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 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 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
 265 int dmesg_restrict = 1;
 266 #else
 267 int dmesg_restrict;
 268 #endif
 269
 270 int do_syslog(int type, char __user *buf, int len, bool from_file)
 271 {
 272         unsigned i, j, limit, count;
 273         int do_clear = 0;
 274         char c;
 275         int error = 0;
 276
 277         error = security_syslog(type, from_file);
 278         if (error)
 279                 return error;
 280
 281         switch (type) {
 282         case SYSLOG_ACTION_CLOSE:       /* Close log */
 283                 break;
 284         case SYSLOG_ACTION_OPEN:        /* Open log */
 285                 break;
 286         case SYSLOG_ACTION_READ:        /* Read from log */
 287                 error = -EINVAL;
 288                 if (!buf || len < 0)
 289                         goto out;
 290                 error = 0;
 291                 if (!len)
 292                         goto out;
 293                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 294                         error = -EFAULT;
 295                         goto out;
 296                 }
 297                 error = wait_event_interruptible(log_wait,
 298                                                         (log_start - log_end));
 299                 if (error)
 300                         goto out;
 301                 i = 0;
 302                 spin_lock_irq(&logbuf_lock);
 303                 while (!error && (log_start != log_end) && i < len) {
 304                         c = LOG_BUF(log_start);
 305                         log_start++;
 306                         spin_unlock_irq(&logbuf_lock);
 307                         error = __put_user(c,buf);
 308                         buf++;
 309                         i++;
 310                         cond_resched();
 311                         spin_lock_irq(&logbuf_lock);
 312                 }
 313                 spin_unlock_irq(&logbuf_lock);
 314                 if (!error)
 315                         error = i;
 316                 break;
 317         /* Read/clear last kernel messages */
 318         case SYSLOG_ACTION_READ_CLEAR:
 319                 do_clear = 1;
 320                 /* FALL THRU */
 321         /* Read last kernel messages */
 322         case SYSLOG_ACTION_READ_ALL:
 323                 error = -EINVAL;
 324                 if (!buf || len < 0)
 325                         goto out;
 326                 error = 0;
 327                 if (!len)
 328                         goto out;
 329                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 330                         error = -EFAULT;
 331                         goto out;
 332                 }
 333                 count = len;
 334                 if (count > log_buf_len)
 335                         count = log_buf_len;
 336                 spin_lock_irq(&logbuf_lock);
 337                 if (count > logged_chars)
 338                         count = logged_chars;
 339                 if (do_clear)
 340                         logged_chars = 0;
 341                 limit = log_end;
 342                 /*
 343                  * __put_user() could sleep, and while we sleep
 344                  * printk() could overwrite the messages
 345                  * we try to copy to user space. Therefore
 346                  * the messages are copied in reverse. <manfreds>
 347                  */
 348                 for (i = 0; i < count && !error; i++) {
 349                         j = limit-1-i;
 350                         if (j + log_buf_len < log_end)
 351                                 break;
 352                         c = LOG_BUF(j);
 353                         spin_unlock_irq(&logbuf_lock);
 354                         error = __put_user(c,&buf[count-1-i]);
 355                         cond_resched();
 356                         spin_lock_irq(&logbuf_lock);
 357                 }
 358                 spin_unlock_irq(&logbuf_lock);
 359                 if (error)
 360                         break;
 361                 error = i;
 362                 if (i != count) {
 363                         int offset = count-error;
 364                         /* buffer overflow during copy, correct user buffer. */
 365                         for (i = 0; i < error; i++) {
 366                                 if (__get_user(c,&buf[i+offset]) ||
 367                                     __put_user(c,&buf[i])) {
 368                                         error = -EFAULT;
 369                                         break;
 370                                 }
 371                                 cond_resched();
 372                         }
 373                 }
 374                 break;
 375         /* Clear ring buffer */
 376         case SYSLOG_ACTION_CLEAR:
 377                 logged_chars = 0;
 378                 break;
 379         /* Disable logging to console */
 380         case SYSLOG_ACTION_CONSOLE_OFF:
 381                 if (saved_console_loglevel == -1)
 382                         saved_console_loglevel = console_loglevel;
 383                 console_loglevel = minimum_console_loglevel;
 384                 break;
 385         /* Enable logging to console */
 386         case SYSLOG_ACTION_CONSOLE_ON:
 387                 if (saved_console_loglevel != -1) {
 388                         console_loglevel = saved_console_loglevel;
 389                         saved_console_loglevel = -1;
 390                 }
 391                 break;
 392         /* Set level of messages printed to console */
 393         case SYSLOG_ACTION_CONSOLE_LEVEL:
 394                 error = -EINVAL;
 395                 if (len < 1 || len > 8)
 396                         goto out;
 397                 if (len < minimum_console_loglevel)
 398                         len = minimum_console_loglevel;
 399                 console_loglevel = len;
 400                 /* Implicitly re-enable logging to console */
 401                 saved_console_loglevel = -1;
 402                 error = 0;
 403                 break;
 404         /* Number of chars in the log buffer */
 405         case SYSLOG_ACTION_SIZE_UNREAD:
 406                 error = log_end - log_start;
 407                 break;
 408         /* Size of the log buffer */
 409         case SYSLOG_ACTION_SIZE_BUFFER:
 410                 error = log_buf_len;
 411                 break;
 412         default:
 413                 error = -EINVAL;
 414                 break;
 415         }
 416 out:
 417         return error;
 418 }
 419
 420 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
 421 {
 422         return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
 423 }
 424
 425 #ifdef  CONFIG_KGDB_KDB
 426 /* kdb dmesg command needs access to the syslog buffer.  do_syslog()
 427  * uses locks so it cannot be used during debugging.  Just tell kdb
 428  * where the start and end of the physical and logical logs are.  This
 429  * is equivalent to do_syslog(3).
