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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/interrupt.h> /* For in_interrupt() */
30#include <linux/delay.h>
31#include <linux/smp.h>
32#include <linux/security.h>
33#include <linux/bootmem.h>
34#include <linux/memblock.h>
35#include <linux/aio.h>
36#include <linux/syscalls.h>
37#include <linux/kexec.h>
38#include <linux/kdb.h>
39#include <linux/ratelimit.h>
40#include <linux/kmsg_dump.h>
41#include <linux/syslog.h>
42#include <linux/cpu.h>
43#include <linux/notifier.h>
44#include <linux/rculist.h>
45#include <linux/poll.h>
46#include <linux/irq_work.h>
47#include <linux/utsname.h>
48
49#include <asm/uaccess.h>
50
51#define CREATE_TRACE_POINTS
52#include <trace/events/printk.h>
53
54#include "console_cmdline.h"
55#include "braille.h"
56
57/* printk's without a loglevel use this.. */
58#define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
59
60/* We show everything that is MORE important than this.. */
61#define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
62#define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
63
64int console_printk[4] = {
65 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
66 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
67 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
68 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
69};
70
71/*
72 * Low level drivers may need that to know if they can schedule in
73 * their unblank() callback or not. So let's export it.
74 */
75int oops_in_progress;
76EXPORT_SYMBOL(oops_in_progress);
77
78/*
79 * console_sem protects the console_drivers list, and also
80 * provides serialisation for access to the entire console
81 * driver system.
82 */
83static DEFINE_SEMAPHORE(console_sem);
84struct console *console_drivers;
85EXPORT_SYMBOL_GPL(console_drivers);
86
87#ifdef CONFIG_LOCKDEP
88static struct lockdep_map console_lock_dep_map = {
89 .name = "console_lock"
90};
91#endif
92
93/*
94 * This is used for debugging the mess that is the VT code by
95 * keeping track if we have the console semaphore held. It's
96 * definitely not the perfect debug tool (we don't know if _WE_
97 * hold it are racing, but it helps tracking those weird code
98 * path in the console code where we end up in places I want
99 * locked without the console sempahore held
100 */
101static int console_locked, console_suspended;
102
103/*
104 * If exclusive_console is non-NULL then only this console is to be printed to.
105 */
106static struct console *exclusive_console;
107
108/*
109 * Array of consoles built from command line options (console=)
110 */
111
112#define MAX_CMDLINECONSOLES 8
113
114static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
115
116static int selected_console = -1;
117static int preferred_console = -1;
118int console_set_on_cmdline;
119EXPORT_SYMBOL(console_set_on_cmdline);
120
121/* Flag: console code may call schedule() */
122static int console_may_schedule;
123
124/*
125 * The printk log buffer consists of a chain of concatenated variable
126 * length records. Every record starts with a record header, containing
127 * the overall length of the record.
128 *
129 * The heads to the first and last entry in the buffer, as well as the
130 * sequence numbers of these both entries are maintained when messages
131 * are stored..
132 *
133 * If the heads indicate available messages, the length in the header
134 * tells the start next message. A length == 0 for the next message
135 * indicates a wrap-around to the beginning of the buffer.
136 *
137 * Every record carries the monotonic timestamp in microseconds, as well as
138 * the standard userspace syslog level and syslog facility. The usual
139 * kernel messages use LOG_KERN; userspace-injected messages always carry
140 * a matching syslog facility, by default LOG_USER. The origin of every
141 * message can be reliably determined that way.
142 *
143 * The human readable log message directly follows the message header. The
144 * length of the message text is stored in the header, the stored message
145 * is not terminated.
146 *
147 * Optionally, a message can carry a dictionary of properties (key/value pairs),
148 * to provide userspace with a machine-readable message context.
149 *
150 * Examples for well-defined, commonly used property names are:
151 * DEVICE=b12:8 device identifier
152 * b12:8 block dev_t
153 * c127:3 char dev_t
154 * n8 netdev ifindex
155 * +sound:card0 subsystem:devname
156 * SUBSYSTEM=pci driver-core subsystem name
157 *
158 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
159 * follows directly after a '=' character. Every property is terminated by
160 * a '\0' character. The last property is not terminated.
161 *
162 * Example of a message structure:
163 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
164 * 0008 34 00 record is 52 bytes long
165 * 000a 0b 00 text is 11 bytes long
166 * 000c 1f 00 dictionary is 23 bytes long
167 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
168 * 0010 69 74 27 73 20 61 20 6c "it's a l"
169 * 69 6e 65 "ine"
170 * 001b 44 45 56 49 43 "DEVIC"
171 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
172 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
173 * 67 "g"
174 * 0032 00 00 00 padding to next message header
175 *
176 * The 'struct printk_log' buffer header must never be directly exported to
177 * userspace, it is a kernel-private implementation detail that might
178 * need to be changed in the future, when the requirements change.
179 *
180 * /dev/kmsg exports the structured data in the following line format:
181 * "level,sequnum,timestamp;<message text>\n"
182 *
183 * The optional key/value pairs are attached as continuation lines starting
184 * with a space character and terminated by a newline. All possible
185 * non-prinatable characters are escaped in the "\xff" notation.
186 *
187 * Users of the export format should ignore possible additional values
188 * separated by ',', and find the message after the ';' character.
189 */
190
191enum log_flags {
192 LOG_NOCONS = 1, /* already flushed, do not print to console */
193 LOG_NEWLINE = 2, /* text ended with a newline */
194 LOG_PREFIX = 4, /* text started with a prefix */
195 LOG_CONT = 8, /* text is a fragment of a continuation line */
196};
197
198struct printk_log {
199 u64 ts_nsec; /* timestamp in nanoseconds */
200 u16 len; /* length of entire record */
201 u16 text_len; /* length of text buffer */
202 u16 dict_len; /* length of dictionary buffer */
203 u8 facility; /* syslog facility */
204 u8 flags:5; /* internal record flags */
205 u8 level:3; /* syslog level */
206};
207
208/*
209 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
210 * used in interesting ways to provide interlocking in console_unlock();
211 */
212static DEFINE_RAW_SPINLOCK(logbuf_lock);
213
214#ifdef CONFIG_PRINTK
215DECLARE_WAIT_QUEUE_HEAD(log_wait);
216/* the next printk record to read by syslog(READ) or /proc/kmsg */
217static u64 syslog_seq;
218static u32 syslog_idx;
219static enum log_flags syslog_prev;
220static size_t syslog_partial;
221
222/* index and sequence number of the first record stored in the buffer */
223static u64 log_first_seq;
224static u32 log_first_idx;
225
226/* index and sequence number of the next record to store in the buffer */
227static u64 log_next_seq;
228static u32 log_next_idx;
229
230/* the next printk record to write to the console */
231static u64 console_seq;
232static u32 console_idx;
233static enum log_flags console_prev;
234
235/* the next printk record to read after the last 'clear' command */
236static u64 clear_seq;
237static u32 clear_idx;
238
239#define PREFIX_MAX 32
240#define LOG_LINE_MAX 1024 - PREFIX_MAX
241
242/* record buffer */
243#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
244#define LOG_ALIGN 4
245#else
246#define LOG_ALIGN __alignof__(struct printk_log)
247#endif
248#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
249static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
250static char *log_buf = __log_buf;
251static u32 log_buf_len = __LOG_BUF_LEN;
252
253/* cpu currently holding logbuf_lock */
254static volatile unsigned int logbuf_cpu = UINT_MAX;
255
256/* human readable text of the record */
257static char *log_text(const struct printk_log *msg)
258{
259 return (char *)msg + sizeof(struct printk_log);
260}
261
262/* optional key/value pair dictionary attached to the record */
263static char *log_dict(const struct printk_log *msg)
264{
265 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
266}
267
268/* get record by index; idx must point to valid msg */
269static struct printk_log *log_from_idx(u32 idx)
270{
271 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
272
273 /*
274 * A length == 0 record is the end of buffer marker. Wrap around and
275 * read the message at the start of the buffer.
276 */
277 if (!msg->len)
278 return (struct printk_log *)log_buf;
279 return msg;
280}
281
282/* get next record; idx must point to valid msg */
283static u32 log_next(u32 idx)
284{
285 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
286
287 /* length == 0 indicates the end of the buffer; wrap */
288 /*
289 * A length == 0 record is the end of buffer marker. Wrap around and
290 * read the message at the start of the buffer as *this* one, and
291 * return the one after that.
292 */
293 if (!msg->len) {
294 msg = (struct printk_log *)log_buf;
295 return msg->len;
296 }
297 return idx + msg->len;
298}
299
300/* insert record into the buffer, discard old ones, update heads */
301static void log_store(int facility, int level,
302 enum log_flags flags, u64 ts_nsec,
303 const char *dict, u16 dict_len,
304 const char *text, u16 text_len)
305{
306 struct printk_log *msg;
307 u32 size, pad_len;
308
309 /* number of '\0' padding bytes to next message */
310 size = sizeof(struct printk_log) + text_len + dict_len;
311 pad_len = (-size) & (LOG_ALIGN - 1);
312 size += pad_len;
313
314 while (log_first_seq < log_next_seq) {
315 u32 free;
316
317 if (log_next_idx > log_first_idx)
318 free = max(log_buf_len - log_next_idx, log_first_idx);
319 else
320 free = log_first_idx - log_next_idx;
321
322 if (free >= size + sizeof(struct printk_log))
323 break;
324
325 /* drop old messages until we have enough contiuous space */
326 log_first_idx = log_next(log_first_idx);
327 log_first_seq++;
328 }
329
330 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
331 /*
332 * This message + an additional empty header does not fit
333 * at the end of the buffer. Add an empty header with len == 0
334 * to signify a wrap around.
335 */
336 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
337 log_next_idx = 0;
338 }
339
340 /* fill message */
341 msg = (struct printk_log *)(log_buf + log_next_idx);
342 memcpy(log_text(msg), text, text_len);
343 msg->text_len = text_len;
344 memcpy(log_dict(msg), dict, dict_len);
345 msg->dict_len = dict_len;
346 msg->facility = facility;
347 msg->level = level & 7;
348 msg->flags = flags & 0x1f;
349 if (ts_nsec > 0)
350 msg->ts_nsec = ts_nsec;
351 else
352 msg->ts_nsec = local_clock();
353 memset(log_dict(msg) + dict_len, 0, pad_len);
354 msg->len = size;
355
356 /* insert message */
357 log_next_idx += msg->len;
358 log_next_seq++;
359}
360
361#ifdef CONFIG_SECURITY_DMESG_RESTRICT
362int dmesg_restrict = 1;
363#else
364int dmesg_restrict;
365#endif
366
367static int syslog_action_restricted(int type)
368{
369 if (dmesg_restrict)
370 return 1;
371 /*
372 * Unless restricted, we allow "read all" and "get buffer size"
373 * for everybody.
374 */
375 return type != SYSLOG_ACTION_READ_ALL &&
376 type != SYSLOG_ACTION_SIZE_BUFFER;
377}
378
379static int check_syslog_permissions(int type, bool from_file)
380{
381 /*
382 * If this is from /proc/kmsg and we've already opened it, then we've
383 * already done the capabilities checks at open time.
384 */
385 if (from_file && type != SYSLOG_ACTION_OPEN)
386 return 0;
387
388 if (syslog_action_restricted(type)) {
389 if (capable(CAP_SYSLOG))
390 return 0;
391 /*
392 * For historical reasons, accept CAP_SYS_ADMIN too, with
393 * a warning.
394 */
395 if (capable(CAP_SYS_ADMIN)) {
396 pr_warn_once("%s (%d): Attempt to access syslog with "
397 "CAP_SYS_ADMIN but no CAP_SYSLOG "
398 "(deprecated).\n",
399 current->comm, task_pid_nr(current));
400 return 0;
401 }
402 return -EPERM;
403 }
404 return security_syslog(type);
405}
406
407
408/* /dev/kmsg - userspace message inject/listen interface */
409struct devkmsg_user {
410 u64 seq;
411 u32 idx;
412 enum log_flags prev;
413 struct mutex lock;
414 char buf[8192];
415};
416
417static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
418 unsigned long count, loff_t pos)
419{
420 char *buf, *line;
421 int i;
422 int level = default_message_loglevel;
423 int facility = 1; /* LOG_USER */
424 size_t len = iov_length(iv, count);
425 ssize_t ret = len;
426
427 if (len > LOG_LINE_MAX)
428 return -EINVAL;
429 buf = kmalloc(len+1, GFP_KERNEL);
430 if (buf == NULL)
431 return -ENOMEM;
432
433 line = buf;
434 for (i = 0; i < count; i++) {
435 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
436 ret = -EFAULT;
437 goto out;
438 }
439 line += iv[i].iov_len;
440 }
441
442 /*
443 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
444 * the decimal value represents 32bit, the lower 3 bit are the log
445 * level, the rest are the log facility.
446 *
447 * If no prefix or no userspace facility is specified, we
448 * enforce LOG_USER, to be able to reliably distinguish
449 * kernel-generated messages from userspace-injected ones.
450 */
451 line = buf;
452 if (line[0] == '<') {
453 char *endp = NULL;
454
455 i = simple_strtoul(line+1, &endp, 10);
456 if (endp && endp[0] == '>') {
457 level = i & 7;
458 if (i >> 3)
459 facility = i >> 3;
460 endp++;
461 len -= endp - line;
462 line = endp;
463 }
464 }
465 line[len] = '\0';
466
467 printk_emit(facility, level, NULL, 0, "%s", line);
468out:
469 kfree(buf);
470 return ret;
471}
472
473static ssize_t devkmsg_read(struct file *file, char __user *buf,
474 size_t count, loff_t *ppos)
475{
476 struct devkmsg_user *user = file->private_data;
477 struct printk_log *msg;
478 u64 ts_usec;
479 size_t i;
480 char cont = '-';
481 size_t len;
482 ssize_t ret;
483
484 if (!user)
485 return -EBADF;
486
487 ret = mutex_lock_interruptible(&user->lock);
488 if (ret)
489 return ret;
490 raw_spin_lock_irq(&logbuf_lock);
491 while (user->seq == log_next_seq) {
492 if (file->f_flags & O_NONBLOCK) {
493 ret = -EAGAIN;
494 raw_spin_unlock_irq(&logbuf_lock);
495 goto out;
496 }
497
498 raw_spin_unlock_irq(&logbuf_lock);
499 ret = wait_event_interruptible(log_wait,
500 user->seq != log_next_seq);
501 if (ret)
502 goto out;
503 raw_spin_lock_irq(&logbuf_lock);
504 }
505
506 if (user->seq < log_first_seq) {
507 /* our last seen message is gone, return error and reset */
508 user->idx = log_first_idx;
509 user->seq = log_first_seq;
510 ret = -EPIPE;
511 raw_spin_unlock_irq(&logbuf_lock);
512 goto out;
513 }
514
515 msg = log_from_idx(user->idx);
516 ts_usec = msg->ts_nsec;
517 do_div(ts_usec, 1000);
518
519 /*
520 * If we couldn't merge continuation line fragments during the print,
521 * export the stored flags to allow an optional external merge of the
522 * records. Merging the records isn't always neccessarily correct, like
523 * when we hit a race during printing. In most cases though, it produces
524 * better readable output. 'c' in the record flags mark the first
525 * fragment of a line, '+' the following.
526 */
527 if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
528 cont = 'c';
529 else if ((msg->flags & LOG_CONT) ||
530 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
531 cont = '+';
532
533 len = sprintf(user->buf, "%u,%llu,%llu,%c;",
534 (msg->facility << 3) | msg->level,
535 user->seq, ts_usec, cont);
536 user->prev = msg->flags;
537
538 /* escape non-printable characters */
539 for (i = 0; i < msg->text_len; i++) {
540 unsigned char c = log_text(msg)[i];
541
542 if (c < ' ' || c >= 127 || c == '\\')
543 len += sprintf(user->buf + len, "\\x%02x", c);
544 else
545 user->buf[len++] = c;
546 }
547 user->buf[len++] = '\n';
548
549 if (msg->dict_len) {
550 bool line = true;
551
552 for (i = 0; i < msg->dict_len; i++) {
553 unsigned char c = log_dict(msg)[i];
554
555 if (line) {
556 user->buf[len++] = ' ';
557 line = false;
558 }
559
560 if (c == '\0') {
561 user->buf[len++] = '\n';
562 line = true;
563 continue;
564 }
565
566 if (c < ' ' || c >= 127 || c == '\\') {
567 len += sprintf(user->buf + len, "\\x%02x", c);
568 continue;
569 }
570
571 user->buf[len++] = c;
572 }
573 user->buf[len++] = '\n';
574 }
575
576 user->idx = log_next(user->idx);
577 user->seq++;
578 raw_spin_unlock_irq(&logbuf_lock);
579
580 if (len > count) {
581 ret = -EINVAL;
582 goto out;
583 }
584
585 if (copy_to_user(buf, user->buf, len)) {
586 ret = -EFAULT;
587 goto out;
588 }
589 ret = len;
590out:
591 mutex_unlock(&user->lock);
592 return ret;
593}
594
595static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
596{
597 struct devkmsg_user *user = file->private_data;
598 loff_t ret = 0;
599
600 if (!user)
601 return -EBADF;
602 if (offset)
603 return -ESPIPE;
604
605 raw_spin_lock_irq(&logbuf_lock);
606 switch (whence) {
607 case SEEK_SET:
608 /* the first record */
609 user->idx = log_first_idx;
610 user->seq = log_first_seq;
611 break;
612 case SEEK_DATA:
613 /*
614 * The first record after the last SYSLOG_ACTION_CLEAR,
615 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
616 * changes no global state, and does not clear anything.
617 */
618 user->idx = clear_idx;
619 user->seq = clear_seq;
620 break;
621 case SEEK_END:
622 /* after the last record */
623 user->idx = log_next_idx;
624 user->seq = log_next_seq;
625 break;
626 default:
627 ret = -EINVAL;
628 }
629 raw_spin_unlock_irq(&logbuf_lock);
630 return ret;
631}
632
633static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
634{
635 struct devkmsg_user *user = file->private_data;
636 int ret = 0;
637
638 if (!user)
639 return POLLERR|POLLNVAL;
640
641 poll_wait(file, &log_wait, wait);
642
643 raw_spin_lock_irq(&logbuf_lock);
644 if (user->seq < log_next_seq) {
645 /* return error when data has vanished underneath us */
646 if (user->seq < log_first_seq)
647 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
648 else
649 ret = POLLIN|POLLRDNORM;
650 }
651 raw_spin_unlock_irq(&logbuf_lock);
652
653 return ret;
654}
655
656static int devkmsg_open(struct inode *inode, struct file *file)
657{
658 struct devkmsg_user *user;
659 int err;
660
661 /* write-only does not need any file context */
662 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
663 return 0;
664
665 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
666 SYSLOG_FROM_READER);
667 if (err)
668 return err;
669
670 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
671 if (!user)
672 return -ENOMEM;
673
674 mutex_init(&user->lock);
675
676 raw_spin_lock_irq(&logbuf_lock);
677 user->idx = log_first_idx;
678 user->seq = log_first_seq;
679 raw_spin_unlock_irq(&logbuf_lock);
680
681 file->private_data = user;
682 return 0;
683}
684
685static int devkmsg_release(struct inode *inode, struct file *file)
686{
687 struct devkmsg_user *user = file->private_data;
688
689 if (!user)
690 return 0;
691
692 mutex_destroy(&user->lock);
693 kfree(user);
694 return 0;
695}
696
697const struct file_operations kmsg_fops = {
698 .open = devkmsg_open,
699 .read = devkmsg_read,
700 .aio_write = devkmsg_writev,
701 .llseek = devkmsg_llseek,
702 .poll = devkmsg_poll,
703 .release = devkmsg_release,
704};
705
706#ifdef CONFIG_KEXEC
707/*
708 * This appends the listed symbols to /proc/vmcore
709 *
710 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
711 * obtain access to symbols that are otherwise very difficult to locate. These
712 * symbols are specifically used so that utilities can access and extract the
713 * dmesg log from a vmcore file after a crash.
714 */
715void log_buf_kexec_setup(void)
716{
717 VMCOREINFO_SYMBOL(log_buf);
718 VMCOREINFO_SYMBOL(log_buf_len);
719 VMCOREINFO_SYMBOL(log_first_idx);
720 VMCOREINFO_SYMBOL(log_next_idx);
721 /*
722 * Export struct printk_log size and field offsets. User space tools can
723 * parse it and detect any changes to structure down the line.
724 */
725 VMCOREINFO_STRUCT_SIZE(printk_log);
726 VMCOREINFO_OFFSET(printk_log, ts_nsec);
727 VMCOREINFO_OFFSET(printk_log, len);
728 VMCOREINFO_OFFSET(printk_log, text_len);
729 VMCOREINFO_OFFSET(printk_log, dict_len);
730}
731#endif
732
733/* requested log_buf_len from kernel cmdline */
734static unsigned long __initdata new_log_buf_len;
735
736/* save requested log_buf_len since it's too early to process it */
737static int __init log_buf_len_setup(char *str)
738{
739 unsigned size = memparse(str, &str);
740
741 if (size)
742 size = roundup_pow_of_two(size);
743 if (size > log_buf_len)
744 new_log_buf_len = size;
745
746 return 0;
747}
748early_param("log_buf_len", log_buf_len_setup);
749
750void __init setup_log_buf(int early)
751{
752 unsigned long flags;
753 char *new_log_buf;
754 int free;
755
756 if (!new_log_buf_len)
757 return;
758
759 if (early) {
760 new_log_buf =
761 memblock_virt_alloc(new_log_buf_len, PAGE_SIZE);
762 } else {
763 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len, 0);
764 }
765
766 if (unlikely(!new_log_buf)) {
767 pr_err("log_buf_len: %ld bytes not available\n",
768 new_log_buf_len);
769 return;
770 }
771
772 raw_spin_lock_irqsave(&logbuf_lock, flags);
773 log_buf_len = new_log_buf_len;
774 log_buf = new_log_buf;
775 new_log_buf_len = 0;
776 free = __LOG_BUF_LEN - log_next_idx;
777 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
778 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
779
780 pr_info("log_buf_len: %d\n", log_buf_len);
781 pr_info("early log buf free: %d(%d%%)\n",
782 free, (free * 100) / __LOG_BUF_LEN);
783}
784
785static bool __read_mostly ignore_loglevel;
786
787static int __init ignore_loglevel_setup(char *str)
788{
789 ignore_loglevel = 1;
790 pr_info("debug: ignoring loglevel setting.\n");
791
792 return 0;
793}
794
795early_param("ignore_loglevel", ignore_loglevel_setup);
796module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
797MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
798 "print all kernel messages to the console.");
799
800#ifdef CONFIG_BOOT_PRINTK_DELAY
801
802static int boot_delay; /* msecs delay after each printk during bootup */
803static unsigned long long loops_per_msec; /* based on boot_delay */
804
805static int __init boot_delay_setup(char *str)
806{
807 unsigned long lpj;
808
809 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
810 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
811
812 get_option(&str, &boot_delay);
813 if (boot_delay > 10 * 1000)
814 boot_delay = 0;
815
816 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
817 "HZ: %d, loops_per_msec: %llu\n",
818 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
819 return 0;
820}
821early_param("boot_delay", boot_delay_setup);
822
823static void boot_delay_msec(int level)
824{
825 unsigned long long k;
826 unsigned long timeout;
827
828 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
829 || (level >= console_loglevel && !ignore_loglevel)) {
830 return;
831 }
832
833 k = (unsigned long long)loops_per_msec * boot_delay;
834
835 timeout = jiffies + msecs_to_jiffies(boot_delay);
836 while (k) {
837 k--;
838 cpu_relax();
839 /*
840 * use (volatile) jiffies to prevent
841 * compiler reduction; loop termination via jiffies
842 * is secondary and may or may not happen.
