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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/kernel/printk.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 *
7 * Modified to make sys_syslog() more flexible: added commands to
8 * return the last 4k of kernel messages, regardless of whether
9 * they've been read or not. Added option to suppress kernel printk's
10 * to the console. Added hook for sending the console messages
11 * elsewhere, in preparation for a serial line console (someday).
12 * Ted Ts'o, 2/11/93.
13 * Modified for sysctl support, 1/8/97, Chris Horn.
14 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
15 * manfred@colorfullife.com
16 * Rewrote bits to get rid of console_lock
17 * 01Mar01 Andrew Morton
18 */
19
20#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
21
22#include <linux/kernel.h>
23#include <linux/mm.h>
24#include <linux/tty.h>
25#include <linux/tty_driver.h>
26#include <linux/console.h>
27#include <linux/init.h>
28#include <linux/jiffies.h>
29#include <linux/nmi.h>
30#include <linux/module.h>
31#include <linux/moduleparam.h>
32#include <linux/delay.h>
33#include <linux/smp.h>
34#include <linux/security.h>
35#include <linux/memblock.h>
36#include <linux/syscalls.h>
37#include <linux/crash_core.h>
38#include <linux/kdb.h>
39#include <linux/ratelimit.h>
40#include <linux/kmsg_dump.h>
41#include <linux/syslog.h>
42#include <linux/cpu.h>
43#include <linux/rculist.h>
44#include <linux/poll.h>
45#include <linux/irq_work.h>
46#include <linux/ctype.h>
47#include <linux/uio.h>
48#include <linux/sched/clock.h>
49#include <linux/sched/debug.h>
50#include <linux/sched/task_stack.h>
51
52#include <linux/uaccess.h>
53#include <asm/sections.h>
54
55#include <trace/events/initcall.h>
56#define CREATE_TRACE_POINTS
57#include <trace/events/printk.h>
58
59#include "console_cmdline.h"
60#include "braille.h"
61#include "internal.h"
62
63int console_printk[4] = {
64 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
65 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
66 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
67 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
68};
69EXPORT_SYMBOL_GPL(console_printk);
70
71atomic_t ignore_console_lock_warning __read_mostly = ATOMIC_INIT(0);
72EXPORT_SYMBOL(ignore_console_lock_warning);
73
74/*
75 * Low level drivers may need that to know if they can schedule in
76 * their unblank() callback or not. So let's export it.
77 */
78int oops_in_progress;
79EXPORT_SYMBOL(oops_in_progress);
80
81/*
82 * console_sem protects the console_drivers list, and also
83 * provides serialisation for access to the entire console
84 * driver system.
85 */
86static DEFINE_SEMAPHORE(console_sem);
87struct console *console_drivers;
88EXPORT_SYMBOL_GPL(console_drivers);
89
90/*
91 * System may need to suppress printk message under certain
92 * circumstances, like after kernel panic happens.
93 */
94int __read_mostly suppress_printk;
95
96#ifdef CONFIG_LOCKDEP
97static struct lockdep_map console_lock_dep_map = {
98 .name = "console_lock"
99};
100#endif
101
102enum devkmsg_log_bits {
103 __DEVKMSG_LOG_BIT_ON = 0,
104 __DEVKMSG_LOG_BIT_OFF,
105 __DEVKMSG_LOG_BIT_LOCK,
106};
107
108enum devkmsg_log_masks {
109 DEVKMSG_LOG_MASK_ON = BIT(__DEVKMSG_LOG_BIT_ON),
110 DEVKMSG_LOG_MASK_OFF = BIT(__DEVKMSG_LOG_BIT_OFF),
111 DEVKMSG_LOG_MASK_LOCK = BIT(__DEVKMSG_LOG_BIT_LOCK),
112};
113
114/* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
115#define DEVKMSG_LOG_MASK_DEFAULT 0
116
117static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
118
119static int __control_devkmsg(char *str)
120{
121 size_t len;
122
123 if (!str)
124 return -EINVAL;
125
126 len = str_has_prefix(str, "on");
127 if (len) {
128 devkmsg_log = DEVKMSG_LOG_MASK_ON;
129 return len;
130 }
131
132 len = str_has_prefix(str, "off");
133 if (len) {
134 devkmsg_log = DEVKMSG_LOG_MASK_OFF;
135 return len;
136 }
137
138 len = str_has_prefix(str, "ratelimit");
139 if (len) {
140 devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
141 return len;
142 }
143
144 return -EINVAL;
145}
146
147static int __init control_devkmsg(char *str)
148{
149 if (__control_devkmsg(str) < 0)
150 return 1;
151
152 /*
153 * Set sysctl string accordingly:
154 */
155 if (devkmsg_log == DEVKMSG_LOG_MASK_ON)
156 strcpy(devkmsg_log_str, "on");
157 else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF)
158 strcpy(devkmsg_log_str, "off");
159 /* else "ratelimit" which is set by default. */
160
161 /*
162 * Sysctl cannot change it anymore. The kernel command line setting of
163 * this parameter is to force the setting to be permanent throughout the
164 * runtime of the system. This is a precation measure against userspace
165 * trying to be a smarta** and attempting to change it up on us.
166 */
167 devkmsg_log |= DEVKMSG_LOG_MASK_LOCK;
168
169 return 0;
170}
171__setup("printk.devkmsg=", control_devkmsg);
172
173char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit";
174
175int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
176 void __user *buffer, size_t *lenp, loff_t *ppos)
177{
178 char old_str[DEVKMSG_STR_MAX_SIZE];
179 unsigned int old;
180 int err;
181
182 if (write) {
183 if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK)
184 return -EINVAL;
185
186 old = devkmsg_log;
187 strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE);
188 }
189
190 err = proc_dostring(table, write, buffer, lenp, ppos);
191 if (err)
192 return err;
193
194 if (write) {
195 err = __control_devkmsg(devkmsg_log_str);
196
197 /*
198 * Do not accept an unknown string OR a known string with
199 * trailing crap...
200 */
201 if (err < 0 || (err + 1 != *lenp)) {
202
203 /* ... and restore old setting. */
204 devkmsg_log = old;
205 strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE);
206
207 return -EINVAL;
208 }
209 }
210
211 return 0;
212}
213
214/* Number of registered extended console drivers. */
215static int nr_ext_console_drivers;
216
217/*
218 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
219 * macros instead of functions so that _RET_IP_ contains useful information.
220 */
221#define down_console_sem() do { \
222 down(&console_sem);\
223 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
224} while (0)
225
226static int __down_trylock_console_sem(unsigned long ip)
227{
228 int lock_failed;
229 unsigned long flags;
230
231 /*
232 * Here and in __up_console_sem() we need to be in safe mode,
233 * because spindump/WARN/etc from under console ->lock will
234 * deadlock in printk()->down_trylock_console_sem() otherwise.
235 */
236 printk_safe_enter_irqsave(flags);
237 lock_failed = down_trylock(&console_sem);
238 printk_safe_exit_irqrestore(flags);
239
240 if (lock_failed)
241 return 1;
242 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
243 return 0;
244}
245#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
246
247static void __up_console_sem(unsigned long ip)
248{
249 unsigned long flags;
250
251 mutex_release(&console_lock_dep_map, 1, ip);
252
253 printk_safe_enter_irqsave(flags);
254 up(&console_sem);
255 printk_safe_exit_irqrestore(flags);
256}
257#define up_console_sem() __up_console_sem(_RET_IP_)
258
259/*
260 * This is used for debugging the mess that is the VT code by
261 * keeping track if we have the console semaphore held. It's
262 * definitely not the perfect debug tool (we don't know if _WE_
263 * hold it and are racing, but it helps tracking those weird code
264 * paths in the console code where we end up in places I want
265 * locked without the console sempahore held).
266 */
267static int console_locked, console_suspended;
268
269/*
270 * If exclusive_console is non-NULL then only this console is to be printed to.
271 */
272static struct console *exclusive_console;
273
274/*
275 * Array of consoles built from command line options (console=)
276 */
277
278#define MAX_CMDLINECONSOLES 8
279
280static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
281
282static int preferred_console = -1;
283int console_set_on_cmdline;
284EXPORT_SYMBOL(console_set_on_cmdline);
285
286/* Flag: console code may call schedule() */
287static int console_may_schedule;
288
289enum con_msg_format_flags {
290 MSG_FORMAT_DEFAULT = 0,
291 MSG_FORMAT_SYSLOG = (1 << 0),
292};
293
294static int console_msg_format = MSG_FORMAT_DEFAULT;
295
296/*
297 * The printk log buffer consists of a chain of concatenated variable
298 * length records. Every record starts with a record header, containing
299 * the overall length of the record.
300 *
301 * The heads to the first and last entry in the buffer, as well as the
302 * sequence numbers of these entries are maintained when messages are
303 * stored.
304 *
305 * If the heads indicate available messages, the length in the header
306 * tells the start next message. A length == 0 for the next message
307 * indicates a wrap-around to the beginning of the buffer.
308 *
309 * Every record carries the monotonic timestamp in microseconds, as well as
310 * the standard userspace syslog level and syslog facility. The usual
311 * kernel messages use LOG_KERN; userspace-injected messages always carry
312 * a matching syslog facility, by default LOG_USER. The origin of every
313 * message can be reliably determined that way.
314 *
315 * The human readable log message directly follows the message header. The
316 * length of the message text is stored in the header, the stored message
317 * is not terminated.
318 *
319 * Optionally, a message can carry a dictionary of properties (key/value pairs),
320 * to provide userspace with a machine-readable message context.
321 *
322 * Examples for well-defined, commonly used property names are:
323 * DEVICE=b12:8 device identifier
324 * b12:8 block dev_t
325 * c127:3 char dev_t
326 * n8 netdev ifindex
327 * +sound:card0 subsystem:devname
328 * SUBSYSTEM=pci driver-core subsystem name
329 *
330 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
331 * follows directly after a '=' character. Every property is terminated by
332 * a '\0' character. The last property is not terminated.
333 *
334 * Example of a message structure:
335 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
336 * 0008 34 00 record is 52 bytes long
337 * 000a 0b 00 text is 11 bytes long
338 * 000c 1f 00 dictionary is 23 bytes long
339 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
340 * 0010 69 74 27 73 20 61 20 6c "it's a l"
341 * 69 6e 65 "ine"
342 * 001b 44 45 56 49 43 "DEVIC"
343 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
344 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
345 * 67 "g"
346 * 0032 00 00 00 padding to next message header
347 *
348 * The 'struct printk_log' buffer header must never be directly exported to
349 * userspace, it is a kernel-private implementation detail that might
350 * need to be changed in the future, when the requirements change.
351 *
352 * /dev/kmsg exports the structured data in the following line format:
353 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
354 *
355 * Users of the export format should ignore possible additional values
356 * separated by ',', and find the message after the ';' character.
357 *
358 * The optional key/value pairs are attached as continuation lines starting
359 * with a space character and terminated by a newline. All possible
360 * non-prinatable characters are escaped in the "\xff" notation.
361 */
362
363enum log_flags {
364 LOG_NEWLINE = 2, /* text ended with a newline */
365 LOG_CONT = 8, /* text is a fragment of a continuation line */
366};
367
368struct printk_log {
369 u64 ts_nsec; /* timestamp in nanoseconds */
370 u16 len; /* length of entire record */
371 u16 text_len; /* length of text buffer */
372 u16 dict_len; /* length of dictionary buffer */
373 u8 facility; /* syslog facility */
374 u8 flags:5; /* internal record flags */
375 u8 level:3; /* syslog level */
376#ifdef CONFIG_PRINTK_CALLER
377 u32 caller_id; /* thread id or processor id */
378#endif
379}
380#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
381__packed __aligned(4)
382#endif
383;
384
385/*
386 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
387 * within the scheduler's rq lock. It must be released before calling
388 * console_unlock() or anything else that might wake up a process.
389 */
390DEFINE_RAW_SPINLOCK(logbuf_lock);
391
392/*
393 * Helper macros to lock/unlock logbuf_lock and switch between
394 * printk-safe/unsafe modes.
395 */
396#define logbuf_lock_irq() \
397 do { \
398 printk_safe_enter_irq(); \
399 raw_spin_lock(&logbuf_lock); \
400 } while (0)
401
402#define logbuf_unlock_irq() \
403 do { \
404 raw_spin_unlock(&logbuf_lock); \
405 printk_safe_exit_irq(); \
406 } while (0)
407
408#define logbuf_lock_irqsave(flags) \
409 do { \
410 printk_safe_enter_irqsave(flags); \
411 raw_spin_lock(&logbuf_lock); \
412 } while (0)
413
414#define logbuf_unlock_irqrestore(flags) \
415 do { \
416 raw_spin_unlock(&logbuf_lock); \
417 printk_safe_exit_irqrestore(flags); \
418 } while (0)
419
420#ifdef CONFIG_PRINTK
421DECLARE_WAIT_QUEUE_HEAD(log_wait);
422/* the next printk record to read by syslog(READ) or /proc/kmsg */
423static u64 syslog_seq;
424static u32 syslog_idx;
425static size_t syslog_partial;
426static bool syslog_time;
427
428/* index and sequence number of the first record stored in the buffer */
429static u64 log_first_seq;
430static u32 log_first_idx;
431
432/* index and sequence number of the next record to store in the buffer */
433static u64 log_next_seq;
434static u32 log_next_idx;
435
436/* the next printk record to write to the console */
437static u64 console_seq;
438static u32 console_idx;
439static u64 exclusive_console_stop_seq;
440
441/* the next printk record to read after the last 'clear' command */
442static u64 clear_seq;
443static u32 clear_idx;
444
445#ifdef CONFIG_PRINTK_CALLER
446#define PREFIX_MAX 48
447#else
448#define PREFIX_MAX 32
449#endif
450#define LOG_LINE_MAX (1024 - PREFIX_MAX)
451
452#define LOG_LEVEL(v) ((v) & 0x07)
453#define LOG_FACILITY(v) ((v) >> 3 & 0xff)
454
455/* record buffer */
456#define LOG_ALIGN __alignof__(struct printk_log)
457#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
458#define LOG_BUF_LEN_MAX (u32)(1 << 31)
459static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
460static char *log_buf = __log_buf;
461static u32 log_buf_len = __LOG_BUF_LEN;
462
463/* Return log buffer address */
464char *log_buf_addr_get(void)
465{
466 return log_buf;
467}
468
469/* Return log buffer size */
470u32 log_buf_len_get(void)
471{
472 return log_buf_len;
473}
474
475/* human readable text of the record */
476static char *log_text(const struct printk_log *msg)
477{
478 return (char *)msg + sizeof(struct printk_log);
479}
480
481/* optional key/value pair dictionary attached to the record */
482static char *log_dict(const struct printk_log *msg)
483{
484 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
485}
486
487/* get record by index; idx must point to valid msg */
488static struct printk_log *log_from_idx(u32 idx)
489{
490 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
491
492 /*
493 * A length == 0 record is the end of buffer marker. Wrap around and
494 * read the message at the start of the buffer.
495 */
496 if (!msg->len)
497 return (struct printk_log *)log_buf;
498 return msg;
499}
500
501/* get next record; idx must point to valid msg */
502static u32 log_next(u32 idx)
503{
504 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
505
506 /* length == 0 indicates the end of the buffer; wrap */
507 /*
508 * A length == 0 record is the end of buffer marker. Wrap around and
509 * read the message at the start of the buffer as *this* one, and
510 * return the one after that.
511 */
512 if (!msg->len) {
513 msg = (struct printk_log *)log_buf;
514 return msg->len;
515 }
516 return idx + msg->len;
517}
518
519/*
520 * Check whether there is enough free space for the given message.
521 *
522 * The same values of first_idx and next_idx mean that the buffer
523 * is either empty or full.
524 *
525 * If the buffer is empty, we must respect the position of the indexes.
526 * They cannot be reset to the beginning of the buffer.
527 */
528static int logbuf_has_space(u32 msg_size, bool empty)
529{
530 u32 free;
531
532 if (log_next_idx > log_first_idx || empty)
533 free = max(log_buf_len - log_next_idx, log_first_idx);
534 else
535 free = log_first_idx - log_next_idx;
536
537 /*
538 * We need space also for an empty header that signalizes wrapping
539 * of the buffer.
540 */
541 return free >= msg_size + sizeof(struct printk_log);
542}
543
544static int log_make_free_space(u32 msg_size)
545{
546 while (log_first_seq < log_next_seq &&
547 !logbuf_has_space(msg_size, false)) {
548 /* drop old messages until we have enough contiguous space */
549 log_first_idx = log_next(log_first_idx);
550 log_first_seq++;
551 }
552
553 if (clear_seq < log_first_seq) {
554 clear_seq = log_first_seq;
555 clear_idx = log_first_idx;
556 }
557
558 /* sequence numbers are equal, so the log buffer is empty */
559 if (logbuf_has_space(msg_size, log_first_seq == log_next_seq))
560 return 0;
561
562 return -ENOMEM;
563}
564
565/* compute the message size including the padding bytes */
566static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
567{
568 u32 size;
569
570 size = sizeof(struct printk_log) + text_len + dict_len;
571 *pad_len = (-size) & (LOG_ALIGN - 1);
572 size += *pad_len;
573
574 return size;
575}
576
577/*
578 * Define how much of the log buffer we could take at maximum. The value
579 * must be greater than two. Note that only half of the buffer is available
580 * when the index points to the middle.
581 */
582#define MAX_LOG_TAKE_PART 4
583static const char trunc_msg[] = "<truncated>";
584
585static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
586 u16 *dict_len, u32 *pad_len)
587{
588 /*
589 * The message should not take the whole buffer. Otherwise, it might
590 * get removed too soon.
591 */
592 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
593 if (*text_len > max_text_len)
594 *text_len = max_text_len;
595 /* enable the warning message */
596 *trunc_msg_len = strlen(trunc_msg);
597 /* disable the "dict" completely */
598 *dict_len = 0;
599 /* compute the size again, count also the warning message */
600 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
601}
602
603/* insert record into the buffer, discard old ones, update heads */
604static int log_store(u32 caller_id, int facility, int level,
605 enum log_flags flags, u64 ts_nsec,
606 const char *dict, u16 dict_len,
607 const char *text, u16 text_len)
608{
609 struct printk_log *msg;
610 u32 size, pad_len;
611 u16 trunc_msg_len = 0;
612
613 /* number of '\0' padding bytes to next message */
614 size = msg_used_size(text_len, dict_len, &pad_len);
615
616 if (log_make_free_space(size)) {
617 /* truncate the message if it is too long for empty buffer */
618 size = truncate_msg(&text_len, &trunc_msg_len,
619 &dict_len, &pad_len);
620 /* survive when the log buffer is too small for trunc_msg */
621 if (log_make_free_space(size))
622 return 0;
623 }
624
625 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
626 /*
627 * This message + an additional empty header does not fit
628 * at the end of the buffer. Add an empty header with len == 0
629 * to signify a wrap around.
630 */
631 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
632 log_next_idx = 0;
633 }
634
635 /* fill message */
636 msg = (struct printk_log *)(log_buf + log_next_idx);
637 memcpy(log_text(msg), text, text_len);
638 msg->text_len = text_len;
639 if (trunc_msg_len) {
640 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
641 msg->text_len += trunc_msg_len;
642 }
643 memcpy(log_dict(msg), dict, dict_len);
644 msg->dict_len = dict_len;
645 msg->facility = facility;
646 msg->level = level & 7;
647 msg->flags = flags & 0x1f;
648 if (ts_nsec > 0)
649 msg->ts_nsec = ts_nsec;
650 else
651 msg->ts_nsec = local_clock();
652#ifdef CONFIG_PRINTK_CALLER
653 msg->caller_id = caller_id;
654#endif
655 memset(log_dict(msg) + dict_len, 0, pad_len);
656 msg->len = size;
657
658 /* insert message */
659 log_next_idx += msg->len;
660 log_next_seq++;
661
662 return msg->text_len;
663}
664
665int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
666
667static int syslog_action_restricted(int type)
668{
669 if (dmesg_restrict)
670 return 1;
671 /*
672 * Unless restricted, we allow "read all" and "get buffer size"
673 * for everybody.
674 */
675 return type != SYSLOG_ACTION_READ_ALL &&
676 type != SYSLOG_ACTION_SIZE_BUFFER;
677}
678
679static int check_syslog_permissions(int type, int source)
680{
681 /*
682 * If this is from /proc/kmsg and we've already opened it, then we've
683 * already done the capabilities checks at open time.
684 */
685 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
686 goto ok;
687
688 if (syslog_action_restricted(type)) {
689 if (capable(CAP_SYSLOG))
690 goto ok;
691 /*
692 * For historical reasons, accept CAP_SYS_ADMIN too, with
693 * a warning.
694 */
695 if (capable(CAP_SYS_ADMIN)) {
696 pr_warn_once("%s (%d): Attempt to access syslog with "
697 "CAP_SYS_ADMIN but no CAP_SYSLOG "
698 "(deprecated).\n",
699 current->comm, task_pid_nr(current));
700 goto ok;
701 }
702 return -EPERM;
703 }
704ok:
705 return security_syslog(type);
706}
707
708static void append_char(char **pp, char *e, char c)
709{
710 if (*pp < e)
711 *(*pp)++ = c;
712}
713
714static ssize_t msg_print_ext_header(char *buf, size_t size,
715 struct printk_log *msg, u64 seq)
716{
717 u64 ts_usec = msg->ts_nsec;
718 char caller[20];
719#ifdef CONFIG_PRINTK_CALLER
720 u32 id = msg->caller_id;
721
722 snprintf(caller, sizeof(caller), ",caller=%c%u",
723 id & 0x80000000 ? 'C' : 'T', id & ~0x80000000);
724#else
725 caller[0] = '\0';
726#endif
727
728 do_div(ts_usec, 1000);
729
730 return scnprintf(buf, size, "%u,%llu,%llu,%c%s;",
731 (msg->facility << 3) | msg->level, seq, ts_usec,
732 msg->flags & LOG_CONT ? 'c' : '-', caller);
733}
734
735static ssize_t msg_print_ext_body(char *buf, size_t size,
736 char *dict, size_t dict_len,
737 char *text, size_t text_len)
738{
739 char *p = buf, *e = buf + size;
740 size_t i;
741
742 /* escape non-printable characters */
743 for (i = 0; i < text_len; i++) {
744 unsigned char c = text[i];
745
746 if (c < ' ' || c >= 127 || c == '\\')
747 p += scnprintf(p, e - p, "\\x%02x", c);
748 else
749 append_char(&p, e, c);
750 }
751 append_char(&p, e, '\n');
752
753 if (dict_len) {
754 bool line = true;
755
756 for (i = 0; i < dict_len; i++) {
757 unsigned char c = dict[i];
758
759 if (line) {
760 append_char(&p, e, ' ');
761 line = false;
762 }
763
764 if (c == '\0') {
765 append_char(&p, e, '\n');
766 line = true;
767 continue;
768 }
769
770 if (c < ' ' || c >= 127 || c == '\\') {
771 p += scnprintf(p, e - p, "\\x%02x", c);
772 continue;
773 }
774
775 append_char(&p, e, c);
776 }
777 append_char(&p, e, '\n');
778 }
779
780 return p - buf;
781}
782
783/* /dev/kmsg - userspace message inject/listen interface */
784struct devkmsg_user {
785 u64 seq;
786 u32 idx;
787 struct ratelimit_state rs;
788 struct mutex lock;
789 char buf[CONSOLE_EXT_LOG_MAX];
790};
791
792static __printf(3, 4) __cold
793int devkmsg_emit(int facility, int level, const char *fmt, ...)
794{
795 va_list args;
796 int r;
797
798 va_start(args, fmt);
799 r = vprintk_emit(facility, level, NULL, 0, fmt, args);
800 va_end(args);
801
802 return r;
803}
804
805static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
806{
807 char *buf, *line;
808 int level = default_message_loglevel;
809 int facility = 1; /* LOG_USER */
810 struct file *file = iocb->ki_filp;
811 struct devkmsg_user *user = file->private_data;
812 size_t len = iov_iter_count(from);
813 ssize_t ret = len;
814
815 if (!user || len > LOG_LINE_MAX)
816 return -EINVAL;
817
818 /* Ignore when user logging is disabled. */
819 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
820 return len;
821
822 /* Ratelimit when not explicitly enabled. */
823 if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) {
824 if (!___ratelimit(&user->rs, current->comm))
825 return ret;
826 }
827
828 buf = kmalloc(len+1, GFP_KERNEL);
829 if (buf == NULL)
830 return -ENOMEM;
831
832 buf[len] = '\0';
833 if (!copy_from_iter_full(buf, len, from)) {
834 kfree(buf);
835 return -EFAULT;
836 }
837
838 /*
839 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
840 * the decimal value represents 32bit, the lower 3 bit are the log
841 * level, the rest are the log facility.
842 *
843 * If no prefix or no userspace facility is specified, we
844 * enforce LOG_USER, to be able to reliably distinguish
845 * kernel-generated messages from userspace-injected ones.
846 */
847 line = buf;
848 if (line[0] == '<') {
849 char *endp = NULL;
850 unsigned int u;
851
852 u = simple_strtoul(line + 1, &endp, 10);
853 if (endp && endp[0] == '>') {
854 level = LOG_LEVEL(u);
855 if (LOG_FACILITY(u) != 0)
856 facility = LOG_FACILITY(u);
857 endp++;
858 len -= endp - line;
859 line = endp;
860 }
861 }
862
863 devkmsg_emit(facility, level, "%s", line);
864 kfree(buf);
865 return ret;
866}
867
868static ssize_t devkmsg_read(struct file *file, char __user *buf,
869 size_t count, loff_t *ppos)
870{
871 struct devkmsg_user *user = file->private_data;
872 struct printk_log *msg;
873 size_t len;
874 ssize_t ret;
875
876 if (!user)
877 return -EBADF;
878
879 ret = mutex_lock_interruptible(&user->lock);
880 if (ret)
881 return ret;
882
883 logbuf_lock_irq();
884 while (user->seq == log_next_seq) {
885 if (file->f_flags & O_NONBLOCK) {
886 ret = -EAGAIN;
887 logbuf_unlock_irq();
888 goto out;
889 }
890
891 logbuf_unlock_irq();
892 ret = wait_event_interruptible(log_wait,
893 user->seq != log_next_seq);
894 if (ret)
895 goto out;
896 logbuf_lock_irq();
897 }
898
899 if (user->seq < log_first_seq) {
900 /* our last seen message is gone, return error and reset */
901 user->idx = log_first_idx;
902 user->seq = log_first_seq;
903 ret = -EPIPE;
904 logbuf_unlock_irq();
905 goto out;
906 }
907
908 msg = log_from_idx(user->idx);
909 len = msg_print_ext_header(user->buf, sizeof(user->buf),
910 msg, user->seq);
911 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
912 log_dict(msg), msg->dict_len,
913 log_text(msg), msg->text_len);
914
915 user->idx = log_next(user->idx);
916 user->seq++;
917 logbuf_unlock_irq();
918
919 if (len > count) {
920 ret = -EINVAL;
921 goto out;
922 }
923
924 if (copy_to_user(buf, user->buf, len)) {
925 ret = -EFAULT;
926 goto out;
927 }
928 ret = len;
929out:
930 mutex_unlock(&user->lock);
931 return ret;
932}
933
934static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
935{
936 struct devkmsg_user *user = file->private_data;
937 loff_t ret = 0;
938
939 if (!user)
940 return -EBADF;
941 if (offset)
942 return -ESPIPE;
943
944 logbuf_lock_irq();
945 switch (whence) {
946 case SEEK_SET:
947 /* the first record */
948 user->idx = log_first_idx;
949 user->seq = log_first_seq;
950 break;
951 case SEEK_DATA:
952 /*
953 * The first record after the last SYSLOG_ACTION_CLEAR,
954 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
955 * changes no global state, and does not clear anything.
956 */
957 user->idx = clear_idx;
958 user->seq = clear_seq;
959 break;
960 case SEEK_END:
961 /* after the last record */
962 user->idx = log_next_idx;
963 user->seq = log_next_seq;
964 break;
965 default:
966 ret = -EINVAL;
967 }
968 logbuf_unlock_irq();
969 return ret;
970}
971
972static __poll_t devkmsg_poll(struct file *file, poll_table *wait)
973{
974 struct devkmsg_user *user = file->private_data;
975 __poll_t ret = 0;
976
977 if (!user)
978 return EPOLLERR|EPOLLNVAL;
979
980 poll_wait(file, &log_wait, wait);
981
982 logbuf_lock_irq();
983 if (user->seq < log_next_seq) {
984 /* return error when data has vanished underneath us */
985 if (user->seq < log_first_seq)
986 ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI;
987 else
988 ret = EPOLLIN|EPOLLRDNORM;
989 }
990 logbuf_unlock_irq();
991
992 return ret;
993}
994
995static int devkmsg_open(struct inode *inode, struct file *file)
996{
997 struct devkmsg_user *user;
998 int err;
999
1000 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
1001 return -EPERM;
1002
1003 /* write-only does not need any file context */
1004 if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
1005 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
1006 SYSLOG_FROM_READER);
1007 if (err)
1008 return err;
1009 }
1010
1011 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
1012 if (!user)
1013 return -ENOMEM;
1014
1015 ratelimit_default_init(&user->rs);
1016 ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);
1017
1018 mutex_init(&user->lock);
1019
1020 logbuf_lock_irq();
1021 user->idx = log_first_idx;
1022 user->seq = log_first_seq;
1023 logbuf_unlock_irq();
1024
1025 file->private_data = user;
1026 return 0;
1027}
1028
1029static int devkmsg_release(struct inode *inode, struct file *file)
1030{
1031 struct devkmsg_user *user = file->private_data;
1032
1033 if (!user)
1034 return 0;
1035
1036 ratelimit_state_exit(&user->rs);
1037
1038 mutex_destroy(&user->lock);
1039 kfree(user);
1040 return 0;
1041}
1042
1043const struct file_operations kmsg_fops = {
1044 .open = devkmsg_open,
1045 .read = devkmsg_read,
1046 .write_iter = devkmsg_write,
1047 .llseek = devkmsg_llseek,
1048 .poll = devkmsg_poll,
1049 .release = devkmsg_release,
1050};
1051
1052#ifdef CONFIG_CRASH_CORE
1053/*
1054 * This appends the listed symbols to /proc/vmcore
1055 *
1056 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
1057 * obtain access to symbols that are otherwise very difficult to locate. These
1058 * symbols are specifically used so that utilities can access and extract the
1059 * dmesg log from a vmcore file after a crash.
