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);
508 static void append_char(char **pp, char *e, char c)
514 static ssize_t msg_print_ext_header(char *buf, size_t size,
515 struct printk_log *msg, u64 seq,
516 enum log_flags prev_flags)
518 u64 ts_usec = msg->ts_nsec;
521 do_div(ts_usec, 1000);
524 * If we couldn't merge continuation line fragments during the print,
525 * export the stored flags to allow an optional external merge of the
526 * records. Merging the records isn't always neccessarily correct, like
527 * when we hit a race during printing. In most cases though, it produces
528 * better readable output. 'c' in the record flags mark the first
529 * fragment of a line, '+' the following.
531 if (msg->flags & LOG_CONT && !(prev_flags & LOG_CONT))
533 else if ((msg->flags & LOG_CONT) ||
534 ((prev_flags & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
537 return scnprintf(buf, size, "%u,%llu,%llu,%c;",
538 (msg->facility << 3) | msg->level, seq, ts_usec, cont);
541 static ssize_t msg_print_ext_body(char *buf, size_t size,
542 char *dict, size_t dict_len,
543 char *text, size_t text_len)
545 char *p = buf, *e = buf + size;
548 /* escape non-printable characters */
549 for (i = 0; i < text_len; i++) {
550 unsigned char c = text[i];
552 if (c < ' ' || c >= 127 || c == '\\')
553 p += scnprintf(p, e - p, "\\x%02x", c);
555 append_char(&p, e, c);
557 append_char(&p, e, '\n');
562 for (i = 0; i < dict_len; i++) {
563 unsigned char c = dict[i];
566 append_char(&p, e, ' ');
571 append_char(&p, e, '\n');
576 if (c < ' ' || c >= 127 || c == '\\') {
577 p += scnprintf(p, e - p, "\\x%02x", c);
581 append_char(&p, e, c);
583 append_char(&p, e, '\n');
589 /* /dev/kmsg - userspace message inject/listen interface */
590 struct devkmsg_user {
595 char buf[CONSOLE_EXT_LOG_MAX];
598 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
602 int level = default_message_loglevel;
603 int facility = 1; /* LOG_USER */
604 size_t len = iov_iter_count(from);
607 if (len > LOG_LINE_MAX)
609 buf = kmalloc(len+1, GFP_KERNEL);
614 if (copy_from_iter(buf, len, from) != len) {
620 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
621 * the decimal value represents 32bit, the lower 3 bit are the log
622 * level, the rest are the log facility.
624 * If no prefix or no userspace facility is specified, we
625 * enforce LOG_USER, to be able to reliably distinguish
626 * kernel-generated messages from userspace-injected ones.
629 if (line[0] == '<') {
632 i = simple_strtoul(line+1, &endp, 10);
633 if (endp && endp[0] == '>') {
643 printk_emit(facility, level, NULL, 0, "%s", line);
648 static ssize_t devkmsg_read(struct file *file, char __user *buf,
649 size_t count, loff_t *ppos)
651 struct devkmsg_user *user = file->private_data;
652 struct printk_log *msg;
659 ret = mutex_lock_interruptible(&user->lock);
662 raw_spin_lock_irq(&logbuf_lock);
663 while (user->seq == log_next_seq) {
664 if (file->f_flags & O_NONBLOCK) {
666 raw_spin_unlock_irq(&logbuf_lock);
670 raw_spin_unlock_irq(&logbuf_lock);
671 ret = wait_event_interruptible(log_wait,
672 user->seq != log_next_seq);
675 raw_spin_lock_irq(&logbuf_lock);
678 if (user->seq < log_first_seq) {
679 /* our last seen message is gone, return error and reset */
680 user->idx = log_first_idx;
681 user->seq = log_first_seq;
683 raw_spin_unlock_irq(&logbuf_lock);
687 msg = log_from_idx(user->idx);
688 len = msg_print_ext_header(user->buf, sizeof(user->buf),
689 msg, user->seq, user->prev);
690 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
691 log_dict(msg), msg->dict_len,
692 log_text(msg), msg->text_len);
694 user->prev = msg->flags;
695 user->idx = log_next(user->idx);
697 raw_spin_unlock_irq(&logbuf_lock);
704 if (copy_to_user(buf, user->buf, len)) {
710 mutex_unlock(&user->lock);
714 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
716 struct devkmsg_user *user = file->private_data;
724 raw_spin_lock_irq(&logbuf_lock);
727 /* the first record */
728 user->idx = log_first_idx;
729 user->seq = log_first_seq;
733 * The first record after the last SYSLOG_ACTION_CLEAR,
734 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
735 * changes no global state, and does not clear anything.
737 user->idx = clear_idx;
738 user->seq = clear_seq;
741 /* after the last record */
742 user->idx = log_next_idx;
743 user->seq = log_next_seq;
748 raw_spin_unlock_irq(&logbuf_lock);
752 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
754 struct devkmsg_user *user = file->private_data;
758 return POLLERR|POLLNVAL;
760 poll_wait(file, &log_wait, wait);
762 raw_spin_lock_irq(&logbuf_lock);
763 if (user->seq < log_next_seq) {
764 /* return error when data has vanished underneath us */
765 if (user->seq < log_first_seq)
766 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
768 ret = POLLIN|POLLRDNORM;
770 raw_spin_unlock_irq(&logbuf_lock);
775 static int devkmsg_open(struct inode *inode, struct file *file)
777 struct devkmsg_user *user;
780 /* write-only does not need any file context */
781 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
784 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
789 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
793 mutex_init(&user->lock);
795 raw_spin_lock_irq(&logbuf_lock);
796 user->idx = log_first_idx;
797 user->seq = log_first_seq;
798 raw_spin_unlock_irq(&logbuf_lock);
800 file->private_data = user;
804 static int devkmsg_release(struct inode *inode, struct file *file)
806 struct devkmsg_user *user = file->private_data;
811 mutex_destroy(&user->lock);
816 const struct file_operations kmsg_fops = {
817 .open = devkmsg_open,
818 .read = devkmsg_read,
819 .write_iter = devkmsg_write,
820 .llseek = devkmsg_llseek,
821 .poll = devkmsg_poll,
822 .release = devkmsg_release,
827 * This appends the listed symbols to /proc/vmcore
829 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
830 * obtain access to symbols that are otherwise very difficult to locate. These
831 * symbols are specifically used so that utilities can access and extract the
832 * dmesg log from a vmcore file after a crash.
834 void log_buf_kexec_setup(void)
836 VMCOREINFO_SYMBOL(log_buf);
837 VMCOREINFO_SYMBOL(log_buf_len);
838 VMCOREINFO_SYMBOL(log_first_idx);
839 VMCOREINFO_SYMBOL(log_next_idx);
841 * Export struct printk_log size and field offsets. User space tools can
842 * parse it and detect any changes to structure down the line.
