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