2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/memblock.h>
35 #include <linux/syscalls.h>
36 #include <linux/kexec.h>
37 #include <linux/kdb.h>
38 #include <linux/ratelimit.h>
39 #include <linux/kmsg_dump.h>
40 #include <linux/syslog.h>
41 #include <linux/cpu.h>
42 #include <linux/notifier.h>
43 #include <linux/rculist.h>
44 #include <linux/poll.h>
46 #include <asm/uaccess.h>
48 #define CREATE_TRACE_POINTS
49 #include <trace/events/printk.h>
52 * Architectures can override it:
54 void asmlinkage
__attribute__((weak
)) early_printk(const char *fmt
, ...)
58 /* printk's without a loglevel use this.. */
59 #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
61 /* We show everything that is MORE important than this.. */
62 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
63 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
65 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
67 int console_printk
[4] = {
68 DEFAULT_CONSOLE_LOGLEVEL
, /* console_loglevel */
69 DEFAULT_MESSAGE_LOGLEVEL
, /* default_message_loglevel */
70 MINIMUM_CONSOLE_LOGLEVEL
, /* minimum_console_loglevel */
71 DEFAULT_CONSOLE_LOGLEVEL
, /* default_console_loglevel */
75 * Low level drivers may need that to know if they can schedule in
76 * their unblank() callback or not. So let's export it.
79 EXPORT_SYMBOL(oops_in_progress
);
82 * console_sem protects the console_drivers list, and also
83 * provides serialisation for access to the entire console
86 static DEFINE_SEMAPHORE(console_sem
);
87 struct console
*console_drivers
;
88 EXPORT_SYMBOL_GPL(console_drivers
);
91 * This is used for debugging the mess that is the VT code by
92 * keeping track if we have the console semaphore held. It's
93 * definitely not the perfect debug tool (we don't know if _WE_
94 * hold it are racing, but it helps tracking those weird code
95 * path in the console code where we end up in places I want
96 * locked without the console sempahore held
98 static int console_locked
, console_suspended
;
101 * If exclusive_console is non-NULL then only this console is to be printed to.
103 static struct console
*exclusive_console
;
106 * Array of consoles built from command line options (console=)
108 struct console_cmdline
110 char name
[8]; /* Name of the driver */
111 int index
; /* Minor dev. to use */
112 char *options
; /* Options for the driver */
113 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
114 char *brl_options
; /* Options for braille driver */
118 #define MAX_CMDLINECONSOLES 8
120 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
121 static int selected_console
= -1;
122 static int preferred_console
= -1;
123 int console_set_on_cmdline
;
124 EXPORT_SYMBOL(console_set_on_cmdline
);
126 /* Flag: console code may call schedule() */
127 static int console_may_schedule
;
130 * The printk log buffer consists of a chain of concatenated variable
131 * length records. Every record starts with a record header, containing
132 * the overall length of the record.
134 * The heads to the first and last entry in the buffer, as well as the
135 * sequence numbers of these both entries are maintained when messages
138 * If the heads indicate available messages, the length in the header
139 * tells the start next message. A length == 0 for the next message
140 * indicates a wrap-around to the beginning of the buffer.
142 * Every record carries the monotonic timestamp in microseconds, as well as
143 * the standard userspace syslog level and syslog facility. The usual
144 * kernel messages use LOG_KERN; userspace-injected messages always carry
145 * a matching syslog facility, by default LOG_USER. The origin of every
146 * message can be reliably determined that way.
148 * The human readable log message directly follows the message header. The
149 * length of the message text is stored in the header, the stored message
152 * Optionally, a message can carry a dictionary of properties (key/value pairs),
153 * to provide userspace with a machine-readable message context.
155 * Examples for well-defined, commonly used property names are:
156 * DEVICE=b12:8 device identifier
160 * +sound:card0 subsystem:devname
161 * SUBSYSTEM=pci driver-core subsystem name
163 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
164 * follows directly after a '=' character. Every property is terminated by
165 * a '\0' character. The last property is not terminated.
167 * Example of a message structure:
168 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
169 * 0008 34 00 record is 52 bytes long
170 * 000a 0b 00 text is 11 bytes long
171 * 000c 1f 00 dictionary is 23 bytes long
172 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
173 * 0010 69 74 27 73 20 61 20 6c "it's a l"
175 * 001b 44 45 56 49 43 "DEVIC"
176 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
177 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
179 * 0032 00 00 00 padding to next message header
181 * The 'struct log' buffer header must never be directly exported to
182 * userspace, it is a kernel-private implementation detail that might
183 * need to be changed in the future, when the requirements change.
185 * /dev/kmsg exports the structured data in the following line format:
186 * "level,sequnum,timestamp;<message text>\n"
188 * The optional key/value pairs are attached as continuation lines starting
189 * with a space character and terminated by a newline. All possible
190 * non-prinatable characters are escaped in the "\xff" notation.
192 * Users of the export format should ignore possible additional values
193 * separated by ',', and find the message after the ';' character.
197 u64 ts_nsec
; /* timestamp in nanoseconds */
198 u16 len
; /* length of entire record */
199 u16 text_len
; /* length of text buffer */
200 u16 dict_len
; /* length of dictionary buffer */
201 u16 level
; /* syslog level + facility */
205 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
206 * used in interesting ways to provide interlocking in console_unlock();
208 static DEFINE_RAW_SPINLOCK(logbuf_lock
);
210 /* the next printk record to read by syslog(READ) or /proc/kmsg */
211 static u64 syslog_seq
;
212 static u32 syslog_idx
;
214 /* index and sequence number of the first record stored in the buffer */
215 static u64 log_first_seq
;
216 static u32 log_first_idx
;
218 /* index and sequence number of the next record to store in the buffer */
219 static u64 log_next_seq
;
221 static u32 log_next_idx
;
223 /* the next printk record to read after the last 'clear' command */
224 static u64 clear_seq
;
225 static u32 clear_idx
;
227 #define LOG_LINE_MAX 1024
230 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
233 #define LOG_ALIGN __alignof__(struct log)
235 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
236 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
237 static char *log_buf
= __log_buf
;
238 static u32 log_buf_len
= __LOG_BUF_LEN
;
240 /* cpu currently holding logbuf_lock */
241 static volatile unsigned int logbuf_cpu
= UINT_MAX
;
243 /* human readable text of the record */
244 static char *log_text(const struct log
*msg
)
246 return (char *)msg
+ sizeof(struct log
);
249 /* optional key/value pair dictionary attached to the record */
250 static char *log_dict(const struct log
*msg
)
252 return (char *)msg
+ sizeof(struct log
) + msg
->text_len
;
255 /* get record by index; idx must point to valid msg */
256 static struct log
*log_from_idx(u32 idx
)
258 struct log
*msg
= (struct log
*)(log_buf
+ idx
);
261 * A length == 0 record is the end of buffer marker. Wrap around and
262 * read the message at the start of the buffer.
265 return (struct log
*)log_buf
;
269 /* get next record; idx must point to valid msg */
270 static u32
log_next(u32 idx
)
272 struct log
*msg
= (struct log
*)(log_buf
+ idx
);
274 /* length == 0 indicates the end of the buffer; wrap */
276 * A length == 0 record is the end of buffer marker. Wrap around and
277 * read the message at the start of the buffer as *this* one, and
278 * return the one after that.
