printk.c 73.1 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1
2
3
4
5
6
7
8
9
10
11
12
/*
 *  linux/kernel/printk.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 * Modified to make sys_syslog() more flexible: added commands to
 * return the last 4k of kernel messages, regardless of whether
 * they've been read or not.  Added option to suppress kernel printk's
 * to the console.  Added hook for sending the console messages
 * elsewhere, in preparation for a serial line console (someday).
 * Ted Ts'o, 2/11/93.
 * Modified for sysctl support, 1/8/97, Chris Horn.
13
 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14
 *     manfred@colorfullife.com
Linus Torvalds's avatar
Linus Torvalds committed
15
 * Rewrote bits to get rid of console_lock
16
 *	01Mar01 Andrew Morton
Linus Torvalds's avatar
Linus Torvalds committed
17
18
19
20
21
22
23
24
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/console.h>
#include <linux/init.h>
Randy Dunlap's avatar
Randy Dunlap committed
25
26
#include <linux/jiffies.h>
#include <linux/nmi.h>
Linus Torvalds's avatar
Linus Torvalds committed
27
#include <linux/module.h>
Jan Engelhardt's avatar
Jan Engelhardt committed
28
#include <linux/moduleparam.h>
Linus Torvalds's avatar
Linus Torvalds committed
29
30
31
32
33
#include <linux/interrupt.h>			/* For in_interrupt() */
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/security.h>
#include <linux/bootmem.h>
34
#include <linux/memblock.h>
35
#include <linux/aio.h>
Linus Torvalds's avatar
Linus Torvalds committed
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
43
#include <linux/cpu.h>
#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>
Linus Torvalds's avatar
Linus Torvalds committed
48
49
50

#include <asm/uaccess.h>

51
52
53
#define CREATE_TRACE_POINTS
#include <trace/events/printk.h>

Joe Perches's avatar
Joe Perches committed
54
#include "console_cmdline.h"
55
#include "braille.h"
Joe Perches's avatar
Joe Perches committed
56

Linus Torvalds's avatar
Linus Torvalds committed
57
/* printk's without a loglevel use this.. */
58
#define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
Linus Torvalds's avatar
Linus Torvalds committed
59
60
61
62
63
64
65
66
67
68
69
70
71

/* We show everything that is MORE important than this.. */
#define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
#define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */

int console_printk[4] = {
	DEFAULT_CONSOLE_LOGLEVEL,	/* console_loglevel */
	DEFAULT_MESSAGE_LOGLEVEL,	/* default_message_loglevel */
	MINIMUM_CONSOLE_LOGLEVEL,	/* minimum_console_loglevel */
	DEFAULT_CONSOLE_LOGLEVEL,	/* default_console_loglevel */
};

/*
72
 * Low level drivers may need that to know if they can schedule in
Linus Torvalds's avatar
Linus Torvalds committed
73
74
75
76
77
78
79
80
81
82
 * their unblank() callback or not. So let's export it.
 */
int oops_in_progress;
EXPORT_SYMBOL(oops_in_progress);

/*
 * console_sem protects the console_drivers list, and also
 * provides serialisation for access to the entire console
 * driver system.
 */
83
static DEFINE_SEMAPHORE(console_sem);
Linus Torvalds's avatar
Linus Torvalds committed
84
struct console *console_drivers;
Ingo Molnar's avatar
Ingo Molnar committed
85
86
EXPORT_SYMBOL_GPL(console_drivers);

87
88
89
90
91
92
#ifdef CONFIG_LOCKDEP
static struct lockdep_map console_lock_dep_map = {
	.name = "console_lock"
};
#endif

Linus Torvalds's avatar
Linus Torvalds committed
93
94
95
96
97
98
99
100
/*
 * This is used for debugging the mess that is the VT code by
 * keeping track if we have the console semaphore held. It's
 * definitely not the perfect debug tool (we don't know if _WE_
 * hold it are racing, but it helps tracking those weird code
 * path in the console code where we end up in places I want
 * locked without the console sempahore held
 */
101
static int console_locked, console_suspended;
Linus Torvalds's avatar
Linus Torvalds committed
102

103
104
105
106
107
/*
 * If exclusive_console is non-NULL then only this console is to be printed to.
 */
static struct console *exclusive_console;

Linus Torvalds's avatar
Linus Torvalds committed
108
109
110
111
112
113
114
/*
 *	Array of consoles built from command line options (console=)
 */

#define MAX_CMDLINECONSOLES 8

static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
Joe Perches's avatar
Joe Perches committed
115

Linus Torvalds's avatar
Linus Torvalds committed
116
117
static int selected_console = -1;
static int preferred_console = -1;
118
119
int console_set_on_cmdline;
EXPORT_SYMBOL(console_set_on_cmdline);
Linus Torvalds's avatar
Linus Torvalds committed
120
121
122
123

/* Flag: console code may call schedule() */
static int console_may_schedule;

