printk.c 83.4 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];
Joe Perches's avatar
Joe Perches committed
272

Linus Torvalds's avatar
Linus Torvalds committed
273
static int preferred_console = -1;
274
275
int console_set_on_cmdline;
EXPORT_SYMBOL(console_set_on_cmdline);
Linus Torvalds's avatar
Linus Torvalds committed
276
277
278
279

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

280
281
282
283
284
285
/*
 * 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
286
287
 * sequence numbers of these entries are maintained when messages are
 * stored.
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
 *
 * 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.
 *
303
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
 * 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
 *
332
 * The 'struct printk_log' buffer header must never be directly exported to
333
334
335
336
 * 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:
337
338
339
340
 *   "<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.
341
342
343
344
 *
 * 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.
345
346
 */

347
enum log_flags {
348
349
350
351
	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 */
352
353
};

354
struct printk_log {
355
356
357
358
	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 */
359
360
361
	u8 facility;		/* syslog facility */
	u8 flags:5;		/* internal record flags */
	u8 level:3;		/* syslog level */
362
363
364
365
366
}
#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
__packed __aligned(4)
#endif
;
367
368

/*
369
370
371
 * 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.
372
 */
373
DEFINE_RAW_SPINLOCK(logbuf_lock);
374

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
/*
 * 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)

403
#ifdef CONFIG_PRINTK
404
DECLARE_WAIT_QUEUE_HEAD(log_wait);
405
406
407
/* the next printk record to read by syslog(READ) or /proc/kmsg */
static u64 syslog_seq;
static u32 syslog_idx;
408
static size_t syslog_partial;
409
410
411
412
413
414
415
416
417

/* 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;

418
419
420
421
/* the next printk record to write to the console */
static u64 console_seq;
static u32 console_idx;

422
423
424
425
/* the next printk record to read after the last 'clear' command */
static u64 clear_seq;
static u32 clear_idx;

426
#define PREFIX_MAX		32
Alex Elder's avatar
Alex Elder committed
427
#define LOG_LINE_MAX		(1024 - PREFIX_MAX)
428

429
430
431
#define LOG_LEVEL(v)		((v) & 0x07)
#define LOG_FACILITY(v)		((v) >> 3 & 0xff)

432
/* record buffer */
433
#define LOG_ALIGN __alignof__(struct printk_log)
434
#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
435
static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
436
437
438
static char *log_buf = __log_buf;
static u32 log_buf_len = __LOG_BUF_LEN;

439
440
441
442
443
444
445
446
447
448
449
450
/* 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;
}

451
/* human readable text of the record */
452
static char *log_text(const struct printk_log *msg)
453
{
454
	return (char *)msg + sizeof(struct printk_log);
455
456
457
}

/* optional key/value pair dictionary attached to the record */
458
static char *log_dict(const struct printk_log *msg)
459
{
460
	return (char *)msg + sizeof(struct printk_log) + msg->text_len;
461
462
463
}

/* get record by index; idx must point to valid msg */
464
static struct printk_log *log_from_idx(u32 idx)
465
{
466
	struct printk_log *msg = (struct printk_log *)(log_buf + idx);
467
468
469
470
471
472

	/*
	 * 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)
473
		return (struct printk_log *)log_buf;
474
475
476
477
478
479
	return msg;
}

/* get next record; idx must point to valid msg */
static u32 log_next(u32 idx)
{
480
	struct printk_log *msg = (struct printk_log *)(log_buf + idx);
481
482
483
484
485
486
487
488

	/* 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) {
489
		msg = (struct printk_log *)log_buf;
490
491
492
493
494
		return msg->len;
	}
	return idx + msg->len;
}

Petr Mladek's avatar
Petr Mladek committed
495
496
497
498
499
500
501
502
503
504
/*
 * 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)
505
506
507
{
	u32 free;

Petr Mladek's avatar
Petr Mladek committed
508
	if (log_next_idx > log_first_idx || empty)
509
510
511
512
513
514
515
516
517
518
519
		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
520
static int log_make_free_space(u32 msg_size)
521
{
522
523
	while (log_first_seq < log_next_seq &&
	       !logbuf_has_space(msg_size, false)) {
Alex Elder's avatar
Alex Elder committed
524
		/* drop old messages until we have enough contiguous space */
525
526
527
		log_first_idx = log_next(log_first_idx);
		log_first_seq++;
	}
Petr Mladek's avatar
Petr Mladek committed
528

