x86: add the capability to print fuzzy backtraces

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / arch / x86 / kernel / traps_32.c

/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  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 'asm.s'.
 */
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/highmem.h>
#include <linux/kallsyms.h>
#include <linux/ptrace.h>
#include <linux/utsname.h>
#include <linux/kprobes.h>
#include <linux/kexec.h>
#include <linux/unwind.h>
#include <linux/uaccess.h>
#include <linux/nmi.h>
#include <linux/bug.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/processor.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/atomic.h>
#include <asm/debugreg.h>
#include <asm/desc.h>
#include <asm/i387.h>
#include <asm/nmi.h>
#include <asm/unwind.h>
#include <asm/smp.h>
#include <asm/arch_hooks.h>
#include <linux/kdebug.h>
#include <asm/stacktrace.h>

#include <linux/module.h>

#include "mach_traps.h"

int panic_on_unrecovered_nmi;

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

asmlinkage int system_call(void);

/* Do we ignore FPU interrupts ? */
char ignore_fpu_irq = 0;

/*
 * The IDT has to be page-aligned to simplify the Pentium
 * F0 0F bug workaround.. We have a special link segment
 * for this.
 */
gate_desc idt_table[256]
        __attribute__((__section__(".data.idt"))) = { { { { 0, 0 } } }, };

asmlinkage void divide_error(void);
asmlinkage void debug(void);
asmlinkage void nmi(void);
asmlinkage void int3(void);
asmlinkage void overflow(void);
asmlinkage void bounds(void);
asmlinkage void invalid_op(void);
asmlinkage void device_not_available(void);
asmlinkage void coprocessor_segment_overrun(void);
asmlinkage void invalid_TSS(void);
asmlinkage void segment_not_present(void);
asmlinkage void stack_segment(void);
asmlinkage void general_protection(void);
asmlinkage void page_fault(void);
asmlinkage void coprocessor_error(void);
asmlinkage void simd_coprocessor_error(void);
asmlinkage void alignment_check(void);
asmlinkage void spurious_interrupt_bug(void);
asmlinkage void machine_check(void);

int kstack_depth_to_print = 24;
static unsigned int code_bytes = 64;

static inline int valid_stack_ptr(struct thread_info *tinfo, void *p, unsigned size)
{
        return  p > (void *)tinfo &&
                p <= (void *)tinfo + 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)
{
#ifdef  CONFIG_FRAME_POINTER
        struct stack_frame *frame = (struct stack_frame *)bp;
        while (valid_stack_ptr(tinfo, frame, sizeof(*frame))) {
                struct stack_frame *next;
                unsigned long addr;

                addr = frame->return_address;
                if (__kernel_text_address(addr))
                        ops->address(data, addr, 1);
                /*
                 * break out of recursive entries (such as
                 * end_of_stack_stop_unwind_function). Also,
                 * we can never allow a frame pointer to
                 * move downwards!
                 */
                next = frame->next_frame;
                bp = (unsigned long) next;
                if (next <= frame)
                        break;
                frame = next;
        }
#else
        while (valid_stack_ptr(tinfo, stack, sizeof(*stack))) {
                unsigned long addr;

                addr = *stack++;
                if (__kernel_text_address(addr))
                        ops->address(data, addr, 1);
        }
#endif
        return bp;
}

#define MSG(msg) ops->warning(data, msg)

void dump_trace(struct task_struct *task, struct pt_regs *regs,
                unsigned long *stack,
                const struct stacktrace_ops *ops, void *data)
{
        unsigned long bp = 0;

        if (!task)
                task = current;

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

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

        while (1) {
                struct thread_info *context;
                context = (struct thread_info *)
                        ((unsigned long)stack & (~(THREAD_SIZE - 1)));
                bp = print_context_stack(context, stack, bp, ops, data);
                /* Should be after the line below, but somewhere
                   in early boot context comes out corrupted and we
                   can't reference it -AK */
                if (ops->stack(data, "IRQ") < 0)
                        break;
                stack = (unsigned long*)context->previous_esp;
                if (!stack)
                        break;
                touch_nmi_watchdog();
        }
}
EXPORT_SYMBOL(dump_trace);

