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.
211 static DEFINE_RAW_SPINLOCK(logbuf_lock);
214 DECLARE_WAIT_QUEUE_HEAD(log_wait);
215 /* the next printk record to read by syslog(READ) or /proc/kmsg */
216 static u64 syslog_seq;
217 static u32 syslog_idx;
218 static enum log_flags syslog_prev;
219 static size_t syslog_partial;
221 /* index and sequence number of the first record stored in the buffer */
222 static u64 log_first_seq;
223 static u32 log_first_idx;
225 /* index and sequence number of the next record to store in the buffer */
226 static u64 log_next_seq;
227 static u32 log_next_idx;
229 /* the next printk record to write to the console */
230 static u64 console_seq;
231 static u32 console_idx;
232 static enum log_flags console_prev;
234 /* the next printk record to read after the last 'clear' command */
235 static u64 clear_seq;
236 static u32 clear_idx;
238 #define PREFIX_MAX 32
239 #define LOG_LINE_MAX 1024 - PREFIX_MAX
242 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
245 #define LOG_ALIGN __alignof__(struct printk_log)
247 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
248 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
249 static char *log_buf = __log_buf;
250 static u32 log_buf_len = __LOG_BUF_LEN;
252 /* human readable text of the record */
253 static char *log_text(const struct printk_log *msg)
255 return (char *)msg + sizeof(struct printk_log);
258 /* optional key/value pair dictionary attached to the record */
259 static char *log_dict(const struct printk_log *msg)
261 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
264 /* get record by index; idx must point to valid msg */
265 static struct printk_log *log_from_idx(u32 idx)
267 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
270 * A length == 0 record is the end of buffer marker. Wrap around and
271 * read the message at the start of the buffer.
274 return (struct printk_log *)log_buf;
278 /* get next record; idx must point to valid msg */
279 static u32 log_next(u32 idx)
281 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
283 /* length == 0 indicates the end of the buffer; wrap */
285 * A length == 0 record is the end of buffer marker. Wrap around and
286 * read the message at the start of the buffer as *this* one, and
287 * return the one after that.
290 msg = (struct printk_log *)log_buf;
293 return idx + msg->len;
297 * Check whether there is enough free space for the given message.
299 * The same values of first_idx and next_idx mean that the buffer
300 * is either empty or full.
302 * If the buffer is empty, we must respect the position of the indexes.
303 * They cannot be reset to the beginning of the buffer.
305 static int logbuf_has_space(u32 msg_size, bool empty)
309 if (log_next_idx > log_first_idx || empty)
310 free = max(log_buf_len - log_next_idx, log_first_idx);
312 free = log_first_idx - log_next_idx;
315 * We need space also for an empty header that signalizes wrapping
318 return free >= msg_size + sizeof(struct printk_log);
321 static int log_make_free_space(u32 msg_size)
323 while (log_first_seq < log_next_seq) {
324 if (logbuf_has_space(msg_size, false))
326 /* drop old messages until we have enough continuous space */
327 log_first_idx = log_next(log_first_idx);
331 /* sequence numbers are equal, so the log buffer is empty */
332 if (logbuf_has_space(msg_size, true))
338 /* compute the message size including the padding bytes */
339 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
343 size = sizeof(struct printk_log) + text_len + dict_len;
344 *pad_len = (-size) & (LOG_ALIGN - 1);
351 * Define how much of the log buffer we could take at maximum. The value
352 * must be greater than two. Note that only half of the buffer is available
353 * when the index points to the middle.
355 #define MAX_LOG_TAKE_PART 4
356 static const char trunc_msg[] = "<truncated>";
358 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
359 u16 *dict_len, u32 *pad_len)
362 * The message should not take the whole buffer. Otherwise, it might
363 * get removed too soon.
365 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
366 if (*text_len > max_text_len)
367 *text_len = max_text_len;
368 /* enable the warning message */
369 *trunc_msg_len = strlen(trunc_msg);
370 /* disable the "dict" completely */
372 /* compute the size again, count also the warning message */
373 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
376 /* insert record into the buffer, discard old ones, update heads */
377 static int log_store(int facility, int level,
378 enum log_flags flags, u64 ts_nsec,
379 const char *dict, u16 dict_len,
380 const char *text, u16 text_len)
382 struct printk_log *msg;
384 u16 trunc_msg_len = 0;
386 /* number of '\0' padding bytes to next message */
387 size = msg_used_size(text_len, dict_len, &pad_len);
389 if (log_make_free_space(size)) {
390 /* truncate the message if it is too long for empty buffer */
391 size = truncate_msg(&text_len, &trunc_msg_len,
392 &dict_len, &pad_len);
393 /* survive when the log buffer is too small for trunc_msg */
394 if (log_make_free_space(size))
398 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
400 * This message + an additional empty header does not fit
401 * at the end of the buffer. Add an empty header with len == 0
402 * to signify a wrap around.
404 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
409 msg = (struct printk_log *)(log_buf + log_next_idx);
410 memcpy(log_text(msg), text, text_len);
411 msg->text_len = text_len;
413 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
414 msg->text_len += trunc_msg_len;
416 memcpy(log_dict(msg), dict, dict_len);
417 msg->dict_len = dict_len;
418 msg->facility = facility;
419 msg->level = level & 7;
420 msg->flags = flags & 0x1f;
422 msg->ts_nsec = ts_nsec;
424 msg->ts_nsec = local_clock();
425 memset(log_dict(msg) + dict_len, 0, pad_len);
429 log_next_idx += msg->len;
432 return msg->text_len;
435 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
436 int dmesg_restrict = 1;
441 static int syslog_action_restricted(int type)
446 * Unless restricted, we allow "read all" and "get buffer size"
449 return type != SYSLOG_ACTION_READ_ALL &&
450 type != SYSLOG_ACTION_SIZE_BUFFER;
453 static int check_syslog_permissions(int type, bool from_file)
456 * If this is from /proc/kmsg and we've already opened it, then we've
457 * already done the capabilities checks at open time.
459 if (from_file && type != SYSLOG_ACTION_OPEN)
462 if (syslog_action_restricted(type)) {
463 if (capable(CAP_SYSLOG))
466 * For historical reasons, accept CAP_SYS_ADMIN too, with
469 if (capable(CAP_SYS_ADMIN)) {
470 pr_warn_once("%s (%d): Attempt to access syslog with "
471 "CAP_SYS_ADMIN but no CAP_SYSLOG "
473 current->comm, task_pid_nr(current));
478 return security_syslog(type);
482 /* /dev/kmsg - userspace message inject/listen interface */
483 struct devkmsg_user {
491 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
492 unsigned long count, loff_t pos)
496 int level = default_message_loglevel;
497 int facility = 1; /* LOG_USER */
498 size_t len = iov_length(iv, count);
501 if (len > LOG_LINE_MAX)
503 buf = kmalloc(len+1, GFP_KERNEL);
508 for (i = 0; i < count; i++) {
509 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
513 line += iv[i].iov_len;
517 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
518 * the decimal value represents 32bit, the lower 3 bit are the log
519 * level, the rest are the log facility.
521 * If no prefix or no userspace facility is specified, we
522 * enforce LOG_USER, to be able to reliably distinguish
523 * kernel-generated messages from userspace-injected ones.