529
530
531
532
533
	if (clear_seq < log_first_seq) {
		clear_seq = log_first_seq;
		clear_idx = log_first_idx;
	}

Petr Mladek's avatar
Petr Mladek committed
534
	/* sequence numbers are equal, so the log buffer is empty */
535
	if (logbuf_has_space(msg_size, log_first_seq == log_next_seq))
Petr Mladek's avatar
Petr Mladek committed
536
537
538
		return 0;

	return -ENOMEM;
539
540
}

541
542
543
544
545
546
547
548
549
550
551
552
/* 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
553
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
/*
 * 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);
}

579
/* insert record into the buffer, discard old ones, update heads */
580
581
582
583
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)
584
{
585
	struct printk_log *msg;
586
	u32 size, pad_len;
Petr Mladek's avatar
Petr Mladek committed
587
	u16 trunc_msg_len = 0;
588
589

	/* number of '\0' padding bytes to next message */
590
	size = msg_used_size(text_len, dict_len, &pad_len);
591

Petr Mladek's avatar
Petr Mladek committed
592
593
594
595
596
597
	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))
598
			return 0;
Petr Mladek's avatar
Petr Mladek committed
599
	}
600

601
	if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
602
603
604
605
606
		/*
		 * 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.
		 */
607
		memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
608
609
610
611
		log_next_idx = 0;
	}

	/* fill message */
612
	msg = (struct printk_log *)(log_buf + log_next_idx);
613
614
	memcpy(log_text(msg), text, text_len);
	msg->text_len = text_len;
Petr Mladek's avatar
Petr Mladek committed
615
616
617
618
	if (trunc_msg_len) {
		memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
		msg->text_len += trunc_msg_len;
	}
619
620
	memcpy(log_dict(msg), dict, dict_len);
	msg->dict_len = dict_len;
621
622
623
624
625
626
627
	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();
628
	memset(log_dict(msg) + dict_len, 0, pad_len);
629
	msg->len = size;
630
631
632
633

	/* insert message */
	log_next_idx += msg->len;
	log_next_seq++;
634
635

	return msg->text_len;
636
}
637

Alex Elder's avatar
Alex Elder committed
638
int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
639
640
641
642
643
644
645
646
647
648
649
650
651

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;
}

652
static int check_syslog_permissions(int type, int source)
653
654
655
656
657
{
	/*
	 * If this is from /proc/kmsg and we've already opened it, then we've
	 * already done the capabilities checks at open time.
	 */
658
	if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
659
		goto ok;
660
661
662

	if (syslog_action_restricted(type)) {
		if (capable(CAP_SYSLOG))
663
			goto ok;
664
665
666
667
668
669
670
671
672
		/*
		 * 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));
673
			goto ok;
674
675
676
		}
		return -EPERM;
	}
677
ok:
678
679
680
	return security_syslog(type);
}

681
682
683
684
685
static void append_char(char **pp, char *e, char c)
{
	if (*pp < e)
		*(*pp)++ = c;
}
686

687
static ssize_t msg_print_ext_header(char *buf, size_t size,
688
				    struct printk_log *msg, u64 seq)
689
690
691
692
693
694
{
	u64 ts_usec = msg->ts_nsec;

	do_div(ts_usec, 1000);

	return scnprintf(buf, size, "%u,%llu,%llu,%c;",
695
696
		       (msg->facility << 3) | msg->level, seq, ts_usec,
		       msg->flags & LOG_CONT ? 'c' : '-');
697
698
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
}

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;
}

747
748
749
750
/* /dev/kmsg - userspace message inject/listen interface */
struct devkmsg_user {
	u64 seq;
	u32 idx;
751
	struct ratelimit_state rs;
752
	struct mutex lock;
753
	char buf[CONSOLE_EXT_LOG_MAX];
754
755
};

