2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/memblock.h>
35 #include <linux/aio.h>
36 #include <linux/syscalls.h>
37 #include <linux/kexec.h>
38 #include <linux/kdb.h>
39 #include <linux/ratelimit.h>
40 #include <linux/kmsg_dump.h>
41 #include <linux/syslog.h>
42 #include <linux/cpu.h>
43 #include <linux/notifier.h>
44 #include <linux/rculist.h>
45 #include <linux/poll.h>
46 #include <linux/irq_work.h>
47 #include <linux/utsname.h>
49 #include <asm/uaccess.h>
51 #define CREATE_TRACE_POINTS
52 #include <trace/events/printk.h>
54 #include "console_cmdline.h"
56 /* printk's without a loglevel use this.. */
57 #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
59 /* We show everything that is MORE important than this.. */
60 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
61 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
63 int console_printk[4] = {
64 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
65 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
66 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
67 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
71 * Low level drivers may need that to know if they can schedule in
72 * their unblank() callback or not. So let's export it.
75 EXPORT_SYMBOL(oops_in_progress);
78 * console_sem protects the console_drivers list, and also
79 * provides serialisation for access to the entire console
82 static DEFINE_SEMAPHORE(console_sem);
83 struct console *console_drivers;
84 EXPORT_SYMBOL_GPL(console_drivers);
87 static struct lockdep_map console_lock_dep_map = {
88 .name = "console_lock"
93 * This is used for debugging the mess that is the VT code by
94 * keeping track if we have the console semaphore held. It's
95 * definitely not the perfect debug tool (we don't know if _WE_
96 * hold it are racing, but it helps tracking those weird code
97 * path in the console code where we end up in places I want
98 * locked without the console sempahore held
100 static int console_locked, console_suspended;
103 * If exclusive_console is non-NULL then only this console is to be printed to.
105 static struct console *exclusive_console;
108 * Array of consoles built from command line options (console=)
111 #define MAX_CMDLINECONSOLES 8
113 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
115 static int selected_console = -1;
116 static int preferred_console = -1;
117 int console_set_on_cmdline;
118 EXPORT_SYMBOL(console_set_on_cmdline);
120 /* Flag: console code may call schedule() */
121 static int console_may_schedule;
124 * The printk log buffer consists of a chain of concatenated variable
125 * length records. Every record starts with a record header, containing
126 * the overall length of the record.
128 * The heads to the first and last entry in the buffer, as well as the
129 * sequence numbers of these both entries are maintained when messages
132 * If the heads indicate available messages, the length in the header
133 * tells the start next message. A length == 0 for the next message
134 * indicates a wrap-around to the beginning of the buffer.
136 * Every record carries the monotonic timestamp in microseconds, as well as
137 * the standard userspace syslog level and syslog facility. The usual
138 * kernel messages use LOG_KERN; userspace-injected messages always carry
139 * a matching syslog facility, by default LOG_USER. The origin of every
140 * message can be reliably determined that way.
142 * The human readable log message directly follows the message header. The
143 * length of the message text is stored in the header, the stored message
146 * Optionally, a message can carry a dictionary of properties (key/value pairs),
147 * to provide userspace with a machine-readable message context.
149 * Examples for well-defined, commonly used property names are:
150 * DEVICE=b12:8 device identifier
154 * +sound:card0 subsystem:devname
155 * SUBSYSTEM=pci driver-core subsystem name
157 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
158 * follows directly after a '=' character. Every property is terminated by
159 * a '\0' character. The last property is not terminated.
161 * Example of a message structure:
162 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
163 * 0008 34 00 record is 52 bytes long
164 * 000a 0b 00 text is 11 bytes long
165 * 000c 1f 00 dictionary is 23 bytes long
166 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
167 * 0010 69 74 27 73 20 61 20 6c "it's a l"
169 * 001b 44 45 56 49 43 "DEVIC"
170 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
171 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
173 * 0032 00 00 00 padding to next message header
175 * The 'struct log' buffer header must never be directly exported to
176 * userspace, it is a kernel-private implementation detail that might
177 * need to be changed in the future, when the requirements change.
179 * /dev/kmsg exports the structured data in the following line format:
180 * "level,sequnum,timestamp;<message text>\n"
182 * The optional key/value pairs are attached as continuation lines starting
183 * with a space character and terminated by a newline. All possible
184 * non-prinatable characters are escaped in the "\xff" notation.
186 * Users of the export format should ignore possible additional values
187 * separated by ',', and find the message after the ';' character.
191 LOG_NOCONS = 1, /* already flushed, do not print to console */
192 LOG_NEWLINE = 2, /* text ended with a newline */
193 LOG_PREFIX = 4, /* text started with a prefix */
194 LOG_CONT = 8, /* text is a fragment of a continuation line */
198 u64 ts_nsec; /* timestamp in nanoseconds */
199 u16 len; /* length of entire record */
200 u16 text_len; /* length of text buffer */
201 u16 dict_len; /* length of dictionary buffer */
202 u8 facility; /* syslog facility */
203 u8 flags:5; /* internal record flags */
204 u8 level:3; /* syslog level */
208 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
209 * used in interesting ways to provide interlocking in console_unlock();
211 static DEFINE_RAW_SPINLOCK(logbuf_lock);
214 DECLARE_WAIT_QUEUE_HEAD(log_wait);
215 /* the next printk record to read by syslog(READ) or /proc/kmsg */
216 static u64 syslog_seq;
217 static u32 syslog_idx;
218 static enum log_flags syslog_prev;
219 static size_t syslog_partial;
221 /* index and sequence number of the first record stored in the buffer */
222 static u64 log_first_seq;
223 static u32 log_first_idx;
225 /* index and sequence number of the next record to store in the buffer */
226 static u64 log_next_seq;
227 static u32 log_next_idx;
229 /* the next printk record to write to the console */
230 static u64 console_seq;
231 static u32 console_idx;
232 static enum log_flags console_prev;
234 /* the next printk record to read after the last 'clear' command */
235 static u64 clear_seq;
236 static u32 clear_idx;
238 #define PREFIX_MAX 32
239 #define LOG_LINE_MAX 1024 - PREFIX_MAX
242 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
245 #define LOG_ALIGN __alignof__(struct log)
247 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
248 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
249 static char *log_buf = __log_buf;
250 static u32 log_buf_len = __LOG_BUF_LEN;
252 /* cpu currently holding logbuf_lock */
253 static volatile unsigned int logbuf_cpu = UINT_MAX;
255 /* human readable text of the record */
256 static char *log_text(const struct log *msg)
258 return (char *)msg + sizeof(struct log);
261 /* optional key/value pair dictionary attached to the record */
262 static char *log_dict(const struct log *msg)
264 return (char *)msg + sizeof(struct log) + msg->text_len;
267 /* get record by index; idx must point to valid msg */
268 static struct log *log_from_idx(u32 idx)
270 struct log *msg = (struct log *)(log_buf + idx);
273 * A length == 0 record is the end of buffer marker. Wrap around and
274 * read the message at the start of the buffer.
277 return (struct log *)log_buf;
281 /* get next record; idx must point to valid msg */
282 static u32 log_next(u32 idx)
284 struct log *msg = (struct log *)(log_buf + idx);
286 /* length == 0 indicates the end of the buffer; wrap */
288 * A length == 0 record is the end of buffer marker. Wrap around and
289 * read the message at the start of the buffer as *this* one, and
290 * return the one after that.
293 msg = (struct log *)log_buf;
296 return idx + msg->len;
299 /* insert record into the buffer, discard old ones, update heads */
300 static void log_store(int facility, int level,
301 enum log_flags flags, u64 ts_nsec,
302 const char *dict, u16 dict_len,
303 const char *text, u16 text_len)
308 /* number of '\0' padding bytes to next message */
309 size = sizeof(struct log) + text_len + dict_len;
310 pad_len = (-size) & (LOG_ALIGN - 1);
313 while (log_first_seq < log_next_seq) {
316 if (log_next_idx > log_first_idx)
317 free = max(log_buf_len - log_next_idx, log_first_idx);
319 free = log_first_idx - log_next_idx;
321 if (free > size + sizeof(struct log))
324 /* drop old messages until we have enough contiuous space */
325 log_first_idx = log_next(log_first_idx);
329 if (log_next_idx + size + sizeof(struct log) >= log_buf_len) {
331 * This message + an additional empty header does not fit
332 * at the end of the buffer. Add an empty header with len == 0
333 * to signify a wrap around.
