printk.c 80 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
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/security.h>
#include <linux/bootmem.h>
33
#include <linux/memblock.h>
Linus Torvalds's avatar
Linus Torvalds committed
34
#include <linux/syscalls.h>
35
#include <linux/crash_core.h>
36
#include <linux/kdb.h>
37
#include <linux/ratelimit.h>
38
#include <linux/kmsg_dump.h>
39
#include <linux/syslog.h>
40
41
#include <linux/cpu.h>
#include <linux/notifier.h>
42
#include <linux/rculist.h>
43
#include <linux/poll.h>
44
#include <linux/irq_work.h>
45
#include <linux/utsname.h>
Alex Elder's avatar
Alex Elder committed
46
#include <linux/ctype.h>
47
#include <linux/uio.h>
48
#include <linux/sched/clock.h>
49
#include <linux/sched/debug.h>
50
#include <linux/sched/task_stack.h>
Linus Torvalds's avatar
Linus Torvalds committed
51

52
#include <linux/uaccess.h>
53
#include <asm/sections.h>
Linus Torvalds's avatar
Linus Torvalds committed
54

55
56
57
#define CREATE_TRACE_POINTS
#include <trace/events/printk.h>

Joe Perches's avatar
Joe Perches committed
58
#include "console_cmdline.h"
59
#include "braille.h"
60
#include "internal.h"
Joe Perches's avatar
Joe Perches committed
61

Linus Torvalds's avatar
Linus Torvalds committed
62
int console_printk[4] = {
63
	CONSOLE_LOGLEVEL_DEFAULT,	/* console_loglevel */
64
	MESSAGE_LOGLEVEL_DEFAULT,	/* default_message_loglevel */
65
66
	CONSOLE_LOGLEVEL_MIN,		/* minimum_console_loglevel */
	CONSOLE_LOGLEVEL_DEFAULT,	/* default_console_loglevel */
Linus Torvalds's avatar
Linus Torvalds committed
67
68
69
};

/*
70
 * Low level drivers may need that to know if they can schedule in
Linus Torvalds's avatar
Linus Torvalds committed
71
72
73
74
75
76
77
78
79
80
 * 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.
 */
81
static DEFINE_SEMAPHORE(console_sem);
Linus Torvalds's avatar
Linus Torvalds committed
82
struct console *console_drivers;
Ingo Molnar's avatar
Ingo Molnar committed
83
84
EXPORT_SYMBOL_GPL(console_drivers);

85
86
87
88
89
90
#ifdef CONFIG_LOCKDEP
static struct lockdep_map console_lock_dep_map = {
	.name = "console_lock"
};
#endif

91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
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
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
enum devkmsg_log_bits {
	__DEVKMSG_LOG_BIT_ON = 0,
	__DEVKMSG_LOG_BIT_OFF,
	__DEVKMSG_LOG_BIT_LOCK,
};

enum devkmsg_log_masks {
	DEVKMSG_LOG_MASK_ON             = BIT(__DEVKMSG_LOG_BIT_ON),
	DEVKMSG_LOG_MASK_OFF            = BIT(__DEVKMSG_LOG_BIT_OFF),
	DEVKMSG_LOG_MASK_LOCK           = BIT(__DEVKMSG_LOG_BIT_LOCK),
};

/* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
#define DEVKMSG_LOG_MASK_DEFAULT	0

static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;

static int __control_devkmsg(char *str)
{
	if (!str)
		return -EINVAL;

	if (!strncmp(str, "on", 2)) {
		devkmsg_log = DEVKMSG_LOG_MASK_ON;
		return 2;
	} else if (!strncmp(str, "off", 3)) {
		devkmsg_log = DEVKMSG_LOG_MASK_OFF;
		return 3;
	} else if (!strncmp(str, "ratelimit", 9)) {
		devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
		return 9;
	}
	return -EINVAL;
}

static int __init control_devkmsg(char *str)
{
	if (__control_devkmsg(str) < 0)
		return 1;

