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/aio.h>
36 #include <linux/syscalls.h>
37 #include <linux/kexec.h>
38 #include <linux/kdb.h>
39 #include <linux/ratelimit.h>
40 #include <linux/kmsg_dump.h>
41 #include <linux/syslog.h>
42 #include <linux/cpu.h>
43 #include <linux/notifier.h>
44 #include <linux/rculist.h>
45 #include <linux/poll.h>
46 #include <linux/irq_work.h>
47 #include <linux/utsname.h>
49 #include <asm/uaccess.h>
51 #define CREATE_TRACE_POINTS
52 #include <trace/events/printk.h>
54 #include "console_cmdline.h"
57 /* printk's without a loglevel use this.. */
58 #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
60 /* We show everything that is MORE important than this.. */
61 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
62 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
64 int console_printk[4] = {
65 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
66 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
67 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
68 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
72 * Low level drivers may need that to know if they can schedule in
73 * their unblank() callback or not. So let's export it.
76 EXPORT_SYMBOL(oops_in_progress);
79 * console_sem protects the console_drivers list, and also
80 * provides serialisation for access to the entire console
83 static DEFINE_SEMAPHORE(console_sem);
84 struct console *console_drivers;
85 EXPORT_SYMBOL_GPL(console_drivers);
88 static struct lockdep_map console_lock_dep_map = {
89 .name = "console_lock"
94 * This is used for debugging the mess that is the VT code by
95 * keeping track if we have the console semaphore held. It's
96 * definitely not the perfect debug tool (we don't know if _WE_
97 * hold it are racing, but it helps tracking those weird code
98 * path in the console code where we end up in places I want
99 * locked without the console sempahore held
101 static int console_locked, console_suspended;
104 * If exclusive_console is non-NULL then only this console is to be printed to.
106 static struct console *exclusive_console;
109 * Array of consoles built from command line options (console=)
112 #define MAX_CMDLINECONSOLES 8
114 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
116 static int selected_console = -1;
117 static int preferred_console = -1;
118 int console_set_on_cmdline;
119 EXPORT_SYMBOL(console_set_on_cmdline);
121 /* Flag: console code may call schedule() */
122 static int console_may_schedule;
125 * The printk log buffer consists of a chain of concatenated variable
126 * length records. Every record starts with a record header, containing
127 * the overall length of the record.
129 * The heads to the first and last entry in the buffer, as well as the
130 * sequence numbers of these both entries are maintained when messages
133 * If the heads indicate available messages, the length in the header
134 * tells the start next message. A length == 0 for the next message
135 * indicates a wrap-around to the beginning of the buffer.
137 * Every record carries the monotonic timestamp in microseconds, as well as
138 * the standard userspace syslog level and syslog facility. The usual
139 * kernel messages use LOG_KERN; userspace-injected messages always carry
140 * a matching syslog facility, by default LOG_USER. The origin of every
141 * message can be reliably determined that way.
143 * The human readable log message directly follows the message header. The
144 * length of the message text is stored in the header, the stored message
147 * Optionally, a message can carry a dictionary of properties (key/value pairs),
148 * to provide userspace with a machine-readable message context.
150 * Examples for well-defined, commonly used property names are:
151 * DEVICE=b12:8 device identifier
155 * +sound:card0 subsystem:devname
156 * SUBSYSTEM=pci driver-core subsystem name
158 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
159 * follows directly after a '=' character. Every property is terminated by
160 * a '\0' character. The last property is not terminated.
162 * Example of a message structure:
163 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
164 * 0008 34 00 record is 52 bytes long
165 * 000a 0b 00 text is 11 bytes long
166 * 000c 1f 00 dictionary is 23 bytes long
167 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
168 * 0010 69 74 27 73 20 61 20 6c "it's a l"
170 * 001b 44 45 56 49 43 "DEVIC"
171 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
172 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
174 * 0032 00 00 00 padding to next message header
176 * The 'struct printk_log' buffer header must never be directly exported to
177 * userspace, it is a kernel-private implementation detail that might
178 * need to be changed in the future, when the requirements change.
180 * /dev/kmsg exports the structured data in the following line format:
181 * "level,sequnum,timestamp;<message text>\n"
183 * The optional key/value pairs are attached as continuation lines starting
184 * with a space character and terminated by a newline. All possible
185 * non-prinatable characters are escaped in the "\xff" notation.
187 * Users of the export format should ignore possible additional values
188 * separated by ',', and find the message after the ';' character.
192 LOG_NOCONS = 1, /* already flushed, do not print to console */
193 LOG_NEWLINE = 2, /* text ended with a newline */
194 LOG_PREFIX = 4, /* text started with a prefix */
195 LOG_CONT = 8, /* text is a fragment of a continuation line */
199 u64 ts_nsec; /* timestamp in nanoseconds */
200 u16 len; /* length of entire record */
201 u16 text_len; /* length of text buffer */
202 u16 dict_len; /* length of dictionary buffer */
203 u8 facility; /* syslog facility */
204 u8 flags:5; /* internal record flags */
205 u8 level:3; /* syslog level */
209 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
210 * used in interesting ways to provide interlocking in console_unlock();
212 static DEFINE_RAW_SPINLOCK(logbuf_lock);
215 DECLARE_WAIT_QUEUE_HEAD(log_wait);
216 /* the next printk record to read by syslog(READ) or /proc/kmsg */
217 static u64 syslog_seq;
218 static u32 syslog_idx;
219 static enum log_flags syslog_prev;
220 static size_t syslog_partial;
222 /* index and sequence number of the first record stored in the buffer */
223 static u64 log_first_seq;
224 static u32 log_first_idx;
226 /* index and sequence number of the next record to store in the buffer */
227 static u64 log_next_seq;
228 static u32 log_next_idx;
230 /* the next printk record to write to the console */
231 static u64 console_seq;
232 static u32 console_idx;
233 static enum log_flags console_prev;
235 /* the next printk record to read after the last 'clear' command */
236 static u64 clear_seq;
237 static u32 clear_idx;
239 #define PREFIX_MAX 32
240 #define LOG_LINE_MAX 1024 - PREFIX_MAX
243 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
246 #define LOG_ALIGN __alignof__(struct printk_log)
248 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
249 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
250 static char *log_buf = __log_buf;
251 static u32 log_buf_len = __LOG_BUF_LEN;
253 /* cpu currently holding logbuf_lock */
254 static volatile unsigned int logbuf_cpu = UINT_MAX;
256 /* human readable text of the record */
257 static char *log_text(const struct printk_log *msg)
259 return (char *)msg + sizeof(struct printk_log);
262 /* optional key/value pair dictionary attached to the record */
263 static char *log_dict(const struct printk_log *msg)
265 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
268 /* get record by index; idx must point to valid msg */
269 static struct printk_log *log_from_idx(u32 idx)
271 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
274 * A length == 0 record is the end of buffer marker. Wrap around and
275 * read the message at the start of the buffer.
278 return (struct printk_log *)log_buf;
282 /* get next record; idx must point to valid msg */
283 static u32 log_next(u32 idx)
285 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
287 /* length == 0 indicates the end of the buffer; wrap */
289 * A length == 0 record is the end of buffer marker. Wrap around and
290 * read the message at the start of the buffer as *this* one, and
291 * return the one after that.
294 msg = (struct printk_log *)log_buf;
297 return idx + msg->len;
300 /* insert record into the buffer, discard old ones, update heads */
301 static void log_store(int facility, int level,
302 enum log_flags flags, u64 ts_nsec,
303 const char *dict, u16 dict_len,
304 const char *text, u16 text_len)
306 struct printk_log *msg;
309 /* number of '\0' padding bytes to next message */
310 size = sizeof(struct printk_log) + text_len + dict_len;
311 pad_len = (-size) & (LOG_ALIGN - 1);
314 while (log_first_seq < log_next_seq) {
317 if (log_next_idx > log_first_idx)
318 free = max(log_buf_len - log_next_idx, log_first_idx);
320 free = log_first_idx - log_next_idx;
322 if (free > size + sizeof(struct printk_log))
325 /* drop old messages until we have enough contiuous space */
326 log_first_idx = log_next(log_first_idx);
330 if (log_next_idx + size + sizeof(struct printk_log) >= log_buf_len) {
332 * This message + an additional empty header does not fit
333 * at the end of the buffer. Add an empty header with len == 0
334 * to signify a wrap around.