526 if (line[0] == '<') {
529 i = simple_strtoul(line+1, &endp, 10);
530 if (endp && endp[0] == '>') {
541 printk_emit(facility, level, NULL, 0, "%s", line);
547 static ssize_t devkmsg_read(struct file *file, char __user *buf,
548 size_t count, loff_t *ppos)
550 struct devkmsg_user *user = file->private_data;
551 struct printk_log *msg;
561 ret = mutex_lock_interruptible(&user->lock);
564 raw_spin_lock_irq(&logbuf_lock);
565 while (user->seq == log_next_seq) {
566 if (file->f_flags & O_NONBLOCK) {
568 raw_spin_unlock_irq(&logbuf_lock);
572 raw_spin_unlock_irq(&logbuf_lock);
573 ret = wait_event_interruptible(log_wait,
574 user->seq != log_next_seq);
577 raw_spin_lock_irq(&logbuf_lock);
580 if (user->seq < log_first_seq) {
581 /* our last seen message is gone, return error and reset */
582 user->idx = log_first_idx;
583 user->seq = log_first_seq;
585 raw_spin_unlock_irq(&logbuf_lock);
589 msg = log_from_idx(user->idx);
590 ts_usec = msg->ts_nsec;
591 do_div(ts_usec, 1000);
594 * If we couldn't merge continuation line fragments during the print,
595 * export the stored flags to allow an optional external merge of the
596 * records. Merging the records isn't always neccessarily correct, like
597 * when we hit a race during printing. In most cases though, it produces
598 * better readable output. 'c' in the record flags mark the first
599 * fragment of a line, '+' the following.
601 if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
603 else if ((msg->flags & LOG_CONT) ||
604 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
607 len = sprintf(user->buf, "%u,%llu,%llu,%c;",
608 (msg->facility << 3) | msg->level,
609 user->seq, ts_usec, cont);
610 user->prev = msg->flags;
612 /* escape non-printable characters */
613 for (i = 0; i < msg->text_len; i++) {
614 unsigned char c = log_text(msg)[i];
616 if (c < ' ' || c >= 127 || c == '\\')
617 len += sprintf(user->buf + len, "\\x%02x", c);
619 user->buf[len++] = c;
621 user->buf[len++] = '\n';
626 for (i = 0; i < msg->dict_len; i++) {
627 unsigned char c = log_dict(msg)[i];
630 user->buf[len++] = ' ';
635 user->buf[len++] = '\n';
640 if (c < ' ' || c >= 127 || c == '\\') {
641 len += sprintf(user->buf + len, "\\x%02x", c);
645 user->buf[len++] = c;
647 user->buf[len++] = '\n';
650 user->idx = log_next(user->idx);
652 raw_spin_unlock_irq(&logbuf_lock);
659 if (copy_to_user(buf, user->buf, len)) {
665 mutex_unlock(&user->lock);
669 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
671 struct devkmsg_user *user = file->private_data;
679 raw_spin_lock_irq(&logbuf_lock);
682 /* the first record */
683 user->idx = log_first_idx;
684 user->seq = log_first_seq;
688 * The first record after the last SYSLOG_ACTION_CLEAR,
689 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
690 * changes no global state, and does not clear anything.
692 user->idx = clear_idx;
693 user->seq = clear_seq;
696 /* after the last record */
697 user->idx = log_next_idx;
698 user->seq = log_next_seq;
703 raw_spin_unlock_irq(&logbuf_lock);
707 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
709 struct devkmsg_user *user = file->private_data;
713 return POLLERR|POLLNVAL;
715 poll_wait(file, &log_wait, wait);
717 raw_spin_lock_irq(&logbuf_lock);
718 if (user->seq < log_next_seq) {
719 /* return error when data has vanished underneath us */
720 if (user->seq < log_first_seq)
721 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
723 ret = POLLIN|POLLRDNORM;
725 raw_spin_unlock_irq(&logbuf_lock);
730 static int devkmsg_open(struct inode *inode, struct file *file)
732 struct devkmsg_user *user;
735 /* write-only does not need any file context */
736 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
739 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
744 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
748 mutex_init(&user->lock);
750 raw_spin_lock_irq(&logbuf_lock);
751 user->idx = log_first_idx;
752 user->seq = log_first_seq;
753 raw_spin_unlock_irq(&logbuf_lock);
755 file->private_data = user;
759 static int devkmsg_release(struct inode *inode, struct file *file)
761 struct devkmsg_user *user = file->private_data;
766 mutex_destroy(&user->lock);
771 const struct file_operations kmsg_fops = {
772 .open = devkmsg_open,
773 .read = devkmsg_read,
774 .aio_write = devkmsg_writev,
775 .llseek = devkmsg_llseek,
776 .poll = devkmsg_poll,
777 .release = devkmsg_release,
782 * This appends the listed symbols to /proc/vmcore
784 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
785 * obtain access to symbols that are otherwise very difficult to locate. These
786 * symbols are specifically used so that utilities can access and extract the
787 * dmesg log from a vmcore file after a crash.
789 void log_buf_kexec_setup(void)
791 VMCOREINFO_SYMBOL(log_buf);
792 VMCOREINFO_SYMBOL(log_buf_len);
793 VMCOREINFO_SYMBOL(log_first_idx);
794 VMCOREINFO_SYMBOL(log_next_idx);
796 * Export struct printk_log size and field offsets. User space tools can
797 * parse it and detect any changes to structure down the line.
799 VMCOREINFO_STRUCT_SIZE(printk_log);
800 VMCOREINFO_OFFSET(printk_log, ts_nsec);
801 VMCOREINFO_OFFSET(printk_log, len);
802 VMCOREINFO_OFFSET(printk_log, text_len);
803 VMCOREINFO_OFFSET(printk_log, dict_len);
807 /* requested log_buf_len from kernel cmdline */
808 static unsigned long __initdata new_log_buf_len;
810 /* save requested log_buf_len since it's too early to process it */
811 static int __init log_buf_len_setup(char *str)
813 unsigned size = memparse(str, &str);
816 size = roundup_pow_of_two(size);
817 if (size > log_buf_len)
818 new_log_buf_len = size;
822 early_param("log_buf_len", log_buf_len_setup);
824 void __init setup_log_buf(int early)
830 if (!new_log_buf_len)
835 memblock_virt_alloc(new_log_buf_len, PAGE_SIZE);
837 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len, 0);
840 if (unlikely(!new_log_buf)) {
841 pr_err("log_buf_len: %ld bytes not available\n",
846 raw_spin_lock_irqsave(&logbuf_lock, flags);
847 log_buf_len = new_log_buf_len;
848 log_buf = new_log_buf;
850 free = __LOG_BUF_LEN - log_next_idx;
851 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
852 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
854 pr_info("log_buf_len: %d\n", log_buf_len);
855 pr_info("early log buf free: %d(%d%%)\n",
856 free, (free * 100) / __LOG_BUF_LEN);
859 static bool __read_mostly ignore_loglevel;
861 static int __init ignore_loglevel_setup(char *str)
864 pr_info("debug: ignoring loglevel setting.\n");
869 early_param("ignore_loglevel", ignore_loglevel_setup);
870 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
871 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
872 "print all kernel messages to the console.");
874 #ifdef CONFIG_BOOT_PRINTK_DELAY
876 static int boot_delay; /* msecs delay after each printk during bootup */
877 static unsigned long long loops_per_msec; /* based on boot_delay */
879 static int __init boot_delay_setup(char *str)
883 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
884 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
886 get_option(&str, &boot_delay);
887 if (boot_delay > 10 * 1000)
890 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
891 "HZ: %d, loops_per_msec: %llu\n",
892 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
895 early_param("boot_delay", boot_delay_setup);
897 static void boot_delay_msec(int level)
899 unsigned long long k;
900 unsigned long timeout;
902 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
903 || (level >= console_loglevel && !ignore_loglevel)) {
907 k = (unsigned long long)loops_per_msec * boot_delay;
909 timeout = jiffies + msecs_to_jiffies(boot_delay);
914 * use (volatile) jiffies to prevent
915 * compiler reduction; loop termination via jiffies
916 * is secondary and may or may not happen.
