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 #ifdef CONFIG_EARLY_PRINTK_DIRECT
59 extern void printascii(char *);
62 int console_printk[4] = {
63 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
64 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
65 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
66 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
70 * Low level drivers may need that to know if they can schedule in
71 * their unblank() callback or not. So let's export it.
74 EXPORT_SYMBOL(oops_in_progress);
77 * console_sem protects the console_drivers list, and also
78 * provides serialisation for access to the entire console
81 static DEFINE_SEMAPHORE(console_sem);
82 struct console *console_drivers;
83 EXPORT_SYMBOL_GPL(console_drivers);
86 static struct lockdep_map console_lock_dep_map = {
87 .name = "console_lock"
92 * Number of registered extended console drivers.
94 * If extended consoles are present, in-kernel cont reassembly is disabled
95 * and each fragment is stored as a separate log entry with proper
96 * continuation flag so that every emitted message has full metadata. This
97 * doesn't change the result for regular consoles or /proc/kmsg. For
98 * /dev/kmsg, as long as the reader concatenates messages according to
99 * consecutive continuation flags, the end result should be the same too.
101 static int nr_ext_console_drivers;
104 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
105 * macros instead of functions so that _RET_IP_ contains useful information.
107 #define down_console_sem() do { \
109 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
112 static int __down_trylock_console_sem(unsigned long ip)
114 if (down_trylock(&console_sem))
116 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
119 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
121 #define up_console_sem() do { \
122 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
127 * This is used for debugging the mess that is the VT code by
128 * keeping track if we have the console semaphore held. It's
129 * definitely not the perfect debug tool (we don't know if _WE_
130 * hold it and are racing, but it helps tracking those weird code
131 * paths in the console code where we end up in places I want
132 * locked without the console sempahore held).
134 static int console_locked, console_suspended;
137 * If exclusive_console is non-NULL then only this console is to be printed to.
139 static struct console *exclusive_console;
142 * Array of consoles built from command line options (console=)
145 #define MAX_CMDLINECONSOLES 8
147 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
149 static int selected_console = -1;
150 static int preferred_console = -1;
151 int console_set_on_cmdline;
152 EXPORT_SYMBOL(console_set_on_cmdline);
154 /* Flag: console code may call schedule() */
155 static int console_may_schedule;
158 * The printk log buffer consists of a chain of concatenated variable
159 * length records. Every record starts with a record header, containing
160 * the overall length of the record.
162 * The heads to the first and last entry in the buffer, as well as the
163 * sequence numbers of these entries are maintained when messages are
166 * If the heads indicate available messages, the length in the header
167 * tells the start next message. A length == 0 for the next message
168 * indicates a wrap-around to the beginning of the buffer.
170 * Every record carries the monotonic timestamp in microseconds, as well as
171 * the standard userspace syslog level and syslog facility. The usual
172 * kernel messages use LOG_KERN; userspace-injected messages always carry
173 * a matching syslog facility, by default LOG_USER. The origin of every
174 * message can be reliably determined that way.
176 * The human readable log message directly follows the message header. The
177 * length of the message text is stored in the header, the stored message
180 * Optionally, a message can carry a dictionary of properties (key/value pairs),
181 * to provide userspace with a machine-readable message context.
183 * Examples for well-defined, commonly used property names are:
184 * DEVICE=b12:8 device identifier
188 * +sound:card0 subsystem:devname
189 * SUBSYSTEM=pci driver-core subsystem name
191 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
192 * follows directly after a '=' character. Every property is terminated by
193 * a '\0' character. The last property is not terminated.
195 * Example of a message structure:
196 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
197 * 0008 34 00 record is 52 bytes long
198 * 000a 0b 00 text is 11 bytes long
199 * 000c 1f 00 dictionary is 23 bytes long
200 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
201 * 0010 69 74 27 73 20 61 20 6c "it's a l"
203 * 001b 44 45 56 49 43 "DEVIC"
204 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
205 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
207 * 0032 00 00 00 padding to next message header
209 * The 'struct printk_log' buffer header must never be directly exported to
210 * userspace, it is a kernel-private implementation detail that might
211 * need to be changed in the future, when the requirements change.
213 * /dev/kmsg exports the structured data in the following line format:
214 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
216 * Users of the export format should ignore possible additional values
217 * separated by ',', and find the message after the ';' character.
219 * The optional key/value pairs are attached as continuation lines starting
220 * with a space character and terminated by a newline. All possible
221 * non-prinatable characters are escaped in the "\xff" notation.
225 LOG_NOCONS = 1, /* already flushed, do not print to console */
226 LOG_NEWLINE = 2, /* text ended with a newline */
227 LOG_PREFIX = 4, /* text started with a prefix */
228 LOG_CONT = 8, /* text is a fragment of a continuation line */
232 u64 ts_nsec; /* timestamp in nanoseconds */
233 u16 len; /* length of entire record */
234 u16 text_len; /* length of text buffer */
235 u16 dict_len; /* length of dictionary buffer */
236 u8 facility; /* syslog facility */
237 u8 flags:5; /* internal record flags */
238 u8 level:3; /* syslog level */
240 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
241 __packed __aligned(4)
246 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
247 * within the scheduler's rq lock. It must be released before calling
248 * console_unlock() or anything else that might wake up a process.
250 static DEFINE_RAW_SPINLOCK(logbuf_lock);
253 DECLARE_WAIT_QUEUE_HEAD(log_wait);
254 /* the next printk record to read by syslog(READ) or /proc/kmsg */
255 static u64 syslog_seq;
256 static u32 syslog_idx;
257 static enum log_flags syslog_prev;
258 static size_t syslog_partial;
260 /* index and sequence number of the first record stored in the buffer */
261 static u64 log_first_seq;
262 static u32 log_first_idx;
264 /* index and sequence number of the next record to store in the buffer */
265 static u64 log_next_seq;
266 static u32 log_next_idx;
268 /* the next printk record to write to the console */
269 static u64 console_seq;
270 static u32 console_idx;
271 static enum log_flags console_prev;
273 /* the next printk record to read after the last 'clear' command */
274 static u64 clear_seq;
275 static u32 clear_idx;
277 #define PREFIX_MAX 32
278 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
280 #define LOG_LEVEL(v) ((v) & 0x07)
281 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
284 #define LOG_ALIGN __alignof__(struct printk_log)
285 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
286 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
287 static char *log_buf = __log_buf;
288 static u32 log_buf_len = __LOG_BUF_LEN;
290 /* Return log buffer address */
291 char *log_buf_addr_get(void)
296 /* Return log buffer size */
297 u32 log_buf_len_get(void)
302 /* human readable text of the record */
303 static char *log_text(const struct printk_log *msg)
305 return (char *)msg + sizeof(struct printk_log);
308 /* optional key/value pair dictionary attached to the record */
309 static char *log_dict(const struct printk_log *msg)
311 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
314 /* get record by index; idx must point to valid msg */
315 static struct printk_log *log_from_idx(u32 idx)
317 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
320 * A length == 0 record is the end of buffer marker. Wrap around and
321 * read the message at the start of the buffer.
324 return (struct printk_log *)log_buf;
328 /* get next record; idx must point to valid msg */
329 static u32 log_next(u32 idx)
331 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
333 /* length == 0 indicates the end of the buffer; wrap */
335 * A length == 0 record is the end of buffer marker. Wrap around and
336 * read the message at the start of the buffer as *this* one, and
337 * return the one after that.
