kernel/printk.c

   1 /*
   2  *  linux/kernel/printk.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  * Modified to make sys_syslog() more flexible: added commands to
   7  * return the last 4k of kernel messages, regardless of whether
   8  * they've been read or not.  Added option to suppress kernel printk's
   9  * to the console.  Added hook for sending the console messages
  10  * elsewhere, in preparation for a serial line console (someday).
  11  * Ted Ts'o, 2/11/93.
  12  * Modified for sysctl support, 1/8/97, Chris Horn.
  13  * Fixed SMP synchronization, 08/08/99, Manfred Spraul
  14  *     manfred@colorfullife.com
  15  * Rewrote bits to get rid of console_lock
  16  *      01Mar01 Andrew Morton
  17  */
  18
  19 #include <linux/kernel.h>
  20 #include <linux/mm.h>
  21 #include <linux/tty.h>
  22 #include <linux/tty_driver.h>
  23 #include <linux/console.h>
  24 #include <linux/init.h>
  25 #include <linux/jiffies.h>
  26 #include <linux/nmi.h>
  27 #include <linux/module.h>
  28 #include <linux/moduleparam.h>
  29 #include <linux/interrupt.h>                    /* For in_interrupt() */
  30 #include <linux/delay.h>
  31 #include <linux/smp.h>
  32 #include <linux/security.h>
  33 #include <linux/bootmem.h>
  34 #include <linux/syscalls.h>
  35
  36 #include <asm/uaccess.h>
  37
  38 /*
  39  * Architectures can override it:
  40  */
  41 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
  42 {
  43 }
  44
  45 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
  46
  47 /* printk's without a loglevel use this.. */
  48 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  49
  50 /* We show everything that is MORE important than this.. */
  51 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  52 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  53
  54 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  55
  56 int console_printk[4] = {
  57         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  58         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  59         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  60         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  61 };
  62
  63 /*
  64  * Low level drivers may need that to know if they can schedule in
  65  * their unblank() callback or not. So let's export it.
  66  */
  67 int oops_in_progress;
  68 EXPORT_SYMBOL(oops_in_progress);
  69
  70 /*
  71  * console_sem protects the console_drivers list, and also
  72  * provides serialisation for access to the entire console
  73  * driver system.
  74  */
  75 static DECLARE_MUTEX(console_sem);
  76 struct console *console_drivers;
  77 EXPORT_SYMBOL_GPL(console_drivers);
  78
  79 /*
  80  * This is used for debugging the mess that is the VT code by
  81  * keeping track if we have the console semaphore held. It's
  82  * definitely not the perfect debug tool (we don't know if _WE_
  83  * hold it are racing, but it helps tracking those weird code
  84  * path in the console code where we end up in places I want
  85  * locked without the console sempahore held
  86  */
  87 static int console_locked, console_suspended;
  88
  89 /*
  90  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
  91  * It is also used in interesting ways to provide interlocking in
  92  * release_console_sem().
  93  */
  94 static DEFINE_SPINLOCK(logbuf_lock);
  95
  96 #define LOG_BUF_MASK (log_buf_len-1)
  97 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
  98
  99 /*
 100  * The indices into log_buf are not constrained to log_buf_len - they
 101  * must be masked before subscripting
 102  */
 103 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
 104 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
 105 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 106
 107 /*
 108  *      Array of consoles built from command line options (console=)
 109  */
 110 struct console_cmdline
 111 {
 112         char    name[8];                        /* Name of the driver       */
 113         int     index;                          /* Minor dev. to use        */
 114         char    *options;                       /* Options for the driver   */
 115 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 116         char    *brl_options;                   /* Options for braille driver */
 117 #endif
 118 };
 119
 120 #define MAX_CMDLINECONSOLES 8
 121
 122 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 123 static int selected_console = -1;
 124 static int preferred_console = -1;
 125 int console_set_on_cmdline;
 126 EXPORT_SYMBOL(console_set_on_cmdline);
 127
 128 /* Flag: console code may call schedule() */
 129 static int console_may_schedule;
 130
 131 #ifdef CONFIG_PRINTK
 132
 133 static char __log_buf[__LOG_BUF_LEN];
 134 static char *log_buf = __log_buf;
 135 static int log_buf_len = __LOG_BUF_LEN;
 136 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 137
 138 static int __init log_buf_len_setup(char *str)
 139 {
 140         unsigned size = memparse(str, &str);
 141         unsigned long flags;
 142
 143         if (size)
 144                 size = roundup_pow_of_two(size);
 145         if (size > log_buf_len) {
 146                 unsigned start, dest_idx, offset;
 147                 char *new_log_buf;
 148
 149                 new_log_buf = alloc_bootmem(size);
 150                 if (!new_log_buf) {
 151                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 152                         goto out;
 153                 }
 154
 155                 spin_lock_irqsave(&logbuf_lock, flags);
 156                 log_buf_len = size;
 157                 log_buf = new_log_buf;
 158
 159                 offset = start = min(con_start, log_start);
 160                 dest_idx = 0;
 161                 while (start != log_end) {
 162                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 163                         start++;
 164                         dest_idx++;
 165                 }
 166                 log_start -= offset;
 167                 con_start -= offset;
 168                 log_end -= offset;
 169                 spin_unlock_irqrestore(&logbuf_lock, flags);
 170
 171                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 172         }
 173 out:
 174         return 1;
 175 }
 176
 177 __setup("log_buf_len=", log_buf_len_setup);
 178
 179 #ifdef CONFIG_BOOT_PRINTK_DELAY
 180
