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