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CommitLineData
1da177e4
LT
1/*
2 * linux/kernel/printk.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
11 * Ted Ts'o, 2/11/93.
12 * Modified for sysctl support, 1/8/97, Chris Horn.
40dc5651 13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
624dffcb 14 * manfred@colorfullife.com
1da177e4 15 * Rewrote bits to get rid of console_lock
e1f8e874 16 * 01Mar01 Andrew Morton
1da177e4
LT
17 */
18
19#include <linux/kernel.h>
20#include <linux/mm.h>
21#include <linux/tty.h>
22#include <linux/tty_driver.h>
1da177e4
LT
23#include <linux/console.h>
24#include <linux/init.h>
bfe8df3d
RD
25#include <linux/jiffies.h>
26#include <linux/nmi.h>
1da177e4 27#include <linux/module.h>
3b9c0410 28#include <linux/moduleparam.h>
1da177e4 29#include <linux/interrupt.h> /* For in_interrupt() */
1da177e4
LT
30#include <linux/delay.h>
31#include <linux/smp.h>
32#include <linux/security.h>
33#include <linux/bootmem.h>
162a7e75 34#include <linux/memblock.h>
1da177e4 35#include <linux/syscalls.h>
04d491ab 36#include <linux/kexec.h>
d37d39ae 37#include <linux/kdb.h>
3fff4c42 38#include <linux/ratelimit.h>
456b565c 39#include <linux/kmsg_dump.h>
00234592 40#include <linux/syslog.h>
034260d6
KC
41#include <linux/cpu.h>
42#include <linux/notifier.h>
fb842b00 43#include <linux/rculist.h>
e11fea92 44#include <linux/poll.h>
74876a98 45#include <linux/irq_work.h>
196779b9 46#include <linux/utsname.h>
249771b8 47#include <linux/ctype.h>
e2e40f2c 48#include <linux/uio.h>
1da177e4
LT
49
50#include <asm/uaccess.h>
51
95100358
JB
52#define CREATE_TRACE_POINTS
53#include <trace/events/printk.h>
54
d197c43d 55#include "console_cmdline.h"
bbeddf52 56#include "braille.h"
d197c43d 57
1da177e4 58int console_printk[4] = {
a8fe19eb 59 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
42a9dc0b 60 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
a8fe19eb
BP
61 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
62 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
1da177e4
LT
63};
64
1da177e4 65/*
0bbfb7c2 66 * Low level drivers may need that to know if they can schedule in
1da177e4
LT
67 * their unblank() callback or not. So let's export it.
68 */
69int oops_in_progress;
70EXPORT_SYMBOL(oops_in_progress);
71
72/*
73 * console_sem protects the console_drivers list, and also
74 * provides serialisation for access to the entire console
75 * driver system.
76 */
5b8c4f23 77static DEFINE_SEMAPHORE(console_sem);
1da177e4 78struct console *console_drivers;
a29d1cfe
IM
79EXPORT_SYMBOL_GPL(console_drivers);
80
daee7797
DV
81#ifdef CONFIG_LOCKDEP
82static struct lockdep_map console_lock_dep_map = {
83 .name = "console_lock"
84};
85#endif
86
bd8d7cf5
JK
87/*
88 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
89 * macros instead of functions so that _RET_IP_ contains useful information.
90 */
91#define down_console_sem() do { \
92 down(&console_sem);\
93 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
94} while (0)
95
96static int __down_trylock_console_sem(unsigned long ip)
97{
98 if (down_trylock(&console_sem))
99 return 1;
100 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
101 return 0;
102}
103#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
104
105#define up_console_sem() do { \
106 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
107 up(&console_sem);\
108} while (0)
109
1da177e4
LT
110/*
111 * This is used for debugging the mess that is the VT code by
112 * keeping track if we have the console semaphore held. It's
113 * definitely not the perfect debug tool (we don't know if _WE_
0b90fec3
AE
114 * hold it and are racing, but it helps tracking those weird code
115 * paths in the console code where we end up in places I want
116 * locked without the console sempahore held).
1da177e4 117 */
557240b4 118static int console_locked, console_suspended;
1da177e4 119
fe3d8ad3
FT
120/*
121 * If exclusive_console is non-NULL then only this console is to be printed to.
122 */
123static struct console *exclusive_console;
124
1da177e4
LT
125/*
126 * Array of consoles built from command line options (console=)
127 */
1da177e4
LT
128
129#define MAX_CMDLINECONSOLES 8
130
131static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
d197c43d 132
1da177e4
LT
133static int selected_console = -1;
134static int preferred_console = -1;
9e124fe1
MA
135int console_set_on_cmdline;
136EXPORT_SYMBOL(console_set_on_cmdline);
1da177e4
LT
137
138/* Flag: console code may call schedule() */
139static int console_may_schedule;
140
7ff9554b
KS
141/*
142 * The printk log buffer consists of a chain of concatenated variable
143 * length records. Every record starts with a record header, containing
144 * the overall length of the record.
145 *
146 * The heads to the first and last entry in the buffer, as well as the
0b90fec3
AE
147 * sequence numbers of these entries are maintained when messages are
148 * stored.
7ff9554b
KS
149 *
150 * If the heads indicate available messages, the length in the header
151 * tells the start next message. A length == 0 for the next message
152 * indicates a wrap-around to the beginning of the buffer.
153 *
154 * Every record carries the monotonic timestamp in microseconds, as well as
155 * the standard userspace syslog level and syslog facility. The usual
156 * kernel messages use LOG_KERN; userspace-injected messages always carry
157 * a matching syslog facility, by default LOG_USER. The origin of every
158 * message can be reliably determined that way.
159 *
160 * The human readable log message directly follows the message header. The
161 * length of the message text is stored in the header, the stored message
162 * is not terminated.
163 *
e11fea92
KS
164 * Optionally, a message can carry a dictionary of properties (key/value pairs),
165 * to provide userspace with a machine-readable message context.
166 *
167 * Examples for well-defined, commonly used property names are:
168 * DEVICE=b12:8 device identifier
169 * b12:8 block dev_t
170 * c127:3 char dev_t
171 * n8 netdev ifindex
172 * +sound:card0 subsystem:devname
173 * SUBSYSTEM=pci driver-core subsystem name
174 *
175 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
176 * follows directly after a '=' character. Every property is terminated by
177 * a '\0' character. The last property is not terminated.
178 *
179 * Example of a message structure:
180 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
181 * 0008 34 00 record is 52 bytes long
182 * 000a 0b 00 text is 11 bytes long
183 * 000c 1f 00 dictionary is 23 bytes long
184 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
185 * 0010 69 74 27 73 20 61 20 6c "it's a l"
186 * 69 6e 65 "ine"
187 * 001b 44 45 56 49 43 "DEVIC"
188 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
189 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
190 * 67 "g"
191 * 0032 00 00 00 padding to next message header
192 *
62e32ac3 193 * The 'struct printk_log' buffer header must never be directly exported to
e11fea92
KS
194 * userspace, it is a kernel-private implementation detail that might
195 * need to be changed in the future, when the requirements change.
196 *
197 * /dev/kmsg exports the structured data in the following line format:
198 * "level,sequnum,timestamp;<message text>\n"
199 *
200 * The optional key/value pairs are attached as continuation lines starting
201 * with a space character and terminated by a newline. All possible
202 * non-prinatable characters are escaped in the "\xff" notation.
203 *
204 * Users of the export format should ignore possible additional values
205 * separated by ',', and find the message after the ';' character.
7ff9554b
KS
206 */
207
084681d1 208enum log_flags {
5becfb1d
KS
209 LOG_NOCONS = 1, /* already flushed, do not print to console */
210 LOG_NEWLINE = 2, /* text ended with a newline */
211 LOG_PREFIX = 4, /* text started with a prefix */
212 LOG_CONT = 8, /* text is a fragment of a continuation line */
084681d1
KS
213};
214
62e32ac3 215struct printk_log {
7ff9554b
KS
216 u64 ts_nsec; /* timestamp in nanoseconds */
217 u16 len; /* length of entire record */
218 u16 text_len; /* length of text buffer */
219 u16 dict_len; /* length of dictionary buffer */
084681d1
KS
220 u8 facility; /* syslog facility */
221 u8 flags:5; /* internal record flags */
222 u8 level:3; /* syslog level */
7ff9554b
KS
223};
224
225/*
458df9fd
SR
226 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
227 * within the scheduler's rq lock. It must be released before calling
228 * console_unlock() or anything else that might wake up a process.
7ff9554b
KS
229 */
230static DEFINE_RAW_SPINLOCK(logbuf_lock);
d59745ce 231
96efedf1 232#ifdef CONFIG_PRINTK
dc72c32e 233DECLARE_WAIT_QUEUE_HEAD(log_wait);
7f3a781d
KS
234/* the next printk record to read by syslog(READ) or /proc/kmsg */
235static u64 syslog_seq;
236static u32 syslog_idx;
5becfb1d 237static enum log_flags syslog_prev;
eb02dac9 238static size_t syslog_partial;
7ff9554b
KS
239
240/* index and sequence number of the first record stored in the buffer */
241static u64 log_first_seq;
242static u32 log_first_idx;
243
244/* index and sequence number of the next record to store in the buffer */
245static u64 log_next_seq;
246static u32 log_next_idx;
247
eab07260
KS
248/* the next printk record to write to the console */
249static u64 console_seq;
250static u32 console_idx;
251static enum log_flags console_prev;
252
7ff9554b
KS
253/* the next printk record to read after the last 'clear' command */
254static u64 clear_seq;
255static u32 clear_idx;
256
70498253 257#define PREFIX_MAX 32
249771b8 258#define LOG_LINE_MAX (1024 - PREFIX_MAX)
7f3a781d
KS
259
260/* record buffer */
6ebb017d 261#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
f8450fca
SW
262#define LOG_ALIGN 4
263#else
62e32ac3 264#define LOG_ALIGN __alignof__(struct printk_log)
f8450fca 265#endif
7f3a781d 266#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
f8450fca 267static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
7f3a781d
KS
268static char *log_buf = __log_buf;
269static u32 log_buf_len = __LOG_BUF_LEN;
270
14c4000a
VH
271/* Return log buffer address */
272char *log_buf_addr_get(void)
273{
274 return log_buf;
275}
276
277/* Return log buffer size */
278u32 log_buf_len_get(void)
279{
280 return log_buf_len;
281}
282
7ff9554b 283/* human readable text of the record */
62e32ac3 284static char *log_text(const struct printk_log *msg)
7ff9554b 285{
62e32ac3 286 return (char *)msg + sizeof(struct printk_log);
7ff9554b
KS
287}
288
289/* optional key/value pair dictionary attached to the record */
62e32ac3 290static char *log_dict(const struct printk_log *msg)
7ff9554b 291{
62e32ac3 292 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
7ff9554b
KS
293}
294
295/* get record by index; idx must point to valid msg */
62e32ac3 296static struct printk_log *log_from_idx(u32 idx)
7ff9554b 297{
62e32ac3 298 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
7ff9554b
KS
299
300 /*
301 * A length == 0 record is the end of buffer marker. Wrap around and
302 * read the message at the start of the buffer.
303 */
304 if (!msg->len)
62e32ac3 305 return (struct printk_log *)log_buf;
7ff9554b
KS
306 return msg;
307}
308
309/* get next record; idx must point to valid msg */
310static u32 log_next(u32 idx)
311{
62e32ac3 312 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
7ff9554b
KS
313
314 /* length == 0 indicates the end of the buffer; wrap */
315 /*
316 * A length == 0 record is the end of buffer marker. Wrap around and
317 * read the message at the start of the buffer as *this* one, and
318 * return the one after that.
319 */
320 if (!msg->len) {
62e32ac3 321 msg = (struct printk_log *)log_buf;
7ff9554b
KS
322 return msg->len;
323 }
324 return idx + msg->len;
325}
326
f40e4b9f
PM
327/*
328 * Check whether there is enough free space for the given message.
329 *
330 * The same values of first_idx and next_idx mean that the buffer
331 * is either empty or full.
332 *
333 * If the buffer is empty, we must respect the position of the indexes.
334 * They cannot be reset to the beginning of the buffer.
335 */
336static int logbuf_has_space(u32 msg_size, bool empty)
0a581694
PM
337{
338 u32 free;
339
f40e4b9f 340 if (log_next_idx > log_first_idx || empty)
0a581694
PM
341 free = max(log_buf_len - log_next_idx, log_first_idx);
342 else
343 free = log_first_idx - log_next_idx;
344
345 /*
346 * We need space also for an empty header that signalizes wrapping
347 * of the buffer.
348 */
349 return free >= msg_size + sizeof(struct printk_log);
350}
351
f40e4b9f 352static int log_make_free_space(u32 msg_size)
0a581694
PM
353{
354 while (log_first_seq < log_next_seq) {
f40e4b9f
PM
355 if (logbuf_has_space(msg_size, false))
356 return 0;
0b90fec3 357 /* drop old messages until we have enough contiguous space */
0a581694
PM
358 log_first_idx = log_next(log_first_idx);
359 log_first_seq++;
360 }
f40e4b9f
PM
361
362 /* sequence numbers are equal, so the log buffer is empty */
363 if (logbuf_has_space(msg_size, true))
364 return 0;
365
366 return -ENOMEM;
0a581694
PM
367}
368
85c87043
PM
369/* compute the message size including the padding bytes */
370static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
371{
372 u32 size;
373
374 size = sizeof(struct printk_log) + text_len + dict_len;
375 *pad_len = (-size) & (LOG_ALIGN - 1);
376 size += *pad_len;
377
378 return size;
379}
380
55bd53a4
PM
381/*
382 * Define how much of the log buffer we could take at maximum. The value
383 * must be greater than two. Note that only half of the buffer is available
384 * when the index points to the middle.
385 */
386#define MAX_LOG_TAKE_PART 4
387static const char trunc_msg[] = "<truncated>";
388
389static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
390 u16 *dict_len, u32 *pad_len)
391{
392 /*
393 * The message should not take the whole buffer. Otherwise, it might
394 * get removed too soon.