1060 */
1061void log_buf_vmcoreinfo_setup(void)
1062{
1063 VMCOREINFO_SYMBOL(log_buf);
1064 VMCOREINFO_SYMBOL(log_buf_len);
1065 VMCOREINFO_SYMBOL(log_first_idx);
1066 VMCOREINFO_SYMBOL(clear_idx);
1067 VMCOREINFO_SYMBOL(log_next_idx);
1068 /*
1069 * Export struct printk_log size and field offsets. User space tools can
1070 * parse it and detect any changes to structure down the line.
1071 */
1072 VMCOREINFO_STRUCT_SIZE(printk_log);
1073 VMCOREINFO_OFFSET(printk_log, ts_nsec);
1074 VMCOREINFO_OFFSET(printk_log, len);
1075 VMCOREINFO_OFFSET(printk_log, text_len);
1076 VMCOREINFO_OFFSET(printk_log, dict_len);
1077#ifdef CONFIG_PRINTK_CALLER
1078 VMCOREINFO_OFFSET(printk_log, caller_id);
1079#endif
1080}
1081#endif
1082
1083/* requested log_buf_len from kernel cmdline */
1084static unsigned long __initdata new_log_buf_len;
1085
1086/* we practice scaling the ring buffer by powers of 2 */
1087static void __init log_buf_len_update(u64 size)
1088{
1089 if (size > (u64)LOG_BUF_LEN_MAX) {
1090 size = (u64)LOG_BUF_LEN_MAX;
1091 pr_err("log_buf over 2G is not supported.\n");
1092 }
1093
1094 if (size)
1095 size = roundup_pow_of_two(size);
1096 if (size > log_buf_len)
1097 new_log_buf_len = (unsigned long)size;
1098}
1099
1100/* save requested log_buf_len since it's too early to process it */
1101static int __init log_buf_len_setup(char *str)
1102{
1103 u64 size;
1104
1105 if (!str)
1106 return -EINVAL;
1107
1108 size = memparse(str, &str);
1109
1110 log_buf_len_update(size);
1111
1112 return 0;
1113}
1114early_param("log_buf_len", log_buf_len_setup);
1115
1116#ifdef CONFIG_SMP
1117#define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1118
1119static void __init log_buf_add_cpu(void)
1120{
1121 unsigned int cpu_extra;
1122
1123 /*
1124 * archs should set up cpu_possible_bits properly with
1125 * set_cpu_possible() after setup_arch() but just in
1126 * case lets ensure this is valid.
1127 */
1128 if (num_possible_cpus() == 1)
1129 return;
1130
1131 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
1132
1133 /* by default this will only continue through for large > 64 CPUs */
1134 if (cpu_extra <= __LOG_BUF_LEN / 2)
1135 return;
1136
1137 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1138 __LOG_CPU_MAX_BUF_LEN);
1139 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1140 cpu_extra);
1141 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
1142
1143 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
1144}
1145#else /* !CONFIG_SMP */
1146static inline void log_buf_add_cpu(void) {}
1147#endif /* CONFIG_SMP */
1148
1149void __init setup_log_buf(int early)
1150{
1151 unsigned long flags;
1152 char *new_log_buf;
1153 unsigned int free;
1154
1155 if (log_buf != __log_buf)
1156 return;
1157
1158 if (!early && !new_log_buf_len)
1159 log_buf_add_cpu();
1160
1161 if (!new_log_buf_len)
1162 return;
1163
1164 new_log_buf = memblock_alloc(new_log_buf_len, LOG_ALIGN);
1165 if (unlikely(!new_log_buf)) {
1166 pr_err("log_buf_len: %lu bytes not available\n",
1167 new_log_buf_len);
1168 return;
1169 }
1170
1171 logbuf_lock_irqsave(flags);
1172 log_buf_len = new_log_buf_len;
1173 log_buf = new_log_buf;
1174 new_log_buf_len = 0;
1175 free = __LOG_BUF_LEN - log_next_idx;
1176 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
1177 logbuf_unlock_irqrestore(flags);
1178
1179 pr_info("log_buf_len: %u bytes\n", log_buf_len);
1180 pr_info("early log buf free: %u(%u%%)\n",
1181 free, (free * 100) / __LOG_BUF_LEN);
1182}
1183
1184static bool __read_mostly ignore_loglevel;
1185
1186static int __init ignore_loglevel_setup(char *str)
1187{
1188 ignore_loglevel = true;
1189 pr_info("debug: ignoring loglevel setting.\n");
1190
1191 return 0;
1192}
1193
1194early_param("ignore_loglevel", ignore_loglevel_setup);
1195module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1196MODULE_PARM_DESC(ignore_loglevel,
1197 "ignore loglevel setting (prints all kernel messages to the console)");
1198
1199static bool suppress_message_printing(int level)
1200{
1201 return (level >= console_loglevel && !ignore_loglevel);
1202}
1203
1204#ifdef CONFIG_BOOT_PRINTK_DELAY
1205
1206static int boot_delay; /* msecs delay after each printk during bootup */
1207static unsigned long long loops_per_msec; /* based on boot_delay */
1208
1209static int __init boot_delay_setup(char *str)
1210{
1211 unsigned long lpj;
1212
1213 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
1214 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
1215
1216 get_option(&str, &boot_delay);
1217 if (boot_delay > 10 * 1000)
1218 boot_delay = 0;
1219
1220 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1221 "HZ: %d, loops_per_msec: %llu\n",
1222 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1223 return 0;
1224}
1225early_param("boot_delay", boot_delay_setup);
1226
1227static void boot_delay_msec(int level)
1228{
1229 unsigned long long k;
1230 unsigned long timeout;
1231
1232 if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING)
1233 || suppress_message_printing(level)) {
1234 return;
1235 }
1236
1237 k = (unsigned long long)loops_per_msec * boot_delay;
1238
1239 timeout = jiffies + msecs_to_jiffies(boot_delay);
1240 while (k) {
1241 k--;
1242 cpu_relax();
1243 /*
1244 * use (volatile) jiffies to prevent
1245 * compiler reduction; loop termination via jiffies
1246 * is secondary and may or may not happen.
1247 */
1248 if (time_after(jiffies, timeout))
1249 break;
1250 touch_nmi_watchdog();
1251 }
1252}
1253#else
1254static inline void boot_delay_msec(int level)
1255{
1256}
1257#endif
1258
1259static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1260module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1261
1262static size_t print_syslog(unsigned int level, char *buf)
1263{
1264 return sprintf(buf, "<%u>", level);
1265}
1266
1267static size_t print_time(u64 ts, char *buf)
1268{
1269 unsigned long rem_nsec = do_div(ts, 1000000000);
1270
1271 return sprintf(buf, "[%5lu.%06lu]",
1272 (unsigned long)ts, rem_nsec / 1000);
1273}
1274
1275#ifdef CONFIG_PRINTK_CALLER
1276static size_t print_caller(u32 id, char *buf)
1277{
1278 char caller[12];
1279
1280 snprintf(caller, sizeof(caller), "%c%u",
1281 id & 0x80000000 ? 'C' : 'T', id & ~0x80000000);
1282 return sprintf(buf, "[%6s]", caller);
1283}
1284#else
1285#define print_caller(id, buf) 0
1286#endif
1287
1288static size_t print_prefix(const struct printk_log *msg, bool syslog,
1289 bool time, char *buf)
1290{
1291 size_t len = 0;
1292
1293 if (syslog)
1294 len = print_syslog((msg->facility << 3) | msg->level, buf);
1295
1296 if (time)
1297 len += print_time(msg->ts_nsec, buf + len);
1298
1299 len += print_caller(msg->caller_id, buf + len);
1300
1301 if (IS_ENABLED(CONFIG_PRINTK_CALLER) || time) {
1302 buf[len++] = ' ';
1303 buf[len] = '\0';
1304 }
1305
1306 return len;
1307}
1308
1309static size_t msg_print_text(const struct printk_log *msg, bool syslog,
1310 bool time, char *buf, size_t size)
1311{
1312 const char *text = log_text(msg);
1313 size_t text_size = msg->text_len;
1314 size_t len = 0;
1315 char prefix[PREFIX_MAX];
1316 const size_t prefix_len = print_prefix(msg, syslog, time, prefix);
1317
1318 do {
1319 const char *next = memchr(text, '\n', text_size);
1320 size_t text_len;
1321
1322 if (next) {
1323 text_len = next - text;
1324 next++;
1325 text_size -= next - text;
1326 } else {
1327 text_len = text_size;
1328 }
1329
1330 if (buf) {
1331 if (prefix_len + text_len + 1 >= size - len)
1332 break;
1333
1334 memcpy(buf + len, prefix, prefix_len);
1335 len += prefix_len;
1336 memcpy(buf + len, text, text_len);
1337 len += text_len;
1338 buf[len++] = '\n';
1339 } else {
1340 /* SYSLOG_ACTION_* buffer size only calculation */
1341 len += prefix_len + text_len + 1;
1342 }
1343
1344 text = next;
1345 } while (text);
1346
1347 return len;
1348}
1349
1350static int syslog_print(char __user *buf, int size)
1351{
1352 char *text;
1353 struct printk_log *msg;
1354 int len = 0;
1355
1356 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1357 if (!text)
1358 return -ENOMEM;
1359
1360 while (size > 0) {
1361 size_t n;
1362 size_t skip;
1363
1364 logbuf_lock_irq();
1365 if (syslog_seq < log_first_seq) {
1366 /* messages are gone, move to first one */
1367 syslog_seq = log_first_seq;
1368 syslog_idx = log_first_idx;
1369 syslog_partial = 0;
1370 }
1371 if (syslog_seq == log_next_seq) {
1372 logbuf_unlock_irq();
1373 break;
1374 }
1375
1376 /*
1377 * To keep reading/counting partial line consistent,
1378 * use printk_time value as of the beginning of a line.
1379 */
1380 if (!syslog_partial)
1381 syslog_time = printk_time;
1382
1383 skip = syslog_partial;
1384 msg = log_from_idx(syslog_idx);
1385 n = msg_print_text(msg, true, syslog_time, text,
1386 LOG_LINE_MAX + PREFIX_MAX);
1387 if (n - syslog_partial <= size) {
1388 /* message fits into buffer, move forward */
1389 syslog_idx = log_next(syslog_idx);
1390 syslog_seq++;
1391 n -= syslog_partial;
1392 syslog_partial = 0;
1393 } else if (!len){
1394 /* partial read(), remember position */
1395 n = size;
1396 syslog_partial += n;
1397 } else
1398 n = 0;
1399 logbuf_unlock_irq();
1400
1401 if (!n)
1402 break;
1403
1404 if (copy_to_user(buf, text + skip, n)) {
1405 if (!len)
1406 len = -EFAULT;
1407 break;
1408 }
1409
1410 len += n;
1411 size -= n;
1412 buf += n;
1413 }
1414
1415 kfree(text);
1416 return len;
1417}
1418
1419static int syslog_print_all(char __user *buf, int size, bool clear)
1420{
1421 char *text;
1422 int len = 0;
1423 u64 next_seq;
1424 u64 seq;
1425 u32 idx;
1426 bool time;
1427
1428 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1429 if (!text)
1430 return -ENOMEM;
1431
1432 time = printk_time;
1433 logbuf_lock_irq();
1434 /*
1435 * Find first record that fits, including all following records,
1436 * into the user-provided buffer for this dump.
1437 */
1438 seq = clear_seq;
1439 idx = clear_idx;
1440 while (seq < log_next_seq) {
1441 struct printk_log *msg = log_from_idx(idx);
1442
1443 len += msg_print_text(msg, true, time, NULL, 0);
1444 idx = log_next(idx);
1445 seq++;
1446 }
1447
1448 /* move first record forward until length fits into the buffer */
1449 seq = clear_seq;
1450 idx = clear_idx;
1451 while (len > size && seq < log_next_seq) {
1452 struct printk_log *msg = log_from_idx(idx);
1453
1454 len -= msg_print_text(msg, true, time, NULL, 0);
1455 idx = log_next(idx);
1456 seq++;
1457 }
1458
1459 /* last message fitting into this dump */
1460 next_seq = log_next_seq;
1461
1462 len = 0;
1463 while (len >= 0 && seq < next_seq) {
1464 struct printk_log *msg = log_from_idx(idx);
1465 int textlen = msg_print_text(msg, true, time, text,
1466 LOG_LINE_MAX + PREFIX_MAX);
1467
1468 idx = log_next(idx);
1469 seq++;
1470
1471 logbuf_unlock_irq();
1472 if (copy_to_user(buf + len, text, textlen))
1473 len = -EFAULT;
1474 else
1475 len += textlen;
1476 logbuf_lock_irq();
1477
1478 if (seq < log_first_seq) {
1479 /* messages are gone, move to next one */
1480 seq = log_first_seq;
1481 idx = log_first_idx;
1482 }
1483 }
1484
1485 if (clear) {
1486 clear_seq = log_next_seq;
1487 clear_idx = log_next_idx;
1488 }
1489 logbuf_unlock_irq();
1490
1491 kfree(text);
1492 return len;
1493}
1494
1495static void syslog_clear(void)
1496{
1497 logbuf_lock_irq();
1498 clear_seq = log_next_seq;
1499 clear_idx = log_next_idx;
1500 logbuf_unlock_irq();
1501}
1502
1503int do_syslog(int type, char __user *buf, int len, int source)
1504{
1505 bool clear = false;
1506 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1507 int error;
1508
1509 error = check_syslog_permissions(type, source);
1510 if (error)
1511 return error;
1512
1513 switch (type) {
1514 case SYSLOG_ACTION_CLOSE: /* Close log */
1515 break;
1516 case SYSLOG_ACTION_OPEN: /* Open log */
1517 break;
1518 case SYSLOG_ACTION_READ: /* Read from log */
1519 if (!buf || len < 0)
1520 return -EINVAL;
1521 if (!len)
1522 return 0;
1523 if (!access_ok(buf, len))
1524 return -EFAULT;
1525 error = wait_event_interruptible(log_wait,
1526 syslog_seq != log_next_seq);
1527 if (error)
1528 return error;
1529 error = syslog_print(buf, len);
1530 break;
1531 /* Read/clear last kernel messages */
1532 case SYSLOG_ACTION_READ_CLEAR:
1533 clear = true;
1534 /* FALL THRU */
1535 /* Read last kernel messages */
1536 case SYSLOG_ACTION_READ_ALL:
1537 if (!buf || len < 0)
1538 return -EINVAL;
1539 if (!len)
1540 return 0;
1541 if (!access_ok(buf, len))
1542 return -EFAULT;
1543 error = syslog_print_all(buf, len, clear);
1544 break;
1545 /* Clear ring buffer */
1546 case SYSLOG_ACTION_CLEAR:
1547 syslog_clear();
1548 break;
1549 /* Disable logging to console */
1550 case SYSLOG_ACTION_CONSOLE_OFF:
1551 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1552 saved_console_loglevel = console_loglevel;
1553 console_loglevel = minimum_console_loglevel;
1554 break;
1555 /* Enable logging to console */
1556 case SYSLOG_ACTION_CONSOLE_ON:
1557 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1558 console_loglevel = saved_console_loglevel;
1559 saved_console_loglevel = LOGLEVEL_DEFAULT;
1560 }
1561 break;
1562 /* Set level of messages printed to console */
1563 case SYSLOG_ACTION_CONSOLE_LEVEL:
1564 if (len < 1 || len > 8)
1565 return -EINVAL;
1566 if (len < minimum_console_loglevel)
1567 len = minimum_console_loglevel;
1568 console_loglevel = len;
1569 /* Implicitly re-enable logging to console */
1570 saved_console_loglevel = LOGLEVEL_DEFAULT;
1571 break;
1572 /* Number of chars in the log buffer */
1573 case SYSLOG_ACTION_SIZE_UNREAD:
1574 logbuf_lock_irq();
1575 if (syslog_seq < log_first_seq) {
1576 /* messages are gone, move to first one */
1577 syslog_seq = log_first_seq;
1578 syslog_idx = log_first_idx;
1579 syslog_partial = 0;
1580 }
1581 if (source == SYSLOG_FROM_PROC) {
1582 /*
1583 * Short-cut for poll(/"proc/kmsg") which simply checks
1584 * for pending data, not the size; return the count of
1585 * records, not the length.
1586 */
1587 error = log_next_seq - syslog_seq;
1588 } else {
1589 u64 seq = syslog_seq;
1590 u32 idx = syslog_idx;
1591 bool time = syslog_partial ? syslog_time : printk_time;
1592
1593 while (seq < log_next_seq) {
1594 struct printk_log *msg = log_from_idx(idx);
1595
1596 error += msg_print_text(msg, true, time, NULL,
1597 0);
1598 time = printk_time;
1599 idx = log_next(idx);
1600 seq++;
1601 }
1602 error -= syslog_partial;
1603 }
1604 logbuf_unlock_irq();
1605 break;
1606 /* Size of the log buffer */
1607 case SYSLOG_ACTION_SIZE_BUFFER:
1608 error = log_buf_len;
1609 break;
1610 default:
1611 error = -EINVAL;
1612 break;
1613 }
1614
1615 return error;
1616}
1617
1618SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1619{
1620 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1621}
1622
1623/*
1624 * Special console_lock variants that help to reduce the risk of soft-lockups.
1625 * They allow to pass console_lock to another printk() call using a busy wait.
1626 */
1627
1628#ifdef CONFIG_LOCKDEP
1629static struct lockdep_map console_owner_dep_map = {
1630 .name = "console_owner"
1631};
1632#endif
1633
1634static DEFINE_RAW_SPINLOCK(console_owner_lock);
1635static struct task_struct *console_owner;
1636static bool console_waiter;
1637
1638/**
1639 * console_lock_spinning_enable - mark beginning of code where another
1640 * thread might safely busy wait
1641 *
1642 * This basically converts console_lock into a spinlock. This marks
1643 * the section where the console_lock owner can not sleep, because
1644 * there may be a waiter spinning (like a spinlock). Also it must be
1645 * ready to hand over the lock at the end of the section.
1646 */
1647static void console_lock_spinning_enable(void)
1648{
1649 raw_spin_lock(&console_owner_lock);
1650 console_owner = current;
1651 raw_spin_unlock(&console_owner_lock);
1652
1653 /* The waiter may spin on us after setting console_owner */
1654 spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_);
1655}
1656
1657/**
1658 * console_lock_spinning_disable_and_check - mark end of code where another
1659 * thread was able to busy wait and check if there is a waiter
1660 *
1661 * This is called at the end of the section where spinning is allowed.
1662 * It has two functions. First, it is a signal that it is no longer
1663 * safe to start busy waiting for the lock. Second, it checks if
1664 * there is a busy waiter and passes the lock rights to her.
1665 *
1666 * Important: Callers lose the lock if there was a busy waiter.
1667 * They must not touch items synchronized by console_lock
1668 * in this case.
1669 *
1670 * Return: 1 if the lock rights were passed, 0 otherwise.
1671 */
1672static int console_lock_spinning_disable_and_check(void)
1673{
1674 int waiter;
1675
1676 raw_spin_lock(&console_owner_lock);
1677 waiter = READ_ONCE(console_waiter);
1678 console_owner = NULL;
1679 raw_spin_unlock(&console_owner_lock);
1680
1681 if (!waiter) {
1682 spin_release(&console_owner_dep_map, 1, _THIS_IP_);
1683 return 0;
1684 }
1685
1686 /* The waiter is now free to continue */
1687 WRITE_ONCE(console_waiter, false);
1688
1689 spin_release(&console_owner_dep_map, 1, _THIS_IP_);
1690
1691 /*
1692 * Hand off console_lock to waiter. The waiter will perform
1693 * the up(). After this, the waiter is the console_lock owner.
1694 */
1695 mutex_release(&console_lock_dep_map, 1, _THIS_IP_);
1696 return 1;
1697}
1698
1699/**
1700 * console_trylock_spinning - try to get console_lock by busy waiting
1701 *
1702 * This allows to busy wait for the console_lock when the current
1703 * owner is running in specially marked sections. It means that
1704 * the current owner is running and cannot reschedule until it
1705 * is ready to lose the lock.
1706 *
1707 * Return: 1 if we got the lock, 0 othrewise
1708 */
1709static int console_trylock_spinning(void)
1710{
1711 struct task_struct *owner = NULL;
1712 bool waiter;
1713 bool spin = false;
1714 unsigned long flags;
1715
1716 if (console_trylock())
1717 return 1;
1718
1719 printk_safe_enter_irqsave(flags);
1720
1721 raw_spin_lock(&console_owner_lock);
1722 owner = READ_ONCE(console_owner);
1723 waiter = READ_ONCE(console_waiter);
1724 if (!waiter && owner && owner != current) {
1725 WRITE_ONCE(console_waiter, true);
1726 spin = true;
1727 }
1728 raw_spin_unlock(&console_owner_lock);
1729
1730 /*
1731 * If there is an active printk() writing to the
1732 * consoles, instead of having it write our data too,
1733 * see if we can offload that load from the active
1734 * printer, and do some printing ourselves.
1735 * Go into a spin only if there isn't already a waiter
1736 * spinning, and there is an active printer, and
1737 * that active printer isn't us (recursive printk?).
1738 */
1739 if (!spin) {
1740 printk_safe_exit_irqrestore(flags);
1741 return 0;
1742 }
1743
1744 /* We spin waiting for the owner to release us */
1745 spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_);
1746 /* Owner will clear console_waiter on hand off */
1747 while (READ_ONCE(console_waiter))
1748 cpu_relax();
1749 spin_release(&console_owner_dep_map, 1, _THIS_IP_);
1750
1751 printk_safe_exit_irqrestore(flags);
1752 /*
1753 * The owner passed the console lock to us.
1754 * Since we did not spin on console lock, annotate
1755 * this as a trylock. Otherwise lockdep will
1756 * complain.
1757 */
1758 mutex_acquire(&console_lock_dep_map, 0, 1, _THIS_IP_);
1759
1760 return 1;
1761}
1762
1763/*
1764 * Call the console drivers, asking them to write out
1765 * log_buf[start] to log_buf[end - 1].
1766 * The console_lock must be held.
1767 */
1768static void call_console_drivers(const char *ext_text, size_t ext_len,
1769 const char *text, size_t len)
1770{
1771 struct console *con;
1772
1773 trace_console_rcuidle(text, len);
1774
1775 if (!console_drivers)
1776 return;
1777
1778 for_each_console(con) {
1779 if (exclusive_console && con != exclusive_console)
1780 continue;
1781 if (!(con->flags & CON_ENABLED))
1782 continue;
1783 if (!con->write)
1784 continue;
1785 if (!cpu_online(smp_processor_id()) &&
1786 !(con->flags & CON_ANYTIME))
1787 continue;
1788 if (con->flags & CON_EXTENDED)
1789 con->write(con, ext_text, ext_len);
1790 else
1791 con->write(con, text, len);
1792 }
1793}
1794
1795int printk_delay_msec __read_mostly;
1796
1797static inline void printk_delay(void)
1798{
1799 if (unlikely(printk_delay_msec)) {
1800 int m = printk_delay_msec;
1801
1802 while (m--) {
1803 mdelay(1);
1804 touch_nmi_watchdog();
1805 }
1806 }
1807}
1808
1809static inline u32 printk_caller_id(void)
1810{
1811 return in_task() ? task_pid_nr(current) :
1812 0x80000000 + raw_smp_processor_id();
1813}
1814
1815/*
1816 * Continuation lines are buffered, and not committed to the record buffer
1817 * until the line is complete, or a race forces it. The line fragments
1818 * though, are printed immediately to the consoles to ensure everything has
1819 * reached the console in case of a kernel crash.
1820 */
1821static struct cont {
1822 char buf[LOG_LINE_MAX];
1823 size_t len; /* length == 0 means unused buffer */
1824 u32 caller_id; /* printk_caller_id() of first print */
1825 u64 ts_nsec; /* time of first print */
1826 u8 level; /* log level of first message */
1827 u8 facility; /* log facility of first message */
1828 enum log_flags flags; /* prefix, newline flags */
1829} cont;
1830
1831static void cont_flush(void)
1832{
1833 if (cont.len == 0)
1834 return;
1835
1836 log_store(cont.caller_id, cont.facility, cont.level, cont.flags,
1837 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1838 cont.len = 0;
1839}
1840
1841static bool cont_add(u32 caller_id, int facility, int level,
1842 enum log_flags flags, const char *text, size_t len)
1843{
1844 /* If the line gets too long, split it up in separate records. */
1845 if (cont.len + len > sizeof(cont.buf)) {
1846 cont_flush();
1847 return false;
1848 }
1849
1850 if (!cont.len) {
1851 cont.facility = facility;
1852 cont.level = level;
1853 cont.caller_id = caller_id;
1854 cont.ts_nsec = local_clock();
1855 cont.flags = flags;
1856 }
1857
1858 memcpy(cont.buf + cont.len, text, len);
1859 cont.len += len;
1860
1861 // The original flags come from the first line,
1862 // but later continuations can add a newline.
1863 if (flags & LOG_NEWLINE) {
1864 cont.flags |= LOG_NEWLINE;
1865 cont_flush();
1866 }
1867
1868 return true;
1869}
1870
1871static size_t log_output(int facility, int level, enum log_flags lflags, const char *dict, size_t dictlen, char *text, size_t text_len)
1872{
1873 const u32 caller_id = printk_caller_id();
1874
1875 /*
1876 * If an earlier line was buffered, and we're a continuation
1877 * write from the same context, try to add it to the buffer.
1878 */
1879 if (cont.len) {
1880 if (cont.caller_id == caller_id && (lflags & LOG_CONT)) {
1881 if (cont_add(caller_id, facility, level, lflags, text, text_len))
1882 return text_len;
1883 }
1884 /* Otherwise, make sure it's flushed */
1885 cont_flush();
1886 }
1887
1888 /* Skip empty continuation lines that couldn't be added - they just flush */
1889 if (!text_len && (lflags & LOG_CONT))
1890 return 0;
1891
1892 /* If it doesn't end in a newline, try to buffer the current line */
1893 if (!(lflags & LOG_NEWLINE)) {
1894 if (cont_add(caller_id, facility, level, lflags, text, text_len))
1895 return text_len;
1896 }
1897
1898 /* Store it in the record log */
1899 return log_store(caller_id, facility, level, lflags, 0,
1900 dict, dictlen, text, text_len);
1901}
1902
1903/* Must be called under logbuf_lock. */
1904int vprintk_store(int facility, int level,
1905 const char *dict, size_t dictlen,
1906 const char *fmt, va_list args)
1907{
1908 static char textbuf[LOG_LINE_MAX];
1909 char *text = textbuf;
1910 size_t text_len;
1911 enum log_flags lflags = 0;
1912
1913 /*
1914 * The printf needs to come first; we need the syslog
1915 * prefix which might be passed-in as a parameter.
1916 */
1917 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1918
1919 /* mark and strip a trailing newline */
1920 if (text_len && text[text_len-1] == '\n') {
1921 text_len--;
1922 lflags |= LOG_NEWLINE;
1923 }
1924
1925 /* strip kernel syslog prefix and extract log level or control flags */
1926 if (facility == 0) {
1927 int kern_level;
1928
1929 while ((kern_level = printk_get_level(text)) != 0) {
1930 switch (kern_level) {
1931 case '0' ... '7':
1932 if (level == LOGLEVEL_DEFAULT)
1933 level = kern_level - '0';
1934 break;
1935 case 'c': /* KERN_CONT */
1936 lflags |= LOG_CONT;
1937 }
1938
1939 text_len -= 2;
1940 text += 2;
1941 }
1942 }
1943
1944 if (level == LOGLEVEL_DEFAULT)
1945 level = default_message_loglevel;
1946
1947 if (dict)
1948 lflags |= LOG_NEWLINE;
1949
1950 return log_output(facility, level, lflags,
1951 dict, dictlen, text, text_len);
1952}
1953
1954asmlinkage int vprintk_emit(int facility, int level,
1955 const char *dict, size_t dictlen,
1956 const char *fmt, va_list args)
1957{
1958 int printed_len;
1959 bool in_sched = false, pending_output;
1960 unsigned long flags;
1961 u64 curr_log_seq;
1962
1963 /* Suppress unimportant messages after panic happens */
1964 if (unlikely(suppress_printk))
1965 return 0;
1966
1967 if (level == LOGLEVEL_SCHED) {
1968 level = LOGLEVEL_DEFAULT;
1969 in_sched = true;
1970 }
1971
1972 boot_delay_msec(level);
1973 printk_delay();
1974
1975 /* This stops the holder of console_sem just where we want him */
1976 logbuf_lock_irqsave(flags);
1977 curr_log_seq = log_next_seq;
1978 printed_len = vprintk_store(facility, level, dict, dictlen, fmt, args);
1979 pending_output = (curr_log_seq != log_next_seq);
1980 logbuf_unlock_irqrestore(flags);
1981
1982 /* If called from the scheduler, we can not call up(). */
1983 if (!in_sched && pending_output) {
1984 /*
1985 * Disable preemption to avoid being preempted while holding
1986 * console_sem which would prevent anyone from printing to
1987 * console
1988 */
1989 preempt_disable();
1990 /*
1991 * Try to acquire and then immediately release the console
1992 * semaphore. The release will print out buffers and wake up
1993 * /dev/kmsg and syslog() users.
1994 */
1995 if (console_trylock_spinning())
1996 console_unlock();
1997 preempt_enable();
1998 }
1999
2000 if (pending_output)
2001 wake_up_klogd();
2002 return printed_len;
2003}
2004EXPORT_SYMBOL(vprintk_emit);
2005
2006asmlinkage int vprintk(const char *fmt, va_list args)
2007{
2008 return vprintk_func(fmt, args);
2009}
2010EXPORT_SYMBOL(vprintk);
2011
2012int vprintk_default(const char *fmt, va_list args)
2013{
2014 int r;
2015
2016#ifdef CONFIG_KGDB_KDB
2017 /* Allow to pass printk() to kdb but avoid a recursion. */
2018 if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0)) {
2019 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
2020 return r;
2021 }
2022#endif
2023 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
2024
2025 return r;
2026}
2027EXPORT_SYMBOL_GPL(vprintk_default);
2028
2029/**
2030 * printk - print a kernel message
2031 * @fmt: format string
2032 *
2033 * This is printk(). It can be called from any context. We want it to work.
