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         /*
 278          * If this is from /proc/kmsg we only do the capabilities checks
 279          * at open time.
 280          */
 281         if (type == SYSLOG_ACTION_OPEN || !from_file) {
 282                 if (dmesg_restrict && !capable(CAP_SYS_ADMIN))
 283                         return -EPERM;
 284                 if ((type != SYSLOG_ACTION_READ_ALL &&
 285                      type != SYSLOG_ACTION_SIZE_BUFFER) &&
 286                     !capable(CAP_SYSLOG)) {
 287                         /* remove after 2.6.38 */
 288                         if (capable(CAP_SYS_ADMIN))
 289                                 WARN_ONCE(1, "Attempt to access syslog with "
 290                                   "CAP_SYS_ADMIN but no CAP_SYSLOG "
 291                                   "(deprecated and denied).\n");
 292                         return -EPERM;
 293                 }
 294         }
 295
 296         error = security_syslog(type);
 297         if (error)
 298                 return error;
 299
 300         switch (type) {
 301         case SYSLOG_ACTION_CLOSE:       /* Close log */
 302                 break;
 303         case SYSLOG_ACTION_OPEN:        /* Open log */
 304                 break;
 305         case SYSLOG_ACTION_READ:        /* Read from log */
 306                 error = -EINVAL;
 307                 if (!buf || len < 0)
 308                         goto out;
 309                 error = 0;
 310                 if (!len)
 311                         goto out;
 312                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 313                         error = -EFAULT;
 314                         goto out;
 315                 }
 316                 error = wait_event_interruptible(log_wait,
 317                                                         (log_start - log_end));
 318                 if (error)
 319                         goto out;
 320                 i = 0;
 321                 spin_lock_irq(&logbuf_lock);
 322                 while (!error && (log_start != log_end) && i < len) {
 323                         c = LOG_BUF(log_start);
 324                         log_start++;
 325                         spin_unlock_irq(&logbuf_lock);
 326                         error = __put_user(c,buf);
 327                         buf++;
 328                         i++;
 329                         cond_resched();
 330                         spin_lock_irq(&logbuf_lock);
 331                 }
 332                 spin_unlock_irq(&logbuf_lock);
 333                 if (!error)
 334                         error = i;
 335                 break;
 336         /* Read/clear last kernel messages */
 337         case SYSLOG_ACTION_READ_CLEAR:
 338                 do_clear = 1;
 339                 /* FALL THRU */
 340         /* Read last kernel messages */
 341         case SYSLOG_ACTION_READ_ALL:
 342                 error = -EINVAL;
 343                 if (!buf || len < 0)
 344                         goto out;
 345                 error = 0;
 346                 if (!len)
 347                         goto out;
 348                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 349                         error = -EFAULT;
 350                         goto out;
 351                 }
 352                 count = len;
 353                 if (count > log_buf_len)
 354                         count = log_buf_len;
 355                 spin_lock_irq(&logbuf_lock);
 356                 if (count > logged_chars)
 357                         count = logged_chars;
 358                 if (do_clear)
 359                         logged_chars = 0;
 360                 limit = log_end;
 361                 /*
 362                  * __put_user() could sleep, and while we sleep
 363                  * printk() could overwrite the messages
 364                  * we try to copy to user space. Therefore
 365                  * the messages are copied in reverse. <manfreds>
 366                  */
 367                 for (i = 0; i < count && !error; i++) {
 368                         j = limit-1-i;
 369                         if (j + log_buf_len < log_end)
 370                                 break;
 371                         c = LOG_BUF(j);
 372                         spin_unlock_irq(&logbuf_lock);
 373                         error = __put_user(c,&buf[count-1-i]);
 374                         cond_resched();
 375                         spin_lock_irq(&logbuf_lock);
 376                 }
 377                 spin_unlock_irq(&logbuf_lock);
 378                 if (error)
 379                         break;
 380                 error = i;
 381                 if (i != count) {
 382                         int offset = count-error;
 383                         /* buffer overflow during copy, correct user buffer. */
 384                         for (i = 0; i < error; i++) {
 385                                 if (__get_user(c,&buf[i+offset]) ||
 386                                     __put_user(c,&buf[i])) {
 387                                         error = -EFAULT;
 388                                         break;
 389                                 }
 390                                 cond_resched();
 391                         }
 392                 }
 393                 break;
 394         /* Clear ring buffer */
 395         case SYSLOG_ACTION_CLEAR:
 396                 logged_chars = 0;
 397                 break;
 398         /* Disable logging to console */
 399         case SYSLOG_ACTION_CONSOLE_OFF:
 400                 if (saved_console_loglevel == -1)
 401                         saved_console_loglevel = console_loglevel;
 402                 console_loglevel = minimum_console_loglevel;
 403                 break;
 404         /* Enable logging to console */
 405         case SYSLOG_ACTION_CONSOLE_ON:
 406                 if (saved_console_loglevel != -1) {
 407                         console_loglevel = saved_console_loglevel;
 408                         saved_console_loglevel = -1;
 409                 }
 410                 break;
 411         /* Set level of messages printed to console */
 412         case SYSLOG_ACTION_CONSOLE_LEVEL:
 413                 error = -EINVAL;
 414                 if (len < 1 || len > 8)
 415                         goto out;
 416                 if (len < minimum_console_loglevel)
 417                         len = minimum_console_loglevel;
 418                 console_loglevel = len;
 419                 /* Implicitly re-enable logging to console */
 420                 saved_console_loglevel = -1;
 421                 error = 0;
 422                 break;
 423         /* Number of chars in the log buffer */
 424         case SYSLOG_ACTION_SIZE_UNREAD:
 425                 error = log_end - log_start;
 426                 break;
 427         /* Size of the log buffer */
 428         case SYSLOG_ACTION_SIZE_BUFFER:
 429                 error = log_buf_len;
 430                 break;
 431         default:
 432                 error = -EINVAL;
 433                 break;
 434         }
 435 out:
 436         return error;
 437 }
 438
 439 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
 440 {
 441         return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
 442 }
 443
 444 #ifdef  CONFIG_KGDB_KDB
 445 /* kdb dmesg command needs access to the syslog buffer.  do_syslog()
 446  * uses locks so it cannot be used during debugging.  Just tell kdb
 447  * where the start and end of the physical and logical logs are.  This
 448  * is equivalent to do_syslog(3).
