2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/memblock.h>
35 #include <linux/syscalls.h>
36 #include <linux/kexec.h>
37 #include <linux/kdb.h>
38 #include <linux/ratelimit.h>
39 #include <linux/kmsg_dump.h>
40 #include <linux/syslog.h>
41 #include <linux/cpu.h>
42 #include <linux/notifier.h>
43 #include <linux/rculist.h>
44 #include <linux/poll.h>
46 #include <asm/uaccess.h>
48 #define CREATE_TRACE_POINTS
49 #include <trace/events/printk.h>
52 * Architectures can override it:
54 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
58 /* printk's without a loglevel use this.. */
59 #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
61 /* We show everything that is MORE important than this.. */
62 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
63 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
65 DECLARE_WAIT_QUEUE_HEAD(log_wait);
67 int console_printk[4] = {
68 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
69 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
70 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
71 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
75 * Low level drivers may need that to know if they can schedule in
76 * their unblank() callback or not. So let's export it.
79 EXPORT_SYMBOL(oops_in_progress);
82 * console_sem protects the console_drivers list, and also
83 * provides serialisation for access to the entire console
86 static DEFINE_SEMAPHORE(console_sem);
87 struct console *console_drivers;
88 EXPORT_SYMBOL_GPL(console_drivers);
91 * This is used for debugging the mess that is the VT code by
92 * keeping track if we have the console semaphore held. It's
93 * definitely not the perfect debug tool (we don't know if _WE_
94 * hold it are racing, but it helps tracking those weird code
95 * path in the console code where we end up in places I want
96 * locked without the console sempahore held
98 static int console_locked, console_suspended;
101 * If exclusive_console is non-NULL then only this console is to be printed to.
103 static struct console *exclusive_console;
106 * Array of consoles built from command line options (console=)
108 struct console_cmdline
110 char name[8]; /* Name of the driver */
111 int index; /* Minor dev. to use */
112 char *options; /* Options for the driver */
113 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
114 char *brl_options; /* Options for braille driver */
118 #define MAX_CMDLINECONSOLES 8
120 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
121 static int selected_console = -1;
122 static int preferred_console = -1;
123 int console_set_on_cmdline;
124 EXPORT_SYMBOL(console_set_on_cmdline);
126 /* Flag: console code may call schedule() */
127 static int console_may_schedule;
130 * The printk log buffer consists of a chain of concatenated variable
131 * length records. Every record starts with a record header, containing
132 * the overall length of the record.
134 * The heads to the first and last entry in the buffer, as well as the
135 * sequence numbers of these both entries are maintained when messages
138 * If the heads indicate available messages, the length in the header
139 * tells the start next message. A length == 0 for the next message
140 * indicates a wrap-around to the beginning of the buffer.
142 * Every record carries the monotonic timestamp in microseconds, as well as
143 * the standard userspace syslog level and syslog facility. The usual
144 * kernel messages use LOG_KERN; userspace-injected messages always carry
145 * a matching syslog facility, by default LOG_USER. The origin of every
146 * message can be reliably determined that way.
148 * The human readable log message directly follows the message header. The
149 * length of the message text is stored in the header, the stored message
152 * Optionally, a message can carry a dictionary of properties (key/value pairs),
153 * to provide userspace with a machine-readable message context.
155 * Examples for well-defined, commonly used property names are:
156 * DEVICE=b12:8 device identifier
160 * +sound:card0 subsystem:devname
161 * SUBSYSTEM=pci driver-core subsystem name
163 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
164 * follows directly after a '=' character. Every property is terminated by
165 * a '\0' character. The last property is not terminated.
167 * Example of a message structure:
168 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
169 * 0008 34 00 record is 52 bytes long
170 * 000a 0b 00 text is 11 bytes long
171 * 000c 1f 00 dictionary is 23 bytes long
172 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
173 * 0010 69 74 27 73 20 61 20 6c "it's a l"
175 * 001b 44 45 56 49 43 "DEVIC"
176 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
177 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
179 * 0032 00 00 00 padding to next message header
181 * The 'struct log' buffer header must never be directly exported to
182 * userspace, it is a kernel-private implementation detail that might
183 * need to be changed in the future, when the requirements change.
185 * /dev/kmsg exports the structured data in the following line format:
186 * "level,sequnum,timestamp;<message text>\n"
188 * The optional key/value pairs are attached as continuation lines starting
189 * with a space character and terminated by a newline. All possible
190 * non-prinatable characters are escaped in the "\xff" notation.
192 * Users of the export format should ignore possible additional values
193 * separated by ',', and find the message after the ';' character.
197 LOG_NOCONS = 1, /* already flushed, do not print to console */
198 LOG_NEWLINE = 2, /* text ended with a newline */
199 LOG_PREFIX = 4, /* text started with a prefix */
200 LOG_CONT = 8, /* text is a fragment of a continuation line */
204 u64 ts_nsec; /* timestamp in nanoseconds */
205 u16 len; /* length of entire record */
206 u16 text_len; /* length of text buffer */
207 u16 dict_len; /* length of dictionary buffer */
208 u8 facility; /* syslog facility */
209 u8 flags:5; /* internal record flags */
210 u8 level:3; /* syslog level */
214 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
215 * used in interesting ways to provide interlocking in console_unlock();
217 static DEFINE_RAW_SPINLOCK(logbuf_lock);
219 /* the next printk record to read by syslog(READ) or /proc/kmsg */
220 static u64 syslog_seq;
221 static u32 syslog_idx;
222 static enum log_flags syslog_prev;
223 static size_t syslog_partial;
225 /* index and sequence number of the first record stored in the buffer */
226 static u64 log_first_seq;
227 static u32 log_first_idx;
229 /* index and sequence number of the next record to store in the buffer */
230 static u64 log_next_seq;
232 static u32 log_next_idx;
234 /* the next printk record to read after the last 'clear' command */
235 static u64 clear_seq;
236 static u32 clear_idx;
238 #define LOG_LINE_MAX 1024
241 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
244 #define LOG_ALIGN __alignof__(struct log)
246 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
247 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
248 static char *log_buf = __log_buf;
249 static u32 log_buf_len = __LOG_BUF_LEN;
251 /* cpu currently holding logbuf_lock */
252 static volatile unsigned int logbuf_cpu = UINT_MAX;
254 /* human readable text of the record */
255 static char *log_text(const struct log *msg)
257 return (char *)msg + sizeof(struct log);
260 /* optional key/value pair dictionary attached to the record */
261 static char *log_dict(const struct log *msg)
263 return (char *)msg + sizeof(struct log) + msg->text_len;
266 /* get record by index; idx must point to valid msg */
267 static struct log *log_from_idx(u32 idx)
269 struct log *msg = (struct log *)(log_buf + idx);
272 * A length == 0 record is the end of buffer marker. Wrap around and
273 * read the message at the start of the buffer.
276 return (struct log *)log_buf;
280 /* get next record; idx must point to valid msg */
281 static u32 log_next(u32 idx)
283 struct log *msg = (struct log *)(log_buf + idx);
285 /* length == 0 indicates the end of the buffer; wrap */
287 * A length == 0 record is the end of buffer marker. Wrap around and
288 * read the message at the start of the buffer as *this* one, and
289 * return the one after that.
