2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/memblock.h>
35 #include <linux/syscalls.h>
36 #include <linux/kexec.h>
37 #include <linux/kdb.h>
38 #include <linux/ratelimit.h>
39 #include <linux/kmsg_dump.h>
40 #include <linux/syslog.h>
41 #include <linux/cpu.h>
42 #include <linux/notifier.h>
43 #include <linux/rculist.h>
44 #include <linux/poll.h>
45 #include <linux/irq_work.h>
46 #include <linux/utsname.h>
47 #include <linux/ctype.h>
48 #include <linux/uio.h>
50 #include <asm/uaccess.h>
52 #define CREATE_TRACE_POINTS
53 #include <trace/events/printk.h>
55 #include "console_cmdline.h"
58 int console_printk[4] = {
59 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
60 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
61 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
62 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
66 * Low level drivers may need that to know if they can schedule in
67 * their unblank() callback or not. So let's export it.
70 EXPORT_SYMBOL(oops_in_progress);
73 * console_sem protects the console_drivers list, and also
74 * provides serialisation for access to the entire console
77 static DEFINE_SEMAPHORE(console_sem);
78 struct console *console_drivers;
79 EXPORT_SYMBOL_GPL(console_drivers);
82 static struct lockdep_map console_lock_dep_map = {
83 .name = "console_lock"
88 * Number of registered extended console drivers.
90 * If extended consoles are present, in-kernel cont reassembly is disabled
91 * and each fragment is stored as a separate log entry with proper
92 * continuation flag so that every emitted message has full metadata. This
93 * doesn't change the result for regular consoles or /proc/kmsg. For
94 * /dev/kmsg, as long as the reader concatenates messages according to
95 * consecutive continuation flags, the end result should be the same too.
97 static int nr_ext_console_drivers;
100 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
101 * macros instead of functions so that _RET_IP_ contains useful information.
103 #define down_console_sem() do { \
105 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
108 static int __down_trylock_console_sem(unsigned long ip)
110 if (down_trylock(&console_sem))
112 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
115 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
117 #define up_console_sem() do { \
118 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
123 * This is used for debugging the mess that is the VT code by
124 * keeping track if we have the console semaphore held. It's
125 * definitely not the perfect debug tool (we don't know if _WE_
126 * hold it and are racing, but it helps tracking those weird code
127 * paths in the console code where we end up in places I want
128 * locked without the console sempahore held).
130 static int console_locked, console_suspended;
133 * If exclusive_console is non-NULL then only this console is to be printed to.
135 static struct console *exclusive_console;
138 * Array of consoles built from command line options (console=)
141 #define MAX_CMDLINECONSOLES 8
143 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
145 static int selected_console = -1;
146 static int preferred_console = -1;
147 int console_set_on_cmdline;
148 EXPORT_SYMBOL(console_set_on_cmdline);
150 /* Flag: console code may call schedule() */
151 static int console_may_schedule;
154 * The printk log buffer consists of a chain of concatenated variable
155 * length records. Every record starts with a record header, containing
156 * the overall length of the record.
158 * The heads to the first and last entry in the buffer, as well as the
159 * sequence numbers of these entries are maintained when messages are
162 * If the heads indicate available messages, the length in the header
163 * tells the start next message. A length == 0 for the next message
164 * indicates a wrap-around to the beginning of the buffer.
166 * Every record carries the monotonic timestamp in microseconds, as well as
167 * the standard userspace syslog level and syslog facility. The usual
168 * kernel messages use LOG_KERN; userspace-injected messages always carry
169 * a matching syslog facility, by default LOG_USER. The origin of every
170 * message can be reliably determined that way.
172 * The human readable log message directly follows the message header. The
173 * length of the message text is stored in the header, the stored message
176 * Optionally, a message can carry a dictionary of properties (key/value pairs),
177 * to provide userspace with a machine-readable message context.
179 * Examples for well-defined, commonly used property names are:
180 * DEVICE=b12:8 device identifier
184 * +sound:card0 subsystem:devname
185 * SUBSYSTEM=pci driver-core subsystem name
187 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
188 * follows directly after a '=' character. Every property is terminated by
189 * a '\0' character. The last property is not terminated.
191 * Example of a message structure:
192 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
193 * 0008 34 00 record is 52 bytes long
194 * 000a 0b 00 text is 11 bytes long
195 * 000c 1f 00 dictionary is 23 bytes long
196 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
197 * 0010 69 74 27 73 20 61 20 6c "it's a l"
199 * 001b 44 45 56 49 43 "DEVIC"
200 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
201 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
203 * 0032 00 00 00 padding to next message header
205 * The 'struct printk_log' buffer header must never be directly exported to
206 * userspace, it is a kernel-private implementation detail that might
207 * need to be changed in the future, when the requirements change.
209 * /dev/kmsg exports the structured data in the following line format:
210 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
212 * Users of the export format should ignore possible additional values
213 * separated by ',', and find the message after the ';' character.
215 * The optional key/value pairs are attached as continuation lines starting
216 * with a space character and terminated by a newline. All possible
217 * non-prinatable characters are escaped in the "\xff" notation.
221 LOG_NOCONS = 1, /* already flushed, do not print to console */
222 LOG_NEWLINE = 2, /* text ended with a newline */
223 LOG_PREFIX = 4, /* text started with a prefix */
224 LOG_CONT = 8, /* text is a fragment of a continuation line */
228 u64 ts_nsec; /* timestamp in nanoseconds */
229 u16 len; /* length of entire record */
230 u16 text_len; /* length of text buffer */
231 u16 dict_len; /* length of dictionary buffer */
232 u8 facility; /* syslog facility */
233 u8 flags:5; /* internal record flags */
234 u8 level:3; /* syslog level */
238 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
239 * within the scheduler's rq lock. It must be released before calling
240 * console_unlock() or anything else that might wake up a process.
242 static DEFINE_RAW_SPINLOCK(logbuf_lock);
245 DECLARE_WAIT_QUEUE_HEAD(log_wait);
246 /* the next printk record to read by syslog(READ) or /proc/kmsg */
247 static u64 syslog_seq;
248 static u32 syslog_idx;
249 static enum log_flags syslog_prev;
250 static size_t syslog_partial;
252 /* index and sequence number of the first record stored in the buffer */
253 static u64 log_first_seq;
254 static u32 log_first_idx;
256 /* index and sequence number of the next record to store in the buffer */
257 static u64 log_next_seq;
258 static u32 log_next_idx;
260 /* the next printk record to write to the console */
261 static u64 console_seq;
262 static u32 console_idx;
263 static enum log_flags console_prev;
265 /* the next printk record to read after the last 'clear' command */
266 static u64 clear_seq;
267 static u32 clear_idx;
269 #define PREFIX_MAX 32
270 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
272 #define LOG_LEVEL(v) ((v) & 0x07)
273 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
276 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
279 #define LOG_ALIGN __alignof__(struct printk_log)
281 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
282 #define LOG_BUF_LEN_MAX (u32)(1 << 31)
283 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
284 static char *log_buf = __log_buf;
285 static u32 log_buf_len = __LOG_BUF_LEN;
287 /* Return log buffer address */
288 char *log_buf_addr_get(void)
293 /* Return log buffer size */
294 u32 log_buf_len_get(void)
299 /* human readable text of the record */
300 static char *log_text(const struct printk_log *msg)
302 return (char *)msg + sizeof(struct printk_log);
305 /* optional key/value pair dictionary attached to the record */
306 static char *log_dict(const struct printk_log *msg)
308 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
311 /* get record by index; idx must point to valid msg */
312 static struct printk_log *log_from_idx(u32 idx)
314 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
317 * A length == 0 record is the end of buffer marker. Wrap around and
318 * read the message at the start of the buffer.
321 return (struct printk_log *)log_buf;
325 /* get next record; idx must point to valid msg */
326 static u32 log_next(u32 idx)
328 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
330 /* length == 0 indicates the end of the buffer; wrap */
332 * A length == 0 record is the end of buffer marker. Wrap around and
333 * read the message at the start of the buffer as *this* one, and
334 * return the one after that.
337 msg = (struct printk_log *)log_buf;
340 return idx + msg->len;
344 * Check whether there is enough free space for the given message.
346 * The same values of first_idx and next_idx mean that the buffer
347 * is either empty or full.
349 * If the buffer is empty, we must respect the position of the indexes.
350 * They cannot be reset to the beginning of the buffer.
352 static int logbuf_has_space(u32 msg_size, bool empty)
356 if (log_next_idx > log_first_idx || empty)
357 free = max(log_buf_len - log_next_idx, log_first_idx);
359 free = log_first_idx - log_next_idx;
362 * We need space also for an empty header that signalizes wrapping
365 return free >= msg_size + sizeof(struct printk_log);
368 static int log_make_free_space(u32 msg_size)
370 while (log_first_seq < log_next_seq) {
371 if (logbuf_has_space(msg_size, false))
373 /* drop old messages until we have enough contiguous space */
374 log_first_idx = log_next(log_first_idx);
378 /* sequence numbers are equal, so the log buffer is empty */
379 if (logbuf_has_space(msg_size, true))
385 /* compute the message size including the padding bytes */
386 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
390 size = sizeof(struct printk_log) + text_len + dict_len;
391 *pad_len = (-size) & (LOG_ALIGN - 1);
398 * Define how much of the log buffer we could take at maximum. The value
399 * must be greater than two. Note that only half of the buffer is available
400 * when the index points to the middle.
