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>
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 #ifdef CONFIG_DEBUG_LL
57 extern void printascii(char *);
60 /* printk's without a loglevel use this.. */
61 #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
63 /* We show everything that is MORE important than this.. */
64 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
65 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
67 DECLARE_WAIT_QUEUE_HEAD(log_wait);
69 int console_printk[4] = {
70 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
71 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
72 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
73 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
77 * Low level drivers may need that to know if they can schedule in
78 * their unblank() callback or not. So let's export it.
81 EXPORT_SYMBOL(oops_in_progress);
84 * console_sem protects the console_drivers list, and also
85 * provides serialisation for access to the entire console
88 static DEFINE_SEMAPHORE(console_sem);
89 struct console *console_drivers;
90 EXPORT_SYMBOL_GPL(console_drivers);
93 * This is used for debugging the mess that is the VT code by
94 * keeping track if we have the console semaphore held. It's
95 * definitely not the perfect debug tool (we don't know if _WE_
96 * hold it are racing, but it helps tracking those weird code
97 * path in the console code where we end up in places I want
98 * locked without the console sempahore held
100 static int console_locked, console_suspended;
103 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
104 * It is also used in interesting ways to provide interlocking in
107 static DEFINE_SPINLOCK(logbuf_lock);
109 #define LOG_BUF_MASK (log_buf_len-1)
110 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
113 * The indices into log_buf are not constrained to log_buf_len - they
114 * must be masked before subscripting
116 static unsigned log_start; /* Index into log_buf: next char to be read by syslog() */
117 static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */
118 static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */
121 * If exclusive_console is non-NULL then only this console is to be printed to.
123 static struct console *exclusive_console;
126 * Array of consoles built from command line options (console=)
128 struct console_cmdline
130 char name[8]; /* Name of the driver */
131 int index; /* Minor dev. to use */
132 char *options; /* Options for the driver */
133 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
134 char *brl_options; /* Options for braille driver */
138 #define MAX_CMDLINECONSOLES 8
140 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
141 static int selected_console = -1;
142 static int preferred_console = -1;
143 int console_set_on_cmdline;
144 EXPORT_SYMBOL(console_set_on_cmdline);
146 /* Flag: console code may call schedule() */
147 static int console_may_schedule;
151 static char __log_buf[__LOG_BUF_LEN];
152 static char *log_buf = __log_buf;
153 static int log_buf_len = __LOG_BUF_LEN;
154 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
155 static int saved_console_loglevel = -1;
159 * This appends the listed symbols to /proc/vmcoreinfo
161 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
162 * obtain access to symbols that are otherwise very difficult to locate. These
163 * symbols are specifically used so that utilities can access and extract the
164 * dmesg log from a vmcore file after a crash.
166 void log_buf_kexec_setup(void)
168 VMCOREINFO_SYMBOL(log_buf);
169 VMCOREINFO_SYMBOL(log_end);
170 VMCOREINFO_SYMBOL(log_buf_len);
171 VMCOREINFO_SYMBOL(logged_chars);
175 /* requested log_buf_len from kernel cmdline */
176 static unsigned long __initdata new_log_buf_len;
178 /* save requested log_buf_len since it's too early to process it */
179 static int __init log_buf_len_setup(char *str)
181 unsigned size = memparse(str, &str);
184 size = roundup_pow_of_two(size);
185 if (size > log_buf_len)
186 new_log_buf_len = size;
190 early_param("log_buf_len", log_buf_len_setup);
192 void __init setup_log_buf(int early)
195 unsigned start, dest_idx, offset;
199 if (!new_log_buf_len)
205 mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
206 if (mem == MEMBLOCK_ERROR)
208 new_log_buf = __va(mem);
210 new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
213 if (unlikely(!new_log_buf)) {
214 pr_err("log_buf_len: %ld bytes not available\n",
219 spin_lock_irqsave(&logbuf_lock, flags);
220 log_buf_len = new_log_buf_len;
221 log_buf = new_log_buf;
223 free = __LOG_BUF_LEN - log_end;
225 offset = start = min(con_start, log_start);
227 while (start != log_end) {
228 unsigned log_idx_mask = start & (__LOG_BUF_LEN - 1);
230 log_buf[dest_idx] = __log_buf[log_idx_mask];
237 spin_unlock_irqrestore(&logbuf_lock, flags);
239 pr_info("log_buf_len: %d\n", log_buf_len);
240 pr_info("early log buf free: %d(%d%%)\n",
241 free, (free * 100) / __LOG_BUF_LEN);
244 #ifdef CONFIG_BOOT_PRINTK_DELAY
246 static int boot_delay; /* msecs delay after each printk during bootup */
247 static unsigned long long loops_per_msec; /* based on boot_delay */
249 static int __init boot_delay_setup(char *str)
253 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
254 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
256 get_option(&str, &boot_delay);
257 if (boot_delay > 10 * 1000)
260 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
261 "HZ: %d, loops_per_msec: %llu\n",
262 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
265 __setup("boot_delay=", boot_delay_setup);
267 static void boot_delay_msec(void)
269 unsigned long long k;
270 unsigned long timeout;
272 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
275 k = (unsigned long long)loops_per_msec * boot_delay;
277 timeout = jiffies + msecs_to_jiffies(boot_delay);
282 * use (volatile) jiffies to prevent
283 * compiler reduction; loop termination via jiffies
284 * is secondary and may or may not happen.
