2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/memblock.h>
35 #include <linux/syscalls.h>
36 #include <linux/kexec.h>
37 #include <linux/kdb.h>
38 #include <linux/ratelimit.h>
39 #include <linux/kmsg_dump.h>
40 #include <linux/syslog.h>
41 #include <linux/cpu.h>
42 #include <linux/notifier.h>
43 #include <linux/rculist.h>
44 #include <linux/poll.h>
46 #include <asm/uaccess.h>
48 #define CREATE_TRACE_POINTS
49 #include <trace/events/printk.h>
52 * Architectures can override it:
54 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
58 /* printk's without a loglevel use this.. */
59 #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
61 /* We show everything that is MORE important than this.. */
62 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
63 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
65 DECLARE_WAIT_QUEUE_HEAD(log_wait);
67 int console_printk[4] = {
68 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
69 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
70 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
71 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
75 * Low level drivers may need that to know if they can schedule in
76 * their unblank() callback or not. So let's export it.
79 EXPORT_SYMBOL(oops_in_progress);
82 * console_sem protects the console_drivers list, and also
83 * provides serialisation for access to the entire console
86 static DEFINE_SEMAPHORE(console_sem);
87 struct console *console_drivers;
88 EXPORT_SYMBOL_GPL(console_drivers);
91 * This is used for debugging the mess that is the VT code by
92 * keeping track if we have the console semaphore held. It's
93 * definitely not the perfect debug tool (we don't know if _WE_
94 * hold it are racing, but it helps tracking those weird code
95 * path in the console code where we end up in places I want
96 * locked without the console sempahore held
98 static int console_locked, console_suspended;
101 * If exclusive_console is non-NULL then only this console is to be printed to.
103 static struct console *exclusive_console;
106 * Array of consoles built from command line options (console=)
108 struct console_cmdline
110 char name[8]; /* Name of the driver */
111 int index; /* Minor dev. to use */
112 char *options; /* Options for the driver */
113 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
114 char *brl_options; /* Options for braille driver */
118 #define MAX_CMDLINECONSOLES 8
120 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
121 static int selected_console = -1;
122 static int preferred_console = -1;
123 int console_set_on_cmdline;
124 EXPORT_SYMBOL(console_set_on_cmdline);
126 /* Flag: console code may call schedule() */
127 static int console_may_schedule;
131 * The printk log buffer consists of a chain of concatenated variable
132 * length records. Every record starts with a record header, containing
133 * the overall length of the record.
135 * The heads to the first and last entry in the buffer, as well as the
136 * sequence numbers of these both entries are maintained when messages
139 * If the heads indicate available messages, the length in the header
140 * tells the start next message. A length == 0 for the next message
141 * indicates a wrap-around to the beginning of the buffer.
143 * Every record carries the monotonic timestamp in microseconds, as well as
144 * the standard userspace syslog level and syslog facility. The usual
145 * kernel messages use LOG_KERN; userspace-injected messages always carry
146 * a matching syslog facility, by default LOG_USER. The origin of every
147 * message can be reliably determined that way.
149 * The human readable log message directly follows the message header. The
150 * length of the message text is stored in the header, the stored message
153 * Optionally, a message can carry a dictionary of properties (key/value pairs),
154 * to provide userspace with a machine-readable message context.
156 * Examples for well-defined, commonly used property names are:
157 * DEVICE=b12:8 device identifier
161 * +sound:card0 subsystem:devname
162 * SUBSYSTEM=pci driver-core subsystem name
164 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
165 * follows directly after a '=' character. Every property is terminated by
166 * a '\0' character. The last property is not terminated.
168 * Example of a message structure:
169 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
170 * 0008 34 00 record is 52 bytes long
171 * 000a 0b 00 text is 11 bytes long
172 * 000c 1f 00 dictionary is 23 bytes long
173 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
174 * 0010 69 74 27 73 20 61 20 6c "it's a l"
176 * 001b 44 45 56 49 43 "DEVIC"
177 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
178 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
180 * 0032 00 00 00 padding to next message header
182 * The 'struct log' buffer header must never be directly exported to
183 * userspace, it is a kernel-private implementation detail that might
184 * need to be changed in the future, when the requirements change.
186 * /dev/kmsg exports the structured data in the following line format:
187 * "level,sequnum,timestamp;<message text>\n"
189 * The optional key/value pairs are attached as continuation lines starting
190 * with a space character and terminated by a newline. All possible
191 * non-prinatable characters are escaped in the "\xff" notation.
193 * Users of the export format should ignore possible additional values
194 * separated by ',', and find the message after the ';' character.
198 u64 ts_nsec; /* timestamp in nanoseconds */
199 u16 len; /* length of entire record */
200 u16 text_len; /* length of text buffer */
201 u16 dict_len; /* length of dictionary buffer */
202 u16 level; /* syslog level + facility */
206 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
207 * used in interesting ways to provide interlocking in console_unlock();
209 static DEFINE_RAW_SPINLOCK(logbuf_lock);
211 /* cpu currently holding logbuf_lock */
212 static volatile unsigned int logbuf_cpu = UINT_MAX;
214 #define LOG_LINE_MAX 1024
217 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
218 static char __log_buf[__LOG_BUF_LEN];
219 static char *log_buf = __log_buf;
220 static u32 log_buf_len = __LOG_BUF_LEN;
222 /* index and sequence number of the first record stored in the buffer */
223 static u64 log_first_seq;
224 static u32 log_first_idx;
226 /* index and sequence number of the next record to store in the buffer */
227 static u64 log_next_seq;
228 static u32 log_next_idx;
230 /* the next printk record to read after the last 'clear' command */
231 static u64 clear_seq;
232 static u32 clear_idx;
234 /* the next printk record to read by syslog(READ) or /proc/kmsg */
235 static u64 syslog_seq;
236 static u32 syslog_idx;
238 /* human readable text of the record */
239 static char *log_text(const struct log *msg)
241 return (char *)msg + sizeof(struct log);
244 /* optional key/value pair dictionary attached to the record */
245 static char *log_dict(const struct log *msg)
247 return (char *)msg + sizeof(struct log) + msg->text_len;
250 /* get record by index; idx must point to valid msg */
251 static struct log *log_from_idx(u32 idx)
253 struct log *msg = (struct log *)(log_buf + idx);
256 * A length == 0 record is the end of buffer marker. Wrap around and
257 * read the message at the start of the buffer.
