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>
51 #include <asm-generic/sections.h>
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/printk.h>
56 #include "console_cmdline.h"
59 int console_printk[4] = {
60 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
61 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
62 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
63 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
67 * Low level drivers may need that to know if they can schedule in
68 * their unblank() callback or not. So let's export it.
71 EXPORT_SYMBOL(oops_in_progress);
74 * console_sem protects the console_drivers list, and also
75 * provides serialisation for access to the entire console
78 static DEFINE_SEMAPHORE(console_sem);
79 struct console *console_drivers;
80 EXPORT_SYMBOL_GPL(console_drivers);
83 static struct lockdep_map console_lock_dep_map = {
84 .name = "console_lock"
89 * Number of registered extended console drivers.
91 * If extended consoles are present, in-kernel cont reassembly is disabled
92 * and each fragment is stored as a separate log entry with proper
93 * continuation flag so that every emitted message has full metadata. This
94 * doesn't change the result for regular consoles or /proc/kmsg. For
95 * /dev/kmsg, as long as the reader concatenates messages according to
96 * consecutive continuation flags, the end result should be the same too.
98 static int nr_ext_console_drivers;
101 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
102 * macros instead of functions so that _RET_IP_ contains useful information.
104 #define down_console_sem() do { \
106 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
109 static int __down_trylock_console_sem(unsigned long ip)
111 if (down_trylock(&console_sem))
113 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
116 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
118 #define up_console_sem() do { \
119 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
124 * This is used for debugging the mess that is the VT code by
125 * keeping track if we have the console semaphore held. It's
126 * definitely not the perfect debug tool (we don't know if _WE_
127 * hold it and are racing, but it helps tracking those weird code
128 * paths in the console code where we end up in places I want
129 * locked without the console sempahore held).
131 static int console_locked, console_suspended;
134 * If exclusive_console is non-NULL then only this console is to be printed to.
136 static struct console *exclusive_console;
139 * Array of consoles built from command line options (console=)
142 #define MAX_CMDLINECONSOLES 8
144 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
146 static int selected_console = -1;
147 static int preferred_console = -1;
148 int console_set_on_cmdline;
149 EXPORT_SYMBOL(console_set_on_cmdline);
151 /* Flag: console code may call schedule() */
152 static int console_may_schedule;
155 * The printk log buffer consists of a chain of concatenated variable
156 * length records. Every record starts with a record header, containing
157 * the overall length of the record.
159 * The heads to the first and last entry in the buffer, as well as the
160 * sequence numbers of these entries are maintained when messages are
163 * If the heads indicate available messages, the length in the header
164 * tells the start next message. A length == 0 for the next message
165 * indicates a wrap-around to the beginning of the buffer.
167 * Every record carries the monotonic timestamp in microseconds, as well as
168 * the standard userspace syslog level and syslog facility. The usual
169 * kernel messages use LOG_KERN; userspace-injected messages always carry
170 * a matching syslog facility, by default LOG_USER. The origin of every
171 * message can be reliably determined that way.
173 * The human readable log message directly follows the message header. The
174 * length of the message text is stored in the header, the stored message
177 * Optionally, a message can carry a dictionary of properties (key/value pairs),
178 * to provide userspace with a machine-readable message context.
180 * Examples for well-defined, commonly used property names are:
181 * DEVICE=b12:8 device identifier
185 * +sound:card0 subsystem:devname
186 * SUBSYSTEM=pci driver-core subsystem name
188 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
189 * follows directly after a '=' character. Every property is terminated by
190 * a '\0' character. The last property is not terminated.
192 * Example of a message structure:
193 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
194 * 0008 34 00 record is 52 bytes long
195 * 000a 0b 00 text is 11 bytes long
196 * 000c 1f 00 dictionary is 23 bytes long
197 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
198 * 0010 69 74 27 73 20 61 20 6c "it's a l"
200 * 001b 44 45 56 49 43 "DEVIC"
201 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
202 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
204 * 0032 00 00 00 padding to next message header
206 * The 'struct printk_log' buffer header must never be directly exported to
207 * userspace, it is a kernel-private implementation detail that might
208 * need to be changed in the future, when the requirements change.
210 * /dev/kmsg exports the structured data in the following line format:
211 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
213 * Users of the export format should ignore possible additional values
214 * separated by ',', and find the message after the ';' character.
216 * The optional key/value pairs are attached as continuation lines starting
217 * with a space character and terminated by a newline. All possible
218 * non-prinatable characters are escaped in the "\xff" notation.
222 LOG_NOCONS = 1, /* already flushed, do not print to console */
223 LOG_NEWLINE = 2, /* text ended with a newline */
224 LOG_PREFIX = 4, /* text started with a prefix */
225 LOG_CONT = 8, /* text is a fragment of a continuation line */
229 u64 ts_nsec; /* timestamp in nanoseconds */
230 u16 len; /* length of entire record */
231 u16 text_len; /* length of text buffer */
232 u16 dict_len; /* length of dictionary buffer */
233 u8 facility; /* syslog facility */
234 u8 flags:5; /* internal record flags */
235 u8 level:3; /* syslog level */
237 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
238 __packed __aligned(4)
243 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
244 * within the scheduler's rq lock. It must be released before calling
245 * console_unlock() or anything else that might wake up a process.
247 static DEFINE_RAW_SPINLOCK(logbuf_lock);
250 DECLARE_WAIT_QUEUE_HEAD(log_wait);
251 /* the next printk record to read by syslog(READ) or /proc/kmsg */
252 static u64 syslog_seq;
253 static u32 syslog_idx;
254 static enum log_flags syslog_prev;
255 static size_t syslog_partial;
257 /* index and sequence number of the first record stored in the buffer */
258 static u64 log_first_seq;
259 static u32 log_first_idx;
261 /* index and sequence number of the next record to store in the buffer */
262 static u64 log_next_seq;
263 static u32 log_next_idx;
265 /* the next printk record to write to the console */
266 static u64 console_seq;
267 static u32 console_idx;
268 static enum log_flags console_prev;
270 /* the next printk record to read after the last 'clear' command */
271 static u64 clear_seq;
272 static u32 clear_idx;
274 #define PREFIX_MAX 32
275 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
277 #define LOG_LEVEL(v) ((v) & 0x07)
278 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
281 #define LOG_ALIGN __alignof__(struct printk_log)
282 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
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(unsigned size)
877 size = roundup_pow_of_two(size);
878 if (size > log_buf_len)
879 new_log_buf_len = size;
882 /* save requested log_buf_len since it's too early to process it */
883 static int __init log_buf_len_setup(char *str)
885 unsigned size = memparse(str, &str);
887 log_buf_len_update(size);
891 early_param("log_buf_len", log_buf_len_setup);
894 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
896 static void __init log_buf_add_cpu(void)
898 unsigned int cpu_extra;
901 * archs should set up cpu_possible_bits properly with
902 * set_cpu_possible() after setup_arch() but just in
903 * case lets ensure this is valid.