286 if (time_after(jiffies, timeout))
288 touch_nmi_watchdog();
292 static inline void boot_delay_msec(void)
298 * Return the number of unread characters in the log buffer.
300 static int log_buf_get_len(void)
306 * Clears the ring-buffer
308 void log_buf_clear(void)
314 * Copy a range of characters from the log buffer.
316 int log_buf_copy(char *dest, int idx, int len)
319 bool took_lock = false;
321 if (!oops_in_progress) {
322 spin_lock_irq(&logbuf_lock);
326 max = log_buf_get_len();
327 if (idx < 0 || idx >= max) {
333 idx += (log_end - max);
335 dest[len] = LOG_BUF(idx + len);
339 spin_unlock_irq(&logbuf_lock);
344 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
345 int dmesg_restrict = 1;
350 static int syslog_action_restricted(int type)
354 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
355 return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
358 static int check_syslog_permissions(int type, bool from_file)
361 * If this is from /proc/kmsg and we've already opened it, then we've
362 * already done the capabilities checks at open time.
364 if (from_file && type != SYSLOG_ACTION_OPEN)
367 if (syslog_action_restricted(type)) {
368 if (capable(CAP_SYSLOG))
370 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
371 if (capable(CAP_SYS_ADMIN)) {
372 printk_once(KERN_WARNING "%s (%d): "
373 "Attempt to access syslog with CAP_SYS_ADMIN "
374 "but no CAP_SYSLOG (deprecated).\n",
375 current->comm, task_pid_nr(current));
383 int do_syslog(int type, char __user *buf, int len, bool from_file)
385 unsigned i, j, limit, count;
390 error = check_syslog_permissions(type, from_file);
394 error = security_syslog(type);
399 case SYSLOG_ACTION_CLOSE: /* Close log */
401 case SYSLOG_ACTION_OPEN: /* Open log */
403 case SYSLOG_ACTION_READ: /* Read from log */
410 if (!access_ok(VERIFY_WRITE, buf, len)) {
414 error = wait_event_interruptible(log_wait,
415 (log_start - log_end));
419 spin_lock_irq(&logbuf_lock);
420 while (!error && (log_start != log_end) && i < len) {
421 c = LOG_BUF(log_start);
423 spin_unlock_irq(&logbuf_lock);
424 error = __put_user(c,buf);
428 spin_lock_irq(&logbuf_lock);
430 spin_unlock_irq(&logbuf_lock);
434 /* Read/clear last kernel messages */
435 case SYSLOG_ACTION_READ_CLEAR:
438 /* Read last kernel messages */
439 case SYSLOG_ACTION_READ_ALL:
446 if (!access_ok(VERIFY_WRITE, buf, len)) {
451 if (count > log_buf_len)
453 spin_lock_irq(&logbuf_lock);
454 if (count > logged_chars)
455 count = logged_chars;
460 * __put_user() could sleep, and while we sleep
461 * printk() could overwrite the messages
462 * we try to copy to user space. Therefore
463 * the messages are copied in reverse. <manfreds>
465 for (i = 0; i < count && !error; i++) {
467 if (j + log_buf_len < log_end)
470 spin_unlock_irq(&logbuf_lock);
471 error = __put_user(c,&buf[count-1-i]);
473 spin_lock_irq(&logbuf_lock);
475 spin_unlock_irq(&logbuf_lock);
480 int offset = count-error;
481 /* buffer overflow during copy, correct user buffer. */
482 for (i = 0; i < error; i++) {
483 if (__get_user(c,&buf[i+offset]) ||
484 __put_user(c,&buf[i])) {
492 /* Clear ring buffer */
493 case SYSLOG_ACTION_CLEAR:
496 /* Disable logging to console */
497 case SYSLOG_ACTION_CONSOLE_OFF:
498 if (saved_console_loglevel == -1)
499 saved_console_loglevel = console_loglevel;
500 console_loglevel = minimum_console_loglevel;
502 /* Enable logging to console */
503 case SYSLOG_ACTION_CONSOLE_ON:
504 if (saved_console_loglevel != -1) {
505 console_loglevel = saved_console_loglevel;
506 saved_console_loglevel = -1;
509 /* Set level of messages printed to console */
510 case SYSLOG_ACTION_CONSOLE_LEVEL:
512 if (len < 1 || len > 8)
514 if (len < minimum_console_loglevel)
515 len = minimum_console_loglevel;
516 console_loglevel = len;
517 /* Implicitly re-enable logging to console */
518 saved_console_loglevel = -1;
521 /* Number of chars in the log buffer */
522 case SYSLOG_ACTION_SIZE_UNREAD:
523 error = log_end - log_start;
525 /* Size of the log buffer */
526 case SYSLOG_ACTION_SIZE_BUFFER:
537 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
539 return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
542 #ifdef CONFIG_KGDB_KDB
543 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
544 * uses locks so it cannot be used during debugging. Just tell kdb
545 * where the start and end of the physical and logical logs are. This
546 * is equivalent to do_syslog(3).