 430  */
 431 void kdb_syslog_data(char *syslog_data[4])
 432 {
 433         syslog_data[0] = log_buf;
 434         syslog_data[1] = log_buf + log_buf_len;
 435         syslog_data[2] = log_buf + log_end -
 436                 (logged_chars < log_buf_len ? logged_chars : log_buf_len);
 437         syslog_data[3] = log_buf + log_end;
 438 }
 439 #endif  /* CONFIG_KGDB_KDB */
 440
 441 /*
 442  * Call the console drivers on a range of log_buf
 443  */
 444 static void __call_console_drivers(unsigned start, unsigned end)
 445 {
 446         struct console *con;
 447
 448         for_each_console(con) {
 449                 if ((con->flags & CON_ENABLED) && con->write &&
 450                                 (cpu_online(smp_processor_id()) ||
 451                                 (con->flags & CON_ANYTIME)))
 452                         con->write(con, &LOG_BUF(start), end - start);
 453         }
 454 }
 455
 456 static int __read_mostly ignore_loglevel;
 457
 458 static int __init ignore_loglevel_setup(char *str)
 459 {
 460         ignore_loglevel = 1;
 461         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 462
 463         return 0;
 464 }
 465
 466 early_param("ignore_loglevel", ignore_loglevel_setup);
 467
 468 /*
 469  * Write out chars from start to end - 1 inclusive
 470  */
 471 static void _call_console_drivers(unsigned start,
 472                                 unsigned end, int msg_log_level)
 473 {
 474         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 475                         console_drivers && start != end) {
 476                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 477                         /* wrapped write */
 478                         __call_console_drivers(start & LOG_BUF_MASK,
 479                                                 log_buf_len);
 480                         __call_console_drivers(0, end & LOG_BUF_MASK);
 481                 } else {
 482                         __call_console_drivers(start, end);
 483                 }
 484         }
 485 }
 486
 487 /*
 488  * Call the console drivers, asking them to write out
 489  * log_buf[start] to log_buf[end - 1].
 490  * The console_sem must be held.
 491  */
 492 static void call_console_drivers(unsigned start, unsigned end)
 493 {
 494         unsigned cur_index, start_print;
 495         static int msg_level = -1;
 496
 497         BUG_ON(((int)(start - end)) > 0);
 498
 499         cur_index = start;
 500         start_print = start;
 501         while (cur_index != end) {
 502                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 503                                 LOG_BUF(cur_index + 0) == '<' &&
 504                                 LOG_BUF(cur_index + 1) >= '0' &&
 505                                 LOG_BUF(cur_index + 1) <= '7' &&
 506                                 LOG_BUF(cur_index + 2) == '>') {
 507                         msg_level = LOG_BUF(cur_index + 1) - '0';
 508                         cur_index += 3;
 509                         start_print = cur_index;
 510                 }
 511                 while (cur_index != end) {
 512                         char c = LOG_BUF(cur_index);
 513
 514                         cur_index++;
 515                         if (c == '\n') {
 516                                 if (msg_level < 0) {
 517                                         /*
 518                                          * printk() has already given us loglevel tags in
 519                                          * the buffer.  This code is here in case the
 520                                          * log buffer has wrapped right round and scribbled
 521                                          * on those tags
 522                                          */
 523                                         msg_level = default_message_loglevel;
 524                                 }
 525                                 _call_console_drivers(start_print, cur_index, msg_level);
 526                                 msg_level = -1;
 527                                 start_print = cur_index;
 528                                 break;
 529                         }
 530                 }
 531         }
 532         _call_console_drivers(start_print, end, msg_level);
 533 }
 534
 535 static void emit_log_char(char c)
 536 {
 537         LOG_BUF(log_end) = c;
 538         log_end++;
 539         if (log_end - log_start > log_buf_len)
 540                 log_start = log_end - log_buf_len;
 541         if (log_end - con_start > log_buf_len)
 542                 con_start = log_end - log_buf_len;
 543         if (logged_chars < log_buf_len)
 544                 logged_chars++;
 545 }
 546
 547 /*
 548  * Zap console related locks when oopsing. Only zap at most once
 549  * every 10 seconds, to leave time for slow consoles to print a
 550  * full oops.
 551  */
 552 static void zap_locks(void)
 553 {
 554         static unsigned long oops_timestamp;
 555
 556         if (time_after_eq(jiffies, oops_timestamp) &&
 557                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 558                 return;
 559
 560         oops_timestamp = jiffies;
 561
 562         /* If a crash is occurring, make sure we can't deadlock */
 563         spin_lock_init(&logbuf_lock);
 564         /* And make sure that we print immediately */
 565         sema_init(&console_sem, 1);
 566 }
 567
 568 #if defined(CONFIG_PRINTK_TIME)
 569 static int printk_time = 1;
 570 #else
 571 static int printk_time = 0;
 572 #endif
 573 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 574
 575 /* Check if we have any console registered that can be called early in boot. */
 576 static int have_callable_console(void)
 577 {
 578         struct console *con;
 579
 580         for_each_console(con)
 581                 if (con->flags & CON_ANYTIME)
 582                         return 1;
 583
 584         return 0;
 585 }
 586
 587 /**
 588  * printk - print a kernel message
 589  * @fmt: format string
 590  *
 591  * This is printk().  It can be called from any context.  We want it to work.
