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