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  * for_each_console() allows you to iterate on each console
  47  */
  48 #define for_each_console(con) \
  49         for (con = console_drivers; con != NULL; con = con->next)
  50
  51 /*
  52  * Architectures can override it:
  53  */
  54 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
  55 {
  56 }
  57
  58 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
  59
  60 /* printk's without a loglevel use this.. */
  61 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  62
  63 /* We show everything that is MORE important than this.. */
  64 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  65 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  66
  67 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  68
  69 int console_printk[4] = {
  70         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  71         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  72         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  73         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  74 };
  75
  76 /*
  77  * Low level drivers may need that to know if they can schedule in
  78  * their unblank() callback or not. So let's export it.
  79  */
  80 int oops_in_progress;
  81 EXPORT_SYMBOL(oops_in_progress);
  82
  83 /*
  84  * console_sem protects the console_drivers list, and also
  85  * provides serialisation for access to the entire console
  86  * driver system.
  87  */
  88 static DEFINE_SEMAPHORE(console_sem);
  89 struct console *console_drivers;
  90 EXPORT_SYMBOL_GPL(console_drivers);
  91
  92 /*
  93  * This is used for debugging the mess that is the VT code by
  94  * keeping track if we have the console semaphore held. It's
  95  * definitely not the perfect debug tool (we don't know if _WE_
  96  * hold it are racing, but it helps tracking those weird code
  97  * path in the console code where we end up in places I want
  98  * locked without the console sempahore held
  99  */
 100 static int console_locked, console_suspended;
 101
 102 /*
 103  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
 104  * It is also used in interesting ways to provide interlocking in
 105  * release_console_sem().
 106  */
 107 static DEFINE_SPINLOCK(logbuf_lock);
 108
 109 #define LOG_BUF_MASK (log_buf_len-1)
 110 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
 111
 112 /*
 113  * The indices into log_buf are not constrained to log_buf_len - they
 114  * must be masked before subscripting
 115  */
 116 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
 117 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
 118 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 119
 120 /*
 121  *      Array of consoles built from command line options (console=)
 122  */
 123 struct console_cmdline
 124 {
 125         char    name[8];                        /* Name of the driver       */
 126         int     index;                          /* Minor dev. to use        */
 127         char    *options;                       /* Options for the driver   */
 128 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 129         char    *brl_options;                   /* Options for braille driver */
 130 #endif
 131 };
 132
 133 #define MAX_CMDLINECONSOLES 8
 134
 135 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 136 static int selected_console = -1;
 137 static int preferred_console = -1;
 138 int console_set_on_cmdline;
 139 EXPORT_SYMBOL(console_set_on_cmdline);
 140
 141 /* Flag: console code may call schedule() */
 142 static int console_may_schedule;
 143
 144 #ifdef CONFIG_PRINTK
 145
 146 static char __log_buf[__LOG_BUF_LEN];
 147 static char *log_buf = __log_buf;
 148 static int log_buf_len = __LOG_BUF_LEN;
 149 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 150 static int saved_console_loglevel = -1;
 151
 152 #ifdef CONFIG_KEXEC
 153 /*
 154  * This appends the listed symbols to /proc/vmcoreinfo
 155  *
 156  * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
 157  * obtain access to symbols that are otherwise very difficult to locate.  These
 158  * symbols are specifically used so that utilities can access and extract the
 159  * dmesg log from a vmcore file after a crash.
 160  */
 161 void log_buf_kexec_setup(void)
 162 {
 163         VMCOREINFO_SYMBOL(log_buf);
 164         VMCOREINFO_SYMBOL(log_end);
 165         VMCOREINFO_SYMBOL(log_buf_len);
 166         VMCOREINFO_SYMBOL(logged_chars);
 167 }
 168 #endif
 169
 170 static int __init log_buf_len_setup(char *str)
 171 {
 172         unsigned size = memparse(str, &str);
 173         unsigned long flags;
 174
 175         if (size)
 176                 size = roundup_pow_of_two(size);
 177         if (size > log_buf_len) {
 178                 unsigned start, dest_idx, offset;
 179                 char *new_log_buf;
 180
 181                 new_log_buf = alloc_bootmem(size);
 182                 if (!new_log_buf) {
 183                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 184                         goto out;
 185                 }
 186
 187                 spin_lock_irqsave(&logbuf_lock, flags);
 188                 log_buf_len = size;
 189                 log_buf = new_log_buf;
 190
 191                 offset = start = min(con_start, log_start);
 192                 dest_idx = 0;
 193                 while (start != log_end) {
 194                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 195                         start++;
 196                         dest_idx++;
 197                 }
 198                 log_start -= offset;
 199                 con_start -= offset;
 200                 log_end -= offset;
 201                 spin_unlock_irqrestore(&logbuf_lock, flags);
 202
 203                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 204         }
 205 out:
 206         return 1;
 207 }
 208
 209 __setup("log_buf_len=", log_buf_len_setup);
 210
 211 #ifdef CONFIG_BOOT_PRINTK_DELAY
 212
 213 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 214 static unsigned long long loops_per_msec;       /* based on boot_delay */
 215
 216 static int __init boot_delay_setup(char *str)
 217 {
 218         unsigned long lpj;
 219
 220         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 221         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 222
 223         get_option(&str, &boot_delay);
 224         if (boot_delay > 10 * 1000)
 225                 boot_delay = 0;
 226
 227         pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 228                 "HZ: %d, loops_per_msec: %llu\n",
 229                 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
 230         return 1;
 231 }
 232 __setup("boot_delay=", boot_delay_setup);
 233
 234 static void boot_delay_msec(void)
 235 {
 236         unsigned long long k;
 237         unsigned long timeout;
 238
 239         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 240                 return;
 241
 242         k = (unsigned long long)loops_per_msec * boot_delay;
 243
 244         timeout = jiffies + msecs_to_jiffies(boot_delay);
 245         while (k) {
 246                 k--;
 247                 cpu_relax();
 248                 /*
 249                  * use (volatile) jiffies to prevent
 250                  * compiler reduction; loop termination via jiffies
 251                  * is secondary and may or may not happen.
