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 <andrewm@uow.edu.au>
  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
 127 /* Flag: console code may call schedule() */
 128 static int console_may_schedule;
 129
 130 #ifdef CONFIG_PRINTK
 131
 132 static char __log_buf[__LOG_BUF_LEN];
 133 static char *log_buf = __log_buf;
 134 static int log_buf_len = __LOG_BUF_LEN;
 135 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 136
 137 static int __init log_buf_len_setup(char *str)
 138 {
 139         unsigned size = memparse(str, &str);
 140         unsigned long flags;
 141
 142         if (size)
 143                 size = roundup_pow_of_two(size);
 144         if (size > log_buf_len) {
 145                 unsigned start, dest_idx, offset;
 146                 char *new_log_buf;
 147
 148                 new_log_buf = alloc_bootmem(size);
 149                 if (!new_log_buf) {
 150                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 151                         goto out;
 152                 }
 153
 154                 spin_lock_irqsave(&logbuf_lock, flags);
 155                 log_buf_len = size;
 156                 log_buf = new_log_buf;
 157
 158                 offset = start = min(con_start, log_start);
 159                 dest_idx = 0;
 160                 while (start != log_end) {
 161                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 162                         start++;
 163                         dest_idx++;
 164                 }
 165                 log_start -= offset;
 166                 con_start -= offset;
 167                 log_end -= offset;
 168                 spin_unlock_irqrestore(&logbuf_lock, flags);
 169
 170                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 171         }
 172 out:
 173         return 1;
 174 }
 175
 176 __setup("log_buf_len=", log_buf_len_setup);
 177
 178 #ifdef CONFIG_BOOT_PRINTK_DELAY
 179
 180 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 181 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
 182
 183 static int __init boot_delay_setup(char *str)
 184 {
 185         unsigned long lpj;
 186         unsigned long long loops_per_msec;
 187
 188         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 189         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 190
 191         get_option(&str, &boot_delay);
 192         if (boot_delay > 10 * 1000)
 193                 boot_delay = 0;
 194
 195         printk_delay_msec = loops_per_msec;
 196         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 197                 "HZ: %d, printk_delay_msec: %llu\n",
 198                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
 199         return 1;
 200 }
 201 __setup("boot_delay=", boot_delay_setup);
 202
 203 static void boot_delay_msec(void)
 204 {
 205         unsigned long long k;
 206         unsigned long timeout;
 207
 208         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 209                 return;
 210
 211         k = (unsigned long long)printk_delay_msec * boot_delay;
 212
 213         timeout = jiffies + msecs_to_jiffies(boot_delay);
 214         while (k) {
 215                 k--;
 216                 cpu_relax();
 217                 /*
 218                  * use (volatile) jiffies to prevent
 219                  * compiler reduction; loop termination via jiffies
 220                  * is secondary and may or may not happen.
 221                  */
 222                 if (time_after(jiffies, timeout))
 223                         break;
 224                 touch_nmi_watchdog();
 225         }
 226 }
 227 #else
 228 static inline void boot_delay_msec(void)
 229 {
 230 }
 231 #endif
 232
 233 /*
 234  * Return the number of unread characters in the log buffer.
 235  */
 236 static int log_buf_get_len(void)
 237 {
 238         return logged_chars;
 239 }
 240
 241 /*
 242  * Copy a range of characters from the log buffer.
 243  */
 244 int log_buf_copy(char *dest, int idx, int len)
 245 {
 246         int ret, max;
 247         bool took_lock = false;
 248
 249         if (!oops_in_progress) {
 250                 spin_lock_irq(&logbuf_lock);
 251                 took_lock = true;
 252         }
 253
 254         max = log_buf_get_len();
 255         if (idx < 0 || idx >= max) {
 256                 ret = -1;
 257         } else {
 258                 if (len > max)
 259                         len = max;
 260                 ret = len;
 261                 idx += (log_end - max);
 262                 while (len-- > 0)
 263                         dest[len] = LOG_BUF(idx + len);
 264         }
 265
 266         if (took_lock)
 267                 spin_unlock_irq(&logbuf_lock);
 268
 269         return ret;
 270 }
 271
 272 /*
 273  * Commands to do_syslog:
 274  *
 275  *      0 -- Close the log.  Currently a NOP.
 276  *      1 -- Open the log. Currently a NOP.
 277  *      2 -- Read from the log.
 278  *      3 -- Read all messages remaining in the ring buffer.
 279  *      4 -- Read and clear all messages remaining in the ring buffer
 280  *      5 -- Clear ring buffer.