335 memset(log_buf + log_next_idx, 0, sizeof(struct log));
340 msg = (struct log *)(log_buf + log_next_idx);
341 memcpy(log_text(msg), text, text_len);
342 msg->text_len = text_len;
343 memcpy(log_dict(msg), dict, dict_len);
344 msg->dict_len = dict_len;
345 msg->facility = facility;
346 msg->level = level & 7;
347 msg->flags = flags & 0x1f;
349 msg->ts_nsec = ts_nsec;
351 msg->ts_nsec = local_clock();
352 memset(log_dict(msg) + dict_len, 0, pad_len);
353 msg->len = sizeof(struct log) + text_len + dict_len + pad_len;
356 log_next_idx += msg->len;
360 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
361 int dmesg_restrict = 1;
366 static int syslog_action_restricted(int type)
371 * Unless restricted, we allow "read all" and "get buffer size"
374 return type != SYSLOG_ACTION_READ_ALL &&
375 type != SYSLOG_ACTION_SIZE_BUFFER;
378 static int check_syslog_permissions(int type, bool from_file)
381 * If this is from /proc/kmsg and we've already opened it, then we've
382 * already done the capabilities checks at open time.
384 if (from_file && type != SYSLOG_ACTION_OPEN)
387 if (syslog_action_restricted(type)) {
388 if (capable(CAP_SYSLOG))
391 * For historical reasons, accept CAP_SYS_ADMIN too, with
394 if (capable(CAP_SYS_ADMIN)) {
395 pr_warn_once("%s (%d): Attempt to access syslog with "
396 "CAP_SYS_ADMIN but no CAP_SYSLOG "
398 current->comm, task_pid_nr(current));
403 return security_syslog(type);
407 /* /dev/kmsg - userspace message inject/listen interface */
408 struct devkmsg_user {
416 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
417 unsigned long count, loff_t pos)
421 int level = default_message_loglevel;
422 int facility = 1; /* LOG_USER */
423 size_t len = iov_length(iv, count);
426 if (len > LOG_LINE_MAX)
428 buf = kmalloc(len+1, GFP_KERNEL);
433 for (i = 0; i < count; i++) {
434 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
438 line += iv[i].iov_len;
442 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
443 * the decimal value represents 32bit, the lower 3 bit are the log
444 * level, the rest are the log facility.
446 * If no prefix or no userspace facility is specified, we
447 * enforce LOG_USER, to be able to reliably distinguish
448 * kernel-generated messages from userspace-injected ones.
451 if (line[0] == '<') {
454 i = simple_strtoul(line+1, &endp, 10);
455 if (endp && endp[0] == '>') {
466 printk_emit(facility, level, NULL, 0, "%s", line);
472 static ssize_t devkmsg_read(struct file *file, char __user *buf,
473 size_t count, loff_t *ppos)
475 struct devkmsg_user *user = file->private_data;
486 ret = mutex_lock_interruptible(&user->lock);
489 raw_spin_lock_irq(&logbuf_lock);
490 while (user->seq == log_next_seq) {
491 if (file->f_flags & O_NONBLOCK) {
493 raw_spin_unlock_irq(&logbuf_lock);
497 raw_spin_unlock_irq(&logbuf_lock);
498 ret = wait_event_interruptible(log_wait,
499 user->seq != log_next_seq);
502 raw_spin_lock_irq(&logbuf_lock);
505 if (user->seq < log_first_seq) {
506 /* our last seen message is gone, return error and reset */
507 user->idx = log_first_idx;
508 user->seq = log_first_seq;
510 raw_spin_unlock_irq(&logbuf_lock);
514 msg = log_from_idx(user->idx);
515 ts_usec = msg->ts_nsec;
516 do_div(ts_usec, 1000);
519 * If we couldn't merge continuation line fragments during the print,
520 * export the stored flags to allow an optional external merge of the
521 * records. Merging the records isn't always neccessarily correct, like
522 * when we hit a race during printing. In most cases though, it produces
523 * better readable output. 'c' in the record flags mark the first
524 * fragment of a line, '+' the following.
526 if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
528 else if ((msg->flags & LOG_CONT) ||
529 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
532 len = sprintf(user->buf, "%u,%llu,%llu,%c;",
533 (msg->facility << 3) | msg->level,
534 user->seq, ts_usec, cont);
535 user->prev = msg->flags;
537 /* escape non-printable characters */
538 for (i = 0; i < msg->text_len; i++) {
539 unsigned char c = log_text(msg)[i];
541 if (c < ' ' || c >= 127 || c == '\\')
542 len += sprintf(user->buf + len, "\\x%02x", c);
544 user->buf[len++] = c;
546 user->buf[len++] = '\n';
551 for (i = 0; i < msg->dict_len; i++) {
552 unsigned char c = log_dict(msg)[i];
555 user->buf[len++] = ' ';
560 user->buf[len++] = '\n';
565 if (c < ' ' || c >= 127 || c == '\\') {
566 len += sprintf(user->buf + len, "\\x%02x", c);
570 user->buf[len++] = c;
572 user->buf[len++] = '\n';
575 user->idx = log_next(user->idx);
577 raw_spin_unlock_irq(&logbuf_lock);
584 if (copy_to_user(buf, user->buf, len)) {
590 mutex_unlock(&user->lock);
594 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
596 struct devkmsg_user *user = file->private_data;
604 raw_spin_lock_irq(&logbuf_lock);
607 /* the first record */
608 user->idx = log_first_idx;
609 user->seq = log_first_seq;
613 * The first record after the last SYSLOG_ACTION_CLEAR,
614 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
615 * changes no global state, and does not clear anything.
617 user->idx = clear_idx;
618 user->seq = clear_seq;
621 /* after the last record */
622 user->idx = log_next_idx;
623 user->seq = log_next_seq;
628 raw_spin_unlock_irq(&logbuf_lock);
632 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
634 struct devkmsg_user *user = file->private_data;
638 return POLLERR|POLLNVAL;
640 poll_wait(file, &log_wait, wait);
642 raw_spin_lock_irq(&logbuf_lock);
643 if (user->seq < log_next_seq) {
644 /* return error when data has vanished underneath us */
645 if (user->seq < log_first_seq)
646 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
648 ret = POLLIN|POLLRDNORM;
650 raw_spin_unlock_irq(&logbuf_lock);
655 static int devkmsg_open(struct inode *inode, struct file *file)
657 struct devkmsg_user *user;
660 /* write-only does not need any file context */
661 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
664 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
669 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
673 mutex_init(&user->lock);
675 raw_spin_lock_irq(&logbuf_lock);
676 user->idx = log_first_idx;
677 user->seq = log_first_seq;
678 raw_spin_unlock_irq(&logbuf_lock);
680 file->private_data = user;
684 static int devkmsg_release(struct inode *inode, struct file *file)
686 struct devkmsg_user *user = file->private_data;
691 mutex_destroy(&user->lock);
696 const struct file_operations kmsg_fops = {
697 .open = devkmsg_open,
698 .read = devkmsg_read,
699 .aio_write = devkmsg_writev,
700 .llseek = devkmsg_llseek,
701 .poll = devkmsg_poll,
702 .release = devkmsg_release,
707 * This appends the listed symbols to /proc/vmcoreinfo
709 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
710 * obtain access to symbols that are otherwise very difficult to locate. These
711 * symbols are specifically used so that utilities can access and extract the
712 * dmesg log from a vmcore file after a crash.
714 void log_buf_kexec_setup(void)
716 VMCOREINFO_SYMBOL(log_buf);
717 VMCOREINFO_SYMBOL(log_buf_len);
718 VMCOREINFO_SYMBOL(log_first_idx);
719 VMCOREINFO_SYMBOL(log_next_idx);
721 * Export struct log size and field offsets. User space tools can
722 * parse it and detect any changes to structure down the line.