905 if (num_possible_cpus() == 1)
908 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
910 /* by default this will only continue through for large > 64 CPUs */
911 if (cpu_extra <= __LOG_BUF_LEN / 2)
914 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
915 __LOG_CPU_MAX_BUF_LEN);
916 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
918 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
920 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
922 #else /* !CONFIG_SMP */
923 static inline void log_buf_add_cpu(void) {}
924 #endif /* CONFIG_SMP */
926 void __init setup_log_buf(int early)
932 if (log_buf != __log_buf)
935 if (!early && !new_log_buf_len)
938 if (!new_log_buf_len)
943 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
945 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
949 if (unlikely(!new_log_buf)) {
950 pr_err("log_buf_len: %ld bytes not available\n",
955 raw_spin_lock_irqsave(&logbuf_lock, flags);
956 log_buf_len = new_log_buf_len;
957 log_buf = new_log_buf;
959 free = __LOG_BUF_LEN - log_next_idx;
960 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
961 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
963 pr_info("log_buf_len: %d bytes\n", log_buf_len);
964 pr_info("early log buf free: %d(%d%%)\n",
965 free, (free * 100) / __LOG_BUF_LEN);
968 static bool __read_mostly ignore_loglevel;
970 static int __init ignore_loglevel_setup(char *str)
972 ignore_loglevel = true;
973 pr_info("debug: ignoring loglevel setting.\n");
978 early_param("ignore_loglevel", ignore_loglevel_setup);
979 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
980 MODULE_PARM_DESC(ignore_loglevel,
981 "ignore loglevel setting (prints all kernel messages to the console)");
983 #ifdef CONFIG_BOOT_PRINTK_DELAY
985 static int boot_delay; /* msecs delay after each printk during bootup */
986 static unsigned long long loops_per_msec; /* based on boot_delay */
988 static int __init boot_delay_setup(char *str)
992 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
993 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
995 get_option(&str, &boot_delay);
996 if (boot_delay > 10 * 1000)
999 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1000 "HZ: %d, loops_per_msec: %llu\n",
1001 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1004 early_param("boot_delay", boot_delay_setup);
1006 static void boot_delay_msec(int level)
1008 unsigned long long k;
1009 unsigned long timeout;
1011 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
1012 || (level >= console_loglevel && !ignore_loglevel)) {
1016 k = (unsigned long long)loops_per_msec * boot_delay;
1018 timeout = jiffies + msecs_to_jiffies(boot_delay);
1023 * use (volatile) jiffies to prevent
1024 * compiler reduction; loop termination via jiffies
1025 * is secondary and may or may not happen.
1027 if (time_after(jiffies, timeout))
1029 touch_nmi_watchdog();
1033 static inline void boot_delay_msec(int level)
1038 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1039 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1041 static size_t print_time(u64 ts, char *buf)
1043 unsigned long rem_nsec;
1048 rem_nsec = do_div(ts, 1000000000);
1051 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1053 return sprintf(buf, "[%5lu.%06lu] ",
1054 (unsigned long)ts, rem_nsec / 1000);
1057 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1060 unsigned int prefix = (msg->facility << 3) | msg->level;
1064 len += sprintf(buf, "<%u>", prefix);
1069 else if (prefix > 99)
1071 else if (prefix > 9)
1076 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1080 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1081 bool syslog, char *buf, size_t size)
1083 const char *text = log_text(msg);
1084 size_t text_size = msg->text_len;
1086 bool newline = true;
1089 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1092 if (msg->flags & LOG_CONT) {
1093 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1096 if (!(msg->flags & LOG_NEWLINE))
1101 const char *next = memchr(text, '\n', text_size);
1105 text_len = next - text;
1107 text_size -= next - text;
1109 text_len = text_size;
1113 if (print_prefix(msg, syslog, NULL) +
1114 text_len + 1 >= size - len)
1118 len += print_prefix(msg, syslog, buf + len);
1119 memcpy(buf + len, text, text_len);
1121 if (next || newline)
1124 /* SYSLOG_ACTION_* buffer size only calculation */
1126 len += print_prefix(msg, syslog, NULL);
1128 if (next || newline)
1139 static int syslog_print(char __user *buf, int size)
1142 struct printk_log *msg;
1145 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1153 raw_spin_lock_irq(&logbuf_lock);
1154 if (syslog_seq < log_first_seq) {
1155 /* messages are gone, move to first one */
1156 syslog_seq = log_first_seq;
1157 syslog_idx = log_first_idx;
1161 if (syslog_seq == log_next_seq) {
1162 raw_spin_unlock_irq(&logbuf_lock);
1166 skip = syslog_partial;
1167 msg = log_from_idx(syslog_idx);
1168 n = msg_print_text(msg, syslog_prev, true, text,
1169 LOG_LINE_MAX + PREFIX_MAX);
1170 if (n - syslog_partial <= size) {
1171 /* message fits into buffer, move forward */
1172 syslog_idx = log_next(syslog_idx);
1174 syslog_prev = msg->flags;
1175 n -= syslog_partial;
1178 /* partial read(), remember position */
1180 syslog_partial += n;
1183 raw_spin_unlock_irq(&logbuf_lock);
1188 if (copy_to_user(buf, text + skip, n)) {
1203 static int syslog_print_all(char __user *buf, int size, bool clear)
1208 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1212 raw_spin_lock_irq(&logbuf_lock);
1217 enum log_flags prev;
1219 if (clear_seq < log_first_seq) {
1220 /* messages are gone, move to first available one */
1221 clear_seq = log_first_seq;
1222 clear_idx = log_first_idx;
1226 * Find first record that fits, including all following records,
1227 * into the user-provided buffer for this dump.
1232 while (seq < log_next_seq) {
1233 struct printk_log *msg = log_from_idx(idx);
1235 len += msg_print_text(msg, prev, true, NULL, 0);
1237 idx = log_next(idx);
1241 /* move first record forward until length fits into the buffer */
1245 while (len > size && seq < log_next_seq) {
1246 struct printk_log *msg = log_from_idx(idx);
1248 len -= msg_print_text(msg, prev, true, NULL, 0);
1250 idx = log_next(idx);
1254 /* last message fitting into this dump */
1255 next_seq = log_next_seq;
1258 while (len >= 0 && seq < next_seq) {
1259 struct printk_log *msg = log_from_idx(idx);
1262 textlen = msg_print_text(msg, prev, true, text,
1263 LOG_LINE_MAX + PREFIX_MAX);
1268 idx = log_next(idx);
1272 raw_spin_unlock_irq(&logbuf_lock);
1273 if (copy_to_user(buf + len, text, textlen))
1277 raw_spin_lock_irq(&logbuf_lock);
1279 if (seq < log_first_seq) {
1280 /* messages are gone, move to next one */
1281 seq = log_first_seq;
1282 idx = log_first_idx;
1289 clear_seq = log_next_seq;
1290 clear_idx = log_next_idx;
1292 raw_spin_unlock_irq(&logbuf_lock);
1298 int do_syslog(int type, char __user *buf, int len, int source)
1301 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1304 error = check_syslog_permissions(type, source);
1309 case SYSLOG_ACTION_CLOSE: /* Close log */
1311 case SYSLOG_ACTION_OPEN: /* Open log */
1313 case SYSLOG_ACTION_READ: /* Read from log */
1315 if (!buf || len < 0)
1320 if (!access_ok(VERIFY_WRITE, buf, len)) {
1324 error = wait_event_interruptible(log_wait,
1325 syslog_seq != log_next_seq);
1328 error = syslog_print(buf, len);
1330 /* Read/clear last kernel messages */
1331 case SYSLOG_ACTION_READ_CLEAR:
1334 /* Read last kernel messages */
1335 case SYSLOG_ACTION_READ_ALL:
1337 if (!buf || len < 0)
1342 if (!access_ok(VERIFY_WRITE, buf, len)) {
1346 error = syslog_print_all(buf, len, clear);
1348 /* Clear ring buffer */
1349 case SYSLOG_ACTION_CLEAR:
1350 syslog_print_all(NULL, 0, true);
1352 /* Disable logging to console */
1353 case SYSLOG_ACTION_CONSOLE_OFF:
1354 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1355 saved_console_loglevel = console_loglevel;
1356 console_loglevel = minimum_console_loglevel;
1358 /* Enable logging to console */
1359 case SYSLOG_ACTION_CONSOLE_ON:
1360 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1361 console_loglevel = saved_console_loglevel;
1362 saved_console_loglevel = LOGLEVEL_DEFAULT;
1365 /* Set level of messages printed to console */
1366 case SYSLOG_ACTION_CONSOLE_LEVEL:
1368 if (len < 1 || len > 8)
1370 if (len < minimum_console_loglevel)
1371 len = minimum_console_loglevel;
1372 console_loglevel = len;
1373 /* Implicitly re-enable logging to console */
1374 saved_console_loglevel = LOGLEVEL_DEFAULT;
1377 /* Number of chars in the log buffer */
1378 case SYSLOG_ACTION_SIZE_UNREAD:
1379 raw_spin_lock_irq(&logbuf_lock);
1380 if (syslog_seq < log_first_seq) {
1381 /* messages are gone, move to first one */
1382 syslog_seq = log_first_seq;
1383 syslog_idx = log_first_idx;
1387 if (source == SYSLOG_FROM_PROC) {
1389 * Short-cut for poll(/"proc/kmsg") which simply checks
1390 * for pending data, not the size; return the count of
1391 * records, not the length.
