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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/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
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_mutex protects console_list updates and console->flags updates.
83 * The flags are synchronized only for consoles that are registered, i.e.
84 * accessible via the console list.
85 */
86static DEFINE_MUTEX(console_mutex);
87
88/*
89 * console_sem protects updates to console->seq and console_suspended,
90 * and also provides serialization for console printing.
91 */
92static DEFINE_SEMAPHORE(console_sem);
93HLIST_HEAD(console_list);
94EXPORT_SYMBOL_GPL(console_list);
95DEFINE_STATIC_SRCU(console_srcu);
96
97/*
98 * System may need to suppress printk message under certain
99 * circumstances, like after kernel panic happens.
100 */
101int __read_mostly suppress_printk;
102
103/*
104 * During panic, heavy printk by other CPUs can delay the
105 * panic and risk deadlock on console resources.
106 */
107static int __read_mostly suppress_panic_printk;
108
109#ifdef CONFIG_LOCKDEP
110static struct lockdep_map console_lock_dep_map = {
111 .name = "console_lock"
112};
113
114void lockdep_assert_console_list_lock_held(void)
115{
116 lockdep_assert_held(&console_mutex);
117}
118EXPORT_SYMBOL(lockdep_assert_console_list_lock_held);
119#endif
120
121#ifdef CONFIG_DEBUG_LOCK_ALLOC
122bool console_srcu_read_lock_is_held(void)
123{
124 return srcu_read_lock_held(&console_srcu);
125}
126EXPORT_SYMBOL(console_srcu_read_lock_is_held);
127#endif
128
129enum devkmsg_log_bits {
130 __DEVKMSG_LOG_BIT_ON = 0,
131 __DEVKMSG_LOG_BIT_OFF,
132 __DEVKMSG_LOG_BIT_LOCK,
133};
134
135enum devkmsg_log_masks {
136 DEVKMSG_LOG_MASK_ON = BIT(__DEVKMSG_LOG_BIT_ON),
137 DEVKMSG_LOG_MASK_OFF = BIT(__DEVKMSG_LOG_BIT_OFF),
138 DEVKMSG_LOG_MASK_LOCK = BIT(__DEVKMSG_LOG_BIT_LOCK),
139};
140
141/* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
142#define DEVKMSG_LOG_MASK_DEFAULT 0
143
144static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
145
146static int __control_devkmsg(char *str)
147{
148 size_t len;
149
150 if (!str)
151 return -EINVAL;
152
153 len = str_has_prefix(str, "on");
154 if (len) {
155 devkmsg_log = DEVKMSG_LOG_MASK_ON;
156 return len;
157 }
158
159 len = str_has_prefix(str, "off");
160 if (len) {
161 devkmsg_log = DEVKMSG_LOG_MASK_OFF;
162 return len;
163 }
164
165 len = str_has_prefix(str, "ratelimit");
166 if (len) {
167 devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
168 return len;
169 }
170
171 return -EINVAL;
172}
173
174static int __init control_devkmsg(char *str)
175{
176 if (__control_devkmsg(str) < 0) {
177 pr_warn("printk.devkmsg: bad option string '%s'\n", str);
178 return 1;
179 }
180
181 /*
182 * Set sysctl string accordingly:
183 */
184 if (devkmsg_log == DEVKMSG_LOG_MASK_ON)
185 strcpy(devkmsg_log_str, "on");
186 else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF)
187 strcpy(devkmsg_log_str, "off");
188 /* else "ratelimit" which is set by default. */
189
190 /*
191 * Sysctl cannot change it anymore. The kernel command line setting of
192 * this parameter is to force the setting to be permanent throughout the
193 * runtime of the system. This is a precation measure against userspace
194 * trying to be a smarta** and attempting to change it up on us.
195 */
196 devkmsg_log |= DEVKMSG_LOG_MASK_LOCK;
197
198 return 1;
199}
200__setup("printk.devkmsg=", control_devkmsg);
201
202char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit";
203#if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL)
204int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
205 void *buffer, size_t *lenp, loff_t *ppos)
206{
207 char old_str[DEVKMSG_STR_MAX_SIZE];
208 unsigned int old;
209 int err;
210
211 if (write) {
212 if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK)
213 return -EINVAL;
214
215 old = devkmsg_log;
216 strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE);
217 }
218
219 err = proc_dostring(table, write, buffer, lenp, ppos);
220 if (err)
221 return err;
222
223 if (write) {
224 err = __control_devkmsg(devkmsg_log_str);
225
226 /*
227 * Do not accept an unknown string OR a known string with
228 * trailing crap...
229 */
230 if (err < 0 || (err + 1 != *lenp)) {
231
232 /* ... and restore old setting. */
233 devkmsg_log = old;
234 strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE);
235
236 return -EINVAL;
237 }
238 }
239
240 return 0;
241}
242#endif /* CONFIG_PRINTK && CONFIG_SYSCTL */
243
244/**
245 * console_list_lock - Lock the console list
246 *
247 * For console list or console->flags updates
248 */
249void console_list_lock(void)
250{
251 /*
252 * In unregister_console() and console_force_preferred_locked(),
253 * synchronize_srcu() is called with the console_list_lock held.
254 * Therefore it is not allowed that the console_list_lock is taken
255 * with the srcu_lock held.
256 *
257 * Detecting if this context is really in the read-side critical
258 * section is only possible if the appropriate debug options are
259 * enabled.
260 */
261 WARN_ON_ONCE(debug_lockdep_rcu_enabled() &&
262 srcu_read_lock_held(&console_srcu));
263
264 mutex_lock(&console_mutex);
265}
266EXPORT_SYMBOL(console_list_lock);
267
268/**
269 * console_list_unlock - Unlock the console list
270 *
271 * Counterpart to console_list_lock()
272 */
273void console_list_unlock(void)
274{
275 mutex_unlock(&console_mutex);
276}
277EXPORT_SYMBOL(console_list_unlock);
278
279/**
280 * console_srcu_read_lock - Register a new reader for the
281 * SRCU-protected console list
282 *
283 * Use for_each_console_srcu() to iterate the console list
284 *
285 * Context: Any context.
286 * Return: A cookie to pass to console_srcu_read_unlock().
287 */
288int console_srcu_read_lock(void)
289{
290 return srcu_read_lock_nmisafe(&console_srcu);
291}
292EXPORT_SYMBOL(console_srcu_read_lock);
293
294/**
295 * console_srcu_read_unlock - Unregister an old reader from
296 * the SRCU-protected console list
297 * @cookie: cookie returned from console_srcu_read_lock()
298 *
299 * Counterpart to console_srcu_read_lock()
300 */
301void console_srcu_read_unlock(int cookie)
302{
303 srcu_read_unlock_nmisafe(&console_srcu, cookie);
304}
305EXPORT_SYMBOL(console_srcu_read_unlock);
306
307/*
308 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
309 * macros instead of functions so that _RET_IP_ contains useful information.
310 */
311#define down_console_sem() do { \
312 down(&console_sem);\
313 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
314} while (0)
315
316static int __down_trylock_console_sem(unsigned long ip)
317{
318 int lock_failed;
319 unsigned long flags;
320
321 /*
322 * Here and in __up_console_sem() we need to be in safe mode,
323 * because spindump/WARN/etc from under console ->lock will
324 * deadlock in printk()->down_trylock_console_sem() otherwise.
325 */
326 printk_safe_enter_irqsave(flags);
327 lock_failed = down_trylock(&console_sem);
328 printk_safe_exit_irqrestore(flags);
329
330 if (lock_failed)
331 return 1;
332 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
333 return 0;
334}
335#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
336
337static void __up_console_sem(unsigned long ip)
338{
339 unsigned long flags;
340
341 mutex_release(&console_lock_dep_map, ip);
342
343 printk_safe_enter_irqsave(flags);
344 up(&console_sem);
345 printk_safe_exit_irqrestore(flags);
346}
347#define up_console_sem() __up_console_sem(_RET_IP_)
348
349static bool panic_in_progress(void)
350{
351 return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID);
352}
353
354/*
355 * This is used for debugging the mess that is the VT code by
356 * keeping track if we have the console semaphore held. It's
357 * definitely not the perfect debug tool (we don't know if _WE_
358 * hold it and are racing, but it helps tracking those weird code
359 * paths in the console code where we end up in places I want
360 * locked without the console semaphore held).
361 */
362static int console_locked, console_suspended;
363
364/*
365 * Array of consoles built from command line options (console=)
366 */
367
368#define MAX_CMDLINECONSOLES 8
369
370static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
371
372static int preferred_console = -1;
373int console_set_on_cmdline;
374EXPORT_SYMBOL(console_set_on_cmdline);
375
376/* Flag: console code may call schedule() */
377static int console_may_schedule;
378
379enum con_msg_format_flags {
380 MSG_FORMAT_DEFAULT = 0,
381 MSG_FORMAT_SYSLOG = (1 << 0),
382};
383
384static int console_msg_format = MSG_FORMAT_DEFAULT;
385
386/*
387 * The printk log buffer consists of a sequenced collection of records, each
388 * containing variable length message text. Every record also contains its
389 * own meta-data (@info).
390 *
391 * Every record meta-data carries the timestamp in microseconds, as well as
392 * the standard userspace syslog level and syslog facility. The usual kernel
393 * messages use LOG_KERN; userspace-injected messages always carry a matching
394 * syslog facility, by default LOG_USER. The origin of every message can be
395 * reliably determined that way.
396 *
397 * The human readable log message of a record is available in @text, the
398 * length of the message text in @text_len. The stored message is not
399 * terminated.
400 *
401 * Optionally, a record can carry a dictionary of properties (key/value
402 * pairs), to provide userspace with a machine-readable message context.
403 *
404 * Examples for well-defined, commonly used property names are:
405 * DEVICE=b12:8 device identifier
406 * b12:8 block dev_t
407 * c127:3 char dev_t
408 * n8 netdev ifindex
409 * +sound:card0 subsystem:devname
410 * SUBSYSTEM=pci driver-core subsystem name
411 *
412 * Valid characters in property names are [a-zA-Z0-9.-_]. Property names
413 * and values are terminated by a '\0' character.
414 *
415 * Example of record values:
416 * record.text_buf = "it's a line" (unterminated)
417 * record.info.seq = 56
418 * record.info.ts_nsec = 36863
419 * record.info.text_len = 11
420 * record.info.facility = 0 (LOG_KERN)
421 * record.info.flags = 0
422 * record.info.level = 3 (LOG_ERR)
423 * record.info.caller_id = 299 (task 299)
424 * record.info.dev_info.subsystem = "pci" (terminated)
425 * record.info.dev_info.device = "+pci:0000:00:01.0" (terminated)
426 *
427 * The 'struct printk_info' buffer must never be directly exported to
428 * userspace, it is a kernel-private implementation detail that might
429 * need to be changed in the future, when the requirements change.
430 *
431 * /dev/kmsg exports the structured data in the following line format:
432 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
433 *
434 * Users of the export format should ignore possible additional values
435 * separated by ',', and find the message after the ';' character.
436 *
437 * The optional key/value pairs are attached as continuation lines starting
438 * with a space character and terminated by a newline. All possible
439 * non-prinatable characters are escaped in the "\xff" notation.
440 */
441
442/* syslog_lock protects syslog_* variables and write access to clear_seq. */
443static DEFINE_MUTEX(syslog_lock);
444
445#ifdef CONFIG_PRINTK
446DECLARE_WAIT_QUEUE_HEAD(log_wait);
447/* All 3 protected by @syslog_lock. */
448/* the next printk record to read by syslog(READ) or /proc/kmsg */
449static u64 syslog_seq;
450static size_t syslog_partial;
451static bool syslog_time;
452
453struct latched_seq {
454 seqcount_latch_t latch;
455 u64 val[2];
456};
457
458/*
459 * The next printk record to read after the last 'clear' command. There are
460 * two copies (updated with seqcount_latch) so that reads can locklessly
461 * access a valid value. Writers are synchronized by @syslog_lock.
462 */
463static struct latched_seq clear_seq = {
464 .latch = SEQCNT_LATCH_ZERO(clear_seq.latch),
465 .val[0] = 0,
466 .val[1] = 0,
467};
468
469#ifdef CONFIG_PRINTK_CALLER
470#define PREFIX_MAX 48
471#else
472#define PREFIX_MAX 32
473#endif
474
475/* the maximum size of a formatted record (i.e. with prefix added per line) */
476#define CONSOLE_LOG_MAX 1024
477
478/* the maximum size for a dropped text message */
479#define DROPPED_TEXT_MAX 64
480
481/* the maximum size allowed to be reserved for a record */
482#define LOG_LINE_MAX (CONSOLE_LOG_MAX - PREFIX_MAX)
483
484#define LOG_LEVEL(v) ((v) & 0x07)
485#define LOG_FACILITY(v) ((v) >> 3 & 0xff)
486
487/* record buffer */
488#define LOG_ALIGN __alignof__(unsigned long)
489#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
490#define LOG_BUF_LEN_MAX (u32)(1 << 31)
491static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
492static char *log_buf = __log_buf;
493static u32 log_buf_len = __LOG_BUF_LEN;
494
495/*
496 * Define the average message size. This only affects the number of
497 * descriptors that will be available. Underestimating is better than
498 * overestimating (too many available descriptors is better than not enough).
499 */
500#define PRB_AVGBITS 5 /* 32 character average length */
501
502#if CONFIG_LOG_BUF_SHIFT <= PRB_AVGBITS
503#error CONFIG_LOG_BUF_SHIFT value too small.
504#endif
505_DEFINE_PRINTKRB(printk_rb_static, CONFIG_LOG_BUF_SHIFT - PRB_AVGBITS,
506 PRB_AVGBITS, &__log_buf[0]);
507
508static struct printk_ringbuffer printk_rb_dynamic;
509
510static struct printk_ringbuffer *prb = &printk_rb_static;
511
512/*
513 * We cannot access per-CPU data (e.g. per-CPU flush irq_work) before
514 * per_cpu_areas are initialised. This variable is set to true when
515 * it's safe to access per-CPU data.
516 */
517static bool __printk_percpu_data_ready __ro_after_init;
518
519bool printk_percpu_data_ready(void)
520{
521 return __printk_percpu_data_ready;
522}
523
524/* Must be called under syslog_lock. */
525static void latched_seq_write(struct latched_seq *ls, u64 val)
526{
527 raw_write_seqcount_latch(&ls->latch);
528 ls->val[0] = val;
529 raw_write_seqcount_latch(&ls->latch);
530 ls->val[1] = val;
531}
532
533/* Can be called from any context. */
534static u64 latched_seq_read_nolock(struct latched_seq *ls)
535{
536 unsigned int seq;
537 unsigned int idx;
538 u64 val;
539
540 do {
541 seq = raw_read_seqcount_latch(&ls->latch);
542 idx = seq & 0x1;
543 val = ls->val[idx];
544 } while (read_seqcount_latch_retry(&ls->latch, seq));
545
546 return val;
547}
548
549/* Return log buffer address */
550char *log_buf_addr_get(void)
551{
552 return log_buf;
553}
554
555/* Return log buffer size */
556u32 log_buf_len_get(void)
557{
558 return log_buf_len;
559}
560
561/*
562 * Define how much of the log buffer we could take at maximum. The value
563 * must be greater than two. Note that only half of the buffer is available
564 * when the index points to the middle.
565 */
566#define MAX_LOG_TAKE_PART 4
567static const char trunc_msg[] = "<truncated>";
568
569static void truncate_msg(u16 *text_len, u16 *trunc_msg_len)
570{
571 /*
572 * The message should not take the whole buffer. Otherwise, it might
573 * get removed too soon.
574 */
575 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
576
577 if (*text_len > max_text_len)
578 *text_len = max_text_len;
579
580 /* enable the warning message (if there is room) */
581 *trunc_msg_len = strlen(trunc_msg);
582 if (*text_len >= *trunc_msg_len)
583 *text_len -= *trunc_msg_len;
584 else
585 *trunc_msg_len = 0;
586}
587
588int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
589
590static int syslog_action_restricted(int type)
591{
592 if (dmesg_restrict)
593 return 1;
594 /*
595 * Unless restricted, we allow "read all" and "get buffer size"
596 * for everybody.
597 */
598 return type != SYSLOG_ACTION_READ_ALL &&
599 type != SYSLOG_ACTION_SIZE_BUFFER;
600}
601
602static int check_syslog_permissions(int type, int source)
603{
604 /*
605 * If this is from /proc/kmsg and we've already opened it, then we've
606 * already done the capabilities checks at open time.
607 */
608 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
609 goto ok;
610
611 if (syslog_action_restricted(type)) {
612 if (capable(CAP_SYSLOG))
613 goto ok;
614 /*
615 * For historical reasons, accept CAP_SYS_ADMIN too, with
616 * a warning.
617 */
618 if (capable(CAP_SYS_ADMIN)) {
619 pr_warn_once("%s (%d): Attempt to access syslog with "
620 "CAP_SYS_ADMIN but no CAP_SYSLOG "
621 "(deprecated).\n",
622 current->comm, task_pid_nr(current));
623 goto ok;
624 }
625 return -EPERM;
626 }
627ok:
628 return security_syslog(type);
629}
630
631static void append_char(char **pp, char *e, char c)
632{
633 if (*pp < e)
634 *(*pp)++ = c;
635}
636
637static ssize_t info_print_ext_header(char *buf, size_t size,
638 struct printk_info *info)
639{
640 u64 ts_usec = info->ts_nsec;
641 char caller[20];
642#ifdef CONFIG_PRINTK_CALLER
643 u32 id = info->caller_id;
644
645 snprintf(caller, sizeof(caller), ",caller=%c%u",
646 id & 0x80000000 ? 'C' : 'T', id & ~0x80000000);
647#else
648 caller[0] = '\0';
649#endif
650
651 do_div(ts_usec, 1000);
652
653 return scnprintf(buf, size, "%u,%llu,%llu,%c%s;",
654 (info->facility << 3) | info->level, info->seq,
655 ts_usec, info->flags & LOG_CONT ? 'c' : '-', caller);
656}
657
658static ssize_t msg_add_ext_text(char *buf, size_t size,
659 const char *text, size_t text_len,
660 unsigned char endc)
661{
662 char *p = buf, *e = buf + size;
663 size_t i;
664
665 /* escape non-printable characters */
666 for (i = 0; i < text_len; i++) {
667 unsigned char c = text[i];
668
669 if (c < ' ' || c >= 127 || c == '\\')
670 p += scnprintf(p, e - p, "\\x%02x", c);
671 else
672 append_char(&p, e, c);
673 }
674 append_char(&p, e, endc);
675
676 return p - buf;
677}
678
679static ssize_t msg_add_dict_text(char *buf, size_t size,
680 const char *key, const char *val)
681{
682 size_t val_len = strlen(val);
683 ssize_t len;
684
685 if (!val_len)
686 return 0;
687
688 len = msg_add_ext_text(buf, size, "", 0, ' '); /* dict prefix */
689 len += msg_add_ext_text(buf + len, size - len, key, strlen(key), '=');
690 len += msg_add_ext_text(buf + len, size - len, val, val_len, '\n');
691
692 return len;
693}
694
695static ssize_t msg_print_ext_body(char *buf, size_t size,
696 char *text, size_t text_len,
697 struct dev_printk_info *dev_info)
698{
699 ssize_t len;
700
701 len = msg_add_ext_text(buf, size, text, text_len, '\n');
702
703 if (!dev_info)
704 goto out;
705
706 len += msg_add_dict_text(buf + len, size - len, "SUBSYSTEM",
707 dev_info->subsystem);
708 len += msg_add_dict_text(buf + len, size - len, "DEVICE",
709 dev_info->device);
710out:
711 return len;
712}
713
714/* /dev/kmsg - userspace message inject/listen interface */
715struct devkmsg_user {
716 atomic64_t seq;
717 struct ratelimit_state rs;
718 struct mutex lock;
719 char buf[CONSOLE_EXT_LOG_MAX];
720
721 struct printk_info info;
722 char text_buf[CONSOLE_EXT_LOG_MAX];
723 struct printk_record record;
724};
725
726static __printf(3, 4) __cold
727int devkmsg_emit(int facility, int level, const char *fmt, ...)
728{
729 va_list args;
730 int r;
731
732 va_start(args, fmt);
733 r = vprintk_emit(facility, level, NULL, fmt, args);
734 va_end(args);
735
736 return r;
737}
738
739static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
740{
741 char *buf, *line;
742 int level = default_message_loglevel;
743 int facility = 1; /* LOG_USER */
744 struct file *file = iocb->ki_filp;
745 struct devkmsg_user *user = file->private_data;
746 size_t len = iov_iter_count(from);
747 ssize_t ret = len;
748
749 if (!user || len > LOG_LINE_MAX)
750 return -EINVAL;
751
752 /* Ignore when user logging is disabled. */
753 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
754 return len;
755
756 /* Ratelimit when not explicitly enabled. */
757 if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) {
758 if (!___ratelimit(&user->rs, current->comm))
759 return ret;
760 }
761
762 buf = kmalloc(len+1, GFP_KERNEL);
763 if (buf == NULL)
764 return -ENOMEM;
765
766 buf[len] = '\0';
767 if (!copy_from_iter_full(buf, len, from)) {
768 kfree(buf);
769 return -EFAULT;
770 }
771
772 /*
773 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
774 * the decimal value represents 32bit, the lower 3 bit are the log
775 * level, the rest are the log facility.
776 *
777 * If no prefix or no userspace facility is specified, we
778 * enforce LOG_USER, to be able to reliably distinguish
779 * kernel-generated messages from userspace-injected ones.
780 */
781 line = buf;
782 if (line[0] == '<') {
783 char *endp = NULL;
784 unsigned int u;
785
786 u = simple_strtoul(line + 1, &endp, 10);
787 if (endp && endp[0] == '>') {
788 level = LOG_LEVEL(u);
789 if (LOG_FACILITY(u) != 0)
790 facility = LOG_FACILITY(u);
791 endp++;
792 line = endp;
793 }
794 }
795
796 devkmsg_emit(facility, level, "%s", line);
797 kfree(buf);
798 return ret;
799}
800
801static ssize_t devkmsg_read(struct file *file, char __user *buf,
802 size_t count, loff_t *ppos)
803{
804 struct devkmsg_user *user = file->private_data;
805 struct printk_record *r = &user->record;
806 size_t len;
807 ssize_t ret;
808
809 if (!user)
810 return -EBADF;
811
812 ret = mutex_lock_interruptible(&user->lock);
813 if (ret)
814 return ret;
815
816 if (!prb_read_valid(prb, atomic64_read(&user->seq), r)) {
817 if (file->f_flags & O_NONBLOCK) {
818 ret = -EAGAIN;
819 goto out;
820 }
821
822 /*
823 * Guarantee this task is visible on the waitqueue before
824 * checking the wake condition.
825 *
826 * The full memory barrier within set_current_state() of
827 * prepare_to_wait_event() pairs with the full memory barrier
828 * within wq_has_sleeper().
829 *
830 * This pairs with __wake_up_klogd:A.
831 */
832 ret = wait_event_interruptible(log_wait,
833 prb_read_valid(prb,
834 atomic64_read(&user->seq), r)); /* LMM(devkmsg_read:A) */
835 if (ret)
836 goto out;
837 }
838
839 if (r->info->seq != atomic64_read(&user->seq)) {
840 /* our last seen message is gone, return error and reset */
841 atomic64_set(&user->seq, r->info->seq);
842 ret = -EPIPE;
843 goto out;
844 }
845
846 len = info_print_ext_header(user->buf, sizeof(user->buf), r->info);
847 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
848 &r->text_buf[0], r->info->text_len,
849 &r->info->dev_info);
850
851 atomic64_set(&user->seq, r->info->seq + 1);
852
853 if (len > count) {
854 ret = -EINVAL;
855 goto out;
856 }
857
858 if (copy_to_user(buf, user->buf, len)) {
859 ret = -EFAULT;
860 goto out;
861 }
862 ret = len;
863out:
864 mutex_unlock(&user->lock);
865 return ret;
866}
867
868/*
869 * Be careful when modifying this function!!!
870 *
871 * Only few operations are supported because the device works only with the
872 * entire variable length messages (records). Non-standard values are
873 * returned in the other cases and has been this way for quite some time.
874 * User space applications might depend on this behavior.
875 */
876static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
877{
878 struct devkmsg_user *user = file->private_data;
879 loff_t ret = 0;
880
881 if (!user)
882 return -EBADF;
883 if (offset)
884 return -ESPIPE;
885
886 switch (whence) {
887 case SEEK_SET:
888 /* the first record */
889 atomic64_set(&user->seq, prb_first_valid_seq(prb));
890 break;
891 case SEEK_DATA:
892 /*
893 * The first record after the last SYSLOG_ACTION_CLEAR,
894 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
895 * changes no global state, and does not clear anything.
896 */
897 atomic64_set(&user->seq, latched_seq_read_nolock(&clear_seq));
898 break;
899 case SEEK_END:
900 /* after the last record */
901 atomic64_set(&user->seq, prb_next_seq(prb));
902 break;
903 default:
904 ret = -EINVAL;
905 }
906 return ret;
907}
908
909static __poll_t devkmsg_poll(struct file *file, poll_table *wait)
910{
911 struct devkmsg_user *user = file->private_data;
912 struct printk_info info;
913 __poll_t ret = 0;
914
915 if (!user)
916 return EPOLLERR|EPOLLNVAL;
917
918 poll_wait(file, &log_wait, wait);
919
920 if (prb_read_valid_info(prb, atomic64_read(&user->seq), &info, NULL)) {
921 /* return error when data has vanished underneath us */
922 if (info.seq != atomic64_read(&user->seq))
923 ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI;
924 else
925 ret = EPOLLIN|EPOLLRDNORM;
926 }
927
928 return ret;
929}
930
931static int devkmsg_open(struct inode *inode, struct file *file)
932{
933 struct devkmsg_user *user;
934 int err;
935
936 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
937 return -EPERM;
938
939 /* write-only does not need any file context */
940 if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
941 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
942 SYSLOG_FROM_READER);
943 if (err)
944 return err;
945 }
946
947 user = kvmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
948 if (!user)
949 return -ENOMEM;
950
951 ratelimit_default_init(&user->rs);
952 ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);
953
954 mutex_init(&user->lock);
955
956 prb_rec_init_rd(&user->record, &user->info,
957 &user->text_buf[0], sizeof(user->text_buf));
958
959 atomic64_set(&user->seq, prb_first_valid_seq(prb));
960
961 file->private_data = user;
962 return 0;
963}
964
965static int devkmsg_release(struct inode *inode, struct file *file)
966{
967 struct devkmsg_user *user = file->private_data;
968
969 if (!user)
970 return 0;
971
972 ratelimit_state_exit(&user->rs);
973
974 mutex_destroy(&user->lock);
975 kvfree(user);
976 return 0;
977}
978
979const struct file_operations kmsg_fops = {
980 .open = devkmsg_open,
981 .read = devkmsg_read,
982 .write_iter = devkmsg_write,
983 .llseek = devkmsg_llseek,
984 .poll = devkmsg_poll,
985 .release = devkmsg_release,
986};
987
988#ifdef CONFIG_CRASH_CORE
989/*
990 * This appends the listed symbols to /proc/vmcore
991 *
992 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
993 * obtain access to symbols that are otherwise very difficult to locate. These
994 * symbols are specifically used so that utilities can access and extract the
995 * dmesg log from a vmcore file after a crash.
996 */
997void log_buf_vmcoreinfo_setup(void)
998{
999 struct dev_printk_info *dev_info = NULL;
1000
1001 VMCOREINFO_SYMBOL(prb);
1002 VMCOREINFO_SYMBOL(printk_rb_static);
1003 VMCOREINFO_SYMBOL(clear_seq);
1004
1005 /*
1006 * Export struct size and field offsets. User space tools can
1007 * parse it and detect any changes to structure down the line.
