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.
198 LOG_NOCONS = 1, /* already flushed, do not print to console */
202 u64 ts_nsec; /* timestamp in nanoseconds */
203 u16 len; /* length of entire record */
204 u16 text_len; /* length of text buffer */
205 u16 dict_len; /* length of dictionary buffer */
206 u8 facility; /* syslog facility */
207 u8 flags:5; /* internal record flags */
208 u8 level:3; /* syslog level */
212 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
213 * used in interesting ways to provide interlocking in console_unlock();
215 static DEFINE_RAW_SPINLOCK(logbuf_lock);
217 /* the next printk record to read by syslog(READ) or /proc/kmsg */
218 static u64 syslog_seq;
219 static u32 syslog_idx;
221 /* index and sequence number of the first record stored in the buffer */
222 static u64 log_first_seq;
223 static u32 log_first_idx;
225 /* index and sequence number of the next record to store in the buffer */
226 static u64 log_next_seq;
228 static u32 log_next_idx;
230 /* the next printk record to read after the last 'clear' command */
231 static u64 clear_seq;
232 static u32 clear_idx;
234 #define LOG_LINE_MAX 1024
237 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
240 #define LOG_ALIGN __alignof__(struct log)
242 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
243 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
244 static char *log_buf = __log_buf;
245 static u32 log_buf_len = __LOG_BUF_LEN;
247 /* cpu currently holding logbuf_lock */
248 static volatile unsigned int logbuf_cpu = UINT_MAX;
250 /* human readable text of the record */
251 static char *log_text(const struct log *msg)
253 return (char *)msg + sizeof(struct log);
256 /* optional key/value pair dictionary attached to the record */
257 static char *log_dict(const struct log *msg)
259 return (char *)msg + sizeof(struct log) + msg->text_len;
262 /* get record by index; idx must point to valid msg */
263 static struct log *log_from_idx(u32 idx)
265 struct log *msg = (struct log *)(log_buf + idx);
268 * A length == 0 record is the end of buffer marker. Wrap around and
269 * read the message at the start of the buffer.
272 return (struct log *)log_buf;
276 /* get next record; idx must point to valid msg */
277 static u32 log_next(u32 idx)
279 struct log *msg = (struct log *)(log_buf + idx);
281 /* length == 0 indicates the end of the buffer; wrap */
283 * A length == 0 record is the end of buffer marker. Wrap around and
284 * read the message at the start of the buffer as *this* one, and
285 * return the one after that.
288 msg = (struct log *)log_buf;
291 return idx + msg->len;
294 /* insert record into the buffer, discard old ones, update heads */
295 static void log_store(int facility, int level,
296 enum log_flags flags, u64 ts_nsec,
297 const char *dict, u16 dict_len,
298 const char *text, u16 text_len)
303 /* number of '\0' padding bytes to next message */
304 size = sizeof(struct log) + text_len + dict_len;
305 pad_len = (-size) & (LOG_ALIGN - 1);
308 while (log_first_seq < log_next_seq) {
311 if (log_next_idx > log_first_idx)
312 free = max(log_buf_len - log_next_idx, log_first_idx);
314 free = log_first_idx - log_next_idx;
316 if (free > size + sizeof(struct log))
319 /* drop old messages until we have enough contiuous space */
320 log_first_idx = log_next(log_first_idx);
324 if (log_next_idx + size + sizeof(struct log) >= log_buf_len) {
326 * This message + an additional empty header does not fit
327 * at the end of the buffer. Add an empty header with len == 0
328 * to signify a wrap around.
330 memset(log_buf + log_next_idx, 0, sizeof(struct log));
335 msg = (struct log *)(log_buf + log_next_idx);
336 memcpy(log_text(msg), text, text_len);
337 msg->text_len = text_len;
338 memcpy(log_dict(msg), dict, dict_len);
339 msg->dict_len = dict_len;
340 msg->facility = facility;
341 msg->level = level & 7;
342 msg->flags = flags & 0x1f;
344 msg->ts_nsec = ts_nsec;
346 msg->ts_nsec = local_clock();
347 memset(log_dict(msg) + dict_len, 0, pad_len);
348 msg->len = sizeof(struct log) + text_len + dict_len + pad_len;
351 log_next_idx += msg->len;
355 /* /dev/kmsg - userspace message inject/listen interface */
356 struct devkmsg_user {
363 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
364 unsigned long count, loff_t pos)
368 int level = default_message_loglevel;
369 int facility = 1; /* LOG_USER */
370 size_t len = iov_length(iv, count);
373 if (len > LOG_LINE_MAX)
375 buf = kmalloc(len+1, GFP_KERNEL);
380 for (i = 0; i < count; i++) {
381 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len))
383 line += iv[i].iov_len;
387 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
388 * the decimal value represents 32bit, the lower 3 bit are the log
389 * level, the rest are the log facility.
391 * If no prefix or no userspace facility is specified, we
392 * enforce LOG_USER, to be able to reliably distinguish
393 * kernel-generated messages from userspace-injected ones.
396 if (line[0] == '<') {
399 i = simple_strtoul(line+1, &endp, 10);
400 if (endp && endp[0] == '>') {
411 printk_emit(facility, level, NULL, 0, "%s", line);
417 static ssize_t devkmsg_read(struct file *file, char __user *buf,
418 size_t count, loff_t *ppos)
420 struct devkmsg_user *user = file->private_data;
430 ret = mutex_lock_interruptible(&user->lock);
433 raw_spin_lock_irq(&logbuf_lock);
434 while (user->seq == log_next_seq) {
435 if (file->f_flags & O_NONBLOCK) {
437 raw_spin_unlock_irq(&logbuf_lock);
441 raw_spin_unlock_irq(&logbuf_lock);
442 ret = wait_event_interruptible(log_wait,
443 user->seq != log_next_seq);
446 raw_spin_lock_irq(&logbuf_lock);
449 if (user->seq < log_first_seq) {
450 /* our last seen message is gone, return error and reset */
451 user->idx = log_first_idx;
452 user->seq = log_first_seq;
454 raw_spin_unlock_irq(&logbuf_lock);
458 msg = log_from_idx(user->idx);
459 ts_usec = msg->ts_nsec;
460 do_div(ts_usec, 1000);
461 len = sprintf(user->buf, "%u,%llu,%llu;",
462 (msg->facility << 3) | msg->level, user->seq, ts_usec);
464 /* escape non-printable characters */
465 for (i = 0; i < msg->text_len; i++) {
466 unsigned char c = log_text(msg)[i];
468 if (c < ' ' || c >= 128)
469 len += sprintf(user->buf + len, "\\x%02x", c);
471 user->buf[len++] = c;
473 user->buf[len++] = '\n';
478 for (i = 0; i < msg->dict_len; i++) {
479 unsigned char c = log_dict(msg)[i];
482 user->buf[len++] = ' ';
487 user->buf[len++] = '\n';
492 if (c < ' ' || c >= 128) {
493 len += sprintf(user->buf + len, "\\x%02x", c);
497 user->buf[len++] = c;
499 user->buf[len++] = '\n';
502 user->idx = log_next(user->idx);
504 raw_spin_unlock_irq(&logbuf_lock);
511 if (copy_to_user(buf, user->buf, len)) {
517 mutex_unlock(&user->lock);
521 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
523 struct devkmsg_user *user = file->private_data;
531 raw_spin_lock_irq(&logbuf_lock);
534 /* the first record */
535 user->idx = log_first_idx;
536 user->seq = log_first_seq;
540 * The first record after the last SYSLOG_ACTION_CLEAR,
541 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
542 * changes no global state, and does not clear anything.