395 */
396 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
397 if (*text_len > max_text_len)
398 *text_len = max_text_len;
399 /* enable the warning message */
400 *trunc_msg_len = strlen(trunc_msg);
401 /* disable the "dict" completely */
402 *dict_len = 0;
403 /* compute the size again, count also the warning message */
404 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
405}
406
7ff9554b 407/* insert record into the buffer, discard old ones, update heads */
034633cc
PM
408static int log_store(int facility, int level,
409 enum log_flags flags, u64 ts_nsec,
410 const char *dict, u16 dict_len,
411 const char *text, u16 text_len)
7ff9554b 412{
62e32ac3 413 struct printk_log *msg;
7ff9554b 414 u32 size, pad_len;
55bd53a4 415 u16 trunc_msg_len = 0;
7ff9554b
KS
416
417 /* number of '\0' padding bytes to next message */
85c87043 418 size = msg_used_size(text_len, dict_len, &pad_len);
7ff9554b 419
55bd53a4
PM
420 if (log_make_free_space(size)) {
421 /* truncate the message if it is too long for empty buffer */
422 size = truncate_msg(&text_len, &trunc_msg_len,
423 &dict_len, &pad_len);
424 /* survive when the log buffer is too small for trunc_msg */
425 if (log_make_free_space(size))
034633cc 426 return 0;
55bd53a4 427 }
7ff9554b 428
39b25109 429 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
7ff9554b
KS
430 /*
431 * This message + an additional empty header does not fit
432 * at the end of the buffer. Add an empty header with len == 0
433 * to signify a wrap around.
434 */
62e32ac3 435 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
7ff9554b
KS
436 log_next_idx = 0;
437 }
438
439 /* fill message */
62e32ac3 440 msg = (struct printk_log *)(log_buf + log_next_idx);
7ff9554b
KS
441 memcpy(log_text(msg), text, text_len);
442 msg->text_len = text_len;
55bd53a4
PM
443 if (trunc_msg_len) {
444 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
445 msg->text_len += trunc_msg_len;
446 }
7ff9554b
KS
447 memcpy(log_dict(msg), dict, dict_len);
448 msg->dict_len = dict_len;
084681d1
KS
449 msg->facility = facility;
450 msg->level = level & 7;
451 msg->flags = flags & 0x1f;
452 if (ts_nsec > 0)
453 msg->ts_nsec = ts_nsec;
454 else
455 msg->ts_nsec = local_clock();
7ff9554b 456 memset(log_dict(msg) + dict_len, 0, pad_len);
fce6e033 457 msg->len = size;
7ff9554b
KS
458
459 /* insert message */
460 log_next_idx += msg->len;
461 log_next_seq++;
034633cc
PM
462
463 return msg->text_len;
7ff9554b 464}
d59745ce 465
e99aa461 466int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
637241a9
KC
467
468static int syslog_action_restricted(int type)
469{
470 if (dmesg_restrict)
471 return 1;
472 /*
473 * Unless restricted, we allow "read all" and "get buffer size"
474 * for everybody.
475 */
476 return type != SYSLOG_ACTION_READ_ALL &&
477 type != SYSLOG_ACTION_SIZE_BUFFER;
478}
479
68c4a4f8 480int check_syslog_permissions(int type, bool from_file)
637241a9
KC
481{
482 /*
483 * If this is from /proc/kmsg and we've already opened it, then we've
484 * already done the capabilities checks at open time.
485 */
486 if (from_file && type != SYSLOG_ACTION_OPEN)
487 return 0;
488
489 if (syslog_action_restricted(type)) {
490 if (capable(CAP_SYSLOG))
491 return 0;
492 /*
493 * For historical reasons, accept CAP_SYS_ADMIN too, with
494 * a warning.
495 */
496 if (capable(CAP_SYS_ADMIN)) {
497 pr_warn_once("%s (%d): Attempt to access syslog with "
498 "CAP_SYS_ADMIN but no CAP_SYSLOG "
499 "(deprecated).\n",
500 current->comm, task_pid_nr(current));
501 return 0;
502 }
503 return -EPERM;
504 }
505 return security_syslog(type);
506}
507
d43ff430
TH
508static void append_char(char **pp, char *e, char c)
509{
510 if (*pp < e)
511 *(*pp)++ = c;
512}
637241a9 513
e11fea92
KS
514/* /dev/kmsg - userspace message inject/listen interface */
515struct devkmsg_user {
516 u64 seq;
517 u32 idx;
d39f3d77 518 enum log_flags prev;
e11fea92 519 struct mutex lock;
d43ff430 520 char buf[CONSOLE_EXT_LOG_MAX];
e11fea92
KS
521};
522
849f3127 523static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
e11fea92
KS
524{
525 char *buf, *line;
526 int i;
527 int level = default_message_loglevel;
528 int facility = 1; /* LOG_USER */
66ee59af 529 size_t len = iov_iter_count(from);
e11fea92
KS
530 ssize_t ret = len;
531
532 if (len > LOG_LINE_MAX)
533 return -EINVAL;
534 buf = kmalloc(len+1, GFP_KERNEL);
535 if (buf == NULL)
536 return -ENOMEM;
537
849f3127
AV
538 buf[len] = '\0';
539 if (copy_from_iter(buf, len, from) != len) {
540 kfree(buf);
541 return -EFAULT;
e11fea92
KS
542 }
543
544 /*
545 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
546 * the decimal value represents 32bit, the lower 3 bit are the log
547 * level, the rest are the log facility.
548 *
549 * If no prefix or no userspace facility is specified, we
550 * enforce LOG_USER, to be able to reliably distinguish
551 * kernel-generated messages from userspace-injected ones.
552 */
553 line = buf;
554 if (line[0] == '<') {
555 char *endp = NULL;
556
557 i = simple_strtoul(line+1, &endp, 10);
558 if (endp && endp[0] == '>') {
559 level = i & 7;
560 if (i >> 3)
561 facility = i >> 3;
562 endp++;
563 len -= endp - line;
564 line = endp;
565 }
566 }
e11fea92
KS
567
568 printk_emit(facility, level, NULL, 0, "%s", line);
e11fea92
KS
569 kfree(buf);
570 return ret;
571}
572
573static ssize_t devkmsg_read(struct file *file, char __user *buf,
574 size_t count, loff_t *ppos)
575{
576 struct devkmsg_user *user = file->private_data;
62e32ac3 577 struct printk_log *msg;
d43ff430 578 char *p, *e;
5fc32490 579 u64 ts_usec;
e11fea92 580 size_t i;
d39f3d77 581 char cont = '-';
e11fea92
KS
582 size_t len;
583 ssize_t ret;
584
585 if (!user)
586 return -EBADF;
587
d43ff430
TH
588 p = user->buf;
589 e = user->buf + sizeof(user->buf);
590
4a77a5a0
YL
591 ret = mutex_lock_interruptible(&user->lock);
592 if (ret)
593 return ret;
5c53d819 594 raw_spin_lock_irq(&logbuf_lock);
e11fea92
KS
595 while (user->seq == log_next_seq) {
596 if (file->f_flags & O_NONBLOCK) {
597 ret = -EAGAIN;
5c53d819 598 raw_spin_unlock_irq(&logbuf_lock);
e11fea92
KS
599 goto out;
600 }
601
5c53d819 602 raw_spin_unlock_irq(&logbuf_lock);
e11fea92
KS
603 ret = wait_event_interruptible(log_wait,
604 user->seq != log_next_seq);
605 if (ret)
606 goto out;
5c53d819 607 raw_spin_lock_irq(&logbuf_lock);
e11fea92
KS
608 }
609
610 if (user->seq < log_first_seq) {
611 /* our last seen message is gone, return error and reset */
612 user->idx = log_first_idx;
613 user->seq = log_first_seq;
614 ret = -EPIPE;
5c53d819 615 raw_spin_unlock_irq(&logbuf_lock);
e11fea92
KS
616 goto out;
617 }
618
619 msg = log_from_idx(user->idx);
5fc32490
KS
620 ts_usec = msg->ts_nsec;
621 do_div(ts_usec, 1000);
d39f3d77
KS
622
623 /*
624 * If we couldn't merge continuation line fragments during the print,
625 * export the stored flags to allow an optional external merge of the
626 * records. Merging the records isn't always neccessarily correct, like
627 * when we hit a race during printing. In most cases though, it produces
628 * better readable output. 'c' in the record flags mark the first
629 * fragment of a line, '+' the following.
630 */
631 if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
632 cont = 'c';
633 else if ((msg->flags & LOG_CONT) ||
634 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
635 cont = '+';
636
d43ff430
TH
637 p += scnprintf(p, e - p, "%u,%llu,%llu,%c;",
638 (msg->facility << 3) | msg->level,
639 user->seq, ts_usec, cont);
d39f3d77 640 user->prev = msg->flags;
e11fea92
KS
641
642 /* escape non-printable characters */
643 for (i = 0; i < msg->text_len; i++) {
3ce9a7c0 644 unsigned char c = log_text(msg)[i];
e11fea92 645
e3f5a5f2 646 if (c < ' ' || c >= 127 || c == '\\')
d43ff430 647 p += scnprintf(p, e - p, "\\x%02x", c);
e11fea92 648 else
d43ff430 649 append_char(&p, e, c);
e11fea92 650 }
d43ff430 651 append_char(&p, e, '\n');
e11fea92
KS
652
653 if (msg->dict_len) {
654 bool line = true;
655
656 for (i = 0; i < msg->dict_len; i++) {
3ce9a7c0 657 unsigned char c = log_dict(msg)[i];
e11fea92
KS
658
659 if (line) {
d43ff430 660 append_char(&p, e, ' ');
e11fea92
KS
661 line = false;
662 }
663
664 if (c == '\0') {
d43ff430 665 append_char(&p, e, '\n');
e11fea92
KS
666 line = true;
667 continue;
668 }
669
e3f5a5f2 670 if (c < ' ' || c >= 127 || c == '\\') {
d43ff430 671 p += scnprintf(p, e - p, "\\x%02x", c);
e11fea92
KS
672 continue;
673 }
674
d43ff430 675 append_char(&p, e, c);
e11fea92 676 }
d43ff430 677 append_char(&p, e, '\n');
e11fea92
KS
678 }
679
680 user->idx = log_next(user->idx);
681 user->seq++;
5c53d819 682 raw_spin_unlock_irq(&logbuf_lock);
e11fea92 683
d43ff430 684 len = p - user->buf;
e11fea92
KS
685 if (len > count) {
686 ret = -EINVAL;
687 goto out;
688 }
689
690 if (copy_to_user(buf, user->buf, len)) {
691 ret = -EFAULT;
692 goto out;
693 }
694 ret = len;
695out:
696 mutex_unlock(&user->lock);
697 return ret;
698}
699
700static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
701{
702 struct devkmsg_user *user = file->private_data;
703 loff_t ret = 0;
704
705 if (!user)
706 return -EBADF;
707 if (offset)
708 return -ESPIPE;
709
5c53d819 710 raw_spin_lock_irq(&logbuf_lock);
e11fea92
KS
711 switch (whence) {
712 case SEEK_SET:
713 /* the first record */
714 user->idx = log_first_idx;
715 user->seq = log_first_seq;
716 break;
717 case SEEK_DATA:
718 /*
719 * The first record after the last SYSLOG_ACTION_CLEAR,
720 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
721 * changes no global state, and does not clear anything.
722 */
723 user->idx = clear_idx;
724 user->seq = clear_seq;
725 break;
726 case SEEK_END:
727 /* after the last record */
728 user->idx = log_next_idx;
729 user->seq = log_next_seq;
730 break;
731 default:
732 ret = -EINVAL;
733 }
5c53d819 734 raw_spin_unlock_irq(&logbuf_lock);
e11fea92
KS
735 return ret;
736}
737
738static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
739{
740 struct devkmsg_user *user = file->private_data;
741 int ret = 0;
742
743 if (!user)
744 return POLLERR|POLLNVAL;
745
746 poll_wait(file, &log_wait, wait);
747
5c53d819 748 raw_spin_lock_irq(&logbuf_lock);
e11fea92
KS
749 if (user->seq < log_next_seq) {
750 /* return error when data has vanished underneath us */
751 if (user->seq < log_first_seq)
752 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
0a285317
NK
753 else
754 ret = POLLIN|POLLRDNORM;
e11fea92 755 }
5c53d819 756 raw_spin_unlock_irq(&logbuf_lock);
e11fea92
KS
757
758 return ret;
759}
760
761static int devkmsg_open(struct inode *inode, struct file *file)
762{
763 struct devkmsg_user *user;
764 int err;
765
766 /* write-only does not need any file context */
767 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
768 return 0;
769
637241a9
KC
770 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
771 SYSLOG_FROM_READER);
e11fea92
KS
772 if (err)
773 return err;
774
775 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
776 if (!user)
777 return -ENOMEM;
778
779 mutex_init(&user->lock);
780
5c53d819 781 raw_spin_lock_irq(&logbuf_lock);
e11fea92
KS
782 user->idx = log_first_idx;
783 user->seq = log_first_seq;
5c53d819 784 raw_spin_unlock_irq(&logbuf_lock);
e11fea92
KS
785
786 file->private_data = user;
787 return 0;
788}
789
790static int devkmsg_release(struct inode *inode, struct file *file)
791{
792 struct devkmsg_user *user = file->private_data;
793
794 if (!user)
795 return 0;
796
797 mutex_destroy(&user->lock);
798 kfree(user);
799 return 0;
800}
801
802const struct file_operations kmsg_fops = {
803 .open = devkmsg_open,
804 .read = devkmsg_read,
849f3127 805 .write_iter = devkmsg_write,
e11fea92
KS
806 .llseek = devkmsg_llseek,
807 .poll = devkmsg_poll,
808 .release = devkmsg_release,
809};
810
04d491ab
NH
811#ifdef CONFIG_KEXEC
812/*
4c1ace64 813 * This appends the listed symbols to /proc/vmcore
04d491ab 814 *
4c1ace64 815 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
04d491ab
NH
816 * obtain access to symbols that are otherwise very difficult to locate. These
817 * symbols are specifically used so that utilities can access and extract the
818 * dmesg log from a vmcore file after a crash.
