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/syscalls.h>
35 #include <linux/kexec.h>
36 #include <linux/kdb.h>
37 #include <linux/ratelimit.h>
38 #include <linux/kmsg_dump.h>
39 #include <linux/syslog.h>
40 #include <linux/cpu.h>
41 #include <linux/notifier.h>
43 #include <asm/uaccess.h>
46 * for_each_console() allows you to iterate on each console
48 #define for_each_console(con) \
49 for (con = console_drivers; con != NULL; con = con->next)
52 * Architectures can override it:
54 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
58 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
60 #ifdef CONFIG_DEBUG_LL
61 extern void printascii(char *);
64 /* printk's without a loglevel use this.. */
65 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
67 /* We show everything that is MORE important than this.. */
68 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
69 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
71 DECLARE_WAIT_QUEUE_HEAD(log_wait);
73 int console_printk[4] = {
74 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
75 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
76 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
77 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
81 * Low level drivers may need that to know if they can schedule in
82 * their unblank() callback or not. So let's export it.
85 EXPORT_SYMBOL(oops_in_progress);
88 * console_sem protects the console_drivers list, and also
89 * provides serialisation for access to the entire console
92 static DECLARE_MUTEX(console_sem);
93 struct console *console_drivers;
94 EXPORT_SYMBOL_GPL(console_drivers);
97 * This is used for debugging the mess that is the VT code by
98 * keeping track if we have the console semaphore held. It's
99 * definitely not the perfect debug tool (we don't know if _WE_
100 * hold it are racing, but it helps tracking those weird code
101 * path in the console code where we end up in places I want
102 * locked without the console sempahore held
104 static int console_locked, console_suspended;
107 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
108 * It is also used in interesting ways to provide interlocking in
109 * release_console_sem().
111 static DEFINE_SPINLOCK(logbuf_lock);
113 #define LOG_BUF_MASK (log_buf_len-1)
114 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
117 * The indices into log_buf are not constrained to log_buf_len - they
118 * must be masked before subscripting
120 static unsigned log_start; /* Index into log_buf: next char to be read by syslog() */
121 static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */
122 static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */
125 * Array of consoles built from command line options (console=)
127 struct console_cmdline
129 char name[8]; /* Name of the driver */
130 int index; /* Minor dev. to use */
131 char *options; /* Options for the driver */
132 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
133 char *brl_options; /* Options for braille driver */
137 #define MAX_CMDLINECONSOLES 8
139 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
140 static int selected_console = -1;
141 static int preferred_console = -1;
142 int console_set_on_cmdline;
143 EXPORT_SYMBOL(console_set_on_cmdline);
145 /* Flag: console code may call schedule() */
146 static int console_may_schedule;
150 static char __log_buf[__LOG_BUF_LEN];
151 static char *log_buf = __log_buf;
152 static int log_buf_len = __LOG_BUF_LEN;
153 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
154 static int saved_console_loglevel = -1;
158 * This appends the listed symbols to /proc/vmcoreinfo
160 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
161 * obtain access to symbols that are otherwise very difficult to locate. These
162 * symbols are specifically used so that utilities can access and extract the
163 * dmesg log from a vmcore file after a crash.
165 void log_buf_kexec_setup(void)
167 VMCOREINFO_SYMBOL(log_buf);
168 VMCOREINFO_SYMBOL(log_end);
169 VMCOREINFO_SYMBOL(log_buf_len);
170 VMCOREINFO_SYMBOL(logged_chars);
174 static int __init log_buf_len_setup(char *str)
176 unsigned size = memparse(str, &str);
180 size = roundup_pow_of_two(size);
181 if (size > log_buf_len) {
182 unsigned start, dest_idx, offset;
185 new_log_buf = alloc_bootmem(size);
187 printk(KERN_WARNING "log_buf_len: allocation failed\n");
191 spin_lock_irqsave(&logbuf_lock, flags);
193 log_buf = new_log_buf;
195 offset = start = min(con_start, log_start);
197 while (start != log_end) {
198 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
205 spin_unlock_irqrestore(&logbuf_lock, flags);
207 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
213 __setup("log_buf_len=", log_buf_len_setup);
215 #ifdef CONFIG_BOOT_PRINTK_DELAY
217 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
218 static unsigned long long loops_per_msec; /* based on boot_delay */
220 static int __init boot_delay_setup(char *str)
224 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
225 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
227 get_option(&str, &boot_delay);
228 if (boot_delay > 10 * 1000)
231 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
232 "HZ: %d, loops_per_msec: %llu\n",
233 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
236 __setup("boot_delay=", boot_delay_setup);
238 static void boot_delay_msec(void)
240 unsigned long long k;
241 unsigned long timeout;
243 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
246 k = (unsigned long long)loops_per_msec * boot_delay;
248 timeout = jiffies + msecs_to_jiffies(boot_delay);
253 * use (volatile) jiffies to prevent
254 * compiler reduction; loop termination via jiffies
255 * is secondary and may or may not happen.