340 msg = (struct printk_log *)log_buf;
343 return idx + msg->len;
347 * Check whether there is enough free space for the given message.
349 * The same values of first_idx and next_idx mean that the buffer
350 * is either empty or full.
352 * If the buffer is empty, we must respect the position of the indexes.
353 * They cannot be reset to the beginning of the buffer.
355 static int logbuf_has_space(u32 msg_size, bool empty)
359 if (log_next_idx > log_first_idx || empty)
360 free = max(log_buf_len - log_next_idx, log_first_idx);
362 free = log_first_idx - log_next_idx;
365 * We need space also for an empty header that signalizes wrapping
368 return free >= msg_size + sizeof(struct printk_log);
371 static int log_make_free_space(u32 msg_size)
373 while (log_first_seq < log_next_seq) {
374 if (logbuf_has_space(msg_size, false))
376 /* drop old messages until we have enough contiguous space */
377 log_first_idx = log_next(log_first_idx);
381 /* sequence numbers are equal, so the log buffer is empty */
382 if (logbuf_has_space(msg_size, true))
388 /* compute the message size including the padding bytes */
389 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
393 size = sizeof(struct printk_log) + text_len + dict_len;
394 *pad_len = (-size) & (LOG_ALIGN - 1);
401 * Define how much of the log buffer we could take at maximum. The value
402 * must be greater than two. Note that only half of the buffer is available
403 * when the index points to the middle.
405 #define MAX_LOG_TAKE_PART 4
406 static const char trunc_msg[] = "<truncated>";
408 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
409 u16 *dict_len, u32 *pad_len)
412 * The message should not take the whole buffer. Otherwise, it might
413 * get removed too soon.
415 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
416 if (*text_len > max_text_len)
417 *text_len = max_text_len;
418 /* enable the warning message */
419 *trunc_msg_len = strlen(trunc_msg);
420 /* disable the "dict" completely */
422 /* compute the size again, count also the warning message */
423 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
426 /* insert record into the buffer, discard old ones, update heads */
427 static int log_store(int facility, int level,
428 enum log_flags flags, u64 ts_nsec,
429 const char *dict, u16 dict_len,
430 const char *text, u16 text_len)
432 struct printk_log *msg;
434 u16 trunc_msg_len = 0;
436 /* number of '\0' padding bytes to next message */
437 size = msg_used_size(text_len, dict_len, &pad_len);
439 if (log_make_free_space(size)) {
440 /* truncate the message if it is too long for empty buffer */
441 size = truncate_msg(&text_len, &trunc_msg_len,
442 &dict_len, &pad_len);
443 /* survive when the log buffer is too small for trunc_msg */
444 if (log_make_free_space(size))
448 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
450 * This message + an additional empty header does not fit
451 * at the end of the buffer. Add an empty header with len == 0
452 * to signify a wrap around.
454 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
459 msg = (struct printk_log *)(log_buf + log_next_idx);
460 memcpy(log_text(msg), text, text_len);
461 msg->text_len = text_len;
463 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
464 msg->text_len += trunc_msg_len;
466 memcpy(log_dict(msg), dict, dict_len);
467 msg->dict_len = dict_len;
468 msg->facility = facility;
469 msg->level = level & 7;
470 msg->flags = flags & 0x1f;
472 msg->ts_nsec = ts_nsec;
474 msg->ts_nsec = local_clock();
475 memset(log_dict(msg) + dict_len, 0, pad_len);
479 log_next_idx += msg->len;
482 return msg->text_len;
485 int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
487 static int syslog_action_restricted(int type)
492 * Unless restricted, we allow "read all" and "get buffer size"
495 return type != SYSLOG_ACTION_READ_ALL &&
496 type != SYSLOG_ACTION_SIZE_BUFFER;
499 int check_syslog_permissions(int type, int source)
502 * If this is from /proc/kmsg and we've already opened it, then we've
503 * already done the capabilities checks at open time.
505 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
508 if (syslog_action_restricted(type)) {
509 if (capable(CAP_SYSLOG))
512 * For historical reasons, accept CAP_SYS_ADMIN too, with
515 if (capable(CAP_SYS_ADMIN)) {
516 pr_warn_once("%s (%d): Attempt to access syslog with "
517 "CAP_SYS_ADMIN but no CAP_SYSLOG "
519 current->comm, task_pid_nr(current));
525 return security_syslog(type);
527 EXPORT_SYMBOL_GPL(check_syslog_permissions);
529 static void append_char(char **pp, char *e, char c)
535 static ssize_t msg_print_ext_header(char *buf, size_t size,
536 struct printk_log *msg, u64 seq,
537 enum log_flags prev_flags)
539 u64 ts_usec = msg->ts_nsec;
542 do_div(ts_usec, 1000);
545 * If we couldn't merge continuation line fragments during the print,
546 * export the stored flags to allow an optional external merge of the
547 * records. Merging the records isn't always neccessarily correct, like
548 * when we hit a race during printing. In most cases though, it produces
549 * better readable output. 'c' in the record flags mark the first
550 * fragment of a line, '+' the following.
552 if (msg->flags & LOG_CONT && !(prev_flags & LOG_CONT))
554 else if ((msg->flags & LOG_CONT) ||
555 ((prev_flags & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
558 return scnprintf(buf, size, "%u,%llu,%llu,%c;",
559 (msg->facility << 3) | msg->level, seq, ts_usec, cont);
562 static ssize_t msg_print_ext_body(char *buf, size_t size,
563 char *dict, size_t dict_len,
564 char *text, size_t text_len)
566 char *p = buf, *e = buf + size;
569 /* escape non-printable characters */
570 for (i = 0; i < text_len; i++) {
571 unsigned char c = text[i];
573 if (c < ' ' || c >= 127 || c == '\\')
574 p += scnprintf(p, e - p, "\\x%02x", c);
576 append_char(&p, e, c);
578 append_char(&p, e, '\n');
583 for (i = 0; i < dict_len; i++) {
584 unsigned char c = dict[i];
587 append_char(&p, e, ' ');
592 append_char(&p, e, '\n');
597 if (c < ' ' || c >= 127 || c == '\\') {
598 p += scnprintf(p, e - p, "\\x%02x", c);
602 append_char(&p, e, c);
604 append_char(&p, e, '\n');
610 /* /dev/kmsg - userspace message inject/listen interface */
611 struct devkmsg_user {
616 char buf[CONSOLE_EXT_LOG_MAX];
619 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
622 int level = default_message_loglevel;
623 int facility = 1; /* LOG_USER */
624 size_t len = iov_iter_count(from);
627 if (len > LOG_LINE_MAX)
629 buf = kmalloc(len+1, GFP_KERNEL);
634 if (copy_from_iter(buf, len, from) != len) {
640 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
641 * the decimal value represents 32bit, the lower 3 bit are the log
642 * level, the rest are the log facility.
644 * If no prefix or no userspace facility is specified, we
645 * enforce LOG_USER, to be able to reliably distinguish
646 * kernel-generated messages from userspace-injected ones.
