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.
198 LOG_NOCONS
= 1, /* already flushed, do not print to console */
202 u64 ts_nsec
; /* timestamp in nanoseconds */
203 u16 len
; /* length of entire record */
204 u16 text_len
; /* length of text buffer */
205 u16 dict_len
; /* length of dictionary buffer */
206 u8 facility
; /* syslog facility */
207 u8 flags
:5; /* internal record flags */
208 u8 level
:3; /* syslog level */
212 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
213 * used in interesting ways to provide interlocking in console_unlock();
215 static DEFINE_RAW_SPINLOCK(logbuf_lock
);
217 /* the next printk record to read by syslog(READ) or /proc/kmsg */
218 static u64 syslog_seq
;
219 static u32 syslog_idx
;
221 /* index and sequence number of the first record stored in the buffer */
222 static u64 log_first_seq
;
223 static u32 log_first_idx
;
225 /* index and sequence number of the next record to store in the buffer */
226 static u64 log_next_seq
;
228 static u32 log_next_idx
;
230 /* the next printk record to read after the last 'clear' command */
231 static u64 clear_seq
;
232 static u32 clear_idx
;
234 #define LOG_LINE_MAX 1024
237 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
240 #define LOG_ALIGN __alignof__(struct log)
242 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
243 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
244 static char *log_buf
= __log_buf
;
245 static u32 log_buf_len
= __LOG_BUF_LEN
;
247 /* cpu currently holding logbuf_lock */
248 static volatile unsigned int logbuf_cpu
= UINT_MAX
;
250 /* human readable text of the record */
251 static char *log_text(const struct log
*msg
)
253 return (char *)msg
+ sizeof(struct log
);
256 /* optional key/value pair dictionary attached to the record */
257 static char *log_dict(const struct log
*msg
)
259 return (char *)msg
+ sizeof(struct log
) + msg
->text_len
;
262 /* get record by index; idx must point to valid msg */
263 static struct log
*log_from_idx(u32 idx
)
265 struct log
*msg
= (struct log
*)(log_buf
+ idx
);
268 * A length == 0 record is the end of buffer marker. Wrap around and
269 * read the message at the start of the buffer.
272 return (struct log
*)log_buf
;
276 /* get next record; idx must point to valid msg */
277 static u32
log_next(u32 idx
)
279 struct log
*msg
= (struct log
*)(log_buf
+ idx
);
281 /* length == 0 indicates the end of the buffer; wrap */
283 * A length == 0 record is the end of buffer marker. Wrap around and
284 * read the message at the start of the buffer as *this* one, and
285 * return the one after that.
288 msg
= (struct log
*)log_buf
;
291 return idx
+ msg
->len
;
294 /* insert record into the buffer, discard old ones, update heads */
295 static void log_store(int facility
, int level
,
296 enum log_flags flags
, u64 ts_nsec
,
297 const char *dict
, u16 dict_len
,
298 const char *text
, u16 text_len
)
303 /* number of '\0' padding bytes to next message */
304 size
= sizeof(struct log
) + text_len
+ dict_len
;
305 pad_len
= (-size
) & (LOG_ALIGN
- 1);
308 while (log_first_seq
< log_next_seq
) {
311 if (log_next_idx
> log_first_idx
)
312 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
314 free
= log_first_idx
- log_next_idx
;
316 if (free
> size
+ sizeof(struct log
))
319 /* drop old messages until we have enough contiuous space */
320 log_first_idx
= log_next(log_first_idx
);
324 if (log_next_idx
+ size
+ sizeof(struct log
) >= log_buf_len
) {
326 * This message + an additional empty header does not fit
327 * at the end of the buffer. Add an empty header with len == 0
328 * to signify a wrap around.
330 memset(log_buf
+ log_next_idx
, 0, sizeof(struct log
));
335 msg
= (struct log
*)(log_buf
+ log_next_idx
);
336 memcpy(log_text(msg
), text
, text_len
);
337 msg
->text_len
= text_len
;
338 memcpy(log_dict(msg
), dict
, dict_len
);
339 msg
->dict_len
= dict_len
;
340 msg
->facility
= facility
;
341 msg
->level
= level
& 7;
342 msg
->flags
= flags
& 0x1f;
344 msg
->ts_nsec
= ts_nsec
;
346 msg
->ts_nsec
= local_clock();
347 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
348 msg
->len
= sizeof(struct log
) + text_len
+ dict_len
+ pad_len
;
351 log_next_idx
+= msg
->len
;
355 /* /dev/kmsg - userspace message inject/listen interface */
356 struct devkmsg_user
{
363 static ssize_t
devkmsg_writev(struct kiocb
*iocb
, const struct iovec
*iv
,
364 unsigned long count
, loff_t pos
)
368 int level
= default_message_loglevel
;
369 int facility
= 1; /* LOG_USER */
370 size_t len
= iov_length(iv
, count
);
373 if (len
> LOG_LINE_MAX
)
375 buf
= kmalloc(len
+1, GFP_KERNEL
);
380 for (i
= 0; i
< count
; i
++) {
381 if (copy_from_user(line
, iv
[i
].iov_base
, iv
[i
].iov_len
))
383 line
+= iv
[i
].iov_len
;
387 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
388 * the decimal value represents 32bit, the lower 3 bit are the log
389 * level, the rest are the log facility.
391 * If no prefix or no userspace facility is specified, we
392 * enforce LOG_USER, to be able to reliably distinguish
393 * kernel-generated messages from userspace-injected ones.
396 if (line
[0] == '<') {
399 i
= simple_strtoul(line
+1, &endp
, 10);
400 if (endp
&& endp
[0] == '>') {
411 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
417 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
418 size_t count
, loff_t
*ppos
)
420 struct devkmsg_user
*user
= file
->private_data
;
430 ret
= mutex_lock_interruptible(&user
->lock
);
433 raw_spin_lock_irq(&logbuf_lock
);
434 while (user
->seq
== log_next_seq
) {
435 if (file
->f_flags
& O_NONBLOCK
) {
437 raw_spin_unlock_irq(&logbuf_lock
);
441 raw_spin_unlock_irq(&logbuf_lock
);
442 ret
= wait_event_interruptible(log_wait
,
443 user
->seq
!= log_next_seq
);
446 raw_spin_lock_irq(&logbuf_lock
);
449 if (user
->seq
< log_first_seq
) {
450 /* our last seen message is gone, return error and reset */
451 user
->idx
= log_first_idx
;
452 user
->seq
= log_first_seq
;
454 raw_spin_unlock_irq(&logbuf_lock
);
458 msg
= log_from_idx(user
->idx
);
459 ts_usec
= msg
->ts_nsec
;
460 do_div(ts_usec
, 1000);
461 len
= sprintf(user
->buf
, "%u,%llu,%llu;",
462 (msg
->facility
<< 3) | msg
->level
, user
->seq
, ts_usec
);
464 /* escape non-printable characters */
465 for (i
= 0; i
< msg
->text_len
; i
++) {
466 unsigned char c
= log_text(msg
)[i
];
468 if (c
< ' ' || c
>= 127 || c
== '\\')
469 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
471 user
->buf
[len
++] = c
;
473 user
->buf
[len
++] = '\n';
478 for (i
= 0; i
< msg
->dict_len
; i
++) {
479 unsigned char c
= log_dict(msg
)[i
];
482 user
->buf
[len
++] = ' ';
487 user
->buf
[len
++] = '\n';
492 if (c
< ' ' || c
>= 127 || c
== '\\') {
493 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
497 user
->buf
[len
++] = c
;
499 user
->buf
[len
++] = '\n';
502 user
->idx
= log_next(user
->idx
);
504 raw_spin_unlock_irq(&logbuf_lock
);
511 if (copy_to_user(buf
, user
->buf
, len
)) {
517 mutex_unlock(&user
->lock
);
521 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
523 struct devkmsg_user
*user
= file
->private_data
;
531 raw_spin_lock_irq(&logbuf_lock
);
534 /* the first record */
535 user
->idx
= log_first_idx
;
536 user
->seq
= log_first_seq
;
540 * The first record after the last SYSLOG_ACTION_CLEAR,
541 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
542 * changes no global state, and does not clear anything.