844 VMCOREINFO_STRUCT_SIZE(printk_log);
845 VMCOREINFO_OFFSET(printk_log, ts_nsec);
846 VMCOREINFO_OFFSET(printk_log, len);
847 VMCOREINFO_OFFSET(printk_log, text_len);
848 VMCOREINFO_OFFSET(printk_log, dict_len);
852 /* requested log_buf_len from kernel cmdline */
853 static unsigned long __initdata new_log_buf_len;
855 /* we practice scaling the ring buffer by powers of 2 */
856 static void __init log_buf_len_update(unsigned size)
859 size = roundup_pow_of_two(size);
860 if (size > log_buf_len)
861 new_log_buf_len = size;
864 /* save requested log_buf_len since it's too early to process it */
865 static int __init log_buf_len_setup(char *str)
867 unsigned size = memparse(str, &str);
869 log_buf_len_update(size);
873 early_param("log_buf_len", log_buf_len_setup);
876 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
878 static void __init log_buf_add_cpu(void)
880 unsigned int cpu_extra;
883 * archs should set up cpu_possible_bits properly with
884 * set_cpu_possible() after setup_arch() but just in
885 * case lets ensure this is valid.
887 if (num_possible_cpus() == 1)
890 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
892 /* by default this will only continue through for large > 64 CPUs */
893 if (cpu_extra <= __LOG_BUF_LEN / 2)
896 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
897 __LOG_CPU_MAX_BUF_LEN);
898 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
900 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
902 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
904 #else /* !CONFIG_SMP */
905 static inline void log_buf_add_cpu(void) {}
906 #endif /* CONFIG_SMP */
908 void __init setup_log_buf(int early)
914 if (log_buf != __log_buf)
917 if (!early && !new_log_buf_len)
920 if (!new_log_buf_len)
925 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
927 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
931 if (unlikely(!new_log_buf)) {
932 pr_err("log_buf_len: %ld bytes not available\n",
937 raw_spin_lock_irqsave(&logbuf_lock, flags);
938 log_buf_len = new_log_buf_len;
939 log_buf = new_log_buf;
941 free = __LOG_BUF_LEN - log_next_idx;
942 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
943 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
945 pr_info("log_buf_len: %d bytes\n", log_buf_len);
946 pr_info("early log buf free: %d(%d%%)\n",
947 free, (free * 100) / __LOG_BUF_LEN);
950 static bool __read_mostly ignore_loglevel;
952 static int __init ignore_loglevel_setup(char *str)
954 ignore_loglevel = true;
955 pr_info("debug: ignoring loglevel setting.\n");
960 early_param("ignore_loglevel", ignore_loglevel_setup);
961 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
962 MODULE_PARM_DESC(ignore_loglevel,
963 "ignore loglevel setting (prints all kernel messages to the console)");
965 #ifdef CONFIG_BOOT_PRINTK_DELAY
967 static int boot_delay; /* msecs delay after each printk during bootup */
968 static unsigned long long loops_per_msec; /* based on boot_delay */
970 static int __init boot_delay_setup(char *str)
974 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
975 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
977 get_option(&str, &boot_delay);
978 if (boot_delay > 10 * 1000)
981 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
982 "HZ: %d, loops_per_msec: %llu\n",
983 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
986 early_param("boot_delay", boot_delay_setup);
988 static void boot_delay_msec(int level)
990 unsigned long long k;
991 unsigned long timeout;
993 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
994 || (level >= console_loglevel && !ignore_loglevel)) {
998 k = (unsigned long long)loops_per_msec * boot_delay;
1000 timeout = jiffies + msecs_to_jiffies(boot_delay);
1005 * use (volatile) jiffies to prevent
1006 * compiler reduction; loop termination via jiffies
1007 * is secondary and may or may not happen.
1009 if (time_after(jiffies, timeout))
1011 touch_nmi_watchdog();
1015 static inline void boot_delay_msec(int level)
1020 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1021 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1023 static size_t print_time(u64 ts, char *buf)
1025 unsigned long rem_nsec;
1030 rem_nsec = do_div(ts, 1000000000);
1033 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1035 return sprintf(buf, "[%5lu.%06lu] ",
1036 (unsigned long)ts, rem_nsec / 1000);
1039 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1042 unsigned int prefix = (msg->facility << 3) | msg->level;
1046 len += sprintf(buf, "<%u>", prefix);
1051 else if (prefix > 99)
1053 else if (prefix > 9)
1058 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1062 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1063 bool syslog, char *buf, size_t size)
1065 const char *text = log_text(msg);
1066 size_t text_size = msg->text_len;
1068 bool newline = true;
1071 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1074 if (msg->flags & LOG_CONT) {
1075 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1078 if (!(msg->flags & LOG_NEWLINE))
1083 const char *next = memchr(text, '\n', text_size);
1087 text_len = next - text;
1089 text_size -= next - text;
1091 text_len = text_size;
1095 if (print_prefix(msg, syslog, NULL) +
1096 text_len + 1 >= size - len)
1100 len += print_prefix(msg, syslog, buf + len);
1101 memcpy(buf + len, text, text_len);
1103 if (next || newline)
1106 /* SYSLOG_ACTION_* buffer size only calculation */
1108 len += print_prefix(msg, syslog, NULL);
1110 if (next || newline)
1121 static int syslog_print(char __user *buf, int size)
1124 struct printk_log *msg;
1127 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1135 raw_spin_lock_irq(&logbuf_lock);
1136 if (syslog_seq < log_first_seq) {
1137 /* messages are gone, move to first one */
1138 syslog_seq = log_first_seq;
1139 syslog_idx = log_first_idx;
1143 if (syslog_seq == log_next_seq) {
1144 raw_spin_unlock_irq(&logbuf_lock);
1148 skip = syslog_partial;
1149 msg = log_from_idx(syslog_idx);
1150 n = msg_print_text(msg, syslog_prev, true, text,
1151 LOG_LINE_MAX + PREFIX_MAX);
1152 if (n - syslog_partial <= size) {
1153 /* message fits into buffer, move forward */
1154 syslog_idx = log_next(syslog_idx);
1156 syslog_prev = msg->flags;
1157 n -= syslog_partial;
1160 /* partial read(), remember position */
1162 syslog_partial += n;
1165 raw_spin_unlock_irq(&logbuf_lock);
1170 if (copy_to_user(buf, text + skip, n)) {
1185 static int syslog_print_all(char __user *buf, int size, bool clear)
1190 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1194 raw_spin_lock_irq(&logbuf_lock);
1199 enum log_flags prev;
1201 if (clear_seq < log_first_seq) {
1202 /* messages are gone, move to first available one */
1203 clear_seq = log_first_seq;
1204 clear_idx = log_first_idx;
1208 * Find first record that fits, including all following records,
1209 * into the user-provided buffer for this dump.
