2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/memblock.h>
35 #include <linux/aio.h>
36 #include <linux/syscalls.h>
37 #include <linux/kexec.h>
38 #include <linux/kdb.h>
39 #include <linux/ratelimit.h>
40 #include <linux/kmsg_dump.h>
41 #include <linux/syslog.h>
42 #include <linux/cpu.h>
43 #include <linux/notifier.h>
44 #include <linux/rculist.h>
45 #include <linux/poll.h>
46 #include <linux/irq_work.h>
47 #include <linux/utsname.h>
48 #include <linux/ctype.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 */
65 /* Deferred messaged from sched code are marked by this special level */
66 #define SCHED_MESSAGE_LOGLEVEL -2
69 * Low level drivers may need that to know if they can schedule in
70 * their unblank() callback or not. So let's export it.
73 EXPORT_SYMBOL(oops_in_progress);
76 * console_sem protects the console_drivers list, and also
77 * provides serialisation for access to the entire console
80 static DEFINE_SEMAPHORE(console_sem);
81 struct console *console_drivers;
82 EXPORT_SYMBOL_GPL(console_drivers);
85 static struct lockdep_map console_lock_dep_map = {
86 .name = "console_lock"
91 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
92 * macros instead of functions so that _RET_IP_ contains useful information.
94 #define down_console_sem() do { \
96 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
99 static int __down_trylock_console_sem(unsigned long ip)
101 if (down_trylock(&console_sem))
103 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
106 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
108 #define up_console_sem() do { \
109 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
114 * This is used for debugging the mess that is the VT code by
115 * keeping track if we have the console semaphore held. It's
116 * definitely not the perfect debug tool (we don't know if _WE_
117 * hold it and are racing, but it helps tracking those weird code
118 * paths in the console code where we end up in places I want
119 * locked without the console sempahore held).
121 static int console_locked, console_suspended;
124 * If exclusive_console is non-NULL then only this console is to be printed to.
126 static struct console *exclusive_console;
129 * Array of consoles built from command line options (console=)
132 #define MAX_CMDLINECONSOLES 8
134 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
136 static int selected_console = -1;
137 static int preferred_console = -1;
138 int console_set_on_cmdline;
139 EXPORT_SYMBOL(console_set_on_cmdline);
141 /* Flag: console code may call schedule() */
142 static int console_may_schedule;
145 * The printk log buffer consists of a chain of concatenated variable
146 * length records. Every record starts with a record header, containing
147 * the overall length of the record.
149 * The heads to the first and last entry in the buffer, as well as the
150 * sequence numbers of these entries are maintained when messages are
153 * If the heads indicate available messages, the length in the header
154 * tells the start next message. A length == 0 for the next message
155 * indicates a wrap-around to the beginning of the buffer.
157 * Every record carries the monotonic timestamp in microseconds, as well as
158 * the standard userspace syslog level and syslog facility. The usual
159 * kernel messages use LOG_KERN; userspace-injected messages always carry
160 * a matching syslog facility, by default LOG_USER. The origin of every
161 * message can be reliably determined that way.
163 * The human readable log message directly follows the message header. The
164 * length of the message text is stored in the header, the stored message
167 * Optionally, a message can carry a dictionary of properties (key/value pairs),
168 * to provide userspace with a machine-readable message context.
170 * Examples for well-defined, commonly used property names are:
171 * DEVICE=b12:8 device identifier
175 * +sound:card0 subsystem:devname
176 * SUBSYSTEM=pci driver-core subsystem name
178 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
179 * follows directly after a '=' character. Every property is terminated by
180 * a '\0' character. The last property is not terminated.
182 * Example of a message structure:
183 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
184 * 0008 34 00 record is 52 bytes long
185 * 000a 0b 00 text is 11 bytes long
186 * 000c 1f 00 dictionary is 23 bytes long
187 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
188 * 0010 69 74 27 73 20 61 20 6c "it's a l"
190 * 001b 44 45 56 49 43 "DEVIC"
191 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
192 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
194 * 0032 00 00 00 padding to next message header
196 * The 'struct printk_log' buffer header must never be directly exported to
197 * userspace, it is a kernel-private implementation detail that might
198 * need to be changed in the future, when the requirements change.
200 * /dev/kmsg exports the structured data in the following line format:
201 * "level,sequnum,timestamp;<message text>\n"
203 * The optional key/value pairs are attached as continuation lines starting
204 * with a space character and terminated by a newline. All possible
205 * non-prinatable characters are escaped in the "\xff" notation.
207 * Users of the export format should ignore possible additional values
208 * separated by ',', and find the message after the ';' character.
212 LOG_NOCONS = 1, /* already flushed, do not print to console */
213 LOG_NEWLINE = 2, /* text ended with a newline */
214 LOG_PREFIX = 4, /* text started with a prefix */
215 LOG_CONT = 8, /* text is a fragment of a continuation line */
219 u64 ts_nsec; /* timestamp in nanoseconds */
220 u16 len; /* length of entire record */
221 u16 text_len; /* length of text buffer */
222 u16 dict_len; /* length of dictionary buffer */
223 u8 facility; /* syslog facility */
224 u8 flags:5; /* internal record flags */
225 u8 level:3; /* syslog level */
229 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
230 * within the scheduler's rq lock. It must be released before calling
231 * console_unlock() or anything else that might wake up a process.
233 static DEFINE_RAW_SPINLOCK(logbuf_lock);
236 DECLARE_WAIT_QUEUE_HEAD(log_wait);
237 /* the next printk record to read by syslog(READ) or /proc/kmsg */
238 static u64 syslog_seq;
239 static u32 syslog_idx;
240 static enum log_flags syslog_prev;
241 static size_t syslog_partial;
243 /* index and sequence number of the first record stored in the buffer */
244 static u64 log_first_seq;
245 static u32 log_first_idx;
247 /* index and sequence number of the next record to store in the buffer */
248 static u64 log_next_seq;
249 static u32 log_next_idx;
251 /* the next printk record to write to the console */
252 static u64 console_seq;
253 static u32 console_idx;
254 static enum log_flags console_prev;
256 /* the next printk record to read after the last 'clear' command */
257 static u64 clear_seq;
258 static u32 clear_idx;
260 #define PREFIX_MAX 32
261 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
264 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
267 #define LOG_ALIGN __alignof__(struct printk_log)
269 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
270 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
271 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
272 static char *log_buf = __log_buf;
273 static u32 log_buf_len = __LOG_BUF_LEN;
275 /* Return log buffer address */
276 char *log_buf_addr_get(void)
281 /* Return log buffer size */
282 u32 log_buf_len_get(void)
287 /* human readable text of the record */
288 static char *log_text(const struct printk_log *msg)
290 return (char *)msg + sizeof(struct printk_log);
293 /* optional key/value pair dictionary attached to the record */
294 static char *log_dict(const struct printk_log *msg)
296 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
299 /* get record by index; idx must point to valid msg */
300 static struct printk_log *log_from_idx(u32 idx)
302 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
305 * A length == 0 record is the end of buffer marker. Wrap around and
306 * read the message at the start of the buffer.
309 return (struct printk_log *)log_buf;
313 /* get next record; idx must point to valid msg */
314 static u32 log_next(u32 idx)
316 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
318 /* length == 0 indicates the end of the buffer; wrap */
320 * A length == 0 record is the end of buffer marker. Wrap around and
321 * read the message at the start of the buffer as *this* one, and
322 * return the one after that.
325 msg = (struct printk_log *)log_buf;
328 return idx + msg->len;
332 * Check whether there is enough free space for the given message.
334 * The same values of first_idx and next_idx mean that the buffer
335 * is either empty or full.
337 * If the buffer is empty, we must respect the position of the indexes.
338 * They cannot be reset to the beginning of the buffer.
340 static int logbuf_has_space(u32 msg_size, bool empty)
344 if (log_next_idx > log_first_idx || empty)
345 free = max(log_buf_len - log_next_idx, log_first_idx);
347 free = log_first_idx - log_next_idx;
350 * We need space also for an empty header that signalizes wrapping
353 return free >= msg_size + sizeof(struct printk_log);
356 static int log_make_free_space(u32 msg_size)
358 while (log_first_seq < log_next_seq) {
359 if (logbuf_has_space(msg_size, false))
361 /* drop old messages until we have enough contiguous space */
362 log_first_idx = log_next(log_first_idx);
366 /* sequence numbers are equal, so the log buffer is empty */
367 if (logbuf_has_space(msg_size, true))
373 /* compute the message size including the padding bytes */
374 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
378 size = sizeof(struct printk_log) + text_len + dict_len;
379 *pad_len = (-size) & (LOG_ALIGN - 1);
386 * Define how much of the log buffer we could take at maximum. The value
387 * must be greater than two. Note that only half of the buffer is available
388 * when the index points to the middle.
