kernel/printk.c

   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/syscalls.h>
  35 #include <linux/kexec.h>
  36 #include <linux/kdb.h>
  37 #include <linux/ratelimit.h>
  38 #include <linux/kmsg_dump.h>
  39 #include <linux/syslog.h>
  40 #include <linux/cpu.h>
  41 #include <linux/notifier.h>
  42
  43 #include <asm/uaccess.h>
  44
  45 /*
  46  * Architectures can override it:
  47  */
  48 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
  49 {
  50 }
  51
  52 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
  53
  54 /* printk's without a loglevel use this.. */
  55 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  56
  57 /* We show everything that is MORE important than this.. */
  58 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  59 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  60
  61 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  62
  63 int console_printk[4] = {
  64         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  65         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  66         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  67         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  68 };
  69
  70 /*
  71  * Low level drivers may need that to know if they can schedule in
  72  * their unblank() callback or not. So let's export it.
  73  */
  74 int oops_in_progress;
  75 EXPORT_SYMBOL(oops_in_progress);
  76
  77 /*
  78  * console_sem protects the console_drivers list, and also
  79  * provides serialisation for access to the entire console
  80  * driver system.
  81  */
  82 static DEFINE_SEMAPHORE(console_sem);
  83 struct console *console_drivers;
  84 EXPORT_SYMBOL_GPL(console_drivers);
  85
  86 /*
  87  * This is used for debugging the mess that is the VT code by
  88  * keeping track if we have the console semaphore held. It's
  89  * definitely not the perfect debug tool (we don't know if _WE_
  90  * hold it are racing, but it helps tracking those weird code
  91  * path in the console code where we end up in places I want
  92  * locked without the console sempahore held
  93  */
  94 static int console_locked, console_suspended;
  95
  96 /*
  97  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
  98  * It is also used in interesting ways to provide interlocking in
  99  * release_console_sem().
 100  */
 101 static DEFINE_SPINLOCK(logbuf_lock);
 102
 103 #define LOG_BUF_MASK (log_buf_len-1)
 104 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
 105
 106 /*
 107  * The indices into log_buf are not constrained to log_buf_len - they
 108  * must be masked before subscripting
 109  */
 110 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
 111 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
 112 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 113
 114 /*
 115  *      Array of consoles built from command line options (console=)
 116  */
 117 struct console_cmdline
 118 {
 119         char    name[8];                        /* Name of the driver       */
 120         int     index;                          /* Minor dev. to use        */
 121         char    *options;                       /* Options for the driver   */
 122 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 123         char    *brl_options;                   /* Options for braille driver */
 124 #endif
 125 };
 126
 127 #define MAX_CMDLINECONSOLES 8
 128
 129 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 130 static int selected_console = -1;
 131 static int preferred_console = -1;
 132 int console_set_on_cmdline;
 133 EXPORT_SYMBOL(console_set_on_cmdline);
 134
 135 /* Flag: console code may call schedule() */
 136 static int console_may_schedule;
 137
 138 #ifdef CONFIG_PRINTK
 139
 140 static char __log_buf[__LOG_BUF_LEN];
 141 static char *log_buf = __log_buf;
 142 static int log_buf_len = __LOG_BUF_LEN;
 143 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 144 static int saved_console_loglevel = -1;
 145
 146 #ifdef CONFIG_KEXEC
 147 /*
 148  * This appends the listed symbols to /proc/vmcoreinfo
 149  *
 150  * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
 151  * obtain access to symbols that are otherwise very difficult to locate.  These
 152  * symbols are specifically used so that utilities can access and extract the
 153  * dmesg log from a vmcore file after a crash.
 154  */
 155 void log_buf_kexec_setup(void)
 156 {
 157         VMCOREINFO_SYMBOL(log_buf);
 158         VMCOREINFO_SYMBOL(log_end);
 159         VMCOREINFO_SYMBOL(log_buf_len);
 160         VMCOREINFO_SYMBOL(logged_chars);
 161 }
 162 #endif
 163
 164 static int __init log_buf_len_setup(char *str)
 165 {
 166         unsigned size = memparse(str, &str);
 167         unsigned long flags;
 168
 169         if (size)
 170                 size = roundup_pow_of_two(size);
 171         if (size > log_buf_len) {
 172                 unsigned start, dest_idx, offset;
 173                 char *new_log_buf;
 174
 175                 new_log_buf = alloc_bootmem(size);
 176                 if (!new_log_buf) {
 177                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 178                         goto out;
 179                 }
 180
 181                 spin_lock_irqsave(&logbuf_lock, flags);
 182                 log_buf_len = size;
 183                 log_buf = new_log_buf;
 184
 185                 offset = start = min(con_start, log_start);
 186                 dest_idx = 0;
 187                 while (start != log_end) {
 188                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 189                         start++;
 190                         dest_idx++;
 191                 }
 192                 log_start -= offset;
 193                 con_start -= offset;
 194                 log_end -= offset;
 195                 spin_unlock_irqrestore(&logbuf_lock, flags);
 196
 197                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 198         }
 199 out:
 200         return 1;
 201 }
 202
 203 __setup("log_buf_len=", log_buf_len_setup);
 204
 205 #ifdef CONFIG_BOOT_PRINTK_DELAY
 206
 207 static int boot_delay; /* msecs delay after each printk during bootup */
 208 static unsigned long long loops_per_msec;       /* based on boot_delay */
 209
 210 static int __init boot_delay_setup(char *str)
 211 {
 212         unsigned long lpj;
 213
 214         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 215         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 216
 217         get_option(&str, &boot_delay);
 218         if (boot_delay > 10 * 1000)
 219                 boot_delay = 0;
 220
 221         pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 222                 "HZ: %d, loops_per_msec: %llu\n",
 223                 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
 224         return 1;
 225 }
 226 __setup("boot_delay=", boot_delay_setup);
 227
 228 static void boot_delay_msec(void)
 229 {
 230         unsigned long long k;
 231         unsigned long timeout;
 232
 233         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 234                 return;
 235
 236         k = (unsigned long long)loops_per_msec * boot_delay;
 237
 238         timeout = jiffies + msecs_to_jiffies(boot_delay);
 239         while (k) {
 240                 k--;
 241                 cpu_relax();
 242                 /*
 243                  * use (volatile) jiffies to prevent
 244                  * compiler reduction; loop termination via jiffies
 245                  * is secondary and may or may not happen.
