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 struct console *console_drivers;
  81 EXPORT_SYMBOL_GPL(console_drivers);
  82
  83 /*
  84  * This is used for debugging the mess that is the VT code by
  85  * keeping track if we have the console semaphore held. It's
  86  * definitely not the perfect debug tool (we don't know if _WE_
  87  * hold it are racing, but it helps tracking those weird code
  88  * path in the console code where we end up in places I want
  89  * locked without the console sempahore held
  90  */
  91 static int console_locked, console_suspended;
  92
  93 /*
  94  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
  95  * It is also used in interesting ways to provide interlocking in
  96  * release_console_sem().
  97  */
  98 static DEFINE_SPINLOCK(logbuf_lock);
  99
 100 #define LOG_BUF_MASK (log_buf_len-1)
 101 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
 102
 103 /*
 104  * The indices into log_buf are not constrained to log_buf_len - they
 105  * must be masked before subscripting
 106  */
 107 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
 108 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
 109 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 110
 111 /*
 112  *      Array of consoles built from command line options (console=)
 113  */
 114 struct console_cmdline
 115 {
 116         char    name[8];                        /* Name of the driver       */
 117         int     index;                          /* Minor dev. to use        */
 118         char    *options;                       /* Options for the driver   */
 119 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 120         char    *brl_options;                   /* Options for braille driver */
 121 #endif
 122 };
 123
 124 #define MAX_CMDLINECONSOLES 8
 125
 126 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 127 static int selected_console = -1;
 128 static int preferred_console = -1;
 129 int console_set_on_cmdline;
 130 EXPORT_SYMBOL(console_set_on_cmdline);
 131
 132 /* Flag: console code may call schedule() */
 133 static int console_may_schedule;
 134
 135 #ifdef CONFIG_PRINTK
 136
 137 static char __log_buf[__LOG_BUF_LEN];
 138 static char *log_buf = __log_buf;
 139 static int log_buf_len = __LOG_BUF_LEN;
 140 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 141
 142 static int __init log_buf_len_setup(char *str)
 143 {
 144         unsigned size = memparse(str, &str);
 145         unsigned long flags;
 146
 147         if (size)
 148                 size = roundup_pow_of_two(size);
 149         if (size > log_buf_len) {
 150                 unsigned start, dest_idx, offset;
 151                 char *new_log_buf;
 152
 153                 new_log_buf = alloc_bootmem(size);
 154                 if (!new_log_buf) {
 155                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 156                         goto out;
 157                 }
 158
 159                 spin_lock_irqsave(&logbuf_lock, flags);
 160                 log_buf_len = size;
 161                 log_buf = new_log_buf;
 162
 163                 offset = start = min(con_start, log_start);
 164                 dest_idx = 0;
 165                 while (start != log_end) {
 166                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 167                         start++;
 168                         dest_idx++;
 169                 }
 170                 log_start -= offset;
 171                 con_start -= offset;
 172                 log_end -= offset;
 173                 spin_unlock_irqrestore(&logbuf_lock, flags);
 174
 175                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 176         }
 177 out:
 178         return 1;
 179 }
 180
 181 __setup("log_buf_len=", log_buf_len_setup);
 182
 183 #ifdef CONFIG_BOOT_PRINTK_DELAY
 184
 185 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 186 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
 187
 188 static int __init boot_delay_setup(char *str)
 189 {
 190         unsigned long lpj;
 191         unsigned long long loops_per_msec;
 192
 193         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 194         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 195
 196         get_option(&str, &boot_delay);
 197         if (boot_delay > 10 * 1000)
 198                 boot_delay = 0;
 199
 200         printk_delay_msec = loops_per_msec;
 201         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 202                 "HZ: %d, printk_delay_msec: %llu\n",
 203                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
 204         return 1;
 205 }
 206 __setup("boot_delay=", boot_delay_setup);
 207
 208 static void boot_delay_msec(void)
 209 {
 210         unsigned long long k;
 211         unsigned long timeout;
 212
 213         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 214                 return;
 215
 216         k = (unsigned long long)printk_delay_msec * boot_delay;
 217
 218         timeout = jiffies + msecs_to_jiffies(boot_delay);
 219         while (k) {
 220                 k--;
 221                 cpu_relax();
 222                 /*
 223                  * use (volatile) jiffies to prevent
 224                  * compiler reduction; loop termination via jiffies
 225                  * is secondary and may or may not happen.
 226                  */
 227                 if (time_after(jiffies, timeout))
 228                         break;
 229                 touch_nmi_watchdog();
 230         }
 231 }
 232 #else
 233 static inline void boot_delay_msec(void)
 234 {
 235 }
 236 #endif
 237
 238 /*
 239  * Commands to do_syslog:
 240  *
 241  *      0 -- Close the log.  Currently a NOP.
 242  *      1 -- Open the log. Currently a NOP.
 243  *      2 -- Read from the log.