390 #define MAX_LOG_TAKE_PART 4
391 static const char trunc_msg[] = "<truncated>";
393 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
394 u16 *dict_len, u32 *pad_len)
397 * The message should not take the whole buffer. Otherwise, it might
398 * get removed too soon.
400 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
401 if (*text_len > max_text_len)
402 *text_len = max_text_len;
403 /* enable the warning message */
404 *trunc_msg_len = strlen(trunc_msg);
405 /* disable the "dict" completely */
407 /* compute the size again, count also the warning message */
408 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
411 /* insert record into the buffer, discard old ones, update heads */
412 static int log_store(int facility, int level,
413 enum log_flags flags, u64 ts_nsec,
414 const char *dict, u16 dict_len,
415 const char *text, u16 text_len)
417 struct printk_log *msg;
419 u16 trunc_msg_len = 0;
421 /* number of '\0' padding bytes to next message */
422 size = msg_used_size(text_len, dict_len, &pad_len);
424 if (log_make_free_space(size)) {
425 /* truncate the message if it is too long for empty buffer */
426 size = truncate_msg(&text_len, &trunc_msg_len,
427 &dict_len, &pad_len);
428 /* survive when the log buffer is too small for trunc_msg */
429 if (log_make_free_space(size))
433 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
435 * This message + an additional empty header does not fit
436 * at the end of the buffer. Add an empty header with len == 0
437 * to signify a wrap around.
439 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
444 msg = (struct printk_log *)(log_buf + log_next_idx);
445 memcpy(log_text(msg), text, text_len);
446 msg->text_len = text_len;
448 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
449 msg->text_len += trunc_msg_len;
451 memcpy(log_dict(msg), dict, dict_len);
452 msg->dict_len = dict_len;
453 msg->facility = facility;
454 msg->level = level & 7;
455 msg->flags = flags & 0x1f;
457 msg->ts_nsec = ts_nsec;
459 msg->ts_nsec = local_clock();
460 memset(log_dict(msg) + dict_len, 0, pad_len);
464 log_next_idx += msg->len;
467 return msg->text_len;
470 int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
472 static int syslog_action_restricted(int type)
477 * Unless restricted, we allow "read all" and "get buffer size"
480 return type != SYSLOG_ACTION_READ_ALL &&
481 type != SYSLOG_ACTION_SIZE_BUFFER;
484 static int check_syslog_permissions(int type, bool from_file)
487 * If this is from /proc/kmsg and we've already opened it, then we've
488 * already done the capabilities checks at open time.
490 if (from_file && type != SYSLOG_ACTION_OPEN)
493 if (syslog_action_restricted(type)) {
494 if (capable(CAP_SYSLOG))
497 * For historical reasons, accept CAP_SYS_ADMIN too, with
500 if (capable(CAP_SYS_ADMIN)) {
501 pr_warn_once("%s (%d): Attempt to access syslog with "
502 "CAP_SYS_ADMIN but no CAP_SYSLOG "
504 current->comm, task_pid_nr(current));
509 return security_syslog(type);
513 /* /dev/kmsg - userspace message inject/listen interface */
514 struct devkmsg_user {
522 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
523 unsigned long count, loff_t pos)
527 int level = default_message_loglevel;
528 int facility = 1; /* LOG_USER */
529 size_t len = iov_length(iv, count);
532 if (len > LOG_LINE_MAX)
534 buf = kmalloc(len+1, GFP_KERNEL);
539 for (i = 0; i < count; i++) {
540 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
544 line += iv[i].iov_len;
548 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
549 * the decimal value represents 32bit, the lower 3 bit are the log
550 * level, the rest are the log facility.
552 * If no prefix or no userspace facility is specified, we
553 * enforce LOG_USER, to be able to reliably distinguish
554 * kernel-generated messages from userspace-injected ones.
557 if (line[0] == '<') {
560 i = simple_strtoul(line+1, &endp, 10);
561 if (endp && endp[0] == '>') {
572 printk_emit(facility, level, NULL, 0, "%s", line);
578 static ssize_t devkmsg_read(struct file *file, char __user *buf,
579 size_t count, loff_t *ppos)
581 struct devkmsg_user *user = file->private_data;
582 struct printk_log *msg;
592 ret = mutex_lock_interruptible(&user->lock);
595 raw_spin_lock_irq(&logbuf_lock);
596 while (user->seq == log_next_seq) {
597 if (file->f_flags & O_NONBLOCK) {
599 raw_spin_unlock_irq(&logbuf_lock);
603 raw_spin_unlock_irq(&logbuf_lock);
604 ret = wait_event_interruptible(log_wait,
605 user->seq != log_next_seq);
608 raw_spin_lock_irq(&logbuf_lock);
611 if (user->seq < log_first_seq) {
612 /* our last seen message is gone, return error and reset */
613 user->idx = log_first_idx;
614 user->seq = log_first_seq;
616 raw_spin_unlock_irq(&logbuf_lock);
620 msg = log_from_idx(user->idx);
621 ts_usec = msg->ts_nsec;
622 do_div(ts_usec, 1000);
625 * If we couldn't merge continuation line fragments during the print,
626 * export the stored flags to allow an optional external merge of the
627 * records. Merging the records isn't always neccessarily correct, like
628 * when we hit a race during printing. In most cases though, it produces
629 * better readable output. 'c' in the record flags mark the first
630 * fragment of a line, '+' the following.
632 if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
634 else if ((msg->flags & LOG_CONT) ||
635 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
638 len = sprintf(user->buf, "%u,%llu,%llu,%c;",
639 (msg->facility << 3) | msg->level,
640 user->seq, ts_usec, cont);
641 user->prev = msg->flags;
643 /* escape non-printable characters */
644 for (i = 0; i < msg->text_len; i++) {
645 unsigned char c = log_text(msg)[i];
647 if (c < ' ' || c >= 127 || c == '\\')
648 len += sprintf(user->buf + len, "\\x%02x", c);
650 user->buf[len++] = c;
652 user->buf[len++] = '\n';
657 for (i = 0; i < msg->dict_len; i++) {
658 unsigned char c = log_dict(msg)[i];
661 user->buf[len++] = ' ';
666 user->buf[len++] = '\n';
671 if (c < ' ' || c >= 127 || c == '\\') {
672 len += sprintf(user->buf + len, "\\x%02x", c);
676 user->buf[len++] = c;
678 user->buf[len++] = '\n';
681 user->idx = log_next(user->idx);
683 raw_spin_unlock_irq(&logbuf_lock);
690 if (copy_to_user(buf, user->buf, len)) {
696 mutex_unlock(&user->lock);
700 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
702 struct devkmsg_user *user = file->private_data;
710 raw_spin_lock_irq(&logbuf_lock);
713 /* the first record */
714 user->idx = log_first_idx;
715 user->seq = log_first_seq;
719 * The first record after the last SYSLOG_ACTION_CLEAR,
720 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
721 * changes no global state, and does not clear anything.
723 user->idx = clear_idx;
724 user->seq = clear_seq;
727 /* after the last record */
728 user->idx = log_next_idx;
729 user->seq = log_next_seq;
734 raw_spin_unlock_irq(&logbuf_lock);
738 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
740 struct devkmsg_user *user = file->private_data;
744 return POLLERR|POLLNVAL;
746 poll_wait(file, &log_wait, wait);
748 raw_spin_lock_irq(&logbuf_lock);
749 if (user->seq < log_next_seq) {
750 /* return error when data has vanished underneath us */
751 if (user->seq < log_first_seq)
752 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
754 ret = POLLIN|POLLRDNORM;
756 raw_spin_unlock_irq(&logbuf_lock);
761 static int devkmsg_open(struct inode *inode, struct file *file)
763 struct devkmsg_user *user;
766 /* write-only does not need any file context */
767 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
770 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
775 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
779 mutex_init(&user->lock);
781 raw_spin_lock_irq(&logbuf_lock);
782 user->idx = log_first_idx;
783 user->seq = log_first_seq;
784 raw_spin_unlock_irq(&logbuf_lock);
786 file->private_data = user;
790 static int devkmsg_release(struct inode *inode, struct file *file)
792 struct devkmsg_user *user = file->private_data;
797 mutex_destroy(&user->lock);
802 const struct file_operations kmsg_fops = {
803 .open = devkmsg_open,
804 .read = devkmsg_read,
805 .aio_write = devkmsg_writev,
806 .llseek = devkmsg_llseek,
807 .poll = devkmsg_poll,
808 .release = devkmsg_release,
813 * This appends the listed symbols to /proc/vmcore
815 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
816 * obtain access to symbols that are otherwise very difficult to locate. These
817 * symbols are specifically used so that utilities can access and extract the
818 * dmesg log from a vmcore file after a crash.
