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