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/jiffies.h>
  37 #include <linux/vs_cvirt.h>
  38
  39 #include <asm/uaccess.h>
  40
  41 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
  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 lever 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 #ifdef CONFIG_BOOT_DELAY
 170
 171 extern unsigned int boot_delay; /* msecs to delay after each printk during bootup */
 172 extern long preset_lpj;
 173 extern unsigned long long printk_delay_msec;
 174
 175 static void boot_delay_msec(int millisecs)
 176 {
 177         unsigned long long k = printk_delay_msec * millisecs;
 178         unsigned long timeout;
 179
 180         timeout = jiffies + msecs_to_jiffies(millisecs);
 181         while (k) {
 182                 k--;
 183                 cpu_relax();
 184                 /*
 185                  * use (volatile) jiffies to prevent
 186                  * compiler reduction; loop termination via jiffies
 187                  * is secondary and may or may not happen.
 188                  */
 189                 if (time_after(jiffies, timeout))
 190                         break;
 191                 touch_nmi_watchdog();
 192         }
 193 }
 194
 195 #endif
 196
 197 /*
 198  * Commands to do_syslog:
 199  *
 200  *      0 -- Close the log.  Currently a NOP.
 201  *      1 -- Open the log. Currently a NOP.
 202  *      2 -- Read from the log.
 203  *      3 -- Read all messages remaining in the ring buffer.
 204  *      4 -- Read and clear all messages remaining in the ring buffer
 205  *      5 -- Clear ring buffer.
 206  *      6 -- Disable printk's to console
 207  *      7 -- Enable printk's to console
 208  *      8 -- Set level of messages printed to console
 209  *      9 -- Return number of unread characters in the log buffer
 210  *     10 -- Return size of the log buffer
 211  */
 212 int do_syslog(int type, char __user *buf, int len)
 213 {
 214         unsigned long i, j, limit, count;
 215         int do_clear = 0;
 216         char c;
 217         int error;
 218
 219         error = security_syslog(type);
 220         if (error)
 221                 return error;
 222
 223         if ((type >= 2) && (type <= 4)) {
 224                 error = -EINVAL;
 225                 if (!buf || len < 0)
 226                         goto out;
 227                 error = 0;
 228                 if (!len)
 229                         goto out;
 230                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 231                         error = -EFAULT;
 232                         goto out;
 233                 }
 234         }
 235         if (!vx_check(0, VS_ADMIN|VS_WATCH))
 236                 return vx_do_syslog(type, buf, len);
 237
 238         switch (type) {
 239         case 0:         /* Close log */
 240                 break;
 241         case 1:         /* Open log */
 242                 break;
 243         case 2:         /* Read from log */
 244                 error = wait_event_interruptible(log_wait,
 245                                                         (log_start - log_end));
 246                 if (error)
 247                         goto out;
 248                 i = 0;
 249                 spin_lock_irq(&logbuf_lock);
 250                 while (!error && (log_start != log_end) && i < len) {
 251                         c = LOG_BUF(log_start);
 252                         log_start++;
 253                         spin_unlock_irq(&logbuf_lock);
 254                         error = __put_user(c,buf);
 255                         buf++;
 256                         i++;
 257                         cond_resched();
 258                         spin_lock_irq(&logbuf_lock);
 259                 }
 260                 spin_unlock_irq(&logbuf_lock);
 261                 if (!error)
 262                         error = i;
 263                 break;
 264         case 4:         /* Read/clear last kernel messages */
 265                 do_clear = 1;
 266                 /* FALL THRU */
 267         case 3:         /* Read last kernel messages */
 268                 count = len;
 269                 if (count > log_buf_len)
 270                         count = log_buf_len;
 271                 spin_lock_irq(&logbuf_lock);
 272                 if (count > logged_chars)
 273                         count = logged_chars;
 274                 if (do_clear)
 275                         logged_chars = 0;
 276                 limit = log_end;
 277                 /*
 278                  * __put_user() could sleep, and while we sleep
 279                  * printk() could overwrite the messages
 280                  * we try to copy to user space. Therefore