281 msg
= (struct log
*)log_buf
;
284 return idx
+ msg
->len
;
287 /* insert record into the buffer, discard old ones, update heads */
288 static void log_store(int facility
, int level
,
289 const char *dict
, u16 dict_len
,
290 const char *text
, u16 text_len
)
295 /* number of '\0' padding bytes to next message */
296 size
= sizeof(struct log
) + text_len
+ dict_len
;
297 pad_len
= (-size
) & (LOG_ALIGN
- 1);
300 while (log_first_seq
< log_next_seq
) {
303 if (log_next_idx
> log_first_idx
)
304 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
306 free
= log_first_idx
- log_next_idx
;
308 if (free
> size
+ sizeof(struct log
))
311 /* drop old messages until we have enough contiuous space */
312 log_first_idx
= log_next(log_first_idx
);
316 if (log_next_idx
+ size
+ sizeof(struct log
) >= log_buf_len
) {
318 * This message + an additional empty header does not fit
319 * at the end of the buffer. Add an empty header with len == 0
320 * to signify a wrap around.
322 memset(log_buf
+ log_next_idx
, 0, sizeof(struct log
));
327 msg
= (struct log
*)(log_buf
+ log_next_idx
);
328 memcpy(log_text(msg
), text
, text_len
);
329 msg
->text_len
= text_len
;
330 memcpy(log_dict(msg
), dict
, dict_len
);
331 msg
->dict_len
= dict_len
;
332 msg
->level
= (facility
<< 3) | (level
& 7);
333 msg
->ts_nsec
= local_clock();
334 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
335 msg
->len
= sizeof(struct log
) + text_len
+ dict_len
+ pad_len
;
338 log_next_idx
+= msg
->len
;
342 /* /dev/kmsg - userspace message inject/listen interface */
343 struct devkmsg_user
{
350 static ssize_t
devkmsg_writev(struct kiocb
*iocb
, const struct iovec
*iv
,
351 unsigned long count
, loff_t pos
)
355 int level
= default_message_loglevel
;
356 int facility
= 1; /* LOG_USER */
357 size_t len
= iov_length(iv
, count
);
360 if (len
> LOG_LINE_MAX
)
362 buf
= kmalloc(len
+1, GFP_KERNEL
);
367 for (i
= 0; i
< count
; i
++) {
368 if (copy_from_user(line
, iv
[i
].iov_base
, iv
[i
].iov_len
))
370 line
+= iv
[i
].iov_len
;
374 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
375 * the decimal value represents 32bit, the lower 3 bit are the log
376 * level, the rest are the log facility.
378 * If no prefix or no userspace facility is specified, we
379 * enforce LOG_USER, to be able to reliably distinguish
380 * kernel-generated messages from userspace-injected ones.
383 if (line
[0] == '<') {
386 i
= simple_strtoul(line
+1, &endp
, 10);
387 if (endp
&& endp
[0] == '>') {
398 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
404 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
405 size_t count
, loff_t
*ppos
)
407 struct devkmsg_user
*user
= file
->private_data
;
417 ret
= mutex_lock_interruptible(&user
->lock
);
420 raw_spin_lock(&logbuf_lock
);
421 while (user
->seq
== log_next_seq
) {
422 if (file
->f_flags
& O_NONBLOCK
) {
424 raw_spin_unlock(&logbuf_lock
);
428 raw_spin_unlock(&logbuf_lock
);
429 ret
= wait_event_interruptible(log_wait
,
430 user
->seq
!= log_next_seq
);
433 raw_spin_lock(&logbuf_lock
);
436 if (user
->seq
< log_first_seq
) {
437 /* our last seen message is gone, return error and reset */
438 user
->idx
= log_first_idx
;
439 user
->seq
= log_first_seq
;
441 raw_spin_unlock(&logbuf_lock
);
445 msg
= log_from_idx(user
->idx
);
446 ts_usec
= msg
->ts_nsec
;
447 do_div(ts_usec
, 1000);
448 len
= sprintf(user
->buf
, "%u,%llu,%llu;",
449 msg
->level
, user
->seq
, ts_usec
);
451 /* escape non-printable characters */
452 for (i
= 0; i
< msg
->text_len
; i
++) {
453 unsigned char c
= log_text(msg
)[i
];
455 if (c
< ' ' || c
>= 128)
456 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
458 user
->buf
[len
++] = c
;
460 user
->buf
[len
++] = '\n';
465 for (i
= 0; i
< msg
->dict_len
; i
++) {
466 unsigned char c
= log_dict(msg
)[i
];
469 user
->buf
[len
++] = ' ';
474 user
->buf
[len
++] = '\n';
479 if (c
< ' ' || c
>= 128) {
480 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
484 user
->buf
[len
++] = c
;
486 user
->buf
[len
++] = '\n';
489 user
->idx
= log_next(user
->idx
);
491 raw_spin_unlock(&logbuf_lock
);
498 if (copy_to_user(buf
, user
->buf
, len
)) {
504 mutex_unlock(&user
->lock
);
508 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
510 struct devkmsg_user
*user
= file
->private_data
;
518 raw_spin_lock(&logbuf_lock
);
521 /* the first record */
522 user
->idx
= log_first_idx
;
523 user
->seq
= log_first_seq
;
527 * The first record after the last SYSLOG_ACTION_CLEAR,
528 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
529 * changes no global state, and does not clear anything.
531 user
->idx
= clear_idx
;
532 user
->seq
= clear_seq
;
535 /* after the last record */
536 user
->idx
= log_next_idx
;
537 user
->seq
= log_next_seq
;
542 raw_spin_unlock(&logbuf_lock
);
546 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
548 struct devkmsg_user
*user
= file
->private_data
;
552 return POLLERR
|POLLNVAL
;
554 poll_wait(file
, &log_wait
, wait
);
556 raw_spin_lock(&logbuf_lock
);
557 if (user
->seq
< log_next_seq
) {
558 /* return error when data has vanished underneath us */
559 if (user
->seq
< log_first_seq
)
560 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
561 ret
= POLLIN
|POLLRDNORM
;
563 raw_spin_unlock(&logbuf_lock
);
568 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
570 struct devkmsg_user
*user
;
573 /* write-only does not need any file context */
574 if ((file
->f_flags
& O_ACCMODE
) == O_WRONLY
)
577 err
= security_syslog(SYSLOG_ACTION_READ_ALL
);
581 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
585 mutex_init(&user
->lock
);
587 raw_spin_lock(&logbuf_lock
);
588 user
->idx
= log_first_idx
;
589 user
->seq
= log_first_seq
;
590 raw_spin_unlock(&logbuf_lock
);
592 file
->private_data
= user
;
596 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
598 struct devkmsg_user
*user
= file
->private_data
;
603 mutex_destroy(&user
->lock
);
608 const struct file_operations kmsg_fops
= {
609 .open
= devkmsg_open
,
610 .read
= devkmsg_read
,
611 .aio_write
= devkmsg_writev
,
612 .llseek
= devkmsg_llseek
,
613 .poll
= devkmsg_poll
,
614 .release
= devkmsg_release
,
619 * This appends the listed symbols to /proc/vmcoreinfo
621 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
622 * obtain access to symbols that are otherwise very difficult to locate. These
623 * symbols are specifically used so that utilities can access and extract the
624 * dmesg log from a vmcore file after a crash.
