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
;
220 static size_t syslog_partial
;
222 /* index and sequence number of the first record stored in the buffer */
223 static u64 log_first_seq
;
224 static u32 log_first_idx
;
226 /* index and sequence number of the next record to store in the buffer */
227 static u64 log_next_seq
;
229 static u32 log_next_idx
;
231 /* the next printk record to read after the last 'clear' command */
232 static u64 clear_seq
;
233 static u32 clear_idx
;
235 #define LOG_LINE_MAX 1024
238 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
241 #define LOG_ALIGN __alignof__(struct log)
243 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
244 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
245 static char *log_buf
= __log_buf
;
246 static u32 log_buf_len
= __LOG_BUF_LEN
;
248 /* cpu currently holding logbuf_lock */
249 static volatile unsigned int logbuf_cpu
= UINT_MAX
;
251 /* human readable text of the record */
252 static char *log_text(const struct log
*msg
)
254 return (char *)msg
+ sizeof(struct log
);
257 /* optional key/value pair dictionary attached to the record */
258 static char *log_dict(const struct log
*msg
)
260 return (char *)msg
+ sizeof(struct log
) + msg
->text_len
;
263 /* get record by index; idx must point to valid msg */
264 static struct log
*log_from_idx(u32 idx
)
266 struct log
*msg
= (struct log
*)(log_buf
+ idx
);
269 * A length == 0 record is the end of buffer marker. Wrap around and
270 * read the message at the start of the buffer.
273 return (struct log
*)log_buf
;
277 /* get next record; idx must point to valid msg */
278 static u32
log_next(u32 idx
)
280 struct log
*msg
= (struct log
*)(log_buf
+ idx
);
282 /* length == 0 indicates the end of the buffer; wrap */
284 * A length == 0 record is the end of buffer marker. Wrap around and
285 * read the message at the start of the buffer as *this* one, and
286 * return the one after that.
289 msg
= (struct log
*)log_buf
;
292 return idx
+ msg
->len
;
295 /* insert record into the buffer, discard old ones, update heads */
296 static void log_store(int facility
, int level
,
297 enum log_flags flags
, u64 ts_nsec
,
298 const char *dict
, u16 dict_len
,
299 const char *text
, u16 text_len
)
304 /* number of '\0' padding bytes to next message */
305 size
= sizeof(struct log
) + text_len
+ dict_len
;
306 pad_len
= (-size
) & (LOG_ALIGN
- 1);
309 while (log_first_seq
< log_next_seq
) {
312 if (log_next_idx
> log_first_idx
)
313 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
315 free
= log_first_idx
- log_next_idx
;
317 if (free
> size
+ sizeof(struct log
))
320 /* drop old messages until we have enough contiuous space */
321 log_first_idx
= log_next(log_first_idx
);
325 if (log_next_idx
+ size
+ sizeof(struct log
) >= log_buf_len
) {
327 * This message + an additional empty header does not fit
328 * at the end of the buffer. Add an empty header with len == 0
329 * to signify a wrap around.
331 memset(log_buf
+ log_next_idx
, 0, sizeof(struct log
));
336 msg
= (struct log
*)(log_buf
+ log_next_idx
);
337 memcpy(log_text(msg
), text
, text_len
);
338 msg
->text_len
= text_len
;
339 memcpy(log_dict(msg
), dict
, dict_len
);
340 msg
->dict_len
= dict_len
;
341 msg
->facility
= facility
;
342 msg
->level
= level
& 7;
343 msg
->flags
= flags
& 0x1f;
345 msg
->ts_nsec
= ts_nsec
;
347 msg
->ts_nsec
= local_clock();
348 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
349 msg
->len
= sizeof(struct log
) + text_len
+ dict_len
+ pad_len
;
352 log_next_idx
+= msg
->len
;
356 /* /dev/kmsg - userspace message inject/listen interface */
357 struct devkmsg_user
{
364 static ssize_t
devkmsg_writev(struct kiocb
*iocb
, const struct iovec
*iv
,
365 unsigned long count
, loff_t pos
)
369 int level
= default_message_loglevel
;
370 int facility
= 1; /* LOG_USER */
371 size_t len
= iov_length(iv
, count
);
374 if (len
> LOG_LINE_MAX
)
376 buf
= kmalloc(len
+1, GFP_KERNEL
);
381 for (i
= 0; i
< count
; i
++) {
382 if (copy_from_user(line
, iv
[i
].iov_base
, iv
[i
].iov_len
))
384 line
+= iv
[i
].iov_len
;
388 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
389 * the decimal value represents 32bit, the lower 3 bit are the log
390 * level, the rest are the log facility.
392 * If no prefix or no userspace facility is specified, we
393 * enforce LOG_USER, to be able to reliably distinguish
394 * kernel-generated messages from userspace-injected ones.
397 if (line
[0] == '<') {
400 i
= simple_strtoul(line
+1, &endp
, 10);
401 if (endp
&& endp
[0] == '>') {
412 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
418 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
419 size_t count
, loff_t
*ppos
)
421 struct devkmsg_user
*user
= file
->private_data
;
431 ret
= mutex_lock_interruptible(&user
->lock
);
434 raw_spin_lock_irq(&logbuf_lock
);
435 while (user
->seq
== log_next_seq
) {
436 if (file
->f_flags
& O_NONBLOCK
) {
438 raw_spin_unlock_irq(&logbuf_lock
);
442 raw_spin_unlock_irq(&logbuf_lock
);
443 ret
= wait_event_interruptible(log_wait
,
444 user
->seq
!= log_next_seq
);
447 raw_spin_lock_irq(&logbuf_lock
);
450 if (user
->seq
< log_first_seq
) {
451 /* our last seen message is gone, return error and reset */
452 user
->idx
= log_first_idx
;
453 user
->seq
= log_first_seq
;
455 raw_spin_unlock_irq(&logbuf_lock
);
459 msg
= log_from_idx(user
->idx
);
460 ts_usec
= msg
->ts_nsec
;
461 do_div(ts_usec
, 1000);
462 len
= sprintf(user
->buf
, "%u,%llu,%llu;",
463 (msg
->facility
<< 3) | msg
->level
, user
->seq
, ts_usec
);
465 /* escape non-printable characters */
466 for (i
= 0; i
< msg
->text_len
; i
++) {
467 unsigned char c
= log_text(msg
)[i
];
469 if (c
< ' ' || c
>= 127 || c
== '\\')
470 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
472 user
->buf
[len
++] = c
;
474 user
->buf
[len
++] = '\n';
479 for (i
= 0; i
< msg
->dict_len
; i
++) {
480 unsigned char c
= log_dict(msg
)[i
];
483 user
->buf
[len
++] = ' ';
488 user
->buf
[len
++] = '\n';
493 if (c
< ' ' || c
>= 127 || c
== '\\') {
494 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
498 user
->buf
[len
++] = c
;
500 user
->buf
[len
++] = '\n';
503 user
->idx
= log_next(user
->idx
);
505 raw_spin_unlock_irq(&logbuf_lock
);
512 if (copy_to_user(buf
, user
->buf
, len
)) {
518 mutex_unlock(&user
->lock
);
522 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
524 struct devkmsg_user
*user
= file
->private_data
;
532 raw_spin_lock_irq(&logbuf_lock
);
535 /* the first record */
536 user
->idx
= log_first_idx
;
537 user
->seq
= log_first_seq
;
541 * The first record after the last SYSLOG_ACTION_CLEAR,
542 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
543 * changes no global state, and does not clear anything.
