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);
883 if (len > 0 && copy_to_user(buf, text, len))
890 static int syslog_print_all(char __user *buf, int size, bool clear)
895 text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
899 raw_spin_lock_irq(&logbuf_lock);
905 if (clear_seq < log_first_seq) {
906 /* messages are gone, move to first available one */
907 clear_seq = log_first_seq;
908 clear_idx = log_first_idx;
912 * Find first record that fits, including all following records,
913 * into the user-provided buffer for this dump.
917 while (seq < log_next_seq) {
918 struct log *msg = log_from_idx(idx);
920 len += msg_print_text(msg, true, NULL, 0);
925 /* move first record forward until length fits into the buffer */
928 while (len > size && seq < log_next_seq) {
929 struct log *msg = log_from_idx(idx);
931 len -= msg_print_text(msg, true, NULL, 0);
936 /* last message fitting into this dump */
937 next_seq = log_next_seq;
940 while (len >= 0 && seq < next_seq) {
941 struct log *msg = log_from_idx(idx);
944 textlen = msg_print_text(msg, true, text, LOG_LINE_MAX);
952 raw_spin_unlock_irq(&logbuf_lock);
953 if (copy_to_user(buf + len, text, textlen))
957 raw_spin_lock_irq(&logbuf_lock);
959 if (seq < log_first_seq) {
960 /* messages are gone, move to next one */
968 clear_seq = log_next_seq;
969 clear_idx = log_next_idx;
971 raw_spin_unlock_irq(&logbuf_lock);
977 int do_syslog(int type, char __user *buf, int len, bool from_file)
980 static int saved_console_loglevel = -1;
981 static DEFINE_MUTEX(syslog_mutex);
984 error = check_syslog_permissions(type, from_file);
988 error = security_syslog(type);
993 case SYSLOG_ACTION_CLOSE: /* Close log */
995 case SYSLOG_ACTION_OPEN: /* Open log */
997 case SYSLOG_ACTION_READ: /* Read from log */
1004 if (!access_ok(VERIFY_WRITE, buf, len)) {
1008 error = mutex_lock_interruptible(&syslog_mutex);
1011 error = wait_event_interruptible(log_wait,
1012 syslog_seq != log_next_seq);
1014 mutex_unlock(&syslog_mutex);
1017 error = syslog_print(buf, len);
1018 mutex_unlock(&syslog_mutex);
1020 /* Read/clear last kernel messages */
1021 case SYSLOG_ACTION_READ_CLEAR:
1024 /* Read last kernel messages */
1025 case SYSLOG_ACTION_READ_ALL:
1027 if (!buf || len < 0)
1032 if (!access_ok(VERIFY_WRITE, buf, len)) {
1036 error = syslog_print_all(buf, len, clear);
1038 /* Clear ring buffer */
1039 case SYSLOG_ACTION_CLEAR:
1040 syslog_print_all(NULL, 0, true);
1042 /* Disable logging to console */
1043 case SYSLOG_ACTION_CONSOLE_OFF:
1044 if (saved_console_loglevel == -1)
1045 saved_console_loglevel = console_loglevel;
1046 console_loglevel = minimum_console_loglevel;
1048 /* Enable logging to console */
1049 case SYSLOG_ACTION_CONSOLE_ON:
1050 if (saved_console_loglevel != -1) {
1051 console_loglevel = saved_console_loglevel;
1052 saved_console_loglevel = -1;
1055 /* Set level of messages printed to console */
1056 case SYSLOG_ACTION_CONSOLE_LEVEL:
1058 if (len < 1 || len > 8)
1060 if (len < minimum_console_loglevel)
1061 len = minimum_console_loglevel;
1062 console_loglevel = len;
1063 /* Implicitly re-enable logging to console */
1064 saved_console_loglevel = -1;
1067 /* Number of chars in the log buffer */
1068 case SYSLOG_ACTION_SIZE_UNREAD:
1069 raw_spin_lock_irq(&logbuf_lock);
1070 if (syslog_seq < log_first_seq) {
1071 /* messages are gone, move to first one */
1072 syslog_seq = log_first_seq;
1073 syslog_idx = log_first_idx;
1077 * Short-cut for poll(/"proc/kmsg") which simply checks
1078 * for pending data, not the size; return the count of
1079 * records, not the length.
1081 error = log_next_idx - syslog_idx;
1089 while (seq < log_next_seq) {
1090 struct log *msg = log_from_idx(idx);
1092 error += msg_print_text(msg, true, NULL, 0);
1093 idx = log_next(idx);
1097 raw_spin_unlock_irq(&logbuf_lock);
1099 /* Size of the log buffer */
1100 case SYSLOG_ACTION_SIZE_BUFFER:
1101 error = log_buf_len;
1111 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1113 return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
1116 #ifdef CONFIG_KGDB_KDB
1117 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
1118 * uses locks so it cannot be used during debugging. Just tell kdb
1119 * where the start and end of the physical and logical logs are. This
1120 * is equivalent to do_syslog(3).