820 void log_buf_kexec_setup(void)
822 VMCOREINFO_SYMBOL(log_buf);
823 VMCOREINFO_SYMBOL(log_buf_len);
824 VMCOREINFO_SYMBOL(log_first_idx);
825 VMCOREINFO_SYMBOL(log_next_idx);
827 * Export struct printk_log size and field offsets. User space tools can
828 * parse it and detect any changes to structure down the line.
830 VMCOREINFO_STRUCT_SIZE(printk_log);
831 VMCOREINFO_OFFSET(printk_log, ts_nsec);
832 VMCOREINFO_OFFSET(printk_log, len);
833 VMCOREINFO_OFFSET(printk_log, text_len);
834 VMCOREINFO_OFFSET(printk_log, dict_len);
838 /* requested log_buf_len from kernel cmdline */
839 static unsigned long __initdata new_log_buf_len;
841 /* we practice scaling the ring buffer by powers of 2 */
842 static void __init log_buf_len_update(unsigned size)
845 size = roundup_pow_of_two(size);
846 if (size > log_buf_len)
847 new_log_buf_len = size;
850 /* save requested log_buf_len since it's too early to process it */
851 static int __init log_buf_len_setup(char *str)
853 unsigned size = memparse(str, &str);
855 log_buf_len_update(size);
859 early_param("log_buf_len", log_buf_len_setup);
861 static void __init log_buf_add_cpu(void)
863 unsigned int cpu_extra;
866 * archs should set up cpu_possible_bits properly with
867 * set_cpu_possible() after setup_arch() but just in
868 * case lets ensure this is valid.
870 if (num_possible_cpus() == 1)
873 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
875 /* by default this will only continue through for large > 64 CPUs */
876 if (cpu_extra <= __LOG_BUF_LEN / 2)
879 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
880 __LOG_CPU_MAX_BUF_LEN);
881 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
883 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
885 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
888 void __init setup_log_buf(int early)
894 if (log_buf != __log_buf)
897 if (!early && !new_log_buf_len)
900 if (!new_log_buf_len)
905 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
907 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
911 if (unlikely(!new_log_buf)) {
912 pr_err("log_buf_len: %ld bytes not available\n",
917 raw_spin_lock_irqsave(&logbuf_lock, flags);
918 log_buf_len = new_log_buf_len;
919 log_buf = new_log_buf;
921 free = __LOG_BUF_LEN - log_next_idx;
922 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
923 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
925 pr_info("log_buf_len: %d bytes\n", log_buf_len);
926 pr_info("early log buf free: %d(%d%%)\n",
927 free, (free * 100) / __LOG_BUF_LEN);
930 static bool __read_mostly ignore_loglevel;
932 static int __init ignore_loglevel_setup(char *str)
934 ignore_loglevel = true;
935 pr_info("debug: ignoring loglevel setting.\n");
940 early_param("ignore_loglevel", ignore_loglevel_setup);
941 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
942 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
943 "print all kernel messages to the console.");
945 #ifdef CONFIG_BOOT_PRINTK_DELAY
947 static int boot_delay; /* msecs delay after each printk during bootup */
948 static unsigned long long loops_per_msec; /* based on boot_delay */
950 static int __init boot_delay_setup(char *str)
954 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
955 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
957 get_option(&str, &boot_delay);
958 if (boot_delay > 10 * 1000)
961 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
962 "HZ: %d, loops_per_msec: %llu\n",
963 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
966 early_param("boot_delay", boot_delay_setup);
968 static void boot_delay_msec(int level)
970 unsigned long long k;
971 unsigned long timeout;
973 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
974 || (level >= console_loglevel && !ignore_loglevel)) {
978 k = (unsigned long long)loops_per_msec * boot_delay;
980 timeout = jiffies + msecs_to_jiffies(boot_delay);
985 * use (volatile) jiffies to prevent
986 * compiler reduction; loop termination via jiffies
987 * is secondary and may or may not happen.
989 if (time_after(jiffies, timeout))
991 touch_nmi_watchdog();
995 static inline void boot_delay_msec(int level)
1000 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1001 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1003 static size_t print_time(u64 ts, char *buf)
1005 unsigned long rem_nsec;
1010 rem_nsec = do_div(ts, 1000000000);
1013 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1015 return sprintf(buf, "[%5lu.%06lu] ",
1016 (unsigned long)ts, rem_nsec / 1000);
1019 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1022 unsigned int prefix = (msg->facility << 3) | msg->level;
1026 len += sprintf(buf, "<%u>", prefix);
1031 else if (prefix > 99)
1033 else if (prefix > 9)
1038 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1042 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1043 bool syslog, char *buf, size_t size)
1045 const char *text = log_text(msg);
1046 size_t text_size = msg->text_len;
1048 bool newline = true;
1051 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1054 if (msg->flags & LOG_CONT) {
1055 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1058 if (!(msg->flags & LOG_NEWLINE))
1063 const char *next = memchr(text, '\n', text_size);
1067 text_len = next - text;
1069 text_size -= next - text;
1071 text_len = text_size;
1075 if (print_prefix(msg, syslog, NULL) +
1076 text_len + 1 >= size - len)
1080 len += print_prefix(msg, syslog, buf + len);
1081 memcpy(buf + len, text, text_len);
1083 if (next || newline)
1086 /* SYSLOG_ACTION_* buffer size only calculation */
1088 len += print_prefix(msg, syslog, NULL);
1090 if (next || newline)
1101 static int syslog_print(char __user *buf, int size)
1104 struct printk_log *msg;
1107 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1115 raw_spin_lock_irq(&logbuf_lock);
1116 if (syslog_seq < log_first_seq) {
1117 /* messages are gone, move to first one */
1118 syslog_seq = log_first_seq;
1119 syslog_idx = log_first_idx;
1123 if (syslog_seq == log_next_seq) {
1124 raw_spin_unlock_irq(&logbuf_lock);
1128 skip = syslog_partial;
1129 msg = log_from_idx(syslog_idx);
1130 n = msg_print_text(msg, syslog_prev, true, text,
1131 LOG_LINE_MAX + PREFIX_MAX);
1132 if (n - syslog_partial <= size) {
1133 /* message fits into buffer, move forward */
1134 syslog_idx = log_next(syslog_idx);
1136 syslog_prev = msg->flags;
1137 n -= syslog_partial;
1140 /* partial read(), remember position */
1142 syslog_partial += n;
1145 raw_spin_unlock_irq(&logbuf_lock);
1150 if (copy_to_user(buf, text + skip, n)) {
1165 static int syslog_print_all(char __user *buf, int size, bool clear)
1170 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1174 raw_spin_lock_irq(&logbuf_lock);
1179 enum log_flags prev;
1181 if (clear_seq < log_first_seq) {
1182 /* messages are gone, move to first available one */
1183 clear_seq = log_first_seq;
1184 clear_idx = log_first_idx;
1188 * Find first record that fits, including all following records,
1189 * into the user-provided buffer for this dump.