626 void log_buf_kexec_setup(void)
628 VMCOREINFO_SYMBOL(log_buf
);
629 VMCOREINFO_SYMBOL(log_buf_len
);
630 VMCOREINFO_SYMBOL(log_first_idx
);
631 VMCOREINFO_SYMBOL(log_next_idx
);
635 /* requested log_buf_len from kernel cmdline */
636 static unsigned long __initdata new_log_buf_len
;
638 /* save requested log_buf_len since it's too early to process it */
639 static int __init
log_buf_len_setup(char *str
)
641 unsigned size
= memparse(str
, &str
);
644 size
= roundup_pow_of_two(size
);
645 if (size
> log_buf_len
)
646 new_log_buf_len
= size
;
650 early_param("log_buf_len", log_buf_len_setup
);
652 void __init
setup_log_buf(int early
)
658 if (!new_log_buf_len
)
664 mem
= memblock_alloc(new_log_buf_len
, PAGE_SIZE
);
667 new_log_buf
= __va(mem
);
669 new_log_buf
= alloc_bootmem_nopanic(new_log_buf_len
);
672 if (unlikely(!new_log_buf
)) {
673 pr_err("log_buf_len: %ld bytes not available\n",
678 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
679 log_buf_len
= new_log_buf_len
;
680 log_buf
= new_log_buf
;
682 free
= __LOG_BUF_LEN
- log_next_idx
;
683 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
684 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
686 pr_info("log_buf_len: %d\n", log_buf_len
);
687 pr_info("early log buf free: %d(%d%%)\n",
688 free
, (free
* 100) / __LOG_BUF_LEN
);
691 #ifdef CONFIG_BOOT_PRINTK_DELAY
693 static int boot_delay
; /* msecs delay after each printk during bootup */
694 static unsigned long long loops_per_msec
; /* based on boot_delay */
696 static int __init
boot_delay_setup(char *str
)
700 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
701 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
703 get_option(&str
, &boot_delay
);
704 if (boot_delay
> 10 * 1000)
707 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
708 "HZ: %d, loops_per_msec: %llu\n",
709 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
712 __setup("boot_delay=", boot_delay_setup
);
714 static void boot_delay_msec(void)
716 unsigned long long k
;
717 unsigned long timeout
;
719 if (boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
722 k
= (unsigned long long)loops_per_msec
* boot_delay
;
724 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
729 * use (volatile) jiffies to prevent
730 * compiler reduction; loop termination via jiffies
731 * is secondary and may or may not happen.
733 if (time_after(jiffies
, timeout
))
735 touch_nmi_watchdog();
739 static inline void boot_delay_msec(void)
744 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
745 int dmesg_restrict
= 1;
750 static int syslog_action_restricted(int type
)
754 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
755 return type
!= SYSLOG_ACTION_READ_ALL
&& type
!= SYSLOG_ACTION_SIZE_BUFFER
;
758 static int check_syslog_permissions(int type
, bool from_file
)
761 * If this is from /proc/kmsg and we've already opened it, then we've
762 * already done the capabilities checks at open time.
764 if (from_file
&& type
!= SYSLOG_ACTION_OPEN
)
767 if (syslog_action_restricted(type
)) {
768 if (capable(CAP_SYSLOG
))
770 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
771 if (capable(CAP_SYS_ADMIN
)) {
772 printk_once(KERN_WARNING
"%s (%d): "
773 "Attempt to access syslog with CAP_SYS_ADMIN "
774 "but no CAP_SYSLOG (deprecated).\n",
775 current
->comm
, task_pid_nr(current
));
783 #if defined(CONFIG_PRINTK_TIME)
784 static bool printk_time
= 1;
786 static bool printk_time
;
788 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
790 static size_t print_prefix(const struct log
*msg
, bool syslog
, char *buf
)
796 len
+= sprintf(buf
, "<%u>", msg
->level
);
808 unsigned long long ts
= msg
->ts_nsec
;
809 unsigned long rem_nsec
= do_div(ts
, 1000000000);
811 len
+= sprintf(buf
+ len
, "[%5lu.%06lu] ",
812 (unsigned long) ts
, rem_nsec
/ 1000);
821 static size_t msg_print_text(const struct log
*msg
, bool syslog
,
822 char *buf
, size_t size
)
824 const char *text
= log_text(msg
);
825 size_t text_size
= msg
->text_len
;
829 const char *next
= memchr(text
, '\n', text_size
);
833 text_len
= next
- text
;
835 text_size
-= next
- text
;
837 text_len
= text_size
;
841 if (print_prefix(msg
, syslog
, NULL
) +
842 text_len
+ 1>= size
- len
)
845 len
+= print_prefix(msg
, syslog
, buf
+ len
);
846 memcpy(buf
+ len
, text
, text_len
);
850 /* SYSLOG_ACTION_* buffer size only calculation */
851 len
+= print_prefix(msg
, syslog
, NULL
);
861 static int syslog_print(char __user
*buf
, int size
)
867 text
= kmalloc(LOG_LINE_MAX
, GFP_KERNEL
);
871 raw_spin_lock_irq(&logbuf_lock
);
872 if (syslog_seq
< log_first_seq
) {
873 /* messages are gone, move to first one */
874 syslog_seq
= log_first_seq
;
875 syslog_idx
= log_first_idx
;
877 msg
= log_from_idx(syslog_idx
);
878 len
= msg_print_text(msg
, true, text
, LOG_LINE_MAX
);
879 syslog_idx
= log_next(syslog_idx
);
881 raw_spin_unlock_irq(&logbuf_lock
);
885 else if (len
> 0 && copy_to_user(buf
, text
, len
))
892 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
897 text
= kmalloc(LOG_LINE_MAX
, GFP_KERNEL
);
901 raw_spin_lock_irq(&logbuf_lock
);
907 if (clear_seq
< log_first_seq
) {
908 /* messages are gone, move to first available one */
909 clear_seq
= log_first_seq
;
910 clear_idx
= log_first_idx
;
914 * Find first record that fits, including all following records,
915 * into the user-provided buffer for this dump.
