kernel/printk.c

   1 /*
   2  *  linux/kernel/printk.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  * Modified to make sys_syslog() more flexible: added commands to
   7  * return the last 4k of kernel messages, regardless of whether
   8  * they've been read or not.  Added option to suppress kernel printk's
   9  * to the console.  Added hook for sending the console messages
  10  * elsewhere, in preparation for a serial line console (someday).
  11  * Ted Ts'o, 2/11/93.
  12  * Modified for sysctl support, 1/8/97, Chris Horn.
  13  * Fixed SMP synchronization, 08/08/99, Manfred Spraul
  14  *     manfred@colorfullife.com
  15  * Rewrote bits to get rid of console_lock
  16  *      01Mar01 Andrew Morton <andrewm@uow.edu.au>
  17  */
  18
  19 #include <linux/kernel.h>
  20 #include <linux/mm.h>
  21 #include <linux/tty.h>
  22 #include <linux/tty_driver.h>
  23 #include <linux/console.h>
  24 #include <linux/init.h>
  25 #include <linux/module.h>
  26 #include <linux/moduleparam.h>
  27 #include <linux/interrupt.h>                    /* For in_interrupt() */
  28 #include <linux/delay.h>
  29 #include <linux/smp.h>
  30 #include <linux/security.h>
  31 #include <linux/bootmem.h>
  32 #include <linux/syscalls.h>
  33 #include <linux/jiffies.h>
  34
  35 #include <asm/uaccess.h>
  36
  37 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
  38
  39 #ifdef        CONFIG_DEBUG_LL
  40 extern void printascii(char *);
  41 #endif
  42
  43 /* printk's without a loglevel use this.. */
  44 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  45
  46 /* We show everything that is MORE important than this.. */
  47 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  48 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  49
  50 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  51
  52 int console_printk[4] = {
  53         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  54         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  55         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  56         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  57 };
  58
  59 /*
  60  * Low level drivers may need that to know if they can schedule in
  61  * their unblank() callback or not. So let's export it.
  62  */
  63 int oops_in_progress;
  64 EXPORT_SYMBOL(oops_in_progress);
  65
  66 /*
  67  * console_sem protects the console_drivers list, and also
  68  * provides serialisation for access to the entire console
  69  * driver system.
  70  */
  71 static DECLARE_MUTEX(console_sem);
  72 static DECLARE_MUTEX(secondary_console_sem);
  73 struct console *console_drivers;
  74 /*
  75  * This is used for debugging the mess that is the VT code by
  76  * keeping track if we have the console semaphore held. It's
  77  * definitely not the perfect debug tool (we don't know if _WE_
  78  * hold it are racing, but it helps tracking those weird code
  79  * path in the console code where we end up in places I want
  80  * locked without the console sempahore held
  81  */
  82 static int console_locked, console_suspended;
  83
  84 /*
  85  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
  86  * It is also used in interesting ways to provide interlocking in
  87  * release_console_sem().
  88  */
  89 static DEFINE_SPINLOCK(logbuf_lock);
  90
  91 #define LOG_BUF_MASK    (log_buf_len-1)
  92 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
  93
  94 /*
  95  * The indices into log_buf are not constrained to log_buf_len - they
  96  * must be masked before subscripting
  97  */
  98 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
  99 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
 100 static unsigned long log_end;   /* Index into log_buf: most-recently-written-char + 1 */
 101
 102 /*
 103  *      Array of consoles built from command line options (console=)
 104  */
 105 struct console_cmdline
 106 {
 107         char    name[8];                        /* Name of the driver       */
 108         int     index;                          /* Minor dev. to use        */
 109         char    *options;                       /* Options for the driver   */
 110 };
 111
 112 #define MAX_CMDLINECONSOLES 8
 113
 114 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 115 static int selected_console = -1;
 116 static int preferred_console = -1;
 117
 118 /* Flag: console code may call schedule() */
 119 static int console_may_schedule;
 120
 121 #ifdef CONFIG_PRINTK
 122
 123 static char __log_buf[__LOG_BUF_LEN];
 124 static char *log_buf = __log_buf;
 125 static int log_buf_len = __LOG_BUF_LEN;
 126 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
 127
 128 static int __init log_buf_len_setup(char *str)
 129 {
 130         unsigned long size = memparse(str, &str);
 131         unsigned long flags;
 132
 133         if (size)
 134                 size = roundup_pow_of_two(size);
 135         if (size > log_buf_len) {
 136                 unsigned long start, dest_idx, offset;
 137                 char *new_log_buf;
 138
 139                 new_log_buf = alloc_bootmem(size);
 140                 if (!new_log_buf) {
 141                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 142                         goto out;
 143                 }
 144
 145                 spin_lock_irqsave(&logbuf_lock, flags);
 146                 log_buf_len = size;
 147                 log_buf = new_log_buf;
 148
 149                 offset = start = min(con_start, log_start);
 150                 dest_idx = 0;
 151                 while (start != log_end) {
 152                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 153                         start++;
 154                         dest_idx++;
 155                 }
 156                 log_start -= offset;
 157                 con_start -= offset;
 158                 log_end -= offset;
 159                 spin_unlock_irqrestore(&logbuf_lock, flags);
 160
 161                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 162         }
 163 out:
 164         return 1;
 165 }
 166
 167 __setup("log_buf_len=", log_buf_len_setup);
 168
 169 /*
 170  * Commands to do_syslog:
 171  *
 172  *      0 -- Close the log.  Currently a NOP.
