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 * Number of registered extended console drivers.
90 * If extended consoles are present, in-kernel cont reassembly is disabled
91 * and each fragment is stored as a separate log entry with proper
92 * continuation flag so that every emitted message has full metadata. This
93 * doesn't change the result for regular consoles or /proc/kmsg. For
94 * /dev/kmsg, as long as the reader concatenates messages according to
95 * consecutive continuation flags, the end result should be the same too.
97 static int nr_ext_console_drivers;
100 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
101 * macros instead of functions so that _RET_IP_ contains useful information.
103 #define down_console_sem() do { \
105 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
108 static int __down_trylock_console_sem(unsigned long ip)
110 if (down_trylock(&console_sem))
112 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
115 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
117 #define up_console_sem() do { \
118 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
123 * This is used for debugging the mess that is the VT code by
124 * keeping track if we have the console semaphore held. It's
125 * definitely not the perfect debug tool (we don't know if _WE_
126 * hold it and are racing, but it helps tracking those weird code
127 * paths in the console code where we end up in places I want
128 * locked without the console sempahore held).
130 static int console_locked, console_suspended;
133 * If exclusive_console is non-NULL then only this console is to be printed to.
135 static struct console *exclusive_console;
138 * Array of consoles built from command line options (console=)
141 #define MAX_CMDLINECONSOLES 8
143 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
145 static int selected_console = -1;
146 static int preferred_console = -1;
147 int console_set_on_cmdline;
148 EXPORT_SYMBOL(console_set_on_cmdline);
150 /* Flag: console code may call schedule() */
151 static int console_may_schedule;
154 * The printk log buffer consists of a chain of concatenated variable
155 * length records. Every record starts with a record header, containing
156 * the overall length of the record.
158 * The heads to the first and last entry in the buffer, as well as the
159 * sequence numbers of these entries are maintained when messages are
162 * If the heads indicate available messages, the length in the header
163 * tells the start next message. A length == 0 for the next message
164 * indicates a wrap-around to the beginning of the buffer.
166 * Every record carries the monotonic timestamp in microseconds, as well as
167 * the standard userspace syslog level and syslog facility. The usual
168 * kernel messages use LOG_KERN; userspace-injected messages always carry
169 * a matching syslog facility, by default LOG_USER. The origin of every
170 * message can be reliably determined that way.
172 * The human readable log message directly follows the message header. The
173 * length of the message text is stored in the header, the stored message
176 * Optionally, a message can carry a dictionary of properties (key/value pairs),
177 * to provide userspace with a machine-readable message context.
179 * Examples for well-defined, commonly used property names are:
180 * DEVICE=b12:8 device identifier
184 * +sound:card0 subsystem:devname
185 * SUBSYSTEM=pci driver-core subsystem name
187 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
188 * follows directly after a '=' character. Every property is terminated by
189 * a '\0' character. The last property is not terminated.
191 * Example of a message structure:
192 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
193 * 0008 34 00 record is 52 bytes long
194 * 000a 0b 00 text is 11 bytes long
195 * 000c 1f 00 dictionary is 23 bytes long
196 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
197 * 0010 69 74 27 73 20 61 20 6c "it's a l"
199 * 001b 44 45 56 49 43 "DEVIC"
200 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
201 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
203 * 0032 00 00 00 padding to next message header
205 * The 'struct printk_log' buffer header must never be directly exported to
206 * userspace, it is a kernel-private implementation detail that might
207 * need to be changed in the future, when the requirements change.
209 * /dev/kmsg exports the structured data in the following line format:
210 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
212 * Users of the export format should ignore possible additional values
213 * separated by ',', and find the message after the ';' character.
215 * The optional key/value pairs are attached as continuation lines starting
216 * with a space character and terminated by a newline. All possible
217 * non-prinatable characters are escaped in the "\xff" notation.
221 LOG_NOCONS = 1, /* already flushed, do not print to console */
222 LOG_NEWLINE = 2, /* text ended with a newline */
223 LOG_PREFIX = 4, /* text started with a prefix */
224 LOG_CONT = 8, /* text is a fragment of a continuation line */
228 u64 ts_nsec; /* timestamp in nanoseconds */
229 u16 len; /* length of entire record */
230 u16 text_len; /* length of text buffer */
231 u16 dict_len; /* length of dictionary buffer */
232 u8 facility; /* syslog facility */
233 u8 flags:5; /* internal record flags */
234 u8 level:3; /* syslog level */
238 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
239 * within the scheduler's rq lock. It must be released before calling
240 * console_unlock() or anything else that might wake up a process.
242 static DEFINE_RAW_SPINLOCK(logbuf_lock);
245 DECLARE_WAIT_QUEUE_HEAD(log_wait);
246 /* the next printk record to read by syslog(READ) or /proc/kmsg */
247 static u64 syslog_seq;
248 static u32 syslog_idx;
249 static enum log_flags syslog_prev;
250 static size_t syslog_partial;
252 /* index and sequence number of the first record stored in the buffer */
253 static u64 log_first_seq;
254 static u32 log_first_idx;
256 /* index and sequence number of the next record to store in the buffer */
257 static u64 log_next_seq;
258 static u32 log_next_idx;
260 /* the next printk record to write to the console */
261 static u64 console_seq;
262 static u32 console_idx;
263 static enum log_flags console_prev;
265 /* the next printk record to read after the last 'clear' command */
266 static u64 clear_seq;
267 static u32 clear_idx;
269 #define PREFIX_MAX 32
270 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
273 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
276 #define LOG_ALIGN __alignof__(struct printk_log)
278 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
279 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
280 static char *log_buf = __log_buf;
281 static u32 log_buf_len = __LOG_BUF_LEN;
283 /* Return log buffer address */
284 char *log_buf_addr_get(void)
289 /* Return log buffer size */
290 u32 log_buf_len_get(void)
295 /* human readable text of the record */
296 static char *log_text(const struct printk_log *msg)
298 return (char *)msg + sizeof(struct printk_log);
301 /* optional key/value pair dictionary attached to the record */
302 static char *log_dict(const struct printk_log *msg)
304 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
307 /* get record by index; idx must point to valid msg */
308 static struct printk_log *log_from_idx(u32 idx)
310 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
313 * A length == 0 record is the end of buffer marker. Wrap around and
314 * read the message at the start of the buffer.
317 return (struct printk_log *)log_buf;
321 /* get next record; idx must point to valid msg */
322 static u32 log_next(u32 idx)
324 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
326 /* length == 0 indicates the end of the buffer; wrap */
328 * A length == 0 record is the end of buffer marker. Wrap around and
329 * read the message at the start of the buffer as *this* one, and
330 * return the one after that.
333 msg = (struct printk_log *)log_buf;
336 return idx + msg->len;
340 * Check whether there is enough free space for the given message.
342 * The same values of first_idx and next_idx mean that the buffer
343 * is either empty or full.
345 * If the buffer is empty, we must respect the position of the indexes.
346 * They cannot be reset to the beginning of the buffer.
348 static int logbuf_has_space(u32 msg_size, bool empty)
352 if (log_next_idx > log_first_idx || empty)
353 free = max(log_buf_len - log_next_idx, log_first_idx);
355 free = log_first_idx - log_next_idx;
358 * We need space also for an empty header that signalizes wrapping
361 return free >= msg_size + sizeof(struct printk_log);
364 static int log_make_free_space(u32 msg_size)
366 while (log_first_seq < log_next_seq) {
367 if (logbuf_has_space(msg_size, false))
369 /* drop old messages until we have enough contiguous space */
370 log_first_idx = log_next(log_first_idx);
374 /* sequence numbers are equal, so the log buffer is empty */
375 if (logbuf_has_space(msg_size, true))
381 /* compute the message size including the padding bytes */
382 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
386 size = sizeof(struct printk_log) + text_len + dict_len;
387 *pad_len = (-size) & (LOG_ALIGN - 1);
394 * Define how much of the log buffer we could take at maximum. The value
395 * must be greater than two. Note that only half of the buffer is available
396 * when the index points to the middle.
398 #define MAX_LOG_TAKE_PART 4
399 static const char trunc_msg[] = "<truncated>";
401 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
402 u16 *dict_len, u32 *pad_len)
405 * The message should not take the whole buffer. Otherwise, it might
406 * get removed too soon.