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

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

static int print_trace_stack(void *data, char *name)
{
        return 0;
}

/*
 * Print one address/symbol entries per line.
 */
static void print_trace_address(void *data, unsigned long addr, int reliable)
{
        printk("%s [<%08lx>] ", (char *)data, addr);
        if (!reliable)
                printk("? ");
        print_symbol("%s\n", addr);
        touch_nmi_watchdog();
}

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, char *log_lvl)
{
        dump_trace(task, regs, stack, &print_trace_ops, log_lvl);
        printk("%s =======================\n", log_lvl);
}

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

static void show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
                               unsigned long *sp, char *log_lvl)
{
        unsigned long *stack;
        int i;

        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 (kstack_end(stack))
                        break;
                if (i && ((i % 8) == 0))
                        printk("\n%s       ", log_lvl);
                printk("%08lx ", *stack++);
        }
        printk("\n%sCall Trace:\n", log_lvl);
        show_trace_log_lvl(task, regs, sp, log_lvl);
}

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

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

        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(current, NULL, &stack);
}

EXPORT_SYMBOL(dump_stack);

void show_registers(struct pt_regs *regs)
{
        int i;

        print_modules();
        __show_registers(regs, 0);
        printk(KERN_EMERG "Process %.*s (pid: %d, ti=%p task=%p task.ti=%p)",
                TASK_COMM_LEN, current->comm, task_pid_nr(current),
                current_thread_info(), current, task_thread_info(current));
        /*
         * When in-kernel, we also print out the stack and code at the
         * time of the fault..
         */
        if (!user_mode_vm(regs)) {
                u8 *ip;
                unsigned int code_prologue = code_bytes * 43 / 64;
                unsigned int code_len = code_bytes;
                unsigned char c;

                printk("\n" KERN_EMERG "Stack: ");
                show_stack_log_lvl(NULL, regs, &regs->sp, KERN_EMERG);

                printk(KERN_EMERG "Code: ");

                ip = (u8 *)regs->ip - code_prologue;
                if (ip < (u8 *)PAGE_OFFSET ||
                        probe_kernel_address(ip, c)) {
                        /* try starting at EIP */
                        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 EIP 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 (ip < PAGE_OFFSET)
                return 0;
        if (probe_kernel_address((unsigned short *)ip, ud2))
                return 0;

        return ud2 == 0x0b0f;
}

static int die_counter;

int __kprobes __die(const char * str, struct pt_regs * regs, long err)
{
        unsigned long sp;
        unsigned short ss;

        printk(KERN_EMERG "%s: %04lx [#%d] ", 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) {
                show_registers(regs);
                /* Executive summary in case the oops scrolled away */
                sp = (unsigned long) (&regs->sp);
                savesegment(ss, ss);
                if (user_mode(regs)) {
                        sp = regs->sp;
                        ss = regs->ss & 0xffff;
                }
                printk(KERN_EMERG "EIP: [<%08lx>] ", regs->ip);
                print_symbol("%s", regs->ip);
                printk(" SS:ESP %04x:%08lx\n", ss, sp);
                return 0;
        } else {
                return 1;
        }
}

/*
 * This is gone through when something in the kernel has done something bad and
 * is about to be terminated.
 */
void die(const char * str, struct pt_regs * regs, long err)
{
        static struct {
                raw_spinlock_t lock;
                u32 lock_owner;
                int lock_owner_depth;
        } die = {
                .lock =                 __RAW_SPIN_LOCK_UNLOCKED,
                .lock_owner =           -1,
                .lock_owner_depth =     0
        };
        unsigned long flags;

        oops_enter();

        if (die.lock_owner != raw_smp_processor_id()) {
                console_verbose();
                raw_local_irq_save(flags);
                __raw_spin_lock(&die.lock);
                die.lock_owner = smp_processor_id();
                die.lock_owner_depth = 0;
                bust_spinlocks(1);
        } else
                raw_local_irq_save(flags);

        if (++die.lock_owner_depth < 3) {
                report_bug(regs->ip, regs);

                if (__die(str, regs, err))
                        regs = NULL;
        } else {
                printk(KERN_EMERG "Recursive die() failure, output suppressed\n");
        }

        bust_spinlocks(0);
        die.lock_owner = -1;
        add_taint(TAINT_DIE);
        __raw_spin_unlock(&die.lock);
        raw_local_irq_restore(flags);