 281  *      6 -- Disable printk's to console
 282  *      7 -- Enable printk's to console
 283  *      8 -- Set level of messages printed to console
 284  *      9 -- Return number of unread characters in the log buffer
 285  *     10 -- Return size of the log buffer
 286  */
 287 int do_syslog(int type, char __user *buf, int len)
 288 {
 289         unsigned i, j, limit, count;
 290         int do_clear = 0;
 291         char c;
 292         int error = 0;
 293
 294         error = security_syslog(type);
 295         if (error)
 296                 return error;
 297
 298         switch (type) {
 299         case 0:         /* Close log */
 300                 break;
 301         case 1:         /* Open log */
 302                 break;
 303         case 2:         /* Read from log */
 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                 error = wait_event_interruptible(log_wait,
 315                                                         (log_start - log_end));
 316                 if (error)
 317                         goto out;
 318                 i = 0;
 319                 spin_lock_irq(&logbuf_lock);
 320                 while (!error && (log_start != log_end) && i < len) {
 321                         c = LOG_BUF(log_start);
 322                         log_start++;
 323                         spin_unlock_irq(&logbuf_lock);
 324                         error = __put_user(c,buf);
 325                         buf++;
 326                         i++;
 327                         cond_resched();
 328                         spin_lock_irq(&logbuf_lock);
 329                 }
 330                 spin_unlock_irq(&logbuf_lock);
 331                 if (!error)
 332                         error = i;
 333                 break;
 334         case 4:         /* Read/clear last kernel messages */
 335                 do_clear = 1;
 336                 /* FALL THRU */
 337         case 3:         /* Read last kernel messages */
 338                 error = -EINVAL;
 339                 if (!buf || len < 0)
 340                         goto out;
 341                 error = 0;
 342                 if (!len)
 343                         goto out;
 344                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 345                         error = -EFAULT;
 346                         goto out;
 347                 }
 348                 count = len;
 349                 if (count > log_buf_len)
 350                         count = log_buf_len;
 351                 spin_lock_irq(&logbuf_lock);
 352                 if (count > logged_chars)
 353                         count = logged_chars;
 354                 if (do_clear)
 355                         logged_chars = 0;
 356                 limit = log_end;
 357                 /*
 358                  * __put_user() could sleep, and while we sleep
 359                  * printk() could overwrite the messages
 360                  * we try to copy to user space. Therefore
 361                  * the messages are copied in reverse. <manfreds>
 362                  */
 363                 for (i = 0; i < count && !error; i++) {
 364                         j = limit-1-i;
 365                         if (j + log_buf_len < log_end)
 366                                 break;
 367                         c = LOG_BUF(j);
 368                         spin_unlock_irq(&logbuf_lock);
 369                         error = __put_user(c,&buf[count-1-i]);
 370                         cond_resched();
 371                         spin_lock_irq(&logbuf_lock);
 372                 }
 373                 spin_unlock_irq(&logbuf_lock);
 374                 if (error)
 375                         break;
 376                 error = i;
 377                 if (i != count) {
 378                         int offset = count-error;
 379                         /* buffer overflow during copy, correct user buffer. */
 380                         for (i = 0; i < error; i++) {
 381                                 if (__get_user(c,&buf[i+offset]) ||
 382                                     __put_user(c,&buf[i])) {
 383                                         error = -EFAULT;
 384                                         break;
 385                                 }
 386                                 cond_resched();
 387                         }
 388                 }
 389                 break;
 390         case 5:         /* Clear ring buffer */
 391                 logged_chars = 0;
 392                 break;
 393         case 6:         /* Disable logging to console */
 394                 console_loglevel = minimum_console_loglevel;
 395                 break;
 396         case 7:         /* Enable logging to console */
 397                 console_loglevel = default_console_loglevel;
 398                 break;
 399         case 8:         /* Set level of messages printed to console */
 400                 error = -EINVAL;
 401                 if (len < 1 || len > 8)
 402                         goto out;
 403                 if (len < minimum_console_loglevel)
 404                         len = minimum_console_loglevel;
 405                 console_loglevel = len;
 406                 error = 0;
 407                 break;
 408         case 9:         /* Number of chars in the log buffer */
 409                 error = log_end - log_start;
 410                 break;
 411         case 10:        /* Size of the log buffer */
 412                 error = log_buf_len;
 413                 break;
 414         default:
 415                 error = -EINVAL;
 416                 break;
 417         }
 418 out:
 419         return error;
 420 }
 421
 422 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 423 {
 424         return do_syslog(type, buf, len);
 425 }
 426
 427 /*
 428  * Call the console drivers on a range of log_buf
 429  */
 430 static void __call_console_drivers(unsigned start, unsigned end)
 431 {
 432         struct console *con;
 433
 434         for (con = console_drivers; con; con = con->next) {
 435                 if ((con->flags & CON_ENABLED) && con->write &&
 436                                 (cpu_online(smp_processor_id()) ||
 437                                 (con->flags & CON_ANYTIME)))
 438                         con->write(con, &LOG_BUF(start), end - start);
 439         }
 440 }
 441
 442 static int __read_mostly ignore_loglevel;
 443
 444 static int __init ignore_loglevel_setup(char *str)
 445 {
 446         ignore_loglevel = 1;
 447         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 448
 449         return 0;
 450 }
 451
 452 early_param("ignore_loglevel", ignore_loglevel_setup);
 453
 454 /*
 455  * Write out chars from start to end - 1 inclusive
 456  */
 457 static void _call_console_drivers(unsigned start,
 458                                 unsigned end, int msg_log_level)
 459 {
 460         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 461                         console_drivers && start != end) {
 462                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 463                         /* wrapped write */
 464                         __call_console_drivers(start & LOG_BUF_MASK,
 465                                                 log_buf_len);
 466                         __call_console_drivers(0, end & LOG_BUF_MASK);
 467                 } else {
 468                         __call_console_drivers(start, end);
 469                 }
 470         }
 471 }
 472
 473 /*
 474  * Call the console drivers, asking them to write out
 475  * log_buf[start] to log_buf[end - 1].