408 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
409 if (*text_len > max_text_len)
410 *text_len = max_text_len;
411 /* enable the warning message */
412 *trunc_msg_len = strlen(trunc_msg);
413 /* disable the "dict" completely */
415 /* compute the size again, count also the warning message */
416 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
419 /* insert record into the buffer, discard old ones, update heads */
420 static int log_store(int facility, int level,
421 enum log_flags flags, u64 ts_nsec,
422 const char *dict, u16 dict_len,
423 const char *text, u16 text_len)
425 struct printk_log *msg;
427 u16 trunc_msg_len = 0;
429 /* number of '\0' padding bytes to next message */
430 size = msg_used_size(text_len, dict_len, &pad_len);
432 if (log_make_free_space(size)) {
433 /* truncate the message if it is too long for empty buffer */
434 size = truncate_msg(&text_len, &trunc_msg_len,
435 &dict_len, &pad_len);
436 /* survive when the log buffer is too small for trunc_msg */
437 if (log_make_free_space(size))
441 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
443 * This message + an additional empty header does not fit
444 * at the end of the buffer. Add an empty header with len == 0
445 * to signify a wrap around.
447 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
452 msg = (struct printk_log *)(log_buf + log_next_idx);
453 memcpy(log_text(msg), text, text_len);
454 msg->text_len = text_len;
456 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
457 msg->text_len += trunc_msg_len;
459 memcpy(log_dict(msg), dict, dict_len);
460 msg->dict_len = dict_len;
461 msg->facility = facility;
462 msg->level = level & 7;
463 msg->flags = flags & 0x1f;
465 msg->ts_nsec = ts_nsec;
467 msg->ts_nsec = local_clock();
468 memset(log_dict(msg) + dict_len, 0, pad_len);
472 log_next_idx += msg->len;
475 return msg->text_len;
478 int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
480 static int syslog_action_restricted(int type)
485 * Unless restricted, we allow "read all" and "get buffer size"
488 return type != SYSLOG_ACTION_READ_ALL &&
489 type != SYSLOG_ACTION_SIZE_BUFFER;
492 int check_syslog_permissions(int type, int source)
495 * If this is from /proc/kmsg and we've already opened it, then we've
496 * already done the capabilities checks at open time.
498 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
501 if (syslog_action_restricted(type)) {
502 if (capable(CAP_SYSLOG))
505 * For historical reasons, accept CAP_SYS_ADMIN too, with
508 if (capable(CAP_SYS_ADMIN)) {
509 pr_warn_once("%s (%d): Attempt to access syslog with "
510 "CAP_SYS_ADMIN but no CAP_SYSLOG "
512 current->comm, task_pid_nr(current));
518 return security_syslog(type);
520 EXPORT_SYMBOL_GPL(check_syslog_permissions);
522 static void append_char(char **pp, char *e, char c)
528 static ssize_t msg_print_ext_header(char *buf, size_t size,
529 struct printk_log *msg, u64 seq,
530 enum log_flags prev_flags)
532 u64 ts_usec = msg->ts_nsec;
535 do_div(ts_usec, 1000);
538 * If we couldn't merge continuation line fragments during the print,
539 * export the stored flags to allow an optional external merge of the
540 * records. Merging the records isn't always neccessarily correct, like
541 * when we hit a race during printing. In most cases though, it produces
542 * better readable output. 'c' in the record flags mark the first
543 * fragment of a line, '+' the following.
545 if (msg->flags & LOG_CONT && !(prev_flags & LOG_CONT))
547 else if ((msg->flags & LOG_CONT) ||
548 ((prev_flags & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
551 return scnprintf(buf, size, "%u,%llu,%llu,%c;",
552 (msg->facility << 3) | msg->level, seq, ts_usec, cont);
555 static ssize_t msg_print_ext_body(char *buf, size_t size,
556 char *dict, size_t dict_len,
557 char *text, size_t text_len)
559 char *p = buf, *e = buf + size;
562 /* escape non-printable characters */
563 for (i = 0; i < text_len; i++) {
564 unsigned char c = text[i];
566 if (c < ' ' || c >= 127 || c == '\\')
567 p += scnprintf(p, e - p, "\\x%02x", c);
569 append_char(&p, e, c);
571 append_char(&p, e, '\n');
576 for (i = 0; i < dict_len; i++) {
577 unsigned char c = dict[i];
580 append_char(&p, e, ' ');
585 append_char(&p, e, '\n');
590 if (c < ' ' || c >= 127 || c == '\\') {
591 p += scnprintf(p, e - p, "\\x%02x", c);
595 append_char(&p, e, c);
597 append_char(&p, e, '\n');
603 /* /dev/kmsg - userspace message inject/listen interface */
604 struct devkmsg_user {
609 char buf[CONSOLE_EXT_LOG_MAX];
612 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
616 int level = default_message_loglevel;
617 int facility = 1; /* LOG_USER */
618 size_t len = iov_iter_count(from);
621 if (len > LOG_LINE_MAX)
623 buf = kmalloc(len+1, GFP_KERNEL);
628 if (copy_from_iter(buf, len, from) != len) {
634 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
635 * the decimal value represents 32bit, the lower 3 bit are the log
636 * level, the rest are the log facility.
638 * If no prefix or no userspace facility is specified, we
639 * enforce LOG_USER, to be able to reliably distinguish
640 * kernel-generated messages from userspace-injected ones.
643 if (line[0] == '<') {
646 i = simple_strtoul(line+1, &endp, 10);
647 if (endp && endp[0] == '>') {
657 printk_emit(facility, level, NULL, 0, "%s", line);
662 static ssize_t devkmsg_read(struct file *file, char __user *buf,
663 size_t count, loff_t *ppos)
665 struct devkmsg_user *user = file->private_data;
666 struct printk_log *msg;
673 ret = mutex_lock_interruptible(&user->lock);
676 raw_spin_lock_irq(&logbuf_lock);
677 while (user->seq == log_next_seq) {
678 if (file->f_flags & O_NONBLOCK) {
680 raw_spin_unlock_irq(&logbuf_lock);
684 raw_spin_unlock_irq(&logbuf_lock);
685 ret = wait_event_interruptible(log_wait,
686 user->seq != log_next_seq);
689 raw_spin_lock_irq(&logbuf_lock);
692 if (user->seq < log_first_seq) {
693 /* our last seen message is gone, return error and reset */
694 user->idx = log_first_idx;
695 user->seq = log_first_seq;
697 raw_spin_unlock_irq(&logbuf_lock);
701 msg = log_from_idx(user->idx);
702 len = msg_print_ext_header(user->buf, sizeof(user->buf),
703 msg, user->seq, user->prev);
704 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
705 log_dict(msg), msg->dict_len,
706 log_text(msg), msg->text_len);
708 user->prev = msg->flags;
709 user->idx = log_next(user->idx);
711 raw_spin_unlock_irq(&logbuf_lock);
718 if (copy_to_user(buf, user->buf, len)) {
724 mutex_unlock(&user->lock);
728 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
730 struct devkmsg_user *user = file->private_data;
738 raw_spin_lock_irq(&logbuf_lock);
741 /* the first record */
742 user->idx = log_first_idx;
743 user->seq = log_first_seq;
747 * The first record after the last SYSLOG_ACTION_CLEAR,
748 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
749 * changes no global state, and does not clear anything.
751 user->idx = clear_idx;
752 user->seq = clear_seq;
755 /* after the last record */
756 user->idx = log_next_idx;
757 user->seq = log_next_seq;
762 raw_spin_unlock_irq(&logbuf_lock);
766 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
768 struct devkmsg_user *user = file->private_data;
772 return POLLERR|POLLNVAL;
774 poll_wait(file, &log_wait, wait);
776 raw_spin_lock_irq(&logbuf_lock);
777 if (user->seq < log_next_seq) {
778 /* return error when data has vanished underneath us */
779 if (user->seq < log_first_seq)
780 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
782 ret = POLLIN|POLLRDNORM;
784 raw_spin_unlock_irq(&logbuf_lock);
789 static int devkmsg_open(struct inode *inode, struct file *file)
791 struct devkmsg_user *user;
794 /* write-only does not need any file context */
795 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
798 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
803 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
807 mutex_init(&user->lock);
809 raw_spin_lock_irq(&logbuf_lock);
810 user->idx = log_first_idx;
811 user->seq = log_first_seq;
812 raw_spin_unlock_irq(&logbuf_lock);
814 file->private_data = user;
818 static int devkmsg_release(struct inode *inode, struct file *file)
820 struct devkmsg_user *user = file->private_data;
825 mutex_destroy(&user->lock);
830 const struct file_operations kmsg_fops = {
831 .open = devkmsg_open,
832 .read = devkmsg_read,
833 .write_iter = devkmsg_write,
834 .llseek = devkmsg_llseek,
835 .poll = devkmsg_poll,
836 .release = devkmsg_release,
839 #ifdef CONFIG_KEXEC_CORE
841 * This appends the listed symbols to /proc/vmcore
843 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
844 * obtain access to symbols that are otherwise very difficult to locate. These
845 * symbols are specifically used so that utilities can access and extract the
846 * dmesg log from a vmcore file after a crash.
