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 u64 ts_nsec; /* timestamp in nanoseconds */
198 u16 len; /* length of entire record */
199 u16 text_len; /* length of text buffer */
200 u16 dict_len; /* length of dictionary buffer */
201 u16 level; /* syslog level + facility */
205 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
206 * used in interesting ways to provide interlocking in console_unlock();
208 static DEFINE_RAW_SPINLOCK(logbuf_lock);
210 /* the next printk record to read by syslog(READ) or /proc/kmsg */
211 static u64 syslog_seq;
212 static u32 syslog_idx;
214 /* index and sequence number of the first record stored in the buffer */
215 static u64 log_first_seq;
216 static u32 log_first_idx;
218 /* index and sequence number of the next record to store in the buffer */
219 static u64 log_next_seq;
221 static u32 log_next_idx;
223 /* the next printk record to read after the last 'clear' command */
224 static u64 clear_seq;
225 static u32 clear_idx;
227 #define LOG_LINE_MAX 1024
230 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
233 #define LOG_ALIGN __alignof__(struct log)
235 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
236 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
237 static char *log_buf = __log_buf;
238 static u32 log_buf_len = __LOG_BUF_LEN;
240 /* cpu currently holding logbuf_lock */
241 static volatile unsigned int logbuf_cpu = UINT_MAX;
243 /* human readable text of the record */
244 static char *log_text(const struct log *msg)
246 return (char *)msg + sizeof(struct log);
249 /* optional key/value pair dictionary attached to the record */
250 static char *log_dict(const struct log *msg)
252 return (char *)msg + sizeof(struct log) + msg->text_len;
255 /* get record by index; idx must point to valid msg */
256 static struct log *log_from_idx(u32 idx)
258 struct log *msg = (struct log *)(log_buf + idx);
261 * A length == 0 record is the end of buffer marker. Wrap around and
262 * read the message at the start of the buffer.
265 return (struct log *)log_buf;
269 /* get next record; idx must point to valid msg */
270 static u32 log_next(u32 idx)
272 struct log *msg = (struct log *)(log_buf + idx);
274 /* length == 0 indicates the end of the buffer; wrap */
276 * A length == 0 record is the end of buffer marker. Wrap around and
277 * read the message at the start of the buffer as *this* one, and
278 * return the one after that.
281 msg = (struct log *)log_buf;
284 return idx + msg->len;
287 /* insert record into the buffer, discard old ones, update heads */
288 static void log_store(int facility, int level,
289 const char *dict, u16 dict_len,
290 const char *text, u16 text_len)
295 /* number of '\0' padding bytes to next message */
296 size = sizeof(struct log) + text_len + dict_len;
297 pad_len = (-size) & (LOG_ALIGN - 1);
300 while (log_first_seq < log_next_seq) {
303 if (log_next_idx > log_first_idx)
304 free = max(log_buf_len - log_next_idx, log_first_idx);
306 free = log_first_idx - log_next_idx;
308 if (free > size + sizeof(struct log))
311 /* drop old messages until we have enough contiuous space */
312 log_first_idx = log_next(log_first_idx);
316 if (log_next_idx + size + sizeof(struct log) >= log_buf_len) {
318 * This message + an additional empty header does not fit
319 * at the end of the buffer. Add an empty header with len == 0
320 * to signify a wrap around.
322 memset(log_buf + log_next_idx, 0, sizeof(struct log));
327 msg = (struct log *)(log_buf + log_next_idx);
328 memcpy(log_text(msg), text, text_len);
329 msg->text_len = text_len;
330 memcpy(log_dict(msg), dict, dict_len);
331 msg->dict_len = dict_len;
332 msg->level = (facility << 3) | (level & 7);
333 msg->ts_nsec = local_clock();
334 memset(log_dict(msg) + dict_len, 0, pad_len);
335 msg->len = sizeof(struct log) + text_len + dict_len + pad_len;
338 log_next_idx += msg->len;
342 /* /dev/kmsg - userspace message inject/listen interface */
343 struct devkmsg_user {
350 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
351 unsigned long count, loff_t pos)
355 int level = default_message_loglevel;
356 int facility = 1; /* LOG_USER */
357 size_t len = iov_length(iv, count);
360 if (len > LOG_LINE_MAX)
362 buf = kmalloc(len+1, GFP_KERNEL);
367 for (i = 0; i < count; i++) {
368 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len))
370 line += iv[i].iov_len;
374 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
375 * the decimal value represents 32bit, the lower 3 bit are the log
376 * level, the rest are the log facility.
378 * If no prefix or no userspace facility is specified, we
379 * enforce LOG_USER, to be able to reliably distinguish
380 * kernel-generated messages from userspace-injected ones.
383 if (line[0] == '<') {
386 i = simple_strtoul(line+1, &endp, 10);
387 if (endp && endp[0] == '>') {
398 printk_emit(facility, level, NULL, 0, "%s", line);
404 static ssize_t devkmsg_read(struct file *file, char __user *buf,
405 size_t count, loff_t *ppos)
407 struct devkmsg_user *user = file->private_data;
417 ret = mutex_lock_interruptible(&user->lock);
420 raw_spin_lock(&logbuf_lock);
421 while (user->seq == log_next_seq) {
422 if (file->f_flags & O_NONBLOCK) {
424 raw_spin_unlock(&logbuf_lock);
428 raw_spin_unlock(&logbuf_lock);
429 ret = wait_event_interruptible(log_wait,
430 user->seq != log_next_seq);
433 raw_spin_lock(&logbuf_lock);
436 if (user->seq < log_first_seq) {
437 /* our last seen message is gone, return error and reset */
438 user->idx = log_first_idx;
439 user->seq = log_first_seq;
441 raw_spin_unlock(&logbuf_lock);
445 msg = log_from_idx(user->idx);
446 ts_usec = msg->ts_nsec;
447 do_div(ts_usec, 1000);
448 len = sprintf(user->buf, "%u,%llu,%llu;",
449 msg->level, user->seq, ts_usec);
451 /* escape non-printable characters */
452 for (i = 0; i < msg->text_len; i++) {
453 unsigned char c = log_text(msg)[i];
455 if (c < ' ' || c >= 128)
456 len += sprintf(user->buf + len, "\\x%02x", c);
458 user->buf[len++] = c;
460 user->buf[len++] = '\n';
465 for (i = 0; i < msg->dict_len; i++) {
466 unsigned char c = log_dict(msg)[i];
469 user->buf[len++] = ' ';
474 user->buf[len++] = '\n';
479 if (c < ' ' || c >= 128) {
480 len += sprintf(user->buf + len, "\\x%02x", c);
484 user->buf[len++] = c;
486 user->buf[len++] = '\n';
489 user->idx = log_next(user->idx);
491 raw_spin_unlock(&logbuf_lock);
498 if (copy_to_user(buf, user->buf, len)) {
504 mutex_unlock(&user->lock);
508 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
510 struct devkmsg_user *user = file->private_data;
518 raw_spin_lock(&logbuf_lock);
521 /* the first record */
522 user->idx = log_first_idx;
523 user->seq = log_first_seq;
527 * The first record after the last SYSLOG_ACTION_CLEAR,
528 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
529 * changes no global state, and does not clear anything.