724 VMCOREINFO_STRUCT_SIZE(log);
725 VMCOREINFO_OFFSET(log, ts_nsec);
726 VMCOREINFO_OFFSET(log, len);
727 VMCOREINFO_OFFSET(log, text_len);
728 VMCOREINFO_OFFSET(log, dict_len);
732 /* requested log_buf_len from kernel cmdline */
733 static unsigned long __initdata new_log_buf_len;
735 /* save requested log_buf_len since it's too early to process it */
736 static int __init log_buf_len_setup(char *str)
738 unsigned size = memparse(str, &str);
741 size = roundup_pow_of_two(size);
742 if (size > log_buf_len)
743 new_log_buf_len = size;
747 early_param("log_buf_len", log_buf_len_setup);
749 void __init setup_log_buf(int early)
755 if (!new_log_buf_len)
761 mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
764 new_log_buf = __va(mem);
766 new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
769 if (unlikely(!new_log_buf)) {
770 pr_err("log_buf_len: %ld bytes not available\n",
775 raw_spin_lock_irqsave(&logbuf_lock, flags);
776 log_buf_len = new_log_buf_len;
777 log_buf = new_log_buf;
779 free = __LOG_BUF_LEN - log_next_idx;
780 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
781 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
783 pr_info("log_buf_len: %d\n", log_buf_len);
784 pr_info("early log buf free: %d(%d%%)\n",
785 free, (free * 100) / __LOG_BUF_LEN);
788 static bool __read_mostly ignore_loglevel;
790 static int __init ignore_loglevel_setup(char *str)
793 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
798 early_param("ignore_loglevel", ignore_loglevel_setup);
799 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
800 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
801 "print all kernel messages to the console.");
803 #ifdef CONFIG_BOOT_PRINTK_DELAY
805 static int boot_delay; /* msecs delay after each printk during bootup */
806 static unsigned long long loops_per_msec; /* based on boot_delay */
808 static int __init boot_delay_setup(char *str)
812 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
813 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
815 get_option(&str, &boot_delay);
816 if (boot_delay > 10 * 1000)
819 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
820 "HZ: %d, loops_per_msec: %llu\n",
821 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
824 __setup("boot_delay=", boot_delay_setup);
826 static void boot_delay_msec(int level)
828 unsigned long long k;
829 unsigned long timeout;
831 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
832 || (level >= console_loglevel && !ignore_loglevel)) {
836 k = (unsigned long long)loops_per_msec * boot_delay;
838 timeout = jiffies + msecs_to_jiffies(boot_delay);
843 * use (volatile) jiffies to prevent
844 * compiler reduction; loop termination via jiffies
845 * is secondary and may or may not happen.
847 if (time_after(jiffies, timeout))
849 touch_nmi_watchdog();
853 static inline void boot_delay_msec(int level)
858 #if defined(CONFIG_PRINTK_TIME)
859 static bool printk_time = 1;
861 static bool printk_time;
863 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
865 static size_t print_time(u64 ts, char *buf)
867 unsigned long rem_nsec;
872 rem_nsec = do_div(ts, 1000000000);
875 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
877 return sprintf(buf, "[%5lu.%06lu] ",
878 (unsigned long)ts, rem_nsec / 1000);
881 static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
884 unsigned int prefix = (msg->facility << 3) | msg->level;
888 len += sprintf(buf, "<%u>", prefix);
893 else if (prefix > 99)
900 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
904 static size_t msg_print_text(const struct log *msg, enum log_flags prev,
905 bool syslog, char *buf, size_t size)
907 const char *text = log_text(msg);
908 size_t text_size = msg->text_len;
913 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
916 if (msg->flags & LOG_CONT) {
917 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
920 if (!(msg->flags & LOG_NEWLINE))
925 const char *next = memchr(text, '\n', text_size);
929 text_len = next - text;
931 text_size -= next - text;
933 text_len = text_size;
937 if (print_prefix(msg, syslog, NULL) +
938 text_len + 1 >= size - len)
942 len += print_prefix(msg, syslog, buf + len);
943 memcpy(buf + len, text, text_len);
948 /* SYSLOG_ACTION_* buffer size only calculation */
950 len += print_prefix(msg, syslog, NULL);
963 static int syslog_print(char __user *buf, int size)
969 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
977 raw_spin_lock_irq(&logbuf_lock);
978 if (syslog_seq < log_first_seq) {
979 /* messages are gone, move to first one */
980 syslog_seq = log_first_seq;
981 syslog_idx = log_first_idx;
985 if (syslog_seq == log_next_seq) {
986 raw_spin_unlock_irq(&logbuf_lock);
990 skip = syslog_partial;
991 msg = log_from_idx(syslog_idx);
992 n = msg_print_text(msg, syslog_prev, true, text,
993 LOG_LINE_MAX + PREFIX_MAX);
994 if (n - syslog_partial <= size) {
995 /* message fits into buffer, move forward */
996 syslog_idx = log_next(syslog_idx);
998 syslog_prev = msg->flags;
1002 /* partial read(), remember position */
1004 syslog_partial += n;
1007 raw_spin_unlock_irq(&logbuf_lock);
1012 if (copy_to_user(buf, text + skip, n)) {
1027 static int syslog_print_all(char __user *buf, int size, bool clear)
1032 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1036 raw_spin_lock_irq(&logbuf_lock);
1041 enum log_flags prev;
1043 if (clear_seq < log_first_seq) {
1044 /* messages are gone, move to first available one */
1045 clear_seq = log_first_seq;
1046 clear_idx = log_first_idx;
1050 * Find first record that fits, including all following records,
1051 * into the user-provided buffer for this dump.
1056 while (seq < log_next_seq) {
1057 struct log *msg = log_from_idx(idx);
1059 len += msg_print_text(msg, prev, true, NULL, 0);
1061 idx = log_next(idx);
1065 /* move first record forward until length fits into the buffer */
1069 while (len > size && seq < log_next_seq) {
1070 struct log *msg = log_from_idx(idx);
1072 len -= msg_print_text(msg, prev, true, NULL, 0);
1074 idx = log_next(idx);
1078 /* last message fitting into this dump */
1079 next_seq = log_next_seq;
1083 while (len >= 0 && seq < next_seq) {
1084 struct log *msg = log_from_idx(idx);
1087 textlen = msg_print_text(msg, prev, true, text,
1088 LOG_LINE_MAX + PREFIX_MAX);
1093 idx = log_next(idx);
1097 raw_spin_unlock_irq(&logbuf_lock);
1098 if (copy_to_user(buf + len, text, textlen))
1102 raw_spin_lock_irq(&logbuf_lock);
1104 if (seq < log_first_seq) {
1105 /* messages are gone, move to next one */
1106 seq = log_first_seq;
1107 idx = log_first_idx;
1114 clear_seq = log_next_seq;
1115 clear_idx = log_next_idx;
1117 raw_spin_unlock_irq(&logbuf_lock);
1123 int do_syslog(int type, char __user *buf, int len, bool from_file)
1126 static int saved_console_loglevel = -1;
1129 error = check_syslog_permissions(type, from_file);
1133 error = security_syslog(type);
1138 case SYSLOG_ACTION_CLOSE: /* Close log */
1140 case SYSLOG_ACTION_OPEN: /* Open log */
1142 case SYSLOG_ACTION_READ: /* Read from log */
1144 if (!buf || len < 0)
1149 if (!access_ok(VERIFY_WRITE, buf, len)) {
1153 error = wait_event_interruptible(log_wait,
1154 syslog_seq != log_next_seq);
1157 error = syslog_print(buf, len);
1159 /* Read/clear last kernel messages */
1160 case SYSLOG_ACTION_READ_CLEAR:
1163 /* Read last kernel messages */
1164 case SYSLOG_ACTION_READ_ALL:
1166 if (!buf || len < 0)
1171 if (!access_ok(VERIFY_WRITE, buf, len)) {
1175 error = syslog_print_all(buf, len, clear);
1177 /* Clear ring buffer */
1178 case SYSLOG_ACTION_CLEAR:
1179 syslog_print_all(NULL, 0, true);
1181 /* Disable logging to console */
1182 case SYSLOG_ACTION_CONSOLE_OFF:
1183 if (saved_console_loglevel == -1)
1184 saved_console_loglevel = console_loglevel;
1185 console_loglevel = minimum_console_loglevel;
1187 /* Enable logging to console */
1188 case SYSLOG_ACTION_CONSOLE_ON:
1189 if (saved_console_loglevel != -1) {
1190 console_loglevel = saved_console_loglevel;
1191 saved_console_loglevel = -1;
1194 /* Set level of messages printed to console */
1195 case SYSLOG_ACTION_CONSOLE_LEVEL:
1197 if (len < 1 || len > 8)
1199 if (len < minimum_console_loglevel)
1200 len = minimum_console_loglevel;
1201 console_loglevel = len;
1202 /* Implicitly re-enable logging to console */
1203 saved_console_loglevel = -1;
1206 /* Number of chars in the log buffer */
1207 case SYSLOG_ACTION_SIZE_UNREAD:
1208 raw_spin_lock_irq(&logbuf_lock);
1209 if (syslog_seq < log_first_seq) {
1210 /* messages are gone, move to first one */
1211 syslog_seq = log_first_seq;
1212 syslog_idx = log_first_idx;
1218 * Short-cut for poll(/"proc/kmsg") which simply checks
1219 * for pending data, not the size; return the count of
1220 * records, not the length.
