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 #ifdef CONFIG_DEBUG_LL
  48 extern void printascii(char *);
  49 #endif
  50
  51 /* printk's without a loglevel use this.. */
  52 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  53
  54 /* We show everything that is MORE important than this.. */
  55 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  56 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  57
  58 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  59
  60 int console_printk[4] = {
  61         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  62         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  63         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  64         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  65 };
  66
  67 /*
  68  * Low level drivers may need that to know if they can schedule in
  69  * their unblank() callback or not. So let's export it.
  70  */
  71 int oops_in_progress;
  72 EXPORT_SYMBOL(oops_in_progress);
  73
  74 /*
  75  * console_sem protects the console_drivers list, and also
  76  * provides serialisation for access to the entire console
  77  * driver system.
  78  */
  79 static DECLARE_MUTEX(console_sem);
  80 static DECLARE_MUTEX(secondary_console_sem);
  81 struct console *console_drivers;
  82 EXPORT_SYMBOL_GPL(console_drivers);
  83
  84 /*
  85  * This is used for debugging the mess that is the VT code by
  86  * keeping track if we have the console semaphore held. It's
  87  * definitely not the perfect debug tool (we don't know if _WE_
  88  * hold it are racing, but it helps tracking those weird code
  89  * path in the console code where we end up in places I want
  90  * locked without the console sempahore held
  91  */
  92 static int console_locked, console_suspended;
  93
  94 /*
  95  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
  96  * It is also used in interesting ways to provide interlocking in
  97  * release_console_sem().
  98  */
  99 static DEFINE_SPINLOCK(logbuf_lock);
 100
 101 #define LOG_BUF_MASK (log_buf_len-1)
 102 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
 103
 104 /*
 105  * The indices into log_buf are not constrained to log_buf_len - they
 106  * must be masked before subscripting
 107  */
 108 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
 109 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
 110 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 111
 112 /*
 113  *      Array of consoles built from command line options (console=)
 114  */
 115 struct console_cmdline
 116 {
 117         char    name[8];                        /* Name of the driver       */
 118         int     index;                          /* Minor dev. to use        */
 119         char    *options;                       /* Options for the driver   */
 120 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 121         char    *brl_options;                   /* Options for braille driver */
 122 #endif
 123 };
 124
 125 #define MAX_CMDLINECONSOLES 8
 126
 127 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 128 static int selected_console = -1;
 129 static int preferred_console = -1;
 130 int console_set_on_cmdline;
 131 EXPORT_SYMBOL(console_set_on_cmdline);
 132
 133 /* Flag: console code may call schedule() */
 134 static int console_may_schedule;
 135
 136 #ifdef CONFIG_PRINTK
 137
 138 static char __log_buf[__LOG_BUF_LEN];
 139 static char *log_buf = __log_buf;
 140 static int log_buf_len = __LOG_BUF_LEN;
 141 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 142
 143 static int __init log_buf_len_setup(char *str)
 144 {
 145         unsigned size = memparse(str, &str);
 146         unsigned long flags;
 147
 148         if (size)
 149                 size = roundup_pow_of_two(size);
 150         if (size > log_buf_len) {
 151                 unsigned start, dest_idx, offset;
 152                 char *new_log_buf;
 153
 154                 new_log_buf = alloc_bootmem(size);
 155                 if (!new_log_buf) {
 156                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 157                         goto out;
 158                 }
 159
 160                 spin_lock_irqsave(&logbuf_lock, flags);
 161                 log_buf_len = size;
 162                 log_buf = new_log_buf;
 163
 164                 offset = start = min(con_start, log_start);
 165                 dest_idx = 0;
 166                 while (start != log_end) {
 167                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 168                         start++;
 169                         dest_idx++;
 170                 }
 171                 log_start -= offset;
 172                 con_start -= offset;
 173                 log_end -= offset;
 174                 spin_unlock_irqrestore(&logbuf_lock, flags);
 175
 176                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 177         }
 178 out:
 179         return 1;
 180 }
 181
 182 __setup("log_buf_len=", log_buf_len_setup);
 183
 184 #ifdef CONFIG_BOOT_PRINTK_DELAY
 185
 186 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 187 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
 188
 189 static int __init boot_delay_setup(char *str)
 190 {
 191         unsigned long lpj;
 192         unsigned long long loops_per_msec;
 193
 194         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 195         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 196
 197         get_option(&str, &boot_delay);
 198         if (boot_delay > 10 * 1000)
 199                 boot_delay = 0;
 200
 201         printk_delay_msec = loops_per_msec;
 202         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 203                 "HZ: %d, printk_delay_msec: %llu\n",
 204                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
 205         return 1;
 206 }
 207 __setup("boot_delay=", boot_delay_setup);
 208
 209 static void boot_delay_msec(void)
 210 {
 211         unsigned long long k;
 212         unsigned long timeout;
 213
 214         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 215                 return;
 216
 217         k = (unsigned long long)printk_delay_msec * boot_delay;
 218
 219         timeout = jiffies + msecs_to_jiffies(boot_delay);
 220         while (k) {
 221                 k--;
 222                 cpu_relax();
 223                 /*
 224                  * use (volatile) jiffies to prevent
 225                  * compiler reduction; loop termination via jiffies
 226                  * is secondary and may or may not happen.