1194 while (seq < log_next_seq) {
1195 struct printk_log *msg = log_from_idx(idx);
1197 len += msg_print_text(msg, prev, true, NULL, 0);
1199 idx = log_next(idx);
1203 /* move first record forward until length fits into the buffer */
1207 while (len > size && seq < log_next_seq) {
1208 struct printk_log *msg = log_from_idx(idx);
1210 len -= msg_print_text(msg, prev, true, NULL, 0);
1212 idx = log_next(idx);
1216 /* last message fitting into this dump */
1217 next_seq = log_next_seq;
1220 while (len >= 0 && seq < next_seq) {
1221 struct printk_log *msg = log_from_idx(idx);
1224 textlen = msg_print_text(msg, prev, true, text,
1225 LOG_LINE_MAX + PREFIX_MAX);
1230 idx = log_next(idx);
1234 raw_spin_unlock_irq(&logbuf_lock);
1235 if (copy_to_user(buf + len, text, textlen))
1239 raw_spin_lock_irq(&logbuf_lock);
1241 if (seq < log_first_seq) {
1242 /* messages are gone, move to next one */
1243 seq = log_first_seq;
1244 idx = log_first_idx;
1251 clear_seq = log_next_seq;
1252 clear_idx = log_next_idx;
1254 raw_spin_unlock_irq(&logbuf_lock);
1260 int do_syslog(int type, char __user *buf, int len, bool from_file)
1263 static int saved_console_loglevel = -1;
1266 error = check_syslog_permissions(type, from_file);
1270 error = security_syslog(type);
1275 case SYSLOG_ACTION_CLOSE: /* Close log */
1277 case SYSLOG_ACTION_OPEN: /* Open log */
1279 case SYSLOG_ACTION_READ: /* Read from log */
1281 if (!buf || len < 0)
1286 if (!access_ok(VERIFY_WRITE, buf, len)) {
1290 error = wait_event_interruptible(log_wait,
1291 syslog_seq != log_next_seq);
1294 error = syslog_print(buf, len);
1296 /* Read/clear last kernel messages */
1297 case SYSLOG_ACTION_READ_CLEAR:
1300 /* Read last kernel messages */
1301 case SYSLOG_ACTION_READ_ALL:
1303 if (!buf || len < 0)
1308 if (!access_ok(VERIFY_WRITE, buf, len)) {
1312 error = syslog_print_all(buf, len, clear);
1314 /* Clear ring buffer */
1315 case SYSLOG_ACTION_CLEAR:
1316 syslog_print_all(NULL, 0, true);
1318 /* Disable logging to console */
1319 case SYSLOG_ACTION_CONSOLE_OFF:
1320 if (saved_console_loglevel == -1)
1321 saved_console_loglevel = console_loglevel;
1322 console_loglevel = minimum_console_loglevel;
1324 /* Enable logging to console */
1325 case SYSLOG_ACTION_CONSOLE_ON:
1326 if (saved_console_loglevel != -1) {
1327 console_loglevel = saved_console_loglevel;
1328 saved_console_loglevel = -1;
1331 /* Set level of messages printed to console */
1332 case SYSLOG_ACTION_CONSOLE_LEVEL:
1334 if (len < 1 || len > 8)
1336 if (len < minimum_console_loglevel)
1337 len = minimum_console_loglevel;
1338 console_loglevel = len;
1339 /* Implicitly re-enable logging to console */
1340 saved_console_loglevel = -1;
1343 /* Number of chars in the log buffer */
1344 case SYSLOG_ACTION_SIZE_UNREAD:
1345 raw_spin_lock_irq(&logbuf_lock);
1346 if (syslog_seq < log_first_seq) {
1347 /* messages are gone, move to first one */
1348 syslog_seq = log_first_seq;
1349 syslog_idx = log_first_idx;
1355 * Short-cut for poll(/"proc/kmsg") which simply checks
1356 * for pending data, not the size; return the count of
1357 * records, not the length.
1359 error = log_next_seq - syslog_seq;
1361 u64 seq = syslog_seq;
1362 u32 idx = syslog_idx;
1363 enum log_flags prev = syslog_prev;
1366 while (seq < log_next_seq) {
1367 struct printk_log *msg = log_from_idx(idx);
1369 error += msg_print_text(msg, prev, true, NULL, 0);
1370 idx = log_next(idx);
1374 error -= syslog_partial;
1376 raw_spin_unlock_irq(&logbuf_lock);
1378 /* Size of the log buffer */
1379 case SYSLOG_ACTION_SIZE_BUFFER:
1380 error = log_buf_len;
1390 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1392 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1396 * Call the console drivers, asking them to write out
1397 * log_buf[start] to log_buf[end - 1].
1398 * The console_lock must be held.
1400 static void call_console_drivers(int level, const char *text, size_t len)
1402 struct console *con;
1404 trace_console(text, len);
1406 if (level >= console_loglevel && !ignore_loglevel)
1408 if (!console_drivers)
1411 for_each_console(con) {
1412 if (exclusive_console && con != exclusive_console)
1414 if (!(con->flags & CON_ENABLED))
1418 if (!cpu_online(smp_processor_id()) &&
1419 !(con->flags & CON_ANYTIME))
1421 con->write(con, text, len);
1426 * Zap console related locks when oopsing. Only zap at most once
1427 * every 10 seconds, to leave time for slow consoles to print a
1430 static void zap_locks(void)
1432 static unsigned long oops_timestamp;
1434 if (time_after_eq(jiffies, oops_timestamp) &&
1435 !time_after(jiffies, oops_timestamp + 30 * HZ))
1438 oops_timestamp = jiffies;
1441 /* If a crash is occurring, make sure we can't deadlock */
1442 raw_spin_lock_init(&logbuf_lock);
1443 /* And make sure that we print immediately */
1444 sema_init(&console_sem, 1);
1448 * Check if we have any console that is capable of printing while cpu is
1449 * booting or shutting down. Requires console_sem.
1451 static int have_callable_console(void)
1453 struct console *con;
1455 for_each_console(con)
1456 if (con->flags & CON_ANYTIME)
1463 * Can we actually use the console at this time on this cpu?
1465 * Console drivers may assume that per-cpu resources have been allocated. So
1466 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1467 * call them until this CPU is officially up.
1469 static inline int can_use_console(unsigned int cpu)
1471 return cpu_online(cpu) || have_callable_console();
1475 * Try to get console ownership to actually show the kernel
1476 * messages from a 'printk'. Return true (and with the
1477 * console_lock held, and 'console_locked' set) if it
1478 * is successful, false otherwise.
1480 static int console_trylock_for_printk(void)
1482 unsigned int cpu = smp_processor_id();
1484 if (!console_trylock())
1487 * If we can't use the console, we need to release the console
1488 * semaphore by hand to avoid flushing the buffer. We need to hold the
1489 * console semaphore in order to do this test safely.
1491 if (!can_use_console(cpu)) {
1499 int printk_delay_msec __read_mostly;
1501 static inline void printk_delay(void)
1503 if (unlikely(printk_delay_msec)) {
1504 int m = printk_delay_msec;
1508 touch_nmi_watchdog();
1514 * Continuation lines are buffered, and not committed to the record buffer
1515 * until the line is complete, or a race forces it. The line fragments
1516 * though, are printed immediately to the consoles to ensure everything has
1517 * reached the console in case of a kernel crash.
1519 static struct cont {
1520 char buf[LOG_LINE_MAX];
1521 size_t len; /* length == 0 means unused buffer */
1522 size_t cons; /* bytes written to console */
1523 struct task_struct *owner; /* task of first print*/
1524 u64 ts_nsec; /* time of first print */
1525 u8 level; /* log level of first message */
1526 u8 facility; /* log facility of first message */
1527 enum log_flags flags; /* prefix, newline flags */
1528 bool flushed:1; /* buffer sealed and committed */
1531 static void cont_flush(enum log_flags flags)
1540 * If a fragment of this line was directly flushed to the
1541 * console; wait for the console to pick up the rest of the
1542 * line. LOG_NOCONS suppresses a duplicated output.
1544 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1545 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1547 cont.flushed = true;
1550 * If no fragment of this line ever reached the console,
1551 * just submit it to the store and free the buffer.
1553 log_store(cont.facility, cont.level, flags, 0,
1554 NULL, 0, cont.buf, cont.len);
1559 static bool cont_add(int facility, int level, const char *text, size_t len)
1561 if (cont.len && cont.flushed)
1564 if (cont.len + len > sizeof(cont.buf)) {
1565 /* the line gets too long, split it up in separate records */
1566 cont_flush(LOG_CONT);
1571 cont.facility = facility;
1573 cont.owner = current;
1574 cont.ts_nsec = local_clock();
1577 cont.flushed = false;
1580 memcpy(cont.buf + cont.len, text, len);
1583 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1584 cont_flush(LOG_CONT);
1589 static size_t cont_print_text(char *text, size_t size)
1594 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1595 textlen += print_time(cont.ts_nsec, text);
1599 len = cont.len - cont.cons;
1603 memcpy(text + textlen, cont.buf + cont.cons, len);
1605 cont.cons = cont.len;
1609 if (cont.flags & LOG_NEWLINE)
1610 text[textlen++] = '\n';
1611 /* got everything, release buffer */
1617 asmlinkage int vprintk_emit(int facility, int level,
1618 const char *dict, size_t dictlen,
1619 const char *fmt, va_list args)
1621 static int recursion_bug;
1622 static char textbuf[LOG_LINE_MAX];
1623 char *text = textbuf;
1624 size_t text_len = 0;
1625 enum log_flags lflags = 0;
1626 unsigned long flags;
1628 int printed_len = 0;
1629 bool in_sched = false;
1630 /* cpu currently holding logbuf_lock in this function */
1631 static volatile unsigned int logbuf_cpu = UINT_MAX;
1633 if (level == SCHED_MESSAGE_LOGLEVEL) {
1638 boot_delay_msec(level);
1641 /* This stops the holder of console_sem just where we want him */
1642 local_irq_save(flags);
1643 this_cpu = smp_processor_id();
1646 * Ouch, printk recursed into itself!
