printk.c 75.8 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
int console_printk[4] = {
58
	CONSOLE_LOGLEVEL_DEFAULT,	/* console_loglevel */
Linus Torvalds's avatar
Linus Torvalds committed
59
	DEFAULT_MESSAGE_LOGLEVEL,	/* default_message_loglevel */
60
61
	CONSOLE_LOGLEVEL_MIN,		/* minimum_console_loglevel */
	CONSOLE_LOGLEVEL_DEFAULT,	/* default_console_loglevel */
Linus Torvalds's avatar
Linus Torvalds committed
62
63
};

64
65
66
/* Deferred messaged from sched code are marked by this special level */
#define SCHED_MESSAGE_LOGLEVEL -2

Linus Torvalds's avatar
Linus Torvalds committed
67
/*
68
 * Low level drivers may need that to know if they can schedule in
Linus Torvalds's avatar
Linus Torvalds committed
69
70
71
72
73
74
75
76
77
78
 * 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.
 */
79
static DEFINE_SEMAPHORE(console_sem);
Linus Torvalds's avatar
Linus Torvalds committed
80
struct console *console_drivers;
Ingo Molnar's avatar
Ingo Molnar committed
81
82
EXPORT_SYMBOL_GPL(console_drivers);

83
84
85
86
87
88
#ifdef CONFIG_LOCKDEP
static struct lockdep_map console_lock_dep_map = {
	.name = "console_lock"
};
#endif

89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
/*
 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
 * macros instead of functions so that _RET_IP_ contains useful information.
 */
#define down_console_sem() do { \
	down(&console_sem);\
	mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
} while (0)

static int __down_trylock_console_sem(unsigned long ip)
{
	if (down_trylock(&console_sem))
		return 1;
	mutex_acquire(&console_lock_dep_map, 0, 1, ip);
	return 0;
}
#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)

#define up_console_sem() do { \
	mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
	up(&console_sem);\
} while (0)

Linus Torvalds's avatar
Linus Torvalds committed
112
113
114
115
116
117
118
119
/*
 * 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
 */
120
static int console_locked, console_suspended;
Linus Torvalds's avatar
Linus Torvalds committed
121

122
123
124
125
126
/*
 * 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
127
128
129
130
131
132
133
/*
 *	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
134

Linus Torvalds's avatar
Linus Torvalds committed
135
136
static int selected_console = -1;
static int preferred_console = -1;
137
138
int console_set_on_cmdline;
EXPORT_SYMBOL(console_set_on_cmdline);
Linus Torvalds's avatar
Linus Torvalds committed
139
140
141
142

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

143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
/*
 * 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.
 *
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
 * 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
 *
195
 * The 'struct printk_log' buffer header must never be directly exported to
196
197
198
199
200
201
202
203
204
205
206
207
 * 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.
208
209
 */

210
enum log_flags {
211
212
213
214
	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 */
215
216
};

217
struct printk_log {
218
219
220
221
	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 */
222
223
224
	u8 facility;		/* syslog facility */
	u8 flags:5;		/* internal record flags */
	u8 level:3;		/* syslog level */
225
226
227
};

/*
228
229
230
 * The logbuf_lock protects kmsg buffer, indices, counters.  This can be taken
 * within the scheduler's rq lock. It must be released before calling
 * console_unlock() or anything else that might wake up a process.
231
232
 */
static DEFINE_RAW_SPINLOCK(logbuf_lock);
233

234
#ifdef CONFIG_PRINTK
235
DECLARE_WAIT_QUEUE_HEAD(log_wait);
236
237
238
/* the next printk record to read by syslog(READ) or /proc/kmsg */
static u64 syslog_seq;
static u32 syslog_idx;
239
static enum log_flags syslog_prev;
240
static size_t syslog_partial;
241
242
243
244
245
246
247
248
249

/* 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;