 252                  */
 253                 if (time_after(jiffies, timeout))
 254                         break;
 255                 touch_nmi_watchdog();
 256         }
 257 }
 258 #else
 259 static inline void boot_delay_msec(void)
 260 {
 261 }
 262 #endif
 263
 264 int do_syslog(int type, char __user *buf, int len, bool from_file)
 265 {
 266         unsigned i, j, limit, count;
 267         int do_clear = 0;
 268         char c;
 269         int error = 0;
 270
 271         error = security_syslog(type, from_file);
 272         if (error)
 273                 return error;
 274
 275         switch (type) {
 276         case SYSLOG_ACTION_CLOSE:       /* Close log */
 277                 break;
 278         case SYSLOG_ACTION_OPEN:        /* Open log */
 279                 break;
 280         case SYSLOG_ACTION_READ:        /* Read from log */
 281                 error = -EINVAL;
 282                 if (!buf || len < 0)
 283                         goto out;
 284                 error = 0;
 285                 if (!len)
 286                         goto out;
 287                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 288                         error = -EFAULT;
 289                         goto out;
 290                 }
 291                 error = wait_event_interruptible(log_wait,
 292                                                         (log_start - log_end));
 293                 if (error)
 294                         goto out;
 295                 i = 0;
 296                 spin_lock_irq(&logbuf_lock);
 297                 while (!error && (log_start != log_end) && i < len) {
 298                         c = LOG_BUF(log_start);
 299                         log_start++;
 300                         spin_unlock_irq(&logbuf_lock);
 301                         error = __put_user(c,buf);
 302                         buf++;
 303                         i++;
 304                         cond_resched();
 305                         spin_lock_irq(&logbuf_lock);
 306                 }
 307                 spin_unlock_irq(&logbuf_lock);
 308                 if (!error)
 309                         error = i;
 310                 break;
 311         /* Read/clear last kernel messages */
 312         case SYSLOG_ACTION_READ_CLEAR:
 313                 do_clear = 1;
 314                 /* FALL THRU */
 315         /* Read last kernel messages */
 316         case SYSLOG_ACTION_READ_ALL:
 317                 error = -EINVAL;
 318                 if (!buf || len < 0)
 319                         goto out;
 320                 error = 0;
 321                 if (!len)
 322                         goto out;
 323                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 324                         error = -EFAULT;
 325                         goto out;
 326                 }
 327                 count = len;
 328                 if (count > log_buf_len)
 329                         count = log_buf_len;
 330                 spin_lock_irq(&logbuf_lock);
 331                 if (count > logged_chars)
 332                         count = logged_chars;
 333                 if (do_clear)
 334                         logged_chars = 0;
 335                 limit = log_end;
 336                 /*
 337                  * __put_user() could sleep, and while we sleep
 338                  * printk() could overwrite the messages
 339                  * we try to copy to user space. Therefore
 340                  * the messages are copied in reverse. <manfreds>
 341                  */
 342                 for (i = 0; i < count && !error; i++) {
 343                         j = limit-1-i;
 344                         if (j + log_buf_len < log_end)
 345                                 break;
 346                         c = LOG_BUF(j);
 347                         spin_unlock_irq(&logbuf_lock);
 348                         error = __put_user(c,&buf[count-1-i]);
 349                         cond_resched();
 350                         spin_lock_irq(&logbuf_lock);
 351                 }
 352                 spin_unlock_irq(&logbuf_lock);
 353                 if (error)
 354                         break;
 355                 error = i;
 356                 if (i != count) {
 357                         int offset = count-error;
 358                         /* buffer overflow during copy, correct user buffer. */
 359                         for (i = 0; i < error; i++) {
 360                                 if (__get_user(c,&buf[i+offset]) ||
 361                                     __put_user(c,&buf[i])) {
 362                                         error = -EFAULT;
 363                                         break;
 364                                 }
 365                                 cond_resched();
 366                         }
 367                 }
 368                 break;
 369         /* Clear ring buffer */
 370         case SYSLOG_ACTION_CLEAR:
 371                 logged_chars = 0;
 372                 break;
 373         /* Disable logging to console */
 374         case SYSLOG_ACTION_CONSOLE_OFF:
 375                 if (saved_console_loglevel == -1)
 376                         saved_console_loglevel = console_loglevel;
 377                 console_loglevel = minimum_console_loglevel;
 378                 break;
 379         /* Enable logging to console */
 380         case SYSLOG_ACTION_CONSOLE_ON:
 381                 if (saved_console_loglevel != -1) {
 382                         console_loglevel = saved_console_loglevel;
 383                         saved_console_loglevel = -1;
 384                 }
 385                 break;
 386         /* Set level of messages printed to console */
 387         case SYSLOG_ACTION_CONSOLE_LEVEL:
 388                 error = -EINVAL;
 389                 if (len < 1 || len > 8)
 390                         goto out;
 391                 if (len < minimum_console_loglevel)
 392                         len = minimum_console_loglevel;
 393                 console_loglevel = len;
 394                 /* Implicitly re-enable logging to console */
 395                 saved_console_loglevel = -1;
 396                 error = 0;
 397                 break;
 398         /* Number of chars in the log buffer */
 399         case SYSLOG_ACTION_SIZE_UNREAD:
 400                 error = log_end - log_start;
 401                 break;
 402         /* Size of the log buffer */
 403         case SYSLOG_ACTION_SIZE_BUFFER:
 404                 error = log_buf_len;
 405                 break;
 406         default:
 407                 error = -EINVAL;
 408                 break;
 409         }
 410 out:
 411         return error;
 412 }
 413
 414 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
 415 {
 416         return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
 417 }
 418
 419 #ifdef  CONFIG_KGDB_KDB
 420 /* kdb dmesg command needs access to the syslog buffer.  do_syslog()
 421  * uses locks so it cannot be used during debugging.  Just tell kdb
 422  * where the start and end of the physical and logical logs are.  This
 423  * is equivalent to do_syslog(3).