 173  *      1 -- Open the log. Currently a NOP.
 174  *      2 -- Read from the log.
 175  *      3 -- Read all messages remaining in the ring buffer.
 176  *      4 -- Read and clear all messages remaining in the ring buffer
 177  *      5 -- Clear ring buffer.
 178  *      6 -- Disable printk's to console
 179  *      7 -- Enable printk's to console
 180  *      8 -- Set level of messages printed to console
 181  *      9 -- Return number of unread characters in the log buffer
 182  *     10 -- Return size of the log buffer
 183  */
 184 int do_syslog(int type, char __user *buf, int len)
 185 {
 186         unsigned long i, j, limit, count;
 187         int do_clear = 0;
 188         char c;
 189         int error = 0;
 190
 191         error = security_syslog(type);
 192         if (error)
 193                 return error;
 194
 195         switch (type) {
 196         case 0:         /* Close log */
 197                 break;
 198         case 1:         /* Open log */
 199                 break;
 200         case 2:         /* Read from log */
 201                 error = -EINVAL;
 202                 if (!buf || len < 0)
 203                         goto out;
 204                 error = 0;
 205                 if (!len)
 206                         goto out;
 207                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 208                         error = -EFAULT;
 209                         goto out;
 210                 }
 211                 error = wait_event_interruptible(log_wait,
 212                                                         (log_start - log_end));
 213                 if (error)
 214                         goto out;
 215                 i = 0;
 216                 spin_lock_irq(&logbuf_lock);
 217                 while (!error && (log_start != log_end) && i < len) {
 218                         c = LOG_BUF(log_start);
 219                         log_start++;
 220                         spin_unlock_irq(&logbuf_lock);
 221                         error = __put_user(c,buf);
 222                         buf++;
 223                         i++;
 224                         cond_resched();
 225                         spin_lock_irq(&logbuf_lock);
 226                 }
 227                 spin_unlock_irq(&logbuf_lock);
 228                 if (!error)
 229                         error = i;
 230                 break;
 231         case 4:         /* Read/clear last kernel messages */
 232                 do_clear = 1;
 233                 /* FALL THRU */
 234         case 3:         /* Read last kernel messages */
 235                 error = -EINVAL;
 236                 if (!buf || len < 0)
 237                         goto out;
 238                 error = 0;
 239                 if (!len)
 240                         goto out;
 241                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 242                         error = -EFAULT;
 243                         goto out;
 244                 }
 245                 count = len;
 246                 if (count > log_buf_len)
 247                         count = log_buf_len;
 248                 spin_lock_irq(&logbuf_lock);
 249                 if (count > logged_chars)
 250                         count = logged_chars;
 251                 if (do_clear)
 252                         logged_chars = 0;
 253                 limit = log_end;
 254                 /*
 255                  * __put_user() could sleep, and while we sleep
 256                  * printk() could overwrite the messages
 257                  * we try to copy to user space. Therefore
 258                  * the messages are copied in reverse. <manfreds>
 259                  */
 260                 for (i = 0; i < count && !error; i++) {
 261                         j = limit-1-i;
 262                         if (j + log_buf_len < log_end)
 263                                 break;
 264                         c = LOG_BUF(j);
 265                         spin_unlock_irq(&logbuf_lock);
 266                         error = __put_user(c,&buf[count-1-i]);
 267                         cond_resched();
 268                         spin_lock_irq(&logbuf_lock);
 269                 }
 270                 spin_unlock_irq(&logbuf_lock);
 271                 if (error)
 272                         break;
 273                 error = i;
 274                 if (i != count) {
 275                         int offset = count-error;
 276                         /* buffer overflow during copy, correct user buffer. */
 277                         for (i = 0; i < error; i++) {
 278                                 if (__get_user(c,&buf[i+offset]) ||
 279                                     __put_user(c,&buf[i])) {
 280                                         error = -EFAULT;
 281                                         break;
 282                                 }
 283                                 cond_resched();
 284                         }
 285                 }
 286                 break;
 287         case 5:         /* Clear ring buffer */
 288                 logged_chars = 0;
 289                 break;
 290         case 6:         /* Disable logging to console */
 291                 console_loglevel = minimum_console_loglevel;
 292                 break;
 293         case 7:         /* Enable logging to console */
 294                 console_loglevel = default_console_loglevel;
 295                 break;