848 void log_buf_kexec_setup(void)
850 VMCOREINFO_SYMBOL(log_buf);
851 VMCOREINFO_SYMBOL(log_buf_len);
852 VMCOREINFO_SYMBOL(log_first_idx);
853 VMCOREINFO_SYMBOL(log_next_idx);
855 * Export struct printk_log size and field offsets. User space tools can
856 * parse it and detect any changes to structure down the line.
858 VMCOREINFO_STRUCT_SIZE(printk_log);
859 VMCOREINFO_OFFSET(printk_log, ts_nsec);
860 VMCOREINFO_OFFSET(printk_log, len);
861 VMCOREINFO_OFFSET(printk_log, text_len);
862 VMCOREINFO_OFFSET(printk_log, dict_len);
866 /* requested log_buf_len from kernel cmdline */
867 static unsigned long __initdata new_log_buf_len;
869 /* we practice scaling the ring buffer by powers of 2 */
870 static void __init log_buf_len_update(unsigned size)
873 size = roundup_pow_of_two(size);
874 if (size > log_buf_len)
875 new_log_buf_len = size;
878 /* save requested log_buf_len since it's too early to process it */
879 static int __init log_buf_len_setup(char *str)
881 unsigned size = memparse(str, &str);
883 log_buf_len_update(size);
887 early_param("log_buf_len", log_buf_len_setup);
890 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
892 static void __init log_buf_add_cpu(void)
894 unsigned int cpu_extra;
897 * archs should set up cpu_possible_bits properly with
898 * set_cpu_possible() after setup_arch() but just in
899 * case lets ensure this is valid.
901 if (num_possible_cpus() == 1)
904 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
906 /* by default this will only continue through for large > 64 CPUs */
907 if (cpu_extra <= __LOG_BUF_LEN / 2)
910 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
911 __LOG_CPU_MAX_BUF_LEN);
912 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
914 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
916 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
918 #else /* !CONFIG_SMP */
919 static inline void log_buf_add_cpu(void) {}
920 #endif /* CONFIG_SMP */
922 void __init setup_log_buf(int early)
928 if (log_buf != __log_buf)
931 if (!early && !new_log_buf_len)
934 if (!new_log_buf_len)
939 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
941 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
945 if (unlikely(!new_log_buf)) {
946 pr_err("log_buf_len: %ld bytes not available\n",
951 raw_spin_lock_irqsave(&logbuf_lock, flags);
952 log_buf_len = new_log_buf_len;
953 log_buf = new_log_buf;
955 free = __LOG_BUF_LEN - log_next_idx;
956 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
957 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
959 pr_info("log_buf_len: %d bytes\n", log_buf_len);
960 pr_info("early log buf free: %d(%d%%)\n",
961 free, (free * 100) / __LOG_BUF_LEN);
964 static bool __read_mostly ignore_loglevel;
966 static int __init ignore_loglevel_setup(char *str)
968 ignore_loglevel = true;
969 pr_info("debug: ignoring loglevel setting.\n");
974 early_param("ignore_loglevel", ignore_loglevel_setup);
975 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
976 MODULE_PARM_DESC(ignore_loglevel,
977 "ignore loglevel setting (prints all kernel messages to the console)");
979 #ifdef CONFIG_BOOT_PRINTK_DELAY
981 static int boot_delay; /* msecs delay after each printk during bootup */
982 static unsigned long long loops_per_msec; /* based on boot_delay */
984 static int __init boot_delay_setup(char *str)
988 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
989 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
991 get_option(&str, &boot_delay);
992 if (boot_delay > 10 * 1000)
995 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
996 "HZ: %d, loops_per_msec: %llu\n",
997 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1000 early_param("boot_delay", boot_delay_setup);
1002 static void boot_delay_msec(int level)
1004 unsigned long long k;
1005 unsigned long timeout;
1007 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
1008 || (level >= console_loglevel && !ignore_loglevel)) {
1012 k = (unsigned long long)loops_per_msec * boot_delay;
1014 timeout = jiffies + msecs_to_jiffies(boot_delay);
1019 * use (volatile) jiffies to prevent
1020 * compiler reduction; loop termination via jiffies
1021 * is secondary and may or may not happen.
1023 if (time_after(jiffies, timeout))
1025 touch_nmi_watchdog();
1029 static inline void boot_delay_msec(int level)
1034 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1035 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1037 static size_t print_time(u64 ts, char *buf)
1039 unsigned long rem_nsec;
1044 rem_nsec = do_div(ts, 1000000000);
1047 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1049 return sprintf(buf, "[%5lu.%06lu] ",
1050 (unsigned long)ts, rem_nsec / 1000);
1053 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1056 unsigned int prefix = (msg->facility << 3) | msg->level;
1060 len += sprintf(buf, "<%u>", prefix);
1065 else if (prefix > 99)
1067 else if (prefix > 9)
1072 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1076 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1077 bool syslog, char *buf, size_t size)
1079 const char *text = log_text(msg);
1080 size_t text_size = msg->text_len;
1082 bool newline = true;
1085 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1088 if (msg->flags & LOG_CONT) {
1089 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1092 if (!(msg->flags & LOG_NEWLINE))
1097 const char *next = memchr(text, '\n', text_size);
1101 text_len = next - text;
1103 text_size -= next - text;
1105 text_len = text_size;
1109 if (print_prefix(msg, syslog, NULL) +
1110 text_len + 1 >= size - len)
1114 len += print_prefix(msg, syslog, buf + len);
1115 memcpy(buf + len, text, text_len);
1117 if (next || newline)
1120 /* SYSLOG_ACTION_* buffer size only calculation */
1122 len += print_prefix(msg, syslog, NULL);
1124 if (next || newline)
1135 static int syslog_print(char __user *buf, int size)
1138 struct printk_log *msg;
1141 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1149 raw_spin_lock_irq(&logbuf_lock);
1150 if (syslog_seq < log_first_seq) {
1151 /* messages are gone, move to first one */
1152 syslog_seq = log_first_seq;
1153 syslog_idx = log_first_idx;
1157 if (syslog_seq == log_next_seq) {
1158 raw_spin_unlock_irq(&logbuf_lock);
1162 skip = syslog_partial;
1163 msg = log_from_idx(syslog_idx);
1164 n = msg_print_text(msg, syslog_prev, true, text,
1165 LOG_LINE_MAX + PREFIX_MAX);
1166 if (n - syslog_partial <= size) {
1167 /* message fits into buffer, move forward */
1168 syslog_idx = log_next(syslog_idx);
1170 syslog_prev = msg->flags;
1171 n -= syslog_partial;
1174 /* partial read(), remember position */
1176 syslog_partial += n;
1179 raw_spin_unlock_irq(&logbuf_lock);
1184 if (copy_to_user(buf, text + skip, n)) {
1199 static int syslog_print_all(char __user *buf, int size, bool clear)
1204 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1208 raw_spin_lock_irq(&logbuf_lock);
1213 enum log_flags prev;
1215 if (clear_seq < log_first_seq) {
1216 /* messages are gone, move to first available one */
1217 clear_seq = log_first_seq;
1218 clear_idx = log_first_idx;
1222 * Find first record that fits, including all following records,
1223 * into the user-provided buffer for this dump.