2034 *
2035 * We try to grab the console_lock. If we succeed, it's easy - we log the
2036 * output and call the console drivers. If we fail to get the semaphore, we
2037 * place the output into the log buffer and return. The current holder of
2038 * the console_sem will notice the new output in console_unlock(); and will
2039 * send it to the consoles before releasing the lock.
2040 *
2041 * One effect of this deferred printing is that code which calls printk() and
2042 * then changes console_loglevel may break. This is because console_loglevel
2043 * is inspected when the actual printing occurs.
2044 *
2045 * See also:
2046 * printf(3)
2047 *
2048 * See the vsnprintf() documentation for format string extensions over C99.
2049 */
2050asmlinkage __visible int printk(const char *fmt, ...)
2051{
2052 va_list args;
2053 int r;
2054
2055 va_start(args, fmt);
2056 r = vprintk_func(fmt, args);
2057 va_end(args);
2058
2059 return r;
2060}
2061EXPORT_SYMBOL(printk);
2062
2063#else /* CONFIG_PRINTK */
2064
2065#define LOG_LINE_MAX 0
2066#define PREFIX_MAX 0
2067#define printk_time false
2068
2069static u64 syslog_seq;
2070static u32 syslog_idx;
2071static u64 console_seq;
2072static u32 console_idx;
2073static u64 exclusive_console_stop_seq;
2074static u64 log_first_seq;
2075static u32 log_first_idx;
2076static u64 log_next_seq;
2077static char *log_text(const struct printk_log *msg) { return NULL; }
2078static char *log_dict(const struct printk_log *msg) { return NULL; }
2079static struct printk_log *log_from_idx(u32 idx) { return NULL; }
2080static u32 log_next(u32 idx) { return 0; }
2081static ssize_t msg_print_ext_header(char *buf, size_t size,
2082 struct printk_log *msg,
2083 u64 seq) { return 0; }
2084static ssize_t msg_print_ext_body(char *buf, size_t size,
2085 char *dict, size_t dict_len,
2086 char *text, size_t text_len) { return 0; }
2087static void console_lock_spinning_enable(void) { }
2088static int console_lock_spinning_disable_and_check(void) { return 0; }
2089static void call_console_drivers(const char *ext_text, size_t ext_len,
2090 const char *text, size_t len) {}
2091static size_t msg_print_text(const struct printk_log *msg, bool syslog,
2092 bool time, char *buf, size_t size) { return 0; }
2093static bool suppress_message_printing(int level) { return false; }
2094
2095#endif /* CONFIG_PRINTK */
2096
2097#ifdef CONFIG_EARLY_PRINTK
2098struct console *early_console;
2099
2100asmlinkage __visible void early_printk(const char *fmt, ...)
2101{
2102 va_list ap;
2103 char buf[512];
2104 int n;
2105
2106 if (!early_console)
2107 return;
2108
2109 va_start(ap, fmt);
2110 n = vscnprintf(buf, sizeof(buf), fmt, ap);
2111 va_end(ap);
2112
2113 early_console->write(early_console, buf, n);
2114}
2115#endif
2116
2117static int __add_preferred_console(char *name, int idx, char *options,
2118 char *brl_options)
2119{
2120 struct console_cmdline *c;
2121 int i;
2122
2123 /*
2124 * See if this tty is not yet registered, and
2125 * if we have a slot free.
2126 */
2127 for (i = 0, c = console_cmdline;
2128 i < MAX_CMDLINECONSOLES && c->name[0];
2129 i++, c++) {
2130 if (strcmp(c->name, name) == 0 && c->index == idx) {
2131 if (!brl_options)
2132 preferred_console = i;
2133 return 0;
2134 }
2135 }
2136 if (i == MAX_CMDLINECONSOLES)
2137 return -E2BIG;
2138 if (!brl_options)
2139 preferred_console = i;
2140 strlcpy(c->name, name, sizeof(c->name));
2141 c->options = options;
2142 braille_set_options(c, brl_options);
2143
2144 c->index = idx;
2145 return 0;
2146}
2147
2148static int __init console_msg_format_setup(char *str)
2149{
2150 if (!strcmp(str, "syslog"))
2151 console_msg_format = MSG_FORMAT_SYSLOG;
2152 if (!strcmp(str, "default"))
2153 console_msg_format = MSG_FORMAT_DEFAULT;
2154 return 1;
2155}
2156__setup("console_msg_format=", console_msg_format_setup);
2157
2158/*
2159 * Set up a console. Called via do_early_param() in init/main.c
2160 * for each "console=" parameter in the boot command line.
2161 */
2162static int __init console_setup(char *str)
2163{
2164 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
2165 char *s, *options, *brl_options = NULL;
2166 int idx;
2167
2168 if (_braille_console_setup(&str, &brl_options))
2169 return 1;
2170
2171 /*
2172 * Decode str into name, index, options.
2173 */
2174 if (str[0] >= '0' && str[0] <= '9') {
2175 strcpy(buf, "ttyS");
2176 strncpy(buf + 4, str, sizeof(buf) - 5);
2177 } else {
2178 strncpy(buf, str, sizeof(buf) - 1);
2179 }
2180 buf[sizeof(buf) - 1] = 0;
2181 options = strchr(str, ',');
2182 if (options)
2183 *(options++) = 0;
2184#ifdef __sparc__
2185 if (!strcmp(str, "ttya"))
2186 strcpy(buf, "ttyS0");
2187 if (!strcmp(str, "ttyb"))
2188 strcpy(buf, "ttyS1");
2189#endif
2190 for (s = buf; *s; s++)
2191 if (isdigit(*s) || *s == ',')
2192 break;
2193 idx = simple_strtoul(s, NULL, 10);
2194 *s = 0;
2195
2196 __add_preferred_console(buf, idx, options, brl_options);
2197 console_set_on_cmdline = 1;
2198 return 1;
2199}
2200__setup("console=", console_setup);
2201
2202/**
2203 * add_preferred_console - add a device to the list of preferred consoles.
2204 * @name: device name
2205 * @idx: device index
2206 * @options: options for this console
2207 *
2208 * The last preferred console added will be used for kernel messages
2209 * and stdin/out/err for init. Normally this is used by console_setup
2210 * above to handle user-supplied console arguments; however it can also
2211 * be used by arch-specific code either to override the user or more
2212 * commonly to provide a default console (ie from PROM variables) when
2213 * the user has not supplied one.
2214 */
2215int add_preferred_console(char *name, int idx, char *options)
2216{
2217 return __add_preferred_console(name, idx, options, NULL);
2218}
2219
2220bool console_suspend_enabled = true;
2221EXPORT_SYMBOL(console_suspend_enabled);
2222
2223static int __init console_suspend_disable(char *str)
2224{
2225 console_suspend_enabled = false;
2226 return 1;
2227}
2228__setup("no_console_suspend", console_suspend_disable);
2229module_param_named(console_suspend, console_suspend_enabled,
2230 bool, S_IRUGO | S_IWUSR);
2231MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2232 " and hibernate operations");
2233
2234/**
2235 * suspend_console - suspend the console subsystem
2236 *
2237 * This disables printk() while we go into suspend states
2238 */
2239void suspend_console(void)
2240{
2241 if (!console_suspend_enabled)
2242 return;
2243 pr_info("Suspending console(s) (use no_console_suspend to debug)\n");
2244 console_lock();
2245 console_suspended = 1;
2246 up_console_sem();
2247}
2248
2249void resume_console(void)
2250{
2251 if (!console_suspend_enabled)
2252 return;
2253 down_console_sem();
2254 console_suspended = 0;
2255 console_unlock();
2256}
2257
2258/**
2259 * console_cpu_notify - print deferred console messages after CPU hotplug
2260 * @cpu: unused
2261 *
2262 * If printk() is called from a CPU that is not online yet, the messages
2263 * will be printed on the console only if there are CON_ANYTIME consoles.
2264 * This function is called when a new CPU comes online (or fails to come
2265 * up) or goes offline.
2266 */
2267static int console_cpu_notify(unsigned int cpu)
2268{
2269 if (!cpuhp_tasks_frozen) {
2270 /* If trylock fails, someone else is doing the printing */
2271 if (console_trylock())
2272 console_unlock();
2273 }
2274 return 0;
2275}
2276
2277/**
2278 * console_lock - lock the console system for exclusive use.
2279 *
2280 * Acquires a lock which guarantees that the caller has
2281 * exclusive access to the console system and the console_drivers list.
2282 *
2283 * Can sleep, returns nothing.
2284 */
2285void console_lock(void)
2286{
2287 might_sleep();
2288
2289 down_console_sem();
2290 if (console_suspended)
2291 return;
2292 console_locked = 1;
2293 console_may_schedule = 1;
2294}
2295EXPORT_SYMBOL(console_lock);
2296
2297/**
2298 * console_trylock - try to lock the console system for exclusive use.
2299 *
2300 * Try to acquire a lock which guarantees that the caller has exclusive
2301 * access to the console system and the console_drivers list.
2302 *
2303 * returns 1 on success, and 0 on failure to acquire the lock.
2304 */
2305int console_trylock(void)
2306{
2307 if (down_trylock_console_sem())
2308 return 0;
2309 if (console_suspended) {
2310 up_console_sem();
2311 return 0;
2312 }
2313 console_locked = 1;
2314 console_may_schedule = 0;
2315 return 1;
2316}
2317EXPORT_SYMBOL(console_trylock);
2318
2319int is_console_locked(void)
2320{
2321 return console_locked;
2322}
2323EXPORT_SYMBOL(is_console_locked);
2324
2325/*
2326 * Check if we have any console that is capable of printing while cpu is
2327 * booting or shutting down. Requires console_sem.
2328 */
2329static int have_callable_console(void)
2330{
2331 struct console *con;
2332
2333 for_each_console(con)
2334 if ((con->flags & CON_ENABLED) &&
2335 (con->flags & CON_ANYTIME))
2336 return 1;
2337
2338 return 0;
2339}
2340
2341/*
2342 * Can we actually use the console at this time on this cpu?
2343 *
2344 * Console drivers may assume that per-cpu resources have been allocated. So
2345 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2346 * call them until this CPU is officially up.
2347 */
2348static inline int can_use_console(void)
2349{
2350 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2351}
2352
2353/**
2354 * console_unlock - unlock the console system
2355 *
2356 * Releases the console_lock which the caller holds on the console system
2357 * and the console driver list.
2358 *
2359 * While the console_lock was held, console output may have been buffered
2360 * by printk(). If this is the case, console_unlock(); emits
2361 * the output prior to releasing the lock.
2362 *
2363 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2364 *
2365 * console_unlock(); may be called from any context.
2366 */
2367void console_unlock(void)
2368{
2369 static char ext_text[CONSOLE_EXT_LOG_MAX];
2370 static char text[LOG_LINE_MAX + PREFIX_MAX];
2371 unsigned long flags;
2372 bool do_cond_resched, retry;
2373
2374 if (console_suspended) {
2375 up_console_sem();
2376 return;
2377 }
2378
2379 /*
2380 * Console drivers are called with interrupts disabled, so
2381 * @console_may_schedule should be cleared before; however, we may
2382 * end up dumping a lot of lines, for example, if called from
2383 * console registration path, and should invoke cond_resched()
2384 * between lines if allowable. Not doing so can cause a very long
2385 * scheduling stall on a slow console leading to RCU stall and
2386 * softlockup warnings which exacerbate the issue with more
2387 * messages practically incapacitating the system.
2388 *
2389 * console_trylock() is not able to detect the preemptive
2390 * context reliably. Therefore the value must be stored before
2391 * and cleared after the the "again" goto label.
2392 */
2393 do_cond_resched = console_may_schedule;
2394again:
2395 console_may_schedule = 0;
2396
2397 /*
2398 * We released the console_sem lock, so we need to recheck if
2399 * cpu is online and (if not) is there at least one CON_ANYTIME
2400 * console.
2401 */
2402 if (!can_use_console()) {
2403 console_locked = 0;
2404 up_console_sem();
2405 return;
2406 }
2407
2408 for (;;) {
2409 struct printk_log *msg;
2410 size_t ext_len = 0;
2411 size_t len;
2412
2413 printk_safe_enter_irqsave(flags);
2414 raw_spin_lock(&logbuf_lock);
2415 if (console_seq < log_first_seq) {
2416 len = sprintf(text,
2417 "** %llu printk messages dropped **\n",
2418 log_first_seq - console_seq);
2419
2420 /* messages are gone, move to first one */
2421 console_seq = log_first_seq;
2422 console_idx = log_first_idx;
2423 } else {
2424 len = 0;
2425 }
2426skip:
2427 if (console_seq == log_next_seq)
2428 break;
2429
2430 msg = log_from_idx(console_idx);
2431 if (suppress_message_printing(msg->level)) {
2432 /*
2433 * Skip record we have buffered and already printed
2434 * directly to the console when we received it, and
2435 * record that has level above the console loglevel.
2436 */
2437 console_idx = log_next(console_idx);
2438 console_seq++;
2439 goto skip;
2440 }
2441
2442 /* Output to all consoles once old messages replayed. */
2443 if (unlikely(exclusive_console &&
2444 console_seq >= exclusive_console_stop_seq)) {
2445 exclusive_console = NULL;
2446 }
2447
2448 len += msg_print_text(msg,
2449 console_msg_format & MSG_FORMAT_SYSLOG,
2450 printk_time, text + len, sizeof(text) - len);
2451 if (nr_ext_console_drivers) {
2452 ext_len = msg_print_ext_header(ext_text,
2453 sizeof(ext_text),
2454 msg, console_seq);
2455 ext_len += msg_print_ext_body(ext_text + ext_len,
2456 sizeof(ext_text) - ext_len,
2457 log_dict(msg), msg->dict_len,
2458 log_text(msg), msg->text_len);
2459 }
2460 console_idx = log_next(console_idx);
2461 console_seq++;
2462 raw_spin_unlock(&logbuf_lock);
2463
2464 /*
2465 * While actively printing out messages, if another printk()
2466 * were to occur on another CPU, it may wait for this one to
2467 * finish. This task can not be preempted if there is a
2468 * waiter waiting to take over.
2469 */
2470 console_lock_spinning_enable();
2471
2472 stop_critical_timings(); /* don't trace print latency */
2473 call_console_drivers(ext_text, ext_len, text, len);
2474 start_critical_timings();
2475
2476 if (console_lock_spinning_disable_and_check()) {
2477 printk_safe_exit_irqrestore(flags);
2478 return;
2479 }
2480
2481 printk_safe_exit_irqrestore(flags);
2482
2483 if (do_cond_resched)
2484 cond_resched();
2485 }
2486
2487 console_locked = 0;
2488
2489 raw_spin_unlock(&logbuf_lock);
2490
2491 up_console_sem();
2492
2493 /*
2494 * Someone could have filled up the buffer again, so re-check if there's
2495 * something to flush. In case we cannot trylock the console_sem again,
2496 * there's a new owner and the console_unlock() from them will do the
2497 * flush, no worries.
2498 */
2499 raw_spin_lock(&logbuf_lock);
2500 retry = console_seq != log_next_seq;
2501 raw_spin_unlock(&logbuf_lock);
2502 printk_safe_exit_irqrestore(flags);
2503
2504 if (retry && console_trylock())
2505 goto again;
2506}
2507EXPORT_SYMBOL(console_unlock);
2508
2509/**
2510 * console_conditional_schedule - yield the CPU if required
2511 *
2512 * If the console code is currently allowed to sleep, and
2513 * if this CPU should yield the CPU to another task, do
2514 * so here.
2515 *
2516 * Must be called within console_lock();.
2517 */
2518void __sched console_conditional_schedule(void)
2519{
2520 if (console_may_schedule)
2521 cond_resched();
2522}
2523EXPORT_SYMBOL(console_conditional_schedule);
2524
2525void console_unblank(void)
2526{
2527 struct console *c;
2528
2529 /*
2530 * console_unblank can no longer be called in interrupt context unless
2531 * oops_in_progress is set to 1..
2532 */
2533 if (oops_in_progress) {
2534 if (down_trylock_console_sem() != 0)
2535 return;
2536 } else
2537 console_lock();
2538
2539 console_locked = 1;
2540 console_may_schedule = 0;
2541 for_each_console(c)
2542 if ((c->flags & CON_ENABLED) && c->unblank)
2543 c->unblank();
2544 console_unlock();
2545}
2546
2547/**
2548 * console_flush_on_panic - flush console content on panic
2549 * @mode: flush all messages in buffer or just the pending ones
2550 *
2551 * Immediately output all pending messages no matter what.
2552 */
2553void console_flush_on_panic(enum con_flush_mode mode)
2554{
2555 /*
2556 * If someone else is holding the console lock, trylock will fail
2557 * and may_schedule may be set. Ignore and proceed to unlock so
2558 * that messages are flushed out. As this can be called from any
2559 * context and we don't want to get preempted while flushing,
2560 * ensure may_schedule is cleared.
2561 */
2562 console_trylock();
2563 console_may_schedule = 0;
2564
2565 if (mode == CONSOLE_REPLAY_ALL) {
2566 unsigned long flags;
2567
2568 logbuf_lock_irqsave(flags);
2569 console_seq = log_first_seq;
2570 console_idx = log_first_idx;
2571 logbuf_unlock_irqrestore(flags);
2572 }
2573 console_unlock();
2574}
2575
2576/*
2577 * Return the console tty driver structure and its associated index
2578 */
2579struct tty_driver *console_device(int *index)
2580{
2581 struct console *c;
2582 struct tty_driver *driver = NULL;
2583
2584 console_lock();
2585 for_each_console(c) {
2586 if (!c->device)
2587 continue;
2588 driver = c->device(c, index);
2589 if (driver)
2590 break;
2591 }
2592 console_unlock();
2593 return driver;
2594}
2595
2596/*
2597 * Prevent further output on the passed console device so that (for example)
2598 * serial drivers can disable console output before suspending a port, and can
2599 * re-enable output afterwards.
2600 */
2601void console_stop(struct console *console)
2602{
2603 console_lock();
2604 console->flags &= ~CON_ENABLED;
2605 console_unlock();
2606}
2607EXPORT_SYMBOL(console_stop);
2608
2609void console_start(struct console *console)
2610{
2611 console_lock();
2612 console->flags |= CON_ENABLED;
2613 console_unlock();
2614}
2615EXPORT_SYMBOL(console_start);
2616
2617static int __read_mostly keep_bootcon;
2618
2619static int __init keep_bootcon_setup(char *str)
2620{
2621 keep_bootcon = 1;
2622 pr_info("debug: skip boot console de-registration.\n");
2623
2624 return 0;
2625}
2626
2627early_param("keep_bootcon", keep_bootcon_setup);
2628
2629/*
2630 * The console driver calls this routine during kernel initialization
2631 * to register the console printing procedure with printk() and to
2632 * print any messages that were printed by the kernel before the
2633 * console driver was initialized.
2634 *
2635 * This can happen pretty early during the boot process (because of
2636 * early_printk) - sometimes before setup_arch() completes - be careful
2637 * of what kernel features are used - they may not be initialised yet.
2638 *
2639 * There are two types of consoles - bootconsoles (early_printk) and
2640 * "real" consoles (everything which is not a bootconsole) which are
2641 * handled differently.
2642 * - Any number of bootconsoles can be registered at any time.
2643 * - As soon as a "real" console is registered, all bootconsoles
2644 * will be unregistered automatically.
2645 * - Once a "real" console is registered, any attempt to register a
2646 * bootconsoles will be rejected
2647 */
2648void register_console(struct console *newcon)
2649{
2650 int i;
2651 unsigned long flags;
2652 struct console *bcon = NULL;
2653 struct console_cmdline *c;
2654 static bool has_preferred;
2655
2656 if (console_drivers)
2657 for_each_console(bcon)
2658 if (WARN(bcon == newcon,
2659 "console '%s%d' already registered\n",
2660 bcon->name, bcon->index))
2661 return;
2662
2663 /*
2664 * before we register a new CON_BOOT console, make sure we don't
2665 * already have a valid console
2666 */
2667 if (console_drivers && newcon->flags & CON_BOOT) {
2668 /* find the last or real console */
2669 for_each_console(bcon) {
2670 if (!(bcon->flags & CON_BOOT)) {
2671 pr_info("Too late to register bootconsole %s%d\n",
2672 newcon->name, newcon->index);
2673 return;
2674 }
2675 }
2676 }
2677
2678 if (console_drivers && console_drivers->flags & CON_BOOT)
2679 bcon = console_drivers;
2680
2681 if (!has_preferred || bcon || !console_drivers)
2682 has_preferred = preferred_console >= 0;
2683
2684 /*
2685 * See if we want to use this console driver. If we
2686 * didn't select a console we take the first one
2687 * that registers here.
2688 */
2689 if (!has_preferred) {
2690 if (newcon->index < 0)
2691 newcon->index = 0;
2692 if (newcon->setup == NULL ||
2693 newcon->setup(newcon, NULL) == 0) {
2694 newcon->flags |= CON_ENABLED;
2695 if (newcon->device) {
2696 newcon->flags |= CON_CONSDEV;
2697 has_preferred = true;
2698 }
2699 }
2700 }
2701
2702 /*
2703 * See if this console matches one we selected on
2704 * the command line.
2705 */
2706 for (i = 0, c = console_cmdline;
2707 i < MAX_CMDLINECONSOLES && c->name[0];
2708 i++, c++) {
2709 if (!newcon->match ||
2710 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2711 /* default matching */
2712 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2713 if (strcmp(c->name, newcon->name) != 0)
2714 continue;
2715 if (newcon->index >= 0 &&
2716 newcon->index != c->index)
2717 continue;
2718 if (newcon->index < 0)
2719 newcon->index = c->index;
2720
2721 if (_braille_register_console(newcon, c))
2722 return;
2723
2724 if (newcon->setup &&
2725 newcon->setup(newcon, c->options) != 0)
2726 break;
2727 }
2728
2729 newcon->flags |= CON_ENABLED;
2730 if (i == preferred_console) {
2731 newcon->flags |= CON_CONSDEV;
2732 has_preferred = true;
2733 }
2734 break;
2735 }
2736
2737 if (!(newcon->flags & CON_ENABLED))
2738 return;
2739
2740 /*
2741 * If we have a bootconsole, and are switching to a real console,
2742 * don't print everything out again, since when the boot console, and
2743 * the real console are the same physical device, it's annoying to
2744 * see the beginning boot messages twice
2745 */
2746 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2747 newcon->flags &= ~CON_PRINTBUFFER;
2748
2749 /*
2750 * Put this console in the list - keep the
2751 * preferred driver at the head of the list.
2752 */
2753 console_lock();
2754 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2755 newcon->next = console_drivers;
2756 console_drivers = newcon;
2757 if (newcon->next)
2758 newcon->next->flags &= ~CON_CONSDEV;
2759 } else {
2760 newcon->next = console_drivers->next;
2761 console_drivers->next = newcon;
2762 }
2763
2764 if (newcon->flags & CON_EXTENDED)
2765 nr_ext_console_drivers++;
2766
2767 if (newcon->flags & CON_PRINTBUFFER) {
2768 /*
2769 * console_unlock(); will print out the buffered messages
2770 * for us.
2771 */
2772 logbuf_lock_irqsave(flags);
2773 console_seq = syslog_seq;
2774 console_idx = syslog_idx;
2775 /*
2776 * We're about to replay the log buffer. Only do this to the
2777 * just-registered console to avoid excessive message spam to
2778 * the already-registered consoles.
2779 *
2780 * Set exclusive_console with disabled interrupts to reduce
2781 * race window with eventual console_flush_on_panic() that
2782 * ignores console_lock.
2783 */
2784 exclusive_console = newcon;
2785 exclusive_console_stop_seq = console_seq;
2786 logbuf_unlock_irqrestore(flags);
2787 }
2788 console_unlock();
2789 console_sysfs_notify();
2790
2791 /*
2792 * By unregistering the bootconsoles after we enable the real console
2793 * we get the "console xxx enabled" message on all the consoles -
2794 * boot consoles, real consoles, etc - this is to ensure that end
2795 * users know there might be something in the kernel's log buffer that
2796 * went to the bootconsole (that they do not see on the real console)
2797 */
2798 pr_info("%sconsole [%s%d] enabled\n",
2799 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2800 newcon->name, newcon->index);
2801 if (bcon &&
2802 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2803 !keep_bootcon) {
2804 /* We need to iterate through all boot consoles, to make
2805 * sure we print everything out, before we unregister them.
2806 */
2807 for_each_console(bcon)
2808 if (bcon->flags & CON_BOOT)
2809 unregister_console(bcon);
2810 }
2811}
2812EXPORT_SYMBOL(register_console);
2813
2814int unregister_console(struct console *console)
2815{
2816 struct console *a, *b;
2817 int res;
2818
2819 pr_info("%sconsole [%s%d] disabled\n",
2820 (console->flags & CON_BOOT) ? "boot" : "" ,
2821 console->name, console->index);
2822
2823 res = _braille_unregister_console(console);
2824 if (res)
2825 return res;
2826
2827 res = 1;
2828 console_lock();
2829 if (console_drivers == console) {
2830 console_drivers=console->next;
2831 res = 0;
2832 } else if (console_drivers) {
2833 for (a=console_drivers->next, b=console_drivers ;
2834 a; b=a, a=b->next) {
2835 if (a == console) {
2836 b->next = a->next;
2837 res = 0;
2838 break;
2839 }
2840 }
2841 }
2842
2843 if (!res && (console->flags & CON_EXTENDED))
2844 nr_ext_console_drivers--;
2845
2846 /*
2847 * If this isn't the last console and it has CON_CONSDEV set, we
2848 * need to set it on the next preferred console.
2849 */
2850 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2851 console_drivers->flags |= CON_CONSDEV;
2852
2853 console->flags &= ~CON_ENABLED;
2854 console_unlock();
2855 console_sysfs_notify();
2856 return res;
2857}
2858EXPORT_SYMBOL(unregister_console);
2859
2860/*
2861 * Initialize the console device. This is called *early*, so
2862 * we can't necessarily depend on lots of kernel help here.
2863 * Just do some early initializations, and do the complex setup
2864 * later.
2865 */
2866void __init console_init(void)
2867{
2868 int ret;
2869 initcall_t call;
2870 initcall_entry_t *ce;
2871
2872 /* Setup the default TTY line discipline. */
2873 n_tty_init();
2874
2875 /*
2876 * set up the console device so that later boot sequences can
2877 * inform about problems etc..
2878 */
2879 ce = __con_initcall_start;
2880 trace_initcall_level("console");
2881 while (ce < __con_initcall_end) {
2882 call = initcall_from_entry(ce);
2883 trace_initcall_start(call);
2884 ret = call();
2885 trace_initcall_finish(call, ret);
2886 ce++;
2887 }
2888}
2889
2890/*
2891 * Some boot consoles access data that is in the init section and which will
2892 * be discarded after the initcalls have been run. To make sure that no code
2893 * will access this data, unregister the boot consoles in a late initcall.
2894 *
2895 * If for some reason, such as deferred probe or the driver being a loadable
2896 * module, the real console hasn't registered yet at this point, there will
2897 * be a brief interval in which no messages are logged to the console, which
2898 * makes it difficult to diagnose problems that occur during this time.
2899 *
2900 * To mitigate this problem somewhat, only unregister consoles whose memory
2901 * intersects with the init section. Note that all other boot consoles will
2902 * get unregistred when the real preferred console is registered.
2903 */
2904static int __init printk_late_init(void)
2905{
2906 struct console *con;
2907 int ret;
2908
2909 for_each_console(con) {
2910 if (!(con->flags & CON_BOOT))
2911 continue;
2912
2913 /* Check addresses that might be used for enabled consoles. */
2914 if (init_section_intersects(con, sizeof(*con)) ||
2915 init_section_contains(con->write, 0) ||
2916 init_section_contains(con->read, 0) ||
2917 init_section_contains(con->device, 0) ||
2918 init_section_contains(con->unblank, 0) ||
2919 init_section_contains(con->data, 0)) {
2920 /*
2921 * Please, consider moving the reported consoles out
2922 * of the init section.
2923 */
2924 pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n",
2925 con->name, con->index);
2926 unregister_console(con);
2927 }
2928 }
2929 ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL,
2930 console_cpu_notify);
2931 WARN_ON(ret < 0);
2932 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online",
2933 console_cpu_notify, NULL);
2934 WARN_ON(ret < 0);
2935 return 0;
2936}
2937late_initcall(printk_late_init);
2938
2939#if defined CONFIG_PRINTK
2940/*
2941 * Delayed printk version, for scheduler-internal messages:
2942 */
2943#define PRINTK_PENDING_WAKEUP 0x01
2944#define PRINTK_PENDING_OUTPUT 0x02
2945
2946static DEFINE_PER_CPU(int, printk_pending);
2947
2948static void wake_up_klogd_work_func(struct irq_work *irq_work)
2949{
2950 int pending = __this_cpu_xchg(printk_pending, 0);
2951
2952 if (pending & PRINTK_PENDING_OUTPUT) {
2953 /* If trylock fails, someone else is doing the printing */
2954 if (console_trylock())
2955 console_unlock();
2956 }
2957
2958 if (pending & PRINTK_PENDING_WAKEUP)
2959 wake_up_interruptible(&log_wait);
2960}
2961
2962static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2963 .func = wake_up_klogd_work_func,
2964 .flags = IRQ_WORK_LAZY,
2965};
2966
2967void wake_up_klogd(void)
2968{
2969 preempt_disable();
2970 if (waitqueue_active(&log_wait)) {
2971 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2972 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2973 }
2974 preempt_enable();
2975}
2976
2977void defer_console_output(void)
2978{
2979 preempt_disable();
2980 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2981 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2982 preempt_enable();
2983}
2984
2985int vprintk_deferred(const char *fmt, va_list args)
2986{
2987 int r;
2988
2989 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2990 defer_console_output();
2991
2992 return r;
2993}
2994
2995int printk_deferred(const char *fmt, ...)
2996{
2997 va_list args;
2998 int r;
2999
3000 va_start(args, fmt);
3001 r = vprintk_deferred(fmt, args);
3002 va_end(args);
3003
3004 return r;
3005}
3006
3007/*
3008 * printk rate limiting, lifted from the networking subsystem.
3009 *
3010 * This enforces a rate limit: not more than 10 kernel messages
3011 * every 5s to make a denial-of-service attack impossible.