1008 */
1009
1010 VMCOREINFO_STRUCT_SIZE(printk_ringbuffer);
1011 VMCOREINFO_OFFSET(printk_ringbuffer, desc_ring);
1012 VMCOREINFO_OFFSET(printk_ringbuffer, text_data_ring);
1013 VMCOREINFO_OFFSET(printk_ringbuffer, fail);
1014
1015 VMCOREINFO_STRUCT_SIZE(prb_desc_ring);
1016 VMCOREINFO_OFFSET(prb_desc_ring, count_bits);
1017 VMCOREINFO_OFFSET(prb_desc_ring, descs);
1018 VMCOREINFO_OFFSET(prb_desc_ring, infos);
1019 VMCOREINFO_OFFSET(prb_desc_ring, head_id);
1020 VMCOREINFO_OFFSET(prb_desc_ring, tail_id);
1021
1022 VMCOREINFO_STRUCT_SIZE(prb_desc);
1023 VMCOREINFO_OFFSET(prb_desc, state_var);
1024 VMCOREINFO_OFFSET(prb_desc, text_blk_lpos);
1025
1026 VMCOREINFO_STRUCT_SIZE(prb_data_blk_lpos);
1027 VMCOREINFO_OFFSET(prb_data_blk_lpos, begin);
1028 VMCOREINFO_OFFSET(prb_data_blk_lpos, next);
1029
1030 VMCOREINFO_STRUCT_SIZE(printk_info);
1031 VMCOREINFO_OFFSET(printk_info, seq);
1032 VMCOREINFO_OFFSET(printk_info, ts_nsec);
1033 VMCOREINFO_OFFSET(printk_info, text_len);
1034 VMCOREINFO_OFFSET(printk_info, caller_id);
1035 VMCOREINFO_OFFSET(printk_info, dev_info);
1036
1037 VMCOREINFO_STRUCT_SIZE(dev_printk_info);
1038 VMCOREINFO_OFFSET(dev_printk_info, subsystem);
1039 VMCOREINFO_LENGTH(printk_info_subsystem, sizeof(dev_info->subsystem));
1040 VMCOREINFO_OFFSET(dev_printk_info, device);
1041 VMCOREINFO_LENGTH(printk_info_device, sizeof(dev_info->device));
1042
1043 VMCOREINFO_STRUCT_SIZE(prb_data_ring);
1044 VMCOREINFO_OFFSET(prb_data_ring, size_bits);
1045 VMCOREINFO_OFFSET(prb_data_ring, data);
1046 VMCOREINFO_OFFSET(prb_data_ring, head_lpos);
1047 VMCOREINFO_OFFSET(prb_data_ring, tail_lpos);
1048
1049 VMCOREINFO_SIZE(atomic_long_t);
1050 VMCOREINFO_TYPE_OFFSET(atomic_long_t, counter);
1051
1052 VMCOREINFO_STRUCT_SIZE(latched_seq);
1053 VMCOREINFO_OFFSET(latched_seq, val);
1054}
1055#endif
1056
1057/* requested log_buf_len from kernel cmdline */
1058static unsigned long __initdata new_log_buf_len;
1059
1060/* we practice scaling the ring buffer by powers of 2 */
1061static void __init log_buf_len_update(u64 size)
1062{
1063 if (size > (u64)LOG_BUF_LEN_MAX) {
1064 size = (u64)LOG_BUF_LEN_MAX;
1065 pr_err("log_buf over 2G is not supported.\n");
1066 }
1067
1068 if (size)
1069 size = roundup_pow_of_two(size);
1070 if (size > log_buf_len)
1071 new_log_buf_len = (unsigned long)size;
1072}
1073
1074/* save requested log_buf_len since it's too early to process it */
1075static int __init log_buf_len_setup(char *str)
1076{
1077 u64 size;
1078
1079 if (!str)
1080 return -EINVAL;
1081
1082 size = memparse(str, &str);
1083
1084 log_buf_len_update(size);
1085
1086 return 0;
1087}
1088early_param("log_buf_len", log_buf_len_setup);
1089
1090#ifdef CONFIG_SMP
1091#define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1092
1093static void __init log_buf_add_cpu(void)
1094{
1095 unsigned int cpu_extra;
1096
1097 /*
1098 * archs should set up cpu_possible_bits properly with
1099 * set_cpu_possible() after setup_arch() but just in
1100 * case lets ensure this is valid.
1101 */
1102 if (num_possible_cpus() == 1)
1103 return;
1104
1105 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
1106
1107 /* by default this will only continue through for large > 64 CPUs */
1108 if (cpu_extra <= __LOG_BUF_LEN / 2)
1109 return;
1110
1111 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1112 __LOG_CPU_MAX_BUF_LEN);
1113 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1114 cpu_extra);
1115 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
1116
1117 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
1118}
1119#else /* !CONFIG_SMP */
1120static inline void log_buf_add_cpu(void) {}
1121#endif /* CONFIG_SMP */
1122
1123static void __init set_percpu_data_ready(void)
1124{
1125 __printk_percpu_data_ready = true;
1126}
1127
1128static unsigned int __init add_to_rb(struct printk_ringbuffer *rb,
1129 struct printk_record *r)
1130{
1131 struct prb_reserved_entry e;
1132 struct printk_record dest_r;
1133
1134 prb_rec_init_wr(&dest_r, r->info->text_len);
1135
1136 if (!prb_reserve(&e, rb, &dest_r))
1137 return 0;
1138
1139 memcpy(&dest_r.text_buf[0], &r->text_buf[0], r->info->text_len);
1140 dest_r.info->text_len = r->info->text_len;
1141 dest_r.info->facility = r->info->facility;
1142 dest_r.info->level = r->info->level;
1143 dest_r.info->flags = r->info->flags;
1144 dest_r.info->ts_nsec = r->info->ts_nsec;
1145 dest_r.info->caller_id = r->info->caller_id;
1146 memcpy(&dest_r.info->dev_info, &r->info->dev_info, sizeof(dest_r.info->dev_info));
1147
1148 prb_final_commit(&e);
1149
1150 return prb_record_text_space(&e);
1151}
1152
1153static char setup_text_buf[LOG_LINE_MAX] __initdata;
1154
1155void __init setup_log_buf(int early)
1156{
1157 struct printk_info *new_infos;
1158 unsigned int new_descs_count;
1159 struct prb_desc *new_descs;
1160 struct printk_info info;
1161 struct printk_record r;
1162 unsigned int text_size;
1163 size_t new_descs_size;
1164 size_t new_infos_size;
1165 unsigned long flags;
1166 char *new_log_buf;
1167 unsigned int free;
1168 u64 seq;
1169
1170 /*
1171 * Some archs call setup_log_buf() multiple times - first is very
1172 * early, e.g. from setup_arch(), and second - when percpu_areas
1173 * are initialised.
1174 */
1175 if (!early)
1176 set_percpu_data_ready();
1177
1178 if (log_buf != __log_buf)
1179 return;
1180
1181 if (!early && !new_log_buf_len)
1182 log_buf_add_cpu();
1183
1184 if (!new_log_buf_len)
1185 return;
1186
1187 new_descs_count = new_log_buf_len >> PRB_AVGBITS;
1188 if (new_descs_count == 0) {
1189 pr_err("new_log_buf_len: %lu too small\n", new_log_buf_len);
1190 return;
1191 }
1192
1193 new_log_buf = memblock_alloc(new_log_buf_len, LOG_ALIGN);
1194 if (unlikely(!new_log_buf)) {
1195 pr_err("log_buf_len: %lu text bytes not available\n",
1196 new_log_buf_len);
1197 return;
1198 }
1199
1200 new_descs_size = new_descs_count * sizeof(struct prb_desc);
1201 new_descs = memblock_alloc(new_descs_size, LOG_ALIGN);
1202 if (unlikely(!new_descs)) {
1203 pr_err("log_buf_len: %zu desc bytes not available\n",
1204 new_descs_size);
1205 goto err_free_log_buf;
1206 }
1207
1208 new_infos_size = new_descs_count * sizeof(struct printk_info);
1209 new_infos = memblock_alloc(new_infos_size, LOG_ALIGN);
1210 if (unlikely(!new_infos)) {
1211 pr_err("log_buf_len: %zu info bytes not available\n",
1212 new_infos_size);
1213 goto err_free_descs;
1214 }
1215
1216 prb_rec_init_rd(&r, &info, &setup_text_buf[0], sizeof(setup_text_buf));
1217
1218 prb_init(&printk_rb_dynamic,
1219 new_log_buf, ilog2(new_log_buf_len),
1220 new_descs, ilog2(new_descs_count),
1221 new_infos);
1222
1223 local_irq_save(flags);
1224
1225 log_buf_len = new_log_buf_len;
1226 log_buf = new_log_buf;
1227 new_log_buf_len = 0;
1228
1229 free = __LOG_BUF_LEN;
1230 prb_for_each_record(0, &printk_rb_static, seq, &r) {
1231 text_size = add_to_rb(&printk_rb_dynamic, &r);
1232 if (text_size > free)
1233 free = 0;
1234 else
1235 free -= text_size;
1236 }
1237
1238 prb = &printk_rb_dynamic;
1239
1240 local_irq_restore(flags);
1241
1242 /*
1243 * Copy any remaining messages that might have appeared from
1244 * NMI context after copying but before switching to the
1245 * dynamic buffer.
1246 */
1247 prb_for_each_record(seq, &printk_rb_static, seq, &r) {
1248 text_size = add_to_rb(&printk_rb_dynamic, &r);
1249 if (text_size > free)
1250 free = 0;
1251 else
1252 free -= text_size;
1253 }
1254
1255 if (seq != prb_next_seq(&printk_rb_static)) {
1256 pr_err("dropped %llu messages\n",
1257 prb_next_seq(&printk_rb_static) - seq);
1258 }
1259
1260 pr_info("log_buf_len: %u bytes\n", log_buf_len);
1261 pr_info("early log buf free: %u(%u%%)\n",
1262 free, (free * 100) / __LOG_BUF_LEN);
1263 return;
1264
1265err_free_descs:
1266 memblock_free(new_descs, new_descs_size);
1267err_free_log_buf:
1268 memblock_free(new_log_buf, new_log_buf_len);
1269}
1270
1271static bool __read_mostly ignore_loglevel;
1272
1273static int __init ignore_loglevel_setup(char *str)
1274{
1275 ignore_loglevel = true;
1276 pr_info("debug: ignoring loglevel setting.\n");
1277
1278 return 0;
1279}
1280
1281early_param("ignore_loglevel", ignore_loglevel_setup);
1282module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1283MODULE_PARM_DESC(ignore_loglevel,
1284 "ignore loglevel setting (prints all kernel messages to the console)");
1285
1286static bool suppress_message_printing(int level)
1287{
1288 return (level >= console_loglevel && !ignore_loglevel);
1289}
1290
1291#ifdef CONFIG_BOOT_PRINTK_DELAY
1292
1293static int boot_delay; /* msecs delay after each printk during bootup */
1294static unsigned long long loops_per_msec; /* based on boot_delay */
1295
1296static int __init boot_delay_setup(char *str)
1297{
1298 unsigned long lpj;
1299
1300 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
1301 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
1302
1303 get_option(&str, &boot_delay);
1304 if (boot_delay > 10 * 1000)
1305 boot_delay = 0;
1306
1307 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1308 "HZ: %d, loops_per_msec: %llu\n",
1309 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1310 return 0;
1311}
1312early_param("boot_delay", boot_delay_setup);
1313
1314static void boot_delay_msec(int level)
1315{
1316 unsigned long long k;
1317 unsigned long timeout;
1318
1319 if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING)
1320 || suppress_message_printing(level)) {
1321 return;
1322 }
1323
1324 k = (unsigned long long)loops_per_msec * boot_delay;
1325
1326 timeout = jiffies + msecs_to_jiffies(boot_delay);
1327 while (k) {
1328 k--;
1329 cpu_relax();
1330 /*
1331 * use (volatile) jiffies to prevent
1332 * compiler reduction; loop termination via jiffies
1333 * is secondary and may or may not happen.
1334 */
1335 if (time_after(jiffies, timeout))
1336 break;
1337 touch_nmi_watchdog();
1338 }
1339}
1340#else
1341static inline void boot_delay_msec(int level)
1342{
1343}
1344#endif
1345
1346static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1347module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1348
1349static size_t print_syslog(unsigned int level, char *buf)
1350{
1351 return sprintf(buf, "<%u>", level);
1352}
1353
1354static size_t print_time(u64 ts, char *buf)
1355{
1356 unsigned long rem_nsec = do_div(ts, 1000000000);
1357
1358 return sprintf(buf, "[%5lu.%06lu]",
1359 (unsigned long)ts, rem_nsec / 1000);
1360}
1361
1362#ifdef CONFIG_PRINTK_CALLER
1363static size_t print_caller(u32 id, char *buf)
1364{
1365 char caller[12];
1366
1367 snprintf(caller, sizeof(caller), "%c%u",
1368 id & 0x80000000 ? 'C' : 'T', id & ~0x80000000);
1369 return sprintf(buf, "[%6s]", caller);
1370}
1371#else
1372#define print_caller(id, buf) 0
1373#endif
1374
1375static size_t info_print_prefix(const struct printk_info *info, bool syslog,
1376 bool time, char *buf)
1377{
1378 size_t len = 0;
1379
1380 if (syslog)
1381 len = print_syslog((info->facility << 3) | info->level, buf);
1382
1383 if (time)
1384 len += print_time(info->ts_nsec, buf + len);
1385
1386 len += print_caller(info->caller_id, buf + len);
1387
1388 if (IS_ENABLED(CONFIG_PRINTK_CALLER) || time) {
1389 buf[len++] = ' ';
1390 buf[len] = '\0';
1391 }
1392
1393 return len;
1394}
1395
1396/*
1397 * Prepare the record for printing. The text is shifted within the given
1398 * buffer to avoid a need for another one. The following operations are
1399 * done:
1400 *
1401 * - Add prefix for each line.
1402 * - Drop truncated lines that no longer fit into the buffer.
1403 * - Add the trailing newline that has been removed in vprintk_store().
1404 * - Add a string terminator.
1405 *
1406 * Since the produced string is always terminated, the maximum possible
1407 * return value is @r->text_buf_size - 1;
1408 *
1409 * Return: The length of the updated/prepared text, including the added
1410 * prefixes and the newline. The terminator is not counted. The dropped
1411 * line(s) are not counted.
1412 */
1413static size_t record_print_text(struct printk_record *r, bool syslog,
1414 bool time)
1415{
1416 size_t text_len = r->info->text_len;
1417 size_t buf_size = r->text_buf_size;
1418 char *text = r->text_buf;
1419 char prefix[PREFIX_MAX];
1420 bool truncated = false;
1421 size_t prefix_len;
1422 size_t line_len;
1423 size_t len = 0;
1424 char *next;
1425
1426 /*
1427 * If the message was truncated because the buffer was not large
1428 * enough, treat the available text as if it were the full text.
1429 */
1430 if (text_len > buf_size)
1431 text_len = buf_size;
1432
1433 prefix_len = info_print_prefix(r->info, syslog, time, prefix);
1434
1435 /*
1436 * @text_len: bytes of unprocessed text
1437 * @line_len: bytes of current line _without_ newline
1438 * @text: pointer to beginning of current line
1439 * @len: number of bytes prepared in r->text_buf
1440 */
1441 for (;;) {
1442 next = memchr(text, '\n', text_len);
1443 if (next) {
1444 line_len = next - text;
1445 } else {
1446 /* Drop truncated line(s). */
1447 if (truncated)
1448 break;
1449 line_len = text_len;
1450 }
1451
1452 /*
1453 * Truncate the text if there is not enough space to add the
1454 * prefix and a trailing newline and a terminator.
1455 */
1456 if (len + prefix_len + text_len + 1 + 1 > buf_size) {
1457 /* Drop even the current line if no space. */
1458 if (len + prefix_len + line_len + 1 + 1 > buf_size)
1459 break;
1460
1461 text_len = buf_size - len - prefix_len - 1 - 1;
1462 truncated = true;
1463 }
1464
1465 memmove(text + prefix_len, text, text_len);
1466 memcpy(text, prefix, prefix_len);
1467
1468 /*
1469 * Increment the prepared length to include the text and
1470 * prefix that were just moved+copied. Also increment for the
1471 * newline at the end of this line. If this is the last line,
1472 * there is no newline, but it will be added immediately below.
1473 */
1474 len += prefix_len + line_len + 1;
1475 if (text_len == line_len) {
1476 /*
1477 * This is the last line. Add the trailing newline
1478 * removed in vprintk_store().
1479 */
1480 text[prefix_len + line_len] = '\n';
1481 break;
1482 }
1483
1484 /*
1485 * Advance beyond the added prefix and the related line with
1486 * its newline.
1487 */
1488 text += prefix_len + line_len + 1;
1489
1490 /*
1491 * The remaining text has only decreased by the line with its
1492 * newline.
1493 *
1494 * Note that @text_len can become zero. It happens when @text
1495 * ended with a newline (either due to truncation or the
1496 * original string ending with "\n\n"). The loop is correctly
1497 * repeated and (if not truncated) an empty line with a prefix
1498 * will be prepared.
1499 */
1500 text_len -= line_len + 1;
1501 }
1502
1503 /*
1504 * If a buffer was provided, it will be terminated. Space for the
1505 * string terminator is guaranteed to be available. The terminator is
1506 * not counted in the return value.
1507 */
1508 if (buf_size > 0)
1509 r->text_buf[len] = 0;
1510
1511 return len;
1512}
1513
1514static size_t get_record_print_text_size(struct printk_info *info,
1515 unsigned int line_count,
1516 bool syslog, bool time)
1517{
1518 char prefix[PREFIX_MAX];
1519 size_t prefix_len;
1520
1521 prefix_len = info_print_prefix(info, syslog, time, prefix);
1522
1523 /*
1524 * Each line will be preceded with a prefix. The intermediate
1525 * newlines are already within the text, but a final trailing
1526 * newline will be added.
1527 */
1528 return ((prefix_len * line_count) + info->text_len + 1);
1529}
1530
1531/*
1532 * Beginning with @start_seq, find the first record where it and all following
1533 * records up to (but not including) @max_seq fit into @size.
1534 *
1535 * @max_seq is simply an upper bound and does not need to exist. If the caller
1536 * does not require an upper bound, -1 can be used for @max_seq.
1537 */
1538static u64 find_first_fitting_seq(u64 start_seq, u64 max_seq, size_t size,
1539 bool syslog, bool time)
1540{
1541 struct printk_info info;
1542 unsigned int line_count;
1543 size_t len = 0;
1544 u64 seq;
1545
1546 /* Determine the size of the records up to @max_seq. */
1547 prb_for_each_info(start_seq, prb, seq, &info, &line_count) {
1548 if (info.seq >= max_seq)
1549 break;
1550 len += get_record_print_text_size(&info, line_count, syslog, time);
1551 }
1552
1553 /*
1554 * Adjust the upper bound for the next loop to avoid subtracting
1555 * lengths that were never added.
1556 */
1557 if (seq < max_seq)
1558 max_seq = seq;
1559
1560 /*
1561 * Move first record forward until length fits into the buffer. Ignore
1562 * newest messages that were not counted in the above cycle. Messages
1563 * might appear and get lost in the meantime. This is a best effort
1564 * that prevents an infinite loop that could occur with a retry.
1565 */
1566 prb_for_each_info(start_seq, prb, seq, &info, &line_count) {
1567 if (len <= size || info.seq >= max_seq)
1568 break;
1569 len -= get_record_print_text_size(&info, line_count, syslog, time);
1570 }
1571
1572 return seq;
1573}
1574
1575/* The caller is responsible for making sure @size is greater than 0. */
1576static int syslog_print(char __user *buf, int size)
1577{
1578 struct printk_info info;
1579 struct printk_record r;
1580 char *text;
1581 int len = 0;
1582 u64 seq;
1583
1584 text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL);
1585 if (!text)
1586 return -ENOMEM;
1587
1588 prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX);
1589
1590 mutex_lock(&syslog_lock);
1591
1592 /*
1593 * Wait for the @syslog_seq record to be available. @syslog_seq may
1594 * change while waiting.
1595 */
1596 do {
1597 seq = syslog_seq;
1598
1599 mutex_unlock(&syslog_lock);
1600 /*
1601 * Guarantee this task is visible on the waitqueue before
1602 * checking the wake condition.
1603 *
1604 * The full memory barrier within set_current_state() of
1605 * prepare_to_wait_event() pairs with the full memory barrier
1606 * within wq_has_sleeper().
1607 *
1608 * This pairs with __wake_up_klogd:A.
1609 */
1610 len = wait_event_interruptible(log_wait,
1611 prb_read_valid(prb, seq, NULL)); /* LMM(syslog_print:A) */
1612 mutex_lock(&syslog_lock);
1613
1614 if (len)
1615 goto out;
1616 } while (syslog_seq != seq);
1617
1618 /*
1619 * Copy records that fit into the buffer. The above cycle makes sure
1620 * that the first record is always available.
1621 */
1622 do {
1623 size_t n;
1624 size_t skip;
1625 int err;
1626
1627 if (!prb_read_valid(prb, syslog_seq, &r))
1628 break;
1629
1630 if (r.info->seq != syslog_seq) {
1631 /* message is gone, move to next valid one */
1632 syslog_seq = r.info->seq;
1633 syslog_partial = 0;
1634 }
1635
1636 /*
1637 * To keep reading/counting partial line consistent,
1638 * use printk_time value as of the beginning of a line.
1639 */
1640 if (!syslog_partial)
1641 syslog_time = printk_time;
1642
1643 skip = syslog_partial;
1644 n = record_print_text(&r, true, syslog_time);
1645 if (n - syslog_partial <= size) {
1646 /* message fits into buffer, move forward */
1647 syslog_seq = r.info->seq + 1;
1648 n -= syslog_partial;
1649 syslog_partial = 0;
1650 } else if (!len){
1651 /* partial read(), remember position */
1652 n = size;
1653 syslog_partial += n;
1654 } else
1655 n = 0;
1656
1657 if (!n)
1658 break;
1659
1660 mutex_unlock(&syslog_lock);
1661 err = copy_to_user(buf, text + skip, n);
1662 mutex_lock(&syslog_lock);
1663
1664 if (err) {
1665 if (!len)
1666 len = -EFAULT;
1667 break;
1668 }
1669
1670 len += n;
1671 size -= n;
1672 buf += n;
1673 } while (size);
1674out:
1675 mutex_unlock(&syslog_lock);
1676 kfree(text);
1677 return len;
1678}
1679
1680static int syslog_print_all(char __user *buf, int size, bool clear)
1681{
1682 struct printk_info info;
1683 struct printk_record r;
1684 char *text;
1685 int len = 0;
1686 u64 seq;
1687 bool time;
1688
1689 text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL);
1690 if (!text)
1691 return -ENOMEM;
1692
1693 time = printk_time;
1694 /*
1695 * Find first record that fits, including all following records,
1696 * into the user-provided buffer for this dump.
1697 */
1698 seq = find_first_fitting_seq(latched_seq_read_nolock(&clear_seq), -1,
1699 size, true, time);
1700
1701 prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX);
1702
1703 len = 0;
1704 prb_for_each_record(seq, prb, seq, &r) {
1705 int textlen;
1706
1707 textlen = record_print_text(&r, true, time);
1708
1709 if (len + textlen > size) {
1710 seq--;
1711 break;
1712 }
1713
1714 if (copy_to_user(buf + len, text, textlen))
1715 len = -EFAULT;
1716 else
1717 len += textlen;
1718
1719 if (len < 0)
1720 break;
1721 }
1722
1723 if (clear) {
1724 mutex_lock(&syslog_lock);
1725 latched_seq_write(&clear_seq, seq);
1726 mutex_unlock(&syslog_lock);
1727 }
1728
1729 kfree(text);
1730 return len;
1731}
1732
1733static void syslog_clear(void)
1734{
1735 mutex_lock(&syslog_lock);
1736 latched_seq_write(&clear_seq, prb_next_seq(prb));
1737 mutex_unlock(&syslog_lock);
1738}
1739
1740int do_syslog(int type, char __user *buf, int len, int source)
1741{
1742 struct printk_info info;
1743 bool clear = false;
1744 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1745 int error;
1746
1747 error = check_syslog_permissions(type, source);
1748 if (error)
1749 return error;
1750
1751 switch (type) {
1752 case SYSLOG_ACTION_CLOSE: /* Close log */
1753 break;
1754 case SYSLOG_ACTION_OPEN: /* Open log */
1755 break;
1756 case SYSLOG_ACTION_READ: /* Read from log */
1757 if (!buf || len < 0)
1758 return -EINVAL;
1759 if (!len)
1760 return 0;
1761 if (!access_ok(buf, len))
1762 return -EFAULT;
1763 error = syslog_print(buf, len);
1764 break;
1765 /* Read/clear last kernel messages */
1766 case SYSLOG_ACTION_READ_CLEAR:
1767 clear = true;
1768 fallthrough;
1769 /* Read last kernel messages */
1770 case SYSLOG_ACTION_READ_ALL:
1771 if (!buf || len < 0)
1772 return -EINVAL;
1773 if (!len)
1774 return 0;
1775 if (!access_ok(buf, len))
1776 return -EFAULT;
1777 error = syslog_print_all(buf, len, clear);
1778 break;
1779 /* Clear ring buffer */
1780 case SYSLOG_ACTION_CLEAR:
1781 syslog_clear();
1782 break;
1783 /* Disable logging to console */
1784 case SYSLOG_ACTION_CONSOLE_OFF:
1785 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1786 saved_console_loglevel = console_loglevel;
1787 console_loglevel = minimum_console_loglevel;
1788 break;
1789 /* Enable logging to console */
1790 case SYSLOG_ACTION_CONSOLE_ON:
1791 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1792 console_loglevel = saved_console_loglevel;
1793 saved_console_loglevel = LOGLEVEL_DEFAULT;
1794 }
1795 break;
1796 /* Set level of messages printed to console */
1797 case SYSLOG_ACTION_CONSOLE_LEVEL:
1798 if (len < 1 || len > 8)
1799 return -EINVAL;
1800 if (len < minimum_console_loglevel)
1801 len = minimum_console_loglevel;
1802 console_loglevel = len;
1803 /* Implicitly re-enable logging to console */
1804 saved_console_loglevel = LOGLEVEL_DEFAULT;
1805 break;
1806 /* Number of chars in the log buffer */
1807 case SYSLOG_ACTION_SIZE_UNREAD:
1808 mutex_lock(&syslog_lock);
1809 if (!prb_read_valid_info(prb, syslog_seq, &info, NULL)) {
1810 /* No unread messages. */
1811 mutex_unlock(&syslog_lock);
1812 return 0;
1813 }
1814 if (info.seq != syslog_seq) {
1815 /* messages are gone, move to first one */
1816 syslog_seq = info.seq;
1817 syslog_partial = 0;
1818 }
1819 if (source == SYSLOG_FROM_PROC) {
1820 /*
1821 * Short-cut for poll(/"proc/kmsg") which simply checks
1822 * for pending data, not the size; return the count of
1823 * records, not the length.
1824 */
1825 error = prb_next_seq(prb) - syslog_seq;
1826 } else {
1827 bool time = syslog_partial ? syslog_time : printk_time;
1828 unsigned int line_count;
1829 u64 seq;
1830
1831 prb_for_each_info(syslog_seq, prb, seq, &info,
1832 &line_count) {
1833 error += get_record_print_text_size(&info, line_count,
1834 true, time);
1835 time = printk_time;
1836 }
1837 error -= syslog_partial;
1838 }
1839 mutex_unlock(&syslog_lock);
1840 break;
1841 /* Size of the log buffer */
1842 case SYSLOG_ACTION_SIZE_BUFFER:
1843 error = log_buf_len;
1844 break;
1845 default:
1846 error = -EINVAL;
1847 break;
1848 }
1849
1850 return error;
1851}
1852
1853SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1854{
1855 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1856}
1857
1858/*
1859 * Special console_lock variants that help to reduce the risk of soft-lockups.
1860 * They allow to pass console_lock to another printk() call using a busy wait.
1861 */
1862
1863#ifdef CONFIG_LOCKDEP
1864static struct lockdep_map console_owner_dep_map = {
1865 .name = "console_owner"
1866};
1867#endif
1868
1869static DEFINE_RAW_SPINLOCK(console_owner_lock);
1870static struct task_struct *console_owner;
1871static bool console_waiter;
1872
1873/**
1874 * console_lock_spinning_enable - mark beginning of code where another
1875 * thread might safely busy wait
1876 *
1877 * This basically converts console_lock into a spinlock. This marks
1878 * the section where the console_lock owner can not sleep, because
1879 * there may be a waiter spinning (like a spinlock). Also it must be
1880 * ready to hand over the lock at the end of the section.
