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 #ifdef        CONFIG_DEBUG_LL
  61 extern void printascii(char *);
  62 #endif
  63
  64 /* printk's without a loglevel use this.. */
  65 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  66
  67 /* We show everything that is MORE important than this.. */
  68 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  69 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  70
  71 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  72
  73 int console_printk[4] = {
  74         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  75         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  76         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  77         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  78 };
  79
  80 /*
  81  * Low level drivers may need that to know if they can schedule in
  82  * their unblank() callback or not. So let's export it.
  83  */
  84 int oops_in_progress;
  85 EXPORT_SYMBOL(oops_in_progress);
  86
  87 /*
  88  * console_sem protects the console_drivers list, and also
  89  * provides serialisation for access to the entire console
  90  * driver system.
  91  */
  92 static DECLARE_MUTEX(console_sem);
  93 struct console *console_drivers;
  94 EXPORT_SYMBOL_GPL(console_drivers);
  95
  96 /*
  97  * This is used for debugging the mess that is the VT code by
  98  * keeping track if we have the console semaphore held. It's
  99  * definitely not the perfect debug tool (we don't know if _WE_
 100  * hold it are racing, but it helps tracking those weird code
 101  * path in the console code where we end up in places I want
 102  * locked without the console sempahore held
 103  */
 104 static int console_locked, console_suspended;
 105
 106 /*
 107  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
 108  * It is also used in interesting ways to provide interlocking in
 109  * release_console_sem().
 110  */
 111 static DEFINE_SPINLOCK(logbuf_lock);
 112
 113 #define LOG_BUF_MASK (log_buf_len-1)
 114 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
 115
 116 /*
 117  * The indices into log_buf are not constrained to log_buf_len - they
 118  * must be masked before subscripting
 119  */
 120 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
 121 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
 122 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 123
 124 /*
 125  *      Array of consoles built from command line options (console=)
 126  */
 127 struct console_cmdline
 128 {
 129         char    name[8];                        /* Name of the driver       */
 130         int     index;                          /* Minor dev. to use        */
 131         char    *options;                       /* Options for the driver   */
 132 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 133         char    *brl_options;                   /* Options for braille driver */
 134 #endif
 135 };
 136
 137 #define MAX_CMDLINECONSOLES 8
 138
 139 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 140 static int selected_console = -1;
 141 static int preferred_console = -1;
 142 int console_set_on_cmdline;
 143 EXPORT_SYMBOL(console_set_on_cmdline);
 144
 145 /* Flag: console code may call schedule() */
 146 static int console_may_schedule;
 147
 148 #ifdef CONFIG_PRINTK
 149
 150 static char __log_buf[__LOG_BUF_LEN];
 151 static char *log_buf = __log_buf;
 152 static int log_buf_len = __LOG_BUF_LEN;
 153 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 154 static int saved_console_loglevel = -1;
 155
 156 #ifdef CONFIG_KEXEC
 157 /*
 158  * This appends the listed symbols to /proc/vmcoreinfo
 159  *
 160  * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
 161  * obtain access to symbols that are otherwise very difficult to locate.  These
 162  * symbols are specifically used so that utilities can access and extract the
 163  * dmesg log from a vmcore file after a crash.
 164  */
 165 void log_buf_kexec_setup(void)
 166 {
 167         VMCOREINFO_SYMBOL(log_buf);
 168         VMCOREINFO_SYMBOL(log_end);
 169         VMCOREINFO_SYMBOL(log_buf_len);
 170         VMCOREINFO_SYMBOL(logged_chars);
 171 }
 172 #endif
 173
 174 static int __init log_buf_len_setup(char *str)
 175 {
 176         unsigned size = memparse(str, &str);
 177         unsigned long flags;
 178
 179         if (size)
 180                 size = roundup_pow_of_two(size);
 181         if (size > log_buf_len) {
 182                 unsigned start, dest_idx, offset;
 183                 char *new_log_buf;
 184
 185                 new_log_buf = alloc_bootmem(size);
 186                 if (!new_log_buf) {
 187                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 188                         goto out;
 189                 }
 190
 191                 spin_lock_irqsave(&logbuf_lock, flags);
 192                 log_buf_len = size;
 193                 log_buf = new_log_buf;
 194
 195                 offset = start = min(con_start, log_start);
 196                 dest_idx = 0;
 197                 while (start != log_end) {
 198                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 199                         start++;
 200                         dest_idx++;
 201                 }
 202                 log_start -= offset;
 203                 con_start -= offset;
 204                 log_end -= offset;
 205                 spin_unlock_irqrestore(&logbuf_lock, flags);
 206
 207                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 208         }
 209 out:
 210         return 1;
 211 }
 212
 213 __setup("log_buf_len=", log_buf_len_setup);
 214
 215 #ifdef CONFIG_BOOT_PRINTK_DELAY
 216
 217 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 218 static unsigned long long loops_per_msec;       /* based on boot_delay */
 219
 220 static int __init boot_delay_setup(char *str)
 221 {
 222         unsigned long lpj;
 223
 224         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 225         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 226
 227         get_option(&str, &boot_delay);
 228         if (boot_delay > 10 * 1000)
 229                 boot_delay = 0;
 230
 231         pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 232                 "HZ: %d, loops_per_msec: %llu\n",
 233                 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
 234         return 1;
 235 }
 236 __setup("boot_delay=", boot_delay_setup);
 237
 238 static void boot_delay_msec(void)
 239 {
 240         unsigned long long k;
 241         unsigned long timeout;
 242
 243         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 244                 return;
 245
 246         k = (unsigned long long)loops_per_msec * boot_delay;
 247
 248         timeout = jiffies + msecs_to_jiffies(boot_delay);
 249         while (k) {
 250                 k--;
 251                 cpu_relax();
 252                 /*
 253                  * use (volatile) jiffies to prevent
 254                  * compiler reduction; loop termination via jiffies
 255                  * is secondary and may or may not happen.
 256                  */
 257                 if (time_after(jiffies, timeout))
 258                         break;
 259                 touch_nmi_watchdog();
 260         }
 261 }
 262 #else
 263 static inline void boot_delay_msec(void)
 264 {
 265 }
 266 #endif
 267
 268 /*
 269  * Return the number of unread characters in the log buffer.