 227                  */
 228                 if (time_after(jiffies, timeout))
 229                         break;
 230                 touch_nmi_watchdog();
 231         }
 232 }
 233 #else
 234 static inline void boot_delay_msec(void)
 235 {
 236 }
 237 #endif
 238
 239 /*
 240  * Return the number of unread characters in the log buffer.
 241  */
 242 static int log_buf_get_len(void)
 243 {
 244         return logged_chars;
 245 }
 246
 247 /*
 248  * Copy a range of characters from the log buffer.
 249  */
 250 int log_buf_copy(char *dest, int idx, int len)
 251 {
 252         int ret, max;
 253         bool took_lock = false;
 254
 255         if (!oops_in_progress) {
 256                 spin_lock_irq(&logbuf_lock);
 257                 took_lock = true;
 258         }
 259
 260         max = log_buf_get_len();
 261         if (idx < 0 || idx >= max) {
 262                 ret = -1;
 263         } else {
 264                 if (len > max)
 265                         len = max;
 266                 ret = len;
 267                 idx += (log_end - max);
 268                 while (len-- > 0)
 269                         dest[len] = LOG_BUF(idx + len);
 270         }
 271
 272         if (took_lock)
 273                 spin_unlock_irq(&logbuf_lock);
 274
 275         return ret;
 276 }
 277
 278 /*
 279  * Commands to do_syslog:
 280  *
 281  *      0 -- Close the log.  Currently a NOP.
 282  *      1 -- Open the log. Currently a NOP.
 283  *      2 -- Read from the log.
 284  *      3 -- Read all messages remaining in the ring buffer.
 285  *      4 -- Read and clear all messages remaining in the ring buffer
 286  *      5 -- Clear ring buffer.
 287  *      6 -- Disable printk's to console
 288  *      7 -- Enable printk's to console
 289  *      8 -- Set level of messages printed to console
 290  *      9 -- Return number of unread characters in the log buffer
 291  *     10 -- Return size of the log buffer
 292  */
 293 int do_syslog(int type, char __user *buf, int len)
 294 {
 295         unsigned i, j, limit, count;
 296         int do_clear = 0;
 297         char c;
 298         int error = 0;
 299
 300         error = security_syslog(type);
 301         if (error)
 302                 return error;
 303
 304         switch (type) {
 305         case 0:         /* Close log */
 306                 break;
 307         case 1:         /* Open log */
 308                 break;
 309         case 2:         /* Read from log */
 310                 error = -EINVAL;
 311                 if (!buf || len < 0)
 312                         goto out;
 313                 error = 0;
 314                 if (!len)
 315                         goto out;
 316                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 317                         error = -EFAULT;
 318                         goto out;
 319                 }
 320                 error = wait_event_interruptible(log_wait,
 321                                                         (log_start - log_end));
 322                 if (error)
 323                         goto out;
 324                 i = 0;
 325                 spin_lock_irq(&logbuf_lock);
 326                 while (!error && (log_start != log_end) && i < len) {
 327                         c = LOG_BUF(log_start);
 328                         log_start++;
 329                         spin_unlock_irq(&logbuf_lock);
 330                         error = __put_user(c,buf);
 331                         buf++;
 332                         i++;
 333                         cond_resched();
 334                         spin_lock_irq(&logbuf_lock);
 335                 }
 336                 spin_unlock_irq(&logbuf_lock);
 337                 if (!error)
 338                         error = i;
 339                 break;
 340         case 4:         /* Read/clear last kernel messages */
 341                 do_clear = 1;
 342                 /* FALL THRU */
 343         case 3:         /* Read last kernel messages */
 344                 error = -EINVAL;
 345                 if (!buf || len < 0)
 346                         goto out;
 347                 error = 0;
 348                 if (!len)
 349                         goto out;
 350                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 351                         error = -EFAULT;
 352                         goto out;
 353                 }
 354                 count = len;
 355                 if (count > log_buf_len)
 356                         count = log_buf_len;
 357                 spin_lock_irq(&logbuf_lock);
 358                 if (count > logged_chars)
 359                         count = logged_chars;
 360                 if (do_clear)
 361                         logged_chars = 0;
 362                 limit = log_end;
 363                 /*
 364                  * __put_user() could sleep, and while we sleep
 365                  * printk() could overwrite the messages
 366                  * we try to copy to user space. Therefore
 367                  * the messages are copied in reverse. <manfreds>
 368                  */
 369                 for (i = 0; i < count && !error; i++) {
 370                         j = limit-1-i;
 371                         if (j + log_buf_len < log_end)
 372                                 break;
 373                         c = LOG_BUF(j);
 374                         spin_unlock_irq(&logbuf_lock);
 375                         error = __put_user(c,&buf[count-1-i]);
 376                         cond_resched();
 377                         spin_lock_irq(&logbuf_lock);
 378                 }
 379                 spin_unlock_irq(&logbuf_lock);
 380                 if (error)
 381                         break;
 382                 error = i;
 383                 if (i != count) {
 384                         int offset = count-error;
 385                         /* buffer overflow during copy, correct user buffer. */
 386                         for (i = 0; i < error; i++) {
 387                                 if (__get_user(c,&buf[i+offset]) ||
 388                                     __put_user(c,&buf[i])) {
