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 /* cpu currently holding logbuf_lock */
253 static volatile unsigned int logbuf_cpu = UINT_MAX;
255 /* human readable text of the record */
256 static char *log_text(const struct printk_log *msg)
258 return (char *)msg + sizeof(struct printk_log);
261 /* optional key/value pair dictionary attached to the record */
262 static char *log_dict(const struct printk_log *msg)
264 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
267 /* get record by index; idx must point to valid msg */
268 static struct printk_log *log_from_idx(u32 idx)
270 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
273 * A length == 0 record is the end of buffer marker. Wrap around and
274 * read the message at the start of the buffer.
277 return (struct printk_log *)log_buf;
281 /* get next record; idx must point to valid msg */
282 static u32 log_next(u32 idx)
284 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
286 /* length == 0 indicates the end of the buffer; wrap */
288 * A length == 0 record is the end of buffer marker. Wrap around and
289 * read the message at the start of the buffer as *this* one, and
290 * return the one after that.
293 msg = (struct printk_log *)log_buf;
296 return idx + msg->len;
300 * Check whether there is enough free space for the given message.
302 * The same values of first_idx and next_idx mean that the buffer
303 * is either empty or full.
305 * If the buffer is empty, we must respect the position of the indexes.
306 * They cannot be reset to the beginning of the buffer.
308 static int logbuf_has_space(u32 msg_size, bool empty)
312 if (log_next_idx > log_first_idx || empty)
313 free = max(log_buf_len - log_next_idx, log_first_idx);
315 free = log_first_idx - log_next_idx;
318 * We need space also for an empty header that signalizes wrapping
321 return free >= msg_size + sizeof(struct printk_log);
324 static int log_make_free_space(u32 msg_size)
326 while (log_first_seq < log_next_seq) {
327 if (logbuf_has_space(msg_size, false))
329 /* drop old messages until we have enough continuous space */
330 log_first_idx = log_next(log_first_idx);
334 /* sequence numbers are equal, so the log buffer is empty */
335 if (logbuf_has_space(msg_size, true))
341 /* compute the message size including the padding bytes */
342 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
346 size = sizeof(struct printk_log) + text_len + dict_len;
347 *pad_len = (-size) & (LOG_ALIGN - 1);
354 * Define how much of the log buffer we could take at maximum. The value
355 * must be greater than two. Note that only half of the buffer is available
356 * when the index points to the middle.
358 #define MAX_LOG_TAKE_PART 4
359 static const char trunc_msg[] = "<truncated>";
361 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
362 u16 *dict_len, u32 *pad_len)
365 * The message should not take the whole buffer. Otherwise, it might
366 * get removed too soon.
368 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
369 if (*text_len > max_text_len)
370 *text_len = max_text_len;
371 /* enable the warning message */
372 *trunc_msg_len = strlen(trunc_msg);
373 /* disable the "dict" completely */
375 /* compute the size again, count also the warning message */
376 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
379 /* insert record into the buffer, discard old ones, update heads */
380 static int log_store(int facility, int level,
381 enum log_flags flags, u64 ts_nsec,
382 const char *dict, u16 dict_len,
383 const char *text, u16 text_len)
385 struct printk_log *msg;
387 u16 trunc_msg_len = 0;
389 /* number of '\0' padding bytes to next message */
390 size = msg_used_size(text_len, dict_len, &pad_len);
392 if (log_make_free_space(size)) {
393 /* truncate the message if it is too long for empty buffer */
394 size = truncate_msg(&text_len, &trunc_msg_len,
395 &dict_len, &pad_len);
396 /* survive when the log buffer is too small for trunc_msg */
397 if (log_make_free_space(size))
401 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
403 * This message + an additional empty header does not fit
404 * at the end of the buffer. Add an empty header with len == 0
405 * to signify a wrap around.
407 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
412 msg = (struct printk_log *)(log_buf + log_next_idx);
413 memcpy(log_text(msg), text, text_len);
414 msg->text_len = text_len;
416 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
417 msg->text_len += trunc_msg_len;
419 memcpy(log_dict(msg), dict, dict_len);
420 msg->dict_len = dict_len;
421 msg->facility = facility;
422 msg->level = level & 7;
423 msg->flags = flags & 0x1f;
425 msg->ts_nsec = ts_nsec;
427 msg->ts_nsec = local_clock();
428 memset(log_dict(msg) + dict_len, 0, pad_len);
432 log_next_idx += msg->len;
435 return msg->text_len;
438 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
439 int dmesg_restrict = 1;
444 static int syslog_action_restricted(int type)
449 * Unless restricted, we allow "read all" and "get buffer size"
452 return type != SYSLOG_ACTION_READ_ALL &&
453 type != SYSLOG_ACTION_SIZE_BUFFER;
456 static int check_syslog_permissions(int type, bool from_file)
459 * If this is from /proc/kmsg and we've already opened it, then we've
460 * already done the capabilities checks at open time.
462 if (from_file && type != SYSLOG_ACTION_OPEN)
465 if (syslog_action_restricted(type)) {
466 if (capable(CAP_SYSLOG))
469 * For historical reasons, accept CAP_SYS_ADMIN too, with
472 if (capable(CAP_SYS_ADMIN)) {
473 pr_warn_once("%s (%d): Attempt to access syslog with "
474 "CAP_SYS_ADMIN but no CAP_SYSLOG "
476 current->comm, task_pid_nr(current));
481 return security_syslog(type);
485 /* /dev/kmsg - userspace message inject/listen interface */
486 struct devkmsg_user {
494 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
495 unsigned long count, loff_t pos)
499 int level = default_message_loglevel;
500 int facility = 1; /* LOG_USER */
501 size_t len = iov_length(iv, count);
504 if (len > LOG_LINE_MAX)
506 buf = kmalloc(len+1, GFP_KERNEL);
511 for (i = 0; i < count; i++) {
512 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
516 line += iv[i].iov_len;
520 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
521 * the decimal value represents 32bit, the lower 3 bit are the log
522 * level, the rest are the log facility.
524 * If no prefix or no userspace facility is specified, we
525 * enforce LOG_USER, to be able to reliably distinguish
526 * kernel-generated messages from userspace-injected ones.
529 if (line[0] == '<') {
532 i = simple_strtoul(line+1, &endp, 10);
533 if (endp && endp[0] == '>') {
544 printk_emit(facility, level, NULL, 0, "%s", line);
550 static ssize_t devkmsg_read(struct file *file, char __user *buf,
551 size_t count, loff_t *ppos)
553 struct devkmsg_user *user = file->private_data;
554 struct printk_log *msg;
564 ret = mutex_lock_interruptible(&user->lock);
567 raw_spin_lock_irq(&logbuf_lock);
568 while (user->seq == log_next_seq) {
569 if (file->f_flags & O_NONBLOCK) {
571 raw_spin_unlock_irq(&logbuf_lock);
575 raw_spin_unlock_irq(&logbuf_lock);
576 ret = wait_event_interruptible(log_wait,
577 user->seq != log_next_seq);
580 raw_spin_lock_irq(&logbuf_lock);
583 if (user->seq < log_first_seq) {
584 /* our last seen message is gone, return error and reset */
585 user->idx = log_first_idx;
586 user->seq = log_first_seq;
588 raw_spin_unlock_irq(&logbuf_lock);
592 msg = log_from_idx(user->idx);
593 ts_usec = msg->ts_nsec;
594 do_div(ts_usec, 1000);
597 * If we couldn't merge continuation line fragments during the print,
598 * export the stored flags to allow an optional external merge of the
599 * records. Merging the records isn't always neccessarily correct, like
600 * when we hit a race during printing. In most cases though, it produces
601 * better readable output. 'c' in the record flags mark the first
602 * fragment of a line, '+' the following.
