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
  36 #include <asm/uaccess.h>
  37
  38 /*
  39  * Architectures can override it:
  40  */
  41 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
  42 {
  43 }
  44
  45 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
  46
  47 #ifdef CONFIG_DEBUG_LL
  48 extern void printascii(char *);
  49 #endif
  50
  51 /* printk's without a loglevel use this.. */
  52 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  53
  54 /* We show everything that is MORE important than this.. */
  55 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  56 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  57
  58 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  59
  60 int console_printk[4] = {
  61         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  62         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  63         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  64         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  65 };
  66
  67 /*
  68  * Low level drivers may need that to know if they can schedule in
  69  * their unblank() callback or not. So let's export it.
  70  */
  71 int oops_in_progress;
  72 EXPORT_SYMBOL(oops_in_progress);
  73
  74 /*
  75  * console_sem protects the console_drivers list, and also
  76  * provides serialisation for access to the entire console
  77  * driver system.
  78  */
  79 static DECLARE_MUTEX(console_sem);
  80 static DECLARE_MUTEX(secondary_console_sem);
  81 struct console *console_drivers;
  82 EXPORT_SYMBOL_GPL(console_drivers);
  83
  84 /*
  85  * This is used for debugging the mess that is the VT code by
  86  * keeping track if we have the console semaphore held. It's
  87  * definitely not the perfect debug tool (we don't know if _WE_
  88  * hold it are racing, but it helps tracking those weird code
  89  * path in the console code where we end up in places I want
  90  * locked without the console sempahore held
  91  */
  92 static int console_locked, console_suspended;
  93
  94 /*
  95  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
  96  * It is also used in interesting ways to provide interlocking in
  97  * release_console_sem().
  98  */
  99 static DEFINE_SPINLOCK(logbuf_lock);
 100
 101 #define LOG_BUF_MASK (log_buf_len-1)
 102 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
 103
 104 /*
 105  * The indices into log_buf are not constrained to log_buf_len - they
 106  * must be masked before subscripting
 107  */
 108 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
 109 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
 110 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 111
 112 /*
 113  *      Array of consoles built from command line options (console=)
 114  */
 115 struct console_cmdline
 116 {
 117         char    name[8];                        /* Name of the driver       */
 118         int     index;                          /* Minor dev. to use        */
 119         char    *options;                       /* Options for the driver   */
 120 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 121         char    *brl_options;                   /* Options for braille driver */
 122 #endif
 123 };
 124
 125 #define MAX_CMDLINECONSOLES 8
 126
 127 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 128 static int selected_console = -1;
 129 static int preferred_console = -1;
 130 int console_set_on_cmdline;
 131 EXPORT_SYMBOL(console_set_on_cmdline);
 132
 133 /* Flag: console code may call schedule() */
 134 static int console_may_schedule;
 135
 136 #ifdef CONFIG_PRINTK
 137
 138 static char __log_buf[__LOG_BUF_LEN];
 139 static char *log_buf = __log_buf;
 140 static int log_buf_len = __LOG_BUF_LEN;
 141 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 142
 143 static int __init log_buf_len_setup(char *str)
 144 {
 145         unsigned size = memparse(str, &str);
 146         unsigned long flags;
 147
 148         if (size)
 149                 size = roundup_pow_of_two(size);
 150         if (size > log_buf_len) {
 151                 unsigned start, dest_idx, offset;
 152                 char *new_log_buf;
 153
 154                 new_log_buf = alloc_bootmem(size);
 155                 if (!new_log_buf) {
 156                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 157                         goto out;
 158                 }
 159
 160                 spin_lock_irqsave(&logbuf_lock, flags);
 161                 log_buf_len = size;
 162                 log_buf = new_log_buf;
 163
 164                 offset = start = min(con_start, log_start);
 165                 dest_idx = 0;
 166                 while (start != log_end) {
 167                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 168                         start++;
 169                         dest_idx++;
 170                 }
 171                 log_start -= offset;
 172                 con_start -= offset;
 173                 log_end -= offset;
 174                 spin_unlock_irqrestore(&logbuf_lock, flags);
 175
 176                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 177         }
 178 out:
 179         return 1;
 180 }
 181
 182 __setup("log_buf_len=", log_buf_len_setup);
 183
 184 #ifdef CONFIG_BOOT_PRINTK_DELAY
 185
 186 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 187 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
 188
 189 static int __init boot_delay_setup(char *str)
 190 {
 191         unsigned long lpj;
 192         unsigned long long loops_per_msec;
 193
 194         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 195         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 196
 197         get_option(&str, &boot_delay);
 198         if (boot_delay > 10 * 1000)
 199                 boot_delay = 0;
 200
 201         printk_delay_msec = loops_per_msec;
 202         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 203                 "HZ: %d, printk_delay_msec: %llu\n",
 204                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
 205         return 1;
 206 }
 207 __setup("boot_delay=", boot_delay_setup);
 208
 209 static void boot_delay_msec(void)
 210 {
 211         unsigned long long k;
 212         unsigned long timeout;
 213
 214         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 215                 return;
 216
 217         k = (unsigned long long)printk_delay_msec * boot_delay;
 218
 219         timeout = jiffies + msecs_to_jiffies(boot_delay);
 220         while (k) {
 221                 k--;
 222                 cpu_relax();
 223                 /*
 224                  * use (volatile) jiffies to prevent
 225                  * compiler reduction; loop termination via jiffies
 226                  * is secondary and may or may not happen.