1393 error = log_next_seq - syslog_seq;
1395 u64 seq = syslog_seq;
1396 u32 idx = syslog_idx;
1397 enum log_flags prev = syslog_prev;
1400 while (seq < log_next_seq) {
1401 struct printk_log *msg = log_from_idx(idx);
1403 error += msg_print_text(msg, prev, true, NULL, 0);
1404 idx = log_next(idx);
1408 error -= syslog_partial;
1410 raw_spin_unlock_irq(&logbuf_lock);
1412 /* Size of the log buffer */
1413 case SYSLOG_ACTION_SIZE_BUFFER:
1414 error = log_buf_len;
1424 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1426 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1430 * Call the console drivers, asking them to write out
1431 * log_buf[start] to log_buf[end - 1].
1432 * The console_lock must be held.
1434 static void call_console_drivers(int level,
1435 const char *ext_text, size_t ext_len,
1436 const char *text, size_t len)
1438 struct console *con;
1440 trace_console(text, len);
1442 if (level >= console_loglevel && !ignore_loglevel)
1444 if (!console_drivers)
1447 for_each_console(con) {
1448 if (exclusive_console && con != exclusive_console)
1450 if (!(con->flags & CON_ENABLED))
1454 if (!cpu_online(smp_processor_id()) &&
1455 !(con->flags & CON_ANYTIME))
1457 if (con->flags & CON_EXTENDED)
1458 con->write(con, ext_text, ext_len);
1460 con->write(con, text, len);
1465 * Zap console related locks when oopsing.
1466 * To leave time for slow consoles to print a full oops,
1467 * only zap at most once every 30 seconds.
1469 static void zap_locks(void)
1471 static unsigned long oops_timestamp;
1473 if (time_after_eq(jiffies, oops_timestamp) &&
1474 !time_after(jiffies, oops_timestamp + 30 * HZ))
1477 oops_timestamp = jiffies;
1480 /* If a crash is occurring, make sure we can't deadlock */
1481 raw_spin_lock_init(&logbuf_lock);
1482 /* And make sure that we print immediately */
1483 sema_init(&console_sem, 1);
1486 int printk_delay_msec __read_mostly;
1488 static inline void printk_delay(void)
1490 if (unlikely(printk_delay_msec)) {
1491 int m = printk_delay_msec;
1495 touch_nmi_watchdog();
1501 * Continuation lines are buffered, and not committed to the record buffer
1502 * until the line is complete, or a race forces it. The line fragments
1503 * though, are printed immediately to the consoles to ensure everything has
1504 * reached the console in case of a kernel crash.
1506 static struct cont {
1507 char buf[LOG_LINE_MAX];
1508 size_t len; /* length == 0 means unused buffer */
1509 size_t cons; /* bytes written to console */
1510 struct task_struct *owner; /* task of first print*/
1511 u64 ts_nsec; /* time of first print */
1512 u8 level; /* log level of first message */
1513 u8 facility; /* log facility of first message */
1514 enum log_flags flags; /* prefix, newline flags */
1515 bool flushed:1; /* buffer sealed and committed */
1518 static void cont_flush(enum log_flags flags)
1527 * If a fragment of this line was directly flushed to the
1528 * console; wait for the console to pick up the rest of the
1529 * line. LOG_NOCONS suppresses a duplicated output.
1531 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1532 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1534 cont.flushed = true;
1537 * If no fragment of this line ever reached the console,
1538 * just submit it to the store and free the buffer.
1540 log_store(cont.facility, cont.level, flags, 0,
1541 NULL, 0, cont.buf, cont.len);
1546 static bool cont_add(int facility, int level, const char *text, size_t len)
1548 if (cont.len && cont.flushed)
1552 * If ext consoles are present, flush and skip in-kernel
1553 * continuation. See nr_ext_console_drivers definition. Also, if
1554 * the line gets too long, split it up in separate records.
1556 if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
1557 cont_flush(LOG_CONT);
1562 cont.facility = facility;
1564 cont.owner = current;
1565 cont.ts_nsec = local_clock();
1568 cont.flushed = false;
1571 memcpy(cont.buf + cont.len, text, len);
1574 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1575 cont_flush(LOG_CONT);
1580 static size_t cont_print_text(char *text, size_t size)
1585 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1586 textlen += print_time(cont.ts_nsec, text);
1590 len = cont.len - cont.cons;
1594 memcpy(text + textlen, cont.buf + cont.cons, len);
1596 cont.cons = cont.len;
1600 if (cont.flags & LOG_NEWLINE)
1601 text[textlen++] = '\n';
1602 /* got everything, release buffer */
1608 asmlinkage int vprintk_emit(int facility, int level,
1609 const char *dict, size_t dictlen,
1610 const char *fmt, va_list args)
1612 static bool recursion_bug;
1613 static char textbuf[LOG_LINE_MAX];
1614 char *text = textbuf;
1615 size_t text_len = 0;
1616 enum log_flags lflags = 0;
1617 unsigned long flags;
1619 int printed_len = 0;
1620 bool in_sched = false;
1621 /* cpu currently holding logbuf_lock in this function */
1622 static unsigned int logbuf_cpu = UINT_MAX;
1624 if (level == LOGLEVEL_SCHED) {
1625 level = LOGLEVEL_DEFAULT;
1629 boot_delay_msec(level);
1632 local_irq_save(flags);
1633 this_cpu = smp_processor_id();
1636 * Ouch, printk recursed into itself!
