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 <andrewm@uow.edu.au>
  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/jiffies.h>
  36
  37 #include <asm/uaccess.h>
  38
  39 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
  40
  41 #ifdef        CONFIG_DEBUG_LL
  42 extern void printascii(char *);
  43 #endif
  44
  45 /* printk's without a loglevel use this.. */
  46 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
  47
  48 /* We show everything that is MORE important than this.. */
  49 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  50 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  51
  52 DECLARE_WAIT_QUEUE_HEAD(log_wait);
  53
  54 int console_printk[4] = {
  55         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  56         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  57         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  58         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  59 };
  60
  61 /*
  62  * Low level drivers may need that to know if they can schedule in
  63  * their unblank() callback or not. So let's export it.
  64  */
  65 int oops_in_progress;
  66 EXPORT_SYMBOL(oops_in_progress);
  67
  68 /*
  69  * console_sem protects the console_drivers list, and also
  70  * provides serialisation for access to the entire console
  71  * driver system.
  72  */
  73 static DECLARE_MUTEX(console_sem);
  74 static DECLARE_MUTEX(secondary_console_sem);
  75 struct console *console_drivers;
  76 /*
  77  * This is used for debugging the mess that is the VT code by
  78  * keeping track if we have the console semaphore held. It's
  79  * definitely not the perfect debug tool (we don't know if _WE_
  80  * hold it are racing, but it helps tracking those weird code
  81  * path in the console code where we end up in places I want
  82  * locked without the console sempahore held
  83  */
  84 static int console_locked, console_suspended;
  85
  86 /*
  87  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
  88  * It is also used in interesting ways to provide interlocking in
  89  * release_console_sem().
  90  */
  91 static DEFINE_SPINLOCK(logbuf_lock);
  92
  93 #define LOG_BUF_MASK    (log_buf_len-1)
  94 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
  95
  96 /*
  97  * The indices into log_buf are not constrained to log_buf_len - they
  98  * must be masked before subscripting
  99  */
 100 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
 101 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
 102 static unsigned long log_end;   /* Index into log_buf: most-recently-written-char + 1 */
 103
 104 /*
 105  *      Array of consoles built from command line options (console=)
 106  */
 107 struct console_cmdline
 108 {
 109         char    name[8];                        /* Name of the driver       */
 110         int     index;                          /* Minor dev. to use        */
 111         char    *options;                       /* Options for the driver   */
 112 };
 113
 114 #define MAX_CMDLINECONSOLES 8
 115
 116 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 117 static int selected_console = -1;
 118 static int preferred_console = -1;
 119
 120 /* Flag: console code may call schedule() */
 121 static int console_may_schedule;
 122
 123 #ifdef CONFIG_PRINTK
 124
 125 static char __log_buf[__LOG_BUF_LEN];
 126 static char *log_buf = __log_buf;
 127 static int log_buf_len = __LOG_BUF_LEN;
 128 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
 129
 130 static int __init log_buf_len_setup(char *str)
 131 {
 132         unsigned long size = memparse(str, &str);
 133         unsigned long flags;
 134
 135         if (size)
 136                 size = roundup_pow_of_two(size);
 137         if (size > log_buf_len) {
 138                 unsigned long start, dest_idx, offset;
 139                 char *new_log_buf;
 140
 141                 new_log_buf = alloc_bootmem(size);
 142                 if (!new_log_buf) {
 143                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
 144                         goto out;
 145                 }
 146
 147                 spin_lock_irqsave(&logbuf_lock, flags);
 148                 log_buf_len = size;
 149                 log_buf = new_log_buf;
 150
 151                 offset = start = min(con_start, log_start);
 152                 dest_idx = 0;
 153                 while (start != log_end) {
 154                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
 155                         start++;
 156                         dest_idx++;
 157                 }
 158                 log_start -= offset;
 159                 con_start -= offset;
 160                 log_end -= offset;
 161                 spin_unlock_irqrestore(&logbuf_lock, flags);
 162
 163                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
 164         }
 165 out:
 166         return 1;
 167 }
 168
 169 __setup("log_buf_len=", log_buf_len_setup);
 170
 171 #ifdef CONFIG_BOOT_PRINTK_DELAY
 172
 173 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
 174 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
 175
 176 static int __init boot_delay_setup(char *str)
 177 {
 178         unsigned long lpj;
 179         unsigned long long loops_per_msec;
 180
 181         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 182         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 183
 184         get_option(&str, &boot_delay);
 185         if (boot_delay > 10 * 1000)
 186                 boot_delay = 0;
 187
 188         printk_delay_msec = loops_per_msec;
 189         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 190                 "HZ: %d, printk_delay_msec: %llu\n",
 191                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
 192         return 1;
 193 }
 194 __setup("boot_delay=", boot_delay_setup);
 195
 196 static void boot_delay_msec(void)
 197 {
 198         unsigned long long k;
 199         unsigned long timeout;
 200
 201         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
 202                 return;
 203
 204         k = (unsigned long long)printk_delay_msec * boot_delay;
 205
 206         timeout = jiffies + msecs_to_jiffies(boot_delay);
 207         while (k) {
 208                 k--;
 209                 cpu_relax();
 210                 /*
 211                  * use (volatile) jiffies to prevent
 212                  * compiler reduction; loop termination via jiffies
 213                  * is secondary and may or may not happen.
