kernel/printk.c

   1 /*
   2  *  linux/kernel/printk.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  * Modified to make sys_syslog() more flexible: added commands to
   7  * return the last 4k of kernel messages, regardless of whether
   8  * they've been read or not.  Added option to suppress kernel printk's
   9  * to the console.  Added hook for sending the console messages
  10  * elsewhere, in preparation for a serial line console (someday).
  11  * Ted Ts'o, 2/11/93.
  12  * Modified for sysctl support, 1/8/97, Chris Horn.
  13  * Fixed SMP synchronization, 08/08/99, Manfred Spraul
  14  *     manfred@colorfullife.com
  15  * Rewrote bits to get rid of console_lock
  16  *      01Mar01 Andrew Morton
  17  */
  18
  19 #include <linux/kernel.h>
  20 #include <linux/mm.h>
  21 #include <linux/tty.h>
  22 #include <linux/tty_driver.h>
  23 #include <linux/console.h>
  24 #include <linux/init.h>
  25 #include <linux/jiffies.h>
  26 #include <linux/nmi.h>
  27 #include <linux/module.h>
  28 #include <linux/moduleparam.h>
  29 #include <linux/interrupt.h>                    /* For in_interrupt() */
  30 #include <linux/delay.h>
  31 #include <linux/smp.h>
  32 #include <linux/security.h>
  33 #include <linux/bootmem.h>
  34 #include <linux/syscalls.h>
  35
  36 #include <asm/uaccess.h>
  37
  38 /*
  39  * Architectures can override it:
  40  */
  41 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
  42 {
  43 }
  44
  45 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
  46
  47 #ifdef CONFIG_DEBUG_LL
  48 extern void printascii(char *);
  49 #endif
  50
  51 /* printk's without a loglevel use this.. */
  52 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  53
  54 /* We show everything that is MORE important than this.. */
  55 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  56 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  57
  58 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  59
  60 int console_printk[4] = {
  61         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  62         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  63         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  64         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  65 };
  66
  67 /*
  68  * Low level drivers may need that to know if they can schedule in
  69  * their unblank() callback or not. So let's export it.
  70  */
  71 int oops_in_progress;
  72 EXPORT_SYMBOL(oops_in_progress);
  73
  74 /*
  75  * console_sem protects the console_drivers list, and also
  76  * provides serialisation for access to the entire console
  77  * driver system.
  78  */
  79 static DECLARE_MUTEX(console_sem);
  80 static DECLARE_MUTEX(secondary_console_sem);
  81 struct console *console_drivers;
  82 EXPORT_SYMBOL_GPL(console_drivers);
  83
  84 /*
  85  * This is used for debugging the mess that is the VT code by
  86  * keeping track if we have the console semaphore held. It's
  87  * definitely not the perfect debug tool (we don't know if _WE_
  88  * hold it are racing, but it helps tracking those weird code
  89  * path in the console code where we end up in places I want
  90  * locked without the console sempahore held
  91  */
  92 static int console_locked, console_suspended;
  93
  94 /*
  95  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
  96  * It is also used in interesting ways to provide interlocking in
  97  * release_console_sem().
