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/smp_lock.h>
  24 #include <linux/console.h>
  25 #include <linux/init.h>
  26 #include <linux/jiffies.h>
  27 #include <linux/nmi.h>
  28 #include <linux/module.h>
  29 #include <linux/moduleparam.h>
  30 #include <linux/interrupt.h>                    /* For in_interrupt() */
  31 #include <linux/delay.h>
  32 #include <linux/smp.h>
  33 #include <linux/security.h>
  34 #include <linux/bootmem.h>
  35 #include <linux/syscalls.h>
  36 #include <linux/vserver/cvirt.h>
  37
  38 #include <asm/uaccess.h>
  39
  40 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
  41
  42 /* printk's without a loglevel use this.. */
  43 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  44
  45 /* We show everything that is MORE important than this.. */
  46 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  47 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  48
  49 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  50
  51 int console_printk[4] = {
  52         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  53         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  54         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  55         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  56 };
  57
  58 EXPORT_UNUSED_SYMBOL(console_printk);  /*  June 2006  */
  59
  60 /*
  61  * Low lever drivers may need that to know if they can schedule in
  62  * their unblank() callback or not. So let's export it.
  63  */
  64 int oops_in_progress;
  65 EXPORT_SYMBOL(oops_in_progress);
  66
  67 /*
  68  * console_sem protects the console_drivers list, and also
  69  * provides serialisation for access to the entire console
  70  * driver system.
  71  */
  72 static DECLARE_MUTEX(console_sem);
  73 static DECLARE_MUTEX(secondary_console_sem);
  74 struct console *console_drivers;
  75 /*
  76  * This is used for debugging the mess that is the VT code by
  77  * keeping track if we have the console semaphore held. It's
  78  * definitely not the perfect debug tool (we don't know if _WE_
  79  * hold it are racing, but it helps tracking those weird code
  80  * path in the console code where we end up in places I want
  81  * locked without the console sempahore held
  82  */
  83 static int console_locked, console_suspended;
  84
  85 /*
  86  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
  87  * It is also used in interesting ways to provide interlocking in
  88  * release_console_sem().
  89  */
  90 static DEFINE_SPINLOCK(logbuf_lock);
  91
  92 #define LOG_BUF_MASK    (log_buf_len-1)
  93 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
  94
  95 /*
  96  * The indices into log_buf are not constrained to log_buf_len - they
  97  * must be masked before subscripting
  98  */
  99 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
 100 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
 101 static unsigned long log_end;   /* Index into log_buf: most-recently-written-char + 1 */
 102
 103 /*
 104  *      Array of consoles built from command line options (console=)
 105  */
 106 struct console_cmdline
 107 {
 108         char    name[8];                        /* Name of the driver       */
 109         int     index;                          /* Minor dev. to use        */
 110         char    *options;                       /* Options for the driver   */
 111 };
 112
 113 #define MAX_CMDLINECONSOLES 8
 114
 115 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 116 static int selected_console = -1;
 117 static int preferred_console = -1;
 118
 119 /* Flag: console code may call schedule() */
 120 static int console_may_schedule;
 121
 122 #ifdef CONFIG_PRINTK
 123
 124 static char __log_buf[__LOG_BUF_LEN];
 125 static char *log_buf = __log_buf;
 126 static int log_buf_len = __LOG_BUF_LEN;
 127 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
 128
 129 static int __init log_buf_len_setup(char *str)
 130 {
 131         unsigned long size = memparse(str, &str);
 132         unsigned long flags;
 133
 134         if (size)
 135                 size = roundup_pow_of_two(size);
 136         if (size > log_buf_len) {
 137                 unsigned long start, dest_idx, offset;
 138                 char *new_log_buf;
 139
 140                 new_log_buf = alloc_bootmem(size);
 141                 if (!new_log_buf) {
 142                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 143                         goto out;
 144                 }
 145
 146                 spin_lock_irqsave(&logbuf_lock, flags);
 147                 log_buf_len = size;
 148                 log_buf = new_log_buf;
 149
 150                 offset = start = min(con_start, log_start);
 151                 dest_idx = 0;
 152                 while (start != log_end) {
 153                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 154                         start++;
 155                         dest_idx++;
 156                 }
 157                 log_start -= offset;
 158                 con_start -= offset;
 159                 log_end -= offset;
 160                 spin_unlock_irqrestore(&logbuf_lock, flags);
 161
 162                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 163         }
 164 out:
 165         return 1;
 166 }
 167
 168 __setup("log_buf_len=", log_buf_len_setup);
 169
 170 #ifdef CONFIG_BOOT_DELAY
 171
 172 extern unsigned int boot_delay; /* msecs to delay after each printk during bootup */
 173 extern long preset_lpj;
 174 extern unsigned long long printk_delay_msec;
 175
 176 static void boot_delay_msec(int millisecs)
 177 {
 178         unsigned long long k = printk_delay_msec * millisecs;
 179         unsigned long timeout;
 180
 181         timeout = jiffies + msecs_to_jiffies(millisecs);
 182         while (k) {
 183                 k--;
 184                 cpu_relax();
 185                 /*
 186                  * use (volatile) jiffies to prevent
 187                  * compiler reduction; loop termination via jiffies
 188                  * is secondary and may or may not happen.