250
251
252
253
254
/* the next printk record to write to the console */
static u64 console_seq;
static u32 console_idx;
static enum log_flags console_prev;

255
256
257
258
/* the next printk record to read after the last 'clear' command */
static u64 clear_seq;
static u32 clear_idx;

259
260
#define PREFIX_MAX		32
#define LOG_LINE_MAX		1024 - PREFIX_MAX
261
262

/* record buffer */
263
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
264
265
#define LOG_ALIGN 4
#else
266
#define LOG_ALIGN __alignof__(struct printk_log)
267
#endif
268
#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
269
#define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
270
static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
271
272
273
static char *log_buf = __log_buf;
static u32 log_buf_len = __LOG_BUF_LEN;

274
/* human readable text of the record */
275
static char *log_text(const struct printk_log *msg)
276
{
277
	return (char *)msg + sizeof(struct printk_log);
278
279
280
}

/* optional key/value pair dictionary attached to the record */
281
static char *log_dict(const struct printk_log *msg)
282
{
283
	return (char *)msg + sizeof(struct printk_log) + msg->text_len;
284
285
286
}

/* get record by index; idx must point to valid msg */
287
static struct printk_log *log_from_idx(u32 idx)
288
{
289
	struct printk_log *msg = (struct printk_log *)(log_buf + idx);
290
291
292
293
294
295

	/*
	 * 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)
296
		return (struct printk_log *)log_buf;
297
298
299
300
301
302
	return msg;
}

/* get next record; idx must point to valid msg */
static u32 log_next(u32 idx)
{
303
	struct printk_log *msg = (struct printk_log *)(log_buf + idx);
304
305
306
307
308
309
310
311

	/* 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) {
312
		msg = (struct printk_log *)log_buf;
313
314
315
316
317
		return msg->len;
	}
	return idx + msg->len;
}

Petr Mladek's avatar
Petr Mladek committed
318
319
320
321
322
323
324
325
326
327
/*
 * 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)
328
329
330
{
	u32 free;

Petr Mladek's avatar
Petr Mladek committed
331
	if (log_next_idx > log_first_idx || empty)
332
333
334
335
336
337
338
339
340
341
342
		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
343
static int log_make_free_space(u32 msg_size)
344
345
{
	while (log_first_seq < log_next_seq) {
Petr Mladek's avatar
Petr Mladek committed
346
347
		if (logbuf_has_space(msg_size, false))
			return 0;
348
349
350
351
		/* 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
352
353
354
355
356
357

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

	return -ENOMEM;
358
359
}

360
361
362
363
364
365
366
367
368
369
370
371
/* compute the message size including the padding bytes */
static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
{
	u32 size;

	size = sizeof(struct printk_log) + text_len + dict_len;
	*pad_len = (-size) & (LOG_ALIGN - 1);
	size += *pad_len;

	return size;
}

Petr Mladek's avatar
Petr Mladek committed
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
/*
 * Define how much of the log buffer we could take at maximum. The value
 * must be greater than two. Note that only half of the buffer is available
 * when the index points to the middle.
 */
#define MAX_LOG_TAKE_PART 4
static const char trunc_msg[] = "<truncated>";

static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
			u16 *dict_len, u32 *pad_len)
{
	/*
	 * The message should not take the whole buffer. Otherwise, it might
	 * get removed too soon.
	 */
	u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
	if (*text_len > max_text_len)
		*text_len = max_text_len;
	/* enable the warning message */
	*trunc_msg_len = strlen(trunc_msg);
	/* disable the "dict" completely */
	*dict_len = 0;
	/* compute the size again, count also the warning message */
	return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
}

398
/* insert record into the buffer, discard old ones, update heads */
399
400
401
402
static int log_store(int facility, int level,
		     enum log_flags flags, u64 ts_nsec,
		     const char *dict, u16 dict_len,
		     const char *text, u16 text_len)
403
{
404
	struct printk_log *msg;
405
	u32 size, pad_len;
Petr Mladek's avatar
Petr Mladek committed
406
	u16 trunc_msg_len = 0;
407
408

