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 int console_printk[4] = {
58 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
59 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
60 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
61 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
64 /* Deferred messaged from sched code are marked by this special level */
65 #define SCHED_MESSAGE_LOGLEVEL -2
68 * Low level drivers may need that to know if they can schedule in
69 * their unblank() callback or not. So let's export it.
72 EXPORT_SYMBOL(oops_in_progress);
75 * console_sem protects the console_drivers list, and also
76 * provides serialisation for access to the entire console
79 static DEFINE_SEMAPHORE(console_sem);
80 struct console *console_drivers;
81 EXPORT_SYMBOL_GPL(console_drivers);
84 static struct lockdep_map console_lock_dep_map = {
85 .name = "console_lock"
90 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
91 * macros instead of functions so that _RET_IP_ contains useful information.
93 #define down_console_sem() do { \
95 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
98 static int __down_trylock_console_sem(unsigned long ip)
100 if (down_trylock(&console_sem))
102 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
105 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
107 #define up_console_sem() do { \
108 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
113 * This is used for debugging the mess that is the VT code by
114 * keeping track if we have the console semaphore held. It's
115 * definitely not the perfect debug tool (we don't know if _WE_
116 * hold it are racing, but it helps tracking those weird code
117 * path in the console code where we end up in places I want
118 * locked without the console sempahore held
120 static int console_locked, console_suspended;
123 * If exclusive_console is non-NULL then only this console is to be printed to.
125 static struct console *exclusive_console;
128 * Array of consoles built from command line options (console=)
131 #define MAX_CMDLINECONSOLES 8
133 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
135 static int selected_console = -1;
136 static int preferred_console = -1;
137 int console_set_on_cmdline;
138 EXPORT_SYMBOL(console_set_on_cmdline);
140 /* Flag: console code may call schedule() */
141 static int console_may_schedule;
144 * The printk log buffer consists of a chain of concatenated variable
145 * length records. Every record starts with a record header, containing
146 * the overall length of the record.
148 * The heads to the first and last entry in the buffer, as well as the
149 * sequence numbers of these both entries are maintained when messages
152 * If the heads indicate available messages, the length in the header
153 * tells the start next message. A length == 0 for the next message
154 * indicates a wrap-around to the beginning of the buffer.
156 * Every record carries the monotonic timestamp in microseconds, as well as
157 * the standard userspace syslog level and syslog facility. The usual
158 * kernel messages use LOG_KERN; userspace-injected messages always carry
159 * a matching syslog facility, by default LOG_USER. The origin of every
160 * message can be reliably determined that way.
162 * The human readable log message directly follows the message header. The
163 * length of the message text is stored in the header, the stored message
166 * Optionally, a message can carry a dictionary of properties (key/value pairs),
167 * to provide userspace with a machine-readable message context.
169 * Examples for well-defined, commonly used property names are:
170 * DEVICE=b12:8 device identifier
174 * +sound:card0 subsystem:devname
175 * SUBSYSTEM=pci driver-core subsystem name
177 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
178 * follows directly after a '=' character. Every property is terminated by
179 * a '\0' character. The last property is not terminated.
181 * Example of a message structure:
182 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
183 * 0008 34 00 record is 52 bytes long
184 * 000a 0b 00 text is 11 bytes long
185 * 000c 1f 00 dictionary is 23 bytes long
186 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
187 * 0010 69 74 27 73 20 61 20 6c "it's a l"
189 * 001b 44 45 56 49 43 "DEVIC"
190 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
191 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
193 * 0032 00 00 00 padding to next message header
195 * The 'struct printk_log' buffer header must never be directly exported to
196 * userspace, it is a kernel-private implementation detail that might
197 * need to be changed in the future, when the requirements change.
199 * /dev/kmsg exports the structured data in the following line format:
200 * "level,sequnum,timestamp;<message text>\n"
202 * The optional key/value pairs are attached as continuation lines starting
203 * with a space character and terminated by a newline. All possible
204 * non-prinatable characters are escaped in the "\xff" notation.
206 * Users of the export format should ignore possible additional values
207 * separated by ',', and find the message after the ';' character.
211 LOG_NOCONS = 1, /* already flushed, do not print to console */
212 LOG_NEWLINE = 2, /* text ended with a newline */
213 LOG_PREFIX = 4, /* text started with a prefix */
214 LOG_CONT = 8, /* text is a fragment of a continuation line */
218 u64 ts_nsec; /* timestamp in nanoseconds */
219 u16 len; /* length of entire record */
220 u16 text_len; /* length of text buffer */
221 u16 dict_len; /* length of dictionary buffer */
222 u8 facility; /* syslog facility */
223 u8 flags:5; /* internal record flags */
224 u8 level:3; /* syslog level */
228 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
229 * within the scheduler's rq lock. It must be released before calling
230 * console_unlock() or anything else that might wake up a process.
232 static DEFINE_RAW_SPINLOCK(logbuf_lock);
235 DECLARE_WAIT_QUEUE_HEAD(log_wait);
236 /* the next printk record to read by syslog(READ) or /proc/kmsg */
237 static u64 syslog_seq;
238 static u32 syslog_idx;
239 static enum log_flags syslog_prev;
240 static size_t syslog_partial;
242 /* index and sequence number of the first record stored in the buffer */
243 static u64 log_first_seq;
244 static u32 log_first_idx;
246 /* index and sequence number of the next record to store in the buffer */
247 static u64 log_next_seq;
248 static u32 log_next_idx;
250 /* the next printk record to write to the console */
251 static u64 console_seq;
252 static u32 console_idx;
253 static enum log_flags console_prev;
255 /* the next printk record to read after the last 'clear' command */
256 static u64 clear_seq;
257 static u32 clear_idx;
259 #define PREFIX_MAX 32
260 #define LOG_LINE_MAX 1024 - PREFIX_MAX
263 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
266 #define LOG_ALIGN __alignof__(struct printk_log)
268 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
269 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
270 static char *log_buf = __log_buf;
271 static u32 log_buf_len = __LOG_BUF_LEN;
273 /* human readable text of the record */
274 static char *log_text(const struct printk_log *msg)
276 return (char *)msg + sizeof(struct printk_log);
279 /* optional key/value pair dictionary attached to the record */
280 static char *log_dict(const struct printk_log *msg)
282 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
285 /* get record by index; idx must point to valid msg */
286 static struct printk_log *log_from_idx(u32 idx)
288 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
291 * A length == 0 record is the end of buffer marker. Wrap around and
292 * read the message at the start of the buffer.
295 return (struct printk_log *)log_buf;
299 /* get next record; idx must point to valid msg */
300 static u32 log_next(u32 idx)
302 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
304 /* length == 0 indicates the end of the buffer; wrap */
306 * A length == 0 record is the end of buffer marker. Wrap around and
307 * read the message at the start of the buffer as *this* one, and
308 * return the one after that.
311 msg = (struct printk_log *)log_buf;
314 return idx + msg->len;
318 * Check whether there is enough free space for the given message.
320 * The same values of first_idx and next_idx mean that the buffer
321 * is either empty or full.
323 * If the buffer is empty, we must respect the position of the indexes.
324 * They cannot be reset to the beginning of the buffer.
326 static int logbuf_has_space(u32 msg_size, bool empty)
330 if (log_next_idx > log_first_idx || empty)
331 free = max(log_buf_len - log_next_idx, log_first_idx);
333 free = log_first_idx - log_next_idx;
336 * We need space also for an empty header that signalizes wrapping
339 return free >= msg_size + sizeof(struct printk_log);
342 static int log_make_free_space(u32 msg_size)
344 while (log_first_seq < log_next_seq) {
345 if (logbuf_has_space(msg_size, false))
347 /* drop old messages until we have enough continuous space */
348 log_first_idx = log_next(log_first_idx);
352 /* sequence numbers are equal, so the log buffer is empty */
353 if (logbuf_has_space(msg_size, true))
359 /* compute the message size including the padding bytes */
360 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
364 size = sizeof(struct printk_log) + text_len + dict_len;
365 *pad_len = (-size) & (LOG_ALIGN - 1);
372 * Define how much of the log buffer we could take at maximum. The value
373 * must be greater than two. Note that only half of the buffer is available
374 * when the index points to the middle.
376 #define MAX_LOG_TAKE_PART 4
377 static const char trunc_msg[] = "<truncated>";
379 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
380 u16 *dict_len, u32 *pad_len)
383 * The message should not take the whole buffer. Otherwise, it might
384 * get removed too soon.