 389                                         error = -EFAULT;
 390                                         break;
 391                                 }
 392                                 cond_resched();
 393                         }
 394                 }
 395                 break;
 396         case 5:         /* Clear ring buffer */
 397                 logged_chars = 0;
 398                 break;
 399         case 6:         /* Disable logging to console */
 400                 console_loglevel = minimum_console_loglevel;
 401                 break;
 402         case 7:         /* Enable logging to console */
 403                 console_loglevel = default_console_loglevel;
 404                 break;
 405         case 8:         /* Set level of messages printed to console */
 406                 error = -EINVAL;
 407                 if (len < 1 || len > 8)
 408                         goto out;
 409                 if (len < minimum_console_loglevel)
 410                         len = minimum_console_loglevel;
 411                 console_loglevel = len;
 412                 error = 0;
 413                 break;
 414         case 9:         /* Number of chars in the log buffer */
 415                 error = log_end - log_start;
 416                 break;
 417         case 10:        /* Size of the log buffer */
 418                 error = log_buf_len;
 419                 break;
 420         default:
 421                 error = -EINVAL;
 422                 break;
 423         }
 424 out:
 425         return error;
 426 }
 427
 428 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 429 {
 430         return do_syslog(type, buf, len);
 431 }
 432
 433 /*
 434  * Call the console drivers on a range of log_buf
 435  */
 436 static void __call_console_drivers(unsigned start, unsigned end)
 437 {
 438         struct console *con;
 439
 440         for (con = console_drivers; con; con = con->next) {
 441                 if ((con->flags & CON_ENABLED) && con->write &&
 442                                 (cpu_online(smp_processor_id()) ||
 443                                 (con->flags & CON_ANYTIME)))
 444                         con->write(con, &LOG_BUF(start), end - start);
 445         }
 446 }
 447
 448 static int __read_mostly ignore_loglevel;
 449
 450 static int __init ignore_loglevel_setup(char *str)
 451 {
 452         ignore_loglevel = 1;
 453         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 454
 455         return 0;
 456 }
 457
 458 early_param("ignore_loglevel", ignore_loglevel_setup);
 459
 460 /*
 461  * Write out chars from start to end - 1 inclusive
 462  */
 463 static void _call_console_drivers(unsigned start,
 464                                 unsigned end, int msg_log_level)
 465 {
 466         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 467                         console_drivers && start != end) {
 468                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 469                         /* wrapped write */
 470                         __call_console_drivers(start & LOG_BUF_MASK,
 471                                                 log_buf_len);
 472                         __call_console_drivers(0, end & LOG_BUF_MASK);
 473                 } else {
 474                         __call_console_drivers(start, end);
 475                 }
 476         }
 477 }
 478
 479 /*
 480  * Call the console drivers, asking them to write out
 481  * log_buf[start] to log_buf[end - 1].
 482  * The console_sem must be held.
 483  */
 484 static void call_console_drivers(unsigned start, unsigned end)
 485 {
 486         unsigned cur_index, start_print;
 487         static int msg_level = -1;
 488
 489         BUG_ON(((int)(start - end)) > 0);
 490
 491         cur_index = start;
 492         start_print = start;
 493         while (cur_index != end) {
 494                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 495                                 LOG_BUF(cur_index + 0) == '<' &&
 496                                 LOG_BUF(cur_index + 1) >= '0' &&
 497                                 LOG_BUF(cur_index + 1) <= '7' &&
 498                                 LOG_BUF(cur_index + 2) == '>') {
 499                         msg_level = LOG_BUF(cur_index + 1) - '0';
 500                         cur_index += 3;
 501                         start_print = cur_index;
 502                 }
 503                 while (cur_index != end) {
 504                         char c = LOG_BUF(cur_index);
 505
 506                         cur_index++;
 507                         if (c == '\n') {
 508                                 if (msg_level < 0) {
 509                                         /*
 510                                          * printk() has already given us loglevel tags in
 511                                          * the buffer.  This code is here in case the
 512                                          * log buffer has wrapped right round and scribbled
 513                                          * on those tags
 514                                          */
 515                                         msg_level = default_message_loglevel;
 516                                 }
 517                                 _call_console_drivers(start_print, cur_index, msg_level);
 518                                 msg_level = -1;
 519                                 start_print = cur_index;
 520                                 break;
 521                         }
 522                 }
 523         }
 524         _call_console_drivers(start_print, end, msg_level);
 525 }
 526
 527 static void emit_log_char(char c)
 528 {
 529         LOG_BUF(log_end) = c;
 530         log_end++;
 531         if (log_end - log_start > log_buf_len)
 532                 log_start = log_end - log_buf_len;
 533         if (log_end - con_start > log_buf_len)
 534                 con_start = log_end - log_buf_len;
 535         if (logged_chars < log_buf_len)
 536                 logged_chars++;
 537 }
 538
 539 /*
 540  * Zap console related locks when oopsing. Only zap at most once
 541  * every 10 seconds, to leave time for slow consoles to print a
 542  * full oops.
