linux/kernel/panic.c
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   1/*
   2 *  linux/kernel/panic.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 */
   6
   7/*
   8 * This function is used through-out the kernel (including mm and fs)
   9 * to indicate a major problem.
  10 */
  11#include <linux/debug_locks.h>
  12#include <linux/interrupt.h>
  13#include <linux/kmsg_dump.h>
  14#include <linux/kallsyms.h>
  15#include <linux/notifier.h>
  16#include <linux/module.h>
  17#include <linux/random.h>
  18#include <linux/reboot.h>
  19#include <linux/delay.h>
  20#include <linux/kexec.h>
  21#include <linux/sched.h>
  22#include <linux/sysrq.h>
  23#include <linux/init.h>
  24#include <linux/nmi.h>
  25#include <linux/dmi.h>
  26
  27#define PANIC_TIMER_STEP 100
  28#define PANIC_BLINK_SPD 18
  29
  30int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
  31static unsigned long tainted_mask;
  32static int pause_on_oops;
  33static int pause_on_oops_flag;
  34static DEFINE_SPINLOCK(pause_on_oops_lock);
  35
  36int panic_timeout;
  37EXPORT_SYMBOL_GPL(panic_timeout);
  38
  39ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
  40
  41EXPORT_SYMBOL(panic_notifier_list);
  42
  43static long no_blink(int state)
  44{
  45        return 0;
  46}
  47
  48/* Returns how long it waited in ms */
  49long (*panic_blink)(int state);
  50EXPORT_SYMBOL(panic_blink);
  51
  52/*
  53 * Stop ourself in panic -- architecture code may override this
  54 */
  55void __weak panic_smp_self_stop(void)
  56{
  57        while (1)
  58                cpu_relax();
  59}
  60
  61/**
  62 *      panic - halt the system
  63 *      @fmt: The text string to print
  64 *
  65 *      Display a message, then perform cleanups.
  66 *
  67 *      This function never returns.
  68 */
  69void panic(const char *fmt, ...)
  70{
  71        static DEFINE_SPINLOCK(panic_lock);
  72        static char buf[1024];
  73        va_list args;
  74        long i, i_next = 0;
  75        int state = 0;
  76
  77        /*
  78         * Disable local interrupts. This will prevent panic_smp_self_stop
  79         * from deadlocking the first cpu that invokes the panic, since
  80         * there is nothing to prevent an interrupt handler (that runs
  81         * after the panic_lock is acquired) from invoking panic again.
  82         */
  83        local_irq_disable();
  84
  85        /*
  86         * It's possible to come here directly from a panic-assertion and
  87         * not have preempt disabled. Some functions called from here want
  88         * preempt to be disabled. No point enabling it later though...
  89         *
  90         * Only one CPU is allowed to execute the panic code from here. For
  91         * multiple parallel invocations of panic, all other CPUs either
  92         * stop themself or will wait until they are stopped by the 1st CPU
  93         * with smp_send_stop().
  94         */
  95        if (!spin_trylock(&panic_lock))
  96                panic_smp_self_stop();
  97
  98        console_verbose();
  99        bust_spinlocks(1);
 100        va_start(args, fmt);
 101        vsnprintf(buf, sizeof(buf), fmt, args);
 102        va_end(args);
 103        printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
 104#ifdef CONFIG_DEBUG_BUGVERBOSE
 105        /*
 106         * Avoid nested stack-dumping if a panic occurs during oops processing
 107         */
 108        if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
 109                dump_stack();
 110#endif
 111
 112        /*
 113         * If we have crashed and we have a crash kernel loaded let it handle
 114         * everything else.
 115         * Do we want to call this before we try to display a message?
 116         */
 117        crash_kexec(NULL);
 118
 119        /*
 120         * Note smp_send_stop is the usual smp shutdown function, which
 121         * unfortunately means it may not be hardened to work in a panic
 122         * situation.