 244  *      3 -- Read all messages remaining in the ring buffer.
 245  *      4 -- Read and clear all messages remaining in the ring buffer
 246  *      5 -- Clear ring buffer.
 247  *      6 -- Disable printk's to console
 248  *      7 -- Enable printk's to console
 249  *      8 -- Set level of messages printed to console
 250  *      9 -- Return number of unread characters in the log buffer
 251  *     10 -- Return size of the log buffer
 252  */
 253 int do_syslog(int type, char __user *buf, int len)
 254 {
 255         unsigned i, j, limit, count;
 256         int do_clear = 0;
 257         char c;
 258         int error = 0;
 259
 260         error = security_syslog(type);
 261         if (error)
 262                 return error;
 263
 264         switch (type) {
 265         case 0:         /* Close log */
 266                 break;
 267         case 1:         /* Open log */
 268                 break;
 269         case 2:         /* Read from log */
 270                 error = -EINVAL;
 271                 if (!buf || len < 0)
 272                         goto out;
 273                 error = 0;
 274                 if (!len)
 275                         goto out;
 276                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 277                         error = -EFAULT;
 278                         goto out;
 279                 }
 280                 error = wait_event_interruptible(log_wait,
 281                                                         (log_start - log_end));
 282                 if (error)
 283                         goto out;
 284                 i = 0;
 285                 spin_lock_irq(&logbuf_lock);
 286                 while (!error && (log_start != log_end) && i < len) {
 287                         c = LOG_BUF(log_start);
 288                         log_start++;
 289                         spin_unlock_irq(&logbuf_lock);
 290                         error = __put_user(c,buf);
 291                         buf++;
 292                         i++;
 293                         cond_resched();
 294                         spin_lock_irq(&logbuf_lock);
 295                 }
 296                 spin_unlock_irq(&logbuf_lock);
 297                 if (!error)
 298                         error = i;
 299                 break;
 300         case 4:         /* Read/clear last kernel messages */
 301                 do_clear = 1;
 302                 /* FALL THRU */
 303         case 3:         /* Read last kernel messages */
 304                 error = -EINVAL;
 305                 if (!buf || len < 0)
 306                         goto out;
 307                 error = 0;
 308                 if (!len)
 309                         goto out;
 310                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 311                         error = -EFAULT;
 312                         goto out;
 313                 }
 314                 count = len;
 315                 if (count > log_buf_len)
 316                         count = log_buf_len;
 317                 spin_lock_irq(&logbuf_lock);
 318                 if (count > logged_chars)
 319                         count = logged_chars;
 320                 if (do_clear)
 321                         logged_chars = 0;
 322                 limit = log_end;
 323                 /*
 324                  * __put_user() could sleep, and while we sleep
 325                  * printk() could overwrite the messages
 326                  * we try to copy to user space. Therefore
 327                  * the messages are copied in reverse. <manfreds>
 328                  */
 329                 for (i = 0; i < count && !error; i++) {
 330                         j = limit-1-i;
 331                         if (j + log_buf_len < log_end)
 332                                 break;
 333                         c = LOG_BUF(j);
 334                         spin_unlock_irq(&logbuf_lock);
 335                         error = __put_user(c,&buf[count-1-i]);
 336                         cond_resched();
 337                         spin_lock_irq(&logbuf_lock);
 338                 }
 339                 spin_unlock_irq(&logbuf_lock);
 340                 if (error)
 341                         break;
 342                 error = i;
 343                 if (i != count) {
 344                         int offset = count-error;
 345                         /* buffer overflow during copy, correct user buffer. */
 346                         for (i = 0; i < error; i++) {
 347                                 if (__get_user(c,&buf[i+offset]) ||
 348                                     __put_user(c,&buf[i])) {
 349                                         error = -EFAULT;
 350                                         break;
 351                                 }
 352                                 cond_resched();
 353                         }
 354                 }
 355                 break;
 356         case 5:         /* Clear ring buffer */
 357                 logged_chars = 0;
 358                 break;
 359         case 6:         /* Disable logging to console */
 360                 console_loglevel = minimum_console_loglevel;
 361                 break;
 362         case 7:         /* Enable logging to console */
 363                 console_loglevel = default_console_loglevel;
 364                 break;
 365         case 8:         /* Set level of messages printed to console */
 366                 error = -EINVAL;
 367                 if (len < 1 || len > 8)
 368                         goto out;
 369                 if (len < minimum_console_loglevel)
 370                         len = minimum_console_loglevel;
 371                 console_loglevel = len;
 372                 error = 0;
 373                 break;
 374         case 9:         /* Number of chars in the log buffer */
 375                 error = log_end - log_start;
 376                 break;
 377         case 10:        /* Size of the log buffer */
 378                 error = log_buf_len;
 379                 break;