 189                  */
 190                 if (time_after(jiffies, timeout))
 191                         break;
 192                 touch_nmi_watchdog();
 193         }
 194 }
 195
 196 #endif
 197
 198 /*
 199  * Commands to do_syslog:
 200  *
 201  *      0 -- Close the log.  Currently a NOP.
 202  *      1 -- Open the log. Currently a NOP.
 203  *      2 -- Read from the log.
 204  *      3 -- Read all messages remaining in the ring buffer.
 205  *      4 -- Read and clear all messages remaining in the ring buffer
 206  *      5 -- Clear ring buffer.
 207  *      6 -- Disable printk's to console
 208  *      7 -- Enable printk's to console
 209  *      8 -- Set level of messages printed to console
 210  *      9 -- Return number of unread characters in the log buffer
 211  *     10 -- Return size of the log buffer
 212  */
 213 int do_syslog(int type, char __user *buf, int len)
 214 {
 215         unsigned long i, j, limit, count;
 216         int do_clear = 0;
 217         char c;
 218         int error;
 219
 220         error = security_syslog(type);
 221         if (error)
 222                 return error;
 223
 224         if ((type >= 2) && (type <= 4)) {
 225                 error = -EINVAL;
 226                 if (!buf || len < 0)
 227                         goto out;
 228                 error = 0;
 229                 if (!len)
 230                         goto out;
 231                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 232                         error = -EFAULT;
 233                         goto out;
 234                 }
 235         }
 236         if (!vx_check(0, VX_ADMIN|VX_WATCH))
 237                 return vx_do_syslog(type, buf, len);
 238
 239         switch (type) {
 240         case 0:         /* Close log */
 241                 break;
 242         case 1:         /* Open log */
 243                 break;
 244         case 2:         /* Read from log */
 245                 error = wait_event_interruptible(log_wait,
 246                                                         (log_start - log_end));
 247                 if (error)
 248                         goto out;
 249                 i = 0;
 250                 spin_lock_irq(&logbuf_lock);
 251                 while (!error && (log_start != log_end) && i < len) {
 252                         c = LOG_BUF(log_start);
 253                         log_start++;
 254                         spin_unlock_irq(&logbuf_lock);
 255                         error = __put_user(c,buf);
 256                         buf++;
 257                         i++;
 258                         cond_resched();
 259                         spin_lock_irq(&logbuf_lock);
 260                 }
 261                 spin_unlock_irq(&logbuf_lock);
 262                 if (!error)
 263                         error = i;
 264                 break;
 265         case 4:         /* Read/clear last kernel messages */
 266                 do_clear = 1;
 267                 /* FALL THRU */
 268         case 3:         /* Read last kernel messages */
 269                 count = len;
 270                 if (count > log_buf_len)
 271                         count = log_buf_len;
 272                 spin_lock_irq(&logbuf_lock);
 273                 if (count > logged_chars)
 274                         count = logged_chars;
 275                 if (do_clear)
 276                         logged_chars = 0;
 277                 limit = log_end;
 278                 /*
 279                  * __put_user() could sleep, and while we sleep
 280                  * printk() could overwrite the messages
 281                  * we try to copy to user space. Therefore
 282                  * the messages are copied in reverse. <manfreds>
 283                  */
 284                 for (i = 0; i < count && !error; i++) {
 285                         j = limit-1-i;
 286                         if (j + log_buf_len < log_end)
 287                                 break;
 288                         c = LOG_BUF(j);
 289                         spin_unlock_irq(&logbuf_lock);
 290                         error = __put_user(c,&buf[count-1-i]);
 291                         cond_resched();
 292                         spin_lock_irq(&logbuf_lock);
 293                 }
 294                 spin_unlock_irq(&logbuf_lock);
 295                 if (error)
 296                         break;
 297                 error = i;
 298                 if (i != count) {
 299                         int offset = count-error;
 300                         /* buffer overflow during copy, correct user buffer. */
 301                         for (i = 0; i < error; i++) {
 302                                 if (__get_user(c,&buf[i+offset]) ||
 303                                     __put_user(c,&buf[i])) {
 304                                         error = -EFAULT;
 305                                         break;
 306                                 }
 307                                 cond_resched();
 308                         }
 309                 }
 310                 break;
 311         case 5:         /* Clear ring buffer */
 312                 logged_chars = 0;
 313                 break;
 314         case 6:         /* Disable logging to console */
 315                 console_loglevel = minimum_console_loglevel;
 316                 break;