918 if (time_after(jiffies, timeout))
920 touch_nmi_watchdog();
924 static inline void boot_delay_msec(int level)
929 #if defined(CONFIG_PRINTK_TIME)
930 static bool printk_time = 1;
932 static bool printk_time;
934 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
936 static size_t print_time(u64 ts, char *buf)
938 unsigned long rem_nsec;
943 rem_nsec = do_div(ts, 1000000000);
946 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
948 return sprintf(buf, "[%5lu.%06lu] ",
949 (unsigned long)ts, rem_nsec / 1000);
952 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
955 unsigned int prefix = (msg->facility << 3) | msg->level;
959 len += sprintf(buf, "<%u>", prefix);
964 else if (prefix > 99)
971 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
975 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
976 bool syslog, char *buf, size_t size)
978 const char *text = log_text(msg);
979 size_t text_size = msg->text_len;
984 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
987 if (msg->flags & LOG_CONT) {
988 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
991 if (!(msg->flags & LOG_NEWLINE))
996 const char *next = memchr(text, '\n', text_size);
1000 text_len = next - text;
1002 text_size -= next - text;
1004 text_len = text_size;
1008 if (print_prefix(msg, syslog, NULL) +
1009 text_len + 1 >= size - len)
1013 len += print_prefix(msg, syslog, buf + len);
1014 memcpy(buf + len, text, text_len);
1016 if (next || newline)
1019 /* SYSLOG_ACTION_* buffer size only calculation */
1021 len += print_prefix(msg, syslog, NULL);
1023 if (next || newline)
1034 static int syslog_print(char __user *buf, int size)
1037 struct printk_log *msg;
1040 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1048 raw_spin_lock_irq(&logbuf_lock);
1049 if (syslog_seq < log_first_seq) {
1050 /* messages are gone, move to first one */
1051 syslog_seq = log_first_seq;
1052 syslog_idx = log_first_idx;
1056 if (syslog_seq == log_next_seq) {
1057 raw_spin_unlock_irq(&logbuf_lock);
1061 skip = syslog_partial;
1062 msg = log_from_idx(syslog_idx);
1063 n = msg_print_text(msg, syslog_prev, true, text,
1064 LOG_LINE_MAX + PREFIX_MAX);
1065 if (n - syslog_partial <= size) {
1066 /* message fits into buffer, move forward */
1067 syslog_idx = log_next(syslog_idx);
1069 syslog_prev = msg->flags;
1070 n -= syslog_partial;
1073 /* partial read(), remember position */
1075 syslog_partial += n;
1078 raw_spin_unlock_irq(&logbuf_lock);
1083 if (copy_to_user(buf, text + skip, n)) {
1098 static int syslog_print_all(char __user *buf, int size, bool clear)
1103 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1107 raw_spin_lock_irq(&logbuf_lock);
1112 enum log_flags prev;
1114 if (clear_seq < log_first_seq) {
1115 /* messages are gone, move to first available one */
1116 clear_seq = log_first_seq;
1117 clear_idx = log_first_idx;
1121 * Find first record that fits, including all following records,
1122 * into the user-provided buffer for this dump.
1127 while (seq < log_next_seq) {
1128 struct printk_log *msg = log_from_idx(idx);
1130 len += msg_print_text(msg, prev, true, NULL, 0);
1132 idx = log_next(idx);
1136 /* move first record forward until length fits into the buffer */
1140 while (len > size && seq < log_next_seq) {
1141 struct printk_log *msg = log_from_idx(idx);
1143 len -= msg_print_text(msg, prev, true, NULL, 0);
1145 idx = log_next(idx);
1149 /* last message fitting into this dump */
1150 next_seq = log_next_seq;
1153 while (len >= 0 && seq < next_seq) {
1154 struct printk_log *msg = log_from_idx(idx);
1157 textlen = msg_print_text(msg, prev, true, text,
1158 LOG_LINE_MAX + PREFIX_MAX);
1163 idx = log_next(idx);
1167 raw_spin_unlock_irq(&logbuf_lock);
1168 if (copy_to_user(buf + len, text, textlen))
1172 raw_spin_lock_irq(&logbuf_lock);
1174 if (seq < log_first_seq) {
1175 /* messages are gone, move to next one */
1176 seq = log_first_seq;
1177 idx = log_first_idx;
1184 clear_seq = log_next_seq;
1185 clear_idx = log_next_idx;
1187 raw_spin_unlock_irq(&logbuf_lock);
1193 int do_syslog(int type, char __user *buf, int len, bool from_file)
1196 static int saved_console_loglevel = -1;
1199 error = check_syslog_permissions(type, from_file);
1203 error = security_syslog(type);
1208 case SYSLOG_ACTION_CLOSE: /* Close log */
1210 case SYSLOG_ACTION_OPEN: /* Open log */
1212 case SYSLOG_ACTION_READ: /* Read from log */
1214 if (!buf || len < 0)
1219 if (!access_ok(VERIFY_WRITE, buf, len)) {
1223 error = wait_event_interruptible(log_wait,
1224 syslog_seq != log_next_seq);
1227 error = syslog_print(buf, len);
1229 /* Read/clear last kernel messages */
1230 case SYSLOG_ACTION_READ_CLEAR:
1233 /* Read last kernel messages */
1234 case SYSLOG_ACTION_READ_ALL:
1236 if (!buf || len < 0)
1241 if (!access_ok(VERIFY_WRITE, buf, len)) {
1245 error = syslog_print_all(buf, len, clear);
1247 /* Clear ring buffer */
1248 case SYSLOG_ACTION_CLEAR:
1249 syslog_print_all(NULL, 0, true);
1251 /* Disable logging to console */
1252 case SYSLOG_ACTION_CONSOLE_OFF:
1253 if (saved_console_loglevel == -1)
1254 saved_console_loglevel = console_loglevel;
1255 console_loglevel = minimum_console_loglevel;
1257 /* Enable logging to console */
1258 case SYSLOG_ACTION_CONSOLE_ON:
1259 if (saved_console_loglevel != -1) {
1260 console_loglevel = saved_console_loglevel;
1261 saved_console_loglevel = -1;
1264 /* Set level of messages printed to console */
1265 case SYSLOG_ACTION_CONSOLE_LEVEL:
1267 if (len < 1 || len > 8)
1269 if (len < minimum_console_loglevel)
1270 len = minimum_console_loglevel;
1271 console_loglevel = len;
1272 /* Implicitly re-enable logging to console */
1273 saved_console_loglevel = -1;
1276 /* Number of chars in the log buffer */
1277 case SYSLOG_ACTION_SIZE_UNREAD:
1278 raw_spin_lock_irq(&logbuf_lock);
1279 if (syslog_seq < log_first_seq) {
1280 /* messages are gone, move to first one */
1281 syslog_seq = log_first_seq;
1282 syslog_idx = log_first_idx;
1288 * Short-cut for poll(/"proc/kmsg") which simply checks
1289 * for pending data, not the size; return the count of
1290 * records, not the length.
1292 error = log_next_idx - syslog_idx;
1294 u64 seq = syslog_seq;
1295 u32 idx = syslog_idx;
1296 enum log_flags prev = syslog_prev;
1299 while (seq < log_next_seq) {
1300 struct printk_log *msg = log_from_idx(idx);
1302 error += msg_print_text(msg, prev, true, NULL, 0);
1303 idx = log_next(idx);
1307 error -= syslog_partial;
1309 raw_spin_unlock_irq(&logbuf_lock);
1311 /* Size of the log buffer */
1312 case SYSLOG_ACTION_SIZE_BUFFER:
1313 error = log_buf_len;
1323 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1325 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1329 * Call the console drivers, asking them to write out
1330 * log_buf[start] to log_buf[end - 1].
1331 * The console_lock must be held.