 424  */
 425 void kdb_syslog_data(char *syslog_data[4])
 426 {
 427         syslog_data[0] = log_buf;
 428         syslog_data[1] = log_buf + log_buf_len;
 429         syslog_data[2] = log_buf + log_end -
 430                 (logged_chars < log_buf_len ? logged_chars : log_buf_len);
 431         syslog_data[3] = log_buf + log_end;
 432 }
 433 #endif  /* CONFIG_KGDB_KDB */
 434
 435 /*
 436  * Call the console drivers on a range of log_buf
 437  */
 438 static void __call_console_drivers(unsigned start, unsigned end)
 439 {
 440         struct console *con;
 441
 442         for_each_console(con) {
 443                 if ((con->flags & CON_ENABLED) && con->write &&
 444                                 (cpu_online(smp_processor_id()) ||
 445                                 (con->flags & CON_ANYTIME)))
 446                         con->write(con, &LOG_BUF(start), end - start);
 447         }
 448 }
 449
 450 static int __read_mostly ignore_loglevel;
 451
 452 static int __init ignore_loglevel_setup(char *str)
 453 {
 454         ignore_loglevel = 1;
 455         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 456
 457         return 0;
 458 }
 459
 460 early_param("ignore_loglevel", ignore_loglevel_setup);
 461
 462 /*
 463  * Write out chars from start to end - 1 inclusive
 464  */
 465 static void _call_console_drivers(unsigned start,
 466                                 unsigned end, int msg_log_level)
 467 {
 468         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 469                         console_drivers && start != end) {
 470                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 471                         /* wrapped write */
 472                         __call_console_drivers(start & LOG_BUF_MASK,
 473                                                 log_buf_len);
 474                         __call_console_drivers(0, end & LOG_BUF_MASK);
 475                 } else {
 476                         __call_console_drivers(start, end);
 477                 }
 478         }
 479 }
 480
 481 /*
 482  * Call the console drivers, asking them to write out
 483  * log_buf[start] to log_buf[end - 1].
 484  * The console_sem must be held.
 485  */
 486 static void call_console_drivers(unsigned start, unsigned end)
 487 {
 488         unsigned cur_index, start_print;
 489         static int msg_level = -1;
 490
 491         BUG_ON(((int)(start - end)) > 0);
 492
 493         cur_index = start;
 494         start_print = start;
 495         while (cur_index != end) {
 496                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 497                                 LOG_BUF(cur_index + 0) == '<' &&
 498                                 LOG_BUF(cur_index + 1) >= '0' &&
 499                                 LOG_BUF(cur_index + 1) <= '7' &&
 500                                 LOG_BUF(cur_index + 2) == '>') {
 501                         msg_level = LOG_BUF(cur_index + 1) - '0';
 502                         cur_index += 3;
 503                         start_print = cur_index;
 504                 }
 505                 while (cur_index != end) {
 506                         char c = LOG_BUF(cur_index);
 507
 508                         cur_index++;
 509                         if (c == '\n') {
 510                                 if (msg_level < 0) {
 511                                         /*
 512                                          * printk() has already given us loglevel tags in
 513                                          * the buffer.  This code is here in case the
 514                                          * log buffer has wrapped right round and scribbled
 515                                          * on those tags
 516                                          */
 517                                         msg_level = default_message_loglevel;
 518                                 }
 519                                 _call_console_drivers(start_print, cur_index, msg_level);
 520                                 msg_level = -1;
 521                                 start_print = cur_index;
 522                                 break;
 523                         }
 524                 }
 525         }
 526         _call_console_drivers(start_print, end, msg_level);
 527 }
 528
 529 static void emit_log_char(char c)
 530 {
 531         LOG_BUF(log_end) = c;
 532         log_end++;
 533         if (log_end - log_start > log_buf_len)
 534                 log_start = log_end - log_buf_len;
 535         if (log_end - con_start > log_buf_len)
 536                 con_start = log_end - log_buf_len;
 537         if (logged_chars < log_buf_len)
 538                 logged_chars++;
 539 }
 540
 541 /*
 542  * Zap console related locks when oopsing. Only zap at most once
 543  * every 10 seconds, to leave time for slow consoles to print a
 544  * full oops.
 545  */
 546 static void zap_locks(void)
 547 {
 548         static unsigned long oops_timestamp;
 549
 550         if (time_after_eq(jiffies, oops_timestamp) &&
 551                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 552                 return;
 553
 554         oops_timestamp = jiffies;
 555
 556         /* If a crash is occurring, make sure we can't deadlock */
 557         spin_lock_init(&logbuf_lock);
 558         /* And make sure that we print immediately */
 559         sema_init(&console_sem, 1);
 560 }
 561
 562 #if defined(CONFIG_PRINTK_TIME)
 563 static int printk_time = 1;
 564 #else
 565 static int printk_time = 0;
 566 #endif
 567 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 568
 569 /* Check if we have any console registered that can be called early in boot. */
 570 static int have_callable_console(void)
 571 {
 572         struct console *con;
 573
 574         for_each_console(con)
 575                 if (con->flags & CON_ANYTIME)
 576                         return 1;
 577
 578         return 0;
 579 }
 580
 581 /**
 582  * printk - print a kernel message
 583  * @fmt: format string
 584  *
 585  * This is printk().  It can be called from any context.  We want it to work.
 586  *
 587  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 588  * call the console drivers.  If we fail to get the semaphore we place the output
 589  * into the log buffer and return.  The current holder of the console_sem will
 590  * notice the new output in release_console_sem() and will send it to the
 591  * consoles before releasing the semaphore.
 592  *
 593  * One effect of this deferred printing is that code which calls printk() and
 594  * then changes console_loglevel may break. This is because console_loglevel
 595  * is inspected when the actual printing occurs.
 596  *
 597  * See also:
 598  * printf(3)
 599  *
 600  * See the vsnprintf() documentation for format string extensions over C99.
 601  */
 602
 603 asmlinkage int printk(const char *fmt, ...)
 604 {
 605         va_list args;
 606         int r;
 607
 608 #ifdef CONFIG_KGDB_KDB
 609         if (unlikely(kdb_trap_printk)) {
 610                 va_start(args, fmt);
 611                 r = vkdb_printf(fmt, args);
 612                 va_end(args);
 613                 return r;
 614         }
 615 #endif
 616         va_start(args, fmt);
 617         r = vprintk(fmt, args);
 618         va_end(args);
 619
 620         return r;
 621 }
 622
 623 /* cpu currently holding logbuf_lock */
 624 static volatile unsigned int printk_cpu = UINT_MAX;
 625
 626 /*
 627  * Can we actually use the console at this time on this cpu?