257 if (time_after(jiffies, timeout))
259 touch_nmi_watchdog();
263 static inline void boot_delay_msec(void)
269 * Return the number of unread characters in the log buffer.
271 static int log_buf_get_len(void)
277 * Clears the ring-buffer
279 void log_buf_clear(void)
285 * Copy a range of characters from the log buffer.
287 int log_buf_copy(char *dest, int idx, int len)
290 bool took_lock = false;
292 if (!oops_in_progress) {
293 spin_lock_irq(&logbuf_lock);
297 max = log_buf_get_len();
298 if (idx < 0 || idx >= max) {
304 idx += (log_end - max);
306 dest[len] = LOG_BUF(idx + len);
310 spin_unlock_irq(&logbuf_lock);
316 * Commands to do_syslog:
318 * 0 -- Close the log. Currently a NOP.
319 * 1 -- Open the log. Currently a NOP.
320 * 2 -- Read from the log.
321 * 3 -- Read all messages remaining in the ring buffer.
322 * 4 -- Read and clear all messages remaining in the ring buffer
323 * 5 -- Clear ring buffer.
324 * 6 -- Disable printk's to console
325 * 7 -- Enable printk's to console
326 * 8 -- Set level of messages printed to console
327 * 9 -- Return number of unread characters in the log buffer
328 * 10 -- Return size of the log buffer
330 int do_syslog(int type, char __user *buf, int len, bool from_file)
332 unsigned i, j, limit, count;
337 error = security_syslog(type, from_file);
342 case SYSLOG_ACTION_CLOSE: /* Close log */
344 case SYSLOG_ACTION_OPEN: /* Open log */
346 case SYSLOG_ACTION_READ: /* Read from log */
353 if (!access_ok(VERIFY_WRITE, buf, len)) {
357 error = wait_event_interruptible(log_wait,
358 (log_start - log_end));
362 spin_lock_irq(&logbuf_lock);
363 while (!error && (log_start != log_end) && i < len) {
364 c = LOG_BUF(log_start);
366 spin_unlock_irq(&logbuf_lock);
367 error = __put_user(c,buf);
371 spin_lock_irq(&logbuf_lock);
373 spin_unlock_irq(&logbuf_lock);
377 /* Read/clear last kernel messages */
378 case SYSLOG_ACTION_READ_CLEAR:
381 /* Read last kernel messages */
382 case SYSLOG_ACTION_READ_ALL:
389 if (!access_ok(VERIFY_WRITE, buf, len)) {
394 if (count > log_buf_len)
396 spin_lock_irq(&logbuf_lock);
397 if (count > logged_chars)
398 count = logged_chars;
403 * __put_user() could sleep, and while we sleep
404 * printk() could overwrite the messages
405 * we try to copy to user space. Therefore
406 * the messages are copied in reverse. <manfreds>
408 for (i = 0; i < count && !error; i++) {
410 if (j + log_buf_len < log_end)
413 spin_unlock_irq(&logbuf_lock);
414 error = __put_user(c,&buf[count-1-i]);
416 spin_lock_irq(&logbuf_lock);
418 spin_unlock_irq(&logbuf_lock);
423 int offset = count-error;
424 /* buffer overflow during copy, correct user buffer. */
425 for (i = 0; i < error; i++) {
426 if (__get_user(c,&buf[i+offset]) ||
427 __put_user(c,&buf[i])) {
435 /* Clear ring buffer */
436 case SYSLOG_ACTION_CLEAR:
439 /* Disable logging to console */
440 case SYSLOG_ACTION_CONSOLE_OFF:
441 if (saved_console_loglevel == -1)
442 saved_console_loglevel = console_loglevel;
443 console_loglevel = minimum_console_loglevel;
445 /* Enable logging to console */
446 case SYSLOG_ACTION_CONSOLE_ON:
447 if (saved_console_loglevel != -1) {
448 console_loglevel = saved_console_loglevel;
449 saved_console_loglevel = -1;
452 /* Set level of messages printed to console */
453 case SYSLOG_ACTION_CONSOLE_LEVEL:
455 if (len < 1 || len > 8)
457 if (len < minimum_console_loglevel)
458 len = minimum_console_loglevel;
459 console_loglevel = len;
460 /* Implicitly re-enable logging to console */
461 saved_console_loglevel = -1;
464 /* Number of chars in the log buffer */
465 case SYSLOG_ACTION_SIZE_UNREAD:
466 error = log_end - log_start;
468 /* Size of the log buffer */
469 case SYSLOG_ACTION_SIZE_BUFFER:
480 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
482 return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
485 #ifdef CONFIG_KGDB_KDB
486 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
487 * uses locks so it cannot be used during debugging. Just tell kdb
488 * where the start and end of the physical and logical logs are. This
489 * is equivalent to do_syslog(3).