 227                  */
 228                 if (time_after(jiffies, timeout))
 229                         break;
 230                 touch_nmi_watchdog();
 231         }
 232 }
 233 #else
 234 static inline void boot_delay_msec(void)
 235 {
 236 }
 237 #endif
 238
 239 /*
 240  * Commands to do_syslog:
 241  *
 242  *      0 -- Close the log.  Currently a NOP.
 243  *      1 -- Open the log. Currently a NOP.
 244  *      2 -- Read from the log.
 245  *      3 -- Read all messages remaining in the ring buffer.
 246  *      4 -- Read and clear all messages remaining in the ring buffer
 247  *      5 -- Clear ring buffer.
 248  *      6 -- Disable printk's to console
 249  *      7 -- Enable printk's to console
 250  *      8 -- Set level of messages printed to console
 251  *      9 -- Return number of unread characters in the log buffer
 252  *     10 -- Return size of the log buffer
 253  */
 254 int do_syslog(int type, char __user *buf, int len)
 255 {
 256         unsigned i, j, limit, count;
 257         int do_clear = 0;
 258         char c;
 259         int error = 0;
 260
 261         error = security_syslog(type);
 262         if (error)
 263                 return error;
 264
 265         switch (type) {
 266         case 0:         /* Close log */
 267                 break;
 268         case 1:         /* Open log */
 269                 break;
 270         case 2:         /* Read from log */
 271                 error = -EINVAL;
 272                 if (!buf || len < 0)
 273                         goto out;
 274                 error = 0;
 275                 if (!len)
 276                         goto out;
 277                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 278                         error = -EFAULT;
 279                         goto out;
 280                 }
 281                 error = wait_event_interruptible(log_wait,
 282                                                         (log_start - log_end));
 283                 if (error)
 284                         goto out;
 285                 i = 0;
 286                 spin_lock_irq(&logbuf_lock);
 287                 while (!error && (log_start != log_end) && i < len) {
 288                         c = LOG_BUF(log_start);
 289                         log_start++;
 290                         spin_unlock_irq(&logbuf_lock);
 291                         error = __put_user(c,buf);
 292                         buf++;
 293                         i++;
 294                         cond_resched();
 295                         spin_lock_irq(&logbuf_lock);
 296                 }
 297                 spin_unlock_irq(&logbuf_lock);
 298                 if (!error)
 299                         error = i;
 300                 break;
 301         case 4:         /* Read/clear last kernel messages */
 302                 do_clear = 1;
 303                 /* FALL THRU */
 304         case 3:         /* Read last kernel messages */
 305                 error = -EINVAL;
 306                 if (!buf || len < 0)
 307                         goto out;
 308                 error = 0;
 309                 if (!len)
 310                         goto out;
 311                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 312                         error = -EFAULT;
 313                         goto out;
 314                 }
 315                 count = len;
 316                 if (count > log_buf_len)
 317                         count = log_buf_len;
 318                 spin_lock_irq(&logbuf_lock);
 319                 if (count > logged_chars)
 320                         count = logged_chars;
 321                 if (do_clear)
 322                         logged_chars = 0;
 323                 limit = log_end;
 324                 /*
 325                  * __put_user() could sleep, and while we sleep
 326                  * printk() could overwrite the messages
 327                  * we try to copy to user space. Therefore
 328                  * the messages are copied in reverse. <manfreds>
 329                  */
 330                 for (i = 0; i < count && !error; i++) {
 331                         j = limit-1-i;
 332                         if (j + log_buf_len < log_end)
 333                                 break;
 334                         c = LOG_BUF(j);
 335                         spin_unlock_irq(&logbuf_lock);
 336                         error = __put_user(c,&buf[count-1-i]);
 337                         cond_resched();
 338                         spin_lock_irq(&logbuf_lock);
 339                 }
 340                 spin_unlock_irq(&logbuf_lock);
 341                 if (error)
 342                         break;
 343                 error = i;
 344                 if (i != count) {
 345                         int offset = count-error;
 346                         /* buffer overflow during copy, correct user buffer. */
 347                         for (i = 0; i < error; i++) {
 348                                 if (__get_user(c,&buf[i+offset]) ||
 349                                     __put_user(c,&buf[i])) {
 350                                         error = -EFAULT;
 351                                         break;
 352                                 }
 353                                 cond_resched();
 354                         }
 355                 }
 356                 break;
 357         case 5:         /* Clear ring buffer */
 358                 logged_chars = 0;
 359                 break;
 360         case 6:         /* Disable logging to console */
 361                 console_loglevel = minimum_console_loglevel;
 362                 break;
