kconfig/streamline-config.pl: Simplify backslash line concatination
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / printk.c
blob084982f61deed58700ae80204285e86496454474
1 /*
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).
11 * Ted Ts'o, 2/11/93.
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>
20 #include <linux/mm.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>
45 #include <asm/uaccess.h>
48 * Architectures can override it:
50 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
54 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
56 /* printk's without a loglevel use this.. */
57 #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
59 /* We show everything that is MORE important than this.. */
60 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
61 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
63 DECLARE_WAIT_QUEUE_HEAD(log_wait);
65 int console_printk[4] = {
66 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
67 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
68 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
69 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
73 * Low level drivers may need that to know if they can schedule in
74 * their unblank() callback or not. So let's export it.
76 int oops_in_progress;
77 EXPORT_SYMBOL(oops_in_progress);
80 * console_sem protects the console_drivers list, and also
81 * provides serialisation for access to the entire console
82 * driver system.
84 static DEFINE_SEMAPHORE(console_sem);
85 struct console *console_drivers;
86 EXPORT_SYMBOL_GPL(console_drivers);
89 * This is used for debugging the mess that is the VT code by
90 * keeping track if we have the console semaphore held. It's
91 * definitely not the perfect debug tool (we don't know if _WE_
92 * hold it are racing, but it helps tracking those weird code
93 * path in the console code where we end up in places I want
94 * locked without the console sempahore held
96 static int console_locked, console_suspended;
99 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
100 * It is also used in interesting ways to provide interlocking in
101 * console_unlock();.
103 static DEFINE_SPINLOCK(logbuf_lock);
105 #define LOG_BUF_MASK (log_buf_len-1)
106 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
109 * The indices into log_buf are not constrained to log_buf_len - they
110 * must be masked before subscripting
112 static unsigned log_start; /* Index into log_buf: next char to be read by syslog() */
113 static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */
114 static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */
117 * If exclusive_console is non-NULL then only this console is to be printed to.
119 static struct console *exclusive_console;
122 * Array of consoles built from command line options (console=)
124 struct console_cmdline
126 char name[8]; /* Name of the driver */
127 int index; /* Minor dev. to use */
128 char *options; /* Options for the driver */
129 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
130 char *brl_options; /* Options for braille driver */
131 #endif
134 #define MAX_CMDLINECONSOLES 8
136 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
137 static int selected_console = -1;
138 static int preferred_console = -1;
139 int console_set_on_cmdline;
140 EXPORT_SYMBOL(console_set_on_cmdline);
142 /* Flag: console code may call schedule() */
143 static int console_may_schedule;
145 #ifdef CONFIG_PRINTK
147 static char __log_buf[__LOG_BUF_LEN];
148 static char *log_buf = __log_buf;
149 static int log_buf_len = __LOG_BUF_LEN;
150 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
151 static int saved_console_loglevel = -1;
153 #ifdef CONFIG_KEXEC
155 * This appends the listed symbols to /proc/vmcoreinfo
157 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
158 * obtain access to symbols that are otherwise very difficult to locate. These
159 * symbols are specifically used so that utilities can access and extract the
160 * dmesg log from a vmcore file after a crash.
162 void log_buf_kexec_setup(void)
164 VMCOREINFO_SYMBOL(log_buf);
165 VMCOREINFO_SYMBOL(log_end);
166 VMCOREINFO_SYMBOL(log_buf_len);
167 VMCOREINFO_SYMBOL(logged_chars);
169 #endif
171 /* requested log_buf_len from kernel cmdline */
172 static unsigned long __initdata new_log_buf_len;
174 /* save requested log_buf_len since it's too early to process it */
175 static int __init log_buf_len_setup(char *str)
177 unsigned size = memparse(str, &str);
179 if (size)
180 size = roundup_pow_of_two(size);
181 if (size > log_buf_len)
182 new_log_buf_len = size;
184 return 0;
186 early_param("log_buf_len", log_buf_len_setup);
188 void __init setup_log_buf(int early)
190 unsigned long flags;
191 unsigned start, dest_idx, offset;
192 char *new_log_buf;
193 int free;
195 if (!new_log_buf_len)
196 return;
198 if (early) {
199 unsigned long mem;
201 mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
202 if (mem == MEMBLOCK_ERROR)
203 return;
204 new_log_buf = __va(mem);
205 } else {
206 new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
209 if (unlikely(!new_log_buf)) {
210 pr_err("log_buf_len: %ld bytes not available\n",
211 new_log_buf_len);
212 return;
215 spin_lock_irqsave(&logbuf_lock, flags);
216 log_buf_len = new_log_buf_len;
217 log_buf = new_log_buf;
218 new_log_buf_len = 0;
219 free = __LOG_BUF_LEN - log_end;
221 offset = start = min(con_start, log_start);
222 dest_idx = 0;
223 while (start != log_end) {
224 unsigned log_idx_mask = start & (__LOG_BUF_LEN - 1);
226 log_buf[dest_idx] = __log_buf[log_idx_mask];
227 start++;
228 dest_idx++;
230 log_start -= offset;
231 con_start -= offset;
232 log_end -= offset;
233 spin_unlock_irqrestore(&logbuf_lock, flags);
235 pr_info("log_buf_len: %d\n", log_buf_len);
236 pr_info("early log buf free: %d(%d%%)\n",
237 free, (free * 100) / __LOG_BUF_LEN);
240 #ifdef CONFIG_BOOT_PRINTK_DELAY
242 static int boot_delay; /* msecs delay after each printk during bootup */
243 static unsigned long long loops_per_msec; /* based on boot_delay */
245 static int __init boot_delay_setup(char *str)
247 unsigned long lpj;
249 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
250 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
252 get_option(&str, &boot_delay);
253 if (boot_delay > 10 * 1000)
254 boot_delay = 0;
256 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
257 "HZ: %d, loops_per_msec: %llu\n",
258 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
259 return 1;
261 __setup("boot_delay=", boot_delay_setup);
263 static void boot_delay_msec(void)
265 unsigned long long k;
266 unsigned long timeout;
268 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
269 return;
271 k = (unsigned long long)loops_per_msec * boot_delay;
273 timeout = jiffies + msecs_to_jiffies(boot_delay);
274 while (k) {
275 k--;
276 cpu_relax();
278 * use (volatile) jiffies to prevent
279 * compiler reduction; loop termination via jiffies
280 * is secondary and may or may not happen.