 317         case 7:         /* Enable logging to console */
 318                 console_loglevel = default_console_loglevel;
 319                 break;
 320         case 8:         /* Set level of messages printed to console */
 321                 error = -EINVAL;
 322                 if (len < 1 || len > 8)
 323                         goto out;
 324                 if (len < minimum_console_loglevel)
 325                         len = minimum_console_loglevel;
 326                 console_loglevel = len;
 327                 error = 0;
 328                 break;
 329         case 9:         /* Number of chars in the log buffer */
 330                 error = log_end - log_start;
 331                 break;
 332         case 10:        /* Size of the log buffer */
 333                 error = log_buf_len;
 334                 break;
 335         default:
 336                 error = -EINVAL;
 337                 break;
 338         }
 339 out:
 340         return error;
 341 }
 342
 343 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 344 {
 345         return do_syslog(type, buf, len);
 346 }
 347
 348 /*
 349  * Call the console drivers on a range of log_buf
 350  */
 351 static void __call_console_drivers(unsigned long start, unsigned long end)
 352 {
 353         struct console *con;
 354
 355         for (con = console_drivers; con; con = con->next) {
 356                 if ((con->flags & CON_ENABLED) && con->write &&
 357                                 (cpu_online(smp_processor_id()) ||
 358                                 (con->flags & CON_ANYTIME)))
 359                         con->write(con, &LOG_BUF(start), end - start);
 360         }
 361 }
 362
 363 /*
 364  * Write out chars from start to end - 1 inclusive
 365  */
 366 static void _call_console_drivers(unsigned long start,
 367                                 unsigned long end, int msg_log_level)
 368 {
 369         if (msg_log_level < console_loglevel &&
 370                         console_drivers && start != end) {
 371                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 372                         /* wrapped write */
 373                         __call_console_drivers(start & LOG_BUF_MASK,
 374                                                 log_buf_len);
 375                         __call_console_drivers(0, end & LOG_BUF_MASK);
 376                 } else {
 377                         __call_console_drivers(start, end);
 378                 }
 379         }
 380 }
 381
 382 /*
 383  * Call the console drivers, asking them to write out
 384  * log_buf[start] to log_buf[end - 1].
 385  * The console_sem must be held.
 386  */
 387 static void call_console_drivers(unsigned long start, unsigned long end)
 388 {
 389         unsigned long cur_index, start_print;
 390         static int msg_level = -1;
 391
 392         BUG_ON(((long)(start - end)) > 0);
 393
 394         cur_index = start;
 395         start_print = start;
 396         while (cur_index != end) {
 397                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 398                                 LOG_BUF(cur_index + 0) == '<' &&
 399                                 LOG_BUF(cur_index + 1) >= '0' &&
 400                                 LOG_BUF(cur_index + 1) <= '7' &&
 401                                 LOG_BUF(cur_index + 2) == '>') {
 402                         msg_level = LOG_BUF(cur_index + 1) - '0';
 403                         cur_index += 3;
 404                         start_print = cur_index;
 405                 }
 406                 while (cur_index != end) {
 407                         char c = LOG_BUF(cur_index);
 408
 409                         cur_index++;
 410                         if (c == '\n') {
 411                                 if (msg_level < 0) {
 412                                         /*
 413                                          * printk() has already given us loglevel tags in
 414                                          * the buffer.  This code is here in case the
 415                                          * log buffer has wrapped right round and scribbled
 416                                          * on those tags
 417                                          */
 418                                         msg_level = default_message_loglevel;
 419                                 }
 420                                 _call_console_drivers(start_print, cur_index, msg_level);
 421                                 msg_level = -1;
 422                                 start_print = cur_index;
 423                                 break;
 424                         }
 425                 }
 426         }
 427         _call_console_drivers(start_print, end, msg_level);
 428 }
 429
 430 static void emit_log_char(char c)
 431 {
 432         LOG_BUF(log_end) = c;
 433         log_end++;
 434         if (log_end - log_start > log_buf_len)
 435                 log_start = log_end - log_buf_len;
 436         if (log_end - con_start > log_buf_len)
 437                 con_start = log_end - log_buf_len;
 438         if (logged_chars < log_buf_len)
 439                 logged_chars++;
 440 }
 441
 442 /*
 443  * Zap console related locks when oopsing. Only zap at most once
 444  * every 10 seconds, to leave time for slow consoles to print a
 445  * full oops.