 476  * The console_sem must be held.
 477  */
 478 static void call_console_drivers(unsigned start, unsigned end)
 479 {
 480         unsigned cur_index, start_print;
 481         static int msg_level = -1;
 482
 483         BUG_ON(((int)(start - end)) > 0);
 484
 485         cur_index = start;
 486         start_print = start;
 487         while (cur_index != end) {
 488                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 489                                 LOG_BUF(cur_index + 0) == '<' &&
 490                                 LOG_BUF(cur_index + 1) >= '0' &&
 491                                 LOG_BUF(cur_index + 1) <= '7' &&
 492                                 LOG_BUF(cur_index + 2) == '>') {
 493                         msg_level = LOG_BUF(cur_index + 1) - '0';
 494                         cur_index += 3;
 495                         start_print = cur_index;
 496                 }
 497                 while (cur_index != end) {
 498                         char c = LOG_BUF(cur_index);
 499
 500                         cur_index++;
 501                         if (c == '\n') {
 502                                 if (msg_level < 0) {
 503                                         /*
 504                                          * printk() has already given us loglevel tags in
 505                                          * the buffer.  This code is here in case the
 506                                          * log buffer has wrapped right round and scribbled
 507                                          * on those tags
 508                                          */
 509                                         msg_level = default_message_loglevel;
 510                                 }
 511                                 _call_console_drivers(start_print, cur_index, msg_level);
 512                                 msg_level = -1;
 513                                 start_print = cur_index;
 514                                 break;
 515                         }
 516                 }
 517         }
 518         _call_console_drivers(start_print, end, msg_level);
 519 }
 520
 521 static void emit_log_char(char c)
 522 {
 523         LOG_BUF(log_end) = c;
 524         log_end++;
 525         if (log_end - log_start > log_buf_len)
 526                 log_start = log_end - log_buf_len;
 527         if (log_end - con_start > log_buf_len)
 528                 con_start = log_end - log_buf_len;
 529         if (logged_chars < log_buf_len)
 530                 logged_chars++;
 531 }
 532
 533 /*
 534  * Zap console related locks when oopsing. Only zap at most once
 535  * every 10 seconds, to leave time for slow consoles to print a
 536  * full oops.
 537  */
 538 static void zap_locks(void)
 539 {
 540         static unsigned long oops_timestamp;
 541
 542         if (time_after_eq(jiffies, oops_timestamp) &&
 543                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 544                 return;
 545
 546         oops_timestamp = jiffies;
 547
 548         /* If a crash is occurring, make sure we can't deadlock */
 549         spin_lock_init(&logbuf_lock);
 550         /* And make sure that we print immediately */
 551         init_MUTEX(&console_sem);
 552 }
 553
 554 #if defined(CONFIG_PRINTK_TIME)
 555 static int printk_time = 1;
 556 #else
 557 static int printk_time = 0;
 558 #endif
 559 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 560
 561 /* Check if we have any console registered that can be called early in boot. */
 562 static int have_callable_console(void)
 563 {
 564         struct console *con;
 565
 566         for (con = console_drivers; con; con = con->next)
 567                 if (con->flags & CON_ANYTIME)
 568                         return 1;
 569
 570         return 0;
 571 }
 572
 573 /**
 574  * printk - print a kernel message
 575  * @fmt: format string
 576  *
 577  * This is printk().  It can be called from any context.  We want it to work.
 578  * Be aware of the fact that if oops_in_progress is not set, we might try to
 579  * wake klogd up which could deadlock on runqueue lock if printk() is called
 580  * from scheduler code.
 581  *
 582  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 583  * call the console drivers.  If we fail to get the semaphore we place the output
 584  * into the log buffer and return.  The current holder of the console_sem will
 585  * notice the new output in release_console_sem() and will send it to the
 586  * consoles before releasing the semaphore.
