2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/memblock.h>
35 #include <linux/syscalls.h>
36 #include <linux/kexec.h>
37 #include <linux/kdb.h>
38 #include <linux/ratelimit.h>
39 #include <linux/kmsg_dump.h>
40 #include <linux/syslog.h>
41 #include <linux/cpu.h>
42 #include <linux/notifier.h>
43 #include <linux/rculist.h>
44 #include <linux/poll.h>
45 #include <linux/irq_work.h>
46 #include <linux/utsname.h>
47 #include <linux/ctype.h>
48 #include <linux/uio.h>
50 #include <asm/uaccess.h>
52 #define CREATE_TRACE_POINTS
53 #include <trace/events/printk.h>
55 #include "console_cmdline.h"
58 int console_printk[4] = {
59 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
60 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
61 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
62 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
66 * Low level drivers may need that to know if they can schedule in
67 * their unblank() callback or not. So let's export it.
70 EXPORT_SYMBOL(oops_in_progress);
73 * console_sem protects the console_drivers list, and also
74 * provides serialisation for access to the entire console
77 static DEFINE_SEMAPHORE(console_sem);
78 struct console *console_drivers;
79 EXPORT_SYMBOL_GPL(console_drivers);
82 static struct lockdep_map console_lock_dep_map = {
83 .name = "console_lock"
88 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
89 * macros instead of functions so that _RET_IP_ contains useful information.
91 #define down_console_sem() do { \
93 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
96 static int __down_trylock_console_sem(unsigned long ip)
98 if (down_trylock(&console_sem))
100 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
103 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
105 #define up_console_sem() do { \
106 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
111 * This is used for debugging the mess that is the VT code by
112 * keeping track if we have the console semaphore held. It's
113 * definitely not the perfect debug tool (we don't know if _WE_
114 * hold it and are racing, but it helps tracking those weird code
115 * paths in the console code where we end up in places I want
116 * locked without the console sempahore held).
118 static int console_locked, console_suspended;
121 * If exclusive_console is non-NULL then only this console is to be printed to.
123 static struct console *exclusive_console;
126 * Array of consoles built from command line options (console=)
129 #define MAX_CMDLINECONSOLES 8
131 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
133 static int selected_console = -1;
134 static int preferred_console = -1;
135 int console_set_on_cmdline;
136 EXPORT_SYMBOL(console_set_on_cmdline);
138 /* Flag: console code may call schedule() */
139 static int console_may_schedule;
142 * The printk log buffer consists of a chain of concatenated variable
143 * length records. Every record starts with a record header, containing
144 * the overall length of the record.
146 * The heads to the first and last entry in the buffer, as well as the
147 * sequence numbers of these entries are maintained when messages are
150 * If the heads indicate available messages, the length in the header
151 * tells the start next message. A length == 0 for the next message
152 * indicates a wrap-around to the beginning of the buffer.
154 * Every record carries the monotonic timestamp in microseconds, as well as
155 * the standard userspace syslog level and syslog facility. The usual
156 * kernel messages use LOG_KERN; userspace-injected messages always carry
157 * a matching syslog facility, by default LOG_USER. The origin of every
158 * message can be reliably determined that way.
160 * The human readable log message directly follows the message header. The
161 * length of the message text is stored in the header, the stored message
164 * Optionally, a message can carry a dictionary of properties (key/value pairs),
165 * to provide userspace with a machine-readable message context.
167 * Examples for well-defined, commonly used property names are:
168 * DEVICE=b12:8 device identifier
172 * +sound:card0 subsystem:devname
173 * SUBSYSTEM=pci driver-core subsystem name
175 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
176 * follows directly after a '=' character. Every property is terminated by
177 * a '\0' character. The last property is not terminated.
179 * Example of a message structure:
180 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
181 * 0008 34 00 record is 52 bytes long
182 * 000a 0b 00 text is 11 bytes long
183 * 000c 1f 00 dictionary is 23 bytes long
184 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
185 * 0010 69 74 27 73 20 61 20 6c "it's a l"
187 * 001b 44 45 56 49 43 "DEVIC"
188 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
189 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
191 * 0032 00 00 00 padding to next message header
193 * The 'struct printk_log' buffer header must never be directly exported to
194 * userspace, it is a kernel-private implementation detail that might
195 * need to be changed in the future, when the requirements change.
197 * /dev/kmsg exports the structured data in the following line format:
198 * "level,sequnum,timestamp;<message text>\n"
200 * The optional key/value pairs are attached as continuation lines starting
201 * with a space character and terminated by a newline. All possible
202 * non-prinatable characters are escaped in the "\xff" notation.
204 * Users of the export format should ignore possible additional values
205 * separated by ',', and find the message after the ';' character.
209 LOG_NOCONS = 1, /* already flushed, do not print to console */
210 LOG_NEWLINE = 2, /* text ended with a newline */
211 LOG_PREFIX = 4, /* text started with a prefix */
212 LOG_CONT = 8, /* text is a fragment of a continuation line */
216 u64 ts_nsec; /* timestamp in nanoseconds */
217 u16 len; /* length of entire record */
218 u16 text_len; /* length of text buffer */
219 u16 dict_len; /* length of dictionary buffer */
220 u8 facility; /* syslog facility */
221 u8 flags:5; /* internal record flags */
222 u8 level:3; /* syslog level */
226 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
227 * within the scheduler's rq lock. It must be released before calling
228 * console_unlock() or anything else that might wake up a process.
230 static DEFINE_RAW_SPINLOCK(logbuf_lock);
233 DECLARE_WAIT_QUEUE_HEAD(log_wait);
234 /* the next printk record to read by syslog(READ) or /proc/kmsg */
235 static u64 syslog_seq;
236 static u32 syslog_idx;
237 static enum log_flags syslog_prev;
238 static size_t syslog_partial;
240 /* index and sequence number of the first record stored in the buffer */
241 static u64 log_first_seq;
242 static u32 log_first_idx;
244 /* index and sequence number of the next record to store in the buffer */
245 static u64 log_next_seq;
246 static u32 log_next_idx;
248 /* the next printk record to write to the console */
249 static u64 console_seq;
250 static u32 console_idx;
251 static enum log_flags console_prev;
253 /* the next printk record to read after the last 'clear' command */
254 static u64 clear_seq;
255 static u32 clear_idx;
257 #define PREFIX_MAX 32
258 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
261 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
264 #define LOG_ALIGN __alignof__(struct printk_log)
266 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
267 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
268 static char *log_buf = __log_buf;
269 static u32 log_buf_len = __LOG_BUF_LEN;
271 /* Return log buffer address */
272 char *log_buf_addr_get(void)
277 /* Return log buffer size */
278 u32 log_buf_len_get(void)
283 /* human readable text of the record */
284 static char *log_text(const struct printk_log *msg)
286 return (char *)msg + sizeof(struct printk_log);
289 /* optional key/value pair dictionary attached to the record */
290 static char *log_dict(const struct printk_log *msg)
292 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
295 /* get record by index; idx must point to valid msg */
296 static struct printk_log *log_from_idx(u32 idx)
298 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
301 * A length == 0 record is the end of buffer marker. Wrap around and
302 * read the message at the start of the buffer.
305 return (struct printk_log *)log_buf;
309 /* get next record; idx must point to valid msg */
310 static u32 log_next(u32 idx)
312 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
314 /* length == 0 indicates the end of the buffer; wrap */
316 * A length == 0 record is the end of buffer marker. Wrap around and
317 * read the message at the start of the buffer as *this* one, and
318 * return the one after that.
321 msg = (struct printk_log *)log_buf;
324 return idx + msg->len;
328 * Check whether there is enough free space for the given message.
330 * The same values of first_idx and next_idx mean that the buffer
331 * is either empty or full.
333 * If the buffer is empty, we must respect the position of the indexes.
334 * They cannot be reset to the beginning of the buffer.