124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
/*
 * The printk log buffer consists of a chain of concatenated variable
 * length records. Every record starts with a record header, containing
 * the overall length of the record.
 *
 * The heads to the first and last entry in the buffer, as well as the
 * sequence numbers of these both entries are maintained when messages
 * are stored..
 *
 * If the heads indicate available messages, the length in the header
 * tells the start next message. A length == 0 for the next message
 * indicates a wrap-around to the beginning of the buffer.
 *
 * Every record carries the monotonic timestamp in microseconds, as well as
 * the standard userspace syslog level and syslog facility. The usual
 * kernel messages use LOG_KERN; userspace-injected messages always carry
 * a matching syslog facility, by default LOG_USER. The origin of every
 * message can be reliably determined that way.
 *
 * The human readable log message directly follows the message header. The
 * length of the message text is stored in the header, the stored message
 * is not terminated.
 *
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
 * Optionally, a message can carry a dictionary of properties (key/value pairs),
 * to provide userspace with a machine-readable message context.
 *
 * Examples for well-defined, commonly used property names are:
 *   DEVICE=b12:8               device identifier
 *                                b12:8         block dev_t
 *                                c127:3        char dev_t
 *                                n8            netdev ifindex
 *                                +sound:card0  subsystem:devname
 *   SUBSYSTEM=pci              driver-core subsystem name
 *
 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
 * follows directly after a '=' character. Every property is terminated by
 * a '\0' character. The last property is not terminated.
 *
 * Example of a message structure:
 *   0000  ff 8f 00 00 00 00 00 00      monotonic time in nsec
 *   0008  34 00                        record is 52 bytes long
 *   000a        0b 00                  text is 11 bytes long
 *   000c              1f 00            dictionary is 23 bytes long
 *   000e                    03 00      LOG_KERN (facility) LOG_ERR (level)
 *   0010  69 74 27 73 20 61 20 6c      "it's a l"
 *         69 6e 65                     "ine"
 *   001b           44 45 56 49 43      "DEVIC"
 *         45 3d 62 38 3a 32 00 44      "E=b8:2\0D"
 *         52 49 56 45 52 3d 62 75      "RIVER=bu"
 *         67                           "g"
 *   0032     00 00 00                  padding to next message header
 *
176
 * The 'struct printk_log' buffer header must never be directly exported to
177
178
179
180
181
182
183
184
185
186
187
188
 * userspace, it is a kernel-private implementation detail that might
 * need to be changed in the future, when the requirements change.
 *
 * /dev/kmsg exports the structured data in the following line format:
 *   "level,sequnum,timestamp;<message text>\n"
 *
 * The optional key/value pairs are attached as continuation lines starting
 * with a space character and terminated by a newline. All possible
 * non-prinatable characters are escaped in the "\xff" notation.
 *
 * Users of the export format should ignore possible additional values
 * separated by ',', and find the message after the ';' character.
189
190
 */

191
enum log_flags {
192
193
194
195
	LOG_NOCONS	= 1,	/* already flushed, do not print to console */
	LOG_NEWLINE	= 2,	/* text ended with a newline */
	LOG_PREFIX	= 4,	/* text started with a prefix */
	LOG_CONT	= 8,	/* text is a fragment of a continuation line */
196
197
};

198
struct printk_log {
199
200
201
202
	u64 ts_nsec;		/* timestamp in nanoseconds */
	u16 len;		/* length of entire record */
	u16 text_len;		/* length of text buffer */
	u16 dict_len;		/* length of dictionary buffer */
203
204
205
	u8 facility;		/* syslog facility */
	u8 flags:5;		/* internal record flags */
	u8 level:3;		/* syslog level */
206
207
208
209
210
211
212
};

/*
 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
 * used in interesting ways to provide interlocking in console_unlock();
 */
static DEFINE_RAW_SPINLOCK(logbuf_lock);
213

214
#ifdef CONFIG_PRINTK
215
DECLARE_WAIT_QUEUE_HEAD(log_wait);
216
217
218
/* the next printk record to read by syslog(READ) or /proc/kmsg */
static u64 syslog_seq;
static u32 syslog_idx;
219
static enum log_flags syslog_prev;
220
static size_t syslog_partial;
221
222
223
224
225
226
227
228
229

/* index and sequence number of the first record stored in the buffer */
static u64 log_first_seq;
static u32 log_first_idx;

/* index and sequence number of the next record to store in the buffer */
static u64 log_next_seq;
static u32 log_next_idx;

230
231
232
233
234
/* the next printk record to write to the console */
static u64 console_seq;
static u32 console_idx;
static enum log_flags console_prev;

235
236
237
238
/* the next printk record to read after the last 'clear' command */
static u64 clear_seq;
static u32 clear_idx;

239
240
#define PREFIX_MAX		32
#define LOG_LINE_MAX		1024 - PREFIX_MAX
241
242

/* record buffer */
243
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
244
245
#define LOG_ALIGN 4
#else
246
#define LOG_ALIGN __alignof__(struct printk_log)
247
#endif
248
#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
249
static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
250
251
252
253
254
static char *log_buf = __log_buf;
static u32 log_buf_len = __LOG_BUF_LEN;

/* cpu currently holding logbuf_lock */
static volatile unsigned int logbuf_cpu = UINT_MAX;
255
256

/* human readable text of the record */
257
static char *log_text(const struct printk_log *msg)
258
{
259
	return (char *)msg + sizeof(struct printk_log);
260
261
262
}

/* optional key/value pair dictionary attached to the record */
263
static char *log_dict(const struct printk_log *msg)
264
{
265
	return (char *)msg + sizeof(struct printk_log) + msg->text_len;
266
267
268
}

/* get record by index; idx must point to valid msg */
269
static struct printk_log *log_from_idx(u32 idx)
270
{
271
	struct printk_log *msg = (struct printk_log *)(log_buf + idx);
272
273
274
275
276
277

	/*
	 * A length == 0 record is the end of buffer marker. Wrap around and
	 * read the message at the start of the buffer.
	 */
	if (!msg->len)
278
		return (struct printk_log *)log_buf;
279
280
281
282
283
284
	return msg;
}

/* get next record; idx must point to valid msg */
static u32 log_next(u32 idx)
{
285
	struct printk_log *msg = (struct printk_log *)(log_buf + idx);
286
287
288
289
290
291
292
293