 281                  * the messages are copied in reverse. <manfreds>
 282                  */
 283                 for (i = 0; i < count && !error; i++) {
 284                         j = limit-1-i;
 285                         if (j + log_buf_len < log_end)
 286                                 break;
 287                         c = LOG_BUF(j);
 288                         spin_unlock_irq(&logbuf_lock);
 289                         error = __put_user(c,&buf[count-1-i]);
 290                         cond_resched();
 291                         spin_lock_irq(&logbuf_lock);
 292                 }
 293                 spin_unlock_irq(&logbuf_lock);
 294                 if (error)
 295                         break;
 296                 error = i;
 297                 if (i != count) {
 298                         int offset = count-error;
 299                         /* buffer overflow during copy, correct user buffer. */
 300                         for (i = 0; i < error; i++) {
 301                                 if (__get_user(c,&buf[i+offset]) ||
 302                                     __put_user(c,&buf[i])) {
 303                                         error = -EFAULT;
 304                                         break;
 305                                 }
 306                                 cond_resched();
 307                         }
 308                 }
 309                 break;
 310         case 5:         /* Clear ring buffer */
 311                 logged_chars = 0;
 312                 break;
 313         case 6:         /* Disable logging to console */
 314                 console_loglevel = minimum_console_loglevel;
 315                 break;
 316         case 7:         /* Enable logging to console */
 317                 console_loglevel = default_console_loglevel;
 318                 break;
 319         case 8:         /* Set level of messages printed to console */
 320                 error = -EINVAL;
 321                 if (len < 1 || len > 8)
 322                         goto out;
 323                 if (len < minimum_console_loglevel)
 324                         len = minimum_console_loglevel;
 325                 console_loglevel = len;
 326                 error = 0;
 327                 break;
 328         case 9:         /* Number of chars in the log buffer */
 329                 error = log_end - log_start;
 330                 break;
 331         case 10:        /* Size of the log buffer */
 332                 error = log_buf_len;
 333                 break;
 334         default:
 335                 error = -EINVAL;
 336                 break;
 337         }
 338 out:
 339         return error;
 340 }
 341
 342 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 343 {
 344         return do_syslog(type, buf, len);
 345 }
 346
 347 /*
 348  * Call the console drivers on a range of log_buf
 349  */
 350 static void __call_console_drivers(unsigned long start, unsigned long end)
 351 {
 352         struct console *con;
 353
 354         for (con = console_drivers; con; con = con->next) {
 355                 if ((con->flags & CON_ENABLED) && con->write &&
 356                                 (cpu_online(smp_processor_id()) ||
 357                                 (con->flags & CON_ANYTIME)))
 358                         con->write(con, &LOG_BUF(start), end - start);
 359         }
 360 }
 361
 362 static int __read_mostly ignore_loglevel;
 363
 364 static int __init ignore_loglevel_setup(char *str)
 365 {
 366         ignore_loglevel = 1;
 367         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 368
 369         return 1;
 370 }
 371
 372 __setup("ignore_loglevel", ignore_loglevel_setup);
 373
 374 /*
 375  * Write out chars from start to end - 1 inclusive
 376  */
 377 static void _call_console_drivers(unsigned long start,
 378                                 unsigned long end, int msg_log_level)
 379 {
 380         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 381                         console_drivers && start != end) {
 382                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 383                         /* wrapped write */
 384                         __call_console_drivers(start & LOG_BUF_MASK,
 385                                                 log_buf_len);
 386                         __call_console_drivers(0, end & LOG_BUF_MASK);
 387                 } else {
 388                         __call_console_drivers(start, end);
 389                 }
 390         }
 391 }
 392
 393 /*
 394  * Call the console drivers, asking them to write out
 395  * log_buf[start] to log_buf[end - 1].
 396  * The console_sem must be held.