819 */
820void log_buf_kexec_setup(void)
821{
822 VMCOREINFO_SYMBOL(log_buf);
04d491ab 823 VMCOREINFO_SYMBOL(log_buf_len);
7ff9554b
KS
824 VMCOREINFO_SYMBOL(log_first_idx);
825 VMCOREINFO_SYMBOL(log_next_idx);
6791457a 826 /*
62e32ac3 827 * Export struct printk_log size and field offsets. User space tools can
6791457a
VG
828 * parse it and detect any changes to structure down the line.
829 */
62e32ac3
JP
830 VMCOREINFO_STRUCT_SIZE(printk_log);
831 VMCOREINFO_OFFSET(printk_log, ts_nsec);
832 VMCOREINFO_OFFSET(printk_log, len);
833 VMCOREINFO_OFFSET(printk_log, text_len);
834 VMCOREINFO_OFFSET(printk_log, dict_len);
04d491ab
NH
835}
836#endif
837
162a7e75
MT
838/* requested log_buf_len from kernel cmdline */
839static unsigned long __initdata new_log_buf_len;
840
c0a318a3
LR
841/* we practice scaling the ring buffer by powers of 2 */
842static void __init log_buf_len_update(unsigned size)
1da177e4 843{
1da177e4
LT
844 if (size)
845 size = roundup_pow_of_two(size);
162a7e75
MT
846 if (size > log_buf_len)
847 new_log_buf_len = size;
c0a318a3
LR
848}
849
850/* save requested log_buf_len since it's too early to process it */
851static int __init log_buf_len_setup(char *str)
852{
853 unsigned size = memparse(str, &str);
854
855 log_buf_len_update(size);
162a7e75
MT
856
857 return 0;
1da177e4 858}
162a7e75
MT
859early_param("log_buf_len", log_buf_len_setup);
860
2240a31d
GU
861#ifdef CONFIG_SMP
862#define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
863
23b2899f
LR
864static void __init log_buf_add_cpu(void)
865{
866 unsigned int cpu_extra;
867
868 /*
869 * archs should set up cpu_possible_bits properly with
870 * set_cpu_possible() after setup_arch() but just in
871 * case lets ensure this is valid.
872 */
873 if (num_possible_cpus() == 1)
874 return;
875
876 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
877
878 /* by default this will only continue through for large > 64 CPUs */
879 if (cpu_extra <= __LOG_BUF_LEN / 2)
880 return;
881
882 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
883 __LOG_CPU_MAX_BUF_LEN);
884 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
885 cpu_extra);
886 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
887
888 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
889}
2240a31d
GU
890#else /* !CONFIG_SMP */
891static inline void log_buf_add_cpu(void) {}
892#endif /* CONFIG_SMP */
23b2899f 893
162a7e75
MT
894void __init setup_log_buf(int early)
895{
896 unsigned long flags;
162a7e75
MT
897 char *new_log_buf;
898 int free;
899
23b2899f
LR
900 if (log_buf != __log_buf)
901 return;
902
903 if (!early && !new_log_buf_len)
904 log_buf_add_cpu();
905
162a7e75
MT
906 if (!new_log_buf_len)
907 return;
1da177e4 908
162a7e75 909 if (early) {
9da791df 910 new_log_buf =
70300177 911 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
162a7e75 912 } else {
70300177
LR
913 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
914 LOG_ALIGN);
162a7e75
MT
915 }
916
917 if (unlikely(!new_log_buf)) {
918 pr_err("log_buf_len: %ld bytes not available\n",
919 new_log_buf_len);
920 return;
921 }
922
07354eb1 923 raw_spin_lock_irqsave(&logbuf_lock, flags);
162a7e75
MT
924 log_buf_len = new_log_buf_len;
925 log_buf = new_log_buf;
926 new_log_buf_len = 0;
7ff9554b
KS
927 free = __LOG_BUF_LEN - log_next_idx;
928 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
07354eb1 929 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
162a7e75 930
f5405172 931 pr_info("log_buf_len: %d bytes\n", log_buf_len);
162a7e75
MT
932 pr_info("early log buf free: %d(%d%%)\n",
933 free, (free * 100) / __LOG_BUF_LEN);
934}
1da177e4 935
2fa72c8f
AC
936static bool __read_mostly ignore_loglevel;
937
938static int __init ignore_loglevel_setup(char *str)
939{
d25d9fec 940 ignore_loglevel = true;
27083bac 941 pr_info("debug: ignoring loglevel setting.\n");
2fa72c8f
AC
942
943 return 0;
944}
945
946early_param("ignore_loglevel", ignore_loglevel_setup);
947module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
205bd3d2
JP
948MODULE_PARM_DESC(ignore_loglevel,
949 "ignore loglevel setting (prints all kernel messages to the console)");
2fa72c8f 950
bfe8df3d
RD
951#ifdef CONFIG_BOOT_PRINTK_DELAY
952
674dff65 953static int boot_delay; /* msecs delay after each printk during bootup */
3a3b6ed2 954static unsigned long long loops_per_msec; /* based on boot_delay */
bfe8df3d
RD
955
956static int __init boot_delay_setup(char *str)
957{
958 unsigned long lpj;
bfe8df3d
RD
959
960 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
961 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
962
963 get_option(&str, &boot_delay);
964 if (boot_delay > 10 * 1000)
965 boot_delay = 0;
966
3a3b6ed2
DY
967 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
968 "HZ: %d, loops_per_msec: %llu\n",
969 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
29e9d225 970 return 0;
bfe8df3d 971}
29e9d225 972early_param("boot_delay", boot_delay_setup);
bfe8df3d 973
2fa72c8f 974static void boot_delay_msec(int level)
bfe8df3d
RD
975{
976 unsigned long long k;
977 unsigned long timeout;
978
2fa72c8f
AC
979 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
980 || (level >= console_loglevel && !ignore_loglevel)) {
bfe8df3d 981 return;
2fa72c8f 982 }
bfe8df3d 983
3a3b6ed2 984 k = (unsigned long long)loops_per_msec * boot_delay;
bfe8df3d
RD
985
986 timeout = jiffies + msecs_to_jiffies(boot_delay);
987 while (k) {
988 k--;
989 cpu_relax();
990 /*
991 * use (volatile) jiffies to prevent
992 * compiler reduction; loop termination via jiffies
993 * is secondary and may or may not happen.
994 */
995 if (time_after(jiffies, timeout))
996 break;
997 touch_nmi_watchdog();
998 }
999}
1000#else
2fa72c8f 1001static inline void boot_delay_msec(int level)
bfe8df3d
RD
1002{
1003}
1004#endif
1005
e99aa461 1006static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
7ff9554b
KS
1007module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1008
084681d1
KS
1009static size_t print_time(u64 ts, char *buf)
1010{
1011 unsigned long rem_nsec;
1012
1013 if (!printk_time)
1014 return 0;
1015
35dac27c
RD
1016 rem_nsec = do_div(ts, 1000000000);
1017
084681d1 1018 if (!buf)
35dac27c 1019 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
084681d1 1020
084681d1
KS
1021 return sprintf(buf, "[%5lu.%06lu] ",
1022 (unsigned long)ts, rem_nsec / 1000);
1023}
1024
62e32ac3 1025static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
649e6ee3 1026{
3ce9a7c0 1027 size_t len = 0;
43a73a50 1028 unsigned int prefix = (msg->facility << 3) | msg->level;
649e6ee3 1029
3ce9a7c0
KS
1030 if (syslog) {
1031 if (buf) {
43a73a50 1032 len += sprintf(buf, "<%u>", prefix);
3ce9a7c0
KS
1033 } else {
1034 len += 3;
43a73a50
KS
1035 if (prefix > 999)
1036 len += 3;
1037 else if (prefix > 99)
1038 len += 2;
1039 else if (prefix > 9)
3ce9a7c0
KS
1040 len++;
1041 }
1042 }
649e6ee3 1043
084681d1 1044 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
3ce9a7c0 1045 return len;
649e6ee3
KS
1046}
1047
62e32ac3 1048static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
5becfb1d 1049 bool syslog, char *buf, size_t size)
7ff9554b 1050{
3ce9a7c0
KS
1051 const char *text = log_text(msg);
1052 size_t text_size = msg->text_len;
5becfb1d
KS
1053 bool prefix = true;
1054 bool newline = true;
3ce9a7c0
KS
1055 size_t len = 0;
1056
5becfb1d
KS
1057 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1058 prefix = false;
1059
1060 if (msg->flags & LOG_CONT) {
1061 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1062 prefix = false;
1063
1064 if (!(msg->flags & LOG_NEWLINE))
1065 newline = false;
1066 }
1067
3ce9a7c0
KS
1068 do {
1069 const char *next = memchr(text, '\n', text_size);
1070 size_t text_len;
1071
1072 if (next) {
1073 text_len = next - text;
1074 next++;
1075 text_size -= next - text;
1076 } else {
1077 text_len = text_size;
1078 }
7ff9554b 1079
3ce9a7c0
KS
1080 if (buf) {
1081 if (print_prefix(msg, syslog, NULL) +
70498253 1082 text_len + 1 >= size - len)
3ce9a7c0 1083 break;
7ff9554b 1084
5becfb1d
KS
1085 if (prefix)
1086 len += print_prefix(msg, syslog, buf + len);
3ce9a7c0
KS
1087 memcpy(buf + len, text, text_len);
1088 len += text_len;
5becfb1d
KS
1089 if (next || newline)
1090 buf[len++] = '\n';
3ce9a7c0
KS
1091 } else {
1092 /* SYSLOG_ACTION_* buffer size only calculation */
5becfb1d
KS
1093 if (prefix)
1094 len += print_prefix(msg, syslog, NULL);
1095 len += text_len;
1096 if (next || newline)
1097 len++;
3ce9a7c0 1098 }
7ff9554b 1099
5becfb1d 1100 prefix = true;
3ce9a7c0
KS
1101 text = next;
1102 } while (text);
7ff9554b 1103
7ff9554b
KS
1104 return len;
1105}
1106
1107static int syslog_print(char __user *buf, int size)
1108{
1109 char *text;
62e32ac3 1110 struct printk_log *msg;
116e90b2 1111 int len = 0;
7ff9554b 1112
70498253 1113 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
7ff9554b
KS
1114 if (!text)
1115 return -ENOMEM;
1116
116e90b2
JB
1117 while (size > 0) {
1118 size_t n;
eb02dac9 1119 size_t skip;
116e90b2
JB
1120
1121 raw_spin_lock_irq(&logbuf_lock);
1122 if (syslog_seq < log_first_seq) {
1123 /* messages are gone, move to first one */
1124 syslog_seq = log_first_seq;
1125 syslog_idx = log_first_idx;
5becfb1d 1126 syslog_prev = 0;
eb02dac9 1127 syslog_partial = 0;
116e90b2
JB
1128 }
1129 if (syslog_seq == log_next_seq) {
1130 raw_spin_unlock_irq(&logbuf_lock);
1131 break;
1132 }
eb02dac9
KS
1133
1134 skip = syslog_partial;
116e90b2 1135 msg = log_from_idx(syslog_idx);
70498253
KS
1136 n = msg_print_text(msg, syslog_prev, true, text,
1137 LOG_LINE_MAX + PREFIX_MAX);
eb02dac9
KS
1138 if (n - syslog_partial <= size) {
1139 /* message fits into buffer, move forward */
116e90b2
JB
1140 syslog_idx = log_next(syslog_idx);
1141 syslog_seq++;
5becfb1d 1142 syslog_prev = msg->flags;
eb02dac9
KS
1143 n -= syslog_partial;
1144 syslog_partial = 0;
1145 } else if (!len){
1146 /* partial read(), remember position */
1147 n = size;
1148 syslog_partial += n;
116e90b2
JB
1149 } else
1150 n = 0;
1151 raw_spin_unlock_irq(&logbuf_lock);
1152
1153 if (!n)
1154 break;
1155
eb02dac9 1156 if (copy_to_user(buf, text + skip, n)) {
116e90b2
JB
1157 if (!len)
1158 len = -EFAULT;
1159 break;
1160 }
eb02dac9
KS
1161
1162 len += n;
1163 size -= n;
1164 buf += n;
7ff9554b 1165 }
7ff9554b
KS
1166
1167 kfree(text);
1168 return len;
1169}
1170
1171static int syslog_print_all(char __user *buf, int size, bool clear)
1172{
1173 char *text;
1174 int len = 0;
1175
70498253 1176 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
7ff9554b
KS
1177 if (!text)
1178 return -ENOMEM;
1179
1180 raw_spin_lock_irq(&logbuf_lock);
1181 if (buf) {
1182 u64 next_seq;
1183 u64 seq;
1184 u32 idx;
5becfb1d 1185 enum log_flags prev;
7ff9554b
KS
1186
1187 if (clear_seq < log_first_seq) {
1188 /* messages are gone, move to first available one */
1189 clear_seq = log_first_seq;
1190 clear_idx = log_first_idx;
1191 }
1192
1193 /*
1194 * Find first record that fits, including all following records,
1195 * into the user-provided buffer for this dump.