843 */
844 if (time_after(jiffies, timeout))
845 break;
846 touch_nmi_watchdog();
847 }
848}
849#else
850static inline void boot_delay_msec(int level)
851{
852}
853#endif
854
855#if defined(CONFIG_PRINTK_TIME)
856static bool printk_time = 1;
857#else
858static bool printk_time;
859#endif
860module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
861
862static size_t print_time(u64 ts, char *buf)
863{
864 unsigned long rem_nsec;
865
866 if (!printk_time)
867 return 0;
868
869 rem_nsec = do_div(ts, 1000000000);
870
871 if (!buf)
872 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
873
874 return sprintf(buf, "[%5lu.%06lu] ",
875 (unsigned long)ts, rem_nsec / 1000);
876}
877
878static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
879{
880 size_t len = 0;
881 unsigned int prefix = (msg->facility << 3) | msg->level;
882
883 if (syslog) {
884 if (buf) {
885 len += sprintf(buf, "<%u>", prefix);
886 } else {
887 len += 3;
888 if (prefix > 999)
889 len += 3;
890 else if (prefix > 99)
891 len += 2;
892 else if (prefix > 9)
893 len++;
894 }
895 }
896
897 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
898 return len;
899}
900
901static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
902 bool syslog, char *buf, size_t size)
903{
904 const char *text = log_text(msg);
905 size_t text_size = msg->text_len;
906 bool prefix = true;
907 bool newline = true;
908 size_t len = 0;
909
910 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
911 prefix = false;
912
913 if (msg->flags & LOG_CONT) {
914 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
915 prefix = false;
916
917 if (!(msg->flags & LOG_NEWLINE))
918 newline = false;
919 }
920
921 do {
922 const char *next = memchr(text, '\n', text_size);
923 size_t text_len;
924
925 if (next) {
926 text_len = next - text;
927 next++;
928 text_size -= next - text;
929 } else {
930 text_len = text_size;
931 }
932
933 if (buf) {
934 if (print_prefix(msg, syslog, NULL) +
935 text_len + 1 >= size - len)
936 break;
937
938 if (prefix)
939 len += print_prefix(msg, syslog, buf + len);
940 memcpy(buf + len, text, text_len);
941 len += text_len;
942 if (next || newline)
943 buf[len++] = '\n';
944 } else {
945 /* SYSLOG_ACTION_* buffer size only calculation */
946 if (prefix)
947 len += print_prefix(msg, syslog, NULL);
948 len += text_len;
949 if (next || newline)
950 len++;
951 }
952
953 prefix = true;
954 text = next;
955 } while (text);
956
957 return len;
958}
959
960static int syslog_print(char __user *buf, int size)
961{
962 char *text;
963 struct printk_log *msg;
964 int len = 0;
965
966 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
967 if (!text)
968 return -ENOMEM;
969
970 while (size > 0) {
971 size_t n;
972 size_t skip;
973
974 raw_spin_lock_irq(&logbuf_lock);
975 if (syslog_seq < log_first_seq) {
976 /* messages are gone, move to first one */
977 syslog_seq = log_first_seq;
978 syslog_idx = log_first_idx;
979 syslog_prev = 0;
980 syslog_partial = 0;
981 }
982 if (syslog_seq == log_next_seq) {
983 raw_spin_unlock_irq(&logbuf_lock);
984 break;
985 }
986
987 skip = syslog_partial;
988 msg = log_from_idx(syslog_idx);
989 n = msg_print_text(msg, syslog_prev, true, text,
990 LOG_LINE_MAX + PREFIX_MAX);
991 if (n - syslog_partial <= size) {
992 /* message fits into buffer, move forward */
993 syslog_idx = log_next(syslog_idx);
994 syslog_seq++;
995 syslog_prev = msg->flags;
996 n -= syslog_partial;
997 syslog_partial = 0;
998 } else if (!len){
999 /* partial read(), remember position */
1000 n = size;
1001 syslog_partial += n;
1002 } else
1003 n = 0;
1004 raw_spin_unlock_irq(&logbuf_lock);
1005
1006 if (!n)
1007 break;
1008
1009 if (copy_to_user(buf, text + skip, n)) {
1010 if (!len)
1011 len = -EFAULT;
1012 break;
1013 }
1014
1015 len += n;
1016 size -= n;
1017 buf += n;
1018 }
1019
1020 kfree(text);
1021 return len;
1022}
1023
1024static int syslog_print_all(char __user *buf, int size, bool clear)
1025{
1026 char *text;
1027 int len = 0;
1028
1029 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1030 if (!text)
1031 return -ENOMEM;
1032
1033 raw_spin_lock_irq(&logbuf_lock);
1034 if (buf) {
1035 u64 next_seq;
1036 u64 seq;
1037 u32 idx;
1038 enum log_flags prev;
1039
1040 if (clear_seq < log_first_seq) {
1041 /* messages are gone, move to first available one */
1042 clear_seq = log_first_seq;
1043 clear_idx = log_first_idx;
1044 }
1045
1046 /*
1047 * Find first record that fits, including all following records,
1048 * into the user-provided buffer for this dump.
1049 */
1050 seq = clear_seq;
1051 idx = clear_idx;
1052 prev = 0;
1053 while (seq < log_next_seq) {
1054 struct printk_log *msg = log_from_idx(idx);
1055
1056 len += msg_print_text(msg, prev, true, NULL, 0);
1057 prev = msg->flags;
1058 idx = log_next(idx);
1059 seq++;
1060 }
1061
1062 /* move first record forward until length fits into the buffer */
1063 seq = clear_seq;
1064 idx = clear_idx;
1065 prev = 0;
1066 while (len > size && seq < log_next_seq) {
1067 struct printk_log *msg = log_from_idx(idx);
1068
1069 len -= msg_print_text(msg, prev, true, NULL, 0);
1070 prev = msg->flags;
1071 idx = log_next(idx);
1072 seq++;
1073 }
1074
1075 /* last message fitting into this dump */
1076 next_seq = log_next_seq;
1077
1078 len = 0;
1079 while (len >= 0 && seq < next_seq) {
1080 struct printk_log *msg = log_from_idx(idx);
1081 int textlen;
1082
1083 textlen = msg_print_text(msg, prev, true, text,
1084 LOG_LINE_MAX + PREFIX_MAX);
1085 if (textlen < 0) {
1086 len = textlen;
1087 break;
1088 }
1089 idx = log_next(idx);
1090 seq++;
1091 prev = msg->flags;
1092
1093 raw_spin_unlock_irq(&logbuf_lock);
1094 if (copy_to_user(buf + len, text, textlen))
1095 len = -EFAULT;
1096 else
1097 len += textlen;
1098 raw_spin_lock_irq(&logbuf_lock);
1099
1100 if (seq < log_first_seq) {
1101 /* messages are gone, move to next one */
1102 seq = log_first_seq;
1103 idx = log_first_idx;
1104 prev = 0;
1105 }
1106 }
1107 }
1108
1109 if (clear) {
1110 clear_seq = log_next_seq;
1111 clear_idx = log_next_idx;
1112 }
1113 raw_spin_unlock_irq(&logbuf_lock);
1114
1115 kfree(text);
1116 return len;
1117}
1118
1119int do_syslog(int type, char __user *buf, int len, bool from_file)
1120{
1121 bool clear = false;
1122 static int saved_console_loglevel = -1;
1123 int error;
1124
1125 error = check_syslog_permissions(type, from_file);
1126 if (error)
1127 goto out;
1128
1129 error = security_syslog(type);
1130 if (error)
1131 return error;
1132
1133 switch (type) {
1134 case SYSLOG_ACTION_CLOSE: /* Close log */
1135 break;
1136 case SYSLOG_ACTION_OPEN: /* Open log */
1137 break;
1138 case SYSLOG_ACTION_READ: /* Read from log */
1139 error = -EINVAL;
1140 if (!buf || len < 0)
1141 goto out;
1142 error = 0;
1143 if (!len)
1144 goto out;
1145 if (!access_ok(VERIFY_WRITE, buf, len)) {
1146 error = -EFAULT;
1147 goto out;
1148 }
1149 error = wait_event_interruptible(log_wait,
1150 syslog_seq != log_next_seq);
1151 if (error)
1152 goto out;
1153 error = syslog_print(buf, len);
1154 break;
1155 /* Read/clear last kernel messages */
1156 case SYSLOG_ACTION_READ_CLEAR:
1157 clear = true;
1158 /* FALL THRU */
1159 /* Read last kernel messages */
1160 case SYSLOG_ACTION_READ_ALL:
1161 error = -EINVAL;
1162 if (!buf || len < 0)
1163 goto out;
1164 error = 0;
1165 if (!len)
1166 goto out;
1167 if (!access_ok(VERIFY_WRITE, buf, len)) {
1168 error = -EFAULT;
1169 goto out;
1170 }
1171 error = syslog_print_all(buf, len, clear);
1172 break;
1173 /* Clear ring buffer */
1174 case SYSLOG_ACTION_CLEAR:
1175 syslog_print_all(NULL, 0, true);
1176 break;
1177 /* Disable logging to console */
1178 case SYSLOG_ACTION_CONSOLE_OFF:
1179 if (saved_console_loglevel == -1)
1180 saved_console_loglevel = console_loglevel;
1181 console_loglevel = minimum_console_loglevel;
1182 break;
1183 /* Enable logging to console */
1184 case SYSLOG_ACTION_CONSOLE_ON:
1185 if (saved_console_loglevel != -1) {
1186 console_loglevel = saved_console_loglevel;
1187 saved_console_loglevel = -1;
1188 }
1189 break;
1190 /* Set level of messages printed to console */
1191 case SYSLOG_ACTION_CONSOLE_LEVEL:
1192 error = -EINVAL;
1193 if (len < 1 || len > 8)
1194 goto out;
1195 if (len < minimum_console_loglevel)
1196 len = minimum_console_loglevel;
1197 console_loglevel = len;
1198 /* Implicitly re-enable logging to console */
1199 saved_console_loglevel = -1;
1200 error = 0;
1201 break;
1202 /* Number of chars in the log buffer */
1203 case SYSLOG_ACTION_SIZE_UNREAD:
1204 raw_spin_lock_irq(&logbuf_lock);
1205 if (syslog_seq < log_first_seq) {
1206 /* messages are gone, move to first one */
1207 syslog_seq = log_first_seq;
1208 syslog_idx = log_first_idx;
1209 syslog_prev = 0;
1210 syslog_partial = 0;
1211 }
1212 if (from_file) {
1213 /*
1214 * Short-cut for poll(/"proc/kmsg") which simply checks
1215 * for pending data, not the size; return the count of
1216 * records, not the length.
1217 */
1218 error = log_next_idx - syslog_idx;
1219 } else {
1220 u64 seq = syslog_seq;
1221 u32 idx = syslog_idx;
1222 enum log_flags prev = syslog_prev;
1223
1224 error = 0;
1225 while (seq < log_next_seq) {
1226 struct printk_log *msg = log_from_idx(idx);
1227
1228 error += msg_print_text(msg, prev, true, NULL, 0);
1229 idx = log_next(idx);
1230 seq++;
1231 prev = msg->flags;
1232 }
1233 error -= syslog_partial;
1234 }
1235 raw_spin_unlock_irq(&logbuf_lock);
1236 break;
1237 /* Size of the log buffer */
1238 case SYSLOG_ACTION_SIZE_BUFFER:
1239 error = log_buf_len;
1240 break;
1241 default:
1242 error = -EINVAL;
1243 break;
1244 }
1245out:
1246 return error;
1247}
1248
1249SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1250{
1251 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1252}
1253
1254/*
1255 * Call the console drivers, asking them to write out
1256 * log_buf[start] to log_buf[end - 1].
1257 * The console_lock must be held.
1258 */
1259static void call_console_drivers(int level, const char *text, size_t len)
1260{
1261 struct console *con;
1262
1263 trace_console(text, len);
1264
1265 if (level >= console_loglevel && !ignore_loglevel)
1266 return;
1267 if (!console_drivers)
1268 return;
1269
1270 for_each_console(con) {
1271 if (exclusive_console && con != exclusive_console)
1272 continue;
1273 if (!(con->flags & CON_ENABLED))
1274 continue;
1275 if (!con->write)
1276 continue;
1277 if (!cpu_online(smp_processor_id()) &&
1278 !(con->flags & CON_ANYTIME))
1279 continue;
1280 con->write(con, text, len);
1281 }
1282}
1283
1284/*
1285 * Zap console related locks when oopsing. Only zap at most once
1286 * every 10 seconds, to leave time for slow consoles to print a
1287 * full oops.
1288 */
1289static void zap_locks(void)
1290{
1291 static unsigned long oops_timestamp;
1292
1293 if (time_after_eq(jiffies, oops_timestamp) &&
1294 !time_after(jiffies, oops_timestamp + 30 * HZ))
1295 return;
1296
1297 oops_timestamp = jiffies;
1298
1299 debug_locks_off();
1300 /* If a crash is occurring, make sure we can't deadlock */
1301 raw_spin_lock_init(&logbuf_lock);
1302 /* And make sure that we print immediately */
1303 sema_init(&console_sem, 1);
1304}
1305
1306/* Check if we have any console registered that can be called early in boot. */
1307static int have_callable_console(void)
1308{
1309 struct console *con;
1310
1311 for_each_console(con)
1312 if (con->flags & CON_ANYTIME)
1313 return 1;
1314
1315 return 0;
1316}
1317
1318/*
1319 * Can we actually use the console at this time on this cpu?
1320 *
1321 * Console drivers may assume that per-cpu resources have
1322 * been allocated. So unless they're explicitly marked as
1323 * being able to cope (CON_ANYTIME) don't call them until
1324 * this CPU is officially up.
1325 */
1326static inline int can_use_console(unsigned int cpu)
1327{
1328 return cpu_online(cpu) || have_callable_console();
1329}
1330
1331/*
1332 * Try to get console ownership to actually show the kernel
1333 * messages from a 'printk'. Return true (and with the
1334 * console_lock held, and 'console_locked' set) if it
1335 * is successful, false otherwise.
1336 *
1337 * This gets called with the 'logbuf_lock' spinlock held and
1338 * interrupts disabled. It should return with 'lockbuf_lock'
1339 * released but interrupts still disabled.
1340 */
1341static int console_trylock_for_printk(unsigned int cpu)
1342 __releases(&logbuf_lock)
1343{
1344 int retval = 0, wake = 0;
1345
1346 if (console_trylock()) {
1347 retval = 1;
1348
1349 /*
1350 * If we can't use the console, we need to release
1351 * the console semaphore by hand to avoid flushing
1352 * the buffer. We need to hold the console semaphore
1353 * in order to do this test safely.
1354 */
1355 if (!can_use_console(cpu)) {
1356 console_locked = 0;
1357 wake = 1;
1358 retval = 0;
1359 }
1360 }
1361 logbuf_cpu = UINT_MAX;
1362 raw_spin_unlock(&logbuf_lock);
1363 if (wake)
1364 up(&console_sem);
1365 return retval;
1366}
1367
1368int printk_delay_msec __read_mostly;
1369
1370static inline void printk_delay(void)
1371{
1372 if (unlikely(printk_delay_msec)) {
1373 int m = printk_delay_msec;
1374
1375 while (m--) {
1376 mdelay(1);
1377 touch_nmi_watchdog();
1378 }
1379 }
1380}
1381
1382/*
1383 * Continuation lines are buffered, and not committed to the record buffer
1384 * until the line is complete, or a race forces it. The line fragments
1385 * though, are printed immediately to the consoles to ensure everything has
1386 * reached the console in case of a kernel crash.
1387 */
1388static struct cont {
1389 char buf[LOG_LINE_MAX];
1390 size_t len; /* length == 0 means unused buffer */
1391 size_t cons; /* bytes written to console */
1392 struct task_struct *owner; /* task of first print*/
1393 u64 ts_nsec; /* time of first print */
1394 u8 level; /* log level of first message */
1395 u8 facility; /* log level of first message */
1396 enum log_flags flags; /* prefix, newline flags */
1397 bool flushed:1; /* buffer sealed and committed */
1398} cont;
1399
1400static void cont_flush(enum log_flags flags)
1401{
1402 if (cont.flushed)
1403 return;
1404 if (cont.len == 0)
1405 return;
1406
1407 if (cont.cons) {
1408 /*
1409 * If a fragment of this line was directly flushed to the
1410 * console; wait for the console to pick up the rest of the
1411 * line. LOG_NOCONS suppresses a duplicated output.
1412 */
1413 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1414 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1415 cont.flags = flags;
1416 cont.flushed = true;
1417 } else {
1418 /*
1419 * If no fragment of this line ever reached the console,
1420 * just submit it to the store and free the buffer.
1421 */
1422 log_store(cont.facility, cont.level, flags, 0,
1423 NULL, 0, cont.buf, cont.len);
1424 cont.len = 0;
1425 }
1426}
1427
1428static bool cont_add(int facility, int level, const char *text, size_t len)
1429{
1430 if (cont.len && cont.flushed)
1431 return false;
1432
1433 if (cont.len + len > sizeof(cont.buf)) {
1434 /* the line gets too long, split it up in separate records */
1435 cont_flush(LOG_CONT);
1436 return false;
1437 }
1438
1439 if (!cont.len) {
1440 cont.facility = facility;
1441 cont.level = level;
1442 cont.owner = current;
1443 cont.ts_nsec = local_clock();
1444 cont.flags = 0;
1445 cont.cons = 0;
1446 cont.flushed = false;
1447 }
1448
1449 memcpy(cont.buf + cont.len, text, len);
1450 cont.len += len;
1451
1452 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1453 cont_flush(LOG_CONT);
1454
1455 return true;
1456}
1457
1458static size_t cont_print_text(char *text, size_t size)
1459{
1460 size_t textlen = 0;
1461 size_t len;
1462
1463 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1464 textlen += print_time(cont.ts_nsec, text);
1465 size -= textlen;
1466 }
1467
1468 len = cont.len - cont.cons;
1469 if (len > 0) {
1470 if (len+1 > size)
1471 len = size-1;
1472 memcpy(text + textlen, cont.buf + cont.cons, len);
1473 textlen += len;
1474 cont.cons = cont.len;
1475 }
1476
1477 if (cont.flushed) {
1478 if (cont.flags & LOG_NEWLINE)
1479 text[textlen++] = '\n';
1480 /* got everything, release buffer */
1481 cont.len = 0;
1482 }
1483 return textlen;
1484}
1485
1486asmlinkage int vprintk_emit(int facility, int level,
1487 const char *dict, size_t dictlen,
1488 const char *fmt, va_list args)
1489{
1490 static int recursion_bug;
1491 static char textbuf[LOG_LINE_MAX];
1492 char *text = textbuf;
1493 size_t text_len;
1494 enum log_flags lflags = 0;
1495 unsigned long flags;
1496 int this_cpu;
1497 int printed_len = 0;
1498
1499 boot_delay_msec(level);
1500 printk_delay();
1501
1502 /* This stops the holder of console_sem just where we want him */
1503 local_irq_save(flags);
1504 this_cpu = smp_processor_id();
1505
1506 /*
1507 * Ouch, printk recursed into itself!
1508 */
1509 if (unlikely(logbuf_cpu == this_cpu)) {
1510 /*
1511 * If a crash is occurring during printk() on this CPU,
1512 * then try to get the crash message out but make sure
1513 * we can't deadlock. Otherwise just return to avoid the
1514 * recursion and return - but flag the recursion so that
1515 * it can be printed at the next appropriate moment:
1516 */
1517 if (!oops_in_progress && !lockdep_recursing(current)) {
1518 recursion_bug = 1;
1519 goto out_restore_irqs;
1520 }
1521 zap_locks();
1522 }
1523
1524 lockdep_off();
1525 raw_spin_lock(&logbuf_lock);
1526 logbuf_cpu = this_cpu;
1527
1528 if (recursion_bug) {
1529 static const char recursion_msg[] =
1530 "BUG: recent printk recursion!";
1531
1532 recursion_bug = 0;
1533 printed_len += strlen(recursion_msg);
1534 /* emit KERN_CRIT message */
1535 log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1536 NULL, 0, recursion_msg, printed_len);
1537 }
1538
1539 /*
1540 * The printf needs to come first; we need the syslog
1541 * prefix which might be passed-in as a parameter.
1542 */
1543 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1544
1545 /* mark and strip a trailing newline */
1546 if (text_len && text[text_len-1] == '\n') {
1547 text_len--;
1548 lflags |= LOG_NEWLINE;
1549 }
1550
1551 /* strip kernel syslog prefix and extract log level or control flags */
1552 if (facility == 0) {
1553 int kern_level = printk_get_level(text);
1554
1555 if (kern_level) {
1556 const char *end_of_header = printk_skip_level(text);
1557 switch (kern_level) {
1558 case '0' ... '7':
1559 if (level == -1)
1560 level = kern_level - '0';
1561 case 'd': /* KERN_DEFAULT */
1562 lflags |= LOG_PREFIX;
1563 }
1564 /*
1565 * No need to check length here because vscnprintf
1566 * put '\0' at the end of the string. Only valid and
1567 * newly printed level is detected.