1881 */
1882static void console_lock_spinning_enable(void)
1883{
1884 raw_spin_lock(&console_owner_lock);
1885 console_owner = current;
1886 raw_spin_unlock(&console_owner_lock);
1887
1888 /* The waiter may spin on us after setting console_owner */
1889 spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_);
1890}
1891
1892/**
1893 * console_lock_spinning_disable_and_check - mark end of code where another
1894 * thread was able to busy wait and check if there is a waiter
1895 * @cookie: cookie returned from console_srcu_read_lock()
1896 *
1897 * This is called at the end of the section where spinning is allowed.
1898 * It has two functions. First, it is a signal that it is no longer
1899 * safe to start busy waiting for the lock. Second, it checks if
1900 * there is a busy waiter and passes the lock rights to her.
1901 *
1902 * Important: Callers lose both the console_lock and the SRCU read lock if
1903 * there was a busy waiter. They must not touch items synchronized by
1904 * console_lock or SRCU read lock in this case.
1905 *
1906 * Return: 1 if the lock rights were passed, 0 otherwise.
1907 */
1908static int console_lock_spinning_disable_and_check(int cookie)
1909{
1910 int waiter;
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 return 1;
2013}
2014
2015/*
2016 * Call the specified console driver, asking it to write out the specified
2017 * text and length. If @dropped_text is non-NULL and any records have been
2018 * dropped, a dropped message will be written out first.
2019 */
2020static void call_console_driver(struct console *con, const char *text, size_t len,
2021 char *dropped_text)
2022{
2023 size_t dropped_len;
2024
2025 if (con->dropped && dropped_text) {
2026 dropped_len = snprintf(dropped_text, DROPPED_TEXT_MAX,
2027 "** %lu printk messages dropped **\n",
2028 con->dropped);
2029 con->dropped = 0;
2030 con->write(con, dropped_text, dropped_len);
2031 }
2032
2033 con->write(con, text, len);
2034}
2035
2036/*
2037 * Recursion is tracked separately on each CPU. If NMIs are supported, an
2038 * additional NMI context per CPU is also separately tracked. Until per-CPU
2039 * is available, a separate "early tracking" is performed.
2040 */
2041static DEFINE_PER_CPU(u8, printk_count);
2042static u8 printk_count_early;
2043#ifdef CONFIG_HAVE_NMI
2044static DEFINE_PER_CPU(u8, printk_count_nmi);
2045static u8 printk_count_nmi_early;
2046#endif
2047
2048/*
2049 * Recursion is limited to keep the output sane. printk() should not require
2050 * more than 1 level of recursion (allowing, for example, printk() to trigger
2051 * a WARN), but a higher value is used in case some printk-internal errors
2052 * exist, such as the ringbuffer validation checks failing.
2053 */
2054#define PRINTK_MAX_RECURSION 3
2055
2056/*
2057 * Return a pointer to the dedicated counter for the CPU+context of the
2058 * caller.
2059 */
2060static u8 *__printk_recursion_counter(void)
2061{
2062#ifdef CONFIG_HAVE_NMI
2063 if (in_nmi()) {
2064 if (printk_percpu_data_ready())
2065 return this_cpu_ptr(&printk_count_nmi);
2066 return &printk_count_nmi_early;
2067 }
2068#endif
2069 if (printk_percpu_data_ready())
2070 return this_cpu_ptr(&printk_count);
2071 return &printk_count_early;
2072}
2073
2074/*
2075 * Enter recursion tracking. Interrupts are disabled to simplify tracking.
2076 * The caller must check the boolean return value to see if the recursion is
2077 * allowed. On failure, interrupts are not disabled.
2078 *
2079 * @recursion_ptr must be a variable of type (u8 *) and is the same variable
2080 * that is passed to printk_exit_irqrestore().
2081 */
2082#define printk_enter_irqsave(recursion_ptr, flags) \
2083({ \
2084 bool success = true; \
2085 \
2086 typecheck(u8 *, recursion_ptr); \
2087 local_irq_save(flags); \
2088 (recursion_ptr) = __printk_recursion_counter(); \
2089 if (*(recursion_ptr) > PRINTK_MAX_RECURSION) { \
2090 local_irq_restore(flags); \
2091 success = false; \
2092 } else { \
2093 (*(recursion_ptr))++; \
2094 } \
2095 success; \
2096})
2097
2098/* Exit recursion tracking, restoring interrupts. */
2099#define printk_exit_irqrestore(recursion_ptr, flags) \
2100 do { \
2101 typecheck(u8 *, recursion_ptr); \
2102 (*(recursion_ptr))--; \
2103 local_irq_restore(flags); \
2104 } while (0)
2105
2106int printk_delay_msec __read_mostly;
2107
2108static inline void printk_delay(int level)
2109{
2110 boot_delay_msec(level);
2111
2112 if (unlikely(printk_delay_msec)) {
2113 int m = printk_delay_msec;
2114
2115 while (m--) {
2116 mdelay(1);
2117 touch_nmi_watchdog();
2118 }
2119 }
2120}
2121
2122static inline u32 printk_caller_id(void)
2123{
2124 return in_task() ? task_pid_nr(current) :
2125 0x80000000 + smp_processor_id();
2126}
2127
2128/**
2129 * printk_parse_prefix - Parse level and control flags.
2130 *
2131 * @text: The terminated text message.
2132 * @level: A pointer to the current level value, will be updated.
2133 * @flags: A pointer to the current printk_info flags, will be updated.
2134 *
2135 * @level may be NULL if the caller is not interested in the parsed value.
2136 * Otherwise the variable pointed to by @level must be set to
2137 * LOGLEVEL_DEFAULT in order to be updated with the parsed value.
2138 *
2139 * @flags may be NULL if the caller is not interested in the parsed value.
2140 * Otherwise the variable pointed to by @flags will be OR'd with the parsed
2141 * value.
2142 *
2143 * Return: The length of the parsed level and control flags.
2144 */
2145u16 printk_parse_prefix(const char *text, int *level,
2146 enum printk_info_flags *flags)
2147{
2148 u16 prefix_len = 0;
2149 int kern_level;
2150
2151 while (*text) {
2152 kern_level = printk_get_level(text);
2153 if (!kern_level)
2154 break;
2155
2156 switch (kern_level) {
2157 case '0' ... '7':
2158 if (level && *level == LOGLEVEL_DEFAULT)
2159 *level = kern_level - '0';
2160 break;
2161 case 'c': /* KERN_CONT */
2162 if (flags)
2163 *flags |= LOG_CONT;
2164 }
2165
2166 prefix_len += 2;
2167 text += 2;
2168 }
2169
2170 return prefix_len;
2171}
2172
2173__printf(5, 0)
2174static u16 printk_sprint(char *text, u16 size, int facility,
2175 enum printk_info_flags *flags, const char *fmt,
2176 va_list args)
2177{
2178 u16 text_len;
2179
2180 text_len = vscnprintf(text, size, fmt, args);
2181
2182 /* Mark and strip a trailing newline. */
2183 if (text_len && text[text_len - 1] == '\n') {
2184 text_len--;
2185 *flags |= LOG_NEWLINE;
2186 }
2187
2188 /* Strip log level and control flags. */
2189 if (facility == 0) {
2190 u16 prefix_len;
2191
2192 prefix_len = printk_parse_prefix(text, NULL, NULL);
2193 if (prefix_len) {
2194 text_len -= prefix_len;
2195 memmove(text, text + prefix_len, text_len);
2196 }
2197 }
2198
2199 trace_console_rcuidle(text, text_len);
2200
2201 return text_len;
2202}
2203
2204__printf(4, 0)
2205int vprintk_store(int facility, int level,
2206 const struct dev_printk_info *dev_info,
2207 const char *fmt, va_list args)
2208{
2209 struct prb_reserved_entry e;
2210 enum printk_info_flags flags = 0;
2211 struct printk_record r;
2212 unsigned long irqflags;
2213 u16 trunc_msg_len = 0;
2214 char prefix_buf[8];
2215 u8 *recursion_ptr;
2216 u16 reserve_size;
2217 va_list args2;
2218 u32 caller_id;
2219 u16 text_len;
2220 int ret = 0;
2221 u64 ts_nsec;
2222
2223 if (!printk_enter_irqsave(recursion_ptr, irqflags))
2224 return 0;
2225
2226 /*
2227 * Since the duration of printk() can vary depending on the message
2228 * and state of the ringbuffer, grab the timestamp now so that it is
2229 * close to the call of printk(). This provides a more deterministic
2230 * timestamp with respect to the caller.
2231 */
2232 ts_nsec = local_clock();
2233
2234 caller_id = printk_caller_id();
2235
2236 /*
2237 * The sprintf needs to come first since the syslog prefix might be
2238 * passed in as a parameter. An extra byte must be reserved so that
2239 * later the vscnprintf() into the reserved buffer has room for the
2240 * terminating '\0', which is not counted by vsnprintf().
2241 */
2242 va_copy(args2, args);
2243 reserve_size = vsnprintf(&prefix_buf[0], sizeof(prefix_buf), fmt, args2) + 1;
2244 va_end(args2);
2245
2246 if (reserve_size > LOG_LINE_MAX)
2247 reserve_size = LOG_LINE_MAX;
2248
2249 /* Extract log level or control flags. */
2250 if (facility == 0)
2251 printk_parse_prefix(&prefix_buf[0], &level, &flags);
2252
2253 if (level == LOGLEVEL_DEFAULT)
2254 level = default_message_loglevel;
2255
2256 if (dev_info)
2257 flags |= LOG_NEWLINE;
2258
2259 if (flags & LOG_CONT) {
2260 prb_rec_init_wr(&r, reserve_size);
2261 if (prb_reserve_in_last(&e, prb, &r, caller_id, LOG_LINE_MAX)) {
2262 text_len = printk_sprint(&r.text_buf[r.info->text_len], reserve_size,
2263 facility, &flags, fmt, args);
2264 r.info->text_len += text_len;
2265
2266 if (flags & LOG_NEWLINE) {
2267 r.info->flags |= LOG_NEWLINE;
2268 prb_final_commit(&e);
2269 } else {
2270 prb_commit(&e);
2271 }
2272
2273 ret = text_len;
2274 goto out;
2275 }
2276 }
2277
2278 /*
2279 * Explicitly initialize the record before every prb_reserve() call.
2280 * prb_reserve_in_last() and prb_reserve() purposely invalidate the
2281 * structure when they fail.
2282 */
2283 prb_rec_init_wr(&r, reserve_size);
2284 if (!prb_reserve(&e, prb, &r)) {
2285 /* truncate the message if it is too long for empty buffer */
2286 truncate_msg(&reserve_size, &trunc_msg_len);
2287
2288 prb_rec_init_wr(&r, reserve_size + trunc_msg_len);
2289 if (!prb_reserve(&e, prb, &r))
2290 goto out;
2291 }
2292
2293 /* fill message */
2294 text_len = printk_sprint(&r.text_buf[0], reserve_size, facility, &flags, fmt, args);
2295 if (trunc_msg_len)
2296 memcpy(&r.text_buf[text_len], trunc_msg, trunc_msg_len);
2297 r.info->text_len = text_len + trunc_msg_len;
2298 r.info->facility = facility;
2299 r.info->level = level & 7;
2300 r.info->flags = flags & 0x1f;
2301 r.info->ts_nsec = ts_nsec;
2302 r.info->caller_id = caller_id;
2303 if (dev_info)
2304 memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info));
2305
2306 /* A message without a trailing newline can be continued. */
2307 if (!(flags & LOG_NEWLINE))
2308 prb_commit(&e);
2309 else
2310 prb_final_commit(&e);
2311
2312 ret = text_len + trunc_msg_len;
2313out:
2314 printk_exit_irqrestore(recursion_ptr, irqflags);
2315 return ret;
2316}
2317
2318asmlinkage int vprintk_emit(int facility, int level,
2319 const struct dev_printk_info *dev_info,
2320 const char *fmt, va_list args)
2321{
2322 int printed_len;
2323 bool in_sched = false;
2324
2325 /* Suppress unimportant messages after panic happens */
2326 if (unlikely(suppress_printk))
2327 return 0;
2328
2329 if (unlikely(suppress_panic_printk) &&
2330 atomic_read(&panic_cpu) != raw_smp_processor_id())
2331 return 0;
2332
2333 if (level == LOGLEVEL_SCHED) {
2334 level = LOGLEVEL_DEFAULT;
2335 in_sched = true;
2336 }
2337
2338 printk_delay(level);
2339
2340 printed_len = vprintk_store(facility, level, dev_info, fmt, args);
2341
2342 /* If called from the scheduler, we can not call up(). */
2343 if (!in_sched) {
2344 /*
2345 * The caller may be holding system-critical or
2346 * timing-sensitive locks. Disable preemption during
2347 * printing of all remaining records to all consoles so that
2348 * this context can return as soon as possible. Hopefully
2349 * another printk() caller will take over the printing.
2350 */
2351 preempt_disable();
2352 /*
2353 * Try to acquire and then immediately release the console
2354 * semaphore. The release will print out buffers. With the
2355 * spinning variant, this context tries to take over the
2356 * printing from another printing context.
2357 */
2358 if (console_trylock_spinning())
2359 console_unlock();
2360 preempt_enable();
2361 }
2362
2363 wake_up_klogd();
2364 return printed_len;
2365}
2366EXPORT_SYMBOL(vprintk_emit);
2367
2368int vprintk_default(const char *fmt, va_list args)
2369{
2370 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
2371}
2372EXPORT_SYMBOL_GPL(vprintk_default);
2373
2374asmlinkage __visible int _printk(const char *fmt, ...)
2375{
2376 va_list args;
2377 int r;
2378
2379 va_start(args, fmt);
2380 r = vprintk(fmt, args);
2381 va_end(args);
2382
2383 return r;
2384}
2385EXPORT_SYMBOL(_printk);
2386
2387static bool pr_flush(int timeout_ms, bool reset_on_progress);
2388static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress);
2389
2390#else /* CONFIG_PRINTK */
2391
2392#define CONSOLE_LOG_MAX 0
2393#define DROPPED_TEXT_MAX 0
2394#define printk_time false
2395
2396#define prb_read_valid(rb, seq, r) false
2397#define prb_first_valid_seq(rb) 0
2398#define prb_next_seq(rb) 0
2399
2400static u64 syslog_seq;
2401
2402static size_t record_print_text(const struct printk_record *r,
2403 bool syslog, bool time)
2404{
2405 return 0;
2406}
2407static ssize_t info_print_ext_header(char *buf, size_t size,
2408 struct printk_info *info)
2409{
2410 return 0;
2411}
2412static ssize_t msg_print_ext_body(char *buf, size_t size,
2413 char *text, size_t text_len,
2414 struct dev_printk_info *dev_info) { return 0; }
2415static void console_lock_spinning_enable(void) { }
2416static int console_lock_spinning_disable_and_check(int cookie) { return 0; }
2417static void call_console_driver(struct console *con, const char *text, size_t len,
2418 char *dropped_text)
2419{
2420}
2421static bool suppress_message_printing(int level) { return false; }
2422static bool pr_flush(int timeout_ms, bool reset_on_progress) { return true; }
2423static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; }
2424
2425#endif /* CONFIG_PRINTK */
2426
2427#ifdef CONFIG_EARLY_PRINTK
2428struct console *early_console;
2429
2430asmlinkage __visible void early_printk(const char *fmt, ...)
2431{
2432 va_list ap;
2433 char buf[512];
2434 int n;
2435
2436 if (!early_console)
2437 return;
2438
2439 va_start(ap, fmt);
2440 n = vscnprintf(buf, sizeof(buf), fmt, ap);
2441 va_end(ap);
2442
2443 early_console->write(early_console, buf, n);
2444}
2445#endif
2446
2447static void set_user_specified(struct console_cmdline *c, bool user_specified)
2448{
2449 if (!user_specified)
2450 return;
2451
2452 /*
2453 * @c console was defined by the user on the command line.
2454 * Do not clear when added twice also by SPCR or the device tree.
2455 */
2456 c->user_specified = true;
2457 /* At least one console defined by the user on the command line. */
2458 console_set_on_cmdline = 1;
2459}
2460
2461static int __add_preferred_console(char *name, int idx, char *options,
2462 char *brl_options, bool user_specified)
2463{
2464 struct console_cmdline *c;
2465 int i;
2466
2467 /*
2468 * See if this tty is not yet registered, and
2469 * if we have a slot free.
2470 */
2471 for (i = 0, c = console_cmdline;
2472 i < MAX_CMDLINECONSOLES && c->name[0];
2473 i++, c++) {
2474 if (strcmp(c->name, name) == 0 && c->index == idx) {
2475 if (!brl_options)
2476 preferred_console = i;
2477 set_user_specified(c, user_specified);
2478 return 0;
2479 }
2480 }
2481 if (i == MAX_CMDLINECONSOLES)
2482 return -E2BIG;
2483 if (!brl_options)
2484 preferred_console = i;
2485 strscpy(c->name, name, sizeof(c->name));
2486 c->options = options;
2487 set_user_specified(c, user_specified);
2488 braille_set_options(c, brl_options);
2489
2490 c->index = idx;
2491 return 0;
2492}
2493
2494static int __init console_msg_format_setup(char *str)
2495{
2496 if (!strcmp(str, "syslog"))
2497 console_msg_format = MSG_FORMAT_SYSLOG;
2498 if (!strcmp(str, "default"))
2499 console_msg_format = MSG_FORMAT_DEFAULT;
2500 return 1;
2501}
2502__setup("console_msg_format=", console_msg_format_setup);
2503
2504/*
2505 * Set up a console. Called via do_early_param() in init/main.c
2506 * for each "console=" parameter in the boot command line.
2507 */
2508static int __init console_setup(char *str)
2509{
2510 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
2511 char *s, *options, *brl_options = NULL;
2512 int idx;
2513
2514 /*
2515 * console="" or console=null have been suggested as a way to
2516 * disable console output. Use ttynull that has been created
2517 * for exactly this purpose.
2518 */
2519 if (str[0] == 0 || strcmp(str, "null") == 0) {
2520 __add_preferred_console("ttynull", 0, NULL, NULL, true);
2521 return 1;
2522 }
2523
2524 if (_braille_console_setup(&str, &brl_options))
2525 return 1;
2526
2527 /*
2528 * Decode str into name, index, options.
2529 */
2530 if (str[0] >= '0' && str[0] <= '9') {
2531 strcpy(buf, "ttyS");
2532 strncpy(buf + 4, str, sizeof(buf) - 5);
2533 } else {
2534 strncpy(buf, str, sizeof(buf) - 1);
2535 }
2536 buf[sizeof(buf) - 1] = 0;
2537 options = strchr(str, ',');
2538 if (options)
2539 *(options++) = 0;
2540#ifdef __sparc__
2541 if (!strcmp(str, "ttya"))
2542 strcpy(buf, "ttyS0");
2543 if (!strcmp(str, "ttyb"))
2544 strcpy(buf, "ttyS1");
2545#endif
2546 for (s = buf; *s; s++)
2547 if (isdigit(*s) || *s == ',')
2548 break;
2549 idx = simple_strtoul(s, NULL, 10);
2550 *s = 0;
2551
2552 __add_preferred_console(buf, idx, options, brl_options, true);
2553 return 1;
2554}
2555__setup("console=", console_setup);
2556
2557/**
2558 * add_preferred_console - add a device to the list of preferred consoles.
2559 * @name: device name
2560 * @idx: device index
2561 * @options: options for this console
2562 *
2563 * The last preferred console added will be used for kernel messages
2564 * and stdin/out/err for init. Normally this is used by console_setup
2565 * above to handle user-supplied console arguments; however it can also
2566 * be used by arch-specific code either to override the user or more
2567 * commonly to provide a default console (ie from PROM variables) when
2568 * the user has not supplied one.
2569 */
2570int add_preferred_console(char *name, int idx, char *options)
2571{
2572 return __add_preferred_console(name, idx, options, NULL, false);
2573}
2574
2575bool console_suspend_enabled = true;
2576EXPORT_SYMBOL(console_suspend_enabled);
2577
2578static int __init console_suspend_disable(char *str)
2579{
2580 console_suspend_enabled = false;
2581 return 1;
2582}
2583__setup("no_console_suspend", console_suspend_disable);
2584module_param_named(console_suspend, console_suspend_enabled,
2585 bool, S_IRUGO | S_IWUSR);
2586MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2587 " and hibernate operations");
2588
2589static bool printk_console_no_auto_verbose;
2590
2591void console_verbose(void)
2592{
2593 if (console_loglevel && !printk_console_no_auto_verbose)
2594 console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
2595}
2596EXPORT_SYMBOL_GPL(console_verbose);
2597
2598module_param_named(console_no_auto_verbose, printk_console_no_auto_verbose, bool, 0644);
2599MODULE_PARM_DESC(console_no_auto_verbose, "Disable console loglevel raise to highest on oops/panic/etc");
2600
2601/**
2602 * suspend_console - suspend the console subsystem
2603 *
2604 * This disables printk() while we go into suspend states
2605 */
2606void suspend_console(void)
2607{
2608 if (!console_suspend_enabled)
2609 return;
2610 pr_info("Suspending console(s) (use no_console_suspend to debug)\n");
2611 pr_flush(1000, true);
2612 console_lock();
2613 console_suspended = 1;
2614 up_console_sem();
2615}
2616
2617void resume_console(void)
2618{
2619 if (!console_suspend_enabled)
2620 return;
2621 down_console_sem();
2622 console_suspended = 0;
2623 console_unlock();
2624 pr_flush(1000, true);
2625}
2626
2627/**
2628 * console_cpu_notify - print deferred console messages after CPU hotplug
2629 * @cpu: unused
2630 *
2631 * If printk() is called from a CPU that is not online yet, the messages
2632 * will be printed on the console only if there are CON_ANYTIME consoles.
2633 * This function is called when a new CPU comes online (or fails to come
2634 * up) or goes offline.
2635 */
2636static int console_cpu_notify(unsigned int cpu)
2637{
2638 if (!cpuhp_tasks_frozen) {
2639 /* If trylock fails, someone else is doing the printing */
2640 if (console_trylock())
2641 console_unlock();
2642 }
2643 return 0;
2644}
2645
2646/**
2647 * console_lock - block the console subsystem from printing
2648 *
2649 * Acquires a lock which guarantees that no consoles will
2650 * be in or enter their write() callback.
2651 *
2652 * Can sleep, returns nothing.
2653 */
2654void console_lock(void)
2655{
2656 might_sleep();
2657
2658 down_console_sem();
2659 if (console_suspended)
2660 return;
2661 console_locked = 1;
2662 console_may_schedule = 1;
2663}
2664EXPORT_SYMBOL(console_lock);
2665
2666/**
2667 * console_trylock - try to block the console subsystem from printing
2668 *
2669 * Try to acquire a lock which guarantees that no consoles will
2670 * be in or enter their write() callback.
2671 *
2672 * returns 1 on success, and 0 on failure to acquire the lock.
2673 */
2674int console_trylock(void)
2675{
2676 if (down_trylock_console_sem())
2677 return 0;
2678 if (console_suspended) {
2679 up_console_sem();
2680 return 0;
2681 }
2682 console_locked = 1;
2683 console_may_schedule = 0;
2684 return 1;
2685}
2686EXPORT_SYMBOL(console_trylock);
2687
2688int is_console_locked(void)
2689{
2690 return console_locked;
2691}
2692EXPORT_SYMBOL(is_console_locked);
2693
2694/*
2695 * Return true when this CPU should unlock console_sem without pushing all
2696 * messages to the console. This reduces the chance that the console is
2697 * locked when the panic CPU tries to use it.
2698 */
2699static bool abandon_console_lock_in_panic(void)
2700{
2701 if (!panic_in_progress())
2702 return false;
2703
2704 /*
2705 * We can use raw_smp_processor_id() here because it is impossible for
2706 * the task to be migrated to the panic_cpu, or away from it. If
2707 * panic_cpu has already been set, and we're not currently executing on
2708 * that CPU, then we never will be.
2709 */
2710 return atomic_read(&panic_cpu) != raw_smp_processor_id();
2711}
2712
2713/*
2714 * Check if the given console is currently capable and allowed to print
2715 * records.
2716 *
2717 * Requires the console_srcu_read_lock.
2718 */
2719static inline bool console_is_usable(struct console *con)
2720{
2721 short flags = console_srcu_read_flags(con);
2722
2723 if (!(flags & CON_ENABLED))
2724 return false;
2725
2726 if (!con->write)
2727 return false;
2728
2729 /*
2730 * Console drivers may assume that per-cpu resources have been
2731 * allocated. So unless they're explicitly marked as being able to
2732 * cope (CON_ANYTIME) don't call them until this CPU is officially up.
2733 */
2734 if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME))
2735 return false;
2736
2737 return true;
2738}
2739
2740static void __console_unlock(void)
2741{
2742 console_locked = 0;
2743 up_console_sem();
2744}
2745
2746/*
2747 * Print one record for the given console. The record printed is whatever
2748 * record is the next available record for the given console.
2749 *
2750 * @text is a buffer of size CONSOLE_LOG_MAX.
2751 *
2752 * If extended messages should be printed, @ext_text is a buffer of size
2753 * CONSOLE_EXT_LOG_MAX. Otherwise @ext_text must be NULL.
2754 *
2755 * If dropped messages should be printed, @dropped_text is a buffer of size
2756 * DROPPED_TEXT_MAX. Otherwise @dropped_text must be NULL.
2757 *
2758 * @handover will be set to true if a printk waiter has taken over the
2759 * console_lock, in which case the caller is no longer holding both the
2760 * console_lock and the SRCU read lock. Otherwise it is set to false.
2761 *
2762 * @cookie is the cookie from the SRCU read lock.
2763 *
2764 * Returns false if the given console has no next record to print, otherwise
2765 * true.
2766 *
2767 * Requires the console_lock and the SRCU read lock.
2768 */
2769static bool console_emit_next_record(struct console *con, char *text, char *ext_text,
2770 char *dropped_text, bool *handover, int cookie)
2771{
2772 static int panic_console_dropped;
2773 struct printk_info info;
2774 struct printk_record r;
2775 unsigned long flags;
2776 char *write_text;
2777 size_t len;
2778
2779 prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX);
2780
2781 *handover = false;
2782
2783 if (!prb_read_valid(prb, con->seq, &r))
2784 return false;
2785
2786 if (con->seq != r.info->seq) {
2787 con->dropped += r.info->seq - con->seq;
2788 con->seq = r.info->seq;
2789 if (panic_in_progress() && panic_console_dropped++ > 10) {
2790 suppress_panic_printk = 1;
2791 pr_warn_once("Too many dropped messages. Suppress messages on non-panic CPUs to prevent livelock.\n");
2792 }
2793 }
2794
2795 /* Skip record that has level above the console loglevel. */
2796 if (suppress_message_printing(r.info->level)) {
2797 con->seq++;
2798 goto skip;
2799 }
2800
2801 if (ext_text) {
2802 write_text = ext_text;
2803 len = info_print_ext_header(ext_text, CONSOLE_EXT_LOG_MAX, r.info);
2804 len += msg_print_ext_body(ext_text + len, CONSOLE_EXT_LOG_MAX - len,
2805 &r.text_buf[0], r.info->text_len, &r.info->dev_info);
2806 } else {
2807 write_text = text;
2808 len = record_print_text(&r, console_msg_format & MSG_FORMAT_SYSLOG, printk_time);
2809 }
2810
2811 /*
2812 * While actively printing out messages, if another printk()
2813 * were to occur on another CPU, it may wait for this one to
2814 * finish. This task can not be preempted if there is a
2815 * waiter waiting to take over.
2816 *
2817 * Interrupts are disabled because the hand over to a waiter
2818 * must not be interrupted until the hand over is completed
2819 * (@console_waiter is cleared).
2820 */
2821 printk_safe_enter_irqsave(flags);
2822 console_lock_spinning_enable();
2823
2824 stop_critical_timings(); /* don't trace print latency */
2825 call_console_driver(con, write_text, len, dropped_text);
2826 start_critical_timings();
2827
2828 con->seq++;
2829
2830 *handover = console_lock_spinning_disable_and_check(cookie);
2831 printk_safe_exit_irqrestore(flags);
2832skip:
2833 return true;
2834}
2835
2836/*
2837 * Print out all remaining records to all consoles.
2838 *
2839 * @do_cond_resched is set by the caller. It can be true only in schedulable
2840 * context.