 296         case 8:         /* Set level of messages printed to console */
 297                 error = -EINVAL;
 298                 if (len < 1 || len > 8)
 299                         goto out;
 300                 if (len < minimum_console_loglevel)
 301                         len = minimum_console_loglevel;
 302                 console_loglevel = len;
 303                 error = 0;
 304                 break;
 305         case 9:         /* Number of chars in the log buffer */
 306                 error = log_end - log_start;
 307                 break;
 308         case 10:        /* Size of the log buffer */
 309                 error = log_buf_len;
 310                 break;
 311         default:
 312                 error = -EINVAL;
 313                 break;
 314         }
 315 out:
 316         return error;
 317 }
 318
 319 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 320 {
 321         return do_syslog(type, buf, len);
 322 }
 323
 324 /*
 325  * Call the console drivers on a range of log_buf
 326  */
 327 static void __call_console_drivers(unsigned long start, unsigned long end)
 328 {
 329         struct console *con;
 330
 331         for (con = console_drivers; con; con = con->next) {
 332                 if ((con->flags & CON_ENABLED) && con->write &&
 333                                 (cpu_online(smp_processor_id()) ||
 334                                 (con->flags & CON_ANYTIME)))
 335                         con->write(con, &LOG_BUF(start), end - start);
 336         }
 337 }
 338
 339 static int __read_mostly ignore_loglevel;
 340
 341 static int __init ignore_loglevel_setup(char *str)
 342 {
 343         ignore_loglevel = 1;
 344         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 345
 346         return 1;
 347 }
 348
 349 __setup("ignore_loglevel", ignore_loglevel_setup);
 350
 351 /*
 352  * Write out chars from start to end - 1 inclusive
 353  */
 354 static void _call_console_drivers(unsigned long start,
 355                                 unsigned long end, int msg_log_level)
 356 {
 357         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 358                         console_drivers && start != end) {
 359                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 360                         /* wrapped write */
 361                         __call_console_drivers(start & LOG_BUF_MASK,
 362                                                 log_buf_len);
 363                         __call_console_drivers(0, end & LOG_BUF_MASK);
 364                 } else {
 365                         __call_console_drivers(start, end);
 366                 }
 367         }
 368 }
 369
 370 /*
 371  * Call the console drivers, asking them to write out
 372  * log_buf[start] to log_buf[end - 1].
 373  * The console_sem must be held.
 374  */
 375 static void call_console_drivers(unsigned long start, unsigned long end)
 376 {
 377         unsigned long cur_index, start_print;
 378         static int msg_level = -1;
 379
 380         BUG_ON(((long)(start - end)) > 0);
 381
 382         cur_index = start;
 383         start_print = start;
 384         while (cur_index != end) {
 385                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 386                                 LOG_BUF(cur_index + 0) == '<' &&
 387                                 LOG_BUF(cur_index + 1) >= '0' &&
 388                                 LOG_BUF(cur_index + 1) <= '7' &&
 389                                 LOG_BUF(cur_index + 2) == '>') {
 390                         msg_level = LOG_BUF(cur_index + 1) - '0';
 391                         cur_index += 3;
 392                         start_print = cur_index;
 393                 }
 394                 while (cur_index != end) {
 395                         char c = LOG_BUF(cur_index);
 396
 397                         cur_index++;
 398                         if (c == '\n') {
 399                                 if (msg_level < 0) {
 400                                         /*
 401                                          * printk() has already given us loglevel tags in
 402                                          * the buffer.  This code is here in case the
 403                                          * log buffer has wrapped right round and scribbled
 404                                          * on those tags
 405                                          */
 406                                         msg_level = default_message_loglevel;
 407                                 }
 408                                 _call_console_drivers(start_print, cur_index, msg_level);
 409                                 msg_level = -1;
 410                                 start_print = cur_index;
 411                                 break;
 412                         }
 413                 }
 414         }
 415         _call_console_drivers(start_print, end, msg_level);
 416 }
 417
 418 static void emit_log_char(char c)
 419 {
 420         LOG_BUF(log_end) = c;
 421         log_end++;
 422         if (log_end - log_start > log_buf_len)
 423                 log_start = log_end - log_buf_len;
 424         if (log_end - con_start > log_buf_len)
 425                 con_start = log_end - log_buf_len;
 426         if (logged_chars < log_buf_len)
 427                 logged_chars++;
 428 }
 429
 430 /*
 431  * Zap console related locks when oopsing. Only zap at most once
 432  * every 10 seconds, to leave time for slow consoles to print a
 433  * full oops.