604 if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
606 else if ((msg->flags & LOG_CONT) ||
607 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
610 len = sprintf(user->buf, "%u,%llu,%llu,%c;",
611 (msg->facility << 3) | msg->level,
612 user->seq, ts_usec, cont);
613 user->prev = msg->flags;
615 /* escape non-printable characters */
616 for (i = 0; i < msg->text_len; i++) {
617 unsigned char c = log_text(msg)[i];
619 if (c < ' ' || c >= 127 || c == '\\')
620 len += sprintf(user->buf + len, "\\x%02x", c);
622 user->buf[len++] = c;
624 user->buf[len++] = '\n';
629 for (i = 0; i < msg->dict_len; i++) {
630 unsigned char c = log_dict(msg)[i];
633 user->buf[len++] = ' ';
638 user->buf[len++] = '\n';
643 if (c < ' ' || c >= 127 || c == '\\') {
644 len += sprintf(user->buf + len, "\\x%02x", c);
648 user->buf[len++] = c;
650 user->buf[len++] = '\n';
653 user->idx = log_next(user->idx);
655 raw_spin_unlock_irq(&logbuf_lock);
662 if (copy_to_user(buf, user->buf, len)) {
668 mutex_unlock(&user->lock);
672 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
674 struct devkmsg_user *user = file->private_data;
682 raw_spin_lock_irq(&logbuf_lock);
685 /* the first record */
686 user->idx = log_first_idx;
687 user->seq = log_first_seq;
691 * The first record after the last SYSLOG_ACTION_CLEAR,
692 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
693 * changes no global state, and does not clear anything.
695 user->idx = clear_idx;
696 user->seq = clear_seq;
699 /* after the last record */
700 user->idx = log_next_idx;
701 user->seq = log_next_seq;
706 raw_spin_unlock_irq(&logbuf_lock);
710 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
712 struct devkmsg_user *user = file->private_data;
716 return POLLERR|POLLNVAL;
718 poll_wait(file, &log_wait, wait);
720 raw_spin_lock_irq(&logbuf_lock);
721 if (user->seq < log_next_seq) {
722 /* return error when data has vanished underneath us */
723 if (user->seq < log_first_seq)
724 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
726 ret = POLLIN|POLLRDNORM;
728 raw_spin_unlock_irq(&logbuf_lock);
733 static int devkmsg_open(struct inode *inode, struct file *file)
735 struct devkmsg_user *user;
738 /* write-only does not need any file context */
739 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
742 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
747 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
751 mutex_init(&user->lock);
753 raw_spin_lock_irq(&logbuf_lock);
754 user->idx = log_first_idx;
755 user->seq = log_first_seq;
756 raw_spin_unlock_irq(&logbuf_lock);
758 file->private_data = user;
762 static int devkmsg_release(struct inode *inode, struct file *file)
764 struct devkmsg_user *user = file->private_data;
769 mutex_destroy(&user->lock);
774 const struct file_operations kmsg_fops = {
775 .open = devkmsg_open,
776 .read = devkmsg_read,
777 .aio_write = devkmsg_writev,
778 .llseek = devkmsg_llseek,
779 .poll = devkmsg_poll,
780 .release = devkmsg_release,
785 * This appends the listed symbols to /proc/vmcore
787 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
788 * obtain access to symbols that are otherwise very difficult to locate. These
789 * symbols are specifically used so that utilities can access and extract the
790 * dmesg log from a vmcore file after a crash.
792 void log_buf_kexec_setup(void)
794 VMCOREINFO_SYMBOL(log_buf);
795 VMCOREINFO_SYMBOL(log_buf_len);
796 VMCOREINFO_SYMBOL(log_first_idx);
797 VMCOREINFO_SYMBOL(log_next_idx);
799 * Export struct printk_log size and field offsets. User space tools can
800 * parse it and detect any changes to structure down the line.
802 VMCOREINFO_STRUCT_SIZE(printk_log);
803 VMCOREINFO_OFFSET(printk_log, ts_nsec);
804 VMCOREINFO_OFFSET(printk_log, len);
805 VMCOREINFO_OFFSET(printk_log, text_len);
806 VMCOREINFO_OFFSET(printk_log, dict_len);
810 /* requested log_buf_len from kernel cmdline */
811 static unsigned long __initdata new_log_buf_len;
813 /* save requested log_buf_len since it's too early to process it */
814 static int __init log_buf_len_setup(char *str)
816 unsigned size = memparse(str, &str);
819 size = roundup_pow_of_two(size);
820 if (size > log_buf_len)
821 new_log_buf_len = size;
825 early_param("log_buf_len", log_buf_len_setup);
827 void __init setup_log_buf(int early)
833 if (!new_log_buf_len)
838 memblock_virt_alloc(new_log_buf_len, PAGE_SIZE);
840 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len, 0);
843 if (unlikely(!new_log_buf)) {
844 pr_err("log_buf_len: %ld bytes not available\n",
849 raw_spin_lock_irqsave(&logbuf_lock, flags);
850 log_buf_len = new_log_buf_len;
851 log_buf = new_log_buf;
853 free = __LOG_BUF_LEN - log_next_idx;
854 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
855 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
857 pr_info("log_buf_len: %d\n", log_buf_len);
858 pr_info("early log buf free: %d(%d%%)\n",
859 free, (free * 100) / __LOG_BUF_LEN);
862 static bool __read_mostly ignore_loglevel;
864 static int __init ignore_loglevel_setup(char *str)
867 pr_info("debug: ignoring loglevel setting.\n");
872 early_param("ignore_loglevel", ignore_loglevel_setup);
873 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
874 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
875 "print all kernel messages to the console.");
877 #ifdef CONFIG_BOOT_PRINTK_DELAY
879 static int boot_delay; /* msecs delay after each printk during bootup */
880 static unsigned long long loops_per_msec; /* based on boot_delay */
882 static int __init boot_delay_setup(char *str)
886 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
887 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
889 get_option(&str, &boot_delay);
890 if (boot_delay > 10 * 1000)
893 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
894 "HZ: %d, loops_per_msec: %llu\n",
895 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
898 early_param("boot_delay", boot_delay_setup);
900 static void boot_delay_msec(int level)
902 unsigned long long k;
903 unsigned long timeout;
905 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
906 || (level >= console_loglevel && !ignore_loglevel)) {
910 k = (unsigned long long)loops_per_msec * boot_delay;
912 timeout = jiffies + msecs_to_jiffies(boot_delay);
917 * use (volatile) jiffies to prevent
918 * compiler reduction; loop termination via jiffies
919 * is secondary and may or may not happen.