Al Viro's avatar
Al Viro committed
756
static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
757
758
759
760
{
	char *buf, *line;
	int level = default_message_loglevel;
	int facility = 1;	/* LOG_USER */
761
762
	struct file *file = iocb->ki_filp;
	struct devkmsg_user *user = file->private_data;
Christoph Hellwig's avatar
Christoph Hellwig committed
763
	size_t len = iov_iter_count(from);
764
765
	ssize_t ret = len;

766
	if (!user || len > LOG_LINE_MAX)
767
		return -EINVAL;
768
769
770
771
772
773
774
775
776
777
778

	/* 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;
	}

779
780
781
782
	buf = kmalloc(len+1, GFP_KERNEL);
	if (buf == NULL)
		return -ENOMEM;

Al Viro's avatar
Al Viro committed
783
	buf[len] = '\0';
784
	if (!copy_from_iter_full(buf, len, from)) {
Al Viro's avatar
Al Viro committed
785
786
		kfree(buf);
		return -EFAULT;
787
788
789
790
791
792
793
794
795
796
797
798
799
800
	}

	/*
	 * 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;
801
		unsigned int u;
802

803
		u = simple_strtoul(line + 1, &endp, 10);
804
		if (endp && endp[0] == '>') {
805
806
807
			level = LOG_LEVEL(u);
			if (LOG_FACILITY(u) != 0)
				facility = LOG_FACILITY(u);
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
			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;
823
	struct printk_log *msg;
824
825
826
827
828
829
	size_t len;
	ssize_t ret;

	if (!user)
		return -EBADF;

830
831
832
	ret = mutex_lock_interruptible(&user->lock);
	if (ret)
		return ret;
833
834

	logbuf_lock_irq();
835
836
837
	while (user->seq == log_next_seq) {
		if (file->f_flags & O_NONBLOCK) {
			ret = -EAGAIN;
838
			logbuf_unlock_irq();
839
840
841
			goto out;
		}

842
		logbuf_unlock_irq();
843
844
845
846
		ret = wait_event_interruptible(log_wait,
					       user->seq != log_next_seq);
		if (ret)
			goto out;
847
		logbuf_lock_irq();
848
849
850
851
852
853
854
	}

	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;
855
		logbuf_unlock_irq();
856
857
858
859
		goto out;
	}

	msg = log_from_idx(user->idx);
860
	len = msg_print_ext_header(user->buf, sizeof(user->buf),
861
				   msg, user->seq);
862
863
864
	len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
				  log_dict(msg), msg->dict_len,
				  log_text(msg), msg->text_len);
865

866
867
	user->idx = log_next(user->idx);
	user->seq++;
868
	logbuf_unlock_irq();
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894

	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;

895
	logbuf_lock_irq();
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
	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;
	}
919
	logbuf_unlock_irq();
920
921
922
923
924
925
926
927
928
929
930
931
932
	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);

933
	logbuf_lock_irq();
934
935
936
937
	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;
938
939
		else
			ret = POLLIN|POLLRDNORM;
940
	}
941
	logbuf_unlock_irq();
942
943
944
945
946
947
948
949
950

	return ret;
}

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

951
952
	if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
		return -EPERM;
953

954
955
956
957
958
959
960
	/* 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;
	}
961
962
963
964
965

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

966
967
968
	ratelimit_default_init(&user->rs);
	ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);

969
970
	mutex_init(&user->lock);

971
	logbuf_lock_irq();
972
973
	user->idx = log_first_idx;
	user->seq = log_first_seq;
974
	logbuf_unlock_irq();
975
976
977
978
979
980
981
982
983
984
985
986

	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;

987
988
	ratelimit_state_exit(&user->rs);

989
990
991
992
993
994
995
996
	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
997
	.write_iter = devkmsg_write,
998
999
1000
1001
1002
	.llseek = devkmsg_llseek,
	.poll = devkmsg_poll,
	.release = devkmsg_release,
};

1003
#ifdef CONFIG_CRASH_CORE
1004
/*
1005
 * This appends the listed symbols to /proc/vmcore
1006
 *
1007
 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
1008
1009
1010
1011
 * 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.
 */
1012
void log_buf_vmcoreinfo_setup(void)
1013
1014
1015
{
	VMCOREINFO_SYMBOL(log_buf);
	VMCOREINFO_SYMBOL(log_buf_len);
1016
	VMCOREINFO_SYMBOL(log_first_idx);
1017
	VMCOREINFO_SYMBOL(clear_idx);
1018
	VMCOREINFO_SYMBOL(log_next_idx);
1019
	/*
1020
	 * Export struct printk_log size and field offsets. User space tools can
1021
1022
	 * parse it and detect any changes to structure down the line.
	 */
1023
1024
1025
1026
1027
	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);
1028
1029
1030
}
#endif