 246                  */
 247                 if (time_after(jiffies, timeout))
 248                         break;
 249                 touch_nmi_watchdog();
 250         }
 251 }
 252 #else
 253 static inline void boot_delay_msec(void)
 254 {
 255 }
 256 #endif
 257
 258 int do_syslog(int type, char __user *buf, int len, bool from_file)
 259 {
 260         unsigned i, j, limit, count;
 261         int do_clear = 0;
 262         char c;
 263         int error = 0;
 264
 265         error = security_syslog(type, from_file);
 266         if (error)
 267                 return error;
 268
 269         switch (type) {
 270         case SYSLOG_ACTION_CLOSE:       /* Close log */
 271                 break;
 272         case SYSLOG_ACTION_OPEN:        /* Open log */
 273                 break;
 274         case SYSLOG_ACTION_READ:        /* Read from log */
 275                 error = -EINVAL;
 276                 if (!buf || len < 0)
 277                         goto out;
 278                 error = 0;
 279                 if (!len)
 280                         goto out;
 281                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 282                         error = -EFAULT;
 283                         goto out;
 284                 }
 285                 error = wait_event_interruptible(log_wait,
 286                                                         (log_start - log_end));
 287                 if (error)
 288                         goto out;
 289                 i = 0;
 290                 spin_lock_irq(&logbuf_lock);
 291                 while (!error && (log_start != log_end) && i < len) {
 292                         c = LOG_BUF(log_start);
 293                         log_start++;
 294                         spin_unlock_irq(&logbuf_lock);
 295                         error = __put_user(c,buf);
 296                         buf++;
 297                         i++;
 298                         cond_resched();
 299                         spin_lock_irq(&logbuf_lock);
 300                 }
 301                 spin_unlock_irq(&logbuf_lock);
 302                 if (!error)
 303                         error = i;
 304                 break;
 305         /* Read/clear last kernel messages */
 306         case SYSLOG_ACTION_READ_CLEAR:
 307                 do_clear = 1;
 308                 /* FALL THRU */
 309         /* Read last kernel messages */
 310         case SYSLOG_ACTION_READ_ALL:
 311                 error = -EINVAL;
 312                 if (!buf || len < 0)
 313                         goto out;
 314                 error = 0;
 315                 if (!len)
 316                         goto out;
 317                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 318                         error = -EFAULT;
 319                         goto out;
 320                 }
 321                 count = len;
 322                 if (count > log_buf_len)
 323                         count = log_buf_len;
 324                 spin_lock_irq(&logbuf_lock);
 325                 if (count > logged_chars)
 326                         count = logged_chars;
 327                 if (do_clear)
 328                         logged_chars = 0;
 329                 limit = log_end;
 330                 /*
 331                  * __put_user() could sleep, and while we sleep
 332                  * printk() could overwrite the messages
 333                  * we try to copy to user space. Therefore
 334                  * the messages are copied in reverse. <manfreds>
 335                  */
 336                 for (i = 0; i < count && !error; i++) {
 337                         j = limit-1-i;
 338                         if (j + log_buf_len < log_end)
 339                                 break;
 340                         c = LOG_BUF(j);
 341                         spin_unlock_irq(&logbuf_lock);
 342                         error = __put_user(c,&buf[count-1-i]);
 343                         cond_resched();
 344                         spin_lock_irq(&logbuf_lock);
 345                 }
 346                 spin_unlock_irq(&logbuf_lock);
 347                 if (error)
 348                         break;
 349                 error = i;
 350                 if (i != count) {
 351                         int offset = count-error;
 352                         /* buffer overflow during copy, correct user buffer. */
 353                         for (i = 0; i < error; i++) {
 354                                 if (__get_user(c,&buf[i+offset]) ||
 355                                     __put_user(c,&buf[i])) {
 356                                         error = -EFAULT;
 357                                         break;
 358                                 }
 359                                 cond_resched();
 360                         }
 361                 }
 362                 break;
 363         /* Clear ring buffer */
 364         case SYSLOG_ACTION_CLEAR:
 365                 logged_chars = 0;
 366                 break;
 367         /* Disable logging to console */
 368         case SYSLOG_ACTION_CONSOLE_OFF:
 369                 if (saved_console_loglevel == -1)
 370                         saved_console_loglevel = console_loglevel;
 371                 console_loglevel = minimum_console_loglevel;
 372                 break;
 373         /* Enable logging to console */
 374         case SYSLOG_ACTION_CONSOLE_ON:
 375                 if (saved_console_loglevel != -1) {
 376                         console_loglevel = saved_console_loglevel;
 377                         saved_console_loglevel = -1;
 378                 }
 379                 break;
 380         /* Set level of messages printed to console */
 381         case SYSLOG_ACTION_CONSOLE_LEVEL:
 382                 error = -EINVAL;
 383                 if (len < 1 || len > 8)
 384                         goto out;
 385                 if (len < minimum_console_loglevel)
 386                         len = minimum_console_loglevel;
 387                 console_loglevel = len;
 388                 /* Implicitly re-enable logging to console */
 389                 saved_console_loglevel = -1;
 390                 error = 0;
 391                 break;
 392         /* Number of chars in the log buffer */
 393         case SYSLOG_ACTION_SIZE_UNREAD:
 394                 error = log_end - log_start;
 395                 break;
 396         /* Size of the log buffer */
 397         case SYSLOG_ACTION_SIZE_BUFFER:
 398                 error = log_buf_len;
 399                 break;
 400         default:
 401                 error = -EINVAL;
 402                 break;
 403         }
 404 out:
 405         return error;
 406 }
 407
 408 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
 409 {
 410         return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
 411 }
 412
 413 #ifdef  CONFIG_KGDB_KDB
 414 /* kdb dmesg command needs access to the syslog buffer.  do_syslog()
 415  * uses locks so it cannot be used during debugging.  Just tell kdb
 416  * where the start and end of the physical and logical logs are.  This
 417  * is equivalent to do_syslog(3).