282 if (time_after(jiffies, timeout))
283 break;
284 touch_nmi_watchdog();
287 #else
288 static inline void boot_delay_msec(void)
291 #endif
293 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
294 int dmesg_restrict = 1;
295 #else
296 int dmesg_restrict;
297 #endif
299 static int syslog_action_restricted(int type)
301 if (dmesg_restrict)
302 return 1;
303 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
304 return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
307 static int check_syslog_permissions(int type, bool from_file)
310 * If this is from /proc/kmsg and we've already opened it, then we've
311 * already done the capabilities checks at open time.
313 if (from_file && type != SYSLOG_ACTION_OPEN)
314 return 0;
316 if (syslog_action_restricted(type)) {
317 if (capable(CAP_SYSLOG))
318 return 0;
319 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
320 if (capable(CAP_SYS_ADMIN)) {
321 WARN_ONCE(1, "Attempt to access syslog with CAP_SYS_ADMIN "
322 "but no CAP_SYSLOG (deprecated).\n");
323 return 0;
325 return -EPERM;
327 return 0;
330 int do_syslog(int type, char __user *buf, int len, bool from_file)
332 unsigned i, j, limit, count;
333 int do_clear = 0;
334 char c;
335 int error;
337 error = check_syslog_permissions(type, from_file);
338 if (error)
339 goto out;
341 error = security_syslog(type);
342 if (error)
343 return error;
345 switch (type) {
346 case SYSLOG_ACTION_CLOSE: /* Close log */
347 break;
348 case SYSLOG_ACTION_OPEN: /* Open log */
349 break;
350 case SYSLOG_ACTION_READ: /* Read from log */
351 error = -EINVAL;
352 if (!buf || len < 0)
353 goto out;
354 error = 0;
355 if (!len)
356 goto out;
357 if (!access_ok(VERIFY_WRITE, buf, len)) {
358 error = -EFAULT;
359 goto out;
361 error = wait_event_interruptible(log_wait,
362 (log_start - log_end));
363 if (error)
364 goto out;
365 i = 0;
366 spin_lock_irq(&logbuf_lock);
367 while (!error && (log_start != log_end) && i < len) {
368 c = LOG_BUF(log_start);
369 log_start++;
370 spin_unlock_irq(&logbuf_lock);
371 error = __put_user(c,buf);
372 buf++;
373 i++;
374 cond_resched();
375 spin_lock_irq(&logbuf_lock);
377 spin_unlock_irq(&logbuf_lock);
378 if (!error)
379 error = i;
380 break;
381 /* Read/clear last kernel messages */
382 case SYSLOG_ACTION_READ_CLEAR:
383 do_clear = 1;
384 /* FALL THRU */
385 /* Read last kernel messages */
386 case SYSLOG_ACTION_READ_ALL:
387 error = -EINVAL;
388 if (!buf || len < 0)
389 goto out;
390 error = 0;
391 if (!len)
392 goto out;
393 if (!access_ok(VERIFY_WRITE, buf, len)) {
394 error = -EFAULT;
395 goto out;
397 count = len;
398 if (count > log_buf_len)
399 count = log_buf_len;
400 spin_lock_irq(&logbuf_lock);
401 if (count > logged_chars)
402 count = logged_chars;
403 if (do_clear)
404 logged_chars = 0;
405 limit = log_end;
407 * __put_user() could sleep, and while we sleep
408 * printk() could overwrite the messages
409 * we try to copy to user space. Therefore
410 * the messages are copied in reverse. <manfreds>
412 for (i = 0; i < count && !error; i++) {
413 j = limit-1-i;
414 if (j + log_buf_len < log_end)
415 break;
416 c = LOG_BUF(j);
417 spin_unlock_irq(&logbuf_lock);
418 error = __put_user(c,&buf[count-1-i]);
419 cond_resched();
420 spin_lock_irq(&logbuf_lock);
422 spin_unlock_irq(&logbuf_lock);
423 if (error)
424 break;
425 error = i;
426 if (i != count) {
427 int offset = count-error;
428 /* buffer overflow during copy, correct user buffer. */
429 for (i = 0; i < error; i++) {
430 if (__get_user(c,&buf[i+offset]) ||
431 __put_user(c,&buf[i])) {
432 error = -EFAULT;
433 break;
435 cond_resched();
438 break;
439 /* Clear ring buffer */
440 case SYSLOG_ACTION_CLEAR:
441 logged_chars = 0;
442 break;
443 /* Disable logging to console */
444 case SYSLOG_ACTION_CONSOLE_OFF:
445 if (saved_console_loglevel == -1)
446 saved_console_loglevel = console_loglevel;
447 console_loglevel = minimum_console_loglevel;
448 break;
449 /* Enable logging to console */
450 case SYSLOG_ACTION_CONSOLE_ON:
451 if (saved_console_loglevel != -1) {
452 console_loglevel = saved_console_loglevel;
453 saved_console_loglevel = -1;
455 break;
456 /* Set level of messages printed to console */
457 case SYSLOG_ACTION_CONSOLE_LEVEL:
458 error = -EINVAL;
459 if (len < 1 || len > 8)
460 goto out;
461 if (len < minimum_console_loglevel)
462 len = minimum_console_loglevel;
463 console_loglevel = len;
464 /* Implicitly re-enable logging to console */
465 saved_console_loglevel = -1;
466 error = 0;
467 break;
468 /* Number of chars in the log buffer */
469 case SYSLOG_ACTION_SIZE_UNREAD:
470 error = log_end - log_start;
471 break;
472 /* Size of the log buffer */
473 case SYSLOG_ACTION_SIZE_BUFFER:
474 error = log_buf_len;
475 break;
476 default:
477 error = -EINVAL;
478 break;
480 out:
481 return error;
484 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
486 return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
489 #ifdef CONFIG_KGDB_KDB
490 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
491 * uses locks so it cannot be used during debugging. Just tell kdb
492 * where the start and end of the physical and logical logs are. This
493 * is equivalent to do_syslog(3).