1648 if (unlikely(logbuf_cpu == this_cpu)) {
1650 * If a crash is occurring during printk() on this CPU,
1651 * then try to get the crash message out but make sure
1652 * we can't deadlock. Otherwise just return to avoid the
1653 * recursion and return - but flag the recursion so that
1654 * it can be printed at the next appropriate moment:
1656 if (!oops_in_progress && !lockdep_recursing(current)) {
1658 local_irq_restore(flags);
1665 raw_spin_lock(&logbuf_lock);
1666 logbuf_cpu = this_cpu;
1668 if (recursion_bug) {
1669 static const char recursion_msg[] =
1670 "BUG: recent printk recursion!";
1673 text_len = strlen(recursion_msg);
1674 /* emit KERN_CRIT message */
1675 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1676 NULL, 0, recursion_msg, text_len);
1680 * The printf needs to come first; we need the syslog
1681 * prefix which might be passed-in as a parameter.
1684 text_len = scnprintf(text, sizeof(textbuf),
1685 KERN_WARNING "[sched_delayed] ");
1687 text_len += vscnprintf(text + text_len,
1688 sizeof(textbuf) - text_len, fmt, args);
1690 /* mark and strip a trailing newline */
1691 if (text_len && text[text_len-1] == '\n') {
1693 lflags |= LOG_NEWLINE;
1696 /* strip kernel syslog prefix and extract log level or control flags */
1697 if (facility == 0) {
1698 int kern_level = printk_get_level(text);
1701 const char *end_of_header = printk_skip_level(text);
1702 switch (kern_level) {
1705 level = kern_level - '0';
1706 case 'd': /* KERN_DEFAULT */
1707 lflags |= LOG_PREFIX;
1710 * No need to check length here because vscnprintf
1711 * put '\0' at the end of the string. Only valid and
1712 * newly printed level is detected.
1714 text_len -= end_of_header - text;
1715 text = (char *)end_of_header;
1720 level = default_message_loglevel;
1723 lflags |= LOG_PREFIX|LOG_NEWLINE;
1725 if (!(lflags & LOG_NEWLINE)) {
1727 * Flush the conflicting buffer. An earlier newline was missing,
1728 * or another task also prints continuation lines.
1730 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1731 cont_flush(LOG_NEWLINE);
1733 /* buffer line if possible, otherwise store it right away */
1734 if (cont_add(facility, level, text, text_len))
1735 printed_len += text_len;
1737 printed_len += log_store(facility, level,
1738 lflags | LOG_CONT, 0,
1739 dict, dictlen, text, text_len);
1741 bool stored = false;
1744 * If an earlier newline was missing and it was the same task,
1745 * either merge it with the current buffer and flush, or if
1746 * there was a race with interrupts (prefix == true) then just
1747 * flush it out and store this line separately.
1748 * If the preceding printk was from a different task and missed
1749 * a newline, flush and append the newline.
1752 if (cont.owner == current && !(lflags & LOG_PREFIX))
1753 stored = cont_add(facility, level, text,
1755 cont_flush(LOG_NEWLINE);
1759 printed_len += text_len;
1761 printed_len += log_store(facility, level, lflags, 0,
1762 dict, dictlen, text, text_len);
1765 logbuf_cpu = UINT_MAX;
1766 raw_spin_unlock(&logbuf_lock);
1768 local_irq_restore(flags);
1770 /* If called from the scheduler, we can not call up(). */
1774 * Disable preemption to avoid being preempted while holding
1775 * console_sem which would prevent anyone from printing to
1781 * Try to acquire and then immediately release the console
1782 * semaphore. The release will print out buffers and wake up
1783 * /dev/kmsg and syslog() users.
1785 if (console_trylock_for_printk())
1793 EXPORT_SYMBOL(vprintk_emit);
1795 asmlinkage int vprintk(const char *fmt, va_list args)
1797 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1799 EXPORT_SYMBOL(vprintk);
1801 asmlinkage int printk_emit(int facility, int level,
1802 const char *dict, size_t dictlen,
1803 const char *fmt, ...)
1808 va_start(args, fmt);
1809 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1814 EXPORT_SYMBOL(printk_emit);
1817 * printk - print a kernel message
1818 * @fmt: format string
1820 * This is printk(). It can be called from any context. We want it to work.
1822 * We try to grab the console_lock. If we succeed, it's easy - we log the
1823 * output and call the console drivers. If we fail to get the semaphore, we
1824 * place the output into the log buffer and return. The current holder of
1825 * the console_sem will notice the new output in console_unlock(); and will
1826 * send it to the consoles before releasing the lock.
1828 * One effect of this deferred printing is that code which calls printk() and
1829 * then changes console_loglevel may break. This is because console_loglevel
1830 * is inspected when the actual printing occurs.
1835 * See the vsnprintf() documentation for format string extensions over C99.
1837 asmlinkage __visible int printk(const char *fmt, ...)
1842 #ifdef CONFIG_KGDB_KDB
1843 if (unlikely(kdb_trap_printk)) {
1844 va_start(args, fmt);
1845 r = vkdb_printf(fmt, args);
1850 va_start(args, fmt);
1851 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1856 EXPORT_SYMBOL(printk);
1858 #else /* CONFIG_PRINTK */
1860 #define LOG_LINE_MAX 0
1861 #define PREFIX_MAX 0
1863 static u64 syslog_seq;
1864 static u32 syslog_idx;
1865 static u64 console_seq;
1866 static u32 console_idx;
1867 static enum log_flags syslog_prev;
1868 static u64 log_first_seq;
1869 static u32 log_first_idx;
1870 static u64 log_next_seq;
1871 static enum log_flags console_prev;
1872 static struct cont {
1878 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1879 static u32 log_next(u32 idx) { return 0; }
1880 static void call_console_drivers(int level, const char *text, size_t len) {}
1881 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1882 bool syslog, char *buf, size_t size) { return 0; }
1883 static size_t cont_print_text(char *text, size_t size) { return 0; }
1885 #endif /* CONFIG_PRINTK */
1887 #ifdef CONFIG_EARLY_PRINTK
1888 struct console *early_console;
1890 void early_vprintk(const char *fmt, va_list ap)
1892 if (early_console) {
1894 int n = vscnprintf(buf, sizeof(buf), fmt, ap);
1896 early_console->write(early_console, buf, n);
1900 asmlinkage __visible void early_printk(const char *fmt, ...)
1905 early_vprintk(fmt, ap);
1910 static int __add_preferred_console(char *name, int idx, char *options,
1913 struct console_cmdline *c;
1917 * See if this tty is not yet registered, and
1918 * if we have a slot free.
1920 for (i = 0, c = console_cmdline;
1921 i < MAX_CMDLINECONSOLES && c->name[0];
1923 if (strcmp(c->name, name) == 0 && c->index == idx) {
1925 selected_console = i;
1929 if (i == MAX_CMDLINECONSOLES)
1932 selected_console = i;
1933 strlcpy(c->name, name, sizeof(c->name));
1934 c->options = options;
1935 braille_set_options(c, brl_options);
1941 * Set up a console. Called via do_early_param() in init/main.c
1942 * for each "console=" parameter in the boot command line.
1944 static int __init console_setup(char *str)
1946 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
1947 char *s, *options, *brl_options = NULL;
1950 if (_braille_console_setup(&str, &brl_options))
1954 * Decode str into name, index, options.