2841 *
2842 * @next_seq is set to the sequence number after the last available record.
2843 * The value is valid only when this function returns true. It means that all
2844 * usable consoles are completely flushed.
2845 *
2846 * @handover will be set to true if a printk waiter has taken over the
2847 * console_lock, in which case the caller is no longer holding the
2848 * console_lock. Otherwise it is set to false.
2849 *
2850 * Returns true when there was at least one usable console and all messages
2851 * were flushed to all usable consoles. A returned false informs the caller
2852 * that everything was not flushed (either there were no usable consoles or
2853 * another context has taken over printing or it is a panic situation and this
2854 * is not the panic CPU). Regardless the reason, the caller should assume it
2855 * is not useful to immediately try again.
2856 *
2857 * Requires the console_lock.
2858 */
2859static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handover)
2860{
2861 static char dropped_text[DROPPED_TEXT_MAX];
2862 static char ext_text[CONSOLE_EXT_LOG_MAX];
2863 static char text[CONSOLE_LOG_MAX];
2864 bool any_usable = false;
2865 struct console *con;
2866 bool any_progress;
2867 int cookie;
2868
2869 *next_seq = 0;
2870 *handover = false;
2871
2872 do {
2873 any_progress = false;
2874
2875 cookie = console_srcu_read_lock();
2876 for_each_console_srcu(con) {
2877 bool progress;
2878
2879 if (!console_is_usable(con))
2880 continue;
2881 any_usable = true;
2882
2883 if (console_srcu_read_flags(con) & CON_EXTENDED) {
2884 /* Extended consoles do not print "dropped messages". */
2885 progress = console_emit_next_record(con, &text[0],
2886 &ext_text[0], NULL,
2887 handover, cookie);
2888 } else {
2889 progress = console_emit_next_record(con, &text[0],
2890 NULL, &dropped_text[0],
2891 handover, cookie);
2892 }
2893
2894 /*
2895 * If a handover has occurred, the SRCU read lock
2896 * is already released.
2897 */
2898 if (*handover)
2899 return false;
2900
2901 /* Track the next of the highest seq flushed. */
2902 if (con->seq > *next_seq)
2903 *next_seq = con->seq;
2904
2905 if (!progress)
2906 continue;
2907 any_progress = true;
2908
2909 /* Allow panic_cpu to take over the consoles safely. */
2910 if (abandon_console_lock_in_panic())
2911 goto abandon;
2912
2913 if (do_cond_resched)
2914 cond_resched();
2915 }
2916 console_srcu_read_unlock(cookie);
2917 } while (any_progress);
2918
2919 return any_usable;
2920
2921abandon:
2922 console_srcu_read_unlock(cookie);
2923 return false;
2924}
2925
2926/**
2927 * console_unlock - unblock the console subsystem from printing
2928 *
2929 * Releases the console_lock which the caller holds to block printing of
2930 * the console subsystem.
2931 *
2932 * While the console_lock was held, console output may have been buffered
2933 * by printk(). If this is the case, console_unlock(); emits
2934 * the output prior to releasing the lock.
2935 *
2936 * console_unlock(); may be called from any context.
2937 */
2938void console_unlock(void)
2939{
2940 bool do_cond_resched;
2941 bool handover;
2942 bool flushed;
2943 u64 next_seq;
2944
2945 if (console_suspended) {
2946 up_console_sem();
2947 return;
2948 }
2949
2950 /*
2951 * Console drivers are called with interrupts disabled, so
2952 * @console_may_schedule should be cleared before; however, we may
2953 * end up dumping a lot of lines, for example, if called from
2954 * console registration path, and should invoke cond_resched()
2955 * between lines if allowable. Not doing so can cause a very long
2956 * scheduling stall on a slow console leading to RCU stall and
2957 * softlockup warnings which exacerbate the issue with more
2958 * messages practically incapacitating the system. Therefore, create
2959 * a local to use for the printing loop.
2960 */
2961 do_cond_resched = console_may_schedule;
2962
2963 do {
2964 console_may_schedule = 0;
2965
2966 flushed = console_flush_all(do_cond_resched, &next_seq, &handover);
2967 if (!handover)
2968 __console_unlock();
2969
2970 /*
2971 * Abort if there was a failure to flush all messages to all
2972 * usable consoles. Either it is not possible to flush (in
2973 * which case it would be an infinite loop of retrying) or
2974 * another context has taken over printing.
2975 */
2976 if (!flushed)
2977 break;
2978
2979 /*
2980 * Some context may have added new records after
2981 * console_flush_all() but before unlocking the console.
2982 * Re-check if there is a new record to flush. If the trylock
2983 * fails, another context is already handling the printing.
2984 */
2985 } while (prb_read_valid(prb, next_seq, NULL) && console_trylock());
2986}
2987EXPORT_SYMBOL(console_unlock);
2988
2989/**
2990 * console_conditional_schedule - yield the CPU if required
2991 *
2992 * If the console code is currently allowed to sleep, and
2993 * if this CPU should yield the CPU to another task, do
2994 * so here.
2995 *
2996 * Must be called within console_lock();.
2997 */
2998void __sched console_conditional_schedule(void)
2999{
3000 if (console_may_schedule)
3001 cond_resched();
3002}
3003EXPORT_SYMBOL(console_conditional_schedule);
3004
3005void console_unblank(void)
3006{
3007 struct console *c;
3008 int cookie;
3009
3010 /*
3011 * Stop console printing because the unblank() callback may
3012 * assume the console is not within its write() callback.
3013 *
3014 * If @oops_in_progress is set, this may be an atomic context.
3015 * In that case, attempt a trylock as best-effort.
3016 */
3017 if (oops_in_progress) {
3018 if (down_trylock_console_sem() != 0)
3019 return;
3020 } else
3021 console_lock();
3022
3023 console_locked = 1;
3024 console_may_schedule = 0;
3025
3026 cookie = console_srcu_read_lock();
3027 for_each_console_srcu(c) {
3028 if ((console_srcu_read_flags(c) & CON_ENABLED) && c->unblank)
3029 c->unblank();
3030 }
3031 console_srcu_read_unlock(cookie);
3032
3033 console_unlock();
3034
3035 if (!oops_in_progress)
3036 pr_flush(1000, true);
3037}
3038
3039/**
3040 * console_flush_on_panic - flush console content on panic
3041 * @mode: flush all messages in buffer or just the pending ones
3042 *
3043 * Immediately output all pending messages no matter what.
3044 */
3045void console_flush_on_panic(enum con_flush_mode mode)
3046{
3047 /*
3048 * If someone else is holding the console lock, trylock will fail
3049 * and may_schedule may be set. Ignore and proceed to unlock so
3050 * that messages are flushed out. As this can be called from any
3051 * context and we don't want to get preempted while flushing,
3052 * ensure may_schedule is cleared.
3053 */
3054 console_trylock();
3055 console_may_schedule = 0;
3056
3057 if (mode == CONSOLE_REPLAY_ALL) {
3058 struct console *c;
3059 int cookie;
3060 u64 seq;
3061
3062 seq = prb_first_valid_seq(prb);
3063
3064 cookie = console_srcu_read_lock();
3065 for_each_console_srcu(c) {
3066 /*
3067 * If the above console_trylock() failed, this is an
3068 * unsynchronized assignment. But in that case, the
3069 * kernel is in "hope and pray" mode anyway.
3070 */
3071 c->seq = seq;
3072 }
3073 console_srcu_read_unlock(cookie);
3074 }
3075 console_unlock();
3076}
3077
3078/*
3079 * Return the console tty driver structure and its associated index
3080 */
3081struct tty_driver *console_device(int *index)
3082{
3083 struct console *c;
3084 struct tty_driver *driver = NULL;
3085 int cookie;
3086
3087 /*
3088 * Take console_lock to serialize device() callback with
3089 * other console operations. For example, fg_console is
3090 * modified under console_lock when switching vt.
3091 */
3092 console_lock();
3093
3094 cookie = console_srcu_read_lock();
3095 for_each_console_srcu(c) {
3096 if (!c->device)
3097 continue;
3098 driver = c->device(c, index);
3099 if (driver)
3100 break;
3101 }
3102 console_srcu_read_unlock(cookie);
3103
3104 console_unlock();
3105 return driver;
3106}
3107
3108/*
3109 * Prevent further output on the passed console device so that (for example)
3110 * serial drivers can disable console output before suspending a port, and can
3111 * re-enable output afterwards.
3112 */
3113void console_stop(struct console *console)
3114{
3115 __pr_flush(console, 1000, true);
3116 console_list_lock();
3117 console_srcu_write_flags(console, console->flags & ~CON_ENABLED);
3118 console_list_unlock();
3119
3120 /*
3121 * Ensure that all SRCU list walks have completed. All contexts must
3122 * be able to see that this console is disabled so that (for example)
3123 * the caller can suspend the port without risk of another context
3124 * using the port.
3125 */
3126 synchronize_srcu(&console_srcu);
3127}
3128EXPORT_SYMBOL(console_stop);
3129
3130void console_start(struct console *console)
3131{
3132 console_list_lock();
3133 console_srcu_write_flags(console, console->flags | CON_ENABLED);
3134 console_list_unlock();
3135 __pr_flush(console, 1000, true);
3136}
3137EXPORT_SYMBOL(console_start);
3138
3139static int __read_mostly keep_bootcon;
3140
3141static int __init keep_bootcon_setup(char *str)
3142{
3143 keep_bootcon = 1;
3144 pr_info("debug: skip boot console de-registration.\n");
3145
3146 return 0;
3147}
3148
3149early_param("keep_bootcon", keep_bootcon_setup);
3150
3151/*
3152 * This is called by register_console() to try to match
3153 * the newly registered console with any of the ones selected
3154 * by either the command line or add_preferred_console() and
3155 * setup/enable it.
3156 *
3157 * Care need to be taken with consoles that are statically
3158 * enabled such as netconsole
3159 */
3160static int try_enable_preferred_console(struct console *newcon,
3161 bool user_specified)
3162{
3163 struct console_cmdline *c;
3164 int i, err;
3165
3166 for (i = 0, c = console_cmdline;
3167 i < MAX_CMDLINECONSOLES && c->name[0];
3168 i++, c++) {
3169 if (c->user_specified != user_specified)
3170 continue;
3171 if (!newcon->match ||
3172 newcon->match(newcon, c->name, c->index, c->options) != 0) {
3173 /* default matching */
3174 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
3175 if (strcmp(c->name, newcon->name) != 0)
3176 continue;
3177 if (newcon->index >= 0 &&
3178 newcon->index != c->index)
3179 continue;
3180 if (newcon->index < 0)
3181 newcon->index = c->index;
3182
3183 if (_braille_register_console(newcon, c))
3184 return 0;
3185
3186 if (newcon->setup &&
3187 (err = newcon->setup(newcon, c->options)) != 0)
3188 return err;
3189 }
3190 newcon->flags |= CON_ENABLED;
3191 if (i == preferred_console)
3192 newcon->flags |= CON_CONSDEV;
3193 return 0;
3194 }
3195
3196 /*
3197 * Some consoles, such as pstore and netconsole, can be enabled even
3198 * without matching. Accept the pre-enabled consoles only when match()
3199 * and setup() had a chance to be called.
3200 */
3201 if (newcon->flags & CON_ENABLED && c->user_specified == user_specified)
3202 return 0;
3203
3204 return -ENOENT;
3205}
3206
3207/* Try to enable the console unconditionally */
3208static void try_enable_default_console(struct console *newcon)
3209{
3210 if (newcon->index < 0)
3211 newcon->index = 0;
3212
3213 if (newcon->setup && newcon->setup(newcon, NULL) != 0)
3214 return;
3215
3216 newcon->flags |= CON_ENABLED;
3217
3218 if (newcon->device)
3219 newcon->flags |= CON_CONSDEV;
3220}
3221
3222#define con_printk(lvl, con, fmt, ...) \
3223 printk(lvl pr_fmt("%sconsole [%s%d] " fmt), \
3224 (con->flags & CON_BOOT) ? "boot" : "", \
3225 con->name, con->index, ##__VA_ARGS__)
3226
3227static void console_init_seq(struct console *newcon, bool bootcon_registered)
3228{
3229 struct console *con;
3230 bool handover;
3231
3232 if (newcon->flags & (CON_PRINTBUFFER | CON_BOOT)) {
3233 /* Get a consistent copy of @syslog_seq. */
3234 mutex_lock(&syslog_lock);
3235 newcon->seq = syslog_seq;
3236 mutex_unlock(&syslog_lock);
3237 } else {
3238 /* Begin with next message added to ringbuffer. */
3239 newcon->seq = prb_next_seq(prb);
3240
3241 /*
3242 * If any enabled boot consoles are due to be unregistered
3243 * shortly, some may not be caught up and may be the same
3244 * device as @newcon. Since it is not known which boot console
3245 * is the same device, flush all consoles and, if necessary,
3246 * start with the message of the enabled boot console that is
3247 * the furthest behind.
3248 */
3249 if (bootcon_registered && !keep_bootcon) {
3250 /*
3251 * Hold the console_lock to stop console printing and
3252 * guarantee safe access to console->seq.
3253 */
3254 console_lock();
3255
3256 /*
3257 * Flush all consoles and set the console to start at
3258 * the next unprinted sequence number.
3259 */
3260 if (!console_flush_all(true, &newcon->seq, &handover)) {
3261 /*
3262 * Flushing failed. Just choose the lowest
3263 * sequence of the enabled boot consoles.
3264 */
3265
3266 /*
3267 * If there was a handover, this context no
3268 * longer holds the console_lock.
3269 */
3270 if (handover)
3271 console_lock();
3272
3273 newcon->seq = prb_next_seq(prb);
3274 for_each_console(con) {
3275 if ((con->flags & CON_BOOT) &&
3276 (con->flags & CON_ENABLED) &&
3277 con->seq < newcon->seq) {
3278 newcon->seq = con->seq;
3279 }
3280 }
3281 }
3282
3283 console_unlock();
3284 }
3285 }
3286}
3287
3288#define console_first() \
3289 hlist_entry(console_list.first, struct console, node)
3290
3291static int unregister_console_locked(struct console *console);
3292
3293/*
3294 * The console driver calls this routine during kernel initialization
3295 * to register the console printing procedure with printk() and to
3296 * print any messages that were printed by the kernel before the
3297 * console driver was initialized.
3298 *
3299 * This can happen pretty early during the boot process (because of
3300 * early_printk) - sometimes before setup_arch() completes - be careful
3301 * of what kernel features are used - they may not be initialised yet.
3302 *
3303 * There are two types of consoles - bootconsoles (early_printk) and
3304 * "real" consoles (everything which is not a bootconsole) which are
3305 * handled differently.
3306 * - Any number of bootconsoles can be registered at any time.
3307 * - As soon as a "real" console is registered, all bootconsoles
3308 * will be unregistered automatically.
3309 * - Once a "real" console is registered, any attempt to register a
3310 * bootconsoles will be rejected
3311 */
3312void register_console(struct console *newcon)
3313{
3314 struct console *con;
3315 bool bootcon_registered = false;
3316 bool realcon_registered = false;
3317 int err;
3318
3319 console_list_lock();
3320
3321 for_each_console(con) {
3322 if (WARN(con == newcon, "console '%s%d' already registered\n",
3323 con->name, con->index)) {
3324 goto unlock;
3325 }
3326
3327 if (con->flags & CON_BOOT)
3328 bootcon_registered = true;
3329 else
3330 realcon_registered = true;
3331 }
3332
3333 /* Do not register boot consoles when there already is a real one. */
3334 if ((newcon->flags & CON_BOOT) && realcon_registered) {
3335 pr_info("Too late to register bootconsole %s%d\n",
3336 newcon->name, newcon->index);
3337 goto unlock;
3338 }
3339
3340 /*
3341 * See if we want to enable this console driver by default.
3342 *
3343 * Nope when a console is preferred by the command line, device
3344 * tree, or SPCR.
3345 *
3346 * The first real console with tty binding (driver) wins. More
3347 * consoles might get enabled before the right one is found.
3348 *
3349 * Note that a console with tty binding will have CON_CONSDEV
3350 * flag set and will be first in the list.
3351 */
3352 if (preferred_console < 0) {
3353 if (hlist_empty(&console_list) || !console_first()->device ||
3354 console_first()->flags & CON_BOOT) {
3355 try_enable_default_console(newcon);
3356 }
3357 }
3358
3359 /* See if this console matches one we selected on the command line */
3360 err = try_enable_preferred_console(newcon, true);
3361
3362 /* If not, try to match against the platform default(s) */
3363 if (err == -ENOENT)
3364 err = try_enable_preferred_console(newcon, false);
3365
3366 /* printk() messages are not printed to the Braille console. */
3367 if (err || newcon->flags & CON_BRL)
3368 goto unlock;
3369
3370 /*
3371 * If we have a bootconsole, and are switching to a real console,
3372 * don't print everything out again, since when the boot console, and
3373 * the real console are the same physical device, it's annoying to
3374 * see the beginning boot messages twice
3375 */
3376 if (bootcon_registered &&
3377 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
3378 newcon->flags &= ~CON_PRINTBUFFER;
3379 }
3380
3381 newcon->dropped = 0;
3382 console_init_seq(newcon, bootcon_registered);
3383
3384 /*
3385 * Put this console in the list - keep the
3386 * preferred driver at the head of the list.
3387 */
3388 if (hlist_empty(&console_list)) {
3389 /* Ensure CON_CONSDEV is always set for the head. */
3390 newcon->flags |= CON_CONSDEV;
3391 hlist_add_head_rcu(&newcon->node, &console_list);
3392
3393 } else if (newcon->flags & CON_CONSDEV) {
3394 /* Only the new head can have CON_CONSDEV set. */
3395 console_srcu_write_flags(console_first(), console_first()->flags & ~CON_CONSDEV);
3396 hlist_add_head_rcu(&newcon->node, &console_list);
3397
3398 } else {
3399 hlist_add_behind_rcu(&newcon->node, console_list.first);
3400 }
3401
3402 /*
3403 * No need to synchronize SRCU here! The caller does not rely
3404 * on all contexts being able to see the new console before
3405 * register_console() completes.
3406 */
3407
3408 console_sysfs_notify();
3409
3410 /*
3411 * By unregistering the bootconsoles after we enable the real console
3412 * we get the "console xxx enabled" message on all the consoles -
3413 * boot consoles, real consoles, etc - this is to ensure that end
3414 * users know there might be something in the kernel's log buffer that
3415 * went to the bootconsole (that they do not see on the real console)
3416 */
3417 con_printk(KERN_INFO, newcon, "enabled\n");
3418 if (bootcon_registered &&
3419 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
3420 !keep_bootcon) {
3421 struct hlist_node *tmp;
3422
3423 hlist_for_each_entry_safe(con, tmp, &console_list, node) {
3424 if (con->flags & CON_BOOT)
3425 unregister_console_locked(con);
3426 }
3427 }
3428unlock:
3429 console_list_unlock();
3430}
3431EXPORT_SYMBOL(register_console);
3432
3433/* Must be called under console_list_lock(). */
3434static int unregister_console_locked(struct console *console)
3435{
3436 int res;
3437
3438 lockdep_assert_console_list_lock_held();
3439
3440 con_printk(KERN_INFO, console, "disabled\n");
3441
3442 res = _braille_unregister_console(console);
3443 if (res < 0)
3444 return res;
3445 if (res > 0)
3446 return 0;
3447
3448 /* Disable it unconditionally */
3449 console_srcu_write_flags(console, console->flags & ~CON_ENABLED);
3450
3451 if (!console_is_registered_locked(console))
3452 return -ENODEV;
3453
3454 hlist_del_init_rcu(&console->node);
3455
3456 /*
3457 * <HISTORICAL>
3458 * If this isn't the last console and it has CON_CONSDEV set, we
3459 * need to set it on the next preferred console.
3460 * </HISTORICAL>
3461 *
3462 * The above makes no sense as there is no guarantee that the next
3463 * console has any device attached. Oh well....
3464 */
3465 if (!hlist_empty(&console_list) && console->flags & CON_CONSDEV)
3466 console_srcu_write_flags(console_first(), console_first()->flags | CON_CONSDEV);
3467
3468 /*
3469 * Ensure that all SRCU list walks have completed. All contexts
3470 * must not be able to see this console in the list so that any
3471 * exit/cleanup routines can be performed safely.
3472 */
3473 synchronize_srcu(&console_srcu);
3474
3475 console_sysfs_notify();
3476
3477 if (console->exit)
3478 res = console->exit(console);
3479
3480 return res;
3481}
3482
3483int unregister_console(struct console *console)
3484{
3485 int res;
3486
3487 console_list_lock();
3488 res = unregister_console_locked(console);
3489 console_list_unlock();
3490 return res;
3491}
3492EXPORT_SYMBOL(unregister_console);
3493
3494/**
3495 * console_force_preferred_locked - force a registered console preferred
3496 * @con: The registered console to force preferred.
3497 *
3498 * Must be called under console_list_lock().
3499 */
3500void console_force_preferred_locked(struct console *con)
3501{
3502 struct console *cur_pref_con;
3503
3504 if (!console_is_registered_locked(con))
3505 return;
3506
3507 cur_pref_con = console_first();
3508
3509 /* Already preferred? */
3510 if (cur_pref_con == con)
3511 return;
3512
3513 /*
3514 * Delete, but do not re-initialize the entry. This allows the console
3515 * to continue to appear registered (via any hlist_unhashed_lockless()
3516 * checks), even though it was briefly removed from the console list.
3517 */
3518 hlist_del_rcu(&con->node);
3519
3520 /*
3521 * Ensure that all SRCU list walks have completed so that the console
3522 * can be added to the beginning of the console list and its forward
3523 * list pointer can be re-initialized.
3524 */
3525 synchronize_srcu(&console_srcu);
3526
3527 con->flags |= CON_CONSDEV;
3528 WARN_ON(!con->device);
3529
3530 /* Only the new head can have CON_CONSDEV set. */
3531 console_srcu_write_flags(cur_pref_con, cur_pref_con->flags & ~CON_CONSDEV);
3532 hlist_add_head_rcu(&con->node, &console_list);
3533}
3534EXPORT_SYMBOL(console_force_preferred_locked);
3535
3536/*
3537 * Initialize the console device. This is called *early*, so
3538 * we can't necessarily depend on lots of kernel help here.
3539 * Just do some early initializations, and do the complex setup
3540 * later.
3541 */
3542void __init console_init(void)
3543{
3544 int ret;
3545 initcall_t call;
3546 initcall_entry_t *ce;
3547
3548 /* Setup the default TTY line discipline. */
3549 n_tty_init();
3550
3551 /*
3552 * set up the console device so that later boot sequences can
3553 * inform about problems etc..
3554 */
3555 ce = __con_initcall_start;
3556 trace_initcall_level("console");
3557 while (ce < __con_initcall_end) {
3558 call = initcall_from_entry(ce);
3559 trace_initcall_start(call);
3560 ret = call();
3561 trace_initcall_finish(call, ret);
3562 ce++;
3563 }
3564}
3565
3566/*
3567 * Some boot consoles access data that is in the init section and which will
3568 * be discarded after the initcalls have been run. To make sure that no code
3569 * will access this data, unregister the boot consoles in a late initcall.
3570 *
3571 * If for some reason, such as deferred probe or the driver being a loadable
3572 * module, the real console hasn't registered yet at this point, there will
3573 * be a brief interval in which no messages are logged to the console, which
3574 * makes it difficult to diagnose problems that occur during this time.
3575 *
3576 * To mitigate this problem somewhat, only unregister consoles whose memory
3577 * intersects with the init section. Note that all other boot consoles will
3578 * get unregistered when the real preferred console is registered.
3579 */
3580static int __init printk_late_init(void)
3581{
3582 struct hlist_node *tmp;
3583 struct console *con;
3584 int ret;
3585
3586 console_list_lock();
3587 hlist_for_each_entry_safe(con, tmp, &console_list, node) {
3588 if (!(con->flags & CON_BOOT))
3589 continue;
3590
3591 /* Check addresses that might be used for enabled consoles. */
3592 if (init_section_intersects(con, sizeof(*con)) ||
3593 init_section_contains(con->write, 0) ||
3594 init_section_contains(con->read, 0) ||
3595 init_section_contains(con->device, 0) ||
3596 init_section_contains(con->unblank, 0) ||
3597 init_section_contains(con->data, 0)) {
3598 /*
3599 * Please, consider moving the reported consoles out
3600 * of the init section.
3601 */
3602 pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n",
3603 con->name, con->index);
3604 unregister_console_locked(con);
3605 }
3606 }
3607 console_list_unlock();
3608
3609 ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL,
3610 console_cpu_notify);
3611 WARN_ON(ret < 0);
3612 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online",
3613 console_cpu_notify, NULL);
3614 WARN_ON(ret < 0);
3615 printk_sysctl_init();
3616 return 0;
3617}
3618late_initcall(printk_late_init);
3619
3620#if defined CONFIG_PRINTK
3621/* If @con is specified, only wait for that console. Otherwise wait for all. */
3622static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress)
3623{
3624 int remaining = timeout_ms;
3625 struct console *c;
3626 u64 last_diff = 0;
3627 u64 printk_seq;
3628 int cookie;
3629 u64 diff;
3630 u64 seq;
3631
3632 might_sleep();
3633
3634 seq = prb_next_seq(prb);
3635
3636 for (;;) {
3637 diff = 0;
3638
3639 /*
3640 * Hold the console_lock to guarantee safe access to
3641 * console->seq and to prevent changes to @console_suspended
3642 * until all consoles have been processed.
3643 */
3644 console_lock();
3645
3646 cookie = console_srcu_read_lock();
3647 for_each_console_srcu(c) {
3648 if (con && con != c)
3649 continue;
3650 if (!console_is_usable(c))
3651 continue;
3652 printk_seq = c->seq;
3653 if (printk_seq < seq)
3654 diff += seq - printk_seq;
3655 }
3656 console_srcu_read_unlock(cookie);
3657
3658 /*
3659 * If consoles are suspended, it cannot be expected that they
3660 * make forward progress, so timeout immediately. @diff is
3661 * still used to return a valid flush status.
3662 */
3663 if (console_suspended)
3664 remaining = 0;
3665 else if (diff != last_diff && reset_on_progress)
3666 remaining = timeout_ms;
3667
3668 console_unlock();
3669
3670 if (diff == 0 || remaining == 0)
3671 break;
3672
3673 if (remaining < 0) {
3674 /* no timeout limit */
3675 msleep(100);
3676 } else if (remaining < 100) {
3677 msleep(remaining);
3678 remaining = 0;
3679 } else {
3680 msleep(100);
3681 remaining -= 100;
3682 }
3683
3684 last_diff = diff;
3685 }
3686
3687 return (diff == 0);
3688}
3689
3690/**
3691 * pr_flush() - Wait for printing threads to catch up.
3692 *
3693 * @timeout_ms: The maximum time (in ms) to wait.
3694 * @reset_on_progress: Reset the timeout if forward progress is seen.
3695 *
3696 * A value of 0 for @timeout_ms means no waiting will occur. A value of -1
3697 * represents infinite waiting.
3698 *
3699 * If @reset_on_progress is true, the timeout will be reset whenever any
3700 * printer has been seen to make some forward progress.
3701 *
3702 * Context: Process context. May sleep while acquiring console lock.
3703 * Return: true if all enabled printers are caught up.
3704 */
3705static bool pr_flush(int timeout_ms, bool reset_on_progress)
3706{
3707 return __pr_flush(NULL, timeout_ms, reset_on_progress);
3708}
3709
3710/*
3711 * Delayed printk version, for scheduler-internal messages:
3712 */
3713#define PRINTK_PENDING_WAKEUP 0x01
3714#define PRINTK_PENDING_OUTPUT 0x02
3715
3716static DEFINE_PER_CPU(int, printk_pending);
3717
3718static void wake_up_klogd_work_func(struct irq_work *irq_work)
3719{
3720 int pending = this_cpu_xchg(printk_pending, 0);
3721
3722 if (pending & PRINTK_PENDING_OUTPUT) {
3723 /* If trylock fails, someone else is doing the printing */
3724 if (console_trylock())
3725 console_unlock();
3726 }
3727
3728 if (pending & PRINTK_PENDING_WAKEUP)
3729 wake_up_interruptible(&log_wait);
3730}
3731
3732static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) =
3733 IRQ_WORK_INIT_LAZY(wake_up_klogd_work_func);
3734
3735static void __wake_up_klogd(int val)
3736{
3737 if (!printk_percpu_data_ready())
3738 return;
3739
3740 preempt_disable();
3741 /*
3742 * Guarantee any new records can be seen by tasks preparing to wait
3743 * before this context checks if the wait queue is empty.