495 void kdb_syslog_data(char *syslog_data[4])
497 syslog_data[0] = log_buf;
498 syslog_data[1] = log_buf + log_buf_len;
499 syslog_data[2] = log_buf + log_end -
500 (logged_chars < log_buf_len ? logged_chars : log_buf_len);
501 syslog_data[3] = log_buf + log_end;
503 #endif /* CONFIG_KGDB_KDB */
506 * Call the console drivers on a range of log_buf
508 static void __call_console_drivers(unsigned start, unsigned end)
510 struct console *con;
512 for_each_console(con) {
513 if (exclusive_console && con != exclusive_console)
514 continue;
515 if ((con->flags & CON_ENABLED) && con->write &&
516 (cpu_online(smp_processor_id()) ||
517 (con->flags & CON_ANYTIME)))
518 con->write(con, &LOG_BUF(start), end - start);
522 static int __read_mostly ignore_loglevel;
524 static int __init ignore_loglevel_setup(char *str)
526 ignore_loglevel = 1;
527 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
529 return 0;
532 early_param("ignore_loglevel", ignore_loglevel_setup);
535 * Write out chars from start to end - 1 inclusive
537 static void _call_console_drivers(unsigned start,
538 unsigned end, int msg_log_level)
540 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
541 console_drivers && start != end) {
542 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
543 /* wrapped write */
544 __call_console_drivers(start & LOG_BUF_MASK,
545 log_buf_len);
546 __call_console_drivers(0, end & LOG_BUF_MASK);
547 } else {
548 __call_console_drivers(start, end);
554 * Parse the syslog header <[0-9]*>. The decimal value represents 32bit, the
555 * lower 3 bit are the log level, the rest are the log facility. In case
556 * userspace passes usual userspace syslog messages to /dev/kmsg or
557 * /dev/ttyprintk, the log prefix might contain the facility. Printk needs
558 * to extract the correct log level for in-kernel processing, and not mangle
559 * the original value.
561 * If a prefix is found, the length of the prefix is returned. If 'level' is
562 * passed, it will be filled in with the log level without a possible facility
563 * value. If 'special' is passed, the special printk prefix chars are accepted
564 * and returned. If no valid header is found, 0 is returned and the passed
565 * variables are not touched.
567 static size_t log_prefix(const char *p, unsigned int *level, char *special)
569 unsigned int lev = 0;
570 char sp = '\0';
571 size_t len;
573 if (p[0] != '<' || !p[1])
574 return 0;
575 if (p[2] == '>') {
576 /* usual single digit level number or special char */
577 switch (p[1]) {
578 case '0' ... '7':
579 lev = p[1] - '0';
580 break;
581 case 'c': /* KERN_CONT */
582 case 'd': /* KERN_DEFAULT */
583 sp = p[1];
584 break;
585 default:
586 return 0;
588 len = 3;
589 } else {
590 /* multi digit including the level and facility number */
591 char *endp = NULL;
593 if (p[1] < '0' && p[1] > '9')
594 return 0;
596 lev = (simple_strtoul(&p[1], &endp, 10) & 7);
597 if (endp == NULL || endp[0] != '>')
598 return 0;
599 len = (endp + 1) - p;
602 /* do not accept special char if not asked for */
603 if (sp && !special)
604 return 0;
606 if (special) {
607 *special = sp;
608 /* return special char, do not touch level */
609 if (sp)
610 return len;
613 if (level)
614 *level = lev;
615 return len;
619 * Call the console drivers, asking them to write out
620 * log_buf[start] to log_buf[end - 1].
621 * The console_lock must be held.
623 static void call_console_drivers(unsigned start, unsigned end)
625 unsigned cur_index, start_print;
626 static int msg_level = -1;
628 BUG_ON(((int)(start - end)) > 0);
630 cur_index = start;
631 start_print = start;
632 while (cur_index != end) {
633 if (msg_level < 0 && ((end - cur_index) > 2)) {
634 /* strip log prefix */
635 cur_index += log_prefix(&LOG_BUF(cur_index), &msg_level, NULL);
636 start_print = cur_index;
638 while (cur_index != end) {
639 char c = LOG_BUF(cur_index);
641 cur_index++;
642 if (c == '\n') {
643 if (msg_level < 0) {
645 * printk() has already given us loglevel tags in
646 * the buffer. This code is here in case the
647 * log buffer has wrapped right round and scribbled
648 * on those tags
650 msg_level = default_message_loglevel;
652 _call_console_drivers(start_print, cur_index, msg_level);
653 msg_level = -1;
654 start_print = cur_index;
655 break;
659 _call_console_drivers(start_print, end, msg_level);
662 static void emit_log_char(char c)
664 LOG_BUF(log_end) = c;
665 log_end++;
666 if (log_end - log_start > log_buf_len)
667 log_start = log_end - log_buf_len;
668 if (log_end - con_start > log_buf_len)
669 con_start = log_end - log_buf_len;
670 if (logged_chars < log_buf_len)
671 logged_chars++;
675 * Zap console related locks when oopsing. Only zap at most once
676 * every 10 seconds, to leave time for slow consoles to print a
677 * full oops.