1228 while (seq < log_next_seq) {
1229 struct printk_log *msg = log_from_idx(idx);
1231 len += msg_print_text(msg, prev, true, NULL, 0);
1233 idx = log_next(idx);
1237 /* move first record forward until length fits into the buffer */
1241 while (len > size && seq < log_next_seq) {
1242 struct printk_log *msg = log_from_idx(idx);
1244 len -= msg_print_text(msg, prev, true, NULL, 0);
1246 idx = log_next(idx);
1250 /* last message fitting into this dump */
1251 next_seq = log_next_seq;
1254 while (len >= 0 && seq < next_seq) {
1255 struct printk_log *msg = log_from_idx(idx);
1258 textlen = msg_print_text(msg, prev, true, text,
1259 LOG_LINE_MAX + PREFIX_MAX);
1264 idx = log_next(idx);
1268 raw_spin_unlock_irq(&logbuf_lock);
1269 if (copy_to_user(buf + len, text, textlen))
1273 raw_spin_lock_irq(&logbuf_lock);
1275 if (seq < log_first_seq) {
1276 /* messages are gone, move to next one */
1277 seq = log_first_seq;
1278 idx = log_first_idx;
1285 clear_seq = log_next_seq;
1286 clear_idx = log_next_idx;
1288 raw_spin_unlock_irq(&logbuf_lock);
1294 int do_syslog(int type, char __user *buf, int len, int source)
1297 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1300 error = check_syslog_permissions(type, source);
1305 case SYSLOG_ACTION_CLOSE: /* Close log */
1307 case SYSLOG_ACTION_OPEN: /* Open log */
1309 case SYSLOG_ACTION_READ: /* Read from log */
1311 if (!buf || len < 0)
1316 if (!access_ok(VERIFY_WRITE, buf, len)) {
1320 error = wait_event_interruptible(log_wait,
1321 syslog_seq != log_next_seq);
1324 error = syslog_print(buf, len);
1326 /* Read/clear last kernel messages */
1327 case SYSLOG_ACTION_READ_CLEAR:
1330 /* Read last kernel messages */
1331 case SYSLOG_ACTION_READ_ALL:
1333 if (!buf || len < 0)
1338 if (!access_ok(VERIFY_WRITE, buf, len)) {
1342 error = syslog_print_all(buf, len, clear);
1344 /* Clear ring buffer */
1345 case SYSLOG_ACTION_CLEAR:
1346 syslog_print_all(NULL, 0, true);
1348 /* Disable logging to console */
1349 case SYSLOG_ACTION_CONSOLE_OFF:
1350 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1351 saved_console_loglevel = console_loglevel;
1352 console_loglevel = minimum_console_loglevel;
1354 /* Enable logging to console */
1355 case SYSLOG_ACTION_CONSOLE_ON:
1356 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1357 console_loglevel = saved_console_loglevel;
1358 saved_console_loglevel = LOGLEVEL_DEFAULT;
1361 /* Set level of messages printed to console */
1362 case SYSLOG_ACTION_CONSOLE_LEVEL:
1364 if (len < 1 || len > 8)
1366 if (len < minimum_console_loglevel)
1367 len = minimum_console_loglevel;
1368 console_loglevel = len;
1369 /* Implicitly re-enable logging to console */
1370 saved_console_loglevel = LOGLEVEL_DEFAULT;
1373 /* Number of chars in the log buffer */
1374 case SYSLOG_ACTION_SIZE_UNREAD:
1375 raw_spin_lock_irq(&logbuf_lock);
1376 if (syslog_seq < log_first_seq) {
1377 /* messages are gone, move to first one */
1378 syslog_seq = log_first_seq;
1379 syslog_idx = log_first_idx;
1383 if (source == SYSLOG_FROM_PROC) {
1385 * Short-cut for poll(/"proc/kmsg") which simply checks
1386 * for pending data, not the size; return the count of
1387 * records, not the length.
1389 error = log_next_seq - syslog_seq;
1391 u64 seq = syslog_seq;
1392 u32 idx = syslog_idx;
1393 enum log_flags prev = syslog_prev;
1396 while (seq < log_next_seq) {
1397 struct printk_log *msg = log_from_idx(idx);
1399 error += msg_print_text(msg, prev, true, NULL, 0);
1400 idx = log_next(idx);
1404 error -= syslog_partial;
1406 raw_spin_unlock_irq(&logbuf_lock);
1408 /* Size of the log buffer */
1409 case SYSLOG_ACTION_SIZE_BUFFER:
1410 error = log_buf_len;
1420 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1422 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1426 * Call the console drivers, asking them to write out
1427 * log_buf[start] to log_buf[end - 1].
1428 * The console_lock must be held.
1430 static void call_console_drivers(int level,
1431 const char *ext_text, size_t ext_len,
1432 const char *text, size_t len)
1434 struct console *con;
1436 trace_console(text, len);
1438 if (level >= console_loglevel && !ignore_loglevel)
1440 if (!console_drivers)
1443 for_each_console(con) {
1444 if (exclusive_console && con != exclusive_console)
1446 if (!(con->flags & CON_ENABLED))
1450 if (!cpu_online(smp_processor_id()) &&
1451 !(con->flags & CON_ANYTIME))
1453 if (con->flags & CON_EXTENDED)
1454 con->write(con, ext_text, ext_len);
1456 con->write(con, text, len);
1461 * Zap console related locks when oopsing.
1462 * To leave time for slow consoles to print a full oops,
1463 * only zap at most once every 30 seconds.
1465 static void zap_locks(void)
1467 static unsigned long oops_timestamp;
1469 if (time_after_eq(jiffies, oops_timestamp) &&
1470 !time_after(jiffies, oops_timestamp + 30 * HZ))
1473 oops_timestamp = jiffies;
1476 /* If a crash is occurring, make sure we can't deadlock */
1477 raw_spin_lock_init(&logbuf_lock);
1478 /* And make sure that we print immediately */
1479 sema_init(&console_sem, 1);
1483 * Check if we have any console that is capable of printing while cpu is
1484 * booting or shutting down. Requires console_sem.
1486 static int have_callable_console(void)
1488 struct console *con;
1490 for_each_console(con)
1491 if (con->flags & CON_ANYTIME)
1498 * Can we actually use the console at this time on this cpu?
1500 * Console drivers may assume that per-cpu resources have been allocated. So
1501 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1502 * call them until this CPU is officially up.
1504 static inline int can_use_console(unsigned int cpu)
1506 return cpu_online(cpu) || have_callable_console();
1510 * Try to get console ownership to actually show the kernel
1511 * messages from a 'printk'. Return true (and with the
1512 * console_lock held, and 'console_locked' set) if it
1513 * is successful, false otherwise.
1515 static int console_trylock_for_printk(void)
1517 unsigned int cpu = smp_processor_id();
1519 if (!console_trylock())
1522 * If we can't use the console, we need to release the console
1523 * semaphore by hand to avoid flushing the buffer. We need to hold the
1524 * console semaphore in order to do this test safely.
1526 if (!can_use_console(cpu)) {
1534 int printk_delay_msec __read_mostly;
1536 static inline void printk_delay(void)
1538 if (unlikely(printk_delay_msec)) {
1539 int m = printk_delay_msec;
1543 touch_nmi_watchdog();
1549 * Continuation lines are buffered, and not committed to the record buffer
1550 * until the line is complete, or a race forces it. The line fragments
1551 * though, are printed immediately to the consoles to ensure everything has
1552 * reached the console in case of a kernel crash.
1554 static struct cont {
1555 char buf[LOG_LINE_MAX];
1556 size_t len; /* length == 0 means unused buffer */
1557 size_t cons; /* bytes written to console */
1558 struct task_struct *owner; /* task of first print*/
1559 u64 ts_nsec; /* time of first print */
1560 u8 level; /* log level of first message */
1561 u8 facility; /* log facility of first message */
1562 enum log_flags flags; /* prefix, newline flags */
1563 bool flushed:1; /* buffer sealed and committed */
1566 static void cont_flush(enum log_flags flags)
1575 * If a fragment of this line was directly flushed to the
1576 * console; wait for the console to pick up the rest of the
1577 * line. LOG_NOCONS suppresses a duplicated output.
1579 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1580 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1582 cont.flushed = true;
1585 * If no fragment of this line ever reached the console,
1586 * just submit it to the store and free the buffer.
1588 log_store(cont.facility, cont.level, flags, 0,
1589 NULL, 0, cont.buf, cont.len);
1594 static bool cont_add(int facility, int level, const char *text, size_t len)
1596 if (cont.len && cont.flushed)
1600 * If ext consoles are present, flush and skip in-kernel
1601 * continuation. See nr_ext_console_drivers definition. Also, if
1602 * the line gets too long, split it up in separate records.
1604 if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
1605 cont_flush(LOG_CONT);
1610 cont.facility = facility;
1612 cont.owner = current;
1613 cont.ts_nsec = local_clock();
1616 cont.flushed = false;
1619 memcpy(cont.buf + cont.len, text, len);
1622 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1623 cont_flush(LOG_CONT);
1628 static size_t cont_print_text(char *text, size_t size)
1633 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1634 textlen += print_time(cont.ts_nsec, text);
1638 len = cont.len - cont.cons;
1642 memcpy(text + textlen, cont.buf + cont.cons, len);
1644 cont.cons = cont.len;
1648 if (cont.flags & LOG_NEWLINE)
1649 text[textlen++] = '\n';
1650 /* got everything, release buffer */
1656 asmlinkage int vprintk_emit(int facility, int level,
1657 const char *dict, size_t dictlen,
1658 const char *fmt, va_list args)
1660 static int recursion_bug;
1661 static char textbuf[LOG_LINE_MAX];
1662 char *text = textbuf;
1663 size_t text_len = 0;
1664 enum log_flags lflags = 0;
1665 unsigned long flags;
1667 int printed_len = 0;
1668 bool in_sched = false;
1669 /* cpu currently holding logbuf_lock in this function */
1670 static unsigned int logbuf_cpu = UINT_MAX;
1672 if (level == LOGLEVEL_SCHED) {
1673 level = LOGLEVEL_DEFAULT;
1677 boot_delay_msec(level);
1680 /* This stops the holder of console_sem just where we want him */
1681 local_irq_save(flags);
1682 this_cpu = smp_processor_id();
1685 * Ouch, printk recursed into itself!