1333 static void call_console_drivers(int level, const char *text, size_t len)
1335 struct console *con;
1337 trace_console(text, len);
1339 if (level >= console_loglevel && !ignore_loglevel)
1341 if (!console_drivers)
1344 for_each_console(con) {
1345 if (exclusive_console && con != exclusive_console)
1347 if (!(con->flags & CON_ENABLED))
1351 if (!cpu_online(smp_processor_id()) &&
1352 !(con->flags & CON_ANYTIME))
1354 con->write(con, text, len);
1359 * Zap console related locks when oopsing. Only zap at most once
1360 * every 10 seconds, to leave time for slow consoles to print a
1363 static void zap_locks(void)
1365 static unsigned long oops_timestamp;
1367 if (time_after_eq(jiffies, oops_timestamp) &&
1368 !time_after(jiffies, oops_timestamp + 30 * HZ))
1371 oops_timestamp = jiffies;
1374 /* If a crash is occurring, make sure we can't deadlock */
1375 raw_spin_lock_init(&logbuf_lock);
1376 /* And make sure that we print immediately */
1377 sema_init(&console_sem, 1);
1381 * Check if we have any console that is capable of printing while cpu is
1382 * booting or shutting down. Requires console_sem.
1384 static int have_callable_console(void)
1386 struct console *con;
1388 for_each_console(con)
1389 if (con->flags & CON_ANYTIME)
1396 * Can we actually use the console at this time on this cpu?
1398 * Console drivers may assume that per-cpu resources have
1399 * been allocated. So unless they're explicitly marked as
1400 * being able to cope (CON_ANYTIME) don't call them until
1401 * this CPU is officially up.
1403 static inline int can_use_console(unsigned int cpu)
1405 return cpu_online(cpu) || have_callable_console();
1409 * Try to get console ownership to actually show the kernel
1410 * messages from a 'printk'. Return true (and with the
1411 * console_lock held, and 'console_locked' set) if it
1412 * is successful, false otherwise.
1414 static int console_trylock_for_printk(unsigned int cpu)
1416 if (!console_trylock())
1419 * If we can't use the console, we need to release the console
1420 * semaphore by hand to avoid flushing the buffer. We need to hold the
1421 * console semaphore in order to do this test safely.
1423 if (!can_use_console(cpu)) {
1431 int printk_delay_msec __read_mostly;
1433 static inline void printk_delay(void)
1435 if (unlikely(printk_delay_msec)) {
1436 int m = printk_delay_msec;
1440 touch_nmi_watchdog();
1446 * Continuation lines are buffered, and not committed to the record buffer
1447 * until the line is complete, or a race forces it. The line fragments
1448 * though, are printed immediately to the consoles to ensure everything has
1449 * reached the console in case of a kernel crash.
1451 static struct cont {
1452 char buf[LOG_LINE_MAX];
1453 size_t len; /* length == 0 means unused buffer */
1454 size_t cons; /* bytes written to console */
1455 struct task_struct *owner; /* task of first print*/
1456 u64 ts_nsec; /* time of first print */
1457 u8 level; /* log level of first message */
1458 u8 facility; /* log level of first message */
1459 enum log_flags flags; /* prefix, newline flags */
1460 bool flushed:1; /* buffer sealed and committed */
1463 static void cont_flush(enum log_flags flags)
1472 * If a fragment of this line was directly flushed to the
1473 * console; wait for the console to pick up the rest of the
1474 * line. LOG_NOCONS suppresses a duplicated output.
1476 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1477 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1479 cont.flushed = true;
1482 * If no fragment of this line ever reached the console,
1483 * just submit it to the store and free the buffer.
1485 log_store(cont.facility, cont.level, flags, 0,
1486 NULL, 0, cont.buf, cont.len);
1491 static bool cont_add(int facility, int level, const char *text, size_t len)
1493 if (cont.len && cont.flushed)
1496 if (cont.len + len > sizeof(cont.buf)) {
1497 /* the line gets too long, split it up in separate records */
1498 cont_flush(LOG_CONT);
1503 cont.facility = facility;
1505 cont.owner = current;
1506 cont.ts_nsec = local_clock();
1509 cont.flushed = false;
1512 memcpy(cont.buf + cont.len, text, len);
1515 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1516 cont_flush(LOG_CONT);
1521 static size_t cont_print_text(char *text, size_t size)
1526 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1527 textlen += print_time(cont.ts_nsec, text);
1531 len = cont.len - cont.cons;
1535 memcpy(text + textlen, cont.buf + cont.cons, len);
1537 cont.cons = cont.len;
1541 if (cont.flags & LOG_NEWLINE)
1542 text[textlen++] = '\n';
1543 /* got everything, release buffer */
1549 asmlinkage int vprintk_emit(int facility, int level,
1550 const char *dict, size_t dictlen,
1551 const char *fmt, va_list args)
1553 static int recursion_bug;
1554 static char textbuf[LOG_LINE_MAX];
1555 char *text = textbuf;
1557 enum log_flags lflags = 0;
1558 unsigned long flags;
1560 int printed_len = 0;
1561 /* cpu currently holding logbuf_lock in this function */
1562 static volatile unsigned int logbuf_cpu = UINT_MAX;
1565 boot_delay_msec(level);
1568 /* This stops the holder of console_sem just where we want him */
1569 local_irq_save(flags);
1570 this_cpu = smp_processor_id();
1573 * Ouch, printk recursed into itself!
1575 if (unlikely(logbuf_cpu == this_cpu)) {
1577 * If a crash is occurring during printk() on this CPU,
1578 * then try to get the crash message out but make sure
1579 * we can't deadlock. Otherwise just return to avoid the
1580 * recursion and return - but flag the recursion so that
1581 * it can be printed at the next appropriate moment:
1583 if (!oops_in_progress && !lockdep_recursing(current)) {
1585 goto out_restore_irqs;
1591 raw_spin_lock(&logbuf_lock);
1592 logbuf_cpu = this_cpu;
1594 if (recursion_bug) {
1595 static const char recursion_msg[] =
1596 "BUG: recent printk recursion!";
1599 text_len = strlen(recursion_msg);
1600 /* emit KERN_CRIT message */
1601 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1602 NULL, 0, recursion_msg, text_len);
1606 * The printf needs to come first; we need the syslog
1607 * prefix which might be passed-in as a parameter.
1609 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1611 /* mark and strip a trailing newline */
1612 if (text_len && text[text_len-1] == '\n') {
1614 lflags |= LOG_NEWLINE;
1617 /* strip kernel syslog prefix and extract log level or control flags */
1618 if (facility == 0) {
1619 int kern_level = printk_get_level(text);
1622 const char *end_of_header = printk_skip_level(text);
1623 switch (kern_level) {
1626 level = kern_level - '0';
1627 case 'd': /* KERN_DEFAULT */
1628 lflags |= LOG_PREFIX;
1631 * No need to check length here because vscnprintf
1632 * put '\0' at the end of the string. Only valid and
1633 * newly printed level is detected.
1635 text_len -= end_of_header - text;
1636 text = (char *)end_of_header;
1641 level = default_message_loglevel;
1644 lflags |= LOG_PREFIX|LOG_NEWLINE;
1646 if (!(lflags & LOG_NEWLINE)) {
1648 * Flush the conflicting buffer. An earlier newline was missing,
1649 * or another task also prints continuation lines.
1651 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1652 cont_flush(LOG_NEWLINE);
1654 /* buffer line if possible, otherwise store it right away */
1655 if (cont_add(facility, level, text, text_len))
1656 printed_len += text_len;
1658 printed_len += log_store(facility, level,
1659 lflags | LOG_CONT, 0,
1660 dict, dictlen, text, text_len);
1662 bool stored = false;
1665 * If an earlier newline was missing and it was the same task,
1666 * either merge it with the current buffer and flush, or if
1667 * there was a race with interrupts (prefix == true) then just
1668 * flush it out and store this line separately.