	/* length == 0 indicates the end of the buffer; wrap */
	/*
	 * A length == 0 record is the end of buffer marker. Wrap around and
	 * read the message at the start of the buffer as *this* one, and
	 * return the one after that.
	 */
	if (!msg->len) {
294
		msg = (struct printk_log *)log_buf;
295
296
297
298
299
		return msg->len;
	}
	return idx + msg->len;
}

Petr Mladek's avatar
Petr Mladek committed
300
301
302
303
304
305
306
307
308
309
/*
 * Check whether there is enough free space for the given message.
 *
 * The same values of first_idx and next_idx mean that the buffer
 * is either empty or full.
 *
 * If the buffer is empty, we must respect the position of the indexes.
 * They cannot be reset to the beginning of the buffer.
 */
static int logbuf_has_space(u32 msg_size, bool empty)
310
311
312
{
	u32 free;

Petr Mladek's avatar
Petr Mladek committed
313
	if (log_next_idx > log_first_idx || empty)
314
315
316
317
318
319
320
321
322
323
324
		free = max(log_buf_len - log_next_idx, log_first_idx);
	else
		free = log_first_idx - log_next_idx;

	/*
	 * We need space also for an empty header that signalizes wrapping
	 * of the buffer.
	 */
	return free >= msg_size + sizeof(struct printk_log);
}

Petr Mladek's avatar
Petr Mladek committed
325
static int log_make_free_space(u32 msg_size)
326
327
{
	while (log_first_seq < log_next_seq) {
Petr Mladek's avatar
Petr Mladek committed
328
329
		if (logbuf_has_space(msg_size, false))
			return 0;
330
331
332
333
		/* drop old messages until we have enough continuous space */
		log_first_idx = log_next(log_first_idx);
		log_first_seq++;
	}
Petr Mladek's avatar
Petr Mladek committed
334
335
336
337
338
339

	/* sequence numbers are equal, so the log buffer is empty */
	if (logbuf_has_space(msg_size, true))
		return 0;

	return -ENOMEM;
340
341
}

342
343
/* insert record into the buffer, discard old ones, update heads */
static void log_store(int facility, int level,
344
		      enum log_flags flags, u64 ts_nsec,
345
346
347
		      const char *dict, u16 dict_len,
		      const char *text, u16 text_len)
{
348
	struct printk_log *msg;
349
350
351
	u32 size, pad_len;

	/* number of '\0' padding bytes to next message */
352
	size = sizeof(struct printk_log) + text_len + dict_len;
353
354
355
	pad_len = (-size) & (LOG_ALIGN - 1);
	size += pad_len;

Petr Mladek's avatar
Petr Mladek committed
356
357
358
	/* if message does not fit empty log buffer, ignore it */
	if (log_make_free_space(size))
		return;
359

360
	if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
361
362
363
364
365
		/*
		 * This message + an additional empty header does not fit
		 * at the end of the buffer. Add an empty header with len == 0
		 * to signify a wrap around.
		 */
366
		memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
367
368
369
370
		log_next_idx = 0;
	}

	/* fill message */
371
	msg = (struct printk_log *)(log_buf + log_next_idx);
372
373
374
375
	memcpy(log_text(msg), text, text_len);
	msg->text_len = text_len;
	memcpy(log_dict(msg), dict, dict_len);
	msg->dict_len = dict_len;
376
377
378
379
380
381
382
	msg->facility = facility;
	msg->level = level & 7;
	msg->flags = flags & 0x1f;
	if (ts_nsec > 0)
		msg->ts_nsec = ts_nsec;
	else
		msg->ts_nsec = local_clock();
383
	memset(log_dict(msg) + dict_len, 0, pad_len);
384
	msg->len = size;
385
386
387
388
389

	/* insert message */
	log_next_idx += msg->len;
	log_next_seq++;
}
390

391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
#ifdef CONFIG_SECURITY_DMESG_RESTRICT
int dmesg_restrict = 1;
#else
int dmesg_restrict;
#endif

static int syslog_action_restricted(int type)
{
	if (dmesg_restrict)
		return 1;
	/*
	 * Unless restricted, we allow "read all" and "get buffer size"
	 * for everybody.
	 */
	return type != SYSLOG_ACTION_READ_ALL &&
	       type != SYSLOG_ACTION_SIZE_BUFFER;
}

static int check_syslog_permissions(int type, bool from_file)
{
	/*
	 * If this is from /proc/kmsg and we've already opened it, then we've
	 * already done the capabilities checks at open time.
	 */
	if (from_file && type != SYSLOG_ACTION_OPEN)
		return 0;

	if (syslog_action_restricted(type)) {
		if (capable(CAP_SYSLOG))
			return 0;
		/*
		 * For historical reasons, accept CAP_SYS_ADMIN too, with
		 * a warning.
		 */
		if (capable(CAP_SYS_ADMIN)) {
			pr_warn_once("%s (%d): Attempt to access syslog with "
				     "CAP_SYS_ADMIN but no CAP_SYSLOG "
				     "(deprecated).\n",
				 current->comm, task_pid_nr(current));
			return 0;
		}
		return -EPERM;
	}
	return security_syslog(type);
}


438
439
440
441
/* /dev/kmsg - userspace message inject/listen interface */
struct devkmsg_user {
	u64 seq;
	u32 idx;
442
	enum log_flags prev;
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
	struct mutex lock;
	char buf[8192];
};

static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
			      unsigned long count, loff_t pos)
{
	char *buf, *line;
	int i;
	int level = default_message_loglevel;
	int facility = 1;	/* LOG_USER */
	size_t len = iov_length(iv, count);
	ssize_t ret = len;

	if (len > LOG_LINE_MAX)
		return -EINVAL;
	buf = kmalloc(len+1, GFP_KERNEL);
	if (buf == NULL)
		return -ENOMEM;

	line = buf;
	for (i = 0; i < count; i++) {
465
466
		if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
			ret = -EFAULT;
467
			goto out;
468
		}
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
		line += iv[i].iov_len;
	}