  98  */
  99 static DEFINE_SPINLOCK(logbuf_lock);
 100
 101 #define LOG_BUF_MASK (log_buf_len-1)
 102 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
 103
 104 /*
 105  * The indices into log_buf are not constrained to log_buf_len - they
 106  * must be masked before subscripting
 107  */
 108 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
 109 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
 110 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 111
 112 /*
 113  *      Array of consoles built from command line options (console=)
 114  */
 115 struct console_cmdline
 116 {
 117         char    name[8];                        /* Name of the driver       */
 118         int     index;                          /* Minor dev. to use        */
 119         char    *options;                       /* Options for the driver   */
 120 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 121         char    *brl_options;                   /* Options for braille driver */
 122 #endif
 123 };
 124
 125 #define MAX_CMDLINECONSOLES 8
 126
 127 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 128 static int selected_console = -1;
 129 static int preferred_console = -1;
 130 int console_set_on_cmdline;
 131 EXPORT_SYMBOL(console_set_on_cmdline);
 132
 133 /* Flag: console code may call schedule() */
 134 static int console_may_schedule;
 135
 136 #ifdef CONFIG_PRINTK
 137
 138 static char __log_buf[__LOG_BUF_LEN];
 139 static char *log_buf = __log_buf;
 140 static int log_buf_len = __LOG_BUF_LEN;
 141 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 142
 143 static int __init log_buf_len_setup(char *str)
 144 {
 145         unsigned size = memparse(str, &str);
 146         unsigned long flags;
 147
 148         if (size)
 149                 size = roundup_pow_of_two(size);
 150         if (size > log_buf_len) {
 151                 unsigned start, dest_idx, offset;
 152                 char *new_log_buf;
 153
 154                 new_log_buf = alloc_bootmem(size);
 155                 if (!new_log_buf) {
 156                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 157                         goto out;
 158                 }
 159
 160                 spin_lock_irqsave(&logbuf_lock, flags);
 161                 log_buf_len = size;
 162                 log_buf = new_log_buf;
 163
 164                 offset = start = min(con_start, log_start);
 165                 dest_idx = 0;
 166                 while (start != log_end) {
 167                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 168                         start++;
 169                         dest_idx++;
 170                 }
 171                 log_start -= offset;
 172                 con_start -= offset;
 173                 log_end -= offset;
 174                 spin_unlock_irqrestore(&logbuf_lock, flags);
 175
 176                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 177         }
 178 out:
 179         return 1;
 180 }
 181
 182 __setup("log_buf_len=", log_buf_len_setup);
 183
 184 #ifdef CONFIG_BOOT_PRINTK_DELAY
 185
 186 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 187 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
 188
 189 static int __init boot_delay_setup(char *str)
 190 {
 191         unsigned long lpj;
 192         unsigned long long loops_per_msec;
 193
 194         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 195         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 196
 197         get_option(&str, &boot_delay);
 198         if (boot_delay > 10 * 1000)
 199                 boot_delay = 0;
 200
 201         printk_delay_msec = loops_per_msec;
 202         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 203                 "HZ: %d, printk_delay_msec: %llu\n",
 204                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
 205         return 1;
 206 }
 207 __setup("boot_delay=", boot_delay_setup);
 208
 209 static void boot_delay_msec(void)
 210 {
 211         unsigned long long k;
 212         unsigned long timeout;
 213
 214         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 215                 return;
 216
 217         k = (unsigned long long)printk_delay_msec * boot_delay;
 218
 219         timeout = jiffies + msecs_to_jiffies(boot_delay);
 220         while (k) {
 221                 k--;
 222                 cpu_relax();
 223                 /*
 224                  * use (volatile) jiffies to prevent
 225                  * compiler reduction; loop termination via jiffies
 226                  * is secondary and may or may not happen.
 227                  */
 228                 if (time_after(jiffies, timeout))
 229                         break;
 230                 touch_nmi_watchdog();
 231         }
 232 }
 233 #else
 234 static inline void boot_delay_msec(void)
 235 {
 236 }
 237 #endif
 238
 239 /*
 240  * 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  *
 585  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 586  * call the console drivers.  If we fail to get the semaphore we place the output
 587  * into the log buffer and return.  The current holder of the console_sem will
 588  * notice the new output in release_console_sem() and will send it to the
 589  * consoles before releasing the semaphore.
 590  *
 591  * One effect of this deferred printing is that code which calls printk() and
 592  * then changes console_loglevel may break. This is because console_loglevel
 593  * is inspected when the actual printing occurs.
 594  *
 595  * See also:
 596  * printf(3)
 597  *
 598  * See the vsnprintf() documentation for format string extensions over C99.
 599  */
 600
 601 asmlinkage int printk(const char *fmt, ...)