1122 void kdb_syslog_data(char *syslog_data[4])
1124 syslog_data[0] = log_buf;
1125 syslog_data[1] = log_buf + log_buf_len;
1126 syslog_data[2] = log_buf + log_first_idx;
1127 syslog_data[3] = log_buf + log_next_idx;
1129 #endif /* CONFIG_KGDB_KDB */
1131 static bool __read_mostly ignore_loglevel;
1133 static int __init ignore_loglevel_setup(char *str)
1135 ignore_loglevel = 1;
1136 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
1141 early_param("ignore_loglevel", ignore_loglevel_setup);
1142 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1143 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
1144 "print all kernel messages to the console.");
1147 * Call the console drivers, asking them to write out
1148 * log_buf[start] to log_buf[end - 1].
1149 * The console_lock must be held.
1151 static void call_console_drivers(int level, const char *text, size_t len)
1153 struct console *con;
1155 trace_console(text, 0, len, len);
1157 if (level >= console_loglevel && !ignore_loglevel)
1159 if (!console_drivers)
1162 for_each_console(con) {
1163 if (exclusive_console && con != exclusive_console)
1165 if (!(con->flags & CON_ENABLED))
1169 if (!cpu_online(smp_processor_id()) &&
1170 !(con->flags & CON_ANYTIME))
1172 con->write(con, text, len);
1177 * Zap console related locks when oopsing. Only zap at most once
1178 * every 10 seconds, to leave time for slow consoles to print a
1181 static void zap_locks(void)
1183 static unsigned long oops_timestamp;
1185 if (time_after_eq(jiffies, oops_timestamp) &&
1186 !time_after(jiffies, oops_timestamp + 30 * HZ))
1189 oops_timestamp = jiffies;
1192 /* If a crash is occurring, make sure we can't deadlock */
1193 raw_spin_lock_init(&logbuf_lock);
1194 /* And make sure that we print immediately */
1195 sema_init(&console_sem, 1);
1198 /* Check if we have any console registered that can be called early in boot. */
1199 static int have_callable_console(void)
1201 struct console *con;
1203 for_each_console(con)
1204 if (con->flags & CON_ANYTIME)
1211 * Can we actually use the console at this time on this cpu?
1213 * Console drivers may assume that per-cpu resources have
1214 * been allocated. So unless they're explicitly marked as
1215 * being able to cope (CON_ANYTIME) don't call them until
1216 * this CPU is officially up.
1218 static inline int can_use_console(unsigned int cpu)
1220 return cpu_online(cpu) || have_callable_console();
1224 * Try to get console ownership to actually show the kernel
1225 * messages from a 'printk'. Return true (and with the
1226 * console_lock held, and 'console_locked' set) if it
1227 * is successful, false otherwise.
1229 * This gets called with the 'logbuf_lock' spinlock held and
1230 * interrupts disabled. It should return with 'lockbuf_lock'
1231 * released but interrupts still disabled.
1233 static int console_trylock_for_printk(unsigned int cpu)
1234 __releases(&logbuf_lock)
1236 int retval = 0, wake = 0;
1238 if (console_trylock()) {
1242 * If we can't use the console, we need to release
1243 * the console semaphore by hand to avoid flushing
1244 * the buffer. We need to hold the console semaphore
1245 * in order to do this test safely.
1247 if (!can_use_console(cpu)) {
1253 logbuf_cpu = UINT_MAX;
1256 raw_spin_unlock(&logbuf_lock);
1260 int printk_delay_msec __read_mostly;
1262 static inline void printk_delay(void)
1264 if (unlikely(printk_delay_msec)) {
1265 int m = printk_delay_msec;
1269 touch_nmi_watchdog();
1274 asmlinkage int vprintk_emit(int facility, int level,
1275 const char *dict, size_t dictlen,
1276 const char *fmt, va_list args)
1278 static int recursion_bug;
1279 static char cont_buf[LOG_LINE_MAX];
1280 static size_t cont_len;
1281 static int cont_level;
1282 static struct task_struct *cont_task;
1283 static char textbuf[LOG_LINE_MAX];
1284 char *text = textbuf;
1286 unsigned long flags;
1288 bool newline = false;
1289 bool prefix = false;
1290 int printed_len = 0;
1295 /* This stops the holder of console_sem just where we want him */
1296 local_irq_save(flags);
1297 this_cpu = smp_processor_id();
1300 * Ouch, printk recursed into itself!