336 static int logbuf_has_space(u32 msg_size, bool empty)
340 if (log_next_idx > log_first_idx || empty)
341 free = max(log_buf_len - log_next_idx, log_first_idx);
343 free = log_first_idx - log_next_idx;
346 * We need space also for an empty header that signalizes wrapping
349 return free >= msg_size + sizeof(struct printk_log);
352 static int log_make_free_space(u32 msg_size)
354 while (log_first_seq < log_next_seq) {
355 if (logbuf_has_space(msg_size, false))
357 /* drop old messages until we have enough contiguous space */
358 log_first_idx = log_next(log_first_idx);
362 /* sequence numbers are equal, so the log buffer is empty */
363 if (logbuf_has_space(msg_size, true))
369 /* compute the message size including the padding bytes */
370 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
374 size = sizeof(struct printk_log) + text_len + dict_len;
375 *pad_len = (-size) & (LOG_ALIGN - 1);
382 * Define how much of the log buffer we could take at maximum. The value
383 * must be greater than two. Note that only half of the buffer is available
384 * when the index points to the middle.
386 #define MAX_LOG_TAKE_PART 4
387 static const char trunc_msg[] = "<truncated>";
389 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
390 u16 *dict_len, u32 *pad_len)
393 * The message should not take the whole buffer. Otherwise, it might
394 * get removed too soon.
396 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
397 if (*text_len > max_text_len)
398 *text_len = max_text_len;
399 /* enable the warning message */
400 *trunc_msg_len = strlen(trunc_msg);
401 /* disable the "dict" completely */
403 /* compute the size again, count also the warning message */
404 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
407 /* insert record into the buffer, discard old ones, update heads */
408 static int log_store(int facility, int level,
409 enum log_flags flags, u64 ts_nsec,
410 const char *dict, u16 dict_len,
411 const char *text, u16 text_len)
413 struct printk_log *msg;
415 u16 trunc_msg_len = 0;
417 /* number of '\0' padding bytes to next message */
418 size = msg_used_size(text_len, dict_len, &pad_len);
420 if (log_make_free_space(size)) {
421 /* truncate the message if it is too long for empty buffer */
422 size = truncate_msg(&text_len, &trunc_msg_len,
423 &dict_len, &pad_len);
424 /* survive when the log buffer is too small for trunc_msg */
425 if (log_make_free_space(size))
429 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
431 * This message + an additional empty header does not fit
432 * at the end of the buffer. Add an empty header with len == 0
433 * to signify a wrap around.
435 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
440 msg = (struct printk_log *)(log_buf + log_next_idx);
441 memcpy(log_text(msg), text, text_len);
442 msg->text_len = text_len;
444 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
445 msg->text_len += trunc_msg_len;
447 memcpy(log_dict(msg), dict, dict_len);
448 msg->dict_len = dict_len;
449 msg->facility = facility;
450 msg->level = level & 7;
451 msg->flags = flags & 0x1f;
453 msg->ts_nsec = ts_nsec;
455 msg->ts_nsec = local_clock();
456 memset(log_dict(msg) + dict_len, 0, pad_len);
460 log_next_idx += msg->len;
463 return msg->text_len;
466 int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
468 static int syslog_action_restricted(int type)
473 * Unless restricted, we allow "read all" and "get buffer size"
476 return type != SYSLOG_ACTION_READ_ALL &&
477 type != SYSLOG_ACTION_SIZE_BUFFER;
480 int check_syslog_permissions(int type, bool from_file)
483 * If this is from /proc/kmsg and we've already opened it, then we've
484 * already done the capabilities checks at open time.
486 if (from_file && type != SYSLOG_ACTION_OPEN)
489 if (syslog_action_restricted(type)) {
490 if (capable(CAP_SYSLOG))
493 * For historical reasons, accept CAP_SYS_ADMIN too, with
496 if (capable(CAP_SYS_ADMIN)) {
497 pr_warn_once("%s (%d): Attempt to access syslog with "
498 "CAP_SYS_ADMIN but no CAP_SYSLOG "
500 current->comm, task_pid_nr(current));
505 return security_syslog(type);
509 /* /dev/kmsg - userspace message inject/listen interface */
510 struct devkmsg_user {
518 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
522 int level = default_message_loglevel;
523 int facility = 1; /* LOG_USER */
524 size_t len = iov_iter_count(from);
527 if (len > LOG_LINE_MAX)
529 buf = kmalloc(len+1, GFP_KERNEL);
534 if (copy_from_iter(buf, len, from) != len) {
540 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
541 * the decimal value represents 32bit, the lower 3 bit are the log
542 * level, the rest are the log facility.
544 * If no prefix or no userspace facility is specified, we
545 * enforce LOG_USER, to be able to reliably distinguish
546 * kernel-generated messages from userspace-injected ones.
549 if (line[0] == '<') {
552 i = simple_strtoul(line+1, &endp, 10);
553 if (endp && endp[0] == '>') {
563 printk_emit(facility, level, NULL, 0, "%s", line);
568 static ssize_t devkmsg_read(struct file *file, char __user *buf,
569 size_t count, loff_t *ppos)
571 struct devkmsg_user *user = file->private_data;
572 struct printk_log *msg;
582 ret = mutex_lock_interruptible(&user->lock);
585 raw_spin_lock_irq(&logbuf_lock);
586 while (user->seq == log_next_seq) {
587 if (file->f_flags & O_NONBLOCK) {
589 raw_spin_unlock_irq(&logbuf_lock);
593 raw_spin_unlock_irq(&logbuf_lock);
594 ret = wait_event_interruptible(log_wait,
595 user->seq != log_next_seq);
598 raw_spin_lock_irq(&logbuf_lock);
601 if (user->seq < log_first_seq) {
602 /* our last seen message is gone, return error and reset */
603 user->idx = log_first_idx;
604 user->seq = log_first_seq;
606 raw_spin_unlock_irq(&logbuf_lock);
610 msg = log_from_idx(user->idx);
611 ts_usec = msg->ts_nsec;
612 do_div(ts_usec, 1000);
615 * If we couldn't merge continuation line fragments during the print,
616 * export the stored flags to allow an optional external merge of the
617 * records. Merging the records isn't always neccessarily correct, like
618 * when we hit a race during printing. In most cases though, it produces
619 * better readable output. 'c' in the record flags mark the first
620 * fragment of a line, '+' the following.
622 if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
624 else if ((msg->flags & LOG_CONT) ||
625 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
628 len = sprintf(user->buf, "%u,%llu,%llu,%c;",
629 (msg->facility << 3) | msg->level,
630 user->seq, ts_usec, cont);
631 user->prev = msg->flags;
633 /* escape non-printable characters */
634 for (i = 0; i < msg->text_len; i++) {
635 unsigned char c = log_text(msg)[i];
637 if (c < ' ' || c >= 127 || c == '\\')
638 len += sprintf(user->buf + len, "\\x%02x", c);
640 user->buf[len++] = c;
642 user->buf[len++] = '\n';
647 for (i = 0; i < msg->dict_len; i++) {
648 unsigned char c = log_dict(msg)[i];
651 user->buf[len++] = ' ';
656 user->buf[len++] = '\n';
661 if (c < ' ' || c >= 127 || c == '\\') {
662 len += sprintf(user->buf + len, "\\x%02x", c);
666 user->buf[len++] = c;
668 user->buf[len++] = '\n';
671 user->idx = log_next(user->idx);
673 raw_spin_unlock_irq(&logbuf_lock);
680 if (copy_to_user(buf, user->buf, len)) {
686 mutex_unlock(&user->lock);
690 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
692 struct devkmsg_user *user = file->private_data;
700 raw_spin_lock_irq(&logbuf_lock);
703 /* the first record */
704 user->idx = log_first_idx;
705 user->seq = log_first_seq;
709 * The first record after the last SYSLOG_ACTION_CLEAR,
710 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
711 * changes no global state, and does not clear anything.
