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>
46 #include <asm/uaccess.h>
48 #define CREATE_TRACE_POINTS
49 #include <trace/events/printk.h>
52 * Architectures can override it:
54 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
58 /* printk's without a loglevel use this.. */
59 #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
61 /* We show everything that is MORE important than this.. */
62 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
63 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
65 DECLARE_WAIT_QUEUE_HEAD(log_wait);
67 int console_printk[4] = {
68 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
69 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
70 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
71 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
75 * Low level drivers may need that to know if they can schedule in
76 * their unblank() callback or not. So let's export it.
79 EXPORT_SYMBOL(oops_in_progress);
82 * console_sem protects the console_drivers list, and also
83 * provides serialisation for access to the entire console
86 static DEFINE_SEMAPHORE(console_sem);
87 struct console *console_drivers;
88 EXPORT_SYMBOL_GPL(console_drivers);
91 static struct lockdep_map console_lock_dep_map = {
92 .name = "console_lock"
97 * This is used for debugging the mess that is the VT code by
98 * keeping track if we have the console semaphore held. It's
99 * definitely not the perfect debug tool (we don't know if _WE_
100 * hold it are racing, but it helps tracking those weird code
101 * path in the console code where we end up in places I want
102 * locked without the console sempahore held
104 static int console_locked, console_suspended;
107 * If exclusive_console is non-NULL then only this console is to be printed to.
109 static struct console *exclusive_console;
112 * Array of consoles built from command line options (console=)
114 struct console_cmdline
116 char name[8]; /* Name of the driver */
117 int index; /* Minor dev. to use */
118 char *options; /* Options for the driver */
119 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
120 char *brl_options; /* Options for braille driver */
124 #define MAX_CMDLINECONSOLES 8
126 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
127 static int selected_console = -1;
128 static int preferred_console = -1;
129 int console_set_on_cmdline;
130 EXPORT_SYMBOL(console_set_on_cmdline);
132 /* Flag: console code may call schedule() */
133 static int console_may_schedule;
136 * The printk log buffer consists of a chain of concatenated variable
137 * length records. Every record starts with a record header, containing
138 * the overall length of the record.
140 * The heads to the first and last entry in the buffer, as well as the
141 * sequence numbers of these both entries are maintained when messages
144 * If the heads indicate available messages, the length in the header
145 * tells the start next message. A length == 0 for the next message
146 * indicates a wrap-around to the beginning of the buffer.
148 * Every record carries the monotonic timestamp in microseconds, as well as
149 * the standard userspace syslog level and syslog facility. The usual
150 * kernel messages use LOG_KERN; userspace-injected messages always carry
151 * a matching syslog facility, by default LOG_USER. The origin of every
152 * message can be reliably determined that way.
154 * The human readable log message directly follows the message header. The
155 * length of the message text is stored in the header, the stored message
158 * Optionally, a message can carry a dictionary of properties (key/value pairs),
159 * to provide userspace with a machine-readable message context.
161 * Examples for well-defined, commonly used property names are:
162 * DEVICE=b12:8 device identifier
166 * +sound:card0 subsystem:devname
167 * SUBSYSTEM=pci driver-core subsystem name
169 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
170 * follows directly after a '=' character. Every property is terminated by
171 * a '\0' character. The last property is not terminated.
173 * Example of a message structure:
174 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
175 * 0008 34 00 record is 52 bytes long
176 * 000a 0b 00 text is 11 bytes long
177 * 000c 1f 00 dictionary is 23 bytes long
178 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
179 * 0010 69 74 27 73 20 61 20 6c "it's a l"
181 * 001b 44 45 56 49 43 "DEVIC"
182 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
183 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
185 * 0032 00 00 00 padding to next message header
187 * The 'struct log' buffer header must never be directly exported to
188 * userspace, it is a kernel-private implementation detail that might
189 * need to be changed in the future, when the requirements change.
191 * /dev/kmsg exports the structured data in the following line format:
192 * "level,sequnum,timestamp;<message text>\n"
194 * The optional key/value pairs are attached as continuation lines starting
195 * with a space character and terminated by a newline. All possible
196 * non-prinatable characters are escaped in the "\xff" notation.
198 * Users of the export format should ignore possible additional values
199 * separated by ',', and find the message after the ';' character.
203 LOG_NOCONS = 1, /* already flushed, do not print to console */
204 LOG_NEWLINE = 2, /* text ended with a newline */
205 LOG_PREFIX = 4, /* text started with a prefix */
206 LOG_CONT = 8, /* text is a fragment of a continuation line */
210 u64 ts_nsec; /* timestamp in nanoseconds */
211 u16 len; /* length of entire record */
212 u16 text_len; /* length of text buffer */
213 u16 dict_len; /* length of dictionary buffer */
214 u8 facility; /* syslog facility */
215 u8 flags:5; /* internal record flags */
216 u8 level:3; /* syslog level */
220 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
221 * used in interesting ways to provide interlocking in console_unlock();
223 static DEFINE_RAW_SPINLOCK(logbuf_lock);
226 /* the next printk record to read by syslog(READ) or /proc/kmsg */
227 static u64 syslog_seq;
228 static u32 syslog_idx;
229 static enum log_flags syslog_prev;
230 static size_t syslog_partial;
232 /* index and sequence number of the first record stored in the buffer */
233 static u64 log_first_seq;
234 static u32 log_first_idx;
236 /* index and sequence number of the next record to store in the buffer */
237 static u64 log_next_seq;
238 static u32 log_next_idx;
240 /* the next printk record to write to the console */
241 static u64 console_seq;
242 static u32 console_idx;
243 static enum log_flags console_prev;
245 /* the next printk record to read after the last 'clear' command */
246 static u64 clear_seq;
247 static u32 clear_idx;
249 #define PREFIX_MAX 32
250 #define LOG_LINE_MAX 1024 - PREFIX_MAX
253 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
256 #define LOG_ALIGN __alignof__(struct log)
258 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
259 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
260 static char *log_buf = __log_buf;
261 static u32 log_buf_len = __LOG_BUF_LEN;
263 /* cpu currently holding logbuf_lock */
264 static volatile unsigned int logbuf_cpu = UINT_MAX;
266 /* human readable text of the record */
267 static char *log_text(const struct log *msg)
269 return (char *)msg + sizeof(struct log);
272 /* optional key/value pair dictionary attached to the record */
273 static char *log_dict(const struct log *msg)
275 return (char *)msg + sizeof(struct log) + msg->text_len;
278 /* get record by index; idx must point to valid msg */
279 static struct log *log_from_idx(u32 idx)
281 struct log *msg = (struct log *)(log_buf + idx);
284 * A length == 0 record is the end of buffer marker. Wrap around and
285 * read the message at the start of the buffer.
288 return (struct log *)log_buf;
292 /* get next record; idx must point to valid msg */
293 static u32 log_next(u32 idx)
295 struct log *msg = (struct log *)(log_buf + idx);
297 /* length == 0 indicates the end of the buffer; wrap */
299 * A length == 0 record is the end of buffer marker. Wrap around and
300 * read the message at the start of the buffer as *this* one, and
301 * return the one after that.
304 msg = (struct log *)log_buf;
307 return idx + msg->len;
310 /* insert record into the buffer, discard old ones, update heads */
311 static void log_store(int facility, int level,
312 enum log_flags flags, u64 ts_nsec,
313 const char *dict, u16 dict_len,
314 const char *text, u16 text_len)
319 /* number of '\0' padding bytes to next message */
320 size = sizeof(struct log) + text_len + dict_len;
321 pad_len = (-size) & (LOG_ALIGN - 1);
324 while (log_first_seq < log_next_seq) {
327 if (log_next_idx > log_first_idx)
328 free = max(log_buf_len - log_next_idx, log_first_idx);
330 free = log_first_idx - log_next_idx;
332 if (free > size + sizeof(struct log))
335 /* drop old messages until we have enough contiuous space */
336 log_first_idx = log_next(log_first_idx);
340 if (log_next_idx + size + sizeof(struct log) >= log_buf_len) {
342 * This message + an additional empty header does not fit
343 * at the end of the buffer. Add an empty header with len == 0
344 * to signify a wrap around.