 628  *
 629  * Console drivers may assume that per-cpu resources have
 630  * been allocated. So unless they're explicitly marked as
 631  * being able to cope (CON_ANYTIME) don't call them until
 632  * this CPU is officially up.
 633  */
 634 static inline int can_use_console(unsigned int cpu)
 635 {
 636         return cpu_online(cpu) || have_callable_console();
 637 }
 638
 639 /*
 640  * Try to get console ownership to actually show the kernel
 641  * messages from a 'printk'. Return true (and with the
 642  * console_semaphore held, and 'console_locked' set) if it
 643  * is successful, false otherwise.
 644  *
 645  * This gets called with the 'logbuf_lock' spinlock held and
 646  * interrupts disabled. It should return with 'lockbuf_lock'
 647  * released but interrupts still disabled.
 648  */
 649 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 650 {
 651         int retval = 0;
 652
 653         if (!try_acquire_console_sem()) {
 654                 retval = 1;
 655
 656                 /*
 657                  * If we can't use the console, we need to release
 658                  * the console semaphore by hand to avoid flushing
 659                  * the buffer. We need to hold the console semaphore
 660                  * in order to do this test safely.
 661                  */
 662                 if (!can_use_console(cpu)) {
 663                         console_locked = 0;
 664                         up(&console_sem);
 665                         retval = 0;
 666                 }
 667         }
 668         printk_cpu = UINT_MAX;
 669         spin_unlock(&logbuf_lock);
 670         return retval;
 671 }
 672 static const char recursion_bug_msg [] =
 673                 KERN_CRIT "BUG: recent printk recursion!\n";
 674 static int recursion_bug;
 675 static int new_text_line = 1;
 676 static char printk_buf[1024];
 677
 678 int printk_delay_msec __read_mostly;
 679
 680 static inline void printk_delay(void)
 681 {
 682         if (unlikely(printk_delay_msec)) {
 683                 int m = printk_delay_msec;
 684
 685                 while (m--) {
 686                         mdelay(1);
 687                         touch_nmi_watchdog();
 688                 }
 689         }
 690 }
 691
 692 asmlinkage int vprintk(const char *fmt, va_list args)
 693 {
 694         int printed_len = 0;
 695         int current_log_level = default_message_loglevel;
 696         unsigned long flags;
 697         int this_cpu;
 698         char *p;
 699
 700         boot_delay_msec();
 701         printk_delay();
 702
 703         preempt_disable();
 704         /* This stops the holder of console_sem just where we want him */
 705         raw_local_irq_save(flags);
 706         this_cpu = smp_processor_id();
 707
 708         /*
 709          * Ouch, printk recursed into itself!
 710          */
 711         if (unlikely(printk_cpu == this_cpu)) {
 712                 /*
 713                  * If a crash is occurring during printk() on this CPU,
 714                  * then try to get the crash message out but make sure
 715                  * we can't deadlock. Otherwise just return to avoid the
 716                  * recursion and return - but flag the recursion so that
 717                  * it can be printed at the next appropriate moment:
 718                  */
 719                 if (!oops_in_progress) {
 720                         recursion_bug = 1;
 721                         goto out_restore_irqs;
 722                 }
 723                 zap_locks();
 724         }
 725
 726         lockdep_off();
 727         spin_lock(&logbuf_lock);
 728         printk_cpu = this_cpu;
 729
 730         if (recursion_bug) {
 731                 recursion_bug = 0;
 732                 strcpy(printk_buf, recursion_bug_msg);
 733                 printed_len = strlen(recursion_bug_msg);
 734         }
 735         /* Emit the output into the temporary buffer */
 736         printed_len += vscnprintf(printk_buf + printed_len,
 737                                   sizeof(printk_buf) - printed_len, fmt, args);
 738
 739
 740         p = printk_buf;
 741
 742         /* Do we have a loglevel in the string? */
 743         if (p[0] == '<') {
 744                 unsigned char c = p[1];
 745                 if (c && p[2] == '>') {
 746                         switch (c) {
 747                         case '0' ... '7': /* loglevel */
 748                                 current_log_level = c - '0';
 749                         /* Fallthrough - make sure we're on a new line */
 750                         case 'd': /* KERN_DEFAULT */
 751                                 if (!new_text_line) {
 752                                         emit_log_char('\n');
 753                                         new_text_line = 1;
 754                                 }
 755                         /* Fallthrough - skip the loglevel */
 756                         case 'c': /* KERN_CONT */
 757                                 p += 3;
 758                                 break;
 759                         }
 760                 }
 761         }
 762
 763         /*
 764          * Copy the output into log_buf.  If the caller didn't provide
 765          * appropriate log level tags, we insert them here
 766          */
 767         for ( ; *p; p++) {
 768                 if (new_text_line) {
 769                         /* Always output the token */
 770                         emit_log_char('<');
 771                         emit_log_char(current_log_level + '0');
 772                         emit_log_char('>');
 773                         printed_len += 3;
 774                         new_text_line = 0;
 775
 776                         if (printk_time) {
 777                                 /* Follow the token with the time */
 778                                 char tbuf[50], *tp;
 779                                 unsigned tlen;
 780                                 unsigned long long t;
 781                                 unsigned long nanosec_rem;
 782
 783                                 t = cpu_clock(printk_cpu);
 784                                 nanosec_rem = do_div(t, 1000000000);
 785                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 786                                                 (unsigned long) t,
 787                                                 nanosec_rem / 1000);
 788
 789                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 790                                         emit_log_char(*tp);
 791                                 printed_len += tlen;
 792                         }
 793
 794                         if (!*p)
 795                                 break;
 796                 }
 797
 798                 emit_log_char(*p);
 799                 if (*p == '\n')
 800                         new_text_line = 1;
 801         }
 802
 803         /*
 804          * Try to acquire and then immediately release the
 805          * console semaphore. The release will do all the
 806          * actual magic (print out buffers, wake up klogd,
 807          * etc).