649 if (line[0] == '<') {
653 u = simple_strtoul(line + 1, &endp, 10);
654 if (endp && endp[0] == '>') {
655 level = LOG_LEVEL(u);
656 if (LOG_FACILITY(u) != 0)
657 facility = LOG_FACILITY(u);
664 printk_emit(facility, level, NULL, 0, "%s", line);
669 static ssize_t devkmsg_read(struct file *file, char __user *buf,
670 size_t count, loff_t *ppos)
672 struct devkmsg_user *user = file->private_data;
673 struct printk_log *msg;
680 ret = mutex_lock_interruptible(&user->lock);
683 raw_spin_lock_irq(&logbuf_lock);
684 while (user->seq == log_next_seq) {
685 if (file->f_flags & O_NONBLOCK) {
687 raw_spin_unlock_irq(&logbuf_lock);
691 raw_spin_unlock_irq(&logbuf_lock);
692 ret = wait_event_interruptible(log_wait,
693 user->seq != log_next_seq);
696 raw_spin_lock_irq(&logbuf_lock);
699 if (user->seq < log_first_seq) {
700 /* our last seen message is gone, return error and reset */
701 user->idx = log_first_idx;
702 user->seq = log_first_seq;
704 raw_spin_unlock_irq(&logbuf_lock);
708 msg = log_from_idx(user->idx);
709 len = msg_print_ext_header(user->buf, sizeof(user->buf),
710 msg, user->seq, user->prev);
711 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
712 log_dict(msg), msg->dict_len,
713 log_text(msg), msg->text_len);
715 user->prev = msg->flags;
716 user->idx = log_next(user->idx);
718 raw_spin_unlock_irq(&logbuf_lock);
725 if (copy_to_user(buf, user->buf, len)) {
731 mutex_unlock(&user->lock);
735 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
737 struct devkmsg_user *user = file->private_data;
745 raw_spin_lock_irq(&logbuf_lock);
748 /* the first record */
749 user->idx = log_first_idx;
750 user->seq = log_first_seq;
754 * The first record after the last SYSLOG_ACTION_CLEAR,
755 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
756 * changes no global state, and does not clear anything.
758 user->idx = clear_idx;
759 user->seq = clear_seq;
762 /* after the last record */
763 user->idx = log_next_idx;
764 user->seq = log_next_seq;
769 raw_spin_unlock_irq(&logbuf_lock);
773 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
775 struct devkmsg_user *user = file->private_data;
779 return POLLERR|POLLNVAL;
781 poll_wait(file, &log_wait, wait);
783 raw_spin_lock_irq(&logbuf_lock);
784 if (user->seq < log_next_seq) {
785 /* return error when data has vanished underneath us */
786 if (user->seq < log_first_seq)
787 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
789 ret = POLLIN|POLLRDNORM;
791 raw_spin_unlock_irq(&logbuf_lock);
796 static int devkmsg_open(struct inode *inode, struct file *file)
798 struct devkmsg_user *user;
801 /* write-only does not need any file context */
802 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
805 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
810 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
814 mutex_init(&user->lock);
816 raw_spin_lock_irq(&logbuf_lock);
817 user->idx = log_first_idx;
818 user->seq = log_first_seq;
819 raw_spin_unlock_irq(&logbuf_lock);
821 file->private_data = user;
825 static int devkmsg_release(struct inode *inode, struct file *file)
827 struct devkmsg_user *user = file->private_data;
832 mutex_destroy(&user->lock);
837 const struct file_operations kmsg_fops = {
838 .open = devkmsg_open,
839 .read = devkmsg_read,
840 .write_iter = devkmsg_write,
841 .llseek = devkmsg_llseek,
842 .poll = devkmsg_poll,
843 .release = devkmsg_release,
846 #ifdef CONFIG_KEXEC_CORE
848 * This appends the listed symbols to /proc/vmcore
850 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
851 * obtain access to symbols that are otherwise very difficult to locate. These
852 * symbols are specifically used so that utilities can access and extract the
853 * dmesg log from a vmcore file after a crash.
855 void log_buf_kexec_setup(void)
857 VMCOREINFO_SYMBOL(log_buf);
858 VMCOREINFO_SYMBOL(log_buf_len);
859 VMCOREINFO_SYMBOL(log_first_idx);
860 VMCOREINFO_SYMBOL(log_next_idx);
862 * Export struct printk_log size and field offsets. User space tools can
863 * parse it and detect any changes to structure down the line.
865 VMCOREINFO_STRUCT_SIZE(printk_log);
866 VMCOREINFO_OFFSET(printk_log, ts_nsec);
867 VMCOREINFO_OFFSET(printk_log, len);
868 VMCOREINFO_OFFSET(printk_log, text_len);
869 VMCOREINFO_OFFSET(printk_log, dict_len);
873 /* requested log_buf_len from kernel cmdline */
874 static unsigned long __initdata new_log_buf_len;
876 /* we practice scaling the ring buffer by powers of 2 */
877 static void __init log_buf_len_update(unsigned size)
880 size = roundup_pow_of_two(size);
881 if (size > log_buf_len)
882 new_log_buf_len = size;
885 /* save requested log_buf_len since it's too early to process it */
886 static int __init log_buf_len_setup(char *str)
893 size = memparse(str, &str);
895 log_buf_len_update(size);
899 early_param("log_buf_len", log_buf_len_setup);
902 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
904 static void __init log_buf_add_cpu(void)
906 unsigned int cpu_extra;
909 * archs should set up cpu_possible_bits properly with
910 * set_cpu_possible() after setup_arch() but just in
911 * case lets ensure this is valid.
913 if (num_possible_cpus() == 1)
916 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
918 /* by default this will only continue through for large > 64 CPUs */
919 if (cpu_extra <= __LOG_BUF_LEN / 2)
922 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
923 __LOG_CPU_MAX_BUF_LEN);
924 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
926 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
928 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
930 #else /* !CONFIG_SMP */
931 static inline void log_buf_add_cpu(void) {}
932 #endif /* CONFIG_SMP */
934 void __init setup_log_buf(int early)
940 if (log_buf != __log_buf)
943 if (!early && !new_log_buf_len)
946 if (!new_log_buf_len)
951 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
953 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
957 if (unlikely(!new_log_buf)) {
958 pr_err("log_buf_len: %ld bytes not available\n",
963 raw_spin_lock_irqsave(&logbuf_lock, flags);
964 log_buf_len = new_log_buf_len;
965 log_buf = new_log_buf;
967 free = __LOG_BUF_LEN - log_next_idx;
968 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
969 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
971 pr_info("log_buf_len: %d bytes\n", log_buf_len);
972 pr_info("early log buf free: %d(%d%%)\n",
973 free, (free * 100) / __LOG_BUF_LEN);
976 static bool __read_mostly ignore_loglevel;
978 static int __init ignore_loglevel_setup(char *str)
980 ignore_loglevel = true;
981 pr_info("debug: ignoring loglevel setting.\n");
986 early_param("ignore_loglevel", ignore_loglevel_setup);
987 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
988 MODULE_PARM_DESC(ignore_loglevel,
989 "ignore loglevel setting (prints all kernel messages to the console)");
991 #ifdef CONFIG_BOOT_PRINTK_DELAY
993 static int boot_delay; /* msecs delay after each printk during bootup */
994 static unsigned long long loops_per_msec; /* based on boot_delay */
996 static int __init boot_delay_setup(char *str)
1000 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
1001 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
1003 get_option(&str, &boot_delay);
1004 if (boot_delay > 10 * 1000)
1007 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1008 "HZ: %d, loops_per_msec: %llu\n",
1009 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1012 early_param("boot_delay", boot_delay_setup);
1014 static void boot_delay_msec(int level)
1016 unsigned long long k;
1017 unsigned long timeout;
1019 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
1020 || (level >= console_loglevel && !ignore_loglevel)) {
1024 k = (unsigned long long)loops_per_msec * boot_delay;
1026 timeout = jiffies + msecs_to_jiffies(boot_delay);
1031 * use (volatile) jiffies to prevent
1032 * compiler reduction; loop termination via jiffies
1033 * is secondary and may or may not happen.
