x86, xsave: context switch support using xsave/xrstor

[linux-2.6/mini2440.git] / arch / x86 / kernel / traps_64.c

/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
 *
 *  Pentium III FXSR, SSE support
 *      Gareth Hughes <gareth@valinux.com>, May 2000
 */

/*
 * 'Traps.c' handles hardware traps and faults after we have saved some
 * state in 'entry.S'.
 */
#include <linux/moduleparam.h>
#include <linux/interrupt.h>
#include <linux/kallsyms.h>
#include <linux/spinlock.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <linux/utsname.h>
#include <linux/kdebug.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/string.h>
#include <linux/unwind.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/kexec.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/init.h>
#include <linux/bug.h>
#include <linux/nmi.h>
#include <linux/mm.h>

#if defined(CONFIG_EDAC)
#include <linux/edac.h>
#endif

#include <asm/stacktrace.h>
#include <asm/processor.h>
#include <asm/debugreg.h>
#include <asm/atomic.h>
#include <asm/system.h>
#include <asm/unwind.h>
#include <asm/desc.h>
#include <asm/i387.h>
#include <asm/nmi.h>
#include <asm/smp.h>
#include <asm/io.h>
#include <asm/pgalloc.h>
#include <asm/proto.h>
#include <asm/pda.h>
#include <asm/traps.h>

#include <mach_traps.h>

int panic_on_unrecovered_nmi;
int kstack_depth_to_print = 12;
static unsigned int code_bytes = 64;
static int ignore_nmis;
static int die_counter;

static inline void conditional_sti(struct pt_regs *regs)
{
        if (regs->flags & X86_EFLAGS_IF)
                local_irq_enable();
}

static inline void preempt_conditional_sti(struct pt_regs *regs)
{
        inc_preempt_count();
        if (regs->flags & X86_EFLAGS_IF)
                local_irq_enable();
}

static inline void preempt_conditional_cli(struct pt_regs *regs)
{
        if (regs->flags & X86_EFLAGS_IF)
                local_irq_disable();
        /* Make sure to not schedule here because we could be running
           on an exception stack. */
        dec_preempt_count();
}

void printk_address(unsigned long address, int reliable)
{
        printk(" [<%016lx>] %s%pS\n", address, reliable ? "": "? ", (void *) address);
}

static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
                                        unsigned *usedp, char **idp)
{
        static char ids[][8] = {
                [DEBUG_STACK - 1] = "#DB",
                [NMI_STACK - 1] = "NMI",
                [DOUBLEFAULT_STACK - 1] = "#DF",
                [STACKFAULT_STACK - 1] = "#SS",
                [MCE_STACK - 1] = "#MC",
#if DEBUG_STKSZ > EXCEPTION_STKSZ
                [N_EXCEPTION_STACKS ... N_EXCEPTION_STACKS + DEBUG_STKSZ / EXCEPTION_STKSZ - 2] = "#DB[?]"
#endif
        };
        unsigned k;

        /*
         * Iterate over all exception stacks, and figure out whether
         * 'stack' is in one of them:
         */
        for (k = 0; k < N_EXCEPTION_STACKS; k++) {
                unsigned long end = per_cpu(orig_ist, cpu).ist[k];
                /*
                 * Is 'stack' above this exception frame's end?
                 * If yes then skip to the next frame.
                 */
                if (stack >= end)
                        continue;
                /*
                 * Is 'stack' above this exception frame's start address?
                 * If yes then we found the right frame.
                 */
                if (stack >= end - EXCEPTION_STKSZ) {
                        /*
                         * Make sure we only iterate through an exception
                         * stack once. If it comes up for the second time
                         * then there's something wrong going on - just
                         * break out and return NULL:
                         */
                        if (*usedp & (1U << k))
                                break;
                        *usedp |= 1U << k;
                        *idp = ids[k];
                        return (unsigned long *)end;
                }
                /*
                 * If this is a debug stack, and if it has a larger size than
                 * the usual exception stacks, then 'stack' might still
                 * be within the lower portion of the debug stack:
                 */
#if DEBUG_STKSZ > EXCEPTION_STKSZ
                if (k == DEBUG_STACK - 1 && stack >= end - DEBUG_STKSZ) {
                        unsigned j = N_EXCEPTION_STACKS - 1;

                        /*
                         * Black magic. A large debug stack is composed of
                         * multiple exception stack entries, which we
                         * iterate through now. Dont look:
                         */
                        do {
                                ++j;
                                end -= EXCEPTION_STKSZ;
                                ids[j][4] = '1' + (j - N_EXCEPTION_STACKS);
                        } while (stack < end - EXCEPTION_STKSZ);
                        if (*usedp & (1U << j))
                                break;
                        *usedp |= 1U << j;
                        *idp = ids[j];
                        return (unsigned long *)end;
                }
#endif
        }
        return NULL;
}