548 void kdb_syslog_data(char *syslog_data[4])
550 syslog_data[0] = log_buf;
551 syslog_data[1] = log_buf + log_buf_len;
552 syslog_data[2] = log_buf + log_end -
553 (logged_chars < log_buf_len ? logged_chars : log_buf_len);
554 syslog_data[3] = log_buf + log_end;
556 #endif /* CONFIG_KGDB_KDB */
559 * Call the console drivers on a range of log_buf
561 static void __call_console_drivers(unsigned start, unsigned end)
565 for_each_console(con) {
566 if (exclusive_console && con != exclusive_console)
568 if ((con->flags & CON_ENABLED) && con->write &&
569 (cpu_online(smp_processor_id()) ||
570 (con->flags & CON_ANYTIME)))
571 con->write(con, &LOG_BUF(start), end - start);
575 static int __read_mostly ignore_loglevel;
577 static int __init ignore_loglevel_setup(char *str)
580 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
585 early_param("ignore_loglevel", ignore_loglevel_setup);
588 * Write out chars from start to end - 1 inclusive
590 static void _call_console_drivers(unsigned start,
591 unsigned end, int msg_log_level)
593 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
594 console_drivers && start != end) {
595 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
597 __call_console_drivers(start & LOG_BUF_MASK,
599 __call_console_drivers(0, end & LOG_BUF_MASK);
601 __call_console_drivers(start, end);
607 * Parse the syslog header <[0-9]*>. The decimal value represents 32bit, the
608 * lower 3 bit are the log level, the rest are the log facility. In case
609 * userspace passes usual userspace syslog messages to /dev/kmsg or
610 * /dev/ttyprintk, the log prefix might contain the facility. Printk needs
611 * to extract the correct log level for in-kernel processing, and not mangle
612 * the original value.
614 * If a prefix is found, the length of the prefix is returned. If 'level' is
615 * passed, it will be filled in with the log level without a possible facility
616 * value. If 'special' is passed, the special printk prefix chars are accepted
617 * and returned. If no valid header is found, 0 is returned and the passed
618 * variables are not touched.
620 static size_t log_prefix(const char *p, unsigned int *level, char *special)
622 unsigned int lev = 0;
626 if (p[0] != '<' || !p[1])
629 /* usual single digit level number or special char */
634 case 'c': /* KERN_CONT */
635 case 'd': /* KERN_DEFAULT */
643 /* multi digit including the level and facility number */
646 if (p[1] < '0' && p[1] > '9')
649 lev = (simple_strtoul(&p[1], &endp, 10) & 7);
650 if (endp == NULL || endp[0] != '>')
652 len = (endp + 1) - p;
655 /* do not accept special char if not asked for */
661 /* return special char, do not touch level */
672 * Call the console drivers, asking them to write out
673 * log_buf[start] to log_buf[end - 1].
674 * The console_lock must be held.
676 static void call_console_drivers(unsigned start, unsigned end)
678 unsigned cur_index, start_print;
679 static int msg_level = -1;
681 BUG_ON(((int)(start - end)) > 0);
685 while (cur_index != end) {
686 if (msg_level < 0 && ((end - cur_index) > 2)) {
687 /* strip log prefix */
688 cur_index += log_prefix(&LOG_BUF(cur_index), &msg_level, NULL);
689 start_print = cur_index;
691 while (cur_index != end) {
692 char c = LOG_BUF(cur_index);
698 * printk() has already given us loglevel tags in
699 * the buffer. This code is here in case the
700 * log buffer has wrapped right round and scribbled
703 msg_level = default_message_loglevel;
705 _call_console_drivers(start_print, cur_index, msg_level);
707 start_print = cur_index;
712 _call_console_drivers(start_print, end, msg_level);
715 static void emit_log_char(char c)
717 LOG_BUF(log_end) = c;
719 if (log_end - log_start > log_buf_len)
720 log_start = log_end - log_buf_len;
721 if (log_end - con_start > log_buf_len)
722 con_start = log_end - log_buf_len;
723 if (logged_chars < log_buf_len)
728 * Zap console related locks when oopsing. Only zap at most once
729 * every 10 seconds, to leave time for slow consoles to print a
732 static void zap_locks(void)
734 static unsigned long oops_timestamp;
736 if (time_after_eq(jiffies, oops_timestamp) &&
737 !time_after(jiffies, oops_timestamp + 30 * HZ))
740 oops_timestamp = jiffies;
742 /* If a crash is occurring, make sure we can't deadlock */
743 spin_lock_init(&logbuf_lock);
744 /* And make sure that we print immediately */
745 sema_init(&console_sem, 1);
748 #if defined(CONFIG_PRINTK_TIME)
749 static int printk_time = 1;
751 static int printk_time = 0;
753 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
755 /* Check if we have any console registered that can be called early in boot. */
756 static int have_callable_console(void)
760 for_each_console(con)
761 if (con->flags & CON_ANYTIME)
768 * printk - print a kernel message
769 * @fmt: format string
771 * This is printk(). It can be called from any context. We want it to work.