1302 if (unlikely(logbuf_cpu == this_cpu)) {
1304 * If a crash is occurring during printk() on this CPU,
1305 * then try to get the crash message out but make sure
1306 * we can't deadlock. Otherwise just return to avoid the
1307 * recursion and return - but flag the recursion so that
1308 * it can be printed at the next appropriate moment:
1310 if (!oops_in_progress && !lockdep_recursing(current)) {
1312 goto out_restore_irqs;
1318 raw_spin_lock(&logbuf_lock);
1319 logbuf_cpu = this_cpu;
1321 if (recursion_bug) {
1322 static const char recursion_msg[] =
1323 "BUG: recent printk recursion!";
1326 printed_len += strlen(recursion_msg);
1327 /* emit KERN_CRIT message */
1328 log_store(0, 2, NULL, 0, recursion_msg, printed_len);
1332 * The printf needs to come first; we need the syslog
1333 * prefix which might be passed-in as a parameter.
1335 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1337 /* mark and strip a trailing newline */
1338 if (text_len && text[text_len-1] == '\n') {
1343 /* strip syslog prefix and extract log level or control flags */
1344 if (text[0] == '<' && text[1] && text[2] == '>') {
1348 level = text[1] - '0';
1349 case 'd': /* KERN_DEFAULT */
1351 case 'c': /* KERN_CONT */
1358 level = default_message_loglevel;
1366 if (cont_len && (prefix || cont_task != current)) {
1368 * Flush earlier buffer, which is either from a
1369 * different thread, or when we got a new prefix.
1371 log_store(facility, cont_level, NULL, 0, cont_buf, cont_len);
1377 cont_task = current;
1380 /* buffer or append to earlier buffer from the same thread */
1381 if (cont_len + text_len > sizeof(cont_buf))
1382 text_len = sizeof(cont_buf) - cont_len;
1383 memcpy(cont_buf + cont_len, text, text_len);
1384 cont_len += text_len;
1386 if (cont_len && cont_task == current) {
1389 * New prefix from the same thread; flush. We
1390 * either got no earlier newline, or we race
1391 * with an interrupt.
1393 log_store(facility, cont_level,
1394 NULL, 0, cont_buf, cont_len);
1398 /* append to the earlier buffer and flush */
1399 if (cont_len + text_len > sizeof(cont_buf))
1400 text_len = sizeof(cont_buf) - cont_len;
1401 memcpy(cont_buf + cont_len, text, text_len);
1402 cont_len += text_len;
1403 log_store(facility, cont_level,
1404 NULL, 0, cont_buf, cont_len);
1407 printed_len = cont_len;
1409 /* ordinary single and terminated line */
1410 log_store(facility, level,
1411 dict, dictlen, text, text_len);
1412 printed_len = text_len;
1417 * Try to acquire and then immediately release the console semaphore.
1418 * The release will print out buffers and wake up /dev/kmsg and syslog()
1421 * The console_trylock_for_printk() function will release 'logbuf_lock'
1422 * regardless of whether it actually gets the console semaphore or not.
1424 if (console_trylock_for_printk(this_cpu))
1429 local_irq_restore(flags);
1433 EXPORT_SYMBOL(vprintk_emit);
1435 asmlinkage int vprintk(const char *fmt, va_list args)
1437 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1439 EXPORT_SYMBOL(vprintk);
1441 asmlinkage int printk_emit(int facility, int level,
1442 const char *dict, size_t dictlen,
1443 const char *fmt, ...)
1448 va_start(args, fmt);
1449 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1454 EXPORT_SYMBOL(printk_emit);
1457 * printk - print a kernel message
1458 * @fmt: format string
1460 * This is printk(). It can be called from any context. We want it to work.
1462 * We try to grab the console_lock. If we succeed, it's easy - we log the
1463 * output and call the console drivers. If we fail to get the semaphore, we
1464 * place the output into the log buffer and return. The current holder of
1465 * the console_sem will notice the new output in console_unlock(); and will
1466 * send it to the consoles before releasing the lock.
1468 * One effect of this deferred printing is that code which calls printk() and
1469 * then changes console_loglevel may break. This is because console_loglevel
1470 * is inspected when the actual printing occurs.
1475 * See the vsnprintf() documentation for format string extensions over C99.
1477 asmlinkage int printk(const char *fmt, ...)
1482 #ifdef CONFIG_KGDB_KDB
1483 if (unlikely(kdb_trap_printk)) {
1484 va_start(args, fmt);
1485 r = vkdb_printf(fmt, args);
1490 va_start(args, fmt);
1491 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1496 EXPORT_SYMBOL(printk);
1500 #define LOG_LINE_MAX 0
1501 static struct log *log_from_idx(u32 idx) { return NULL; }
1502 static u32 log_next(u32 idx) { return 0; }
1503 static void call_console_drivers(int level, const char *text, size_t len) {}
1504 static size_t msg_print_text(const struct log *msg, bool syslog,
1505 char *buf, size_t size) { return 0; }
1507 #endif /* CONFIG_PRINTK */
1509 static int __add_preferred_console(char *name, int idx, char *options,
1512 struct console_cmdline *c;
1516 * See if this tty is not yet registered, and
1517 * if we have a slot free.