 214                  */
 215                 if (time_after(jiffies, timeout))
 216                         break;
 217                 touch_nmi_watchdog();
 218         }
 219 }
 220 #else
 221 static inline void boot_delay_msec(void)
 222 {
 223 }
 224 #endif
 225
 226 /*
 227  * Return the number of unread characters in the log buffer.
 228  */
 229 int log_buf_get_len(void)
 230 {
 231         return logged_chars;
 232 }
 233
 234 /*
 235  * Copy a range of characters from the log buffer.
 236  */
 237 int log_buf_copy(char *dest, int idx, int len)
 238 {
 239         int ret, max;
 240         bool took_lock = false;
 241
 242         if (!oops_in_progress) {
 243                 spin_lock_irq(&logbuf_lock);
 244                 took_lock = true;
 245         }
 246
 247         max = log_buf_get_len();
 248         if (idx < 0 || idx >= max) {
 249                 ret = -1;
 250         } else {
 251                 if (len > max)
 252                         len = max;
 253                 ret = len;
 254                 idx += (log_end - max);
 255                 while (len-- > 0)
 256                         dest[len] = LOG_BUF(idx + len);
 257         }
 258
 259         if (took_lock)
 260                 spin_unlock_irq(&logbuf_lock);
 261
 262         return ret;
 263 }
 264
 265 /*
 266  * Extract a single character from the log buffer.
 267  */
 268 int log_buf_read(int idx)
 269 {
 270         char ret;
 271
 272         if (log_buf_copy(&ret, idx, 1) == 1)
 273                 return ret;
 274         else
 275                 return -1;
 276 }
 277
 278 /*
 279  * Commands to do_syslog:
 280  *
 281  *      0 -- Close the log.  Currently a NOP.
 282  *      1 -- Open the log. Currently a NOP.
 283  *      2 -- Read from the log.
 284  *      3 -- Read all messages remaining in the ring buffer.
 285  *      4 -- Read and clear all messages remaining in the ring buffer
 286  *      5 -- Clear ring buffer.
 287  *      6 -- Disable printk's to console
 288  *      7 -- Enable printk's to console
 289  *      8 -- Set level of messages printed to console
 290  *      9 -- Return number of unread characters in the log buffer
 291  *     10 -- Return size of the log buffer
 292  */
 293 int do_syslog(int type, char __user *buf, int len)
 294 {
 295         unsigned long i, j, limit, count;
 296         int do_clear = 0;
 297         char c;
 298         int error = 0;
 299
 300         error = security_syslog(type);
 301         if (error)
 302                 return error;
 303
 304         switch (type) {
 305         case 0:         /* Close log */
 306                 break;
 307         case 1:         /* Open log */
 308                 break;
 309         case 2:         /* Read from log */
 310                 error = -EINVAL;
 311                 if (!buf || len < 0)
 312                         goto out;
 313                 error = 0;
 314                 if (!len)
 315                         goto out;
 316                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 317                         error = -EFAULT;
 318                         goto out;
 319                 }
 320                 error = wait_event_interruptible(log_wait,
 321                                                         (log_start - log_end));
 322                 if (error)
 323                         goto out;
 324                 i = 0;
 325                 spin_lock_irq(&logbuf_lock);
 326                 while (!error && (log_start != log_end) && i < len) {
 327                         c = LOG_BUF(log_start);
 328                         log_start++;
 329                         spin_unlock_irq(&logbuf_lock);
 330                         error = __put_user(c,buf);
 331                         buf++;
 332                         i++;
 333                         cond_resched();
 334                         spin_lock_irq(&logbuf_lock);
 335                 }
 336                 spin_unlock_irq(&logbuf_lock);
 337                 if (!error)
 338                         error = i;
 339                 break;
 340         case 4:         /* Read/clear last kernel messages */
 341                 do_clear = 1;
 342                 /* FALL THRU */
 343         case 3:         /* Read last kernel messages */
 344                 error = -EINVAL;
 345                 if (!buf || len < 0)
 346                         goto out;
 347                 error = 0;
 348                 if (!len)
 349                         goto out;
 350                 if (!access_ok(VERIFY_WRITE, buf, len)) {
 351                         error = -EFAULT;
 352                         goto out;
 353                 }
 354                 count = len;
 355                 if (count > log_buf_len)
 356                         count = log_buf_len;
 357                 spin_lock_irq(&logbuf_lock);
 358                 if (count > logged_chars)
 359                         count = logged_chars;
 360                 if (do_clear)
 361                         logged_chars = 0;
 362                 limit = log_end;
 363                 /*
 364                  * __put_user() could sleep, and while we sleep
 365                  * printk() could overwrite the messages
 366                  * we try to copy to user space. Therefore
 367                  * the messages are copied in reverse. <manfreds>
 368                  */
 369                 for (i = 0; i < count && !error; i++) {
 370                         j = limit-1-i;
 371                         if (j + log_buf_len < log_end)
 372                                 break;
 373                         c = LOG_BUF(j);
 374                         spin_unlock_irq(&logbuf_lock);
 375                         error = __put_user(c,&buf[count-1-i]);
 376                         cond_resched();
 377                         spin_lock_irq(&logbuf_lock);
 378                 }
 379                 spin_unlock_irq(&logbuf_lock);
 380                 if (error)
 381                         break;
 382                 error = i;
 383                 if (i != count) {
 384                         int offset = count-error;
 385                         /* buffer overflow during copy, correct user buffer. */
 386                         for (i = 0; i < error; i++) {
 387                                 if (__get_user(c,&buf[i+offset]) ||