336 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
341 msg = (struct printk_log *)(log_buf + log_next_idx);
342 memcpy(log_text(msg), text, text_len);
343 msg->text_len = text_len;
344 memcpy(log_dict(msg), dict, dict_len);
345 msg->dict_len = dict_len;
346 msg->facility = facility;
347 msg->level = level & 7;
348 msg->flags = flags & 0x1f;
350 msg->ts_nsec = ts_nsec;
352 msg->ts_nsec = local_clock();
353 memset(log_dict(msg) + dict_len, 0, pad_len);
354 msg->len = sizeof(struct printk_log) + text_len + dict_len + pad_len;
357 log_next_idx += msg->len;
361 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
362 int dmesg_restrict = 1;
367 static int syslog_action_restricted(int type)
372 * Unless restricted, we allow "read all" and "get buffer size"
375 return type != SYSLOG_ACTION_READ_ALL &&
376 type != SYSLOG_ACTION_SIZE_BUFFER;
379 static int check_syslog_permissions(int type, bool from_file)
382 * If this is from /proc/kmsg and we've already opened it, then we've
383 * already done the capabilities checks at open time.
385 if (from_file && type != SYSLOG_ACTION_OPEN)
388 if (syslog_action_restricted(type)) {
389 if (capable(CAP_SYSLOG))
392 * For historical reasons, accept CAP_SYS_ADMIN too, with
395 if (capable(CAP_SYS_ADMIN)) {
396 pr_warn_once("%s (%d): Attempt to access syslog with "
397 "CAP_SYS_ADMIN but no CAP_SYSLOG "
399 current->comm, task_pid_nr(current));
404 return security_syslog(type);
408 /* /dev/kmsg - userspace message inject/listen interface */
409 struct devkmsg_user {
417 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
418 unsigned long count, loff_t pos)
422 int level = default_message_loglevel;
423 int facility = 1; /* LOG_USER */
424 size_t len = iov_length(iv, count);
427 if (len > LOG_LINE_MAX)
429 buf = kmalloc(len+1, GFP_KERNEL);
434 for (i = 0; i < count; i++) {
435 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
439 line += iv[i].iov_len;
443 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
444 * the decimal value represents 32bit, the lower 3 bit are the log
445 * level, the rest are the log facility.
447 * If no prefix or no userspace facility is specified, we
448 * enforce LOG_USER, to be able to reliably distinguish
449 * kernel-generated messages from userspace-injected ones.
452 if (line[0] == '<') {
455 i = simple_strtoul(line+1, &endp, 10);
456 if (endp && endp[0] == '>') {
467 printk_emit(facility, level, NULL, 0, "%s", line);
473 static ssize_t devkmsg_read(struct file *file, char __user *buf,
474 size_t count, loff_t *ppos)
476 struct devkmsg_user *user = file->private_data;
477 struct printk_log *msg;
487 ret = mutex_lock_interruptible(&user->lock);
490 raw_spin_lock_irq(&logbuf_lock);
491 while (user->seq == log_next_seq) {
492 if (file->f_flags & O_NONBLOCK) {
494 raw_spin_unlock_irq(&logbuf_lock);
498 raw_spin_unlock_irq(&logbuf_lock);
499 ret = wait_event_interruptible(log_wait,
500 user->seq != log_next_seq);
503 raw_spin_lock_irq(&logbuf_lock);
506 if (user->seq < log_first_seq) {
507 /* our last seen message is gone, return error and reset */
508 user->idx = log_first_idx;
509 user->seq = log_first_seq;
511 raw_spin_unlock_irq(&logbuf_lock);
515 msg = log_from_idx(user->idx);
516 ts_usec = msg->ts_nsec;
517 do_div(ts_usec, 1000);
520 * If we couldn't merge continuation line fragments during the print,
521 * export the stored flags to allow an optional external merge of the
522 * records. Merging the records isn't always neccessarily correct, like
523 * when we hit a race during printing. In most cases though, it produces
524 * better readable output. 'c' in the record flags mark the first
525 * fragment of a line, '+' the following.
527 if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
529 else if ((msg->flags & LOG_CONT) ||
530 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
533 len = sprintf(user->buf, "%u,%llu,%llu,%c;",
534 (msg->facility << 3) | msg->level,
535 user->seq, ts_usec, cont);
536 user->prev = msg->flags;
538 /* escape non-printable characters */
539 for (i = 0; i < msg->text_len; i++) {
540 unsigned char c = log_text(msg)[i];
542 if (c < ' ' || c >= 127 || c == '\\')
543 len += sprintf(user->buf + len, "\\x%02x", c);
545 user->buf[len++] = c;
547 user->buf[len++] = '\n';
552 for (i = 0; i < msg->dict_len; i++) {
553 unsigned char c = log_dict(msg)[i];
556 user->buf[len++] = ' ';
561 user->buf[len++] = '\n';
566 if (c < ' ' || c >= 127 || c == '\\') {
567 len += sprintf(user->buf + len, "\\x%02x", c);
571 user->buf[len++] = c;
573 user->buf[len++] = '\n';
576 user->idx = log_next(user->idx);
578 raw_spin_unlock_irq(&logbuf_lock);
585 if (copy_to_user(buf, user->buf, len)) {
591 mutex_unlock(&user->lock);
595 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
597 struct devkmsg_user *user = file->private_data;
605 raw_spin_lock_irq(&logbuf_lock);
608 /* the first record */
609 user->idx = log_first_idx;
610 user->seq = log_first_seq;
614 * The first record after the last SYSLOG_ACTION_CLEAR,
615 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
616 * changes no global state, and does not clear anything.
618 user->idx = clear_idx;
619 user->seq = clear_seq;
622 /* after the last record */
623 user->idx = log_next_idx;
624 user->seq = log_next_seq;
629 raw_spin_unlock_irq(&logbuf_lock);
633 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
635 struct devkmsg_user *user = file->private_data;
639 return POLLERR|POLLNVAL;
641 poll_wait(file, &log_wait, wait);
643 raw_spin_lock_irq(&logbuf_lock);
644 if (user->seq < log_next_seq) {
645 /* return error when data has vanished underneath us */
646 if (user->seq < log_first_seq)
647 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
649 ret = POLLIN|POLLRDNORM;
651 raw_spin_unlock_irq(&logbuf_lock);
656 static int devkmsg_open(struct inode *inode, struct file *file)
658 struct devkmsg_user *user;
661 /* write-only does not need any file context */
662 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
665 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
670 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
674 mutex_init(&user->lock);
676 raw_spin_lock_irq(&logbuf_lock);
677 user->idx = log_first_idx;
678 user->seq = log_first_seq;
679 raw_spin_unlock_irq(&logbuf_lock);
681 file->private_data = user;
685 static int devkmsg_release(struct inode *inode, struct file *file)
687 struct devkmsg_user *user = file->private_data;
692 mutex_destroy(&user->lock);
697 const struct file_operations kmsg_fops = {
698 .open = devkmsg_open,
699 .read = devkmsg_read,
700 .aio_write = devkmsg_writev,
701 .llseek = devkmsg_llseek,
702 .poll = devkmsg_poll,
703 .release = devkmsg_release,
708 * This appends the listed symbols to /proc/vmcoreinfo
710 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
711 * obtain access to symbols that are otherwise very difficult to locate. These
712 * symbols are specifically used so that utilities can access and extract the
713 * dmesg log from a vmcore file after a crash.
715 void log_buf_kexec_setup(void)
717 VMCOREINFO_SYMBOL(log_buf);
718 VMCOREINFO_SYMBOL(log_buf_len);
719 VMCOREINFO_SYMBOL(log_first_idx);
720 VMCOREINFO_SYMBOL(log_next_idx);
722 * Export struct printk_log size and field offsets. User space tools can
723 * parse it and detect any changes to structure down the line.