e2ae715d 1196 */
7ff9554b
KS
1197 seq = clear_seq;
1198 idx = clear_idx;
5becfb1d 1199 prev = 0;
7ff9554b 1200 while (seq < log_next_seq) {
62e32ac3 1201 struct printk_log *msg = log_from_idx(idx);
3ce9a7c0 1202
5becfb1d 1203 len += msg_print_text(msg, prev, true, NULL, 0);
e3756477 1204 prev = msg->flags;
7ff9554b
KS
1205 idx = log_next(idx);
1206 seq++;
1207 }
e2ae715d
KS
1208
1209 /* move first record forward until length fits into the buffer */
7ff9554b
KS
1210 seq = clear_seq;
1211 idx = clear_idx;
5becfb1d 1212 prev = 0;
7ff9554b 1213 while (len > size && seq < log_next_seq) {
62e32ac3 1214 struct printk_log *msg = log_from_idx(idx);
3ce9a7c0 1215
5becfb1d 1216 len -= msg_print_text(msg, prev, true, NULL, 0);
e3756477 1217 prev = msg->flags;
7ff9554b
KS
1218 idx = log_next(idx);
1219 seq++;
1220 }
1221
e2ae715d 1222 /* last message fitting into this dump */
7ff9554b
KS
1223 next_seq = log_next_seq;
1224
1225 len = 0;
1226 while (len >= 0 && seq < next_seq) {
62e32ac3 1227 struct printk_log *msg = log_from_idx(idx);
7ff9554b
KS
1228 int textlen;
1229
70498253
KS
1230 textlen = msg_print_text(msg, prev, true, text,
1231 LOG_LINE_MAX + PREFIX_MAX);
7ff9554b
KS
1232 if (textlen < 0) {
1233 len = textlen;
1234 break;
1235 }
1236 idx = log_next(idx);
1237 seq++;
5becfb1d 1238 prev = msg->flags;
7ff9554b
KS
1239
1240 raw_spin_unlock_irq(&logbuf_lock);
1241 if (copy_to_user(buf + len, text, textlen))
1242 len = -EFAULT;
1243 else
1244 len += textlen;
1245 raw_spin_lock_irq(&logbuf_lock);
1246
1247 if (seq < log_first_seq) {
1248 /* messages are gone, move to next one */
1249 seq = log_first_seq;
1250 idx = log_first_idx;
5becfb1d 1251 prev = 0;
7ff9554b
KS
1252 }
1253 }
1254 }
1255
1256 if (clear) {
1257 clear_seq = log_next_seq;
1258 clear_idx = log_next_idx;
1259 }
1260 raw_spin_unlock_irq(&logbuf_lock);
1261
1262 kfree(text);
1263 return len;
1264}
1265
00234592 1266int do_syslog(int type, char __user *buf, int len, bool from_file)
1da177e4 1267{
7ff9554b 1268 bool clear = false;
a39d4a85 1269 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
ee24aebf 1270 int error;
1da177e4 1271
ee24aebf
LT
1272 error = check_syslog_permissions(type, from_file);
1273 if (error)
1274 goto out;
12b3052c
EP
1275
1276 error = security_syslog(type);
1da177e4
LT
1277 if (error)
1278 return error;
1279
1280 switch (type) {
d78ca3cd 1281 case SYSLOG_ACTION_CLOSE: /* Close log */
1da177e4 1282 break;
d78ca3cd 1283 case SYSLOG_ACTION_OPEN: /* Open log */
1da177e4 1284 break;
d78ca3cd 1285 case SYSLOG_ACTION_READ: /* Read from log */
1da177e4
LT
1286 error = -EINVAL;
1287 if (!buf || len < 0)
1288 goto out;
1289 error = 0;
1290 if (!len)
1291 goto out;
1292 if (!access_ok(VERIFY_WRITE, buf, len)) {
1293 error = -EFAULT;
1294 goto out;
1295 }
40dc5651 1296 error = wait_event_interruptible(log_wait,
7ff9554b 1297 syslog_seq != log_next_seq);
cb424ffe 1298 if (error)
1da177e4 1299 goto out;
7ff9554b 1300 error = syslog_print(buf, len);
1da177e4 1301 break;
d78ca3cd
KC
1302 /* Read/clear last kernel messages */
1303 case SYSLOG_ACTION_READ_CLEAR:
7ff9554b 1304 clear = true;
1da177e4 1305 /* FALL THRU */
d78ca3cd
KC
1306 /* Read last kernel messages */
1307 case SYSLOG_ACTION_READ_ALL:
1da177e4
LT
1308 error = -EINVAL;
1309 if (!buf || len < 0)
1310 goto out;
1311 error = 0;
1312 if (!len)
1313 goto out;
1314 if (!access_ok(VERIFY_WRITE, buf, len)) {
1315 error = -EFAULT;
1316 goto out;
1317 }
7ff9554b 1318 error = syslog_print_all(buf, len, clear);
1da177e4 1319 break;
d78ca3cd
KC
1320 /* Clear ring buffer */
1321 case SYSLOG_ACTION_CLEAR:
7ff9554b 1322 syslog_print_all(NULL, 0, true);
4661e356 1323 break;
d78ca3cd
KC
1324 /* Disable logging to console */
1325 case SYSLOG_ACTION_CONSOLE_OFF:
a39d4a85 1326 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1aaad49e 1327 saved_console_loglevel = console_loglevel;
1da177e4
LT
1328 console_loglevel = minimum_console_loglevel;
1329 break;
d78ca3cd
KC
1330 /* Enable logging to console */
1331 case SYSLOG_ACTION_CONSOLE_ON:
a39d4a85 1332 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1aaad49e 1333 console_loglevel = saved_console_loglevel;
a39d4a85 1334 saved_console_loglevel = LOGLEVEL_DEFAULT;
1aaad49e 1335 }
1da177e4 1336 break;
d78ca3cd
KC
1337 /* Set level of messages printed to console */
1338 case SYSLOG_ACTION_CONSOLE_LEVEL:
1da177e4
LT
1339 error = -EINVAL;
1340 if (len < 1 || len > 8)
1341 goto out;
1342 if (len < minimum_console_loglevel)
1343 len = minimum_console_loglevel;
1344 console_loglevel = len;
1aaad49e 1345 /* Implicitly re-enable logging to console */
a39d4a85 1346 saved_console_loglevel = LOGLEVEL_DEFAULT;
1da177e4
LT
1347 error = 0;
1348 break;
d78ca3cd
KC
1349 /* Number of chars in the log buffer */
1350 case SYSLOG_ACTION_SIZE_UNREAD:
7ff9554b
KS
1351 raw_spin_lock_irq(&logbuf_lock);
1352 if (syslog_seq < log_first_seq) {
1353 /* messages are gone, move to first one */
1354 syslog_seq = log_first_seq;
1355 syslog_idx = log_first_idx;
5becfb1d 1356 syslog_prev = 0;
eb02dac9 1357 syslog_partial = 0;
7ff9554b
KS
1358 }
1359 if (from_file) {
1360 /*
1361 * Short-cut for poll(/"proc/kmsg") which simply checks
1362 * for pending data, not the size; return the count of
1363 * records, not the length.
1364 */
e97e1267 1365 error = log_next_seq - syslog_seq;
7ff9554b 1366 } else {
5becfb1d
KS
1367 u64 seq = syslog_seq;
1368 u32 idx = syslog_idx;
1369 enum log_flags prev = syslog_prev;
7ff9554b
KS
1370
1371 error = 0;
7ff9554b 1372 while (seq < log_next_seq) {
62e32ac3 1373 struct printk_log *msg = log_from_idx(idx);
3ce9a7c0 1374
5becfb1d 1375 error += msg_print_text(msg, prev, true, NULL, 0);
7ff9554b
KS
1376 idx = log_next(idx);
1377 seq++;
5becfb1d 1378 prev = msg->flags;
7ff9554b 1379 }
eb02dac9 1380 error -= syslog_partial;
7ff9554b
KS
1381 }
1382 raw_spin_unlock_irq(&logbuf_lock);
1da177e4 1383 break;
d78ca3cd
KC
1384 /* Size of the log buffer */
1385 case SYSLOG_ACTION_SIZE_BUFFER:
1da177e4
LT
1386 error = log_buf_len;
1387 break;
1388 default:
1389 error = -EINVAL;
1390 break;
1391 }
1392out:
1393 return error;
1394}
1395
1e7bfb21 1396SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1da177e4 1397{
637241a9 1398 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1da177e4
LT
1399}
1400
1da177e4
LT
1401/*
1402 * Call the console drivers, asking them to write out
1403 * log_buf[start] to log_buf[end - 1].
ac751efa 1404 * The console_lock must be held.
1da177e4 1405 */
7ff9554b 1406static void call_console_drivers(int level, const char *text, size_t len)
1da177e4 1407{
7ff9554b 1408 struct console *con;
1da177e4 1409
07c65f4d 1410 trace_console(text, len);
7ff9554b
KS
1411
1412 if (level >= console_loglevel && !ignore_loglevel)
1413 return;
1414 if (!console_drivers)
1415 return;
1416
1417 for_each_console(con) {
1418 if (exclusive_console && con != exclusive_console)
1419 continue;
1420 if (!(con->flags & CON_ENABLED))
1421 continue;
1422 if (!con->write)
1423 continue;
1424 if (!cpu_online(smp_processor_id()) &&
1425 !(con->flags & CON_ANYTIME))
1426 continue;
1427 con->write(con, text, len);
1428 }
1da177e4
LT
1429}
1430
1431/*
205bd3d2
JP
1432 * Zap console related locks when oopsing.
1433 * To leave time for slow consoles to print a full oops,
1434 * only zap at most once every 30 seconds.
1da177e4
LT
1435 */
1436static void zap_locks(void)
1437{
1438 static unsigned long oops_timestamp;
1439
1440 if (time_after_eq(jiffies, oops_timestamp) &&
205bd3d2 1441 !time_after(jiffies, oops_timestamp + 30 * HZ))
1da177e4
LT
1442 return;
1443
1444 oops_timestamp = jiffies;
1445
94d24fc4 1446 debug_locks_off();
1da177e4 1447 /* If a crash is occurring, make sure we can't deadlock */
07354eb1 1448 raw_spin_lock_init(&logbuf_lock);
1da177e4 1449 /* And make sure that we print immediately */
5b8c4f23 1450 sema_init(&console_sem, 1);
1da177e4
LT
1451}
1452
608873ca
JK
1453/*
1454 * Check if we have any console that is capable of printing while cpu is
1455 * booting or shutting down. Requires console_sem.
1456 */
76a8ad29
ME
1457static int have_callable_console(void)
1458{
1459 struct console *con;
1460
4d091611 1461 for_each_console(con)
76a8ad29
ME
1462 if (con->flags & CON_ANYTIME)
1463 return 1;
1464
1465 return 0;
1466}
1467
266c2e0a
LT
1468/*
1469 * Can we actually use the console at this time on this cpu?
1470 *
5874af20
JK
1471 * Console drivers may assume that per-cpu resources have been allocated. So
1472 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1473 * call them until this CPU is officially up.
266c2e0a
LT
1474 */
1475static inline int can_use_console(unsigned int cpu)
1476{
1477 return cpu_online(cpu) || have_callable_console();
1478}
1479
1480/*
1481 * Try to get console ownership to actually show the kernel
1482 * messages from a 'printk'. Return true (and with the
ac751efa 1483 * console_lock held, and 'console_locked' set) if it
266c2e0a 1484 * is successful, false otherwise.
266c2e0a 1485 */
5874af20 1486static int console_trylock_for_printk(void)
266c2e0a 1487{
5874af20
JK
1488 unsigned int cpu = smp_processor_id();
1489
608873ca
JK
1490 if (!console_trylock())
1491 return 0;
1492 /*
1493 * If we can't use the console, we need to release the console
1494 * semaphore by hand to avoid flushing the buffer. We need to hold the
1495 * console semaphore in order to do this test safely.
1496 */
1497 if (!can_use_console(cpu)) {
1498 console_locked = 0;
bd8d7cf5 1499 up_console_sem();
608873ca
JK
1500 return 0;
1501 }
1502 return 1;
266c2e0a 1503}
32a76006 1504
af91322e
DY
1505int printk_delay_msec __read_mostly;
1506
1507static inline void printk_delay(void)
1508{
1509 if (unlikely(printk_delay_msec)) {
1510 int m = printk_delay_msec;
1511
1512 while (m--) {
1513 mdelay(1);
1514 touch_nmi_watchdog();
1515 }
1516 }
1517}
1518
084681d1
KS
1519/*
1520 * Continuation lines are buffered, and not committed to the record buffer
1521 * until the line is complete, or a race forces it. The line fragments
1522 * though, are printed immediately to the consoles to ensure everything has
1523 * reached the console in case of a kernel crash.
1524 */
1525static struct cont {
1526 char buf[LOG_LINE_MAX];
1527 size_t len; /* length == 0 means unused buffer */
1528 size_t cons; /* bytes written to console */
1529 struct task_struct *owner; /* task of first print*/
1530 u64 ts_nsec; /* time of first print */
1531 u8 level; /* log level of first message */
0b90fec3 1532 u8 facility; /* log facility of first message */
eab07260 1533 enum log_flags flags; /* prefix, newline flags */
084681d1
KS
1534 bool flushed:1; /* buffer sealed and committed */
1535} cont;
1536
70498253 1537static void cont_flush(enum log_flags flags)
084681d1
KS
1538{
1539 if (cont.flushed)
1540 return;
1541 if (cont.len == 0)
1542 return;
1543
eab07260
KS
1544 if (cont.cons) {
1545 /*
1546 * If a fragment of this line was directly flushed to the
1547 * console; wait for the console to pick up the rest of the
1548 * line. LOG_NOCONS suppresses a duplicated output.
1549 */
1550 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1551 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1552 cont.flags = flags;
1553 cont.flushed = true;
1554 } else {
1555 /*
1556 * If no fragment of this line ever reached the console,
1557 * just submit it to the store and free the buffer.