1031
1032
1033
/* requested log_buf_len from kernel cmdline */
static unsigned long __initdata new_log_buf_len;

1034
1035
/* 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
1036
1037
1038
{
	if (size)
		size = roundup_pow_of_two(size);
1039
1040
	if (size > log_buf_len)
		new_log_buf_len = size;
1041
1042
1043
1044
1045
1046
1047
1048
}

/* 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);
1049
1050

	return 0;
Linus Torvalds's avatar
Linus Torvalds committed
1051
}
1052
1053
early_param("log_buf_len", log_buf_len_setup);

1054
1055
1056
#ifdef CONFIG_SMP
#define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)

1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
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);
}
1083
1084
1085
#else /* !CONFIG_SMP */
static inline void log_buf_add_cpu(void) {}
#endif /* CONFIG_SMP */
1086

1087
1088
1089
1090
1091
1092
void __init setup_log_buf(int early)
{
	unsigned long flags;
	char *new_log_buf;
	int free;

1093
1094
1095
1096
1097
1098
	if (log_buf != __log_buf)
		return;

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

1099
1100
	if (!new_log_buf_len)
		return;
Linus Torvalds's avatar
Linus Torvalds committed
1101

1102
	if (early) {
1103
		new_log_buf =
1104
			memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
1105
	} else {
1106
1107
		new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
							  LOG_ALIGN);
1108
1109
1110
1111
1112
1113
1114
1115
	}

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

1116
	logbuf_lock_irqsave(flags);
1117
1118
1119
	log_buf_len = new_log_buf_len;
	log_buf = new_log_buf;
	new_log_buf_len = 0;
1120
1121
	free = __LOG_BUF_LEN - log_next_idx;
	memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
1122
	logbuf_unlock_irqrestore(flags);
1123

1124
	pr_info("log_buf_len: %d bytes\n", log_buf_len);
1125
1126
1127
	pr_info("early log buf free: %d(%d%%)\n",
		free, (free * 100) / __LOG_BUF_LEN);
}
Linus Torvalds's avatar
Linus Torvalds committed
1128

1129
1130
1131
1132
static bool __read_mostly ignore_loglevel;

static int __init ignore_loglevel_setup(char *str)
{
1133
	ignore_loglevel = true;
1134
	pr_info("debug: ignoring loglevel setting.\n");
1135
1136
1137
1138
1139
1140

	return 0;
}

early_param("ignore_loglevel", ignore_loglevel_setup);
module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1141
1142
MODULE_PARM_DESC(ignore_loglevel,
		 "ignore loglevel setting (prints all kernel messages to the console)");
1143

1144
1145
1146
1147
1148
static bool suppress_message_printing(int level)
{
	return (level >= console_loglevel && !ignore_loglevel);
}

Randy Dunlap's avatar
Randy Dunlap committed
1149
1150
#ifdef CONFIG_BOOT_PRINTK_DELAY

1151
static int boot_delay; /* msecs delay after each printk during bootup */
1152
static unsigned long long loops_per_msec;	/* based on boot_delay */
Randy Dunlap's avatar
Randy Dunlap committed
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164

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;

1165
1166
1167
	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);
1168
	return 0;
Randy Dunlap's avatar
Randy Dunlap committed
1169
}
1170
early_param("boot_delay", boot_delay_setup);
Randy Dunlap's avatar
Randy Dunlap committed
1171

1172
static void boot_delay_msec(int level)
Randy Dunlap's avatar
Randy Dunlap committed
1173
1174
1175
1176
{
	unsigned long long k;
	unsigned long timeout;

1177
	if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING)
1178
		|| suppress_message_printing(level)) {
Randy Dunlap's avatar
Randy Dunlap committed
1179
		return;
1180
	}
Randy Dunlap's avatar
Randy Dunlap committed
1181