 449  */
 450 void kdb_syslog_data(char *syslog_data[4])
 451 {
 452         syslog_data[0] = log_buf;
 453         syslog_data[1] = log_buf + log_buf_len;
 454         syslog_data[2] = log_buf + log_end -
 455                 (logged_chars < log_buf_len ? logged_chars : log_buf_len);
 456         syslog_data[3] = log_buf + log_end;
 457 }
 458 #endif  /* CONFIG_KGDB_KDB */
 459
 460 /*
 461  * Call the console drivers on a range of log_buf
 462  */
 463 static void __call_console_drivers(unsigned start, unsigned end)
 464 {
 465         struct console *con;
 466
 467         for_each_console(con) {
 468                 if ((con->flags & CON_ENABLED) && con->write &&
 469                                 (cpu_online(smp_processor_id()) ||
 470                                 (con->flags & CON_ANYTIME)))
 471                         con->write(con, &LOG_BUF(start), end - start);
 472         }
 473 }
 474
 475 static int __read_mostly ignore_loglevel;
 476
 477 static int __init ignore_loglevel_setup(char *str)
 478 {
 479         ignore_loglevel = 1;
 480         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 481
 482         return 0;
 483 }
 484
 485 early_param("ignore_loglevel", ignore_loglevel_setup);
 486
 487 /*
 488  * Write out chars from start to end - 1 inclusive
 489  */
 490 static void _call_console_drivers(unsigned start,
 491                                 unsigned end, int msg_log_level)
 492 {
 493         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 494                         console_drivers && start != end) {
 495                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 496                         /* wrapped write */
 497                         __call_console_drivers(start & LOG_BUF_MASK,
 498                                                 log_buf_len);
 499                         __call_console_drivers(0, end & LOG_BUF_MASK);
 500                 } else {
 501                         __call_console_drivers(start, end);
 502                 }
 503         }
 504 }
 505
 506 /*
 507  * Call the console drivers, asking them to write out
 508  * log_buf[start] to log_buf[end - 1].
 509  * The console_sem must be held.
 510  */
 511 static void call_console_drivers(unsigned start, unsigned end)
 512 {
 513         unsigned cur_index, start_print;
 514         static int msg_level = -1;
 515
 516         BUG_ON(((int)(start - end)) > 0);
 517
 518         cur_index = start;
 519         start_print = start;
 520         while (cur_index != end) {
 521                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 522                                 LOG_BUF(cur_index + 0) == '<' &&
 523                                 LOG_BUF(cur_index + 1) >= '0' &&
 524                                 LOG_BUF(cur_index + 1) <= '7' &&
 525                                 LOG_BUF(cur_index + 2) == '>') {
 526                         msg_level = LOG_BUF(cur_index + 1) - '0';
 527                         cur_index += 3;
 528                         start_print = cur_index;
 529                 }
 530                 while (cur_index != end) {
 531                         char c = LOG_BUF(cur_index);
 532
 533                         cur_index++;
 534                         if (c == '\n') {
 535                                 if (msg_level < 0) {
 536                                         /*
 537                                          * printk() has already given us loglevel tags in
 538                                          * the buffer.  This code is here in case the
 539                                          * log buffer has wrapped right round and scribbled
 540                                          * on those tags
 541                                          */
 542                                         msg_level = default_message_loglevel;
 543                                 }
 544                                 _call_console_drivers(start_print, cur_index, msg_level);
 545                                 msg_level = -1;
 546                                 start_print = cur_index;
 547                                 break;
 548                         }
 549                 }
 550         }
 551         _call_console_drivers(start_print, end, msg_level);
 552 }
 553
 554 static void emit_log_char(char c)
 555 {
 556         LOG_BUF(log_end) = c;
 557         log_end++;
 558         if (log_end - log_start > log_buf_len)
 559                 log_start = log_end - log_buf_len;
 560         if (log_end - con_start > log_buf_len)
 561                 con_start = log_end - log_buf_len;
 562         if (logged_chars < log_buf_len)
 563                 logged_chars++;
 564 }
 565
 566 /*
 567  * Zap console related locks when oopsing. Only zap at most once
 568  * every 10 seconds, to leave time for slow consoles to print a
 569  * full oops.