 434  */
 435 static void zap_locks(void)
 436 {
 437         static unsigned long oops_timestamp;
 438
 439         if (time_after_eq(jiffies, oops_timestamp) &&
 440                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 441                 return;
 442
 443         oops_timestamp = jiffies;
 444
 445         /* If a crash is occurring, make sure we can't deadlock */
 446         spin_lock_init(&logbuf_lock);
 447         /* And make sure that we print immediately */
 448         init_MUTEX(&console_sem);
 449 }
 450
 451 static int printk_time = 0;
 452
 453 #ifdef CONFIG_PRINTK_TIME
 454
 455 /*
 456  * Initialize printk time. Note that on some systems sched_clock()
 457  * does not work until timer is initialized.
 458  */
 459 static int __init printk_time_init(void)
 460 {
 461         printk_time = 1;
 462
 463         return 0;
 464 }
 465 subsys_initcall(printk_time_init);
 466
 467 #else
 468
 469 static int __init printk_time_setup(char *str)
 470 {
 471         if (*str)
 472                 return 0;
 473         printk_time = 1;
 474         printk(KERN_NOTICE "The 'time' option is deprecated and "
 475                 "is scheduled for removal in early 2008\n");
 476         printk(KERN_NOTICE "Use 'printk.time=<value>' instead\n");
 477         return 1;
 478 }
 479
 480 __setup("time", printk_time_setup);
 481
 482 #endif
 483 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 484
 485 __attribute__((weak)) unsigned long long printk_clock(void)
 486 {
 487         return sched_clock();
 488 }
 489
 490 /* Check if we have any console registered that can be called early in boot. */
 491 static int have_callable_console(void)
 492 {
 493         struct console *con;
 494
 495         for (con = console_drivers; con; con = con->next)
 496                 if (con->flags & CON_ANYTIME)
 497                         return 1;
 498
 499         return 0;
 500 }
 501
 502 /**
 503  * printk - print a kernel message
 504  * @fmt: format string
 505  *
 506  * This is printk().  It can be called from any context.  We want it to work.
 507  * Be aware of the fact that if oops_in_progress is not set, we might try to
 508  * wake klogd up which could deadlock on runqueue lock if printk() is called
 509  * from scheduler code.
 510  *
 511  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 512  * call the console drivers.  If we fail to get the semaphore we place the output
 513  * into the log buffer and return.  The current holder of the console_sem will
 514  * notice the new output in release_console_sem() and will send it to the
 515  * consoles before releasing the semaphore.
 516  *
 517  * One effect of this deferred printing is that code which calls printk() and
 518  * then changes console_loglevel may break. This is because console_loglevel
 519  * is inspected when the actual printing occurs.
 520  *
 521  * See also:
 522  * printf(3)
 523  */
 524
 525 asmlinkage int printk(const char *fmt, ...)
 526 {
 527         va_list args;
 528         int r;
 529
 530         va_start(args, fmt);
 531         r = vprintk(fmt, args);
 532         va_end(args);
 533
 534         return r;
 535 }
 536
 537 /* cpu currently holding logbuf_lock */
 538 static volatile unsigned int printk_cpu = UINT_MAX;
 539
 540 asmlinkage int vprintk(const char *fmt, va_list args)
 541 {
 542         unsigned long flags;
 543         int printed_len;
 544         char *p;
 545         static char printk_buf[1024];
 546         static int log_level_unknown = 1;
 547
 548         preempt_disable();
 549         if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
 550                 /* If a crash is occurring during printk() on this CPU,
 551                  * make sure we can't deadlock */
 552                 zap_locks();
 553
 554         /* This stops the holder of console_sem just where we want him */
 555         raw_local_irq_save(flags);
 556         lockdep_off();
 557         spin_lock(&logbuf_lock);
 558         printk_cpu = smp_processor_id();
 559
 560         /* Emit the output into the temporary buffer */
 561         printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
 562
 563 #ifdef  CONFIG_DEBUG_LL
 564         printascii(printk_buf);
 565 #endif
 566
 567         /*
 568          * Copy the output into log_buf.  If the caller didn't provide
 569          * appropriate log level tags, we insert them here
 570          */
 571         for (p = printk_buf; *p; p++) {
 572                 if (log_level_unknown) {
 573                         /* log_level_unknown signals the start of a new line */
 574                         if (printk_time) {
 575                                 int loglev_char;
 576                                 char tbuf[50], *tp;
 577                                 unsigned tlen;
 578                                 unsigned long long t;
 579                                 unsigned long nanosec_rem;
 580
 581                                 /*
 582                                  * force the log level token to be
 583                                  * before the time output.