921 if (time_after(jiffies, timeout))
923 touch_nmi_watchdog();
927 static inline void boot_delay_msec(int level)
932 #if defined(CONFIG_PRINTK_TIME)
933 static bool printk_time = 1;
935 static bool printk_time;
937 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
939 static size_t print_time(u64 ts, char *buf)
941 unsigned long rem_nsec;
946 rem_nsec = do_div(ts, 1000000000);
949 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
951 return sprintf(buf, "[%5lu.%06lu] ",
952 (unsigned long)ts, rem_nsec / 1000);
955 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
958 unsigned int prefix = (msg->facility << 3) | msg->level;
962 len += sprintf(buf, "<%u>", prefix);
967 else if (prefix > 99)
974 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
978 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
979 bool syslog, char *buf, size_t size)
981 const char *text = log_text(msg);
982 size_t text_size = msg->text_len;
987 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
990 if (msg->flags & LOG_CONT) {
991 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
994 if (!(msg->flags & LOG_NEWLINE))
999 const char *next = memchr(text, '\n', text_size);
1003 text_len = next - text;
1005 text_size -= next - text;
1007 text_len = text_size;
1011 if (print_prefix(msg, syslog, NULL) +
1012 text_len + 1 >= size - len)
1016 len += print_prefix(msg, syslog, buf + len);
1017 memcpy(buf + len, text, text_len);
1019 if (next || newline)
1022 /* SYSLOG_ACTION_* buffer size only calculation */
1024 len += print_prefix(msg, syslog, NULL);
1026 if (next || newline)
1037 static int syslog_print(char __user *buf, int size)
1040 struct printk_log *msg;
1043 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1051 raw_spin_lock_irq(&logbuf_lock);
1052 if (syslog_seq < log_first_seq) {
1053 /* messages are gone, move to first one */
1054 syslog_seq = log_first_seq;
1055 syslog_idx = log_first_idx;
1059 if (syslog_seq == log_next_seq) {
1060 raw_spin_unlock_irq(&logbuf_lock);
1064 skip = syslog_partial;
1065 msg = log_from_idx(syslog_idx);
1066 n = msg_print_text(msg, syslog_prev, true, text,
1067 LOG_LINE_MAX + PREFIX_MAX);
1068 if (n - syslog_partial <= size) {
1069 /* message fits into buffer, move forward */
1070 syslog_idx = log_next(syslog_idx);
1072 syslog_prev = msg->flags;
1073 n -= syslog_partial;
1076 /* partial read(), remember position */
1078 syslog_partial += n;
1081 raw_spin_unlock_irq(&logbuf_lock);
1086 if (copy_to_user(buf, text + skip, n)) {
1101 static int syslog_print_all(char __user *buf, int size, bool clear)
1106 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1110 raw_spin_lock_irq(&logbuf_lock);
1115 enum log_flags prev;
1117 if (clear_seq < log_first_seq) {
1118 /* messages are gone, move to first available one */
1119 clear_seq = log_first_seq;
1120 clear_idx = log_first_idx;
1124 * Find first record that fits, including all following records,
1125 * into the user-provided buffer for this dump.
1130 while (seq < log_next_seq) {
1131 struct printk_log *msg = log_from_idx(idx);
1133 len += msg_print_text(msg, prev, true, NULL, 0);
1135 idx = log_next(idx);
1139 /* move first record forward until length fits into the buffer */
1143 while (len > size && seq < log_next_seq) {
1144 struct printk_log *msg = log_from_idx(idx);
1146 len -= msg_print_text(msg, prev, true, NULL, 0);
1148 idx = log_next(idx);
1152 /* last message fitting into this dump */
1153 next_seq = log_next_seq;
1156 while (len >= 0 && seq < next_seq) {
1157 struct printk_log *msg = log_from_idx(idx);
1160 textlen = msg_print_text(msg, prev, true, text,
1161 LOG_LINE_MAX + PREFIX_MAX);
1166 idx = log_next(idx);
1170 raw_spin_unlock_irq(&logbuf_lock);
1171 if (copy_to_user(buf + len, text, textlen))
1175 raw_spin_lock_irq(&logbuf_lock);
1177 if (seq < log_first_seq) {
1178 /* messages are gone, move to next one */
1179 seq = log_first_seq;
1180 idx = log_first_idx;
1187 clear_seq = log_next_seq;
1188 clear_idx = log_next_idx;
1190 raw_spin_unlock_irq(&logbuf_lock);
1196 int do_syslog(int type, char __user *buf, int len, bool from_file)
1199 static int saved_console_loglevel = -1;
1202 error = check_syslog_permissions(type, from_file);
1206 error = security_syslog(type);
1211 case SYSLOG_ACTION_CLOSE: /* Close log */
1213 case SYSLOG_ACTION_OPEN: /* Open log */
1215 case SYSLOG_ACTION_READ: /* Read from log */
1217 if (!buf || len < 0)
1222 if (!access_ok(VERIFY_WRITE, buf, len)) {
1226 error = wait_event_interruptible(log_wait,
1227 syslog_seq != log_next_seq);
1230 error = syslog_print(buf, len);
1232 /* Read/clear last kernel messages */
1233 case SYSLOG_ACTION_READ_CLEAR:
1236 /* Read last kernel messages */
1237 case SYSLOG_ACTION_READ_ALL:
1239 if (!buf || len < 0)
1244 if (!access_ok(VERIFY_WRITE, buf, len)) {
1248 error = syslog_print_all(buf, len, clear);
1250 /* Clear ring buffer */
1251 case SYSLOG_ACTION_CLEAR:
1252 syslog_print_all(NULL, 0, true);
1254 /* Disable logging to console */
1255 case SYSLOG_ACTION_CONSOLE_OFF:
1256 if (saved_console_loglevel == -1)
1257 saved_console_loglevel = console_loglevel;
1258 console_loglevel = minimum_console_loglevel;
1260 /* Enable logging to console */
1261 case SYSLOG_ACTION_CONSOLE_ON:
1262 if (saved_console_loglevel != -1) {
1263 console_loglevel = saved_console_loglevel;
1264 saved_console_loglevel = -1;
1267 /* Set level of messages printed to console */
1268 case SYSLOG_ACTION_CONSOLE_LEVEL:
1270 if (len < 1 || len > 8)
1272 if (len < minimum_console_loglevel)
1273 len = minimum_console_loglevel;
1274 console_loglevel = len;
1275 /* Implicitly re-enable logging to console */
1276 saved_console_loglevel = -1;
1279 /* Number of chars in the log buffer */
1280 case SYSLOG_ACTION_SIZE_UNREAD:
1281 raw_spin_lock_irq(&logbuf_lock);
1282 if (syslog_seq < log_first_seq) {
1283 /* messages are gone, move to first one */
1284 syslog_seq = log_first_seq;
1285 syslog_idx = log_first_idx;
1291 * Short-cut for poll(/"proc/kmsg") which simply checks
1292 * for pending data, not the size; return the count of
1293 * records, not the length.
1295 error = log_next_idx - syslog_idx;
1297 u64 seq = syslog_seq;
1298 u32 idx = syslog_idx;
1299 enum log_flags prev = syslog_prev;
1302 while (seq < log_next_seq) {
1303 struct printk_log *msg = log_from_idx(idx);
1305 error += msg_print_text(msg, prev, true, NULL, 0);
1306 idx = log_next(idx);
1310 error -= syslog_partial;
1312 raw_spin_unlock_irq(&logbuf_lock);
1314 /* Size of the log buffer */
1315 case SYSLOG_ACTION_SIZE_BUFFER:
1316 error = log_buf_len;
1326 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1328 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1332 * Call the console drivers, asking them to write out
1333 * log_buf[start] to log_buf[end - 1].
1334 * The console_lock must be held.