292 msg = (struct log *)log_buf;
295 return idx + msg->len;
298 /* insert record into the buffer, discard old ones, update heads */
299 static void log_store(int facility, int level,
300 enum log_flags flags, u64 ts_nsec,
301 const char *dict, u16 dict_len,
302 const char *text, u16 text_len)
307 /* number of '\0' padding bytes to next message */
308 size = sizeof(struct log) + text_len + dict_len;
309 pad_len = (-size) & (LOG_ALIGN - 1);
312 while (log_first_seq < log_next_seq) {
315 if (log_next_idx > log_first_idx)
316 free = max(log_buf_len - log_next_idx, log_first_idx);
318 free = log_first_idx - log_next_idx;
320 if (free > size + sizeof(struct log))
323 /* drop old messages until we have enough contiuous space */
324 log_first_idx = log_next(log_first_idx);
328 if (log_next_idx + size + sizeof(struct log) >= log_buf_len) {
330 * This message + an additional empty header does not fit
331 * at the end of the buffer. Add an empty header with len == 0
332 * to signify a wrap around.
334 memset(log_buf + log_next_idx, 0, sizeof(struct log));
339 msg = (struct log *)(log_buf + log_next_idx);
340 memcpy(log_text(msg), text, text_len);
341 msg->text_len = text_len;
342 memcpy(log_dict(msg), dict, dict_len);
343 msg->dict_len = dict_len;
344 msg->facility = facility;
345 msg->level = level & 7;
346 msg->flags = flags & 0x1f;
348 msg->ts_nsec = ts_nsec;
350 msg->ts_nsec = local_clock();
351 memset(log_dict(msg) + dict_len, 0, pad_len);
352 msg->len = sizeof(struct log) + text_len + dict_len + pad_len;
355 log_next_idx += msg->len;
359 /* /dev/kmsg - userspace message inject/listen interface */
360 struct devkmsg_user {
367 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
368 unsigned long count, loff_t pos)
372 int level = default_message_loglevel;
373 int facility = 1; /* LOG_USER */
374 size_t len = iov_length(iv, count);
377 if (len > LOG_LINE_MAX)
379 buf = kmalloc(len+1, GFP_KERNEL);
384 for (i = 0; i < count; i++) {
385 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len))
387 line += iv[i].iov_len;
391 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
392 * the decimal value represents 32bit, the lower 3 bit are the log
393 * level, the rest are the log facility.
395 * If no prefix or no userspace facility is specified, we
396 * enforce LOG_USER, to be able to reliably distinguish
397 * kernel-generated messages from userspace-injected ones.
400 if (line[0] == '<') {
403 i = simple_strtoul(line+1, &endp, 10);
404 if (endp && endp[0] == '>') {
415 printk_emit(facility, level, NULL, 0, "%s", line);
421 static ssize_t devkmsg_read(struct file *file, char __user *buf,
422 size_t count, loff_t *ppos)
424 struct devkmsg_user *user = file->private_data;
434 ret = mutex_lock_interruptible(&user->lock);
437 raw_spin_lock_irq(&logbuf_lock);
438 while (user->seq == log_next_seq) {
439 if (file->f_flags & O_NONBLOCK) {
441 raw_spin_unlock_irq(&logbuf_lock);
445 raw_spin_unlock_irq(&logbuf_lock);
446 ret = wait_event_interruptible(log_wait,
447 user->seq != log_next_seq);
450 raw_spin_lock_irq(&logbuf_lock);
453 if (user->seq < log_first_seq) {
454 /* our last seen message is gone, return error and reset */
455 user->idx = log_first_idx;
456 user->seq = log_first_seq;
458 raw_spin_unlock_irq(&logbuf_lock);
462 msg = log_from_idx(user->idx);
463 ts_usec = msg->ts_nsec;
464 do_div(ts_usec, 1000);
465 len = sprintf(user->buf, "%u,%llu,%llu;",
466 (msg->facility << 3) | msg->level, user->seq, ts_usec);
468 /* escape non-printable characters */
469 for (i = 0; i < msg->text_len; i++) {
470 unsigned char c = log_text(msg)[i];
472 if (c < ' ' || c >= 127 || c == '\\')
473 len += sprintf(user->buf + len, "\\x%02x", c);
475 user->buf[len++] = c;
477 user->buf[len++] = '\n';
482 for (i = 0; i < msg->dict_len; i++) {
483 unsigned char c = log_dict(msg)[i];
486 user->buf[len++] = ' ';
491 user->buf[len++] = '\n';
496 if (c < ' ' || c >= 127 || c == '\\') {
497 len += sprintf(user->buf + len, "\\x%02x", c);
501 user->buf[len++] = c;
503 user->buf[len++] = '\n';
506 user->idx = log_next(user->idx);
508 raw_spin_unlock_irq(&logbuf_lock);
515 if (copy_to_user(buf, user->buf, len)) {
521 mutex_unlock(&user->lock);
525 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
527 struct devkmsg_user *user = file->private_data;
535 raw_spin_lock_irq(&logbuf_lock);
538 /* the first record */
539 user->idx = log_first_idx;
540 user->seq = log_first_seq;
544 * The first record after the last SYSLOG_ACTION_CLEAR,
545 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
546 * changes no global state, and does not clear anything.
548 user->idx = clear_idx;
549 user->seq = clear_seq;
552 /* after the last record */
553 user->idx = log_next_idx;
554 user->seq = log_next_seq;
559 raw_spin_unlock_irq(&logbuf_lock);
563 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
565 struct devkmsg_user *user = file->private_data;
569 return POLLERR|POLLNVAL;
571 poll_wait(file, &log_wait, wait);
573 raw_spin_lock_irq(&logbuf_lock);
574 if (user->seq < log_next_seq) {
575 /* return error when data has vanished underneath us */
576 if (user->seq < log_first_seq)
577 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
578 ret = POLLIN|POLLRDNORM;
580 raw_spin_unlock_irq(&logbuf_lock);
585 static int devkmsg_open(struct inode *inode, struct file *file)
587 struct devkmsg_user *user;
590 /* write-only does not need any file context */
591 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
594 err = security_syslog(SYSLOG_ACTION_READ_ALL);
598 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
602 mutex_init(&user->lock);
604 raw_spin_lock_irq(&logbuf_lock);
605 user->idx = log_first_idx;
606 user->seq = log_first_seq;
607 raw_spin_unlock_irq(&logbuf_lock);
609 file->private_data = user;
613 static int devkmsg_release(struct inode *inode, struct file *file)
615 struct devkmsg_user *user = file->private_data;
620 mutex_destroy(&user->lock);
625 const struct file_operations kmsg_fops = {
626 .open = devkmsg_open,
627 .read = devkmsg_read,
628 .aio_write = devkmsg_writev,
629 .llseek = devkmsg_llseek,
630 .poll = devkmsg_poll,
631 .release = devkmsg_release,
636 * This appends the listed symbols to /proc/vmcoreinfo
638 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
639 * obtain access to symbols that are otherwise very difficult to locate. These
640 * symbols are specifically used so that utilities can access and extract the
641 * dmesg log from a vmcore file after a crash.