725 VMCOREINFO_STRUCT_SIZE(printk_log);
726 VMCOREINFO_OFFSET(printk_log, ts_nsec);
727 VMCOREINFO_OFFSET(printk_log, len);
728 VMCOREINFO_OFFSET(printk_log, text_len);
729 VMCOREINFO_OFFSET(printk_log, dict_len);
733 /* requested log_buf_len from kernel cmdline */
734 static unsigned long __initdata new_log_buf_len;
736 /* save requested log_buf_len since it's too early to process it */
737 static int __init log_buf_len_setup(char *str)
739 unsigned size = memparse(str, &str);
742 size = roundup_pow_of_two(size);
743 if (size > log_buf_len)
744 new_log_buf_len = size;
748 early_param("log_buf_len", log_buf_len_setup);
750 void __init setup_log_buf(int early)
756 if (!new_log_buf_len)
762 mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
765 new_log_buf = __va(mem);
767 new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
770 if (unlikely(!new_log_buf)) {
771 pr_err("log_buf_len: %ld bytes not available\n",
776 raw_spin_lock_irqsave(&logbuf_lock, flags);
777 log_buf_len = new_log_buf_len;
778 log_buf = new_log_buf;
780 free = __LOG_BUF_LEN - log_next_idx;
781 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
782 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
784 pr_info("log_buf_len: %d\n", log_buf_len);
785 pr_info("early log buf free: %d(%d%%)\n",
786 free, (free * 100) / __LOG_BUF_LEN);
789 static bool __read_mostly ignore_loglevel;
791 static int __init ignore_loglevel_setup(char *str)
794 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
799 early_param("ignore_loglevel", ignore_loglevel_setup);
800 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
801 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
802 "print all kernel messages to the console.");
804 #ifdef CONFIG_BOOT_PRINTK_DELAY
806 static int boot_delay; /* msecs delay after each printk during bootup */
807 static unsigned long long loops_per_msec; /* based on boot_delay */
809 static int __init boot_delay_setup(char *str)
813 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
814 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
816 get_option(&str, &boot_delay);
817 if (boot_delay > 10 * 1000)
820 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
821 "HZ: %d, loops_per_msec: %llu\n",
822 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
825 __setup("boot_delay=", boot_delay_setup);
827 static void boot_delay_msec(int level)
829 unsigned long long k;
830 unsigned long timeout;
832 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
833 || (level >= console_loglevel && !ignore_loglevel)) {
837 k = (unsigned long long)loops_per_msec * boot_delay;
839 timeout = jiffies + msecs_to_jiffies(boot_delay);
844 * use (volatile) jiffies to prevent
845 * compiler reduction; loop termination via jiffies
846 * is secondary and may or may not happen.
848 if (time_after(jiffies, timeout))
850 touch_nmi_watchdog();
854 static inline void boot_delay_msec(int level)
859 #if defined(CONFIG_PRINTK_TIME)
860 static bool printk_time = 1;
862 static bool printk_time;
864 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
866 static size_t print_time(u64 ts, char *buf)
868 unsigned long rem_nsec;
873 rem_nsec = do_div(ts, 1000000000);
876 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
878 return sprintf(buf, "[%5lu.%06lu] ",
879 (unsigned long)ts, rem_nsec / 1000);
882 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
885 unsigned int prefix = (msg->facility << 3) | msg->level;
889 len += sprintf(buf, "<%u>", prefix);
894 else if (prefix > 99)
901 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
905 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
906 bool syslog, char *buf, size_t size)
908 const char *text = log_text(msg);
909 size_t text_size = msg->text_len;
914 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
917 if (msg->flags & LOG_CONT) {
918 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
921 if (!(msg->flags & LOG_NEWLINE))
926 const char *next = memchr(text, '\n', text_size);
930 text_len = next - text;
932 text_size -= next - text;
934 text_len = text_size;
938 if (print_prefix(msg, syslog, NULL) +
939 text_len + 1 >= size - len)
943 len += print_prefix(msg, syslog, buf + len);
944 memcpy(buf + len, text, text_len);
949 /* SYSLOG_ACTION_* buffer size only calculation */
951 len += print_prefix(msg, syslog, NULL);
964 static int syslog_print(char __user *buf, int size)
967 struct printk_log *msg;
970 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
978 raw_spin_lock_irq(&logbuf_lock);
979 if (syslog_seq < log_first_seq) {
980 /* messages are gone, move to first one */
981 syslog_seq = log_first_seq;
982 syslog_idx = log_first_idx;
986 if (syslog_seq == log_next_seq) {
987 raw_spin_unlock_irq(&logbuf_lock);
991 skip = syslog_partial;
992 msg = log_from_idx(syslog_idx);
993 n = msg_print_text(msg, syslog_prev, true, text,
994 LOG_LINE_MAX + PREFIX_MAX);
995 if (n - syslog_partial <= size) {
996 /* message fits into buffer, move forward */
997 syslog_idx = log_next(syslog_idx);
999 syslog_prev = msg->flags;
1000 n -= syslog_partial;
1003 /* partial read(), remember position */
1005 syslog_partial += n;
1008 raw_spin_unlock_irq(&logbuf_lock);
1013 if (copy_to_user(buf, text + skip, n)) {
1028 static int syslog_print_all(char __user *buf, int size, bool clear)
1033 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1037 raw_spin_lock_irq(&logbuf_lock);
1042 enum log_flags prev;
1044 if (clear_seq < log_first_seq) {
1045 /* messages are gone, move to first available one */
1046 clear_seq = log_first_seq;
1047 clear_idx = log_first_idx;
1051 * Find first record that fits, including all following records,
1052 * into the user-provided buffer for this dump.
1057 while (seq < log_next_seq) {
1058 struct printk_log *msg = log_from_idx(idx);
1060 len += msg_print_text(msg, prev, true, NULL, 0);
1062 idx = log_next(idx);
1066 /* move first record forward until length fits into the buffer */
1070 while (len > size && seq < log_next_seq) {
1071 struct printk_log *msg = log_from_idx(idx);
1073 len -= msg_print_text(msg, prev, true, NULL, 0);
1075 idx = log_next(idx);
1079 /* last message fitting into this dump */
1080 next_seq = log_next_seq;
1084 while (len >= 0 && seq < next_seq) {
1085 struct printk_log *msg = log_from_idx(idx);
1088 textlen = msg_print_text(msg, prev, true, text,
1089 LOG_LINE_MAX + PREFIX_MAX);
1094 idx = log_next(idx);
1098 raw_spin_unlock_irq(&logbuf_lock);
1099 if (copy_to_user(buf + len, text, textlen))
1103 raw_spin_lock_irq(&logbuf_lock);
1105 if (seq < log_first_seq) {
1106 /* messages are gone, move to next one */
1107 seq = log_first_seq;
1108 idx = log_first_idx;
1115 clear_seq = log_next_seq;
1116 clear_idx = log_next_idx;
1118 raw_spin_unlock_irq(&logbuf_lock);
1124 int do_syslog(int type, char __user *buf, int len, bool from_file)
1127 static int saved_console_loglevel = -1;
1130 error = check_syslog_permissions(type, from_file);
1134 error = security_syslog(type);
1139 case SYSLOG_ACTION_CLOSE: /* Close log */
1141 case SYSLOG_ACTION_OPEN: /* Open log */
1143 case SYSLOG_ACTION_READ: /* Read from log */
1145 if (!buf || len < 0)
1150 if (!access_ok(VERIFY_WRITE, buf, len)) {
1154 error = wait_event_interruptible(log_wait,
1155 syslog_seq != log_next_seq);
1158 error = syslog_print(buf, len);
1160 /* Read/clear last kernel messages */
1161 case SYSLOG_ACTION_READ_CLEAR:
1164 /* Read last kernel messages */
1165 case SYSLOG_ACTION_READ_ALL:
1167 if (!buf || len < 0)
1172 if (!access_ok(VERIFY_WRITE, buf, len)) {
1176 error = syslog_print_all(buf, len, clear);
1178 /* Clear ring buffer */
1179 case SYSLOG_ACTION_CLEAR:
1180 syslog_print_all(NULL, 0, true);
1182 /* Disable logging to console */
1183 case SYSLOG_ACTION_CONSOLE_OFF:
1184 if (saved_console_loglevel == -1)
1185 saved_console_loglevel = console_loglevel;
1186 console_loglevel = minimum_console_loglevel;
1188 /* Enable logging to console */
1189 case SYSLOG_ACTION_CONSOLE_ON:
1190 if (saved_console_loglevel != -1) {
1191 console_loglevel = saved_console_loglevel;
1192 saved_console_loglevel = -1;
1195 /* Set level of messages printed to console */
1196 case SYSLOG_ACTION_CONSOLE_LEVEL:
1198 if (len < 1 || len > 8)
1200 if (len < minimum_console_loglevel)
1201 len = minimum_console_loglevel;
1202 console_loglevel = len;
1203 /* Implicitly re-enable logging to console */
1204 saved_console_loglevel = -1;
1207 /* Number of chars in the log buffer */
1208 case SYSLOG_ACTION_SIZE_UNREAD:
1209 raw_spin_lock_irq(&logbuf_lock);
1210 if (syslog_seq < log_first_seq) {
1211 /* messages are gone, move to first one */
1212 syslog_seq = log_first_seq;
1213 syslog_idx = log_first_idx;
1219 * Short-cut for poll(/"proc/kmsg") which simply checks
1220 * for pending data, not the size; return the count of
1221 * records, not the length.