773 * We try to grab the console_lock. If we succeed, it's easy - we log the output and
774 * call the console drivers. If we fail to get the semaphore we place the output
775 * into the log buffer and return. The current holder of the console_sem will
776 * notice the new output in console_unlock(); and will send it to the
777 * consoles before releasing the lock.
779 * One effect of this deferred printing is that code which calls printk() and
780 * then changes console_loglevel may break. This is because console_loglevel
781 * is inspected when the actual printing occurs.
786 * See the vsnprintf() documentation for format string extensions over C99.
789 asmlinkage int printk(const char *fmt, ...)
794 #ifdef CONFIG_KGDB_KDB
795 if (unlikely(kdb_trap_printk)) {
797 r = vkdb_printf(fmt, args);
803 r = vprintk(fmt, args);
809 /* cpu currently holding logbuf_lock */
810 static volatile unsigned int printk_cpu = UINT_MAX;
813 * Can we actually use the console at this time on this cpu?
815 * Console drivers may assume that per-cpu resources have
816 * been allocated. So unless they're explicitly marked as
817 * being able to cope (CON_ANYTIME) don't call them until
818 * this CPU is officially up.
820 static inline int can_use_console(unsigned int cpu)
822 return cpu_online(cpu) || have_callable_console();
826 * Try to get console ownership to actually show the kernel
827 * messages from a 'printk'. Return true (and with the
828 * console_lock held, and 'console_locked' set) if it
829 * is successful, false otherwise.
831 * This gets called with the 'logbuf_lock' spinlock held and
832 * interrupts disabled. It should return with 'lockbuf_lock'
833 * released but interrupts still disabled.
835 static int console_trylock_for_printk(unsigned int cpu)
836 __releases(&logbuf_lock)
840 if (console_trylock()) {
844 * If we can't use the console, we need to release
845 * the console semaphore by hand to avoid flushing
846 * the buffer. We need to hold the console semaphore
847 * in order to do this test safely.
849 if (!can_use_console(cpu)) {
855 printk_cpu = UINT_MAX;
856 spin_unlock(&logbuf_lock);
859 static const char recursion_bug_msg [] =
860 KERN_CRIT "BUG: recent printk recursion!\n";
861 static int recursion_bug;
862 static int new_text_line = 1;
863 static char printk_buf[1024];
865 int printk_delay_msec __read_mostly;
867 static inline void printk_delay(void)
869 if (unlikely(printk_delay_msec)) {
870 int m = printk_delay_msec;
874 touch_nmi_watchdog();
879 asmlinkage int vprintk(const char *fmt, va_list args)
882 int current_log_level = default_message_loglevel;
893 /* This stops the holder of console_sem just where we want him */
894 raw_local_irq_save(flags);
895 this_cpu = smp_processor_id();
898 * Ouch, printk recursed into itself!
900 if (unlikely(printk_cpu == this_cpu)) {
902 * If a crash is occurring during printk() on this CPU,
903 * then try to get the crash message out but make sure
904 * we can't deadlock. Otherwise just return to avoid the
905 * recursion and return - but flag the recursion so that
906 * it can be printed at the next appropriate moment:
908 if (!oops_in_progress) {
910 goto out_restore_irqs;
916 spin_lock(&logbuf_lock);
917 printk_cpu = this_cpu;
921 strcpy(printk_buf, recursion_bug_msg);
922 printed_len = strlen(recursion_bug_msg);
924 /* Emit the output into the temporary buffer */
925 printed_len += vscnprintf(printk_buf + printed_len,
926 sizeof(printk_buf) - printed_len, fmt, args);
928 #ifdef CONFIG_DEBUG_LL
929 printascii(printk_buf);
934 /* Read log level and handle special printk prefix */
935 plen = log_prefix(p, ¤t_log_level, &special);
940 case 'c': /* Strip <c> KERN_CONT, continue line */
943 case 'd': /* Strip <d> KERN_DEFAULT, start new line */
946 if (!new_text_line) {
954 * Copy the output into log_buf. If the caller didn't provide
955 * the appropriate log prefix, we insert them here
962 /* Copy original log prefix */
965 for (i = 0; i < plen; i++)
966 emit_log_char(printk_buf[i]);
971 emit_log_char(current_log_level + '0');
977 /* Add the current time stamp */
980 unsigned long long t;
981 unsigned long nanosec_rem;
983 t = cpu_clock(printk_cpu);
984 nanosec_rem = do_div(t, 1000000000);
985 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
989 for (tp = tbuf; tp < tbuf + tlen; tp++)
1004 * Try to acquire and then immediately release the
1005 * console semaphore. The release will do all the
1006 * actual magic (print out buffers, wake up klogd,
1009 * The console_trylock_for_printk() function
1010 * will release 'logbuf_lock' regardless of whether it
1011 * actually gets the semaphore or not.