386 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
387 if (*text_len > max_text_len)
388 *text_len = max_text_len;
389 /* enable the warning message */
390 *trunc_msg_len = strlen(trunc_msg);
391 /* disable the "dict" completely */
393 /* compute the size again, count also the warning message */
394 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
397 /* insert record into the buffer, discard old ones, update heads */
398 static int log_store(int facility, int level,
399 enum log_flags flags, u64 ts_nsec,
400 const char *dict, u16 dict_len,
401 const char *text, u16 text_len)
403 struct printk_log *msg;
405 u16 trunc_msg_len = 0;
407 /* number of '\0' padding bytes to next message */
408 size = msg_used_size(text_len, dict_len, &pad_len);
410 if (log_make_free_space(size)) {
411 /* truncate the message if it is too long for empty buffer */
412 size = truncate_msg(&text_len, &trunc_msg_len,
413 &dict_len, &pad_len);
414 /* survive when the log buffer is too small for trunc_msg */
415 if (log_make_free_space(size))
419 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
421 * This message + an additional empty header does not fit
422 * at the end of the buffer. Add an empty header with len == 0
423 * to signify a wrap around.
425 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
430 msg = (struct printk_log *)(log_buf + log_next_idx);
431 memcpy(log_text(msg), text, text_len);
432 msg->text_len = text_len;
434 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
435 msg->text_len += trunc_msg_len;
437 memcpy(log_dict(msg), dict, dict_len);
438 msg->dict_len = dict_len;
439 msg->facility = facility;
440 msg->level = level & 7;
441 msg->flags = flags & 0x1f;
443 msg->ts_nsec = ts_nsec;
445 msg->ts_nsec = local_clock();
446 memset(log_dict(msg) + dict_len, 0, pad_len);
450 log_next_idx += msg->len;
453 return msg->text_len;
456 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
457 int dmesg_restrict = 1;
462 static int syslog_action_restricted(int type)
467 * Unless restricted, we allow "read all" and "get buffer size"
470 return type != SYSLOG_ACTION_READ_ALL &&
471 type != SYSLOG_ACTION_SIZE_BUFFER;
474 static int check_syslog_permissions(int type, bool from_file)
477 * If this is from /proc/kmsg and we've already opened it, then we've
478 * already done the capabilities checks at open time.
480 if (from_file && type != SYSLOG_ACTION_OPEN)
483 if (syslog_action_restricted(type)) {
484 if (capable(CAP_SYSLOG))
487 * For historical reasons, accept CAP_SYS_ADMIN too, with
490 if (capable(CAP_SYS_ADMIN)) {
491 pr_warn_once("%s (%d): Attempt to access syslog with "
492 "CAP_SYS_ADMIN but no CAP_SYSLOG "
494 current->comm, task_pid_nr(current));
499 return security_syslog(type);
503 /* /dev/kmsg - userspace message inject/listen interface */
504 struct devkmsg_user {
512 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
513 unsigned long count, loff_t pos)
517 int level = default_message_loglevel;
518 int facility = 1; /* LOG_USER */
519 size_t len = iov_length(iv, count);
522 if (len > LOG_LINE_MAX)
524 buf = kmalloc(len+1, GFP_KERNEL);
529 for (i = 0; i < count; i++) {
530 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
534 line += iv[i].iov_len;
538 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
539 * the decimal value represents 32bit, the lower 3 bit are the log
540 * level, the rest are the log facility.
542 * If no prefix or no userspace facility is specified, we
543 * enforce LOG_USER, to be able to reliably distinguish
544 * kernel-generated messages from userspace-injected ones.
547 if (line[0] == '<') {
550 i = simple_strtoul(line+1, &endp, 10);
551 if (endp && endp[0] == '>') {
562 printk_emit(facility, level, NULL, 0, "%s", line);
568 static ssize_t devkmsg_read(struct file *file, char __user *buf,
569 size_t count, loff_t *ppos)
571 struct devkmsg_user *user = file->private_data;
572 struct printk_log *msg;
582 ret = mutex_lock_interruptible(&user->lock);
585 raw_spin_lock_irq(&logbuf_lock);
586 while (user->seq == log_next_seq) {
587 if (file->f_flags & O_NONBLOCK) {
589 raw_spin_unlock_irq(&logbuf_lock);
593 raw_spin_unlock_irq(&logbuf_lock);
594 ret = wait_event_interruptible(log_wait,
595 user->seq != log_next_seq);
598 raw_spin_lock_irq(&logbuf_lock);
601 if (user->seq < log_first_seq) {
602 /* our last seen message is gone, return error and reset */
603 user->idx = log_first_idx;
604 user->seq = log_first_seq;
606 raw_spin_unlock_irq(&logbuf_lock);
610 msg = log_from_idx(user->idx);
611 ts_usec = msg->ts_nsec;
612 do_div(ts_usec, 1000);
615 * If we couldn't merge continuation line fragments during the print,
616 * export the stored flags to allow an optional external merge of the
617 * records. Merging the records isn't always neccessarily correct, like
618 * when we hit a race during printing. In most cases though, it produces
619 * better readable output. 'c' in the record flags mark the first
620 * fragment of a line, '+' the following.
622 if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
624 else if ((msg->flags & LOG_CONT) ||
625 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
628 len = sprintf(user->buf, "%u,%llu,%llu,%c;",
629 (msg->facility << 3) | msg->level,
630 user->seq, ts_usec, cont);
631 user->prev = msg->flags;
633 /* escape non-printable characters */
634 for (i = 0; i < msg->text_len; i++) {
635 unsigned char c = log_text(msg)[i];
637 if (c < ' ' || c >= 127 || c == '\\')
638 len += sprintf(user->buf + len, "\\x%02x", c);
640 user->buf[len++] = c;
642 user->buf[len++] = '\n';
647 for (i = 0; i < msg->dict_len; i++) {
648 unsigned char c = log_dict(msg)[i];
651 user->buf[len++] = ' ';
656 user->buf[len++] = '\n';
661 if (c < ' ' || c >= 127 || c == '\\') {
662 len += sprintf(user->buf + len, "\\x%02x", c);
666 user->buf[len++] = c;
668 user->buf[len++] = '\n';
671 user->idx = log_next(user->idx);
673 raw_spin_unlock_irq(&logbuf_lock);
680 if (copy_to_user(buf, user->buf, len)) {
686 mutex_unlock(&user->lock);
690 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
692 struct devkmsg_user *user = file->private_data;
700 raw_spin_lock_irq(&logbuf_lock);
703 /* the first record */
704 user->idx = log_first_idx;
705 user->seq = log_first_seq;
709 * The first record after the last SYSLOG_ACTION_CLEAR,
710 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
711 * changes no global state, and does not clear anything.
713 user->idx = clear_idx;
714 user->seq = clear_seq;
717 /* after the last record */
718 user->idx = log_next_idx;
719 user->seq = log_next_seq;
724 raw_spin_unlock_irq(&logbuf_lock);
728 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
730 struct devkmsg_user *user = file->private_data;
734 return POLLERR|POLLNVAL;
736 poll_wait(file, &log_wait, wait);
738 raw_spin_lock_irq(&logbuf_lock);
739 if (user->seq < log_next_seq) {
740 /* return error when data has vanished underneath us */
741 if (user->seq < log_first_seq)
742 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
744 ret = POLLIN|POLLRDNORM;
746 raw_spin_unlock_irq(&logbuf_lock);
751 static int devkmsg_open(struct inode *inode, struct file *file)
753 struct devkmsg_user *user;
756 /* write-only does not need any file context */
757 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
760 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
765 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
769 mutex_init(&user->lock);
771 raw_spin_lock_irq(&logbuf_lock);
772 user->idx = log_first_idx;
773 user->seq = log_first_seq;
774 raw_spin_unlock_irq(&logbuf_lock);
776 file->private_data = user;
780 static int devkmsg_release(struct inode *inode, struct file *file)
782 struct devkmsg_user *user = file->private_data;
787 mutex_destroy(&user->lock);
792 const struct file_operations kmsg_fops = {
793 .open = devkmsg_open,
794 .read = devkmsg_read,
795 .aio_write = devkmsg_writev,
796 .llseek = devkmsg_llseek,
797 .poll = devkmsg_poll,
798 .release = devkmsg_release,
803 * This appends the listed symbols to /proc/vmcore
805 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
806 * obtain access to symbols that are otherwise very difficult to locate. These
807 * symbols are specifically used so that utilities can access and extract the
808 * dmesg log from a vmcore file after a crash.