 808          *
 809          * The acquire_console_semaphore_for_printk() function
 810          * will release 'logbuf_lock' regardless of whether it
 811          * actually gets the semaphore or not.
 812          */
 813         if (acquire_console_semaphore_for_printk(this_cpu))
 814                 release_console_sem();
 815
 816         lockdep_on();
 817 out_restore_irqs:
 818         raw_local_irq_restore(flags);
 819
 820         preempt_enable();
 821         return printed_len;
 822 }
 823 EXPORT_SYMBOL(printk);
 824 EXPORT_SYMBOL(vprintk);
 825
 826 #else
 827
 828 static void call_console_drivers(unsigned start, unsigned end)
 829 {
 830 }
 831
 832 #endif
 833
 834 static int __add_preferred_console(char *name, int idx, char *options,
 835                                    char *brl_options)
 836 {
 837         struct console_cmdline *c;
 838         int i;
 839
 840         /*
 841          *      See if this tty is not yet registered, and
 842          *      if we have a slot free.
 843          */
 844         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 845                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 846                           console_cmdline[i].index == idx) {
 847                                 if (!brl_options)
 848                                         selected_console = i;
 849                                 return 0;
 850                 }
 851         if (i == MAX_CMDLINECONSOLES)
 852                 return -E2BIG;
 853         if (!brl_options)
 854                 selected_console = i;
 855         c = &console_cmdline[i];
 856         strlcpy(c->name, name, sizeof(c->name));
 857         c->options = options;
 858 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 859         c->brl_options = brl_options;
 860 #endif
 861         c->index = idx;
 862         return 0;
 863 }
 864 /*
 865  * Set up a list of consoles.  Called from init/main.c
 866  */
 867 static int __init console_setup(char *str)
 868 {
 869         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 870         char *s, *options, *brl_options = NULL;
 871         int idx;
 872
 873 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 874         if (!memcmp(str, "brl,", 4)) {
 875                 brl_options = "";
 876                 str += 4;
 877         } else if (!memcmp(str, "brl=", 4)) {
 878                 brl_options = str + 4;
 879                 str = strchr(brl_options, ',');
 880                 if (!str) {
 881                         printk(KERN_ERR "need port name after brl=\n");
 882                         return 1;
 883                 }
 884                 *(str++) = 0;
 885         }
 886 #endif
 887
 888         /*
 889          * Decode str into name, index, options.
 890          */
 891         if (str[0] >= '0' && str[0] <= '9') {
 892                 strcpy(buf, "ttyS");
 893                 strncpy(buf + 4, str, sizeof(buf) - 5);
 894         } else {
 895                 strncpy(buf, str, sizeof(buf) - 1);
 896         }
 897         buf[sizeof(buf) - 1] = 0;
 898         if ((options = strchr(str, ',')) != NULL)
 899                 *(options++) = 0;
 900 #ifdef __sparc__
 901         if (!strcmp(str, "ttya"))
 902                 strcpy(buf, "ttyS0");
 903         if (!strcmp(str, "ttyb"))
 904                 strcpy(buf, "ttyS1");
 905 #endif
 906         for (s = buf; *s; s++)
 907                 if ((*s >= '0' && *s <= '9') || *s == ',')
 908                         break;
 909         idx = simple_strtoul(s, NULL, 10);
 910         *s = 0;
 911
 912         __add_preferred_console(buf, idx, options, brl_options);
 913         console_set_on_cmdline = 1;
 914         return 1;
 915 }
 916 __setup("console=", console_setup);
 917
 918 /**
 919  * add_preferred_console - add a device to the list of preferred consoles.
 920  * @name: device name
 921  * @idx: device index
 922  * @options: options for this console
 923  *
 924  * The last preferred console added will be used for kernel messages
 925  * and stdin/out/err for init.  Normally this is used by console_setup
 926  * above to handle user-supplied console arguments; however it can also
 927  * be used by arch-specific code either to override the user or more
 928  * commonly to provide a default console (ie from PROM variables) when
 929  * the user has not supplied one.
 930  */
 931 int add_preferred_console(char *name, int idx, char *options)
 932 {
 933         return __add_preferred_console(name, idx, options, NULL);
 934 }
 935
 936 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 937 {
 938         struct console_cmdline *c;
 939         int i;
 940
 941         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 942                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 943                           console_cmdline[i].index == idx) {
 944                                 c = &console_cmdline[i];
 945                                 strlcpy(c->name, name_new, sizeof(c->name));
 946                                 c->name[sizeof(c->name) - 1] = 0;
 947                                 c->options = options;
 948                                 c->index = idx_new;
 949                                 return i;
 950                 }
 951         /* not found */
 952         return -1;
 953 }
 954
 955 int console_suspend_enabled = 1;
 956 EXPORT_SYMBOL(console_suspend_enabled);
 957
 958 static int __init console_suspend_disable(char *str)
 959 {
 960         console_suspend_enabled = 0;
 961         return 1;
 962 }
 963 __setup("no_console_suspend", console_suspend_disable);
 964
 965 /**
 966  * suspend_console - suspend the console subsystem
 967  *
 968  * This disables printk() while we go into suspend states
 969  */
 970 void suspend_console(void)
 971 {
 972         if (!console_suspend_enabled)
 973                 return;
 974         printk("Suspending console(s) (use no_console_suspend to debug)\n");
 975         acquire_console_sem();
 976         console_suspended = 1;
 977         up(&console_sem);
 978 }
 979
 980 void resume_console(void)
 981 {
 982         if (!console_suspend_enabled)
 983                 return;
 984         down(&console_sem);
 985         console_suspended = 0;
 986         release_console_sem();
 987 }
 988
 989 /**
 990  * console_cpu_notify - print deferred console messages after CPU hotplug
 991  * @self: notifier struct
 992  * @action: CPU hotplug event
 993  * @hcpu: unused
 994  *
 995  * If printk() is called from a CPU that is not online yet, the messages
 996  * will be spooled but will not show up on the console.  This function is
 997  * called when a new CPU comes online (or fails to come up), and ensures
 998  * that any such output gets printed.