919 while (seq
< log_next_seq
) {
920 struct log
*msg
= log_from_idx(idx
);
922 len
+= msg_print_text(msg
, true, NULL
, 0);
927 /* move first record forward until length fits into the buffer */
930 while (len
> size
&& seq
< log_next_seq
) {
931 struct log
*msg
= log_from_idx(idx
);
933 len
-= msg_print_text(msg
, true, NULL
, 0);
938 /* last message fitting into this dump */
939 next_seq
= log_next_seq
;
942 while (len
>= 0 && seq
< next_seq
) {
943 struct log
*msg
= log_from_idx(idx
);
946 textlen
= msg_print_text(msg
, true, text
, LOG_LINE_MAX
);
954 raw_spin_unlock_irq(&logbuf_lock
);
955 if (copy_to_user(buf
+ len
, text
, textlen
))
959 raw_spin_lock_irq(&logbuf_lock
);
961 if (seq
< log_first_seq
) {
962 /* messages are gone, move to next one */
970 clear_seq
= log_next_seq
;
971 clear_idx
= log_next_idx
;
973 raw_spin_unlock_irq(&logbuf_lock
);
979 int do_syslog(int type
, char __user
*buf
, int len
, bool from_file
)
982 static int saved_console_loglevel
= -1;
983 static DEFINE_MUTEX(syslog_mutex
);
986 error
= check_syslog_permissions(type
, from_file
);
990 error
= security_syslog(type
);
995 case SYSLOG_ACTION_CLOSE
: /* Close log */
997 case SYSLOG_ACTION_OPEN
: /* Open log */
999 case SYSLOG_ACTION_READ
: /* Read from log */
1001 if (!buf
|| len
< 0)
1006 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1010 error
= mutex_lock_interruptible(&syslog_mutex
);
1013 error
= wait_event_interruptible(log_wait
,
1014 syslog_seq
!= log_next_seq
);
1016 mutex_unlock(&syslog_mutex
);
1019 error
= syslog_print(buf
, len
);
1020 mutex_unlock(&syslog_mutex
);
1022 /* Read/clear last kernel messages */
1023 case SYSLOG_ACTION_READ_CLEAR
:
1026 /* Read last kernel messages */
1027 case SYSLOG_ACTION_READ_ALL
:
1029 if (!buf
|| len
< 0)
1034 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1038 error
= syslog_print_all(buf
, len
, clear
);
1040 /* Clear ring buffer */
1041 case SYSLOG_ACTION_CLEAR
:
1042 syslog_print_all(NULL
, 0, true);
1043 /* Disable logging to console */
1044 case SYSLOG_ACTION_CONSOLE_OFF
:
1045 if (saved_console_loglevel
== -1)
1046 saved_console_loglevel
= console_loglevel
;
1047 console_loglevel
= minimum_console_loglevel
;
1049 /* Enable logging to console */
1050 case SYSLOG_ACTION_CONSOLE_ON
:
1051 if (saved_console_loglevel
!= -1) {
1052 console_loglevel
= saved_console_loglevel
;
1053 saved_console_loglevel
= -1;
1056 /* Set level of messages printed to console */
1057 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1059 if (len
< 1 || len
> 8)
1061 if (len
< minimum_console_loglevel
)
1062 len
= minimum_console_loglevel
;
1063 console_loglevel
= len
;
1064 /* Implicitly re-enable logging to console */
1065 saved_console_loglevel
= -1;
1068 /* Number of chars in the log buffer */
1069 case SYSLOG_ACTION_SIZE_UNREAD
:
1070 raw_spin_lock_irq(&logbuf_lock
);
1071 if (syslog_seq
< log_first_seq
) {
1072 /* messages are gone, move to first one */
1073 syslog_seq
= log_first_seq
;
1074 syslog_idx
= log_first_idx
;
1078 * Short-cut for poll(/"proc/kmsg") which simply checks
1079 * for pending data, not the size; return the count of
1080 * records, not the length.
1082 error
= log_next_idx
- syslog_idx
;
1090 while (seq
< log_next_seq
) {
1091 struct log
*msg
= log_from_idx(idx
);
1093 error
+= msg_print_text(msg
, true, NULL
, 0);
1094 idx
= log_next(idx
);
1098 raw_spin_unlock_irq(&logbuf_lock
);
1100 /* Size of the log buffer */
1101 case SYSLOG_ACTION_SIZE_BUFFER
:
1102 error
= log_buf_len
;
1112 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1114 return do_syslog(type
, buf
, len
, SYSLOG_FROM_CALL
);
1117 #ifdef CONFIG_KGDB_KDB
1118 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
1119 * uses locks so it cannot be used during debugging. Just tell kdb
1120 * where the start and end of the physical and logical logs are. This
1121 * is equivalent to do_syslog(3).
1123 void kdb_syslog_data(char *syslog_data
[4])
1125 syslog_data
[0] = log_buf
;
1126 syslog_data
[1] = log_buf
+ log_buf_len
;
1127 syslog_data
[2] = log_buf
+ log_first_idx
;
1128 syslog_data
[3] = log_buf
+ log_next_idx
;
1130 #endif /* CONFIG_KGDB_KDB */
1132 static bool __read_mostly ignore_loglevel
;
1134 static int __init
ignore_loglevel_setup(char *str
)
1136 ignore_loglevel
= 1;
1137 printk(KERN_INFO
"debug: ignoring loglevel setting.\n");
1142 early_param("ignore_loglevel", ignore_loglevel_setup
);
1143 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1144 MODULE_PARM_DESC(ignore_loglevel
, "ignore loglevel setting, to"
1145 "print all kernel messages to the console.");
1148 * Call the console drivers, asking them to write out
1149 * log_buf[start] to log_buf[end - 1].
1150 * The console_lock must be held.
1152 static void call_console_drivers(int level
, const char *text
, size_t len
)
1154 struct console
*con
;
1156 trace_console(text
, 0, len
, len
);
1158 if (level
>= console_loglevel
&& !ignore_loglevel
)
1160 if (!console_drivers
)
1163 for_each_console(con
) {
1164 if (exclusive_console
&& con
!= exclusive_console
)
1166 if (!(con
->flags
& CON_ENABLED
))
1170 if (!cpu_online(smp_processor_id()) &&
1171 !(con
->flags
& CON_ANYTIME
))
1173 con
->write(con
, text
, len
);
1178 * Zap console related locks when oopsing. Only zap at most once
1179 * every 10 seconds, to leave time for slow consoles to print a
1182 static void zap_locks(void)
1184 static unsigned long oops_timestamp
;
1186 if (time_after_eq(jiffies
, oops_timestamp
) &&
1187 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1190 oops_timestamp
= jiffies
;
1193 /* If a crash is occurring, make sure we can't deadlock */
1194 raw_spin_lock_init(&logbuf_lock
);
1195 /* And make sure that we print immediately */
1196 sema_init(&console_sem
, 1);
1199 /* Check if we have any console registered that can be called early in boot. */
1200 static int have_callable_console(void)
1202 struct console
*con
;
1204 for_each_console(con
)
1205 if (con
->flags
& CON_ANYTIME
)
1212 * Can we actually use the console at this time on this cpu?
1214 * Console drivers may assume that per-cpu resources have
1215 * been allocated. So unless they're explicitly marked as
1216 * being able to cope (CON_ANYTIME) don't call them until
1217 * this CPU is officially up.
1219 static inline int can_use_console(unsigned int cpu
)
1221 return cpu_online(cpu
) || have_callable_console();
1225 * Try to get console ownership to actually show the kernel
1226 * messages from a 'printk'. Return true (and with the
1227 * console_lock held, and 'console_locked' set) if it
1228 * is successful, false otherwise.
1230 * This gets called with the 'logbuf_lock' spinlock held and
1231 * interrupts disabled. It should return with 'lockbuf_lock'
1232 * released but interrupts still disabled.
1234 static int console_trylock_for_printk(unsigned int cpu
)
1235 __releases(&logbuf_lock
)
1237 int retval
= 0, wake
= 0;
1239 if (console_trylock()) {
1243 * If we can't use the console, we need to release
1244 * the console semaphore by hand to avoid flushing
1245 * the buffer. We need to hold the console semaphore
1246 * in order to do this test safely.
1248 if (!can_use_console(cpu
)) {
1254 logbuf_cpu
= UINT_MAX
;
1257 raw_spin_unlock(&logbuf_lock
);
1261 int printk_delay_msec __read_mostly
;
1263 static inline void printk_delay(void)
1265 if (unlikely(printk_delay_msec
)) {
1266 int m
= printk_delay_msec
;
1270 touch_nmi_watchdog();
1275 asmlinkage
int vprintk_emit(int facility
, int level
,
1276 const char *dict
, size_t dictlen
,
1277 const char *fmt
, va_list args
)
1279 static int recursion_bug
;
1280 static char cont_buf
[LOG_LINE_MAX
];
1281 static size_t cont_len
;
1282 static int cont_level
;
1283 static struct task_struct
*cont_task
;
1284 static char textbuf
[LOG_LINE_MAX
];
1285 char *text
= textbuf
;
1287 unsigned long flags
;
1289 bool newline
= false;
1290 bool prefix
= false;
1291 int printed_len
= 0;
1296 /* This stops the holder of console_sem just where we want him */
1297 local_irq_save(flags
);
1298 this_cpu
= smp_processor_id();
1301 * Ouch, printk recursed into itself!