1214 while (seq < log_next_seq) {
1215 struct printk_log *msg = log_from_idx(idx);
1217 len += msg_print_text(msg, prev, true, NULL, 0);
1219 idx = log_next(idx);
1223 /* move first record forward until length fits into the buffer */
1227 while (len > size && seq < log_next_seq) {
1228 struct printk_log *msg = log_from_idx(idx);
1230 len -= msg_print_text(msg, prev, true, NULL, 0);
1232 idx = log_next(idx);
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;
1274 raw_spin_unlock_irq(&logbuf_lock);
1280 int do_syslog(int type, char __user *buf, int len, bool from_file)
1283 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1286 error = check_syslog_permissions(type, from_file);
1290 error = security_syslog(type);
1295 case SYSLOG_ACTION_CLOSE: /* Close log */
1297 case SYSLOG_ACTION_OPEN: /* Open log */
1299 case SYSLOG_ACTION_READ: /* Read from log */
1301 if (!buf || len < 0)
1306 if (!access_ok(VERIFY_WRITE, buf, len)) {
1310 error = wait_event_interruptible(log_wait,
1311 syslog_seq != log_next_seq);
1314 error = syslog_print(buf, len);
1316 /* Read/clear last kernel messages */
1317 case SYSLOG_ACTION_READ_CLEAR:
1320 /* Read last kernel messages */
1321 case SYSLOG_ACTION_READ_ALL:
1323 if (!buf || len < 0)
1328 if (!access_ok(VERIFY_WRITE, buf, len)) {
1332 error = syslog_print_all(buf, len, clear);
1334 /* Clear ring buffer */
1335 case SYSLOG_ACTION_CLEAR:
1336 syslog_print_all(NULL, 0, true);
1338 /* Disable logging to console */
1339 case SYSLOG_ACTION_CONSOLE_OFF:
1340 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1341 saved_console_loglevel = console_loglevel;
1342 console_loglevel = minimum_console_loglevel;
1344 /* Enable logging to console */
1345 case SYSLOG_ACTION_CONSOLE_ON:
1346 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1347 console_loglevel = saved_console_loglevel;
1348 saved_console_loglevel = LOGLEVEL_DEFAULT;
1351 /* Set level of messages printed to console */
1352 case SYSLOG_ACTION_CONSOLE_LEVEL:
1354 if (len < 1 || len > 8)
1356 if (len < minimum_console_loglevel)
1357 len = minimum_console_loglevel;
1358 console_loglevel = len;
1359 /* Implicitly re-enable logging to console */
1360 saved_console_loglevel = LOGLEVEL_DEFAULT;
1363 /* Number of chars in the log buffer */
1364 case SYSLOG_ACTION_SIZE_UNREAD:
1365 raw_spin_lock_irq(&logbuf_lock);
1366 if (syslog_seq < log_first_seq) {
1367 /* messages are gone, move to first one */
1368 syslog_seq = log_first_seq;
1369 syslog_idx = log_first_idx;
1375 * Short-cut for poll(/"proc/kmsg") which simply checks
1376 * for pending data, not the size; return the count of
1377 * records, not the length.
1379 error = log_next_seq - syslog_seq;
1381 u64 seq = syslog_seq;
1382 u32 idx = syslog_idx;
1383 enum log_flags prev = syslog_prev;
1386 while (seq < log_next_seq) {
1387 struct printk_log *msg = log_from_idx(idx);
1389 error += msg_print_text(msg, prev, true, NULL, 0);
1390 idx = log_next(idx);
1394 error -= syslog_partial;
1396 raw_spin_unlock_irq(&logbuf_lock);
1398 /* Size of the log buffer */
1399 case SYSLOG_ACTION_SIZE_BUFFER:
1400 error = log_buf_len;
1410 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1412 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1416 * Call the console drivers, asking them to write out
1417 * log_buf[start] to log_buf[end - 1].
1418 * The console_lock must be held.
1420 static void call_console_drivers(int level, const char *text, size_t len)
1422 struct console *con;
1424 trace_console(text, len);
1426 if (level >= console_loglevel && !ignore_loglevel)
1428 if (!console_drivers)
1431 for_each_console(con) {
1432 if (exclusive_console && con != exclusive_console)
1434 if (!(con->flags & CON_ENABLED))
1438 if (!cpu_online(smp_processor_id()) &&
1439 !(con->flags & CON_ANYTIME))
1441 con->write(con, text, len);
1446 * Zap console related locks when oopsing.
1447 * To leave time for slow consoles to print a full oops,
1448 * only zap at most once every 30 seconds.
1450 static void zap_locks(void)
1452 static unsigned long oops_timestamp;
1454 if (time_after_eq(jiffies, oops_timestamp) &&
1455 !time_after(jiffies, oops_timestamp + 30 * HZ))
1458 oops_timestamp = jiffies;
1461 /* If a crash is occurring, make sure we can't deadlock */
1462 raw_spin_lock_init(&logbuf_lock);
1463 /* And make sure that we print immediately */
1464 sema_init(&console_sem, 1);
1468 * Check if we have any console that is capable of printing while cpu is
1469 * booting or shutting down. Requires console_sem.
1471 static int have_callable_console(void)
1473 struct console *con;
1475 for_each_console(con)
1476 if (con->flags & CON_ANYTIME)
1483 * Can we actually use the console at this time on this cpu?
1485 * Console drivers may assume that per-cpu resources have been allocated. So
1486 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1487 * call them until this CPU is officially up.
1489 static inline int can_use_console(unsigned int cpu)
1491 return cpu_online(cpu) || have_callable_console();
1495 * Try to get console ownership to actually show the kernel
1496 * messages from a 'printk'. Return true (and with the
1497 * console_lock held, and 'console_locked' set) if it
1498 * is successful, false otherwise.
1500 static int console_trylock_for_printk(void)
1502 unsigned int cpu = smp_processor_id();
1504 if (!console_trylock())
1507 * If we can't use the console, we need to release the console
1508 * semaphore by hand to avoid flushing the buffer. We need to hold the
1509 * console semaphore in order to do this test safely.
1511 if (!can_use_console(cpu)) {
1519 int printk_delay_msec __read_mostly;
1521 static inline void printk_delay(void)
1523 if (unlikely(printk_delay_msec)) {
1524 int m = printk_delay_msec;
1528 touch_nmi_watchdog();
1534 * Continuation lines are buffered, and not committed to the record buffer
1535 * until the line is complete, or a race forces it. The line fragments
1536 * though, are printed immediately to the consoles to ensure everything has
1537 * reached the console in case of a kernel crash.
1539 static struct cont {
1540 char buf[LOG_LINE_MAX];
1541 size_t len; /* length == 0 means unused buffer */
1542 size_t cons; /* bytes written to console */
1543 struct task_struct *owner; /* task of first print*/
1544 u64 ts_nsec; /* time of first print */
1545 u8 level; /* log level of first message */
1546 u8 facility; /* log facility of first message */
1547 enum log_flags flags; /* prefix, newline flags */
1548 bool flushed:1; /* buffer sealed and committed */
1551 static void cont_flush(enum log_flags flags)
1560 * If a fragment of this line was directly flushed to the
1561 * console; wait for the console to pick up the rest of the
1562 * line. LOG_NOCONS suppresses a duplicated output.
1564 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1565 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1567 cont.flushed = true;
1570 * If no fragment of this line ever reached the console,
1571 * just submit it to the store and free the buffer.