/*
 * x86-64 can have up to three kernel stacks: 
 * process stack
 * interrupt stack
 * severe exception (double fault, nmi, stack fault, debug, mce) hardware stack
 */

static inline int valid_stack_ptr(struct thread_info *tinfo,
                        void *p, unsigned int size, void *end)
{
        void *t = tinfo;
        if (end) {
                if (p < end && p >= (end-THREAD_SIZE))
                        return 1;
                else
                        return 0;
        }
        return p > t && p < t + THREAD_SIZE - size;
}

/* The form of the top of the frame on the stack */
struct stack_frame {
        struct stack_frame *next_frame;
        unsigned long return_address;
};

static inline unsigned long
print_context_stack(struct thread_info *tinfo,
                unsigned long *stack, unsigned long bp,
                const struct stacktrace_ops *ops, void *data,
                unsigned long *end)
{
        struct stack_frame *frame = (struct stack_frame *)bp;

        while (valid_stack_ptr(tinfo, stack, sizeof(*stack), end)) {
                unsigned long addr;

                addr = *stack;
                if (__kernel_text_address(addr)) {
                        if ((unsigned long) stack == bp + 8) {
                                ops->address(data, addr, 1);
                                frame = frame->next_frame;
                                bp = (unsigned long) frame;
                        } else {
                                ops->address(data, addr, bp == 0);
                        }
                }
                stack++;
        }
        return bp;
}

void dump_trace(struct task_struct *task, struct pt_regs *regs,
                unsigned long *stack, unsigned long bp,
                const struct stacktrace_ops *ops, void *data)
{
        const unsigned cpu = get_cpu();
        unsigned long *irqstack_end = (unsigned long*)cpu_pda(cpu)->irqstackptr;
        unsigned used = 0;
        struct thread_info *tinfo;

        if (!task)
                task = current;

        if (!stack) {
                unsigned long dummy;
                stack = &dummy;
                if (task && task != current)
                        stack = (unsigned long *)task->thread.sp;
        }

#ifdef CONFIG_FRAME_POINTER
        if (!bp) {
                if (task == current) {
                        /* Grab bp right from our regs */
                        asm("movq %%rbp, %0" : "=r" (bp) :);
                } else {
                        /* bp is the last reg pushed by switch_to */
                        bp = *(unsigned long *) task->thread.sp;
                }
        }
#endif

        /*
         * Print function call entries in all stacks, starting at the
         * current stack address. If the stacks consist of nested
         * exceptions
         */
        tinfo = task_thread_info(task);
        for (;;) {
                char *id;
                unsigned long *estack_end;
                estack_end = in_exception_stack(cpu, (unsigned long)stack,
                                                &used, &id);

                if (estack_end) {
                        if (ops->stack(data, id) < 0)
                                break;

                        bp = print_context_stack(tinfo, stack, bp, ops,
                                                        data, estack_end);
                        ops->stack(data, "<EOE>");
                        /*
                         * We link to the next stack via the
                         * second-to-last pointer (index -2 to end) in the
                         * exception stack:
                         */
                        stack = (unsigned long *) estack_end[-2];
                        continue;
                }
                if (irqstack_end) {
                        unsigned long *irqstack;
                        irqstack = irqstack_end -
                                (IRQSTACKSIZE - 64) / sizeof(*irqstack);

                        if (stack >= irqstack && stack < irqstack_end) {
                                if (ops->stack(data, "IRQ") < 0)
                                        break;
                                bp = print_context_stack(tinfo, stack, bp,
                                                ops, data, irqstack_end);
                                /*
                                 * We link to the next stack (which would be
                                 * the process stack normally) the last
                                 * pointer (index -1 to end) in the IRQ stack:
                                 */
                                stack = (unsigned long *) (irqstack_end[-1]);
                                irqstack_end = NULL;
                                ops->stack(data, "EOI");
                                continue;
                        }
                }
                break;
        }