 570  */
 571 static void zap_locks(void)
 572 {
 573         static unsigned long oops_timestamp;
 574
 575         if (time_after_eq(jiffies, oops_timestamp) &&
 576                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 577                 return;
 578
 579         oops_timestamp = jiffies;
 580
 581         /* If a crash is occurring, make sure we can't deadlock */
 582         spin_lock_init(&logbuf_lock);
 583         /* And make sure that we print immediately */
 584         sema_init(&console_sem, 1);
 585 }
 586
 587 #if defined(CONFIG_PRINTK_TIME)
 588 static int printk_time = 1;
 589 #else
 590 static int printk_time = 0;
 591 #endif
 592 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 593
 594 /* Check if we have any console registered that can be called early in boot. */
 595 static int have_callable_console(void)
 596 {
 597         struct console *con;
 598
 599         for_each_console(con)
 600                 if (con->flags & CON_ANYTIME)
 601                         return 1;
 602
 603         return 0;
 604 }
 605
 606 /**
 607  * printk - print a kernel message
 608  * @fmt: format string
 609  *
 610  * This is printk().  It can be called from any context.  We want it to work.
 611  *
 612  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 613  * call the console drivers.  If we fail to get the semaphore we place the output
 614  * into the log buffer and return.  The current holder of the console_sem will
 615  * notice the new output in release_console_sem() and will send it to the
 616  * consoles before releasing the semaphore.
 617  *
 618  * One effect of this deferred printing is that code which calls printk() and
 619  * then changes console_loglevel may break. This is because console_loglevel
 620  * is inspected when the actual printing occurs.
 621  *
 622  * See also:
 623  * printf(3)
 624  *
 625  * See the vsnprintf() documentation for format string extensions over C99.
 626  */
 627
 628 asmlinkage int printk(const char *fmt, ...)
 629 {
 630         va_list args;
 631         int r;
 632
 633 #ifdef CONFIG_KGDB_KDB
 634         if (unlikely(kdb_trap_printk)) {
 635                 va_start(args, fmt);
 636                 r = vkdb_printf(fmt, args);
 637                 va_end(args);
 638                 return r;
 639         }
 640 #endif
 641         va_start(args, fmt);
 642         r = vprintk(fmt, args);
 643         va_end(args);
 644
 645         return r;
 646 }
 647
 648 /* cpu currently holding logbuf_lock */
 649 static volatile unsigned int printk_cpu = UINT_MAX;
 650
 651 /*
 652  * Can we actually use the console at this time on this cpu?
 653  *
 654  * Console drivers may assume that per-cpu resources have
 655  * been allocated. So unless they're explicitly marked as
 656  * being able to cope (CON_ANYTIME) don't call them until
 657  * this CPU is officially up.
 658  */
 659 static inline int can_use_console(unsigned int cpu)
 660 {
 661         return cpu_online(cpu) || have_callable_console();
 662 }
 663
 664 /*
 665  * Try to get console ownership to actually show the kernel
 666  * messages from a 'printk'. Return true (and with the
 667  * console_semaphore held, and 'console_locked' set) if it
 668  * is successful, false otherwise.
 669  *
 670  * This gets called with the 'logbuf_lock' spinlock held and
 671  * interrupts disabled. It should return with 'lockbuf_lock'
 672  * released but interrupts still disabled.
 673  */
 674 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 675         __releases(&logbuf_lock)
 676 {
 677         int retval = 0;
 678
 679         if (!try_acquire_console_sem()) {
 680                 retval = 1;
 681
 682                 /*
 683                  * If we can't use the console, we need to release
 684                  * the console semaphore by hand to avoid flushing
 685                  * the buffer. We need to hold the console semaphore
 686                  * in order to do this test safely.
 687                  */
 688                 if (!can_use_console(cpu)) {
 689                         console_locked = 0;
 690                         up(&console_sem);
 691                         retval = 0;
 692                 }
 693         }
 694         printk_cpu = UINT_MAX;
 695         spin_unlock(&logbuf_lock);
 696         return retval;
 697 }
 698 static const char recursion_bug_msg [] =
 699                 KERN_CRIT "BUG: recent printk recursion!\n";
 700 static int recursion_bug;
 701 static int new_text_line = 1;
 702 static char printk_buf[1024];
 703
 704 int printk_delay_msec __read_mostly;
 705
 706 static inline void printk_delay(void)
 707 {
 708         if (unlikely(printk_delay_msec)) {
 709                 int m = printk_delay_msec;
 710
 711                 while (m--) {
 712                         mdelay(1);
 713                         touch_nmi_watchdog();
 714                 }
 715         }
 716 }
 717
 718 asmlinkage int vprintk(const char *fmt, va_list args)
 719 {
 720         int printed_len = 0;
 721         int current_log_level = default_message_loglevel;
 722         unsigned long flags;
 723         int this_cpu;
 724         char *p;
 725
 726         boot_delay_msec();
 727         printk_delay();
 728
 729         preempt_disable();
 730         /* This stops the holder of console_sem just where we want him */
 731         raw_local_irq_save(flags);
 732         this_cpu = smp_processor_id();
 733
 734         /*
 735          * Ouch, printk recursed into itself!