1573 log_store(cont.facility, cont.level, flags, 0,
1574 NULL, 0, cont.buf, cont.len);
1579 static bool cont_add(int facility, int level, const char *text, size_t len)
1581 if (cont.len && cont.flushed)
1584 if (cont.len + len > sizeof(cont.buf)) {
1585 /* the line gets too long, split it up in separate records */
1586 cont_flush(LOG_CONT);
1591 cont.facility = facility;
1593 cont.owner = current;
1594 cont.ts_nsec = local_clock();
1597 cont.flushed = false;
1600 memcpy(cont.buf + cont.len, text, len);
1603 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1604 cont_flush(LOG_CONT);
1609 static size_t cont_print_text(char *text, size_t size)
1614 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1615 textlen += print_time(cont.ts_nsec, text);
1619 len = cont.len - cont.cons;
1623 memcpy(text + textlen, cont.buf + cont.cons, len);
1625 cont.cons = cont.len;
1629 if (cont.flags & LOG_NEWLINE)
1630 text[textlen++] = '\n';
1631 /* got everything, release buffer */
1637 asmlinkage int vprintk_emit(int facility, int level,
1638 const char *dict, size_t dictlen,
1639 const char *fmt, va_list args)
1641 static int recursion_bug;
1642 static char textbuf[LOG_LINE_MAX];
1643 char *text = textbuf;
1644 size_t text_len = 0;
1645 enum log_flags lflags = 0;
1646 unsigned long flags;
1648 int printed_len = 0;
1649 bool in_sched = false;
1650 /* cpu currently holding logbuf_lock in this function */
1651 static unsigned int logbuf_cpu = UINT_MAX;
1653 if (level == LOGLEVEL_SCHED) {
1654 level = LOGLEVEL_DEFAULT;
1658 boot_delay_msec(level);
1661 /* This stops the holder of console_sem just where we want him */
1662 local_irq_save(flags);
1663 this_cpu = smp_processor_id();
1666 * Ouch, printk recursed into itself!
1668 if (unlikely(logbuf_cpu == this_cpu)) {
1670 * If a crash is occurring during printk() on this CPU,
1671 * then try to get the crash message out but make sure
1672 * we can't deadlock. Otherwise just return to avoid the
1673 * recursion and return - but flag the recursion so that
1674 * it can be printed at the next appropriate moment:
1676 if (!oops_in_progress && !lockdep_recursing(current)) {
1678 local_irq_restore(flags);
1685 raw_spin_lock(&logbuf_lock);
1686 logbuf_cpu = this_cpu;
1688 if (unlikely(recursion_bug)) {
1689 static const char recursion_msg[] =
1690 "BUG: recent printk recursion!";
1693 /* emit KERN_CRIT message */
1694 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1695 NULL, 0, recursion_msg,
1696 strlen(recursion_msg));
1700 * The printf needs to come first; we need the syslog
1701 * prefix which might be passed-in as a parameter.
1703 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1705 /* mark and strip a trailing newline */
1706 if (text_len && text[text_len-1] == '\n') {
1708 lflags |= LOG_NEWLINE;
1711 /* strip kernel syslog prefix and extract log level or control flags */
1712 if (facility == 0) {
1713 int kern_level = printk_get_level(text);
1716 const char *end_of_header = printk_skip_level(text);
1717 switch (kern_level) {
1719 if (level == LOGLEVEL_DEFAULT)
1720 level = kern_level - '0';
1722 case 'd': /* KERN_DEFAULT */
1723 lflags |= LOG_PREFIX;
1726 * No need to check length here because vscnprintf
1727 * put '\0' at the end of the string. Only valid and
1728 * newly printed level is detected.
1730 text_len -= end_of_header - text;
1731 text = (char *)end_of_header;
1735 if (level == LOGLEVEL_DEFAULT)
1736 level = default_message_loglevel;
1739 lflags |= LOG_PREFIX|LOG_NEWLINE;
1741 if (!(lflags & LOG_NEWLINE)) {
1743 * Flush the conflicting buffer. An earlier newline was missing,
1744 * or another task also prints continuation lines.
1746 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1747 cont_flush(LOG_NEWLINE);
1749 /* buffer line if possible, otherwise store it right away */
1750 if (cont_add(facility, level, text, text_len))
1751 printed_len += text_len;
1753 printed_len += log_store(facility, level,
1754 lflags | LOG_CONT, 0,
1755 dict, dictlen, text, text_len);
1757 bool stored = false;
1760 * If an earlier newline was missing and it was the same task,
1761 * either merge it with the current buffer and flush, or if
1762 * there was a race with interrupts (prefix == true) then just
1763 * flush it out and store this line separately.
1764 * If the preceding printk was from a different task and missed
1765 * a newline, flush and append the newline.
1768 if (cont.owner == current && !(lflags & LOG_PREFIX))
1769 stored = cont_add(facility, level, text,
1771 cont_flush(LOG_NEWLINE);
1775 printed_len += text_len;
1777 printed_len += log_store(facility, level, lflags, 0,
1778 dict, dictlen, text, text_len);
1781 logbuf_cpu = UINT_MAX;
1782 raw_spin_unlock(&logbuf_lock);
1784 local_irq_restore(flags);
1786 /* If called from the scheduler, we can not call up(). */
1790 * Disable preemption to avoid being preempted while holding
1791 * console_sem which would prevent anyone from printing to
1797 * Try to acquire and then immediately release the console
1798 * semaphore. The release will print out buffers and wake up
1799 * /dev/kmsg and syslog() users.
1801 if (console_trylock_for_printk())
1809 EXPORT_SYMBOL(vprintk_emit);
1811 asmlinkage int vprintk(const char *fmt, va_list args)
1813 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1815 EXPORT_SYMBOL(vprintk);
1817 asmlinkage int printk_emit(int facility, int level,
1818 const char *dict, size_t dictlen,
1819 const char *fmt, ...)
1824 va_start(args, fmt);
1825 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1830 EXPORT_SYMBOL(printk_emit);
1832 int vprintk_default(const char *fmt, va_list args)
1836 #ifdef CONFIG_KGDB_KDB
1837 if (unlikely(kdb_trap_printk)) {
1838 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1842 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1846 EXPORT_SYMBOL_GPL(vprintk_default);
1849 * This allows printk to be diverted to another function per cpu.
1850 * This is useful for calling printk functions from within NMI
1851 * without worrying about race conditions that can lock up the
1854 DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
1857 * printk - print a kernel message
1858 * @fmt: format string
1860 * This is printk(). It can be called from any context. We want it to work.
1862 * We try to grab the console_lock. If we succeed, it's easy - we log the
1863 * output and call the console drivers. If we fail to get the semaphore, we
1864 * place the output into the log buffer and return. The current holder of
1865 * the console_sem will notice the new output in console_unlock(); and will
1866 * send it to the consoles before releasing the lock.
1868 * One effect of this deferred printing is that code which calls printk() and
1869 * then changes console_loglevel may break. This is because console_loglevel
1870 * is inspected when the actual printing occurs.
1875 * See the vsnprintf() documentation for format string extensions over C99.