 380         default:
 381                 error = -EINVAL;
 382                 break;
 383         }
 384 out:
 385         return error;
 386 }
 387
 388 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
 389 {
 390         return do_syslog(type, buf, len);
 391 }
 392
 393 /*
 394  * Call the console drivers on a range of log_buf
 395  */
 396 static void __call_console_drivers(unsigned start, unsigned end)
 397 {
 398         struct console *con;
 399
 400         for (con = console_drivers; con; con = con->next) {
 401                 if ((con->flags & CON_ENABLED) && con->write &&
 402                                 (cpu_online(smp_processor_id()) ||
 403                                 (con->flags & CON_ANYTIME)))
 404                         con->write(con, &LOG_BUF(start), end - start);
 405         }
 406 }
 407
 408 static int __read_mostly ignore_loglevel;
 409
 410 static int __init ignore_loglevel_setup(char *str)
 411 {
 412         ignore_loglevel = 1;
 413         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 414
 415         return 0;
 416 }
 417
 418 early_param("ignore_loglevel", ignore_loglevel_setup);
 419
 420 /*
 421  * Write out chars from start to end - 1 inclusive
 422  */
 423 static void _call_console_drivers(unsigned start,
 424                                 unsigned end, int msg_log_level)
 425 {
 426         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 427                         console_drivers && start != end) {
 428                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 429                         /* wrapped write */
 430                         __call_console_drivers(start & LOG_BUF_MASK,
 431                                                 log_buf_len);
 432                         __call_console_drivers(0, end & LOG_BUF_MASK);
 433                 } else {
 434                         __call_console_drivers(start, end);
 435                 }
 436         }
 437 }
 438
 439 /*
 440  * Call the console drivers, asking them to write out
 441  * log_buf[start] to log_buf[end - 1].
 442  * The console_sem must be held.
 443  */
 444 static void call_console_drivers(unsigned start, unsigned end)
 445 {
 446         unsigned cur_index, start_print;
 447         static int msg_level = -1;
 448
 449         BUG_ON(((int)(start - end)) > 0);
 450
 451         cur_index = start;
 452         start_print = start;
 453         while (cur_index != end) {
 454                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 455                                 LOG_BUF(cur_index + 0) == '<' &&
 456                                 LOG_BUF(cur_index + 1) >= '0' &&
 457                                 LOG_BUF(cur_index + 1) <= '7' &&
 458                                 LOG_BUF(cur_index + 2) == '>') {
 459                         msg_level = LOG_BUF(cur_index + 1) - '0';
 460                         cur_index += 3;
 461                         start_print = cur_index;
 462                 }
 463                 while (cur_index != end) {
 464                         char c = LOG_BUF(cur_index);
 465
 466                         cur_index++;
 467                         if (c == '\n') {
 468                                 if (msg_level < 0) {
 469                                         /*
 470                                          * printk() has already given us loglevel tags in
 471                                          * the buffer.  This code is here in case the
 472                                          * log buffer has wrapped right round and scribbled
 473                                          * on those tags
 474                                          */
 475                                         msg_level = default_message_loglevel;
 476                                 }
 477                                 _call_console_drivers(start_print, cur_index, msg_level);
 478                                 msg_level = -1;
 479                                 start_print = cur_index;
 480                                 break;
 481                         }
 482                 }
 483         }
 484         _call_console_drivers(start_print, end, msg_level);
 485 }
 486
 487 static void emit_log_char(char c)
 488 {
 489         LOG_BUF(log_end) = c;
 490         log_end++;
 491         if (log_end - log_start > log_buf_len)
 492                 log_start = log_end - log_buf_len;
 493         if (log_end - con_start > log_buf_len)
 494                 con_start = log_end - log_buf_len;
 495         if (logged_chars < log_buf_len)
 496                 logged_chars++;
 497 }
 498
 499 /*
 500  * Zap console related locks when oopsing. Only zap at most once
 501  * every 10 seconds, to leave time for slow consoles to print a
 502  * full oops.
 503  */
 504 static void zap_locks(void)
 505 {
 506         static unsigned long oops_timestamp;
 507
 508         if (time_after_eq(jiffies, oops_timestamp) &&
 509                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 510                 return;
 511
 512         oops_timestamp = jiffies;
 513
 514         /* If a crash is occurring, make sure we can't deadlock */
 515         spin_lock_init(&logbuf_lock);
 516         /* And make sure that we print immediately */
 517         init_MUTEX(&console_sem);
 518 }
 519
 520 #if defined(CONFIG_PRINTK_TIME)
 521 static int printk_time = 1;
 522 #else
 523 static int printk_time = 0;
 524 #endif
 525 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 526
 527 /* Check if we have any console registered that can be called early in boot. */
 528 static int have_callable_console(void)
 529 {
 530         struct console *con;
 531
 532         for (con = console_drivers; con; con = con->next)
 533                 if (con->flags & CON_ANYTIME)
 534                         return 1;
 535
 536         return 0;
 537 }
 538
 539 /**
 540  * printk - print a kernel message
 541  * @fmt: format string
 542  *
 543  * This is printk().  It can be called from any context.  We want it to work.
