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