 736          */
 737         if (unlikely(printk_cpu == this_cpu)) {
 738                 /*
 739                  * If a crash is occurring during printk() on this CPU,
 740                  * then try to get the crash message out but make sure
 741                  * we can't deadlock. Otherwise just return to avoid the
 742                  * recursion and return - but flag the recursion so that
 743                  * it can be printed at the next appropriate moment:
 744                  */
 745                 if (!oops_in_progress) {
 746                         recursion_bug = 1;
 747                         goto out_restore_irqs;
 748                 }
 749                 zap_locks();
 750         }
 751
 752         lockdep_off();
 753         spin_lock(&logbuf_lock);
 754         printk_cpu = this_cpu;
 755
 756         if (recursion_bug) {
 757                 recursion_bug = 0;
 758                 strcpy(printk_buf, recursion_bug_msg);
 759                 printed_len = strlen(recursion_bug_msg);
 760         }
 761         /* Emit the output into the temporary buffer */
 762         printed_len += vscnprintf(printk_buf + printed_len,
 763                                   sizeof(printk_buf) - printed_len, fmt, args);
 764
 765
 766         p = printk_buf;
 767
 768         /* Do we have a loglevel in the string? */
 769         if (p[0] == '<') {
 770                 unsigned char c = p[1];
 771                 if (c && p[2] == '>') {
 772                         switch (c) {
 773                         case '0' ... '7': /* loglevel */
 774                                 current_log_level = c - '0';
 775                         /* Fallthrough - make sure we're on a new line */
 776                         case 'd': /* KERN_DEFAULT */
 777                                 if (!new_text_line) {
 778                                         emit_log_char('\n');
 779                                         new_text_line = 1;
 780                                 }
 781                         /* Fallthrough - skip the loglevel */
 782                         case 'c': /* KERN_CONT */
 783                                 p += 3;
 784                                 break;
 785                         }
 786                 }
 787         }
 788
 789         /*
 790          * Copy the output into log_buf.  If the caller didn't provide
 791          * appropriate log level tags, we insert them here
 792          */
 793         for ( ; *p; p++) {
 794                 if (new_text_line) {
 795                         /* Always output the token */
 796                         emit_log_char('<');
 797                         emit_log_char(current_log_level + '0');
 798                         emit_log_char('>');
 799                         printed_len += 3;
 800                         new_text_line = 0;
 801
 802                         if (printk_time) {
 803                                 /* Follow the token with the time */
 804                                 char tbuf[50], *tp;
 805                                 unsigned tlen;
 806                                 unsigned long long t;
 807                                 unsigned long nanosec_rem;
 808
 809                                 t = cpu_clock(printk_cpu);
 810                                 nanosec_rem = do_div(t, 1000000000);
 811                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 812                                                 (unsigned long) t,
 813                                                 nanosec_rem / 1000);
 814
 815                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 816                                         emit_log_char(*tp);
 817                                 printed_len += tlen;
 818                         }
 819
 820                         if (!*p)
 821                                 break;
 822                 }
 823
 824                 emit_log_char(*p);
 825                 if (*p == '\n')
 826                         new_text_line = 1;
 827         }
 828
 829         /*
 830          * Try to acquire and then immediately release the
 831          * console semaphore. The release will do all the
 832          * actual magic (print out buffers, wake up klogd,
 833          * etc).
 834          *
 835          * The acquire_console_semaphore_for_printk() function
 836          * will release 'logbuf_lock' regardless of whether it
 837          * actually gets the semaphore or not.
 838          */
 839         if (acquire_console_semaphore_for_printk(this_cpu))
 840                 release_console_sem();
 841
 842         lockdep_on();
 843 out_restore_irqs:
 844         raw_local_irq_restore(flags);
 845
 846         preempt_enable();
 847         return printed_len;
 848 }
 849 EXPORT_SYMBOL(printk);
 850 EXPORT_SYMBOL(vprintk);
 851
 852 #else
 853
 854 static void call_console_drivers(unsigned start, unsigned end)
 855 {
 856 }
 857
 858 #endif
 859
 860 static int __add_preferred_console(char *name, int idx, char *options,
 861                                    char *brl_options)
 862 {
 863         struct console_cmdline *c;
 864         int i;
 865
 866         /*
 867          *      See if this tty is not yet registered, and
 868          *      if we have a slot free.
 869          */
 870         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 871                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 872                           console_cmdline[i].index == idx) {
 873                                 if (!brl_options)
 874                                         selected_console = i;
 875                                 return 0;
 876                 }
 877         if (i == MAX_CMDLINECONSOLES)
 878                 return -E2BIG;
 879         if (!brl_options)
 880                 selected_console = i;
 881         c = &console_cmdline[i];
 882         strlcpy(c->name, name, sizeof(c->name));
 883         c->options = options;
 884 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 885         c->brl_options = brl_options;
 886 #endif
 887         c->index = idx;
 888         return 0;
 889 }
 890 /*
 891  * Set up a list of consoles.  Called from init/main.c
 892  */
 893 static int __init console_setup(char *str)
 894 {
 895         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 896         char *s, *options, *brl_options = NULL;
 897         int idx;
 898
 899 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 900         if (!memcmp(str, "brl,", 4)) {
 901                 brl_options = "";
 902                 str += 4;
 903         } else if (!memcmp(str, "brl=", 4)) {
 904                 brl_options = str + 4;
 905                 str = strchr(brl_options, ',');
 906                 if (!str) {
 907                         printk(KERN_ERR "need port name after brl=\n");
 908                         return 1;
 909                 }
 910                 *(str++) = 0;
 911         }
 912 #endif
 913
 914         /*
 915          * Decode str into name, index, options.
