/*
 *  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/module.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/reboot.h>
#include <linux/notifier.h>
#include <linux/init.h>
#include <linux/sysrq.h>
#include <linux/interrupt.h>
#include <linux/nmi.h>
#include <linux/kexec.h>
#include <linux/debug_locks.h>
#include <linux/random.h>

int panic_on_oops;
int tainted;
static int pause_on_oops;
static int pause_on_oops_flag;
static DEFINE_SPINLOCK(pause_on_oops_lock);

int panic_timeout;

ATOMIC_NOTIFIER_HEAD(panic_notifier_list);

EXPORT_SYMBOL(panic_notifier_list);

static int __init panic_setup(char *str)
{
        panic_timeout = simple_strtoul(str, NULL, 0);
        return 1;
}
__setup("panic=", panic_setup);

static long no_blink(long time)
{
        return 0;
}

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

/**
 *      panic - halt the system
 *      @fmt: The text string to print
 *
 *      Display a message, then perform cleanups.
 *
 *      This function never returns.
 */

NORET_TYPE void panic(const char * fmt, ...)
{
        long i;
        static char buf[1024];
        va_list args;
#if defined(CONFIG_S390)
        unsigned long caller = (unsigned long) __builtin_return_address(0);
#endif

        /*
         * 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...
         */
        preempt_disable();

        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);
        bust_spinlocks(0);

        /*
         * 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);

#ifdef CONFIG_SMP
        /*
         * 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();
#endif

        atomic_notifier_call_chain(&panic_notifier_list, 0, buf);

        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; ) {
                        touch_nmi_watchdog();
                        i += panic_blink(i);
                        mdelay(1);
                        i++;
                }
                /*      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)
        disabled_wait(caller);
#endif
        local_irq_enable();
        for (i = 0;;) {
                touch_softlockup_watchdog();
                i += panic_blink(i);
                mdelay(1);
                i++;
        }
}

EXPORT_SYMBOL(panic);

/**
 *      print_tainted - return a string to represent the kernel taint state.
 *
 *  'P' - Proprietary module has been loaded.
 *  'F' - Module has been forcibly loaded.
 *  'S' - SMP with CPUs not designed for SMP.
 *  'R' - User forced a module unload.
 *  'M' - System experienced a machine check exception.
 *  'B' - System has hit bad_page.
 *  'U' - Userspace-defined naughtiness.
 *
 *      The string is overwritten by the next call to print_taint().
 */

const char *print_tainted(void)
{
        static char buf[20];
        if (tainted) {
                snprintf(buf, sizeof(buf), "Tainted: %c%c%c%c%c%c%c%c",
                        tainted & TAINT_PROPRIETARY_MODULE ? 'P' : 'G',
                        tainted & TAINT_FORCED_MODULE ? 'F' : ' ',
                        tainted & TAINT_UNSAFE_SMP ? 'S' : ' ',
                        tainted & TAINT_FORCED_RMMOD ? 'R' : ' ',
                        tainted & TAINT_MACHINE_CHECK ? 'M' : ' ',
                        tainted & TAINT_BAD_PAGE ? 'B' : ' ',
                        tainted & TAINT_USER ? 'U' : ' ',
                        tainted & TAINT_DIE ? 'D' : ' ');
        }
        else
                snprintf(buf, sizeof(buf), "Not tainted");
        return(buf);
}

void add_taint(unsigned flag)
{
        debug_locks = 0; /* can't trust the integrity of the kernel anymore */
        tainted |= flag;
}
EXPORT_SYMBOL(add_taint);

static int __init pause_on_oops_setup(char *str)
{
        pause_on_oops = simple_strtoul(str, NULL, 0);
        return 1;
}
__setup("pause_on_oops=", pause_on_oops_setup);

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)
{
        debug_locks_off(); /* can't trust the integrity of the kernel anymore */
        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));

        return 0;
}
late_initcall(init_oops_id);

/*
 * Called when the architecture exits its oops handler, after printing
 * everything.
 */
void oops_exit(void)
{
        do_oops_enter_exit();
        init_oops_id();
        printk(KERN_WARNING "---[ end trace %016llx ]---\n",
                (unsigned long long)oops_id);
}

#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");
}
EXPORT_SYMBOL(__stack_chk_fail);
#endif