1687 if (unlikely(logbuf_cpu == this_cpu)) {
1689 * If a crash is occurring during printk() on this CPU,
1690 * then try to get the crash message out but make sure
1691 * we can't deadlock. Otherwise just return to avoid the
1692 * recursion and return - but flag the recursion so that
1693 * it can be printed at the next appropriate moment:
1695 if (!oops_in_progress && !lockdep_recursing(current)) {
1697 local_irq_restore(flags);
1704 raw_spin_lock(&logbuf_lock);
1705 logbuf_cpu = this_cpu;
1707 if (unlikely(recursion_bug)) {
1708 static const char recursion_msg[] =
1709 "BUG: recent printk recursion!";
1712 /* emit KERN_CRIT message */
1713 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1714 NULL, 0, recursion_msg,
1715 strlen(recursion_msg));
1719 * The printf needs to come first; we need the syslog
1720 * prefix which might be passed-in as a parameter.
1722 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1724 /* mark and strip a trailing newline */
1725 if (text_len && text[text_len-1] == '\n') {
1727 lflags |= LOG_NEWLINE;
1730 /* strip kernel syslog prefix and extract log level or control flags */
1731 if (facility == 0) {
1732 int kern_level = printk_get_level(text);
1735 const char *end_of_header = printk_skip_level(text);
1736 switch (kern_level) {
1738 if (level == LOGLEVEL_DEFAULT)
1739 level = kern_level - '0';
1741 case 'd': /* KERN_DEFAULT */
1742 lflags |= LOG_PREFIX;
1745 * No need to check length here because vscnprintf
1746 * put '\0' at the end of the string. Only valid and
1747 * newly printed level is detected.
1749 text_len -= end_of_header - text;
1750 text = (char *)end_of_header;
1754 if (level == LOGLEVEL_DEFAULT)
1755 level = default_message_loglevel;
1758 lflags |= LOG_PREFIX|LOG_NEWLINE;
1760 if (!(lflags & LOG_NEWLINE)) {
1762 * Flush the conflicting buffer. An earlier newline was missing,
1763 * or another task also prints continuation lines.
1765 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1766 cont_flush(LOG_NEWLINE);
1768 /* buffer line if possible, otherwise store it right away */
1769 if (cont_add(facility, level, text, text_len))
1770 printed_len += text_len;
1772 printed_len += log_store(facility, level,
1773 lflags | LOG_CONT, 0,
1774 dict, dictlen, text, text_len);
1776 bool stored = false;
1779 * If an earlier newline was missing and it was the same task,
1780 * either merge it with the current buffer and flush, or if
1781 * there was a race with interrupts (prefix == true) then just
1782 * flush it out and store this line separately.
1783 * If the preceding printk was from a different task and missed
1784 * a newline, flush and append the newline.
1787 if (cont.owner == current && !(lflags & LOG_PREFIX))
1788 stored = cont_add(facility, level, text,
1790 cont_flush(LOG_NEWLINE);
1794 printed_len += text_len;
1796 printed_len += log_store(facility, level, lflags, 0,
1797 dict, dictlen, text, text_len);
1800 logbuf_cpu = UINT_MAX;
1801 raw_spin_unlock(&logbuf_lock);
1803 local_irq_restore(flags);
1805 /* If called from the scheduler, we can not call up(). */
1809 * Disable preemption to avoid being preempted while holding
1810 * console_sem which would prevent anyone from printing to
1816 * Try to acquire and then immediately release the console
1817 * semaphore. The release will print out buffers and wake up
1818 * /dev/kmsg and syslog() users.
1820 if (console_trylock_for_printk())
1828 EXPORT_SYMBOL(vprintk_emit);
1830 asmlinkage int vprintk(const char *fmt, va_list args)
1832 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1834 EXPORT_SYMBOL(vprintk);
1836 asmlinkage int printk_emit(int facility, int level,
1837 const char *dict, size_t dictlen,
1838 const char *fmt, ...)
1843 va_start(args, fmt);
1844 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1849 EXPORT_SYMBOL(printk_emit);
1851 int vprintk_default(const char *fmt, va_list args)
1855 #ifdef CONFIG_KGDB_KDB
1856 if (unlikely(kdb_trap_printk)) {
1857 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1861 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1865 EXPORT_SYMBOL_GPL(vprintk_default);
1868 * This allows printk to be diverted to another function per cpu.
1869 * This is useful for calling printk functions from within NMI
1870 * without worrying about race conditions that can lock up the
1873 DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
1876 * printk - print a kernel message
1877 * @fmt: format string
1879 * This is printk(). It can be called from any context. We want it to work.
1881 * We try to grab the console_lock. If we succeed, it's easy - we log the
1882 * output and call the console drivers. If we fail to get the semaphore, we
1883 * place the output into the log buffer and return. The current holder of
1884 * the console_sem will notice the new output in console_unlock(); and will
1885 * send it to the consoles before releasing the lock.
1887 * One effect of this deferred printing is that code which calls printk() and
1888 * then changes console_loglevel may break. This is because console_loglevel
1889 * is inspected when the actual printing occurs.
1894 * See the vsnprintf() documentation for format string extensions over C99.
1896 asmlinkage __visible int printk(const char *fmt, ...)
1898 printk_func_t vprintk_func;
1902 va_start(args, fmt);
1905 * If a caller overrides the per_cpu printk_func, then it needs
1906 * to disable preemption when calling printk(). Otherwise
1907 * the printk_func should be set to the default. No need to
1908 * disable preemption here.
1910 vprintk_func = this_cpu_read(printk_func);
1911 r = vprintk_func(fmt, args);
1917 EXPORT_SYMBOL(printk);
1919 #else /* CONFIG_PRINTK */
1921 #define LOG_LINE_MAX 0
1922 #define PREFIX_MAX 0
1924 static u64 syslog_seq;
1925 static u32 syslog_idx;
1926 static u64 console_seq;
1927 static u32 console_idx;
1928 static enum log_flags syslog_prev;
1929 static u64 log_first_seq;
1930 static u32 log_first_idx;
1931 static u64 log_next_seq;
1932 static enum log_flags console_prev;
1933 static struct cont {
1939 static char *log_text(const struct printk_log *msg) { return NULL; }
1940 static char *log_dict(const struct printk_log *msg) { return NULL; }
1941 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1942 static u32 log_next(u32 idx) { return 0; }
1943 static ssize_t msg_print_ext_header(char *buf, size_t size,
1944 struct printk_log *msg, u64 seq,
1945 enum log_flags prev_flags) { return 0; }
1946 static ssize_t msg_print_ext_body(char *buf, size_t size,
1947 char *dict, size_t dict_len,
1948 char *text, size_t text_len) { return 0; }
1949 static void call_console_drivers(int level,
1950 const char *ext_text, size_t ext_len,
1951 const char *text, size_t len) {}
1952 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1953 bool syslog, char *buf, size_t size) { return 0; }
1954 static size_t cont_print_text(char *text, size_t size) { return 0; }
1956 /* Still needs to be defined for users */
1957 DEFINE_PER_CPU(printk_func_t, printk_func);
1959 #endif /* CONFIG_PRINTK */
1961 #ifdef CONFIG_EARLY_PRINTK
1962 struct console *early_console;
1964 asmlinkage __visible void early_printk(const char *fmt, ...)
1974 n = vscnprintf(buf, sizeof(buf), fmt, ap);
1977 early_console->write(early_console, buf, n);
1981 static int __add_preferred_console(char *name, int idx, char *options,
1984 struct console_cmdline *c;
1988 * See if this tty is not yet registered, and
1989 * if we have a slot free.
1991 for (i = 0, c = console_cmdline;
1992 i < MAX_CMDLINECONSOLES && c->name[0];
1994 if (strcmp(c->name, name) == 0 && c->index == idx) {
1996 selected_console = i;
2000 if (i == MAX_CMDLINECONSOLES)
2003 selected_console = i;
2004 strlcpy(c->name, name, sizeof(c->name));
2005 c->options = options;
2006 braille_set_options(c, brl_options);
2012 * Set up a console. Called via do_early_param() in init/main.c
2013 * for each "console=" parameter in the boot command line.
2015 static int __init console_setup(char *str)
2017 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
2018 char *s, *options, *brl_options = NULL;
2021 if (_braille_console_setup(&str, &brl_options))
2025 * Decode str into name, index, options.