 446  */
 447 static void zap_locks(void)
 448 {
 449         static unsigned long oops_timestamp;
 450
 451         if (time_after_eq(jiffies, oops_timestamp) &&
 452                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 453                 return;
 454
 455         oops_timestamp = jiffies;
 456
 457         /* If a crash is occurring, make sure we can't deadlock */
 458         spin_lock_init(&logbuf_lock);
 459         /* And make sure that we print immediately */
 460         init_MUTEX(&console_sem);
 461 }
 462
 463 #if defined(CONFIG_PRINTK_TIME)
 464 static int printk_time = 1;
 465 #else
 466 static int printk_time = 0;
 467 #endif
 468 module_param(printk_time, int, S_IRUGO | S_IWUSR);
 469
 470 static int __init printk_time_setup(char *str)
 471 {
 472         if (*str)
 473                 return 0;
 474         printk_time = 1;
 475         return 1;
 476 }
 477
 478 __setup("time", printk_time_setup);
 479
 480 __attribute__((weak)) unsigned long long printk_clock(void)
 481 {
 482         return sched_clock();
 483 }
 484
 485 /* Check if we have any console registered that can be called early in boot. */
 486 static int have_callable_console(void)
 487 {
 488         struct console *con;
 489
 490         for (con = console_drivers; con; con = con->next)
 491                 if (con->flags & CON_ANYTIME)
 492                         return 1;
 493
 494         return 0;
 495 }
 496
 497 /**
 498  * printk - print a kernel message
 499  * @fmt: format string
 500  *
 501  * This is printk.  It can be called from any context.  We want it to work.
 502  *
 503  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 504  * call the console drivers.  If we fail to get the semaphore we place the output
 505  * into the log buffer and return.  The current holder of the console_sem will
 506  * notice the new output in release_console_sem() and will send it to the
 507  * consoles before releasing the semaphore.
 508  *
 509  * One effect of this deferred printing is that code which calls printk() and
 510  * then changes console_loglevel may break. This is because console_loglevel
 511  * is inspected when the actual printing occurs.
 512  *
 513  * See also:
 514  * printf(3)
 515  */
 516
 517 asmlinkage int printk(const char *fmt, ...)
 518 {
 519         va_list args;
 520         int r;
 521
 522         va_start(args, fmt);
 523         r = vprintk(fmt, args);
 524         va_end(args);
 525
 526 #ifdef CONFIG_BOOT_DELAY
 527         if (boot_delay && system_state == SYSTEM_BOOTING)
 528                 boot_delay_msec(boot_delay);
 529 #endif
 530
 531         return r;
 532 }
 533
 534 /* cpu currently holding logbuf_lock */
 535 static volatile unsigned int printk_cpu = UINT_MAX;
 536
 537 asmlinkage int vprintk(const char *fmt, va_list args)
 538 {
 539         unsigned long flags;
 540         int printed_len;
 541         char *p;
 542         static char printk_buf[1024];
 543         static int log_level_unknown = 1;
 544
 545         preempt_disable();
 546         if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
 547                 /* If a crash is occurring during printk() on this CPU,
 548                  * make sure we can't deadlock */
 549                 zap_locks();
 550
 551         /* This stops the holder of console_sem just where we want him */
 552         local_irq_save(flags);
 553         lockdep_off();
 554         spin_lock(&logbuf_lock);
 555         printk_cpu = smp_processor_id();
 556
 557         /* Emit the output into the temporary buffer */
 558         printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
 559
 560         /*
 561          * Copy the output into log_buf.  If the caller didn't provide
 562          * appropriate log level tags, we insert them here
 563          */
 564         for (p = printk_buf; *p; p++) {
 565                 if (log_level_unknown) {
 566                         /* log_level_unknown signals the start of a new line */
 567                         if (printk_time) {
 568                                 int loglev_char;
 569                                 char tbuf[50], *tp;
 570                                 unsigned tlen;
 571                                 unsigned long long t;
 572                                 unsigned long nanosec_rem;
 573
 574                                 /*
 575                                  * force the log level token to be
 576                                  * before the time output.