544 user->idx = clear_idx;
545 user->seq = clear_seq;
548 /* after the last record */
549 user->idx = log_next_idx;
550 user->seq = log_next_seq;
555 raw_spin_unlock_irq(&logbuf_lock);
559 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
561 struct devkmsg_user *user = file->private_data;
565 return POLLERR|POLLNVAL;
567 poll_wait(file, &log_wait, wait);
569 raw_spin_lock_irq(&logbuf_lock);
570 if (user->seq < log_next_seq) {
571 /* return error when data has vanished underneath us */
572 if (user->seq < log_first_seq)
573 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
574 ret = POLLIN|POLLRDNORM;
576 raw_spin_unlock_irq(&logbuf_lock);
581 static int devkmsg_open(struct inode *inode, struct file *file)
583 struct devkmsg_user *user;
586 /* write-only does not need any file context */
587 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
590 err = security_syslog(SYSLOG_ACTION_READ_ALL);
594 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
598 mutex_init(&user->lock);
600 raw_spin_lock_irq(&logbuf_lock);
601 user->idx = log_first_idx;
602 user->seq = log_first_seq;
603 raw_spin_unlock_irq(&logbuf_lock);
605 file->private_data = user;
609 static int devkmsg_release(struct inode *inode, struct file *file)
611 struct devkmsg_user *user = file->private_data;
616 mutex_destroy(&user->lock);
621 const struct file_operations kmsg_fops = {
622 .open = devkmsg_open,
623 .read = devkmsg_read,
624 .aio_write = devkmsg_writev,
625 .llseek = devkmsg_llseek,
626 .poll = devkmsg_poll,
627 .release = devkmsg_release,
632 * This appends the listed symbols to /proc/vmcoreinfo
634 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
635 * obtain access to symbols that are otherwise very difficult to locate. These
636 * symbols are specifically used so that utilities can access and extract the
637 * dmesg log from a vmcore file after a crash.
639 void log_buf_kexec_setup(void)
641 VMCOREINFO_SYMBOL(log_buf);
642 VMCOREINFO_SYMBOL(log_buf_len);
643 VMCOREINFO_SYMBOL(log_first_idx);
644 VMCOREINFO_SYMBOL(log_next_idx);
648 /* requested log_buf_len from kernel cmdline */
649 static unsigned long __initdata new_log_buf_len;
651 /* save requested log_buf_len since it's too early to process it */
652 static int __init log_buf_len_setup(char *str)
654 unsigned size = memparse(str, &str);
657 size = roundup_pow_of_two(size);
658 if (size > log_buf_len)
659 new_log_buf_len = size;
663 early_param("log_buf_len", log_buf_len_setup);
665 void __init setup_log_buf(int early)
671 if (!new_log_buf_len)
677 mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
680 new_log_buf = __va(mem);
682 new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
685 if (unlikely(!new_log_buf)) {
686 pr_err("log_buf_len: %ld bytes not available\n",
691 raw_spin_lock_irqsave(&logbuf_lock, flags);
692 log_buf_len = new_log_buf_len;
693 log_buf = new_log_buf;
695 free = __LOG_BUF_LEN - log_next_idx;
696 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
697 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
699 pr_info("log_buf_len: %d\n", log_buf_len);
700 pr_info("early log buf free: %d(%d%%)\n",
701 free, (free * 100) / __LOG_BUF_LEN);
704 #ifdef CONFIG_BOOT_PRINTK_DELAY
706 static int boot_delay; /* msecs delay after each printk during bootup */
707 static unsigned long long loops_per_msec; /* based on boot_delay */
709 static int __init boot_delay_setup(char *str)
713 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
714 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
716 get_option(&str, &boot_delay);
717 if (boot_delay > 10 * 1000)
720 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
721 "HZ: %d, loops_per_msec: %llu\n",
722 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
725 __setup("boot_delay=", boot_delay_setup);
727 static void boot_delay_msec(void)
729 unsigned long long k;
730 unsigned long timeout;
732 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
735 k = (unsigned long long)loops_per_msec * boot_delay;
737 timeout = jiffies + msecs_to_jiffies(boot_delay);
742 * use (volatile) jiffies to prevent
743 * compiler reduction; loop termination via jiffies
744 * is secondary and may or may not happen.
746 if (time_after(jiffies, timeout))
748 touch_nmi_watchdog();
752 static inline void boot_delay_msec(void)
757 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
758 int dmesg_restrict = 1;
763 static int syslog_action_restricted(int type)
767 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
768 return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
771 static int check_syslog_permissions(int type, bool from_file)
774 * If this is from /proc/kmsg and we've already opened it, then we've
775 * already done the capabilities checks at open time.