	/* number of '\0' padding bytes to next message */
409
	size = msg_used_size(text_len, dict_len, &pad_len);
410

Petr Mladek's avatar
Petr Mladek committed
411
412
413
414
415
416
	if (log_make_free_space(size)) {
		/* truncate the message if it is too long for empty buffer */
		size = truncate_msg(&text_len, &trunc_msg_len,
				    &dict_len, &pad_len);
		/* survive when the log buffer is too small for trunc_msg */
		if (log_make_free_space(size))
417
			return 0;
Petr Mladek's avatar
Petr Mladek committed
418
	}
419

420
	if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
421
422
423
424
425
		/*
		 * 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.
		 */
426
		memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
427
428
429
430
		log_next_idx = 0;
	}

	/* fill message */
431
	msg = (struct printk_log *)(log_buf + log_next_idx);
432
433
	memcpy(log_text(msg), text, text_len);
	msg->text_len = text_len;
Petr Mladek's avatar
Petr Mladek committed
434
435
436
437
	if (trunc_msg_len) {
		memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
		msg->text_len += trunc_msg_len;
	}
438
439
	memcpy(log_dict(msg), dict, dict_len);
	msg->dict_len = dict_len;
440
441
442
443
444
445
446
	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();
447
	memset(log_dict(msg) + dict_len, 0, pad_len);
448
	msg->len = size;
449
450
451
452

	/* insert message */
	log_next_idx += msg->len;
	log_next_seq++;
453
454

	return msg->text_len;
455
}
456

457
458
459
460
461
462
463
464
465
466
467
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
#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);
}


504
505
506
507
/* /dev/kmsg - userspace message inject/listen interface */
struct devkmsg_user {
	u64 seq;
	u32 idx;
508
	enum log_flags prev;
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
	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++) {
531
532
		if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
			ret = -EFAULT;
533
			goto out;
534
		}
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
		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;
573
	struct printk_log *msg;
574
	u64 ts_usec;
575
	size_t i;
576
	char cont = '-';
577
578
579
580
581
582
	size_t len;
	ssize_t ret;

	if (!user)
		return -EBADF;

583
584
585
	ret = mutex_lock_interruptible(&user->lock);
	if (ret)
		return ret;
586
	raw_spin_lock_irq(&logbuf_lock);
587
588
589
	while (user->seq == log_next_seq) {
		if (file->f_flags & O_NONBLOCK) {
			ret = -EAGAIN;
590
			raw_spin_unlock_irq(&logbuf_lock);
591
592
593
			goto out;
		}

594
		raw_spin_unlock_irq(&logbuf_lock);
595
596
597
598
		ret = wait_event_interruptible(log_wait,
					       user->seq != log_next_seq);
		if (ret)
			goto out;
599
		raw_spin_lock_irq(&logbuf_lock);
600
601
602
603
604
605
606
	}

	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;
607
		raw_spin_unlock_irq(&logbuf_lock);
608
609
610
611
		goto out;
	}

	msg = log_from_idx(user->idx);
612
613
	ts_usec = msg->ts_nsec;
	do_div(ts_usec, 1000);
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632

	/*
	 * 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;
633
634
635

	/* escape non-printable characters */
	for (i = 0; i < msg->text_len; i++) {
636
		unsigned char c = log_text(msg)[i];
637

638
		if (c < ' ' || c >= 127 || c == '\\')
639
640
641
642
643
644
645
646
647
648
			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++) {
649
			unsigned char c = log_dict(msg)[i];
650
651
652
653
654
655
656
657
658
659
660
661

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

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

662
			if (c < ' ' || c >= 127 || c == '\\') {
663
664
665
666
667
668
669
670
671
672
673
				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++;
674
	raw_spin_unlock_irq(&logbuf_lock);
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700