 916          */
 917         if (str[0] >= '0' && str[0] <= '9') {
 918                 strcpy(buf, "ttyS");
 919                 strncpy(buf + 4, str, sizeof(buf) - 5);
 920         } else {
 921                 strncpy(buf, str, sizeof(buf) - 1);
 922         }
 923         buf[sizeof(buf) - 1] = 0;
 924         if ((options = strchr(str, ',')) != NULL)
 925                 *(options++) = 0;
 926 #ifdef __sparc__
 927         if (!strcmp(str, "ttya"))
 928                 strcpy(buf, "ttyS0");
 929         if (!strcmp(str, "ttyb"))
 930                 strcpy(buf, "ttyS1");
 931 #endif
 932         for (s = buf; *s; s++)
 933                 if ((*s >= '0' && *s <= '9') || *s == ',')
 934                         break;
 935         idx = simple_strtoul(s, NULL, 10);
 936         *s = 0;
 937
 938         __add_preferred_console(buf, idx, options, brl_options);
 939         console_set_on_cmdline = 1;
 940         return 1;
 941 }
 942 __setup("console=", console_setup);
 943
 944 /**
 945  * add_preferred_console - add a device to the list of preferred consoles.
 946  * @name: device name
 947  * @idx: device index
 948  * @options: options for this console
 949  *
 950  * The last preferred console added will be used for kernel messages
 951  * and stdin/out/err for init.  Normally this is used by console_setup
 952  * above to handle user-supplied console arguments; however it can also
 953  * be used by arch-specific code either to override the user or more
 954  * commonly to provide a default console (ie from PROM variables) when
 955  * the user has not supplied one.
 956  */
 957 int add_preferred_console(char *name, int idx, char *options)
 958 {
 959         return __add_preferred_console(name, idx, options, NULL);
 960 }
 961
 962 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 963 {
 964         struct console_cmdline *c;
 965         int i;
 966
 967         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 968                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 969                           console_cmdline[i].index == idx) {
 970                                 c = &console_cmdline[i];
 971                                 strlcpy(c->name, name_new, sizeof(c->name));
 972                                 c->name[sizeof(c->name) - 1] = 0;
 973                                 c->options = options;
 974                                 c->index = idx_new;
 975                                 return i;
 976                 }
 977         /* not found */
 978         return -1;
 979 }
 980
 981 int console_suspend_enabled = 1;
 982 EXPORT_SYMBOL(console_suspend_enabled);
 983
 984 static int __init console_suspend_disable(char *str)
 985 {
 986         console_suspend_enabled = 0;
 987         return 1;
 988 }
 989 __setup("no_console_suspend", console_suspend_disable);
 990
 991 /**
 992  * suspend_console - suspend the console subsystem
 993  *
 994  * This disables printk() while we go into suspend states
 995  */
 996 void suspend_console(void)
 997 {
 998         if (!console_suspend_enabled)
 999                 return;
1000         printk("Suspending console(s) (use no_console_suspend to debug)\n");
1001         acquire_console_sem();
1002         console_suspended = 1;
1003         up(&console_sem);
1004 }
1005
1006 void resume_console(void)
1007 {
1008         if (!console_suspend_enabled)
1009                 return;
1010         down(&console_sem);
1011         console_suspended = 0;
1012         release_console_sem();
1013 }
1014
1015 /**
1016  * console_cpu_notify - print deferred console messages after CPU hotplug
1017  * @self: notifier struct
1018  * @action: CPU hotplug event
1019  * @hcpu: unused
1020  *
1021  * If printk() is called from a CPU that is not online yet, the messages
1022  * will be spooled but will not show up on the console.  This function is
1023  * called when a new CPU comes online (or fails to come up), and ensures
1024  * that any such output gets printed.
1025  */
1026 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1027         unsigned long action, void *hcpu)
1028 {
1029         switch (action) {
1030         case CPU_ONLINE:
1031         case CPU_DEAD:
1032         case CPU_DYING:
1033         case CPU_DOWN_FAILED:
1034         case CPU_UP_CANCELED:
1035                 acquire_console_sem();
1036                 release_console_sem();
1037         }
1038         return NOTIFY_OK;
1039 }
1040
1041 /**
1042  * acquire_console_sem - lock the console system for exclusive use.
1043  *
1044  * Acquires a semaphore which guarantees that the caller has
1045  * exclusive access to the console system and the console_drivers list.
1046  *
1047  * Can sleep, returns nothing.
1048  */
1049 void acquire_console_sem(void)
1050 {
1051         BUG_ON(in_interrupt());
1052         down(&console_sem);
1053         if (console_suspended)
1054                 return;
1055         console_locked = 1;
1056         console_may_schedule = 1;
1057 }
1058 EXPORT_SYMBOL(acquire_console_sem);
1059
1060 int try_acquire_console_sem(void)
1061 {
1062         if (down_trylock(&console_sem))
1063                 return -1;
1064         if (console_suspended) {
1065                 up(&console_sem);
1066                 return -1;
1067         }
1068         console_locked = 1;
1069         console_may_schedule = 0;
1070         return 0;
1071 }
1072 EXPORT_SYMBOL(try_acquire_console_sem);
1073
1074 int is_console_locked(void)
1075 {
1076         return console_locked;
1077 }
1078
1079 static DEFINE_PER_CPU(int, printk_pending);
1080
1081 void printk_tick(void)
1082 {
1083         if (__get_cpu_var(printk_pending)) {
1084                 __get_cpu_var(printk_pending) = 0;
1085                 wake_up_interruptible(&log_wait);
1086         }
1087 }
1088
1089 int printk_needs_cpu(int cpu)
1090 {
1091         return per_cpu(printk_pending, cpu);
1092 }
1093
1094 void wake_up_klogd(void)
1095 {
1096         if (waitqueue_active(&log_wait))
1097                 __raw_get_cpu_var(printk_pending) = 1;
1098 }
1099
1100 /**
1101  * release_console_sem - unlock the console system
1102  *
1103  * Releases the semaphore which the caller holds on the console system
1104  * and the console driver list.