 388                                     __put_user(c,&buf[i])) {
 389                                         error = -EFAULT;
 390                                         break;
 391                                 }
 392                                 cond_resched();
 393                         }
 394                 }
 395                 break;
 396         case 5:         /* Clear ring buffer */
 397                 logged_chars = 0;
 398                 break;
 399         case 6:         /* Disable logging to console */
 400                 console_loglevel = minimum_console_loglevel;
 401                 break;
 402         case 7:         /* Enable logging to console */
 403                 console_loglevel = default_console_loglevel;
 404                 break;
 405         case 8:         /* Set level of messages printed to console */
 406                 error = -EINVAL;
 407                 if (len < 1 || len > 8)
 408                         goto out;
 409                 if (len < minimum_console_loglevel)
 410                         len = minimum_console_loglevel;
 411                 console_loglevel = len;
 412                 error = 0;
 413                 break;
 414         case 9:         /* Number of chars in the log buffer */
 415                 error = log_end - log_start;
 416                 break;
 417         case 10:        /* Size of the log buffer */
 418                 error = log_buf_len;
 419                 break;
 420         default:
 421                 error = -EINVAL;
 422                 break;
 423         }
 424 out:
 425         return error;
 426 }
 427
 428 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 429 {
 430         return do_syslog(type, buf, len);
 431 }
 432
 433 /*
 434  * Call the console drivers on a range of log_buf
 435  */
 436 static void __call_console_drivers(unsigned long start, unsigned long end)
 437 {
 438         struct console *con;
 439
 440         for (con = console_drivers; con; con = con->next) {
 441                 if ((con->flags & CON_ENABLED) && con->write &&
 442                                 (cpu_online(smp_processor_id()) ||
 443                                 (con->flags & CON_ANYTIME)))
 444                         con->write(con, &LOG_BUF(start), end - start);
 445         }
 446 }
 447
 448 static int __read_mostly ignore_loglevel;
 449
 450 static int __init ignore_loglevel_setup(char *str)
 451 {
 452         ignore_loglevel = 1;
 453         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 454
 455         return 1;
 456 }
 457
 458 __setup("ignore_loglevel", ignore_loglevel_setup);
 459
 460 /*
 461  * Write out chars from start to end - 1 inclusive
 462  */
 463 static void _call_console_drivers(unsigned long start,
 464                                 unsigned long end, int msg_log_level)
 465 {
 466         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
 467                         console_drivers && start != end) {
 468                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
 469                         /* wrapped write */
 470                         __call_console_drivers(start & LOG_BUF_MASK,
 471                                                 log_buf_len);
 472                         __call_console_drivers(0, end & LOG_BUF_MASK);
 473                 } else {
 474                         __call_console_drivers(start, end);
 475                 }
 476         }
 477 }
 478
 479 /*
 480  * Call the console drivers, asking them to write out
 481  * log_buf[start] to log_buf[end - 1].
 482  * The console_sem must be held.
 483  */
 484 static void call_console_drivers(unsigned long start, unsigned long end)
 485 {
 486         unsigned long cur_index, start_print;
 487         static int msg_level = -1;
 488
 489         BUG_ON(((long)(start - end)) > 0);
 490
 491         cur_index = start;
 492         start_print = start;
 493         while (cur_index != end) {
 494                 if (msg_level < 0 && ((end - cur_index) > 2) &&
 495                                 LOG_BUF(cur_index + 0) == '<' &&
 496                                 LOG_BUF(cur_index + 1) >= '0' &&
 497                                 LOG_BUF(cur_index + 1) <= '7' &&
 498                                 LOG_BUF(cur_index + 2) == '>') {
 499                         msg_level = LOG_BUF(cur_index + 1) - '0';
 500                         cur_index += 3;
 501                         start_print = cur_index;
 502                 }
 503                 while (cur_index != end) {
 504                         char c = LOG_BUF(cur_index);
 505
 506                         cur_index++;
 507                         if (c == '\n') {
 508                                 if (msg_level < 0) {
 509                                         /*
 510                                          * printk() has already given us loglevel tags in
 511                                          * the buffer.  This code is here in case the
 512                                          * log buffer has wrapped right round and scribbled
 513                                          * on those tags
 514                                          */
 515                                         msg_level = default_message_loglevel;
 516                                 }
 517                                 _call_console_drivers(start_print, cur_index, msg_level);
 518                                 msg_level = -1;
 519                                 start_print = cur_index;
 520                                 break;
 521                         }
 522                 }
 523         }
 524         _call_console_drivers(start_print, end, msg_level);
 525 }
 526
 527 static void emit_log_char(char c)
 528 {
 529         LOG_BUF(log_end) = c;
 530         log_end++;
 531         if (log_end - log_start > log_buf_len)
 532                 log_start = log_end - log_buf_len;
 533         if (log_end - con_start > log_buf_len)
 534                 con_start = log_end - log_buf_len;
 535         if (logged_chars < log_buf_len)
 536                 logged_chars++;
 537 }
 538
 539 /*
 540  * Zap console related locks when oopsing. Only zap at most once
 541  * every 10 seconds, to leave time for slow consoles to print a
 542  * full oops.