1519 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1520 if (strcmp(console_cmdline[i].name, name) == 0 &&
1521 console_cmdline[i].index == idx) {
1523 selected_console = i;
1526 if (i == MAX_CMDLINECONSOLES)
1529 selected_console = i;
1530 c = &console_cmdline[i];
1531 strlcpy(c->name, name, sizeof(c->name));
1532 c->options = options;
1533 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1534 c->brl_options = brl_options;
1540 * Set up a list of consoles. Called from init/main.c
1542 static int __init console_setup(char *str)
1544 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1545 char *s, *options, *brl_options = NULL;
1548 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1549 if (!memcmp(str, "brl,", 4)) {
1552 } else if (!memcmp(str, "brl=", 4)) {
1553 brl_options = str + 4;
1554 str = strchr(brl_options, ',');
1556 printk(KERN_ERR "need port name after brl=\n");
1564 * Decode str into name, index, options.
1566 if (str[0] >= '0' && str[0] <= '9') {
1567 strcpy(buf, "ttyS");
1568 strncpy(buf + 4, str, sizeof(buf) - 5);
1570 strncpy(buf, str, sizeof(buf) - 1);
1572 buf[sizeof(buf) - 1] = 0;
1573 if ((options = strchr(str, ',')) != NULL)
1576 if (!strcmp(str, "ttya"))
1577 strcpy(buf, "ttyS0");
1578 if (!strcmp(str, "ttyb"))
1579 strcpy(buf, "ttyS1");
1581 for (s = buf; *s; s++)
1582 if ((*s >= '0' && *s <= '9') || *s == ',')
1584 idx = simple_strtoul(s, NULL, 10);
1587 __add_preferred_console(buf, idx, options, brl_options);
1588 console_set_on_cmdline = 1;
1591 __setup("console=", console_setup);
1594 * add_preferred_console - add a device to the list of preferred consoles.
1595 * @name: device name
1596 * @idx: device index
1597 * @options: options for this console
1599 * The last preferred console added will be used for kernel messages
1600 * and stdin/out/err for init. Normally this is used by console_setup
1601 * above to handle user-supplied console arguments; however it can also
1602 * be used by arch-specific code either to override the user or more
1603 * commonly to provide a default console (ie from PROM variables) when
1604 * the user has not supplied one.
1606 int add_preferred_console(char *name, int idx, char *options)
1608 return __add_preferred_console(name, idx, options, NULL);
1611 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1613 struct console_cmdline *c;
1616 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1617 if (strcmp(console_cmdline[i].name, name) == 0 &&
1618 console_cmdline[i].index == idx) {
1619 c = &console_cmdline[i];
1620 strlcpy(c->name, name_new, sizeof(c->name));
1621 c->name[sizeof(c->name) - 1] = 0;
1622 c->options = options;
1630 bool console_suspend_enabled = 1;
1631 EXPORT_SYMBOL(console_suspend_enabled);
1633 static int __init console_suspend_disable(char *str)
1635 console_suspend_enabled = 0;
1638 __setup("no_console_suspend", console_suspend_disable);
1639 module_param_named(console_suspend, console_suspend_enabled,
1640 bool, S_IRUGO | S_IWUSR);
1641 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1642 " and hibernate operations");
1645 * suspend_console - suspend the console subsystem
1647 * This disables printk() while we go into suspend states
1649 void suspend_console(void)
1651 if (!console_suspend_enabled)
1653 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1655 console_suspended = 1;
1659 void resume_console(void)
1661 if (!console_suspend_enabled)
1664 console_suspended = 0;
1669 * console_cpu_notify - print deferred console messages after CPU hotplug
1670 * @self: notifier struct
1671 * @action: CPU hotplug event
1674 * If printk() is called from a CPU that is not online yet, the messages
1675 * will be spooled but will not show up on the console. This function is
1676 * called when a new CPU comes online (or fails to come up), and ensures
1677 * that any such output gets printed.
1679 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1680 unsigned long action, void *hcpu)
1686 case CPU_DOWN_FAILED:
1687 case CPU_UP_CANCELED:
1695 * console_lock - lock the console system for exclusive use.
1697 * Acquires a lock which guarantees that the caller has
1698 * exclusive access to the console system and the console_drivers list.
1700 * Can sleep, returns nothing.
1702 void console_lock(void)
1704 BUG_ON(in_interrupt());
1706 if (console_suspended)
1709 console_may_schedule = 1;
1711 EXPORT_SYMBOL(console_lock);
1714 * console_trylock - try to lock the console system for exclusive use.