 577                                  */
 578                                 if (p[0] == '<' && p[1] >='0' &&
 579                                    p[1] <= '7' && p[2] == '>') {
 580                                         loglev_char = p[1];
 581                                         p += 3;
 582                                         printed_len -= 3;
 583                                 } else {
 584                                         loglev_char = default_message_loglevel
 585                                                 + '0';
 586                                 }
 587                                 t = printk_clock();
 588                                 nanosec_rem = do_div(t, 1000000000);
 589                                 tlen = sprintf(tbuf,
 590                                                 "<%c>[%5lu.%06lu] ",
 591                                                 loglev_char,
 592                                                 (unsigned long)t,
 593                                                 nanosec_rem/1000);
 594
 595                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 596                                         emit_log_char(*tp);
 597                                 printed_len += tlen;
 598                         } else {
 599                                 if (p[0] != '<' || p[1] < '0' ||
 600                                    p[1] > '7' || p[2] != '>') {
 601                                         emit_log_char('<');
 602                                         emit_log_char(default_message_loglevel
 603                                                 + '0');
 604                                         emit_log_char('>');
 605                                         printed_len += 3;
 606                                 }
 607                         }
 608                         log_level_unknown = 0;
 609                         if (!*p)
 610                                 break;
 611                 }
 612                 emit_log_char(*p);
 613                 if (*p == '\n')
 614                         log_level_unknown = 1;
 615         }
 616
 617         if (!down_trylock(&console_sem)) {
 618                 /*
 619                  * We own the drivers.  We can drop the spinlock and
 620                  * let release_console_sem() print the text, maybe ...
 621                  */
 622                 console_locked = 1;
 623                 printk_cpu = UINT_MAX;
 624                 spin_unlock(&logbuf_lock);
 625
 626                 /*
 627                  * Console drivers may assume that per-cpu resources have
 628                  * been allocated. So unless they're explicitly marked as
 629                  * being able to cope (CON_ANYTIME) don't call them until
 630                  * this CPU is officially up.
 631                  */
 632                 if (cpu_online(smp_processor_id()) || have_callable_console()) {
 633                         console_may_schedule = 0;
 634                         release_console_sem();
 635                 } else {
 636                         /* Release by hand to avoid flushing the buffer. */
 637                         console_locked = 0;
 638                         up(&console_sem);
 639                 }
 640                 lockdep_on();
 641                 local_irq_restore(flags);
 642         } else {
 643                 /*
 644                  * Someone else owns the drivers.  We drop the spinlock, which
 645                  * allows the semaphore holder to proceed and to call the
 646                  * console drivers with the output which we just produced.
 647                  */
 648                 printk_cpu = UINT_MAX;
 649                 spin_unlock(&logbuf_lock);
 650                 lockdep_on();
 651                 local_irq_restore(flags);
 652         }
 653
 654         preempt_enable();
 655         return printed_len;
 656 }
 657 EXPORT_SYMBOL(printk);
 658 EXPORT_SYMBOL(vprintk);
 659
 660 #else
 661
 662 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 663 {
 664         return 0;
 665 }
 666
 667 int do_syslog(int type, char __user *buf, int len)
 668 {
 669         return 0;
 670 }
 671
 672 static void call_console_drivers(unsigned long start, unsigned long end)
 673 {
 674 }
 675
 676 #endif
 677
 678 /*
 679  * Set up a list of consoles.  Called from init/main.c
 680  */
 681 static int __init console_setup(char *str)
 682 {
 683         char name[sizeof(console_cmdline[0].name)];
 684         char *s, *options;
 685         int idx;
 686
 687         /*
 688          * Decode str into name, index, options.
 689          */
 690         if (str[0] >= '0' && str[0] <= '9') {
 691                 strcpy(name, "ttyS");
 692                 strncpy(name + 4, str, sizeof(name) - 5);
 693         } else {
 694                 strncpy(name, str, sizeof(name) - 1);
 695         }
 696         name[sizeof(name) - 1] = 0;
 697         if ((options = strchr(str, ',')) != NULL)
 698                 *(options++) = 0;
 699 #ifdef __sparc__
 700         if (!strcmp(str, "ttya"))
 701                 strcpy(name, "ttyS0");
 702         if (!strcmp(str, "ttyb"))
 703                 strcpy(name, "ttyS1");
 704 #endif
 705         for (s = name; *s; s++)
 706                 if ((*s >= '0' && *s <= '9') || *s == ',')
 707                         break;
 708         idx = simple_strtoul(s, NULL, 10);
 709         *s = 0;
 710
 711         add_preferred_console(name, idx, options);
 712         return 1;
 713 }
 714 __setup("console=", console_setup);
 715
 716 /**
 717  * add_preferred_console - add a device to the list of preferred consoles.