 543  */
 544 static void zap_locks(void)
 545 {
 546         static unsigned long oops_timestamp;
 547
 548         if (time_after_eq(jiffies, oops_timestamp) &&
 549                         !time_after(jiffies, oops_timestamp + 30 * HZ))
 550                 return;
 551
 552         oops_timestamp = jiffies;
 553
 554         /* If a crash is occurring, make sure we can't deadlock */
 555         spin_lock_init(&logbuf_lock);
 556         /* And make sure that we print immediately */
 557         init_MUTEX(&console_sem);
 558 }
 559
 560 static int printk_time = 0;
 561
 562 #ifdef CONFIG_PRINTK_TIME
 563
 564 /*
 565  * Initialize printk time. Note that on some systems sched_clock()
 566  * does not work until timer is initialized.
 567  */
 568 static int __init printk_time_init(void)
 569 {
 570         printk_time = 1;
 571
 572         return 0;
 573 }
 574 subsys_initcall(printk_time_init);
 575
 576 #else
 577
 578 static int __init printk_time_setup(char *str)
 579 {
 580         if (*str)
 581                 return 0;
 582         printk_time = 1;
 583         printk(KERN_NOTICE "The 'time' option is deprecated and "
 584                 "is scheduled for removal in early 2008\n");
 585         printk(KERN_NOTICE "Use 'printk.time=<value>' instead\n");
 586         return 1;
 587 }
 588
 589 __setup("time", printk_time_setup);
 590
 591 #endif
 592 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 593
 594 __attribute__((weak)) unsigned long long printk_clock(void)
 595 {
 596         return sched_clock();
 597 }
 598
 599 /* Check if we have any console registered that can be called early in boot. */
 600 static int have_callable_console(void)
 601 {
 602         struct console *con;
 603
 604         for (con = console_drivers; con; con = con->next)
 605                 if (con->flags & CON_ANYTIME)
 606                         return 1;
 607
 608         return 0;
 609 }
 610
 611 /**
 612  * printk - print a kernel message
 613  * @fmt: format string
 614  *
 615  * This is printk().  It can be called from any context.  We want it to work.
 616  * Be aware of the fact that if oops_in_progress is not set, we might try to
 617  * wake klogd up which could deadlock on runqueue lock if printk() is called
 618  * from scheduler code.
 619  *
 620  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
 621  * call the console drivers.  If we fail to get the semaphore we place the output
 622  * into the log buffer and return.  The current holder of the console_sem will
 623  * notice the new output in release_console_sem() and will send it to the
 624  * consoles before releasing the semaphore.
 625  *
 626  * One effect of this deferred printing is that code which calls printk() and
 627  * then changes console_loglevel may break. This is because console_loglevel
 628  * is inspected when the actual printing occurs.
 629  *
 630  * See also:
 631  * printf(3)
 632  */
 633
 634 asmlinkage int printk(const char *fmt, ...)
 635 {
 636         va_list args;
 637         int r;
 638
 639         va_start(args, fmt);
 640         r = vprintk(fmt, args);
 641         va_end(args);
 642
 643         return r;
 644 }
 645
 646 /* cpu currently holding logbuf_lock */
 647 static volatile unsigned int printk_cpu = UINT_MAX;
 648
 649 asmlinkage int vprintk(const char *fmt, va_list args)
 650 {
 651         unsigned long flags;
 652         int printed_len;
 653         char *p;
 654         static char printk_buf[1024];
 655         static int log_level_unknown = 1;
 656
 657         boot_delay_msec();
 658
 659         preempt_disable();
 660         if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
 661                 /* If a crash is occurring during printk() on this CPU,
 662                  * make sure we can't deadlock */
 663                 zap_locks();
 664
 665         /* This stops the holder of console_sem just where we want him */
 666         raw_local_irq_save(flags);
 667         lockdep_off();
 668         spin_lock(&logbuf_lock);
 669         printk_cpu = smp_processor_id();
 670
 671         /* Emit the output into the temporary buffer */
 672         printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
 673
 674 #ifdef  CONFIG_DEBUG_LL
 675         printascii(printk_buf);
 676 #endif
 677
 678         /*
 679          * Copy the output into log_buf.  If the caller didn't provide
 680          * appropriate log level tags, we insert them here
 681          */
 682         for (p = printk_buf; *p; p++) {
 683                 if (log_level_unknown) {
 684                         /* log_level_unknown signals the start of a new line */
 685                         if (printk_time) {
 686                                 int loglev_char;
 687                                 char tbuf[50], *tp;
 688                                 unsigned tlen;
 689                                 unsigned long long t;
 690                                 unsigned long nanosec_rem;
 691
 692                                 /*
 693                                  * force the log level token to be
 694                                  * before the time output.