        /*
         * This handles the process stack:
         */
        bp = print_context_stack(tinfo, stack, bp, ops, data, NULL);
        put_cpu();
}
EXPORT_SYMBOL(dump_trace);

static void
print_trace_warning_symbol(void *data, char *msg, unsigned long symbol)
{
        print_symbol(msg, symbol);
        printk("\n");
}

static void print_trace_warning(void *data, char *msg)
{
        printk("%s\n", msg);
}

static int print_trace_stack(void *data, char *name)
{
        printk(" <%s> ", name);
        return 0;
}

static void print_trace_address(void *data, unsigned long addr, int reliable)
{
        touch_nmi_watchdog();
        printk_address(addr, reliable);
}

static const struct stacktrace_ops print_trace_ops = {
        .warning = print_trace_warning,
        .warning_symbol = print_trace_warning_symbol,
        .stack = print_trace_stack,
        .address = print_trace_address,
};

static void
show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
                unsigned long *stack, unsigned long bp, char *log_lvl)
{
        printk("\nCall Trace:\n");
        dump_trace(task, regs, stack, bp, &print_trace_ops, log_lvl);
        printk("\n");
}

void show_trace(struct task_struct *task, struct pt_regs *regs,
                unsigned long *stack, unsigned long bp)
{
        show_trace_log_lvl(task, regs, stack, bp, "");
}

static void
show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
                unsigned long *sp, unsigned long bp, char *log_lvl)
{
        unsigned long *stack;
        int i;
        const int cpu = smp_processor_id();
        unsigned long *irqstack_end = (unsigned long *) (cpu_pda(cpu)->irqstackptr);
        unsigned long *irqstack = (unsigned long *) (cpu_pda(cpu)->irqstackptr - IRQSTACKSIZE);

        // debugging aid: "show_stack(NULL, NULL);" prints the
        // back trace for this cpu.

        if (sp == NULL) {
                if (task)
                        sp = (unsigned long *)task->thread.sp;
                else
                        sp = (unsigned long *)&sp;
        }

        stack = sp;
        for (i = 0; i < kstack_depth_to_print; i++) {
                if (stack >= irqstack && stack <= irqstack_end) {
                        if (stack == irqstack_end) {
                                stack = (unsigned long *) (irqstack_end[-1]);
                                printk(" <EOI> ");
                        }
                } else {
                if (((long) stack & (THREAD_SIZE-1)) == 0)
                        break;
                }
                if (i && ((i % 4) == 0))
                        printk("\n");
                printk(" %016lx", *stack++);
                touch_nmi_watchdog();
        }
        show_trace_log_lvl(task, regs, sp, bp, log_lvl);
}

void show_stack(struct task_struct *task, unsigned long *sp)
{
        show_stack_log_lvl(task, NULL, sp, 0, "");
}

/*
 * The architecture-independent dump_stack generator
 */
void dump_stack(void)
{
        unsigned long bp = 0;
        unsigned long stack;

#ifdef CONFIG_FRAME_POINTER
        if (!bp)
                asm("movq %%rbp, %0" : "=r" (bp):);
#endif

        printk("Pid: %d, comm: %.20s %s %s %.*s\n",
                current->pid, current->comm, print_tainted(),
                init_utsname()->release,
                (int)strcspn(init_utsname()->version, " "),
                init_utsname()->version);
        show_trace(NULL, NULL, &stack, bp);
}

EXPORT_SYMBOL(dump_stack);

void show_registers(struct pt_regs *regs)
{
        int i;
        unsigned long sp;
        const int cpu = smp_processor_id();
        struct task_struct *cur = cpu_pda(cpu)->pcurrent;

        sp = regs->sp;
        printk("CPU %d ", cpu);
        __show_regs(regs);
        printk("Process %s (pid: %d, threadinfo %p, task %p)\n",
                cur->comm, cur->pid, task_thread_info(cur), cur);

        /*
         * When in-kernel, we also print out the stack and code at the
         * time of the fault..
         */
        if (!user_mode(regs)) {
                unsigned int code_prologue = code_bytes * 43 / 64;
                unsigned int code_len = code_bytes;
                unsigned char c;
                u8 *ip;

                printk("Stack: ");
                show_stack_log_lvl(NULL, regs, (unsigned long *)sp,
                                regs->bp, "");
                printk("\n");

                printk(KERN_EMERG "Code: ");

                ip = (u8 *)regs->ip - code_prologue;
                if (ip < (u8 *)PAGE_OFFSET || probe_kernel_address(ip, c)) {
                        /* try starting at RIP */
                        ip = (u8 *)regs->ip;
                        code_len = code_len - code_prologue + 1;
                }
                for (i = 0; i < code_len; i++, ip++) {
                        if (ip < (u8 *)PAGE_OFFSET ||
                                        probe_kernel_address(ip, c)) {
                                printk(" Bad RIP value.");
                                break;
                        }
                        if (ip == (u8 *)regs->ip)
                                printk("<%02x> ", c);
                        else
                                printk("%02x ", c);
                }
        }
        printk("\n");
}

int is_valid_bugaddr(unsigned long ip)
{
        unsigned short ud2;

        if (__copy_from_user(&ud2, (const void __user *) ip, sizeof(ud2)))
                return 0;

        return ud2 == 0x0b0f;
}

static raw_spinlock_t die_lock = __RAW_SPIN_LOCK_UNLOCKED;
static int die_owner = -1;
static unsigned int die_nest_count;

unsigned __kprobes long oops_begin(void)
{
        int cpu;
        unsigned long flags;

        oops_enter();