 584                                  */
 585                                 if (p[0] == '<' && p[1] >='0' &&
 586                                    p[1] <= '7' && p[2] == '>') {
 587                                         loglev_char = p[1];
 588                                         p += 3;
 589                                         printed_len -= 3;
 590                                 } else {
 591                                         loglev_char = default_message_loglevel
 592                                                 + '0';
 593                                 }
 594                                 t = printk_clock();
 595                                 nanosec_rem = do_div(t, 1000000000);
 596                                 tlen = sprintf(tbuf,
 597                                                 "<%c>[%5lu.%06lu] ",
 598                                                 loglev_char,
 599                                                 (unsigned long)t,
 600                                                 nanosec_rem/1000);
 601
 602                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 603                                         emit_log_char(*tp);
 604                                 printed_len += tlen;
 605                         } else {
 606                                 if (p[0] != '<' || p[1] < '0' ||
 607                                    p[1] > '7' || p[2] != '>') {
 608                                         emit_log_char('<');
 609                                         emit_log_char(default_message_loglevel
 610                                                 + '0');
 611                                         emit_log_char('>');
 612                                         printed_len += 3;
 613                                 }
 614                         }
 615                         log_level_unknown = 0;
 616                         if (!*p)
 617                                 break;
 618                 }
 619                 emit_log_char(*p);
 620                 if (*p == '\n')
 621                         log_level_unknown = 1;
 622         }
 623
 624         if (!down_trylock(&console_sem)) {
 625                 /*
 626                  * We own the drivers.  We can drop the spinlock and
 627                  * let release_console_sem() print the text, maybe ...
 628                  */
 629                 console_locked = 1;
 630                 printk_cpu = UINT_MAX;
 631                 spin_unlock(&logbuf_lock);
 632
 633                 /*
 634                  * Console drivers may assume that per-cpu resources have
 635                  * been allocated. So unless they're explicitly marked as
 636                  * being able to cope (CON_ANYTIME) don't call them until
 637                  * this CPU is officially up.
 638                  */
 639                 if (cpu_online(smp_processor_id()) || have_callable_console()) {
 640                         console_may_schedule = 0;
 641                         release_console_sem();
 642                 } else {
 643                         /* Release by hand to avoid flushing the buffer. */
 644                         console_locked = 0;
 645                         up(&console_sem);
 646                 }
 647                 lockdep_on();
 648                 raw_local_irq_restore(flags);
 649         } else {
 650                 /*
 651                  * Someone else owns the drivers.  We drop the spinlock, which
 652                  * allows the semaphore holder to proceed and to call the
 653                  * console drivers with the output which we just produced.
 654                  */
 655                 printk_cpu = UINT_MAX;
 656                 spin_unlock(&logbuf_lock);
 657                 lockdep_on();
 658                 raw_local_irq_restore(flags);
 659         }
 660
 661         preempt_enable();
 662         return printed_len;
 663 }
 664 EXPORT_SYMBOL(printk);
 665 EXPORT_SYMBOL(vprintk);
 666
 667 #else
 668
 669 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 670 {
 671         return -ENOSYS;
 672 }
 673
 674 static void call_console_drivers(unsigned long start, unsigned long end)
 675 {
 676 }
 677
 678 #endif
 679
 680 /*
 681  * Set up a list of consoles.  Called from init/main.c
 682  */
 683 static int __init console_setup(char *str)
 684 {
 685         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 686         char *s, *options;
 687         int idx;
 688
 689         /*
 690          * Decode str into name, index, options.
 691          */
 692         if (str[0] >= '0' && str[0] <= '9') {
 693                 strcpy(buf, "ttyS");
 694                 strncpy(buf + 4, str, sizeof(buf) - 5);
 695         } else {
 696                 strncpy(buf, str, sizeof(buf) - 1);
 697         }
 698         buf[sizeof(buf) - 1] = 0;
 699         if ((options = strchr(str, ',')) != NULL)
 700                 *(options++) = 0;
 701 #ifdef __sparc__
 702         if (!strcmp(str, "ttya"))
 703                 strcpy(buf, "ttyS0");
 704         if (!strcmp(str, "ttyb"))
 705                 strcpy(buf, "ttyS1");
 706 #endif
 707         for (s = buf; *s; s++)
 708                 if ((*s >= '0' && *s <= '9') || *s == ',')
 709                         break;
 710         idx = simple_strtoul(s, NULL, 10);
 711         *s = 0;
 712
 713         add_preferred_console(buf, idx, options);
 714         return 1;
 715 }
 716 __setup("console=", console_setup);
 717
 718 /**
 719  * add_preferred_console - add a device to the list of preferred consoles.
 720  * @name: device name
 721  * @idx: device index
 722  * @options: options for this console
 723  *
 724  * The last preferred console added will be used for kernel messages
 725  * and stdin/out/err for init.  Normally this is used by console_setup
 726  * above to handle user-supplied console arguments; however it can also
 727  * be used by arch-specific code either to override the user or more
 728  * commonly to provide a default console (ie from PROM variables) when
 729  * the user has not supplied one.
 730  */
 731 int __init add_preferred_console(char *name, int idx, char *options)
 732 {
 733         struct console_cmdline *c;
 734         int i;
 735
 736         /*
 737          *      See if this tty is not yet registered, and
 738          *      if we have a slot free.
