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 /* printk's without a loglevel use this.. */
  48 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  49
  50 /* We show everything that is MORE important than this.. */
  51 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  52 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  53
  54 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  55
  56 int console_printk[4] = {
  57         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  58         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  59         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  60         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  61 };
  62
  63 /*
  64  * Low level drivers may need that to know if they can schedule in
  65  * their unblank() callback or not. So let's export it.
  66  */
  67 int oops_in_progress;
  68 EXPORT_SYMBOL(oops_in_progress);
  69
  70 /*
  71  * console_sem protects the console_drivers list, and also
  72  * provides serialisation for access to the entire console
  73  * driver system.
  74  */
  75 static DECLARE_MUTEX(console_sem);
  76 static DECLARE_MUTEX(secondary_console_sem);
  77 struct console *console_drivers;
  78 EXPORT_SYMBOL_GPL(console_drivers);
  79
  80 /*
  81  * This is used for debugging the mess that is the VT code by
  82  * keeping track if we have the console semaphore held. It's
  83  * definitely not the perfect debug tool (we don't know if _WE_
  84  * hold it are racing, but it helps tracking those weird code
  85  * path in the console code where we end up in places I want
  86  * locked without the console sempahore held
  87  */
  88 static int console_locked, console_suspended;
  89
  90 /*
  91  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
  92  * It is also used in interesting ways to provide interlocking in
  93  * release_console_sem().
  94  */
  95 static DEFINE_SPINLOCK(logbuf_lock);
  96
  97 #define LOG_BUF_MASK (log_buf_len-1)
  98 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
  99
 100 /*
 101  * The indices into log_buf are not constrained to log_buf_len - they
 102  * must be masked before subscripting
 103  */
 104 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
 105 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
 106 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 107
 108 /*
 109  *      Array of consoles built from command line options (console=)
 110  */
 111 struct console_cmdline
 112 {
 113         char    name[8];                        /* Name of the driver       */
 114         int     index;                          /* Minor dev. to use        */
 115         char    *options;                       /* Options for the driver   */
 116 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 117         char    *brl_options;                   /* Options for braille driver */
 118 #endif
 119 };
 120
 121 #define MAX_CMDLINECONSOLES 8
 122
 123 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 124 static int selected_console = -1;
 125 static int preferred_console = -1;
 126 int console_set_on_cmdline;
 127 EXPORT_SYMBOL(console_set_on_cmdline);
 128
 129 /* Flag: console code may call schedule() */
 130 static int console_may_schedule;
 131
 132 #ifdef CONFIG_PRINTK
 133
 134 static char __log_buf[__LOG_BUF_LEN];
 135 static char *log_buf = __log_buf;
 136 static int log_buf_len = __LOG_BUF_LEN;
 137 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 138
 139 static int __init log_buf_len_setup(char *str)
 140 {
 141         unsigned size = memparse(str, &str);
 142         unsigned long flags;
 143
 144         if (size)
 145                 size = roundup_pow_of_two(size);
 146         if (size > log_buf_len) {
 147                 unsigned start, dest_idx, offset;
 148                 char *new_log_buf;
 149
 150                 new_log_buf = alloc_bootmem(size);
 151                 if (!new_log_buf) {
 152                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 153                         goto out;
 154                 }
 155
 156                 spin_lock_irqsave(&logbuf_lock, flags);
 157                 log_buf_len = size;
 158                 log_buf = new_log_buf;
 159
 160                 offset = start = min(con_start, log_start);
 161                 dest_idx = 0;
 162                 while (start != log_end) {
 163                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 164                         start++;
 165                         dest_idx++;
 166                 }
 167                 log_start -= offset;
 168                 con_start -= offset;
 169                 log_end -= offset;
 170                 spin_unlock_irqrestore(&logbuf_lock, flags);
 171
 172                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 173         }
 174 out:
 175         return 1;
 176 }
 177
 178 __setup("log_buf_len=", log_buf_len_setup);
 179
 180 #ifdef CONFIG_BOOT_PRINTK_DELAY
 181
 182 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 183 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
 184
 185 static int __init boot_delay_setup(char *str)
 186 {
 187         unsigned long lpj;
 188         unsigned long long loops_per_msec;
 189
 190         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 191         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 192
 193         get_option(&str, &boot_delay);
 194         if (boot_delay > 10 * 1000)
 195                 boot_delay = 0;
 196
 197         printk_delay_msec = loops_per_msec;
 198         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 199                 "HZ: %d, printk_delay_msec: %llu\n",
 200                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
 201         return 1;
 202 }
 203 __setup("boot_delay=", boot_delay_setup);
 204
 205 static void boot_delay_msec(void)
 206 {
 207         unsigned long long k;
 208         unsigned long timeout;
 209
 210         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 211                 return;
 212
 213         k = (unsigned long long)printk_delay_msec * boot_delay;
 214
 215         timeout = jiffies + msecs_to_jiffies(boot_delay);
 216         while (k) {
 217                 k--;
 218                 cpu_relax();
 219                 /*
 220                  * use (volatile) jiffies to prevent
 221                  * compiler reduction; loop termination via jiffies
 222                  * is secondary and may or may not happen.