 718  * @name: device name
 719  * @idx: device index
 720  * @options: options for this console
 721  *
 722  * The last preferred console added will be used for kernel messages
 723  * and stdin/out/err for init.  Normally this is used by console_setup
 724  * above to handle user-supplied console arguments; however it can also
 725  * be used by arch-specific code either to override the user or more
 726  * commonly to provide a default console (ie from PROM variables) when
 727  * the user has not supplied one.
 728  */
 729 int __init add_preferred_console(char *name, int idx, char *options)
 730 {
 731         struct console_cmdline *c;
 732         int i;
 733
 734         /*
 735          *      See if this tty is not yet registered, and
 736          *      if we have a slot free.
 737          */
 738         for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 739                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 740                           console_cmdline[i].index == idx) {
 741                                 selected_console = i;
 742                                 return 0;
 743                 }
 744         if (i == MAX_CMDLINECONSOLES)
 745                 return -E2BIG;
 746         selected_console = i;
 747         c = &console_cmdline[i];
 748         memcpy(c->name, name, sizeof(c->name));
 749         c->name[sizeof(c->name) - 1] = 0;
 750         c->options = options;
 751         c->index = idx;
 752         return 0;
 753 }
 754
 755 /**
 756  * suspend_console - suspend the console subsystem
 757  *
 758  * This disables printk() while we go into suspend states
 759  */
 760 void suspend_console(void)
 761 {
 762         acquire_console_sem();
 763         console_suspended = 1;
 764 }
 765
 766 void resume_console(void)
 767 {
 768         console_suspended = 0;
 769         release_console_sem();
 770 }
 771
 772 /**
 773  * acquire_console_sem - lock the console system for exclusive use.
 774  *
 775  * Acquires a semaphore which guarantees that the caller has
 776  * exclusive access to the console system and the console_drivers list.
 777  *
 778  * Can sleep, returns nothing.
 779  */
 780 void acquire_console_sem(void)
 781 {
 782         BUG_ON(in_interrupt());
 783         if (console_suspended) {
 784                 down(&secondary_console_sem);
 785                 return;
 786         }
 787         down(&console_sem);
 788         console_locked = 1;
 789         console_may_schedule = 1;
 790 }
 791 EXPORT_SYMBOL(acquire_console_sem);
 792
 793 int try_acquire_console_sem(void)
 794 {
 795         if (down_trylock(&console_sem))
 796                 return -1;
 797         console_locked = 1;
 798         console_may_schedule = 0;
 799         return 0;
 800 }
 801 EXPORT_SYMBOL(try_acquire_console_sem);
 802
 803 int is_console_locked(void)
 804 {
 805         return console_locked;
 806 }
 807 EXPORT_UNUSED_SYMBOL(is_console_locked);  /*  June 2006  */
 808
 809 /**
 810  * release_console_sem - unlock the console system
 811  *
 812  * Releases the semaphore which the caller holds on the console system
 813  * and the console driver list.
 814  *
 815  * While the semaphore was held, console output may have been buffered
 816  * by printk().  If this is the case, release_console_sem() emits
 817  * the output prior to releasing the semaphore.
 818  *
 819  * If there is output waiting for klogd, we wake it up.
 820  *
 821  * release_console_sem() may be called from any context.
 822  */
 823 void release_console_sem(void)
 824 {
 825         unsigned long flags;
 826         unsigned long _con_start, _log_end;
 827         unsigned long wake_klogd = 0;
 828
 829         if (console_suspended) {
 830                 up(&secondary_console_sem);
 831                 return;
 832         }
 833
 834         console_may_schedule = 0;
 835
 836         for ( ; ; ) {
 837                 spin_lock_irqsave(&logbuf_lock, flags);
 838                 wake_klogd |= log_start - log_end;
 839                 if (con_start == log_end)
 840                         break;                  /* Nothing to print */
 841                 _con_start = con_start;
 842                 _log_end = log_end;
 843                 con_start = log_end;            /* Flush */
 844                 spin_unlock(&logbuf_lock);
 845                 call_console_drivers(_con_start, _log_end);
 846                 local_irq_restore(flags);
 847         }
 848         console_locked = 0;
 849         up(&console_sem);
 850         spin_unlock_irqrestore(&logbuf_lock, flags);
 851         if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait)) {
 852                 /*
 853                  * If we printk from within the lock dependency code,
 854                  * from within the scheduler code, then do not lock
 855                  * up due to self-recursion:
 856                  */
 857                 if (!lockdep_internal())
 858                         wake_up_interruptible(&log_wait);
 859         }
 860 }
 861 EXPORT_SYMBOL(release_console_sem);
 862
 863 /**
 864  * console_conditional_schedule - yield the CPU if required
 865  *
 866  * If the console code is currently allowed to sleep, and
 867  * if this CPU should yield the CPU to another task, do
 868  * so here.