 592  *
 593  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 594  * call the console drivers.  If we fail to get the semaphore we place the output
 595  * into the log buffer and return.  The current holder of the console_sem will
 596  * notice the new output in release_console_sem() and will send it to the
 597  * consoles before releasing the semaphore.
 598  *
 599  * One effect of this deferred printing is that code which calls printk() and
 600  * then changes console_loglevel may break. This is because console_loglevel
 601  * is inspected when the actual printing occurs.
 602  *
 603  * See also:
 604  * printf(3)
 605  *
 606  * See the vsnprintf() documentation for format string extensions over C99.
 607  */
 608
 609 asmlinkage int printk(const char *fmt, ...)
 610 {
 611         va_list args;
 612         int r;
 613
 614 #ifdef CONFIG_KGDB_KDB
 615         if (unlikely(kdb_trap_printk)) {
 616                 va_start(args, fmt);
 617                 r = vkdb_printf(fmt, args);
 618                 va_end(args);
 619                 return r;
 620         }
 621 #endif
 622         va_start(args, fmt);
 623         r = vprintk(fmt, args);
 624         va_end(args);
 625
 626         return r;
 627 }
 628
 629 /* cpu currently holding logbuf_lock */
 630 static volatile unsigned int printk_cpu = UINT_MAX;
 631
 632 /*
 633  * Can we actually use the console at this time on this cpu?
 634  *
 635  * Console drivers may assume that per-cpu resources have
 636  * been allocated. So unless they're explicitly marked as
 637  * being able to cope (CON_ANYTIME) don't call them until
 638  * this CPU is officially up.
 639  */
 640 static inline int can_use_console(unsigned int cpu)
 641 {
 642         return cpu_online(cpu) || have_callable_console();
 643 }
 644
 645 /*
 646  * Try to get console ownership to actually show the kernel
 647  * messages from a 'printk'. Return true (and with the
 648  * console_semaphore held, and 'console_locked' set) if it
 649  * is successful, false otherwise.
 650  *
 651  * This gets called with the 'logbuf_lock' spinlock held and
 652  * interrupts disabled. It should return with 'lockbuf_lock'
 653  * released but interrupts still disabled.
 654  */
 655 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 656         __releases(&logbuf_lock)
 657 {
 658         int retval = 0;
 659
 660         if (!try_acquire_console_sem()) {
 661                 retval = 1;
 662
 663                 /*
 664                  * If we can't use the console, we need to release
 665                  * the console semaphore by hand to avoid flushing
 666                  * the buffer. We need to hold the console semaphore
 667                  * in order to do this test safely.
 668                  */
 669                 if (!can_use_console(cpu)) {
 670                         console_locked = 0;
 671                         up(&console_sem);
 672                         retval = 0;
 673                 }
 674         }
 675         printk_cpu = UINT_MAX;
 676         spin_unlock(&logbuf_lock);
 677         return retval;
 678 }
 679 static const char recursion_bug_msg [] =
 680                 KERN_CRIT "BUG: recent printk recursion!\n";
 681 static int recursion_bug;
 682 static int new_text_line = 1;
 683 static char printk_buf[1024];
 684
 685 int printk_delay_msec __read_mostly;
 686
 687 static inline void printk_delay(void)
 688 {
 689         if (unlikely(printk_delay_msec)) {
 690                 int m = printk_delay_msec;
 691
 692                 while (m--) {
 693                         mdelay(1);
 694                         touch_nmi_watchdog();
 695                 }
 696         }
 697 }
 698
 699 asmlinkage int vprintk(const char *fmt, va_list args)
 700 {
 701         int printed_len = 0;
 702         int current_log_level = default_message_loglevel;
 703         unsigned long flags;
 704         int this_cpu;
 705         char *p;
 706
 707         boot_delay_msec();
 708         printk_delay();
 709
 710         preempt_disable();
 711         /* This stops the holder of console_sem just where we want him */
 712         raw_local_irq_save(flags);
 713         this_cpu = smp_processor_id();
 714
 715         /*
 716          * Ouch, printk recursed into itself!