713 user->idx = clear_idx;
714 user->seq = clear_seq;
717 /* after the last record */
718 user->idx = log_next_idx;
719 user->seq = log_next_seq;
724 raw_spin_unlock_irq(&logbuf_lock);
728 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
730 struct devkmsg_user *user = file->private_data;
734 return POLLERR|POLLNVAL;
736 poll_wait(file, &log_wait, wait);
738 raw_spin_lock_irq(&logbuf_lock);
739 if (user->seq < log_next_seq) {
740 /* return error when data has vanished underneath us */
741 if (user->seq < log_first_seq)
742 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
744 ret = POLLIN|POLLRDNORM;
746 raw_spin_unlock_irq(&logbuf_lock);
751 static int devkmsg_open(struct inode *inode, struct file *file)
753 struct devkmsg_user *user;
756 /* write-only does not need any file context */
757 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
760 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
765 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
769 mutex_init(&user->lock);
771 raw_spin_lock_irq(&logbuf_lock);
772 user->idx = log_first_idx;
773 user->seq = log_first_seq;
774 raw_spin_unlock_irq(&logbuf_lock);
776 file->private_data = user;
780 static int devkmsg_release(struct inode *inode, struct file *file)
782 struct devkmsg_user *user = file->private_data;
787 mutex_destroy(&user->lock);
792 const struct file_operations kmsg_fops = {
793 .open = devkmsg_open,
794 .read = devkmsg_read,
795 .write_iter = devkmsg_write,
796 .llseek = devkmsg_llseek,
797 .poll = devkmsg_poll,
798 .release = devkmsg_release,
803 * This appends the listed symbols to /proc/vmcore
805 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
806 * obtain access to symbols that are otherwise very difficult to locate. These
807 * symbols are specifically used so that utilities can access and extract the
808 * dmesg log from a vmcore file after a crash.
810 void log_buf_kexec_setup(void)
812 VMCOREINFO_SYMBOL(log_buf);
813 VMCOREINFO_SYMBOL(log_buf_len);
814 VMCOREINFO_SYMBOL(log_first_idx);
815 VMCOREINFO_SYMBOL(log_next_idx);
817 * Export struct printk_log size and field offsets. User space tools can
818 * parse it and detect any changes to structure down the line.
820 VMCOREINFO_STRUCT_SIZE(printk_log);
821 VMCOREINFO_OFFSET(printk_log, ts_nsec);
822 VMCOREINFO_OFFSET(printk_log, len);
823 VMCOREINFO_OFFSET(printk_log, text_len);
824 VMCOREINFO_OFFSET(printk_log, dict_len);
828 /* requested log_buf_len from kernel cmdline */
829 static unsigned long __initdata new_log_buf_len;
831 /* we practice scaling the ring buffer by powers of 2 */
832 static void __init log_buf_len_update(unsigned size)
835 size = roundup_pow_of_two(size);
836 if (size > log_buf_len)
837 new_log_buf_len = size;
840 /* save requested log_buf_len since it's too early to process it */
841 static int __init log_buf_len_setup(char *str)
843 unsigned size = memparse(str, &str);
845 log_buf_len_update(size);
849 early_param("log_buf_len", log_buf_len_setup);
852 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
854 static void __init log_buf_add_cpu(void)
856 unsigned int cpu_extra;
859 * archs should set up cpu_possible_bits properly with
860 * set_cpu_possible() after setup_arch() but just in
861 * case lets ensure this is valid.
863 if (num_possible_cpus() == 1)
866 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
868 /* by default this will only continue through for large > 64 CPUs */
869 if (cpu_extra <= __LOG_BUF_LEN / 2)
872 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
873 __LOG_CPU_MAX_BUF_LEN);
874 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
876 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
878 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
880 #else /* !CONFIG_SMP */
881 static inline void log_buf_add_cpu(void) {}
882 #endif /* CONFIG_SMP */
884 void __init setup_log_buf(int early)
890 if (log_buf != __log_buf)
893 if (!early && !new_log_buf_len)
896 if (!new_log_buf_len)
901 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
903 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
907 if (unlikely(!new_log_buf)) {
908 pr_err("log_buf_len: %ld bytes not available\n",
913 raw_spin_lock_irqsave(&logbuf_lock, flags);
914 log_buf_len = new_log_buf_len;
915 log_buf = new_log_buf;
917 free = __LOG_BUF_LEN - log_next_idx;
918 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
919 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
921 pr_info("log_buf_len: %d bytes\n", log_buf_len);
922 pr_info("early log buf free: %d(%d%%)\n",
923 free, (free * 100) / __LOG_BUF_LEN);
926 static bool __read_mostly ignore_loglevel;
928 static int __init ignore_loglevel_setup(char *str)
930 ignore_loglevel = true;
931 pr_info("debug: ignoring loglevel setting.\n");
936 early_param("ignore_loglevel", ignore_loglevel_setup);
937 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
938 MODULE_PARM_DESC(ignore_loglevel,
939 "ignore loglevel setting (prints all kernel messages to the console)");
941 #ifdef CONFIG_BOOT_PRINTK_DELAY
943 static int boot_delay; /* msecs delay after each printk during bootup */
944 static unsigned long long loops_per_msec; /* based on boot_delay */
946 static int __init boot_delay_setup(char *str)
950 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
951 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
953 get_option(&str, &boot_delay);
954 if (boot_delay > 10 * 1000)
957 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
958 "HZ: %d, loops_per_msec: %llu\n",
959 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
962 early_param("boot_delay", boot_delay_setup);
964 static void boot_delay_msec(int level)
966 unsigned long long k;
967 unsigned long timeout;
969 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
970 || (level >= console_loglevel && !ignore_loglevel)) {
974 k = (unsigned long long)loops_per_msec * boot_delay;
976 timeout = jiffies + msecs_to_jiffies(boot_delay);
981 * use (volatile) jiffies to prevent
982 * compiler reduction; loop termination via jiffies
983 * is secondary and may or may not happen.
985 if (time_after(jiffies, timeout))
987 touch_nmi_watchdog();
991 static inline void boot_delay_msec(int level)
996 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
997 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
999 static size_t print_time(u64 ts, char *buf)
1001 unsigned long rem_nsec;
1006 rem_nsec = do_div(ts, 1000000000);
1009 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1011 return sprintf(buf, "[%5lu.%06lu] ",
1012 (unsigned long)ts, rem_nsec / 1000);
1015 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1018 unsigned int prefix = (msg->facility << 3) | msg->level;
1022 len += sprintf(buf, "<%u>", prefix);
1027 else if (prefix > 99)
1029 else if (prefix > 9)
1034 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1038 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1039 bool syslog, char *buf, size_t size)
1041 const char *text = log_text(msg);
1042 size_t text_size = msg->text_len;
1044 bool newline = true;
1047 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1050 if (msg->flags & LOG_CONT) {
1051 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1054 if (!(msg->flags & LOG_NEWLINE))
1059 const char *next = memchr(text, '\n', text_size);
1063 text_len = next - text;
1065 text_size -= next - text;
1067 text_len = text_size;
1071 if (print_prefix(msg, syslog, NULL) +
1072 text_len + 1 >= size - len)
1076 len += print_prefix(msg, syslog, buf + len);
1077 memcpy(buf + len, text, text_len);
1079 if (next || newline)
1082 /* SYSLOG_ACTION_* buffer size only calculation */
1084 len += print_prefix(msg, syslog, NULL);
1086 if (next || newline)
1097 static int syslog_print(char __user *buf, int size)
1100 struct printk_log *msg;
1103 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1111 raw_spin_lock_irq(&logbuf_lock);
1112 if (syslog_seq < log_first_seq) {
1113 /* messages are gone, move to first one */
1114 syslog_seq = log_first_seq;
1115 syslog_idx = log_first_idx;
1119 if (syslog_seq == log_next_seq) {
1120 raw_spin_unlock_irq(&logbuf_lock);
1124 skip = syslog_partial;
1125 msg = log_from_idx(syslog_idx);
1126 n = msg_print_text(msg, syslog_prev, true, text,
1127 LOG_LINE_MAX + PREFIX_MAX);
1128 if (n - syslog_partial <= size) {
1129 /* message fits into buffer, move forward */
1130 syslog_idx = log_next(syslog_idx);
1132 syslog_prev = msg->flags;
1133 n -= syslog_partial;
1136 /* partial read(), remember position */
1138 syslog_partial += n;
1141 raw_spin_unlock_irq(&logbuf_lock);
1146 if (copy_to_user(buf, text + skip, n)) {
1161 static int syslog_print_all(char __user *buf, int size, bool clear)
1167 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1171 raw_spin_lock_irq(&logbuf_lock);
1176 enum log_flags prev;
1180 if (attempts > 10) {
1185 if (clear_seq < log_first_seq) {
1186 /* messages are gone, move to first available one */
1187 clear_seq = log_first_seq;
1188 clear_idx = log_first_idx;
1192 * Find first record that fits, including all following records,
1193 * into the user-provided buffer for this dump.