1558 */
1559 log_store(cont.facility, cont.level, flags, 0,
1560 NULL, 0, cont.buf, cont.len);
1561 cont.len = 0;
1562 }
084681d1
KS
1563}
1564
1565static bool cont_add(int facility, int level, const char *text, size_t len)
1566{
1567 if (cont.len && cont.flushed)
1568 return false;
1569
1570 if (cont.len + len > sizeof(cont.buf)) {
70498253
KS
1571 /* the line gets too long, split it up in separate records */
1572 cont_flush(LOG_CONT);
084681d1
KS
1573 return false;
1574 }
1575
1576 if (!cont.len) {
1577 cont.facility = facility;
1578 cont.level = level;
1579 cont.owner = current;
1580 cont.ts_nsec = local_clock();
eab07260 1581 cont.flags = 0;
084681d1
KS
1582 cont.cons = 0;
1583 cont.flushed = false;
1584 }
1585
1586 memcpy(cont.buf + cont.len, text, len);
1587 cont.len += len;
eab07260
KS
1588
1589 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1590 cont_flush(LOG_CONT);
1591
084681d1
KS
1592 return true;
1593}
1594
1595static size_t cont_print_text(char *text, size_t size)
1596{
1597 size_t textlen = 0;
1598 size_t len;
1599
eab07260 1600 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
084681d1
KS
1601 textlen += print_time(cont.ts_nsec, text);
1602 size -= textlen;
1603 }
1604
1605 len = cont.len - cont.cons;
1606 if (len > 0) {
1607 if (len+1 > size)
1608 len = size-1;
1609 memcpy(text + textlen, cont.buf + cont.cons, len);
1610 textlen += len;
1611 cont.cons = cont.len;
1612 }
1613
1614 if (cont.flushed) {
eab07260
KS
1615 if (cont.flags & LOG_NEWLINE)
1616 text[textlen++] = '\n';
084681d1
KS
1617 /* got everything, release buffer */
1618 cont.len = 0;
1619 }
1620 return textlen;
1621}
1622
7ff9554b
KS
1623asmlinkage int vprintk_emit(int facility, int level,
1624 const char *dict, size_t dictlen,
1625 const char *fmt, va_list args)
1da177e4 1626{
7ff9554b 1627 static int recursion_bug;
7ff9554b
KS
1628 static char textbuf[LOG_LINE_MAX];
1629 char *text = textbuf;
458df9fd 1630 size_t text_len = 0;
5becfb1d 1631 enum log_flags lflags = 0;
ac60ad74 1632 unsigned long flags;
32a76006 1633 int this_cpu;
7ff9554b 1634 int printed_len = 0;
458df9fd 1635 bool in_sched = false;
608873ca 1636 /* cpu currently holding logbuf_lock in this function */
f099755d 1637 static unsigned int logbuf_cpu = UINT_MAX;
608873ca 1638
a39d4a85
JP
1639 if (level == LOGLEVEL_SCHED) {
1640 level = LOGLEVEL_DEFAULT;
458df9fd
SR
1641 in_sched = true;
1642 }
1da177e4 1643
2fa72c8f 1644 boot_delay_msec(level);
af91322e 1645 printk_delay();
bfe8df3d 1646
1da177e4 1647 /* This stops the holder of console_sem just where we want him */
1a9a8aef 1648 local_irq_save(flags);
32a76006
IM
1649 this_cpu = smp_processor_id();
1650
1651 /*
1652 * Ouch, printk recursed into itself!
1653 */
7ff9554b 1654 if (unlikely(logbuf_cpu == this_cpu)) {
32a76006
IM
1655 /*
1656 * If a crash is occurring during printk() on this CPU,
1657 * then try to get the crash message out but make sure
1658 * we can't deadlock. Otherwise just return to avoid the
1659 * recursion and return - but flag the recursion so that
1660 * it can be printed at the next appropriate moment:
1661 */
94d24fc4 1662 if (!oops_in_progress && !lockdep_recursing(current)) {
3b8945e8 1663 recursion_bug = 1;
5874af20
JK
1664 local_irq_restore(flags);
1665 return 0;
32a76006
IM
1666 }
1667 zap_locks();
1668 }
1669
a0f1ccfd 1670 lockdep_off();
07354eb1 1671 raw_spin_lock(&logbuf_lock);
7ff9554b 1672 logbuf_cpu = this_cpu;
1da177e4 1673
000a7d66 1674 if (unlikely(recursion_bug)) {
7ff9554b
KS
1675 static const char recursion_msg[] =
1676 "BUG: recent printk recursion!";
1677
3b8945e8 1678 recursion_bug = 0;
7ff9554b 1679 /* emit KERN_CRIT message */
034633cc 1680 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
000a7d66
PP
1681 NULL, 0, recursion_msg,
1682 strlen(recursion_msg));
32a76006 1683 }
1da177e4 1684
7ff9554b
KS
1685 /*
1686 * The printf needs to come first; we need the syslog
1687 * prefix which might be passed-in as a parameter.
1688 */
98e35f58 1689 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
5fd29d6c 1690
7ff9554b 1691 /* mark and strip a trailing newline */
c313af14
KS
1692 if (text_len && text[text_len-1] == '\n') {
1693 text_len--;
5becfb1d 1694 lflags |= LOG_NEWLINE;
7ff9554b 1695 }
9d90c8d9 1696
088a52aa
JP
1697 /* strip kernel syslog prefix and extract log level or control flags */
1698 if (facility == 0) {
1699 int kern_level = printk_get_level(text);
1700
1701 if (kern_level) {
1702 const char *end_of_header = printk_skip_level(text);
1703 switch (kern_level) {
1704 case '0' ... '7':
a39d4a85 1705 if (level == LOGLEVEL_DEFAULT)
088a52aa 1706 level = kern_level - '0';
a39d4a85 1707 /* fallthrough */
088a52aa
JP
1708 case 'd': /* KERN_DEFAULT */
1709 lflags |= LOG_PREFIX;
088a52aa 1710 }
e8c42d36
PM
1711 /*
1712 * No need to check length here because vscnprintf
1713 * put '\0' at the end of the string. Only valid and
1714 * newly printed level is detected.
1715 */
088a52aa
JP
1716 text_len -= end_of_header - text;
1717 text = (char *)end_of_header;
5fd29d6c
LT
1718 }
1719 }
1720
a39d4a85 1721 if (level == LOGLEVEL_DEFAULT)
c313af14 1722 level = default_message_loglevel;
9d90c8d9 1723
5becfb1d
KS
1724 if (dict)
1725 lflags |= LOG_PREFIX|LOG_NEWLINE;
ac60ad74 1726
5becfb1d 1727 if (!(lflags & LOG_NEWLINE)) {
084681d1
KS
1728 /*
1729 * Flush the conflicting buffer. An earlier newline was missing,
1730 * or another task also prints continuation lines.
1731 */
5becfb1d 1732 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
eab07260 1733 cont_flush(LOG_NEWLINE);
c313af14 1734
084681d1 1735 /* buffer line if possible, otherwise store it right away */
034633cc
PM
1736 if (cont_add(facility, level, text, text_len))
1737 printed_len += text_len;
1738 else
1739 printed_len += log_store(facility, level,
1740 lflags | LOG_CONT, 0,
1741 dict, dictlen, text, text_len);
5c5d5ca5 1742 } else {
084681d1 1743 bool stored = false;
c313af14 1744
084681d1 1745 /*
d3620822
SR
1746 * If an earlier newline was missing and it was the same task,
1747 * either merge it with the current buffer and flush, or if
1748 * there was a race with interrupts (prefix == true) then just
1749 * flush it out and store this line separately.
1d3fa370
AK
1750 * If the preceding printk was from a different task and missed
1751 * a newline, flush and append the newline.
084681d1 1752 */
1d3fa370
AK
1753 if (cont.len) {
1754 if (cont.owner == current && !(lflags & LOG_PREFIX))
1755 stored = cont_add(facility, level, text,
1756 text_len);
eab07260 1757 cont_flush(LOG_NEWLINE);
c313af14 1758 }
084681d1 1759
034633cc
PM
1760 if (stored)
1761 printed_len += text_len;
1762 else
1763 printed_len += log_store(facility, level, lflags, 0,
1764 dict, dictlen, text, text_len);
1da177e4
LT
1765 }
1766
608873ca
JK
1767 logbuf_cpu = UINT_MAX;
1768 raw_spin_unlock(&logbuf_lock);
5874af20
JK
1769 lockdep_on();
1770 local_irq_restore(flags);
939f04be 1771
458df9fd 1772 /* If called from the scheduler, we can not call up(). */
d18bbc21 1773 if (!in_sched) {
5874af20
JK
1774 lockdep_off();
1775 /*
1776 * Disable preemption to avoid being preempted while holding
1777 * console_sem which would prevent anyone from printing to
1778 * console
1779 */
1780 preempt_disable();
1781
d18bbc21
AM
1782 /*
1783 * Try to acquire and then immediately release the console
1784 * semaphore. The release will print out buffers and wake up
1785 * /dev/kmsg and syslog() users.
1786 */
5874af20 1787 if (console_trylock_for_printk())
d18bbc21 1788 console_unlock();
5874af20
JK
1789 preempt_enable();
1790 lockdep_on();
d18bbc21 1791 }
76a8ad29 1792
1da177e4
LT
1793 return printed_len;
1794}
7ff9554b
KS
1795EXPORT_SYMBOL(vprintk_emit);
1796
1797asmlinkage int vprintk(const char *fmt, va_list args)
1798{
a39d4a85 1799 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
7ff9554b 1800}
1da177e4
LT
1801EXPORT_SYMBOL(vprintk);
1802
7ff9554b
KS
1803asmlinkage int printk_emit(int facility, int level,
1804 const char *dict, size_t dictlen,
1805 const char *fmt, ...)
1806{
1807 va_list args;
1808 int r;
1809
1810 va_start(args, fmt);
1811 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1812 va_end(args);
1813
1814 return r;
1815}
1816EXPORT_SYMBOL(printk_emit);
1817
afdc34a3
SRRH
1818int vprintk_default(const char *fmt, va_list args)
1819{
1820 int r;
1821
1822#ifdef CONFIG_KGDB_KDB
1823 if (unlikely(kdb_trap_printk)) {
f7d4ca8b 1824 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
afdc34a3
SRRH
1825 return r;
1826 }
1827#endif
350e4f49 1828 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
afdc34a3
SRRH
1829
1830 return r;
1831}
1832EXPORT_SYMBOL_GPL(vprintk_default);
1833
1834/*
1835 * This allows printk to be diverted to another function per cpu.
1836 * This is useful for calling printk functions from within NMI
1837 * without worrying about race conditions that can lock up the
1838 * box.
1839 */
1840DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
1841
7ff9554b
KS
1842/**
1843 * printk - print a kernel message
1844 * @fmt: format string
1845 *
1846 * This is printk(). It can be called from any context. We want it to work.
1847 *
1848 * We try to grab the console_lock. If we succeed, it's easy - we log the
1849 * output and call the console drivers. If we fail to get the semaphore, we
1850 * place the output into the log buffer and return. The current holder of
1851 * the console_sem will notice the new output in console_unlock(); and will
1852 * send it to the consoles before releasing the lock.
1853 *
1854 * One effect of this deferred printing is that code which calls printk() and
1855 * then changes console_loglevel may break. This is because console_loglevel
1856 * is inspected when the actual printing occurs.
1857 *
1858 * See also:
1859 * printf(3)
1860 *
1861 * See the vsnprintf() documentation for format string extensions over C99.
1862 */
722a9f92 1863asmlinkage __visible int printk(const char *fmt, ...)
7ff9554b 1864{
afdc34a3 1865 printk_func_t vprintk_func;
7ff9554b
KS
1866 va_list args;
1867 int r;
1868
7ff9554b 1869 va_start(args, fmt);
1fb8915b
SRRH
1870
1871 /*
1872 * If a caller overrides the per_cpu printk_func, then it needs
1873 * to disable preemption when calling printk(). Otherwise
1874 * the printk_func should be set to the default. No need to
1875 * disable preemption here.
1876 */
afdc34a3
SRRH
1877 vprintk_func = this_cpu_read(printk_func);
1878 r = vprintk_func(fmt, args);
1fb8915b 1879
7ff9554b
KS
1880 va_end(args);
1881
1882 return r;
1883}
1884EXPORT_SYMBOL(printk);
7f3a781d 1885
96efedf1 1886#else /* CONFIG_PRINTK */
d59745ce 1887
70498253
KS
1888#define LOG_LINE_MAX 0
1889#define PREFIX_MAX 0
249771b8 1890
96efedf1
KS
1891static u64 syslog_seq;
1892static u32 syslog_idx;
eab07260
KS
1893static u64 console_seq;
1894static u32 console_idx;
96efedf1
KS
1895static enum log_flags syslog_prev;
1896static u64 log_first_seq;
1897static u32 log_first_idx;
1898static u64 log_next_seq;
eab07260 1899static enum log_flags console_prev;
084681d1
KS
1900static struct cont {
1901 size_t len;
1902 size_t cons;
1903 u8 level;
1904 bool flushed:1;
1905} cont;
62e32ac3 1906static struct printk_log *log_from_idx(u32 idx) { return NULL; }
7f3a781d 1907static u32 log_next(u32 idx) { return 0; }
7f3a781d 1908static void call_console_drivers(int level, const char *text, size_t len) {}
62e32ac3 1909static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
5becfb1d 1910 bool syslog, char *buf, size_t size) { return 0; }
084681d1 1911static size_t cont_print_text(char *text, size_t size) { return 0; }
d59745ce 1912
04b74b27
SRRH
1913/* Still needs to be defined for users */
1914DEFINE_PER_CPU(printk_func_t, printk_func);
1915
7f3a781d 1916#endif /* CONFIG_PRINTK */
d59745ce 1917
d0380e6c
TG
1918#ifdef CONFIG_EARLY_PRINTK
1919struct console *early_console;
1920
722a9f92 1921asmlinkage __visible void early_printk(const char *fmt, ...)
d0380e6c
TG
1922{
1923 va_list ap;
1dc6244b
JP
1924 char buf[512];
1925 int n;
1926
1927 if (!early_console)
1928 return;
d0380e6c
TG
1929
1930 va_start(ap, fmt);
1dc6244b 1931 n = vscnprintf(buf, sizeof(buf), fmt, ap);
d0380e6c 1932 va_end(ap);
1dc6244b
JP
1933
1934 early_console->write(early_console, buf, n);
d0380e6c
TG
1935}
1936#endif
1937
f7511d5f
ST
1938static int __add_preferred_console(char *name, int idx, char *options,
1939 char *brl_options)
1940{
1941 struct console_cmdline *c;
1942 int i;
1943
1944 /*
1945 * See if this tty is not yet registered, and
1946 * if we have a slot free.
