
->device
) {
1958 newcon
->flags
|= CON_CONSDEV
;
1959 preferred_console
= 0;
1965 * See if this console matches one we selected on
1968 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
1970 if (strcmp(console_cmdline
[i
].name
, newcon
->name
) != 0)
1972 if (newcon
->index
>= 0 &&
1973 newcon
->index
!= console_cmdline
[i
].index
)
1975 if (newcon
->index
< 0)
1976 newcon
->index
= console_cmdline
[i
].index
;
1977 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1978 if (console_cmdline
[i
].brl_options
) {
1979 newcon
->flags
|= CON_BRL
;
1980 braille_register_console(newcon
,
1981 console_cmdline
[i
].index
,
1982 console_cmdline
[i
].options
,
1983 console_cmdline
[i
].brl_options
);
1987 if (newcon
->setup
&&
1988 newcon
->setup(newcon
, console_cmdline
[i
].options
) != 0)
1990 newcon
->flags
|= CON_ENABLED
;
1991 newcon
->index
= console_cmdline
[i
].index
;
1992 if (i
== selected_console
) {
1993 newcon
->flags
|= CON_CONSDEV
;
1994 preferred_console
= selected_console
;
1999 if (!(newcon
->flags
& CON_ENABLED
))
2003 * If we have a bootconsole, and are switching to a real console,
2004 * don't print everything out again, since when the boot console, and
2005 * the real console are the same physical device, it's annoying to
2006 * see the beginning boot messages twice
2008 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2009 newcon
->flags
&= ~CON_PRINTBUFFER
;
2012 * Put this console in the list - keep the
2013 * preferred driver at the head of the list.
2016 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2017 newcon
->next
= console_drivers
;
2018 console_drivers
= newcon
;
2020 newcon
->next
->flags
&= ~CON_CONSDEV
;
2022 newcon
->next
= console_drivers
->next
;
2023 console_drivers
->next
= newcon
;
2025 if (newcon
->flags
& CON_PRINTBUFFER
) {
2027 * console_unlock(); will print out the buffered messages
2030 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2031 console_seq
= syslog_seq
;
2032 console_idx
= syslog_idx
;
2033 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2035 * We're about to replay the log buffer. Only do this to the
2036 * just-registered console to avoid excessive message spam to
2037 * the already-registered consoles.
2039 exclusive_console
= newcon
;
2042 console_sysfs_notify();
2045 * By unregistering the bootconsoles after we enable the real console
2046 * we get the "console xxx enabled" message on all the consoles -
2047 * boot consoles, real consoles, etc - this is to ensure that end
2048 * users know there might be something in the kernel's log buffer that
2049 * went to the bootconsole (that they do not see on the real console)
2052 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2054 /* we need to iterate through twice, to make sure we print
2055 * everything out, before we unregister the console(s)
2057 printk(KERN_INFO
"console [%s%d] enabled, bootconsole disabled\n",
2058 newcon
->name
, newcon
->index
);
2059 for_each_console(bcon
)
2060 if (bcon
->flags
& CON_BOOT
)
2061 unregister_console(bcon
);
2063 printk(KERN_INFO
"%sconsole [%s%d] enabled\n",
2064 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2065 newcon
->name
, newcon
->index
);
2068 EXPORT_SYMBOL(register_console
);
2070 int unregister_console(struct console
*console
)
2072 struct console
*a
, *b
;
2075 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2076 if (console
->flags
& CON_BRL
)
2077 return braille_unregister_console(console
);
2081 if (console_drivers
== console
) {
2082 console_drivers
=console
->next
;
2084 } else if (console_drivers
) {
2085 for (a
=console_drivers
->next
, b
=console_drivers
;
2086 a
; b
=a
, a
=b
->next
) {
2096 * If this isn't the last console and it has CON_CONSDEV set, we
2097 * need to set it on the next preferred console.