402 #define MAX_LOG_TAKE_PART 4
403 static const char trunc_msg[] = "<truncated>";
405 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
406 u16 *dict_len, u32 *pad_len)
409 * The message should not take the whole buffer. Otherwise, it might
410 * get removed too soon.
412 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
413 if (*text_len > max_text_len)
414 *text_len = max_text_len;
415 /* enable the warning message */
416 *trunc_msg_len = strlen(trunc_msg);
417 /* disable the "dict" completely */
419 /* compute the size again, count also the warning message */
420 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
423 /* insert record into the buffer, discard old ones, update heads */
424 static int log_store(int facility, int level,
425 enum log_flags flags, u64 ts_nsec,
426 const char *dict, u16 dict_len,
427 const char *text, u16 text_len)
429 struct printk_log *msg;
431 u16 trunc_msg_len = 0;
433 /* number of '\0' padding bytes to next message */
434 size = msg_used_size(text_len, dict_len, &pad_len);
436 if (log_make_free_space(size)) {
437 /* truncate the message if it is too long for empty buffer */
438 size = truncate_msg(&text_len, &trunc_msg_len,
439 &dict_len, &pad_len);
440 /* survive when the log buffer is too small for trunc_msg */
441 if (log_make_free_space(size))
445 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
447 * This message + an additional empty header does not fit
448 * at the end of the buffer. Add an empty header with len == 0
449 * to signify a wrap around.
451 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
456 msg = (struct printk_log *)(log_buf + log_next_idx);
457 memcpy(log_text(msg), text, text_len);
458 msg->text_len = text_len;
460 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
461 msg->text_len += trunc_msg_len;
463 memcpy(log_dict(msg), dict, dict_len);
464 msg->dict_len = dict_len;
465 msg->facility = facility;
466 msg->level = level & 7;
467 msg->flags = flags & 0x1f;
469 msg->ts_nsec = ts_nsec;
471 msg->ts_nsec = local_clock();
472 memset(log_dict(msg) + dict_len, 0, pad_len);
476 log_next_idx += msg->len;
479 return msg->text_len;
482 int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
484 static int syslog_action_restricted(int type)
489 * Unless restricted, we allow "read all" and "get buffer size"
492 return type != SYSLOG_ACTION_READ_ALL &&
493 type != SYSLOG_ACTION_SIZE_BUFFER;
496 int check_syslog_permissions(int type, int source)
499 * If this is from /proc/kmsg and we've already opened it, then we've
500 * already done the capabilities checks at open time.
502 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
505 if (syslog_action_restricted(type)) {
506 if (capable(CAP_SYSLOG))
509 * For historical reasons, accept CAP_SYS_ADMIN too, with
512 if (capable(CAP_SYS_ADMIN)) {
513 pr_warn_once("%s (%d): Attempt to access syslog with "
514 "CAP_SYS_ADMIN but no CAP_SYSLOG "
516 current->comm, task_pid_nr(current));
522 return security_syslog(type);
524 EXPORT_SYMBOL_GPL(check_syslog_permissions);
526 static void append_char(char **pp, char *e, char c)
532 static ssize_t msg_print_ext_header(char *buf, size_t size,
533 struct printk_log *msg, u64 seq,
534 enum log_flags prev_flags)
536 u64 ts_usec = msg->ts_nsec;
539 do_div(ts_usec, 1000);
542 * If we couldn't merge continuation line fragments during the print,
543 * export the stored flags to allow an optional external merge of the
544 * records. Merging the records isn't always neccessarily correct, like
545 * when we hit a race during printing. In most cases though, it produces
546 * better readable output. 'c' in the record flags mark the first
547 * fragment of a line, '+' the following.
549 if (msg->flags & LOG_CONT && !(prev_flags & LOG_CONT))
551 else if ((msg->flags & LOG_CONT) ||
552 ((prev_flags & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
555 return scnprintf(buf, size, "%u,%llu,%llu,%c;",
556 (msg->facility << 3) | msg->level, seq, ts_usec, cont);
559 static ssize_t msg_print_ext_body(char *buf, size_t size,
560 char *dict, size_t dict_len,
561 char *text, size_t text_len)
563 char *p = buf, *e = buf + size;
566 /* escape non-printable characters */
567 for (i = 0; i < text_len; i++) {
568 unsigned char c = text[i];
570 if (c < ' ' || c >= 127 || c == '\\')
571 p += scnprintf(p, e - p, "\\x%02x", c);
573 append_char(&p, e, c);
575 append_char(&p, e, '\n');
580 for (i = 0; i < dict_len; i++) {
581 unsigned char c = dict[i];
584 append_char(&p, e, ' ');
589 append_char(&p, e, '\n');
594 if (c < ' ' || c >= 127 || c == '\\') {
595 p += scnprintf(p, e - p, "\\x%02x", c);
599 append_char(&p, e, c);
601 append_char(&p, e, '\n');
607 /* /dev/kmsg - userspace message inject/listen interface */
608 struct devkmsg_user {
613 char buf[CONSOLE_EXT_LOG_MAX];
616 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
619 int level = default_message_loglevel;
620 int facility = 1; /* LOG_USER */
621 size_t len = iov_iter_count(from);
624 if (len > LOG_LINE_MAX)
626 buf = kmalloc(len+1, GFP_KERNEL);
631 if (copy_from_iter(buf, len, from) != len) {
637 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
638 * the decimal value represents 32bit, the lower 3 bit are the log
639 * level, the rest are the log facility.
641 * If no prefix or no userspace facility is specified, we
642 * enforce LOG_USER, to be able to reliably distinguish
643 * kernel-generated messages from userspace-injected ones.
646 if (line[0] == '<') {
650 u = simple_strtoul(line + 1, &endp, 10);
651 if (endp && endp[0] == '>') {
652 level = LOG_LEVEL(u);
653 if (LOG_FACILITY(u) != 0)
654 facility = LOG_FACILITY(u);
661 printk_emit(facility, level, NULL, 0, "%s", line);
666 static ssize_t devkmsg_read(struct file *file, char __user *buf,
667 size_t count, loff_t *ppos)
669 struct devkmsg_user *user = file->private_data;
670 struct printk_log *msg;
677 ret = mutex_lock_interruptible(&user->lock);
680 raw_spin_lock_irq(&logbuf_lock);
681 while (user->seq == log_next_seq) {
682 if (file->f_flags & O_NONBLOCK) {
684 raw_spin_unlock_irq(&logbuf_lock);
688 raw_spin_unlock_irq(&logbuf_lock);
689 ret = wait_event_interruptible(log_wait,
690 user->seq != log_next_seq);
693 raw_spin_lock_irq(&logbuf_lock);
696 if (user->seq < log_first_seq) {
697 /* our last seen message is gone, return error and reset */
698 user->idx = log_first_idx;
699 user->seq = log_first_seq;
701 raw_spin_unlock_irq(&logbuf_lock);
705 msg = log_from_idx(user->idx);
706 len = msg_print_ext_header(user->buf, sizeof(user->buf),
707 msg, user->seq, user->prev);
708 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
709 log_dict(msg), msg->dict_len,
710 log_text(msg), msg->text_len);
712 user->prev = msg->flags;
713 user->idx = log_next(user->idx);
715 raw_spin_unlock_irq(&logbuf_lock);
722 if (copy_to_user(buf, user->buf, len)) {
728 mutex_unlock(&user->lock);
732 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
734 struct devkmsg_user *user = file->private_data;
742 raw_spin_lock_irq(&logbuf_lock);
745 /* the first record */
746 user->idx = log_first_idx;
747 user->seq = log_first_seq;
751 * The first record after the last SYSLOG_ACTION_CLEAR,
752 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
753 * changes no global state, and does not clear anything.
755 user->idx = clear_idx;
756 user->seq = clear_seq;
759 /* after the last record */
760 user->idx = log_next_idx;
761 user->seq = log_next_seq;
766 raw_spin_unlock_irq(&logbuf_lock);
770 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
772 struct devkmsg_user *user = file->private_data;
776 return POLLERR|POLLNVAL;
778 poll_wait(file, &log_wait, wait);
780 raw_spin_lock_irq(&logbuf_lock);
781 if (user->seq < log_next_seq) {
782 /* return error when data has vanished underneath us */
783 if (user->seq < log_first_seq)
784 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
786 ret = POLLIN|POLLRDNORM;
788 raw_spin_unlock_irq(&logbuf_lock);
793 static int devkmsg_open(struct inode *inode, struct file *file)
795 struct devkmsg_user *user;
798 /* write-only does not need any file context */
799 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
802 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
807 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
811 mutex_init(&user->lock);
813 raw_spin_lock_irq(&logbuf_lock);
814 user->idx = log_first_idx;
815 user->seq = log_first_seq;
816 raw_spin_unlock_irq(&logbuf_lock);
818 file->private_data = user;
822 static int devkmsg_release(struct inode *inode, struct file *file)
824 struct devkmsg_user *user = file->private_data;
829 mutex_destroy(&user->lock);
834 const struct file_operations kmsg_fops = {
835 .open = devkmsg_open,
836 .read = devkmsg_read,
837 .write_iter = devkmsg_write,
838 .llseek = devkmsg_llseek,
839 .poll = devkmsg_poll,
840 .release = devkmsg_release,
843 #ifdef CONFIG_KEXEC_CORE
845 * This appends the listed symbols to /proc/vmcore
847 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
848 * obtain access to symbols that are otherwise very difficult to locate. These
849 * symbols are specifically used so that utilities can access and extract the
850 * dmesg log from a vmcore file after a crash.