260 return (struct log *)log_buf;
264 /* get next record; idx must point to valid msg */
265 static u32 log_next(u32 idx)
267 struct log *msg = (struct log *)(log_buf + idx);
269 /* length == 0 indicates the end of the buffer; wrap */
271 * A length == 0 record is the end of buffer marker. Wrap around and
272 * read the message at the start of the buffer as *this* one, and
273 * return the one after that.
276 msg = (struct log *)log_buf;
279 return idx + msg->len;
282 #if !defined(CONFIG_64BIT) || defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
288 /* insert record into the buffer, discard old ones, update heads */
289 static void log_store(int facility, int level,
290 const char *dict, u16 dict_len,
291 const char *text, u16 text_len)
296 /* number of '\0' padding bytes to next message */
297 size = sizeof(struct log) + text_len + dict_len;
298 pad_len = (-size) & (LOG_ALIGN - 1);
301 while (log_first_seq < log_next_seq) {
304 if (log_next_idx > log_first_idx)
305 free = max(log_buf_len - log_next_idx, log_first_idx);
307 free = log_first_idx - log_next_idx;
309 if (free > size + sizeof(struct log))
312 /* drop old messages until we have enough contiuous space */
313 log_first_idx = log_next(log_first_idx);
317 if (log_next_idx + size + sizeof(struct log) >= log_buf_len) {
319 * This message + an additional empty header does not fit
320 * at the end of the buffer. Add an empty header with len == 0
321 * to signify a wrap around.
323 memset(log_buf + log_next_idx, 0, sizeof(struct log));
328 msg = (struct log *)(log_buf + log_next_idx);
329 memcpy(log_text(msg), text, text_len);
330 msg->text_len = text_len;
331 memcpy(log_dict(msg), dict, dict_len);
332 msg->dict_len = dict_len;
333 msg->level = (facility << 3) | (level & 7);
334 msg->ts_nsec = local_clock();
335 memset(log_dict(msg) + dict_len, 0, pad_len);
336 msg->len = sizeof(struct log) + text_len + dict_len + pad_len;
339 log_next_idx += msg->len;
343 /* /dev/kmsg - userspace message inject/listen interface */
344 struct devkmsg_user {
351 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
352 unsigned long count, loff_t pos)
356 int level = default_message_loglevel;
357 int facility = 1; /* LOG_USER */
358 size_t len = iov_length(iv, count);
361 if (len > LOG_LINE_MAX)
363 buf = kmalloc(len+1, GFP_KERNEL);
368 for (i = 0; i < count; i++) {
369 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len))
371 line += iv[i].iov_len;
375 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
376 * the decimal value represents 32bit, the lower 3 bit are the log
377 * level, the rest are the log facility.
379 * If no prefix or no userspace facility is specified, we
380 * enforce LOG_USER, to be able to reliably distinguish
381 * kernel-generated messages from userspace-injected ones.
384 if (line[0] == '<') {
387 i = simple_strtoul(line+1, &endp, 10);
388 if (endp && endp[0] == '>') {
399 printk_emit(facility, level, NULL, 0, "%s", line);
405 static ssize_t devkmsg_read(struct file *file, char __user *buf,
406 size_t count, loff_t *ppos)
408 struct devkmsg_user *user = file->private_data;
417 mutex_lock(&user->lock);
418 raw_spin_lock(&logbuf_lock);
419 while (user->seq == log_next_seq) {
420 if (file->f_flags & O_NONBLOCK) {
422 raw_spin_unlock(&logbuf_lock);
426 raw_spin_unlock(&logbuf_lock);
427 ret = wait_event_interruptible(log_wait,
428 user->seq != log_next_seq);
431 raw_spin_lock(&logbuf_lock);
434 if (user->seq < log_first_seq) {
435 /* our last seen message is gone, return error and reset */
436 user->idx = log_first_idx;
437 user->seq = log_first_seq;
439 raw_spin_unlock(&logbuf_lock);
443 msg = log_from_idx(user->idx);
444 len = sprintf(user->buf, "%u,%llu,%llu;",
445 msg->level, user->seq, msg->ts_nsec / 1000);
447 /* escape non-printable characters */
448 for (i = 0; i < msg->text_len; i++) {
449 char c = log_text(msg)[i];
451 if (c < ' ' || c >= 128)
452 len += sprintf(user->buf + len, "\\x%02x", c);
454 user->buf[len++] = c;
456 user->buf[len++] = '\n';
461 for (i = 0; i < msg->dict_len; i++) {
462 char c = log_dict(msg)[i];
465 user->buf[len++] = ' ';
470 user->buf[len++] = '\n';
475 if (c < ' ' || c >= 128) {
476 len += sprintf(user->buf + len, "\\x%02x", c);
480 user->buf[len++] = c;
482 user->buf[len++] = '\n';
485 user->idx = log_next(user->idx);
487 raw_spin_unlock(&logbuf_lock);
494 if (copy_to_user(buf, user->buf, len)) {
500 mutex_unlock(&user->lock);
504 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
506 struct devkmsg_user *user = file->private_data;
514 raw_spin_lock(&logbuf_lock);
517 /* the first record */
518 user->idx = log_first_idx;
519 user->seq = log_first_seq;
523 * The first record after the last SYSLOG_ACTION_CLEAR,
524 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
525 * changes no global state, and does not clear anything.