	/*
	 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
	 * the decimal value represents 32bit, the lower 3 bit are the log
	 * level, the rest are the log facility.
	 *
	 * If no prefix or no userspace facility is specified, we
	 * enforce LOG_USER, to be able to reliably distinguish
	 * kernel-generated messages from userspace-injected ones.
	 */
	line = buf;
	if (line[0] == '<') {
		char *endp = NULL;

		i = simple_strtoul(line+1, &endp, 10);
		if (endp && endp[0] == '>') {
			level = i & 7;
			if (i >> 3)
				facility = i >> 3;
			endp++;
			len -= endp - line;
			line = endp;
		}
	}
	line[len] = '\0';

	printk_emit(facility, level, NULL, 0, "%s", line);
out:
	kfree(buf);
	return ret;
}

static ssize_t devkmsg_read(struct file *file, char __user *buf,
			    size_t count, loff_t *ppos)
{
	struct devkmsg_user *user = file->private_data;
507
	struct printk_log *msg;
508
	u64 ts_usec;
509
	size_t i;
510
	char cont = '-';
511
512
513
514
515
516
	size_t len;
	ssize_t ret;

	if (!user)
		return -EBADF;

517
518
519
	ret = mutex_lock_interruptible(&user->lock);
	if (ret)
		return ret;
520
	raw_spin_lock_irq(&logbuf_lock);
521
522
523
	while (user->seq == log_next_seq) {
		if (file->f_flags & O_NONBLOCK) {
			ret = -EAGAIN;
524
			raw_spin_unlock_irq(&logbuf_lock);
525
526
527
			goto out;
		}

528
		raw_spin_unlock_irq(&logbuf_lock);
529
530
531
532
		ret = wait_event_interruptible(log_wait,
					       user->seq != log_next_seq);
		if (ret)
			goto out;
533
		raw_spin_lock_irq(&logbuf_lock);
534
535
536
537
538
539
540
	}

	if (user->seq < log_first_seq) {
		/* our last seen message is gone, return error and reset */
		user->idx = log_first_idx;
		user->seq = log_first_seq;
		ret = -EPIPE;
541
		raw_spin_unlock_irq(&logbuf_lock);
542
543
544
545
		goto out;
	}

	msg = log_from_idx(user->idx);
546
547
	ts_usec = msg->ts_nsec;
	do_div(ts_usec, 1000);
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566

	/*
	 * If we couldn't merge continuation line fragments during the print,
	 * export the stored flags to allow an optional external merge of the
	 * records. Merging the records isn't always neccessarily correct, like
	 * when we hit a race during printing. In most cases though, it produces
	 * better readable output. 'c' in the record flags mark the first
	 * fragment of a line, '+' the following.
	 */
	if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
		cont = 'c';
	else if ((msg->flags & LOG_CONT) ||
		 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
		cont = '+';

	len = sprintf(user->buf, "%u,%llu,%llu,%c;",
		      (msg->facility << 3) | msg->level,
		      user->seq, ts_usec, cont);
	user->prev = msg->flags;
567
568
569

	/* escape non-printable characters */
	for (i = 0; i < msg->text_len; i++) {
570
		unsigned char c = log_text(msg)[i];
571

572
		if (c < ' ' || c >= 127 || c == '\\')
573
574
575
576
577
578
579
580
581
582
			len += sprintf(user->buf + len, "\\x%02x", c);
		else
			user->buf[len++] = c;
	}
	user->buf[len++] = '\n';

	if (msg->dict_len) {
		bool line = true;

		for (i = 0; i < msg->dict_len; i++) {
583
			unsigned char c = log_dict(msg)[i];
584
585
586
587
588
589
590
591
592
593
594
595

			if (line) {
				user->buf[len++] = ' ';
				line = false;
			}

			if (c == '\0') {
				user->buf[len++] = '\n';
				line = true;
				continue;
			}

596
			if (c < ' ' || c >= 127 || c == '\\') {
597
598
599
600
601
602
603
604
605
606
607
				len += sprintf(user->buf + len, "\\x%02x", c);
				continue;
			}

			user->buf[len++] = c;
		}
		user->buf[len++] = '\n';
	}

	user->idx = log_next(user->idx);
	user->seq++;
608
	raw_spin_unlock_irq(&logbuf_lock);
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634

	if (len > count) {
		ret = -EINVAL;
		goto out;
	}

	if (copy_to_user(buf, user->buf, len)) {
		ret = -EFAULT;
		goto out;
	}
	ret = len;
out:
	mutex_unlock(&user->lock);
	return ret;
}

static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
{
	struct devkmsg_user *user = file->private_data;
	loff_t ret = 0;

	if (!user)
		return -EBADF;
	if (offset)
		return -ESPIPE;

635
	raw_spin_lock_irq(&logbuf_lock);
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
	switch (whence) {
	case SEEK_SET:
		/* the first record */
		user->idx = log_first_idx;
		user->seq = log_first_seq;
		break;
	case SEEK_DATA:
		/*
		 * The first record after the last SYSLOG_ACTION_CLEAR,
		 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
		 * changes no global state, and does not clear anything.
		 */
		user->idx = clear_idx;
		user->seq = clear_seq;
		break;
	case SEEK_END:
		/* after the last record */
		user->idx = log_next_idx;
		user->seq = log_next_seq;
		break;
	default:
		ret = -EINVAL;
	}
659
	raw_spin_unlock_irq(&logbuf_lock);
660
661
662
663
664
665
666
667
668
669
670
671
672
	return ret;
}

static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
{
	struct devkmsg_user *user = file->private_data;
	int ret = 0;

	if (!user)
		return POLLERR|POLLNVAL;

	poll_wait(file, &log_wait, wait);