1013 if (console_trylock_for_printk(this_cpu))
1018 raw_local_irq_restore(flags);
1023 EXPORT_SYMBOL(printk);
1024 EXPORT_SYMBOL(vprintk);
1026 #ifdef CONFIG_PLAT_RK
1027 void pm_emit_log_char(char c)
1033 #ifdef CONFIG_RK29_LAST_LOG
1034 void switch_log_buf(char *new_log_buf, int size)
1036 unsigned long flags;
1038 if (!new_log_buf || log_buf_len > size)
1041 spin_lock_irqsave(&logbuf_lock, flags);
1042 memcpy(new_log_buf, log_buf, min(log_buf_len, size));
1043 log_buf = new_log_buf;
1045 spin_unlock_irqrestore(&logbuf_lock, flags);
1047 #endif /* CONFIG_RK29_LAST_LOG */
1050 static void call_console_drivers(unsigned start, unsigned end)
1056 static int __add_preferred_console(char *name, int idx, char *options,
1059 struct console_cmdline *c;
1063 * See if this tty is not yet registered, and
1064 * if we have a slot free.
1066 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1067 if (strcmp(console_cmdline[i].name, name) == 0 &&
1068 console_cmdline[i].index == idx) {
1070 selected_console = i;
1073 if (i == MAX_CMDLINECONSOLES)
1076 selected_console = i;
1077 c = &console_cmdline[i];
1078 strlcpy(c->name, name, sizeof(c->name));
1079 c->options = options;
1080 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1081 c->brl_options = brl_options;
1087 * Set up a list of consoles. Called from init/main.c
1089 static int __init console_setup(char *str)
1091 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1092 char *s, *options, *brl_options = NULL;
1095 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1096 if (!memcmp(str, "brl,", 4)) {
1099 } else if (!memcmp(str, "brl=", 4)) {
1100 brl_options = str + 4;
1101 str = strchr(brl_options, ',');
1103 printk(KERN_ERR "need port name after brl=\n");
1111 * Decode str into name, index, options.
1113 if (str[0] >= '0' && str[0] <= '9') {
1114 strcpy(buf, "ttyS");
1115 strncpy(buf + 4, str, sizeof(buf) - 5);
1117 strncpy(buf, str, sizeof(buf) - 1);
1119 buf[sizeof(buf) - 1] = 0;
1120 if ((options = strchr(str, ',')) != NULL)
1123 if (!strcmp(str, "ttya"))
1124 strcpy(buf, "ttyS0");
1125 if (!strcmp(str, "ttyb"))
1126 strcpy(buf, "ttyS1");
1128 for (s = buf; *s; s++)
1129 if ((*s >= '0' && *s <= '9') || *s == ',')
1131 idx = simple_strtoul(s, NULL, 10);
1134 __add_preferred_console(buf, idx, options, brl_options);
1135 console_set_on_cmdline = 1;
1138 __setup("console=", console_setup);
1141 * add_preferred_console - add a device to the list of preferred consoles.
1142 * @name: device name
1143 * @idx: device index
1144 * @options: options for this console
1146 * The last preferred console added will be used for kernel messages
1147 * and stdin/out/err for init. Normally this is used by console_setup
1148 * above to handle user-supplied console arguments; however it can also
1149 * be used by arch-specific code either to override the user or more
1150 * commonly to provide a default console (ie from PROM variables) when
1151 * the user has not supplied one.
1153 int add_preferred_console(char *name, int idx, char *options)
1155 return __add_preferred_console(name, idx, options, NULL);
1158 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1160 struct console_cmdline *c;
1163 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1164 if (strcmp(console_cmdline[i].name, name) == 0 &&
1165 console_cmdline[i].index == idx) {
1166 c = &console_cmdline[i];
1167 strlcpy(c->name, name_new, sizeof(c->name));
1168 c->name[sizeof(c->name) - 1] = 0;
1169 c->options = options;
1177 int console_suspend_enabled = 1;
1178 EXPORT_SYMBOL(console_suspend_enabled);
1180 static int __init console_suspend_disable(char *str)
1182 console_suspend_enabled = 0;
1185 __setup("no_console_suspend", console_suspend_disable);
1188 * suspend_console - suspend the console subsystem
1190 * This disables printk() while we go into suspend states
1192 void suspend_console(void)
1194 if (!console_suspend_enabled)
1196 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1198 console_suspended = 1;
1202 void resume_console(void)
1204 if (!console_suspend_enabled)
1207 console_suspended = 0;
1212 * console_cpu_notify - print deferred console messages after CPU hotplug
1213 * @self: notifier struct
1214 * @action: CPU hotplug event
1217 * If printk() is called from a CPU that is not online yet, the messages
1218 * will be spooled but will not show up on the console. This function is
1219 * called when a new CPU comes online (or fails to come up), and ensures
1220 * that any such output gets printed.