1223 error = log_next_idx - syslog_idx;
1225 u64 seq = syslog_seq;
1226 u32 idx = syslog_idx;
1227 enum log_flags prev = syslog_prev;
1230 while (seq < log_next_seq) {
1231 struct printk_log *msg = log_from_idx(idx);
1233 error += msg_print_text(msg, prev, true, NULL, 0);
1234 idx = log_next(idx);
1238 error -= syslog_partial;
1240 raw_spin_unlock_irq(&logbuf_lock);
1242 /* Size of the log buffer */
1243 case SYSLOG_ACTION_SIZE_BUFFER:
1244 error = log_buf_len;
1254 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1256 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1260 * Call the console drivers, asking them to write out
1261 * log_buf[start] to log_buf[end - 1].
1262 * The console_lock must be held.
1264 static void call_console_drivers(int level, const char *text, size_t len)
1266 struct console *con;
1268 trace_console(text, len);
1270 if (!console_drivers)
1273 for_each_console(con) {
1274 if (exclusive_console && con != exclusive_console)
1276 if (!(con->flags & CON_ENABLED))
1280 if (!cpu_online(smp_processor_id()) &&
1281 !(con->flags & CON_ANYTIME))
1283 if (level >= console_loglevel && !ignore_loglevel &&
1284 !(con->flags & CON_ALLDATA))
1286 con->write(con, text, len);
1291 * Zap console related locks when oopsing. Only zap at most once
1292 * every 10 seconds, to leave time for slow consoles to print a
1295 static void zap_locks(void)
1297 static unsigned long oops_timestamp;
1299 if (time_after_eq(jiffies, oops_timestamp) &&
1300 !time_after(jiffies, oops_timestamp + 30 * HZ))
1303 oops_timestamp = jiffies;
1306 /* If a crash is occurring, make sure we can't deadlock */
1307 raw_spin_lock_init(&logbuf_lock);
1308 /* And make sure that we print immediately */
1309 sema_init(&console_sem, 1);
1312 /* Check if we have any console registered that can be called early in boot. */
1313 static int have_callable_console(void)
1315 struct console *con;
1317 for_each_console(con)
1318 if (con->flags & CON_ANYTIME)
1325 * Can we actually use the console at this time on this cpu?
1327 * Console drivers may assume that per-cpu resources have
1328 * been allocated. So unless they're explicitly marked as
1329 * being able to cope (CON_ANYTIME) don't call them until
1330 * this CPU is officially up.
1332 static inline int can_use_console(unsigned int cpu)
1334 return cpu_online(cpu) || have_callable_console();
1338 * Try to get console ownership to actually show the kernel
1339 * messages from a 'printk'. Return true (and with the
1340 * console_lock held, and 'console_locked' set) if it
1341 * is successful, false otherwise.
1343 * This gets called with the 'logbuf_lock' spinlock held and
1344 * interrupts disabled. It should return with 'lockbuf_lock'
1345 * released but interrupts still disabled.
1347 static int console_trylock_for_printk(unsigned int cpu)
1348 __releases(&logbuf_lock)
1350 int retval = 0, wake = 0;
1352 if (console_trylock()) {
1356 * If we can't use the console, we need to release
1357 * the console semaphore by hand to avoid flushing
1358 * the buffer. We need to hold the console semaphore
1359 * in order to do this test safely.
1361 if (!can_use_console(cpu)) {
1367 logbuf_cpu = UINT_MAX;
1368 raw_spin_unlock(&logbuf_lock);
1374 int printk_delay_msec __read_mostly;
1376 static inline void printk_delay(void)
1378 if (unlikely(printk_delay_msec)) {
1379 int m = printk_delay_msec;
1383 touch_nmi_watchdog();
1389 * Continuation lines are buffered, and not committed to the record buffer
1390 * until the line is complete, or a race forces it. The line fragments
1391 * though, are printed immediately to the consoles to ensure everything has
1392 * reached the console in case of a kernel crash.
1394 static struct cont {
1395 char buf[LOG_LINE_MAX];
1396 size_t len; /* length == 0 means unused buffer */
1397 size_t cons; /* bytes written to console */
1398 struct task_struct *owner; /* task of first print*/
1399 u64 ts_nsec; /* time of first print */
1400 u8 level; /* log level of first message */
1401 u8 facility; /* log level of first message */
1402 enum log_flags flags; /* prefix, newline flags */
1403 bool flushed:1; /* buffer sealed and committed */
1406 static void cont_flush(enum log_flags flags)
1415 * If a fragment of this line was directly flushed to the
1416 * console; wait for the console to pick up the rest of the
1417 * line. LOG_NOCONS suppresses a duplicated output.
1419 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1420 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1422 cont.flushed = true;
1425 * If no fragment of this line ever reached the console,
1426 * just submit it to the store and free the buffer.
1428 log_store(cont.facility, cont.level, flags, 0,
1429 NULL, 0, cont.buf, cont.len);
1434 static bool cont_add(int facility, int level, const char *text, size_t len)
1436 if (cont.len && cont.flushed)
1439 if (cont.len + len > sizeof(cont.buf)) {
1440 /* the line gets too long, split it up in separate records */
1441 cont_flush(LOG_CONT);
1446 cont.facility = facility;
1448 cont.owner = current;
1449 cont.ts_nsec = local_clock();
1452 cont.flushed = false;
1455 memcpy(cont.buf + cont.len, text, len);
1458 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1459 cont_flush(LOG_CONT);
1464 static size_t cont_print_text(char *text, size_t size)
1469 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1470 textlen += print_time(cont.ts_nsec, text);
1474 len = cont.len - cont.cons;
1478 memcpy(text + textlen, cont.buf + cont.cons, len);
1480 cont.cons = cont.len;
1484 if (cont.flags & LOG_NEWLINE)
1485 text[textlen++] = '\n';
1486 /* got everything, release buffer */
1492 asmlinkage int vprintk_emit(int facility, int level,
1493 const char *dict, size_t dictlen,
1494 const char *fmt, va_list args)
1496 static int recursion_bug;
1497 static char textbuf[LOG_LINE_MAX];
1498 char *text = textbuf;
1500 enum log_flags lflags = 0;
1501 unsigned long flags;
1503 int printed_len = 0;
1505 boot_delay_msec(level);
1508 /* This stops the holder of console_sem just where we want him */
1509 local_irq_save(flags);
1510 this_cpu = smp_processor_id();
1513 * Ouch, printk recursed into itself!