 717          */
 718         if (unlikely(printk_cpu == this_cpu)) {
 719                 /*
 720                  * If a crash is occurring during printk() on this CPU,
 721                  * then try to get the crash message out but make sure
 722                  * we can't deadlock. Otherwise just return to avoid the
 723                  * recursion and return - but flag the recursion so that
 724                  * it can be printed at the next appropriate moment:
 725                  */
 726                 if (!oops_in_progress) {
 727                         recursion_bug = 1;
 728                         goto out_restore_irqs;
 729                 }
 730                 zap_locks();
 731         }
 732
 733         lockdep_off();
 734         spin_lock(&logbuf_lock);
 735         printk_cpu = this_cpu;
 736
 737         if (recursion_bug) {
 738                 recursion_bug = 0;
 739                 strcpy(printk_buf, recursion_bug_msg);
 740                 printed_len = strlen(recursion_bug_msg);
 741         }
 742         /* Emit the output into the temporary buffer */
 743         printed_len += vscnprintf(printk_buf + printed_len,
 744                                   sizeof(printk_buf) - printed_len, fmt, args);
 745
 746
 747         p = printk_buf;
 748
 749         /* Do we have a loglevel in the string? */
 750         if (p[0] == '<') {
 751                 unsigned char c = p[1];
 752                 if (c && p[2] == '>') {
 753                         switch (c) {
 754                         case '0' ... '7': /* loglevel */
 755                                 current_log_level = c - '0';
 756                         /* Fallthrough - make sure we're on a new line */
 757                         case 'd': /* KERN_DEFAULT */
 758                                 if (!new_text_line) {
 759                                         emit_log_char('\n');
 760                                         new_text_line = 1;
 761                                 }
 762                         /* Fallthrough - skip the loglevel */
 763                         case 'c': /* KERN_CONT */
 764                                 p += 3;
 765                                 break;
 766                         }
 767                 }
 768         }
 769
 770         /*
 771          * Copy the output into log_buf.  If the caller didn't provide
 772          * appropriate log level tags, we insert them here
 773          */
 774         for ( ; *p; p++) {
 775                 if (new_text_line) {
 776                         /* Always output the token */
 777                         emit_log_char('<');
 778                         emit_log_char(current_log_level + '0');
 779                         emit_log_char('>');
 780                         printed_len += 3;
 781                         new_text_line = 0;
 782
 783                         if (printk_time) {
 784                                 /* Follow the token with the time */
 785                                 char tbuf[50], *tp;
 786                                 unsigned tlen;
 787                                 unsigned long long t;
 788                                 unsigned long nanosec_rem;
 789
 790                                 t = cpu_clock(printk_cpu);
 791                                 nanosec_rem = do_div(t, 1000000000);
 792                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 793                                                 (unsigned long) t,
 794                                                 nanosec_rem / 1000);
 795
 796                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 797                                         emit_log_char(*tp);
 798                                 printed_len += tlen;
 799                         }
 800
 801                         if (!*p)
 802                                 break;
 803                 }
 804
 805                 emit_log_char(*p);
 806                 if (*p == '\n')
 807                         new_text_line = 1;
 808         }
 809
 810         /*
 811          * Try to acquire and then immediately release the
 812          * console semaphore. The release will do all the
 813          * actual magic (print out buffers, wake up klogd,
 814          * etc).
 815          *
 816          * The acquire_console_semaphore_for_printk() function
 817          * will release 'logbuf_lock' regardless of whether it
 818          * actually gets the semaphore or not.
 819          */
 820         if (acquire_console_semaphore_for_printk(this_cpu))
 821                 release_console_sem();
 822
 823         lockdep_on();
 824 out_restore_irqs:
 825         raw_local_irq_restore(flags);
 826
 827         preempt_enable();
 828         return printed_len;
 829 }
 830 EXPORT_SYMBOL(printk);
 831 EXPORT_SYMBOL(vprintk);
 832
 833 #else
 834
 835 static void call_console_drivers(unsigned start, unsigned end)
 836 {
 837 }
 838
 839 #endif
 840
 841 static int __add_preferred_console(char *name, int idx, char *options,
 842                                    char *brl_options)
 843 {
 844         struct console_cmdline *c;
 845         int i;
 846
 847         /*
 848          *      See if this tty is not yet registered, and
 849          *      if we have a slot free.
 850          */
 851         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 852                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 853                           console_cmdline[i].index == idx) {
 854                                 if (!brl_options)
 855                                         selected_console = i;
 856                                 return 0;
 857                 }
 858         if (i == MAX_CMDLINECONSOLES)
 859                 return -E2BIG;
 860         if (!brl_options)
 861                 selected_console = i;
 862         c = &console_cmdline[i];
 863         strlcpy(c->name, name, sizeof(c->name));
 864         c->options = options;
 865 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 866         c->brl_options = brl_options;
 867 #endif
 868         c->index = idx;
 869         return 0;
 870 }
 871 /*
 872  * Set up a list of consoles.  Called from init/main.c
 873  */
 874 static int __init console_setup(char *str)
 875 {
 876         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 877         char *s, *options, *brl_options = NULL;
 878         int idx;
 879
 880 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 881         if (!memcmp(str, "brl,", 4)) {
 882                 brl_options = "";
 883                 str += 4;
 884         } else if (!memcmp(str, "brl=", 4)) {
 885                 brl_options = str + 4;
 886                 str = strchr(brl_options, ',');
 887                 if (!str) {
 888                         printk(KERN_ERR "need port name after brl=\n");
 889                         return 1;
 890                 }
 891                 *(str++) = 0;
 892         }
 893 #endif
 894
 895         /*
 896          * Decode str into name, index, options.
 897          */
 898         if (str[0] >= '0' && str[0] <= '9') {
 899                 strcpy(buf, "ttyS");
 900                 strncpy(buf + 4, str, sizeof(buf) - 5);
 901         } else {
 902                 strncpy(buf, str, sizeof(buf) - 1);
 903         }
 904         buf[sizeof(buf) - 1] = 0;
 905         if ((options = strchr(str, ',')) != NULL)
 906                 *(options++) = 0;
 907 #ifdef __sparc__
 908         if (!strcmp(str, "ttya"))
 909                 strcpy(buf, "ttyS0");
 910         if (!strcmp(str, "ttyb"))
 911                 strcpy(buf, "ttyS1");
 912 #endif
 913         for (s = buf; *s; s++)
 914                 if ((*s >= '0' && *s <= '9') || *s == ',')
 915                         break;
 916         idx = simple_strtoul(s, NULL, 10);
 917         *s = 0;
 918
 919         __add_preferred_console(buf, idx, options, brl_options);
 920         console_set_on_cmdline = 1;
 921         return 1;
 922 }
 923 __setup("console=", console_setup);
 924
 925 /**
 926  * add_preferred_console - add a device to the list of preferred consoles.
