panic.c

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/*
 *  linux/kernel/panic.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * This function is used through-out the kernel (including mm and fs)
 * to indicate a major problem.
 */
#include <linux/debug_locks.h>
#include <linux/interrupt.h>
#include <linux/kmsg_dump.h>
#include <linux/kallsyms.h>
#include <linux/notifier.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/reboot.h>
#include <linux/delay.h>
#include <linux/kexec.h>
#include <linux/sched.h>
#include <linux/sysrq.h>
#include <linux/init.h>
#include <linux/nmi.h>
#include <linux/dmi.h>

#define PANIC_TIMER_STEP 100
#define PANIC_BLINK_SPD 18

int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
static unsigned long tainted_mask;
static int pause_on_oops;
static int pause_on_oops_flag;
static DEFINE_SPINLOCK(pause_on_oops_lock);

int panic_timeout;
EXPORT_SYMBOL_GPL(panic_timeout);

ATOMIC_NOTIFIER_HEAD(panic_notifier_list);

EXPORT_SYMBOL(panic_notifier_list);

static long no_blink(int state)
{
    return 0;
}

/* Returns how long it waited in ms */
long (*panic_blink)(int state);
EXPORT_SYMBOL(panic_blink);

/*
 * Stop ourself in panic -- architecture code may override this
 */
void __weak panic_smp_self_stop(void)
{
    while (1)
        cpu_relax();
}

void panic(const char *fmt, ...)
{
    static DEFINE_SPINLOCK(panic_lock);
    static char buf[1024];
    va_list args;
    long i, i_next = 0;
    int state = 0;

    /*
     * Disable local interrupts. This will prevent panic_smp_self_stop
     * from deadlocking the first cpu that invokes the panic, since
     * there is nothing to prevent an interrupt handler (that runs
     * after the panic_lock is acquired) from invoking panic again.
     */
    local_irq_disable();

    /*
     * It's possible to come here directly from a panic-assertion and
     * not have preempt disabled. Some functions called from here want
     * preempt to be disabled. No point enabling it later though...
     *
     * Only one CPU is allowed to execute the panic code from here. For
     * multiple parallel invocations of panic, all other CPUs either
     * stop themself or will wait until they are stopped by the 1st CPU
     * with smp_send_stop().
     */
    if (!spin_trylock(&panic_lock))
        panic_smp_self_stop();

    console_verbose();
    bust_spinlocks(1);
    va_start(args, fmt);
    vsnprintf(buf, sizeof(buf), fmt, args);
    va_end(args);
    printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
#ifdef CONFIG_DEBUG_BUGVERBOSE
    /*
     * Avoid nested stack-dumping if a panic occurs during oops processing
     */
    if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
        dump_stack();
#endif

    /*
     * If we have crashed and we have a crash kernel loaded let it handle
     * everything else.
     * Do we want to call this before we try to display a message?
     */
    crash_kexec(NULL);

    /*
     * Note smp_send_stop is the usual smp shutdown function, which
     * unfortunately means it may not be hardened to work in a panic
     * situation.
     */
    smp_send_stop();

    kmsg_dump(KMSG_DUMP_PANIC);

    atomic_notifier_call_chain(&panic_notifier_list, 0, buf);

    bust_spinlocks(0);

    if (!panic_blink)
        panic_blink = no_blink;

    if (panic_timeout > 0) {
        /*
         * Delay timeout seconds before rebooting the machine.
         * We can't use the "normal" timers since we just panicked.
         */
        printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);

        for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
            touch_nmi_watchdog();
            if (i >= i_next) {
                i += panic_blink(state ^= 1);
                i_next = i + 3600 / PANIC_BLINK_SPD;
            }
            mdelay(PANIC_TIMER_STEP);
        }
    }
    if (panic_timeout != 0) {
        /*
         * This will not be a clean reboot, with everything
         * shutting down.  But if there is a chance of
         * rebooting the system it will be rebooted.
         */
        emergency_restart();
    }
#ifdef __sparc__
    {
        extern int stop_a_enabled;
        /* Make sure the user can actually press Stop-A (L1-A) */
        stop_a_enabled = 1;
        printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
    }
#endif
#if defined(CONFIG_S390)
    {
        unsigned long caller;

        caller = (unsigned long)__builtin_return_address(0);
        disabled_wait(caller);
    }
#endif
    local_irq_enable();
    for (i = 0; ; i += PANIC_TIMER_STEP) {
        touch_softlockup_watchdog();
        if (i >= i_next) {
            i += panic_blink(state ^= 1);
            i_next = i + 3600 / PANIC_BLINK_SPD;
        }
        mdelay(PANIC_TIMER_STEP);
    }
}