2099 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2100 console_drivers
->flags
|= CON_CONSDEV
;
2103 console_sysfs_notify();
2106 EXPORT_SYMBOL(unregister_console
);
2108 static int __init
printk_late_init(void)
2110 struct console
*con
;
2112 for_each_console(con
) {
2113 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2114 printk(KERN_INFO
"turn off boot console %s%d\n",
2115 con
->name
, con
->index
);
2116 unregister_console(con
);
2119 hotcpu_notifier(console_cpu_notify
, 0);
2122 late_initcall(printk_late_init
);
2124 #if defined CONFIG_PRINTK
2126 int printk_sched(const char *fmt
, ...)
2128 unsigned long flags
;
2133 local_irq_save(flags
);
2134 buf
= __get_cpu_var(printk_sched_buf
);
2136 va_start(args
, fmt
);
2137 r
= vsnprintf(buf
, PRINTK_BUF_SIZE
, fmt
, args
);
2140 __this_cpu_or(printk_pending
, PRINTK_PENDING_SCHED
);
2141 local_irq_restore(flags
);
2147 * printk rate limiting, lifted from the networking subsystem.
2149 * This enforces a rate limit: not more than 10 kernel messages
2150 * every 5s to make a denial-of-service attack impossible.
2152 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2154 int __printk_ratelimit(const char *func
)
2156 return ___ratelimit(&printk_ratelimit_state
, func
);
2158 EXPORT_SYMBOL(__printk_ratelimit
);
2161 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2162 * @caller_jiffies: pointer to caller's state
2163 * @interval_msecs: minimum interval between prints
2165 * printk_timed_ratelimit() returns true if more than @interval_msecs
2166 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2169 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2170 unsigned int interval_msecs
)
2172 if (*caller_jiffies
== 0
2173 || !time_in_range(jiffies
, *caller_jiffies
,
2175 + msecs_to_jiffies(interval_msecs
))) {
2176 *caller_jiffies
= jiffies
;
2181 EXPORT_SYMBOL(printk_timed_ratelimit
);
2183 static DEFINE_SPINLOCK(dump_list_lock
);
2184 static LIST_HEAD(dump_list
);
2187 * kmsg_dump_register - register a kernel log dumper.
2188 * @dumper: pointer to the kmsg_dumper structure
2190 * Adds a kernel log dumper to the system. The dump callback in the
2191 * structure will be called when the kernel oopses or panics and must be
2192 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2194 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2196 unsigned long flags
;
2199 /* The dump callback needs to be set */
2203 spin_lock_irqsave(&dump_list_lock
, flags
);
2204 /* Don't allow registering multiple times */
2205 if (!dumper
->registered
) {
2206 dumper
->registered
= 1;
2207 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2210 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2214 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2217 * kmsg_dump_unregister - unregister a kmsg dumper.
2218 * @dumper: pointer to the kmsg_dumper structure
2220 * Removes a dump device from the system. Returns zero on success and
2221 * %-EINVAL otherwise.
2223 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2225 unsigned long flags
;
2228 spin_lock_irqsave(&dump_list_lock
, flags
);
2229 if (dumper
->registered
) {
2230 dumper
->registered
= 0;
2231 list_del_rcu(&dumper
->list
);
2234 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2239 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2241 static bool always_kmsg_dump
;
2242 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2245 * kmsg_dump - dump kernel log to kernel message dumpers.
2246 * @reason: the reason (oops, panic etc) for dumping
2248 * Iterate through each of the dump devices and call the oops/panic
2249 * callbacks with the log buffer.
2251 void kmsg_dump(enum kmsg_dump_reason reason
)
2254 struct kmsg_dumper
*dumper
;
2255 const char *s1
, *s2
;
2256 unsigned long l1
, l2
;
2257 unsigned long flags
;
2259 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2262 /* Theoretically, the log could move on after we do this, but
2263 there's not a lot we can do about that. The new messages
2264 will overwrite the start of what we dump. */
2266 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2267 if (syslog_seq
< log_first_seq
)
2270 idx
= log_first_idx
;
2272 if (idx
> log_next_idx
) {
2277 l2
= log_buf_len
- idx
;
2283 l2
= log_next_idx
- idx
;
2285 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2288 list_for_each_entry_rcu(dumper
, &dump_list
, list
)
2289 dumper
->dump(dumper
, reason
, s1
, l1
, s2
, l2
);