1222 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1223 unsigned long action, void *hcpu)
1228 case CPU_DOWN_FAILED:
1229 case CPU_UP_CANCELED:
1237 * console_lock - lock the console system for exclusive use.
1239 * Acquires a lock which guarantees that the caller has
1240 * exclusive access to the console system and the console_drivers list.
1242 * Can sleep, returns nothing.
1244 void console_lock(void)
1246 BUG_ON(in_interrupt());
1248 if (console_suspended)
1251 console_may_schedule = 1;
1253 EXPORT_SYMBOL(console_lock);
1256 * console_trylock - try to lock the console system for exclusive use.
1258 * Tried to acquire a lock which guarantees that the caller has
1259 * exclusive access to the console system and the console_drivers list.
1261 * returns 1 on success, and 0 on failure to acquire the lock.
1263 int console_trylock(void)
1265 if (down_trylock(&console_sem))
1267 if (console_suspended) {
1272 console_may_schedule = 0;
1275 EXPORT_SYMBOL(console_trylock);
1277 int is_console_locked(void)
1279 return console_locked;
1282 static DEFINE_PER_CPU(int, printk_pending);
1284 void printk_tick(void)
1286 if (__this_cpu_read(printk_pending)) {
1287 __this_cpu_write(printk_pending, 0);
1288 wake_up_interruptible(&log_wait);
1292 int printk_needs_cpu(int cpu)
1294 if (cpu_is_offline(cpu))
1296 return __this_cpu_read(printk_pending);
1299 void wake_up_klogd(void)
1301 if (waitqueue_active(&log_wait))
1302 this_cpu_write(printk_pending, 1);
1306 * console_unlock - unlock the console system
1308 * Releases the console_lock which the caller holds on the console system
1309 * and the console driver list.
1311 * While the console_lock was held, console output may have been buffered
1312 * by printk(). If this is the case, console_unlock(); emits
1313 * the output prior to releasing the lock.
1315 * If there is output waiting for klogd, we wake it up.
1317 * console_unlock(); may be called from any context.
1319 void console_unlock(void)
1321 unsigned long flags;
1322 unsigned _con_start, _log_end;
1323 unsigned wake_klogd = 0;
1325 if (console_suspended) {
1330 console_may_schedule = 0;
1333 spin_lock_irqsave(&logbuf_lock, flags);
1334 wake_klogd |= log_start - log_end;
1335 if (con_start == log_end)
1336 break; /* Nothing to print */
1337 _con_start = con_start;
1339 con_start = log_end; /* Flush */
1340 spin_unlock(&logbuf_lock);
1341 stop_critical_timings(); /* don't trace print latency */
1342 call_console_drivers(_con_start, _log_end);
1343 start_critical_timings();
1344 local_irq_restore(flags);
1348 /* Release the exclusive_console once it is used */
1349 if (unlikely(exclusive_console))
1350 exclusive_console = NULL;
1353 spin_unlock_irqrestore(&logbuf_lock, flags);
1357 EXPORT_SYMBOL(console_unlock);
1360 * console_conditional_schedule - yield the CPU if required
1362 * If the console code is currently allowed to sleep, and
1363 * if this CPU should yield the CPU to another task, do
1366 * Must be called within console_lock();.
1368 void __sched console_conditional_schedule(void)
1370 if (console_may_schedule)
1373 EXPORT_SYMBOL(console_conditional_schedule);
1375 void console_unblank(void)
1380 * console_unblank can no longer be called in interrupt context unless
1381 * oops_in_progress is set to 1..
1383 if (oops_in_progress) {
1384 if (down_trylock(&console_sem) != 0)
1390 console_may_schedule = 0;
1392 if ((c->flags & CON_ENABLED) && c->unblank)
1398 * Return the console tty driver structure and its associated index
1400 struct tty_driver *console_device(int *index)
1403 struct tty_driver *driver = NULL;
1406 for_each_console(c) {
1409 driver = c->device(c, index);
1418 * Prevent further output on the passed console device so that (for example)
1419 * serial drivers can disable console output before suspending a port, and can
1420 * re-enable output afterwards.