1638 if (unlikely(logbuf_cpu == this_cpu)) {
1640 * If a crash is occurring during printk() on this CPU,
1641 * then try to get the crash message out but make sure
1642 * we can't deadlock. Otherwise just return to avoid the
1643 * recursion and return - but flag the recursion so that
1644 * it can be printed at the next appropriate moment:
1646 if (!oops_in_progress && !lockdep_recursing(current)) {
1647 recursion_bug = true;
1648 local_irq_restore(flags);
1655 /* This stops the holder of console_sem just where we want him */
1656 raw_spin_lock(&logbuf_lock);
1657 logbuf_cpu = this_cpu;
1659 if (unlikely(recursion_bug)) {
1660 static const char recursion_msg[] =
1661 "BUG: recent printk recursion!";
1663 recursion_bug = false;
1664 /* emit KERN_CRIT message */
1665 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1666 NULL, 0, recursion_msg,
1667 strlen(recursion_msg));
1671 * The printf needs to come first; we need the syslog
1672 * prefix which might be passed-in as a parameter.
1674 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1676 /* mark and strip a trailing newline */
1677 if (text_len && text[text_len-1] == '\n') {
1679 lflags |= LOG_NEWLINE;
1682 /* strip kernel syslog prefix and extract log level or control flags */
1683 if (facility == 0) {
1684 int kern_level = printk_get_level(text);
1687 const char *end_of_header = printk_skip_level(text);
1688 switch (kern_level) {
1690 if (level == LOGLEVEL_DEFAULT)
1691 level = kern_level - '0';
1693 case 'd': /* KERN_DEFAULT */
1694 lflags |= LOG_PREFIX;
1697 * No need to check length here because vscnprintf
1698 * put '\0' at the end of the string. Only valid and
1699 * newly printed level is detected.
1701 text_len -= end_of_header - text;
1702 text = (char *)end_of_header;
1706 if (level == LOGLEVEL_DEFAULT)
1707 level = default_message_loglevel;
1710 lflags |= LOG_PREFIX|LOG_NEWLINE;
1712 if (!(lflags & LOG_NEWLINE)) {
1714 * Flush the conflicting buffer. An earlier newline was missing,
1715 * or another task also prints continuation lines.
1717 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1718 cont_flush(LOG_NEWLINE);
1720 /* buffer line if possible, otherwise store it right away */
1721 if (cont_add(facility, level, text, text_len))
1722 printed_len += text_len;
1724 printed_len += log_store(facility, level,
1725 lflags | LOG_CONT, 0,
1726 dict, dictlen, text, text_len);
1728 bool stored = false;
1731 * If an earlier newline was missing and it was the same task,
1732 * either merge it with the current buffer and flush, or if
1733 * there was a race with interrupts (prefix == true) then just
1734 * flush it out and store this line separately.
1735 * If the preceding printk was from a different task and missed
1736 * a newline, flush and append the newline.
1739 if (cont.owner == current && !(lflags & LOG_PREFIX))
1740 stored = cont_add(facility, level, text,
1742 cont_flush(LOG_NEWLINE);
1746 printed_len += text_len;
1748 printed_len += log_store(facility, level, lflags, 0,
1749 dict, dictlen, text, text_len);
1752 logbuf_cpu = UINT_MAX;
1753 raw_spin_unlock(&logbuf_lock);
1755 local_irq_restore(flags);
1757 /* If called from the scheduler, we can not call up(). */
1761 * Disable preemption to avoid being preempted while holding
1762 * console_sem which would prevent anyone from printing to
1768 * Try to acquire and then immediately release the console
1769 * semaphore. The release will print out buffers and wake up
1770 * /dev/kmsg and syslog() users.
1772 if (console_trylock())
1780 EXPORT_SYMBOL(vprintk_emit);
1782 asmlinkage int vprintk(const char *fmt, va_list args)
1784 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1786 EXPORT_SYMBOL(vprintk);
1788 asmlinkage int printk_emit(int facility, int level,
1789 const char *dict, size_t dictlen,
1790 const char *fmt, ...)
1795 va_start(args, fmt);
1796 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1801 EXPORT_SYMBOL(printk_emit);
1803 int vprintk_default(const char *fmt, va_list args)
1807 #ifdef CONFIG_KGDB_KDB
1808 if (unlikely(kdb_trap_printk)) {
1809 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1813 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1817 EXPORT_SYMBOL_GPL(vprintk_default);
1820 * This allows printk to be diverted to another function per cpu.
1821 * This is useful for calling printk functions from within NMI
1822 * without worrying about race conditions that can lock up the
1825 DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
1828 * printk - print a kernel message
1829 * @fmt: format string
1831 * This is printk(). It can be called from any context. We want it to work.
1833 * We try to grab the console_lock. If we succeed, it's easy - we log the
1834 * output and call the console drivers. If we fail to get the semaphore, we
1835 * place the output into the log buffer and return. The current holder of
1836 * the console_sem will notice the new output in console_unlock(); and will
1837 * send it to the consoles before releasing the lock.
1839 * One effect of this deferred printing is that code which calls printk() and
1840 * then changes console_loglevel may break. This is because console_loglevel
1841 * is inspected when the actual printing occurs.
1846 * See the vsnprintf() documentation for format string extensions over C99.
1848 asmlinkage __visible int printk(const char *fmt, ...)
1850 printk_func_t vprintk_func;
1854 va_start(args, fmt);
1857 * If a caller overrides the per_cpu printk_func, then it needs
1858 * to disable preemption when calling printk(). Otherwise
1859 * the printk_func should be set to the default. No need to
1860 * disable preemption here.
1862 vprintk_func = this_cpu_read(printk_func);
1863 r = vprintk_func(fmt, args);
1869 EXPORT_SYMBOL(printk);
1871 #else /* CONFIG_PRINTK */
1873 #define LOG_LINE_MAX 0
1874 #define PREFIX_MAX 0
1876 static u64 syslog_seq;
1877 static u32 syslog_idx;
1878 static u64 console_seq;
1879 static u32 console_idx;
1880 static enum log_flags syslog_prev;
1881 static u64 log_first_seq;
1882 static u32 log_first_idx;
1883 static u64 log_next_seq;
1884 static enum log_flags console_prev;
1885 static struct cont {
1891 static char *log_text(const struct printk_log *msg) { return NULL; }
1892 static char *log_dict(const struct printk_log *msg) { return NULL; }
1893 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1894 static u32 log_next(u32 idx) { return 0; }
1895 static ssize_t msg_print_ext_header(char *buf, size_t size,
1896 struct printk_log *msg, u64 seq,
1897 enum log_flags prev_flags) { return 0; }
1898 static ssize_t msg_print_ext_body(char *buf, size_t size,
1899 char *dict, size_t dict_len,
1900 char *text, size_t text_len) { return 0; }
1901 static void call_console_drivers(int level,
1902 const char *ext_text, size_t ext_len,
1903 const char *text, size_t len) {}
1904 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1905 bool syslog, char *buf, size_t size) { return 0; }
1906 static size_t cont_print_text(char *text, size_t size) { return 0; }
1908 /* Still needs to be defined for users */
1909 DEFINE_PER_CPU(printk_func_t, printk_func);
1911 #endif /* CONFIG_PRINTK */
1913 #ifdef CONFIG_EARLY_PRINTK
1914 struct console *early_console;
1916 asmlinkage __visible void early_printk(const char *fmt, ...)
1926 n = vscnprintf(buf, sizeof(buf), fmt, ap);
1929 early_console->write(early_console, buf, n);
1933 static int __add_preferred_console(char *name, int idx, char *options,
1936 struct console_cmdline *c;
1940 * See if this tty is not yet registered, and
1941 * if we have a slot free.