852 void log_buf_kexec_setup(void)
854 VMCOREINFO_SYMBOL(log_buf);
855 VMCOREINFO_SYMBOL(log_buf_len);
856 VMCOREINFO_SYMBOL(log_first_idx);
857 VMCOREINFO_SYMBOL(log_next_idx);
859 * Export struct printk_log size and field offsets. User space tools can
860 * parse it and detect any changes to structure down the line.
862 VMCOREINFO_STRUCT_SIZE(printk_log);
863 VMCOREINFO_OFFSET(printk_log, ts_nsec);
864 VMCOREINFO_OFFSET(printk_log, len);
865 VMCOREINFO_OFFSET(printk_log, text_len);
866 VMCOREINFO_OFFSET(printk_log, dict_len);
870 /* requested log_buf_len from kernel cmdline */
871 static unsigned long __initdata new_log_buf_len;
873 /* we practice scaling the ring buffer by powers of 2 */
874 static void __init log_buf_len_update(u64 size)
876 if (size > (u64)LOG_BUF_LEN_MAX) {
877 size = (u64)LOG_BUF_LEN_MAX;
878 pr_err("log_buf over 2G is not supported.\n");
882 size = roundup_pow_of_two(size);
883 if (size > log_buf_len)
884 new_log_buf_len = (unsigned long)size;
887 /* save requested log_buf_len since it's too early to process it */
888 static int __init log_buf_len_setup(char *str)
895 size = memparse(str, &str);
897 log_buf_len_update(size);
901 early_param("log_buf_len", log_buf_len_setup);
904 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
906 static void __init log_buf_add_cpu(void)
908 unsigned int cpu_extra;
911 * archs should set up cpu_possible_bits properly with
912 * set_cpu_possible() after setup_arch() but just in
913 * case lets ensure this is valid.
915 if (num_possible_cpus() == 1)
918 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
920 /* by default this will only continue through for large > 64 CPUs */
921 if (cpu_extra <= __LOG_BUF_LEN / 2)
924 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
925 __LOG_CPU_MAX_BUF_LEN);
926 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
928 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
930 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
932 #else /* !CONFIG_SMP */
933 static inline void log_buf_add_cpu(void) {}
934 #endif /* CONFIG_SMP */
936 void __init setup_log_buf(int early)
942 if (log_buf != __log_buf)
945 if (!early && !new_log_buf_len)
948 if (!new_log_buf_len)
953 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
955 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
959 if (unlikely(!new_log_buf)) {
960 pr_err("log_buf_len: %lu bytes not available\n",
965 raw_spin_lock_irqsave(&logbuf_lock, flags);
966 log_buf_len = new_log_buf_len;
967 log_buf = new_log_buf;
969 free = __LOG_BUF_LEN - log_next_idx;
970 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
971 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
973 pr_info("log_buf_len: %u bytes\n", log_buf_len);
974 pr_info("early log buf free: %u(%u%%)\n",
975 free, (free * 100) / __LOG_BUF_LEN);
978 static bool __read_mostly ignore_loglevel;
980 static int __init ignore_loglevel_setup(char *str)
982 ignore_loglevel = true;
983 pr_info("debug: ignoring loglevel setting.\n");
988 early_param("ignore_loglevel", ignore_loglevel_setup);
989 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
990 MODULE_PARM_DESC(ignore_loglevel,
991 "ignore loglevel setting (prints all kernel messages to the console)");
993 #ifdef CONFIG_BOOT_PRINTK_DELAY
995 static int boot_delay; /* msecs delay after each printk during bootup */
996 static unsigned long long loops_per_msec; /* based on boot_delay */
998 static int __init boot_delay_setup(char *str)
1002 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
1003 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
1005 get_option(&str, &boot_delay);
1006 if (boot_delay > 10 * 1000)
1009 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1010 "HZ: %d, loops_per_msec: %llu\n",
1011 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1014 early_param("boot_delay", boot_delay_setup);
1016 static void boot_delay_msec(int level)
1018 unsigned long long k;
1019 unsigned long timeout;
1021 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
1022 || (level >= console_loglevel && !ignore_loglevel)) {
1026 k = (unsigned long long)loops_per_msec * boot_delay;
1028 timeout = jiffies + msecs_to_jiffies(boot_delay);
1033 * use (volatile) jiffies to prevent
1034 * compiler reduction; loop termination via jiffies
1035 * is secondary and may or may not happen.
1037 if (time_after(jiffies, timeout))
1039 touch_nmi_watchdog();
1043 static inline void boot_delay_msec(int level)
1048 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1049 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1051 static size_t print_time(u64 ts, char *buf)
1053 unsigned long rem_nsec;
1058 rem_nsec = do_div(ts, 1000000000);
1061 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1063 return sprintf(buf, "[%5lu.%06lu] ",
1064 (unsigned long)ts, rem_nsec / 1000);
1067 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1070 unsigned int prefix = (msg->facility << 3) | msg->level;
1074 len += sprintf(buf, "<%u>", prefix);
1079 else if (prefix > 99)
1081 else if (prefix > 9)
1086 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1090 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1091 bool syslog, char *buf, size_t size)
1093 const char *text = log_text(msg);
1094 size_t text_size = msg->text_len;
1096 bool newline = true;
1099 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1102 if (msg->flags & LOG_CONT) {
1103 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1106 if (!(msg->flags & LOG_NEWLINE))
1111 const char *next = memchr(text, '\n', text_size);
1115 text_len = next - text;
1117 text_size -= next - text;
1119 text_len = text_size;
1123 if (print_prefix(msg, syslog, NULL) +
1124 text_len + 1 >= size - len)
1128 len += print_prefix(msg, syslog, buf + len);
1129 memcpy(buf + len, text, text_len);
1131 if (next || newline)
1134 /* SYSLOG_ACTION_* buffer size only calculation */
1136 len += print_prefix(msg, syslog, NULL);
1138 if (next || newline)
1149 static int syslog_print(char __user *buf, int size)
1152 struct printk_log *msg;
1155 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1163 raw_spin_lock_irq(&logbuf_lock);
1164 if (syslog_seq < log_first_seq) {
1165 /* messages are gone, move to first one */
1166 syslog_seq = log_first_seq;
1167 syslog_idx = log_first_idx;
1171 if (syslog_seq == log_next_seq) {
1172 raw_spin_unlock_irq(&logbuf_lock);
1176 skip = syslog_partial;
1177 msg = log_from_idx(syslog_idx);
1178 n = msg_print_text(msg, syslog_prev, true, text,
1179 LOG_LINE_MAX + PREFIX_MAX);
1180 if (n - syslog_partial <= size) {
1181 /* message fits into buffer, move forward */
1182 syslog_idx = log_next(syslog_idx);
1184 syslog_prev = msg->flags;
1185 n -= syslog_partial;
1188 /* partial read(), remember position */
1190 syslog_partial += n;
1193 raw_spin_unlock_irq(&logbuf_lock);
1198 if (copy_to_user(buf, text + skip, n)) {
1213 static int syslog_print_all(char __user *buf, int size, bool clear)
1218 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1222 raw_spin_lock_irq(&logbuf_lock);
1227 enum log_flags prev;
1229 if (clear_seq < log_first_seq) {
1230 /* messages are gone, move to first available one */
1231 clear_seq = log_first_seq;
1232 clear_idx = log_first_idx;
1236 * Find first record that fits, including all following records,
1237 * into the user-provided buffer for this dump.