531 user->idx = clear_idx;
532 user->seq = clear_seq;
535 /* after the last record */
536 user->idx = log_next_idx;
537 user->seq = log_next_seq;
542 raw_spin_unlock(&logbuf_lock);
546 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
548 struct devkmsg_user *user = file->private_data;
552 return POLLERR|POLLNVAL;
554 poll_wait(file, &log_wait, wait);
556 raw_spin_lock(&logbuf_lock);
557 if (user->seq < log_next_seq) {
558 /* return error when data has vanished underneath us */
559 if (user->seq < log_first_seq)
560 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
561 ret = POLLIN|POLLRDNORM;
563 raw_spin_unlock(&logbuf_lock);
568 static int devkmsg_open(struct inode *inode, struct file *file)
570 struct devkmsg_user *user;
573 /* write-only does not need any file context */
574 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
577 err = security_syslog(SYSLOG_ACTION_READ_ALL);
581 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
585 mutex_init(&user->lock);
587 raw_spin_lock(&logbuf_lock);
588 user->idx = log_first_idx;
589 user->seq = log_first_seq;
590 raw_spin_unlock(&logbuf_lock);
592 file->private_data = user;
596 static int devkmsg_release(struct inode *inode, struct file *file)
598 struct devkmsg_user *user = file->private_data;
603 mutex_destroy(&user->lock);
608 const struct file_operations kmsg_fops = {
609 .open = devkmsg_open,
610 .read = devkmsg_read,
611 .aio_write = devkmsg_writev,
612 .llseek = devkmsg_llseek,
613 .poll = devkmsg_poll,
614 .release = devkmsg_release,
619 * This appends the listed symbols to /proc/vmcoreinfo
621 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
622 * obtain access to symbols that are otherwise very difficult to locate. These
623 * symbols are specifically used so that utilities can access and extract the
624 * dmesg log from a vmcore file after a crash.
626 void log_buf_kexec_setup(void)
628 VMCOREINFO_SYMBOL(log_buf);
629 VMCOREINFO_SYMBOL(log_buf_len);
630 VMCOREINFO_SYMBOL(log_first_idx);
631 VMCOREINFO_SYMBOL(log_next_idx);
635 /* requested log_buf_len from kernel cmdline */
636 static unsigned long __initdata new_log_buf_len;
638 /* save requested log_buf_len since it's too early to process it */
639 static int __init log_buf_len_setup(char *str)
641 unsigned size = memparse(str, &str);
644 size = roundup_pow_of_two(size);
645 if (size > log_buf_len)
646 new_log_buf_len = size;
650 early_param("log_buf_len", log_buf_len_setup);
652 void __init setup_log_buf(int early)
658 if (!new_log_buf_len)
664 mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
667 new_log_buf = __va(mem);
669 new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
672 if (unlikely(!new_log_buf)) {
673 pr_err("log_buf_len: %ld bytes not available\n",
678 raw_spin_lock_irqsave(&logbuf_lock, flags);
679 log_buf_len = new_log_buf_len;
680 log_buf = new_log_buf;
682 free = __LOG_BUF_LEN - log_next_idx;
683 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
684 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
686 pr_info("log_buf_len: %d\n", log_buf_len);
687 pr_info("early log buf free: %d(%d%%)\n",
688 free, (free * 100) / __LOG_BUF_LEN);
691 #ifdef CONFIG_BOOT_PRINTK_DELAY
693 static int boot_delay; /* msecs delay after each printk during bootup */
694 static unsigned long long loops_per_msec; /* based on boot_delay */
696 static int __init boot_delay_setup(char *str)
700 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
701 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
703 get_option(&str, &boot_delay);
704 if (boot_delay > 10 * 1000)
707 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
708 "HZ: %d, loops_per_msec: %llu\n",
709 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
712 __setup("boot_delay=", boot_delay_setup);
714 static void boot_delay_msec(void)
716 unsigned long long k;
717 unsigned long timeout;
719 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
722 k = (unsigned long long)loops_per_msec * boot_delay;
724 timeout = jiffies + msecs_to_jiffies(boot_delay);
729 * use (volatile) jiffies to prevent
730 * compiler reduction; loop termination via jiffies
731 * is secondary and may or may not happen.
733 if (time_after(jiffies, timeout))
735 touch_nmi_watchdog();
739 static inline void boot_delay_msec(void)
744 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
745 int dmesg_restrict = 1;
750 static int syslog_action_restricted(int type)
754 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
755 return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
758 static int check_syslog_permissions(int type, bool from_file)
761 * If this is from /proc/kmsg and we've already opened it, then we've
762 * already done the capabilities checks at open time.