1222 error = log_next_idx - syslog_idx;
1224 u64 seq = syslog_seq;
1225 u32 idx = syslog_idx;
1226 enum log_flags prev = syslog_prev;
1229 while (seq < log_next_seq) {
1230 struct log *msg = log_from_idx(idx);
1232 error += msg_print_text(msg, prev, true, NULL, 0);
1233 idx = log_next(idx);
1237 error -= syslog_partial;
1239 raw_spin_unlock_irq(&logbuf_lock);
1241 /* Size of the log buffer */
1242 case SYSLOG_ACTION_SIZE_BUFFER:
1243 error = log_buf_len;
1253 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1255 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1259 * Call the console drivers, asking them to write out
1260 * log_buf[start] to log_buf[end - 1].
1261 * The console_lock must be held.
1263 static void call_console_drivers(int level, const char *text, size_t len)
1265 struct console *con;
1267 trace_console(text, len);
1269 if (level >= console_loglevel && !ignore_loglevel)
1271 if (!console_drivers)
1274 for_each_console(con) {
1275 if (exclusive_console && con != exclusive_console)
1277 if (!(con->flags & CON_ENABLED))
1281 if (!cpu_online(smp_processor_id()) &&
1282 !(con->flags & CON_ANYTIME))
1284 con->write(con, text, len);
1289 * Zap console related locks when oopsing. Only zap at most once
1290 * every 10 seconds, to leave time for slow consoles to print a
1293 static void zap_locks(void)
1295 static unsigned long oops_timestamp;
1297 if (time_after_eq(jiffies, oops_timestamp) &&
1298 !time_after(jiffies, oops_timestamp + 30 * HZ))
1301 oops_timestamp = jiffies;
1304 /* If a crash is occurring, make sure we can't deadlock */
1305 raw_spin_lock_init(&logbuf_lock);
1306 /* And make sure that we print immediately */
1307 sema_init(&console_sem, 1);
1310 /* Check if we have any console registered that can be called early in boot. */
1311 static int have_callable_console(void)
1313 struct console *con;
1315 for_each_console(con)
1316 if (con->flags & CON_ANYTIME)
1323 * Can we actually use the console at this time on this cpu?
1325 * Console drivers may assume that per-cpu resources have
1326 * been allocated. So unless they're explicitly marked as
1327 * being able to cope (CON_ANYTIME) don't call them until
1328 * this CPU is officially up.
1330 static inline int can_use_console(unsigned int cpu)
1332 return cpu_online(cpu) || have_callable_console();
1336 * Try to get console ownership to actually show the kernel
1337 * messages from a 'printk'. Return true (and with the
1338 * console_lock held, and 'console_locked' set) if it
1339 * is successful, false otherwise.
1341 * This gets called with the 'logbuf_lock' spinlock held and
1342 * interrupts disabled. It should return with 'lockbuf_lock'
1343 * released but interrupts still disabled.
1345 static int console_trylock_for_printk(unsigned int cpu)
1346 __releases(&logbuf_lock)
1348 int retval = 0, wake = 0;
1350 if (console_trylock()) {
1354 * If we can't use the console, we need to release
1355 * the console semaphore by hand to avoid flushing
1356 * the buffer. We need to hold the console semaphore
1357 * in order to do this test safely.
1359 if (!can_use_console(cpu)) {
1365 logbuf_cpu = UINT_MAX;
1366 raw_spin_unlock(&logbuf_lock);
1372 int printk_delay_msec __read_mostly;
1374 static inline void printk_delay(void)
1376 if (unlikely(printk_delay_msec)) {
1377 int m = printk_delay_msec;
1381 touch_nmi_watchdog();
1387 * Continuation lines are buffered, and not committed to the record buffer
1388 * until the line is complete, or a race forces it. The line fragments
1389 * though, are printed immediately to the consoles to ensure everything has
1390 * reached the console in case of a kernel crash.
1392 static struct cont {
1393 char buf[LOG_LINE_MAX];
1394 size_t len; /* length == 0 means unused buffer */
1395 size_t cons; /* bytes written to console */
1396 struct task_struct *owner; /* task of first print*/
1397 u64 ts_nsec; /* time of first print */
1398 u8 level; /* log level of first message */
1399 u8 facility; /* log level of first message */
1400 enum log_flags flags; /* prefix, newline flags */
1401 bool flushed:1; /* buffer sealed and committed */
1404 static void cont_flush(enum log_flags flags)
1413 * If a fragment of this line was directly flushed to the
1414 * console; wait for the console to pick up the rest of the
1415 * line. LOG_NOCONS suppresses a duplicated output.
1417 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1418 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1420 cont.flushed = true;
1423 * If no fragment of this line ever reached the console,
1424 * just submit it to the store and free the buffer.
1426 log_store(cont.facility, cont.level, flags, 0,
1427 NULL, 0, cont.buf, cont.len);
1432 static bool cont_add(int facility, int level, const char *text, size_t len)
1434 if (cont.len && cont.flushed)
1437 if (cont.len + len > sizeof(cont.buf)) {
1438 /* the line gets too long, split it up in separate records */
1439 cont_flush(LOG_CONT);
1444 cont.facility = facility;
1446 cont.owner = current;
1447 cont.ts_nsec = local_clock();
1450 cont.flushed = false;
1453 memcpy(cont.buf + cont.len, text, len);
1456 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1457 cont_flush(LOG_CONT);
1462 static size_t cont_print_text(char *text, size_t size)
1467 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1468 textlen += print_time(cont.ts_nsec, text);
1472 len = cont.len - cont.cons;
1476 memcpy(text + textlen, cont.buf + cont.cons, len);
1478 cont.cons = cont.len;
1482 if (cont.flags & LOG_NEWLINE)
1483 text[textlen++] = '\n';
1484 /* got everything, release buffer */
1490 asmlinkage int vprintk_emit(int facility, int level,
1491 const char *dict, size_t dictlen,
1492 const char *fmt, va_list args)
1494 static int recursion_bug;
1495 static char textbuf[LOG_LINE_MAX];
1496 char *text = textbuf;
1498 enum log_flags lflags = 0;
1499 unsigned long flags;
1501 int printed_len = 0;
1503 boot_delay_msec(level);
1506 /* This stops the holder of console_sem just where we want him */
1507 local_irq_save(flags);
1508 this_cpu = smp_processor_id();
1511 * Ouch, printk recursed into itself!