1947 */
23475408
JP
1948 for (i = 0, c = console_cmdline;
1949 i < MAX_CMDLINECONSOLES && c->name[0];
1950 i++, c++) {
1951 if (strcmp(c->name, name) == 0 && c->index == idx) {
1952 if (!brl_options)
1953 selected_console = i;
1954 return 0;
f7511d5f 1955 }
23475408 1956 }
f7511d5f
ST
1957 if (i == MAX_CMDLINECONSOLES)
1958 return -E2BIG;
1959 if (!brl_options)
1960 selected_console = i;
f7511d5f
ST
1961 strlcpy(c->name, name, sizeof(c->name));
1962 c->options = options;
bbeddf52
JP
1963 braille_set_options(c, brl_options);
1964
f7511d5f
ST
1965 c->index = idx;
1966 return 0;
1967}
2ea1c539 1968/*
0b90fec3
AE
1969 * Set up a console. Called via do_early_param() in init/main.c
1970 * for each "console=" parameter in the boot command line.
2ea1c539
JB
1971 */
1972static int __init console_setup(char *str)
1973{
0b90fec3 1974 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
f7511d5f 1975 char *s, *options, *brl_options = NULL;
2ea1c539
JB
1976 int idx;
1977
bbeddf52
JP
1978 if (_braille_console_setup(&str, &brl_options))
1979 return 1;
f7511d5f 1980
2ea1c539
JB
1981 /*
1982 * Decode str into name, index, options.
1983 */
1984 if (str[0] >= '0' && str[0] <= '9') {
eaa944af
YL
1985 strcpy(buf, "ttyS");
1986 strncpy(buf + 4, str, sizeof(buf) - 5);
2ea1c539 1987 } else {
eaa944af 1988 strncpy(buf, str, sizeof(buf) - 1);
2ea1c539 1989 }
eaa944af 1990 buf[sizeof(buf) - 1] = 0;
249771b8
AE
1991 options = strchr(str, ',');
1992 if (options)
2ea1c539
JB
1993 *(options++) = 0;
1994#ifdef __sparc__
1995 if (!strcmp(str, "ttya"))
eaa944af 1996 strcpy(buf, "ttyS0");
2ea1c539 1997 if (!strcmp(str, "ttyb"))
eaa944af 1998 strcpy(buf, "ttyS1");
2ea1c539 1999#endif
eaa944af 2000 for (s = buf; *s; s++)
249771b8 2001 if (isdigit(*s) || *s == ',')
2ea1c539
JB
2002 break;
2003 idx = simple_strtoul(s, NULL, 10);
2004 *s = 0;
2005
f7511d5f 2006 __add_preferred_console(buf, idx, options, brl_options);
9e124fe1 2007 console_set_on_cmdline = 1;
2ea1c539
JB
2008 return 1;
2009}
2010__setup("console=", console_setup);
2011
3c0547ba
MM
2012/**
2013 * add_preferred_console - add a device to the list of preferred consoles.
ddad86c2
MW
2014 * @name: device name
2015 * @idx: device index
2016 * @options: options for this console
3c0547ba
MM
2017 *
2018 * The last preferred console added will be used for kernel messages
2019 * and stdin/out/err for init. Normally this is used by console_setup
2020 * above to handle user-supplied console arguments; however it can also
2021 * be used by arch-specific code either to override the user or more
2022 * commonly to provide a default console (ie from PROM variables) when
2023 * the user has not supplied one.
2024 */
fb445ee5 2025int add_preferred_console(char *name, int idx, char *options)
3c0547ba 2026{
f7511d5f 2027 return __add_preferred_console(name, idx, options, NULL);
3c0547ba
MM
2028}
2029
d25d9fec 2030bool console_suspend_enabled = true;
8f4ce8c3
AS
2031EXPORT_SYMBOL(console_suspend_enabled);
2032
2033static int __init console_suspend_disable(char *str)
2034{
d25d9fec 2035 console_suspend_enabled = false;
8f4ce8c3
AS
2036 return 1;
2037}
2038__setup("no_console_suspend", console_suspend_disable);
134620f7
YZ
2039module_param_named(console_suspend, console_suspend_enabled,
2040 bool, S_IRUGO | S_IWUSR);
2041MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2042 " and hibernate operations");
8f4ce8c3 2043
557240b4
LT
2044/**
2045 * suspend_console - suspend the console subsystem
2046 *
2047 * This disables printk() while we go into suspend states
2048 */
2049void suspend_console(void)
2050{
8f4ce8c3
AS
2051 if (!console_suspend_enabled)
2052 return;
0d63081d 2053 printk("Suspending console(s) (use no_console_suspend to debug)\n");
ac751efa 2054 console_lock();
557240b4 2055 console_suspended = 1;
bd8d7cf5 2056 up_console_sem();
557240b4
LT
2057}
2058
2059void resume_console(void)
2060{
8f4ce8c3
AS
2061 if (!console_suspend_enabled)
2062 return;
bd8d7cf5 2063 down_console_sem();
557240b4 2064 console_suspended = 0;
ac751efa 2065 console_unlock();
557240b4
LT
2066}
2067
034260d6
KC
2068/**
2069 * console_cpu_notify - print deferred console messages after CPU hotplug
2070 * @self: notifier struct
2071 * @action: CPU hotplug event
2072 * @hcpu: unused
2073 *
2074 * If printk() is called from a CPU that is not online yet, the messages
2075 * will be spooled but will not show up on the console. This function is
2076 * called when a new CPU comes online (or fails to come up), and ensures
2077 * that any such output gets printed.
2078 */
0db0628d 2079static int console_cpu_notify(struct notifier_block *self,
034260d6
KC
2080 unsigned long action, void *hcpu)
2081{
2082 switch (action) {
2083 case CPU_ONLINE:
2084 case CPU_DEAD:
034260d6
KC
2085 case CPU_DOWN_FAILED:
2086 case CPU_UP_CANCELED:
ac751efa
TH
2087 console_lock();
2088 console_unlock();
034260d6
KC
2089 }
2090 return NOTIFY_OK;
2091}
2092
1da177e4 2093/**
ac751efa 2094 * console_lock - lock the console system for exclusive use.
1da177e4 2095 *
ac751efa 2096 * Acquires a lock which guarantees that the caller has
1da177e4
LT
2097 * exclusive access to the console system and the console_drivers list.
2098 *
2099 * Can sleep, returns nothing.
2100 */
ac751efa 2101void console_lock(void)
1da177e4 2102{
6b898c07
DV
2103 might_sleep();
2104
bd8d7cf5 2105 down_console_sem();
403f3075
AH
2106 if (console_suspended)
2107 return;
1da177e4
LT
2108 console_locked = 1;
2109 console_may_schedule = 1;
2110}
ac751efa 2111EXPORT_SYMBOL(console_lock);
1da177e4 2112
ac751efa
TH
2113/**
2114 * console_trylock - try to lock the console system for exclusive use.
2115 *
0b90fec3
AE
2116 * Try to acquire a lock which guarantees that the caller has exclusive
2117 * access to the console system and the console_drivers list.
ac751efa
TH
2118 *
2119 * returns 1 on success, and 0 on failure to acquire the lock.
2120 */
2121int console_trylock(void)
1da177e4 2122{
bd8d7cf5 2123 if (down_trylock_console_sem())
ac751efa 2124 return 0;
403f3075 2125 if (console_suspended) {
bd8d7cf5 2126 up_console_sem();
ac751efa 2127 return 0;
403f3075 2128 }
1da177e4
LT
2129 console_locked = 1;
2130 console_may_schedule = 0;
ac751efa 2131 return 1;
1da177e4 2132}
ac751efa 2133EXPORT_SYMBOL(console_trylock);
1da177e4
LT
2134
2135int is_console_locked(void)
2136{
2137 return console_locked;
2138}
1da177e4 2139
eab07260
KS
2140static void console_cont_flush(char *text, size_t size)
2141{
2142 unsigned long flags;
2143 size_t len;
2144
2145 raw_spin_lock_irqsave(&logbuf_lock, flags);
2146
2147 if (!cont.len)
2148 goto out;
2149
2150 /*
2151 * We still queue earlier records, likely because the console was
2152 * busy. The earlier ones need to be printed before this one, we
2153 * did not flush any fragment so far, so just let it queue up.
2154 */
2155 if (console_seq < log_next_seq && !cont.cons)
2156 goto out;
2157
2158 len = cont_print_text(text, size);
2159 raw_spin_unlock(&logbuf_lock);
2160 stop_critical_timings();
2161 call_console_drivers(cont.level, text, len);
2162 start_critical_timings();
2163 local_irq_restore(flags);
2164 return;
2165out:
2166 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2167}
7ff9554b 2168
1da177e4 2169/**
ac751efa 2170 * console_unlock - unlock the console system
1da177e4 2171 *
ac751efa 2172 * Releases the console_lock which the caller holds on the console system
1da177e4
LT
2173 * and the console driver list.
2174 *
ac751efa
TH
2175 * While the console_lock was held, console output may have been buffered
2176 * by printk(). If this is the case, console_unlock(); emits
2177 * the output prior to releasing the lock.
1da177e4 2178 *
7f3a781d 2179 * If there is output waiting, we wake /dev/kmsg and syslog() users.
1da177e4 2180 *
ac751efa 2181 * console_unlock(); may be called from any context.
1da177e4 2182 */
ac751efa 2183void console_unlock(void)
1da177e4 2184{
70498253 2185 static char text[LOG_LINE_MAX + PREFIX_MAX];
7ff9554b 2186 static u64 seen_seq;
1da177e4 2187 unsigned long flags;
7ff9554b
KS
2188 bool wake_klogd = false;
2189 bool retry;
1da177e4 2190
557240b4 2191 if (console_suspended) {
bd8d7cf5 2192 up_console_sem();
557240b4
LT
2193 return;
2194 }
78944e54
AD
2195
2196 console_may_schedule = 0;
2197
084681d1 2198 /* flush buffered message fragment immediately to console */
eab07260 2199 console_cont_flush(text, sizeof(text));
4f2a8d3c 2200again:
7ff9554b 2201 for (;;) {
62e32ac3 2202 struct printk_log *msg;
3ce9a7c0 2203 size_t len;
7ff9554b
KS
2204 int level;
2205
07354eb1 2206 raw_spin_lock_irqsave(&logbuf_lock, flags);
7ff9554b
KS
2207 if (seen_seq != log_next_seq) {
2208 wake_klogd = true;
2209 seen_seq = log_next_seq;
2210 }
2211
2212 if (console_seq < log_first_seq) {
84b5ec8a
WD
2213 len = sprintf(text, "** %u printk messages dropped ** ",
2214 (unsigned)(log_first_seq - console_seq));
2215
7ff9554b
KS
2216 /* messages are gone, move to first one */
2217 console_seq = log_first_seq;
2218 console_idx = log_first_idx;
5becfb1d 2219 console_prev = 0;
84b5ec8a
WD
2220 } else {
2221 len = 0;
7ff9554b 2222 }
084681d1 2223skip:
7ff9554b
KS
2224 if (console_seq == log_next_seq)
2225 break;
2226
2227 msg = log_from_idx(console_idx);
084681d1
KS
2228 if (msg->flags & LOG_NOCONS) {
2229 /*
2230 * Skip record we have buffered and already printed
2231 * directly to the console when we received it.
2232 */
2233 console_idx = log_next(console_idx);
2234 console_seq++;
68b6507d
KS
2235 /*
2236 * We will get here again when we register a new
2237 * CON_PRINTBUFFER console. Clear the flag so we
2238 * will properly dump everything later.
2239 */
2240 msg->flags &= ~LOG_NOCONS;
eab07260 2241 console_prev = msg->flags;
084681d1
KS
2242 goto skip;
2243 }
649e6ee3 2244
084681d1 2245 level = msg->level;
84b5ec8a
WD
2246 len += msg_print_text(msg, console_prev, false,
2247 text + len, sizeof(text) - len);
7ff9554b
KS
2248 console_idx = log_next(console_idx);
2249 console_seq++;
5becfb1d 2250 console_prev = msg->flags;
07354eb1 2251 raw_spin_unlock(&logbuf_lock);
7ff9554b 2252
81d68a96 2253 stop_critical_timings(); /* don't trace print latency */
7ff9554b 2254 call_console_drivers(level, text, len);
81d68a96 2255 start_critical_timings();
1da177e4
LT
2256 local_irq_restore(flags);
2257 }
2258 console_locked = 0;
fe3d8ad3
FT
2259
2260 /* Release the exclusive_console once it is used */
2261 if (unlikely(exclusive_console))
2262 exclusive_console = NULL;
2263
07354eb1 2264 raw_spin_unlock(&logbuf_lock);
4f2a8d3c 2265
bd8d7cf5 2266 up_console_sem();
4f2a8d3c
PZ
2267
2268 /*
2269 * Someone could have filled up the buffer again, so re-check if there's
2270 * something to flush. In case we cannot trylock the console_sem again,
2271 * there's a new owner and the console_unlock() from them will do the
2272 * flush, no worries.
2273 */
07354eb1 2274 raw_spin_lock(&logbuf_lock);
7ff9554b 2275 retry = console_seq != log_next_seq;
09dc3cf9
PZ
2276 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2277
4f2a8d3c
PZ
2278 if (retry && console_trylock())
2279 goto again;
2280
e3e8a75d
KK
2281 if (wake_klogd)
2282 wake_up_klogd();
1da177e4 2283}
ac751efa 2284EXPORT_SYMBOL(console_unlock);
1da177e4 2285
ddad86c2
MW
2286/**
2287 * console_conditional_schedule - yield the CPU if required
1da177e4
LT
2288 *
2289 * If the console code is currently allowed to sleep, and
2290 * if this CPU should yield the CPU to another task, do
2291 * so here.
2292 *
ac751efa 2293 * Must be called within console_lock();.