643 void log_buf_kexec_setup(void)
645 VMCOREINFO_SYMBOL(log_buf);
646 VMCOREINFO_SYMBOL(log_buf_len);
647 VMCOREINFO_SYMBOL(log_first_idx);
648 VMCOREINFO_SYMBOL(log_next_idx);
652 /* requested log_buf_len from kernel cmdline */
653 static unsigned long __initdata new_log_buf_len;
655 /* save requested log_buf_len since it's too early to process it */
656 static int __init log_buf_len_setup(char *str)
658 unsigned size = memparse(str, &str);
661 size = roundup_pow_of_two(size);
662 if (size > log_buf_len)
663 new_log_buf_len = size;
667 early_param("log_buf_len", log_buf_len_setup);
669 void __init setup_log_buf(int early)
675 if (!new_log_buf_len)
681 mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
684 new_log_buf = __va(mem);
686 new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
689 if (unlikely(!new_log_buf)) {
690 pr_err("log_buf_len: %ld bytes not available\n",
695 raw_spin_lock_irqsave(&logbuf_lock, flags);
696 log_buf_len = new_log_buf_len;
697 log_buf = new_log_buf;
699 free = __LOG_BUF_LEN - log_next_idx;
700 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
701 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
703 pr_info("log_buf_len: %d\n", log_buf_len);
704 pr_info("early log buf free: %d(%d%%)\n",
705 free, (free * 100) / __LOG_BUF_LEN);
708 #ifdef CONFIG_BOOT_PRINTK_DELAY
710 static int boot_delay; /* msecs delay after each printk during bootup */
711 static unsigned long long loops_per_msec; /* based on boot_delay */
713 static int __init boot_delay_setup(char *str)
717 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
718 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
720 get_option(&str, &boot_delay);
721 if (boot_delay > 10 * 1000)
724 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
725 "HZ: %d, loops_per_msec: %llu\n",
726 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
729 __setup("boot_delay=", boot_delay_setup);
731 static void boot_delay_msec(void)
733 unsigned long long k;
734 unsigned long timeout;
736 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
739 k = (unsigned long long)loops_per_msec * boot_delay;
741 timeout = jiffies + msecs_to_jiffies(boot_delay);
746 * use (volatile) jiffies to prevent
747 * compiler reduction; loop termination via jiffies
748 * is secondary and may or may not happen.
750 if (time_after(jiffies, timeout))
752 touch_nmi_watchdog();
756 static inline void boot_delay_msec(void)
761 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
762 int dmesg_restrict = 1;
767 static int syslog_action_restricted(int type)
771 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
772 return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
775 static int check_syslog_permissions(int type, bool from_file)
778 * If this is from /proc/kmsg and we've already opened it, then we've
779 * already done the capabilities checks at open time.
781 if (from_file && type != SYSLOG_ACTION_OPEN)
784 if (syslog_action_restricted(type)) {
785 if (capable(CAP_SYSLOG))
787 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
788 if (capable(CAP_SYS_ADMIN)) {
789 printk_once(KERN_WARNING "%s (%d): "
790 "Attempt to access syslog with CAP_SYS_ADMIN "
791 "but no CAP_SYSLOG (deprecated).\n",
792 current->comm, task_pid_nr(current));
800 #if defined(CONFIG_PRINTK_TIME)
801 static bool printk_time = 1;
803 static bool printk_time;
805 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
807 static size_t print_time(u64 ts, char *buf)
809 unsigned long rem_nsec;
817 rem_nsec = do_div(ts, 1000000000);
818 return sprintf(buf, "[%5lu.%06lu] ",
819 (unsigned long)ts, rem_nsec / 1000);
822 static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
825 unsigned int prefix = (msg->facility << 3) | msg->level;
829 len += sprintf(buf, "<%u>", prefix);
834 else if (prefix > 99)
841 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
845 static size_t msg_print_text(const struct log *msg, enum log_flags prev,
846 bool syslog, char *buf, size_t size)
848 const char *text = log_text(msg);
849 size_t text_size = msg->text_len;
854 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
857 if (msg->flags & LOG_CONT) {
858 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
861 if (!(msg->flags & LOG_NEWLINE))
866 const char *next = memchr(text, '\n', text_size);
870 text_len = next - text;
872 text_size -= next - text;
874 text_len = text_size;
878 if (print_prefix(msg, syslog, NULL) +
879 text_len + 1>= size - len)
883 len += print_prefix(msg, syslog, buf + len);
884 memcpy(buf + len, text, text_len);
889 /* SYSLOG_ACTION_* buffer size only calculation */
891 len += print_prefix(msg, syslog, NULL);
904 static int syslog_print(char __user *buf, int size)
910 text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
918 raw_spin_lock_irq(&logbuf_lock);
919 if (syslog_seq < log_first_seq) {
920 /* messages are gone, move to first one */
921 syslog_seq = log_first_seq;
922 syslog_idx = log_first_idx;
926 if (syslog_seq == log_next_seq) {
927 raw_spin_unlock_irq(&logbuf_lock);
931 skip = syslog_partial;
932 msg = log_from_idx(syslog_idx);
933 n = msg_print_text(msg, syslog_prev, true, text, LOG_LINE_MAX);
934 if (n - syslog_partial <= size) {
935 /* message fits into buffer, move forward */
936 syslog_idx = log_next(syslog_idx);
938 syslog_prev = msg->flags;
942 /* partial read(), remember position */
947 raw_spin_unlock_irq(&logbuf_lock);
952 if (copy_to_user(buf, text + skip, n)) {
967 static int syslog_print_all(char __user *buf, int size, bool clear)
972 text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
976 raw_spin_lock_irq(&logbuf_lock);
983 if (clear_seq < log_first_seq) {
984 /* messages are gone, move to first available one */
985 clear_seq = log_first_seq;
986 clear_idx = log_first_idx;
990 * Find first record that fits, including all following records,
991 * into the user-provided buffer for this dump.
996 while (seq < log_next_seq) {
997 struct log *msg = log_from_idx(idx);
999 len += msg_print_text(msg, prev, true, NULL, 0);
1000 idx = log_next(idx);
1004 /* move first record forward until length fits into the buffer */
1008 while (len > size && seq < log_next_seq) {
1009 struct log *msg = log_from_idx(idx);
1011 len -= msg_print_text(msg, prev, true, NULL, 0);
1012 idx = log_next(idx);
1016 /* last message fitting into this dump */
1017 next_seq = log_next_seq;
1021 while (len >= 0 && seq < next_seq) {
1022 struct log *msg = log_from_idx(idx);
1025 textlen = msg_print_text(msg, prev, true, text, LOG_LINE_MAX);
1030 idx = log_next(idx);
1034 raw_spin_unlock_irq(&logbuf_lock);
1035 if (copy_to_user(buf + len, text, textlen))
1039 raw_spin_lock_irq(&logbuf_lock);
1041 if (seq < log_first_seq) {
1042 /* messages are gone, move to next one */
1043 seq = log_first_seq;
1044 idx = log_first_idx;
1051 clear_seq = log_next_seq;
1052 clear_idx = log_next_idx;
1054 raw_spin_unlock_irq(&logbuf_lock);
1060 int do_syslog(int type, char __user *buf, int len, bool from_file)
1063 static int saved_console_loglevel = -1;
1066 error = check_syslog_permissions(type, from_file);
1070 error = security_syslog(type);
1075 case SYSLOG_ACTION_CLOSE: /* Close log */
1077 case SYSLOG_ACTION_OPEN: /* Open log */
1079 case SYSLOG_ACTION_READ: /* Read from log */
1081 if (!buf || len < 0)
1086 if (!access_ok(VERIFY_WRITE, buf, len)) {
1090 error = wait_event_interruptible(log_wait,
1091 syslog_seq != log_next_seq);
1094 error = syslog_print(buf, len);
1096 /* Read/clear last kernel messages */
1097 case SYSLOG_ACTION_READ_CLEAR:
1100 /* Read last kernel messages */
1101 case SYSLOG_ACTION_READ_ALL:
1103 if (!buf || len < 0)
1108 if (!access_ok(VERIFY_WRITE, buf, len)) {
1112 error = syslog_print_all(buf, len, clear);
1114 /* Clear ring buffer */
1115 case SYSLOG_ACTION_CLEAR:
1116 syslog_print_all(NULL, 0, true);
1118 /* Disable logging to console */
1119 case SYSLOG_ACTION_CONSOLE_OFF:
1120 if (saved_console_loglevel == -1)
1121 saved_console_loglevel = console_loglevel;
1122 console_loglevel = minimum_console_loglevel;
1124 /* Enable logging to console */
1125 case SYSLOG_ACTION_CONSOLE_ON:
1126 if (saved_console_loglevel != -1) {
1127 console_loglevel = saved_console_loglevel;
1128 saved_console_loglevel = -1;
1131 /* Set level of messages printed to console */
1132 case SYSLOG_ACTION_CONSOLE_LEVEL:
1134 if (len < 1 || len > 8)
1136 if (len < minimum_console_loglevel)
1137 len = minimum_console_loglevel;
1138 console_loglevel = len;
1139 /* Implicitly re-enable logging to console */
1140 saved_console_loglevel = -1;
1143 /* Number of chars in the log buffer */
1144 case SYSLOG_ACTION_SIZE_UNREAD:
1145 raw_spin_lock_irq(&logbuf_lock);
1146 if (syslog_seq < log_first_seq) {
1147 /* messages are gone, move to first one */
1148 syslog_seq = log_first_seq;
1149 syslog_idx = log_first_idx;
1155 * Short-cut for poll(/"proc/kmsg") which simply checks
1156 * for pending data, not the size; return the count of
1157 * records, not the length.