1669 * If the preceding printk was from a different task and missed
1670 * a newline, flush and append the newline.
1673 if (cont.owner == current && !(lflags & LOG_PREFIX))
1674 stored = cont_add(facility, level, text,
1676 cont_flush(LOG_NEWLINE);
1680 printed_len += text_len;
1682 printed_len += log_store(facility, level, lflags, 0,
1683 dict, dictlen, text, text_len);
1686 logbuf_cpu = UINT_MAX;
1687 raw_spin_unlock(&logbuf_lock);
1689 * Try to acquire and then immediately release the console semaphore.
1690 * The release will print out buffers and wake up /dev/kmsg and syslog()
1693 if (console_trylock_for_printk(this_cpu))
1698 local_irq_restore(flags);
1702 EXPORT_SYMBOL(vprintk_emit);
1704 asmlinkage int vprintk(const char *fmt, va_list args)
1706 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1708 EXPORT_SYMBOL(vprintk);
1710 asmlinkage int printk_emit(int facility, int level,
1711 const char *dict, size_t dictlen,
1712 const char *fmt, ...)
1717 va_start(args, fmt);
1718 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1723 EXPORT_SYMBOL(printk_emit);
1726 * printk - print a kernel message
1727 * @fmt: format string
1729 * This is printk(). It can be called from any context. We want it to work.
1731 * We try to grab the console_lock. If we succeed, it's easy - we log the
1732 * output and call the console drivers. If we fail to get the semaphore, we
1733 * place the output into the log buffer and return. The current holder of
1734 * the console_sem will notice the new output in console_unlock(); and will
1735 * send it to the consoles before releasing the lock.
1737 * One effect of this deferred printing is that code which calls printk() and
1738 * then changes console_loglevel may break. This is because console_loglevel
1739 * is inspected when the actual printing occurs.
1744 * See the vsnprintf() documentation for format string extensions over C99.
1746 asmlinkage __visible int printk(const char *fmt, ...)
1751 #ifdef CONFIG_KGDB_KDB
1752 if (unlikely(kdb_trap_printk)) {
1753 va_start(args, fmt);
1754 r = vkdb_printf(fmt, args);
1759 va_start(args, fmt);
1760 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1765 EXPORT_SYMBOL(printk);
1767 #else /* CONFIG_PRINTK */
1769 #define LOG_LINE_MAX 0
1770 #define PREFIX_MAX 0
1771 #define LOG_LINE_MAX 0
1772 static u64 syslog_seq;
1773 static u32 syslog_idx;
1774 static u64 console_seq;
1775 static u32 console_idx;
1776 static enum log_flags syslog_prev;
1777 static u64 log_first_seq;
1778 static u32 log_first_idx;
1779 static u64 log_next_seq;
1780 static enum log_flags console_prev;
1781 static struct cont {
1787 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1788 static u32 log_next(u32 idx) { return 0; }
1789 static void call_console_drivers(int level, const char *text, size_t len) {}
1790 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1791 bool syslog, char *buf, size_t size) { return 0; }
1792 static size_t cont_print_text(char *text, size_t size) { return 0; }
1794 #endif /* CONFIG_PRINTK */
1796 #ifdef CONFIG_EARLY_PRINTK
1797 struct console *early_console;
1799 void early_vprintk(const char *fmt, va_list ap)
1801 if (early_console) {
1803 int n = vscnprintf(buf, sizeof(buf), fmt, ap);
1805 early_console->write(early_console, buf, n);
1809 asmlinkage __visible void early_printk(const char *fmt, ...)
1814 early_vprintk(fmt, ap);
1819 static int __add_preferred_console(char *name, int idx, char *options,
1822 struct console_cmdline *c;
1826 * See if this tty is not yet registered, and
1827 * if we have a slot free.
1829 for (i = 0, c = console_cmdline;
1830 i < MAX_CMDLINECONSOLES && c->name[0];
1832 if (strcmp(c->name, name) == 0 && c->index == idx) {
1834 selected_console = i;
1838 if (i == MAX_CMDLINECONSOLES)
1841 selected_console = i;
1842 strlcpy(c->name, name, sizeof(c->name));
1843 c->options = options;
1844 braille_set_options(c, brl_options);
1850 * Set up a list of consoles. Called from init/main.c
1852 static int __init console_setup(char *str)
1854 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1855 char *s, *options, *brl_options = NULL;
1858 if (_braille_console_setup(&str, &brl_options))
1862 * Decode str into name, index, options.
1864 if (str[0] >= '0' && str[0] <= '9') {
1865 strcpy(buf, "ttyS");
1866 strncpy(buf + 4, str, sizeof(buf) - 5);
1868 strncpy(buf, str, sizeof(buf) - 1);
1870 buf[sizeof(buf) - 1] = 0;
1871 if ((options = strchr(str, ',')) != NULL)
1874 if (!strcmp(str, "ttya"))
1875 strcpy(buf, "ttyS0");
1876 if (!strcmp(str, "ttyb"))
1877 strcpy(buf, "ttyS1");
1879 for (s = buf; *s; s++)
1880 if ((*s >= '0' && *s <= '9') || *s == ',')
1882 idx = simple_strtoul(s, NULL, 10);
1885 __add_preferred_console(buf, idx, options, brl_options);
1886 console_set_on_cmdline = 1;
1889 __setup("console=", console_setup);
1892 * add_preferred_console - add a device to the list of preferred consoles.
1893 * @name: device name
1894 * @idx: device index
1895 * @options: options for this console
1897 * The last preferred console added will be used for kernel messages
1898 * and stdin/out/err for init. Normally this is used by console_setup
1899 * above to handle user-supplied console arguments; however it can also
1900 * be used by arch-specific code either to override the user or more
1901 * commonly to provide a default console (ie from PROM variables) when
1902 * the user has not supplied one.
1904 int add_preferred_console(char *name, int idx, char *options)
1906 return __add_preferred_console(name, idx, options, NULL);
1909 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1911 struct console_cmdline *c;
1914 for (i = 0, c = console_cmdline;
1915 i < MAX_CMDLINECONSOLES && c->name[0];
1917 if (strcmp(c->name, name) == 0 && c->index == idx) {
1918 strlcpy(c->name, name_new, sizeof(c->name));
1919 c->name[sizeof(c->name) - 1] = 0;
1920 c->options = options;
1928 bool console_suspend_enabled = 1;
1929 EXPORT_SYMBOL(console_suspend_enabled);
1931 static int __init console_suspend_disable(char *str)
1933 console_suspend_enabled = 0;
1936 __setup("no_console_suspend", console_suspend_disable);
1937 module_param_named(console_suspend, console_suspend_enabled,
1938 bool, S_IRUGO | S_IWUSR);
1939 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1940 " and hibernate operations");
1943 * suspend_console - suspend the console subsystem
1945 * This disables printk() while we go into suspend states
1947 void suspend_console(void)
1949 if (!console_suspend_enabled)
1951 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1953 console_suspended = 1;
1955 mutex_release(&console_lock_dep_map, 1, _RET_IP_);
1958 void resume_console(void)
1960 if (!console_suspend_enabled)
1963 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
1964 console_suspended = 0;
1969 * console_cpu_notify - print deferred console messages after CPU hotplug
1970 * @self: notifier struct
1971 * @action: CPU hotplug event
1974 * If printk() is called from a CPU that is not online yet, the messages
1975 * will be spooled but will not show up on the console. This function is
1976 * called when a new CPU comes online (or fails to come up), and ensures
1977 * that any such output gets printed.