 999  */
1000 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1001         unsigned long action, void *hcpu)
1002 {
1003         switch (action) {
1004         case CPU_ONLINE:
1005         case CPU_DEAD:
1006         case CPU_DYING:
1007         case CPU_DOWN_FAILED:
1008         case CPU_UP_CANCELED:
1009                 acquire_console_sem();
1010                 release_console_sem();
1011         }
1012         return NOTIFY_OK;
1013 }
1014
1015 /**
1016  * acquire_console_sem - lock the console system for exclusive use.
1017  *
1018  * Acquires a semaphore which guarantees that the caller has
1019  * exclusive access to the console system and the console_drivers list.
1020  *
1021  * Can sleep, returns nothing.
1022  */
1023 void acquire_console_sem(void)
1024 {
1025         BUG_ON(in_interrupt());
1026         down(&console_sem);
1027         if (console_suspended)
1028                 return;
1029         console_locked = 1;
1030         console_may_schedule = 1;
1031 }
1032 EXPORT_SYMBOL(acquire_console_sem);
1033
1034 int try_acquire_console_sem(void)
1035 {
1036         if (down_trylock(&console_sem))
1037                 return -1;
1038         if (console_suspended) {
1039                 up(&console_sem);
1040                 return -1;
1041         }
1042         console_locked = 1;
1043         console_may_schedule = 0;
1044         return 0;
1045 }
1046 EXPORT_SYMBOL(try_acquire_console_sem);
1047
1048 int is_console_locked(void)
1049 {
1050         return console_locked;
1051 }
1052
1053 static DEFINE_PER_CPU(int, printk_pending);
1054
1055 void printk_tick(void)
1056 {
1057         if (__get_cpu_var(printk_pending)) {
1058                 __get_cpu_var(printk_pending) = 0;
1059                 wake_up_interruptible(&log_wait);
1060         }
1061 }
1062
1063 int printk_needs_cpu(int cpu)
1064 {
1065         return per_cpu(printk_pending, cpu);
1066 }
1067
1068 void wake_up_klogd(void)
1069 {
1070         if (waitqueue_active(&log_wait))
1071                 __raw_get_cpu_var(printk_pending) = 1;
1072 }
1073
1074 /**
1075  * release_console_sem - unlock the console system
1076  *
1077  * Releases the semaphore which the caller holds on the console system
1078  * and the console driver list.
1079  *
1080  * While the semaphore was held, console output may have been buffered
1081  * by printk().  If this is the case, release_console_sem() emits
1082  * the output prior to releasing the semaphore.
1083  *
1084  * If there is output waiting for klogd, we wake it up.
1085  *
1086  * release_console_sem() may be called from any context.
1087  */
1088 void release_console_sem(void)
1089 {
1090         unsigned long flags;
1091         unsigned _con_start, _log_end;
1092         unsigned wake_klogd = 0;
1093
1094         if (console_suspended) {
1095                 up(&console_sem);
1096                 return;
1097         }
1098
1099         console_may_schedule = 0;
1100
1101         for ( ; ; ) {
1102                 spin_lock_irqsave(&logbuf_lock, flags);
1103                 wake_klogd |= log_start - log_end;
1104                 if (con_start == log_end)
1105                         break;                  /* Nothing to print */
1106                 _con_start = con_start;
1107                 _log_end = log_end;
1108                 con_start = log_end;            /* Flush */
1109                 spin_unlock(&logbuf_lock);
1110                 stop_critical_timings();        /* don't trace print latency */
1111                 call_console_drivers(_con_start, _log_end);
1112                 start_critical_timings();
1113                 local_irq_restore(flags);
1114         }
1115         console_locked = 0;
1116         up(&console_sem);
1117         spin_unlock_irqrestore(&logbuf_lock, flags);
1118         if (wake_klogd)
1119                 wake_up_klogd();
1120 }
1121 EXPORT_SYMBOL(release_console_sem);
1122
1123 /**
1124  * console_conditional_schedule - yield the CPU if required
1125  *
1126  * If the console code is currently allowed to sleep, and
1127  * if this CPU should yield the CPU to another task, do
1128  * so here.
1129  *
1130  * Must be called within acquire_console_sem().
1131  */
1132 void __sched console_conditional_schedule(void)
1133 {
1134         if (console_may_schedule)
1135                 cond_resched();
1136 }
1137 EXPORT_SYMBOL(console_conditional_schedule);
1138
1139 void console_unblank(void)
1140 {
1141         struct console *c;
1142
1143         /*
1144          * console_unblank can no longer be called in interrupt context unless
1145          * oops_in_progress is set to 1..
1146          */
1147         if (oops_in_progress) {
1148                 if (down_trylock(&console_sem) != 0)
1149                         return;
1150         } else
1151                 acquire_console_sem();
1152
1153         console_locked = 1;
1154         console_may_schedule = 0;
1155         for_each_console(c)
1156                 if ((c->flags & CON_ENABLED) && c->unblank)
1157                         c->unblank();
1158         release_console_sem();
1159 }
1160
1161 /*
1162  * Return the console tty driver structure and its associated index
1163  */
1164 struct tty_driver *console_device(int *index)
1165 {
1166         struct console *c;
1167         struct tty_driver *driver = NULL;
1168
1169         acquire_console_sem();
1170         for_each_console(c) {
1171                 if (!c->device)
1172                         continue;
1173                 driver = c->device(c, index);
1174                 if (driver)
1175                         break;
1176         }
1177         release_console_sem();
1178         return driver;
1179 }
1180
1181 /*
1182  * Prevent further output on the passed console device so that (for example)
1183  * serial drivers can disable console output before suspending a port, and can
1184  * re-enable output afterwards.
1185  */
1186 void console_stop(struct console *console)
1187 {
1188         acquire_console_sem();
1189         console->flags &= ~CON_ENABLED;
1190         release_console_sem();
1191 }
1192 EXPORT_SYMBOL(console_stop);
1193
1194 void console_start(struct console *console)
1195 {
1196         acquire_console_sem();
1197         console->flags |= CON_ENABLED;
1198         release_console_sem();
1199 }
1200 EXPORT_SYMBOL(console_start);
1201
1202 /*
1203  * The console driver calls this routine during kernel initialization
1204  * to register the console printing procedure with printk() and to
1205  * print any messages that were printed by the kernel before the
1206  * console driver was initialized.