1943 for (i = 0, c = console_cmdline;
1944 i < MAX_CMDLINECONSOLES && c->name[0];
1946 if (strcmp(c->name, name) == 0 && c->index == idx) {
1948 selected_console = i;
1952 if (i == MAX_CMDLINECONSOLES)
1955 selected_console = i;
1956 strlcpy(c->name, name, sizeof(c->name));
1957 c->options = options;
1958 braille_set_options(c, brl_options);
1964 * Set up a console. Called via do_early_param() in init/main.c
1965 * for each "console=" parameter in the boot command line.
1967 static int __init console_setup(char *str)
1969 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
1970 char *s, *options, *brl_options = NULL;
1973 if (_braille_console_setup(&str, &brl_options))
1977 * Decode str into name, index, options.
1979 if (str[0] >= '0' && str[0] <= '9') {
1980 strcpy(buf, "ttyS");
1981 strncpy(buf + 4, str, sizeof(buf) - 5);
1983 strncpy(buf, str, sizeof(buf) - 1);
1985 buf[sizeof(buf) - 1] = 0;
1986 options = strchr(str, ',');
1990 if (!strcmp(str, "ttya"))
1991 strcpy(buf, "ttyS0");
1992 if (!strcmp(str, "ttyb"))
1993 strcpy(buf, "ttyS1");
1995 for (s = buf; *s; s++)
1996 if (isdigit(*s) || *s == ',')
1998 idx = simple_strtoul(s, NULL, 10);
2001 __add_preferred_console(buf, idx, options, brl_options);
2002 console_set_on_cmdline = 1;
2005 __setup("console=", console_setup);
2008 * add_preferred_console - add a device to the list of preferred consoles.
2009 * @name: device name
2010 * @idx: device index
2011 * @options: options for this console
2013 * The last preferred console added will be used for kernel messages
2014 * and stdin/out/err for init. Normally this is used by console_setup
2015 * above to handle user-supplied console arguments; however it can also
2016 * be used by arch-specific code either to override the user or more
2017 * commonly to provide a default console (ie from PROM variables) when
2018 * the user has not supplied one.
2020 int add_preferred_console(char *name, int idx, char *options)
2022 return __add_preferred_console(name, idx, options, NULL);
2025 bool console_suspend_enabled = true;
2026 EXPORT_SYMBOL(console_suspend_enabled);
2028 static int __init console_suspend_disable(char *str)
2030 console_suspend_enabled = false;
2033 __setup("no_console_suspend", console_suspend_disable);
2034 module_param_named(console_suspend, console_suspend_enabled,
2035 bool, S_IRUGO | S_IWUSR);
2036 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2037 " and hibernate operations");
2040 * suspend_console - suspend the console subsystem
2042 * This disables printk() while we go into suspend states
2044 void suspend_console(void)
2046 if (!console_suspend_enabled)
2048 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2050 console_suspended = 1;
2054 void resume_console(void)
2056 if (!console_suspend_enabled)
2059 console_suspended = 0;
2064 * console_cpu_notify - print deferred console messages after CPU hotplug
2065 * @self: notifier struct
2066 * @action: CPU hotplug event
2069 * If printk() is called from a CPU that is not online yet, the messages
2070 * will be spooled but will not show up on the console. This function is
2071 * called when a new CPU comes online (or fails to come up), and ensures
2072 * that any such output gets printed.
2074 static int console_cpu_notify(struct notifier_block *self,
2075 unsigned long action, void *hcpu)
2080 case CPU_DOWN_FAILED:
2081 case CPU_UP_CANCELED:
2089 * console_lock - lock the console system for exclusive use.
2091 * Acquires a lock which guarantees that the caller has
2092 * exclusive access to the console system and the console_drivers list.
2094 * Can sleep, returns nothing.
2096 void console_lock(void)
2101 if (console_suspended)
2104 console_may_schedule = 1;
2106 EXPORT_SYMBOL(console_lock);
2109 * console_trylock - try to lock the console system for exclusive use.
2111 * Try to acquire a lock which guarantees that the caller has exclusive
2112 * access to the console system and the console_drivers list.
2114 * returns 1 on success, and 0 on failure to acquire the lock.
2116 int console_trylock(void)
2118 if (down_trylock_console_sem())
2120 if (console_suspended) {
2125 console_may_schedule = 0;
2128 EXPORT_SYMBOL(console_trylock);
2130 int is_console_locked(void)
2132 return console_locked;
2136 * Check if we have any console that is capable of printing while cpu is
2137 * booting or shutting down. Requires console_sem.
2139 static int have_callable_console(void)
2141 struct console *con;
2143 for_each_console(con)
2144 if (con->flags & CON_ANYTIME)
2151 * Can we actually use the console at this time on this cpu?
2153 * Console drivers may assume that per-cpu resources have been allocated. So
2154 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2155 * call them until this CPU is officially up.
2157 static inline int can_use_console(void)
2159 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2162 static void console_cont_flush(char *text, size_t size)
2164 unsigned long flags;
2167 raw_spin_lock_irqsave(&logbuf_lock, flags);
2173 * We still queue earlier records, likely because the console was
2174 * busy. The earlier ones need to be printed before this one, we
2175 * did not flush any fragment so far, so just let it queue up.
2177 if (console_seq < log_next_seq && !cont.cons)
2180 len = cont_print_text(text, size);
2181 raw_spin_unlock(&logbuf_lock);
2182 stop_critical_timings();
2183 call_console_drivers(cont.level, NULL, 0, text, len);
2184 start_critical_timings();
2185 local_irq_restore(flags);
2188 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2192 * console_unlock - unlock the console system
2194 * Releases the console_lock which the caller holds on the console system
2195 * and the console driver list.
2197 * While the console_lock was held, console output may have been buffered
2198 * by printk(). If this is the case, console_unlock(); emits
2199 * the output prior to releasing the lock.
2201 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2203 * console_unlock(); may be called from any context.
2205 void console_unlock(void)
2207 static char ext_text[CONSOLE_EXT_LOG_MAX];
2208 static char text[LOG_LINE_MAX + PREFIX_MAX];
2209 static u64 seen_seq;
2210 unsigned long flags;
2211 bool wake_klogd = false;
2212 bool do_cond_resched, retry;
2214 if (console_suspended) {
2220 * Console drivers are called under logbuf_lock, so
2221 * @console_may_schedule should be cleared before; however, we may
2222 * end up dumping a lot of lines, for example, if called from
2223 * console registration path, and should invoke cond_resched()
2224 * between lines if allowable. Not doing so can cause a very long
2225 * scheduling stall on a slow console leading to RCU stall and
2226 * softlockup warnings which exacerbate the issue with more
2227 * messages practically incapacitating the system.
2229 do_cond_resched = console_may_schedule;
2230 console_may_schedule = 0;
2234 * We released the console_sem lock, so we need to recheck if
2235 * cpu is online and (if not) is there at least one CON_ANYTIME
2238 if (!can_use_console()) {
2244 /* flush buffered message fragment immediately to console */
2245 console_cont_flush(text, sizeof(text));
2248 struct printk_log *msg;
2253 raw_spin_lock_irqsave(&logbuf_lock, flags);
2254 if (seen_seq != log_next_seq) {
2256 seen_seq = log_next_seq;
2259 if (console_seq < log_first_seq) {
2260 len = sprintf(text, "** %u printk messages dropped ** ",
2261 (unsigned)(log_first_seq - console_seq));
2263 /* messages are gone, move to first one */
2264 console_seq = log_first_seq;
2265 console_idx = log_first_idx;
2271 if (console_seq == log_next_seq)
2274 msg = log_from_idx(console_idx);
2275 if (msg->flags & LOG_NOCONS) {
2277 * Skip record we have buffered and already printed
2278 * directly to the console when we received it.