 363         case 7:         /* Enable logging to console */
 364                 console_loglevel = default_console_loglevel;
 365                 break;
 366         case 8:         /* Set level of messages printed to console */
 367                 error = -EINVAL;
 368                 if (len < 1 || len > 8)
 369                         goto out;
 370                 if (len < minimum_console_loglevel)
 371                         len = minimum_console_loglevel;
 372                 console_loglevel = len;
 373                 error = 0;
 374                 break;
 375         case 9:         /* Number of chars in the log buffer */
 376                 error = log_end - log_start;
 377                 break;
 378         case 10:        /* Size of the log buffer */
 379                 error = log_buf_len;
 380                 break;
 381         default:
 382                 error = -EINVAL;
 383                 break;
 384         }
 385 out:
 386         return error;
 387 }
 388
 389 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
 390 {
 391         return do_syslog(type, buf, len);
 392 }
 393
 394 /*
 395  * Call the console drivers on a range of log_buf
 396  */
 397 static void __call_console_drivers(unsigned start, unsigned end)
 398 {
 399         struct console *con;
 400
 401         for (con = console_drivers; con; con = con->next) {
 402                 if ((con->flags & CON_ENABLED) && con->write &&
 403                                 (cpu_online(smp_processor_id()) ||
 404                                 (con->flags & CON_ANYTIME)))
 405                         con->write(con, &LOG_BUF(start), end - start);
 406         }
 407 }
 408
 409 static int __read_mostly ignore_loglevel;
 410
 411 static int __init ignore_loglevel_setup(char *str)
 412 {
 413         ignore_loglevel = 1;
 414         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 415
 416         return 0;
 417 }
 418
 419 early_param("ignore_loglevel", ignore_loglevel_setup);
 420
 421 /*
 422  * Write out chars from start to end - 1 inclusive
 423  */
 424 static void _call_console_drivers(unsigned start,
 425                                 unsigned end, int msg_log_level)
 426 {
 427         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 428                         console_drivers && start != end) {
 429                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 430                         /* wrapped write */
 431                         __call_console_drivers(start & LOG_BUF_MASK,
 432                                                 log_buf_len);
 433                         __call_console_drivers(0, end & LOG_BUF_MASK);
 434                 } else {
 435                         __call_console_drivers(start, end);
 436                 }
 437         }
 438 }
 439
 440 /*
 441  * Call the console drivers, asking them to write out
 442  * log_buf[start] to log_buf[end - 1].
 443  * The console_sem must be held.
 444  */
 445 static void call_console_drivers(unsigned start, unsigned end)
 446 {
 447         unsigned cur_index, start_print;
 448         static int msg_level = -1;
 449
 450         BUG_ON(((int)(start - end)) > 0);
 451
 452         cur_index = start;
 453         start_print = start;
 454         while (cur_index != end) {
 455                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 456                                 LOG_BUF(cur_index + 0) == '<' &&
 457                                 LOG_BUF(cur_index + 1) >= '0' &&
 458                                 LOG_BUF(cur_index + 1) <= '7' &&
 459                                 LOG_BUF(cur_index + 2) == '>') {
 460                         msg_level = LOG_BUF(cur_index + 1) - '0';
 461                         cur_index += 3;
 462                         start_print = cur_index;
 463                 }
 464                 while (cur_index != end) {
 465                         char c = LOG_BUF(cur_index);
 466
 467                         cur_index++;
 468                         if (c == '\n') {
 469                                 if (msg_level < 0) {
 470                                         /*
 471                                          * printk() has already given us loglevel tags in
 472                                          * the buffer.  This code is here in case the
 473                                          * log buffer has wrapped right round and scribbled
 474                                          * on those tags
 475                                          */
 476                                         msg_level = default_message_loglevel;
 477                                 }
 478                                 _call_console_drivers(start_print, cur_index, msg_level);
 479                                 msg_level = -1;
 480                                 start_print = cur_index;
 481                                 break;
 482                         }
 483                 }
 484         }
 485         _call_console_drivers(start_print, end, msg_level);
 486 }
 487
 488 static void emit_log_char(char c)
 489 {
 490         LOG_BUF(log_end) = c;
 491         log_end++;
 492         if (log_end - log_start > log_buf_len)
 493                 log_start = log_end - log_buf_len;
 494         if (log_end - con_start > log_buf_len)
 495                 con_start = log_end - log_buf_len;
 496         if (logged_chars < log_buf_len)
 497                 logged_chars++;
 498 }
 499
 500 /*
 501  * Zap console related locks when oopsing. Only zap at most once
 502  * every 10 seconds, to leave time for slow consoles to print a
 503  * full oops.