        if (!regs)
                return;

        if (kexec_should_crash(current))
                crash_kexec(regs);

        if (in_interrupt())
                panic("Fatal exception in interrupt");

        if (panic_on_oops)
                panic("Fatal exception");

        oops_exit();
        do_exit(SIGSEGV);
}

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

static void __kprobes do_trap(int trapnr, int signr, char *str, int vm86,
                              struct pt_regs * regs, long error_code,
                              siginfo_t *info)
{
        struct task_struct *tsk = current;

        if (regs->flags & VM_MASK) {
                if (vm86)
                        goto vm86_trap;
                goto trap_signal;
        }

        if (!user_mode(regs))
                goto kernel_trap;

        trap_signal: {
                /*
                 * 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 (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;
        }

        vm86_trap: {
                int ret = handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, trapnr);
                if (ret) goto trap_signal;
                return;
        }
}

#define DO_ERROR(trapnr, signr, str, name) \
void do_##name(struct pt_regs * regs, long error_code) \
{ \
        if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
                                                == NOTIFY_STOP) \
                return; \
        do_trap(trapnr, signr, str, 0, regs, error_code, NULL); \
}

#define DO_ERROR_INFO(trapnr, signr, str, name, sicode, siaddr, irq) \
void do_##name(struct pt_regs * regs, long error_code) \
{ \
        siginfo_t info; \
        if (irq) \
                local_irq_enable(); \
        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; \
        do_trap(trapnr, signr, str, 0, regs, error_code, &info); \
}

#define DO_VM86_ERROR(trapnr, signr, str, name) \
void do_##name(struct pt_regs * regs, long error_code) \
{ \
        if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) \
                                                == NOTIFY_STOP) \
                return; \
        do_trap(trapnr, signr, str, 1, regs, error_code, NULL); \
}

#define DO_VM86_ERROR_INFO(trapnr, signr, str, name, sicode, siaddr) \
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; \
        do_trap(trapnr, signr, str, 1, regs, error_code, &info); \
}

DO_VM86_ERROR_INFO( 0, SIGFPE,  "divide error", divide_error, FPE_INTDIV, regs->ip)
#ifndef CONFIG_KPROBES
DO_VM86_ERROR( 3, SIGTRAP, "int3", int3)
#endif
DO_VM86_ERROR( 4, SIGSEGV, "overflow", overflow)
DO_VM86_ERROR( 5, SIGSEGV, "bounds", bounds)
DO_ERROR_INFO( 6, SIGILL,  "invalid opcode", invalid_op, ILL_ILLOPN, regs->ip, 0)
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(12, SIGBUS,  "stack segment", stack_segment)
DO_ERROR_INFO(17, SIGBUS, "alignment check", alignment_check, BUS_ADRALN, 0, 0)
DO_ERROR_INFO(32, SIGSEGV, "iret exception", iret_error, ILL_BADSTK, 0, 1)

void __kprobes do_general_protection(struct pt_regs * regs,
                                              long error_code)
{
        int cpu = get_cpu();
        struct tss_struct *tss = &per_cpu(init_tss, cpu);
        struct thread_struct *thread = &current->thread;

        /*
         * Perform the lazy TSS's I/O bitmap copy. If the TSS has an
         * invalid offset set (the LAZY one) and the faulting thread has
         * a valid I/O bitmap pointer, we copy the I/O bitmap in the TSS
         * and we set the offset field correctly. Then we let the CPU to
         * restart the faulting instruction.
         */
        if (tss->x86_tss.io_bitmap_base == INVALID_IO_BITMAP_OFFSET_LAZY &&
            thread->io_bitmap_ptr) {
                memcpy(tss->io_bitmap, thread->io_bitmap_ptr,
                       thread->io_bitmap_max);
                /*
                 * If the previously set map was extending to higher ports
                 * than the current one, pad extra space with 0xff (no access).
                 */
                if (thread->io_bitmap_max < tss->io_bitmap_max)
                        memset((char *) tss->io_bitmap +
                                thread->io_bitmap_max, 0xff,
                                tss->io_bitmap_max - thread->io_bitmap_max);
                tss->io_bitmap_max = thread->io_bitmap_max;
                tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
                tss->io_bitmap_owner = thread;
                put_cpu();
                return;
        }
        put_cpu();

