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 #include <linux/kexec.h>
  36 #include <linux/ratelimit.h>
  37
  38 #include <asm/uaccess.h>
  39
  40 /*
  41  * for_each_console() allows you to iterate on each console
  42  */
  43 #define for_each_console(con) \
  44         for (con = console_drivers; con != NULL; con = con->next)
  45
  46 /*
  47  * Architectures can override it:
  48  */
  49 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
  50 {
  51 }
  52
  53 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
  54
  55 /* printk's without a loglevel use this.. */
  56 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  57
  58 /* We show everything that is MORE important than this.. */
  59 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  60 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  61
  62 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  63
  64 int console_printk[4] = {
  65         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  66         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  67         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  68         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  69 };
  70
  71 static int saved_console_loglevel = -1;
  72
  73 /*
  74  * Low level drivers may need that to know if they can schedule in
  75  * their unblank() callback or not. So let's export it.
  76  */
  77 int oops_in_progress;
  78 EXPORT_SYMBOL(oops_in_progress);
  79
  80 /*
  81  * console_sem protects the console_drivers list, and also
  82  * provides serialisation for access to the entire console
  83  * driver system.
  84  */
  85 static DECLARE_MUTEX(console_sem);
  86 struct console *console_drivers;
  87 EXPORT_SYMBOL_GPL(console_drivers);
  88
  89 /*
  90  * This is used for debugging the mess that is the VT code by
  91  * keeping track if we have the console semaphore held. It's
  92  * definitely not the perfect debug tool (we don't know if _WE_
  93  * hold it are racing, but it helps tracking those weird code
  94  * path in the console code where we end up in places I want
  95  * locked without the console sempahore held
  96  */
  97 static int console_locked, console_suspended;
  98
  99 /*
 100  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
 101  * It is also used in interesting ways to provide interlocking in
 102  * release_console_sem().
 103  */
 104 static DEFINE_SPINLOCK(logbuf_lock);
 105
 106 #define LOG_BUF_MASK (log_buf_len-1)
 107 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
 108
 109 /*
 110  * The indices into log_buf are not constrained to log_buf_len - they
 111  * must be masked before subscripting
 112  */
 113 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
 114 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
 115 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 116
 117 /*
 118  *      Array of consoles built from command line options (console=)
 119  */
 120 struct console_cmdline
 121 {
 122         char    name[8];                        /* Name of the driver       */
 123         int     index;                          /* Minor dev. to use        */
 124         char    *options;                       /* Options for the driver   */
 125 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 126         char    *brl_options;                   /* Options for braille driver */
 127 #endif
 128 };
 129
 130 #define MAX_CMDLINECONSOLES 8
 131
 132 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 133 static int selected_console = -1;
 134 static int preferred_console = -1;
 135 int console_set_on_cmdline;
 136 EXPORT_SYMBOL(console_set_on_cmdline);
 137
 138 /* Flag: console code may call schedule() */
 139 static int console_may_schedule;
 140
 141 #ifdef CONFIG_PRINTK
 142
 143 static char __log_buf[__LOG_BUF_LEN];
 144 static char *log_buf = __log_buf;
 145 static int log_buf_len = __LOG_BUF_LEN;
 146 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 147
 148 #ifdef CONFIG_KEXEC
 149 /*
 150  * This appends the listed symbols to /proc/vmcoreinfo
 151  *
 152  * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
 153  * obtain access to symbols that are otherwise very difficult to locate.  These
 154  * symbols are specifically used so that utilities can access and extract the
 155  * dmesg log from a vmcore file after a crash.
 156  */
 157 void log_buf_kexec_setup(void)
 158 {
 159         VMCOREINFO_SYMBOL(log_buf);
 160         VMCOREINFO_SYMBOL(log_end);
 161         VMCOREINFO_SYMBOL(log_buf_len);
 162         VMCOREINFO_SYMBOL(logged_chars);
 163 }
 164 #endif
 165
 166 static int __init log_buf_len_setup(char *str)
 167 {
 168         unsigned size = memparse(str, &str);
 169         unsigned long flags;
 170
 171         if (size)
 172                 size = roundup_pow_of_two(size);
 173         if (size > log_buf_len) {
 174                 unsigned start, dest_idx, offset;
 175                 char *new_log_buf;
 176
 177                 new_log_buf = alloc_bootmem(size);
 178                 if (!new_log_buf) {
 179                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 180                         goto out;
 181                 }
 182
 183                 spin_lock_irqsave(&logbuf_lock, flags);
 184                 log_buf_len = size;
 185                 log_buf = new_log_buf;
 186
 187                 offset = start = min(con_start, log_start);
 188                 dest_idx = 0;
 189                 while (start != log_end) {
 190                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 191                         start++;
 192                         dest_idx++;
 193                 }
 194                 log_start -= offset;
 195                 con_start -= offset;
 196                 log_end -= offset;
 197                 spin_unlock_irqrestore(&logbuf_lock, flags);
 198
 199                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 200         }
 201 out:
 202         return 1;
 203 }
 204
 205 __setup("log_buf_len=", log_buf_len_setup);
 206
 207 #ifdef CONFIG_BOOT_PRINTK_DELAY
 208
 209 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 210 static unsigned long long loops_per_msec;       /* based on boot_delay */
 211
 212 static int __init boot_delay_setup(char *str)
 213 {
 214         unsigned long lpj;
 215
 216         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 217         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 218
 219         get_option(&str, &boot_delay);
 220         if (boot_delay > 10 * 1000)
 221                 boot_delay = 0;
 222
 223         pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 224                 "HZ: %d, loops_per_msec: %llu\n",
 225                 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
 226         return 1;
 227 }
 228 __setup("boot_delay=", boot_delay_setup);
 229
 230 static void boot_delay_msec(void)
 231 {
 232         unsigned long long k;
 233         unsigned long timeout;
 234
 235         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 236                 return;
 237
 238         k = (unsigned long long)loops_per_msec * boot_delay;
 239
 240         timeout = jiffies + msecs_to_jiffies(boot_delay);
 241         while (k) {
 242                 k--;
 243                 cpu_relax();
 244                 /*
 245                  * use (volatile) jiffies to prevent
 246                  * compiler reduction; loop termination via jiffies
 247                  * is secondary and may or may not happen.