1035 if (time_after(jiffies, timeout))
1037 touch_nmi_watchdog();
1041 static inline void boot_delay_msec(int level)
1046 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1047 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1049 static size_t print_time(u64 ts, char *buf)
1051 unsigned long rem_nsec;
1056 rem_nsec = do_div(ts, 1000000000);
1059 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1061 return sprintf(buf, "[%5lu.%06lu] ",
1062 (unsigned long)ts, rem_nsec / 1000);
1065 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1068 unsigned int prefix = (msg->facility << 3) | msg->level;
1072 len += sprintf(buf, "<%u>", prefix);
1077 else if (prefix > 99)
1079 else if (prefix > 9)
1084 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1088 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1089 bool syslog, char *buf, size_t size)
1091 const char *text = log_text(msg);
1092 size_t text_size = msg->text_len;
1094 bool newline = true;
1097 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1100 if (msg->flags & LOG_CONT) {
1101 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1104 if (!(msg->flags & LOG_NEWLINE))
1109 const char *next = memchr(text, '\n', text_size);
1113 text_len = next - text;
1115 text_size -= next - text;
1117 text_len = text_size;
1121 if (print_prefix(msg, syslog, NULL) +
1122 text_len + 1 >= size - len)
1126 len += print_prefix(msg, syslog, buf + len);
1127 memcpy(buf + len, text, text_len);
1129 if (next || newline)
1132 /* SYSLOG_ACTION_* buffer size only calculation */
1134 len += print_prefix(msg, syslog, NULL);
1136 if (next || newline)
1147 static int syslog_print(char __user *buf, int size)
1150 struct printk_log *msg;
1153 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1161 raw_spin_lock_irq(&logbuf_lock);
1162 if (syslog_seq < log_first_seq) {
1163 /* messages are gone, move to first one */
1164 syslog_seq = log_first_seq;
1165 syslog_idx = log_first_idx;
1169 if (syslog_seq == log_next_seq) {
1170 raw_spin_unlock_irq(&logbuf_lock);
1174 skip = syslog_partial;
1175 msg = log_from_idx(syslog_idx);
1176 n = msg_print_text(msg, syslog_prev, true, text,
1177 LOG_LINE_MAX + PREFIX_MAX);
1178 if (n - syslog_partial <= size) {
1179 /* message fits into buffer, move forward */
1180 syslog_idx = log_next(syslog_idx);
1182 syslog_prev = msg->flags;
1183 n -= syslog_partial;
1186 /* partial read(), remember position */
1188 syslog_partial += n;
1191 raw_spin_unlock_irq(&logbuf_lock);
1196 if (copy_to_user(buf, text + skip, n)) {
1211 static int syslog_print_all(char __user *buf, int size, bool clear)
1216 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1220 raw_spin_lock_irq(&logbuf_lock);
1225 enum log_flags prev;
1227 if (clear_seq < log_first_seq) {
1228 /* messages are gone, move to first available one */
1229 clear_seq = log_first_seq;
1230 clear_idx = log_first_idx;
1234 * Find first record that fits, including all following records,
1235 * into the user-provided buffer for this dump.
1240 while (seq < log_next_seq) {
1241 struct printk_log *msg = log_from_idx(idx);
1243 len += msg_print_text(msg, prev, true, NULL, 0);
1245 idx = log_next(idx);
1249 /* move first record forward until length fits into the buffer */
1253 while (len > size && seq < log_next_seq) {
1254 struct printk_log *msg = log_from_idx(idx);
1256 len -= msg_print_text(msg, prev, true, NULL, 0);
1258 idx = log_next(idx);
1262 /* last message fitting into this dump */
1263 next_seq = log_next_seq;
1266 while (len >= 0 && seq < next_seq) {
1267 struct printk_log *msg = log_from_idx(idx);
1270 textlen = msg_print_text(msg, prev, true, text,
1271 LOG_LINE_MAX + PREFIX_MAX);
1276 idx = log_next(idx);
1280 raw_spin_unlock_irq(&logbuf_lock);
1281 if (copy_to_user(buf + len, text, textlen))
1285 raw_spin_lock_irq(&logbuf_lock);
1287 if (seq < log_first_seq) {
1288 /* messages are gone, move to next one */
1289 seq = log_first_seq;
1290 idx = log_first_idx;
1297 clear_seq = log_next_seq;
1298 clear_idx = log_next_idx;
1300 raw_spin_unlock_irq(&logbuf_lock);
1306 int do_syslog(int type, char __user *buf, int len, int source)
1309 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1312 error = check_syslog_permissions(type, source);
1317 case SYSLOG_ACTION_CLOSE: /* Close log */
1319 case SYSLOG_ACTION_OPEN: /* Open log */
1321 case SYSLOG_ACTION_READ: /* Read from log */
1323 if (!buf || len < 0)
1328 if (!access_ok(VERIFY_WRITE, buf, len)) {
1332 error = wait_event_interruptible(log_wait,
1333 syslog_seq != log_next_seq);
1336 error = syslog_print(buf, len);
1338 /* Read/clear last kernel messages */
1339 case SYSLOG_ACTION_READ_CLEAR:
1342 /* Read last kernel messages */
1343 case SYSLOG_ACTION_READ_ALL:
1345 if (!buf || len < 0)
1350 if (!access_ok(VERIFY_WRITE, buf, len)) {
1354 error = syslog_print_all(buf, len, clear);
1356 /* Clear ring buffer */
1357 case SYSLOG_ACTION_CLEAR:
1358 syslog_print_all(NULL, 0, true);
1360 /* Disable logging to console */
1361 case SYSLOG_ACTION_CONSOLE_OFF:
1362 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1363 saved_console_loglevel = console_loglevel;
1364 console_loglevel = minimum_console_loglevel;
1366 /* Enable logging to console */
1367 case SYSLOG_ACTION_CONSOLE_ON:
1368 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1369 console_loglevel = saved_console_loglevel;
1370 saved_console_loglevel = LOGLEVEL_DEFAULT;
1373 /* Set level of messages printed to console */
1374 case SYSLOG_ACTION_CONSOLE_LEVEL:
1376 if (len < 1 || len > 8)
1378 if (len < minimum_console_loglevel)
1379 len = minimum_console_loglevel;
1380 console_loglevel = len;
1381 /* Implicitly re-enable logging to console */
1382 saved_console_loglevel = LOGLEVEL_DEFAULT;
1385 /* Number of chars in the log buffer */
1386 case SYSLOG_ACTION_SIZE_UNREAD:
1387 raw_spin_lock_irq(&logbuf_lock);
1388 if (syslog_seq < log_first_seq) {
1389 /* messages are gone, move to first one */
1390 syslog_seq = log_first_seq;
1391 syslog_idx = log_first_idx;
1395 if (source == SYSLOG_FROM_PROC) {
1397 * Short-cut for poll(/"proc/kmsg") which simply checks
1398 * for pending data, not the size; return the count of
1399 * records, not the length.