1336 static void call_console_drivers(int level, const char *text, size_t len)
1338 struct console *con;
1340 trace_console(text, len);
1342 if (level >= console_loglevel && !ignore_loglevel)
1344 if (!console_drivers)
1347 for_each_console(con) {
1348 if (exclusive_console && con != exclusive_console)
1350 if (!(con->flags & CON_ENABLED))
1354 if (!cpu_online(smp_processor_id()) &&
1355 !(con->flags & CON_ANYTIME))
1357 con->write(con, text, len);
1362 * Zap console related locks when oopsing. Only zap at most once
1363 * every 10 seconds, to leave time for slow consoles to print a
1366 static void zap_locks(void)
1368 static unsigned long oops_timestamp;
1370 if (time_after_eq(jiffies, oops_timestamp) &&
1371 !time_after(jiffies, oops_timestamp + 30 * HZ))
1374 oops_timestamp = jiffies;
1377 /* If a crash is occurring, make sure we can't deadlock */
1378 raw_spin_lock_init(&logbuf_lock);
1379 /* And make sure that we print immediately */
1380 sema_init(&console_sem, 1);
1383 /* Check if we have any console registered that can be called early in boot. */
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 * This gets called with the 'logbuf_lock' spinlock held and
1415 * interrupts disabled. It should return with 'lockbuf_lock'
1416 * released but interrupts still disabled.
1418 static int console_trylock_for_printk(unsigned int cpu)
1419 __releases(&logbuf_lock)
1421 int retval = 0, wake = 0;
1423 if (console_trylock()) {
1427 * If we can't use the console, we need to release
1428 * the console semaphore by hand to avoid flushing
1429 * the buffer. We need to hold the console semaphore
1430 * in order to do this test safely.
1432 if (!can_use_console(cpu)) {
1438 logbuf_cpu = UINT_MAX;
1439 raw_spin_unlock(&logbuf_lock);
1445 int printk_delay_msec __read_mostly;
1447 static inline void printk_delay(void)
1449 if (unlikely(printk_delay_msec)) {
1450 int m = printk_delay_msec;
1454 touch_nmi_watchdog();
1460 * Continuation lines are buffered, and not committed to the record buffer
1461 * until the line is complete, or a race forces it. The line fragments
1462 * though, are printed immediately to the consoles to ensure everything has
1463 * reached the console in case of a kernel crash.
1465 static struct cont {
1466 char buf[LOG_LINE_MAX];
1467 size_t len; /* length == 0 means unused buffer */
1468 size_t cons; /* bytes written to console */
1469 struct task_struct *owner; /* task of first print*/
1470 u64 ts_nsec; /* time of first print */
1471 u8 level; /* log level of first message */
1472 u8 facility; /* log level of first message */
1473 enum log_flags flags; /* prefix, newline flags */
1474 bool flushed:1; /* buffer sealed and committed */
1477 static void cont_flush(enum log_flags flags)
1486 * If a fragment of this line was directly flushed to the
1487 * console; wait for the console to pick up the rest of the
1488 * line. LOG_NOCONS suppresses a duplicated output.
1490 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1491 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1493 cont.flushed = true;
1496 * If no fragment of this line ever reached the console,
1497 * just submit it to the store and free the buffer.
1499 log_store(cont.facility, cont.level, flags, 0,
1500 NULL, 0, cont.buf, cont.len);
1505 static bool cont_add(int facility, int level, const char *text, size_t len)
1507 if (cont.len && cont.flushed)
1510 if (cont.len + len > sizeof(cont.buf)) {
1511 /* the line gets too long, split it up in separate records */
1512 cont_flush(LOG_CONT);
1517 cont.facility = facility;
1519 cont.owner = current;
1520 cont.ts_nsec = local_clock();
1523 cont.flushed = false;
1526 memcpy(cont.buf + cont.len, text, len);
1529 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1530 cont_flush(LOG_CONT);
1535 static size_t cont_print_text(char *text, size_t size)
1540 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1541 textlen += print_time(cont.ts_nsec, text);
1545 len = cont.len - cont.cons;
1549 memcpy(text + textlen, cont.buf + cont.cons, len);
1551 cont.cons = cont.len;
1555 if (cont.flags & LOG_NEWLINE)
1556 text[textlen++] = '\n';
1557 /* got everything, release buffer */
1563 asmlinkage int vprintk_emit(int facility, int level,
1564 const char *dict, size_t dictlen,
1565 const char *fmt, va_list args)
1567 static int recursion_bug;
1568 static char textbuf[LOG_LINE_MAX];
1569 char *text = textbuf;
1571 enum log_flags lflags = 0;
1572 unsigned long flags;
1574 int printed_len = 0;
1576 boot_delay_msec(level);
1579 /* This stops the holder of console_sem just where we want him */
1580 local_irq_save(flags);
1581 this_cpu = smp_processor_id();
1584 * Ouch, printk recursed into itself!
1586 if (unlikely(logbuf_cpu == this_cpu)) {
1588 * If a crash is occurring during printk() on this CPU,
1589 * then try to get the crash message out but make sure
1590 * we can't deadlock. Otherwise just return to avoid the
1591 * recursion and return - but flag the recursion so that
1592 * it can be printed at the next appropriate moment:
1594 if (!oops_in_progress && !lockdep_recursing(current)) {
1596 goto out_restore_irqs;
1602 raw_spin_lock(&logbuf_lock);
1603 logbuf_cpu = this_cpu;
1605 if (recursion_bug) {
1606 static const char recursion_msg[] =
1607 "BUG: recent printk recursion!";
1610 text_len = strlen(recursion_msg);
1611 /* emit KERN_CRIT message */
1612 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1613 NULL, 0, recursion_msg, text_len);
1617 * The printf needs to come first; we need the syslog
1618 * prefix which might be passed-in as a parameter.
1620 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1622 /* mark and strip a trailing newline */
1623 if (text_len && text[text_len-1] == '\n') {
1625 lflags |= LOG_NEWLINE;
1628 /* strip kernel syslog prefix and extract log level or control flags */
1629 if (facility == 0) {
1630 int kern_level = printk_get_level(text);
1633 const char *end_of_header = printk_skip_level(text);
1634 switch (kern_level) {
1637 level = kern_level - '0';
1638 case 'd': /* KERN_DEFAULT */
1639 lflags |= LOG_PREFIX;
1642 * No need to check length here because vscnprintf
1643 * put '\0' at the end of the string. Only valid and
1644 * newly printed level is detected.
1646 text_len -= end_of_header - text;
1647 text = (char *)end_of_header;
1652 level = default_message_loglevel;
1655 lflags |= LOG_PREFIX|LOG_NEWLINE;
1657 if (!(lflags & LOG_NEWLINE)) {
1659 * Flush the conflicting buffer. An earlier newline was missing,
1660 * or another task also prints continuation lines.
1662 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1663 cont_flush(LOG_NEWLINE);
1665 /* buffer line if possible, otherwise store it right away */
1666 if (cont_add(facility, level, text, text_len))
1667 printed_len += text_len;
1669 printed_len += log_store(facility, level,
1670 lflags | LOG_CONT, 0,
1671 dict, dictlen, text, text_len);
1673 bool stored = false;
1676 * If an earlier newline was missing and it was the same task,
1677 * either merge it with the current buffer and flush, or if
1678 * there was a race with interrupts (prefix == true) then just
1679 * flush it out and store this line separately.
1680 * If the preceding printk was from a different task and missed
1681 * a newline, flush and append the newline.
1684 if (cont.owner == current && !(lflags & LOG_PREFIX))
1685 stored = cont_add(facility, level, text,
1687 cont_flush(LOG_NEWLINE);
1691 printed_len += text_len;
1693 printed_len += log_store(facility, level, lflags, 0,
1694 dict, dictlen, text, text_len);
1698 * Try to acquire and then immediately release the console semaphore.
1699 * The release will print out buffers and wake up /dev/kmsg and syslog()
1702 * The console_trylock_for_printk() function will release 'logbuf_lock'
1703 * regardless of whether it actually gets the console semaphore or not.