 418  */
 419 void kdb_syslog_data(char *syslog_data[4])
 420 {
 421         syslog_data[0] = log_buf;
 422         syslog_data[1] = log_buf + log_buf_len;
 423         syslog_data[2] = log_buf + log_end -
 424                 (logged_chars < log_buf_len ? logged_chars : log_buf_len);
 425         syslog_data[3] = log_buf + log_end;
 426 }
 427 #endif  /* CONFIG_KGDB_KDB */
 428
 429 /*
 430  * Call the console drivers on a range of log_buf
 431  */
 432 static void __call_console_drivers(unsigned start, unsigned end)
 433 {
 434         struct console *con;
 435
 436         for_each_console(con) {
 437                 if ((con->flags & CON_ENABLED) && con->write &&
 438                                 (cpu_online(smp_processor_id()) ||
 439                                 (con->flags & CON_ANYTIME)))
 440                         con->write(con, &LOG_BUF(start), end - start);
 441         }
 442 }
 443
 444 static int __read_mostly ignore_loglevel;
 445
 446 static int __init ignore_loglevel_setup(char *str)
 447 {
 448         ignore_loglevel = 1;
 449         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 450
 451         return 0;
 452 }
 453
 454 early_param("ignore_loglevel", ignore_loglevel_setup);
 455
 456 /*
 457  * Write out chars from start to end - 1 inclusive
 458  */
 459 static void _call_console_drivers(unsigned start,
 460                                 unsigned end, int msg_log_level)
 461 {
 462         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 463                         console_drivers && start != end) {
 464                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 465                         /* wrapped write */
 466                         __call_console_drivers(start & LOG_BUF_MASK,
 467                                                 log_buf_len);
 468                         __call_console_drivers(0, end & LOG_BUF_MASK);
 469                 } else {
 470                         __call_console_drivers(start, end);
 471                 }
 472         }
 473 }
 474
 475 /*
 476  * Call the console drivers, asking them to write out
 477  * log_buf[start] to log_buf[end - 1].
 478  * The console_sem must be held.
 479  */
 480 static void call_console_drivers(unsigned start, unsigned end)
 481 {
 482         unsigned cur_index, start_print;
 483         static int msg_level = -1;
 484
 485         BUG_ON(((int)(start - end)) > 0);
 486
 487         cur_index = start;
 488         start_print = start;
 489         while (cur_index != end) {
 490                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 491                                 LOG_BUF(cur_index + 0) == '<' &&
 492                                 LOG_BUF(cur_index + 1) >= '0' &&
 493                                 LOG_BUF(cur_index + 1) <= '7' &&
 494                                 LOG_BUF(cur_index + 2) == '>') {
 495                         msg_level = LOG_BUF(cur_index + 1) - '0';
 496                         cur_index += 3;
 497                         start_print = cur_index;
 498                 }
 499                 while (cur_index != end) {
 500                         char c = LOG_BUF(cur_index);
 501
 502                         cur_index++;
 503                         if (c == '\n') {
 504                                 if (msg_level < 0) {
 505                                         /*
 506                                          * printk() has already given us loglevel tags in
 507                                          * the buffer.  This code is here in case the
 508                                          * log buffer has wrapped right round and scribbled
 509                                          * on those tags
 510                                          */
 511                                         msg_level = default_message_loglevel;
 512                                 }
 513                                 _call_console_drivers(start_print, cur_index, msg_level);
 514                                 msg_level = -1;
 515                                 start_print = cur_index;
 516                                 break;
 517                         }
 518                 }
 519         }
 520         _call_console_drivers(start_print, end, msg_level);
 521 }
 522
 523 static void emit_log_char(char c)
 524 {
 525         LOG_BUF(log_end) = c;
 526         log_end++;
 527         if (log_end - log_start > log_buf_len)
 528                 log_start = log_end - log_buf_len;
 529         if (log_end - con_start > log_buf_len)
 530                 con_start = log_end - log_buf_len;
 531         if (logged_chars < log_buf_len)
 532                 logged_chars++;
 533 }
 534
 535 /*
 536  * Zap console related locks when oopsing. Only zap at most once
 537  * every 10 seconds, to leave time for slow consoles to print a
 538  * full oops.
 539  */
 540 static void zap_locks(void)
 541 {
 542         static unsigned long oops_timestamp;
 543
 544         if (time_after_eq(jiffies, oops_timestamp) &&
 545                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 546                 return;
 547
 548         oops_timestamp = jiffies;
 549
 550         /* If a crash is occurring, make sure we can't deadlock */
 551         spin_lock_init(&logbuf_lock);
 552         /* And make sure that we print immediately */
 553         sema_init(&console_sem, 1);
 554 }
 555
 556 #if defined(CONFIG_PRINTK_TIME)
 557 static int printk_time = 1;
 558 #else
 559 static int printk_time = 0;
 560 #endif
 561 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 562
 563 /* Check if we have any console registered that can be called early in boot. */
 564 static int have_callable_console(void)
 565 {
 566         struct console *con;
 567
 568         for_each_console(con)
 569                 if (con->flags & CON_ANYTIME)
 570                         return 1;
 571
 572         return 0;
 573 }
 574
 575 /**
 576  * printk - print a kernel message
 577  * @fmt: format string
 578  *
 579  * This is printk().  It can be called from any context.  We want it to work.
 580  *
 581  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 582  * call the console drivers.  If we fail to get the semaphore we place the output
 583  * into the log buffer and return.  The current holder of the console_sem will
 584  * notice the new output in release_console_sem() and will send it to the
 585  * consoles before releasing the semaphore.
 586  *
 587  * One effect of this deferred printing is that code which calls printk() and
 588  * then changes console_loglevel may break. This is because console_loglevel
 589  * is inspected when the actual printing occurs.
 590  *
 591  * See also:
 592  * printf(3)
 593  *
 594  * See the vsnprintf() documentation for format string extensions over C99.
 595  */
 596
 597 asmlinkage int printk(const char *fmt, ...)
 598 {
 599         va_list args;
 600         int r;
 601
 602 #ifdef CONFIG_KGDB_KDB
 603         if (unlikely(kdb_trap_printk)) {
 604                 va_start(args, fmt);
 605                 r = vkdb_printf(fmt, args);
 606                 va_end(args);
 607                 return r;
 608         }
 609 #endif
 610         va_start(args, fmt);
 611         r = vprintk(fmt, args);
 612         va_end(args);
 613
 614         return r;
 615 }
 616
 617 /* cpu currently holding logbuf_lock */
 618 static volatile unsigned int printk_cpu = UINT_MAX;
 619
 620 /*
 621  * Can we actually use the console at this time on this cpu?