        /* racy, but better than risking deadlock. */
        raw_local_irq_save(flags);
        cpu = smp_processor_id();
        if (!__raw_spin_trylock(&die_lock)) {
                if (cpu == die_owner) 
                        /* nested oops. should stop eventually */;
                else
                        __raw_spin_lock(&die_lock);
        }
        die_nest_count++;
        die_owner = cpu;
        console_verbose();
        bust_spinlocks(1);
        return flags;
}

void __kprobes oops_end(unsigned long flags, struct pt_regs *regs, int signr)
{
        die_owner = -1;
        bust_spinlocks(0);
        die_nest_count--;
        if (!die_nest_count)
                /* Nest count reaches zero, release the lock. */
                __raw_spin_unlock(&die_lock);
        raw_local_irq_restore(flags);
        if (!regs) {
                oops_exit();
                return;
        }
        if (panic_on_oops)
                panic("Fatal exception");
        oops_exit();
        do_exit(signr);
}

int __kprobes __die(const char *str, struct pt_regs *regs, long err)
{
        printk(KERN_EMERG "%s: %04lx [%u] ", str, err & 0xffff, ++die_counter);
#ifdef CONFIG_PREEMPT
        printk("PREEMPT ");
#endif
#ifdef CONFIG_SMP
        printk("SMP ");
#endif
#ifdef CONFIG_DEBUG_PAGEALLOC
        printk("DEBUG_PAGEALLOC");
#endif
        printk("\n");
        if (notify_die(DIE_OOPS, str, regs, err,
                        current->thread.trap_no, SIGSEGV) == NOTIFY_STOP)
                return 1;

        show_registers(regs);
        add_taint(TAINT_DIE);
        /* Executive summary in case the oops scrolled away */
        printk(KERN_ALERT "RIP ");
        printk_address(regs->ip, 1);
        printk(" RSP <%016lx>\n", regs->sp);
        if (kexec_should_crash(current))
                crash_kexec(regs);
        return 0;
}

void die(const char *str, struct pt_regs *regs, long err)
{
        unsigned long flags = oops_begin();

        if (!user_mode(regs))
                report_bug(regs->ip, regs);

        if (__die(str, regs, err))
                regs = NULL;
        oops_end(flags, regs, SIGSEGV);
}

notrace __kprobes void
die_nmi(char *str, struct pt_regs *regs, int do_panic)
{
        unsigned long flags;

        if (notify_die(DIE_NMIWATCHDOG, str, regs, 0, 2, SIGINT) == NOTIFY_STOP)
                return;

        flags = oops_begin();
        /*
         * We are in trouble anyway, lets at least try
         * to get a message out.
         */
        printk(KERN_EMERG "%s", str);
        printk(" on CPU%d, ip %08lx, registers:\n",
                smp_processor_id(), regs->ip);
        show_registers(regs);
        if (kexec_should_crash(current))
                crash_kexec(regs);
        if (do_panic || panic_on_oops)
                panic("Non maskable interrupt");
        oops_end(flags, NULL, SIGBUS);
        nmi_exit();
        local_irq_enable();
        do_exit(SIGBUS);
}

static void __kprobes
do_trap(int trapnr, int signr, char *str, struct pt_regs *regs,
        long error_code, siginfo_t *info)
{
        struct task_struct *tsk = current;

        if (!user_mode(regs))
                goto kernel_trap;

        /*
         * We want error_code and trap_no set for userspace faults and
         * kernelspace faults which result in die(), but not
         * kernelspace faults which are fixed up.  die() gives the
         * process no chance to handle the signal and notice the
         * kernel fault information, so that won't result in polluting
         * the information about previously queued, but not yet
         * delivered, faults.  See also do_general_protection below.
         */
        tsk->thread.error_code = error_code;
        tsk->thread.trap_no = trapnr;

        if (show_unhandled_signals && unhandled_signal(tsk, signr) &&
            printk_ratelimit()) {
                printk(KERN_INFO
                       "%s[%d] trap %s ip:%lx sp:%lx error:%lx",
                       tsk->comm, tsk->pid, str,
                       regs->ip, regs->sp, error_code);
                print_vma_addr(" in ", regs->ip);
                printk("\n");
        }

        if (info)
                force_sig_info(signr, info, tsk);
        else
                force_sig(signr, tsk);
        return;

kernel_trap:
        if (!fixup_exception(regs)) {
                tsk->thread.error_code = error_code;
                tsk->thread.trap_no = trapnr;
                die(str, regs, error_code);
        }
        return;
}