3744 *
3745 * The full memory barrier within wq_has_sleeper() pairs with the full
3746 * memory barrier within set_current_state() of
3747 * prepare_to_wait_event(), which is called after ___wait_event() adds
3748 * the waiter but before it has checked the wait condition.
3749 *
3750 * This pairs with devkmsg_read:A and syslog_print:A.
3751 */
3752 if (wq_has_sleeper(&log_wait) || /* LMM(__wake_up_klogd:A) */
3753 (val & PRINTK_PENDING_OUTPUT)) {
3754 this_cpu_or(printk_pending, val);
3755 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
3756 }
3757 preempt_enable();
3758}
3759
3760void wake_up_klogd(void)
3761{
3762 __wake_up_klogd(PRINTK_PENDING_WAKEUP);
3763}
3764
3765void defer_console_output(void)
3766{
3767 /*
3768 * New messages may have been added directly to the ringbuffer
3769 * using vprintk_store(), so wake any waiters as well.
3770 */
3771 __wake_up_klogd(PRINTK_PENDING_WAKEUP | PRINTK_PENDING_OUTPUT);
3772}
3773
3774void printk_trigger_flush(void)
3775{
3776 defer_console_output();
3777}
3778
3779int vprintk_deferred(const char *fmt, va_list args)
3780{
3781 int r;
3782
3783 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, fmt, args);
3784 defer_console_output();
3785
3786 return r;
3787}
3788
3789int _printk_deferred(const char *fmt, ...)
3790{
3791 va_list args;
3792 int r;
3793
3794 va_start(args, fmt);
3795 r = vprintk_deferred(fmt, args);
3796 va_end(args);
3797
3798 return r;
3799}
3800
3801/*
3802 * printk rate limiting, lifted from the networking subsystem.
3803 *
3804 * This enforces a rate limit: not more than 10 kernel messages
3805 * every 5s to make a denial-of-service attack impossible.
3806 */
3807DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
3808
3809int __printk_ratelimit(const char *func)
3810{
3811 return ___ratelimit(&printk_ratelimit_state, func);
3812}
3813EXPORT_SYMBOL(__printk_ratelimit);
3814
3815/**
3816 * printk_timed_ratelimit - caller-controlled printk ratelimiting
3817 * @caller_jiffies: pointer to caller's state
3818 * @interval_msecs: minimum interval between prints
3819 *
3820 * printk_timed_ratelimit() returns true if more than @interval_msecs
3821 * milliseconds have elapsed since the last time printk_timed_ratelimit()
3822 * returned true.
3823 */
3824bool printk_timed_ratelimit(unsigned long *caller_jiffies,
3825 unsigned int interval_msecs)
3826{
3827 unsigned long elapsed = jiffies - *caller_jiffies;
3828
3829 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
3830 return false;
3831
3832 *caller_jiffies = jiffies;
3833 return true;
3834}
3835EXPORT_SYMBOL(printk_timed_ratelimit);
3836
3837static DEFINE_SPINLOCK(dump_list_lock);
3838static LIST_HEAD(dump_list);
3839
3840/**
3841 * kmsg_dump_register - register a kernel log dumper.
3842 * @dumper: pointer to the kmsg_dumper structure
3843 *
3844 * Adds a kernel log dumper to the system. The dump callback in the
3845 * structure will be called when the kernel oopses or panics and must be
3846 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
3847 */
3848int kmsg_dump_register(struct kmsg_dumper *dumper)
3849{
3850 unsigned long flags;
3851 int err = -EBUSY;
3852
3853 /* The dump callback needs to be set */
3854 if (!dumper->dump)
3855 return -EINVAL;
3856
3857 spin_lock_irqsave(&dump_list_lock, flags);
3858 /* Don't allow registering multiple times */
3859 if (!dumper->registered) {
3860 dumper->registered = 1;
3861 list_add_tail_rcu(&dumper->list, &dump_list);
3862 err = 0;
3863 }
3864 spin_unlock_irqrestore(&dump_list_lock, flags);
3865
3866 return err;
3867}
3868EXPORT_SYMBOL_GPL(kmsg_dump_register);
3869
3870/**
3871 * kmsg_dump_unregister - unregister a kmsg dumper.
3872 * @dumper: pointer to the kmsg_dumper structure
3873 *
3874 * Removes a dump device from the system. Returns zero on success and
3875 * %-EINVAL otherwise.
3876 */
3877int kmsg_dump_unregister(struct kmsg_dumper *dumper)
3878{
3879 unsigned long flags;
3880 int err = -EINVAL;
3881
3882 spin_lock_irqsave(&dump_list_lock, flags);
3883 if (dumper->registered) {
3884 dumper->registered = 0;
3885 list_del_rcu(&dumper->list);
3886 err = 0;
3887 }
3888 spin_unlock_irqrestore(&dump_list_lock, flags);
3889 synchronize_rcu();
3890
3891 return err;
3892}
3893EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
3894
3895static bool always_kmsg_dump;
3896module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
3897
3898const char *kmsg_dump_reason_str(enum kmsg_dump_reason reason)
3899{
3900 switch (reason) {
3901 case KMSG_DUMP_PANIC:
3902 return "Panic";
3903 case KMSG_DUMP_OOPS:
3904 return "Oops";
3905 case KMSG_DUMP_EMERG:
3906 return "Emergency";
3907 case KMSG_DUMP_SHUTDOWN:
3908 return "Shutdown";
3909 default:
3910 return "Unknown";
3911 }
3912}
3913EXPORT_SYMBOL_GPL(kmsg_dump_reason_str);
3914
3915/**
3916 * kmsg_dump - dump kernel log to kernel message dumpers.
3917 * @reason: the reason (oops, panic etc) for dumping
3918 *
3919 * Call each of the registered dumper's dump() callback, which can
3920 * retrieve the kmsg records with kmsg_dump_get_line() or
3921 * kmsg_dump_get_buffer().
3922 */
3923void kmsg_dump(enum kmsg_dump_reason reason)
3924{
3925 struct kmsg_dumper *dumper;
3926
3927 rcu_read_lock();
3928 list_for_each_entry_rcu(dumper, &dump_list, list) {
3929 enum kmsg_dump_reason max_reason = dumper->max_reason;
3930
3931 /*
3932 * If client has not provided a specific max_reason, default
3933 * to KMSG_DUMP_OOPS, unless always_kmsg_dump was set.
3934 */
3935 if (max_reason == KMSG_DUMP_UNDEF) {
3936 max_reason = always_kmsg_dump ? KMSG_DUMP_MAX :
3937 KMSG_DUMP_OOPS;
3938 }
3939 if (reason > max_reason)
3940 continue;
3941
3942 /* invoke dumper which will iterate over records */
3943 dumper->dump(dumper, reason);
3944 }
3945 rcu_read_unlock();
3946}
3947
3948/**
3949 * kmsg_dump_get_line - retrieve one kmsg log line
3950 * @iter: kmsg dump iterator
3951 * @syslog: include the "<4>" prefixes
3952 * @line: buffer to copy the line to
3953 * @size: maximum size of the buffer
3954 * @len: length of line placed into buffer
3955 *
3956 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3957 * record, and copy one record into the provided buffer.
3958 *
3959 * Consecutive calls will return the next available record moving
3960 * towards the end of the buffer with the youngest messages.
3961 *
3962 * A return value of FALSE indicates that there are no more records to
3963 * read.
3964 */
3965bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
3966 char *line, size_t size, size_t *len)
3967{
3968 u64 min_seq = latched_seq_read_nolock(&clear_seq);
3969 struct printk_info info;
3970 unsigned int line_count;
3971 struct printk_record r;
3972 size_t l = 0;
3973 bool ret = false;
3974
3975 if (iter->cur_seq < min_seq)
3976 iter->cur_seq = min_seq;
3977
3978 prb_rec_init_rd(&r, &info, line, size);
3979
3980 /* Read text or count text lines? */
3981 if (line) {
3982 if (!prb_read_valid(prb, iter->cur_seq, &r))
3983 goto out;
3984 l = record_print_text(&r, syslog, printk_time);
3985 } else {
3986 if (!prb_read_valid_info(prb, iter->cur_seq,
3987 &info, &line_count)) {
3988 goto out;
3989 }
3990 l = get_record_print_text_size(&info, line_count, syslog,
3991 printk_time);
3992
3993 }
3994
3995 iter->cur_seq = r.info->seq + 1;
3996 ret = true;
3997out:
3998 if (len)
3999 *len = l;
4000 return ret;
4001}
4002EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
4003
4004/**
4005 * kmsg_dump_get_buffer - copy kmsg log lines
4006 * @iter: kmsg dump iterator
4007 * @syslog: include the "<4>" prefixes
4008 * @buf: buffer to copy the line to
4009 * @size: maximum size of the buffer
4010 * @len_out: length of line placed into buffer
4011 *
4012 * Start at the end of the kmsg buffer and fill the provided buffer
4013 * with as many of the *youngest* kmsg records that fit into it.
4014 * If the buffer is large enough, all available kmsg records will be
4015 * copied with a single call.
4016 *
4017 * Consecutive calls will fill the buffer with the next block of
4018 * available older records, not including the earlier retrieved ones.
4019 *
4020 * A return value of FALSE indicates that there are no more records to
4021 * read.
4022 */
4023bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
4024 char *buf, size_t size, size_t *len_out)
4025{
4026 u64 min_seq = latched_seq_read_nolock(&clear_seq);
4027 struct printk_info info;
4028 struct printk_record r;
4029 u64 seq;
4030 u64 next_seq;
4031 size_t len = 0;
4032 bool ret = false;
4033 bool time = printk_time;
4034
4035 if (!buf || !size)
4036 goto out;
4037
4038 if (iter->cur_seq < min_seq)
4039 iter->cur_seq = min_seq;
4040
4041 if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) {
4042 if (info.seq != iter->cur_seq) {
4043 /* messages are gone, move to first available one */
4044 iter->cur_seq = info.seq;
4045 }
4046 }
4047
4048 /* last entry */
4049 if (iter->cur_seq >= iter->next_seq)
4050 goto out;
4051
4052 /*
4053 * Find first record that fits, including all following records,
4054 * into the user-provided buffer for this dump. Pass in size-1
4055 * because this function (by way of record_print_text()) will
4056 * not write more than size-1 bytes of text into @buf.
4057 */
4058 seq = find_first_fitting_seq(iter->cur_seq, iter->next_seq,
4059 size - 1, syslog, time);
4060
4061 /*
4062 * Next kmsg_dump_get_buffer() invocation will dump block of
4063 * older records stored right before this one.
4064 */
4065 next_seq = seq;
4066
4067 prb_rec_init_rd(&r, &info, buf, size);
4068
4069 len = 0;
4070 prb_for_each_record(seq, prb, seq, &r) {
4071 if (r.info->seq >= iter->next_seq)
4072 break;
4073
4074 len += record_print_text(&r, syslog, time);
4075
4076 /* Adjust record to store to remaining buffer space. */
4077 prb_rec_init_rd(&r, &info, buf + len, size - len);
4078 }
4079
4080 iter->next_seq = next_seq;
4081 ret = true;
4082out:
4083 if (len_out)
4084 *len_out = len;
4085 return ret;
4086}
4087EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
4088
4089/**
4090 * kmsg_dump_rewind - reset the iterator
4091 * @iter: kmsg dump iterator
4092 *
4093 * Reset the dumper's iterator so that kmsg_dump_get_line() and
4094 * kmsg_dump_get_buffer() can be called again and used multiple
4095 * times within the same dumper.dump() callback.
4096 */
4097void kmsg_dump_rewind(struct kmsg_dump_iter *iter)
4098{
4099 iter->cur_seq = latched_seq_read_nolock(&clear_seq);
4100 iter->next_seq = prb_next_seq(prb);
4101}
4102EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
4103
4104#endif
4105
4106#ifdef CONFIG_SMP
4107static atomic_t printk_cpu_sync_owner = ATOMIC_INIT(-1);
4108static atomic_t printk_cpu_sync_nested = ATOMIC_INIT(0);
4109
4110/**
4111 * __printk_cpu_sync_wait() - Busy wait until the printk cpu-reentrant
4112 * spinning lock is not owned by any CPU.
4113 *
4114 * Context: Any context.
4115 */
4116void __printk_cpu_sync_wait(void)
4117{
4118 do {
4119 cpu_relax();
4120 } while (atomic_read(&printk_cpu_sync_owner) != -1);
4121}
4122EXPORT_SYMBOL(__printk_cpu_sync_wait);
4123
4124/**
4125 * __printk_cpu_sync_try_get() - Try to acquire the printk cpu-reentrant
4126 * spinning lock.
4127 *
4128 * If no processor has the lock, the calling processor takes the lock and
4129 * becomes the owner. If the calling processor is already the owner of the
4130 * lock, this function succeeds immediately.
4131 *
4132 * Context: Any context. Expects interrupts to be disabled.
4133 * Return: 1 on success, otherwise 0.
4134 */
4135int __printk_cpu_sync_try_get(void)
4136{
4137 int cpu;
4138 int old;
4139
4140 cpu = smp_processor_id();
4141
4142 /*
4143 * Guarantee loads and stores from this CPU when it is the lock owner
4144 * are _not_ visible to the previous lock owner. This pairs with
4145 * __printk_cpu_sync_put:B.
4146 *
4147 * Memory barrier involvement:
4148 *
4149 * If __printk_cpu_sync_try_get:A reads from __printk_cpu_sync_put:B,
4150 * then __printk_cpu_sync_put:A can never read from
4151 * __printk_cpu_sync_try_get:B.
4152 *
4153 * Relies on:
4154 *
4155 * RELEASE from __printk_cpu_sync_put:A to __printk_cpu_sync_put:B
4156 * of the previous CPU
4157 * matching
4158 * ACQUIRE from __printk_cpu_sync_try_get:A to
4159 * __printk_cpu_sync_try_get:B of this CPU
4160 */
4161 old = atomic_cmpxchg_acquire(&printk_cpu_sync_owner, -1,
4162 cpu); /* LMM(__printk_cpu_sync_try_get:A) */
4163 if (old == -1) {
4164 /*
4165 * This CPU is now the owner and begins loading/storing
4166 * data: LMM(__printk_cpu_sync_try_get:B)
4167 */
4168 return 1;
4169
4170 } else if (old == cpu) {
4171 /* This CPU is already the owner. */
4172 atomic_inc(&printk_cpu_sync_nested);
4173 return 1;
4174 }
4175
4176 return 0;
4177}
4178EXPORT_SYMBOL(__printk_cpu_sync_try_get);
4179
4180/**
4181 * __printk_cpu_sync_put() - Release the printk cpu-reentrant spinning lock.
4182 *
4183 * The calling processor must be the owner of the lock.
4184 *
4185 * Context: Any context. Expects interrupts to be disabled.
4186 */
4187void __printk_cpu_sync_put(void)
4188{
4189 if (atomic_read(&printk_cpu_sync_nested)) {
4190 atomic_dec(&printk_cpu_sync_nested);
4191 return;
4192 }
4193
4194 /*
4195 * This CPU is finished loading/storing data:
4196 * LMM(__printk_cpu_sync_put:A)
4197 */
4198
4199 /*
4200 * Guarantee loads and stores from this CPU when it was the
4201 * lock owner are visible to the next lock owner. This pairs
4202 * with __printk_cpu_sync_try_get:A.
4203 *
4204 * Memory barrier involvement:
4205 *
4206 * If __printk_cpu_sync_try_get:A reads from __printk_cpu_sync_put:B,
4207 * then __printk_cpu_sync_try_get:B reads from __printk_cpu_sync_put:A.
4208 *
4209 * Relies on:
4210 *
4211 * RELEASE from __printk_cpu_sync_put:A to __printk_cpu_sync_put:B
4212 * of this CPU
4213 * matching
4214 * ACQUIRE from __printk_cpu_sync_try_get:A to
4215 * __printk_cpu_sync_try_get:B of the next CPU
4216 */
4217 atomic_set_release(&printk_cpu_sync_owner,
4218 -1); /* LMM(__printk_cpu_sync_put:B) */
4219}
4220EXPORT_SYMBOL(__printk_cpu_sync_put);
4221#endif /* CONFIG_SMP */
1/*
2 * linux/kernel/printk.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
11 * Ted Ts'o, 2/11/93.
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton
17 */
18
19#include <linux/kernel.h>
20#include <linux/mm.h>
21#include <linux/tty.h>
22#include <linux/tty_driver.h>
23#include <linux/console.h>
24#include <linux/init.h>
25#include <linux/jiffies.h>
26#include <linux/nmi.h>
27#include <linux/module.h>
28#include <linux/moduleparam.h>
29#include <linux/delay.h>
30#include <linux/smp.h>
31#include <linux/security.h>
32#include <linux/bootmem.h>
33#include <linux/memblock.h>
34#include <linux/syscalls.h>
35#include <linux/crash_core.h>
36#include <linux/kdb.h>
37#include <linux/ratelimit.h>
38#include <linux/kmsg_dump.h>
39#include <linux/syslog.h>
40#include <linux/cpu.h>
41#include <linux/notifier.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 "console_cmdline.h"
59#include "braille.h"
60#include "internal.h"
61
62int console_printk[4] = {
63 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
64 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
65 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
66 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
67};
68
69/*
70 * Low level drivers may need that to know if they can schedule in
71 * their unblank() callback or not. So let's export it.
72 */
73int oops_in_progress;
74EXPORT_SYMBOL(oops_in_progress);
75
76/*
77 * console_sem protects the console_drivers list, and also
78 * provides serialisation for access to the entire console
79 * driver system.
80 */
81static DEFINE_SEMAPHORE(console_sem);
82struct console *console_drivers;
83EXPORT_SYMBOL_GPL(console_drivers);
84
85#ifdef CONFIG_LOCKDEP
86static struct lockdep_map console_lock_dep_map = {
87 .name = "console_lock"
88};
89#endif
90
91enum devkmsg_log_bits {
92 __DEVKMSG_LOG_BIT_ON = 0,
93 __DEVKMSG_LOG_BIT_OFF,
94 __DEVKMSG_LOG_BIT_LOCK,
95};
96
97enum devkmsg_log_masks {
98 DEVKMSG_LOG_MASK_ON = BIT(__DEVKMSG_LOG_BIT_ON),
99 DEVKMSG_LOG_MASK_OFF = BIT(__DEVKMSG_LOG_BIT_OFF),
100 DEVKMSG_LOG_MASK_LOCK = BIT(__DEVKMSG_LOG_BIT_LOCK),
101};
102
103/* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
104#define DEVKMSG_LOG_MASK_DEFAULT 0
105
106static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
107
108static int __control_devkmsg(char *str)
109{
110 if (!str)
111 return -EINVAL;
112
113 if (!strncmp(str, "on", 2)) {
114 devkmsg_log = DEVKMSG_LOG_MASK_ON;
115 return 2;
116 } else if (!strncmp(str, "off", 3)) {
117 devkmsg_log = DEVKMSG_LOG_MASK_OFF;
118 return 3;
119 } else if (!strncmp(str, "ratelimit", 9)) {
120 devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
121 return 9;
122 }
123 return -EINVAL;
124}
125
126static int __init control_devkmsg(char *str)
127{
128 if (__control_devkmsg(str) < 0)
129 return 1;
130
131 /*
132 * Set sysctl string accordingly:
133 */
134 if (devkmsg_log == DEVKMSG_LOG_MASK_ON)
135 strcpy(devkmsg_log_str, "on");
136 else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF)
137 strcpy(devkmsg_log_str, "off");
138 /* else "ratelimit" which is set by default. */
139
140 /*
141 * Sysctl cannot change it anymore. The kernel command line setting of
142 * this parameter is to force the setting to be permanent throughout the
143 * runtime of the system. This is a precation measure against userspace
144 * trying to be a smarta** and attempting to change it up on us.
145 */
146 devkmsg_log |= DEVKMSG_LOG_MASK_LOCK;
147
148 return 0;
149}
150__setup("printk.devkmsg=", control_devkmsg);
151
152char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit";
153
154int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
155 void __user *buffer, size_t *lenp, loff_t *ppos)
156{
157 char old_str[DEVKMSG_STR_MAX_SIZE];
158 unsigned int old;
159 int err;
160
161 if (write) {
162 if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK)
163 return -EINVAL;
164
165 old = devkmsg_log;
166 strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE);
167 }
168
169 err = proc_dostring(table, write, buffer, lenp, ppos);
170 if (err)
171 return err;
172
173 if (write) {
174 err = __control_devkmsg(devkmsg_log_str);
175
176 /*
177 * Do not accept an unknown string OR a known string with
178 * trailing crap...
179 */
180 if (err < 0 || (err + 1 != *lenp)) {
181
182 /* ... and restore old setting. */
183 devkmsg_log = old;
184 strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE);
185
186 return -EINVAL;
187 }
188 }
189
190 return 0;
191}
192
193/*
194 * Number of registered extended console drivers.
195 *
196 * If extended consoles are present, in-kernel cont reassembly is disabled
197 * and each fragment is stored as a separate log entry with proper
198 * continuation flag so that every emitted message has full metadata. This
199 * doesn't change the result for regular consoles or /proc/kmsg. For
200 * /dev/kmsg, as long as the reader concatenates messages according to
201 * consecutive continuation flags, the end result should be the same too.
202 */
203static int nr_ext_console_drivers;
204
205/*
206 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
207 * macros instead of functions so that _RET_IP_ contains useful information.
208 */
209#define down_console_sem() do { \
210 down(&console_sem);\
211 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
212} while (0)
213
214static int __down_trylock_console_sem(unsigned long ip)
215{
216 int lock_failed;
217 unsigned long flags;
218
219 /*
220 * Here and in __up_console_sem() we need to be in safe mode,
221 * because spindump/WARN/etc from under console ->lock will
222 * deadlock in printk()->down_trylock_console_sem() otherwise.
223 */
224 printk_safe_enter_irqsave(flags);
225 lock_failed = down_trylock(&console_sem);
226 printk_safe_exit_irqrestore(flags);
227
228 if (lock_failed)
229 return 1;
230 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
231 return 0;
232}
233#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
234
235static void __up_console_sem(unsigned long ip)
236{
237 unsigned long flags;
238
239 mutex_release(&console_lock_dep_map, 1, ip);
240
241 printk_safe_enter_irqsave(flags);
242 up(&console_sem);
243 printk_safe_exit_irqrestore(flags);
244}
245#define up_console_sem() __up_console_sem(_RET_IP_)
246
247/*
248 * This is used for debugging the mess that is the VT code by
249 * keeping track if we have the console semaphore held. It's
250 * definitely not the perfect debug tool (we don't know if _WE_
251 * hold it and are racing, but it helps tracking those weird code
252 * paths in the console code where we end up in places I want
253 * locked without the console sempahore held).
254 */
255static int console_locked, console_suspended;
256
257/*
258 * If exclusive_console is non-NULL then only this console is to be printed to.
259 */
260static struct console *exclusive_console;
261
262/*
263 * Array of consoles built from command line options (console=)
264 */
265
266#define MAX_CMDLINECONSOLES 8
267
268static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
269
270static int preferred_console = -1;
271int console_set_on_cmdline;
272EXPORT_SYMBOL(console_set_on_cmdline);
273
274/* Flag: console code may call schedule() */
275static int console_may_schedule;
276
277enum con_msg_format_flags {
278 MSG_FORMAT_DEFAULT = 0,
279 MSG_FORMAT_SYSLOG = (1 << 0),
280};
281
282static int console_msg_format = MSG_FORMAT_DEFAULT;
283
284/*
285 * The printk log buffer consists of a chain of concatenated variable
286 * length records. Every record starts with a record header, containing
287 * the overall length of the record.
288 *
289 * The heads to the first and last entry in the buffer, as well as the
290 * sequence numbers of these entries are maintained when messages are
291 * stored.
292 *
293 * If the heads indicate available messages, the length in the header
294 * tells the start next message. A length == 0 for the next message
295 * indicates a wrap-around to the beginning of the buffer.
296 *
297 * Every record carries the monotonic timestamp in microseconds, as well as
298 * the standard userspace syslog level and syslog facility. The usual
299 * kernel messages use LOG_KERN; userspace-injected messages always carry
300 * a matching syslog facility, by default LOG_USER. The origin of every
301 * message can be reliably determined that way.
302 *
303 * The human readable log message directly follows the message header. The
304 * length of the message text is stored in the header, the stored message
305 * is not terminated.
306 *
307 * Optionally, a message can carry a dictionary of properties (key/value pairs),
308 * to provide userspace with a machine-readable message context.
309 *
310 * Examples for well-defined, commonly used property names are:
311 * DEVICE=b12:8 device identifier
312 * b12:8 block dev_t
313 * c127:3 char dev_t
314 * n8 netdev ifindex
315 * +sound:card0 subsystem:devname
316 * SUBSYSTEM=pci driver-core subsystem name
317 *
318 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
319 * follows directly after a '=' character. Every property is terminated by
320 * a '\0' character. The last property is not terminated.
321 *
322 * Example of a message structure:
323 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
324 * 0008 34 00 record is 52 bytes long
325 * 000a 0b 00 text is 11 bytes long
326 * 000c 1f 00 dictionary is 23 bytes long
327 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
328 * 0010 69 74 27 73 20 61 20 6c "it's a l"
329 * 69 6e 65 "ine"
330 * 001b 44 45 56 49 43 "DEVIC"
331 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
332 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
333 * 67 "g"
334 * 0032 00 00 00 padding to next message header
335 *
336 * The 'struct printk_log' buffer header must never be directly exported to
337 * userspace, it is a kernel-private implementation detail that might
338 * need to be changed in the future, when the requirements change.
339 *
340 * /dev/kmsg exports the structured data in the following line format:
341 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
342 *
343 * Users of the export format should ignore possible additional values
344 * separated by ',', and find the message after the ';' character.
345 *
346 * The optional key/value pairs are attached as continuation lines starting
347 * with a space character and terminated by a newline. All possible
348 * non-prinatable characters are escaped in the "\xff" notation.
349 */
350
351enum log_flags {
352 LOG_NOCONS = 1, /* already flushed, do not print to console */
353 LOG_NEWLINE = 2, /* text ended with a newline */
354 LOG_PREFIX = 4, /* text started with a prefix */
355 LOG_CONT = 8, /* text is a fragment of a continuation line */
356};
357
358struct printk_log {
359 u64 ts_nsec; /* timestamp in nanoseconds */
360 u16 len; /* length of entire record */
361 u16 text_len; /* length of text buffer */
362 u16 dict_len; /* length of dictionary buffer */
363 u8 facility; /* syslog facility */
364 u8 flags:5; /* internal record flags */
365 u8 level:3; /* syslog level */
366}
367#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
368__packed __aligned(4)
369#endif
370;
371
372/*
373 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
374 * within the scheduler's rq lock. It must be released before calling
375 * console_unlock() or anything else that might wake up a process.
376 */
377DEFINE_RAW_SPINLOCK(logbuf_lock);
378
379/*
380 * Helper macros to lock/unlock logbuf_lock and switch between
381 * printk-safe/unsafe modes.