679 static void zap_locks(void)
681 static unsigned long oops_timestamp;
683 if (time_after_eq(jiffies, oops_timestamp) &&
684 !time_after(jiffies, oops_timestamp + 30 * HZ))
685 return;
687 oops_timestamp = jiffies;
689 /* If a crash is occurring, make sure we can't deadlock */
690 spin_lock_init(&logbuf_lock);
691 /* And make sure that we print immediately */
692 sema_init(&console_sem, 1);
695 #if defined(CONFIG_PRINTK_TIME)
696 static int printk_time = 1;
697 #else
698 static int printk_time = 0;
699 #endif
700 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
702 /* Check if we have any console registered that can be called early in boot. */
703 static int have_callable_console(void)
705 struct console *con;
707 for_each_console(con)
708 if (con->flags & CON_ANYTIME)
709 return 1;
711 return 0;
715 * printk - print a kernel message
716 * @fmt: format string
718 * This is printk(). It can be called from any context. We want it to work.
720 * We try to grab the console_lock. If we succeed, it's easy - we log the output and
721 * call the console drivers. If we fail to get the semaphore we place the output
722 * into the log buffer and return. The current holder of the console_sem will
723 * notice the new output in console_unlock(); and will send it to the
724 * consoles before releasing the lock.
726 * One effect of this deferred printing is that code which calls printk() and
727 * then changes console_loglevel may break. This is because console_loglevel
728 * is inspected when the actual printing occurs.
730 * See also:
731 * printf(3)
733 * See the vsnprintf() documentation for format string extensions over C99.
736 asmlinkage int printk(const char *fmt, ...)
738 va_list args;
739 int r;
741 #ifdef CONFIG_KGDB_KDB
742 if (unlikely(kdb_trap_printk)) {
743 va_start(args, fmt);
744 r = vkdb_printf(fmt, args);
745 va_end(args);
746 return r;
748 #endif
749 va_start(args, fmt);
750 r = vprintk(fmt, args);
751 va_end(args);
753 return r;
756 /* cpu currently holding logbuf_lock */
757 static volatile unsigned int printk_cpu = UINT_MAX;
760 * Can we actually use the console at this time on this cpu?
762 * Console drivers may assume that per-cpu resources have
763 * been allocated. So unless they're explicitly marked as
764 * being able to cope (CON_ANYTIME) don't call them until
765 * this CPU is officially up.
767 static inline int can_use_console(unsigned int cpu)
769 return cpu_online(cpu) || have_callable_console();
773 * Try to get console ownership to actually show the kernel
774 * messages from a 'printk'. Return true (and with the
775 * console_lock held, and 'console_locked' set) if it
776 * is successful, false otherwise.
778 * This gets called with the 'logbuf_lock' spinlock held and
779 * interrupts disabled. It should return with 'lockbuf_lock'
780 * released but interrupts still disabled.
782 static int console_trylock_for_printk(unsigned int cpu)
783 __releases(&logbuf_lock)
785 int retval = 0;
787 if (console_trylock()) {
788 retval = 1;
791 * If we can't use the console, we need to release
792 * the console semaphore by hand to avoid flushing
793 * the buffer. We need to hold the console semaphore
794 * in order to do this test safely.
796 if (!can_use_console(cpu)) {
797 console_locked = 0;
798 up(&console_sem);
799 retval = 0;
802 printk_cpu = UINT_MAX;
803 spin_unlock(&logbuf_lock);
804 return retval;
806 static const char recursion_bug_msg [] =
807 KERN_CRIT "BUG: recent printk recursion!\n";
808 static int recursion_bug;
809 static int new_text_line = 1;
810 static char printk_buf[1024];
812 int printk_delay_msec __read_mostly;
814 static inline void printk_delay(void)
816 if (unlikely(printk_delay_msec)) {
817 int m = printk_delay_msec;
819 while (m--) {
820 mdelay(1);
821 touch_nmi_watchdog();
826 asmlinkage int vprintk(const char *fmt, va_list args)
828 int printed_len = 0;
829 int current_log_level = default_message_loglevel;
830 unsigned long flags;
831 int this_cpu;
832 char *p;
833 size_t plen;
834 char special;
836 boot_delay_msec();
837 printk_delay();
839 preempt_disable();
840 /* This stops the holder of console_sem just where we want him */
841 raw_local_irq_save(flags);
842 this_cpu = smp_processor_id();
845 * Ouch, printk recursed into itself!