	/*
	 * Set sysctl string accordingly:
	 */
	if (devkmsg_log == DEVKMSG_LOG_MASK_ON) {
		memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE);
		strncpy(devkmsg_log_str, "on", 2);
	} else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF) {
		memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE);
		strncpy(devkmsg_log_str, "off", 3);
	}
	/* else "ratelimit" which is set by default. */

	/*
	 * Sysctl cannot change it anymore. The kernel command line setting of
	 * this parameter is to force the setting to be permanent throughout the
	 * runtime of the system. This is a precation measure against userspace
	 * trying to be a smarta** and attempting to change it up on us.
	 */
	devkmsg_log |= DEVKMSG_LOG_MASK_LOCK;

	return 0;
}
__setup("printk.devkmsg=", control_devkmsg);

char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit";

int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
			      void __user *buffer, size_t *lenp, loff_t *ppos)
{
	char old_str[DEVKMSG_STR_MAX_SIZE];
	unsigned int old;
	int err;

	if (write) {
		if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK)
			return -EINVAL;

		old = devkmsg_log;
		strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE);
	}

	err = proc_dostring(table, write, buffer, lenp, ppos);
	if (err)
		return err;

	if (write) {
		err = __control_devkmsg(devkmsg_log_str);

		/*
		 * Do not accept an unknown string OR a known string with
		 * trailing crap...
		 */
		if (err < 0 || (err + 1 != *lenp)) {

			/* ... and restore old setting. */
			devkmsg_log = old;
			strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE);

			return -EINVAL;
		}
	}

	return 0;
}

196
197
198
199
200
201
202
203
204
205
206
207
/*
 * Number of registered extended console drivers.
 *
 * If extended consoles are present, in-kernel cont reassembly is disabled
 * and each fragment is stored as a separate log entry with proper
 * continuation flag so that every emitted message has full metadata.  This
 * doesn't change the result for regular consoles or /proc/kmsg.  For
 * /dev/kmsg, as long as the reader concatenates messages according to
 * consecutive continuation flags, the end result should be the same too.
 */
static int nr_ext_console_drivers;

208
209
210
211
212
213
214
215
216
217
218
/*
 * 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)
{
219
220
221
222
223
224
225
226
227
228
229
230
231
	int lock_failed;
	unsigned long flags;

	/*
	 * Here and in __up_console_sem() we need to be in safe mode,
	 * because spindump/WARN/etc from under console ->lock will
	 * deadlock in printk()->down_trylock_console_sem() otherwise.
	 */
	printk_safe_enter_irqsave(flags);
	lock_failed = down_trylock(&console_sem);
	printk_safe_exit_irqrestore(flags);

	if (lock_failed)
232
233
234
235
236
237
		return 1;
	mutex_acquire(&console_lock_dep_map, 0, 1, ip);
	return 0;
}
#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)

238
239
240
241
242
243
244
245
246
247
248
static void __up_console_sem(unsigned long ip)
{
	unsigned long flags;

	mutex_release(&console_lock_dep_map, 1, ip);

	printk_safe_enter_irqsave(flags);
	up(&console_sem);
	printk_safe_exit_irqrestore(flags);
}
#define up_console_sem() __up_console_sem(_RET_IP_)
249

Linus Torvalds's avatar
Linus Torvalds committed
250
251
252
253
/*
 * 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_
Alex Elder's avatar
Alex Elder committed
254
255
256
 * hold it and are racing, but it helps tracking those weird code
 * paths in the console code where we end up in places I want
 * locked without the console sempahore held).
Linus Torvalds's avatar
Linus Torvalds committed
257
 */
258
static int console_locked, console_suspended;
Linus Torvalds's avatar
Linus Torvalds committed
259

260
261
262
263
264
/*
 * 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
265
266
267
268
269
270
271
/*
 *	Array of consoles built from command line options (console=)
 */

#define MAX_CMDLINECONSOLES 8

static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
272
static int console_cmdline_cnt;
Joe Perches's avatar
Joe Perches committed
273