1705 if (console_trylock_for_printk(this_cpu))
1710 local_irq_restore(flags);
1714 EXPORT_SYMBOL(vprintk_emit);
1716 asmlinkage int vprintk(const char *fmt, va_list args)
1718 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1720 EXPORT_SYMBOL(vprintk);
1722 asmlinkage int printk_emit(int facility, int level,
1723 const char *dict, size_t dictlen,
1724 const char *fmt, ...)
1729 va_start(args, fmt);
1730 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1735 EXPORT_SYMBOL(printk_emit);
1738 * printk - print a kernel message
1739 * @fmt: format string
1741 * This is printk(). It can be called from any context. We want it to work.
1743 * We try to grab the console_lock. If we succeed, it's easy - we log the
1744 * output and call the console drivers. If we fail to get the semaphore, we
1745 * place the output into the log buffer and return. The current holder of
1746 * the console_sem will notice the new output in console_unlock(); and will
1747 * send it to the consoles before releasing the lock.
1749 * One effect of this deferred printing is that code which calls printk() and
1750 * then changes console_loglevel may break. This is because console_loglevel
1751 * is inspected when the actual printing occurs.
1756 * See the vsnprintf() documentation for format string extensions over C99.
1758 asmlinkage __visible int printk(const char *fmt, ...)
1763 #ifdef CONFIG_KGDB_KDB
1764 if (unlikely(kdb_trap_printk)) {
1765 va_start(args, fmt);
1766 r = vkdb_printf(fmt, args);
1771 va_start(args, fmt);
1772 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1777 EXPORT_SYMBOL(printk);
1779 #else /* CONFIG_PRINTK */
1781 #define LOG_LINE_MAX 0
1782 #define PREFIX_MAX 0
1783 #define LOG_LINE_MAX 0
1784 static u64 syslog_seq;
1785 static u32 syslog_idx;
1786 static u64 console_seq;
1787 static u32 console_idx;
1788 static enum log_flags syslog_prev;
1789 static u64 log_first_seq;
1790 static u32 log_first_idx;
1791 static u64 log_next_seq;
1792 static enum log_flags console_prev;
1793 static struct cont {
1799 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1800 static u32 log_next(u32 idx) { return 0; }
1801 static void call_console_drivers(int level, const char *text, size_t len) {}
1802 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1803 bool syslog, char *buf, size_t size) { return 0; }
1804 static size_t cont_print_text(char *text, size_t size) { return 0; }
1806 #endif /* CONFIG_PRINTK */
1808 #ifdef CONFIG_EARLY_PRINTK
1809 struct console *early_console;
1811 void early_vprintk(const char *fmt, va_list ap)
1813 if (early_console) {
1815 int n = vscnprintf(buf, sizeof(buf), fmt, ap);
1817 early_console->write(early_console, buf, n);
1821 asmlinkage __visible void early_printk(const char *fmt, ...)
1826 early_vprintk(fmt, ap);
1831 static int __add_preferred_console(char *name, int idx, char *options,
1834 struct console_cmdline *c;
1838 * See if this tty is not yet registered, and
1839 * if we have a slot free.
1841 for (i = 0, c = console_cmdline;
1842 i < MAX_CMDLINECONSOLES && c->name[0];
1844 if (strcmp(c->name, name) == 0 && c->index == idx) {
1846 selected_console = i;
1850 if (i == MAX_CMDLINECONSOLES)
1853 selected_console = i;
1854 strlcpy(c->name, name, sizeof(c->name));
1855 c->options = options;
1856 braille_set_options(c, brl_options);
1862 * Set up a list of consoles. Called from init/main.c
1864 static int __init console_setup(char *str)
1866 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1867 char *s, *options, *brl_options = NULL;
1870 if (_braille_console_setup(&str, &brl_options))
1874 * Decode str into name, index, options.
1876 if (str[0] >= '0' && str[0] <= '9') {
1877 strcpy(buf, "ttyS");
1878 strncpy(buf + 4, str, sizeof(buf) - 5);
1880 strncpy(buf, str, sizeof(buf) - 1);
1882 buf[sizeof(buf) - 1] = 0;
1883 if ((options = strchr(str, ',')) != NULL)
1886 if (!strcmp(str, "ttya"))
1887 strcpy(buf, "ttyS0");
1888 if (!strcmp(str, "ttyb"))
1889 strcpy(buf, "ttyS1");
1891 for (s = buf; *s; s++)
1892 if ((*s >= '0' && *s <= '9') || *s == ',')
1894 idx = simple_strtoul(s, NULL, 10);
1897 __add_preferred_console(buf, idx, options, brl_options);
1898 console_set_on_cmdline = 1;
1901 __setup("console=", console_setup);
1904 * add_preferred_console - add a device to the list of preferred consoles.
1905 * @name: device name
1906 * @idx: device index
1907 * @options: options for this console
1909 * The last preferred console added will be used for kernel messages
1910 * and stdin/out/err for init. Normally this is used by console_setup
1911 * above to handle user-supplied console arguments; however it can also
1912 * be used by arch-specific code either to override the user or more
1913 * commonly to provide a default console (ie from PROM variables) when
1914 * the user has not supplied one.
1916 int add_preferred_console(char *name, int idx, char *options)
1918 return __add_preferred_console(name, idx, options, NULL);
1921 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1923 struct console_cmdline *c;
1926 for (i = 0, c = console_cmdline;
1927 i < MAX_CMDLINECONSOLES && c->name[0];
1929 if (strcmp(c->name, name) == 0 && c->index == idx) {
1930 strlcpy(c->name, name_new, sizeof(c->name));
1931 c->name[sizeof(c->name) - 1] = 0;
1932 c->options = options;
1940 bool console_suspend_enabled = 1;
1941 EXPORT_SYMBOL(console_suspend_enabled);
1943 static int __init console_suspend_disable(char *str)
1945 console_suspend_enabled = 0;
1948 __setup("no_console_suspend", console_suspend_disable);
1949 module_param_named(console_suspend, console_suspend_enabled,
1950 bool, S_IRUGO | S_IWUSR);
1951 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1952 " and hibernate operations");
1955 * suspend_console - suspend the console subsystem
1957 * This disables printk() while we go into suspend states
1959 void suspend_console(void)
1961 if (!console_suspend_enabled)
1963 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1965 console_suspended = 1;
1967 mutex_release(&console_lock_dep_map, 1, _RET_IP_);
1970 void resume_console(void)
1972 if (!console_suspend_enabled)
1975 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
1976 console_suspended = 0;
1981 * console_cpu_notify - print deferred console messages after CPU hotplug
1982 * @self: notifier struct
1983 * @action: CPU hotplug event
1986 * If printk() is called from a CPU that is not online yet, the messages
1987 * will be spooled but will not show up on the console. This function is
1988 * called when a new CPU comes online (or fails to come up), and ensures
1989 * that any such output gets printed.
1991 static int console_cpu_notify(struct notifier_block *self,
1992 unsigned long action, void *hcpu)
1997 case CPU_DOWN_FAILED:
1998 case CPU_UP_CANCELED:
2006 * console_lock - lock the console system for exclusive use.
2008 * Acquires a lock which guarantees that the caller has
2009 * exclusive access to the console system and the console_drivers list.
2011 * Can sleep, returns nothing.
2013 void console_lock(void)
2018 if (console_suspended)
2021 console_may_schedule = 1;
2022 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
2024 EXPORT_SYMBOL(console_lock);
2027 * console_trylock - try to lock the console system for exclusive use.