544 user
->idx
= clear_idx
;
545 user
->seq
= clear_seq
;
548 /* after the last record */
549 user
->idx
= log_next_idx
;
550 user
->seq
= log_next_seq
;
555 raw_spin_unlock_irq(&logbuf_lock
);
559 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
561 struct devkmsg_user
*user
= file
->private_data
;
565 return POLLERR
|POLLNVAL
;
567 poll_wait(file
, &log_wait
, wait
);
569 raw_spin_lock_irq(&logbuf_lock
);
570 if (user
->seq
< log_next_seq
) {
571 /* return error when data has vanished underneath us */
572 if (user
->seq
< log_first_seq
)
573 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
574 ret
= POLLIN
|POLLRDNORM
;
576 raw_spin_unlock_irq(&logbuf_lock
);
581 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
583 struct devkmsg_user
*user
;
586 /* write-only does not need any file context */
587 if ((file
->f_flags
& O_ACCMODE
) == O_WRONLY
)
590 err
= security_syslog(SYSLOG_ACTION_READ_ALL
);
594 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
598 mutex_init(&user
->lock
);
600 raw_spin_lock_irq(&logbuf_lock
);
601 user
->idx
= log_first_idx
;
602 user
->seq
= log_first_seq
;
603 raw_spin_unlock_irq(&logbuf_lock
);
605 file
->private_data
= user
;
609 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
611 struct devkmsg_user
*user
= file
->private_data
;
616 mutex_destroy(&user
->lock
);
621 const struct file_operations kmsg_fops
= {
622 .open
= devkmsg_open
,
623 .read
= devkmsg_read
,
624 .aio_write
= devkmsg_writev
,
625 .llseek
= devkmsg_llseek
,
626 .poll
= devkmsg_poll
,
627 .release
= devkmsg_release
,
632 * This appends the listed symbols to /proc/vmcoreinfo
634 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
635 * obtain access to symbols that are otherwise very difficult to locate. These
636 * symbols are specifically used so that utilities can access and extract the
637 * dmesg log from a vmcore file after a crash.
639 void log_buf_kexec_setup(void)
641 VMCOREINFO_SYMBOL(log_buf
);
642 VMCOREINFO_SYMBOL(log_buf_len
);
643 VMCOREINFO_SYMBOL(log_first_idx
);
644 VMCOREINFO_SYMBOL(log_next_idx
);
648 /* requested log_buf_len from kernel cmdline */
649 static unsigned long __initdata new_log_buf_len
;
651 /* save requested log_buf_len since it's too early to process it */
652 static int __init
log_buf_len_setup(char *str
)
654 unsigned size
= memparse(str
, &str
);
657 size
= roundup_pow_of_two(size
);
658 if (size
> log_buf_len
)
659 new_log_buf_len
= size
;
663 early_param("log_buf_len", log_buf_len_setup
);
665 void __init
setup_log_buf(int early
)
671 if (!new_log_buf_len
)
677 mem
= memblock_alloc(new_log_buf_len
, PAGE_SIZE
);
680 new_log_buf
= __va(mem
);
682 new_log_buf
= alloc_bootmem_nopanic(new_log_buf_len
);
685 if (unlikely(!new_log_buf
)) {
686 pr_err("log_buf_len: %ld bytes not available\n",
691 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
692 log_buf_len
= new_log_buf_len
;
693 log_buf
= new_log_buf
;
695 free
= __LOG_BUF_LEN
- log_next_idx
;
696 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
697 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
699 pr_info("log_buf_len: %d\n", log_buf_len
);
700 pr_info("early log buf free: %d(%d%%)\n",
701 free
, (free
* 100) / __LOG_BUF_LEN
);
704 #ifdef CONFIG_BOOT_PRINTK_DELAY
706 static int boot_delay
; /* msecs delay after each printk during bootup */
707 static unsigned long long loops_per_msec
; /* based on boot_delay */
709 static int __init
boot_delay_setup(char *str
)
713 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
714 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
716 get_option(&str
, &boot_delay
);
717 if (boot_delay
> 10 * 1000)
720 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
721 "HZ: %d, loops_per_msec: %llu\n",
722 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
725 __setup("boot_delay=", boot_delay_setup
);
727 static void boot_delay_msec(void)
729 unsigned long long k
;
730 unsigned long timeout
;
732 if (boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
735 k
= (unsigned long long)loops_per_msec
* boot_delay
;
737 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
742 * use (volatile) jiffies to prevent
743 * compiler reduction; loop termination via jiffies
744 * is secondary and may or may not happen.
746 if (time_after(jiffies
, timeout
))
748 touch_nmi_watchdog();
752 static inline void boot_delay_msec(void)
757 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
758 int dmesg_restrict
= 1;
763 static int syslog_action_restricted(int type
)
767 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
768 return type
!= SYSLOG_ACTION_READ_ALL
&& type
!= SYSLOG_ACTION_SIZE_BUFFER
;
771 static int check_syslog_permissions(int type
, bool from_file
)
774 * If this is from /proc/kmsg and we've already opened it, then we've
775 * already done the capabilities checks at open time.