 544  *
 545  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 546  * call the console drivers.  If we fail to get the semaphore we place the output
 547  * into the log buffer and return.  The current holder of the console_sem will
 548  * notice the new output in release_console_sem() and will send it to the
 549  * consoles before releasing the semaphore.
 550  *
 551  * One effect of this deferred printing is that code which calls printk() and
 552  * then changes console_loglevel may break. This is because console_loglevel
 553  * is inspected when the actual printing occurs.
 554  *
 555  * See also:
 556  * printf(3)
 557  *
 558  * See the vsnprintf() documentation for format string extensions over C99.
 559  */
 560
 561 asmlinkage int printk(const char *fmt, ...)
 562 {
 563         va_list args;
 564         int r;
 565
 566         va_start(args, fmt);
 567         r = vprintk(fmt, args);
 568         va_end(args);
 569
 570         return r;
 571 }
 572
 573 /* cpu currently holding logbuf_lock */
 574 static volatile unsigned int printk_cpu = UINT_MAX;
 575
 576 /*
 577  * Can we actually use the console at this time on this cpu?
 578  *
 579  * Console drivers may assume that per-cpu resources have
 580  * been allocated. So unless they're explicitly marked as
 581  * being able to cope (CON_ANYTIME) don't call them until
 582  * this CPU is officially up.
 583  */
 584 static inline int can_use_console(unsigned int cpu)
 585 {
 586         return cpu_online(cpu) || have_callable_console();
 587 }
 588
 589 /*
 590  * Try to get console ownership to actually show the kernel
 591  * messages from a 'printk'. Return true (and with the
 592  * console_semaphore held, and 'console_locked' set) if it
 593  * is successful, false otherwise.
 594  *
 595  * This gets called with the 'logbuf_lock' spinlock held and
 596  * interrupts disabled. It should return with 'lockbuf_lock'
 597  * released but interrupts still disabled.
 598  */
 599 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 600 {
 601         int retval = 0;
 602
 603         if (!try_acquire_console_sem()) {
 604                 retval = 1;
 605
 606                 /*
 607                  * If we can't use the console, we need to release
 608                  * the console semaphore by hand to avoid flushing
 609                  * the buffer. We need to hold the console semaphore
 610                  * in order to do this test safely.
 611                  */
 612                 if (!can_use_console(cpu)) {
 613                         console_locked = 0;
 614                         up(&console_sem);
 615                         retval = 0;
 616                 }
 617         }
 618         printk_cpu = UINT_MAX;
 619         spin_unlock(&logbuf_lock);
 620         return retval;
 621 }
 622 static const char recursion_bug_msg [] =
 623                 KERN_CRIT "BUG: recent printk recursion!\n";
 624 static int recursion_bug;
 625 static int new_text_line = 1;
 626 static char printk_buf[1024];
 627
 628 asmlinkage int vprintk(const char *fmt, va_list args)
 629 {
 630         int printed_len = 0;
 631         int current_log_level = default_message_loglevel;
 632         unsigned long flags;
 633         int this_cpu;
 634         char *p;
 635
 636         boot_delay_msec();
 637
 638         preempt_disable();
 639         /* This stops the holder of console_sem just where we want him */
 640         raw_local_irq_save(flags);
 641         this_cpu = smp_processor_id();
 642
 643         /*
 644          * Ouch, printk recursed into itself!