1716 * Tried to acquire a lock which guarantees that the caller has
1717 * exclusive access to the console system and the console_drivers list.
1719 * returns 1 on success, and 0 on failure to acquire the lock.
1721 int console_trylock(void)
1723 if (down_trylock(&console_sem))
1725 if (console_suspended) {
1730 console_may_schedule = 0;
1733 EXPORT_SYMBOL(console_trylock);
1735 int is_console_locked(void)
1737 return console_locked;
1741 * Delayed printk version, for scheduler-internal messages:
1743 #define PRINTK_BUF_SIZE 512
1745 #define PRINTK_PENDING_WAKEUP 0x01
1746 #define PRINTK_PENDING_SCHED 0x02
1748 static DEFINE_PER_CPU(int, printk_pending);
1749 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
1751 void printk_tick(void)
1753 if (__this_cpu_read(printk_pending)) {
1754 int pending = __this_cpu_xchg(printk_pending, 0);
1755 if (pending & PRINTK_PENDING_SCHED) {
1756 char *buf = __get_cpu_var(printk_sched_buf);
1757 printk(KERN_WARNING "[sched_delayed] %s", buf);
1759 if (pending & PRINTK_PENDING_WAKEUP)
1760 wake_up_interruptible(&log_wait);
1764 int printk_needs_cpu(int cpu)
1766 if (cpu_is_offline(cpu))
1768 return __this_cpu_read(printk_pending);
1771 void wake_up_klogd(void)
1773 if (waitqueue_active(&log_wait))
1774 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
1777 /* the next printk record to write to the console */
1778 static u64 console_seq;
1779 static u32 console_idx;
1782 * console_unlock - unlock the console system
1784 * Releases the console_lock which the caller holds on the console system
1785 * and the console driver list.
1787 * While the console_lock was held, console output may have been buffered
1788 * by printk(). If this is the case, console_unlock(); emits
1789 * the output prior to releasing the lock.
1791 * If there is output waiting, we wake /dev/kmsg and syslog() users.
1793 * console_unlock(); may be called from any context.
1795 void console_unlock(void)
1797 static u64 seen_seq;
1798 unsigned long flags;
1799 bool wake_klogd = false;
1802 if (console_suspended) {
1807 console_may_schedule = 0;
1812 static char text[LOG_LINE_MAX];
1816 raw_spin_lock_irqsave(&logbuf_lock, flags);
1817 if (seen_seq != log_next_seq) {
1819 seen_seq = log_next_seq;
1822 if (console_seq < log_first_seq) {
1823 /* messages are gone, move to first one */
1824 console_seq = log_first_seq;
1825 console_idx = log_first_idx;
1828 if (console_seq == log_next_seq)
1831 msg = log_from_idx(console_idx);
1832 level = msg->level & 7;
1834 len = msg_print_text(msg, false, text, sizeof(text));
1836 console_idx = log_next(console_idx);
1838 raw_spin_unlock(&logbuf_lock);
1840 stop_critical_timings(); /* don't trace print latency */
1841 call_console_drivers(level, text, len);
1842 start_critical_timings();
1843 local_irq_restore(flags);
1847 /* Release the exclusive_console once it is used */
1848 if (unlikely(exclusive_console))
1849 exclusive_console = NULL;
1851 raw_spin_unlock(&logbuf_lock);
1856 * Someone could have filled up the buffer again, so re-check if there's
1857 * something to flush. In case we cannot trylock the console_sem again,
1858 * there's a new owner and the console_unlock() from them will do the
1859 * flush, no worries.
1861 raw_spin_lock(&logbuf_lock);
1862 retry = console_seq != log_next_seq;
1863 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
1865 if (retry && console_trylock())
1871 EXPORT_SYMBOL(console_unlock);
1874 * console_conditional_schedule - yield the CPU if required
1876 * If the console code is currently allowed to sleep, and
1877 * if this CPU should yield the CPU to another task, do
1880 * Must be called within console_lock();.
1882 void __sched console_conditional_schedule(void)
1884 if (console_may_schedule)
1887 EXPORT_SYMBOL(console_conditional_schedule);
1889 void console_unblank(void)
1894 * console_unblank can no longer be called in interrupt context unless
1895 * oops_in_progress is set to 1..
1897 if (oops_in_progress) {
1898 if (down_trylock(&console_sem) != 0)
1904 console_may_schedule = 0;
1906 if ((c->flags & CON_ENABLED) && c->unblank)
1912 * Return the console tty driver structure and its associated index
1914 struct tty_driver *console_device(int *index)
1917 struct tty_driver *driver = NULL;
1920 for_each_console(c) {
1923 driver = c->device(c, index);
1932 * Prevent further output on the passed console device so that (for example)
1933 * serial drivers can disable console output before suspending a port, and can
1934 * re-enable output afterwards.