 270  */
 271 static int log_buf_get_len(void)
 272 {
 273         return logged_chars;
 274 }
 275
 276 /*
 277  * Clears the ring-buffer
 278  */
 279 void log_buf_clear(void)
 280 {
 281         logged_chars = 0;
 282 }
 283
 284 /*
 285  * Copy a range of characters from the log buffer.
 286  */
 287 int log_buf_copy(char *dest, int idx, int len)
 288 {
 289         int ret, max;
 290         bool took_lock = false;
 291
 292         if (!oops_in_progress) {
 293                 spin_lock_irq(&logbuf_lock);
 294                 took_lock = true;
 295         }
 296
 297         max = log_buf_get_len();
 298         if (idx < 0 || idx >= max) {
 299                 ret = -1;
 300         } else {
 301                 if (len > max - idx)
 302                         len = max - idx;
 303                 ret = len;
 304                 idx += (log_end - max);
 305                 while (len-- > 0)
 306                         dest[len] = LOG_BUF(idx + len);
 307         }
 308
 309         if (took_lock)
 310                 spin_unlock_irq(&logbuf_lock);
 311
 312         return ret;
 313 }
 314
 315 /*
 316  * Commands to do_syslog:
 317  *
 318  *      0 -- Close the log.  Currently a NOP.
 319  *      1 -- Open the log. Currently a NOP.
 320  *      2 -- Read from the log.
 321  *      3 -- Read all messages remaining in the ring buffer.
 322  *      4 -- Read and clear all messages remaining in the ring buffer
 323  *      5 -- Clear ring buffer.
 324  *      6 -- Disable printk's to console
 325  *      7 -- Enable printk's to console
 326  *      8 -- Set level of messages printed to console
 327  *      9 -- Return number of unread characters in the log buffer
 328  *     10 -- Return size of the log buffer
 329  */
 330 int do_syslog(int type, char __user *buf, int len, bool from_file)
 331 {
 332         unsigned i, j, limit, count;
 333         int do_clear = 0;
 334         char c;
 335         int error = 0;
 336
 337         error = security_syslog(type, from_file);
 338         if (error)
 339                 return error;
 340
 341         switch (type) {
 342         case SYSLOG_ACTION_CLOSE:       /* Close log */
 343                 break;
 344         case SYSLOG_ACTION_OPEN:        /* Open log */
 345                 break;
 346         case SYSLOG_ACTION_READ:        /* Read from log */
 347                 error = -EINVAL;
 348                 if (!buf || len < 0)
 349                         goto out;
 350                 error = 0;
 351                 if (!len)
 352                         goto out;
 353                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 354                         error = -EFAULT;
 355                         goto out;
 356                 }
 357                 error = wait_event_interruptible(log_wait,
 358                                                         (log_start - log_end));
 359                 if (error)
 360                         goto out;
 361                 i = 0;
 362                 spin_lock_irq(&logbuf_lock);
 363                 while (!error && (log_start != log_end) && i < len) {
 364                         c = LOG_BUF(log_start);
 365                         log_start++;
 366                         spin_unlock_irq(&logbuf_lock);
 367                         error = __put_user(c,buf);
 368                         buf++;
 369                         i++;
 370                         cond_resched();
 371                         spin_lock_irq(&logbuf_lock);
 372                 }
 373                 spin_unlock_irq(&logbuf_lock);
 374                 if (!error)
 375                         error = i;
 376                 break;
 377         /* Read/clear last kernel messages */
 378         case SYSLOG_ACTION_READ_CLEAR:
 379                 do_clear = 1;
 380                 /* FALL THRU */
 381         /* Read last kernel messages */
 382         case SYSLOG_ACTION_READ_ALL:
 383                 error = -EINVAL;
 384                 if (!buf || len < 0)
 385                         goto out;
 386                 error = 0;
 387                 if (!len)
 388                         goto out;
 389                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 390                         error = -EFAULT;
 391                         goto out;
 392                 }
 393                 count = len;
 394                 if (count > log_buf_len)
 395                         count = log_buf_len;
 396                 spin_lock_irq(&logbuf_lock);
 397                 if (count > logged_chars)
 398                         count = logged_chars;
 399                 if (do_clear)
 400                         logged_chars = 0;
 401                 limit = log_end;
 402                 /*
 403                  * __put_user() could sleep, and while we sleep
 404                  * printk() could overwrite the messages
 405                  * we try to copy to user space. Therefore
 406                  * the messages are copied in reverse. <manfreds>
 407                  */
 408                 for (i = 0; i < count && !error; i++) {
 409                         j = limit-1-i;
 410                         if (j + log_buf_len < log_end)
 411                                 break;
 412                         c = LOG_BUF(j);
 413                         spin_unlock_irq(&logbuf_lock);
 414                         error = __put_user(c,&buf[count-1-i]);
 415                         cond_resched();
 416                         spin_lock_irq(&logbuf_lock);
 417                 }
 418                 spin_unlock_irq(&logbuf_lock);
 419                 if (error)
 420                         break;
 421                 error = i;
 422                 if (i != count) {
 423                         int offset = count-error;
 424                         /* buffer overflow during copy, correct user buffer. */
 425                         for (i = 0; i < error; i++) {
 426                                 if (__get_user(c,&buf[i+offset]) ||
 427                                     __put_user(c,&buf[i])) {
 428                                         error = -EFAULT;
 429                                         break;
 430                                 }
 431                                 cond_resched();
 432                         }
 433                 }
 434                 break;
 435         /* Clear ring buffer */
 436         case SYSLOG_ACTION_CLEAR:
 437                 logged_chars = 0;
 438                 break;
 439         /* Disable logging to console */
 440         case SYSLOG_ACTION_CONSOLE_OFF:
 441                 if (saved_console_loglevel == -1)
 442                         saved_console_loglevel = console_loglevel;
 443                 console_loglevel = minimum_console_loglevel;
 444                 break;
 445         /* Enable logging to console */
 446         case SYSLOG_ACTION_CONSOLE_ON:
 447                 if (saved_console_loglevel != -1) {
 448                         console_loglevel = saved_console_loglevel;
 449                         saved_console_loglevel = -1;
 450                 }
 451                 break;
 452         /* Set level of messages printed to console */
 453         case SYSLOG_ACTION_CONSOLE_LEVEL:
 454                 error = -EINVAL;
 455                 if (len < 1 || len > 8)
 456                         goto out;
 457                 if (len < minimum_console_loglevel)
 458                         len = minimum_console_loglevel;
 459                 console_loglevel = len;
 460                 /* Implicitly re-enable logging to console */
 461                 saved_console_loglevel = -1;
 462                 error = 0;
 463                 break;
 464         /* Number of chars in the log buffer */
 465         case SYSLOG_ACTION_SIZE_UNREAD:
 466                 error = log_end - log_start;
 467                 break;
 468         /* Size of the log buffer */
 469         case SYSLOG_ACTION_SIZE_BUFFER:
 470                 error = log_buf_len;
 471                 break;
 472         default:
 473                 error = -EINVAL;
 474                 break;
 475         }
 476 out:
 477         return error;
 478 }
 479
 480 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
 481 {
 482         return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
 483 }
 484
 485 #ifdef  CONFIG_KGDB_KDB
 486 /* kdb dmesg command needs access to the syslog buffer.  do_syslog()
 487  * uses locks so it cannot be used during debugging.  Just tell kdb
 488  * where the start and end of the physical and logical logs are.  This
 489  * is equivalent to do_syslog(3).