1159 error = log_next_idx - syslog_idx;
1161 u64 seq = syslog_seq;
1162 u32 idx = syslog_idx;
1163 enum log_flags prev = syslog_prev;
1166 while (seq < log_next_seq) {
1167 struct log *msg = log_from_idx(idx);
1169 error += msg_print_text(msg, prev, true, NULL, 0);
1170 idx = log_next(idx);
1174 error -= syslog_partial;
1176 raw_spin_unlock_irq(&logbuf_lock);
1178 /* Size of the log buffer */
1179 case SYSLOG_ACTION_SIZE_BUFFER:
1180 error = log_buf_len;
1190 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1192 return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
1195 #ifdef CONFIG_KGDB_KDB
1196 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
1197 * uses locks so it cannot be used during debugging. Just tell kdb
1198 * where the start and end of the physical and logical logs are. This
1199 * is equivalent to do_syslog(3).
1201 void kdb_syslog_data(char *syslog_data[4])
1203 syslog_data[0] = log_buf;
1204 syslog_data[1] = log_buf + log_buf_len;
1205 syslog_data[2] = log_buf + log_first_idx;
1206 syslog_data[3] = log_buf + log_next_idx;
1208 #endif /* CONFIG_KGDB_KDB */
1210 static bool __read_mostly ignore_loglevel;
1212 static int __init ignore_loglevel_setup(char *str)
1214 ignore_loglevel = 1;
1215 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
1220 early_param("ignore_loglevel", ignore_loglevel_setup);
1221 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1222 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
1223 "print all kernel messages to the console.");
1226 * Call the console drivers, asking them to write out
1227 * log_buf[start] to log_buf[end - 1].
1228 * The console_lock must be held.
1230 static void call_console_drivers(int level, const char *text, size_t len)
1232 struct console *con;
1234 trace_console(text, 0, len, len);
1236 if (level >= console_loglevel && !ignore_loglevel)
1238 if (!console_drivers)
1241 for_each_console(con) {
1242 if (exclusive_console && con != exclusive_console)
1244 if (!(con->flags & CON_ENABLED))
1248 if (!cpu_online(smp_processor_id()) &&
1249 !(con->flags & CON_ANYTIME))
1251 con->write(con, text, len);
1256 * Zap console related locks when oopsing. Only zap at most once
1257 * every 10 seconds, to leave time for slow consoles to print a
1260 static void zap_locks(void)
1262 static unsigned long oops_timestamp;
1264 if (time_after_eq(jiffies, oops_timestamp) &&
1265 !time_after(jiffies, oops_timestamp + 30 * HZ))
1268 oops_timestamp = jiffies;
1271 /* If a crash is occurring, make sure we can't deadlock */
1272 raw_spin_lock_init(&logbuf_lock);
1273 /* And make sure that we print immediately */
1274 sema_init(&console_sem, 1);
1277 /* Check if we have any console registered that can be called early in boot. */
1278 static int have_callable_console(void)
1280 struct console *con;
1282 for_each_console(con)
1283 if (con->flags & CON_ANYTIME)
1290 * Can we actually use the console at this time on this cpu?
1292 * Console drivers may assume that per-cpu resources have
1293 * been allocated. So unless they're explicitly marked as
1294 * being able to cope (CON_ANYTIME) don't call them until
1295 * this CPU is officially up.
1297 static inline int can_use_console(unsigned int cpu)
1299 return cpu_online(cpu) || have_callable_console();
1303 * Try to get console ownership to actually show the kernel
1304 * messages from a 'printk'. Return true (and with the
1305 * console_lock held, and 'console_locked' set) if it
1306 * is successful, false otherwise.
1308 * This gets called with the 'logbuf_lock' spinlock held and
1309 * interrupts disabled. It should return with 'lockbuf_lock'
1310 * released but interrupts still disabled.
1312 static int console_trylock_for_printk(unsigned int cpu)
1313 __releases(&logbuf_lock)
1315 int retval = 0, wake = 0;
1317 if (console_trylock()) {
1321 * If we can't use the console, we need to release
1322 * the console semaphore by hand to avoid flushing
1323 * the buffer. We need to hold the console semaphore
1324 * in order to do this test safely.
1326 if (!can_use_console(cpu)) {
1332 logbuf_cpu = UINT_MAX;
1335 raw_spin_unlock(&logbuf_lock);
1339 int printk_delay_msec __read_mostly;
1341 static inline void printk_delay(void)
1343 if (unlikely(printk_delay_msec)) {
1344 int m = printk_delay_msec;
1348 touch_nmi_watchdog();
1354 * Continuation lines are buffered, and not committed to the record buffer
1355 * until the line is complete, or a race forces it. The line fragments
1356 * though, are printed immediately to the consoles to ensure everything has
1357 * reached the console in case of a kernel crash.
1359 static struct cont {
1360 char buf[LOG_LINE_MAX];
1361 size_t len; /* length == 0 means unused buffer */
1362 size_t cons; /* bytes written to console */
1363 struct task_struct *owner; /* task of first print*/
1364 u64 ts_nsec; /* time of first print */
1365 u8 level; /* log level of first message */
1366 u8 facility; /* log level of first message */
1367 bool flushed:1; /* buffer sealed and committed */
1370 static void cont_flush(void)
1377 log_store(cont.facility, cont.level, LOG_NOCONS, cont.ts_nsec,
1378 NULL, 0, cont.buf, cont.len);
1380 cont.flushed = true;
1383 static bool cont_add(int facility, int level, const char *text, size_t len)
1385 if (cont.len && cont.flushed)
1388 if (cont.len + len > sizeof(cont.buf)) {
1394 cont.facility = facility;
1396 cont.owner = current;
1397 cont.ts_nsec = local_clock();
1399 cont.flushed = false;
1402 memcpy(cont.buf + cont.len, text, len);
1407 static size_t cont_print_text(char *text, size_t size)
1412 if (cont.cons == 0) {
1413 textlen += print_time(cont.ts_nsec, text);
1417 len = cont.len - cont.cons;
1421 memcpy(text + textlen, cont.buf + cont.cons, len);
1423 cont.cons = cont.len;
1427 text[textlen++] = '\n';
1428 /* got everything, release buffer */
1434 asmlinkage int vprintk_emit(int facility, int level,
1435 const char *dict, size_t dictlen,
1436 const char *fmt, va_list args)
1438 static int recursion_bug;
1439 static char textbuf[LOG_LINE_MAX];
1440 char *text = textbuf;
1442 enum log_flags lflags = 0;
1443 unsigned long flags;
1445 int printed_len = 0;
1450 /* This stops the holder of console_sem just where we want him */
1451 local_irq_save(flags);
1452 this_cpu = smp_processor_id();
1455 * Ouch, printk recursed into itself!