2027 if (str[0] >= '0' && str[0] <= '9') {
2028 strcpy(buf, "ttyS");
2029 strncpy(buf + 4, str, sizeof(buf) - 5);
2031 strncpy(buf, str, sizeof(buf) - 1);
2033 buf[sizeof(buf) - 1] = 0;
2034 options = strchr(str, ',');
2038 if (!strcmp(str, "ttya"))
2039 strcpy(buf, "ttyS0");
2040 if (!strcmp(str, "ttyb"))
2041 strcpy(buf, "ttyS1");
2043 for (s = buf; *s; s++)
2044 if (isdigit(*s) || *s == ',')
2046 idx = simple_strtoul(s, NULL, 10);
2049 __add_preferred_console(buf, idx, options, brl_options);
2050 console_set_on_cmdline = 1;
2053 __setup("console=", console_setup);
2056 * add_preferred_console - add a device to the list of preferred consoles.
2057 * @name: device name
2058 * @idx: device index
2059 * @options: options for this console
2061 * The last preferred console added will be used for kernel messages
2062 * and stdin/out/err for init. Normally this is used by console_setup
2063 * above to handle user-supplied console arguments; however it can also
2064 * be used by arch-specific code either to override the user or more
2065 * commonly to provide a default console (ie from PROM variables) when
2066 * the user has not supplied one.
2068 int add_preferred_console(char *name, int idx, char *options)
2070 return __add_preferred_console(name, idx, options, NULL);
2073 bool console_suspend_enabled = true;
2074 EXPORT_SYMBOL(console_suspend_enabled);
2076 static int __init console_suspend_disable(char *str)
2078 console_suspend_enabled = false;
2081 __setup("no_console_suspend", console_suspend_disable);
2082 module_param_named(console_suspend, console_suspend_enabled,
2083 bool, S_IRUGO | S_IWUSR);
2084 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2085 " and hibernate operations");
2088 * suspend_console - suspend the console subsystem
2090 * This disables printk() while we go into suspend states
2092 void suspend_console(void)
2094 if (!console_suspend_enabled)
2096 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2098 console_suspended = 1;
2102 void resume_console(void)
2104 if (!console_suspend_enabled)
2107 console_suspended = 0;
2112 * console_cpu_notify - print deferred console messages after CPU hotplug
2113 * @self: notifier struct
2114 * @action: CPU hotplug event
2117 * If printk() is called from a CPU that is not online yet, the messages
2118 * will be spooled but will not show up on the console. This function is
2119 * called when a new CPU comes online (or fails to come up), and ensures
2120 * that any such output gets printed.
2122 static int console_cpu_notify(struct notifier_block *self,
2123 unsigned long action, void *hcpu)
2128 case CPU_DOWN_FAILED:
2129 case CPU_UP_CANCELED:
2137 * console_lock - lock the console system for exclusive use.
2139 * Acquires a lock which guarantees that the caller has
2140 * exclusive access to the console system and the console_drivers list.
2142 * Can sleep, returns nothing.
2144 void console_lock(void)
2149 if (console_suspended)
2152 console_may_schedule = 1;
2154 EXPORT_SYMBOL(console_lock);
2157 * console_trylock - try to lock the console system for exclusive use.
2159 * Try to acquire a lock which guarantees that the caller has exclusive
2160 * access to the console system and the console_drivers list.
2162 * returns 1 on success, and 0 on failure to acquire the lock.
2164 int console_trylock(void)
2166 if (down_trylock_console_sem())
2168 if (console_suspended) {
2173 console_may_schedule = 0;
2176 EXPORT_SYMBOL(console_trylock);
2178 int is_console_locked(void)
2180 return console_locked;
2183 static void console_cont_flush(char *text, size_t size)
2185 unsigned long flags;
2188 raw_spin_lock_irqsave(&logbuf_lock, flags);
2194 * We still queue earlier records, likely because the console was
2195 * busy. The earlier ones need to be printed before this one, we
2196 * did not flush any fragment so far, so just let it queue up.
2198 if (console_seq < log_next_seq && !cont.cons)
2201 len = cont_print_text(text, size);
2202 raw_spin_unlock(&logbuf_lock);
2203 stop_critical_timings();
2204 call_console_drivers(cont.level, NULL, 0, text, len);
2205 start_critical_timings();
2206 local_irq_restore(flags);
2209 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2213 * console_unlock - unlock the console system
2215 * Releases the console_lock which the caller holds on the console system
2216 * and the console driver list.
2218 * While the console_lock was held, console output may have been buffered
2219 * by printk(). If this is the case, console_unlock(); emits
2220 * the output prior to releasing the lock.
2222 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2224 * console_unlock(); may be called from any context.
2226 void console_unlock(void)
2228 static char ext_text[CONSOLE_EXT_LOG_MAX];
2229 static char text[LOG_LINE_MAX + PREFIX_MAX];
2230 static u64 seen_seq;
2231 unsigned long flags;
2232 bool wake_klogd = false;
2235 if (console_suspended) {
2240 console_may_schedule = 0;
2242 /* flush buffered message fragment immediately to console */
2243 console_cont_flush(text, sizeof(text));
2246 struct printk_log *msg;
2251 raw_spin_lock_irqsave(&logbuf_lock, flags);
2252 if (seen_seq != log_next_seq) {
2254 seen_seq = log_next_seq;
2257 if (console_seq < log_first_seq) {
2258 len = sprintf(text, "** %u printk messages dropped ** ",
2259 (unsigned)(log_first_seq - console_seq));
2261 /* messages are gone, move to first one */
2262 console_seq = log_first_seq;
2263 console_idx = log_first_idx;
2269 if (console_seq == log_next_seq)
2272 msg = log_from_idx(console_idx);
2273 if (msg->flags & LOG_NOCONS) {
2275 * Skip record we have buffered and already printed
2276 * directly to the console when we received it.
2278 console_idx = log_next(console_idx);
2281 * We will get here again when we register a new
2282 * CON_PRINTBUFFER console. Clear the flag so we
2283 * will properly dump everything later.
2285 msg->flags &= ~LOG_NOCONS;
2286 console_prev = msg->flags;
2291 len += msg_print_text(msg, console_prev, false,
2292 text + len, sizeof(text) - len);
2293 if (nr_ext_console_drivers) {
2294 ext_len = msg_print_ext_header(ext_text,
2296 msg, console_seq, console_prev);
2297 ext_len += msg_print_ext_body(ext_text + ext_len,
2298 sizeof(ext_text) - ext_len,
2299 log_dict(msg), msg->dict_len,
2300 log_text(msg), msg->text_len);
2302 console_idx = log_next(console_idx);
2304 console_prev = msg->flags;
2305 raw_spin_unlock(&logbuf_lock);
2307 stop_critical_timings(); /* don't trace print latency */
2308 call_console_drivers(level, ext_text, ext_len, text, len);
2309 start_critical_timings();
2310 local_irq_restore(flags);
2314 /* Release the exclusive_console once it is used */
2315 if (unlikely(exclusive_console))
2316 exclusive_console = NULL;
2318 raw_spin_unlock(&logbuf_lock);
2323 * Someone could have filled up the buffer again, so re-check if there's
2324 * something to flush. In case we cannot trylock the console_sem again,
2325 * there's a new owner and the console_unlock() from them will do the
2326 * flush, no worries.
2328 raw_spin_lock(&logbuf_lock);
2329 retry = console_seq != log_next_seq;
2330 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2332 if (retry && console_trylock())
2338 EXPORT_SYMBOL(console_unlock);
2341 * console_conditional_schedule - yield the CPU if required
2343 * If the console code is currently allowed to sleep, and
2344 * if this CPU should yield the CPU to another task, do
2347 * Must be called within console_lock();.
2349 void __sched console_conditional_schedule(void)
2351 if (console_may_schedule)
2354 EXPORT_SYMBOL(console_conditional_schedule);
2356 void console_unblank(void)
2361 * console_unblank can no longer be called in interrupt context unless
2362 * oops_in_progress is set to 1..
2364 if (oops_in_progress) {
2365 if (down_trylock_console_sem() != 0)
2371 console_may_schedule = 0;
2373 if ((c->flags & CON_ENABLED) && c->unblank)
2379 * Return the console tty driver structure and its associated index
2381 struct tty_driver *console_device(int *index)
2384 struct tty_driver *driver = NULL;
2387 for_each_console(c) {
2390 driver = c->device(c, index);
2399 * Prevent further output on the passed console device so that (for example)
2400 * serial drivers can disable console output before suspending a port, and can
2401 * re-enable output afterwards.