1568 */
1569 text_len -= end_of_header - text;
1570 text = (char *)end_of_header;
1571 }
1572 }
1573
1574 if (level == -1)
1575 level = default_message_loglevel;
1576
1577 if (dict)
1578 lflags |= LOG_PREFIX|LOG_NEWLINE;
1579
1580 if (!(lflags & LOG_NEWLINE)) {
1581 /*
1582 * Flush the conflicting buffer. An earlier newline was missing,
1583 * or another task also prints continuation lines.
1584 */
1585 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1586 cont_flush(LOG_NEWLINE);
1587
1588 /* buffer line if possible, otherwise store it right away */
1589 if (!cont_add(facility, level, text, text_len))
1590 log_store(facility, level, lflags | LOG_CONT, 0,
1591 dict, dictlen, text, text_len);
1592 } else {
1593 bool stored = false;
1594
1595 /*
1596 * If an earlier newline was missing and it was the same task,
1597 * either merge it with the current buffer and flush, or if
1598 * there was a race with interrupts (prefix == true) then just
1599 * flush it out and store this line separately.
1600 * If the preceding printk was from a different task and missed
1601 * a newline, flush and append the newline.
1602 */
1603 if (cont.len) {
1604 if (cont.owner == current && !(lflags & LOG_PREFIX))
1605 stored = cont_add(facility, level, text,
1606 text_len);
1607 cont_flush(LOG_NEWLINE);
1608 }
1609
1610 if (!stored)
1611 log_store(facility, level, lflags, 0,
1612 dict, dictlen, text, text_len);
1613 }
1614 printed_len += text_len;
1615
1616 /*
1617 * Try to acquire and then immediately release the console semaphore.
1618 * The release will print out buffers and wake up /dev/kmsg and syslog()
1619 * users.
1620 *
1621 * The console_trylock_for_printk() function will release 'logbuf_lock'
1622 * regardless of whether it actually gets the console semaphore or not.
1623 */
1624 if (console_trylock_for_printk(this_cpu))
1625 console_unlock();
1626
1627 lockdep_on();
1628out_restore_irqs:
1629 local_irq_restore(flags);
1630
1631 return printed_len;
1632}
1633EXPORT_SYMBOL(vprintk_emit);
1634
1635asmlinkage int vprintk(const char *fmt, va_list args)
1636{
1637 return vprintk_emit(0, -1, NULL, 0, fmt, args);
1638}
1639EXPORT_SYMBOL(vprintk);
1640
1641asmlinkage int printk_emit(int facility, int level,
1642 const char *dict, size_t dictlen,
1643 const char *fmt, ...)
1644{
1645 va_list args;
1646 int r;
1647
1648 va_start(args, fmt);
1649 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1650 va_end(args);
1651
1652 return r;
1653}
1654EXPORT_SYMBOL(printk_emit);
1655
1656/**
1657 * printk - print a kernel message
1658 * @fmt: format string
1659 *
1660 * This is printk(). It can be called from any context. We want it to work.
1661 *
1662 * We try to grab the console_lock. If we succeed, it's easy - we log the
1663 * output and call the console drivers. If we fail to get the semaphore, we
1664 * place the output into the log buffer and return. The current holder of
1665 * the console_sem will notice the new output in console_unlock(); and will
1666 * send it to the consoles before releasing the lock.
1667 *
1668 * One effect of this deferred printing is that code which calls printk() and
1669 * then changes console_loglevel may break. This is because console_loglevel
1670 * is inspected when the actual printing occurs.
1671 *
1672 * See also:
1673 * printf(3)
1674 *
1675 * See the vsnprintf() documentation for format string extensions over C99.
1676 */
1677asmlinkage __visible int printk(const char *fmt, ...)
1678{
1679 va_list args;
1680 int r;
1681
1682#ifdef CONFIG_KGDB_KDB
1683 if (unlikely(kdb_trap_printk)) {
1684 va_start(args, fmt);
1685 r = vkdb_printf(fmt, args);
1686 va_end(args);
1687 return r;
1688 }
1689#endif
1690 va_start(args, fmt);
1691 r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1692 va_end(args);
1693
1694 return r;
1695}
1696EXPORT_SYMBOL(printk);
1697
1698#else /* CONFIG_PRINTK */
1699
1700#define LOG_LINE_MAX 0
1701#define PREFIX_MAX 0
1702#define LOG_LINE_MAX 0
1703static u64 syslog_seq;
1704static u32 syslog_idx;
1705static u64 console_seq;
1706static u32 console_idx;
1707static enum log_flags syslog_prev;
1708static u64 log_first_seq;
1709static u32 log_first_idx;
1710static u64 log_next_seq;
1711static enum log_flags console_prev;
1712static struct cont {
1713 size_t len;
1714 size_t cons;
1715 u8 level;
1716 bool flushed:1;
1717} cont;
1718static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1719static u32 log_next(u32 idx) { return 0; }
1720static void call_console_drivers(int level, const char *text, size_t len) {}
1721static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1722 bool syslog, char *buf, size_t size) { return 0; }
1723static size_t cont_print_text(char *text, size_t size) { return 0; }
1724
1725#endif /* CONFIG_PRINTK */
1726
1727#ifdef CONFIG_EARLY_PRINTK
1728struct console *early_console;
1729
1730void early_vprintk(const char *fmt, va_list ap)
1731{
1732 if (early_console) {
1733 char buf[512];
1734 int n = vscnprintf(buf, sizeof(buf), fmt, ap);
1735
1736 early_console->write(early_console, buf, n);
1737 }
1738}
1739
1740asmlinkage __visible void early_printk(const char *fmt, ...)
1741{
1742 va_list ap;
1743
1744 va_start(ap, fmt);
1745 early_vprintk(fmt, ap);
1746 va_end(ap);
1747}
1748#endif
1749
1750static int __add_preferred_console(char *name, int idx, char *options,
1751 char *brl_options)
1752{
1753 struct console_cmdline *c;
1754 int i;
1755
1756 /*
1757 * See if this tty is not yet registered, and
1758 * if we have a slot free.
1759 */
1760 for (i = 0, c = console_cmdline;
1761 i < MAX_CMDLINECONSOLES && c->name[0];
1762 i++, c++) {
1763 if (strcmp(c->name, name) == 0 && c->index == idx) {
1764 if (!brl_options)
1765 selected_console = i;
1766 return 0;
1767 }
1768 }
1769 if (i == MAX_CMDLINECONSOLES)
1770 return -E2BIG;
1771 if (!brl_options)
1772 selected_console = i;
1773 strlcpy(c->name, name, sizeof(c->name));
1774 c->options = options;
1775 braille_set_options(c, brl_options);
1776
1777 c->index = idx;
1778 return 0;
1779}
1780/*
1781 * Set up a list of consoles. Called from init/main.c
1782 */
1783static int __init console_setup(char *str)
1784{
1785 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1786 char *s, *options, *brl_options = NULL;
1787 int idx;
1788
1789 if (_braille_console_setup(&str, &brl_options))
1790 return 1;
1791
1792 /*
1793 * Decode str into name, index, options.
1794 */
1795 if (str[0] >= '0' && str[0] <= '9') {
1796 strcpy(buf, "ttyS");
1797 strncpy(buf + 4, str, sizeof(buf) - 5);
1798 } else {
1799 strncpy(buf, str, sizeof(buf) - 1);
1800 }
1801 buf[sizeof(buf) - 1] = 0;
1802 if ((options = strchr(str, ',')) != NULL)
1803 *(options++) = 0;
1804#ifdef __sparc__
1805 if (!strcmp(str, "ttya"))
1806 strcpy(buf, "ttyS0");
1807 if (!strcmp(str, "ttyb"))
1808 strcpy(buf, "ttyS1");
1809#endif
1810 for (s = buf; *s; s++)
1811 if ((*s >= '0' && *s <= '9') || *s == ',')
1812 break;
1813 idx = simple_strtoul(s, NULL, 10);
1814 *s = 0;
1815
1816 __add_preferred_console(buf, idx, options, brl_options);
1817 console_set_on_cmdline = 1;
1818 return 1;
1819}
1820__setup("console=", console_setup);
1821
1822/**
1823 * add_preferred_console - add a device to the list of preferred consoles.
1824 * @name: device name
1825 * @idx: device index
1826 * @options: options for this console
1827 *
1828 * The last preferred console added will be used for kernel messages
1829 * and stdin/out/err for init. Normally this is used by console_setup
1830 * above to handle user-supplied console arguments; however it can also
1831 * be used by arch-specific code either to override the user or more
1832 * commonly to provide a default console (ie from PROM variables) when
1833 * the user has not supplied one.
1834 */
1835int add_preferred_console(char *name, int idx, char *options)
1836{
1837 return __add_preferred_console(name, idx, options, NULL);
1838}
1839
1840int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1841{
1842 struct console_cmdline *c;
1843 int i;
1844
1845 for (i = 0, c = console_cmdline;
1846 i < MAX_CMDLINECONSOLES && c->name[0];
1847 i++, c++)
1848 if (strcmp(c->name, name) == 0 && c->index == idx) {
1849 strlcpy(c->name, name_new, sizeof(c->name));
1850 c->name[sizeof(c->name) - 1] = 0;
1851 c->options = options;
1852 c->index = idx_new;
1853 return i;
1854 }
1855 /* not found */
1856 return -1;
1857}
1858
1859bool console_suspend_enabled = 1;
1860EXPORT_SYMBOL(console_suspend_enabled);
1861
1862static int __init console_suspend_disable(char *str)
1863{
1864 console_suspend_enabled = 0;
1865 return 1;
1866}
1867__setup("no_console_suspend", console_suspend_disable);
1868module_param_named(console_suspend, console_suspend_enabled,
1869 bool, S_IRUGO | S_IWUSR);
1870MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1871 " and hibernate operations");
1872
1873/**
1874 * suspend_console - suspend the console subsystem
1875 *
1876 * This disables printk() while we go into suspend states
1877 */
1878void suspend_console(void)
1879{
1880 if (!console_suspend_enabled)
1881 return;
1882 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1883 console_lock();
1884 console_suspended = 1;
1885 up(&console_sem);
1886 mutex_release(&console_lock_dep_map, 1, _RET_IP_);
1887}
1888
1889void resume_console(void)
1890{
1891 if (!console_suspend_enabled)
1892 return;
1893 down(&console_sem);
1894 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
1895 console_suspended = 0;
1896 console_unlock();
1897}
1898
1899/**
1900 * console_cpu_notify - print deferred console messages after CPU hotplug
1901 * @self: notifier struct
1902 * @action: CPU hotplug event
1903 * @hcpu: unused
1904 *
1905 * If printk() is called from a CPU that is not online yet, the messages
1906 * will be spooled but will not show up on the console. This function is
1907 * called when a new CPU comes online (or fails to come up), and ensures
1908 * that any such output gets printed.
1909 */
1910static int console_cpu_notify(struct notifier_block *self,
1911 unsigned long action, void *hcpu)
1912{
1913 switch (action) {
1914 case CPU_ONLINE:
1915 case CPU_DEAD:
1916 case CPU_DOWN_FAILED:
1917 case CPU_UP_CANCELED:
1918 console_lock();
1919 console_unlock();
1920 }
1921 return NOTIFY_OK;
1922}
1923
1924/**
1925 * console_lock - lock the console system for exclusive use.
1926 *
1927 * Acquires a lock which guarantees that the caller has
1928 * exclusive access to the console system and the console_drivers list.
1929 *
1930 * Can sleep, returns nothing.
1931 */
1932void console_lock(void)
1933{
1934 might_sleep();
1935
1936 down(&console_sem);
1937 if (console_suspended)
1938 return;
1939 console_locked = 1;
1940 console_may_schedule = 1;
1941 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
1942}
1943EXPORT_SYMBOL(console_lock);
1944
1945/**
1946 * console_trylock - try to lock the console system for exclusive use.
1947 *
1948 * Tried to acquire a lock which guarantees that the caller has
1949 * exclusive access to the console system and the console_drivers list.
1950 *
1951 * returns 1 on success, and 0 on failure to acquire the lock.
1952 */
1953int console_trylock(void)
1954{
1955 if (down_trylock(&console_sem))
1956 return 0;
1957 if (console_suspended) {
1958 up(&console_sem);
1959 return 0;
1960 }
1961 console_locked = 1;
1962 console_may_schedule = 0;
1963 mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);
1964 return 1;
1965}
1966EXPORT_SYMBOL(console_trylock);
1967
1968int is_console_locked(void)
1969{
1970 return console_locked;
1971}
1972
1973static void console_cont_flush(char *text, size_t size)
1974{
1975 unsigned long flags;
1976 size_t len;
1977
1978 raw_spin_lock_irqsave(&logbuf_lock, flags);
1979
1980 if (!cont.len)
1981 goto out;
1982
1983 /*
1984 * We still queue earlier records, likely because the console was
1985 * busy. The earlier ones need to be printed before this one, we
1986 * did not flush any fragment so far, so just let it queue up.
1987 */
1988 if (console_seq < log_next_seq && !cont.cons)
1989 goto out;
1990
1991 len = cont_print_text(text, size);
1992 raw_spin_unlock(&logbuf_lock);
1993 stop_critical_timings();
1994 call_console_drivers(cont.level, text, len);
1995 start_critical_timings();
1996 local_irq_restore(flags);
1997 return;
1998out:
1999 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2000}
2001
2002/**
2003 * console_unlock - unlock the console system
2004 *
2005 * Releases the console_lock which the caller holds on the console system
2006 * and the console driver list.
2007 *
2008 * While the console_lock was held, console output may have been buffered
2009 * by printk(). If this is the case, console_unlock(); emits
2010 * the output prior to releasing the lock.
2011 *
2012 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2013 *
2014 * console_unlock(); may be called from any context.
2015 */
2016void console_unlock(void)
2017{
2018 static char text[LOG_LINE_MAX + PREFIX_MAX];
2019 static u64 seen_seq;
2020 unsigned long flags;
2021 bool wake_klogd = false;
2022 bool retry;
2023
2024 if (console_suspended) {
2025 up(&console_sem);
2026 return;
2027 }
2028
2029 console_may_schedule = 0;
2030
2031 /* flush buffered message fragment immediately to console */
2032 console_cont_flush(text, sizeof(text));
2033again:
2034 for (;;) {
2035 struct printk_log *msg;
2036 size_t len;
2037 int level;
2038
2039 raw_spin_lock_irqsave(&logbuf_lock, flags);
2040 if (seen_seq != log_next_seq) {
2041 wake_klogd = true;
2042 seen_seq = log_next_seq;
2043 }
2044
2045 if (console_seq < log_first_seq) {
2046 /* messages are gone, move to first one */
2047 console_seq = log_first_seq;
2048 console_idx = log_first_idx;
2049 console_prev = 0;
2050 }
2051skip:
2052 if (console_seq == log_next_seq)
2053 break;
2054
2055 msg = log_from_idx(console_idx);
2056 if (msg->flags & LOG_NOCONS) {
2057 /*
2058 * Skip record we have buffered and already printed
2059 * directly to the console when we received it.
2060 */
2061 console_idx = log_next(console_idx);
2062 console_seq++;
2063 /*
2064 * We will get here again when we register a new
2065 * CON_PRINTBUFFER console. Clear the flag so we
2066 * will properly dump everything later.
2067 */
2068 msg->flags &= ~LOG_NOCONS;
2069 console_prev = msg->flags;
2070 goto skip;
2071 }
2072
2073 level = msg->level;
2074 len = msg_print_text(msg, console_prev, false,
2075 text, sizeof(text));
2076 console_idx = log_next(console_idx);
2077 console_seq++;
2078 console_prev = msg->flags;
2079 raw_spin_unlock(&logbuf_lock);
2080
2081 stop_critical_timings(); /* don't trace print latency */
2082 call_console_drivers(level, text, len);
2083 start_critical_timings();
2084 local_irq_restore(flags);
2085 }
2086 console_locked = 0;
2087 mutex_release(&console_lock_dep_map, 1, _RET_IP_);
2088
2089 /* Release the exclusive_console once it is used */
2090 if (unlikely(exclusive_console))
2091 exclusive_console = NULL;
2092
2093 raw_spin_unlock(&logbuf_lock);
2094
2095 up(&console_sem);
2096
2097 /*
2098 * Someone could have filled up the buffer again, so re-check if there's
2099 * something to flush. In case we cannot trylock the console_sem again,
2100 * there's a new owner and the console_unlock() from them will do the
2101 * flush, no worries.
2102 */
2103 raw_spin_lock(&logbuf_lock);
2104 retry = console_seq != log_next_seq;
2105 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2106
2107 if (retry && console_trylock())
2108 goto again;
2109
2110 if (wake_klogd)
2111 wake_up_klogd();
2112}
2113EXPORT_SYMBOL(console_unlock);
2114
2115/**
2116 * console_conditional_schedule - yield the CPU if required
2117 *
2118 * If the console code is currently allowed to sleep, and
2119 * if this CPU should yield the CPU to another task, do
2120 * so here.
2121 *
2122 * Must be called within console_lock();.
2123 */
2124void __sched console_conditional_schedule(void)
2125{
2126 if (console_may_schedule)
2127 cond_resched();
2128}
2129EXPORT_SYMBOL(console_conditional_schedule);
2130
2131void console_unblank(void)
2132{
2133 struct console *c;
2134
2135 /*
2136 * console_unblank can no longer be called in interrupt context unless
2137 * oops_in_progress is set to 1..
2138 */
2139 if (oops_in_progress) {
2140 if (down_trylock(&console_sem) != 0)
2141 return;
2142 } else
2143 console_lock();
2144
2145 console_locked = 1;
2146 console_may_schedule = 0;
2147 for_each_console(c)
2148 if ((c->flags & CON_ENABLED) && c->unblank)
2149 c->unblank();
2150 console_unlock();
2151}
2152
2153/*
2154 * Return the console tty driver structure and its associated index
2155 */
2156struct tty_driver *console_device(int *index)
2157{
2158 struct console *c;
2159 struct tty_driver *driver = NULL;
2160
2161 console_lock();
2162 for_each_console(c) {
2163 if (!c->device)
2164 continue;
2165 driver = c->device(c, index);
2166 if (driver)
2167 break;
2168 }
2169 console_unlock();
2170 return driver;
2171}
2172
2173/*
2174 * Prevent further output on the passed console device so that (for example)
2175 * serial drivers can disable console output before suspending a port, and can
2176 * re-enable output afterwards.
2177 */
2178void console_stop(struct console *console)
2179{
2180 console_lock();
2181 console->flags &= ~CON_ENABLED;
2182 console_unlock();
2183}
2184EXPORT_SYMBOL(console_stop);
2185
2186void console_start(struct console *console)
2187{
2188 console_lock();
2189 console->flags |= CON_ENABLED;
2190 console_unlock();
2191}
2192EXPORT_SYMBOL(console_start);
2193
2194static int __read_mostly keep_bootcon;
2195
2196static int __init keep_bootcon_setup(char *str)
2197{
2198 keep_bootcon = 1;
2199 pr_info("debug: skip boot console de-registration.\n");
2200
2201 return 0;
2202}
2203
2204early_param("keep_bootcon", keep_bootcon_setup);
2205
2206/*
2207 * The console driver calls this routine during kernel initialization
2208 * to register the console printing procedure with printk() and to
2209 * print any messages that were printed by the kernel before the
2210 * console driver was initialized.
2211 *
2212 * This can happen pretty early during the boot process (because of
2213 * early_printk) - sometimes before setup_arch() completes - be careful
2214 * of what kernel features are used - they may not be initialised yet.
2215 *
2216 * There are two types of consoles - bootconsoles (early_printk) and
2217 * "real" consoles (everything which is not a bootconsole) which are
2218 * handled differently.
2219 * - Any number of bootconsoles can be registered at any time.
2220 * - As soon as a "real" console is registered, all bootconsoles
2221 * will be unregistered automatically.
2222 * - Once a "real" console is registered, any attempt to register a
2223 * bootconsoles will be rejected
2224 */
2225void register_console(struct console *newcon)
2226{
2227 int i;
2228 unsigned long flags;
2229 struct console *bcon = NULL;
2230 struct console_cmdline *c;
2231
2232 if (console_drivers)
2233 for_each_console(bcon)
2234 if (WARN(bcon == newcon,
2235 "console '%s%d' already registered\n",
2236 bcon->name, bcon->index))
2237 return;
2238
2239 /*
2240 * before we register a new CON_BOOT console, make sure we don't
2241 * already have a valid console
2242 */
2243 if (console_drivers && newcon->flags & CON_BOOT) {
2244 /* find the last or real console */
2245 for_each_console(bcon) {
2246 if (!(bcon->flags & CON_BOOT)) {
2247 pr_info("Too late to register bootconsole %s%d\n",
2248 newcon->name, newcon->index);
2249 return;
2250 }
2251 }
2252 }
2253
2254 if (console_drivers && console_drivers->flags & CON_BOOT)
2255 bcon = console_drivers;
2256
2257 if (preferred_console < 0 || bcon || !console_drivers)
2258 preferred_console = selected_console;
2259
2260 if (newcon->early_setup)
2261 newcon->early_setup();
2262
2263 /*
2264 * See if we want to use this console driver. If we
2265 * didn't select a console we take the first one
2266 * that registers here.
2267 */
2268 if (preferred_console < 0) {
2269 if (newcon->index < 0)
2270 newcon->index = 0;
2271 if (newcon->setup == NULL ||
2272 newcon->setup(newcon, NULL) == 0) {
2273 newcon->flags |= CON_ENABLED;
2274 if (newcon->device) {
2275 newcon->flags |= CON_CONSDEV;
2276 preferred_console = 0;
2277 }
2278 }
2279 }
2280
2281 /*
2282 * See if this console matches one we selected on
2283 * the command line.
2284 */
2285 for (i = 0, c = console_cmdline;
2286 i < MAX_CMDLINECONSOLES && c->name[0];
2287 i++, c++) {
2288 if (strcmp(c->name, newcon->name) != 0)
2289 continue;
2290 if (newcon->index >= 0 &&
2291 newcon->index != c->index)
2292 continue;
2293 if (newcon->index < 0)
2294 newcon->index = c->index;
2295
2296 if (_braille_register_console(newcon, c))
2297 return;
2298
2299 if (newcon->setup &&
2300 newcon->setup(newcon, console_cmdline[i].options) != 0)
2301 break;
2302 newcon->flags |= CON_ENABLED;
2303 newcon->index = c->index;
2304 if (i == selected_console) {
2305 newcon->flags |= CON_CONSDEV;
2306 preferred_console = selected_console;
2307 }
2308 break;
2309 }
2310
2311 if (!(newcon->flags & CON_ENABLED))
2312 return;
2313
2314 /*
2315 * If we have a bootconsole, and are switching to a real console,
2316 * don't print everything out again, since when the boot console, and
2317 * the real console are the same physical device, it's annoying to
2318 * see the beginning boot messages twice
2319 */
2320 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2321 newcon->flags &= ~CON_PRINTBUFFER;
2322
2323 /*
2324 * Put this console in the list - keep the
2325 * preferred driver at the head of the list.