1877 asmlinkage __visible int printk(const char *fmt, ...)
1879 printk_func_t vprintk_func;
1883 va_start(args, fmt);
1886 * If a caller overrides the per_cpu printk_func, then it needs
1887 * to disable preemption when calling printk(). Otherwise
1888 * the printk_func should be set to the default. No need to
1889 * disable preemption here.
1891 vprintk_func = this_cpu_read(printk_func);
1892 r = vprintk_func(fmt, args);
1898 EXPORT_SYMBOL(printk);
1900 #else /* CONFIG_PRINTK */
1902 #define LOG_LINE_MAX 0
1903 #define PREFIX_MAX 0
1905 static u64 syslog_seq;
1906 static u32 syslog_idx;
1907 static u64 console_seq;
1908 static u32 console_idx;
1909 static enum log_flags syslog_prev;
1910 static u64 log_first_seq;
1911 static u32 log_first_idx;
1912 static u64 log_next_seq;
1913 static enum log_flags console_prev;
1914 static struct cont {
1920 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1921 static u32 log_next(u32 idx) { return 0; }
1922 static void call_console_drivers(int level, const char *text, size_t len) {}
1923 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1924 bool syslog, char *buf, size_t size) { return 0; }
1925 static size_t cont_print_text(char *text, size_t size) { return 0; }
1927 /* Still needs to be defined for users */
1928 DEFINE_PER_CPU(printk_func_t, printk_func);
1930 #endif /* CONFIG_PRINTK */
1932 #ifdef CONFIG_EARLY_PRINTK
1933 struct console *early_console;
1935 asmlinkage __visible void early_printk(const char *fmt, ...)
1945 n = vscnprintf(buf, sizeof(buf), fmt, ap);
1948 early_console->write(early_console, buf, n);
1952 static int __add_preferred_console(char *name, int idx, char *options,
1955 struct console_cmdline *c;
1959 * See if this tty is not yet registered, and
1960 * if we have a slot free.
1962 for (i = 0, c = console_cmdline;
1963 i < MAX_CMDLINECONSOLES && c->name[0];
1965 if (strcmp(c->name, name) == 0 && c->index == idx) {
1967 selected_console = i;
1971 if (i == MAX_CMDLINECONSOLES)
1974 selected_console = i;
1975 strlcpy(c->name, name, sizeof(c->name));
1976 c->options = options;
1977 braille_set_options(c, brl_options);
1983 * Set up a console. Called via do_early_param() in init/main.c
1984 * for each "console=" parameter in the boot command line.
1986 static int __init console_setup(char *str)
1988 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
1989 char *s, *options, *brl_options = NULL;
1992 if (_braille_console_setup(&str, &brl_options))
1996 * Decode str into name, index, options.
1998 if (str[0] >= '0' && str[0] <= '9') {
1999 strcpy(buf, "ttyS");
2000 strncpy(buf + 4, str, sizeof(buf) - 5);
2002 strncpy(buf, str, sizeof(buf) - 1);
2004 buf[sizeof(buf) - 1] = 0;
2005 options = strchr(str, ',');
2009 if (!strcmp(str, "ttya"))
2010 strcpy(buf, "ttyS0");
2011 if (!strcmp(str, "ttyb"))
2012 strcpy(buf, "ttyS1");
2014 for (s = buf; *s; s++)
2015 if (isdigit(*s) || *s == ',')
2017 idx = simple_strtoul(s, NULL, 10);
2020 __add_preferred_console(buf, idx, options, brl_options);
2021 console_set_on_cmdline = 1;
2024 __setup("console=", console_setup);
2027 * add_preferred_console - add a device to the list of preferred consoles.
2028 * @name: device name
2029 * @idx: device index
2030 * @options: options for this console
2032 * The last preferred console added will be used for kernel messages
2033 * and stdin/out/err for init. Normally this is used by console_setup
2034 * above to handle user-supplied console arguments; however it can also
2035 * be used by arch-specific code either to override the user or more
2036 * commonly to provide a default console (ie from PROM variables) when
2037 * the user has not supplied one.
2039 int add_preferred_console(char *name, int idx, char *options)
2041 return __add_preferred_console(name, idx, options, NULL);
2044 bool console_suspend_enabled = true;
2045 EXPORT_SYMBOL(console_suspend_enabled);
2047 static int __init console_suspend_disable(char *str)
2049 console_suspend_enabled = false;
2052 __setup("no_console_suspend", console_suspend_disable);
2053 module_param_named(console_suspend, console_suspend_enabled,
2054 bool, S_IRUGO | S_IWUSR);
2055 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2056 " and hibernate operations");
2059 * suspend_console - suspend the console subsystem
2061 * This disables printk() while we go into suspend states
2063 void suspend_console(void)
2065 if (!console_suspend_enabled)
2067 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2069 console_suspended = 1;
2073 void resume_console(void)
2075 if (!console_suspend_enabled)
2078 console_suspended = 0;
2083 * console_cpu_notify - print deferred console messages after CPU hotplug
2084 * @self: notifier struct
2085 * @action: CPU hotplug event
2088 * If printk() is called from a CPU that is not online yet, the messages
2089 * will be spooled but will not show up on the console. This function is
2090 * called when a new CPU comes online (or fails to come up), and ensures
2091 * that any such output gets printed.
2093 static int console_cpu_notify(struct notifier_block *self,
2094 unsigned long action, void *hcpu)
2099 case CPU_DOWN_FAILED:
2100 case CPU_UP_CANCELED:
2108 * console_lock - lock the console system for exclusive use.
2110 * Acquires a lock which guarantees that the caller has
2111 * exclusive access to the console system and the console_drivers list.
2113 * Can sleep, returns nothing.
2115 void console_lock(void)
2120 if (console_suspended)
2123 console_may_schedule = 1;
2125 EXPORT_SYMBOL(console_lock);
2128 * console_trylock - try to lock the console system for exclusive use.
2130 * Try to acquire a lock which guarantees that the caller has exclusive
2131 * access to the console system and the console_drivers list.
2133 * returns 1 on success, and 0 on failure to acquire the lock.
2135 int console_trylock(void)
2137 if (down_trylock_console_sem())
2139 if (console_suspended) {
2144 console_may_schedule = 0;
2147 EXPORT_SYMBOL(console_trylock);
2149 int is_console_locked(void)
2151 return console_locked;
2154 static void console_cont_flush(char *text, size_t size)
2156 unsigned long flags;
2159 raw_spin_lock_irqsave(&logbuf_lock, flags);
2165 * We still queue earlier records, likely because the console was
2166 * busy. The earlier ones need to be printed before this one, we
2167 * did not flush any fragment so far, so just let it queue up.
2169 if (console_seq < log_next_seq && !cont.cons)
2172 len = cont_print_text(text, size);
2173 raw_spin_unlock(&logbuf_lock);
2174 stop_critical_timings();
2175 call_console_drivers(cont.level, text, len);
2176 start_critical_timings();
2177 local_irq_restore(flags);
2180 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2184 * console_unlock - unlock the console system
2186 * Releases the console_lock which the caller holds on the console system
2187 * and the console driver list.