 543  */
 544 static void zap_locks(void)
 545 {
 546         static unsigned long oops_timestamp;
 547
 548         if (time_after_eq(jiffies, oops_timestamp) &&
 549                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 550                 return;
 551
 552         oops_timestamp = jiffies;
 553
 554         /* If a crash is occurring, make sure we can't deadlock */
 555         spin_lock_init(&logbuf_lock);
 556         /* And make sure that we print immediately */
 557         init_MUTEX(&console_sem);
 558 }
 559
 560 #if defined(CONFIG_PRINTK_TIME)
 561 static int printk_time = 1;
 562 #else
 563 static int printk_time = 0;
 564 #endif
 565 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 566
 567 /* Check if we have any console registered that can be called early in boot. */
 568 static int have_callable_console(void)
 569 {
 570         struct console *con;
 571
 572         for (con = console_drivers; con; con = con->next)
 573                 if (con->flags & CON_ANYTIME)
 574                         return 1;
 575
 576         return 0;
 577 }
 578
 579 /**
 580  * printk - print a kernel message
 581  * @fmt: format string
 582  *
 583  * This is printk().  It can be called from any context.  We want it to work.
 584  * Be aware of the fact that if oops_in_progress is not set, we might try to
 585  * wake klogd up which could deadlock on runqueue lock if printk() is called
 586  * from scheduler code.
 587  *
 588  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 589  * call the console drivers.  If we fail to get the semaphore we place the output
 590  * into the log buffer and return.  The current holder of the console_sem will
 591  * notice the new output in release_console_sem() and will send it to the
 592  * consoles before releasing the semaphore.
 593  *
 594  * One effect of this deferred printing is that code which calls printk() and
 595  * then changes console_loglevel may break. This is because console_loglevel
 596  * is inspected when the actual printing occurs.
 597  *
 598  * See also:
 599  * printf(3)
 600  */
 601
 602 asmlinkage int printk(const char *fmt, ...)
 603 {
 604         va_list args;
 605         int r;
 606
 607         va_start(args, fmt);
 608         r = vprintk(fmt, args);
 609         va_end(args);
 610
 611         return r;
 612 }
 613
 614 /* cpu currently holding logbuf_lock */
 615 static volatile unsigned int printk_cpu = UINT_MAX;
 616
 617 /*
 618  * Can we actually use the console at this time on this cpu?
 619  *
 620  * Console drivers may assume that per-cpu resources have
 621  * been allocated. So unless they're explicitly marked as
 622  * being able to cope (CON_ANYTIME) don't call them until
 623  * this CPU is officially up.
 624  */
 625 static inline int can_use_console(unsigned int cpu)
 626 {
 627         return cpu_online(cpu) || have_callable_console();
 628 }
 629
 630 /*
 631  * Try to get console ownership to actually show the kernel
 632  * messages from a 'printk'. Return true (and with the
 633  * console_semaphore held, and 'console_locked' set) if it
 634  * is successful, false otherwise.
 635  *
 636  * This gets called with the 'logbuf_lock' spinlock held and
 637  * interrupts disabled. It should return with 'lockbuf_lock'
 638  * released but interrupts still disabled.
 639  */
 640 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 641 {
 642         int retval = 0;
 643
 644         if (!try_acquire_console_sem()) {
 645                 retval = 1;
 646
 647                 /*
 648                  * If we can't use the console, we need to release
 649                  * the console semaphore by hand to avoid flushing
 650                  * the buffer. We need to hold the console semaphore
 651                  * in order to do this test safely.
 652                  */
 653                 if (!can_use_console(cpu)) {
 654                         console_locked = 0;
 655                         up(&console_sem);
 656                         retval = 0;
 657                 }
 658         }
 659         printk_cpu = UINT_MAX;
 660         spin_unlock(&logbuf_lock);
 661         return retval;
 662 }
 663 static const char recursion_bug_msg [] =
 664                 KERN_CRIT "BUG: recent printk recursion!\n";
 665 static int recursion_bug;
 666         static int new_text_line = 1;
 667 static char printk_buf[1024];
 668
 669 asmlinkage int vprintk(const char *fmt, va_list args)
 670 {
 671         int printed_len = 0;
 672         int current_log_level = default_message_loglevel;
 673         unsigned long flags;
 674         int this_cpu;
 675         char *p;
 676
 677         boot_delay_msec();
 678
 679         preempt_disable();
 680         /* This stops the holder of console_sem just where we want him */
 681         raw_local_irq_save(flags);
 682         this_cpu = smp_processor_id();
 683
 684         /*
 685          * Ouch, printk recursed into itself!