 739          */
 740         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 741                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 742                           console_cmdline[i].index == idx) {
 743                                 selected_console = i;
 744                                 return 0;
 745                 }
 746         if (i == MAX_CMDLINECONSOLES)
 747                 return -E2BIG;
 748         selected_console = i;
 749         c = &console_cmdline[i];
 750         memcpy(c->name, name, sizeof(c->name));
 751         c->name[sizeof(c->name) - 1] = 0;
 752         c->options = options;
 753         c->index = idx;
 754         return 0;
 755 }
 756
 757 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 758 {
 759         struct console_cmdline *c;
 760         int i;
 761
 762         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 763                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 764                           console_cmdline[i].index == idx) {
 765                                 c = &console_cmdline[i];
 766                                 memcpy(c->name, name_new, sizeof(c->name));
 767                                 c->name[sizeof(c->name) - 1] = 0;
 768                                 c->options = options;
 769                                 c->index = idx_new;
 770                                 return i;
 771                 }
 772         /* not found */
 773         return -1;
 774 }
 775
 776 #ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
 777 /**
 778  * suspend_console - suspend the console subsystem
 779  *
 780  * This disables printk() while we go into suspend states
 781  */
 782 void suspend_console(void)
 783 {
 784         printk("Suspending console(s)\n");
 785         acquire_console_sem();
 786         console_suspended = 1;
 787 }
 788
 789 void resume_console(void)
 790 {
 791         console_suspended = 0;
 792         release_console_sem();
 793 }
 794 #endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
 795
 796 /**
 797  * acquire_console_sem - lock the console system for exclusive use.
 798  *
 799  * Acquires a semaphore which guarantees that the caller has
 800  * exclusive access to the console system and the console_drivers list.
 801  *
 802  * Can sleep, returns nothing.
 803  */
 804 void acquire_console_sem(void)
 805 {
 806         BUG_ON(in_interrupt());
 807         if (console_suspended) {
 808                 down(&secondary_console_sem);
 809                 return;
 810         }
 811         down(&console_sem);
 812         console_locked = 1;
 813         console_may_schedule = 1;
 814 }
 815 EXPORT_SYMBOL(acquire_console_sem);
 816
 817 int try_acquire_console_sem(void)
 818 {
 819         if (down_trylock(&console_sem))
 820                 return -1;
 821         console_locked = 1;
 822         console_may_schedule = 0;
 823         return 0;
 824 }
 825 EXPORT_SYMBOL(try_acquire_console_sem);
 826
 827 int is_console_locked(void)
 828 {
 829         return console_locked;
 830 }
 831
 832 void wake_up_klogd(void)
 833 {
 834         if (!oops_in_progress && waitqueue_active(&log_wait))
 835                 wake_up_interruptible(&log_wait);
 836 }
 837
 838 /**
 839  * release_console_sem - unlock the console system
 840  *
 841  * Releases the semaphore which the caller holds on the console system
 842  * and the console driver list.
 843  *
 844  * While the semaphore was held, console output may have been buffered
 845  * by printk().  If this is the case, release_console_sem() emits
 846  * the output prior to releasing the semaphore.
 847  *
 848  * If there is output waiting for klogd, we wake it up.
 849  *
 850  * release_console_sem() may be called from any context.
 851  */
 852 void release_console_sem(void)
 853 {
 854         unsigned long flags;
 855         unsigned long _con_start, _log_end;
 856         unsigned long wake_klogd = 0;
 857
 858         if (console_suspended) {
 859                 up(&secondary_console_sem);
 860                 return;
 861         }
 862
 863         console_may_schedule = 0;
 864
 865         for ( ; ; ) {
 866                 spin_lock_irqsave(&logbuf_lock, flags);
 867                 wake_klogd |= log_start - log_end;
 868                 if (con_start == log_end)
 869                         break;                  /* Nothing to print */
 870                 _con_start = con_start;
 871                 _log_end = log_end;
 872                 con_start = log_end;            /* Flush */
 873                 spin_unlock(&logbuf_lock);
 874                 call_console_drivers(_con_start, _log_end);
 875                 local_irq_restore(flags);
 876         }
 877         console_locked = 0;
 878         up(&console_sem);
 879         spin_unlock_irqrestore(&logbuf_lock, flags);
 880         if (wake_klogd)
 881                 wake_up_klogd();
 882 }
 883 EXPORT_SYMBOL(release_console_sem);
 884
 885 /**
 886  * console_conditional_schedule - yield the CPU if required
 887  *
 888  * If the console code is currently allowed to sleep, and
 889  * if this CPU should yield the CPU to another task, do
 890  * so here.
 891  *
 892  * Must be called within acquire_console_sem().