 397  */
 398 static void call_console_drivers(unsigned long start, unsigned long end)
 399 {
 400         unsigned long cur_index, start_print;
 401         static int msg_level = -1;
 402
 403         BUG_ON(((long)(start - end)) > 0);
 404
 405         cur_index = start;
 406         start_print = start;
 407         while (cur_index != end) {
 408                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 409                                 LOG_BUF(cur_index + 0) == '<' &&
 410                                 LOG_BUF(cur_index + 1) >= '0' &&
 411                                 LOG_BUF(cur_index + 1) <= '7' &&
 412                                 LOG_BUF(cur_index + 2) == '>') {
 413                         msg_level = LOG_BUF(cur_index + 1) - '0';
 414                         cur_index += 3;
 415                         start_print = cur_index;
 416                 }
 417                 while (cur_index != end) {
 418                         char c = LOG_BUF(cur_index);
 419
 420                         cur_index++;
 421                         if (c == '\n') {
 422                                 if (msg_level < 0) {
 423                                         /*
 424                                          * printk() has already given us loglevel tags in
 425                                          * the buffer.  This code is here in case the
 426                                          * log buffer has wrapped right round and scribbled
 427                                          * on those tags
 428                                          */
 429                                         msg_level = default_message_loglevel;
 430                                 }
 431                                 _call_console_drivers(start_print, cur_index, msg_level);
 432                                 msg_level = -1;
 433                                 start_print = cur_index;
 434                                 break;
 435                         }
 436                 }
 437         }
 438         _call_console_drivers(start_print, end, msg_level);
 439 }
 440
 441 static void emit_log_char(char c)
 442 {
 443         LOG_BUF(log_end) = c;
 444         log_end++;
 445         if (log_end - log_start > log_buf_len)
 446                 log_start = log_end - log_buf_len;
 447         if (log_end - con_start > log_buf_len)
 448                 con_start = log_end - log_buf_len;
 449         if (logged_chars < log_buf_len)
 450                 logged_chars++;
 451 }
 452
 453 /*
 454  * Zap console related locks when oopsing. Only zap at most once
 455  * every 10 seconds, to leave time for slow consoles to print a
 456  * full oops.
 457  */
 458 static void zap_locks(void)
 459 {
 460         static unsigned long oops_timestamp;
 461
 462         if (time_after_eq(jiffies, oops_timestamp) &&
 463                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 464                 return;
 465
 466         oops_timestamp = jiffies;
 467
 468         /* If a crash is occurring, make sure we can't deadlock */
 469         spin_lock_init(&logbuf_lock);
 470         /* And make sure that we print immediately */
 471         init_MUTEX(&console_sem);
 472 }
 473
 474 #if defined(CONFIG_PRINTK_TIME)
 475 static int printk_time = 1;
 476 #else
 477 static int printk_time = 0;
 478 #endif
 479 module_param(printk_time, int, S_IRUGO | S_IWUSR);
 480
 481 static int __init printk_time_setup(char *str)
 482 {
 483         if (*str)
 484                 return 0;
 485         printk_time = 1;
 486         return 1;
 487 }
 488
 489 __setup("time", printk_time_setup);
 490
 491 __attribute__((weak)) unsigned long long printk_clock(void)
 492 {
 493         return sched_clock();
 494 }
 495
 496 /* Check if we have any console registered that can be called early in boot. */
 497 static int have_callable_console(void)
 498 {
 499         struct console *con;
 500
 501         for (con = console_drivers; con; con = con->next)
 502                 if (con->flags & CON_ANYTIME)
 503                         return 1;
 504
 505         return 0;
 506 }
 507
 508 /**
 509  * printk - print a kernel message
 510  * @fmt: format string
 511  *
 512  * This is printk.  It can be called from any context.  We want it to work.
 513  *
 514  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 515  * call the console drivers.  If we fail to get the semaphore we place the output
 516  * into the log buffer and return.  The current holder of the console_sem will
 517  * notice the new output in release_console_sem() and will send it to the
 518  * consoles before releasing the semaphore.
 519  *
 520  * One effect of this deferred printing is that code which calls printk() and
 521  * then changes console_loglevel may break. This is because console_loglevel
 522  * is inspected when the actual printing occurs.
 523  *
 524  * See also:
 525  * printf(3)
 526  */
 527
 528 asmlinkage int printk(const char *fmt, ...)