 695                                  */
 696                                 if (p[0] == '<' && p[1] >='0' &&
 697                                    p[1] <= '7' && p[2] == '>') {
 698                                         loglev_char = p[1];
 699                                         p += 3;
 700                                         printed_len -= 3;
 701                                 } else {
 702                                         loglev_char = default_message_loglevel
 703                                                 + '0';
 704                                 }
 705                                 t = printk_clock();
 706                                 nanosec_rem = do_div(t, 1000000000);
 707                                 tlen = sprintf(tbuf,
 708                                                 "<%c>[%5lu.%06lu] ",
 709                                                 loglev_char,
 710                                                 (unsigned long)t,
 711                                                 nanosec_rem/1000);
 712
 713                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
 714                                         emit_log_char(*tp);
 715                                 printed_len += tlen;
 716                         } else {
 717                                 if (p[0] != '<' || p[1] < '0' ||
 718                                    p[1] > '7' || p[2] != '>') {
 719                                         emit_log_char('<');
 720                                         emit_log_char(default_message_loglevel
 721                                                 + '0');
 722                                         emit_log_char('>');
 723                                         printed_len += 3;
 724                                 }
 725                         }
 726                         log_level_unknown = 0;
 727                         if (!*p)
 728                                 break;
 729                 }
 730                 emit_log_char(*p);
 731                 if (*p == '\n')
 732                         log_level_unknown = 1;
 733         }
 734
 735         if (!down_trylock(&console_sem)) {
 736                 /*
 737                  * We own the drivers.  We can drop the spinlock and
 738                  * let release_console_sem() print the text, maybe ...
 739                  */
 740                 console_locked = 1;
 741                 printk_cpu = UINT_MAX;
 742                 spin_unlock(&logbuf_lock);
 743
 744                 /*
 745                  * Console drivers may assume that per-cpu resources have
 746                  * been allocated. So unless they're explicitly marked as
 747                  * being able to cope (CON_ANYTIME) don't call them until
 748                  * this CPU is officially up.
 749                  */
 750                 if (cpu_online(smp_processor_id()) || have_callable_console()) {
 751                         console_may_schedule = 0;
 752                         release_console_sem();
 753                 } else {
 754                         /* Release by hand to avoid flushing the buffer. */
 755                         console_locked = 0;
 756                         up(&console_sem);
 757                 }
 758                 lockdep_on();
 759                 raw_local_irq_restore(flags);
 760         } else {
 761                 /*
 762                  * Someone else owns the drivers.  We drop the spinlock, which
 763                  * allows the semaphore holder to proceed and to call the
 764                  * console drivers with the output which we just produced.
 765                  */
 766                 printk_cpu = UINT_MAX;
 767                 spin_unlock(&logbuf_lock);
 768                 lockdep_on();
 769                 raw_local_irq_restore(flags);
 770         }
 771
 772         preempt_enable();
 773         return printed_len;
 774 }
 775 EXPORT_SYMBOL(printk);
 776 EXPORT_SYMBOL(vprintk);
 777
 778 #else
 779
 780 asmlinkage long sys_syslog(int type, char __user *buf, int len)
 781 {
 782         return -ENOSYS;
 783 }
 784
 785 static void call_console_drivers(unsigned long start, unsigned long end)
 786 {
 787 }
 788
 789 #endif
 790
 791 /*
 792  * Set up a list of consoles.  Called from init/main.c
 793  */
 794 static int __init console_setup(char *str)
 795 {
 796         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
 797         char *s, *options;
 798         int idx;
 799
 800         /*
 801          * Decode str into name, index, options.
 802          */
 803         if (str[0] >= '0' && str[0] <= '9') {
 804                 strcpy(buf, "ttyS");
 805                 strncpy(buf + 4, str, sizeof(buf) - 5);
 806         } else {
 807                 strncpy(buf, str, sizeof(buf) - 1);
 808         }
 809         buf[sizeof(buf) - 1] = 0;
 810         if ((options = strchr(str, ',')) != NULL)
 811                 *(options++) = 0;
 812 #ifdef __sparc__
 813         if (!strcmp(str, "ttya"))
 814                 strcpy(buf, "ttyS0");
 815         if (!strcmp(str, "ttyb"))
 816                 strcpy(buf, "ttyS1");
 817 #endif
 818         for (s = buf; *s; s++)
 819                 if ((*s >= '0' && *s <= '9') || *s == ',')
 820                         break;
 821         idx = simple_strtoul(s, NULL, 10);
 822         *s = 0;
 823
 824         add_preferred_console(buf, idx, options);
 825         return 1;
 826 }
 827 __setup("console=", console_setup);
 828
 829 /**
 830  * add_preferred_console - add a device to the list of preferred consoles.
 831  * @name: device name
 832  * @idx: device index
 833  * @options: options for this console
 834  *
 835  * The last preferred console added will be used for kernel messages
 836  * and stdin/out/err for init.  Normally this is used by console_setup
 837  * above to handle user-supplied console arguments; however it can also
 838  * be used by arch-specific code either to override the user or more
 839  * commonly to provide a default console (ie from PROM variables) when
 840  * the user has not supplied one.