777 if (from_file
&& type
!= SYSLOG_ACTION_OPEN
)
780 if (syslog_action_restricted(type
)) {
781 if (capable(CAP_SYSLOG
))
783 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
784 if (capable(CAP_SYS_ADMIN
)) {
785 printk_once(KERN_WARNING
"%s (%d): "
786 "Attempt to access syslog with CAP_SYS_ADMIN "
787 "but no CAP_SYSLOG (deprecated).\n",
788 current
->comm
, task_pid_nr(current
));
796 #if defined(CONFIG_PRINTK_TIME)
797 static bool printk_time
= 1;
799 static bool printk_time
;
801 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
803 static size_t print_time(u64 ts
, char *buf
)
805 unsigned long rem_nsec
;
813 rem_nsec
= do_div(ts
, 1000000000);
814 return sprintf(buf
, "[%5lu.%06lu] ",
815 (unsigned long)ts
, rem_nsec
/ 1000);
818 static size_t print_prefix(const struct log
*msg
, bool syslog
, char *buf
)
821 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
825 len
+= sprintf(buf
, "<%u>", prefix
);
830 else if (prefix
> 99)
837 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
841 static size_t msg_print_text(const struct log
*msg
, bool syslog
,
842 char *buf
, size_t size
)
844 const char *text
= log_text(msg
);
845 size_t text_size
= msg
->text_len
;
849 const char *next
= memchr(text
, '\n', text_size
);
853 text_len
= next
- text
;
855 text_size
-= next
- text
;
857 text_len
= text_size
;
861 if (print_prefix(msg
, syslog
, NULL
) +
862 text_len
+ 1>= size
- len
)
865 len
+= print_prefix(msg
, syslog
, buf
+ len
);
866 memcpy(buf
+ len
, text
, text_len
);
870 /* SYSLOG_ACTION_* buffer size only calculation */
871 len
+= print_prefix(msg
, syslog
, NULL
);
881 static int syslog_print(char __user
*buf
, int size
)
887 text
= kmalloc(LOG_LINE_MAX
, GFP_KERNEL
);
894 raw_spin_lock_irq(&logbuf_lock
);
895 if (syslog_seq
< log_first_seq
) {
896 /* messages are gone, move to first one */
897 syslog_seq
= log_first_seq
;
898 syslog_idx
= log_first_idx
;
900 if (syslog_seq
== log_next_seq
) {
901 raw_spin_unlock_irq(&logbuf_lock
);
904 msg
= log_from_idx(syslog_idx
);
905 n
= msg_print_text(msg
, true, text
, LOG_LINE_MAX
);
907 syslog_idx
= log_next(syslog_idx
);
911 raw_spin_unlock_irq(&logbuf_lock
);
919 n
= copy_to_user(buf
- n
, text
, n
);
933 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
938 text
= kmalloc(LOG_LINE_MAX
, GFP_KERNEL
);
942 raw_spin_lock_irq(&logbuf_lock
);
948 if (clear_seq
< log_first_seq
) {
949 /* messages are gone, move to first available one */
950 clear_seq
= log_first_seq
;
951 clear_idx
= log_first_idx
;
955 * Find first record that fits, including all following records,
956 * into the user-provided buffer for this dump.
960 while (seq
< log_next_seq
) {
961 struct log
*msg
= log_from_idx(idx
);
963 len
+= msg_print_text(msg
, true, NULL
, 0);
968 /* move first record forward until length fits into the buffer */
971 while (len
> size
&& seq
< log_next_seq
) {
972 struct log
*msg
= log_from_idx(idx
);
974 len
-= msg_print_text(msg
, true, NULL
, 0);
979 /* last message fitting into this dump */
980 next_seq
= log_next_seq
;
983 while (len
>= 0 && seq
< next_seq
) {
984 struct log
*msg
= log_from_idx(idx
);
987 textlen
= msg_print_text(msg
, true, text
, LOG_LINE_MAX
);
995 raw_spin_unlock_irq(&logbuf_lock
);
996 if (copy_to_user(buf
+ len
, text
, textlen
))
1000 raw_spin_lock_irq(&logbuf_lock
);
1002 if (seq
< log_first_seq
) {
1003 /* messages are gone, move to next one */
1004 seq
= log_first_seq
;
1005 idx
= log_first_idx
;
1011 clear_seq
= log_next_seq
;
1012 clear_idx
= log_next_idx
;
1014 raw_spin_unlock_irq(&logbuf_lock
);
1020 int do_syslog(int type
, char __user
*buf
, int len
, bool from_file
)
1023 static int saved_console_loglevel
= -1;
1026 error
= check_syslog_permissions(type
, from_file
);
1030 error
= security_syslog(type
);
1035 case SYSLOG_ACTION_CLOSE
: /* Close log */
1037 case SYSLOG_ACTION_OPEN
: /* Open log */
1039 case SYSLOG_ACTION_READ
: /* Read from log */
1041 if (!buf
|| len
< 0)
1046 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1050 error
= wait_event_interruptible(log_wait
,
1051 syslog_seq
!= log_next_seq
);
1054 error
= syslog_print(buf
, len
);
1056 /* Read/clear last kernel messages */
1057 case SYSLOG_ACTION_READ_CLEAR
:
1060 /* Read last kernel messages */
1061 case SYSLOG_ACTION_READ_ALL
:
1063 if (!buf
|| len
< 0)
1068 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1072 error
= syslog_print_all(buf
, len
, clear
);
1074 /* Clear ring buffer */
1075 case SYSLOG_ACTION_CLEAR
:
1076 syslog_print_all(NULL
, 0, true);
1078 /* Disable logging to console */
1079 case SYSLOG_ACTION_CONSOLE_OFF
:
1080 if (saved_console_loglevel
== -1)
1081 saved_console_loglevel
= console_loglevel
;
1082 console_loglevel
= minimum_console_loglevel
;
1084 /* Enable logging to console */
1085 case SYSLOG_ACTION_CONSOLE_ON
:
1086 if (saved_console_loglevel
!= -1) {
1087 console_loglevel
= saved_console_loglevel
;
1088 saved_console_loglevel
= -1;
1091 /* Set level of messages printed to console */
1092 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1094 if (len
< 1 || len
> 8)
1096 if (len
< minimum_console_loglevel
)
1097 len
= minimum_console_loglevel
;
1098 console_loglevel
= len
;
1099 /* Implicitly re-enable logging to console */
1100 saved_console_loglevel
= -1;
1103 /* Number of chars in the log buffer */
1104 case SYSLOG_ACTION_SIZE_UNREAD
:
1105 raw_spin_lock_irq(&logbuf_lock
);
1106 if (syslog_seq
< log_first_seq
) {
1107 /* messages are gone, move to first one */
1108 syslog_seq
= log_first_seq
;
1109 syslog_idx
= log_first_idx
;
1113 * Short-cut for poll(/"proc/kmsg") which simply checks
1114 * for pending data, not the size; return the count of
1115 * records, not the length.
1117 error
= log_next_idx
- syslog_idx
;
1125 while (seq
< log_next_seq
) {
1126 struct log
*msg
= log_from_idx(idx
);
1128 error
+= msg_print_text(msg
, true, NULL
, 0);
1129 idx
= log_next(idx
);
1133 raw_spin_unlock_irq(&logbuf_lock
);
1135 /* Size of the log buffer */
1136 case SYSLOG_ACTION_SIZE_BUFFER
:
1137 error
= log_buf_len
;
1147 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1149 return do_syslog(type
, buf
, len
, SYSLOG_FROM_CALL
);
1152 #ifdef CONFIG_KGDB_KDB
1153 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
1154 * uses locks so it cannot be used during debugging. Just tell kdb
1155 * where the start and end of the physical and logical logs are. This
1156 * is equivalent to do_syslog(3).