 123         */
 124        smp_send_stop();
 125
 126        kmsg_dump(KMSG_DUMP_PANIC);
 127
 128        atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
 129
 130        bust_spinlocks(0);
 131
 132        if (!panic_blink)
 133                panic_blink = no_blink;
 134
 135        if (panic_timeout > 0) {
 136                /*
 137                 * Delay timeout seconds before rebooting the machine.
 138                 * We can't use the "normal" timers since we just panicked.
 139                 */
 140                printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
 141
 142                for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
 143                        touch_nmi_watchdog();
 144                        if (i >= i_next) {
 145                                i += panic_blink(state ^= 1);
 146                                i_next = i + 3600 / PANIC_BLINK_SPD;
 147                        }
 148                        mdelay(PANIC_TIMER_STEP);
 149                }
 150        }
 151        if (panic_timeout != 0) {
 152                /*
 153                 * This will not be a clean reboot, with everything
 154                 * shutting down.  But if there is a chance of
 155                 * rebooting the system it will be rebooted.
 156                 */
 157                emergency_restart();
 158        }
 159#ifdef __sparc__
 160        {
 161                extern int stop_a_enabled;
 162                /* Make sure the user can actually press Stop-A (L1-A) */
 163                stop_a_enabled = 1;
 164                printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
 165        }
 166#endif
 167#if defined(CONFIG_S390)
 168        {
 169                unsigned long caller;
 170
 171                caller = (unsigned long)__builtin_return_address(0);
 172                disabled_wait(caller);
 173        }
 174#endif
 175        local_irq_enable();
 176        for (i = 0; ; i += PANIC_TIMER_STEP) {
 177                touch_softlockup_watchdog();
 178                if (i >= i_next) {
 179                        i += panic_blink(state ^= 1);
 180                        i_next = i + 3600 / PANIC_BLINK_SPD;
 181                }
 182                mdelay(PANIC_TIMER_STEP);
 183        }
 184}
 185
 186EXPORT_SYMBOL(panic);
 187
 188
 189struct tnt {
 190        u8      bit;
 191        char    true;
 192        char    false;
 193};
 194
 195static const struct tnt tnts[] = {
 196        { TAINT_PROPRIETARY_MODULE,     'P', 'G' },
 197        { TAINT_FORCED_MODULE,          'F', ' ' },
 198        { TAINT_UNSAFE_SMP,             'S', ' ' },
 199        { TAINT_FORCED_RMMOD,           'R', ' ' },
 200        { TAINT_MACHINE_CHECK,          'M', ' ' },
 201        { TAINT_BAD_PAGE,               'B', ' ' },
 202        { TAINT_USER,                   'U', ' ' },
 203        { TAINT_DIE,                    'D', ' ' },
 204        { TAINT_OVERRIDDEN_ACPI_TABLE,  'A', ' ' },
 205        { TAINT_WARN,                   'W', ' ' },
 206        { TAINT_CRAP,                   'C', ' ' },
 207        { TAINT_FIRMWARE_WORKAROUND,    'I', ' ' },
 208        { TAINT_OOT_MODULE,             'O', ' ' },
 209};
 210
 211/**
 212 *      print_tainted - return a string to represent the kernel taint state.
 213 *
 214 *  'P' - Proprietary module has been loaded.
 215 *  'F' - Module has been forcibly loaded.
 216 *  'S' - SMP with CPUs not designed for SMP.
 217 *  'R' - User forced a module unload.
 218 *  'M' - System experienced a machine check exception.
 219 *  'B' - System has hit bad_page.
 220 *  'U' - Userspace-defined naughtiness.
 221 *  'D' - Kernel has oopsed before
 222 *  'A' - ACPI table overridden.
 223 *  'W' - Taint on warning.
 224 *  'C' - modules from drivers/staging are loaded.
 225 *  'I' - Working around severe firmware bug.
 226 *  'O' - Out-of-tree module has been loaded.
 227 *
 228 *      The string is overwritten by the next call to print_tainted().