1207  *
1208  * This can happen pretty early during the boot process (because of
1209  * early_printk) - sometimes before setup_arch() completes - be careful
1210  * of what kernel features are used - they may not be initialised yet.
1211  *
1212  * There are two types of consoles - bootconsoles (early_printk) and
1213  * "real" consoles (everything which is not a bootconsole) which are
1214  * handled differently.
1215  *  - Any number of bootconsoles can be registered at any time.
1216  *  - As soon as a "real" console is registered, all bootconsoles
1217  *    will be unregistered automatically.
1218  *  - Once a "real" console is registered, any attempt to register a
1219  *    bootconsoles will be rejected
1220  */
1221 void register_console(struct console *newcon)
1222 {
1223         int i;
1224         unsigned long flags;
1225         struct console *bcon = NULL;
1226
1227         /*
1228          * before we register a new CON_BOOT console, make sure we don't
1229          * already have a valid console
1230          */
1231         if (console_drivers && newcon->flags & CON_BOOT) {
1232                 /* find the last or real console */
1233                 for_each_console(bcon) {
1234                         if (!(bcon->flags & CON_BOOT)) {
1235                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1236                                         newcon->name, newcon->index);
1237                                 return;
1238                         }
1239                 }
1240         }
1241
1242         if (console_drivers && console_drivers->flags & CON_BOOT)
1243                 bcon = console_drivers;
1244
1245         if (preferred_console < 0 || bcon || !console_drivers)
1246                 preferred_console = selected_console;
1247
1248         if (newcon->early_setup)
1249                 newcon->early_setup();
1250
1251         /*
1252          *      See if we want to use this console driver. If we
1253          *      didn't select a console we take the first one
1254          *      that registers here.
1255          */
1256         if (preferred_console < 0) {
1257                 if (newcon->index < 0)
1258                         newcon->index = 0;
1259                 if (newcon->setup == NULL ||
1260                     newcon->setup(newcon, NULL) == 0) {
1261                         newcon->flags |= CON_ENABLED;
1262                         if (newcon->device) {
1263                                 newcon->flags |= CON_CONSDEV;
1264                                 preferred_console = 0;
1265                         }
1266                 }
1267         }
1268
1269         /*
1270          *      See if this console matches one we selected on
1271          *      the command line.
1272          */
1273         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1274                         i++) {
1275                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1276                         continue;
1277                 if (newcon->index >= 0 &&
1278                     newcon->index != console_cmdline[i].index)
1279                         continue;
1280                 if (newcon->index < 0)
1281                         newcon->index = console_cmdline[i].index;
1282 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1283                 if (console_cmdline[i].brl_options) {
1284                         newcon->flags |= CON_BRL;
1285                         braille_register_console(newcon,
1286                                         console_cmdline[i].index,
1287                                         console_cmdline[i].options,
1288                                         console_cmdline[i].brl_options);
1289                         return;
1290                 }
1291 #endif
1292                 if (newcon->setup &&
1293                     newcon->setup(newcon, console_cmdline[i].options) != 0)
1294                         break;
1295                 newcon->flags |= CON_ENABLED;
1296                 newcon->index = console_cmdline[i].index;
1297                 if (i == selected_console) {
1298                         newcon->flags |= CON_CONSDEV;
1299                         preferred_console = selected_console;
1300                 }
1301                 break;
1302         }
1303
1304         if (!(newcon->flags & CON_ENABLED))
1305                 return;
1306
1307         /*
1308          * If we have a bootconsole, and are switching to a real console,
1309          * don't print everything out again, since when the boot console, and
1310          * the real console are the same physical device, it's annoying to
1311          * see the beginning boot messages twice
1312          */
1313         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1314                 newcon->flags &= ~CON_PRINTBUFFER;
1315
1316         /*
1317          *      Put this console in the list - keep the
1318          *      preferred driver at the head of the list.
1319          */
1320         acquire_console_sem();
1321         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1322                 newcon->next = console_drivers;
1323                 console_drivers = newcon;
1324                 if (newcon->next)
1325                         newcon->next->flags &= ~CON_CONSDEV;
1326         } else {
1327                 newcon->next = console_drivers->next;
1328                 console_drivers->next = newcon;
1329         }
1330         if (newcon->flags & CON_PRINTBUFFER) {
1331                 /*
1332                  * release_console_sem() will print out the buffered messages
1333                  * for us.
1334                  */
1335                 spin_lock_irqsave(&logbuf_lock, flags);
1336                 con_start = log_start;
1337                 spin_unlock_irqrestore(&logbuf_lock, flags);
1338         }
1339         release_console_sem();
1340
1341         /*
1342          * By unregistering the bootconsoles after we enable the real console
1343          * we get the "console xxx enabled" message on all the consoles -
1344          * boot consoles, real consoles, etc - this is to ensure that end
1345          * users know there might be something in the kernel's log buffer that
1346          * went to the bootconsole (that they do not see on the real console)
1347          */
1348         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1349                 /* we need to iterate through twice, to make sure we print
1350                  * everything out, before we unregister the console(s)
1351                  */
1352                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1353                         newcon->name, newcon->index);
1354                 for_each_console(bcon)
1355                         if (bcon->flags & CON_BOOT)
1356                                 unregister_console(bcon);
1357         } else {
1358                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1359                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
1360                         newcon->name, newcon->index);
1361         }
1362 }
1363 EXPORT_SYMBOL(register_console);
1364
1365 int unregister_console(struct console *console)
1366 {
1367         struct console *a, *b;
1368         int res = 1;
1369
1370 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1371         if (console->flags & CON_BRL)
1372                 return braille_unregister_console(console);
1373 #endif
1374
1375         acquire_console_sem();
1376         if (console_drivers == console) {
1377                 console_drivers=console->next;
1378                 res = 0;
1379         } else if (console_drivers) {
1380                 for (a=console_drivers->next, b=console_drivers ;
1381                      a; b=a, a=b->next) {
1382                         if (a == console) {
1383                                 b->next = a->next;
1384                                 res = 0;
1385                                 break;
1386                         }
1387                 }
1388         }
1389
1390         /*
1391          * If this isn't the last console and it has CON_CONSDEV set, we
1392          * need to set it on the next preferred console.