545 user
->idx
= clear_idx
;
546 user
->seq
= clear_seq
;
549 /* after the last record */
550 user
->idx
= log_next_idx
;
551 user
->seq
= log_next_seq
;
556 raw_spin_unlock_irq(&logbuf_lock
);
560 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
562 struct devkmsg_user
*user
= file
->private_data
;
566 return POLLERR
|POLLNVAL
;
568 poll_wait(file
, &log_wait
, wait
);
570 raw_spin_lock_irq(&logbuf_lock
);
571 if (user
->seq
< log_next_seq
) {
572 /* return error when data has vanished underneath us */
573 if (user
->seq
< log_first_seq
)
574 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
575 ret
= POLLIN
|POLLRDNORM
;
577 raw_spin_unlock_irq(&logbuf_lock
);
582 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
584 struct devkmsg_user
*user
;
587 /* write-only does not need any file context */
588 if ((file
->f_flags
& O_ACCMODE
) == O_WRONLY
)
591 err
= security_syslog(SYSLOG_ACTION_READ_ALL
);
595 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
599 mutex_init(&user
->lock
);
601 raw_spin_lock_irq(&logbuf_lock
);
602 user
->idx
= log_first_idx
;
603 user
->seq
= log_first_seq
;
604 raw_spin_unlock_irq(&logbuf_lock
);
606 file
->private_data
= user
;
610 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
612 struct devkmsg_user
*user
= file
->private_data
;
617 mutex_destroy(&user
->lock
);
622 const struct file_operations kmsg_fops
= {
623 .open
= devkmsg_open
,
624 .read
= devkmsg_read
,
625 .aio_write
= devkmsg_writev
,
626 .llseek
= devkmsg_llseek
,
627 .poll
= devkmsg_poll
,
628 .release
= devkmsg_release
,
633 * This appends the listed symbols to /proc/vmcoreinfo
635 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
636 * obtain access to symbols that are otherwise very difficult to locate. These
637 * symbols are specifically used so that utilities can access and extract the
638 * dmesg log from a vmcore file after a crash.
640 void log_buf_kexec_setup(void)
642 VMCOREINFO_SYMBOL(log_buf
);
643 VMCOREINFO_SYMBOL(log_buf_len
);
644 VMCOREINFO_SYMBOL(log_first_idx
);
645 VMCOREINFO_SYMBOL(log_next_idx
);
649 /* requested log_buf_len from kernel cmdline */
650 static unsigned long __initdata new_log_buf_len
;
652 /* save requested log_buf_len since it's too early to process it */
653 static int __init
log_buf_len_setup(char *str
)
655 unsigned size
= memparse(str
, &str
);
658 size
= roundup_pow_of_two(size
);
659 if (size
> log_buf_len
)
660 new_log_buf_len
= size
;
664 early_param("log_buf_len", log_buf_len_setup
);
666 void __init
setup_log_buf(int early
)
672 if (!new_log_buf_len
)
678 mem
= memblock_alloc(new_log_buf_len
, PAGE_SIZE
);
681 new_log_buf
= __va(mem
);
683 new_log_buf
= alloc_bootmem_nopanic(new_log_buf_len
);
686 if (unlikely(!new_log_buf
)) {
687 pr_err("log_buf_len: %ld bytes not available\n",
692 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
693 log_buf_len
= new_log_buf_len
;
694 log_buf
= new_log_buf
;
696 free
= __LOG_BUF_LEN
- log_next_idx
;
697 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
698 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
700 pr_info("log_buf_len: %d\n", log_buf_len
);
701 pr_info("early log buf free: %d(%d%%)\n",
702 free
, (free
* 100) / __LOG_BUF_LEN
);
705 #ifdef CONFIG_BOOT_PRINTK_DELAY
707 static int boot_delay
; /* msecs delay after each printk during bootup */
708 static unsigned long long loops_per_msec
; /* based on boot_delay */
710 static int __init
boot_delay_setup(char *str
)
714 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
715 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
717 get_option(&str
, &boot_delay
);
718 if (boot_delay
> 10 * 1000)
721 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
722 "HZ: %d, loops_per_msec: %llu\n",
723 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
726 __setup("boot_delay=", boot_delay_setup
);
728 static void boot_delay_msec(void)
730 unsigned long long k
;
731 unsigned long timeout
;
733 if (boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
736 k
= (unsigned long long)loops_per_msec
* boot_delay
;
738 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
743 * use (volatile) jiffies to prevent
744 * compiler reduction; loop termination via jiffies
745 * is secondary and may or may not happen.
747 if (time_after(jiffies
, timeout
))
749 touch_nmi_watchdog();
753 static inline void boot_delay_msec(void)
758 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
759 int dmesg_restrict
= 1;
764 static int syslog_action_restricted(int type
)
768 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
769 return type
!= SYSLOG_ACTION_READ_ALL
&& type
!= SYSLOG_ACTION_SIZE_BUFFER
;
772 static int check_syslog_permissions(int type
, bool from_file
)
775 * If this is from /proc/kmsg and we've already opened it, then we've
776 * already done the capabilities checks at open time.