1303 if (unlikely(logbuf_cpu
== this_cpu
)) {
1305 * If a crash is occurring during printk() on this CPU,
1306 * then try to get the crash message out but make sure
1307 * we can't deadlock. Otherwise just return to avoid the
1308 * recursion and return - but flag the recursion so that
1309 * it can be printed at the next appropriate moment:
1311 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1313 goto out_restore_irqs
;
1319 raw_spin_lock(&logbuf_lock
);
1320 logbuf_cpu
= this_cpu
;
1322 if (recursion_bug
) {
1323 static const char recursion_msg
[] =
1324 "BUG: recent printk recursion!";
1327 printed_len
+= strlen(recursion_msg
);
1328 /* emit KERN_CRIT message */
1329 log_store(0, 2, NULL
, 0, recursion_msg
, printed_len
);
1333 * The printf needs to come first; we need the syslog
1334 * prefix which might be passed-in as a parameter.
1336 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1338 /* mark and strip a trailing newline */
1339 if (text_len
&& text
[text_len
-1] == '\n') {
1344 /* strip syslog prefix and extract log level or control flags */
1345 if (text
[0] == '<' && text
[1] && text
[2] == '>') {
1349 level
= text
[1] - '0';
1350 case 'd': /* KERN_DEFAULT */
1352 case 'c': /* KERN_CONT */
1359 level
= default_message_loglevel
;
1367 if (cont_len
&& (prefix
|| cont_task
!= current
)) {
1369 * Flush earlier buffer, which is either from a
1370 * different thread, or when we got a new prefix.
1372 log_store(facility
, cont_level
, NULL
, 0, cont_buf
, cont_len
);
1378 cont_task
= current
;
1381 /* buffer or append to earlier buffer from the same thread */
1382 if (cont_len
+ text_len
> sizeof(cont_buf
))
1383 text_len
= sizeof(cont_buf
) - cont_len
;
1384 memcpy(cont_buf
+ cont_len
, text
, text_len
);
1385 cont_len
+= text_len
;
1387 if (cont_len
&& cont_task
== current
) {
1390 * New prefix from the same thread; flush. We
1391 * either got no earlier newline, or we race
1392 * with an interrupt.
1394 log_store(facility
, cont_level
,
1395 NULL
, 0, cont_buf
, cont_len
);
1399 /* append to the earlier buffer and flush */
1400 if (cont_len
+ text_len
> sizeof(cont_buf
))
1401 text_len
= sizeof(cont_buf
) - cont_len
;
1402 memcpy(cont_buf
+ cont_len
, text
, text_len
);
1403 cont_len
+= text_len
;
1404 log_store(facility
, cont_level
,
1405 NULL
, 0, cont_buf
, cont_len
);
1408 printed_len
= cont_len
;
1410 /* ordinary single and terminated line */
1411 log_store(facility
, level
,
1412 dict
, dictlen
, text
, text_len
);
1413 printed_len
= text_len
;
1418 * Try to acquire and then immediately release the console semaphore.
1419 * The release will print out buffers and wake up /dev/kmsg and syslog()
1422 * The console_trylock_for_printk() function will release 'logbuf_lock'
1423 * regardless of whether it actually gets the console semaphore or not.
1425 if (console_trylock_for_printk(this_cpu
))
1430 local_irq_restore(flags
);
1434 EXPORT_SYMBOL(vprintk_emit
);
1436 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1438 return vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1440 EXPORT_SYMBOL(vprintk
);
1442 asmlinkage
int printk_emit(int facility
, int level
,
1443 const char *dict
, size_t dictlen
,
1444 const char *fmt
, ...)
1449 va_start(args
, fmt
);
1450 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1455 EXPORT_SYMBOL(printk_emit
);
1458 * printk - print a kernel message
1459 * @fmt: format string
1461 * This is printk(). It can be called from any context. We want it to work.
1463 * We try to grab the console_lock. If we succeed, it's easy - we log the
1464 * output and call the console drivers. If we fail to get the semaphore, we
1465 * place the output into the log buffer and return. The current holder of
1466 * the console_sem will notice the new output in console_unlock(); and will
1467 * send it to the consoles before releasing the lock.
1469 * One effect of this deferred printing is that code which calls printk() and
1470 * then changes console_loglevel may break. This is because console_loglevel
1471 * is inspected when the actual printing occurs.
1476 * See the vsnprintf() documentation for format string extensions over C99.
1478 asmlinkage
int printk(const char *fmt
, ...)
1483 #ifdef CONFIG_KGDB_KDB
1484 if (unlikely(kdb_trap_printk
)) {
1485 va_start(args
, fmt
);
1486 r
= vkdb_printf(fmt
, args
);
1491 va_start(args
, fmt
);
1492 r
= vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1497 EXPORT_SYMBOL(printk
);
1501 #define LOG_LINE_MAX 0
1502 static struct log
*log_from_idx(u32 idx
) { return NULL
; }
1503 static u32
log_next(u32 idx
) { return 0; }
1504 static void call_console_drivers(int level
, const char *text
, size_t len
) {}
1505 static size_t msg_print_text(const struct log
*msg
, bool syslog
,
1506 char *buf
, size_t size
) { return 0; }
1508 #endif /* CONFIG_PRINTK */
1510 static int __add_preferred_console(char *name
, int idx
, char *options
,
1513 struct console_cmdline
*c
;
1517 * See if this tty is not yet registered, and
1518 * if we have a slot free.
1520 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
1521 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
1522 console_cmdline
[i
].index
== idx
) {
1524 selected_console
= i
;
1527 if (i
== MAX_CMDLINECONSOLES
)
1530 selected_console
= i
;
1531 c
= &console_cmdline
[i
];
1532 strlcpy(c
->name
, name
, sizeof(c
->name
));
1533 c
->options
= options
;
1534 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1535 c
->brl_options
= brl_options
;
1541 * Set up a list of consoles. Called from init/main.c
1543 static int __init
console_setup(char *str
)
1545 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for index */
1546 char *s
, *options
, *brl_options
= NULL
;
1549 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1550 if (!memcmp(str
, "brl,", 4)) {
1553 } else if (!memcmp(str
, "brl=", 4)) {
1554 brl_options
= str
+ 4;
1555 str
= strchr(brl_options
, ',');
1557 printk(KERN_ERR
"need port name after brl=\n");
1565 * Decode str into name, index, options.
1567 if (str
[0] >= '0' && str
[0] <= '9') {
1568 strcpy(buf
, "ttyS");
1569 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1571 strncpy(buf
, str
, sizeof(buf
) - 1);
1573 buf
[sizeof(buf
) - 1] = 0;
1574 if ((options
= strchr(str
, ',')) != NULL
)
1577 if (!strcmp(str
, "ttya"))
1578 strcpy(buf
, "ttyS0");
1579 if (!strcmp(str
, "ttyb"))
1580 strcpy(buf
, "ttyS1");
1582 for (s
= buf
; *s
; s
++)
1583 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
1585 idx
= simple_strtoul(s
, NULL
, 10);
1588 __add_preferred_console(buf
, idx
, options
, brl_options
);
1589 console_set_on_cmdline
= 1;
1592 __setup("console=", console_setup
);
1595 * add_preferred_console - add a device to the list of preferred consoles.