527 user->idx = clear_idx;
528 user->seq = clear_seq;
531 /* after the last record */
532 user->idx = log_next_idx;
533 user->seq = log_next_seq;
538 raw_spin_unlock(&logbuf_lock);
542 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
544 struct devkmsg_user *user = file->private_data;
548 return POLLERR|POLLNVAL;
550 poll_wait(file, &log_wait, wait);
552 raw_spin_lock(&logbuf_lock);
553 if (user->seq < log_next_seq) {
554 /* return error when data has vanished underneath us */
555 if (user->seq < log_first_seq)
556 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
557 ret = POLLIN|POLLRDNORM;
559 raw_spin_unlock(&logbuf_lock);
564 static int devkmsg_open(struct inode *inode, struct file *file)
566 struct devkmsg_user *user;
569 /* write-only does not need any file context */
570 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
573 err = security_syslog(SYSLOG_ACTION_READ_ALL);
577 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
581 mutex_init(&user->lock);
583 raw_spin_lock(&logbuf_lock);
584 user->idx = log_first_idx;
585 user->seq = log_first_seq;
586 raw_spin_unlock(&logbuf_lock);
588 file->private_data = user;
592 static int devkmsg_release(struct inode *inode, struct file *file)
594 struct devkmsg_user *user = file->private_data;
599 mutex_destroy(&user->lock);
604 const struct file_operations kmsg_fops = {
605 .open = devkmsg_open,
606 .read = devkmsg_read,
607 .aio_write = devkmsg_writev,
608 .llseek = devkmsg_llseek,
609 .poll = devkmsg_poll,
610 .release = devkmsg_release,
615 * This appends the listed symbols to /proc/vmcoreinfo
617 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
618 * obtain access to symbols that are otherwise very difficult to locate. These
619 * symbols are specifically used so that utilities can access and extract the
620 * dmesg log from a vmcore file after a crash.
622 void log_buf_kexec_setup(void)
624 VMCOREINFO_SYMBOL(log_buf);
625 VMCOREINFO_SYMBOL(log_buf_len);
626 VMCOREINFO_SYMBOL(log_first_idx);
627 VMCOREINFO_SYMBOL(log_next_idx);
631 /* requested log_buf_len from kernel cmdline */
632 static unsigned long __initdata new_log_buf_len;
634 /* save requested log_buf_len since it's too early to process it */
635 static int __init log_buf_len_setup(char *str)
637 unsigned size = memparse(str, &str);
640 size = roundup_pow_of_two(size);
641 if (size > log_buf_len)
642 new_log_buf_len = size;
646 early_param("log_buf_len", log_buf_len_setup);
648 void __init setup_log_buf(int early)
654 if (!new_log_buf_len)
660 mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
663 new_log_buf = __va(mem);
665 new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
668 if (unlikely(!new_log_buf)) {
669 pr_err("log_buf_len: %ld bytes not available\n",
674 raw_spin_lock_irqsave(&logbuf_lock, flags);
675 log_buf_len = new_log_buf_len;
676 log_buf = new_log_buf;
678 free = __LOG_BUF_LEN - log_next_idx;
679 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
680 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
682 pr_info("log_buf_len: %d\n", log_buf_len);
683 pr_info("early log buf free: %d(%d%%)\n",
684 free, (free * 100) / __LOG_BUF_LEN);
687 #ifdef CONFIG_BOOT_PRINTK_DELAY
689 static int boot_delay; /* msecs delay after each printk during bootup */
690 static unsigned long long loops_per_msec; /* based on boot_delay */
692 static int __init boot_delay_setup(char *str)
696 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
697 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
699 get_option(&str, &boot_delay);
700 if (boot_delay > 10 * 1000)
703 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
704 "HZ: %d, loops_per_msec: %llu\n",
705 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
708 __setup("boot_delay=", boot_delay_setup);
710 static void boot_delay_msec(void)
712 unsigned long long k;
713 unsigned long timeout;
715 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
718 k = (unsigned long long)loops_per_msec * boot_delay;
720 timeout = jiffies + msecs_to_jiffies(boot_delay);
725 * use (volatile) jiffies to prevent
726 * compiler reduction; loop termination via jiffies
727 * is secondary and may or may not happen.
729 if (time_after(jiffies, timeout))
731 touch_nmi_watchdog();
735 static inline void boot_delay_msec(void)
740 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
741 int dmesg_restrict = 1;
746 static int syslog_action_restricted(int type)
750 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
751 return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
754 static int check_syslog_permissions(int type, bool from_file)
757 * If this is from /proc/kmsg and we've already opened it, then we've
758 * already done the capabilities checks at open time.
760 if (from_file && type != SYSLOG_ACTION_OPEN)
763 if (syslog_action_restricted(type)) {
764 if (capable(CAP_SYSLOG))
766 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
767 if (capable(CAP_SYS_ADMIN)) {
768 printk_once(KERN_WARNING "%s (%d): "
769 "Attempt to access syslog with CAP_SYS_ADMIN "
770 "but no CAP_SYSLOG (deprecated).\n",
771 current->comm, task_pid_nr(current));
779 #if defined(CONFIG_PRINTK_TIME)
780 static bool printk_time = 1;
782 static bool printk_time;
784 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
786 static int syslog_print_line(u32 idx, char *text, size_t size)
791 msg = log_from_idx(idx);
793 /* calculate length only */
804 len += msg->text_len;
809 len = sprintf(text, "<%u>", msg->level);
812 unsigned long long t = msg->ts_nsec;
813 unsigned long rem_ns = do_div(t, 1000000000);
815 len += sprintf(text + len, "[%5lu.%06lu] ",
816 (unsigned long) t, rem_ns / 1000);
819 if (len + msg->text_len > size)
821 memcpy(text + len, log_text(msg), msg->text_len);
822 len += msg->text_len;
827 static int syslog_print(char __user *buf, int size)
832 text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
836 raw_spin_lock_irq(&logbuf_lock);
837 if (syslog_seq < log_first_seq) {
838 /* messages are gone, move to first one */
839 syslog_seq = log_first_seq;
840 syslog_idx = log_first_idx;
842 len = syslog_print_line(syslog_idx, text, LOG_LINE_MAX);
843 syslog_idx = log_next(syslog_idx);
845 raw_spin_unlock_irq(&logbuf_lock);
847 if (len > 0 && copy_to_user(buf, text, len))
854 static int syslog_print_all(char __user *buf, int size, bool clear)
859 text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
863 raw_spin_lock_irq(&logbuf_lock);
869 if (clear_seq < log_first_seq) {
870 /* messages are gone, move to first available one */
871 clear_seq = log_first_seq;
872 clear_idx = log_first_idx;
876 * Find first record that fits, including all following records,
877 * into the user-provided buffer for this dump.