778 if (from_file
&& type
!= SYSLOG_ACTION_OPEN
)
781 if (syslog_action_restricted(type
)) {
782 if (capable(CAP_SYSLOG
))
784 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
785 if (capable(CAP_SYS_ADMIN
)) {
786 printk_once(KERN_WARNING
"%s (%d): "
787 "Attempt to access syslog with CAP_SYS_ADMIN "
788 "but no CAP_SYSLOG (deprecated).\n",
789 current
->comm
, task_pid_nr(current
));
797 #if defined(CONFIG_PRINTK_TIME)
798 static bool printk_time
= 1;
800 static bool printk_time
;
802 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
804 static size_t print_time(u64 ts
, char *buf
)
806 unsigned long rem_nsec
;
814 rem_nsec
= do_div(ts
, 1000000000);
815 return sprintf(buf
, "[%5lu.%06lu] ",
816 (unsigned long)ts
, rem_nsec
/ 1000);
819 static size_t print_prefix(const struct log
*msg
, bool syslog
, char *buf
)
822 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
826 len
+= sprintf(buf
, "<%u>", prefix
);
831 else if (prefix
> 99)
838 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
842 static size_t msg_print_text(const struct log
*msg
, bool syslog
,
843 char *buf
, size_t size
)
845 const char *text
= log_text(msg
);
846 size_t text_size
= msg
->text_len
;
850 const char *next
= memchr(text
, '\n', text_size
);
854 text_len
= next
- text
;
856 text_size
-= next
- text
;
858 text_len
= text_size
;
862 if (print_prefix(msg
, syslog
, NULL
) +
863 text_len
+ 1>= size
- len
)
866 len
+= print_prefix(msg
, syslog
, buf
+ len
);
867 memcpy(buf
+ len
, text
, text_len
);
871 /* SYSLOG_ACTION_* buffer size only calculation */
872 len
+= print_prefix(msg
, syslog
, NULL
);
882 static int syslog_print(char __user
*buf
, int size
)
888 text
= kmalloc(LOG_LINE_MAX
, GFP_KERNEL
);
896 raw_spin_lock_irq(&logbuf_lock
);
897 if (syslog_seq
< log_first_seq
) {
898 /* messages are gone, move to first one */
899 syslog_seq
= log_first_seq
;
900 syslog_idx
= log_first_idx
;
903 if (syslog_seq
== log_next_seq
) {
904 raw_spin_unlock_irq(&logbuf_lock
);
908 skip
= syslog_partial
;
909 msg
= log_from_idx(syslog_idx
);
910 n
= msg_print_text(msg
, true, text
, LOG_LINE_MAX
);
911 if (n
- syslog_partial
<= size
) {
912 /* message fits into buffer, move forward */
913 syslog_idx
= log_next(syslog_idx
);
918 /* partial read(), remember position */
923 raw_spin_unlock_irq(&logbuf_lock
);
928 if (copy_to_user(buf
, text
+ skip
, n
)) {
943 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
948 text
= kmalloc(LOG_LINE_MAX
, GFP_KERNEL
);
952 raw_spin_lock_irq(&logbuf_lock
);
958 if (clear_seq
< log_first_seq
) {
959 /* messages are gone, move to first available one */
960 clear_seq
= log_first_seq
;
961 clear_idx
= log_first_idx
;
965 * Find first record that fits, including all following records,
966 * into the user-provided buffer for this dump.
970 while (seq
< log_next_seq
) {
971 struct log
*msg
= log_from_idx(idx
);
973 len
+= msg_print_text(msg
, true, NULL
, 0);
978 /* move first record forward until length fits into the buffer */
981 while (len
> size
&& seq
< log_next_seq
) {
982 struct log
*msg
= log_from_idx(idx
);
984 len
-= msg_print_text(msg
, true, NULL
, 0);
989 /* last message fitting into this dump */
990 next_seq
= log_next_seq
;
993 while (len
>= 0 && seq
< next_seq
) {
994 struct log
*msg
= log_from_idx(idx
);
997 textlen
= msg_print_text(msg
, true, text
, LOG_LINE_MAX
);
1002 idx
= log_next(idx
);
1005 raw_spin_unlock_irq(&logbuf_lock
);
1006 if (copy_to_user(buf
+ len
, text
, textlen
))
1010 raw_spin_lock_irq(&logbuf_lock
);
1012 if (seq
< log_first_seq
) {
1013 /* messages are gone, move to next one */
1014 seq
= log_first_seq
;
1015 idx
= log_first_idx
;
1021 clear_seq
= log_next_seq
;
1022 clear_idx
= log_next_idx
;
1024 raw_spin_unlock_irq(&logbuf_lock
);
1030 int do_syslog(int type
, char __user
*buf
, int len
, bool from_file
)
1033 static int saved_console_loglevel
= -1;
1036 error
= check_syslog_permissions(type
, from_file
);
1040 error
= security_syslog(type
);
1045 case SYSLOG_ACTION_CLOSE
: /* Close log */
1047 case SYSLOG_ACTION_OPEN
: /* Open log */
1049 case SYSLOG_ACTION_READ
: /* Read from log */
1051 if (!buf
|| len
< 0)
1056 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1060 error
= wait_event_interruptible(log_wait
,
1061 syslog_seq
!= log_next_seq
);
1064 error
= syslog_print(buf
, len
);
1066 /* Read/clear last kernel messages */
1067 case SYSLOG_ACTION_READ_CLEAR
:
1070 /* Read last kernel messages */
1071 case SYSLOG_ACTION_READ_ALL
:
1073 if (!buf
|| len
< 0)
1078 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1082 error
= syslog_print_all(buf
, len
, clear
);
1084 /* Clear ring buffer */
1085 case SYSLOG_ACTION_CLEAR
:
1086 syslog_print_all(NULL
, 0, true);
1088 /* Disable logging to console */
1089 case SYSLOG_ACTION_CONSOLE_OFF
:
1090 if (saved_console_loglevel
== -1)
1091 saved_console_loglevel
= console_loglevel
;
1092 console_loglevel
= minimum_console_loglevel
;
1094 /* Enable logging to console */
1095 case SYSLOG_ACTION_CONSOLE_ON
:
1096 if (saved_console_loglevel
!= -1) {
1097 console_loglevel
= saved_console_loglevel
;
1098 saved_console_loglevel
= -1;
1101 /* Set level of messages printed to console */
1102 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1104 if (len
< 1 || len
> 8)
1106 if (len
< minimum_console_loglevel
)
1107 len
= minimum_console_loglevel
;
1108 console_loglevel
= len
;
1109 /* Implicitly re-enable logging to console */
1110 saved_console_loglevel
= -1;
1113 /* Number of chars in the log buffer */
1114 case SYSLOG_ACTION_SIZE_UNREAD
:
1115 raw_spin_lock_irq(&logbuf_lock
);
1116 if (syslog_seq
< log_first_seq
) {
1117 /* messages are gone, move to first one */
1118 syslog_seq
= log_first_seq
;
1119 syslog_idx
= log_first_idx
;
1124 * Short-cut for poll(/"proc/kmsg") which simply checks
1125 * for pending data, not the size; return the count of
1126 * records, not the length.
1128 error
= log_next_idx
- syslog_idx
;
1136 while (seq
< log_next_seq
) {
1137 struct log
*msg
= log_from_idx(idx
);
1139 error
+= msg_print_text(msg
, true, NULL
, 0);
1140 idx
= log_next(idx
);
1143 error
-= syslog_partial
;
1145 raw_spin_unlock_irq(&logbuf_lock
);
1147 /* Size of the log buffer */
1148 case SYSLOG_ACTION_SIZE_BUFFER
:
1149 error
= log_buf_len
;
1159 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1161 return do_syslog(type
, buf
, len
, SYSLOG_FROM_CALL
);
1164 #ifdef CONFIG_KGDB_KDB
1165 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
1166 * uses locks so it cannot be used during debugging. Just tell kdb
1167 * where the start and end of the physical and logical logs are. This
1168 * is equivalent to do_syslog(3).
1170 void kdb_syslog_data(char *syslog_data
[4])
1172 syslog_data
[0] = log_buf
;
1173 syslog_data
[1] = log_buf
+ log_buf_len
;
1174 syslog_data
[2] = log_buf
+ log_first_idx
;
1175 syslog_data
[3] = log_buf
+ log_next_idx
;
1177 #endif /* CONFIG_KGDB_KDB */
1179 static bool __read_mostly ignore_loglevel
;
1181 static int __init
ignore_loglevel_setup(char *str
)
1183 ignore_loglevel
= 1;
1184 printk(KERN_INFO
"debug: ignoring loglevel setting.\n");
1189 early_param("ignore_loglevel", ignore_loglevel_setup
);
1190 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1191 MODULE_PARM_DESC(ignore_loglevel
, "ignore loglevel setting, to"
1192 "print all kernel messages to the console.");
1195 * Call the console drivers, asking them to write out
1196 * log_buf[start] to log_buf[end - 1].
