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
  23int panic_on_oops;
  24int tainted;
  25static int pause_on_oops;
  26static int pause_on_oops_flag;
  27static DEFINE_SPINLOCK(pause_on_oops_lock);
  28
  29int panic_timeout;
  30
  31ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
  32
  33EXPORT_SYMBOL(panic_notifier_list);
  34
  35static int __init panic_setup(char *str)
  36{
  37        panic_timeout = simple_strtoul(str, NULL, 0);
  38        return 1;
  39}
  40__setup("panic=", panic_setup);
  41
  42static long no_blink(long time)
  43{
  44        return 0;
  45}
  46
  47/* Returns how long it waited in ms */
  48long (*panic_blink)(long time);
  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 */
  59 
  60NORET_TYPE void panic(const char * fmt, ...)
  61{
  62        long i;
  63        static char buf[1024];
  64        va_list args;
  65#if defined(CONFIG_S390)
  66        unsigned long caller = (unsigned long) __builtin_return_address(0);
  67#endif
  68
  69        /*
  70         * It's possible to come here directly from a panic-assertion and not
  71         * have preempt disabled. Some functions called from here want
  72         * preempt to be disabled. No point enabling it later though...
  73         */
  74        preempt_disable();
  75
  76        bust_spinlocks(1);
  77        va_start(args, fmt);
  78        vsnprintf(buf, sizeof(buf), fmt, args);
  79        va_end(args);
  80        printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
  81        bust_spinlocks(0);
  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#ifdef CONFIG_SMP
  91        /*
  92         * Note smp_send_stop is the usual smp shutdown function, which
  93         * unfortunately means it may not be hardened to work in a panic
  94         * situation.
  95         */
  96        smp_send_stop();
  97#endif
  98
  99        atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
 100
 101        if (!panic_blink)
 102                panic_blink = no_blink;
 103
 104        if (panic_timeout > 0) {
 105                /*
 106                 * Delay timeout seconds before rebooting the machine. 
 107                 * We can't use the "normal" timers since we just panicked..
 108                 */
 109                printk(KERN_EMERG "Rebooting in %d seconds..",panic_timeout);
 110                for (i = 0; i < panic_timeout*1000; ) {
 111                        touch_nmi_watchdog();
 112                        i += panic_blink(i);
 113                        mdelay(1);
 114                        i++;
 115                }
 116                /*      This will not be a clean reboot, with everything
 117                 *      shutting down.  But if there is a chance of
 118                 *      rebooting the system it will be rebooted.
 119                 */
 120                emergency_restart();
 121        }
 122#ifdef __sparc__
 123        {
 124                extern int stop_a_enabled;
 125                /* Make sure the user can actually press Stop-A (L1-A) */
 126                stop_a_enabled = 1;
 127                printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
 128        }
 129#endif
 130#if defined(CONFIG_S390)
 131        disabled_wait(caller);
 132#endif
 133        local_irq_enable();
 134        for (i = 0;;) {
 135                touch_softlockup_watchdog();
 136                i += panic_blink(i);
 137                mdelay(1);
 138                i++;
 139        }
 140}
 141
 142EXPORT_SYMBOL(panic);
 143
 144/**
 145 *      print_tainted - return a string to represent the kernel taint state.
 146 *
 147 *  'P' - Proprietary module has been loaded.
 148 *  'F' - Module has been forcibly loaded.
 149 *  'S' - SMP with CPUs not designed for SMP.
 150 *  'R' - User forced a module unload.
 151 *  'M' - Machine had a machine check experience.
 152 *  'B' - System has hit bad_page.
 153 *
 154 *      The string is overwritten by the next call to print_taint().