1422 void console_stop(struct console *console)
1425 console->flags &= ~CON_ENABLED;
1428 EXPORT_SYMBOL(console_stop);
1430 void console_start(struct console *console)
1433 console->flags |= CON_ENABLED;
1436 EXPORT_SYMBOL(console_start);
1438 static int __read_mostly keep_bootcon;
1440 static int __init keep_bootcon_setup(char *str)
1443 printk(KERN_INFO "debug: skip boot console de-registration.\n");
1448 early_param("keep_bootcon", keep_bootcon_setup);
1451 * The console driver calls this routine during kernel initialization
1452 * to register the console printing procedure with printk() and to
1453 * print any messages that were printed by the kernel before the
1454 * console driver was initialized.
1456 * This can happen pretty early during the boot process (because of
1457 * early_printk) - sometimes before setup_arch() completes - be careful
1458 * of what kernel features are used - they may not be initialised yet.
1460 * There are two types of consoles - bootconsoles (early_printk) and
1461 * "real" consoles (everything which is not a bootconsole) which are
1462 * handled differently.
1463 * - Any number of bootconsoles can be registered at any time.
1464 * - As soon as a "real" console is registered, all bootconsoles
1465 * will be unregistered automatically.
1466 * - Once a "real" console is registered, any attempt to register a
1467 * bootconsoles will be rejected
1469 void register_console(struct console *newcon)
1472 unsigned long flags;
1473 struct console *bcon = NULL;
1476 * before we register a new CON_BOOT console, make sure we don't
1477 * already have a valid console
1479 if (console_drivers && newcon->flags & CON_BOOT) {
1480 /* find the last or real console */
1481 for_each_console(bcon) {
1482 if (!(bcon->flags & CON_BOOT)) {
1483 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1484 newcon->name, newcon->index);
1490 if (console_drivers && console_drivers->flags & CON_BOOT)
1491 bcon = console_drivers;
1493 if (preferred_console < 0 || bcon || !console_drivers)
1494 preferred_console = selected_console;
1496 if (newcon->early_setup)
1497 newcon->early_setup();
1500 * See if we want to use this console driver. If we
1501 * didn't select a console we take the first one
1502 * that registers here.
1504 if (preferred_console < 0) {
1505 if (newcon->index < 0)
1507 if (newcon->setup == NULL ||
1508 newcon->setup(newcon, NULL) == 0) {
1509 newcon->flags |= CON_ENABLED;
1510 if (newcon->device) {
1511 newcon->flags |= CON_CONSDEV;
1512 preferred_console = 0;
1518 * See if this console matches one we selected on
1521 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1523 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1525 if (newcon->index >= 0 &&
1526 newcon->index != console_cmdline[i].index)
1528 if (newcon->index < 0)
1529 newcon->index = console_cmdline[i].index;
1530 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1531 if (console_cmdline[i].brl_options) {
1532 newcon->flags |= CON_BRL;
1533 braille_register_console(newcon,
1534 console_cmdline[i].index,
1535 console_cmdline[i].options,
1536 console_cmdline[i].brl_options);
1540 if (newcon->setup &&
1541 newcon->setup(newcon, console_cmdline[i].options) != 0)
1543 newcon->flags |= CON_ENABLED;
1544 newcon->index = console_cmdline[i].index;
1545 if (i == selected_console) {
1546 newcon->flags |= CON_CONSDEV;
1547 preferred_console = selected_console;
1552 if (!(newcon->flags & CON_ENABLED))
1556 * If we have a bootconsole, and are switching to a real console,
1557 * don't print everything out again, since when the boot console, and
1558 * the real console are the same physical device, it's annoying to
1559 * see the beginning boot messages twice
1561 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1562 newcon->flags &= ~CON_PRINTBUFFER;
1565 * Put this console in the list - keep the
1566 * preferred driver at the head of the list.
1569 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1570 newcon->next = console_drivers;
1571 console_drivers = newcon;
1573 newcon->next->flags &= ~CON_CONSDEV;
1575 newcon->next = console_drivers->next;
1576 console_drivers->next = newcon;
1578 if (newcon->flags & CON_PRINTBUFFER) {
1580 * console_unlock(); will print out the buffered messages
1583 spin_lock_irqsave(&logbuf_lock, flags);
1584 con_start = log_start;
1585 spin_unlock_irqrestore(&logbuf_lock, flags);
1587 * We're about to replay the log buffer. Only do this to the
1588 * just-registered console to avoid excessive message spam to
1589 * the already-registered consoles.