810 void log_buf_kexec_setup(void)
812 VMCOREINFO_SYMBOL(log_buf);
813 VMCOREINFO_SYMBOL(log_buf_len);
814 VMCOREINFO_SYMBOL(log_first_idx);
815 VMCOREINFO_SYMBOL(log_next_idx);
817 * Export struct printk_log size and field offsets. User space tools can
818 * parse it and detect any changes to structure down the line.
820 VMCOREINFO_STRUCT_SIZE(printk_log);
821 VMCOREINFO_OFFSET(printk_log, ts_nsec);
822 VMCOREINFO_OFFSET(printk_log, len);
823 VMCOREINFO_OFFSET(printk_log, text_len);
824 VMCOREINFO_OFFSET(printk_log, dict_len);
828 /* requested log_buf_len from kernel cmdline */
829 static unsigned long __initdata new_log_buf_len;
831 /* save requested log_buf_len since it's too early to process it */
832 static int __init log_buf_len_setup(char *str)
834 unsigned size = memparse(str, &str);
837 size = roundup_pow_of_two(size);
838 if (size > log_buf_len)
839 new_log_buf_len = size;
843 early_param("log_buf_len", log_buf_len_setup);
845 void __init setup_log_buf(int early)
851 if (!new_log_buf_len)
856 memblock_virt_alloc(new_log_buf_len, PAGE_SIZE);
858 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len, 0);
861 if (unlikely(!new_log_buf)) {
862 pr_err("log_buf_len: %ld bytes not available\n",
867 raw_spin_lock_irqsave(&logbuf_lock, flags);
868 log_buf_len = new_log_buf_len;
869 log_buf = new_log_buf;
871 free = __LOG_BUF_LEN - log_next_idx;
872 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
873 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
875 pr_info("log_buf_len: %d\n", log_buf_len);
876 pr_info("early log buf free: %d(%d%%)\n",
877 free, (free * 100) / __LOG_BUF_LEN);
880 static bool __read_mostly ignore_loglevel;
882 static int __init ignore_loglevel_setup(char *str)
885 pr_info("debug: ignoring loglevel setting.\n");
890 early_param("ignore_loglevel", ignore_loglevel_setup);
891 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
892 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
893 "print all kernel messages to the console.");
895 #ifdef CONFIG_BOOT_PRINTK_DELAY
897 static int boot_delay; /* msecs delay after each printk during bootup */
898 static unsigned long long loops_per_msec; /* based on boot_delay */
900 static int __init boot_delay_setup(char *str)
904 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
905 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
907 get_option(&str, &boot_delay);
908 if (boot_delay > 10 * 1000)
911 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
912 "HZ: %d, loops_per_msec: %llu\n",
913 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
916 early_param("boot_delay", boot_delay_setup);
918 static void boot_delay_msec(int level)
920 unsigned long long k;
921 unsigned long timeout;
923 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
924 || (level >= console_loglevel && !ignore_loglevel)) {
928 k = (unsigned long long)loops_per_msec * boot_delay;
930 timeout = jiffies + msecs_to_jiffies(boot_delay);
935 * use (volatile) jiffies to prevent
936 * compiler reduction; loop termination via jiffies
937 * is secondary and may or may not happen.
939 if (time_after(jiffies, timeout))
941 touch_nmi_watchdog();
945 static inline void boot_delay_msec(int level)
950 #if defined(CONFIG_PRINTK_TIME)
951 static bool printk_time = 1;
953 static bool printk_time;
955 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
957 static size_t print_time(u64 ts, char *buf)
959 unsigned long rem_nsec;
964 rem_nsec = do_div(ts, 1000000000);
967 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
969 return sprintf(buf, "[%5lu.%06lu] ",
970 (unsigned long)ts, rem_nsec / 1000);
973 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
976 unsigned int prefix = (msg->facility << 3) | msg->level;
980 len += sprintf(buf, "<%u>", prefix);
985 else if (prefix > 99)
992 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
996 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
997 bool syslog, char *buf, size_t size)
999 const char *text = log_text(msg);
1000 size_t text_size = msg->text_len;
1002 bool newline = true;
1005 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1008 if (msg->flags & LOG_CONT) {
1009 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1012 if (!(msg->flags & LOG_NEWLINE))
1017 const char *next = memchr(text, '\n', text_size);
1021 text_len = next - text;
1023 text_size -= next - text;
1025 text_len = text_size;
1029 if (print_prefix(msg, syslog, NULL) +
1030 text_len + 1 >= size - len)
1034 len += print_prefix(msg, syslog, buf + len);
1035 memcpy(buf + len, text, text_len);
1037 if (next || newline)
1040 /* SYSLOG_ACTION_* buffer size only calculation */
1042 len += print_prefix(msg, syslog, NULL);
1044 if (next || newline)
1055 static int syslog_print(char __user *buf, int size)
1058 struct printk_log *msg;
1061 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1069 raw_spin_lock_irq(&logbuf_lock);
1070 if (syslog_seq < log_first_seq) {
1071 /* messages are gone, move to first one */
1072 syslog_seq = log_first_seq;
1073 syslog_idx = log_first_idx;
1077 if (syslog_seq == log_next_seq) {
1078 raw_spin_unlock_irq(&logbuf_lock);
1082 skip = syslog_partial;
1083 msg = log_from_idx(syslog_idx);
1084 n = msg_print_text(msg, syslog_prev, true, text,
1085 LOG_LINE_MAX + PREFIX_MAX);
1086 if (n - syslog_partial <= size) {
1087 /* message fits into buffer, move forward */
1088 syslog_idx = log_next(syslog_idx);
1090 syslog_prev = msg->flags;
1091 n -= syslog_partial;
1094 /* partial read(), remember position */
1096 syslog_partial += n;
1099 raw_spin_unlock_irq(&logbuf_lock);
1104 if (copy_to_user(buf, text + skip, n)) {
1119 static int syslog_print_all(char __user *buf, int size, bool clear)
1124 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1128 raw_spin_lock_irq(&logbuf_lock);
1133 enum log_flags prev;
1135 if (clear_seq < log_first_seq) {
1136 /* messages are gone, move to first available one */
1137 clear_seq = log_first_seq;
1138 clear_idx = log_first_idx;
1142 * Find first record that fits, including all following records,
1143 * into the user-provided buffer for this dump.