 587  *
 588  * One effect of this deferred printing is that code which calls printk() and
 589  * then changes console_loglevel may break. This is because console_loglevel
 590  * is inspected when the actual printing occurs.
 591  *
 592  * See also:
 593  * printf(3)
 594  */
 595
 596 asmlinkage int printk(const char *fmt, ...)
 597 {
 598         va_list args;
 599         int r;
 600
 601         va_start(args, fmt);
 602         r = vprintk(fmt, args);
 603         va_end(args);
 604
 605         return r;
 606 }
 607
 608 /* cpu currently holding logbuf_lock */
 609 static volatile unsigned int printk_cpu = UINT_MAX;
 610
 611 /*
 612  * Can we actually use the console at this time on this cpu?
 613  *
 614  * Console drivers may assume that per-cpu resources have
 615  * been allocated. So unless they're explicitly marked as
 616  * being able to cope (CON_ANYTIME) don't call them until
 617  * this CPU is officially up.
 618  */
 619 static inline int can_use_console(unsigned int cpu)
 620 {
 621         return cpu_online(cpu) || have_callable_console();
 622 }
 623
 624 /*
 625  * Try to get console ownership to actually show the kernel
 626  * messages from a 'printk'. Return true (and with the
 627  * console_semaphore held, and 'console_locked' set) if it
 628  * is successful, false otherwise.
 629  *
 630  * This gets called with the 'logbuf_lock' spinlock held and
 631  * interrupts disabled. It should return with 'lockbuf_lock'
 632  * released but interrupts still disabled.
 633  */
 634 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 635 {
 636         int retval = 0;
 637
 638         if (!try_acquire_console_sem()) {
 639                 retval = 1;
 640
 641                 /*
 642                  * If we can't use the console, we need to release
 643                  * the console semaphore by hand to avoid flushing
 644                  * the buffer. We need to hold the console semaphore
 645                  * in order to do this test safely.
 646                  */
 647                 if (!can_use_console(cpu)) {
 648                         console_locked = 0;
 649                         up(&console_sem);
 650                         retval = 0;
 651                 }
 652         }
 653         printk_cpu = UINT_MAX;
 654         spin_unlock(&logbuf_lock);
 655         return retval;
 656 }
 657 static const char recursion_bug_msg [] =
 658                 KERN_CRIT "BUG: recent printk recursion!\n";
 659 static int recursion_bug;
 660         static int new_text_line = 1;
 661 static char printk_buf[1024];
 662
 663 asmlinkage int vprintk(const char *fmt, va_list args)
 664 {
 665         int printed_len = 0;
 666         int current_log_level = default_message_loglevel;
 667         unsigned long flags;
 668         int this_cpu;
 669         char *p;
 670
 671         boot_delay_msec();
 672
 673         preempt_disable();
 674         /* This stops the holder of console_sem just where we want him */
 675         raw_local_irq_save(flags);
 676         this_cpu = smp_processor_id();
 677
 678         /*
 679          * Ouch, printk recursed into itself!
 680          */
 681         if (unlikely(printk_cpu == this_cpu)) {
 682                 /*
 683                  * If a crash is occurring during printk() on this CPU,
 684                  * then try to get the crash message out but make sure
 685                  * we can't deadlock. Otherwise just return to avoid the
 686                  * recursion and return - but flag the recursion so that
 687                  * it can be printed at the next appropriate moment:
 688                  */
 689                 if (!oops_in_progress) {
 690                         recursion_bug = 1;
 691                         goto out_restore_irqs;
 692                 }
 693                 zap_locks();
 694         }
 695
 696         lockdep_off();
 697         spin_lock(&logbuf_lock);
 698         printk_cpu = this_cpu;
 699
 700         if (recursion_bug) {
 701                 recursion_bug = 0;
 702                 strcpy(printk_buf, recursion_bug_msg);
 703                 printed_len = sizeof(recursion_bug_msg);
 704         }
 705         /* Emit the output into the temporary buffer */
 706         printed_len += vscnprintf(printk_buf + printed_len,
 707                                   sizeof(printk_buf) - printed_len, fmt, args);
 708
 709
 710         /*
 711          * Copy the output into log_buf.  If the caller didn't provide
 712          * appropriate log level tags, we insert them here
 713          */
 714         for (p = printk_buf; *p; p++) {
 715                 if (new_text_line) {
 716                         /* If a token, set current_log_level and skip over */
 717                         if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
 718                             p[2] == '>') {
 719                                 current_log_level = p[1] - '0';
 720                                 p += 3;
 721                                 printed_len -= 3;
 722                         }
 723
 724                         /* Always output the token */
 725                         emit_log_char('<');
 726                         emit_log_char(current_log_level + '0');
 727                         emit_log_char('>');
 728                         printed_len += 3;
 729                         new_text_line = 0;
 730
 731                         if (printk_time) {
 732                                 /* Follow the token with the time */
 733                                 char tbuf[50], *tp;
 734                                 unsigned tlen;
 735                                 unsigned long long t;
 736                                 unsigned long nanosec_rem;
 737
 738                                 t = cpu_clock(printk_cpu);
 739                                 nanosec_rem = do_div(t, 1000000000);
 740                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 741                                                 (unsigned long) t,
 742                                                 nanosec_rem / 1000);
 743
 744                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 745                                         emit_log_char(*tp);
 746                                 printed_len += tlen;
 747                         }
 748
 749                         if (!*p)
 750                                 break;
 751                 }
 752
 753                 emit_log_char(*p);
 754                 if (*p == '\n')
 755                         new_text_line = 1;
 756         }
 757
 758         /*
 759          * Try to acquire and then immediately release the
 760          * console semaphore. The release will do all the
 761          * actual magic (print out buffers, wake up klogd,
 762          * etc).