491 void kdb_syslog_data(char *syslog_data[4])
493 syslog_data[0] = log_buf;
494 syslog_data[1] = log_buf + log_buf_len;
495 syslog_data[2] = log_buf + log_end -
496 (logged_chars < log_buf_len ? logged_chars : log_buf_len);
497 syslog_data[3] = log_buf + log_end;
499 #endif /* CONFIG_KGDB_KDB */
502 * Call the console drivers on a range of log_buf
504 static void __call_console_drivers(unsigned start, unsigned end)
508 for_each_console(con) {
509 if ((con->flags & CON_ENABLED) && con->write &&
510 (cpu_online(smp_processor_id()) ||
511 (con->flags & CON_ANYTIME)))
512 con->write(con, &LOG_BUF(start), end - start);
516 static int __read_mostly ignore_loglevel;
518 static int __init ignore_loglevel_setup(char *str)
521 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
526 early_param("ignore_loglevel", ignore_loglevel_setup);
529 * Write out chars from start to end - 1 inclusive
531 static void _call_console_drivers(unsigned start,
532 unsigned end, int msg_log_level)
534 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
535 console_drivers && start != end) {
536 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
538 __call_console_drivers(start & LOG_BUF_MASK,
540 __call_console_drivers(0, end & LOG_BUF_MASK);
542 __call_console_drivers(start, end);
548 * Call the console drivers, asking them to write out
549 * log_buf[start] to log_buf[end - 1].
550 * The console_sem must be held.
552 static void call_console_drivers(unsigned start, unsigned end)
554 unsigned cur_index, start_print;
555 static int msg_level = -1;
557 BUG_ON(((int)(start - end)) > 0);
561 while (cur_index != end) {
562 if (msg_level < 0 && ((end - cur_index) > 2) &&
563 LOG_BUF(cur_index + 0) == '<' &&
564 LOG_BUF(cur_index + 1) >= '0' &&
565 LOG_BUF(cur_index + 1) <= '7' &&
566 LOG_BUF(cur_index + 2) == '>') {
567 msg_level = LOG_BUF(cur_index + 1) - '0';
569 start_print = cur_index;
571 while (cur_index != end) {
572 char c = LOG_BUF(cur_index);
578 * printk() has already given us loglevel tags in
579 * the buffer. This code is here in case the
580 * log buffer has wrapped right round and scribbled
583 msg_level = default_message_loglevel;
585 _call_console_drivers(start_print, cur_index, msg_level);
587 start_print = cur_index;
592 _call_console_drivers(start_print, end, msg_level);
595 static void emit_log_char(char c)
597 LOG_BUF(log_end) = c;
599 if (log_end - log_start > log_buf_len)
600 log_start = log_end - log_buf_len;
601 if (log_end - con_start > log_buf_len)
602 con_start = log_end - log_buf_len;
603 if (logged_chars < log_buf_len)
608 * Zap console related locks when oopsing. Only zap at most once
609 * every 10 seconds, to leave time for slow consoles to print a
612 static void zap_locks(void)
614 static unsigned long oops_timestamp;
616 if (time_after_eq(jiffies, oops_timestamp) &&
617 !time_after(jiffies, oops_timestamp + 30 * HZ))
620 oops_timestamp = jiffies;
622 /* If a crash is occurring, make sure we can't deadlock */
623 spin_lock_init(&logbuf_lock);
624 /* And make sure that we print immediately */
625 init_MUTEX(&console_sem);
628 #if defined(CONFIG_PRINTK_TIME)
629 static int printk_time = 1;
631 static int printk_time = 0;
633 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
635 /* Check if we have any console registered that can be called early in boot. */
636 static int have_callable_console(void)
640 for_each_console(con)
641 if (con->flags & CON_ANYTIME)
648 * printk - print a kernel message
649 * @fmt: format string
651 * This is printk(). It can be called from any context. We want it to work.