1596 * @name: device name
1597 * @idx: device index
1598 * @options: options for this console
1600 * The last preferred console added will be used for kernel messages
1601 * and stdin/out/err for init. Normally this is used by console_setup
1602 * above to handle user-supplied console arguments; however it can also
1603 * be used by arch-specific code either to override the user or more
1604 * commonly to provide a default console (ie from PROM variables) when
1605 * the user has not supplied one.
1607 int add_preferred_console(char *name
, int idx
, char *options
)
1609 return __add_preferred_console(name
, idx
, options
, NULL
);
1612 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
1614 struct console_cmdline
*c
;
1617 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
1618 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
1619 console_cmdline
[i
].index
== idx
) {
1620 c
= &console_cmdline
[i
];
1621 strlcpy(c
->name
, name_new
, sizeof(c
->name
));
1622 c
->name
[sizeof(c
->name
) - 1] = 0;
1623 c
->options
= options
;
1631 bool console_suspend_enabled
= 1;
1632 EXPORT_SYMBOL(console_suspend_enabled
);
1634 static int __init
console_suspend_disable(char *str
)
1636 console_suspend_enabled
= 0;
1639 __setup("no_console_suspend", console_suspend_disable
);
1640 module_param_named(console_suspend
, console_suspend_enabled
,
1641 bool, S_IRUGO
| S_IWUSR
);
1642 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
1643 " and hibernate operations");
1646 * suspend_console - suspend the console subsystem
1648 * This disables printk() while we go into suspend states
1650 void suspend_console(void)
1652 if (!console_suspend_enabled
)
1654 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1656 console_suspended
= 1;
1660 void resume_console(void)
1662 if (!console_suspend_enabled
)
1665 console_suspended
= 0;
1670 * console_cpu_notify - print deferred console messages after CPU hotplug
1671 * @self: notifier struct
1672 * @action: CPU hotplug event
1675 * If printk() is called from a CPU that is not online yet, the messages
1676 * will be spooled but will not show up on the console. This function is
1677 * called when a new CPU comes online (or fails to come up), and ensures
1678 * that any such output gets printed.
1680 static int __cpuinit
console_cpu_notify(struct notifier_block
*self
,
1681 unsigned long action
, void *hcpu
)
1687 case CPU_DOWN_FAILED
:
1688 case CPU_UP_CANCELED
:
1696 * console_lock - lock the console system for exclusive use.
1698 * Acquires a lock which guarantees that the caller has
1699 * exclusive access to the console system and the console_drivers list.
1701 * Can sleep, returns nothing.
1703 void console_lock(void)
1705 BUG_ON(in_interrupt());
1707 if (console_suspended
)
1710 console_may_schedule
= 1;
1712 EXPORT_SYMBOL(console_lock
);
1715 * console_trylock - try to lock the console system for exclusive use.
1717 * Tried to acquire a lock which guarantees that the caller has
1718 * exclusive access to the console system and the console_drivers list.
1720 * returns 1 on success, and 0 on failure to acquire the lock.
1722 int console_trylock(void)
1724 if (down_trylock(&console_sem
))
1726 if (console_suspended
) {
1731 console_may_schedule
= 0;
1734 EXPORT_SYMBOL(console_trylock
);
1736 int is_console_locked(void)
1738 return console_locked
;
1742 * Delayed printk version, for scheduler-internal messages:
1744 #define PRINTK_BUF_SIZE 512
1746 #define PRINTK_PENDING_WAKEUP 0x01
1747 #define PRINTK_PENDING_SCHED 0x02
1749 static DEFINE_PER_CPU(int, printk_pending
);
1750 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE
], printk_sched_buf
);
1752 void printk_tick(void)
1754 if (__this_cpu_read(printk_pending
)) {
1755 int pending
= __this_cpu_xchg(printk_pending
, 0);
1756 if (pending
& PRINTK_PENDING_SCHED
) {
1757 char *buf
= __get_cpu_var(printk_sched_buf
);
1758 printk(KERN_WARNING
"[sched_delayed] %s", buf
);
1760 if (pending
& PRINTK_PENDING_WAKEUP
)
1761 wake_up_interruptible(&log_wait
);
1765 int printk_needs_cpu(int cpu
)
1767 if (cpu_is_offline(cpu
))
1769 return __this_cpu_read(printk_pending
);
1772 void wake_up_klogd(void)
1774 if (waitqueue_active(&log_wait
))
1775 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
1778 /* the next printk record to write to the console */
1779 static u64 console_seq
;
1780 static u32 console_idx
;
1783 * console_unlock - unlock the console system
1785 * Releases the console_lock which the caller holds on the console system
1786 * and the console driver list.
1788 * While the console_lock was held, console output may have been buffered
1789 * by printk(). If this is the case, console_unlock(); emits
1790 * the output prior to releasing the lock.
1792 * If there is output waiting, we wake /dev/kmsg and syslog() users.
1794 * console_unlock(); may be called from any context.
1796 void console_unlock(void)
1798 static u64 seen_seq
;
1799 unsigned long flags
;
1800 bool wake_klogd
= false;
1803 if (console_suspended
) {
1808 console_may_schedule
= 0;
1813 static char text
[LOG_LINE_MAX
];
1817 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
1818 if (seen_seq
!= log_next_seq
) {
1820 seen_seq
= log_next_seq
;
1823 if (console_seq
< log_first_seq
) {
1824 /* messages are gone, move to first one */
1825 console_seq
= log_first_seq
;
1826 console_idx
= log_first_idx
;
1829 if (console_seq
== log_next_seq
)
1832 msg
= log_from_idx(console_idx
);
1833 level
= msg
->level
& 7;
1835 len
= msg_print_text(msg
, false, text
, sizeof(text
));
1837 console_idx
= log_next(console_idx
);
1839 raw_spin_unlock(&logbuf_lock
);
1841 stop_critical_timings(); /* don't trace print latency */
1842 call_console_drivers(level
, text
, len
);
1843 start_critical_timings();
1844 local_irq_restore(flags
);
1848 /* Release the exclusive_console once it is used */
1849 if (unlikely(exclusive_console
))
1850 exclusive_console
= NULL
;
1852 raw_spin_unlock(&logbuf_lock
);
1857 * Someone could have filled up the buffer again, so re-check if there's
1858 * something to flush. In case we cannot trylock the console_sem again,
1859 * there's a new owner and the console_unlock() from them will do the
1860 * flush, no worries.
1862 raw_spin_lock(&logbuf_lock
);
1863 retry
= console_seq
!= log_next_seq
;
1864 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
1866 if (retry
&& console_trylock())
1872 EXPORT_SYMBOL(console_unlock
);
1875 * console_conditional_schedule - yield the CPU if required
1877 * If the console code is currently allowed to sleep, and
1878 * if this CPU should yield the CPU to another task, do
1881 * Must be called within console_lock();.
1883 void __sched
console_conditional_schedule(void)
1885 if (console_may_schedule
)
1888 EXPORT_SYMBOL(console_conditional_schedule
);
1890 void console_unblank(void)
1895 * console_unblank can no longer be called in interrupt context unless
1896 * oops_in_progress is set to 1..