847 if (unlikely(printk_cpu == this_cpu)) {
849 * If a crash is occurring during printk() on this CPU,
850 * then try to get the crash message out but make sure
851 * we can't deadlock. Otherwise just return to avoid the
852 * recursion and return - but flag the recursion so that
853 * it can be printed at the next appropriate moment:
855 if (!oops_in_progress) {
856 recursion_bug = 1;
857 goto out_restore_irqs;
859 zap_locks();
862 lockdep_off();
863 spin_lock(&logbuf_lock);
864 printk_cpu = this_cpu;
866 if (recursion_bug) {
867 recursion_bug = 0;
868 strcpy(printk_buf, recursion_bug_msg);
869 printed_len = strlen(recursion_bug_msg);
871 /* Emit the output into the temporary buffer */
872 printed_len += vscnprintf(printk_buf + printed_len,
873 sizeof(printk_buf) - printed_len, fmt, args);
875 p = printk_buf;
877 /* Read log level and handle special printk prefix */
878 plen = log_prefix(p, &current_log_level, &special);
879 if (plen) {
880 p += plen;
882 switch (special) {
883 case 'c': /* Strip <c> KERN_CONT, continue line */
884 plen = 0;
885 break;
886 case 'd': /* Strip <d> KERN_DEFAULT, start new line */
887 plen = 0;
888 default:
889 if (!new_text_line) {
890 emit_log_char('\n');
891 new_text_line = 1;
897 * Copy the output into log_buf. If the caller didn't provide
898 * the appropriate log prefix, we insert them here
900 for (; *p; p++) {
901 if (new_text_line) {
902 new_text_line = 0;
904 if (plen) {
905 /* Copy original log prefix */
906 int i;
908 for (i = 0; i < plen; i++)
909 emit_log_char(printk_buf[i]);
910 printed_len += plen;
911 } else {
912 /* Add log prefix */
913 emit_log_char('<');
914 emit_log_char(current_log_level + '0');
915 emit_log_char('>');
916 printed_len += 3;
919 if (printk_time) {
920 /* Add the current time stamp */
921 char tbuf[50], *tp;
922 unsigned tlen;
923 unsigned long long t;
924 unsigned long nanosec_rem;
926 t = cpu_clock(printk_cpu);
927 nanosec_rem = do_div(t, 1000000000);
928 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
929 (unsigned long) t,
930 nanosec_rem / 1000);
932 for (tp = tbuf; tp < tbuf + tlen; tp++)
933 emit_log_char(*tp);
934 printed_len += tlen;
937 if (!*p)
938 break;
941 emit_log_char(*p);
942 if (*p == '\n')
943 new_text_line = 1;
947 * Try to acquire and then immediately release the
948 * console semaphore. The release will do all the
949 * actual magic (print out buffers, wake up klogd,
950 * etc).
952 * The console_trylock_for_printk() function
953 * will release 'logbuf_lock' regardless of whether it
954 * actually gets the semaphore or not.
956 if (console_trylock_for_printk(this_cpu))
957 console_unlock();
959 lockdep_on();
960 out_restore_irqs:
961 raw_local_irq_restore(flags);
963 preempt_enable();
964 return printed_len;
966 EXPORT_SYMBOL(printk);
967 EXPORT_SYMBOL(vprintk);
969 #else
971 static void call_console_drivers(unsigned start, unsigned end)
975 #endif
977 static int __add_preferred_console(char *name, int idx, char *options,
978 char *brl_options)
980 struct console_cmdline *c;
981 int i;
984 * See if this tty is not yet registered, and
985 * if we have a slot free.
987 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
988 if (strcmp(console_cmdline[i].name, name) == 0 &&
989 console_cmdline[i].index == idx) {
990 if (!brl_options)
991 selected_console = i;
992 return 0;
994 if (i == MAX_CMDLINECONSOLES)
995 return -E2BIG;
996 if (!brl_options)
997 selected_console = i;
998 c = &console_cmdline[i];
999 strlcpy(c->name, name, sizeof(c->name));
1000 c->options = options;
1001 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1002 c->brl_options = brl_options;
1003 #endif
1004 c->index = idx;
1005 return 0;
1008 * Set up a list of consoles. Called from init/main.c
1010 static int __init console_setup(char *str)
1012 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1013 char *s, *options, *brl_options = NULL;
1014 int idx;
1016 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1017 if (!memcmp(str, "brl,", 4)) {
1018 brl_options = "";
1019 str += 4;
1020 } else if (!memcmp(str, "brl=", 4)) {
1021 brl_options = str + 4;
1022 str = strchr(brl_options, ',');
1023 if (!str) {
1024 printk(KERN_ERR "need port name after brl=\n");
1025 return 1;
1027 *(str++) = 0;
1029 #endif
1032 * Decode str into name, index, options.
1034 if (str[0] >= '0' && str[0] <= '9') {
1035 strcpy(buf, "ttyS");
1036 strncpy(buf + 4, str, sizeof(buf) - 5);
1037 } else {
1038 strncpy(buf, str, sizeof(buf) - 1);
1040 buf[sizeof(buf) - 1] = 0;
1041 if ((options = strchr(str, ',')) != NULL)
1042 *(options++) = 0;
1043 #ifdef __sparc__
1044 if (!strcmp(str, "ttya"))
1045 strcpy(buf, "ttyS0");
1046 if (!strcmp(str, "ttyb"))
1047 strcpy(buf, "ttyS1");
1048 #endif
1049 for (s = buf; *s; s++)
1050 if ((*s >= '0' && *s <= '9') || *s == ',')
1051 break;
1052 idx = simple_strtoul(s, NULL, 10);
1053 *s = 0;
1055 __add_preferred_console(buf, idx, options, brl_options);
1056 console_set_on_cmdline = 1;
1057 return 1;
1059 __setup("console=", console_setup);
1062 * add_preferred_console - add a device to the list of preferred consoles.
1063 * @name: device name
1064 * @idx: device index
1065 * @options: options for this console
1067 * The last preferred console added will be used for kernel messages
1068 * and stdin/out/err for init. Normally this is used by console_setup
1069 * above to handle user-supplied console arguments; however it can also
1070 * be used by arch-specific code either to override the user or more
1071 * commonly to provide a default console (ie from PROM variables) when
1072 * the user has not supplied one.
1074 int add_preferred_console(char *name, int idx, char *options)
1076 return __add_preferred_console(name, idx, options, NULL);
1079 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1081 struct console_cmdline *c;
1082 int i;
1084 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1085 if (strcmp(console_cmdline[i].name, name) == 0 &&
1086 console_cmdline[i].index == idx) {
1087 c = &console_cmdline[i];
1088 strlcpy(c->name, name_new, sizeof(c->name));
1089 c->name[sizeof(c->name) - 1] = 0;
1090 c->options = options;
1091 c->index = idx_new;
1092 return i;
1094 /* not found */
1095 return -1;
1098 int console_suspend_enabled = 1;
1099 EXPORT_SYMBOL(console_suspend_enabled);
1101 static int __init console_suspend_disable(char *str)
1103 console_suspend_enabled = 0;
1104 return 1;
1106 __setup("no_console_suspend", console_suspend_disable);
1109 * suspend_console - suspend the console subsystem
1111 * This disables printk() while we go into suspend states
1113 void suspend_console(void)
1115 if (!console_suspend_enabled)
1116 return;
1117 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1118 console_lock();
1119 console_suspended = 1;
1120 up(&console_sem);
1123 void resume_console(void)
1125 if (!console_suspend_enabled)
1126 return;
1127 down(&console_sem);
1128 console_suspended = 0;
1129 console_unlock();
1133 * console_cpu_notify - print deferred console messages after CPU hotplug
1134 * @self: notifier struct
1135 * @action: CPU hotplug event
1136 * @hcpu: unused
1138 * If printk() is called from a CPU that is not online yet, the messages
1139 * will be spooled but will not show up on the console. This function is
1140 * called when a new CPU comes online (or fails to come up), and ensures
1141 * that any such output gets printed.