653 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
654 * call the console drivers. If we fail to get the semaphore we place the output
655 * into the log buffer and return. The current holder of the console_sem will
656 * notice the new output in release_console_sem() and will send it to the
657 * consoles before releasing the semaphore.
659 * One effect of this deferred printing is that code which calls printk() and
660 * then changes console_loglevel may break. This is because console_loglevel
661 * is inspected when the actual printing occurs.
666 * See the vsnprintf() documentation for format string extensions over C99.
669 asmlinkage int printk(const char *fmt, ...)
674 #ifdef CONFIG_KGDB_KDB
675 if (unlikely(kdb_trap_printk)) {
677 r = vkdb_printf(fmt, args);
683 r = vprintk(fmt, args);
689 /* cpu currently holding logbuf_lock */
690 static volatile unsigned int printk_cpu = UINT_MAX;
693 * Can we actually use the console at this time on this cpu?
695 * Console drivers may assume that per-cpu resources have
696 * been allocated. So unless they're explicitly marked as
697 * being able to cope (CON_ANYTIME) don't call them until
698 * this CPU is officially up.
700 static inline int can_use_console(unsigned int cpu)
702 return cpu_online(cpu) || have_callable_console();
706 * Try to get console ownership to actually show the kernel
707 * messages from a 'printk'. Return true (and with the
708 * console_semaphore held, and 'console_locked' set) if it
709 * is successful, false otherwise.
711 * This gets called with the 'logbuf_lock' spinlock held and
712 * interrupts disabled. It should return with 'lockbuf_lock'
713 * released but interrupts still disabled.
715 static int acquire_console_semaphore_for_printk(unsigned int cpu)
719 if (!try_acquire_console_sem()) {
723 * If we can't use the console, we need to release
724 * the console semaphore by hand to avoid flushing
725 * the buffer. We need to hold the console semaphore
726 * in order to do this test safely.
728 if (!can_use_console(cpu)) {
734 printk_cpu = UINT_MAX;
735 spin_unlock(&logbuf_lock);
738 static const char recursion_bug_msg [] =
739 KERN_CRIT "BUG: recent printk recursion!\n";
740 static int recursion_bug;
741 static int new_text_line = 1;
742 static char printk_buf[1024];
744 int printk_delay_msec __read_mostly;
746 static inline void printk_delay(void)
748 if (unlikely(printk_delay_msec)) {
749 int m = printk_delay_msec;
753 touch_nmi_watchdog();
758 asmlinkage int vprintk(const char *fmt, va_list args)
761 int current_log_level = default_message_loglevel;
770 /* This stops the holder of console_sem just where we want him */
771 raw_local_irq_save(flags);
772 this_cpu = smp_processor_id();
775 * Ouch, printk recursed into itself!
777 if (unlikely(printk_cpu == this_cpu)) {
779 * If a crash is occurring during printk() on this CPU,
780 * then try to get the crash message out but make sure
781 * we can't deadlock. Otherwise just return to avoid the
782 * recursion and return - but flag the recursion so that
783 * it can be printed at the next appropriate moment:
785 if (!oops_in_progress) {
787 goto out_restore_irqs;
793 spin_lock(&logbuf_lock);
794 printk_cpu = this_cpu;
798 strcpy(printk_buf, recursion_bug_msg);
799 printed_len = strlen(recursion_bug_msg);
801 /* Emit the output into the temporary buffer */
802 printed_len += vscnprintf(printk_buf + printed_len,
803 sizeof(printk_buf) - printed_len, fmt, args);
805 #ifdef CONFIG_DEBUG_LL
806 printascii(printk_buf);
811 /* Do we have a loglevel in the string? */
813 unsigned char c = p[1];
814 if (c && p[2] == '>') {
816 case '0' ... '7': /* loglevel */
817 current_log_level = c - '0';
818 /* Fallthrough - make sure we're on a new line */
819 case 'd': /* KERN_DEFAULT */
820 if (!new_text_line) {
824 /* Fallthrough - skip the loglevel */
825 case 'c': /* KERN_CONT */
833 * Copy the output into log_buf. If the caller didn't provide
834 * appropriate log level tags, we insert them here
838 /* Always output the token */
840 emit_log_char(current_log_level + '0');
846 /* Follow the token with the time */
849 unsigned long long t;
850 unsigned long nanosec_rem;
852 t = cpu_clock(printk_cpu);
853 nanosec_rem = do_div(t, 1000000000);
854 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
858 for (tp = tbuf; tp < tbuf + tlen; tp++)
873 * Try to acquire and then immediately release the
874 * console semaphore. The release will do all the
875 * actual magic (print out buffers, wake up klogd,
878 * The acquire_console_semaphore_for_printk() function
879 * will release 'logbuf_lock' regardless of whether it
880 * actually gets the semaphore or not.