1936 void console_stop(struct console *console)
1939 console->flags &= ~CON_ENABLED;
1942 EXPORT_SYMBOL(console_stop);
1944 void console_start(struct console *console)
1947 console->flags |= CON_ENABLED;
1950 EXPORT_SYMBOL(console_start);
1952 static int __read_mostly keep_bootcon;
1954 static int __init keep_bootcon_setup(char *str)
1957 printk(KERN_INFO "debug: skip boot console de-registration.\n");
1962 early_param("keep_bootcon", keep_bootcon_setup);
1965 * The console driver calls this routine during kernel initialization
1966 * to register the console printing procedure with printk() and to
1967 * print any messages that were printed by the kernel before the
1968 * console driver was initialized.
1970 * This can happen pretty early during the boot process (because of
1971 * early_printk) - sometimes before setup_arch() completes - be careful
1972 * of what kernel features are used - they may not be initialised yet.
1974 * There are two types of consoles - bootconsoles (early_printk) and
1975 * "real" consoles (everything which is not a bootconsole) which are
1976 * handled differently.
1977 * - Any number of bootconsoles can be registered at any time.
1978 * - As soon as a "real" console is registered, all bootconsoles
1979 * will be unregistered automatically.
1980 * - Once a "real" console is registered, any attempt to register a
1981 * bootconsoles will be rejected
1983 void register_console(struct console *newcon)
1986 unsigned long flags;
1987 struct console *bcon = NULL;
1990 * before we register a new CON_BOOT console, make sure we don't
1991 * already have a valid console
1993 if (console_drivers && newcon->flags & CON_BOOT) {
1994 /* find the last or real console */
1995 for_each_console(bcon) {
1996 if (!(bcon->flags & CON_BOOT)) {
1997 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1998 newcon->name, newcon->index);
2004 if (console_drivers && console_drivers->flags & CON_BOOT)
2005 bcon = console_drivers;
2007 if (preferred_console < 0 || bcon || !console_drivers)
2008 preferred_console = selected_console;
2010 if (newcon->early_setup)
2011 newcon->early_setup();
2014 * See if we want to use this console driver. If we
2015 * didn't select a console we take the first one
2016 * that registers here.
2018 if (preferred_console < 0) {
2019 if (newcon->index < 0)
2021 if (newcon->setup == NULL ||
2022 newcon->setup(newcon, NULL) == 0) {
2023 newcon->flags |= CON_ENABLED;
2024 if (newcon->device) {
2025 newcon->flags |= CON_CONSDEV;
2026 preferred_console = 0;
2032 * See if this console matches one we selected on
2035 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
2037 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
2039 if (newcon->index >= 0 &&
2040 newcon->index != console_cmdline[i].index)
2042 if (newcon->index < 0)
2043 newcon->index = console_cmdline[i].index;
2044 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2045 if (console_cmdline[i].brl_options) {
2046 newcon->flags |= CON_BRL;
2047 braille_register_console(newcon,
2048 console_cmdline[i].index,
2049 console_cmdline[i].options,
2050 console_cmdline[i].brl_options);
2054 if (newcon->setup &&
2055 newcon->setup(newcon, console_cmdline[i].options) != 0)
2057 newcon->flags |= CON_ENABLED;
2058 newcon->index = console_cmdline[i].index;
2059 if (i == selected_console) {
2060 newcon->flags |= CON_CONSDEV;
2061 preferred_console = selected_console;
2066 if (!(newcon->flags & CON_ENABLED))
2070 * If we have a bootconsole, and are switching to a real console,
2071 * don't print everything out again, since when the boot console, and
2072 * the real console are the same physical device, it's annoying to
2073 * see the beginning boot messages twice
2075 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2076 newcon->flags &= ~CON_PRINTBUFFER;
2079 * Put this console in the list - keep the
2080 * preferred driver at the head of the list.
2083 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2084 newcon->next = console_drivers;
2085 console_drivers = newcon;
2087 newcon->next->flags &= ~CON_CONSDEV;
2089 newcon->next = console_drivers->next;
2090 console_drivers->next = newcon;
2092 if (newcon->flags & CON_PRINTBUFFER) {
2094 * console_unlock(); will print out the buffered messages
2097 raw_spin_lock_irqsave(&logbuf_lock, flags);
2098 console_seq = syslog_seq;
2099 console_idx = syslog_idx;
2100 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2102 * We're about to replay the log buffer. Only do this to the
2103 * just-registered console to avoid excessive message spam to
2104 * the already-registered consoles.