 248                  */
 249                 if (time_after(jiffies, timeout))
 250                         break;
 251                 touch_nmi_watchdog();
 252         }
 253 }
 254 #else
 255 static inline void boot_delay_msec(void)
 256 {
 257 }
 258 #endif
 259
 260 /*
 261  * Commands to do_syslog:
 262  *
 263  *      0 -- Close the log.  Currently a NOP.
 264  *      1 -- Open the log. Currently a NOP.
 265  *      2 -- Read from the log.
 266  *      3 -- Read all messages remaining in the ring buffer.
 267  *      4 -- Read and clear all messages remaining in the ring buffer
 268  *      5 -- Clear ring buffer.
 269  *      6 -- Disable printk's to console
 270  *      7 -- Enable printk's to console
 271  *      8 -- Set level of messages printed to console
 272  *      9 -- Return number of unread characters in the log buffer
 273  *     10 -- Return size of the log buffer
 274  */
 275 int do_syslog(int type, char __user *buf, int len)
 276 {
 277         unsigned i, j, limit, count;
 278         int do_clear = 0;
 279         char c;
 280         int error = 0;
 281
 282         error = security_syslog(type);
 283         if (error)
 284                 return error;
 285
 286         switch (type) {
 287         case 0:         /* Close log */
 288                 break;
 289         case 1:         /* Open log */
 290                 break;
 291         case 2:         /* Read from log */
 292                 error = -EINVAL;
 293                 if (!buf || len < 0)
 294                         goto out;
 295                 error = 0;
 296                 if (!len)
 297                         goto out;
 298                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 299                         error = -EFAULT;
 300                         goto out;
 301                 }
 302                 error = wait_event_interruptible(log_wait,
 303                                                         (log_start - log_end));
 304                 if (error)
 305                         goto out;
 306                 i = 0;
 307                 spin_lock_irq(&logbuf_lock);
 308                 while (!error && (log_start != log_end) && i < len) {
 309                         c = LOG_BUF(log_start);
 310                         log_start++;
 311                         spin_unlock_irq(&logbuf_lock);
 312                         error = __put_user(c,buf);
 313                         buf++;
 314                         i++;
 315                         cond_resched();
 316                         spin_lock_irq(&logbuf_lock);
 317                 }
 318                 spin_unlock_irq(&logbuf_lock);
 319                 if (!error)
 320                         error = i;
 321                 break;
 322         case 4:         /* Read/clear last kernel messages */
 323                 do_clear = 1;
 324                 /* FALL THRU */
 325         case 3:         /* Read last kernel messages */
 326                 error = -EINVAL;
 327                 if (!buf || len < 0)
 328                         goto out;
 329                 error = 0;
 330                 if (!len)
 331                         goto out;
 332                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 333                         error = -EFAULT;
 334                         goto out;
 335                 }
 336                 count = len;
 337                 if (count > log_buf_len)
 338                         count = log_buf_len;
 339                 spin_lock_irq(&logbuf_lock);
 340                 if (count > logged_chars)
 341                         count = logged_chars;
 342                 if (do_clear)
 343                         logged_chars = 0;
 344                 limit = log_end;
 345                 /*
 346                  * __put_user() could sleep, and while we sleep
 347                  * printk() could overwrite the messages
 348                  * we try to copy to user space. Therefore
 349                  * the messages are copied in reverse. <manfreds>
 350                  */
 351                 for (i = 0; i < count && !error; i++) {
 352                         j = limit-1-i;
 353                         if (j + log_buf_len < log_end)
 354                                 break;
 355                         c = LOG_BUF(j);
 356                         spin_unlock_irq(&logbuf_lock);
 357                         error = __put_user(c,&buf[count-1-i]);
 358                         cond_resched();
 359                         spin_lock_irq(&logbuf_lock);
 360                 }
 361                 spin_unlock_irq(&logbuf_lock);
 362                 if (error)
 363                         break;
 364                 error = i;
 365                 if (i != count) {
 366                         int offset = count-error;
 367                         /* buffer overflow during copy, correct user buffer. */
 368                         for (i = 0; i < error; i++) {
 369                                 if (__get_user(c,&buf[i+offset]) ||
 370                                     __put_user(c,&buf[i])) {
 371                                         error = -EFAULT;
 372                                         break;
 373                                 }
 374                                 cond_resched();
 375                         }
 376                 }
 377                 break;
 378         case 5:         /* Clear ring buffer */
 379                 logged_chars = 0;
 380                 break;
 381         case 6:         /* Disable logging to console */
 382                 if (saved_console_loglevel == -1)
 383                         saved_console_loglevel = console_loglevel;
 384                 console_loglevel = minimum_console_loglevel;
 385                 break;
 386         case 7:         /* Enable logging to console */
 387                 if (saved_console_loglevel != -1) {
 388                         console_loglevel = saved_console_loglevel;
 389                         saved_console_loglevel = -1;
 390                 }
 391                 break;
 392         case 8:         /* Set level of messages printed to console */
 393                 error = -EINVAL;
 394                 if (len < 1 || len > 8)
 395                         goto out;
 396                 if (len < minimum_console_loglevel)
 397                         len = minimum_console_loglevel;
 398                 console_loglevel = len;