777 if (from_file && type != SYSLOG_ACTION_OPEN)
780 if (syslog_action_restricted(type)) {
781 if (capable(CAP_SYSLOG))
783 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
784 if (capable(CAP_SYS_ADMIN)) {
785 printk_once(KERN_WARNING "%s (%d): "
786 "Attempt to access syslog with CAP_SYS_ADMIN "
787 "but no CAP_SYSLOG (deprecated).\n",
788 current->comm, task_pid_nr(current));
796 #if defined(CONFIG_PRINTK_TIME)
797 static bool printk_time = 1;
799 static bool printk_time;
801 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
803 static size_t print_time(u64 ts, char *buf)
805 unsigned long rem_nsec;
813 rem_nsec = do_div(ts, 1000000000);
814 return sprintf(buf, "[%5lu.%06lu] ",
815 (unsigned long)ts, rem_nsec / 1000);
818 static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
824 len += sprintf(buf, "<%u>", msg->level);
834 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
838 static size_t msg_print_text(const struct log *msg, bool syslog,
839 char *buf, size_t size)
841 const char *text = log_text(msg);
842 size_t text_size = msg->text_len;
846 const char *next = memchr(text, '\n', text_size);
850 text_len = next - text;
852 text_size -= next - text;
854 text_len = text_size;
858 if (print_prefix(msg, syslog, NULL) +
859 text_len + 1>= size - len)
862 len += print_prefix(msg, syslog, buf + len);
863 memcpy(buf + len, text, text_len);
867 /* SYSLOG_ACTION_* buffer size only calculation */
868 len += print_prefix(msg, syslog, NULL);
878 static int syslog_print(char __user *buf, int size)
884 text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
891 raw_spin_lock_irq(&logbuf_lock);
892 if (syslog_seq < log_first_seq) {
893 /* messages are gone, move to first one */
894 syslog_seq = log_first_seq;
895 syslog_idx = log_first_idx;
897 if (syslog_seq == log_next_seq) {
898 raw_spin_unlock_irq(&logbuf_lock);
901 msg = log_from_idx(syslog_idx);
902 n = msg_print_text(msg, true, text, LOG_LINE_MAX);
904 syslog_idx = log_next(syslog_idx);
908 raw_spin_unlock_irq(&logbuf_lock);
916 n = copy_to_user(buf - n, text, n);
930 static int syslog_print_all(char __user *buf, int size, bool clear)
935 text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
939 raw_spin_lock_irq(&logbuf_lock);
945 if (clear_seq < log_first_seq) {
946 /* messages are gone, move to first available one */
947 clear_seq = log_first_seq;
948 clear_idx = log_first_idx;
952 * Find first record that fits, including all following records,
953 * into the user-provided buffer for this dump.
957 while (seq < log_next_seq) {
958 struct log *msg = log_from_idx(idx);
960 len += msg_print_text(msg, true, NULL, 0);
965 /* move first record forward until length fits into the buffer */
968 while (len > size && seq < log_next_seq) {
969 struct log *msg = log_from_idx(idx);
971 len -= msg_print_text(msg, true, NULL, 0);
976 /* last message fitting into this dump */
977 next_seq = log_next_seq;
980 while (len >= 0 && seq < next_seq) {
981 struct log *msg = log_from_idx(idx);
984 textlen = msg_print_text(msg, true, text, LOG_LINE_MAX);
992 raw_spin_unlock_irq(&logbuf_lock);
993 if (copy_to_user(buf + len, text, textlen))
997 raw_spin_lock_irq(&logbuf_lock);
999 if (seq < log_first_seq) {
1000 /* messages are gone, move to next one */
1001 seq = log_first_seq;
1002 idx = log_first_idx;
1008 clear_seq = log_next_seq;
1009 clear_idx = log_next_idx;
1011 raw_spin_unlock_irq(&logbuf_lock);
1017 int do_syslog(int type, char __user *buf, int len, bool from_file)
1020 static int saved_console_loglevel = -1;
1021 static DEFINE_MUTEX(syslog_mutex);
1024 error = check_syslog_permissions(type, from_file);
1028 error = security_syslog(type);
1033 case SYSLOG_ACTION_CLOSE: /* Close log */
1035 case SYSLOG_ACTION_OPEN: /* Open log */
1037 case SYSLOG_ACTION_READ: /* Read from log */
1039 if (!buf || len < 0)
1044 if (!access_ok(VERIFY_WRITE, buf, len)) {
1048 error = mutex_lock_interruptible(&syslog_mutex);
1051 error = wait_event_interruptible(log_wait,
1052 syslog_seq != log_next_seq);
1054 mutex_unlock(&syslog_mutex);
1057 error = syslog_print(buf, len);
1058 mutex_unlock(&syslog_mutex);
1060 /* Read/clear last kernel messages */
1061 case SYSLOG_ACTION_READ_CLEAR:
1064 /* Read last kernel messages */
1065 case SYSLOG_ACTION_READ_ALL:
1067 if (!buf || len < 0)
1072 if (!access_ok(VERIFY_WRITE, buf, len)) {
1076 error = syslog_print_all(buf, len, clear);
1078 /* Clear ring buffer */
1079 case SYSLOG_ACTION_CLEAR:
1080 syslog_print_all(NULL, 0, true);
1082 /* Disable logging to console */
1083 case SYSLOG_ACTION_CONSOLE_OFF:
1084 if (saved_console_loglevel == -1)
1085 saved_console_loglevel = console_loglevel;
1086 console_loglevel = minimum_console_loglevel;
1088 /* Enable logging to console */
1089 case SYSLOG_ACTION_CONSOLE_ON:
1090 if (saved_console_loglevel != -1) {
1091 console_loglevel = saved_console_loglevel;
1092 saved_console_loglevel = -1;
1095 /* Set level of messages printed to console */
1096 case SYSLOG_ACTION_CONSOLE_LEVEL:
1098 if (len < 1 || len > 8)
1100 if (len < minimum_console_loglevel)
1101 len = minimum_console_loglevel;
1102 console_loglevel = len;
1103 /* Implicitly re-enable logging to console */
1104 saved_console_loglevel = -1;
1107 /* Number of chars in the log buffer */
1108 case SYSLOG_ACTION_SIZE_UNREAD:
1109 raw_spin_lock_irq(&logbuf_lock);
1110 if (syslog_seq < log_first_seq) {
1111 /* messages are gone, move to first one */
1112 syslog_seq = log_first_seq;
1113 syslog_idx = log_first_idx;
1117 * Short-cut for poll(/"proc/kmsg") which simply checks
1118 * for pending data, not the size; return the count of
1119 * records, not the length.
1121 error = log_next_idx - syslog_idx;
1129 while (seq < log_next_seq) {
1130 struct log *msg = log_from_idx(idx);
1132 error += msg_print_text(msg, true, NULL, 0);
1133 idx = log_next(idx);
1137 raw_spin_unlock_irq(&logbuf_lock);
1139 /* Size of the log buffer */
1140 case SYSLOG_ACTION_SIZE_BUFFER:
1141 error = log_buf_len;
1151 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1153 return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
1156 #ifdef CONFIG_KGDB_KDB
1157 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
1158 * uses locks so it cannot be used during debugging. Just tell kdb
1159 * where the start and end of the physical and logical logs are. This
1160 * is equivalent to do_syslog(3).
1162 void kdb_syslog_data(char *syslog_data[4])
1164 syslog_data[0] = log_buf;
1165 syslog_data[1] = log_buf + log_buf_len;
1166 syslog_data[2] = log_buf + log_first_idx;
1167 syslog_data[3] = log_buf + log_next_idx;
1169 #endif /* CONFIG_KGDB_KDB */
1171 static bool __read_mostly ignore_loglevel;
1173 static int __init ignore_loglevel_setup(char *str)
1175 ignore_loglevel = 1;
1176 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
1181 early_param("ignore_loglevel", ignore_loglevel_setup);
1182 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1183 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
1184 "print all kernel messages to the console.");
1187 * Call the console drivers, asking them to write out
1188 * log_buf[start] to log_buf[end - 1].