346 memset(log_buf + log_next_idx, 0, sizeof(struct log));
351 msg = (struct log *)(log_buf + log_next_idx);
352 memcpy(log_text(msg), text, text_len);
353 msg->text_len = text_len;
354 memcpy(log_dict(msg), dict, dict_len);
355 msg->dict_len = dict_len;
356 msg->facility = facility;
357 msg->level = level & 7;
358 msg->flags = flags & 0x1f;
360 msg->ts_nsec = ts_nsec;
362 msg->ts_nsec = local_clock();
363 memset(log_dict(msg) + dict_len, 0, pad_len);
364 msg->len = sizeof(struct log) + text_len + dict_len + pad_len;
367 log_next_idx += msg->len;
371 /* /dev/kmsg - userspace message inject/listen interface */
372 struct devkmsg_user {
380 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
381 unsigned long count, loff_t pos)
385 int level = default_message_loglevel;
386 int facility = 1; /* LOG_USER */
387 size_t len = iov_length(iv, count);
390 if (len > LOG_LINE_MAX)
392 buf = kmalloc(len+1, GFP_KERNEL);
397 for (i = 0; i < count; i++) {
398 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
402 line += iv[i].iov_len;
406 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
407 * the decimal value represents 32bit, the lower 3 bit are the log
408 * level, the rest are the log facility.
410 * If no prefix or no userspace facility is specified, we
411 * enforce LOG_USER, to be able to reliably distinguish
412 * kernel-generated messages from userspace-injected ones.
415 if (line[0] == '<') {
418 i = simple_strtoul(line+1, &endp, 10);
419 if (endp && endp[0] == '>') {
430 printk_emit(facility, level, NULL, 0, "%s", line);
436 static ssize_t devkmsg_read(struct file *file, char __user *buf,
437 size_t count, loff_t *ppos)
439 struct devkmsg_user *user = file->private_data;
450 ret = mutex_lock_interruptible(&user->lock);
453 raw_spin_lock_irq(&logbuf_lock);
454 while (user->seq == log_next_seq) {
455 if (file->f_flags & O_NONBLOCK) {
457 raw_spin_unlock_irq(&logbuf_lock);
461 raw_spin_unlock_irq(&logbuf_lock);
462 ret = wait_event_interruptible(log_wait,
463 user->seq != log_next_seq);
466 raw_spin_lock_irq(&logbuf_lock);
469 if (user->seq < log_first_seq) {
470 /* our last seen message is gone, return error and reset */
471 user->idx = log_first_idx;
472 user->seq = log_first_seq;
474 raw_spin_unlock_irq(&logbuf_lock);
478 msg = log_from_idx(user->idx);
479 ts_usec = msg->ts_nsec;
480 do_div(ts_usec, 1000);
483 * If we couldn't merge continuation line fragments during the print,
484 * export the stored flags to allow an optional external merge of the
485 * records. Merging the records isn't always neccessarily correct, like
486 * when we hit a race during printing. In most cases though, it produces
487 * better readable output. 'c' in the record flags mark the first
488 * fragment of a line, '+' the following.
490 if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
492 else if ((msg->flags & LOG_CONT) ||
493 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
496 len = sprintf(user->buf, "%u,%llu,%llu,%c;",
497 (msg->facility << 3) | msg->level,
498 user->seq, ts_usec, cont);
499 user->prev = msg->flags;
501 /* escape non-printable characters */
502 for (i = 0; i < msg->text_len; i++) {
503 unsigned char c = log_text(msg)[i];
505 if (c < ' ' || c >= 127 || c == '\\')
506 len += sprintf(user->buf + len, "\\x%02x", c);
508 user->buf[len++] = c;
510 user->buf[len++] = '\n';
515 for (i = 0; i < msg->dict_len; i++) {
516 unsigned char c = log_dict(msg)[i];
519 user->buf[len++] = ' ';
524 user->buf[len++] = '\n';
529 if (c < ' ' || c >= 127 || c == '\\') {
530 len += sprintf(user->buf + len, "\\x%02x", c);
534 user->buf[len++] = c;
536 user->buf[len++] = '\n';
539 user->idx = log_next(user->idx);
541 raw_spin_unlock_irq(&logbuf_lock);
548 if (copy_to_user(buf, user->buf, len)) {
554 mutex_unlock(&user->lock);
558 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
560 struct devkmsg_user *user = file->private_data;
568 raw_spin_lock_irq(&logbuf_lock);
571 /* the first record */
572 user->idx = log_first_idx;
573 user->seq = log_first_seq;
577 * The first record after the last SYSLOG_ACTION_CLEAR,
578 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
579 * changes no global state, and does not clear anything.
581 user->idx = clear_idx;
582 user->seq = clear_seq;
585 /* after the last record */
586 user->idx = log_next_idx;
587 user->seq = log_next_seq;
592 raw_spin_unlock_irq(&logbuf_lock);
596 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
598 struct devkmsg_user *user = file->private_data;
602 return POLLERR|POLLNVAL;
604 poll_wait(file, &log_wait, wait);
606 raw_spin_lock_irq(&logbuf_lock);
607 if (user->seq < log_next_seq) {
608 /* return error when data has vanished underneath us */
609 if (user->seq < log_first_seq)
610 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
611 ret = POLLIN|POLLRDNORM;
613 raw_spin_unlock_irq(&logbuf_lock);
618 static int devkmsg_open(struct inode *inode, struct file *file)
620 struct devkmsg_user *user;
623 /* write-only does not need any file context */
624 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
627 err = security_syslog(SYSLOG_ACTION_READ_ALL);
631 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
635 mutex_init(&user->lock);
637 raw_spin_lock_irq(&logbuf_lock);
638 user->idx = log_first_idx;
639 user->seq = log_first_seq;
640 raw_spin_unlock_irq(&logbuf_lock);
642 file->private_data = user;
646 static int devkmsg_release(struct inode *inode, struct file *file)
648 struct devkmsg_user *user = file->private_data;
653 mutex_destroy(&user->lock);
658 const struct file_operations kmsg_fops = {
659 .open = devkmsg_open,
660 .read = devkmsg_read,
661 .aio_write = devkmsg_writev,
662 .llseek = devkmsg_llseek,
663 .poll = devkmsg_poll,
664 .release = devkmsg_release,
669 * This appends the listed symbols to /proc/vmcoreinfo
671 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
672 * obtain access to symbols that are otherwise very difficult to locate. These
673 * symbols are specifically used so that utilities can access and extract the
674 * dmesg log from a vmcore file after a crash.
676 void log_buf_kexec_setup(void)
678 VMCOREINFO_SYMBOL(log_buf);
679 VMCOREINFO_SYMBOL(log_buf_len);
680 VMCOREINFO_SYMBOL(log_first_idx);
681 VMCOREINFO_SYMBOL(log_next_idx);
683 * Export struct log size and field offsets. User space tools can
684 * parse it and detect any changes to structure down the line.