 181 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 182 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
 183
 184 static int __init boot_delay_setup(char *str)
 185 {
 186         unsigned long lpj;
 187         unsigned long long loops_per_msec;
 188
 189         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 190         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 191
 192         get_option(&str, &boot_delay);
 193         if (boot_delay > 10 * 1000)
 194                 boot_delay = 0;
 195
 196         printk_delay_msec = loops_per_msec;
 197         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 198                 "HZ: %d, printk_delay_msec: %llu\n",
 199                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
 200         return 1;
 201 }
 202 __setup("boot_delay=", boot_delay_setup);
 203
 204 static void boot_delay_msec(void)
 205 {
 206         unsigned long long k;
 207         unsigned long timeout;
 208
 209         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 210                 return;
 211
 212         k = (unsigned long long)printk_delay_msec * boot_delay;
 213
 214         timeout = jiffies + msecs_to_jiffies(boot_delay);
 215         while (k) {
 216                 k--;
 217                 cpu_relax();
 218                 /*
 219                  * use (volatile) jiffies to prevent
 220                  * compiler reduction; loop termination via jiffies
 221                  * is secondary and may or may not happen.
 222                  */
 223                 if (time_after(jiffies, timeout))
 224                         break;
 225                 touch_nmi_watchdog();
 226         }
 227 }
 228 #else
 229 static inline void boot_delay_msec(void)
 230 {
 231 }
 232 #endif
 233
 234 /*
 235  * Commands to do_syslog:
 236  *
 237  *      0 -- Close the log.  Currently a NOP.
 238  *      1 -- Open the log. Currently a NOP.
 239  *      2 -- Read from the log.
 240  *      3 -- Read all messages remaining in the ring buffer.
 241  *      4 -- Read and clear all messages remaining in the ring buffer
 242  *      5 -- Clear ring buffer.
 243  *      6 -- Disable printk's to console
 244  *      7 -- Enable printk's to console
 245  *      8 -- Set level of messages printed to console
 246  *      9 -- Return number of unread characters in the log buffer
 247  *     10 -- Return size of the log buffer
 248  */
 249 int do_syslog(int type, char __user *buf, int len)
 250 {
 251         unsigned i, j, limit, count;
 252         int do_clear = 0;
 253         char c;
 254         int error = 0;
 255
 256         error = security_syslog(type);
 257         if (error)
 258                 return error;
 259
 260         switch (type) {
 261         case 0:         /* Close log */
 262                 break;
 263         case 1:         /* Open log */
 264                 break;
 265         case 2:         /* Read from log */
 266                 error = -EINVAL;
 267                 if (!buf || len < 0)
 268                         goto out;
 269                 error = 0;
 270                 if (!len)
 271                         goto out;
 272                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 273                         error = -EFAULT;
 274                         goto out;
 275                 }
 276                 error = wait_event_interruptible(log_wait,
 277                                                         (log_start - log_end));
 278                 if (error)
 279                         goto out;
 280                 i = 0;
 281                 spin_lock_irq(&logbuf_lock);
 282                 while (!error && (log_start != log_end) && i < len) {
 283                         c = LOG_BUF(log_start);
 284                         log_start++;
 285                         spin_unlock_irq(&logbuf_lock);
 286                         error = __put_user(c,buf);
 287                         buf++;
 288                         i++;
 289                         cond_resched();
 290                         spin_lock_irq(&logbuf_lock);
 291                 }
 292                 spin_unlock_irq(&logbuf_lock);
 293                 if (!error)
 294                         error = i;
 295                 break;
 296         case 4:         /* Read/clear last kernel messages */
 297                 do_clear = 1;
 298                 /* FALL THRU */
 299         case 3:         /* Read last kernel messages */
 300                 error = -EINVAL;
 301                 if (!buf || len < 0)
 302                         goto out;
 303                 error = 0;
 304                 if (!len)
 305                         goto out;
 306                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 307                         error = -EFAULT;
 308                         goto out;
 309                 }
 310                 count = len;
 311                 if (count > log_buf_len)
 312                         count = log_buf_len;
 313                 spin_lock_irq(&logbuf_lock);
 314                 if (count > logged_chars)
 315                         count = logged_chars;
 316                 if (do_clear)
 317                         logged_chars = 0;
 318                 limit = log_end;
 319                 /*
 320                  * __put_user() could sleep, and while we sleep
 321                  * printk() could overwrite the messages
 322                  * we try to copy to user space. Therefore
 323                  * the messages are copied in reverse. <manfreds>
 324                  */
 325                 for (i = 0; i < count && !error; i++) {
 326                         j = limit-1-i;
 327                         if (j + log_buf_len < log_end)
 328                                 break;
 329                         c = LOG_BUF(j);
 330                         spin_unlock_irq(&logbuf_lock);
 331                         error = __put_user(c,&buf[count-1-i]);
 332                         cond_resched();
 333                         spin_lock_irq(&logbuf_lock);
 334                 }
 335                 spin_unlock_irq(&logbuf_lock);
 336                 if (error)
 337                         break;
 338                 error = i;
 339                 if (i != count) {
 340                         int offset = count-error;
 341                         /* buffer overflow during copy, correct user buffer. */