 529 {
 530         va_list args;
 531         int r;
 532
 533         va_start(args, fmt);
 534         r = vprintk(fmt, args);
 535         va_end(args);
 536
 537 #ifdef CONFIG_BOOT_DELAY
 538         if (boot_delay && system_state == SYSTEM_BOOTING)
 539                 boot_delay_msec(boot_delay);
 540 #endif
 541
 542         return r;
 543 }
 544
 545 /* cpu currently holding logbuf_lock */
 546 static volatile unsigned int printk_cpu = UINT_MAX;
 547
 548 asmlinkage int vprintk(const char *fmt, va_list args)
 549 {
 550         unsigned long flags;
 551         int printed_len;
 552         char *p;
 553         static char printk_buf[1024];
 554         static int log_level_unknown = 1;
 555
 556         preempt_disable();
 557         if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
 558                 /* If a crash is occurring during printk() on this CPU,
 559                  * make sure we can't deadlock */
 560                 zap_locks();
 561
 562         /* This stops the holder of console_sem just where we want him */
 563         local_irq_save(flags);
 564         lockdep_off();
 565         spin_lock(&logbuf_lock);
 566         printk_cpu = smp_processor_id();
 567
 568         /* Emit the output into the temporary buffer */
 569         printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
 570
 571         /*
 572          * Copy the output into log_buf.  If the caller didn't provide
 573          * appropriate log level tags, we insert them here
 574          */
 575         for (p = printk_buf; *p; p++) {
 576                 if (log_level_unknown) {
 577                         /* log_level_unknown signals the start of a new line */
 578                         if (printk_time) {
 579                                 int loglev_char;
 580                                 char tbuf[50], *tp;
 581                                 unsigned tlen;
 582                                 unsigned long long t;
 583                                 unsigned long nanosec_rem;
 584
 585                                 /*
 586                                  * force the log level token to be
 587                                  * before the time output.
 588                                  */
 589                                 if (p[0] == '<' && p[1] >='0' &&
 590                                    p[1] <= '7' && p[2] == '>') {
 591                                         loglev_char = p[1];
 592                                         p += 3;
 593                                         printed_len -= 3;
 594                                 } else {
 595                                         loglev_char = default_message_loglevel
 596                                                 + '0';
 597                                 }
 598                                 t = printk_clock();
 599                                 nanosec_rem = do_div(t, 1000000000);
 600                                 tlen = sprintf(tbuf,
 601                                                 "<%c>[%5lu.%06lu] ",
 602                                                 loglev_char,
 603                                                 (unsigned long)t,
 604                                                 nanosec_rem/1000);
 605
 606                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 607                                         emit_log_char(*tp);
 608                                 printed_len += tlen;
 609                         } else {
 610                                 if (p[0] != '<' || p[1] < '0' ||
 611                                    p[1] > '7' || p[2] != '>') {
 612                                         emit_log_char('<');
 613                                         emit_log_char(default_message_loglevel
 614                                                 + '0');
 615                                         emit_log_char('>');
 616                                         printed_len += 3;
 617                                 }
 618                         }
 619                         log_level_unknown = 0;
 620                         if (!*p)
 621                                 break;
 622                 }
 623                 emit_log_char(*p);
 624                 if (*p == '\n')
 625                         log_level_unknown = 1;
 626         }
 627
 628         if (!down_trylock(&console_sem)) {
 629                 /*
 630                  * We own the drivers.  We can drop the spinlock and
 631                  * let release_console_sem() print the text, maybe ...
 632                  */
 633                 console_locked = 1;
 634                 printk_cpu = UINT_MAX;
 635                 spin_unlock(&logbuf_lock);
 636
 637                 /*
 638                  * Console drivers may assume that per-cpu resources have
 639                  * been allocated. So unless they're explicitly marked as
 640                  * being able to cope (CON_ANYTIME) don't call them until
 641                  * this CPU is officially up.