 602 {
 603         va_list args;
 604         int r;
 605
 606         va_start(args, fmt);
 607         r = vprintk(fmt, args);
 608         va_end(args);
 609
 610         return r;
 611 }
 612
 613 /* cpu currently holding logbuf_lock */
 614 static volatile unsigned int printk_cpu = UINT_MAX;
 615
 616 /*
 617  * Can we actually use the console at this time on this cpu?
 618  *
 619  * Console drivers may assume that per-cpu resources have
 620  * been allocated. So unless they're explicitly marked as
 621  * being able to cope (CON_ANYTIME) don't call them until
 622  * this CPU is officially up.
 623  */
 624 static inline int can_use_console(unsigned int cpu)
 625 {
 626         return cpu_online(cpu) || have_callable_console();
 627 }
 628
 629 /*
 630  * Try to get console ownership to actually show the kernel
 631  * messages from a 'printk'. Return true (and with the
 632  * console_semaphore held, and 'console_locked' set) if it
 633  * is successful, false otherwise.
 634  *
 635  * This gets called with the 'logbuf_lock' spinlock held and
 636  * interrupts disabled. It should return with 'lockbuf_lock'
 637  * released but interrupts still disabled.
 638  */
 639 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 640 {
 641         int retval = 0;
 642
 643         if (!try_acquire_console_sem()) {
 644                 retval = 1;
 645
 646                 /*
 647                  * If we can't use the console, we need to release
 648                  * the console semaphore by hand to avoid flushing
 649                  * the buffer. We need to hold the console semaphore
 650                  * in order to do this test safely.
 651                  */
 652                 if (!can_use_console(cpu)) {
 653                         console_locked = 0;
 654                         up(&console_sem);
 655                         retval = 0;
 656                 }
 657         }
 658         printk_cpu = UINT_MAX;
 659         spin_unlock(&logbuf_lock);
 660         return retval;
 661 }
 662 static const char recursion_bug_msg [] =
 663                 KERN_CRIT "BUG: recent printk recursion!\n";
 664 static int recursion_bug;
 665         static int new_text_line = 1;
 666 static char printk_buf[1024];
 667
 668 asmlinkage int vprintk(const char *fmt, va_list args)
 669 {
 670         int printed_len = 0;
 671         int current_log_level = default_message_loglevel;
 672         unsigned long flags;
 673         int this_cpu;
 674         char *p;
 675
 676         boot_delay_msec();
 677
 678         preempt_disable();
 679         /* This stops the holder of console_sem just where we want him */
 680         raw_local_irq_save(flags);
 681         this_cpu = smp_processor_id();
 682
 683         /*
 684          * Ouch, printk recursed into itself!
 685          */
 686         if (unlikely(printk_cpu == this_cpu)) {
 687                 /*
 688                  * If a crash is occurring during printk() on this CPU,
 689                  * then try to get the crash message out but make sure
 690                  * we can't deadlock. Otherwise just return to avoid the
 691                  * recursion and return - but flag the recursion so that
 692                  * it can be printed at the next appropriate moment:
 693                  */
 694                 if (!oops_in_progress) {
 695                         recursion_bug = 1;
 696                         goto out_restore_irqs;
 697                 }
 698                 zap_locks();
 699         }
 700
 701         lockdep_off();
 702         spin_lock(&logbuf_lock);
 703         printk_cpu = this_cpu;
 704
 705         if (recursion_bug) {
 706                 recursion_bug = 0;
 707                 strcpy(printk_buf, recursion_bug_msg);
 708                 printed_len = sizeof(recursion_bug_msg);
 709         }
 710         /* Emit the output into the temporary buffer */
 711         printed_len += vscnprintf(printk_buf + printed_len,
 712                                   sizeof(printk_buf) - printed_len, fmt, args);
 713
 714 #ifdef  CONFIG_DEBUG_LL
 715         printascii(printk_buf);
 716 #endif
 717
 718         /*
 719          * Copy the output into log_buf.  If the caller didn't provide
 720          * appropriate log level tags, we insert them here
 721          */
 722         for (p = printk_buf; *p; p++) {
 723                 if (new_text_line) {
 724                         /* If a token, set current_log_level and skip over */
 725                         if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
 726                             p[2] == '>') {
 727                                 current_log_level = p[1] - '0';
 728                                 p += 3;