764 if (from_file && type != SYSLOG_ACTION_OPEN)
767 if (syslog_action_restricted(type)) {
768 if (capable(CAP_SYSLOG))
770 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
771 if (capable(CAP_SYS_ADMIN)) {
772 printk_once(KERN_WARNING "%s (%d): "
773 "Attempt to access syslog with CAP_SYS_ADMIN "
774 "but no CAP_SYSLOG (deprecated).\n",
775 current->comm, task_pid_nr(current));
783 #if defined(CONFIG_PRINTK_TIME)
784 static bool printk_time = 1;
786 static bool printk_time;
788 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
790 static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
796 len += sprintf(buf, "<%u>", msg->level);
808 unsigned long long ts = msg->ts_nsec;
809 unsigned long rem_nsec = do_div(ts, 1000000000);
811 len += sprintf(buf + len, "[%5lu.%06lu] ",
812 (unsigned long) ts, rem_nsec / 1000);
821 static size_t msg_print_text(const struct log *msg, bool syslog,
822 char *buf, size_t size)
824 const char *text = log_text(msg);
825 size_t text_size = msg->text_len;
829 const char *next = memchr(text, '\n', text_size);
833 text_len = next - text;
835 text_size -= next - text;
837 text_len = text_size;
841 if (print_prefix(msg, syslog, NULL) +
842 text_len + 1>= size - len)
845 len += print_prefix(msg, syslog, buf + len);
846 memcpy(buf + len, text, text_len);
850 /* SYSLOG_ACTION_* buffer size only calculation */
851 len += print_prefix(msg, syslog, NULL);
861 static int syslog_print(char __user *buf, int size)
867 text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
871 raw_spin_lock_irq(&logbuf_lock);
872 if (syslog_seq < log_first_seq) {
873 /* messages are gone, move to first one */
874 syslog_seq = log_first_seq;
875 syslog_idx = log_first_idx;
877 msg = log_from_idx(syslog_idx);
878 len = msg_print_text(msg, true, text, LOG_LINE_MAX);
879 syslog_idx = log_next(syslog_idx);
881 raw_spin_unlock_irq(&logbuf_lock);
885 else if (len > 0 && copy_to_user(buf, text, len))
892 static int syslog_print_all(char __user *buf, int size, bool clear)
897 text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
901 raw_spin_lock_irq(&logbuf_lock);
907 if (clear_seq < log_first_seq) {
908 /* messages are gone, move to first available one */
909 clear_seq = log_first_seq;
910 clear_idx = log_first_idx;
914 * Find first record that fits, including all following records,
915 * into the user-provided buffer for this dump.
919 while (seq < log_next_seq) {
920 struct log *msg = log_from_idx(idx);
922 len += msg_print_text(msg, true, NULL, 0);
927 /* move first record forward until length fits into the buffer */
930 while (len > size && seq < log_next_seq) {
931 struct log *msg = log_from_idx(idx);
933 len -= msg_print_text(msg, true, NULL, 0);
938 /* last message fitting into this dump */
939 next_seq = log_next_seq;
942 while (len >= 0 && seq < next_seq) {
943 struct log *msg = log_from_idx(idx);
946 textlen = msg_print_text(msg, true, text, LOG_LINE_MAX);
954 raw_spin_unlock_irq(&logbuf_lock);
955 if (copy_to_user(buf + len, text, textlen))
959 raw_spin_lock_irq(&logbuf_lock);
961 if (seq < log_first_seq) {
962 /* messages are gone, move to next one */
970 clear_seq = log_next_seq;
971 clear_idx = log_next_idx;
973 raw_spin_unlock_irq(&logbuf_lock);
979 int do_syslog(int type, char __user *buf, int len, bool from_file)
982 static int saved_console_loglevel = -1;
983 static DEFINE_MUTEX(syslog_mutex);
986 error = check_syslog_permissions(type, from_file);
990 error = security_syslog(type);
995 case SYSLOG_ACTION_CLOSE: /* Close log */
997 case SYSLOG_ACTION_OPEN: /* Open log */
999 case SYSLOG_ACTION_READ: /* Read from log */
1001 if (!buf || len < 0)
1006 if (!access_ok(VERIFY_WRITE, buf, len)) {
1010 error = mutex_lock_interruptible(&syslog_mutex);
1013 error = wait_event_interruptible(log_wait,
1014 syslog_seq != log_next_seq);
1016 mutex_unlock(&syslog_mutex);
1019 error = syslog_print(buf, len);
1020 mutex_unlock(&syslog_mutex);
1022 /* Read/clear last kernel messages */
1023 case SYSLOG_ACTION_READ_CLEAR:
1026 /* Read last kernel messages */
1027 case SYSLOG_ACTION_READ_ALL:
1029 if (!buf || len < 0)
1034 if (!access_ok(VERIFY_WRITE, buf, len)) {
1038 error = syslog_print_all(buf, len, clear);
1040 /* Clear ring buffer */
1041 case SYSLOG_ACTION_CLEAR:
1042 syslog_print_all(NULL, 0, true);
1044 /* Disable logging to console */
1045 case SYSLOG_ACTION_CONSOLE_OFF:
1046 if (saved_console_loglevel == -1)
1047 saved_console_loglevel = console_loglevel;
1048 console_loglevel = minimum_console_loglevel;
1050 /* Enable logging to console */
1051 case SYSLOG_ACTION_CONSOLE_ON:
1052 if (saved_console_loglevel != -1) {
1053 console_loglevel = saved_console_loglevel;
1054 saved_console_loglevel = -1;
1057 /* Set level of messages printed to console */
1058 case SYSLOG_ACTION_CONSOLE_LEVEL:
1060 if (len < 1 || len > 8)
1062 if (len < minimum_console_loglevel)
1063 len = minimum_console_loglevel;
1064 console_loglevel = len;
1065 /* Implicitly re-enable logging to console */
1066 saved_console_loglevel = -1;
1069 /* Number of chars in the log buffer */
1070 case SYSLOG_ACTION_SIZE_UNREAD:
1071 raw_spin_lock_irq(&logbuf_lock);
1072 if (syslog_seq < log_first_seq) {
1073 /* messages are gone, move to first one */
1074 syslog_seq = log_first_seq;
1075 syslog_idx = log_first_idx;
1079 * Short-cut for poll(/"proc/kmsg") which simply checks
1080 * for pending data, not the size; return the count of
1081 * records, not the length.
1083 error = log_next_idx - syslog_idx;
1091 while (seq < log_next_seq) {
1092 struct log *msg = log_from_idx(idx);
1094 error += msg_print_text(msg, true, NULL, 0);
1095 idx = log_next(idx);
1099 raw_spin_unlock_irq(&logbuf_lock);
1101 /* Size of the log buffer */
1102 case SYSLOG_ACTION_SIZE_BUFFER:
1103 error = log_buf_len;
1113 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1115 return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
1118 #ifdef CONFIG_KGDB_KDB
1119 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
1120 * uses locks so it cannot be used during debugging. Just tell kdb
1121 * where the start and end of the physical and logical logs are. This
1122 * is equivalent to do_syslog(3).
1124 void kdb_syslog_data(char *syslog_data[4])
1126 syslog_data[0] = log_buf;
1127 syslog_data[1] = log_buf + log_buf_len;
1128 syslog_data[2] = log_buf + log_first_idx;
1129 syslog_data[3] = log_buf + log_next_idx;
1131 #endif /* CONFIG_KGDB_KDB */
1133 static bool __read_mostly ignore_loglevel;
1135 static int __init ignore_loglevel_setup(char *str)
1137 ignore_loglevel = 1;
1138 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
1143 early_param("ignore_loglevel", ignore_loglevel_setup);
1144 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1145 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
1146 "print all kernel messages to the console.");
1149 * Call the console drivers, asking them to write out
1150 * log_buf[start] to log_buf[end - 1].