Linus Torvalds's avatar
Linus Torvalds committed
274
static int preferred_console = -1;
275
276
int console_set_on_cmdline;
EXPORT_SYMBOL(console_set_on_cmdline);
Linus Torvalds's avatar
Linus Torvalds committed
277
278
279
280

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

281
282
283
284
285
286
/*
 * 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
Alex Elder's avatar
Alex Elder committed
287
288
 * sequence numbers of these entries are maintained when messages are
 * stored.
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
 *
 * 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.
 *
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
 * 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
 *
333
 * The 'struct printk_log' buffer header must never be directly exported to
334
335
336
337
 * 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:
338
339
340
341
 *   "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
 *
 * Users of the export format should ignore possible additional values
 * separated by ',', and find the message after the ';' character.
342
343
344
345
 *
 * 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.
346
347
 */

348
enum log_flags {
349
350
351
352
	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 */
353
354
};

355
struct printk_log {
356
357
358
359
	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 */
360
361
362
	u8 facility;		/* syslog facility */
	u8 flags:5;		/* internal record flags */
	u8 level:3;		/* syslog level */
363
364
365
366
367
}
#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
__packed __aligned(4)
#endif
;
368
369

/*
370
371
372
 * 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.
373
 */
374
DEFINE_RAW_SPINLOCK(logbuf_lock);
375

376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
/*
 * Helper macros to lock/unlock logbuf_lock and switch between
 * printk-safe/unsafe modes.
 */
#define logbuf_lock_irq()				\
	do {						\
		printk_safe_enter_irq();		\
		raw_spin_lock(&logbuf_lock);		\
	} while (0)

#define logbuf_unlock_irq()				\
	do {						\
		raw_spin_unlock(&logbuf_lock);		\
		printk_safe_exit_irq();			\
	} while (0)

#define logbuf_lock_irqsave(flags)			\
	do {						\
		printk_safe_enter_irqsave(flags);	\
		raw_spin_lock(&logbuf_lock);		\
	} while (0)

#define logbuf_unlock_irqrestore(flags)		\
	do {						\
		raw_spin_unlock(&logbuf_lock);		\
		printk_safe_exit_irqrestore(flags);	\
	} while (0)

404
#ifdef CONFIG_PRINTK
405
DECLARE_WAIT_QUEUE_HEAD(log_wait);
406
407
408
/* the next printk record to read by syslog(READ) or /proc/kmsg */
static u64 syslog_seq;
static u32 syslog_idx;
409
static size_t syslog_partial;
410
411
412
413
414
415
416
417
418

/* 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;

419
420
421
422
/* the next printk record to write to the console */
static u64 console_seq;
static u32 console_idx;

423
424
425
426
/* the next printk record to read after the last 'clear' command */
static u64 clear_seq;
static u32 clear_idx;

427
#define PREFIX_MAX		32
Alex Elder's avatar
Alex Elder committed
428
#define LOG_LINE_MAX		(1024 - PREFIX_MAX)
429

430
431
432
#define LOG_LEVEL(v)		((v) & 0x07)
#define LOG_FACILITY(v)		((v) >> 3 & 0xff)

433
/* record buffer */
434
#define LOG_ALIGN __alignof__(struct printk_log)
435
#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
436
static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
437
438
439
static char *log_buf = __log_buf;
static u32 log_buf_len = __LOG_BUF_LEN;

440
441
442
443
444
445
446
447
448
449
450
451
/* Return log buffer address */
char *log_buf_addr_get(void)
{
	return log_buf;
}

/* Return log buffer size */
u32 log_buf_len_get(void)
{
	return log_buf_len;
}

452
/* human readable text of the record */
453
static char *log_text(const struct printk_log *msg)
454
{
455
	return (char *)msg + sizeof(struct printk_log);
456
457
458
}

/* optional key/value pair dictionary attached to the record */
459
static char *log_dict(const struct printk_log *msg)
460
{
461
	return (char *)msg + sizeof(struct printk_log) + msg->text_len;
462
463
464
}