	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;

701
	raw_spin_lock_irq(&logbuf_lock);
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
	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;
	}
725
	raw_spin_unlock_irq(&logbuf_lock);
726
727
728
729
730
731
732
733
734
735
736
737
738
	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);

739
	raw_spin_lock_irq(&logbuf_lock);
740
741
742
743
	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;
744
745
		else
			ret = POLLIN|POLLRDNORM;
746
	}
747
	raw_spin_unlock_irq(&logbuf_lock);
748
749
750
751
752
753
754
755
756
757
758
759
760

	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;

761
762
	err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
				       SYSLOG_FROM_READER);
763
764
765
766
767
768
769
770
771
	if (err)
		return err;

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

	mutex_init(&user->lock);

772
	raw_spin_lock_irq(&logbuf_lock);
773
774
	user->idx = log_first_idx;
	user->seq = log_first_seq;
775
	raw_spin_unlock_irq(&logbuf_lock);
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801

	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,
};

802
803
#ifdef CONFIG_KEXEC
/*
804
 * This appends the listed symbols to /proc/vmcore
805
 *
806
 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
807
808
809
810
811
812
813
814
 * 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);
815
816
	VMCOREINFO_SYMBOL(log_first_idx);
	VMCOREINFO_SYMBOL(log_next_idx);
817
	/*
818
	 * Export struct printk_log size and field offsets. User space tools can
819
820
	 * parse it and detect any changes to structure down the line.
	 */
821
822
823
824
825
	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);
826
827
828
}
#endif

829
830
831
/* requested log_buf_len from kernel cmdline */
static unsigned long __initdata new_log_buf_len;

832
833
/* we practice scaling the ring buffer by powers of 2 */
static void __init log_buf_len_update(unsigned size)
Linus Torvalds's avatar
Linus Torvalds committed
834
835
836
{
	if (size)
		size = roundup_pow_of_two(size);
837
838
	if (size > log_buf_len)
		new_log_buf_len = size;
839
840
841
842
843
844
845
846
}

/* save requested log_buf_len since it's too early to process it */
static int __init log_buf_len_setup(char *str)
{
	unsigned size = memparse(str, &str);

	log_buf_len_update(size);
847
848

	return 0;
Linus Torvalds's avatar
Linus Torvalds committed
849
}
850
851
early_param("log_buf_len", log_buf_len_setup);

852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
static void __init log_buf_add_cpu(void)
{
	unsigned int cpu_extra;

	/*
	 * archs should set up cpu_possible_bits properly with
	 * set_cpu_possible() after setup_arch() but just in
	 * case lets ensure this is valid.
	 */
	if (num_possible_cpus() == 1)
		return;

	cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;

	/* by default this will only continue through for large > 64 CPUs */
	if (cpu_extra <= __LOG_BUF_LEN / 2)
		return;

	pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
		__LOG_CPU_MAX_BUF_LEN);
	pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
		cpu_extra);
	pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);

	log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
}

879
880
881
882
883
884
void __init setup_log_buf(int early)
{
	unsigned long flags;
	char *new_log_buf;
	int free;

885
886
887
888
889
890
	if (log_buf != __log_buf)
		return;

	if (!early && !new_log_buf_len)
		log_buf_add_cpu();

891
892
	if (!new_log_buf_len)
		return;
Linus Torvalds's avatar
Linus Torvalds committed
893

894
	if (early) {
895
		new_log_buf =
896
			memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
897
	} else {
898
899
		new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
							  LOG_ALIGN);
900
901
902
903
904
905
906
907
	}

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

908
	raw_spin_lock_irqsave(&logbuf_lock, flags);
909
910
911
	log_buf_len = new_log_buf_len;
	log_buf = new_log_buf;
	new_log_buf_len = 0;
912
913
	free = __LOG_BUF_LEN - log_next_idx;
	memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
914
	raw_spin_unlock_irqrestore(&logbuf_lock, flags);
915