#define DO_ERROR(trapnr, signr, str, name) \
asmlinkage void do_##name(struct pt_regs * regs, long error_code)       \
{                                                                       \
        if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr)  \
                                                        == NOTIFY_STOP) \
                return;                                                 \
        conditional_sti(regs);                                          \
        do_trap(trapnr, signr, str, regs, error_code, NULL);            \
}

#define DO_ERROR_INFO(trapnr, signr, str, name, sicode, siaddr)         \
asmlinkage void do_##name(struct pt_regs * regs, long error_code)       \
{                                                                       \
        siginfo_t info;                                                 \
        info.si_signo = signr;                                          \
        info.si_errno = 0;                                              \
        info.si_code = sicode;                                          \
        info.si_addr = (void __user *)siaddr;                           \
        trace_hardirqs_fixup();                                         \
        if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr)  \
                                                        == NOTIFY_STOP) \
                return;                                                 \
        conditional_sti(regs);                                          \
        do_trap(trapnr, signr, str, regs, error_code, &info);           \
}

DO_ERROR_INFO(0, SIGFPE, "divide error", divide_error, FPE_INTDIV, regs->ip)
DO_ERROR(4, SIGSEGV, "overflow", overflow)
DO_ERROR(5, SIGSEGV, "bounds", bounds)
DO_ERROR_INFO(6, SIGILL, "invalid opcode", invalid_op, ILL_ILLOPN, regs->ip)
DO_ERROR(9, SIGFPE, "coprocessor segment overrun", coprocessor_segment_overrun)
DO_ERROR(10, SIGSEGV, "invalid TSS", invalid_TSS)
DO_ERROR(11, SIGBUS, "segment not present", segment_not_present)
DO_ERROR_INFO(17, SIGBUS, "alignment check", alignment_check, BUS_ADRALN, 0)

/* Runs on IST stack */
asmlinkage void do_stack_segment(struct pt_regs *regs, long error_code)
{
        if (notify_die(DIE_TRAP, "stack segment", regs, error_code,
                        12, SIGBUS) == NOTIFY_STOP)
                return;
        preempt_conditional_sti(regs);
        do_trap(12, SIGBUS, "stack segment", regs, error_code, NULL);
        preempt_conditional_cli(regs);
}

asmlinkage void do_double_fault(struct pt_regs * regs, long error_code)
{
        static const char str[] = "double fault";
        struct task_struct *tsk = current;

        /* Return not checked because double check cannot be ignored */
        notify_die(DIE_TRAP, str, regs, error_code, 8, SIGSEGV);

        tsk->thread.error_code = error_code;
        tsk->thread.trap_no = 8;

        /* This is always a kernel trap and never fixable (and thus must
           never return). */
        for (;;)
                die(str, regs, error_code);
}

asmlinkage void __kprobes
do_general_protection(struct pt_regs *regs, long error_code)
{
        struct task_struct *tsk;

        conditional_sti(regs);

        tsk = current;
        if (!user_mode(regs))
                goto gp_in_kernel;

        tsk->thread.error_code = error_code;
        tsk->thread.trap_no = 13;

        if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
                        printk_ratelimit()) {
                printk(KERN_INFO
                        "%s[%d] general protection ip:%lx sp:%lx error:%lx",
                        tsk->comm, tsk->pid,
                        regs->ip, regs->sp, error_code);
                print_vma_addr(" in ", regs->ip);
                printk("\n");
        }

        force_sig(SIGSEGV, tsk);
        return;

gp_in_kernel:
        if (fixup_exception(regs))
                return;

        tsk->thread.error_code = error_code;
        tsk->thread.trap_no = 13;
        if (notify_die(DIE_GPF, "general protection fault", regs,
                                error_code, 13, SIGSEGV) == NOTIFY_STOP)
                return;
        die("general protection fault", regs, error_code);
}

static notrace __kprobes void
mem_parity_error(unsigned char reason, struct pt_regs *regs)
{
        printk(KERN_EMERG "Uhhuh. NMI received for unknown reason %02x.\n",
                reason);
        printk(KERN_EMERG "You have some hardware problem, likely on the PCI bus.\n");

#if defined(CONFIG_EDAC)
        if (edac_handler_set()) {
                edac_atomic_assert_error();
                return;
        }
#endif

        if (panic_on_unrecovered_nmi)
                panic("NMI: Not continuing");

        printk(KERN_EMERG "Dazed and confused, but trying to continue\n");