1189 * The console_lock must be held.
1191 static void call_console_drivers(int level, const char *text, size_t len)
1193 struct console *con;
1195 trace_console(text, 0, len, len);
1197 if (level >= console_loglevel && !ignore_loglevel)
1199 if (!console_drivers)
1202 for_each_console(con) {
1203 if (exclusive_console && con != exclusive_console)
1205 if (!(con->flags & CON_ENABLED))
1209 if (!cpu_online(smp_processor_id()) &&
1210 !(con->flags & CON_ANYTIME))
1212 con->write(con, text, len);
1217 * Zap console related locks when oopsing. Only zap at most once
1218 * every 10 seconds, to leave time for slow consoles to print a
1221 static void zap_locks(void)
1223 static unsigned long oops_timestamp;
1225 if (time_after_eq(jiffies, oops_timestamp) &&
1226 !time_after(jiffies, oops_timestamp + 30 * HZ))
1229 oops_timestamp = jiffies;
1232 /* If a crash is occurring, make sure we can't deadlock */
1233 raw_spin_lock_init(&logbuf_lock);
1234 /* And make sure that we print immediately */
1235 sema_init(&console_sem, 1);
1238 /* Check if we have any console registered that can be called early in boot. */
1239 static int have_callable_console(void)
1241 struct console *con;
1243 for_each_console(con)
1244 if (con->flags & CON_ANYTIME)
1251 * Can we actually use the console at this time on this cpu?
1253 * Console drivers may assume that per-cpu resources have
1254 * been allocated. So unless they're explicitly marked as
1255 * being able to cope (CON_ANYTIME) don't call them until
1256 * this CPU is officially up.
1258 static inline int can_use_console(unsigned int cpu)
1260 return cpu_online(cpu) || have_callable_console();
1264 * Try to get console ownership to actually show the kernel
1265 * messages from a 'printk'. Return true (and with the
1266 * console_lock held, and 'console_locked' set) if it
1267 * is successful, false otherwise.
1269 * This gets called with the 'logbuf_lock' spinlock held and
1270 * interrupts disabled. It should return with 'lockbuf_lock'
1271 * released but interrupts still disabled.
1273 static int console_trylock_for_printk(unsigned int cpu)
1274 __releases(&logbuf_lock)
1276 int retval = 0, wake = 0;
1278 if (console_trylock()) {
1282 * If we can't use the console, we need to release
1283 * the console semaphore by hand to avoid flushing
1284 * the buffer. We need to hold the console semaphore
1285 * in order to do this test safely.
1287 if (!can_use_console(cpu)) {
1293 logbuf_cpu = UINT_MAX;
1296 raw_spin_unlock(&logbuf_lock);
1300 int printk_delay_msec __read_mostly;
1302 static inline void printk_delay(void)
1304 if (unlikely(printk_delay_msec)) {
1305 int m = printk_delay_msec;
1309 touch_nmi_watchdog();
1315 * Continuation lines are buffered, and not committed to the record buffer
1316 * until the line is complete, or a race forces it. The line fragments
1317 * though, are printed immediately to the consoles to ensure everything has
1318 * reached the console in case of a kernel crash.
1320 static struct cont {
1321 char buf[LOG_LINE_MAX];
1322 size_t len; /* length == 0 means unused buffer */
1323 size_t cons; /* bytes written to console */
1324 struct task_struct *owner; /* task of first print*/
1325 u64 ts_nsec; /* time of first print */
1326 u8 level; /* log level of first message */
1327 u8 facility; /* log level of first message */
1328 bool flushed:1; /* buffer sealed and committed */
1331 static void cont_flush(void)
1338 log_store(cont.facility, cont.level, LOG_NOCONS, cont.ts_nsec,
1339 NULL, 0, cont.buf, cont.len);
1341 cont.flushed = true;
1344 static bool cont_add(int facility, int level, const char *text, size_t len)
1346 if (cont.len && cont.flushed)
1349 if (cont.len + len > sizeof(cont.buf)) {
1355 cont.facility = facility;
1357 cont.owner = current;
1358 cont.ts_nsec = local_clock();
1360 cont.flushed = false;
1363 memcpy(cont.buf + cont.len, text, len);
1368 static size_t cont_print_text(char *text, size_t size)
1373 if (cont.cons == 0) {
1374 textlen += print_time(cont.ts_nsec, text);
1378 len = cont.len - cont.cons;
1382 memcpy(text + textlen, cont.buf + cont.cons, len);
1384 cont.cons = cont.len;
1388 text[textlen++] = '\n';
1389 /* got everything, release buffer */
1395 asmlinkage int vprintk_emit(int facility, int level,
1396 const char *dict, size_t dictlen,
1397 const char *fmt, va_list args)
1399 static int recursion_bug;
1400 static char textbuf[LOG_LINE_MAX];
1401 char *text = textbuf;
1403 unsigned long flags;
1405 bool newline = false;
1406 bool prefix = false;
1407 int printed_len = 0;
1412 /* This stops the holder of console_sem just where we want him */
1413 local_irq_save(flags);
1414 this_cpu = smp_processor_id();
1417 * Ouch, printk recursed into itself!
1419 if (unlikely(logbuf_cpu == this_cpu)) {
1421 * If a crash is occurring during printk() on this CPU,
1422 * then try to get the crash message out but make sure
1423 * we can't deadlock. Otherwise just return to avoid the
1424 * recursion and return - but flag the recursion so that
1425 * it can be printed at the next appropriate moment:
1427 if (!oops_in_progress && !lockdep_recursing(current)) {
1429 goto out_restore_irqs;
1435 raw_spin_lock(&logbuf_lock);
1436 logbuf_cpu = this_cpu;
1438 if (recursion_bug) {
1439 static const char recursion_msg[] =
1440 "BUG: recent printk recursion!";
1443 printed_len += strlen(recursion_msg);
1444 /* emit KERN_CRIT message */
1445 log_store(0, 2, LOG_DEFAULT, 0,
1446 NULL, 0, recursion_msg, printed_len);
1450 * The printf needs to come first; we need the syslog
1451 * prefix which might be passed-in as a parameter.
1453 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1455 /* mark and strip a trailing newline */
1456 if (text_len && text[text_len-1] == '\n') {
1461 /* strip syslog prefix and extract log level or control flags */
1462 if (text[0] == '<' && text[1] && text[2] == '>') {
1466 level = text[1] - '0';
1467 case 'd': /* KERN_DEFAULT */
1469 case 'c': /* KERN_CONT */
1476 level = default_message_loglevel;
1485 * Flush the conflicting buffer. An earlier newline was missing,
1486 * or another task also prints continuation lines.