 645          */
 646         if (unlikely(printk_cpu == this_cpu)) {
 647                 /*
 648                  * If a crash is occurring during printk() on this CPU,
 649                  * then try to get the crash message out but make sure
 650                  * we can't deadlock. Otherwise just return to avoid the
 651                  * recursion and return - but flag the recursion so that
 652                  * it can be printed at the next appropriate moment:
 653                  */
 654                 if (!oops_in_progress) {
 655                         recursion_bug = 1;
 656                         goto out_restore_irqs;
 657                 }
 658                 zap_locks();
 659         }
 660
 661         lockdep_off();
 662         spin_lock(&logbuf_lock);
 663         printk_cpu = this_cpu;
 664
 665         if (recursion_bug) {
 666                 recursion_bug = 0;
 667                 strcpy(printk_buf, recursion_bug_msg);
 668                 printed_len = strlen(recursion_bug_msg);
 669         }
 670         /* Emit the output into the temporary buffer */
 671         printed_len += vscnprintf(printk_buf + printed_len,
 672                                   sizeof(printk_buf) - printed_len, fmt, args);
 673
 674 #ifdef  CONFIG_DEBUG_LL
 675         printascii(printk_buf);
 676 #endif
 677
 678         /*
 679          * Copy the output into log_buf.  If the caller didn't provide
 680          * appropriate log level tags, we insert them here
 681          */
 682         for (p = printk_buf; *p; p++) {
 683                 if (new_text_line) {
 684                         /* If a token, set current_log_level and skip over */
 685                         if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
 686                             p[2] == '>') {
 687                                 current_log_level = p[1] - '0';
 688                                 p += 3;
 689                                 printed_len -= 3;
 690                         }
 691
 692                         /* Always output the token */
 693                         emit_log_char('<');
 694                         emit_log_char(current_log_level + '0');
 695                         emit_log_char('>');
 696                         printed_len += 3;
 697                         new_text_line = 0;
 698
 699                         if (printk_time) {
 700                                 /* Follow the token with the time */
 701                                 char tbuf[50], *tp;
 702                                 unsigned tlen;
 703                                 unsigned long long t;
 704                                 unsigned long nanosec_rem;
 705
 706                                 t = cpu_clock(printk_cpu);
 707                                 nanosec_rem = do_div(t, 1000000000);
 708                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 709                                                 (unsigned long) t,
 710                                                 nanosec_rem / 1000);
 711
 712                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 713                                         emit_log_char(*tp);
 714                                 printed_len += tlen;
 715                         }
 716
 717                         if (!*p)
 718                                 break;
 719                 }
 720
 721                 emit_log_char(*p);
 722                 if (*p == '\n')
 723                         new_text_line = 1;
 724         }
 725
 726         /*
 727          * Try to acquire and then immediately release the
 728          * console semaphore. The release will do all the
 729          * actual magic (print out buffers, wake up klogd,
 730          * etc).
 731          *
 732          * The acquire_console_semaphore_for_printk() function
 733          * will release 'logbuf_lock' regardless of whether it
 734          * actually gets the semaphore or not.
 735          */
 736         if (acquire_console_semaphore_for_printk(this_cpu))
 737                 release_console_sem();
 738
 739         lockdep_on();
 740 out_restore_irqs:
 741         raw_local_irq_restore(flags);
 742
 743         preempt_enable();
 744         return printed_len;
 745 }
 746 EXPORT_SYMBOL(printk);
 747 EXPORT_SYMBOL(vprintk);
 748
 749 #else
 750
 751 static void call_console_drivers(unsigned start, unsigned end)
 752 {
 753 }
 754
 755 #endif
 756
 757 static int __add_preferred_console(char *name, int idx, char *options,
 758                                    char *brl_options)
 759 {
 760         struct console_cmdline *c;
 761         int i;
 762
 763         /*
 764          *      See if this tty is not yet registered, and
 765          *      if we have a slot free.
 766          */
 767         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 768                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 769                           console_cmdline[i].index == idx) {
 770                                 if (!brl_options)
 771                                         selected_console = i;
 772                                 return 0;
 773                 }
 774         if (i == MAX_CMDLINECONSOLES)
 775                 return -E2BIG;
 776         if (!brl_options)
 777                 selected_console = i;
 778         c = &console_cmdline[i];
 779         strlcpy(c->name, name, sizeof(c->name));
 780         c->options = options;
 781 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 782         c->brl_options = brl_options;
 783 #endif
 784         c->index = idx;
 785         return 0;
 786 }
 787 /*
 788  * Set up a list of consoles.  Called from init/main.c
 789  */
 790 static int __init console_setup(char *str)
 791 {
 792         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 793         char *s, *options, *brl_options = NULL;
 794         int idx;
 795
 796 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 797         if (!memcmp(str, "brl,", 4)) {
 798                 brl_options = "";
 799                 str += 4;
 800         } else if (!memcmp(str, "brl=", 4)) {
 801                 brl_options = str + 4;
 802                 str = strchr(brl_options, ',');
 803                 if (!str) {
 804                         printk(KERN_ERR "need port name after brl=\n");
 805                         return 1;
 806                 }
 807                 *(str++) = 0;
 808         }
 809 #endif
 810
 811         /*
 812          * Decode str into name, index, options.
 813          */
 814         if (str[0] >= '0' && str[0] <= '9') {
 815                 strcpy(buf, "ttyS");
 816                 strncpy(buf + 4, str, sizeof(buf) - 5);
 817         } else {
 818                 strncpy(buf, str, sizeof(buf) - 1);
 819         }
 820         buf[sizeof(buf) - 1] = 0;
 821         if ((options = strchr(str, ',')) != NULL)
 822                 *(options++) = 0;
 823 #ifdef __sparc__
 824         if (!strcmp(str, "ttya"))
 825                 strcpy(buf, "ttyS0");
 826         if (!strcmp(str, "ttyb"))
 827                 strcpy(buf, "ttyS1");
 828 #endif
 829         for (s = buf; *s; s++)
 830                 if ((*s >= '0' && *s <= '9') || *s == ',')
 831                         break;
 832         idx = simple_strtoul(s, NULL, 10);
 833         *s = 0;
 834
 835         __add_preferred_console(buf, idx, options, brl_options);
 836         console_set_on_cmdline = 1;
 837         return 1;
 838 }
 839 __setup("console=", console_setup);
 840
 841 /**
 842  * add_preferred_console - add a device to the list of preferred consoles.