382 */
383#define logbuf_lock_irq() \
384 do { \
385 printk_safe_enter_irq(); \
386 raw_spin_lock(&logbuf_lock); \
387 } while (0)
388
389#define logbuf_unlock_irq() \
390 do { \
391 raw_spin_unlock(&logbuf_lock); \
392 printk_safe_exit_irq(); \
393 } while (0)
394
395#define logbuf_lock_irqsave(flags) \
396 do { \
397 printk_safe_enter_irqsave(flags); \
398 raw_spin_lock(&logbuf_lock); \
399 } while (0)
400
401#define logbuf_unlock_irqrestore(flags) \
402 do { \
403 raw_spin_unlock(&logbuf_lock); \
404 printk_safe_exit_irqrestore(flags); \
405 } while (0)
406
407#ifdef CONFIG_PRINTK
408DECLARE_WAIT_QUEUE_HEAD(log_wait);
409/* the next printk record to read by syslog(READ) or /proc/kmsg */
410static u64 syslog_seq;
411static u32 syslog_idx;
412static size_t syslog_partial;
413
414/* index and sequence number of the first record stored in the buffer */
415static u64 log_first_seq;
416static u32 log_first_idx;
417
418/* index and sequence number of the next record to store in the buffer */
419static u64 log_next_seq;
420static u32 log_next_idx;
421
422/* the next printk record to write to the console */
423static u64 console_seq;
424static u32 console_idx;
425
426/* the next printk record to read after the last 'clear' command */
427static u64 clear_seq;
428static u32 clear_idx;
429
430#define PREFIX_MAX 32
431#define LOG_LINE_MAX (1024 - PREFIX_MAX)
432
433#define LOG_LEVEL(v) ((v) & 0x07)
434#define LOG_FACILITY(v) ((v) >> 3 & 0xff)
435
436/* record buffer */
437#define LOG_ALIGN __alignof__(struct printk_log)
438#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
439static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
440static char *log_buf = __log_buf;
441static u32 log_buf_len = __LOG_BUF_LEN;
442
443/* Return log buffer address */
444char *log_buf_addr_get(void)
445{
446 return log_buf;
447}
448
449/* Return log buffer size */
450u32 log_buf_len_get(void)
451{
452 return log_buf_len;
453}
454
455/* human readable text of the record */
456static char *log_text(const struct printk_log *msg)
457{
458 return (char *)msg + sizeof(struct printk_log);
459}
460
461/* optional key/value pair dictionary attached to the record */
462static char *log_dict(const struct printk_log *msg)
463{
464 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
465}
466
467/* get record by index; idx must point to valid msg */
468static struct printk_log *log_from_idx(u32 idx)
469{
470 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
471
472 /*
473 * A length == 0 record is the end of buffer marker. Wrap around and
474 * read the message at the start of the buffer.
475 */
476 if (!msg->len)
477 return (struct printk_log *)log_buf;
478 return msg;
479}
480
481/* get next record; idx must point to valid msg */
482static u32 log_next(u32 idx)
483{
484 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
485
486 /* length == 0 indicates the end of the buffer; wrap */
487 /*
488 * A length == 0 record is the end of buffer marker. Wrap around and
489 * read the message at the start of the buffer as *this* one, and
490 * return the one after that.
491 */
492 if (!msg->len) {
493 msg = (struct printk_log *)log_buf;
494 return msg->len;
495 }
496 return idx + msg->len;
497}
498
499/*
500 * Check whether there is enough free space for the given message.
501 *
502 * The same values of first_idx and next_idx mean that the buffer
503 * is either empty or full.
504 *
505 * If the buffer is empty, we must respect the position of the indexes.
506 * They cannot be reset to the beginning of the buffer.
507 */
508static int logbuf_has_space(u32 msg_size, bool empty)
509{
510 u32 free;
511
512 if (log_next_idx > log_first_idx || empty)
513 free = max(log_buf_len - log_next_idx, log_first_idx);
514 else
515 free = log_first_idx - log_next_idx;
516
517 /*
518 * We need space also for an empty header that signalizes wrapping
519 * of the buffer.
520 */
521 return free >= msg_size + sizeof(struct printk_log);
522}
523
524static int log_make_free_space(u32 msg_size)
525{
526 while (log_first_seq < log_next_seq &&
527 !logbuf_has_space(msg_size, false)) {
528 /* drop old messages until we have enough contiguous space */
529 log_first_idx = log_next(log_first_idx);
530 log_first_seq++;
531 }
532
533 if (clear_seq < log_first_seq) {
534 clear_seq = log_first_seq;
535 clear_idx = log_first_idx;
536 }
537
538 /* sequence numbers are equal, so the log buffer is empty */
539 if (logbuf_has_space(msg_size, log_first_seq == log_next_seq))
540 return 0;
541
542 return -ENOMEM;
543}
544
545/* compute the message size including the padding bytes */
546static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
547{
548 u32 size;
549
550 size = sizeof(struct printk_log) + text_len + dict_len;
551 *pad_len = (-size) & (LOG_ALIGN - 1);
552 size += *pad_len;
553
554 return size;
555}
556
557/*
558 * Define how much of the log buffer we could take at maximum. The value
559 * must be greater than two. Note that only half of the buffer is available
560 * when the index points to the middle.
561 */
562#define MAX_LOG_TAKE_PART 4
563static const char trunc_msg[] = "<truncated>";
564
565static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
566 u16 *dict_len, u32 *pad_len)
567{
568 /*
569 * The message should not take the whole buffer. Otherwise, it might
570 * get removed too soon.
571 */
572 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
573 if (*text_len > max_text_len)
574 *text_len = max_text_len;
575 /* enable the warning message */
576 *trunc_msg_len = strlen(trunc_msg);
577 /* disable the "dict" completely */
578 *dict_len = 0;
579 /* compute the size again, count also the warning message */
580 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
581}
582
583/* insert record into the buffer, discard old ones, update heads */
584static int log_store(int facility, int level,
585 enum log_flags flags, u64 ts_nsec,
586 const char *dict, u16 dict_len,
587 const char *text, u16 text_len)
588{
589 struct printk_log *msg;
590 u32 size, pad_len;
591 u16 trunc_msg_len = 0;
592
593 /* number of '\0' padding bytes to next message */
594 size = msg_used_size(text_len, dict_len, &pad_len);
595
596 if (log_make_free_space(size)) {
597 /* truncate the message if it is too long for empty buffer */
598 size = truncate_msg(&text_len, &trunc_msg_len,
599 &dict_len, &pad_len);
600 /* survive when the log buffer is too small for trunc_msg */
601 if (log_make_free_space(size))
602 return 0;
603 }
604
605 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
606 /*
607 * This message + an additional empty header does not fit
608 * at the end of the buffer. Add an empty header with len == 0
609 * to signify a wrap around.
610 */
611 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
612 log_next_idx = 0;
613 }
614
615 /* fill message */
616 msg = (struct printk_log *)(log_buf + log_next_idx);
617 memcpy(log_text(msg), text, text_len);
618 msg->text_len = text_len;
619 if (trunc_msg_len) {
620 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
621 msg->text_len += trunc_msg_len;
622 }
623 memcpy(log_dict(msg), dict, dict_len);
624 msg->dict_len = dict_len;
625 msg->facility = facility;
626 msg->level = level & 7;
627 msg->flags = flags & 0x1f;
628 if (ts_nsec > 0)
629 msg->ts_nsec = ts_nsec;
630 else
631 msg->ts_nsec = local_clock();
632 memset(log_dict(msg) + dict_len, 0, pad_len);
633 msg->len = size;
634
635 /* insert message */
636 log_next_idx += msg->len;
637 log_next_seq++;
638
639 return msg->text_len;
640}
641
642int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
643
644static int syslog_action_restricted(int type)
645{
646 if (dmesg_restrict)
647 return 1;
648 /*
649 * Unless restricted, we allow "read all" and "get buffer size"
650 * for everybody.
651 */
652 return type != SYSLOG_ACTION_READ_ALL &&
653 type != SYSLOG_ACTION_SIZE_BUFFER;
654}
655
656static int check_syslog_permissions(int type, int source)
657{
658 /*
659 * If this is from /proc/kmsg and we've already opened it, then we've
660 * already done the capabilities checks at open time.
661 */
662 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
663 goto ok;
664
665 if (syslog_action_restricted(type)) {
666 if (capable(CAP_SYSLOG))
667 goto ok;
668 /*
669 * For historical reasons, accept CAP_SYS_ADMIN too, with
670 * a warning.
671 */
672 if (capable(CAP_SYS_ADMIN)) {
673 pr_warn_once("%s (%d): Attempt to access syslog with "
674 "CAP_SYS_ADMIN but no CAP_SYSLOG "
675 "(deprecated).\n",
676 current->comm, task_pid_nr(current));
677 goto ok;
678 }
679 return -EPERM;
680 }
681ok:
682 return security_syslog(type);
683}
684
685static void append_char(char **pp, char *e, char c)
686{
687 if (*pp < e)
688 *(*pp)++ = c;
689}
690
691static ssize_t msg_print_ext_header(char *buf, size_t size,
692 struct printk_log *msg, u64 seq)
693{
694 u64 ts_usec = msg->ts_nsec;
695
696 do_div(ts_usec, 1000);
697
698 return scnprintf(buf, size, "%u,%llu,%llu,%c;",
699 (msg->facility << 3) | msg->level, seq, ts_usec,
700 msg->flags & LOG_CONT ? 'c' : '-');
701}
702
703static ssize_t msg_print_ext_body(char *buf, size_t size,
704 char *dict, size_t dict_len,
705 char *text, size_t text_len)
706{
707 char *p = buf, *e = buf + size;
708 size_t i;
709
710 /* escape non-printable characters */
711 for (i = 0; i < text_len; i++) {
712 unsigned char c = text[i];
713
714 if (c < ' ' || c >= 127 || c == '\\')
715 p += scnprintf(p, e - p, "\\x%02x", c);
716 else
717 append_char(&p, e, c);
718 }
719 append_char(&p, e, '\n');
720
721 if (dict_len) {
722 bool line = true;
723
724 for (i = 0; i < dict_len; i++) {
725 unsigned char c = dict[i];
726
727 if (line) {
728 append_char(&p, e, ' ');
729 line = false;
730 }
731
732 if (c == '\0') {
733 append_char(&p, e, '\n');
734 line = true;
735 continue;
736 }
737
738 if (c < ' ' || c >= 127 || c == '\\') {
739 p += scnprintf(p, e - p, "\\x%02x", c);
740 continue;
741 }
742
743 append_char(&p, e, c);
744 }
745 append_char(&p, e, '\n');
746 }
747
748 return p - buf;
749}
750
751/* /dev/kmsg - userspace message inject/listen interface */
752struct devkmsg_user {
753 u64 seq;
754 u32 idx;
755 struct ratelimit_state rs;
756 struct mutex lock;
757 char buf[CONSOLE_EXT_LOG_MAX];
758};
759
760static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
761{
762 char *buf, *line;
763 int level = default_message_loglevel;
764 int facility = 1; /* LOG_USER */
765 struct file *file = iocb->ki_filp;
766 struct devkmsg_user *user = file->private_data;
767 size_t len = iov_iter_count(from);
768 ssize_t ret = len;
769
770 if (!user || len > LOG_LINE_MAX)
771 return -EINVAL;
772
773 /* Ignore when user logging is disabled. */
774 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
775 return len;
776
777 /* Ratelimit when not explicitly enabled. */
778 if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) {
779 if (!___ratelimit(&user->rs, current->comm))
780 return ret;
781 }
782
783 buf = kmalloc(len+1, GFP_KERNEL);
784 if (buf == NULL)
785 return -ENOMEM;
786
787 buf[len] = '\0';
788 if (!copy_from_iter_full(buf, len, from)) {
789 kfree(buf);
790 return -EFAULT;
791 }
792
793 /*
794 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
795 * the decimal value represents 32bit, the lower 3 bit are the log
796 * level, the rest are the log facility.
797 *
798 * If no prefix or no userspace facility is specified, we
799 * enforce LOG_USER, to be able to reliably distinguish
800 * kernel-generated messages from userspace-injected ones.
801 */
802 line = buf;
803 if (line[0] == '<') {
804 char *endp = NULL;
805 unsigned int u;
806
807 u = simple_strtoul(line + 1, &endp, 10);
808 if (endp && endp[0] == '>') {
809 level = LOG_LEVEL(u);
810 if (LOG_FACILITY(u) != 0)
811 facility = LOG_FACILITY(u);
812 endp++;
813 len -= endp - line;
814 line = endp;
815 }
816 }
817
818 printk_emit(facility, level, NULL, 0, "%s", line);
819 kfree(buf);
820 return ret;
821}
822
823static ssize_t devkmsg_read(struct file *file, char __user *buf,
824 size_t count, loff_t *ppos)
825{
826 struct devkmsg_user *user = file->private_data;
827 struct printk_log *msg;
828 size_t len;
829 ssize_t ret;
830
831 if (!user)
832 return -EBADF;
833
834 ret = mutex_lock_interruptible(&user->lock);
835 if (ret)
836 return ret;
837
838 logbuf_lock_irq();
839 while (user->seq == log_next_seq) {
840 if (file->f_flags & O_NONBLOCK) {
841 ret = -EAGAIN;
842 logbuf_unlock_irq();
843 goto out;
844 }
845
846 logbuf_unlock_irq();
847 ret = wait_event_interruptible(log_wait,
848 user->seq != log_next_seq);
849 if (ret)
850 goto out;
851 logbuf_lock_irq();
852 }
853
854 if (user->seq < log_first_seq) {
855 /* our last seen message is gone, return error and reset */
856 user->idx = log_first_idx;
857 user->seq = log_first_seq;
858 ret = -EPIPE;
859 logbuf_unlock_irq();
860 goto out;
861 }
862
863 msg = log_from_idx(user->idx);
864 len = msg_print_ext_header(user->buf, sizeof(user->buf),
865 msg, user->seq);
866 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
867 log_dict(msg), msg->dict_len,
868 log_text(msg), msg->text_len);
869
870 user->idx = log_next(user->idx);
871 user->seq++;
872 logbuf_unlock_irq();
873
874 if (len > count) {
875 ret = -EINVAL;
876 goto out;
877 }
878
879 if (copy_to_user(buf, user->buf, len)) {
880 ret = -EFAULT;
881 goto out;
882 }
883 ret = len;
884out:
885 mutex_unlock(&user->lock);
886 return ret;
887}
888
889static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
890{
891 struct devkmsg_user *user = file->private_data;
892 loff_t ret = 0;
893
894 if (!user)
895 return -EBADF;
896 if (offset)
897 return -ESPIPE;
898
899 logbuf_lock_irq();
900 switch (whence) {
901 case SEEK_SET:
902 /* the first record */
903 user->idx = log_first_idx;
904 user->seq = log_first_seq;
905 break;
906 case SEEK_DATA:
907 /*
908 * The first record after the last SYSLOG_ACTION_CLEAR,
909 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
910 * changes no global state, and does not clear anything.
911 */
912 user->idx = clear_idx;
913 user->seq = clear_seq;
914 break;
915 case SEEK_END:
916 /* after the last record */
917 user->idx = log_next_idx;
918 user->seq = log_next_seq;
919 break;
920 default:
921 ret = -EINVAL;
922 }
923 logbuf_unlock_irq();
924 return ret;
925}
926
927static __poll_t devkmsg_poll(struct file *file, poll_table *wait)
928{
929 struct devkmsg_user *user = file->private_data;
930 __poll_t ret = 0;
931
932 if (!user)
933 return EPOLLERR|EPOLLNVAL;
934
935 poll_wait(file, &log_wait, wait);
936
937 logbuf_lock_irq();
938 if (user->seq < log_next_seq) {
939 /* return error when data has vanished underneath us */
940 if (user->seq < log_first_seq)
941 ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI;
942 else
943 ret = EPOLLIN|EPOLLRDNORM;
944 }
945 logbuf_unlock_irq();
946
947 return ret;
948}
949
950static int devkmsg_open(struct inode *inode, struct file *file)
951{
952 struct devkmsg_user *user;
953 int err;
954
955 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
956 return -EPERM;
957
958 /* write-only does not need any file context */
959 if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
960 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
961 SYSLOG_FROM_READER);
962 if (err)
963 return err;
964 }
965
966 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
967 if (!user)
968 return -ENOMEM;
969
970 ratelimit_default_init(&user->rs);
971 ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);
972
973 mutex_init(&user->lock);
974
975 logbuf_lock_irq();
976 user->idx = log_first_idx;
977 user->seq = log_first_seq;
978 logbuf_unlock_irq();
979
980 file->private_data = user;
981 return 0;
982}
983
984static int devkmsg_release(struct inode *inode, struct file *file)
985{
986 struct devkmsg_user *user = file->private_data;
987
988 if (!user)
989 return 0;
990
991 ratelimit_state_exit(&user->rs);
992
993 mutex_destroy(&user->lock);
994 kfree(user);
995 return 0;
996}
997
998const struct file_operations kmsg_fops = {
999 .open = devkmsg_open,
1000 .read = devkmsg_read,
1001 .write_iter = devkmsg_write,
1002 .llseek = devkmsg_llseek,
1003 .poll = devkmsg_poll,
1004 .release = devkmsg_release,
1005};
1006
1007#ifdef CONFIG_CRASH_CORE
1008/*
1009 * This appends the listed symbols to /proc/vmcore
1010 *
1011 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
1012 * obtain access to symbols that are otherwise very difficult to locate. These
1013 * symbols are specifically used so that utilities can access and extract the
1014 * dmesg log from a vmcore file after a crash.
1015 */
1016void log_buf_vmcoreinfo_setup(void)
1017{
1018 VMCOREINFO_SYMBOL(log_buf);
1019 VMCOREINFO_SYMBOL(log_buf_len);
1020 VMCOREINFO_SYMBOL(log_first_idx);
1021 VMCOREINFO_SYMBOL(clear_idx);
1022 VMCOREINFO_SYMBOL(log_next_idx);
1023 /*
1024 * Export struct printk_log size and field offsets. User space tools can
1025 * parse it and detect any changes to structure down the line.
1026 */
1027 VMCOREINFO_STRUCT_SIZE(printk_log);
1028 VMCOREINFO_OFFSET(printk_log, ts_nsec);
1029 VMCOREINFO_OFFSET(printk_log, len);
1030 VMCOREINFO_OFFSET(printk_log, text_len);
1031 VMCOREINFO_OFFSET(printk_log, dict_len);
1032}
1033#endif
1034
1035/* requested log_buf_len from kernel cmdline */
1036static unsigned long __initdata new_log_buf_len;
1037
1038/* we practice scaling the ring buffer by powers of 2 */
1039static void __init log_buf_len_update(unsigned size)
1040{
1041 if (size)
1042 size = roundup_pow_of_two(size);
1043 if (size > log_buf_len)
1044 new_log_buf_len = size;
1045}
1046
1047/* save requested log_buf_len since it's too early to process it */
1048static int __init log_buf_len_setup(char *str)
1049{
1050 unsigned size = memparse(str, &str);
1051
1052 log_buf_len_update(size);
1053
1054 return 0;
1055}
1056early_param("log_buf_len", log_buf_len_setup);
1057
1058#ifdef CONFIG_SMP
1059#define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1060
1061static void __init log_buf_add_cpu(void)
1062{
1063 unsigned int cpu_extra;
1064
1065 /*
1066 * archs should set up cpu_possible_bits properly with
1067 * set_cpu_possible() after setup_arch() but just in
1068 * case lets ensure this is valid.
1069 */
1070 if (num_possible_cpus() == 1)
1071 return;
1072
1073 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
1074
1075 /* by default this will only continue through for large > 64 CPUs */
1076 if (cpu_extra <= __LOG_BUF_LEN / 2)
1077 return;
1078
1079 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1080 __LOG_CPU_MAX_BUF_LEN);
1081 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1082 cpu_extra);
1083 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
1084
1085 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
1086}
1087#else /* !CONFIG_SMP */
1088static inline void log_buf_add_cpu(void) {}
1089#endif /* CONFIG_SMP */
1090
1091void __init setup_log_buf(int early)
1092{
1093 unsigned long flags;
1094 char *new_log_buf;
1095 int free;
1096
1097 if (log_buf != __log_buf)
1098 return;
1099
1100 if (!early && !new_log_buf_len)
1101 log_buf_add_cpu();
1102
1103 if (!new_log_buf_len)
1104 return;
1105
1106 if (early) {
1107 new_log_buf =
1108 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
1109 } else {
1110 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
1111 LOG_ALIGN);
1112 }
1113
1114 if (unlikely(!new_log_buf)) {
1115 pr_err("log_buf_len: %ld bytes not available\n",
1116 new_log_buf_len);
1117 return;
1118 }
1119
1120 logbuf_lock_irqsave(flags);
1121 log_buf_len = new_log_buf_len;
1122 log_buf = new_log_buf;
1123 new_log_buf_len = 0;
1124 free = __LOG_BUF_LEN - log_next_idx;
1125 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
1126 logbuf_unlock_irqrestore(flags);
1127
1128 pr_info("log_buf_len: %d bytes\n", log_buf_len);
1129 pr_info("early log buf free: %d(%d%%)\n",
1130 free, (free * 100) / __LOG_BUF_LEN);
1131}
1132
1133static bool __read_mostly ignore_loglevel;
1134
1135static int __init ignore_loglevel_setup(char *str)
1136{
1137 ignore_loglevel = true;
1138 pr_info("debug: ignoring loglevel setting.\n");
1139
1140 return 0;
1141}
1142
1143early_param("ignore_loglevel", ignore_loglevel_setup);
1144module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1145MODULE_PARM_DESC(ignore_loglevel,
1146 "ignore loglevel setting (prints all kernel messages to the console)");
1147
1148static bool suppress_message_printing(int level)
1149{
1150 return (level >= console_loglevel && !ignore_loglevel);
1151}
1152
1153#ifdef CONFIG_BOOT_PRINTK_DELAY
1154
1155static int boot_delay; /* msecs delay after each printk during bootup */
1156static unsigned long long loops_per_msec; /* based on boot_delay */
1157
1158static int __init boot_delay_setup(char *str)
1159{
1160 unsigned long lpj;
1161
1162 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
1163 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
1164
1165 get_option(&str, &boot_delay);
1166 if (boot_delay > 10 * 1000)
1167 boot_delay = 0;
1168
1169 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1170 "HZ: %d, loops_per_msec: %llu\n",
1171 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1172 return 0;
1173}
1174early_param("boot_delay", boot_delay_setup);
1175
1176static void boot_delay_msec(int level)
1177{
1178 unsigned long long k;
1179 unsigned long timeout;
1180
1181 if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING)
1182 || suppress_message_printing(level)) {
1183 return;
1184 }
1185
1186 k = (unsigned long long)loops_per_msec * boot_delay;
1187
1188 timeout = jiffies + msecs_to_jiffies(boot_delay);
1189 while (k) {
1190 k--;
1191 cpu_relax();
1192 /*
1193 * use (volatile) jiffies to prevent
1194 * compiler reduction; loop termination via jiffies
1195 * is secondary and may or may not happen.
1196 */
1197 if (time_after(jiffies, timeout))
1198 break;
1199 touch_nmi_watchdog();
1200 }
1201}
1202#else
1203static inline void boot_delay_msec(int level)
1204{
1205}
1206#endif
1207
1208static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1209module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1210
1211static size_t print_time(u64 ts, char *buf)
1212{
1213 unsigned long rem_nsec;
1214
1215 if (!printk_time)
1216 return 0;
1217
1218 rem_nsec = do_div(ts, 1000000000);
1219
1220 if (!buf)
1221 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1222
1223 return sprintf(buf, "[%5lu.%06lu] ",
1224 (unsigned long)ts, rem_nsec / 1000);
1225}
1226
1227static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1228{
1229 size_t len = 0;
1230 unsigned int prefix = (msg->facility << 3) | msg->level;
1231
1232 if (syslog) {
1233 if (buf) {
1234 len += sprintf(buf, "<%u>", prefix);
1235 } else {
1236 len += 3;
1237 if (prefix > 999)
1238 len += 3;
1239 else if (prefix > 99)
1240 len += 2;
1241 else if (prefix > 9)
1242 len++;
1243 }
1244 }
1245
1246 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1247 return len;
1248}
1249
1250static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *buf, size_t size)
1251{
1252 const char *text = log_text(msg);
1253 size_t text_size = msg->text_len;
1254 size_t len = 0;
1255
1256 do {
1257 const char *next = memchr(text, '\n', text_size);
1258 size_t text_len;
1259
1260 if (next) {
1261 text_len = next - text;
1262 next++;
1263 text_size -= next - text;
1264 } else {
1265 text_len = text_size;
1266 }
1267
1268 if (buf) {
1269 if (print_prefix(msg, syslog, NULL) +
1270 text_len + 1 >= size - len)
1271 break;
1272
1273 len += print_prefix(msg, syslog, buf + len);
1274 memcpy(buf + len, text, text_len);
1275 len += text_len;
1276 buf[len++] = '\n';
1277 } else {
1278 /* SYSLOG_ACTION_* buffer size only calculation */
1279 len += print_prefix(msg, syslog, NULL);
1280 len += text_len;
1281 len++;
1282 }
1283
1284 text = next;
1285 } while (text);
1286
1287 return len;
1288}
1289
1290static int syslog_print(char __user *buf, int size)
1291{
1292 char *text;
1293 struct printk_log *msg;
1294 int len = 0;
1295
1296 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1297 if (!text)
1298 return -ENOMEM;
1299
1300 while (size > 0) {
1301 size_t n;
1302 size_t skip;
1303
1304 logbuf_lock_irq();
1305 if (syslog_seq < log_first_seq) {
1306 /* messages are gone, move to first one */
1307 syslog_seq = log_first_seq;
1308 syslog_idx = log_first_idx;
1309 syslog_partial = 0;
1310 }
1311 if (syslog_seq == log_next_seq) {
1312 logbuf_unlock_irq();
1313 break;
1314 }
1315
1316 skip = syslog_partial;
1317 msg = log_from_idx(syslog_idx);
1318 n = msg_print_text(msg, true, text, LOG_LINE_MAX + PREFIX_MAX);
1319 if (n - syslog_partial <= size) {
1320 /* message fits into buffer, move forward */
1321 syslog_idx = log_next(syslog_idx);
1322 syslog_seq++;
1323 n -= syslog_partial;
1324 syslog_partial = 0;
1325 } else if (!len){
1326 /* partial read(), remember position */
1327 n = size;
1328 syslog_partial += n;
1329 } else
1330 n = 0;
1331 logbuf_unlock_irq();
1332
1333 if (!n)
1334 break;
1335
1336 if (copy_to_user(buf, text + skip, n)) {
1337 if (!len)
1338 len = -EFAULT;
1339 break;
1340 }
1341
1342 len += n;
1343 size -= n;
1344 buf += n;
1345 }
1346
1347 kfree(text);
1348 return len;
1349}
1350
1351static int syslog_print_all(char __user *buf, int size, bool clear)
1352{
1353 char *text;
1354 int len = 0;
1355
1356 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1357 if (!text)
1358 return -ENOMEM;
1359
1360 logbuf_lock_irq();
1361 if (buf) {
1362 u64 next_seq;
1363 u64 seq;
1364 u32 idx;
1365
1366 /*
1367 * Find first record that fits, including all following records,
1368 * into the user-provided buffer for this dump.