 399                 /* Implicitly re-enable logging to console */
 400                 saved_console_loglevel = -1;
 401                 error = 0;
 402                 break;
 403         case 9:         /* Number of chars in the log buffer */
 404                 error = log_end - log_start;
 405                 break;
 406         case 10:        /* Size of the log buffer */
 407                 error = log_buf_len;
 408                 break;
 409         default:
 410                 error = -EINVAL;
 411                 break;
 412         }
 413 out:
 414         return error;
 415 }
 416
 417 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
 418 {
 419         return do_syslog(type, buf, len);
 420 }
 421
 422 /*
 423  * Call the console drivers on a range of log_buf
 424  */
 425 static void __call_console_drivers(unsigned start, unsigned end)
 426 {
 427         struct console *con;
 428
 429         for_each_console(con) {
 430                 if ((con->flags & CON_ENABLED) && con->write &&
 431                                 (cpu_online(smp_processor_id()) ||
 432                                 (con->flags & CON_ANYTIME)))
 433                         con->write(con, &LOG_BUF(start), end - start);
 434         }
 435 }
 436
 437 static int __read_mostly ignore_loglevel;
 438
 439 static int __init ignore_loglevel_setup(char *str)
 440 {
 441         ignore_loglevel = 1;
 442         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 443
 444         return 0;
 445 }
 446
 447 early_param("ignore_loglevel", ignore_loglevel_setup);
 448
 449 /*
 450  * Write out chars from start to end - 1 inclusive
 451  */
 452 static void _call_console_drivers(unsigned start,
 453                                 unsigned end, int msg_log_level)
 454 {
 455         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 456                         console_drivers && start != end) {
 457                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 458                         /* wrapped write */
 459                         __call_console_drivers(start & LOG_BUF_MASK,
 460                                                 log_buf_len);
 461                         __call_console_drivers(0, end & LOG_BUF_MASK);
 462                 } else {
 463                         __call_console_drivers(start, end);
 464                 }
 465         }
 466 }
 467
 468 /*
 469  * Call the console drivers, asking them to write out
 470  * log_buf[start] to log_buf[end - 1].
 471  * The console_sem must be held.
 472  */
 473 static void call_console_drivers(unsigned start, unsigned end)
 474 {
 475         unsigned cur_index, start_print;
 476         static int msg_level = -1;
 477
 478         BUG_ON(((int)(start - end)) > 0);
 479
 480         cur_index = start;
 481         start_print = start;
 482         while (cur_index != end) {
 483                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 484                                 LOG_BUF(cur_index + 0) == '<' &&
 485                                 LOG_BUF(cur_index + 1) >= '0' &&
 486                                 LOG_BUF(cur_index + 1) <= '7' &&
 487                                 LOG_BUF(cur_index + 2) == '>') {
 488                         msg_level = LOG_BUF(cur_index + 1) - '0';
 489                         cur_index += 3;
 490                         start_print = cur_index;
 491                 }
 492                 while (cur_index != end) {
 493                         char c = LOG_BUF(cur_index);
 494
 495                         cur_index++;
 496                         if (c == '\n') {
 497                                 if (msg_level < 0) {
 498                                         /*
 499                                          * printk() has already given us loglevel tags in
 500                                          * the buffer.  This code is here in case the
 501                                          * log buffer has wrapped right round and scribbled
 502                                          * on those tags
 503                                          */
 504                                         msg_level = default_message_loglevel;
 505                                 }
 506                                 _call_console_drivers(start_print, cur_index, msg_level);
 507                                 msg_level = -1;
 508                                 start_print = cur_index;
 509                                 break;
 510                         }
 511                 }
 512         }
 513         _call_console_drivers(start_print, end, msg_level);
 514 }
 515
 516 static void emit_log_char(char c)
 517 {
 518         LOG_BUF(log_end) = c;
 519         log_end++;
 520         if (log_end - log_start > log_buf_len)
 521                 log_start = log_end - log_buf_len;
 522         if (log_end - con_start > log_buf_len)
 523                 con_start = log_end - log_buf_len;
 524         if (logged_chars < log_buf_len)
 525                 logged_chars++;
 526 }
 527
 528 /*
 529  * Zap console related locks when oopsing. Only zap at most once
 530  * every 10 seconds, to leave time for slow consoles to print a
 531  * full oops.
 532  */
 533 static void zap_locks(void)
 534 {
 535         static unsigned long oops_timestamp;
 536
 537         if (time_after_eq(jiffies, oops_timestamp) &&
 538                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 539                 return;
 540
 541         oops_timestamp = jiffies;
 542
 543         /* If a crash is occurring, make sure we can't deadlock */
 544         spin_lock_init(&logbuf_lock);
 545         /* And make sure that we print immediately */
 546         init_MUTEX(&console_sem);
 547 }
 548
 549 #if defined(CONFIG_PRINTK_TIME)
 550 static int printk_time = 1;
 551 #else
 552 static int printk_time = 0;
 553 #endif
 554 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 555
 556 /* Check if we have any console registered that can be called early in boot. */
 557 static int have_callable_console(void)
 558 {
 559         struct console *con;
 560
 561         for_each_console(con)
 562                 if (con->flags & CON_ANYTIME)
 563                         return 1;
 564
 565         return 0;
 566 }
 567
 568 /**
 569  * printk - print a kernel message
 570  * @fmt: format string
 571  *
 572  * This is printk().  It can be called from any context.  We want it to work.