 223                  */
 224                 if (time_after(jiffies, timeout))
 225                         break;
 226                 touch_nmi_watchdog();
 227         }
 228 }
 229 #else
 230 static inline void boot_delay_msec(void)
 231 {
 232 }
 233 #endif
 234
 235 /*
 236  * Return the number of unread characters in the log buffer.
 237  */
 238 static int log_buf_get_len(void)
 239 {
 240         return logged_chars;
 241 }
 242
 243 /*
 244  * Copy a range of characters from the log buffer.
 245  */
 246 int log_buf_copy(char *dest, int idx, int len)
 247 {
 248         int ret, max;
 249         bool took_lock = false;
 250
 251         if (!oops_in_progress) {
 252                 spin_lock_irq(&logbuf_lock);
 253                 took_lock = true;
 254         }
 255
 256         max = log_buf_get_len();
 257         if (idx < 0 || idx >= max) {
 258                 ret = -1;
 259         } else {
 260                 if (len > max)
 261                         len = max;
 262                 ret = len;
 263                 idx += (log_end - max);
 264                 while (len-- > 0)
 265                         dest[len] = LOG_BUF(idx + len);
 266         }
 267
 268         if (took_lock)
 269                 spin_unlock_irq(&logbuf_lock);
 270
 271         return ret;
 272 }
 273
 274 /*
 275  * Commands to do_syslog:
 276  *
 277  *      0 -- Close the log.  Currently a NOP.
 278  *      1 -- Open the log. Currently a NOP.
 279  *      2 -- Read from the log.
 280  *      3 -- Read all messages remaining in the ring buffer.
 281  *      4 -- Read and clear all messages remaining in the ring buffer
 282  *      5 -- Clear ring buffer.
 283  *      6 -- Disable printk's to console
 284  *      7 -- Enable printk's to console
 285  *      8 -- Set level of messages printed to console
 286  *      9 -- Return number of unread characters in the log buffer
 287  *     10 -- Return size of the log buffer
 288  */
 289 int do_syslog(int type, char __user *buf, int len)
 290 {
 291         unsigned i, j, limit, count;
 292         int do_clear = 0;
 293         char c;
 294         int error = 0;
 295
 296         error = security_syslog(type);
 297         if (error)
 298                 return error;
 299
 300         switch (type) {
 301         case 0:         /* Close log */
 302                 break;
 303         case 1:         /* Open log */
 304                 break;
 305         case 2:         /* Read from log */
 306                 error = -EINVAL;
 307                 if (!buf || len < 0)
 308                         goto out;
 309                 error = 0;
 310                 if (!len)
 311                         goto out;
 312                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 313                         error = -EFAULT;
 314                         goto out;
 315                 }
 316                 error = wait_event_interruptible(log_wait,
 317                                                         (log_start - log_end));
 318                 if (error)
 319                         goto out;
 320                 i = 0;
 321                 spin_lock_irq(&logbuf_lock);
 322                 while (!error && (log_start != log_end) && i < len) {
 323                         c = LOG_BUF(log_start);
 324                         log_start++;
 325                         spin_unlock_irq(&logbuf_lock);
 326                         error = __put_user(c,buf);
 327                         buf++;
 328                         i++;
 329                         cond_resched();
 330                         spin_lock_irq(&logbuf_lock);
 331                 }
 332                 spin_unlock_irq(&logbuf_lock);
 333                 if (!error)
 334                         error = i;
 335                 break;
 336         case 4:         /* Read/clear last kernel messages */
 337                 do_clear = 1;
 338                 /* FALL THRU */
 339         case 3:         /* Read last kernel messages */
 340                 error = -EINVAL;
 341                 if (!buf || len < 0)
 342                         goto out;
 343                 error = 0;
 344                 if (!len)
 345                         goto out;
 346                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 347                         error = -EFAULT;
 348                         goto out;
 349                 }
 350                 count = len;
 351                 if (count > log_buf_len)
 352                         count = log_buf_len;
 353                 spin_lock_irq(&logbuf_lock);
 354                 if (count > logged_chars)
 355                         count = logged_chars;
 356                 if (do_clear)
 357                         logged_chars = 0;
 358                 limit = log_end;
 359                 /*
 360                  * __put_user() could sleep, and while we sleep
 361                  * printk() could overwrite the messages
 362                  * we try to copy to user space. Therefore
 363                  * the messages are copied in reverse. <manfreds>
 364                  */
 365                 for (i = 0; i < count && !error; i++) {
 366                         j = limit-1-i;
 367                         if (j + log_buf_len < log_end)
 368                                 break;
 369                         c = LOG_BUF(j);
 370                         spin_unlock_irq(&logbuf_lock);
 371                         error = __put_user(c,&buf[count-1-i]);
 372                         cond_resched();
 373                         spin_lock_irq(&logbuf_lock);
 374                 }
 375                 spin_unlock_irq(&logbuf_lock);
 376                 if (error)
 377                         break;
 378                 error = i;
 379                 if (i != count) {
 380                         int offset = count-error;
 381                         /* buffer overflow during copy, correct user buffer. */
 382                         for (i = 0; i < error; i++) {
 383                                 if (__get_user(c,&buf[i+offset]) ||
 384                                     __put_user(c,&buf[i])) {