1369 */
1370 seq = clear_seq;
1371 idx = clear_idx;
1372 while (seq < log_next_seq) {
1373 struct printk_log *msg = log_from_idx(idx);
1374
1375 len += msg_print_text(msg, true, NULL, 0);
1376 idx = log_next(idx);
1377 seq++;
1378 }
1379
1380 /* move first record forward until length fits into the buffer */
1381 seq = clear_seq;
1382 idx = clear_idx;
1383 while (len > size && seq < log_next_seq) {
1384 struct printk_log *msg = log_from_idx(idx);
1385
1386 len -= msg_print_text(msg, true, NULL, 0);
1387 idx = log_next(idx);
1388 seq++;
1389 }
1390
1391 /* last message fitting into this dump */
1392 next_seq = log_next_seq;
1393
1394 len = 0;
1395 while (len >= 0 && seq < next_seq) {
1396 struct printk_log *msg = log_from_idx(idx);
1397 int textlen;
1398
1399 textlen = msg_print_text(msg, true, text,
1400 LOG_LINE_MAX + PREFIX_MAX);
1401 if (textlen < 0) {
1402 len = textlen;
1403 break;
1404 }
1405 idx = log_next(idx);
1406 seq++;
1407
1408 logbuf_unlock_irq();
1409 if (copy_to_user(buf + len, text, textlen))
1410 len = -EFAULT;
1411 else
1412 len += textlen;
1413 logbuf_lock_irq();
1414
1415 if (seq < log_first_seq) {
1416 /* messages are gone, move to next one */
1417 seq = log_first_seq;
1418 idx = log_first_idx;
1419 }
1420 }
1421 }
1422
1423 if (clear) {
1424 clear_seq = log_next_seq;
1425 clear_idx = log_next_idx;
1426 }
1427 logbuf_unlock_irq();
1428
1429 kfree(text);
1430 return len;
1431}
1432
1433int do_syslog(int type, char __user *buf, int len, int source)
1434{
1435 bool clear = false;
1436 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1437 int error;
1438
1439 error = check_syslog_permissions(type, source);
1440 if (error)
1441 return error;
1442
1443 switch (type) {
1444 case SYSLOG_ACTION_CLOSE: /* Close log */
1445 break;
1446 case SYSLOG_ACTION_OPEN: /* Open log */
1447 break;
1448 case SYSLOG_ACTION_READ: /* Read from log */
1449 if (!buf || len < 0)
1450 return -EINVAL;
1451 if (!len)
1452 return 0;
1453 if (!access_ok(VERIFY_WRITE, buf, len))
1454 return -EFAULT;
1455 error = wait_event_interruptible(log_wait,
1456 syslog_seq != log_next_seq);
1457 if (error)
1458 return error;
1459 error = syslog_print(buf, len);
1460 break;
1461 /* Read/clear last kernel messages */
1462 case SYSLOG_ACTION_READ_CLEAR:
1463 clear = true;
1464 /* FALL THRU */
1465 /* Read last kernel messages */
1466 case SYSLOG_ACTION_READ_ALL:
1467 if (!buf || len < 0)
1468 return -EINVAL;
1469 if (!len)
1470 return 0;
1471 if (!access_ok(VERIFY_WRITE, buf, len))
1472 return -EFAULT;
1473 error = syslog_print_all(buf, len, clear);
1474 break;
1475 /* Clear ring buffer */
1476 case SYSLOG_ACTION_CLEAR:
1477 syslog_print_all(NULL, 0, true);
1478 break;
1479 /* Disable logging to console */
1480 case SYSLOG_ACTION_CONSOLE_OFF:
1481 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1482 saved_console_loglevel = console_loglevel;
1483 console_loglevel = minimum_console_loglevel;
1484 break;
1485 /* Enable logging to console */
1486 case SYSLOG_ACTION_CONSOLE_ON:
1487 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1488 console_loglevel = saved_console_loglevel;
1489 saved_console_loglevel = LOGLEVEL_DEFAULT;
1490 }
1491 break;
1492 /* Set level of messages printed to console */
1493 case SYSLOG_ACTION_CONSOLE_LEVEL:
1494 if (len < 1 || len > 8)
1495 return -EINVAL;
1496 if (len < minimum_console_loglevel)
1497 len = minimum_console_loglevel;
1498 console_loglevel = len;
1499 /* Implicitly re-enable logging to console */
1500 saved_console_loglevel = LOGLEVEL_DEFAULT;
1501 break;
1502 /* Number of chars in the log buffer */
1503 case SYSLOG_ACTION_SIZE_UNREAD:
1504 logbuf_lock_irq();
1505 if (syslog_seq < log_first_seq) {
1506 /* messages are gone, move to first one */
1507 syslog_seq = log_first_seq;
1508 syslog_idx = log_first_idx;
1509 syslog_partial = 0;
1510 }
1511 if (source == SYSLOG_FROM_PROC) {
1512 /*
1513 * Short-cut for poll(/"proc/kmsg") which simply checks
1514 * for pending data, not the size; return the count of
1515 * records, not the length.
1516 */
1517 error = log_next_seq - syslog_seq;
1518 } else {
1519 u64 seq = syslog_seq;
1520 u32 idx = syslog_idx;
1521
1522 while (seq < log_next_seq) {
1523 struct printk_log *msg = log_from_idx(idx);
1524
1525 error += msg_print_text(msg, true, NULL, 0);
1526 idx = log_next(idx);
1527 seq++;
1528 }
1529 error -= syslog_partial;
1530 }
1531 logbuf_unlock_irq();
1532 break;
1533 /* Size of the log buffer */
1534 case SYSLOG_ACTION_SIZE_BUFFER:
1535 error = log_buf_len;
1536 break;
1537 default:
1538 error = -EINVAL;
1539 break;
1540 }
1541
1542 return error;
1543}
1544
1545SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1546{
1547 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1548}
1549
1550/*
1551 * Special console_lock variants that help to reduce the risk of soft-lockups.
1552 * They allow to pass console_lock to another printk() call using a busy wait.
1553 */
1554
1555#ifdef CONFIG_LOCKDEP
1556static struct lockdep_map console_owner_dep_map = {
1557 .name = "console_owner"
1558};
1559#endif
1560
1561static DEFINE_RAW_SPINLOCK(console_owner_lock);
1562static struct task_struct *console_owner;
1563static bool console_waiter;
1564
1565/**
1566 * console_lock_spinning_enable - mark beginning of code where another
1567 * thread might safely busy wait
1568 *
1569 * This basically converts console_lock into a spinlock. This marks
1570 * the section where the console_lock owner can not sleep, because
1571 * there may be a waiter spinning (like a spinlock). Also it must be
1572 * ready to hand over the lock at the end of the section.
1573 */
1574static void console_lock_spinning_enable(void)
1575{
1576 raw_spin_lock(&console_owner_lock);
1577 console_owner = current;
1578 raw_spin_unlock(&console_owner_lock);
1579
1580 /* The waiter may spin on us after setting console_owner */
1581 spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_);
1582}
1583
1584/**
1585 * console_lock_spinning_disable_and_check - mark end of code where another
1586 * thread was able to busy wait and check if there is a waiter
1587 *
1588 * This is called at the end of the section where spinning is allowed.
1589 * It has two functions. First, it is a signal that it is no longer
1590 * safe to start busy waiting for the lock. Second, it checks if
1591 * there is a busy waiter and passes the lock rights to her.
1592 *
1593 * Important: Callers lose the lock if there was a busy waiter.
1594 * They must not touch items synchronized by console_lock
1595 * in this case.
1596 *
1597 * Return: 1 if the lock rights were passed, 0 otherwise.
1598 */
1599static int console_lock_spinning_disable_and_check(void)
1600{
1601 int waiter;
1602
1603 raw_spin_lock(&console_owner_lock);
1604 waiter = READ_ONCE(console_waiter);
1605 console_owner = NULL;
1606 raw_spin_unlock(&console_owner_lock);
1607
1608 if (!waiter) {
1609 spin_release(&console_owner_dep_map, 1, _THIS_IP_);
1610 return 0;
1611 }
1612
1613 /* The waiter is now free to continue */
1614 WRITE_ONCE(console_waiter, false);
1615
1616 spin_release(&console_owner_dep_map, 1, _THIS_IP_);
1617
1618 /*
1619 * Hand off console_lock to waiter. The waiter will perform
1620 * the up(). After this, the waiter is the console_lock owner.
1621 */
1622 mutex_release(&console_lock_dep_map, 1, _THIS_IP_);
1623 return 1;
1624}
1625
1626/**
1627 * console_trylock_spinning - try to get console_lock by busy waiting
1628 *
1629 * This allows to busy wait for the console_lock when the current
1630 * owner is running in specially marked sections. It means that
1631 * the current owner is running and cannot reschedule until it
1632 * is ready to lose the lock.
1633 *
1634 * Return: 1 if we got the lock, 0 othrewise
1635 */
1636static int console_trylock_spinning(void)
1637{
1638 struct task_struct *owner = NULL;
1639 bool waiter;
1640 bool spin = false;
1641 unsigned long flags;
1642
1643 if (console_trylock())
1644 return 1;
1645
1646 printk_safe_enter_irqsave(flags);
1647
1648 raw_spin_lock(&console_owner_lock);
1649 owner = READ_ONCE(console_owner);
1650 waiter = READ_ONCE(console_waiter);
1651 if (!waiter && owner && owner != current) {
1652 WRITE_ONCE(console_waiter, true);
1653 spin = true;
1654 }
1655 raw_spin_unlock(&console_owner_lock);
1656
1657 /*
1658 * If there is an active printk() writing to the
1659 * consoles, instead of having it write our data too,
1660 * see if we can offload that load from the active
1661 * printer, and do some printing ourselves.
1662 * Go into a spin only if there isn't already a waiter
1663 * spinning, and there is an active printer, and
1664 * that active printer isn't us (recursive printk?).
1665 */
1666 if (!spin) {
1667 printk_safe_exit_irqrestore(flags);
1668 return 0;
1669 }
1670
1671 /* We spin waiting for the owner to release us */
1672 spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_);
1673 /* Owner will clear console_waiter on hand off */
1674 while (READ_ONCE(console_waiter))
1675 cpu_relax();
1676 spin_release(&console_owner_dep_map, 1, _THIS_IP_);
1677
1678 printk_safe_exit_irqrestore(flags);
1679 /*
1680 * The owner passed the console lock to us.
1681 * Since we did not spin on console lock, annotate
1682 * this as a trylock. Otherwise lockdep will
1683 * complain.
1684 */
1685 mutex_acquire(&console_lock_dep_map, 0, 1, _THIS_IP_);
1686
1687 return 1;
1688}
1689
1690/*
1691 * Call the console drivers, asking them to write out
1692 * log_buf[start] to log_buf[end - 1].
1693 * The console_lock must be held.
1694 */
1695static void call_console_drivers(const char *ext_text, size_t ext_len,
1696 const char *text, size_t len)
1697{
1698 struct console *con;
1699
1700 trace_console_rcuidle(text, len);
1701
1702 if (!console_drivers)
1703 return;
1704
1705 for_each_console(con) {
1706 if (exclusive_console && con != exclusive_console)
1707 continue;
1708 if (!(con->flags & CON_ENABLED))
1709 continue;
1710 if (!con->write)
1711 continue;
1712 if (!cpu_online(smp_processor_id()) &&
1713 !(con->flags & CON_ANYTIME))
1714 continue;
1715 if (con->flags & CON_EXTENDED)
1716 con->write(con, ext_text, ext_len);
1717 else
1718 con->write(con, text, len);
1719 }
1720}
1721
1722int printk_delay_msec __read_mostly;
1723
1724static inline void printk_delay(void)
1725{
1726 if (unlikely(printk_delay_msec)) {
1727 int m = printk_delay_msec;
1728
1729 while (m--) {
1730 mdelay(1);
1731 touch_nmi_watchdog();
1732 }
1733 }
1734}
1735
1736/*
1737 * Continuation lines are buffered, and not committed to the record buffer
1738 * until the line is complete, or a race forces it. The line fragments
1739 * though, are printed immediately to the consoles to ensure everything has
1740 * reached the console in case of a kernel crash.
1741 */
1742static struct cont {
1743 char buf[LOG_LINE_MAX];
1744 size_t len; /* length == 0 means unused buffer */
1745 struct task_struct *owner; /* task of first print*/
1746 u64 ts_nsec; /* time of first print */
1747 u8 level; /* log level of first message */
1748 u8 facility; /* log facility of first message */
1749 enum log_flags flags; /* prefix, newline flags */
1750} cont;
1751
1752static void cont_flush(void)
1753{
1754 if (cont.len == 0)
1755 return;
1756
1757 log_store(cont.facility, cont.level, cont.flags, cont.ts_nsec,
1758 NULL, 0, cont.buf, cont.len);
1759 cont.len = 0;
1760}
1761
1762static bool cont_add(int facility, int level, enum log_flags flags, const char *text, size_t len)
1763{
1764 /*
1765 * If ext consoles are present, flush and skip in-kernel
1766 * continuation. See nr_ext_console_drivers definition. Also, if
1767 * the line gets too long, split it up in separate records.
1768 */
1769 if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
1770 cont_flush();
1771 return false;
1772 }
1773
1774 if (!cont.len) {
1775 cont.facility = facility;
1776 cont.level = level;
1777 cont.owner = current;
1778 cont.ts_nsec = local_clock();
1779 cont.flags = flags;
1780 }
1781
1782 memcpy(cont.buf + cont.len, text, len);
1783 cont.len += len;
1784
1785 // The original flags come from the first line,
1786 // but later continuations can add a newline.
1787 if (flags & LOG_NEWLINE) {
1788 cont.flags |= LOG_NEWLINE;
1789 cont_flush();
1790 }
1791
1792 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1793 cont_flush();
1794
1795 return true;
1796}
1797
1798static size_t log_output(int facility, int level, enum log_flags lflags, const char *dict, size_t dictlen, char *text, size_t text_len)
1799{
1800 /*
1801 * If an earlier line was buffered, and we're a continuation
1802 * write from the same process, try to add it to the buffer.
1803 */
1804 if (cont.len) {
1805 if (cont.owner == current && (lflags & LOG_CONT)) {
1806 if (cont_add(facility, level, lflags, text, text_len))
1807 return text_len;
1808 }
1809 /* Otherwise, make sure it's flushed */
1810 cont_flush();
1811 }
1812
1813 /* Skip empty continuation lines that couldn't be added - they just flush */
1814 if (!text_len && (lflags & LOG_CONT))
1815 return 0;
1816
1817 /* If it doesn't end in a newline, try to buffer the current line */
1818 if (!(lflags & LOG_NEWLINE)) {
1819 if (cont_add(facility, level, lflags, text, text_len))
1820 return text_len;
1821 }
1822
1823 /* Store it in the record log */
1824 return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len);
1825}
1826
1827asmlinkage int vprintk_emit(int facility, int level,
1828 const char *dict, size_t dictlen,
1829 const char *fmt, va_list args)
1830{
1831 static char textbuf[LOG_LINE_MAX];
1832 char *text = textbuf;
1833 size_t text_len;
1834 enum log_flags lflags = 0;
1835 unsigned long flags;
1836 int printed_len;
1837 bool in_sched = false;
1838
1839 if (level == LOGLEVEL_SCHED) {
1840 level = LOGLEVEL_DEFAULT;
1841 in_sched = true;
1842 }
1843
1844 boot_delay_msec(level);
1845 printk_delay();
1846
1847 /* This stops the holder of console_sem just where we want him */
1848 logbuf_lock_irqsave(flags);
1849 /*
1850 * The printf needs to come first; we need the syslog
1851 * prefix which might be passed-in as a parameter.
1852 */
1853 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1854
1855 /* mark and strip a trailing newline */
1856 if (text_len && text[text_len-1] == '\n') {
1857 text_len--;
1858 lflags |= LOG_NEWLINE;
1859 }
1860
1861 /* strip kernel syslog prefix and extract log level or control flags */
1862 if (facility == 0) {
1863 int kern_level;
1864
1865 while ((kern_level = printk_get_level(text)) != 0) {
1866 switch (kern_level) {
1867 case '0' ... '7':
1868 if (level == LOGLEVEL_DEFAULT)
1869 level = kern_level - '0';
1870 /* fallthrough */
1871 case 'd': /* KERN_DEFAULT */
1872 lflags |= LOG_PREFIX;
1873 break;
1874 case 'c': /* KERN_CONT */
1875 lflags |= LOG_CONT;
1876 }
1877
1878 text_len -= 2;
1879 text += 2;
1880 }
1881 }
1882
1883 if (level == LOGLEVEL_DEFAULT)
1884 level = default_message_loglevel;
1885
1886 if (dict)
1887 lflags |= LOG_PREFIX|LOG_NEWLINE;
1888
1889 printed_len = log_output(facility, level, lflags, dict, dictlen, text, text_len);
1890
1891 logbuf_unlock_irqrestore(flags);
1892
1893 /* If called from the scheduler, we can not call up(). */
1894 if (!in_sched) {
1895 /*
1896 * Disable preemption to avoid being preempted while holding
1897 * console_sem which would prevent anyone from printing to
1898 * console
1899 */
1900 preempt_disable();
1901 /*
1902 * Try to acquire and then immediately release the console
1903 * semaphore. The release will print out buffers and wake up
1904 * /dev/kmsg and syslog() users.
1905 */
1906 if (console_trylock_spinning())
1907 console_unlock();
1908 preempt_enable();
1909 }
1910
1911 return printed_len;
1912}
1913EXPORT_SYMBOL(vprintk_emit);
1914
1915asmlinkage int vprintk(const char *fmt, va_list args)
1916{
1917 return vprintk_func(fmt, args);
1918}
1919EXPORT_SYMBOL(vprintk);
1920
1921asmlinkage int printk_emit(int facility, int level,
1922 const char *dict, size_t dictlen,
1923 const char *fmt, ...)
1924{
1925 va_list args;
1926 int r;
1927
1928 va_start(args, fmt);
1929 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1930 va_end(args);
1931
1932 return r;
1933}
1934EXPORT_SYMBOL(printk_emit);
1935
1936int vprintk_default(const char *fmt, va_list args)
1937{
1938 int r;
1939
1940#ifdef CONFIG_KGDB_KDB
1941 /* Allow to pass printk() to kdb but avoid a recursion. */
1942 if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0)) {
1943 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1944 return r;
1945 }
1946#endif
1947 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1948
1949 return r;
1950}
1951EXPORT_SYMBOL_GPL(vprintk_default);
1952
1953/**
1954 * printk - print a kernel message
1955 * @fmt: format string
1956 *
1957 * This is printk(). It can be called from any context. We want it to work.
1958 *
1959 * We try to grab the console_lock. If we succeed, it's easy - we log the
1960 * output and call the console drivers. If we fail to get the semaphore, we
1961 * place the output into the log buffer and return. The current holder of
1962 * the console_sem will notice the new output in console_unlock(); and will
1963 * send it to the consoles before releasing the lock.
1964 *
1965 * One effect of this deferred printing is that code which calls printk() and
1966 * then changes console_loglevel may break. This is because console_loglevel
1967 * is inspected when the actual printing occurs.
1968 *
1969 * See also:
1970 * printf(3)
1971 *
1972 * See the vsnprintf() documentation for format string extensions over C99.
1973 */
1974asmlinkage __visible int printk(const char *fmt, ...)
1975{
1976 va_list args;
1977 int r;
1978
1979 va_start(args, fmt);
1980 r = vprintk_func(fmt, args);
1981 va_end(args);
1982
1983 return r;
1984}
1985EXPORT_SYMBOL(printk);
1986
1987#else /* CONFIG_PRINTK */
1988
1989#define LOG_LINE_MAX 0
1990#define PREFIX_MAX 0
1991
1992static u64 syslog_seq;
1993static u32 syslog_idx;
1994static u64 console_seq;
1995static u32 console_idx;
1996static u64 log_first_seq;
1997static u32 log_first_idx;
1998static u64 log_next_seq;
1999static char *log_text(const struct printk_log *msg) { return NULL; }
2000static char *log_dict(const struct printk_log *msg) { return NULL; }
2001static struct printk_log *log_from_idx(u32 idx) { return NULL; }
2002static u32 log_next(u32 idx) { return 0; }
2003static ssize_t msg_print_ext_header(char *buf, size_t size,
2004 struct printk_log *msg,
2005 u64 seq) { return 0; }
2006static ssize_t msg_print_ext_body(char *buf, size_t size,
2007 char *dict, size_t dict_len,
2008 char *text, size_t text_len) { return 0; }
2009static void console_lock_spinning_enable(void) { }
2010static int console_lock_spinning_disable_and_check(void) { return 0; }
2011static void call_console_drivers(const char *ext_text, size_t ext_len,
2012 const char *text, size_t len) {}
2013static size_t msg_print_text(const struct printk_log *msg,
2014 bool syslog, char *buf, size_t size) { return 0; }
2015static bool suppress_message_printing(int level) { return false; }
2016
2017#endif /* CONFIG_PRINTK */
2018
2019#ifdef CONFIG_EARLY_PRINTK
2020struct console *early_console;
2021
2022asmlinkage __visible void early_printk(const char *fmt, ...)
2023{
2024 va_list ap;
2025 char buf[512];
2026 int n;
2027
2028 if (!early_console)
2029 return;
2030
2031 va_start(ap, fmt);
2032 n = vscnprintf(buf, sizeof(buf), fmt, ap);
2033 va_end(ap);
2034
2035 early_console->write(early_console, buf, n);
2036}
2037#endif
2038
2039static int __add_preferred_console(char *name, int idx, char *options,
2040 char *brl_options)
2041{
2042 struct console_cmdline *c;
2043 int i;
2044
2045 /*
2046 * See if this tty is not yet registered, and
2047 * if we have a slot free.
2048 */
2049 for (i = 0, c = console_cmdline;
2050 i < MAX_CMDLINECONSOLES && c->name[0];
2051 i++, c++) {
2052 if (strcmp(c->name, name) == 0 && c->index == idx) {
2053 if (!brl_options)
2054 preferred_console = i;
2055 return 0;
2056 }
2057 }
2058 if (i == MAX_CMDLINECONSOLES)
2059 return -E2BIG;
2060 if (!brl_options)
2061 preferred_console = i;
2062 strlcpy(c->name, name, sizeof(c->name));
2063 c->options = options;
2064 braille_set_options(c, brl_options);
2065
2066 c->index = idx;
2067 return 0;
2068}
2069
2070static int __init console_msg_format_setup(char *str)
2071{
2072 if (!strcmp(str, "syslog"))
2073 console_msg_format = MSG_FORMAT_SYSLOG;
2074 if (!strcmp(str, "default"))
2075 console_msg_format = MSG_FORMAT_DEFAULT;
2076 return 1;
2077}
2078__setup("console_msg_format=", console_msg_format_setup);
2079
2080/*
2081 * Set up a console. Called via do_early_param() in init/main.c
2082 * for each "console=" parameter in the boot command line.
2083 */
2084static int __init console_setup(char *str)
2085{
2086 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
2087 char *s, *options, *brl_options = NULL;
2088 int idx;
2089
2090 if (_braille_console_setup(&str, &brl_options))
2091 return 1;
2092
2093 /*
2094 * Decode str into name, index, options.
2095 */
2096 if (str[0] >= '0' && str[0] <= '9') {
2097 strcpy(buf, "ttyS");
2098 strncpy(buf + 4, str, sizeof(buf) - 5);
2099 } else {
2100 strncpy(buf, str, sizeof(buf) - 1);
2101 }
2102 buf[sizeof(buf) - 1] = 0;
2103 options = strchr(str, ',');
2104 if (options)
2105 *(options++) = 0;
2106#ifdef __sparc__
2107 if (!strcmp(str, "ttya"))
2108 strcpy(buf, "ttyS0");
2109 if (!strcmp(str, "ttyb"))
2110 strcpy(buf, "ttyS1");
2111#endif
2112 for (s = buf; *s; s++)
2113 if (isdigit(*s) || *s == ',')
2114 break;
2115 idx = simple_strtoul(s, NULL, 10);
2116 *s = 0;
2117
2118 __add_preferred_console(buf, idx, options, brl_options);
2119 console_set_on_cmdline = 1;
2120 return 1;
2121}
2122__setup("console=", console_setup);
2123
2124/**
2125 * add_preferred_console - add a device to the list of preferred consoles.
2126 * @name: device name
2127 * @idx: device index
2128 * @options: options for this console
2129 *
2130 * The last preferred console added will be used for kernel messages
2131 * and stdin/out/err for init. Normally this is used by console_setup
2132 * above to handle user-supplied console arguments; however it can also
2133 * be used by arch-specific code either to override the user or more
2134 * commonly to provide a default console (ie from PROM variables) when
2135 * the user has not supplied one.
2136 */
2137int add_preferred_console(char *name, int idx, char *options)
2138{
2139 return __add_preferred_console(name, idx, options, NULL);
2140}
2141
2142bool console_suspend_enabled = true;
2143EXPORT_SYMBOL(console_suspend_enabled);
2144
2145static int __init console_suspend_disable(char *str)
2146{
2147 console_suspend_enabled = false;
2148 return 1;
2149}
2150__setup("no_console_suspend", console_suspend_disable);
2151module_param_named(console_suspend, console_suspend_enabled,
2152 bool, S_IRUGO | S_IWUSR);
2153MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2154 " and hibernate operations");
2155
2156/**
2157 * suspend_console - suspend the console subsystem
2158 *
2159 * This disables printk() while we go into suspend states
2160 */
2161void suspend_console(void)
2162{
2163 if (!console_suspend_enabled)
2164 return;
2165 pr_info("Suspending console(s) (use no_console_suspend to debug)\n");
2166 console_lock();
2167 console_suspended = 1;
2168 up_console_sem();
2169}
2170
2171void resume_console(void)
2172{
2173 if (!console_suspend_enabled)
2174 return;
2175 down_console_sem();
2176 console_suspended = 0;
2177 console_unlock();
2178}
2179
2180/**
2181 * console_cpu_notify - print deferred console messages after CPU hotplug
2182 * @cpu: unused
2183 *
2184 * If printk() is called from a CPU that is not online yet, the messages
2185 * will be printed on the console only if there are CON_ANYTIME consoles.
2186 * This function is called when a new CPU comes online (or fails to come
2187 * up) or goes offline.
2188 */
2189static int console_cpu_notify(unsigned int cpu)
2190{
2191 if (!cpuhp_tasks_frozen) {
2192 /* If trylock fails, someone else is doing the printing */
2193 if (console_trylock())
2194 console_unlock();
2195 }
2196 return 0;
2197}
2198
2199/**
2200 * console_lock - lock the console system for exclusive use.
2201 *
2202 * Acquires a lock which guarantees that the caller has
2203 * exclusive access to the console system and the console_drivers list.
2204 *
2205 * Can sleep, returns nothing.
2206 */
2207void console_lock(void)
2208{
2209 might_sleep();
2210
2211 down_console_sem();
2212 if (console_suspended)
2213 return;
2214 console_locked = 1;
2215 console_may_schedule = 1;
2216}
2217EXPORT_SYMBOL(console_lock);
2218
2219/**
2220 * console_trylock - try to lock the console system for exclusive use.
2221 *
2222 * Try to acquire a lock which guarantees that the caller has exclusive
2223 * access to the console system and the console_drivers list.
2224 *
2225 * returns 1 on success, and 0 on failure to acquire the lock.
2226 */
2227int console_trylock(void)
2228{
2229 if (down_trylock_console_sem())
2230 return 0;
2231 if (console_suspended) {
2232 up_console_sem();
2233 return 0;
2234 }
2235 console_locked = 1;
2236 console_may_schedule = 0;
2237 return 1;
2238}
2239EXPORT_SYMBOL(console_trylock);
2240
2241int is_console_locked(void)
2242{
2243 return console_locked;
2244}
2245
2246/*
2247 * Check if we have any console that is capable of printing while cpu is
2248 * booting or shutting down. Requires console_sem.
2249 */
2250static int have_callable_console(void)
2251{
2252 struct console *con;
2253
2254 for_each_console(con)
2255 if ((con->flags & CON_ENABLED) &&
2256 (con->flags & CON_ANYTIME))
2257 return 1;
2258
2259 return 0;
2260}
2261
2262/*
2263 * Can we actually use the console at this time on this cpu?
2264 *
2265 * Console drivers may assume that per-cpu resources have been allocated. So
2266 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2267 * call them until this CPU is officially up.
2268 */
2269static inline int can_use_console(void)
2270{
2271 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2272}
2273
2274/**
2275 * console_unlock - unlock the console system
2276 *
2277 * Releases the console_lock which the caller holds on the console system
2278 * and the console driver list.
2279 *
2280 * While the console_lock was held, console output may have been buffered
2281 * by printk(). If this is the case, console_unlock(); emits
2282 * the output prior to releasing the lock.
2283 *
2284 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2285 *
2286 * console_unlock(); may be called from any context.
2287 */
2288void console_unlock(void)
2289{
2290 static char ext_text[CONSOLE_EXT_LOG_MAX];
2291 static char text[LOG_LINE_MAX + PREFIX_MAX];
2292 static u64 seen_seq;
2293 unsigned long flags;
2294 bool wake_klogd = false;
2295 bool do_cond_resched, retry;
2296
2297 if (console_suspended) {
2298 up_console_sem();
2299 return;
2300 }
2301
2302 /*
2303 * Console drivers are called with interrupts disabled, so
2304 * @console_may_schedule should be cleared before; however, we may
2305 * end up dumping a lot of lines, for example, if called from
2306 * console registration path, and should invoke cond_resched()
2307 * between lines if allowable. Not doing so can cause a very long
2308 * scheduling stall on a slow console leading to RCU stall and
2309 * softlockup warnings which exacerbate the issue with more
2310 * messages practically incapacitating the system.
2311 *
2312 * console_trylock() is not able to detect the preemptive
2313 * context reliably. Therefore the value must be stored before
2314 * and cleared after the the "again" goto label.
2315 */
2316 do_cond_resched = console_may_schedule;
2317again:
2318 console_may_schedule = 0;
2319
2320 /*
2321 * We released the console_sem lock, so we need to recheck if
2322 * cpu is online and (if not) is there at least one CON_ANYTIME
2323 * console.