        /* Clear and disable the memory parity error line. */
        reason = (reason & 0xf) | 4;
        outb(reason, 0x61);
}

static notrace __kprobes void
io_check_error(unsigned char reason, struct pt_regs *regs)
{
        printk("NMI: IOCK error (debug interrupt?)\n");
        show_registers(regs);

        /* Re-enable the IOCK line, wait for a few seconds */
        reason = (reason & 0xf) | 8;
        outb(reason, 0x61);
        mdelay(2000);
        reason &= ~8;
        outb(reason, 0x61);
}

static notrace __kprobes void
unknown_nmi_error(unsigned char reason, struct pt_regs * regs)
{
        if (notify_die(DIE_NMIUNKNOWN, "nmi", regs, reason, 2, SIGINT) == NOTIFY_STOP)
                return;
        printk(KERN_EMERG "Uhhuh. NMI received for unknown reason %02x.\n",
                reason);
        printk(KERN_EMERG "Do you have a strange power saving mode enabled?\n");

        if (panic_on_unrecovered_nmi)
                panic("NMI: Not continuing");

        printk(KERN_EMERG "Dazed and confused, but trying to continue\n");
}

/* Runs on IST stack. This code must keep interrupts off all the time.
   Nested NMIs are prevented by the CPU. */
asmlinkage notrace __kprobes void default_do_nmi(struct pt_regs *regs)
{
        unsigned char reason = 0;
        int cpu;

        cpu = smp_processor_id();

        /* Only the BSP gets external NMIs from the system. */
        if (!cpu)
                reason = get_nmi_reason();

        if (!(reason & 0xc0)) {
                if (notify_die(DIE_NMI_IPI, "nmi_ipi", regs, reason, 2, SIGINT)
                                                                == NOTIFY_STOP)
                        return;
                /*
                 * Ok, so this is none of the documented NMI sources,
                 * so it must be the NMI watchdog.
                 */
                if (nmi_watchdog_tick(regs, reason))
                        return;
                if (!do_nmi_callback(regs, cpu))
                        unknown_nmi_error(reason, regs);

                return;
        }
        if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT) == NOTIFY_STOP)
                return;

        /* AK: following checks seem to be broken on modern chipsets. FIXME */
        if (reason & 0x80)
                mem_parity_error(reason, regs);
        if (reason & 0x40)
                io_check_error(reason, regs);
}

asmlinkage notrace __kprobes void
do_nmi(struct pt_regs *regs, long error_code)
{
        nmi_enter();

        add_pda(__nmi_count, 1);

        if (!ignore_nmis)
                default_do_nmi(regs);

        nmi_exit();
}

void stop_nmi(void)
{
        acpi_nmi_disable();
        ignore_nmis++;
}

void restart_nmi(void)
{
        ignore_nmis--;
        acpi_nmi_enable();
}

/* runs on IST stack. */
asmlinkage void __kprobes do_int3(struct pt_regs *regs, long error_code)
{
        trace_hardirqs_fixup();

        if (notify_die(DIE_INT3, "int3", regs, error_code, 3, SIGTRAP)
                        == NOTIFY_STOP)
                return;

        preempt_conditional_sti(regs);
        do_trap(3, SIGTRAP, "int3", regs, error_code, NULL);
        preempt_conditional_cli(regs);
}

/* Help handler running on IST stack to switch back to user stack
   for scheduling or signal handling. The actual stack switch is done in
   entry.S */
asmlinkage __kprobes struct pt_regs *sync_regs(struct pt_regs *eregs)
{
        struct pt_regs *regs = eregs;
        /* Did already sync */
        if (eregs == (struct pt_regs *)eregs->sp)
                ;
        /* Exception from user space */
        else if (user_mode(eregs))
                regs = task_pt_regs(current);
        /* Exception from kernel and interrupts are enabled. Move to
           kernel process stack. */
        else if (eregs->flags & X86_EFLAGS_IF)
                regs = (struct pt_regs *)(eregs->sp -= sizeof(struct pt_regs));
        if (eregs != regs)
                *regs = *eregs;
        return regs;
}

/* runs on IST stack. */
asmlinkage void __kprobes do_debug(struct pt_regs * regs,
                                   unsigned long error_code)
{
        struct task_struct *tsk = current;
        unsigned long condition;
        siginfo_t info;

        trace_hardirqs_fixup();

        get_debugreg(condition, 6);