1198 while (seq < log_next_seq) {
1199 struct printk_log *msg = log_from_idx(idx);
1201 len += msg_print_text(msg, prev, true, NULL, 0);
1203 idx = log_next(idx);
1208 raw_spin_unlock_irq(&logbuf_lock);
1209 raw_spin_lock_irq(&logbuf_lock);
1210 if (clear_seq < log_first_seq)
1215 /* move first record forward until length fits into the buffer */
1219 while (len > size && seq < log_next_seq) {
1220 struct printk_log *msg = log_from_idx(idx);
1222 len -= msg_print_text(msg, prev, true, NULL, 0);
1224 idx = log_next(idx);
1229 raw_spin_unlock_irq(&logbuf_lock);
1230 raw_spin_lock_irq(&logbuf_lock);
1231 if (clear_seq < log_first_seq)
1236 /* last message fitting into this dump */
1237 next_seq = log_next_seq;
1240 while (len >= 0 && seq < next_seq) {
1241 struct printk_log *msg = log_from_idx(idx);
1244 textlen = msg_print_text(msg, prev, true, text,
1245 LOG_LINE_MAX + PREFIX_MAX);
1250 idx = log_next(idx);
1254 raw_spin_unlock_irq(&logbuf_lock);
1255 if (copy_to_user(buf + len, text, textlen))
1259 raw_spin_lock_irq(&logbuf_lock);
1261 if (seq < log_first_seq) {
1262 /* messages are gone, move to next one */
1263 seq = log_first_seq;
1264 idx = log_first_idx;
1271 clear_seq = log_next_seq;
1272 clear_idx = log_next_idx;
1275 raw_spin_unlock_irq(&logbuf_lock);
1281 int do_syslog(int type, char __user *buf, int len, bool from_file)
1284 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1287 error = check_syslog_permissions(type, from_file);
1291 error = security_syslog(type);
1296 case SYSLOG_ACTION_CLOSE: /* Close log */
1298 case SYSLOG_ACTION_OPEN: /* Open log */
1300 case SYSLOG_ACTION_READ: /* Read from log */
1302 if (!buf || len < 0)
1307 if (!access_ok(VERIFY_WRITE, buf, len)) {
1311 error = wait_event_interruptible(log_wait,
1312 syslog_seq != log_next_seq);
1315 error = syslog_print(buf, len);
1317 /* Read/clear last kernel messages */
1318 case SYSLOG_ACTION_READ_CLEAR:
1321 /* Read last kernel messages */
1322 case SYSLOG_ACTION_READ_ALL:
1324 if (!buf || len < 0)
1329 if (!access_ok(VERIFY_WRITE, buf, len)) {
1333 error = syslog_print_all(buf, len, clear);
1335 /* Clear ring buffer */
1336 case SYSLOG_ACTION_CLEAR:
1337 syslog_print_all(NULL, 0, true);
1339 /* Disable logging to console */
1340 case SYSLOG_ACTION_CONSOLE_OFF:
1341 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1342 saved_console_loglevel = console_loglevel;
1343 console_loglevel = minimum_console_loglevel;
1345 /* Enable logging to console */
1346 case SYSLOG_ACTION_CONSOLE_ON:
1347 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1348 console_loglevel = saved_console_loglevel;
1349 saved_console_loglevel = LOGLEVEL_DEFAULT;
1352 /* Set level of messages printed to console */
1353 case SYSLOG_ACTION_CONSOLE_LEVEL:
1355 if (len < 1 || len > 8)
1357 if (len < minimum_console_loglevel)
1358 len = minimum_console_loglevel;
1359 console_loglevel = len;
1360 /* Implicitly re-enable logging to console */
1361 saved_console_loglevel = LOGLEVEL_DEFAULT;
1364 /* Number of chars in the log buffer */
1365 case SYSLOG_ACTION_SIZE_UNREAD:
1366 raw_spin_lock_irq(&logbuf_lock);
1367 if (syslog_seq < log_first_seq) {
1368 /* messages are gone, move to first one */
1369 syslog_seq = log_first_seq;
1370 syslog_idx = log_first_idx;
1376 * Short-cut for poll(/"proc/kmsg") which simply checks
1377 * for pending data, not the size; return the count of
1378 * records, not the length.
1380 error = log_next_seq - syslog_seq;
1382 u64 seq = syslog_seq;
1383 u32 idx = syslog_idx;
1384 enum log_flags prev = syslog_prev;
1387 while (seq < log_next_seq) {
1388 struct printk_log *msg = log_from_idx(idx);
1390 error += msg_print_text(msg, prev, true, NULL, 0);
1391 idx = log_next(idx);
1395 error -= syslog_partial;
1397 raw_spin_unlock_irq(&logbuf_lock);
1399 /* Size of the log buffer */
1400 case SYSLOG_ACTION_SIZE_BUFFER:
1401 error = log_buf_len;
1411 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1413 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1417 * Call the console drivers, asking them to write out
1418 * log_buf[start] to log_buf[end - 1].
1419 * The console_lock must be held.
1421 static void call_console_drivers(int level, const char *text, size_t len)
1423 struct console *con;
1425 trace_console(text, len);
1427 if (level >= console_loglevel && !ignore_loglevel)
1429 if (!console_drivers)
1433 for_each_console(con) {
1434 if (exclusive_console && con != exclusive_console)
1436 if (!(con->flags & CON_ENABLED))
1440 if (!cpu_online(smp_processor_id()) &&
1441 !(con->flags & CON_ANYTIME))
1443 con->write(con, text, len);
1449 * Zap console related locks when oopsing.
1450 * To leave time for slow consoles to print a full oops,
1451 * only zap at most once every 30 seconds.
1453 static void zap_locks(void)
1455 static unsigned long oops_timestamp;
1457 if (time_after_eq(jiffies, oops_timestamp) &&
1458 !time_after(jiffies, oops_timestamp + 30 * HZ))
1461 oops_timestamp = jiffies;
1464 /* If a crash is occurring, make sure we can't deadlock */
1465 raw_spin_lock_init(&logbuf_lock);
1466 /* And make sure that we print immediately */
1467 sema_init(&console_sem, 1);
1471 * Check if we have any console that is capable of printing while cpu is
1472 * booting or shutting down. Requires console_sem.
1474 static int have_callable_console(void)
1476 struct console *con;
1478 for_each_console(con)
1479 if (con->flags & CON_ANYTIME)
1486 * Can we actually use the console at this time on this cpu?
1488 * Console drivers may assume that per-cpu resources have been allocated. So
1489 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1490 * call them until this CPU is officially up.
1492 static inline int can_use_console(unsigned int cpu)
1494 return cpu_online(cpu) || have_callable_console();
1498 * Try to get console ownership to actually show the kernel
1499 * messages from a 'printk'. Return true (and with the
1500 * console_lock held, and 'console_locked' set) if it
1501 * is successful, false otherwise.
1503 static int console_trylock_for_printk(void)
1505 unsigned int cpu = smp_processor_id();
1506 #ifdef CONFIG_PREEMPT_RT_FULL
1507 int lock = !early_boot_irqs_disabled && (preempt_count() == 0) &&
1516 if (!console_trylock())
1519 * If we can't use the console, we need to release the console
1520 * semaphore by hand to avoid flushing the buffer. We need to hold the
1521 * console semaphore in order to do this test safely.
1523 if (!can_use_console(cpu)) {
1531 int printk_delay_msec __read_mostly;
1533 static inline void printk_delay(void)
1535 if (unlikely(printk_delay_msec)) {
1536 int m = printk_delay_msec;
1540 touch_nmi_watchdog();
1546 * Continuation lines are buffered, and not committed to the record buffer
1547 * until the line is complete, or a race forces it. The line fragments
1548 * though, are printed immediately to the consoles to ensure everything has
1549 * reached the console in case of a kernel crash.