 763          *
 764          * The acquire_console_semaphore_for_printk() function
 765          * will release 'logbuf_lock' regardless of whether it
 766          * actually gets the semaphore or not.
 767          */
 768         if (acquire_console_semaphore_for_printk(this_cpu))
 769                 release_console_sem();
 770
 771         lockdep_on();
 772 out_restore_irqs:
 773         raw_local_irq_restore(flags);
 774
 775         preempt_enable();
 776         return printed_len;
 777 }
 778 EXPORT_SYMBOL(printk);
 779 EXPORT_SYMBOL(vprintk);
 780
 781 #else
 782
 783 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 784 {
 785         return -ENOSYS;
 786 }
 787
 788 static void call_console_drivers(unsigned start, unsigned end)
 789 {
 790 }
 791
 792 #endif
 793
 794 static int __add_preferred_console(char *name, int idx, char *options,
 795                                    char *brl_options)
 796 {
 797         struct console_cmdline *c;
 798         int i;
 799
 800         /*
 801          *      See if this tty is not yet registered, and
 802          *      if we have a slot free.
 803          */
 804         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 805                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 806                           console_cmdline[i].index == idx) {
 807                                 if (!brl_options)
 808                                         selected_console = i;
 809                                 return 0;
 810                 }
 811         if (i == MAX_CMDLINECONSOLES)
 812                 return -E2BIG;
 813         if (!brl_options)
 814                 selected_console = i;
 815         c = &console_cmdline[i];
 816         strlcpy(c->name, name, sizeof(c->name));
 817         c->options = options;
 818 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 819         c->brl_options = brl_options;
 820 #endif
 821         c->index = idx;
 822         return 0;
 823 }
 824 /*
 825  * Set up a list of consoles.  Called from init/main.c
 826  */
 827 static int __init console_setup(char *str)
 828 {
 829         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 830         char *s, *options, *brl_options = NULL;
 831         int idx;
 832
 833 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 834         if (!memcmp(str, "brl,", 4)) {
 835                 brl_options = "";
 836                 str += 4;
 837         } else if (!memcmp(str, "brl=", 4)) {
 838                 brl_options = str + 4;
 839                 str = strchr(brl_options, ',');
 840                 if (!str) {
 841                         printk(KERN_ERR "need port name after brl=\n");
 842                         return 1;
 843                 }
 844                 *(str++) = 0;
 845         }
 846 #endif
 847
 848         /*
 849          * Decode str into name, index, options.
 850          */
 851         if (str[0] >= '0' && str[0] <= '9') {
 852                 strcpy(buf, "ttyS");
 853                 strncpy(buf + 4, str, sizeof(buf) - 5);
 854         } else {
 855                 strncpy(buf, str, sizeof(buf) - 1);
 856         }
 857         buf[sizeof(buf) - 1] = 0;
 858         if ((options = strchr(str, ',')) != NULL)
 859                 *(options++) = 0;
 860 #ifdef __sparc__
 861         if (!strcmp(str, "ttya"))
 862                 strcpy(buf, "ttyS0");
 863         if (!strcmp(str, "ttyb"))
 864                 strcpy(buf, "ttyS1");
 865 #endif
 866         for (s = buf; *s; s++)
 867                 if ((*s >= '0' && *s <= '9') || *s == ',')
 868                         break;
 869         idx = simple_strtoul(s, NULL, 10);
 870         *s = 0;
 871
 872         __add_preferred_console(buf, idx, options, brl_options);
 873         return 1;
 874 }
 875 __setup("console=", console_setup);
 876
 877 /**
 878  * add_preferred_console - add a device to the list of preferred consoles.
 879  * @name: device name
 880  * @idx: device index
 881  * @options: options for this console
 882  *
 883  * The last preferred console added will be used for kernel messages
 884  * and stdin/out/err for init.  Normally this is used by console_setup
 885  * above to handle user-supplied console arguments; however it can also
 886  * be used by arch-specific code either to override the user or more
 887  * commonly to provide a default console (ie from PROM variables) when
 888  * the user has not supplied one.