1956 if (str[0] >= '0' && str[0] <= '9') {
1957 strcpy(buf, "ttyS");
1958 strncpy(buf + 4, str, sizeof(buf) - 5);
1960 strncpy(buf, str, sizeof(buf) - 1);
1962 buf[sizeof(buf) - 1] = 0;
1963 options = strchr(str, ',');
1967 if (!strcmp(str, "ttya"))
1968 strcpy(buf, "ttyS0");
1969 if (!strcmp(str, "ttyb"))
1970 strcpy(buf, "ttyS1");
1972 for (s = buf; *s; s++)
1973 if (isdigit(*s) || *s == ',')
1975 idx = simple_strtoul(s, NULL, 10);
1978 __add_preferred_console(buf, idx, options, brl_options);
1979 console_set_on_cmdline = 1;
1982 __setup("console=", console_setup);
1985 * add_preferred_console - add a device to the list of preferred consoles.
1986 * @name: device name
1987 * @idx: device index
1988 * @options: options for this console
1990 * The last preferred console added will be used for kernel messages
1991 * and stdin/out/err for init. Normally this is used by console_setup
1992 * above to handle user-supplied console arguments; however it can also
1993 * be used by arch-specific code either to override the user or more
1994 * commonly to provide a default console (ie from PROM variables) when
1995 * the user has not supplied one.
1997 int add_preferred_console(char *name, int idx, char *options)
1999 return __add_preferred_console(name, idx, options, NULL);
2002 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
2004 struct console_cmdline *c;
2007 for (i = 0, c = console_cmdline;
2008 i < MAX_CMDLINECONSOLES && c->name[0];
2010 if (strcmp(c->name, name) == 0 && c->index == idx) {
2011 strlcpy(c->name, name_new, sizeof(c->name));
2012 c->options = options;
2020 bool console_suspend_enabled = true;
2021 EXPORT_SYMBOL(console_suspend_enabled);
2023 static int __init console_suspend_disable(char *str)
2025 console_suspend_enabled = false;
2028 __setup("no_console_suspend", console_suspend_disable);
2029 module_param_named(console_suspend, console_suspend_enabled,
2030 bool, S_IRUGO | S_IWUSR);
2031 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2032 " and hibernate operations");
2035 * suspend_console - suspend the console subsystem
2037 * This disables printk() while we go into suspend states
2039 void suspend_console(void)
2041 if (!console_suspend_enabled)
2043 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2045 console_suspended = 1;
2049 void resume_console(void)
2051 if (!console_suspend_enabled)
2054 console_suspended = 0;
2059 * console_cpu_notify - print deferred console messages after CPU hotplug
2060 * @self: notifier struct
2061 * @action: CPU hotplug event
2064 * If printk() is called from a CPU that is not online yet, the messages
2065 * will be spooled but will not show up on the console. This function is
2066 * called when a new CPU comes online (or fails to come up), and ensures
2067 * that any such output gets printed.
2069 static int console_cpu_notify(struct notifier_block *self,
2070 unsigned long action, void *hcpu)
2075 case CPU_DOWN_FAILED:
2076 case CPU_UP_CANCELED:
2084 * console_lock - lock the console system for exclusive use.
2086 * Acquires a lock which guarantees that the caller has
2087 * exclusive access to the console system and the console_drivers list.
2089 * Can sleep, returns nothing.
2091 void console_lock(void)
2096 if (console_suspended)
2099 console_may_schedule = 1;
2101 EXPORT_SYMBOL(console_lock);
2104 * console_trylock - try to lock the console system for exclusive use.
2106 * Try to acquire a lock which guarantees that the caller has exclusive
2107 * access to the console system and the console_drivers list.
2109 * returns 1 on success, and 0 on failure to acquire the lock.
2111 int console_trylock(void)
2113 if (down_trylock_console_sem())
2115 if (console_suspended) {
2120 console_may_schedule = 0;
2123 EXPORT_SYMBOL(console_trylock);
2125 int is_console_locked(void)
2127 return console_locked;
2130 static void console_cont_flush(char *text, size_t size)
2132 unsigned long flags;
2135 raw_spin_lock_irqsave(&logbuf_lock, flags);
2141 * We still queue earlier records, likely because the console was
2142 * busy. The earlier ones need to be printed before this one, we
2143 * did not flush any fragment so far, so just let it queue up.
2145 if (console_seq < log_next_seq && !cont.cons)
2148 len = cont_print_text(text, size);
2149 raw_spin_unlock(&logbuf_lock);
2150 stop_critical_timings();
2151 call_console_drivers(cont.level, text, len);
2152 start_critical_timings();
2153 local_irq_restore(flags);
2156 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2160 * console_unlock - unlock the console system
2162 * Releases the console_lock which the caller holds on the console system
2163 * and the console driver list.
2165 * While the console_lock was held, console output may have been buffered
2166 * by printk(). If this is the case, console_unlock(); emits
2167 * the output prior to releasing the lock.
2169 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2171 * console_unlock(); may be called from any context.
2173 void console_unlock(void)
2175 static char text[LOG_LINE_MAX + PREFIX_MAX];
2176 static u64 seen_seq;
2177 unsigned long flags;
2178 bool wake_klogd = false;
2181 if (console_suspended) {
2186 console_may_schedule = 0;
2188 /* flush buffered message fragment immediately to console */
2189 console_cont_flush(text, sizeof(text));
2192 struct printk_log *msg;
2196 raw_spin_lock_irqsave(&logbuf_lock, flags);
2197 if (seen_seq != log_next_seq) {
2199 seen_seq = log_next_seq;
2202 if (console_seq < log_first_seq) {
2203 len = sprintf(text, "** %u printk messages dropped ** ",
2204 (unsigned)(log_first_seq - console_seq));
2206 /* messages are gone, move to first one */
2207 console_seq = log_first_seq;
2208 console_idx = log_first_idx;
2214 if (console_seq == log_next_seq)
2217 msg = log_from_idx(console_idx);
2218 if (msg->flags & LOG_NOCONS) {
2220 * Skip record we have buffered and already printed
2221 * directly to the console when we received it.
2223 console_idx = log_next(console_idx);
2226 * We will get here again when we register a new
2227 * CON_PRINTBUFFER console. Clear the flag so we
2228 * will properly dump everything later.
2230 msg->flags &= ~LOG_NOCONS;
2231 console_prev = msg->flags;
2236 len += msg_print_text(msg, console_prev, false,
2237 text + len, sizeof(text) - len);
2238 console_idx = log_next(console_idx);
2240 console_prev = msg->flags;
2241 raw_spin_unlock(&logbuf_lock);
2243 stop_critical_timings(); /* don't trace print latency */
2244 call_console_drivers(level, text, len);
2245 start_critical_timings();
2246 local_irq_restore(flags);
2250 /* Release the exclusive_console once it is used */
2251 if (unlikely(exclusive_console))
2252 exclusive_console = NULL;
2254 raw_spin_unlock(&logbuf_lock);
2259 * Someone could have filled up the buffer again, so re-check if there's
2260 * something to flush. In case we cannot trylock the console_sem again,
2261 * there's a new owner and the console_unlock() from them will do the
2262 * flush, no worries.
2264 raw_spin_lock(&logbuf_lock);
2265 retry = console_seq != log_next_seq;
2266 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2268 if (retry && console_trylock())
2274 EXPORT_SYMBOL(console_unlock);
2277 * console_conditional_schedule - yield the CPU if required
2279 * If the console code is currently allowed to sleep, and
2280 * if this CPU should yield the CPU to another task, do
2283 * Must be called within console_lock();.
2285 void __sched console_conditional_schedule(void)
2287 if (console_may_schedule)
2290 EXPORT_SYMBOL(console_conditional_schedule);
2292 void console_unblank(void)
2297 * console_unblank can no longer be called in interrupt context unless
2298 * oops_in_progress is set to 1..
2300 if (oops_in_progress) {
2301 if (down_trylock_console_sem() != 0)
2307 console_may_schedule = 0;
2309 if ((c->flags & CON_ENABLED) && c->unblank)
2315 * Return the console tty driver structure and its associated index
2317 struct tty_driver *console_device(int *index)
2320 struct tty_driver *driver = NULL;
2323 for_each_console(c) {
2326 driver = c->device(c, index);
2335 * Prevent further output on the passed console device so that (for example)
2336 * serial drivers can disable console output before suspending a port, and can
2337 * re-enable output afterwards.
2339 void console_stop(struct console *console)
2342 console->flags &= ~CON_ENABLED;
2345 EXPORT_SYMBOL(console_stop);
2347 void console_start(struct console *console)
2350 console->flags |= CON_ENABLED;
2353 EXPORT_SYMBOL(console_start);
2355 static int __read_mostly keep_bootcon;
2357 static int __init keep_bootcon_setup(char *str)
2360 pr_info("debug: skip boot console de-registration.\n");
2365 early_param("keep_bootcon", keep_bootcon_setup);
2368 * The console driver calls this routine during kernel initialization
2369 * to register the console printing procedure with printk() and to
2370 * print any messages that were printed by the kernel before the
2371 * console driver was initialized.