1551 static struct cont {
1552 char buf[LOG_LINE_MAX];
1553 size_t len; /* length == 0 means unused buffer */
1554 size_t cons; /* bytes written to console */
1555 struct task_struct *owner; /* task of first print*/
1556 u64 ts_nsec; /* time of first print */
1557 u8 level; /* log level of first message */
1558 u8 facility; /* log facility of first message */
1559 enum log_flags flags; /* prefix, newline flags */
1560 bool flushed:1; /* buffer sealed and committed */
1563 static void cont_flush(enum log_flags flags)
1572 * If a fragment of this line was directly flushed to the
1573 * console; wait for the console to pick up the rest of the
1574 * line. LOG_NOCONS suppresses a duplicated output.
1576 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1577 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1579 cont.flushed = true;
1582 * If no fragment of this line ever reached the console,
1583 * just submit it to the store and free the buffer.
1585 log_store(cont.facility, cont.level, flags, 0,
1586 NULL, 0, cont.buf, cont.len);
1591 static bool cont_add(int facility, int level, const char *text, size_t len)
1593 if (cont.len && cont.flushed)
1596 if (cont.len + len > sizeof(cont.buf)) {
1597 /* the line gets too long, split it up in separate records */
1598 cont_flush(LOG_CONT);
1603 cont.facility = facility;
1605 cont.owner = current;
1606 cont.ts_nsec = local_clock();
1609 cont.flushed = false;
1612 memcpy(cont.buf + cont.len, text, len);
1615 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1616 cont_flush(LOG_CONT);
1621 static size_t cont_print_text(char *text, size_t size)
1626 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1627 textlen += print_time(cont.ts_nsec, text);
1631 len = cont.len - cont.cons;
1635 memcpy(text + textlen, cont.buf + cont.cons, len);
1637 cont.cons = cont.len;
1641 if (cont.flags & LOG_NEWLINE)
1642 text[textlen++] = '\n';
1643 /* got everything, release buffer */
1649 #ifdef CONFIG_EARLY_PRINTK
1650 struct console *early_console;
1652 static void early_vprintk(const char *fmt, va_list ap)
1654 if (early_console) {
1656 int n = vscnprintf(buf, sizeof(buf), fmt, ap);
1658 early_console->write(early_console, buf, n);
1662 asmlinkage void early_printk(const char *fmt, ...)
1667 early_vprintk(fmt, ap);
1672 * This is independent of any log levels - a global
1673 * kill switch that turns off all of printk.
1675 * Used by the NMI watchdog if early-printk is enabled.
1677 static bool __read_mostly printk_killswitch;
1679 static int __init force_early_printk_setup(char *str)
1681 printk_killswitch = true;
1684 early_param("force_early_printk", force_early_printk_setup);
1686 void printk_kill(void)
1688 printk_killswitch = true;
1691 static int forced_early_printk(const char *fmt, va_list ap)
1693 if (!printk_killswitch)
1695 early_vprintk(fmt, ap);
1699 static inline int forced_early_printk(const char *fmt, va_list ap)
1705 asmlinkage int vprintk_emit(int facility, int level,
1706 const char *dict, size_t dictlen,
1707 const char *fmt, va_list args)
1709 static int recursion_bug;
1710 static char textbuf[LOG_LINE_MAX];
1711 char *text = textbuf;
1712 size_t text_len = 0;
1713 enum log_flags lflags = 0;
1714 unsigned long flags;
1716 int printed_len = 0;
1717 bool in_sched = false;
1718 /* cpu currently holding logbuf_lock in this function */
1719 static unsigned int logbuf_cpu = UINT_MAX;
1722 * Fall back to early_printk if a debugging subsystem has
1723 * killed printk output
1725 if (unlikely(forced_early_printk(fmt, args)))
1728 if (level == LOGLEVEL_SCHED) {
1729 level = LOGLEVEL_DEFAULT;
1733 boot_delay_msec(level);
1736 /* This stops the holder of console_sem just where we want him */
1737 local_irq_save(flags);
1738 this_cpu = smp_processor_id();
1741 * Ouch, printk recursed into itself!
1743 if (unlikely(logbuf_cpu == this_cpu)) {
1745 * If a crash is occurring during printk() on this CPU,
1746 * then try to get the crash message out but make sure
1747 * we can't deadlock. Otherwise just return to avoid the
1748 * recursion and return - but flag the recursion so that
1749 * it can be printed at the next appropriate moment:
1751 if (!oops_in_progress && !lockdep_recursing(current)) {
1753 local_irq_restore(flags);
1760 raw_spin_lock(&logbuf_lock);
1761 logbuf_cpu = this_cpu;
1763 if (unlikely(recursion_bug)) {
1764 static const char recursion_msg[] =
1765 "BUG: recent printk recursion!";
1768 /* emit KERN_CRIT message */
1769 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1770 NULL, 0, recursion_msg,
1771 strlen(recursion_msg));
1775 * The printf needs to come first; we need the syslog
1776 * prefix which might be passed-in as a parameter.
1778 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1780 /* mark and strip a trailing newline */
1781 if (text_len && text[text_len-1] == '\n') {
1783 lflags |= LOG_NEWLINE;
1786 /* strip kernel syslog prefix and extract log level or control flags */
1787 if (facility == 0) {
1788 int kern_level = printk_get_level(text);
1791 const char *end_of_header = printk_skip_level(text);
1792 switch (kern_level) {
1794 if (level == LOGLEVEL_DEFAULT)
1795 level = kern_level - '0';
1797 case 'd': /* KERN_DEFAULT */
1798 lflags |= LOG_PREFIX;
1801 * No need to check length here because vscnprintf
1802 * put '\0' at the end of the string. Only valid and
1803 * newly printed level is detected.
1805 text_len -= end_of_header - text;
1806 text = (char *)end_of_header;
1810 if (level == LOGLEVEL_DEFAULT)
1811 level = default_message_loglevel;
1814 lflags |= LOG_PREFIX|LOG_NEWLINE;
1816 if (!(lflags & LOG_NEWLINE)) {
1818 * Flush the conflicting buffer. An earlier newline was missing,
1819 * or another task also prints continuation lines.
1821 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1822 cont_flush(LOG_NEWLINE);
1824 /* buffer line if possible, otherwise store it right away */
1825 if (cont_add(facility, level, text, text_len))
1826 printed_len += text_len;
1828 printed_len += log_store(facility, level,
1829 lflags | LOG_CONT, 0,
1830 dict, dictlen, text, text_len);
1832 bool stored = false;
1835 * If an earlier newline was missing and it was the same task,
1836 * either merge it with the current buffer and flush, or if
1837 * there was a race with interrupts (prefix == true) then just
1838 * flush it out and store this line separately.
1839 * If the preceding printk was from a different task and missed
1840 * a newline, flush and append the newline.
1843 if (cont.owner == current && !(lflags & LOG_PREFIX))
1844 stored = cont_add(facility, level, text,
1846 cont_flush(LOG_NEWLINE);
1850 printed_len += text_len;
1852 printed_len += log_store(facility, level, lflags, 0,
1853 dict, dictlen, text, text_len);
1856 logbuf_cpu = UINT_MAX;
1857 raw_spin_unlock(&logbuf_lock);
1859 local_irq_restore(flags);
1861 /* If called from the scheduler, we can not call up(). */
1865 * Disable preemption to avoid being preempted while holding
1866 * console_sem which would prevent anyone from printing to
1871 * Try to acquire and then immediately release the console
1872 * semaphore. The release will print out buffers and wake up
1873 * /dev/kmsg and syslog() users.
1875 if (console_trylock_for_printk())
1883 EXPORT_SYMBOL(vprintk_emit);
1885 asmlinkage int vprintk(const char *fmt, va_list args)
1887 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1889 EXPORT_SYMBOL(vprintk);
1891 asmlinkage int printk_emit(int facility, int level,
1892 const char *dict, size_t dictlen,
1893 const char *fmt, ...)