1515 if (unlikely(logbuf_cpu == this_cpu)) {
1517 * If a crash is occurring during printk() on this CPU,
1518 * then try to get the crash message out but make sure
1519 * we can't deadlock. Otherwise just return to avoid the
1520 * recursion and return - but flag the recursion so that
1521 * it can be printed at the next appropriate moment:
1523 if (!oops_in_progress && !lockdep_recursing(current)) {
1525 goto out_restore_irqs;
1531 raw_spin_lock(&logbuf_lock);
1532 logbuf_cpu = this_cpu;
1534 if (recursion_bug) {
1535 static const char recursion_msg[] =
1536 "BUG: recent printk recursion!";
1539 printed_len += strlen(recursion_msg);
1540 /* emit KERN_CRIT message */
1541 log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1542 NULL, 0, recursion_msg, printed_len);
1546 * The printf needs to come first; we need the syslog
1547 * prefix which might be passed-in as a parameter.
1549 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1551 /* mark and strip a trailing newline */
1552 if (text_len && text[text_len-1] == '\n') {
1554 lflags |= LOG_NEWLINE;
1557 /* strip kernel syslog prefix and extract log level or control flags */
1558 if (facility == 0) {
1559 int kern_level = printk_get_level(text);
1562 const char *end_of_header = printk_skip_level(text);
1563 switch (kern_level) {
1566 level = kern_level - '0';
1567 case 'd': /* KERN_DEFAULT */
1568 lflags |= LOG_PREFIX;
1569 case 'c': /* KERN_CONT */
1572 text_len -= end_of_header - text;
1573 text = (char *)end_of_header;
1578 level = default_message_loglevel;
1581 lflags |= LOG_PREFIX|LOG_NEWLINE;
1583 if (!(lflags & LOG_NEWLINE)) {
1585 * Flush the conflicting buffer. An earlier newline was missing,
1586 * or another task also prints continuation lines.
1588 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1589 cont_flush(LOG_NEWLINE);
1591 /* buffer line if possible, otherwise store it right away */
1592 if (!cont_add(facility, level, text, text_len))
1593 log_store(facility, level, lflags | LOG_CONT, 0,
1594 dict, dictlen, text, text_len);
1596 bool stored = false;
1599 * If an earlier newline was missing and it was the same task,
1600 * either merge it with the current buffer and flush, or if
1601 * there was a race with interrupts (prefix == true) then just
1602 * flush it out and store this line separately.
1604 if (cont.len && cont.owner == current) {
1605 if (!(lflags & LOG_PREFIX))
1606 stored = cont_add(facility, level, text, text_len);
1607 cont_flush(LOG_NEWLINE);
1611 log_store(facility, level, lflags, 0,
1612 dict, dictlen, text, text_len);
1614 printed_len += text_len;
1617 * Try to acquire and then immediately release the console semaphore.
1618 * The release will print out buffers and wake up /dev/kmsg and syslog()
1621 * The console_trylock_for_printk() function will release 'logbuf_lock'
1622 * regardless of whether it actually gets the console semaphore or not.
1624 if (console_trylock_for_printk(this_cpu))
1629 local_irq_restore(flags);
1633 EXPORT_SYMBOL(vprintk_emit);
1635 asmlinkage int vprintk(const char *fmt, va_list args)
1637 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1639 EXPORT_SYMBOL(vprintk);
1641 asmlinkage int printk_emit(int facility, int level,
1642 const char *dict, size_t dictlen,
1643 const char *fmt, ...)
1648 va_start(args, fmt);
1649 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1654 EXPORT_SYMBOL(printk_emit);
1657 * printk - print a kernel message
1658 * @fmt: format string
1660 * This is printk(). It can be called from any context. We want it to work.
1662 * We try to grab the console_lock. If we succeed, it's easy - we log the
1663 * output and call the console drivers. If we fail to get the semaphore, we
1664 * place the output into the log buffer and return. The current holder of
1665 * the console_sem will notice the new output in console_unlock(); and will
1666 * send it to the consoles before releasing the lock.
1668 * One effect of this deferred printing is that code which calls printk() and
1669 * then changes console_loglevel may break. This is because console_loglevel
1670 * is inspected when the actual printing occurs.
1675 * See the vsnprintf() documentation for format string extensions over C99.
1677 asmlinkage int printk(const char *fmt, ...)
1682 #ifdef CONFIG_KGDB_KDB
1683 if (unlikely(kdb_trap_printk)) {
1684 va_start(args, fmt);
1685 r = vkdb_printf(fmt, args);
1690 va_start(args, fmt);
1691 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1696 EXPORT_SYMBOL(printk);
1698 #else /* CONFIG_PRINTK */
1700 #define LOG_LINE_MAX 0
1701 #define PREFIX_MAX 0
1702 #define LOG_LINE_MAX 0
1703 static u64 syslog_seq;
1704 static u32 syslog_idx;
1705 static u64 console_seq;
1706 static u32 console_idx;
1707 static enum log_flags syslog_prev;
1708 static u64 log_first_seq;
1709 static u32 log_first_idx;
1710 static u64 log_next_seq;
1711 static enum log_flags console_prev;
1712 static struct cont {
1718 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1719 static u32 log_next(u32 idx) { return 0; }
1720 static void call_console_drivers(int level, const char *text, size_t len) {}
1721 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1722 bool syslog, char *buf, size_t size) { return 0; }
1723 static size_t cont_print_text(char *text, size_t size) { return 0; }
1725 #endif /* CONFIG_PRINTK */
1727 #ifdef CONFIG_EARLY_PRINTK
1728 struct console *early_console;
1730 void early_vprintk(const char *fmt, va_list ap)
1732 if (early_console) {
1734 int n = vscnprintf(buf, sizeof(buf), fmt, ap);
1736 early_console->write(early_console, buf, n);
1740 asmlinkage void early_printk(const char *fmt, ...)
1745 early_vprintk(fmt, ap);
1750 static int __add_preferred_console(char *name, int idx, char *options,
1753 struct console_cmdline *c;
1757 * See if this tty is not yet registered, and
1758 * if we have a slot free.
1760 for (i = 0, c = console_cmdline;
1761 i < MAX_CMDLINECONSOLES && c->name[0];
1763 if (strcmp(c->name, name) == 0 && c->index == idx) {
1765 selected_console = i;
1769 if (i == MAX_CMDLINECONSOLES)
1772 selected_console = i;
1773 strlcpy(c->name, name, sizeof(c->name));
1774 c->options = options;
1775 braille_set_options(c, brl_options);
1781 * Set up a list of consoles. Called from init/main.c
1783 static int __init console_setup(char *str)
1785 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1786 char *s, *options, *brl_options = NULL;
1789 if (_braille_console_setup(&str, &brl_options))
1793 * Decode str into name, index, options.
1795 if (str[0] >= '0' && str[0] <= '9') {
1796 strcpy(buf, "ttyS");
1797 strncpy(buf + 4, str, sizeof(buf) - 5);
1799 strncpy(buf, str, sizeof(buf) - 1);
1801 buf[sizeof(buf) - 1] = 0;
1802 if ((options = strchr(str, ',')) != NULL)
1805 if (!strcmp(str, "ttya"))
1806 strcpy(buf, "ttyS0");
1807 if (!strcmp(str, "ttyb"))
1808 strcpy(buf, "ttyS1");
1810 for (s = buf; *s; s++)
1811 if ((*s >= '0' && *s <= '9') || *s == ',')
1813 idx = simple_strtoul(s, NULL, 10);
1816 __add_preferred_console(buf, idx, options, brl_options);
1817 console_set_on_cmdline = 1;
1820 __setup("console=", console_setup);
1823 * add_preferred_console - add a device to the list of preferred consoles.
1824 * @name: device name
1825 * @idx: device index
1826 * @options: options for this console
1828 * The last preferred console added will be used for kernel messages
1829 * and stdin/out/err for init. Normally this is used by console_setup
1830 * above to handle user-supplied console arguments; however it can also
1831 * be used by arch-specific code either to override the user or more
1832 * commonly to provide a default console (ie from PROM variables) when
1833 * the user has not supplied one.