686 VMCOREINFO_STRUCT_SIZE(log);
687 VMCOREINFO_OFFSET(log, ts_nsec);
688 VMCOREINFO_OFFSET(log, len);
689 VMCOREINFO_OFFSET(log, text_len);
690 VMCOREINFO_OFFSET(log, dict_len);
694 /* requested log_buf_len from kernel cmdline */
695 static unsigned long __initdata new_log_buf_len;
697 /* save requested log_buf_len since it's too early to process it */
698 static int __init log_buf_len_setup(char *str)
700 unsigned size = memparse(str, &str);
703 size = roundup_pow_of_two(size);
704 if (size > log_buf_len)
705 new_log_buf_len = size;
709 early_param("log_buf_len", log_buf_len_setup);
711 void __init setup_log_buf(int early)
717 if (!new_log_buf_len)
723 mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
726 new_log_buf = __va(mem);
728 new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
731 if (unlikely(!new_log_buf)) {
732 pr_err("log_buf_len: %ld bytes not available\n",
737 raw_spin_lock_irqsave(&logbuf_lock, flags);
738 log_buf_len = new_log_buf_len;
739 log_buf = new_log_buf;
741 free = __LOG_BUF_LEN - log_next_idx;
742 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
743 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
745 pr_info("log_buf_len: %d\n", log_buf_len);
746 pr_info("early log buf free: %d(%d%%)\n",
747 free, (free * 100) / __LOG_BUF_LEN);
750 static bool __read_mostly ignore_loglevel;
752 static int __init ignore_loglevel_setup(char *str)
755 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
760 early_param("ignore_loglevel", ignore_loglevel_setup);
761 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
762 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
763 "print all kernel messages to the console.");
765 #ifdef CONFIG_BOOT_PRINTK_DELAY
767 static int boot_delay; /* msecs delay after each printk during bootup */
768 static unsigned long long loops_per_msec; /* based on boot_delay */
770 static int __init boot_delay_setup(char *str)
774 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
775 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
777 get_option(&str, &boot_delay);
778 if (boot_delay > 10 * 1000)
781 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
782 "HZ: %d, loops_per_msec: %llu\n",
783 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
786 __setup("boot_delay=", boot_delay_setup);
788 static void boot_delay_msec(int level)
790 unsigned long long k;
791 unsigned long timeout;
793 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
794 || (level >= console_loglevel && !ignore_loglevel)) {
798 k = (unsigned long long)loops_per_msec * boot_delay;
800 timeout = jiffies + msecs_to_jiffies(boot_delay);
805 * use (volatile) jiffies to prevent
806 * compiler reduction; loop termination via jiffies
807 * is secondary and may or may not happen.
809 if (time_after(jiffies, timeout))
811 touch_nmi_watchdog();
815 static inline void boot_delay_msec(int level)
820 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
821 int dmesg_restrict = 1;
826 static int syslog_action_restricted(int type)
830 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
831 return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
834 static int check_syslog_permissions(int type, bool from_file)
837 * If this is from /proc/kmsg and we've already opened it, then we've
838 * already done the capabilities checks at open time.
840 if (from_file && type != SYSLOG_ACTION_OPEN)
843 if (syslog_action_restricted(type)) {
844 if (capable(CAP_SYSLOG))
846 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
847 if (capable(CAP_SYS_ADMIN)) {
848 printk_once(KERN_WARNING "%s (%d): "
849 "Attempt to access syslog with CAP_SYS_ADMIN "
850 "but no CAP_SYSLOG (deprecated).\n",
851 current->comm, task_pid_nr(current));
859 #if defined(CONFIG_PRINTK_TIME)
860 static bool printk_time = 1;
862 static bool printk_time;
864 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
866 static size_t print_time(u64 ts, char *buf)
868 unsigned long rem_nsec;
873 rem_nsec = do_div(ts, 1000000000);
876 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
878 return sprintf(buf, "[%5lu.%06lu] ",
879 (unsigned long)ts, rem_nsec / 1000);
882 static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
885 unsigned int prefix = (msg->facility << 3) | msg->level;
889 len += sprintf(buf, "<%u>", prefix);
894 else if (prefix > 99)
901 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
905 static size_t msg_print_text(const struct log *msg, enum log_flags prev,
906 bool syslog, char *buf, size_t size)
908 const char *text = log_text(msg);
909 size_t text_size = msg->text_len;
914 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
917 if (msg->flags & LOG_CONT) {
918 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
921 if (!(msg->flags & LOG_NEWLINE))
926 const char *next = memchr(text, '\n', text_size);
930 text_len = next - text;
932 text_size -= next - text;
934 text_len = text_size;
938 if (print_prefix(msg, syslog, NULL) +
939 text_len + 1 >= size - len)
943 len += print_prefix(msg, syslog, buf + len);
944 memcpy(buf + len, text, text_len);
949 /* SYSLOG_ACTION_* buffer size only calculation */
951 len += print_prefix(msg, syslog, NULL);
964 static int syslog_print(char __user *buf, int size)
970 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
978 raw_spin_lock_irq(&logbuf_lock);
979 if (syslog_seq < log_first_seq) {
980 /* messages are gone, move to first one */
981 syslog_seq = log_first_seq;
982 syslog_idx = log_first_idx;
986 if (syslog_seq == log_next_seq) {
987 raw_spin_unlock_irq(&logbuf_lock);
991 skip = syslog_partial;
992 msg = log_from_idx(syslog_idx);
993 n = msg_print_text(msg, syslog_prev, true, text,
994 LOG_LINE_MAX + PREFIX_MAX);
995 if (n - syslog_partial <= size) {
996 /* message fits into buffer, move forward */
997 syslog_idx = log_next(syslog_idx);
999 syslog_prev = msg->flags;
1000 n -= syslog_partial;
1003 /* partial read(), remember position */
1005 syslog_partial += n;
1008 raw_spin_unlock_irq(&logbuf_lock);
1013 if (copy_to_user(buf, text + skip, n)) {
1028 static int syslog_print_all(char __user *buf, int size, bool clear)
1033 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1037 raw_spin_lock_irq(&logbuf_lock);
1042 enum log_flags prev;
1044 if (clear_seq < log_first_seq) {
1045 /* messages are gone, move to first available one */
1046 clear_seq = log_first_seq;
1047 clear_idx = log_first_idx;
1051 * Find first record that fits, including all following records,
1052 * into the user-provided buffer for this dump.
1057 while (seq < log_next_seq) {
1058 struct log *msg = log_from_idx(idx);
1060 len += msg_print_text(msg, prev, true, NULL, 0);
1062 idx = log_next(idx);
1066 /* move first record forward until length fits into the buffer */
1070 while (len > size && seq < log_next_seq) {
1071 struct log *msg = log_from_idx(idx);
1073 len -= msg_print_text(msg, prev, true, NULL, 0);
1075 idx = log_next(idx);
1079 /* last message fitting into this dump */
1080 next_seq = log_next_seq;
1084 while (len >= 0 && seq < next_seq) {
1085 struct log *msg = log_from_idx(idx);
1088 textlen = msg_print_text(msg, prev, true, text,
1089 LOG_LINE_MAX + PREFIX_MAX);
1094 idx = log_next(idx);
1098 raw_spin_unlock_irq(&logbuf_lock);
1099 if (copy_to_user(buf + len, text, textlen))
1103 raw_spin_lock_irq(&logbuf_lock);
1105 if (seq < log_first_seq) {
1106 /* messages are gone, move to next one */
1107 seq = log_first_seq;
1108 idx = log_first_idx;
1115 clear_seq = log_next_seq;
1116 clear_idx = log_next_idx;
1118 raw_spin_unlock_irq(&logbuf_lock);
1124 int do_syslog(int type, char __user *buf, int len, bool from_file)
1127 static int saved_console_loglevel = -1;
1130 error = check_syslog_permissions(type, from_file);
1134 error = security_syslog(type);
1139 case SYSLOG_ACTION_CLOSE: /* Close log */
1141 case SYSLOG_ACTION_OPEN: /* Open log */
1143 case SYSLOG_ACTION_READ: /* Read from log */
1145 if (!buf || len < 0)
1150 if (!access_ok(VERIFY_WRITE, buf, len)) {
1154 error = wait_event_interruptible(log_wait,
1155 syslog_seq != log_next_seq);
1158 error = syslog_print(buf, len);
1160 /* Read/clear last kernel messages */
1161 case SYSLOG_ACTION_READ_CLEAR:
1164 /* Read last kernel messages */
1165 case SYSLOG_ACTION_READ_ALL:
1167 if (!buf || len < 0)
1172 if (!access_ok(VERIFY_WRITE, buf, len)) {
1176 error = syslog_print_all(buf, len, clear);
1178 /* Clear ring buffer */
1179 case SYSLOG_ACTION_CLEAR:
1180 syslog_print_all(NULL, 0, true);
1182 /* Disable logging to console */
1183 case SYSLOG_ACTION_CONSOLE_OFF:
1184 if (saved_console_loglevel == -1)
1185 saved_console_loglevel = console_loglevel;
1186 console_loglevel = minimum_console_loglevel;
1188 /* Enable logging to console */
1189 case SYSLOG_ACTION_CONSOLE_ON:
1190 if (saved_console_loglevel != -1) {
1191 console_loglevel = saved_console_loglevel;
1192 saved_console_loglevel = -1;
1195 /* Set level of messages printed to console */
1196 case SYSLOG_ACTION_CONSOLE_LEVEL:
1198 if (len < 1 || len > 8)
1200 if (len < minimum_console_loglevel)
1201 len = minimum_console_loglevel;
1202 console_loglevel = len;
1203 /* Implicitly re-enable logging to console */
1204 saved_console_loglevel = -1;
1207 /* Number of chars in the log buffer */
1208 case SYSLOG_ACTION_SIZE_UNREAD:
1209 raw_spin_lock_irq(&logbuf_lock);
1210 if (syslog_seq < log_first_seq) {
1211 /* messages are gone, move to first one */
1212 syslog_seq = log_first_seq;
1213 syslog_idx = log_first_idx;
1219 * Short-cut for poll(/"proc/kmsg") which simply checks
1220 * for pending data, not the size; return the count of
1221 * records, not the length.