882 if (acquire_console_semaphore_for_printk(this_cpu))
883 release_console_sem();
887 raw_local_irq_restore(flags);
892 EXPORT_SYMBOL(printk);
893 EXPORT_SYMBOL(vprintk);
897 static void call_console_drivers(unsigned start, unsigned end)
903 static int __add_preferred_console(char *name, int idx, char *options,
906 struct console_cmdline *c;
910 * See if this tty is not yet registered, and
911 * if we have a slot free.
913 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
914 if (strcmp(console_cmdline[i].name, name) == 0 &&
915 console_cmdline[i].index == idx) {
917 selected_console = i;
920 if (i == MAX_CMDLINECONSOLES)
923 selected_console = i;
924 c = &console_cmdline[i];
925 strlcpy(c->name, name, sizeof(c->name));
926 c->options = options;
927 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
928 c->brl_options = brl_options;
934 * Set up a list of consoles. Called from init/main.c
936 static int __init console_setup(char *str)
938 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
939 char *s, *options, *brl_options = NULL;
942 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
943 if (!memcmp(str, "brl,", 4)) {
946 } else if (!memcmp(str, "brl=", 4)) {
947 brl_options = str + 4;
948 str = strchr(brl_options, ',');
950 printk(KERN_ERR "need port name after brl=\n");
958 * Decode str into name, index, options.
960 if (str[0] >= '0' && str[0] <= '9') {
962 strncpy(buf + 4, str, sizeof(buf) - 5);
964 strncpy(buf, str, sizeof(buf) - 1);
966 buf[sizeof(buf) - 1] = 0;
967 if ((options = strchr(str, ',')) != NULL)
970 if (!strcmp(str, "ttya"))
971 strcpy(buf, "ttyS0");
972 if (!strcmp(str, "ttyb"))
973 strcpy(buf, "ttyS1");
975 for (s = buf; *s; s++)
976 if ((*s >= '0' && *s <= '9') || *s == ',')
978 idx = simple_strtoul(s, NULL, 10);
981 __add_preferred_console(buf, idx, options, brl_options);
982 console_set_on_cmdline = 1;
985 __setup("console=", console_setup);
988 * add_preferred_console - add a device to the list of preferred consoles.
991 * @options: options for this console
993 * The last preferred console added will be used for kernel messages
994 * and stdin/out/err for init. Normally this is used by console_setup
995 * above to handle user-supplied console arguments; however it can also
996 * be used by arch-specific code either to override the user or more
997 * commonly to provide a default console (ie from PROM variables) when
998 * the user has not supplied one.
1000 int add_preferred_console(char *name, int idx, char *options)
1002 return __add_preferred_console(name, idx, options, NULL);
1005 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1007 struct console_cmdline *c;
1010 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1011 if (strcmp(console_cmdline[i].name, name) == 0 &&
1012 console_cmdline[i].index == idx) {
1013 c = &console_cmdline[i];
1014 strlcpy(c->name, name_new, sizeof(c->name));
1015 c->name[sizeof(c->name) - 1] = 0;
1016 c->options = options;
1024 int console_suspend_enabled = 1;
1025 EXPORT_SYMBOL(console_suspend_enabled);
1027 static int __init console_suspend_disable(char *str)
1029 console_suspend_enabled = 0;
1032 __setup("no_console_suspend", console_suspend_disable);
1035 * suspend_console - suspend the console subsystem
1037 * This disables printk() while we go into suspend states
1039 void suspend_console(void)
1041 if (!console_suspend_enabled)
1043 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1044 acquire_console_sem();
1045 console_suspended = 1;
1049 void resume_console(void)
1051 if (!console_suspend_enabled)
1054 console_suspended = 0;
1055 release_console_sem();
1059 * console_cpu_notify - print deferred console messages after CPU hotplug
1060 * @self: notifier struct
1061 * @action: CPU hotplug event
1064 * If printk() is called from a CPU that is not online yet, the messages
1065 * will be spooled but will not show up on the console. This function is
1066 * called when a new CPU comes online (or fails to come up), and ensures
1067 * that any such output gets printed.
1069 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1070 unsigned long action, void *hcpu)
1076 case CPU_DOWN_FAILED:
1077 case CPU_UP_CANCELED:
1078 acquire_console_sem();
1079 release_console_sem();
1085 * acquire_console_sem - lock the console system for exclusive use.
1087 * Acquires a semaphore which guarantees that the caller has
1088 * exclusive access to the console system and the console_drivers list.