1105  *
1106  * While the semaphore was held, console output may have been buffered
1107  * by printk().  If this is the case, release_console_sem() emits
1108  * the output prior to releasing the semaphore.
1109  *
1110  * If there is output waiting for klogd, we wake it up.
1111  *
1112  * release_console_sem() may be called from any context.
1113  */
1114 void release_console_sem(void)
1115 {
1116         unsigned long flags;
1117         unsigned _con_start, _log_end;
1118         unsigned wake_klogd = 0;
1119
1120         if (console_suspended) {
1121                 up(&console_sem);
1122                 return;
1123         }
1124
1125         console_may_schedule = 0;
1126
1127         for ( ; ; ) {
1128                 spin_lock_irqsave(&logbuf_lock, flags);
1129                 wake_klogd |= log_start - log_end;
1130                 if (con_start == log_end)
1131                         break;                  /* Nothing to print */
1132                 _con_start = con_start;
1133                 _log_end = log_end;
1134                 con_start = log_end;            /* Flush */
1135                 spin_unlock(&logbuf_lock);
1136                 stop_critical_timings();        /* don't trace print latency */
1137                 call_console_drivers(_con_start, _log_end);
1138                 start_critical_timings();
1139                 local_irq_restore(flags);
1140         }
1141         console_locked = 0;
1142         up(&console_sem);
1143         spin_unlock_irqrestore(&logbuf_lock, flags);
1144         if (wake_klogd)
1145                 wake_up_klogd();
1146 }
1147 EXPORT_SYMBOL(release_console_sem);
1148
1149 /**
1150  * console_conditional_schedule - yield the CPU if required
1151  *
1152  * If the console code is currently allowed to sleep, and
1153  * if this CPU should yield the CPU to another task, do
1154  * so here.
1155  *
1156  * Must be called within acquire_console_sem().
1157  */
1158 void __sched console_conditional_schedule(void)
1159 {
1160         if (console_may_schedule)
1161                 cond_resched();
1162 }
1163 EXPORT_SYMBOL(console_conditional_schedule);
1164
1165 void console_unblank(void)
1166 {
1167         struct console *c;
1168
1169         /*
1170          * console_unblank can no longer be called in interrupt context unless
1171          * oops_in_progress is set to 1..
1172          */
1173         if (oops_in_progress) {
1174                 if (down_trylock(&console_sem) != 0)
1175                         return;
1176         } else
1177                 acquire_console_sem();
1178
1179         console_locked = 1;
1180         console_may_schedule = 0;
1181         for_each_console(c)
1182                 if ((c->flags & CON_ENABLED) && c->unblank)
1183                         c->unblank();
1184         release_console_sem();
1185 }
1186
1187 /*
1188  * Return the console tty driver structure and its associated index
1189  */
1190 struct tty_driver *console_device(int *index)
1191 {
1192         struct console *c;
1193         struct tty_driver *driver = NULL;
1194
1195         acquire_console_sem();
1196         for_each_console(c) {
1197                 if (!c->device)
1198                         continue;
1199                 driver = c->device(c, index);
1200                 if (driver)
1201                         break;
1202         }
1203         release_console_sem();
1204         return driver;
1205 }
1206
1207 /*
1208  * Prevent further output on the passed console device so that (for example)
1209  * serial drivers can disable console output before suspending a port, and can
1210  * re-enable output afterwards.
1211  */
1212 void console_stop(struct console *console)
1213 {
1214         acquire_console_sem();
1215         console->flags &= ~CON_ENABLED;
1216         release_console_sem();
1217 }
1218 EXPORT_SYMBOL(console_stop);
1219
1220 void console_start(struct console *console)
1221 {
1222         acquire_console_sem();
1223         console->flags |= CON_ENABLED;
1224         release_console_sem();
1225 }
1226 EXPORT_SYMBOL(console_start);
1227
1228 /*
1229  * The console driver calls this routine during kernel initialization
1230  * to register the console printing procedure with printk() and to
1231  * print any messages that were printed by the kernel before the
1232  * console driver was initialized.
1233  *
1234  * This can happen pretty early during the boot process (because of
1235  * early_printk) - sometimes before setup_arch() completes - be careful
1236  * of what kernel features are used - they may not be initialised yet.
1237  *
1238  * There are two types of consoles - bootconsoles (early_printk) and
1239  * "real" consoles (everything which is not a bootconsole) which are
1240  * handled differently.
1241  *  - Any number of bootconsoles can be registered at any time.
1242  *  - As soon as a "real" console is registered, all bootconsoles
1243  *    will be unregistered automatically.
1244  *  - Once a "real" console is registered, any attempt to register a
1245  *    bootconsoles will be rejected
1246  */
1247 void register_console(struct console *newcon)
1248 {
1249         int i;
1250         unsigned long flags;
1251         struct console *bcon = NULL;
1252
1253         /*
1254          * before we register a new CON_BOOT console, make sure we don't
1255          * already have a valid console
1256          */
1257         if (console_drivers && newcon->flags & CON_BOOT) {
1258                 /* find the last or real console */
1259                 for_each_console(bcon) {
1260                         if (!(bcon->flags & CON_BOOT)) {
1261                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1262                                         newcon->name, newcon->index);
1263                                 return;
1264                         }
1265                 }
1266         }
1267
1268         if (console_drivers && console_drivers->flags & CON_BOOT)
1269                 bcon = console_drivers;
1270
1271         if (preferred_console < 0 || bcon || !console_drivers)
1272                 preferred_console = selected_console;
1273
1274         if (newcon->early_setup)
1275                 newcon->early_setup();
1276
1277         /*
1278          *      See if we want to use this console driver. If we
1279          *      didn't select a console we take the first one
1280          *      that registers here.