2280 console_idx = log_next(console_idx);
2283 * We will get here again when we register a new
2284 * CON_PRINTBUFFER console. Clear the flag so we
2285 * will properly dump everything later.
2287 msg->flags &= ~LOG_NOCONS;
2288 console_prev = msg->flags;
2293 len += msg_print_text(msg, console_prev, false,
2294 text + len, sizeof(text) - len);
2295 if (nr_ext_console_drivers) {
2296 ext_len = msg_print_ext_header(ext_text,
2298 msg, console_seq, console_prev);
2299 ext_len += msg_print_ext_body(ext_text + ext_len,
2300 sizeof(ext_text) - ext_len,
2301 log_dict(msg), msg->dict_len,
2302 log_text(msg), msg->text_len);
2304 console_idx = log_next(console_idx);
2306 console_prev = msg->flags;
2307 raw_spin_unlock(&logbuf_lock);
2309 stop_critical_timings(); /* don't trace print latency */
2310 call_console_drivers(level, ext_text, ext_len, text, len);
2311 start_critical_timings();
2312 local_irq_restore(flags);
2314 if (do_cond_resched)
2319 /* Release the exclusive_console once it is used */
2320 if (unlikely(exclusive_console))
2321 exclusive_console = NULL;
2323 raw_spin_unlock(&logbuf_lock);
2328 * Someone could have filled up the buffer again, so re-check if there's
2329 * something to flush. In case we cannot trylock the console_sem again,
2330 * there's a new owner and the console_unlock() from them will do the
2331 * flush, no worries.
2333 raw_spin_lock(&logbuf_lock);
2334 retry = console_seq != log_next_seq;
2335 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2337 if (retry && console_trylock())
2343 EXPORT_SYMBOL(console_unlock);
2346 * console_conditional_schedule - yield the CPU if required
2348 * If the console code is currently allowed to sleep, and
2349 * if this CPU should yield the CPU to another task, do
2352 * Must be called within console_lock();.
2354 void __sched console_conditional_schedule(void)
2356 if (console_may_schedule)
2359 EXPORT_SYMBOL(console_conditional_schedule);
2361 void console_unblank(void)
2366 * console_unblank can no longer be called in interrupt context unless
2367 * oops_in_progress is set to 1..
2369 if (oops_in_progress) {
2370 if (down_trylock_console_sem() != 0)
2376 console_may_schedule = 0;
2378 if ((c->flags & CON_ENABLED) && c->unblank)
2384 * console_flush_on_panic - flush console content on panic
2386 * Immediately output all pending messages no matter what.
2388 void console_flush_on_panic(void)
2391 * If someone else is holding the console lock, trylock will fail
2392 * and may_schedule may be set. Ignore and proceed to unlock so
2393 * that messages are flushed out. As this can be called from any
2394 * context and we don't want to get preempted while flushing,
2395 * ensure may_schedule is cleared.
2398 console_may_schedule = 0;
2403 * Return the console tty driver structure and its associated index
2405 struct tty_driver *console_device(int *index)
2408 struct tty_driver *driver = NULL;
2411 for_each_console(c) {
2414 driver = c->device(c, index);
2423 * Prevent further output on the passed console device so that (for example)
2424 * serial drivers can disable console output before suspending a port, and can
2425 * re-enable output afterwards.
2427 void console_stop(struct console *console)
2430 console->flags &= ~CON_ENABLED;
2433 EXPORT_SYMBOL(console_stop);
2435 void console_start(struct console *console)
2438 console->flags |= CON_ENABLED;
2441 EXPORT_SYMBOL(console_start);
2443 static int __read_mostly keep_bootcon;
2445 static int __init keep_bootcon_setup(char *str)
2448 pr_info("debug: skip boot console de-registration.\n");
2453 early_param("keep_bootcon", keep_bootcon_setup);
2456 * The console driver calls this routine during kernel initialization
2457 * to register the console printing procedure with printk() and to
2458 * print any messages that were printed by the kernel before the
2459 * console driver was initialized.
2461 * This can happen pretty early during the boot process (because of
2462 * early_printk) - sometimes before setup_arch() completes - be careful
2463 * of what kernel features are used - they may not be initialised yet.
2465 * There are two types of consoles - bootconsoles (early_printk) and
2466 * "real" consoles (everything which is not a bootconsole) which are
2467 * handled differently.
2468 * - Any number of bootconsoles can be registered at any time.
2469 * - As soon as a "real" console is registered, all bootconsoles
2470 * will be unregistered automatically.
2471 * - Once a "real" console is registered, any attempt to register a
2472 * bootconsoles will be rejected
2474 void register_console(struct console *newcon)
2477 unsigned long flags;
2478 struct console *bcon = NULL;
2479 struct console_cmdline *c;
2481 if (console_drivers)
2482 for_each_console(bcon)
2483 if (WARN(bcon == newcon,
2484 "console '%s%d' already registered\n",
2485 bcon->name, bcon->index))
2489 * before we register a new CON_BOOT console, make sure we don't
2490 * already have a valid console
2492 if (console_drivers && newcon->flags & CON_BOOT) {
2493 /* find the last or real console */
2494 for_each_console(bcon) {
2495 if (!(bcon->flags & CON_BOOT)) {
2496 pr_info("Too late to register bootconsole %s%d\n",
2497 newcon->name, newcon->index);
2503 if (console_drivers && console_drivers->flags & CON_BOOT)
2504 bcon = console_drivers;
2506 if (preferred_console < 0 || bcon || !console_drivers)
2507 preferred_console = selected_console;
2510 * See if we want to use this console driver. If we
2511 * didn't select a console we take the first one
2512 * that registers here.
2514 if (preferred_console < 0) {
2515 if (newcon->index < 0)
2517 if (newcon->setup == NULL ||
2518 newcon->setup(newcon, NULL) == 0) {
2519 newcon->flags |= CON_ENABLED;
2520 if (newcon->device) {
2521 newcon->flags |= CON_CONSDEV;
2522 preferred_console = 0;
2528 * See if this console matches one we selected on
2531 for (i = 0, c = console_cmdline;
2532 i < MAX_CMDLINECONSOLES && c->name[0];
2534 if (!newcon->match ||
2535 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2536 /* default matching */
2537 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2538 if (strcmp(c->name, newcon->name) != 0)
2540 if (newcon->index >= 0 &&
2541 newcon->index != c->index)
2543 if (newcon->index < 0)
2544 newcon->index = c->index;
2546 if (_braille_register_console(newcon, c))
2549 if (newcon->setup &&
2550 newcon->setup(newcon, c->options) != 0)
2554 newcon->flags |= CON_ENABLED;
2555 if (i == selected_console) {
2556 newcon->flags |= CON_CONSDEV;
2557 preferred_console = selected_console;
2562 if (!(newcon->flags & CON_ENABLED))
2566 * If we have a bootconsole, and are switching to a real console,
2567 * don't print everything out again, since when the boot console, and
2568 * the real console are the same physical device, it's annoying to
2569 * see the beginning boot messages twice
2571 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2572 newcon->flags &= ~CON_PRINTBUFFER;
2575 * Put this console in the list - keep the
2576 * preferred driver at the head of the list.