1143 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1144 unsigned long action, void *hcpu)
1146 switch (action) {
1147 case CPU_ONLINE:
1148 case CPU_DEAD:
1149 case CPU_DYING:
1150 case CPU_DOWN_FAILED:
1151 case CPU_UP_CANCELED:
1152 console_lock();
1153 console_unlock();
1155 return NOTIFY_OK;
1159 * console_lock - lock the console system for exclusive use.
1161 * Acquires a lock which guarantees that the caller has
1162 * exclusive access to the console system and the console_drivers list.
1164 * Can sleep, returns nothing.
1166 void console_lock(void)
1168 BUG_ON(in_interrupt());
1169 down(&console_sem);
1170 if (console_suspended)
1171 return;
1172 console_locked = 1;
1173 console_may_schedule = 1;
1175 EXPORT_SYMBOL(console_lock);
1178 * console_trylock - try to lock the console system for exclusive use.
1180 * Tried to acquire a lock which guarantees that the caller has
1181 * exclusive access to the console system and the console_drivers list.
1183 * returns 1 on success, and 0 on failure to acquire the lock.
1185 int console_trylock(void)
1187 if (down_trylock(&console_sem))
1188 return 0;
1189 if (console_suspended) {
1190 up(&console_sem);
1191 return 0;
1193 console_locked = 1;
1194 console_may_schedule = 0;
1195 return 1;
1197 EXPORT_SYMBOL(console_trylock);
1199 int is_console_locked(void)
1201 return console_locked;
1204 static DEFINE_PER_CPU(int, printk_pending);
1206 void printk_tick(void)
1208 if (__this_cpu_read(printk_pending)) {
1209 __this_cpu_write(printk_pending, 0);
1210 wake_up_interruptible(&log_wait);
1214 int printk_needs_cpu(int cpu)
1216 if (cpu_is_offline(cpu))
1217 printk_tick();
1218 return __this_cpu_read(printk_pending);
1221 void wake_up_klogd(void)
1223 if (waitqueue_active(&log_wait))
1224 this_cpu_write(printk_pending, 1);
1228 * console_unlock - unlock the console system
1230 * Releases the console_lock which the caller holds on the console system
1231 * and the console driver list.
1233 * While the console_lock was held, console output may have been buffered
1234 * by printk(). If this is the case, console_unlock(); emits
1235 * the output prior to releasing the lock.
1237 * If there is output waiting for klogd, we wake it up.
1239 * console_unlock(); may be called from any context.
1241 void console_unlock(void)
1243 unsigned long flags;
1244 unsigned _con_start, _log_end;
1245 unsigned wake_klogd = 0;
1247 if (console_suspended) {
1248 up(&console_sem);
1249 return;
1252 console_may_schedule = 0;
1254 for ( ; ; ) {
1255 spin_lock_irqsave(&logbuf_lock, flags);
1256 wake_klogd |= log_start - log_end;
1257 if (con_start == log_end)
1258 break; /* Nothing to print */
1259 _con_start = con_start;
1260 _log_end = log_end;
1261 con_start = log_end; /* Flush */
1262 spin_unlock(&logbuf_lock);
1263 stop_critical_timings(); /* don't trace print latency */
1264 call_console_drivers(_con_start, _log_end);
1265 start_critical_timings();
1266 local_irq_restore(flags);
1268 console_locked = 0;
1270 /* Release the exclusive_console once it is used */
1271 if (unlikely(exclusive_console))
1272 exclusive_console = NULL;
1274 up(&console_sem);
1275 spin_unlock_irqrestore(&logbuf_lock, flags);
1276 if (wake_klogd)
1277 wake_up_klogd();
1279 EXPORT_SYMBOL(console_unlock);
1282 * console_conditional_schedule - yield the CPU if required
1284 * If the console code is currently allowed to sleep, and
1285 * if this CPU should yield the CPU to another task, do
1286 * so here.
1288 * Must be called within console_lock();.
1290 void __sched console_conditional_schedule(void)
1292 if (console_may_schedule)
1293 cond_resched();
1295 EXPORT_SYMBOL(console_conditional_schedule);
1297 void console_unblank(void)
1299 struct console *c;
1302 * console_unblank can no longer be called in interrupt context unless
1303 * oops_in_progress is set to 1..
1305 if (oops_in_progress) {
1306 if (down_trylock(&console_sem) != 0)
1307 return;
1308 } else
1309 console_lock();
1311 console_locked = 1;
1312 console_may_schedule = 0;
1313 for_each_console(c)
1314 if ((c->flags & CON_ENABLED) && c->unblank)
1315 c->unblank();
1316 console_unlock();
1320 * Return the console tty driver structure and its associated index
1322 struct tty_driver *console_device(int *index)
1324 struct console *c;
1325 struct tty_driver *driver = NULL;
1327 console_lock();
1328 for_each_console(c) {
1329 if (!c->device)
1330 continue;
1331 driver = c->device(c, index);
1332 if (driver)
1333 break;
1335 console_unlock();
1336 return driver;
1340 * Prevent further output on the passed console device so that (for example)
1341 * serial drivers can disable console output before suspending a port, and can
1342 * re-enable output afterwards.