916
	pr_info("log_buf_len: %d bytes\n", log_buf_len);
917
918
919
	pr_info("early log buf free: %d(%d%%)\n",
		free, (free * 100) / __LOG_BUF_LEN);
}
Linus Torvalds's avatar
Linus Torvalds committed
920

921
922
923
924
925
static bool __read_mostly ignore_loglevel;

static int __init ignore_loglevel_setup(char *str)
{
	ignore_loglevel = 1;
926
	pr_info("debug: ignoring loglevel setting.\n");
927
928
929
930
931
932
933
934
935

	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
936
937
#ifdef CONFIG_BOOT_PRINTK_DELAY

938
static int boot_delay; /* msecs delay after each printk during bootup */
939
static unsigned long long loops_per_msec;	/* based on boot_delay */
Randy Dunlap's avatar
Randy Dunlap committed
940
941
942
943
944
945
946
947
948
949
950
951

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;

952
953
954
	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);
955
	return 0;
Randy Dunlap's avatar
Randy Dunlap committed
956
}
957
early_param("boot_delay", boot_delay_setup);
Randy Dunlap's avatar
Randy Dunlap committed
958

959
static void boot_delay_msec(int level)
Randy Dunlap's avatar
Randy Dunlap committed
960
961
962
963
{
	unsigned long long k;
	unsigned long timeout;

964
965
	if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
		|| (level >= console_loglevel && !ignore_loglevel)) {
Randy Dunlap's avatar
Randy Dunlap committed
966
		return;
967
	}
Randy Dunlap's avatar
Randy Dunlap committed
968

969
	k = (unsigned long long)loops_per_msec * boot_delay;
Randy Dunlap's avatar
Randy Dunlap committed
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985

	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
986
static inline void boot_delay_msec(int level)
Randy Dunlap's avatar
Randy Dunlap committed
987
988
989
990
{
}
#endif

991
992
993
994
995
996
997
#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);

998
999
1000
1001
1002
1003
1004
static size_t print_time(u64 ts, char *buf)
{
	unsigned long rem_nsec;

	if (!printk_time)
		return 0;

1005
1006
	rem_nsec = do_div(ts, 1000000000);

1007
	if (!buf)
1008
		return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1009
1010
1011
1012
1013

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

1014
static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1015
{
1016
	size_t len = 0;
1017
	unsigned int prefix = (msg->facility << 3) | msg->level;
1018

1019
1020
	if (syslog) {
		if (buf) {
1021
			len += sprintf(buf, "<%u>", prefix);
1022
1023
		} else {
			len += 3;
1024
1025
1026
1027
1028
			if (prefix > 999)
				len += 3;
			else if (prefix > 99)
				len += 2;
			else if (prefix > 9)
1029
1030
1031
				len++;
		}
	}
1032

1033
	len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1034
	return len;
1035
1036
}

1037
static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1038
			     bool syslog, char *buf, size_t size)
1039
{
1040
1041
	const char *text = log_text(msg);
	size_t text_size = msg->text_len;
1042
1043
	bool prefix = true;
	bool newline = true;
1044
1045
	size_t len = 0;

1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
	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;
	}

1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
	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;
		}
1068

1069
1070
		if (buf) {
			if (print_prefix(msg, syslog, NULL) +
1071
			    text_len + 1 >= size - len)
1072
				break;
1073

1074
1075
			if (prefix)
				len += print_prefix(msg, syslog, buf + len);
1076
1077
			memcpy(buf + len, text, text_len);
			len += text_len;
1078
1079
			if (next || newline)
				buf[len++] = '\n';
1080
1081
		} else {
			/* SYSLOG_ACTION_* buffer size only calculation */
1082
1083
1084
1085
1086
			if (prefix)
				len += print_prefix(msg, syslog, NULL);
			len += text_len;
			if (next || newline)
				len++;
1087
		}
1088