 843  * @name: device name
 844  * @idx: device index
 845  * @options: options for this console
 846  *
 847  * The last preferred console added will be used for kernel messages
 848  * and stdin/out/err for init.  Normally this is used by console_setup
 849  * above to handle user-supplied console arguments; however it can also
 850  * be used by arch-specific code either to override the user or more
 851  * commonly to provide a default console (ie from PROM variables) when
 852  * the user has not supplied one.
 853  */
 854 int add_preferred_console(char *name, int idx, char *options)
 855 {
 856         return __add_preferred_console(name, idx, options, NULL);
 857 }
 858
 859 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 860 {
 861         struct console_cmdline *c;
 862         int i;
 863
 864         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 865                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 866                           console_cmdline[i].index == idx) {
 867                                 c = &console_cmdline[i];
 868                                 strlcpy(c->name, name_new, sizeof(c->name));
 869                                 c->name[sizeof(c->name) - 1] = 0;
 870                                 c->options = options;
 871                                 c->index = idx_new;
 872                                 return i;
 873                 }
 874         /* not found */
 875         return -1;
 876 }
 877
 878 int console_suspend_enabled = 1;
 879 EXPORT_SYMBOL(console_suspend_enabled);
 880
 881 static int __init console_suspend_disable(char *str)
 882 {
 883         console_suspend_enabled = 0;
 884         return 1;
 885 }
 886 __setup("no_console_suspend", console_suspend_disable);
 887
 888 /**
 889  * suspend_console - suspend the console subsystem
 890  *
 891  * This disables printk() while we go into suspend states
 892  */
 893 void suspend_console(void)
 894 {
 895         if (!console_suspend_enabled)
 896                 return;
 897         printk("Suspending console(s) (use no_console_suspend to debug)\n");
 898         acquire_console_sem();
 899         console_suspended = 1;
 900         up(&console_sem);
 901 }
 902
 903 void resume_console(void)
 904 {
 905         if (!console_suspend_enabled)
 906                 return;
 907         down(&console_sem);
 908         console_suspended = 0;
 909         release_console_sem();
 910 }
 911
 912 /**
 913  * acquire_console_sem - lock the console system for exclusive use.
 914  *
 915  * Acquires a semaphore which guarantees that the caller has
 916  * exclusive access to the console system and the console_drivers list.
 917  *
 918  * Can sleep, returns nothing.
 919  */
 920 void acquire_console_sem(void)
 921 {
 922         BUG_ON(in_interrupt());
 923         down(&console_sem);
 924         if (console_suspended)
 925                 return;
 926         console_locked = 1;
 927         console_may_schedule = 1;
 928 }
 929 EXPORT_SYMBOL(acquire_console_sem);
 930
 931 int try_acquire_console_sem(void)
 932 {
 933         if (down_trylock(&console_sem))
 934                 return -1;
 935         if (console_suspended) {
 936                 up(&console_sem);
 937                 return -1;
 938         }
 939         console_locked = 1;
 940         console_may_schedule = 0;
 941         return 0;
 942 }
 943 EXPORT_SYMBOL(try_acquire_console_sem);
 944
 945 int is_console_locked(void)
 946 {
 947         return console_locked;
 948 }
 949
 950 static DEFINE_PER_CPU(int, printk_pending);
 951
 952 void printk_tick(void)
 953 {
 954         if (__get_cpu_var(printk_pending)) {
 955                 __get_cpu_var(printk_pending) = 0;
 956                 wake_up_interruptible(&log_wait);
 957         }
 958 }
 959
 960 int printk_needs_cpu(int cpu)
 961 {
 962         return per_cpu(printk_pending, cpu);
 963 }
 964
 965 void wake_up_klogd(void)
 966 {
 967         if (waitqueue_active(&log_wait))
 968                 __raw_get_cpu_var(printk_pending) = 1;
 969 }
 970
 971 /**
 972  * release_console_sem - unlock the console system
 973  *
 974  * Releases the semaphore which the caller holds on the console system
 975  * and the console driver list.
 976  *
 977  * While the semaphore was held, console output may have been buffered
 978  * by printk().  If this is the case, release_console_sem() emits
 979  * the output prior to releasing the semaphore.
 980  *
 981  * If there is output waiting for klogd, we wake it up.
 982  *
 983  * release_console_sem() may be called from any context.