1979 static int console_cpu_notify(struct notifier_block *self,
1980 unsigned long action, void *hcpu)
1985 case CPU_DOWN_FAILED:
1986 case CPU_UP_CANCELED:
1994 * console_lock - lock the console system for exclusive use.
1996 * Acquires a lock which guarantees that the caller has
1997 * exclusive access to the console system and the console_drivers list.
1999 * Can sleep, returns nothing.
2001 void console_lock(void)
2006 if (console_suspended)
2009 console_may_schedule = 1;
2010 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
2012 EXPORT_SYMBOL(console_lock);
2015 * console_trylock - try to lock the console system for exclusive use.
2017 * Tried to acquire a lock which guarantees that the caller has
2018 * exclusive access to the console system and the console_drivers list.
2020 * returns 1 on success, and 0 on failure to acquire the lock.
2022 int console_trylock(void)
2024 if (down_trylock(&console_sem))
2026 if (console_suspended) {
2031 console_may_schedule = 0;
2032 mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);
2035 EXPORT_SYMBOL(console_trylock);
2037 int is_console_locked(void)
2039 return console_locked;
2042 static void console_cont_flush(char *text, size_t size)
2044 unsigned long flags;
2047 raw_spin_lock_irqsave(&logbuf_lock, flags);
2053 * We still queue earlier records, likely because the console was
2054 * busy. The earlier ones need to be printed before this one, we
2055 * did not flush any fragment so far, so just let it queue up.
2057 if (console_seq < log_next_seq && !cont.cons)
2060 len = cont_print_text(text, size);
2061 raw_spin_unlock(&logbuf_lock);
2062 stop_critical_timings();
2063 call_console_drivers(cont.level, text, len);
2064 start_critical_timings();
2065 local_irq_restore(flags);
2068 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2072 * console_unlock - unlock the console system
2074 * Releases the console_lock which the caller holds on the console system
2075 * and the console driver list.
2077 * While the console_lock was held, console output may have been buffered
2078 * by printk(). If this is the case, console_unlock(); emits
2079 * the output prior to releasing the lock.
2081 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2083 * console_unlock(); may be called from any context.
2085 void console_unlock(void)
2087 static char text[LOG_LINE_MAX + PREFIX_MAX];
2088 static u64 seen_seq;
2089 unsigned long flags;
2090 bool wake_klogd = false;
2093 if (console_suspended) {
2098 console_may_schedule = 0;
2100 /* flush buffered message fragment immediately to console */
2101 console_cont_flush(text, sizeof(text));
2104 struct printk_log *msg;
2108 raw_spin_lock_irqsave(&logbuf_lock, flags);
2109 if (seen_seq != log_next_seq) {
2111 seen_seq = log_next_seq;
2114 if (console_seq < log_first_seq) {
2115 /* messages are gone, move to first one */
2116 console_seq = log_first_seq;
2117 console_idx = log_first_idx;
2121 if (console_seq == log_next_seq)
2124 msg = log_from_idx(console_idx);
2125 if (msg->flags & LOG_NOCONS) {
2127 * Skip record we have buffered and already printed
2128 * directly to the console when we received it.
2130 console_idx = log_next(console_idx);
2133 * We will get here again when we register a new
2134 * CON_PRINTBUFFER console. Clear the flag so we
2135 * will properly dump everything later.
2137 msg->flags &= ~LOG_NOCONS;
2138 console_prev = msg->flags;
2143 len = msg_print_text(msg, console_prev, false,
2144 text, sizeof(text));
2145 console_idx = log_next(console_idx);
2147 console_prev = msg->flags;
2148 raw_spin_unlock(&logbuf_lock);
2150 stop_critical_timings(); /* don't trace print latency */
2151 call_console_drivers(level, text, len);
2152 start_critical_timings();
2153 local_irq_restore(flags);
2156 mutex_release(&console_lock_dep_map, 1, _RET_IP_);
2158 /* Release the exclusive_console once it is used */
2159 if (unlikely(exclusive_console))
2160 exclusive_console = NULL;
2162 raw_spin_unlock(&logbuf_lock);
2167 * Someone could have filled up the buffer again, so re-check if there's
2168 * something to flush. In case we cannot trylock the console_sem again,
2169 * there's a new owner and the console_unlock() from them will do the
2170 * flush, no worries.
2172 raw_spin_lock(&logbuf_lock);
2173 retry = console_seq != log_next_seq;
2174 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2176 if (retry && console_trylock())
2182 EXPORT_SYMBOL(console_unlock);
2185 * console_conditional_schedule - yield the CPU if required
2187 * If the console code is currently allowed to sleep, and
2188 * if this CPU should yield the CPU to another task, do
2191 * Must be called within console_lock();.
2193 void __sched console_conditional_schedule(void)
2195 if (console_may_schedule)
2198 EXPORT_SYMBOL(console_conditional_schedule);
2200 void console_unblank(void)
2205 * console_unblank can no longer be called in interrupt context unless
2206 * oops_in_progress is set to 1..
2208 if (oops_in_progress) {
2209 if (down_trylock(&console_sem) != 0)
2215 console_may_schedule = 0;
2217 if ((c->flags & CON_ENABLED) && c->unblank)
2223 * Return the console tty driver structure and its associated index
2225 struct tty_driver *console_device(int *index)
2228 struct tty_driver *driver = NULL;
2231 for_each_console(c) {
2234 driver = c->device(c, index);
2243 * Prevent further output on the passed console device so that (for example)
2244 * serial drivers can disable console output before suspending a port, and can
2245 * re-enable output afterwards.
2247 void console_stop(struct console *console)
2250 console->flags &= ~CON_ENABLED;
2253 EXPORT_SYMBOL(console_stop);
2255 void console_start(struct console *console)
2258 console->flags |= CON_ENABLED;
2261 EXPORT_SYMBOL(console_start);
2263 static int __read_mostly keep_bootcon;
2265 static int __init keep_bootcon_setup(char *str)
2268 pr_info("debug: skip boot console de-registration.\n");
2273 early_param("keep_bootcon", keep_bootcon_setup);
2276 * The console driver calls this routine during kernel initialization
2277 * to register the console printing procedure with printk() and to
2278 * print any messages that were printed by the kernel before the
2279 * console driver was initialized.
2281 * This can happen pretty early during the boot process (because of
2282 * early_printk) - sometimes before setup_arch() completes - be careful
2283 * of what kernel features are used - they may not be initialised yet.
2285 * There are two types of consoles - bootconsoles (early_printk) and
2286 * "real" consoles (everything which is not a bootconsole) which are
2287 * handled differently.
2288 * - Any number of bootconsoles can be registered at any time.
2289 * - As soon as a "real" console is registered, all bootconsoles
2290 * will be unregistered automatically.
2291 * - Once a "real" console is registered, any attempt to register a
2292 * bootconsoles will be rejected
2294 void register_console(struct console *newcon)
2297 unsigned long flags;
2298 struct console *bcon = NULL;
2299 struct console_cmdline *c;
2301 if (console_drivers)
2302 for_each_console(bcon)
2303 if (WARN(bcon == newcon,
2304 "console '%s%d' already registered\n",
2305 bcon->name, bcon->index))
2309 * before we register a new CON_BOOT console, make sure we don't
2310 * already have a valid console
2312 if (console_drivers && newcon->flags & CON_BOOT) {
2313 /* find the last or real console */
2314 for_each_console(bcon) {
2315 if (!(bcon->flags & CON_BOOT)) {
2316 pr_info("Too late to register bootconsole %s%d\n",
2317 newcon->name, newcon->index);
2323 if (console_drivers && console_drivers->flags & CON_BOOT)
2324 bcon = console_drivers;
2326 if (preferred_console < 0 || bcon || !console_drivers)
2327 preferred_console = selected_console;
2329 if (newcon->early_setup)
2330 newcon->early_setup();
2333 * See if we want to use this console driver. If we
2334 * didn't select a console we take the first one
2335 * that registers here.