1281          */
1282         if (preferred_console < 0) {
1283                 if (newcon->index < 0)
1284                         newcon->index = 0;
1285                 if (newcon->setup == NULL ||
1286                     newcon->setup(newcon, NULL) == 0) {
1287                         newcon->flags |= CON_ENABLED;
1288                         if (newcon->device) {
1289                                 newcon->flags |= CON_CONSDEV;
1290                                 preferred_console = 0;
1291                         }
1292                 }
1293         }
1294
1295         /*
1296          *      See if this console matches one we selected on
1297          *      the command line.
1298          */
1299         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1300                         i++) {
1301                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1302                         continue;
1303                 if (newcon->index >= 0 &&
1304                     newcon->index != console_cmdline[i].index)
1305                         continue;
1306                 if (newcon->index < 0)
1307                         newcon->index = console_cmdline[i].index;
1308 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1309                 if (console_cmdline[i].brl_options) {
1310                         newcon->flags |= CON_BRL;
1311                         braille_register_console(newcon,
1312                                         console_cmdline[i].index,
1313                                         console_cmdline[i].options,
1314                                         console_cmdline[i].brl_options);
1315                         return;
1316                 }
1317 #endif
1318                 if (newcon->setup &&
1319                     newcon->setup(newcon, console_cmdline[i].options) != 0)
1320                         break;
1321                 newcon->flags |= CON_ENABLED;
1322                 newcon->index = console_cmdline[i].index;
1323                 if (i == selected_console) {
1324                         newcon->flags |= CON_CONSDEV;
1325                         preferred_console = selected_console;
1326                 }
1327                 break;
1328         }
1329
1330         if (!(newcon->flags & CON_ENABLED))
1331                 return;
1332
1333         /*
1334          * If we have a bootconsole, and are switching to a real console,
1335          * don't print everything out again, since when the boot console, and
1336          * the real console are the same physical device, it's annoying to
1337          * see the beginning boot messages twice
1338          */
1339         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1340                 newcon->flags &= ~CON_PRINTBUFFER;
1341
1342         /*
1343          *      Put this console in the list - keep the
1344          *      preferred driver at the head of the list.
1345          */
1346         acquire_console_sem();
1347         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1348                 newcon->next = console_drivers;
1349                 console_drivers = newcon;
1350                 if (newcon->next)
1351                         newcon->next->flags &= ~CON_CONSDEV;
1352         } else {
1353                 newcon->next = console_drivers->next;
1354                 console_drivers->next = newcon;
1355         }
1356         if (newcon->flags & CON_PRINTBUFFER) {
1357                 /*
1358                  * release_console_sem() will print out the buffered messages
1359                  * for us.
1360                  */
1361                 spin_lock_irqsave(&logbuf_lock, flags);
1362                 con_start = log_start;
1363                 spin_unlock_irqrestore(&logbuf_lock, flags);
1364         }
1365         release_console_sem();
1366
1367         /*
1368          * By unregistering the bootconsoles after we enable the real console
1369          * we get the "console xxx enabled" message on all the consoles -
1370          * boot consoles, real consoles, etc - this is to ensure that end
1371          * users know there might be something in the kernel's log buffer that
1372          * went to the bootconsole (that they do not see on the real console)
1373          */
1374         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1375                 /* we need to iterate through twice, to make sure we print
1376                  * everything out, before we unregister the console(s)
1377                  */
1378                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1379                         newcon->name, newcon->index);
1380                 for_each_console(bcon)
1381                         if (bcon->flags & CON_BOOT)
1382                                 unregister_console(bcon);
1383         } else {
1384                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1385                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
1386                         newcon->name, newcon->index);
1387         }
1388 }
1389 EXPORT_SYMBOL(register_console);
1390
1391 int unregister_console(struct console *console)
1392 {
1393         struct console *a, *b;
1394         int res = 1;
1395
1396 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1397         if (console->flags & CON_BRL)
1398                 return braille_unregister_console(console);
1399 #endif
1400
1401         acquire_console_sem();
1402         if (console_drivers == console) {
1403                 console_drivers=console->next;
1404                 res = 0;
1405         } else if (console_drivers) {
1406                 for (a=console_drivers->next, b=console_drivers ;
1407                      a; b=a, a=b->next) {
1408                         if (a == console) {
1409                                 b->next = a->next;
1410                                 res = 0;
1411                                 break;
1412                         }
1413                 }
1414         }
1415
1416         /*
1417          * If this isn't the last console and it has CON_CONSDEV set, we
1418          * need to set it on the next preferred console.
1419          */
1420         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1421                 console_drivers->flags |= CON_CONSDEV;
1422
1423         release_console_sem();
1424         return res;
1425 }
1426 EXPORT_SYMBOL(unregister_console);
1427
1428 static int __init printk_late_init(void)
1429 {
1430         struct console *con;
1431
1432         for_each_console(con) {
1433                 if (con->flags & CON_BOOT) {
1434                         printk(KERN_INFO "turn off boot console %s%d\n",
1435                                 con->name, con->index);
1436                         unregister_console(con);
1437                 }
1438         }
1439         hotcpu_notifier(console_cpu_notify, 0);
1440         return 0;
1441 }
1442 late_initcall(printk_late_init);
1443
1444 #if defined CONFIG_PRINTK
1445
1446 /*
1447  * printk rate limiting, lifted from the networking subsystem.