1898 va_start(args, fmt);
1899 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1904 EXPORT_SYMBOL(printk_emit);
1906 int vprintk_default(const char *fmt, va_list args)
1910 #ifdef CONFIG_KGDB_KDB
1911 if (unlikely(kdb_trap_printk)) {
1912 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1916 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1920 EXPORT_SYMBOL_GPL(vprintk_default);
1923 * This allows printk to be diverted to another function per cpu.
1924 * This is useful for calling printk functions from within NMI
1925 * without worrying about race conditions that can lock up the
1928 DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
1931 * printk - print a kernel message
1932 * @fmt: format string
1934 * This is printk(). It can be called from any context. We want it to work.
1936 * We try to grab the console_lock. If we succeed, it's easy - we log the
1937 * output and call the console drivers. If we fail to get the semaphore, we
1938 * place the output into the log buffer and return. The current holder of
1939 * the console_sem will notice the new output in console_unlock(); and will
1940 * send it to the consoles before releasing the lock.
1942 * One effect of this deferred printing is that code which calls printk() and
1943 * then changes console_loglevel may break. This is because console_loglevel
1944 * is inspected when the actual printing occurs.
1949 * See the vsnprintf() documentation for format string extensions over C99.
1951 asmlinkage __visible int printk(const char *fmt, ...)
1953 printk_func_t vprintk_func;
1957 va_start(args, fmt);
1960 * If a caller overrides the per_cpu printk_func, then it needs
1961 * to disable preemption when calling printk(). Otherwise
1962 * the printk_func should be set to the default. No need to
1963 * disable preemption here.
1965 vprintk_func = this_cpu_read(printk_func);
1966 r = vprintk_func(fmt, args);
1972 EXPORT_SYMBOL(printk);
1974 #else /* CONFIG_PRINTK */
1976 #define LOG_LINE_MAX 0
1977 #define PREFIX_MAX 0
1979 static u64 syslog_seq;
1980 static u32 syslog_idx;
1981 static u64 console_seq;
1982 static u32 console_idx;
1983 static enum log_flags syslog_prev;
1984 static u64 log_first_seq;
1985 static u32 log_first_idx;
1986 static u64 log_next_seq;
1987 static enum log_flags console_prev;
1988 static struct cont {
1994 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1995 static u32 log_next(u32 idx) { return 0; }
1996 static void call_console_drivers(int level, const char *text, size_t len) {}
1997 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1998 bool syslog, char *buf, size_t size) { return 0; }
1999 static size_t cont_print_text(char *text, size_t size) { return 0; }
2001 /* Still needs to be defined for users */
2002 DEFINE_PER_CPU(printk_func_t, printk_func);
2004 #endif /* CONFIG_PRINTK */
2006 static int __add_preferred_console(char *name, int idx, char *options,
2009 struct console_cmdline *c;
2013 * See if this tty is not yet registered, and
2014 * if we have a slot free.
2016 for (i = 0, c = console_cmdline;
2017 i < MAX_CMDLINECONSOLES && c->name[0];
2019 if (strcmp(c->name, name) == 0 && c->index == idx) {
2021 selected_console = i;
2025 if (i == MAX_CMDLINECONSOLES)
2028 selected_console = i;
2029 strlcpy(c->name, name, sizeof(c->name));
2030 c->options = options;
2031 braille_set_options(c, brl_options);
2037 * Set up a console. Called via do_early_param() in init/main.c
2038 * for each "console=" parameter in the boot command line.
2040 static int __init console_setup(char *str)
2042 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
2043 char *s, *options, *brl_options = NULL;
2046 if (_braille_console_setup(&str, &brl_options))
2050 * Decode str into name, index, options.
2052 if (str[0] >= '0' && str[0] <= '9') {
2053 strcpy(buf, "ttyS");
2054 strncpy(buf + 4, str, sizeof(buf) - 5);
2056 strncpy(buf, str, sizeof(buf) - 1);
2058 buf[sizeof(buf) - 1] = 0;
2059 options = strchr(str, ',');
2063 if (!strcmp(str, "ttya"))
2064 strcpy(buf, "ttyS0");
2065 if (!strcmp(str, "ttyb"))
2066 strcpy(buf, "ttyS1");
2068 for (s = buf; *s; s++)
2069 if (isdigit(*s) || *s == ',')
2071 idx = simple_strtoul(s, NULL, 10);
2074 __add_preferred_console(buf, idx, options, brl_options);
2075 console_set_on_cmdline = 1;
2078 __setup("console=", console_setup);
2081 * add_preferred_console - add a device to the list of preferred consoles.
2082 * @name: device name
2083 * @idx: device index
2084 * @options: options for this console
2086 * The last preferred console added will be used for kernel messages
2087 * and stdin/out/err for init. Normally this is used by console_setup
2088 * above to handle user-supplied console arguments; however it can also
2089 * be used by arch-specific code either to override the user or more
2090 * commonly to provide a default console (ie from PROM variables) when
2091 * the user has not supplied one.
2093 int add_preferred_console(char *name, int idx, char *options)
2095 return __add_preferred_console(name, idx, options, NULL);
2098 bool console_suspend_enabled = true;
2099 EXPORT_SYMBOL(console_suspend_enabled);
2101 static int __init console_suspend_disable(char *str)
2103 console_suspend_enabled = false;
2106 __setup("no_console_suspend", console_suspend_disable);
2107 module_param_named(console_suspend, console_suspend_enabled,
2108 bool, S_IRUGO | S_IWUSR);
2109 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2110 " and hibernate operations");
2113 * suspend_console - suspend the console subsystem
2115 * This disables printk() while we go into suspend states
2117 void suspend_console(void)
2119 if (!console_suspend_enabled)
2121 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2123 console_suspended = 1;
2127 void resume_console(void)
2129 if (!console_suspend_enabled)
2132 console_suspended = 0;
2137 * console_cpu_notify - print deferred console messages after CPU hotplug
2138 * @self: notifier struct
2139 * @action: CPU hotplug event
2142 * If printk() is called from a CPU that is not online yet, the messages
2143 * will be spooled but will not show up on the console. This function is
2144 * called when a new CPU comes online (or fails to come up), and ensures
2145 * that any such output gets printed.
2147 static int console_cpu_notify(struct notifier_block *self,
2148 unsigned long action, void *hcpu)
2153 case CPU_DOWN_FAILED:
2154 case CPU_UP_CANCELED:
2162 * console_lock - lock the console system for exclusive use.
2164 * Acquires a lock which guarantees that the caller has
2165 * exclusive access to the console system and the console_drivers list.
2167 * Can sleep, returns nothing.
2169 void console_lock(void)
2174 if (console_suspended)
2177 console_may_schedule = 1;
2179 EXPORT_SYMBOL(console_lock);
2182 * console_trylock - try to lock the console system for exclusive use.
2184 * Try to acquire a lock which guarantees that the caller has exclusive
2185 * access to the console system and the console_drivers list.
2187 * returns 1 on success, and 0 on failure to acquire the lock.
2189 int console_trylock(void)
2191 if (down_trylock_console_sem())
2193 if (console_suspended) {
2198 console_may_schedule = 0;
2201 EXPORT_SYMBOL(console_trylock);
2203 int is_console_locked(void)
2205 return console_locked;
2208 static void console_cont_flush(char *text, size_t size)
2210 unsigned long flags;
2213 raw_spin_lock_irqsave(&logbuf_lock, flags);
2219 * We still queue earlier records, likely because the console was
2220 * busy. The earlier ones need to be printed before this one, we
2221 * did not flush any fragment so far, so just let it queue up.
2223 if (console_seq < log_next_seq && !cont.cons)
2226 len = cont_print_text(text, size);
2227 #ifndef CONFIG_PREEMPT_RT_FULL
2228 raw_spin_unlock(&logbuf_lock);
2229 stop_critical_timings();
2230 call_console_drivers(cont.level, text, len);
2231 start_critical_timings();
2232 local_irq_restore(flags);
2234 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2235 call_console_drivers(cont.level, text, len);
2239 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2243 * console_unlock - unlock the console system
2245 * Releases the console_lock which the caller holds on the console system
2246 * and the console driver list.
2248 * While the console_lock was held, console output may have been buffered
2249 * by printk(). If this is the case, console_unlock(); emits
2250 * the output prior to releasing the lock.
2252 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2254 * console_unlock(); may be called from any context.