2579 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2580 newcon->next = console_drivers;
2581 console_drivers = newcon;
2583 newcon->next->flags &= ~CON_CONSDEV;
2585 newcon->next = console_drivers->next;
2586 console_drivers->next = newcon;
2589 if (newcon->flags & CON_EXTENDED)
2590 if (!nr_ext_console_drivers++)
2591 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2593 if (newcon->flags & CON_PRINTBUFFER) {
2595 * console_unlock(); will print out the buffered messages
2598 raw_spin_lock_irqsave(&logbuf_lock, flags);
2599 console_seq = syslog_seq;
2600 console_idx = syslog_idx;
2601 console_prev = syslog_prev;
2602 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2604 * We're about to replay the log buffer. Only do this to the
2605 * just-registered console to avoid excessive message spam to
2606 * the already-registered consoles.
2608 exclusive_console = newcon;
2611 console_sysfs_notify();
2614 * By unregistering the bootconsoles after we enable the real console
2615 * we get the "console xxx enabled" message on all the consoles -
2616 * boot consoles, real consoles, etc - this is to ensure that end
2617 * users know there might be something in the kernel's log buffer that
2618 * went to the bootconsole (that they do not see on the real console)
2620 pr_info("%sconsole [%s%d] enabled\n",
2621 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2622 newcon->name, newcon->index);
2624 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2626 /* We need to iterate through all boot consoles, to make
2627 * sure we print everything out, before we unregister them.
2629 for_each_console(bcon)
2630 if (bcon->flags & CON_BOOT)
2631 unregister_console(bcon);
2634 EXPORT_SYMBOL(register_console);
2636 int unregister_console(struct console *console)
2638 struct console *a, *b;
2641 pr_info("%sconsole [%s%d] disabled\n",
2642 (console->flags & CON_BOOT) ? "boot" : "" ,
2643 console->name, console->index);
2645 res = _braille_unregister_console(console);
2651 if (console_drivers == console) {
2652 console_drivers=console->next;
2654 } else if (console_drivers) {
2655 for (a=console_drivers->next, b=console_drivers ;
2656 a; b=a, a=b->next) {
2665 if (!res && (console->flags & CON_EXTENDED))
2666 nr_ext_console_drivers--;
2669 * If this isn't the last console and it has CON_CONSDEV set, we
2670 * need to set it on the next preferred console.
2672 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2673 console_drivers->flags |= CON_CONSDEV;
2675 console->flags &= ~CON_ENABLED;
2677 console_sysfs_notify();
2680 EXPORT_SYMBOL(unregister_console);
2683 * Some boot consoles access data that is in the init section and which will
2684 * be discarded after the initcalls have been run. To make sure that no code
2685 * will access this data, unregister the boot consoles in a late initcall.
2687 * If for some reason, such as deferred probe or the driver being a loadable
2688 * module, the real console hasn't registered yet at this point, there will
2689 * be a brief interval in which no messages are logged to the console, which
2690 * makes it difficult to diagnose problems that occur during this time.
2692 * To mitigate this problem somewhat, only unregister consoles whose memory
2693 * intersects with the init section. Note that code exists elsewhere to get
2694 * rid of the boot console as soon as the proper console shows up, so there
2695 * won't be side-effects from postponing the removal.
2697 static int __init printk_late_init(void)
2699 struct console *con;
2701 for_each_console(con) {
2702 if (!keep_bootcon && con->flags & CON_BOOT) {
2704 * Make sure to unregister boot consoles whose data
2705 * resides in the init section before the init section
2706 * is discarded. Boot consoles whose data will stick
2707 * around will automatically be unregistered when the
2708 * proper console replaces them.
2710 if (init_section_intersects(con, sizeof(*con)))
2711 unregister_console(con);
2714 hotcpu_notifier(console_cpu_notify, 0);
2717 late_initcall(printk_late_init);
2719 #if defined CONFIG_PRINTK
2721 * Delayed printk version, for scheduler-internal messages:
2723 #define PRINTK_PENDING_WAKEUP 0x01
2724 #define PRINTK_PENDING_OUTPUT 0x02
2726 static DEFINE_PER_CPU(int, printk_pending);
2728 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2730 int pending = __this_cpu_xchg(printk_pending, 0);
2732 if (pending & PRINTK_PENDING_OUTPUT) {
2733 /* If trylock fails, someone else is doing the printing */
2734 if (console_trylock())
2738 if (pending & PRINTK_PENDING_WAKEUP)
2739 wake_up_interruptible(&log_wait);
2742 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2743 .func = wake_up_klogd_work_func,
2744 .flags = IRQ_WORK_LAZY,
2747 void wake_up_klogd(void)
2750 if (waitqueue_active(&log_wait)) {
2751 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2752 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2757 int printk_deferred(const char *fmt, ...)
2763 va_start(args, fmt);
2764 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2767 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2768 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2775 * printk rate limiting, lifted from the networking subsystem.
2777 * This enforces a rate limit: not more than 10 kernel messages
2778 * every 5s to make a denial-of-service attack impossible.
2780 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2782 int __printk_ratelimit(const char *func)
2784 return ___ratelimit(&printk_ratelimit_state, func);
2786 EXPORT_SYMBOL(__printk_ratelimit);
2789 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2790 * @caller_jiffies: pointer to caller's state
2791 * @interval_msecs: minimum interval between prints
2793 * printk_timed_ratelimit() returns true if more than @interval_msecs
2794 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2797 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2798 unsigned int interval_msecs)
2800 unsigned long elapsed = jiffies - *caller_jiffies;
2802 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2805 *caller_jiffies = jiffies;
2808 EXPORT_SYMBOL(printk_timed_ratelimit);
2810 static DEFINE_SPINLOCK(dump_list_lock);
2811 static LIST_HEAD(dump_list);
2814 * kmsg_dump_register - register a kernel log dumper.
2815 * @dumper: pointer to the kmsg_dumper structure
2817 * Adds a kernel log dumper to the system. The dump callback in the
2818 * structure will be called when the kernel oopses or panics and must be
2819 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2821 int kmsg_dump_register(struct kmsg_dumper *dumper)
2823 unsigned long flags;
2826 /* The dump callback needs to be set */
2830 spin_lock_irqsave(&dump_list_lock, flags);
2831 /* Don't allow registering multiple times */
2832 if (!dumper->registered) {
2833 dumper->registered = 1;
2834 list_add_tail_rcu(&dumper->list, &dump_list);
2837 spin_unlock_irqrestore(&dump_list_lock, flags);
2841 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2844 * kmsg_dump_unregister - unregister a kmsg dumper.
2845 * @dumper: pointer to the kmsg_dumper structure
2847 * Removes a dump device from the system. Returns zero on success and
2848 * %-EINVAL otherwise.
2850 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2852 unsigned long flags;
2855 spin_lock_irqsave(&dump_list_lock, flags);
2856 if (dumper->registered) {
2857 dumper->registered = 0;
2858 list_del_rcu(&dumper->list);
2861 spin_unlock_irqrestore(&dump_list_lock, flags);
2866 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2868 static bool always_kmsg_dump;
2869 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2872 * kmsg_dump - dump kernel log to kernel message dumpers.