1197 * The console_lock must be held.
1199 static void call_console_drivers(int level
, const char *text
, size_t len
)
1201 struct console
*con
;
1203 trace_console(text
, 0, len
, len
);
1205 if (level
>= console_loglevel
&& !ignore_loglevel
)
1207 if (!console_drivers
)
1210 for_each_console(con
) {
1211 if (exclusive_console
&& con
!= exclusive_console
)
1213 if (!(con
->flags
& CON_ENABLED
))
1217 if (!cpu_online(smp_processor_id()) &&
1218 !(con
->flags
& CON_ANYTIME
))
1220 con
->write(con
, text
, len
);
1225 * Zap console related locks when oopsing. Only zap at most once
1226 * every 10 seconds, to leave time for slow consoles to print a
1229 static void zap_locks(void)
1231 static unsigned long oops_timestamp
;
1233 if (time_after_eq(jiffies
, oops_timestamp
) &&
1234 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1237 oops_timestamp
= jiffies
;
1240 /* If a crash is occurring, make sure we can't deadlock */
1241 raw_spin_lock_init(&logbuf_lock
);
1242 /* And make sure that we print immediately */
1243 sema_init(&console_sem
, 1);
1246 /* Check if we have any console registered that can be called early in boot. */
1247 static int have_callable_console(void)
1249 struct console
*con
;
1251 for_each_console(con
)
1252 if (con
->flags
& CON_ANYTIME
)
1259 * Can we actually use the console at this time on this cpu?
1261 * Console drivers may assume that per-cpu resources have
1262 * been allocated. So unless they're explicitly marked as
1263 * being able to cope (CON_ANYTIME) don't call them until
1264 * this CPU is officially up.
1266 static inline int can_use_console(unsigned int cpu
)
1268 return cpu_online(cpu
) || have_callable_console();
1272 * Try to get console ownership to actually show the kernel
1273 * messages from a 'printk'. Return true (and with the
1274 * console_lock held, and 'console_locked' set) if it
1275 * is successful, false otherwise.
1277 * This gets called with the 'logbuf_lock' spinlock held and
1278 * interrupts disabled. It should return with 'lockbuf_lock'
1279 * released but interrupts still disabled.
1281 static int console_trylock_for_printk(unsigned int cpu
)
1282 __releases(&logbuf_lock
)
1284 int retval
= 0, wake
= 0;
1286 if (console_trylock()) {
1290 * If we can't use the console, we need to release
1291 * the console semaphore by hand to avoid flushing
1292 * the buffer. We need to hold the console semaphore
1293 * in order to do this test safely.
1295 if (!can_use_console(cpu
)) {
1301 logbuf_cpu
= UINT_MAX
;
1304 raw_spin_unlock(&logbuf_lock
);
1308 int printk_delay_msec __read_mostly
;
1310 static inline void printk_delay(void)
1312 if (unlikely(printk_delay_msec
)) {
1313 int m
= printk_delay_msec
;
1317 touch_nmi_watchdog();
1323 * Continuation lines are buffered, and not committed to the record buffer
1324 * until the line is complete, or a race forces it. The line fragments
1325 * though, are printed immediately to the consoles to ensure everything has
1326 * reached the console in case of a kernel crash.
1328 static struct cont
{
1329 char buf
[LOG_LINE_MAX
];
1330 size_t len
; /* length == 0 means unused buffer */
1331 size_t cons
; /* bytes written to console */
1332 struct task_struct
*owner
; /* task of first print*/
1333 u64 ts_nsec
; /* time of first print */
1334 u8 level
; /* log level of first message */
1335 u8 facility
; /* log level of first message */
1336 bool flushed
:1; /* buffer sealed and committed */
1339 static void cont_flush(void)
1346 log_store(cont
.facility
, cont
.level
, LOG_NOCONS
, cont
.ts_nsec
,
1347 NULL
, 0, cont
.buf
, cont
.len
);
1349 cont
.flushed
= true;
1352 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1354 if (cont
.len
&& cont
.flushed
)
1357 if (cont
.len
+ len
> sizeof(cont
.buf
)) {
1363 cont
.facility
= facility
;
1365 cont
.owner
= current
;
1366 cont
.ts_nsec
= local_clock();
1368 cont
.flushed
= false;
1371 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1376 static size_t cont_print_text(char *text
, size_t size
)
1381 if (cont
.cons
== 0) {
1382 textlen
+= print_time(cont
.ts_nsec
, text
);
1386 len
= cont
.len
- cont
.cons
;
1390 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1392 cont
.cons
= cont
.len
;
1396 text
[textlen
++] = '\n';
1397 /* got everything, release buffer */
1403 asmlinkage
int vprintk_emit(int facility
, int level
,
1404 const char *dict
, size_t dictlen
,
1405 const char *fmt
, va_list args
)
1407 static int recursion_bug
;
1408 static char textbuf
[LOG_LINE_MAX
];
1409 char *text
= textbuf
;
1411 unsigned long flags
;
1413 bool newline
= false;
1414 bool prefix
= false;
1415 int printed_len
= 0;
1420 /* This stops the holder of console_sem just where we want him */
1421 local_irq_save(flags
);
1422 this_cpu
= smp_processor_id();
1425 * Ouch, printk recursed into itself!
1427 if (unlikely(logbuf_cpu
== this_cpu
)) {
1429 * If a crash is occurring during printk() on this CPU,
1430 * then try to get the crash message out but make sure
1431 * we can't deadlock. Otherwise just return to avoid the
1432 * recursion and return - but flag the recursion so that
1433 * it can be printed at the next appropriate moment:
1435 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1437 goto out_restore_irqs
;
1443 raw_spin_lock(&logbuf_lock
);
1444 logbuf_cpu
= this_cpu
;
1446 if (recursion_bug
) {
1447 static const char recursion_msg
[] =
1448 "BUG: recent printk recursion!";
1451 printed_len
+= strlen(recursion_msg
);
1452 /* emit KERN_CRIT message */
1453 log_store(0, 2, LOG_DEFAULT
, 0,
1454 NULL
, 0, recursion_msg
, printed_len
);
1458 * The printf needs to come first; we need the syslog
1459 * prefix which might be passed-in as a parameter.
1461 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1463 /* mark and strip a trailing newline */
1464 if (text_len
&& text
[text_len
-1] == '\n') {
1469 /* strip syslog prefix and extract log level or control flags */
1470 if (text
[0] == '<' && text
[1] && text
[2] == '>') {
1474 level
= text
[1] - '0';
1475 case 'd': /* KERN_DEFAULT */
1477 case 'c': /* KERN_CONT */
1484 level
= default_message_loglevel
;
1493 * Flush the conflicting buffer. An earlier newline was missing,
1494 * or another task also prints continuation lines.