2326 */
2327 console_lock();
2328 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2329 newcon->next = console_drivers;
2330 console_drivers = newcon;
2331 if (newcon->next)
2332 newcon->next->flags &= ~CON_CONSDEV;
2333 } else {
2334 newcon->next = console_drivers->next;
2335 console_drivers->next = newcon;
2336 }
2337 if (newcon->flags & CON_PRINTBUFFER) {
2338 /*
2339 * console_unlock(); will print out the buffered messages
2340 * for us.
2341 */
2342 raw_spin_lock_irqsave(&logbuf_lock, flags);
2343 console_seq = syslog_seq;
2344 console_idx = syslog_idx;
2345 console_prev = syslog_prev;
2346 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2347 /*
2348 * We're about to replay the log buffer. Only do this to the
2349 * just-registered console to avoid excessive message spam to
2350 * the already-registered consoles.
2351 */
2352 exclusive_console = newcon;
2353 }
2354 console_unlock();
2355 console_sysfs_notify();
2356
2357 /*
2358 * By unregistering the bootconsoles after we enable the real console
2359 * we get the "console xxx enabled" message on all the consoles -
2360 * boot consoles, real consoles, etc - this is to ensure that end
2361 * users know there might be something in the kernel's log buffer that
2362 * went to the bootconsole (that they do not see on the real console)
2363 */
2364 pr_info("%sconsole [%s%d] enabled\n",
2365 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2366 newcon->name, newcon->index);
2367 if (bcon &&
2368 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2369 !keep_bootcon) {
2370 /* We need to iterate through all boot consoles, to make
2371 * sure we print everything out, before we unregister them.
2372 */
2373 for_each_console(bcon)
2374 if (bcon->flags & CON_BOOT)
2375 unregister_console(bcon);
2376 }
2377}
2378EXPORT_SYMBOL(register_console);
2379
2380int unregister_console(struct console *console)
2381{
2382 struct console *a, *b;
2383 int res;
2384
2385 pr_info("%sconsole [%s%d] disabled\n",
2386 (console->flags & CON_BOOT) ? "boot" : "" ,
2387 console->name, console->index);
2388
2389 res = _braille_unregister_console(console);
2390 if (res)
2391 return res;
2392
2393 res = 1;
2394 console_lock();
2395 if (console_drivers == console) {
2396 console_drivers=console->next;
2397 res = 0;
2398 } else if (console_drivers) {
2399 for (a=console_drivers->next, b=console_drivers ;
2400 a; b=a, a=b->next) {
2401 if (a == console) {
2402 b->next = a->next;
2403 res = 0;
2404 break;
2405 }
2406 }
2407 }
2408
2409 /*
2410 * If this isn't the last console and it has CON_CONSDEV set, we
2411 * need to set it on the next preferred console.
2412 */
2413 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2414 console_drivers->flags |= CON_CONSDEV;
2415
2416 console_unlock();
2417 console_sysfs_notify();
2418 return res;
2419}
2420EXPORT_SYMBOL(unregister_console);
2421
2422static int __init printk_late_init(void)
2423{
2424 struct console *con;
2425
2426 for_each_console(con) {
2427 if (!keep_bootcon && con->flags & CON_BOOT) {
2428 unregister_console(con);
2429 }
2430 }
2431 hotcpu_notifier(console_cpu_notify, 0);
2432 return 0;
2433}
2434late_initcall(printk_late_init);
2435
2436#if defined CONFIG_PRINTK
2437/*
2438 * Delayed printk version, for scheduler-internal messages:
2439 */
2440#define PRINTK_BUF_SIZE 512
2441
2442#define PRINTK_PENDING_WAKEUP 0x01
2443#define PRINTK_PENDING_SCHED 0x02
2444
2445static DEFINE_PER_CPU(int, printk_pending);
2446static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
2447
2448static void wake_up_klogd_work_func(struct irq_work *irq_work)
2449{
2450 int pending = __this_cpu_xchg(printk_pending, 0);
2451
2452 if (pending & PRINTK_PENDING_SCHED) {
2453 char *buf = __get_cpu_var(printk_sched_buf);
2454 pr_warn("[sched_delayed] %s", buf);
2455 }
2456
2457 if (pending & PRINTK_PENDING_WAKEUP)
2458 wake_up_interruptible(&log_wait);
2459}
2460
2461static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2462 .func = wake_up_klogd_work_func,
2463 .flags = IRQ_WORK_LAZY,
2464};
2465
2466void wake_up_klogd(void)
2467{
2468 preempt_disable();
2469 if (waitqueue_active(&log_wait)) {
2470 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2471 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2472 }
2473 preempt_enable();
2474}
2475
2476int printk_sched(const char *fmt, ...)
2477{
2478 unsigned long flags;
2479 va_list args;
2480 char *buf;
2481 int r;
2482
2483 local_irq_save(flags);
2484 buf = __get_cpu_var(printk_sched_buf);
2485
2486 va_start(args, fmt);
2487 r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2488 va_end(args);
2489
2490 __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2491 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2492 local_irq_restore(flags);
2493
2494 return r;
2495}
2496
2497/*
2498 * printk rate limiting, lifted from the networking subsystem.
2499 *
2500 * This enforces a rate limit: not more than 10 kernel messages
2501 * every 5s to make a denial-of-service attack impossible.
2502 */
2503DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2504
2505int __printk_ratelimit(const char *func)
2506{
2507 return ___ratelimit(&printk_ratelimit_state, func);
2508}
2509EXPORT_SYMBOL(__printk_ratelimit);
2510
2511/**
2512 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2513 * @caller_jiffies: pointer to caller's state
2514 * @interval_msecs: minimum interval between prints
2515 *
2516 * printk_timed_ratelimit() returns true if more than @interval_msecs
2517 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2518 * returned true.
2519 */
2520bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2521 unsigned int interval_msecs)
2522{
2523 if (*caller_jiffies == 0
2524 || !time_in_range(jiffies, *caller_jiffies,
2525 *caller_jiffies
2526 + msecs_to_jiffies(interval_msecs))) {
2527 *caller_jiffies = jiffies;
2528 return true;
2529 }
2530 return false;
2531}
2532EXPORT_SYMBOL(printk_timed_ratelimit);
2533
2534static DEFINE_SPINLOCK(dump_list_lock);
2535static LIST_HEAD(dump_list);
2536
2537/**
2538 * kmsg_dump_register - register a kernel log dumper.
2539 * @dumper: pointer to the kmsg_dumper structure
2540 *
2541 * Adds a kernel log dumper to the system. The dump callback in the
2542 * structure will be called when the kernel oopses or panics and must be
2543 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2544 */
2545int kmsg_dump_register(struct kmsg_dumper *dumper)
2546{
2547 unsigned long flags;
2548 int err = -EBUSY;
2549
2550 /* The dump callback needs to be set */
2551 if (!dumper->dump)
2552 return -EINVAL;
2553
2554 spin_lock_irqsave(&dump_list_lock, flags);
2555 /* Don't allow registering multiple times */
2556 if (!dumper->registered) {
2557 dumper->registered = 1;
2558 list_add_tail_rcu(&dumper->list, &dump_list);
2559 err = 0;
2560 }
2561 spin_unlock_irqrestore(&dump_list_lock, flags);
2562
2563 return err;
2564}
2565EXPORT_SYMBOL_GPL(kmsg_dump_register);
2566
2567/**
2568 * kmsg_dump_unregister - unregister a kmsg dumper.
2569 * @dumper: pointer to the kmsg_dumper structure
2570 *
2571 * Removes a dump device from the system. Returns zero on success and
2572 * %-EINVAL otherwise.
2573 */
2574int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2575{
2576 unsigned long flags;
2577 int err = -EINVAL;
2578
2579 spin_lock_irqsave(&dump_list_lock, flags);
2580 if (dumper->registered) {
2581 dumper->registered = 0;
2582 list_del_rcu(&dumper->list);
2583 err = 0;
2584 }
2585 spin_unlock_irqrestore(&dump_list_lock, flags);
2586 synchronize_rcu();
2587
2588 return err;
2589}
2590EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2591
2592static bool always_kmsg_dump;
2593module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2594
2595/**
2596 * kmsg_dump - dump kernel log to kernel message dumpers.
2597 * @reason: the reason (oops, panic etc) for dumping
2598 *
2599 * Call each of the registered dumper's dump() callback, which can
2600 * retrieve the kmsg records with kmsg_dump_get_line() or
2601 * kmsg_dump_get_buffer().
2602 */
2603void kmsg_dump(enum kmsg_dump_reason reason)
2604{
2605 struct kmsg_dumper *dumper;
2606 unsigned long flags;
2607
2608 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2609 return;
2610
2611 rcu_read_lock();
2612 list_for_each_entry_rcu(dumper, &dump_list, list) {
2613 if (dumper->max_reason && reason > dumper->max_reason)
2614 continue;
2615
2616 /* initialize iterator with data about the stored records */
2617 dumper->active = true;
2618
2619 raw_spin_lock_irqsave(&logbuf_lock, flags);
2620 dumper->cur_seq = clear_seq;
2621 dumper->cur_idx = clear_idx;
2622 dumper->next_seq = log_next_seq;
2623 dumper->next_idx = log_next_idx;
2624 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2625
2626 /* invoke dumper which will iterate over records */
2627 dumper->dump(dumper, reason);
2628
2629 /* reset iterator */
2630 dumper->active = false;
2631 }
2632 rcu_read_unlock();
2633}
2634
2635/**
2636 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2637 * @dumper: registered kmsg dumper
2638 * @syslog: include the "<4>" prefixes
2639 * @line: buffer to copy the line to
2640 * @size: maximum size of the buffer
2641 * @len: length of line placed into buffer
2642 *
2643 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2644 * record, and copy one record into the provided buffer.
2645 *
2646 * Consecutive calls will return the next available record moving
2647 * towards the end of the buffer with the youngest messages.
2648 *
2649 * A return value of FALSE indicates that there are no more records to
2650 * read.
2651 *
2652 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2653 */
2654bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2655 char *line, size_t size, size_t *len)
2656{
2657 struct printk_log *msg;
2658 size_t l = 0;
2659 bool ret = false;
2660
2661 if (!dumper->active)
2662 goto out;
2663
2664 if (dumper->cur_seq < log_first_seq) {
2665 /* messages are gone, move to first available one */
2666 dumper->cur_seq = log_first_seq;
2667 dumper->cur_idx = log_first_idx;
2668 }
2669
2670 /* last entry */
2671 if (dumper->cur_seq >= log_next_seq)
2672 goto out;
2673
2674 msg = log_from_idx(dumper->cur_idx);
2675 l = msg_print_text(msg, 0, syslog, line, size);
2676
2677 dumper->cur_idx = log_next(dumper->cur_idx);
2678 dumper->cur_seq++;
2679 ret = true;
2680out:
2681 if (len)
2682 *len = l;
2683 return ret;
2684}
2685
2686/**
2687 * kmsg_dump_get_line - retrieve one kmsg log line
2688 * @dumper: registered kmsg dumper
2689 * @syslog: include the "<4>" prefixes
2690 * @line: buffer to copy the line to
2691 * @size: maximum size of the buffer
2692 * @len: length of line placed into buffer
2693 *
2694 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2695 * record, and copy one record into the provided buffer.
2696 *
2697 * Consecutive calls will return the next available record moving
2698 * towards the end of the buffer with the youngest messages.
2699 *
2700 * A return value of FALSE indicates that there are no more records to
2701 * read.
2702 */
2703bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2704 char *line, size_t size, size_t *len)
2705{
2706 unsigned long flags;
2707 bool ret;
2708
2709 raw_spin_lock_irqsave(&logbuf_lock, flags);
2710 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2711 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2712
2713 return ret;
2714}
2715EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2716
2717/**
2718 * kmsg_dump_get_buffer - copy kmsg log lines
2719 * @dumper: registered kmsg dumper
2720 * @syslog: include the "<4>" prefixes
2721 * @buf: buffer to copy the line to
2722 * @size: maximum size of the buffer
2723 * @len: length of line placed into buffer
2724 *
2725 * Start at the end of the kmsg buffer and fill the provided buffer
2726 * with as many of the the *youngest* kmsg records that fit into it.
2727 * If the buffer is large enough, all available kmsg records will be
2728 * copied with a single call.
2729 *
2730 * Consecutive calls will fill the buffer with the next block of
2731 * available older records, not including the earlier retrieved ones.
2732 *
2733 * A return value of FALSE indicates that there are no more records to
2734 * read.
2735 */
2736bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2737 char *buf, size_t size, size_t *len)
2738{
2739 unsigned long flags;
2740 u64 seq;
2741 u32 idx;
2742 u64 next_seq;
2743 u32 next_idx;
2744 enum log_flags prev;
2745 size_t l = 0;
2746 bool ret = false;
2747
2748 if (!dumper->active)
2749 goto out;
2750
2751 raw_spin_lock_irqsave(&logbuf_lock, flags);
2752 if (dumper->cur_seq < log_first_seq) {
2753 /* messages are gone, move to first available one */
2754 dumper->cur_seq = log_first_seq;
2755 dumper->cur_idx = log_first_idx;
2756 }
2757
2758 /* last entry */
2759 if (dumper->cur_seq >= dumper->next_seq) {
2760 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2761 goto out;
2762 }
2763
2764 /* calculate length of entire buffer */
2765 seq = dumper->cur_seq;
2766 idx = dumper->cur_idx;
2767 prev = 0;
2768 while (seq < dumper->next_seq) {
2769 struct printk_log *msg = log_from_idx(idx);
2770
2771 l += msg_print_text(msg, prev, true, NULL, 0);
2772 idx = log_next(idx);
2773 seq++;
2774 prev = msg->flags;
2775 }
2776
2777 /* move first record forward until length fits into the buffer */
2778 seq = dumper->cur_seq;
2779 idx = dumper->cur_idx;
2780 prev = 0;
2781 while (l > size && seq < dumper->next_seq) {
2782 struct printk_log *msg = log_from_idx(idx);
2783
2784 l -= msg_print_text(msg, prev, true, NULL, 0);
2785 idx = log_next(idx);
2786 seq++;
2787 prev = msg->flags;
2788 }
2789
2790 /* last message in next interation */
2791 next_seq = seq;
2792 next_idx = idx;
2793
2794 l = 0;
2795 while (seq < dumper->next_seq) {
2796 struct printk_log *msg = log_from_idx(idx);
2797
2798 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2799 idx = log_next(idx);
2800 seq++;
2801 prev = msg->flags;
2802 }
2803
2804 dumper->next_seq = next_seq;
2805 dumper->next_idx = next_idx;
2806 ret = true;
2807 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2808out:
2809 if (len)
2810 *len = l;
2811 return ret;
2812}
2813EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2814
2815/**
2816 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2817 * @dumper: registered kmsg dumper
2818 *
2819 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2820 * kmsg_dump_get_buffer() can be called again and used multiple
2821 * times within the same dumper.dump() callback.
2822 *
2823 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2824 */
2825void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
2826{
2827 dumper->cur_seq = clear_seq;
2828 dumper->cur_idx = clear_idx;
2829 dumper->next_seq = log_next_seq;
2830 dumper->next_idx = log_next_idx;
2831}
2832
2833/**
2834 * kmsg_dump_rewind - reset the interator
2835 * @dumper: registered kmsg dumper
2836 *
2837 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2838 * kmsg_dump_get_buffer() can be called again and used multiple
2839 * times within the same dumper.dump() callback.
2840 */
2841void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2842{
2843 unsigned long flags;
2844
2845 raw_spin_lock_irqsave(&logbuf_lock, flags);
2846 kmsg_dump_rewind_nolock(dumper);
2847 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2848}
2849EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
2850
2851static char dump_stack_arch_desc_str[128];
2852
2853/**
2854 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
2855 * @fmt: printf-style format string
2856 * @...: arguments for the format string
2857 *
2858 * The configured string will be printed right after utsname during task
2859 * dumps. Usually used to add arch-specific system identifiers. If an
2860 * arch wants to make use of such an ID string, it should initialize this
2861 * as soon as possible during boot.
2862 */
2863void __init dump_stack_set_arch_desc(const char *fmt, ...)
2864{
2865 va_list args;
2866
2867 va_start(args, fmt);
2868 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
2869 fmt, args);
2870 va_end(args);
2871}
2872
2873/**
2874 * dump_stack_print_info - print generic debug info for dump_stack()
2875 * @log_lvl: log level
2876 *
2877 * Arch-specific dump_stack() implementations can use this function to
2878 * print out the same debug information as the generic dump_stack().
2879 */
2880void dump_stack_print_info(const char *log_lvl)
2881{
2882 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
2883 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
2884 print_tainted(), init_utsname()->release,
2885 (int)strcspn(init_utsname()->version, " "),
2886 init_utsname()->version);
2887
2888 if (dump_stack_arch_desc_str[0] != '\0')
2889 printk("%sHardware name: %s\n",
2890 log_lvl, dump_stack_arch_desc_str);
2891
2892 print_worker_info(log_lvl, current);
2893}
2894
2895/**
2896 * show_regs_print_info - print generic debug info for show_regs()
2897 * @log_lvl: log level
2898 *
2899 * show_regs() implementations can use this function to print out generic
2900 * debug information.
2901 */
2902void show_regs_print_info(const char *log_lvl)
2903{
2904 dump_stack_print_info(log_lvl);
2905
2906 printk("%stask: %p ti: %p task.ti: %p\n",
2907 log_lvl, current, current_thread_info(),
2908 task_thread_info(current));
2909}
2910
2911#endif
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/interrupt.h> /* For in_interrupt() */
30#include <linux/delay.h>
31#include <linux/smp.h>
32#include <linux/security.h>
33#include <linux/bootmem.h>
34#include <linux/memblock.h>
35#include <linux/syscalls.h>
36#include <linux/kexec.h>
37#include <linux/kdb.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/notifier.h>
43#include <linux/rculist.h>
44#include <linux/poll.h>
45#include <linux/irq_work.h>
46#include <linux/utsname.h>
47#include <linux/ctype.h>
48#include <linux/uio.h>
49
50#include <asm/uaccess.h>
51#include <asm-generic/sections.h>
52
53#define CREATE_TRACE_POINTS
54#include <trace/events/printk.h>
55
56#include "console_cmdline.h"
57#include "braille.h"
58
59int console_printk[4] = {
60 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
61 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
62 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
63 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
64};
65
66/*
67 * Low level drivers may need that to know if they can schedule in
68 * their unblank() callback or not. So let's export it.
69 */
70int oops_in_progress;
71EXPORT_SYMBOL(oops_in_progress);
72
73/*
74 * console_sem protects the console_drivers list, and also
75 * provides serialisation for access to the entire console
76 * driver system.
77 */
78static DEFINE_SEMAPHORE(console_sem);
79struct console *console_drivers;
80EXPORT_SYMBOL_GPL(console_drivers);
81
82#ifdef CONFIG_LOCKDEP
83static struct lockdep_map console_lock_dep_map = {
84 .name = "console_lock"
85};
86#endif
87
88/*
89 * Number of registered extended console drivers.
90 *
91 * If extended consoles are present, in-kernel cont reassembly is disabled
92 * and each fragment is stored as a separate log entry with proper
93 * continuation flag so that every emitted message has full metadata. This
94 * doesn't change the result for regular consoles or /proc/kmsg. For
95 * /dev/kmsg, as long as the reader concatenates messages according to
96 * consecutive continuation flags, the end result should be the same too.
97 */
98static int nr_ext_console_drivers;
99
100/*
101 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
102 * macros instead of functions so that _RET_IP_ contains useful information.
103 */
104#define down_console_sem() do { \
105 down(&console_sem);\
106 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
107} while (0)
108
109static int __down_trylock_console_sem(unsigned long ip)
110{
111 if (down_trylock(&console_sem))
112 return 1;
113 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
114 return 0;
115}
116#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
117
118#define up_console_sem() do { \
119 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
120 up(&console_sem);\
121} while (0)
122
123/*
124 * This is used for debugging the mess that is the VT code by
125 * keeping track if we have the console semaphore held. It's
126 * definitely not the perfect debug tool (we don't know if _WE_
127 * hold it and are racing, but it helps tracking those weird code
128 * paths in the console code where we end up in places I want
129 * locked without the console sempahore held).
130 */
131static int console_locked, console_suspended;
132
133/*
134 * If exclusive_console is non-NULL then only this console is to be printed to.
135 */
136static struct console *exclusive_console;
137
138/*
139 * Array of consoles built from command line options (console=)
140 */
141
142#define MAX_CMDLINECONSOLES 8
143
144static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
145
146static int selected_console = -1;
147static int preferred_console = -1;
148int console_set_on_cmdline;
149EXPORT_SYMBOL(console_set_on_cmdline);
150
151/* Flag: console code may call schedule() */
152static int console_may_schedule;
153
154/*
155 * The printk log buffer consists of a chain of concatenated variable
156 * length records. Every record starts with a record header, containing
157 * the overall length of the record.
158 *
159 * The heads to the first and last entry in the buffer, as well as the
160 * sequence numbers of these entries are maintained when messages are
161 * stored.
162 *
163 * If the heads indicate available messages, the length in the header
164 * tells the start next message. A length == 0 for the next message
165 * indicates a wrap-around to the beginning of the buffer.
166 *
167 * Every record carries the monotonic timestamp in microseconds, as well as
168 * the standard userspace syslog level and syslog facility. The usual
169 * kernel messages use LOG_KERN; userspace-injected messages always carry
170 * a matching syslog facility, by default LOG_USER. The origin of every
171 * message can be reliably determined that way.
172 *
173 * The human readable log message directly follows the message header. The
174 * length of the message text is stored in the header, the stored message
175 * is not terminated.
176 *
177 * Optionally, a message can carry a dictionary of properties (key/value pairs),
178 * to provide userspace with a machine-readable message context.
