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Linux/kernel/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/aio.h>
 36 #include <linux/syscalls.h>
 37 #include <linux/kexec.h>
 38 #include <linux/kdb.h>
 39 #include <linux/ratelimit.h>
 40 #include <linux/kmsg_dump.h>
 41 #include <linux/syslog.h>
 42 #include <linux/cpu.h>
 43 #include <linux/notifier.h>
 44 #include <linux/rculist.h>
 45 #include <linux/poll.h>
 46 #include <linux/irq_work.h>
 47 #include <linux/utsname.h>
 48 
 49 #include <asm/uaccess.h>
 50 
 51 #define CREATE_TRACE_POINTS
 52 #include <trace/events/printk.h>
 53 
 54 /* printk's without a loglevel use this.. */
 55 #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
 56 
 57 /* We show everything that is MORE important than this.. */
 58 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
 59 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
 60 
 61 int console_printk[4] = {
 62         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
 63         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
 64         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
 65         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
 66 };
 67 
 68 /*
 69  * Low level drivers may need that to know if they can schedule in
 70  * their unblank() callback or not. So let's export it.
 71  */
 72 int oops_in_progress;
 73 EXPORT_SYMBOL(oops_in_progress);
 74 
 75 /*
 76  * console_sem protects the console_drivers list, and also
 77  * provides serialisation for access to the entire console
 78  * driver system.
 79  */
 80 static DEFINE_SEMAPHORE(console_sem);
 81 struct console *console_drivers;
 82 EXPORT_SYMBOL_GPL(console_drivers);
 83 
 84 #ifdef CONFIG_LOCKDEP
 85 static struct lockdep_map console_lock_dep_map = {
 86         .name = "console_lock"
 87 };
 88 #endif
 89 
 90 /*
 91  * This is used for debugging the mess that is the VT code by
 92  * keeping track if we have the console semaphore held. It's
 93  * definitely not the perfect debug tool (we don't know if _WE_
 94  * hold it are racing, but it helps tracking those weird code
 95  * path in the console code where we end up in places I want
 96  * locked without the console sempahore held
 97  */
 98 static int console_locked, console_suspended;
 99 
100 /*
101  * If exclusive_console is non-NULL then only this console is to be printed to.
102  */
103 static struct console *exclusive_console;
104 
105 /*
106  *      Array of consoles built from command line options (console=)
107  */
108 struct console_cmdline
109 {
110         char    name[16];                       /* Name of the driver       */
111         int     index;                          /* Minor dev. to use        */
112         char    *options;                       /* Options for the driver   */
113 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
114         char    *brl_options;                   /* Options for braille driver */
115 #endif
116 };
117 
118 #define MAX_CMDLINECONSOLES 8
119 
120 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
121 static int selected_console = -1;
122 static int preferred_console = -1;
123 int console_set_on_cmdline;
124 EXPORT_SYMBOL(console_set_on_cmdline);
125 
126 /* Flag: console code may call schedule() */
127 static int console_may_schedule;
128 
129 /*
130  * The printk log buffer consists of a chain of concatenated variable
131  * length records. Every record starts with a record header, containing
132  * the overall length of the record.
133  *
134  * The heads to the first and last entry in the buffer, as well as the
135  * sequence numbers of these both entries are maintained when messages
136  * are stored..
137  *
138  * If the heads indicate available messages, the length in the header
139  * tells the start next message. A length == 0 for the next message
140  * indicates a wrap-around to the beginning of the buffer.
141  *
142  * Every record carries the monotonic timestamp in microseconds, as well as
143  * the standard userspace syslog level and syslog facility. The usual
144  * kernel messages use LOG_KERN; userspace-injected messages always carry
145  * a matching syslog facility, by default LOG_USER. The origin of every
146  * message can be reliably determined that way.
147  *
148  * The human readable log message directly follows the message header. The
149  * length of the message text is stored in the header, the stored message
150  * is not terminated.
151  *
152  * Optionally, a message can carry a dictionary of properties (key/value pairs),
153  * to provide userspace with a machine-readable message context.
154  *
155  * Examples for well-defined, commonly used property names are:
156  *   DEVICE=b12:8               device identifier
157  *                                b12:8         block dev_t
158  *                                c127:3        char dev_t
159  *                                n8            netdev ifindex
160  *                                +sound:card0  subsystem:devname
161  *   SUBSYSTEM=pci              driver-core subsystem name
162  *
163  * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
164  * follows directly after a '=' character. Every property is terminated by
165  * a '\0' character. The last property is not terminated.
166  *
167  * Example of a message structure:
168  *   0000  ff 8f 00 00 00 00 00 00      monotonic time in nsec
169  *   0008  34 00                        record is 52 bytes long
170  *   000a        0b 00                  text is 11 bytes long
171  *   000c              1f 00            dictionary is 23 bytes long
172  *   000e                    03 00      LOG_KERN (facility) LOG_ERR (level)
173  *   0010  69 74 27 73 20 61 20 6c      "it's a l"
174  *         69 6e 65                     "ine"
175  *   001b           44 45 56 49 43      "DEVIC"
176  *         45 3d 62 38 3a 32 00 44      "E=b8:2\0D"
177  *         52 49 56 45 52 3d 62 75      "RIVER=bu"
178  *         67                           "g"
179  *   0032     00 00 00                  padding to next message header
180  *
181  * The 'struct log' buffer header must never be directly exported to
182  * userspace, it is a kernel-private implementation detail that might
183  * need to be changed in the future, when the requirements change.
184  *
185  * /dev/kmsg exports the structured data in the following line format:
186  *   "level,sequnum,timestamp;<message text>\n"
187  *
188  * The optional key/value pairs are attached as continuation lines starting
189  * with a space character and terminated by a newline. All possible
190  * non-prinatable characters are escaped in the "\xff" notation.
191  *
192  * Users of the export format should ignore possible additional values
193  * separated by ',', and find the message after the ';' character.
194  */
195 
196 enum log_flags {
197         LOG_NOCONS      = 1,    /* already flushed, do not print to console */
198         LOG_NEWLINE     = 2,    /* text ended with a newline */
199         LOG_PREFIX      = 4,    /* text started with a prefix */
200         LOG_CONT        = 8,    /* text is a fragment of a continuation line */
201 };
202 
203 struct log {
204         u64 ts_nsec;            /* timestamp in nanoseconds */
205         u16 len;                /* length of entire record */
206         u16 text_len;           /* length of text buffer */
207         u16 dict_len;           /* length of dictionary buffer */
208         u8 facility;            /* syslog facility */
209         u8 flags:5;             /* internal record flags */
210         u8 level:3;             /* syslog level */
211 };
212 
213 /*
214  * The logbuf_lock protects kmsg buffer, indices, counters. It is also
215  * used in interesting ways to provide interlocking in console_unlock();
216  */
217 static DEFINE_RAW_SPINLOCK(logbuf_lock);
218 
219 #ifdef CONFIG_PRINTK
220 DECLARE_WAIT_QUEUE_HEAD(log_wait);
221 /* the next printk record to read by syslog(READ) or /proc/kmsg */
222 static u64 syslog_seq;
223 static u32 syslog_idx;
224 static enum log_flags syslog_prev;
225 static size_t syslog_partial;
226 
227 /* index and sequence number of the first record stored in the buffer */
228 static u64 log_first_seq;
229 static u32 log_first_idx;
230 
231 /* index and sequence number of the next record to store in the buffer */
232 static u64 log_next_seq;
233 static u32 log_next_idx;
234 
235 /* the next printk record to write to the console */
236 static u64 console_seq;
237 static u32 console_idx;
238 static enum log_flags console_prev;
239 
240 /* the next printk record to read after the last 'clear' command */
241 static u64 clear_seq;
242 static u32 clear_idx;
243 
244 #define PREFIX_MAX              32
245 #define LOG_LINE_MAX            1024 - PREFIX_MAX
246 
247 /* record buffer */
248 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
249 #define LOG_ALIGN 4
250 #else
251 #define LOG_ALIGN __alignof__(struct log)
252 #endif
253 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
254 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
255 static char *log_buf = __log_buf;
256 static u32 log_buf_len = __LOG_BUF_LEN;
257 
258 /* cpu currently holding logbuf_lock */
259 static volatile unsigned int logbuf_cpu = UINT_MAX;
260 
261 /* human readable text of the record */
262 static char *log_text(const struct log *msg)
263 {
264         return (char *)msg + sizeof(struct log);
265 }
266 
267 /* optional key/value pair dictionary attached to the record */
268 static char *log_dict(const struct log *msg)
269 {
270         return (char *)msg + sizeof(struct log) + msg->text_len;
271 }
272 
273 /* get record by index; idx must point to valid msg */
274 static struct log *log_from_idx(u32 idx)
275 {
276         struct log *msg = (struct log *)(log_buf + idx);
277 
278         /*
279          * A length == 0 record is the end of buffer marker. Wrap around and
280          * read the message at the start of the buffer.
281          */
282         if (!msg->len)
283                 return (struct log *)log_buf;
284         return msg;
285 }
286 
287 /* get next record; idx must point to valid msg */
288 static u32 log_next(u32 idx)
289 {
290         struct log *msg = (struct log *)(log_buf + idx);
291 
292         /* length == 0 indicates the end of the buffer; wrap */
293         /*
294          * A length == 0 record is the end of buffer marker. Wrap around and
295          * read the message at the start of the buffer as *this* one, and
296          * return the one after that.
297          */
298         if (!msg->len) {
299                 msg = (struct log *)log_buf;
300                 return msg->len;
301         }
302         return idx + msg->len;
303 }
304 
305 /* insert record into the buffer, discard old ones, update heads */
306 static void log_store(int facility, int level,
307                       enum log_flags flags, u64 ts_nsec,
308                       const char *dict, u16 dict_len,
309                       const char *text, u16 text_len)
310 {
311         struct log *msg;
312         u32 size, pad_len;
313 
314         /* number of '\0' padding bytes to next message */
315         size = sizeof(struct log) + text_len + dict_len;
316         pad_len = (-size) & (LOG_ALIGN - 1);
317         size += pad_len;
318 
319         while (log_first_seq < log_next_seq) {
320                 u32 free;
321 
322                 if (log_next_idx > log_first_idx)
323                         free = max(log_buf_len - log_next_idx, log_first_idx);
324                 else
325                         free = log_first_idx - log_next_idx;
326 
327                 if (free > size + sizeof(struct log))
328                         break;
329 
330                 /* drop old messages until we have enough contiuous space */
331                 log_first_idx = log_next(log_first_idx);
332                 log_first_seq++;
333         }
334 
335         if (log_next_idx + size + sizeof(struct log) >= log_buf_len) {
336                 /*
337                  * This message + an additional empty header does not fit
338                  * at the end of the buffer. Add an empty header with len == 0
339                  * to signify a wrap around.
340                  */
341                 memset(log_buf + log_next_idx, 0, sizeof(struct log));
342                 log_next_idx = 0;
343         }
344 
345         /* fill message */
346         msg = (struct log *)(log_buf + log_next_idx);
347         memcpy(log_text(msg), text, text_len);
348         msg->text_len = text_len;
349         memcpy(log_dict(msg), dict, dict_len);
350         msg->dict_len = dict_len;
351         msg->facility = facility;
352         msg->level = level & 7;
353         msg->flags = flags & 0x1f;
354         if (ts_nsec > 0)
355                 msg->ts_nsec = ts_nsec;
356         else
357                 msg->ts_nsec = local_clock();
358         memset(log_dict(msg) + dict_len, 0, pad_len);
359         msg->len = sizeof(struct log) + text_len + dict_len + pad_len;
360 
361         /* insert message */
362         log_next_idx += msg->len;
363         log_next_seq++;
364 }
365 
366 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
367 int dmesg_restrict = 1;
368 #else
369 int dmesg_restrict;
370 #endif
371 
372 static int syslog_action_restricted(int type)
373 {
374         if (dmesg_restrict)
375                 return 1;
376         /*
377          * Unless restricted, we allow "read all" and "get buffer size"
378          * for everybody.