 841  */
 842 int add_preferred_console(char *name, int idx, char *options)
 843 {
 844         struct console_cmdline *c;
 845         int i;
 846
 847         /*
 848          *      See if this tty is not yet registered, and
 849          *      if we have a slot free.
 850          */
 851         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 852                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 853                           console_cmdline[i].index == idx) {
 854                                 selected_console = i;
 855                                 return 0;
 856                 }
 857         if (i == MAX_CMDLINECONSOLES)
 858                 return -E2BIG;
 859         selected_console = i;
 860         c = &console_cmdline[i];
 861         memcpy(c->name, name, sizeof(c->name));
 862         c->name[sizeof(c->name) - 1] = 0;
 863         c->options = options;
 864         c->index = idx;
 865         return 0;
 866 }
 867
 868 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
 869 {
 870         struct console_cmdline *c;
 871         int i;
 872
 873         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
 874                 if (strcmp(console_cmdline[i].name, name) == 0 &&
 875                           console_cmdline[i].index == idx) {
 876                                 c = &console_cmdline[i];
 877                                 memcpy(c->name, name_new, sizeof(c->name));
 878                                 c->name[sizeof(c->name) - 1] = 0;
 879                                 c->options = options;
 880                                 c->index = idx_new;
 881                                 return i;
 882                 }
 883         /* not found */
 884         return -1;
 885 }
 886
 887 int console_suspend_enabled = 1;
 888 EXPORT_SYMBOL(console_suspend_enabled);
 889
 890 static int __init console_suspend_disable(char *str)
 891 {
 892         console_suspend_enabled = 0;
 893         return 1;
 894 }
 895 __setup("no_console_suspend", console_suspend_disable);
 896
 897 /**
 898  * suspend_console - suspend the console subsystem
 899  *
 900  * This disables printk() while we go into suspend states
 901  */
 902 void suspend_console(void)
 903 {
 904         if (!console_suspend_enabled)
 905                 return;
 906         printk("Suspending console(s)\n");
 907         acquire_console_sem();
 908         console_suspended = 1;
 909 }
 910
 911 void resume_console(void)
 912 {
 913         if (!console_suspend_enabled)
 914                 return;
 915         console_suspended = 0;
 916         release_console_sem();
 917 }
 918
 919 /**
 920  * acquire_console_sem - lock the console system for exclusive use.
 921  *
 922  * Acquires a semaphore which guarantees that the caller has
 923  * exclusive access to the console system and the console_drivers list.
 924  *
 925  * Can sleep, returns nothing.
 926  */
 927 void acquire_console_sem(void)
 928 {
 929         BUG_ON(in_interrupt());
 930         if (console_suspended) {
 931                 down(&secondary_console_sem);
 932                 return;
 933         }
 934         down(&console_sem);
 935         console_locked = 1;
 936         console_may_schedule = 1;
 937 }
 938 EXPORT_SYMBOL(acquire_console_sem);
 939
 940 int try_acquire_console_sem(void)
 941 {
 942         if (down_trylock(&console_sem))
 943                 return -1;
 944         console_locked = 1;
 945         console_may_schedule = 0;
 946         return 0;
 947 }
 948 EXPORT_SYMBOL(try_acquire_console_sem);
 949
 950 int is_console_locked(void)
 951 {
 952         return console_locked;
 953 }
 954
 955 void wake_up_klogd(void)
 956 {
 957         if (!oops_in_progress && waitqueue_active(&log_wait))
 958                 wake_up_interruptible(&log_wait);
 959 }
 960
 961 /**
 962  * release_console_sem - unlock the console system
 963  *
 964  * Releases the semaphore which the caller holds on the console system
 965  * and the console driver list.
 966  *
 967  * While the semaphore was held, console output may have been buffered
 968  * by printk().  If this is the case, release_console_sem() emits
 969  * the output prior to releasing the semaphore.
 970  *
 971  * If there is output waiting for klogd, we wake it up.
 972  *
 973  * release_console_sem() may be called from any context.
 974  */
 975 void release_console_sem(void)
 976 {
 977         unsigned long flags;
 978         unsigned long _con_start, _log_end;
 979         unsigned long wake_klogd = 0;
 980
 981         if (console_suspended) {
 982                 up(&secondary_console_sem);
 983                 return;
 984         }
 985
 986         console_may_schedule = 0;
 987
 988         for ( ; ; ) {
 989                 spin_lock_irqsave(&logbuf_lock, flags);
 990                 wake_klogd |= log_start - log_end;
 991                 if (con_start == log_end)
 992                         break;                  /* Nothing to print */
 993                 _con_start = con_start;
 994                 _log_end = log_end;
 995                 con_start = log_end;            /* Flush */
 996                 spin_unlock(&logbuf_lock);
 997                 call_console_drivers(_con_start, _log_end);
 998                 local_irq_restore(flags);
 999         }
1000         console_locked = 0;
1001         up(&console_sem);
1002         spin_unlock_irqrestore(&logbuf_lock, flags);
1003         if (wake_klogd)
1004                 wake_up_klogd();
1005 }
1006 EXPORT_SYMBOL(release_console_sem);
1007
1008 /**
1009  * console_conditional_schedule - yield the CPU if required
1010  *
1011  * If the console code is currently allowed to sleep, and
1012  * if this CPU should yield the CPU to another task, do
1013  * so here.