 893  */
 894 void __sched console_conditional_schedule(void)
 895 {
 896         if (console_may_schedule)
 897                 cond_resched();
 898 }
 899 EXPORT_SYMBOL(console_conditional_schedule);
 900
 901 void console_print(const char *s)
 902 {
 903         printk(KERN_EMERG "%s", s);
 904 }
 905 EXPORT_SYMBOL(console_print);
 906
 907 void console_unblank(void)
 908 {
 909         struct console *c;
 910
 911         /*
 912          * console_unblank can no longer be called in interrupt context unless
 913          * oops_in_progress is set to 1..
 914          */
 915         if (oops_in_progress) {
 916                 if (down_trylock(&console_sem) != 0)
 917                         return;
 918         } else
 919                 acquire_console_sem();
 920
 921         console_locked = 1;
 922         console_may_schedule = 0;
 923         for (c = console_drivers; c != NULL; c = c->next)
 924                 if ((c->flags & CON_ENABLED) && c->unblank)
 925                         c->unblank();
 926         release_console_sem();
 927 }
 928
 929 /*
 930  * Return the console tty driver structure and its associated index
 931  */
 932 struct tty_driver *console_device(int *index)
 933 {
 934         struct console *c;
 935         struct tty_driver *driver = NULL;
 936
 937         acquire_console_sem();
 938         for (c = console_drivers; c != NULL; c = c->next) {
 939                 if (!c->device)
 940                         continue;
 941                 driver = c->device(c, index);
 942                 if (driver)
 943                         break;
 944         }
 945         release_console_sem();
 946         return driver;
 947 }
 948
 949 /*
 950  * Prevent further output on the passed console device so that (for example)
 951  * serial drivers can disable console output before suspending a port, and can
 952  * re-enable output afterwards.
 953  */
 954 void console_stop(struct console *console)
 955 {
 956         acquire_console_sem();
 957         console->flags &= ~CON_ENABLED;
 958         release_console_sem();
 959 }
 960 EXPORT_SYMBOL(console_stop);
 961
 962 void console_start(struct console *console)
 963 {
 964         acquire_console_sem();
 965         console->flags |= CON_ENABLED;
 966         release_console_sem();
 967 }
 968 EXPORT_SYMBOL(console_start);
 969
 970 /*
 971  * The console driver calls this routine during kernel initialization
 972  * to register the console printing procedure with printk() and to
 973  * print any messages that were printed by the kernel before the
 974  * console driver was initialized.
 975  */
 976 void register_console(struct console *console)
 977 {
 978         int i;
 979         unsigned long flags;
 980         struct console *bootconsole = NULL;
 981
 982         if (console_drivers) {
 983                 if (console->flags & CON_BOOT)
 984                         return;
 985                 if (console_drivers->flags & CON_BOOT)
 986                         bootconsole = console_drivers;
 987         }
 988
 989         if (preferred_console < 0 || bootconsole || !console_drivers)
 990                 preferred_console = selected_console;
 991
 992         if (console->early_setup)
 993                 console->early_setup();
 994
 995         /*
 996          *      See if we want to use this console driver. If we
 997          *      didn't select a console we take the first one
 998          *      that registers here.
 999          */
1000         if (preferred_console < 0) {
1001                 if (console->index < 0)
1002                         console->index = 0;
1003                 if (console->setup == NULL ||
1004                     console->setup(console, NULL) == 0) {
1005                         console->flags |= CON_ENABLED | CON_CONSDEV;
1006                         preferred_console = 0;
1007                 }
1008         }
1009
1010         /*
1011          *      See if this console matches one we selected on
1012          *      the command line.
1013          */
1014         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1015                         i++) {
1016                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1017                         continue;
1018                 if (console->index >= 0 &&
1019                     console->index != console_cmdline[i].index)
1020                         continue;
1021                 if (console->index < 0)
1022                         console->index = console_cmdline[i].index;
1023                 if (console->setup &&
1024                     console->setup(console, console_cmdline[i].options) != 0)
1025                         break;
1026                 console->flags |= CON_ENABLED;
1027                 console->index = console_cmdline[i].index;
1028                 if (i == selected_console) {
1029                         console->flags |= CON_CONSDEV;
1030                         preferred_console = selected_console;
1031                 }
1032                 break;
1033         }
1034
1035         if (!(console->flags & CON_ENABLED))
1036                 return;
1037
1038         if (bootconsole && (console->flags & CON_CONSDEV)) {
1039                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1040                        bootconsole->name, bootconsole->index,
1041                        console->name, console->index);
1042                 unregister_console(bootconsole);
1043                 console->flags &= ~CON_PRINTBUFFER;
1044         } else {
1045                 printk(KERN_INFO "console [%s%d] enabled\n",
1046                        console->name, console->index);
1047         }
1048
1049         /*
1050          *      Put this console in the list - keep the
1051          *      preferred driver at the head of the list.