379          */
380         return type != SYSLOG_ACTION_READ_ALL &&
381                type != SYSLOG_ACTION_SIZE_BUFFER;
382 }
383 
384 static int check_syslog_permissions(int type, bool from_file)
385 {
386         /*
387          * If this is from /proc/kmsg and we've already opened it, then we've
388          * already done the capabilities checks at open time.
389          */
390         if (from_file && type != SYSLOG_ACTION_OPEN)
391                 return 0;
392 
393         if (syslog_action_restricted(type)) {
394                 if (capable(CAP_SYSLOG))
395                         return 0;
396                 /*
397                  * For historical reasons, accept CAP_SYS_ADMIN too, with
398                  * a warning.
399                  */
400                 if (capable(CAP_SYS_ADMIN)) {
401                         pr_warn_once("%s (%d): Attempt to access syslog with "
402                                      "CAP_SYS_ADMIN but no CAP_SYSLOG "
403                                      "(deprecated).\n",
404                                  current->comm, task_pid_nr(current));
405                         return 0;
406                 }
407                 return -EPERM;
408         }
409         return security_syslog(type);
410 }
411 
412 
413 /* /dev/kmsg - userspace message inject/listen interface */
414 struct devkmsg_user {
415         u64 seq;
416         u32 idx;
417         enum log_flags prev;
418         struct mutex lock;
419         char buf[8192];
420 };
421 
422 static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
423                               unsigned long count, loff_t pos)
424 {
425         char *buf, *line;
426         int i;
427         int level = default_message_loglevel;
428         int facility = 1;       /* LOG_USER */
429         size_t len = iov_length(iv, count);
430         ssize_t ret = len;
431 
432         if (len > LOG_LINE_MAX)
433                 return -EINVAL;
434         buf = kmalloc(len+1, GFP_KERNEL);
435         if (buf == NULL)
436                 return -ENOMEM;
437 
438         line = buf;
439         for (i = 0; i < count; i++) {
440                 if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
441                         ret = -EFAULT;
442                         goto out;
443                 }
444                 line += iv[i].iov_len;
445         }
446 
447         /*
448          * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
449          * the decimal value represents 32bit, the lower 3 bit are the log
450          * level, the rest are the log facility.
451          *
452          * If no prefix or no userspace facility is specified, we
453          * enforce LOG_USER, to be able to reliably distinguish
454          * kernel-generated messages from userspace-injected ones.
455          */
456         line = buf;
457         if (line[0] == '<') {
458                 char *endp = NULL;
459 
460                 i = simple_strtoul(line+1, &endp, 10);
461                 if (endp && endp[0] == '>') {
462                         level = i & 7;
463                         if (i >> 3)
464                                 facility = i >> 3;
465                         endp++;
466                         len -= endp - line;
467                         line = endp;
468                 }
469         }
470         line[len] = '\0';
471 
472         printk_emit(facility, level, NULL, 0, "%s", line);
473 out:
474         kfree(buf);
475         return ret;
476 }
477 
478 static ssize_t devkmsg_read(struct file *file, char __user *buf,
479                             size_t count, loff_t *ppos)
480 {
481         struct devkmsg_user *user = file->private_data;
482         struct log *msg;
483         u64 ts_usec;
484         size_t i;
485         char cont = '-';
486         size_t len;
487         ssize_t ret;
488 
489         if (!user)
490                 return -EBADF;
491 
492         ret = mutex_lock_interruptible(&user->lock);
493         if (ret)
494                 return ret;
495         raw_spin_lock_irq(&logbuf_lock);
496         while (user->seq == log_next_seq) {
497                 if (file->f_flags & O_NONBLOCK) {
498                         ret = -EAGAIN;
499                         raw_spin_unlock_irq(&logbuf_lock);
500                         goto out;
501                 }
502 
503                 raw_spin_unlock_irq(&logbuf_lock);
504                 ret = wait_event_interruptible(log_wait,
505                                                user->seq != log_next_seq);
506                 if (ret)
507                         goto out;
508                 raw_spin_lock_irq(&logbuf_lock);
509         }
510 
511         if (user->seq < log_first_seq) {
512                 /* our last seen message is gone, return error and reset */
513                 user->idx = log_first_idx;
514                 user->seq = log_first_seq;
515                 ret = -EPIPE;
516                 raw_spin_unlock_irq(&logbuf_lock);
517                 goto out;
518         }
519 
520         msg = log_from_idx(user->idx);
521         ts_usec = msg->ts_nsec;
522         do_div(ts_usec, 1000);
523 
524         /*
525          * If we couldn't merge continuation line fragments during the print,
526          * export the stored flags to allow an optional external merge of the
527          * records. Merging the records isn't always neccessarily correct, like
528          * when we hit a race during printing. In most cases though, it produces
529          * better readable output. 'c' in the record flags mark the first
530          * fragment of a line, '+' the following.
531          */
532         if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
533                 cont = 'c';
534         else if ((msg->flags & LOG_CONT) ||
535                  ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
536                 cont = '+';
537 
538         len = sprintf(user->buf, "%u,%llu,%llu,%c;",
539                       (msg->facility << 3) | msg->level,
540                       user->seq, ts_usec, cont);
541         user->prev = msg->flags;
542 
543         /* escape non-printable characters */
544         for (i = 0; i < msg->text_len; i++) {
545                 unsigned char c = log_text(msg)[i];
546 
547                 if (c < ' ' || c >= 127 || c == '\\')
548                         len += sprintf(user->buf + len, "\\x%02x", c);
549                 else
550                         user->buf[len++] = c;
551         }
552         user->buf[len++] = '\n';
553 
554         if (msg->dict_len) {
555                 bool line = true;
556 
557                 for (i = 0; i < msg->dict_len; i++) {
558                         unsigned char c = log_dict(msg)[i];
559 
560                         if (line) {
561                                 user->buf[len++] = ' ';
562                                 line = false;
563                         }
564 
565                         if (c == '\0') {
566                                 user->buf[len++] = '\n';
567                                 line = true;
568                                 continue;
569                         }
570 
571                         if (c < ' ' || c >= 127 || c == '\\') {
572                                 len += sprintf(user->buf + len, "\\x%02x", c);
573                                 continue;
574                         }
575 
576                         user->buf[len++] = c;
577                 }
578                 user->buf[len++] = '\n';
579         }
580 
581         user->idx = log_next(user->idx);
582         user->seq++;
583         raw_spin_unlock_irq(&logbuf_lock);
584 
585         if (len > count) {
586                 ret = -EINVAL;
587                 goto out;
588         }
589 
590         if (copy_to_user(buf, user->buf, len)) {
591                 ret = -EFAULT;
592                 goto out;
593         }
594         ret = len;
595 out:
596         mutex_unlock(&user->lock);
597         return ret;
598 }
599 
600 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
601 {
602         struct devkmsg_user *user = file->private_data;
603         loff_t ret = 0;
604 
605         if (!user)
606                 return -EBADF;
607         if (offset)
608                 return -ESPIPE;
609 
610         raw_spin_lock_irq(&logbuf_lock);
611         switch (whence) {
612         case SEEK_SET:
613                 /* the first record */
614                 user->idx = log_first_idx;
615                 user->seq = log_first_seq;
616                 break;
617         case SEEK_DATA:
618                 /*
619                  * The first record after the last SYSLOG_ACTION_CLEAR,
620                  * like issued by 'dmesg -c'. Reading /dev/kmsg itself
621                  * changes no global state, and does not clear anything.
622                  */
623                 user->idx = clear_idx;
624                 user->seq = clear_seq;
625                 break;
626         case SEEK_END:
627                 /* after the last record */
628                 user->idx = log_next_idx;
629                 user->seq = log_next_seq;
630                 break;
631         default:
632                 ret = -EINVAL;
633         }
634         raw_spin_unlock_irq(&logbuf_lock);
635         return ret;
636 }
637 
638 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
639 {
640         struct devkmsg_user *user = file->private_data;
641         int ret = 0;
642 
643         if (!user)
644                 return POLLERR|POLLNVAL;
645 
646         poll_wait(file, &log_wait, wait);
647 
648         raw_spin_lock_irq(&logbuf_lock);
649         if (user->seq < log_next_seq) {
650                 /* return error when data has vanished underneath us */
651                 if (user->seq < log_first_seq)
652                         ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
653                 else
654                         ret = POLLIN|POLLRDNORM;
655         }
656         raw_spin_unlock_irq(&logbuf_lock);
657 
658         return ret;
659 }
660 
661 static int devkmsg_open(struct inode *inode, struct file *file)
662 {
663         struct devkmsg_user *user;
664         int err;
665 
666         /* write-only does not need any file context */
667         if ((file->f_flags & O_ACCMODE) == O_WRONLY)
668                 return 0;
669 
670         err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
671                                        SYSLOG_FROM_READER);
672         if (err)
673                 return err;
674 
675         user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
676         if (!user)
677                 return -ENOMEM;
678 
679         mutex_init(&user->lock);
680 
681         raw_spin_lock_irq(&logbuf_lock);
682         user->idx = log_first_idx;
683         user->seq = log_first_seq;
684         raw_spin_unlock_irq(&logbuf_lock);
685 
686         file->private_data = user;
687         return 0;
688 }
689 
690 static int devkmsg_release(struct inode *inode, struct file *file)
691 {
692         struct devkmsg_user *user = file->private_data;
693 
694         if (!user)
695                 return 0;
696 
697         mutex_destroy(&user->lock);
698         kfree(user);
699         return 0;
700 }
701 
702 const struct file_operations kmsg_fops = {
703         .open = devkmsg_open,
704         .read = devkmsg_read,
705         .aio_write = devkmsg_writev,
706         .llseek = devkmsg_llseek,
707         .poll = devkmsg_poll,
708         .release = devkmsg_release,
709 };
710 
711 #ifdef CONFIG_KEXEC
712 /*
713  * This appends the listed symbols to /proc/vmcoreinfo
714  *
715  * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
716  * obtain access to symbols that are otherwise very difficult to locate.  These
717  * symbols are specifically used so that utilities can access and extract the
718  * dmesg log from a vmcore file after a crash.
719  */
720 void log_buf_kexec_setup(void)
721 {
722         VMCOREINFO_SYMBOL(log_buf);
723         VMCOREINFO_SYMBOL(log_buf_len);
724         VMCOREINFO_SYMBOL(log_first_idx);
725         VMCOREINFO_SYMBOL(log_next_idx);
726         /*
727          * Export struct log size and field offsets. User space tools can
728          * parse it and detect any changes to structure down the line.