2373 * This can happen pretty early during the boot process (because of
2374 * early_printk) - sometimes before setup_arch() completes - be careful
2375 * of what kernel features are used - they may not be initialised yet.
2377 * There are two types of consoles - bootconsoles (early_printk) and
2378 * "real" consoles (everything which is not a bootconsole) which are
2379 * handled differently.
2380 * - Any number of bootconsoles can be registered at any time.
2381 * - As soon as a "real" console is registered, all bootconsoles
2382 * will be unregistered automatically.
2383 * - Once a "real" console is registered, any attempt to register a
2384 * bootconsoles will be rejected
2386 void register_console(struct console *newcon)
2389 unsigned long flags;
2390 struct console *bcon = NULL;
2391 struct console_cmdline *c;
2393 if (console_drivers)
2394 for_each_console(bcon)
2395 if (WARN(bcon == newcon,
2396 "console '%s%d' already registered\n",
2397 bcon->name, bcon->index))
2401 * before we register a new CON_BOOT console, make sure we don't
2402 * already have a valid console
2404 if (console_drivers && newcon->flags & CON_BOOT) {
2405 /* find the last or real console */
2406 for_each_console(bcon) {
2407 if (!(bcon->flags & CON_BOOT)) {
2408 pr_info("Too late to register bootconsole %s%d\n",
2409 newcon->name, newcon->index);
2415 if (console_drivers && console_drivers->flags & CON_BOOT)
2416 bcon = console_drivers;
2418 if (preferred_console < 0 || bcon || !console_drivers)
2419 preferred_console = selected_console;
2421 if (newcon->early_setup)
2422 newcon->early_setup();
2425 * See if we want to use this console driver. If we
2426 * didn't select a console we take the first one
2427 * that registers here.
2429 if (preferred_console < 0) {
2430 if (newcon->index < 0)
2432 if (newcon->setup == NULL ||
2433 newcon->setup(newcon, NULL) == 0) {
2434 newcon->flags |= CON_ENABLED;
2435 if (newcon->device) {
2436 newcon->flags |= CON_CONSDEV;
2437 preferred_console = 0;
2443 * See if this console matches one we selected on
2446 for (i = 0, c = console_cmdline;
2447 i < MAX_CMDLINECONSOLES && c->name[0];
2449 if (strcmp(c->name, newcon->name) != 0)
2451 if (newcon->index >= 0 &&
2452 newcon->index != c->index)
2454 if (newcon->index < 0)
2455 newcon->index = c->index;
2457 if (_braille_register_console(newcon, c))
2460 if (newcon->setup &&
2461 newcon->setup(newcon, console_cmdline[i].options) != 0)
2463 newcon->flags |= CON_ENABLED;
2464 newcon->index = c->index;
2465 if (i == selected_console) {
2466 newcon->flags |= CON_CONSDEV;
2467 preferred_console = selected_console;
2472 if (!(newcon->flags & CON_ENABLED))
2476 * If we have a bootconsole, and are switching to a real console,
2477 * don't print everything out again, since when the boot console, and
2478 * the real console are the same physical device, it's annoying to
2479 * see the beginning boot messages twice
2481 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2482 newcon->flags &= ~CON_PRINTBUFFER;
2485 * Put this console in the list - keep the
2486 * preferred driver at the head of the list.
2489 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2490 newcon->next = console_drivers;
2491 console_drivers = newcon;
2493 newcon->next->flags &= ~CON_CONSDEV;
2495 newcon->next = console_drivers->next;
2496 console_drivers->next = newcon;
2498 if (newcon->flags & CON_PRINTBUFFER) {
2500 * console_unlock(); will print out the buffered messages
2503 raw_spin_lock_irqsave(&logbuf_lock, flags);
2504 console_seq = syslog_seq;
2505 console_idx = syslog_idx;
2506 console_prev = syslog_prev;
2507 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2509 * We're about to replay the log buffer. Only do this to the
2510 * just-registered console to avoid excessive message spam to
2511 * the already-registered consoles.
2513 exclusive_console = newcon;
2516 console_sysfs_notify();
2519 * By unregistering the bootconsoles after we enable the real console
2520 * we get the "console xxx enabled" message on all the consoles -
2521 * boot consoles, real consoles, etc - this is to ensure that end
2522 * users know there might be something in the kernel's log buffer that
2523 * went to the bootconsole (that they do not see on the real console)
2525 pr_info("%sconsole [%s%d] enabled\n",
2526 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2527 newcon->name, newcon->index);
2529 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2531 /* We need to iterate through all boot consoles, to make
2532 * sure we print everything out, before we unregister them.
2534 for_each_console(bcon)
2535 if (bcon->flags & CON_BOOT)
2536 unregister_console(bcon);
2539 EXPORT_SYMBOL(register_console);
2541 int unregister_console(struct console *console)
2543 struct console *a, *b;
2546 pr_info("%sconsole [%s%d] disabled\n",
2547 (console->flags & CON_BOOT) ? "boot" : "" ,
2548 console->name, console->index);
2550 res = _braille_unregister_console(console);
2556 if (console_drivers == console) {
2557 console_drivers=console->next;
2559 } else if (console_drivers) {
2560 for (a=console_drivers->next, b=console_drivers ;
2561 a; b=a, a=b->next) {
2571 * If this isn't the last console and it has CON_CONSDEV set, we
2572 * need to set it on the next preferred console.
2574 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2575 console_drivers->flags |= CON_CONSDEV;
2577 console->flags &= ~CON_ENABLED;
2579 console_sysfs_notify();
2582 EXPORT_SYMBOL(unregister_console);
2584 static int __init printk_late_init(void)
2586 struct console *con;
2588 for_each_console(con) {
2589 if (!keep_bootcon && con->flags & CON_BOOT) {
2590 unregister_console(con);
2593 hotcpu_notifier(console_cpu_notify, 0);
2596 late_initcall(printk_late_init);
2598 #if defined CONFIG_PRINTK
2600 * Delayed printk version, for scheduler-internal messages:
2602 #define PRINTK_PENDING_WAKEUP 0x01
2603 #define PRINTK_PENDING_OUTPUT 0x02
2605 static DEFINE_PER_CPU(int, printk_pending);
2607 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2609 int pending = __this_cpu_xchg(printk_pending, 0);
2611 if (pending & PRINTK_PENDING_OUTPUT) {
2612 /* If trylock fails, someone else is doing the printing */
2613 if (console_trylock())
2617 if (pending & PRINTK_PENDING_WAKEUP)
2618 wake_up_interruptible(&log_wait);
2621 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2622 .func = wake_up_klogd_work_func,
2623 .flags = IRQ_WORK_LAZY,
2626 void wake_up_klogd(void)
2629 if (waitqueue_active(&log_wait)) {
2630 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2631 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2636 int printk_deferred(const char *fmt, ...)
2642 va_start(args, fmt);
2643 r = vprintk_emit(0, SCHED_MESSAGE_LOGLEVEL, NULL, 0, fmt, args);
2646 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2647 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2654 * printk rate limiting, lifted from the networking subsystem.
2656 * This enforces a rate limit: not more than 10 kernel messages
2657 * every 5s to make a denial-of-service attack impossible.
2659 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2661 int __printk_ratelimit(const char *func)
2663 return ___ratelimit(&printk_ratelimit_state, func);
2665 EXPORT_SYMBOL(__printk_ratelimit);
2668 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2669 * @caller_jiffies: pointer to caller's state
2670 * @interval_msecs: minimum interval between prints
2672 * printk_timed_ratelimit() returns true if more than @interval_msecs
2673 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2676 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2677 unsigned int interval_msecs)
2679 unsigned long elapsed = jiffies - *caller_jiffies;
2681 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2684 *caller_jiffies = jiffies;
2687 EXPORT_SYMBOL(printk_timed_ratelimit);
2689 static DEFINE_SPINLOCK(dump_list_lock);
2690 static LIST_HEAD(dump_list);
2693 * kmsg_dump_register - register a kernel log dumper.