1448  *
1449  * This enforces a rate limit: not more than 10 kernel messages
1450  * every 5s to make a denial-of-service attack impossible.
1451  */
1452 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1453
1454 int __printk_ratelimit(const char *func)
1455 {
1456         return ___ratelimit(&printk_ratelimit_state, func);
1457 }
1458 EXPORT_SYMBOL(__printk_ratelimit);
1459
1460 /**
1461  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1462  * @caller_jiffies: pointer to caller's state
1463  * @interval_msecs: minimum interval between prints
1464  *
1465  * printk_timed_ratelimit() returns true if more than @interval_msecs
1466  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1467  * returned true.
1468  */
1469 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1470                         unsigned int interval_msecs)
1471 {
1472         if (*caller_jiffies == 0
1473                         || !time_in_range(jiffies, *caller_jiffies,
1474                                         *caller_jiffies
1475                                         + msecs_to_jiffies(interval_msecs))) {
1476                 *caller_jiffies = jiffies;
1477                 return true;
1478         }
1479         return false;
1480 }
1481 EXPORT_SYMBOL(printk_timed_ratelimit);
1482
1483 static DEFINE_SPINLOCK(dump_list_lock);
1484 static LIST_HEAD(dump_list);
1485
1486 /**
1487  * kmsg_dump_register - register a kernel log dumper.
1488  * @dumper: pointer to the kmsg_dumper structure
1489  *
1490  * Adds a kernel log dumper to the system. The dump callback in the
1491  * structure will be called when the kernel oopses or panics and must be
1492  * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1493  */
1494 int kmsg_dump_register(struct kmsg_dumper *dumper)
1495 {
1496         unsigned long flags;
1497         int err = -EBUSY;
1498
1499         /* The dump callback needs to be set */
1500         if (!dumper->dump)
1501                 return -EINVAL;
1502
1503         spin_lock_irqsave(&dump_list_lock, flags);
1504         /* Don't allow registering multiple times */
1505         if (!dumper->registered) {
1506                 dumper->registered = 1;
1507                 list_add_tail(&dumper->list, &dump_list);
1508                 err = 0;
1509         }
1510         spin_unlock_irqrestore(&dump_list_lock, flags);
1511
1512         return err;
1513 }
1514 EXPORT_SYMBOL_GPL(kmsg_dump_register);
1515
1516 /**
1517  * kmsg_dump_unregister - unregister a kmsg dumper.
1518  * @dumper: pointer to the kmsg_dumper structure
1519  *
1520  * Removes a dump device from the system. Returns zero on success and
1521  * %-EINVAL otherwise.
1522  */
1523 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
1524 {
1525         unsigned long flags;
1526         int err = -EINVAL;
1527
1528         spin_lock_irqsave(&dump_list_lock, flags);
1529         if (dumper->registered) {
1530                 dumper->registered = 0;
1531                 list_del(&dumper->list);
1532                 err = 0;
1533         }
1534         spin_unlock_irqrestore(&dump_list_lock, flags);
1535
1536         return err;
1537 }
1538 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
1539
1540 static const char * const kmsg_reasons[] = {
1541         [KMSG_DUMP_OOPS]        = "oops",
1542         [KMSG_DUMP_PANIC]       = "panic",
1543         [KMSG_DUMP_KEXEC]       = "kexec",
1544 };
1545
1546 static const char *kmsg_to_str(enum kmsg_dump_reason reason)
1547 {
1548         if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0)
1549                 return "unknown";
1550
1551         return kmsg_reasons[reason];
1552 }
1553
1554 /**
1555  * kmsg_dump - dump kernel log to kernel message dumpers.
1556  * @reason: the reason (oops, panic etc) for dumping
1557  *
1558  * Iterate through each of the dump devices and call the oops/panic
1559  * callbacks with the log buffer.
1560  */
1561 void kmsg_dump(enum kmsg_dump_reason reason)
1562 {
1563         unsigned long end;
1564         unsigned chars;
1565         struct kmsg_dumper *dumper;
1566         const char *s1, *s2;
1567         unsigned long l1, l2;
1568         unsigned long flags;
1569
1570         /* Theoretically, the log could move on after we do this, but
1571            there's not a lot we can do about that. The new messages
1572            will overwrite the start of what we dump. */
1573         spin_lock_irqsave(&logbuf_lock, flags);
1574         end = log_end & LOG_BUF_MASK;
1575         chars = logged_chars;
1576         spin_unlock_irqrestore(&logbuf_lock, flags);
1577
1578         if (chars > end) {
1579                 s1 = log_buf + log_buf_len - chars + end;
1580                 l1 = chars - end;
1581
1582                 s2 = log_buf;
1583                 l2 = end;
1584         } else {
1585                 s1 = "";
1586                 l1 = 0;
1587
1588                 s2 = log_buf + end - chars;
1589                 l2 = chars;
1590         }
1591
1592         if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
1593                 printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n",
1594                                 kmsg_to_str(reason));
1595                 return;
1596         }
1597         list_for_each_entry(dumper, &dump_list, list)
1598                 dumper->dump(dumper, reason, s1, l1, s2, l2);
1599         spin_unlock_irqrestore(&dump_list_lock, flags);
1600 }
1601 #endif