 622  *
 623  * Console drivers may assume that per-cpu resources have
 624  * been allocated. So unless they're explicitly marked as
 625  * being able to cope (CON_ANYTIME) don't call them until
 626  * this CPU is officially up.
 627  */
 628 static inline int can_use_console(unsigned int cpu)
 629 {
 630         return cpu_online(cpu) || have_callable_console();
 631 }
 632
 633 /*
 634  * Try to get console ownership to actually show the kernel
 635  * messages from a 'printk'. Return true (and with the
 636  * console_semaphore held, and 'console_locked' set) if it
 637  * is successful, false otherwise.
 638  *
 639  * This gets called with the 'logbuf_lock' spinlock held and
 640  * interrupts disabled. It should return with 'lockbuf_lock'
 641  * released but interrupts still disabled.
 642  */
 643 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 644         __releases(&logbuf_lock)
 645 {
 646         int retval = 0;
 647
 648         if (!try_acquire_console_sem()) {
 649                 retval = 1;
 650
 651                 /*
 652                  * If we can't use the console, we need to release
 653                  * the console semaphore by hand to avoid flushing
 654                  * the buffer. We need to hold the console semaphore
 655                  * in order to do this test safely.
 656                  */
 657                 if (!can_use_console(cpu)) {
 658                         console_locked = 0;
 659                         up(&console_sem);
 660                         retval = 0;
 661                 }
 662         }
 663         printk_cpu = UINT_MAX;
 664         spin_unlock(&logbuf_lock);
 665         return retval;
 666 }
 667 static const char recursion_bug_msg [] =
 668                 KERN_CRIT "BUG: recent printk recursion!\n";
 669 static int recursion_bug;
 670 static int new_text_line = 1;
 671 static char printk_buf[1024];
 672
 673 int printk_delay_msec __read_mostly;
 674
 675 static inline void printk_delay(void)
 676 {
 677         if (unlikely(printk_delay_msec)) {
 678                 int m = printk_delay_msec;
 679
 680                 while (m--) {
 681                         mdelay(1);
 682                         touch_nmi_watchdog();
 683                 }
 684         }
 685 }
 686
 687 asmlinkage int vprintk(const char *fmt, va_list args)
 688 {
 689         int printed_len = 0;
 690         int current_log_level = default_message_loglevel;
 691         unsigned long flags;
 692         int this_cpu;
 693         char *p;
 694
 695         boot_delay_msec();
 696         printk_delay();
 697
 698         preempt_disable();
 699         /* This stops the holder of console_sem just where we want him */
 700         raw_local_irq_save(flags);
 701         this_cpu = smp_processor_id();
 702
 703         /*
 704          * Ouch, printk recursed into itself!
 705          */
 706         if (unlikely(printk_cpu == this_cpu)) {
 707                 /*
 708                  * If a crash is occurring during printk() on this CPU,
 709                  * then try to get the crash message out but make sure
 710                  * we can't deadlock. Otherwise just return to avoid the
 711                  * recursion and return - but flag the recursion so that
 712                  * it can be printed at the next appropriate moment:
 713                  */
 714                 if (!oops_in_progress) {
 715                         recursion_bug = 1;
 716                         goto out_restore_irqs;
 717                 }
 718                 zap_locks();
 719         }
 720
 721         lockdep_off();
 722         spin_lock(&logbuf_lock);
 723         printk_cpu = this_cpu;
 724
 725         if (recursion_bug) {
 726                 recursion_bug = 0;
 727                 strcpy(printk_buf, recursion_bug_msg);
 728                 printed_len = strlen(recursion_bug_msg);
 729         }
 730         /* Emit the output into the temporary buffer */
 731         printed_len += vscnprintf(printk_buf + printed_len,
 732                                   sizeof(printk_buf) - printed_len, fmt, args);
 733
 734
 735         p = printk_buf;
 736
 737         /* Do we have a loglevel in the string? */
 738         if (p[0] == '<') {
 739                 unsigned char c = p[1];
 740                 if (c && p[2] == '>') {
 741                         switch (c) {
 742                         case '0' ... '7': /* loglevel */
 743                                 current_log_level = c - '0';
 744                         /* Fallthrough - make sure we're on a new line */
 745                         case 'd': /* KERN_DEFAULT */
 746                                 if (!new_text_line) {
 747                                         emit_log_char('\n');
 748                                         new_text_line = 1;
 749                                 }
 750                         /* Fallthrough - skip the loglevel */
 751                         case 'c': /* KERN_CONT */
 752                                 p += 3;
 753                                 break;
 754                         }
 755                 }
 756         }
 757
 758         /*
 759          * Copy the output into log_buf.  If the caller didn't provide
 760          * appropriate log level tags, we insert them here
 761          */
 762         for ( ; *p; p++) {
 763                 if (new_text_line) {
 764                         /* Always output the token */
 765                         emit_log_char('<');
 766                         emit_log_char(current_log_level + '0');
 767                         emit_log_char('>');
 768                         printed_len += 3;
 769                         new_text_line = 0;
 770
 771                         if (printk_time) {
 772                                 /* Follow the token with the time */
 773                                 char tbuf[50], *tp;
 774                                 unsigned tlen;
 775                                 unsigned long long t;
 776                                 unsigned long nanosec_rem;
 777
 778                                 t = cpu_clock(printk_cpu);
 779                                 nanosec_rem = do_div(t, 1000000000);
 780                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 781                                                 (unsigned long) t,
 782                                                 nanosec_rem / 1000);
 783
 784                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 785                                         emit_log_char(*tp);
 786                                 printed_len += tlen;
 787                         }
 788
 789                         if (!*p)
 790                                 break;
 791                 }
 792
 793                 emit_log_char(*p);
 794                 if (*p == '\n')
 795                         new_text_line = 1;
 796         }
 797
 798         /*
 799          * Try to acquire and then immediately release the
 800          * console semaphore. The release will do all the
 801          * actual magic (print out buffers, wake up klogd,
 802          * etc).