 573  *
 574  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 575  * call the console drivers.  If we fail to get the semaphore we place the output
 576  * into the log buffer and return.  The current holder of the console_sem will
 577  * notice the new output in release_console_sem() and will send it to the
 578  * consoles before releasing the semaphore.
 579  *
 580  * One effect of this deferred printing is that code which calls printk() and
 581  * then changes console_loglevel may break. This is because console_loglevel
 582  * is inspected when the actual printing occurs.
 583  *
 584  * See also:
 585  * printf(3)
 586  *
 587  * See the vsnprintf() documentation for format string extensions over C99.
 588  */
 589
 590 asmlinkage int printk(const char *fmt, ...)
 591 {
 592         va_list args;
 593         int r;
 594
 595         va_start(args, fmt);
 596         r = vprintk(fmt, args);
 597         va_end(args);
 598
 599         return r;
 600 }
 601
 602 /* cpu currently holding logbuf_lock */
 603 static volatile unsigned int printk_cpu = UINT_MAX;
 604
 605 /*
 606  * Can we actually use the console at this time on this cpu?
 607  *
 608  * Console drivers may assume that per-cpu resources have
 609  * been allocated. So unless they're explicitly marked as
 610  * being able to cope (CON_ANYTIME) don't call them until
 611  * this CPU is officially up.
 612  */
 613 static inline int can_use_console(unsigned int cpu)
 614 {
 615         return cpu_online(cpu) || have_callable_console();
 616 }
 617
 618 /*
 619  * Try to get console ownership to actually show the kernel
 620  * messages from a 'printk'. Return true (and with the
 621  * console_semaphore held, and 'console_locked' set) if it
 622  * is successful, false otherwise.
 623  *
 624  * This gets called with the 'logbuf_lock' spinlock held and
 625  * interrupts disabled. It should return with 'lockbuf_lock'
 626  * released but interrupts still disabled.
 627  */
 628 static int acquire_console_semaphore_for_printk(unsigned int cpu)
 629 {
 630         int retval = 0;
 631
 632         if (!try_acquire_console_sem()) {
 633                 retval = 1;
 634
 635                 /*
 636                  * If we can't use the console, we need to release
 637                  * the console semaphore by hand to avoid flushing
 638                  * the buffer. We need to hold the console semaphore
 639                  * in order to do this test safely.
 640                  */
 641                 if (!can_use_console(cpu)) {
 642                         console_locked = 0;
 643                         up(&console_sem);
 644                         retval = 0;
 645                 }
 646         }
 647         printk_cpu = UINT_MAX;
 648         spin_unlock(&logbuf_lock);
 649         return retval;
 650 }
 651 static const char recursion_bug_msg [] =
 652                 KERN_CRIT "BUG: recent printk recursion!\n";
 653 static int recursion_bug;
 654 static int new_text_line = 1;
 655 static char printk_buf[1024];
 656
 657 int printk_delay_msec __read_mostly;
 658
 659 static inline void printk_delay(void)
 660 {
 661         if (unlikely(printk_delay_msec)) {
 662                 int m = printk_delay_msec;
 663
 664                 while (m--) {
 665                         mdelay(1);
 666                         touch_nmi_watchdog();
 667                 }
 668         }
 669 }
 670
 671 asmlinkage int vprintk(const char *fmt, va_list args)
 672 {
 673         int printed_len = 0;
 674         int current_log_level = default_message_loglevel;
 675         unsigned long flags;
 676         int this_cpu;
 677         char *p;
 678
 679         boot_delay_msec();
 680         printk_delay();
 681
 682         preempt_disable();
 683         /* This stops the holder of console_sem just where we want him */
 684         raw_local_irq_save(flags);
 685         this_cpu = smp_processor_id();
 686
 687         /*
 688          * Ouch, printk recursed into itself!