        /*
         * The processor cleared BTF, so don't mark that we need it set.
         */
        clear_tsk_thread_flag(tsk, TIF_DEBUGCTLMSR);
        tsk->thread.debugctlmsr = 0;

        if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
                                                SIGTRAP) == NOTIFY_STOP)
                return;

        preempt_conditional_sti(regs);

        /* Mask out spurious debug traps due to lazy DR7 setting */
        if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3)) {
                if (!tsk->thread.debugreg7)
                        goto clear_dr7;
        }

        tsk->thread.debugreg6 = condition;

        /*
         * Single-stepping through TF: make sure we ignore any events in
         * kernel space (but re-enable TF when returning to user mode).
         */
        if (condition & DR_STEP) {
                if (!user_mode(regs))
                        goto clear_TF_reenable;
        }

        /* Ok, finally something we can handle */
        tsk->thread.trap_no = 1;
        tsk->thread.error_code = error_code;
        info.si_signo = SIGTRAP;
        info.si_errno = 0;
        info.si_code = TRAP_BRKPT;
        info.si_addr = user_mode(regs) ? (void __user *)regs->ip : NULL;
        force_sig_info(SIGTRAP, &info, tsk);

clear_dr7:
        set_debugreg(0, 7);
        preempt_conditional_cli(regs);
        return;

clear_TF_reenable:
        set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
        regs->flags &= ~X86_EFLAGS_TF;
        preempt_conditional_cli(regs);
        return;
}

static int kernel_math_error(struct pt_regs *regs, const char *str, int trapnr)
{
        if (fixup_exception(regs))
                return 1;

        notify_die(DIE_GPF, str, regs, 0, trapnr, SIGFPE);
        /* Illegal floating point operation in the kernel */
        current->thread.trap_no = trapnr;
        die(str, regs, 0);
        return 0;
}

/*
 * Note that we play around with the 'TS' bit in an attempt to get
 * the correct behaviour even in the presence of the asynchronous
 * IRQ13 behaviour
 */
asmlinkage void do_coprocessor_error(struct pt_regs *regs)
{
        void __user *ip = (void __user *)(regs->ip);
        struct task_struct *task;
        siginfo_t info;
        unsigned short cwd, swd;

        conditional_sti(regs);
        if (!user_mode(regs) &&
            kernel_math_error(regs, "kernel x87 math error", 16))
                return;

        /*
         * Save the info for the exception handler and clear the error.
         */
        task = current;
        save_init_fpu(task);
        task->thread.trap_no = 16;
        task->thread.error_code = 0;
        info.si_signo = SIGFPE;
        info.si_errno = 0;
        info.si_code = __SI_FAULT;
        info.si_addr = ip;
        /*
         * (~cwd & swd) will mask out exceptions that are not set to unmasked
         * status.  0x3f is the exception bits in these regs, 0x200 is the
         * C1 reg you need in case of a stack fault, 0x040 is the stack
         * fault bit.  We should only be taking one exception at a time,
         * so if this combination doesn't produce any single exception,
         * then we have a bad program that isn't synchronizing its FPU usage
         * and it will suffer the consequences since we won't be able to
         * fully reproduce the context of the exception
         */
        cwd = get_fpu_cwd(task);
        swd = get_fpu_swd(task);
        switch (swd & ~cwd & 0x3f) {
        case 0x000: /* No unmasked exception */
        default: /* Multiple exceptions */
                break;
        case 0x001: /* Invalid Op */
                /*
                 * swd & 0x240 == 0x040: Stack Underflow
                 * swd & 0x240 == 0x240: Stack Overflow
                 * User must clear the SF bit (0x40) if set
                 */
                info.si_code = FPE_FLTINV;
                break;
        case 0x002: /* Denormalize */
        case 0x010: /* Underflow */
                info.si_code = FPE_FLTUND;
                break;
        case 0x004: /* Zero Divide */
                info.si_code = FPE_FLTDIV;
                break;
        case 0x008: /* Overflow */
                info.si_code = FPE_FLTOVF;
                break;
        case 0x020: /* Precision */
                info.si_code = FPE_FLTRES;
                break;
        }
        force_sig_info(SIGFPE, &info, task);
}

asmlinkage void bad_intr(void)
{
        printk("bad interrupt"); 
}

asmlinkage void do_simd_coprocessor_error(struct pt_regs *regs)
{
        void __user *ip = (void __user *)(regs->ip);
        struct task_struct *task;
        siginfo_t info;
        unsigned short mxcsr;

        conditional_sti(regs);
        if (!user_mode(regs) &&
                kernel_math_error(regs, "kernel simd math error", 19))
                return;