729          */
730         VMCOREINFO_STRUCT_SIZE(log);
731         VMCOREINFO_OFFSET(log, ts_nsec);
732         VMCOREINFO_OFFSET(log, len);
733         VMCOREINFO_OFFSET(log, text_len);
734         VMCOREINFO_OFFSET(log, dict_len);
735 }
736 #endif
737 
738 /* requested log_buf_len from kernel cmdline */
739 static unsigned long __initdata new_log_buf_len;
740 
741 /* save requested log_buf_len since it's too early to process it */
742 static int __init log_buf_len_setup(char *str)
743 {
744         unsigned size = memparse(str, &str);
745 
746         if (size)
747                 size = roundup_pow_of_two(size);
748         if (size > log_buf_len)
749                 new_log_buf_len = size;
750 
751         return 0;
752 }
753 early_param("log_buf_len", log_buf_len_setup);
754 
755 void __init setup_log_buf(int early)
756 {
757         unsigned long flags;
758         char *new_log_buf;
759         int free;
760 
761         if (!new_log_buf_len)
762                 return;
763 
764         if (early) {
765                 unsigned long mem;
766 
767                 mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
768                 if (!mem)
769                         return;
770                 new_log_buf = __va(mem);
771         } else {
772                 new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
773         }
774 
775         if (unlikely(!new_log_buf)) {
776                 pr_err("log_buf_len: %ld bytes not available\n",
777                         new_log_buf_len);
778                 return;
779         }
780 
781         raw_spin_lock_irqsave(&logbuf_lock, flags);
782         log_buf_len = new_log_buf_len;
783         log_buf = new_log_buf;
784         new_log_buf_len = 0;
785         free = __LOG_BUF_LEN - log_next_idx;
786         memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
787         raw_spin_unlock_irqrestore(&logbuf_lock, flags);
788 
789         pr_info("log_buf_len: %d\n", log_buf_len);
790         pr_info("early log buf free: %d(%d%%)\n",
791                 free, (free * 100) / __LOG_BUF_LEN);
792 }
793 
794 static bool __read_mostly ignore_loglevel;
795 
796 static int __init ignore_loglevel_setup(char *str)
797 {
798         ignore_loglevel = 1;
799         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
800 
801         return 0;
802 }
803 
804 early_param("ignore_loglevel", ignore_loglevel_setup);
805 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
806 MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
807         "print all kernel messages to the console.");
808 
809 #ifdef CONFIG_BOOT_PRINTK_DELAY
810 
811 static int boot_delay; /* msecs delay after each printk during bootup */
812 static unsigned long long loops_per_msec;       /* based on boot_delay */
813 
814 static int __init boot_delay_setup(char *str)
815 {
816         unsigned long lpj;
817 
818         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
819         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
820 
821         get_option(&str, &boot_delay);
822         if (boot_delay > 10 * 1000)
823                 boot_delay = 0;
824 
825         pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
826                 "HZ: %d, loops_per_msec: %llu\n",
827                 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
828         return 1;
829 }
830 __setup("boot_delay=", boot_delay_setup);
831 
832 static void boot_delay_msec(int level)
833 {
834         unsigned long long k;
835         unsigned long timeout;
836 
837         if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
838                 || (level >= console_loglevel && !ignore_loglevel)) {
839                 return;
840         }
841 
842         k = (unsigned long long)loops_per_msec * boot_delay;
843 
844         timeout = jiffies + msecs_to_jiffies(boot_delay);
845         while (k) {
846                 k--;
847                 cpu_relax();
848                 /*
849                  * use (volatile) jiffies to prevent
850                  * compiler reduction; loop termination via jiffies
851                  * is secondary and may or may not happen.
852                  */
853                 if (time_after(jiffies, timeout))
854                         break;
855                 touch_nmi_watchdog();
856         }
857 }
858 #else
859 static inline void boot_delay_msec(int level)
860 {
861 }
862 #endif
863 
864 #if defined(CONFIG_PRINTK_TIME)
865 static bool printk_time = 1;
866 #else
867 static bool printk_time;
868 #endif
869 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
870 
871 static size_t print_time(u64 ts, char *buf)
872 {
873         unsigned long rem_nsec;
874 
875         if (!printk_time)
876                 return 0;
877 
878         rem_nsec = do_div(ts, 1000000000);
879 
880         if (!buf)
881                 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
882 
883         return sprintf(buf, "[%5lu.%06lu] ",
884                        (unsigned long)ts, rem_nsec / 1000);
885 }
886 
887 static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
888 {
889         size_t len = 0;
890         unsigned int prefix = (msg->facility << 3) | msg->level;
891 
892         if (syslog) {
893                 if (buf) {
894                         len += sprintf(buf, "<%u>", prefix);
895                 } else {
896                         len += 3;
897                         if (prefix > 999)
898                                 len += 3;
899                         else if (prefix > 99)
900                                 len += 2;
901                         else if (prefix > 9)
902                                 len++;
903                 }
904         }
905 
906         len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
907         return len;
908 }
909 
910 static size_t msg_print_text(const struct log *msg, enum log_flags prev,
911                              bool syslog, char *buf, size_t size)
912 {
913         const char *text = log_text(msg);
914         size_t text_size = msg->text_len;
915         bool prefix = true;
916         bool newline = true;
917         size_t len = 0;
918 
919         if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
920                 prefix = false;
921 
922         if (msg->flags & LOG_CONT) {
923                 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
924                         prefix = false;
925 
926                 if (!(msg->flags & LOG_NEWLINE))
927                         newline = false;
928         }
929 
930         do {
931                 const char *next = memchr(text, '\n', text_size);
932                 size_t text_len;
933 
934                 if (next) {
935                         text_len = next - text;
936                         next++;
937                         text_size -= next - text;
938                 } else {
939                         text_len = text_size;
940                 }
941 
942                 if (buf) {
943                         if (print_prefix(msg, syslog, NULL) +
944                             text_len + 1 >= size - len)
945                                 break;
946 
947                         if (prefix)
948                                 len += print_prefix(msg, syslog, buf + len);
949                         memcpy(buf + len, text, text_len);
950                         len += text_len;
951                         if (next || newline)
952                                 buf[len++] = '\n';
953                 } else {
954                         /* SYSLOG_ACTION_* buffer size only calculation */
955                         if (prefix)
956                                 len += print_prefix(msg, syslog, NULL);
957                         len += text_len;
958                         if (next || newline)
959                                 len++;
960                 }
961 
962                 prefix = true;
963                 text = next;
964         } while (text);
965 
966         return len;
967 }
968 
969 static int syslog_print(char __user *buf, int size)
970 {
971         char *text;
972         struct log *msg;
973         int len = 0;
974 
975         text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
976         if (!text)
977                 return -ENOMEM;
978 
979         while (size > 0) {
980                 size_t n;
981                 size_t skip;
982 
983                 raw_spin_lock_irq(&logbuf_lock);
984                 if (syslog_seq < log_first_seq) {
985                         /* messages are gone, move to first one */
986                         syslog_seq = log_first_seq;
987                         syslog_idx = log_first_idx;
988                         syslog_prev = 0;
989                         syslog_partial = 0;
990                 }
991                 if (syslog_seq == log_next_seq) {
992                         raw_spin_unlock_irq(&logbuf_lock);
993                         break;
994                 }
995 
996                 skip = syslog_partial;
997                 msg = log_from_idx(syslog_idx);
998                 n = msg_print_text(msg, syslog_prev, true, text,
999                                    LOG_LINE_MAX + PREFIX_MAX);
1000                 if (n - syslog_partial <= size) {
1001                         /* message fits into buffer, move forward */
1002                         syslog_idx = log_next(syslog_idx);
1003                         syslog_seq++;
1004                         syslog_prev = msg->flags;
1005                         n -= syslog_partial;
1006                         syslog_partial = 0;
1007                 } else if (!len){
1008                         /* partial read(), remember position */
1009                         n = size;
1010                         syslog_partial += n;
1011                 } else
1012                         n = 0;
1013                 raw_spin_unlock_irq(&logbuf_lock);
1014 
1015                 if (!n)
1016                         break;
1017 
1018                 if (copy_to_user(buf, text + skip, n)) {
1019                         if (!len)
1020                                 len = -EFAULT;
1021                         break;
1022                 }
1023 
1024                 len += n;
1025                 size -= n;
1026                 buf += n;
1027         }
1028 
1029         kfree(text);
1030         return len;
1031 }
1032 
1033 static int syslog_print_all(char __user *buf, int size, bool clear)
1034 {
1035         char *text;
1036         int len = 0;
1037 
1038         text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1039         if (!text)
1040                 return -ENOMEM;
1041 
1042         raw_spin_lock_irq(&logbuf_lock);
1043         if (buf) {
1044                 u64 next_seq;
1045                 u64 seq;
1046                 u32 idx;
1047                 enum log_flags prev;
1048 
1049                 if (clear_seq < log_first_seq) {
1050                         /* messages are gone, move to first available one */
1051                         clear_seq = log_first_seq;
1052                         clear_idx = log_first_idx;
1053                 }
1054 
1055                 /*
1056                  * Find first record that fits, including all following records,
1057                  * into the user-provided buffer for this dump.
1058                  */
1059                 seq = clear_seq;
1060                 idx = clear_idx;
1061                 prev = 0;
1062                 while (seq < log_next_seq) {
1063                         struct log *msg = log_from_idx(idx);
1064 
1065                         len += msg_print_text(msg, prev, true, NULL, 0);
1066                         prev = msg->flags;
1067                         idx = log_next(idx);
1068                         seq++;
1069                 }
1070 
1071                 /* move first record forward until length fits into the buffer */
1072                 seq = clear_seq;
1073                 idx = clear_idx;
1074                 prev = 0;
1075                 while (len > size && seq < log_next_seq) {
1076                         struct log *msg = log_from_idx(idx);
1077 
1078                         len -= msg_print_text(msg, prev, true, NULL, 0);
1079                         prev = msg->flags;
1080                         idx = log_next(idx);
1081                         seq++;
1082                 }
1083 
1084                 /* last message fitting into this dump */
1085                 next_seq = log_next_seq;
1086 
1087                 len = 0;
1088                 prev = 0;
1089                 while (len >= 0 && seq < next_seq) {
1090                         struct log *msg = log_from_idx(idx);
1091                         int textlen;
1092 
1093                         textlen = msg_print_text(msg, prev, true, text,
1094                                                  LOG_LINE_MAX + PREFIX_MAX);
1095                         if (textlen < 0) {
1096                                 len = textlen;
1097                                 break;
1098                         }
1099                         idx = log_next(idx);
1100                         seq++;
1101                         prev = msg->flags;
1102 
1103                         raw_spin_unlock_irq(&logbuf_lock);
1104                         if (copy_to_user(buf + len, text, textlen))
1105                                 len = -EFAULT;
1106                         else
1107                                 len += textlen;
1108                         raw_spin_lock_irq(&logbuf_lock);
1109 
1110                         if (seq < log_first_seq) {
1111                                 /* messages are gone, move to next one */
1112                                 seq = log_first_seq;
1113                                 idx = log_first_idx;
1114                                 prev = 0;
1115                         }
1116                 }
1117         }
1118 
1119         if (clear) {
1120                 clear_seq = log_next_seq;
1121                 clear_idx = log_next_idx;
1122         }
1123         raw_spin_unlock_irq(&logbuf_lock);
1124 
1125         kfree(text);
1126         return len;
1127 }
1128 
1129 int do_syslog(int type, char __user *buf, int len, bool from_file)
1130 {
1131         bool clear = false;
1132         static int saved_console_loglevel = -1;
1133         int error;
1134 
1135         error = check_syslog_permissions(type, from_file);
1136         if (error)
1137                 goto out;
1138 
1139         error = security_syslog(type);
1140         if (error)
1141                 return error;
1142 
1143         switch (type) {
1144         case SYSLOG_ACTION_CLOSE:       /* Close log */
1145                 break;
1146         case SYSLOG_ACTION_OPEN:        /* Open log */
1147                 break;
1148         case SYSLOG_ACTION_READ:        /* Read from log */
1149                 error = -EINVAL;
1150                 if (!buf || len < 0)
1151                         goto out;
1152                 error = 0;
1153                 if (!len)
1154                         goto out;
1155                 if (!access_ok(VERIFY_WRITE, buf, len)) {
1156                         error = -EFAULT;
1157                         goto out;
1158                 }
1159                 error = wait_event_interruptible(log_wait,
1160                                                  syslog_seq != log_next_seq);
1161                 if (error)
1162                         goto out;
1163                 error = syslog_print(buf, len);
1164                 break;
1165         /* Read/clear last kernel messages */
1166         case SYSLOG_ACTION_READ_CLEAR:
1167                 clear = true;
1168                 /* FALL THRU */
1169         /* Read last kernel messages */
1170         case SYSLOG_ACTION_READ_ALL:
1171                 error = -EINVAL;
1172                 if (!buf || len < 0)
1173                         goto out;
1174                 error = 0;
1175                 if (!len)
1176                         goto out;
1177                 if (!access_ok(VERIFY_WRITE, buf, len)) {
1178                         error = -EFAULT;
1179                         goto out;
1180                 }
1181                 error = syslog_print_all(buf, len, clear);
1182                 break;
1183         /* Clear ring buffer */
1184         case SYSLOG_ACTION_CLEAR:
1185                 syslog_print_all(NULL, 0, true);
1186                 break;
1187         /* Disable logging to console */
1188         case SYSLOG_ACTION_CONSOLE_OFF:
1189                 if (saved_console_loglevel == -1)
1190                         saved_console_loglevel = console_loglevel;
1191                 console_loglevel = minimum_console_loglevel;
1192                 break;
1193         /* Enable logging to console */
1194         case SYSLOG_ACTION_CONSOLE_ON:
1195                 if (saved_console_loglevel != -1) {
1196                         console_loglevel = saved_console_loglevel;
1197                         saved_console_loglevel = -1;
1198                 }
1199                 break;
1200         /* Set level of messages printed to console */
1201         case SYSLOG_ACTION_CONSOLE_LEVEL:
1202                 error = -EINVAL;
1203                 if (len < 1 || len > 8)
1204                         goto out;
1205                 if (len < minimum_console_loglevel)
1206                         len = minimum_console_loglevel;
1207                 console_loglevel = len;
1208                 /* Implicitly re-enable logging to console */
1209                 saved_console_loglevel = -1;
1210                 error = 0;
1211                 break;
1212         /* Number of chars in the log buffer */
1213         case SYSLOG_ACTION_SIZE_UNREAD:
1214                 raw_spin_lock_irq(&logbuf_lock);
1215                 if (syslog_seq < log_first_seq) {
1216                         /* messages are gone, move to first one */
1217                         syslog_seq = log_first_seq;
1218                         syslog_idx = log_first_idx;
1219                         syslog_prev = 0;
1220                         syslog_partial = 0;
1221                 }
1222                 if (from_file) {
1223                         /*
1224                          * Short-cut for poll(/"proc/kmsg") which simply checks
1225                          * for pending data, not the size; return the count of
1226                          * records, not the length.