 385                                         error = -EFAULT;
 386                                         break;
 387                                 }
 388                                 cond_resched();
 389                         }
 390                 }
 391                 break;
 392         case 5:         /* Clear ring buffer */
 393                 logged_chars = 0;
 394                 break;
 395         case 6:         /* Disable logging to console */
 396                 console_loglevel = minimum_console_loglevel;
 397                 break;
 398         case 7:         /* Enable logging to console */
 399                 console_loglevel = default_console_loglevel;
 400                 break;
 401         case 8:         /* Set level of messages printed to console */
 402                 error = -EINVAL;
 403                 if (len < 1 || len > 8)
 404                         goto out;
 405                 if (len < minimum_console_loglevel)
 406                         len = minimum_console_loglevel;
 407                 console_loglevel = len;
 408                 error = 0;
 409                 break;
 410         case 9:         /* Number of chars in the log buffer */
 411                 error = log_end - log_start;
 412                 break;
 413         case 10:        /* Size of the log buffer */
 414                 error = log_buf_len;
 415                 break;
 416         default:
 417                 error = -EINVAL;
 418                 break;
 419         }
 420 out:
 421         return error;
 422 }
 423
 424 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 425 {
 426         return do_syslog(type, buf, len);
 427 }
 428
 429 /*
 430  * Call the console drivers on a range of log_buf
 431  */
 432 static void __call_console_drivers(unsigned start, unsigned end)
 433 {
 434         struct console *con;
 435
 436         for (con = console_drivers; con; con = con->next) {
 437                 if ((con->flags & CON_ENABLED) && con->write &&
 438                                 (cpu_online(smp_processor_id()) ||
 439                                 (con->flags & CON_ANYTIME)))
 440                         con->write(con, &LOG_BUF(start), end - start);
 441         }
 442 }
 443
 444 static int __read_mostly ignore_loglevel;
 445
 446 static int __init ignore_loglevel_setup(char *str)
 447 {
 448         ignore_loglevel = 1;
 449         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 450
 451         return 0;
 452 }
 453
 454 early_param("ignore_loglevel", ignore_loglevel_setup);
 455
 456 /*
 457  * Write out chars from start to end - 1 inclusive
 458  */
 459 static void _call_console_drivers(unsigned start,
 460                                 unsigned end, int msg_log_level)
 461 {
 462         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 463                         console_drivers && start != end) {
 464                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 465                         /* wrapped write */
 466                         __call_console_drivers(start & LOG_BUF_MASK,
 467                                                 log_buf_len);
 468                         __call_console_drivers(0, end & LOG_BUF_MASK);
 469                 } else {
 470                         __call_console_drivers(start, end);
 471                 }
 472         }
 473 }
 474
 475 /*
 476  * Call the console drivers, asking them to write out
 477  * log_buf[start] to log_buf[end - 1].
 478  * The console_sem must be held.
 479  */
 480 static void call_console_drivers(unsigned start, unsigned end)
 481 {
 482         unsigned cur_index, start_print;
 483         static int msg_level = -1;
 484
 485         BUG_ON(((int)(start - end)) > 0);
 486
 487         cur_index = start;
 488         start_print = start;
 489         while (cur_index != end) {
 490                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 491                                 LOG_BUF(cur_index + 0) == '<' &&
 492                                 LOG_BUF(cur_index + 1) >= '0' &&
 493                                 LOG_BUF(cur_index + 1) <= '7' &&
 494                                 LOG_BUF(cur_index + 2) == '>') {
 495                         msg_level = LOG_BUF(cur_index + 1) - '0';
 496                         cur_index += 3;
 497                         start_print = cur_index;
 498                 }
 499                 while (cur_index != end) {
 500                         char c = LOG_BUF(cur_index);
 501
 502                         cur_index++;
 503                         if (c == '\n') {
 504                                 if (msg_level < 0) {
 505                                         /*
 506                                          * printk() has already given us loglevel tags in
 507                                          * the buffer.  This code is here in case the
 508                                          * log buffer has wrapped right round and scribbled
 509                                          * on those tags
 510                                          */
 511                                         msg_level = default_message_loglevel;
 512                                 }
 513                                 _call_console_drivers(start_print, cur_index, msg_level);
 514                                 msg_level = -1;
 515                                 start_print = cur_index;
 516                                 break;
 517                         }
 518                 }
 519         }
 520         _call_console_drivers(start_print, end, msg_level);
 521 }
 522
 523 static void emit_log_char(char c)
 524 {
 525         LOG_BUF(log_end) = c;
 526         log_end++;
 527         if (log_end - log_start > log_buf_len)
 528                 log_start = log_end - log_buf_len;
 529         if (log_end - con_start > log_buf_len)
 530                 con_start = log_end - log_buf_len;
 531         if (logged_chars < log_buf_len)
 532                 logged_chars++;
 533 }
 534
 535 /*
 536  * Zap console related locks when oopsing. Only zap at most once
 537  * every 10 seconds, to leave time for slow consoles to print a
 538  * full oops.