 229 */
 230const char *print_tainted(void)
 231{
 232        static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
 233
 234        if (tainted_mask) {
 235                char *s;
 236                int i;
 237
 238                s = buf + sprintf(buf, "Tainted: ");
 239                for (i = 0; i < ARRAY_SIZE(tnts); i++) {
 240                        const struct tnt *t = &tnts[i];
 241                        *s++ = test_bit(t->bit, &tainted_mask) ?
 242                                        t->true : t->false;
 243                }
 244                *s = 0;
 245        } else
 246                snprintf(buf, sizeof(buf), "Not tainted");
 247
 248        return buf;
 249}
 250
 251int test_taint(unsigned flag)
 252{
 253        return test_bit(flag, &tainted_mask);
 254}
 255EXPORT_SYMBOL(test_taint);
 256
 257unsigned long get_taint(void)
 258{
 259        return tainted_mask;
 260}
 261
 262void add_taint(unsigned flag)
 263{
 264        /*
 265         * Can't trust the integrity of the kernel anymore.
 266         * We don't call directly debug_locks_off() because the issue
 267         * is not necessarily serious enough to set oops_in_progress to 1
 268         * Also we want to keep up lockdep for staging/out-of-tree
 269         * development and post-warning case.
 270         */
 271        switch (flag) {
 272        case TAINT_CRAP:
 273        case TAINT_OOT_MODULE:
 274        case TAINT_WARN:
 275        case TAINT_FIRMWARE_WORKAROUND:
 276                break;
 277
 278        default:
 279                if (__debug_locks_off())
 280                        printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
 281        }
 282
 283        set_bit(flag, &tainted_mask);
 284}
 285EXPORT_SYMBOL(add_taint);
 286
 287static void spin_msec(int msecs)
 288{
 289        int i;
 290
 291        for (i = 0; i < msecs; i++) {
 292                touch_nmi_watchdog();
 293                mdelay(1);
 294        }
 295}
 296
 297/*
 298 * It just happens that oops_enter() and oops_exit() are identically
 299 * implemented...
 300 */
 301static void do_oops_enter_exit(void)
 302{
 303        unsigned long flags;
 304        static int spin_counter;
 305
 306        if (!pause_on_oops)
 307                return;
 308
 309        spin_lock_irqsave(&pause_on_oops_lock, flags);
 310        if (pause_on_oops_flag == 0) {
 311                /* This CPU may now print the oops message */
 312                pause_on_oops_flag = 1;
 313        } else {
 314                /* We need to stall this CPU */
 315                if (!spin_counter) {
 316                        /* This CPU gets to do the counting */
 317                        spin_counter = pause_on_oops;
 318                        do {
 319                                spin_unlock(&pause_on_oops_lock);
 320                                spin_msec(MSEC_PER_SEC);
 321                                spin_lock(&pause_on_oops_lock);
 322                        } while (--spin_counter);
 323                        pause_on_oops_flag = 0;
 324                } else {
 325                        /* This CPU waits for a different one */
 326                        while (spin_counter) {
 327                                spin_unlock(&pause_on_oops_lock);
 328                                spin_msec(1);
 329                                spin_lock(&pause_on_oops_lock);
 330                        }
 331                }
 332        }
 333        spin_unlock_irqrestore(&pause_on_oops_lock, flags);
 334}
 335
 336/*
 337 * Return true if the calling CPU is allowed to print oops-related info.
 338 * This is a bit racy..
 339 */
 340int oops_may_print(void)
 341{
 342        return pause_on_oops_flag == 0;
 343}
 344
 345/*
 346 * Called when the architecture enters its oops handler, before it prints
 347 * anything.  If this is the first CPU to oops, and it's oopsing the first
 348 * time then let it proceed.
 349 *
 350 * This is all enabled by the pause_on_oops kernel boot option.  We do all
 351 * this to ensure that oopses don't scroll off the screen.  It has the
 352 * side-effect of preventing later-oopsing CPUs from mucking up the display,
 353 * too.
 354 *
 355 * It turns out that the CPU which is allowed to print ends up pausing for
 356 * the right duration, whereas all the other CPUs pause for twice as long:
 357 * once in oops_enter(), once in oops_exit().