 642                  */
 643                 if (cpu_online(smp_processor_id()) || have_callable_console()) {
 644                         console_may_schedule = 0;
 645                         release_console_sem();
 646                 } else {
 647                         /* Release by hand to avoid flushing the buffer. */
 648                         console_locked = 0;
 649                         up(&console_sem);
 650                 }
 651                 lockdep_on();
 652                 local_irq_restore(flags);
 653         } else {
 654                 /*
 655                  * Someone else owns the drivers.  We drop the spinlock, which
 656                  * allows the semaphore holder to proceed and to call the
 657                  * console drivers with the output which we just produced.
 658                  */
 659                 printk_cpu = UINT_MAX;
 660                 spin_unlock(&logbuf_lock);
 661                 lockdep_on();
 662                 local_irq_restore(flags);
 663         }
 664
 665         preempt_enable();
 666         return printed_len;
 667 }
 668 EXPORT_SYMBOL(printk);
 669 EXPORT_SYMBOL(vprintk);
 670
 671 #else
 672
 673 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 674 {
 675         return -ENOSYS;
 676 }
 677
 678 static void call_console_drivers(unsigned long start, unsigned long end)
 679 {
 680 }
 681
 682 #endif
 683
 684 /*
 685  * Set up a list of consoles.  Called from init/main.c
 686  */
 687 static int __init console_setup(char *str)
 688 {
 689         char name[sizeof(console_cmdline[0].name)];
 690         char *s, *options;
 691         int idx;
 692
 693         /*
 694          * Decode str into name, index, options.
 695          */
 696         if (str[0] >= '0' && str[0] <= '9') {
 697                 strcpy(name, "ttyS");
 698                 strncpy(name + 4, str, sizeof(name) - 5);
 699         } else {
 700                 strncpy(name, str, sizeof(name) - 1);
 701         }
 702         name[sizeof(name) - 1] = 0;
 703         if ((options = strchr(str, ',')) != NULL)
 704                 *(options++) = 0;
 705 #ifdef __sparc__
 706         if (!strcmp(str, "ttya"))
 707                 strcpy(name, "ttyS0");
 708         if (!strcmp(str, "ttyb"))
 709                 strcpy(name, "ttyS1");
 710 #endif
 711         for (s = name; *s; s++)
 712                 if ((*s >= '0' && *s <= '9') || *s == ',')
 713                         break;
 714         idx = simple_strtoul(s, NULL, 10);
 715         *s = 0;
 716
 717         add_preferred_console(name, idx, options);
 718         return 1;
 719 }
 720 __setup("console=", console_setup);
 721
 722 /**
 723  * add_preferred_console - add a device to the list of preferred consoles.
 724  * @name: device name
 725  * @idx: device index
 726  * @options: options for this console
 727  *
 728  * The last preferred console added will be used for kernel messages
 729  * and stdin/out/err for init.  Normally this is used by console_setup
 730  * above to handle user-supplied console arguments; however it can also
 731  * be used by arch-specific code either to override the user or more
 732  * commonly to provide a default console (ie from PROM variables) when
 733  * the user has not supplied one.
 734  */
 735 int __init add_preferred_console(char *name, int idx, char *options)
 736 {
 737         struct console_cmdline *c;
 738         int i;
 739
 740         /*
 741          *      See if this tty is not yet registered, and
 742          *      if we have a slot free.
 743          */
 744         for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 745                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 746                           console_cmdline[i].index == idx) {
 747                                 selected_console = i;
 748                                 return 0;
 749                 }
 750         if (i == MAX_CMDLINECONSOLES)
 751                 return -E2BIG;
 752         selected_console = i;
 753         c = &console_cmdline[i];
 754         memcpy(c->name, name, sizeof(c->name));
 755         c->name[sizeof(c->name) - 1] = 0;
 756         c->options = options;
 757         c->index = idx;
 758         return 0;
 759 }
 760
 761 #ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
 762 /**
 763  * suspend_console - suspend the console subsystem
 764  *
 765  * This disables printk() while we go into suspend states
 766  */
 767 void suspend_console(void)
 768 {
 769         printk("Suspending console(s)\n");
 770         acquire_console_sem();
 771         console_suspended = 1;
 772 }
 773
 774 void resume_console(void)
 775 {
 776         console_suspended = 0;
 777         release_console_sem();
 778 }
 779 #endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
 780
 781 /**
 782  * acquire_console_sem - lock the console system for exclusive use.