 539  */
 540 static void zap_locks(void)
 541 {
 542         static unsigned long oops_timestamp;
 543
 544         if (time_after_eq(jiffies, oops_timestamp) &&
 545                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 546                 return;
 547
 548         oops_timestamp = jiffies;
 549
 550         /* If a crash is occurring, make sure we can't deadlock */
 551         spin_lock_init(&logbuf_lock);
 552         /* And make sure that we print immediately */
 553         init_MUTEX(&console_sem);
 554 }
 555
 556 #if defined(CONFIG_PRINTK_TIME)
 557 static int printk_time = 1;
 558 #else
 559 static int printk_time = 0;
 560 #endif
 561 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 562
 563 /* Check if we have any console registered that can be called early in boot. */
 564 static int have_callable_console(void)
 565 {
 566         struct console *con;
 567
 568         for (con = console_drivers; con; con = con->next)
 569                 if (con->flags & CON_ANYTIME)
 570                         return 1;
 571
 572         return 0;
 573 }
 574
 575 /**
 576  * printk - print a kernel message
 577  * @fmt: format string
 578  *
 579  * This is printk().  It can be called from any context.  We want it to work.
 580  *
 581  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 582  * call the console drivers.  If we fail to get the semaphore we place the output
 583  * into the log buffer and return.  The current holder of the console_sem will
 584  * notice the new output in release_console_sem() and will send it to the
 585  * consoles before releasing the semaphore.
 586  *
 587  * One effect of this deferred printing is that code which calls printk() and
 588  * then changes console_loglevel may break. This is because console_loglevel
 589  * is inspected when the actual printing occurs.
 590  *
 591  * See also:
 592  * printf(3)
 593  *
 594  * See the vsnprintf() documentation for format string extensions over C99.
 595  */
 596
 597 asmlinkage int printk(const char *fmt, ...)
 598 {
 599         va_list args;
 600         int r;
 601
 602         va_start(args, fmt);
 603         r = vprintk(fmt, args);
 604         va_end(args);
 605
 606         return r;
 607 }
 608
 609 /* cpu currently holding logbuf_lock */
 610 static volatile unsigned int printk_cpu = UINT_MAX;
 611
 612 /*
 613  * Can we actually use the console at this time on this cpu?
 614  *
 615  * Console drivers may assume that per-cpu resources have
 616  * been allocated. So unless they're explicitly marked as
 617  * being able to cope (CON_ANYTIME) don't call them until
 618  * this CPU is officially up.
 619  */
 620 static inline int can_use_console(unsigned int cpu)
 621 {
 622         return cpu_online(cpu) || have_callable_console();
 623 }
 624
 625 /*
 626  * Try to get console ownership to actually show the kernel
 627  * messages from a 'printk'. Return true (and with the
 628  * console_semaphore held, and 'console_locked' set) if it
 629  * is successful, false otherwise.
 630  *
 631  * This gets called with the 'logbuf_lock' spinlock held and
 632  * interrupts disabled. It should return with 'lockbuf_lock'
 633  * released but interrupts still disabled.
 634  */
 635 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 636 {
 637         int retval = 0;
 638
 639         if (!try_acquire_console_sem()) {
 640                 retval = 1;
 641
 642                 /*
 643                  * If we can't use the console, we need to release
 644                  * the console semaphore by hand to avoid flushing
 645                  * the buffer. We need to hold the console semaphore
 646                  * in order to do this test safely.
 647                  */
 648                 if (!can_use_console(cpu)) {
 649                         console_locked = 0;
 650                         up(&console_sem);
 651                         retval = 0;
 652                 }
 653         }
 654         printk_cpu = UINT_MAX;
 655         spin_unlock(&logbuf_lock);
 656         return retval;
 657 }
 658 static const char recursion_bug_msg [] =
 659                 KERN_CRIT "BUG: recent printk recursion!\n";
 660 static int recursion_bug;
 661         static int new_text_line = 1;
 662 static char printk_buf[1024];
 663
 664 asmlinkage int vprintk(const char *fmt, va_list args)
 665 {
 666         int printed_len = 0;
 667         int current_log_level = default_message_loglevel;
 668         unsigned long flags;
 669         int this_cpu;
 670         char *p;
 671
 672         boot_delay_msec();
 673
 674         preempt_disable();
 675         /* This stops the holder of console_sem just where we want him */
 676         raw_local_irq_save(flags);
 677         this_cpu = smp_processor_id();
 678
 679         /*
 680          * Ouch, printk recursed into itself!