 342                         for (i = 0; i < error; i++) {
 343                                 if (__get_user(c,&buf[i+offset]) ||
 344                                     __put_user(c,&buf[i])) {
 345                                         error = -EFAULT;
 346                                         break;
 347                                 }
 348                                 cond_resched();
 349                         }
 350                 }
 351                 break;
 352         case 5:         /* Clear ring buffer */
 353                 logged_chars = 0;
 354                 break;
 355         case 6:         /* Disable logging to console */
 356                 console_loglevel = minimum_console_loglevel;
 357                 break;
 358         case 7:         /* Enable logging to console */
 359                 console_loglevel = default_console_loglevel;
 360                 break;
 361         case 8:         /* Set level of messages printed to console */
 362                 error = -EINVAL;
 363                 if (len < 1 || len > 8)
 364                         goto out;
 365                 if (len < minimum_console_loglevel)
 366                         len = minimum_console_loglevel;
 367                 console_loglevel = len;
 368                 error = 0;
 369                 break;
 370         case 9:         /* Number of chars in the log buffer */
 371                 error = log_end - log_start;
 372                 break;
 373         case 10:        /* Size of the log buffer */
 374                 error = log_buf_len;
 375                 break;
 376         default:
 377                 error = -EINVAL;
 378                 break;
 379         }
 380 out:
 381         return error;
 382 }
 383
 384 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
 385 {
 386         return do_syslog(type, buf, len);
 387 }
 388
 389 /*
 390  * Call the console drivers on a range of log_buf
 391  */
 392 static void __call_console_drivers(unsigned start, unsigned end)
 393 {
 394         struct console *con;
 395
 396         for (con = console_drivers; con; con = con->next) {
 397                 if ((con->flags & CON_ENABLED) && con->write &&
 398                                 (cpu_online(smp_processor_id()) ||
 399                                 (con->flags & CON_ANYTIME)))
 400                         con->write(con, &LOG_BUF(start), end - start);
 401         }
 402 }
 403
 404 static int __read_mostly ignore_loglevel;
 405
 406 static int __init ignore_loglevel_setup(char *str)
 407 {
 408         ignore_loglevel = 1;
 409         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 410
 411         return 0;
 412 }
 413
 414 early_param("ignore_loglevel", ignore_loglevel_setup);
 415
 416 /*
 417  * Write out chars from start to end - 1 inclusive
 418  */
 419 static void _call_console_drivers(unsigned start,
 420                                 unsigned end, int msg_log_level)
 421 {
 422         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 423                         console_drivers && start != end) {
 424                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 425                         /* wrapped write */
 426                         __call_console_drivers(start & LOG_BUF_MASK,
 427                                                 log_buf_len);
 428                         __call_console_drivers(0, end & LOG_BUF_MASK);
 429                 } else {
 430                         __call_console_drivers(start, end);
 431                 }
 432         }
 433 }
 434
 435 /*
 436  * Call the console drivers, asking them to write out
 437  * log_buf[start] to log_buf[end - 1].
 438  * The console_sem must be held.
 439  */
 440 static void call_console_drivers(unsigned start, unsigned end)
 441 {
 442         unsigned cur_index, start_print;
 443         static int msg_level = -1;
 444
 445         BUG_ON(((int)(start - end)) > 0);
 446
 447         cur_index = start;
 448         start_print = start;
 449         while (cur_index != end) {
 450                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 451                                 LOG_BUF(cur_index + 0) == '<' &&
 452                                 LOG_BUF(cur_index + 1) >= '0' &&
 453                                 LOG_BUF(cur_index + 1) <= '7' &&
 454                                 LOG_BUF(cur_index + 2) == '>') {
 455                         msg_level = LOG_BUF(cur_index + 1) - '0';
 456                         cur_index += 3;
 457                         start_print = cur_index;
 458                 }
 459                 while (cur_index != end) {
 460                         char c = LOG_BUF(cur_index);
 461
 462                         cur_index++;
 463                         if (c == '\n') {
 464                                 if (msg_level < 0) {
 465                                         /*
 466                                          * printk() has already given us loglevel tags in
 467                                          * the buffer.  This code is here in case the
 468                                          * log buffer has wrapped right round and scribbled
 469                                          * on those tags
 470                                          */
 471                                         msg_level = default_message_loglevel;
 472                                 }
 473                                 _call_console_drivers(start_print, cur_index, msg_level);
 474                                 msg_level = -1;
 475                                 start_print = cur_index;
 476                                 break;
 477                         }
 478                 }
 479         }
 480         _call_console_drivers(start_print, end, msg_level);
 481 }
 482
 483 static void emit_log_char(char c)
 484 {
 485         LOG_BUF(log_end) = c;
 486         log_end++;
 487         if (log_end - log_start > log_buf_len)
 488                 log_start = log_end - log_buf_len;
 489         if (log_end - con_start > log_buf_len)
 490                 con_start = log_end - log_buf_len;
 491         if (logged_chars < log_buf_len)
 492                 logged_chars++;
 493 }
 494
 495 /*
 496  * Zap console related locks when oopsing. Only zap at most once
 497  * every 10 seconds, to leave time for slow consoles to print a
 498  * full oops.