2029 * Tried to acquire a lock which guarantees that the caller has
2030 * exclusive access to the console system and the console_drivers list.
2032 * returns 1 on success, and 0 on failure to acquire the lock.
2034 int console_trylock(void)
2036 if (down_trylock(&console_sem))
2038 if (console_suspended) {
2043 console_may_schedule = 0;
2044 mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);
2047 EXPORT_SYMBOL(console_trylock);
2049 int is_console_locked(void)
2051 return console_locked;
2054 static void console_cont_flush(char *text, size_t size)
2056 unsigned long flags;
2059 raw_spin_lock_irqsave(&logbuf_lock, flags);
2065 * We still queue earlier records, likely because the console was
2066 * busy. The earlier ones need to be printed before this one, we
2067 * did not flush any fragment so far, so just let it queue up.
2069 if (console_seq < log_next_seq && !cont.cons)
2072 len = cont_print_text(text, size);
2073 raw_spin_unlock(&logbuf_lock);
2074 stop_critical_timings();
2075 call_console_drivers(cont.level, text, len);
2076 start_critical_timings();
2077 local_irq_restore(flags);
2080 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2084 * console_unlock - unlock the console system
2086 * Releases the console_lock which the caller holds on the console system
2087 * and the console driver list.
2089 * While the console_lock was held, console output may have been buffered
2090 * by printk(). If this is the case, console_unlock(); emits
2091 * the output prior to releasing the lock.
2093 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2095 * console_unlock(); may be called from any context.
2097 void console_unlock(void)
2099 static char text[LOG_LINE_MAX + PREFIX_MAX];
2100 static u64 seen_seq;
2101 unsigned long flags;
2102 bool wake_klogd = false;
2105 if (console_suspended) {
2110 console_may_schedule = 0;
2112 /* flush buffered message fragment immediately to console */
2113 console_cont_flush(text, sizeof(text));
2116 struct printk_log *msg;
2120 raw_spin_lock_irqsave(&logbuf_lock, flags);
2121 if (seen_seq != log_next_seq) {
2123 seen_seq = log_next_seq;
2126 if (console_seq < log_first_seq) {
2127 /* messages are gone, move to first one */
2128 console_seq = log_first_seq;
2129 console_idx = log_first_idx;
2133 if (console_seq == log_next_seq)
2136 msg = log_from_idx(console_idx);
2137 if (msg->flags & LOG_NOCONS) {
2139 * Skip record we have buffered and already printed
2140 * directly to the console when we received it.
2142 console_idx = log_next(console_idx);
2145 * We will get here again when we register a new
2146 * CON_PRINTBUFFER console. Clear the flag so we
2147 * will properly dump everything later.
2149 msg->flags &= ~LOG_NOCONS;
2150 console_prev = msg->flags;
2155 len = msg_print_text(msg, console_prev, false,
2156 text, sizeof(text));
2157 console_idx = log_next(console_idx);
2159 console_prev = msg->flags;
2160 raw_spin_unlock(&logbuf_lock);
2162 stop_critical_timings(); /* don't trace print latency */
2163 call_console_drivers(level, text, len);
2164 start_critical_timings();
2165 local_irq_restore(flags);
2168 mutex_release(&console_lock_dep_map, 1, _RET_IP_);
2170 /* Release the exclusive_console once it is used */
2171 if (unlikely(exclusive_console))
2172 exclusive_console = NULL;
2174 raw_spin_unlock(&logbuf_lock);
2179 * Someone could have filled up the buffer again, so re-check if there's
2180 * something to flush. In case we cannot trylock the console_sem again,
2181 * there's a new owner and the console_unlock() from them will do the
2182 * flush, no worries.
2184 raw_spin_lock(&logbuf_lock);
2185 retry = console_seq != log_next_seq;
2186 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2188 if (retry && console_trylock())
2194 EXPORT_SYMBOL(console_unlock);
2197 * console_conditional_schedule - yield the CPU if required
2199 * If the console code is currently allowed to sleep, and
2200 * if this CPU should yield the CPU to another task, do
2203 * Must be called within console_lock();.
2205 void __sched console_conditional_schedule(void)
2207 if (console_may_schedule)
2210 EXPORT_SYMBOL(console_conditional_schedule);
2212 void console_unblank(void)
2217 * console_unblank can no longer be called in interrupt context unless
2218 * oops_in_progress is set to 1..
2220 if (oops_in_progress) {
2221 if (down_trylock(&console_sem) != 0)
2227 console_may_schedule = 0;
2229 if ((c->flags & CON_ENABLED) && c->unblank)
2235 * Return the console tty driver structure and its associated index
2237 struct tty_driver *console_device(int *index)
2240 struct tty_driver *driver = NULL;
2243 for_each_console(c) {
2246 driver = c->device(c, index);
2255 * Prevent further output on the passed console device so that (for example)
2256 * serial drivers can disable console output before suspending a port, and can
2257 * re-enable output afterwards.
2259 void console_stop(struct console *console)
2262 console->flags &= ~CON_ENABLED;
2265 EXPORT_SYMBOL(console_stop);
2267 void console_start(struct console *console)
2270 console->flags |= CON_ENABLED;
2273 EXPORT_SYMBOL(console_start);
2275 static int __read_mostly keep_bootcon;
2277 static int __init keep_bootcon_setup(char *str)
2280 pr_info("debug: skip boot console de-registration.\n");
2285 early_param("keep_bootcon", keep_bootcon_setup);
2288 * The console driver calls this routine during kernel initialization
2289 * to register the console printing procedure with printk() and to
2290 * print any messages that were printed by the kernel before the
2291 * console driver was initialized.
2293 * This can happen pretty early during the boot process (because of
2294 * early_printk) - sometimes before setup_arch() completes - be careful
2295 * of what kernel features are used - they may not be initialised yet.
2297 * There are two types of consoles - bootconsoles (early_printk) and
2298 * "real" consoles (everything which is not a bootconsole) which are
2299 * handled differently.
2300 * - Any number of bootconsoles can be registered at any time.
2301 * - As soon as a "real" console is registered, all bootconsoles
2302 * will be unregistered automatically.
2303 * - Once a "real" console is registered, any attempt to register a
2304 * bootconsoles will be rejected
2306 void register_console(struct console *newcon)
2309 unsigned long flags;
2310 struct console *bcon = NULL;
2311 struct console_cmdline *c;
2313 if (console_drivers)
2314 for_each_console(bcon)
2315 if (WARN(bcon == newcon,
2316 "console '%s%d' already registered\n",
2317 bcon->name, bcon->index))
2321 * before we register a new CON_BOOT console, make sure we don't
2322 * already have a valid console
2324 if (console_drivers && newcon->flags & CON_BOOT) {
2325 /* find the last or real console */
2326 for_each_console(bcon) {
2327 if (!(bcon->flags & CON_BOOT)) {
2328 pr_info("Too late to register bootconsole %s%d\n",
2329 newcon->name, newcon->index);
2335 if (console_drivers && console_drivers->flags & CON_BOOT)
2336 bcon = console_drivers;
2338 if (preferred_console < 0 || bcon || !console_drivers)
2339 preferred_console = selected_console;
2341 if (newcon->early_setup)
2342 newcon->early_setup();
2345 * See if we want to use this console driver. If we
2346 * didn't select a console we take the first one
2347 * that registers here.