2106 exclusive_console = newcon;
2109 console_sysfs_notify();
2112 * By unregistering the bootconsoles after we enable the real console
2113 * we get the "console xxx enabled" message on all the consoles -
2114 * boot consoles, real consoles, etc - this is to ensure that end
2115 * users know there might be something in the kernel's log buffer that
2116 * went to the bootconsole (that they do not see on the real console)
2119 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2121 /* we need to iterate through twice, to make sure we print
2122 * everything out, before we unregister the console(s)
2124 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
2125 newcon->name, newcon->index);
2126 for_each_console(bcon)
2127 if (bcon->flags & CON_BOOT)
2128 unregister_console(bcon);
2130 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
2131 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2132 newcon->name, newcon->index);
2135 EXPORT_SYMBOL(register_console);
2137 int unregister_console(struct console *console)
2139 struct console *a, *b;
2142 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2143 if (console->flags & CON_BRL)
2144 return braille_unregister_console(console);
2148 if (console_drivers == console) {
2149 console_drivers=console->next;
2151 } else if (console_drivers) {
2152 for (a=console_drivers->next, b=console_drivers ;
2153 a; b=a, a=b->next) {
2163 * If this isn't the last console and it has CON_CONSDEV set, we
2164 * need to set it on the next preferred console.
2166 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2167 console_drivers->flags |= CON_CONSDEV;
2170 console_sysfs_notify();
2173 EXPORT_SYMBOL(unregister_console);
2175 static int __init printk_late_init(void)
2177 struct console *con;
2179 for_each_console(con) {
2180 if (!keep_bootcon && con->flags & CON_BOOT) {
2181 printk(KERN_INFO "turn off boot console %s%d\n",
2182 con->name, con->index);
2183 unregister_console(con);
2186 hotcpu_notifier(console_cpu_notify, 0);
2189 late_initcall(printk_late_init);
2191 #if defined CONFIG_PRINTK
2193 int printk_sched(const char *fmt, ...)
2195 unsigned long flags;
2200 local_irq_save(flags);
2201 buf = __get_cpu_var(printk_sched_buf);
2203 va_start(args, fmt);
2204 r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2207 __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2208 local_irq_restore(flags);
2214 * printk rate limiting, lifted from the networking subsystem.
2216 * This enforces a rate limit: not more than 10 kernel messages
2217 * every 5s to make a denial-of-service attack impossible.
2219 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2221 int __printk_ratelimit(const char *func)
2223 return ___ratelimit(&printk_ratelimit_state, func);
2225 EXPORT_SYMBOL(__printk_ratelimit);
2228 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2229 * @caller_jiffies: pointer to caller's state
2230 * @interval_msecs: minimum interval between prints
2232 * printk_timed_ratelimit() returns true if more than @interval_msecs
2233 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2236 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2237 unsigned int interval_msecs)
2239 if (*caller_jiffies == 0
2240 || !time_in_range(jiffies, *caller_jiffies,
2242 + msecs_to_jiffies(interval_msecs))) {
2243 *caller_jiffies = jiffies;
2248 EXPORT_SYMBOL(printk_timed_ratelimit);
2250 static DEFINE_SPINLOCK(dump_list_lock);
2251 static LIST_HEAD(dump_list);
2254 * kmsg_dump_register - register a kernel log dumper.
2255 * @dumper: pointer to the kmsg_dumper structure
2257 * Adds a kernel log dumper to the system. The dump callback in the
2258 * structure will be called when the kernel oopses or panics and must be
2259 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2261 int kmsg_dump_register(struct kmsg_dumper *dumper)
2263 unsigned long flags;
2266 /* The dump callback needs to be set */
2270 spin_lock_irqsave(&dump_list_lock, flags);
2271 /* Don't allow registering multiple times */
2272 if (!dumper->registered) {
2273 dumper->registered = 1;
2274 list_add_tail_rcu(&dumper->list, &dump_list);
2277 spin_unlock_irqrestore(&dump_list_lock, flags);
2281 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2284 * kmsg_dump_unregister - unregister a kmsg dumper.
2285 * @dumper: pointer to the kmsg_dumper structure
2287 * Removes a dump device from the system. Returns zero on success and
2288 * %-EINVAL otherwise.
2290 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2292 unsigned long flags;
2295 spin_lock_irqsave(&dump_list_lock, flags);
2296 if (dumper->registered) {
2297 dumper->registered = 0;
2298 list_del_rcu(&dumper->list);
2301 spin_unlock_irqrestore(&dump_list_lock, flags);
2306 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2308 static bool always_kmsg_dump;
2309 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2312 * kmsg_dump - dump kernel log to kernel message dumpers.
2313 * @reason: the reason (oops, panic etc) for dumping
2315 * Call each of the registered dumper's dump() callback, which can
2316 * retrieve the kmsg records with kmsg_dump_get_line() or
2317 * kmsg_dump_get_buffer().