1344 void console_stop(struct console *console)
1346 console_lock();
1347 console->flags &= ~CON_ENABLED;
1348 console_unlock();
1350 EXPORT_SYMBOL(console_stop);
1352 void console_start(struct console *console)
1354 console_lock();
1355 console->flags |= CON_ENABLED;
1356 console_unlock();
1358 EXPORT_SYMBOL(console_start);
1360 static int __read_mostly keep_bootcon;
1362 static int __init keep_bootcon_setup(char *str)
1364 keep_bootcon = 1;
1365 printk(KERN_INFO "debug: skip boot console de-registration.\n");
1367 return 0;
1370 early_param("keep_bootcon", keep_bootcon_setup);
1373 * The console driver calls this routine during kernel initialization
1374 * to register the console printing procedure with printk() and to
1375 * print any messages that were printed by the kernel before the
1376 * console driver was initialized.
1378 * This can happen pretty early during the boot process (because of
1379 * early_printk) - sometimes before setup_arch() completes - be careful
1380 * of what kernel features are used - they may not be initialised yet.
1382 * There are two types of consoles - bootconsoles (early_printk) and
1383 * "real" consoles (everything which is not a bootconsole) which are
1384 * handled differently.
1385 * - Any number of bootconsoles can be registered at any time.
1386 * - As soon as a "real" console is registered, all bootconsoles
1387 * will be unregistered automatically.
1388 * - Once a "real" console is registered, any attempt to register a
1389 * bootconsoles will be rejected
1391 void register_console(struct console *newcon)
1393 int i;
1394 unsigned long flags;
1395 struct console *bcon = NULL;
1398 * before we register a new CON_BOOT console, make sure we don't
1399 * already have a valid console
1401 if (console_drivers && newcon->flags & CON_BOOT) {
1402 /* find the last or real console */
1403 for_each_console(bcon) {
1404 if (!(bcon->flags & CON_BOOT)) {
1405 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1406 newcon->name, newcon->index);
1407 return;
1412 if (console_drivers && console_drivers->flags & CON_BOOT)
1413 bcon = console_drivers;
1415 if (preferred_console < 0 || bcon || !console_drivers)
1416 preferred_console = selected_console;
1418 if (newcon->early_setup)
1419 newcon->early_setup();
1422 * See if we want to use this console driver. If we
1423 * didn't select a console we take the first one
1424 * that registers here.
1426 if (preferred_console < 0) {
1427 if (newcon->index < 0)
1428 newcon->index = 0;
1429 if (newcon->setup == NULL ||
1430 newcon->setup(newcon, NULL) == 0) {
1431 newcon->flags |= CON_ENABLED;
1432 if (newcon->device) {
1433 newcon->flags |= CON_CONSDEV;
1434 preferred_console = 0;
1440 * See if this console matches one we selected on
1441 * the command line.
1443 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1444 i++) {
1445 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1446 continue;
1447 if (newcon->index >= 0 &&
1448 newcon->index != console_cmdline[i].index)
1449 continue;
1450 if (newcon->index < 0)
1451 newcon->index = console_cmdline[i].index;
1452 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1453 if (console_cmdline[i].brl_options) {
1454 newcon->flags |= CON_BRL;
1455 braille_register_console(newcon,
1456 console_cmdline[i].index,
1457 console_cmdline[i].options,
1458 console_cmdline[i].brl_options);
1459 return;
1461 #endif
1462 if (newcon->setup &&
1463 newcon->setup(newcon, console_cmdline[i].options) != 0)
1464 break;
1465 newcon->flags |= CON_ENABLED;
1466 newcon->index = console_cmdline[i].index;
1467 if (i == selected_console) {
1468 newcon->flags |= CON_CONSDEV;
1469 preferred_console = selected_console;
1471 break;
1474 if (!(newcon->flags & CON_ENABLED))
1475 return;
1478 * If we have a bootconsole, and are switching to a real console,
1479 * don't print everything out again, since when the boot console, and
1480 * the real console are the same physical device, it's annoying to
1481 * see the beginning boot messages twice
1483 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1484 newcon->flags &= ~CON_PRINTBUFFER;
1487 * Put this console in the list - keep the
1488 * preferred driver at the head of the list.
1490 console_lock();
1491 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1492 newcon->next = console_drivers;
1493 console_drivers = newcon;
1494 if (newcon->next)
1495 newcon->next->flags &= ~CON_CONSDEV;
1496 } else {
1497 newcon->next = console_drivers->next;
1498 console_drivers->next = newcon;
1500 if (newcon->flags & CON_PRINTBUFFER) {
1502 * console_unlock(); will print out the buffered messages
1503 * for us.
1505 spin_lock_irqsave(&logbuf_lock, flags);
1506 con_start = log_start;
1507 spin_unlock_irqrestore(&logbuf_lock, flags);
1509 * We're about to replay the log buffer. Only do this to the
1510 * just-registered console to avoid excessive message spam to
1511 * the already-registered consoles.