 686          */
 687         if (unlikely(printk_cpu == this_cpu)) {
 688                 /*
 689                  * If a crash is occurring during printk() on this CPU,
 690                  * then try to get the crash message out but make sure
 691                  * we can't deadlock. Otherwise just return to avoid the
 692                  * recursion and return - but flag the recursion so that
 693                  * it can be printed at the next appropriate moment:
 694                  */
 695                 if (!oops_in_progress) {
 696                         recursion_bug = 1;
 697                         goto out_restore_irqs;
 698                 }
 699                 zap_locks();
 700         }
 701
 702         lockdep_off();
 703         spin_lock(&logbuf_lock);
 704         printk_cpu = this_cpu;
 705
 706         if (recursion_bug) {
 707                 recursion_bug = 0;
 708                 strcpy(printk_buf, recursion_bug_msg);
 709                 printed_len = sizeof(recursion_bug_msg);
 710         }
 711         /* Emit the output into the temporary buffer */
 712         printed_len += vscnprintf(printk_buf + printed_len,
 713                                   sizeof(printk_buf) - printed_len, fmt, args);
 714
 715 #ifdef  CONFIG_DEBUG_LL
 716         printascii(printk_buf);
 717 #endif
 718
 719         /*
 720          * Copy the output into log_buf.  If the caller didn't provide
 721          * appropriate log level tags, we insert them here
 722          */
 723         for (p = printk_buf; *p; p++) {
 724                 if (new_text_line) {
 725                         /* If a token, set current_log_level and skip over */
 726                         if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
 727                             p[2] == '>') {
 728                                 current_log_level = p[1] - '0';
 729                                 p += 3;
 730                                 printed_len -= 3;
 731                         }
 732
 733                         /* Always output the token */
 734                         emit_log_char('<');
 735                         emit_log_char(current_log_level + '0');
 736                         emit_log_char('>');
 737                         printed_len += 3;
 738                         new_text_line = 0;
 739
 740                         if (printk_time) {
 741                                 /* Follow the token with the time */
 742                                 char tbuf[50], *tp;
 743                                 unsigned tlen;
 744                                 unsigned long long t;
 745                                 unsigned long nanosec_rem;
 746
 747                                 t = cpu_clock(printk_cpu);
 748                                 nanosec_rem = do_div(t, 1000000000);
 749                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 750                                                 (unsigned long) t,
 751                                                 nanosec_rem / 1000);
 752
 753                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 754                                         emit_log_char(*tp);
 755                                 printed_len += tlen;
 756                         }
 757
 758                         if (!*p)
 759                                 break;
 760                 }
 761
 762                 emit_log_char(*p);
 763                 if (*p == '\n')
 764                         new_text_line = 1;
 765         }
 766
 767         /*
 768          * Try to acquire and then immediately release the
 769          * console semaphore. The release will do all the
 770          * actual magic (print out buffers, wake up klogd,
 771          * etc).
 772          *
 773          * The acquire_console_semaphore_for_printk() function
 774          * will release 'logbuf_lock' regardless of whether it
 775          * actually gets the semaphore or not.
 776          */
 777         if (acquire_console_semaphore_for_printk(this_cpu))
 778                 release_console_sem();
 779
 780         lockdep_on();
 781 out_restore_irqs:
 782         raw_local_irq_restore(flags);
 783
 784         preempt_enable();
 785         return printed_len;
 786 }
 787 EXPORT_SYMBOL(printk);
 788 EXPORT_SYMBOL(vprintk);
 789
 790 #else
 791
 792 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 793 {
 794         return -ENOSYS;
 795 }
 796
 797 static void call_console_drivers(unsigned start, unsigned end)
 798 {
 799 }
 800
 801 #endif
 802
 803 static int __add_preferred_console(char *name, int idx, char *options,
 804                                    char *brl_options)
 805 {
 806         struct console_cmdline *c;
 807         int i;
 808
 809         /*
 810          *      See if this tty is not yet registered, and
 811          *      if we have a slot free.
 812          */
 813         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 814                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 815                           console_cmdline[i].index == idx) {
 816                                 if (!brl_options)
 817                                         selected_console = i;
 818                                 return 0;
 819                 }
 820         if (i == MAX_CMDLINECONSOLES)
 821                 return -E2BIG;
 822         if (!brl_options)
 823                 selected_console = i;
 824         c = &console_cmdline[i];
 825         strlcpy(c->name, name, sizeof(c->name));
 826         c->options = options;
 827 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 828         c->brl_options = brl_options;
 829 #endif
 830         c->index = idx;
 831         return 0;
 832 }
 833 /*
 834  * Set up a list of consoles.  Called from init/main.c
 835  */
 836 static int __init console_setup(char *str)
 837 {
 838         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 839         char *s, *options, *brl_options = NULL;
 840         int idx;
 841
 842 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 843         if (!memcmp(str, "brl,", 4)) {
 844                 brl_options = "";
 845                 str += 4;
 846         } else if (!memcmp(str, "brl=", 4)) {
 847                 brl_options = str + 4;
 848                 str = strchr(brl_options, ',');
 849                 if (!str) {
 850                         printk(KERN_ERR "need port name after brl=\n");
 851                         return 1;
 852                 }
 853                 *(str++) = 0;
 854         }
 855 #endif
 856
 857         /*
 858          * Decode str into name, index, options.