 803          *
 804          * The acquire_console_semaphore_for_printk() function
 805          * will release 'logbuf_lock' regardless of whether it
 806          * actually gets the semaphore or not.
 807          */
 808         if (acquire_console_semaphore_for_printk(this_cpu))
 809                 release_console_sem();
 810
 811         lockdep_on();
 812 out_restore_irqs:
 813         raw_local_irq_restore(flags);
 814
 815         preempt_enable();
 816         return printed_len;
 817 }
 818 EXPORT_SYMBOL(printk);
 819 EXPORT_SYMBOL(vprintk);
 820
 821 #else
 822
 823 static void call_console_drivers(unsigned start, unsigned end)
 824 {
 825 }
 826
 827 #endif
 828
 829 static int __add_preferred_console(char *name, int idx, char *options,
 830                                    char *brl_options)
 831 {
 832         struct console_cmdline *c;
 833         int i;
 834
 835         /*
 836          *      See if this tty is not yet registered, and
 837          *      if we have a slot free.
 838          */
 839         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 840                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 841                           console_cmdline[i].index == idx) {
 842                                 if (!brl_options)
 843                                         selected_console = i;
 844                                 return 0;
 845                 }
 846         if (i == MAX_CMDLINECONSOLES)
 847                 return -E2BIG;
 848         if (!brl_options)
 849                 selected_console = i;
 850         c = &console_cmdline[i];
 851         strlcpy(c->name, name, sizeof(c->name));
 852         c->options = options;
 853 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 854         c->brl_options = brl_options;
 855 #endif
 856         c->index = idx;
 857         return 0;
 858 }
 859 /*
 860  * Set up a list of consoles.  Called from init/main.c
 861  */
 862 static int __init console_setup(char *str)
 863 {
 864         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 865         char *s, *options, *brl_options = NULL;
 866         int idx;
 867
 868 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 869         if (!memcmp(str, "brl,", 4)) {
 870                 brl_options = "";
 871                 str += 4;
 872         } else if (!memcmp(str, "brl=", 4)) {
 873                 brl_options = str + 4;
 874                 str = strchr(brl_options, ',');
 875                 if (!str) {
 876                         printk(KERN_ERR "need port name after brl=\n");
 877                         return 1;
 878                 }
 879                 *(str++) = 0;
 880         }
 881 #endif
 882
 883         /*
 884          * Decode str into name, index, options.
 885          */
 886         if (str[0] >= '0' && str[0] <= '9') {
 887                 strcpy(buf, "ttyS");
 888                 strncpy(buf + 4, str, sizeof(buf) - 5);
 889         } else {
 890                 strncpy(buf, str, sizeof(buf) - 1);
 891         }
 892         buf[sizeof(buf) - 1] = 0;
 893         if ((options = strchr(str, ',')) != NULL)
 894                 *(options++) = 0;
 895 #ifdef __sparc__
 896         if (!strcmp(str, "ttya"))
 897                 strcpy(buf, "ttyS0");
 898         if (!strcmp(str, "ttyb"))
 899                 strcpy(buf, "ttyS1");
 900 #endif
 901         for (s = buf; *s; s++)
 902                 if ((*s >= '0' && *s <= '9') || *s == ',')
 903                         break;
 904         idx = simple_strtoul(s, NULL, 10);
 905         *s = 0;
 906
 907         __add_preferred_console(buf, idx, options, brl_options);
 908         console_set_on_cmdline = 1;
 909         return 1;
 910 }
 911 __setup("console=", console_setup);
 912
 913 /**
 914  * add_preferred_console - add a device to the list of preferred consoles.
 915  * @name: device name
 916  * @idx: device index
 917  * @options: options for this console
 918  *
 919  * The last preferred console added will be used for kernel messages
 920  * and stdin/out/err for init.  Normally this is used by console_setup
 921  * above to handle user-supplied console arguments; however it can also
 922  * be used by arch-specific code either to override the user or more
 923  * commonly to provide a default console (ie from PROM variables) when
 924  * the user has not supplied one.
 925  */
 926 int add_preferred_console(char *name, int idx, char *options)
 927 {
 928         return __add_preferred_console(name, idx, options, NULL);
 929 }
 930
 931 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 932 {
 933         struct console_cmdline *c;
 934         int i;
 935
 936         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 937                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 938                           console_cmdline[i].index == idx) {
 939                                 c = &console_cmdline[i];
 940                                 strlcpy(c->name, name_new, sizeof(c->name));
 941                                 c->name[sizeof(c->name) - 1] = 0;
 942                                 c->options = options;
 943                                 c->index = idx_new;
 944                                 return i;
 945                 }
 946         /* not found */
 947         return -1;
 948 }
 949
 950 int console_suspend_enabled = 1;
 951 EXPORT_SYMBOL(console_suspend_enabled);
 952
 953 static int __init console_suspend_disable(char *str)
 954 {
 955         console_suspend_enabled = 0;
 956         return 1;
 957 }
 958 __setup("no_console_suspend", console_suspend_disable);
 959
 960 /**
 961  * suspend_console - suspend the console subsystem
 962  *
 963  * This disables printk() while we go into suspend states
 964  */
 965 void suspend_console(void)
 966 {
 967         if (!console_suspend_enabled)
 968                 return;
 969         printk("Suspending console(s) (use no_console_suspend to debug)\n");
 970         acquire_console_sem();
 971         console_suspended = 1;
 972         up(&console_sem);
 973 }
 974
 975 void resume_console(void)
 976 {
 977         if (!console_suspend_enabled)
 978                 return;
 979         down(&console_sem);
 980         console_suspended = 0;
 981         release_console_sem();
 982 }
 983
 984 /**
 985  * console_cpu_notify - print deferred console messages after CPU hotplug
 986  * @self: notifier struct
 987  * @action: CPU hotplug event
 988  * @hcpu: unused
 989  *
 990  * If printk() is called from a CPU that is not online yet, the messages
 991  * will be spooled but will not show up on the console.  This function is
 992  * called when a new CPU comes online (or fails to come up), and ensures
 993  * that any such output gets printed.