1151 * The console_lock must be held.
1153 static void call_console_drivers(int level, const char *text, size_t len)
1155 struct console *con;
1157 trace_console(text, 0, len, len);
1159 if (level >= console_loglevel && !ignore_loglevel)
1161 if (!console_drivers)
1164 for_each_console(con) {
1165 if (exclusive_console && con != exclusive_console)
1167 if (!(con->flags & CON_ENABLED))
1171 if (!cpu_online(smp_processor_id()) &&
1172 !(con->flags & CON_ANYTIME))
1174 con->write(con, text, len);
1179 * Zap console related locks when oopsing. Only zap at most once
1180 * every 10 seconds, to leave time for slow consoles to print a
1183 static void zap_locks(void)
1185 static unsigned long oops_timestamp;
1187 if (time_after_eq(jiffies, oops_timestamp) &&
1188 !time_after(jiffies, oops_timestamp + 30 * HZ))
1191 oops_timestamp = jiffies;
1194 /* If a crash is occurring, make sure we can't deadlock */
1195 raw_spin_lock_init(&logbuf_lock);
1196 /* And make sure that we print immediately */
1197 sema_init(&console_sem, 1);
1200 /* Check if we have any console registered that can be called early in boot. */
1201 static int have_callable_console(void)
1203 struct console *con;
1205 for_each_console(con)
1206 if (con->flags & CON_ANYTIME)
1213 * Can we actually use the console at this time on this cpu?
1215 * Console drivers may assume that per-cpu resources have
1216 * been allocated. So unless they're explicitly marked as
1217 * being able to cope (CON_ANYTIME) don't call them until
1218 * this CPU is officially up.
1220 static inline int can_use_console(unsigned int cpu)
1222 return cpu_online(cpu) || have_callable_console();
1226 * Try to get console ownership to actually show the kernel
1227 * messages from a 'printk'. Return true (and with the
1228 * console_lock held, and 'console_locked' set) if it
1229 * is successful, false otherwise.
1231 * This gets called with the 'logbuf_lock' spinlock held and
1232 * interrupts disabled. It should return with 'lockbuf_lock'
1233 * released but interrupts still disabled.
1235 static int console_trylock_for_printk(unsigned int cpu)
1236 __releases(&logbuf_lock)
1238 int retval = 0, wake = 0;
1240 if (console_trylock()) {
1244 * If we can't use the console, we need to release
1245 * the console semaphore by hand to avoid flushing
1246 * the buffer. We need to hold the console semaphore
1247 * in order to do this test safely.
1249 if (!can_use_console(cpu)) {
1255 logbuf_cpu = UINT_MAX;
1258 raw_spin_unlock(&logbuf_lock);
1262 int printk_delay_msec __read_mostly;
1264 static inline void printk_delay(void)
1266 if (unlikely(printk_delay_msec)) {
1267 int m = printk_delay_msec;
1271 touch_nmi_watchdog();
1276 asmlinkage int vprintk_emit(int facility, int level,
1277 const char *dict, size_t dictlen,
1278 const char *fmt, va_list args)
1280 static int recursion_bug;
1281 static char cont_buf[LOG_LINE_MAX];
1282 static size_t cont_len;
1283 static int cont_level;
1284 static struct task_struct *cont_task;
1285 static char textbuf[LOG_LINE_MAX];
1286 char *text = textbuf;
1288 unsigned long flags;
1290 bool newline = false;
1291 bool prefix = false;
1292 int printed_len = 0;
1297 /* This stops the holder of console_sem just where we want him */
1298 local_irq_save(flags);
1299 this_cpu = smp_processor_id();
1302 * Ouch, printk recursed into itself!
1304 if (unlikely(logbuf_cpu == this_cpu)) {
1306 * If a crash is occurring during printk() on this CPU,
1307 * then try to get the crash message out but make sure
1308 * we can't deadlock. Otherwise just return to avoid the
1309 * recursion and return - but flag the recursion so that
1310 * it can be printed at the next appropriate moment:
1312 if (!oops_in_progress && !lockdep_recursing(current)) {
1314 goto out_restore_irqs;
1320 raw_spin_lock(&logbuf_lock);
1321 logbuf_cpu = this_cpu;
1323 if (recursion_bug) {
1324 static const char recursion_msg[] =
1325 "BUG: recent printk recursion!";
1328 printed_len += strlen(recursion_msg);
1329 /* emit KERN_CRIT message */
1330 log_store(0, 2, NULL, 0, recursion_msg, printed_len);
1334 * The printf needs to come first; we need the syslog
1335 * prefix which might be passed-in as a parameter.
1337 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1339 /* mark and strip a trailing newline */
1340 if (text_len && text[text_len-1] == '\n') {
1345 /* strip syslog prefix and extract log level or control flags */
1346 if (text[0] == '<' && text[1] && text[2] == '>') {
1350 level = text[1] - '0';
1351 case 'd': /* KERN_DEFAULT */
1353 case 'c': /* KERN_CONT */
1360 level = default_message_loglevel;
1368 if (cont_len && (prefix || cont_task != current)) {
1370 * Flush earlier buffer, which is either from a
1371 * different thread, or when we got a new prefix.
1373 log_store(facility, cont_level, NULL, 0, cont_buf, cont_len);
1379 cont_task = current;
1382 /* buffer or append to earlier buffer from the same thread */
1383 if (cont_len + text_len > sizeof(cont_buf))
1384 text_len = sizeof(cont_buf) - cont_len;
1385 memcpy(cont_buf + cont_len, text, text_len);
1386 cont_len += text_len;
1388 if (cont_len && cont_task == current) {
1391 * New prefix from the same thread; flush. We
1392 * either got no earlier newline, or we race
1393 * with an interrupt.
1395 log_store(facility, cont_level,
1396 NULL, 0, cont_buf, cont_len);
1400 /* append to the earlier buffer and flush */
1401 if (cont_len + text_len > sizeof(cont_buf))
1402 text_len = sizeof(cont_buf) - cont_len;
1403 memcpy(cont_buf + cont_len, text, text_len);
1404 cont_len += text_len;
1405 log_store(facility, cont_level,
1406 NULL, 0, cont_buf, cont_len);
1409 printed_len = cont_len;
1411 /* ordinary single and terminated line */
1412 log_store(facility, level,
1413 dict, dictlen, text, text_len);
1414 printed_len = text_len;
1419 * Try to acquire and then immediately release the console semaphore.