 729                                 printed_len -= 3;
 730                         }
 731
 732                         /* Always output the token */
 733                         emit_log_char('<');
 734                         emit_log_char(current_log_level + '0');
 735                         emit_log_char('>');
 736                         printed_len += 3;
 737                         new_text_line = 0;
 738
 739                         if (printk_time) {
 740                                 /* Follow the token with the time */
 741                                 char tbuf[50], *tp;
 742                                 unsigned tlen;
 743                                 unsigned long long t;
 744                                 unsigned long nanosec_rem;
 745
 746                                 t = cpu_clock(printk_cpu);
 747                                 nanosec_rem = do_div(t, 1000000000);
 748                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 749                                                 (unsigned long) t,
 750                                                 nanosec_rem / 1000);
 751
 752                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 753                                         emit_log_char(*tp);
 754                                 printed_len += tlen;
 755                         }
 756
 757                         if (!*p)
 758                                 break;
 759                 }
 760
 761                 emit_log_char(*p);
 762                 if (*p == '\n')
 763                         new_text_line = 1;
 764         }
 765
 766         /*
 767          * Try to acquire and then immediately release the
 768          * console semaphore. The release will do all the
 769          * actual magic (print out buffers, wake up klogd,
 770          * etc).
 771          *
 772          * The acquire_console_semaphore_for_printk() function
 773          * will release 'logbuf_lock' regardless of whether it
 774          * actually gets the semaphore or not.
 775          */
 776         if (acquire_console_semaphore_for_printk(this_cpu))
 777                 release_console_sem();
 778
 779         lockdep_on();
 780 out_restore_irqs:
 781         raw_local_irq_restore(flags);
 782
 783         preempt_enable();
 784         return printed_len;
 785 }
 786 EXPORT_SYMBOL(printk);
 787 EXPORT_SYMBOL(vprintk);
 788
 789 #else
 790
 791 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 792 {
 793         return -ENOSYS;
 794 }
 795
 796 static void call_console_drivers(unsigned start, unsigned end)
 797 {
 798 }
 799
 800 #endif
 801
 802 static int __add_preferred_console(char *name, int idx, char *options,
 803                                    char *brl_options)
 804 {
 805         struct console_cmdline *c;
 806         int i;
 807
 808         /*
 809          *      See if this tty is not yet registered, and
 810          *      if we have a slot free.
 811          */
 812         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 813                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 814                           console_cmdline[i].index == idx) {
 815                                 if (!brl_options)
 816                                         selected_console = i;
 817                                 return 0;
 818                 }
 819         if (i == MAX_CMDLINECONSOLES)
 820                 return -E2BIG;
 821         if (!brl_options)
 822                 selected_console = i;
 823         c = &console_cmdline[i];
 824         strlcpy(c->name, name, sizeof(c->name));
 825         c->options = options;
 826 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 827         c->brl_options = brl_options;
 828 #endif
 829         c->index = idx;
 830         return 0;
 831 }
 832 /*
 833  * Set up a list of consoles.  Called from init/main.c
 834  */
 835 static int __init console_setup(char *str)
 836 {
 837         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 838         char *s, *options, *brl_options = NULL;
 839         int idx;
 840
 841 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 842         if (!memcmp(str, "brl,", 4)) {
 843                 brl_options = "";
 844                 str += 4;
 845         } else if (!memcmp(str, "brl=", 4)) {
 846                 brl_options = str + 4;
 847                 str = strchr(brl_options, ',');
 848                 if (!str) {
 849                         printk(KERN_ERR "need port name after brl=\n");
 850                         return 1;
 851                 }
 852                 *(str++) = 0;
 853         }
 854 #endif
 855
 856         /*
 857          * Decode str into name, index, options.