 490  */
 491 void kdb_syslog_data(char *syslog_data[4])
 492 {
 493         syslog_data[0] = log_buf;
 494         syslog_data[1] = log_buf + log_buf_len;
 495         syslog_data[2] = log_buf + log_end -
 496                 (logged_chars < log_buf_len ? logged_chars : log_buf_len);
 497         syslog_data[3] = log_buf + log_end;
 498 }
 499 #endif  /* CONFIG_KGDB_KDB */
 500
 501 /*
 502  * Call the console drivers on a range of log_buf
 503  */
 504 static void __call_console_drivers(unsigned start, unsigned end)
 505 {
 506         struct console *con;
 507
 508         for_each_console(con) {
 509                 if ((con->flags & CON_ENABLED) && con->write &&
 510                                 (cpu_online(smp_processor_id()) ||
 511                                 (con->flags & CON_ANYTIME)))
 512                         con->write(con, &LOG_BUF(start), end - start);
 513         }
 514 }
 515
 516 static int __read_mostly ignore_loglevel;
 517
 518 static int __init ignore_loglevel_setup(char *str)
 519 {
 520         ignore_loglevel = 1;
 521         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 522
 523         return 0;
 524 }
 525
 526 early_param("ignore_loglevel", ignore_loglevel_setup);
 527
 528 /*
 529  * Write out chars from start to end - 1 inclusive
 530  */
 531 static void _call_console_drivers(unsigned start,
 532                                 unsigned end, int msg_log_level)
 533 {
 534         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 535                         console_drivers && start != end) {
 536                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 537                         /* wrapped write */
 538                         __call_console_drivers(start & LOG_BUF_MASK,
 539                                                 log_buf_len);
 540                         __call_console_drivers(0, end & LOG_BUF_MASK);
 541                 } else {
 542                         __call_console_drivers(start, end);
 543                 }
 544         }
 545 }
 546
 547 /*
 548  * Call the console drivers, asking them to write out
 549  * log_buf[start] to log_buf[end - 1].
 550  * The console_sem must be held.
 551  */
 552 static void call_console_drivers(unsigned start, unsigned end)
 553 {
 554         unsigned cur_index, start_print;
 555         static int msg_level = -1;
 556
 557         BUG_ON(((int)(start - end)) > 0);
 558
 559         cur_index = start;
 560         start_print = start;
 561         while (cur_index != end) {
 562                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 563                                 LOG_BUF(cur_index + 0) == '<' &&
 564                                 LOG_BUF(cur_index + 1) >= '0' &&
 565                                 LOG_BUF(cur_index + 1) <= '7' &&
 566                                 LOG_BUF(cur_index + 2) == '>') {
 567                         msg_level = LOG_BUF(cur_index + 1) - '0';
 568                         cur_index += 3;
 569                         start_print = cur_index;
 570                 }
 571                 while (cur_index != end) {
 572                         char c = LOG_BUF(cur_index);
 573
 574                         cur_index++;
 575                         if (c == '\n') {
 576                                 if (msg_level < 0) {
 577                                         /*
 578                                          * printk() has already given us loglevel tags in
 579                                          * the buffer.  This code is here in case the
 580                                          * log buffer has wrapped right round and scribbled
 581                                          * on those tags
 582                                          */
 583                                         msg_level = default_message_loglevel;
 584                                 }
 585                                 _call_console_drivers(start_print, cur_index, msg_level);
 586                                 msg_level = -1;
 587                                 start_print = cur_index;
 588                                 break;
 589                         }
 590                 }
 591         }
 592         _call_console_drivers(start_print, end, msg_level);
 593 }
 594
 595 static void emit_log_char(char c)
 596 {
 597         LOG_BUF(log_end) = c;
 598         log_end++;
 599         if (log_end - log_start > log_buf_len)
 600                 log_start = log_end - log_buf_len;
 601         if (log_end - con_start > log_buf_len)
 602                 con_start = log_end - log_buf_len;
 603         if (logged_chars < log_buf_len)
 604                 logged_chars++;
 605 }
 606
 607 /*
 608  * Zap console related locks when oopsing. Only zap at most once
 609  * every 10 seconds, to leave time for slow consoles to print a
 610  * full oops.
 611  */
 612 static void zap_locks(void)
 613 {
 614         static unsigned long oops_timestamp;
 615
 616         if (time_after_eq(jiffies, oops_timestamp) &&
 617                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 618                 return;
 619
 620         oops_timestamp = jiffies;
 621
 622         /* If a crash is occurring, make sure we can't deadlock */
 623         spin_lock_init(&logbuf_lock);
 624         /* And make sure that we print immediately */
 625         init_MUTEX(&console_sem);
 626 }
 627
 628 #if defined(CONFIG_PRINTK_TIME)
 629 static int printk_time = 1;
 630 #else
 631 static int printk_time = 0;
 632 #endif
 633 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 634
 635 /* Check if we have any console registered that can be called early in boot. */
 636 static int have_callable_console(void)
 637 {
 638         struct console *con;
 639
 640         for_each_console(con)
 641                 if (con->flags & CON_ANYTIME)
 642                         return 1;
 643
 644         return 0;
 645 }
 646
 647 /**
 648  * printk - print a kernel message
 649  * @fmt: format string
 650  *
 651  * This is printk().  It can be called from any context.  We want it to work.
 652  *
 653  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 654  * call the console drivers.  If we fail to get the semaphore we place the output
 655  * into the log buffer and return.  The current holder of the console_sem will
 656  * notice the new output in release_console_sem() and will send it to the
 657  * consoles before releasing the semaphore.
