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