 858          */
 859         if (str[0] >= '0' && str[0] <= '9') {
 860                 strcpy(buf, "ttyS");
 861                 strncpy(buf + 4, str, sizeof(buf) - 5);
 862         } else {
 863                 strncpy(buf, str, sizeof(buf) - 1);
 864         }
 865         buf[sizeof(buf) - 1] = 0;
 866         if ((options = strchr(str, ',')) != NULL)
 867                 *(options++) = 0;
 868 #ifdef __sparc__
 869         if (!strcmp(str, "ttya"))
 870                 strcpy(buf, "ttyS0");
 871         if (!strcmp(str, "ttyb"))
 872                 strcpy(buf, "ttyS1");
 873 #endif
 874         for (s = buf; *s; s++)
 875                 if ((*s >= '0' && *s <= '9') || *s == ',')
 876                         break;
 877         idx = simple_strtoul(s, NULL, 10);
 878         *s = 0;
 879
 880         __add_preferred_console(buf, idx, options, brl_options);
 881         console_set_on_cmdline = 1;
 882         return 1;
 883 }
 884 __setup("console=", console_setup);
 885
 886 /**
 887  * add_preferred_console - add a device to the list of preferred consoles.
 888  * @name: device name
 889  * @idx: device index
 890  * @options: options for this console
 891  *
 892  * The last preferred console added will be used for kernel messages
 893  * and stdin/out/err for init.  Normally this is used by console_setup
 894  * above to handle user-supplied console arguments; however it can also
 895  * be used by arch-specific code either to override the user or more
 896  * commonly to provide a default console (ie from PROM variables) when
 897  * the user has not supplied one.
 898  */
 899 int add_preferred_console(char *name, int idx, char *options)
 900 {
 901         return __add_preferred_console(name, idx, options, NULL);
 902 }
 903
 904 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 905 {
 906         struct console_cmdline *c;
 907         int i;
 908
 909         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 910                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 911                           console_cmdline[i].index == idx) {
 912                                 c = &console_cmdline[i];
 913                                 strlcpy(c->name, name_new, sizeof(c->name));
 914                                 c->name[sizeof(c->name) - 1] = 0;
 915                                 c->options = options;
 916                                 c->index = idx_new;
 917                                 return i;
 918                 }
 919         /* not found */
 920         return -1;
 921 }
 922
 923 int console_suspend_enabled = 1;
 924 EXPORT_SYMBOL(console_suspend_enabled);
 925
 926 static int __init console_suspend_disable(char *str)
 927 {
 928         console_suspend_enabled = 0;
 929         return 1;
 930 }
 931 __setup("no_console_suspend", console_suspend_disable);
 932
 933 /**
 934  * suspend_console - suspend the console subsystem
 935  *
 936  * This disables printk() while we go into suspend states
 937  */
 938 void suspend_console(void)
 939 {
 940         if (!console_suspend_enabled)
 941                 return;
 942         printk("Suspending console(s) (use no_console_suspend to debug)\n");
 943         acquire_console_sem();
 944         console_suspended = 1;
 945 }
 946
 947 void resume_console(void)
 948 {
 949         if (!console_suspend_enabled)
 950                 return;
 951         console_suspended = 0;
 952         release_console_sem();
 953 }
 954
 955 /**
 956  * acquire_console_sem - lock the console system for exclusive use.
 957  *
 958  * Acquires a semaphore which guarantees that the caller has
 959  * exclusive access to the console system and the console_drivers list.
 960  *
 961  * Can sleep, returns nothing.