 689          */
 690         if (unlikely(printk_cpu == this_cpu)) {
 691                 /*
 692                  * If a crash is occurring during printk() on this CPU,
 693                  * then try to get the crash message out but make sure
 694                  * we can't deadlock. Otherwise just return to avoid the
 695                  * recursion and return - but flag the recursion so that
 696                  * it can be printed at the next appropriate moment:
 697                  */
 698                 if (!oops_in_progress) {
 699                         recursion_bug = 1;
 700                         goto out_restore_irqs;
 701                 }
 702                 zap_locks();
 703         }
 704
 705         lockdep_off();
 706         spin_lock(&logbuf_lock);
 707         printk_cpu = this_cpu;
 708
 709         if (recursion_bug) {
 710                 recursion_bug = 0;
 711                 strcpy(printk_buf, recursion_bug_msg);
 712                 printed_len = strlen(recursion_bug_msg);
 713         }
 714         /* Emit the output into the temporary buffer */
 715         printed_len += vscnprintf(printk_buf + printed_len,
 716                                   sizeof(printk_buf) - printed_len, fmt, args);
 717
 718
 719         p = printk_buf;
 720
 721         /* Do we have a loglevel in the string? */
 722         if (p[0] == '<') {
 723                 unsigned char c = p[1];
 724                 if (c && p[2] == '>') {
 725                         switch (c) {
 726                         case '0' ... '7': /* loglevel */
 727                                 current_log_level = c - '0';
 728                         /* Fallthrough - make sure we're on a new line */
 729                         case 'd': /* KERN_DEFAULT */
 730                                 if (!new_text_line) {
 731                                         emit_log_char('\n');
 732                                         new_text_line = 1;
 733                                 }
 734                         /* Fallthrough - skip the loglevel */
 735                         case 'c': /* KERN_CONT */
 736                                 p += 3;
 737                                 break;
 738                         }
 739                 }
 740         }
 741
 742         /*
 743          * Copy the output into log_buf.  If the caller didn't provide
 744          * appropriate log level tags, we insert them here
 745          */
 746         for ( ; *p; p++) {
 747                 if (new_text_line) {
 748                         /* Always output the token */
 749                         emit_log_char('<');
 750                         emit_log_char(current_log_level + '0');
 751                         emit_log_char('>');
 752                         printed_len += 3;
 753                         new_text_line = 0;
 754
 755                         if (printk_time) {
 756                                 /* Follow the token with the time */
 757                                 char tbuf[50], *tp;
 758                                 unsigned tlen;
 759                                 unsigned long long t;
 760                                 unsigned long nanosec_rem;
 761
 762                                 t = cpu_clock(printk_cpu);
 763                                 nanosec_rem = do_div(t, 1000000000);
 764                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
 765                                                 (unsigned long) t,
 766                                                 nanosec_rem / 1000);
 767
 768                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 769                                         emit_log_char(*tp);
 770                                 printed_len += tlen;
 771                         }
 772
 773                         if (!*p)
 774                                 break;
 775                 }
 776
 777                 emit_log_char(*p);
 778                 if (*p == '\n')
 779                         new_text_line = 1;
 780         }
 781
 782         /*
 783          * Try to acquire and then immediately release the
 784          * console semaphore. The release will do all the
 785          * actual magic (print out buffers, wake up klogd,
 786          * etc).
 787          *
 788          * The acquire_console_semaphore_for_printk() function
 789          * will release 'logbuf_lock' regardless of whether it
 790          * actually gets the semaphore or not.
 791          */
 792         if (acquire_console_semaphore_for_printk(this_cpu))
 793                 release_console_sem();
 794
 795         lockdep_on();
 796 out_restore_irqs:
 797         raw_local_irq_restore(flags);
 798
 799         preempt_enable();
 800         return printed_len;
 801 }
 802 EXPORT_SYMBOL(printk);
 803 EXPORT_SYMBOL(vprintk);
 804
 805 #else
 806
 807 static void call_console_drivers(unsigned start, unsigned end)
 808 {
 809 }
 810
 811 #endif
 812
 813 static int __add_preferred_console(char *name, int idx, char *options,
 814                                    char *brl_options)
 815 {
 816         struct console_cmdline *c;
 817         int i;
 818
 819         /*
 820          *      See if this tty is not yet registered, and
 821          *      if we have a slot free.
 822          */
 823         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 824                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 825                           console_cmdline[i].index == idx) {
 826                                 if (!brl_options)
 827                                         selected_console = i;
 828                                 return 0;
 829                 }
 830         if (i == MAX_CMDLINECONSOLES)
 831                 return -E2BIG;
 832         if (!brl_options)
 833                 selected_console = i;
 834         c = &console_cmdline[i];
 835         strlcpy(c->name, name, sizeof(c->name));
 836         c->options = options;
 837 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 838         c->brl_options = brl_options;
 839 #endif
 840         c->index = idx;
 841         return 0;
 842 }
 843 /*
 844  * Set up a list of consoles.  Called from init/main.c
 845  */
 846 static int __init console_setup(char *str)
 847 {
 848         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 849         char *s, *options, *brl_options = NULL;
 850         int idx;
 851
 852 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 853         if (!memcmp(str, "brl,", 4)) {
 854                 brl_options = "";
 855                 str += 4;
 856         } else if (!memcmp(str, "brl=", 4)) {
 857                 brl_options = str + 4;
 858                 str = strchr(brl_options, ',');
 859                 if (!str) {
 860                         printk(KERN_ERR "need port name after brl=\n");
 861                         return 1;
 862                 }
 863                 *(str++) = 0;
 864         }
 865 #endif
 866
 867         /*
 868          * Decode str into name, index, options.
 869          */
 870         if (str[0] >= '0' && str[0] <= '9') {
 871                 strcpy(buf, "ttyS");
 872                 strncpy(buf + 4, str, sizeof(buf) - 5);
 873         } else {
 874                 strncpy(buf, str, sizeof(buf) - 1);
 875         }
 876         buf[sizeof(buf) - 1] = 0;
 877         if ((options = strchr(str, ',')) != NULL)
 878                 *(options++) = 0;
 879 #ifdef __sparc__
 880         if (!strcmp(str, "ttya"))
 881                 strcpy(buf, "ttyS0");
 882         if (!strcmp(str, "ttyb"))
 883                 strcpy(buf, "ttyS1");
 884 #endif
 885         for (s = buf; *s; s++)
 886                 if ((*s >= '0' && *s <= '9') || *s == ',')
 887                         break;
 888         idx = simple_strtoul(s, NULL, 10);
 889         *s = 0;
 890
 891         __add_preferred_console(buf, idx, options, brl_options);
 892         console_set_on_cmdline = 1;
 893         return 1;
 894 }
 895 __setup("console=", console_setup);
 896
 897 /**
 898  * add_preferred_console - add a device to the list of preferred consoles.