1090 * Can sleep, returns nothing.
1092 void acquire_console_sem(void)
1094 BUG_ON(in_interrupt());
1096 if (console_suspended)
1099 console_may_schedule = 1;
1101 EXPORT_SYMBOL(acquire_console_sem);
1103 int try_acquire_console_sem(void)
1105 if (down_trylock(&console_sem))
1107 if (console_suspended) {
1112 console_may_schedule = 0;
1115 EXPORT_SYMBOL(try_acquire_console_sem);
1117 int is_console_locked(void)
1119 return console_locked;
1122 static DEFINE_PER_CPU(int, printk_pending);
1124 void printk_tick(void)
1126 if (__get_cpu_var(printk_pending)) {
1127 __get_cpu_var(printk_pending) = 0;
1128 wake_up_interruptible(&log_wait);
1132 int printk_needs_cpu(int cpu)
1134 return per_cpu(printk_pending, cpu);
1137 void wake_up_klogd(void)
1139 if (waitqueue_active(&log_wait))
1140 __raw_get_cpu_var(printk_pending) = 1;
1144 * release_console_sem - unlock the console system
1146 * Releases the semaphore which the caller holds on the console system
1147 * and the console driver list.
1149 * While the semaphore was held, console output may have been buffered
1150 * by printk(). If this is the case, release_console_sem() emits
1151 * the output prior to releasing the semaphore.
1153 * If there is output waiting for klogd, we wake it up.
1155 * release_console_sem() may be called from any context.
1157 void release_console_sem(void)
1159 unsigned long flags;
1160 unsigned _con_start, _log_end;
1161 unsigned wake_klogd = 0;
1163 if (console_suspended) {
1168 console_may_schedule = 0;
1171 spin_lock_irqsave(&logbuf_lock, flags);
1172 wake_klogd |= log_start - log_end;
1173 if (con_start == log_end)
1174 break; /* Nothing to print */
1175 _con_start = con_start;
1177 con_start = log_end; /* Flush */
1178 spin_unlock(&logbuf_lock);
1179 stop_critical_timings(); /* don't trace print latency */
1180 call_console_drivers(_con_start, _log_end);
1181 start_critical_timings();
1182 local_irq_restore(flags);
1186 spin_unlock_irqrestore(&logbuf_lock, flags);
1190 EXPORT_SYMBOL(release_console_sem);
1193 * console_conditional_schedule - yield the CPU if required
1195 * If the console code is currently allowed to sleep, and
1196 * if this CPU should yield the CPU to another task, do
1199 * Must be called within acquire_console_sem().
1201 void __sched console_conditional_schedule(void)
1203 if (console_may_schedule)
1206 EXPORT_SYMBOL(console_conditional_schedule);
1208 void console_unblank(void)
1213 * console_unblank can no longer be called in interrupt context unless
1214 * oops_in_progress is set to 1..
1216 if (oops_in_progress) {
1217 if (down_trylock(&console_sem) != 0)
1220 acquire_console_sem();
1223 console_may_schedule = 0;
1225 if ((c->flags & CON_ENABLED) && c->unblank)
1227 release_console_sem();
1231 * Return the console tty driver structure and its associated index
1233 struct tty_driver *console_device(int *index)
1236 struct tty_driver *driver = NULL;
1238 acquire_console_sem();
1239 for_each_console(c) {
1242 driver = c->device(c, index);
1246 release_console_sem();
1251 * Prevent further output on the passed console device so that (for example)
1252 * serial drivers can disable console output before suspending a port, and can
1253 * re-enable output afterwards.
1255 void console_stop(struct console *console)
1257 acquire_console_sem();
1258 console->flags &= ~CON_ENABLED;
1259 release_console_sem();
1261 EXPORT_SYMBOL(console_stop);
1263 void console_start(struct console *console)
1265 acquire_console_sem();
1266 console->flags |= CON_ENABLED;
1267 release_console_sem();
1269 EXPORT_SYMBOL(console_start);
1272 * The console driver calls this routine during kernel initialization
1273 * to register the console printing procedure with printk() and to
1274 * print any messages that were printed by the kernel before the
1275 * console driver was initialized.
1277 * This can happen pretty early during the boot process (because of
1278 * early_printk) - sometimes before setup_arch() completes - be careful
1279 * of what kernel features are used - they may not be initialised yet.
1281 * There are two types of consoles - bootconsoles (early_printk) and
1282 * "real" consoles (everything which is not a bootconsole) which are
1283 * handled differently.
1284 * - Any number of bootconsoles can be registered at any time.