1148 while (seq < log_next_seq) {
1149 struct printk_log *msg = log_from_idx(idx);
1151 len += msg_print_text(msg, prev, true, NULL, 0);
1153 idx = log_next(idx);
1157 /* move first record forward until length fits into the buffer */
1161 while (len > size && seq < log_next_seq) {
1162 struct printk_log *msg = log_from_idx(idx);
1164 len -= msg_print_text(msg, prev, true, NULL, 0);
1166 idx = log_next(idx);
1170 /* last message fitting into this dump */
1171 next_seq = log_next_seq;
1174 while (len >= 0 && seq < next_seq) {
1175 struct printk_log *msg = log_from_idx(idx);
1178 textlen = msg_print_text(msg, prev, true, text,
1179 LOG_LINE_MAX + PREFIX_MAX);
1184 idx = log_next(idx);
1188 raw_spin_unlock_irq(&logbuf_lock);
1189 if (copy_to_user(buf + len, text, textlen))
1193 raw_spin_lock_irq(&logbuf_lock);
1195 if (seq < log_first_seq) {
1196 /* messages are gone, move to next one */
1197 seq = log_first_seq;
1198 idx = log_first_idx;
1205 clear_seq = log_next_seq;
1206 clear_idx = log_next_idx;
1208 raw_spin_unlock_irq(&logbuf_lock);
1214 int do_syslog(int type, char __user *buf, int len, bool from_file)
1217 static int saved_console_loglevel = -1;
1220 error = check_syslog_permissions(type, from_file);
1224 error = security_syslog(type);
1229 case SYSLOG_ACTION_CLOSE: /* Close log */
1231 case SYSLOG_ACTION_OPEN: /* Open log */
1233 case SYSLOG_ACTION_READ: /* Read from log */
1235 if (!buf || len < 0)
1240 if (!access_ok(VERIFY_WRITE, buf, len)) {
1244 error = wait_event_interruptible(log_wait,
1245 syslog_seq != log_next_seq);
1248 error = syslog_print(buf, len);
1250 /* Read/clear last kernel messages */
1251 case SYSLOG_ACTION_READ_CLEAR:
1254 /* Read last kernel messages */
1255 case SYSLOG_ACTION_READ_ALL:
1257 if (!buf || len < 0)
1262 if (!access_ok(VERIFY_WRITE, buf, len)) {
1266 error = syslog_print_all(buf, len, clear);
1268 /* Clear ring buffer */
1269 case SYSLOG_ACTION_CLEAR:
1270 syslog_print_all(NULL, 0, true);
1272 /* Disable logging to console */
1273 case SYSLOG_ACTION_CONSOLE_OFF:
1274 if (saved_console_loglevel == -1)
1275 saved_console_loglevel = console_loglevel;
1276 console_loglevel = minimum_console_loglevel;
1278 /* Enable logging to console */
1279 case SYSLOG_ACTION_CONSOLE_ON:
1280 if (saved_console_loglevel != -1) {
1281 console_loglevel = saved_console_loglevel;
1282 saved_console_loglevel = -1;
1285 /* Set level of messages printed to console */
1286 case SYSLOG_ACTION_CONSOLE_LEVEL:
1288 if (len < 1 || len > 8)
1290 if (len < minimum_console_loglevel)
1291 len = minimum_console_loglevel;
1292 console_loglevel = len;
1293 /* Implicitly re-enable logging to console */
1294 saved_console_loglevel = -1;
1297 /* Number of chars in the log buffer */
1298 case SYSLOG_ACTION_SIZE_UNREAD:
1299 raw_spin_lock_irq(&logbuf_lock);
1300 if (syslog_seq < log_first_seq) {
1301 /* messages are gone, move to first one */
1302 syslog_seq = log_first_seq;
1303 syslog_idx = log_first_idx;
1309 * Short-cut for poll(/"proc/kmsg") which simply checks
1310 * for pending data, not the size; return the count of
1311 * records, not the length.
1313 error = log_next_idx - syslog_idx;
1315 u64 seq = syslog_seq;
1316 u32 idx = syslog_idx;
1317 enum log_flags prev = syslog_prev;
1320 while (seq < log_next_seq) {
1321 struct printk_log *msg = log_from_idx(idx);
1323 error += msg_print_text(msg, prev, true, NULL, 0);
1324 idx = log_next(idx);
1328 error -= syslog_partial;
1330 raw_spin_unlock_irq(&logbuf_lock);
1332 /* Size of the log buffer */
1333 case SYSLOG_ACTION_SIZE_BUFFER:
1334 error = log_buf_len;
1344 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1346 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1350 * Call the console drivers, asking them to write out
1351 * log_buf[start] to log_buf[end - 1].
1352 * The console_lock must be held.
1354 static void call_console_drivers(int level, const char *text, size_t len)
1356 struct console *con;
1358 trace_console(text, len);
1360 if (level >= console_loglevel && !ignore_loglevel)
1362 if (!console_drivers)
1365 for_each_console(con) {
1366 if (exclusive_console && con != exclusive_console)
1368 if (!(con->flags & CON_ENABLED))
1372 if (!cpu_online(smp_processor_id()) &&
1373 !(con->flags & CON_ANYTIME))
1375 con->write(con, text, len);
1380 * Zap console related locks when oopsing. Only zap at most once
1381 * every 10 seconds, to leave time for slow consoles to print a
1384 static void zap_locks(void)
1386 static unsigned long oops_timestamp;
1388 if (time_after_eq(jiffies, oops_timestamp) &&
1389 !time_after(jiffies, oops_timestamp + 30 * HZ))
1392 oops_timestamp = jiffies;
1395 /* If a crash is occurring, make sure we can't deadlock */
1396 raw_spin_lock_init(&logbuf_lock);
1397 /* And make sure that we print immediately */
1398 sema_init(&console_sem, 1);
1402 * Check if we have any console that is capable of printing while cpu is
1403 * booting or shutting down. Requires console_sem.
1405 static int have_callable_console(void)
1407 struct console *con;
1409 for_each_console(con)
1410 if (con->flags & CON_ANYTIME)
1417 * Can we actually use the console at this time on this cpu?
1419 * Console drivers may assume that per-cpu resources have been allocated. So
1420 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1421 * call them until this CPU is officially up.
1423 static inline int can_use_console(unsigned int cpu)
1425 return cpu_online(cpu) || have_callable_console();
1429 * Try to get console ownership to actually show the kernel
1430 * messages from a 'printk'. Return true (and with the
1431 * console_lock held, and 'console_locked' set) if it
1432 * is successful, false otherwise.
1434 static int console_trylock_for_printk(void)
1436 unsigned int cpu = smp_processor_id();
1438 if (!console_trylock())
1441 * If we can't use the console, we need to release the console
1442 * semaphore by hand to avoid flushing the buffer. We need to hold the
1443 * console semaphore in order to do this test safely.
1445 if (!can_use_console(cpu)) {
1453 int printk_delay_msec __read_mostly;
1455 static inline void printk_delay(void)
1457 if (unlikely(printk_delay_msec)) {
1458 int m = printk_delay_msec;
1462 touch_nmi_watchdog();
1468 * Continuation lines are buffered, and not committed to the record buffer
1469 * until the line is complete, or a race forces it. The line fragments
1470 * though, are printed immediately to the consoles to ensure everything has
1471 * reached the console in case of a kernel crash.
1473 static struct cont {
1474 char buf[LOG_LINE_MAX];
1475 size_t len; /* length == 0 means unused buffer */
1476 size_t cons; /* bytes written to console */
1477 struct task_struct *owner; /* task of first print*/
1478 u64 ts_nsec; /* time of first print */
1479 u8 level; /* log level of first message */
1480 u8 facility; /* log level of first message */
1481 enum log_flags flags; /* prefix, newline flags */
1482 bool flushed:1; /* buffer sealed and committed */
1485 static void cont_flush(enum log_flags flags)
1494 * If a fragment of this line was directly flushed to the
1495 * console; wait for the console to pick up the rest of the
1496 * line. LOG_NOCONS suppresses a duplicated output.
1498 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1499 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1501 cont.flushed = true;
1504 * If no fragment of this line ever reached the console,
1505 * just submit it to the store and free the buffer.
1507 log_store(cont.facility, cont.level, flags, 0,
1508 NULL, 0, cont.buf, cont.len);
1513 static bool cont_add(int facility, int level, const char *text, size_t len)
1515 if (cont.len && cont.flushed)
1518 if (cont.len + len > sizeof(cont.buf)) {
1519 /* the line gets too long, split it up in separate records */
1520 cont_flush(LOG_CONT);
1525 cont.facility = facility;
1527 cont.owner = current;
1528 cont.ts_nsec = local_clock();
1531 cont.flushed = false;
1534 memcpy(cont.buf + cont.len, text, len);
1537 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1538 cont_flush(LOG_CONT);
1543 static size_t cont_print_text(char *text, size_t size)
1548 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1549 textlen += print_time(cont.ts_nsec, text);
1553 len = cont.len - cont.cons;
1557 memcpy(text + textlen, cont.buf + cont.cons, len);
1559 cont.cons = cont.len;
1563 if (cont.flags & LOG_NEWLINE)
1564 text[textlen++] = '\n';
1565 /* got everything, release buffer */
1571 asmlinkage int vprintk_emit(int facility, int level,
1572 const char *dict, size_t dictlen,
1573 const char *fmt, va_list args)
1575 static int recursion_bug;
1576 static char textbuf[LOG_LINE_MAX];
1577 char *text = textbuf;
1578 size_t text_len = 0;
1579 enum log_flags lflags = 0;
1580 unsigned long flags;
1582 int printed_len = 0;
1583 bool in_sched = false;
1584 /* cpu currently holding logbuf_lock in this function */
1585 static volatile unsigned int logbuf_cpu = UINT_MAX;
1587 if (level == SCHED_MESSAGE_LOGLEVEL) {
1592 boot_delay_msec(level);
1595 /* This stops the holder of console_sem just where we want him */
1596 local_irq_save(flags);
1597 this_cpu = smp_processor_id();
1600 * Ouch, printk recursed into itself!
