/*
 *  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
 */

/*
 * Handle hardware traps and faults.
 */
#include <linux/interrupt.h>
#include <linux/kallsyms.h>
#include <linux/spinlock.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <linux/kdebug.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/string.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>
#include <linux/smp.h>
#include <linux/io.h>

#ifdef CONFIG_EISA
#include <linux/ioport.h>
#include <linux/eisa.h>
#endif

#ifdef CONFIG_MCA
#include <linux/mca.h>
#endif

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

#include <asm/kmemcheck.h>
#include <asm/stacktrace.h>
#include <asm/processor.h>
#include <asm/debugreg.h>
#include <asm/atomic.h>
#include <asm/system.h>
#include <asm/traps.h>
#include <asm/desc.h>
#include <asm/i387.h>
#include <asm/mce.h>

#include <asm/mach_traps.h>

#ifdef CONFIG_X86_64
#include <asm/x86_init.h>
#include <asm/pgalloc.h>
#include <asm/proto.h>
#else
#include <asm/processor-flags.h>
#include <asm/setup.h>

asmlinkage int system_call(void);

/* Do we ignore FPU interrupts ? */
char ignore_fpu_irq;

/*
 * The IDT has to be page-aligned to simplify the Pentium
 * F0 0F bug workaround.
 */
gate_desc idt_table[NR_VECTORS] __page_aligned_data = { { { { 0, 0 } } }, };
#endif

DECLARE_BITMAP(used_vectors, NR_VECTORS);
EXPORT_SYMBOL_GPL(used_vectors);

static int ignore_nmis;

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 conditional_cli(struct pt_regs *regs)
{
        if (regs->flags & X86_EFLAGS_IF)
                local_irq_disable();
}

static inline void preempt_conditional_cli(struct pt_regs *regs)
{
        if (regs->flags & X86_EFLAGS_IF)
                local_irq_disable();
        dec_preempt_count();
}

#ifdef CONFIG_X86_32
static inline void
die_if_kernel(const char *str, struct pt_regs *regs, long err)
{
        if (!user_mode_vm(regs))
                die(str, regs, err);
}
#endif

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;

#ifdef CONFIG_X86_32
        if (regs->flags & X86_VM_MASK) {
                /*
                 * traps 0, 1, 3, 4, and 5 should be forwarded to vm86.
                 * On nmi (interrupt 2), do_trap should not be called.
                 */
                if (trapnr < 6)
                        goto vm86_trap;
                goto trap_signal;
        }
#endif

        if (!user_mode(regs))
                goto kernel_trap;

#ifdef CONFIG_X86_32
trap_signal:
#endif
        /*
         * 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;

#ifdef CONFIG_X86_64
        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");
        }
#endif

        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;

#ifdef CONFIG_X86_32
vm86_trap:
        if (handle_vm86_trap((struct kernel_vm86_regs *) regs,
                                                error_code, trapnr))
                goto trap_signal;
        return;
#endif
}

#define DO_ERROR(trapnr, signr, str, name)                              \
dotraplinkage 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)         \
dotraplinkage 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;                           \
        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)
#ifdef CONFIG_X86_32
DO_ERROR(12, SIGBUS, "stack segment", stack_segment)
#endif
DO_ERROR_INFO(17, SIGBUS, "alignment check", alignment_check, BUS_ADRALN, 0)

#ifdef CONFIG_X86_64
/* Runs on IST stack */
dotraplinkage 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);
}

dotraplinkage 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);
}
#endif

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

        conditional_sti(regs);

#ifdef CONFIG_X86_32
        if (regs->flags & X86_VM_MASK)
                goto gp_in_vm86;
#endif

        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, task_pid_nr(tsk),
                        regs->ip, regs->sp, error_code);
                print_vma_addr(" in ", regs->ip);
                printk("\n");
        }

        force_sig(SIGSEGV, tsk);
        return;

#ifdef CONFIG_X86_32
gp_in_vm86:
        local_irq_enable();
        handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code);
        return;
#endif

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 on CPU %d.\n",
                        reason, smp_processor_id());

        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)
{
        unsigned long i;

        printk(KERN_EMERG "NMI: IOCK error (debug interrupt?)\n");
        show_registers(regs);

        if (panic_on_io_nmi)
                panic("NMI IOCK error: Not continuing");

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

        i = 2000;
        while (--i)
                udelay(1000);

        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;
#ifdef CONFIG_MCA
        /*
         * Might actually be able to figure out what the guilty party
         * is:
         */
        if (MCA_bus) {
                mca_handle_nmi();
                return;
        }
#endif
        printk(KERN_EMERG
                "Uhhuh. NMI received for unknown reason %02x on CPU %d.\n",
                        reason, smp_processor_id());

        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");
}

static 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;
#ifdef CONFIG_X86_LOCAL_APIC
                /*
                 * 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);
#else
                unknown_nmi_error(reason, regs);
#endif

                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);
#ifdef CONFIG_X86_32
        /*
         * Reassert NMI in case it became active meanwhile
         * as it's edge-triggered:
         */
        reassert_nmi();
#endif
}