 658  *
 659  * One effect of this deferred printing is that code which calls printk() and
 660  * then changes console_loglevel may break. This is because console_loglevel
 661  * is inspected when the actual printing occurs.
 662  *
 663  * See also:
 664  * printf(3)
 665  *
 666  * See the vsnprintf() documentation for format string extensions over C99.
 667  */
 668
 669 asmlinkage int printk(const char *fmt, ...)
 670 {
 671         va_list args;
 672         int r;
 673
 674 #ifdef CONFIG_KGDB_KDB
 675         if (unlikely(kdb_trap_printk)) {
 676                 va_start(args, fmt);
 677                 r = vkdb_printf(fmt, args);
 678                 va_end(args);
 679                 return r;
 680         }
 681 #endif
 682         va_start(args, fmt);
 683         r = vprintk(fmt, args);
 684         va_end(args);
 685
 686         return r;
 687 }
 688
 689 /* cpu currently holding logbuf_lock */
 690 static volatile unsigned int printk_cpu = UINT_MAX;
 691
 692 /*
 693  * Can we actually use the console at this time on this cpu?
 694  *
 695  * Console drivers may assume that per-cpu resources have
 696  * been allocated. So unless they're explicitly marked as
 697  * being able to cope (CON_ANYTIME) don't call them until
 698  * this CPU is officially up.
 699  */
 700 static inline int can_use_console(unsigned int cpu)
 701 {
 702         return cpu_online(cpu) || have_callable_console();
 703 }
 704
 705 /*
 706  * Try to get console ownership to actually show the kernel
 707  * messages from a 'printk'. Return true (and with the
 708  * console_semaphore held, and 'console_locked' set) if it
 709  * is successful, false otherwise.
 710  *
 711  * This gets called with the 'logbuf_lock' spinlock held and
 712  * interrupts disabled. It should return with 'lockbuf_lock'
 713  * released but interrupts still disabled.
 714  */
 715 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 716 {
 717         int retval = 0;
 718
 719         if (!try_acquire_console_sem()) {
 720                 retval = 1;
 721
 722                 /*
 723                  * If we can't use the console, we need to release
 724                  * the console semaphore by hand to avoid flushing
 725                  * the buffer. We need to hold the console semaphore
 726                  * in order to do this test safely.
 727                  */
 728                 if (!can_use_console(cpu)) {
 729                         console_locked = 0;
 730                         up(&console_sem);
 731                         retval = 0;
 732                 }
 733         }
 734         printk_cpu = UINT_MAX;
 735         spin_unlock(&logbuf_lock);
 736         return retval;
 737 }
 738 static const char recursion_bug_msg [] =
 739                 KERN_CRIT "BUG: recent printk recursion!\n";
 740 static int recursion_bug;
 741 static int new_text_line = 1;
 742 static char printk_buf[1024];
 743
 744 int printk_delay_msec __read_mostly;
 745
 746 static inline void printk_delay(void)
 747 {
 748         if (unlikely(printk_delay_msec)) {
 749                 int m = printk_delay_msec;
 750
 751                 while (m--) {
 752                         mdelay(1);
 753                         touch_nmi_watchdog();
 754                 }
 755         }
 756 }
 757
 758 asmlinkage int vprintk(const char *fmt, va_list args)
 759 {
 760         int printed_len = 0;
 761         int current_log_level = default_message_loglevel;
 762         unsigned long flags;
 763         int this_cpu;
 764         char *p;
 765
 766         boot_delay_msec();
 767         printk_delay();
 768
 769         preempt_disable();
 770         /* This stops the holder of console_sem just where we want him */
 771         raw_local_irq_save(flags);
 772         this_cpu = smp_processor_id();
 773
 774         /*
 775          * Ouch, printk recursed into itself!
 776          */
 777         if (unlikely(printk_cpu == this_cpu)) {
 778                 /*
 779                  * If a crash is occurring during printk() on this CPU,
 780                  * then try to get the crash message out but make sure
 781                  * we can't deadlock. Otherwise just return to avoid the
 782                  * recursion and return - but flag the recursion so that
 783                  * it can be printed at the next appropriate moment:
 784                  */
 785                 if (!oops_in_progress) {
 786                         recursion_bug = 1;
 787                         goto out_restore_irqs;
 788                 }
 789                 zap_locks();
 790         }
 791
 792         lockdep_off();
 793         spin_lock(&logbuf_lock);
 794         printk_cpu = this_cpu;
 795
 796         if (recursion_bug) {
 797                 recursion_bug = 0;
 798                 strcpy(printk_buf, recursion_bug_msg);
 799                 printed_len = strlen(recursion_bug_msg);
 800         }
 801         /* Emit the output into the temporary buffer */
 802         printed_len += vscnprintf(printk_buf + printed_len,
 803                                   sizeof(printk_buf) - printed_len, fmt, args);
 804
 805 #ifdef  CONFIG_DEBUG_LL
 806         printascii(printk_buf);
 807 #endif
 808
 809         p = printk_buf;
 810
 811         /* Do we have a loglevel in the string? */
 812         if (p[0] == '<') {
 813                 unsigned char c = p[1];
 814                 if (c && p[2] == '>') {
 815                         switch (c) {
 816                         case '0' ... '7': /* loglevel */
 817                                 current_log_level = c - '0';
 818                         /* Fallthrough - make sure we're on a new line */
 819                         case 'd': /* KERN_DEFAULT */
 820                                 if (!new_text_line) {
 821                                         emit_log_char('\n');
 822                                         new_text_line = 1;
 823                                 }
 824                         /* Fallthrough - skip the loglevel */
 825                         case 'c': /* KERN_CONT */
 826                                 p += 3;
 827                                 break;
 828                         }
 829                 }
 830         }
 831
 832         /*
 833          * Copy the output into log_buf.  If the caller didn't provide
 834          * appropriate log level tags, we insert them here
 835          */
 836         for ( ; *p; p++) {
 837                 if (new_text_line) {
 838                         /* Always output the token */
 839                         emit_log_char('<');
 840                         emit_log_char(current_log_level + '0');
 841                         emit_log_char('>');
 842                         printed_len += 3;
 843                         new_text_line = 0;
 844
 845                         if (printk_time) {
 846                                 /* Follow the token with the time */
 847                                 char tbuf[50], *tp;
 848                                 unsigned tlen;
 849                                 unsigned long long t;
 850                                 unsigned long nanosec_rem;
 851
 852                                 t = cpu_clock(printk_cpu);
 853                                 nanosec_rem = do_div(t, 1000000000);
 854                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 855                                                 (unsigned long) t,
 856                                                 nanosec_rem / 1000);
 857
 858                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 859                                         emit_log_char(*tp);
 860                                 printed_len += tlen;
 861                         }
 862
 863                         if (!*p)
 864                                 break;
 865                 }
 866
 867                 emit_log_char(*p);
 868                 if (*p == '\n')
 869                         new_text_line = 1;
 870         }
 871
 872         /*
 873          * Try to acquire and then immediately release the
 874          * console semaphore. The release will do all the
 875          * actual magic (print out buffers, wake up klogd,
 876          * etc).