1014  *
1015  * Must be called within acquire_console_sem().
1016  */
1017 void __sched console_conditional_schedule(void)
1018 {
1019         if (console_may_schedule)
1020                 cond_resched();
1021 }
1022 EXPORT_SYMBOL(console_conditional_schedule);
1023
1024 void console_print(const char *s)
1025 {
1026         printk(KERN_EMERG "%s", s);
1027 }
1028 EXPORT_SYMBOL(console_print);
1029
1030 void console_unblank(void)
1031 {
1032         struct console *c;
1033
1034         /*
1035          * console_unblank can no longer be called in interrupt context unless
1036          * oops_in_progress is set to 1..
1037          */
1038         if (oops_in_progress) {
1039                 if (down_trylock(&console_sem) != 0)
1040                         return;
1041         } else
1042                 acquire_console_sem();
1043
1044         console_locked = 1;
1045         console_may_schedule = 0;
1046         for (c = console_drivers; c != NULL; c = c->next)
1047                 if ((c->flags & CON_ENABLED) && c->unblank)
1048                         c->unblank();
1049         release_console_sem();
1050 }
1051
1052 /*
1053  * Return the console tty driver structure and its associated index
1054  */
1055 struct tty_driver *console_device(int *index)
1056 {
1057         struct console *c;
1058         struct tty_driver *driver = NULL;
1059
1060         acquire_console_sem();
1061         for (c = console_drivers; c != NULL; c = c->next) {
1062                 if (!c->device)
1063                         continue;
1064                 driver = c->device(c, index);
1065                 if (driver)
1066                         break;
1067         }
1068         release_console_sem();
1069         return driver;
1070 }
1071
1072 /*
1073  * Prevent further output on the passed console device so that (for example)
1074  * serial drivers can disable console output before suspending a port, and can
1075  * re-enable output afterwards.
1076  */
1077 void console_stop(struct console *console)
1078 {
1079         acquire_console_sem();
1080         console->flags &= ~CON_ENABLED;
1081         release_console_sem();
1082 }
1083 EXPORT_SYMBOL(console_stop);
1084
1085 void console_start(struct console *console)
1086 {
1087         acquire_console_sem();
1088         console->flags |= CON_ENABLED;
1089         release_console_sem();
1090 }
1091 EXPORT_SYMBOL(console_start);
1092
1093 /*
1094  * The console driver calls this routine during kernel initialization
1095  * to register the console printing procedure with printk() and to
1096  * print any messages that were printed by the kernel before the
1097  * console driver was initialized.
1098  */
1099 void register_console(struct console *console)
1100 {
1101         int i;
1102         unsigned long flags;
1103         struct console *bootconsole = NULL;
1104
1105         if (console_drivers) {
1106                 if (console->flags & CON_BOOT)
1107                         return;
1108                 if (console_drivers->flags & CON_BOOT)
1109                         bootconsole = console_drivers;
1110         }
1111
1112         if (preferred_console < 0 || bootconsole || !console_drivers)
1113                 preferred_console = selected_console;
1114
1115         if (console->early_setup)
1116                 console->early_setup();
1117
1118         /*
1119          *      See if we want to use this console driver. If we
1120          *      didn't select a console we take the first one
1121          *      that registers here.
1122          */
1123         if (preferred_console < 0) {
1124                 if (console->index < 0)
1125                         console->index = 0;
1126                 if (console->setup == NULL ||
1127                     console->setup(console, NULL) == 0) {
1128                         console->flags |= CON_ENABLED | CON_CONSDEV;
1129                         preferred_console = 0;
1130                 }
1131         }
1132
1133         /*
1134          *      See if this console matches one we selected on
1135          *      the command line.
1136          */
1137         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1138                         i++) {
1139                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1140                         continue;
1141                 if (console->index >= 0 &&
1142                     console->index != console_cmdline[i].index)
1143                         continue;
1144                 if (console->index < 0)
1145                         console->index = console_cmdline[i].index;
1146                 if (console->setup &&
1147                     console->setup(console, console_cmdline[i].options) != 0)
1148                         break;
1149                 console->flags |= CON_ENABLED;
1150                 console->index = console_cmdline[i].index;
1151                 if (i == selected_console) {
1152                         console->flags |= CON_CONSDEV;
1153                         preferred_console = selected_console;
1154                 }
1155                 break;
1156         }
1157
1158         if (!(console->flags & CON_ENABLED))
1159                 return;
1160
1161         if (bootconsole && (console->flags & CON_CONSDEV)) {
1162                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1163                        bootconsole->name, bootconsole->index,
1164                        console->name, console->index);
1165                 unregister_console(bootconsole);
1166                 console->flags &= ~CON_PRINTBUFFER;
1167         } else {
1168                 printk(KERN_INFO "console [%s%d] enabled\n",
1169                        console->name, console->index);
1170         }
1171
1172         /*
1173          *      Put this console in the list - keep the
1174          *      preferred driver at the head of the list.