1401 error = log_next_seq - syslog_seq;
1403 u64 seq = syslog_seq;
1404 u32 idx = syslog_idx;
1405 enum log_flags prev = syslog_prev;
1408 while (seq < log_next_seq) {
1409 struct printk_log *msg = log_from_idx(idx);
1411 error += msg_print_text(msg, prev, true, NULL, 0);
1412 idx = log_next(idx);
1416 error -= syslog_partial;
1418 raw_spin_unlock_irq(&logbuf_lock);
1420 /* Size of the log buffer */
1421 case SYSLOG_ACTION_SIZE_BUFFER:
1422 error = log_buf_len;
1432 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1434 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1438 * Call the console drivers, asking them to write out
1439 * log_buf[start] to log_buf[end - 1].
1440 * The console_lock must be held.
1442 static void call_console_drivers(int level,
1443 const char *ext_text, size_t ext_len,
1444 const char *text, size_t len)
1446 struct console *con;
1448 trace_console_rcuidle(text, len);
1450 if (level >= console_loglevel && !ignore_loglevel)
1452 if (!console_drivers)
1455 for_each_console(con) {
1456 if (exclusive_console && con != exclusive_console)
1458 if (!(con->flags & CON_ENABLED))
1462 if (!cpu_online(smp_processor_id()) &&
1463 !(con->flags & CON_ANYTIME))
1465 if (con->flags & CON_EXTENDED)
1466 con->write(con, ext_text, ext_len);
1468 con->write(con, text, len);
1473 * Zap console related locks when oopsing.
1474 * To leave time for slow consoles to print a full oops,
1475 * only zap at most once every 30 seconds.
1477 static void zap_locks(void)
1479 static unsigned long oops_timestamp;
1481 if (time_after_eq(jiffies, oops_timestamp) &&
1482 !time_after(jiffies, oops_timestamp + 30 * HZ))
1485 oops_timestamp = jiffies;
1488 /* If a crash is occurring, make sure we can't deadlock */
1489 raw_spin_lock_init(&logbuf_lock);
1490 /* And make sure that we print immediately */
1491 sema_init(&console_sem, 1);
1495 * Check if we have any console that is capable of printing while cpu is
1496 * booting or shutting down. Requires console_sem.
1498 static int have_callable_console(void)
1500 struct console *con;
1502 for_each_console(con)
1503 if (con->flags & CON_ANYTIME)
1510 * Can we actually use the console at this time on this cpu?
1512 * Console drivers may assume that per-cpu resources have been allocated. So
1513 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1514 * call them until this CPU is officially up.
1516 static inline int can_use_console(unsigned int cpu)
1518 return cpu_online(cpu) || have_callable_console();
1522 * Try to get console ownership to actually show the kernel
1523 * messages from a 'printk'. Return true (and with the
1524 * console_lock held, and 'console_locked' set) if it
1525 * is successful, false otherwise.
1527 static int console_trylock_for_printk(void)
1529 unsigned int cpu = smp_processor_id();
1531 if (!console_trylock())
1534 * If we can't use the console, we need to release the console
1535 * semaphore by hand to avoid flushing the buffer. We need to hold the
1536 * console semaphore in order to do this test safely.
1538 if (!can_use_console(cpu)) {
1546 int printk_delay_msec __read_mostly;
1548 static inline void printk_delay(void)
1550 if (unlikely(printk_delay_msec)) {
1551 int m = printk_delay_msec;
1555 touch_nmi_watchdog();
1561 * Continuation lines are buffered, and not committed to the record buffer
1562 * until the line is complete, or a race forces it. The line fragments
1563 * though, are printed immediately to the consoles to ensure everything has
1564 * reached the console in case of a kernel crash.
1566 static struct cont {
1567 char buf[LOG_LINE_MAX];
1568 size_t len; /* length == 0 means unused buffer */
1569 size_t cons; /* bytes written to console */
1570 struct task_struct *owner; /* task of first print*/
1571 u64 ts_nsec; /* time of first print */
1572 u8 level; /* log level of first message */
1573 u8 facility; /* log facility of first message */
1574 enum log_flags flags; /* prefix, newline flags */
1575 bool flushed:1; /* buffer sealed and committed */
1578 static void cont_flush(enum log_flags flags)
1587 * If a fragment of this line was directly flushed to the
1588 * console; wait for the console to pick up the rest of the
1589 * line. LOG_NOCONS suppresses a duplicated output.
1591 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1592 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1594 cont.flushed = true;
1597 * If no fragment of this line ever reached the console,
1598 * just submit it to the store and free the buffer.
1600 log_store(cont.facility, cont.level, flags, 0,
1601 NULL, 0, cont.buf, cont.len);
1606 static bool cont_add(int facility, int level, const char *text, size_t len)
1608 if (cont.len && cont.flushed)
1612 * If ext consoles are present, flush and skip in-kernel
1613 * continuation. See nr_ext_console_drivers definition. Also, if
1614 * the line gets too long, split it up in separate records.
1616 if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
1617 cont_flush(LOG_CONT);
1622 cont.facility = facility;
1624 cont.owner = current;
1625 cont.ts_nsec = local_clock();
1628 cont.flushed = false;
1631 memcpy(cont.buf + cont.len, text, len);
1634 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1635 cont_flush(LOG_CONT);
1640 static size_t cont_print_text(char *text, size_t size)
1645 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1646 textlen += print_time(cont.ts_nsec, text);
1650 len = cont.len - cont.cons;
1654 memcpy(text + textlen, cont.buf + cont.cons, len);
1656 cont.cons = cont.len;
1660 if (cont.flags & LOG_NEWLINE)
1661 text[textlen++] = '\n';
1662 /* got everything, release buffer */
1668 asmlinkage int vprintk_emit(int facility, int level,
1669 const char *dict, size_t dictlen,
1670 const char *fmt, va_list args)
1672 static int recursion_bug;
1673 static char textbuf[LOG_LINE_MAX];
1674 char *text = textbuf;
1675 size_t text_len = 0;
1676 enum log_flags lflags = 0;
1677 unsigned long flags;
1679 int printed_len = 0;
1680 bool in_sched = false;
1681 /* cpu currently holding logbuf_lock in this function */
1682 static unsigned int logbuf_cpu = UINT_MAX;
1684 if (level == LOGLEVEL_SCHED) {
1685 level = LOGLEVEL_DEFAULT;
1689 boot_delay_msec(level);
1692 /* This stops the holder of console_sem just where we want him */
1693 local_irq_save(flags);
1694 this_cpu = smp_processor_id();
1697 * Ouch, printk recursed into itself!