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

        inc_irq_stat(__nmi_count);

        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();
}

/* May run on IST stack. */
dotraplinkage void __kprobes do_int3(struct pt_regs *regs, long error_code)
{
#ifdef CONFIG_KPROBES
        if (notify_die(DIE_INT3, "int3", regs, error_code, 3, SIGTRAP)
                        == NOTIFY_STOP)
                return;
#else
        if (notify_die(DIE_TRAP, "int3", regs, error_code, 3, SIGTRAP)
                        == NOTIFY_STOP)
                return;
#endif

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

#ifdef CONFIG_X86_64
/*
 * 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;
}
#endif

/*
 * Our handling of the processor debug registers is non-trivial.
 * We do not clear them on entry and exit from the kernel. Therefore
 * it is possible to get a watchpoint trap here from inside the kernel.
 * However, the code in ./ptrace.c has ensured that the user can
 * only set watchpoints on userspace addresses. Therefore the in-kernel
 * watchpoint trap can only occur in code which is reading/writing
 * from user space. Such code must not hold kernel locks (since it
 * can equally take a page fault), therefore it is safe to call
 * force_sig_info even though that claims and releases locks.
 *
 * Code in ./signal.c ensures that the debug control register
 * is restored before we deliver any signal, and therefore that
 * user code runs with the correct debug control register even though
 * we clear it here.
 *
 * Being careful here means that we don't have to be as careful in a
 * lot of more complicated places (task switching can be a bit lazy
 * about restoring all the debug state, and ptrace doesn't have to
 * find every occurrence of the TF bit that could be saved away even
 * by user code)
 *
 * May run on IST stack.
 */
dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
{
        struct task_struct *tsk = current;
        unsigned long condition;
        int si_code;

        get_debugreg(condition, 6);

        /* Catch kmemcheck conditions first of all! */
        if (condition & DR_STEP && kmemcheck_trap(regs))
                return;

        /*
         * 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;

        /* It's safe to allow irq's after DR6 has been saved */
        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;
        }

#ifdef CONFIG_X86_32
        if (regs->flags & X86_VM_MASK)
                goto debug_vm86;
#endif

        /* Save debug status register where ptrace can see it */
        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;
        }

        si_code = get_si_code(condition);
        /* Ok, finally something we can handle */
        send_sigtrap(tsk, regs, error_code, si_code);

        /*
         * Disable additional traps. They'll be re-enabled when
         * the signal is delivered.
         */
clear_dr7:
        set_debugreg(0, 7);
        preempt_conditional_cli(regs);
        return;

#ifdef CONFIG_X86_32
debug_vm86:
        /* reenable preemption: handle_vm86_trap() might sleep */
        dec_preempt_count();
        handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, 1);
        conditional_cli(regs);
        return;
#endif

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

#ifdef CONFIG_X86_64
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;
}
#endif

/*
 * 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
 */
void math_error(void __user *ip)
{
        struct task_struct *task;
        siginfo_t info;
        unsigned short cwd, swd, err;

        /*
         * 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_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);

        err = swd & ~cwd;

        if (err & 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;
        } else if (err & 0x004) { /* Divide by Zero */
                info.si_code = FPE_FLTDIV;
        } else if (err & 0x008) { /* Overflow */
                info.si_code = FPE_FLTOVF;
        } else if (err & 0x012) { /* Denormal, Underflow */
                info.si_code = FPE_FLTUND;
        } else if (err & 0x020) { /* Precision */
                info.si_code = FPE_FLTRES;
        } else {
                /*
                 * If we're using IRQ 13, or supposedly even some trap 16
                 * implementations, it's possible we get a spurious trap...
                 */
                return;         /* Spurious trap, no error */
        }
        force_sig_info(SIGFPE, &info, task);
}

dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code)
{
        conditional_sti(regs);

#ifdef CONFIG_X86_32
        ignore_fpu_irq = 1;
#else
        if (!user_mode(regs) &&
            kernel_math_error(regs, "kernel x87 math error", 16))
                return;
#endif

        math_error((void __user *)regs->ip);
}

static void simd_math_error(void __user *ip)
{
        struct task_struct *task;
        siginfo_t info;
        unsigned short mxcsr;

        /*
         * 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);
}

dotraplinkage void
do_simd_coprocessor_error(struct pt_regs *regs, long error_code)
{
        conditional_sti(regs);

#ifdef CONFIG_X86_32
        if (cpu_has_xmm) {
                /* Handle SIMD FPU exceptions on PIII+ processors. */
                ignore_fpu_irq = 1;
                simd_math_error((void __user *)regs->ip);
                return;
        }
        /*
         * Handle strange cache flush from user space exception
         * in all other cases.  This is undocumented behaviour.
         */
        if (regs->flags & X86_VM_MASK) {
                handle_vm86_fault((struct kernel_vm86_regs *)regs, error_code);
                return;
        }
        current->thread.trap_no = 19;
        current->thread.error_code = error_code;
        die_if_kernel("cache flush denied", regs, error_code);
        force_sig(SIGSEGV, current);
#else
        if (!user_mode(regs) &&
                        kernel_math_error(regs, "kernel simd math error", 19))
                return;
        simd_math_error((void __user *)regs->ip);
#endif
}

dotraplinkage void
do_spurious_interrupt_bug(struct pt_regs *regs, long error_code)
{
        conditional_sti(regs);
#if 0
        /* No need to warn about this any longer. */
        printk(KERN_INFO "Ignoring P6 Local APIC Spurious Interrupt Bug...\n");
#endif
}