 783  *
 784  * Acquires a semaphore which guarantees that the caller has
 785  * exclusive access to the console system and the console_drivers list.
 786  *
 787  * Can sleep, returns nothing.
 788  */
 789 void acquire_console_sem(void)
 790 {
 791         BUG_ON(in_interrupt());
 792         if (console_suspended) {
 793                 down(&secondary_console_sem);
 794                 return;
 795         }
 796         down(&console_sem);
 797         console_locked = 1;
 798         console_may_schedule = 1;
 799 }
 800 EXPORT_SYMBOL(acquire_console_sem);
 801
 802 int try_acquire_console_sem(void)
 803 {
 804         if (down_trylock(&console_sem))
 805                 return -1;
 806         console_locked = 1;
 807         console_may_schedule = 0;
 808         return 0;
 809 }
 810 EXPORT_SYMBOL(try_acquire_console_sem);
 811
 812 int is_console_locked(void)
 813 {
 814         return console_locked;
 815 }
 816
 817 /**
 818  * release_console_sem - unlock the console system
 819  *
 820  * Releases the semaphore which the caller holds on the console system
 821  * and the console driver list.
 822  *
 823  * While the semaphore was held, console output may have been buffered
 824  * by printk().  If this is the case, release_console_sem() emits
 825  * the output prior to releasing the semaphore.
 826  *
 827  * If there is output waiting for klogd, we wake it up.
 828  *
 829  * release_console_sem() may be called from any context.
 830  */
 831 void release_console_sem(void)
 832 {
 833         unsigned long flags;
 834         unsigned long _con_start, _log_end;
 835         unsigned long wake_klogd = 0;
 836
 837         if (console_suspended) {
 838                 up(&secondary_console_sem);
 839                 return;
 840         }
 841
 842         console_may_schedule = 0;
 843
 844         for ( ; ; ) {
 845                 spin_lock_irqsave(&logbuf_lock, flags);
 846                 wake_klogd |= log_start - log_end;
 847                 if (con_start == log_end)
 848                         break;                  /* Nothing to print */
 849                 _con_start = con_start;
 850                 _log_end = log_end;
 851                 con_start = log_end;            /* Flush */
 852                 spin_unlock(&logbuf_lock);
 853                 call_console_drivers(_con_start, _log_end);
 854                 local_irq_restore(flags);
 855         }
 856         console_locked = 0;
 857         up(&console_sem);
 858         spin_unlock_irqrestore(&logbuf_lock, flags);
 859         if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
 860                 wake_up_interruptible(&log_wait);
 861 }
 862 EXPORT_SYMBOL(release_console_sem);
 863
 864 /**
 865  * console_conditional_schedule - yield the CPU if required
 866  *
 867  * If the console code is currently allowed to sleep, and
 868  * if this CPU should yield the CPU to another task, do
 869  * so here.
 870  *
 871  * Must be called within acquire_console_sem().
 872  */
 873 void __sched console_conditional_schedule(void)
 874 {
 875         if (console_may_schedule)
 876                 cond_resched();
 877 }
 878 EXPORT_SYMBOL(console_conditional_schedule);
 879
 880 void console_print(const char *s)
 881 {
 882         printk(KERN_EMERG "%s", s);
 883 }
 884 EXPORT_SYMBOL(console_print);
 885
 886 void console_unblank(void)
 887 {
 888         struct console *c;
 889
 890         /*
 891          * console_unblank can no longer be called in interrupt context unless
 892          * oops_in_progress is set to 1..