 504  */
 505 static void zap_locks(void)
 506 {
 507         static unsigned long oops_timestamp;
 508
 509         if (time_after_eq(jiffies, oops_timestamp) &&
 510                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 511                 return;
 512
 513         oops_timestamp = jiffies;
 514
 515         /* If a crash is occurring, make sure we can't deadlock */
 516         spin_lock_init(&logbuf_lock);
 517         /* And make sure that we print immediately */
 518         init_MUTEX(&console_sem);
 519 }
 520
 521 #if defined(CONFIG_PRINTK_TIME)
 522 static int printk_time = 1;
 523 #else
 524 static int printk_time = 0;
 525 #endif
 526 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 527
 528 /* Check if we have any console registered that can be called early in boot. */
 529 static int have_callable_console(void)
 530 {
 531         struct console *con;
 532
 533         for (con = console_drivers; con; con = con->next)
 534                 if (con->flags & CON_ANYTIME)
 535                         return 1;
 536
 537         return 0;
 538 }
 539
 540 /**
 541  * printk - print a kernel message
 542  * @fmt: format string
 543  *
 544  * This is printk().  It can be called from any context.  We want it to work.
 545  *
 546  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 547  * call the console drivers.  If we fail to get the semaphore we place the output
 548  * into the log buffer and return.  The current holder of the console_sem will
 549  * notice the new output in release_console_sem() and will send it to the
 550  * consoles before releasing the semaphore.
 551  *
 552  * One effect of this deferred printing is that code which calls printk() and
 553  * then changes console_loglevel may break. This is because console_loglevel
 554  * is inspected when the actual printing occurs.
 555  *
 556  * See also:
 557  * printf(3)
 558  *
 559  * See the vsnprintf() documentation for format string extensions over C99.
 560  */
 561
 562 asmlinkage int printk(const char *fmt, ...)
 563 {
 564         va_list args;
 565         int r;
 566
 567         va_start(args, fmt);
 568         r = vprintk(fmt, args);
 569         va_end(args);
 570
 571         return r;
 572 }
 573
 574 /* cpu currently holding logbuf_lock */
 575 static volatile unsigned int printk_cpu = UINT_MAX;
 576
 577 /*
 578  * Can we actually use the console at this time on this cpu?
 579  *
 580  * Console drivers may assume that per-cpu resources have
 581  * been allocated. So unless they're explicitly marked as
 582  * being able to cope (CON_ANYTIME) don't call them until
 583  * this CPU is officially up.
 584  */
 585 static inline int can_use_console(unsigned int cpu)
 586 {
 587         return cpu_online(cpu) || have_callable_console();
 588 }
 589
 590 /*
 591  * Try to get console ownership to actually show the kernel
 592  * messages from a 'printk'. Return true (and with the
 593  * console_semaphore held, and 'console_locked' set) if it
 594  * is successful, false otherwise.
 595  *
 596  * This gets called with the 'logbuf_lock' spinlock held and
 597  * interrupts disabled. It should return with 'lockbuf_lock'
 598  * released but interrupts still disabled.
 599  */
 600 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 601 {
 602         int retval = 0;
 603
 604         if (!try_acquire_console_sem()) {
 605                 retval = 1;
 606
 607                 /*
 608                  * If we can't use the console, we need to release
 609                  * the console semaphore by hand to avoid flushing
 610                  * the buffer. We need to hold the console semaphore
 611                  * in order to do this test safely.
 612                  */
 613                 if (!can_use_console(cpu)) {
 614                         console_locked = 0;
 615                         up(&console_sem);
 616                         retval = 0;
 617                 }
 618         }
 619         printk_cpu = UINT_MAX;
 620         spin_unlock(&logbuf_lock);
 621         return retval;
 622 }
 623 static const char recursion_bug_msg [] =
 624                 KERN_CRIT "BUG: recent printk recursion!\n";
 625 static int recursion_bug;
 626 static int new_text_line = 1;
 627 static char printk_buf[1024];
 628
 629 asmlinkage int vprintk(const char *fmt, va_list args)
 630 {
 631         int printed_len = 0;
 632         int current_log_level = default_message_loglevel;
 633         unsigned long flags;
 634         int this_cpu;
 635         char *p;
 636
 637         boot_delay_msec();
 638
 639         preempt_disable();
 640         /* This stops the holder of console_sem just where we want him */
 641         raw_local_irq_save(flags);
 642         this_cpu = smp_processor_id();
 643
 644         /*
 645          * Ouch, printk recursed into itself!