 681          */
 682         if (unlikely(printk_cpu == this_cpu)) {
 683                 /*
 684                  * If a crash is occurring during printk() on this CPU,
 685                  * then try to get the crash message out but make sure
 686                  * we can't deadlock. Otherwise just return to avoid the
 687                  * recursion and return - but flag the recursion so that
 688                  * it can be printed at the next appropriate moment:
 689                  */
 690                 if (!oops_in_progress) {
 691                         recursion_bug = 1;
 692                         goto out_restore_irqs;
 693                 }
 694                 zap_locks();
 695         }
 696
 697         lockdep_off();
 698         spin_lock(&logbuf_lock);
 699         printk_cpu = this_cpu;
 700
 701         if (recursion_bug) {
 702                 recursion_bug = 0;
 703                 strcpy(printk_buf, recursion_bug_msg);
 704                 printed_len = sizeof(recursion_bug_msg);
 705         }
 706         /* Emit the output into the temporary buffer */
 707         printed_len += vscnprintf(printk_buf + printed_len,
 708                                   sizeof(printk_buf) - printed_len, fmt, args);
 709
 710
 711         /*
 712          * Copy the output into log_buf.  If the caller didn't provide
 713          * appropriate log level tags, we insert them here
 714          */
 715         for (p = printk_buf; *p; p++) {
 716                 if (new_text_line) {
 717                         /* If a token, set current_log_level and skip over */
 718                         if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
 719                             p[2] == '>') {
 720                                 current_log_level = p[1] - '0';
 721                                 p += 3;
 722                                 printed_len -= 3;
 723                         }
 724
 725                         /* Always output the token */
 726                         emit_log_char('<');
 727                         emit_log_char(current_log_level + '0');
 728                         emit_log_char('>');
 729                         printed_len += 3;
 730                         new_text_line = 0;
 731
 732                         if (printk_time) {
 733                                 /* Follow the token with the time */
 734                                 char tbuf[50], *tp;
 735                                 unsigned tlen;
 736                                 unsigned long long t;
 737                                 unsigned long nanosec_rem;
 738
 739                                 t = cpu_clock(printk_cpu);
 740                                 nanosec_rem = do_div(t, 1000000000);
 741                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 742                                                 (unsigned long) t,
 743                                                 nanosec_rem / 1000);
 744
 745                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 746                                         emit_log_char(*tp);
 747                                 printed_len += tlen;
 748                         }
 749
 750                         if (!*p)
 751                                 break;
 752                 }
 753
 754                 emit_log_char(*p);
 755                 if (*p == '\n')
 756                         new_text_line = 1;
 757         }
 758
 759         /*
 760          * Try to acquire and then immediately release the
 761          * console semaphore. The release will do all the
 762          * actual magic (print out buffers, wake up klogd,
 763          * etc).
 764          *
 765          * The acquire_console_semaphore_for_printk() function
 766          * will release 'logbuf_lock' regardless of whether it
 767          * actually gets the semaphore or not.
 768          */
 769         if (acquire_console_semaphore_for_printk(this_cpu))
 770                 release_console_sem();
 771
 772         lockdep_on();
 773 out_restore_irqs:
 774         raw_local_irq_restore(flags);
 775
 776         preempt_enable();
 777         return printed_len;
 778 }
 779 EXPORT_SYMBOL(printk);
 780 EXPORT_SYMBOL(vprintk);
 781
 782 #else
 783
 784 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 785 {
 786         return -ENOSYS;
 787 }
 788
 789 static void call_console_drivers(unsigned start, unsigned end)
 790 {
 791 }
 792
 793 #endif
 794
 795 static int __add_preferred_console(char *name, int idx, char *options,
 796                                    char *brl_options)
 797 {
 798         struct console_cmdline *c;
 799         int i;
 800
 801         /*
 802          *      See if this tty is not yet registered, and
 803          *      if we have a slot free.
 804          */
 805         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 806                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 807                           console_cmdline[i].index == idx) {
 808                                 if (!brl_options)
 809                                         selected_console = i;
 810                                 return 0;
 811                 }
 812         if (i == MAX_CMDLINECONSOLES)
 813                 return -E2BIG;
 814         if (!brl_options)
 815                 selected_console = i;
 816         c = &console_cmdline[i];
 817         strlcpy(c->name, name, sizeof(c->name));
 818         c->options = options;
 819 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 820         c->brl_options = brl_options;
 821 #endif
 822         c->index = idx;
 823         return 0;
 824 }
 825 /*
 826  * Set up a list of consoles.  Called from init/main.c
 827  */
 828 static int __init console_setup(char *str)
 829 {
 830         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 831         char *s, *options, *brl_options = NULL;
 832         int idx;
 833
 834 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 835         if (!memcmp(str, "brl,", 4)) {
 836                 brl_options = "";
 837                 str += 4;
 838         } else if (!memcmp(str, "brl=", 4)) {
 839                 brl_options = str + 4;
 840                 str = strchr(brl_options, ',');
 841                 if (!str) {
 842                         printk(KERN_ERR "need port name after brl=\n");
 843                         return 1;
 844                 }
 845                 *(str++) = 0;
 846         }
 847 #endif
 848
 849         /*
 850          * Decode str into name, index, options.