 899  * @name: device name
 900  * @idx: device index
 901  * @options: options for this console
 902  *
 903  * The last preferred console added will be used for kernel messages
 904  * and stdin/out/err for init.  Normally this is used by console_setup
 905  * above to handle user-supplied console arguments; however it can also
 906  * be used by arch-specific code either to override the user or more
 907  * commonly to provide a default console (ie from PROM variables) when
 908  * the user has not supplied one.
 909  */
 910 int add_preferred_console(char *name, int idx, char *options)
 911 {
 912         return __add_preferred_console(name, idx, options, NULL);
 913 }
 914
 915 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 916 {
 917         struct console_cmdline *c;
 918         int i;
 919
 920         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 921                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 922                           console_cmdline[i].index == idx) {
 923                                 c = &console_cmdline[i];
 924                                 strlcpy(c->name, name_new, sizeof(c->name));
 925                                 c->name[sizeof(c->name) - 1] = 0;
 926                                 c->options = options;
 927                                 c->index = idx_new;
 928                                 return i;
 929                 }
 930         /* not found */
 931         return -1;
 932 }
 933
 934 int console_suspend_enabled = 1;
 935 EXPORT_SYMBOL(console_suspend_enabled);
 936
 937 static int __init console_suspend_disable(char *str)
 938 {
 939         console_suspend_enabled = 0;
 940         return 1;
 941 }
 942 __setup("no_console_suspend", console_suspend_disable);
 943
 944 /**
 945  * suspend_console - suspend the console subsystem
 946  *
 947  * This disables printk() while we go into suspend states
 948  */
 949 void suspend_console(void)
 950 {
 951         if (!console_suspend_enabled)
 952                 return;
 953         printk("Suspending console(s) (use no_console_suspend to debug)\n");
 954         acquire_console_sem();
 955         console_suspended = 1;
 956         up(&console_sem);
 957 }
 958
 959 void resume_console(void)
 960 {
 961         if (!console_suspend_enabled)
 962                 return;
 963         down(&console_sem);
 964         console_suspended = 0;
 965         release_console_sem();
 966 }
 967
 968 /**
 969  * acquire_console_sem - lock the console system for exclusive use.
 970  *
 971  * Acquires a semaphore which guarantees that the caller has
 972  * exclusive access to the console system and the console_drivers list.
 973  *
 974  * Can sleep, returns nothing.
 975  */
 976 void acquire_console_sem(void)
 977 {
 978         BUG_ON(in_interrupt());
 979         down(&console_sem);
 980         if (console_suspended)
 981                 return;
 982         console_locked = 1;
 983         console_may_schedule = 1;
 984 }
 985 EXPORT_SYMBOL(acquire_console_sem);
 986
 987 int try_acquire_console_sem(void)
 988 {
 989         if (down_trylock(&console_sem))
 990                 return -1;
 991         if (console_suspended) {
 992                 up(&console_sem);
 993                 return -1;
 994         }
 995         console_locked = 1;
 996         console_may_schedule = 0;
 997         return 0;
 998 }
 999 EXPORT_SYMBOL(try_acquire_console_sem);
1000
1001 int is_console_locked(void)
1002 {
1003         return console_locked;
1004 }
1005
1006 static DEFINE_PER_CPU(int, printk_pending);
1007
1008 void printk_tick(void)
1009 {
1010         if (__get_cpu_var(printk_pending)) {
1011                 __get_cpu_var(printk_pending) = 0;
1012                 wake_up_interruptible(&log_wait);
1013         }
1014 }
1015
1016 int printk_needs_cpu(int cpu)
1017 {
1018         return per_cpu(printk_pending, cpu);
1019 }
1020
1021 void wake_up_klogd(void)
1022 {
1023         if (waitqueue_active(&log_wait))
1024                 __raw_get_cpu_var(printk_pending) = 1;
1025 }
1026
1027 /**
1028  * release_console_sem - unlock the console system
1029  *
1030  * Releases the semaphore which the caller holds on the console system
1031  * and the console driver list.
1032  *
1033  * While the semaphore was held, console output may have been buffered
1034  * by printk().  If this is the case, release_console_sem() emits
1035  * the output prior to releasing the semaphore.
1036  *
1037  * If there is output waiting for klogd, we wake it up.
1038  *
1039  * release_console_sem() may be called from any context.
1040  */
1041 void release_console_sem(void)
1042 {
1043         unsigned long flags;
1044         unsigned _con_start, _log_end;
1045         unsigned wake_klogd = 0;
1046
1047         if (console_suspended) {
1048                 up(&console_sem);
1049                 return;
1050         }
1051
1052         console_may_schedule = 0;
1053
1054         for ( ; ; ) {
1055                 spin_lock_irqsave(&logbuf_lock, flags);
1056                 wake_klogd |= log_start - log_end;
1057                 if (con_start == log_end)
1058                         break;                  /* Nothing to print */
1059                 _con_start = con_start;
1060                 _log_end = log_end;
1061                 con_start = log_end;            /* Flush */
1062                 spin_unlock(&logbuf_lock);
1063                 stop_critical_timings();        /* don't trace print latency */
1064                 call_console_drivers(_con_start, _log_end);
1065                 start_critical_timings();
1066                 local_irq_restore(flags);
1067         }
1068         console_locked = 0;
1069         up(&console_sem);
1070         spin_unlock_irqrestore(&logbuf_lock, flags);
1071         if (wake_klogd)
1072                 wake_up_klogd();
1073 }
1074 EXPORT_SYMBOL(release_console_sem);
1075
1076 /**
1077  * console_conditional_schedule - yield the CPU if required
1078  *
1079  * If the console code is currently allowed to sleep, and
1080  * if this CPU should yield the CPU to another task, do
1081  * so here.