1420 * The release will print out buffers and wake up /dev/kmsg and syslog()
1423 * The console_trylock_for_printk() function will release 'logbuf_lock'
1424 * regardless of whether it actually gets the console semaphore or not.
1426 if (console_trylock_for_printk(this_cpu))
1431 local_irq_restore(flags);
1435 EXPORT_SYMBOL(vprintk_emit);
1437 asmlinkage int vprintk(const char *fmt, va_list args)
1439 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1441 EXPORT_SYMBOL(vprintk);
1443 asmlinkage int printk_emit(int facility, int level,
1444 const char *dict, size_t dictlen,
1445 const char *fmt, ...)
1450 va_start(args, fmt);
1451 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1456 EXPORT_SYMBOL(printk_emit);
1459 * printk - print a kernel message
1460 * @fmt: format string
1462 * This is printk(). It can be called from any context. We want it to work.
1464 * We try to grab the console_lock. If we succeed, it's easy - we log the
1465 * output and call the console drivers. If we fail to get the semaphore, we
1466 * place the output into the log buffer and return. The current holder of
1467 * the console_sem will notice the new output in console_unlock(); and will
1468 * send it to the consoles before releasing the lock.
1470 * One effect of this deferred printing is that code which calls printk() and
1471 * then changes console_loglevel may break. This is because console_loglevel
1472 * is inspected when the actual printing occurs.
1477 * See the vsnprintf() documentation for format string extensions over C99.
1479 asmlinkage int printk(const char *fmt, ...)
1484 #ifdef CONFIG_KGDB_KDB
1485 if (unlikely(kdb_trap_printk)) {
1486 va_start(args, fmt);
1487 r = vkdb_printf(fmt, args);
1492 va_start(args, fmt);
1493 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1498 EXPORT_SYMBOL(printk);
1502 #define LOG_LINE_MAX 0
1503 static struct log *log_from_idx(u32 idx) { return NULL; }
1504 static u32 log_next(u32 idx) { return 0; }
1505 static void call_console_drivers(int level, const char *text, size_t len) {}
1506 static size_t msg_print_text(const struct log *msg, bool syslog,
1507 char *buf, size_t size) { return 0; }
1509 #endif /* CONFIG_PRINTK */
1511 static int __add_preferred_console(char *name, int idx, char *options,
1514 struct console_cmdline *c;
1518 * See if this tty is not yet registered, and
1519 * if we have a slot free.
1521 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1522 if (strcmp(console_cmdline[i].name, name) == 0 &&
1523 console_cmdline[i].index == idx) {
1525 selected_console = i;
1528 if (i == MAX_CMDLINECONSOLES)
1531 selected_console = i;
1532 c = &console_cmdline[i];
1533 strlcpy(c->name, name, sizeof(c->name));
1534 c->options = options;
1535 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1536 c->brl_options = brl_options;
1542 * Set up a list of consoles. Called from init/main.c
1544 static int __init console_setup(char *str)
1546 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1547 char *s, *options, *brl_options = NULL;
1550 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1551 if (!memcmp(str, "brl,", 4)) {
1554 } else if (!memcmp(str, "brl=", 4)) {
1555 brl_options = str + 4;
1556 str = strchr(brl_options, ',');
1558 printk(KERN_ERR "need port name after brl=\n");
1566 * Decode str into name, index, options.
1568 if (str[0] >= '0' && str[0] <= '9') {
1569 strcpy(buf, "ttyS");
1570 strncpy(buf + 4, str, sizeof(buf) - 5);
1572 strncpy(buf, str, sizeof(buf) - 1);
1574 buf[sizeof(buf) - 1] = 0;
1575 if ((options = strchr(str, ',')) != NULL)
1578 if (!strcmp(str, "ttya"))
1579 strcpy(buf, "ttyS0");
1580 if (!strcmp(str, "ttyb"))
1581 strcpy(buf, "ttyS1");
1583 for (s = buf; *s; s++)
1584 if ((*s >= '0' && *s <= '9') || *s == ',')
1586 idx = simple_strtoul(s, NULL, 10);
1589 __add_preferred_console(buf, idx, options, brl_options);
1590 console_set_on_cmdline = 1;
1593 __setup("console=", console_setup);
1596 * add_preferred_console - add a device to the list of preferred consoles.
1597 * @name: device name
1598 * @idx: device index
1599 * @options: options for this console
1601 * The last preferred console added will be used for kernel messages
1602 * and stdin/out/err for init. Normally this is used by console_setup
1603 * above to handle user-supplied console arguments; however it can also
1604 * be used by arch-specific code either to override the user or more
1605 * commonly to provide a default console (ie from PROM variables) when
1606 * the user has not supplied one.
1608 int add_preferred_console(char *name, int idx, char *options)
1610 return __add_preferred_console(name, idx, options, NULL);
1613 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1615 struct console_cmdline *c;
1618 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1619 if (strcmp(console_cmdline[i].name, name) == 0 &&
1620 console_cmdline[i].index == idx) {
1621 c = &console_cmdline[i];
1622 strlcpy(c->name, name_new, sizeof(c->name));
1623 c->name[sizeof(c->name) - 1] = 0;
1624 c->options = options;
1632 bool console_suspend_enabled = 1;
1633 EXPORT_SYMBOL(console_suspend_enabled);
1635 static int __init console_suspend_disable(char *str)
1637 console_suspend_enabled = 0;
1640 __setup("no_console_suspend", console_suspend_disable);
1641 module_param_named(console_suspend, console_suspend_enabled,
1642 bool, S_IRUGO | S_IWUSR);
1643 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1644 " and hibernate operations");
1647 * suspend_console - suspend the console subsystem
1649 * This disables printk() while we go into suspend states
1651 void suspend_console(void)
1653 if (!console_suspend_enabled)
1655 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1657 console_suspended = 1;
1661 void resume_console(void)
1663 if (!console_suspend_enabled)
1666 console_suspended = 0;
1671 * console_cpu_notify - print deferred console messages after CPU hotplug
1672 * @self: notifier struct
1673 * @action: CPU hotplug event
1676 * If printk() is called from a CPU that is not online yet, the messages
1677 * will be spooled but will not show up on the console. This function is
1678 * called when a new CPU comes online (or fails to come up), and ensures
1679 * that any such output gets printed.