2256 void console_unlock(void)
2258 static char text[LOG_LINE_MAX + PREFIX_MAX];
2259 static u64 seen_seq;
2260 unsigned long flags;
2261 bool wake_klogd = false;
2264 if (console_suspended) {
2269 console_may_schedule = 0;
2271 /* flush buffered message fragment immediately to console */
2272 console_cont_flush(text, sizeof(text));
2275 struct printk_log *msg;
2279 raw_spin_lock_irqsave(&logbuf_lock, flags);
2280 if (seen_seq != log_next_seq) {
2282 seen_seq = log_next_seq;
2285 if (console_seq < log_first_seq) {
2286 len = sprintf(text, "** %u printk messages dropped ** ",
2287 (unsigned)(log_first_seq - console_seq));
2289 /* messages are gone, move to first one */
2290 console_seq = log_first_seq;
2291 console_idx = log_first_idx;
2297 if (console_seq == log_next_seq)
2300 msg = log_from_idx(console_idx);
2301 if (msg->flags & LOG_NOCONS) {
2303 * Skip record we have buffered and already printed
2304 * directly to the console when we received it.
2306 console_idx = log_next(console_idx);
2309 * We will get here again when we register a new
2310 * CON_PRINTBUFFER console. Clear the flag so we
2311 * will properly dump everything later.
2313 msg->flags &= ~LOG_NOCONS;
2314 console_prev = msg->flags;
2319 len += msg_print_text(msg, console_prev, false,
2320 text + len, sizeof(text) - len);
2321 console_idx = log_next(console_idx);
2323 console_prev = msg->flags;
2324 #ifdef CONFIG_PREEMPT_RT_FULL
2325 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2326 call_console_drivers(level, text, len);
2328 raw_spin_unlock(&logbuf_lock);
2330 stop_critical_timings(); /* don't trace print latency */
2331 call_console_drivers(level, text, len);
2332 start_critical_timings();
2333 local_irq_restore(flags);
2338 /* Release the exclusive_console once it is used */
2339 if (unlikely(exclusive_console))
2340 exclusive_console = NULL;
2342 raw_spin_unlock(&logbuf_lock);
2347 * Someone could have filled up the buffer again, so re-check if there's
2348 * something to flush. In case we cannot trylock the console_sem again,
2349 * there's a new owner and the console_unlock() from them will do the
2350 * flush, no worries.
2352 raw_spin_lock(&logbuf_lock);
2353 retry = console_seq != log_next_seq;
2354 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2356 if (retry && console_trylock())
2362 EXPORT_SYMBOL(console_unlock);
2365 * console_conditional_schedule - yield the CPU if required
2367 * If the console code is currently allowed to sleep, and
2368 * if this CPU should yield the CPU to another task, do
2371 * Must be called within console_lock();.
2373 void __sched console_conditional_schedule(void)
2375 if (console_may_schedule)
2378 EXPORT_SYMBOL(console_conditional_schedule);
2380 void console_unblank(void)
2385 * console_unblank can no longer be called in interrupt context unless
2386 * oops_in_progress is set to 1..
2388 if (oops_in_progress) {
2389 if (down_trylock_console_sem() != 0)
2395 console_may_schedule = 0;
2397 if ((c->flags & CON_ENABLED) && c->unblank)
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;
2588 if (newcon->flags & CON_PRINTBUFFER) {
2590 * console_unlock(); will print out the buffered messages
2593 raw_spin_lock_irqsave(&logbuf_lock, flags);
2594 console_seq = syslog_seq;
2595 console_idx = syslog_idx;
2596 console_prev = syslog_prev;
2597 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2599 * We're about to replay the log buffer. Only do this to the
2600 * just-registered console to avoid excessive message spam to
2601 * the already-registered consoles.
2603 exclusive_console = newcon;
2606 console_sysfs_notify();
2609 * By unregistering the bootconsoles after we enable the real console
2610 * we get the "console xxx enabled" message on all the consoles -
2611 * boot consoles, real consoles, etc - this is to ensure that end
2612 * users know there might be something in the kernel's log buffer that
2613 * went to the bootconsole (that they do not see on the real console)
2615 pr_info("%sconsole [%s%d] enabled\n",
2616 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2617 newcon->name, newcon->index);
2619 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2621 /* We need to iterate through all boot consoles, to make
2622 * sure we print everything out, before we unregister them.
2624 for_each_console(bcon)
2625 if (bcon->flags & CON_BOOT)
2626 unregister_console(bcon);
2629 EXPORT_SYMBOL(register_console);
2631 int unregister_console(struct console *console)
2633 struct console *a, *b;
2636 pr_info("%sconsole [%s%d] disabled\n",
2637 (console->flags & CON_BOOT) ? "boot" : "" ,
2638 console->name, console->index);
2640 res = _braille_unregister_console(console);
2646 if (console_drivers == console) {
2647 console_drivers=console->next;
2649 } else if (console_drivers) {
2650 for (a=console_drivers->next, b=console_drivers ;
2651 a; b=a, a=b->next) {
2661 * If this isn't the last console and it has CON_CONSDEV set, we
2662 * need to set it on the next preferred console.
2664 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2665 console_drivers->flags |= CON_CONSDEV;
2667 console->flags &= ~CON_ENABLED;
2669 console_sysfs_notify();
2672 EXPORT_SYMBOL(unregister_console);
2674 static int __init printk_late_init(void)
2676 struct console *con;
2678 for_each_console(con) {
2679 if (!keep_bootcon && con->flags & CON_BOOT) {
2680 unregister_console(con);
2683 hotcpu_notifier(console_cpu_notify, 0);
2686 late_initcall(printk_late_init);
2688 #if defined CONFIG_PRINTK
2690 * Delayed printk version, for scheduler-internal messages:
2692 #define PRINTK_PENDING_WAKEUP 0x01
2693 #define PRINTK_PENDING_OUTPUT 0x02
2695 static DEFINE_PER_CPU(int, printk_pending);
2697 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2699 int pending = __this_cpu_xchg(printk_pending, 0);
2701 if (pending & PRINTK_PENDING_OUTPUT) {
2702 /* If trylock fails, someone else is doing the printing */
2703 if (console_trylock())
2707 if (pending & PRINTK_PENDING_WAKEUP)
2708 wake_up_interruptible(&log_wait);
2711 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2712 .func = wake_up_klogd_work_func,
2713 .flags = IRQ_WORK_LAZY,
2716 void wake_up_klogd(void)
2719 if (waitqueue_active(&log_wait)) {
2720 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2721 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2726 int printk_deferred(const char *fmt, ...)
2732 va_start(args, fmt);
2733 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2736 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2737 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2744 * printk rate limiting, lifted from the networking subsystem.
2746 * This enforces a rate limit: not more than 10 kernel messages
2747 * every 5s to make a denial-of-service attack impossible.
2749 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2751 int __printk_ratelimit(const char *func)
2753 return ___ratelimit(&printk_ratelimit_state, func);
2755 EXPORT_SYMBOL(__printk_ratelimit);
2758 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2759 * @caller_jiffies: pointer to caller's state
2760 * @interval_msecs: minimum interval between prints
2762 * printk_timed_ratelimit() returns true if more than @interval_msecs
2763 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2766 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2767 unsigned int interval_msecs)
2769 unsigned long elapsed = jiffies - *caller_jiffies;
2771 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2774 *caller_jiffies = jiffies;
2777 EXPORT_SYMBOL(printk_timed_ratelimit);
2779 static DEFINE_SPINLOCK(dump_list_lock);
2780 static LIST_HEAD(dump_list);
2783 * kmsg_dump_register - register a kernel log dumper.
2784 * @dumper: pointer to the kmsg_dumper structure
2786 * Adds a kernel log dumper to the system. The dump callback in the
2787 * structure will be called when the kernel oopses or panics and must be
2788 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2790 int kmsg_dump_register(struct kmsg_dumper *dumper)
2792 unsigned long flags;
2795 /* The dump callback needs to be set */
2799 spin_lock_irqsave(&dump_list_lock, flags);
2800 /* Don't allow registering multiple times */
2801 if (!dumper->registered) {
2802 dumper->registered = 1;
2803 list_add_tail_rcu(&dumper->list, &dump_list);
2806 spin_unlock_irqrestore(&dump_list_lock, flags);
2810 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2813 * kmsg_dump_unregister - unregister a kmsg dumper.