 859          */
 860         if (str[0] >= '0' && str[0] <= '9') {
 861                 strcpy(buf, "ttyS");
 862                 strncpy(buf + 4, str, sizeof(buf) - 5);
 863         } else {
 864                 strncpy(buf, str, sizeof(buf) - 1);
 865         }
 866         buf[sizeof(buf) - 1] = 0;
 867         if ((options = strchr(str, ',')) != NULL)
 868                 *(options++) = 0;
 869 #ifdef __sparc__
 870         if (!strcmp(str, "ttya"))
 871                 strcpy(buf, "ttyS0");
 872         if (!strcmp(str, "ttyb"))
 873                 strcpy(buf, "ttyS1");
 874 #endif
 875         for (s = buf; *s; s++)
 876                 if ((*s >= '0' && *s <= '9') || *s == ',')
 877                         break;
 878         idx = simple_strtoul(s, NULL, 10);
 879         *s = 0;
 880
 881         __add_preferred_console(buf, idx, options, brl_options);
 882         console_set_on_cmdline = 1;
 883         return 1;
 884 }
 885 __setup("console=", console_setup);
 886
 887 /**
 888  * add_preferred_console - add a device to the list of preferred consoles.
 889  * @name: device name
 890  * @idx: device index
 891  * @options: options for this console
 892  *
 893  * The last preferred console added will be used for kernel messages
 894  * and stdin/out/err for init.  Normally this is used by console_setup
 895  * above to handle user-supplied console arguments; however it can also
 896  * be used by arch-specific code either to override the user or more
 897  * commonly to provide a default console (ie from PROM variables) when
 898  * the user has not supplied one.
 899  */
 900 int add_preferred_console(char *name, int idx, char *options)
 901 {
 902         return __add_preferred_console(name, idx, options, NULL);
 903 }
 904
 905 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 906 {
 907         struct console_cmdline *c;
 908         int i;
 909
 910         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 911                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 912                           console_cmdline[i].index == idx) {
 913                                 c = &console_cmdline[i];
 914                                 strlcpy(c->name, name_new, sizeof(c->name));
 915                                 c->name[sizeof(c->name) - 1] = 0;
 916                                 c->options = options;
 917                                 c->index = idx_new;
 918                                 return i;
 919                 }
 920         /* not found */
 921         return -1;
 922 }
 923
 924 int console_suspend_enabled = 1;
 925 EXPORT_SYMBOL(console_suspend_enabled);
 926
 927 static int __init console_suspend_disable(char *str)
 928 {
 929         console_suspend_enabled = 0;
 930         return 1;
 931 }
 932 __setup("no_console_suspend", console_suspend_disable);
 933
 934 /**
 935  * suspend_console - suspend the console subsystem
 936  *
 937  * This disables printk() while we go into suspend states
 938  */
 939 void suspend_console(void)
 940 {
 941         if (!console_suspend_enabled)
 942                 return;
 943         printk("Suspending console(s) (use no_console_suspend to debug)\n");
 944         acquire_console_sem();
 945         console_suspended = 1;
 946 }
 947
 948 void resume_console(void)
 949 {
 950         if (!console_suspend_enabled)
 951                 return;
 952         console_suspended = 0;
 953         release_console_sem();
 954 }
 955
 956 /**
 957  * acquire_console_sem - lock the console system for exclusive use.
 958  *
 959  * Acquires a semaphore which guarantees that the caller has
 960  * exclusive access to the console system and the console_drivers list.
 961  *
 962  * Can sleep, returns nothing.
 963  */
 964 void acquire_console_sem(void)
 965 {
 966         BUG_ON(in_interrupt());
 967         if (console_suspended) {
 968                 down(&secondary_console_sem);
 969                 return;
 970         }
 971         down(&console_sem);
 972         console_locked = 1;
 973         console_may_schedule = 1;
 974 }
 975 EXPORT_SYMBOL(acquire_console_sem);
 976
 977 int try_acquire_console_sem(void)
 978 {
 979         if (down_trylock(&console_sem))
 980                 return -1;
 981         console_locked = 1;
 982         console_may_schedule = 0;
 983         return 0;
 984 }
 985 EXPORT_SYMBOL(try_acquire_console_sem);
 986
 987 int is_console_locked(void)
 988 {
 989         return console_locked;
 990 }
 991
 992 void wake_up_klogd(void)
 993 {
 994         if (!oops_in_progress && waitqueue_active(&log_wait))
 995                 wake_up_interruptible(&log_wait);
 996 }
 997
 998 /**
 999  * release_console_sem - unlock the console system
1000  *
1001  * Releases the semaphore which the caller holds on the console system
1002  * and the console driver list.
1003  *
1004  * While the semaphore was held, console output may have been buffered
1005  * by printk().  If this is the case, release_console_sem() emits
1006  * the output prior to releasing the semaphore.
1007  *
1008  * If there is output waiting for klogd, we wake it up.
1009  *
1010  * release_console_sem() may be called from any context.