2319 void kmsg_dump(enum kmsg_dump_reason reason)
2321 struct kmsg_dumper *dumper;
2322 unsigned long flags;
2324 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2328 list_for_each_entry_rcu(dumper, &dump_list, list) {
2329 if (dumper->max_reason && reason > dumper->max_reason)
2332 /* initialize iterator with data about the stored records */
2333 dumper->active = true;
2335 raw_spin_lock_irqsave(&logbuf_lock, flags);
2336 dumper->cur_seq = clear_seq;
2337 dumper->cur_idx = clear_idx;
2338 dumper->next_seq = log_next_seq;
2339 dumper->next_idx = log_next_idx;
2340 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2342 /* invoke dumper which will iterate over records */
2343 dumper->dump(dumper, reason);
2345 /* reset iterator */
2346 dumper->active = false;
2352 * kmsg_dump_get_line - retrieve one kmsg log line
2353 * @dumper: registered kmsg dumper
2354 * @syslog: include the "<4>" prefixes
2355 * @line: buffer to copy the line to
2356 * @size: maximum size of the buffer
2357 * @len: length of line placed into buffer
2359 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2360 * record, and copy one record into the provided buffer.
2362 * Consecutive calls will return the next available record moving
2363 * towards the end of the buffer with the youngest messages.
2365 * A return value of FALSE indicates that there are no more records to
2368 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2369 char *line, size_t size, size_t *len)
2371 unsigned long flags;
2376 if (!dumper->active)
2379 raw_spin_lock_irqsave(&logbuf_lock, flags);
2380 if (dumper->cur_seq < log_first_seq) {
2381 /* messages are gone, move to first available one */
2382 dumper->cur_seq = log_first_seq;
2383 dumper->cur_idx = log_first_idx;
2387 if (dumper->cur_seq >= log_next_seq) {
2388 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2392 msg = log_from_idx(dumper->cur_idx);
2393 l = msg_print_text(msg, syslog,
2396 dumper->cur_idx = log_next(dumper->cur_idx);
2399 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2405 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2408 * kmsg_dump_get_buffer - copy kmsg log lines
2409 * @dumper: registered kmsg dumper
2410 * @syslog: include the "<4>" prefixes
2411 * @line: buffer to copy the line to
2412 * @size: maximum size of the buffer
2413 * @len: length of line placed into buffer
2415 * Start at the end of the kmsg buffer and fill the provided buffer
2416 * with as many of the the *youngest* kmsg records that fit into it.
2417 * If the buffer is large enough, all available kmsg records will be
2418 * copied with a single call.
2420 * Consecutive calls will fill the buffer with the next block of
2421 * available older records, not including the earlier retrieved ones.
2423 * A return value of FALSE indicates that there are no more records to
2426 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2427 char *buf, size_t size, size_t *len)
2429 unsigned long flags;
2437 if (!dumper->active)
2440 raw_spin_lock_irqsave(&logbuf_lock, flags);
2441 if (dumper->cur_seq < log_first_seq) {
2442 /* messages are gone, move to first available one */
2443 dumper->cur_seq = log_first_seq;
2444 dumper->cur_idx = log_first_idx;
2448 if (dumper->cur_seq >= dumper->next_seq) {
2449 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2453 /* calculate length of entire buffer */
2454 seq = dumper->cur_seq;
2455 idx = dumper->cur_idx;
2456 while (seq < dumper->next_seq) {
2457 struct log *msg = log_from_idx(idx);
2459 l += msg_print_text(msg, true, NULL, 0);
2460 idx = log_next(idx);
2464 /* move first record forward until length fits into the buffer */
2465 seq = dumper->cur_seq;
2466 idx = dumper->cur_idx;
2467 while (l > size && seq < dumper->next_seq) {
2468 struct log *msg = log_from_idx(idx);
2470 l -= msg_print_text(msg, true, NULL, 0);
2471 idx = log_next(idx);
2475 /* last message in next interation */
2480 while (seq < dumper->next_seq) {
2481 struct log *msg = log_from_idx(idx);
2483 l += msg_print_text(msg, syslog,
2486 idx = log_next(idx);
2490 dumper->next_seq = next_seq;
2491 dumper->next_idx = next_idx;
2493 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2499 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2502 * kmsg_dump_rewind - reset the interator
2503 * @dumper: registered kmsg dumper
2505 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2506 * kmsg_dump_get_buffer() can be called again and used multiple
2507 * times within the same dumper.dump() callback.
2509 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2511 unsigned long flags;
2513 raw_spin_lock_irqsave(&logbuf_lock, flags);
2514 dumper->cur_seq = clear_seq;
2515 dumper->cur_idx = clear_idx;
2516 dumper->next_seq = log_next_seq;
2517 dumper->next_idx = log_next_idx;
2518 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2520 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);