673
	raw_spin_lock_irq(&logbuf_lock);
674
675
676
677
	if (user->seq < log_next_seq) {
		/* return error when data has vanished underneath us */
		if (user->seq < log_first_seq)
			ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
678
679
		else
			ret = POLLIN|POLLRDNORM;
680
	}
681
	raw_spin_unlock_irq(&logbuf_lock);
682
683
684
685
686
687
688
689
690
691
692
693
694

	return ret;
}

static int devkmsg_open(struct inode *inode, struct file *file)
{
	struct devkmsg_user *user;
	int err;

	/* write-only does not need any file context */
	if ((file->f_flags & O_ACCMODE) == O_WRONLY)
		return 0;

695
696
	err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
				       SYSLOG_FROM_READER);
697
698
699
700
701
702
703
704
705
	if (err)
		return err;

	user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
	if (!user)
		return -ENOMEM;

	mutex_init(&user->lock);

706
	raw_spin_lock_irq(&logbuf_lock);
707
708
	user->idx = log_first_idx;
	user->seq = log_first_seq;
709
	raw_spin_unlock_irq(&logbuf_lock);
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735

	file->private_data = user;
	return 0;
}

static int devkmsg_release(struct inode *inode, struct file *file)
{
	struct devkmsg_user *user = file->private_data;

	if (!user)
		return 0;

	mutex_destroy(&user->lock);
	kfree(user);
	return 0;
}

const struct file_operations kmsg_fops = {
	.open = devkmsg_open,
	.read = devkmsg_read,
	.aio_write = devkmsg_writev,
	.llseek = devkmsg_llseek,
	.poll = devkmsg_poll,
	.release = devkmsg_release,
};

736
737
#ifdef CONFIG_KEXEC
/*
738
 * This appends the listed symbols to /proc/vmcore
739
 *
740
 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
741
742
743
744
745
746
747
748
 * obtain access to symbols that are otherwise very difficult to locate.  These
 * symbols are specifically used so that utilities can access and extract the
 * dmesg log from a vmcore file after a crash.
 */
void log_buf_kexec_setup(void)
{
	VMCOREINFO_SYMBOL(log_buf);
	VMCOREINFO_SYMBOL(log_buf_len);
749
750
	VMCOREINFO_SYMBOL(log_first_idx);
	VMCOREINFO_SYMBOL(log_next_idx);
751
	/*
752
	 * Export struct printk_log size and field offsets. User space tools can
753
754
	 * parse it and detect any changes to structure down the line.
	 */
755
756
757
758
759
	VMCOREINFO_STRUCT_SIZE(printk_log);
	VMCOREINFO_OFFSET(printk_log, ts_nsec);
	VMCOREINFO_OFFSET(printk_log, len);
	VMCOREINFO_OFFSET(printk_log, text_len);
	VMCOREINFO_OFFSET(printk_log, dict_len);
760
761
762
}
#endif

763
764
765
766
/* requested log_buf_len from kernel cmdline */
static unsigned long __initdata new_log_buf_len;

/* save requested log_buf_len since it's too early to process it */
Linus Torvalds's avatar
Linus Torvalds committed
767
768
static int __init log_buf_len_setup(char *str)
{
769
	unsigned size = memparse(str, &str);
Linus Torvalds's avatar
Linus Torvalds committed
770
771
772

	if (size)
		size = roundup_pow_of_two(size);
773
774
775
776
	if (size > log_buf_len)
		new_log_buf_len = size;

	return 0;
Linus Torvalds's avatar
Linus Torvalds committed
777
}
778
779
780
781
782
783
784
785
786
787
early_param("log_buf_len", log_buf_len_setup);

void __init setup_log_buf(int early)
{
	unsigned long flags;
	char *new_log_buf;
	int free;

	if (!new_log_buf_len)
		return;
Linus Torvalds's avatar
Linus Torvalds committed
788

789
	if (early) {
790
791
		new_log_buf =
			memblock_virt_alloc(new_log_buf_len, PAGE_SIZE);
792
	} else {
793
		new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len, 0);
794
795
796
797
798
799
800
801
	}

	if (unlikely(!new_log_buf)) {
		pr_err("log_buf_len: %ld bytes not available\n",
			new_log_buf_len);
		return;
	}

802
	raw_spin_lock_irqsave(&logbuf_lock, flags);
803
804
805
	log_buf_len = new_log_buf_len;
	log_buf = new_log_buf;
	new_log_buf_len = 0;
806
807
	free = __LOG_BUF_LEN - log_next_idx;
	memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
808
	raw_spin_unlock_irqrestore(&logbuf_lock, flags);
809
810
811
812
813

	pr_info("log_buf_len: %d\n", log_buf_len);
	pr_info("early log buf free: %d(%d%%)\n",
		free, (free * 100) / __LOG_BUF_LEN);
}
Linus Torvalds's avatar
Linus Torvalds committed
814

815
816
817
818
819
static bool __read_mostly ignore_loglevel;

static int __init ignore_loglevel_setup(char *str)
{
	ignore_loglevel = 1;
820
	pr_info("debug: ignoring loglevel setting.\n");
821
822
823
824
825
826
827
828
829

	return 0;
}

early_param("ignore_loglevel", ignore_loglevel_setup);
module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
	"print all kernel messages to the console.");

Randy Dunlap's avatar
Randy Dunlap committed
830
831
#ifdef CONFIG_BOOT_PRINTK_DELAY