        if (regs->flags & VM_MASK)
                goto gp_in_vm86;

        if (!user_mode(regs))
                goto gp_in_kernel;

        current->thread.error_code = error_code;
        current->thread.trap_no = 13;
        if (show_unhandled_signals && unhandled_signal(current, SIGSEGV) &&
            printk_ratelimit())
                printk(KERN_INFO
                    "%s[%d] general protection ip:%lx sp:%lx error:%lx\n",
                    current->comm, task_pid_nr(current),
                    regs->ip, regs->sp, error_code);

        force_sig(SIGSEGV, current);
        return;

gp_in_vm86:
        local_irq_enable();
        handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code);
        return;

gp_in_kernel:
        if (!fixup_exception(regs)) {
                current->thread.error_code = error_code;
                current->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 __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. */
        clear_mem_error(reason);
}

static __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);

        /* 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 __kprobes void
unknown_nmi_error(unsigned char reason, struct pt_regs * regs)
{
#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 DEFINE_SPINLOCK(nmi_print_lock);

void __kprobes die_nmi(struct pt_regs *regs, const char *msg)
{
        if (notify_die(DIE_NMIWATCHDOG, msg, regs, 0, 2, SIGINT) ==
            NOTIFY_STOP)
                return;

        spin_lock(&nmi_print_lock);
        /*
        * We are in trouble anyway, lets at least try
        * to get a message out.
        */
        bust_spinlocks(1);
        printk(KERN_EMERG "%s", msg);
        printk(" on CPU%d, ip %08lx, registers:\n",
                smp_processor_id(), regs->ip);
        show_registers(regs);
        console_silent();
        spin_unlock(&nmi_print_lock);
        bust_spinlocks(0);

        /* If we are in kernel we are probably nested up pretty bad
         * and might aswell get out now while we still can.
        */
        if (!user_mode_vm(regs)) {
                current->thread.trap_no = 2;
                crash_kexec(regs);
        }

        do_exit(SIGSEGV);
}

static __kprobes void default_do_nmi(struct pt_regs * regs)
{
        unsigned char reason = 0;

        /* Only the BSP gets external NMIs from the system.  */
        if (!smp_processor_id())
                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, smp_processor_id()))
#endif
                        unknown_nmi_error(reason, regs);

                return;
        }
        if (notify_die(DIE_NMI, "nmi", regs, reason, 2, SIGINT) == NOTIFY_STOP)
                return;
        if (reason & 0x80)
                mem_parity_error(reason, regs);
        if (reason & 0x40)
                io_check_error(reason, regs);
        /*
         * Reassert NMI in case it became active meanwhile
         * as it's edge-triggered.
         */
        reassert_nmi();
}

static int ignore_nmis;

__kprobes void do_nmi(struct pt_regs * regs, long error_code)
{
        int cpu;

        nmi_enter();

        cpu = smp_processor_id();

        ++nmi_count(cpu);

        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();
}

#ifdef CONFIG_KPROBES
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;
        /* This is an interrupt gate, because kprobes wants interrupts
        disabled.  Normal trap handlers don't. */
        restore_interrupts(regs);
        do_trap(3, SIGTRAP, "int3", 1, regs, error_code, NULL);
}
#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)
 */
void __kprobes do_debug(struct pt_regs * regs, long error_code)
{
        unsigned int condition;
        struct task_struct *tsk = current;

        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;
        /* It's safe to allow irq's after DR6 has been saved */
        if (regs->flags & X86_EFLAGS_IF)
                local_irq_enable();

        /* 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;
        }

        if (regs->flags & VM_MASK)
                goto debug_vm86;

        /* 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) {
                /*
                 * We already checked v86 mode above, so we can
                 * check for kernel mode by just checking the CPL
                 * of CS.
                 */
                if (!user_mode(regs))
                        goto clear_TF_reenable;
        }

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

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

debug_vm86:
        handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, 1);
        return;

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

/*
 * 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;