179 *
180 * Examples for well-defined, commonly used property names are:
181 * DEVICE=b12:8 device identifier
182 * b12:8 block dev_t
183 * c127:3 char dev_t
184 * n8 netdev ifindex
185 * +sound:card0 subsystem:devname
186 * SUBSYSTEM=pci driver-core subsystem name
187 *
188 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
189 * follows directly after a '=' character. Every property is terminated by
190 * a '\0' character. The last property is not terminated.
191 *
192 * Example of a message structure:
193 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
194 * 0008 34 00 record is 52 bytes long
195 * 000a 0b 00 text is 11 bytes long
196 * 000c 1f 00 dictionary is 23 bytes long
197 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
198 * 0010 69 74 27 73 20 61 20 6c "it's a l"
199 * 69 6e 65 "ine"
200 * 001b 44 45 56 49 43 "DEVIC"
201 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
202 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
203 * 67 "g"
204 * 0032 00 00 00 padding to next message header
205 *
206 * The 'struct printk_log' buffer header must never be directly exported to
207 * userspace, it is a kernel-private implementation detail that might
208 * need to be changed in the future, when the requirements change.
209 *
210 * /dev/kmsg exports the structured data in the following line format:
211 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
212 *
213 * Users of the export format should ignore possible additional values
214 * separated by ',', and find the message after the ';' character.
215 *
216 * The optional key/value pairs are attached as continuation lines starting
217 * with a space character and terminated by a newline. All possible
218 * non-prinatable characters are escaped in the "\xff" notation.
219 */
220
221enum log_flags {
222 LOG_NOCONS = 1, /* already flushed, do not print to console */
223 LOG_NEWLINE = 2, /* text ended with a newline */
224 LOG_PREFIX = 4, /* text started with a prefix */
225 LOG_CONT = 8, /* text is a fragment of a continuation line */
226};
227
228struct printk_log {
229 u64 ts_nsec; /* timestamp in nanoseconds */
230 u16 len; /* length of entire record */
231 u16 text_len; /* length of text buffer */
232 u16 dict_len; /* length of dictionary buffer */
233 u8 facility; /* syslog facility */
234 u8 flags:5; /* internal record flags */
235 u8 level:3; /* syslog level */
236}
237#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
238__packed __aligned(4)
239#endif
240;
241
242/*
243 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
244 * within the scheduler's rq lock. It must be released before calling
245 * console_unlock() or anything else that might wake up a process.
246 */
247static DEFINE_RAW_SPINLOCK(logbuf_lock);
248
249#ifdef CONFIG_PRINTK
250DECLARE_WAIT_QUEUE_HEAD(log_wait);
251/* the next printk record to read by syslog(READ) or /proc/kmsg */
252static u64 syslog_seq;
253static u32 syslog_idx;
254static enum log_flags syslog_prev;
255static size_t syslog_partial;
256
257/* index and sequence number of the first record stored in the buffer */
258static u64 log_first_seq;
259static u32 log_first_idx;
260
261/* index and sequence number of the next record to store in the buffer */
262static u64 log_next_seq;
263static u32 log_next_idx;
264
265/* the next printk record to write to the console */
266static u64 console_seq;
267static u32 console_idx;
268static enum log_flags console_prev;
269
270/* the next printk record to read after the last 'clear' command */
271static u64 clear_seq;
272static u32 clear_idx;
273
274#define PREFIX_MAX 32
275#define LOG_LINE_MAX (1024 - PREFIX_MAX)
276
277#define LOG_LEVEL(v) ((v) & 0x07)
278#define LOG_FACILITY(v) ((v) >> 3 & 0xff)
279
280/* record buffer */
281#define LOG_ALIGN __alignof__(struct printk_log)
282#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
283static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
284static char *log_buf = __log_buf;
285static u32 log_buf_len = __LOG_BUF_LEN;
286
287/* Return log buffer address */
288char *log_buf_addr_get(void)
289{
290 return log_buf;
291}
292
293/* Return log buffer size */
294u32 log_buf_len_get(void)
295{
296 return log_buf_len;
297}
298
299/* human readable text of the record */
300static char *log_text(const struct printk_log *msg)
301{
302 return (char *)msg + sizeof(struct printk_log);
303}
304
305/* optional key/value pair dictionary attached to the record */
306static char *log_dict(const struct printk_log *msg)
307{
308 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
309}
310
311/* get record by index; idx must point to valid msg */
312static struct printk_log *log_from_idx(u32 idx)
313{
314 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
315
316 /*
317 * A length == 0 record is the end of buffer marker. Wrap around and
318 * read the message at the start of the buffer.
319 */
320 if (!msg->len)
321 return (struct printk_log *)log_buf;
322 return msg;
323}
324
325/* get next record; idx must point to valid msg */
326static u32 log_next(u32 idx)
327{
328 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
329
330 /* length == 0 indicates the end of the buffer; wrap */
331 /*
332 * A length == 0 record is the end of buffer marker. Wrap around and
333 * read the message at the start of the buffer as *this* one, and
334 * return the one after that.
335 */
336 if (!msg->len) {
337 msg = (struct printk_log *)log_buf;
338 return msg->len;
339 }
340 return idx + msg->len;
341}
342
343/*
344 * Check whether there is enough free space for the given message.
345 *
346 * The same values of first_idx and next_idx mean that the buffer
347 * is either empty or full.
348 *
349 * If the buffer is empty, we must respect the position of the indexes.
350 * They cannot be reset to the beginning of the buffer.
351 */
352static int logbuf_has_space(u32 msg_size, bool empty)
353{
354 u32 free;
355
356 if (log_next_idx > log_first_idx || empty)
357 free = max(log_buf_len - log_next_idx, log_first_idx);
358 else
359 free = log_first_idx - log_next_idx;
360
361 /*
362 * We need space also for an empty header that signalizes wrapping
363 * of the buffer.
364 */
365 return free >= msg_size + sizeof(struct printk_log);
366}
367
368static int log_make_free_space(u32 msg_size)
369{
370 while (log_first_seq < log_next_seq &&
371 !logbuf_has_space(msg_size, false)) {
372 /* drop old messages until we have enough contiguous space */
373 log_first_idx = log_next(log_first_idx);
374 log_first_seq++;
375 }
376
377 if (clear_seq < log_first_seq) {
378 clear_seq = log_first_seq;
379 clear_idx = log_first_idx;
380 }
381
382 /* sequence numbers are equal, so the log buffer is empty */
383 if (logbuf_has_space(msg_size, log_first_seq == log_next_seq))
384 return 0;
385
386 return -ENOMEM;
387}
388
389/* compute the message size including the padding bytes */
390static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
391{
392 u32 size;
393
394 size = sizeof(struct printk_log) + text_len + dict_len;
395 *pad_len = (-size) & (LOG_ALIGN - 1);
396 size += *pad_len;
397
398 return size;
399}
400
401/*
402 * Define how much of the log buffer we could take at maximum. The value
403 * must be greater than two. Note that only half of the buffer is available
404 * when the index points to the middle.
405 */
406#define MAX_LOG_TAKE_PART 4
407static const char trunc_msg[] = "<truncated>";
408
409static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
410 u16 *dict_len, u32 *pad_len)
411{
412 /*
413 * The message should not take the whole buffer. Otherwise, it might
414 * get removed too soon.
415 */
416 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
417 if (*text_len > max_text_len)
418 *text_len = max_text_len;
419 /* enable the warning message */
420 *trunc_msg_len = strlen(trunc_msg);
421 /* disable the "dict" completely */
422 *dict_len = 0;
423 /* compute the size again, count also the warning message */
424 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
425}
426
427/* insert record into the buffer, discard old ones, update heads */
428static int log_store(int facility, int level,
429 enum log_flags flags, u64 ts_nsec,
430 const char *dict, u16 dict_len,
431 const char *text, u16 text_len)
432{
433 struct printk_log *msg;
434 u32 size, pad_len;
435 u16 trunc_msg_len = 0;
436
437 /* number of '\0' padding bytes to next message */
438 size = msg_used_size(text_len, dict_len, &pad_len);
439
440 if (log_make_free_space(size)) {
441 /* truncate the message if it is too long for empty buffer */
442 size = truncate_msg(&text_len, &trunc_msg_len,
443 &dict_len, &pad_len);
444 /* survive when the log buffer is too small for trunc_msg */
445 if (log_make_free_space(size))
446 return 0;
447 }
448
449 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
450 /*
451 * This message + an additional empty header does not fit
452 * at the end of the buffer. Add an empty header with len == 0
453 * to signify a wrap around.
454 */
455 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
456 log_next_idx = 0;
457 }
458
459 /* fill message */
460 msg = (struct printk_log *)(log_buf + log_next_idx);
461 memcpy(log_text(msg), text, text_len);
462 msg->text_len = text_len;
463 if (trunc_msg_len) {
464 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
465 msg->text_len += trunc_msg_len;
466 }
467 memcpy(log_dict(msg), dict, dict_len);
468 msg->dict_len = dict_len;
469 msg->facility = facility;
470 msg->level = level & 7;
471 msg->flags = flags & 0x1f;
472 if (ts_nsec > 0)
473 msg->ts_nsec = ts_nsec;
474 else
475 msg->ts_nsec = local_clock();
476 memset(log_dict(msg) + dict_len, 0, pad_len);
477 msg->len = size;
478
479 /* insert message */
480 log_next_idx += msg->len;
481 log_next_seq++;
482
483 return msg->text_len;
484}
485
486int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
487
488static int syslog_action_restricted(int type)
489{
490 if (dmesg_restrict)
491 return 1;
492 /*
493 * Unless restricted, we allow "read all" and "get buffer size"
494 * for everybody.
495 */
496 return type != SYSLOG_ACTION_READ_ALL &&
497 type != SYSLOG_ACTION_SIZE_BUFFER;
498}
499
500int check_syslog_permissions(int type, int source)
501{
502 /*
503 * If this is from /proc/kmsg and we've already opened it, then we've
504 * already done the capabilities checks at open time.
505 */
506 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
507 goto ok;
508
509 if (syslog_action_restricted(type)) {
510 if (capable(CAP_SYSLOG))
511 goto ok;
512 /*
513 * For historical reasons, accept CAP_SYS_ADMIN too, with
514 * a warning.
515 */
516 if (capable(CAP_SYS_ADMIN)) {
517 pr_warn_once("%s (%d): Attempt to access syslog with "
518 "CAP_SYS_ADMIN but no CAP_SYSLOG "
519 "(deprecated).\n",
520 current->comm, task_pid_nr(current));
521 goto ok;
522 }
523 return -EPERM;
524 }
525ok:
526 return security_syslog(type);
527}
528EXPORT_SYMBOL_GPL(check_syslog_permissions);
529
530static void append_char(char **pp, char *e, char c)
531{
532 if (*pp < e)
533 *(*pp)++ = c;
534}
535
536static ssize_t msg_print_ext_header(char *buf, size_t size,
537 struct printk_log *msg, u64 seq,
538 enum log_flags prev_flags)
539{
540 u64 ts_usec = msg->ts_nsec;
541 char cont = '-';
542
543 do_div(ts_usec, 1000);
544
545 /*
546 * If we couldn't merge continuation line fragments during the print,
547 * export the stored flags to allow an optional external merge of the
548 * records. Merging the records isn't always neccessarily correct, like
549 * when we hit a race during printing. In most cases though, it produces
550 * better readable output. 'c' in the record flags mark the first
551 * fragment of a line, '+' the following.
552 */
553 if (msg->flags & LOG_CONT && !(prev_flags & LOG_CONT))
554 cont = 'c';
555 else if ((msg->flags & LOG_CONT) ||
556 ((prev_flags & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
557 cont = '+';
558
559 return scnprintf(buf, size, "%u,%llu,%llu,%c;",
560 (msg->facility << 3) | msg->level, seq, ts_usec, cont);
561}
562
563static ssize_t msg_print_ext_body(char *buf, size_t size,
564 char *dict, size_t dict_len,
565 char *text, size_t text_len)
566{
567 char *p = buf, *e = buf + size;
568 size_t i;
569
570 /* escape non-printable characters */
571 for (i = 0; i < text_len; i++) {
572 unsigned char c = text[i];
573
574 if (c < ' ' || c >= 127 || c == '\\')
575 p += scnprintf(p, e - p, "\\x%02x", c);
576 else
577 append_char(&p, e, c);
578 }
579 append_char(&p, e, '\n');
580
581 if (dict_len) {
582 bool line = true;
583
584 for (i = 0; i < dict_len; i++) {
585 unsigned char c = dict[i];
586
587 if (line) {
588 append_char(&p, e, ' ');
589 line = false;
590 }
591
592 if (c == '\0') {
593 append_char(&p, e, '\n');
594 line = true;
595 continue;
596 }
597
598 if (c < ' ' || c >= 127 || c == '\\') {
599 p += scnprintf(p, e - p, "\\x%02x", c);
600 continue;
601 }
602
603 append_char(&p, e, c);
604 }
605 append_char(&p, e, '\n');
606 }
607
608 return p - buf;
609}
610
611/* /dev/kmsg - userspace message inject/listen interface */
612struct devkmsg_user {
613 u64 seq;
614 u32 idx;
615 enum log_flags prev;
616 struct mutex lock;
617 char buf[CONSOLE_EXT_LOG_MAX];
618};
619
620static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
621{
622 char *buf, *line;
623 int level = default_message_loglevel;
624 int facility = 1; /* LOG_USER */
625 size_t len = iov_iter_count(from);
626 ssize_t ret = len;
627
628 if (len > LOG_LINE_MAX)
629 return -EINVAL;
630 buf = kmalloc(len+1, GFP_KERNEL);
631 if (buf == NULL)
632 return -ENOMEM;
633
634 buf[len] = '\0';
635 if (copy_from_iter(buf, len, from) != len) {
636 kfree(buf);
637 return -EFAULT;
638 }
639
640 /*
641 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
642 * the decimal value represents 32bit, the lower 3 bit are the log
643 * level, the rest are the log facility.
644 *
645 * If no prefix or no userspace facility is specified, we
646 * enforce LOG_USER, to be able to reliably distinguish
647 * kernel-generated messages from userspace-injected ones.
648 */
649 line = buf;
650 if (line[0] == '<') {
651 char *endp = NULL;
652 unsigned int u;
653
654 u = simple_strtoul(line + 1, &endp, 10);
655 if (endp && endp[0] == '>') {
656 level = LOG_LEVEL(u);
657 if (LOG_FACILITY(u) != 0)
658 facility = LOG_FACILITY(u);
659 endp++;
660 len -= endp - line;
661 line = endp;
662 }
663 }
664
665 printk_emit(facility, level, NULL, 0, "%s", line);
666 kfree(buf);
667 return ret;
668}
669
670static ssize_t devkmsg_read(struct file *file, char __user *buf,
671 size_t count, loff_t *ppos)
672{
673 struct devkmsg_user *user = file->private_data;
674 struct printk_log *msg;
675 size_t len;
676 ssize_t ret;
677
678 if (!user)
679 return -EBADF;
680
681 ret = mutex_lock_interruptible(&user->lock);
682 if (ret)
683 return ret;
684 raw_spin_lock_irq(&logbuf_lock);
685 while (user->seq == log_next_seq) {
686 if (file->f_flags & O_NONBLOCK) {
687 ret = -EAGAIN;
688 raw_spin_unlock_irq(&logbuf_lock);
689 goto out;
690 }
691
692 raw_spin_unlock_irq(&logbuf_lock);
693 ret = wait_event_interruptible(log_wait,
694 user->seq != log_next_seq);
695 if (ret)
696 goto out;
697 raw_spin_lock_irq(&logbuf_lock);
698 }
699
700 if (user->seq < log_first_seq) {
701 /* our last seen message is gone, return error and reset */
702 user->idx = log_first_idx;
703 user->seq = log_first_seq;
704 ret = -EPIPE;
705 raw_spin_unlock_irq(&logbuf_lock);
706 goto out;
707 }
708
709 msg = log_from_idx(user->idx);
710 len = msg_print_ext_header(user->buf, sizeof(user->buf),
711 msg, user->seq, user->prev);
712 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
713 log_dict(msg), msg->dict_len,
714 log_text(msg), msg->text_len);
715
716 user->prev = msg->flags;
717 user->idx = log_next(user->idx);
718 user->seq++;
719 raw_spin_unlock_irq(&logbuf_lock);
720
721 if (len > count) {
722 ret = -EINVAL;
723 goto out;
724 }
725
726 if (copy_to_user(buf, user->buf, len)) {
727 ret = -EFAULT;
728 goto out;
729 }
730 ret = len;
731out:
732 mutex_unlock(&user->lock);
733 return ret;
734}
735
736static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
737{
738 struct devkmsg_user *user = file->private_data;
739 loff_t ret = 0;
740
741 if (!user)
742 return -EBADF;
743 if (offset)
744 return -ESPIPE;
745
746 raw_spin_lock_irq(&logbuf_lock);
747 switch (whence) {
748 case SEEK_SET:
749 /* the first record */
750 user->idx = log_first_idx;
751 user->seq = log_first_seq;
752 break;
753 case SEEK_DATA:
754 /*
755 * The first record after the last SYSLOG_ACTION_CLEAR,
756 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
757 * changes no global state, and does not clear anything.
758 */
759 user->idx = clear_idx;
760 user->seq = clear_seq;
761 break;
762 case SEEK_END:
763 /* after the last record */
764 user->idx = log_next_idx;
765 user->seq = log_next_seq;
766 break;
767 default:
768 ret = -EINVAL;
769 }
770 raw_spin_unlock_irq(&logbuf_lock);
771 return ret;
772}
773
774static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
775{
776 struct devkmsg_user *user = file->private_data;
777 int ret = 0;
778
779 if (!user)
780 return POLLERR|POLLNVAL;
781
782 poll_wait(file, &log_wait, wait);
783
784 raw_spin_lock_irq(&logbuf_lock);
785 if (user->seq < log_next_seq) {
786 /* return error when data has vanished underneath us */
787 if (user->seq < log_first_seq)
788 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
789 else
790 ret = POLLIN|POLLRDNORM;
791 }
792 raw_spin_unlock_irq(&logbuf_lock);
793
794 return ret;
795}
796
797static int devkmsg_open(struct inode *inode, struct file *file)
798{
799 struct devkmsg_user *user;
800 int err;
801
802 /* write-only does not need any file context */
803 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
804 return 0;
805
806 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
807 SYSLOG_FROM_READER);
808 if (err)
809 return err;
810
811 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
812 if (!user)
813 return -ENOMEM;
814
815 mutex_init(&user->lock);
816
817 raw_spin_lock_irq(&logbuf_lock);
818 user->idx = log_first_idx;
819 user->seq = log_first_seq;
820 raw_spin_unlock_irq(&logbuf_lock);
821
822 file->private_data = user;
823 return 0;
824}
825
826static int devkmsg_release(struct inode *inode, struct file *file)
827{
828 struct devkmsg_user *user = file->private_data;
829
830 if (!user)
831 return 0;
832
833 mutex_destroy(&user->lock);
834 kfree(user);
835 return 0;
836}
837
838const struct file_operations kmsg_fops = {
839 .open = devkmsg_open,
840 .read = devkmsg_read,
841 .write_iter = devkmsg_write,
842 .llseek = devkmsg_llseek,
843 .poll = devkmsg_poll,
844 .release = devkmsg_release,
845};
846
847#ifdef CONFIG_KEXEC_CORE
848/*
849 * This appends the listed symbols to /proc/vmcore
850 *
851 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
852 * obtain access to symbols that are otherwise very difficult to locate. These
853 * symbols are specifically used so that utilities can access and extract the
854 * dmesg log from a vmcore file after a crash.
855 */
856void log_buf_kexec_setup(void)
857{
858 VMCOREINFO_SYMBOL(log_buf);
859 VMCOREINFO_SYMBOL(log_buf_len);
860 VMCOREINFO_SYMBOL(log_first_idx);
861 VMCOREINFO_SYMBOL(clear_idx);
862 VMCOREINFO_SYMBOL(log_next_idx);
863 /*
864 * Export struct printk_log size and field offsets. User space tools can
865 * parse it and detect any changes to structure down the line.
866 */
867 VMCOREINFO_STRUCT_SIZE(printk_log);
868 VMCOREINFO_OFFSET(printk_log, ts_nsec);
869 VMCOREINFO_OFFSET(printk_log, len);
870 VMCOREINFO_OFFSET(printk_log, text_len);
871 VMCOREINFO_OFFSET(printk_log, dict_len);
872}
873#endif
874
875/* requested log_buf_len from kernel cmdline */
876static unsigned long __initdata new_log_buf_len;
877
878/* we practice scaling the ring buffer by powers of 2 */
879static void __init log_buf_len_update(unsigned size)
880{
881 if (size)
882 size = roundup_pow_of_two(size);
883 if (size > log_buf_len)
884 new_log_buf_len = size;
885}
886
887/* save requested log_buf_len since it's too early to process it */
888static int __init log_buf_len_setup(char *str)
889{
890 unsigned size = memparse(str, &str);
891
892 log_buf_len_update(size);
893
894 return 0;
895}
896early_param("log_buf_len", log_buf_len_setup);
897
898#ifdef CONFIG_SMP
899#define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
900
901static void __init log_buf_add_cpu(void)
902{
903 unsigned int cpu_extra;
904
905 /*
906 * archs should set up cpu_possible_bits properly with
907 * set_cpu_possible() after setup_arch() but just in
908 * case lets ensure this is valid.