1681 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1682 unsigned long action, void *hcpu)
1688 case CPU_DOWN_FAILED:
1689 case CPU_UP_CANCELED:
1697 * console_lock - lock the console system for exclusive use.
1699 * Acquires a lock which guarantees that the caller has
1700 * exclusive access to the console system and the console_drivers list.
1702 * Can sleep, returns nothing.
1704 void console_lock(void)
1706 BUG_ON(in_interrupt());
1708 if (console_suspended)
1711 console_may_schedule = 1;
1713 EXPORT_SYMBOL(console_lock);
1716 * console_trylock - try to lock the console system for exclusive use.
1718 * Tried to acquire a lock which guarantees that the caller has
1719 * exclusive access to the console system and the console_drivers list.
1721 * returns 1 on success, and 0 on failure to acquire the lock.
1723 int console_trylock(void)
1725 if (down_trylock(&console_sem))
1727 if (console_suspended) {
1732 console_may_schedule = 0;
1735 EXPORT_SYMBOL(console_trylock);
1737 int is_console_locked(void)
1739 return console_locked;
1743 * Delayed printk version, for scheduler-internal messages:
1745 #define PRINTK_BUF_SIZE 512
1747 #define PRINTK_PENDING_WAKEUP 0x01
1748 #define PRINTK_PENDING_SCHED 0x02
1750 static DEFINE_PER_CPU(int, printk_pending);
1751 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
1753 void printk_tick(void)
1755 if (__this_cpu_read(printk_pending)) {
1756 int pending = __this_cpu_xchg(printk_pending, 0);
1757 if (pending & PRINTK_PENDING_SCHED) {
1758 char *buf = __get_cpu_var(printk_sched_buf);
1759 printk(KERN_WARNING "[sched_delayed] %s", buf);
1761 if (pending & PRINTK_PENDING_WAKEUP)
1762 wake_up_interruptible(&log_wait);
1766 int printk_needs_cpu(int cpu)
1768 if (cpu_is_offline(cpu))
1770 return __this_cpu_read(printk_pending);
1773 void wake_up_klogd(void)
1775 if (waitqueue_active(&log_wait))
1776 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
1779 /* the next printk record to write to the console */
1780 static u64 console_seq;
1781 static u32 console_idx;
1784 * console_unlock - unlock the console system
1786 * Releases the console_lock which the caller holds on the console system
1787 * and the console driver list.
1789 * While the console_lock was held, console output may have been buffered
1790 * by printk(). If this is the case, console_unlock(); emits
1791 * the output prior to releasing the lock.
1793 * If there is output waiting, we wake /dev/kmsg and syslog() users.
1795 * console_unlock(); may be called from any context.
1797 void console_unlock(void)
1799 static u64 seen_seq;
1800 unsigned long flags;
1801 bool wake_klogd = false;
1804 if (console_suspended) {
1809 console_may_schedule = 0;
1814 static char text[LOG_LINE_MAX];
1818 raw_spin_lock_irqsave(&logbuf_lock, flags);
1819 if (seen_seq != log_next_seq) {
1821 seen_seq = log_next_seq;
1824 if (console_seq < log_first_seq) {
1825 /* messages are gone, move to first one */
1826 console_seq = log_first_seq;
1827 console_idx = log_first_idx;
1830 if (console_seq == log_next_seq)
1833 msg = log_from_idx(console_idx);
1834 level = msg->level & 7;
1836 len = msg_print_text(msg, false, text, sizeof(text));
1838 console_idx = log_next(console_idx);
1840 raw_spin_unlock(&logbuf_lock);
1842 stop_critical_timings(); /* don't trace print latency */
1843 call_console_drivers(level, text, len);
1844 start_critical_timings();
1845 local_irq_restore(flags);
1849 /* Release the exclusive_console once it is used */
1850 if (unlikely(exclusive_console))
1851 exclusive_console = NULL;
1853 raw_spin_unlock(&logbuf_lock);
1858 * Someone could have filled up the buffer again, so re-check if there's
1859 * something to flush. In case we cannot trylock the console_sem again,
1860 * there's a new owner and the console_unlock() from them will do the
1861 * flush, no worries.
1863 raw_spin_lock(&logbuf_lock);
1864 retry = console_seq != log_next_seq;
1865 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
1867 if (retry && console_trylock())
1873 EXPORT_SYMBOL(console_unlock);
1876 * console_conditional_schedule - yield the CPU if required
1878 * If the console code is currently allowed to sleep, and
1879 * if this CPU should yield the CPU to another task, do
1882 * Must be called within console_lock();.
1884 void __sched console_conditional_schedule(void)
1886 if (console_may_schedule)
1889 EXPORT_SYMBOL(console_conditional_schedule);
1891 void console_unblank(void)
1896 * console_unblank can no longer be called in interrupt context unless
1897 * oops_in_progress is set to 1..
1899 if (oops_in_progress) {
1900 if (down_trylock(&console_sem) != 0)
1906 console_may_schedule = 0;
1908 if ((c->flags & CON_ENABLED) && c->unblank)
1914 * Return the console tty driver structure and its associated index
1916 struct tty_driver *console_device(int *index)
1919 struct tty_driver *driver = NULL;
1922 for_each_console(c) {
1925 driver = c->device(c, index);
1934 * Prevent further output on the passed console device so that (for example)
1935 * serial drivers can disable console output before suspending a port, and can
1936 * re-enable output afterwards.
1938 void console_stop(struct console *console)
1941 console->flags &= ~CON_ENABLED;
1944 EXPORT_SYMBOL(console_stop);
1946 void console_start(struct console *console)
1949 console->flags |= CON_ENABLED;
1952 EXPORT_SYMBOL(console_start);
1954 static int __read_mostly keep_bootcon;
1956 static int __init keep_bootcon_setup(char *str)
1959 printk(KERN_INFO "debug: skip boot console de-registration.\n");
1964 early_param("keep_bootcon", keep_bootcon_setup);
1967 * The console driver calls this routine during kernel initialization
1968 * to register the console printing procedure with printk() and to
1969 * print any messages that were printed by the kernel before the
1970 * console driver was initialized.
1972 * This can happen pretty early during the boot process (because of
1973 * early_printk) - sometimes before setup_arch() completes - be careful
1974 * of what kernel features are used - they may not be initialised yet.
1976 * There are two types of consoles - bootconsoles (early_printk) and
1977 * "real" consoles (everything which is not a bootconsole) which are
1978 * handled differently.
1979 * - Any number of bootconsoles can be registered at any time.