2324 */
2325 if (!can_use_console()) {
2326 console_locked = 0;
2327 up_console_sem();
2328 return;
2329 }
2330
2331 for (;;) {
2332 struct printk_log *msg;
2333 size_t ext_len = 0;
2334 size_t len;
2335
2336 printk_safe_enter_irqsave(flags);
2337 raw_spin_lock(&logbuf_lock);
2338 if (seen_seq != log_next_seq) {
2339 wake_klogd = true;
2340 seen_seq = log_next_seq;
2341 }
2342
2343 if (console_seq < log_first_seq) {
2344 len = sprintf(text, "** %u printk messages dropped **\n",
2345 (unsigned)(log_first_seq - console_seq));
2346
2347 /* messages are gone, move to first one */
2348 console_seq = log_first_seq;
2349 console_idx = log_first_idx;
2350 } else {
2351 len = 0;
2352 }
2353skip:
2354 if (console_seq == log_next_seq)
2355 break;
2356
2357 msg = log_from_idx(console_idx);
2358 if (suppress_message_printing(msg->level)) {
2359 /*
2360 * Skip record we have buffered and already printed
2361 * directly to the console when we received it, and
2362 * record that has level above the console loglevel.
2363 */
2364 console_idx = log_next(console_idx);
2365 console_seq++;
2366 goto skip;
2367 }
2368
2369 len += msg_print_text(msg,
2370 console_msg_format & MSG_FORMAT_SYSLOG,
2371 text + len,
2372 sizeof(text) - len);
2373 if (nr_ext_console_drivers) {
2374 ext_len = msg_print_ext_header(ext_text,
2375 sizeof(ext_text),
2376 msg, console_seq);
2377 ext_len += msg_print_ext_body(ext_text + ext_len,
2378 sizeof(ext_text) - ext_len,
2379 log_dict(msg), msg->dict_len,
2380 log_text(msg), msg->text_len);
2381 }
2382 console_idx = log_next(console_idx);
2383 console_seq++;
2384 raw_spin_unlock(&logbuf_lock);
2385
2386 /*
2387 * While actively printing out messages, if another printk()
2388 * were to occur on another CPU, it may wait for this one to
2389 * finish. This task can not be preempted if there is a
2390 * waiter waiting to take over.
2391 */
2392 console_lock_spinning_enable();
2393
2394 stop_critical_timings(); /* don't trace print latency */
2395 call_console_drivers(ext_text, ext_len, text, len);
2396 start_critical_timings();
2397
2398 if (console_lock_spinning_disable_and_check()) {
2399 printk_safe_exit_irqrestore(flags);
2400 goto out;
2401 }
2402
2403 printk_safe_exit_irqrestore(flags);
2404
2405 if (do_cond_resched)
2406 cond_resched();
2407 }
2408
2409 console_locked = 0;
2410
2411 /* Release the exclusive_console once it is used */
2412 if (unlikely(exclusive_console))
2413 exclusive_console = NULL;
2414
2415 raw_spin_unlock(&logbuf_lock);
2416
2417 up_console_sem();
2418
2419 /*
2420 * Someone could have filled up the buffer again, so re-check if there's
2421 * something to flush. In case we cannot trylock the console_sem again,
2422 * there's a new owner and the console_unlock() from them will do the
2423 * flush, no worries.
2424 */
2425 raw_spin_lock(&logbuf_lock);
2426 retry = console_seq != log_next_seq;
2427 raw_spin_unlock(&logbuf_lock);
2428 printk_safe_exit_irqrestore(flags);
2429
2430 if (retry && console_trylock())
2431 goto again;
2432
2433out:
2434 if (wake_klogd)
2435 wake_up_klogd();
2436}
2437EXPORT_SYMBOL(console_unlock);
2438
2439/**
2440 * console_conditional_schedule - yield the CPU if required
2441 *
2442 * If the console code is currently allowed to sleep, and
2443 * if this CPU should yield the CPU to another task, do
2444 * so here.
2445 *
2446 * Must be called within console_lock();.
2447 */
2448void __sched console_conditional_schedule(void)
2449{
2450 if (console_may_schedule)
2451 cond_resched();
2452}
2453EXPORT_SYMBOL(console_conditional_schedule);
2454
2455void console_unblank(void)
2456{
2457 struct console *c;
2458
2459 /*
2460 * console_unblank can no longer be called in interrupt context unless
2461 * oops_in_progress is set to 1..
2462 */
2463 if (oops_in_progress) {
2464 if (down_trylock_console_sem() != 0)
2465 return;
2466 } else
2467 console_lock();
2468
2469 console_locked = 1;
2470 console_may_schedule = 0;
2471 for_each_console(c)
2472 if ((c->flags & CON_ENABLED) && c->unblank)
2473 c->unblank();
2474 console_unlock();
2475}
2476
2477/**
2478 * console_flush_on_panic - flush console content on panic
2479 *
2480 * Immediately output all pending messages no matter what.
2481 */
2482void console_flush_on_panic(void)
2483{
2484 /*
2485 * If someone else is holding the console lock, trylock will fail
2486 * and may_schedule may be set. Ignore and proceed to unlock so
2487 * that messages are flushed out. As this can be called from any
2488 * context and we don't want to get preempted while flushing,
2489 * ensure may_schedule is cleared.
2490 */
2491 console_trylock();
2492 console_may_schedule = 0;
2493 console_unlock();
2494}
2495
2496/*
2497 * Return the console tty driver structure and its associated index
2498 */
2499struct tty_driver *console_device(int *index)
2500{
2501 struct console *c;
2502 struct tty_driver *driver = NULL;
2503
2504 console_lock();
2505 for_each_console(c) {
2506 if (!c->device)
2507 continue;
2508 driver = c->device(c, index);
2509 if (driver)
2510 break;
2511 }
2512 console_unlock();
2513 return driver;
2514}
2515
2516/*
2517 * Prevent further output on the passed console device so that (for example)
2518 * serial drivers can disable console output before suspending a port, and can
2519 * re-enable output afterwards.
2520 */
2521void console_stop(struct console *console)
2522{
2523 console_lock();
2524 console->flags &= ~CON_ENABLED;
2525 console_unlock();
2526}
2527EXPORT_SYMBOL(console_stop);
2528
2529void console_start(struct console *console)
2530{
2531 console_lock();
2532 console->flags |= CON_ENABLED;
2533 console_unlock();
2534}
2535EXPORT_SYMBOL(console_start);
2536
2537static int __read_mostly keep_bootcon;
2538
2539static int __init keep_bootcon_setup(char *str)
2540{
2541 keep_bootcon = 1;
2542 pr_info("debug: skip boot console de-registration.\n");
2543
2544 return 0;
2545}
2546
2547early_param("keep_bootcon", keep_bootcon_setup);
2548
2549/*
2550 * The console driver calls this routine during kernel initialization
2551 * to register the console printing procedure with printk() and to
2552 * print any messages that were printed by the kernel before the
2553 * console driver was initialized.
2554 *
2555 * This can happen pretty early during the boot process (because of
2556 * early_printk) - sometimes before setup_arch() completes - be careful
2557 * of what kernel features are used - they may not be initialised yet.
2558 *
2559 * There are two types of consoles - bootconsoles (early_printk) and
2560 * "real" consoles (everything which is not a bootconsole) which are
2561 * handled differently.
2562 * - Any number of bootconsoles can be registered at any time.
2563 * - As soon as a "real" console is registered, all bootconsoles
2564 * will be unregistered automatically.
2565 * - Once a "real" console is registered, any attempt to register a
2566 * bootconsoles will be rejected
2567 */
2568void register_console(struct console *newcon)
2569{
2570 int i;
2571 unsigned long flags;
2572 struct console *bcon = NULL;
2573 struct console_cmdline *c;
2574 static bool has_preferred;
2575
2576 if (console_drivers)
2577 for_each_console(bcon)
2578 if (WARN(bcon == newcon,
2579 "console '%s%d' already registered\n",
2580 bcon->name, bcon->index))
2581 return;
2582
2583 /*
2584 * before we register a new CON_BOOT console, make sure we don't
2585 * already have a valid console
2586 */
2587 if (console_drivers && newcon->flags & CON_BOOT) {
2588 /* find the last or real console */
2589 for_each_console(bcon) {
2590 if (!(bcon->flags & CON_BOOT)) {
2591 pr_info("Too late to register bootconsole %s%d\n",
2592 newcon->name, newcon->index);
2593 return;
2594 }
2595 }
2596 }
2597
2598 if (console_drivers && console_drivers->flags & CON_BOOT)
2599 bcon = console_drivers;
2600
2601 if (!has_preferred || bcon || !console_drivers)
2602 has_preferred = preferred_console >= 0;
2603
2604 /*
2605 * See if we want to use this console driver. If we
2606 * didn't select a console we take the first one
2607 * that registers here.
2608 */
2609 if (!has_preferred) {
2610 if (newcon->index < 0)
2611 newcon->index = 0;
2612 if (newcon->setup == NULL ||
2613 newcon->setup(newcon, NULL) == 0) {
2614 newcon->flags |= CON_ENABLED;
2615 if (newcon->device) {
2616 newcon->flags |= CON_CONSDEV;
2617 has_preferred = true;
2618 }
2619 }
2620 }
2621
2622 /*
2623 * See if this console matches one we selected on
2624 * the command line.
2625 */
2626 for (i = 0, c = console_cmdline;
2627 i < MAX_CMDLINECONSOLES && c->name[0];
2628 i++, c++) {
2629 if (!newcon->match ||
2630 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2631 /* default matching */
2632 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2633 if (strcmp(c->name, newcon->name) != 0)
2634 continue;
2635 if (newcon->index >= 0 &&
2636 newcon->index != c->index)
2637 continue;
2638 if (newcon->index < 0)
2639 newcon->index = c->index;
2640
2641 if (_braille_register_console(newcon, c))
2642 return;
2643
2644 if (newcon->setup &&
2645 newcon->setup(newcon, c->options) != 0)
2646 break;
2647 }
2648
2649 newcon->flags |= CON_ENABLED;
2650 if (i == preferred_console) {
2651 newcon->flags |= CON_CONSDEV;
2652 has_preferred = true;
2653 }
2654 break;
2655 }
2656
2657 if (!(newcon->flags & CON_ENABLED))
2658 return;
2659
2660 /*
2661 * If we have a bootconsole, and are switching to a real console,
2662 * don't print everything out again, since when the boot console, and
2663 * the real console are the same physical device, it's annoying to
2664 * see the beginning boot messages twice
2665 */
2666 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2667 newcon->flags &= ~CON_PRINTBUFFER;
2668
2669 /*
2670 * Put this console in the list - keep the
2671 * preferred driver at the head of the list.
2672 */
2673 console_lock();
2674 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2675 newcon->next = console_drivers;
2676 console_drivers = newcon;
2677 if (newcon->next)
2678 newcon->next->flags &= ~CON_CONSDEV;
2679 } else {
2680 newcon->next = console_drivers->next;
2681 console_drivers->next = newcon;
2682 }
2683
2684 if (newcon->flags & CON_EXTENDED)
2685 if (!nr_ext_console_drivers++)
2686 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2687
2688 if (newcon->flags & CON_PRINTBUFFER) {
2689 /*
2690 * console_unlock(); will print out the buffered messages
2691 * for us.
2692 */
2693 logbuf_lock_irqsave(flags);
2694 console_seq = syslog_seq;
2695 console_idx = syslog_idx;
2696 logbuf_unlock_irqrestore(flags);
2697 /*
2698 * We're about to replay the log buffer. Only do this to the
2699 * just-registered console to avoid excessive message spam to
2700 * the already-registered consoles.
2701 */
2702 exclusive_console = newcon;
2703 }
2704 console_unlock();
2705 console_sysfs_notify();
2706
2707 /*
2708 * By unregistering the bootconsoles after we enable the real console
2709 * we get the "console xxx enabled" message on all the consoles -
2710 * boot consoles, real consoles, etc - this is to ensure that end
2711 * users know there might be something in the kernel's log buffer that
2712 * went to the bootconsole (that they do not see on the real console)
2713 */
2714 pr_info("%sconsole [%s%d] enabled\n",
2715 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2716 newcon->name, newcon->index);
2717 if (bcon &&
2718 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2719 !keep_bootcon) {
2720 /* We need to iterate through all boot consoles, to make
2721 * sure we print everything out, before we unregister them.
2722 */
2723 for_each_console(bcon)
2724 if (bcon->flags & CON_BOOT)
2725 unregister_console(bcon);
2726 }
2727}
2728EXPORT_SYMBOL(register_console);
2729
2730int unregister_console(struct console *console)
2731{
2732 struct console *a, *b;
2733 int res;
2734
2735 pr_info("%sconsole [%s%d] disabled\n",
2736 (console->flags & CON_BOOT) ? "boot" : "" ,
2737 console->name, console->index);
2738
2739 res = _braille_unregister_console(console);
2740 if (res)
2741 return res;
2742
2743 res = 1;
2744 console_lock();
2745 if (console_drivers == console) {
2746 console_drivers=console->next;
2747 res = 0;
2748 } else if (console_drivers) {
2749 for (a=console_drivers->next, b=console_drivers ;
2750 a; b=a, a=b->next) {
2751 if (a == console) {
2752 b->next = a->next;
2753 res = 0;
2754 break;
2755 }
2756 }
2757 }
2758
2759 if (!res && (console->flags & CON_EXTENDED))
2760 nr_ext_console_drivers--;
2761
2762 /*
2763 * If this isn't the last console and it has CON_CONSDEV set, we
2764 * need to set it on the next preferred console.
2765 */
2766 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2767 console_drivers->flags |= CON_CONSDEV;
2768
2769 console->flags &= ~CON_ENABLED;
2770 console_unlock();
2771 console_sysfs_notify();
2772 return res;
2773}
2774EXPORT_SYMBOL(unregister_console);
2775
2776/*
2777 * Initialize the console device. This is called *early*, so
2778 * we can't necessarily depend on lots of kernel help here.
2779 * Just do some early initializations, and do the complex setup
2780 * later.
2781 */
2782void __init console_init(void)
2783{
2784 int ret;
2785 initcall_t *call;
2786
2787 /* Setup the default TTY line discipline. */
2788 n_tty_init();
2789
2790 /*
2791 * set up the console device so that later boot sequences can
2792 * inform about problems etc..
2793 */
2794 call = __con_initcall_start;
2795 trace_initcall_level("console");
2796 while (call < __con_initcall_end) {
2797 trace_initcall_start((*call));
2798 ret = (*call)();
2799 trace_initcall_finish((*call), ret);
2800 call++;
2801 }
2802}
2803
2804/*
2805 * Some boot consoles access data that is in the init section and which will
2806 * be discarded after the initcalls have been run. To make sure that no code
2807 * will access this data, unregister the boot consoles in a late initcall.
2808 *
2809 * If for some reason, such as deferred probe or the driver being a loadable
2810 * module, the real console hasn't registered yet at this point, there will
2811 * be a brief interval in which no messages are logged to the console, which
2812 * makes it difficult to diagnose problems that occur during this time.
2813 *
2814 * To mitigate this problem somewhat, only unregister consoles whose memory
2815 * intersects with the init section. Note that all other boot consoles will
2816 * get unregistred when the real preferred console is registered.
2817 */
2818static int __init printk_late_init(void)
2819{
2820 struct console *con;
2821 int ret;
2822
2823 for_each_console(con) {
2824 if (!(con->flags & CON_BOOT))
2825 continue;
2826
2827 /* Check addresses that might be used for enabled consoles. */
2828 if (init_section_intersects(con, sizeof(*con)) ||
2829 init_section_contains(con->write, 0) ||
2830 init_section_contains(con->read, 0) ||
2831 init_section_contains(con->device, 0) ||
2832 init_section_contains(con->unblank, 0) ||
2833 init_section_contains(con->data, 0)) {
2834 /*
2835 * Please, consider moving the reported consoles out
2836 * of the init section.
2837 */
2838 pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n",
2839 con->name, con->index);
2840 unregister_console(con);
2841 }
2842 }
2843 ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL,
2844 console_cpu_notify);
2845 WARN_ON(ret < 0);
2846 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online",
2847 console_cpu_notify, NULL);
2848 WARN_ON(ret < 0);
2849 return 0;
2850}
2851late_initcall(printk_late_init);
2852
2853#if defined CONFIG_PRINTK
2854/*
2855 * Delayed printk version, for scheduler-internal messages:
2856 */
2857#define PRINTK_PENDING_WAKEUP 0x01
2858#define PRINTK_PENDING_OUTPUT 0x02
2859
2860static DEFINE_PER_CPU(int, printk_pending);
2861
2862static void wake_up_klogd_work_func(struct irq_work *irq_work)
2863{
2864 int pending = __this_cpu_xchg(printk_pending, 0);
2865
2866 if (pending & PRINTK_PENDING_OUTPUT) {
2867 /* If trylock fails, someone else is doing the printing */
2868 if (console_trylock())
2869 console_unlock();
2870 }
2871
2872 if (pending & PRINTK_PENDING_WAKEUP)
2873 wake_up_interruptible(&log_wait);
2874}
2875
2876static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2877 .func = wake_up_klogd_work_func,
2878 .flags = IRQ_WORK_LAZY,
2879};
2880
2881void wake_up_klogd(void)
2882{
2883 preempt_disable();
2884 if (waitqueue_active(&log_wait)) {
2885 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2886 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2887 }
2888 preempt_enable();
2889}
2890
2891int vprintk_deferred(const char *fmt, va_list args)
2892{
2893 int r;
2894
2895 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2896
2897 preempt_disable();
2898 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2899 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2900 preempt_enable();
2901
2902 return r;
2903}
2904
2905int printk_deferred(const char *fmt, ...)
2906{
2907 va_list args;
2908 int r;
2909
2910 va_start(args, fmt);
2911 r = vprintk_deferred(fmt, args);
2912 va_end(args);
2913
2914 return r;
2915}
2916
2917/*
2918 * printk rate limiting, lifted from the networking subsystem.
2919 *
2920 * This enforces a rate limit: not more than 10 kernel messages
2921 * every 5s to make a denial-of-service attack impossible.
2922 */
2923DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2924
2925int __printk_ratelimit(const char *func)
2926{
2927 return ___ratelimit(&printk_ratelimit_state, func);
2928}
2929EXPORT_SYMBOL(__printk_ratelimit);
2930
2931/**
2932 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2933 * @caller_jiffies: pointer to caller's state
2934 * @interval_msecs: minimum interval between prints
2935 *
2936 * printk_timed_ratelimit() returns true if more than @interval_msecs
2937 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2938 * returned true.
2939 */
2940bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2941 unsigned int interval_msecs)
2942{
2943 unsigned long elapsed = jiffies - *caller_jiffies;
2944
2945 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2946 return false;
2947
2948 *caller_jiffies = jiffies;
2949 return true;
2950}
2951EXPORT_SYMBOL(printk_timed_ratelimit);
2952
2953static DEFINE_SPINLOCK(dump_list_lock);
2954static LIST_HEAD(dump_list);
2955
2956/**
2957 * kmsg_dump_register - register a kernel log dumper.
2958 * @dumper: pointer to the kmsg_dumper structure
2959 *
2960 * Adds a kernel log dumper to the system. The dump callback in the
2961 * structure will be called when the kernel oopses or panics and must be
2962 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2963 */
2964int kmsg_dump_register(struct kmsg_dumper *dumper)
2965{
2966 unsigned long flags;
2967 int err = -EBUSY;
2968
2969 /* The dump callback needs to be set */
2970 if (!dumper->dump)
2971 return -EINVAL;
2972
2973 spin_lock_irqsave(&dump_list_lock, flags);
2974 /* Don't allow registering multiple times */
2975 if (!dumper->registered) {
2976 dumper->registered = 1;
2977 list_add_tail_rcu(&dumper->list, &dump_list);
2978 err = 0;
2979 }
2980 spin_unlock_irqrestore(&dump_list_lock, flags);
2981
2982 return err;
2983}
2984EXPORT_SYMBOL_GPL(kmsg_dump_register);
2985
2986/**
2987 * kmsg_dump_unregister - unregister a kmsg dumper.
2988 * @dumper: pointer to the kmsg_dumper structure
2989 *
2990 * Removes a dump device from the system. Returns zero on success and
2991 * %-EINVAL otherwise.
2992 */
2993int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2994{
2995 unsigned long flags;
2996 int err = -EINVAL;
2997
2998 spin_lock_irqsave(&dump_list_lock, flags);
2999 if (dumper->registered) {
3000 dumper->registered = 0;
3001 list_del_rcu(&dumper->list);
3002 err = 0;
3003 }
3004 spin_unlock_irqrestore(&dump_list_lock, flags);
3005 synchronize_rcu();
3006
3007 return err;
3008}
3009EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
3010
3011static bool always_kmsg_dump;
3012module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
3013
3014/**
3015 * kmsg_dump - dump kernel log to kernel message dumpers.
3016 * @reason: the reason (oops, panic etc) for dumping
3017 *
3018 * Call each of the registered dumper's dump() callback, which can
3019 * retrieve the kmsg records with kmsg_dump_get_line() or
3020 * kmsg_dump_get_buffer().
3021 */
3022void kmsg_dump(enum kmsg_dump_reason reason)
3023{
3024 struct kmsg_dumper *dumper;
3025 unsigned long flags;
3026
3027 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
3028 return;
3029
3030 rcu_read_lock();
3031 list_for_each_entry_rcu(dumper, &dump_list, list) {
3032 if (dumper->max_reason && reason > dumper->max_reason)
3033 continue;
3034
3035 /* initialize iterator with data about the stored records */
3036 dumper->active = true;
3037
3038 logbuf_lock_irqsave(flags);
3039 dumper->cur_seq = clear_seq;
3040 dumper->cur_idx = clear_idx;
3041 dumper->next_seq = log_next_seq;
3042 dumper->next_idx = log_next_idx;
3043 logbuf_unlock_irqrestore(flags);
3044
3045 /* invoke dumper which will iterate over records */
3046 dumper->dump(dumper, reason);
3047
3048 /* reset iterator */
3049 dumper->active = false;
3050 }
3051 rcu_read_unlock();
3052}
3053
3054/**
3055 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
3056 * @dumper: registered kmsg dumper
3057 * @syslog: include the "<4>" prefixes
3058 * @line: buffer to copy the line to
3059 * @size: maximum size of the buffer
3060 * @len: length of line placed into buffer
3061 *
3062 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3063 * record, and copy one record into the provided buffer.
3064 *
3065 * Consecutive calls will return the next available record moving
3066 * towards the end of the buffer with the youngest messages.
3067 *
3068 * A return value of FALSE indicates that there are no more records to
3069 * read.
3070 *
3071 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
3072 */
3073bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
3074 char *line, size_t size, size_t *len)
3075{
3076 struct printk_log *msg;
3077 size_t l = 0;
3078 bool ret = false;
3079
3080 if (!dumper->active)
3081 goto out;
3082
3083 if (dumper->cur_seq < log_first_seq) {
3084 /* messages are gone, move to first available one */
3085 dumper->cur_seq = log_first_seq;
3086 dumper->cur_idx = log_first_idx;
3087 }
3088
3089 /* last entry */
3090 if (dumper->cur_seq >= log_next_seq)
3091 goto out;
3092
3093 msg = log_from_idx(dumper->cur_idx);
3094 l = msg_print_text(msg, syslog, line, size);
3095
3096 dumper->cur_idx = log_next(dumper->cur_idx);
3097 dumper->cur_seq++;
3098 ret = true;
3099out:
3100 if (len)
3101 *len = l;
3102 return ret;
3103}
3104
3105/**
3106 * kmsg_dump_get_line - retrieve one kmsg log line
3107 * @dumper: registered kmsg dumper
3108 * @syslog: include the "<4>" prefixes
3109 * @line: buffer to copy the line to
3110 * @size: maximum size of the buffer
3111 * @len: length of line placed into buffer
3112 *
3113 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3114 * record, and copy one record into the provided buffer.
3115 *
3116 * Consecutive calls will return the next available record moving
3117 * towards the end of the buffer with the youngest messages.
3118 *
3119 * A return value of FALSE indicates that there are no more records to
3120 * read.
3121 */
3122bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
3123 char *line, size_t size, size_t *len)
3124{
3125 unsigned long flags;
3126 bool ret;
3127
3128 logbuf_lock_irqsave(flags);
3129 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
3130 logbuf_unlock_irqrestore(flags);
3131
3132 return ret;
3133}
3134EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
3135
3136/**
3137 * kmsg_dump_get_buffer - copy kmsg log lines
3138 * @dumper: registered kmsg dumper
3139 * @syslog: include the "<4>" prefixes
3140 * @buf: buffer to copy the line to
3141 * @size: maximum size of the buffer
3142 * @len: length of line placed into buffer
3143 *
3144 * Start at the end of the kmsg buffer and fill the provided buffer
3145 * with as many of the the *youngest* kmsg records that fit into it.
3146 * If the buffer is large enough, all available kmsg records will be
3147 * copied with a single call.
3148 *
3149 * Consecutive calls will fill the buffer with the next block of
3150 * available older records, not including the earlier retrieved ones.
3151 *
3152 * A return value of FALSE indicates that there are no more records to
3153 * read.
3154 */
3155bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
3156 char *buf, size_t size, size_t *len)
3157{
3158 unsigned long flags;
3159 u64 seq;
3160 u32 idx;
3161 u64 next_seq;
3162 u32 next_idx;
3163 size_t l = 0;
3164 bool ret = false;
3165
3166 if (!dumper->active)
3167 goto out;
3168
3169 logbuf_lock_irqsave(flags);
3170 if (dumper->cur_seq < log_first_seq) {
3171 /* messages are gone, move to first available one */
3172 dumper->cur_seq = log_first_seq;
3173 dumper->cur_idx = log_first_idx;
3174 }
3175
3176 /* last entry */
3177 if (dumper->cur_seq >= dumper->next_seq) {
3178 logbuf_unlock_irqrestore(flags);
3179 goto out;
3180 }
3181
3182 /* calculate length of entire buffer */
3183 seq = dumper->cur_seq;
3184 idx = dumper->cur_idx;
3185 while (seq < dumper->next_seq) {
3186 struct printk_log *msg = log_from_idx(idx);
3187
3188 l += msg_print_text(msg, true, NULL, 0);
3189 idx = log_next(idx);
3190 seq++;
3191 }
3192
3193 /* move first record forward until length fits into the buffer */
3194 seq = dumper->cur_seq;
3195 idx = dumper->cur_idx;
3196 while (l > size && seq < dumper->next_seq) {
3197 struct printk_log *msg = log_from_idx(idx);
3198
3199 l -= msg_print_text(msg, true, NULL, 0);
3200 idx = log_next(idx);
3201 seq++;
3202 }
3203
3204 /* last message in next interation */
3205 next_seq = seq;
3206 next_idx = idx;
3207
3208 l = 0;
3209 while (seq < dumper->next_seq) {
3210 struct printk_log *msg = log_from_idx(idx);
3211
3212 l += msg_print_text(msg, syslog, buf + l, size - l);
3213 idx = log_next(idx);
3214 seq++;
3215 }
3216
3217 dumper->next_seq = next_seq;
3218 dumper->next_idx = next_idx;
3219 ret = true;
3220 logbuf_unlock_irqrestore(flags);
3221out:
3222 if (len)
3223 *len = l;
3224 return ret;
3225}
3226EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3227
3228/**
3229 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3230 * @dumper: registered kmsg dumper
3231 *
3232 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3233 * kmsg_dump_get_buffer() can be called again and used multiple
3234 * times within the same dumper.dump() callback.
3235 *
3236 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3237 */
3238void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3239{
3240 dumper->cur_seq = clear_seq;
3241 dumper->cur_idx = clear_idx;
3242 dumper->next_seq = log_next_seq;
3243 dumper->next_idx = log_next_idx;
3244}
3245
3246/**
3247 * kmsg_dump_rewind - reset the interator
3248 * @dumper: registered kmsg dumper
3249 *
3250 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3251 * kmsg_dump_get_buffer() can be called again and used multiple
3252 * times within the same dumper.dump() callback.
3253 */
3254void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3255{
3256 unsigned long flags;
3257
3258 logbuf_lock_irqsave(flags);
3259 kmsg_dump_rewind_nolock(dumper);
3260 logbuf_unlock_irqrestore(flags);
3261}
3262EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3263
3264#endif