 646          */
 647         if (unlikely(printk_cpu == this_cpu)) {
 648                 /*
 649                  * If a crash is occurring during printk() on this CPU,
 650                  * then try to get the crash message out but make sure
 651                  * we can't deadlock. Otherwise just return to avoid the
 652                  * recursion and return - but flag the recursion so that
 653                  * it can be printed at the next appropriate moment:
 654                  */
 655                 if (!oops_in_progress) {
 656                         recursion_bug = 1;
 657                         goto out_restore_irqs;
 658                 }
 659                 zap_locks();
 660         }
 661
 662         lockdep_off();
 663         spin_lock(&logbuf_lock);
 664         printk_cpu = this_cpu;
 665
 666         if (recursion_bug) {
 667                 recursion_bug = 0;
 668                 strcpy(printk_buf, recursion_bug_msg);
 669                 printed_len = strlen(recursion_bug_msg);
 670         }
 671         /* Emit the output into the temporary buffer */
 672         printed_len += vscnprintf(printk_buf + printed_len,
 673                                   sizeof(printk_buf) - printed_len, fmt, args);
 674
 675 #ifdef  CONFIG_DEBUG_LL
 676         printascii(printk_buf);
 677 #endif
 678
 679         /*
 680          * Copy the output into log_buf.  If the caller didn't provide
 681          * appropriate log level tags, we insert them here
 682          */
 683         for (p = printk_buf; *p; p++) {
 684                 if (new_text_line) {
 685                         /* If a token, set current_log_level and skip over */
 686                         if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
 687                             p[2] == '>') {
 688                                 current_log_level = p[1] - '0';
 689                                 p += 3;
 690                                 printed_len -= 3;
 691                         }
 692
 693                         /* Always output the token */
 694                         emit_log_char('<');
 695                         emit_log_char(current_log_level + '0');
 696                         emit_log_char('>');
 697                         printed_len += 3;
 698                         new_text_line = 0;
 699
 700                         if (printk_time) {
 701                                 /* Follow the token with the time */
 702                                 char tbuf[50], *tp;
 703                                 unsigned tlen;
 704                                 unsigned long long t;
 705                                 unsigned long nanosec_rem;
 706
 707                                 t = cpu_clock(printk_cpu);
 708                                 nanosec_rem = do_div(t, 1000000000);
 709                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 710                                                 (unsigned long) t,
 711                                                 nanosec_rem / 1000);
 712
 713                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 714                                         emit_log_char(*tp);
 715                                 printed_len += tlen;
 716                         }
 717
 718                         if (!*p)
 719                                 break;
 720                 }
 721
 722                 emit_log_char(*p);
 723                 if (*p == '\n')
 724                         new_text_line = 1;
 725         }
 726
 727         /*
 728          * Try to acquire and then immediately release the
 729          * console semaphore. The release will do all the
 730          * actual magic (print out buffers, wake up klogd,
 731          * etc).
 732          *
 733          * The acquire_console_semaphore_for_printk() function
 734          * will release 'logbuf_lock' regardless of whether it
 735          * actually gets the semaphore or not.
 736          */
 737         if (acquire_console_semaphore_for_printk(this_cpu))
 738                 release_console_sem();
 739
 740         lockdep_on();
 741 out_restore_irqs:
 742         raw_local_irq_restore(flags);
 743
 744         preempt_enable();
 745         return printed_len;
 746 }
 747 EXPORT_SYMBOL(printk);
 748 EXPORT_SYMBOL(vprintk);
 749
 750 #else
 751
 752 static void call_console_drivers(unsigned start, unsigned end)
 753 {
 754 }
 755
 756 #endif
 757
 758 static int __add_preferred_console(char *name, int idx, char *options,
 759                                    char *brl_options)
 760 {
 761         struct console_cmdline *c;
 762         int i;
 763
 764         /*
 765          *      See if this tty is not yet registered, and
 766          *      if we have a slot free.
 767          */
 768         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 769                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 770                           console_cmdline[i].index == idx) {
 771                                 if (!brl_options)
 772                                         selected_console = i;
 773                                 return 0;
 774                 }
 775         if (i == MAX_CMDLINECONSOLES)
 776                 return -E2BIG;
 777         if (!brl_options)
 778                 selected_console = i;
 779         c = &console_cmdline[i];
 780         strlcpy(c->name, name, sizeof(c->name));
 781         c->options = options;
 782 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 783         c->brl_options = brl_options;
 784 #endif
 785         c->index = idx;
 786         return 0;
 787 }
 788 /*
 789  * Set up a list of consoles.  Called from init/main.c
 790  */
 791 static int __init console_setup(char *str)
 792 {
 793         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 794         char *s, *options, *brl_options = NULL;
 795         int idx;
 796
 797 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 798         if (!memcmp(str, "brl,", 4)) {
 799                 brl_options = "";
 800                 str += 4;
 801         } else if (!memcmp(str, "brl=", 4)) {
 802                 brl_options = str + 4;
 803                 str = strchr(brl_options, ',');
 804                 if (!str) {
 805                         printk(KERN_ERR "need port name after brl=\n");
 806                         return 1;
 807                 }
 808                 *(str++) = 0;
 809         }
 810 #endif
 811
 812         /*
 813          * Decode str into name, index, options.