1980 * - As soon as a "real" console is registered, all bootconsoles
1981 * will be unregistered automatically.
1982 * - Once a "real" console is registered, any attempt to register a
1983 * bootconsoles will be rejected
1985 void register_console(struct console *newcon)
1988 unsigned long flags;
1989 struct console *bcon = NULL;
1992 * before we register a new CON_BOOT console, make sure we don't
1993 * already have a valid console
1995 if (console_drivers && newcon->flags & CON_BOOT) {
1996 /* find the last or real console */
1997 for_each_console(bcon) {
1998 if (!(bcon->flags & CON_BOOT)) {
1999 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
2000 newcon->name, newcon->index);
2006 if (console_drivers && console_drivers->flags & CON_BOOT)
2007 bcon = console_drivers;
2009 if (preferred_console < 0 || bcon || !console_drivers)
2010 preferred_console = selected_console;
2012 if (newcon->early_setup)
2013 newcon->early_setup();
2016 * See if we want to use this console driver. If we
2017 * didn't select a console we take the first one
2018 * that registers here.
2020 if (preferred_console < 0) {
2021 if (newcon->index < 0)
2023 if (newcon->setup == NULL ||
2024 newcon->setup(newcon, NULL) == 0) {
2025 newcon->flags |= CON_ENABLED;
2026 if (newcon->device) {
2027 newcon->flags |= CON_CONSDEV;
2028 preferred_console = 0;
2034 * See if this console matches one we selected on
2037 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
2039 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
2041 if (newcon->index >= 0 &&
2042 newcon->index != console_cmdline[i].index)
2044 if (newcon->index < 0)
2045 newcon->index = console_cmdline[i].index;
2046 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2047 if (console_cmdline[i].brl_options) {
2048 newcon->flags |= CON_BRL;
2049 braille_register_console(newcon,
2050 console_cmdline[i].index,
2051 console_cmdline[i].options,
2052 console_cmdline[i].brl_options);
2056 if (newcon->setup &&
2057 newcon->setup(newcon, console_cmdline[i].options) != 0)
2059 newcon->flags |= CON_ENABLED;
2060 newcon->index = console_cmdline[i].index;
2061 if (i == selected_console) {
2062 newcon->flags |= CON_CONSDEV;
2063 preferred_console = selected_console;
2068 if (!(newcon->flags & CON_ENABLED))
2072 * If we have a bootconsole, and are switching to a real console,
2073 * don't print everything out again, since when the boot console, and
2074 * the real console are the same physical device, it's annoying to
2075 * see the beginning boot messages twice
2077 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2078 newcon->flags &= ~CON_PRINTBUFFER;
2081 * Put this console in the list - keep the
2082 * preferred driver at the head of the list.
2085 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2086 newcon->next = console_drivers;
2087 console_drivers = newcon;
2089 newcon->next->flags &= ~CON_CONSDEV;
2091 newcon->next = console_drivers->next;
2092 console_drivers->next = newcon;
2094 if (newcon->flags & CON_PRINTBUFFER) {
2096 * console_unlock(); will print out the buffered messages
2099 raw_spin_lock_irqsave(&logbuf_lock, flags);
2100 console_seq = syslog_seq;
2101 console_idx = syslog_idx;
2102 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2104 * We're about to replay the log buffer. Only do this to the
2105 * just-registered console to avoid excessive message spam to
2106 * the already-registered consoles.
2108 exclusive_console = newcon;
2111 console_sysfs_notify();
2114 * By unregistering the bootconsoles after we enable the real console
2115 * we get the "console xxx enabled" message on all the consoles -
2116 * boot consoles, real consoles, etc - this is to ensure that end
2117 * users know there might be something in the kernel's log buffer that
2118 * went to the bootconsole (that they do not see on the real console)
2121 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2123 /* we need to iterate through twice, to make sure we print
2124 * everything out, before we unregister the console(s)
2126 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
2127 newcon->name, newcon->index);
2128 for_each_console(bcon)
2129 if (bcon->flags & CON_BOOT)
2130 unregister_console(bcon);
2132 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
2133 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2134 newcon->name, newcon->index);
2137 EXPORT_SYMBOL(register_console);
2139 int unregister_console(struct console *console)
2141 struct console *a, *b;
2144 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2145 if (console->flags & CON_BRL)
2146 return braille_unregister_console(console);
2150 if (console_drivers == console) {
2151 console_drivers=console->next;
2153 } else if (console_drivers) {
2154 for (a=console_drivers->next, b=console_drivers ;
2155 a; b=a, a=b->next) {
2165 * If this isn't the last console and it has CON_CONSDEV set, we
2166 * need to set it on the next preferred console.
2168 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2169 console_drivers->flags |= CON_CONSDEV;
2172 console_sysfs_notify();
2175 EXPORT_SYMBOL(unregister_console);
2177 static int __init printk_late_init(void)
2179 struct console *con;
2181 for_each_console(con) {
2182 if (!keep_bootcon && con->flags & CON_BOOT) {
2183 printk(KERN_INFO "turn off boot console %s%d\n",
2184 con->name, con->index);
2185 unregister_console(con);
2188 hotcpu_notifier(console_cpu_notify, 0);
2191 late_initcall(printk_late_init);
2193 #if defined CONFIG_PRINTK
2195 int printk_sched(const char *fmt, ...)
2197 unsigned long flags;
2202 local_irq_save(flags);
2203 buf = __get_cpu_var(printk_sched_buf);
2205 va_start(args, fmt);
2206 r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2209 __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2210 local_irq_restore(flags);
2216 * printk rate limiting, lifted from the networking subsystem.
2218 * This enforces a rate limit: not more than 10 kernel messages
2219 * every 5s to make a denial-of-service attack impossible.
2221 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2223 int __printk_ratelimit(const char *func)
2225 return ___ratelimit(&printk_ratelimit_state, func);
2227 EXPORT_SYMBOL(__printk_ratelimit);
2230 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2231 * @caller_jiffies: pointer to caller's state
2232 * @interval_msecs: minimum interval between prints
2234 * printk_timed_ratelimit() returns true if more than @interval_msecs
2235 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2238 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2239 unsigned int interval_msecs)
2241 if (*caller_jiffies == 0
2242 || !time_in_range(jiffies, *caller_jiffies,
2244 + msecs_to_jiffies(interval_msecs))) {
2245 *caller_jiffies = jiffies;
2250 EXPORT_SYMBOL(printk_timed_ratelimit);
2252 static DEFINE_SPINLOCK(dump_list_lock);
2253 static LIST_HEAD(dump_list);
2256 * kmsg_dump_register - register a kernel log dumper.