1227                          */
1228                         error = log_next_idx - syslog_idx;
1229                 } else {
1230                         u64 seq = syslog_seq;
1231                         u32 idx = syslog_idx;
1232                         enum log_flags prev = syslog_prev;
1233 
1234                         error = 0;
1235                         while (seq < log_next_seq) {
1236                                 struct log *msg = log_from_idx(idx);
1237 
1238                                 error += msg_print_text(msg, prev, true, NULL, 0);
1239                                 idx = log_next(idx);
1240                                 seq++;
1241                                 prev = msg->flags;
1242                         }
1243                         error -= syslog_partial;
1244                 }
1245                 raw_spin_unlock_irq(&logbuf_lock);
1246                 break;
1247         /* Size of the log buffer */
1248         case SYSLOG_ACTION_SIZE_BUFFER:
1249                 error = log_buf_len;
1250                 break;
1251         default:
1252                 error = -EINVAL;
1253                 break;
1254         }
1255 out:
1256         return error;
1257 }
1258 
1259 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1260 {
1261         return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1262 }
1263 
1264 /*
1265  * Call the console drivers, asking them to write out
1266  * log_buf[start] to log_buf[end - 1].
1267  * The console_lock must be held.
1268  */
1269 static void call_console_drivers(int level, const char *text, size_t len)
1270 {
1271         struct console *con;
1272 
1273         trace_console_rcuidle(text, len);
1274 
1275         if (level >= console_loglevel && !ignore_loglevel)
1276                 return;
1277         if (!console_drivers)
1278                 return;
1279 
1280         for_each_console(con) {
1281                 if (exclusive_console && con != exclusive_console)
1282                         continue;
1283                 if (!(con->flags & CON_ENABLED))
1284                         continue;
1285                 if (!con->write)
1286                         continue;
1287                 if (!cpu_online(smp_processor_id()) &&
1288                     !(con->flags & CON_ANYTIME))
1289                         continue;
1290                 con->write(con, text, len);
1291         }
1292 }
1293 
1294 /*
1295  * Zap console related locks when oopsing. Only zap at most once
1296  * every 10 seconds, to leave time for slow consoles to print a
1297  * full oops.
1298  */
1299 static void zap_locks(void)
1300 {
1301         static unsigned long oops_timestamp;
1302 
1303         if (time_after_eq(jiffies, oops_timestamp) &&
1304                         !time_after(jiffies, oops_timestamp + 30 * HZ))
1305                 return;
1306 
1307         oops_timestamp = jiffies;
1308 
1309         debug_locks_off();
1310         /* If a crash is occurring, make sure we can't deadlock */
1311         raw_spin_lock_init(&logbuf_lock);
1312         /* And make sure that we print immediately */
1313         sema_init(&console_sem, 1);
1314 }
1315 
1316 /* Check if we have any console registered that can be called early in boot. */
1317 static int have_callable_console(void)
1318 {
1319         struct console *con;
1320 
1321         for_each_console(con)
1322                 if (con->flags & CON_ANYTIME)
1323                         return 1;
1324 
1325         return 0;
1326 }
1327 
1328 /*
1329  * Can we actually use the console at this time on this cpu?
1330  *
1331  * Console drivers may assume that per-cpu resources have
1332  * been allocated. So unless they're explicitly marked as
1333  * being able to cope (CON_ANYTIME) don't call them until
1334  * this CPU is officially up.
1335  */
1336 static inline int can_use_console(unsigned int cpu)
1337 {
1338         return cpu_online(cpu) || have_callable_console();
1339 }
1340 
1341 /*
1342  * Try to get console ownership to actually show the kernel
1343  * messages from a 'printk'. Return true (and with the
1344  * console_lock held, and 'console_locked' set) if it
1345  * is successful, false otherwise.
1346  *
1347  * This gets called with the 'logbuf_lock' spinlock held and
1348  * interrupts disabled. It should return with 'lockbuf_lock'
1349  * released but interrupts still disabled.
1350  */
1351 static int console_trylock_for_printk(unsigned int cpu)
1352         __releases(&logbuf_lock)
1353 {
1354         int retval = 0, wake = 0;
1355 
1356         if (console_trylock()) {
1357                 retval = 1;
1358 
1359                 /*
1360                  * If we can't use the console, we need to release
1361                  * the console semaphore by hand to avoid flushing
1362                  * the buffer. We need to hold the console semaphore
1363                  * in order to do this test safely.
1364                  */
1365                 if (!can_use_console(cpu)) {
1366                         console_locked = 0;
1367                         wake = 1;
1368                         retval = 0;
1369                 }
1370         }
1371         logbuf_cpu = UINT_MAX;
1372         raw_spin_unlock(&logbuf_lock);
1373         if (wake)
1374                 up(&console_sem);
1375         return retval;
1376 }
1377 
1378 int printk_delay_msec __read_mostly;
1379 
1380 static inline void printk_delay(void)
1381 {
1382         if (unlikely(printk_delay_msec)) {
1383                 int m = printk_delay_msec;
1384 
1385                 while (m--) {
1386                         mdelay(1);
1387                         touch_nmi_watchdog();
1388                 }
1389         }
1390 }
1391 
1392 /*
1393  * Continuation lines are buffered, and not committed to the record buffer
1394  * until the line is complete, or a race forces it. The line fragments
1395  * though, are printed immediately to the consoles to ensure everything has
1396  * reached the console in case of a kernel crash.
1397  */
1398 static struct cont {
1399         char buf[LOG_LINE_MAX];
1400         size_t len;                     /* length == 0 means unused buffer */
1401         size_t cons;                    /* bytes written to console */
1402         struct task_struct *owner;      /* task of first print*/
1403         u64 ts_nsec;                    /* time of first print */
1404         u8 level;                       /* log level of first message */
1405         u8 facility;                    /* log level of first message */
1406         enum log_flags flags;           /* prefix, newline flags */
1407         bool flushed:1;                 /* buffer sealed and committed */
1408 } cont;
1409 
1410 static void cont_flush(enum log_flags flags)
1411 {
1412         if (cont.flushed)
1413                 return;
1414         if (cont.len == 0)
1415                 return;
1416 
1417         if (cont.cons) {
1418                 /*
1419                  * If a fragment of this line was directly flushed to the
1420                  * console; wait for the console to pick up the rest of the
1421                  * line. LOG_NOCONS suppresses a duplicated output.
1422                  */
1423                 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1424                           cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1425                 cont.flags = flags;
1426                 cont.flushed = true;
1427         } else {
1428                 /*
1429                  * If no fragment of this line ever reached the console,
1430                  * just submit it to the store and free the buffer.
1431                  */
1432                 log_store(cont.facility, cont.level, flags, 0,
1433                           NULL, 0, cont.buf, cont.len);
1434                 cont.len = 0;
1435         }
1436 }
1437 
1438 static bool cont_add(int facility, int level, const char *text, size_t len)
1439 {
1440         if (cont.len && cont.flushed)
1441                 return false;
1442 
1443         if (cont.len + len > sizeof(cont.buf)) {
1444                 /* the line gets too long, split it up in separate records */
1445                 cont_flush(LOG_CONT);
1446                 return false;
1447         }
1448 
1449         if (!cont.len) {
1450                 cont.facility = facility;
1451                 cont.level = level;
1452                 cont.owner = current;
1453                 cont.ts_nsec = local_clock();
1454                 cont.flags = 0;
1455                 cont.cons = 0;
1456                 cont.flushed = false;
1457         }
1458 
1459         memcpy(cont.buf + cont.len, text, len);
1460         cont.len += len;
1461 
1462         if (cont.len > (sizeof(cont.buf) * 80) / 100)
1463                 cont_flush(LOG_CONT);
1464 
1465         return true;
1466 }
1467 
1468 static size_t cont_print_text(char *text, size_t size)
1469 {
1470         size_t textlen = 0;
1471         size_t len;
1472 
1473         if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1474                 textlen += print_time(cont.ts_nsec, text);
1475                 size -= textlen;
1476         }
1477 
1478         len = cont.len - cont.cons;
1479         if (len > 0) {
1480                 if (len+1 > size)
1481                         len = size-1;
1482                 memcpy(text + textlen, cont.buf + cont.cons, len);
1483                 textlen += len;
1484                 cont.cons = cont.len;
1485         }
1486 
1487         if (cont.flushed) {
1488                 if (cont.flags & LOG_NEWLINE)
1489                         text[textlen++] = '\n';
1490                 /* got everything, release buffer */
1491                 cont.len = 0;
1492         }
1493         return textlen;
1494 }
1495 
1496 asmlinkage int vprintk_emit(int facility, int level,
1497                             const char *dict, size_t dictlen,
1498                             const char *fmt, va_list args)
1499 {
1500         static int recursion_bug;
1501         static char textbuf[LOG_LINE_MAX];
1502         char *text = textbuf;
1503         size_t text_len;
1504         enum log_flags lflags = 0;
1505         unsigned long flags;
1506         int this_cpu;
1507         int printed_len = 0;
1508 
1509         boot_delay_msec(level);
1510         printk_delay();
1511 
1512         /* This stops the holder of console_sem just where we want him */
1513         local_irq_save(flags);
1514         this_cpu = smp_processor_id();
1515 
1516         /*
1517          * Ouch, printk recursed into itself!