 814          */
 815         if (str[0] >= '0' && str[0] <= '9') {
 816                 strcpy(buf, "ttyS");
 817                 strncpy(buf + 4, str, sizeof(buf) - 5);
 818         } else {
 819                 strncpy(buf, str, sizeof(buf) - 1);
 820         }
 821         buf[sizeof(buf) - 1] = 0;
 822         if ((options = strchr(str, ',')) != NULL)
 823                 *(options++) = 0;
 824 #ifdef __sparc__
 825         if (!strcmp(str, "ttya"))
 826                 strcpy(buf, "ttyS0");
 827         if (!strcmp(str, "ttyb"))
 828                 strcpy(buf, "ttyS1");
 829 #endif
 830         for (s = buf; *s; s++)
 831                 if ((*s >= '0' && *s <= '9') || *s == ',')
 832                         break;
 833         idx = simple_strtoul(s, NULL, 10);
 834         *s = 0;
 835
 836         __add_preferred_console(buf, idx, options, brl_options);
 837         console_set_on_cmdline = 1;
 838         return 1;
 839 }
 840 __setup("console=", console_setup);
 841
 842 /**
 843  * add_preferred_console - add a device to the list of preferred consoles.
 844  * @name: device name
 845  * @idx: device index
 846  * @options: options for this console
 847  *
 848  * The last preferred console added will be used for kernel messages
 849  * and stdin/out/err for init.  Normally this is used by console_setup
 850  * above to handle user-supplied console arguments; however it can also
 851  * be used by arch-specific code either to override the user or more
 852  * commonly to provide a default console (ie from PROM variables) when
 853  * the user has not supplied one.
 854  */
 855 int add_preferred_console(char *name, int idx, char *options)
 856 {
 857         return __add_preferred_console(name, idx, options, NULL);
 858 }
 859
 860 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 861 {
 862         struct console_cmdline *c;
 863         int i;
 864
 865         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 866                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 867                           console_cmdline[i].index == idx) {
 868                                 c = &console_cmdline[i];
 869                                 strlcpy(c->name, name_new, sizeof(c->name));
 870                                 c->name[sizeof(c->name) - 1] = 0;
 871                                 c->options = options;
 872                                 c->index = idx_new;
 873                                 return i;
 874                 }
 875         /* not found */
 876         return -1;
 877 }
 878
 879 int console_suspend_enabled = 1;
 880 EXPORT_SYMBOL(console_suspend_enabled);
 881
 882 static int __init console_suspend_disable(char *str)
 883 {
 884         console_suspend_enabled = 0;
 885         return 1;
 886 }
 887 __setup("no_console_suspend", console_suspend_disable);
 888
 889 /**
 890  * suspend_console - suspend the console subsystem
 891  *
 892  * This disables printk() while we go into suspend states
 893  */
 894 void suspend_console(void)
 895 {
 896         if (!console_suspend_enabled)
 897                 return;
 898         printk("Suspending console(s) (use no_console_suspend to debug)\n");
 899         acquire_console_sem();
 900         console_suspended = 1;
 901 }
 902
 903 void resume_console(void)
 904 {
 905         if (!console_suspend_enabled)
 906                 return;
 907         console_suspended = 0;
 908         release_console_sem();
 909 }
 910
 911 /**
 912  * acquire_console_sem - lock the console system for exclusive use.
 913  *
 914  * Acquires a semaphore which guarantees that the caller has
 915  * exclusive access to the console system and the console_drivers list.
 916  *
 917  * Can sleep, returns nothing.
 918  */
 919 void acquire_console_sem(void)
 920 {
 921         BUG_ON(in_interrupt());
 922         if (console_suspended) {
 923                 down(&secondary_console_sem);
 924                 return;
 925         }
 926         down(&console_sem);
 927         console_locked = 1;
 928         console_may_schedule = 1;
 929 }
 930 EXPORT_SYMBOL(acquire_console_sem);
 931
 932 int try_acquire_console_sem(void)
 933 {
 934         if (down_trylock(&console_sem))
 935                 return -1;
 936         console_locked = 1;
 937         console_may_schedule = 0;
 938         return 0;
 939 }
 940 EXPORT_SYMBOL(try_acquire_console_sem);
 941
 942 int is_console_locked(void)
 943 {
 944         return console_locked;
 945 }
 946
 947 static DEFINE_PER_CPU(int, printk_pending);
 948
 949 void printk_tick(void)
 950 {
 951         if (__get_cpu_var(printk_pending)) {
 952                 __get_cpu_var(printk_pending) = 0;
 953                 wake_up_interruptible(&log_wait);
 954         }
 955 }
 956
 957 int printk_needs_cpu(int cpu)
 958 {
 959         return per_cpu(printk_pending, cpu);
 960 }
 961
 962 void wake_up_klogd(void)
 963 {
 964         if (waitqueue_active(&log_wait))
 965                 __raw_get_cpu_var(printk_pending) = 1;
 966 }
 967
 968 /**
 969  * release_console_sem - unlock the console system
 970  *
 971  * Releases the semaphore which the caller holds on the console system
 972  * and the console driver list.
 973  *
 974  * While the semaphore was held, console output may have been buffered
 975  * by printk().  If this is the case, release_console_sem() emits
 976  * the output prior to releasing the semaphore.
 977  *
 978  * If there is output waiting for klogd, we wake it up.
 979  *
 980  * release_console_sem() may be called from any context.