        /*
         * Save the info for the exception handler and clear the error.
         */
        task = current;
        save_init_fpu(task);
        task->thread.trap_no = 19;
        task->thread.error_code = 0;
        info.si_signo = SIGFPE;
        info.si_errno = 0;
        info.si_code = __SI_FAULT;
        info.si_addr = ip;
        /*
         * The SIMD FPU exceptions are handled a little differently, as there
         * is only a single status/control register.  Thus, to determine which
         * unmasked exception was caught we must mask the exception mask bits
         * at 0x1f80, and then use these to mask the exception bits at 0x3f.
         */
        mxcsr = get_fpu_mxcsr(task);
        switch (~((mxcsr & 0x1f80) >> 7) & (mxcsr & 0x3f)) {
        case 0x000:
        default:
                break;
        case 0x001: /* Invalid Op */
                info.si_code = FPE_FLTINV;
                break;
        case 0x002: /* Denormalize */
        case 0x010: /* Underflow */
                info.si_code = FPE_FLTUND;
                break;
        case 0x004: /* Zero Divide */
                info.si_code = FPE_FLTDIV;
                break;
        case 0x008: /* Overflow */
                info.si_code = FPE_FLTOVF;
                break;
        case 0x020: /* Precision */
                info.si_code = FPE_FLTRES;
                break;
        }
        force_sig_info(SIGFPE, &info, task);
}

asmlinkage void do_spurious_interrupt_bug(struct pt_regs * regs)
{
}

asmlinkage void __attribute__((weak)) smp_thermal_interrupt(void)
{
}

asmlinkage void __attribute__((weak)) mce_threshold_interrupt(void)
{
}

/*
 * 'math_state_restore()' saves the current math information in the
 * old math state array, and gets the new ones from the current task
 *
 * Careful.. There are problems with IBM-designed IRQ13 behaviour.
 * Don't touch unless you *really* know how it works.
 */
asmlinkage void math_state_restore(void)
{
        struct task_struct *me = current;

        if (!used_math()) {
                local_irq_enable();
                /*
                 * does a slab alloc which can sleep
                 */
                if (init_fpu(me)) {
                        /*
                         * ran out of memory!
                         */
                        do_group_exit(SIGKILL);
                        return;
                }
                local_irq_disable();
        }

        clts();                         /* Allow maths ops (or we recurse) */
        /*
         * Paranoid restore. send a SIGSEGV if we fail to restore the state.
         */
        if (unlikely(restore_fpu_checking(me))) {
                stts();
                force_sig(SIGSEGV, me);
                return;
        }
        task_thread_info(me)->status |= TS_USEDFPU;
        me->fpu_counter++;
}
EXPORT_SYMBOL_GPL(math_state_restore);

void __init trap_init(void)
{
        set_intr_gate(0, &divide_error);
        set_intr_gate_ist(1, &debug, DEBUG_STACK);
        set_intr_gate_ist(2, &nmi, NMI_STACK);
        set_system_gate_ist(3, &int3, DEBUG_STACK); /* int3 can be called from all */
        set_system_gate(4, &overflow); /* int4 can be called from all */
        set_intr_gate(5, &bounds);
        set_intr_gate(6, &invalid_op);
        set_intr_gate(7, &device_not_available);
        set_intr_gate_ist(8, &double_fault, DOUBLEFAULT_STACK);
        set_intr_gate(9, &coprocessor_segment_overrun);
        set_intr_gate(10, &invalid_TSS);
        set_intr_gate(11, &segment_not_present);
        set_intr_gate_ist(12, &stack_segment, STACKFAULT_STACK);
        set_intr_gate(13, &general_protection);
        set_intr_gate(14, &page_fault);
        set_intr_gate(15, &spurious_interrupt_bug);
        set_intr_gate(16, &coprocessor_error);
        set_intr_gate(17, &alignment_check);
#ifdef CONFIG_X86_MCE
        set_intr_gate_ist(18, &machine_check, MCE_STACK);
#endif
        set_intr_gate(19, &simd_coprocessor_error);

#ifdef CONFIG_IA32_EMULATION
        set_system_gate(IA32_SYSCALL_VECTOR, ia32_syscall);
#endif
        /*
         * Should be a barrier for any external CPU state:
         */
        cpu_init();
}

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);

static int __init kstack_setup(char *s)
{
        if (!s)
                return -EINVAL;
        kstack_depth_to_print = simple_strtoul(s, NULL, 0);
        return 0;
}
early_param("kstack", kstack_setup);

static int __init code_bytes_setup(char *s)
{
        code_bytes = simple_strtoul(s, NULL, 0);
        if (code_bytes > 8192)
                code_bytes = 8192;

        return 1;
}
__setup("code_bytes=", code_bytes_setup);