EXPORT_SYMBOL(panic);


struct tnt {
    u8  bit;
    char    true;
    char    false;
};

static const struct tnt tnts[] = {
    { TAINT_PROPRIETARY_MODULE, 'P', 'G' },
    { TAINT_FORCED_MODULE,      'F', ' ' },
    { TAINT_UNSAFE_SMP,     'S', ' ' },
    { TAINT_FORCED_RMMOD,       'R', ' ' },
    { TAINT_MACHINE_CHECK,      'M', ' ' },
    { TAINT_BAD_PAGE,       'B', ' ' },
    { TAINT_USER,           'U', ' ' },
    { TAINT_DIE,            'D', ' ' },
    { TAINT_OVERRIDDEN_ACPI_TABLE,  'A', ' ' },
    { TAINT_WARN,           'W', ' ' },
    { TAINT_CRAP,           'C', ' ' },
    { TAINT_FIRMWARE_WORKAROUND,    'I', ' ' },
    { TAINT_OOT_MODULE,     'O', ' ' },
};

const char *print_tainted(void)
{
    static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];

    if (tainted_mask) {
        char *s;
        int i;

        s = buf + sprintf(buf, "Tainted: ");
        for (i = 0; i < ARRAY_SIZE(tnts); i++) {
            const struct tnt *t = &tnts[i];
            *s++ = test_bit(t->bit, &tainted_mask) ?
                    t->true : t->false;
        }
        *s = 0;
    } else
        snprintf(buf, sizeof(buf), "Not tainted");

    return buf;
}

int test_taint(unsigned flag)
{
    return test_bit(flag, &tainted_mask);
}
EXPORT_SYMBOL(test_taint);

unsigned long get_taint(void)
{
    return tainted_mask;
}

void add_taint(unsigned flag)
{
    /*
     * Can't trust the integrity of the kernel anymore.
     * We don't call directly debug_locks_off() because the issue
     * is not necessarily serious enough to set oops_in_progress to 1
     * Also we want to keep up lockdep for staging/out-of-tree
     * development and post-warning case.
     */
    switch (flag) {
    case TAINT_CRAP:
    case TAINT_OOT_MODULE:
    case TAINT_WARN:
    case TAINT_FIRMWARE_WORKAROUND:
        break;

    default:
        if (__debug_locks_off())
            printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
    }

    set_bit(flag, &tainted_mask);
}
EXPORT_SYMBOL(add_taint);

static void spin_msec(int msecs)
{
    int i;

    for (i = 0; i < msecs; i++) {
        touch_nmi_watchdog();
        mdelay(1);
    }
}

/*
 * It just happens that oops_enter() and oops_exit() are identically
 * implemented...
 */
static void do_oops_enter_exit(void)
{
    unsigned long flags;
    static int spin_counter;

    if (!pause_on_oops)
        return;

    spin_lock_irqsave(&pause_on_oops_lock, flags);
    if (pause_on_oops_flag == 0) {
        /* This CPU may now print the oops message */
        pause_on_oops_flag = 1;
    } else {
        /* We need to stall this CPU */
        if (!spin_counter) {
            /* This CPU gets to do the counting */
            spin_counter = pause_on_oops;
            do {
                spin_unlock(&pause_on_oops_lock);
                spin_msec(MSEC_PER_SEC);
                spin_lock(&pause_on_oops_lock);
            } while (--spin_counter);
            pause_on_oops_flag = 0;
        } else {
            /* This CPU waits for a different one */
            while (spin_counter) {
                spin_unlock(&pause_on_oops_lock);
                spin_msec(1);
                spin_lock(&pause_on_oops_lock);
            }
        }
    }
    spin_unlock_irqrestore(&pause_on_oops_lock, flags);
}