1513 if (unlikely(logbuf_cpu == this_cpu)) {
1515 * If a crash is occurring during printk() on this CPU,
1516 * then try to get the crash message out but make sure
1517 * we can't deadlock. Otherwise just return to avoid the
1518 * recursion and return - but flag the recursion so that
1519 * it can be printed at the next appropriate moment:
1521 if (!oops_in_progress && !lockdep_recursing(current)) {
1523 goto out_restore_irqs;
1529 raw_spin_lock(&logbuf_lock);
1530 logbuf_cpu = this_cpu;
1532 if (recursion_bug) {
1533 static const char recursion_msg[] =
1534 "BUG: recent printk recursion!";
1537 printed_len += strlen(recursion_msg);
1538 /* emit KERN_CRIT message */
1539 log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1540 NULL, 0, recursion_msg, printed_len);
1544 * The printf needs to come first; we need the syslog
1545 * prefix which might be passed-in as a parameter.
1547 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1549 /* mark and strip a trailing newline */
1550 if (text_len && text[text_len-1] == '\n') {
1552 lflags |= LOG_NEWLINE;
1555 /* strip kernel syslog prefix and extract log level or control flags */
1556 if (facility == 0) {
1557 int kern_level = printk_get_level(text);
1560 const char *end_of_header = printk_skip_level(text);
1561 switch (kern_level) {
1564 level = kern_level - '0';
1565 case 'd': /* KERN_DEFAULT */
1566 lflags |= LOG_PREFIX;
1567 case 'c': /* KERN_CONT */
1570 text_len -= end_of_header - text;
1571 text = (char *)end_of_header;
1576 level = default_message_loglevel;
1579 lflags |= LOG_PREFIX|LOG_NEWLINE;
1581 if (!(lflags & LOG_NEWLINE)) {
1583 * Flush the conflicting buffer. An earlier newline was missing,
1584 * or another task also prints continuation lines.
1586 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1587 cont_flush(LOG_NEWLINE);
1589 /* buffer line if possible, otherwise store it right away */
1590 if (!cont_add(facility, level, text, text_len))
1591 log_store(facility, level, lflags | LOG_CONT, 0,
1592 dict, dictlen, text, text_len);
1594 bool stored = false;
1597 * If an earlier newline was missing and it was the same task,
1598 * either merge it with the current buffer and flush, or if
1599 * there was a race with interrupts (prefix == true) then just
1600 * flush it out and store this line separately.
1602 if (cont.len && cont.owner == current) {
1603 if (!(lflags & LOG_PREFIX))
1604 stored = cont_add(facility, level, text, text_len);
1605 cont_flush(LOG_NEWLINE);
1609 log_store(facility, level, lflags, 0,
1610 dict, dictlen, text, text_len);
1612 printed_len += text_len;
1615 * Try to acquire and then immediately release the console semaphore.
1616 * The release will print out buffers and wake up /dev/kmsg and syslog()
1619 * The console_trylock_for_printk() function will release 'logbuf_lock'
1620 * regardless of whether it actually gets the console semaphore or not.
1622 if (console_trylock_for_printk(this_cpu))
1627 local_irq_restore(flags);
1631 EXPORT_SYMBOL(vprintk_emit);
1633 asmlinkage int vprintk(const char *fmt, va_list args)
1635 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1637 EXPORT_SYMBOL(vprintk);
1639 asmlinkage int printk_emit(int facility, int level,
1640 const char *dict, size_t dictlen,
1641 const char *fmt, ...)
1646 va_start(args, fmt);
1647 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1652 EXPORT_SYMBOL(printk_emit);
1655 * printk - print a kernel message
1656 * @fmt: format string
1658 * This is printk(). It can be called from any context. We want it to work.
1660 * We try to grab the console_lock. If we succeed, it's easy - we log the
1661 * output and call the console drivers. If we fail to get the semaphore, we
1662 * place the output into the log buffer and return. The current holder of
1663 * the console_sem will notice the new output in console_unlock(); and will
1664 * send it to the consoles before releasing the lock.
1666 * One effect of this deferred printing is that code which calls printk() and
1667 * then changes console_loglevel may break. This is because console_loglevel
1668 * is inspected when the actual printing occurs.
1673 * See the vsnprintf() documentation for format string extensions over C99.
1675 asmlinkage int printk(const char *fmt, ...)
1680 #ifdef CONFIG_KGDB_KDB
1681 if (unlikely(kdb_trap_printk)) {
1682 va_start(args, fmt);
1683 r = vkdb_printf(fmt, args);
1688 va_start(args, fmt);
1689 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1694 EXPORT_SYMBOL(printk);
1696 #else /* CONFIG_PRINTK */
1698 #define LOG_LINE_MAX 0
1699 #define PREFIX_MAX 0
1700 #define LOG_LINE_MAX 0
1701 static u64 syslog_seq;
1702 static u32 syslog_idx;
1703 static u64 console_seq;
1704 static u32 console_idx;
1705 static enum log_flags syslog_prev;
1706 static u64 log_first_seq;
1707 static u32 log_first_idx;
1708 static u64 log_next_seq;
1709 static enum log_flags console_prev;
1710 static struct cont {
1716 static struct log *log_from_idx(u32 idx) { return NULL; }
1717 static u32 log_next(u32 idx) { return 0; }
1718 static void call_console_drivers(int level, const char *text, size_t len) {}
1719 static size_t msg_print_text(const struct log *msg, enum log_flags prev,
1720 bool syslog, char *buf, size_t size) { return 0; }
1721 static size_t cont_print_text(char *text, size_t size) { return 0; }
1723 #endif /* CONFIG_PRINTK */
1725 #ifdef CONFIG_EARLY_PRINTK
1726 struct console *early_console;
1728 void early_vprintk(const char *fmt, va_list ap)
1730 if (early_console) {
1732 int n = vscnprintf(buf, sizeof(buf), fmt, ap);
1734 early_console->write(early_console, buf, n);
1738 asmlinkage void early_printk(const char *fmt, ...)
1743 early_vprintk(fmt, ap);
1748 static int __add_preferred_console(char *name, int idx, char *options,
1751 struct console_cmdline *c;
1755 * See if this tty is not yet registered, and
1756 * if we have a slot free.
1758 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1759 if (strcmp(console_cmdline[i].name, name) == 0 &&
1760 console_cmdline[i].index == idx) {
1762 selected_console = i;
1765 if (i == MAX_CMDLINECONSOLES)
1768 selected_console = i;
1769 c = &console_cmdline[i];
1770 strlcpy(c->name, name, sizeof(c->name));
1771 c->options = options;
1772 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1773 c->brl_options = brl_options;
1779 * Set up a list of consoles. Called from init/main.c
1781 static int __init console_setup(char *str)
1783 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1784 char *s, *options, *brl_options = NULL;
1787 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1788 if (!memcmp(str, "brl,", 4)) {
1791 } else if (!memcmp(str, "brl=", 4)) {
1792 brl_options = str + 4;
1793 str = strchr(brl_options, ',');
1795 printk(KERN_ERR "need port name after brl=\n");
1803 * Decode str into name, index, options.
1805 if (str[0] >= '0' && str[0] <= '9') {
1806 strcpy(buf, "ttyS");
1807 strncpy(buf + 4, str, sizeof(buf) - 5);
1809 strncpy(buf, str, sizeof(buf) - 1);
1811 buf[sizeof(buf) - 1] = 0;
1812 if ((options = strchr(str, ',')) != NULL)
1815 if (!strcmp(str, "ttya"))
1816 strcpy(buf, "ttyS0");
1817 if (!strcmp(str, "ttyb"))
1818 strcpy(buf, "ttyS1");
1820 for (s = buf; *s; s++)
1821 if ((*s >= '0' && *s <= '9') || *s == ',')
1823 idx = simple_strtoul(s, NULL, 10);
1826 __add_preferred_console(buf, idx, options, brl_options);
1827 console_set_on_cmdline = 1;
1830 __setup("console=", console_setup);
1833 * add_preferred_console - add a device to the list of preferred consoles.
1834 * @name: device name
1835 * @idx: device index
1836 * @options: options for this console
1838 * The last preferred console added will be used for kernel messages
1839 * and stdin/out/err for init. Normally this is used by console_setup
1840 * above to handle user-supplied console arguments; however it can also
1841 * be used by arch-specific code either to override the user or more
1842 * commonly to provide a default console (ie from PROM variables) when
1843 * the user has not supplied one.