 877          *
 878          * The acquire_console_semaphore_for_printk() function
 879          * will release 'logbuf_lock' regardless of whether it
 880          * actually gets the semaphore or not.
 881          */
 882         if (acquire_console_semaphore_for_printk(this_cpu))
 883                 release_console_sem();
 884
 885         lockdep_on();
 886 out_restore_irqs:
 887         raw_local_irq_restore(flags);
 888
 889         preempt_enable();
 890         return printed_len;
 891 }
 892 EXPORT_SYMBOL(printk);
 893 EXPORT_SYMBOL(vprintk);
 894
 895 #else
 896
 897 static void call_console_drivers(unsigned start, unsigned end)
 898 {
 899 }
 900
 901 #endif
 902
 903 static int __add_preferred_console(char *name, int idx, char *options,
 904                                    char *brl_options)
 905 {
 906         struct console_cmdline *c;
 907         int i;
 908
 909         /*
 910          *      See if this tty is not yet registered, and
 911          *      if we have a slot free.
 912          */
 913         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 914                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 915                           console_cmdline[i].index == idx) {
 916                                 if (!brl_options)
 917                                         selected_console = i;
 918                                 return 0;
 919                 }
 920         if (i == MAX_CMDLINECONSOLES)
 921                 return -E2BIG;
 922         if (!brl_options)
 923                 selected_console = i;
 924         c = &console_cmdline[i];
 925         strlcpy(c->name, name, sizeof(c->name));
 926         c->options = options;
 927 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 928         c->brl_options = brl_options;
 929 #endif
 930         c->index = idx;
 931         return 0;
 932 }
 933 /*
 934  * Set up a list of consoles.  Called from init/main.c
 935  */
 936 static int __init console_setup(char *str)
 937 {
 938         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 939         char *s, *options, *brl_options = NULL;
 940         int idx;
 941
 942 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 943         if (!memcmp(str, "brl,", 4)) {
 944                 brl_options = "";
 945                 str += 4;
 946         } else if (!memcmp(str, "brl=", 4)) {
 947                 brl_options = str + 4;
 948                 str = strchr(brl_options, ',');
 949                 if (!str) {
 950                         printk(KERN_ERR "need port name after brl=\n");
 951                         return 1;
 952                 }
 953                 *(str++) = 0;
 954         }
 955 #endif
 956
 957         /*
 958          * Decode str into name, index, options.
 959          */
 960         if (str[0] >= '0' && str[0] <= '9') {
 961                 strcpy(buf, "ttyS");
 962                 strncpy(buf + 4, str, sizeof(buf) - 5);
 963         } else {
 964                 strncpy(buf, str, sizeof(buf) - 1);
 965         }
 966         buf[sizeof(buf) - 1] = 0;
 967         if ((options = strchr(str, ',')) != NULL)
 968                 *(options++) = 0;
 969 #ifdef __sparc__
 970         if (!strcmp(str, "ttya"))
 971                 strcpy(buf, "ttyS0");
 972         if (!strcmp(str, "ttyb"))
 973                 strcpy(buf, "ttyS1");
 974 #endif
 975         for (s = buf; *s; s++)
 976                 if ((*s >= '0' && *s <= '9') || *s == ',')
 977                         break;
 978         idx = simple_strtoul(s, NULL, 10);
 979         *s = 0;
 980
 981         __add_preferred_console(buf, idx, options, brl_options);
 982         console_set_on_cmdline = 1;
 983         return 1;
 984 }
 985 __setup("console=", console_setup);
 986
 987 /**
 988  * add_preferred_console - add a device to the list of preferred consoles.
 989  * @name: device name
 990  * @idx: device index
 991  * @options: options for this console
 992  *
 993  * The last preferred console added will be used for kernel messages
 994  * and stdin/out/err for init.  Normally this is used by console_setup
 995  * above to handle user-supplied console arguments; however it can also
 996  * be used by arch-specific code either to override the user or more
 997  * commonly to provide a default console (ie from PROM variables) when
 998  * the user has not supplied one.
 999  */
1000 int add_preferred_console(char *name, int idx, char *options)
1001 {
1002         return __add_preferred_console(name, idx, options, NULL);
1003 }
1004
1005 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1006 {
1007         struct console_cmdline *c;
1008         int i;
1009
1010         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1011                 if (strcmp(console_cmdline[i].name, name) == 0 &&
1012                           console_cmdline[i].index == idx) {
1013                                 c = &console_cmdline[i];
1014                                 strlcpy(c->name, name_new, sizeof(c->name));
1015                                 c->name[sizeof(c->name) - 1] = 0;
1016                                 c->options = options;
1017                                 c->index = idx_new;
1018                                 return i;
1019                 }
1020         /* not found */
1021         return -1;
1022 }
1023
1024 int console_suspend_enabled = 1;
1025 EXPORT_SYMBOL(console_suspend_enabled);
1026
1027 static int __init console_suspend_disable(char *str)
1028 {
1029         console_suspend_enabled = 0;
1030         return 1;
1031 }
1032 __setup("no_console_suspend", console_suspend_disable);
1033
1034 /**
1035  * suspend_console - suspend the console subsystem
1036  *
1037  * This disables printk() while we go into suspend states
1038  */
1039 void suspend_console(void)
1040 {
1041         if (!console_suspend_enabled)
1042                 return;
1043         printk("Suspending console(s) (use no_console_suspend to debug)\n");
1044         acquire_console_sem();
1045         console_suspended = 1;
1046         up(&console_sem);
1047 }
1048
1049 void resume_console(void)
1050 {
1051         if (!console_suspend_enabled)
1052                 return;
1053         down(&console_sem);
1054         console_suspended = 0;
1055         release_console_sem();
1056 }
1057
1058 /**
1059  * console_cpu_notify - print deferred console messages after CPU hotplug
1060  * @self: notifier struct
1061  * @action: CPU hotplug event
1062  * @hcpu: unused
1063  *
1064  * If printk() is called from a CPU that is not online yet, the messages
1065  * will be spooled but will not show up on the console.  This function is
1066  * called when a new CPU comes online (or fails to come up), and ensures
1067  * that any such output gets printed.