 984  */
 985 void release_console_sem(void)
 986 {
 987         unsigned long flags;
 988         unsigned _con_start, _log_end;
 989         unsigned wake_klogd = 0;
 990
 991         if (console_suspended) {
 992                 up(&console_sem);
 993                 return;
 994         }
 995
 996         console_may_schedule = 0;
 997
 998         for ( ; ; ) {
 999                 spin_lock_irqsave(&logbuf_lock, flags);
1000                 wake_klogd |= log_start - log_end;
1001                 if (con_start == log_end)
1002                         break;                  /* Nothing to print */
1003                 _con_start = con_start;
1004                 _log_end = log_end;
1005                 con_start = log_end;            /* Flush */
1006                 spin_unlock(&logbuf_lock);
1007                 stop_critical_timings();        /* don't trace print latency */
1008                 call_console_drivers(_con_start, _log_end);
1009                 start_critical_timings();
1010                 local_irq_restore(flags);
1011         }
1012         console_locked = 0;
1013         up(&console_sem);
1014         spin_unlock_irqrestore(&logbuf_lock, flags);
1015         if (wake_klogd)
1016                 wake_up_klogd();
1017 }
1018 EXPORT_SYMBOL(release_console_sem);
1019
1020 /**
1021  * console_conditional_schedule - yield the CPU if required
1022  *
1023  * If the console code is currently allowed to sleep, and
1024  * if this CPU should yield the CPU to another task, do
1025  * so here.
1026  *
1027  * Must be called within acquire_console_sem().
1028  */
1029 void __sched console_conditional_schedule(void)
1030 {
1031         if (console_may_schedule)
1032                 cond_resched();
1033 }
1034 EXPORT_SYMBOL(console_conditional_schedule);
1035
1036 void console_print(const char *s)
1037 {
1038         printk(KERN_EMERG "%s", s);
1039 }
1040 EXPORT_SYMBOL(console_print);
1041
1042 void console_unblank(void)
1043 {
1044         struct console *c;
1045
1046         /*
1047          * console_unblank can no longer be called in interrupt context unless
1048          * oops_in_progress is set to 1..
1049          */
1050         if (oops_in_progress) {
1051                 if (down_trylock(&console_sem) != 0)
1052                         return;
1053         } else
1054                 acquire_console_sem();
1055
1056         console_locked = 1;
1057         console_may_schedule = 0;
1058         for (c = console_drivers; c != NULL; c = c->next)
1059                 if ((c->flags & CON_ENABLED) && c->unblank)
1060                         c->unblank();
1061         release_console_sem();
1062 }
1063
1064 /*
1065  * Return the console tty driver structure and its associated index
1066  */
1067 struct tty_driver *console_device(int *index)
1068 {
1069         struct console *c;
1070         struct tty_driver *driver = NULL;
1071
1072         acquire_console_sem();
1073         for (c = console_drivers; c != NULL; c = c->next) {
1074                 if (!c->device)
1075                         continue;
1076                 driver = c->device(c, index);
1077                 if (driver)
1078                         break;
1079         }
1080         release_console_sem();
1081         return driver;
1082 }
1083
1084 /*
1085  * Prevent further output on the passed console device so that (for example)
1086  * serial drivers can disable console output before suspending a port, and can
1087  * re-enable output afterwards.
1088  */
1089 void console_stop(struct console *console)
1090 {
1091         acquire_console_sem();
1092         console->flags &= ~CON_ENABLED;
1093         release_console_sem();
1094 }
1095 EXPORT_SYMBOL(console_stop);
1096
1097 void console_start(struct console *console)
1098 {
1099         acquire_console_sem();
1100         console->flags |= CON_ENABLED;
1101         release_console_sem();
1102 }
1103 EXPORT_SYMBOL(console_start);
1104
1105 /*
1106  * The console driver calls this routine during kernel initialization
1107  * to register the console printing procedure with printk() and to
1108  * print any messages that were printed by the kernel before the
1109  * console driver was initialized.
1110  */
1111 void register_console(struct console *console)
1112 {
1113         int i;
1114         unsigned long flags;
1115         struct console *bootconsole = NULL;
1116
1117         if (console_drivers) {
1118                 if (console->flags & CON_BOOT)
1119                         return;
1120                 if (console_drivers->flags & CON_BOOT)
1121                         bootconsole = console_drivers;
1122         }
1123
1124         if (preferred_console < 0 || bootconsole || !console_drivers)
1125                 preferred_console = selected_console;
1126
1127         if (console->early_setup)
1128                 console->early_setup();
1129
1130         /*
1131          *      See if we want to use this console driver. If we
1132          *      didn't select a console we take the first one
1133          *      that registers here.
1134          */
1135         if (preferred_console < 0) {
1136                 if (console->index < 0)
1137                         console->index = 0;
1138                 if (console->setup == NULL ||
1139                     console->setup(console, NULL) == 0) {
1140                         console->flags |= CON_ENABLED;
1141                         if (console->device) {
1142                                 console->flags |= CON_CONSDEV;
1143                                 preferred_console = 0;
1144                         }
1145                 }
1146         }
1147
1148         /*
1149          *      See if this console matches one we selected on
1150          *      the command line.