1242 while (seq < log_next_seq) {
1243 struct printk_log *msg = log_from_idx(idx);
1245 len += msg_print_text(msg, prev, true, NULL, 0);
1247 idx = log_next(idx);
1251 /* move first record forward until length fits into the buffer */
1255 while (len > size && seq < log_next_seq) {
1256 struct printk_log *msg = log_from_idx(idx);
1258 len -= msg_print_text(msg, prev, true, NULL, 0);
1260 idx = log_next(idx);
1264 /* last message fitting into this dump */
1265 next_seq = log_next_seq;
1268 while (len >= 0 && seq < next_seq) {
1269 struct printk_log *msg = log_from_idx(idx);
1272 textlen = msg_print_text(msg, prev, true, text,
1273 LOG_LINE_MAX + PREFIX_MAX);
1278 idx = log_next(idx);
1282 raw_spin_unlock_irq(&logbuf_lock);
1283 if (copy_to_user(buf + len, text, textlen))
1287 raw_spin_lock_irq(&logbuf_lock);
1289 if (seq < log_first_seq) {
1290 /* messages are gone, move to next one */
1291 seq = log_first_seq;
1292 idx = log_first_idx;
1299 clear_seq = log_next_seq;
1300 clear_idx = log_next_idx;
1302 raw_spin_unlock_irq(&logbuf_lock);
1308 int do_syslog(int type, char __user *buf, int len, int source)
1311 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1314 error = check_syslog_permissions(type, source);
1319 case SYSLOG_ACTION_CLOSE: /* Close log */
1321 case SYSLOG_ACTION_OPEN: /* Open log */
1323 case SYSLOG_ACTION_READ: /* Read from log */
1325 if (!buf || len < 0)
1330 if (!access_ok(VERIFY_WRITE, buf, len)) {
1334 error = wait_event_interruptible(log_wait,
1335 syslog_seq != log_next_seq);
1338 error = syslog_print(buf, len);
1340 /* Read/clear last kernel messages */
1341 case SYSLOG_ACTION_READ_CLEAR:
1344 /* Read last kernel messages */
1345 case SYSLOG_ACTION_READ_ALL:
1347 if (!buf || len < 0)
1352 if (!access_ok(VERIFY_WRITE, buf, len)) {
1356 error = syslog_print_all(buf, len, clear);
1358 /* Clear ring buffer */
1359 case SYSLOG_ACTION_CLEAR:
1360 syslog_print_all(NULL, 0, true);
1362 /* Disable logging to console */
1363 case SYSLOG_ACTION_CONSOLE_OFF:
1364 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1365 saved_console_loglevel = console_loglevel;
1366 console_loglevel = minimum_console_loglevel;
1368 /* Enable logging to console */
1369 case SYSLOG_ACTION_CONSOLE_ON:
1370 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1371 console_loglevel = saved_console_loglevel;
1372 saved_console_loglevel = LOGLEVEL_DEFAULT;
1375 /* Set level of messages printed to console */
1376 case SYSLOG_ACTION_CONSOLE_LEVEL:
1378 if (len < 1 || len > 8)
1380 if (len < minimum_console_loglevel)
1381 len = minimum_console_loglevel;
1382 console_loglevel = len;
1383 /* Implicitly re-enable logging to console */
1384 saved_console_loglevel = LOGLEVEL_DEFAULT;
1387 /* Number of chars in the log buffer */
1388 case SYSLOG_ACTION_SIZE_UNREAD:
1389 raw_spin_lock_irq(&logbuf_lock);
1390 if (syslog_seq < log_first_seq) {
1391 /* messages are gone, move to first one */
1392 syslog_seq = log_first_seq;
1393 syslog_idx = log_first_idx;
1397 if (source == SYSLOG_FROM_PROC) {
1399 * Short-cut for poll(/"proc/kmsg") which simply checks
1400 * for pending data, not the size; return the count of
1401 * records, not the length.
1403 error = log_next_seq - syslog_seq;
1405 u64 seq = syslog_seq;
1406 u32 idx = syslog_idx;
1407 enum log_flags prev = syslog_prev;
1410 while (seq < log_next_seq) {
1411 struct printk_log *msg = log_from_idx(idx);
1413 error += msg_print_text(msg, prev, true, NULL, 0);
1414 idx = log_next(idx);
1418 error -= syslog_partial;
1420 raw_spin_unlock_irq(&logbuf_lock);
1422 /* Size of the log buffer */
1423 case SYSLOG_ACTION_SIZE_BUFFER:
1424 error = log_buf_len;
1434 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1436 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1440 * Call the console drivers, asking them to write out
1441 * log_buf[start] to log_buf[end - 1].
1442 * The console_lock must be held.
1444 static void call_console_drivers(int level,
1445 const char *ext_text, size_t ext_len,
1446 const char *text, size_t len)
1448 struct console *con;
1450 trace_console_rcuidle(text, len);
1452 if (level >= console_loglevel && !ignore_loglevel)
1454 if (!console_drivers)
1457 for_each_console(con) {
1458 if (exclusive_console && con != exclusive_console)
1460 if (!(con->flags & CON_ENABLED))
1464 if (!cpu_online(smp_processor_id()) &&
1465 !(con->flags & CON_ANYTIME))
1467 if (con->flags & CON_EXTENDED)
1468 con->write(con, ext_text, ext_len);
1470 con->write(con, text, len);
1475 * Zap console related locks when oopsing.
1476 * To leave time for slow consoles to print a full oops,
1477 * only zap at most once every 30 seconds.
1479 static void zap_locks(void)
1481 static unsigned long oops_timestamp;
1483 if (time_after_eq(jiffies, oops_timestamp) &&
1484 !time_after(jiffies, oops_timestamp + 30 * HZ))
1487 oops_timestamp = jiffies;
1490 /* If a crash is occurring, make sure we can't deadlock */
1491 raw_spin_lock_init(&logbuf_lock);
1492 /* And make sure that we print immediately */
1493 sema_init(&console_sem, 1);
1497 * Check if we have any console that is capable of printing while cpu is
1498 * booting or shutting down. Requires console_sem.
1500 static int have_callable_console(void)
1502 struct console *con;
1504 for_each_console(con)
1505 if (con->flags & CON_ANYTIME)
1512 * Can we actually use the console at this time on this cpu?
1514 * Console drivers may assume that per-cpu resources have been allocated. So
1515 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1516 * call them until this CPU is officially up.
1518 static inline int can_use_console(unsigned int cpu)
1520 return cpu_online(cpu) || have_callable_console();
1524 * Try to get console ownership to actually show the kernel
1525 * messages from a 'printk'. Return true (and with the
1526 * console_lock held, and 'console_locked' set) if it
1527 * is successful, false otherwise.
1529 static int console_trylock_for_printk(void)
1531 unsigned int cpu = smp_processor_id();
1533 if (!console_trylock())
1536 * If we can't use the console, we need to release the console
1537 * semaphore by hand to avoid flushing the buffer. We need to hold the
1538 * console semaphore in order to do this test safely.
1540 if (!can_use_console(cpu)) {
1548 int printk_delay_msec __read_mostly;
1550 static inline void printk_delay(void)
1552 if (unlikely(printk_delay_msec)) {
1553 int m = printk_delay_msec;
1557 touch_nmi_watchdog();
1563 * Continuation lines are buffered, and not committed to the record buffer
1564 * until the line is complete, or a race forces it. The line fragments
1565 * though, are printed immediately to the consoles to ensure everything has
1566 * reached the console in case of a kernel crash.
1568 static struct cont {
1569 char buf[LOG_LINE_MAX];
1570 size_t len; /* length == 0 means unused buffer */
1571 size_t cons; /* bytes written to console */
1572 struct task_struct *owner; /* task of first print*/
1573 u64 ts_nsec; /* time of first print */
1574 u8 level; /* log level of first message */
1575 u8 facility; /* log facility of first message */
1576 enum log_flags flags; /* prefix, newline flags */
1577 bool flushed:1; /* buffer sealed and committed */
1580 static void cont_flush(enum log_flags flags)
1589 * If a fragment of this line was directly flushed to the
1590 * console; wait for the console to pick up the rest of the
1591 * line. LOG_NOCONS suppresses a duplicated output.
1593 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1594 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1596 cont.flushed = true;
1599 * If no fragment of this line ever reached the console,
1600 * just submit it to the store and free the buffer.
1602 log_store(cont.facility, cont.level, flags, 0,
1603 NULL, 0, cont.buf, cont.len);
1608 static bool cont_add(int facility, int level, const char *text, size_t len)
1610 if (cont.len && cont.flushed)
1614 * If ext consoles are present, flush and skip in-kernel
1615 * continuation. See nr_ext_console_drivers definition. Also, if
1616 * the line gets too long, split it up in separate records.
1618 if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
1619 cont_flush(LOG_CONT);
1624 cont.facility = facility;
1626 cont.owner = current;
1627 cont.ts_nsec = local_clock();
1630 cont.flushed = false;
1633 memcpy(cont.buf + cont.len, text, len);
1636 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1637 cont_flush(LOG_CONT);
1642 static size_t cont_print_text(char *text, size_t size)
1647 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1648 textlen += print_time(cont.ts_nsec, text);
1652 len = cont.len - cont.cons;
1656 memcpy(text + textlen, cont.buf + cont.cons, len);
1658 cont.cons = cont.len;
1662 if (cont.flags & LOG_NEWLINE)
1663 text[textlen++] = '\n';
1664 /* got everything, release buffer */
1670 asmlinkage int vprintk_emit(int facility, int level,
1671 const char *dict, size_t dictlen,
1672 const char *fmt, va_list args)
1674 static int recursion_bug;
1675 static char textbuf[LOG_LINE_MAX];
1676 char *text = textbuf;
1677 size_t text_len = 0;
1678 enum log_flags lflags = 0;
1679 unsigned long flags;
1681 int printed_len = 0;
1682 bool in_sched = false;
1683 /* cpu currently holding logbuf_lock in this function */
1684 static unsigned int logbuf_cpu = UINT_MAX;
1686 if (level == LOGLEVEL_SCHED) {
1687 level = LOGLEVEL_DEFAULT;
1691 boot_delay_msec(level);
1694 /* This stops the holder of console_sem just where we want him */
1695 local_irq_save(flags);
1696 this_cpu = smp_processor_id();
1699 * Ouch, printk recursed into itself!