1518          */
1519         if (unlikely(logbuf_cpu == this_cpu)) {
1520                 /*
1521                  * If a crash is occurring during printk() on this CPU,
1522                  * then try to get the crash message out but make sure
1523                  * we can't deadlock. Otherwise just return to avoid the
1524                  * recursion and return - but flag the recursion so that
1525                  * it can be printed at the next appropriate moment:
1526                  */
1527                 if (!oops_in_progress && !lockdep_recursing(current)) {
1528                         recursion_bug = 1;
1529                         goto out_restore_irqs;
1530                 }
1531                 zap_locks();
1532         }
1533 
1534         lockdep_off();
1535         raw_spin_lock(&logbuf_lock);
1536         logbuf_cpu = this_cpu;
1537 
1538         if (recursion_bug) {
1539                 static const char recursion_msg[] =
1540                         "BUG: recent printk recursion!";
1541 
1542                 recursion_bug = 0;
1543                 printed_len += strlen(recursion_msg);
1544                 /* emit KERN_CRIT message */
1545                 log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1546                           NULL, 0, recursion_msg, printed_len);
1547         }
1548 
1549         /*
1550          * The printf needs to come first; we need the syslog
1551          * prefix which might be passed-in as a parameter.
1552          */
1553         text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1554 
1555         /* mark and strip a trailing newline */
1556         if (text_len && text[text_len-1] == '\n') {
1557                 text_len--;
1558                 lflags |= LOG_NEWLINE;
1559         }
1560 
1561         /* strip kernel syslog prefix and extract log level or control flags */
1562         if (facility == 0) {
1563                 int kern_level = printk_get_level(text);
1564 
1565                 if (kern_level) {
1566                         const char *end_of_header = printk_skip_level(text);
1567                         switch (kern_level) {
1568                         case '' ... '7':
1569                                 if (level == -1)
1570                                         level = kern_level - '';
1571                         case 'd':       /* KERN_DEFAULT */
1572                                 lflags |= LOG_PREFIX;
1573                         case 'c':       /* KERN_CONT */
1574                                 break;
1575                         }
1576                         text_len -= end_of_header - text;
1577                         text = (char *)end_of_header;
1578                 }
1579         }
1580 
1581         if (level == -1)
1582                 level = default_message_loglevel;
1583 
1584         if (dict)
1585                 lflags |= LOG_PREFIX|LOG_NEWLINE;
1586 
1587         if (!(lflags & LOG_NEWLINE)) {
1588                 /*
1589                  * Flush the conflicting buffer. An earlier newline was missing,
1590                  * or another task also prints continuation lines.
1591                  */
1592                 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1593                         cont_flush(LOG_NEWLINE);
1594 
1595                 /* buffer line if possible, otherwise store it right away */
1596                 if (!cont_add(facility, level, text, text_len))
1597                         log_store(facility, level, lflags | LOG_CONT, 0,
1598                                   dict, dictlen, text, text_len);
1599         } else {
1600                 bool stored = false;
1601 
1602                 /*
1603                  * If an earlier newline was missing and it was the same task,
1604                  * either merge it with the current buffer and flush, or if
1605                  * there was a race with interrupts (prefix == true) then just
1606                  * flush it out and store this line separately.
1607                  */
1608                 if (cont.len && cont.owner == current) {
1609                         if (!(lflags & LOG_PREFIX))
1610                                 stored = cont_add(facility, level, text, text_len);
1611                         cont_flush(LOG_NEWLINE);
1612                 }
1613 
1614                 if (!stored)
1615                         log_store(facility, level, lflags, 0,
1616                                   dict, dictlen, text, text_len);
1617         }
1618         printed_len += text_len;
1619 
1620         /*
1621          * Try to acquire and then immediately release the console semaphore.
1622          * The release will print out buffers and wake up /dev/kmsg and syslog()
1623          * users.
1624          *
1625          * The console_trylock_for_printk() function will release 'logbuf_lock'
1626          * regardless of whether it actually gets the console semaphore or not.
1627          */
1628         if (console_trylock_for_printk(this_cpu))
1629                 console_unlock();
1630 
1631         lockdep_on();
1632 out_restore_irqs:
1633         local_irq_restore(flags);
1634 
1635         return printed_len;
1636 }
1637 EXPORT_SYMBOL(vprintk_emit);
1638 
1639 asmlinkage int vprintk(const char *fmt, va_list args)
1640 {
1641         return vprintk_emit(0, -1, NULL, 0, fmt, args);
1642 }
1643 EXPORT_SYMBOL(vprintk);
1644 
1645 asmlinkage int printk_emit(int facility, int level,
1646                            const char *dict, size_t dictlen,
1647                            const char *fmt, ...)
1648 {
1649         va_list args;
1650         int r;
1651 
1652         va_start(args, fmt);
1653         r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1654         va_end(args);
1655 
1656         return r;
1657 }
1658 EXPORT_SYMBOL(printk_emit);
1659 
1660 /**
1661  * printk - print a kernel message
1662  * @fmt: format string
1663  *
1664  * This is printk(). It can be called from any context. We want it to work.
1665  *
1666  * We try to grab the console_lock. If we succeed, it's easy - we log the
1667  * output and call the console drivers.  If we fail to get the semaphore, we
1668  * place the output into the log buffer and return. The current holder of
1669  * the console_sem will notice the new output in console_unlock(); and will
1670  * send it to the consoles before releasing the lock.
1671  *
1672  * One effect of this deferred printing is that code which calls printk() and
1673  * then changes console_loglevel may break. This is because console_loglevel
1674  * is inspected when the actual printing occurs.
1675  *
1676  * See also:
1677  * printf(3)
1678  *
1679  * See the vsnprintf() documentation for format string extensions over C99.
1680  */
1681 asmlinkage int printk(const char *fmt, ...)
1682 {
1683         va_list args;
1684         int r;
1685 
1686 #ifdef CONFIG_KGDB_KDB
1687         if (unlikely(kdb_trap_printk)) {
1688                 va_start(args, fmt);
1689                 r = vkdb_printf(fmt, args);
1690                 va_end(args);
1691                 return r;
1692         }
1693 #endif
1694         va_start(args, fmt);
1695         r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1696         va_end(args);
1697 
1698         return r;
1699 }
1700 EXPORT_SYMBOL(printk);
1701 
1702 #else /* CONFIG_PRINTK */
1703 
1704 #define LOG_LINE_MAX            0
1705 #define PREFIX_MAX              0
1706 #define LOG_LINE_MAX 0
1707 static u64 syslog_seq;
1708 static u32 syslog_idx;
1709 static u64 console_seq;
1710 static u32 console_idx;
1711 static enum log_flags syslog_prev;
1712 static u64 log_first_seq;
1713 static u32 log_first_idx;
1714 static u64 log_next_seq;
1715 static enum log_flags console_prev;
1716 static struct cont {
1717         size_t len;
1718         size_t cons;
1719         u8 level;
1720         bool flushed:1;
1721 } cont;
1722 static struct log *log_from_idx(u32 idx) { return NULL; }
1723 static u32 log_next(u32 idx) { return 0; }
1724 static void call_console_drivers(int level, const char *text, size_t len) {}
1725 static size_t msg_print_text(const struct log *msg, enum log_flags prev,
1726                              bool syslog, char *buf, size_t size) { return 0; }
1727 static size_t cont_print_text(char *text, size_t size) { return 0; }
1728 
1729 #endif /* CONFIG_PRINTK */
1730 
1731 #ifdef CONFIG_EARLY_PRINTK
1732 struct console *early_console;
1733 
1734 void early_vprintk(const char *fmt, va_list ap)
1735 {
1736         if (early_console) {
1737                 char buf[512];
1738                 int n = vscnprintf(buf, sizeof(buf), fmt, ap);
1739 
1740                 early_console->write(early_console, buf, n);
1741         }
1742 }
1743 
1744 asmlinkage void early_printk(const char *fmt, ...)
1745 {
1746         va_list ap;
1747 
1748         va_start(ap, fmt);
1749         early_vprintk(fmt, ap);
1750         va_end(ap);
1751 }
1752 #endif
1753 
1754 static int __add_preferred_console(char *name, int idx, char *options,
1755                                    char *brl_options)
1756 {
1757         struct console_cmdline *c;
1758         int i;
1759 
1760         /*
1761          *      See if this tty is not yet registered, and
1762          *      if we have a slot free.
1763          */
1764         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1765                 if (strcmp(console_cmdline[i].name, name) == 0 &&
1766                           console_cmdline[i].index == idx) {
1767                                 if (!brl_options)
1768                                         selected_console = i;
1769                                 return 0;
1770                 }
1771         if (i == MAX_CMDLINECONSOLES)
1772                 return -E2BIG;
1773         if (!brl_options)
1774                 selected_console = i;
1775         c = &console_cmdline[i];
1776         strlcpy(c->name, name, sizeof(c->name));
1777         c->options = options;
1778 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1779         c->brl_options = brl_options;
1780 #endif
1781         c->index = idx;
1782         return 0;
1783 }
1784 /*
1785  * Set up a list of consoles.  Called from init/main.c
1786  */
1787 static int __init console_setup(char *str)
1788 {
1789         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1790         char *s, *options, *brl_options = NULL;
1791         int idx;
1792 
1793 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1794         if (!memcmp(str, "brl,", 4)) {
1795                 brl_options = "";
1796                 str += 4;
1797         } else if (!memcmp(str, "brl=", 4)) {
1798                 brl_options = str + 4;
1799                 str = strchr(brl_options, ',');
1800                 if (!str) {
1801                         printk(KERN_ERR "need port name after brl=\n");
1802                         return 1;
1803                 }
1804                 *(str++) = 0;
1805         }
1806 #endif
1807 
1808         /*
1809          * Decode str into name, index, options.
1810          */
1811         if (str[0] >= '' && str[0] <= '9') {
1812                 strcpy(buf, "ttyS");
1813                 strncpy(buf + 4, str, sizeof(buf) - 5);
1814         } else {
1815                 strncpy(buf, str, sizeof(buf) - 1);
1816         }
1817         buf[sizeof(buf) - 1] = 0;
1818         if ((options = strchr(str, ',')) != NULL)
1819                 *(options++) = 0;
1820 #ifdef __sparc__
1821         if (!strcmp(str, "ttya"))
1822                 strcpy(buf, "ttyS0");
1823         if (!strcmp(str, "ttyb"))
1824                 strcpy(buf, "ttyS1");
1825 #endif
1826         for (s = buf; *s; s++)
1827                 if ((*s >= '' && *s <= '9') || *s == ',')
1828                         break;
1829         idx = simple_strtoul(s, NULL, 10);
1830         *s = 0;
1831 
1832         __add_preferred_console(buf, idx, options, brl_options);
1833         console_set_on_cmdline = 1;
1834         return 1;
1835 }
1836 __setup("console=", console_setup);
1837 
1838 /**
1839  * add_preferred_console - add a device to the list of preferred consoles.
1840  * @name: device name
1841  * @idx: device index
1842  * @options: options for this console
1843  *
1844  * The last preferred console added will be used for kernel messages
1845  * and stdin/out/err for init.  Normally this is used by console_setup
1846  * above to handle user-supplied console arguments; however it can also
1847  * be used by arch-specific code either to override the user or more
1848  * commonly to provide a default console (ie from PROM variables) when
1849  * the user has not supplied one.