1699 if (unlikely(logbuf_cpu == this_cpu)) {
1701 * If a crash is occurring during printk() on this CPU,
1702 * then try to get the crash message out but make sure
1703 * we can't deadlock. Otherwise just return to avoid the
1704 * recursion and return - but flag the recursion so that
1705 * it can be printed at the next appropriate moment:
1707 if (!oops_in_progress && !lockdep_recursing(current)) {
1709 local_irq_restore(flags);
1716 raw_spin_lock(&logbuf_lock);
1717 logbuf_cpu = this_cpu;
1719 if (unlikely(recursion_bug)) {
1720 static const char recursion_msg[] =
1721 "BUG: recent printk recursion!";
1724 /* emit KERN_CRIT message */
1725 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1726 NULL, 0, recursion_msg,
1727 strlen(recursion_msg));
1731 * The printf needs to come first; we need the syslog
1732 * prefix which might be passed-in as a parameter.
1734 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1736 /* mark and strip a trailing newline */
1737 if (text_len && text[text_len-1] == '\n') {
1739 lflags |= LOG_NEWLINE;
1742 /* strip kernel syslog prefix and extract log level or control flags */
1743 if (facility == 0) {
1744 int kern_level = printk_get_level(text);
1747 const char *end_of_header = printk_skip_level(text);
1748 switch (kern_level) {
1750 if (level == LOGLEVEL_DEFAULT)
1751 level = kern_level - '0';
1753 case 'd': /* KERN_DEFAULT */
1754 lflags |= LOG_PREFIX;
1757 * No need to check length here because vscnprintf
1758 * put '\0' at the end of the string. Only valid and
1759 * newly printed level is detected.
1761 text_len -= end_of_header - text;
1762 text = (char *)end_of_header;
1766 #ifdef CONFIG_EARLY_PRINTK_DIRECT
1770 if (level == LOGLEVEL_DEFAULT)
1771 level = default_message_loglevel;
1774 lflags |= LOG_PREFIX|LOG_NEWLINE;
1776 if (!(lflags & LOG_NEWLINE)) {
1778 * Flush the conflicting buffer. An earlier newline was missing,
1779 * or another task also prints continuation lines.
1781 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1782 cont_flush(LOG_NEWLINE);
1784 /* buffer line if possible, otherwise store it right away */
1785 if (cont_add(facility, level, text, text_len))
1786 printed_len += text_len;
1788 printed_len += log_store(facility, level,
1789 lflags | LOG_CONT, 0,
1790 dict, dictlen, text, text_len);
1792 bool stored = false;
1795 * If an earlier newline was missing and it was the same task,
1796 * either merge it with the current buffer and flush, or if
1797 * there was a race with interrupts (prefix == true) then just
1798 * flush it out and store this line separately.
1799 * If the preceding printk was from a different task and missed
1800 * a newline, flush and append the newline.
1803 if (cont.owner == current && !(lflags & LOG_PREFIX))
1804 stored = cont_add(facility, level, text,
1806 cont_flush(LOG_NEWLINE);
1810 printed_len += text_len;
1812 printed_len += log_store(facility, level, lflags, 0,
1813 dict, dictlen, text, text_len);
1816 logbuf_cpu = UINT_MAX;
1817 raw_spin_unlock(&logbuf_lock);
1819 local_irq_restore(flags);
1821 /* If called from the scheduler, we can not call up(). */
1825 * Disable preemption to avoid being preempted while holding
1826 * console_sem which would prevent anyone from printing to
1832 * Try to acquire and then immediately release the console
1833 * semaphore. The release will print out buffers and wake up
1834 * /dev/kmsg and syslog() users.
1836 if (console_trylock_for_printk())
1844 EXPORT_SYMBOL(vprintk_emit);
1846 asmlinkage int vprintk(const char *fmt, va_list args)
1848 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1850 EXPORT_SYMBOL(vprintk);
1852 asmlinkage int printk_emit(int facility, int level,
1853 const char *dict, size_t dictlen,
1854 const char *fmt, ...)
1859 va_start(args, fmt);
1860 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1865 EXPORT_SYMBOL(printk_emit);
1867 int vprintk_default(const char *fmt, va_list args)
1871 #ifdef CONFIG_KGDB_KDB
1872 if (unlikely(kdb_trap_printk)) {
1873 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1877 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1881 EXPORT_SYMBOL_GPL(vprintk_default);
1884 * This allows printk to be diverted to another function per cpu.
1885 * This is useful for calling printk functions from within NMI
1886 * without worrying about race conditions that can lock up the
1889 DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
1892 * printk - print a kernel message
1893 * @fmt: format string
1895 * This is printk(). It can be called from any context. We want it to work.
1897 * We try to grab the console_lock. If we succeed, it's easy - we log the
1898 * output and call the console drivers. If we fail to get the semaphore, we
1899 * place the output into the log buffer and return. The current holder of
1900 * the console_sem will notice the new output in console_unlock(); and will
1901 * send it to the consoles before releasing the lock.
1903 * One effect of this deferred printing is that code which calls printk() and
1904 * then changes console_loglevel may break. This is because console_loglevel
1905 * is inspected when the actual printing occurs.
1910 * See the vsnprintf() documentation for format string extensions over C99.
1912 asmlinkage __visible int printk(const char *fmt, ...)
1914 printk_func_t vprintk_func;
1918 va_start(args, fmt);
1921 * If a caller overrides the per_cpu printk_func, then it needs
1922 * to disable preemption when calling printk(). Otherwise
1923 * the printk_func should be set to the default. No need to
1924 * disable preemption here.
1926 vprintk_func = this_cpu_read(printk_func);
1927 r = vprintk_func(fmt, args);
1933 EXPORT_SYMBOL(printk);
1935 #else /* CONFIG_PRINTK */
1937 #define LOG_LINE_MAX 0
1938 #define PREFIX_MAX 0
1940 static u64 syslog_seq;
1941 static u32 syslog_idx;
1942 static u64 console_seq;
1943 static u32 console_idx;
1944 static enum log_flags syslog_prev;
1945 static u64 log_first_seq;
1946 static u32 log_first_idx;
1947 static u64 log_next_seq;
1948 static enum log_flags console_prev;
1949 static struct cont {
1955 static char *log_text(const struct printk_log *msg) { return NULL; }
1956 static char *log_dict(const struct printk_log *msg) { return NULL; }
1957 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1958 static u32 log_next(u32 idx) { return 0; }
1959 static ssize_t msg_print_ext_header(char *buf, size_t size,
1960 struct printk_log *msg, u64 seq,
1961 enum log_flags prev_flags) { return 0; }
1962 static ssize_t msg_print_ext_body(char *buf, size_t size,
1963 char *dict, size_t dict_len,
1964 char *text, size_t text_len) { return 0; }
1965 static void call_console_drivers(int level,
1966 const char *ext_text, size_t ext_len,
1967 const char *text, size_t len) {}
1968 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1969 bool syslog, char *buf, size_t size) { return 0; }
1970 static size_t cont_print_text(char *text, size_t size) { return 0; }
1972 /* Still needs to be defined for users */
1973 DEFINE_PER_CPU(printk_func_t, printk_func);
1975 #endif /* CONFIG_PRINTK */
1977 #ifdef CONFIG_EARLY_PRINTK
1978 struct console *early_console;
1980 asmlinkage __visible void early_printk(const char *fmt, ...)
1990 n = vscnprintf(buf, sizeof(buf), fmt, ap);
1993 early_console->write(early_console, buf, n);
1997 static int __add_preferred_console(char *name, int idx, char *options,
2000 struct console_cmdline *c;
2004 * See if this tty is not yet registered, and
2005 * if we have a slot free.