 851          */
 852         if (str[0] >= '0' && str[0] <= '9') {
 853                 strcpy(buf, "ttyS");
 854                 strncpy(buf + 4, str, sizeof(buf) - 5);
 855         } else {
 856                 strncpy(buf, str, sizeof(buf) - 1);
 857         }
 858         buf[sizeof(buf) - 1] = 0;
 859         if ((options = strchr(str, ',')) != NULL)
 860                 *(options++) = 0;
 861 #ifdef __sparc__
 862         if (!strcmp(str, "ttya"))
 863                 strcpy(buf, "ttyS0");
 864         if (!strcmp(str, "ttyb"))
 865                 strcpy(buf, "ttyS1");
 866 #endif
 867         for (s = buf; *s; s++)
 868                 if ((*s >= '0' && *s <= '9') || *s == ',')
 869                         break;
 870         idx = simple_strtoul(s, NULL, 10);
 871         *s = 0;
 872
 873         __add_preferred_console(buf, idx, options, brl_options);
 874         console_set_on_cmdline = 1;
 875         return 1;
 876 }
 877 __setup("console=", console_setup);
 878
 879 /**
 880  * add_preferred_console - add a device to the list of preferred consoles.
 881  * @name: device name
 882  * @idx: device index
 883  * @options: options for this console
 884  *
 885  * The last preferred console added will be used for kernel messages
 886  * and stdin/out/err for init.  Normally this is used by console_setup
 887  * above to handle user-supplied console arguments; however it can also
 888  * be used by arch-specific code either to override the user or more
 889  * commonly to provide a default console (ie from PROM variables) when
 890  * the user has not supplied one.
 891  */
 892 int add_preferred_console(char *name, int idx, char *options)
 893 {
 894         return __add_preferred_console(name, idx, options, NULL);
 895 }
 896
 897 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 898 {
 899         struct console_cmdline *c;
 900         int i;
 901
 902         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 903                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 904                           console_cmdline[i].index == idx) {
 905                                 c = &console_cmdline[i];
 906                                 strlcpy(c->name, name_new, sizeof(c->name));
 907                                 c->name[sizeof(c->name) - 1] = 0;
 908                                 c->options = options;
 909                                 c->index = idx_new;
 910                                 return i;
 911                 }
 912         /* not found */
 913         return -1;
 914 }
 915
 916 int console_suspend_enabled = 1;
 917 EXPORT_SYMBOL(console_suspend_enabled);
 918
 919 static int __init console_suspend_disable(char *str)
 920 {
 921         console_suspend_enabled = 0;
 922         return 1;
 923 }
 924 __setup("no_console_suspend", console_suspend_disable);
 925
 926 /**
 927  * suspend_console - suspend the console subsystem
 928  *
 929  * This disables printk() while we go into suspend states
 930  */
 931 void suspend_console(void)
 932 {
 933         if (!console_suspend_enabled)
 934                 return;
 935         printk("Suspending console(s) (use no_console_suspend to debug)\n");
 936         acquire_console_sem();
 937         console_suspended = 1;
 938 }
 939
 940 void resume_console(void)
 941 {
 942         if (!console_suspend_enabled)
 943                 return;
 944         console_suspended = 0;
 945         release_console_sem();
 946 }
 947
 948 /**
 949  * acquire_console_sem - lock the console system for exclusive use.
 950  *
 951  * Acquires a semaphore which guarantees that the caller has
 952  * exclusive access to the console system and the console_drivers list.
 953  *
 954  * Can sleep, returns nothing.
 955  */
 956 void acquire_console_sem(void)
 957 {
 958         BUG_ON(in_interrupt());
 959         if (console_suspended) {
 960                 down(&secondary_console_sem);
 961                 return;
 962         }
 963         down(&console_sem);
 964         console_locked = 1;
 965         console_may_schedule = 1;
 966 }
 967 EXPORT_SYMBOL(acquire_console_sem);
 968
 969 int try_acquire_console_sem(void)
 970 {
 971         if (down_trylock(&console_sem))
 972                 return -1;
 973         console_locked = 1;
 974         console_may_schedule = 0;
 975         return 0;
 976 }
 977 EXPORT_SYMBOL(try_acquire_console_sem);
 978
 979 int is_console_locked(void)
 980 {
 981         return console_locked;
 982 }
 983
 984 static DEFINE_PER_CPU(int, printk_pending);
 985
 986 void printk_tick(void)
 987 {
 988         if (__get_cpu_var(printk_pending)) {
 989                 __get_cpu_var(printk_pending) = 0;
 990                 wake_up_interruptible(&log_wait);
 991         }
 992 }
 993
 994 int printk_needs_cpu(int cpu)
 995 {
 996         return per_cpu(printk_pending, cpu);
 997 }
 998
 999 void wake_up_klogd(void)
1000 {
1001         if (waitqueue_active(&log_wait))
1002                 __raw_get_cpu_var(printk_pending) = 1;
1003 }
1004
1005 /**
1006  * release_console_sem - unlock the console system
1007  *
1008  * Releases the semaphore which the caller holds on the console system
1009  * and the console driver list.
1010  *
1011  * While the semaphore was held, console output may have been buffered
1012  * by printk().  If this is the case, release_console_sem() emits
1013  * the output prior to releasing the semaphore.
1014  *
1015  * If there is output waiting for klogd, we wake it up.