 499  */
 500 static void zap_locks(void)
 501 {
 502         static unsigned long oops_timestamp;
 503
 504         if (time_after_eq(jiffies, oops_timestamp) &&
 505                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 506                 return;
 507
 508         oops_timestamp = jiffies;
 509
 510         /* If a crash is occurring, make sure we can't deadlock */
 511         spin_lock_init(&logbuf_lock);
 512         /* And make sure that we print immediately */
 513         init_MUTEX(&console_sem);
 514 }
 515
 516 #if defined(CONFIG_PRINTK_TIME)
 517 static int printk_time = 1;
 518 #else
 519 static int printk_time = 0;
 520 #endif
 521 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 522
 523 /* Check if we have any console registered that can be called early in boot. */
 524 static int have_callable_console(void)
 525 {
 526         struct console *con;
 527
 528         for (con = console_drivers; con; con = con->next)
 529                 if (con->flags & CON_ANYTIME)
 530                         return 1;
 531
 532         return 0;
 533 }
 534
 535 /**
 536  * printk - print a kernel message
 537  * @fmt: format string
 538  *
 539  * This is printk().  It can be called from any context.  We want it to work.
 540  *
 541  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 542  * call the console drivers.  If we fail to get the semaphore we place the output
 543  * into the log buffer and return.  The current holder of the console_sem will
 544  * notice the new output in release_console_sem() and will send it to the
 545  * consoles before releasing the semaphore.
 546  *
 547  * One effect of this deferred printing is that code which calls printk() and
 548  * then changes console_loglevel may break. This is because console_loglevel
 549  * is inspected when the actual printing occurs.
 550  *
 551  * See also:
 552  * printf(3)
 553  *
 554  * See the vsnprintf() documentation for format string extensions over C99.
 555  */
 556
 557 asmlinkage int printk(const char *fmt, ...)
 558 {
 559         va_list args;
 560         int r;
 561
 562         va_start(args, fmt);
 563         r = vprintk(fmt, args);
 564         va_end(args);
 565
 566         return r;
 567 }
 568
 569 /* cpu currently holding logbuf_lock */
 570 static volatile unsigned int printk_cpu = UINT_MAX;
 571
 572 /*
 573  * Can we actually use the console at this time on this cpu?
 574  *
 575  * Console drivers may assume that per-cpu resources have
 576  * been allocated. So unless they're explicitly marked as
 577  * being able to cope (CON_ANYTIME) don't call them until
 578  * this CPU is officially up.
 579  */
 580 static inline int can_use_console(unsigned int cpu)
 581 {
 582         return cpu_online(cpu) || have_callable_console();
 583 }
 584
 585 /*
 586  * Try to get console ownership to actually show the kernel
 587  * messages from a 'printk'. Return true (and with the
 588  * console_semaphore held, and 'console_locked' set) if it
 589  * is successful, false otherwise.
 590  *
 591  * This gets called with the 'logbuf_lock' spinlock held and
 592  * interrupts disabled. It should return with 'lockbuf_lock'
 593  * released but interrupts still disabled.
 594  */
 595 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 596 {
 597         int retval = 0;
 598
 599         if (!try_acquire_console_sem()) {
 600                 retval = 1;
 601
 602                 /*
 603                  * If we can't use the console, we need to release
 604                  * the console semaphore by hand to avoid flushing
 605                  * the buffer. We need to hold the console semaphore
 606                  * in order to do this test safely.
 607                  */
 608                 if (!can_use_console(cpu)) {
 609                         console_locked = 0;
 610                         up(&console_sem);
 611                         retval = 0;
 612                 }
 613         }
 614         printk_cpu = UINT_MAX;
 615         spin_unlock(&logbuf_lock);
 616         return retval;
 617 }
 618 static const char recursion_bug_msg [] =
 619                 KERN_CRIT "BUG: recent printk recursion!\n";
 620 static int recursion_bug;
 621 static int new_text_line = 1;
 622 static char printk_buf[1024];
 623
 624 asmlinkage int vprintk(const char *fmt, va_list args)
 625 {
 626         int printed_len = 0;
 627         int current_log_level = default_message_loglevel;
 628         unsigned long flags;
 629         int this_cpu;
 630         char *p;
 631
 632         boot_delay_msec();
 633
 634         preempt_disable();
 635         /* This stops the holder of console_sem just where we want him */
 636         raw_local_irq_save(flags);
 637         this_cpu = smp_processor_id();
 638
 639         /*
 640          * Ouch, printk recursed into itself!