2403 void console_stop(struct console *console)
2406 console->flags &= ~CON_ENABLED;
2409 EXPORT_SYMBOL(console_stop);
2411 void console_start(struct console *console)
2414 console->flags |= CON_ENABLED;
2417 EXPORT_SYMBOL(console_start);
2419 static int __read_mostly keep_bootcon;
2421 static int __init keep_bootcon_setup(char *str)
2424 pr_info("debug: skip boot console de-registration.\n");
2429 early_param("keep_bootcon", keep_bootcon_setup);
2432 * The console driver calls this routine during kernel initialization
2433 * to register the console printing procedure with printk() and to
2434 * print any messages that were printed by the kernel before the
2435 * console driver was initialized.
2437 * This can happen pretty early during the boot process (because of
2438 * early_printk) - sometimes before setup_arch() completes - be careful
2439 * of what kernel features are used - they may not be initialised yet.
2441 * There are two types of consoles - bootconsoles (early_printk) and
2442 * "real" consoles (everything which is not a bootconsole) which are
2443 * handled differently.
2444 * - Any number of bootconsoles can be registered at any time.
2445 * - As soon as a "real" console is registered, all bootconsoles
2446 * will be unregistered automatically.
2447 * - Once a "real" console is registered, any attempt to register a
2448 * bootconsoles will be rejected
2450 void register_console(struct console *newcon)
2453 unsigned long flags;
2454 struct console *bcon = NULL;
2455 struct console_cmdline *c;
2457 if (console_drivers)
2458 for_each_console(bcon)
2459 if (WARN(bcon == newcon,
2460 "console '%s%d' already registered\n",
2461 bcon->name, bcon->index))
2465 * before we register a new CON_BOOT console, make sure we don't
2466 * already have a valid console
2468 if (console_drivers && newcon->flags & CON_BOOT) {
2469 /* find the last or real console */
2470 for_each_console(bcon) {
2471 if (!(bcon->flags & CON_BOOT)) {
2472 pr_info("Too late to register bootconsole %s%d\n",
2473 newcon->name, newcon->index);
2479 if (console_drivers && console_drivers->flags & CON_BOOT)
2480 bcon = console_drivers;
2482 if (preferred_console < 0 || bcon || !console_drivers)
2483 preferred_console = selected_console;
2486 * See if we want to use this console driver. If we
2487 * didn't select a console we take the first one
2488 * that registers here.
2490 if (preferred_console < 0) {
2491 if (newcon->index < 0)
2493 if (newcon->setup == NULL ||
2494 newcon->setup(newcon, NULL) == 0) {
2495 newcon->flags |= CON_ENABLED;
2496 if (newcon->device) {
2497 newcon->flags |= CON_CONSDEV;
2498 preferred_console = 0;
2504 * See if this console matches one we selected on
2507 for (i = 0, c = console_cmdline;
2508 i < MAX_CMDLINECONSOLES && c->name[0];
2510 if (!newcon->match ||
2511 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2512 /* default matching */
2513 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2514 if (strcmp(c->name, newcon->name) != 0)
2516 if (newcon->index >= 0 &&
2517 newcon->index != c->index)
2519 if (newcon->index < 0)
2520 newcon->index = c->index;
2522 if (_braille_register_console(newcon, c))
2525 if (newcon->setup &&
2526 newcon->setup(newcon, c->options) != 0)
2530 newcon->flags |= CON_ENABLED;
2531 if (i == selected_console) {
2532 newcon->flags |= CON_CONSDEV;
2533 preferred_console = selected_console;
2538 if (!(newcon->flags & CON_ENABLED))
2542 * If we have a bootconsole, and are switching to a real console,
2543 * don't print everything out again, since when the boot console, and
2544 * the real console are the same physical device, it's annoying to
2545 * see the beginning boot messages twice
2547 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2548 newcon->flags &= ~CON_PRINTBUFFER;
2551 * Put this console in the list - keep the
2552 * preferred driver at the head of the list.
2555 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2556 newcon->next = console_drivers;
2557 console_drivers = newcon;
2559 newcon->next->flags &= ~CON_CONSDEV;
2561 newcon->next = console_drivers->next;
2562 console_drivers->next = newcon;
2565 if (newcon->flags & CON_EXTENDED)
2566 if (!nr_ext_console_drivers++)
2567 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2569 if (newcon->flags & CON_PRINTBUFFER) {
2571 * console_unlock(); will print out the buffered messages
2574 raw_spin_lock_irqsave(&logbuf_lock, flags);
2575 console_seq = syslog_seq;
2576 console_idx = syslog_idx;
2577 console_prev = syslog_prev;
2578 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2580 * We're about to replay the log buffer. Only do this to the
2581 * just-registered console to avoid excessive message spam to
2582 * the already-registered consoles.
2584 exclusive_console = newcon;
2587 console_sysfs_notify();
2590 * By unregistering the bootconsoles after we enable the real console
2591 * we get the "console xxx enabled" message on all the consoles -
2592 * boot consoles, real consoles, etc - this is to ensure that end
2593 * users know there might be something in the kernel's log buffer that
2594 * went to the bootconsole (that they do not see on the real console)
2596 pr_info("%sconsole [%s%d] enabled\n",
2597 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2598 newcon->name, newcon->index);
2600 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2602 /* We need to iterate through all boot consoles, to make
2603 * sure we print everything out, before we unregister them.
2605 for_each_console(bcon)
2606 if (bcon->flags & CON_BOOT)
2607 unregister_console(bcon);
2610 EXPORT_SYMBOL(register_console);
2612 int unregister_console(struct console *console)
2614 struct console *a, *b;
2617 pr_info("%sconsole [%s%d] disabled\n",
2618 (console->flags & CON_BOOT) ? "boot" : "" ,
2619 console->name, console->index);
2621 res = _braille_unregister_console(console);
2627 if (console_drivers == console) {
2628 console_drivers=console->next;
2630 } else if (console_drivers) {
2631 for (a=console_drivers->next, b=console_drivers ;
2632 a; b=a, a=b->next) {
2641 if (!res && (console->flags & CON_EXTENDED))
2642 nr_ext_console_drivers--;
2645 * If this isn't the last console and it has CON_CONSDEV set, we
2646 * need to set it on the next preferred console.
2648 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2649 console_drivers->flags |= CON_CONSDEV;
2651 console->flags &= ~CON_ENABLED;
2653 console_sysfs_notify();
2656 EXPORT_SYMBOL(unregister_console);
2658 static int __init printk_late_init(void)
2660 struct console *con;
2662 for_each_console(con) {
2663 if (!keep_bootcon && con->flags & CON_BOOT) {
2664 unregister_console(con);
2667 hotcpu_notifier(console_cpu_notify, 0);
2670 late_initcall(printk_late_init);
2672 #if defined CONFIG_PRINTK
2674 * Delayed printk version, for scheduler-internal messages:
2676 #define PRINTK_PENDING_WAKEUP 0x01
2677 #define PRINTK_PENDING_OUTPUT 0x02
2679 static DEFINE_PER_CPU(int, printk_pending);
2681 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2683 int pending = __this_cpu_xchg(printk_pending, 0);
2685 if (pending & PRINTK_PENDING_OUTPUT) {
2686 /* If trylock fails, someone else is doing the printing */
2687 if (console_trylock())
2691 if (pending & PRINTK_PENDING_WAKEUP)
2692 wake_up_interruptible(&log_wait);
2695 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2696 .func = wake_up_klogd_work_func,
2697 .flags = IRQ_WORK_LAZY,
2700 void wake_up_klogd(void)
2703 if (waitqueue_active(&log_wait)) {
2704 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2705 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2710 int printk_deferred(const char *fmt, ...)
2716 va_start(args, fmt);
2717 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2720 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2721 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2728 * printk rate limiting, lifted from the networking subsystem.
2730 * This enforces a rate limit: not more than 10 kernel messages
2731 * every 5s to make a denial-of-service attack impossible.
2733 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2735 int __printk_ratelimit(const char *func)
2737 return ___ratelimit(&printk_ratelimit_state, func);
2739 EXPORT_SYMBOL(__printk_ratelimit);
2742 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2743 * @caller_jiffies: pointer to caller's state
2744 * @interval_msecs: minimum interval between prints
2746 * printk_timed_ratelimit() returns true if more than @interval_msecs
2747 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2750 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2751 unsigned int interval_msecs)
2753 unsigned long elapsed = jiffies - *caller_jiffies;
2755 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2758 *caller_jiffies = jiffies;
2761 EXPORT_SYMBOL(printk_timed_ratelimit);
2763 static DEFINE_SPINLOCK(dump_list_lock);
2764 static LIST_HEAD(dump_list);
2767 * kmsg_dump_register - register a kernel log dumper.