1158 void kdb_syslog_data(char *syslog_data
[4])
1160 syslog_data
[0] = log_buf
;
1161 syslog_data
[1] = log_buf
+ log_buf_len
;
1162 syslog_data
[2] = log_buf
+ log_first_idx
;
1163 syslog_data
[3] = log_buf
+ log_next_idx
;
1165 #endif /* CONFIG_KGDB_KDB */
1167 static bool __read_mostly ignore_loglevel
;
1169 static int __init
ignore_loglevel_setup(char *str
)
1171 ignore_loglevel
= 1;
1172 printk(KERN_INFO
"debug: ignoring loglevel setting.\n");
1177 early_param("ignore_loglevel", ignore_loglevel_setup
);
1178 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1179 MODULE_PARM_DESC(ignore_loglevel
, "ignore loglevel setting, to"
1180 "print all kernel messages to the console.");
1183 * Call the console drivers, asking them to write out
1184 * log_buf[start] to log_buf[end - 1].
1185 * The console_lock must be held.
1187 static void call_console_drivers(int level
, const char *text
, size_t len
)
1189 struct console
*con
;
1191 trace_console(text
, 0, len
, len
);
1193 if (level
>= console_loglevel
&& !ignore_loglevel
)
1195 if (!console_drivers
)
1198 for_each_console(con
) {
1199 if (exclusive_console
&& con
!= exclusive_console
)
1201 if (!(con
->flags
& CON_ENABLED
))
1205 if (!cpu_online(smp_processor_id()) &&
1206 !(con
->flags
& CON_ANYTIME
))
1208 con
->write(con
, text
, len
);
1213 * Zap console related locks when oopsing. Only zap at most once
1214 * every 10 seconds, to leave time for slow consoles to print a
1217 static void zap_locks(void)
1219 static unsigned long oops_timestamp
;
1221 if (time_after_eq(jiffies
, oops_timestamp
) &&
1222 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1225 oops_timestamp
= jiffies
;
1228 /* If a crash is occurring, make sure we can't deadlock */
1229 raw_spin_lock_init(&logbuf_lock
);
1230 /* And make sure that we print immediately */
1231 sema_init(&console_sem
, 1);
1234 /* Check if we have any console registered that can be called early in boot. */
1235 static int have_callable_console(void)
1237 struct console
*con
;
1239 for_each_console(con
)
1240 if (con
->flags
& CON_ANYTIME
)
1247 * Can we actually use the console at this time on this cpu?
1249 * Console drivers may assume that per-cpu resources have
1250 * been allocated. So unless they're explicitly marked as
1251 * being able to cope (CON_ANYTIME) don't call them until
1252 * this CPU is officially up.
1254 static inline int can_use_console(unsigned int cpu
)
1256 return cpu_online(cpu
) || have_callable_console();
1260 * Try to get console ownership to actually show the kernel
1261 * messages from a 'printk'. Return true (and with the
1262 * console_lock held, and 'console_locked' set) if it
1263 * is successful, false otherwise.
1265 * This gets called with the 'logbuf_lock' spinlock held and
1266 * interrupts disabled. It should return with 'lockbuf_lock'
1267 * released but interrupts still disabled.
1269 static int console_trylock_for_printk(unsigned int cpu
)
1270 __releases(&logbuf_lock
)
1272 int retval
= 0, wake
= 0;
1274 if (console_trylock()) {
1278 * If we can't use the console, we need to release
1279 * the console semaphore by hand to avoid flushing
1280 * the buffer. We need to hold the console semaphore
1281 * in order to do this test safely.
1283 if (!can_use_console(cpu
)) {
1289 logbuf_cpu
= UINT_MAX
;
1292 raw_spin_unlock(&logbuf_lock
);
1296 int printk_delay_msec __read_mostly
;
1298 static inline void printk_delay(void)
1300 if (unlikely(printk_delay_msec
)) {
1301 int m
= printk_delay_msec
;
1305 touch_nmi_watchdog();
1311 * Continuation lines are buffered, and not committed to the record buffer
1312 * until the line is complete, or a race forces it. The line fragments
1313 * though, are printed immediately to the consoles to ensure everything has
1314 * reached the console in case of a kernel crash.
1316 static struct cont
{
1317 char buf
[LOG_LINE_MAX
];
1318 size_t len
; /* length == 0 means unused buffer */
1319 size_t cons
; /* bytes written to console */
1320 struct task_struct
*owner
; /* task of first print*/
1321 u64 ts_nsec
; /* time of first print */
1322 u8 level
; /* log level of first message */
1323 u8 facility
; /* log level of first message */
1324 bool flushed
:1; /* buffer sealed and committed */
1327 static void cont_flush(void)
1334 log_store(cont
.facility
, cont
.level
, LOG_NOCONS
, cont
.ts_nsec
,
1335 NULL
, 0, cont
.buf
, cont
.len
);
1337 cont
.flushed
= true;
1340 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1342 if (cont
.len
&& cont
.flushed
)
1345 if (cont
.len
+ len
> sizeof(cont
.buf
)) {
1351 cont
.facility
= facility
;
1353 cont
.owner
= current
;
1354 cont
.ts_nsec
= local_clock();
1356 cont
.flushed
= false;
1359 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1364 static size_t cont_print_text(char *text
, size_t size
)
1369 if (cont
.cons
== 0) {
1370 textlen
+= print_time(cont
.ts_nsec
, text
);
1374 len
= cont
.len
- cont
.cons
;
1378 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1380 cont
.cons
= cont
.len
;
1384 text
[textlen
++] = '\n';
1385 /* got everything, release buffer */
1391 asmlinkage
int vprintk_emit(int facility
, int level
,
1392 const char *dict
, size_t dictlen
,
1393 const char *fmt
, va_list args
)
1395 static int recursion_bug
;
1396 static char textbuf
[LOG_LINE_MAX
];
1397 char *text
= textbuf
;
1399 unsigned long flags
;
1401 bool newline
= false;
1402 bool prefix
= false;
1403 int printed_len
= 0;
1408 /* This stops the holder of console_sem just where we want him */
1409 local_irq_save(flags
);
1410 this_cpu
= smp_processor_id();
1413 * Ouch, printk recursed into itself!
1415 if (unlikely(logbuf_cpu
== this_cpu
)) {
1417 * If a crash is occurring during printk() on this CPU,
1418 * then try to get the crash message out but make sure
1419 * we can't deadlock. Otherwise just return to avoid the
1420 * recursion and return - but flag the recursion so that
1421 * it can be printed at the next appropriate moment:
1423 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1425 goto out_restore_irqs
;
1431 raw_spin_lock(&logbuf_lock
);
1432 logbuf_cpu
= this_cpu
;
1434 if (recursion_bug
) {
1435 static const char recursion_msg
[] =
1436 "BUG: recent printk recursion!";
1439 printed_len
+= strlen(recursion_msg
);
1440 /* emit KERN_CRIT message */
1441 log_store(0, 2, LOG_DEFAULT
, 0,
1442 NULL
, 0, recursion_msg
, printed_len
);
1446 * The printf needs to come first; we need the syslog
1447 * prefix which might be passed-in as a parameter.
1449 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1451 /* mark and strip a trailing newline */
1452 if (text_len
&& text
[text_len
-1] == '\n') {
1457 /* strip syslog prefix and extract log level or control flags */
1458 if (text
[0] == '<' && text
[1] && text
[2] == '>') {
1462 level
= text
[1] - '0';
1463 case 'd': /* KERN_DEFAULT */
1465 case 'c': /* KERN_CONT */
1472 level
= default_message_loglevel
;
1481 * Flush the conflicting buffer. An earlier newline was missing,
1482 * or another task also prints continuation lines.