1052          */
1053         acquire_console_sem();
1054         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1055                 console->next = console_drivers;
1056                 console_drivers = console;
1057                 if (console->next)
1058                         console->next->flags &= ~CON_CONSDEV;
1059         } else {
1060                 console->next = console_drivers->next;
1061                 console_drivers->next = console;
1062         }
1063         if (console->flags & CON_PRINTBUFFER) {
1064                 /*
1065                  * release_console_sem() will print out the buffered messages
1066                  * for us.
1067                  */
1068                 spin_lock_irqsave(&logbuf_lock, flags);
1069                 con_start = log_start;
1070                 spin_unlock_irqrestore(&logbuf_lock, flags);
1071         }
1072         release_console_sem();
1073 }
1074 EXPORT_SYMBOL(register_console);
1075
1076 int unregister_console(struct console *console)
1077 {
1078         struct console *a, *b;
1079         int res = 1;
1080
1081         acquire_console_sem();
1082         if (console_drivers == console) {
1083                 console_drivers=console->next;
1084                 res = 0;
1085         } else if (console_drivers) {
1086                 for (a=console_drivers->next, b=console_drivers ;
1087                      a; b=a, a=b->next) {
1088                         if (a == console) {
1089                                 b->next = a->next;
1090                                 res = 0;
1091                                 break;
1092                         }
1093                 }
1094         }
1095
1096         /*
1097          * If this isn't the last console and it has CON_CONSDEV set, we
1098          * need to set it on the next preferred console.
1099          */
1100         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1101                 console_drivers->flags |= CON_CONSDEV;
1102
1103         release_console_sem();
1104         return res;
1105 }
1106 EXPORT_SYMBOL(unregister_console);
1107
1108 static int __init disable_boot_consoles(void)
1109 {
1110         if (console_drivers != NULL) {
1111                 if (console_drivers->flags & CON_BOOT) {
1112                         printk(KERN_INFO "turn off boot console %s%d\n",
1113                                 console_drivers->name, console_drivers->index);
1114                         return unregister_console(console_drivers);
1115                 }
1116         }
1117         return 0;
1118 }
1119 late_initcall(disable_boot_consoles);
1120
1121 /**
1122  * tty_write_message - write a message to a certain tty, not just the console.
1123  * @tty: the destination tty_struct
1124  * @msg: the message to write
1125  *
1126  * This is used for messages that need to be redirected to a specific tty.
1127  * We don't put it into the syslog queue right now maybe in the future if
1128  * really needed.
1129  */
1130 void tty_write_message(struct tty_struct *tty, char *msg)
1131 {
1132         if (tty && tty->driver->write)
1133                 tty->driver->write(tty, msg, strlen(msg));
1134         return;
1135 }
1136
1137 /*
1138  * printk rate limiting, lifted from the networking subsystem.
1139  *
1140  * This enforces a rate limit: not more than one kernel message
1141  * every printk_ratelimit_jiffies to make a denial-of-service
1142  * attack impossible.
1143  */
1144 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1145 {
1146         static DEFINE_SPINLOCK(ratelimit_lock);
1147         static unsigned long toks = 10 * 5 * HZ;
1148         static unsigned long last_msg;
1149         static int missed;
1150         unsigned long flags;
1151         unsigned long now = jiffies;
1152
1153         spin_lock_irqsave(&ratelimit_lock, flags);
1154         toks += now - last_msg;
1155         last_msg = now;
1156         if (toks > (ratelimit_burst * ratelimit_jiffies))
1157                 toks = ratelimit_burst * ratelimit_jiffies;
1158         if (toks >= ratelimit_jiffies) {
1159                 int lost = missed;
1160
1161                 missed = 0;
1162                 toks -= ratelimit_jiffies;
1163                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1164                 if (lost)
1165                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1166                 return 1;
1167         }
1168         missed++;
1169         spin_unlock_irqrestore(&ratelimit_lock, flags);
1170         return 0;
1171 }
1172 EXPORT_SYMBOL(__printk_ratelimit);
1173
1174 /* minimum time in jiffies between messages */
1175 int printk_ratelimit_jiffies = 5 * HZ;
1176
1177 /* number of messages we send before ratelimiting */
1178 int printk_ratelimit_burst = 10;
1179
1180 int printk_ratelimit(void)
1181 {
1182         return __printk_ratelimit(printk_ratelimit_jiffies,
1183                                 printk_ratelimit_burst);
1184 }
1185 EXPORT_SYMBOL(printk_ratelimit);
1186
1187 /**
1188  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1189  * @caller_jiffies: pointer to caller's state
1190  * @interval_msecs: minimum interval between prints
1191  *
1192  * printk_timed_ratelimit() returns true if more than @interval_msecs
1193  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1194  * returned true.
1195  */
1196 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1197                         unsigned int interval_msecs)
1198 {
1199         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1200                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1201                 return true;
1202         }
1203         return false;
1204 }
1205 EXPORT_SYMBOL(printk_timed_ratelimit);