1602 if (unlikely(logbuf_cpu == this_cpu)) {
1604 * If a crash is occurring during printk() on this CPU,
1605 * then try to get the crash message out but make sure
1606 * we can't deadlock. Otherwise just return to avoid the
1607 * recursion and return - but flag the recursion so that
1608 * it can be printed at the next appropriate moment:
1610 if (!oops_in_progress && !lockdep_recursing(current)) {
1612 local_irq_restore(flags);
1619 raw_spin_lock(&logbuf_lock);
1620 logbuf_cpu = this_cpu;
1622 if (recursion_bug) {
1623 static const char recursion_msg[] =
1624 "BUG: recent printk recursion!";
1627 text_len = strlen(recursion_msg);
1628 /* emit KERN_CRIT message */
1629 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1630 NULL, 0, recursion_msg, text_len);
1634 * The printf needs to come first; we need the syslog
1635 * prefix which might be passed-in as a parameter.
1638 text_len = scnprintf(text, sizeof(textbuf),
1639 KERN_WARNING "[sched_delayed] ");
1641 text_len += vscnprintf(text + text_len,
1642 sizeof(textbuf) - text_len, fmt, args);
1644 /* mark and strip a trailing newline */
1645 if (text_len && text[text_len-1] == '\n') {
1647 lflags |= LOG_NEWLINE;
1650 /* strip kernel syslog prefix and extract log level or control flags */
1651 if (facility == 0) {
1652 int kern_level = printk_get_level(text);
1655 const char *end_of_header = printk_skip_level(text);
1656 switch (kern_level) {
1659 level = kern_level - '0';
1660 case 'd': /* KERN_DEFAULT */
1661 lflags |= LOG_PREFIX;
1664 * No need to check length here because vscnprintf
1665 * put '\0' at the end of the string. Only valid and
1666 * newly printed level is detected.
1668 text_len -= end_of_header - text;
1669 text = (char *)end_of_header;
1674 level = default_message_loglevel;
1677 lflags |= LOG_PREFIX|LOG_NEWLINE;
1679 if (!(lflags & LOG_NEWLINE)) {
1681 * Flush the conflicting buffer. An earlier newline was missing,
1682 * or another task also prints continuation lines.
1684 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1685 cont_flush(LOG_NEWLINE);
1687 /* buffer line if possible, otherwise store it right away */
1688 if (cont_add(facility, level, text, text_len))
1689 printed_len += text_len;
1691 printed_len += log_store(facility, level,
1692 lflags | LOG_CONT, 0,
1693 dict, dictlen, text, text_len);
1695 bool stored = false;
1698 * If an earlier newline was missing and it was the same task,
1699 * either merge it with the current buffer and flush, or if
1700 * there was a race with interrupts (prefix == true) then just
1701 * flush it out and store this line separately.
1702 * If the preceding printk was from a different task and missed
1703 * a newline, flush and append the newline.
1706 if (cont.owner == current && !(lflags & LOG_PREFIX))
1707 stored = cont_add(facility, level, text,
1709 cont_flush(LOG_NEWLINE);
1713 printed_len += text_len;
1715 printed_len += log_store(facility, level, lflags, 0,
1716 dict, dictlen, text, text_len);
1719 logbuf_cpu = UINT_MAX;
1720 raw_spin_unlock(&logbuf_lock);
1722 local_irq_restore(flags);
1724 /* If called from the scheduler, we can not call up(). */
1729 * Disable preemption to avoid being preempted while holding
1730 * console_sem which would prevent anyone from printing to console
1734 * Try to acquire and then immediately release the console semaphore.
1735 * The release will print out buffers and wake up /dev/kmsg and syslog()
1738 if (console_trylock_for_printk())
1744 EXPORT_SYMBOL(vprintk_emit);
1746 asmlinkage int vprintk(const char *fmt, va_list args)
1748 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1750 EXPORT_SYMBOL(vprintk);
1752 asmlinkage int printk_emit(int facility, int level,
1753 const char *dict, size_t dictlen,
1754 const char *fmt, ...)
1759 va_start(args, fmt);
1760 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1765 EXPORT_SYMBOL(printk_emit);
1768 * printk - print a kernel message
1769 * @fmt: format string
1771 * This is printk(). It can be called from any context. We want it to work.
1773 * We try to grab the console_lock. If we succeed, it's easy - we log the
1774 * output and call the console drivers. If we fail to get the semaphore, we
1775 * place the output into the log buffer and return. The current holder of
1776 * the console_sem will notice the new output in console_unlock(); and will
1777 * send it to the consoles before releasing the lock.
1779 * One effect of this deferred printing is that code which calls printk() and
1780 * then changes console_loglevel may break. This is because console_loglevel
1781 * is inspected when the actual printing occurs.
1786 * See the vsnprintf() documentation for format string extensions over C99.
1788 asmlinkage __visible int printk(const char *fmt, ...)
1793 #ifdef CONFIG_KGDB_KDB
1794 if (unlikely(kdb_trap_printk)) {
1795 va_start(args, fmt);
1796 r = vkdb_printf(fmt, args);
1801 va_start(args, fmt);
1802 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1807 EXPORT_SYMBOL(printk);
1809 #else /* CONFIG_PRINTK */
1811 #define LOG_LINE_MAX 0
1812 #define PREFIX_MAX 0
1813 #define LOG_LINE_MAX 0
1814 static u64 syslog_seq;
1815 static u32 syslog_idx;
1816 static u64 console_seq;
1817 static u32 console_idx;
1818 static enum log_flags syslog_prev;
1819 static u64 log_first_seq;
1820 static u32 log_first_idx;
1821 static u64 log_next_seq;
1822 static enum log_flags console_prev;
1823 static struct cont {
1829 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1830 static u32 log_next(u32 idx) { return 0; }
1831 static void call_console_drivers(int level, const char *text, size_t len) {}
1832 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1833 bool syslog, char *buf, size_t size) { return 0; }
1834 static size_t cont_print_text(char *text, size_t size) { return 0; }
1836 #endif /* CONFIG_PRINTK */
1838 #ifdef CONFIG_EARLY_PRINTK
1839 struct console *early_console;
1841 void early_vprintk(const char *fmt, va_list ap)
1843 if (early_console) {
1845 int n = vscnprintf(buf, sizeof(buf), fmt, ap);
1847 early_console->write(early_console, buf, n);
1851 asmlinkage __visible void early_printk(const char *fmt, ...)
1856 early_vprintk(fmt, ap);
1861 static int __add_preferred_console(char *name, int idx, char *options,
1864 struct console_cmdline *c;
1868 * See if this tty is not yet registered, and
1869 * if we have a slot free.
1871 for (i = 0, c = console_cmdline;
1872 i < MAX_CMDLINECONSOLES && c->name[0];
1874 if (strcmp(c->name, name) == 0 && c->index == idx) {
1876 selected_console = i;
1880 if (i == MAX_CMDLINECONSOLES)
1883 selected_console = i;
1884 strlcpy(c->name, name, sizeof(c->name));
1885 c->options = options;
1886 braille_set_options(c, brl_options);
1892 * Set up a list of consoles. Called from init/main.c
1894 static int __init console_setup(char *str)
1896 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1897 char *s, *options, *brl_options = NULL;
1900 if (_braille_console_setup(&str, &brl_options))
1904 * Decode str into name, index, options.
1906 if (str[0] >= '0' && str[0] <= '9') {
1907 strcpy(buf, "ttyS");
1908 strncpy(buf + 4, str, sizeof(buf) - 5);
1910 strncpy(buf, str, sizeof(buf) - 1);
1912 buf[sizeof(buf) - 1] = 0;
1913 if ((options = strchr(str, ',')) != NULL)
1916 if (!strcmp(str, "ttya"))
1917 strcpy(buf, "ttyS0");
1918 if (!strcmp(str, "ttyb"))
1919 strcpy(buf, "ttyS1");
1921 for (s = buf; *s; s++)
1922 if ((*s >= '0' && *s <= '9') || *s == ',')
1924 idx = simple_strtoul(s, NULL, 10);
1927 __add_preferred_console(buf, idx, options, brl_options);
1928 console_set_on_cmdline = 1;
1931 __setup("console=", console_setup);
1934 * add_preferred_console - add a device to the list of preferred consoles.