1845 int add_preferred_console(char *name, int idx, char *options)
1847 return __add_preferred_console(name, idx, options, NULL);
1850 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1852 struct console_cmdline *c;
1855 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1856 if (strcmp(console_cmdline[i].name, name) == 0 &&
1857 console_cmdline[i].index == idx) {
1858 c = &console_cmdline[i];
1859 strlcpy(c->name, name_new, sizeof(c->name));
1860 c->name[sizeof(c->name) - 1] = 0;
1861 c->options = options;
1869 bool console_suspend_enabled = 1;
1870 EXPORT_SYMBOL(console_suspend_enabled);
1872 static int __init console_suspend_disable(char *str)
1874 console_suspend_enabled = 0;
1877 __setup("no_console_suspend", console_suspend_disable);
1878 module_param_named(console_suspend, console_suspend_enabled,
1879 bool, S_IRUGO | S_IWUSR);
1880 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1881 " and hibernate operations");
1884 * suspend_console - suspend the console subsystem
1886 * This disables printk() while we go into suspend states
1888 void suspend_console(void)
1890 if (!console_suspend_enabled)
1892 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1894 console_suspended = 1;
1898 void resume_console(void)
1900 if (!console_suspend_enabled)
1903 console_suspended = 0;
1908 * console_cpu_notify - print deferred console messages after CPU hotplug
1909 * @self: notifier struct
1910 * @action: CPU hotplug event
1913 * If printk() is called from a CPU that is not online yet, the messages
1914 * will be spooled but will not show up on the console. This function is
1915 * called when a new CPU comes online (or fails to come up), and ensures
1916 * that any such output gets printed.
1918 static int console_cpu_notify(struct notifier_block *self,
1919 unsigned long action, void *hcpu)
1924 case CPU_DOWN_FAILED:
1925 case CPU_UP_CANCELED:
1933 * console_lock - lock the console system for exclusive use.
1935 * Acquires a lock which guarantees that the caller has
1936 * exclusive access to the console system and the console_drivers list.
1938 * Can sleep, returns nothing.
1940 void console_lock(void)
1945 if (console_suspended)
1948 console_may_schedule = 1;
1949 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
1951 EXPORT_SYMBOL(console_lock);
1954 * console_trylock - try to lock the console system for exclusive use.
1956 * Tried to acquire a lock which guarantees that the caller has
1957 * exclusive access to the console system and the console_drivers list.
1959 * returns 1 on success, and 0 on failure to acquire the lock.
1961 int console_trylock(void)
1963 if (down_trylock(&console_sem))
1965 if (console_suspended) {
1970 console_may_schedule = 0;
1971 mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);
1974 EXPORT_SYMBOL(console_trylock);
1976 int is_console_locked(void)
1978 return console_locked;
1981 static void console_cont_flush(char *text, size_t size)
1983 unsigned long flags;
1986 raw_spin_lock_irqsave(&logbuf_lock, flags);
1992 * We still queue earlier records, likely because the console was
1993 * busy. The earlier ones need to be printed before this one, we
1994 * did not flush any fragment so far, so just let it queue up.
1996 if (console_seq < log_next_seq && !cont.cons)
1999 len = cont_print_text(text, size);
2000 raw_spin_unlock(&logbuf_lock);
2001 stop_critical_timings();
2002 call_console_drivers(cont.level, text, len);
2003 start_critical_timings();
2004 local_irq_restore(flags);
2007 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2011 * console_unlock - unlock the console system
2013 * Releases the console_lock which the caller holds on the console system
2014 * and the console driver list.
2016 * While the console_lock was held, console output may have been buffered
2017 * by printk(). If this is the case, console_unlock(); emits
2018 * the output prior to releasing the lock.
2020 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2022 * console_unlock(); may be called from any context.
2024 void console_unlock(void)
2026 static char text[LOG_LINE_MAX + PREFIX_MAX];
2027 static u64 seen_seq;
2028 unsigned long flags;
2029 bool wake_klogd = false;
2032 if (console_suspended) {
2037 console_may_schedule = 0;
2039 /* flush buffered message fragment immediately to console */
2040 console_cont_flush(text, sizeof(text));
2047 raw_spin_lock_irqsave(&logbuf_lock, flags);
2048 if (seen_seq != log_next_seq) {
2050 seen_seq = log_next_seq;
2053 if (console_seq < log_first_seq) {
2054 /* messages are gone, move to first one */
2055 console_seq = log_first_seq;
2056 console_idx = log_first_idx;
2060 if (console_seq == log_next_seq)
2063 msg = log_from_idx(console_idx);
2064 if (msg->flags & LOG_NOCONS) {
2066 * Skip record we have buffered and already printed
2067 * directly to the console when we received it.
2069 console_idx = log_next(console_idx);
2072 * We will get here again when we register a new
2073 * CON_PRINTBUFFER console. Clear the flag so we
2074 * will properly dump everything later.
2076 msg->flags &= ~LOG_NOCONS;
2077 console_prev = msg->flags;
2082 len = msg_print_text(msg, console_prev, false,
2083 text, sizeof(text));
2084 console_idx = log_next(console_idx);
2086 console_prev = msg->flags;
2087 raw_spin_unlock(&logbuf_lock);
2089 stop_critical_timings(); /* don't trace print latency */
2090 call_console_drivers(level, text, len);
2091 start_critical_timings();
2092 local_irq_restore(flags);
2095 mutex_release(&console_lock_dep_map, 1, _RET_IP_);
2097 /* Release the exclusive_console once it is used */
2098 if (unlikely(exclusive_console))
2099 exclusive_console = NULL;
2101 raw_spin_unlock(&logbuf_lock);
2106 * Someone could have filled up the buffer again, so re-check if there's
2107 * something to flush. In case we cannot trylock the console_sem again,
2108 * there's a new owner and the console_unlock() from them will do the
2109 * flush, no worries.
2111 raw_spin_lock(&logbuf_lock);
2112 retry = console_seq != log_next_seq;
2113 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2115 if (retry && console_trylock())
2121 EXPORT_SYMBOL(console_unlock);
2124 * console_conditional_schedule - yield the CPU if required
2126 * If the console code is currently allowed to sleep, and
2127 * if this CPU should yield the CPU to another task, do
2130 * Must be called within console_lock();.
2132 void __sched console_conditional_schedule(void)
2134 if (console_may_schedule)
2137 EXPORT_SYMBOL(console_conditional_schedule);
2139 void console_unblank(void)
2144 * console_unblank can no longer be called in interrupt context unless
2145 * oops_in_progress is set to 1..
2147 if (oops_in_progress) {
2148 if (down_trylock(&console_sem) != 0)
2154 console_may_schedule = 0;
2156 if ((c->flags & CON_ENABLED) && c->unblank)
2162 * Return the console tty driver structure and its associated index
2164 struct tty_driver *console_device(int *index)
2167 struct tty_driver *driver = NULL;
2170 for_each_console(c) {
2173 driver = c->device(c, index);
2182 * Prevent further output on the passed console device so that (for example)
2183 * serial drivers can disable console output before suspending a port, and can
2184 * re-enable output afterwards.
2186 void console_stop(struct console *console)
2189 console->flags &= ~CON_ENABLED;
2192 EXPORT_SYMBOL(console_stop);
2194 void console_start(struct console *console)
2197 console->flags |= CON_ENABLED;
2200 EXPORT_SYMBOL(console_start);
2202 static int __read_mostly keep_bootcon;
2204 static int __init keep_bootcon_setup(char *str)
2207 printk(KERN_INFO "debug: skip boot console de-registration.\n");
2212 early_param("keep_bootcon", keep_bootcon_setup);
2215 * The console driver calls this routine during kernel initialization
2216 * to register the console printing procedure with printk() and to
2217 * print any messages that were printed by the kernel before the
2218 * console driver was initialized.
2220 * This can happen pretty early during the boot process (because of
2221 * early_printk) - sometimes before setup_arch() completes - be careful
2222 * of what kernel features are used - they may not be initialised yet.
2224 * There are two types of consoles - bootconsoles (early_printk) and
2225 * "real" consoles (everything which is not a bootconsole) which are
2226 * handled differently.
2227 * - Any number of bootconsoles can be registered at any time.