1068  */
1069 static int __cpuinit console_cpu_notify(struct notifier_block *self,
1070         unsigned long action, void *hcpu)
1071 {
1072         switch (action) {
1073         case CPU_ONLINE:
1074         case CPU_DEAD:
1075         case CPU_DYING:
1076         case CPU_DOWN_FAILED:
1077         case CPU_UP_CANCELED:
1078                 acquire_console_sem();
1079                 release_console_sem();
1080         }
1081         return NOTIFY_OK;
1082 }
1083
1084 /**
1085  * acquire_console_sem - lock the console system for exclusive use.
1086  *
1087  * Acquires a semaphore which guarantees that the caller has
1088  * exclusive access to the console system and the console_drivers list.
1089  *
1090  * Can sleep, returns nothing.
1091  */
1092 void acquire_console_sem(void)
1093 {
1094         BUG_ON(in_interrupt());
1095         down(&console_sem);
1096         if (console_suspended)
1097                 return;
1098         console_locked = 1;
1099         console_may_schedule = 1;
1100 }
1101 EXPORT_SYMBOL(acquire_console_sem);
1102
1103 int try_acquire_console_sem(void)
1104 {
1105         if (down_trylock(&console_sem))
1106                 return -1;
1107         if (console_suspended) {
1108                 up(&console_sem);
1109                 return -1;
1110         }
1111         console_locked = 1;
1112         console_may_schedule = 0;
1113         return 0;
1114 }
1115 EXPORT_SYMBOL(try_acquire_console_sem);
1116
1117 int is_console_locked(void)
1118 {
1119         return console_locked;
1120 }
1121
1122 static DEFINE_PER_CPU(int, printk_pending);
1123
1124 void printk_tick(void)
1125 {
1126         if (__get_cpu_var(printk_pending)) {
1127                 __get_cpu_var(printk_pending) = 0;
1128                 wake_up_interruptible(&log_wait);
1129         }
1130 }
1131
1132 int printk_needs_cpu(int cpu)
1133 {
1134         if (unlikely(cpu_is_offline(cpu)))
1135                 printk_tick();
1136         return per_cpu(printk_pending, cpu);
1137 }
1138
1139 void wake_up_klogd(void)
1140 {
1141         if (waitqueue_active(&log_wait))
1142                 this_cpu_write(printk_pending, 1);
1143 }
1144
1145 /**
1146  * release_console_sem - unlock the console system
1147  *
1148  * Releases the semaphore which the caller holds on the console system
1149  * and the console driver list.
1150  *
1151  * While the semaphore was held, console output may have been buffered
1152  * by printk().  If this is the case, release_console_sem() emits
1153  * the output prior to releasing the semaphore.
1154  *
1155  * If there is output waiting for klogd, we wake it up.
1156  *
1157  * release_console_sem() may be called from any context.
1158  */
1159 void release_console_sem(void)
1160 {
1161         unsigned long flags;
1162         unsigned _con_start, _log_end;
1163         unsigned wake_klogd = 0;
1164
1165         if (console_suspended) {
1166                 up(&console_sem);
1167                 return;
1168         }
1169
1170         console_may_schedule = 0;
1171
1172         for ( ; ; ) {
1173                 spin_lock_irqsave(&logbuf_lock, flags);
1174                 wake_klogd |= log_start - log_end;
1175                 if (con_start == log_end)
1176                         break;                  /* Nothing to print */
1177                 _con_start = con_start;
1178                 _log_end = log_end;
1179                 con_start = log_end;            /* Flush */
1180                 spin_unlock(&logbuf_lock);
1181                 stop_critical_timings();        /* don't trace print latency */
1182                 call_console_drivers(_con_start, _log_end);
1183                 start_critical_timings();
1184                 local_irq_restore(flags);
1185         }
1186         console_locked = 0;
1187         up(&console_sem);
1188         spin_unlock_irqrestore(&logbuf_lock, flags);
1189         if (wake_klogd)
1190                 wake_up_klogd();
1191 }
1192 EXPORT_SYMBOL(release_console_sem);
1193
1194 /**
1195  * console_conditional_schedule - yield the CPU if required
1196  *
1197  * If the console code is currently allowed to sleep, and
1198  * if this CPU should yield the CPU to another task, do
1199  * so here.
1200  *
1201  * Must be called within acquire_console_sem().
1202  */
1203 void __sched console_conditional_schedule(void)
1204 {
1205         if (console_may_schedule)
1206                 cond_resched();
1207 }
1208 EXPORT_SYMBOL(console_conditional_schedule);
1209
1210 void console_unblank(void)
1211 {
1212         struct console *c;
1213
1214         /*
1215          * console_unblank can no longer be called in interrupt context unless
1216          * oops_in_progress is set to 1..
1217          */
1218         if (oops_in_progress) {
1219                 if (down_trylock(&console_sem) != 0)
1220                         return;
1221         } else
1222                 acquire_console_sem();
1223
1224         console_locked = 1;
1225         console_may_schedule = 0;
1226         for_each_console(c)
1227                 if ((c->flags & CON_ENABLED) && c->unblank)
1228                         c->unblank();
1229         release_console_sem();
1230 }
1231
1232 /*
1233  * Return the console tty driver structure and its associated index
1234  */
1235 struct tty_driver *console_device(int *index)
1236 {
1237         struct console *c;
1238         struct tty_driver *driver = NULL;
1239
1240         acquire_console_sem();
1241         for_each_console(c) {
1242                 if (!c->device)
1243                         continue;
1244                 driver = c->device(c, index);
1245                 if (driver)
1246                         break;
1247         }
1248         release_console_sem();
1249         return driver;
1250 }
1251
1252 /*
1253  * Prevent further output on the passed console device so that (for example)
1254  * serial drivers can disable console output before suspending a port, and can
1255  * re-enable output afterwards.
