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