1223 error = log_next_idx - syslog_idx;
1225 u64 seq = syslog_seq;
1226 u32 idx = syslog_idx;
1227 enum log_flags prev = syslog_prev;
1230 while (seq < log_next_seq) {
1231 struct log *msg = log_from_idx(idx);
1233 error += msg_print_text(msg, prev, true, NULL, 0);
1234 idx = log_next(idx);
1238 error -= syslog_partial;
1240 raw_spin_unlock_irq(&logbuf_lock);
1242 /* Size of the log buffer */
1243 case SYSLOG_ACTION_SIZE_BUFFER:
1244 error = log_buf_len;
1254 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1256 return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
1260 * Call the console drivers, asking them to write out
1261 * log_buf[start] to log_buf[end - 1].
1262 * The console_lock must be held.
1264 static void call_console_drivers(int level, const char *text, size_t len)
1266 struct console *con;
1268 trace_console(text, 0, len, len);
1270 if (level >= console_loglevel && !ignore_loglevel)
1272 if (!console_drivers)
1275 for_each_console(con) {
1276 if (exclusive_console && con != exclusive_console)
1278 if (!(con->flags & CON_ENABLED))
1282 if (!cpu_online(smp_processor_id()) &&
1283 !(con->flags & CON_ANYTIME))
1285 con->write(con, text, len);
1290 * Zap console related locks when oopsing. Only zap at most once
1291 * every 10 seconds, to leave time for slow consoles to print a
1294 static void zap_locks(void)
1296 static unsigned long oops_timestamp;
1298 if (time_after_eq(jiffies, oops_timestamp) &&
1299 !time_after(jiffies, oops_timestamp + 30 * HZ))
1302 oops_timestamp = jiffies;
1305 /* If a crash is occurring, make sure we can't deadlock */
1306 raw_spin_lock_init(&logbuf_lock);
1307 /* And make sure that we print immediately */
1308 sema_init(&console_sem, 1);
1311 /* Check if we have any console registered that can be called early in boot. */
1312 static int have_callable_console(void)
1314 struct console *con;
1316 for_each_console(con)
1317 if (con->flags & CON_ANYTIME)
1324 * Can we actually use the console at this time on this cpu?
1326 * Console drivers may assume that per-cpu resources have
1327 * been allocated. So unless they're explicitly marked as
1328 * being able to cope (CON_ANYTIME) don't call them until
1329 * this CPU is officially up.
1331 static inline int can_use_console(unsigned int cpu)
1333 return cpu_online(cpu) || have_callable_console();
1337 * Try to get console ownership to actually show the kernel
1338 * messages from a 'printk'. Return true (and with the
1339 * console_lock held, and 'console_locked' set) if it
1340 * is successful, false otherwise.
1342 * This gets called with the 'logbuf_lock' spinlock held and
1343 * interrupts disabled. It should return with 'lockbuf_lock'
1344 * released but interrupts still disabled.
1346 static int console_trylock_for_printk(unsigned int cpu)
1347 __releases(&logbuf_lock)
1349 int retval = 0, wake = 0;
1351 if (console_trylock()) {
1355 * If we can't use the console, we need to release
1356 * the console semaphore by hand to avoid flushing
1357 * the buffer. We need to hold the console semaphore
1358 * in order to do this test safely.
1360 if (!can_use_console(cpu)) {
1366 logbuf_cpu = UINT_MAX;
1369 raw_spin_unlock(&logbuf_lock);
1373 int printk_delay_msec __read_mostly;
1375 static inline void printk_delay(void)
1377 if (unlikely(printk_delay_msec)) {
1378 int m = printk_delay_msec;
1382 touch_nmi_watchdog();
1388 * Continuation lines are buffered, and not committed to the record buffer
1389 * until the line is complete, or a race forces it. The line fragments
1390 * though, are printed immediately to the consoles to ensure everything has
1391 * reached the console in case of a kernel crash.
1393 static struct cont {
1394 char buf[LOG_LINE_MAX];
1395 size_t len; /* length == 0 means unused buffer */
1396 size_t cons; /* bytes written to console */
1397 struct task_struct *owner; /* task of first print*/
1398 u64 ts_nsec; /* time of first print */
1399 u8 level; /* log level of first message */
1400 u8 facility; /* log level of first message */
1401 enum log_flags flags; /* prefix, newline flags */
1402 bool flushed:1; /* buffer sealed and committed */
1405 static void cont_flush(enum log_flags flags)
1414 * If a fragment of this line was directly flushed to the
1415 * console; wait for the console to pick up the rest of the
1416 * line. LOG_NOCONS suppresses a duplicated output.
1418 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1419 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1421 cont.flushed = true;
1424 * If no fragment of this line ever reached the console,
1425 * just submit it to the store and free the buffer.
1427 log_store(cont.facility, cont.level, flags, 0,
1428 NULL, 0, cont.buf, cont.len);
1433 static bool cont_add(int facility, int level, const char *text, size_t len)
1435 if (cont.len && cont.flushed)
1438 if (cont.len + len > sizeof(cont.buf)) {
1439 /* the line gets too long, split it up in separate records */
1440 cont_flush(LOG_CONT);
1445 cont.facility = facility;
1447 cont.owner = current;
1448 cont.ts_nsec = local_clock();
1451 cont.flushed = false;
1454 memcpy(cont.buf + cont.len, text, len);
1457 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1458 cont_flush(LOG_CONT);
1463 static size_t cont_print_text(char *text, size_t size)
1468 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1469 textlen += print_time(cont.ts_nsec, text);
1473 len = cont.len - cont.cons;
1477 memcpy(text + textlen, cont.buf + cont.cons, len);
1479 cont.cons = cont.len;
1483 if (cont.flags & LOG_NEWLINE)
1484 text[textlen++] = '\n';
1485 /* got everything, release buffer */
1491 asmlinkage int vprintk_emit(int facility, int level,
1492 const char *dict, size_t dictlen,
1493 const char *fmt, va_list args)
1495 static int recursion_bug;
1496 static char textbuf[LOG_LINE_MAX];
1497 char *text = textbuf;
1499 enum log_flags lflags = 0;
1500 unsigned long flags;
1502 int printed_len = 0;
1504 boot_delay_msec(level);
1507 /* This stops the holder of console_sem just where we want him */
1508 local_irq_save(flags);
1509 this_cpu = smp_processor_id();
1512 * Ouch, printk recursed into itself!