2873 * @reason: the reason (oops, panic etc) for dumping
2875 * Call each of the registered dumper's dump() callback, which can
2876 * retrieve the kmsg records with kmsg_dump_get_line() or
2877 * kmsg_dump_get_buffer().
2879 void kmsg_dump(enum kmsg_dump_reason reason)
2881 struct kmsg_dumper *dumper;
2882 unsigned long flags;
2884 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2888 list_for_each_entry_rcu(dumper, &dump_list, list) {
2889 if (dumper->max_reason && reason > dumper->max_reason)
2892 /* initialize iterator with data about the stored records */
2893 dumper->active = true;
2895 raw_spin_lock_irqsave(&logbuf_lock, flags);
2896 dumper->cur_seq = clear_seq;
2897 dumper->cur_idx = clear_idx;
2898 dumper->next_seq = log_next_seq;
2899 dumper->next_idx = log_next_idx;
2900 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2902 /* invoke dumper which will iterate over records */
2903 dumper->dump(dumper, reason);
2905 /* reset iterator */
2906 dumper->active = false;
2912 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2913 * @dumper: registered kmsg dumper
2914 * @syslog: include the "<4>" prefixes
2915 * @line: buffer to copy the line to
2916 * @size: maximum size of the buffer
2917 * @len: length of line placed into buffer
2919 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2920 * record, and copy one record into the provided buffer.
2922 * Consecutive calls will return the next available record moving
2923 * towards the end of the buffer with the youngest messages.
2925 * A return value of FALSE indicates that there are no more records to
2928 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2930 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2931 char *line, size_t size, size_t *len)
2933 struct printk_log *msg;
2937 if (!dumper->active)
2940 if (dumper->cur_seq < log_first_seq) {
2941 /* messages are gone, move to first available one */
2942 dumper->cur_seq = log_first_seq;
2943 dumper->cur_idx = log_first_idx;
2947 if (dumper->cur_seq >= log_next_seq)
2950 msg = log_from_idx(dumper->cur_idx);
2951 l = msg_print_text(msg, 0, syslog, line, size);
2953 dumper->cur_idx = log_next(dumper->cur_idx);
2963 * kmsg_dump_get_line - retrieve one kmsg log line
2964 * @dumper: registered kmsg dumper
2965 * @syslog: include the "<4>" prefixes
2966 * @line: buffer to copy the line to
2967 * @size: maximum size of the buffer
2968 * @len: length of line placed into buffer
2970 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2971 * record, and copy one record into the provided buffer.
2973 * Consecutive calls will return the next available record moving
2974 * towards the end of the buffer with the youngest messages.
2976 * A return value of FALSE indicates that there are no more records to
2979 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2980 char *line, size_t size, size_t *len)
2982 unsigned long flags;
2985 raw_spin_lock_irqsave(&logbuf_lock, flags);
2986 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2987 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2991 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2994 * kmsg_dump_get_buffer - copy kmsg log lines
2995 * @dumper: registered kmsg dumper
2996 * @syslog: include the "<4>" prefixes
2997 * @buf: buffer to copy the line to
2998 * @size: maximum size of the buffer
2999 * @len: length of line placed into buffer
3001 * Start at the end of the kmsg buffer and fill the provided buffer
3002 * with as many of the the *youngest* kmsg records that fit into it.
3003 * If the buffer is large enough, all available kmsg records will be
3004 * copied with a single call.
3006 * Consecutive calls will fill the buffer with the next block of
3007 * available older records, not including the earlier retrieved ones.
3009 * A return value of FALSE indicates that there are no more records to
3012 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
3013 char *buf, size_t size, size_t *len)
3015 unsigned long flags;
3020 enum log_flags prev;
3024 if (!dumper->active)
3027 raw_spin_lock_irqsave(&logbuf_lock, flags);
3028 if (dumper->cur_seq < log_first_seq) {
3029 /* messages are gone, move to first available one */
3030 dumper->cur_seq = log_first_seq;
3031 dumper->cur_idx = log_first_idx;
3035 if (dumper->cur_seq >= dumper->next_seq) {
3036 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3040 /* calculate length of entire buffer */
3041 seq = dumper->cur_seq;
3042 idx = dumper->cur_idx;
3044 while (seq < dumper->next_seq) {
3045 struct printk_log *msg = log_from_idx(idx);
3047 l += msg_print_text(msg, prev, true, NULL, 0);
3048 idx = log_next(idx);
3053 /* move first record forward until length fits into the buffer */
3054 seq = dumper->cur_seq;
3055 idx = dumper->cur_idx;
3057 while (l > size && seq < dumper->next_seq) {
3058 struct printk_log *msg = log_from_idx(idx);
3060 l -= msg_print_text(msg, prev, true, NULL, 0);
3061 idx = log_next(idx);
3066 /* last message in next interation */
3071 while (seq < dumper->next_seq) {
3072 struct printk_log *msg = log_from_idx(idx);
3074 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
3075 idx = log_next(idx);
3080 dumper->next_seq = next_seq;
3081 dumper->next_idx = next_idx;
3083 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3089 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3092 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3093 * @dumper: registered kmsg dumper
3095 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3096 * kmsg_dump_get_buffer() can be called again and used multiple
3097 * times within the same dumper.dump() callback.
3099 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3101 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3103 dumper->cur_seq = clear_seq;
3104 dumper->cur_idx = clear_idx;
3105 dumper->next_seq = log_next_seq;
3106 dumper->next_idx = log_next_idx;
3110 * kmsg_dump_rewind - reset the interator
3111 * @dumper: registered kmsg dumper
3113 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3114 * kmsg_dump_get_buffer() can be called again and used multiple
3115 * times within the same dumper.dump() callback.
3117 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3119 unsigned long flags;
3121 raw_spin_lock_irqsave(&logbuf_lock, flags);
3122 kmsg_dump_rewind_nolock(dumper);
3123 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3125 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3127 static char dump_stack_arch_desc_str[128];
3130 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3131 * @fmt: printf-style format string
3132 * @...: arguments for the format string
3134 * The configured string will be printed right after utsname during task
3135 * dumps. Usually used to add arch-specific system identifiers. If an
3136 * arch wants to make use of such an ID string, it should initialize this
3137 * as soon as possible during boot.
3139 void __init dump_stack_set_arch_desc(const char *fmt, ...)
3143 va_start(args, fmt);
3144 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3150 * dump_stack_print_info - print generic debug info for dump_stack()
3151 * @log_lvl: log level
3153 * Arch-specific dump_stack() implementations can use this function to
3154 * print out the same debug information as the generic dump_stack().
3156 void dump_stack_print_info(const char *log_lvl)
3158 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3159 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3160 print_tainted(), init_utsname()->release,
3161 (int)strcspn(init_utsname()->version, " "),
3162 init_utsname()->version);
3164 if (dump_stack_arch_desc_str[0] != '\0')
3165 printk("%sHardware name: %s\n",
3166 log_lvl, dump_stack_arch_desc_str);
3168 print_worker_info(log_lvl, current);
3172 * show_regs_print_info - print generic debug info for show_regs()
3173 * @log_lvl: log level
3175 * show_regs() implementations can use this function to print out generic
3176 * debug information.
3178 void show_regs_print_info(const char *log_lvl)
3180 dump_stack_print_info(log_lvl);
3182 printk("%stask: %p ti: %p task.ti: %p\n",
3183 log_lvl, current, current_thread_info(),
3184 task_thread_info(current));