2814 * @dumper: pointer to the kmsg_dumper structure
2816 * Removes a dump device from the system. Returns zero on success and
2817 * %-EINVAL otherwise.
2819 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2821 unsigned long flags;
2824 spin_lock_irqsave(&dump_list_lock, flags);
2825 if (dumper->registered) {
2826 dumper->registered = 0;
2827 list_del_rcu(&dumper->list);
2830 spin_unlock_irqrestore(&dump_list_lock, flags);
2835 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2837 static bool always_kmsg_dump;
2838 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2841 * kmsg_dump - dump kernel log to kernel message dumpers.
2842 * @reason: the reason (oops, panic etc) for dumping
2844 * Call each of the registered dumper's dump() callback, which can
2845 * retrieve the kmsg records with kmsg_dump_get_line() or
2846 * kmsg_dump_get_buffer().
2848 void kmsg_dump(enum kmsg_dump_reason reason)
2850 struct kmsg_dumper *dumper;
2851 unsigned long flags;
2853 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2857 list_for_each_entry_rcu(dumper, &dump_list, list) {
2858 if (dumper->max_reason && reason > dumper->max_reason)
2861 /* initialize iterator with data about the stored records */
2862 dumper->active = true;
2864 raw_spin_lock_irqsave(&logbuf_lock, flags);
2865 dumper->cur_seq = clear_seq;
2866 dumper->cur_idx = clear_idx;
2867 dumper->next_seq = log_next_seq;
2868 dumper->next_idx = log_next_idx;
2869 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2871 /* invoke dumper which will iterate over records */
2872 dumper->dump(dumper, reason);
2874 /* reset iterator */
2875 dumper->active = false;
2881 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2882 * @dumper: registered kmsg dumper
2883 * @syslog: include the "<4>" prefixes
2884 * @line: buffer to copy the line to
2885 * @size: maximum size of the buffer
2886 * @len: length of line placed into buffer
2888 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2889 * record, and copy one record into the provided buffer.
2891 * Consecutive calls will return the next available record moving
2892 * towards the end of the buffer with the youngest messages.
2894 * A return value of FALSE indicates that there are no more records to
2897 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2899 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2900 char *line, size_t size, size_t *len)
2902 struct printk_log *msg;
2906 if (!dumper->active)
2909 if (dumper->cur_seq < log_first_seq) {
2910 /* messages are gone, move to first available one */
2911 dumper->cur_seq = log_first_seq;
2912 dumper->cur_idx = log_first_idx;
2916 if (dumper->cur_seq >= log_next_seq)
2919 msg = log_from_idx(dumper->cur_idx);
2920 l = msg_print_text(msg, 0, syslog, line, size);
2922 dumper->cur_idx = log_next(dumper->cur_idx);
2932 * kmsg_dump_get_line - retrieve one kmsg log line
2933 * @dumper: registered kmsg dumper
2934 * @syslog: include the "<4>" prefixes
2935 * @line: buffer to copy the line to
2936 * @size: maximum size of the buffer
2937 * @len: length of line placed into buffer
2939 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2940 * record, and copy one record into the provided buffer.
2942 * Consecutive calls will return the next available record moving
2943 * towards the end of the buffer with the youngest messages.
2945 * A return value of FALSE indicates that there are no more records to
2948 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2949 char *line, size_t size, size_t *len)
2951 unsigned long flags;
2954 raw_spin_lock_irqsave(&logbuf_lock, flags);
2955 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2956 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2960 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2963 * kmsg_dump_get_buffer - copy kmsg log lines
2964 * @dumper: registered kmsg dumper
2965 * @syslog: include the "<4>" prefixes
2966 * @buf: 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 end of the kmsg buffer and fill the provided buffer
2971 * with as many of the the *youngest* kmsg records that fit into it.
2972 * If the buffer is large enough, all available kmsg records will be
2973 * copied with a single call.
2975 * Consecutive calls will fill the buffer with the next block of
2976 * available older records, not including the earlier retrieved ones.
2978 * A return value of FALSE indicates that there are no more records to
2981 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2982 char *buf, size_t size, size_t *len)
2984 unsigned long flags;
2989 enum log_flags prev;
2993 if (!dumper->active)
2996 raw_spin_lock_irqsave(&logbuf_lock, flags);
2997 if (dumper->cur_seq < log_first_seq) {
2998 /* messages are gone, move to first available one */
2999 dumper->cur_seq = log_first_seq;
3000 dumper->cur_idx = log_first_idx;
3004 if (dumper->cur_seq >= dumper->next_seq) {
3005 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3009 /* calculate length of entire buffer */
3010 seq = dumper->cur_seq;
3011 idx = dumper->cur_idx;
3013 while (seq < dumper->next_seq) {
3014 struct printk_log *msg = log_from_idx(idx);
3016 l += msg_print_text(msg, prev, true, NULL, 0);
3017 idx = log_next(idx);
3022 /* move first record forward until length fits into the buffer */
3023 seq = dumper->cur_seq;
3024 idx = dumper->cur_idx;
3026 while (l > size && seq < dumper->next_seq) {
3027 struct printk_log *msg = log_from_idx(idx);
3029 l -= msg_print_text(msg, prev, true, NULL, 0);
3030 idx = log_next(idx);
3035 /* last message in next interation */
3040 while (seq < dumper->next_seq) {
3041 struct printk_log *msg = log_from_idx(idx);
3043 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
3044 idx = log_next(idx);
3049 dumper->next_seq = next_seq;
3050 dumper->next_idx = next_idx;
3052 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3058 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3061 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3062 * @dumper: registered kmsg dumper
3064 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3065 * kmsg_dump_get_buffer() can be called again and used multiple
3066 * times within the same dumper.dump() callback.
3068 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3070 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3072 dumper->cur_seq = clear_seq;
3073 dumper->cur_idx = clear_idx;
3074 dumper->next_seq = log_next_seq;
3075 dumper->next_idx = log_next_idx;
3079 * kmsg_dump_rewind - reset the interator
3080 * @dumper: registered kmsg dumper
3082 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3083 * kmsg_dump_get_buffer() can be called again and used multiple
3084 * times within the same dumper.dump() callback.
3086 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3088 unsigned long flags;
3090 raw_spin_lock_irqsave(&logbuf_lock, flags);
3091 kmsg_dump_rewind_nolock(dumper);
3092 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3094 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3096 static char dump_stack_arch_desc_str[128];
3099 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3100 * @fmt: printf-style format string
3101 * @...: arguments for the format string
3103 * The configured string will be printed right after utsname during task
3104 * dumps. Usually used to add arch-specific system identifiers. If an
3105 * arch wants to make use of such an ID string, it should initialize this
3106 * as soon as possible during boot.
3108 void __init dump_stack_set_arch_desc(const char *fmt, ...)
3112 va_start(args, fmt);
3113 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3119 * dump_stack_print_info - print generic debug info for dump_stack()
3120 * @log_lvl: log level
3122 * Arch-specific dump_stack() implementations can use this function to
3123 * print out the same debug information as the generic dump_stack().
3125 void dump_stack_print_info(const char *log_lvl)
3127 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3128 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3129 print_tainted(), init_utsname()->release,
3130 (int)strcspn(init_utsname()->version, " "),
3131 init_utsname()->version);
3133 if (dump_stack_arch_desc_str[0] != '\0')
3134 printk("%sHardware name: %s\n",
3135 log_lvl, dump_stack_arch_desc_str);
3137 print_worker_info(log_lvl, current);
3141 * show_regs_print_info - print generic debug info for show_regs()
3142 * @log_lvl: log level
3144 * show_regs() implementations can use this function to print out generic
3145 * debug information.
3147 void show_regs_print_info(const char *log_lvl)
3149 dump_stack_print_info(log_lvl);
3151 printk("%stask: %p ti: %p task.ti: %p\n",
3152 log_lvl, current, current_thread_info(),
3153 task_thread_info(current));