1514 if (unlikely(logbuf_cpu == this_cpu)) {
1516 * If a crash is occurring during printk() on this CPU,
1517 * then try to get the crash message out but make sure
1518 * we can't deadlock. Otherwise just return to avoid the
1519 * recursion and return - but flag the recursion so that
1520 * it can be printed at the next appropriate moment:
1522 if (!oops_in_progress && !lockdep_recursing(current)) {
1524 goto out_restore_irqs;
1530 raw_spin_lock(&logbuf_lock);
1531 logbuf_cpu = this_cpu;
1533 if (recursion_bug) {
1534 static const char recursion_msg[] =
1535 "BUG: recent printk recursion!";
1538 printed_len += strlen(recursion_msg);
1539 /* emit KERN_CRIT message */
1540 log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1541 NULL, 0, recursion_msg, printed_len);
1545 * The printf needs to come first; we need the syslog
1546 * prefix which might be passed-in as a parameter.
1548 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1550 /* mark and strip a trailing newline */
1551 if (text_len && text[text_len-1] == '\n') {
1553 lflags |= LOG_NEWLINE;
1556 /* strip kernel syslog prefix and extract log level or control flags */
1557 if (facility == 0) {
1558 int kern_level = printk_get_level(text);
1561 const char *end_of_header = printk_skip_level(text);
1562 switch (kern_level) {
1565 level = kern_level - '0';
1566 case 'd': /* KERN_DEFAULT */
1567 lflags |= LOG_PREFIX;
1568 case 'c': /* KERN_CONT */
1571 text_len -= end_of_header - text;
1572 text = (char *)end_of_header;
1577 level = default_message_loglevel;
1580 lflags |= LOG_PREFIX|LOG_NEWLINE;
1582 if (!(lflags & LOG_NEWLINE)) {
1584 * Flush the conflicting buffer. An earlier newline was missing,
1585 * or another task also prints continuation lines.
1587 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1588 cont_flush(LOG_NEWLINE);
1590 /* buffer line if possible, otherwise store it right away */
1591 if (!cont_add(facility, level, text, text_len))
1592 log_store(facility, level, lflags | LOG_CONT, 0,
1593 dict, dictlen, text, text_len);
1595 bool stored = false;
1598 * If an earlier newline was missing and it was the same task,
1599 * either merge it with the current buffer and flush, or if
1600 * there was a race with interrupts (prefix == true) then just
1601 * flush it out and store this line separately.
1603 if (cont.len && cont.owner == current) {
1604 if (!(lflags & LOG_PREFIX))
1605 stored = cont_add(facility, level, text, text_len);
1606 cont_flush(LOG_NEWLINE);
1610 log_store(facility, level, lflags, 0,
1611 dict, dictlen, text, text_len);
1613 printed_len += text_len;
1616 * Try to acquire and then immediately release the console semaphore.
1617 * The release will print out buffers and wake up /dev/kmsg and syslog()
1620 * The console_trylock_for_printk() function will release 'logbuf_lock'
1621 * regardless of whether it actually gets the console semaphore or not.
1623 if (console_trylock_for_printk(this_cpu))
1628 local_irq_restore(flags);
1632 EXPORT_SYMBOL(vprintk_emit);
1634 asmlinkage int vprintk(const char *fmt, va_list args)
1636 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1638 EXPORT_SYMBOL(vprintk);
1640 asmlinkage int printk_emit(int facility, int level,
1641 const char *dict, size_t dictlen,
1642 const char *fmt, ...)
1647 va_start(args, fmt);
1648 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1653 EXPORT_SYMBOL(printk_emit);
1656 * printk - print a kernel message
1657 * @fmt: format string
1659 * This is printk(). It can be called from any context. We want it to work.
1661 * We try to grab the console_lock. If we succeed, it's easy - we log the
1662 * output and call the console drivers. If we fail to get the semaphore, we
1663 * place the output into the log buffer and return. The current holder of
1664 * the console_sem will notice the new output in console_unlock(); and will
1665 * send it to the consoles before releasing the lock.
1667 * One effect of this deferred printing is that code which calls printk() and
1668 * then changes console_loglevel may break. This is because console_loglevel
1669 * is inspected when the actual printing occurs.
1674 * See the vsnprintf() documentation for format string extensions over C99.
1676 asmlinkage int printk(const char *fmt, ...)
1681 #ifdef CONFIG_KGDB_KDB
1682 if (unlikely(kdb_trap_printk)) {
1683 va_start(args, fmt);
1684 r = vkdb_printf(fmt, args);
1689 va_start(args, fmt);
1690 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1695 EXPORT_SYMBOL(printk);
1697 #else /* CONFIG_PRINTK */
1699 #define LOG_LINE_MAX 0
1700 #define PREFIX_MAX 0
1701 #define LOG_LINE_MAX 0
1702 static u64 syslog_seq;
1703 static u32 syslog_idx;
1704 static u64 console_seq;
1705 static u32 console_idx;
1706 static enum log_flags syslog_prev;
1707 static u64 log_first_seq;
1708 static u32 log_first_idx;
1709 static u64 log_next_seq;
1710 static enum log_flags console_prev;
1711 static struct cont {
1717 static struct log *log_from_idx(u32 idx) { return NULL; }
1718 static u32 log_next(u32 idx) { return 0; }
1719 static void call_console_drivers(int level, const char *text, size_t len) {}
1720 static size_t msg_print_text(const struct log *msg, enum log_flags prev,
1721 bool syslog, char *buf, size_t size) { return 0; }
1722 static size_t cont_print_text(char *text, size_t size) { return 0; }
1724 #endif /* CONFIG_PRINTK */
1726 static int __add_preferred_console(char *name, int idx, char *options,
1729 struct console_cmdline *c;
1733 * See if this tty is not yet registered, and
1734 * if we have a slot free.
1736 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1737 if (strcmp(console_cmdline[i].name, name) == 0 &&
1738 console_cmdline[i].index == idx) {
1740 selected_console = i;
1743 if (i == MAX_CMDLINECONSOLES)
1746 selected_console = i;
1747 c = &console_cmdline[i];
1748 strlcpy(c->name, name, sizeof(c->name));
1749 c->options = options;
1750 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1751 c->brl_options = brl_options;
1757 * Set up a list of consoles. Called from init/main.c
1759 static int __init console_setup(char *str)
1761 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1762 char *s, *options, *brl_options = NULL;
1765 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1766 if (!memcmp(str, "brl,", 4)) {
1769 } else if (!memcmp(str, "brl=", 4)) {
1770 brl_options = str + 4;
1771 str = strchr(brl_options, ',');
1773 printk(KERN_ERR "need port name after brl=\n");
1781 * Decode str into name, index, options.
1783 if (str[0] >= '0' && str[0] <= '9') {
1784 strcpy(buf, "ttyS");
1785 strncpy(buf + 4, str, sizeof(buf) - 5);
1787 strncpy(buf, str, sizeof(buf) - 1);
1789 buf[sizeof(buf) - 1] = 0;
1790 if ((options = strchr(str, ',')) != NULL)
1793 if (!strcmp(str, "ttya"))
1794 strcpy(buf, "ttyS0");
1795 if (!strcmp(str, "ttyb"))
1796 strcpy(buf, "ttyS1");
1798 for (s = buf; *s; s++)
1799 if ((*s >= '0' && *s <= '9') || *s == ',')
1801 idx = simple_strtoul(s, NULL, 10);
1804 __add_preferred_console(buf, idx, options, brl_options);
1805 console_set_on_cmdline = 1;
1808 __setup("console=", console_setup);
1811 * add_preferred_console - add a device to the list of preferred consoles.