1082  *
1083  * Must be called within acquire_console_sem().
1084  */
1085 void __sched console_conditional_schedule(void)
1086 {
1087         if (console_may_schedule)
1088                 cond_resched();
1089 }
1090 EXPORT_SYMBOL(console_conditional_schedule);
1091
1092 void console_unblank(void)
1093 {
1094         struct console *c;
1095
1096         /*
1097          * console_unblank can no longer be called in interrupt context unless
1098          * oops_in_progress is set to 1..
1099          */
1100         if (oops_in_progress) {
1101                 if (down_trylock(&console_sem) != 0)
1102                         return;
1103         } else
1104                 acquire_console_sem();
1105
1106         console_locked = 1;
1107         console_may_schedule = 0;
1108         for_each_console(c)
1109                 if ((c->flags & CON_ENABLED) && c->unblank)
1110                         c->unblank();
1111         release_console_sem();
1112 }
1113
1114 /*
1115  * Return the console tty driver structure and its associated index
1116  */
1117 struct tty_driver *console_device(int *index)
1118 {
1119         struct console *c;
1120         struct tty_driver *driver = NULL;
1121
1122         acquire_console_sem();
1123         for_each_console(c) {
1124                 if (!c->device)
1125                         continue;
1126                 driver = c->device(c, index);
1127                 if (driver)
1128                         break;
1129         }
1130         release_console_sem();
1131         return driver;
1132 }
1133
1134 /*
1135  * Prevent further output on the passed console device so that (for example)
1136  * serial drivers can disable console output before suspending a port, and can
1137  * re-enable output afterwards.
1138  */
1139 void console_stop(struct console *console)
1140 {
1141         acquire_console_sem();
1142         console->flags &= ~CON_ENABLED;
1143         release_console_sem();
1144 }
1145 EXPORT_SYMBOL(console_stop);
1146
1147 void console_start(struct console *console)
1148 {
1149         acquire_console_sem();
1150         console->flags |= CON_ENABLED;
1151         release_console_sem();
1152 }
1153 EXPORT_SYMBOL(console_start);
1154
1155 /*
1156  * The console driver calls this routine during kernel initialization
1157  * to register the console printing procedure with printk() and to
1158  * print any messages that were printed by the kernel before the
1159  * console driver was initialized.
1160  *
1161  * This can happen pretty early during the boot process (because of
1162  * early_printk) - sometimes before setup_arch() completes - be careful
1163  * of what kernel features are used - they may not be initialised yet.
1164  *
1165  * There are two types of consoles - bootconsoles (early_printk) and
1166  * "real" consoles (everything which is not a bootconsole) which are
1167  * handled differently.
1168  *  - Any number of bootconsoles can be registered at any time.
1169  *  - As soon as a "real" console is registered, all bootconsoles
1170  *    will be unregistered automatically.
1171  *  - Once a "real" console is registered, any attempt to register a
1172  *    bootconsoles will be rejected
1173  */
1174 void register_console(struct console *newcon)
1175 {
1176         int i;
1177         unsigned long flags;
1178         struct console *bcon = NULL;
1179
1180         /*
1181          * before we register a new CON_BOOT console, make sure we don't
1182          * already have a valid console
1183          */
1184         if (console_drivers && newcon->flags & CON_BOOT) {
1185                 /* find the last or real console */
1186                 for_each_console(bcon) {
1187                         if (!(bcon->flags & CON_BOOT)) {
1188                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1189                                         newcon->name, newcon->index);
1190                                 return;
1191                         }
1192                 }
1193         }
1194
1195         if (console_drivers && console_drivers->flags & CON_BOOT)
1196                 bcon = console_drivers;
1197
1198         if (preferred_console < 0 || bcon || !console_drivers)
1199                 preferred_console = selected_console;
1200
1201         if (newcon->early_setup)
1202                 newcon->early_setup();
1203
1204         /*
1205          *      See if we want to use this console driver. If we
1206          *      didn't select a console we take the first one
1207          *      that registers here.
1208          */
1209         if (preferred_console < 0) {
1210                 if (newcon->index < 0)
1211                         newcon->index = 0;
1212                 if (newcon->setup == NULL ||
1213                     newcon->setup(newcon, NULL) == 0) {
1214                         newcon->flags |= CON_ENABLED;
1215                         if (newcon->device) {
1216                                 newcon->flags |= CON_CONSDEV;
1217                                 preferred_console = 0;
1218                         }
1219                 }
1220         }
1221
1222         /*
1223          *      See if this console matches one we selected on
1224          *      the command line.