1011  */
1012 void release_console_sem(void)
1013 {
1014         unsigned long flags;
1015         unsigned _con_start, _log_end;
1016         unsigned wake_klogd = 0;
1017
1018         if (console_suspended) {
1019                 up(&secondary_console_sem);
1020                 return;
1021         }
1022
1023         console_may_schedule = 0;
1024
1025         for ( ; ; ) {
1026                 spin_lock_irqsave(&logbuf_lock, flags);
1027                 wake_klogd |= log_start - log_end;
1028                 if (con_start == log_end)
1029                         break;                  /* Nothing to print */
1030                 _con_start = con_start;
1031                 _log_end = log_end;
1032                 con_start = log_end;            /* Flush */
1033                 spin_unlock(&logbuf_lock);
1034                 stop_critical_timings();        /* don't trace print latency */
1035                 call_console_drivers(_con_start, _log_end);
1036                 start_critical_timings();
1037                 local_irq_restore(flags);
1038         }
1039         console_locked = 0;
1040         up(&console_sem);
1041         spin_unlock_irqrestore(&logbuf_lock, flags);
1042         if (wake_klogd)
1043                 wake_up_klogd();
1044 }
1045 EXPORT_SYMBOL(release_console_sem);
1046
1047 /**
1048  * console_conditional_schedule - yield the CPU if required
1049  *
1050  * If the console code is currently allowed to sleep, and
1051  * if this CPU should yield the CPU to another task, do
1052  * so here.
1053  *
1054  * Must be called within acquire_console_sem().
1055  */
1056 void __sched console_conditional_schedule(void)
1057 {
1058         if (console_may_schedule)
1059                 cond_resched();
1060 }
1061 EXPORT_SYMBOL(console_conditional_schedule);
1062
1063 void console_print(const char *s)
1064 {
1065         printk(KERN_EMERG "%s", s);
1066 }
1067 EXPORT_SYMBOL(console_print);
1068
1069 void console_unblank(void)
1070 {
1071         struct console *c;
1072
1073         /*
1074          * console_unblank can no longer be called in interrupt context unless
1075          * oops_in_progress is set to 1..
1076          */
1077         if (oops_in_progress) {
1078                 if (down_trylock(&console_sem) != 0)
1079                         return;
1080         } else
1081                 acquire_console_sem();
1082
1083         console_locked = 1;
1084         console_may_schedule = 0;
1085         for (c = console_drivers; c != NULL; c = c->next)
1086                 if ((c->flags & CON_ENABLED) && c->unblank)
1087                         c->unblank();
1088         release_console_sem();
1089 }
1090
1091 /*
1092  * Return the console tty driver structure and its associated index
1093  */
1094 struct tty_driver *console_device(int *index)
1095 {
1096         struct console *c;
1097         struct tty_driver *driver = NULL;
1098
1099         acquire_console_sem();
1100         for (c = console_drivers; c != NULL; c = c->next) {
1101                 if (!c->device)
1102                         continue;
1103                 driver = c->device(c, index);
1104                 if (driver)
1105                         break;
1106         }
1107         release_console_sem();
1108         return driver;
1109 }
1110
1111 /*
1112  * Prevent further output on the passed console device so that (for example)
1113  * serial drivers can disable console output before suspending a port, and can
1114  * re-enable output afterwards.
1115  */
1116 void console_stop(struct console *console)
1117 {
1118         acquire_console_sem();
1119         console->flags &= ~CON_ENABLED;
1120         release_console_sem();
1121 }
1122 EXPORT_SYMBOL(console_stop);
1123
1124 void console_start(struct console *console)
1125 {
1126         acquire_console_sem();
1127         console->flags |= CON_ENABLED;
1128         release_console_sem();
1129 }
1130 EXPORT_SYMBOL(console_start);
1131
1132 /*
1133  * The console driver calls this routine during kernel initialization
1134  * to register the console printing procedure with printk() and to
1135  * print any messages that were printed by the kernel before the
1136  * console driver was initialized.
1137  */
1138 void register_console(struct console *console)
1139 {
1140         int i;
1141         unsigned long flags;
1142         struct console *bootconsole = NULL;
1143
1144         if (console_drivers) {
1145                 if (console->flags & CON_BOOT)
1146                         return;
1147                 if (console_drivers->flags & CON_BOOT)
1148                         bootconsole = console_drivers;
1149         }
1150
1151         if (preferred_console < 0 || bootconsole || !console_drivers)
1152                 preferred_console = selected_console;
1153
1154         if (console->early_setup)
1155                 console->early_setup();
1156
1157         /*
1158          *      See if we want to use this console driver. If we
1159          *      didn't select a console we take the first one
1160          *      that registers here.
1161          */
1162         if (preferred_console < 0) {
1163                 if (console->index < 0)
1164                         console->index = 0;
1165                 if (console->setup == NULL ||
1166                     console->setup(console, NULL) == 0) {
1167                         console->flags |= CON_ENABLED;
1168                         if (console->device) {
1169                                 console->flags |= CON_CONSDEV;
1170                                 preferred_console = 0;
1171                         }
1172                 }
1173         }
1174
1175         /*
1176          *      See if this console matches one we selected on
1177          *      the command line.