 889  */
 890 int add_preferred_console(char *name, int idx, char *options)
 891 {
 892         return __add_preferred_console(name, idx, options, NULL);
 893 }
 894
 895 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 896 {
 897         struct console_cmdline *c;
 898         int i;
 899
 900         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 901                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 902                           console_cmdline[i].index == idx) {
 903                                 c = &console_cmdline[i];
 904                                 strlcpy(c->name, name_new, sizeof(c->name));
 905                                 c->name[sizeof(c->name) - 1] = 0;
 906                                 c->options = options;
 907                                 c->index = idx_new;
 908                                 return i;
 909                 }
 910         /* not found */
 911         return -1;
 912 }
 913
 914 int console_suspend_enabled = 1;
 915 EXPORT_SYMBOL(console_suspend_enabled);
 916
 917 static int __init console_suspend_disable(char *str)
 918 {
 919         console_suspend_enabled = 0;
 920         return 1;
 921 }
 922 __setup("no_console_suspend", console_suspend_disable);
 923
 924 /**
 925  * suspend_console - suspend the console subsystem
 926  *
 927  * This disables printk() while we go into suspend states
 928  */
 929 void suspend_console(void)
 930 {
 931         if (!console_suspend_enabled)
 932                 return;
 933         printk("Suspending console(s)\n");
 934         acquire_console_sem();
 935         console_suspended = 1;
 936 }
 937
 938 void resume_console(void)
 939 {
 940         if (!console_suspend_enabled)
 941                 return;
 942         console_suspended = 0;
 943         release_console_sem();
 944 }
 945
 946 /**
 947  * acquire_console_sem - lock the console system for exclusive use.
 948  *
 949  * Acquires a semaphore which guarantees that the caller has
 950  * exclusive access to the console system and the console_drivers list.
 951  *
 952  * Can sleep, returns nothing.
 953  */
 954 void acquire_console_sem(void)
 955 {
 956         BUG_ON(in_interrupt());
 957         if (console_suspended) {
 958                 down(&secondary_console_sem);
 959                 return;
 960         }
 961         down(&console_sem);
 962         console_locked = 1;
 963         console_may_schedule = 1;
 964 }
 965 EXPORT_SYMBOL(acquire_console_sem);
 966
 967 int try_acquire_console_sem(void)
 968 {
 969         if (down_trylock(&console_sem))
 970                 return -1;
 971         console_locked = 1;
 972         console_may_schedule = 0;
 973         return 0;
 974 }
 975 EXPORT_SYMBOL(try_acquire_console_sem);
 976
 977 int is_console_locked(void)
 978 {
 979         return console_locked;
 980 }
 981
 982 void wake_up_klogd(void)
 983 {
 984         if (!oops_in_progress && waitqueue_active(&log_wait))
 985                 wake_up_interruptible(&log_wait);
 986 }
 987
 988 /**
 989  * release_console_sem - unlock the console system
 990  *
 991  * Releases the semaphore which the caller holds on the console system
 992  * and the console driver list.
 993  *
 994  * While the semaphore was held, console output may have been buffered
 995  * by printk().  If this is the case, release_console_sem() emits
 996  * the output prior to releasing the semaphore.
 997  *
 998  * If there is output waiting for klogd, we wake it up.
 999  *
1000  * release_console_sem() may be called from any context.
1001  */
1002 void release_console_sem(void)
1003 {
1004         unsigned long flags;
1005         unsigned _con_start, _log_end;
1006         unsigned wake_klogd = 0;
1007
1008         if (console_suspended) {
1009                 up(&secondary_console_sem);
1010                 return;
1011         }
1012
1013         console_may_schedule = 0;
1014
1015         for ( ; ; ) {
1016                 spin_lock_irqsave(&logbuf_lock, flags);
1017                 wake_klogd |= log_start - log_end;
1018                 if (con_start == log_end)
1019                         break;                  /* Nothing to print */
1020                 _con_start = con_start;
1021                 _log_end = log_end;
1022                 con_start = log_end;            /* Flush */
1023                 spin_unlock(&logbuf_lock);
1024                 call_console_drivers(_con_start, _log_end);
1025                 local_irq_restore(flags);
1026         }
1027         console_locked = 0;
1028         up(&console_sem);
1029         spin_unlock_irqrestore(&logbuf_lock, flags);
1030         if (wake_klogd)
1031                 wake_up_klogd();
1032 }
1033 EXPORT_SYMBOL(release_console_sem);
1034
1035 /**
1036  * console_conditional_schedule - yield the CPU if required
1037  *
1038  * If the console code is currently allowed to sleep, and
1039  * if this CPU should yield the CPU to another task, do
1040  * so here.
1041  *
1042  * Must be called within acquire_console_sem().