1850  */
1851 int add_preferred_console(char *name, int idx, char *options)
1852 {
1853         return __add_preferred_console(name, idx, options, NULL);
1854 }
1855 
1856 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1857 {
1858         struct console_cmdline *c;
1859         int i;
1860 
1861         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1862                 if (strcmp(console_cmdline[i].name, name) == 0 &&
1863                           console_cmdline[i].index == idx) {
1864                                 c = &console_cmdline[i];
1865                                 strlcpy(c->name, name_new, sizeof(c->name));
1866                                 c->name[sizeof(c->name) - 1] = 0;
1867                                 c->options = options;
1868                                 c->index = idx_new;
1869                                 return i;
1870                 }
1871         /* not found */
1872         return -1;
1873 }
1874 
1875 bool console_suspend_enabled = 1;
1876 EXPORT_SYMBOL(console_suspend_enabled);
1877 
1878 static int __init console_suspend_disable(char *str)
1879 {
1880         console_suspend_enabled = 0;
1881         return 1;
1882 }
1883 __setup("no_console_suspend", console_suspend_disable);
1884 module_param_named(console_suspend, console_suspend_enabled,
1885                 bool, S_IRUGO | S_IWUSR);
1886 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1887         " and hibernate operations");
1888 
1889 /**
1890  * suspend_console - suspend the console subsystem
1891  *
1892  * This disables printk() while we go into suspend states
1893  */
1894 void suspend_console(void)
1895 {
1896         if (!console_suspend_enabled)
1897                 return;
1898         printk("Suspending console(s) (use no_console_suspend to debug)\n");
1899         console_lock();
1900         console_suspended = 1;
1901         up(&console_sem);
1902 }
1903 
1904 void resume_console(void)
1905 {
1906         if (!console_suspend_enabled)
1907                 return;
1908         down(&console_sem);
1909         console_suspended = 0;
1910         console_unlock();
1911 }
1912 
1913 /**
1914  * console_cpu_notify - print deferred console messages after CPU hotplug
1915  * @self: notifier struct
1916  * @action: CPU hotplug event
1917  * @hcpu: unused
1918  *
1919  * If printk() is called from a CPU that is not online yet, the messages
1920  * will be spooled but will not show up on the console.  This function is
1921  * called when a new CPU comes online (or fails to come up), and ensures
1922  * that any such output gets printed.
1923  */
1924 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1925         unsigned long action, void *hcpu)
1926 {
1927         switch (action) {
1928         case CPU_ONLINE:
1929         case CPU_DEAD:
1930         case CPU_DOWN_FAILED:
1931         case CPU_UP_CANCELED:
1932                 console_lock();
1933                 console_unlock();
1934         }
1935         return NOTIFY_OK;
1936 }
1937 
1938 /**
1939  * console_lock - lock the console system for exclusive use.
1940  *
1941  * Acquires a lock which guarantees that the caller has
1942  * exclusive access to the console system and the console_drivers list.
1943  *
1944  * Can sleep, returns nothing.
1945  */
1946 void console_lock(void)
1947 {
1948         might_sleep();
1949 
1950         down(&console_sem);
1951         if (console_suspended)
1952                 return;
1953         console_locked = 1;
1954         console_may_schedule = 1;
1955         mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
1956 }
1957 EXPORT_SYMBOL(console_lock);
1958 
1959 /**
1960  * console_trylock - try to lock the console system for exclusive use.
1961  *
1962  * Tried to acquire a lock which guarantees that the caller has
1963  * exclusive access to the console system and the console_drivers list.
1964  *
1965  * returns 1 on success, and 0 on failure to acquire the lock.
1966  */
1967 int console_trylock(void)
1968 {
1969         if (down_trylock(&console_sem))
1970                 return 0;
1971         if (console_suspended) {
1972                 up(&console_sem);
1973                 return 0;
1974         }
1975         console_locked = 1;
1976         console_may_schedule = 0;
1977         mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);
1978         return 1;
1979 }
1980 EXPORT_SYMBOL(console_trylock);
1981 
1982 int is_console_locked(void)
1983 {
1984         return console_locked;
1985 }
1986 
1987 static void console_cont_flush(char *text, size_t size)
1988 {
1989         unsigned long flags;
1990         size_t len;
1991 
1992         raw_spin_lock_irqsave(&logbuf_lock, flags);
1993 
1994         if (!cont.len)
1995                 goto out;
1996 
1997         /*
1998          * We still queue earlier records, likely because the console was
1999          * busy. The earlier ones need to be printed before this one, we
2000          * did not flush any fragment so far, so just let it queue up.
2001          */
2002         if (console_seq < log_next_seq && !cont.cons)
2003                 goto out;
2004 
2005         len = cont_print_text(text, size);
2006         raw_spin_unlock(&logbuf_lock);
2007         stop_critical_timings();
2008         call_console_drivers(cont.level, text, len);
2009         start_critical_timings();
2010         local_irq_restore(flags);
2011         return;
2012 out:
2013         raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2014 }
2015 
2016 /**
2017  * console_unlock - unlock the console system
2018  *
2019  * Releases the console_lock which the caller holds on the console system
2020  * and the console driver list.
2021  *
2022  * While the console_lock was held, console output may have been buffered
2023  * by printk().  If this is the case, console_unlock(); emits
2024  * the output prior to releasing the lock.
2025  *
2026  * If there is output waiting, we wake /dev/kmsg and syslog() users.
2027  *
2028  * console_unlock(); may be called from any context.
2029  */
2030 void console_unlock(void)
2031 {
2032         static char text[LOG_LINE_MAX + PREFIX_MAX];
2033         static u64 seen_seq;
2034         unsigned long flags;
2035         bool wake_klogd = false;
2036         bool do_cond_resched, retry;
2037 
2038         if (console_suspended) {
2039                 up(&console_sem);
2040                 return;
2041         }
2042 
2043         /*
2044          * Console drivers are called under logbuf_lock, so
2045          * @console_may_schedule should be cleared before; however, we may
2046          * end up dumping a lot of lines, for example, if called from
2047          * console registration path, and should invoke cond_resched()
2048          * between lines if allowable.  Not doing so can cause a very long
2049          * scheduling stall on a slow console leading to RCU stall and
2050          * softlockup warnings which exacerbate the issue with more
2051          * messages practically incapacitating the system.
2052          */
2053         do_cond_resched = console_may_schedule;
2054         console_may_schedule = 0;
2055 
2056         /* flush buffered message fragment immediately to console */
2057         console_cont_flush(text, sizeof(text));
2058 again:
2059         for (;;) {
2060                 struct log *msg;
2061                 size_t len;
2062                 int level;
2063 
2064                 raw_spin_lock_irqsave(&logbuf_lock, flags);
2065                 if (seen_seq != log_next_seq) {
2066                         wake_klogd = true;
2067                         seen_seq = log_next_seq;
2068                 }
2069 
2070                 if (console_seq < log_first_seq) {
2071                         /* messages are gone, move to first one */
2072                         console_seq = log_first_seq;
2073                         console_idx = log_first_idx;
2074                         console_prev = 0;
2075                 }
2076 skip:
2077                 if (console_seq == log_next_seq)
2078                         break;
2079 
2080                 msg = log_from_idx(console_idx);
2081                 if (msg->flags & LOG_NOCONS) {
2082                         /*
2083                          * Skip record we have buffered and already printed
2084                          * directly to the console when we received it.
2085                          */
2086                         console_idx = log_next(console_idx);
2087                         console_seq++;
2088                         /*
2089                          * We will get here again when we register a new
2090                          * CON_PRINTBUFFER console. Clear the flag so we
2091                          * will properly dump everything later.
2092                          */
2093                         msg->flags &= ~LOG_NOCONS;
2094                         console_prev = msg->flags;
2095                         goto skip;
2096                 }
2097 
2098                 level = msg->level;
2099                 len = msg_print_text(msg, console_prev, false,
2100                                      text, sizeof(text));
2101                 console_idx = log_next(console_idx);
2102                 console_seq++;
2103                 console_prev = msg->flags;
2104                 raw_spin_unlock(&logbuf_lock);
2105 
2106                 stop_critical_timings();        /* don't trace print latency */
2107                 call_console_drivers(level, text, len);
2108                 start_critical_timings();
2109                 local_irq_restore(flags);
2110 
2111                 if (do_cond_resched)
2112                         cond_resched();
2113         }
2114         console_locked = 0;
2115         mutex_release(&console_lock_dep_map, 1, _RET_IP_);
2116 
2117         /* Release the exclusive_console once it is used */
2118         if (unlikely(exclusive_console))
2119                 exclusive_console = NULL;
2120 
2121         raw_spin_unlock(&logbuf_lock);
2122 
2123         up(&console_sem);
2124 
2125         /*
2126          * Someone could have filled up the buffer again, so re-check if there's
2127          * something to flush. In case we cannot trylock the console_sem again,
2128          * there's a new owner and the console_unlock() from them will do the
2129          * flush, no worries.
2130          */
2131         raw_spin_lock(&logbuf_lock);
2132         retry = console_seq != log_next_seq;
2133         raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2134 
2135         if (retry && console_trylock())
2136                 goto again;
2137 
2138         if (wake_klogd)
2139                 wake_up_klogd();
2140 }
2141 EXPORT_SYMBOL(console_unlock);
2142 
2143 /**
2144  * console_conditional_schedule - yield the CPU if required
2145  *
2146  * If the console code is currently allowed to sleep, and
2147  * if this CPU should yield the CPU to another task, do
2148  * so here.
2149  *
2150  * Must be called within console_lock();.
2151  */
2152 void __sched console_conditional_schedule(void)
2153 {
2154         if (console_may_schedule)
2155                 cond_resched();
2156 }
2157 EXPORT_SYMBOL(console_conditional_schedule);
2158 
2159 void console_unblank(void)
2160 {
2161         struct console *c;
2162 
2163         /*
2164          * console_unblank can no longer be called in interrupt context unless
2165          * oops_in_progress is set to 1..
2166          */
2167         if (oops_in_progress) {
2168                 if (down_trylock(&console_sem) != 0)
2169                         return;
2170         } else
2171                 console_lock();
2172 
2173         console_locked = 1;
2174         console_may_schedule = 0;
2175         for_each_console(c)
2176                 if ((c->flags & CON_ENABLED) && c->unblank)
2177                         c->unblank();
2178         console_unlock();
2179 }
2180 
2181 /**
2182  * console_flush_on_panic - flush console content on panic
2183  *
2184  * Immediately output all pending messages no matter what.
2185  */
2186 void console_flush_on_panic(void)
2187 {
2188         /*
2189          * If someone else is holding the console lock, trylock will fail
2190          * and may_schedule may be set.  Ignore and proceed to unlock so
2191          * that messages are flushed out.  As this can be called from any
2192          * context and we don't want to get preempted while flushing,
2193          * ensure may_schedule is cleared.
2194          */
2195         console_trylock();
2196         console_may_schedule = 0;
2197         console_unlock();
2198 }
2199 
2200 /*
2201  * Return the console tty driver structure and its associated index
2202  */
2203 struct tty_driver *console_device(int *index)
2204 {
2205         struct console *c;
2206         struct tty_driver *driver = NULL;
2207 
2208         console_lock();
2209         for_each_console(c) {
2210                 if (!c->device)
2211                         continue;
2212                 driver = c->device(c, index);
2213                 if (driver)
2214                         break;
2215         }
2216         console_unlock();
2217         return driver;
2218 }
2219 
2220 /*
2221  * Prevent further output on the passed console device so that (for example)
2222  * serial drivers can disable console output before suspending a port, and can
2223  * re-enable output afterwards.