2189 * While the console_lock was held, console output may have been buffered
2190 * by printk(). If this is the case, console_unlock(); emits
2191 * the output prior to releasing the lock.
2193 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2195 * console_unlock(); may be called from any context.
2197 void console_unlock(void)
2199 static char text[LOG_LINE_MAX + PREFIX_MAX];
2200 static u64 seen_seq;
2201 unsigned long flags;
2202 bool wake_klogd = false;
2205 if (console_suspended) {
2210 console_may_schedule = 0;
2212 /* flush buffered message fragment immediately to console */
2213 console_cont_flush(text, sizeof(text));
2216 struct printk_log *msg;
2220 raw_spin_lock_irqsave(&logbuf_lock, flags);
2221 if (seen_seq != log_next_seq) {
2223 seen_seq = log_next_seq;
2226 if (console_seq < log_first_seq) {
2227 len = sprintf(text, "** %u printk messages dropped ** ",
2228 (unsigned)(log_first_seq - console_seq));
2230 /* messages are gone, move to first one */
2231 console_seq = log_first_seq;
2232 console_idx = log_first_idx;
2238 if (console_seq == log_next_seq)
2241 msg = log_from_idx(console_idx);
2242 if (msg->flags & LOG_NOCONS) {
2244 * Skip record we have buffered and already printed
2245 * directly to the console when we received it.
2247 console_idx = log_next(console_idx);
2250 * We will get here again when we register a new
2251 * CON_PRINTBUFFER console. Clear the flag so we
2252 * will properly dump everything later.
2254 msg->flags &= ~LOG_NOCONS;
2255 console_prev = msg->flags;
2260 len += msg_print_text(msg, console_prev, false,
2261 text + len, sizeof(text) - len);
2262 console_idx = log_next(console_idx);
2264 console_prev = msg->flags;
2265 raw_spin_unlock(&logbuf_lock);
2267 stop_critical_timings(); /* don't trace print latency */
2268 call_console_drivers(level, text, len);
2269 start_critical_timings();
2270 local_irq_restore(flags);
2274 /* Release the exclusive_console once it is used */
2275 if (unlikely(exclusive_console))
2276 exclusive_console = NULL;
2278 raw_spin_unlock(&logbuf_lock);
2283 * Someone could have filled up the buffer again, so re-check if there's
2284 * something to flush. In case we cannot trylock the console_sem again,
2285 * there's a new owner and the console_unlock() from them will do the
2286 * flush, no worries.
2288 raw_spin_lock(&logbuf_lock);
2289 retry = console_seq != log_next_seq;
2290 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2292 if (retry && console_trylock())
2298 EXPORT_SYMBOL(console_unlock);
2301 * console_conditional_schedule - yield the CPU if required
2303 * If the console code is currently allowed to sleep, and
2304 * if this CPU should yield the CPU to another task, do
2307 * Must be called within console_lock();.
2309 void __sched console_conditional_schedule(void)
2311 if (console_may_schedule)
2314 EXPORT_SYMBOL(console_conditional_schedule);
2316 void console_unblank(void)
2321 * console_unblank can no longer be called in interrupt context unless
2322 * oops_in_progress is set to 1..
2324 if (oops_in_progress) {
2325 if (down_trylock_console_sem() != 0)
2331 console_may_schedule = 0;
2333 if ((c->flags & CON_ENABLED) && c->unblank)
2339 * Return the console tty driver structure and its associated index
2341 struct tty_driver *console_device(int *index)
2344 struct tty_driver *driver = NULL;
2347 for_each_console(c) {
2350 driver = c->device(c, index);
2359 * Prevent further output on the passed console device so that (for example)
2360 * serial drivers can disable console output before suspending a port, and can
2361 * re-enable output afterwards.
2363 void console_stop(struct console *console)
2366 console->flags &= ~CON_ENABLED;
2369 EXPORT_SYMBOL(console_stop);
2371 void console_start(struct console *console)
2374 console->flags |= CON_ENABLED;
2377 EXPORT_SYMBOL(console_start);
2379 static int __read_mostly keep_bootcon;
2381 static int __init keep_bootcon_setup(char *str)
2384 pr_info("debug: skip boot console de-registration.\n");
2389 early_param("keep_bootcon", keep_bootcon_setup);
2392 * The console driver calls this routine during kernel initialization
2393 * to register the console printing procedure with printk() and to
2394 * print any messages that were printed by the kernel before the
2395 * console driver was initialized.
2397 * This can happen pretty early during the boot process (because of
2398 * early_printk) - sometimes before setup_arch() completes - be careful
2399 * of what kernel features are used - they may not be initialised yet.
2401 * There are two types of consoles - bootconsoles (early_printk) and
2402 * "real" consoles (everything which is not a bootconsole) which are
2403 * handled differently.
2404 * - Any number of bootconsoles can be registered at any time.
2405 * - As soon as a "real" console is registered, all bootconsoles
2406 * will be unregistered automatically.
2407 * - Once a "real" console is registered, any attempt to register a
2408 * bootconsoles will be rejected
2410 void register_console(struct console *newcon)
2413 unsigned long flags;
2414 struct console *bcon = NULL;
2415 struct console_cmdline *c;
2417 if (console_drivers)
2418 for_each_console(bcon)
2419 if (WARN(bcon == newcon,
2420 "console '%s%d' already registered\n",
2421 bcon->name, bcon->index))
2425 * before we register a new CON_BOOT console, make sure we don't
2426 * already have a valid console
2428 if (console_drivers && newcon->flags & CON_BOOT) {
2429 /* find the last or real console */
2430 for_each_console(bcon) {
2431 if (!(bcon->flags & CON_BOOT)) {
2432 pr_info("Too late to register bootconsole %s%d\n",
2433 newcon->name, newcon->index);
2439 if (console_drivers && console_drivers->flags & CON_BOOT)
2440 bcon = console_drivers;
2442 if (preferred_console < 0 || bcon || !console_drivers)
2443 preferred_console = selected_console;
2446 * See if we want to use this console driver. If we
2447 * didn't select a console we take the first one
2448 * that registers here.
2450 if (preferred_console < 0) {
2451 if (newcon->index < 0)
2453 if (newcon->setup == NULL ||
2454 newcon->setup(newcon, NULL) == 0) {
2455 newcon->flags |= CON_ENABLED;
2456 if (newcon->device) {
2457 newcon->flags |= CON_CONSDEV;
2458 preferred_console = 0;
2464 * See if this console matches one we selected on
2467 for (i = 0, c = console_cmdline;
2468 i < MAX_CMDLINECONSOLES && c->name[0];
2470 if (!newcon->match ||
2471 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2472 /* default matching */
2473 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2474 if (strcmp(c->name, newcon->name) != 0)
2476 if (newcon->index >= 0 &&
2477 newcon->index != c->index)
2479 if (newcon->index < 0)
2480 newcon->index = c->index;
2482 if (_braille_register_console(newcon, c))
2485 if (newcon->setup &&
2486 newcon->setup(newcon, c->options) != 0)
2490 newcon->flags |= CON_ENABLED;
2491 if (i == selected_console) {
2492 newcon->flags |= CON_CONSDEV;
2493 preferred_console = selected_console;
2498 if (!(newcon->flags & CON_ENABLED))
2502 * If we have a bootconsole, and are switching to a real console,
2503 * don't print everything out again, since when the boot console, and
2504 * the real console are the same physical device, it's annoying to
2505 * see the beginning boot messages twice
2507 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2508 newcon->flags &= ~CON_PRINTBUFFER;
2511 * Put this console in the list - keep the
2512 * preferred driver at the head of the list.