1da177e4
LT
2294 */
2295void __sched console_conditional_schedule(void)
2296{
2297 if (console_may_schedule)
2298 cond_resched();
2299}
2300EXPORT_SYMBOL(console_conditional_schedule);
2301
1da177e4
LT
2302void console_unblank(void)
2303{
2304 struct console *c;
2305
2306 /*
2307 * console_unblank can no longer be called in interrupt context unless
2308 * oops_in_progress is set to 1..
2309 */
2310 if (oops_in_progress) {
bd8d7cf5 2311 if (down_trylock_console_sem() != 0)
1da177e4
LT
2312 return;
2313 } else
ac751efa 2314 console_lock();
1da177e4
LT
2315
2316 console_locked = 1;
2317 console_may_schedule = 0;
4d091611 2318 for_each_console(c)
1da177e4
LT
2319 if ((c->flags & CON_ENABLED) && c->unblank)
2320 c->unblank();
ac751efa 2321 console_unlock();
1da177e4 2322}
1da177e4
LT
2323
2324/*
2325 * Return the console tty driver structure and its associated index
2326 */
2327struct tty_driver *console_device(int *index)
2328{
2329 struct console *c;
2330 struct tty_driver *driver = NULL;
2331
ac751efa 2332 console_lock();
4d091611 2333 for_each_console(c) {
1da177e4
LT
2334 if (!c->device)
2335 continue;
2336 driver = c->device(c, index);
2337 if (driver)
2338 break;
2339 }
ac751efa 2340 console_unlock();
1da177e4
LT
2341 return driver;
2342}
2343
2344/*
2345 * Prevent further output on the passed console device so that (for example)
2346 * serial drivers can disable console output before suspending a port, and can
2347 * re-enable output afterwards.
2348 */
2349void console_stop(struct console *console)
2350{
ac751efa 2351 console_lock();
1da177e4 2352 console->flags &= ~CON_ENABLED;
ac751efa 2353 console_unlock();
1da177e4
LT
2354}
2355EXPORT_SYMBOL(console_stop);
2356
2357void console_start(struct console *console)
2358{
ac751efa 2359 console_lock();
1da177e4 2360 console->flags |= CON_ENABLED;
ac751efa 2361 console_unlock();
1da177e4
LT
2362}
2363EXPORT_SYMBOL(console_start);
2364
7bf69395
FDN
2365static int __read_mostly keep_bootcon;
2366
2367static int __init keep_bootcon_setup(char *str)
2368{
2369 keep_bootcon = 1;
27083bac 2370 pr_info("debug: skip boot console de-registration.\n");
7bf69395
FDN
2371
2372 return 0;
2373}
2374
2375early_param("keep_bootcon", keep_bootcon_setup);
2376
1da177e4
LT
2377/*
2378 * The console driver calls this routine during kernel initialization
2379 * to register the console printing procedure with printk() and to
2380 * print any messages that were printed by the kernel before the
2381 * console driver was initialized.
4d091611
RG
2382 *
2383 * This can happen pretty early during the boot process (because of
2384 * early_printk) - sometimes before setup_arch() completes - be careful
2385 * of what kernel features are used - they may not be initialised yet.
2386 *
2387 * There are two types of consoles - bootconsoles (early_printk) and
2388 * "real" consoles (everything which is not a bootconsole) which are
2389 * handled differently.
2390 * - Any number of bootconsoles can be registered at any time.
2391 * - As soon as a "real" console is registered, all bootconsoles
2392 * will be unregistered automatically.
2393 * - Once a "real" console is registered, any attempt to register a
2394 * bootconsoles will be rejected
1da177e4 2395 */
4d091611 2396void register_console(struct console *newcon)
1da177e4 2397{
40dc5651 2398 int i;
1da177e4 2399 unsigned long flags;
4d091611 2400 struct console *bcon = NULL;
23475408 2401 struct console_cmdline *c;
1da177e4 2402
16cf48a6
AB
2403 if (console_drivers)
2404 for_each_console(bcon)
2405 if (WARN(bcon == newcon,
2406 "console '%s%d' already registered\n",
2407 bcon->name, bcon->index))
2408 return;
2409
4d091611
RG
2410 /*
2411 * before we register a new CON_BOOT console, make sure we don't
2412 * already have a valid console
2413 */
2414 if (console_drivers && newcon->flags & CON_BOOT) {
2415 /* find the last or real console */
2416 for_each_console(bcon) {
2417 if (!(bcon->flags & CON_BOOT)) {
27083bac 2418 pr_info("Too late to register bootconsole %s%d\n",
4d091611
RG
2419 newcon->name, newcon->index);
2420 return;
2421 }
2422 }
69331af7
GH
2423 }
2424
4d091611
RG
2425 if (console_drivers && console_drivers->flags & CON_BOOT)
2426 bcon = console_drivers;
2427
2428 if (preferred_console < 0 || bcon || !console_drivers)
1da177e4
LT
2429 preferred_console = selected_console;
2430
2431 /*
2432 * See if we want to use this console driver. If we
2433 * didn't select a console we take the first one
2434 * that registers here.
2435 */
2436 if (preferred_console < 0) {
4d091611
RG
2437 if (newcon->index < 0)
2438 newcon->index = 0;
2439 if (newcon->setup == NULL ||
2440 newcon->setup(newcon, NULL) == 0) {
2441 newcon->flags |= CON_ENABLED;
2442 if (newcon->device) {
2443 newcon->flags |= CON_CONSDEV;
cd3a1b85
JK
2444 preferred_console = 0;
2445 }
1da177e4
LT
2446 }
2447 }
2448
2449 /*
2450 * See if this console matches one we selected on
2451 * the command line.
2452 */
23475408
JP
2453 for (i = 0, c = console_cmdline;
2454 i < MAX_CMDLINECONSOLES && c->name[0];
2455 i++, c++) {
c7cef0a8
PH
2456 if (!newcon->match ||
2457 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2458 /* default matching */
2459 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2460 if (strcmp(c->name, newcon->name) != 0)
2461 continue;
2462 if (newcon->index >= 0 &&
2463 newcon->index != c->index)
2464 continue;
2465 if (newcon->index < 0)
2466 newcon->index = c->index;
bbeddf52 2467
c7cef0a8
PH
2468 if (_braille_register_console(newcon, c))
2469 return;
2470
2471 if (newcon->setup &&
2472 newcon->setup(newcon, c->options) != 0)
2473 break;
2474 }
bbeddf52 2475
4d091611 2476 newcon->flags |= CON_ENABLED;
ab4af03a 2477 if (i == selected_console) {
4d091611 2478 newcon->flags |= CON_CONSDEV;
ab4af03a
GE
2479 preferred_console = selected_console;
2480 }
1da177e4
LT
2481 break;
2482 }
2483
4d091611 2484 if (!(newcon->flags & CON_ENABLED))
1da177e4
LT
2485 return;
2486
8259cf43
RG
2487 /*
2488 * If we have a bootconsole, and are switching to a real console,
2489 * don't print everything out again, since when the boot console, and
2490 * the real console are the same physical device, it's annoying to
2491 * see the beginning boot messages twice
2492 */
2493 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
4d091611 2494 newcon->flags &= ~CON_PRINTBUFFER;
1da177e4
LT
2495
2496 /*
2497 * Put this console in the list - keep the
2498 * preferred driver at the head of the list.
2499 */
ac751efa 2500 console_lock();
4d091611
RG
2501 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2502 newcon->next = console_drivers;
2503 console_drivers = newcon;
2504 if (newcon->next)
2505 newcon->next->flags &= ~CON_CONSDEV;
1da177e4 2506 } else {
4d091611
RG
2507 newcon->next = console_drivers->next;
2508 console_drivers->next = newcon;
1da177e4 2509 }
4d091611 2510 if (newcon->flags & CON_PRINTBUFFER) {
1da177e4 2511 /*
ac751efa 2512 * console_unlock(); will print out the buffered messages
1da177e4
LT
2513 * for us.
2514 */
07354eb1 2515 raw_spin_lock_irqsave(&logbuf_lock, flags);
7ff9554b
KS
2516 console_seq = syslog_seq;
2517 console_idx = syslog_idx;
5becfb1d 2518 console_prev = syslog_prev;
07354eb1 2519 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
fe3d8ad3
FT
2520 /*
2521 * We're about to replay the log buffer. Only do this to the
2522 * just-registered console to avoid excessive message spam to
2523 * the already-registered consoles.
2524 */
2525 exclusive_console = newcon;
1da177e4 2526 }
ac751efa 2527 console_unlock();
fbc92a34 2528 console_sysfs_notify();
8259cf43
RG
2529
2530 /*
2531 * By unregistering the bootconsoles after we enable the real console
2532 * we get the "console xxx enabled" message on all the consoles -
2533 * boot consoles, real consoles, etc - this is to ensure that end
2534 * users know there might be something in the kernel's log buffer that
2535 * went to the bootconsole (that they do not see on the real console)
2536 */
27083bac 2537 pr_info("%sconsole [%s%d] enabled\n",
6b802394
KC
2538 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2539 newcon->name, newcon->index);
7bf69395
FDN
2540 if (bcon &&
2541 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2542 !keep_bootcon) {
6b802394
KC
2543 /* We need to iterate through all boot consoles, to make
2544 * sure we print everything out, before we unregister them.
8259cf43 2545 */
8259cf43
RG
2546 for_each_console(bcon)
2547 if (bcon->flags & CON_BOOT)
2548 unregister_console(bcon);
8259cf43 2549 }
1da177e4
LT
2550}
2551EXPORT_SYMBOL(register_console);
2552
40dc5651 2553int unregister_console(struct console *console)
1da177e4 2554{
40dc5651 2555 struct console *a, *b;
bbeddf52 2556 int res;
1da177e4 2557
27083bac 2558 pr_info("%sconsole [%s%d] disabled\n",
6b802394
KC
2559 (console->flags & CON_BOOT) ? "boot" : "" ,
2560 console->name, console->index);
2561
bbeddf52
JP
2562 res = _braille_unregister_console(console);
2563 if (res)
2564 return res;
f7511d5f 2565
bbeddf52 2566 res = 1;
ac751efa 2567 console_lock();
1da177e4
LT
2568 if (console_drivers == console) {
2569 console_drivers=console->next;
2570 res = 0;
e9b15b54 2571 } else if (console_drivers) {
1da177e4
LT
2572 for (a=console_drivers->next, b=console_drivers ;
2573 a; b=a, a=b->next) {
2574 if (a == console) {
2575 b->next = a->next;
2576 res = 0;
2577 break;
40dc5651 2578 }
1da177e4
LT
2579 }
2580 }
40dc5651 2581
69331af7 2582 /*
ab4af03a
GE
2583 * If this isn't the last console and it has CON_CONSDEV set, we
2584 * need to set it on the next preferred console.
1da177e4 2585 */
69331af7 2586 if (console_drivers != NULL && console->flags & CON_CONSDEV)
ab4af03a 2587 console_drivers->flags |= CON_CONSDEV;
1da177e4 2588
7fa21dd8 2589 console->flags &= ~CON_ENABLED;
ac751efa 2590 console_unlock();
fbc92a34 2591 console_sysfs_notify();
1da177e4
LT
2592 return res;
2593}
2594EXPORT_SYMBOL(unregister_console);
d59745ce 2595
034260d6 2596static int __init printk_late_init(void)
0c5564bd 2597{
4d091611
RG
2598 struct console *con;
2599
2600 for_each_console(con) {
4c30c6f5 2601 if (!keep_bootcon && con->flags & CON_BOOT) {
42c2c8c8 2602 unregister_console(con);
cb00e99c 2603 }
0c5564bd 2604 }
034260d6 2605 hotcpu_notifier(console_cpu_notify, 0);
0c5564bd
RG
2606 return 0;
2607}
034260d6 2608late_initcall(printk_late_init);
0c5564bd 2609
7ef3d2fd 2610#if defined CONFIG_PRINTK
dc72c32e
FW
2611/*
2612 * Delayed printk version, for scheduler-internal messages:
2613 */
dc72c32e 2614#define PRINTK_PENDING_WAKEUP 0x01
458df9fd 2615#define PRINTK_PENDING_OUTPUT 0x02
dc72c32e
FW
2616
2617static DEFINE_PER_CPU(int, printk_pending);
dc72c32e
FW
2618
2619static void wake_up_klogd_work_func(struct irq_work *irq_work)
2620{
2621 int pending = __this_cpu_xchg(printk_pending, 0);
2622
458df9fd
SR
2623 if (pending & PRINTK_PENDING_OUTPUT) {
2624 /* If trylock fails, someone else is doing the printing */
2625 if (console_trylock())
2626 console_unlock();
dc72c32e
FW
2627 }
2628
2629 if (pending & PRINTK_PENDING_WAKEUP)
2630 wake_up_interruptible(&log_wait);
2631}
2632
2633static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2634 .func = wake_up_klogd_work_func,
2635 .flags = IRQ_WORK_LAZY,
2636};
2637
2638void wake_up_klogd(void)
2639{
2640 preempt_disable();
2641 if (waitqueue_active(&log_wait)) {
2642 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
bb964a92 2643 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
dc72c32e
FW
2644 }
2645 preempt_enable();
2646}
717115e1 2647
aac74dc4 2648int printk_deferred(const char *fmt, ...)
600e1458 2649{
600e1458 2650 va_list args;
600e1458
PZ
2651 int r;
2652
81954606 2653 preempt_disable();
600e1458 2654 va_start(args, fmt);
a39d4a85 2655 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
600e1458
PZ
2656 va_end(args);
2657
458df9fd 2658 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
bb964a92 2659 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
81954606 2660 preempt_enable();
600e1458
PZ
2661
2662 return r;
2663}
2664
1da177e4
LT
2665/*
2666 * printk rate limiting, lifted from the networking subsystem.
2667 *
641de9d8
UKK
2668 * This enforces a rate limit: not more than 10 kernel messages
2669 * every 5s to make a denial-of-service attack impossible.