1457 if (unlikely(logbuf_cpu == this_cpu)) {
1459 * If a crash is occurring during printk() on this CPU,
1460 * then try to get the crash message out but make sure
1461 * we can't deadlock. Otherwise just return to avoid the
1462 * recursion and return - but flag the recursion so that
1463 * it can be printed at the next appropriate moment:
1465 if (!oops_in_progress && !lockdep_recursing(current)) {
1467 goto out_restore_irqs;
1473 raw_spin_lock(&logbuf_lock);
1474 logbuf_cpu = this_cpu;
1476 if (recursion_bug) {
1477 static const char recursion_msg[] =
1478 "BUG: recent printk recursion!";
1481 printed_len += strlen(recursion_msg);
1482 /* emit KERN_CRIT message */
1483 log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1484 NULL, 0, recursion_msg, printed_len);
1488 * The printf needs to come first; we need the syslog
1489 * prefix which might be passed-in as a parameter.
1491 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1493 /* mark and strip a trailing newline */
1494 if (text_len && text[text_len-1] == '\n') {
1496 lflags |= LOG_NEWLINE;
1499 /* strip syslog prefix and extract log level or control flags */
1500 if (text[0] == '<' && text[1] && text[2] == '>') {
1504 level = text[1] - '0';
1505 case 'd': /* KERN_DEFAULT */
1506 lflags |= LOG_PREFIX;
1507 case 'c': /* KERN_CONT */
1514 level = default_message_loglevel;
1517 lflags |= LOG_PREFIX|LOG_NEWLINE;
1519 if (!(lflags & LOG_NEWLINE)) {
1521 * Flush the conflicting buffer. An earlier newline was missing,
1522 * or another task also prints continuation lines.
1524 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1527 /* buffer line if possible, otherwise store it right away */
1528 if (!cont_add(facility, level, text, text_len))
1529 log_store(facility, level, lflags | LOG_CONT, 0,
1530 dict, dictlen, text, text_len);
1532 bool stored = false;
1535 * If an earlier newline was missing and it was the same task,
1536 * either merge it with the current buffer and flush, or if
1537 * there was a race with interrupts (prefix == true) then just
1538 * flush it out and store this line separately.
1540 if (cont.len && cont.owner == current) {
1541 if (!(lflags & LOG_PREFIX))
1542 stored = cont_add(facility, level, text, text_len);
1547 log_store(facility, level, lflags, 0,
1548 dict, dictlen, text, text_len);
1550 printed_len += text_len;
1553 * Try to acquire and then immediately release the console semaphore.
1554 * The release will print out buffers and wake up /dev/kmsg and syslog()
1557 * The console_trylock_for_printk() function will release 'logbuf_lock'
1558 * regardless of whether it actually gets the console semaphore or not.
1560 if (console_trylock_for_printk(this_cpu))
1565 local_irq_restore(flags);
1569 EXPORT_SYMBOL(vprintk_emit);
1571 asmlinkage int vprintk(const char *fmt, va_list args)
1573 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1575 EXPORT_SYMBOL(vprintk);
1577 asmlinkage int printk_emit(int facility, int level,
1578 const char *dict, size_t dictlen,
1579 const char *fmt, ...)
1584 va_start(args, fmt);
1585 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1590 EXPORT_SYMBOL(printk_emit);
1593 * printk - print a kernel message
1594 * @fmt: format string
1596 * This is printk(). It can be called from any context. We want it to work.
1598 * We try to grab the console_lock. If we succeed, it's easy - we log the
1599 * output and call the console drivers. If we fail to get the semaphore, we
1600 * place the output into the log buffer and return. The current holder of
1601 * the console_sem will notice the new output in console_unlock(); and will
1602 * send it to the consoles before releasing the lock.
1604 * One effect of this deferred printing is that code which calls printk() and
1605 * then changes console_loglevel may break. This is because console_loglevel
1606 * is inspected when the actual printing occurs.
1611 * See the vsnprintf() documentation for format string extensions over C99.
1613 asmlinkage int printk(const char *fmt, ...)
1618 #ifdef CONFIG_KGDB_KDB
1619 if (unlikely(kdb_trap_printk)) {
1620 va_start(args, fmt);
1621 r = vkdb_printf(fmt, args);
1626 va_start(args, fmt);
1627 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1632 EXPORT_SYMBOL(printk);
1636 #define LOG_LINE_MAX 0
1637 static struct cont {
1643 static struct log *log_from_idx(u32 idx) { return NULL; }
1644 static u32 log_next(u32 idx) { return 0; }
1645 static void call_console_drivers(int level, const char *text, size_t len) {}
1646 static size_t msg_print_text(const struct log *msg, enum log_flags prev,
1647 bool syslog, char *buf, size_t size) { return 0; }
1648 static size_t cont_print_text(char *text, size_t size) { return 0; }
1650 #endif /* CONFIG_PRINTK */
1652 static int __add_preferred_console(char *name, int idx, char *options,
1655 struct console_cmdline *c;
1659 * See if this tty is not yet registered, and
1660 * if we have a slot free.
1662 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1663 if (strcmp(console_cmdline[i].name, name) == 0 &&
1664 console_cmdline[i].index == idx) {
1666 selected_console = i;
1669 if (i == MAX_CMDLINECONSOLES)
1672 selected_console = i;
1673 c = &console_cmdline[i];
1674 strlcpy(c->name, name, sizeof(c->name));
1675 c->options = options;
1676 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1677 c->brl_options = brl_options;
1683 * Set up a list of consoles. Called from init/main.c
1685 static int __init console_setup(char *str)
1687 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1688 char *s, *options, *brl_options = NULL;
1691 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1692 if (!memcmp(str, "brl,", 4)) {
1695 } else if (!memcmp(str, "brl=", 4)) {
1696 brl_options = str + 4;
1697 str = strchr(brl_options, ',');
1699 printk(KERN_ERR "need port name after brl=\n");
1707 * Decode str into name, index, options.
1709 if (str[0] >= '0' && str[0] <= '9') {
1710 strcpy(buf, "ttyS");
1711 strncpy(buf + 4, str, sizeof(buf) - 5);
1713 strncpy(buf, str, sizeof(buf) - 1);
1715 buf[sizeof(buf) - 1] = 0;
1716 if ((options = strchr(str, ',')) != NULL)
1719 if (!strcmp(str, "ttya"))
1720 strcpy(buf, "ttyS0");
1721 if (!strcmp(str, "ttyb"))
1722 strcpy(buf, "ttyS1");
1724 for (s = buf; *s; s++)
1725 if ((*s >= '0' && *s <= '9') || *s == ',')
1727 idx = simple_strtoul(s, NULL, 10);
1730 __add_preferred_console(buf, idx, options, brl_options);
1731 console_set_on_cmdline = 1;
1734 __setup("console=", console_setup);
1737 * add_preferred_console - add a device to the list of preferred consoles.