1043  */
1044 void __sched console_conditional_schedule(void)
1045 {
1046         if (console_may_schedule)
1047                 cond_resched();
1048 }
1049 EXPORT_SYMBOL(console_conditional_schedule);
1050
1051 void console_print(const char *s)
1052 {
1053         printk(KERN_EMERG "%s", s);
1054 }
1055 EXPORT_SYMBOL(console_print);
1056
1057 void console_unblank(void)
1058 {
1059         struct console *c;
1060
1061         /*
1062          * console_unblank can no longer be called in interrupt context unless
1063          * oops_in_progress is set to 1..
1064          */
1065         if (oops_in_progress) {
1066                 if (down_trylock(&console_sem) != 0)
1067                         return;
1068         } else
1069                 acquire_console_sem();
1070
1071         console_locked = 1;
1072         console_may_schedule = 0;
1073         for (c = console_drivers; c != NULL; c = c->next)
1074                 if ((c->flags & CON_ENABLED) && c->unblank)
1075                         c->unblank();
1076         release_console_sem();
1077 }
1078
1079 /*
1080  * Return the console tty driver structure and its associated index
1081  */
1082 struct tty_driver *console_device(int *index)
1083 {
1084         struct console *c;
1085         struct tty_driver *driver = NULL;
1086
1087         acquire_console_sem();
1088         for (c = console_drivers; c != NULL; c = c->next) {
1089                 if (!c->device)
1090                         continue;
1091                 driver = c->device(c, index);
1092                 if (driver)
1093                         break;
1094         }
1095         release_console_sem();
1096         return driver;
1097 }
1098
1099 /*
1100  * Prevent further output on the passed console device so that (for example)
1101  * serial drivers can disable console output before suspending a port, and can
1102  * re-enable output afterwards.
1103  */
1104 void console_stop(struct console *console)
1105 {
1106         acquire_console_sem();
1107         console->flags &= ~CON_ENABLED;
1108         release_console_sem();
1109 }
1110 EXPORT_SYMBOL(console_stop);
1111
1112 void console_start(struct console *console)
1113 {
1114         acquire_console_sem();
1115         console->flags |= CON_ENABLED;
1116         release_console_sem();
1117 }
1118 EXPORT_SYMBOL(console_start);
1119
1120 /*
1121  * The console driver calls this routine during kernel initialization
1122  * to register the console printing procedure with printk() and to
1123  * print any messages that were printed by the kernel before the
1124  * console driver was initialized.
1125  */
1126 void register_console(struct console *console)
1127 {
1128         int i;
1129         unsigned long flags;
1130         struct console *bootconsole = NULL;
1131
1132         if (console_drivers) {
1133                 if (console->flags & CON_BOOT)
1134                         return;
1135                 if (console_drivers->flags & CON_BOOT)
1136                         bootconsole = console_drivers;
1137         }
1138
1139         if (preferred_console < 0 || bootconsole || !console_drivers)
1140                 preferred_console = selected_console;
1141
1142         if (console->early_setup)
1143                 console->early_setup();
1144
1145         /*
1146          *      See if we want to use this console driver. If we
1147          *      didn't select a console we take the first one
1148          *      that registers here.
1149          */
1150         if (preferred_console < 0) {
1151                 if (console->index < 0)
1152                         console->index = 0;
1153                 if (console->setup == NULL ||
1154                     console->setup(console, NULL) == 0) {
1155                         console->flags |= CON_ENABLED;
1156                         if (console->device) {
1157                                 console->flags |= CON_CONSDEV;
1158                                 preferred_console = 0;
1159                         }
1160                 }
1161         }
1162
1163         /*
1164          *      See if this console matches one we selected on
1165          *      the command line.
1166          */
1167         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1168                         i++) {
1169                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1170                         continue;
1171                 if (console->index >= 0 &&
1172                     console->index != console_cmdline[i].index)
1173                         continue;
1174                 if (console->index < 0)
1175                         console->index = console_cmdline[i].index;
1176 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1177                 if (console_cmdline[i].brl_options) {
1178                         console->flags |= CON_BRL;
1179                         braille_register_console(console,
1180                                         console_cmdline[i].index,
1181                                         console_cmdline[i].options,
1182                                         console_cmdline[i].brl_options);
1183                         return;
1184                 }
1185 #endif
1186                 if (console->setup &&
1187                     console->setup(console, console_cmdline[i].options) != 0)
1188                         break;
1189                 console->flags |= CON_ENABLED;
1190                 console->index = console_cmdline[i].index;
1191                 if (i == selected_console) {
1192                         console->flags |= CON_CONSDEV;
1193                         preferred_console = selected_console;
1194                 }
1195                 break;
1196         }
1197
1198         if (!(console->flags & CON_ENABLED))
1199                 return;
1200
1201         if (bootconsole && (console->flags & CON_CONSDEV)) {
1202                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1203                        bootconsole->name, bootconsole->index,
1204                        console->name, console->index);
1205                 unregister_console(bootconsole);
1206                 console->flags &= ~CON_PRINTBUFFER;
1207         } else {
1208                 printk(KERN_INFO "console [%s%d] enabled\n",
1209                        console->name, console->index);
1210         }
1211
1212         /*
1213          *      Put this console in the list - keep the
1214          *      preferred driver at the head of the list.