 927  * @name: device name
 928  * @idx: device index
 929  * @options: options for this console
 930  *
 931  * The last preferred console added will be used for kernel messages
 932  * and stdin/out/err for init.  Normally this is used by console_setup
 933  * above to handle user-supplied console arguments; however it can also
 934  * be used by arch-specific code either to override the user or more
 935  * commonly to provide a default console (ie from PROM variables) when
 936  * the user has not supplied one.
 937  */
 938 int add_preferred_console(char *name, int idx, char *options)
 939 {
 940         return __add_preferred_console(name, idx, options, NULL);
 941 }
 942
 943 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 944 {
 945         struct console_cmdline *c;
 946         int i;
 947
 948         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 949                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 950                           console_cmdline[i].index == idx) {
 951                                 c = &console_cmdline[i];
 952                                 strlcpy(c->name, name_new, sizeof(c->name));
 953                                 c->name[sizeof(c->name) - 1] = 0;
 954                                 c->options = options;
 955                                 c->index = idx_new;
 956                                 return i;
 957                 }
 958         /* not found */
 959         return -1;
 960 }
 961
 962 int console_suspend_enabled = 1;
 963 EXPORT_SYMBOL(console_suspend_enabled);
 964
 965 static int __init console_suspend_disable(char *str)
 966 {
 967         console_suspend_enabled = 0;
 968         return 1;
 969 }
 970 __setup("no_console_suspend", console_suspend_disable);
 971
 972 /**
 973  * suspend_console - suspend the console subsystem
 974  *
 975  * This disables printk() while we go into suspend states
 976  */
 977 void suspend_console(void)
 978 {
 979         if (!console_suspend_enabled)
 980                 return;
 981         printk("Suspending console(s) (use no_console_suspend to debug)\n");
 982         acquire_console_sem();
 983         console_suspended = 1;
 984         up(&console_sem);
 985 }
 986
 987 void resume_console(void)
 988 {
 989         if (!console_suspend_enabled)
 990                 return;
 991         down(&console_sem);
 992         console_suspended = 0;
 993         release_console_sem();
 994 }
 995
 996 /**
 997  * console_cpu_notify - print deferred console messages after CPU hotplug
 998  * @self: notifier struct
 999  * @action: CPU hotplug event
1000  * @hcpu: unused
1001  *
1002  * If printk() is called from a CPU that is not online yet, the messages
1003  * will be spooled but will not show up on the console.  This function is
1004  * called when a new CPU comes online (or fails to come up), and ensures
1005  * that any such output gets printed.
1006  */
1007 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1008         unsigned long action, void *hcpu)
1009 {
1010         switch (action) {
1011         case CPU_ONLINE:
1012         case CPU_DEAD:
1013         case CPU_DYING:
1014         case CPU_DOWN_FAILED:
1015         case CPU_UP_CANCELED:
1016                 acquire_console_sem();
1017                 release_console_sem();
1018         }
1019         return NOTIFY_OK;
1020 }
1021
1022 /**
1023  * acquire_console_sem - lock the console system for exclusive use.
1024  *
1025  * Acquires a semaphore which guarantees that the caller has
1026  * exclusive access to the console system and the console_drivers list.
1027  *
1028  * Can sleep, returns nothing.
1029  */
1030 void acquire_console_sem(void)
1031 {
1032         BUG_ON(in_interrupt());
1033         down(&console_sem);
1034         if (console_suspended)
1035                 return;
1036         console_locked = 1;
1037         console_may_schedule = 1;
1038 }
1039 EXPORT_SYMBOL(acquire_console_sem);
1040
1041 int try_acquire_console_sem(void)
1042 {
1043         if (down_trylock(&console_sem))
1044                 return -1;
1045         if (console_suspended) {
1046                 up(&console_sem);
1047                 return -1;
1048         }
1049         console_locked = 1;
1050         console_may_schedule = 0;
1051         return 0;
1052 }
1053 EXPORT_SYMBOL(try_acquire_console_sem);
1054
1055 int is_console_locked(void)
1056 {
1057         return console_locked;
1058 }
1059
1060 static DEFINE_PER_CPU(int, printk_pending);
1061
1062 void printk_tick(void)
1063 {
1064         if (__get_cpu_var(printk_pending)) {
1065                 __get_cpu_var(printk_pending) = 0;
1066                 wake_up_interruptible(&log_wait);
1067         }
1068 }
1069
1070 int printk_needs_cpu(int cpu)
1071 {
1072         return per_cpu(printk_pending, cpu);
1073 }
1074
1075 void wake_up_klogd(void)
1076 {
1077         if (waitqueue_active(&log_wait))
1078                 __raw_get_cpu_var(printk_pending) = 1;
1079 }
1080
1081 /**
1082  * release_console_sem - unlock the console system
1083  *
1084  * Releases the semaphore which the caller holds on the console system
1085  * and the console driver list.