1488 if (cont.len && (prefix || cont.owner != current))
1491 /* buffer line if possible, otherwise store it right away */
1492 if (!cont_add(facility, level, text, text_len))
1493 log_store(facility, level, LOG_DEFAULT, 0,
1494 dict, dictlen, text, text_len);
1496 bool stored = false;
1499 * If an earlier newline was missing and it was the same task,
1500 * either merge it with the current buffer and flush, or if
1501 * there was a race with interrupts (prefix == true) then just
1502 * flush it out and store this line separately.
1504 if (cont.len && cont.owner == current) {
1506 stored = cont_add(facility, level, text, text_len);
1511 log_store(facility, level, LOG_DEFAULT, 0,
1512 dict, dictlen, text, text_len);
1514 printed_len += text_len;
1517 * Try to acquire and then immediately release the console semaphore.
1518 * The release will print out buffers and wake up /dev/kmsg and syslog()
1521 * The console_trylock_for_printk() function will release 'logbuf_lock'
1522 * regardless of whether it actually gets the console semaphore or not.
1524 if (console_trylock_for_printk(this_cpu))
1529 local_irq_restore(flags);
1533 EXPORT_SYMBOL(vprintk_emit);
1535 asmlinkage int vprintk(const char *fmt, va_list args)
1537 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1539 EXPORT_SYMBOL(vprintk);
1541 asmlinkage int printk_emit(int facility, int level,
1542 const char *dict, size_t dictlen,
1543 const char *fmt, ...)
1548 va_start(args, fmt);
1549 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1554 EXPORT_SYMBOL(printk_emit);
1557 * printk - print a kernel message
1558 * @fmt: format string
1560 * This is printk(). It can be called from any context. We want it to work.
1562 * We try to grab the console_lock. If we succeed, it's easy - we log the
1563 * output and call the console drivers. If we fail to get the semaphore, we
1564 * place the output into the log buffer and return. The current holder of
1565 * the console_sem will notice the new output in console_unlock(); and will
1566 * send it to the consoles before releasing the lock.
1568 * One effect of this deferred printing is that code which calls printk() and
1569 * then changes console_loglevel may break. This is because console_loglevel
1570 * is inspected when the actual printing occurs.
1575 * See the vsnprintf() documentation for format string extensions over C99.
1577 asmlinkage int printk(const char *fmt, ...)
1582 #ifdef CONFIG_KGDB_KDB
1583 if (unlikely(kdb_trap_printk)) {
1584 va_start(args, fmt);
1585 r = vkdb_printf(fmt, args);
1590 va_start(args, fmt);
1591 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1596 EXPORT_SYMBOL(printk);
1600 #define LOG_LINE_MAX 0
1601 static struct cont {
1607 static struct log *log_from_idx(u32 idx) { return NULL; }
1608 static u32 log_next(u32 idx) { return 0; }
1609 static void call_console_drivers(int level, const char *text, size_t len) {}
1610 static size_t msg_print_text(const struct log *msg, bool syslog,
1611 char *buf, size_t size) { return 0; }
1612 static size_t cont_print_text(char *text, size_t size) { return 0; }
1614 #endif /* CONFIG_PRINTK */
1616 static int __add_preferred_console(char *name, int idx, char *options,
1619 struct console_cmdline *c;
1623 * See if this tty is not yet registered, and
1624 * if we have a slot free.
1626 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1627 if (strcmp(console_cmdline[i].name, name) == 0 &&
1628 console_cmdline[i].index == idx) {
1630 selected_console = i;
1633 if (i == MAX_CMDLINECONSOLES)
1636 selected_console = i;
1637 c = &console_cmdline[i];
1638 strlcpy(c->name, name, sizeof(c->name));
1639 c->options = options;
1640 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1641 c->brl_options = brl_options;
1647 * Set up a list of consoles. Called from init/main.c
1649 static int __init console_setup(char *str)
1651 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1652 char *s, *options, *brl_options = NULL;
1655 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1656 if (!memcmp(str, "brl,", 4)) {
1659 } else if (!memcmp(str, "brl=", 4)) {
1660 brl_options = str + 4;
1661 str = strchr(brl_options, ',');
1663 printk(KERN_ERR "need port name after brl=\n");
1671 * Decode str into name, index, options.
1673 if (str[0] >= '0' && str[0] <= '9') {
1674 strcpy(buf, "ttyS");
1675 strncpy(buf + 4, str, sizeof(buf) - 5);
1677 strncpy(buf, str, sizeof(buf) - 1);
1679 buf[sizeof(buf) - 1] = 0;
1680 if ((options = strchr(str, ',')) != NULL)
1683 if (!strcmp(str, "ttya"))
1684 strcpy(buf, "ttyS0");
1685 if (!strcmp(str, "ttyb"))
1686 strcpy(buf, "ttyS1");
1688 for (s = buf; *s; s++)
1689 if ((*s >= '0' && *s <= '9') || *s == ',')
1691 idx = simple_strtoul(s, NULL, 10);
1694 __add_preferred_console(buf, idx, options, brl_options);
1695 console_set_on_cmdline = 1;
1698 __setup("console=", console_setup);
1701 * add_preferred_console - add a device to the list of preferred consoles.
1702 * @name: device name
1703 * @idx: device index
1704 * @options: options for this console
1706 * The last preferred console added will be used for kernel messages
1707 * and stdin/out/err for init. Normally this is used by console_setup
1708 * above to handle user-supplied console arguments; however it can also
1709 * be used by arch-specific code either to override the user or more
1710 * commonly to provide a default console (ie from PROM variables) when
1711 * the user has not supplied one.
1713 int add_preferred_console(char *name, int idx, char *options)
1715 return __add_preferred_console(name, idx, options, NULL);
1718 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1720 struct console_cmdline *c;
1723 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1724 if (strcmp(console_cmdline[i].name, name) == 0 &&
1725 console_cmdline[i].index == idx) {
1726 c = &console_cmdline[i];
1727 strlcpy(c->name, name_new, sizeof(c->name));
1728 c->name[sizeof(c->name) - 1] = 0;
1729 c->options = options;
1737 bool console_suspend_enabled = 1;
1738 EXPORT_SYMBOL(console_suspend_enabled);
1740 static int __init console_suspend_disable(char *str)
1742 console_suspend_enabled = 0;
1745 __setup("no_console_suspend", console_suspend_disable);
1746 module_param_named(console_suspend, console_suspend_enabled,
1747 bool, S_IRUGO | S_IWUSR);
1748 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1749 " and hibernate operations");
1752 * suspend_console - suspend the console subsystem
1754 * This disables printk() while we go into suspend states
1756 void suspend_console(void)
1758 if (!console_suspend_enabled)
1760 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1762 console_suspended = 1;
1766 void resume_console(void)
1768 if (!console_suspend_enabled)
1771 console_suspended = 0;
1776 * console_cpu_notify - print deferred console messages after CPU hotplug
1777 * @self: notifier struct
1778 * @action: CPU hotplug event
1781 * If printk() is called from a CPU that is not online yet, the messages
1782 * will be spooled but will not show up on the console. This function is
1783 * called when a new CPU comes online (or fails to come up), and ensures
1784 * that any such output gets printed.
