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TOMOYO Linux Cross Reference
Linux/kernel/printk/printk.c

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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/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 
 59 int 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  */
 70 int oops_in_progress;
 71 EXPORT_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  */
 78 static DEFINE_SEMAPHORE(console_sem);
 79 struct console *console_drivers;
 80 EXPORT_SYMBOL_GPL(console_drivers);
 81 
 82 #ifdef CONFIG_LOCKDEP
 83 static 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  */
 98 static 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 
109 static 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  */
131 static int console_locked, console_suspended;
132 
133 /*
134  * If exclusive_console is non-NULL then only this console is to be printed to.
135  */
136 static struct console *exclusive_console;
137 
138 /*
139  *      Array of consoles built from command line options (console=)
140  */
141 
142 #define MAX_CMDLINECONSOLES 8
143 
144 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
145 
146 static int selected_console = -1;
147 static int preferred_console = -1;
148 int console_set_on_cmdline;
149 EXPORT_SYMBOL(console_set_on_cmdline);
150 
151 /* Flag: console code may call schedule() */
152 static 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 
221 enum 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 
228 struct 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  */
247 static DEFINE_RAW_SPINLOCK(logbuf_lock);
248 
249 #ifdef CONFIG_PRINTK
250 DECLARE_WAIT_QUEUE_HEAD(log_wait);
251 /* the next printk record to read by syslog(READ) or /proc/kmsg */
252 static u64 syslog_seq;
253 static u32 syslog_idx;
254 static enum log_flags syslog_prev;
255 static size_t syslog_partial;
256 
257 /* index and sequence number of the first record stored in the buffer */
258 static u64 log_first_seq;
259 static u32 log_first_idx;
260 
261 /* index and sequence number of the next record to store in the buffer */
262 static u64 log_next_seq;
263 static u32 log_next_idx;
264 
265 /* the next printk record to write to the console */
266 static u64 console_seq;
267 static u32 console_idx;
268 static enum log_flags console_prev;
269 
270 /* the next printk record to read after the last 'clear' command */
271 static u64 clear_seq;
272 static 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)
283 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
284 static char *log_buf = __log_buf;
285 static u32 log_buf_len = __LOG_BUF_LEN;
286 
287 /* Return log buffer address */
288 char *log_buf_addr_get(void)
289 {
290         return log_buf;
291 }
292 
293 /* Return log buffer size */
294 u32 log_buf_len_get(void)
295 {
296         return log_buf_len;
297 }
298 
299 /* human readable text of the record */
300 static 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 */
306 static 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 */
312 static 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 */
326 static 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  */
352 static 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 
368 static 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 */
390 static 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
407 static const char trunc_msg[] = "<truncated>";
408 
409 static 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 */
428 static 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 
486 int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
487 
488 static 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 
500 int 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         }
525 ok:
526         return security_syslog(type);
527 }
528 EXPORT_SYMBOL_GPL(check_syslog_permissions);
529 
530 static void append_char(char **pp, char *e, char c)
531 {
532         if (*pp < e)
533                 *(*pp)++ = c;
534 }
535 
536 static 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 
563 static 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 */
612 struct 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 
620 static 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 
670 static 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;
731 out:
732         mutex_unlock(&user->lock);
733         return ret;
734 }
735 
736 static 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 
774 static 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 
797 static 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 
826 static 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 
838 const 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  */
856 void 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 */
876 static unsigned long __initdata new_log_buf_len;
877 
878 /* we practice scaling the ring buffer by powers of 2 */
879 static 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 */
888 static 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 }
896 early_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 
901 static 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 */
928 static inline void log_buf_add_cpu(void) {}
929 #endif /* CONFIG_SMP */
930 
931 void __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 
973 static bool __read_mostly ignore_loglevel;
974 
975 static 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 
983 early_param("ignore_loglevel", ignore_loglevel_setup);
984 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
985 MODULE_PARM_DESC(ignore_loglevel,
986                  "ignore loglevel setting (prints all kernel messages to the console)");
987 
988 #ifdef CONFIG_BOOT_PRINTK_DELAY
989 
990 static int boot_delay; /* msecs delay after each printk during bootup */
991 static unsigned long long loops_per_msec;       /* based on boot_delay */
992 
993 static 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 }
1009 early_param("boot_delay", boot_delay_setup);
1010 
1011 static 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
1038 static inline void boot_delay_msec(int level)
1039 {
1040 }
1041 #endif
1042 
1043 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1044 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1045 
1046 static 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 
1062 static 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 
1085 static 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 
1144 static 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 
1208 static 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 
1297 int 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         }
1419 out:
1420         return error;
1421 }
1422 
1423 SYSCALL_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  */
1433 static 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  */
1468 static 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 
1485 int printk_delay_msec __read_mostly;
1486 
1487 static 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  */
1505 static 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 
1517 static 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 
1545 static 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 
1579 static 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 
1607 asmlinkage 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 '' ... '7':
1689                                 if (level == LOGLEVEL_DEFAULT)
1690                                         level = kern_level - '';
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 }
1771 EXPORT_SYMBOL(vprintk_emit);
1772 
1773 asmlinkage int vprintk(const char *fmt, va_list args)
1774 {