 981  */
 982 void release_console_sem(void)
 983 {
 984         unsigned long flags;
 985         unsigned _con_start, _log_end;
 986         unsigned wake_klogd = 0;
 987
 988         if (console_suspended) {
 989                 up(&secondary_console_sem);
 990                 return;
 991         }
 992
 993         console_may_schedule = 0;
 994
 995         for ( ; ; ) {
 996                 spin_lock_irqsave(&logbuf_lock, flags);
 997                 wake_klogd |= log_start - log_end;
 998                 if (con_start == log_end)
 999                         break;                  /* Nothing to print */
1000                 _con_start = con_start;
1001                 _log_end = log_end;
1002                 con_start = log_end;            /* Flush */
1003                 spin_unlock(&logbuf_lock);
1004                 stop_critical_timings();        /* don't trace print latency */
1005                 call_console_drivers(_con_start, _log_end);
1006                 start_critical_timings();
1007                 local_irq_restore(flags);
1008         }
1009         console_locked = 0;
1010         up(&console_sem);
1011         spin_unlock_irqrestore(&logbuf_lock, flags);
1012         if (wake_klogd)
1013                 wake_up_klogd();
1014 }
1015 EXPORT_SYMBOL(release_console_sem);
1016
1017 /**
1018  * console_conditional_schedule - yield the CPU if required
1019  *
1020  * If the console code is currently allowed to sleep, and
1021  * if this CPU should yield the CPU to another task, do
1022  * so here.
1023  *
1024  * Must be called within acquire_console_sem().
1025  */
1026 void __sched console_conditional_schedule(void)
1027 {
1028         if (console_may_schedule)
1029                 cond_resched();
1030 }
1031 EXPORT_SYMBOL(console_conditional_schedule);
1032
1033 void console_print(const char *s)
1034 {
1035         printk(KERN_EMERG "%s", s);
1036 }
1037 EXPORT_SYMBOL(console_print);
1038
1039 void console_unblank(void)
1040 {
1041         struct console *c;
1042
1043         /*
1044          * console_unblank can no longer be called in interrupt context unless
1045          * oops_in_progress is set to 1..
1046          */
1047         if (oops_in_progress) {
1048                 if (down_trylock(&console_sem) != 0)
1049                         return;
1050         } else
1051                 acquire_console_sem();
1052
1053         console_locked = 1;
1054         console_may_schedule = 0;
1055         for (c = console_drivers; c != NULL; c = c->next)
1056                 if ((c->flags & CON_ENABLED) && c->unblank)
1057                         c->unblank();
1058         release_console_sem();
1059 }
1060
1061 /*
1062  * Return the console tty driver structure and its associated index
1063  */
1064 struct tty_driver *console_device(int *index)
1065 {
1066         struct console *c;
1067         struct tty_driver *driver = NULL;
1068
1069         acquire_console_sem();
1070         for (c = console_drivers; c != NULL; c = c->next) {
1071                 if (!c->device)
1072                         continue;
1073                 driver = c->device(c, index);
1074                 if (driver)
1075                         break;
1076         }
1077         release_console_sem();
1078         return driver;
1079 }
1080
1081 /*
1082  * Prevent further output on the passed console device so that (for example)
1083  * serial drivers can disable console output before suspending a port, and can
1084  * re-enable output afterwards.
1085  */
1086 void console_stop(struct console *console)
1087 {
1088         acquire_console_sem();
1089         console->flags &= ~CON_ENABLED;
1090         release_console_sem();
1091 }
1092 EXPORT_SYMBOL(console_stop);
1093
1094 void console_start(struct console *console)
1095 {
1096         acquire_console_sem();
1097         console->flags |= CON_ENABLED;
1098         release_console_sem();
1099 }
1100 EXPORT_SYMBOL(console_start);
1101
1102 /*
1103  * The console driver calls this routine during kernel initialization
1104  * to register the console printing procedure with printk() and to
1105  * print any messages that were printed by the kernel before the
1106  * console driver was initialized.
1107  */
1108 void register_console(struct console *console)
1109 {
1110         int i;
1111         unsigned long flags;
1112         struct console *bootconsole = NULL;
1113
1114         if (console_drivers) {
1115                 if (console->flags & CON_BOOT)
1116                         return;
1117                 if (console_drivers->flags & CON_BOOT)
1118                         bootconsole = console_drivers;
1119         }
1120
1121         if (preferred_console < 0 || bootconsole || !console_drivers)
1122                 preferred_console = selected_console;
1123
1124         if (console->early_setup)
1125                 console->early_setup();
1126
1127         /*
1128          *      See if we want to use this console driver. If we
1129          *      didn't select a console we take the first one
1130          *      that registers here.
1131          */
1132         if (preferred_console < 0) {
1133                 if (console->index < 0)
1134                         console->index = 0;
1135                 if (console->setup == NULL ||
1136                     console->setup(console, NULL) == 0) {
1137                         console->flags |= CON_ENABLED;
1138                         if (console->device) {
1139                                 console->flags |= CON_CONSDEV;
1140                                 preferred_console = 0;
1141                         }
1142                 }
1143         }
1144
1145         /*
1146          *      See if this console matches one we selected on
1147          *      the command line.