1484 if (cont
.len
&& (prefix
|| cont
.owner
!= current
))
1487 /* buffer line if possible, otherwise store it right away */
1488 if (!cont_add(facility
, level
, text
, text_len
))
1489 log_store(facility
, level
, LOG_DEFAULT
, 0,
1490 dict
, dictlen
, text
, text_len
);
1492 bool stored
= false;
1495 * If an earlier newline was missing and it was the same task,
1496 * either merge it with the current buffer and flush, or if
1497 * there was a race with interrupts (prefix == true) then just
1498 * flush it out and store this line separately.
1500 if (cont
.len
&& cont
.owner
== current
) {
1502 stored
= cont_add(facility
, level
, text
, text_len
);
1507 log_store(facility
, level
, LOG_DEFAULT
, 0,
1508 dict
, dictlen
, text
, text_len
);
1510 printed_len
+= text_len
;
1513 * Try to acquire and then immediately release the console semaphore.
1514 * The release will print out buffers and wake up /dev/kmsg and syslog()
1517 * The console_trylock_for_printk() function will release 'logbuf_lock'
1518 * regardless of whether it actually gets the console semaphore or not.
1520 if (console_trylock_for_printk(this_cpu
))
1525 local_irq_restore(flags
);
1529 EXPORT_SYMBOL(vprintk_emit
);
1531 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1533 return vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1535 EXPORT_SYMBOL(vprintk
);
1537 asmlinkage
int printk_emit(int facility
, int level
,
1538 const char *dict
, size_t dictlen
,
1539 const char *fmt
, ...)
1544 va_start(args
, fmt
);
1545 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1550 EXPORT_SYMBOL(printk_emit
);
1553 * printk - print a kernel message
1554 * @fmt: format string
1556 * This is printk(). It can be called from any context. We want it to work.
1558 * We try to grab the console_lock. If we succeed, it's easy - we log the
1559 * output and call the console drivers. If we fail to get the semaphore, we
1560 * place the output into the log buffer and return. The current holder of
1561 * the console_sem will notice the new output in console_unlock(); and will
1562 * send it to the consoles before releasing the lock.
1564 * One effect of this deferred printing is that code which calls printk() and
1565 * then changes console_loglevel may break. This is because console_loglevel
1566 * is inspected when the actual printing occurs.
1571 * See the vsnprintf() documentation for format string extensions over C99.
1573 asmlinkage
int printk(const char *fmt
, ...)
1578 #ifdef CONFIG_KGDB_KDB
1579 if (unlikely(kdb_trap_printk
)) {
1580 va_start(args
, fmt
);
1581 r
= vkdb_printf(fmt
, args
);
1586 va_start(args
, fmt
);
1587 r
= vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1592 EXPORT_SYMBOL(printk
);
1596 #define LOG_LINE_MAX 0
1597 static struct cont
{
1603 static struct log
*log_from_idx(u32 idx
) { return NULL
; }
1604 static u32
log_next(u32 idx
) { return 0; }
1605 static void call_console_drivers(int level
, const char *text
, size_t len
) {}
1606 static size_t msg_print_text(const struct log
*msg
, bool syslog
,
1607 char *buf
, size_t size
) { return 0; }
1608 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
1610 #endif /* CONFIG_PRINTK */
1612 static int __add_preferred_console(char *name
, int idx
, char *options
,
1615 struct console_cmdline
*c
;
1619 * See if this tty is not yet registered, and
1620 * if we have a slot free.
1622 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
1623 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
1624 console_cmdline
[i
].index
== idx
) {
1626 selected_console
= i
;
1629 if (i
== MAX_CMDLINECONSOLES
)
1632 selected_console
= i
;
1633 c
= &console_cmdline
[i
];
1634 strlcpy(c
->name
, name
, sizeof(c
->name
));
1635 c
->options
= options
;
1636 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1637 c
->brl_options
= brl_options
;
1643 * Set up a list of consoles. Called from init/main.c
1645 static int __init
console_setup(char *str
)
1647 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for index */
1648 char *s
, *options
, *brl_options
= NULL
;
1651 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1652 if (!memcmp(str
, "brl,", 4)) {
1655 } else if (!memcmp(str
, "brl=", 4)) {
1656 brl_options
= str
+ 4;
1657 str
= strchr(brl_options
, ',');
1659 printk(KERN_ERR
"need port name after brl=\n");
1667 * Decode str into name, index, options.
1669 if (str
[0] >= '0' && str
[0] <= '9') {
1670 strcpy(buf
, "ttyS");
1671 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1673 strncpy(buf
, str
, sizeof(buf
) - 1);
1675 buf
[sizeof(buf
) - 1] = 0;
1676 if ((options
= strchr(str
, ',')) != NULL
)
1679 if (!strcmp(str
, "ttya"))
1680 strcpy(buf
, "ttyS0");
1681 if (!strcmp(str
, "ttyb"))
1682 strcpy(buf
, "ttyS1");
1684 for (s
= buf
; *s
; s
++)
1685 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
1687 idx
= simple_strtoul(s
, NULL
, 10);
1690 __add_preferred_console(buf
, idx
, options
, brl_options
);
1691 console_set_on_cmdline
= 1;
1694 __setup("console=", console_setup
);
1697 * add_preferred_console - add a device to the list of preferred consoles.
1698 * @name: device name
1699 * @idx: device index
1700 * @options: options for this console
1702 * The last preferred console added will be used for kernel messages
1703 * and stdin/out/err for init. Normally this is used by console_setup
1704 * above to handle user-supplied console arguments; however it can also
1705 * be used by arch-specific code either to override the user or more
1706 * commonly to provide a default console (ie from PROM variables) when
1707 * the user has not supplied one.
1709 int add_preferred_console(char *name
, int idx
, char *options
)
1711 return __add_preferred_console(name
, idx
, options
, NULL
);
1714 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
1716 struct console_cmdline
*c
;
1719 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
1720 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
1721 console_cmdline
[i
].index
== idx
) {
1722 c
= &console_cmdline
[i
];
1723 strlcpy(c
->name
, name_new
, sizeof(c
->name
));
1724 c
->name
[sizeof(c
->name
) - 1] = 0;
1725 c
->options
= options
;
1733 bool console_suspend_enabled
= 1;
1734 EXPORT_SYMBOL(console_suspend_enabled
);
1736 static int __init
console_suspend_disable(char *str
)
1738 console_suspend_enabled
= 0;
1741 __setup("no_console_suspend", console_suspend_disable
);
1742 module_param_named(console_suspend
, console_suspend_enabled
,
1743 bool, S_IRUGO
| S_IWUSR
);
1744 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
1745 " and hibernate operations");
1748 * suspend_console - suspend the console subsystem
1750 * This disables printk() while we go into suspend states
1752 void suspend_console(void)
1754 if (!console_suspend_enabled
)
1756 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1758 console_suspended
= 1;
1762 void resume_console(void)
1764 if (!console_suspend_enabled
)
1767 console_suspended
= 0;
1772 * console_cpu_notify - print deferred console messages after CPU hotplug
1773 * @self: notifier struct
1774 * @action: CPU hotplug event
1777 * If printk() is called from a CPU that is not online yet, the messages
1778 * will be spooled but will not show up on the console. This function is
1779 * called when a new CPU comes online (or fails to come up), and ensures
1780 * that any such output gets printed.