1835 int add_preferred_console(char *name, int idx, char *options)
1837 return __add_preferred_console(name, idx, options, NULL);
1840 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1842 struct console_cmdline *c;
1845 for (i = 0, c = console_cmdline;
1846 i < MAX_CMDLINECONSOLES && c->name[0];
1848 if (strcmp(c->name, name) == 0 && c->index == idx) {
1849 strlcpy(c->name, name_new, sizeof(c->name));
1850 c->name[sizeof(c->name) - 1] = 0;
1851 c->options = options;
1859 bool console_suspend_enabled = 1;
1860 EXPORT_SYMBOL(console_suspend_enabled);
1862 static int __init console_suspend_disable(char *str)
1864 console_suspend_enabled = 0;
1867 __setup("no_console_suspend", console_suspend_disable);
1868 module_param_named(console_suspend, console_suspend_enabled,
1869 bool, S_IRUGO | S_IWUSR);
1870 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1871 " and hibernate operations");
1874 * suspend_console - suspend the console subsystem
1876 * This disables printk() while we go into suspend states
1878 void suspend_console(void)
1880 if (!console_suspend_enabled)
1882 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1884 console_suspended = 1;
1888 void resume_console(void)
1890 if (!console_suspend_enabled)
1893 console_suspended = 0;
1898 * console_cpu_notify - print deferred console messages after CPU hotplug
1899 * @self: notifier struct
1900 * @action: CPU hotplug event
1903 * If printk() is called from a CPU that is not online yet, the messages
1904 * will be spooled but will not show up on the console. This function is
1905 * called when a new CPU comes online (or fails to come up), and ensures
1906 * that any such output gets printed.
1908 static int console_cpu_notify(struct notifier_block *self,
1909 unsigned long action, void *hcpu)
1914 case CPU_DOWN_FAILED:
1915 case CPU_UP_CANCELED:
1923 * console_lock - lock the console system for exclusive use.
1925 * Acquires a lock which guarantees that the caller has
1926 * exclusive access to the console system and the console_drivers list.
1928 * Can sleep, returns nothing.
1930 void console_lock(void)
1935 if (console_suspended)
1938 console_may_schedule = 1;
1939 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
1941 EXPORT_SYMBOL(console_lock);
1944 * console_trylock - try to lock the console system for exclusive use.
1946 * Tried to acquire a lock which guarantees that the caller has
1947 * exclusive access to the console system and the console_drivers list.
1949 * returns 1 on success, and 0 on failure to acquire the lock.
1951 int console_trylock(void)
1953 if (down_trylock(&console_sem))
1955 if (console_suspended) {
1960 console_may_schedule = 0;
1961 mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);
1964 EXPORT_SYMBOL(console_trylock);
1966 int is_console_locked(void)
1968 return console_locked;
1971 static void console_cont_flush(char *text, size_t size)
1973 unsigned long flags;
1976 raw_spin_lock_irqsave(&logbuf_lock, flags);
1982 * We still queue earlier records, likely because the console was
1983 * busy. The earlier ones need to be printed before this one, we
1984 * did not flush any fragment so far, so just let it queue up.
1986 if (console_seq < log_next_seq && !cont.cons)
1989 len = cont_print_text(text, size);
1990 raw_spin_unlock(&logbuf_lock);
1991 stop_critical_timings();
1992 call_console_drivers(cont.level, text, len);
1993 start_critical_timings();
1994 local_irq_restore(flags);
1997 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2001 * console_unlock - unlock the console system
2003 * Releases the console_lock which the caller holds on the console system
2004 * and the console driver list.
2006 * While the console_lock was held, console output may have been buffered
2007 * by printk(). If this is the case, console_unlock(); emits
2008 * the output prior to releasing the lock.
2010 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2012 * console_unlock(); may be called from any context.
2014 void console_unlock(void)
2016 static char text[LOG_LINE_MAX + PREFIX_MAX];
2017 static u64 seen_seq;
2018 unsigned long flags;
2019 bool wake_klogd = false;
2022 if (console_suspended) {
2027 console_may_schedule = 0;
2029 /* flush buffered message fragment immediately to console */
2030 console_cont_flush(text, sizeof(text));
2033 struct printk_log *msg;
2037 raw_spin_lock_irqsave(&logbuf_lock, flags);
2038 if (seen_seq != log_next_seq) {
2040 seen_seq = log_next_seq;
2043 if (console_seq < log_first_seq) {
2044 /* messages are gone, move to first one */
2045 console_seq = log_first_seq;
2046 console_idx = log_first_idx;
2050 if (console_seq == log_next_seq)
2053 msg = log_from_idx(console_idx);
2054 if (msg->flags & LOG_NOCONS) {
2056 * Skip record we have buffered and already printed
2057 * directly to the console when we received it.
2059 console_idx = log_next(console_idx);
2062 * We will get here again when we register a new
2063 * CON_PRINTBUFFER console. Clear the flag so we
2064 * will properly dump everything later.
2066 msg->flags &= ~LOG_NOCONS;
2067 console_prev = msg->flags;
2072 len = msg_print_text(msg, console_prev, false,
2073 text, sizeof(text));
2074 console_idx = log_next(console_idx);
2076 console_prev = msg->flags;
2077 raw_spin_unlock(&logbuf_lock);
2079 stop_critical_timings(); /* don't trace print latency */
2080 call_console_drivers(level, text, len);
2081 start_critical_timings();
2082 local_irq_restore(flags);
2085 mutex_release(&console_lock_dep_map, 1, _RET_IP_);
2087 /* Release the exclusive_console once it is used */
2088 if (unlikely(exclusive_console))
2089 exclusive_console = NULL;
2091 raw_spin_unlock(&logbuf_lock);
2096 * Someone could have filled up the buffer again, so re-check if there's
2097 * something to flush. In case we cannot trylock the console_sem again,
2098 * there's a new owner and the console_unlock() from them will do the
2099 * flush, no worries.
2101 raw_spin_lock(&logbuf_lock);
2102 retry = console_seq != log_next_seq;
2103 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2105 if (retry && console_trylock())
2111 EXPORT_SYMBOL(console_unlock);
2114 * console_conditional_schedule - yield the CPU if required
2116 * If the console code is currently allowed to sleep, and
2117 * if this CPU should yield the CPU to another task, do
2120 * Must be called within console_lock();.
2122 void __sched console_conditional_schedule(void)
2124 if (console_may_schedule)
2127 EXPORT_SYMBOL(console_conditional_schedule);
2129 void console_unblank(void)
2134 * console_unblank can no longer be called in interrupt context unless
2135 * oops_in_progress is set to 1..
2137 if (oops_in_progress) {
2138 if (down_trylock(&console_sem) != 0)
2144 console_may_schedule = 0;
2146 if ((c->flags & CON_ENABLED) && c->unblank)
2152 * Return the console tty driver structure and its associated index
2154 struct tty_driver *console_device(int *index)
2157 struct tty_driver *driver = NULL;
2160 for_each_console(c) {
2163 driver = c->device(c, index);
2172 * Prevent further output on the passed console device so that (for example)
2173 * serial drivers can disable console output before suspending a port, and can
2174 * re-enable output afterwards.
2176 void console_stop(struct console *console)
2179 console->flags &= ~CON_ENABLED;
2182 EXPORT_SYMBOL(console_stop);
2184 void console_start(struct console *console)
2187 console->flags |= CON_ENABLED;
2190 EXPORT_SYMBOL(console_start);
2192 static int __read_mostly keep_bootcon;
2194 static int __init keep_bootcon_setup(char *str)
2197 printk(KERN_INFO "debug: skip boot console de-registration.\n");
2202 early_param("keep_bootcon", keep_bootcon_setup);
2205 * The console driver calls this routine during kernel initialization
2206 * to register the console printing procedure with printk() and to
2207 * print any messages that were printed by the kernel before the
2208 * console driver was initialized.
2210 * This can happen pretty early during the boot process (because of
2211 * early_printk) - sometimes before setup_arch() completes - be careful
2212 * of what kernel features are used - they may not be initialised yet.
2214 * There are two types of consoles - bootconsoles (early_printk) and
2215 * "real" consoles (everything which is not a bootconsole) which are
2216 * handled differently.
2217 * - Any number of bootconsoles can be registered at any time.
2218 * - As soon as a "real" console is registered, all bootconsoles
2219 * will be unregistered automatically.