3012 */
3013DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
3014
3015int __printk_ratelimit(const char *func)
3016{
3017 return ___ratelimit(&printk_ratelimit_state, func);
3018}
3019EXPORT_SYMBOL(__printk_ratelimit);
3020
3021/**
3022 * printk_timed_ratelimit - caller-controlled printk ratelimiting
3023 * @caller_jiffies: pointer to caller's state
3024 * @interval_msecs: minimum interval between prints
3025 *
3026 * printk_timed_ratelimit() returns true if more than @interval_msecs
3027 * milliseconds have elapsed since the last time printk_timed_ratelimit()
3028 * returned true.
3029 */
3030bool printk_timed_ratelimit(unsigned long *caller_jiffies,
3031 unsigned int interval_msecs)
3032{
3033 unsigned long elapsed = jiffies - *caller_jiffies;
3034
3035 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
3036 return false;
3037
3038 *caller_jiffies = jiffies;
3039 return true;
3040}
3041EXPORT_SYMBOL(printk_timed_ratelimit);
3042
3043static DEFINE_SPINLOCK(dump_list_lock);
3044static LIST_HEAD(dump_list);
3045
3046/**
3047 * kmsg_dump_register - register a kernel log dumper.
3048 * @dumper: pointer to the kmsg_dumper structure
3049 *
3050 * Adds a kernel log dumper to the system. The dump callback in the
3051 * structure will be called when the kernel oopses or panics and must be
3052 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
3053 */
3054int kmsg_dump_register(struct kmsg_dumper *dumper)
3055{
3056 unsigned long flags;
3057 int err = -EBUSY;
3058
3059 /* The dump callback needs to be set */
3060 if (!dumper->dump)
3061 return -EINVAL;
3062
3063 spin_lock_irqsave(&dump_list_lock, flags);
3064 /* Don't allow registering multiple times */
3065 if (!dumper->registered) {
3066 dumper->registered = 1;
3067 list_add_tail_rcu(&dumper->list, &dump_list);
3068 err = 0;
3069 }
3070 spin_unlock_irqrestore(&dump_list_lock, flags);
3071
3072 return err;
3073}
3074EXPORT_SYMBOL_GPL(kmsg_dump_register);
3075
3076/**
3077 * kmsg_dump_unregister - unregister a kmsg dumper.
3078 * @dumper: pointer to the kmsg_dumper structure
3079 *
3080 * Removes a dump device from the system. Returns zero on success and
3081 * %-EINVAL otherwise.
3082 */
3083int kmsg_dump_unregister(struct kmsg_dumper *dumper)
3084{
3085 unsigned long flags;
3086 int err = -EINVAL;
3087
3088 spin_lock_irqsave(&dump_list_lock, flags);
3089 if (dumper->registered) {
3090 dumper->registered = 0;
3091 list_del_rcu(&dumper->list);
3092 err = 0;
3093 }
3094 spin_unlock_irqrestore(&dump_list_lock, flags);
3095 synchronize_rcu();
3096
3097 return err;
3098}
3099EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
3100
3101static bool always_kmsg_dump;
3102module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
3103
3104/**
3105 * kmsg_dump - dump kernel log to kernel message dumpers.
3106 * @reason: the reason (oops, panic etc) for dumping
3107 *
3108 * Call each of the registered dumper's dump() callback, which can
3109 * retrieve the kmsg records with kmsg_dump_get_line() or
3110 * kmsg_dump_get_buffer().
3111 */
3112void kmsg_dump(enum kmsg_dump_reason reason)
3113{
3114 struct kmsg_dumper *dumper;
3115 unsigned long flags;
3116
3117 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
3118 return;
3119
3120 rcu_read_lock();
3121 list_for_each_entry_rcu(dumper, &dump_list, list) {
3122 if (dumper->max_reason && reason > dumper->max_reason)
3123 continue;
3124
3125 /* initialize iterator with data about the stored records */
3126 dumper->active = true;
3127
3128 logbuf_lock_irqsave(flags);
3129 dumper->cur_seq = clear_seq;
3130 dumper->cur_idx = clear_idx;
3131 dumper->next_seq = log_next_seq;
3132 dumper->next_idx = log_next_idx;
3133 logbuf_unlock_irqrestore(flags);
3134
3135 /* invoke dumper which will iterate over records */
3136 dumper->dump(dumper, reason);
3137
3138 /* reset iterator */
3139 dumper->active = false;
3140 }
3141 rcu_read_unlock();
3142}
3143
3144/**
3145 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
3146 * @dumper: registered kmsg dumper
3147 * @syslog: include the "<4>" prefixes
3148 * @line: buffer to copy the line to
3149 * @size: maximum size of the buffer
3150 * @len: length of line placed into buffer
3151 *
3152 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3153 * record, and copy one record into the provided buffer.
3154 *
3155 * Consecutive calls will return the next available record moving
3156 * towards the end of the buffer with the youngest messages.
3157 *
3158 * A return value of FALSE indicates that there are no more records to
3159 * read.
3160 *
3161 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
3162 */
3163bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
3164 char *line, size_t size, size_t *len)
3165{
3166 struct printk_log *msg;
3167 size_t l = 0;
3168 bool ret = false;
3169
3170 if (!dumper->active)
3171 goto out;
3172
3173 if (dumper->cur_seq < log_first_seq) {
3174 /* messages are gone, move to first available one */
3175 dumper->cur_seq = log_first_seq;
3176 dumper->cur_idx = log_first_idx;
3177 }
3178
3179 /* last entry */
3180 if (dumper->cur_seq >= log_next_seq)
3181 goto out;
3182
3183 msg = log_from_idx(dumper->cur_idx);
3184 l = msg_print_text(msg, syslog, printk_time, line, size);
3185
3186 dumper->cur_idx = log_next(dumper->cur_idx);
3187 dumper->cur_seq++;
3188 ret = true;
3189out:
3190 if (len)
3191 *len = l;
3192 return ret;
3193}
3194
3195/**
3196 * kmsg_dump_get_line - retrieve one kmsg log line
3197 * @dumper: registered kmsg dumper
3198 * @syslog: include the "<4>" prefixes
3199 * @line: buffer to copy the line to
3200 * @size: maximum size of the buffer
3201 * @len: length of line placed into buffer
3202 *
3203 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3204 * record, and copy one record into the provided buffer.
3205 *
3206 * Consecutive calls will return the next available record moving
3207 * towards the end of the buffer with the youngest messages.
3208 *
3209 * A return value of FALSE indicates that there are no more records to
3210 * read.
3211 */
3212bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
3213 char *line, size_t size, size_t *len)
3214{
3215 unsigned long flags;
3216 bool ret;
3217
3218 logbuf_lock_irqsave(flags);
3219 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
3220 logbuf_unlock_irqrestore(flags);
3221
3222 return ret;
3223}
3224EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
3225
3226/**
3227 * kmsg_dump_get_buffer - copy kmsg log lines
3228 * @dumper: registered kmsg dumper
3229 * @syslog: include the "<4>" prefixes
3230 * @buf: buffer to copy the line to
3231 * @size: maximum size of the buffer
3232 * @len: length of line placed into buffer
3233 *
3234 * Start at the end of the kmsg buffer and fill the provided buffer
3235 * with as many of the the *youngest* kmsg records that fit into it.
3236 * If the buffer is large enough, all available kmsg records will be
3237 * copied with a single call.
3238 *
3239 * Consecutive calls will fill the buffer with the next block of
3240 * available older records, not including the earlier retrieved ones.
3241 *
3242 * A return value of FALSE indicates that there are no more records to
3243 * read.
3244 */
3245bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
3246 char *buf, size_t size, size_t *len)
3247{
3248 unsigned long flags;
3249 u64 seq;
3250 u32 idx;
3251 u64 next_seq;
3252 u32 next_idx;
3253 size_t l = 0;
3254 bool ret = false;
3255 bool time = printk_time;
3256
3257 if (!dumper->active)
3258 goto out;
3259
3260 logbuf_lock_irqsave(flags);
3261 if (dumper->cur_seq < log_first_seq) {
3262 /* messages are gone, move to first available one */
3263 dumper->cur_seq = log_first_seq;
3264 dumper->cur_idx = log_first_idx;
3265 }
3266
3267 /* last entry */
3268 if (dumper->cur_seq >= dumper->next_seq) {
3269 logbuf_unlock_irqrestore(flags);
3270 goto out;
3271 }
3272
3273 /* calculate length of entire buffer */
3274 seq = dumper->cur_seq;
3275 idx = dumper->cur_idx;
3276 while (seq < dumper->next_seq) {
3277 struct printk_log *msg = log_from_idx(idx);
3278
3279 l += msg_print_text(msg, true, time, NULL, 0);
3280 idx = log_next(idx);
3281 seq++;
3282 }
3283
3284 /* move first record forward until length fits into the buffer */
3285 seq = dumper->cur_seq;
3286 idx = dumper->cur_idx;
3287 while (l >= size && seq < dumper->next_seq) {
3288 struct printk_log *msg = log_from_idx(idx);
3289
3290 l -= msg_print_text(msg, true, time, NULL, 0);
3291 idx = log_next(idx);
3292 seq++;
3293 }
3294
3295 /* last message in next interation */
3296 next_seq = seq;
3297 next_idx = idx;
3298
3299 l = 0;
3300 while (seq < dumper->next_seq) {
3301 struct printk_log *msg = log_from_idx(idx);
3302
3303 l += msg_print_text(msg, syslog, time, buf + l, size - l);
3304 idx = log_next(idx);
3305 seq++;
3306 }
3307
3308 dumper->next_seq = next_seq;
3309 dumper->next_idx = next_idx;
3310 ret = true;
3311 logbuf_unlock_irqrestore(flags);
3312out:
3313 if (len)
3314 *len = l;
3315 return ret;
3316}
3317EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3318
3319/**
3320 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3321 * @dumper: registered kmsg dumper
3322 *
3323 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3324 * kmsg_dump_get_buffer() can be called again and used multiple
3325 * times within the same dumper.dump() callback.
3326 *
3327 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3328 */
3329void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3330{
3331 dumper->cur_seq = clear_seq;
3332 dumper->cur_idx = clear_idx;
3333 dumper->next_seq = log_next_seq;
3334 dumper->next_idx = log_next_idx;
3335}
3336
3337/**
3338 * kmsg_dump_rewind - reset the interator
3339 * @dumper: registered kmsg dumper
3340 *
3341 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3342 * kmsg_dump_get_buffer() can be called again and used multiple
3343 * times within the same dumper.dump() callback.
3344 */
3345void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3346{
3347 unsigned long flags;
3348
3349 logbuf_lock_irqsave(flags);
3350 kmsg_dump_rewind_nolock(dumper);
3351 logbuf_unlock_irqrestore(flags);
3352}
3353EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3354
3355#endif
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/kernel/printk.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 *
7 * Modified to make sys_syslog() more flexible: added commands to
8 * return the last 4k of kernel messages, regardless of whether
9 * they've been read or not. Added option to suppress kernel printk's
10 * to the console. Added hook for sending the console messages
11 * elsewhere, in preparation for a serial line console (someday).
12 * Ted Ts'o, 2/11/93.
13 * Modified for sysctl support, 1/8/97, Chris Horn.
14 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
15 * manfred@colorfullife.com
16 * Rewrote bits to get rid of console_lock
17 * 01Mar01 Andrew Morton
18 */
19
20#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
21
22#include <linux/kernel.h>
23#include <linux/mm.h>
24#include <linux/tty.h>
25#include <linux/tty_driver.h>
26#include <linux/console.h>
27#include <linux/init.h>
28#include <linux/jiffies.h>
29#include <linux/nmi.h>
30#include <linux/module.h>
31#include <linux/moduleparam.h>
32#include <linux/delay.h>
33#include <linux/smp.h>
34#include <linux/security.h>
35#include <linux/memblock.h>
36#include <linux/syscalls.h>
37#include <linux/vmcore_info.h>
38#include <linux/ratelimit.h>
39#include <linux/kmsg_dump.h>
40#include <linux/syslog.h>
41#include <linux/cpu.h>
42#include <linux/rculist.h>
43#include <linux/poll.h>
44#include <linux/irq_work.h>
45#include <linux/ctype.h>
46#include <linux/uio.h>
47#include <linux/sched/clock.h>
48#include <linux/sched/debug.h>
49#include <linux/sched/task_stack.h>
50
51#include <linux/uaccess.h>
52#include <asm/sections.h>
53
54#include <trace/events/initcall.h>
55#define CREATE_TRACE_POINTS
56#include <trace/events/printk.h>
57
58#include "printk_ringbuffer.h"
59#include "console_cmdline.h"
60#include "braille.h"
61#include "internal.h"
62
63int console_printk[4] = {
64 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
65 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
66 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
67 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
68};
69EXPORT_SYMBOL_GPL(console_printk);
70
71atomic_t ignore_console_lock_warning __read_mostly = ATOMIC_INIT(0);
72EXPORT_SYMBOL(ignore_console_lock_warning);
73
74EXPORT_TRACEPOINT_SYMBOL_GPL(console);
75
76/*
77 * Low level drivers may need that to know if they can schedule in
78 * their unblank() callback or not. So let's export it.
79 */
80int oops_in_progress;
81EXPORT_SYMBOL(oops_in_progress);
82
83/*
84 * console_mutex protects console_list updates and console->flags updates.
85 * The flags are synchronized only for consoles that are registered, i.e.
86 * accessible via the console list.
87 */
88static DEFINE_MUTEX(console_mutex);
89
90/*
91 * console_sem protects updates to console->seq
92 * and also provides serialization for console printing.
93 */
94static DEFINE_SEMAPHORE(console_sem, 1);
95HLIST_HEAD(console_list);
96EXPORT_SYMBOL_GPL(console_list);
97DEFINE_STATIC_SRCU(console_srcu);
98
99/*
100 * System may need to suppress printk message under certain
101 * circumstances, like after kernel panic happens.
102 */
103int __read_mostly suppress_printk;
104
105#ifdef CONFIG_LOCKDEP
106static struct lockdep_map console_lock_dep_map = {
107 .name = "console_lock"
108};
109
110void lockdep_assert_console_list_lock_held(void)
111{
112 lockdep_assert_held(&console_mutex);
113}
114EXPORT_SYMBOL(lockdep_assert_console_list_lock_held);
115#endif
116
117#ifdef CONFIG_DEBUG_LOCK_ALLOC
118bool console_srcu_read_lock_is_held(void)
119{
120 return srcu_read_lock_held(&console_srcu);
121}
122EXPORT_SYMBOL(console_srcu_read_lock_is_held);
123#endif
124
125enum devkmsg_log_bits {
126 __DEVKMSG_LOG_BIT_ON = 0,
127 __DEVKMSG_LOG_BIT_OFF,
128 __DEVKMSG_LOG_BIT_LOCK,
129};
130
131enum devkmsg_log_masks {
132 DEVKMSG_LOG_MASK_ON = BIT(__DEVKMSG_LOG_BIT_ON),
133 DEVKMSG_LOG_MASK_OFF = BIT(__DEVKMSG_LOG_BIT_OFF),
134 DEVKMSG_LOG_MASK_LOCK = BIT(__DEVKMSG_LOG_BIT_LOCK),
135};
136
137/* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
138#define DEVKMSG_LOG_MASK_DEFAULT 0
139
140static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
141
142static int __control_devkmsg(char *str)
143{
144 size_t len;
145
146 if (!str)
147 return -EINVAL;
148
149 len = str_has_prefix(str, "on");
150 if (len) {
151 devkmsg_log = DEVKMSG_LOG_MASK_ON;
152 return len;
153 }
154
155 len = str_has_prefix(str, "off");
156 if (len) {
157 devkmsg_log = DEVKMSG_LOG_MASK_OFF;
158 return len;
159 }
160
161 len = str_has_prefix(str, "ratelimit");
162 if (len) {
163 devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
164 return len;
165 }
166
167 return -EINVAL;
168}
169
170static int __init control_devkmsg(char *str)
171{
172 if (__control_devkmsg(str) < 0) {
173 pr_warn("printk.devkmsg: bad option string '%s'\n", str);
174 return 1;
175 }
176
177 /*
178 * Set sysctl string accordingly:
179 */
180 if (devkmsg_log == DEVKMSG_LOG_MASK_ON)
181 strcpy(devkmsg_log_str, "on");
182 else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF)
183 strcpy(devkmsg_log_str, "off");
184 /* else "ratelimit" which is set by default. */
185
186 /*
187 * Sysctl cannot change it anymore. The kernel command line setting of
188 * this parameter is to force the setting to be permanent throughout the
189 * runtime of the system. This is a precation measure against userspace
190 * trying to be a smarta** and attempting to change it up on us.
191 */
192 devkmsg_log |= DEVKMSG_LOG_MASK_LOCK;
193
194 return 1;
195}
196__setup("printk.devkmsg=", control_devkmsg);
197
198char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit";
199#if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL)
200int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
201 void *buffer, size_t *lenp, loff_t *ppos)
202{
203 char old_str[DEVKMSG_STR_MAX_SIZE];
204 unsigned int old;
205 int err;
206
207 if (write) {
208 if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK)
209 return -EINVAL;
210
211 old = devkmsg_log;
212 strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE);
213 }
214
215 err = proc_dostring(table, write, buffer, lenp, ppos);
216 if (err)
217 return err;
218
219 if (write) {
220 err = __control_devkmsg(devkmsg_log_str);
221
222 /*
223 * Do not accept an unknown string OR a known string with
224 * trailing crap...
225 */
226 if (err < 0 || (err + 1 != *lenp)) {
227
228 /* ... and restore old setting. */
229 devkmsg_log = old;
230 strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE);
231
232 return -EINVAL;
233 }
234 }
235
236 return 0;
237}
238#endif /* CONFIG_PRINTK && CONFIG_SYSCTL */
239
240/**
241 * console_list_lock - Lock the console list
242 *
243 * For console list or console->flags updates
244 */
245void console_list_lock(void)
246{
247 /*
248 * In unregister_console() and console_force_preferred_locked(),
249 * synchronize_srcu() is called with the console_list_lock held.
250 * Therefore it is not allowed that the console_list_lock is taken
251 * with the srcu_lock held.
252 *
253 * Detecting if this context is really in the read-side critical
254 * section is only possible if the appropriate debug options are
255 * enabled.
256 */
257 WARN_ON_ONCE(debug_lockdep_rcu_enabled() &&
258 srcu_read_lock_held(&console_srcu));
259
260 mutex_lock(&console_mutex);
261}
262EXPORT_SYMBOL(console_list_lock);
263
264/**
265 * console_list_unlock - Unlock the console list
266 *
267 * Counterpart to console_list_lock()
268 */
269void console_list_unlock(void)
270{
271 mutex_unlock(&console_mutex);
272}
273EXPORT_SYMBOL(console_list_unlock);
274
275/**
276 * console_srcu_read_lock - Register a new reader for the
277 * SRCU-protected console list
278 *
279 * Use for_each_console_srcu() to iterate the console list
280 *
281 * Context: Any context.
282 * Return: A cookie to pass to console_srcu_read_unlock().
283 */
284int console_srcu_read_lock(void)
285{
286 return srcu_read_lock_nmisafe(&console_srcu);
287}
288EXPORT_SYMBOL(console_srcu_read_lock);
289
290/**
291 * console_srcu_read_unlock - Unregister an old reader from
292 * the SRCU-protected console list
293 * @cookie: cookie returned from console_srcu_read_lock()
294 *
295 * Counterpart to console_srcu_read_lock()
296 */
297void console_srcu_read_unlock(int cookie)
298{
299 srcu_read_unlock_nmisafe(&console_srcu, cookie);
300}
301EXPORT_SYMBOL(console_srcu_read_unlock);
302
303/*
304 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
305 * macros instead of functions so that _RET_IP_ contains useful information.
306 */
307#define down_console_sem() do { \
308 down(&console_sem);\
309 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
310} while (0)
311
312static int __down_trylock_console_sem(unsigned long ip)
313{
314 int lock_failed;
315 unsigned long flags;
316
317 /*
318 * Here and in __up_console_sem() we need to be in safe mode,
319 * because spindump/WARN/etc from under console ->lock will
320 * deadlock in printk()->down_trylock_console_sem() otherwise.
321 */
322 printk_safe_enter_irqsave(flags);
323 lock_failed = down_trylock(&console_sem);
324 printk_safe_exit_irqrestore(flags);
325
326 if (lock_failed)
327 return 1;
328 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
329 return 0;
330}
331#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
332
333static void __up_console_sem(unsigned long ip)
334{
335 unsigned long flags;
336
337 mutex_release(&console_lock_dep_map, ip);
338
339 printk_safe_enter_irqsave(flags);
340 up(&console_sem);
341 printk_safe_exit_irqrestore(flags);
342}
343#define up_console_sem() __up_console_sem(_RET_IP_)
344
345static bool panic_in_progress(void)
346{
347 return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID);
348}
349
350/* Return true if a panic is in progress on the current CPU. */
351bool this_cpu_in_panic(void)
352{
353 /*
354 * We can use raw_smp_processor_id() here because it is impossible for
355 * the task to be migrated to the panic_cpu, or away from it. If
356 * panic_cpu has already been set, and we're not currently executing on
357 * that CPU, then we never will be.
358 */
359 return unlikely(atomic_read(&panic_cpu) == raw_smp_processor_id());
360}
361
362/*
363 * Return true if a panic is in progress on a remote CPU.
364 *
365 * On true, the local CPU should immediately release any printing resources
366 * that may be needed by the panic CPU.
367 */
368bool other_cpu_in_panic(void)
369{
370 return (panic_in_progress() && !this_cpu_in_panic());
371}
372
373/*
374 * This is used for debugging the mess that is the VT code by
375 * keeping track if we have the console semaphore held. It's
376 * definitely not the perfect debug tool (we don't know if _WE_
377 * hold it and are racing, but it helps tracking those weird code
378 * paths in the console code where we end up in places I want
379 * locked without the console semaphore held).
380 */
381static int console_locked;
382
383/*
384 * Array of consoles built from command line options (console=)
385 */
386
387#define MAX_CMDLINECONSOLES 8
388
389static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
390
391static int preferred_console = -1;
392int console_set_on_cmdline;
393EXPORT_SYMBOL(console_set_on_cmdline);
394
395/* Flag: console code may call schedule() */
396static int console_may_schedule;
397
398enum con_msg_format_flags {
399 MSG_FORMAT_DEFAULT = 0,
400 MSG_FORMAT_SYSLOG = (1 << 0),
401};
402
403static int console_msg_format = MSG_FORMAT_DEFAULT;
404
405/*
406 * The printk log buffer consists of a sequenced collection of records, each
407 * containing variable length message text. Every record also contains its
408 * own meta-data (@info).
409 *
410 * Every record meta-data carries the timestamp in microseconds, as well as
411 * the standard userspace syslog level and syslog facility. The usual kernel
412 * messages use LOG_KERN; userspace-injected messages always carry a matching
413 * syslog facility, by default LOG_USER. The origin of every message can be
414 * reliably determined that way.
415 *
416 * The human readable log message of a record is available in @text, the
417 * length of the message text in @text_len. The stored message is not
418 * terminated.
419 *
420 * Optionally, a record can carry a dictionary of properties (key/value
421 * pairs), to provide userspace with a machine-readable message context.
422 *
423 * Examples for well-defined, commonly used property names are:
424 * DEVICE=b12:8 device identifier
425 * b12:8 block dev_t
426 * c127:3 char dev_t
427 * n8 netdev ifindex
428 * +sound:card0 subsystem:devname
429 * SUBSYSTEM=pci driver-core subsystem name
430 *
431 * Valid characters in property names are [a-zA-Z0-9.-_]. Property names
432 * and values are terminated by a '\0' character.
433 *
434 * Example of record values:
435 * record.text_buf = "it's a line" (unterminated)
436 * record.info.seq = 56
437 * record.info.ts_nsec = 36863
438 * record.info.text_len = 11
439 * record.info.facility = 0 (LOG_KERN)
440 * record.info.flags = 0
441 * record.info.level = 3 (LOG_ERR)
442 * record.info.caller_id = 299 (task 299)
443 * record.info.dev_info.subsystem = "pci" (terminated)
444 * record.info.dev_info.device = "+pci:0000:00:01.0" (terminated)
445 *
446 * The 'struct printk_info' buffer must never be directly exported to
447 * userspace, it is a kernel-private implementation detail that might
448 * need to be changed in the future, when the requirements change.
449 *
450 * /dev/kmsg exports the structured data in the following line format:
451 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
452 *
453 * Users of the export format should ignore possible additional values
454 * separated by ',', and find the message after the ';' character.
455 *
456 * The optional key/value pairs are attached as continuation lines starting
457 * with a space character and terminated by a newline. All possible
458 * non-prinatable characters are escaped in the "\xff" notation.
459 */
460
461/* syslog_lock protects syslog_* variables and write access to clear_seq. */
462static DEFINE_MUTEX(syslog_lock);
463
464#ifdef CONFIG_PRINTK
465DECLARE_WAIT_QUEUE_HEAD(log_wait);
466/* All 3 protected by @syslog_lock. */
467/* the next printk record to read by syslog(READ) or /proc/kmsg */
468static u64 syslog_seq;
469static size_t syslog_partial;
470static bool syslog_time;
471
472struct latched_seq {
473 seqcount_latch_t latch;
474 u64 val[2];
475};
476
477/*
478 * The next printk record to read after the last 'clear' command. There are
479 * two copies (updated with seqcount_latch) so that reads can locklessly
480 * access a valid value. Writers are synchronized by @syslog_lock.
481 */
482static struct latched_seq clear_seq = {
483 .latch = SEQCNT_LATCH_ZERO(clear_seq.latch),
484 .val[0] = 0,
485 .val[1] = 0,
486};
487
488#define LOG_LEVEL(v) ((v) & 0x07)
489#define LOG_FACILITY(v) ((v) >> 3 & 0xff)
490
491/* record buffer */
492#define LOG_ALIGN __alignof__(unsigned long)
493#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
494#define LOG_BUF_LEN_MAX (u32)(1 << 31)
495static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
496static char *log_buf = __log_buf;
497static u32 log_buf_len = __LOG_BUF_LEN;
498
499/*
500 * Define the average message size. This only affects the number of
501 * descriptors that will be available. Underestimating is better than
502 * overestimating (too many available descriptors is better than not enough).
503 */
504#define PRB_AVGBITS 5 /* 32 character average length */
505
506#if CONFIG_LOG_BUF_SHIFT <= PRB_AVGBITS
507#error CONFIG_LOG_BUF_SHIFT value too small.
508#endif
509_DEFINE_PRINTKRB(printk_rb_static, CONFIG_LOG_BUF_SHIFT - PRB_AVGBITS,
510 PRB_AVGBITS, &__log_buf[0]);
511
512static struct printk_ringbuffer printk_rb_dynamic;
513
514struct printk_ringbuffer *prb = &printk_rb_static;
515
516/*
517 * We cannot access per-CPU data (e.g. per-CPU flush irq_work) before
518 * per_cpu_areas are initialised. This variable is set to true when
519 * it's safe to access per-CPU data.
520 */
521static bool __printk_percpu_data_ready __ro_after_init;
522
523bool printk_percpu_data_ready(void)
524{
525 return __printk_percpu_data_ready;
526}
527
528/* Must be called under syslog_lock. */
529static void latched_seq_write(struct latched_seq *ls, u64 val)
530{
531 raw_write_seqcount_latch(&ls->latch);
532 ls->val[0] = val;
533 raw_write_seqcount_latch(&ls->latch);
534 ls->val[1] = val;
535}
536
537/* Can be called from any context. */
538static u64 latched_seq_read_nolock(struct latched_seq *ls)
539{
540 unsigned int seq;
541 unsigned int idx;
542 u64 val;
543
544 do {
545 seq = raw_read_seqcount_latch(&ls->latch);
546 idx = seq & 0x1;
547 val = ls->val[idx];
548 } while (raw_read_seqcount_latch_retry(&ls->latch, seq));
549
550 return val;
551}
552
553/* Return log buffer address */
554char *log_buf_addr_get(void)
555{
556 return log_buf;
557}
558
559/* Return log buffer size */
560u32 log_buf_len_get(void)
561{
562 return log_buf_len;
563}
564
565/*
566 * Define how much of the log buffer we could take at maximum. The value
567 * must be greater than two. Note that only half of the buffer is available
568 * when the index points to the middle.
569 */
570#define MAX_LOG_TAKE_PART 4
571static const char trunc_msg[] = "<truncated>";
572
573static void truncate_msg(u16 *text_len, u16 *trunc_msg_len)
574{
575 /*
576 * The message should not take the whole buffer. Otherwise, it might
577 * get removed too soon.
578 */
579 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
580
581 if (*text_len > max_text_len)
582 *text_len = max_text_len;
583
584 /* enable the warning message (if there is room) */
585 *trunc_msg_len = strlen(trunc_msg);
586 if (*text_len >= *trunc_msg_len)
587 *text_len -= *trunc_msg_len;
588 else
589 *trunc_msg_len = 0;
590}
591
592int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
593
594static int syslog_action_restricted(int type)
595{
596 if (dmesg_restrict)
597 return 1;
598 /*
599 * Unless restricted, we allow "read all" and "get buffer size"
600 * for everybody.
601 */
602 return type != SYSLOG_ACTION_READ_ALL &&
603 type != SYSLOG_ACTION_SIZE_BUFFER;
604}
605
606static int check_syslog_permissions(int type, int source)
607{
608 /*
609 * If this is from /proc/kmsg and we've already opened it, then we've
610 * already done the capabilities checks at open time.