2515 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2516 newcon->next = console_drivers;
2517 console_drivers = newcon;
2519 newcon->next->flags &= ~CON_CONSDEV;
2521 newcon->next = console_drivers->next;
2522 console_drivers->next = newcon;
2524 if (newcon->flags & CON_PRINTBUFFER) {
2526 * console_unlock(); will print out the buffered messages
2529 raw_spin_lock_irqsave(&logbuf_lock, flags);
2530 console_seq = syslog_seq;
2531 console_idx = syslog_idx;
2532 console_prev = syslog_prev;
2533 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2535 * We're about to replay the log buffer. Only do this to the
2536 * just-registered console to avoid excessive message spam to
2537 * the already-registered consoles.
2539 exclusive_console = newcon;
2542 console_sysfs_notify();
2545 * By unregistering the bootconsoles after we enable the real console
2546 * we get the "console xxx enabled" message on all the consoles -
2547 * boot consoles, real consoles, etc - this is to ensure that end
2548 * users know there might be something in the kernel's log buffer that
2549 * went to the bootconsole (that they do not see on the real console)
2551 pr_info("%sconsole [%s%d] enabled\n",
2552 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2553 newcon->name, newcon->index);
2555 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2557 /* We need to iterate through all boot consoles, to make
2558 * sure we print everything out, before we unregister them.
2560 for_each_console(bcon)
2561 if (bcon->flags & CON_BOOT)
2562 unregister_console(bcon);
2565 EXPORT_SYMBOL(register_console);
2567 int unregister_console(struct console *console)
2569 struct console *a, *b;
2572 pr_info("%sconsole [%s%d] disabled\n",
2573 (console->flags & CON_BOOT) ? "boot" : "" ,
2574 console->name, console->index);
2576 res = _braille_unregister_console(console);
2582 if (console_drivers == console) {
2583 console_drivers=console->next;
2585 } else if (console_drivers) {
2586 for (a=console_drivers->next, b=console_drivers ;
2587 a; b=a, a=b->next) {
2597 * If this isn't the last console and it has CON_CONSDEV set, we
2598 * need to set it on the next preferred console.
2600 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2601 console_drivers->flags |= CON_CONSDEV;
2603 console->flags &= ~CON_ENABLED;
2605 console_sysfs_notify();
2608 EXPORT_SYMBOL(unregister_console);
2610 static int __init printk_late_init(void)
2612 struct console *con;
2614 for_each_console(con) {
2615 if (!keep_bootcon && con->flags & CON_BOOT) {
2616 unregister_console(con);
2619 hotcpu_notifier(console_cpu_notify, 0);
2622 late_initcall(printk_late_init);
2624 #if defined CONFIG_PRINTK
2626 * Delayed printk version, for scheduler-internal messages:
2628 #define PRINTK_PENDING_WAKEUP 0x01
2629 #define PRINTK_PENDING_OUTPUT 0x02
2631 static DEFINE_PER_CPU(int, printk_pending);
2633 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2635 int pending = __this_cpu_xchg(printk_pending, 0);
2637 if (pending & PRINTK_PENDING_OUTPUT) {
2638 /* If trylock fails, someone else is doing the printing */
2639 if (console_trylock())
2643 if (pending & PRINTK_PENDING_WAKEUP)
2644 wake_up_interruptible(&log_wait);
2647 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2648 .func = wake_up_klogd_work_func,
2649 .flags = IRQ_WORK_LAZY,
2652 void wake_up_klogd(void)
2655 if (waitqueue_active(&log_wait)) {
2656 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2657 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2662 int printk_deferred(const char *fmt, ...)
2668 va_start(args, fmt);
2669 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2672 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2673 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2680 * printk rate limiting, lifted from the networking subsystem.
2682 * This enforces a rate limit: not more than 10 kernel messages
2683 * every 5s to make a denial-of-service attack impossible.
2685 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2687 int __printk_ratelimit(const char *func)
2689 return ___ratelimit(&printk_ratelimit_state, func);
2691 EXPORT_SYMBOL(__printk_ratelimit);
2694 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2695 * @caller_jiffies: pointer to caller's state
2696 * @interval_msecs: minimum interval between prints
2698 * printk_timed_ratelimit() returns true if more than @interval_msecs
2699 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2702 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2703 unsigned int interval_msecs)
2705 unsigned long elapsed = jiffies - *caller_jiffies;
2707 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2710 *caller_jiffies = jiffies;
2713 EXPORT_SYMBOL(printk_timed_ratelimit);
2715 static DEFINE_SPINLOCK(dump_list_lock);
2716 static LIST_HEAD(dump_list);
2719 * kmsg_dump_register - register a kernel log dumper.
2720 * @dumper: pointer to the kmsg_dumper structure
2722 * Adds a kernel log dumper to the system. The dump callback in the
2723 * structure will be called when the kernel oopses or panics and must be
2724 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2726 int kmsg_dump_register(struct kmsg_dumper *dumper)
2728 unsigned long flags;
2731 /* The dump callback needs to be set */
2735 spin_lock_irqsave(&dump_list_lock, flags);
2736 /* Don't allow registering multiple times */
2737 if (!dumper->registered) {
2738 dumper->registered = 1;
2739 list_add_tail_rcu(&dumper->list, &dump_list);
2742 spin_unlock_irqrestore(&dump_list_lock, flags);
2746 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2749 * kmsg_dump_unregister - unregister a kmsg dumper.
2750 * @dumper: pointer to the kmsg_dumper structure
2752 * Removes a dump device from the system. Returns zero on success and
2753 * %-EINVAL otherwise.
2755 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2757 unsigned long flags;
2760 spin_lock_irqsave(&dump_list_lock, flags);
2761 if (dumper->registered) {
2762 dumper->registered = 0;
2763 list_del_rcu(&dumper->list);
2766 spin_unlock_irqrestore(&dump_list_lock, flags);
2771 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2773 static bool always_kmsg_dump;
2774 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2777 * kmsg_dump - dump kernel log to kernel message dumpers.
2778 * @reason: the reason (oops, panic etc) for dumping
2780 * Call each of the registered dumper's dump() callback, which can
2781 * retrieve the kmsg records with kmsg_dump_get_line() or
2782 * kmsg_dump_get_buffer().