/* get record by index; idx must point to valid msg */
465
static struct printk_log *log_from_idx(u32 idx)
466
{
467
	struct printk_log *msg = (struct printk_log *)(log_buf + idx);
468
469
470
471
472
473

	/*
	 * 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)
474
		return (struct printk_log *)log_buf;
475
476
477
478
479
480
	return msg;
}

/* get next record; idx must point to valid msg */
static u32 log_next(u32 idx)
{
481
	struct printk_log *msg = (struct printk_log *)(log_buf + idx);
482
483
484
485
486
487
488
489

	/* 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) {
490
		msg = (struct printk_log *)log_buf;
491
492
493
494
495
		return msg->len;
	}
	return idx + msg->len;
}

Petr Mladek's avatar
Petr Mladek committed
496
497
498
499
500
501
502
503
504
505
/*
 * 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)
506
507
508
{
	u32 free;

Petr Mladek's avatar
Petr Mladek committed
509
	if (log_next_idx > log_first_idx || empty)
510
511
512
513
514
515
516
517
518
519
520
		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
521
static int log_make_free_space(u32 msg_size)
522
{
523
524
	while (log_first_seq < log_next_seq &&
	       !logbuf_has_space(msg_size, false)) {
Alex Elder's avatar
Alex Elder committed
525
		/* drop old messages until we have enough contiguous space */
526
527
528
		log_first_idx = log_next(log_first_idx);
		log_first_seq++;
	}
Petr Mladek's avatar
Petr Mladek committed
529

530
531
532
533
534
	if (clear_seq < log_first_seq) {
		clear_seq = log_first_seq;
		clear_idx = log_first_idx;
	}

Petr Mladek's avatar
Petr Mladek committed
535
	/* sequence numbers are equal, so the log buffer is empty */
536
	if (logbuf_has_space(msg_size, log_first_seq == log_next_seq))
Petr Mladek's avatar
Petr Mladek committed
537
538
539
		return 0;

	return -ENOMEM;
540
541
}

542
543
544
545
546
547
548
549
550
551
552
553
/* 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
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
/*
 * 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);
}

580
/* insert record into the buffer, discard old ones, update heads */
581
582
583
584
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)
585
{
586
	struct printk_log *msg;
587
	u32 size, pad_len;
Petr Mladek's avatar
Petr Mladek committed
588
	u16 trunc_msg_len = 0;
589
590

	/* number of '\0' padding bytes to next message */
591
	size = msg_used_size(text_len, dict_len, &pad_len);
592

Petr Mladek's avatar
Petr Mladek committed
593
594
595
596
597
598
	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))
599
			return 0;
Petr Mladek's avatar
Petr Mladek committed
600
	}
601

602
	if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
603
604
605
606
607
		/*
		 * 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.
		 */
608
		memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
609
610
611
612
		log_next_idx = 0;
	}

	/* fill message */
613
	msg = (struct printk_log *)(log_buf + log_next_idx);
614
615
	memcpy(log_text(msg), text, text_len);
	msg->text_len = text_len;
Petr Mladek's avatar
Petr Mladek committed
616
617
618
619
	if (trunc_msg_len) {
		memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
		msg->text_len += trunc_msg_len;
	}
620
621
	memcpy(log_dict(msg), dict, dict_len);
	msg->dict_len = dict_len;
622
623
624
625
626
627
628
	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();
629
	memset(log_dict(msg) + dict_len, 0, pad_len);
630
	msg->len = size;
631
632
633
634

	/* insert message */
	log_next_idx += msg->len;
	log_next_seq++;
635
636

	return msg->text_len;
637
}
638

Alex Elder's avatar
Alex Elder committed
639
int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
640
641
642
643
644
645
646
647
648
649
650
651
652