1786 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1787 unsigned long action, void *hcpu)
1793 case CPU_DOWN_FAILED:
1794 case CPU_UP_CANCELED:
1802 * console_lock - lock the console system for exclusive use.
1804 * Acquires a lock which guarantees that the caller has
1805 * exclusive access to the console system and the console_drivers list.
1807 * Can sleep, returns nothing.
1809 void console_lock(void)
1811 BUG_ON(in_interrupt());
1813 if (console_suspended)
1816 console_may_schedule = 1;
1818 EXPORT_SYMBOL(console_lock);
1821 * console_trylock - try to lock the console system for exclusive use.
1823 * Tried to acquire a lock which guarantees that the caller has
1824 * exclusive access to the console system and the console_drivers list.
1826 * returns 1 on success, and 0 on failure to acquire the lock.
1828 int console_trylock(void)
1830 if (down_trylock(&console_sem))
1832 if (console_suspended) {
1837 console_may_schedule = 0;
1840 EXPORT_SYMBOL(console_trylock);
1842 int is_console_locked(void)
1844 return console_locked;
1848 * Delayed printk version, for scheduler-internal messages:
1850 #define PRINTK_BUF_SIZE 512
1852 #define PRINTK_PENDING_WAKEUP 0x01
1853 #define PRINTK_PENDING_SCHED 0x02
1855 static DEFINE_PER_CPU(int, printk_pending);
1856 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
1858 void printk_tick(void)
1860 if (__this_cpu_read(printk_pending)) {
1861 int pending = __this_cpu_xchg(printk_pending, 0);
1862 if (pending & PRINTK_PENDING_SCHED) {
1863 char *buf = __get_cpu_var(printk_sched_buf);
1864 printk(KERN_WARNING "[sched_delayed] %s", buf);
1866 if (pending & PRINTK_PENDING_WAKEUP)
1867 wake_up_interruptible(&log_wait);
1871 int printk_needs_cpu(int cpu)
1873 if (cpu_is_offline(cpu))
1875 return __this_cpu_read(printk_pending);
1878 void wake_up_klogd(void)
1880 if (waitqueue_active(&log_wait))
1881 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
1884 /* the next printk record to write to the console */
1885 static u64 console_seq;
1886 static u32 console_idx;
1889 * console_unlock - unlock the console system
1891 * Releases the console_lock which the caller holds on the console system
1892 * and the console driver list.
1894 * While the console_lock was held, console output may have been buffered
1895 * by printk(). If this is the case, console_unlock(); emits
1896 * the output prior to releasing the lock.
1898 * If there is output waiting, we wake /dev/kmsg and syslog() users.
1900 * console_unlock(); may be called from any context.
1902 void console_unlock(void)
1904 static char text[LOG_LINE_MAX];
1905 static u64 seen_seq;
1906 unsigned long flags;
1907 bool wake_klogd = false;
1910 if (console_suspended) {
1915 console_may_schedule = 0;
1917 /* flush buffered message fragment immediately to console */
1918 raw_spin_lock_irqsave(&logbuf_lock, flags);
1919 if (cont.len && (cont.cons < cont.len || cont.flushed)) {
1922 len = cont_print_text(text, sizeof(text));
1923 raw_spin_unlock(&logbuf_lock);
1924 stop_critical_timings();
1925 call_console_drivers(cont.level, text, len);
1926 start_critical_timings();
1927 local_irq_restore(flags);
1929 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
1937 raw_spin_lock_irqsave(&logbuf_lock, flags);
1938 if (seen_seq != log_next_seq) {
1940 seen_seq = log_next_seq;
1943 if (console_seq < log_first_seq) {
1944 /* messages are gone, move to first one */
1945 console_seq = log_first_seq;
1946 console_idx = log_first_idx;
1949 if (console_seq == log_next_seq)
1952 msg = log_from_idx(console_idx);
1953 if (msg->flags & LOG_NOCONS) {
1955 * Skip record we have buffered and already printed
1956 * directly to the console when we received it.
1958 console_idx = log_next(console_idx);
1964 len = msg_print_text(msg, false, text, sizeof(text));
1966 console_idx = log_next(console_idx);
1968 raw_spin_unlock(&logbuf_lock);
1970 stop_critical_timings(); /* don't trace print latency */
1971 call_console_drivers(level, text, len);
1972 start_critical_timings();
1973 local_irq_restore(flags);
1977 /* Release the exclusive_console once it is used */
1978 if (unlikely(exclusive_console))
1979 exclusive_console = NULL;
1981 raw_spin_unlock(&logbuf_lock);
1986 * Someone could have filled up the buffer again, so re-check if there's
1987 * something to flush. In case we cannot trylock the console_sem again,
1988 * there's a new owner and the console_unlock() from them will do the
1989 * flush, no worries.
1991 raw_spin_lock(&logbuf_lock);
1992 retry = console_seq != log_next_seq;
1993 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
1995 if (retry && console_trylock())
2001 EXPORT_SYMBOL(console_unlock);
2004 * console_conditional_schedule - yield the CPU if required
2006 * If the console code is currently allowed to sleep, and
2007 * if this CPU should yield the CPU to another task, do
2010 * Must be called within console_lock();.
2012 void __sched console_conditional_schedule(void)
2014 if (console_may_schedule)
2017 EXPORT_SYMBOL(console_conditional_schedule);
2019 void console_unblank(void)
2024 * console_unblank can no longer be called in interrupt context unless
2025 * oops_in_progress is set to 1..
2027 if (oops_in_progress) {
2028 if (down_trylock(&console_sem) != 0)
2034 console_may_schedule = 0;
2036 if ((c->flags & CON_ENABLED) && c->unblank)
2042 * Return the console tty driver structure and its associated index
2044 struct tty_driver *console_device(int *index)
2047 struct tty_driver *driver = NULL;
2050 for_each_console(c) {
2053 driver = c->device(c, index);
2062 * Prevent further output on the passed console device so that (for example)
2063 * serial drivers can disable console output before suspending a port, and can
2064 * re-enable output afterwards.
2066 void console_stop(struct console *console)
2069 console->flags &= ~CON_ENABLED;
2072 EXPORT_SYMBOL(console_stop);
2074 void console_start(struct console *console)
2077 console->flags |= CON_ENABLED;
2080 EXPORT_SYMBOL(console_start);
2082 static int __read_mostly keep_bootcon;
2084 static int __init keep_bootcon_setup(char *str)
2087 printk(KERN_INFO "debug: skip boot console de-registration.\n");
2092 early_param("keep_bootcon", keep_bootcon_setup);
2095 * The console driver calls this routine during kernel initialization
2096 * to register the console printing procedure with printk() and to
2097 * print any messages that were printed by the kernel before the
2098 * console driver was initialized.