1178          */
1179         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1180                         i++) {
1181                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1182                         continue;
1183                 if (console->index >= 0 &&
1184                     console->index != console_cmdline[i].index)
1185                         continue;
1186                 if (console->index < 0)
1187                         console->index = console_cmdline[i].index;
1188 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1189                 if (console_cmdline[i].brl_options) {
1190                         console->flags |= CON_BRL;
1191                         braille_register_console(console,
1192                                         console_cmdline[i].index,
1193                                         console_cmdline[i].options,
1194                                         console_cmdline[i].brl_options);
1195                         return;
1196                 }
1197 #endif
1198                 if (console->setup &&
1199                     console->setup(console, console_cmdline[i].options) != 0)
1200                         break;
1201                 console->flags |= CON_ENABLED;
1202                 console->index = console_cmdline[i].index;
1203                 if (i == selected_console) {
1204                         console->flags |= CON_CONSDEV;
1205                         preferred_console = selected_console;
1206                 }
1207                 break;
1208         }
1209
1210         if (!(console->flags & CON_ENABLED))
1211                 return;
1212
1213         if (bootconsole && (console->flags & CON_CONSDEV)) {
1214                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1215                        bootconsole->name, bootconsole->index,
1216                        console->name, console->index);
1217                 unregister_console(bootconsole);
1218                 console->flags &= ~CON_PRINTBUFFER;
1219         } else {
1220                 printk(KERN_INFO "console [%s%d] enabled\n",
1221                        console->name, console->index);
1222         }
1223
1224         /*
1225          *      Put this console in the list - keep the
1226          *      preferred driver at the head of the list.
1227          */
1228         acquire_console_sem();
1229         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1230                 console->next = console_drivers;
1231                 console_drivers = console;
1232                 if (console->next)
1233                         console->next->flags &= ~CON_CONSDEV;
1234         } else {
1235                 console->next = console_drivers->next;
1236                 console_drivers->next = console;
1237         }
1238         if (console->flags & CON_PRINTBUFFER) {
1239                 /*
1240                  * release_console_sem() will print out the buffered messages
1241                  * for us.
1242                  */
1243                 spin_lock_irqsave(&logbuf_lock, flags);
1244                 con_start = log_start;
1245                 spin_unlock_irqrestore(&logbuf_lock, flags);
1246         }
1247         release_console_sem();
1248 }
1249 EXPORT_SYMBOL(register_console);
1250
1251 int unregister_console(struct console *console)
1252 {
1253         struct console *a, *b;
1254         int res = 1;
1255
1256 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1257         if (console->flags & CON_BRL)
1258                 return braille_unregister_console(console);
1259 #endif
1260
1261         acquire_console_sem();
1262         if (console_drivers == console) {
1263                 console_drivers=console->next;
1264                 res = 0;
1265         } else if (console_drivers) {
1266                 for (a=console_drivers->next, b=console_drivers ;
1267                      a; b=a, a=b->next) {
1268                         if (a == console) {
1269                                 b->next = a->next;
1270                                 res = 0;
1271                                 break;
1272                         }
1273                 }
1274         }
1275
1276         /*
1277          * If this isn't the last console and it has CON_CONSDEV set, we
1278          * need to set it on the next preferred console.
1279          */
1280         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1281                 console_drivers->flags |= CON_CONSDEV;
1282
1283         release_console_sem();
1284         return res;
1285 }
1286 EXPORT_SYMBOL(unregister_console);
1287
1288 static int __init disable_boot_consoles(void)
1289 {
1290         if (console_drivers != NULL) {
1291                 if (console_drivers->flags & CON_BOOT) {
1292                         printk(KERN_INFO "turn off boot console %s%d\n",
1293                                 console_drivers->name, console_drivers->index);
1294                         return unregister_console(console_drivers);
1295                 }
1296         }
1297         return 0;
1298 }
1299 late_initcall(disable_boot_consoles);
1300
1301 /**
1302  * tty_write_message - write a message to a certain tty, not just the console.
1303  * @tty: the destination tty_struct
1304  * @msg: the message to write
1305  *
1306  * This is used for messages that need to be redirected to a specific tty.
1307  * We don't put it into the syslog queue right now maybe in the future if
1308  * really needed.
1309  */
1310 void tty_write_message(struct tty_struct *tty, char *msg)
1311 {
1312         if (tty && tty->ops->write)
1313                 tty->ops->write(tty, msg, strlen(msg));
1314         return;
1315 }
1316
1317 #if defined CONFIG_PRINTK
1318
1319 /*
1320  * printk rate limiting, lifted from the networking subsystem.
1321  *
1322  * This enforces a rate limit: not more than 10 kernel messages
1323  * every 5s to make a denial-of-service attack impossible.
1324  */
1325 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1326
1327 int printk_ratelimit(void)
1328 {
1329         return __ratelimit(&printk_ratelimit_state);
1330 }
1331 EXPORT_SYMBOL(printk_ratelimit);
1332
1333 /**
1334  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1335  * @caller_jiffies: pointer to caller's state
1336  * @interval_msecs: minimum interval between prints
1337  *
1338  * printk_timed_ratelimit() returns true if more than @interval_msecs
1339  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1340  * returned true.
1341  */
1342 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1343                         unsigned int interval_msecs)
1344 {
1345         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1346                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1347                 return true;
1348         }
1349         return false;
1350 }
1351 EXPORT_SYMBOL(printk_timed_ratelimit);
1352 #endif