832
static int boot_delay; /* msecs delay after each printk during bootup */
833
static unsigned long long loops_per_msec;	/* based on boot_delay */
Randy Dunlap's avatar
Randy Dunlap committed
834
835
836
837
838
839
840
841
842
843
844
845

static int __init boot_delay_setup(char *str)
{
	unsigned long lpj;

	lpj = preset_lpj ? preset_lpj : 1000000;	/* some guess */
	loops_per_msec = (unsigned long long)lpj / 1000 * HZ;

	get_option(&str, &boot_delay);
	if (boot_delay > 10 * 1000)
		boot_delay = 0;

846
847
848
	pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
		"HZ: %d, loops_per_msec: %llu\n",
		boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
849
	return 0;
Randy Dunlap's avatar
Randy Dunlap committed
850
}
851
early_param("boot_delay", boot_delay_setup);
Randy Dunlap's avatar
Randy Dunlap committed
852

853
static void boot_delay_msec(int level)
Randy Dunlap's avatar
Randy Dunlap committed
854
855
856
857
{
	unsigned long long k;
	unsigned long timeout;

858
859
	if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
		|| (level >= console_loglevel && !ignore_loglevel)) {
Randy Dunlap's avatar
Randy Dunlap committed
860
		return;
861
	}
Randy Dunlap's avatar
Randy Dunlap committed
862

863
	k = (unsigned long long)loops_per_msec * boot_delay;
Randy Dunlap's avatar
Randy Dunlap committed
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879

	timeout = jiffies + msecs_to_jiffies(boot_delay);
	while (k) {
		k--;
		cpu_relax();
		/*
		 * use (volatile) jiffies to prevent
		 * compiler reduction; loop termination via jiffies
		 * is secondary and may or may not happen.
		 */
		if (time_after(jiffies, timeout))
			break;
		touch_nmi_watchdog();
	}
}
#else
880
static inline void boot_delay_msec(int level)
Randy Dunlap's avatar
Randy Dunlap committed
881
882
883
884
{
}
#endif

885
886
887
888
889
890
891
#if defined(CONFIG_PRINTK_TIME)
static bool printk_time = 1;
#else
static bool printk_time;
#endif
module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);

892
893
894
895
896
897
898
static size_t print_time(u64 ts, char *buf)
{
	unsigned long rem_nsec;

	if (!printk_time)
		return 0;

899
900
	rem_nsec = do_div(ts, 1000000000);

901
	if (!buf)
902
		return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
903
904
905
906
907

	return sprintf(buf, "[%5lu.%06lu] ",
		       (unsigned long)ts, rem_nsec / 1000);
}

908
static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
909
{
910
	size_t len = 0;
911
	unsigned int prefix = (msg->facility << 3) | msg->level;
912

913
914
	if (syslog) {
		if (buf) {
915
			len += sprintf(buf, "<%u>", prefix);
916
917
		} else {
			len += 3;
918
919
920
921
922
			if (prefix > 999)
				len += 3;
			else if (prefix > 99)
				len += 2;
			else if (prefix > 9)
923
924
925
				len++;
		}
	}
926

927
	len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
928
	return len;
929
930
}

931
static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
932
			     bool syslog, char *buf, size_t size)
933
{
934
935
	const char *text = log_text(msg);
	size_t text_size = msg->text_len;
936
937
	bool prefix = true;
	bool newline = true;
938
939
	size_t len = 0;

940
941
942
943
944
945
946
947
948
949
950
	if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
		prefix = false;

	if (msg->flags & LOG_CONT) {
		if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
			prefix = false;

		if (!(msg->flags & LOG_NEWLINE))
			newline = false;
	}

951
952
953
954
955
956
957
958
959
960
961
	do {
		const char *next = memchr(text, '\n', text_size);
		size_t text_len;

		if (next) {
			text_len = next - text;
			next++;
			text_size -= next - text;
		} else {
			text_len = text_size;
		}
962

963
964
		if (buf) {
			if (print_prefix(msg, syslog, NULL) +
965
			    text_len + 1 >= size - len)
966
				break;
967

968
969
			if (prefix)
				len += print_prefix(msg, syslog, buf + len);
970
971
			memcpy(buf + len, text, text_len);
			len += text_len;
972
973
			if (next || newline)
				buf[len++] = '\n';
974
975
		} else {
			/* SYSLOG_ACTION_* buffer size only calculation */
976
977
978
979
980
			if (prefix)
				len += print_prefix(msg, syslog, NULL);
			len += text_len;
			if (next || newline)
				len++;
981
		}
982

983
		prefix = true;
984
985
		text = next;
	} while (text);
986
987
988
989
990
991
992

	return len;
}

static int syslog_print(char __user *buf, int size)
{
	char *text;
993
	struct printk_log *msg;
994
	int len = 0;
995

996
	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
997
998
999
	if (!text)
		return -ENOMEM;

1000
1001
	while (size > 0) {
		size_t n;
1002
		size_t skip;
1003
1004
1005
1006
1007
1008

		raw_spin_lock_irq(&logbuf_lock);
		if (syslog_seq < log_first_seq) {
			/* messages are gone, move to first one */
			syslog_seq = log_first_seq;
			syslog_idx = log_first_idx;
1009
			syslog_prev = 0;
1010
			syslog_partial = 0;
1011
1012
1013
1014
1015
		}
		if (syslog_seq == log_next_seq) {
			raw_spin_unlock_irq(&logbuf_lock);
			break;
		}
1016
1017

		skip = syslog_partial;
1018
		msg = log_from_idx(syslog_idx);
1019
1020
		n = msg_print_text(msg, syslog_prev, true, text,
				   LOG_LINE_MAX + PREFIX_MAX);
1021
1022
		if (n - syslog_partial <= size) {
			/* message fits into buffer, move forward */
1023
1024
			syslog_idx = log_next(syslog_idx);
			syslog_seq++;
1025
			syslog_prev = msg->flags;
1026
1027
1028
1029
1030
1031
			n -= syslog_partial;
			syslog_partial = 0;
		} else if (!len){
			/* partial read(), remember position */
			n = size;
			syslog_partial += n;
1032
1033
1034
1035
1036
1037
1038
		} else
			n = 0;
		raw_spin_unlock_irq(&logbuf_lock);

		if (!n)
			break;