611 */
612 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
613 goto ok;
614
615 if (syslog_action_restricted(type)) {
616 if (capable(CAP_SYSLOG))
617 goto ok;
618 return -EPERM;
619 }
620ok:
621 return security_syslog(type);
622}
623
624static void append_char(char **pp, char *e, char c)
625{
626 if (*pp < e)
627 *(*pp)++ = c;
628}
629
630static ssize_t info_print_ext_header(char *buf, size_t size,
631 struct printk_info *info)
632{
633 u64 ts_usec = info->ts_nsec;
634 char caller[20];
635#ifdef CONFIG_PRINTK_CALLER
636 u32 id = info->caller_id;
637
638 snprintf(caller, sizeof(caller), ",caller=%c%u",
639 id & 0x80000000 ? 'C' : 'T', id & ~0x80000000);
640#else
641 caller[0] = '\0';
642#endif
643
644 do_div(ts_usec, 1000);
645
646 return scnprintf(buf, size, "%u,%llu,%llu,%c%s;",
647 (info->facility << 3) | info->level, info->seq,
648 ts_usec, info->flags & LOG_CONT ? 'c' : '-', caller);
649}
650
651static ssize_t msg_add_ext_text(char *buf, size_t size,
652 const char *text, size_t text_len,
653 unsigned char endc)
654{
655 char *p = buf, *e = buf + size;
656 size_t i;
657
658 /* escape non-printable characters */
659 for (i = 0; i < text_len; i++) {
660 unsigned char c = text[i];
661
662 if (c < ' ' || c >= 127 || c == '\\')
663 p += scnprintf(p, e - p, "\\x%02x", c);
664 else
665 append_char(&p, e, c);
666 }
667 append_char(&p, e, endc);
668
669 return p - buf;
670}
671
672static ssize_t msg_add_dict_text(char *buf, size_t size,
673 const char *key, const char *val)
674{
675 size_t val_len = strlen(val);
676 ssize_t len;
677
678 if (!val_len)
679 return 0;
680
681 len = msg_add_ext_text(buf, size, "", 0, ' '); /* dict prefix */
682 len += msg_add_ext_text(buf + len, size - len, key, strlen(key), '=');
683 len += msg_add_ext_text(buf + len, size - len, val, val_len, '\n');
684
685 return len;
686}
687
688static ssize_t msg_print_ext_body(char *buf, size_t size,
689 char *text, size_t text_len,
690 struct dev_printk_info *dev_info)
691{
692 ssize_t len;
693
694 len = msg_add_ext_text(buf, size, text, text_len, '\n');
695
696 if (!dev_info)
697 goto out;
698
699 len += msg_add_dict_text(buf + len, size - len, "SUBSYSTEM",
700 dev_info->subsystem);
701 len += msg_add_dict_text(buf + len, size - len, "DEVICE",
702 dev_info->device);
703out:
704 return len;
705}
706
707/* /dev/kmsg - userspace message inject/listen interface */
708struct devkmsg_user {
709 atomic64_t seq;
710 struct ratelimit_state rs;
711 struct mutex lock;
712 struct printk_buffers pbufs;
713};
714
715static __printf(3, 4) __cold
716int devkmsg_emit(int facility, int level, const char *fmt, ...)
717{
718 va_list args;
719 int r;
720
721 va_start(args, fmt);
722 r = vprintk_emit(facility, level, NULL, fmt, args);
723 va_end(args);
724
725 return r;
726}
727
728static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
729{
730 char *buf, *line;
731 int level = default_message_loglevel;
732 int facility = 1; /* LOG_USER */
733 struct file *file = iocb->ki_filp;
734 struct devkmsg_user *user = file->private_data;
735 size_t len = iov_iter_count(from);
736 ssize_t ret = len;
737
738 if (len > PRINTKRB_RECORD_MAX)
739 return -EINVAL;
740
741 /* Ignore when user logging is disabled. */
742 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
743 return len;
744
745 /* Ratelimit when not explicitly enabled. */
746 if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) {
747 if (!___ratelimit(&user->rs, current->comm))
748 return ret;
749 }
750
751 buf = kmalloc(len+1, GFP_KERNEL);
752 if (buf == NULL)
753 return -ENOMEM;
754
755 buf[len] = '\0';
756 if (!copy_from_iter_full(buf, len, from)) {
757 kfree(buf);
758 return -EFAULT;
759 }
760
761 /*
762 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
763 * the decimal value represents 32bit, the lower 3 bit are the log
764 * level, the rest are the log facility.
765 *
766 * If no prefix or no userspace facility is specified, we
767 * enforce LOG_USER, to be able to reliably distinguish
768 * kernel-generated messages from userspace-injected ones.
769 */
770 line = buf;
771 if (line[0] == '<') {
772 char *endp = NULL;
773 unsigned int u;
774
775 u = simple_strtoul(line + 1, &endp, 10);
776 if (endp && endp[0] == '>') {
777 level = LOG_LEVEL(u);
778 if (LOG_FACILITY(u) != 0)
779 facility = LOG_FACILITY(u);
780 endp++;
781 line = endp;
782 }
783 }
784
785 devkmsg_emit(facility, level, "%s", line);
786 kfree(buf);
787 return ret;
788}
789
790static ssize_t devkmsg_read(struct file *file, char __user *buf,
791 size_t count, loff_t *ppos)
792{
793 struct devkmsg_user *user = file->private_data;
794 char *outbuf = &user->pbufs.outbuf[0];
795 struct printk_message pmsg = {
796 .pbufs = &user->pbufs,
797 };
798 ssize_t ret;
799
800 ret = mutex_lock_interruptible(&user->lock);
801 if (ret)
802 return ret;
803
804 if (!printk_get_next_message(&pmsg, atomic64_read(&user->seq), true, false)) {
805 if (file->f_flags & O_NONBLOCK) {
806 ret = -EAGAIN;
807 goto out;
808 }
809
810 /*
811 * Guarantee this task is visible on the waitqueue before
812 * checking the wake condition.
813 *
814 * The full memory barrier within set_current_state() of
815 * prepare_to_wait_event() pairs with the full memory barrier
816 * within wq_has_sleeper().
817 *
818 * This pairs with __wake_up_klogd:A.
819 */
820 ret = wait_event_interruptible(log_wait,
821 printk_get_next_message(&pmsg, atomic64_read(&user->seq), true,
822 false)); /* LMM(devkmsg_read:A) */
823 if (ret)
824 goto out;
825 }
826
827 if (pmsg.dropped) {
828 /* our last seen message is gone, return error and reset */
829 atomic64_set(&user->seq, pmsg.seq);
830 ret = -EPIPE;
831 goto out;
832 }
833
834 atomic64_set(&user->seq, pmsg.seq + 1);
835
836 if (pmsg.outbuf_len > count) {
837 ret = -EINVAL;
838 goto out;
839 }
840
841 if (copy_to_user(buf, outbuf, pmsg.outbuf_len)) {
842 ret = -EFAULT;
843 goto out;
844 }
845 ret = pmsg.outbuf_len;
846out:
847 mutex_unlock(&user->lock);
848 return ret;
849}
850
851/*
852 * Be careful when modifying this function!!!
853 *
854 * Only few operations are supported because the device works only with the
855 * entire variable length messages (records). Non-standard values are
856 * returned in the other cases and has been this way for quite some time.
857 * User space applications might depend on this behavior.
858 */
859static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
860{
861 struct devkmsg_user *user = file->private_data;
862 loff_t ret = 0;
863
864 if (offset)
865 return -ESPIPE;
866
867 switch (whence) {
868 case SEEK_SET:
869 /* the first record */
870 atomic64_set(&user->seq, prb_first_valid_seq(prb));
871 break;
872 case SEEK_DATA:
873 /*
874 * The first record after the last SYSLOG_ACTION_CLEAR,
875 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
876 * changes no global state, and does not clear anything.
877 */
878 atomic64_set(&user->seq, latched_seq_read_nolock(&clear_seq));
879 break;
880 case SEEK_END:
881 /* after the last record */
882 atomic64_set(&user->seq, prb_next_seq(prb));
883 break;
884 default:
885 ret = -EINVAL;
886 }
887 return ret;
888}
889
890static __poll_t devkmsg_poll(struct file *file, poll_table *wait)
891{
892 struct devkmsg_user *user = file->private_data;
893 struct printk_info info;
894 __poll_t ret = 0;
895
896 poll_wait(file, &log_wait, wait);
897
898 if (prb_read_valid_info(prb, atomic64_read(&user->seq), &info, NULL)) {
899 /* return error when data has vanished underneath us */
900 if (info.seq != atomic64_read(&user->seq))
901 ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI;
902 else
903 ret = EPOLLIN|EPOLLRDNORM;
904 }
905
906 return ret;
907}
908
909static int devkmsg_open(struct inode *inode, struct file *file)
910{
911 struct devkmsg_user *user;
912 int err;
913
914 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
915 return -EPERM;
916
917 /* write-only does not need any file context */
918 if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
919 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
920 SYSLOG_FROM_READER);
921 if (err)
922 return err;
923 }
924
925 user = kvmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
926 if (!user)
927 return -ENOMEM;
928
929 ratelimit_default_init(&user->rs);
930 ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);
931
932 mutex_init(&user->lock);
933
934 atomic64_set(&user->seq, prb_first_valid_seq(prb));
935
936 file->private_data = user;
937 return 0;
938}
939
940static int devkmsg_release(struct inode *inode, struct file *file)
941{
942 struct devkmsg_user *user = file->private_data;
943
944 ratelimit_state_exit(&user->rs);
945
946 mutex_destroy(&user->lock);
947 kvfree(user);
948 return 0;
949}
950
951const struct file_operations kmsg_fops = {
952 .open = devkmsg_open,
953 .read = devkmsg_read,
954 .write_iter = devkmsg_write,
955 .llseek = devkmsg_llseek,
956 .poll = devkmsg_poll,
957 .release = devkmsg_release,
958};
959
960#ifdef CONFIG_VMCORE_INFO
961/*
962 * This appends the listed symbols to /proc/vmcore
963 *
964 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
965 * obtain access to symbols that are otherwise very difficult to locate. These
966 * symbols are specifically used so that utilities can access and extract the
967 * dmesg log from a vmcore file after a crash.
968 */
969void log_buf_vmcoreinfo_setup(void)
970{
971 struct dev_printk_info *dev_info = NULL;
972
973 VMCOREINFO_SYMBOL(prb);
974 VMCOREINFO_SYMBOL(printk_rb_static);
975 VMCOREINFO_SYMBOL(clear_seq);
976
977 /*
978 * Export struct size and field offsets. User space tools can
979 * parse it and detect any changes to structure down the line.
980 */
981
982 VMCOREINFO_STRUCT_SIZE(printk_ringbuffer);
983 VMCOREINFO_OFFSET(printk_ringbuffer, desc_ring);
984 VMCOREINFO_OFFSET(printk_ringbuffer, text_data_ring);
985 VMCOREINFO_OFFSET(printk_ringbuffer, fail);
986
987 VMCOREINFO_STRUCT_SIZE(prb_desc_ring);
988 VMCOREINFO_OFFSET(prb_desc_ring, count_bits);
989 VMCOREINFO_OFFSET(prb_desc_ring, descs);
990 VMCOREINFO_OFFSET(prb_desc_ring, infos);
991 VMCOREINFO_OFFSET(prb_desc_ring, head_id);
992 VMCOREINFO_OFFSET(prb_desc_ring, tail_id);
993
994 VMCOREINFO_STRUCT_SIZE(prb_desc);
995 VMCOREINFO_OFFSET(prb_desc, state_var);
996 VMCOREINFO_OFFSET(prb_desc, text_blk_lpos);
997
998 VMCOREINFO_STRUCT_SIZE(prb_data_blk_lpos);
999 VMCOREINFO_OFFSET(prb_data_blk_lpos, begin);
1000 VMCOREINFO_OFFSET(prb_data_blk_lpos, next);
1001
1002 VMCOREINFO_STRUCT_SIZE(printk_info);
1003 VMCOREINFO_OFFSET(printk_info, seq);
1004 VMCOREINFO_OFFSET(printk_info, ts_nsec);
1005 VMCOREINFO_OFFSET(printk_info, text_len);
1006 VMCOREINFO_OFFSET(printk_info, caller_id);
1007 VMCOREINFO_OFFSET(printk_info, dev_info);
1008
1009 VMCOREINFO_STRUCT_SIZE(dev_printk_info);
1010 VMCOREINFO_OFFSET(dev_printk_info, subsystem);
1011 VMCOREINFO_LENGTH(printk_info_subsystem, sizeof(dev_info->subsystem));
1012 VMCOREINFO_OFFSET(dev_printk_info, device);
1013 VMCOREINFO_LENGTH(printk_info_device, sizeof(dev_info->device));
1014
1015 VMCOREINFO_STRUCT_SIZE(prb_data_ring);
1016 VMCOREINFO_OFFSET(prb_data_ring, size_bits);
1017 VMCOREINFO_OFFSET(prb_data_ring, data);
1018 VMCOREINFO_OFFSET(prb_data_ring, head_lpos);
1019 VMCOREINFO_OFFSET(prb_data_ring, tail_lpos);
1020
1021 VMCOREINFO_SIZE(atomic_long_t);
1022 VMCOREINFO_TYPE_OFFSET(atomic_long_t, counter);
1023
1024 VMCOREINFO_STRUCT_SIZE(latched_seq);
1025 VMCOREINFO_OFFSET(latched_seq, val);
1026}
1027#endif
1028
1029/* requested log_buf_len from kernel cmdline */
1030static unsigned long __initdata new_log_buf_len;
1031
1032/* we practice scaling the ring buffer by powers of 2 */
1033static void __init log_buf_len_update(u64 size)
1034{
1035 if (size > (u64)LOG_BUF_LEN_MAX) {
1036 size = (u64)LOG_BUF_LEN_MAX;
1037 pr_err("log_buf over 2G is not supported.\n");
1038 }
1039
1040 if (size)
1041 size = roundup_pow_of_two(size);
1042 if (size > log_buf_len)
1043 new_log_buf_len = (unsigned long)size;
1044}
1045
1046/* save requested log_buf_len since it's too early to process it */
1047static int __init log_buf_len_setup(char *str)
1048{
1049 u64 size;
1050
1051 if (!str)
1052 return -EINVAL;
1053
1054 size = memparse(str, &str);
1055
1056 log_buf_len_update(size);
1057
1058 return 0;
1059}
1060early_param("log_buf_len", log_buf_len_setup);
1061
1062#ifdef CONFIG_SMP
1063#define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1064
1065static void __init log_buf_add_cpu(void)
1066{
1067 unsigned int cpu_extra;
1068
1069 /*
1070 * archs should set up cpu_possible_bits properly with
1071 * set_cpu_possible() after setup_arch() but just in
1072 * case lets ensure this is valid.
1073 */
1074 if (num_possible_cpus() == 1)
1075 return;
1076
1077 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
1078
1079 /* by default this will only continue through for large > 64 CPUs */
1080 if (cpu_extra <= __LOG_BUF_LEN / 2)
1081 return;
1082
1083 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1084 __LOG_CPU_MAX_BUF_LEN);
1085 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1086 cpu_extra);
1087 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
1088
1089 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
1090}
1091#else /* !CONFIG_SMP */
1092static inline void log_buf_add_cpu(void) {}
1093#endif /* CONFIG_SMP */
1094
1095static void __init set_percpu_data_ready(void)
1096{
1097 __printk_percpu_data_ready = true;
1098}
1099
1100static unsigned int __init add_to_rb(struct printk_ringbuffer *rb,
1101 struct printk_record *r)
1102{
1103 struct prb_reserved_entry e;
1104 struct printk_record dest_r;
1105
1106 prb_rec_init_wr(&dest_r, r->info->text_len);
1107
1108 if (!prb_reserve(&e, rb, &dest_r))
1109 return 0;
1110
1111 memcpy(&dest_r.text_buf[0], &r->text_buf[0], r->info->text_len);
1112 dest_r.info->text_len = r->info->text_len;
1113 dest_r.info->facility = r->info->facility;
1114 dest_r.info->level = r->info->level;
1115 dest_r.info->flags = r->info->flags;
1116 dest_r.info->ts_nsec = r->info->ts_nsec;
1117 dest_r.info->caller_id = r->info->caller_id;
1118 memcpy(&dest_r.info->dev_info, &r->info->dev_info, sizeof(dest_r.info->dev_info));
1119
1120 prb_final_commit(&e);
1121
1122 return prb_record_text_space(&e);
1123}
1124
1125static char setup_text_buf[PRINTKRB_RECORD_MAX] __initdata;
1126
1127void __init setup_log_buf(int early)
1128{
1129 struct printk_info *new_infos;
1130 unsigned int new_descs_count;
1131 struct prb_desc *new_descs;
1132 struct printk_info info;
1133 struct printk_record r;
1134 unsigned int text_size;
1135 size_t new_descs_size;
1136 size_t new_infos_size;
1137 unsigned long flags;
1138 char *new_log_buf;
1139 unsigned int free;
1140 u64 seq;
1141
1142 /*
1143 * Some archs call setup_log_buf() multiple times - first is very
1144 * early, e.g. from setup_arch(), and second - when percpu_areas
1145 * are initialised.
1146 */
1147 if (!early)
1148 set_percpu_data_ready();
1149
1150 if (log_buf != __log_buf)
1151 return;
1152
1153 if (!early && !new_log_buf_len)
1154 log_buf_add_cpu();
1155
1156 if (!new_log_buf_len)
1157 return;
1158
1159 new_descs_count = new_log_buf_len >> PRB_AVGBITS;
1160 if (new_descs_count == 0) {
1161 pr_err("new_log_buf_len: %lu too small\n", new_log_buf_len);
1162 return;
1163 }
1164
1165 new_log_buf = memblock_alloc(new_log_buf_len, LOG_ALIGN);
1166 if (unlikely(!new_log_buf)) {
1167 pr_err("log_buf_len: %lu text bytes not available\n",
1168 new_log_buf_len);
1169 return;
1170 }
1171
1172 new_descs_size = new_descs_count * sizeof(struct prb_desc);
1173 new_descs = memblock_alloc(new_descs_size, LOG_ALIGN);
1174 if (unlikely(!new_descs)) {
1175 pr_err("log_buf_len: %zu desc bytes not available\n",
1176 new_descs_size);
1177 goto err_free_log_buf;
1178 }
1179
1180 new_infos_size = new_descs_count * sizeof(struct printk_info);
1181 new_infos = memblock_alloc(new_infos_size, LOG_ALIGN);
1182 if (unlikely(!new_infos)) {
1183 pr_err("log_buf_len: %zu info bytes not available\n",
1184 new_infos_size);
1185 goto err_free_descs;
1186 }
1187
1188 prb_rec_init_rd(&r, &info, &setup_text_buf[0], sizeof(setup_text_buf));
1189
1190 prb_init(&printk_rb_dynamic,
1191 new_log_buf, ilog2(new_log_buf_len),
1192 new_descs, ilog2(new_descs_count),
1193 new_infos);
1194
1195 local_irq_save(flags);
1196
1197 log_buf_len = new_log_buf_len;
1198 log_buf = new_log_buf;
1199 new_log_buf_len = 0;
1200
1201 free = __LOG_BUF_LEN;
1202 prb_for_each_record(0, &printk_rb_static, seq, &r) {
1203 text_size = add_to_rb(&printk_rb_dynamic, &r);
1204 if (text_size > free)
1205 free = 0;
1206 else
1207 free -= text_size;
1208 }
1209
1210 prb = &printk_rb_dynamic;
1211
1212 local_irq_restore(flags);
1213
1214 /*
1215 * Copy any remaining messages that might have appeared from
1216 * NMI context after copying but before switching to the
1217 * dynamic buffer.
1218 */
1219 prb_for_each_record(seq, &printk_rb_static, seq, &r) {
1220 text_size = add_to_rb(&printk_rb_dynamic, &r);
1221 if (text_size > free)
1222 free = 0;
1223 else
1224 free -= text_size;
1225 }
1226
1227 if (seq != prb_next_seq(&printk_rb_static)) {
1228 pr_err("dropped %llu messages\n",
1229 prb_next_seq(&printk_rb_static) - seq);
1230 }
1231
1232 pr_info("log_buf_len: %u bytes\n", log_buf_len);
1233 pr_info("early log buf free: %u(%u%%)\n",
1234 free, (free * 100) / __LOG_BUF_LEN);
1235 return;
1236
1237err_free_descs:
1238 memblock_free(new_descs, new_descs_size);
1239err_free_log_buf:
1240 memblock_free(new_log_buf, new_log_buf_len);
1241}
1242
1243static bool __read_mostly ignore_loglevel;
1244
1245static int __init ignore_loglevel_setup(char *str)
1246{
1247 ignore_loglevel = true;
1248 pr_info("debug: ignoring loglevel setting.\n");
1249
1250 return 0;
1251}
1252
1253early_param("ignore_loglevel", ignore_loglevel_setup);
1254module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1255MODULE_PARM_DESC(ignore_loglevel,
1256 "ignore loglevel setting (prints all kernel messages to the console)");
1257
1258static bool suppress_message_printing(int level)
1259{
1260 return (level >= console_loglevel && !ignore_loglevel);
1261}
1262
1263#ifdef CONFIG_BOOT_PRINTK_DELAY
1264
1265static int boot_delay; /* msecs delay after each printk during bootup */
1266static unsigned long long loops_per_msec; /* based on boot_delay */
1267
1268static int __init boot_delay_setup(char *str)
1269{
1270 unsigned long lpj;
1271
1272 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
1273 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
1274
1275 get_option(&str, &boot_delay);
1276 if (boot_delay > 10 * 1000)
1277 boot_delay = 0;
1278
1279 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1280 "HZ: %d, loops_per_msec: %llu\n",
1281 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1282 return 0;
1283}
1284early_param("boot_delay", boot_delay_setup);
1285
1286static void boot_delay_msec(int level)
1287{
1288 unsigned long long k;
1289 unsigned long timeout;
1290
1291 if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING)
1292 || suppress_message_printing(level)) {
1293 return;
1294 }
1295
1296 k = (unsigned long long)loops_per_msec * boot_delay;
1297
1298 timeout = jiffies + msecs_to_jiffies(boot_delay);
1299 while (k) {
1300 k--;
1301 cpu_relax();
1302 /*
1303 * use (volatile) jiffies to prevent
1304 * compiler reduction; loop termination via jiffies
1305 * is secondary and may or may not happen.
1306 */
1307 if (time_after(jiffies, timeout))
1308 break;
1309 touch_nmi_watchdog();
1310 }
1311}
1312#else
1313static inline void boot_delay_msec(int level)
1314{
1315}
1316#endif
1317
1318static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1319module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1320
1321static size_t print_syslog(unsigned int level, char *buf)
1322{
1323 return sprintf(buf, "<%u>", level);
1324}
1325
1326static size_t print_time(u64 ts, char *buf)
1327{
1328 unsigned long rem_nsec = do_div(ts, 1000000000);
1329
1330 return sprintf(buf, "[%5lu.%06lu]",
1331 (unsigned long)ts, rem_nsec / 1000);
1332}
1333
1334#ifdef CONFIG_PRINTK_CALLER
1335static size_t print_caller(u32 id, char *buf)
1336{
1337 char caller[12];
1338
1339 snprintf(caller, sizeof(caller), "%c%u",
1340 id & 0x80000000 ? 'C' : 'T', id & ~0x80000000);
1341 return sprintf(buf, "[%6s]", caller);
1342}
1343#else
1344#define print_caller(id, buf) 0
1345#endif
1346
1347static size_t info_print_prefix(const struct printk_info *info, bool syslog,
1348 bool time, char *buf)
1349{
1350 size_t len = 0;
1351
1352 if (syslog)
1353 len = print_syslog((info->facility << 3) | info->level, buf);
1354
1355 if (time)
1356 len += print_time(info->ts_nsec, buf + len);
1357
1358 len += print_caller(info->caller_id, buf + len);
1359
1360 if (IS_ENABLED(CONFIG_PRINTK_CALLER) || time) {
1361 buf[len++] = ' ';
1362 buf[len] = '\0';
1363 }
1364
1365 return len;
1366}
1367
1368/*
1369 * Prepare the record for printing. The text is shifted within the given
1370 * buffer to avoid a need for another one. The following operations are
1371 * done:
1372 *
1373 * - Add prefix for each line.
1374 * - Drop truncated lines that no longer fit into the buffer.
1375 * - Add the trailing newline that has been removed in vprintk_store().
1376 * - Add a string terminator.
1377 *
1378 * Since the produced string is always terminated, the maximum possible
1379 * return value is @r->text_buf_size - 1;
1380 *
1381 * Return: The length of the updated/prepared text, including the added
1382 * prefixes and the newline. The terminator is not counted. The dropped
1383 * line(s) are not counted.
1384 */
1385static size_t record_print_text(struct printk_record *r, bool syslog,
1386 bool time)
1387{
1388 size_t text_len = r->info->text_len;
1389 size_t buf_size = r->text_buf_size;
1390 char *text = r->text_buf;
1391 char prefix[PRINTK_PREFIX_MAX];
1392 bool truncated = false;
1393 size_t prefix_len;
1394 size_t line_len;
1395 size_t len = 0;
1396 char *next;
1397
1398 /*
1399 * If the message was truncated because the buffer was not large
1400 * enough, treat the available text as if it were the full text.
1401 */
1402 if (text_len > buf_size)
1403 text_len = buf_size;
1404
1405 prefix_len = info_print_prefix(r->info, syslog, time, prefix);
1406
1407 /*
1408 * @text_len: bytes of unprocessed text
1409 * @line_len: bytes of current line _without_ newline
1410 * @text: pointer to beginning of current line
1411 * @len: number of bytes prepared in r->text_buf
1412 */
1413 for (;;) {
1414 next = memchr(text, '\n', text_len);
1415 if (next) {
1416 line_len = next - text;
1417 } else {
1418 /* Drop truncated line(s). */
1419 if (truncated)
1420 break;
1421 line_len = text_len;
1422 }
1423
1424 /*
1425 * Truncate the text if there is not enough space to add the
1426 * prefix and a trailing newline and a terminator.
1427 */
1428 if (len + prefix_len + text_len + 1 + 1 > buf_size) {
1429 /* Drop even the current line if no space. */
1430 if (len + prefix_len + line_len + 1 + 1 > buf_size)
1431 break;
1432
1433 text_len = buf_size - len - prefix_len - 1 - 1;
1434 truncated = true;
1435 }
1436
1437 memmove(text + prefix_len, text, text_len);
1438 memcpy(text, prefix, prefix_len);
1439
1440 /*
1441 * Increment the prepared length to include the text and
1442 * prefix that were just moved+copied. Also increment for the
1443 * newline at the end of this line. If this is the last line,
1444 * there is no newline, but it will be added immediately below.
1445 */
1446 len += prefix_len + line_len + 1;
1447 if (text_len == line_len) {
1448 /*
1449 * This is the last line. Add the trailing newline
1450 * removed in vprintk_store().
1451 */
1452 text[prefix_len + line_len] = '\n';
1453 break;
1454 }
1455
1456 /*
1457 * Advance beyond the added prefix and the related line with
1458 * its newline.
1459 */
1460 text += prefix_len + line_len + 1;
1461
1462 /*
1463 * The remaining text has only decreased by the line with its
1464 * newline.
1465 *
1466 * Note that @text_len can become zero. It happens when @text
1467 * ended with a newline (either due to truncation or the
1468 * original string ending with "\n\n"). The loop is correctly
1469 * repeated and (if not truncated) an empty line with a prefix
1470 * will be prepared.
1471 */
1472 text_len -= line_len + 1;
1473 }
1474
1475 /*
1476 * If a buffer was provided, it will be terminated. Space for the
1477 * string terminator is guaranteed to be available. The terminator is
1478 * not counted in the return value.
1479 */
1480 if (buf_size > 0)
1481 r->text_buf[len] = 0;
1482
1483 return len;
1484}
1485
1486static size_t get_record_print_text_size(struct printk_info *info,
1487 unsigned int line_count,
1488 bool syslog, bool time)
1489{
1490 char prefix[PRINTK_PREFIX_MAX];
1491 size_t prefix_len;
1492
1493 prefix_len = info_print_prefix(info, syslog, time, prefix);
1494
1495 /*
1496 * Each line will be preceded with a prefix. The intermediate
1497 * newlines are already within the text, but a final trailing
1498 * newline will be added.
1499 */
1500 return ((prefix_len * line_count) + info->text_len + 1);
1501}
1502
1503/*
1504 * Beginning with @start_seq, find the first record where it and all following
1505 * records up to (but not including) @max_seq fit into @size.
1506 *
1507 * @max_seq is simply an upper bound and does not need to exist. If the caller
1508 * does not require an upper bound, -1 can be used for @max_seq.
1509 */
1510static u64 find_first_fitting_seq(u64 start_seq, u64 max_seq, size_t size,
1511 bool syslog, bool time)
1512{
1513 struct printk_info info;
1514 unsigned int line_count;
1515 size_t len = 0;
1516 u64 seq;
1517
1518 /* Determine the size of the records up to @max_seq. */
1519 prb_for_each_info(start_seq, prb, seq, &info, &line_count) {
1520 if (info.seq >= max_seq)
1521 break;
1522 len += get_record_print_text_size(&info, line_count, syslog, time);
1523 }
1524
1525 /*
1526 * Adjust the upper bound for the next loop to avoid subtracting
1527 * lengths that were never added.
1528 */
1529 if (seq < max_seq)
1530 max_seq = seq;
1531
1532 /*
1533 * Move first record forward until length fits into the buffer. Ignore
1534 * newest messages that were not counted in the above cycle. Messages
1535 * might appear and get lost in the meantime. This is a best effort
1536 * that prevents an infinite loop that could occur with a retry.
1537 */
1538 prb_for_each_info(start_seq, prb, seq, &info, &line_count) {
1539 if (len <= size || info.seq >= max_seq)
1540 break;
1541 len -= get_record_print_text_size(&info, line_count, syslog, time);
1542 }
1543
1544 return seq;
1545}
1546
1547/* The caller is responsible for making sure @size is greater than 0. */
1548static int syslog_print(char __user *buf, int size)
1549{
1550 struct printk_info info;
1551 struct printk_record r;
1552 char *text;
1553 int len = 0;
1554 u64 seq;
1555
1556 text = kmalloc(PRINTK_MESSAGE_MAX, GFP_KERNEL);
1557 if (!text)
1558 return -ENOMEM;
1559
1560 prb_rec_init_rd(&r, &info, text, PRINTK_MESSAGE_MAX);
1561
1562 mutex_lock(&syslog_lock);
1563
1564 /*
1565 * Wait for the @syslog_seq record to be available. @syslog_seq may
1566 * change while waiting.
1567 */
1568 do {
1569 seq = syslog_seq;
1570
1571 mutex_unlock(&syslog_lock);
1572 /*
1573 * Guarantee this task is visible on the waitqueue before
1574 * checking the wake condition.
1575 *
1576 * The full memory barrier within set_current_state() of
1577 * prepare_to_wait_event() pairs with the full memory barrier
1578 * within wq_has_sleeper().
1579 *
1580 * This pairs with __wake_up_klogd:A.
1581 */
1582 len = wait_event_interruptible(log_wait,
1583 prb_read_valid(prb, seq, NULL)); /* LMM(syslog_print:A) */
1584 mutex_lock(&syslog_lock);
1585
1586 if (len)
1587 goto out;
1588 } while (syslog_seq != seq);
1589
1590 /*
1591 * Copy records that fit into the buffer. The above cycle makes sure
1592 * that the first record is always available.