1016  *
1017  * release_console_sem() may be called from any context.
1018  */
1019 void release_console_sem(void)
1020 {
1021         unsigned long flags;
1022         unsigned _con_start, _log_end;
1023         unsigned wake_klogd = 0;
1024
1025         if (console_suspended) {
1026                 up(&secondary_console_sem);
1027                 return;
1028         }
1029
1030         console_may_schedule = 0;
1031
1032         for ( ; ; ) {
1033                 spin_lock_irqsave(&logbuf_lock, flags);
1034                 wake_klogd |= log_start - log_end;
1035                 if (con_start == log_end)
1036                         break;                  /* Nothing to print */
1037                 _con_start = con_start;
1038                 _log_end = log_end;
1039                 con_start = log_end;            /* Flush */
1040                 spin_unlock(&logbuf_lock);
1041                 stop_critical_timings();        /* don't trace print latency */
1042                 call_console_drivers(_con_start, _log_end);
1043                 start_critical_timings();
1044                 local_irq_restore(flags);
1045         }
1046         console_locked = 0;
1047         up(&console_sem);
1048         spin_unlock_irqrestore(&logbuf_lock, flags);
1049         if (wake_klogd)
1050                 wake_up_klogd();
1051 }
1052 EXPORT_SYMBOL(release_console_sem);
1053
1054 /**
1055  * console_conditional_schedule - yield the CPU if required
1056  *
1057  * If the console code is currently allowed to sleep, and
1058  * if this CPU should yield the CPU to another task, do
1059  * so here.
1060  *
1061  * Must be called within acquire_console_sem().
1062  */
1063 void __sched console_conditional_schedule(void)
1064 {
1065         if (console_may_schedule)
1066                 cond_resched();
1067 }
1068 EXPORT_SYMBOL(console_conditional_schedule);
1069
1070 void console_print(const char *s)
1071 {
1072         printk(KERN_EMERG "%s", s);
1073 }
1074 EXPORT_SYMBOL(console_print);
1075
1076 void console_unblank(void)
1077 {
1078         struct console *c;
1079
1080         /*
1081          * console_unblank can no longer be called in interrupt context unless
1082          * oops_in_progress is set to 1..
1083          */
1084         if (oops_in_progress) {
1085                 if (down_trylock(&console_sem) != 0)
1086                         return;
1087         } else
1088                 acquire_console_sem();
1089
1090         console_locked = 1;
1091         console_may_schedule = 0;
1092         for (c = console_drivers; c != NULL; c = c->next)
1093                 if ((c->flags & CON_ENABLED) && c->unblank)
1094                         c->unblank();
1095         release_console_sem();
1096 }
1097
1098 /*
1099  * Return the console tty driver structure and its associated index
1100  */
1101 struct tty_driver *console_device(int *index)
1102 {
1103         struct console *c;
1104         struct tty_driver *driver = NULL;
1105
1106         acquire_console_sem();
1107         for (c = console_drivers; c != NULL; c = c->next) {
1108                 if (!c->device)
1109                         continue;
1110                 driver = c->device(c, index);
1111                 if (driver)
1112                         break;
1113         }
1114         release_console_sem();
1115         return driver;
1116 }
1117
1118 /*
1119  * Prevent further output on the passed console device so that (for example)
1120  * serial drivers can disable console output before suspending a port, and can
1121  * re-enable output afterwards.
1122  */
1123 void console_stop(struct console *console)
1124 {
1125         acquire_console_sem();
1126         console->flags &= ~CON_ENABLED;
1127         release_console_sem();
1128 }
1129 EXPORT_SYMBOL(console_stop);
1130
1131 void console_start(struct console *console)
1132 {
1133         acquire_console_sem();
1134         console->flags |= CON_ENABLED;
1135         release_console_sem();
1136 }
1137 EXPORT_SYMBOL(console_start);
1138
1139 /*
1140  * The console driver calls this routine during kernel initialization
1141  * to register the console printing procedure with printk() and to
1142  * print any messages that were printed by the kernel before the
1143  * console driver was initialized.
1144  */
1145 void register_console(struct console *console)
1146 {
1147         int i;
1148         unsigned long flags;
1149         struct console *bootconsole = NULL;
1150
1151         if (console_drivers) {
1152                 if (console->flags & CON_BOOT)
1153                         return;
1154                 if (console_drivers->flags & CON_BOOT)
1155                         bootconsole = console_drivers;
1156         }
1157
1158         if (preferred_console < 0 || bootconsole || !console_drivers)
1159                 preferred_console = selected_console;
1160
1161         if (console->early_setup)
1162                 console->early_setup();
1163
1164         /*
1165          *      See if we want to use this console driver. If we
1166          *      didn't select a console we take the first one
1167          *      that registers here.
1168          */
1169         if (preferred_console < 0) {
1170                 if (console->index < 0)
1171                         console->index = 0;
1172                 if (console->setup == NULL ||
1173                     console->setup(console, NULL) == 0) {
1174                         console->flags |= CON_ENABLED;
1175                         if (console->device) {
1176                                 console->flags |= CON_CONSDEV;
1177                                 preferred_console = 0;
1178                         }
1179                 }
1180         }
1181
1182         /*
1183          *      See if this console matches one we selected on
1184          *      the command line.