909 */
910 if (num_possible_cpus() == 1)
911 return;
912
913 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
914
915 /* by default this will only continue through for large > 64 CPUs */
916 if (cpu_extra <= __LOG_BUF_LEN / 2)
917 return;
918
919 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
920 __LOG_CPU_MAX_BUF_LEN);
921 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
922 cpu_extra);
923 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
924
925 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
926}
927#else /* !CONFIG_SMP */
928static inline void log_buf_add_cpu(void) {}
929#endif /* CONFIG_SMP */
930
931void __init setup_log_buf(int early)
932{
933 unsigned long flags;
934 char *new_log_buf;
935 int free;
936
937 if (log_buf != __log_buf)
938 return;
939
940 if (!early && !new_log_buf_len)
941 log_buf_add_cpu();
942
943 if (!new_log_buf_len)
944 return;
945
946 if (early) {
947 new_log_buf =
948 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
949 } else {
950 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
951 LOG_ALIGN);
952 }
953
954 if (unlikely(!new_log_buf)) {
955 pr_err("log_buf_len: %ld bytes not available\n",
956 new_log_buf_len);
957 return;
958 }
959
960 raw_spin_lock_irqsave(&logbuf_lock, flags);
961 log_buf_len = new_log_buf_len;
962 log_buf = new_log_buf;
963 new_log_buf_len = 0;
964 free = __LOG_BUF_LEN - log_next_idx;
965 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
966 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
967
968 pr_info("log_buf_len: %d bytes\n", log_buf_len);
969 pr_info("early log buf free: %d(%d%%)\n",
970 free, (free * 100) / __LOG_BUF_LEN);
971}
972
973static bool __read_mostly ignore_loglevel;
974
975static int __init ignore_loglevel_setup(char *str)
976{
977 ignore_loglevel = true;
978 pr_info("debug: ignoring loglevel setting.\n");
979
980 return 0;
981}
982
983early_param("ignore_loglevel", ignore_loglevel_setup);
984module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
985MODULE_PARM_DESC(ignore_loglevel,
986 "ignore loglevel setting (prints all kernel messages to the console)");
987
988#ifdef CONFIG_BOOT_PRINTK_DELAY
989
990static int boot_delay; /* msecs delay after each printk during bootup */
991static unsigned long long loops_per_msec; /* based on boot_delay */
992
993static int __init boot_delay_setup(char *str)
994{
995 unsigned long lpj;
996
997 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
998 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
999
1000 get_option(&str, &boot_delay);
1001 if (boot_delay > 10 * 1000)
1002 boot_delay = 0;
1003
1004 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1005 "HZ: %d, loops_per_msec: %llu\n",
1006 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1007 return 0;
1008}
1009early_param("boot_delay", boot_delay_setup);
1010
1011static void boot_delay_msec(int level)
1012{
1013 unsigned long long k;
1014 unsigned long timeout;
1015
1016 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
1017 || (level >= console_loglevel && !ignore_loglevel)) {
1018 return;
1019 }
1020
1021 k = (unsigned long long)loops_per_msec * boot_delay;
1022
1023 timeout = jiffies + msecs_to_jiffies(boot_delay);
1024 while (k) {
1025 k--;
1026 cpu_relax();
1027 /*
1028 * use (volatile) jiffies to prevent
1029 * compiler reduction; loop termination via jiffies
1030 * is secondary and may or may not happen.
1031 */
1032 if (time_after(jiffies, timeout))
1033 break;
1034 touch_nmi_watchdog();
1035 }
1036}
1037#else
1038static inline void boot_delay_msec(int level)
1039{
1040}
1041#endif
1042
1043static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1044module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1045
1046static size_t print_time(u64 ts, char *buf)
1047{
1048 unsigned long rem_nsec;
1049
1050 if (!printk_time)
1051 return 0;
1052
1053 rem_nsec = do_div(ts, 1000000000);
1054
1055 if (!buf)
1056 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1057
1058 return sprintf(buf, "[%5lu.%06lu] ",
1059 (unsigned long)ts, rem_nsec / 1000);
1060}
1061
1062static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1063{
1064 size_t len = 0;
1065 unsigned int prefix = (msg->facility << 3) | msg->level;
1066
1067 if (syslog) {
1068 if (buf) {
1069 len += sprintf(buf, "<%u>", prefix);
1070 } else {
1071 len += 3;
1072 if (prefix > 999)
1073 len += 3;
1074 else if (prefix > 99)
1075 len += 2;
1076 else if (prefix > 9)
1077 len++;
1078 }
1079 }
1080
1081 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1082 return len;
1083}
1084
1085static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1086 bool syslog, char *buf, size_t size)
1087{
1088 const char *text = log_text(msg);
1089 size_t text_size = msg->text_len;
1090 bool prefix = true;
1091 bool newline = true;
1092 size_t len = 0;
1093
1094 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1095 prefix = false;
1096
1097 if (msg->flags & LOG_CONT) {
1098 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1099 prefix = false;
1100
1101 if (!(msg->flags & LOG_NEWLINE))
1102 newline = false;
1103 }
1104
1105 do {
1106 const char *next = memchr(text, '\n', text_size);
1107 size_t text_len;
1108
1109 if (next) {
1110 text_len = next - text;
1111 next++;
1112 text_size -= next - text;
1113 } else {
1114 text_len = text_size;
1115 }
1116
1117 if (buf) {
1118 if (print_prefix(msg, syslog, NULL) +
1119 text_len + 1 >= size - len)
1120 break;
1121
1122 if (prefix)
1123 len += print_prefix(msg, syslog, buf + len);
1124 memcpy(buf + len, text, text_len);
1125 len += text_len;
1126 if (next || newline)
1127 buf[len++] = '\n';
1128 } else {
1129 /* SYSLOG_ACTION_* buffer size only calculation */
1130 if (prefix)
1131 len += print_prefix(msg, syslog, NULL);
1132 len += text_len;
1133 if (next || newline)
1134 len++;
1135 }
1136
1137 prefix = true;
1138 text = next;
1139 } while (text);
1140
1141 return len;
1142}
1143
1144static int syslog_print(char __user *buf, int size)
1145{
1146 char *text;
1147 struct printk_log *msg;
1148 int len = 0;
1149
1150 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1151 if (!text)
1152 return -ENOMEM;
1153
1154 while (size > 0) {
1155 size_t n;
1156 size_t skip;
1157
1158 raw_spin_lock_irq(&logbuf_lock);
1159 if (syslog_seq < log_first_seq) {
1160 /* messages are gone, move to first one */
1161 syslog_seq = log_first_seq;
1162 syslog_idx = log_first_idx;
1163 syslog_prev = 0;
1164 syslog_partial = 0;
1165 }
1166 if (syslog_seq == log_next_seq) {
1167 raw_spin_unlock_irq(&logbuf_lock);
1168 break;
1169 }
1170
1171 skip = syslog_partial;
1172 msg = log_from_idx(syslog_idx);
1173 n = msg_print_text(msg, syslog_prev, true, text,
1174 LOG_LINE_MAX + PREFIX_MAX);
1175 if (n - syslog_partial <= size) {
1176 /* message fits into buffer, move forward */
1177 syslog_idx = log_next(syslog_idx);
1178 syslog_seq++;
1179 syslog_prev = msg->flags;
1180 n -= syslog_partial;
1181 syslog_partial = 0;
1182 } else if (!len){
1183 /* partial read(), remember position */
1184 n = size;
1185 syslog_partial += n;
1186 } else
1187 n = 0;
1188 raw_spin_unlock_irq(&logbuf_lock);
1189
1190 if (!n)
1191 break;
1192
1193 if (copy_to_user(buf, text + skip, n)) {
1194 if (!len)
1195 len = -EFAULT;
1196 break;
1197 }
1198
1199 len += n;
1200 size -= n;
1201 buf += n;
1202 }
1203
1204 kfree(text);
1205 return len;
1206}
1207
1208static int syslog_print_all(char __user *buf, int size, bool clear)
1209{
1210 char *text;
1211 int len = 0;
1212
1213 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1214 if (!text)
1215 return -ENOMEM;
1216
1217 raw_spin_lock_irq(&logbuf_lock);
1218 if (buf) {
1219 u64 next_seq;
1220 u64 seq;
1221 u32 idx;
1222 enum log_flags prev;
1223
1224 /*
1225 * Find first record that fits, including all following records,
1226 * into the user-provided buffer for this dump.
1227 */
1228 seq = clear_seq;
1229 idx = clear_idx;
1230 prev = 0;
1231 while (seq < log_next_seq) {
1232 struct printk_log *msg = log_from_idx(idx);
1233
1234 len += msg_print_text(msg, prev, true, NULL, 0);
1235 prev = msg->flags;
1236 idx = log_next(idx);
1237 seq++;
1238 }
1239
1240 /* move first record forward until length fits into the buffer */
1241 seq = clear_seq;
1242 idx = clear_idx;
1243 prev = 0;
1244 while (len > size && seq < log_next_seq) {
1245 struct printk_log *msg = log_from_idx(idx);
1246
1247 len -= msg_print_text(msg, prev, true, NULL, 0);
1248 prev = msg->flags;
1249 idx = log_next(idx);
1250 seq++;
1251 }
1252
1253 /* last message fitting into this dump */
1254 next_seq = log_next_seq;
1255
1256 len = 0;
1257 while (len >= 0 && seq < next_seq) {
1258 struct printk_log *msg = log_from_idx(idx);
1259 int textlen;
1260
1261 textlen = msg_print_text(msg, prev, true, text,
1262 LOG_LINE_MAX + PREFIX_MAX);
1263 if (textlen < 0) {
1264 len = textlen;
1265 break;
1266 }
1267 idx = log_next(idx);
1268 seq++;
1269 prev = msg->flags;
1270
1271 raw_spin_unlock_irq(&logbuf_lock);
1272 if (copy_to_user(buf + len, text, textlen))
1273 len = -EFAULT;
1274 else
1275 len += textlen;
1276 raw_spin_lock_irq(&logbuf_lock);
1277
1278 if (seq < log_first_seq) {
1279 /* messages are gone, move to next one */
1280 seq = log_first_seq;
1281 idx = log_first_idx;
1282 prev = 0;
1283 }
1284 }
1285 }
1286
1287 if (clear) {
1288 clear_seq = log_next_seq;
1289 clear_idx = log_next_idx;
1290 }
1291 raw_spin_unlock_irq(&logbuf_lock);
1292
1293 kfree(text);
1294 return len;
1295}
1296
1297int do_syslog(int type, char __user *buf, int len, int source)
1298{
1299 bool clear = false;
1300 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1301 int error;
1302
1303 error = check_syslog_permissions(type, source);
1304 if (error)
1305 goto out;
1306
1307 switch (type) {
1308 case SYSLOG_ACTION_CLOSE: /* Close log */
1309 break;
1310 case SYSLOG_ACTION_OPEN: /* Open log */
1311 break;
1312 case SYSLOG_ACTION_READ: /* Read from log */
1313 error = -EINVAL;
1314 if (!buf || len < 0)
1315 goto out;
1316 error = 0;
1317 if (!len)
1318 goto out;
1319 if (!access_ok(VERIFY_WRITE, buf, len)) {
1320 error = -EFAULT;
1321 goto out;
1322 }
1323 error = wait_event_interruptible(log_wait,
1324 syslog_seq != log_next_seq);
1325 if (error)
1326 goto out;
1327 error = syslog_print(buf, len);
1328 break;
1329 /* Read/clear last kernel messages */
1330 case SYSLOG_ACTION_READ_CLEAR:
1331 clear = true;
1332 /* FALL THRU */
1333 /* Read last kernel messages */
1334 case SYSLOG_ACTION_READ_ALL:
1335 error = -EINVAL;
1336 if (!buf || len < 0)
1337 goto out;
1338 error = 0;
1339 if (!len)
1340 goto out;
1341 if (!access_ok(VERIFY_WRITE, buf, len)) {
1342 error = -EFAULT;
1343 goto out;
1344 }
1345 error = syslog_print_all(buf, len, clear);
1346 break;
1347 /* Clear ring buffer */
1348 case SYSLOG_ACTION_CLEAR:
1349 syslog_print_all(NULL, 0, true);
1350 break;
1351 /* Disable logging to console */
1352 case SYSLOG_ACTION_CONSOLE_OFF:
1353 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1354 saved_console_loglevel = console_loglevel;
1355 console_loglevel = minimum_console_loglevel;
1356 break;
1357 /* Enable logging to console */
1358 case SYSLOG_ACTION_CONSOLE_ON:
1359 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1360 console_loglevel = saved_console_loglevel;
1361 saved_console_loglevel = LOGLEVEL_DEFAULT;
1362 }
1363 break;
1364 /* Set level of messages printed to console */
1365 case SYSLOG_ACTION_CONSOLE_LEVEL:
1366 error = -EINVAL;
1367 if (len < 1 || len > 8)
1368 goto out;
1369 if (len < minimum_console_loglevel)
1370 len = minimum_console_loglevel;
1371 console_loglevel = len;
1372 /* Implicitly re-enable logging to console */
1373 saved_console_loglevel = LOGLEVEL_DEFAULT;
1374 error = 0;
1375 break;
1376 /* Number of chars in the log buffer */
1377 case SYSLOG_ACTION_SIZE_UNREAD:
1378 raw_spin_lock_irq(&logbuf_lock);
1379 if (syslog_seq < log_first_seq) {
1380 /* messages are gone, move to first one */
1381 syslog_seq = log_first_seq;
1382 syslog_idx = log_first_idx;
1383 syslog_prev = 0;
1384 syslog_partial = 0;
1385 }
1386 if (source == SYSLOG_FROM_PROC) {
1387 /*
1388 * Short-cut for poll(/"proc/kmsg") which simply checks
1389 * for pending data, not the size; return the count of
1390 * records, not the length.
1391 */
1392 error = log_next_seq - syslog_seq;
1393 } else {
1394 u64 seq = syslog_seq;
1395 u32 idx = syslog_idx;
1396 enum log_flags prev = syslog_prev;
1397
1398 error = 0;
1399 while (seq < log_next_seq) {
1400 struct printk_log *msg = log_from_idx(idx);
1401
1402 error += msg_print_text(msg, prev, true, NULL, 0);
1403 idx = log_next(idx);
1404 seq++;
1405 prev = msg->flags;
1406 }
1407 error -= syslog_partial;
1408 }
1409 raw_spin_unlock_irq(&logbuf_lock);
1410 break;
1411 /* Size of the log buffer */
1412 case SYSLOG_ACTION_SIZE_BUFFER:
1413 error = log_buf_len;
1414 break;
1415 default:
1416 error = -EINVAL;
1417 break;
1418 }
1419out:
1420 return error;
1421}
1422
1423SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1424{
1425 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1426}
1427
1428/*
1429 * Call the console drivers, asking them to write out
1430 * log_buf[start] to log_buf[end - 1].
1431 * The console_lock must be held.
1432 */
1433static void call_console_drivers(int level,
1434 const char *ext_text, size_t ext_len,
1435 const char *text, size_t len)
1436{
1437 struct console *con;
1438
1439 trace_console(text, len);
1440
1441 if (level >= console_loglevel && !ignore_loglevel)
1442 return;
1443 if (!console_drivers)
1444 return;
1445
1446 for_each_console(con) {
1447 if (exclusive_console && con != exclusive_console)
1448 continue;
1449 if (!(con->flags & CON_ENABLED))
1450 continue;
1451 if (!con->write)
1452 continue;
1453 if (!cpu_online(smp_processor_id()) &&
1454 !(con->flags & CON_ANYTIME))
1455 continue;
1456 if (con->flags & CON_EXTENDED)
1457 con->write(con, ext_text, ext_len);
1458 else
1459 con->write(con, text, len);
1460 }
1461}
1462
1463/*
1464 * Zap console related locks when oopsing.
1465 * To leave time for slow consoles to print a full oops,
1466 * only zap at most once every 30 seconds.
1467 */
1468static void zap_locks(void)
1469{
1470 static unsigned long oops_timestamp;
1471
1472 if (time_after_eq(jiffies, oops_timestamp) &&
1473 !time_after(jiffies, oops_timestamp + 30 * HZ))
1474 return;
1475
1476 oops_timestamp = jiffies;
1477
1478 debug_locks_off();
1479 /* If a crash is occurring, make sure we can't deadlock */
1480 raw_spin_lock_init(&logbuf_lock);
1481 /* And make sure that we print immediately */
1482 sema_init(&console_sem, 1);
1483}
1484
1485int printk_delay_msec __read_mostly;
1486
1487static inline void printk_delay(void)
1488{
1489 if (unlikely(printk_delay_msec)) {
1490 int m = printk_delay_msec;
1491
1492 while (m--) {
1493 mdelay(1);
1494 touch_nmi_watchdog();
1495 }
1496 }
1497}
1498
1499/*
1500 * Continuation lines are buffered, and not committed to the record buffer
1501 * until the line is complete, or a race forces it. The line fragments
1502 * though, are printed immediately to the consoles to ensure everything has
1503 * reached the console in case of a kernel crash.
1504 */
1505static struct cont {
1506 char buf[LOG_LINE_MAX];
1507 size_t len; /* length == 0 means unused buffer */
1508 size_t cons; /* bytes written to console */
1509 struct task_struct *owner; /* task of first print*/
1510 u64 ts_nsec; /* time of first print */
1511 u8 level; /* log level of first message */
1512 u8 facility; /* log facility of first message */
1513 enum log_flags flags; /* prefix, newline flags */
1514 bool flushed:1; /* buffer sealed and committed */
1515} cont;
1516
1517static void cont_flush(enum log_flags flags)
1518{
1519 if (cont.flushed)
1520 return;
1521 if (cont.len == 0)
1522 return;
1523
1524 if (cont.cons) {
1525 /*
1526 * If a fragment of this line was directly flushed to the
1527 * console; wait for the console to pick up the rest of the
1528 * line. LOG_NOCONS suppresses a duplicated output.
1529 */
1530 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1531 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1532 cont.flags = flags;
1533 cont.flushed = true;
1534 } else {
1535 /*
1536 * If no fragment of this line ever reached the console,
1537 * just submit it to the store and free the buffer.
1538 */
1539 log_store(cont.facility, cont.level, flags, 0,
1540 NULL, 0, cont.buf, cont.len);
1541 cont.len = 0;
1542 }
1543}
1544
1545static bool cont_add(int facility, int level, const char *text, size_t len)
1546{
1547 if (cont.len && cont.flushed)
1548 return false;
1549
1550 /*
1551 * If ext consoles are present, flush and skip in-kernel
1552 * continuation. See nr_ext_console_drivers definition. Also, if
1553 * the line gets too long, split it up in separate records.
1554 */
1555 if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
1556 cont_flush(LOG_CONT);
1557 return false;
1558 }
1559
1560 if (!cont.len) {
1561 cont.facility = facility;
1562 cont.level = level;
1563 cont.owner = current;
1564 cont.ts_nsec = local_clock();
1565 cont.flags = 0;
1566 cont.cons = 0;
1567 cont.flushed = false;
1568 }
1569
1570 memcpy(cont.buf + cont.len, text, len);
1571 cont.len += len;
1572
1573 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1574 cont_flush(LOG_CONT);
1575
1576 return true;
1577}
1578
1579static size_t cont_print_text(char *text, size_t size)
1580{
1581 size_t textlen = 0;
1582 size_t len;
1583
1584 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1585 textlen += print_time(cont.ts_nsec, text);
1586 size -= textlen;
1587 }
1588
1589 len = cont.len - cont.cons;
1590 if (len > 0) {
1591 if (len+1 > size)
1592 len = size-1;
1593 memcpy(text + textlen, cont.buf + cont.cons, len);
1594 textlen += len;
1595 cont.cons = cont.len;
1596 }
1597
1598 if (cont.flushed) {
1599 if (cont.flags & LOG_NEWLINE)
1600 text[textlen++] = '\n';
1601 /* got everything, release buffer */
1602 cont.len = 0;
1603 }
1604 return textlen;
1605}
1606
1607asmlinkage int vprintk_emit(int facility, int level,
1608 const char *dict, size_t dictlen,
1609 const char *fmt, va_list args)
1610{
1611 static bool recursion_bug;
1612 static char textbuf[LOG_LINE_MAX];
1613 char *text = textbuf;
1614 size_t text_len = 0;
1615 enum log_flags lflags = 0;
1616 unsigned long flags;
1617 int this_cpu;
1618 int printed_len = 0;
1619 bool in_sched = false;
1620 /* cpu currently holding logbuf_lock in this function */
1621 static unsigned int logbuf_cpu = UINT_MAX;
1622
1623 if (level == LOGLEVEL_SCHED) {
1624 level = LOGLEVEL_DEFAULT;
1625 in_sched = true;
1626 }
1627
1628 boot_delay_msec(level);
1629 printk_delay();
1630
1631 local_irq_save(flags);
1632 this_cpu = smp_processor_id();
1633
1634 /*
1635 * Ouch, printk recursed into itself!
1636 */
1637 if (unlikely(logbuf_cpu == this_cpu)) {
1638 /*
1639 * If a crash is occurring during printk() on this CPU,
1640 * then try to get the crash message out but make sure
1641 * we can't deadlock. Otherwise just return to avoid the
1642 * recursion and return - but flag the recursion so that
1643 * it can be printed at the next appropriate moment:
1644 */
1645 if (!oops_in_progress && !lockdep_recursing(current)) {
1646 recursion_bug = true;
1647 local_irq_restore(flags);
1648 return 0;
1649 }
1650 zap_locks();
1651 }
1652
1653 lockdep_off();
1654 /* This stops the holder of console_sem just where we want him */
1655 raw_spin_lock(&logbuf_lock);
1656 logbuf_cpu = this_cpu;
1657
1658 if (unlikely(recursion_bug)) {
1659 static const char recursion_msg[] =
1660 "BUG: recent printk recursion!";
1661
1662 recursion_bug = false;
1663 /* emit KERN_CRIT message */
1664 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1665 NULL, 0, recursion_msg,
1666 strlen(recursion_msg));
1667 }
1668
1669 /*
1670 * The printf needs to come first; we need the syslog
1671 * prefix which might be passed-in as a parameter.
1672 */
1673 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1674
1675 /* mark and strip a trailing newline */
1676 if (text_len && text[text_len-1] == '\n') {
1677 text_len--;
1678 lflags |= LOG_NEWLINE;
1679 }
1680
1681 /* strip kernel syslog prefix and extract log level or control flags */
1682 if (facility == 0) {
1683 int kern_level = printk_get_level(text);
1684
1685 if (kern_level) {
1686 const char *end_of_header = printk_skip_level(text);
1687 switch (kern_level) {
1688 case '0' ... '7':
1689 if (level == LOGLEVEL_DEFAULT)
1690 level = kern_level - '0';
1691 /* fallthrough */
1692 case 'd': /* KERN_DEFAULT */
1693 lflags |= LOG_PREFIX;
1694 }
1695 /*
1696 * No need to check length here because vscnprintf
1697 * put '\0' at the end of the string. Only valid and
1698 * newly printed level is detected.
1699 */
1700 text_len -= end_of_header - text;
1701 text = (char *)end_of_header;
1702 }
1703 }
1704
1705 if (level == LOGLEVEL_DEFAULT)
1706 level = default_message_loglevel;
1707
1708 if (dict)
1709 lflags |= LOG_PREFIX|LOG_NEWLINE;
1710
1711 if (!(lflags & LOG_NEWLINE)) {
1712 /*
1713 * Flush the conflicting buffer. An earlier newline was missing,
1714 * or another task also prints continuation lines.