1089
		prefix = true;
1090
1091
		text = next;
	} while (text);
1092
1093
1094
1095
1096
1097
1098

	return len;
}

static int syslog_print(char __user *buf, int size)
{
	char *text;
1099
	struct printk_log *msg;
1100
	int len = 0;
1101

1102
	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1103
1104
1105
	if (!text)
		return -ENOMEM;

1106
1107
	while (size > 0) {
		size_t n;
1108
		size_t skip;
1109
1110
1111
1112
1113
1114

		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;
1115
			syslog_prev = 0;
1116
			syslog_partial = 0;
1117
1118
1119
1120
1121
		}
		if (syslog_seq == log_next_seq) {
			raw_spin_unlock_irq(&logbuf_lock);
			break;
		}
1122
1123

		skip = syslog_partial;
1124
		msg = log_from_idx(syslog_idx);
1125
1126
		n = msg_print_text(msg, syslog_prev, true, text,
				   LOG_LINE_MAX + PREFIX_MAX);
1127
1128
		if (n - syslog_partial <= size) {
			/* message fits into buffer, move forward */
1129
1130
			syslog_idx = log_next(syslog_idx);
			syslog_seq++;
1131
			syslog_prev = msg->flags;
1132
1133
1134
1135
1136
1137
			n -= syslog_partial;
			syslog_partial = 0;
		} else if (!len){
			/* partial read(), remember position */
			n = size;
			syslog_partial += n;
1138
1139
1140
1141
1142
1143
1144
		} else
			n = 0;
		raw_spin_unlock_irq(&logbuf_lock);

		if (!n)
			break;

1145
		if (copy_to_user(buf, text + skip, n)) {
1146
1147
1148
1149
			if (!len)
				len = -EFAULT;
			break;
		}
1150
1151
1152
1153

		len += n;
		size -= n;
		buf += n;
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
	}

	kfree(text);
	return len;
}

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

1165
	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1166
1167
1168
1169
1170
1171
1172
1173
	if (!text)
		return -ENOMEM;

	raw_spin_lock_irq(&logbuf_lock);
	if (buf) {
		u64 next_seq;
		u64 seq;
		u32 idx;
1174
		enum log_flags prev;
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184

		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.
1185
		 */
1186
1187
		seq = clear_seq;
		idx = clear_idx;
1188
		prev = 0;
1189
		while (seq < log_next_seq) {
1190
			struct printk_log *msg = log_from_idx(idx);
1191

1192
			len += msg_print_text(msg, prev, true, NULL, 0);
1193
			prev = msg->flags;
1194
1195
1196
			idx = log_next(idx);
			seq++;
		}
1197
1198

		/* move first record forward until length fits into the buffer */
1199
1200
		seq = clear_seq;
		idx = clear_idx;
1201
		prev = 0;
1202
		while (len > size && seq < log_next_seq) {
1203
			struct printk_log *msg = log_from_idx(idx);
1204

1205
			len -= msg_print_text(msg, prev, true, NULL, 0);
1206
			prev = msg->flags;
1207
1208
1209
1210
			idx = log_next(idx);
			seq++;
		}

1211
		/* last message fitting into this dump */
1212
1213
1214
1215
		next_seq = log_next_seq;

		len = 0;
		while (len >= 0 && seq < next_seq) {
1216
			struct printk_log *msg = log_from_idx(idx);
1217
1218
			int textlen;

1219
1220
			textlen = msg_print_text(msg, prev, true, text,
						 LOG_LINE_MAX + PREFIX_MAX);
1221
1222
1223
1224
1225
1226
			if (textlen < 0) {
				len = textlen;
				break;
			}
			idx = log_next(idx);
			seq++;
1227
			prev = msg->flags;
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239

			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;
1240
				prev = 0;
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
			}
		}
	}