 994  */
 995 static int __cpuinit console_cpu_notify(struct notifier_block *self,
 996         unsigned long action, void *hcpu)
 997 {
 998         switch (action) {
 999         case CPU_ONLINE:
1000         case CPU_DEAD:
1001         case CPU_DYING:
1002         case CPU_DOWN_FAILED:
1003         case CPU_UP_CANCELED:
1004                 acquire_console_sem();
1005                 release_console_sem();
1006         }
1007         return NOTIFY_OK;
1008 }
1009
1010 /**
1011  * acquire_console_sem - lock the console system for exclusive use.
1012  *
1013  * Acquires a semaphore which guarantees that the caller has
1014  * exclusive access to the console system and the console_drivers list.
1015  *
1016  * Can sleep, returns nothing.
1017  */
1018 void acquire_console_sem(void)
1019 {
1020         BUG_ON(in_interrupt());
1021         down(&console_sem);
1022         if (console_suspended)
1023                 return;
1024         console_locked = 1;
1025         console_may_schedule = 1;
1026 }
1027 EXPORT_SYMBOL(acquire_console_sem);
1028
1029 int try_acquire_console_sem(void)
1030 {
1031         if (down_trylock(&console_sem))
1032                 return -1;
1033         if (console_suspended) {
1034                 up(&console_sem);
1035                 return -1;
1036         }
1037         console_locked = 1;
1038         console_may_schedule = 0;
1039         return 0;
1040 }
1041 EXPORT_SYMBOL(try_acquire_console_sem);
1042
1043 int is_console_locked(void)
1044 {
1045         return console_locked;
1046 }
1047
1048 static DEFINE_PER_CPU(int, printk_pending);
1049
1050 void printk_tick(void)
1051 {
1052         if (__get_cpu_var(printk_pending)) {
1053                 __get_cpu_var(printk_pending) = 0;
1054                 wake_up_interruptible(&log_wait);
1055         }
1056 }
1057
1058 int printk_needs_cpu(int cpu)
1059 {
1060         return per_cpu(printk_pending, cpu);
1061 }
1062
1063 void wake_up_klogd(void)
1064 {
1065         if (waitqueue_active(&log_wait))
1066                 __raw_get_cpu_var(printk_pending) = 1;
1067 }
1068
1069 /**
1070  * release_console_sem - unlock the console system
1071  *
1072  * Releases the semaphore which the caller holds on the console system
1073  * and the console driver list.
1074  *
1075  * While the semaphore was held, console output may have been buffered
1076  * by printk().  If this is the case, release_console_sem() emits
1077  * the output prior to releasing the semaphore.
1078  *
1079  * If there is output waiting for klogd, we wake it up.
1080  *
1081  * release_console_sem() may be called from any context.
1082  */
1083 void release_console_sem(void)
1084 {
1085         unsigned long flags;
1086         unsigned _con_start, _log_end;
1087         unsigned wake_klogd = 0;
1088
1089         if (console_suspended) {
1090                 up(&console_sem);
1091                 return;
1092         }
1093
1094         console_may_schedule = 0;
1095
1096         for ( ; ; ) {
1097                 spin_lock_irqsave(&logbuf_lock, flags);
1098                 wake_klogd |= log_start - log_end;
1099                 if (con_start == log_end)
1100                         break;                  /* Nothing to print */
1101                 _con_start = con_start;
1102                 _log_end = log_end;
1103                 con_start = log_end;            /* Flush */
1104                 spin_unlock(&logbuf_lock);
1105                 stop_critical_timings();        /* don't trace print latency */
1106                 call_console_drivers(_con_start, _log_end);
1107                 start_critical_timings();
1108                 local_irq_restore(flags);
1109         }
1110         console_locked = 0;
1111         up(&console_sem);
1112         spin_unlock_irqrestore(&logbuf_lock, flags);
1113         if (wake_klogd)
1114                 wake_up_klogd();
1115 }
1116 EXPORT_SYMBOL(release_console_sem);
1117
1118 /**
1119  * console_conditional_schedule - yield the CPU if required
1120  *
1121  * If the console code is currently allowed to sleep, and
1122  * if this CPU should yield the CPU to another task, do
1123  * so here.
1124  *
1125  * Must be called within acquire_console_sem().
1126  */
1127 void __sched console_conditional_schedule(void)
1128 {
1129         if (console_may_schedule)
1130                 cond_resched();
1131 }
1132 EXPORT_SYMBOL(console_conditional_schedule);
1133
1134 void console_unblank(void)
1135 {
1136         struct console *c;
1137
1138         /*
1139          * console_unblank can no longer be called in interrupt context unless
1140          * oops_in_progress is set to 1..
1141          */
1142         if (oops_in_progress) {
1143                 if (down_trylock(&console_sem) != 0)
1144                         return;
1145         } else
1146                 acquire_console_sem();
1147
1148         console_locked = 1;
1149         console_may_schedule = 0;
1150         for_each_console(c)
1151                 if ((c->flags & CON_ENABLED) && c->unblank)
1152                         c->unblank();
1153         release_console_sem();
1154 }
1155
1156 /*
1157  * Return the console tty driver structure and its associated index
1158  */
1159 struct tty_driver *console_device(int *index)
1160 {
1161         struct console *c;
1162         struct tty_driver *driver = NULL;
1163
1164         acquire_console_sem();
1165         for_each_console(c) {
1166                 if (!c->device)
1167                         continue;
1168                 driver = c->device(c, index);
1169                 if (driver)
1170                         break;
1171         }
1172         release_console_sem();
1173         return driver;
1174 }
1175
1176 /*
1177  * Prevent further output on the passed console device so that (for example)
1178  * serial drivers can disable console output before suspending a port, and can
1179  * re-enable output afterwards.
1180  */
1181 void console_stop(struct console *console)
1182 {
1183         acquire_console_sem();
1184         console->flags &= ~CON_ENABLED;
1185         release_console_sem();
1186 }
1187 EXPORT_SYMBOL(console_stop);
1188
1189 void console_start(struct console *console)
1190 {
1191         acquire_console_sem();
1192         console->flags |= CON_ENABLED;
1193         release_console_sem();
1194 }
1195 EXPORT_SYMBOL(console_start);
1196
1197 /*
1198  * The console driver calls this routine during kernel initialization
1199  * to register the console printing procedure with printk() and to
1200  * print any messages that were printed by the kernel before the
1201  * console driver was initialized.