1738 * @name: device name
1739 * @idx: device index
1740 * @options: options for this console
1742 * The last preferred console added will be used for kernel messages
1743 * and stdin/out/err for init. Normally this is used by console_setup
1744 * above to handle user-supplied console arguments; however it can also
1745 * be used by arch-specific code either to override the user or more
1746 * commonly to provide a default console (ie from PROM variables) when
1747 * the user has not supplied one.
1749 int add_preferred_console(char *name, int idx, char *options)
1751 return __add_preferred_console(name, idx, options, NULL);
1754 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1756 struct console_cmdline *c;
1759 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1760 if (strcmp(console_cmdline[i].name, name) == 0 &&
1761 console_cmdline[i].index == idx) {
1762 c = &console_cmdline[i];
1763 strlcpy(c->name, name_new, sizeof(c->name));
1764 c->name[sizeof(c->name) - 1] = 0;
1765 c->options = options;
1773 bool console_suspend_enabled = 1;
1774 EXPORT_SYMBOL(console_suspend_enabled);
1776 static int __init console_suspend_disable(char *str)
1778 console_suspend_enabled = 0;
1781 __setup("no_console_suspend", console_suspend_disable);
1782 module_param_named(console_suspend, console_suspend_enabled,
1783 bool, S_IRUGO | S_IWUSR);
1784 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1785 " and hibernate operations");
1788 * suspend_console - suspend the console subsystem
1790 * This disables printk() while we go into suspend states
1792 void suspend_console(void)
1794 if (!console_suspend_enabled)
1796 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1798 console_suspended = 1;
1802 void resume_console(void)
1804 if (!console_suspend_enabled)
1807 console_suspended = 0;
1812 * console_cpu_notify - print deferred console messages after CPU hotplug
1813 * @self: notifier struct
1814 * @action: CPU hotplug event
1817 * If printk() is called from a CPU that is not online yet, the messages
1818 * will be spooled but will not show up on the console. This function is
1819 * called when a new CPU comes online (or fails to come up), and ensures
1820 * that any such output gets printed.
1822 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1823 unsigned long action, void *hcpu)
1829 case CPU_DOWN_FAILED:
1830 case CPU_UP_CANCELED:
1838 * console_lock - lock the console system for exclusive use.
1840 * Acquires a lock which guarantees that the caller has
1841 * exclusive access to the console system and the console_drivers list.
1843 * Can sleep, returns nothing.
1845 void console_lock(void)
1847 BUG_ON(in_interrupt());
1849 if (console_suspended)
1852 console_may_schedule = 1;
1854 EXPORT_SYMBOL(console_lock);
1857 * console_trylock - try to lock the console system for exclusive use.
1859 * Tried to acquire a lock which guarantees that the caller has
1860 * exclusive access to the console system and the console_drivers list.
1862 * returns 1 on success, and 0 on failure to acquire the lock.
1864 int console_trylock(void)
1866 if (down_trylock(&console_sem))
1868 if (console_suspended) {
1873 console_may_schedule = 0;
1876 EXPORT_SYMBOL(console_trylock);
1878 int is_console_locked(void)
1880 return console_locked;
1884 * Delayed printk version, for scheduler-internal messages:
1886 #define PRINTK_BUF_SIZE 512
1888 #define PRINTK_PENDING_WAKEUP 0x01
1889 #define PRINTK_PENDING_SCHED 0x02
1891 static DEFINE_PER_CPU(int, printk_pending);
1892 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
1894 void printk_tick(void)
1896 if (__this_cpu_read(printk_pending)) {
1897 int pending = __this_cpu_xchg(printk_pending, 0);
1898 if (pending & PRINTK_PENDING_SCHED) {
1899 char *buf = __get_cpu_var(printk_sched_buf);
1900 printk(KERN_WARNING "[sched_delayed] %s", buf);
1902 if (pending & PRINTK_PENDING_WAKEUP)
1903 wake_up_interruptible(&log_wait);
1907 int printk_needs_cpu(int cpu)
1909 if (cpu_is_offline(cpu))
1911 return __this_cpu_read(printk_pending);
1914 void wake_up_klogd(void)
1916 if (waitqueue_active(&log_wait))
1917 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
1920 /* the next printk record to write to the console */
1921 static u64 console_seq;
1922 static u32 console_idx;
1923 static enum log_flags console_prev;
1926 * console_unlock - unlock the console system
1928 * Releases the console_lock which the caller holds on the console system
1929 * and the console driver list.
1931 * While the console_lock was held, console output may have been buffered
1932 * by printk(). If this is the case, console_unlock(); emits
1933 * the output prior to releasing the lock.
1935 * If there is output waiting, we wake /dev/kmsg and syslog() users.
1937 * console_unlock(); may be called from any context.
1939 void console_unlock(void)
1941 static char text[LOG_LINE_MAX];
1942 static u64 seen_seq;
1943 unsigned long flags;
1944 bool wake_klogd = false;
1947 if (console_suspended) {
1952 console_may_schedule = 0;
1954 /* flush buffered message fragment immediately to console */
1955 raw_spin_lock_irqsave(&logbuf_lock, flags);
1956 if (cont.len && (cont.cons < cont.len || cont.flushed)) {
1959 len = cont_print_text(text, sizeof(text));
1960 raw_spin_unlock(&logbuf_lock);
1961 stop_critical_timings();
1962 call_console_drivers(cont.level, text, len);
1963 start_critical_timings();
1964 local_irq_restore(flags);
1966 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
1974 raw_spin_lock_irqsave(&logbuf_lock, flags);
1975 if (seen_seq != log_next_seq) {
1977 seen_seq = log_next_seq;
1980 if (console_seq < log_first_seq) {
1981 /* messages are gone, move to first one */
1982 console_seq = log_first_seq;
1983 console_idx = log_first_idx;
1987 if (console_seq == log_next_seq)
1990 msg = log_from_idx(console_idx);
1991 if (msg->flags & LOG_NOCONS) {
1993 * Skip record we have buffered and already printed
1994 * directly to the console when we received it.
1996 console_idx = log_next(console_idx);
1999 * We will get here again when we register a new
2000 * CON_PRINTBUFFER console. Clear the flag so we
2001 * will properly dump everything later.
2003 msg->flags &= ~LOG_NOCONS;
2008 len = msg_print_text(msg, console_prev, false,
2009 text, sizeof(text));
2010 console_idx = log_next(console_idx);
2012 console_prev = msg->flags;
2013 raw_spin_unlock(&logbuf_lock);
2015 stop_critical_timings(); /* don't trace print latency */
2016 call_console_drivers(level, text, len);
2017 start_critical_timings();
2018 local_irq_restore(flags);
2022 /* Release the exclusive_console once it is used */
2023 if (unlikely(exclusive_console))
2024 exclusive_console = NULL;
2026 raw_spin_unlock(&logbuf_lock);
2031 * Someone could have filled up the buffer again, so re-check if there's
2032 * something to flush. In case we cannot trylock the console_sem again,
2033 * there's a new owner and the console_unlock() from them will do the
2034 * flush, no worries.
2036 raw_spin_lock(&logbuf_lock);
2037 retry = console_seq != log_next_seq;
2038 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2040 if (retry && console_trylock())
2046 EXPORT_SYMBOL(console_unlock);
2049 * console_conditional_schedule - yield the CPU if required
2051 * If the console code is currently allowed to sleep, and
2052 * if this CPU should yield the CPU to another task, do
2055 * Must be called within console_lock();.