1775         return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1776 }
1777 EXPORT_SYMBOL(vprintk);
1778 
1779 asmlinkage 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 }
1792 EXPORT_SYMBOL(printk_emit);
1793 
1794 int 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 }
1808 EXPORT_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  */
1816 DEFINE_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  */
1839 asmlinkage __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 }
1860 EXPORT_SYMBOL(printk);
1861 
1862 #else /* CONFIG_PRINTK */
1863 
1864 #define LOG_LINE_MAX            0
1865 #define PREFIX_MAX              0
1866 
1867 static u64 syslog_seq;
1868 static u32 syslog_idx;
1869 static u64 console_seq;
1870 static u32 console_idx;
1871 static enum log_flags syslog_prev;
1872 static u64 log_first_seq;
1873 static u32 log_first_idx;
1874 static u64 log_next_seq;
1875 static enum log_flags console_prev;
1876 static struct cont {
1877         size_t len;
1878         size_t cons;
1879         u8 level;
1880         bool flushed:1;
1881 } cont;
1882 static char *log_text(const struct printk_log *msg) { return NULL; }
1883 static char *log_dict(const struct printk_log *msg) { return NULL; }
1884 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1885 static u32 log_next(u32 idx) { return 0; }
1886 static 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; }
1889 static 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; }
1892 static void call_console_drivers(int level,
1893                                  const char *ext_text, size_t ext_len,
1894                                  const char *text, size_t len) {}
1895 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1896                              bool syslog, char *buf, size_t size) { return 0; }
1897 static size_t cont_print_text(char *text, size_t size) { return 0; }
1898 
1899 /* Still needs to be defined for users */
1900 DEFINE_PER_CPU(printk_func_t, printk_func);
1901 
1902 #endif /* CONFIG_PRINTK */
1903 
1904 #ifdef CONFIG_EARLY_PRINTK
1905 struct console *early_console;
1906 
1907 asmlinkage __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 
1924 static 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  */
1958 static 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] >= '' && 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  */
2011 int add_preferred_console(char *name, int idx, char *options)
2012 {
2013         return __add_preferred_console(name, idx, options, NULL);
2014 }
2015 
2016 bool console_suspend_enabled = true;
2017 EXPORT_SYMBOL(console_suspend_enabled);
2018 
2019 static 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);
2025 module_param_named(console_suspend, console_suspend_enabled,
2026                 bool, S_IRUGO | S_IWUSR);
2027 MODULE_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  */
2035 void 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 
2045 void 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  */
2065 static 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  */
2087 void 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 }
2097 EXPORT_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  */
2107 int 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 }
2132 EXPORT_SYMBOL(console_trylock);
2133 
2134 int 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  */
2143 static 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  */
2162 static inline int can_use_console(void)
2163 {
2164         return cpu_online(raw_smp_processor_id()) || have_callable_console();
2165 }
2166 
2167 static 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;
2192 out:
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  */
2210 void 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 
2237 again:
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                 }
2275 skip:
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 }
2348 EXPORT_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  */
2359 void __sched console_conditional_schedule(void)
2360 {
2361         if (console_may_schedule)
2362                 cond_resched();
2363 }
2364 EXPORT_SYMBOL(console_conditional_schedule);
2365 
2366 void 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  */
2393 void 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  */
2410 struct 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  */
2432 void console_stop(struct console *console)
2433 {
2434         console_lock();
2435         console->flags &= ~CON_ENABLED;
2436         console_unlock();
2437 }
2438 EXPORT_SYMBOL(console_stop);
2439 
2440 void console_start(struct console *console)
2441 {
2442         console_lock();
2443         console->flags |= CON_ENABLED;
2444         console_unlock();
2445 }
2446 EXPORT_SYMBOL(console_start);
2447 
2448 static int __read_mostly keep_bootcon;
2449 
2450 static 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 
2458 early_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  */
2479 void 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 }
2639 EXPORT_SYMBOL(register_console);
2640 
2641 int 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 }
2685 EXPORT_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  */
2702 static 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 }
2722 late_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 
2731 static DEFINE_PER_CPU(int, printk_pending);
2732 
2733 static 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 
2747 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2748         .func = wake_up_klogd_work_func,
2749         .flags = IRQ_WORK_LAZY,
2750 };
2751 
2752 void 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 
2762 int 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  */
2785 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2786 
2787 int __printk_ratelimit(const char *func)
2788 {
2789         return ___ratelimit(&printk_ratelimit_state, func);
2790 }
2791 EXPORT_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  */
2802 bool 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 }
2813 EXPORT_SYMBOL(printk_timed_ratelimit);
2814 
2815 static DEFINE_SPINLOCK(dump_list_lock);
2816 static 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  */
2826 int 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 }
2846 EXPORT_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  */
2855 int 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 }
2871 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2872 
2873 static bool always_kmsg_dump;
2874 module_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  */
2884 void 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  */
2935 bool 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;
2961 out:
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  */
2984 bool 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 }
2996 EXPORT_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  */
3017 bool 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);
3089 out:
3090         if (len)
3091                 *len = l;
3092         return ret;
3093 }
3094 EXPORT_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  */
3106 void 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  */
3122 void 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 }
3130 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3131 
3132 static 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  */
3144 void __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  */
3161 void 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  */
3183 void 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
3193 

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