1591 exclusive_console = newcon;
1594 console_sysfs_notify();
1597 * By unregistering the bootconsoles after we enable the real console
1598 * we get the "console xxx enabled" message on all the consoles -
1599 * boot consoles, real consoles, etc - this is to ensure that end
1600 * users know there might be something in the kernel's log buffer that
1601 * went to the bootconsole (that they do not see on the real console)
1604 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
1606 /* we need to iterate through twice, to make sure we print
1607 * everything out, before we unregister the console(s)
1609 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1610 newcon->name, newcon->index);
1611 for_each_console(bcon)
1612 if (bcon->flags & CON_BOOT)
1613 unregister_console(bcon);
1615 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1616 (newcon->flags & CON_BOOT) ? "boot" : "" ,
1617 newcon->name, newcon->index);
1620 EXPORT_SYMBOL(register_console);
1622 int unregister_console(struct console *console)
1624 struct console *a, *b;
1627 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1628 if (console->flags & CON_BRL)
1629 return braille_unregister_console(console);
1633 if (console_drivers == console) {
1634 console_drivers=console->next;
1636 } else if (console_drivers) {
1637 for (a=console_drivers->next, b=console_drivers ;
1638 a; b=a, a=b->next) {
1648 * If this isn't the last console and it has CON_CONSDEV set, we
1649 * need to set it on the next preferred console.
1651 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1652 console_drivers->flags |= CON_CONSDEV;
1655 console_sysfs_notify();
1658 EXPORT_SYMBOL(unregister_console);
1660 static int __init printk_late_init(void)
1662 struct console *con;
1664 for_each_console(con) {
1665 if (!keep_bootcon && con->flags & CON_BOOT) {
1666 printk(KERN_INFO "turn off boot console %s%d\n",
1667 con->name, con->index);
1668 unregister_console(con);
1671 hotcpu_notifier(console_cpu_notify, 0);
1674 late_initcall(printk_late_init);
1676 #if defined CONFIG_PRINTK
1679 * printk rate limiting, lifted from the networking subsystem.
1681 * This enforces a rate limit: not more than 10 kernel messages
1682 * every 5s to make a denial-of-service attack impossible.
1684 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1686 int __printk_ratelimit(const char *func)
1688 return ___ratelimit(&printk_ratelimit_state, func);
1690 EXPORT_SYMBOL(__printk_ratelimit);
1693 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1694 * @caller_jiffies: pointer to caller's state
1695 * @interval_msecs: minimum interval between prints
1697 * printk_timed_ratelimit() returns true if more than @interval_msecs
1698 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1701 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1702 unsigned int interval_msecs)
1704 if (*caller_jiffies == 0
1705 || !time_in_range(jiffies, *caller_jiffies,
1707 + msecs_to_jiffies(interval_msecs))) {
1708 *caller_jiffies = jiffies;
1713 EXPORT_SYMBOL(printk_timed_ratelimit);
1715 static DEFINE_SPINLOCK(dump_list_lock);
1716 static LIST_HEAD(dump_list);
1719 * kmsg_dump_register - register a kernel log dumper.
1720 * @dumper: pointer to the kmsg_dumper structure
1722 * Adds a kernel log dumper to the system. The dump callback in the
1723 * structure will be called when the kernel oopses or panics and must be
1724 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1726 int kmsg_dump_register(struct kmsg_dumper *dumper)
1728 unsigned long flags;
1731 /* The dump callback needs to be set */
1735 spin_lock_irqsave(&dump_list_lock, flags);
1736 /* Don't allow registering multiple times */
1737 if (!dumper->registered) {
1738 dumper->registered = 1;
1739 list_add_tail_rcu(&dumper->list, &dump_list);
1742 spin_unlock_irqrestore(&dump_list_lock, flags);
1746 EXPORT_SYMBOL_GPL(kmsg_dump_register);
1749 * kmsg_dump_unregister - unregister a kmsg dumper.
1750 * @dumper: pointer to the kmsg_dumper structure
1752 * Removes a dump device from the system. Returns zero on success and
1753 * %-EINVAL otherwise.
1755 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
1757 unsigned long flags;
1760 spin_lock_irqsave(&dump_list_lock, flags);
1761 if (dumper->registered) {
1762 dumper->registered = 0;
1763 list_del_rcu(&dumper->list);
1766 spin_unlock_irqrestore(&dump_list_lock, flags);
1771 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
1774 * kmsg_dump - dump kernel log to kernel message dumpers.
1775 * @reason: the reason (oops, panic etc) for dumping
1777 * Iterate through each of the dump devices and call the oops/panic
1778 * callbacks with the log buffer.
1780 void kmsg_dump(enum kmsg_dump_reason reason)
1784 struct kmsg_dumper *dumper;
1785 const char *s1, *s2;
1786 unsigned long l1, l2;
1787 unsigned long flags;
1789 /* Theoretically, the log could move on after we do this, but
1790 there's not a lot we can do about that. The new messages
1791 will overwrite the start of what we dump. */
1792 spin_lock_irqsave(&logbuf_lock, flags);
1793 end = log_end & LOG_BUF_MASK;
1794 chars = logged_chars;
1795 spin_unlock_irqrestore(&logbuf_lock, flags);
1798 s1 = log_buf + log_buf_len - chars + end;
1807 s2 = log_buf + end - chars;
1812 list_for_each_entry_rcu(dumper, &dump_list, list)
1813 dumper->dump(dumper, reason, s1, l1, s2, l2);