 641          */
 642         if (unlikely(printk_cpu == this_cpu)) {
 643                 /*
 644                  * If a crash is occurring during printk() on this CPU,
 645                  * then try to get the crash message out but make sure
 646                  * we can't deadlock. Otherwise just return to avoid the
 647                  * recursion and return - but flag the recursion so that
 648                  * it can be printed at the next appropriate moment:
 649                  */
 650                 if (!oops_in_progress) {
 651                         recursion_bug = 1;
 652                         goto out_restore_irqs;
 653                 }
 654                 zap_locks();
 655         }
 656
 657         lockdep_off();
 658         spin_lock(&logbuf_lock);
 659         printk_cpu = this_cpu;
 660
 661         if (recursion_bug) {
 662                 recursion_bug = 0;
 663                 strcpy(printk_buf, recursion_bug_msg);
 664                 printed_len = strlen(recursion_bug_msg);
 665         }
 666         /* Emit the output into the temporary buffer */
 667         printed_len += vscnprintf(printk_buf + printed_len,
 668                                   sizeof(printk_buf) - printed_len, fmt, args);
 669
 670
 671         /*
 672          * Copy the output into log_buf.  If the caller didn't provide
 673          * appropriate log level tags, we insert them here
 674          */
 675         for (p = printk_buf; *p; p++) {
 676                 if (new_text_line) {
 677                         /* If a token, set current_log_level and skip over */
 678                         if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
 679                             p[2] == '>') {
 680                                 current_log_level = p[1] - '0';
 681                                 p += 3;
 682                                 printed_len -= 3;
 683                         }
 684
 685                         /* Always output the token */
 686                         emit_log_char('<');
 687                         emit_log_char(current_log_level + '0');
 688                         emit_log_char('>');
 689                         printed_len += 3;
 690                         new_text_line = 0;
 691
 692                         if (printk_time) {
 693                                 /* Follow the token with the time */
 694                                 char tbuf[50], *tp;
 695                                 unsigned tlen;
 696                                 unsigned long long t;
 697                                 unsigned long nanosec_rem;
 698
 699                                 t = cpu_clock(printk_cpu);
 700                                 nanosec_rem = do_div(t, 1000000000);
 701                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 702                                                 (unsigned long) t,
 703                                                 nanosec_rem / 1000);
 704
 705                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 706                                         emit_log_char(*tp);
 707                                 printed_len += tlen;
 708                         }
 709
 710                         if (!*p)
 711                                 break;
 712                 }
 713
 714                 emit_log_char(*p);
 715                 if (*p == '\n')
 716                         new_text_line = 1;
 717         }
 718
 719         /*
 720          * Try to acquire and then immediately release the
 721          * console semaphore. The release will do all the
 722          * actual magic (print out buffers, wake up klogd,
 723          * etc).
 724          *
 725          * The acquire_console_semaphore_for_printk() function
 726          * will release 'logbuf_lock' regardless of whether it
 727          * actually gets the semaphore or not.
 728          */
 729         if (acquire_console_semaphore_for_printk(this_cpu))
 730                 release_console_sem();
 731
 732         lockdep_on();
 733 out_restore_irqs:
 734         raw_local_irq_restore(flags);
 735
 736         preempt_enable();
 737         return printed_len;
 738 }
 739 EXPORT_SYMBOL(printk);
 740 EXPORT_SYMBOL(vprintk);
 741
 742 #else
 743
 744 static void call_console_drivers(unsigned start, unsigned end)
 745 {
 746 }
 747
 748 #endif
 749
 750 static int __add_preferred_console(char *name, int idx, char *options,
 751                                    char *brl_options)
 752 {
 753         struct console_cmdline *c;
 754         int i;
 755
 756         /*
 757          *      See if this tty is not yet registered, and
 758          *      if we have a slot free.
 759          */
 760         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 761                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 762                           console_cmdline[i].index == idx) {
 763                                 if (!brl_options)
 764                                         selected_console = i;
 765                                 return 0;
 766                 }
 767         if (i == MAX_CMDLINECONSOLES)
 768                 return -E2BIG;
 769         if (!brl_options)
 770                 selected_console = i;
 771         c = &console_cmdline[i];
 772         strlcpy(c->name, name, sizeof(c->name));
 773         c->options = options;
 774 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 775         c->brl_options = brl_options;
 776 #endif
 777         c->index = idx;
 778         return 0;
 779 }
 780 /*
 781  * Set up a list of consoles.  Called from init/main.c
 782  */
 783 static int __init console_setup(char *str)
 784 {
 785         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 786         char *s, *options, *brl_options = NULL;
 787         int idx;
 788
 789 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 790         if (!memcmp(str, "brl,", 4)) {
 791                 brl_options = "";
 792                 str += 4;
 793         } else if (!memcmp(str, "brl=", 4)) {
 794                 brl_options = str + 4;
 795                 str = strchr(brl_options, ',');
 796                 if (!str) {
 797                         printk(KERN_ERR "need port name after brl=\n");
 798                         return 1;
 799                 }
 800                 *(str++) = 0;
 801         }
 802 #endif
 803
 804         /*
 805          * Decode str into name, index, options.