1215          */
1216         acquire_console_sem();
1217         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1218                 console->next = console_drivers;
1219                 console_drivers = console;
1220                 if (console->next)
1221                         console->next->flags &= ~CON_CONSDEV;
1222         } else {
1223                 console->next = console_drivers->next;
1224                 console_drivers->next = console;
1225         }
1226         if (console->flags & CON_PRINTBUFFER) {
1227                 /*
1228                  * release_console_sem() will print out the buffered messages
1229                  * for us.
1230                  */
1231                 spin_lock_irqsave(&logbuf_lock, flags);
1232                 con_start = log_start;
1233                 spin_unlock_irqrestore(&logbuf_lock, flags);
1234         }
1235         release_console_sem();
1236 }
1237 EXPORT_SYMBOL(register_console);
1238
1239 int unregister_console(struct console *console)
1240 {
1241         struct console *a, *b;
1242         int res = 1;
1243
1244 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1245         if (console->flags & CON_BRL)
1246                 return braille_unregister_console(console);
1247 #endif
1248
1249         acquire_console_sem();
1250         if (console_drivers == console) {
1251                 console_drivers=console->next;
1252                 res = 0;
1253         } else if (console_drivers) {
1254                 for (a=console_drivers->next, b=console_drivers ;
1255                      a; b=a, a=b->next) {
1256                         if (a == console) {
1257                                 b->next = a->next;
1258                                 res = 0;
1259                                 break;
1260                         }
1261                 }
1262         }
1263
1264         /*
1265          * If this isn't the last console and it has CON_CONSDEV set, we
1266          * need to set it on the next preferred console.
1267          */
1268         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1269                 console_drivers->flags |= CON_CONSDEV;
1270
1271         release_console_sem();
1272         return res;
1273 }
1274 EXPORT_SYMBOL(unregister_console);
1275
1276 static int __init disable_boot_consoles(void)
1277 {
1278         if (console_drivers != NULL) {
1279                 if (console_drivers->flags & CON_BOOT) {
1280                         printk(KERN_INFO "turn off boot console %s%d\n",
1281                                 console_drivers->name, console_drivers->index);
1282                         return unregister_console(console_drivers);
1283                 }
1284         }
1285         return 0;
1286 }
1287 late_initcall(disable_boot_consoles);
1288
1289 /**
1290  * tty_write_message - write a message to a certain tty, not just the console.
1291  * @tty: the destination tty_struct
1292  * @msg: the message to write
1293  *
1294  * This is used for messages that need to be redirected to a specific tty.
1295  * We don't put it into the syslog queue right now maybe in the future if
1296  * really needed.
1297  */
1298 void tty_write_message(struct tty_struct *tty, char *msg)
1299 {
1300         if (tty && tty->ops->write)
1301                 tty->ops->write(tty, msg, strlen(msg));
1302         return;
1303 }
1304
1305 #if defined CONFIG_PRINTK
1306 /*
1307  * printk rate limiting, lifted from the networking subsystem.
1308  *
1309  * This enforces a rate limit: not more than one kernel message
1310  * every printk_ratelimit_jiffies to make a denial-of-service
1311  * attack impossible.
1312  */
1313 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1314 {
1315         return __ratelimit(ratelimit_jiffies, ratelimit_burst);
1316 }
1317 EXPORT_SYMBOL(__printk_ratelimit);
1318
1319 /* minimum time in jiffies between messages */
1320 int printk_ratelimit_jiffies = 5 * HZ;
1321
1322 /* number of messages we send before ratelimiting */
1323 int printk_ratelimit_burst = 10;
1324
1325 int printk_ratelimit(void)
1326 {
1327         return __printk_ratelimit(printk_ratelimit_jiffies,
1328                                 printk_ratelimit_burst);
1329 }
1330 EXPORT_SYMBOL(printk_ratelimit);
1331
1332 /**
1333  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1334  * @caller_jiffies: pointer to caller's state
1335  * @interval_msecs: minimum interval between prints
1336  *
1337  * printk_timed_ratelimit() returns true if more than @interval_msecs
1338  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1339  * returned true.
1340  */
1341 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1342                         unsigned int interval_msecs)
1343 {
1344         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1345                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1346                 return true;
1347         }
1348         return false;
1349 }
1350 EXPORT_SYMBOL(printk_timed_ratelimit);
1351 #endif