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;
}

653
int check_syslog_permissions(int type, int source)
654
655
656
657
658
{
	/*
	 * If this is from /proc/kmsg and we've already opened it, then we've
	 * already done the capabilities checks at open time.
	 */
659
	if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
660
		goto ok;
661
662
663

	if (syslog_action_restricted(type)) {
		if (capable(CAP_SYSLOG))
664
			goto ok;
665
666
667
668
669
670
671
672
673
		/*
		 * 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));
674
			goto ok;
675
676
677
		}
		return -EPERM;
	}
678
ok:
679
680
	return security_syslog(type);
}
Geliang Tang's avatar
Geliang Tang committed
681
EXPORT_SYMBOL_GPL(check_syslog_permissions);
682

683
684
685
686
687
static void append_char(char **pp, char *e, char c)
{
	if (*pp < e)
		*(*pp)++ = c;
}
688

689
static ssize_t msg_print_ext_header(char *buf, size_t size,
690
				    struct printk_log *msg, u64 seq)
691
692
693
694
695
696
{
	u64 ts_usec = msg->ts_nsec;

	do_div(ts_usec, 1000);

	return scnprintf(buf, size, "%u,%llu,%llu,%c;",
697
698
		       (msg->facility << 3) | msg->level, seq, ts_usec,
		       msg->flags & LOG_CONT ? 'c' : '-');
699
700
701
702
703
704
705
706
707
708
709
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
736
737
738
739
740
741
742
743
744
745
746
747
748
}

static ssize_t msg_print_ext_body(char *buf, size_t size,
				  char *dict, size_t dict_len,
				  char *text, size_t text_len)
{
	char *p = buf, *e = buf + size;
	size_t i;

	/* escape non-printable characters */
	for (i = 0; i < text_len; i++) {
		unsigned char c = text[i];

		if (c < ' ' || c >= 127 || c == '\\')
			p += scnprintf(p, e - p, "\\x%02x", c);
		else
			append_char(&p, e, c);
	}
	append_char(&p, e, '\n');

	if (dict_len) {
		bool line = true;

		for (i = 0; i < dict_len; i++) {
			unsigned char c = dict[i];

			if (line) {
				append_char(&p, e, ' ');
				line = false;
			}

			if (c == '\0') {
				append_char(&p, e, '\n');
				line = true;
				continue;
			}

			if (c < ' ' || c >= 127 || c == '\\') {
				p += scnprintf(p, e - p, "\\x%02x", c);
				continue;
			}

			append_char(&p, e, c);
		}
		append_char(&p, e, '\n');
	}

	return p - buf;
}

749
750
751
752
/* /dev/kmsg - userspace message inject/listen interface */
struct devkmsg_user {
	u64 seq;
	u32 idx;
753
	struct ratelimit_state rs;
754
	struct mutex lock;
755
	char buf[CONSOLE_EXT_LOG_MAX];
756
757
};

Al Viro's avatar
Al Viro committed
758
static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
759
760
761
762
{
	char *buf, *line;
	int level = default_message_loglevel;
	int facility = 1;	/* LOG_USER */
763
764
	struct file *file = iocb->ki_filp;
	struct devkmsg_user *user = file->private_data;
Christoph Hellwig's avatar
Christoph Hellwig committed
765
	size_t len = iov_iter_count(from);
766
767
	ssize_t ret = len;

768
	if (!user || len > LOG_LINE_MAX)
769
		return -EINVAL;
770
771
772
773
774
775
776
777
778
779
780

	/* Ignore when user logging is disabled. */
	if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
		return len;

	/* Ratelimit when not explicitly enabled. */
	if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) {
		if (!___ratelimit(&user->rs, current->comm))
			return ret;
	}

781
782
783
784
	buf = kmalloc(len+1, GFP_KERNEL);
	if (buf == NULL)
		return -ENOMEM;

Al Viro's avatar
Al Viro committed
785
	buf[len] = '\0';
786
	if (!copy_from_iter_full(buf, len, from)) {
Al Viro's avatar
Al Viro committed
787
788
		kfree(buf);
		return -EFAULT;
789
790
791
792
793
794
795
796
797
798
799
800
801
802
	}

	/*
	 * 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;
803
		unsigned int u;
804