1898 if (oops_in_progress
) {
1899 if (down_trylock(&console_sem
) != 0)
1905 console_may_schedule
= 0;
1907 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
1913 * Return the console tty driver structure and its associated index
1915 struct tty_driver
*console_device(int *index
)
1918 struct tty_driver
*driver
= NULL
;
1921 for_each_console(c
) {
1924 driver
= c
->device(c
, index
);
1933 * Prevent further output on the passed console device so that (for example)
1934 * serial drivers can disable console output before suspending a port, and can
1935 * re-enable output afterwards.
1937 void console_stop(struct console
*console
)
1940 console
->flags
&= ~CON_ENABLED
;
1943 EXPORT_SYMBOL(console_stop
);
1945 void console_start(struct console
*console
)
1948 console
->flags
|= CON_ENABLED
;
1951 EXPORT_SYMBOL(console_start
);
1953 static int __read_mostly keep_bootcon
;
1955 static int __init
keep_bootcon_setup(char *str
)
1958 printk(KERN_INFO
"debug: skip boot console de-registration.\n");
1963 early_param("keep_bootcon", keep_bootcon_setup
);
1966 * The console driver calls this routine during kernel initialization
1967 * to register the console printing procedure with printk() and to
1968 * print any messages that were printed by the kernel before the
1969 * console driver was initialized.
1971 * This can happen pretty early during the boot process (because of
1972 * early_printk) - sometimes before setup_arch() completes - be careful
1973 * of what kernel features are used - they may not be initialised yet.
1975 * There are two types of consoles - bootconsoles (early_printk) and
1976 * "real" consoles (everything which is not a bootconsole) which are
1977 * handled differently.
1978 * - Any number of bootconsoles can be registered at any time.
1979 * - As soon as a "real" console is registered, all bootconsoles
1980 * will be unregistered automatically.
1981 * - Once a "real" console is registered, any attempt to register a
1982 * bootconsoles will be rejected
1984 void register_console(struct console
*newcon
)
1987 unsigned long flags
;
1988 struct console
*bcon
= NULL
;
1991 * before we register a new CON_BOOT console, make sure we don't
1992 * already have a valid console
1994 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
1995 /* find the last or real console */
1996 for_each_console(bcon
) {
1997 if (!(bcon
->flags
& CON_BOOT
)) {
1998 printk(KERN_INFO
"Too late to register bootconsole %s%d\n",
1999 newcon
->name
, newcon
->index
);
2005 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2006 bcon
= console_drivers
;
2008 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2009 preferred_console
= selected_console
;
2011 if (newcon
->early_setup
)
2012 newcon
->early_setup();
2015 * See if we want to use this console driver. If we
2016 * didn't select a console we take the first one
2017 * that registers here.
2019 if (preferred_console
< 0) {
2020 if (newcon
->index
< 0)
2022 if (newcon
->setup
== NULL
||
2023 newcon
->setup(newcon
, NULL
) == 0) {
2024 newcon
->flags
|= CON_ENABLED
;
2025 if (newcon
->device
) {
2026 newcon
->flags
|= CON_CONSDEV
;
2027 preferred_console
= 0;
2033 * See if this console matches one we selected on
2036 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
2038 if (strcmp(console_cmdline
[i
].name
, newcon
->name
) != 0)
2040 if (newcon
->index
>= 0 &&
2041 newcon
->index
!= console_cmdline
[i
].index
)
2043 if (newcon
->index
< 0)
2044 newcon
->index
= console_cmdline
[i
].index
;
2045 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2046 if (console_cmdline
[i
].brl_options
) {
2047 newcon
->flags
|= CON_BRL
;
2048 braille_register_console(newcon
,
2049 console_cmdline
[i
].index
,
2050 console_cmdline
[i
].options
,
2051 console_cmdline
[i
].brl_options
);
2055 if (newcon
->setup
&&
2056 newcon
->setup(newcon
, console_cmdline
[i
].options
) != 0)
2058 newcon
->flags
|= CON_ENABLED
;
2059 newcon
->index
= console_cmdline
[i
].index
;
2060 if (i
== selected_console
) {
2061 newcon
->flags
|= CON_CONSDEV
;
2062 preferred_console
= selected_console
;
2067 if (!(newcon
->flags
& CON_ENABLED
))
2071 * If we have a bootconsole, and are switching to a real console,
2072 * don't print everything out again, since when the boot console, and
2073 * the real console are the same physical device, it's annoying to
2074 * see the beginning boot messages twice
2076 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2077 newcon
->flags
&= ~CON_PRINTBUFFER
;
2080 * Put this console in the list - keep the
2081 * preferred driver at the head of the list.
2084 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2085 newcon
->next
= console_drivers
;
2086 console_drivers
= newcon
;
2088 newcon
->next
->flags
&= ~CON_CONSDEV
;
2090 newcon
->next
= console_drivers
->next
;
2091 console_drivers
->next
= newcon
;
2093 if (newcon
->flags
& CON_PRINTBUFFER
) {
2095 * console_unlock(); will print out the buffered messages
2098 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2099 console_seq
= syslog_seq
;
2100 console_idx
= syslog_idx
;
2101 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2103 * We're about to replay the log buffer. Only do this to the
2104 * just-registered console to avoid excessive message spam to
2105 * the already-registered consoles.
2107 exclusive_console
= newcon
;
2110 console_sysfs_notify();
2113 * By unregistering the bootconsoles after we enable the real console
2114 * we get the "console xxx enabled" message on all the consoles -
2115 * boot consoles, real consoles, etc - this is to ensure that end
2116 * users know there might be something in the kernel's log buffer that
2117 * went to the bootconsole (that they do not see on the real console)
2120 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2122 /* we need to iterate through twice, to make sure we print
2123 * everything out, before we unregister the console(s)
2125 printk(KERN_INFO
"console [%s%d] enabled, bootconsole disabled\n",
2126 newcon
->name
, newcon
->index
);
2127 for_each_console(bcon
)
2128 if (bcon
->flags
& CON_BOOT
)
2129 unregister_console(bcon
);
2131 printk(KERN_INFO
"%sconsole [%s%d] enabled\n",
2132 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2133 newcon
->name
, newcon
->index
);
2136 EXPORT_SYMBOL(register_console
);
2138 int unregister_console(struct console
*console
)
2140 struct console
*a
, *b
;
2143 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2144 if (console
->flags
& CON_BRL
)
2145 return braille_unregister_console(console
);
2149 if (console_drivers
== console
) {
2150 console_drivers
=console
->next
;
2152 } else if (console_drivers
) {
2153 for (a
=console_drivers
->next
, b
=console_drivers
;
2154 a
; b
=a
, a
=b
->next
) {
2164 * If this isn't the last console and it has CON_CONSDEV set, we
2165 * need to set it on the next preferred console.
2167 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2168 console_drivers
->flags
|= CON_CONSDEV
;
2171 console_sysfs_notify();
2174 EXPORT_SYMBOL(unregister_console
);
2176 static int __init
printk_late_init(void)
2178 struct console
*con
;
2180 for_each_console(con
) {
2181 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2182 printk(KERN_INFO
"turn off boot console %s%d\n",
2183 con
->name
, con
->index
);
2184 unregister_console(con
);
2187 hotcpu_notifier(console_cpu_notify
, 0);
2190 late_initcall(printk_late_init
);
2192 #if defined CONFIG_PRINTK
2194 int printk_sched(const char *fmt
, ...)