1782 static int __cpuinit
console_cpu_notify(struct notifier_block
*self
,
1783 unsigned long action
, void *hcpu
)
1789 case CPU_DOWN_FAILED
:
1790 case CPU_UP_CANCELED
:
1798 * console_lock - lock the console system for exclusive use.
1800 * Acquires a lock which guarantees that the caller has
1801 * exclusive access to the console system and the console_drivers list.
1803 * Can sleep, returns nothing.
1805 void console_lock(void)
1807 BUG_ON(in_interrupt());
1809 if (console_suspended
)
1812 console_may_schedule
= 1;
1814 EXPORT_SYMBOL(console_lock
);
1817 * console_trylock - try to lock the console system for exclusive use.
1819 * Tried to acquire a lock which guarantees that the caller has
1820 * exclusive access to the console system and the console_drivers list.
1822 * returns 1 on success, and 0 on failure to acquire the lock.
1824 int console_trylock(void)
1826 if (down_trylock(&console_sem
))
1828 if (console_suspended
) {
1833 console_may_schedule
= 0;
1836 EXPORT_SYMBOL(console_trylock
);
1838 int is_console_locked(void)
1840 return console_locked
;
1844 * Delayed printk version, for scheduler-internal messages:
1846 #define PRINTK_BUF_SIZE 512
1848 #define PRINTK_PENDING_WAKEUP 0x01
1849 #define PRINTK_PENDING_SCHED 0x02
1851 static DEFINE_PER_CPU(int, printk_pending
);
1852 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE
], printk_sched_buf
);
1854 void printk_tick(void)
1856 if (__this_cpu_read(printk_pending
)) {
1857 int pending
= __this_cpu_xchg(printk_pending
, 0);
1858 if (pending
& PRINTK_PENDING_SCHED
) {
1859 char *buf
= __get_cpu_var(printk_sched_buf
);
1860 printk(KERN_WARNING
"[sched_delayed] %s", buf
);
1862 if (pending
& PRINTK_PENDING_WAKEUP
)
1863 wake_up_interruptible(&log_wait
);
1867 int printk_needs_cpu(int cpu
)
1869 if (cpu_is_offline(cpu
))
1871 return __this_cpu_read(printk_pending
);
1874 void wake_up_klogd(void)
1876 if (waitqueue_active(&log_wait
))
1877 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
1880 /* the next printk record to write to the console */
1881 static u64 console_seq
;
1882 static u32 console_idx
;
1885 * console_unlock - unlock the console system
1887 * Releases the console_lock which the caller holds on the console system
1888 * and the console driver list.
1890 * While the console_lock was held, console output may have been buffered
1891 * by printk(). If this is the case, console_unlock(); emits
1892 * the output prior to releasing the lock.
1894 * If there is output waiting, we wake /dev/kmsg and syslog() users.
1896 * console_unlock(); may be called from any context.
1898 void console_unlock(void)
1900 static char text
[LOG_LINE_MAX
];
1901 static u64 seen_seq
;
1902 unsigned long flags
;
1903 bool wake_klogd
= false;
1906 if (console_suspended
) {
1911 console_may_schedule
= 0;
1913 /* flush buffered message fragment immediately to console */
1914 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
1915 if (cont
.len
&& (cont
.cons
< cont
.len
|| cont
.flushed
)) {
1918 len
= cont_print_text(text
, sizeof(text
));
1919 raw_spin_unlock(&logbuf_lock
);
1920 stop_critical_timings();
1921 call_console_drivers(cont
.level
, text
, len
);
1922 start_critical_timings();
1923 local_irq_restore(flags
);
1925 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
1933 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
1934 if (seen_seq
!= log_next_seq
) {
1936 seen_seq
= log_next_seq
;
1939 if (console_seq
< log_first_seq
) {
1940 /* messages are gone, move to first one */
1941 console_seq
= log_first_seq
;
1942 console_idx
= log_first_idx
;
1945 if (console_seq
== log_next_seq
)
1948 msg
= log_from_idx(console_idx
);
1949 if (msg
->flags
& LOG_NOCONS
) {
1951 * Skip record we have buffered and already printed
1952 * directly to the console when we received it.
1954 console_idx
= log_next(console_idx
);
1957 * We will get here again when we register a new
1958 * CON_PRINTBUFFER console. Clear the flag so we
1959 * will properly dump everything later.
1961 msg
->flags
&= ~LOG_NOCONS
;
1966 len
= msg_print_text(msg
, false, text
, sizeof(text
));
1968 console_idx
= log_next(console_idx
);
1970 raw_spin_unlock(&logbuf_lock
);
1972 stop_critical_timings(); /* don't trace print latency */
1973 call_console_drivers(level
, text
, len
);
1974 start_critical_timings();
1975 local_irq_restore(flags
);
1979 /* Release the exclusive_console once it is used */
1980 if (unlikely(exclusive_console
))
1981 exclusive_console
= NULL
;
1983 raw_spin_unlock(&logbuf_lock
);
1988 * Someone could have filled up the buffer again, so re-check if there's
1989 * something to flush. In case we cannot trylock the console_sem again,
1990 * there's a new owner and the console_unlock() from them will do the
1991 * flush, no worries.
1993 raw_spin_lock(&logbuf_lock
);
1994 retry
= console_seq
!= log_next_seq
;
1995 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
1997 if (retry
&& console_trylock())
2003 EXPORT_SYMBOL(console_unlock
);
2006 * console_conditional_schedule - yield the CPU if required
2008 * If the console code is currently allowed to sleep, and
2009 * if this CPU should yield the CPU to another task, do
2012 * Must be called within console_lock();.
2014 void __sched
console_conditional_schedule(void)
2016 if (console_may_schedule
)
2019 EXPORT_SYMBOL(console_conditional_schedule
);
2021 void console_unblank(void)
2026 * console_unblank can no longer be called in interrupt context unless
2027 * oops_in_progress is set to 1..
2029 if (oops_in_progress
) {
2030 if (down_trylock(&console_sem
) != 0)
2036 console_may_schedule
= 0;
2038 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2044 * Return the console tty driver structure and its associated index
2046 struct tty_driver
*console_device(int *index
)
2049 struct tty_driver
*driver
= NULL
;
2052 for_each_console(c
) {
2055 driver
= c
->device(c
, index
);
2064 * Prevent further output on the passed console device so that (for example)
2065 * serial drivers can disable console output before suspending a port, and can
2066 * re-enable output afterwards.