1496 if (cont
.len
&& (prefix
|| cont
.owner
!= current
))
1499 /* buffer line if possible, otherwise store it right away */
1500 if (!cont_add(facility
, level
, text
, text_len
))
1501 log_store(facility
, level
, LOG_DEFAULT
, 0,
1502 dict
, dictlen
, text
, text_len
);
1504 bool stored
= false;
1507 * If an earlier newline was missing and it was the same task,
1508 * either merge it with the current buffer and flush, or if
1509 * there was a race with interrupts (prefix == true) then just
1510 * flush it out and store this line separately.
1512 if (cont
.len
&& cont
.owner
== current
) {
1514 stored
= cont_add(facility
, level
, text
, text_len
);
1519 log_store(facility
, level
, LOG_DEFAULT
, 0,
1520 dict
, dictlen
, text
, text_len
);
1522 printed_len
+= text_len
;
1525 * Try to acquire and then immediately release the console semaphore.
1526 * The release will print out buffers and wake up /dev/kmsg and syslog()
1529 * The console_trylock_for_printk() function will release 'logbuf_lock'
1530 * regardless of whether it actually gets the console semaphore or not.
1532 if (console_trylock_for_printk(this_cpu
))
1537 local_irq_restore(flags
);
1541 EXPORT_SYMBOL(vprintk_emit
);
1543 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1545 return vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1547 EXPORT_SYMBOL(vprintk
);
1549 asmlinkage
int printk_emit(int facility
, int level
,
1550 const char *dict
, size_t dictlen
,
1551 const char *fmt
, ...)
1556 va_start(args
, fmt
);
1557 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1562 EXPORT_SYMBOL(printk_emit
);
1565 * printk - print a kernel message
1566 * @fmt: format string
1568 * This is printk(). It can be called from any context. We want it to work.
1570 * We try to grab the console_lock. If we succeed, it's easy - we log the
1571 * output and call the console drivers. If we fail to get the semaphore, we
1572 * place the output into the log buffer and return. The current holder of
1573 * the console_sem will notice the new output in console_unlock(); and will
1574 * send it to the consoles before releasing the lock.
1576 * One effect of this deferred printing is that code which calls printk() and
1577 * then changes console_loglevel may break. This is because console_loglevel
1578 * is inspected when the actual printing occurs.
1583 * See the vsnprintf() documentation for format string extensions over C99.
1585 asmlinkage
int printk(const char *fmt
, ...)
1590 #ifdef CONFIG_KGDB_KDB
1591 if (unlikely(kdb_trap_printk
)) {
1592 va_start(args
, fmt
);
1593 r
= vkdb_printf(fmt
, args
);
1598 va_start(args
, fmt
);
1599 r
= vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1604 EXPORT_SYMBOL(printk
);
1608 #define LOG_LINE_MAX 0
1609 static struct cont
{
1615 static struct log
*log_from_idx(u32 idx
) { return NULL
; }
1616 static u32
log_next(u32 idx
) { return 0; }
1617 static void call_console_drivers(int level
, const char *text
, size_t len
) {}
1618 static size_t msg_print_text(const struct log
*msg
, bool syslog
,
1619 char *buf
, size_t size
) { return 0; }
1620 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
1622 #endif /* CONFIG_PRINTK */
1624 static int __add_preferred_console(char *name
, int idx
, char *options
,
1627 struct console_cmdline
*c
;
1631 * See if this tty is not yet registered, and
1632 * if we have a slot free.
1634 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
1635 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
1636 console_cmdline
[i
].index
== idx
) {
1638 selected_console
= i
;
1641 if (i
== MAX_CMDLINECONSOLES
)
1644 selected_console
= i
;
1645 c
= &console_cmdline
[i
];
1646 strlcpy(c
->name
, name
, sizeof(c
->name
));
1647 c
->options
= options
;
1648 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1649 c
->brl_options
= brl_options
;
1655 * Set up a list of consoles. Called from init/main.c
1657 static int __init
console_setup(char *str
)
1659 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for index */
1660 char *s
, *options
, *brl_options
= NULL
;
1663 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1664 if (!memcmp(str
, "brl,", 4)) {
1667 } else if (!memcmp(str
, "brl=", 4)) {
1668 brl_options
= str
+ 4;
1669 str
= strchr(brl_options
, ',');
1671 printk(KERN_ERR
"need port name after brl=\n");
1679 * Decode str into name, index, options.
1681 if (str
[0] >= '0' && str
[0] <= '9') {
1682 strcpy(buf
, "ttyS");
1683 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1685 strncpy(buf
, str
, sizeof(buf
) - 1);
1687 buf
[sizeof(buf
) - 1] = 0;
1688 if ((options
= strchr(str
, ',')) != NULL
)
1691 if (!strcmp(str
, "ttya"))
1692 strcpy(buf
, "ttyS0");
1693 if (!strcmp(str
, "ttyb"))
1694 strcpy(buf
, "ttyS1");
1696 for (s
= buf
; *s
; s
++)
1697 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
1699 idx
= simple_strtoul(s
, NULL
, 10);
1702 __add_preferred_console(buf
, idx
, options
, brl_options
);
1703 console_set_on_cmdline
= 1;
1706 __setup("console=", console_setup
);
1709 * add_preferred_console - add a device to the list of preferred consoles.
1710 * @name: device name
1711 * @idx: device index
1712 * @options: options for this console
1714 * The last preferred console added will be used for kernel messages
1715 * and stdin/out/err for init. Normally this is used by console_setup
1716 * above to handle user-supplied console arguments; however it can also
1717 * be used by arch-specific code either to override the user or more
1718 * commonly to provide a default console (ie from PROM variables) when
1719 * the user has not supplied one.
1721 int add_preferred_console(char *name
, int idx
, char *options
)
1723 return __add_preferred_console(name
, idx
, options
, NULL
);
1726 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
1728 struct console_cmdline
*c
;
1731 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
1732 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
1733 console_cmdline
[i
].index
== idx
) {
1734 c
= &console_cmdline
[i
];
1735 strlcpy(c
->name
, name_new
, sizeof(c
->name
));
1736 c
->name
[sizeof(c
->name
) - 1] = 0;
1737 c
->options
= options
;
1745 bool console_suspend_enabled
= 1;
1746 EXPORT_SYMBOL(console_suspend_enabled
);
1748 static int __init
console_suspend_disable(char *str
)
1750 console_suspend_enabled
= 0;
1753 __setup("no_console_suspend", console_suspend_disable
);
1754 module_param_named(console_suspend
, console_suspend_enabled
,
1755 bool, S_IRUGO
| S_IWUSR
);
1756 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
1757 " and hibernate operations");
1760 * suspend_console - suspend the console subsystem
1762 * This disables printk() while we go into suspend states
1764 void suspend_console(void)
1766 if (!console_suspend_enabled
)
1768 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1770 console_suspended
= 1;
1774 void resume_console(void)
1776 if (!console_suspend_enabled
)
1779 console_suspended
= 0;
1784 * console_cpu_notify - print deferred console messages after CPU hotplug
1785 * @self: notifier struct
1786 * @action: CPU hotplug event
1789 * If printk() is called from a CPU that is not online yet, the messages
1790 * will be spooled but will not show up on the console. This function is
1791 * called when a new CPU comes online (or fails to come up), and ensures
1792 * that any such output gets printed.