1701 if (unlikely(logbuf_cpu == this_cpu)) {
1703 * If a crash is occurring during printk() on this CPU,
1704 * then try to get the crash message out but make sure
1705 * we can't deadlock. Otherwise just return to avoid the
1706 * recursion and return - but flag the recursion so that
1707 * it can be printed at the next appropriate moment:
1709 if (!oops_in_progress && !lockdep_recursing(current)) {
1711 local_irq_restore(flags);
1718 raw_spin_lock(&logbuf_lock);
1719 logbuf_cpu = this_cpu;
1721 if (unlikely(recursion_bug)) {
1722 static const char recursion_msg[] =
1723 "BUG: recent printk recursion!";
1726 /* emit KERN_CRIT message */
1727 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1728 NULL, 0, recursion_msg,
1729 strlen(recursion_msg));
1733 * The printf needs to come first; we need the syslog
1734 * prefix which might be passed-in as a parameter.
1736 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1738 /* mark and strip a trailing newline */
1739 if (text_len && text[text_len-1] == '\n') {
1741 lflags |= LOG_NEWLINE;
1744 /* strip kernel syslog prefix and extract log level or control flags */
1745 if (facility == 0) {
1746 int kern_level = printk_get_level(text);
1749 const char *end_of_header = printk_skip_level(text);
1750 switch (kern_level) {
1752 if (level == LOGLEVEL_DEFAULT)
1753 level = kern_level - '0';
1755 case 'd': /* KERN_DEFAULT */
1756 lflags |= LOG_PREFIX;
1759 * No need to check length here because vscnprintf
1760 * put '\0' at the end of the string. Only valid and
1761 * newly printed level is detected.
1763 text_len -= end_of_header - text;
1764 text = (char *)end_of_header;
1768 if (level == LOGLEVEL_DEFAULT)
1769 level = default_message_loglevel;
1772 lflags |= LOG_PREFIX|LOG_NEWLINE;
1774 if (!(lflags & LOG_NEWLINE)) {
1776 * Flush the conflicting buffer. An earlier newline was missing,
1777 * or another task also prints continuation lines.
1779 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1780 cont_flush(LOG_NEWLINE);
1782 /* buffer line if possible, otherwise store it right away */
1783 if (cont_add(facility, level, text, text_len))
1784 printed_len += text_len;
1786 printed_len += log_store(facility, level,
1787 lflags | LOG_CONT, 0,
1788 dict, dictlen, text, text_len);
1790 bool stored = false;
1793 * If an earlier newline was missing and it was the same task,
1794 * either merge it with the current buffer and flush, or if
1795 * there was a race with interrupts (prefix == true) then just
1796 * flush it out and store this line separately.
1797 * If the preceding printk was from a different task and missed
1798 * a newline, flush and append the newline.
1801 if (cont.owner == current && !(lflags & LOG_PREFIX))
1802 stored = cont_add(facility, level, text,
1804 cont_flush(LOG_NEWLINE);
1808 printed_len += text_len;
1810 printed_len += log_store(facility, level, lflags, 0,
1811 dict, dictlen, text, text_len);
1814 logbuf_cpu = UINT_MAX;
1815 raw_spin_unlock(&logbuf_lock);
1817 local_irq_restore(flags);
1819 /* If called from the scheduler, we can not call up(). */
1823 * Disable preemption to avoid being preempted while holding
1824 * console_sem which would prevent anyone from printing to
1830 * Try to acquire and then immediately release the console
1831 * semaphore. The release will print out buffers and wake up
1832 * /dev/kmsg and syslog() users.
1834 if (console_trylock_for_printk())
1842 EXPORT_SYMBOL(vprintk_emit);
1844 asmlinkage int vprintk(const char *fmt, va_list args)
1846 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1848 EXPORT_SYMBOL(vprintk);
1850 asmlinkage int printk_emit(int facility, int level,
1851 const char *dict, size_t dictlen,
1852 const char *fmt, ...)
1857 va_start(args, fmt);
1858 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1863 EXPORT_SYMBOL(printk_emit);
1865 int vprintk_default(const char *fmt, va_list args)
1869 #ifdef CONFIG_KGDB_KDB
1870 if (unlikely(kdb_trap_printk)) {
1871 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1875 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1879 EXPORT_SYMBOL_GPL(vprintk_default);
1882 * This allows printk to be diverted to another function per cpu.
1883 * This is useful for calling printk functions from within NMI
1884 * without worrying about race conditions that can lock up the
1887 DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
1890 * printk - print a kernel message
1891 * @fmt: format string
1893 * This is printk(). It can be called from any context. We want it to work.
1895 * We try to grab the console_lock. If we succeed, it's easy - we log the
1896 * output and call the console drivers. If we fail to get the semaphore, we
1897 * place the output into the log buffer and return. The current holder of
1898 * the console_sem will notice the new output in console_unlock(); and will
1899 * send it to the consoles before releasing the lock.
1901 * One effect of this deferred printing is that code which calls printk() and
1902 * then changes console_loglevel may break. This is because console_loglevel
1903 * is inspected when the actual printing occurs.
1908 * See the vsnprintf() documentation for format string extensions over C99.
1910 asmlinkage __visible int printk(const char *fmt, ...)
1912 printk_func_t vprintk_func;
1916 va_start(args, fmt);
1919 * If a caller overrides the per_cpu printk_func, then it needs
1920 * to disable preemption when calling printk(). Otherwise
1921 * the printk_func should be set to the default. No need to
1922 * disable preemption here.
1924 vprintk_func = this_cpu_read(printk_func);
1925 r = vprintk_func(fmt, args);
1931 EXPORT_SYMBOL(printk);
1933 #else /* CONFIG_PRINTK */
1935 #define LOG_LINE_MAX 0
1936 #define PREFIX_MAX 0
1938 static u64 syslog_seq;
1939 static u32 syslog_idx;
1940 static u64 console_seq;
1941 static u32 console_idx;
1942 static enum log_flags syslog_prev;
1943 static u64 log_first_seq;
1944 static u32 log_first_idx;
1945 static u64 log_next_seq;
1946 static enum log_flags console_prev;
1947 static struct cont {
1953 static char *log_text(const struct printk_log *msg) { return NULL; }
1954 static char *log_dict(const struct printk_log *msg) { return NULL; }
1955 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1956 static u32 log_next(u32 idx) { return 0; }
1957 static ssize_t msg_print_ext_header(char *buf, size_t size,
1958 struct printk_log *msg, u64 seq,
1959 enum log_flags prev_flags) { return 0; }
1960 static ssize_t msg_print_ext_body(char *buf, size_t size,
1961 char *dict, size_t dict_len,
1962 char *text, size_t text_len) { return 0; }
1963 static void call_console_drivers(int level,
1964 const char *ext_text, size_t ext_len,
1965 const char *text, size_t len) {}
1966 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1967 bool syslog, char *buf, size_t size) { return 0; }
1968 static size_t cont_print_text(char *text, size_t size) { return 0; }
1970 /* Still needs to be defined for users */
1971 DEFINE_PER_CPU(printk_func_t, printk_func);
1973 #endif /* CONFIG_PRINTK */
1975 #ifdef CONFIG_EARLY_PRINTK
1976 struct console *early_console;
1978 asmlinkage __visible void early_printk(const char *fmt, ...)
1988 n = vscnprintf(buf, sizeof(buf), fmt, ap);
1991 early_console->write(early_console, buf, n);
1995 static int __add_preferred_console(char *name, int idx, char *options,
1998 struct console_cmdline *c;
2002 * See if this tty is not yet registered, and
2003 * if we have a slot free.
2005 for (i = 0, c = console_cmdline;
2006 i < MAX_CMDLINECONSOLES && c->name[0];
2008 if (strcmp(c->name, name) == 0 && c->index == idx) {
2010 selected_console = i;
2014 if (i == MAX_CMDLINECONSOLES)
2017 selected_console = i;
2018 strlcpy(c->name, name, sizeof(c->name));
2019 c->options = options;
2020 braille_set_options(c, brl_options);
2026 * Set up a console. Called via do_early_param() in init/main.c
2027 * for each "console=" parameter in the boot command line.
2029 static int __init console_setup(char *str)
2031 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
2032 char *s, *options, *brl_options = NULL;
2036 * console="" or console=null have been suggested as a way to
2037 * disable console output. Use ttynull that has been created
2038 * for exacly this purpose.
2040 if (str[0] == 0 || strcmp(str, "null") == 0) {
2041 __add_preferred_console("ttynull", 0, NULL, NULL);
2045 if (_braille_console_setup(&str, &brl_options))
2049 * Decode str into name, index, options.