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

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

/*
 * __math_state_restore assumes that cr0.TS is already clear and the
 * fpu state is all ready for use.  Used during context switch.
 */
void __math_state_restore(void)
{
        struct thread_info *thread = current_thread_info();
        struct task_struct *tsk = thread->task;

        /*
         * Paranoid restore. send a SIGSEGV if we fail to restore the state.
         */
        if (unlikely(restore_fpu_checking(tsk))) {
                stts();
                force_sig(SIGSEGV, tsk);
                return;
        }

        thread->status |= TS_USEDFPU;   /* So we fnsave on switch_to() */
        tsk->fpu_counter++;
}

/*
 * '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.
 *
 * Must be called with kernel preemption disabled (in this case,
 * local interrupts are disabled at the call-site in entry.S).
 */
asmlinkage void math_state_restore(void)
{
        struct thread_info *thread = current_thread_info();
        struct task_struct *tsk = thread->task;

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

        clts();                         /* Allow maths ops (or we recurse) */

        __math_state_restore();
}
EXPORT_SYMBOL_GPL(math_state_restore);

#ifndef CONFIG_MATH_EMULATION
void math_emulate(struct math_emu_info *info)
{
        printk(KERN_EMERG
                "math-emulation not enabled and no coprocessor found.\n");
        printk(KERN_EMERG "killing %s.\n", current->comm);
        force_sig(SIGFPE, current);
        schedule();
}
#endif /* CONFIG_MATH_EMULATION */

dotraplinkage void __kprobes
do_device_not_available(struct pt_regs *regs, long error_code)
{
#ifdef CONFIG_X86_32
        if (read_cr0() & X86_CR0_EM) {
                struct math_emu_info info = { };

                conditional_sti(regs);

                info.regs = regs;
                math_emulate(&info);
        } else {
                math_state_restore(); /* interrupts still off */
                conditional_sti(regs);
        }
#else
        math_state_restore();
#endif
}

#ifdef CONFIG_X86_32
dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
{
        siginfo_t info;
        local_irq_enable();

        info.si_signo = SIGILL;
        info.si_errno = 0;
        info.si_code = ILL_BADSTK;
        info.si_addr = NULL;
        if (notify_die(DIE_TRAP, "iret exception",
                        regs, error_code, 32, SIGILL) == NOTIFY_STOP)
                return;
        do_trap(32, SIGILL, "iret exception", regs, error_code, &info);
}
#endif

void __init trap_init(void)
{
        int i;

#ifdef CONFIG_EISA
        void __iomem *p = early_ioremap(0x0FFFD9, 4);

        if (readl(p) == 'E' + ('I'<<8) + ('S'<<16) + ('A'<<24))
                EISA_bus = 1;
        early_iounmap(p, 4);
#endif

        set_intr_gate(0, &divide_error);
        set_intr_gate_ist(1, &debug, DEBUG_STACK);
        set_intr_gate_ist(2, &nmi, NMI_STACK);
        /* int3 can be called from all */
        set_system_intr_gate_ist(3, &int3, DEBUG_STACK);
        /* int4 can be called from all */
        set_system_intr_gate(4, &overflow);
        set_intr_gate(5, &bounds);
        set_intr_gate(6, &invalid_op);
        set_intr_gate(7, &device_not_available);
#ifdef CONFIG_X86_32
        set_task_gate(8, GDT_ENTRY_DOUBLEFAULT_TSS);
#else
        set_intr_gate_ist(8, &double_fault, DOUBLEFAULT_STACK);
#endif
        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);

        /* Reserve all the builtin and the syscall vector: */
        for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++)
                set_bit(i, used_vectors);

#ifdef CONFIG_IA32_EMULATION
        set_system_intr_gate(IA32_SYSCALL_VECTOR, ia32_syscall);
        set_bit(IA32_SYSCALL_VECTOR, used_vectors);
#endif

#ifdef CONFIG_X86_32
        if (cpu_has_fxsr) {
                printk(KERN_INFO "Enabling fast FPU save and restore... ");
                set_in_cr4(X86_CR4_OSFXSR);
                printk("done.\n");
        }
        if (cpu_has_xmm) {
                printk(KERN_INFO
                        "Enabling unmasked SIMD FPU exception support... ");
                set_in_cr4(X86_CR4_OSXMMEXCPT);
                printk("done.\n");
        }

        set_system_trap_gate(SYSCALL_VECTOR, &system_call);
        set_bit(SYSCALL_VECTOR, used_vectors);
#endif

        /*
         * Should be a barrier for any external CPU state:
         */
        cpu_init();

        x86_init.irqs.trap_init();
}