881 while (seq < log_next_seq) {
882 len += syslog_print_line(idx, NULL, 0);
888 while (len > size && seq < log_next_seq) {
889 len -= syslog_print_line(idx, NULL, 0);
894 /* last message in this dump */
895 next_seq = log_next_seq;
898 while (len >= 0 && seq < next_seq) {
901 textlen = syslog_print_line(idx, text, LOG_LINE_MAX);
909 raw_spin_unlock_irq(&logbuf_lock);
910 if (copy_to_user(buf + len, text, textlen))
914 raw_spin_lock_irq(&logbuf_lock);
916 if (seq < log_first_seq) {
917 /* messages are gone, move to next one */
925 clear_seq = log_next_seq;
926 clear_idx = log_next_idx;
928 raw_spin_unlock_irq(&logbuf_lock);
934 int do_syslog(int type, char __user *buf, int len, bool from_file)
937 static int saved_console_loglevel = -1;
940 error = check_syslog_permissions(type, from_file);
944 error = security_syslog(type);
949 case SYSLOG_ACTION_CLOSE: /* Close log */
951 case SYSLOG_ACTION_OPEN: /* Open log */
953 case SYSLOG_ACTION_READ: /* Read from log */
960 if (!access_ok(VERIFY_WRITE, buf, len)) {
964 error = wait_event_interruptible(log_wait,
965 syslog_seq != log_next_seq);
968 error = syslog_print(buf, len);
970 /* Read/clear last kernel messages */
971 case SYSLOG_ACTION_READ_CLEAR:
974 /* Read last kernel messages */
975 case SYSLOG_ACTION_READ_ALL:
982 if (!access_ok(VERIFY_WRITE, buf, len)) {
986 error = syslog_print_all(buf, len, clear);
988 /* Clear ring buffer */
989 case SYSLOG_ACTION_CLEAR:
990 syslog_print_all(NULL, 0, true);
991 /* Disable logging to console */
992 case SYSLOG_ACTION_CONSOLE_OFF:
993 if (saved_console_loglevel == -1)
994 saved_console_loglevel = console_loglevel;
995 console_loglevel = minimum_console_loglevel;
997 /* Enable logging to console */
998 case SYSLOG_ACTION_CONSOLE_ON:
999 if (saved_console_loglevel != -1) {
1000 console_loglevel = saved_console_loglevel;
1001 saved_console_loglevel = -1;
1004 /* Set level of messages printed to console */
1005 case SYSLOG_ACTION_CONSOLE_LEVEL:
1007 if (len < 1 || len > 8)
1009 if (len < minimum_console_loglevel)
1010 len = minimum_console_loglevel;
1011 console_loglevel = len;
1012 /* Implicitly re-enable logging to console */
1013 saved_console_loglevel = -1;
1016 /* Number of chars in the log buffer */
1017 case SYSLOG_ACTION_SIZE_UNREAD:
1018 raw_spin_lock_irq(&logbuf_lock);
1019 if (syslog_seq < log_first_seq) {
1020 /* messages are gone, move to first one */
1021 syslog_seq = log_first_seq;
1022 syslog_idx = log_first_idx;
1026 * Short-cut for poll(/"proc/kmsg") which simply checks
1027 * for pending data, not the size; return the count of
1028 * records, not the length.
1030 error = log_next_idx - syslog_idx;
1038 while (seq < log_next_seq) {
1039 error += syslog_print_line(idx, NULL, 0);
1040 idx = log_next(idx);
1044 raw_spin_unlock_irq(&logbuf_lock);
1046 /* Size of the log buffer */
1047 case SYSLOG_ACTION_SIZE_BUFFER:
1048 error = log_buf_len;
1058 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1060 return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
1063 #ifdef CONFIG_KGDB_KDB
1064 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
1065 * uses locks so it cannot be used during debugging. Just tell kdb
1066 * where the start and end of the physical and logical logs are. This
1067 * is equivalent to do_syslog(3).
1069 void kdb_syslog_data(char *syslog_data[4])
1071 syslog_data[0] = log_buf;
1072 syslog_data[1] = log_buf + log_buf_len;
1073 syslog_data[2] = log_buf + log_first_idx;
1074 syslog_data[3] = log_buf + log_next_idx;
1076 #endif /* CONFIG_KGDB_KDB */
1078 static bool __read_mostly ignore_loglevel;
1080 static int __init ignore_loglevel_setup(char *str)
1082 ignore_loglevel = 1;
1083 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
1088 early_param("ignore_loglevel", ignore_loglevel_setup);
1089 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1090 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
1091 "print all kernel messages to the console.");
1094 * Call the console drivers, asking them to write out
1095 * log_buf[start] to log_buf[end - 1].
1096 * The console_lock must be held.
1098 static void call_console_drivers(int level, const char *text, size_t len)
1100 struct console *con;
1102 trace_console(text, 0, len, len);
1104 if (level >= console_loglevel && !ignore_loglevel)
1106 if (!console_drivers)
1109 for_each_console(con) {
1110 if (exclusive_console && con != exclusive_console)
1112 if (!(con->flags & CON_ENABLED))
1116 if (!cpu_online(smp_processor_id()) &&
1117 !(con->flags & CON_ANYTIME))
1119 con->write(con, text, len);
1124 * Zap console related locks when oopsing. Only zap at most once
1125 * every 10 seconds, to leave time for slow consoles to print a
1128 static void zap_locks(void)
1130 static unsigned long oops_timestamp;
1132 if (time_after_eq(jiffies, oops_timestamp) &&
1133 !time_after(jiffies, oops_timestamp + 30 * HZ))
1136 oops_timestamp = jiffies;
1139 /* If a crash is occurring, make sure we can't deadlock */
1140 raw_spin_lock_init(&logbuf_lock);
1141 /* And make sure that we print immediately */
1142 sema_init(&console_sem, 1);
1145 /* Check if we have any console registered that can be called early in boot. */
1146 static int have_callable_console(void)
1148 struct console *con;
1150 for_each_console(con)
1151 if (con->flags & CON_ANYTIME)
1158 * Can we actually use the console at this time on this cpu?
1160 * Console drivers may assume that per-cpu resources have
1161 * been allocated. So unless they're explicitly marked as
1162 * being able to cope (CON_ANYTIME) don't call them until
1163 * this CPU is officially up.
1165 static inline int can_use_console(unsigned int cpu)
1167 return cpu_online(cpu) || have_callable_console();
1171 * Try to get console ownership to actually show the kernel
1172 * messages from a 'printk'. Return true (and with the
1173 * console_lock held, and 'console_locked' set) if it
1174 * is successful, false otherwise.
1176 * This gets called with the 'logbuf_lock' spinlock held and
1177 * interrupts disabled. It should return with 'lockbuf_lock'
1178 * released but interrupts still disabled.