805
		u = simple_strtoul(line + 1, &endp, 10);
806
		if (endp && endp[0] == '>') {
807
808
809
			level = LOG_LEVEL(u);
			if (LOG_FACILITY(u) != 0)
				facility = LOG_FACILITY(u);
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
			endp++;
			len -= endp - line;
			line = endp;
		}
	}

	printk_emit(facility, level, NULL, 0, "%s", line);
	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;
825
	struct printk_log *msg;
826
827
828
829
830
831
	size_t len;
	ssize_t ret;

	if (!user)
		return -EBADF;

832
833
834
	ret = mutex_lock_interruptible(&user->lock);
	if (ret)
		return ret;
835
836

	logbuf_lock_irq();
837
838
839
	while (user->seq == log_next_seq) {
		if (file->f_flags & O_NONBLOCK) {
			ret = -EAGAIN;
840
			logbuf_unlock_irq();
841
842
843
			goto out;
		}

844
		logbuf_unlock_irq();
845
846
847
848
		ret = wait_event_interruptible(log_wait,
					       user->seq != log_next_seq);
		if (ret)
			goto out;
849
		logbuf_lock_irq();
850
851
852
853
854
855
856
	}

	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;
857
		logbuf_unlock_irq();
858
859
860
861
		goto out;
	}

	msg = log_from_idx(user->idx);
862
	len = msg_print_ext_header(user->buf, sizeof(user->buf),
863
				   msg, user->seq);
864
865
866
	len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
				  log_dict(msg), msg->dict_len,
				  log_text(msg), msg->text_len);
867

868
869
	user->idx = log_next(user->idx);
	user->seq++;
870
	logbuf_unlock_irq();
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896

	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;

897
	logbuf_lock_irq();
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
	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;
	}
921
	logbuf_unlock_irq();
922
923
924
925
926
927
928
929
930
931
932
933
934
	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);

935
	logbuf_lock_irq();
936
937
938
939
	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;
940
941
		else
			ret = POLLIN|POLLRDNORM;
942
	}
943
	logbuf_unlock_irq();
944
945
946
947
948
949
950
951
952

	return ret;
}

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

953
954
	if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
		return -EPERM;
955

956
957
958
959
960
961
962
	/* write-only does not need any file context */
	if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
		err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
					       SYSLOG_FROM_READER);
		if (err)
			return err;
	}
963
964
965
966
967

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

968
969
970
	ratelimit_default_init(&user->rs);
	ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);

971
972
	mutex_init(&user->lock);

973
	logbuf_lock_irq();
974
975
	user->idx = log_first_idx;
	user->seq = log_first_seq;
976
	logbuf_unlock_irq();
977
978
979
980
981
982
983
984
985
986
987
988

	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;

989
990
	ratelimit_state_exit(&user->rs);

991
992
993
994
995
996
997
998
	mutex_destroy(&user->lock);
	kfree(user);
	return 0;
}

const struct file_operations kmsg_fops = {
	.open = devkmsg_open,
	.read = devkmsg_read,
Al Viro's avatar
Al Viro committed
999
	.write_iter = devkmsg_write,
1000
1001
1002
1003
1004
	.llseek = devkmsg_llseek,
	.poll = devkmsg_poll,
	.release = devkmsg_release,
};

1005
#ifdef CONFIG_CRASH_CORE
1006
/*
1007
 * This appends the listed symbols to /proc/vmcore
1008
 *
1009
 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
1010
1011
1012
1013
 * 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.
 */
1014
void log_buf_vmcoreinfo_setup(void)
1015
1016
1017
{
	VMCOREINFO_SYMBOL(log_buf);
	VMCOREINFO_SYMBOL(log_buf_len);
1018
	VMCOREINFO_SYMBOL(log_first_idx);
1019
	VMCOREINFO_SYMBOL(clear_idx);
1020
	VMCOREINFO_SYMBOL(log_next_idx);
1021
	/*
1022
	 * Export struct printk_log size and field offsets. User space tools can
1023
1024
	 * parse it and detect any changes to structure down the line.
	 */
1025
1026
1027
1028
1029
	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);
1030
1031
1032
}
#endif