 806          */
 807         if (str[0] >= '0' && str[0] <= '9') {
 808                 strcpy(buf, "ttyS");
 809                 strncpy(buf + 4, str, sizeof(buf) - 5);
 810         } else {
 811                 strncpy(buf, str, sizeof(buf) - 1);
 812         }
 813         buf[sizeof(buf) - 1] = 0;
 814         if ((options = strchr(str, ',')) != NULL)
 815                 *(options++) = 0;
 816 #ifdef __sparc__
 817         if (!strcmp(str, "ttya"))
 818                 strcpy(buf, "ttyS0");
 819         if (!strcmp(str, "ttyb"))
 820                 strcpy(buf, "ttyS1");
 821 #endif
 822         for (s = buf; *s; s++)
 823                 if ((*s >= '0' && *s <= '9') || *s == ',')
 824                         break;
 825         idx = simple_strtoul(s, NULL, 10);
 826         *s = 0;
 827
 828         __add_preferred_console(buf, idx, options, brl_options);
 829         console_set_on_cmdline = 1;
 830         return 1;
 831 }
 832 __setup("console=", console_setup);
 833
 834 /**
 835  * add_preferred_console - add a device to the list of preferred consoles.
 836  * @name: device name
 837  * @idx: device index
 838  * @options: options for this console
 839  *
 840  * The last preferred console added will be used for kernel messages
 841  * and stdin/out/err for init.  Normally this is used by console_setup
 842  * above to handle user-supplied console arguments; however it can also
 843  * be used by arch-specific code either to override the user or more
 844  * commonly to provide a default console (ie from PROM variables) when
 845  * the user has not supplied one.
 846  */
 847 int add_preferred_console(char *name, int idx, char *options)
 848 {
 849         return __add_preferred_console(name, idx, options, NULL);
 850 }
 851
 852 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 853 {
 854         struct console_cmdline *c;
 855         int i;
 856
 857         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 858                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 859                           console_cmdline[i].index == idx) {
 860                                 c = &console_cmdline[i];
 861                                 strlcpy(c->name, name_new, sizeof(c->name));
 862                                 c->name[sizeof(c->name) - 1] = 0;
 863                                 c->options = options;
 864                                 c->index = idx_new;
 865                                 return i;
 866                 }
 867         /* not found */
 868         return -1;
 869 }
 870
 871 int console_suspend_enabled = 1;
 872 EXPORT_SYMBOL(console_suspend_enabled);
 873
 874 static int __init console_suspend_disable(char *str)
 875 {
 876         console_suspend_enabled = 0;
 877         return 1;
 878 }
 879 __setup("no_console_suspend", console_suspend_disable);
 880
 881 /**
 882  * suspend_console - suspend the console subsystem
 883  *
 884  * This disables printk() while we go into suspend states
 885  */
 886 void suspend_console(void)
 887 {
 888         if (!console_suspend_enabled)
 889                 return;
 890         printk("Suspending console(s) (use no_console_suspend to debug)\n");
 891         acquire_console_sem();
 892         console_suspended = 1;
 893         up(&console_sem);
 894 }
 895
 896 void resume_console(void)
 897 {
 898         if (!console_suspend_enabled)
 899                 return;
 900         down(&console_sem);
 901         console_suspended = 0;
 902         release_console_sem();
 903 }
 904
 905 /**
 906  * acquire_console_sem - lock the console system for exclusive use.
 907  *
 908  * Acquires a semaphore which guarantees that the caller has
 909  * exclusive access to the console system and the console_drivers list.
 910  *
 911  * Can sleep, returns nothing.
 912  */
 913 void acquire_console_sem(void)
 914 {
 915         BUG_ON(in_interrupt());
 916         down(&console_sem);
 917         if (console_suspended)
 918                 return;
 919         console_locked = 1;
 920         console_may_schedule = 1;
 921 }
 922 EXPORT_SYMBOL(acquire_console_sem);
 923
 924 int try_acquire_console_sem(void)
 925 {
 926         if (down_trylock(&console_sem))
 927                 return -1;
 928         if (console_suspended) {
 929                 up(&console_sem);
 930                 return -1;
 931         }
 932         console_locked = 1;
 933         console_may_schedule = 0;
 934         return 0;
 935 }
 936 EXPORT_SYMBOL(try_acquire_console_sem);
 937
 938 int is_console_locked(void)
 939 {
 940         return console_locked;
 941 }
 942
 943 static DEFINE_PER_CPU(int, printk_pending);
 944
 945 void printk_tick(void)
 946 {
 947         if (__get_cpu_var(printk_pending)) {
 948                 __get_cpu_var(printk_pending) = 0;
 949                 wake_up_interruptible(&log_wait);
 950         }
 951 }
 952
 953 int printk_needs_cpu(int cpu)
 954 {
 955         return per_cpu(printk_pending, cpu);
 956 }
 957
 958 void wake_up_klogd(void)
 959 {
 960         if (waitqueue_active(&log_wait))
 961                 __raw_get_cpu_var(printk_pending) = 1;
 962 }
 963
 964 /**
 965  * release_console_sem - unlock the console system
 966  *
 967  * Releases the semaphore which the caller holds on the console system
 968  * and the console driver list.
 969  *
 970  * While the semaphore was held, console output may have been buffered
 971  * by printk().  If this is the case, release_console_sem() emits
 972  * the output prior to releasing the semaphore.