1256  */
1257 void console_stop(struct console *console)
1258 {
1259         acquire_console_sem();
1260         console->flags &= ~CON_ENABLED;
1261         release_console_sem();
1262 }
1263 EXPORT_SYMBOL(console_stop);
1264
1265 void console_start(struct console *console)
1266 {
1267         acquire_console_sem();
1268         console->flags |= CON_ENABLED;
1269         release_console_sem();
1270 }
1271 EXPORT_SYMBOL(console_start);
1272
1273 /*
1274  * The console driver calls this routine during kernel initialization
1275  * to register the console printing procedure with printk() and to
1276  * print any messages that were printed by the kernel before the
1277  * console driver was initialized.
1278  *
1279  * This can happen pretty early during the boot process (because of
1280  * early_printk) - sometimes before setup_arch() completes - be careful
1281  * of what kernel features are used - they may not be initialised yet.
1282  *
1283  * There are two types of consoles - bootconsoles (early_printk) and
1284  * "real" consoles (everything which is not a bootconsole) which are
1285  * handled differently.
1286  *  - Any number of bootconsoles can be registered at any time.
1287  *  - As soon as a "real" console is registered, all bootconsoles
1288  *    will be unregistered automatically.
1289  *  - Once a "real" console is registered, any attempt to register a
1290  *    bootconsoles will be rejected
1291  */
1292 void register_console(struct console *newcon)
1293 {
1294         int i;
1295         unsigned long flags;
1296         struct console *bcon = NULL;
1297
1298         /*
1299          * before we register a new CON_BOOT console, make sure we don't
1300          * already have a valid console
1301          */
1302         if (console_drivers && newcon->flags & CON_BOOT) {
1303                 /* find the last or real console */
1304                 for_each_console(bcon) {
1305                         if (!(bcon->flags & CON_BOOT)) {
1306                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1307                                         newcon->name, newcon->index);
1308                                 return;
1309                         }
1310                 }
1311         }
1312
1313         if (console_drivers && console_drivers->flags & CON_BOOT)
1314                 bcon = console_drivers;
1315
1316         if (preferred_console < 0 || bcon || !console_drivers)
1317                 preferred_console = selected_console;
1318
1319         if (newcon->early_setup)
1320                 newcon->early_setup();
1321
1322         /*
1323          *      See if we want to use this console driver. If we
1324          *      didn't select a console we take the first one
1325          *      that registers here.
1326          */
1327         if (preferred_console < 0) {
1328                 if (newcon->index < 0)
1329                         newcon->index = 0;
1330                 if (newcon->setup == NULL ||
1331                     newcon->setup(newcon, NULL) == 0) {
1332                         newcon->flags |= CON_ENABLED;
1333                         if (newcon->device) {
1334                                 newcon->flags |= CON_CONSDEV;
1335                                 preferred_console = 0;
1336                         }
1337                 }
1338         }
1339
1340         /*
1341          *      See if this console matches one we selected on
1342          *      the command line.
1343          */
1344         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1345                         i++) {
1346                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1347                         continue;
1348                 if (newcon->index >= 0 &&
1349                     newcon->index != console_cmdline[i].index)
1350                         continue;
1351                 if (newcon->index < 0)
1352                         newcon->index = console_cmdline[i].index;
1353 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1354                 if (console_cmdline[i].brl_options) {
1355                         newcon->flags |= CON_BRL;
1356                         braille_register_console(newcon,
1357                                         console_cmdline[i].index,
1358                                         console_cmdline[i].options,
1359                                         console_cmdline[i].brl_options);
1360                         return;
1361                 }
1362 #endif
1363                 if (newcon->setup &&
1364                     newcon->setup(newcon, console_cmdline[i].options) != 0)
1365                         break;
1366                 newcon->flags |= CON_ENABLED;
1367                 newcon->index = console_cmdline[i].index;
1368                 if (i == selected_console) {
1369                         newcon->flags |= CON_CONSDEV;
1370                         preferred_console = selected_console;
1371                 }
1372                 break;
1373         }
1374
1375         if (!(newcon->flags & CON_ENABLED))
1376                 return;
1377
1378         /*
1379          * If we have a bootconsole, and are switching to a real console,
1380          * don't print everything out again, since when the boot console, and
1381          * the real console are the same physical device, it's annoying to
1382          * see the beginning boot messages twice
1383          */
1384         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1385                 newcon->flags &= ~CON_PRINTBUFFER;
1386
1387         /*
1388          *      Put this console in the list - keep the
1389          *      preferred driver at the head of the list.
1390          */
1391         acquire_console_sem();
1392         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1393                 newcon->next = console_drivers;
1394                 console_drivers = newcon;
1395                 if (newcon->next)
1396                         newcon->next->flags &= ~CON_CONSDEV;
1397         } else {
1398                 newcon->next = console_drivers->next;
1399                 console_drivers->next = newcon;
1400         }
1401         if (newcon->flags & CON_PRINTBUFFER) {
1402                 /*
1403                  * release_console_sem() will print out the buffered messages
1404                  * for us.
1405                  */
1406                 spin_lock_irqsave(&logbuf_lock, flags);
1407                 con_start = log_start;
1408                 spin_unlock_irqrestore(&logbuf_lock, flags);
1409         }
1410         release_console_sem();
1411
1412         /*
1413          * By unregistering the bootconsoles after we enable the real console
1414          * we get the "console xxx enabled" message on all the consoles -
1415          * boot consoles, real consoles, etc - this is to ensure that end
1416          * users know there might be something in the kernel's log buffer that
1417          * went to the bootconsole (that they do not see on the real console)
1418          */
1419         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1420                 /* we need to iterate through twice, to make sure we print
1421                  * everything out, before we unregister the console(s)
1422                  */
1423                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1424                         newcon->name, newcon->index);
1425                 for_each_console(bcon)
1426                         if (bcon->flags & CON_BOOT)
1427                                 unregister_console(bcon);
1428         } else {
1429                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1430                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
1431                         newcon->name, newcon->index);
1432         }
1433 }
1434 EXPORT_SYMBOL(register_console);
1435
1436 int unregister_console(struct console *console)
1437 {
1438         struct console *a, *b;
1439         int res = 1;
1440
1441 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1442         if (console->flags & CON_BRL)
1443                 return braille_unregister_console(console);
1444 #endif
1445
1446         acquire_console_sem();
1447         if (console_drivers == console) {
1448                 console_drivers=console->next;
1449                 res = 0;
1450         } else if (console_drivers) {
1451                 for (a=console_drivers->next, b=console_drivers ;
1452                      a; b=a, a=b->next) {
1453                         if (a == console) {
1454                                 b->next = a->next;
1455                                 res = 0;
1456                                 break;
1457                         }
1458                 }
1459         }
1460
1461         /*
1462          * If this isn't the last console and it has CON_CONSDEV set, we
1463          * need to set it on the next preferred console.