2051 if (str[0] >= '0' && str[0] <= '9') {
2052 strcpy(buf, "ttyS");
2053 strncpy(buf + 4, str, sizeof(buf) - 5);
2055 strncpy(buf, str, sizeof(buf) - 1);
2057 buf[sizeof(buf) - 1] = 0;
2058 options = strchr(str, ',');
2062 if (!strcmp(str, "ttya"))
2063 strcpy(buf, "ttyS0");
2064 if (!strcmp(str, "ttyb"))
2065 strcpy(buf, "ttyS1");
2067 for (s = buf; *s; s++)
2068 if (isdigit(*s) || *s == ',')
2070 idx = simple_strtoul(s, NULL, 10);
2073 __add_preferred_console(buf, idx, options, brl_options);
2074 console_set_on_cmdline = 1;
2077 __setup("console=", console_setup);
2080 * add_preferred_console - add a device to the list of preferred consoles.
2081 * @name: device name
2082 * @idx: device index
2083 * @options: options for this console
2085 * The last preferred console added will be used for kernel messages
2086 * and stdin/out/err for init. Normally this is used by console_setup
2087 * above to handle user-supplied console arguments; however it can also
2088 * be used by arch-specific code either to override the user or more
2089 * commonly to provide a default console (ie from PROM variables) when
2090 * the user has not supplied one.
2092 int add_preferred_console(char *name, int idx, char *options)
2094 return __add_preferred_console(name, idx, options, NULL);
2097 bool console_suspend_enabled = true;
2098 EXPORT_SYMBOL(console_suspend_enabled);
2100 static int __init console_suspend_disable(char *str)
2102 console_suspend_enabled = false;
2105 __setup("no_console_suspend", console_suspend_disable);
2106 module_param_named(console_suspend, console_suspend_enabled,
2107 bool, S_IRUGO | S_IWUSR);
2108 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2109 " and hibernate operations");
2112 * suspend_console - suspend the console subsystem
2114 * This disables printk() while we go into suspend states
2116 void suspend_console(void)
2118 if (!console_suspend_enabled)
2120 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2122 console_suspended = 1;
2126 void resume_console(void)
2128 if (!console_suspend_enabled)
2131 console_suspended = 0;
2136 * console_cpu_notify - print deferred console messages after CPU hotplug
2137 * @self: notifier struct
2138 * @action: CPU hotplug event
2141 * If printk() is called from a CPU that is not online yet, the messages
2142 * will be spooled but will not show up on the console. This function is
2143 * called when a new CPU comes online (or fails to come up), and ensures
2144 * that any such output gets printed.
2146 static int console_cpu_notify(struct notifier_block *self,
2147 unsigned long action, void *hcpu)
2152 case CPU_DOWN_FAILED:
2153 case CPU_UP_CANCELED:
2161 * console_lock - lock the console system for exclusive use.
2163 * Acquires a lock which guarantees that the caller has
2164 * exclusive access to the console system and the console_drivers list.
2166 * Can sleep, returns nothing.
2168 void console_lock(void)
2173 if (console_suspended)
2176 console_may_schedule = 1;
2178 EXPORT_SYMBOL(console_lock);
2181 * console_trylock - try to lock the console system for exclusive use.
2183 * Try to acquire a lock which guarantees that the caller has exclusive
2184 * access to the console system and the console_drivers list.
2186 * returns 1 on success, and 0 on failure to acquire the lock.
2188 int console_trylock(void)
2190 if (down_trylock_console_sem())
2192 if (console_suspended) {
2197 console_may_schedule = 0;
2200 EXPORT_SYMBOL(console_trylock);
2202 int is_console_locked(void)
2204 return console_locked;
2207 static void console_cont_flush(char *text, size_t size)
2209 unsigned long flags;
2212 raw_spin_lock_irqsave(&logbuf_lock, flags);
2218 * We still queue earlier records, likely because the console was
2219 * busy. The earlier ones need to be printed before this one, we
2220 * did not flush any fragment so far, so just let it queue up.
2222 if (console_seq < log_next_seq && !cont.cons)
2225 len = cont_print_text(text, size);
2226 raw_spin_unlock(&logbuf_lock);
2227 stop_critical_timings();
2228 call_console_drivers(cont.level, NULL, 0, text, len);
2229 start_critical_timings();
2230 local_irq_restore(flags);
2233 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2237 * console_unlock - unlock the console system
2239 * Releases the console_lock which the caller holds on the console system
2240 * and the console driver list.
2242 * While the console_lock was held, console output may have been buffered
2243 * by printk(). If this is the case, console_unlock(); emits
2244 * the output prior to releasing the lock.
2246 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2248 * console_unlock(); may be called from any context.
2250 void console_unlock(void)
2252 static char ext_text[CONSOLE_EXT_LOG_MAX];
2253 static char text[LOG_LINE_MAX + PREFIX_MAX];
2254 static u64 seen_seq;
2255 unsigned long flags;
2256 bool wake_klogd = false;
2257 bool do_cond_resched, retry;
2259 if (console_suspended) {
2265 * Console drivers are called under logbuf_lock, so
2266 * @console_may_schedule should be cleared before; however, we may
2267 * end up dumping a lot of lines, for example, if called from
2268 * console registration path, and should invoke cond_resched()
2269 * between lines if allowable. Not doing so can cause a very long
2270 * scheduling stall on a slow console leading to RCU stall and
2271 * softlockup warnings which exacerbate the issue with more
2272 * messages practically incapacitating the system.
2274 do_cond_resched = console_may_schedule;
2275 console_may_schedule = 0;
2277 /* flush buffered message fragment immediately to console */
2278 console_cont_flush(text, sizeof(text));
2281 struct printk_log *msg;
2286 raw_spin_lock_irqsave(&logbuf_lock, flags);
2287 if (seen_seq != log_next_seq) {
2289 seen_seq = log_next_seq;
2292 if (console_seq < log_first_seq) {
2293 len = sprintf(text, "** %u printk messages dropped ** ",
2294 (unsigned)(log_first_seq - console_seq));
2296 /* messages are gone, move to first one */
2297 console_seq = log_first_seq;
2298 console_idx = log_first_idx;
2304 if (console_seq == log_next_seq)
2307 msg = log_from_idx(console_idx);
2308 if (msg->flags & LOG_NOCONS) {
2310 * Skip record we have buffered and already printed
2311 * directly to the console when we received it.
2313 console_idx = log_next(console_idx);
2316 * We will get here again when we register a new
2317 * CON_PRINTBUFFER console. Clear the flag so we
2318 * will properly dump everything later.
2320 msg->flags &= ~LOG_NOCONS;
2321 console_prev = msg->flags;
2326 len += msg_print_text(msg, console_prev, false,
2327 text + len, sizeof(text) - len);
2328 if (nr_ext_console_drivers) {
2329 ext_len = msg_print_ext_header(ext_text,
2331 msg, console_seq, console_prev);
2332 ext_len += msg_print_ext_body(ext_text + ext_len,
2333 sizeof(ext_text) - ext_len,
2334 log_dict(msg), msg->dict_len,
2335 log_text(msg), msg->text_len);
2337 console_idx = log_next(console_idx);
2339 console_prev = msg->flags;
2340 raw_spin_unlock(&logbuf_lock);
2342 stop_critical_timings(); /* don't trace print latency */
2343 call_console_drivers(level, ext_text, ext_len, text, len);
2344 start_critical_timings();
2345 local_irq_restore(flags);
2347 if (do_cond_resched)
2352 /* Release the exclusive_console once it is used */
2353 if (unlikely(exclusive_console))
2354 exclusive_console = NULL;
2356 raw_spin_unlock(&logbuf_lock);
2361 * Someone could have filled up the buffer again, so re-check if there's
2362 * something to flush. In case we cannot trylock the console_sem again,
2363 * there's a new owner and the console_unlock() from them will do the
2364 * flush, no worries.
2366 raw_spin_lock(&logbuf_lock);
2367 retry = console_seq != log_next_seq;
2368 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2370 if (retry && console_trylock())
2376 EXPORT_SYMBOL(console_unlock);
2379 * console_conditional_schedule - yield the CPU if required
2381 * If the console code is currently allowed to sleep, and
2382 * if this CPU should yield the CPU to another task, do
2385 * Must be called within console_lock();.
2387 void __sched console_conditional_schedule(void)
2389 if (console_may_schedule)
2392 EXPORT_SYMBOL(console_conditional_schedule);
2394 void console_unblank(void)
2399 * console_unblank can no longer be called in interrupt context unless
2400 * oops_in_progress is set to 1..
2402 if (oops_in_progress) {
2403 if (down_trylock_console_sem() != 0)
2409 console_may_schedule = 0;
2411 if ((c->flags & CON_ENABLED) && c->unblank)
2417 * console_flush_on_panic - flush console content on panic
2419 * Immediately output all pending messages no matter what.