 962  */
 963 void acquire_console_sem(void)
 964 {
 965         BUG_ON(in_interrupt());
 966         if (console_suspended) {
 967                 down(&secondary_console_sem);
 968                 return;
 969         }
 970         down(&console_sem);
 971         console_locked = 1;
 972         console_may_schedule = 1;
 973 }
 974 EXPORT_SYMBOL(acquire_console_sem);
 975
 976 int try_acquire_console_sem(void)
 977 {
 978         if (down_trylock(&console_sem))
 979                 return -1;
 980         console_locked = 1;
 981         console_may_schedule = 0;
 982         return 0;
 983 }
 984 EXPORT_SYMBOL(try_acquire_console_sem);
 985
 986 int is_console_locked(void)
 987 {
 988         return console_locked;
 989 }
 990
 991 static DEFINE_PER_CPU(int, printk_pending);
 992
 993 void printk_tick(void)
 994 {
 995         if (__get_cpu_var(printk_pending)) {
 996                 __get_cpu_var(printk_pending) = 0;
 997                 wake_up_interruptible(&log_wait);
 998         }
 999 }
1000
1001 int printk_needs_cpu(int cpu)
1002 {
1003         return per_cpu(printk_pending, cpu);
1004 }
1005
1006 void wake_up_klogd(void)
1007 {
1008         if (waitqueue_active(&log_wait))
1009                 __raw_get_cpu_var(printk_pending) = 1;
1010 }
1011
1012 /**
1013  * release_console_sem - unlock the console system
1014  *
1015  * Releases the semaphore which the caller holds on the console system
1016  * and the console driver list.
1017  *
1018  * While the semaphore was held, console output may have been buffered
1019  * by printk().  If this is the case, release_console_sem() emits
1020  * the output prior to releasing the semaphore.
1021  *
1022  * If there is output waiting for klogd, we wake it up.
1023  *
1024  * release_console_sem() may be called from any context.
1025  */
1026 void release_console_sem(void)
1027 {
1028         unsigned long flags;
1029         unsigned _con_start, _log_end;
1030         unsigned wake_klogd = 0;
1031
1032         if (console_suspended) {
1033                 up(&secondary_console_sem);
1034                 return;
1035         }
1036
1037         console_may_schedule = 0;
1038
1039         for ( ; ; ) {
1040                 spin_lock_irqsave(&logbuf_lock, flags);
1041                 wake_klogd |= log_start - log_end;
1042                 if (con_start == log_end)
1043                         break;                  /* Nothing to print */
1044                 _con_start = con_start;
1045                 _log_end = log_end;
1046                 con_start = log_end;            /* Flush */
1047                 spin_unlock(&logbuf_lock);
1048                 stop_critical_timings();        /* don't trace print latency */
1049                 call_console_drivers(_con_start, _log_end);
1050                 start_critical_timings();
1051                 local_irq_restore(flags);
1052         }
1053         console_locked = 0;
1054         up(&console_sem);
1055         spin_unlock_irqrestore(&logbuf_lock, flags);
1056         if (wake_klogd)
1057                 wake_up_klogd();
1058 }
1059 EXPORT_SYMBOL(release_console_sem);
1060
1061 /**
1062  * console_conditional_schedule - yield the CPU if required
1063  *
1064  * If the console code is currently allowed to sleep, and
1065  * if this CPU should yield the CPU to another task, do
1066  * so here.
1067  *
1068  * Must be called within acquire_console_sem().
1069  */
1070 void __sched console_conditional_schedule(void)
1071 {
1072         if (console_may_schedule)
1073                 cond_resched();
1074 }
1075 EXPORT_SYMBOL(console_conditional_schedule);
1076
1077 void console_print(const char *s)
1078 {
1079         printk(KERN_EMERG "%s", s);
1080 }
1081 EXPORT_SYMBOL(console_print);
1082
1083 void console_unblank(void)
1084 {
1085         struct console *c;
1086
1087         /*
1088          * console_unblank can no longer be called in interrupt context unless
1089          * oops_in_progress is set to 1..