1935 * @name: device name
1936 * @idx: device index
1937 * @options: options for this console
1939 * The last preferred console added will be used for kernel messages
1940 * and stdin/out/err for init. Normally this is used by console_setup
1941 * above to handle user-supplied console arguments; however it can also
1942 * be used by arch-specific code either to override the user or more
1943 * commonly to provide a default console (ie from PROM variables) when
1944 * the user has not supplied one.
1946 int add_preferred_console(char *name, int idx, char *options)
1948 return __add_preferred_console(name, idx, options, NULL);
1951 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1953 struct console_cmdline *c;
1956 for (i = 0, c = console_cmdline;
1957 i < MAX_CMDLINECONSOLES && c->name[0];
1959 if (strcmp(c->name, name) == 0 && c->index == idx) {
1960 strlcpy(c->name, name_new, sizeof(c->name));
1961 c->name[sizeof(c->name) - 1] = 0;
1962 c->options = options;
1970 bool console_suspend_enabled = 1;
1971 EXPORT_SYMBOL(console_suspend_enabled);
1973 static int __init console_suspend_disable(char *str)
1975 console_suspend_enabled = 0;
1978 __setup("no_console_suspend", console_suspend_disable);
1979 module_param_named(console_suspend, console_suspend_enabled,
1980 bool, S_IRUGO | S_IWUSR);
1981 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1982 " and hibernate operations");
1985 * suspend_console - suspend the console subsystem
1987 * This disables printk() while we go into suspend states
1989 void suspend_console(void)
1991 if (!console_suspend_enabled)
1993 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1995 console_suspended = 1;
1999 void resume_console(void)
2001 if (!console_suspend_enabled)
2004 console_suspended = 0;
2009 * console_cpu_notify - print deferred console messages after CPU hotplug
2010 * @self: notifier struct
2011 * @action: CPU hotplug event
2014 * If printk() is called from a CPU that is not online yet, the messages
2015 * will be spooled but will not show up on the console. This function is
2016 * called when a new CPU comes online (or fails to come up), and ensures
2017 * that any such output gets printed.
2019 static int console_cpu_notify(struct notifier_block *self,
2020 unsigned long action, void *hcpu)
2025 case CPU_DOWN_FAILED:
2026 case CPU_UP_CANCELED:
2034 * console_lock - lock the console system for exclusive use.
2036 * Acquires a lock which guarantees that the caller has
2037 * exclusive access to the console system and the console_drivers list.
2039 * Can sleep, returns nothing.
2041 void console_lock(void)
2046 if (console_suspended)
2049 console_may_schedule = 1;
2051 EXPORT_SYMBOL(console_lock);
2054 * console_trylock - try to lock the console system for exclusive use.
2056 * Tried to acquire a lock which guarantees that the caller has
2057 * exclusive access to the console system and the console_drivers list.
2059 * returns 1 on success, and 0 on failure to acquire the lock.
2061 int console_trylock(void)
2063 if (down_trylock_console_sem())
2065 if (console_suspended) {
2070 console_may_schedule = 0;
2073 EXPORT_SYMBOL(console_trylock);
2075 int is_console_locked(void)
2077 return console_locked;
2080 static void console_cont_flush(char *text, size_t size)
2082 unsigned long flags;
2085 raw_spin_lock_irqsave(&logbuf_lock, flags);
2091 * We still queue earlier records, likely because the console was
2092 * busy. The earlier ones need to be printed before this one, we
2093 * did not flush any fragment so far, so just let it queue up.
2095 if (console_seq < log_next_seq && !cont.cons)
2098 len = cont_print_text(text, size);
2099 raw_spin_unlock(&logbuf_lock);
2100 stop_critical_timings();
2101 call_console_drivers(cont.level, text, len);
2102 start_critical_timings();
2103 local_irq_restore(flags);
2106 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2110 * console_unlock - unlock the console system
2112 * Releases the console_lock which the caller holds on the console system
2113 * and the console driver list.
2115 * While the console_lock was held, console output may have been buffered
2116 * by printk(). If this is the case, console_unlock(); emits
2117 * the output prior to releasing the lock.
2119 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2121 * console_unlock(); may be called from any context.
2123 void console_unlock(void)
2125 static char text[LOG_LINE_MAX + PREFIX_MAX];
2126 static u64 seen_seq;
2127 unsigned long flags;
2128 bool wake_klogd = false;
2131 if (console_suspended) {
2136 console_may_schedule = 0;
2138 /* flush buffered message fragment immediately to console */
2139 console_cont_flush(text, sizeof(text));
2142 struct printk_log *msg;
2146 raw_spin_lock_irqsave(&logbuf_lock, flags);
2147 if (seen_seq != log_next_seq) {
2149 seen_seq = log_next_seq;
2152 if (console_seq < log_first_seq) {
2153 len = sprintf(text, "** %u printk messages dropped ** ",
2154 (unsigned)(log_first_seq - console_seq));
2156 /* messages are gone, move to first one */
2157 console_seq = log_first_seq;
2158 console_idx = log_first_idx;
2164 if (console_seq == log_next_seq)
2167 msg = log_from_idx(console_idx);
2168 if (msg->flags & LOG_NOCONS) {
2170 * Skip record we have buffered and already printed
2171 * directly to the console when we received it.
2173 console_idx = log_next(console_idx);
2176 * We will get here again when we register a new
2177 * CON_PRINTBUFFER console. Clear the flag so we
2178 * will properly dump everything later.
2180 msg->flags &= ~LOG_NOCONS;
2181 console_prev = msg->flags;
2186 len += msg_print_text(msg, console_prev, false,
2187 text + len, sizeof(text) - len);
2188 console_idx = log_next(console_idx);
2190 console_prev = msg->flags;
2191 raw_spin_unlock(&logbuf_lock);
2193 stop_critical_timings(); /* don't trace print latency */
2194 call_console_drivers(level, text, len);
2195 start_critical_timings();
2196 local_irq_restore(flags);
2200 /* Release the exclusive_console once it is used */
2201 if (unlikely(exclusive_console))
2202 exclusive_console = NULL;
2204 raw_spin_unlock(&logbuf_lock);
2209 * Someone could have filled up the buffer again, so re-check if there's
2210 * something to flush. In case we cannot trylock the console_sem again,
2211 * there's a new owner and the console_unlock() from them will do the
2212 * flush, no worries.
2214 raw_spin_lock(&logbuf_lock);
2215 retry = console_seq != log_next_seq;
2216 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2218 if (retry && console_trylock())
2224 EXPORT_SYMBOL(console_unlock);
2227 * console_conditional_schedule - yield the CPU if required
2229 * If the console code is currently allowed to sleep, and
2230 * if this CPU should yield the CPU to another task, do
2233 * Must be called within console_lock();.
2235 void __sched console_conditional_schedule(void)
2237 if (console_may_schedule)
2240 EXPORT_SYMBOL(console_conditional_schedule);
2242 void console_unblank(void)
2247 * console_unblank can no longer be called in interrupt context unless
2248 * oops_in_progress is set to 1..
2250 if (oops_in_progress) {
2251 if (down_trylock_console_sem() != 0)
2257 console_may_schedule = 0;
2259 if ((c->flags & CON_ENABLED) && c->unblank)
2265 * Return the console tty driver structure and its associated index
2267 struct tty_driver *console_device(int *index)
2270 struct tty_driver *driver = NULL;
2273 for_each_console(c) {
2276 driver = c->device(c, index);
2285 * Prevent further output on the passed console device so that (for example)
2286 * serial drivers can disable console output before suspending a port, and can
2287 * re-enable output afterwards.
2289 void console_stop(struct console *console)
2292 console->flags &= ~CON_ENABLED;
2295 EXPORT_SYMBOL(console_stop);
2297 void console_start(struct console *console)
2300 console->flags |= CON_ENABLED;
2303 EXPORT_SYMBOL(console_start);
2305 static int __read_mostly keep_bootcon;
2307 static int __init keep_bootcon_setup(char *str)
2310 pr_info("debug: skip boot console de-registration.\n");
2315 early_param("keep_bootcon", keep_bootcon_setup);
2318 * The console driver calls this routine during kernel initialization
2319 * to register the console printing procedure with printk() and to
2320 * print any messages that were printed by the kernel before the
2321 * console driver was initialized.
2323 * This can happen pretty early during the boot process (because of
2324 * early_printk) - sometimes before setup_arch() completes - be careful
2325 * of what kernel features are used - they may not be initialised yet.
