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

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