1180 static int console_trylock_for_printk(unsigned int cpu)
1181 __releases(&logbuf_lock)
1183 int retval = 0, wake = 0;
1185 if (console_trylock()) {
1189 * If we can't use the console, we need to release
1190 * the console semaphore by hand to avoid flushing
1191 * the buffer. We need to hold the console semaphore
1192 * in order to do this test safely.
1194 if (!can_use_console(cpu)) {
1200 logbuf_cpu = UINT_MAX;
1203 raw_spin_unlock(&logbuf_lock);
1207 int printk_delay_msec __read_mostly;
1209 static inline void printk_delay(void)
1211 if (unlikely(printk_delay_msec)) {
1212 int m = printk_delay_msec;
1216 touch_nmi_watchdog();
1221 asmlinkage int vprintk_emit(int facility, int level,
1222 const char *dict, size_t dictlen,
1223 const char *fmt, va_list args)
1225 static int recursion_bug;
1226 static char buf[LOG_LINE_MAX];
1227 static size_t buflen;
1228 static int buflevel;
1229 static char textbuf[LOG_LINE_MAX];
1230 char *text = textbuf;
1232 unsigned long flags;
1234 bool newline = false;
1236 int printed_len = 0;
1241 /* This stops the holder of console_sem just where we want him */
1242 local_irq_save(flags);
1243 this_cpu = smp_processor_id();
1246 * Ouch, printk recursed into itself!
1248 if (unlikely(logbuf_cpu == this_cpu)) {
1250 * If a crash is occurring during printk() on this CPU,
1251 * then try to get the crash message out but make sure
1252 * we can't deadlock. Otherwise just return to avoid the
1253 * recursion and return - but flag the recursion so that
1254 * it can be printed at the next appropriate moment:
1256 if (!oops_in_progress && !lockdep_recursing(current)) {
1258 goto out_restore_irqs;
1264 raw_spin_lock(&logbuf_lock);
1265 logbuf_cpu = this_cpu;
1267 if (recursion_bug) {
1268 static const char recursion_msg[] =
1269 "BUG: recent printk recursion!";
1272 printed_len += strlen(recursion_msg);
1273 /* emit KERN_CRIT message */
1274 log_store(0, 2, NULL, 0, recursion_msg, printed_len);
1278 * The printf needs to come first; we need the syslog
1279 * prefix which might be passed-in as a parameter.
1281 textlen = vscnprintf(text, sizeof(textbuf), fmt, args);
1283 /* mark and strip a trailing newline */
1284 if (textlen && text[textlen-1] == '\n') {
1289 /* strip syslog prefix and extract log level or flags */
1290 if (text[0] == '<' && text[1] && text[2] == '>') {
1294 level = text[1] - '0';
1298 case 'c': /* KERN_CONT */
1300 case 'd': /* KERN_DEFAULT */
1307 if (buflen && (!cont || dict)) {
1308 /* no continuation; flush existing buffer */
1309 log_store(facility, buflevel, NULL, 0, buf, buflen);
1310 printed_len += buflen;
1315 /* remember level for first message in the buffer */
1317 buflevel = default_message_loglevel;
1322 if (buflen || !newline) {
1323 /* append to existing buffer, or buffer until next message */
1324 if (buflen + textlen > sizeof(buf))
1325 textlen = sizeof(buf) - buflen;
1326 memcpy(buf + buflen, text, textlen);
1331 /* end of line; flush buffer */
1333 log_store(facility, buflevel,
1334 dict, dictlen, buf, buflen);
1335 printed_len += buflen;
1338 log_store(facility, buflevel,
1339 dict, dictlen, text, textlen);
1340 printed_len += textlen;
1345 * Try to acquire and then immediately release the console semaphore.
1346 * The release will print out buffers and wake up /dev/kmsg and syslog()
1349 * The console_trylock_for_printk() function will release 'logbuf_lock'
1350 * regardless of whether it actually gets the console semaphore or not.
1352 if (console_trylock_for_printk(this_cpu))
1357 local_irq_restore(flags);
1361 EXPORT_SYMBOL(vprintk_emit);
1363 asmlinkage int vprintk(const char *fmt, va_list args)
1365 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1367 EXPORT_SYMBOL(vprintk);
1369 asmlinkage int printk_emit(int facility, int level,
1370 const char *dict, size_t dictlen,
1371 const char *fmt, ...)
1376 va_start(args, fmt);
1377 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1382 EXPORT_SYMBOL(printk_emit);
1385 * printk - print a kernel message
1386 * @fmt: format string
1388 * This is printk(). It can be called from any context. We want it to work.
1390 * We try to grab the console_lock. If we succeed, it's easy - we log the
1391 * output and call the console drivers. If we fail to get the semaphore, we
1392 * place the output into the log buffer and return. The current holder of
1393 * the console_sem will notice the new output in console_unlock(); and will
1394 * send it to the consoles before releasing the lock.
1396 * One effect of this deferred printing is that code which calls printk() and
1397 * then changes console_loglevel may break. This is because console_loglevel
1398 * is inspected when the actual printing occurs.
1403 * See the vsnprintf() documentation for format string extensions over C99.
1405 asmlinkage int printk(const char *fmt, ...)
1410 #ifdef CONFIG_KGDB_KDB
1411 if (unlikely(kdb_trap_printk)) {
1412 va_start(args, fmt);
1413 r = vkdb_printf(fmt, args);
1418 va_start(args, fmt);
1419 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1424 EXPORT_SYMBOL(printk);
1427 static void call_console_drivers(int level, const char *text, size_t len)
1433 static int __add_preferred_console(char *name, int idx, char *options,
1436 struct console_cmdline *c;
1440 * See if this tty is not yet registered, and
1441 * if we have a slot free.
1443 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1444 if (strcmp(console_cmdline[i].name, name) == 0 &&
1445 console_cmdline[i].index == idx) {
1447 selected_console = i;
1450 if (i == MAX_CMDLINECONSOLES)
1453 selected_console = i;
1454 c = &console_cmdline[i];
1455 strlcpy(c->name, name, sizeof(c->name));
1456 c->options = options;
1457 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1458 c->brl_options = brl_options;
1464 * Set up a list of consoles. Called from init/main.c
1466 static int __init console_setup(char *str)
1468 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1469 char *s, *options, *brl_options = NULL;
1472 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1473 if (!memcmp(str, "brl,", 4)) {
1476 } else if (!memcmp(str, "brl=", 4)) {
1477 brl_options = str + 4;
1478 str = strchr(brl_options, ',');
1480 printk(KERN_ERR "need port name after brl=\n");
1488 * Decode str into name, index, options.