2228 * - As soon as a "real" console is registered, all bootconsoles
2229 * will be unregistered automatically.
2230 * - Once a "real" console is registered, any attempt to register a
2231 * bootconsoles will be rejected
2233 void register_console(struct console *newcon)
2236 unsigned long flags;
2237 struct console *bcon = NULL;
2240 * before we register a new CON_BOOT console, make sure we don't
2241 * already have a valid console
2243 if (console_drivers && newcon->flags & CON_BOOT) {
2244 /* find the last or real console */
2245 for_each_console(bcon) {
2246 if (!(bcon->flags & CON_BOOT)) {
2247 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
2248 newcon->name, newcon->index);
2254 if (console_drivers && console_drivers->flags & CON_BOOT)
2255 bcon = console_drivers;
2257 if (preferred_console < 0 || bcon || !console_drivers)
2258 preferred_console = selected_console;
2260 if (newcon->early_setup)
2261 newcon->early_setup();
2264 * See if we want to use this console driver. If we
2265 * didn't select a console we take the first one
2266 * that registers here.
2268 if (preferred_console < 0) {
2269 if (newcon->index < 0)
2271 if (newcon->setup == NULL ||
2272 newcon->setup(newcon, NULL) == 0) {
2273 newcon->flags |= CON_ENABLED;
2274 if (newcon->device) {
2275 newcon->flags |= CON_CONSDEV;
2276 preferred_console = 0;
2282 * See if this console matches one we selected on
2285 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
2287 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
2289 if (newcon->index >= 0 &&
2290 newcon->index != console_cmdline[i].index)
2292 if (newcon->index < 0)
2293 newcon->index = console_cmdline[i].index;
2294 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2295 if (console_cmdline[i].brl_options) {
2296 newcon->flags |= CON_BRL;
2297 braille_register_console(newcon,
2298 console_cmdline[i].index,
2299 console_cmdline[i].options,
2300 console_cmdline[i].brl_options);
2304 if (newcon->setup &&
2305 newcon->setup(newcon, console_cmdline[i].options) != 0)
2307 newcon->flags |= CON_ENABLED;
2308 newcon->index = console_cmdline[i].index;
2309 if (i == selected_console) {
2310 newcon->flags |= CON_CONSDEV;
2311 preferred_console = selected_console;
2316 if (!(newcon->flags & CON_ENABLED))
2320 * If we have a bootconsole, and are switching to a real console,
2321 * don't print everything out again, since when the boot console, and
2322 * the real console are the same physical device, it's annoying to
2323 * see the beginning boot messages twice
2325 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2326 newcon->flags &= ~CON_PRINTBUFFER;
2329 * Put this console in the list - keep the
2330 * preferred driver at the head of the list.
2333 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2334 newcon->next = console_drivers;
2335 console_drivers = newcon;
2337 newcon->next->flags &= ~CON_CONSDEV;
2339 newcon->next = console_drivers->next;
2340 console_drivers->next = newcon;
2342 if (newcon->flags & CON_PRINTBUFFER) {
2344 * console_unlock(); will print out the buffered messages
2347 raw_spin_lock_irqsave(&logbuf_lock, flags);
2348 console_seq = syslog_seq;
2349 console_idx = syslog_idx;
2350 console_prev = syslog_prev;
2351 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2353 * We're about to replay the log buffer. Only do this to the
2354 * just-registered console to avoid excessive message spam to
2355 * the already-registered consoles.
2357 exclusive_console = newcon;
2360 console_sysfs_notify();
2363 * By unregistering the bootconsoles after we enable the real console
2364 * we get the "console xxx enabled" message on all the consoles -
2365 * boot consoles, real consoles, etc - this is to ensure that end
2366 * users know there might be something in the kernel's log buffer that
2367 * went to the bootconsole (that they do not see on the real console)
2370 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2372 /* we need to iterate through twice, to make sure we print
2373 * everything out, before we unregister the console(s)
2375 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
2376 newcon->name, newcon->index);
2377 for_each_console(bcon)
2378 if (bcon->flags & CON_BOOT)
2379 unregister_console(bcon);
2381 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
2382 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2383 newcon->name, newcon->index);
2386 EXPORT_SYMBOL(register_console);
2388 int unregister_console(struct console *console)
2390 struct console *a, *b;
2393 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2394 if (console->flags & CON_BRL)
2395 return braille_unregister_console(console);
2399 if (console_drivers == console) {
2400 console_drivers=console->next;
2402 } else if (console_drivers) {
2403 for (a=console_drivers->next, b=console_drivers ;
2404 a; b=a, a=b->next) {
2414 * If this isn't the last console and it has CON_CONSDEV set, we
2415 * need to set it on the next preferred console.
2417 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2418 console_drivers->flags |= CON_CONSDEV;
2421 console_sysfs_notify();
2424 EXPORT_SYMBOL(unregister_console);
2426 static int __init printk_late_init(void)
2428 struct console *con;
2430 for_each_console(con) {
2431 if (!keep_bootcon && con->flags & CON_BOOT) {
2432 printk(KERN_INFO "turn off boot console %s%d\n",
2433 con->name, con->index);
2434 unregister_console(con);
2437 hotcpu_notifier(console_cpu_notify, 0);
2440 late_initcall(printk_late_init);
2442 #if defined CONFIG_PRINTK
2444 * Delayed printk version, for scheduler-internal messages:
2446 #define PRINTK_BUF_SIZE 512
2448 #define PRINTK_PENDING_WAKEUP 0x01
2449 #define PRINTK_PENDING_SCHED 0x02
2451 static DEFINE_PER_CPU(int, printk_pending);
2452 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
2454 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2456 int pending = __this_cpu_xchg(printk_pending, 0);
2458 if (pending & PRINTK_PENDING_SCHED) {
2459 char *buf = __get_cpu_var(printk_sched_buf);
2460 printk(KERN_WARNING "[sched_delayed] %s", buf);
2463 if (pending & PRINTK_PENDING_WAKEUP)
2464 wake_up_interruptible(&log_wait);
2467 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2468 .func = wake_up_klogd_work_func,
2469 .flags = IRQ_WORK_LAZY,
2472 void wake_up_klogd(void)
2475 if (waitqueue_active(&log_wait)) {
2476 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2477 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2482 int printk_sched(const char *fmt, ...)
2484 unsigned long flags;
2489 local_irq_save(flags);
2490 buf = __get_cpu_var(printk_sched_buf);
2492 va_start(args, fmt);
2493 r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2496 __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2497 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2498 local_irq_restore(flags);
2504 * printk rate limiting, lifted from the networking subsystem.
2506 * This enforces a rate limit: not more than 10 kernel messages
2507 * every 5s to make a denial-of-service attack impossible.
2509 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2511 int __printk_ratelimit(const char *func)
2513 return ___ratelimit(&printk_ratelimit_state, func);
2515 EXPORT_SYMBOL(__printk_ratelimit);
2518 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2519 * @caller_jiffies: pointer to caller's state
2520 * @interval_msecs: minimum interval between prints
2522 * printk_timed_ratelimit() returns true if more than @interval_msecs
2523 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2526 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2527 unsigned int interval_msecs)
2529 if (*caller_jiffies == 0
2530 || !time_in_range(jiffies, *caller_jiffies,
2532 + msecs_to_jiffies(interval_msecs))) {
2533 *caller_jiffies = jiffies;
2538 EXPORT_SYMBOL(printk_timed_ratelimit);
2540 static DEFINE_SPINLOCK(dump_list_lock);
2541 static LIST_HEAD(dump_list);
2544 * kmsg_dump_register - register a kernel log dumper.
2545 * @dumper: pointer to the kmsg_dumper structure
2547 * Adds a kernel log dumper to the system. The dump callback in the
2548 * structure will be called when the kernel oopses or panics and must be
2549 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2551 int kmsg_dump_register(struct kmsg_dumper *dumper)
2553 unsigned long flags;
2556 /* The dump callback needs to be set */
2560 spin_lock_irqsave(&dump_list_lock, flags);
2561 /* Don't allow registering multiple times */
2562 if (!dumper->registered) {
2563 dumper->registered = 1;
2564 list_add_tail_rcu(&dumper->list, &dump_list);
2567 spin_unlock_irqrestore(&dump_list_lock, flags);
2571 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2574 * kmsg_dump_unregister - unregister a kmsg dumper.