2768 * @dumper: pointer to the kmsg_dumper structure
2770 * Adds a kernel log dumper to the system. The dump callback in the
2771 * structure will be called when the kernel oopses or panics and must be
2772 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2774 int kmsg_dump_register(struct kmsg_dumper *dumper)
2776 unsigned long flags;
2779 /* The dump callback needs to be set */
2783 spin_lock_irqsave(&dump_list_lock, flags);
2784 /* Don't allow registering multiple times */
2785 if (!dumper->registered) {
2786 dumper->registered = 1;
2787 list_add_tail_rcu(&dumper->list, &dump_list);
2790 spin_unlock_irqrestore(&dump_list_lock, flags);
2794 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2797 * kmsg_dump_unregister - unregister a kmsg dumper.
2798 * @dumper: pointer to the kmsg_dumper structure
2800 * Removes a dump device from the system. Returns zero on success and
2801 * %-EINVAL otherwise.
2803 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2805 unsigned long flags;
2808 spin_lock_irqsave(&dump_list_lock, flags);
2809 if (dumper->registered) {
2810 dumper->registered = 0;
2811 list_del_rcu(&dumper->list);
2814 spin_unlock_irqrestore(&dump_list_lock, flags);
2819 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2821 static bool always_kmsg_dump;
2822 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2825 * kmsg_dump - dump kernel log to kernel message dumpers.
2826 * @reason: the reason (oops, panic etc) for dumping
2828 * Call each of the registered dumper's dump() callback, which can
2829 * retrieve the kmsg records with kmsg_dump_get_line() or
2830 * kmsg_dump_get_buffer().
2832 void kmsg_dump(enum kmsg_dump_reason reason)
2834 struct kmsg_dumper *dumper;
2835 unsigned long flags;
2837 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2841 list_for_each_entry_rcu(dumper, &dump_list, list) {
2842 if (dumper->max_reason && reason > dumper->max_reason)
2845 /* initialize iterator with data about the stored records */
2846 dumper->active = true;
2848 raw_spin_lock_irqsave(&logbuf_lock, flags);
2849 dumper->cur_seq = clear_seq;
2850 dumper->cur_idx = clear_idx;
2851 dumper->next_seq = log_next_seq;
2852 dumper->next_idx = log_next_idx;
2853 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2855 /* invoke dumper which will iterate over records */
2856 dumper->dump(dumper, reason);
2858 /* reset iterator */
2859 dumper->active = false;
2865 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2866 * @dumper: registered kmsg dumper
2867 * @syslog: include the "<4>" prefixes
2868 * @line: buffer to copy the line to
2869 * @size: maximum size of the buffer
2870 * @len: length of line placed into buffer
2872 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2873 * record, and copy one record into the provided buffer.
2875 * Consecutive calls will return the next available record moving
2876 * towards the end of the buffer with the youngest messages.
2878 * A return value of FALSE indicates that there are no more records to
2881 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2883 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2884 char *line, size_t size, size_t *len)
2886 struct printk_log *msg;
2890 if (!dumper->active)
2893 if (dumper->cur_seq < log_first_seq) {
2894 /* messages are gone, move to first available one */
2895 dumper->cur_seq = log_first_seq;
2896 dumper->cur_idx = log_first_idx;
2900 if (dumper->cur_seq >= log_next_seq)
2903 msg = log_from_idx(dumper->cur_idx);
2904 l = msg_print_text(msg, 0, syslog, line, size);
2906 dumper->cur_idx = log_next(dumper->cur_idx);
2916 * kmsg_dump_get_line - retrieve one kmsg log line
2917 * @dumper: registered kmsg dumper
2918 * @syslog: include the "<4>" prefixes
2919 * @line: buffer to copy the line to
2920 * @size: maximum size of the buffer
2921 * @len: length of line placed into buffer
2923 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2924 * record, and copy one record into the provided buffer.
2926 * Consecutive calls will return the next available record moving
2927 * towards the end of the buffer with the youngest messages.
2929 * A return value of FALSE indicates that there are no more records to
2932 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2933 char *line, size_t size, size_t *len)
2935 unsigned long flags;
2938 raw_spin_lock_irqsave(&logbuf_lock, flags);
2939 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2940 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2944 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2947 * kmsg_dump_get_buffer - copy kmsg log lines
2948 * @dumper: registered kmsg dumper
2949 * @syslog: include the "<4>" prefixes
2950 * @buf: buffer to copy the line to
2951 * @size: maximum size of the buffer
2952 * @len: length of line placed into buffer
2954 * Start at the end of the kmsg buffer and fill the provided buffer
2955 * with as many of the the *youngest* kmsg records that fit into it.
2956 * If the buffer is large enough, all available kmsg records will be
2957 * copied with a single call.
2959 * Consecutive calls will fill the buffer with the next block of
2960 * available older records, not including the earlier retrieved ones.
2962 * A return value of FALSE indicates that there are no more records to
2965 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2966 char *buf, size_t size, size_t *len)
2968 unsigned long flags;
2973 enum log_flags prev;
2977 if (!dumper->active)
2980 raw_spin_lock_irqsave(&logbuf_lock, flags);
2981 if (dumper->cur_seq < log_first_seq) {
2982 /* messages are gone, move to first available one */
2983 dumper->cur_seq = log_first_seq;
2984 dumper->cur_idx = log_first_idx;
2988 if (dumper->cur_seq >= dumper->next_seq) {
2989 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2993 /* calculate length of entire buffer */
2994 seq = dumper->cur_seq;
2995 idx = dumper->cur_idx;
2997 while (seq < dumper->next_seq) {
2998 struct printk_log *msg = log_from_idx(idx);
3000 l += msg_print_text(msg, prev, true, NULL, 0);
3001 idx = log_next(idx);
3006 /* move first record forward until length fits into the buffer */
3007 seq = dumper->cur_seq;
3008 idx = dumper->cur_idx;
3010 while (l > size && seq < dumper->next_seq) {
3011 struct printk_log *msg = log_from_idx(idx);
3013 l -= msg_print_text(msg, prev, true, NULL, 0);
3014 idx = log_next(idx);
3019 /* last message in next interation */
3024 while (seq < dumper->next_seq) {
3025 struct printk_log *msg = log_from_idx(idx);
3027 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
3028 idx = log_next(idx);
3033 dumper->next_seq = next_seq;
3034 dumper->next_idx = next_idx;
3036 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3042 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3045 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3046 * @dumper: registered kmsg dumper
3048 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3049 * kmsg_dump_get_buffer() can be called again and used multiple
3050 * times within the same dumper.dump() callback.
3052 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3054 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3056 dumper->cur_seq = clear_seq;
3057 dumper->cur_idx = clear_idx;
3058 dumper->next_seq = log_next_seq;
3059 dumper->next_idx = log_next_idx;
3063 * kmsg_dump_rewind - reset the interator
3064 * @dumper: registered kmsg dumper
3066 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3067 * kmsg_dump_get_buffer() can be called again and used multiple
3068 * times within the same dumper.dump() callback.
3070 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3072 unsigned long flags;
3074 raw_spin_lock_irqsave(&logbuf_lock, flags);
3075 kmsg_dump_rewind_nolock(dumper);
3076 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3078 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3080 static char dump_stack_arch_desc_str[128];
3083 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3084 * @fmt: printf-style format string
3085 * @...: arguments for the format string
3087 * The configured string will be printed right after utsname during task
3088 * dumps. Usually used to add arch-specific system identifiers. If an
3089 * arch wants to make use of such an ID string, it should initialize this
3090 * as soon as possible during boot.
3092 void __init dump_stack_set_arch_desc(const char *fmt, ...)
3096 va_start(args, fmt);
3097 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3103 * dump_stack_print_info - print generic debug info for dump_stack()
3104 * @log_lvl: log level
3106 * Arch-specific dump_stack() implementations can use this function to
3107 * print out the same debug information as the generic dump_stack().
3109 void dump_stack_print_info(const char *log_lvl)
3111 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3112 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3113 print_tainted(), init_utsname()->release,
3114 (int)strcspn(init_utsname()->version, " "),
3115 init_utsname()->version);
3117 if (dump_stack_arch_desc_str[0] != '\0')
3118 printk("%sHardware name: %s\n",
3119 log_lvl, dump_stack_arch_desc_str);
3121 print_worker_info(log_lvl, current);
3125 * show_regs_print_info - print generic debug info for show_regs()
3126 * @log_lvl: log level
3128 * show_regs() implementations can use this function to print out generic
3129 * debug information.
3131 void show_regs_print_info(const char *log_lvl)
3133 dump_stack_print_info(log_lvl);
3135 printk("%stask: %p ti: %p task.ti: %p\n",
3136 log_lvl, current, current_thread_info(),
3137 task_thread_info(current));