2057 void __sched console_conditional_schedule(void)
2059 if (console_may_schedule)
2062 EXPORT_SYMBOL(console_conditional_schedule);
2064 void console_unblank(void)
2069 * console_unblank can no longer be called in interrupt context unless
2070 * oops_in_progress is set to 1..
2072 if (oops_in_progress) {
2073 if (down_trylock(&console_sem) != 0)
2079 console_may_schedule = 0;
2081 if ((c->flags & CON_ENABLED) && c->unblank)
2087 * Return the console tty driver structure and its associated index
2089 struct tty_driver *console_device(int *index)
2092 struct tty_driver *driver = NULL;
2095 for_each_console(c) {
2098 driver = c->device(c, index);
2107 * Prevent further output on the passed console device so that (for example)
2108 * serial drivers can disable console output before suspending a port, and can
2109 * re-enable output afterwards.
2111 void console_stop(struct console *console)
2114 console->flags &= ~CON_ENABLED;
2117 EXPORT_SYMBOL(console_stop);
2119 void console_start(struct console *console)
2122 console->flags |= CON_ENABLED;
2125 EXPORT_SYMBOL(console_start);
2127 static int __read_mostly keep_bootcon;
2129 static int __init keep_bootcon_setup(char *str)
2132 printk(KERN_INFO "debug: skip boot console de-registration.\n");
2137 early_param("keep_bootcon", keep_bootcon_setup);
2140 * The console driver calls this routine during kernel initialization
2141 * to register the console printing procedure with printk() and to
2142 * print any messages that were printed by the kernel before the
2143 * console driver was initialized.
2145 * This can happen pretty early during the boot process (because of
2146 * early_printk) - sometimes before setup_arch() completes - be careful
2147 * of what kernel features are used - they may not be initialised yet.
2149 * There are two types of consoles - bootconsoles (early_printk) and
2150 * "real" consoles (everything which is not a bootconsole) which are
2151 * handled differently.
2152 * - Any number of bootconsoles can be registered at any time.
2153 * - As soon as a "real" console is registered, all bootconsoles
2154 * will be unregistered automatically.
2155 * - Once a "real" console is registered, any attempt to register a
2156 * bootconsoles will be rejected
2158 void register_console(struct console *newcon)
2161 unsigned long flags;
2162 struct console *bcon = NULL;
2165 * before we register a new CON_BOOT console, make sure we don't
2166 * already have a valid console
2168 if (console_drivers && newcon->flags & CON_BOOT) {
2169 /* find the last or real console */
2170 for_each_console(bcon) {
2171 if (!(bcon->flags & CON_BOOT)) {
2172 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
2173 newcon->name, newcon->index);
2179 if (console_drivers && console_drivers->flags & CON_BOOT)
2180 bcon = console_drivers;
2182 if (preferred_console < 0 || bcon || !console_drivers)
2183 preferred_console = selected_console;
2185 if (newcon->early_setup)
2186 newcon->early_setup();
2189 * See if we want to use this console driver. If we
2190 * didn't select a console we take the first one
2191 * that registers here.
2193 if (preferred_console < 0) {
2194 if (newcon->index < 0)
2196 if (newcon->setup == NULL ||
2197 newcon->setup(newcon, NULL) == 0) {
2198 newcon->flags |= CON_ENABLED;
2199 if (newcon->device) {
2200 newcon->flags |= CON_CONSDEV;
2201 preferred_console = 0;
2207 * See if this console matches one we selected on
2210 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
2212 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
2214 if (newcon->index >= 0 &&
2215 newcon->index != console_cmdline[i].index)
2217 if (newcon->index < 0)
2218 newcon->index = console_cmdline[i].index;
2219 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2220 if (console_cmdline[i].brl_options) {
2221 newcon->flags |= CON_BRL;
2222 braille_register_console(newcon,
2223 console_cmdline[i].index,
2224 console_cmdline[i].options,
2225 console_cmdline[i].brl_options);
2229 if (newcon->setup &&
2230 newcon->setup(newcon, console_cmdline[i].options) != 0)
2232 newcon->flags |= CON_ENABLED;
2233 newcon->index = console_cmdline[i].index;
2234 if (i == selected_console) {
2235 newcon->flags |= CON_CONSDEV;
2236 preferred_console = selected_console;
2241 if (!(newcon->flags & CON_ENABLED))
2245 * If we have a bootconsole, and are switching to a real console,
2246 * don't print everything out again, since when the boot console, and
2247 * the real console are the same physical device, it's annoying to
2248 * see the beginning boot messages twice
2250 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2251 newcon->flags &= ~CON_PRINTBUFFER;
2254 * Put this console in the list - keep the
2255 * preferred driver at the head of the list.
2258 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2259 newcon->next = console_drivers;
2260 console_drivers = newcon;
2262 newcon->next->flags &= ~CON_CONSDEV;
2264 newcon->next = console_drivers->next;
2265 console_drivers->next = newcon;
2267 if (newcon->flags & CON_PRINTBUFFER) {
2269 * console_unlock(); will print out the buffered messages
2272 raw_spin_lock_irqsave(&logbuf_lock, flags);
2273 console_seq = syslog_seq;
2274 console_idx = syslog_idx;
2275 console_prev = syslog_prev;
2276 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2278 * We're about to replay the log buffer. Only do this to the
2279 * just-registered console to avoid excessive message spam to
2280 * the already-registered consoles.
2282 exclusive_console = newcon;
2285 console_sysfs_notify();
2288 * By unregistering the bootconsoles after we enable the real console
2289 * we get the "console xxx enabled" message on all the consoles -
2290 * boot consoles, real consoles, etc - this is to ensure that end
2291 * users know there might be something in the kernel's log buffer that
2292 * went to the bootconsole (that they do not see on the real console)
2295 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2297 /* we need to iterate through twice, to make sure we print
2298 * everything out, before we unregister the console(s)
2300 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
2301 newcon->name, newcon->index);
2302 for_each_console(bcon)
2303 if (bcon->flags & CON_BOOT)
2304 unregister_console(bcon);
2306 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
2307 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2308 newcon->name, newcon->index);
2311 EXPORT_SYMBOL(register_console);
2313 int unregister_console(struct console *console)
2315 struct console *a, *b;
2318 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2319 if (console->flags & CON_BRL)
2320 return braille_unregister_console(console);
2324 if (console_drivers == console) {
2325 console_drivers=console->next;
2327 } else if (console_drivers) {
2328 for (a=console_drivers->next, b=console_drivers ;
2329 a; b=a, a=b->next) {
2339 * If this isn't the last console and it has CON_CONSDEV set, we
2340 * need to set it on the next preferred console.
2342 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2343 console_drivers->flags |= CON_CONSDEV;
2346 console_sysfs_notify();
2349 EXPORT_SYMBOL(unregister_console);
2351 static int __init printk_late_init(void)
2353 struct console *con;
2355 for_each_console(con) {
2356 if (!keep_bootcon && con->flags & CON_BOOT) {
2357 printk(KERN_INFO "turn off boot console %s%d\n",
2358 con->name, con->index);
2359 unregister_console(con);
2362 hotcpu_notifier(console_cpu_notify, 0);
2365 late_initcall(printk_late_init);
2367 #if defined CONFIG_PRINTK
2369 int printk_sched(const char *fmt, ...)
2371 unsigned long flags;
2376 local_irq_save(flags);
2377 buf = __get_cpu_var(printk_sched_buf);
2379 va_start(args, fmt);
2380 r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2383 __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2384 local_irq_restore(flags);
2390 * printk rate limiting, lifted from the networking subsystem.