2100 * This can happen pretty early during the boot process (because of
2101 * early_printk) - sometimes before setup_arch() completes - be careful
2102 * of what kernel features are used - they may not be initialised yet.
2104 * There are two types of consoles - bootconsoles (early_printk) and
2105 * "real" consoles (everything which is not a bootconsole) which are
2106 * handled differently.
2107 * - Any number of bootconsoles can be registered at any time.
2108 * - As soon as a "real" console is registered, all bootconsoles
2109 * will be unregistered automatically.
2110 * - Once a "real" console is registered, any attempt to register a
2111 * bootconsoles will be rejected
2113 void register_console(struct console *newcon)
2116 unsigned long flags;
2117 struct console *bcon = NULL;
2120 * before we register a new CON_BOOT console, make sure we don't
2121 * already have a valid console
2123 if (console_drivers && newcon->flags & CON_BOOT) {
2124 /* find the last or real console */
2125 for_each_console(bcon) {
2126 if (!(bcon->flags & CON_BOOT)) {
2127 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
2128 newcon->name, newcon->index);
2134 if (console_drivers && console_drivers->flags & CON_BOOT)
2135 bcon = console_drivers;
2137 if (preferred_console < 0 || bcon || !console_drivers)
2138 preferred_console = selected_console;
2140 if (newcon->early_setup)
2141 newcon->early_setup();
2144 * See if we want to use this console driver. If we
2145 * didn't select a console we take the first one
2146 * that registers here.
2148 if (preferred_console < 0) {
2149 if (newcon->index < 0)
2151 if (newcon->setup == NULL ||
2152 newcon->setup(newcon, NULL) == 0) {
2153 newcon->flags |= CON_ENABLED;
2154 if (newcon->device) {
2155 newcon->flags |= CON_CONSDEV;
2156 preferred_console = 0;
2162 * See if this console matches one we selected on
2165 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
2167 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
2169 if (newcon->index >= 0 &&
2170 newcon->index != console_cmdline[i].index)
2172 if (newcon->index < 0)
2173 newcon->index = console_cmdline[i].index;
2174 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2175 if (console_cmdline[i].brl_options) {
2176 newcon->flags |= CON_BRL;
2177 braille_register_console(newcon,
2178 console_cmdline[i].index,
2179 console_cmdline[i].options,
2180 console_cmdline[i].brl_options);
2184 if (newcon->setup &&
2185 newcon->setup(newcon, console_cmdline[i].options) != 0)
2187 newcon->flags |= CON_ENABLED;
2188 newcon->index = console_cmdline[i].index;
2189 if (i == selected_console) {
2190 newcon->flags |= CON_CONSDEV;
2191 preferred_console = selected_console;
2196 if (!(newcon->flags & CON_ENABLED))
2200 * If we have a bootconsole, and are switching to a real console,
2201 * don't print everything out again, since when the boot console, and
2202 * the real console are the same physical device, it's annoying to
2203 * see the beginning boot messages twice
2205 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2206 newcon->flags &= ~CON_PRINTBUFFER;
2209 * Put this console in the list - keep the
2210 * preferred driver at the head of the list.
2213 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2214 newcon->next = console_drivers;
2215 console_drivers = newcon;
2217 newcon->next->flags &= ~CON_CONSDEV;
2219 newcon->next = console_drivers->next;
2220 console_drivers->next = newcon;
2222 if (newcon->flags & CON_PRINTBUFFER) {
2224 * console_unlock(); will print out the buffered messages
2227 raw_spin_lock_irqsave(&logbuf_lock, flags);
2228 console_seq = syslog_seq;
2229 console_idx = syslog_idx;
2230 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2232 * We're about to replay the log buffer. Only do this to the
2233 * just-registered console to avoid excessive message spam to
2234 * the already-registered consoles.
2236 exclusive_console = newcon;
2239 console_sysfs_notify();
2242 * By unregistering the bootconsoles after we enable the real console
2243 * we get the "console xxx enabled" message on all the consoles -
2244 * boot consoles, real consoles, etc - this is to ensure that end
2245 * users know there might be something in the kernel's log buffer that
2246 * went to the bootconsole (that they do not see on the real console)
2249 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2251 /* we need to iterate through twice, to make sure we print
2252 * everything out, before we unregister the console(s)
2254 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
2255 newcon->name, newcon->index);
2256 for_each_console(bcon)
2257 if (bcon->flags & CON_BOOT)
2258 unregister_console(bcon);
2260 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
2261 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2262 newcon->name, newcon->index);
2265 EXPORT_SYMBOL(register_console);
2267 int unregister_console(struct console *console)
2269 struct console *a, *b;
2272 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2273 if (console->flags & CON_BRL)
2274 return braille_unregister_console(console);
2278 if (console_drivers == console) {
2279 console_drivers=console->next;
2281 } else if (console_drivers) {
2282 for (a=console_drivers->next, b=console_drivers ;
2283 a; b=a, a=b->next) {
2293 * If this isn't the last console and it has CON_CONSDEV set, we
2294 * need to set it on the next preferred console.
2296 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2297 console_drivers->flags |= CON_CONSDEV;
2300 console_sysfs_notify();
2303 EXPORT_SYMBOL(unregister_console);
2305 static int __init printk_late_init(void)
2307 struct console *con;
2309 for_each_console(con) {
2310 if (!keep_bootcon && con->flags & CON_BOOT) {
2311 printk(KERN_INFO "turn off boot console %s%d\n",
2312 con->name, con->index);
2313 unregister_console(con);
2316 hotcpu_notifier(console_cpu_notify, 0);
2319 late_initcall(printk_late_init);
2321 #if defined CONFIG_PRINTK
2323 int printk_sched(const char *fmt, ...)
2325 unsigned long flags;
2330 local_irq_save(flags);
2331 buf = __get_cpu_var(printk_sched_buf);
2333 va_start(args, fmt);
2334 r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2337 __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2338 local_irq_restore(flags);
2344 * printk rate limiting, lifted from the networking subsystem.
2346 * This enforces a rate limit: not more than 10 kernel messages
2347 * every 5s to make a denial-of-service attack impossible.
2349 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2351 int __printk_ratelimit(const char *func)
2353 return ___ratelimit(&printk_ratelimit_state, func);
2355 EXPORT_SYMBOL(__printk_ratelimit);
2358 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2359 * @caller_jiffies: pointer to caller's state
2360 * @interval_msecs: minimum interval between prints
2362 * printk_timed_ratelimit() returns true if more than @interval_msecs
2363 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2366 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2367 unsigned int interval_msecs)
2369 if (*caller_jiffies == 0
2370 || !time_in_range(jiffies, *caller_jiffies,
2372 + msecs_to_jiffies(interval_msecs))) {
2373 *caller_jiffies = jiffies;
2378 EXPORT_SYMBOL(printk_timed_ratelimit);
2380 static DEFINE_SPINLOCK(dump_list_lock);
2381 static LIST_HEAD(dump_list);
2384 * kmsg_dump_register - register a kernel log dumper.