2007 for (i = 0, c = console_cmdline;
2008 i < MAX_CMDLINECONSOLES && c->name[0];
2010 if (strcmp(c->name, name) == 0 && c->index == idx) {
2012 selected_console = i;
2016 if (i == MAX_CMDLINECONSOLES)
2019 selected_console = i;
2020 strlcpy(c->name, name, sizeof(c->name));
2021 c->options = options;
2022 braille_set_options(c, brl_options);
2028 * Set up a console. Called via do_early_param() in init/main.c
2029 * for each "console=" parameter in the boot command line.
2031 static int __init console_setup(char *str)
2033 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
2034 char *s, *options, *brl_options = NULL;
2037 if (_braille_console_setup(&str, &brl_options))
2041 * Decode str into name, index, options.
2043 if (str[0] >= '0' && str[0] <= '9') {
2044 strcpy(buf, "ttyS");
2045 strncpy(buf + 4, str, sizeof(buf) - 5);
2047 strncpy(buf, str, sizeof(buf) - 1);
2049 buf[sizeof(buf) - 1] = 0;
2050 options = strchr(str, ',');
2054 if (!strcmp(str, "ttya"))
2055 strcpy(buf, "ttyS0");
2056 if (!strcmp(str, "ttyb"))
2057 strcpy(buf, "ttyS1");
2059 for (s = buf; *s; s++)
2060 if (isdigit(*s) || *s == ',')
2062 idx = simple_strtoul(s, NULL, 10);
2065 __add_preferred_console(buf, idx, options, brl_options);
2066 console_set_on_cmdline = 1;
2069 __setup("console=", console_setup);
2072 * add_preferred_console - add a device to the list of preferred consoles.
2073 * @name: device name
2074 * @idx: device index
2075 * @options: options for this console
2077 * The last preferred console added will be used for kernel messages
2078 * and stdin/out/err for init. Normally this is used by console_setup
2079 * above to handle user-supplied console arguments; however it can also
2080 * be used by arch-specific code either to override the user or more
2081 * commonly to provide a default console (ie from PROM variables) when
2082 * the user has not supplied one.
2084 int add_preferred_console(char *name, int idx, char *options)
2086 return __add_preferred_console(name, idx, options, NULL);
2089 bool console_suspend_enabled = true;
2090 EXPORT_SYMBOL(console_suspend_enabled);
2092 static int __init console_suspend_disable(char *str)
2094 console_suspend_enabled = false;
2097 __setup("no_console_suspend", console_suspend_disable);
2098 module_param_named(console_suspend, console_suspend_enabled,
2099 bool, S_IRUGO | S_IWUSR);
2100 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2101 " and hibernate operations");
2104 * suspend_console - suspend the console subsystem
2106 * This disables printk() while we go into suspend states
2108 void suspend_console(void)
2110 if (!console_suspend_enabled)
2112 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2114 console_suspended = 1;
2118 void resume_console(void)
2120 if (!console_suspend_enabled)
2123 console_suspended = 0;
2127 #ifdef CONFIG_CONSOLE_FLUSH_ON_HOTPLUG
2130 * console_cpu_notify - print deferred console messages after CPU hotplug
2131 * @self: notifier struct
2132 * @action: CPU hotplug event
2135 * If printk() is called from a CPU that is not online yet, the messages
2136 * will be spooled but will not show up on the console. This function is
2137 * called when a new CPU comes online (or fails to come up), and ensures
2138 * that any such output gets printed.
2140 static int console_cpu_notify(struct notifier_block *self,
2141 unsigned long action, void *hcpu)
2146 case CPU_DOWN_FAILED:
2147 case CPU_UP_CANCELED:
2149 #ifdef CONFIG_CONSOLE_FLUSH_ON_HOTPLUG
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 #ifdef CONFIG_CONSOLE_FLUSH_ON_HOTPLUG
2725 hotcpu_notifier(console_cpu_notify, 0);
2729 late_initcall(printk_late_init);
2731 #if defined CONFIG_PRINTK
2733 * Delayed printk version, for scheduler-internal messages:
2735 #define PRINTK_PENDING_WAKEUP 0x01
2736 #define PRINTK_PENDING_OUTPUT 0x02
2738 static DEFINE_PER_CPU(int, printk_pending);
2740 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2742 int pending = __this_cpu_xchg(printk_pending, 0);
2744 if (pending & PRINTK_PENDING_OUTPUT) {
2745 /* If trylock fails, someone else is doing the printing */
2746 if (console_trylock())
2750 if (pending & PRINTK_PENDING_WAKEUP)
2751 wake_up_interruptible(&log_wait);
2754 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2755 .func = wake_up_klogd_work_func,
2756 .flags = IRQ_WORK_LAZY,
2759 void wake_up_klogd(void)
2762 if (waitqueue_active(&log_wait)) {
2763 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2764 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2769 int printk_deferred(const char *fmt, ...)
2775 va_start(args, fmt);
2776 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2779 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2780 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2787 * printk rate limiting, lifted from the networking subsystem.
2789 * This enforces a rate limit: not more than 10 kernel messages
2790 * every 5s to make a denial-of-service attack impossible.
2792 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2794 int __printk_ratelimit(const char *func)
2796 return ___ratelimit(&printk_ratelimit_state, func);
2798 EXPORT_SYMBOL(__printk_ratelimit);
2801 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2802 * @caller_jiffies: pointer to caller's state
2803 * @interval_msecs: minimum interval between prints
2805 * printk_timed_ratelimit() returns true if more than @interval_msecs
2806 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2809 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2810 unsigned int interval_msecs)
2812 unsigned long elapsed = jiffies - *caller_jiffies;
2814 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2817 *caller_jiffies = jiffies;
2820 EXPORT_SYMBOL(printk_timed_ratelimit);
2822 static DEFINE_SPINLOCK(dump_list_lock);
2823 static LIST_HEAD(dump_list);
2826 * kmsg_dump_register - register a kernel log dumper.
2827 * @dumper: pointer to the kmsg_dumper structure
2829 * Adds a kernel log dumper to the system. The dump callback in the
2830 * structure will be called when the kernel oopses or panics and must be
2831 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2833 int kmsg_dump_register(struct kmsg_dumper *dumper)
2835 unsigned long flags;
2838 /* The dump callback needs to be set */
2842 spin_lock_irqsave(&dump_list_lock, flags);
2843 /* Don't allow registering multiple times */
2844 if (!dumper->registered) {
2845 dumper->registered = 1;
2846 list_add_tail_rcu(&dumper->list, &dump_list);
2849 spin_unlock_irqrestore(&dump_list_lock, flags);
2853 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2856 * kmsg_dump_unregister - unregister a kmsg dumper.
2857 * @dumper: pointer to the kmsg_dumper structure
2859 * Removes a dump device from the system. Returns zero on success and
2860 * %-EINVAL otherwise.
2862 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2864 unsigned long flags;
2867 spin_lock_irqsave(&dump_list_lock, flags);
2868 if (dumper->registered) {
2869 dumper->registered = 0;
2870 list_del_rcu(&dumper->list);
2873 spin_unlock_irqrestore(&dump_list_lock, flags);
2878 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2880 static bool always_kmsg_dump;
2881 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2884 * kmsg_dump - dump kernel log to kernel message dumpers.