1202  *
1203  * This can happen pretty early during the boot process (because of
1204  * early_printk) - sometimes before setup_arch() completes - be careful
1205  * of what kernel features are used - they may not be initialised yet.
1206  *
1207  * There are two types of consoles - bootconsoles (early_printk) and
1208  * "real" consoles (everything which is not a bootconsole) which are
1209  * handled differently.
1210  *  - Any number of bootconsoles can be registered at any time.
1211  *  - As soon as a "real" console is registered, all bootconsoles
1212  *    will be unregistered automatically.
1213  *  - Once a "real" console is registered, any attempt to register a
1214  *    bootconsoles will be rejected
1215  */
1216 void register_console(struct console *newcon)
1217 {
1218         int i;
1219         unsigned long flags;
1220         struct console *bcon = NULL;
1221
1222         /*
1223          * before we register a new CON_BOOT console, make sure we don't
1224          * already have a valid console
1225          */
1226         if (console_drivers && newcon->flags & CON_BOOT) {
1227                 /* find the last or real console */
1228                 for_each_console(bcon) {
1229                         if (!(bcon->flags & CON_BOOT)) {
1230                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1231                                         newcon->name, newcon->index);
1232                                 return;
1233                         }
1234                 }
1235         }
1236
1237         if (console_drivers && console_drivers->flags & CON_BOOT)
1238                 bcon = console_drivers;
1239
1240         if (preferred_console < 0 || bcon || !console_drivers)
1241                 preferred_console = selected_console;
1242
1243         if (newcon->early_setup)
1244                 newcon->early_setup();
1245
1246         /*
1247          *      See if we want to use this console driver. If we
1248          *      didn't select a console we take the first one
1249          *      that registers here.
1250          */
1251         if (preferred_console < 0) {
1252                 if (newcon->index < 0)
1253                         newcon->index = 0;
1254                 if (newcon->setup == NULL ||
1255                     newcon->setup(newcon, NULL) == 0) {
1256                         newcon->flags |= CON_ENABLED;
1257                         if (newcon->device) {
1258                                 newcon->flags |= CON_CONSDEV;
1259                                 preferred_console = 0;
1260                         }
1261                 }
1262         }
1263
1264         /*
1265          *      See if this console matches one we selected on
1266          *      the command line.
1267          */
1268         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1269                         i++) {
1270                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1271                         continue;
1272                 if (newcon->index >= 0 &&
1273                     newcon->index != console_cmdline[i].index)
1274                         continue;
1275                 if (newcon->index < 0)
1276                         newcon->index = console_cmdline[i].index;
1277 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1278                 if (console_cmdline[i].brl_options) {
1279                         newcon->flags |= CON_BRL;
1280                         braille_register_console(newcon,
1281                                         console_cmdline[i].index,
1282                                         console_cmdline[i].options,
1283                                         console_cmdline[i].brl_options);
1284                         return;
1285                 }
1286 #endif
1287                 if (newcon->setup &&
1288                     newcon->setup(newcon, console_cmdline[i].options) != 0)
1289                         break;
1290                 newcon->flags |= CON_ENABLED;
1291                 newcon->index = console_cmdline[i].index;
1292                 if (i == selected_console) {
1293                         newcon->flags |= CON_CONSDEV;
1294                         preferred_console = selected_console;
1295                 }
1296                 break;
1297         }
1298
1299         if (!(newcon->flags & CON_ENABLED))
1300                 return;
1301
1302         /*
1303          * If we have a bootconsole, and are switching to a real console,
1304          * don't print everything out again, since when the boot console, and
1305          * the real console are the same physical device, it's annoying to
1306          * see the beginning boot messages twice
1307          */
1308         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1309                 newcon->flags &= ~CON_PRINTBUFFER;
1310
1311         /*
1312          *      Put this console in the list - keep the
1313          *      preferred driver at the head of the list.
1314          */
1315         acquire_console_sem();
1316         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1317                 newcon->next = console_drivers;
1318                 console_drivers = newcon;
1319                 if (newcon->next)
1320                         newcon->next->flags &= ~CON_CONSDEV;
1321         } else {
1322                 newcon->next = console_drivers->next;
1323                 console_drivers->next = newcon;
1324         }
1325         if (newcon->flags & CON_PRINTBUFFER) {
1326                 /*
1327                  * release_console_sem() will print out the buffered messages
1328                  * for us.
1329                  */
1330                 spin_lock_irqsave(&logbuf_lock, flags);
1331                 con_start = log_start;
1332                 spin_unlock_irqrestore(&logbuf_lock, flags);
1333         }
1334         release_console_sem();
1335         console_sysfs_notify();
1336
1337         /*
1338          * By unregistering the bootconsoles after we enable the real console
1339          * we get the "console xxx enabled" message on all the consoles -
1340          * boot consoles, real consoles, etc - this is to ensure that end
1341          * users know there might be something in the kernel's log buffer that
1342          * went to the bootconsole (that they do not see on the real console)
1343          */
1344         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1345                 /* we need to iterate through twice, to make sure we print
1346                  * everything out, before we unregister the console(s)
1347                  */
1348                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1349                         newcon->name, newcon->index);
1350                 for_each_console(bcon)
1351                         if (bcon->flags & CON_BOOT)
1352                                 unregister_console(bcon);
1353         } else {
1354                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1355                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
1356                         newcon->name, newcon->index);
1357         }
1358 }
1359 EXPORT_SYMBOL(register_console);
1360
1361 int unregister_console(struct console *console)
1362 {
1363         struct console *a, *b;
1364         int res = 1;
1365
1366 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1367         if (console->flags & CON_BRL)
1368                 return braille_unregister_console(console);
1369 #endif
1370
1371         acquire_console_sem();
1372         if (console_drivers == console) {
1373                 console_drivers=console->next;
1374                 res = 0;
1375         } else if (console_drivers) {
1376                 for (a=console_drivers->next, b=console_drivers ;
1377                      a; b=a, a=b->next) {
1378                         if (a == console) {
1379                                 b->next = a->next;
1380                                 res = 0;
1381                                 break;
1382                         }
1383                 }
1384         }
1385
1386         /*
1387          * If this isn't the last console and it has CON_CONSDEV set, we
1388          * need to set it on the next preferred console.