 869  *
 870  * Must be called within acquire_console_sem().
 871  */
 872 void __sched console_conditional_schedule(void)
 873 {
 874         if (console_may_schedule)
 875                 cond_resched();
 876 }
 877 EXPORT_SYMBOL(console_conditional_schedule);
 878
 879 void console_print(const char *s)
 880 {
 881         printk(KERN_EMERG "%s", s);
 882 }
 883 EXPORT_SYMBOL(console_print);
 884
 885 void console_unblank(void)
 886 {
 887         struct console *c;
 888
 889         /*
 890          * console_unblank can no longer be called in interrupt context unless
 891          * oops_in_progress is set to 1..
 892          */
 893         if (oops_in_progress) {
 894                 if (down_trylock(&console_sem) != 0)
 895                         return;
 896         } else
 897                 acquire_console_sem();
 898
 899         console_locked = 1;
 900         console_may_schedule = 0;
 901         for (c = console_drivers; c != NULL; c = c->next)
 902                 if ((c->flags & CON_ENABLED) && c->unblank)
 903                         c->unblank();
 904         release_console_sem();
 905 }
 906
 907 /*
 908  * Return the console tty driver structure and its associated index
 909  */
 910 struct tty_driver *console_device(int *index)
 911 {
 912         struct console *c;
 913         struct tty_driver *driver = NULL;
 914
 915         acquire_console_sem();
 916         for (c = console_drivers; c != NULL; c = c->next) {
 917                 if (!c->device)
 918                         continue;
 919                 driver = c->device(c, index);
 920                 if (driver)
 921                         break;
 922         }
 923         release_console_sem();
 924         return driver;
 925 }
 926
 927 /*
 928  * Prevent further output on the passed console device so that (for example)
 929  * serial drivers can disable console output before suspending a port, and can
 930  * re-enable output afterwards.
 931  */
 932 void console_stop(struct console *console)
 933 {
 934         acquire_console_sem();
 935         console->flags &= ~CON_ENABLED;
 936         release_console_sem();
 937 }
 938 EXPORT_SYMBOL(console_stop);
 939
 940 void console_start(struct console *console)
 941 {
 942         acquire_console_sem();
 943         console->flags |= CON_ENABLED;
 944         release_console_sem();
 945 }
 946 EXPORT_SYMBOL(console_start);
 947
 948 /*
 949  * The console driver calls this routine during kernel initialization
 950  * to register the console printing procedure with printk() and to
 951  * print any messages that were printed by the kernel before the
 952  * console driver was initialized.
 953  */
 954 void register_console(struct console *console)
 955 {
 956         int i;
 957         unsigned long flags;
 958
 959         if (preferred_console < 0)
 960                 preferred_console = selected_console;
 961
 962         /*
 963          *      See if we want to use this console driver. If we
 964          *      didn't select a console we take the first one
 965          *      that registers here.
 966          */
 967         if (preferred_console < 0) {
 968                 if (console->index < 0)
 969                         console->index = 0;
 970                 if (console->setup == NULL ||
 971                     console->setup(console, NULL) == 0) {
 972                         console->flags |= CON_ENABLED | CON_CONSDEV;
 973                         preferred_console = 0;
 974                 }
 975         }
 976
 977         /*
 978          *      See if this console matches one we selected on
 979          *      the command line.
 980          */
 981         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
 982                         i++) {
 983                 if (strcmp(console_cmdline[i].name, console->name) != 0)
 984                         continue;
 985                 if (console->index >= 0 &&
 986                     console->index != console_cmdline[i].index)
 987                         continue;
 988                 if (console->index < 0)
 989                         console->index = console_cmdline[i].index;
 990                 if (console->setup &&
 991                     console->setup(console, console_cmdline[i].options) != 0)
 992                         break;
 993                 console->flags |= CON_ENABLED;
 994                 console->index = console_cmdline[i].index;
 995                 if (i == selected_console) {
 996                         console->flags |= CON_CONSDEV;
 997                         preferred_console = selected_console;
 998                 }
 999                 break;
1000         }
1001
1002         if (!(console->flags & CON_ENABLED))
1003                 return;
1004
1005         if (console_drivers && (console_drivers->flags & CON_BOOT)) {
1006                 unregister_console(console_drivers);
1007                 console->flags &= ~CON_PRINTBUFFER;
1008         }
1009
1010         /*
1011          *      Put this console in the list - keep the
1012          *      preferred driver at the head of the list.