1794 static int __cpuinit
console_cpu_notify(struct notifier_block
*self
,
1795 unsigned long action
, void *hcpu
)
1801 case CPU_DOWN_FAILED
:
1802 case CPU_UP_CANCELED
:
1810 * console_lock - lock the console system for exclusive use.
1812 * Acquires a lock which guarantees that the caller has
1813 * exclusive access to the console system and the console_drivers list.
1815 * Can sleep, returns nothing.
1817 void console_lock(void)
1819 BUG_ON(in_interrupt());
1821 if (console_suspended
)
1824 console_may_schedule
= 1;
1826 EXPORT_SYMBOL(console_lock
);
1829 * console_trylock - try to lock the console system for exclusive use.
1831 * Tried to acquire a lock which guarantees that the caller has
1832 * exclusive access to the console system and the console_drivers list.
1834 * returns 1 on success, and 0 on failure to acquire the lock.
1836 int console_trylock(void)
1838 if (down_trylock(&console_sem
))
1840 if (console_suspended
) {
1845 console_may_schedule
= 0;
1848 EXPORT_SYMBOL(console_trylock
);
1850 int is_console_locked(void)
1852 return console_locked
;
1856 * Delayed printk version, for scheduler-internal messages:
1858 #define PRINTK_BUF_SIZE 512
1860 #define PRINTK_PENDING_WAKEUP 0x01
1861 #define PRINTK_PENDING_SCHED 0x02
1863 static DEFINE_PER_CPU(int, printk_pending
);
1864 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE
], printk_sched_buf
);
1866 void printk_tick(void)
1868 if (__this_cpu_read(printk_pending
)) {
1869 int pending
= __this_cpu_xchg(printk_pending
, 0);
1870 if (pending
& PRINTK_PENDING_SCHED
) {
1871 char *buf
= __get_cpu_var(printk_sched_buf
);
1872 printk(KERN_WARNING
"[sched_delayed] %s", buf
);
1874 if (pending
& PRINTK_PENDING_WAKEUP
)
1875 wake_up_interruptible(&log_wait
);
1879 int printk_needs_cpu(int cpu
)
1881 if (cpu_is_offline(cpu
))
1883 return __this_cpu_read(printk_pending
);
1886 void wake_up_klogd(void)
1888 if (waitqueue_active(&log_wait
))
1889 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
1892 /* the next printk record to write to the console */
1893 static u64 console_seq
;
1894 static u32 console_idx
;
1897 * console_unlock - unlock the console system
1899 * Releases the console_lock which the caller holds on the console system
1900 * and the console driver list.
1902 * While the console_lock was held, console output may have been buffered
1903 * by printk(). If this is the case, console_unlock(); emits
1904 * the output prior to releasing the lock.
1906 * If there is output waiting, we wake /dev/kmsg and syslog() users.
1908 * console_unlock(); may be called from any context.
1910 void console_unlock(void)
1912 static char text
[LOG_LINE_MAX
];
1913 static u64 seen_seq
;
1914 unsigned long flags
;
1915 bool wake_klogd
= false;
1918 if (console_suspended
) {
1923 console_may_schedule
= 0;
1925 /* flush buffered message fragment immediately to console */
1926 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
1927 if (cont
.len
&& (cont
.cons
< cont
.len
|| cont
.flushed
)) {
1930 len
= cont_print_text(text
, sizeof(text
));
1931 raw_spin_unlock(&logbuf_lock
);
1932 stop_critical_timings();
1933 call_console_drivers(cont
.level
, text
, len
);
1934 start_critical_timings();
1935 local_irq_restore(flags
);
1937 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
1945 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
1946 if (seen_seq
!= log_next_seq
) {
1948 seen_seq
= log_next_seq
;
1951 if (console_seq
< log_first_seq
) {
1952 /* messages are gone, move to first one */
1953 console_seq
= log_first_seq
;
1954 console_idx
= log_first_idx
;
1957 if (console_seq
== log_next_seq
)
1960 msg
= log_from_idx(console_idx
);
1961 if (msg
->flags
& LOG_NOCONS
) {
1963 * Skip record we have buffered and already printed
1964 * directly to the console when we received it.
1966 console_idx
= log_next(console_idx
);
1969 * We will get here again when we register a new
1970 * CON_PRINTBUFFER console. Clear the flag so we
1971 * will properly dump everything later.
1973 msg
->flags
&= ~LOG_NOCONS
;
1978 len
= msg_print_text(msg
, false, text
, sizeof(text
));
1980 console_idx
= log_next(console_idx
);
1982 raw_spin_unlock(&logbuf_lock
);
1984 stop_critical_timings(); /* don't trace print latency */
1985 call_console_drivers(level
, text
, len
);
1986 start_critical_timings();
1987 local_irq_restore(flags
);
1991 /* Release the exclusive_console once it is used */
1992 if (unlikely(exclusive_console
))
1993 exclusive_console
= NULL
;
1995 raw_spin_unlock(&logbuf_lock
);
2000 * Someone could have filled up the buffer again, so re-check if there's
2001 * something to flush. In case we cannot trylock the console_sem again,
2002 * there's a new owner and the console_unlock() from them will do the
2003 * flush, no worries.
2005 raw_spin_lock(&logbuf_lock
);
2006 retry
= console_seq
!= log_next_seq
;
2007 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2009 if (retry
&& console_trylock())
2015 EXPORT_SYMBOL(console_unlock
);
2018 * console_conditional_schedule - yield the CPU if required
2020 * If the console code is currently allowed to sleep, and
2021 * if this CPU should yield the CPU to another task, do
2024 * Must be called within console_lock();.
2026 void __sched
console_conditional_schedule(void)
2028 if (console_may_schedule
)
2031 EXPORT_SYMBOL(console_conditional_schedule
);
2033 void console_unblank(void)
2038 * console_unblank can no longer be called in interrupt context unless
2039 * oops_in_progress is set to 1..
2041 if (oops_in_progress
) {
2042 if (down_trylock(&console_sem
) != 0)
2048 console_may_schedule
= 0;
2050 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2056 * Return the console tty driver structure and its associated index
2058 struct tty_driver
*console_device(int *index
)
2061 struct tty_driver
*driver
= NULL
;
2064 for_each_console(c
) {
2067 driver
= c
->device(c
, index
);
2076 * Prevent further output on the passed console device so that (for example)
2077 * serial drivers can disable console output before suspending a port, and can
2078 * re-enable output afterwards.