1593 */
1594 do {
1595 size_t n;
1596 size_t skip;
1597 int err;
1598
1599 if (!prb_read_valid(prb, syslog_seq, &r))
1600 break;
1601
1602 if (r.info->seq != syslog_seq) {
1603 /* message is gone, move to next valid one */
1604 syslog_seq = r.info->seq;
1605 syslog_partial = 0;
1606 }
1607
1608 /*
1609 * To keep reading/counting partial line consistent,
1610 * use printk_time value as of the beginning of a line.
1611 */
1612 if (!syslog_partial)
1613 syslog_time = printk_time;
1614
1615 skip = syslog_partial;
1616 n = record_print_text(&r, true, syslog_time);
1617 if (n - syslog_partial <= size) {
1618 /* message fits into buffer, move forward */
1619 syslog_seq = r.info->seq + 1;
1620 n -= syslog_partial;
1621 syslog_partial = 0;
1622 } else if (!len){
1623 /* partial read(), remember position */
1624 n = size;
1625 syslog_partial += n;
1626 } else
1627 n = 0;
1628
1629 if (!n)
1630 break;
1631
1632 mutex_unlock(&syslog_lock);
1633 err = copy_to_user(buf, text + skip, n);
1634 mutex_lock(&syslog_lock);
1635
1636 if (err) {
1637 if (!len)
1638 len = -EFAULT;
1639 break;
1640 }
1641
1642 len += n;
1643 size -= n;
1644 buf += n;
1645 } while (size);
1646out:
1647 mutex_unlock(&syslog_lock);
1648 kfree(text);
1649 return len;
1650}
1651
1652static int syslog_print_all(char __user *buf, int size, bool clear)
1653{
1654 struct printk_info info;
1655 struct printk_record r;
1656 char *text;
1657 int len = 0;
1658 u64 seq;
1659 bool time;
1660
1661 text = kmalloc(PRINTK_MESSAGE_MAX, GFP_KERNEL);
1662 if (!text)
1663 return -ENOMEM;
1664
1665 time = printk_time;
1666 /*
1667 * Find first record that fits, including all following records,
1668 * into the user-provided buffer for this dump.
1669 */
1670 seq = find_first_fitting_seq(latched_seq_read_nolock(&clear_seq), -1,
1671 size, true, time);
1672
1673 prb_rec_init_rd(&r, &info, text, PRINTK_MESSAGE_MAX);
1674
1675 prb_for_each_record(seq, prb, seq, &r) {
1676 int textlen;
1677
1678 textlen = record_print_text(&r, true, time);
1679
1680 if (len + textlen > size) {
1681 seq--;
1682 break;
1683 }
1684
1685 if (copy_to_user(buf + len, text, textlen))
1686 len = -EFAULT;
1687 else
1688 len += textlen;
1689
1690 if (len < 0)
1691 break;
1692 }
1693
1694 if (clear) {
1695 mutex_lock(&syslog_lock);
1696 latched_seq_write(&clear_seq, seq);
1697 mutex_unlock(&syslog_lock);
1698 }
1699
1700 kfree(text);
1701 return len;
1702}
1703
1704static void syslog_clear(void)
1705{
1706 mutex_lock(&syslog_lock);
1707 latched_seq_write(&clear_seq, prb_next_seq(prb));
1708 mutex_unlock(&syslog_lock);
1709}
1710
1711int do_syslog(int type, char __user *buf, int len, int source)
1712{
1713 struct printk_info info;
1714 bool clear = false;
1715 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1716 int error;
1717
1718 error = check_syslog_permissions(type, source);
1719 if (error)
1720 return error;
1721
1722 switch (type) {
1723 case SYSLOG_ACTION_CLOSE: /* Close log */
1724 break;
1725 case SYSLOG_ACTION_OPEN: /* Open log */
1726 break;
1727 case SYSLOG_ACTION_READ: /* Read from log */
1728 if (!buf || len < 0)
1729 return -EINVAL;
1730 if (!len)
1731 return 0;
1732 if (!access_ok(buf, len))
1733 return -EFAULT;
1734 error = syslog_print(buf, len);
1735 break;
1736 /* Read/clear last kernel messages */
1737 case SYSLOG_ACTION_READ_CLEAR:
1738 clear = true;
1739 fallthrough;
1740 /* Read last kernel messages */
1741 case SYSLOG_ACTION_READ_ALL:
1742 if (!buf || len < 0)
1743 return -EINVAL;
1744 if (!len)
1745 return 0;
1746 if (!access_ok(buf, len))
1747 return -EFAULT;
1748 error = syslog_print_all(buf, len, clear);
1749 break;
1750 /* Clear ring buffer */
1751 case SYSLOG_ACTION_CLEAR:
1752 syslog_clear();
1753 break;
1754 /* Disable logging to console */
1755 case SYSLOG_ACTION_CONSOLE_OFF:
1756 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1757 saved_console_loglevel = console_loglevel;
1758 console_loglevel = minimum_console_loglevel;
1759 break;
1760 /* Enable logging to console */
1761 case SYSLOG_ACTION_CONSOLE_ON:
1762 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1763 console_loglevel = saved_console_loglevel;
1764 saved_console_loglevel = LOGLEVEL_DEFAULT;
1765 }
1766 break;
1767 /* Set level of messages printed to console */
1768 case SYSLOG_ACTION_CONSOLE_LEVEL:
1769 if (len < 1 || len > 8)
1770 return -EINVAL;
1771 if (len < minimum_console_loglevel)
1772 len = minimum_console_loglevel;
1773 console_loglevel = len;
1774 /* Implicitly re-enable logging to console */
1775 saved_console_loglevel = LOGLEVEL_DEFAULT;
1776 break;
1777 /* Number of chars in the log buffer */
1778 case SYSLOG_ACTION_SIZE_UNREAD:
1779 mutex_lock(&syslog_lock);
1780 if (!prb_read_valid_info(prb, syslog_seq, &info, NULL)) {
1781 /* No unread messages. */
1782 mutex_unlock(&syslog_lock);
1783 return 0;
1784 }
1785 if (info.seq != syslog_seq) {
1786 /* messages are gone, move to first one */
1787 syslog_seq = info.seq;
1788 syslog_partial = 0;
1789 }
1790 if (source == SYSLOG_FROM_PROC) {
1791 /*
1792 * Short-cut for poll(/"proc/kmsg") which simply checks
1793 * for pending data, not the size; return the count of
1794 * records, not the length.
1795 */
1796 error = prb_next_seq(prb) - syslog_seq;
1797 } else {
1798 bool time = syslog_partial ? syslog_time : printk_time;
1799 unsigned int line_count;
1800 u64 seq;
1801
1802 prb_for_each_info(syslog_seq, prb, seq, &info,
1803 &line_count) {
1804 error += get_record_print_text_size(&info, line_count,
1805 true, time);
1806 time = printk_time;
1807 }
1808 error -= syslog_partial;
1809 }
1810 mutex_unlock(&syslog_lock);
1811 break;
1812 /* Size of the log buffer */
1813 case SYSLOG_ACTION_SIZE_BUFFER:
1814 error = log_buf_len;
1815 break;
1816 default:
1817 error = -EINVAL;
1818 break;
1819 }
1820
1821 return error;
1822}
1823
1824SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1825{
1826 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1827}
1828
1829/*
1830 * Special console_lock variants that help to reduce the risk of soft-lockups.
1831 * They allow to pass console_lock to another printk() call using a busy wait.
1832 */
1833
1834#ifdef CONFIG_LOCKDEP
1835static struct lockdep_map console_owner_dep_map = {
1836 .name = "console_owner"
1837};
1838#endif
1839
1840static DEFINE_RAW_SPINLOCK(console_owner_lock);
1841static struct task_struct *console_owner;
1842static bool console_waiter;
1843
1844/**
1845 * console_lock_spinning_enable - mark beginning of code where another
1846 * thread might safely busy wait
1847 *
1848 * This basically converts console_lock into a spinlock. This marks
1849 * the section where the console_lock owner can not sleep, because
1850 * there may be a waiter spinning (like a spinlock). Also it must be
1851 * ready to hand over the lock at the end of the section.
1852 */
1853static void console_lock_spinning_enable(void)
1854{
1855 /*
1856 * Do not use spinning in panic(). The panic CPU wants to keep the lock.
1857 * Non-panic CPUs abandon the flush anyway.
1858 *
1859 * Just keep the lockdep annotation. The panic-CPU should avoid
1860 * taking console_owner_lock because it might cause a deadlock.
1861 * This looks like the easiest way how to prevent false lockdep
1862 * reports without handling races a lockless way.
1863 */
1864 if (panic_in_progress())
1865 goto lockdep;
1866
1867 raw_spin_lock(&console_owner_lock);
1868 console_owner = current;
1869 raw_spin_unlock(&console_owner_lock);
1870
1871lockdep:
1872 /* The waiter may spin on us after setting console_owner */
1873 spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_);
1874}
1875
1876/**
1877 * console_lock_spinning_disable_and_check - mark end of code where another
1878 * thread was able to busy wait and check if there is a waiter
1879 * @cookie: cookie returned from console_srcu_read_lock()
1880 *
1881 * This is called at the end of the section where spinning is allowed.
1882 * It has two functions. First, it is a signal that it is no longer
1883 * safe to start busy waiting for the lock. Second, it checks if
1884 * there is a busy waiter and passes the lock rights to her.
1885 *
1886 * Important: Callers lose both the console_lock and the SRCU read lock if
1887 * there was a busy waiter. They must not touch items synchronized by
1888 * console_lock or SRCU read lock in this case.
1889 *
1890 * Return: 1 if the lock rights were passed, 0 otherwise.
1891 */
1892static int console_lock_spinning_disable_and_check(int cookie)
1893{
1894 int waiter;
1895
1896 /*
1897 * Ignore spinning waiters during panic() because they might get stopped
1898 * or blocked at any time,
1899 *
1900 * It is safe because nobody is allowed to start spinning during panic
1901 * in the first place. If there has been a waiter then non panic CPUs
1902 * might stay spinning. They would get stopped anyway. The panic context
1903 * will never start spinning and an interrupted spin on panic CPU will
1904 * never continue.
1905 */
1906 if (panic_in_progress()) {
1907 /* Keep lockdep happy. */
1908 spin_release(&console_owner_dep_map, _THIS_IP_);
1909 return 0;
1910 }
1911
1912 raw_spin_lock(&console_owner_lock);
1913 waiter = READ_ONCE(console_waiter);
1914 console_owner = NULL;
1915 raw_spin_unlock(&console_owner_lock);
1916
1917 if (!waiter) {
1918 spin_release(&console_owner_dep_map, _THIS_IP_);
1919 return 0;
1920 }
1921
1922 /* The waiter is now free to continue */
1923 WRITE_ONCE(console_waiter, false);
1924
1925 spin_release(&console_owner_dep_map, _THIS_IP_);
1926
1927 /*
1928 * Preserve lockdep lock ordering. Release the SRCU read lock before
1929 * releasing the console_lock.
1930 */
1931 console_srcu_read_unlock(cookie);
1932
1933 /*
1934 * Hand off console_lock to waiter. The waiter will perform
1935 * the up(). After this, the waiter is the console_lock owner.
1936 */
1937 mutex_release(&console_lock_dep_map, _THIS_IP_);
1938 return 1;
1939}
1940
1941/**
1942 * console_trylock_spinning - try to get console_lock by busy waiting
1943 *
1944 * This allows to busy wait for the console_lock when the current
1945 * owner is running in specially marked sections. It means that
1946 * the current owner is running and cannot reschedule until it
1947 * is ready to lose the lock.
1948 *
1949 * Return: 1 if we got the lock, 0 othrewise
1950 */
1951static int console_trylock_spinning(void)
1952{
1953 struct task_struct *owner = NULL;
1954 bool waiter;
1955 bool spin = false;
1956 unsigned long flags;
1957
1958 if (console_trylock())
1959 return 1;
1960
1961 /*
1962 * It's unsafe to spin once a panic has begun. If we are the
1963 * panic CPU, we may have already halted the owner of the
1964 * console_sem. If we are not the panic CPU, then we should
1965 * avoid taking console_sem, so the panic CPU has a better
1966 * chance of cleanly acquiring it later.
1967 */
1968 if (panic_in_progress())
1969 return 0;
1970
1971 printk_safe_enter_irqsave(flags);
1972
1973 raw_spin_lock(&console_owner_lock);
1974 owner = READ_ONCE(console_owner);
1975 waiter = READ_ONCE(console_waiter);
1976 if (!waiter && owner && owner != current) {
1977 WRITE_ONCE(console_waiter, true);
1978 spin = true;
1979 }
1980 raw_spin_unlock(&console_owner_lock);
1981
1982 /*
1983 * If there is an active printk() writing to the
1984 * consoles, instead of having it write our data too,
1985 * see if we can offload that load from the active
1986 * printer, and do some printing ourselves.
1987 * Go into a spin only if there isn't already a waiter
1988 * spinning, and there is an active printer, and
1989 * that active printer isn't us (recursive printk?).
1990 */
1991 if (!spin) {
1992 printk_safe_exit_irqrestore(flags);
1993 return 0;
1994 }
1995
1996 /* We spin waiting for the owner to release us */
1997 spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_);
1998 /* Owner will clear console_waiter on hand off */
1999 while (READ_ONCE(console_waiter))
2000 cpu_relax();
2001 spin_release(&console_owner_dep_map, _THIS_IP_);
2002
2003 printk_safe_exit_irqrestore(flags);
2004 /*
2005 * The owner passed the console lock to us.
2006 * Since we did not spin on console lock, annotate
2007 * this as a trylock. Otherwise lockdep will
2008 * complain.
2009 */
2010 mutex_acquire(&console_lock_dep_map, 0, 1, _THIS_IP_);
2011
2012 /*
2013 * Update @console_may_schedule for trylock because the previous
2014 * owner may have been schedulable.
2015 */
2016 console_may_schedule = 0;
2017
2018 return 1;
2019}
2020
2021/*
2022 * Recursion is tracked separately on each CPU. If NMIs are supported, an
2023 * additional NMI context per CPU is also separately tracked. Until per-CPU
2024 * is available, a separate "early tracking" is performed.
2025 */
2026static DEFINE_PER_CPU(u8, printk_count);
2027static u8 printk_count_early;
2028#ifdef CONFIG_HAVE_NMI
2029static DEFINE_PER_CPU(u8, printk_count_nmi);
2030static u8 printk_count_nmi_early;
2031#endif
2032
2033/*
2034 * Recursion is limited to keep the output sane. printk() should not require
2035 * more than 1 level of recursion (allowing, for example, printk() to trigger
2036 * a WARN), but a higher value is used in case some printk-internal errors
2037 * exist, such as the ringbuffer validation checks failing.
2038 */
2039#define PRINTK_MAX_RECURSION 3
2040
2041/*
2042 * Return a pointer to the dedicated counter for the CPU+context of the
2043 * caller.
2044 */
2045static u8 *__printk_recursion_counter(void)
2046{
2047#ifdef CONFIG_HAVE_NMI
2048 if (in_nmi()) {
2049 if (printk_percpu_data_ready())
2050 return this_cpu_ptr(&printk_count_nmi);
2051 return &printk_count_nmi_early;
2052 }
2053#endif
2054 if (printk_percpu_data_ready())
2055 return this_cpu_ptr(&printk_count);
2056 return &printk_count_early;
2057}
2058
2059/*
2060 * Enter recursion tracking. Interrupts are disabled to simplify tracking.
2061 * The caller must check the boolean return value to see if the recursion is
2062 * allowed. On failure, interrupts are not disabled.
2063 *
2064 * @recursion_ptr must be a variable of type (u8 *) and is the same variable
2065 * that is passed to printk_exit_irqrestore().
2066 */
2067#define printk_enter_irqsave(recursion_ptr, flags) \
2068({ \
2069 bool success = true; \
2070 \
2071 typecheck(u8 *, recursion_ptr); \
2072 local_irq_save(flags); \
2073 (recursion_ptr) = __printk_recursion_counter(); \
2074 if (*(recursion_ptr) > PRINTK_MAX_RECURSION) { \
2075 local_irq_restore(flags); \
2076 success = false; \
2077 } else { \
2078 (*(recursion_ptr))++; \
2079 } \
2080 success; \
2081})
2082
2083/* Exit recursion tracking, restoring interrupts. */
2084#define printk_exit_irqrestore(recursion_ptr, flags) \
2085 do { \
2086 typecheck(u8 *, recursion_ptr); \
2087 (*(recursion_ptr))--; \
2088 local_irq_restore(flags); \
2089 } while (0)
2090
2091int printk_delay_msec __read_mostly;
2092
2093static inline void printk_delay(int level)
2094{
2095 boot_delay_msec(level);
2096
2097 if (unlikely(printk_delay_msec)) {
2098 int m = printk_delay_msec;
2099
2100 while (m--) {
2101 mdelay(1);
2102 touch_nmi_watchdog();
2103 }
2104 }
2105}
2106
2107static inline u32 printk_caller_id(void)
2108{
2109 return in_task() ? task_pid_nr(current) :
2110 0x80000000 + smp_processor_id();
2111}
2112
2113/**
2114 * printk_parse_prefix - Parse level and control flags.
2115 *
2116 * @text: The terminated text message.
2117 * @level: A pointer to the current level value, will be updated.
2118 * @flags: A pointer to the current printk_info flags, will be updated.
2119 *
2120 * @level may be NULL if the caller is not interested in the parsed value.
2121 * Otherwise the variable pointed to by @level must be set to
2122 * LOGLEVEL_DEFAULT in order to be updated with the parsed value.
2123 *
2124 * @flags may be NULL if the caller is not interested in the parsed value.
2125 * Otherwise the variable pointed to by @flags will be OR'd with the parsed
2126 * value.
2127 *
2128 * Return: The length of the parsed level and control flags.
2129 */
2130u16 printk_parse_prefix(const char *text, int *level,
2131 enum printk_info_flags *flags)
2132{
2133 u16 prefix_len = 0;
2134 int kern_level;
2135
2136 while (*text) {
2137 kern_level = printk_get_level(text);
2138 if (!kern_level)
2139 break;
2140
2141 switch (kern_level) {
2142 case '0' ... '7':
2143 if (level && *level == LOGLEVEL_DEFAULT)
2144 *level = kern_level - '0';
2145 break;
2146 case 'c': /* KERN_CONT */
2147 if (flags)
2148 *flags |= LOG_CONT;
2149 }
2150
2151 prefix_len += 2;
2152 text += 2;
2153 }
2154
2155 return prefix_len;
2156}
2157
2158__printf(5, 0)
2159static u16 printk_sprint(char *text, u16 size, int facility,
2160 enum printk_info_flags *flags, const char *fmt,
2161 va_list args)
2162{
2163 u16 text_len;
2164
2165 text_len = vscnprintf(text, size, fmt, args);
2166
2167 /* Mark and strip a trailing newline. */
2168 if (text_len && text[text_len - 1] == '\n') {
2169 text_len--;
2170 *flags |= LOG_NEWLINE;
2171 }
2172
2173 /* Strip log level and control flags. */
2174 if (facility == 0) {
2175 u16 prefix_len;
2176
2177 prefix_len = printk_parse_prefix(text, NULL, NULL);
2178 if (prefix_len) {
2179 text_len -= prefix_len;
2180 memmove(text, text + prefix_len, text_len);
2181 }
2182 }
2183
2184 trace_console(text, text_len);
2185
2186 return text_len;
2187}
2188
2189__printf(4, 0)
2190int vprintk_store(int facility, int level,
2191 const struct dev_printk_info *dev_info,
2192 const char *fmt, va_list args)
2193{
2194 struct prb_reserved_entry e;
2195 enum printk_info_flags flags = 0;
2196 struct printk_record r;
2197 unsigned long irqflags;
2198 u16 trunc_msg_len = 0;
2199 char prefix_buf[8];
2200 u8 *recursion_ptr;
2201 u16 reserve_size;
2202 va_list args2;
2203 u32 caller_id;
2204 u16 text_len;
2205 int ret = 0;
2206 u64 ts_nsec;
2207
2208 if (!printk_enter_irqsave(recursion_ptr, irqflags))
2209 return 0;
2210
2211 /*
2212 * Since the duration of printk() can vary depending on the message
2213 * and state of the ringbuffer, grab the timestamp now so that it is
2214 * close to the call of printk(). This provides a more deterministic
2215 * timestamp with respect to the caller.
2216 */
2217 ts_nsec = local_clock();
2218
2219 caller_id = printk_caller_id();
2220
2221 /*
2222 * The sprintf needs to come first since the syslog prefix might be
2223 * passed in as a parameter. An extra byte must be reserved so that
2224 * later the vscnprintf() into the reserved buffer has room for the
2225 * terminating '\0', which is not counted by vsnprintf().
2226 */
2227 va_copy(args2, args);
2228 reserve_size = vsnprintf(&prefix_buf[0], sizeof(prefix_buf), fmt, args2) + 1;
2229 va_end(args2);
2230
2231 if (reserve_size > PRINTKRB_RECORD_MAX)
2232 reserve_size = PRINTKRB_RECORD_MAX;
2233
2234 /* Extract log level or control flags. */
2235 if (facility == 0)
2236 printk_parse_prefix(&prefix_buf[0], &level, &flags);
2237
2238 if (level == LOGLEVEL_DEFAULT)
2239 level = default_message_loglevel;
2240
2241 if (dev_info)
2242 flags |= LOG_NEWLINE;
2243
2244 if (flags & LOG_CONT) {
2245 prb_rec_init_wr(&r, reserve_size);
2246 if (prb_reserve_in_last(&e, prb, &r, caller_id, PRINTKRB_RECORD_MAX)) {
2247 text_len = printk_sprint(&r.text_buf[r.info->text_len], reserve_size,
2248 facility, &flags, fmt, args);
2249 r.info->text_len += text_len;
2250
2251 if (flags & LOG_NEWLINE) {
2252 r.info->flags |= LOG_NEWLINE;
2253 prb_final_commit(&e);
2254 } else {
2255 prb_commit(&e);
2256 }
2257
2258 ret = text_len;
2259 goto out;
2260 }
2261 }
2262
2263 /*
2264 * Explicitly initialize the record before every prb_reserve() call.
2265 * prb_reserve_in_last() and prb_reserve() purposely invalidate the
2266 * structure when they fail.
2267 */
2268 prb_rec_init_wr(&r, reserve_size);
2269 if (!prb_reserve(&e, prb, &r)) {
2270 /* truncate the message if it is too long for empty buffer */
2271 truncate_msg(&reserve_size, &trunc_msg_len);
2272
2273 prb_rec_init_wr(&r, reserve_size + trunc_msg_len);
2274 if (!prb_reserve(&e, prb, &r))
2275 goto out;
2276 }
2277
2278 /* fill message */
2279 text_len = printk_sprint(&r.text_buf[0], reserve_size, facility, &flags, fmt, args);
2280 if (trunc_msg_len)
2281 memcpy(&r.text_buf[text_len], trunc_msg, trunc_msg_len);
2282 r.info->text_len = text_len + trunc_msg_len;
2283 r.info->facility = facility;
2284 r.info->level = level & 7;
2285 r.info->flags = flags & 0x1f;
2286 r.info->ts_nsec = ts_nsec;
2287 r.info->caller_id = caller_id;
2288 if (dev_info)
2289 memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info));
2290
2291 /* A message without a trailing newline can be continued. */
2292 if (!(flags & LOG_NEWLINE))
2293 prb_commit(&e);
2294 else
2295 prb_final_commit(&e);
2296
2297 ret = text_len + trunc_msg_len;
2298out:
2299 printk_exit_irqrestore(recursion_ptr, irqflags);
2300 return ret;
2301}
2302
2303asmlinkage int vprintk_emit(int facility, int level,
2304 const struct dev_printk_info *dev_info,
2305 const char *fmt, va_list args)
2306{
2307 int printed_len;
2308 bool in_sched = false;
2309
2310 /* Suppress unimportant messages after panic happens */
2311 if (unlikely(suppress_printk))
2312 return 0;
2313
2314 /*
2315 * The messages on the panic CPU are the most important. If
2316 * non-panic CPUs are generating any messages, they will be
2317 * silently dropped.
2318 */
2319 if (other_cpu_in_panic())
2320 return 0;
2321
2322 if (level == LOGLEVEL_SCHED) {
2323 level = LOGLEVEL_DEFAULT;
2324 in_sched = true;
2325 }
2326
2327 printk_delay(level);
2328
2329 printed_len = vprintk_store(facility, level, dev_info, fmt, args);
2330
2331 /* If called from the scheduler, we can not call up(). */
2332 if (!in_sched) {
2333 /*
2334 * The caller may be holding system-critical or
2335 * timing-sensitive locks. Disable preemption during
2336 * printing of all remaining records to all consoles so that
2337 * this context can return as soon as possible. Hopefully
2338 * another printk() caller will take over the printing.
2339 */
2340 preempt_disable();
2341 /*
2342 * Try to acquire and then immediately release the console
2343 * semaphore. The release will print out buffers. With the
2344 * spinning variant, this context tries to take over the
2345 * printing from another printing context.
2346 */
2347 if (console_trylock_spinning())
2348 console_unlock();
2349 preempt_enable();
2350 }
2351
2352 if (in_sched)
2353 defer_console_output();
2354 else
2355 wake_up_klogd();
2356
2357 return printed_len;
2358}
2359EXPORT_SYMBOL(vprintk_emit);
2360
2361int vprintk_default(const char *fmt, va_list args)
2362{
2363 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
2364}
2365EXPORT_SYMBOL_GPL(vprintk_default);
2366
2367asmlinkage __visible int _printk(const char *fmt, ...)
2368{
2369 va_list args;
2370 int r;
2371
2372 va_start(args, fmt);
2373 r = vprintk(fmt, args);
2374 va_end(args);
2375
2376 return r;
2377}
2378EXPORT_SYMBOL(_printk);
2379
2380static bool pr_flush(int timeout_ms, bool reset_on_progress);
2381static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress);
2382
2383#else /* CONFIG_PRINTK */
2384
2385#define printk_time false
2386
2387#define prb_read_valid(rb, seq, r) false
2388#define prb_first_valid_seq(rb) 0
2389#define prb_next_seq(rb) 0
2390
2391static u64 syslog_seq;
2392
2393static bool pr_flush(int timeout_ms, bool reset_on_progress) { return true; }
2394static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; }
2395
2396#endif /* CONFIG_PRINTK */
2397
2398#ifdef CONFIG_EARLY_PRINTK
2399struct console *early_console;
2400
2401asmlinkage __visible void early_printk(const char *fmt, ...)
2402{
2403 va_list ap;
2404 char buf[512];
2405 int n;
2406
2407 if (!early_console)
2408 return;
2409
2410 va_start(ap, fmt);
2411 n = vscnprintf(buf, sizeof(buf), fmt, ap);
2412 va_end(ap);
2413
2414 early_console->write(early_console, buf, n);
2415}
2416#endif
2417
2418static void set_user_specified(struct console_cmdline *c, bool user_specified)
2419{
2420 if (!user_specified)
2421 return;
2422
2423 /*
2424 * @c console was defined by the user on the command line.
2425 * Do not clear when added twice also by SPCR or the device tree.
2426 */
2427 c->user_specified = true;
2428 /* At least one console defined by the user on the command line. */
2429 console_set_on_cmdline = 1;
2430}
2431
2432static int __add_preferred_console(const char *name, const short idx, char *options,
2433 char *brl_options, bool user_specified)
2434{
2435 struct console_cmdline *c;
2436 int i;
2437
2438 /*
2439 * We use a signed short index for struct console for device drivers to
2440 * indicate a not yet assigned index or port. However, a negative index
2441 * value is not valid for preferred console.
2442 */
2443 if (idx < 0)
2444 return -EINVAL;
2445
2446 /*
2447 * See if this tty is not yet registered, and
2448 * if we have a slot free.
2449 */
2450 for (i = 0, c = console_cmdline;
2451 i < MAX_CMDLINECONSOLES && c->name[0];
2452 i++, c++) {
2453 if (strcmp(c->name, name) == 0 && c->index == idx) {
2454 if (!brl_options)
2455 preferred_console = i;
2456 set_user_specified(c, user_specified);
2457 return 0;
2458 }
2459 }
2460 if (i == MAX_CMDLINECONSOLES)
2461 return -E2BIG;
2462 if (!brl_options)
2463 preferred_console = i;
2464 strscpy(c->name, name, sizeof(c->name));
2465 c->options = options;
2466 set_user_specified(c, user_specified);
2467 braille_set_options(c, brl_options);
2468
2469 c->index = idx;
2470 return 0;
2471}
2472
2473static int __init console_msg_format_setup(char *str)
2474{
2475 if (!strcmp(str, "syslog"))
2476 console_msg_format = MSG_FORMAT_SYSLOG;
2477 if (!strcmp(str, "default"))
2478 console_msg_format = MSG_FORMAT_DEFAULT;
2479 return 1;
2480}
2481__setup("console_msg_format=", console_msg_format_setup);
2482
2483/*
2484 * Set up a console. Called via do_early_param() in init/main.c
2485 * for each "console=" parameter in the boot command line.
2486 */
2487static int __init console_setup(char *str)
2488{
2489 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
2490 char *s, *options, *brl_options = NULL;
2491 int idx;
2492
2493 /*
2494 * console="" or console=null have been suggested as a way to
2495 * disable console output. Use ttynull that has been created
2496 * for exactly this purpose.
2497 */
2498 if (str[0] == 0 || strcmp(str, "null") == 0) {
2499 __add_preferred_console("ttynull", 0, NULL, NULL, true);
2500 return 1;
2501 }
2502
2503 if (_braille_console_setup(&str, &brl_options))
2504 return 1;
2505
2506 /*
2507 * Decode str into name, index, options.
2508 */
2509 if (str[0] >= '0' && str[0] <= '9') {
2510 strcpy(buf, "ttyS");
2511 strncpy(buf + 4, str, sizeof(buf) - 5);
2512 } else {
2513 strncpy(buf, str, sizeof(buf) - 1);
2514 }
2515 buf[sizeof(buf) - 1] = 0;
2516 options = strchr(str, ',');
2517 if (options)
2518 *(options++) = 0;
2519#ifdef __sparc__
2520 if (!strcmp(str, "ttya"))
2521 strcpy(buf, "ttyS0");
2522 if (!strcmp(str, "ttyb"))
2523 strcpy(buf, "ttyS1");
2524#endif
2525 for (s = buf; *s; s++)
2526 if (isdigit(*s) || *s == ',')
2527 break;
2528 idx = simple_strtoul(s, NULL, 10);
2529 *s = 0;
2530
2531 __add_preferred_console(buf, idx, options, brl_options, true);
2532 return 1;
2533}
2534__setup("console=", console_setup);
2535
2536/**
2537 * add_preferred_console - add a device to the list of preferred consoles.