2068 void console_stop(struct console
*console
)
2071 console
->flags
&= ~CON_ENABLED
;
2074 EXPORT_SYMBOL(console_stop
);
2076 void console_start(struct console
*console
)
2079 console
->flags
|= CON_ENABLED
;
2082 EXPORT_SYMBOL(console_start
);
2084 static int __read_mostly keep_bootcon
;
2086 static int __init
keep_bootcon_setup(char *str
)
2089 printk(KERN_INFO
"debug: skip boot console de-registration.\n");
2094 early_param("keep_bootcon", keep_bootcon_setup
);
2097 * The console driver calls this routine during kernel initialization
2098 * to register the console printing procedure with printk() and to
2099 * print any messages that were printed by the kernel before the
2100 * console driver was initialized.
2102 * This can happen pretty early during the boot process (because of
2103 * early_printk) - sometimes before setup_arch() completes - be careful
2104 * of what kernel features are used - they may not be initialised yet.
2106 * There are two types of consoles - bootconsoles (early_printk) and
2107 * "real" consoles (everything which is not a bootconsole) which are
2108 * handled differently.
2109 * - Any number of bootconsoles can be registered at any time.
2110 * - As soon as a "real" console is registered, all bootconsoles
2111 * will be unregistered automatically.
2112 * - Once a "real" console is registered, any attempt to register a
2113 * bootconsoles will be rejected
2115 void register_console(struct console
*newcon
)
2118 unsigned long flags
;
2119 struct console
*bcon
= NULL
;
2122 * before we register a new CON_BOOT console, make sure we don't
2123 * already have a valid console
2125 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2126 /* find the last or real console */
2127 for_each_console(bcon
) {
2128 if (!(bcon
->flags
& CON_BOOT
)) {
2129 printk(KERN_INFO
"Too late to register bootconsole %s%d\n",
2130 newcon
->name
, newcon
->index
);
2136 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2137 bcon
= console_drivers
;
2139 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2140 preferred_console
= selected_console
;
2142 if (newcon
->early_setup
)
2143 newcon
->early_setup();
2146 * See if we want to use this console driver. If we
2147 * didn't select a console we take the first one
2148 * that registers here.
2150 if (preferred_console
< 0) {
2151 if (newcon
->index
< 0)
2153 if (newcon
->setup
== NULL
||
2154 newcon
->setup(newcon
, NULL
) == 0) {
2155 newcon
->flags
|= CON_ENABLED
;
2156 if (newcon
->device
) {
2157 newcon
->flags
|= CON_CONSDEV
;
2158 preferred_console
= 0;
2164 * See if this console matches one we selected on
2167 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
2169 if (strcmp(console_cmdline
[i
].name
, newcon
->name
) != 0)
2171 if (newcon
->index
>= 0 &&
2172 newcon
->index
!= console_cmdline
[i
].index
)
2174 if (newcon
->index
< 0)
2175 newcon
->index
= console_cmdline
[i
].index
;
2176 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2177 if (console_cmdline
[i
].brl_options
) {
2178 newcon
->flags
|= CON_BRL
;
2179 braille_register_console(newcon
,
2180 console_cmdline
[i
].index
,
2181 console_cmdline
[i
].options
,
2182 console_cmdline
[i
].brl_options
);
2186 if (newcon
->setup
&&
2187 newcon
->setup(newcon
, console_cmdline
[i
].options
) != 0)
2189 newcon
->flags
|= CON_ENABLED
;
2190 newcon
->index
= console_cmdline
[i
].index
;
2191 if (i
== selected_console
) {
2192 newcon
->flags
|= CON_CONSDEV
;
2193 preferred_console
= selected_console
;
2198 if (!(newcon
->flags
& CON_ENABLED
))
2202 * If we have a bootconsole, and are switching to a real console,
2203 * don't print everything out again, since when the boot console, and
2204 * the real console are the same physical device, it's annoying to
2205 * see the beginning boot messages twice
2207 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2208 newcon
->flags
&= ~CON_PRINTBUFFER
;
2211 * Put this console in the list - keep the
2212 * preferred driver at the head of the list.
2215 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2216 newcon
->next
= console_drivers
;
2217 console_drivers
= newcon
;
2219 newcon
->next
->flags
&= ~CON_CONSDEV
;
2221 newcon
->next
= console_drivers
->next
;
2222 console_drivers
->next
= newcon
;
2224 if (newcon
->flags
& CON_PRINTBUFFER
) {
2226 * console_unlock(); will print out the buffered messages
2229 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2230 console_seq
= syslog_seq
;
2231 console_idx
= syslog_idx
;
2232 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2234 * We're about to replay the log buffer. Only do this to the
2235 * just-registered console to avoid excessive message spam to
2236 * the already-registered consoles.
2238 exclusive_console
= newcon
;
2241 console_sysfs_notify();
2244 * By unregistering the bootconsoles after we enable the real console
2245 * we get the "console xxx enabled" message on all the consoles -
2246 * boot consoles, real consoles, etc - this is to ensure that end
2247 * users know there might be something in the kernel's log buffer that
2248 * went to the bootconsole (that they do not see on the real console)
2251 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2253 /* we need to iterate through twice, to make sure we print
2254 * everything out, before we unregister the console(s)
2256 printk(KERN_INFO
"console [%s%d] enabled, bootconsole disabled\n",
2257 newcon
->name
, newcon
->index
);
2258 for_each_console(bcon
)
2259 if (bcon
->flags
& CON_BOOT
)
2260 unregister_console(bcon
);
2262 printk(KERN_INFO
"%sconsole [%s%d] enabled\n",
2263 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2264 newcon
->name
, newcon
->index
);
2267 EXPORT_SYMBOL(register_console
);
2269 int unregister_console(struct console
*console
)
2271 struct console
*a
, *b
;
2274 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2275 if (console
->flags
& CON_BRL
)
2276 return braille_unregister_console(console
);
2280 if (console_drivers
== console
) {
2281 console_drivers
=console
->next
;
2283 } else if (console_drivers
) {
2284 for (a
=console_drivers
->next
, b
=console_drivers
;
2285 a
; b
=a
, a
=b
->next
) {
2295 * If this isn't the last console and it has CON_CONSDEV set, we
2296 * need to set it on the next preferred console.
2298 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2299 console_drivers
->flags
|= CON_CONSDEV
;
2302 console_sysfs_notify();
2305 EXPORT_SYMBOL(unregister_console
);
2307 static int __init
printk_late_init(void)
2309 struct console
*con
;
2311 for_each_console(con
) {
2312 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2313 printk(KERN_INFO
"turn off boot console %s%d\n",
2314 con
->name
, con
->index
);
2315 unregister_console(con
);
2318 hotcpu_notifier(console_cpu_notify
, 0);
2321 late_initcall(printk_late_init
);
2323 #if defined CONFIG_PRINTK
2325 int printk_sched(const char *fmt
, ...)
2327 unsigned long flags
;
2332 local_irq_save(flags
);
2333 buf
= __get_cpu_var(printk_sched_buf
);
2335 va_start(args
, fmt
);
2336 r
= vsnprintf(buf
, PRINTK_BUF_SIZE
, fmt
, args
);
2339 __this_cpu_or(printk_pending
, PRINTK_PENDING_SCHED
);
2340 local_irq_restore(flags
);
2346 * printk rate limiting, lifted from the networking subsystem.