2327 * There are two types of consoles - bootconsoles (early_printk) and
2328 * "real" consoles (everything which is not a bootconsole) which are
2329 * handled differently.
2330 * - Any number of bootconsoles can be registered at any time.
2331 * - As soon as a "real" console is registered, all bootconsoles
2332 * will be unregistered automatically.
2333 * - Once a "real" console is registered, any attempt to register a
2334 * bootconsoles will be rejected
2336 void register_console(struct console *newcon)
2339 unsigned long flags;
2340 struct console *bcon = NULL;
2341 struct console_cmdline *c;
2343 if (console_drivers)
2344 for_each_console(bcon)
2345 if (WARN(bcon == newcon,
2346 "console '%s%d' already registered\n",
2347 bcon->name, bcon->index))
2351 * before we register a new CON_BOOT console, make sure we don't
2352 * already have a valid console
2354 if (console_drivers && newcon->flags & CON_BOOT) {
2355 /* find the last or real console */
2356 for_each_console(bcon) {
2357 if (!(bcon->flags & CON_BOOT)) {
2358 pr_info("Too late to register bootconsole %s%d\n",
2359 newcon->name, newcon->index);
2365 if (console_drivers && console_drivers->flags & CON_BOOT)
2366 bcon = console_drivers;
2368 if (preferred_console < 0 || bcon || !console_drivers)
2369 preferred_console = selected_console;
2371 if (newcon->early_setup)
2372 newcon->early_setup();
2375 * See if we want to use this console driver. If we
2376 * didn't select a console we take the first one
2377 * that registers here.
2379 if (preferred_console < 0) {
2380 if (newcon->index < 0)
2382 if (newcon->setup == NULL ||
2383 newcon->setup(newcon, NULL) == 0) {
2384 newcon->flags |= CON_ENABLED;
2385 if (newcon->device) {
2386 newcon->flags |= CON_CONSDEV;
2387 preferred_console = 0;
2393 * See if this console matches one we selected on
2396 for (i = 0, c = console_cmdline;
2397 i < MAX_CMDLINECONSOLES && c->name[0];
2399 if (strcmp(c->name, newcon->name) != 0)
2401 if (newcon->index >= 0 &&
2402 newcon->index != c->index)
2404 if (newcon->index < 0)
2405 newcon->index = c->index;
2407 if (_braille_register_console(newcon, c))
2410 if (newcon->setup &&
2411 newcon->setup(newcon, console_cmdline[i].options) != 0)
2413 newcon->flags |= CON_ENABLED;
2414 newcon->index = c->index;
2415 if (i == selected_console) {
2416 newcon->flags |= CON_CONSDEV;
2417 preferred_console = selected_console;
2422 if (!(newcon->flags & CON_ENABLED))
2426 * If we have a bootconsole, and are switching to a real console,
2427 * don't print everything out again, since when the boot console, and
2428 * the real console are the same physical device, it's annoying to
2429 * see the beginning boot messages twice
2431 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2432 newcon->flags &= ~CON_PRINTBUFFER;
2435 * Put this console in the list - keep the
2436 * preferred driver at the head of the list.
2439 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2440 newcon->next = console_drivers;
2441 console_drivers = newcon;
2443 newcon->next->flags &= ~CON_CONSDEV;
2445 newcon->next = console_drivers->next;
2446 console_drivers->next = newcon;
2448 if (newcon->flags & CON_PRINTBUFFER) {
2450 * console_unlock(); will print out the buffered messages
2453 raw_spin_lock_irqsave(&logbuf_lock, flags);
2454 console_seq = syslog_seq;
2455 console_idx = syslog_idx;
2456 console_prev = syslog_prev;
2457 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2459 * We're about to replay the log buffer. Only do this to the
2460 * just-registered console to avoid excessive message spam to
2461 * the already-registered consoles.
2463 exclusive_console = newcon;
2466 console_sysfs_notify();
2469 * By unregistering the bootconsoles after we enable the real console
2470 * we get the "console xxx enabled" message on all the consoles -
2471 * boot consoles, real consoles, etc - this is to ensure that end
2472 * users know there might be something in the kernel's log buffer that
2473 * went to the bootconsole (that they do not see on the real console)
2475 pr_info("%sconsole [%s%d] enabled\n",
2476 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2477 newcon->name, newcon->index);
2479 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2481 /* We need to iterate through all boot consoles, to make
2482 * sure we print everything out, before we unregister them.
2484 for_each_console(bcon)
2485 if (bcon->flags & CON_BOOT)
2486 unregister_console(bcon);
2489 EXPORT_SYMBOL(register_console);
2491 int unregister_console(struct console *console)
2493 struct console *a, *b;
2496 pr_info("%sconsole [%s%d] disabled\n",
2497 (console->flags & CON_BOOT) ? "boot" : "" ,
2498 console->name, console->index);
2500 res = _braille_unregister_console(console);
2506 if (console_drivers == console) {
2507 console_drivers=console->next;
2509 } else if (console_drivers) {
2510 for (a=console_drivers->next, b=console_drivers ;
2511 a; b=a, a=b->next) {
2521 * If this isn't the last console and it has CON_CONSDEV set, we
2522 * need to set it on the next preferred console.
2524 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2525 console_drivers->flags |= CON_CONSDEV;
2527 console->flags &= ~CON_ENABLED;
2529 console_sysfs_notify();
2532 EXPORT_SYMBOL(unregister_console);
2534 static int __init printk_late_init(void)
2536 struct console *con;
2538 for_each_console(con) {
2539 if (!keep_bootcon && con->flags & CON_BOOT) {
2540 unregister_console(con);
2543 hotcpu_notifier(console_cpu_notify, 0);
2546 late_initcall(printk_late_init);
2548 #if defined CONFIG_PRINTK
2550 * Delayed printk version, for scheduler-internal messages:
2552 #define PRINTK_PENDING_WAKEUP 0x01
2553 #define PRINTK_PENDING_OUTPUT 0x02
2555 static DEFINE_PER_CPU(int, printk_pending);
2557 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2559 int pending = __this_cpu_xchg(printk_pending, 0);
2561 if (pending & PRINTK_PENDING_OUTPUT) {
2562 /* If trylock fails, someone else is doing the printing */
2563 if (console_trylock())
2567 if (pending & PRINTK_PENDING_WAKEUP)
2568 wake_up_interruptible(&log_wait);
2571 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2572 .func = wake_up_klogd_work_func,
2573 .flags = IRQ_WORK_LAZY,
2576 void wake_up_klogd(void)
2579 if (waitqueue_active(&log_wait)) {
2580 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2581 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2586 int printk_deferred(const char *fmt, ...)
2592 va_start(args, fmt);
2593 r = vprintk_emit(0, SCHED_MESSAGE_LOGLEVEL, NULL, 0, fmt, args);
2596 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2597 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2604 * printk rate limiting, lifted from the networking subsystem.
2606 * This enforces a rate limit: not more than 10 kernel messages
2607 * every 5s to make a denial-of-service attack impossible.
2609 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2611 int __printk_ratelimit(const char *func)
2613 return ___ratelimit(&printk_ratelimit_state, func);
2615 EXPORT_SYMBOL(__printk_ratelimit);
2618 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2619 * @caller_jiffies: pointer to caller's state
2620 * @interval_msecs: minimum interval between prints
2622 * printk_timed_ratelimit() returns true if more than @interval_msecs
2623 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2626 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2627 unsigned int interval_msecs)
2629 if (*caller_jiffies == 0
2630 || !time_in_range(jiffies, *caller_jiffies,
2632 + msecs_to_jiffies(interval_msecs))) {
2633 *caller_jiffies = jiffies;
2638 EXPORT_SYMBOL(printk_timed_ratelimit);
2640 static DEFINE_SPINLOCK(dump_list_lock);
2641 static LIST_HEAD(dump_list);
2644 * kmsg_dump_register - register a kernel log dumper.
2645 * @dumper: pointer to the kmsg_dumper structure
2647 * Adds a kernel log dumper to the system. The dump callback in the
2648 * structure will be called when the kernel oopses or panics and must be
2649 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2651 int kmsg_dump_register(struct kmsg_dumper *dumper)
2653 unsigned long flags;
2656 /* The dump callback needs to be set */
2660 spin_lock_irqsave(&dump_list_lock, flags);
2661 /* Don't allow registering multiple times */
2662 if (!dumper->registered) {
2663 dumper->registered = 1;
2664 list_add_tail_rcu(&dumper->list, &dump_list);
2667 spin_unlock_irqrestore(&dump_list_lock, flags);
2671 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2674 * kmsg_dump_unregister - unregister a kmsg dumper.