2421 void console_flush_on_panic(void)
2424 * If someone else is holding the console lock, trylock will fail
2425 * and may_schedule may be set. Ignore and proceed to unlock so
2426 * that messages are flushed out. As this can be called from any
2427 * context and we don't want to get preempted while flushing,
2428 * ensure may_schedule is cleared.
2431 console_may_schedule = 0;
2436 * Return the console tty driver structure and its associated index
2438 struct tty_driver *console_device(int *index)
2441 struct tty_driver *driver = NULL;
2444 for_each_console(c) {
2447 driver = c->device(c, index);
2456 * Prevent further output on the passed console device so that (for example)
2457 * serial drivers can disable console output before suspending a port, and can
2458 * re-enable output afterwards.
2460 void console_stop(struct console *console)
2463 console->flags &= ~CON_ENABLED;
2466 EXPORT_SYMBOL(console_stop);
2468 void console_start(struct console *console)
2471 console->flags |= CON_ENABLED;
2474 EXPORT_SYMBOL(console_start);
2476 static int __read_mostly keep_bootcon;
2478 static int __init keep_bootcon_setup(char *str)
2481 pr_info("debug: skip boot console de-registration.\n");
2486 early_param("keep_bootcon", keep_bootcon_setup);
2489 * The console driver calls this routine during kernel initialization
2490 * to register the console printing procedure with printk() and to
2491 * print any messages that were printed by the kernel before the
2492 * console driver was initialized.
2494 * This can happen pretty early during the boot process (because of
2495 * early_printk) - sometimes before setup_arch() completes - be careful
2496 * of what kernel features are used - they may not be initialised yet.
2498 * There are two types of consoles - bootconsoles (early_printk) and
2499 * "real" consoles (everything which is not a bootconsole) which are
2500 * handled differently.
2501 * - Any number of bootconsoles can be registered at any time.
2502 * - As soon as a "real" console is registered, all bootconsoles
2503 * will be unregistered automatically.
2504 * - Once a "real" console is registered, any attempt to register a
2505 * bootconsoles will be rejected
2507 void register_console(struct console *newcon)
2510 unsigned long flags;
2511 struct console *bcon = NULL;
2512 struct console_cmdline *c;
2514 if (console_drivers)
2515 for_each_console(bcon)
2516 if (WARN(bcon == newcon,
2517 "console '%s%d' already registered\n",
2518 bcon->name, bcon->index))
2522 * before we register a new CON_BOOT console, make sure we don't
2523 * already have a valid console
2525 if (console_drivers && newcon->flags & CON_BOOT) {
2526 /* find the last or real console */
2527 for_each_console(bcon) {
2528 if (!(bcon->flags & CON_BOOT)) {
2529 pr_info("Too late to register bootconsole %s%d\n",
2530 newcon->name, newcon->index);
2536 if (console_drivers && console_drivers->flags & CON_BOOT)
2537 bcon = console_drivers;
2539 if (preferred_console < 0 || bcon || !console_drivers)
2540 preferred_console = selected_console;
2543 * See if we want to use this console driver. If we
2544 * didn't select a console we take the first one
2545 * that registers here.
2547 if (preferred_console < 0) {
2548 if (newcon->index < 0)
2550 if (newcon->setup == NULL ||
2551 newcon->setup(newcon, NULL) == 0) {
2552 newcon->flags |= CON_ENABLED;
2553 if (newcon->device) {
2554 newcon->flags |= CON_CONSDEV;
2555 preferred_console = 0;
2561 * See if this console matches one we selected on
2564 for (i = 0, c = console_cmdline;
2565 i < MAX_CMDLINECONSOLES && c->name[0];
2567 if (!newcon->match ||
2568 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2569 /* default matching */
2570 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2571 if (strcmp(c->name, newcon->name) != 0)
2573 if (newcon->index >= 0 &&
2574 newcon->index != c->index)
2576 if (newcon->index < 0)
2577 newcon->index = c->index;
2579 if (_braille_register_console(newcon, c))
2582 if (newcon->setup &&
2583 newcon->setup(newcon, c->options) != 0)
2587 newcon->flags |= CON_ENABLED;
2588 if (i == selected_console) {
2589 newcon->flags |= CON_CONSDEV;
2590 preferred_console = selected_console;
2595 if (!(newcon->flags & CON_ENABLED))
2599 * If we have a bootconsole, and are switching to a real console,
2600 * don't print everything out again, since when the boot console, and
2601 * the real console are the same physical device, it's annoying to
2602 * see the beginning boot messages twice
2604 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2605 newcon->flags &= ~CON_PRINTBUFFER;
2608 * Put this console in the list - keep the
2609 * preferred driver at the head of the list.
2612 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2613 newcon->next = console_drivers;
2614 console_drivers = newcon;
2616 newcon->next->flags &= ~CON_CONSDEV;
2618 newcon->next = console_drivers->next;
2619 console_drivers->next = newcon;
2622 if (newcon->flags & CON_EXTENDED)
2623 if (!nr_ext_console_drivers++)
2624 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2626 if (newcon->flags & CON_PRINTBUFFER) {
2628 * console_unlock(); will print out the buffered messages
2631 raw_spin_lock_irqsave(&logbuf_lock, flags);
2632 console_seq = syslog_seq;
2633 console_idx = syslog_idx;
2634 console_prev = syslog_prev;
2635 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2637 * We're about to replay the log buffer. Only do this to the
2638 * just-registered console to avoid excessive message spam to
2639 * the already-registered consoles.
2641 exclusive_console = newcon;
2644 console_sysfs_notify();
2647 * By unregistering the bootconsoles after we enable the real console
2648 * we get the "console xxx enabled" message on all the consoles -
2649 * boot consoles, real consoles, etc - this is to ensure that end
2650 * users know there might be something in the kernel's log buffer that
2651 * went to the bootconsole (that they do not see on the real console)
2653 pr_info("%sconsole [%s%d] enabled\n",
2654 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2655 newcon->name, newcon->index);
2657 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2659 /* We need to iterate through all boot consoles, to make
2660 * sure we print everything out, before we unregister them.
2662 for_each_console(bcon)
2663 if (bcon->flags & CON_BOOT)
2664 unregister_console(bcon);
2667 EXPORT_SYMBOL(register_console);
2669 int unregister_console(struct console *console)
2671 struct console *a, *b;
2674 pr_info("%sconsole [%s%d] disabled\n",
2675 (console->flags & CON_BOOT) ? "boot" : "" ,
2676 console->name, console->index);
2678 res = _braille_unregister_console(console);
2684 if (console_drivers == console) {
2685 console_drivers=console->next;
2687 } else if (console_drivers) {
2688 for (a=console_drivers->next, b=console_drivers ;
2689 a; b=a, a=b->next) {
2698 if (!res && (console->flags & CON_EXTENDED))
2699 nr_ext_console_drivers--;
2702 * If this isn't the last console and it has CON_CONSDEV set, we
2703 * need to set it on the next preferred console.
2705 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2706 console_drivers->flags |= CON_CONSDEV;
2708 console->flags &= ~CON_ENABLED;
2710 console_sysfs_notify();
2713 EXPORT_SYMBOL(unregister_console);
2715 static int __init printk_late_init(void)
2717 struct console *con;
2719 for_each_console(con) {
2720 if (!keep_bootcon && con->flags & CON_BOOT) {
2721 unregister_console(con);
2724 hotcpu_notifier(console_cpu_notify, 0);
2727 late_initcall(printk_late_init);
2729 #if defined CONFIG_PRINTK
2731 * Delayed printk version, for scheduler-internal messages:
2733 #define PRINTK_PENDING_WAKEUP 0x01
2734 #define PRINTK_PENDING_OUTPUT 0x02
2736 static DEFINE_PER_CPU(int, printk_pending);
2738 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2740 int pending = __this_cpu_xchg(printk_pending, 0);
2742 if (pending & PRINTK_PENDING_OUTPUT) {
2743 /* If trylock fails, someone else is doing the printing */
2744 if (console_trylock())
2748 if (pending & PRINTK_PENDING_WAKEUP)
2749 wake_up_interruptible(&log_wait);
2752 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2753 .func = wake_up_klogd_work_func,
2754 .flags = IRQ_WORK_LAZY,
2757 void wake_up_klogd(void)
2760 if (waitqueue_active(&log_wait)) {
2761 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2762 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2767 int printk_deferred(const char *fmt, ...)
2773 va_start(args, fmt);
2774 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2777 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2778 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2785 * printk rate limiting, lifted from the networking subsystem.
2787 * This enforces a rate limit: not more than 10 kernel messages
2788 * every 5s to make a denial-of-service attack impossible.
2790 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2792 int __printk_ratelimit(const char *func)
2794 return ___ratelimit(&printk_ratelimit_state, func);
2796 EXPORT_SYMBOL(__printk_ratelimit);
2799 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2800 * @caller_jiffies: pointer to caller's state
2801 * @interval_msecs: minimum interval between prints
2803 * printk_timed_ratelimit() returns true if more than @interval_msecs
2804 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2807 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2808 unsigned int interval_msecs)
2810 unsigned long elapsed = jiffies - *caller_jiffies;
2812 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2815 *caller_jiffies = jiffies;
2818 EXPORT_SYMBOL(printk_timed_ratelimit);
2820 static DEFINE_SPINLOCK(dump_list_lock);
2821 static LIST_HEAD(dump_list);
2824 * kmsg_dump_register - register a kernel log dumper.