2349 if (preferred_console < 0) {
2350 if (newcon->index < 0)
2352 if (newcon->setup == NULL ||
2353 newcon->setup(newcon, NULL) == 0) {
2354 newcon->flags |= CON_ENABLED;
2355 if (newcon->device) {
2356 newcon->flags |= CON_CONSDEV;
2357 preferred_console = 0;
2363 * See if this console matches one we selected on
2366 for (i = 0, c = console_cmdline;
2367 i < MAX_CMDLINECONSOLES && c->name[0];
2369 if (strcmp(c->name, newcon->name) != 0)
2371 if (newcon->index >= 0 &&
2372 newcon->index != c->index)
2374 if (newcon->index < 0)
2375 newcon->index = c->index;
2377 if (_braille_register_console(newcon, c))
2380 if (newcon->setup &&
2381 newcon->setup(newcon, console_cmdline[i].options) != 0)
2383 newcon->flags |= CON_ENABLED;
2384 newcon->index = c->index;
2385 if (i == selected_console) {
2386 newcon->flags |= CON_CONSDEV;
2387 preferred_console = selected_console;
2392 if (!(newcon->flags & CON_ENABLED))
2396 * If we have a bootconsole, and are switching to a real console,
2397 * don't print everything out again, since when the boot console, and
2398 * the real console are the same physical device, it's annoying to
2399 * see the beginning boot messages twice
2401 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2402 newcon->flags &= ~CON_PRINTBUFFER;
2405 * Put this console in the list - keep the
2406 * preferred driver at the head of the list.
2409 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2410 newcon->next = console_drivers;
2411 console_drivers = newcon;
2413 newcon->next->flags &= ~CON_CONSDEV;
2415 newcon->next = console_drivers->next;
2416 console_drivers->next = newcon;
2418 if (newcon->flags & CON_PRINTBUFFER) {
2420 * console_unlock(); will print out the buffered messages
2423 raw_spin_lock_irqsave(&logbuf_lock, flags);
2424 console_seq = syslog_seq;
2425 console_idx = syslog_idx;
2426 console_prev = syslog_prev;
2427 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2429 * We're about to replay the log buffer. Only do this to the
2430 * just-registered console to avoid excessive message spam to
2431 * the already-registered consoles.
2433 exclusive_console = newcon;
2436 console_sysfs_notify();
2439 * By unregistering the bootconsoles after we enable the real console
2440 * we get the "console xxx enabled" message on all the consoles -
2441 * boot consoles, real consoles, etc - this is to ensure that end
2442 * users know there might be something in the kernel's log buffer that
2443 * went to the bootconsole (that they do not see on the real console)
2445 pr_info("%sconsole [%s%d] enabled\n",
2446 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2447 newcon->name, newcon->index);
2449 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2451 /* We need to iterate through all boot consoles, to make
2452 * sure we print everything out, before we unregister them.
2454 for_each_console(bcon)
2455 if (bcon->flags & CON_BOOT)
2456 unregister_console(bcon);
2459 EXPORT_SYMBOL(register_console);
2461 int unregister_console(struct console *console)
2463 struct console *a, *b;
2466 pr_info("%sconsole [%s%d] disabled\n",
2467 (console->flags & CON_BOOT) ? "boot" : "" ,
2468 console->name, console->index);
2470 res = _braille_unregister_console(console);
2476 if (console_drivers == console) {
2477 console_drivers=console->next;
2479 } else if (console_drivers) {
2480 for (a=console_drivers->next, b=console_drivers ;
2481 a; b=a, a=b->next) {
2491 * If this isn't the last console and it has CON_CONSDEV set, we
2492 * need to set it on the next preferred console.
2494 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2495 console_drivers->flags |= CON_CONSDEV;
2497 console->flags &= ~CON_ENABLED;
2499 console_sysfs_notify();
2502 EXPORT_SYMBOL(unregister_console);
2504 static int __init printk_late_init(void)
2506 struct console *con;
2508 for_each_console(con) {
2509 if (!keep_bootcon && con->flags & CON_BOOT) {
2510 unregister_console(con);
2513 hotcpu_notifier(console_cpu_notify, 0);
2516 late_initcall(printk_late_init);
2518 #if defined CONFIG_PRINTK
2520 * Delayed printk version, for scheduler-internal messages:
2522 #define PRINTK_BUF_SIZE 512
2524 #define PRINTK_PENDING_WAKEUP 0x01
2525 #define PRINTK_PENDING_SCHED 0x02
2527 static DEFINE_PER_CPU(int, printk_pending);
2528 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
2530 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2532 int pending = __this_cpu_xchg(printk_pending, 0);
2534 if (pending & PRINTK_PENDING_SCHED) {
2535 char *buf = __get_cpu_var(printk_sched_buf);
2536 pr_warn("[sched_delayed] %s", buf);
2539 if (pending & PRINTK_PENDING_WAKEUP)
2540 wake_up_interruptible(&log_wait);
2543 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2544 .func = wake_up_klogd_work_func,
2545 .flags = IRQ_WORK_LAZY,
2548 void wake_up_klogd(void)
2551 if (waitqueue_active(&log_wait)) {
2552 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2553 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2558 int printk_sched(const char *fmt, ...)
2560 unsigned long flags;
2565 local_irq_save(flags);
2566 buf = __get_cpu_var(printk_sched_buf);
2568 va_start(args, fmt);
2569 r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2572 __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2573 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2574 local_irq_restore(flags);
2580 * printk rate limiting, lifted from the networking subsystem.
2582 * This enforces a rate limit: not more than 10 kernel messages
2583 * every 5s to make a denial-of-service attack impossible.
2585 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2587 int __printk_ratelimit(const char *func)
2589 return ___ratelimit(&printk_ratelimit_state, func);
2591 EXPORT_SYMBOL(__printk_ratelimit);
2594 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2595 * @caller_jiffies: pointer to caller's state
2596 * @interval_msecs: minimum interval between prints
2598 * printk_timed_ratelimit() returns true if more than @interval_msecs
2599 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2602 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2603 unsigned int interval_msecs)
2605 if (*caller_jiffies == 0
2606 || !time_in_range(jiffies, *caller_jiffies,
2608 + msecs_to_jiffies(interval_msecs))) {
2609 *caller_jiffies = jiffies;
2614 EXPORT_SYMBOL(printk_timed_ratelimit);
2616 static DEFINE_SPINLOCK(dump_list_lock);
2617 static LIST_HEAD(dump_list);
2620 * kmsg_dump_register - register a kernel log dumper.
2621 * @dumper: pointer to the kmsg_dumper structure
2623 * Adds a kernel log dumper to the system. The dump callback in the
2624 * structure will be called when the kernel oopses or panics and must be
2625 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2627 int kmsg_dump_register(struct kmsg_dumper *dumper)
2629 unsigned long flags;
2632 /* The dump callback needs to be set */
2636 spin_lock_irqsave(&dump_list_lock, flags);
2637 /* Don't allow registering multiple times */
2638 if (!dumper->registered) {
2639 dumper->registered = 1;
2640 list_add_tail_rcu(&dumper->list, &dump_list);
2643 spin_unlock_irqrestore(&dump_list_lock, flags);
2647 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2650 * kmsg_dump_unregister - unregister a kmsg dumper.
2651 * @dumper: pointer to the kmsg_dumper structure
2653 * Removes a dump device from the system. Returns zero on success and
2654 * %-EINVAL otherwise.
2656 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2658 unsigned long flags;
2661 spin_lock_irqsave(&dump_list_lock, flags);
2662 if (dumper->registered) {
2663 dumper->registered = 0;
2664 list_del_rcu(&dumper->list);
2667 spin_unlock_irqrestore(&dump_list_lock, flags);
2672 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2674 static bool always_kmsg_dump;
2675 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2678 * kmsg_dump - dump kernel log to kernel message dumpers.