1389          */
1390         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1391                 console_drivers->flags |= CON_CONSDEV;
1392
1393         release_console_sem();
1394         console_sysfs_notify();
1395         return res;
1396 }
1397 EXPORT_SYMBOL(unregister_console);
1398
1399 static int __init printk_late_init(void)
1400 {
1401         struct console *con;
1402
1403         for_each_console(con) {
1404                 if (con->flags & CON_BOOT) {
1405                         printk(KERN_INFO "turn off boot console %s%d\n",
1406                                 con->name, con->index);
1407                         unregister_console(con);
1408                 }
1409         }
1410         hotcpu_notifier(console_cpu_notify, 0);
1411         return 0;
1412 }
1413 late_initcall(printk_late_init);
1414
1415 #if defined CONFIG_PRINTK
1416
1417 /*
1418  * printk rate limiting, lifted from the networking subsystem.
1419  *
1420  * This enforces a rate limit: not more than 10 kernel messages
1421  * every 5s to make a denial-of-service attack impossible.
1422  */
1423 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1424
1425 int __printk_ratelimit(const char *func)
1426 {
1427         return ___ratelimit(&printk_ratelimit_state, func);
1428 }
1429 EXPORT_SYMBOL(__printk_ratelimit);
1430
1431 /**
1432  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1433  * @caller_jiffies: pointer to caller's state
1434  * @interval_msecs: minimum interval between prints
1435  *
1436  * printk_timed_ratelimit() returns true if more than @interval_msecs
1437  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1438  * returned true.
1439  */
1440 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1441                         unsigned int interval_msecs)
1442 {
1443         if (*caller_jiffies == 0
1444                         || !time_in_range(jiffies, *caller_jiffies,
1445                                         *caller_jiffies
1446                                         + msecs_to_jiffies(interval_msecs))) {
1447                 *caller_jiffies = jiffies;
1448                 return true;
1449         }
1450         return false;
1451 }
1452 EXPORT_SYMBOL(printk_timed_ratelimit);
1453
1454 static DEFINE_SPINLOCK(dump_list_lock);
1455 static LIST_HEAD(dump_list);
1456
1457 /**
1458  * kmsg_dump_register - register a kernel log dumper.
1459  * @dumper: pointer to the kmsg_dumper structure
1460  *
1461  * Adds a kernel log dumper to the system. The dump callback in the
1462  * structure will be called when the kernel oopses or panics and must be
1463  * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1464  */
1465 int kmsg_dump_register(struct kmsg_dumper *dumper)
1466 {
1467         unsigned long flags;
1468         int err = -EBUSY;
1469
1470         /* The dump callback needs to be set */
1471         if (!dumper->dump)
1472                 return -EINVAL;
1473
1474         spin_lock_irqsave(&dump_list_lock, flags);
1475         /* Don't allow registering multiple times */
1476         if (!dumper->registered) {
1477                 dumper->registered = 1;
1478                 list_add_tail(&dumper->list, &dump_list);
1479                 err = 0;
1480         }
1481         spin_unlock_irqrestore(&dump_list_lock, flags);
1482
1483         return err;
1484 }
1485 EXPORT_SYMBOL_GPL(kmsg_dump_register);
1486
1487 /**
1488  * kmsg_dump_unregister - unregister a kmsg dumper.
1489  * @dumper: pointer to the kmsg_dumper structure
1490  *
1491  * Removes a dump device from the system. Returns zero on success and
1492  * %-EINVAL otherwise.
1493  */
1494 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
1495 {
1496         unsigned long flags;
1497         int err = -EINVAL;
1498
1499         spin_lock_irqsave(&dump_list_lock, flags);
1500         if (dumper->registered) {
1501                 dumper->registered = 0;
1502                 list_del(&dumper->list);
1503                 err = 0;
1504         }
1505         spin_unlock_irqrestore(&dump_list_lock, flags);
1506
1507         return err;
1508 }
1509 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
1510
1511 static const char * const kmsg_reasons[] = {
1512         [KMSG_DUMP_OOPS]        = "oops",
1513         [KMSG_DUMP_PANIC]       = "panic",
1514         [KMSG_DUMP_KEXEC]       = "kexec",
1515 };
1516
1517 static const char *kmsg_to_str(enum kmsg_dump_reason reason)
1518 {
1519         if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0)
1520                 return "unknown";
1521
1522         return kmsg_reasons[reason];
1523 }
1524
1525 /**
1526  * kmsg_dump - dump kernel log to kernel message dumpers.
1527  * @reason: the reason (oops, panic etc) for dumping
1528  *
1529  * Iterate through each of the dump devices and call the oops/panic
1530  * callbacks with the log buffer.
1531  */
1532 void kmsg_dump(enum kmsg_dump_reason reason)
1533 {
1534         unsigned long end;
1535         unsigned chars;
1536         struct kmsg_dumper *dumper;
1537         const char *s1, *s2;
1538         unsigned long l1, l2;
1539         unsigned long flags;
1540
1541         /* Theoretically, the log could move on after we do this, but
1542            there's not a lot we can do about that. The new messages
1543            will overwrite the start of what we dump. */
1544         spin_lock_irqsave(&logbuf_lock, flags);
1545         end = log_end & LOG_BUF_MASK;
1546         chars = logged_chars;
1547         spin_unlock_irqrestore(&logbuf_lock, flags);
1548
1549         if (chars > end) {
1550                 s1 = log_buf + log_buf_len - chars + end;
1551                 l1 = chars - end;
1552
1553                 s2 = log_buf;
1554                 l2 = end;
1555         } else {
1556                 s1 = "";
1557                 l1 = 0;
1558
1559                 s2 = log_buf + end - chars;
1560                 l2 = chars;
1561         }
1562
1563         if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
1564                 printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n",
1565                                 kmsg_to_str(reason));
1566                 return;
1567         }
1568         list_for_each_entry(dumper, &dump_list, list)
1569                 dumper->dump(dumper, reason, s1, l1, s2, l2);
1570         spin_unlock_irqrestore(&dump_list_lock, flags);
1571 }
1572 #endif