1086  *
1087  * While the semaphore was held, console output may have been buffered
1088  * by printk().  If this is the case, release_console_sem() emits
1089  * the output prior to releasing the semaphore.
1090  *
1091  * If there is output waiting for klogd, we wake it up.
1092  *
1093  * release_console_sem() may be called from any context.
1094  */
1095 void release_console_sem(void)
1096 {
1097         unsigned long flags;
1098         unsigned _con_start, _log_end;
1099         unsigned wake_klogd = 0;
1100
1101         if (console_suspended) {
1102                 up(&console_sem);
1103                 return;
1104         }
1105
1106         console_may_schedule = 0;
1107
1108         for ( ; ; ) {
1109                 spin_lock_irqsave(&logbuf_lock, flags);
1110                 wake_klogd |= log_start - log_end;
1111                 if (con_start == log_end)
1112                         break;                  /* Nothing to print */
1113                 _con_start = con_start;
1114                 _log_end = log_end;
1115                 con_start = log_end;            /* Flush */
1116                 spin_unlock(&logbuf_lock);
1117                 stop_critical_timings();        /* don't trace print latency */
1118                 call_console_drivers(_con_start, _log_end);
1119                 start_critical_timings();
1120                 local_irq_restore(flags);
1121         }
1122         console_locked = 0;
1123         up(&console_sem);
1124         spin_unlock_irqrestore(&logbuf_lock, flags);
1125         if (wake_klogd)
1126                 wake_up_klogd();
1127 }
1128 EXPORT_SYMBOL(release_console_sem);
1129
1130 /**
1131  * console_conditional_schedule - yield the CPU if required
1132  *
1133  * If the console code is currently allowed to sleep, and
1134  * if this CPU should yield the CPU to another task, do
1135  * so here.
1136  *
1137  * Must be called within acquire_console_sem().
1138  */
1139 void __sched console_conditional_schedule(void)
1140 {
1141         if (console_may_schedule)
1142                 cond_resched();
1143 }
1144 EXPORT_SYMBOL(console_conditional_schedule);
1145
1146 void console_unblank(void)
1147 {
1148         struct console *c;
1149
1150         /*
1151          * console_unblank can no longer be called in interrupt context unless
1152          * oops_in_progress is set to 1..
1153          */
1154         if (oops_in_progress) {
1155                 if (down_trylock(&console_sem) != 0)
1156                         return;
1157         } else
1158                 acquire_console_sem();
1159
1160         console_locked = 1;
1161         console_may_schedule = 0;
1162         for_each_console(c)
1163                 if ((c->flags & CON_ENABLED) && c->unblank)
1164                         c->unblank();
1165         release_console_sem();
1166 }
1167
1168 /*
1169  * Return the console tty driver structure and its associated index
1170  */
1171 struct tty_driver *console_device(int *index)
1172 {
1173         struct console *c;
1174         struct tty_driver *driver = NULL;
1175
1176         acquire_console_sem();
1177         for_each_console(c) {
1178                 if (!c->device)
1179                         continue;
1180                 driver = c->device(c, index);
1181                 if (driver)
1182                         break;
1183         }
1184         release_console_sem();
1185         return driver;
1186 }
1187
1188 /*
1189  * Prevent further output on the passed console device so that (for example)
1190  * serial drivers can disable console output before suspending a port, and can
1191  * re-enable output afterwards.
1192  */
1193 void console_stop(struct console *console)
1194 {
1195         acquire_console_sem();
1196         console->flags &= ~CON_ENABLED;
1197         release_console_sem();
1198 }
1199 EXPORT_SYMBOL(console_stop);
1200
1201 void console_start(struct console *console)
1202 {
1203         acquire_console_sem();
1204         console->flags |= CON_ENABLED;
1205         release_console_sem();
1206 }
1207 EXPORT_SYMBOL(console_start);
1208
1209 /*
1210  * The console driver calls this routine during kernel initialization
1211  * to register the console printing procedure with printk() and to
1212  * print any messages that were printed by the kernel before the
1213  * console driver was initialized.
1214  *
1215  * This can happen pretty early during the boot process (because of
1216  * early_printk) - sometimes before setup_arch() completes - be careful
1217  * of what kernel features are used - they may not be initialised yet.
1218  *
1219  * There are two types of consoles - bootconsoles (early_printk) and
1220  * "real" consoles (everything which is not a bootconsole) which are
1221  * handled differently.
1222  *  - Any number of bootconsoles can be registered at any time.
1223  *  - As soon as a "real" console is registered, all bootconsoles
1224  *    will be unregistered automatically.
1225  *  - Once a "real" console is registered, any attempt to register a
1226  *    bootconsoles will be rejected
1227  */
1228 void register_console(struct console *newcon)
1229 {
1230         int i;
1231         unsigned long flags;
1232         struct console *bcon = NULL;
1233
1234         /*
1235          * before we register a new CON_BOOT console, make sure we don't
1236          * already have a valid console
1237          */
1238         if (console_drivers && newcon->flags & CON_BOOT) {
1239                 /* find the last or real console */
1240                 for_each_console(bcon) {
1241                         if (!(bcon->flags & CON_BOOT)) {
1242                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1243                                         newcon->name, newcon->index);
1244                                 return;
1245                         }
1246                 }
1247         }
1248
1249         if (console_drivers && console_drivers->flags & CON_BOOT)
1250                 bcon = console_drivers;
1251
1252         if (preferred_console < 0 || bcon || !console_drivers)
1253                 preferred_console = selected_console;
1254
1255         if (newcon->early_setup)
1256                 newcon->early_setup();
1257
1258         /*
1259          *      See if we want to use this console driver. If we
1260          *      didn't select a console we take the first one
1261          *      that registers here.