1812 * @name: device name
1813 * @idx: device index
1814 * @options: options for this console
1816 * The last preferred console added will be used for kernel messages
1817 * and stdin/out/err for init. Normally this is used by console_setup
1818 * above to handle user-supplied console arguments; however it can also
1819 * be used by arch-specific code either to override the user or more
1820 * commonly to provide a default console (ie from PROM variables) when
1821 * the user has not supplied one.
1823 int add_preferred_console(char *name, int idx, char *options)
1825 return __add_preferred_console(name, idx, options, NULL);
1828 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1830 struct console_cmdline *c;
1833 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1834 if (strcmp(console_cmdline[i].name, name) == 0 &&
1835 console_cmdline[i].index == idx) {
1836 c = &console_cmdline[i];
1837 strlcpy(c->name, name_new, sizeof(c->name));
1838 c->name[sizeof(c->name) - 1] = 0;
1839 c->options = options;
1847 bool console_suspend_enabled = 1;
1848 EXPORT_SYMBOL(console_suspend_enabled);
1850 static int __init console_suspend_disable(char *str)
1852 console_suspend_enabled = 0;
1855 __setup("no_console_suspend", console_suspend_disable);
1856 module_param_named(console_suspend, console_suspend_enabled,
1857 bool, S_IRUGO | S_IWUSR);
1858 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1859 " and hibernate operations");
1862 * suspend_console - suspend the console subsystem
1864 * This disables printk() while we go into suspend states
1866 void suspend_console(void)
1868 if (!console_suspend_enabled)
1870 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1872 console_suspended = 1;
1876 void resume_console(void)
1878 if (!console_suspend_enabled)
1881 console_suspended = 0;
1886 * console_cpu_notify - print deferred console messages after CPU hotplug
1887 * @self: notifier struct
1888 * @action: CPU hotplug event
1891 * If printk() is called from a CPU that is not online yet, the messages
1892 * will be spooled but will not show up on the console. This function is
1893 * called when a new CPU comes online (or fails to come up), and ensures
1894 * that any such output gets printed.
1896 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1897 unsigned long action, void *hcpu)
1902 case CPU_DOWN_FAILED:
1903 case CPU_UP_CANCELED:
1911 * console_lock - lock the console system for exclusive use.
1913 * Acquires a lock which guarantees that the caller has
1914 * exclusive access to the console system and the console_drivers list.
1916 * Can sleep, returns nothing.
1918 void console_lock(void)
1923 if (console_suspended)
1926 console_may_schedule = 1;
1927 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
1929 EXPORT_SYMBOL(console_lock);
1932 * console_trylock - try to lock the console system for exclusive use.
1934 * Tried to acquire a lock which guarantees that the caller has
1935 * exclusive access to the console system and the console_drivers list.
1937 * returns 1 on success, and 0 on failure to acquire the lock.
1939 int console_trylock(void)
1941 if (down_trylock(&console_sem))
1943 if (console_suspended) {
1948 console_may_schedule = 0;
1949 mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);
1952 EXPORT_SYMBOL(console_trylock);
1954 int is_console_locked(void)
1956 return console_locked;
1960 * Delayed printk version, for scheduler-internal messages:
1962 #define PRINTK_BUF_SIZE 512
1964 #define PRINTK_PENDING_WAKEUP 0x01
1965 #define PRINTK_PENDING_SCHED 0x02
1967 static DEFINE_PER_CPU(int, printk_pending);
1968 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
1970 void printk_tick(void)
1972 if (__this_cpu_read(printk_pending)) {
1973 int pending = __this_cpu_xchg(printk_pending, 0);
1974 if (pending & PRINTK_PENDING_SCHED) {
1975 char *buf = __get_cpu_var(printk_sched_buf);
1976 printk(KERN_WARNING "[sched_delayed] %s", buf);
1978 if (pending & PRINTK_PENDING_WAKEUP)
1979 wake_up_interruptible(&log_wait);
1983 int printk_needs_cpu(int cpu)
1985 if (cpu_is_offline(cpu))
1987 return __this_cpu_read(printk_pending);
1990 void wake_up_klogd(void)
1992 if (waitqueue_active(&log_wait))
1993 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
1996 static void console_cont_flush(char *text, size_t size)
1998 unsigned long flags;
2001 raw_spin_lock_irqsave(&logbuf_lock, flags);
2007 * We still queue earlier records, likely because the console was
2008 * busy. The earlier ones need to be printed before this one, we
2009 * did not flush any fragment so far, so just let it queue up.
2011 if (console_seq < log_next_seq && !cont.cons)
2014 len = cont_print_text(text, size);
2015 raw_spin_unlock(&logbuf_lock);
2016 stop_critical_timings();
2017 call_console_drivers(cont.level, text, len);
2018 start_critical_timings();
2019 local_irq_restore(flags);
2022 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2026 * console_unlock - unlock the console system
2028 * Releases the console_lock which the caller holds on the console system
2029 * and the console driver list.
2031 * While the console_lock was held, console output may have been buffered
2032 * by printk(). If this is the case, console_unlock(); emits
2033 * the output prior to releasing the lock.
2035 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2037 * console_unlock(); may be called from any context.
2039 void console_unlock(void)
2041 static char text[LOG_LINE_MAX + PREFIX_MAX];
2042 static u64 seen_seq;
2043 unsigned long flags;
2044 bool wake_klogd = false;
2047 if (console_suspended) {
2052 console_may_schedule = 0;
2054 /* flush buffered message fragment immediately to console */
2055 console_cont_flush(text, sizeof(text));
2062 raw_spin_lock_irqsave(&logbuf_lock, flags);
2063 if (seen_seq != log_next_seq) {
2065 seen_seq = log_next_seq;
2068 if (console_seq < log_first_seq) {
2069 /* messages are gone, move to first one */
2070 console_seq = log_first_seq;
2071 console_idx = log_first_idx;
2075 if (console_seq == log_next_seq)
2078 msg = log_from_idx(console_idx);
2079 if (msg->flags & LOG_NOCONS) {
2081 * Skip record we have buffered and already printed
2082 * directly to the console when we received it.
2084 console_idx = log_next(console_idx);
2087 * We will get here again when we register a new
2088 * CON_PRINTBUFFER console. Clear the flag so we
2089 * will properly dump everything later.
2091 msg->flags &= ~LOG_NOCONS;
2092 console_prev = msg->flags;
2097 len = msg_print_text(msg, console_prev, false,
2098 text, sizeof(text));
2099 console_idx = log_next(console_idx);
2101 console_prev = msg->flags;
2102 raw_spin_unlock(&logbuf_lock);
2104 stop_critical_timings(); /* don't trace print latency */
2105 call_console_drivers(level, text, len);
2106 start_critical_timings();
2107 local_irq_restore(flags);
2110 mutex_release(&console_lock_dep_map, 1, _RET_IP_);
2112 /* Release the exclusive_console once it is used */
2113 if (unlikely(exclusive_console))
2114 exclusive_console = NULL;
2116 raw_spin_unlock(&logbuf_lock);
2121 * Someone could have filled up the buffer again, so re-check if there's
2122 * something to flush. In case we cannot trylock the console_sem again,
2123 * there's a new owner and the console_unlock() from them will do the
2124 * flush, no worries.
2126 raw_spin_lock(&logbuf_lock);
2127 retry = console_seq != log_next_seq;
2128 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2130 if (retry && console_trylock())
2136 EXPORT_SYMBOL(console_unlock);
2139 * console_conditional_schedule - yield the CPU if required
2141 * If the console code is currently allowed to sleep, and
2142 * if this CPU should yield the CPU to another task, do
2145 * Must be called within console_lock();.