2224  */
2225 void console_stop(struct console *console)
2226 {
2227         console_lock();
2228         console->flags &= ~CON_ENABLED;
2229         console_unlock();
2230 }
2231 EXPORT_SYMBOL(console_stop);
2232 
2233 void console_start(struct console *console)
2234 {
2235         console_lock();
2236         console->flags |= CON_ENABLED;
2237         console_unlock();
2238 }
2239 EXPORT_SYMBOL(console_start);
2240 
2241 static int __read_mostly keep_bootcon;
2242 
2243 static int __init keep_bootcon_setup(char *str)
2244 {
2245         keep_bootcon = 1;
2246         printk(KERN_INFO "debug: skip boot console de-registration.\n");
2247 
2248         return 0;
2249 }
2250 
2251 early_param("keep_bootcon", keep_bootcon_setup);
2252 
2253 /*
2254  * The console driver calls this routine during kernel initialization
2255  * to register the console printing procedure with printk() and to
2256  * print any messages that were printed by the kernel before the
2257  * console driver was initialized.
2258  *
2259  * This can happen pretty early during the boot process (because of
2260  * early_printk) - sometimes before setup_arch() completes - be careful
2261  * of what kernel features are used - they may not be initialised yet.
2262  *
2263  * There are two types of consoles - bootconsoles (early_printk) and
2264  * "real" consoles (everything which is not a bootconsole) which are
2265  * handled differently.
2266  *  - Any number of bootconsoles can be registered at any time.
2267  *  - As soon as a "real" console is registered, all bootconsoles
2268  *    will be unregistered automatically.
2269  *  - Once a "real" console is registered, any attempt to register a
2270  *    bootconsoles will be rejected
2271  */
2272 void register_console(struct console *newcon)
2273 {
2274         int i;
2275         unsigned long flags;
2276         struct console *bcon = NULL;
2277 
2278         /*
2279          * before we register a new CON_BOOT console, make sure we don't
2280          * already have a valid console
2281          */
2282         if (console_drivers && newcon->flags & CON_BOOT) {
2283                 /* find the last or real console */
2284                 for_each_console(bcon) {
2285                         if (!(bcon->flags & CON_BOOT)) {
2286                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
2287                                         newcon->name, newcon->index);
2288                                 return;
2289                         }
2290                 }
2291         }
2292 
2293         if (console_drivers && console_drivers->flags & CON_BOOT)
2294                 bcon = console_drivers;
2295 
2296         if (preferred_console < 0 || bcon || !console_drivers)
2297                 preferred_console = selected_console;
2298 
2299         if (newcon->early_setup)
2300                 newcon->early_setup();
2301 
2302         /*
2303          *      See if we want to use this console driver. If we
2304          *      didn't select a console we take the first one
2305          *      that registers here.
2306          */
2307         if (preferred_console < 0) {
2308                 if (newcon->index < 0)
2309                         newcon->index = 0;
2310                 if (newcon->setup == NULL ||
2311                     newcon->setup(newcon, NULL) == 0) {
2312                         newcon->flags |= CON_ENABLED;
2313                         if (newcon->device) {
2314                                 newcon->flags |= CON_CONSDEV;
2315                                 preferred_console = 0;
2316                         }
2317                 }
2318         }
2319 
2320         /*
2321          *      See if this console matches one we selected on
2322          *      the command line.
2323          */
2324         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
2325                         i++) {
2326                 BUILD_BUG_ON(sizeof(console_cmdline[i].name) !=
2327                              sizeof(newcon->name));
2328                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
2329                         continue;
2330                 if (newcon->index >= 0 &&
2331                     newcon->index != console_cmdline[i].index)
2332                         continue;
2333                 if (newcon->index < 0)
2334                         newcon->index = console_cmdline[i].index;
2335 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2336                 if (console_cmdline[i].brl_options) {
2337                         newcon->flags |= CON_BRL;
2338                         braille_register_console(newcon,
2339                                         console_cmdline[i].index,
2340                                         console_cmdline[i].options,
2341                                         console_cmdline[i].brl_options);
2342                         return;
2343                 }
2344 #endif
2345                 if (newcon->setup &&
2346                     newcon->setup(newcon, console_cmdline[i].options) != 0)
2347                         break;
2348                 newcon->flags |= CON_ENABLED;
2349                 newcon->index = console_cmdline[i].index;
2350                 if (i == selected_console) {
2351                         newcon->flags |= CON_CONSDEV;
2352                         preferred_console = selected_console;
2353                 }
2354                 break;
2355         }
2356 
2357         if (!(newcon->flags & CON_ENABLED))
2358                 return;
2359 
2360         /*
2361          * If we have a bootconsole, and are switching to a real console,
2362          * don't print everything out again, since when the boot console, and
2363          * the real console are the same physical device, it's annoying to
2364          * see the beginning boot messages twice
2365          */
2366         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2367                 newcon->flags &= ~CON_PRINTBUFFER;
2368 
2369         /*
2370          *      Put this console in the list - keep the
2371          *      preferred driver at the head of the list.
2372          */
2373         console_lock();
2374         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2375                 newcon->next = console_drivers;
2376                 console_drivers = newcon;
2377                 if (newcon->next)
2378                         newcon->next->flags &= ~CON_CONSDEV;
2379         } else {
2380                 newcon->next = console_drivers->next;
2381                 console_drivers->next = newcon;
2382         }
2383         if (newcon->flags & CON_PRINTBUFFER) {
2384                 /*
2385                  * console_unlock(); will print out the buffered messages
2386                  * for us.
2387                  */
2388                 raw_spin_lock_irqsave(&logbuf_lock, flags);
2389                 console_seq = syslog_seq;
2390                 console_idx = syslog_idx;
2391                 console_prev = syslog_prev;
2392                 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2393                 /*
2394                  * We're about to replay the log buffer.  Only do this to the
2395                  * just-registered console to avoid excessive message spam to
2396                  * the already-registered consoles.
2397                  */
2398                 exclusive_console = newcon;
2399         }
2400         console_unlock();
2401         console_sysfs_notify();
2402 
2403         /*
2404          * By unregistering the bootconsoles after we enable the real console
2405          * we get the "console xxx enabled" message on all the consoles -
2406          * boot consoles, real consoles, etc - this is to ensure that end
2407          * users know there might be something in the kernel's log buffer that
2408          * went to the bootconsole (that they do not see on the real console)
2409          */
2410         if (bcon &&
2411             ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2412             !keep_bootcon) {
2413                 /* we need to iterate through twice, to make sure we print
2414                  * everything out, before we unregister the console(s)
2415                  */
2416                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
2417                         newcon->name, newcon->index);
2418                 for_each_console(bcon)
2419                         if (bcon->flags & CON_BOOT)
2420                                 unregister_console(bcon);
2421         } else {
2422                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
2423                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
2424                         newcon->name, newcon->index);
2425         }
2426 }
2427 EXPORT_SYMBOL(register_console);
2428 
2429 int unregister_console(struct console *console)
2430 {
2431         struct console *a, *b;
2432         int res = 1;
2433 
2434 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2435         if (console->flags & CON_BRL)
2436                 return braille_unregister_console(console);
2437 #endif
2438 
2439         console_lock();
2440         if (console_drivers == console) {
2441                 console_drivers=console->next;
2442                 res = 0;
2443         } else if (console_drivers) {
2444                 for (a=console_drivers->next, b=console_drivers ;
2445                      a; b=a, a=b->next) {
2446                         if (a == console) {
2447                                 b->next = a->next;
2448                                 res = 0;
2449                                 break;
2450                         }
2451                 }
2452         }
2453 
2454         /*
2455          * If this isn't the last console and it has CON_CONSDEV set, we
2456          * need to set it on the next preferred console.
2457          */
2458         if (console_drivers != NULL && console->flags & CON_CONSDEV)
2459                 console_drivers->flags |= CON_CONSDEV;
2460 
2461         console_unlock();
2462         console_sysfs_notify();
2463         return res;
2464 }
2465 EXPORT_SYMBOL(unregister_console);
2466 
2467 static int __init printk_late_init(void)
2468 {
2469         struct console *con;
2470 
2471         for_each_console(con) {
2472                 if (!keep_bootcon && con->flags & CON_BOOT) {
2473                         printk(KERN_INFO "turn off boot console %s%d\n",
2474                                 con->name, con->index);
2475                         unregister_console(con);
2476                 }
2477         }
2478         hotcpu_notifier(console_cpu_notify, 0);
2479         return 0;
2480 }
2481 late_initcall(printk_late_init);
2482 
2483 #if defined CONFIG_PRINTK
2484 /*
2485  * Delayed printk version, for scheduler-internal messages:
2486  */
2487 #define PRINTK_BUF_SIZE         512
2488 
2489 #define PRINTK_PENDING_WAKEUP   0x01
2490 #define PRINTK_PENDING_SCHED    0x02
2491 
2492 static DEFINE_PER_CPU(int, printk_pending);
2493 static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
2494 
2495 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2496 {
2497         int pending = __this_cpu_xchg(printk_pending, 0);
2498 
2499         if (pending & PRINTK_PENDING_SCHED) {
2500                 char *buf = __get_cpu_var(printk_sched_buf);
2501                 printk(KERN_WARNING "[sched_delayed] %s", buf);
2502         }
2503 
2504         if (pending & PRINTK_PENDING_WAKEUP)
2505                 wake_up_interruptible(&log_wait);
2506 }
2507 
2508 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2509         .func = wake_up_klogd_work_func,
2510         .flags = IRQ_WORK_LAZY,
2511 };
2512 
2513 void wake_up_klogd(void)
2514 {
2515         preempt_disable();
2516         if (waitqueue_active(&log_wait)) {
2517                 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2518                 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2519         }
2520         preempt_enable();
2521 }
2522 
2523 int printk_deferred(const char *fmt, ...)
2524 {
2525         unsigned long flags;
2526         va_list args;
2527         char *buf;
2528         int r;
2529 
2530         local_irq_save(flags);
2531         buf = __get_cpu_var(printk_sched_buf);
2532 
2533         va_start(args, fmt);
2534         r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2535         va_end(args);
2536 
2537         __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2538         irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2539         local_irq_restore(flags);
2540 
2541         return r;
2542 }
2543 
2544 /*
2545  * printk rate limiting, lifted from the networking subsystem.
2546  *
2547  * This enforces a rate limit: not more than 10 kernel messages
2548  * every 5s to make a denial-of-service attack impossible.
2549  */
2550 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2551 
2552 int __printk_ratelimit(const char *func)
2553 {
2554         return ___ratelimit(&printk_ratelimit_state, func);
2555 }
2556 EXPORT_SYMBOL(__printk_ratelimit);
2557 
2558 /**
2559  * printk_timed_ratelimit - caller-controlled printk ratelimiting
2560  * @caller_jiffies: pointer to caller's state
2561  * @interval_msecs: minimum interval between prints
2562  *
2563  * printk_timed_ratelimit() returns true if more than @interval_msecs
2564  * milliseconds have elapsed since the last time printk_timed_ratelimit()
2565  * returned true.
2566  */
2567 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2568                         unsigned int interval_msecs)
2569 {
2570         if (*caller_jiffies == 0
2571                         || !time_in_range(jiffies, *caller_jiffies,
2572                                         *caller_jiffies
2573                                         + msecs_to_jiffies(interval_msecs))) {
2574                 *caller_jiffies = jiffies;
2575                 return true;
2576         }
2577         return false;
2578 }
2579 EXPORT_SYMBOL(printk_timed_ratelimit);
2580 
2581 static DEFINE_SPINLOCK(dump_list_lock);
2582 static LIST_HEAD(dump_list);
2583 
2584 /**
2585  * kmsg_dump_register - register a kernel log dumper.