2220 * - Once a "real" console is registered, any attempt to register a
2221 * bootconsoles will be rejected
2223 void register_console(struct console *newcon)
2226 unsigned long flags;
2227 struct console *bcon = NULL;
2228 struct console_cmdline *c;
2231 * before we register a new CON_BOOT console, make sure we don't
2232 * already have a valid console
2234 if (console_drivers && newcon->flags & CON_BOOT) {
2235 /* find the last or real console */
2236 for_each_console(bcon) {
2237 if (!(bcon->flags & CON_BOOT)) {
2238 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
2239 newcon->name, newcon->index);
2245 if (console_drivers && console_drivers->flags & CON_BOOT)
2246 bcon = console_drivers;
2248 if (preferred_console < 0 || bcon || !console_drivers)
2249 preferred_console = selected_console;
2251 if (newcon->early_setup)
2252 newcon->early_setup();
2255 * See if we want to use this console driver. If we
2256 * didn't select a console we take the first one
2257 * that registers here.
2259 if (preferred_console < 0) {
2260 if (newcon->index < 0)
2262 if (newcon->setup == NULL ||
2263 newcon->setup(newcon, NULL) == 0) {
2264 newcon->flags |= CON_ENABLED;
2265 if (newcon->device) {
2266 newcon->flags |= CON_CONSDEV;
2267 preferred_console = 0;
2273 * See if this console matches one we selected on
2276 for (i = 0, c = console_cmdline;
2277 i < MAX_CMDLINECONSOLES && c->name[0];
2279 if (strcmp(c->name, newcon->name) != 0)
2281 if (newcon->index >= 0 &&
2282 newcon->index != c->index)
2284 if (newcon->index < 0)
2285 newcon->index = c->index;
2287 if (_braille_register_console(newcon, c))
2290 if (newcon->setup &&
2291 newcon->setup(newcon, console_cmdline[i].options) != 0)
2293 newcon->flags |= CON_ENABLED;
2294 newcon->index = c->index;
2295 if (i == selected_console) {
2296 newcon->flags |= CON_CONSDEV;
2297 preferred_console = selected_console;
2302 if (!(newcon->flags & CON_ENABLED))
2306 * If we have a bootconsole, and are switching to a real console,
2307 * don't print everything out again, since when the boot console, and
2308 * the real console are the same physical device, it's annoying to
2309 * see the beginning boot messages twice
2311 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2312 newcon->flags &= ~CON_PRINTBUFFER;
2315 * Put this console in the list - keep the
2316 * preferred driver at the head of the list.
2319 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2320 newcon->next = console_drivers;
2321 console_drivers = newcon;
2323 newcon->next->flags &= ~CON_CONSDEV;
2325 newcon->next = console_drivers->next;
2326 console_drivers->next = newcon;
2328 if (newcon->flags & CON_PRINTBUFFER) {
2330 * console_unlock(); will print out the buffered messages
2333 raw_spin_lock_irqsave(&logbuf_lock, flags);
2334 console_seq = syslog_seq;
2335 console_idx = syslog_idx;
2336 console_prev = syslog_prev;
2337 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2339 * We're about to replay the log buffer. Only do this to the
2340 * just-registered console to avoid excessive message spam to
2341 * the already-registered consoles.
2343 exclusive_console = newcon;
2346 console_sysfs_notify();
2349 * By unregistering the bootconsoles after we enable the real console
2350 * we get the "console xxx enabled" message on all the consoles -
2351 * boot consoles, real consoles, etc - this is to ensure that end
2352 * users know there might be something in the kernel's log buffer that
2353 * went to the bootconsole (that they do not see on the real console)
2356 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2358 /* we need to iterate through twice, to make sure we print
2359 * everything out, before we unregister the console(s)
2361 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
2362 newcon->name, newcon->index);
2363 for_each_console(bcon)
2364 if (bcon->flags & CON_BOOT)
2365 unregister_console(bcon);
2367 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
2368 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2369 newcon->name, newcon->index);
2372 EXPORT_SYMBOL(register_console);
2374 int unregister_console(struct console *console)
2376 struct console *a, *b;
2379 res = _braille_unregister_console(console);
2385 if (console_drivers == console) {
2386 console_drivers=console->next;
2388 } else if (console_drivers) {
2389 for (a=console_drivers->next, b=console_drivers ;
2390 a; b=a, a=b->next) {
2400 * If this isn't the last console and it has CON_CONSDEV set, we
2401 * need to set it on the next preferred console.
2403 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2404 console_drivers->flags |= CON_CONSDEV;
2407 console_sysfs_notify();
2410 EXPORT_SYMBOL(unregister_console);
2412 static int __init printk_late_init(void)
2414 struct console *con;
2416 for_each_console(con) {
2417 if (!keep_bootcon && con->flags & CON_BOOT) {
2418 printk(KERN_INFO "turn off boot console %s%d\n",
2419 con->name, con->index);
2420 unregister_console(con);
2423 hotcpu_notifier(console_cpu_notify, 0);
2426 late_initcall(printk_late_init);
2428 #if defined CONFIG_PRINTK
2430 * Delayed printk version, for scheduler-internal messages:
2432 #define PRINTK_BUF_SIZE 512
2434 #define PRINTK_PENDING_WAKEUP 0x01
2435 #define PRINTK_PENDING_SCHED 0x02
2437 static DEFINE_PER_CPU(int, printk_pending);
2438 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
2440 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2442 int pending = __this_cpu_xchg(printk_pending, 0);
2444 if (pending & PRINTK_PENDING_SCHED) {
2445 char *buf = __get_cpu_var(printk_sched_buf);
2446 printk(KERN_WARNING "[sched_delayed] %s", buf);
2449 if (pending & PRINTK_PENDING_WAKEUP)
2450 wake_up_interruptible(&log_wait);
2453 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2454 .func = wake_up_klogd_work_func,
2455 .flags = IRQ_WORK_LAZY,
2458 void wake_up_klogd(void)
2461 if (waitqueue_active(&log_wait)) {
2462 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2463 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2468 int printk_sched(const char *fmt, ...)
2470 unsigned long flags;
2475 local_irq_save(flags);
2476 buf = __get_cpu_var(printk_sched_buf);
2478 va_start(args, fmt);
2479 r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2482 __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2483 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2484 local_irq_restore(flags);
2490 * printk rate limiting, lifted from the networking subsystem.
2492 * This enforces a rate limit: not more than 10 kernel messages
2493 * every 5s to make a denial-of-service attack impossible.
2495 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2497 int __printk_ratelimit(const char *func)
2499 return ___ratelimit(&printk_ratelimit_state, func);
2501 EXPORT_SYMBOL(__printk_ratelimit);
2504 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2505 * @caller_jiffies: pointer to caller's state
2506 * @interval_msecs: minimum interval between prints
2508 * printk_timed_ratelimit() returns true if more than @interval_msecs
2509 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2512 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2513 unsigned int interval_msecs)
2515 if (*caller_jiffies == 0
2516 || !time_in_range(jiffies, *caller_jiffies,
2518 + msecs_to_jiffies(interval_msecs))) {
2519 *caller_jiffies = jiffies;
2524 EXPORT_SYMBOL(printk_timed_ratelimit);
2526 static DEFINE_SPINLOCK(dump_list_lock);
2527 static LIST_HEAD(dump_list);
2530 * kmsg_dump_register - register a kernel log dumper.
2531 * @dumper: pointer to the kmsg_dumper structure
2533 * Adds a kernel log dumper to the system. The dump callback in the
2534 * structure will be called when the kernel oopses or panics and must be
2535 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2537 int kmsg_dump_register(struct kmsg_dumper *dumper)
2539 unsigned long flags;
2542 /* The dump callback needs to be set */
2546 spin_lock_irqsave(&dump_list_lock, flags);
2547 /* Don't allow registering multiple times */
2548 if (!dumper->registered) {
2549 dumper->registered = 1;
2550 list_add_tail_rcu(&dumper->list, &dump_list);
2553 spin_unlock_irqrestore(&dump_list_lock, flags);
2557 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2560 * kmsg_dump_unregister - unregister a kmsg dumper.