2147 void __sched console_conditional_schedule(void)
2149 if (console_may_schedule)
2152 EXPORT_SYMBOL(console_conditional_schedule);
2154 void console_unblank(void)
2159 * console_unblank can no longer be called in interrupt context unless
2160 * oops_in_progress is set to 1..
2162 if (oops_in_progress) {
2163 if (down_trylock(&console_sem) != 0)
2169 console_may_schedule = 0;
2171 if ((c->flags & CON_ENABLED) && c->unblank)
2177 * Return the console tty driver structure and its associated index
2179 struct tty_driver *console_device(int *index)
2182 struct tty_driver *driver = NULL;
2185 for_each_console(c) {
2188 driver = c->device(c, index);
2197 * Prevent further output on the passed console device so that (for example)
2198 * serial drivers can disable console output before suspending a port, and can
2199 * re-enable output afterwards.
2201 void console_stop(struct console *console)
2204 console->flags &= ~CON_ENABLED;
2207 EXPORT_SYMBOL(console_stop);
2209 void console_start(struct console *console)
2212 console->flags |= CON_ENABLED;
2215 EXPORT_SYMBOL(console_start);
2217 static int __read_mostly keep_bootcon;
2219 static int __init keep_bootcon_setup(char *str)
2222 printk(KERN_INFO "debug: skip boot console de-registration.\n");
2227 early_param("keep_bootcon", keep_bootcon_setup);
2230 * The console driver calls this routine during kernel initialization
2231 * to register the console printing procedure with printk() and to
2232 * print any messages that were printed by the kernel before the
2233 * console driver was initialized.
2235 * This can happen pretty early during the boot process (because of
2236 * early_printk) - sometimes before setup_arch() completes - be careful
2237 * of what kernel features are used - they may not be initialised yet.
2239 * There are two types of consoles - bootconsoles (early_printk) and
2240 * "real" consoles (everything which is not a bootconsole) which are
2241 * handled differently.
2242 * - Any number of bootconsoles can be registered at any time.
2243 * - As soon as a "real" console is registered, all bootconsoles
2244 * will be unregistered automatically.
2245 * - Once a "real" console is registered, any attempt to register a
2246 * bootconsoles will be rejected
2248 void register_console(struct console *newcon)
2251 unsigned long flags;
2252 struct console *bcon = NULL;
2255 * before we register a new CON_BOOT console, make sure we don't
2256 * already have a valid console
2258 if (console_drivers && newcon->flags & CON_BOOT) {
2259 /* find the last or real console */
2260 for_each_console(bcon) {
2261 if (!(bcon->flags & CON_BOOT)) {
2262 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
2263 newcon->name, newcon->index);
2269 if (console_drivers && console_drivers->flags & CON_BOOT)
2270 bcon = console_drivers;
2272 if (preferred_console < 0 || bcon || !console_drivers)
2273 preferred_console = selected_console;
2275 if (newcon->early_setup)
2276 newcon->early_setup();
2279 * See if we want to use this console driver. If we
2280 * didn't select a console we take the first one
2281 * that registers here.
2283 if (preferred_console < 0) {
2284 if (newcon->index < 0)
2286 if (newcon->setup == NULL ||
2287 newcon->setup(newcon, NULL) == 0) {
2288 newcon->flags |= CON_ENABLED;
2289 if (newcon->device) {
2290 newcon->flags |= CON_CONSDEV;
2291 preferred_console = 0;
2297 * See if this console matches one we selected on
2300 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
2302 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
2304 if (newcon->index >= 0 &&
2305 newcon->index != console_cmdline[i].index)
2307 if (newcon->index < 0)
2308 newcon->index = console_cmdline[i].index;
2309 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2310 if (console_cmdline[i].brl_options) {
2311 newcon->flags |= CON_BRL;
2312 braille_register_console(newcon,
2313 console_cmdline[i].index,
2314 console_cmdline[i].options,
2315 console_cmdline[i].brl_options);
2319 if (newcon->setup &&
2320 newcon->setup(newcon, console_cmdline[i].options) != 0)
2322 newcon->flags |= CON_ENABLED;
2323 newcon->index = console_cmdline[i].index;
2324 if (i == selected_console) {
2325 newcon->flags |= CON_CONSDEV;
2326 preferred_console = selected_console;
2331 if (!(newcon->flags & CON_ENABLED))
2335 * If we have a bootconsole, and are switching to a real console,
2336 * don't print everything out again, since when the boot console, and
2337 * the real console are the same physical device, it's annoying to
2338 * see the beginning boot messages twice
2340 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2341 newcon->flags &= ~CON_PRINTBUFFER;
2344 * Put this console in the list - keep the
2345 * preferred driver at the head of the list.
2348 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2349 newcon->next = console_drivers;
2350 console_drivers = newcon;
2352 newcon->next->flags &= ~CON_CONSDEV;
2354 newcon->next = console_drivers->next;
2355 console_drivers->next = newcon;
2357 if (newcon->flags & CON_PRINTBUFFER) {
2359 * console_unlock(); will print out the buffered messages
2362 raw_spin_lock_irqsave(&logbuf_lock, flags);
2363 console_seq = syslog_seq;
2364 console_idx = syslog_idx;
2365 console_prev = syslog_prev;
2366 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2368 * We're about to replay the log buffer. Only do this to the
2369 * just-registered console to avoid excessive message spam to
2370 * the already-registered consoles.
2372 exclusive_console = newcon;
2375 console_sysfs_notify();
2378 * By unregistering the bootconsoles after we enable the real console
2379 * we get the "console xxx enabled" message on all the consoles -
2380 * boot consoles, real consoles, etc - this is to ensure that end
2381 * users know there might be something in the kernel's log buffer that
2382 * went to the bootconsole (that they do not see on the real console)
2385 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2387 /* we need to iterate through twice, to make sure we print
2388 * everything out, before we unregister the console(s)
2390 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
2391 newcon->name, newcon->index);
2392 for_each_console(bcon)
2393 if (bcon->flags & CON_BOOT)
2394 unregister_console(bcon);
2396 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
2397 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2398 newcon->name, newcon->index);
2401 EXPORT_SYMBOL(register_console);
2403 int unregister_console(struct console *console)
2405 struct console *a, *b;
2408 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2409 if (console->flags & CON_BRL)
2410 return braille_unregister_console(console);
2414 if (console_drivers == console) {
2415 console_drivers=console->next;
2417 } else if (console_drivers) {
2418 for (a=console_drivers->next, b=console_drivers ;
2419 a; b=a, a=b->next) {
2429 * If this isn't the last console and it has CON_CONSDEV set, we
2430 * need to set it on the next preferred console.
2432 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2433 console_drivers->flags |= CON_CONSDEV;
2436 console_sysfs_notify();
2439 EXPORT_SYMBOL(unregister_console);
2441 static int __init printk_late_init(void)
2443 struct console *con;
2445 for_each_console(con) {
2446 if (!keep_bootcon && con->flags & CON_BOOT) {
2447 printk(KERN_INFO "turn off boot console %s%d\n",
2448 con->name, con->index);
2449 unregister_console(con);
2452 hotcpu_notifier(console_cpu_notify, 0);
2455 late_initcall(printk_late_init);
2457 #if defined CONFIG_PRINTK
2459 int printk_sched(const char *fmt, ...)
2461 unsigned long flags;
2466 local_irq_save(flags);
2467 buf = __get_cpu_var(printk_sched_buf);
2469 va_start(args, fmt);
2470 r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2473 __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2474 local_irq_restore(flags);
2480 * printk rate limiting, lifted from the networking subsystem.
2482 * This enforces a rate limit: not more than 10 kernel messages
2483 * every 5s to make a denial-of-service attack impossible.