1225          */
1226         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1227                         i++) {
1228                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1229                         continue;
1230                 if (newcon->index >= 0 &&
1231                     newcon->index != console_cmdline[i].index)
1232                         continue;
1233                 if (newcon->index < 0)
1234                         newcon->index = console_cmdline[i].index;
1235 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1236                 if (console_cmdline[i].brl_options) {
1237                         newcon->flags |= CON_BRL;
1238                         braille_register_console(newcon,
1239                                         console_cmdline[i].index,
1240                                         console_cmdline[i].options,
1241                                         console_cmdline[i].brl_options);
1242                         return;
1243                 }
1244 #endif
1245                 if (newcon->setup &&
1246                     newcon->setup(newcon, console_cmdline[i].options) != 0)
1247                         break;
1248                 newcon->flags |= CON_ENABLED;
1249                 newcon->index = console_cmdline[i].index;
1250                 if (i == selected_console) {
1251                         newcon->flags |= CON_CONSDEV;
1252                         preferred_console = selected_console;
1253                 }
1254                 break;
1255         }
1256
1257         if (!(newcon->flags & CON_ENABLED))
1258                 return;
1259
1260         /*
1261          * If we have a bootconsole, and are switching to a real console,
1262          * don't print everything out again, since when the boot console, and
1263          * the real console are the same physical device, it's annoying to
1264          * see the beginning boot messages twice
1265          */
1266         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1267                 newcon->flags &= ~CON_PRINTBUFFER;
1268
1269         /*
1270          *      Put this console in the list - keep the
1271          *      preferred driver at the head of the list.
1272          */
1273         acquire_console_sem();
1274         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1275                 newcon->next = console_drivers;
1276                 console_drivers = newcon;
1277                 if (newcon->next)
1278                         newcon->next->flags &= ~CON_CONSDEV;
1279         } else {
1280                 newcon->next = console_drivers->next;
1281                 console_drivers->next = newcon;
1282         }
1283         if (newcon->flags & CON_PRINTBUFFER) {
1284                 /*
1285                  * release_console_sem() will print out the buffered messages
1286                  * for us.
1287                  */
1288                 spin_lock_irqsave(&logbuf_lock, flags);
1289                 con_start = log_start;
1290                 spin_unlock_irqrestore(&logbuf_lock, flags);
1291         }
1292         release_console_sem();
1293
1294         /*
1295          * By unregistering the bootconsoles after we enable the real console
1296          * we get the "console xxx enabled" message on all the consoles -
1297          * boot consoles, real consoles, etc - this is to ensure that end
1298          * users know there might be something in the kernel's log buffer that
1299          * went to the bootconsole (that they do not see on the real console)
1300          */
1301         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1302                 /* we need to iterate through twice, to make sure we print
1303                  * everything out, before we unregister the console(s)
1304                  */
1305                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1306                         newcon->name, newcon->index);
1307                 for_each_console(bcon)
1308                         if (bcon->flags & CON_BOOT)
1309                                 unregister_console(bcon);
1310         } else {
1311                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1312                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
1313                         newcon->name, newcon->index);
1314         }
1315 }
1316 EXPORT_SYMBOL(register_console);
1317
1318 int unregister_console(struct console *console)
1319 {
1320         struct console *a, *b;
1321         int res = 1;
1322
1323 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1324         if (console->flags & CON_BRL)
1325                 return braille_unregister_console(console);
1326 #endif
1327
1328         acquire_console_sem();
1329         if (console_drivers == console) {
1330                 console_drivers=console->next;
1331                 res = 0;
1332         } else if (console_drivers) {
1333                 for (a=console_drivers->next, b=console_drivers ;
1334                      a; b=a, a=b->next) {
1335                         if (a == console) {
1336                                 b->next = a->next;
1337                                 res = 0;
1338                                 break;
1339                         }
1340                 }
1341         }
1342
1343         /*
1344          * If this isn't the last console and it has CON_CONSDEV set, we
1345          * need to set it on the next preferred console.
1346          */
1347         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1348                 console_drivers->flags |= CON_CONSDEV;
1349
1350         release_console_sem();
1351         return res;
1352 }
1353 EXPORT_SYMBOL(unregister_console);
1354
1355 static int __init disable_boot_consoles(void)
1356 {
1357         struct console *con;
1358
1359         for_each_console(con) {
1360                 if (con->flags & CON_BOOT) {
1361                         printk(KERN_INFO "turn off boot console %s%d\n",
1362                                 con->name, con->index);
1363                         unregister_console(con);
1364                 }
1365         }
1366         return 0;
1367 }
1368 late_initcall(disable_boot_consoles);
1369
1370 #if defined CONFIG_PRINTK
1371
1372 /*
1373  * printk rate limiting, lifted from the networking subsystem.
1374  *
1375  * This enforces a rate limit: not more than 10 kernel messages
1376  * every 5s to make a denial-of-service attack impossible.
1377  */
1378 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1379
1380 int __printk_ratelimit(const char *func)
1381 {
1382         return ___ratelimit(&printk_ratelimit_state, func);
1383 }
1384 EXPORT_SYMBOL(__printk_ratelimit);
1385
1386 /**
1387  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1388  * @caller_jiffies: pointer to caller's state
1389  * @interval_msecs: minimum interval between prints
1390  *
1391  * printk_timed_ratelimit() returns true if more than @interval_msecs
1392  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1393  * returned true.
1394  */
1395 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1396                         unsigned int interval_msecs)
1397 {
1398         if (*caller_jiffies == 0
1399                         || !time_in_range(jiffies, *caller_jiffies,
1400                                         *caller_jiffies
1401                                         + msecs_to_jiffies(interval_msecs))) {
1402                 *caller_jiffies = jiffies;
1403                 return true;
1404         }
1405         return false;
1406 }
1407 EXPORT_SYMBOL(printk_timed_ratelimit);
1408 #endif