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