1715 */
1716 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1717 cont_flush(LOG_NEWLINE);
1718
1719 /* buffer line if possible, otherwise store it right away */
1720 if (cont_add(facility, level, text, text_len))
1721 printed_len += text_len;
1722 else
1723 printed_len += log_store(facility, level,
1724 lflags | LOG_CONT, 0,
1725 dict, dictlen, text, text_len);
1726 } else {
1727 bool stored = false;
1728
1729 /*
1730 * If an earlier newline was missing and it was the same task,
1731 * either merge it with the current buffer and flush, or if
1732 * there was a race with interrupts (prefix == true) then just
1733 * flush it out and store this line separately.
1734 * If the preceding printk was from a different task and missed
1735 * a newline, flush and append the newline.
1736 */
1737 if (cont.len) {
1738 if (cont.owner == current && !(lflags & LOG_PREFIX))
1739 stored = cont_add(facility, level, text,
1740 text_len);
1741 cont_flush(LOG_NEWLINE);
1742 }
1743
1744 if (stored)
1745 printed_len += text_len;
1746 else
1747 printed_len += log_store(facility, level, lflags, 0,
1748 dict, dictlen, text, text_len);
1749 }
1750
1751 logbuf_cpu = UINT_MAX;
1752 raw_spin_unlock(&logbuf_lock);
1753 lockdep_on();
1754 local_irq_restore(flags);
1755
1756 /* If called from the scheduler, we can not call up(). */
1757 if (!in_sched) {
1758 lockdep_off();
1759 /*
1760 * Try to acquire and then immediately release the console
1761 * semaphore. The release will print out buffers and wake up
1762 * /dev/kmsg and syslog() users.
1763 */
1764 if (console_trylock())
1765 console_unlock();
1766 lockdep_on();
1767 }
1768
1769 return printed_len;
1770}
1771EXPORT_SYMBOL(vprintk_emit);
1772
1773asmlinkage int vprintk(const char *fmt, va_list args)
1774{
1775 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1776}
1777EXPORT_SYMBOL(vprintk);
1778
1779asmlinkage int printk_emit(int facility, int level,
1780 const char *dict, size_t dictlen,
1781 const char *fmt, ...)
1782{
1783 va_list args;
1784 int r;
1785
1786 va_start(args, fmt);
1787 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1788 va_end(args);
1789
1790 return r;
1791}
1792EXPORT_SYMBOL(printk_emit);
1793
1794int vprintk_default(const char *fmt, va_list args)
1795{
1796 int r;
1797
1798#ifdef CONFIG_KGDB_KDB
1799 if (unlikely(kdb_trap_printk)) {
1800 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1801 return r;
1802 }
1803#endif
1804 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1805
1806 return r;
1807}
1808EXPORT_SYMBOL_GPL(vprintk_default);
1809
1810/*
1811 * This allows printk to be diverted to another function per cpu.
1812 * This is useful for calling printk functions from within NMI
1813 * without worrying about race conditions that can lock up the
1814 * box.
1815 */
1816DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
1817
1818/**
1819 * printk - print a kernel message
1820 * @fmt: format string
1821 *
1822 * This is printk(). It can be called from any context. We want it to work.
1823 *
1824 * We try to grab the console_lock. If we succeed, it's easy - we log the
1825 * output and call the console drivers. If we fail to get the semaphore, we
1826 * place the output into the log buffer and return. The current holder of
1827 * the console_sem will notice the new output in console_unlock(); and will
1828 * send it to the consoles before releasing the lock.
1829 *
1830 * One effect of this deferred printing is that code which calls printk() and
1831 * then changes console_loglevel may break. This is because console_loglevel
1832 * is inspected when the actual printing occurs.
1833 *
1834 * See also:
1835 * printf(3)
1836 *
1837 * See the vsnprintf() documentation for format string extensions over C99.
1838 */
1839asmlinkage __visible int printk(const char *fmt, ...)
1840{
1841 printk_func_t vprintk_func;
1842 va_list args;
1843 int r;
1844
1845 va_start(args, fmt);
1846
1847 /*
1848 * If a caller overrides the per_cpu printk_func, then it needs
1849 * to disable preemption when calling printk(). Otherwise
1850 * the printk_func should be set to the default. No need to
1851 * disable preemption here.
1852 */
1853 vprintk_func = this_cpu_read(printk_func);
1854 r = vprintk_func(fmt, args);
1855
1856 va_end(args);
1857
1858 return r;
1859}
1860EXPORT_SYMBOL(printk);
1861
1862#else /* CONFIG_PRINTK */
1863
1864#define LOG_LINE_MAX 0
1865#define PREFIX_MAX 0
1866
1867static u64 syslog_seq;
1868static u32 syslog_idx;
1869static u64 console_seq;
1870static u32 console_idx;
1871static enum log_flags syslog_prev;
1872static u64 log_first_seq;
1873static u32 log_first_idx;
1874static u64 log_next_seq;
1875static enum log_flags console_prev;
1876static struct cont {
1877 size_t len;
1878 size_t cons;
1879 u8 level;
1880 bool flushed:1;
1881} cont;
1882static char *log_text(const struct printk_log *msg) { return NULL; }
1883static char *log_dict(const struct printk_log *msg) { return NULL; }
1884static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1885static u32 log_next(u32 idx) { return 0; }
1886static ssize_t msg_print_ext_header(char *buf, size_t size,
1887 struct printk_log *msg, u64 seq,
1888 enum log_flags prev_flags) { return 0; }
1889static ssize_t msg_print_ext_body(char *buf, size_t size,
1890 char *dict, size_t dict_len,
1891 char *text, size_t text_len) { return 0; }
1892static void call_console_drivers(int level,
1893 const char *ext_text, size_t ext_len,
1894 const char *text, size_t len) {}
1895static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1896 bool syslog, char *buf, size_t size) { return 0; }
1897static size_t cont_print_text(char *text, size_t size) { return 0; }
1898
1899/* Still needs to be defined for users */
1900DEFINE_PER_CPU(printk_func_t, printk_func);
1901
1902#endif /* CONFIG_PRINTK */
1903
1904#ifdef CONFIG_EARLY_PRINTK
1905struct console *early_console;
1906
1907asmlinkage __visible void early_printk(const char *fmt, ...)
1908{
1909 va_list ap;
1910 char buf[512];
1911 int n;
1912
1913 if (!early_console)
1914 return;
1915
1916 va_start(ap, fmt);
1917 n = vscnprintf(buf, sizeof(buf), fmt, ap);
1918 va_end(ap);
1919
1920 early_console->write(early_console, buf, n);
1921}
1922#endif
1923
1924static int __add_preferred_console(char *name, int idx, char *options,
1925 char *brl_options)
1926{
1927 struct console_cmdline *c;
1928 int i;
1929
1930 /*
1931 * See if this tty is not yet registered, and
1932 * if we have a slot free.
1933 */
1934 for (i = 0, c = console_cmdline;
1935 i < MAX_CMDLINECONSOLES && c->name[0];
1936 i++, c++) {
1937 if (strcmp(c->name, name) == 0 && c->index == idx) {
1938 if (!brl_options)
1939 selected_console = i;
1940 return 0;
1941 }
1942 }
1943 if (i == MAX_CMDLINECONSOLES)
1944 return -E2BIG;
1945 if (!brl_options)
1946 selected_console = i;
1947 strlcpy(c->name, name, sizeof(c->name));
1948 c->options = options;
1949 braille_set_options(c, brl_options);
1950
1951 c->index = idx;
1952 return 0;
1953}
1954/*
1955 * Set up a console. Called via do_early_param() in init/main.c
1956 * for each "console=" parameter in the boot command line.
1957 */
1958static int __init console_setup(char *str)
1959{
1960 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
1961 char *s, *options, *brl_options = NULL;
1962 int idx;
1963
1964 if (_braille_console_setup(&str, &brl_options))
1965 return 1;
1966
1967 /*
1968 * Decode str into name, index, options.
1969 */
1970 if (str[0] >= '0' && str[0] <= '9') {
1971 strcpy(buf, "ttyS");
1972 strncpy(buf + 4, str, sizeof(buf) - 5);
1973 } else {
1974 strncpy(buf, str, sizeof(buf) - 1);
1975 }
1976 buf[sizeof(buf) - 1] = 0;
1977 options = strchr(str, ',');
1978 if (options)
1979 *(options++) = 0;
1980#ifdef __sparc__
1981 if (!strcmp(str, "ttya"))
1982 strcpy(buf, "ttyS0");
1983 if (!strcmp(str, "ttyb"))
1984 strcpy(buf, "ttyS1");
1985#endif
1986 for (s = buf; *s; s++)
1987 if (isdigit(*s) || *s == ',')
1988 break;
1989 idx = simple_strtoul(s, NULL, 10);
1990 *s = 0;
1991
1992 __add_preferred_console(buf, idx, options, brl_options);
1993 console_set_on_cmdline = 1;
1994 return 1;
1995}
1996__setup("console=", console_setup);
1997
1998/**
1999 * add_preferred_console - add a device to the list of preferred consoles.
2000 * @name: device name
2001 * @idx: device index
2002 * @options: options for this console
2003 *
2004 * The last preferred console added will be used for kernel messages
2005 * and stdin/out/err for init. Normally this is used by console_setup
2006 * above to handle user-supplied console arguments; however it can also
2007 * be used by arch-specific code either to override the user or more
2008 * commonly to provide a default console (ie from PROM variables) when
2009 * the user has not supplied one.
2010 */
2011int add_preferred_console(char *name, int idx, char *options)
2012{
2013 return __add_preferred_console(name, idx, options, NULL);
2014}
2015
2016bool console_suspend_enabled = true;
2017EXPORT_SYMBOL(console_suspend_enabled);
2018
2019static int __init console_suspend_disable(char *str)
2020{
2021 console_suspend_enabled = false;
2022 return 1;
2023}
2024__setup("no_console_suspend", console_suspend_disable);
2025module_param_named(console_suspend, console_suspend_enabled,
2026 bool, S_IRUGO | S_IWUSR);
2027MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2028 " and hibernate operations");
2029
2030/**
2031 * suspend_console - suspend the console subsystem
2032 *
2033 * This disables printk() while we go into suspend states
2034 */
2035void suspend_console(void)
2036{
2037 if (!console_suspend_enabled)
2038 return;
2039 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2040 console_lock();
2041 console_suspended = 1;
2042 up_console_sem();
2043}
2044
2045void resume_console(void)
2046{
2047 if (!console_suspend_enabled)
2048 return;
2049 down_console_sem();
2050 console_suspended = 0;
2051 console_unlock();
2052}
2053
2054/**
2055 * console_cpu_notify - print deferred console messages after CPU hotplug
2056 * @self: notifier struct
2057 * @action: CPU hotplug event
2058 * @hcpu: unused
2059 *
2060 * If printk() is called from a CPU that is not online yet, the messages
2061 * will be spooled but will not show up on the console. This function is
2062 * called when a new CPU comes online (or fails to come up), and ensures
2063 * that any such output gets printed.
2064 */
2065static int console_cpu_notify(struct notifier_block *self,
2066 unsigned long action, void *hcpu)
2067{
2068 switch (action) {
2069 case CPU_ONLINE:
2070 case CPU_DEAD:
2071 case CPU_DOWN_FAILED:
2072 case CPU_UP_CANCELED:
2073 console_lock();
2074 console_unlock();
2075 }
2076 return NOTIFY_OK;
2077}
2078
2079/**
2080 * console_lock - lock the console system for exclusive use.
2081 *
2082 * Acquires a lock which guarantees that the caller has
2083 * exclusive access to the console system and the console_drivers list.
2084 *
2085 * Can sleep, returns nothing.
2086 */
2087void console_lock(void)
2088{
2089 might_sleep();
2090
2091 down_console_sem();
2092 if (console_suspended)
2093 return;
2094 console_locked = 1;
2095 console_may_schedule = 1;
2096}
2097EXPORT_SYMBOL(console_lock);
2098
2099/**
2100 * console_trylock - try to lock the console system for exclusive use.
2101 *
2102 * Try to acquire a lock which guarantees that the caller has exclusive
2103 * access to the console system and the console_drivers list.
2104 *
2105 * returns 1 on success, and 0 on failure to acquire the lock.
2106 */
2107int console_trylock(void)
2108{
2109 if (down_trylock_console_sem())
2110 return 0;
2111 if (console_suspended) {
2112 up_console_sem();
2113 return 0;
2114 }
2115 console_locked = 1;
2116 /*
2117 * When PREEMPT_COUNT disabled we can't reliably detect if it's
2118 * safe to schedule (e.g. calling printk while holding a spin_lock),
2119 * because preempt_disable()/preempt_enable() are just barriers there
2120 * and preempt_count() is always 0.
2121 *
2122 * RCU read sections have a separate preemption counter when
2123 * PREEMPT_RCU enabled thus we must take extra care and check
2124 * rcu_preempt_depth(), otherwise RCU read sections modify
2125 * preempt_count().
2126 */
2127 console_may_schedule = !oops_in_progress &&
2128 preemptible() &&
2129 !rcu_preempt_depth();
2130 return 1;
2131}
2132EXPORT_SYMBOL(console_trylock);
2133
2134int is_console_locked(void)
2135{
2136 return console_locked;
2137}
2138
2139/*
2140 * Check if we have any console that is capable of printing while cpu is
2141 * booting or shutting down. Requires console_sem.
2142 */
2143static int have_callable_console(void)
2144{
2145 struct console *con;
2146
2147 for_each_console(con)
2148 if ((con->flags & CON_ENABLED) &&
2149 (con->flags & CON_ANYTIME))
2150 return 1;
2151
2152 return 0;
2153}
2154
2155/*
2156 * Can we actually use the console at this time on this cpu?
2157 *
2158 * Console drivers may assume that per-cpu resources have been allocated. So
2159 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2160 * call them until this CPU is officially up.
2161 */
2162static inline int can_use_console(void)
2163{
2164 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2165}
2166
2167static void console_cont_flush(char *text, size_t size)
2168{
2169 unsigned long flags;
2170 size_t len;
2171
2172 raw_spin_lock_irqsave(&logbuf_lock, flags);
2173
2174 if (!cont.len)
2175 goto out;
2176
2177 /*
2178 * We still queue earlier records, likely because the console was
2179 * busy. The earlier ones need to be printed before this one, we
2180 * did not flush any fragment so far, so just let it queue up.
2181 */
2182 if (console_seq < log_next_seq && !cont.cons)
2183 goto out;
2184
2185 len = cont_print_text(text, size);
2186 raw_spin_unlock(&logbuf_lock);
2187 stop_critical_timings();
2188 call_console_drivers(cont.level, NULL, 0, text, len);
2189 start_critical_timings();
2190 local_irq_restore(flags);
2191 return;
2192out:
2193 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2194}
2195
2196/**
2197 * console_unlock - unlock the console system
2198 *
2199 * Releases the console_lock which the caller holds on the console system
2200 * and the console driver list.
2201 *
2202 * While the console_lock was held, console output may have been buffered
2203 * by printk(). If this is the case, console_unlock(); emits
2204 * the output prior to releasing the lock.
2205 *
2206 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2207 *
2208 * console_unlock(); may be called from any context.
2209 */
2210void console_unlock(void)
2211{
2212 static char ext_text[CONSOLE_EXT_LOG_MAX];
2213 static char text[LOG_LINE_MAX + PREFIX_MAX];
2214 static u64 seen_seq;
2215 unsigned long flags;
2216 bool wake_klogd = false;
2217 bool do_cond_resched, retry;
2218
2219 if (console_suspended) {
2220 up_console_sem();
2221 return;
2222 }
2223
2224 /*
2225 * Console drivers are called under logbuf_lock, so
2226 * @console_may_schedule should be cleared before; however, we may
2227 * end up dumping a lot of lines, for example, if called from
2228 * console registration path, and should invoke cond_resched()
2229 * between lines if allowable. Not doing so can cause a very long
2230 * scheduling stall on a slow console leading to RCU stall and
2231 * softlockup warnings which exacerbate the issue with more
2232 * messages practically incapacitating the system.
2233 */
2234 do_cond_resched = console_may_schedule;
2235 console_may_schedule = 0;
2236
2237again:
2238 /*
2239 * We released the console_sem lock, so we need to recheck if
2240 * cpu is online and (if not) is there at least one CON_ANYTIME
2241 * console.
2242 */
2243 if (!can_use_console()) {
2244 console_locked = 0;
2245 up_console_sem();
2246 return;
2247 }
2248
2249 /* flush buffered message fragment immediately to console */
2250 console_cont_flush(text, sizeof(text));
2251
2252 for (;;) {
2253 struct printk_log *msg;
2254 size_t ext_len = 0;
2255 size_t len;
2256 int level;
2257
2258 raw_spin_lock_irqsave(&logbuf_lock, flags);
2259 if (seen_seq != log_next_seq) {
2260 wake_klogd = true;
2261 seen_seq = log_next_seq;
2262 }
2263
2264 if (console_seq < log_first_seq) {
2265 len = sprintf(text, "** %u printk messages dropped ** ",
2266 (unsigned)(log_first_seq - console_seq));
2267
2268 /* messages are gone, move to first one */
2269 console_seq = log_first_seq;
2270 console_idx = log_first_idx;
2271 console_prev = 0;
2272 } else {
2273 len = 0;
2274 }
2275skip:
2276 if (console_seq == log_next_seq)
2277 break;
2278
2279 msg = log_from_idx(console_idx);
2280 if (msg->flags & LOG_NOCONS) {
2281 /*
2282 * Skip record we have buffered and already printed
2283 * directly to the console when we received it.
2284 */
2285 console_idx = log_next(console_idx);
2286 console_seq++;
2287 /*
2288 * We will get here again when we register a new
2289 * CON_PRINTBUFFER console. Clear the flag so we
2290 * will properly dump everything later.
2291 */
2292 msg->flags &= ~LOG_NOCONS;
2293 console_prev = msg->flags;
2294 goto skip;
2295 }
2296
2297 level = msg->level;
2298 len += msg_print_text(msg, console_prev, false,
2299 text + len, sizeof(text) - len);
2300 if (nr_ext_console_drivers) {
2301 ext_len = msg_print_ext_header(ext_text,
2302 sizeof(ext_text),
2303 msg, console_seq, console_prev);
2304 ext_len += msg_print_ext_body(ext_text + ext_len,
2305 sizeof(ext_text) - ext_len,
2306 log_dict(msg), msg->dict_len,
2307 log_text(msg), msg->text_len);
2308 }
2309 console_idx = log_next(console_idx);
2310 console_seq++;
2311 console_prev = msg->flags;
2312 raw_spin_unlock(&logbuf_lock);
2313
2314 stop_critical_timings(); /* don't trace print latency */
2315 call_console_drivers(level, ext_text, ext_len, text, len);
2316 start_critical_timings();
2317 local_irq_restore(flags);
2318
2319 if (do_cond_resched)
2320 cond_resched();
2321 }
2322 console_locked = 0;
2323
2324 /* Release the exclusive_console once it is used */
2325 if (unlikely(exclusive_console))
2326 exclusive_console = NULL;
2327
2328 raw_spin_unlock(&logbuf_lock);
2329
2330 up_console_sem();
2331
2332 /*
2333 * Someone could have filled up the buffer again, so re-check if there's
2334 * something to flush. In case we cannot trylock the console_sem again,
2335 * there's a new owner and the console_unlock() from them will do the
2336 * flush, no worries.
2337 */
2338 raw_spin_lock(&logbuf_lock);
2339 retry = console_seq != log_next_seq;
2340 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2341
2342 if (retry && console_trylock())
2343 goto again;
2344
2345 if (wake_klogd)
2346 wake_up_klogd();
2347}
2348EXPORT_SYMBOL(console_unlock);
2349
2350/**
2351 * console_conditional_schedule - yield the CPU if required
2352 *
2353 * If the console code is currently allowed to sleep, and
2354 * if this CPU should yield the CPU to another task, do
2355 * so here.
2356 *
2357 * Must be called within console_lock();.
2358 */
2359void __sched console_conditional_schedule(void)
2360{
2361 if (console_may_schedule)
2362 cond_resched();
2363}
2364EXPORT_SYMBOL(console_conditional_schedule);
2365
2366void console_unblank(void)
2367{
2368 struct console *c;
2369
2370 /*
2371 * console_unblank can no longer be called in interrupt context unless
2372 * oops_in_progress is set to 1..
2373 */
2374 if (oops_in_progress) {
2375 if (down_trylock_console_sem() != 0)
2376 return;
2377 } else
2378 console_lock();
2379
2380 console_locked = 1;
2381 console_may_schedule = 0;
2382 for_each_console(c)
2383 if ((c->flags & CON_ENABLED) && c->unblank)
2384 c->unblank();
2385 console_unlock();
2386}
2387
2388/**
2389 * console_flush_on_panic - flush console content on panic
2390 *
2391 * Immediately output all pending messages no matter what.
2392 */
2393void console_flush_on_panic(void)
2394{
2395 /*
2396 * If someone else is holding the console lock, trylock will fail
2397 * and may_schedule may be set. Ignore and proceed to unlock so
2398 * that messages are flushed out. As this can be called from any
2399 * context and we don't want to get preempted while flushing,
2400 * ensure may_schedule is cleared.
2401 */
2402 console_trylock();
2403 console_may_schedule = 0;
2404 console_unlock();
2405}
2406
2407/*
2408 * Return the console tty driver structure and its associated index
2409 */
2410struct tty_driver *console_device(int *index)
2411{
2412 struct console *c;
2413 struct tty_driver *driver = NULL;
2414
2415 console_lock();
2416 for_each_console(c) {
2417 if (!c->device)
2418 continue;
2419 driver = c->device(c, index);
2420 if (driver)
2421 break;
2422 }
2423 console_unlock();
2424 return driver;
2425}
2426
2427/*
2428 * Prevent further output on the passed console device so that (for example)
2429 * serial drivers can disable console output before suspending a port, and can
2430 * re-enable output afterwards.
2431 */
2432void console_stop(struct console *console)
2433{
2434 console_lock();
2435 console->flags &= ~CON_ENABLED;
2436 console_unlock();
2437}
2438EXPORT_SYMBOL(console_stop);
2439
2440void console_start(struct console *console)
2441{
2442 console_lock();
2443 console->flags |= CON_ENABLED;
2444 console_unlock();
2445}
2446EXPORT_SYMBOL(console_start);
2447
2448static int __read_mostly keep_bootcon;
2449
2450static int __init keep_bootcon_setup(char *str)
2451{
2452 keep_bootcon = 1;
2453 pr_info("debug: skip boot console de-registration.\n");
2454
2455 return 0;
2456}
2457
2458early_param("keep_bootcon", keep_bootcon_setup);
2459
2460/*
2461 * The console driver calls this routine during kernel initialization
2462 * to register the console printing procedure with printk() and to
2463 * print any messages that were printed by the kernel before the
2464 * console driver was initialized.