2485 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2487 int __printk_ratelimit(const char *func)
2489 return ___ratelimit(&printk_ratelimit_state, func);
2491 EXPORT_SYMBOL(__printk_ratelimit);
2494 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2495 * @caller_jiffies: pointer to caller's state
2496 * @interval_msecs: minimum interval between prints
2498 * printk_timed_ratelimit() returns true if more than @interval_msecs
2499 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2502 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2503 unsigned int interval_msecs)
2505 if (*caller_jiffies == 0
2506 || !time_in_range(jiffies, *caller_jiffies,
2508 + msecs_to_jiffies(interval_msecs))) {
2509 *caller_jiffies = jiffies;
2514 EXPORT_SYMBOL(printk_timed_ratelimit);
2516 static DEFINE_SPINLOCK(dump_list_lock);
2517 static LIST_HEAD(dump_list);
2520 * kmsg_dump_register - register a kernel log dumper.
2521 * @dumper: pointer to the kmsg_dumper structure
2523 * Adds a kernel log dumper to the system. The dump callback in the
2524 * structure will be called when the kernel oopses or panics and must be
2525 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2527 int kmsg_dump_register(struct kmsg_dumper *dumper)
2529 unsigned long flags;
2532 /* The dump callback needs to be set */
2536 spin_lock_irqsave(&dump_list_lock, flags);
2537 /* Don't allow registering multiple times */
2538 if (!dumper->registered) {
2539 dumper->registered = 1;
2540 list_add_tail_rcu(&dumper->list, &dump_list);
2543 spin_unlock_irqrestore(&dump_list_lock, flags);
2547 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2550 * kmsg_dump_unregister - unregister a kmsg dumper.
2551 * @dumper: pointer to the kmsg_dumper structure
2553 * Removes a dump device from the system. Returns zero on success and
2554 * %-EINVAL otherwise.
2556 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2558 unsigned long flags;
2561 spin_lock_irqsave(&dump_list_lock, flags);
2562 if (dumper->registered) {
2563 dumper->registered = 0;
2564 list_del_rcu(&dumper->list);
2567 spin_unlock_irqrestore(&dump_list_lock, flags);
2572 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2574 static bool always_kmsg_dump;
2575 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2578 * kmsg_dump - dump kernel log to kernel message dumpers.
2579 * @reason: the reason (oops, panic etc) for dumping
2581 * Call each of the registered dumper's dump() callback, which can
2582 * retrieve the kmsg records with kmsg_dump_get_line() or
2583 * kmsg_dump_get_buffer().
2585 void kmsg_dump(enum kmsg_dump_reason reason)
2587 struct kmsg_dumper *dumper;
2588 unsigned long flags;
2590 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2594 list_for_each_entry_rcu(dumper, &dump_list, list) {
2595 if (dumper->max_reason && reason > dumper->max_reason)
2598 /* initialize iterator with data about the stored records */
2599 dumper->active = true;
2601 raw_spin_lock_irqsave(&logbuf_lock, flags);
2602 dumper->cur_seq = clear_seq;
2603 dumper->cur_idx = clear_idx;
2604 dumper->next_seq = log_next_seq;
2605 dumper->next_idx = log_next_idx;
2606 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2608 /* invoke dumper which will iterate over records */
2609 dumper->dump(dumper, reason);
2611 /* reset iterator */
2612 dumper->active = false;
2618 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2619 * @dumper: registered kmsg dumper
2620 * @syslog: include the "<4>" prefixes
2621 * @line: buffer to copy the line to
2622 * @size: maximum size of the buffer
2623 * @len: length of line placed into buffer
2625 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2626 * record, and copy one record into the provided buffer.
2628 * Consecutive calls will return the next available record moving
2629 * towards the end of the buffer with the youngest messages.
2631 * A return value of FALSE indicates that there are no more records to
2634 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2636 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2637 char *line, size_t size, size_t *len)
2643 if (!dumper->active)
2646 if (dumper->cur_seq < log_first_seq) {
2647 /* messages are gone, move to first available one */
2648 dumper->cur_seq = log_first_seq;
2649 dumper->cur_idx = log_first_idx;
2653 if (dumper->cur_seq >= log_next_seq)
2656 msg = log_from_idx(dumper->cur_idx);
2657 l = msg_print_text(msg, 0, syslog, line, size);
2659 dumper->cur_idx = log_next(dumper->cur_idx);
2669 * kmsg_dump_get_line - retrieve one kmsg log line
2670 * @dumper: registered kmsg dumper
2671 * @syslog: include the "<4>" prefixes
2672 * @line: buffer to copy the line to
2673 * @size: maximum size of the buffer
2674 * @len: length of line placed into buffer
2676 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2677 * record, and copy one record into the provided buffer.
2679 * Consecutive calls will return the next available record moving
2680 * towards the end of the buffer with the youngest messages.
2682 * A return value of FALSE indicates that there are no more records to
2685 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2686 char *line, size_t size, size_t *len)
2688 unsigned long flags;
2691 raw_spin_lock_irqsave(&logbuf_lock, flags);
2692 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2693 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2697 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2700 * kmsg_dump_get_buffer - copy kmsg log lines
2701 * @dumper: registered kmsg dumper
2702 * @syslog: include the "<4>" prefixes
2703 * @buf: buffer to copy the line to
2704 * @size: maximum size of the buffer
2705 * @len: length of line placed into buffer
2707 * Start at the end of the kmsg buffer and fill the provided buffer
2708 * with as many of the the *youngest* kmsg records that fit into it.
2709 * If the buffer is large enough, all available kmsg records will be
2710 * copied with a single call.
2712 * Consecutive calls will fill the buffer with the next block of
2713 * available older records, not including the earlier retrieved ones.
2715 * A return value of FALSE indicates that there are no more records to
2718 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2719 char *buf, size_t size, size_t *len)
2721 unsigned long flags;
2726 enum log_flags prev;
2730 if (!dumper->active)
2733 raw_spin_lock_irqsave(&logbuf_lock, flags);
2734 if (dumper->cur_seq < log_first_seq) {
2735 /* messages are gone, move to first available one */
2736 dumper->cur_seq = log_first_seq;
2737 dumper->cur_idx = log_first_idx;
2741 if (dumper->cur_seq >= dumper->next_seq) {
2742 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2746 /* calculate length of entire buffer */
2747 seq = dumper->cur_seq;
2748 idx = dumper->cur_idx;
2750 while (seq < dumper->next_seq) {
2751 struct log *msg = log_from_idx(idx);
2753 l += msg_print_text(msg, prev, true, NULL, 0);
2754 idx = log_next(idx);
2759 /* move first record forward until length fits into the buffer */
2760 seq = dumper->cur_seq;
2761 idx = dumper->cur_idx;
2763 while (l > size && seq < dumper->next_seq) {
2764 struct log *msg = log_from_idx(idx);
2766 l -= msg_print_text(msg, prev, true, NULL, 0);
2767 idx = log_next(idx);
2772 /* last message in next interation */
2778 while (seq < dumper->next_seq) {
2779 struct log *msg = log_from_idx(idx);
2781 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2782 idx = log_next(idx);
2787 dumper->next_seq = next_seq;
2788 dumper->next_idx = next_idx;
2790 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2796 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2799 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2800 * @dumper: registered kmsg dumper
2802 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2803 * kmsg_dump_get_buffer() can be called again and used multiple
2804 * times within the same dumper.dump() callback.
2806 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2808 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
2810 dumper->cur_seq = clear_seq;
2811 dumper->cur_idx = clear_idx;
2812 dumper->next_seq = log_next_seq;
2813 dumper->next_idx = log_next_idx;
2817 * kmsg_dump_rewind - reset the interator
2818 * @dumper: registered kmsg dumper
2820 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2821 * kmsg_dump_get_buffer() can be called again and used multiple
2822 * times within the same dumper.dump() callback.
2824 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2826 unsigned long flags;
2828 raw_spin_lock_irqsave(&logbuf_lock, flags);
2829 kmsg_dump_rewind_nolock(dumper);
2830 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2832 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);