2348 * This enforces a rate limit: not more than 10 kernel messages
2349 * every 5s to make a denial-of-service attack impossible.
2351 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2353 int __printk_ratelimit(const char *func
)
2355 return ___ratelimit(&printk_ratelimit_state
, func
);
2357 EXPORT_SYMBOL(__printk_ratelimit
);
2360 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2361 * @caller_jiffies: pointer to caller's state
2362 * @interval_msecs: minimum interval between prints
2364 * printk_timed_ratelimit() returns true if more than @interval_msecs
2365 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2368 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2369 unsigned int interval_msecs
)
2371 if (*caller_jiffies
== 0
2372 || !time_in_range(jiffies
, *caller_jiffies
,
2374 + msecs_to_jiffies(interval_msecs
))) {
2375 *caller_jiffies
= jiffies
;
2380 EXPORT_SYMBOL(printk_timed_ratelimit
);
2382 static DEFINE_SPINLOCK(dump_list_lock
);
2383 static LIST_HEAD(dump_list
);
2386 * kmsg_dump_register - register a kernel log dumper.
2387 * @dumper: pointer to the kmsg_dumper structure
2389 * Adds a kernel log dumper to the system. The dump callback in the
2390 * structure will be called when the kernel oopses or panics and must be
2391 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2393 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2395 unsigned long flags
;
2398 /* The dump callback needs to be set */
2402 spin_lock_irqsave(&dump_list_lock
, flags
);
2403 /* Don't allow registering multiple times */
2404 if (!dumper
->registered
) {
2405 dumper
->registered
= 1;
2406 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2409 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2413 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2416 * kmsg_dump_unregister - unregister a kmsg dumper.
2417 * @dumper: pointer to the kmsg_dumper structure
2419 * Removes a dump device from the system. Returns zero on success and
2420 * %-EINVAL otherwise.
2422 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2424 unsigned long flags
;
2427 spin_lock_irqsave(&dump_list_lock
, flags
);
2428 if (dumper
->registered
) {
2429 dumper
->registered
= 0;
2430 list_del_rcu(&dumper
->list
);
2433 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2438 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2440 static bool always_kmsg_dump
;
2441 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2444 * kmsg_dump - dump kernel log to kernel message dumpers.
2445 * @reason: the reason (oops, panic etc) for dumping
2447 * Call each of the registered dumper's dump() callback, which can
2448 * retrieve the kmsg records with kmsg_dump_get_line() or
2449 * kmsg_dump_get_buffer().
2451 void kmsg_dump(enum kmsg_dump_reason reason
)
2453 struct kmsg_dumper
*dumper
;
2454 unsigned long flags
;
2456 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2460 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2461 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2464 /* initialize iterator with data about the stored records */
2465 dumper
->active
= true;
2467 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2468 dumper
->cur_seq
= clear_seq
;
2469 dumper
->cur_idx
= clear_idx
;
2470 dumper
->next_seq
= log_next_seq
;
2471 dumper
->next_idx
= log_next_idx
;
2472 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2474 /* invoke dumper which will iterate over records */
2475 dumper
->dump(dumper
, reason
);
2477 /* reset iterator */
2478 dumper
->active
= false;
2484 * kmsg_dump_get_line - retrieve one kmsg log line
2485 * @dumper: registered kmsg dumper
2486 * @syslog: include the "<4>" prefixes
2487 * @line: buffer to copy the line to
2488 * @size: maximum size of the buffer
2489 * @len: length of line placed into buffer
2491 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2492 * record, and copy one record into the provided buffer.
2494 * Consecutive calls will return the next available record moving
2495 * towards the end of the buffer with the youngest messages.
2497 * A return value of FALSE indicates that there are no more records to
2500 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2501 char *line
, size_t size
, size_t *len
)
2503 unsigned long flags
;
2508 if (!dumper
->active
)
2511 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2512 if (dumper
->cur_seq
< log_first_seq
) {
2513 /* messages are gone, move to first available one */
2514 dumper
->cur_seq
= log_first_seq
;
2515 dumper
->cur_idx
= log_first_idx
;
2519 if (dumper
->cur_seq
>= log_next_seq
) {
2520 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2524 msg
= log_from_idx(dumper
->cur_idx
);
2525 l
= msg_print_text(msg
, syslog
,
2528 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2531 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2537 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
2540 * kmsg_dump_get_buffer - copy kmsg log lines
2541 * @dumper: registered kmsg dumper
2542 * @syslog: include the "<4>" prefixes
2543 * @buf: buffer to copy the line to
2544 * @size: maximum size of the buffer
2545 * @len: length of line placed into buffer
2547 * Start at the end of the kmsg buffer and fill the provided buffer
2548 * with as many of the the *youngest* kmsg records that fit into it.
2549 * If the buffer is large enough, all available kmsg records will be
2550 * copied with a single call.
2552 * Consecutive calls will fill the buffer with the next block of
2553 * available older records, not including the earlier retrieved ones.
2555 * A return value of FALSE indicates that there are no more records to
2558 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
2559 char *buf
, size_t size
, size_t *len
)
2561 unsigned long flags
;
2569 if (!dumper
->active
)
2572 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2573 if (dumper
->cur_seq
< log_first_seq
) {
2574 /* messages are gone, move to first available one */
2575 dumper
->cur_seq
= log_first_seq
;
2576 dumper
->cur_idx
= log_first_idx
;
2580 if (dumper
->cur_seq
>= dumper
->next_seq
) {
2581 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2585 /* calculate length of entire buffer */
2586 seq
= dumper
->cur_seq
;
2587 idx
= dumper
->cur_idx
;
2588 while (seq
< dumper
->next_seq
) {
2589 struct log
*msg
= log_from_idx(idx
);
2591 l
+= msg_print_text(msg
, true, NULL
, 0);
2592 idx
= log_next(idx
);
2596 /* move first record forward until length fits into the buffer */
2597 seq
= dumper
->cur_seq
;
2598 idx
= dumper
->cur_idx
;
2599 while (l
> size
&& seq
< dumper
->next_seq
) {
2600 struct log
*msg
= log_from_idx(idx
);
2602 l
-= msg_print_text(msg
, true, NULL
, 0);
2603 idx
= log_next(idx
);
2607 /* last message in next interation */
2612 while (seq
< dumper
->next_seq
) {
2613 struct log
*msg
= log_from_idx(idx
);
2615 l
+= msg_print_text(msg
, syslog
,
2618 idx
= log_next(idx
);
2622 dumper
->next_seq
= next_seq
;
2623 dumper
->next_idx
= next_idx
;
2625 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2631 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
2634 * kmsg_dump_rewind - reset the interator
2635 * @dumper: registered kmsg dumper
2637 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2638 * kmsg_dump_get_buffer() can be called again and used multiple
2639 * times within the same dumper.dump() callback.
2641 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
2643 unsigned long flags
;
2645 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2646 dumper
->cur_seq
= clear_seq
;
2647 dumper
->cur_idx
= clear_idx
;
2648 dumper
->next_seq
= log_next_seq
;
2649 dumper
->next_idx
= log_next_idx
;
2650 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2652 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);