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

	kfree(text);
	return len;
}

1255
int do_syslog(int type, char __user *buf, int len, bool from_file)
Linus Torvalds's avatar
Linus Torvalds committed
1256
{
1257
1258
	bool clear = false;
	static int saved_console_loglevel = -1;
1259
	int error;
Linus Torvalds's avatar
Linus Torvalds committed
1260

1261
1262
1263
	error = check_syslog_permissions(type, from_file);
	if (error)
		goto out;
1264
1265

	error = security_syslog(type);
Linus Torvalds's avatar
Linus Torvalds committed
1266
1267
1268
1269
	if (error)
		return error;

	switch (type) {
1270
	case SYSLOG_ACTION_CLOSE:	/* Close log */
Linus Torvalds's avatar
Linus Torvalds committed
1271
		break;
1272
	case SYSLOG_ACTION_OPEN:	/* Open log */
Linus Torvalds's avatar
Linus Torvalds committed
1273
		break;
1274
	case SYSLOG_ACTION_READ:	/* Read from log */
Linus Torvalds's avatar
Linus Torvalds committed
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
		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;
		}
1285
		error = wait_event_interruptible(log_wait,
1286
						 syslog_seq != log_next_seq);
1287
		if (error)
Linus Torvalds's avatar
Linus Torvalds committed
1288
			goto out;
1289
		error = syslog_print(buf, len);
Linus Torvalds's avatar
Linus Torvalds committed
1290
		break;
1291
1292
	/* Read/clear last kernel messages */
	case SYSLOG_ACTION_READ_CLEAR:
1293
		clear = true;
Linus Torvalds's avatar
Linus Torvalds committed
1294
		/* FALL THRU */
1295
1296
	/* Read last kernel messages */
	case SYSLOG_ACTION_READ_ALL:
Linus Torvalds's avatar
Linus Torvalds committed
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
		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;
		}
1307
		error = syslog_print_all(buf, len, clear);
Linus Torvalds's avatar
Linus Torvalds committed
1308
		break;
1309
1310
	/* Clear ring buffer */
	case SYSLOG_ACTION_CLEAR:
1311
		syslog_print_all(NULL, 0, true);
1312
		break;
1313
1314
	/* Disable logging to console */
	case SYSLOG_ACTION_CONSOLE_OFF:
1315
1316
		if (saved_console_loglevel == -1)
			saved_console_loglevel = console_loglevel;
Linus Torvalds's avatar
Linus Torvalds committed
1317
1318
		console_loglevel = minimum_console_loglevel;
		break;
1319
1320
	/* Enable logging to console */
	case SYSLOG_ACTION_CONSOLE_ON:
1321
1322
1323
1324
		if (saved_console_loglevel != -1) {
			console_loglevel = saved_console_loglevel;
			saved_console_loglevel = -1;
		}
Linus Torvalds's avatar
Linus Torvalds committed
1325
		break;
1326
1327
	/* Set level of messages printed to console */
	case SYSLOG_ACTION_CONSOLE_LEVEL:
Linus Torvalds's avatar
Linus Torvalds committed
1328
1329
1330
1331
1332
1333
		error = -EINVAL;
		if (len < 1 || len > 8)
			goto out;
		if (len < minimum_console_loglevel)
			len = minimum_console_loglevel;
		console_loglevel = len;
1334
1335
		/* Implicitly re-enable logging to console */
		saved_console_loglevel = -1;
Linus Torvalds's avatar
Linus Torvalds committed
1336
1337
		error = 0;
		break;
1338
1339
	/* Number of chars in the log buffer */
	case SYSLOG_ACTION_SIZE_UNREAD:
1340
1341
1342
1343
1344
		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;
1345
			syslog_prev = 0;
1346
			syslog_partial = 0;
1347
1348
1349
1350
1351
1352
1353
		}
		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.
			 */
1354
			error = log_next_seq - syslog_seq;