2538 * @name: device name
2539 * @idx: device index
2540 * @options: options for this console
2541 *
2542 * The last preferred console added will be used for kernel messages
2543 * and stdin/out/err for init. Normally this is used by console_setup
2544 * above to handle user-supplied console arguments; however it can also
2545 * be used by arch-specific code either to override the user or more
2546 * commonly to provide a default console (ie from PROM variables) when
2547 * the user has not supplied one.
2548 */
2549int add_preferred_console(const char *name, const short idx, char *options)
2550{
2551 return __add_preferred_console(name, idx, options, NULL, false);
2552}
2553
2554bool console_suspend_enabled = true;
2555EXPORT_SYMBOL(console_suspend_enabled);
2556
2557static int __init console_suspend_disable(char *str)
2558{
2559 console_suspend_enabled = false;
2560 return 1;
2561}
2562__setup("no_console_suspend", console_suspend_disable);
2563module_param_named(console_suspend, console_suspend_enabled,
2564 bool, S_IRUGO | S_IWUSR);
2565MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2566 " and hibernate operations");
2567
2568static bool printk_console_no_auto_verbose;
2569
2570void console_verbose(void)
2571{
2572 if (console_loglevel && !printk_console_no_auto_verbose)
2573 console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
2574}
2575EXPORT_SYMBOL_GPL(console_verbose);
2576
2577module_param_named(console_no_auto_verbose, printk_console_no_auto_verbose, bool, 0644);
2578MODULE_PARM_DESC(console_no_auto_verbose, "Disable console loglevel raise to highest on oops/panic/etc");
2579
2580/**
2581 * suspend_console - suspend the console subsystem
2582 *
2583 * This disables printk() while we go into suspend states
2584 */
2585void suspend_console(void)
2586{
2587 struct console *con;
2588
2589 if (!console_suspend_enabled)
2590 return;
2591 pr_info("Suspending console(s) (use no_console_suspend to debug)\n");
2592 pr_flush(1000, true);
2593
2594 console_list_lock();
2595 for_each_console(con)
2596 console_srcu_write_flags(con, con->flags | CON_SUSPENDED);
2597 console_list_unlock();
2598
2599 /*
2600 * Ensure that all SRCU list walks have completed. All printing
2601 * contexts must be able to see that they are suspended so that it
2602 * is guaranteed that all printing has stopped when this function
2603 * completes.
2604 */
2605 synchronize_srcu(&console_srcu);
2606}
2607
2608void resume_console(void)
2609{
2610 struct console *con;
2611
2612 if (!console_suspend_enabled)
2613 return;
2614
2615 console_list_lock();
2616 for_each_console(con)
2617 console_srcu_write_flags(con, con->flags & ~CON_SUSPENDED);
2618 console_list_unlock();
2619
2620 /*
2621 * Ensure that all SRCU list walks have completed. All printing
2622 * contexts must be able to see they are no longer suspended so
2623 * that they are guaranteed to wake up and resume printing.
2624 */
2625 synchronize_srcu(&console_srcu);
2626
2627 pr_flush(1000, true);
2628}
2629
2630/**
2631 * console_cpu_notify - print deferred console messages after CPU hotplug
2632 * @cpu: unused
2633 *
2634 * If printk() is called from a CPU that is not online yet, the messages
2635 * will be printed on the console only if there are CON_ANYTIME consoles.
2636 * This function is called when a new CPU comes online (or fails to come
2637 * up) or goes offline.
2638 */
2639static int console_cpu_notify(unsigned int cpu)
2640{
2641 if (!cpuhp_tasks_frozen) {
2642 /* If trylock fails, someone else is doing the printing */
2643 if (console_trylock())
2644 console_unlock();
2645 }
2646 return 0;
2647}
2648
2649/**
2650 * console_lock - block the console subsystem from printing
2651 *
2652 * Acquires a lock which guarantees that no consoles will
2653 * be in or enter their write() callback.
2654 *
2655 * Can sleep, returns nothing.
2656 */
2657void console_lock(void)
2658{
2659 might_sleep();
2660
2661 /* On panic, the console_lock must be left to the panic cpu. */
2662 while (other_cpu_in_panic())
2663 msleep(1000);
2664
2665 down_console_sem();
2666 console_locked = 1;
2667 console_may_schedule = 1;
2668}
2669EXPORT_SYMBOL(console_lock);
2670
2671/**
2672 * console_trylock - try to block the console subsystem from printing
2673 *
2674 * Try to acquire a lock which guarantees that no consoles will
2675 * be in or enter their write() callback.
2676 *
2677 * returns 1 on success, and 0 on failure to acquire the lock.
2678 */
2679int console_trylock(void)
2680{
2681 /* On panic, the console_lock must be left to the panic cpu. */
2682 if (other_cpu_in_panic())
2683 return 0;
2684 if (down_trylock_console_sem())
2685 return 0;
2686 console_locked = 1;
2687 console_may_schedule = 0;
2688 return 1;
2689}
2690EXPORT_SYMBOL(console_trylock);
2691
2692int is_console_locked(void)
2693{
2694 return console_locked;
2695}
2696EXPORT_SYMBOL(is_console_locked);
2697
2698/*
2699 * Check if the given console is currently capable and allowed to print
2700 * records.
2701 *
2702 * Requires the console_srcu_read_lock.
2703 */
2704static inline bool console_is_usable(struct console *con)
2705{
2706 short flags = console_srcu_read_flags(con);
2707
2708 if (!(flags & CON_ENABLED))
2709 return false;
2710
2711 if ((flags & CON_SUSPENDED))
2712 return false;
2713
2714 if (!con->write)
2715 return false;
2716
2717 /*
2718 * Console drivers may assume that per-cpu resources have been
2719 * allocated. So unless they're explicitly marked as being able to
2720 * cope (CON_ANYTIME) don't call them until this CPU is officially up.
2721 */
2722 if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME))
2723 return false;
2724
2725 return true;
2726}
2727
2728static void __console_unlock(void)
2729{
2730 console_locked = 0;
2731 up_console_sem();
2732}
2733
2734#ifdef CONFIG_PRINTK
2735
2736/*
2737 * Prepend the message in @pmsg->pbufs->outbuf with a "dropped message". This
2738 * is achieved by shifting the existing message over and inserting the dropped
2739 * message.
2740 *
2741 * @pmsg is the printk message to prepend.
2742 *
2743 * @dropped is the dropped count to report in the dropped message.
2744 *
2745 * If the message text in @pmsg->pbufs->outbuf does not have enough space for
2746 * the dropped message, the message text will be sufficiently truncated.
2747 *
2748 * If @pmsg->pbufs->outbuf is modified, @pmsg->outbuf_len is updated.
2749 */
2750void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
2751{
2752 struct printk_buffers *pbufs = pmsg->pbufs;
2753 const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);
2754 const size_t outbuf_sz = sizeof(pbufs->outbuf);
2755 char *scratchbuf = &pbufs->scratchbuf[0];
2756 char *outbuf = &pbufs->outbuf[0];
2757 size_t len;
2758
2759 len = scnprintf(scratchbuf, scratchbuf_sz,
2760 "** %lu printk messages dropped **\n", dropped);
2761
2762 /*
2763 * Make sure outbuf is sufficiently large before prepending.
2764 * Keep at least the prefix when the message must be truncated.
2765 * It is a rather theoretical problem when someone tries to
2766 * use a minimalist buffer.
2767 */
2768 if (WARN_ON_ONCE(len + PRINTK_PREFIX_MAX >= outbuf_sz))
2769 return;
2770
2771 if (pmsg->outbuf_len + len >= outbuf_sz) {
2772 /* Truncate the message, but keep it terminated. */
2773 pmsg->outbuf_len = outbuf_sz - (len + 1);
2774 outbuf[pmsg->outbuf_len] = 0;
2775 }
2776
2777 memmove(outbuf + len, outbuf, pmsg->outbuf_len + 1);
2778 memcpy(outbuf, scratchbuf, len);
2779 pmsg->outbuf_len += len;
2780}
2781
2782/*
2783 * Read and format the specified record (or a later record if the specified
2784 * record is not available).
2785 *
2786 * @pmsg will contain the formatted result. @pmsg->pbufs must point to a
2787 * struct printk_buffers.
2788 *
2789 * @seq is the record to read and format. If it is not available, the next
2790 * valid record is read.
2791 *
2792 * @is_extended specifies if the message should be formatted for extended
2793 * console output.
2794 *
2795 * @may_supress specifies if records may be skipped based on loglevel.
2796 *
2797 * Returns false if no record is available. Otherwise true and all fields
2798 * of @pmsg are valid. (See the documentation of struct printk_message
2799 * for information about the @pmsg fields.)
2800 */
2801bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
2802 bool is_extended, bool may_suppress)
2803{
2804 struct printk_buffers *pbufs = pmsg->pbufs;
2805 const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);
2806 const size_t outbuf_sz = sizeof(pbufs->outbuf);
2807 char *scratchbuf = &pbufs->scratchbuf[0];
2808 char *outbuf = &pbufs->outbuf[0];
2809 struct printk_info info;
2810 struct printk_record r;
2811 size_t len = 0;
2812
2813 /*
2814 * Formatting extended messages requires a separate buffer, so use the
2815 * scratch buffer to read in the ringbuffer text.
2816 *
2817 * Formatting normal messages is done in-place, so read the ringbuffer
2818 * text directly into the output buffer.
2819 */
2820 if (is_extended)
2821 prb_rec_init_rd(&r, &info, scratchbuf, scratchbuf_sz);
2822 else
2823 prb_rec_init_rd(&r, &info, outbuf, outbuf_sz);
2824
2825 if (!prb_read_valid(prb, seq, &r))
2826 return false;
2827
2828 pmsg->seq = r.info->seq;
2829 pmsg->dropped = r.info->seq - seq;
2830
2831 /* Skip record that has level above the console loglevel. */
2832 if (may_suppress && suppress_message_printing(r.info->level))
2833 goto out;
2834
2835 if (is_extended) {
2836 len = info_print_ext_header(outbuf, outbuf_sz, r.info);
2837 len += msg_print_ext_body(outbuf + len, outbuf_sz - len,
2838 &r.text_buf[0], r.info->text_len, &r.info->dev_info);
2839 } else {
2840 len = record_print_text(&r, console_msg_format & MSG_FORMAT_SYSLOG, printk_time);
2841 }
2842out:
2843 pmsg->outbuf_len = len;
2844 return true;
2845}
2846
2847/*
2848 * Used as the printk buffers for non-panic, serialized console printing.
2849 * This is for legacy (!CON_NBCON) as well as all boot (CON_BOOT) consoles.
2850 * Its usage requires the console_lock held.
2851 */
2852struct printk_buffers printk_shared_pbufs;
2853
2854/*
2855 * Print one record for the given console. The record printed is whatever
2856 * record is the next available record for the given console.
2857 *
2858 * @handover will be set to true if a printk waiter has taken over the
2859 * console_lock, in which case the caller is no longer holding both the
2860 * console_lock and the SRCU read lock. Otherwise it is set to false.
2861 *
2862 * @cookie is the cookie from the SRCU read lock.
2863 *
2864 * Returns false if the given console has no next record to print, otherwise
2865 * true.
2866 *
2867 * Requires the console_lock and the SRCU read lock.
2868 */
2869static bool console_emit_next_record(struct console *con, bool *handover, int cookie)
2870{
2871 bool is_extended = console_srcu_read_flags(con) & CON_EXTENDED;
2872 char *outbuf = &printk_shared_pbufs.outbuf[0];
2873 struct printk_message pmsg = {
2874 .pbufs = &printk_shared_pbufs,
2875 };
2876 unsigned long flags;
2877
2878 *handover = false;
2879
2880 if (!printk_get_next_message(&pmsg, con->seq, is_extended, true))
2881 return false;
2882
2883 con->dropped += pmsg.dropped;
2884
2885 /* Skip messages of formatted length 0. */
2886 if (pmsg.outbuf_len == 0) {
2887 con->seq = pmsg.seq + 1;
2888 goto skip;
2889 }
2890
2891 if (con->dropped && !is_extended) {
2892 console_prepend_dropped(&pmsg, con->dropped);
2893 con->dropped = 0;
2894 }
2895
2896 /*
2897 * While actively printing out messages, if another printk()
2898 * were to occur on another CPU, it may wait for this one to
2899 * finish. This task can not be preempted if there is a
2900 * waiter waiting to take over.
2901 *
2902 * Interrupts are disabled because the hand over to a waiter
2903 * must not be interrupted until the hand over is completed
2904 * (@console_waiter is cleared).
2905 */
2906 printk_safe_enter_irqsave(flags);
2907 console_lock_spinning_enable();
2908
2909 /* Do not trace print latency. */
2910 stop_critical_timings();
2911
2912 /* Write everything out to the hardware. */
2913 con->write(con, outbuf, pmsg.outbuf_len);
2914
2915 start_critical_timings();
2916
2917 con->seq = pmsg.seq + 1;
2918
2919 *handover = console_lock_spinning_disable_and_check(cookie);
2920 printk_safe_exit_irqrestore(flags);
2921skip:
2922 return true;
2923}
2924
2925#else
2926
2927static bool console_emit_next_record(struct console *con, bool *handover, int cookie)
2928{
2929 *handover = false;
2930 return false;
2931}
2932
2933#endif /* CONFIG_PRINTK */
2934
2935/*
2936 * Print out all remaining records to all consoles.
2937 *
2938 * @do_cond_resched is set by the caller. It can be true only in schedulable
2939 * context.
2940 *
2941 * @next_seq is set to the sequence number after the last available record.
2942 * The value is valid only when this function returns true. It means that all
2943 * usable consoles are completely flushed.
2944 *
2945 * @handover will be set to true if a printk waiter has taken over the
2946 * console_lock, in which case the caller is no longer holding the
2947 * console_lock. Otherwise it is set to false.
2948 *
2949 * Returns true when there was at least one usable console and all messages
2950 * were flushed to all usable consoles. A returned false informs the caller
2951 * that everything was not flushed (either there were no usable consoles or
2952 * another context has taken over printing or it is a panic situation and this
2953 * is not the panic CPU). Regardless the reason, the caller should assume it
2954 * is not useful to immediately try again.
2955 *
2956 * Requires the console_lock.
2957 */
2958static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handover)
2959{
2960 bool any_usable = false;
2961 struct console *con;
2962 bool any_progress;
2963 int cookie;
2964
2965 *next_seq = 0;
2966 *handover = false;
2967
2968 do {
2969 any_progress = false;
2970
2971 cookie = console_srcu_read_lock();
2972 for_each_console_srcu(con) {
2973 bool progress;
2974
2975 if (!console_is_usable(con))
2976 continue;
2977 any_usable = true;
2978
2979 progress = console_emit_next_record(con, handover, cookie);
2980
2981 /*
2982 * If a handover has occurred, the SRCU read lock
2983 * is already released.
2984 */
2985 if (*handover)
2986 return false;
2987
2988 /* Track the next of the highest seq flushed. */
2989 if (con->seq > *next_seq)
2990 *next_seq = con->seq;
2991
2992 if (!progress)
2993 continue;
2994 any_progress = true;
2995
2996 /* Allow panic_cpu to take over the consoles safely. */
2997 if (other_cpu_in_panic())
2998 goto abandon;
2999
3000 if (do_cond_resched)
3001 cond_resched();
3002 }
3003 console_srcu_read_unlock(cookie);
3004 } while (any_progress);
3005
3006 return any_usable;
3007
3008abandon:
3009 console_srcu_read_unlock(cookie);
3010 return false;
3011}
3012
3013/**
3014 * console_unlock - unblock the console subsystem from printing
3015 *
3016 * Releases the console_lock which the caller holds to block printing of
3017 * the console subsystem.
3018 *
3019 * While the console_lock was held, console output may have been buffered
3020 * by printk(). If this is the case, console_unlock(); emits
3021 * the output prior to releasing the lock.
3022 *
3023 * console_unlock(); may be called from any context.
3024 */
3025void console_unlock(void)
3026{
3027 bool do_cond_resched;
3028 bool handover;
3029 bool flushed;
3030 u64 next_seq;
3031
3032 /*
3033 * Console drivers are called with interrupts disabled, so
3034 * @console_may_schedule should be cleared before; however, we may
3035 * end up dumping a lot of lines, for example, if called from
3036 * console registration path, and should invoke cond_resched()
3037 * between lines if allowable. Not doing so can cause a very long
3038 * scheduling stall on a slow console leading to RCU stall and
3039 * softlockup warnings which exacerbate the issue with more
3040 * messages practically incapacitating the system. Therefore, create
3041 * a local to use for the printing loop.
3042 */
3043 do_cond_resched = console_may_schedule;
3044
3045 do {
3046 console_may_schedule = 0;
3047
3048 flushed = console_flush_all(do_cond_resched, &next_seq, &handover);
3049 if (!handover)
3050 __console_unlock();
3051
3052 /*
3053 * Abort if there was a failure to flush all messages to all
3054 * usable consoles. Either it is not possible to flush (in
3055 * which case it would be an infinite loop of retrying) or
3056 * another context has taken over printing.
3057 */
3058 if (!flushed)
3059 break;
3060
3061 /*
3062 * Some context may have added new records after
3063 * console_flush_all() but before unlocking the console.
3064 * Re-check if there is a new record to flush. If the trylock
3065 * fails, another context is already handling the printing.
3066 */
3067 } while (prb_read_valid(prb, next_seq, NULL) && console_trylock());
3068}
3069EXPORT_SYMBOL(console_unlock);
3070
3071/**
3072 * console_conditional_schedule - yield the CPU if required
3073 *
3074 * If the console code is currently allowed to sleep, and
3075 * if this CPU should yield the CPU to another task, do
3076 * so here.
3077 *
3078 * Must be called within console_lock();.
3079 */
3080void __sched console_conditional_schedule(void)
3081{
3082 if (console_may_schedule)
3083 cond_resched();
3084}
3085EXPORT_SYMBOL(console_conditional_schedule);
3086
3087void console_unblank(void)
3088{
3089 bool found_unblank = false;
3090 struct console *c;
3091 int cookie;
3092
3093 /*
3094 * First check if there are any consoles implementing the unblank()
3095 * callback. If not, there is no reason to continue and take the
3096 * console lock, which in particular can be dangerous if
3097 * @oops_in_progress is set.
3098 */
3099 cookie = console_srcu_read_lock();
3100 for_each_console_srcu(c) {
3101 if ((console_srcu_read_flags(c) & CON_ENABLED) && c->unblank) {
3102 found_unblank = true;
3103 break;
3104 }
3105 }
3106 console_srcu_read_unlock(cookie);
3107 if (!found_unblank)
3108 return;
3109
3110 /*
3111 * Stop console printing because the unblank() callback may
3112 * assume the console is not within its write() callback.
3113 *
3114 * If @oops_in_progress is set, this may be an atomic context.
3115 * In that case, attempt a trylock as best-effort.
3116 */
3117 if (oops_in_progress) {
3118 /* Semaphores are not NMI-safe. */
3119 if (in_nmi())
3120 return;
3121
3122 /*
3123 * Attempting to trylock the console lock can deadlock
3124 * if another CPU was stopped while modifying the
3125 * semaphore. "Hope and pray" that this is not the
3126 * current situation.
3127 */
3128 if (down_trylock_console_sem() != 0)
3129 return;
3130 } else
3131 console_lock();
3132
3133 console_locked = 1;
3134 console_may_schedule = 0;
3135
3136 cookie = console_srcu_read_lock();
3137 for_each_console_srcu(c) {
3138 if ((console_srcu_read_flags(c) & CON_ENABLED) && c->unblank)
3139 c->unblank();
3140 }
3141 console_srcu_read_unlock(cookie);
3142
3143 console_unlock();
3144
3145 if (!oops_in_progress)
3146 pr_flush(1000, true);
3147}
3148
3149/**
3150 * console_flush_on_panic - flush console content on panic
3151 * @mode: flush all messages in buffer or just the pending ones
3152 *
3153 * Immediately output all pending messages no matter what.
3154 */
3155void console_flush_on_panic(enum con_flush_mode mode)
3156{
3157 bool handover;
3158 u64 next_seq;
3159
3160 /*
3161 * Ignore the console lock and flush out the messages. Attempting a
3162 * trylock would not be useful because:
3163 *
3164 * - if it is contended, it must be ignored anyway
3165 * - console_lock() and console_trylock() block and fail
3166 * respectively in panic for non-panic CPUs
3167 * - semaphores are not NMI-safe
3168 */
3169
3170 /*
3171 * If another context is holding the console lock,
3172 * @console_may_schedule might be set. Clear it so that
3173 * this context does not call cond_resched() while flushing.
3174 */
3175 console_may_schedule = 0;
3176
3177 if (mode == CONSOLE_REPLAY_ALL) {
3178 struct console *c;
3179 short flags;
3180 int cookie;
3181 u64 seq;
3182
3183 seq = prb_first_valid_seq(prb);
3184
3185 cookie = console_srcu_read_lock();
3186 for_each_console_srcu(c) {
3187 flags = console_srcu_read_flags(c);
3188
3189 if (flags & CON_NBCON) {
3190 nbcon_seq_force(c, seq);
3191 } else {
3192 /*
3193 * This is an unsynchronized assignment. On
3194 * panic legacy consoles are only best effort.
3195 */
3196 c->seq = seq;
3197 }
3198 }
3199 console_srcu_read_unlock(cookie);
3200 }
3201
3202 console_flush_all(false, &next_seq, &handover);
3203}
3204
3205/*
3206 * Return the console tty driver structure and its associated index
3207 */
3208struct tty_driver *console_device(int *index)
3209{
3210 struct console *c;
3211 struct tty_driver *driver = NULL;
3212 int cookie;
3213
3214 /*
3215 * Take console_lock to serialize device() callback with
3216 * other console operations. For example, fg_console is
3217 * modified under console_lock when switching vt.
3218 */
3219 console_lock();
3220
3221 cookie = console_srcu_read_lock();
3222 for_each_console_srcu(c) {
3223 if (!c->device)
3224 continue;
3225 driver = c->device(c, index);
3226 if (driver)
3227 break;
3228 }
3229 console_srcu_read_unlock(cookie);
3230
3231 console_unlock();
3232 return driver;
3233}
3234
3235/*
3236 * Prevent further output on the passed console device so that (for example)
3237 * serial drivers can disable console output before suspending a port, and can
3238 * re-enable output afterwards.
3239 */
3240void console_stop(struct console *console)
3241{
3242 __pr_flush(console, 1000, true);
3243 console_list_lock();
3244 console_srcu_write_flags(console, console->flags & ~CON_ENABLED);
3245 console_list_unlock();
3246
3247 /*
3248 * Ensure that all SRCU list walks have completed. All contexts must
3249 * be able to see that this console is disabled so that (for example)
3250 * the caller can suspend the port without risk of another context
3251 * using the port.
3252 */
3253 synchronize_srcu(&console_srcu);
3254}
3255EXPORT_SYMBOL(console_stop);
3256
3257void console_start(struct console *console)
3258{
3259 console_list_lock();
3260 console_srcu_write_flags(console, console->flags | CON_ENABLED);
3261 console_list_unlock();
3262 __pr_flush(console, 1000, true);
3263}
3264EXPORT_SYMBOL(console_start);
3265
3266static int __read_mostly keep_bootcon;
3267
3268static int __init keep_bootcon_setup(char *str)
3269{
3270 keep_bootcon = 1;
3271 pr_info("debug: skip boot console de-registration.\n");
3272
3273 return 0;
3274}
3275
3276early_param("keep_bootcon", keep_bootcon_setup);
3277
3278static int console_call_setup(struct console *newcon, char *options)
3279{
3280 int err;
3281
3282 if (!newcon->setup)
3283 return 0;
3284
3285 /* Synchronize with possible boot console. */
3286 console_lock();
3287 err = newcon->setup(newcon, options);
3288 console_unlock();
3289
3290 return err;
3291}
3292
3293/*
3294 * This is called by register_console() to try to match
3295 * the newly registered console with any of the ones selected
3296 * by either the command line or add_preferred_console() and
3297 * setup/enable it.
3298 *
3299 * Care need to be taken with consoles that are statically
3300 * enabled such as netconsole
3301 */
3302static int try_enable_preferred_console(struct console *newcon,
3303 bool user_specified)
3304{
3305 struct console_cmdline *c;
3306 int i, err;
3307
3308 for (i = 0, c = console_cmdline;
3309 i < MAX_CMDLINECONSOLES && c->name[0];
3310 i++, c++) {
3311 if (c->user_specified != user_specified)
3312 continue;
3313 if (!newcon->match ||
3314 newcon->match(newcon, c->name, c->index, c->options) != 0) {
3315 /* default matching */
3316 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
3317 if (strcmp(c->name, newcon->name) != 0)
3318 continue;
3319 if (newcon->index >= 0 &&
3320 newcon->index != c->index)
3321 continue;
3322 if (newcon->index < 0)
3323 newcon->index = c->index;
3324
3325 if (_braille_register_console(newcon, c))
3326 return 0;
3327
3328 err = console_call_setup(newcon, c->options);
3329 if (err)
3330 return err;
3331 }
3332 newcon->flags |= CON_ENABLED;
3333 if (i == preferred_console)
3334 newcon->flags |= CON_CONSDEV;
3335 return 0;
3336 }
3337
3338 /*
3339 * Some consoles, such as pstore and netconsole, can be enabled even
3340 * without matching. Accept the pre-enabled consoles only when match()
3341 * and setup() had a chance to be called.
3342 */
3343 if (newcon->flags & CON_ENABLED && c->user_specified == user_specified)
3344 return 0;
3345
3346 return -ENOENT;
3347}
3348
3349/* Try to enable the console unconditionally */
3350static void try_enable_default_console(struct console *newcon)
3351{
3352 if (newcon->index < 0)
3353 newcon->index = 0;
3354
3355 if (console_call_setup(newcon, NULL) != 0)
3356 return;
3357
3358 newcon->flags |= CON_ENABLED;
3359
3360 if (newcon->device)
3361 newcon->flags |= CON_CONSDEV;
3362}
3363
3364static void console_init_seq(struct console *newcon, bool bootcon_registered)
3365{
3366 struct console *con;
3367 bool handover;
3368
3369 if (newcon->flags & (CON_PRINTBUFFER | CON_BOOT)) {
3370 /* Get a consistent copy of @syslog_seq. */
3371 mutex_lock(&syslog_lock);
3372 newcon->seq = syslog_seq;
3373 mutex_unlock(&syslog_lock);
3374 } else {
3375 /* Begin with next message added to ringbuffer. */
3376 newcon->seq = prb_next_seq(prb);
3377
3378 /*
3379 * If any enabled boot consoles are due to be unregistered
3380 * shortly, some may not be caught up and may be the same
3381 * device as @newcon. Since it is not known which boot console
3382 * is the same device, flush all consoles and, if necessary,
3383 * start with the message of the enabled boot console that is
3384 * the furthest behind.
3385 */
3386 if (bootcon_registered && !keep_bootcon) {
3387 /*
3388 * Hold the console_lock to stop console printing and
3389 * guarantee safe access to console->seq.
3390 */
3391 console_lock();
3392
3393 /*
3394 * Flush all consoles and set the console to start at
3395 * the next unprinted sequence number.
3396 */
3397 if (!console_flush_all(true, &newcon->seq, &handover)) {
3398 /*
3399 * Flushing failed. Just choose the lowest
3400 * sequence of the enabled boot consoles.
3401 */
3402
3403 /*
3404 * If there was a handover, this context no
3405 * longer holds the console_lock.
3406 */
3407 if (handover)
3408 console_lock();
3409
3410 newcon->seq = prb_next_seq(prb);
3411 for_each_console(con) {
3412 if ((con->flags & CON_BOOT) &&
3413 (con->flags & CON_ENABLED) &&
3414 con->seq < newcon->seq) {
3415 newcon->seq = con->seq;
3416 }
3417 }
3418 }
3419
3420 console_unlock();
3421 }
3422 }
3423}
3424
3425#define console_first() \
3426 hlist_entry(console_list.first, struct console, node)
3427
3428static int unregister_console_locked(struct console *console);
3429
3430/*
3431 * The console driver calls this routine during kernel initialization
3432 * to register the console printing procedure with printk() and to
3433 * print any messages that were printed by the kernel before the
3434 * console driver was initialized.
3435 *
3436 * This can happen pretty early during the boot process (because of
3437 * early_printk) - sometimes before setup_arch() completes - be careful
3438 * of what kernel features are used - they may not be initialised yet.
3439 *
3440 * There are two types of consoles - bootconsoles (early_printk) and
3441 * "real" consoles (everything which is not a bootconsole) which are
3442 * handled differently.
3443 * - Any number of bootconsoles can be registered at any time.
3444 * - As soon as a "real" console is registered, all bootconsoles
3445 * will be unregistered automatically.
3446 * - Once a "real" console is registered, any attempt to register a
3447 * bootconsoles will be rejected
3448 */
3449void register_console(struct console *newcon)
3450{
3451 struct console *con;
3452 bool bootcon_registered = false;
3453 bool realcon_registered = false;
3454 int err;
3455
3456 console_list_lock();
3457
3458 for_each_console(con) {
3459 if (WARN(con == newcon, "console '%s%d' already registered\n",
3460 con->name, con->index)) {
3461 goto unlock;
3462 }
3463
3464 if (con->flags & CON_BOOT)
3465 bootcon_registered = true;
3466 else
3467 realcon_registered = true;
3468 }
3469
3470 /* Do not register boot consoles when there already is a real one. */
3471 if ((newcon->flags & CON_BOOT) && realcon_registered) {
3472 pr_info("Too late to register bootconsole %s%d\n",
3473 newcon->name, newcon->index);
3474 goto unlock;
3475 }
3476
3477 if (newcon->flags & CON_NBCON) {
3478 /*
3479 * Ensure the nbcon console buffers can be allocated
3480 * before modifying any global data.
3481 */
3482 if (!nbcon_alloc(newcon))
3483 goto unlock;
3484 }
3485
3486 /*
3487 * See if we want to enable this console driver by default.
3488 *
3489 * Nope when a console is preferred by the command line, device
3490 * tree, or SPCR.
3491 *
3492 * The first real console with tty binding (driver) wins. More
3493 * consoles might get enabled before the right one is found.