2575 * @dumper: pointer to the kmsg_dumper structure
2577 * Removes a dump device from the system. Returns zero on success and
2578 * %-EINVAL otherwise.
2580 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2582 unsigned long flags;
2585 spin_lock_irqsave(&dump_list_lock, flags);
2586 if (dumper->registered) {
2587 dumper->registered = 0;
2588 list_del_rcu(&dumper->list);
2591 spin_unlock_irqrestore(&dump_list_lock, flags);
2596 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2598 static bool always_kmsg_dump;
2599 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2602 * kmsg_dump - dump kernel log to kernel message dumpers.
2603 * @reason: the reason (oops, panic etc) for dumping
2605 * Call each of the registered dumper's dump() callback, which can
2606 * retrieve the kmsg records with kmsg_dump_get_line() or
2607 * kmsg_dump_get_buffer().
2609 void kmsg_dump(enum kmsg_dump_reason reason)
2611 struct kmsg_dumper *dumper;
2612 unsigned long flags;
2614 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2618 list_for_each_entry_rcu(dumper, &dump_list, list) {
2619 if (dumper->max_reason && reason > dumper->max_reason)
2622 /* initialize iterator with data about the stored records */
2623 dumper->active = true;
2625 raw_spin_lock_irqsave(&logbuf_lock, flags);
2626 dumper->cur_seq = clear_seq;
2627 dumper->cur_idx = clear_idx;
2628 dumper->next_seq = log_next_seq;
2629 dumper->next_idx = log_next_idx;
2630 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2632 /* invoke dumper which will iterate over records */
2633 dumper->dump(dumper, reason);
2635 /* reset iterator */
2636 dumper->active = false;
2642 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2643 * @dumper: registered kmsg dumper
2644 * @syslog: include the "<4>" prefixes
2645 * @line: buffer to copy the line to
2646 * @size: maximum size of the buffer
2647 * @len: length of line placed into buffer
2649 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2650 * record, and copy one record into the provided buffer.
2652 * Consecutive calls will return the next available record moving
2653 * towards the end of the buffer with the youngest messages.
2655 * A return value of FALSE indicates that there are no more records to
2658 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2660 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2661 char *line, size_t size, size_t *len)
2667 if (!dumper->active)
2670 if (dumper->cur_seq < log_first_seq) {
2671 /* messages are gone, move to first available one */
2672 dumper->cur_seq = log_first_seq;
2673 dumper->cur_idx = log_first_idx;
2677 if (dumper->cur_seq >= log_next_seq)
2680 msg = log_from_idx(dumper->cur_idx);
2681 l = msg_print_text(msg, 0, syslog, line, size);
2683 dumper->cur_idx = log_next(dumper->cur_idx);
2693 * kmsg_dump_get_line - retrieve one kmsg log line
2694 * @dumper: registered kmsg dumper
2695 * @syslog: include the "<4>" prefixes
2696 * @line: buffer to copy the line to
2697 * @size: maximum size of the buffer
2698 * @len: length of line placed into buffer
2700 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2701 * record, and copy one record into the provided buffer.
2703 * Consecutive calls will return the next available record moving
2704 * towards the end of the buffer with the youngest messages.
2706 * A return value of FALSE indicates that there are no more records to
2709 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2710 char *line, size_t size, size_t *len)
2712 unsigned long flags;
2715 raw_spin_lock_irqsave(&logbuf_lock, flags);
2716 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2717 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2721 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2724 * kmsg_dump_get_buffer - copy kmsg log lines
2725 * @dumper: registered kmsg dumper
2726 * @syslog: include the "<4>" prefixes
2727 * @buf: buffer to copy the line to
2728 * @size: maximum size of the buffer
2729 * @len: length of line placed into buffer
2731 * Start at the end of the kmsg buffer and fill the provided buffer
2732 * with as many of the the *youngest* kmsg records that fit into it.
2733 * If the buffer is large enough, all available kmsg records will be
2734 * copied with a single call.
2736 * Consecutive calls will fill the buffer with the next block of
2737 * available older records, not including the earlier retrieved ones.
2739 * A return value of FALSE indicates that there are no more records to
2742 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2743 char *buf, size_t size, size_t *len)
2745 unsigned long flags;
2750 enum log_flags prev;
2754 if (!dumper->active)
2757 raw_spin_lock_irqsave(&logbuf_lock, flags);
2758 if (dumper->cur_seq < log_first_seq) {
2759 /* messages are gone, move to first available one */
2760 dumper->cur_seq = log_first_seq;
2761 dumper->cur_idx = log_first_idx;
2765 if (dumper->cur_seq >= dumper->next_seq) {
2766 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2770 /* calculate length of entire buffer */
2771 seq = dumper->cur_seq;
2772 idx = dumper->cur_idx;
2774 while (seq < dumper->next_seq) {
2775 struct log *msg = log_from_idx(idx);
2777 l += msg_print_text(msg, prev, true, NULL, 0);
2778 idx = log_next(idx);
2783 /* move first record forward until length fits into the buffer */
2784 seq = dumper->cur_seq;
2785 idx = dumper->cur_idx;
2787 while (l > size && seq < dumper->next_seq) {
2788 struct log *msg = log_from_idx(idx);
2790 l -= msg_print_text(msg, prev, true, NULL, 0);
2791 idx = log_next(idx);
2796 /* last message in next interation */
2802 while (seq < dumper->next_seq) {
2803 struct log *msg = log_from_idx(idx);
2805 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2806 idx = log_next(idx);
2811 dumper->next_seq = next_seq;
2812 dumper->next_idx = next_idx;
2814 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2820 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2823 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2824 * @dumper: registered kmsg dumper
2826 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2827 * kmsg_dump_get_buffer() can be called again and used multiple
2828 * times within the same dumper.dump() callback.
2830 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2832 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
2834 dumper->cur_seq = clear_seq;
2835 dumper->cur_idx = clear_idx;
2836 dumper->next_seq = log_next_seq;
2837 dumper->next_idx = log_next_idx;
2841 * kmsg_dump_rewind - reset the interator
2842 * @dumper: registered kmsg dumper
2844 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2845 * kmsg_dump_get_buffer() can be called again and used multiple
2846 * times within the same dumper.dump() callback.
2848 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2850 unsigned long flags;
2852 raw_spin_lock_irqsave(&logbuf_lock, flags);
2853 kmsg_dump_rewind_nolock(dumper);
2854 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2856 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
2858 static char dump_stack_arch_desc_str[128];
2861 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
2862 * @fmt: printf-style format string
2863 * @...: arguments for the format string
2865 * The configured string will be printed right after utsname during task
2866 * dumps. Usually used to add arch-specific system identifiers. If an
2867 * arch wants to make use of such an ID string, it should initialize this
2868 * as soon as possible during boot.
2870 void __init dump_stack_set_arch_desc(const char *fmt, ...)
2874 va_start(args, fmt);
2875 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
2881 * dump_stack_print_info - print generic debug info for dump_stack()
2882 * @log_lvl: log level
2884 * Arch-specific dump_stack() implementations can use this function to
2885 * print out the same debug information as the generic dump_stack().
2887 void dump_stack_print_info(const char *log_lvl)
2889 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
2890 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
2891 print_tainted(), init_utsname()->release,
2892 (int)strcspn(init_utsname()->version, " "),
2893 init_utsname()->version);
2895 if (dump_stack_arch_desc_str[0] != '\0')
2896 printk("%sHardware name: %s\n",
2897 log_lvl, dump_stack_arch_desc_str);
2899 print_worker_info(log_lvl, current);
2903 * show_regs_print_info - print generic debug info for show_regs()
2904 * @log_lvl: log level
2906 * show_regs() implementations can use this function to print out generic
2907 * debug information.
2909 void show_regs_print_info(const char *log_lvl)
2911 dump_stack_print_info(log_lvl);
2913 printk("%stask: %p ti: %p task.ti: %p\n",
2914 log_lvl, current, current_thread_info(),
2915 task_thread_info(current));