1490 if (str[0] >= '0' && str[0] <= '9') {
1491 strcpy(buf, "ttyS");
1492 strncpy(buf + 4, str, sizeof(buf) - 5);
1494 strncpy(buf, str, sizeof(buf) - 1);
1496 buf[sizeof(buf) - 1] = 0;
1497 if ((options = strchr(str, ',')) != NULL)
1500 if (!strcmp(str, "ttya"))
1501 strcpy(buf, "ttyS0");
1502 if (!strcmp(str, "ttyb"))
1503 strcpy(buf, "ttyS1");
1505 for (s = buf; *s; s++)
1506 if ((*s >= '0' && *s <= '9') || *s == ',')
1508 idx = simple_strtoul(s, NULL, 10);
1511 __add_preferred_console(buf, idx, options, brl_options);
1512 console_set_on_cmdline = 1;
1515 __setup("console=", console_setup);
1518 * add_preferred_console - add a device to the list of preferred consoles.
1519 * @name: device name
1520 * @idx: device index
1521 * @options: options for this console
1523 * The last preferred console added will be used for kernel messages
1524 * and stdin/out/err for init. Normally this is used by console_setup
1525 * above to handle user-supplied console arguments; however it can also
1526 * be used by arch-specific code either to override the user or more
1527 * commonly to provide a default console (ie from PROM variables) when
1528 * the user has not supplied one.
1530 int add_preferred_console(char *name, int idx, char *options)
1532 return __add_preferred_console(name, idx, options, NULL);
1535 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1537 struct console_cmdline *c;
1540 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1541 if (strcmp(console_cmdline[i].name, name) == 0 &&
1542 console_cmdline[i].index == idx) {
1543 c = &console_cmdline[i];
1544 strlcpy(c->name, name_new, sizeof(c->name));
1545 c->name[sizeof(c->name) - 1] = 0;
1546 c->options = options;
1554 bool console_suspend_enabled = 1;
1555 EXPORT_SYMBOL(console_suspend_enabled);
1557 static int __init console_suspend_disable(char *str)
1559 console_suspend_enabled = 0;
1562 __setup("no_console_suspend", console_suspend_disable);
1563 module_param_named(console_suspend, console_suspend_enabled,
1564 bool, S_IRUGO | S_IWUSR);
1565 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1566 " and hibernate operations");
1569 * suspend_console - suspend the console subsystem
1571 * This disables printk() while we go into suspend states
1573 void suspend_console(void)
1575 if (!console_suspend_enabled)
1577 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1579 console_suspended = 1;
1583 void resume_console(void)
1585 if (!console_suspend_enabled)
1588 console_suspended = 0;
1593 * console_cpu_notify - print deferred console messages after CPU hotplug
1594 * @self: notifier struct
1595 * @action: CPU hotplug event
1598 * If printk() is called from a CPU that is not online yet, the messages
1599 * will be spooled but will not show up on the console. This function is
1600 * called when a new CPU comes online (or fails to come up), and ensures
1601 * that any such output gets printed.
1603 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1604 unsigned long action, void *hcpu)
1610 case CPU_DOWN_FAILED:
1611 case CPU_UP_CANCELED:
1619 * console_lock - lock the console system for exclusive use.
1621 * Acquires a lock which guarantees that the caller has
1622 * exclusive access to the console system and the console_drivers list.
1624 * Can sleep, returns nothing.
1626 void console_lock(void)
1628 BUG_ON(in_interrupt());
1630 if (console_suspended)
1633 console_may_schedule = 1;
1635 EXPORT_SYMBOL(console_lock);
1638 * console_trylock - try to lock the console system for exclusive use.
1640 * Tried to acquire a lock which guarantees that the caller has
1641 * exclusive access to the console system and the console_drivers list.
1643 * returns 1 on success, and 0 on failure to acquire the lock.
1645 int console_trylock(void)
1647 if (down_trylock(&console_sem))
1649 if (console_suspended) {
1654 console_may_schedule = 0;
1657 EXPORT_SYMBOL(console_trylock);
1659 int is_console_locked(void)
1661 return console_locked;
1665 * Delayed printk version, for scheduler-internal messages:
1667 #define PRINTK_BUF_SIZE 512
1669 #define PRINTK_PENDING_WAKEUP 0x01
1670 #define PRINTK_PENDING_SCHED 0x02
1672 static DEFINE_PER_CPU(int, printk_pending);
1673 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
1675 void printk_tick(void)
1677 if (__this_cpu_read(printk_pending)) {
1678 int pending = __this_cpu_xchg(printk_pending, 0);
1679 if (pending & PRINTK_PENDING_SCHED) {
1680 char *buf = __get_cpu_var(printk_sched_buf);
1681 printk(KERN_WARNING "[sched_delayed] %s", buf);
1683 if (pending & PRINTK_PENDING_WAKEUP)
1684 wake_up_interruptible(&log_wait);
1688 int printk_needs_cpu(int cpu)
1690 if (cpu_is_offline(cpu))
1692 return __this_cpu_read(printk_pending);
1695 void wake_up_klogd(void)
1697 if (waitqueue_active(&log_wait))
1698 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
1701 /* the next printk record to write to the console */
1702 static u64 console_seq;
1703 static u32 console_idx;
1706 * console_unlock - unlock the console system
1708 * Releases the console_lock which the caller holds on the console system
1709 * and the console driver list.
1711 * While the console_lock was held, console output may have been buffered
1712 * by printk(). If this is the case, console_unlock(); emits
1713 * the output prior to releasing the lock.
1715 * If there is output waiting, we wake it /dev/kmsg and syslog() users.
1717 * console_unlock(); may be called from any context.