 358 */
 359void oops_enter(void)
 360{
 361        tracing_off();
 362        /* can't trust the integrity of the kernel anymore: */
 363        debug_locks_off();
 364        do_oops_enter_exit();
 365}
 366
 367/*
 368 * 64-bit random ID for oopses:
 369 */
 370static u64 oops_id;
 371
 372static int init_oops_id(void)
 373{
 374        if (!oops_id)
 375                get_random_bytes(&oops_id, sizeof(oops_id));
 376        else
 377                oops_id++;
 378
 379        return 0;
 380}
 381late_initcall(init_oops_id);
 382
 383void print_oops_end_marker(void)
 384{
 385        init_oops_id();
 386        printk(KERN_WARNING "---[ end trace %016llx ]---\n",
 387                (unsigned long long)oops_id);
 388}
 389
 390/*
 391 * Called when the architecture exits its oops handler, after printing
 392 * everything.
 393 */
 394void oops_exit(void)
 395{
 396        do_oops_enter_exit();
 397        print_oops_end_marker();
 398        kmsg_dump(KMSG_DUMP_OOPS);
 399}
 400
 401#ifdef WANT_WARN_ON_SLOWPATH
 402struct slowpath_args {
 403        const char *fmt;
 404        va_list args;
 405};
 406
 407static void warn_slowpath_common(const char *file, int line, void *caller,
 408                                 unsigned taint, struct slowpath_args *args)
 409{
 410        const char *board;
 411
 412        printk(KERN_WARNING "------------[ cut here ]------------\n");
 413        printk(KERN_WARNING "WARNING: at %s:%d %pS()\n", file, line, caller);
 414        board = dmi_get_system_info(DMI_PRODUCT_NAME);
 415        if (board)
 416                printk(KERN_WARNING "Hardware name: %s\n", board);
 417
 418        if (args)
 419                vprintk(args->fmt, args->args);
 420
 421        print_modules();
 422        dump_stack();
 423        print_oops_end_marker();
 424        add_taint(taint);
 425}
 426
 427void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
 428{
 429        struct slowpath_args args;
 430
 431        args.fmt = fmt;
 432        va_start(args.args, fmt);
 433        warn_slowpath_common(file, line, __builtin_return_address(0),
 434                             TAINT_WARN, &args);
 435        va_end(args.args);
 436}
 437EXPORT_SYMBOL(warn_slowpath_fmt);
 438
 439void warn_slowpath_fmt_taint(const char *file, int line,
 440                             unsigned taint, const char *fmt, ...)
 441{
 442        struct slowpath_args args;
 443
 444        args.fmt = fmt;
 445        va_start(args.args, fmt);
 446        warn_slowpath_common(file, line, __builtin_return_address(0),
 447                             taint, &args);
 448        va_end(args.args);
 449}
 450EXPORT_SYMBOL(warn_slowpath_fmt_taint);
 451
 452void warn_slowpath_null(const char *file, int line)
 453{
 454        warn_slowpath_common(file, line, __builtin_return_address(0),
 455                             TAINT_WARN, NULL);
 456}
 457EXPORT_SYMBOL(warn_slowpath_null);
 458#endif
 459
 460#ifdef CONFIG_CC_STACKPROTECTOR
 461
 462/*
 463 * Called when gcc's -fstack-protector feature is used, and
 464 * gcc detects corruption of the on-stack canary value
 465 */
 466void __stack_chk_fail(void)
 467{
 468        panic("stack-protector: Kernel stack is corrupted in: %p\n",
 469                __builtin_return_address(0));
 470}
 471EXPORT_SYMBOL(__stack_chk_fail);
 472
 473#endif
 474
 475core_param(panic, panic_timeout, int, 0644);
 476core_param(pause_on_oops, pause_on_oops, int, 0644);
 477
 478static int __init oops_setup(char *s)
 479{
 480        if (!s)
 481                return -EINVAL;
 482        if (!strcmp(s, "panic"))
 483                panic_on_oops = 1;
 484        return 0;
 485}
 486early_param("oops", oops_setup);
 487
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