2080 void console_stop(struct console
*console
)
2083 console
->flags
&= ~CON_ENABLED
;
2086 EXPORT_SYMBOL(console_stop
);
2088 void console_start(struct console
*console
)
2091 console
->flags
|= CON_ENABLED
;
2094 EXPORT_SYMBOL(console_start
);
2096 static int __read_mostly keep_bootcon
;
2098 static int __init
keep_bootcon_setup(char *str
)
2101 printk(KERN_INFO
"debug: skip boot console de-registration.\n");
2106 early_param("keep_bootcon", keep_bootcon_setup
);
2109 * The console driver calls this routine during kernel initialization
2110 * to register the console printing procedure with printk() and to
2111 * print any messages that were printed by the kernel before the
2112 * console driver was initialized.
2114 * This can happen pretty early during the boot process (because of
2115 * early_printk) - sometimes before setup_arch() completes - be careful
2116 * of what kernel features are used - they may not be initialised yet.
2118 * There are two types of consoles - bootconsoles (early_printk) and
2119 * "real" consoles (everything which is not a bootconsole) which are
2120 * handled differently.
2121 * - Any number of bootconsoles can be registered at any time.
2122 * - As soon as a "real" console is registered, all bootconsoles
2123 * will be unregistered automatically.
2124 * - Once a "real" console is registered, any attempt to register a
2125 * bootconsoles will be rejected
2127 void register_console(struct console
*newcon
)
2130 unsigned long flags
;
2131 struct console
*bcon
= NULL
;
2134 * before we register a new CON_BOOT console, make sure we don't
2135 * already have a valid console
2137 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2138 /* find the last or real console */
2139 for_each_console(bcon
) {
2140 if (!(bcon
->flags
& CON_BOOT
)) {
2141 printk(KERN_INFO
"Too late to register bootconsole %s%d\n",
2142 newcon
->name
, newcon
->index
);
2148 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2149 bcon
= console_drivers
;
2151 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2152 preferred_console
= selected_console
;
2154 if (newcon
->early_setup
)
2155 newcon
->early_setup();
2158 * See if we want to use this console driver. If we
2159 * didn't select a console we take the first one
2160 * that registers here.
2162 if (preferred_console
< 0) {
2163 if (newcon
->index
< 0)
2165 if (newcon
->setup
== NULL
||
2166 newcon
->setup(newcon
, NULL
) == 0) {
2167 newcon
->flags
|= CON_ENABLED
;
2168 if (newcon
->device
) {
2169 newcon
->flags
|= CON_CONSDEV
;
2170 preferred_console
= 0;
2176 * See if this console matches one we selected on
2179 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
2181 if (strcmp(console_cmdline
[i
].name
, newcon
->name
) != 0)
2183 if (newcon
->index
>= 0 &&
2184 newcon
->index
!= console_cmdline
[i
].index
)
2186 if (newcon
->index
< 0)
2187 newcon
->index
= console_cmdline
[i
].index
;
2188 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2189 if (console_cmdline
[i
].brl_options
) {
2190 newcon
->flags
|= CON_BRL
;
2191 braille_register_console(newcon
,
2192 console_cmdline
[i
].index
,
2193 console_cmdline
[i
].options
,
2194 console_cmdline
[i
].brl_options
);
2198 if (newcon
->setup
&&
2199 newcon
->setup(newcon
, console_cmdline
[i
].options
) != 0)
2201 newcon
->flags
|= CON_ENABLED
;
2202 newcon
->index
= console_cmdline
[i
].index
;
2203 if (i
== selected_console
) {
2204 newcon
->flags
|= CON_CONSDEV
;
2205 preferred_console
= selected_console
;
2210 if (!(newcon
->flags
& CON_ENABLED
))
2214 * If we have a bootconsole, and are switching to a real console,
2215 * don't print everything out again, since when the boot console, and
2216 * the real console are the same physical device, it's annoying to
2217 * see the beginning boot messages twice
2219 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2220 newcon
->flags
&= ~CON_PRINTBUFFER
;
2223 * Put this console in the list - keep the
2224 * preferred driver at the head of the list.
2227 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2228 newcon
->next
= console_drivers
;
2229 console_drivers
= newcon
;
2231 newcon
->next
->flags
&= ~CON_CONSDEV
;
2233 newcon
->next
= console_drivers
->next
;
2234 console_drivers
->next
= newcon
;
2236 if (newcon
->flags
& CON_PRINTBUFFER
) {
2238 * console_unlock(); will print out the buffered messages
2241 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2242 console_seq
= syslog_seq
;
2243 console_idx
= syslog_idx
;
2244 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2246 * We're about to replay the log buffer. Only do this to the
2247 * just-registered console to avoid excessive message spam to
2248 * the already-registered consoles.
2250 exclusive_console
= newcon
;
2253 console_sysfs_notify();
2256 * By unregistering the bootconsoles after we enable the real console
2257 * we get the "console xxx enabled" message on all the consoles -
2258 * boot consoles, real consoles, etc - this is to ensure that end
2259 * users know there might be something in the kernel's log buffer that
2260 * went to the bootconsole (that they do not see on the real console)
2263 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2265 /* we need to iterate through twice, to make sure we print
2266 * everything out, before we unregister the console(s)
2268 printk(KERN_INFO
"console [%s%d] enabled, bootconsole disabled\n",
2269 newcon
->name
, newcon
->index
);
2270 for_each_console(bcon
)
2271 if (bcon
->flags
& CON_BOOT
)
2272 unregister_console(bcon
);
2274 printk(KERN_INFO
"%sconsole [%s%d] enabled\n",
2275 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2276 newcon
->name
, newcon
->index
);
2279 EXPORT_SYMBOL(register_console
);
2281 int unregister_console(struct console
*console
)
2283 struct console
*a
, *b
;
2286 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2287 if (console
->flags
& CON_BRL
)
2288 return braille_unregister_console(console
);
2292 if (console_drivers
== console
) {
2293 console_drivers
=console
->next
;
2295 } else if (console_drivers
) {
2296 for (a
=console_drivers
->next
, b
=console_drivers
;
2297 a
; b
=a
, a
=b
->next
) {
2307 * If this isn't the last console and it has CON_CONSDEV set, we
2308 * need to set it on the next preferred console.
2310 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2311 console_drivers
->flags
|= CON_CONSDEV
;
2314 console_sysfs_notify();
2317 EXPORT_SYMBOL(unregister_console
);
2319 static int __init
printk_late_init(void)
2321 struct console
*con
;
2323 for_each_console(con
) {
2324 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2325 printk(KERN_INFO
"turn off boot console %s%d\n",
2326 con
->name
, con
->index
);
2327 unregister_console(con
);
2330 hotcpu_notifier(console_cpu_notify
, 0);
2333 late_initcall(printk_late_init
);
2335 #if defined CONFIG_PRINTK
2337 int printk_sched(const char *fmt
, ...)
2339 unsigned long flags
;
2344 local_irq_save(flags
);
2345 buf
= __get_cpu_var(printk_sched_buf
);
2347 va_start(args
, fmt
);
2348 r
= vsnprintf(buf
, PRINTK_BUF_SIZE
, fmt
, args
);
2351 __this_cpu_or(printk_pending
, PRINTK_PENDING_SCHED
);
2352 local_irq_restore(flags
);
2358 * printk rate limiting, lifted from the networking subsystem.