2385 * @dumper: pointer to the kmsg_dumper structure
2387 * Adds a kernel log dumper to the system. The dump callback in the
2388 * structure will be called when the kernel oopses or panics and must be
2389 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2391 int kmsg_dump_register(struct kmsg_dumper *dumper)
2393 unsigned long flags;
2396 /* The dump callback needs to be set */
2400 spin_lock_irqsave(&dump_list_lock, flags);
2401 /* Don't allow registering multiple times */
2402 if (!dumper->registered) {
2403 dumper->registered = 1;
2404 list_add_tail_rcu(&dumper->list, &dump_list);
2407 spin_unlock_irqrestore(&dump_list_lock, flags);
2411 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2414 * kmsg_dump_unregister - unregister a kmsg dumper.
2415 * @dumper: pointer to the kmsg_dumper structure
2417 * Removes a dump device from the system. Returns zero on success and
2418 * %-EINVAL otherwise.
2420 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2422 unsigned long flags;
2425 spin_lock_irqsave(&dump_list_lock, flags);
2426 if (dumper->registered) {
2427 dumper->registered = 0;
2428 list_del_rcu(&dumper->list);
2431 spin_unlock_irqrestore(&dump_list_lock, flags);
2436 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2438 static bool always_kmsg_dump;
2439 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2442 * kmsg_dump - dump kernel log to kernel message dumpers.
2443 * @reason: the reason (oops, panic etc) for dumping
2445 * Call each of the registered dumper's dump() callback, which can
2446 * retrieve the kmsg records with kmsg_dump_get_line() or
2447 * kmsg_dump_get_buffer().
2449 void kmsg_dump(enum kmsg_dump_reason reason)
2451 struct kmsg_dumper *dumper;
2452 unsigned long flags;
2454 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2458 list_for_each_entry_rcu(dumper, &dump_list, list) {
2459 if (dumper->max_reason && reason > dumper->max_reason)
2462 /* initialize iterator with data about the stored records */
2463 dumper->active = true;
2465 raw_spin_lock_irqsave(&logbuf_lock, flags);
2466 dumper->cur_seq = clear_seq;
2467 dumper->cur_idx = clear_idx;
2468 dumper->next_seq = log_next_seq;
2469 dumper->next_idx = log_next_idx;
2470 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2472 /* invoke dumper which will iterate over records */
2473 dumper->dump(dumper, reason);
2475 /* reset iterator */
2476 dumper->active = false;
2482 * kmsg_dump_get_line - retrieve one kmsg log line
2483 * @dumper: registered kmsg dumper
2484 * @syslog: include the "<4>" prefixes
2485 * @line: buffer to copy the line to
2486 * @size: maximum size of the buffer
2487 * @len: length of line placed into buffer
2489 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2490 * record, and copy one record into the provided buffer.
2492 * Consecutive calls will return the next available record moving
2493 * towards the end of the buffer with the youngest messages.
2495 * A return value of FALSE indicates that there are no more records to
2498 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2499 char *line, size_t size, size_t *len)
2501 unsigned long flags;
2506 if (!dumper->active)
2509 raw_spin_lock_irqsave(&logbuf_lock, flags);
2510 if (dumper->cur_seq < log_first_seq) {
2511 /* messages are gone, move to first available one */
2512 dumper->cur_seq = log_first_seq;
2513 dumper->cur_idx = log_first_idx;
2517 if (dumper->cur_seq >= log_next_seq) {
2518 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2522 msg = log_from_idx(dumper->cur_idx);
2523 l = msg_print_text(msg, syslog,
2526 dumper->cur_idx = log_next(dumper->cur_idx);
2529 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2535 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2538 * kmsg_dump_get_buffer - copy kmsg log lines
2539 * @dumper: registered kmsg dumper
2540 * @syslog: include the "<4>" prefixes
2541 * @buf: buffer to copy the line to
2542 * @size: maximum size of the buffer
2543 * @len: length of line placed into buffer
2545 * Start at the end of the kmsg buffer and fill the provided buffer
2546 * with as many of the the *youngest* kmsg records that fit into it.
2547 * If the buffer is large enough, all available kmsg records will be
2548 * copied with a single call.
2550 * Consecutive calls will fill the buffer with the next block of
2551 * available older records, not including the earlier retrieved ones.
2553 * A return value of FALSE indicates that there are no more records to
2556 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2557 char *buf, size_t size, size_t *len)
2559 unsigned long flags;
2567 if (!dumper->active)
2570 raw_spin_lock_irqsave(&logbuf_lock, flags);
2571 if (dumper->cur_seq < log_first_seq) {
2572 /* messages are gone, move to first available one */
2573 dumper->cur_seq = log_first_seq;
2574 dumper->cur_idx = log_first_idx;
2578 if (dumper->cur_seq >= dumper->next_seq) {
2579 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2583 /* calculate length of entire buffer */
2584 seq = dumper->cur_seq;
2585 idx = dumper->cur_idx;
2586 while (seq < dumper->next_seq) {
2587 struct log *msg = log_from_idx(idx);
2589 l += msg_print_text(msg, true, NULL, 0);
2590 idx = log_next(idx);
2594 /* move first record forward until length fits into the buffer */
2595 seq = dumper->cur_seq;
2596 idx = dumper->cur_idx;
2597 while (l > size && seq < dumper->next_seq) {
2598 struct log *msg = log_from_idx(idx);
2600 l -= msg_print_text(msg, true, NULL, 0);
2601 idx = log_next(idx);
2605 /* last message in next interation */
2610 while (seq < dumper->next_seq) {
2611 struct log *msg = log_from_idx(idx);
2613 l += msg_print_text(msg, syslog,
2616 idx = log_next(idx);
2620 dumper->next_seq = next_seq;
2621 dumper->next_idx = next_idx;
2623 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2629 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2632 * kmsg_dump_rewind - reset the interator
2633 * @dumper: registered kmsg dumper
2635 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2636 * kmsg_dump_get_buffer() can be called again and used multiple
2637 * times within the same dumper.dump() callback.
2639 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2641 unsigned long flags;
2643 raw_spin_lock_irqsave(&logbuf_lock, flags);
2644 dumper->cur_seq = clear_seq;
2645 dumper->cur_idx = clear_idx;
2646 dumper->next_seq = log_next_seq;
2647 dumper->next_idx = log_next_idx;
2648 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2650 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);