1185          */
1186         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1187                         i++) {
1188                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1189                         continue;
1190                 if (console->index >= 0 &&
1191                     console->index != console_cmdline[i].index)
1192                         continue;
1193                 if (console->index < 0)
1194                         console->index = console_cmdline[i].index;
1195 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1196                 if (console_cmdline[i].brl_options) {
1197                         console->flags |= CON_BRL;
1198                         braille_register_console(console,
1199                                         console_cmdline[i].index,
1200                                         console_cmdline[i].options,
1201                                         console_cmdline[i].brl_options);
1202                         return;
1203                 }
1204 #endif
1205                 if (console->setup &&
1206                     console->setup(console, console_cmdline[i].options) != 0)
1207                         break;
1208                 console->flags |= CON_ENABLED;
1209                 console->index = console_cmdline[i].index;
1210                 if (i == selected_console) {
1211                         console->flags |= CON_CONSDEV;
1212                         preferred_console = selected_console;
1213                 }
1214                 break;
1215         }
1216
1217         if (!(console->flags & CON_ENABLED))
1218                 return;
1219
1220         if (bootconsole && (console->flags & CON_CONSDEV)) {
1221                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1222                        bootconsole->name, bootconsole->index,
1223                        console->name, console->index);
1224                 unregister_console(bootconsole);
1225                 console->flags &= ~CON_PRINTBUFFER;
1226         } else {
1227                 printk(KERN_INFO "console [%s%d] enabled\n",
1228                        console->name, console->index);
1229         }
1230
1231         /*
1232          *      Put this console in the list - keep the
1233          *      preferred driver at the head of the list.
1234          */
1235         acquire_console_sem();
1236         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1237                 console->next = console_drivers;
1238                 console_drivers = console;
1239                 if (console->next)
1240                         console->next->flags &= ~CON_CONSDEV;
1241         } else {
1242                 console->next = console_drivers->next;
1243                 console_drivers->next = console;
1244         }
1245         if (console->flags & CON_PRINTBUFFER) {
1246                 /*
1247                  * release_console_sem() will print out the buffered messages
1248                  * for us.
1249                  */
1250                 spin_lock_irqsave(&logbuf_lock, flags);
1251                 con_start = log_start;
1252                 spin_unlock_irqrestore(&logbuf_lock, flags);
1253         }
1254         release_console_sem();
1255 }
1256 EXPORT_SYMBOL(register_console);
1257
1258 int unregister_console(struct console *console)
1259 {
1260         struct console *a, *b;
1261         int res = 1;
1262
1263 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1264         if (console->flags & CON_BRL)
1265                 return braille_unregister_console(console);
1266 #endif
1267
1268         acquire_console_sem();
1269         if (console_drivers == console) {
1270                 console_drivers=console->next;
1271                 res = 0;
1272         } else if (console_drivers) {
1273                 for (a=console_drivers->next, b=console_drivers ;
1274                      a; b=a, a=b->next) {
1275                         if (a == console) {
1276                                 b->next = a->next;
1277                                 res = 0;
1278                                 break;
1279                         }
1280                 }
1281         }
1282
1283         /*
1284          * If this isn't the last console and it has CON_CONSDEV set, we
1285          * need to set it on the next preferred console.
1286          */
1287         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1288                 console_drivers->flags |= CON_CONSDEV;
1289
1290         release_console_sem();
1291         return res;
1292 }
1293 EXPORT_SYMBOL(unregister_console);
1294
1295 static int __init disable_boot_consoles(void)
1296 {
1297         if (console_drivers != NULL) {
1298                 if (console_drivers->flags & CON_BOOT) {
1299                         printk(KERN_INFO "turn off boot console %s%d\n",
1300                                 console_drivers->name, console_drivers->index);
1301                         return unregister_console(console_drivers);
1302                 }
1303         }
1304         return 0;
1305 }
1306 late_initcall(disable_boot_consoles);
1307
1308 #if defined CONFIG_PRINTK
1309
1310 /*
1311  * printk rate limiting, lifted from the networking subsystem.
1312  *
1313  * This enforces a rate limit: not more than 10 kernel messages
1314  * every 5s to make a denial-of-service attack impossible.
1315  */
1316 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1317
1318 int printk_ratelimit(void)
1319 {
1320         return __ratelimit(&printk_ratelimit_state);
1321 }
1322 EXPORT_SYMBOL(printk_ratelimit);
1323
1324 /**
1325  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1326  * @caller_jiffies: pointer to caller's state
1327  * @interval_msecs: minimum interval between prints
1328  *
1329  * printk_timed_ratelimit() returns true if more than @interval_msecs
1330  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1331  * returned true.
1332  */
1333 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1334                         unsigned int interval_msecs)
1335 {
1336         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1337                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1338                 return true;
1339         }
1340         return false;
1341 }
1342 EXPORT_SYMBOL(printk_timed_ratelimit);
1343 #endif