1262          */
1263         if (preferred_console < 0) {
1264                 if (newcon->index < 0)
1265                         newcon->index = 0;
1266                 if (newcon->setup == NULL ||
1267                     newcon->setup(newcon, NULL) == 0) {
1268                         newcon->flags |= CON_ENABLED;
1269                         if (newcon->device) {
1270                                 newcon->flags |= CON_CONSDEV;
1271                                 preferred_console = 0;
1272                         }
1273                 }
1274         }
1275
1276         /*
1277          *      See if this console matches one we selected on
1278          *      the command line.
1279          */
1280         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1281                         i++) {
1282                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1283                         continue;
1284                 if (newcon->index >= 0 &&
1285                     newcon->index != console_cmdline[i].index)
1286                         continue;
1287                 if (newcon->index < 0)
1288                         newcon->index = console_cmdline[i].index;
1289 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1290                 if (console_cmdline[i].brl_options) {
1291                         newcon->flags |= CON_BRL;
1292                         braille_register_console(newcon,
1293                                         console_cmdline[i].index,
1294                                         console_cmdline[i].options,
1295                                         console_cmdline[i].brl_options);
1296                         return;
1297                 }
1298 #endif
1299                 if (newcon->setup &&
1300                     newcon->setup(newcon, console_cmdline[i].options) != 0)
1301                         break;
1302                 newcon->flags |= CON_ENABLED;
1303                 newcon->index = console_cmdline[i].index;
1304                 if (i == selected_console) {
1305                         newcon->flags |= CON_CONSDEV;
1306                         preferred_console = selected_console;
1307                 }
1308                 break;
1309         }
1310
1311         if (!(newcon->flags & CON_ENABLED))
1312                 return;
1313
1314         /*
1315          * If we have a bootconsole, and are switching to a real console,
1316          * don't print everything out again, since when the boot console, and
1317          * the real console are the same physical device, it's annoying to
1318          * see the beginning boot messages twice
1319          */
1320         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1321                 newcon->flags &= ~CON_PRINTBUFFER;
1322
1323         /*
1324          *      Put this console in the list - keep the
1325          *      preferred driver at the head of the list.
1326          */
1327         acquire_console_sem();
1328         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1329                 newcon->next = console_drivers;
1330                 console_drivers = newcon;
1331                 if (newcon->next)
1332                         newcon->next->flags &= ~CON_CONSDEV;
1333         } else {
1334                 newcon->next = console_drivers->next;
1335                 console_drivers->next = newcon;
1336         }
1337         if (newcon->flags & CON_PRINTBUFFER) {
1338                 /*
1339                  * release_console_sem() will print out the buffered messages
1340                  * for us.
1341                  */
1342                 spin_lock_irqsave(&logbuf_lock, flags);
1343                 con_start = log_start;
1344                 spin_unlock_irqrestore(&logbuf_lock, flags);
1345         }
1346         release_console_sem();
1347
1348         /*
1349          * By unregistering the bootconsoles after we enable the real console
1350          * we get the "console xxx enabled" message on all the consoles -
1351          * boot consoles, real consoles, etc - this is to ensure that end
1352          * users know there might be something in the kernel's log buffer that
1353          * went to the bootconsole (that they do not see on the real console)
1354          */
1355         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1356                 /* we need to iterate through twice, to make sure we print
1357                  * everything out, before we unregister the console(s)
1358                  */
1359                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1360                         newcon->name, newcon->index);
1361                 for_each_console(bcon)
1362                         if (bcon->flags & CON_BOOT)
1363                                 unregister_console(bcon);
1364         } else {
1365                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1366                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
1367                         newcon->name, newcon->index);
1368         }
1369 }
1370 EXPORT_SYMBOL(register_console);
1371
1372 int unregister_console(struct console *console)
1373 {
1374         struct console *a, *b;
1375         int res = 1;
1376
1377 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1378         if (console->flags & CON_BRL)
1379                 return braille_unregister_console(console);
1380 #endif
1381
1382         acquire_console_sem();
1383         if (console_drivers == console) {
1384                 console_drivers=console->next;
1385                 res = 0;
1386         } else if (console_drivers) {
1387                 for (a=console_drivers->next, b=console_drivers ;
1388                      a; b=a, a=b->next) {
1389                         if (a == console) {
1390                                 b->next = a->next;
1391                                 res = 0;
1392                                 break;
1393                         }
1394                 }
1395         }
1396
1397         /*
1398          * If this isn't the last console and it has CON_CONSDEV set, we
1399          * need to set it on the next preferred console.
1400          */
1401         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1402                 console_drivers->flags |= CON_CONSDEV;
1403
1404         release_console_sem();
1405         return res;
1406 }
1407 EXPORT_SYMBOL(unregister_console);
1408
1409 static int __init printk_late_init(void)
1410 {
1411         struct console *con;
1412
1413         for_each_console(con) {
1414                 if (con->flags & CON_BOOT) {
1415                         printk(KERN_INFO "turn off boot console %s%d\n",
1416                                 con->name, con->index);
1417                         unregister_console(con);
1418                 }
1419         }
1420         hotcpu_notifier(console_cpu_notify, 0);
1421         return 0;
1422 }
1423 late_initcall(printk_late_init);
1424
1425 #if defined CONFIG_PRINTK
1426
1427 /*
1428  * printk rate limiting, lifted from the networking subsystem.