1464          */
1465         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1466                 console_drivers->flags |= CON_CONSDEV;
1467
1468         release_console_sem();
1469         return res;
1470 }
1471 EXPORT_SYMBOL(unregister_console);
1472
1473 static int __init printk_late_init(void)
1474 {
1475         struct console *con;
1476
1477         for_each_console(con) {
1478                 if (con->flags & CON_BOOT) {
1479                         printk(KERN_INFO "turn off boot console %s%d\n",
1480                                 con->name, con->index);
1481                         unregister_console(con);
1482                 }
1483         }
1484         hotcpu_notifier(console_cpu_notify, 0);
1485         return 0;
1486 }
1487 late_initcall(printk_late_init);
1488
1489 #if defined CONFIG_PRINTK
1490
1491 /*
1492  * printk rate limiting, lifted from the networking subsystem.
1493  *
1494  * This enforces a rate limit: not more than 10 kernel messages
1495  * every 5s to make a denial-of-service attack impossible.
1496  */
1497 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1498
1499 int __printk_ratelimit(const char *func)
1500 {
1501         return ___ratelimit(&printk_ratelimit_state, func);
1502 }
1503 EXPORT_SYMBOL(__printk_ratelimit);
1504
1505 /**
1506  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1507  * @caller_jiffies: pointer to caller's state
1508  * @interval_msecs: minimum interval between prints
1509  *
1510  * printk_timed_ratelimit() returns true if more than @interval_msecs
1511  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1512  * returned true.
1513  */
1514 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1515                         unsigned int interval_msecs)
1516 {
1517         if (*caller_jiffies == 0
1518                         || !time_in_range(jiffies, *caller_jiffies,
1519                                         *caller_jiffies
1520                                         + msecs_to_jiffies(interval_msecs))) {
1521                 *caller_jiffies = jiffies;
1522                 return true;
1523         }
1524         return false;
1525 }
1526 EXPORT_SYMBOL(printk_timed_ratelimit);
1527
1528 static DEFINE_SPINLOCK(dump_list_lock);
1529 static LIST_HEAD(dump_list);
1530
1531 /**
1532  * kmsg_dump_register - register a kernel log dumper.
1533  * @dumper: pointer to the kmsg_dumper structure
1534  *
1535  * Adds a kernel log dumper to the system. The dump callback in the
1536  * structure will be called when the kernel oopses or panics and must be
1537  * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1538  */
1539 int kmsg_dump_register(struct kmsg_dumper *dumper)
1540 {
1541         unsigned long flags;
1542         int err = -EBUSY;
1543
1544         /* The dump callback needs to be set */
1545         if (!dumper->dump)
1546                 return -EINVAL;
1547
1548         spin_lock_irqsave(&dump_list_lock, flags);
1549         /* Don't allow registering multiple times */
1550         if (!dumper->registered) {
1551                 dumper->registered = 1;
1552                 list_add_tail(&dumper->list, &dump_list);
1553                 err = 0;
1554         }
1555         spin_unlock_irqrestore(&dump_list_lock, flags);
1556
1557         return err;
1558 }
1559 EXPORT_SYMBOL_GPL(kmsg_dump_register);
1560
1561 /**
1562  * kmsg_dump_unregister - unregister a kmsg dumper.
1563  * @dumper: pointer to the kmsg_dumper structure
1564  *
1565  * Removes a dump device from the system. Returns zero on success and
1566  * %-EINVAL otherwise.
1567  */
1568 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
1569 {
1570         unsigned long flags;
1571         int err = -EINVAL;
1572
1573         spin_lock_irqsave(&dump_list_lock, flags);
1574         if (dumper->registered) {
1575                 dumper->registered = 0;
1576                 list_del(&dumper->list);
1577                 err = 0;
1578         }
1579         spin_unlock_irqrestore(&dump_list_lock, flags);
1580
1581         return err;
1582 }
1583 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
1584
1585 static const char const *kmsg_reasons[] = {
1586         [KMSG_DUMP_OOPS]        = "oops",
1587         [KMSG_DUMP_PANIC]       = "panic",
1588         [KMSG_DUMP_KEXEC]       = "kexec",
1589 };
1590
1591 static const char *kmsg_to_str(enum kmsg_dump_reason reason)
1592 {
1593         if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0)
1594                 return "unknown";
1595
1596         return kmsg_reasons[reason];
1597 }
1598
1599 /**
1600  * kmsg_dump - dump kernel log to kernel message dumpers.
1601  * @reason: the reason (oops, panic etc) for dumping
1602  *
1603  * Iterate through each of the dump devices and call the oops/panic
1604  * callbacks with the log buffer.
1605  */
1606 void kmsg_dump(enum kmsg_dump_reason reason)
1607 {
1608         unsigned long end;
1609         unsigned chars;
1610         struct kmsg_dumper *dumper;
1611         const char *s1, *s2;
1612         unsigned long l1, l2;
1613         unsigned long flags;
1614
1615         /* Theoretically, the log could move on after we do this, but
1616            there's not a lot we can do about that. The new messages
1617            will overwrite the start of what we dump. */
1618         spin_lock_irqsave(&logbuf_lock, flags);
1619         end = log_end & LOG_BUF_MASK;
1620         chars = logged_chars;
1621         spin_unlock_irqrestore(&logbuf_lock, flags);
1622
1623         if (chars > end) {
1624                 s1 = log_buf + log_buf_len - chars + end;
1625                 l1 = chars - end;
1626
1627                 s2 = log_buf;
1628                 l2 = end;
1629         } else {
1630                 s1 = "";
1631                 l1 = 0;
1632
1633                 s2 = log_buf + end - chars;
1634                 l2 = chars;
1635         }
1636
1637         if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
1638                 printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n",
1639                                 kmsg_to_str(reason));
1640                 return;
1641         }
1642         list_for_each_entry(dumper, &dump_list, list)
1643                 dumper->dump(dumper, reason, s1, l1, s2, l2);
1644         spin_unlock_irqrestore(&dump_list_lock, flags);
1645 }
1646 #endif