2586  * @dumper: pointer to the kmsg_dumper structure
2587  *
2588  * Adds a kernel log dumper to the system. The dump callback in the
2589  * structure will be called when the kernel oopses or panics and must be
2590  * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2591  */
2592 int kmsg_dump_register(struct kmsg_dumper *dumper)
2593 {
2594         unsigned long flags;
2595         int err = -EBUSY;
2596 
2597         /* The dump callback needs to be set */
2598         if (!dumper->dump)
2599                 return -EINVAL;
2600 
2601         spin_lock_irqsave(&dump_list_lock, flags);
2602         /* Don't allow registering multiple times */
2603         if (!dumper->registered) {
2604                 dumper->registered = 1;
2605                 list_add_tail_rcu(&dumper->list, &dump_list);
2606                 err = 0;
2607         }
2608         spin_unlock_irqrestore(&dump_list_lock, flags);
2609 
2610         return err;
2611 }
2612 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2613 
2614 /**
2615  * kmsg_dump_unregister - unregister a kmsg dumper.
2616  * @dumper: pointer to the kmsg_dumper structure
2617  *
2618  * Removes a dump device from the system. Returns zero on success and
2619  * %-EINVAL otherwise.
2620  */
2621 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2622 {
2623         unsigned long flags;
2624         int err = -EINVAL;
2625 
2626         spin_lock_irqsave(&dump_list_lock, flags);
2627         if (dumper->registered) {
2628                 dumper->registered = 0;
2629                 list_del_rcu(&dumper->list);
2630                 err = 0;
2631         }
2632         spin_unlock_irqrestore(&dump_list_lock, flags);
2633         synchronize_rcu();
2634 
2635         return err;
2636 }
2637 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2638 
2639 static bool always_kmsg_dump;
2640 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2641 
2642 /**
2643  * kmsg_dump - dump kernel log to kernel message dumpers.
2644  * @reason: the reason (oops, panic etc) for dumping
2645  *
2646  * Call each of the registered dumper's dump() callback, which can
2647  * retrieve the kmsg records with kmsg_dump_get_line() or
2648  * kmsg_dump_get_buffer().
2649  */
2650 void kmsg_dump(enum kmsg_dump_reason reason)
2651 {
2652         struct kmsg_dumper *dumper;
2653         unsigned long flags;
2654 
2655         if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2656                 return;
2657 
2658         rcu_read_lock();
2659         list_for_each_entry_rcu(dumper, &dump_list, list) {
2660                 if (dumper->max_reason && reason > dumper->max_reason)
2661                         continue;
2662 
2663                 /* initialize iterator with data about the stored records */
2664                 dumper->active = true;
2665 
2666                 raw_spin_lock_irqsave(&logbuf_lock, flags);
2667                 dumper->cur_seq = clear_seq;
2668                 dumper->cur_idx = clear_idx;
2669                 dumper->next_seq = log_next_seq;
2670                 dumper->next_idx = log_next_idx;
2671                 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2672 
2673                 /* invoke dumper which will iterate over records */
2674                 dumper->dump(dumper, reason);
2675 
2676                 /* reset iterator */
2677                 dumper->active = false;
2678         }
2679         rcu_read_unlock();
2680 }
2681 
2682 /**
2683  * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2684  * @dumper: registered kmsg dumper
2685  * @syslog: include the "<4>" prefixes
2686  * @line: buffer to copy the line to
2687  * @size: maximum size of the buffer
2688  * @len: length of line placed into buffer
2689  *
2690  * Start at the beginning of the kmsg buffer, with the oldest kmsg
2691  * record, and copy one record into the provided buffer.
2692  *
2693  * Consecutive calls will return the next available record moving
2694  * towards the end of the buffer with the youngest messages.
2695  *
2696  * A return value of FALSE indicates that there are no more records to
2697  * read.
2698  *
2699  * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2700  */
2701 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2702                                char *line, size_t size, size_t *len)
2703 {
2704         struct log *msg;
2705         size_t l = 0;
2706         bool ret = false;
2707 
2708         if (!dumper->active)
2709                 goto out;
2710 
2711         if (dumper->cur_seq < log_first_seq) {
2712                 /* messages are gone, move to first available one */
2713                 dumper->cur_seq = log_first_seq;
2714                 dumper->cur_idx = log_first_idx;
2715         }
2716 
2717         /* last entry */
2718         if (dumper->cur_seq >= log_next_seq)
2719                 goto out;
2720 
2721         msg = log_from_idx(dumper->cur_idx);
2722         l = msg_print_text(msg, 0, syslog, line, size);
2723 
2724         dumper->cur_idx = log_next(dumper->cur_idx);
2725         dumper->cur_seq++;
2726         ret = true;
2727 out:
2728         if (len)
2729                 *len = l;
2730         return ret;
2731 }
2732 
2733 /**
2734  * kmsg_dump_get_line - retrieve one kmsg log line
2735  * @dumper: registered kmsg dumper
2736  * @syslog: include the "<4>" prefixes
2737  * @line: buffer to copy the line to
2738  * @size: maximum size of the buffer
2739  * @len: length of line placed into buffer
2740  *
2741  * Start at the beginning of the kmsg buffer, with the oldest kmsg
2742  * record, and copy one record into the provided buffer.
2743  *
2744  * Consecutive calls will return the next available record moving
2745  * towards the end of the buffer with the youngest messages.
2746  *
2747  * A return value of FALSE indicates that there are no more records to
2748  * read.
2749  */
2750 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2751                         char *line, size_t size, size_t *len)
2752 {
2753         unsigned long flags;
2754         bool ret;
2755 
2756         raw_spin_lock_irqsave(&logbuf_lock, flags);
2757         ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2758         raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2759 
2760         return ret;
2761 }
2762 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2763 
2764 /**
2765  * kmsg_dump_get_buffer - copy kmsg log lines
2766  * @dumper: registered kmsg dumper
2767  * @syslog: include the "<4>" prefixes
2768  * @buf: buffer to copy the line to
2769  * @size: maximum size of the buffer
2770  * @len: length of line placed into buffer
2771  *
2772  * Start at the end of the kmsg buffer and fill the provided buffer
2773  * with as many of the the *youngest* kmsg records that fit into it.
2774  * If the buffer is large enough, all available kmsg records will be
2775  * copied with a single call.
2776  *
2777  * Consecutive calls will fill the buffer with the next block of
2778  * available older records, not including the earlier retrieved ones.
2779  *
2780  * A return value of FALSE indicates that there are no more records to
2781  * read.
2782  */
2783 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2784                           char *buf, size_t size, size_t *len)
2785 {
2786         unsigned long flags;
2787         u64 seq;
2788         u32 idx;
2789         u64 next_seq;
2790         u32 next_idx;
2791         enum log_flags prev;
2792         size_t l = 0;
2793         bool ret = false;
2794 
2795         if (!dumper->active)
2796                 goto out;
2797 
2798         raw_spin_lock_irqsave(&logbuf_lock, flags);
2799         if (dumper->cur_seq < log_first_seq) {
2800                 /* messages are gone, move to first available one */
2801                 dumper->cur_seq = log_first_seq;
2802                 dumper->cur_idx = log_first_idx;
2803         }
2804 
2805         /* last entry */
2806         if (dumper->cur_seq >= dumper->next_seq) {
2807                 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2808                 goto out;
2809         }
2810 
2811         /* calculate length of entire buffer */
2812         seq = dumper->cur_seq;
2813         idx = dumper->cur_idx;
2814         prev = 0;
2815         while (seq < dumper->next_seq) {
2816                 struct log *msg = log_from_idx(idx);
2817 
2818                 l += msg_print_text(msg, prev, true, NULL, 0);
2819                 idx = log_next(idx);
2820                 seq++;
2821                 prev = msg->flags;
2822         }
2823 
2824         /* move first record forward until length fits into the buffer */
2825         seq = dumper->cur_seq;
2826         idx = dumper->cur_idx;
2827         prev = 0;
2828         while (l > size && seq < dumper->next_seq) {
2829                 struct log *msg = log_from_idx(idx);
2830 
2831                 l -= msg_print_text(msg, prev, true, NULL, 0);
2832                 idx = log_next(idx);
2833                 seq++;
2834                 prev = msg->flags;
2835         }
2836 
2837         /* last message in next interation */
2838         next_seq = seq;
2839         next_idx = idx;
2840 
2841         l = 0;
2842         prev = 0;
2843         while (seq < dumper->next_seq) {
2844                 struct log *msg = log_from_idx(idx);
2845 
2846                 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2847                 idx = log_next(idx);
2848                 seq++;
2849                 prev = msg->flags;
2850         }
2851 
2852         dumper->next_seq = next_seq;
2853         dumper->next_idx = next_idx;
2854         ret = true;
2855         raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2856 out:
2857         if (len)
2858                 *len = l;
2859         return ret;
2860 }
2861 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2862 
2863 /**
2864  * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2865  * @dumper: registered kmsg dumper
2866  *
2867  * Reset the dumper's iterator so that kmsg_dump_get_line() and
2868  * kmsg_dump_get_buffer() can be called again and used multiple
2869  * times within the same dumper.dump() callback.
2870  *
2871  * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2872  */
2873 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
2874 {
2875         dumper->cur_seq = clear_seq;
2876         dumper->cur_idx = clear_idx;
2877         dumper->next_seq = log_next_seq;
2878         dumper->next_idx = log_next_idx;
2879 }
2880 
2881 /**
2882  * kmsg_dump_rewind - reset the interator
2883  * @dumper: registered kmsg dumper
2884  *
2885  * Reset the dumper's iterator so that kmsg_dump_get_line() and
2886  * kmsg_dump_get_buffer() can be called again and used multiple
2887  * times within the same dumper.dump() callback.
2888  */
2889 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2890 {
2891         unsigned long flags;
2892 
2893         raw_spin_lock_irqsave(&logbuf_lock, flags);
2894         kmsg_dump_rewind_nolock(dumper);
2895         raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2896 }
2897 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
2898 
2899 static char dump_stack_arch_desc_str[128];
2900 
2901 /**
2902  * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
2903  * @fmt: printf-style format string
2904  * @...: arguments for the format string
2905  *
2906  * The configured string will be printed right after utsname during task
2907  * dumps.  Usually used to add arch-specific system identifiers.  If an
2908  * arch wants to make use of such an ID string, it should initialize this
2909  * as soon as possible during boot.
2910  */
2911 void __init dump_stack_set_arch_desc(const char *fmt, ...)
2912 {
2913         va_list args;
2914 
2915         va_start(args, fmt);
2916         vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
2917                   fmt, args);
2918         va_end(args);
2919 }
2920 
2921 /**
2922  * dump_stack_print_info - print generic debug info for dump_stack()
2923  * @log_lvl: log level
2924  *
2925  * Arch-specific dump_stack() implementations can use this function to
2926  * print out the same debug information as the generic dump_stack().
2927  */
2928 void dump_stack_print_info(const char *log_lvl)
2929 {
2930         printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
2931                log_lvl, raw_smp_processor_id(), current->pid, current->comm,
2932                print_tainted(), init_utsname()->release,
2933                (int)strcspn(init_utsname()->version, " "),
2934                init_utsname()->version);
2935 
2936         if (dump_stack_arch_desc_str[0] != '\0')
2937                 printk("%sHardware name: %s\n",
2938                        log_lvl, dump_stack_arch_desc_str);
2939 
2940         print_worker_info(log_lvl, current);
2941 }
2942 
2943 /**
2944  * show_regs_print_info - print generic debug info for show_regs()
2945  * @log_lvl: log level
2946  *
2947  * show_regs() implementations can use this function to print out generic
2948  * debug information.
2949  */
2950 void show_regs_print_info(const char *log_lvl)
2951 {
2952         dump_stack_print_info(log_lvl);
2953 
2954         printk("%stask: %p ti: %p task.ti: %p\n",
2955                log_lvl, current, current_thread_info(),
2956                task_thread_info(current));
2957 }
2958 
2959 #endif
2960 

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