1393          */
1394         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1395                 console_drivers->flags |= CON_CONSDEV;
1396
1397         release_console_sem();
1398         return res;
1399 }
1400 EXPORT_SYMBOL(unregister_console);
1401
1402 static int __init printk_late_init(void)
1403 {
1404         struct console *con;
1405
1406         for_each_console(con) {
1407                 if (con->flags & CON_BOOT) {
1408                         printk(KERN_INFO "turn off boot console %s%d\n",
1409                                 con->name, con->index);
1410                         unregister_console(con);
1411                 }
1412         }
1413         hotcpu_notifier(console_cpu_notify, 0);
1414         return 0;
1415 }
1416 late_initcall(printk_late_init);
1417
1418 #if defined CONFIG_PRINTK
1419
1420 /*
1421  * printk rate limiting, lifted from the networking subsystem.
1422  *
1423  * This enforces a rate limit: not more than 10 kernel messages
1424  * every 5s to make a denial-of-service attack impossible.
1425  */
1426 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1427
1428 int __printk_ratelimit(const char *func)
1429 {
1430         return ___ratelimit(&printk_ratelimit_state, func);
1431 }
1432 EXPORT_SYMBOL(__printk_ratelimit);
1433
1434 /**
1435  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1436  * @caller_jiffies: pointer to caller's state
1437  * @interval_msecs: minimum interval between prints
1438  *
1439  * printk_timed_ratelimit() returns true if more than @interval_msecs
1440  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1441  * returned true.
1442  */
1443 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1444                         unsigned int interval_msecs)
1445 {
1446         if (*caller_jiffies == 0
1447                         || !time_in_range(jiffies, *caller_jiffies,
1448                                         *caller_jiffies
1449                                         + msecs_to_jiffies(interval_msecs))) {
1450                 *caller_jiffies = jiffies;
1451                 return true;
1452         }
1453         return false;
1454 }
1455 EXPORT_SYMBOL(printk_timed_ratelimit);
1456
1457 static DEFINE_SPINLOCK(dump_list_lock);
1458 static LIST_HEAD(dump_list);
1459
1460 /**
1461  * kmsg_dump_register - register a kernel log dumper.
1462  * @dumper: pointer to the kmsg_dumper structure
1463  *
1464  * Adds a kernel log dumper to the system. The dump callback in the
1465  * structure will be called when the kernel oopses or panics and must be
1466  * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1467  */
1468 int kmsg_dump_register(struct kmsg_dumper *dumper)
1469 {
1470         unsigned long flags;
1471         int err = -EBUSY;
1472
1473         /* The dump callback needs to be set */
1474         if (!dumper->dump)
1475                 return -EINVAL;
1476
1477         spin_lock_irqsave(&dump_list_lock, flags);
1478         /* Don't allow registering multiple times */
1479         if (!dumper->registered) {
1480                 dumper->registered = 1;
1481                 list_add_tail(&dumper->list, &dump_list);
1482                 err = 0;
1483         }
1484         spin_unlock_irqrestore(&dump_list_lock, flags);
1485
1486         return err;
1487 }
1488 EXPORT_SYMBOL_GPL(kmsg_dump_register);
1489
1490 /**
1491  * kmsg_dump_unregister - unregister a kmsg dumper.
1492  * @dumper: pointer to the kmsg_dumper structure
1493  *
1494  * Removes a dump device from the system. Returns zero on success and
1495  * %-EINVAL otherwise.
1496  */
1497 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
1498 {
1499         unsigned long flags;
1500         int err = -EINVAL;
1501
1502         spin_lock_irqsave(&dump_list_lock, flags);
1503         if (dumper->registered) {
1504                 dumper->registered = 0;
1505                 list_del(&dumper->list);
1506                 err = 0;
1507         }
1508         spin_unlock_irqrestore(&dump_list_lock, flags);
1509
1510         return err;
1511 }
1512 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
1513
1514 static const char const *kmsg_reasons[] = {
1515         [KMSG_DUMP_OOPS]        = "oops",
1516         [KMSG_DUMP_PANIC]       = "panic",
1517         [KMSG_DUMP_KEXEC]       = "kexec",
1518 };
1519
1520 static const char *kmsg_to_str(enum kmsg_dump_reason reason)
1521 {
1522         if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0)
1523                 return "unknown";
1524
1525         return kmsg_reasons[reason];
1526 }
1527
1528 /**
1529  * kmsg_dump - dump kernel log to kernel message dumpers.
1530  * @reason: the reason (oops, panic etc) for dumping
1531  *
1532  * Iterate through each of the dump devices and call the oops/panic
1533  * callbacks with the log buffer.
1534  */
1535 void kmsg_dump(enum kmsg_dump_reason reason)
1536 {
1537         unsigned long end;
1538         unsigned chars;
1539         struct kmsg_dumper *dumper;
1540         const char *s1, *s2;
1541         unsigned long l1, l2;
1542         unsigned long flags;
1543
1544         /* Theoretically, the log could move on after we do this, but
1545            there's not a lot we can do about that. The new messages
1546            will overwrite the start of what we dump. */
1547         spin_lock_irqsave(&logbuf_lock, flags);
1548         end = log_end & LOG_BUF_MASK;
1549         chars = logged_chars;
1550         spin_unlock_irqrestore(&logbuf_lock, flags);
1551
1552         if (chars > end) {
1553                 s1 = log_buf + log_buf_len - chars + end;
1554                 l1 = chars - end;
1555
1556                 s2 = log_buf;
1557                 l2 = end;
1558         } else {
1559                 s1 = "";
1560                 l1 = 0;
1561
1562                 s2 = log_buf + end - chars;
1563                 l2 = chars;
1564         }
1565
1566         if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
1567                 printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n",
1568                                 kmsg_to_str(reason));
1569                 return;
1570         }
1571         list_for_each_entry(dumper, &dump_list, list)
1572                 dumper->dump(dumper, reason, s1, l1, s2, l2);
1573         spin_unlock_irqrestore(&dump_list_lock, flags);
1574 }
1575 #endif