/*
 * Return true if the calling CPU is allowed to print oops-related info.
 * This is a bit racy..
 */
int oops_may_print(void)
{
    return pause_on_oops_flag == 0;
}

/*
 * Called when the architecture enters its oops handler, before it prints
 * anything.  If this is the first CPU to oops, and it's oopsing the first
 * time then let it proceed.
 *
 * This is all enabled by the pause_on_oops kernel boot option.  We do all
 * this to ensure that oopses don't scroll off the screen.  It has the
 * side-effect of preventing later-oopsing CPUs from mucking up the display,
 * too.
 *
 * It turns out that the CPU which is allowed to print ends up pausing for
 * the right duration, whereas all the other CPUs pause for twice as long:
 * once in oops_enter(), once in oops_exit().
 */
void oops_enter(void)
{
    tracing_off();
    /* can't trust the integrity of the kernel anymore: */
    debug_locks_off();
    do_oops_enter_exit();
}

/*
 * 64-bit random ID for oopses:
 */
static u64 oops_id;

static int init_oops_id(void)
{
    if (!oops_id)
        get_random_bytes(&oops_id, sizeof(oops_id));
    else
        oops_id++;

    return 0;
}
late_initcall(init_oops_id);

void print_oops_end_marker(void)
{
    init_oops_id();
    printk(KERN_WARNING "---[ end trace %016llx ]---\n",
        (unsigned long long)oops_id);
}

/*
 * Called when the architecture exits its oops handler, after printing
 * everything.
 */
void oops_exit(void)
{
    do_oops_enter_exit();
    print_oops_end_marker();
    kmsg_dump(KMSG_DUMP_OOPS);
}

#ifdef WANT_WARN_ON_SLOWPATH
struct slowpath_args {
    const char *fmt;
    va_list args;
};

static void warn_slowpath_common(const char *file, int line, void *caller,
                 unsigned taint, struct slowpath_args *args)
{
    const char *board;

    printk(KERN_WARNING "------------[ cut here ]------------\n");
    printk(KERN_WARNING "WARNING: at %s:%d %pS()\n", file, line, caller);
    board = dmi_get_system_info(DMI_PRODUCT_NAME);
    if (board)
        printk(KERN_WARNING "Hardware name: %s\n", board);

    if (args)
        vprintk(args->fmt, args->args);

    print_modules();
    dump_stack();
    print_oops_end_marker();
    add_taint(taint);
}

void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
{
    struct slowpath_args args;

    args.fmt = fmt;
    va_start(args.args, fmt);
    warn_slowpath_common(file, line, __builtin_return_address(0),
                 TAINT_WARN, &args);
    va_end(args.args);
}
EXPORT_SYMBOL(warn_slowpath_fmt);

void warn_slowpath_fmt_taint(const char *file, int line,
                 unsigned taint, const char *fmt, ...)
{
    struct slowpath_args args;

    args.fmt = fmt;
    va_start(args.args, fmt);
    warn_slowpath_common(file, line, __builtin_return_address(0),
                 taint, &args);
    va_end(args.args);
}
EXPORT_SYMBOL(warn_slowpath_fmt_taint);

void warn_slowpath_null(const char *file, int line)
{
    warn_slowpath_common(file, line, __builtin_return_address(0),
                 TAINT_WARN, NULL);
}
EXPORT_SYMBOL(warn_slowpath_null);
#endif

#ifdef CONFIG_CC_STACKPROTECTOR

/*
 * Called when gcc's -fstack-protector feature is used, and
 * gcc detects corruption of the on-stack canary value
 */
void __stack_chk_fail(void)
{
    panic("stack-protector: Kernel stack is corrupted in: %p\n",
        __builtin_return_address(0));
}
EXPORT_SYMBOL(__stack_chk_fail);

#endif

core_param(panic, panic_timeout, int, 0644);
core_param(pause_on_oops, pause_on_oops, int, 0644);

static int __init oops_setup(char *s)
{
    if (!s)
        return -EINVAL;
    if (!strcmp(s, "panic"))
        panic_on_oops = 1;
    return 0;
}
early_param("oops", oops_setup);