1719 void console_unlock(void)
1721 static u64 seen_seq;
1722 unsigned long flags;
1723 bool wake_klogd = false;
1726 if (console_suspended) {
1731 console_may_schedule = 0;
1736 static char text[LOG_LINE_MAX];
1740 raw_spin_lock_irqsave(&logbuf_lock, flags);
1741 if (seen_seq != log_next_seq) {
1743 seen_seq = log_next_seq;
1746 if (console_seq < log_first_seq) {
1747 /* messages are gone, move to first one */
1748 console_seq = log_first_seq;
1749 console_idx = log_first_idx;
1752 if (console_seq == log_next_seq)
1755 msg = log_from_idx(console_idx);
1756 level = msg->level & 7;
1757 len = msg->text_len;
1758 if (len+1 >= sizeof(text))
1759 len = sizeof(text)-1;
1760 memcpy(text, log_text(msg), len);
1763 console_idx = log_next(console_idx);
1765 raw_spin_unlock(&logbuf_lock);
1767 stop_critical_timings(); /* don't trace print latency */
1768 call_console_drivers(level, text, len);
1769 start_critical_timings();
1770 local_irq_restore(flags);
1774 /* Release the exclusive_console once it is used */
1775 if (unlikely(exclusive_console))
1776 exclusive_console = NULL;
1778 raw_spin_unlock(&logbuf_lock);
1783 * Someone could have filled up the buffer again, so re-check if there's
1784 * something to flush. In case we cannot trylock the console_sem again,
1785 * there's a new owner and the console_unlock() from them will do the
1786 * flush, no worries.
1788 raw_spin_lock(&logbuf_lock);
1789 retry = console_seq != log_next_seq;
1790 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
1792 if (retry && console_trylock())
1798 EXPORT_SYMBOL(console_unlock);
1801 * console_conditional_schedule - yield the CPU if required
1803 * If the console code is currently allowed to sleep, and
1804 * if this CPU should yield the CPU to another task, do
1807 * Must be called within console_lock();.
1809 void __sched console_conditional_schedule(void)
1811 if (console_may_schedule)
1814 EXPORT_SYMBOL(console_conditional_schedule);
1816 void console_unblank(void)
1821 * console_unblank can no longer be called in interrupt context unless
1822 * oops_in_progress is set to 1..
1824 if (oops_in_progress) {
1825 if (down_trylock(&console_sem) != 0)
1831 console_may_schedule = 0;
1833 if ((c->flags & CON_ENABLED) && c->unblank)
1839 * Return the console tty driver structure and its associated index
1841 struct tty_driver *console_device(int *index)
1844 struct tty_driver *driver = NULL;
1847 for_each_console(c) {
1850 driver = c->device(c, index);
1859 * Prevent further output on the passed console device so that (for example)
1860 * serial drivers can disable console output before suspending a port, and can
1861 * re-enable output afterwards.
1863 void console_stop(struct console *console)
1866 console->flags &= ~CON_ENABLED;
1869 EXPORT_SYMBOL(console_stop);
1871 void console_start(struct console *console)
1874 console->flags |= CON_ENABLED;
1877 EXPORT_SYMBOL(console_start);
1879 static int __read_mostly keep_bootcon;
1881 static int __init keep_bootcon_setup(char *str)
1884 printk(KERN_INFO "debug: skip boot console de-registration.\n");
1889 early_param("keep_bootcon", keep_bootcon_setup);
1892 * The console driver calls this routine during kernel initialization
1893 * to register the console printing procedure with printk() and to
1894 * print any messages that were printed by the kernel before the
1895 * console driver was initialized.
1897 * This can happen pretty early during the boot process (because of
1898 * early_printk) - sometimes before setup_arch() completes - be careful
1899 * of what kernel features are used - they may not be initialised yet.
1901 * There are two types of consoles - bootconsoles (early_printk) and
1902 * "real" consoles (everything which is not a bootconsole) which are
1903 * handled differently.
1904 * - Any number of bootconsoles can be registered at any time.
1905 * - As soon as a "real" console is registered, all bootconsoles
1906 * will be unregistered automatically.
1907 * - Once a "real" console is registered, any attempt to register a
1908 * bootconsoles will be rejected
1910 void register_console(struct console *newcon)
1913 unsigned long flags;
1914 struct console *bcon = NULL;
1917 * before we register a new CON_BOOT console, make sure we don't
1918 * already have a valid console
1920 if (console_drivers && newcon->flags & CON_BOOT) {
1921 /* find the last or real console */
1922 for_each_console(bcon) {
1923 if (!(bcon->flags & CON_BOOT)) {
1924 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1925 newcon->name, newcon->index);
1931 if (console_drivers && console_drivers->flags & CON_BOOT)
1932 bcon = console_drivers;
1934 if (preferred_console < 0 || bcon || !console_drivers)
1935 preferred_console = selected_console;
1937 if (newcon->early_setup)
1938 newcon->early_setup();
1941 * See if we want to use this console driver. If we
1942 * didn't select a console we take the first one
1943 * that registers here.
1945 if (preferred_console < 0) {
1946 if (newcon->index < 0)
1948 if (newcon->setup == NULL ||
1949 newcon->setup(newcon, NULL) == 0) {
1950 newcon->flags |= CON_ENABLED;
1951 if (newcon->device) {
1952 newcon->flags |= CON_CONSDEV;
1953 preferred_console = 0;
1959 * See if this console matches one we selected on
1962 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1964 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1966 if (newcon->index >= 0 &&
1967 newcon->index != console_cmdline[i].index)
1969 if (newcon->index < 0)
1970 newcon->index = console_cmdline[i].index;
1971 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1972 if (console_cmdline[i].brl_options) {
1973 newcon->flags |= CON_BRL;
1974 braille_register_console(newcon,
1975 console_cmdline[i].index,
1976 console_cmdline[i].options,
1977 console_cmdline[i].brl_options);
1981 if (newcon->setup &&
1982 newcon->setup(newcon, console_cmdline[i].options) != 0)
1984 newcon->flags |= CON_ENABLED;
1985 newcon->index = console_cmdline[i].index;
1986 if (i == selected_console) {
1987 newcon->flags |= CON_CONSDEV;
1988 preferred_console = selected_console;
1993 if (!(newcon->flags & CON_ENABLED))
1997 * If we have a bootconsole, and are switching to a real console,
1998 * don't print everything out again, since when the boot console, and
1999 * the real console are the same physical device, it's annoying to
2000 * see the beginning boot messages twice
2002 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2003 newcon->flags &= ~CON_PRINTBUFFER;
2006 * Put this console in the list - keep the
2007 * preferred driver at the head of the list.