2196 unsigned long flags
;
2201 local_irq_save(flags
);
2202 buf
= __get_cpu_var(printk_sched_buf
);
2204 va_start(args
, fmt
);
2205 r
= vsnprintf(buf
, PRINTK_BUF_SIZE
, fmt
, args
);
2208 __this_cpu_or(printk_pending
, PRINTK_PENDING_SCHED
);
2209 local_irq_restore(flags
);
2215 * printk rate limiting, lifted from the networking subsystem.
2217 * This enforces a rate limit: not more than 10 kernel messages
2218 * every 5s to make a denial-of-service attack impossible.
2220 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2222 int __printk_ratelimit(const char *func
)
2224 return ___ratelimit(&printk_ratelimit_state
, func
);
2226 EXPORT_SYMBOL(__printk_ratelimit
);
2229 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2230 * @caller_jiffies: pointer to caller's state
2231 * @interval_msecs: minimum interval between prints
2233 * printk_timed_ratelimit() returns true if more than @interval_msecs
2234 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2237 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2238 unsigned int interval_msecs
)
2240 if (*caller_jiffies
== 0
2241 || !time_in_range(jiffies
, *caller_jiffies
,
2243 + msecs_to_jiffies(interval_msecs
))) {
2244 *caller_jiffies
= jiffies
;
2249 EXPORT_SYMBOL(printk_timed_ratelimit
);
2251 static DEFINE_SPINLOCK(dump_list_lock
);
2252 static LIST_HEAD(dump_list
);
2255 * kmsg_dump_register - register a kernel log dumper.
2256 * @dumper: pointer to the kmsg_dumper structure
2258 * Adds a kernel log dumper to the system. The dump callback in the
2259 * structure will be called when the kernel oopses or panics and must be
2260 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2262 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2264 unsigned long flags
;
2267 /* The dump callback needs to be set */
2271 spin_lock_irqsave(&dump_list_lock
, flags
);
2272 /* Don't allow registering multiple times */
2273 if (!dumper
->registered
) {
2274 dumper
->registered
= 1;
2275 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2278 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2282 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2285 * kmsg_dump_unregister - unregister a kmsg dumper.
2286 * @dumper: pointer to the kmsg_dumper structure
2288 * Removes a dump device from the system. Returns zero on success and
2289 * %-EINVAL otherwise.
2291 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2293 unsigned long flags
;
2296 spin_lock_irqsave(&dump_list_lock
, flags
);
2297 if (dumper
->registered
) {
2298 dumper
->registered
= 0;
2299 list_del_rcu(&dumper
->list
);
2302 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2307 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2309 static bool always_kmsg_dump
;
2310 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2313 * kmsg_dump - dump kernel log to kernel message dumpers.
2314 * @reason: the reason (oops, panic etc) for dumping
2316 * Call each of the registered dumper's dump() callback, which can
2317 * retrieve the kmsg records with kmsg_dump_get_line() or
2318 * kmsg_dump_get_buffer().
2320 void kmsg_dump(enum kmsg_dump_reason reason
)
2322 struct kmsg_dumper
*dumper
;
2323 unsigned long flags
;
2325 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2329 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2330 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2333 /* initialize iterator with data about the stored records */
2334 dumper
->active
= true;
2336 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2337 dumper
->cur_seq
= clear_seq
;
2338 dumper
->cur_idx
= clear_idx
;
2339 dumper
->next_seq
= log_next_seq
;
2340 dumper
->next_idx
= log_next_idx
;
2341 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2343 /* invoke dumper which will iterate over records */
2344 dumper
->dump(dumper
, reason
);
2346 /* reset iterator */
2347 dumper
->active
= false;
2353 * kmsg_dump_get_line - retrieve one kmsg log line
2354 * @dumper: registered kmsg dumper
2355 * @syslog: include the "<4>" prefixes
2356 * @line: buffer to copy the line to
2357 * @size: maximum size of the buffer
2358 * @len: length of line placed into buffer
2360 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2361 * record, and copy one record into the provided buffer.
2363 * Consecutive calls will return the next available record moving
2364 * towards the end of the buffer with the youngest messages.
2366 * A return value of FALSE indicates that there are no more records to
2369 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2370 char *line
, size_t size
, size_t *len
)
2372 unsigned long flags
;
2377 if (!dumper
->active
)
2380 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2381 if (dumper
->cur_seq
< log_first_seq
) {
2382 /* messages are gone, move to first available one */
2383 dumper
->cur_seq
= log_first_seq
;
2384 dumper
->cur_idx
= log_first_idx
;
2388 if (dumper
->cur_seq
>= log_next_seq
) {
2389 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2393 msg
= log_from_idx(dumper
->cur_idx
);
2394 l
= msg_print_text(msg
, syslog
,
2397 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2400 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2406 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
2409 * kmsg_dump_get_buffer - copy kmsg log lines
2410 * @dumper: registered kmsg dumper
2411 * @syslog: include the "<4>" prefixes
2412 * @line: buffer to copy the line to
2413 * @size: maximum size of the buffer
2414 * @len: length of line placed into buffer
2416 * Start at the end of the kmsg buffer and fill the provided buffer
2417 * with as many of the the *youngest* kmsg records that fit into it.
2418 * If the buffer is large enough, all available kmsg records will be
2419 * copied with a single call.
2421 * Consecutive calls will fill the buffer with the next block of
2422 * available older records, not including the earlier retrieved ones.
2424 * A return value of FALSE indicates that there are no more records to
2427 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
2428 char *buf
, size_t size
, size_t *len
)
2430 unsigned long flags
;
2438 if (!dumper
->active
)
2441 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2442 if (dumper
->cur_seq
< log_first_seq
) {
2443 /* messages are gone, move to first available one */
2444 dumper
->cur_seq
= log_first_seq
;
2445 dumper
->cur_idx
= log_first_idx
;
2449 if (dumper
->cur_seq
>= dumper
->next_seq
) {
2450 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2454 /* calculate length of entire buffer */
2455 seq
= dumper
->cur_seq
;
2456 idx
= dumper
->cur_idx
;
2457 while (seq
< dumper
->next_seq
) {
2458 struct log
*msg
= log_from_idx(idx
);
2460 l
+= msg_print_text(msg
, true, NULL
, 0);
2461 idx
= log_next(idx
);
2465 /* move first record forward until length fits into the buffer */
2466 seq
= dumper
->cur_seq
;
2467 idx
= dumper
->cur_idx
;
2468 while (l
> size
&& seq
< dumper
->next_seq
) {
2469 struct log
*msg
= log_from_idx(idx
);
2471 l
-= msg_print_text(msg
, true, NULL
, 0);
2472 idx
= log_next(idx
);
2476 /* last message in next interation */
2481 while (seq
< dumper
->next_seq
) {
2482 struct log
*msg
= log_from_idx(idx
);
2484 l
+= msg_print_text(msg
, syslog
,
2487 idx
= log_next(idx
);
2491 dumper
->next_seq
= next_seq
;
2492 dumper
->next_idx
= next_idx
;
2494 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2500 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
2503 * kmsg_dump_rewind - reset the interator
2504 * @dumper: registered kmsg dumper
2506 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2507 * kmsg_dump_get_buffer() can be called again and used multiple
2508 * times within the same dumper.dump() callback.
2510 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
2512 unsigned long flags
;
2514 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2515 dumper
->cur_seq
= clear_seq
;
2516 dumper
->cur_idx
= clear_idx
;
2517 dumper
->next_seq
= log_next_seq
;
2518 dumper
->next_idx
= log_next_idx
;
2519 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2521 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);