1013          */
1014         acquire_console_sem();
1015         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1016                 console->next = console_drivers;
1017                 console_drivers = console;
1018                 if (console->next)
1019                         console->next->flags &= ~CON_CONSDEV;
1020         } else {
1021                 console->next = console_drivers->next;
1022                 console_drivers->next = console;
1023         }
1024         if (console->flags & CON_PRINTBUFFER) {
1025                 /*
1026                  * release_console_sem() will print out the buffered messages
1027                  * for us.
1028                  */
1029                 spin_lock_irqsave(&logbuf_lock, flags);
1030                 con_start = log_start;
1031                 spin_unlock_irqrestore(&logbuf_lock, flags);
1032         }
1033         release_console_sem();
1034 }
1035 EXPORT_SYMBOL(register_console);
1036
1037 int unregister_console(struct console *console)
1038 {
1039         struct console *a, *b;
1040         int res = 1;
1041
1042         acquire_console_sem();
1043         if (console_drivers == console) {
1044                 console_drivers=console->next;
1045                 res = 0;
1046         } else if (console_drivers) {
1047                 for (a=console_drivers->next, b=console_drivers ;
1048                      a; b=a, a=b->next) {
1049                         if (a == console) {
1050                                 b->next = a->next;
1051                                 res = 0;
1052                                 break;
1053                         }
1054                 }
1055         }
1056
1057         /* If last console is removed, we re-enable picking the first
1058          * one that gets registered. Without that, pmac early boot console
1059          * would prevent fbcon from taking over.
1060          *
1061          * If this isn't the last console and it has CON_CONSDEV set, we
1062          * need to set it on the next preferred console.
1063          */
1064         if (console_drivers == NULL)
1065                 preferred_console = selected_console;
1066         else if (console->flags & CON_CONSDEV)
1067                 console_drivers->flags |= CON_CONSDEV;
1068
1069         release_console_sem();
1070         return res;
1071 }
1072 EXPORT_SYMBOL(unregister_console);
1073
1074 /**
1075  * tty_write_message - write a message to a certain tty, not just the console.
1076  * @tty: the destination tty_struct
1077  * @msg: the message to write
1078  *
1079  * This is used for messages that need to be redirected to a specific tty.
1080  * We don't put it into the syslog queue right now maybe in the future if
1081  * really needed.
1082  */
1083 void tty_write_message(struct tty_struct *tty, char *msg)
1084 {
1085         if (tty && tty->driver->write)
1086                 tty->driver->write(tty, msg, strlen(msg));
1087         return;
1088 }
1089
1090 /*
1091  * printk rate limiting, lifted from the networking subsystem.
1092  *
1093  * This enforces a rate limit: not more than one kernel message
1094  * every printk_ratelimit_jiffies to make a denial-of-service
1095  * attack impossible.
1096  */
1097 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1098 {
1099         static DEFINE_SPINLOCK(ratelimit_lock);
1100         static unsigned long toks = 10 * 5 * HZ;
1101         static unsigned long last_msg;
1102         static int missed;
1103         unsigned long flags;
1104         unsigned long now = jiffies;
1105
1106         spin_lock_irqsave(&ratelimit_lock, flags);
1107         toks += now - last_msg;
1108         last_msg = now;
1109         if (toks > (ratelimit_burst * ratelimit_jiffies))
1110                 toks = ratelimit_burst * ratelimit_jiffies;
1111         if (toks >= ratelimit_jiffies) {
1112                 int lost = missed;
1113
1114                 missed = 0;
1115                 toks -= ratelimit_jiffies;
1116                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1117                 if (lost)
1118                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1119                 return 1;
1120         }
1121         missed++;
1122         spin_unlock_irqrestore(&ratelimit_lock, flags);
1123         return 0;
1124 }
1125 EXPORT_SYMBOL(__printk_ratelimit);
1126
1127 /* minimum time in jiffies between messages */
1128 int printk_ratelimit_jiffies = 5 * HZ;
1129
1130 /* number of messages we send before ratelimiting */
1131 int printk_ratelimit_burst = 10;
1132
1133 int printk_ratelimit(void)
1134 {
1135         return __printk_ratelimit(printk_ratelimit_jiffies,
1136                                 printk_ratelimit_burst);
1137 }
1138 EXPORT_SYMBOL(printk_ratelimit);