        /*
         * 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 syncronizing 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 */
                        return;
                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);
}

void do_coprocessor_error(struct pt_regs * regs, long error_code)
{
        ignore_fpu_irq = 1;
        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);
}

void do_simd_coprocessor_error(struct pt_regs * regs,
                                          long error_code)
{
        if (cpu_has_xmm) {
                /* Handle SIMD FPU exceptions on PIII+ processors. */
                ignore_fpu_irq = 1;
                simd_math_error((void __user *)regs->ip);
        } else {
                /*
                 * Handle strange cache flush from user space exception
                 * in all other cases.  This is undocumented behaviour.
                 */
                if (regs->flags & 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);
        }
}

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

unsigned long patch_espfix_desc(unsigned long uesp,
                                          unsigned long kesp)
{
        struct desc_struct *gdt = __get_cpu_var(gdt_page).gdt;
        unsigned long base = (kesp - uesp) & -THREAD_SIZE;
        unsigned long new_kesp = kesp - base;
        unsigned long lim_pages = (new_kesp | (THREAD_SIZE - 1)) >> PAGE_SHIFT;
        __u64 desc = *(__u64 *)&gdt[GDT_ENTRY_ESPFIX_SS];
        /* Set up base for espfix segment */
        desc &= 0x00f0ff0000000000ULL;
        desc |= ((((__u64)base) << 16) & 0x000000ffffff0000ULL) |
                ((((__u64)base) << 32) & 0xff00000000000000ULL) |
                ((((__u64)lim_pages) << 32) & 0x000f000000000000ULL) |
                (lim_pages & 0xffff);
        *(__u64 *)&gdt[GDT_ENTRY_ESPFIX_SS] = desc;
        return new_kesp;
}

/*
 *  '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;

        clts();         /* Allow maths ops (or we recurse) */
        if (!tsk_used_math(tsk))
                init_fpu(tsk);
        restore_fpu(tsk);
        thread->status |= TS_USEDFPU;   /* So we fnsave on switch_to() */
        tsk->fpu_counter++;
}
EXPORT_SYMBOL_GPL(math_state_restore);

#ifndef CONFIG_MATH_EMULATION

asmlinkage void math_emulate(long arg)
{
        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 */


void __init trap_init(void)
{
        int i;

#ifdef CONFIG_EISA
        void __iomem *p = ioremap(0x0FFFD9, 4);
        if (readl(p) == 'E'+('I'<<8)+('S'<<16)+('A'<<24)) {
                EISA_bus = 1;
        }
        iounmap(p);
#endif

#ifdef CONFIG_X86_LOCAL_APIC
        init_apic_mappings();
#endif

        set_trap_gate(0,&divide_error);
        set_intr_gate(1,&debug);
        set_intr_gate(2,&nmi);
        set_system_intr_gate(3, &int3); /* int3/4 can be called from all */
        set_system_gate(4,&overflow);
        set_trap_gate(5,&bounds);
        set_trap_gate(6,&invalid_op);
        set_trap_gate(7,&device_not_available);
        set_task_gate(8,GDT_ENTRY_DOUBLEFAULT_TSS);
        set_trap_gate(9,&coprocessor_segment_overrun);
        set_trap_gate(10,&invalid_TSS);
        set_trap_gate(11,&segment_not_present);
        set_trap_gate(12,&stack_segment);
        set_trap_gate(13,&general_protection);
        set_intr_gate(14,&page_fault);
        set_trap_gate(15,&spurious_interrupt_bug);
        set_trap_gate(16,&coprocessor_error);
        set_trap_gate(17,&alignment_check);
#ifdef CONFIG_X86_MCE
        set_trap_gate(18,&machine_check);
#endif
        set_trap_gate(19,&simd_coprocessor_error);

        if (cpu_has_fxsr) {
                /*
                 * Verify that the FXSAVE/FXRSTOR data will be 16-byte aligned.
                 * Generates a compile-time "error: zero width for bit-field" if
                 * the alignment is wrong.
                 */
                struct fxsrAlignAssert {
                        int _:!(offsetof(struct task_struct,
                                        thread.i387.fxsave) & 15);
                };

                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_gate(SYSCALL_VECTOR,&system_call);

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

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

        trap_init_hook();
}

static int __init kstack_setup(char *s)
{
        kstack_depth_to_print = simple_strtoul(s, NULL, 0);
        return 1;
}
__setup("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);