 893          */
 894         if (oops_in_progress) {
 895                 if (down_trylock(&console_sem) != 0)
 896                         return;
 897         } else
 898                 acquire_console_sem();
 899
 900         console_locked = 1;
 901         console_may_schedule = 0;
 902         for (c = console_drivers; c != NULL; c = c->next)
 903                 if ((c->flags & CON_ENABLED) && c->unblank)
 904                         c->unblank();
 905         release_console_sem();
 906 }
 907
 908 /*
 909  * Return the console tty driver structure and its associated index
 910  */
 911 struct tty_driver *console_device(int *index)
 912 {
 913         struct console *c;
 914         struct tty_driver *driver = NULL;
 915
 916         acquire_console_sem();
 917         for (c = console_drivers; c != NULL; c = c->next) {
 918                 if (!c->device)
 919                         continue;
 920                 driver = c->device(c, index);
 921                 if (driver)
 922                         break;
 923         }
 924         release_console_sem();
 925         return driver;
 926 }
 927
 928 /*
 929  * Prevent further output on the passed console device so that (for example)
 930  * serial drivers can disable console output before suspending a port, and can
 931  * re-enable output afterwards.
 932  */
 933 void console_stop(struct console *console)
 934 {
 935         acquire_console_sem();
 936         console->flags &= ~CON_ENABLED;
 937         release_console_sem();
 938 }
 939 EXPORT_SYMBOL(console_stop);
 940
 941 void console_start(struct console *console)
 942 {
 943         acquire_console_sem();
 944         console->flags |= CON_ENABLED;
 945         release_console_sem();
 946 }
 947 EXPORT_SYMBOL(console_start);
 948
 949 /*
 950  * The console driver calls this routine during kernel initialization
 951  * to register the console printing procedure with printk() and to
 952  * print any messages that were printed by the kernel before the
 953  * console driver was initialized.
 954  */
 955 void register_console(struct console *console)
 956 {
 957         int i;
 958         unsigned long flags;
 959
 960         if (preferred_console < 0)
 961                 preferred_console = selected_console;
 962
 963         /*
 964          *      See if we want to use this console driver. If we
 965          *      didn't select a console we take the first one
 966          *      that registers here.
 967          */
 968         if (preferred_console < 0) {
 969                 if (console->index < 0)
 970                         console->index = 0;
 971                 if (console->setup == NULL ||
 972                     console->setup(console, NULL) == 0) {
 973                         console->flags |= CON_ENABLED | CON_CONSDEV;
 974                         preferred_console = 0;
 975                 }
 976         }
 977
 978         /*
 979          *      See if this console matches one we selected on
 980          *      the command line.
 981          */
 982         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
 983                         i++) {
 984                 if (strcmp(console_cmdline[i].name, console->name) != 0)
 985                         continue;
 986                 if (console->index >= 0 &&
 987                     console->index != console_cmdline[i].index)
 988                         continue;
 989                 if (console->index < 0)
 990                         console->index = console_cmdline[i].index;
 991                 if (console->setup &&
 992                     console->setup(console, console_cmdline[i].options) != 0)
 993                         break;
 994                 console->flags |= CON_ENABLED;
 995                 console->index = console_cmdline[i].index;
 996                 if (i == selected_console) {
 997                         console->flags |= CON_CONSDEV;
 998                         preferred_console = selected_console;
 999                 }
1000                 break;
1001         }
1002
1003         if (!(console->flags & CON_ENABLED))
1004                 return;
1005
1006         if (console_drivers && (console_drivers->flags & CON_BOOT)) {
1007                 unregister_console(console_drivers);
1008                 console->flags &= ~CON_PRINTBUFFER;
1009         }
1010
1011         /*
1012          *      Put this console in the list - keep the
1013          *      preferred driver at the head of the list.
1014          */
1015         acquire_console_sem();
1016         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1017                 console->next = console_drivers;
1018                 console_drivers = console;
1019                 if (console->next)
1020                         console->next->flags &= ~CON_CONSDEV;
1021         } else {
1022                 console->next = console_drivers->next;
1023                 console_drivers->next = console;
1024         }
1025         if (console->flags & CON_PRINTBUFFER) {
1026                 /*
1027                  * release_console_sem() will print out the buffered messages
1028                  * for us.