2257 * @dumper: pointer to the kmsg_dumper structure
2259 * Adds a kernel log dumper to the system. The dump callback in the
2260 * structure will be called when the kernel oopses or panics and must be
2261 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2263 int kmsg_dump_register(struct kmsg_dumper *dumper)
2265 unsigned long flags;
2268 /* The dump callback needs to be set */
2272 spin_lock_irqsave(&dump_list_lock, flags);
2273 /* Don't allow registering multiple times */
2274 if (!dumper->registered) {
2275 dumper->registered = 1;
2276 list_add_tail_rcu(&dumper->list, &dump_list);
2279 spin_unlock_irqrestore(&dump_list_lock, flags);
2283 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2286 * kmsg_dump_unregister - unregister a kmsg dumper.
2287 * @dumper: pointer to the kmsg_dumper structure
2289 * Removes a dump device from the system. Returns zero on success and
2290 * %-EINVAL otherwise.
2292 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2294 unsigned long flags;
2297 spin_lock_irqsave(&dump_list_lock, flags);
2298 if (dumper->registered) {
2299 dumper->registered = 0;
2300 list_del_rcu(&dumper->list);
2303 spin_unlock_irqrestore(&dump_list_lock, flags);
2308 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2310 static bool always_kmsg_dump;
2311 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2314 * kmsg_dump - dump kernel log to kernel message dumpers.
2315 * @reason: the reason (oops, panic etc) for dumping
2317 * Call each of the registered dumper's dump() callback, which can
2318 * retrieve the kmsg records with kmsg_dump_get_line() or
2319 * kmsg_dump_get_buffer().
2321 void kmsg_dump(enum kmsg_dump_reason reason)
2323 struct kmsg_dumper *dumper;
2324 unsigned long flags;
2326 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2330 list_for_each_entry_rcu(dumper, &dump_list, list) {
2331 if (dumper->max_reason && reason > dumper->max_reason)
2334 /* initialize iterator with data about the stored records */
2335 dumper->active = true;
2337 raw_spin_lock_irqsave(&logbuf_lock, flags);
2338 dumper->cur_seq = clear_seq;
2339 dumper->cur_idx = clear_idx;
2340 dumper->next_seq = log_next_seq;
2341 dumper->next_idx = log_next_idx;
2342 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2344 /* invoke dumper which will iterate over records */
2345 dumper->dump(dumper, reason);
2347 /* reset iterator */
2348 dumper->active = false;
2354 * kmsg_dump_get_line - retrieve one kmsg log line
2355 * @dumper: registered kmsg dumper
2356 * @syslog: include the "<4>" prefixes
2357 * @line: buffer to copy the line to
2358 * @size: maximum size of the buffer
2359 * @len: length of line placed into buffer
2361 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2362 * record, and copy one record into the provided buffer.
2364 * Consecutive calls will return the next available record moving
2365 * towards the end of the buffer with the youngest messages.
2367 * A return value of FALSE indicates that there are no more records to
2370 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2371 char *line, size_t size, size_t *len)
2373 unsigned long flags;
2378 if (!dumper->active)
2381 raw_spin_lock_irqsave(&logbuf_lock, flags);
2382 if (dumper->cur_seq < log_first_seq) {
2383 /* messages are gone, move to first available one */
2384 dumper->cur_seq = log_first_seq;
2385 dumper->cur_idx = log_first_idx;
2389 if (dumper->cur_seq >= log_next_seq) {
2390 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2394 msg = log_from_idx(dumper->cur_idx);
2395 l = msg_print_text(msg, syslog,
2398 dumper->cur_idx = log_next(dumper->cur_idx);
2401 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2407 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2410 * kmsg_dump_get_buffer - copy kmsg log lines
2411 * @dumper: registered kmsg dumper
2412 * @syslog: include the "<4>" prefixes
2413 * @line: buffer to copy the line to
2414 * @size: maximum size of the buffer
2415 * @len: length of line placed into buffer
2417 * Start at the end of the kmsg buffer and fill the provided buffer
2418 * with as many of the the *youngest* kmsg records that fit into it.
2419 * If the buffer is large enough, all available kmsg records will be
2420 * copied with a single call.
2422 * Consecutive calls will fill the buffer with the next block of
2423 * available older records, not including the earlier retrieved ones.
2425 * A return value of FALSE indicates that there are no more records to
2428 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2429 char *buf, size_t size, size_t *len)
2431 unsigned long flags;
2439 if (!dumper->active)
2442 raw_spin_lock_irqsave(&logbuf_lock, flags);
2443 if (dumper->cur_seq < log_first_seq) {
2444 /* messages are gone, move to first available one */
2445 dumper->cur_seq = log_first_seq;
2446 dumper->cur_idx = log_first_idx;
2450 if (dumper->cur_seq >= dumper->next_seq) {
2451 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2455 /* calculate length of entire buffer */
2456 seq = dumper->cur_seq;
2457 idx = dumper->cur_idx;
2458 while (seq < dumper->next_seq) {
2459 struct log *msg = log_from_idx(idx);
2461 l += msg_print_text(msg, true, NULL, 0);
2462 idx = log_next(idx);
2466 /* move first record forward until length fits into the buffer */
2467 seq = dumper->cur_seq;
2468 idx = dumper->cur_idx;
2469 while (l > size && seq < dumper->next_seq) {
2470 struct log *msg = log_from_idx(idx);
2472 l -= msg_print_text(msg, true, NULL, 0);
2473 idx = log_next(idx);
2477 /* last message in next interation */
2482 while (seq < dumper->next_seq) {
2483 struct log *msg = log_from_idx(idx);
2485 l += msg_print_text(msg, syslog,
2488 idx = log_next(idx);
2492 dumper->next_seq = next_seq;
2493 dumper->next_idx = next_idx;
2495 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2501 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2504 * kmsg_dump_rewind - reset the interator
2505 * @dumper: registered kmsg dumper
2507 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2508 * kmsg_dump_get_buffer() can be called again and used multiple
2509 * times within the same dumper.dump() callback.
2511 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2513 unsigned long flags;
2515 raw_spin_lock_irqsave(&logbuf_lock, flags);
2516 dumper->cur_seq = clear_seq;
2517 dumper->cur_idx = clear_idx;
2518 dumper->next_seq = log_next_seq;
2519 dumper->next_idx = log_next_idx;
2520 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2522 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);