1033
1034
1035
/* requested log_buf_len from kernel cmdline */
static unsigned long __initdata new_log_buf_len;

1036
1037
/* 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
1038
1039
1040
{
	if (size)
		size = roundup_pow_of_two(size);
1041
1042
	if (size > log_buf_len)
		new_log_buf_len = size;
1043
1044
1045
1046
1047
1048
1049
1050
}

/* 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);
1051
1052

	return 0;
Linus Torvalds's avatar
Linus Torvalds committed
1053
}
1054
1055
early_param("log_buf_len", log_buf_len_setup);

1056
1057
1058
#ifdef CONFIG_SMP
#define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)

1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
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);
}
1085
1086
1087
#else /* !CONFIG_SMP */
static inline void log_buf_add_cpu(void) {}
#endif /* CONFIG_SMP */
1088

1089
1090
1091
1092
1093
1094
void __init setup_log_buf(int early)
{
	unsigned long flags;
	char *new_log_buf;
	int free;

1095
1096
1097
1098
1099
1100
	if (log_buf != __log_buf)
		return;

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

1101
1102
	if (!new_log_buf_len)
		return;
Linus Torvalds's avatar
Linus Torvalds committed
1103

1104
	if (early) {
1105
		new_log_buf =
1106
			memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
1107
	} else {
1108
1109
		new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
							  LOG_ALIGN);
1110
1111
1112
1113
1114
1115
1116
1117
	}

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

1118
	logbuf_lock_irqsave(flags);
1119
1120
1121
	log_buf_len = new_log_buf_len;
	log_buf = new_log_buf;
	new_log_buf_len = 0;
1122
1123
	free = __LOG_BUF_LEN - log_next_idx;
	memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
1124
	logbuf_unlock_irqrestore(flags);
1125

1126
	pr_info("log_buf_len: %d bytes\n", log_buf_len);
1127
1128
1129
	pr_info("early log buf free: %d(%d%%)\n",
		free, (free * 100) / __LOG_BUF_LEN);
}
Linus Torvalds's avatar
Linus Torvalds committed
1130

1131
1132
1133
1134
static bool __read_mostly ignore_loglevel;

static int __init ignore_loglevel_setup(char *str)
{
1135
	ignore_loglevel = true;
1136
	pr_info("debug: ignoring loglevel setting.\n");
1137
1138
1139
1140
1141
1142

	return 0;
}

early_param("ignore_loglevel", ignore_loglevel_setup);
module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1143
1144
MODULE_PARM_DESC(ignore_loglevel,
		 "ignore loglevel setting (prints all kernel messages to the console)");
1145

1146
1147
1148
1149
1150
static bool suppress_message_printing(int level)
{
	return (level >= console_loglevel && !ignore_loglevel);
}

Randy Dunlap's avatar
Randy Dunlap committed
1151
1152
#ifdef CONFIG_BOOT_PRINTK_DELAY

1153
static int boot_delay; /* msecs delay after each printk during bootup */
1154
static unsigned long long loops_per_msec;	/* based on boot_delay */
Randy Dunlap's avatar
Randy Dunlap committed
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166

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;

1167
1168
1169
	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);
1170
	return 0;
Randy Dunlap's avatar
Randy Dunlap committed
1171
}
1172
early_param("boot_delay", boot_delay_setup);
Randy Dunlap's avatar
Randy Dunlap committed
1173

1174
static void boot_delay_msec(int level)
Randy Dunlap's avatar
Randy Dunlap committed
1175
1176
1177
1178
{
	unsigned long long k;
	unsigned long timeout;

1179
	if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
1180
		|| suppress_message_printing(level)) {
Randy Dunlap's avatar
Randy Dunlap committed
1181
		return;
1182
	}
Randy Dunlap's avatar
Randy Dunlap committed
1183