2679 * @reason: the reason (oops, panic etc) for dumping
2681 * Call each of the registered dumper's dump() callback, which can
2682 * retrieve the kmsg records with kmsg_dump_get_line() or
2683 * kmsg_dump_get_buffer().
2685 void kmsg_dump(enum kmsg_dump_reason reason)
2687 struct kmsg_dumper *dumper;
2688 unsigned long flags;
2690 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2694 list_for_each_entry_rcu(dumper, &dump_list, list) {
2695 if (dumper->max_reason && reason > dumper->max_reason)
2698 /* initialize iterator with data about the stored records */
2699 dumper->active = true;
2701 raw_spin_lock_irqsave(&logbuf_lock, flags);
2702 dumper->cur_seq = clear_seq;
2703 dumper->cur_idx = clear_idx;
2704 dumper->next_seq = log_next_seq;
2705 dumper->next_idx = log_next_idx;
2706 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2708 /* invoke dumper which will iterate over records */
2709 dumper->dump(dumper, reason);
2711 /* reset iterator */
2712 dumper->active = false;
2718 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2719 * @dumper: registered kmsg dumper
2720 * @syslog: include the "<4>" prefixes
2721 * @line: buffer to copy the line to
2722 * @size: maximum size of the buffer
2723 * @len: length of line placed into buffer
2725 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2726 * record, and copy one record into the provided buffer.
2728 * Consecutive calls will return the next available record moving
2729 * towards the end of the buffer with the youngest messages.
2731 * A return value of FALSE indicates that there are no more records to
2734 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2736 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2737 char *line, size_t size, size_t *len)
2739 struct printk_log *msg;
2743 if (!dumper->active)
2746 if (dumper->cur_seq < log_first_seq) {
2747 /* messages are gone, move to first available one */
2748 dumper->cur_seq = log_first_seq;
2749 dumper->cur_idx = log_first_idx;
2753 if (dumper->cur_seq >= log_next_seq)
2756 msg = log_from_idx(dumper->cur_idx);
2757 l = msg_print_text(msg, 0, syslog, line, size);
2759 dumper->cur_idx = log_next(dumper->cur_idx);
2769 * kmsg_dump_get_line - retrieve one kmsg log line
2770 * @dumper: registered kmsg dumper
2771 * @syslog: include the "<4>" prefixes
2772 * @line: buffer to copy the line to
2773 * @size: maximum size of the buffer
2774 * @len: length of line placed into buffer
2776 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2777 * record, and copy one record into the provided buffer.
2779 * Consecutive calls will return the next available record moving
2780 * towards the end of the buffer with the youngest messages.
2782 * A return value of FALSE indicates that there are no more records to
2785 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2786 char *line, size_t size, size_t *len)
2788 unsigned long flags;
2791 raw_spin_lock_irqsave(&logbuf_lock, flags);
2792 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2793 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2797 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2800 * kmsg_dump_get_buffer - copy kmsg log lines
2801 * @dumper: registered kmsg dumper
2802 * @syslog: include the "<4>" prefixes
2803 * @buf: buffer to copy the line to
2804 * @size: maximum size of the buffer
2805 * @len: length of line placed into buffer
2807 * Start at the end of the kmsg buffer and fill the provided buffer
2808 * with as many of the the *youngest* kmsg records that fit into it.
2809 * If the buffer is large enough, all available kmsg records will be
2810 * copied with a single call.
2812 * Consecutive calls will fill the buffer with the next block of
2813 * available older records, not including the earlier retrieved ones.
2815 * A return value of FALSE indicates that there are no more records to
2818 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2819 char *buf, size_t size, size_t *len)
2821 unsigned long flags;
2826 enum log_flags prev;
2830 if (!dumper->active)
2833 raw_spin_lock_irqsave(&logbuf_lock, flags);
2834 if (dumper->cur_seq < log_first_seq) {
2835 /* messages are gone, move to first available one */
2836 dumper->cur_seq = log_first_seq;
2837 dumper->cur_idx = log_first_idx;
2841 if (dumper->cur_seq >= dumper->next_seq) {
2842 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2846 /* calculate length of entire buffer */
2847 seq = dumper->cur_seq;
2848 idx = dumper->cur_idx;
2850 while (seq < dumper->next_seq) {
2851 struct printk_log *msg = log_from_idx(idx);
2853 l += msg_print_text(msg, prev, true, NULL, 0);
2854 idx = log_next(idx);
2859 /* move first record forward until length fits into the buffer */
2860 seq = dumper->cur_seq;
2861 idx = dumper->cur_idx;
2863 while (l > size && seq < dumper->next_seq) {
2864 struct printk_log *msg = log_from_idx(idx);
2866 l -= msg_print_text(msg, prev, true, NULL, 0);
2867 idx = log_next(idx);
2872 /* last message in next interation */
2877 while (seq < dumper->next_seq) {
2878 struct printk_log *msg = log_from_idx(idx);
2880 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2881 idx = log_next(idx);
2886 dumper->next_seq = next_seq;
2887 dumper->next_idx = next_idx;
2889 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2895 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2898 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2899 * @dumper: registered kmsg dumper
2901 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2902 * kmsg_dump_get_buffer() can be called again and used multiple
2903 * times within the same dumper.dump() callback.
2905 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2907 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
2909 dumper->cur_seq = clear_seq;
2910 dumper->cur_idx = clear_idx;
2911 dumper->next_seq = log_next_seq;
2912 dumper->next_idx = log_next_idx;
2916 * kmsg_dump_rewind - reset the interator
2917 * @dumper: registered kmsg dumper
2919 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2920 * kmsg_dump_get_buffer() can be called again and used multiple
2921 * times within the same dumper.dump() callback.
2923 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2925 unsigned long flags;
2927 raw_spin_lock_irqsave(&logbuf_lock, flags);
2928 kmsg_dump_rewind_nolock(dumper);
2929 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2931 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
2933 static char dump_stack_arch_desc_str[128];
2936 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
2937 * @fmt: printf-style format string
2938 * @...: arguments for the format string
2940 * The configured string will be printed right after utsname during task
2941 * dumps. Usually used to add arch-specific system identifiers. If an
2942 * arch wants to make use of such an ID string, it should initialize this
2943 * as soon as possible during boot.
2945 void __init dump_stack_set_arch_desc(const char *fmt, ...)
2949 va_start(args, fmt);
2950 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
2956 * dump_stack_print_info - print generic debug info for dump_stack()
2957 * @log_lvl: log level
2959 * Arch-specific dump_stack() implementations can use this function to
2960 * print out the same debug information as the generic dump_stack().
2962 void dump_stack_print_info(const char *log_lvl)
2964 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
2965 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
2966 print_tainted(), init_utsname()->release,
2967 (int)strcspn(init_utsname()->version, " "),
2968 init_utsname()->version);
2970 if (dump_stack_arch_desc_str[0] != '\0')
2971 printk("%sHardware name: %s\n",
2972 log_lvl, dump_stack_arch_desc_str);
2974 print_worker_info(log_lvl, current);
2978 * show_regs_print_info - print generic debug info for show_regs()
2979 * @log_lvl: log level
2981 * show_regs() implementations can use this function to print out generic
2982 * debug information.
2984 void show_regs_print_info(const char *log_lvl)
2986 dump_stack_print_info(log_lvl);
2988 printk("%stask: %p ti: %p task.ti: %p\n",
2989 log_lvl, current, current_thread_info(),
2990 task_thread_info(current));