2337 if (preferred_console < 0) {
2338 if (newcon->index < 0)
2340 if (newcon->setup == NULL ||
2341 newcon->setup(newcon, NULL) == 0) {
2342 newcon->flags |= CON_ENABLED;
2343 if (newcon->device) {
2344 newcon->flags |= CON_CONSDEV;
2345 preferred_console = 0;
2351 * See if this console matches one we selected on
2354 for (i = 0, c = console_cmdline;
2355 i < MAX_CMDLINECONSOLES && c->name[0];
2357 if (strcmp(c->name, newcon->name) != 0)
2359 if (newcon->index >= 0 &&
2360 newcon->index != c->index)
2362 if (newcon->index < 0)
2363 newcon->index = c->index;
2365 if (_braille_register_console(newcon, c))
2368 if (newcon->setup &&
2369 newcon->setup(newcon, console_cmdline[i].options) != 0)
2371 newcon->flags |= CON_ENABLED;
2372 newcon->index = c->index;
2373 if (i == selected_console) {
2374 newcon->flags |= CON_CONSDEV;
2375 preferred_console = selected_console;
2380 if (!(newcon->flags & CON_ENABLED))
2384 * If we have a bootconsole, and are switching to a real console,
2385 * don't print everything out again, since when the boot console, and
2386 * the real console are the same physical device, it's annoying to
2387 * see the beginning boot messages twice
2389 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2390 newcon->flags &= ~CON_PRINTBUFFER;
2393 * Put this console in the list - keep the
2394 * preferred driver at the head of the list.
2397 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2398 newcon->next = console_drivers;
2399 console_drivers = newcon;
2401 newcon->next->flags &= ~CON_CONSDEV;
2403 newcon->next = console_drivers->next;
2404 console_drivers->next = newcon;
2406 if (newcon->flags & CON_PRINTBUFFER) {
2408 * console_unlock(); will print out the buffered messages
2411 raw_spin_lock_irqsave(&logbuf_lock, flags);
2412 console_seq = syslog_seq;
2413 console_idx = syslog_idx;
2414 console_prev = syslog_prev;
2415 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2417 * We're about to replay the log buffer. Only do this to the
2418 * just-registered console to avoid excessive message spam to
2419 * the already-registered consoles.
2421 exclusive_console = newcon;
2424 console_sysfs_notify();
2427 * By unregistering the bootconsoles after we enable the real console
2428 * we get the "console xxx enabled" message on all the consoles -
2429 * boot consoles, real consoles, etc - this is to ensure that end
2430 * users know there might be something in the kernel's log buffer that
2431 * went to the bootconsole (that they do not see on the real console)
2433 pr_info("%sconsole [%s%d] enabled\n",
2434 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2435 newcon->name, newcon->index);
2437 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2439 /* We need to iterate through all boot consoles, to make
2440 * sure we print everything out, before we unregister them.
2442 for_each_console(bcon)
2443 if (bcon->flags & CON_BOOT)
2444 unregister_console(bcon);
2447 EXPORT_SYMBOL(register_console);
2449 int unregister_console(struct console *console)
2451 struct console *a, *b;
2454 pr_info("%sconsole [%s%d] disabled\n",
2455 (console->flags & CON_BOOT) ? "boot" : "" ,
2456 console->name, console->index);
2458 res = _braille_unregister_console(console);
2464 if (console_drivers == console) {
2465 console_drivers=console->next;
2467 } else if (console_drivers) {
2468 for (a=console_drivers->next, b=console_drivers ;
2469 a; b=a, a=b->next) {
2479 * If this isn't the last console and it has CON_CONSDEV set, we
2480 * need to set it on the next preferred console.
2482 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2483 console_drivers->flags |= CON_CONSDEV;
2485 console->flags &= ~CON_ENABLED;
2487 console_sysfs_notify();
2490 EXPORT_SYMBOL(unregister_console);
2492 static int __init printk_late_init(void)
2494 struct console *con;
2496 for_each_console(con) {
2497 if (!keep_bootcon && con->flags & CON_BOOT) {
2498 unregister_console(con);
2501 hotcpu_notifier(console_cpu_notify, 0);
2504 late_initcall(printk_late_init);
2506 #if defined CONFIG_PRINTK
2508 * Delayed printk version, for scheduler-internal messages:
2510 #define PRINTK_BUF_SIZE 512
2512 #define PRINTK_PENDING_WAKEUP 0x01
2513 #define PRINTK_PENDING_SCHED 0x02
2515 static DEFINE_PER_CPU(int, printk_pending);
2516 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
2518 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2520 int pending = __this_cpu_xchg(printk_pending, 0);
2522 if (pending & PRINTK_PENDING_SCHED) {
2523 char *buf = __get_cpu_var(printk_sched_buf);
2524 pr_warn("[sched_delayed] %s", buf);
2527 if (pending & PRINTK_PENDING_WAKEUP)
2528 wake_up_interruptible(&log_wait);
2531 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2532 .func = wake_up_klogd_work_func,
2533 .flags = IRQ_WORK_LAZY,
2536 void wake_up_klogd(void)
2539 if (waitqueue_active(&log_wait)) {
2540 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2541 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2546 int printk_sched(const char *fmt, ...)
2548 unsigned long flags;
2553 local_irq_save(flags);
2554 buf = __get_cpu_var(printk_sched_buf);
2556 va_start(args, fmt);
2557 r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2560 __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2561 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2562 local_irq_restore(flags);
2568 * printk rate limiting, lifted from the networking subsystem.
2570 * This enforces a rate limit: not more than 10 kernel messages
2571 * every 5s to make a denial-of-service attack impossible.
2573 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2575 int __printk_ratelimit(const char *func)
2577 return ___ratelimit(&printk_ratelimit_state, func);
2579 EXPORT_SYMBOL(__printk_ratelimit);
2582 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2583 * @caller_jiffies: pointer to caller's state
2584 * @interval_msecs: minimum interval between prints
2586 * printk_timed_ratelimit() returns true if more than @interval_msecs
2587 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2590 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2591 unsigned int interval_msecs)
2593 if (*caller_jiffies == 0
2594 || !time_in_range(jiffies, *caller_jiffies,
2596 + msecs_to_jiffies(interval_msecs))) {
2597 *caller_jiffies = jiffies;
2602 EXPORT_SYMBOL(printk_timed_ratelimit);
2604 static DEFINE_SPINLOCK(dump_list_lock);
2605 static LIST_HEAD(dump_list);
2608 * kmsg_dump_register - register a kernel log dumper.
2609 * @dumper: pointer to the kmsg_dumper structure
2611 * Adds a kernel log dumper to the system. The dump callback in the
2612 * structure will be called when the kernel oopses or panics and must be
2613 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2615 int kmsg_dump_register(struct kmsg_dumper *dumper)
2617 unsigned long flags;
2620 /* The dump callback needs to be set */
2624 spin_lock_irqsave(&dump_list_lock, flags);
2625 /* Don't allow registering multiple times */
2626 if (!dumper->registered) {
2627 dumper->registered = 1;
2628 list_add_tail_rcu(&dumper->list, &dump_list);
2631 spin_unlock_irqrestore(&dump_list_lock, flags);
2635 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2638 * kmsg_dump_unregister - unregister a kmsg dumper.
2639 * @dumper: pointer to the kmsg_dumper structure
2641 * Removes a dump device from the system. Returns zero on success and
2642 * %-EINVAL otherwise.