2784 void kmsg_dump(enum kmsg_dump_reason reason)
2786 struct kmsg_dumper *dumper;
2787 unsigned long flags;
2789 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2793 list_for_each_entry_rcu(dumper, &dump_list, list) {
2794 if (dumper->max_reason && reason > dumper->max_reason)
2797 /* initialize iterator with data about the stored records */
2798 dumper->active = true;
2800 raw_spin_lock_irqsave(&logbuf_lock, flags);
2801 dumper->cur_seq = clear_seq;
2802 dumper->cur_idx = clear_idx;
2803 dumper->next_seq = log_next_seq;
2804 dumper->next_idx = log_next_idx;
2805 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2807 /* invoke dumper which will iterate over records */
2808 dumper->dump(dumper, reason);
2810 /* reset iterator */
2811 dumper->active = false;
2817 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2818 * @dumper: registered kmsg dumper
2819 * @syslog: include the "<4>" prefixes
2820 * @line: buffer to copy the line to
2821 * @size: maximum size of the buffer
2822 * @len: length of line placed into buffer
2824 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2825 * record, and copy one record into the provided buffer.
2827 * Consecutive calls will return the next available record moving
2828 * towards the end of the buffer with the youngest messages.
2830 * A return value of FALSE indicates that there are no more records to
2833 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2835 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2836 char *line, size_t size, size_t *len)
2838 struct printk_log *msg;
2842 if (!dumper->active)
2845 if (dumper->cur_seq < log_first_seq) {
2846 /* messages are gone, move to first available one */
2847 dumper->cur_seq = log_first_seq;
2848 dumper->cur_idx = log_first_idx;
2852 if (dumper->cur_seq >= log_next_seq)
2855 msg = log_from_idx(dumper->cur_idx);
2856 l = msg_print_text(msg, 0, syslog, line, size);
2858 dumper->cur_idx = log_next(dumper->cur_idx);
2868 * kmsg_dump_get_line - retrieve one kmsg log line
2869 * @dumper: registered kmsg dumper
2870 * @syslog: include the "<4>" prefixes
2871 * @line: buffer to copy the line to
2872 * @size: maximum size of the buffer
2873 * @len: length of line placed into buffer
2875 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2876 * record, and copy one record into the provided buffer.
2878 * Consecutive calls will return the next available record moving
2879 * towards the end of the buffer with the youngest messages.
2881 * A return value of FALSE indicates that there are no more records to
2884 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2885 char *line, size_t size, size_t *len)
2887 unsigned long flags;
2890 raw_spin_lock_irqsave(&logbuf_lock, flags);
2891 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2892 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2896 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2899 * kmsg_dump_get_buffer - copy kmsg log lines
2900 * @dumper: registered kmsg dumper
2901 * @syslog: include the "<4>" prefixes
2902 * @buf: buffer to copy the line to
2903 * @size: maximum size of the buffer
2904 * @len: length of line placed into buffer
2906 * Start at the end of the kmsg buffer and fill the provided buffer
2907 * with as many of the the *youngest* kmsg records that fit into it.
2908 * If the buffer is large enough, all available kmsg records will be
2909 * copied with a single call.
2911 * Consecutive calls will fill the buffer with the next block of
2912 * available older records, not including the earlier retrieved ones.
2914 * A return value of FALSE indicates that there are no more records to
2917 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2918 char *buf, size_t size, size_t *len)
2920 unsigned long flags;
2925 enum log_flags prev;
2929 if (!dumper->active)
2932 raw_spin_lock_irqsave(&logbuf_lock, flags);
2933 if (dumper->cur_seq < log_first_seq) {
2934 /* messages are gone, move to first available one */
2935 dumper->cur_seq = log_first_seq;
2936 dumper->cur_idx = log_first_idx;
2940 if (dumper->cur_seq >= dumper->next_seq) {
2941 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2945 /* calculate length of entire buffer */
2946 seq = dumper->cur_seq;
2947 idx = dumper->cur_idx;
2949 while (seq < dumper->next_seq) {
2950 struct printk_log *msg = log_from_idx(idx);
2952 l += msg_print_text(msg, prev, true, NULL, 0);
2953 idx = log_next(idx);
2958 /* move first record forward until length fits into the buffer */
2959 seq = dumper->cur_seq;
2960 idx = dumper->cur_idx;
2962 while (l > size && seq < dumper->next_seq) {
2963 struct printk_log *msg = log_from_idx(idx);
2965 l -= msg_print_text(msg, prev, true, NULL, 0);
2966 idx = log_next(idx);
2971 /* last message in next interation */
2976 while (seq < dumper->next_seq) {
2977 struct printk_log *msg = log_from_idx(idx);
2979 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2980 idx = log_next(idx);
2985 dumper->next_seq = next_seq;
2986 dumper->next_idx = next_idx;
2988 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2994 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2997 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2998 * @dumper: registered kmsg dumper
3000 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3001 * kmsg_dump_get_buffer() can be called again and used multiple
3002 * times within the same dumper.dump() callback.
3004 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3006 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3008 dumper->cur_seq = clear_seq;
3009 dumper->cur_idx = clear_idx;
3010 dumper->next_seq = log_next_seq;
3011 dumper->next_idx = log_next_idx;
3015 * kmsg_dump_rewind - reset the interator
3016 * @dumper: registered kmsg dumper
3018 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3019 * kmsg_dump_get_buffer() can be called again and used multiple
3020 * times within the same dumper.dump() callback.
3022 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3024 unsigned long flags;
3026 raw_spin_lock_irqsave(&logbuf_lock, flags);
3027 kmsg_dump_rewind_nolock(dumper);
3028 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3030 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3032 static char dump_stack_arch_desc_str[128];
3035 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3036 * @fmt: printf-style format string
3037 * @...: arguments for the format string
3039 * The configured string will be printed right after utsname during task
3040 * dumps. Usually used to add arch-specific system identifiers. If an
3041 * arch wants to make use of such an ID string, it should initialize this
3042 * as soon as possible during boot.
3044 void __init dump_stack_set_arch_desc(const char *fmt, ...)
3048 va_start(args, fmt);
3049 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3055 * dump_stack_print_info - print generic debug info for dump_stack()
3056 * @log_lvl: log level
3058 * Arch-specific dump_stack() implementations can use this function to
3059 * print out the same debug information as the generic dump_stack().
3061 void dump_stack_print_info(const char *log_lvl)
3063 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3064 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3065 print_tainted(), init_utsname()->release,
3066 (int)strcspn(init_utsname()->version, " "),
3067 init_utsname()->version);
3069 if (dump_stack_arch_desc_str[0] != '\0')
3070 printk("%sHardware name: %s\n",
3071 log_lvl, dump_stack_arch_desc_str);
3073 print_worker_info(log_lvl, current);
3077 * show_regs_print_info - print generic debug info for show_regs()
3078 * @log_lvl: log level
3080 * show_regs() implementations can use this function to print out generic
3081 * debug information.
3083 void show_regs_print_info(const char *log_lvl)
3085 dump_stack_print_info(log_lvl);
3087 printk("%stask: %p ti: %p task.ti: %p\n",
3088 log_lvl, current, current_thread_info(),
3089 task_thread_info(current));