1148          */
1149         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1150                         i++) {
1151                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1152                         continue;
1153                 if (console->index >= 0 &&
1154                     console->index != console_cmdline[i].index)
1155                         continue;
1156                 if (console->index < 0)
1157                         console->index = console_cmdline[i].index;
1158 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1159                 if (console_cmdline[i].brl_options) {
1160                         console->flags |= CON_BRL;
1161                         braille_register_console(console,
1162                                         console_cmdline[i].index,
1163                                         console_cmdline[i].options,
1164                                         console_cmdline[i].brl_options);
1165                         return;
1166                 }
1167 #endif
1168                 if (console->setup &&
1169                     console->setup(console, console_cmdline[i].options) != 0)
1170                         break;
1171                 console->flags |= CON_ENABLED;
1172                 console->index = console_cmdline[i].index;
1173                 if (i == selected_console) {
1174                         console->flags |= CON_CONSDEV;
1175                         preferred_console = selected_console;
1176                 }
1177                 break;
1178         }
1179
1180         if (!(console->flags & CON_ENABLED))
1181                 return;
1182
1183         if (bootconsole && (console->flags & CON_CONSDEV)) {
1184                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1185                        bootconsole->name, bootconsole->index,
1186                        console->name, console->index);
1187                 unregister_console(bootconsole);
1188                 console->flags &= ~CON_PRINTBUFFER;
1189         } else {
1190                 printk(KERN_INFO "console [%s%d] enabled\n",
1191                        console->name, console->index);
1192         }
1193
1194         /*
1195          *      Put this console in the list - keep the
1196          *      preferred driver at the head of the list.
1197          */
1198         acquire_console_sem();
1199         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1200                 console->next = console_drivers;
1201                 console_drivers = console;
1202                 if (console->next)
1203                         console->next->flags &= ~CON_CONSDEV;
1204         } else {
1205                 console->next = console_drivers->next;
1206                 console_drivers->next = console;
1207         }
1208         if (console->flags & CON_PRINTBUFFER) {
1209                 /*
1210                  * release_console_sem() will print out the buffered messages
1211                  * for us.
1212                  */
1213                 spin_lock_irqsave(&logbuf_lock, flags);
1214                 con_start = log_start;
1215                 spin_unlock_irqrestore(&logbuf_lock, flags);
1216         }
1217         release_console_sem();
1218 }
1219 EXPORT_SYMBOL(register_console);
1220
1221 int unregister_console(struct console *console)
1222 {
1223         struct console *a, *b;
1224         int res = 1;
1225
1226 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1227         if (console->flags & CON_BRL)
1228                 return braille_unregister_console(console);
1229 #endif
1230
1231         acquire_console_sem();
1232         if (console_drivers == console) {
1233                 console_drivers=console->next;
1234                 res = 0;
1235         } else if (console_drivers) {
1236                 for (a=console_drivers->next, b=console_drivers ;
1237                      a; b=a, a=b->next) {
1238                         if (a == console) {
1239                                 b->next = a->next;
1240                                 res = 0;
1241                                 break;
1242                         }
1243                 }
1244         }
1245
1246         /*
1247          * If this isn't the last console and it has CON_CONSDEV set, we
1248          * need to set it on the next preferred console.
1249          */
1250         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1251                 console_drivers->flags |= CON_CONSDEV;
1252
1253         release_console_sem();
1254         return res;
1255 }
1256 EXPORT_SYMBOL(unregister_console);
1257
1258 static int __init disable_boot_consoles(void)
1259 {
1260         if (console_drivers != NULL) {
1261                 if (console_drivers->flags & CON_BOOT) {
1262                         printk(KERN_INFO "turn off boot console %s%d\n",
1263                                 console_drivers->name, console_drivers->index);
1264                         return unregister_console(console_drivers);
1265                 }
1266         }
1267         return 0;
1268 }
1269 late_initcall(disable_boot_consoles);
1270
1271 #if defined CONFIG_PRINTK
1272
1273 /*
1274  * printk rate limiting, lifted from the networking subsystem.
1275  *
1276  * This enforces a rate limit: not more than 10 kernel messages
1277  * every 5s to make a denial-of-service attack impossible.
1278  */
1279 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1280
1281 int printk_ratelimit(void)
1282 {
1283         return __ratelimit(&printk_ratelimit_state);
1284 }
1285 EXPORT_SYMBOL(printk_ratelimit);
1286
1287 /**
1288  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1289  * @caller_jiffies: pointer to caller's state
1290  * @interval_msecs: minimum interval between prints
1291  *
1292  * printk_timed_ratelimit() returns true if more than @interval_msecs
1293  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1294  * returned true.
1295  */
1296 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1297                         unsigned int interval_msecs)
1298 {
1299         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1300                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1301                 return true;
1302         }
1303         return false;
1304 }
1305 EXPORT_SYMBOL(printk_timed_ratelimit);
1306 #endif