2561 * @dumper: pointer to the kmsg_dumper structure
2563 * Removes a dump device from the system. Returns zero on success and
2564 * %-EINVAL otherwise.
2566 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2568 unsigned long flags;
2571 spin_lock_irqsave(&dump_list_lock, flags);
2572 if (dumper->registered) {
2573 dumper->registered = 0;
2574 list_del_rcu(&dumper->list);
2577 spin_unlock_irqrestore(&dump_list_lock, flags);
2582 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2584 static bool always_kmsg_dump;
2585 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2588 * kmsg_dump - dump kernel log to kernel message dumpers.
2589 * @reason: the reason (oops, panic etc) for dumping
2591 * Call each of the registered dumper's dump() callback, which can
2592 * retrieve the kmsg records with kmsg_dump_get_line() or
2593 * kmsg_dump_get_buffer().
2595 void kmsg_dump(enum kmsg_dump_reason reason)
2597 struct kmsg_dumper *dumper;
2598 unsigned long flags;
2600 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2604 list_for_each_entry_rcu(dumper, &dump_list, list) {
2605 if (dumper->max_reason && reason > dumper->max_reason)
2608 /* initialize iterator with data about the stored records */
2609 dumper->active = true;
2611 raw_spin_lock_irqsave(&logbuf_lock, flags);
2612 dumper->cur_seq = clear_seq;
2613 dumper->cur_idx = clear_idx;
2614 dumper->next_seq = log_next_seq;
2615 dumper->next_idx = log_next_idx;
2616 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2618 /* invoke dumper which will iterate over records */
2619 dumper->dump(dumper, reason);
2621 /* reset iterator */
2622 dumper->active = false;
2628 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2629 * @dumper: registered kmsg dumper
2630 * @syslog: include the "<4>" prefixes
2631 * @line: buffer to copy the line to
2632 * @size: maximum size of the buffer
2633 * @len: length of line placed into buffer
2635 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2636 * record, and copy one record into the provided buffer.
2638 * Consecutive calls will return the next available record moving
2639 * towards the end of the buffer with the youngest messages.
2641 * A return value of FALSE indicates that there are no more records to
2644 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2646 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2647 char *line, size_t size, size_t *len)
2649 struct printk_log *msg;
2653 if (!dumper->active)
2656 if (dumper->cur_seq < log_first_seq) {
2657 /* messages are gone, move to first available one */
2658 dumper->cur_seq = log_first_seq;
2659 dumper->cur_idx = log_first_idx;
2663 if (dumper->cur_seq >= log_next_seq)
2666 msg = log_from_idx(dumper->cur_idx);
2667 l = msg_print_text(msg, 0, syslog, line, size);
2669 dumper->cur_idx = log_next(dumper->cur_idx);
2679 * kmsg_dump_get_line - retrieve one kmsg log line
2680 * @dumper: registered kmsg dumper
2681 * @syslog: include the "<4>" prefixes
2682 * @line: buffer to copy the line to
2683 * @size: maximum size of the buffer
2684 * @len: length of line placed into buffer
2686 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2687 * record, and copy one record into the provided buffer.
2689 * Consecutive calls will return the next available record moving
2690 * towards the end of the buffer with the youngest messages.
2692 * A return value of FALSE indicates that there are no more records to
2695 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2696 char *line, size_t size, size_t *len)
2698 unsigned long flags;
2701 raw_spin_lock_irqsave(&logbuf_lock, flags);
2702 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2703 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2707 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2710 * kmsg_dump_get_buffer - copy kmsg log lines
2711 * @dumper: registered kmsg dumper
2712 * @syslog: include the "<4>" prefixes
2713 * @buf: buffer to copy the line to
2714 * @size: maximum size of the buffer
2715 * @len: length of line placed into buffer
2717 * Start at the end of the kmsg buffer and fill the provided buffer
2718 * with as many of the the *youngest* kmsg records that fit into it.
2719 * If the buffer is large enough, all available kmsg records will be
2720 * copied with a single call.
2722 * Consecutive calls will fill the buffer with the next block of
2723 * available older records, not including the earlier retrieved ones.
2725 * A return value of FALSE indicates that there are no more records to
2728 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2729 char *buf, size_t size, size_t *len)
2731 unsigned long flags;
2736 enum log_flags prev;
2740 if (!dumper->active)
2743 raw_spin_lock_irqsave(&logbuf_lock, flags);
2744 if (dumper->cur_seq < log_first_seq) {
2745 /* messages are gone, move to first available one */
2746 dumper->cur_seq = log_first_seq;
2747 dumper->cur_idx = log_first_idx;
2751 if (dumper->cur_seq >= dumper->next_seq) {
2752 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2756 /* calculate length of entire buffer */
2757 seq = dumper->cur_seq;
2758 idx = dumper->cur_idx;
2760 while (seq < dumper->next_seq) {
2761 struct printk_log *msg = log_from_idx(idx);
2763 l += msg_print_text(msg, prev, true, NULL, 0);
2764 idx = log_next(idx);
2769 /* move first record forward until length fits into the buffer */
2770 seq = dumper->cur_seq;
2771 idx = dumper->cur_idx;
2773 while (l > size && seq < dumper->next_seq) {
2774 struct printk_log *msg = log_from_idx(idx);
2776 l -= msg_print_text(msg, prev, true, NULL, 0);
2777 idx = log_next(idx);
2782 /* last message in next interation */
2788 while (seq < dumper->next_seq) {
2789 struct printk_log *msg = log_from_idx(idx);
2791 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2792 idx = log_next(idx);
2797 dumper->next_seq = next_seq;
2798 dumper->next_idx = next_idx;
2800 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2806 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2809 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2810 * @dumper: registered kmsg dumper
2812 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2813 * kmsg_dump_get_buffer() can be called again and used multiple
2814 * times within the same dumper.dump() callback.
2816 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2818 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
2820 dumper->cur_seq = clear_seq;
2821 dumper->cur_idx = clear_idx;
2822 dumper->next_seq = log_next_seq;
2823 dumper->next_idx = log_next_idx;
2827 * kmsg_dump_rewind - reset the interator
2828 * @dumper: registered kmsg dumper
2830 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2831 * kmsg_dump_get_buffer() can be called again and used multiple
2832 * times within the same dumper.dump() callback.
2834 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2836 unsigned long flags;
2838 raw_spin_lock_irqsave(&logbuf_lock, flags);
2839 kmsg_dump_rewind_nolock(dumper);
2840 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2842 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
2844 static char dump_stack_arch_desc_str[128];
2847 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
2848 * @fmt: printf-style format string
2849 * @...: arguments for the format string
2851 * The configured string will be printed right after utsname during task
2852 * dumps. Usually used to add arch-specific system identifiers. If an
2853 * arch wants to make use of such an ID string, it should initialize this
2854 * as soon as possible during boot.
2856 void __init dump_stack_set_arch_desc(const char *fmt, ...)
2860 va_start(args, fmt);
2861 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
2867 * dump_stack_print_info - print generic debug info for dump_stack()
2868 * @log_lvl: log level
2870 * Arch-specific dump_stack() implementations can use this function to
2871 * print out the same debug information as the generic dump_stack().
2873 void dump_stack_print_info(const char *log_lvl)
2875 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
2876 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
2877 print_tainted(), init_utsname()->release,
2878 (int)strcspn(init_utsname()->version, " "),
2879 init_utsname()->version);
2881 if (dump_stack_arch_desc_str[0] != '\0')
2882 printk("%sHardware name: %s\n",
2883 log_lvl, dump_stack_arch_desc_str);
2885 print_worker_info(log_lvl, current);
2889 * show_regs_print_info - print generic debug info for show_regs()
2890 * @log_lvl: log level
2892 * show_regs() implementations can use this function to print out generic
2893 * debug information.
2895 void show_regs_print_info(const char *log_lvl)
2897 dump_stack_print_info(log_lvl);
2899 printk("%stask: %p ti: %p task.ti: %p\n",
2900 log_lvl, current, current_thread_info(),
2901 task_thread_info(current));