2360 * This enforces a rate limit: not more than 10 kernel messages
2361 * every 5s to make a denial-of-service attack impossible.
2363 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2365 int __printk_ratelimit(const char *func
)
2367 return ___ratelimit(&printk_ratelimit_state
, func
);
2369 EXPORT_SYMBOL(__printk_ratelimit
);
2372 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2373 * @caller_jiffies: pointer to caller's state
2374 * @interval_msecs: minimum interval between prints
2376 * printk_timed_ratelimit() returns true if more than @interval_msecs
2377 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2380 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2381 unsigned int interval_msecs
)
2383 if (*caller_jiffies
== 0
2384 || !time_in_range(jiffies
, *caller_jiffies
,
2386 + msecs_to_jiffies(interval_msecs
))) {
2387 *caller_jiffies
= jiffies
;
2392 EXPORT_SYMBOL(printk_timed_ratelimit
);
2394 static DEFINE_SPINLOCK(dump_list_lock
);
2395 static LIST_HEAD(dump_list
);
2398 * kmsg_dump_register - register a kernel log dumper.
2399 * @dumper: pointer to the kmsg_dumper structure
2401 * Adds a kernel log dumper to the system. The dump callback in the
2402 * structure will be called when the kernel oopses or panics and must be
2403 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2405 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2407 unsigned long flags
;
2410 /* The dump callback needs to be set */
2414 spin_lock_irqsave(&dump_list_lock
, flags
);
2415 /* Don't allow registering multiple times */
2416 if (!dumper
->registered
) {
2417 dumper
->registered
= 1;
2418 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2421 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2425 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2428 * kmsg_dump_unregister - unregister a kmsg dumper.
2429 * @dumper: pointer to the kmsg_dumper structure
2431 * Removes a dump device from the system. Returns zero on success and
2432 * %-EINVAL otherwise.
2434 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2436 unsigned long flags
;
2439 spin_lock_irqsave(&dump_list_lock
, flags
);
2440 if (dumper
->registered
) {
2441 dumper
->registered
= 0;
2442 list_del_rcu(&dumper
->list
);
2445 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2450 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2452 static bool always_kmsg_dump
;
2453 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2456 * kmsg_dump - dump kernel log to kernel message dumpers.
2457 * @reason: the reason (oops, panic etc) for dumping
2459 * Call each of the registered dumper's dump() callback, which can
2460 * retrieve the kmsg records with kmsg_dump_get_line() or
2461 * kmsg_dump_get_buffer().
2463 void kmsg_dump(enum kmsg_dump_reason reason
)
2465 struct kmsg_dumper
*dumper
;
2466 unsigned long flags
;
2468 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2472 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2473 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2476 /* initialize iterator with data about the stored records */
2477 dumper
->active
= true;
2479 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2480 dumper
->cur_seq
= clear_seq
;
2481 dumper
->cur_idx
= clear_idx
;
2482 dumper
->next_seq
= log_next_seq
;
2483 dumper
->next_idx
= log_next_idx
;
2484 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2486 /* invoke dumper which will iterate over records */
2487 dumper
->dump(dumper
, reason
);
2489 /* reset iterator */
2490 dumper
->active
= false;
2496 * kmsg_dump_get_line - retrieve one kmsg log line
2497 * @dumper: registered kmsg dumper
2498 * @syslog: include the "<4>" prefixes
2499 * @line: buffer to copy the line to
2500 * @size: maximum size of the buffer
2501 * @len: length of line placed into buffer
2503 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2504 * record, and copy one record into the provided buffer.
2506 * Consecutive calls will return the next available record moving
2507 * towards the end of the buffer with the youngest messages.
2509 * A return value of FALSE indicates that there are no more records to
2512 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2513 char *line
, size_t size
, size_t *len
)
2515 unsigned long flags
;
2520 if (!dumper
->active
)
2523 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2524 if (dumper
->cur_seq
< log_first_seq
) {
2525 /* messages are gone, move to first available one */
2526 dumper
->cur_seq
= log_first_seq
;
2527 dumper
->cur_idx
= log_first_idx
;
2531 if (dumper
->cur_seq
>= log_next_seq
) {
2532 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2536 msg
= log_from_idx(dumper
->cur_idx
);
2537 l
= msg_print_text(msg
, syslog
,
2540 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2543 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2549 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
2552 * kmsg_dump_get_buffer - copy kmsg log lines
2553 * @dumper: registered kmsg dumper
2554 * @syslog: include the "<4>" prefixes
2555 * @buf: buffer to copy the line to
2556 * @size: maximum size of the buffer
2557 * @len: length of line placed into buffer
2559 * Start at the end of the kmsg buffer and fill the provided buffer
2560 * with as many of the the *youngest* kmsg records that fit into it.
2561 * If the buffer is large enough, all available kmsg records will be
2562 * copied with a single call.
2564 * Consecutive calls will fill the buffer with the next block of
2565 * available older records, not including the earlier retrieved ones.
2567 * A return value of FALSE indicates that there are no more records to
2570 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
2571 char *buf
, size_t size
, size_t *len
)
2573 unsigned long flags
;
2581 if (!dumper
->active
)
2584 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2585 if (dumper
->cur_seq
< log_first_seq
) {
2586 /* messages are gone, move to first available one */
2587 dumper
->cur_seq
= log_first_seq
;
2588 dumper
->cur_idx
= log_first_idx
;
2592 if (dumper
->cur_seq
>= dumper
->next_seq
) {
2593 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2597 /* calculate length of entire buffer */
2598 seq
= dumper
->cur_seq
;
2599 idx
= dumper
->cur_idx
;
2600 while (seq
< dumper
->next_seq
) {
2601 struct log
*msg
= log_from_idx(idx
);
2603 l
+= msg_print_text(msg
, true, NULL
, 0);
2604 idx
= log_next(idx
);
2608 /* move first record forward until length fits into the buffer */
2609 seq
= dumper
->cur_seq
;
2610 idx
= dumper
->cur_idx
;
2611 while (l
> size
&& seq
< dumper
->next_seq
) {
2612 struct log
*msg
= log_from_idx(idx
);
2614 l
-= msg_print_text(msg
, true, NULL
, 0);
2615 idx
= log_next(idx
);
2619 /* last message in next interation */
2624 while (seq
< dumper
->next_seq
) {
2625 struct log
*msg
= log_from_idx(idx
);
2627 l
+= msg_print_text(msg
, syslog
,
2630 idx
= log_next(idx
);
2634 dumper
->next_seq
= next_seq
;
2635 dumper
->next_idx
= next_idx
;
2637 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2643 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
2646 * kmsg_dump_rewind - reset the interator
2647 * @dumper: registered kmsg dumper
2649 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2650 * kmsg_dump_get_buffer() can be called again and used multiple
2651 * times within the same dumper.dump() callback.
2653 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
2655 unsigned long flags
;
2657 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2658 dumper
->cur_seq
= clear_seq
;
2659 dumper
->cur_idx
= clear_idx
;
2660 dumper
->next_seq
= log_next_seq
;
2661 dumper
->next_idx
= log_next_idx
;
2662 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2664 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);