1039
		if (copy_to_user(buf, text + skip, n)) {
1040
1041
1042
1043
			if (!len)
				len = -EFAULT;
			break;
		}
1044
1045
1046
1047

		len += n;
		size -= n;
		buf += n;
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
	}

	kfree(text);
	return len;
}

static int syslog_print_all(char __user *buf, int size, bool clear)
{
	char *text;
	int len = 0;

1059
	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1060
1061
1062
1063
1064
1065
1066
1067
	if (!text)
		return -ENOMEM;

	raw_spin_lock_irq(&logbuf_lock);
	if (buf) {
		u64 next_seq;
		u64 seq;
		u32 idx;
1068
		enum log_flags prev;
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078

		if (clear_seq < log_first_seq) {
			/* messages are gone, move to first available one */
			clear_seq = log_first_seq;
			clear_idx = log_first_idx;
		}

		/*
		 * Find first record that fits, including all following records,
		 * into the user-provided buffer for this dump.
1079
		 */
1080
1081
		seq = clear_seq;
		idx = clear_idx;
1082
		prev = 0;
1083
		while (seq < log_next_seq) {
1084
			struct printk_log *msg = log_from_idx(idx);
1085

1086
			len += msg_print_text(msg, prev, true, NULL, 0);
1087
			prev = msg->flags;
1088
1089
1090
			idx = log_next(idx);
			seq++;
		}
1091
1092

		/* move first record forward until length fits into the buffer */
1093
1094
		seq = clear_seq;
		idx = clear_idx;
1095
		prev = 0;
1096
		while (len > size && seq < log_next_seq) {
1097
			struct printk_log *msg = log_from_idx(idx);
1098

1099
			len -= msg_print_text(msg, prev, true, NULL, 0);
1100
			prev = msg->flags;
1101
1102
1103
1104
			idx = log_next(idx);
			seq++;
		}

1105
		/* last message fitting into this dump */
1106
1107
1108
1109
		next_seq = log_next_seq;

		len = 0;
		while (len >= 0 && seq < next_seq) {
1110
			struct printk_log *msg = log_from_idx(idx);
1111
1112
			int textlen;

1113
1114
			textlen = msg_print_text(msg, prev, true, text,
						 LOG_LINE_MAX + PREFIX_MAX);
1115
1116
1117
1118
1119
1120
			if (textlen < 0) {
				len = textlen;
				break;
			}
			idx = log_next(idx);
			seq++;
1121
			prev = msg->flags;
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133

			raw_spin_unlock_irq(&logbuf_lock);
			if (copy_to_user(buf + len, text, textlen))
				len = -EFAULT;
			else
				len += textlen;
			raw_spin_lock_irq(&logbuf_lock);

			if (seq < log_first_seq) {
				/* messages are gone, move to next one */
				seq = log_first_seq;
				idx = log_first_idx;
1134
				prev = 0;
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
			}
		}
	}

	if (clear) {
		clear_seq = log_next_seq;
		clear_idx = log_next_idx;
	}
	raw_spin_unlock_irq(&logbuf_lock);

	kfree(text);
	return len;
}

1149
int do_syslog(int type, char __user *buf, int len, bool from_file)
Linus Torvalds's avatar
Linus Torvalds committed
1150
{
1151
1152
	bool clear = false;
	static int saved_console_loglevel = -1;
1153
	int error;
Linus Torvalds's avatar
Linus Torvalds committed
1154

1155
1156
1157
	error = check_syslog_permissions(type, from_file);
	if (error)
		goto out;
1158
1159

	error = security_syslog(type);
Linus Torvalds's avatar
Linus Torvalds committed
1160
1161
1162
1163
	if (error)
		return error;