2694 * @dumper: pointer to the kmsg_dumper structure
2696 * Adds a kernel log dumper to the system. The dump callback in the
2697 * structure will be called when the kernel oopses or panics and must be
2698 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2700 int kmsg_dump_register(struct kmsg_dumper *dumper)
2702 unsigned long flags;
2705 /* The dump callback needs to be set */
2709 spin_lock_irqsave(&dump_list_lock, flags);
2710 /* Don't allow registering multiple times */
2711 if (!dumper->registered) {
2712 dumper->registered = 1;
2713 list_add_tail_rcu(&dumper->list, &dump_list);
2716 spin_unlock_irqrestore(&dump_list_lock, flags);
2720 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2723 * kmsg_dump_unregister - unregister a kmsg dumper.
2724 * @dumper: pointer to the kmsg_dumper structure
2726 * Removes a dump device from the system. Returns zero on success and
2727 * %-EINVAL otherwise.
2729 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2731 unsigned long flags;
2734 spin_lock_irqsave(&dump_list_lock, flags);
2735 if (dumper->registered) {
2736 dumper->registered = 0;
2737 list_del_rcu(&dumper->list);
2740 spin_unlock_irqrestore(&dump_list_lock, flags);
2745 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2747 static bool always_kmsg_dump;
2748 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2751 * kmsg_dump - dump kernel log to kernel message dumpers.
2752 * @reason: the reason (oops, panic etc) for dumping
2754 * Call each of the registered dumper's dump() callback, which can
2755 * retrieve the kmsg records with kmsg_dump_get_line() or
2756 * kmsg_dump_get_buffer().
2758 void kmsg_dump(enum kmsg_dump_reason reason)
2760 struct kmsg_dumper *dumper;
2761 unsigned long flags;
2763 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2767 list_for_each_entry_rcu(dumper, &dump_list, list) {
2768 if (dumper->max_reason && reason > dumper->max_reason)
2771 /* initialize iterator with data about the stored records */
2772 dumper->active = true;
2774 raw_spin_lock_irqsave(&logbuf_lock, flags);
2775 dumper->cur_seq = clear_seq;
2776 dumper->cur_idx = clear_idx;
2777 dumper->next_seq = log_next_seq;
2778 dumper->next_idx = log_next_idx;
2779 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2781 /* invoke dumper which will iterate over records */
2782 dumper->dump(dumper, reason);
2784 /* reset iterator */
2785 dumper->active = false;
2791 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2792 * @dumper: registered kmsg dumper
2793 * @syslog: include the "<4>" prefixes
2794 * @line: buffer to copy the line to
2795 * @size: maximum size of the buffer
2796 * @len: length of line placed into buffer
2798 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2799 * record, and copy one record into the provided buffer.
2801 * Consecutive calls will return the next available record moving
2802 * towards the end of the buffer with the youngest messages.
2804 * A return value of FALSE indicates that there are no more records to
2807 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2809 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2810 char *line, size_t size, size_t *len)
2812 struct printk_log *msg;
2816 if (!dumper->active)
2819 if (dumper->cur_seq < log_first_seq) {
2820 /* messages are gone, move to first available one */
2821 dumper->cur_seq = log_first_seq;
2822 dumper->cur_idx = log_first_idx;
2826 if (dumper->cur_seq >= log_next_seq)
2829 msg = log_from_idx(dumper->cur_idx);
2830 l = msg_print_text(msg, 0, syslog, line, size);
2832 dumper->cur_idx = log_next(dumper->cur_idx);
2842 * kmsg_dump_get_line - retrieve one kmsg log line
2843 * @dumper: registered kmsg dumper
2844 * @syslog: include the "<4>" prefixes
2845 * @line: buffer to copy the line to
2846 * @size: maximum size of the buffer
2847 * @len: length of line placed into buffer
2849 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2850 * record, and copy one record into the provided buffer.
2852 * Consecutive calls will return the next available record moving
2853 * towards the end of the buffer with the youngest messages.
2855 * A return value of FALSE indicates that there are no more records to
2858 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2859 char *line, size_t size, size_t *len)
2861 unsigned long flags;
2864 raw_spin_lock_irqsave(&logbuf_lock, flags);
2865 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2866 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2870 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2873 * kmsg_dump_get_buffer - copy kmsg log lines
2874 * @dumper: registered kmsg dumper
2875 * @syslog: include the "<4>" prefixes
2876 * @buf: buffer to copy the line to
2877 * @size: maximum size of the buffer
2878 * @len: length of line placed into buffer
2880 * Start at the end of the kmsg buffer and fill the provided buffer
2881 * with as many of the the *youngest* kmsg records that fit into it.
2882 * If the buffer is large enough, all available kmsg records will be
2883 * copied with a single call.
2885 * Consecutive calls will fill the buffer with the next block of
2886 * available older records, not including the earlier retrieved ones.
2888 * A return value of FALSE indicates that there are no more records to
2891 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2892 char *buf, size_t size, size_t *len)
2894 unsigned long flags;
2899 enum log_flags prev;
2903 if (!dumper->active)
2906 raw_spin_lock_irqsave(&logbuf_lock, flags);
2907 if (dumper->cur_seq < log_first_seq) {
2908 /* messages are gone, move to first available one */
2909 dumper->cur_seq = log_first_seq;
2910 dumper->cur_idx = log_first_idx;
2914 if (dumper->cur_seq >= dumper->next_seq) {
2915 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2919 /* calculate length of entire buffer */
2920 seq = dumper->cur_seq;
2921 idx = dumper->cur_idx;
2923 while (seq < dumper->next_seq) {
2924 struct printk_log *msg = log_from_idx(idx);
2926 l += msg_print_text(msg, prev, true, NULL, 0);
2927 idx = log_next(idx);
2932 /* move first record forward until length fits into the buffer */
2933 seq = dumper->cur_seq;
2934 idx = dumper->cur_idx;
2936 while (l > size && seq < dumper->next_seq) {
2937 struct printk_log *msg = log_from_idx(idx);
2939 l -= msg_print_text(msg, prev, true, NULL, 0);
2940 idx = log_next(idx);
2945 /* last message in next interation */
2950 while (seq < dumper->next_seq) {
2951 struct printk_log *msg = log_from_idx(idx);
2953 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2954 idx = log_next(idx);
2959 dumper->next_seq = next_seq;
2960 dumper->next_idx = next_idx;
2962 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2968 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2971 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2972 * @dumper: registered kmsg dumper
2974 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2975 * kmsg_dump_get_buffer() can be called again and used multiple
2976 * times within the same dumper.dump() callback.
2978 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2980 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
2982 dumper->cur_seq = clear_seq;
2983 dumper->cur_idx = clear_idx;
2984 dumper->next_seq = log_next_seq;
2985 dumper->next_idx = log_next_idx;
2989 * kmsg_dump_rewind - reset the interator
2990 * @dumper: registered kmsg dumper
2992 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2993 * kmsg_dump_get_buffer() can be called again and used multiple
2994 * times within the same dumper.dump() callback.
2996 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2998 unsigned long flags;
3000 raw_spin_lock_irqsave(&logbuf_lock, flags);
3001 kmsg_dump_rewind_nolock(dumper);
3002 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3004 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3006 static char dump_stack_arch_desc_str[128];
3009 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3010 * @fmt: printf-style format string
3011 * @...: arguments for the format string
3013 * The configured string will be printed right after utsname during task
3014 * dumps. Usually used to add arch-specific system identifiers. If an
3015 * arch wants to make use of such an ID string, it should initialize this
3016 * as soon as possible during boot.
3018 void __init dump_stack_set_arch_desc(const char *fmt, ...)
3022 va_start(args, fmt);
3023 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3029 * dump_stack_print_info - print generic debug info for dump_stack()
3030 * @log_lvl: log level
3032 * Arch-specific dump_stack() implementations can use this function to
3033 * print out the same debug information as the generic dump_stack().
3035 void dump_stack_print_info(const char *log_lvl)
3037 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3038 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3039 print_tainted(), init_utsname()->release,
3040 (int)strcspn(init_utsname()->version, " "),
3041 init_utsname()->version);
3043 if (dump_stack_arch_desc_str[0] != '\0')
3044 printk("%sHardware name: %s\n",
3045 log_lvl, dump_stack_arch_desc_str);
3047 print_worker_info(log_lvl, current);
3051 * show_regs_print_info - print generic debug info for show_regs()
3052 * @log_lvl: log level
3054 * show_regs() implementations can use this function to print out generic
3055 * debug information.
3057 void show_regs_print_info(const char *log_lvl)
3059 dump_stack_print_info(log_lvl);
3061 printk("%stask: %p ti: %p task.ti: %p\n",
3062 log_lvl, current, current_thread_info(),
3063 task_thread_info(current));