1175          */
1176         acquire_console_sem();
1177         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1178                 console->next = console_drivers;
1179                 console_drivers = console;
1180                 if (console->next)
1181                         console->next->flags &= ~CON_CONSDEV;
1182         } else {
1183                 console->next = console_drivers->next;
1184                 console_drivers->next = console;
1185         }
1186         if (console->flags & CON_PRINTBUFFER) {
1187                 /*
1188                  * release_console_sem() will print out the buffered messages
1189                  * for us.
1190                  */
1191                 spin_lock_irqsave(&logbuf_lock, flags);
1192                 con_start = log_start;
1193                 spin_unlock_irqrestore(&logbuf_lock, flags);
1194         }
1195         release_console_sem();
1196 }
1197 EXPORT_SYMBOL(register_console);
1198
1199 int unregister_console(struct console *console)
1200 {
1201         struct console *a, *b;
1202         int res = 1;
1203
1204         acquire_console_sem();
1205         if (console_drivers == console) {
1206                 console_drivers=console->next;
1207                 res = 0;
1208         } else if (console_drivers) {
1209                 for (a=console_drivers->next, b=console_drivers ;
1210                      a; b=a, a=b->next) {
1211                         if (a == console) {
1212                                 b->next = a->next;
1213                                 res = 0;
1214                                 break;
1215                         }
1216                 }
1217         }
1218
1219         /*
1220          * If this isn't the last console and it has CON_CONSDEV set, we
1221          * need to set it on the next preferred console.
1222          */
1223         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1224                 console_drivers->flags |= CON_CONSDEV;
1225
1226         release_console_sem();
1227         return res;
1228 }
1229 EXPORT_SYMBOL(unregister_console);
1230
1231 static int __init disable_boot_consoles(void)
1232 {
1233         if (console_drivers != NULL) {
1234                 if (console_drivers->flags & CON_BOOT) {
1235                         printk(KERN_INFO "turn off boot console %s%d\n",
1236                                 console_drivers->name, console_drivers->index);
1237                         return unregister_console(console_drivers);
1238                 }
1239         }
1240         return 0;
1241 }
1242 late_initcall(disable_boot_consoles);
1243
1244 /**
1245  * tty_write_message - write a message to a certain tty, not just the console.
1246  * @tty: the destination tty_struct
1247  * @msg: the message to write
1248  *
1249  * This is used for messages that need to be redirected to a specific tty.
1250  * We don't put it into the syslog queue right now maybe in the future if
1251  * really needed.
1252  */
1253 void tty_write_message(struct tty_struct *tty, char *msg)
1254 {
1255         if (tty && tty->driver->write)
1256                 tty->driver->write(tty, msg, strlen(msg));
1257         return;
1258 }
1259
1260 /*
1261  * printk rate limiting, lifted from the networking subsystem.
1262  *
1263  * This enforces a rate limit: not more than one kernel message
1264  * every printk_ratelimit_jiffies to make a denial-of-service
1265  * attack impossible.
1266  */
1267 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1268 {
1269         static DEFINE_SPINLOCK(ratelimit_lock);
1270         static unsigned long toks = 10 * 5 * HZ;
1271         static unsigned long last_msg;
1272         static int missed;
1273         unsigned long flags;
1274         unsigned long now = jiffies;
1275
1276         spin_lock_irqsave(&ratelimit_lock, flags);
1277         toks += now - last_msg;
1278         last_msg = now;
1279         if (toks > (ratelimit_burst * ratelimit_jiffies))
1280                 toks = ratelimit_burst * ratelimit_jiffies;
1281         if (toks >= ratelimit_jiffies) {
1282                 int lost = missed;
1283
1284                 missed = 0;
1285                 toks -= ratelimit_jiffies;
1286                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1287                 if (lost)
1288                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1289                 return 1;
1290         }
1291         missed++;
1292         spin_unlock_irqrestore(&ratelimit_lock, flags);
1293         return 0;
1294 }
1295 EXPORT_SYMBOL(__printk_ratelimit);
1296
1297 /* minimum time in jiffies between messages */
1298 int printk_ratelimit_jiffies = 5 * HZ;
1299
1300 /* number of messages we send before ratelimiting */
1301 int printk_ratelimit_burst = 10;
1302
1303 int printk_ratelimit(void)
1304 {
1305         return __printk_ratelimit(printk_ratelimit_jiffies,
1306                                 printk_ratelimit_burst);
1307 }
1308 EXPORT_SYMBOL(printk_ratelimit);
1309
1310 /**
1311  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1312  * @caller_jiffies: pointer to caller's state
1313  * @interval_msecs: minimum interval between prints
1314  *
1315  * printk_timed_ratelimit() returns true if more than @interval_msecs
1316  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1317  * returned true.
1318  */
1319 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1320                         unsigned int interval_msecs)
1321 {
1322         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1323                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1324                 return true;
1325         }
1326         return false;
1327 }
1328 EXPORT_SYMBOL(printk_timed_ratelimit);