1513 exclusive_console = newcon;
1515 console_unlock();
1516 console_sysfs_notify();
1519 * By unregistering the bootconsoles after we enable the real console
1520 * we get the "console xxx enabled" message on all the consoles -
1521 * boot consoles, real consoles, etc - this is to ensure that end
1522 * users know there might be something in the kernel's log buffer that
1523 * went to the bootconsole (that they do not see on the real console)
1525 if (bcon &&
1526 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
1527 !keep_bootcon) {
1528 /* we need to iterate through twice, to make sure we print
1529 * everything out, before we unregister the console(s)
1531 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1532 newcon->name, newcon->index);
1533 for_each_console(bcon)
1534 if (bcon->flags & CON_BOOT)
1535 unregister_console(bcon);
1536 } else {
1537 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1538 (newcon->flags & CON_BOOT) ? "boot" : "" ,
1539 newcon->name, newcon->index);
1542 EXPORT_SYMBOL(register_console);
1544 int unregister_console(struct console *console)
1546 struct console *a, *b;
1547 int res = 1;
1549 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1550 if (console->flags & CON_BRL)
1551 return braille_unregister_console(console);
1552 #endif
1554 console_lock();
1555 if (console_drivers == console) {
1556 console_drivers=console->next;
1557 res = 0;
1558 } else if (console_drivers) {
1559 for (a=console_drivers->next, b=console_drivers ;
1560 a; b=a, a=b->next) {
1561 if (a == console) {
1562 b->next = a->next;
1563 res = 0;
1564 break;
1570 * If this isn't the last console and it has CON_CONSDEV set, we
1571 * need to set it on the next preferred console.
1573 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1574 console_drivers->flags |= CON_CONSDEV;
1576 console_unlock();
1577 console_sysfs_notify();
1578 return res;
1580 EXPORT_SYMBOL(unregister_console);
1582 static int __init printk_late_init(void)
1584 struct console *con;
1586 for_each_console(con) {
1587 if (!keep_bootcon && con->flags & CON_BOOT) {
1588 printk(KERN_INFO "turn off boot console %s%d\n",
1589 con->name, con->index);
1590 unregister_console(con);
1593 hotcpu_notifier(console_cpu_notify, 0);
1594 return 0;
1596 late_initcall(printk_late_init);
1598 #if defined CONFIG_PRINTK
1601 * printk rate limiting, lifted from the networking subsystem.
1603 * This enforces a rate limit: not more than 10 kernel messages
1604 * every 5s to make a denial-of-service attack impossible.
1606 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1608 int __printk_ratelimit(const char *func)
1610 return ___ratelimit(&printk_ratelimit_state, func);
1612 EXPORT_SYMBOL(__printk_ratelimit);
1615 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1616 * @caller_jiffies: pointer to caller's state
1617 * @interval_msecs: minimum interval between prints
1619 * printk_timed_ratelimit() returns true if more than @interval_msecs
1620 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1621 * returned true.
1623 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1624 unsigned int interval_msecs)
1626 if (*caller_jiffies == 0
1627 || !time_in_range(jiffies, *caller_jiffies,
1628 *caller_jiffies
1629 + msecs_to_jiffies(interval_msecs))) {
1630 *caller_jiffies = jiffies;
1631 return true;
1633 return false;
1635 EXPORT_SYMBOL(printk_timed_ratelimit);
1637 static DEFINE_SPINLOCK(dump_list_lock);
1638 static LIST_HEAD(dump_list);
1641 * kmsg_dump_register - register a kernel log dumper.
1642 * @dumper: pointer to the kmsg_dumper structure
1644 * Adds a kernel log dumper to the system. The dump callback in the
1645 * structure will be called when the kernel oopses or panics and must be
1646 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1648 int kmsg_dump_register(struct kmsg_dumper *dumper)
1650 unsigned long flags;
1651 int err = -EBUSY;
1653 /* The dump callback needs to be set */
1654 if (!dumper->dump)
1655 return -EINVAL;
1657 spin_lock_irqsave(&dump_list_lock, flags);
1658 /* Don't allow registering multiple times */
1659 if (!dumper->registered) {
1660 dumper->registered = 1;
1661 list_add_tail_rcu(&dumper->list, &dump_list);
1662 err = 0;
1664 spin_unlock_irqrestore(&dump_list_lock, flags);
1666 return err;
1668 EXPORT_SYMBOL_GPL(kmsg_dump_register);
1671 * kmsg_dump_unregister - unregister a kmsg dumper.
1672 * @dumper: pointer to the kmsg_dumper structure
1674 * Removes a dump device from the system. Returns zero on success and
1675 * %-EINVAL otherwise.
1677 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
1679 unsigned long flags;
1680 int err = -EINVAL;
1682 spin_lock_irqsave(&dump_list_lock, flags);
1683 if (dumper->registered) {
1684 dumper->registered = 0;
1685 list_del_rcu(&dumper->list);
1686 err = 0;
1688 spin_unlock_irqrestore(&dump_list_lock, flags);
1689 synchronize_rcu();
1691 return err;
1693 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
1696 * kmsg_dump - dump kernel log to kernel message dumpers.
1697 * @reason: the reason (oops, panic etc) for dumping
1699 * Iterate through each of the dump devices and call the oops/panic
1700 * callbacks with the log buffer.
1702 void kmsg_dump(enum kmsg_dump_reason reason)
1704 unsigned long end;
1705 unsigned chars;
1706 struct kmsg_dumper *dumper;
1707 const char *s1, *s2;
1708 unsigned long l1, l2;
1709 unsigned long flags;
1711 /* Theoretically, the log could move on after we do this, but
1712 there's not a lot we can do about that. The new messages
1713 will overwrite the start of what we dump. */
1714 spin_lock_irqsave(&logbuf_lock, flags);
1715 end = log_end & LOG_BUF_MASK;
1716 chars = logged_chars;
1717 spin_unlock_irqrestore(&logbuf_lock, flags);
1719 if (chars > end) {
1720 s1 = log_buf + log_buf_len - chars + end;
1721 l1 = chars - end;
1723 s2 = log_buf;
1724 l2 = end;
1725 } else {
1726 s1 = "";
1727 l1 = 0;
1729 s2 = log_buf + end - chars;
1730 l2 = chars;
1733 rcu_read_lock();
1734 list_for_each_entry_rcu(dumper, &dump_list, list)
1735 dumper->dump(dumper, reason, s1, l1, s2, l2);
1736 rcu_read_unlock();
1738 #endif