	switch (type) {
1164
	case SYSLOG_ACTION_CLOSE:	/* Close log */
Linus Torvalds's avatar
Linus Torvalds committed
1165
		break;
1166
	case SYSLOG_ACTION_OPEN:	/* Open log */
Linus Torvalds's avatar
Linus Torvalds committed
1167
		break;
1168
	case SYSLOG_ACTION_READ:	/* Read from log */
Linus Torvalds's avatar
Linus Torvalds committed
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
		error = -EINVAL;
		if (!buf || len < 0)
			goto out;
		error = 0;
		if (!len)
			goto out;
		if (!access_ok(VERIFY_WRITE, buf, len)) {
			error = -EFAULT;
			goto out;
		}
1179
		error = wait_event_interruptible(log_wait,
1180
						 syslog_seq != log_next_seq);
1181
		if (error)
Linus Torvalds's avatar
Linus Torvalds committed
1182
			goto out;
1183
		error = syslog_print(buf, len);
Linus Torvalds's avatar
Linus Torvalds committed
1184
		break;
1185
1186
	/* Read/clear last kernel messages */
	case SYSLOG_ACTION_READ_CLEAR:
1187
		clear = true;
Linus Torvalds's avatar
Linus Torvalds committed
1188
		/* FALL THRU */
1189
1190
	/* Read last kernel messages */
	case SYSLOG_ACTION_READ_ALL:
Linus Torvalds's avatar
Linus Torvalds committed
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
		error = -EINVAL;
		if (!buf || len < 0)
			goto out;
		error = 0;
		if (!len)
			goto out;
		if (!access_ok(VERIFY_WRITE, buf, len)) {
			error = -EFAULT;
			goto out;
		}
1201
		error = syslog_print_all(buf, len, clear);
Linus Torvalds's avatar
Linus Torvalds committed
1202
		break;
1203
1204
	/* Clear ring buffer */
	case SYSLOG_ACTION_CLEAR:
1205
		syslog_print_all(NULL, 0, true);
1206
		break;
1207
1208
	/* Disable logging to console */
	case SYSLOG_ACTION_CONSOLE_OFF:
1209
1210
		if (saved_console_loglevel == -1)
			saved_console_loglevel = console_loglevel;
Linus Torvalds's avatar
Linus Torvalds committed
1211
1212
		console_loglevel = minimum_console_loglevel;
		break;
1213
1214
	/* Enable logging to console */
	case SYSLOG_ACTION_CONSOLE_ON:
1215
1216
1217
1218
		if (saved_console_loglevel != -1) {
			console_loglevel = saved_console_loglevel;
			saved_console_loglevel = -1;
		}
Linus Torvalds's avatar
Linus Torvalds committed
1219
		break;
1220
1221
	/* Set level of messages printed to console */
	case SYSLOG_ACTION_CONSOLE_LEVEL:
Linus Torvalds's avatar
Linus Torvalds committed
1222
1223
1224
1225
1226
1227
		error = -EINVAL;
		if (len < 1 || len > 8)
			goto out;
		if (len < minimum_console_loglevel)
			len = minimum_console_loglevel;
		console_loglevel = len;
1228
1229
		/* Implicitly re-enable logging to console */
		saved_console_loglevel = -1;
Linus Torvalds's avatar
Linus Torvalds committed
1230
1231
		error = 0;
		break;
1232
1233
	/* Number of chars in the log buffer */
	case SYSLOG_ACTION_SIZE_UNREAD:
1234
1235
1236
1237
1238
		raw_spin_lock_irq(&logbuf_lock);
		if (syslog_seq < log_first_seq) {
			/* messages are gone, move to first one */
			syslog_seq = log_first_seq;
			syslog_idx = log_first_idx;
1239
			syslog_prev = 0;
1240
			syslog_partial = 0;
1241
1242
1243
1244
1245
1246
1247
1248
1249
		}
		if (from_file) {
			/*
			 * Short-cut for poll(/"proc/kmsg") which simply checks
			 * for pending data, not the size; return the count of
			 * records, not the length.
			 */
			error = log_next_idx - syslog_idx;
		} else {
1250
1251
1252
			u64 seq = syslog_seq;
			u32 idx = syslog_idx;
			enum log_flags prev = syslog_prev;
1253
1254
1255

			error = 0;
			while (seq < log_next_seq) {
1256
				struct printk_log *msg = log_from_idx(idx);
1257

1258
				error += msg_print_text(msg, prev, true, NULL, 0);
1259
1260
				idx = log_next(idx);
				seq++;
1261
				prev = msg->flags;
1262
			}
1263
			error -= syslog_partial;
1264
1265
		}
		raw_spin_unlock_irq(&logbuf_lock);
Linus Torvalds's avatar
Linus Torvalds committed
1266
		break;
1267
1268
	/* Size of the log buffer */
	case SYSLOG_ACTION_SIZE_BUFFER:
Linus Torvalds's avatar
Linus Torvalds committed
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
		error = log_buf_len;
		break;
	default:
		error = -EINVAL;
		break;
	}
out:
	return error;
}

1279
SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
Linus Torvalds's avatar
Linus Torvalds committed
1280
{
1281
	return do_syslog(type, buf, len, SYSLOG_FROM_READER);
Linus Torvalds's avatar
Linus Torvalds committed
1282
1283
1284
1285
1286
}

/*
 * Call the console drivers, asking them to write out
 * log_buf[start] to log_buf[end - 1].
1287
 * The console_lock must be held.
Linus Torvalds's avatar
Linus Torvalds committed
1288
 */
1289
static void call_console_drivers(int level, const char *text, size_t len)
Linus Torvalds's avatar
Linus Torvalds committed
1290
{
1291
	struct console *con;
Linus Torvalds's avatar
Linus Torvalds committed
1292

1293
	trace_console(text, len);
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311

	if (level >= console_loglevel && !ignore_loglevel)
		return;
	if (!console_drivers)
		return;

	for_each_console(con) {
		if (exclusive_console && con != exclusive_console)
			continue;
		if (!(con->flags & CON_ENABLED))
			continue;
		if (!con->write)
			continue;
		if (!cpu_online(smp_processor_id()) &&
		    !(con->flags & CON_ANYTIME))
			continue;
		con->write(con, text, len);
	}
Linus Torvalds's avatar
Linus Torvalds committed
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
}

/*
 * Zap console related locks when oopsing. Only zap at most once
 * every 10 seconds, to leave time for slow consoles to print a
 * full oops.
 */
static void zap_locks(void)
{
	static unsigned long oops_timestamp;

	if (time_after_eq(jiffies, oops_timestamp) &&
1324
			!time_after(jiffies, oops_timestamp + 30 * HZ))
Linus Torvalds's avatar
Linus Torvalds committed
1325
1326
1327
1328
		return;

	oops_timestamp = jiffies;

1329
	debug_locks_off();
Linus Torvalds's avatar
Linus Torvalds committed
1330
	/* If a crash is occurring, make sure we can't deadlock */
1331
	raw_spin_lock_init(&logbuf_lock);
Linus Torvalds's avatar
Linus Torvalds committed
1332
	/* And make sure that we print immediately */
1333
	sema_init(&console_sem, 1);
Linus Torvalds's avatar
Linus Torvalds committed
1334
1335
}