1182
	k = (unsigned long long)loops_per_msec * boot_delay;
Randy Dunlap's avatar
Randy Dunlap committed
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198

	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
1199
static inline void boot_delay_msec(int level)
Randy Dunlap's avatar
Randy Dunlap committed
1200
1201
1202
1203
{
}
#endif

Alex Elder's avatar
Alex Elder committed
1204
static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1205
1206
module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);

1207
1208
1209
1210
1211
1212
1213
static size_t print_time(u64 ts, char *buf)
{
	unsigned long rem_nsec;

	if (!printk_time)
		return 0;

1214
1215
	rem_nsec = do_div(ts, 1000000000);

1216
	if (!buf)
1217
		return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1218
1219
1220
1221
1222

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

1223
static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1224
{
1225
	size_t len = 0;
1226
	unsigned int prefix = (msg->facility << 3) | msg->level;
1227

1228
1229
	if (syslog) {
		if (buf) {
1230
			len += sprintf(buf, "<%u>", prefix);
1231
1232
		} else {
			len += 3;
1233
1234
1235
1236
1237
			if (prefix > 999)
				len += 3;
			else if (prefix > 99)
				len += 2;
			else if (prefix > 9)
1238
1239
1240
				len++;
		}
	}
1241

1242
	len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1243
	return len;
1244
1245
}

1246
static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *buf, size_t size)
1247
{
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
	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;
		}
1263

1264
1265
		if (buf) {
			if (print_prefix(msg, syslog, NULL) +
1266
			    text_len + 1 >= size - len)
1267
				break;
1268

1269
			len += print_prefix(msg, syslog, buf + len);
1270
1271
			memcpy(buf + len, text, text_len);
			len += text_len;
1272
			buf[len++] = '\n';
1273
1274
		} else {
			/* SYSLOG_ACTION_* buffer size only calculation */
1275
			len += print_prefix(msg, syslog, NULL);
1276
			len += text_len;
1277
			len++;
1278
		}
1279

1280
1281
		text = next;
	} while (text);
1282
1283
1284
1285
1286
1287
1288

	return len;
}

static int syslog_print(char __user *buf, int size)
{
	char *text;
1289
	struct printk_log *msg;
1290
	int len = 0;
1291

1292
	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1293
1294
1295
	if (!text)
		return -ENOMEM;

1296
1297
	while (size > 0) {
		size_t n;
1298
		size_t skip;
1299

1300
		logbuf_lock_irq();
1301
1302
1303
1304
		if (syslog_seq < log_first_seq) {
			/* messages are gone, move to first one */
			syslog_seq = log_first_seq;
			syslog_idx = log_first_idx;
1305
			syslog_partial = 0;
1306
1307
		}
		if (syslog_seq == log_next_seq) {
1308
			logbuf_unlock_irq();
1309
1310
			break;
		}
1311
1312

		skip = syslog_partial;
1313
		msg = log_from_idx(syslog_idx);
1314
		n = msg_print_text(msg, true, text, LOG_LINE_MAX + PREFIX_MAX);
1315
1316
		if (n - syslog_partial <= size) {
			/* message fits into buffer, move forward */
1317
1318
			syslog_idx = log_next(syslog_idx);
			syslog_seq++;
1319
1320
1321
1322
1323
1324
			n -= syslog_partial;
			syslog_partial = 0;
		} else if (!len){
			/* partial read(), remember position */
			n = size;
			syslog_partial += n;
1325
1326
		} else
			n = 0;
1327
		logbuf_unlock_irq();
1328
1329
1330
1331

		if (!n)
			break;

1332
		if (copy_to_user(buf, text + skip, n)) {
1333
1334
1335
1336
			if (!len)
				len = -EFAULT;
			break;
		}
1337
1338
1339
1340

		len += n;
		size -= n;
		buf += n;
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
	}

	kfree(text);
	return len;
}

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

1352
	text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1353
1354
1355
	if (!text)
		return -ENOMEM;

1356
	logbuf_lock_irq();
1357
1358
1359
1360
1361
1362
1363
1364
	if (buf) {
		u64 next_seq;
		u64 seq;
		u32 idx;

		/*
		 * Find first record that fits, including all following records,
		 * into the user-provided buffer for this dump.