1151          */
1152         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1153                         i++) {
1154                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1155                         continue;
1156                 if (console->index >= 0 &&
1157                     console->index != console_cmdline[i].index)
1158                         continue;
1159                 if (console->index < 0)
1160                         console->index = console_cmdline[i].index;
1161 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1162                 if (console_cmdline[i].brl_options) {
1163                         console->flags |= CON_BRL;
1164                         braille_register_console(console,
1165                                         console_cmdline[i].index,
1166                                         console_cmdline[i].options,
1167                                         console_cmdline[i].brl_options);
1168                         return;
1169                 }
1170 #endif
1171                 if (console->setup &&
1172                     console->setup(console, console_cmdline[i].options) != 0)
1173                         break;
1174                 console->flags |= CON_ENABLED;
1175                 console->index = console_cmdline[i].index;
1176                 if (i == selected_console) {
1177                         console->flags |= CON_CONSDEV;
1178                         preferred_console = selected_console;
1179                 }
1180                 break;
1181         }
1182
1183         if (!(console->flags & CON_ENABLED))
1184                 return;
1185
1186         if (bootconsole && (console->flags & CON_CONSDEV)) {
1187                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1188                        bootconsole->name, bootconsole->index,
1189                        console->name, console->index);
1190                 unregister_console(bootconsole);
1191                 console->flags &= ~CON_PRINTBUFFER;
1192         } else {
1193                 printk(KERN_INFO "console [%s%d] enabled\n",
1194                        console->name, console->index);
1195         }
1196
1197         /*
1198          *      Put this console in the list - keep the
1199          *      preferred driver at the head of the list.
1200          */
1201         acquire_console_sem();
1202         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1203                 console->next = console_drivers;
1204                 console_drivers = console;
1205                 if (console->next)
1206                         console->next->flags &= ~CON_CONSDEV;
1207         } else {
1208                 console->next = console_drivers->next;
1209                 console_drivers->next = console;
1210         }
1211         if (console->flags & CON_PRINTBUFFER) {
1212                 /*
1213                  * release_console_sem() will print out the buffered messages
1214                  * for us.
1215                  */
1216                 spin_lock_irqsave(&logbuf_lock, flags);
1217                 con_start = log_start;
1218                 spin_unlock_irqrestore(&logbuf_lock, flags);
1219         }
1220         release_console_sem();
1221 }
1222 EXPORT_SYMBOL(register_console);
1223
1224 int unregister_console(struct console *console)
1225 {
1226         struct console *a, *b;
1227         int res = 1;
1228
1229 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1230         if (console->flags & CON_BRL)
1231                 return braille_unregister_console(console);
1232 #endif
1233
1234         acquire_console_sem();
1235         if (console_drivers == console) {
1236                 console_drivers=console->next;
1237                 res = 0;
1238         } else if (console_drivers) {
1239                 for (a=console_drivers->next, b=console_drivers ;
1240                      a; b=a, a=b->next) {
1241                         if (a == console) {
1242                                 b->next = a->next;
1243                                 res = 0;
1244                                 break;
1245                         }
1246                 }
1247         }
1248
1249         /*
1250          * If this isn't the last console and it has CON_CONSDEV set, we
1251          * need to set it on the next preferred console.
1252          */
1253         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1254                 console_drivers->flags |= CON_CONSDEV;
1255
1256         release_console_sem();
1257         return res;
1258 }
1259 EXPORT_SYMBOL(unregister_console);
1260
1261 static int __init disable_boot_consoles(void)
1262 {
1263         if (console_drivers != NULL) {
1264                 if (console_drivers->flags & CON_BOOT) {
1265                         printk(KERN_INFO "turn off boot console %s%d\n",
1266                                 console_drivers->name, console_drivers->index);
1267                         return unregister_console(console_drivers);
1268                 }
1269         }
1270         return 0;
1271 }
1272 late_initcall(disable_boot_consoles);
1273
1274 #if defined CONFIG_PRINTK
1275
1276 /*
1277  * printk rate limiting, lifted from the networking subsystem.
1278  *
1279  * This enforces a rate limit: not more than 10 kernel messages
1280  * every 5s to make a denial-of-service attack impossible.
1281  */
1282 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1283
1284 int printk_ratelimit(void)
1285 {
1286         return __ratelimit(&printk_ratelimit_state);
1287 }
1288 EXPORT_SYMBOL(printk_ratelimit);
1289
1290 /**
1291  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1292  * @caller_jiffies: pointer to caller's state
1293  * @interval_msecs: minimum interval between prints
1294  *
1295  * printk_timed_ratelimit() returns true if more than @interval_msecs
1296  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1297  * returned true.
1298  */
1299 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1300                         unsigned int interval_msecs)
1301 {
1302         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1303                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1304                 return true;
1305         }
1306         return false;
1307 }
1308 EXPORT_SYMBOL(printk_timed_ratelimit);
1309 #endif