 155 */
 156 
 157const char *print_tainted(void)
 158{
 159        static char buf[20];
 160        if (tainted) {
 161                snprintf(buf, sizeof(buf), "Tainted: %c%c%c%c%c%c",
 162                        tainted & TAINT_PROPRIETARY_MODULE ? 'P' : 'G',
 163                        tainted & TAINT_FORCED_MODULE ? 'F' : ' ',
 164                        tainted & TAINT_UNSAFE_SMP ? 'S' : ' ',
 165                        tainted & TAINT_FORCED_RMMOD ? 'R' : ' ',
 166                        tainted & TAINT_MACHINE_CHECK ? 'M' : ' ',
 167                        tainted & TAINT_BAD_PAGE ? 'B' : ' ');
 168        }
 169        else
 170                snprintf(buf, sizeof(buf), "Not tainted");
 171        return(buf);
 172}
 173
 174void add_taint(unsigned flag)
 175{
 176        debug_locks = 0; /* can't trust the integrity of the kernel anymore */
 177        tainted |= flag;
 178}
 179EXPORT_SYMBOL(add_taint);
 180
 181static int __init pause_on_oops_setup(char *str)
 182{
 183        pause_on_oops = simple_strtoul(str, NULL, 0);
 184        return 1;
 185}
 186__setup("pause_on_oops=", pause_on_oops_setup);
 187
 188static void spin_msec(int msecs)
 189{
 190        int i;
 191
 192        for (i = 0; i < msecs; i++) {
 193                touch_nmi_watchdog();
 194                mdelay(1);
 195        }
 196}
 197
 198/*
 199 * It just happens that oops_enter() and oops_exit() are identically
 200 * implemented...
 201 */
 202static void do_oops_enter_exit(void)
 203{
 204        unsigned long flags;
 205        static int spin_counter;
 206
 207        if (!pause_on_oops)
 208                return;
 209
 210        spin_lock_irqsave(&pause_on_oops_lock, flags);
 211        if (pause_on_oops_flag == 0) {
 212                /* This CPU may now print the oops message */
 213                pause_on_oops_flag = 1;
 214        } else {
 215                /* We need to stall this CPU */
 216                if (!spin_counter) {
 217                        /* This CPU gets to do the counting */
 218                        spin_counter = pause_on_oops;
 219                        do {
 220                                spin_unlock(&pause_on_oops_lock);
 221                                spin_msec(MSEC_PER_SEC);
 222                                spin_lock(&pause_on_oops_lock);
 223                        } while (--spin_counter);
 224                        pause_on_oops_flag = 0;
 225                } else {
 226                        /* This CPU waits for a different one */
 227                        while (spin_counter) {
 228                                spin_unlock(&pause_on_oops_lock);
 229                                spin_msec(1);
 230                                spin_lock(&pause_on_oops_lock);
 231                        }
 232                }
 233        }
 234        spin_unlock_irqrestore(&pause_on_oops_lock, flags);
 235}
 236
 237/*
 238 * Return true if the calling CPU is allowed to print oops-related info.  This
 239 * is a bit racy..
 240 */
 241int oops_may_print(void)
 242{
 243        return pause_on_oops_flag == 0;
 244}
 245
 246/*
 247 * Called when the architecture enters its oops handler, before it prints
 248 * anything.  If this is the first CPU to oops, and it's oopsing the first time
 249 * then let it proceed.
 250 *
 251 * This is all enabled by the pause_on_oops kernel boot option.  We do all this
 252 * to ensure that oopses don't scroll off the screen.  It has the side-effect
 253 * of preventing later-oopsing CPUs from mucking up the display, too.
 254 *
 255 * It turns out that the CPU which is allowed to print ends up pausing for the
 256 * right duration, whereas all the other CPUs pause for twice as long: once in
 257 * oops_enter(), once in oops_exit().
 258 */
 259void oops_enter(void)
 260{
 261        debug_locks_off(); /* can't trust the integrity of the kernel anymore */
 262        do_oops_enter_exit();
 263}
 264
 265/*
 266 * Called when the architecture exits its oops handler, after printing
 267 * everything.
 268 */
 269void oops_exit(void)
 270{
 271        do_oops_enter_exit();
 272}
 273
 274#ifdef CONFIG_CC_STACKPROTECTOR
 275/*
 276 * Called when gcc's -fstack-protector feature is used, and
 277 * gcc detects corruption of the on-stack canary value
 278 */
 279void __stack_chk_fail(void)
 280{
 281        panic("stack-protector: Kernel stack is corrupted");
 282}
 283EXPORT_SYMBOL(__stack_chk_fail);
 284#endif
 285