1429  *
1430  * This enforces a rate limit: not more than 10 kernel messages
1431  * every 5s to make a denial-of-service attack impossible.
1432  */
1433 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1434
1435 int __printk_ratelimit(const char *func)
1436 {
1437         return ___ratelimit(&printk_ratelimit_state, func);
1438 }
1439 EXPORT_SYMBOL(__printk_ratelimit);
1440
1441 /**
1442  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1443  * @caller_jiffies: pointer to caller's state
1444  * @interval_msecs: minimum interval between prints
1445  *
1446  * printk_timed_ratelimit() returns true if more than @interval_msecs
1447  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1448  * returned true.
1449  */
1450 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1451                         unsigned int interval_msecs)
1452 {
1453         if (*caller_jiffies == 0
1454                         || !time_in_range(jiffies, *caller_jiffies,
1455                                         *caller_jiffies
1456                                         + msecs_to_jiffies(interval_msecs))) {
1457                 *caller_jiffies = jiffies;
1458                 return true;
1459         }
1460         return false;
1461 }
1462 EXPORT_SYMBOL(printk_timed_ratelimit);
1463
1464 static DEFINE_SPINLOCK(dump_list_lock);
1465 static LIST_HEAD(dump_list);
1466
1467 /**
1468  * kmsg_dump_register - register a kernel log dumper.
1469  * @dumper: pointer to the kmsg_dumper structure
1470  *
1471  * Adds a kernel log dumper to the system. The dump callback in the
1472  * structure will be called when the kernel oopses or panics and must be
1473  * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1474  */
1475 int kmsg_dump_register(struct kmsg_dumper *dumper)
1476 {
1477         unsigned long flags;
1478         int err = -EBUSY;
1479
1480         /* The dump callback needs to be set */
1481         if (!dumper->dump)
1482                 return -EINVAL;
1483
1484         spin_lock_irqsave(&dump_list_lock, flags);
1485         /* Don't allow registering multiple times */
1486         if (!dumper->registered) {
1487                 dumper->registered = 1;
1488                 list_add_tail(&dumper->list, &dump_list);
1489                 err = 0;
1490         }
1491         spin_unlock_irqrestore(&dump_list_lock, flags);
1492
1493         return err;
1494 }
1495 EXPORT_SYMBOL_GPL(kmsg_dump_register);
1496
1497 /**
1498  * kmsg_dump_unregister - unregister a kmsg dumper.
1499  * @dumper: pointer to the kmsg_dumper structure
1500  *
1501  * Removes a dump device from the system. Returns zero on success and
1502  * %-EINVAL otherwise.
1503  */
1504 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
1505 {
1506         unsigned long flags;
1507         int err = -EINVAL;
1508
1509         spin_lock_irqsave(&dump_list_lock, flags);
1510         if (dumper->registered) {
1511                 dumper->registered = 0;
1512                 list_del(&dumper->list);
1513                 err = 0;
1514         }
1515         spin_unlock_irqrestore(&dump_list_lock, flags);
1516
1517         return err;
1518 }
1519 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
1520
1521 static const char * const kmsg_reasons[] = {
1522         [KMSG_DUMP_OOPS]        = "oops",
1523         [KMSG_DUMP_PANIC]       = "panic",
1524         [KMSG_DUMP_KEXEC]       = "kexec",
1525 };
1526
1527 static const char *kmsg_to_str(enum kmsg_dump_reason reason)
1528 {
1529         if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0)
1530                 return "unknown";
1531
1532         return kmsg_reasons[reason];
1533 }
1534
1535 /**
1536  * kmsg_dump - dump kernel log to kernel message dumpers.
1537  * @reason: the reason (oops, panic etc) for dumping
1538  *
1539  * Iterate through each of the dump devices and call the oops/panic
1540  * callbacks with the log buffer.
1541  */
1542 void kmsg_dump(enum kmsg_dump_reason reason)
1543 {
1544         unsigned long end;
1545         unsigned chars;
1546         struct kmsg_dumper *dumper;
1547         const char *s1, *s2;
1548         unsigned long l1, l2;
1549         unsigned long flags;
1550
1551         /* Theoretically, the log could move on after we do this, but
1552            there's not a lot we can do about that. The new messages
1553            will overwrite the start of what we dump. */
1554         spin_lock_irqsave(&logbuf_lock, flags);
1555         end = log_end & LOG_BUF_MASK;
1556         chars = logged_chars;
1557         spin_unlock_irqrestore(&logbuf_lock, flags);
1558
1559         if (chars > end) {
1560                 s1 = log_buf + log_buf_len - chars + end;
1561                 l1 = chars - end;
1562
1563                 s2 = log_buf;
1564                 l2 = end;
1565         } else {
1566                 s1 = "";
1567                 l1 = 0;
1568
1569                 s2 = log_buf + end - chars;
1570                 l2 = chars;
1571         }
1572
1573         if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
1574                 printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n",
1575                                 kmsg_to_str(reason));
1576                 return;
1577         }
1578         list_for_each_entry(dumper, &dump_list, list)
1579                 dumper->dump(dumper, reason, s1, l1, s2, l2);
1580         spin_unlock_irqrestore(&dump_list_lock, flags);
1581 }
1582 #endif