1090          */
1091         if (oops_in_progress) {
1092                 if (down_trylock(&console_sem) != 0)
1093                         return;
1094         } else
1095                 acquire_console_sem();
1096
1097         console_locked = 1;
1098         console_may_schedule = 0;
1099         for (c = console_drivers; c != NULL; c = c->next)
1100                 if ((c->flags & CON_ENABLED) && c->unblank)
1101                         c->unblank();
1102         release_console_sem();
1103 }
1104
1105 /*
1106  * Return the console tty driver structure and its associated index
1107  */
1108 struct tty_driver *console_device(int *index)
1109 {
1110         struct console *c;
1111         struct tty_driver *driver = NULL;
1112
1113         acquire_console_sem();
1114         for (c = console_drivers; c != NULL; c = c->next) {
1115                 if (!c->device)
1116                         continue;
1117                 driver = c->device(c, index);
1118                 if (driver)
1119                         break;
1120         }
1121         release_console_sem();
1122         return driver;
1123 }
1124
1125 /*
1126  * Prevent further output on the passed console device so that (for example)
1127  * serial drivers can disable console output before suspending a port, and can
1128  * re-enable output afterwards.
1129  */
1130 void console_stop(struct console *console)
1131 {
1132         acquire_console_sem();
1133         console->flags &= ~CON_ENABLED;
1134         release_console_sem();
1135 }
1136 EXPORT_SYMBOL(console_stop);
1137
1138 void console_start(struct console *console)
1139 {
1140         acquire_console_sem();
1141         console->flags |= CON_ENABLED;
1142         release_console_sem();
1143 }
1144 EXPORT_SYMBOL(console_start);
1145
1146 /*
1147  * The console driver calls this routine during kernel initialization
1148  * to register the console printing procedure with printk() and to
1149  * print any messages that were printed by the kernel before the
1150  * console driver was initialized.
1151  */
1152 void register_console(struct console *console)
1153 {
1154         int i;
1155         unsigned long flags;
1156         struct console *bootconsole = NULL;
1157
1158         if (console_drivers) {
1159                 if (console->flags & CON_BOOT)
1160                         return;
1161                 if (console_drivers->flags & CON_BOOT)
1162                         bootconsole = console_drivers;
1163         }
1164
1165         if (preferred_console < 0 || bootconsole || !console_drivers)
1166                 preferred_console = selected_console;
1167
1168         if (console->early_setup)
1169                 console->early_setup();
1170
1171         /*
1172          *      See if we want to use this console driver. If we
1173          *      didn't select a console we take the first one
1174          *      that registers here.
1175          */
1176         if (preferred_console < 0) {
1177                 if (console->index < 0)
1178                         console->index = 0;
1179                 if (console->setup == NULL ||
1180                     console->setup(console, NULL) == 0) {
1181                         console->flags |= CON_ENABLED;
1182                         if (console->device) {
1183                                 console->flags |= CON_CONSDEV;
1184                                 preferred_console = 0;
1185                         }
1186                 }
1187         }
1188
1189         /*
1190          *      See if this console matches one we selected on
1191          *      the command line.
1192          */
1193         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1194                         i++) {
1195                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1196                         continue;
1197                 if (console->index >= 0 &&
1198                     console->index != console_cmdline[i].index)
1199                         continue;
1200                 if (console->index < 0)
1201                         console->index = console_cmdline[i].index;
1202 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1203                 if (console_cmdline[i].brl_options) {
1204                         console->flags |= CON_BRL;
1205                         braille_register_console(console,
1206                                         console_cmdline[i].index,
1207                                         console_cmdline[i].options,
1208                                         console_cmdline[i].brl_options);
1209                         return;
1210                 }
1211 #endif
1212                 if (console->setup &&
1213                     console->setup(console, console_cmdline[i].options) != 0)
1214                         break;
1215                 console->flags |= CON_ENABLED;
1216                 console->index = console_cmdline[i].index;
1217                 if (i == selected_console) {
1218                         console->flags |= CON_CONSDEV;
1219                         preferred_console = selected_console;
1220                 }
1221                 break;
1222         }
1223
1224         if (!(console->flags & CON_ENABLED))
1225                 return;
1226
1227         if (bootconsole && (console->flags & CON_CONSDEV)) {
1228                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1229                        bootconsole->name, bootconsole->index,
1230                        console->name, console->index);
1231                 unregister_console(bootconsole);
1232                 console->flags &= ~CON_PRINTBUFFER;
1233         } else {
1234                 printk(KERN_INFO "console [%s%d] enabled\n",
1235                        console->name, console->index);
1236         }
1237
1238         /*
1239          *      Put this console in the list - keep the
1240          *      preferred driver at the head of the list.