2675 * @dumper: pointer to the kmsg_dumper structure
2677 * Removes a dump device from the system. Returns zero on success and
2678 * %-EINVAL otherwise.
2680 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2682 unsigned long flags;
2685 spin_lock_irqsave(&dump_list_lock, flags);
2686 if (dumper->registered) {
2687 dumper->registered = 0;
2688 list_del_rcu(&dumper->list);
2691 spin_unlock_irqrestore(&dump_list_lock, flags);
2696 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2698 static bool always_kmsg_dump;
2699 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2702 * kmsg_dump - dump kernel log to kernel message dumpers.
2703 * @reason: the reason (oops, panic etc) for dumping
2705 * Call each of the registered dumper's dump() callback, which can
2706 * retrieve the kmsg records with kmsg_dump_get_line() or
2707 * kmsg_dump_get_buffer().
2709 void kmsg_dump(enum kmsg_dump_reason reason)
2711 struct kmsg_dumper *dumper;
2712 unsigned long flags;
2714 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2718 list_for_each_entry_rcu(dumper, &dump_list, list) {
2719 if (dumper->max_reason && reason > dumper->max_reason)
2722 /* initialize iterator with data about the stored records */
2723 dumper->active = true;
2725 raw_spin_lock_irqsave(&logbuf_lock, flags);
2726 dumper->cur_seq = clear_seq;
2727 dumper->cur_idx = clear_idx;
2728 dumper->next_seq = log_next_seq;
2729 dumper->next_idx = log_next_idx;
2730 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2732 /* invoke dumper which will iterate over records */
2733 dumper->dump(dumper, reason);
2735 /* reset iterator */
2736 dumper->active = false;
2742 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2743 * @dumper: registered kmsg dumper
2744 * @syslog: include the "<4>" prefixes
2745 * @line: buffer to copy the line to
2746 * @size: maximum size of the buffer
2747 * @len: length of line placed into buffer
2749 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2750 * record, and copy one record into the provided buffer.
2752 * Consecutive calls will return the next available record moving
2753 * towards the end of the buffer with the youngest messages.
2755 * A return value of FALSE indicates that there are no more records to
2758 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2760 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2761 char *line, size_t size, size_t *len)
2763 struct printk_log *msg;
2767 if (!dumper->active)
2770 if (dumper->cur_seq < log_first_seq) {
2771 /* messages are gone, move to first available one */
2772 dumper->cur_seq = log_first_seq;
2773 dumper->cur_idx = log_first_idx;
2777 if (dumper->cur_seq >= log_next_seq)
2780 msg = log_from_idx(dumper->cur_idx);
2781 l = msg_print_text(msg, 0, syslog, line, size);
2783 dumper->cur_idx = log_next(dumper->cur_idx);
2793 * kmsg_dump_get_line - retrieve one kmsg log line
2794 * @dumper: registered kmsg dumper
2795 * @syslog: include the "<4>" prefixes
2796 * @line: buffer to copy the line to
2797 * @size: maximum size of the buffer
2798 * @len: length of line placed into buffer
2800 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2801 * record, and copy one record into the provided buffer.
2803 * Consecutive calls will return the next available record moving
2804 * towards the end of the buffer with the youngest messages.
2806 * A return value of FALSE indicates that there are no more records to
2809 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2810 char *line, size_t size, size_t *len)
2812 unsigned long flags;
2815 raw_spin_lock_irqsave(&logbuf_lock, flags);
2816 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2817 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2821 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2824 * kmsg_dump_get_buffer - copy kmsg log lines
2825 * @dumper: registered kmsg dumper
2826 * @syslog: include the "<4>" prefixes
2827 * @buf: buffer to copy the line to
2828 * @size: maximum size of the buffer
2829 * @len: length of line placed into buffer
2831 * Start at the end of the kmsg buffer and fill the provided buffer
2832 * with as many of the the *youngest* kmsg records that fit into it.
2833 * If the buffer is large enough, all available kmsg records will be
2834 * copied with a single call.
2836 * Consecutive calls will fill the buffer with the next block of
2837 * available older records, not including the earlier retrieved ones.
2839 * A return value of FALSE indicates that there are no more records to
2842 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2843 char *buf, size_t size, size_t *len)
2845 unsigned long flags;
2850 enum log_flags prev;
2854 if (!dumper->active)
2857 raw_spin_lock_irqsave(&logbuf_lock, flags);
2858 if (dumper->cur_seq < log_first_seq) {
2859 /* messages are gone, move to first available one */
2860 dumper->cur_seq = log_first_seq;
2861 dumper->cur_idx = log_first_idx;
2865 if (dumper->cur_seq >= dumper->next_seq) {
2866 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2870 /* calculate length of entire buffer */
2871 seq = dumper->cur_seq;
2872 idx = dumper->cur_idx;
2874 while (seq < dumper->next_seq) {
2875 struct printk_log *msg = log_from_idx(idx);
2877 l += msg_print_text(msg, prev, true, NULL, 0);
2878 idx = log_next(idx);
2883 /* move first record forward until length fits into the buffer */
2884 seq = dumper->cur_seq;
2885 idx = dumper->cur_idx;
2887 while (l > size && seq < dumper->next_seq) {
2888 struct printk_log *msg = log_from_idx(idx);
2890 l -= msg_print_text(msg, prev, true, NULL, 0);
2891 idx = log_next(idx);
2896 /* last message in next interation */
2901 while (seq < dumper->next_seq) {
2902 struct printk_log *msg = log_from_idx(idx);
2904 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2905 idx = log_next(idx);
2910 dumper->next_seq = next_seq;
2911 dumper->next_idx = next_idx;
2913 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2919 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2922 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2923 * @dumper: registered kmsg dumper
2925 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2926 * kmsg_dump_get_buffer() can be called again and used multiple
2927 * times within the same dumper.dump() callback.
2929 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2931 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
2933 dumper->cur_seq = clear_seq;
2934 dumper->cur_idx = clear_idx;
2935 dumper->next_seq = log_next_seq;
2936 dumper->next_idx = log_next_idx;
2940 * kmsg_dump_rewind - reset the interator
2941 * @dumper: registered kmsg dumper
2943 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2944 * kmsg_dump_get_buffer() can be called again and used multiple
2945 * times within the same dumper.dump() callback.
2947 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2949 unsigned long flags;
2951 raw_spin_lock_irqsave(&logbuf_lock, flags);
2952 kmsg_dump_rewind_nolock(dumper);
2953 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2955 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
2957 static char dump_stack_arch_desc_str[128];
2960 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
2961 * @fmt: printf-style format string
2962 * @...: arguments for the format string
2964 * The configured string will be printed right after utsname during task
2965 * dumps. Usually used to add arch-specific system identifiers. If an
2966 * arch wants to make use of such an ID string, it should initialize this
2967 * as soon as possible during boot.
2969 void __init dump_stack_set_arch_desc(const char *fmt, ...)
2973 va_start(args, fmt);
2974 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
2980 * dump_stack_print_info - print generic debug info for dump_stack()
2981 * @log_lvl: log level
2983 * Arch-specific dump_stack() implementations can use this function to
2984 * print out the same debug information as the generic dump_stack().
2986 void dump_stack_print_info(const char *log_lvl)
2988 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
2989 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
2990 print_tainted(), init_utsname()->release,
2991 (int)strcspn(init_utsname()->version, " "),
2992 init_utsname()->version);
2994 if (dump_stack_arch_desc_str[0] != '\0')
2995 printk("%sHardware name: %s\n",
2996 log_lvl, dump_stack_arch_desc_str);
2998 print_worker_info(log_lvl, current);
3002 * show_regs_print_info - print generic debug info for show_regs()
3003 * @log_lvl: log level
3005 * show_regs() implementations can use this function to print out generic
3006 * debug information.
3008 void show_regs_print_info(const char *log_lvl)
3010 dump_stack_print_info(log_lvl);
3012 printk("%stask: %p ti: %p task.ti: %p\n",
3013 log_lvl, current, current_thread_info(),
3014 task_thread_info(current));