3494 *
3495 * Note that a console with tty binding will have CON_CONSDEV
3496 * flag set and will be first in the list.
3497 */
3498 if (preferred_console < 0) {
3499 if (hlist_empty(&console_list) || !console_first()->device ||
3500 console_first()->flags & CON_BOOT) {
3501 try_enable_default_console(newcon);
3502 }
3503 }
3504
3505 /* See if this console matches one we selected on the command line */
3506 err = try_enable_preferred_console(newcon, true);
3507
3508 /* If not, try to match against the platform default(s) */
3509 if (err == -ENOENT)
3510 err = try_enable_preferred_console(newcon, false);
3511
3512 /* printk() messages are not printed to the Braille console. */
3513 if (err || newcon->flags & CON_BRL) {
3514 if (newcon->flags & CON_NBCON)
3515 nbcon_free(newcon);
3516 goto unlock;
3517 }
3518
3519 /*
3520 * If we have a bootconsole, and are switching to a real console,
3521 * don't print everything out again, since when the boot console, and
3522 * the real console are the same physical device, it's annoying to
3523 * see the beginning boot messages twice
3524 */
3525 if (bootcon_registered &&
3526 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
3527 newcon->flags &= ~CON_PRINTBUFFER;
3528 }
3529
3530 newcon->dropped = 0;
3531 console_init_seq(newcon, bootcon_registered);
3532
3533 if (newcon->flags & CON_NBCON)
3534 nbcon_init(newcon);
3535
3536 /*
3537 * Put this console in the list - keep the
3538 * preferred driver at the head of the list.
3539 */
3540 if (hlist_empty(&console_list)) {
3541 /* Ensure CON_CONSDEV is always set for the head. */
3542 newcon->flags |= CON_CONSDEV;
3543 hlist_add_head_rcu(&newcon->node, &console_list);
3544
3545 } else if (newcon->flags & CON_CONSDEV) {
3546 /* Only the new head can have CON_CONSDEV set. */
3547 console_srcu_write_flags(console_first(), console_first()->flags & ~CON_CONSDEV);
3548 hlist_add_head_rcu(&newcon->node, &console_list);
3549
3550 } else {
3551 hlist_add_behind_rcu(&newcon->node, console_list.first);
3552 }
3553
3554 /*
3555 * No need to synchronize SRCU here! The caller does not rely
3556 * on all contexts being able to see the new console before
3557 * register_console() completes.
3558 */
3559
3560 console_sysfs_notify();
3561
3562 /*
3563 * By unregistering the bootconsoles after we enable the real console
3564 * we get the "console xxx enabled" message on all the consoles -
3565 * boot consoles, real consoles, etc - this is to ensure that end
3566 * users know there might be something in the kernel's log buffer that
3567 * went to the bootconsole (that they do not see on the real console)
3568 */
3569 con_printk(KERN_INFO, newcon, "enabled\n");
3570 if (bootcon_registered &&
3571 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
3572 !keep_bootcon) {
3573 struct hlist_node *tmp;
3574
3575 hlist_for_each_entry_safe(con, tmp, &console_list, node) {
3576 if (con->flags & CON_BOOT)
3577 unregister_console_locked(con);
3578 }
3579 }
3580unlock:
3581 console_list_unlock();
3582}
3583EXPORT_SYMBOL(register_console);
3584
3585/* Must be called under console_list_lock(). */
3586static int unregister_console_locked(struct console *console)
3587{
3588 int res;
3589
3590 lockdep_assert_console_list_lock_held();
3591
3592 con_printk(KERN_INFO, console, "disabled\n");
3593
3594 res = _braille_unregister_console(console);
3595 if (res < 0)
3596 return res;
3597 if (res > 0)
3598 return 0;
3599
3600 /* Disable it unconditionally */
3601 console_srcu_write_flags(console, console->flags & ~CON_ENABLED);
3602
3603 if (!console_is_registered_locked(console))
3604 return -ENODEV;
3605
3606 hlist_del_init_rcu(&console->node);
3607
3608 /*
3609 * <HISTORICAL>
3610 * If this isn't the last console and it has CON_CONSDEV set, we
3611 * need to set it on the next preferred console.
3612 * </HISTORICAL>
3613 *
3614 * The above makes no sense as there is no guarantee that the next
3615 * console has any device attached. Oh well....
3616 */
3617 if (!hlist_empty(&console_list) && console->flags & CON_CONSDEV)
3618 console_srcu_write_flags(console_first(), console_first()->flags | CON_CONSDEV);
3619
3620 /*
3621 * Ensure that all SRCU list walks have completed. All contexts
3622 * must not be able to see this console in the list so that any
3623 * exit/cleanup routines can be performed safely.
3624 */
3625 synchronize_srcu(&console_srcu);
3626
3627 if (console->flags & CON_NBCON)
3628 nbcon_free(console);
3629
3630 console_sysfs_notify();
3631
3632 if (console->exit)
3633 res = console->exit(console);
3634
3635 return res;
3636}
3637
3638int unregister_console(struct console *console)
3639{
3640 int res;
3641
3642 console_list_lock();
3643 res = unregister_console_locked(console);
3644 console_list_unlock();
3645 return res;
3646}
3647EXPORT_SYMBOL(unregister_console);
3648
3649/**
3650 * console_force_preferred_locked - force a registered console preferred
3651 * @con: The registered console to force preferred.
3652 *
3653 * Must be called under console_list_lock().
3654 */
3655void console_force_preferred_locked(struct console *con)
3656{
3657 struct console *cur_pref_con;
3658
3659 if (!console_is_registered_locked(con))
3660 return;
3661
3662 cur_pref_con = console_first();
3663
3664 /* Already preferred? */
3665 if (cur_pref_con == con)
3666 return;
3667
3668 /*
3669 * Delete, but do not re-initialize the entry. This allows the console
3670 * to continue to appear registered (via any hlist_unhashed_lockless()
3671 * checks), even though it was briefly removed from the console list.
3672 */
3673 hlist_del_rcu(&con->node);
3674
3675 /*
3676 * Ensure that all SRCU list walks have completed so that the console
3677 * can be added to the beginning of the console list and its forward
3678 * list pointer can be re-initialized.
3679 */
3680 synchronize_srcu(&console_srcu);
3681
3682 con->flags |= CON_CONSDEV;
3683 WARN_ON(!con->device);
3684
3685 /* Only the new head can have CON_CONSDEV set. */
3686 console_srcu_write_flags(cur_pref_con, cur_pref_con->flags & ~CON_CONSDEV);
3687 hlist_add_head_rcu(&con->node, &console_list);
3688}
3689EXPORT_SYMBOL(console_force_preferred_locked);
3690
3691/*
3692 * Initialize the console device. This is called *early*, so
3693 * we can't necessarily depend on lots of kernel help here.
3694 * Just do some early initializations, and do the complex setup
3695 * later.
3696 */
3697void __init console_init(void)
3698{
3699 int ret;
3700 initcall_t call;
3701 initcall_entry_t *ce;
3702
3703 /* Setup the default TTY line discipline. */
3704 n_tty_init();
3705
3706 /*
3707 * set up the console device so that later boot sequences can
3708 * inform about problems etc..
3709 */
3710 ce = __con_initcall_start;
3711 trace_initcall_level("console");
3712 while (ce < __con_initcall_end) {
3713 call = initcall_from_entry(ce);
3714 trace_initcall_start(call);
3715 ret = call();
3716 trace_initcall_finish(call, ret);
3717 ce++;
3718 }
3719}
3720
3721/*
3722 * Some boot consoles access data that is in the init section and which will
3723 * be discarded after the initcalls have been run. To make sure that no code
3724 * will access this data, unregister the boot consoles in a late initcall.
3725 *
3726 * If for some reason, such as deferred probe or the driver being a loadable
3727 * module, the real console hasn't registered yet at this point, there will
3728 * be a brief interval in which no messages are logged to the console, which
3729 * makes it difficult to diagnose problems that occur during this time.
3730 *
3731 * To mitigate this problem somewhat, only unregister consoles whose memory
3732 * intersects with the init section. Note that all other boot consoles will
3733 * get unregistered when the real preferred console is registered.
3734 */
3735static int __init printk_late_init(void)
3736{
3737 struct hlist_node *tmp;
3738 struct console *con;
3739 int ret;
3740
3741 console_list_lock();
3742 hlist_for_each_entry_safe(con, tmp, &console_list, node) {
3743 if (!(con->flags & CON_BOOT))
3744 continue;
3745
3746 /* Check addresses that might be used for enabled consoles. */
3747 if (init_section_intersects(con, sizeof(*con)) ||
3748 init_section_contains(con->write, 0) ||
3749 init_section_contains(con->read, 0) ||
3750 init_section_contains(con->device, 0) ||
3751 init_section_contains(con->unblank, 0) ||
3752 init_section_contains(con->data, 0)) {
3753 /*
3754 * Please, consider moving the reported consoles out
3755 * of the init section.
3756 */
3757 pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n",
3758 con->name, con->index);
3759 unregister_console_locked(con);
3760 }
3761 }
3762 console_list_unlock();
3763
3764 ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL,
3765 console_cpu_notify);
3766 WARN_ON(ret < 0);
3767 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online",
3768 console_cpu_notify, NULL);
3769 WARN_ON(ret < 0);
3770 printk_sysctl_init();
3771 return 0;
3772}
3773late_initcall(printk_late_init);
3774
3775#if defined CONFIG_PRINTK
3776/* If @con is specified, only wait for that console. Otherwise wait for all. */
3777static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress)
3778{
3779 unsigned long timeout_jiffies = msecs_to_jiffies(timeout_ms);
3780 unsigned long remaining_jiffies = timeout_jiffies;
3781 struct console *c;
3782 u64 last_diff = 0;
3783 u64 printk_seq;
3784 short flags;
3785 int cookie;
3786 u64 diff;
3787 u64 seq;
3788
3789 might_sleep();
3790
3791 seq = prb_next_reserve_seq(prb);
3792
3793 /* Flush the consoles so that records up to @seq are printed. */
3794 console_lock();
3795 console_unlock();
3796
3797 for (;;) {
3798 unsigned long begin_jiffies;
3799 unsigned long slept_jiffies;
3800
3801 diff = 0;
3802
3803 /*
3804 * Hold the console_lock to guarantee safe access to
3805 * console->seq. Releasing console_lock flushes more
3806 * records in case @seq is still not printed on all
3807 * usable consoles.
3808 */
3809 console_lock();
3810
3811 cookie = console_srcu_read_lock();
3812 for_each_console_srcu(c) {
3813 if (con && con != c)
3814 continue;
3815
3816 flags = console_srcu_read_flags(c);
3817
3818 /*
3819 * If consoles are not usable, it cannot be expected
3820 * that they make forward progress, so only increment
3821 * @diff for usable consoles.
3822 */
3823 if (!console_is_usable(c))
3824 continue;
3825
3826 if (flags & CON_NBCON) {
3827 printk_seq = nbcon_seq_read(c);
3828 } else {
3829 printk_seq = c->seq;
3830 }
3831
3832 if (printk_seq < seq)
3833 diff += seq - printk_seq;
3834 }
3835 console_srcu_read_unlock(cookie);
3836
3837 if (diff != last_diff && reset_on_progress)
3838 remaining_jiffies = timeout_jiffies;
3839
3840 console_unlock();
3841
3842 /* Note: @diff is 0 if there are no usable consoles. */
3843 if (diff == 0 || remaining_jiffies == 0)
3844 break;
3845
3846 /* msleep(1) might sleep much longer. Check time by jiffies. */
3847 begin_jiffies = jiffies;
3848 msleep(1);
3849 slept_jiffies = jiffies - begin_jiffies;
3850
3851 remaining_jiffies -= min(slept_jiffies, remaining_jiffies);
3852
3853 last_diff = diff;
3854 }
3855
3856 return (diff == 0);
3857}
3858
3859/**
3860 * pr_flush() - Wait for printing threads to catch up.
3861 *
3862 * @timeout_ms: The maximum time (in ms) to wait.
3863 * @reset_on_progress: Reset the timeout if forward progress is seen.
3864 *
3865 * A value of 0 for @timeout_ms means no waiting will occur. A value of -1
3866 * represents infinite waiting.
3867 *
3868 * If @reset_on_progress is true, the timeout will be reset whenever any
3869 * printer has been seen to make some forward progress.
3870 *
3871 * Context: Process context. May sleep while acquiring console lock.
3872 * Return: true if all usable printers are caught up.
3873 */
3874static bool pr_flush(int timeout_ms, bool reset_on_progress)
3875{
3876 return __pr_flush(NULL, timeout_ms, reset_on_progress);
3877}
3878
3879/*
3880 * Delayed printk version, for scheduler-internal messages:
3881 */
3882#define PRINTK_PENDING_WAKEUP 0x01
3883#define PRINTK_PENDING_OUTPUT 0x02
3884
3885static DEFINE_PER_CPU(int, printk_pending);
3886
3887static void wake_up_klogd_work_func(struct irq_work *irq_work)
3888{
3889 int pending = this_cpu_xchg(printk_pending, 0);
3890
3891 if (pending & PRINTK_PENDING_OUTPUT) {
3892 /* If trylock fails, someone else is doing the printing */
3893 if (console_trylock())
3894 console_unlock();
3895 }
3896
3897 if (pending & PRINTK_PENDING_WAKEUP)
3898 wake_up_interruptible(&log_wait);
3899}
3900
3901static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) =
3902 IRQ_WORK_INIT_LAZY(wake_up_klogd_work_func);
3903
3904static void __wake_up_klogd(int val)
3905{
3906 if (!printk_percpu_data_ready())
3907 return;
3908
3909 preempt_disable();
3910 /*
3911 * Guarantee any new records can be seen by tasks preparing to wait
3912 * before this context checks if the wait queue is empty.
3913 *
3914 * The full memory barrier within wq_has_sleeper() pairs with the full
3915 * memory barrier within set_current_state() of
3916 * prepare_to_wait_event(), which is called after ___wait_event() adds
3917 * the waiter but before it has checked the wait condition.
3918 *
3919 * This pairs with devkmsg_read:A and syslog_print:A.
3920 */
3921 if (wq_has_sleeper(&log_wait) || /* LMM(__wake_up_klogd:A) */
3922 (val & PRINTK_PENDING_OUTPUT)) {
3923 this_cpu_or(printk_pending, val);
3924 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
3925 }
3926 preempt_enable();
3927}
3928
3929/**
3930 * wake_up_klogd - Wake kernel logging daemon
3931 *
3932 * Use this function when new records have been added to the ringbuffer
3933 * and the console printing of those records has already occurred or is
3934 * known to be handled by some other context. This function will only
3935 * wake the logging daemon.
3936 *
3937 * Context: Any context.
3938 */
3939void wake_up_klogd(void)
3940{
3941 __wake_up_klogd(PRINTK_PENDING_WAKEUP);
3942}
3943
3944/**
3945 * defer_console_output - Wake kernel logging daemon and trigger
3946 * console printing in a deferred context
3947 *
3948 * Use this function when new records have been added to the ringbuffer,
3949 * this context is responsible for console printing those records, but
3950 * the current context is not allowed to perform the console printing.
3951 * Trigger an irq_work context to perform the console printing. This
3952 * function also wakes the logging daemon.
3953 *
3954 * Context: Any context.
3955 */
3956void defer_console_output(void)
3957{
3958 /*
3959 * New messages may have been added directly to the ringbuffer
3960 * using vprintk_store(), so wake any waiters as well.
3961 */
3962 __wake_up_klogd(PRINTK_PENDING_WAKEUP | PRINTK_PENDING_OUTPUT);
3963}
3964
3965void printk_trigger_flush(void)
3966{
3967 defer_console_output();
3968}
3969
3970int vprintk_deferred(const char *fmt, va_list args)
3971{
3972 return vprintk_emit(0, LOGLEVEL_SCHED, NULL, fmt, args);
3973}
3974
3975int _printk_deferred(const char *fmt, ...)
3976{
3977 va_list args;
3978 int r;
3979
3980 va_start(args, fmt);
3981 r = vprintk_deferred(fmt, args);
3982 va_end(args);
3983
3984 return r;
3985}
3986
3987/*
3988 * printk rate limiting, lifted from the networking subsystem.
3989 *
3990 * This enforces a rate limit: not more than 10 kernel messages
3991 * every 5s to make a denial-of-service attack impossible.
3992 */
3993DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
3994
3995int __printk_ratelimit(const char *func)
3996{
3997 return ___ratelimit(&printk_ratelimit_state, func);
3998}
3999EXPORT_SYMBOL(__printk_ratelimit);
4000
4001/**
4002 * printk_timed_ratelimit - caller-controlled printk ratelimiting
4003 * @caller_jiffies: pointer to caller's state
4004 * @interval_msecs: minimum interval between prints
4005 *
4006 * printk_timed_ratelimit() returns true if more than @interval_msecs
4007 * milliseconds have elapsed since the last time printk_timed_ratelimit()
4008 * returned true.
4009 */
4010bool printk_timed_ratelimit(unsigned long *caller_jiffies,
4011 unsigned int interval_msecs)
4012{
4013 unsigned long elapsed = jiffies - *caller_jiffies;
4014
4015 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
4016 return false;
4017
4018 *caller_jiffies = jiffies;
4019 return true;
4020}
4021EXPORT_SYMBOL(printk_timed_ratelimit);
4022
4023static DEFINE_SPINLOCK(dump_list_lock);
4024static LIST_HEAD(dump_list);
4025
4026/**
4027 * kmsg_dump_register - register a kernel log dumper.
4028 * @dumper: pointer to the kmsg_dumper structure
4029 *
4030 * Adds a kernel log dumper to the system. The dump callback in the
4031 * structure will be called when the kernel oopses or panics and must be
4032 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
4033 */
4034int kmsg_dump_register(struct kmsg_dumper *dumper)
4035{
4036 unsigned long flags;
4037 int err = -EBUSY;
4038
4039 /* The dump callback needs to be set */
4040 if (!dumper->dump)
4041 return -EINVAL;
4042
4043 spin_lock_irqsave(&dump_list_lock, flags);
4044 /* Don't allow registering multiple times */
4045 if (!dumper->registered) {
4046 dumper->registered = 1;
4047 list_add_tail_rcu(&dumper->list, &dump_list);
4048 err = 0;
4049 }
4050 spin_unlock_irqrestore(&dump_list_lock, flags);
4051
4052 return err;
4053}
4054EXPORT_SYMBOL_GPL(kmsg_dump_register);
4055
4056/**
4057 * kmsg_dump_unregister - unregister a kmsg dumper.
4058 * @dumper: pointer to the kmsg_dumper structure
4059 *
4060 * Removes a dump device from the system. Returns zero on success and
4061 * %-EINVAL otherwise.
4062 */
4063int kmsg_dump_unregister(struct kmsg_dumper *dumper)
4064{
4065 unsigned long flags;
4066 int err = -EINVAL;
4067
4068 spin_lock_irqsave(&dump_list_lock, flags);
4069 if (dumper->registered) {
4070 dumper->registered = 0;
4071 list_del_rcu(&dumper->list);
4072 err = 0;
4073 }
4074 spin_unlock_irqrestore(&dump_list_lock, flags);
4075 synchronize_rcu();
4076
4077 return err;
4078}
4079EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
4080
4081static bool always_kmsg_dump;
4082module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
4083
4084const char *kmsg_dump_reason_str(enum kmsg_dump_reason reason)
4085{
4086 switch (reason) {
4087 case KMSG_DUMP_PANIC:
4088 return "Panic";
4089 case KMSG_DUMP_OOPS:
4090 return "Oops";
4091 case KMSG_DUMP_EMERG:
4092 return "Emergency";
4093 case KMSG_DUMP_SHUTDOWN:
4094 return "Shutdown";
4095 default:
4096 return "Unknown";
4097 }
4098}
4099EXPORT_SYMBOL_GPL(kmsg_dump_reason_str);
4100
4101/**
4102 * kmsg_dump - dump kernel log to kernel message dumpers.
4103 * @reason: the reason (oops, panic etc) for dumping
4104 *
4105 * Call each of the registered dumper's dump() callback, which can
4106 * retrieve the kmsg records with kmsg_dump_get_line() or
4107 * kmsg_dump_get_buffer().
4108 */
4109void kmsg_dump(enum kmsg_dump_reason reason)
4110{
4111 struct kmsg_dumper *dumper;
4112
4113 rcu_read_lock();
4114 list_for_each_entry_rcu(dumper, &dump_list, list) {
4115 enum kmsg_dump_reason max_reason = dumper->max_reason;
4116
4117 /*
4118 * If client has not provided a specific max_reason, default
4119 * to KMSG_DUMP_OOPS, unless always_kmsg_dump was set.
4120 */
4121 if (max_reason == KMSG_DUMP_UNDEF) {
4122 max_reason = always_kmsg_dump ? KMSG_DUMP_MAX :
4123 KMSG_DUMP_OOPS;
4124 }
4125 if (reason > max_reason)
4126 continue;
4127
4128 /* invoke dumper which will iterate over records */
4129 dumper->dump(dumper, reason);
4130 }
4131 rcu_read_unlock();
4132}
4133
4134/**
4135 * kmsg_dump_get_line - retrieve one kmsg log line
4136 * @iter: kmsg dump iterator
4137 * @syslog: include the "<4>" prefixes
4138 * @line: buffer to copy the line to
4139 * @size: maximum size of the buffer
4140 * @len: length of line placed into buffer
4141 *
4142 * Start at the beginning of the kmsg buffer, with the oldest kmsg
4143 * record, and copy one record into the provided buffer.
4144 *
4145 * Consecutive calls will return the next available record moving
4146 * towards the end of the buffer with the youngest messages.
4147 *
4148 * A return value of FALSE indicates that there are no more records to
4149 * read.
4150 */
4151bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
4152 char *line, size_t size, size_t *len)
4153{
4154 u64 min_seq = latched_seq_read_nolock(&clear_seq);
4155 struct printk_info info;
4156 unsigned int line_count;
4157 struct printk_record r;
4158 size_t l = 0;
4159 bool ret = false;
4160
4161 if (iter->cur_seq < min_seq)
4162 iter->cur_seq = min_seq;
4163
4164 prb_rec_init_rd(&r, &info, line, size);
4165
4166 /* Read text or count text lines? */
4167 if (line) {
4168 if (!prb_read_valid(prb, iter->cur_seq, &r))
4169 goto out;
4170 l = record_print_text(&r, syslog, printk_time);
4171 } else {
4172 if (!prb_read_valid_info(prb, iter->cur_seq,
4173 &info, &line_count)) {
4174 goto out;
4175 }
4176 l = get_record_print_text_size(&info, line_count, syslog,
4177 printk_time);
4178
4179 }
4180
4181 iter->cur_seq = r.info->seq + 1;
4182 ret = true;
4183out:
4184 if (len)
4185 *len = l;
4186 return ret;
4187}
4188EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
4189
4190/**
4191 * kmsg_dump_get_buffer - copy kmsg log lines
4192 * @iter: kmsg dump iterator
4193 * @syslog: include the "<4>" prefixes
4194 * @buf: buffer to copy the line to
4195 * @size: maximum size of the buffer
4196 * @len_out: length of line placed into buffer
4197 *
4198 * Start at the end of the kmsg buffer and fill the provided buffer
4199 * with as many of the *youngest* kmsg records that fit into it.
4200 * If the buffer is large enough, all available kmsg records will be
4201 * copied with a single call.
4202 *
4203 * Consecutive calls will fill the buffer with the next block of
4204 * available older records, not including the earlier retrieved ones.
4205 *
4206 * A return value of FALSE indicates that there are no more records to
4207 * read.
4208 */
4209bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
4210 char *buf, size_t size, size_t *len_out)
4211{
4212 u64 min_seq = latched_seq_read_nolock(&clear_seq);
4213 struct printk_info info;
4214 struct printk_record r;
4215 u64 seq;
4216 u64 next_seq;
4217 size_t len = 0;
4218 bool ret = false;
4219 bool time = printk_time;
4220
4221 if (!buf || !size)
4222 goto out;
4223
4224 if (iter->cur_seq < min_seq)
4225 iter->cur_seq = min_seq;
4226
4227 if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) {
4228 if (info.seq != iter->cur_seq) {
4229 /* messages are gone, move to first available one */
4230 iter->cur_seq = info.seq;
4231 }
4232 }
4233
4234 /* last entry */
4235 if (iter->cur_seq >= iter->next_seq)
4236 goto out;
4237
4238 /*
4239 * Find first record that fits, including all following records,
4240 * into the user-provided buffer for this dump. Pass in size-1
4241 * because this function (by way of record_print_text()) will
4242 * not write more than size-1 bytes of text into @buf.
4243 */
4244 seq = find_first_fitting_seq(iter->cur_seq, iter->next_seq,
4245 size - 1, syslog, time);
4246
4247 /*
4248 * Next kmsg_dump_get_buffer() invocation will dump block of
4249 * older records stored right before this one.
4250 */
4251 next_seq = seq;
4252
4253 prb_rec_init_rd(&r, &info, buf, size);
4254
4255 prb_for_each_record(seq, prb, seq, &r) {
4256 if (r.info->seq >= iter->next_seq)
4257 break;
4258
4259 len += record_print_text(&r, syslog, time);
4260
4261 /* Adjust record to store to remaining buffer space. */
4262 prb_rec_init_rd(&r, &info, buf + len, size - len);
4263 }
4264
4265 iter->next_seq = next_seq;
4266 ret = true;
4267out:
4268 if (len_out)
4269 *len_out = len;
4270 return ret;
4271}
4272EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
4273
4274/**
4275 * kmsg_dump_rewind - reset the iterator
4276 * @iter: kmsg dump iterator
4277 *
4278 * Reset the dumper's iterator so that kmsg_dump_get_line() and
4279 * kmsg_dump_get_buffer() can be called again and used multiple
4280 * times within the same dumper.dump() callback.
4281 */
4282void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
4283{
4284 iter->cur_seq = latched_seq_read_nolock(&clear_seq);
4285 iter->next_seq = prb_next_seq(prb);
4286}
4287EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
4288
4289#endif
4290
4291#ifdef CONFIG_SMP
4292static atomic_t printk_cpu_sync_owner = ATOMIC_INIT(-1);
4293static atomic_t printk_cpu_sync_nested = ATOMIC_INIT(0);
4294
4295/**
4296 * __printk_cpu_sync_wait() - Busy wait until the printk cpu-reentrant
4297 * spinning lock is not owned by any CPU.
4298 *
4299 * Context: Any context.
4300 */
4301void __printk_cpu_sync_wait(void)
4302{
4303 do {
4304 cpu_relax();
4305 } while (atomic_read(&printk_cpu_sync_owner) != -1);
4306}
4307EXPORT_SYMBOL(__printk_cpu_sync_wait);
4308
4309/**
4310 * __printk_cpu_sync_try_get() - Try to acquire the printk cpu-reentrant
4311 * spinning lock.
4312 *
4313 * If no processor has the lock, the calling processor takes the lock and
4314 * becomes the owner. If the calling processor is already the owner of the
4315 * lock, this function succeeds immediately.
4316 *
4317 * Context: Any context. Expects interrupts to be disabled.
4318 * Return: 1 on success, otherwise 0.
4319 */
4320int __printk_cpu_sync_try_get(void)
4321{
4322 int cpu;
4323 int old;
4324
4325 cpu = smp_processor_id();
4326
4327 /*
4328 * Guarantee loads and stores from this CPU when it is the lock owner
4329 * are _not_ visible to the previous lock owner. This pairs with
4330 * __printk_cpu_sync_put:B.
4331 *
4332 * Memory barrier involvement:
4333 *
4334 * If __printk_cpu_sync_try_get:A reads from __printk_cpu_sync_put:B,
4335 * then __printk_cpu_sync_put:A can never read from
4336 * __printk_cpu_sync_try_get:B.
4337 *
4338 * Relies on:
4339 *
4340 * RELEASE from __printk_cpu_sync_put:A to __printk_cpu_sync_put:B
4341 * of the previous CPU
4342 * matching
4343 * ACQUIRE from __printk_cpu_sync_try_get:A to
4344 * __printk_cpu_sync_try_get:B of this CPU
4345 */
4346 old = atomic_cmpxchg_acquire(&printk_cpu_sync_owner, -1,
4347 cpu); /* LMM(__printk_cpu_sync_try_get:A) */
4348 if (old == -1) {
4349 /*
4350 * This CPU is now the owner and begins loading/storing
4351 * data: LMM(__printk_cpu_sync_try_get:B)
4352 */
4353 return 1;
4354
4355 } else if (old == cpu) {
4356 /* This CPU is already the owner. */
4357 atomic_inc(&printk_cpu_sync_nested);
4358 return 1;
4359 }
4360
4361 return 0;
4362}
4363EXPORT_SYMBOL(__printk_cpu_sync_try_get);
4364
4365/**
4366 * __printk_cpu_sync_put() - Release the printk cpu-reentrant spinning lock.
4367 *
4368 * The calling processor must be the owner of the lock.
4369 *
4370 * Context: Any context. Expects interrupts to be disabled.
4371 */
4372void __printk_cpu_sync_put(void)
4373{
4374 if (atomic_read(&printk_cpu_sync_nested)) {
4375 atomic_dec(&printk_cpu_sync_nested);
4376 return;
4377 }
4378
4379 /*
4380 * This CPU is finished loading/storing data:
4381 * LMM(__printk_cpu_sync_put:A)
4382 */
4383
4384 /*
4385 * Guarantee loads and stores from this CPU when it was the
4386 * lock owner are visible to the next lock owner. This pairs
4387 * with __printk_cpu_sync_try_get:A.
4388 *
4389 * Memory barrier involvement:
4390 *
4391 * If __printk_cpu_sync_try_get:A reads from __printk_cpu_sync_put:B,
4392 * then __printk_cpu_sync_try_get:B reads from __printk_cpu_sync_put:A.
4393 *
4394 * Relies on:
4395 *
4396 * RELEASE from __printk_cpu_sync_put:A to __printk_cpu_sync_put:B
4397 * of this CPU
4398 * matching
4399 * ACQUIRE from __printk_cpu_sync_try_get:A to
4400 * __printk_cpu_sync_try_get:B of the next CPU
4401 */
4402 atomic_set_release(&printk_cpu_sync_owner,
4403 -1); /* LMM(__printk_cpu_sync_put:B) */
4404}
4405EXPORT_SYMBOL(__printk_cpu_sync_put);
4406#endif /* CONFIG_SMP */