2465 *
2466 * This can happen pretty early during the boot process (because of
2467 * early_printk) - sometimes before setup_arch() completes - be careful
2468 * of what kernel features are used - they may not be initialised yet.
2469 *
2470 * There are two types of consoles - bootconsoles (early_printk) and
2471 * "real" consoles (everything which is not a bootconsole) which are
2472 * handled differently.
2473 * - Any number of bootconsoles can be registered at any time.
2474 * - As soon as a "real" console is registered, all bootconsoles
2475 * will be unregistered automatically.
2476 * - Once a "real" console is registered, any attempt to register a
2477 * bootconsoles will be rejected
2478 */
2479void register_console(struct console *newcon)
2480{
2481 int i;
2482 unsigned long flags;
2483 struct console *bcon = NULL;
2484 struct console_cmdline *c;
2485
2486 if (console_drivers)
2487 for_each_console(bcon)
2488 if (WARN(bcon == newcon,
2489 "console '%s%d' already registered\n",
2490 bcon->name, bcon->index))
2491 return;
2492
2493 /*
2494 * before we register a new CON_BOOT console, make sure we don't
2495 * already have a valid console
2496 */
2497 if (console_drivers && newcon->flags & CON_BOOT) {
2498 /* find the last or real console */
2499 for_each_console(bcon) {
2500 if (!(bcon->flags & CON_BOOT)) {
2501 pr_info("Too late to register bootconsole %s%d\n",
2502 newcon->name, newcon->index);
2503 return;
2504 }
2505 }
2506 }
2507
2508 if (console_drivers && console_drivers->flags & CON_BOOT)
2509 bcon = console_drivers;
2510
2511 if (preferred_console < 0 || bcon || !console_drivers)
2512 preferred_console = selected_console;
2513
2514 /*
2515 * See if we want to use this console driver. If we
2516 * didn't select a console we take the first one
2517 * that registers here.
2518 */
2519 if (preferred_console < 0) {
2520 if (newcon->index < 0)
2521 newcon->index = 0;
2522 if (newcon->setup == NULL ||
2523 newcon->setup(newcon, NULL) == 0) {
2524 newcon->flags |= CON_ENABLED;
2525 if (newcon->device) {
2526 newcon->flags |= CON_CONSDEV;
2527 preferred_console = 0;
2528 }
2529 }
2530 }
2531
2532 /*
2533 * See if this console matches one we selected on
2534 * the command line.
2535 */
2536 for (i = 0, c = console_cmdline;
2537 i < MAX_CMDLINECONSOLES && c->name[0];
2538 i++, c++) {
2539 if (!newcon->match ||
2540 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2541 /* default matching */
2542 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2543 if (strcmp(c->name, newcon->name) != 0)
2544 continue;
2545 if (newcon->index >= 0 &&
2546 newcon->index != c->index)
2547 continue;
2548 if (newcon->index < 0)
2549 newcon->index = c->index;
2550
2551 if (_braille_register_console(newcon, c))
2552 return;
2553
2554 if (newcon->setup &&
2555 newcon->setup(newcon, c->options) != 0)
2556 break;
2557 }
2558
2559 newcon->flags |= CON_ENABLED;
2560 if (i == selected_console) {
2561 newcon->flags |= CON_CONSDEV;
2562 preferred_console = selected_console;
2563 }
2564 break;
2565 }
2566
2567 if (!(newcon->flags & CON_ENABLED))
2568 return;
2569
2570 /*
2571 * If we have a bootconsole, and are switching to a real console,
2572 * don't print everything out again, since when the boot console, and
2573 * the real console are the same physical device, it's annoying to
2574 * see the beginning boot messages twice
2575 */
2576 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2577 newcon->flags &= ~CON_PRINTBUFFER;
2578
2579 /*
2580 * Put this console in the list - keep the
2581 * preferred driver at the head of the list.
2582 */
2583 console_lock();
2584 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2585 newcon->next = console_drivers;
2586 console_drivers = newcon;
2587 if (newcon->next)
2588 newcon->next->flags &= ~CON_CONSDEV;
2589 } else {
2590 newcon->next = console_drivers->next;
2591 console_drivers->next = newcon;
2592 }
2593
2594 if (newcon->flags & CON_EXTENDED)
2595 if (!nr_ext_console_drivers++)
2596 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2597
2598 if (newcon->flags & CON_PRINTBUFFER) {
2599 /*
2600 * console_unlock(); will print out the buffered messages
2601 * for us.
2602 */
2603 raw_spin_lock_irqsave(&logbuf_lock, flags);
2604 console_seq = syslog_seq;
2605 console_idx = syslog_idx;
2606 console_prev = syslog_prev;
2607 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2608 /*
2609 * We're about to replay the log buffer. Only do this to the
2610 * just-registered console to avoid excessive message spam to
2611 * the already-registered consoles.
2612 */
2613 exclusive_console = newcon;
2614 }
2615 console_unlock();
2616 console_sysfs_notify();
2617
2618 /*
2619 * By unregistering the bootconsoles after we enable the real console
2620 * we get the "console xxx enabled" message on all the consoles -
2621 * boot consoles, real consoles, etc - this is to ensure that end
2622 * users know there might be something in the kernel's log buffer that
2623 * went to the bootconsole (that they do not see on the real console)
2624 */
2625 pr_info("%sconsole [%s%d] enabled\n",
2626 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2627 newcon->name, newcon->index);
2628 if (bcon &&
2629 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2630 !keep_bootcon) {
2631 /* We need to iterate through all boot consoles, to make
2632 * sure we print everything out, before we unregister them.
2633 */
2634 for_each_console(bcon)
2635 if (bcon->flags & CON_BOOT)
2636 unregister_console(bcon);
2637 }
2638}
2639EXPORT_SYMBOL(register_console);
2640
2641int unregister_console(struct console *console)
2642{
2643 struct console *a, *b;
2644 int res;
2645
2646 pr_info("%sconsole [%s%d] disabled\n",
2647 (console->flags & CON_BOOT) ? "boot" : "" ,
2648 console->name, console->index);
2649
2650 res = _braille_unregister_console(console);
2651 if (res)
2652 return res;
2653
2654 res = 1;
2655 console_lock();
2656 if (console_drivers == console) {
2657 console_drivers=console->next;
2658 res = 0;
2659 } else if (console_drivers) {
2660 for (a=console_drivers->next, b=console_drivers ;
2661 a; b=a, a=b->next) {
2662 if (a == console) {
2663 b->next = a->next;
2664 res = 0;
2665 break;
2666 }
2667 }
2668 }
2669
2670 if (!res && (console->flags & CON_EXTENDED))
2671 nr_ext_console_drivers--;
2672
2673 /*
2674 * If this isn't the last console and it has CON_CONSDEV set, we
2675 * need to set it on the next preferred console.
2676 */
2677 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2678 console_drivers->flags |= CON_CONSDEV;
2679
2680 console->flags &= ~CON_ENABLED;
2681 console_unlock();
2682 console_sysfs_notify();
2683 return res;
2684}
2685EXPORT_SYMBOL(unregister_console);
2686
2687/*
2688 * Some boot consoles access data that is in the init section and which will
2689 * be discarded after the initcalls have been run. To make sure that no code
2690 * will access this data, unregister the boot consoles in a late initcall.
2691 *
2692 * If for some reason, such as deferred probe or the driver being a loadable
2693 * module, the real console hasn't registered yet at this point, there will
2694 * be a brief interval in which no messages are logged to the console, which
2695 * makes it difficult to diagnose problems that occur during this time.
2696 *
2697 * To mitigate this problem somewhat, only unregister consoles whose memory
2698 * intersects with the init section. Note that code exists elsewhere to get
2699 * rid of the boot console as soon as the proper console shows up, so there
2700 * won't be side-effects from postponing the removal.
2701 */
2702static int __init printk_late_init(void)
2703{
2704 struct console *con;
2705
2706 for_each_console(con) {
2707 if (!keep_bootcon && con->flags & CON_BOOT) {
2708 /*
2709 * Make sure to unregister boot consoles whose data
2710 * resides in the init section before the init section
2711 * is discarded. Boot consoles whose data will stick
2712 * around will automatically be unregistered when the
2713 * proper console replaces them.
2714 */
2715 if (init_section_intersects(con, sizeof(*con)))
2716 unregister_console(con);
2717 }
2718 }
2719 hotcpu_notifier(console_cpu_notify, 0);
2720 return 0;
2721}
2722late_initcall(printk_late_init);
2723
2724#if defined CONFIG_PRINTK
2725/*
2726 * Delayed printk version, for scheduler-internal messages:
2727 */
2728#define PRINTK_PENDING_WAKEUP 0x01
2729#define PRINTK_PENDING_OUTPUT 0x02
2730
2731static DEFINE_PER_CPU(int, printk_pending);
2732
2733static void wake_up_klogd_work_func(struct irq_work *irq_work)
2734{
2735 int pending = __this_cpu_xchg(printk_pending, 0);
2736
2737 if (pending & PRINTK_PENDING_OUTPUT) {
2738 /* If trylock fails, someone else is doing the printing */
2739 if (console_trylock())
2740 console_unlock();
2741 }
2742
2743 if (pending & PRINTK_PENDING_WAKEUP)
2744 wake_up_interruptible(&log_wait);
2745}
2746
2747static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2748 .func = wake_up_klogd_work_func,
2749 .flags = IRQ_WORK_LAZY,
2750};
2751
2752void wake_up_klogd(void)
2753{
2754 preempt_disable();
2755 if (waitqueue_active(&log_wait)) {
2756 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2757 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2758 }
2759 preempt_enable();
2760}
2761
2762int printk_deferred(const char *fmt, ...)
2763{
2764 va_list args;
2765 int r;
2766
2767 preempt_disable();
2768 va_start(args, fmt);
2769 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2770 va_end(args);
2771
2772 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2773 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2774 preempt_enable();
2775
2776 return r;
2777}
2778
2779/*
2780 * printk rate limiting, lifted from the networking subsystem.
2781 *
2782 * This enforces a rate limit: not more than 10 kernel messages
2783 * every 5s to make a denial-of-service attack impossible.
2784 */
2785DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2786
2787int __printk_ratelimit(const char *func)
2788{
2789 return ___ratelimit(&printk_ratelimit_state, func);
2790}
2791EXPORT_SYMBOL(__printk_ratelimit);
2792
2793/**
2794 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2795 * @caller_jiffies: pointer to caller's state
2796 * @interval_msecs: minimum interval between prints
2797 *
2798 * printk_timed_ratelimit() returns true if more than @interval_msecs
2799 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2800 * returned true.
2801 */
2802bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2803 unsigned int interval_msecs)
2804{
2805 unsigned long elapsed = jiffies - *caller_jiffies;
2806
2807 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2808 return false;
2809
2810 *caller_jiffies = jiffies;
2811 return true;
2812}
2813EXPORT_SYMBOL(printk_timed_ratelimit);
2814
2815static DEFINE_SPINLOCK(dump_list_lock);
2816static LIST_HEAD(dump_list);
2817
2818/**
2819 * kmsg_dump_register - register a kernel log dumper.
2820 * @dumper: pointer to the kmsg_dumper structure
2821 *
2822 * Adds a kernel log dumper to the system. The dump callback in the
2823 * structure will be called when the kernel oopses or panics and must be
2824 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2825 */
2826int kmsg_dump_register(struct kmsg_dumper *dumper)
2827{
2828 unsigned long flags;
2829 int err = -EBUSY;
2830
2831 /* The dump callback needs to be set */
2832 if (!dumper->dump)
2833 return -EINVAL;
2834
2835 spin_lock_irqsave(&dump_list_lock, flags);
2836 /* Don't allow registering multiple times */
2837 if (!dumper->registered) {
2838 dumper->registered = 1;
2839 list_add_tail_rcu(&dumper->list, &dump_list);
2840 err = 0;
2841 }
2842 spin_unlock_irqrestore(&dump_list_lock, flags);
2843
2844 return err;
2845}
2846EXPORT_SYMBOL_GPL(kmsg_dump_register);
2847
2848/**
2849 * kmsg_dump_unregister - unregister a kmsg dumper.
2850 * @dumper: pointer to the kmsg_dumper structure
2851 *
2852 * Removes a dump device from the system. Returns zero on success and
2853 * %-EINVAL otherwise.
2854 */
2855int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2856{
2857 unsigned long flags;
2858 int err = -EINVAL;
2859
2860 spin_lock_irqsave(&dump_list_lock, flags);
2861 if (dumper->registered) {
2862 dumper->registered = 0;
2863 list_del_rcu(&dumper->list);
2864 err = 0;
2865 }
2866 spin_unlock_irqrestore(&dump_list_lock, flags);
2867 synchronize_rcu();
2868
2869 return err;
2870}
2871EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2872
2873static bool always_kmsg_dump;
2874module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2875
2876/**
2877 * kmsg_dump - dump kernel log to kernel message dumpers.
2878 * @reason: the reason (oops, panic etc) for dumping
2879 *
2880 * Call each of the registered dumper's dump() callback, which can
2881 * retrieve the kmsg records with kmsg_dump_get_line() or
2882 * kmsg_dump_get_buffer().
2883 */
2884void kmsg_dump(enum kmsg_dump_reason reason)
2885{
2886 struct kmsg_dumper *dumper;
2887 unsigned long flags;
2888
2889 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2890 return;
2891
2892 rcu_read_lock();
2893 list_for_each_entry_rcu(dumper, &dump_list, list) {
2894 if (dumper->max_reason && reason > dumper->max_reason)
2895 continue;
2896
2897 /* initialize iterator with data about the stored records */
2898 dumper->active = true;
2899
2900 raw_spin_lock_irqsave(&logbuf_lock, flags);
2901 dumper->cur_seq = clear_seq;
2902 dumper->cur_idx = clear_idx;
2903 dumper->next_seq = log_next_seq;
2904 dumper->next_idx = log_next_idx;
2905 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2906
2907 /* invoke dumper which will iterate over records */
2908 dumper->dump(dumper, reason);
2909
2910 /* reset iterator */
2911 dumper->active = false;
2912 }
2913 rcu_read_unlock();
2914}
2915
2916/**
2917 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2918 * @dumper: registered kmsg dumper
2919 * @syslog: include the "<4>" prefixes
2920 * @line: buffer to copy the line to
2921 * @size: maximum size of the buffer
2922 * @len: length of line placed into buffer
2923 *
2924 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2925 * record, and copy one record into the provided buffer.
2926 *
2927 * Consecutive calls will return the next available record moving
2928 * towards the end of the buffer with the youngest messages.
2929 *
2930 * A return value of FALSE indicates that there are no more records to
2931 * read.
2932 *
2933 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2934 */
2935bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2936 char *line, size_t size, size_t *len)
2937{
2938 struct printk_log *msg;
2939 size_t l = 0;
2940 bool ret = false;
2941
2942 if (!dumper->active)
2943 goto out;
2944
2945 if (dumper->cur_seq < log_first_seq) {
2946 /* messages are gone, move to first available one */
2947 dumper->cur_seq = log_first_seq;
2948 dumper->cur_idx = log_first_idx;
2949 }
2950
2951 /* last entry */
2952 if (dumper->cur_seq >= log_next_seq)
2953 goto out;
2954
2955 msg = log_from_idx(dumper->cur_idx);
2956 l = msg_print_text(msg, 0, syslog, line, size);
2957
2958 dumper->cur_idx = log_next(dumper->cur_idx);
2959 dumper->cur_seq++;
2960 ret = true;
2961out:
2962 if (len)
2963 *len = l;
2964 return ret;
2965}
2966
2967/**
2968 * kmsg_dump_get_line - retrieve one kmsg log line
2969 * @dumper: registered kmsg dumper
2970 * @syslog: include the "<4>" prefixes
2971 * @line: buffer to copy the line to
2972 * @size: maximum size of the buffer
2973 * @len: length of line placed into buffer
2974 *
2975 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2976 * record, and copy one record into the provided buffer.
2977 *
2978 * Consecutive calls will return the next available record moving
2979 * towards the end of the buffer with the youngest messages.
2980 *
2981 * A return value of FALSE indicates that there are no more records to
2982 * read.
2983 */
2984bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2985 char *line, size_t size, size_t *len)
2986{
2987 unsigned long flags;
2988 bool ret;
2989
2990 raw_spin_lock_irqsave(&logbuf_lock, flags);
2991 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2992 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2993
2994 return ret;
2995}
2996EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2997
2998/**
2999 * kmsg_dump_get_buffer - copy kmsg log lines
3000 * @dumper: registered kmsg dumper
3001 * @syslog: include the "<4>" prefixes
3002 * @buf: buffer to copy the line to
3003 * @size: maximum size of the buffer
3004 * @len: length of line placed into buffer
3005 *
3006 * Start at the end of the kmsg buffer and fill the provided buffer
3007 * with as many of the the *youngest* kmsg records that fit into it.
3008 * If the buffer is large enough, all available kmsg records will be
3009 * copied with a single call.
3010 *
3011 * Consecutive calls will fill the buffer with the next block of
3012 * available older records, not including the earlier retrieved ones.
3013 *
3014 * A return value of FALSE indicates that there are no more records to
3015 * read.
3016 */
3017bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
3018 char *buf, size_t size, size_t *len)
3019{
3020 unsigned long flags;
3021 u64 seq;
3022 u32 idx;
3023 u64 next_seq;
3024 u32 next_idx;
3025 enum log_flags prev;
3026 size_t l = 0;
3027 bool ret = false;
3028
3029 if (!dumper->active)
3030 goto out;
3031
3032 raw_spin_lock_irqsave(&logbuf_lock, flags);
3033 if (dumper->cur_seq < log_first_seq) {
3034 /* messages are gone, move to first available one */
3035 dumper->cur_seq = log_first_seq;
3036 dumper->cur_idx = log_first_idx;
3037 }
3038
3039 /* last entry */
3040 if (dumper->cur_seq >= dumper->next_seq) {
3041 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3042 goto out;
3043 }
3044
3045 /* calculate length of entire buffer */
3046 seq = dumper->cur_seq;
3047 idx = dumper->cur_idx;
3048 prev = 0;
3049 while (seq < dumper->next_seq) {
3050 struct printk_log *msg = log_from_idx(idx);
3051
3052 l += msg_print_text(msg, prev, true, NULL, 0);
3053 idx = log_next(idx);
3054 seq++;
3055 prev = msg->flags;
3056 }
3057
3058 /* move first record forward until length fits into the buffer */
3059 seq = dumper->cur_seq;
3060 idx = dumper->cur_idx;
3061 prev = 0;
3062 while (l > size && seq < dumper->next_seq) {
3063 struct printk_log *msg = log_from_idx(idx);
3064
3065 l -= msg_print_text(msg, prev, true, NULL, 0);
3066 idx = log_next(idx);
3067 seq++;
3068 prev = msg->flags;
3069 }
3070
3071 /* last message in next interation */
3072 next_seq = seq;
3073 next_idx = idx;
3074
3075 l = 0;
3076 while (seq < dumper->next_seq) {
3077 struct printk_log *msg = log_from_idx(idx);
3078
3079 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
3080 idx = log_next(idx);
3081 seq++;
3082 prev = msg->flags;
3083 }
3084
3085 dumper->next_seq = next_seq;
3086 dumper->next_idx = next_idx;
3087 ret = true;
3088 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3089out:
3090 if (len)
3091 *len = l;
3092 return ret;
3093}
3094EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3095
3096/**
3097 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3098 * @dumper: registered kmsg dumper
3099 *
3100 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3101 * kmsg_dump_get_buffer() can be called again and used multiple
3102 * times within the same dumper.dump() callback.
3103 *
3104 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3105 */
3106void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3107{
3108 dumper->cur_seq = clear_seq;
3109 dumper->cur_idx = clear_idx;
3110 dumper->next_seq = log_next_seq;
3111 dumper->next_idx = log_next_idx;
3112}
3113
3114/**
3115 * kmsg_dump_rewind - reset the interator
3116 * @dumper: registered kmsg dumper
3117 *
3118 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3119 * kmsg_dump_get_buffer() can be called again and used multiple
3120 * times within the same dumper.dump() callback.
3121 */
3122void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3123{
3124 unsigned long flags;
3125
3126 raw_spin_lock_irqsave(&logbuf_lock, flags);
3127 kmsg_dump_rewind_nolock(dumper);
3128 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3129}
3130EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3131
3132static char dump_stack_arch_desc_str[128];
3133
3134/**
3135 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3136 * @fmt: printf-style format string
3137 * @...: arguments for the format string
3138 *
3139 * The configured string will be printed right after utsname during task
3140 * dumps. Usually used to add arch-specific system identifiers. If an
3141 * arch wants to make use of such an ID string, it should initialize this
3142 * as soon as possible during boot.
3143 */
3144void __init dump_stack_set_arch_desc(const char *fmt, ...)
3145{
3146 va_list args;
3147
3148 va_start(args, fmt);
3149 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3150 fmt, args);
3151 va_end(args);
3152}
3153
3154/**
3155 * dump_stack_print_info - print generic debug info for dump_stack()
3156 * @log_lvl: log level
3157 *
3158 * Arch-specific dump_stack() implementations can use this function to
3159 * print out the same debug information as the generic dump_stack().
3160 */
3161void dump_stack_print_info(const char *log_lvl)
3162{
3163 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3164 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3165 print_tainted(), init_utsname()->release,
3166 (int)strcspn(init_utsname()->version, " "),
3167 init_utsname()->version);
3168
3169 if (dump_stack_arch_desc_str[0] != '\0')
3170 printk("%sHardware name: %s\n",
3171 log_lvl, dump_stack_arch_desc_str);
3172
3173 print_worker_info(log_lvl, current);
3174}
3175
3176/**
3177 * show_regs_print_info - print generic debug info for show_regs()
3178 * @log_lvl: log level
3179 *
3180 * show_regs() implementations can use this function to print out generic
3181 * debug information.
3182 */
3183void show_regs_print_info(const char *log_lvl)
3184{
3185 dump_stack_print_info(log_lvl);
3186
3187 printk("%stask: %p ti: %p task.ti: %p\n",
3188 log_lvl, current, current_thread_info(),
3189 task_thread_info(current));
3190}
3191
3192#endif