1da177e4 2670 */
641de9d8
UKK
2671DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2672
5c828713 2673int __printk_ratelimit(const char *func)
1da177e4 2674{
5c828713 2675 return ___ratelimit(&printk_ratelimit_state, func);
1da177e4 2676}
5c828713 2677EXPORT_SYMBOL(__printk_ratelimit);
f46c4833
AM
2678
2679/**
2680 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2681 * @caller_jiffies: pointer to caller's state
2682 * @interval_msecs: minimum interval between prints
2683 *
2684 * printk_timed_ratelimit() returns true if more than @interval_msecs
2685 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2686 * returned true.
2687 */
2688bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2689 unsigned int interval_msecs)
2690{
249771b8
AE
2691 unsigned long elapsed = jiffies - *caller_jiffies;
2692
2693 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2694 return false;
2695
2696 *caller_jiffies = jiffies;
2697 return true;
f46c4833
AM
2698}
2699EXPORT_SYMBOL(printk_timed_ratelimit);
456b565c
SK
2700
2701static DEFINE_SPINLOCK(dump_list_lock);
2702static LIST_HEAD(dump_list);
2703
2704/**
2705 * kmsg_dump_register - register a kernel log dumper.
6485536b 2706 * @dumper: pointer to the kmsg_dumper structure
456b565c
SK
2707 *
2708 * Adds a kernel log dumper to the system. The dump callback in the
2709 * structure will be called when the kernel oopses or panics and must be
2710 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2711 */
2712int kmsg_dump_register(struct kmsg_dumper *dumper)
2713{
2714 unsigned long flags;
2715 int err = -EBUSY;
2716
2717 /* The dump callback needs to be set */
2718 if (!dumper->dump)
2719 return -EINVAL;
2720
2721 spin_lock_irqsave(&dump_list_lock, flags);
2722 /* Don't allow registering multiple times */
2723 if (!dumper->registered) {
2724 dumper->registered = 1;
fb842b00 2725 list_add_tail_rcu(&dumper->list, &dump_list);
456b565c
SK
2726 err = 0;
2727 }
2728 spin_unlock_irqrestore(&dump_list_lock, flags);
2729
2730 return err;
2731}
2732EXPORT_SYMBOL_GPL(kmsg_dump_register);
2733
2734/**
2735 * kmsg_dump_unregister - unregister a kmsg dumper.
6485536b 2736 * @dumper: pointer to the kmsg_dumper structure
456b565c
SK
2737 *
2738 * Removes a dump device from the system. Returns zero on success and
2739 * %-EINVAL otherwise.
2740 */
2741int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2742{
2743 unsigned long flags;
2744 int err = -EINVAL;
2745
2746 spin_lock_irqsave(&dump_list_lock, flags);
2747 if (dumper->registered) {
2748 dumper->registered = 0;
fb842b00 2749 list_del_rcu(&dumper->list);
456b565c
SK
2750 err = 0;
2751 }
2752 spin_unlock_irqrestore(&dump_list_lock, flags);
fb842b00 2753 synchronize_rcu();
456b565c
SK
2754
2755 return err;
2756}
2757EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2758
7ff9554b
KS
2759static bool always_kmsg_dump;
2760module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2761
456b565c
SK
2762/**
2763 * kmsg_dump - dump kernel log to kernel message dumpers.
2764 * @reason: the reason (oops, panic etc) for dumping
2765 *
e2ae715d
KS
2766 * Call each of the registered dumper's dump() callback, which can
2767 * retrieve the kmsg records with kmsg_dump_get_line() or
2768 * kmsg_dump_get_buffer().
456b565c
SK
2769 */
2770void kmsg_dump(enum kmsg_dump_reason reason)
2771{
456b565c 2772 struct kmsg_dumper *dumper;
456b565c
SK
2773 unsigned long flags;
2774
c22ab332
MG
2775 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2776 return;
2777
e2ae715d
KS
2778 rcu_read_lock();
2779 list_for_each_entry_rcu(dumper, &dump_list, list) {
2780 if (dumper->max_reason && reason > dumper->max_reason)
2781 continue;
2782
2783 /* initialize iterator with data about the stored records */
2784 dumper->active = true;
2785
2786 raw_spin_lock_irqsave(&logbuf_lock, flags);
2787 dumper->cur_seq = clear_seq;
2788 dumper->cur_idx = clear_idx;
2789 dumper->next_seq = log_next_seq;
2790 dumper->next_idx = log_next_idx;
2791 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2792
2793 /* invoke dumper which will iterate over records */
2794 dumper->dump(dumper, reason);
2795
2796 /* reset iterator */
2797 dumper->active = false;
2798 }
2799 rcu_read_unlock();
2800}
2801
2802/**
533827c9 2803 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
e2ae715d
KS
2804 * @dumper: registered kmsg dumper
2805 * @syslog: include the "<4>" prefixes
2806 * @line: buffer to copy the line to
2807 * @size: maximum size of the buffer
2808 * @len: length of line placed into buffer
2809 *
2810 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2811 * record, and copy one record into the provided buffer.
2812 *
2813 * Consecutive calls will return the next available record moving
2814 * towards the end of the buffer with the youngest messages.
2815 *
2816 * A return value of FALSE indicates that there are no more records to
2817 * read.
533827c9
AV
2818 *
2819 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
e2ae715d 2820 */
533827c9
AV
2821bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2822 char *line, size_t size, size_t *len)
e2ae715d 2823{
62e32ac3 2824 struct printk_log *msg;
e2ae715d
KS
2825 size_t l = 0;
2826 bool ret = false;
2827
2828 if (!dumper->active)
2829 goto out;
7ff9554b 2830
e2ae715d
KS
2831 if (dumper->cur_seq < log_first_seq) {
2832 /* messages are gone, move to first available one */
2833 dumper->cur_seq = log_first_seq;
2834 dumper->cur_idx = log_first_idx;
2835 }
456b565c 2836
e2ae715d 2837 /* last entry */
533827c9 2838 if (dumper->cur_seq >= log_next_seq)
e2ae715d 2839 goto out;
456b565c 2840
e2ae715d 2841 msg = log_from_idx(dumper->cur_idx);
5becfb1d 2842 l = msg_print_text(msg, 0, syslog, line, size);
e2ae715d
KS
2843
2844 dumper->cur_idx = log_next(dumper->cur_idx);
2845 dumper->cur_seq++;
2846 ret = true;
e2ae715d
KS
2847out:
2848 if (len)
2849 *len = l;
2850 return ret;
2851}
533827c9
AV
2852
2853/**
2854 * kmsg_dump_get_line - retrieve one kmsg log line
2855 * @dumper: registered kmsg dumper
2856 * @syslog: include the "<4>" prefixes
2857 * @line: buffer to copy the line to
2858 * @size: maximum size of the buffer
2859 * @len: length of line placed into buffer
2860 *
2861 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2862 * record, and copy one record into the provided buffer.
2863 *
2864 * Consecutive calls will return the next available record moving
2865 * towards the end of the buffer with the youngest messages.
2866 *
2867 * A return value of FALSE indicates that there are no more records to
2868 * read.
2869 */
2870bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2871 char *line, size_t size, size_t *len)
2872{
2873 unsigned long flags;
2874 bool ret;
2875
2876 raw_spin_lock_irqsave(&logbuf_lock, flags);
2877 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2878 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2879
2880 return ret;
2881}
e2ae715d
KS
2882EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2883
2884/**
2885 * kmsg_dump_get_buffer - copy kmsg log lines
2886 * @dumper: registered kmsg dumper
2887 * @syslog: include the "<4>" prefixes
4f0f4af5 2888 * @buf: buffer to copy the line to
e2ae715d
KS
2889 * @size: maximum size of the buffer
2890 * @len: length of line placed into buffer
2891 *
2892 * Start at the end of the kmsg buffer and fill the provided buffer
2893 * with as many of the the *youngest* kmsg records that fit into it.
2894 * If the buffer is large enough, all available kmsg records will be
2895 * copied with a single call.
2896 *
2897 * Consecutive calls will fill the buffer with the next block of
2898 * available older records, not including the earlier retrieved ones.
2899 *
2900 * A return value of FALSE indicates that there are no more records to
2901 * read.
2902 */
2903bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2904 char *buf, size_t size, size_t *len)
2905{
2906 unsigned long flags;
2907 u64 seq;
2908 u32 idx;
2909 u64 next_seq;
2910 u32 next_idx;
5becfb1d 2911 enum log_flags prev;
e2ae715d
KS
2912 size_t l = 0;
2913 bool ret = false;
2914
2915 if (!dumper->active)
2916 goto out;
2917
2918 raw_spin_lock_irqsave(&logbuf_lock, flags);
2919 if (dumper->cur_seq < log_first_seq) {
2920 /* messages are gone, move to first available one */
2921 dumper->cur_seq = log_first_seq;
2922 dumper->cur_idx = log_first_idx;
2923 }
2924
2925 /* last entry */
2926 if (dumper->cur_seq >= dumper->next_seq) {
2927 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2928 goto out;
2929 }
2930
2931 /* calculate length of entire buffer */
2932 seq = dumper->cur_seq;
2933 idx = dumper->cur_idx;
5becfb1d 2934 prev = 0;
e2ae715d 2935 while (seq < dumper->next_seq) {
62e32ac3 2936 struct printk_log *msg = log_from_idx(idx);
e2ae715d 2937
5becfb1d 2938 l += msg_print_text(msg, prev, true, NULL, 0);
e2ae715d
KS
2939 idx = log_next(idx);
2940 seq++;
5becfb1d 2941 prev = msg->flags;
e2ae715d
KS
2942 }
2943
2944 /* move first record forward until length fits into the buffer */
2945 seq = dumper->cur_seq;
2946 idx = dumper->cur_idx;
5becfb1d 2947 prev = 0;
e2ae715d 2948 while (l > size && seq < dumper->next_seq) {
62e32ac3 2949 struct printk_log *msg = log_from_idx(idx);
456b565c 2950
5becfb1d 2951 l -= msg_print_text(msg, prev, true, NULL, 0);
e2ae715d
KS
2952 idx = log_next(idx);
2953 seq++;
5becfb1d 2954 prev = msg->flags;
456b565c 2955 }
e2ae715d
KS
2956
2957 /* last message in next interation */
2958 next_seq = seq;
2959 next_idx = idx;
2960
2961 l = 0;
2962 while (seq < dumper->next_seq) {
62e32ac3 2963 struct printk_log *msg = log_from_idx(idx);
e2ae715d 2964
5becfb1d 2965 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
e2ae715d
KS
2966 idx = log_next(idx);
2967 seq++;
5becfb1d 2968 prev = msg->flags;
e2ae715d
KS
2969 }
2970
2971 dumper->next_seq = next_seq;
2972 dumper->next_idx = next_idx;
2973 ret = true;
7ff9554b 2974 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
e2ae715d
KS
2975out:
2976 if (len)
2977 *len = l;
2978 return ret;
2979}
2980EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
456b565c 2981
533827c9
AV
2982/**
2983 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2984 * @dumper: registered kmsg dumper
2985 *
2986 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2987 * kmsg_dump_get_buffer() can be called again and used multiple
2988 * times within the same dumper.dump() callback.
2989 *
2990 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2991 */
2992void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
2993{
2994 dumper->cur_seq = clear_seq;
2995 dumper->cur_idx = clear_idx;
2996 dumper->next_seq = log_next_seq;
2997 dumper->next_idx = log_next_idx;
2998}
2999
e2ae715d
KS
3000/**
3001 * kmsg_dump_rewind - reset the interator
3002 * @dumper: registered kmsg dumper
3003 *
3004 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3005 * kmsg_dump_get_buffer() can be called again and used multiple
3006 * times within the same dumper.dump() callback.
3007 */
3008void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3009{
3010 unsigned long flags;
3011
3012 raw_spin_lock_irqsave(&logbuf_lock, flags);
533827c9 3013 kmsg_dump_rewind_nolock(dumper);
e2ae715d 3014 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
456b565c 3015}
e2ae715d 3016EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
196779b9 3017
98e5e1bf
TH
3018static char dump_stack_arch_desc_str[128];
3019
3020/**
3021 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3022 * @fmt: printf-style format string
3023 * @...: arguments for the format string
3024 *
3025 * The configured string will be printed right after utsname during task
3026 * dumps. Usually used to add arch-specific system identifiers. If an
3027 * arch wants to make use of such an ID string, it should initialize this
3028 * as soon as possible during boot.
3029 */
3030void __init dump_stack_set_arch_desc(const char *fmt, ...)
3031{
3032 va_list args;
3033
3034 va_start(args, fmt);
3035 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3036 fmt, args);
3037 va_end(args);
3038}
3039
196779b9
TH
3040/**
3041 * dump_stack_print_info - print generic debug info for dump_stack()
3042 * @log_lvl: log level
3043 *
3044 * Arch-specific dump_stack() implementations can use this function to
3045 * print out the same debug information as the generic dump_stack().
3046 */
3047void dump_stack_print_info(const char *log_lvl)
3048{
3049 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3050 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3051 print_tainted(), init_utsname()->release,
3052 (int)strcspn(init_utsname()->version, " "),
3053 init_utsname()->version);
98e5e1bf
TH
3054
3055 if (dump_stack_arch_desc_str[0] != '\0')
3056 printk("%sHardware name: %s\n",
3057 log_lvl, dump_stack_arch_desc_str);
3d1cb205
TH
3058
3059 print_worker_info(log_lvl, current);
196779b9
TH
3060}
3061
a43cb95d
TH
3062/**
3063 * show_regs_print_info - print generic debug info for show_regs()
3064 * @log_lvl: log level
3065 *
3066 * show_regs() implementations can use this function to print out generic
3067 * debug information.
3068 */
3069void show_regs_print_info(const char *log_lvl)
3070{
3071 dump_stack_print_info(log_lvl);
3072
3073 printk("%stask: %p ti: %p task.ti: %p\n",
3074 log_lvl, current, current_thread_info(),
3075 task_thread_info(current));
3076}
3077
7ef3d2fd 3078#endif