1285 * - As soon as a "real" console is registered, all bootconsoles
1286 * will be unregistered automatically.
1287 * - Once a "real" console is registered, any attempt to register a
1288 * bootconsoles will be rejected
1290 void register_console(struct console *newcon)
1293 unsigned long flags;
1294 struct console *bcon = NULL;
1297 * before we register a new CON_BOOT console, make sure we don't
1298 * already have a valid console
1300 if (console_drivers && newcon->flags & CON_BOOT) {
1301 /* find the last or real console */
1302 for_each_console(bcon) {
1303 if (!(bcon->flags & CON_BOOT)) {
1304 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1305 newcon->name, newcon->index);
1311 if (console_drivers && console_drivers->flags & CON_BOOT)
1312 bcon = console_drivers;
1314 if (preferred_console < 0 || bcon || !console_drivers)
1315 preferred_console = selected_console;
1317 if (newcon->early_setup)
1318 newcon->early_setup();
1321 * See if we want to use this console driver. If we
1322 * didn't select a console we take the first one
1323 * that registers here.
1325 if (preferred_console < 0) {
1326 if (newcon->index < 0)
1328 if (newcon->setup == NULL ||
1329 newcon->setup(newcon, NULL) == 0) {
1330 newcon->flags |= CON_ENABLED;
1331 if (newcon->device) {
1332 newcon->flags |= CON_CONSDEV;
1333 preferred_console = 0;
1339 * See if this console matches one we selected on
1342 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1344 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1346 if (newcon->index >= 0 &&
1347 newcon->index != console_cmdline[i].index)
1349 if (newcon->index < 0)
1350 newcon->index = console_cmdline[i].index;
1351 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1352 if (console_cmdline[i].brl_options) {
1353 newcon->flags |= CON_BRL;
1354 braille_register_console(newcon,
1355 console_cmdline[i].index,
1356 console_cmdline[i].options,
1357 console_cmdline[i].brl_options);
1361 if (newcon->setup &&
1362 newcon->setup(newcon, console_cmdline[i].options) != 0)
1364 newcon->flags |= CON_ENABLED;
1365 newcon->index = console_cmdline[i].index;
1366 if (i == selected_console) {
1367 newcon->flags |= CON_CONSDEV;
1368 preferred_console = selected_console;
1373 if (!(newcon->flags & CON_ENABLED))
1377 * If we have a bootconsole, and are switching to a real console,
1378 * don't print everything out again, since when the boot console, and
1379 * the real console are the same physical device, it's annoying to
1380 * see the beginning boot messages twice
1382 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1383 newcon->flags &= ~CON_PRINTBUFFER;
1386 * Put this console in the list - keep the
1387 * preferred driver at the head of the list.
1389 acquire_console_sem();
1390 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1391 newcon->next = console_drivers;
1392 console_drivers = newcon;
1394 newcon->next->flags &= ~CON_CONSDEV;
1396 newcon->next = console_drivers->next;
1397 console_drivers->next = newcon;
1399 if (newcon->flags & CON_PRINTBUFFER) {
1401 * release_console_sem() will print out the buffered messages
1404 spin_lock_irqsave(&logbuf_lock, flags);
1405 con_start = log_start;
1406 spin_unlock_irqrestore(&logbuf_lock, flags);
1408 release_console_sem();
1411 * By unregistering the bootconsoles after we enable the real console
1412 * we get the "console xxx enabled" message on all the consoles -
1413 * boot consoles, real consoles, etc - this is to ensure that end
1414 * users know there might be something in the kernel's log buffer that
1415 * went to the bootconsole (that they do not see on the real console)
1417 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1418 /* we need to iterate through twice, to make sure we print
1419 * everything out, before we unregister the console(s)
1421 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1422 newcon->name, newcon->index);
1423 for_each_console(bcon)
1424 if (bcon->flags & CON_BOOT)
1425 unregister_console(bcon);
1427 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1428 (newcon->flags & CON_BOOT) ? "boot" : "" ,
1429 newcon->name, newcon->index);
1432 EXPORT_SYMBOL(register_console);
1434 int unregister_console(struct console *console)
1436 struct console *a, *b;
1439 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1440 if (console->flags & CON_BRL)
1441 return braille_unregister_console(console);
1444 acquire_console_sem();
1445 if (console_drivers == console) {
1446 console_drivers=console->next;
1448 } else if (console_drivers) {
1449 for (a=console_drivers->next, b=console_drivers ;
1450 a; b=a, a=b->next) {
1460 * If this isn't the last console and it has CON_CONSDEV set, we
1461 * need to set it on the next preferred console.