1241          */
1242         acquire_console_sem();
1243         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1244                 console->next = console_drivers;
1245                 console_drivers = console;
1246                 if (console->next)
1247                         console->next->flags &= ~CON_CONSDEV;
1248         } else {
1249                 console->next = console_drivers->next;
1250                 console_drivers->next = console;
1251         }
1252         if (console->flags & CON_PRINTBUFFER) {
1253                 /*
1254                  * release_console_sem() will print out the buffered messages
1255                  * for us.
1256                  */
1257                 spin_lock_irqsave(&logbuf_lock, flags);
1258                 con_start = log_start;
1259                 spin_unlock_irqrestore(&logbuf_lock, flags);
1260         }
1261         release_console_sem();
1262 }
1263 EXPORT_SYMBOL(register_console);
1264
1265 int unregister_console(struct console *console)
1266 {
1267         struct console *a, *b;
1268         int res = 1;
1269
1270 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1271         if (console->flags & CON_BRL)
1272                 return braille_unregister_console(console);
1273 #endif
1274
1275         acquire_console_sem();
1276         if (console_drivers == console) {
1277                 console_drivers=console->next;
1278                 res = 0;
1279         } else if (console_drivers) {
1280                 for (a=console_drivers->next, b=console_drivers ;
1281                      a; b=a, a=b->next) {
1282                         if (a == console) {
1283                                 b->next = a->next;
1284                                 res = 0;
1285                                 break;
1286                         }
1287                 }
1288         }
1289
1290         /*
1291          * If this isn't the last console and it has CON_CONSDEV set, we
1292          * need to set it on the next preferred console.
1293          */
1294         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1295                 console_drivers->flags |= CON_CONSDEV;
1296
1297         release_console_sem();
1298         return res;
1299 }
1300 EXPORT_SYMBOL(unregister_console);
1301
1302 static int __init disable_boot_consoles(void)
1303 {
1304         if (console_drivers != NULL) {
1305                 if (console_drivers->flags & CON_BOOT) {
1306                         printk(KERN_INFO "turn off boot console %s%d\n",
1307                                 console_drivers->name, console_drivers->index);
1308                         return unregister_console(console_drivers);
1309                 }
1310         }
1311         return 0;
1312 }
1313 late_initcall(disable_boot_consoles);
1314
1315 #if defined CONFIG_PRINTK
1316
1317 /*
1318  * printk rate limiting, lifted from the networking subsystem.
1319  *
1320  * This enforces a rate limit: not more than 10 kernel messages
1321  * every 5s to make a denial-of-service attack impossible.
1322  */
1323 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1324
1325 int printk_ratelimit(void)
1326 {
1327         return __ratelimit(&printk_ratelimit_state);
1328 }
1329 EXPORT_SYMBOL(printk_ratelimit);
1330
1331 /**
1332  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1333  * @caller_jiffies: pointer to caller's state
1334  * @interval_msecs: minimum interval between prints
1335  *
1336  * printk_timed_ratelimit() returns true if more than @interval_msecs
1337  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1338  * returned true.
1339  */
1340 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1341                         unsigned int interval_msecs)
1342 {
1343         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1344                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1345                 return true;
1346         }
1347         return false;
1348 }
1349 EXPORT_SYMBOL(printk_timed_ratelimit);
1350 #endif