2644 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2646 unsigned long flags;
2649 spin_lock_irqsave(&dump_list_lock, flags);
2650 if (dumper->registered) {
2651 dumper->registered = 0;
2652 list_del_rcu(&dumper->list);
2655 spin_unlock_irqrestore(&dump_list_lock, flags);
2660 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2662 static bool always_kmsg_dump;
2663 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2666 * kmsg_dump - dump kernel log to kernel message dumpers.
2667 * @reason: the reason (oops, panic etc) for dumping
2669 * Call each of the registered dumper's dump() callback, which can
2670 * retrieve the kmsg records with kmsg_dump_get_line() or
2671 * kmsg_dump_get_buffer().
2673 void kmsg_dump(enum kmsg_dump_reason reason)
2675 struct kmsg_dumper *dumper;
2676 unsigned long flags;
2678 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2682 list_for_each_entry_rcu(dumper, &dump_list, list) {
2683 if (dumper->max_reason && reason > dumper->max_reason)
2686 /* initialize iterator with data about the stored records */
2687 dumper->active = true;
2689 raw_spin_lock_irqsave(&logbuf_lock, flags);
2690 dumper->cur_seq = clear_seq;
2691 dumper->cur_idx = clear_idx;
2692 dumper->next_seq = log_next_seq;
2693 dumper->next_idx = log_next_idx;
2694 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2696 /* invoke dumper which will iterate over records */
2697 dumper->dump(dumper, reason);
2699 /* reset iterator */
2700 dumper->active = false;
2706 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2707 * @dumper: registered kmsg dumper
2708 * @syslog: include the "<4>" prefixes
2709 * @line: buffer to copy the line to
2710 * @size: maximum size of the buffer
2711 * @len: length of line placed into buffer
2713 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2714 * record, and copy one record into the provided buffer.
2716 * Consecutive calls will return the next available record moving
2717 * towards the end of the buffer with the youngest messages.
2719 * A return value of FALSE indicates that there are no more records to
2722 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2724 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2725 char *line, size_t size, size_t *len)
2727 struct printk_log *msg;
2731 if (!dumper->active)
2734 if (dumper->cur_seq < log_first_seq) {
2735 /* messages are gone, move to first available one */
2736 dumper->cur_seq = log_first_seq;
2737 dumper->cur_idx = log_first_idx;
2741 if (dumper->cur_seq >= log_next_seq)
2744 msg = log_from_idx(dumper->cur_idx);
2745 l = msg_print_text(msg, 0, syslog, line, size);
2747 dumper->cur_idx = log_next(dumper->cur_idx);
2757 * kmsg_dump_get_line - retrieve one kmsg log line
2758 * @dumper: registered kmsg dumper
2759 * @syslog: include the "<4>" prefixes
2760 * @line: buffer to copy the line to
2761 * @size: maximum size of the buffer
2762 * @len: length of line placed into buffer
2764 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2765 * record, and copy one record into the provided buffer.
2767 * Consecutive calls will return the next available record moving
2768 * towards the end of the buffer with the youngest messages.
2770 * A return value of FALSE indicates that there are no more records to
2773 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2774 char *line, size_t size, size_t *len)
2776 unsigned long flags;
2779 raw_spin_lock_irqsave(&logbuf_lock, flags);
2780 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2781 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2785 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2788 * kmsg_dump_get_buffer - copy kmsg log lines
2789 * @dumper: registered kmsg dumper
2790 * @syslog: include the "<4>" prefixes
2791 * @buf: buffer to copy the line to
2792 * @size: maximum size of the buffer
2793 * @len: length of line placed into buffer
2795 * Start at the end of the kmsg buffer and fill the provided buffer
2796 * with as many of the the *youngest* kmsg records that fit into it.
2797 * If the buffer is large enough, all available kmsg records will be
2798 * copied with a single call.
2800 * Consecutive calls will fill the buffer with the next block of
2801 * available older records, not including the earlier retrieved ones.
2803 * A return value of FALSE indicates that there are no more records to
2806 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2807 char *buf, size_t size, size_t *len)
2809 unsigned long flags;
2814 enum log_flags prev;
2818 if (!dumper->active)
2821 raw_spin_lock_irqsave(&logbuf_lock, flags);
2822 if (dumper->cur_seq < log_first_seq) {
2823 /* messages are gone, move to first available one */
2824 dumper->cur_seq = log_first_seq;
2825 dumper->cur_idx = log_first_idx;
2829 if (dumper->cur_seq >= dumper->next_seq) {
2830 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2834 /* calculate length of entire buffer */
2835 seq = dumper->cur_seq;
2836 idx = dumper->cur_idx;
2838 while (seq < dumper->next_seq) {
2839 struct printk_log *msg = log_from_idx(idx);
2841 l += msg_print_text(msg, prev, true, NULL, 0);
2842 idx = log_next(idx);
2847 /* move first record forward until length fits into the buffer */
2848 seq = dumper->cur_seq;
2849 idx = dumper->cur_idx;
2851 while (l > size && seq < dumper->next_seq) {
2852 struct printk_log *msg = log_from_idx(idx);
2854 l -= msg_print_text(msg, prev, true, NULL, 0);
2855 idx = log_next(idx);
2860 /* last message in next interation */
2865 while (seq < dumper->next_seq) {
2866 struct printk_log *msg = log_from_idx(idx);
2868 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2869 idx = log_next(idx);
2874 dumper->next_seq = next_seq;
2875 dumper->next_idx = next_idx;
2877 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2883 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2886 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2887 * @dumper: registered kmsg dumper
2889 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2890 * kmsg_dump_get_buffer() can be called again and used multiple
2891 * times within the same dumper.dump() callback.
2893 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2895 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
2897 dumper->cur_seq = clear_seq;
2898 dumper->cur_idx = clear_idx;
2899 dumper->next_seq = log_next_seq;
2900 dumper->next_idx = log_next_idx;
2904 * kmsg_dump_rewind - reset the interator
2905 * @dumper: registered kmsg dumper
2907 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2908 * kmsg_dump_get_buffer() can be called again and used multiple
2909 * times within the same dumper.dump() callback.
2911 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2913 unsigned long flags;
2915 raw_spin_lock_irqsave(&logbuf_lock, flags);
2916 kmsg_dump_rewind_nolock(dumper);
2917 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2919 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
2921 static char dump_stack_arch_desc_str[128];
2924 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
2925 * @fmt: printf-style format string
2926 * @...: arguments for the format string
2928 * The configured string will be printed right after utsname during task
2929 * dumps. Usually used to add arch-specific system identifiers. If an
2930 * arch wants to make use of such an ID string, it should initialize this
2931 * as soon as possible during boot.
2933 void __init dump_stack_set_arch_desc(const char *fmt, ...)
2937 va_start(args, fmt);
2938 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
2944 * dump_stack_print_info - print generic debug info for dump_stack()
2945 * @log_lvl: log level
2947 * Arch-specific dump_stack() implementations can use this function to
2948 * print out the same debug information as the generic dump_stack().
2950 void dump_stack_print_info(const char *log_lvl)
2952 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
2953 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
2954 print_tainted(), init_utsname()->release,
2955 (int)strcspn(init_utsname()->version, " "),
2956 init_utsname()->version);
2958 if (dump_stack_arch_desc_str[0] != '\0')
2959 printk("%sHardware name: %s\n",
2960 log_lvl, dump_stack_arch_desc_str);
2962 print_worker_info(log_lvl, current);
2966 * show_regs_print_info - print generic debug info for show_regs()
2967 * @log_lvl: log level
2969 * show_regs() implementations can use this function to print out generic
2970 * debug information.
2972 void show_regs_print_info(const char *log_lvl)
2974 dump_stack_print_info(log_lvl);
2976 printk("%stask: %p ti: %p task.ti: %p\n",
2977 log_lvl, current, current_thread_info(),
2978 task_thread_info(current));