 973  *
 974  * If there is output waiting for klogd, we wake it up.
 975  *
 976  * release_console_sem() may be called from any context.
 977  */
 978 void release_console_sem(void)
 979 {
 980         unsigned long flags;
 981         unsigned _con_start, _log_end;
 982         unsigned wake_klogd = 0;
 983
 984         if (console_suspended) {
 985                 up(&console_sem);
 986                 return;
 987         }
 988
 989         console_may_schedule = 0;
 990
 991         for ( ; ; ) {
 992                 spin_lock_irqsave(&logbuf_lock, flags);
 993                 wake_klogd |= log_start - log_end;
 994                 if (con_start == log_end)
 995                         break;                  /* Nothing to print */
 996                 _con_start = con_start;
 997                 _log_end = log_end;
 998                 con_start = log_end;            /* Flush */
 999                 spin_unlock(&logbuf_lock);
1000                 stop_critical_timings();        /* don't trace print latency */
1001                 call_console_drivers(_con_start, _log_end);
1002                 start_critical_timings();
1003                 local_irq_restore(flags);
1004         }
1005         console_locked = 0;
1006         up(&console_sem);
1007         spin_unlock_irqrestore(&logbuf_lock, flags);
1008         if (wake_klogd)
1009                 wake_up_klogd();
1010 }
1011 EXPORT_SYMBOL(release_console_sem);
1012
1013 /**
1014  * console_conditional_schedule - yield the CPU if required
1015  *
1016  * If the console code is currently allowed to sleep, and
1017  * if this CPU should yield the CPU to another task, do
1018  * so here.
1019  *
1020  * Must be called within acquire_console_sem().
1021  */
1022 void __sched console_conditional_schedule(void)
1023 {
1024         if (console_may_schedule)
1025                 cond_resched();
1026 }
1027 EXPORT_SYMBOL(console_conditional_schedule);
1028
1029 void console_print(const char *s)
1030 {
1031         printk(KERN_EMERG "%s", s);
1032 }
1033 EXPORT_SYMBOL(console_print);
1034
1035 void console_unblank(void)
1036 {
1037         struct console *c;
1038
1039         /*
1040          * console_unblank can no longer be called in interrupt context unless
1041          * oops_in_progress is set to 1..
1042          */
1043         if (oops_in_progress) {
1044                 if (down_trylock(&console_sem) != 0)
1045                         return;
1046         } else
1047                 acquire_console_sem();
1048
1049         console_locked = 1;
1050         console_may_schedule = 0;
1051         for (c = console_drivers; c != NULL; c = c->next)
1052                 if ((c->flags & CON_ENABLED) && c->unblank)
1053                         c->unblank();
1054         release_console_sem();
1055 }
1056
1057 /*
1058  * Return the console tty driver structure and its associated index
1059  */
1060 struct tty_driver *console_device(int *index)
1061 {
1062         struct console *c;
1063         struct tty_driver *driver = NULL;
1064
1065         acquire_console_sem();
1066         for (c = console_drivers; c != NULL; c = c->next) {
1067                 if (!c->device)
1068                         continue;
1069                 driver = c->device(c, index);
1070                 if (driver)
1071                         break;
1072         }
1073         release_console_sem();
1074         return driver;
1075 }
1076
1077 /*
1078  * Prevent further output on the passed console device so that (for example)
1079  * serial drivers can disable console output before suspending a port, and can
1080  * re-enable output afterwards.
1081  */
1082 void console_stop(struct console *console)
1083 {
1084         acquire_console_sem();
1085         console->flags &= ~CON_ENABLED;
1086         release_console_sem();
1087 }
1088 EXPORT_SYMBOL(console_stop);
1089
1090 void console_start(struct console *console)
1091 {
1092         acquire_console_sem();
1093         console->flags |= CON_ENABLED;
1094         release_console_sem();
1095 }
1096 EXPORT_SYMBOL(console_start);
1097
1098 /*
1099  * The console driver calls this routine during kernel initialization
1100  * to register the console printing procedure with printk() and to
1101  * print any messages that were printed by the kernel before the
1102  * console driver was initialized.
1103  */
1104 void register_console(struct console *console)
1105 {
1106         int i;
1107         unsigned long flags;
1108         struct console *bootconsole = NULL;
1109
1110         if (console_drivers) {
1111                 if (console->flags & CON_BOOT)
1112                         return;
1113                 if (console_drivers->flags & CON_BOOT)
1114                         bootconsole = console_drivers;
1115         }
1116
1117         if (preferred_console < 0 || bootconsole || !console_drivers)
1118                 preferred_console = selected_console;
1119
1120         if (console->early_setup)
1121                 console->early_setup();
1122
1123         /*
1124          *      See if we want to use this console driver. If we
1125          *      didn't select a console we take the first one
1126          *      that registers here.
1127          */
1128         if (preferred_console < 0) {
1129                 if (console->index < 0)
1130                         console->index = 0;
1131                 if (console->setup == NULL ||
1132                     console->setup(console, NULL) == 0) {
1133                         console->flags |= CON_ENABLED;
1134                         if (console->device) {
1135                                 console->flags |= CON_CONSDEV;
1136                                 preferred_console = 0;
1137                         }
1138                 }
1139         }
1140
1141         /*
1142          *      See if this console matches one we selected on
1143          *      the command line.