2010 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2011 newcon->next = console_drivers;
2012 console_drivers = newcon;
2014 newcon->next->flags &= ~CON_CONSDEV;
2016 newcon->next = console_drivers->next;
2017 console_drivers->next = newcon;
2019 if (newcon->flags & CON_PRINTBUFFER) {
2021 * console_unlock(); will print out the buffered messages
2024 raw_spin_lock_irqsave(&logbuf_lock, flags);
2025 console_seq = syslog_seq;
2026 console_idx = syslog_idx;
2027 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2029 * We're about to replay the log buffer. Only do this to the
2030 * just-registered console to avoid excessive message spam to
2031 * the already-registered consoles.
2033 exclusive_console = newcon;
2036 console_sysfs_notify();
2039 * By unregistering the bootconsoles after we enable the real console
2040 * we get the "console xxx enabled" message on all the consoles -
2041 * boot consoles, real consoles, etc - this is to ensure that end
2042 * users know there might be something in the kernel's log buffer that
2043 * went to the bootconsole (that they do not see on the real console)
2046 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2048 /* we need to iterate through twice, to make sure we print
2049 * everything out, before we unregister the console(s)
2051 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
2052 newcon->name, newcon->index);
2053 for_each_console(bcon)
2054 if (bcon->flags & CON_BOOT)
2055 unregister_console(bcon);
2057 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
2058 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2059 newcon->name, newcon->index);
2062 EXPORT_SYMBOL(register_console);
2064 int unregister_console(struct console *console)
2066 struct console *a, *b;
2069 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2070 if (console->flags & CON_BRL)
2071 return braille_unregister_console(console);
2075 if (console_drivers == console) {
2076 console_drivers=console->next;
2078 } else if (console_drivers) {
2079 for (a=console_drivers->next, b=console_drivers ;
2080 a; b=a, a=b->next) {
2090 * If this isn't the last console and it has CON_CONSDEV set, we
2091 * need to set it on the next preferred console.
2093 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2094 console_drivers->flags |= CON_CONSDEV;
2097 console_sysfs_notify();
2100 EXPORT_SYMBOL(unregister_console);
2102 static int __init printk_late_init(void)
2104 struct console *con;
2106 for_each_console(con) {
2107 if (!keep_bootcon && con->flags & CON_BOOT) {
2108 printk(KERN_INFO "turn off boot console %s%d\n",
2109 con->name, con->index);
2110 unregister_console(con);
2113 hotcpu_notifier(console_cpu_notify, 0);
2116 late_initcall(printk_late_init);
2118 #if defined CONFIG_PRINTK
2120 int printk_sched(const char *fmt, ...)
2122 unsigned long flags;
2127 local_irq_save(flags);
2128 buf = __get_cpu_var(printk_sched_buf);
2130 va_start(args, fmt);
2131 r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2134 __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2135 local_irq_restore(flags);
2141 * printk rate limiting, lifted from the networking subsystem.
2143 * This enforces a rate limit: not more than 10 kernel messages
2144 * every 5s to make a denial-of-service attack impossible.
2146 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2148 int __printk_ratelimit(const char *func)
2150 return ___ratelimit(&printk_ratelimit_state, func);
2152 EXPORT_SYMBOL(__printk_ratelimit);
2155 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2156 * @caller_jiffies: pointer to caller's state
2157 * @interval_msecs: minimum interval between prints
2159 * printk_timed_ratelimit() returns true if more than @interval_msecs
2160 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2163 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2164 unsigned int interval_msecs)
2166 if (*caller_jiffies == 0
2167 || !time_in_range(jiffies, *caller_jiffies,
2169 + msecs_to_jiffies(interval_msecs))) {
2170 *caller_jiffies = jiffies;
2175 EXPORT_SYMBOL(printk_timed_ratelimit);
2177 static DEFINE_SPINLOCK(dump_list_lock);
2178 static LIST_HEAD(dump_list);
2181 * kmsg_dump_register - register a kernel log dumper.
2182 * @dumper: pointer to the kmsg_dumper structure
2184 * Adds a kernel log dumper to the system. The dump callback in the
2185 * structure will be called when the kernel oopses or panics and must be
2186 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2188 int kmsg_dump_register(struct kmsg_dumper *dumper)
2190 unsigned long flags;
2193 /* The dump callback needs to be set */
2197 spin_lock_irqsave(&dump_list_lock, flags);
2198 /* Don't allow registering multiple times */
2199 if (!dumper->registered) {
2200 dumper->registered = 1;
2201 list_add_tail_rcu(&dumper->list, &dump_list);
2204 spin_unlock_irqrestore(&dump_list_lock, flags);
2208 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2211 * kmsg_dump_unregister - unregister a kmsg dumper.
2212 * @dumper: pointer to the kmsg_dumper structure
2214 * Removes a dump device from the system. Returns zero on success and
2215 * %-EINVAL otherwise.
2217 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2219 unsigned long flags;
2222 spin_lock_irqsave(&dump_list_lock, flags);
2223 if (dumper->registered) {
2224 dumper->registered = 0;
2225 list_del_rcu(&dumper->list);
2228 spin_unlock_irqrestore(&dump_list_lock, flags);
2233 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2235 static bool always_kmsg_dump;
2236 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2239 * kmsg_dump - dump kernel log to kernel message dumpers.
2240 * @reason: the reason (oops, panic etc) for dumping
2242 * Iterate through each of the dump devices and call the oops/panic
2243 * callbacks with the log buffer.
2245 void kmsg_dump(enum kmsg_dump_reason reason)
2248 struct kmsg_dumper *dumper;
2249 const char *s1, *s2;
2250 unsigned long l1, l2;
2251 unsigned long flags;
2253 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2256 /* Theoretically, the log could move on after we do this, but
2257 there's not a lot we can do about that. The new messages
2258 will overwrite the start of what we dump. */
2260 raw_spin_lock_irqsave(&logbuf_lock, flags);
2261 if (syslog_seq < log_first_seq)
2264 idx = log_first_idx;
2266 if (idx > log_next_idx) {
2271 l2 = log_buf_len - idx;
2277 l2 = log_next_idx - idx;
2279 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2282 list_for_each_entry_rcu(dumper, &dump_list, list)
2283 dumper->dump(dumper, reason, s1, l1, s2, l2);