1463 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1464 console_drivers->flags |= CON_CONSDEV;
1466 release_console_sem();
1469 EXPORT_SYMBOL(unregister_console);
1471 static int __init printk_late_init(void)
1473 struct console *con;
1475 for_each_console(con) {
1476 if (con->flags & CON_BOOT) {
1477 printk(KERN_INFO "turn off boot console %s%d\n",
1478 con->name, con->index);
1479 unregister_console(con);
1482 hotcpu_notifier(console_cpu_notify, 0);
1485 late_initcall(printk_late_init);
1487 #if defined CONFIG_PRINTK
1490 * printk rate limiting, lifted from the networking subsystem.
1492 * This enforces a rate limit: not more than 10 kernel messages
1493 * every 5s to make a denial-of-service attack impossible.
1495 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1497 int __printk_ratelimit(const char *func)
1499 return ___ratelimit(&printk_ratelimit_state, func);
1501 EXPORT_SYMBOL(__printk_ratelimit);
1504 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1505 * @caller_jiffies: pointer to caller's state
1506 * @interval_msecs: minimum interval between prints
1508 * printk_timed_ratelimit() returns true if more than @interval_msecs
1509 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1512 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1513 unsigned int interval_msecs)
1515 if (*caller_jiffies == 0
1516 || !time_in_range(jiffies, *caller_jiffies,
1518 + msecs_to_jiffies(interval_msecs))) {
1519 *caller_jiffies = jiffies;
1524 EXPORT_SYMBOL(printk_timed_ratelimit);
1526 static DEFINE_SPINLOCK(dump_list_lock);
1527 static LIST_HEAD(dump_list);
1530 * kmsg_dump_register - register a kernel log dumper.
1531 * @dumper: pointer to the kmsg_dumper structure
1533 * Adds a kernel log dumper to the system. The dump callback in the
1534 * structure will be called when the kernel oopses or panics and must be
1535 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1537 int kmsg_dump_register(struct kmsg_dumper *dumper)
1539 unsigned long flags;
1542 /* The dump callback needs to be set */
1546 spin_lock_irqsave(&dump_list_lock, flags);
1547 /* Don't allow registering multiple times */
1548 if (!dumper->registered) {
1549 dumper->registered = 1;
1550 list_add_tail(&dumper->list, &dump_list);
1553 spin_unlock_irqrestore(&dump_list_lock, flags);
1557 EXPORT_SYMBOL_GPL(kmsg_dump_register);
1560 * kmsg_dump_unregister - unregister a kmsg dumper.
1561 * @dumper: pointer to the kmsg_dumper structure
1563 * Removes a dump device from the system. Returns zero on success and
1564 * %-EINVAL otherwise.
1566 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
1568 unsigned long flags;
1571 spin_lock_irqsave(&dump_list_lock, flags);
1572 if (dumper->registered) {
1573 dumper->registered = 0;
1574 list_del(&dumper->list);
1577 spin_unlock_irqrestore(&dump_list_lock, flags);
1581 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
1583 static const char const *kmsg_reasons[] = {
1584 [KMSG_DUMP_OOPS] = "oops",
1585 [KMSG_DUMP_PANIC] = "panic",
1586 [KMSG_DUMP_KEXEC] = "kexec",
1589 static const char *kmsg_to_str(enum kmsg_dump_reason reason)
1591 if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0)
1594 return kmsg_reasons[reason];
1598 * kmsg_dump - dump kernel log to kernel message dumpers.
1599 * @reason: the reason (oops, panic etc) for dumping
1601 * Iterate through each of the dump devices and call the oops/panic
1602 * callbacks with the log buffer.
1604 void kmsg_dump(enum kmsg_dump_reason reason)
1608 struct kmsg_dumper *dumper;
1609 const char *s1, *s2;
1610 unsigned long l1, l2;
1611 unsigned long flags;
1613 /* Theoretically, the log could move on after we do this, but
1614 there's not a lot we can do about that. The new messages
1615 will overwrite the start of what we dump. */
1616 spin_lock_irqsave(&logbuf_lock, flags);
1617 end = log_end & LOG_BUF_MASK;
1618 chars = logged_chars;
1619 spin_unlock_irqrestore(&logbuf_lock, flags);
1622 s1 = log_buf + log_buf_len - chars + end;
1631 s2 = log_buf + end - chars;
1635 if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
1636 printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n",
1637 kmsg_to_str(reason));
1640 list_for_each_entry(dumper, &dump_list, list)
1641 dumper->dump(dumper, reason, s1, l1, s2, l2);
1642 spin_unlock_irqrestore(&dump_list_lock, flags);