1144          */
1145         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1146                         i++) {
1147                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1148                         continue;
1149                 if (console->index >= 0 &&
1150                     console->index != console_cmdline[i].index)
1151                         continue;
1152                 if (console->index < 0)
1153                         console->index = console_cmdline[i].index;
1154 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1155                 if (console_cmdline[i].brl_options) {
1156                         console->flags |= CON_BRL;
1157                         braille_register_console(console,
1158                                         console_cmdline[i].index,
1159                                         console_cmdline[i].options,
1160                                         console_cmdline[i].brl_options);
1161                         return;
1162                 }
1163 #endif
1164                 if (console->setup &&
1165                     console->setup(console, console_cmdline[i].options) != 0)
1166                         break;
1167                 console->flags |= CON_ENABLED;
1168                 console->index = console_cmdline[i].index;
1169                 if (i == selected_console) {
1170                         console->flags |= CON_CONSDEV;
1171                         preferred_console = selected_console;
1172                 }
1173                 break;
1174         }
1175
1176         if (!(console->flags & CON_ENABLED))
1177                 return;
1178
1179         if (bootconsole && (console->flags & CON_CONSDEV)) {
1180                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1181                        bootconsole->name, bootconsole->index,
1182                        console->name, console->index);
1183                 unregister_console(bootconsole);
1184                 console->flags &= ~CON_PRINTBUFFER;
1185         } else {
1186                 printk(KERN_INFO "console [%s%d] enabled\n",
1187                        console->name, console->index);
1188         }
1189
1190         /*
1191          *      Put this console in the list - keep the
1192          *      preferred driver at the head of the list.
1193          */
1194         acquire_console_sem();
1195         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1196                 console->next = console_drivers;
1197                 console_drivers = console;
1198                 if (console->next)
1199                         console->next->flags &= ~CON_CONSDEV;
1200         } else {
1201                 console->next = console_drivers->next;
1202                 console_drivers->next = console;
1203         }
1204         if (console->flags & CON_PRINTBUFFER) {
1205                 /*
1206                  * release_console_sem() will print out the buffered messages
1207                  * for us.
1208                  */
1209                 spin_lock_irqsave(&logbuf_lock, flags);
1210                 con_start = log_start;
1211                 spin_unlock_irqrestore(&logbuf_lock, flags);
1212         }
1213         release_console_sem();
1214 }
1215 EXPORT_SYMBOL(register_console);
1216
1217 int unregister_console(struct console *console)
1218 {
1219         struct console *a, *b;
1220         int res = 1;
1221
1222 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1223         if (console->flags & CON_BRL)
1224                 return braille_unregister_console(console);
1225 #endif
1226
1227         acquire_console_sem();
1228         if (console_drivers == console) {
1229                 console_drivers=console->next;
1230                 res = 0;
1231         } else if (console_drivers) {
1232                 for (a=console_drivers->next, b=console_drivers ;
1233                      a; b=a, a=b->next) {
1234                         if (a == console) {
1235                                 b->next = a->next;
1236                                 res = 0;
1237                                 break;
1238                         }
1239                 }
1240         }
1241
1242         /*
1243          * If this isn't the last console and it has CON_CONSDEV set, we
1244          * need to set it on the next preferred console.
1245          */
1246         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1247                 console_drivers->flags |= CON_CONSDEV;
1248
1249         release_console_sem();
1250         return res;
1251 }
1252 EXPORT_SYMBOL(unregister_console);
1253
1254 static int __init disable_boot_consoles(void)
1255 {
1256         if (console_drivers != NULL) {
1257                 if (console_drivers->flags & CON_BOOT) {
1258                         printk(KERN_INFO "turn off boot console %s%d\n",
1259                                 console_drivers->name, console_drivers->index);
1260                         return unregister_console(console_drivers);
1261                 }
1262         }
1263         return 0;
1264 }
1265 late_initcall(disable_boot_consoles);
1266
1267 #if defined CONFIG_PRINTK
1268
1269 /*
1270  * printk rate limiting, lifted from the networking subsystem.
1271  *
1272  * This enforces a rate limit: not more than 10 kernel messages
1273  * every 5s to make a denial-of-service attack impossible.
1274  */
1275 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1276
1277 int printk_ratelimit(void)
1278 {
1279         return __ratelimit(&printk_ratelimit_state);
1280 }
1281 EXPORT_SYMBOL(printk_ratelimit);
1282
1283 /**
1284  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1285  * @caller_jiffies: pointer to caller's state
1286  * @interval_msecs: minimum interval between prints
1287  *
1288  * printk_timed_ratelimit() returns true if more than @interval_msecs
1289  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1290  * returned true.
1291  */
1292 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1293                         unsigned int interval_msecs)
1294 {
1295         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1296                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1297                 return true;
1298         }
1299         return false;
1300 }
1301 EXPORT_SYMBOL(printk_timed_ratelimit);
1302 #endif