1029                  */
1030                 spin_lock_irqsave(&logbuf_lock, flags);
1031                 con_start = log_start;
1032                 spin_unlock_irqrestore(&logbuf_lock, flags);
1033         }
1034         release_console_sem();
1035 }
1036 EXPORT_SYMBOL(register_console);
1037
1038 int unregister_console(struct console *console)
1039 {
1040         struct console *a, *b;
1041         int res = 1;
1042
1043         acquire_console_sem();
1044         if (console_drivers == console) {
1045                 console_drivers=console->next;
1046                 res = 0;
1047         } else if (console_drivers) {
1048                 for (a=console_drivers->next, b=console_drivers ;
1049                      a; b=a, a=b->next) {
1050                         if (a == console) {
1051                                 b->next = a->next;
1052                                 res = 0;
1053                                 break;
1054                         }
1055                 }
1056         }
1057
1058         /* If last console is removed, we re-enable picking the first
1059          * one that gets registered. Without that, pmac early boot console
1060          * would prevent fbcon from taking over.
1061          *
1062          * If this isn't the last console and it has CON_CONSDEV set, we
1063          * need to set it on the next preferred console.
1064          */
1065         if (console_drivers == NULL)
1066                 preferred_console = selected_console;
1067         else if (console->flags & CON_CONSDEV)
1068                 console_drivers->flags |= CON_CONSDEV;
1069
1070         release_console_sem();
1071         return res;
1072 }
1073 EXPORT_SYMBOL(unregister_console);
1074
1075 /**
1076  * tty_write_message - write a message to a certain tty, not just the console.
1077  * @tty: the destination tty_struct
1078  * @msg: the message to write
1079  *
1080  * This is used for messages that need to be redirected to a specific tty.
1081  * We don't put it into the syslog queue right now maybe in the future if
1082  * really needed.
1083  */
1084 void tty_write_message(struct tty_struct *tty, char *msg)
1085 {
1086         if (tty && tty->driver->write)
1087                 tty->driver->write(tty, msg, strlen(msg));
1088         return;
1089 }
1090
1091 /*
1092  * printk rate limiting, lifted from the networking subsystem.
1093  *
1094  * This enforces a rate limit: not more than one kernel message
1095  * every printk_ratelimit_jiffies to make a denial-of-service
1096  * attack impossible.
1097  */
1098 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1099 {
1100         static DEFINE_SPINLOCK(ratelimit_lock);
1101         static unsigned long toks = 10 * 5 * HZ;
1102         static unsigned long last_msg;
1103         static int missed;
1104         unsigned long flags;
1105         unsigned long now = jiffies;
1106
1107         spin_lock_irqsave(&ratelimit_lock, flags);
1108         toks += now - last_msg;
1109         last_msg = now;
1110         if (toks > (ratelimit_burst * ratelimit_jiffies))
1111                 toks = ratelimit_burst * ratelimit_jiffies;
1112         if (toks >= ratelimit_jiffies) {
1113                 int lost = missed;
1114
1115                 missed = 0;
1116                 toks -= ratelimit_jiffies;
1117                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1118                 if (lost)
1119                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1120                 return 1;
1121         }
1122         missed++;
1123         spin_unlock_irqrestore(&ratelimit_lock, flags);
1124         return 0;
1125 }
1126 EXPORT_SYMBOL(__printk_ratelimit);
1127
1128 /* minimum time in jiffies between messages */
1129 int printk_ratelimit_jiffies = 5 * HZ;
1130
1131 /* number of messages we send before ratelimiting */
1132 int printk_ratelimit_burst = 10;
1133
1134 int printk_ratelimit(void)
1135 {
1136         return __printk_ratelimit(printk_ratelimit_jiffies,
1137                                 printk_ratelimit_burst);
1138 }
1139 EXPORT_SYMBOL(printk_ratelimit);
1140
1141 /**
1142  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1143  * @caller_jiffies: pointer to caller's state
1144  * @interval_msecs: minimum interval between prints
1145  *
1146  * printk_timed_ratelimit() returns true if more than @interval_msecs
1147  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1148  * returned true.
1149  */
1150 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1151                         unsigned int interval_msecs)
1152 {
1153         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1154                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1155                 return true;
1156         }
1157         return false;
1158 }
1159 EXPORT_SYMBOL(printk_timed_ratelimit);