1184
	k = (unsigned long long)loops_per_msec * boot_delay;
Randy Dunlap's avatar
Randy Dunlap committed
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200

	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
1201
static inline void boot_delay_msec(int level)
Randy Dunlap's avatar
Randy Dunlap committed
1202
1203
1204
1205
{
}
#endif

Alex Elder's avatar
Alex Elder committed
1206
static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1207
1208
module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);

1209
1210
1211
1212
1213
1214
1215
static size_t print_time(u64 ts, char *buf)
{
	unsigned long rem_nsec;

	if (!printk_time)
		return 0;

1216
1217
	rem_nsec = do_div(ts, 1000000000);

1218
	if (!buf)
1219
		return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1220
1221
1222
1223
1224

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

1225
static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1226
{
1227
	size_t len = 0;
1228
	unsigned int prefix = (msg->facility << 3) | msg->level;
1229

1230
1231
	if (syslog) {
		if (buf) {
1232
			len += sprintf(buf, "<%u>", prefix);
1233
1234
		} else {
			len += 3;
1235
1236
1237
1238
1239
			if (prefix > 999)
				len += 3;
			else if (prefix > 99)
				len += 2;
			else if (prefix > 9)
1240
1241
1242
				len++;
		}
	}
1243

1244
	len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1245
	return len;
1246
1247
}

1248
static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *buf, size_t size)
1249
{
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
	const char *text = log_text(msg);
	size_t text_size = msg->text_len;
	size_t len = 0;

	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;
		}
1265

1266
1267
		if (buf) {
			if (print_prefix(msg, syslog, NULL) +
1268
			    text_len + 1 >= size - len)
1269
				break;
1270

1271
			len += print_prefix(msg, syslog, buf + len);
1272
1273
			memcpy(buf + len, text, text_len);
			len += text_len;
1274
			buf[len++] = '\n';
1275
1276
		} else {
			/* SYSLOG_ACTION_* buffer size only calculation */
1277
			len += print_prefix(msg, syslog, NULL);
1278
			len += text_len;
1279
			len++;
1280
		}
1281

1282
1283
		text = next;
	} while (text);
1284
1285
1286
1287
1288
1289
1290

	return len;
}

static int syslog_print(char __user *buf, int size)
{
	char *text;
1291
	struct printk_log *msg;
1292
	int len = 0;
1293

1294
	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1295
1296
1297
	if (!text)
		return -ENOMEM;

1298
1299
	while (size > 0) {
		size_t n;
1300
		size_t skip;
1301

1302
		logbuf_lock_irq();
1303
1304
1305
1306
		if (syslog_seq < log_first_seq) {
			/* messages are gone, move to first one */
			syslog_seq = log_first_seq;
			syslog_idx = log_first_idx;
1307
			syslog_partial = 0;
1308
1309
		}
		if (syslog_seq == log_next_seq) {
1310
			logbuf_unlock_irq();
1311
1312
			break;
		}
1313
1314

		skip = syslog_partial;
1315
		msg = log_from_idx(syslog_idx);
1316
		n = msg_print_text(msg, true, text, LOG_LINE_MAX + PREFIX_MAX);
1317
1318
		if (n - syslog_partial <= size) {
			/* message fits into buffer, move forward */
1319
1320
			syslog_idx = log_next(syslog_idx);
			syslog_seq++;
1321
1322
1323
1324
1325
1326
			n -= syslog_partial;
			syslog_partial = 0;
		} else if (!len){
			/* partial read(), remember position */
			n = size;
			syslog_partial += n;
1327
1328
		} else
			n = 0;
1329
		logbuf_unlock_irq();
1330
1331
1332
1333

		if (!n)
			break;

1334
		if (copy_to_user(buf, text + skip, n)) {
1335
1336
1337
1338
			if (!len)
				len = -EFAULT;
			break;
		}
1339
1340
1341
1342

		len += n;
		size -= n;
		buf += n;
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
	}

	kfree(text);
	return len;
}

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

1354
	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1355
1356