2392 * This enforces a rate limit: not more than 10 kernel messages
2393 * every 5s to make a denial-of-service attack impossible.
2395 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2397 int __printk_ratelimit(const char *func)
2399 return ___ratelimit(&printk_ratelimit_state, func);
2401 EXPORT_SYMBOL(__printk_ratelimit);
2404 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2405 * @caller_jiffies: pointer to caller's state
2406 * @interval_msecs: minimum interval between prints
2408 * printk_timed_ratelimit() returns true if more than @interval_msecs
2409 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2412 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2413 unsigned int interval_msecs)
2415 if (*caller_jiffies == 0
2416 || !time_in_range(jiffies, *caller_jiffies,
2418 + msecs_to_jiffies(interval_msecs))) {
2419 *caller_jiffies = jiffies;
2424 EXPORT_SYMBOL(printk_timed_ratelimit);
2426 static DEFINE_SPINLOCK(dump_list_lock);
2427 static LIST_HEAD(dump_list);
2430 * kmsg_dump_register - register a kernel log dumper.
2431 * @dumper: pointer to the kmsg_dumper structure
2433 * Adds a kernel log dumper to the system. The dump callback in the
2434 * structure will be called when the kernel oopses or panics and must be
2435 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2437 int kmsg_dump_register(struct kmsg_dumper *dumper)
2439 unsigned long flags;
2442 /* The dump callback needs to be set */
2446 spin_lock_irqsave(&dump_list_lock, flags);
2447 /* Don't allow registering multiple times */
2448 if (!dumper->registered) {
2449 dumper->registered = 1;
2450 list_add_tail_rcu(&dumper->list, &dump_list);
2453 spin_unlock_irqrestore(&dump_list_lock, flags);
2457 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2460 * kmsg_dump_unregister - unregister a kmsg dumper.
2461 * @dumper: pointer to the kmsg_dumper structure
2463 * Removes a dump device from the system. Returns zero on success and
2464 * %-EINVAL otherwise.
2466 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2468 unsigned long flags;
2471 spin_lock_irqsave(&dump_list_lock, flags);
2472 if (dumper->registered) {
2473 dumper->registered = 0;
2474 list_del_rcu(&dumper->list);
2477 spin_unlock_irqrestore(&dump_list_lock, flags);
2482 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2484 static bool always_kmsg_dump;
2485 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2488 * kmsg_dump - dump kernel log to kernel message dumpers.
2489 * @reason: the reason (oops, panic etc) for dumping
2491 * Call each of the registered dumper's dump() callback, which can
2492 * retrieve the kmsg records with kmsg_dump_get_line() or
2493 * kmsg_dump_get_buffer().
2495 void kmsg_dump(enum kmsg_dump_reason reason)
2497 struct kmsg_dumper *dumper;
2498 unsigned long flags;
2500 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2504 list_for_each_entry_rcu(dumper, &dump_list, list) {
2505 if (dumper->max_reason && reason > dumper->max_reason)
2508 /* initialize iterator with data about the stored records */
2509 dumper->active = true;
2511 raw_spin_lock_irqsave(&logbuf_lock, flags);
2512 dumper->cur_seq = clear_seq;
2513 dumper->cur_idx = clear_idx;
2514 dumper->next_seq = log_next_seq;
2515 dumper->next_idx = log_next_idx;
2516 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2518 /* invoke dumper which will iterate over records */
2519 dumper->dump(dumper, reason);
2521 /* reset iterator */
2522 dumper->active = false;
2528 * kmsg_dump_get_line - retrieve one kmsg log line
2529 * @dumper: registered kmsg dumper
2530 * @syslog: include the "<4>" prefixes
2531 * @line: buffer to copy the line to
2532 * @size: maximum size of the buffer
2533 * @len: length of line placed into buffer
2535 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2536 * record, and copy one record into the provided buffer.
2538 * Consecutive calls will return the next available record moving
2539 * towards the end of the buffer with the youngest messages.
2541 * A return value of FALSE indicates that there are no more records to
2544 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2545 char *line, size_t size, size_t *len)
2547 unsigned long flags;
2552 if (!dumper->active)
2555 raw_spin_lock_irqsave(&logbuf_lock, flags);
2556 if (dumper->cur_seq < log_first_seq) {
2557 /* messages are gone, move to first available one */
2558 dumper->cur_seq = log_first_seq;
2559 dumper->cur_idx = log_first_idx;
2563 if (dumper->cur_seq >= log_next_seq) {
2564 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2568 msg = log_from_idx(dumper->cur_idx);
2569 l = msg_print_text(msg, 0, syslog, line, size);
2571 dumper->cur_idx = log_next(dumper->cur_idx);
2574 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2580 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2583 * kmsg_dump_get_buffer - copy kmsg log lines
2584 * @dumper: registered kmsg dumper
2585 * @syslog: include the "<4>" prefixes
2586 * @buf: buffer to copy the line to
2587 * @size: maximum size of the buffer
2588 * @len: length of line placed into buffer
2590 * Start at the end of the kmsg buffer and fill the provided buffer
2591 * with as many of the the *youngest* kmsg records that fit into it.
2592 * If the buffer is large enough, all available kmsg records will be
2593 * copied with a single call.
2595 * Consecutive calls will fill the buffer with the next block of
2596 * available older records, not including the earlier retrieved ones.
2598 * A return value of FALSE indicates that there are no more records to
2601 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2602 char *buf, size_t size, size_t *len)
2604 unsigned long flags;
2609 enum log_flags prev;
2613 if (!dumper->active)
2616 raw_spin_lock_irqsave(&logbuf_lock, flags);
2617 if (dumper->cur_seq < log_first_seq) {
2618 /* messages are gone, move to first available one */
2619 dumper->cur_seq = log_first_seq;
2620 dumper->cur_idx = log_first_idx;
2624 if (dumper->cur_seq >= dumper->next_seq) {
2625 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2629 /* calculate length of entire buffer */
2630 seq = dumper->cur_seq;
2631 idx = dumper->cur_idx;
2633 while (seq < dumper->next_seq) {
2634 struct log *msg = log_from_idx(idx);
2636 l += msg_print_text(msg, prev, true, NULL, 0);
2637 idx = log_next(idx);
2642 /* move first record forward until length fits into the buffer */
2643 seq = dumper->cur_seq;
2644 idx = dumper->cur_idx;
2646 while (l > size && seq < dumper->next_seq) {
2647 struct log *msg = log_from_idx(idx);
2649 l -= msg_print_text(msg, prev, true, NULL, 0);
2650 idx = log_next(idx);
2655 /* last message in next interation */
2661 while (seq < dumper->next_seq) {
2662 struct log *msg = log_from_idx(idx);
2664 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2665 idx = log_next(idx);
2670 dumper->next_seq = next_seq;
2671 dumper->next_idx = next_idx;
2673 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2679 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2682 * kmsg_dump_rewind - reset the interator
2683 * @dumper: registered kmsg dumper
2685 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2686 * kmsg_dump_get_buffer() can be called again and used multiple
2687 * times within the same dumper.dump() callback.
2689 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2691 unsigned long flags;
2693 raw_spin_lock_irqsave(&logbuf_lock, flags);
2694 dumper->cur_seq = clear_seq;
2695 dumper->cur_idx = clear_idx;
2696 dumper->next_seq = log_next_seq;
2697 dumper->next_idx = log_next_idx;
2698 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2700 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);