2825 * @dumper: pointer to the kmsg_dumper structure
2827 * Adds a kernel log dumper to the system. The dump callback in the
2828 * structure will be called when the kernel oopses or panics and must be
2829 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2831 int kmsg_dump_register(struct kmsg_dumper *dumper)
2833 unsigned long flags;
2836 /* The dump callback needs to be set */
2840 spin_lock_irqsave(&dump_list_lock, flags);
2841 /* Don't allow registering multiple times */
2842 if (!dumper->registered) {
2843 dumper->registered = 1;
2844 list_add_tail_rcu(&dumper->list, &dump_list);
2847 spin_unlock_irqrestore(&dump_list_lock, flags);
2851 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2854 * kmsg_dump_unregister - unregister a kmsg dumper.
2855 * @dumper: pointer to the kmsg_dumper structure
2857 * Removes a dump device from the system. Returns zero on success and
2858 * %-EINVAL otherwise.
2860 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2862 unsigned long flags;
2865 spin_lock_irqsave(&dump_list_lock, flags);
2866 if (dumper->registered) {
2867 dumper->registered = 0;
2868 list_del_rcu(&dumper->list);
2871 spin_unlock_irqrestore(&dump_list_lock, flags);
2876 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2878 static bool always_kmsg_dump;
2879 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2882 * kmsg_dump - dump kernel log to kernel message dumpers.
2883 * @reason: the reason (oops, panic etc) for dumping
2885 * Call each of the registered dumper's dump() callback, which can
2886 * retrieve the kmsg records with kmsg_dump_get_line() or
2887 * kmsg_dump_get_buffer().
2889 void kmsg_dump(enum kmsg_dump_reason reason)
2891 struct kmsg_dumper *dumper;
2892 unsigned long flags;
2894 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2898 list_for_each_entry_rcu(dumper, &dump_list, list) {
2899 if (dumper->max_reason && reason > dumper->max_reason)
2902 /* initialize iterator with data about the stored records */
2903 dumper->active = true;
2905 raw_spin_lock_irqsave(&logbuf_lock, flags);
2906 dumper->cur_seq = clear_seq;
2907 dumper->cur_idx = clear_idx;
2908 dumper->next_seq = log_next_seq;
2909 dumper->next_idx = log_next_idx;
2910 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2912 /* invoke dumper which will iterate over records */
2913 dumper->dump(dumper, reason);
2915 /* reset iterator */
2916 dumper->active = false;
2922 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2923 * @dumper: registered kmsg dumper
2924 * @syslog: include the "<4>" prefixes
2925 * @line: buffer to copy the line to
2926 * @size: maximum size of the buffer
2927 * @len: length of line placed into buffer
2929 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2930 * record, and copy one record into the provided buffer.
2932 * Consecutive calls will return the next available record moving
2933 * towards the end of the buffer with the youngest messages.
2935 * A return value of FALSE indicates that there are no more records to
2938 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2940 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2941 char *line, size_t size, size_t *len)
2943 struct printk_log *msg;
2947 if (!dumper->active)
2950 if (dumper->cur_seq < log_first_seq) {
2951 /* messages are gone, move to first available one */
2952 dumper->cur_seq = log_first_seq;
2953 dumper->cur_idx = log_first_idx;
2957 if (dumper->cur_seq >= log_next_seq)
2960 msg = log_from_idx(dumper->cur_idx);
2961 l = msg_print_text(msg, 0, syslog, line, size);
2963 dumper->cur_idx = log_next(dumper->cur_idx);
2973 * kmsg_dump_get_line - retrieve one kmsg log line
2974 * @dumper: registered kmsg dumper
2975 * @syslog: include the "<4>" prefixes
2976 * @line: buffer to copy the line to
2977 * @size: maximum size of the buffer
2978 * @len: length of line placed into buffer
2980 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2981 * record, and copy one record into the provided buffer.
2983 * Consecutive calls will return the next available record moving
2984 * towards the end of the buffer with the youngest messages.
2986 * A return value of FALSE indicates that there are no more records to
2989 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2990 char *line, size_t size, size_t *len)
2992 unsigned long flags;
2995 raw_spin_lock_irqsave(&logbuf_lock, flags);
2996 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2997 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3001 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
3004 * kmsg_dump_get_buffer - copy kmsg log lines
3005 * @dumper: registered kmsg dumper
3006 * @syslog: include the "<4>" prefixes
3007 * @buf: buffer to copy the line to
3008 * @size: maximum size of the buffer
3009 * @len: length of line placed into buffer
3011 * Start at the end of the kmsg buffer and fill the provided buffer
3012 * with as many of the the *youngest* kmsg records that fit into it.
3013 * If the buffer is large enough, all available kmsg records will be
3014 * copied with a single call.
3016 * Consecutive calls will fill the buffer with the next block of
3017 * available older records, not including the earlier retrieved ones.
3019 * A return value of FALSE indicates that there are no more records to
3022 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
3023 char *buf, size_t size, size_t *len)
3025 unsigned long flags;
3030 enum log_flags prev;
3034 if (!dumper->active)
3037 raw_spin_lock_irqsave(&logbuf_lock, flags);
3038 if (dumper->cur_seq < log_first_seq) {
3039 /* messages are gone, move to first available one */
3040 dumper->cur_seq = log_first_seq;
3041 dumper->cur_idx = log_first_idx;
3045 if (dumper->cur_seq >= dumper->next_seq) {
3046 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3050 /* calculate length of entire buffer */
3051 seq = dumper->cur_seq;
3052 idx = dumper->cur_idx;
3054 while (seq < dumper->next_seq) {
3055 struct printk_log *msg = log_from_idx(idx);
3057 l += msg_print_text(msg, prev, true, NULL, 0);
3058 idx = log_next(idx);
3063 /* move first record forward until length fits into the buffer */
3064 seq = dumper->cur_seq;
3065 idx = dumper->cur_idx;
3067 while (l >= size && seq < dumper->next_seq) {
3068 struct printk_log *msg = log_from_idx(idx);
3070 l -= msg_print_text(msg, prev, true, NULL, 0);
3071 idx = log_next(idx);
3076 /* last message in next interation */
3081 while (seq < dumper->next_seq) {
3082 struct printk_log *msg = log_from_idx(idx);
3084 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
3085 idx = log_next(idx);
3090 dumper->next_seq = next_seq;
3091 dumper->next_idx = next_idx;
3093 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3099 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3102 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3103 * @dumper: registered kmsg dumper
3105 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3106 * kmsg_dump_get_buffer() can be called again and used multiple
3107 * times within the same dumper.dump() callback.
3109 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3111 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3113 dumper->cur_seq = clear_seq;
3114 dumper->cur_idx = clear_idx;
3115 dumper->next_seq = log_next_seq;
3116 dumper->next_idx = log_next_idx;
3120 * kmsg_dump_rewind - reset the interator
3121 * @dumper: registered kmsg dumper
3123 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3124 * kmsg_dump_get_buffer() can be called again and used multiple
3125 * times within the same dumper.dump() callback.
3127 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3129 unsigned long flags;
3131 raw_spin_lock_irqsave(&logbuf_lock, flags);
3132 kmsg_dump_rewind_nolock(dumper);
3133 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3135 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3137 static char dump_stack_arch_desc_str[128];
3140 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3141 * @fmt: printf-style format string
3142 * @...: arguments for the format string
3144 * The configured string will be printed right after utsname during task
3145 * dumps. Usually used to add arch-specific system identifiers. If an
3146 * arch wants to make use of such an ID string, it should initialize this
3147 * as soon as possible during boot.
3149 void __init dump_stack_set_arch_desc(const char *fmt, ...)
3153 va_start(args, fmt);
3154 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3160 * dump_stack_print_info - print generic debug info for dump_stack()
3161 * @log_lvl: log level
3163 * Arch-specific dump_stack() implementations can use this function to
3164 * print out the same debug information as the generic dump_stack().
3166 void dump_stack_print_info(const char *log_lvl)
3168 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3169 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3170 print_tainted(), init_utsname()->release,
3171 (int)strcspn(init_utsname()->version, " "),
3172 init_utsname()->version);
3174 if (dump_stack_arch_desc_str[0] != '\0')
3175 printk("%sHardware name: %s\n",
3176 log_lvl, dump_stack_arch_desc_str);
3178 print_worker_info(log_lvl, current);
3182 * show_regs_print_info - print generic debug info for show_regs()
3183 * @log_lvl: log level
3185 * show_regs() implementations can use this function to print out generic
3186 * debug information.
3188 void show_regs_print_info(const char *log_lvl)
3190 dump_stack_print_info(log_lvl);
3192 printk("%stask: %p ti: %p task.ti: %p\n",
3193 log_lvl, current, current_thread_info(),
3194 task_thread_info(current));