2885 * @reason: the reason (oops, panic etc) for dumping
2887 * Call each of the registered dumper's dump() callback, which can
2888 * retrieve the kmsg records with kmsg_dump_get_line() or
2889 * kmsg_dump_get_buffer().
2891 void kmsg_dump(enum kmsg_dump_reason reason)
2893 struct kmsg_dumper *dumper;
2894 unsigned long flags;
2896 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2900 list_for_each_entry_rcu(dumper, &dump_list, list) {
2901 if (dumper->max_reason && reason > dumper->max_reason)
2904 /* initialize iterator with data about the stored records */
2905 dumper->active = true;
2907 raw_spin_lock_irqsave(&logbuf_lock, flags);
2908 dumper->cur_seq = clear_seq;
2909 dumper->cur_idx = clear_idx;
2910 dumper->next_seq = log_next_seq;
2911 dumper->next_idx = log_next_idx;
2912 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2914 /* invoke dumper which will iterate over records */
2915 dumper->dump(dumper, reason);
2917 /* reset iterator */
2918 dumper->active = false;
2924 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2925 * @dumper: registered kmsg dumper
2926 * @syslog: include the "<4>" prefixes
2927 * @line: buffer to copy the line to
2928 * @size: maximum size of the buffer
2929 * @len: length of line placed into buffer
2931 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2932 * record, and copy one record into the provided buffer.
2934 * Consecutive calls will return the next available record moving
2935 * towards the end of the buffer with the youngest messages.
2937 * A return value of FALSE indicates that there are no more records to
2940 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2942 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2943 char *line, size_t size, size_t *len)
2945 struct printk_log *msg;
2949 if (!dumper->active)
2952 if (dumper->cur_seq < log_first_seq) {
2953 /* messages are gone, move to first available one */
2954 dumper->cur_seq = log_first_seq;
2955 dumper->cur_idx = log_first_idx;
2959 if (dumper->cur_seq >= log_next_seq)
2962 msg = log_from_idx(dumper->cur_idx);
2963 l = msg_print_text(msg, 0, syslog, line, size);
2965 dumper->cur_idx = log_next(dumper->cur_idx);
2975 * kmsg_dump_get_line - retrieve one kmsg log line
2976 * @dumper: registered kmsg dumper
2977 * @syslog: include the "<4>" prefixes
2978 * @line: buffer to copy the line to
2979 * @size: maximum size of the buffer
2980 * @len: length of line placed into buffer
2982 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2983 * record, and copy one record into the provided buffer.
2985 * Consecutive calls will return the next available record moving
2986 * towards the end of the buffer with the youngest messages.
2988 * A return value of FALSE indicates that there are no more records to
2991 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2992 char *line, size_t size, size_t *len)
2994 unsigned long flags;
2997 raw_spin_lock_irqsave(&logbuf_lock, flags);
2998 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2999 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3003 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
3006 * kmsg_dump_get_buffer - copy kmsg log lines
3007 * @dumper: registered kmsg dumper
3008 * @syslog: include the "<4>" prefixes
3009 * @buf: buffer to copy the line to
3010 * @size: maximum size of the buffer
3011 * @len: length of line placed into buffer
3013 * Start at the end of the kmsg buffer and fill the provided buffer
3014 * with as many of the the *youngest* kmsg records that fit into it.
3015 * If the buffer is large enough, all available kmsg records will be
3016 * copied with a single call.
3018 * Consecutive calls will fill the buffer with the next block of
3019 * available older records, not including the earlier retrieved ones.
3021 * A return value of FALSE indicates that there are no more records to
3024 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
3025 char *buf, size_t size, size_t *len)
3027 unsigned long flags;
3032 enum log_flags prev;
3036 if (!dumper->active)
3039 raw_spin_lock_irqsave(&logbuf_lock, flags);
3040 if (dumper->cur_seq < log_first_seq) {
3041 /* messages are gone, move to first available one */
3042 dumper->cur_seq = log_first_seq;
3043 dumper->cur_idx = log_first_idx;
3047 if (dumper->cur_seq >= dumper->next_seq) {
3048 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3052 /* calculate length of entire buffer */
3053 seq = dumper->cur_seq;
3054 idx = dumper->cur_idx;
3056 while (seq < dumper->next_seq) {
3057 struct printk_log *msg = log_from_idx(idx);
3059 l += msg_print_text(msg, prev, true, NULL, 0);
3060 idx = log_next(idx);
3065 /* move first record forward until length fits into the buffer */
3066 seq = dumper->cur_seq;
3067 idx = dumper->cur_idx;
3069 while (l > size && seq < dumper->next_seq) {
3070 struct printk_log *msg = log_from_idx(idx);
3072 l -= msg_print_text(msg, prev, true, NULL, 0);
3073 idx = log_next(idx);
3078 /* last message in next interation */
3083 while (seq < dumper->next_seq) {
3084 struct printk_log *msg = log_from_idx(idx);
3086 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
3087 idx = log_next(idx);
3092 dumper->next_seq = next_seq;
3093 dumper->next_idx = next_idx;
3095 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3101 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3104 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3105 * @dumper: registered kmsg dumper
3107 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3108 * kmsg_dump_get_buffer() can be called again and used multiple
3109 * times within the same dumper.dump() callback.
3111 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3113 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3115 dumper->cur_seq = clear_seq;
3116 dumper->cur_idx = clear_idx;
3117 dumper->next_seq = log_next_seq;
3118 dumper->next_idx = log_next_idx;
3122 * kmsg_dump_rewind - reset the interator
3123 * @dumper: registered kmsg dumper
3125 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3126 * kmsg_dump_get_buffer() can be called again and used multiple
3127 * times within the same dumper.dump() callback.
3129 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3131 unsigned long flags;
3133 raw_spin_lock_irqsave(&logbuf_lock, flags);
3134 kmsg_dump_rewind_nolock(dumper);
3135 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3137 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3139 static char dump_stack_arch_desc_str[128];
3142 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3143 * @fmt: printf-style format string
3144 * @...: arguments for the format string
3146 * The configured string will be printed right after utsname during task
3147 * dumps. Usually used to add arch-specific system identifiers. If an
3148 * arch wants to make use of such an ID string, it should initialize this
3149 * as soon as possible during boot.
3151 void __init dump_stack_set_arch_desc(const char *fmt, ...)
3155 va_start(args, fmt);
3156 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3162 * dump_stack_print_info - print generic debug info for dump_stack()
3163 * @log_lvl: log level
3165 * Arch-specific dump_stack() implementations can use this function to
3166 * print out the same debug information as the generic dump_stack().
3168 void dump_stack_print_info(const char *log_lvl)
3170 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3171 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3172 print_tainted(), init_utsname()->release,
3173 (int)strcspn(init_utsname()->version, " "),
3174 init_utsname()->version);
3176 if (dump_stack_arch_desc_str[0] != '\0')
3177 printk("%sHardware name: %s\n",
3178 log_lvl, dump_stack_arch_desc_str);
3180 print_worker_info(log_lvl, current);
3184 * show_regs_print_info - print generic debug info for show_regs()
3185 * @log_lvl: log level
3187 * show_regs() implementations can use this function to print out generic
3188 * debug information.
3190 void show_regs_print_info(const char *log_lvl)
3192 dump_stack_print_info(log_lvl);
3194 printk("%stask: %p task.stack: %p\n",
3195 log_lvl, current, task_stack_page(current));