[apple/xnu.git] / osfmk / i386 / trap.c

/*
 * Copyright (c) 2000-2016 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
* @OSF_COPYRIGHT@
*/
/* 
* Mach Operating System
* Copyright (c) 1991,1990,1989,1988 Carnegie Mellon University
* All Rights Reserved.
* 
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
* 
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
* 
* Carnegie Mellon requests users of this software to return to
* 
*  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
*  School of Computer Science
*  Carnegie Mellon University
*  Pittsburgh PA 15213-3890
* 
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*/
/*
*/

/*
* Hardware trap/fault handler.
 */

#include <mach_kdp.h>
#include <mach_ldebug.h>

#include <types.h>
#include <i386/eflags.h>
#include <i386/trap.h>
#include <i386/pmap.h>
#include <i386/fpu.h>
#include <i386/misc_protos.h> /* panic_io_port_read() */
#include <i386/lapic.h>

#include <mach/exception.h>
#include <mach/kern_return.h>
#include <mach/vm_param.h>
#include <mach/i386/thread_status.h>

#include <vm/vm_kern.h>
#include <vm/vm_fault.h>

#include <kern/kern_types.h>
#include <kern/processor.h>
#include <kern/thread.h>
#include <kern/task.h>
#include <kern/sched.h>
#include <kern/sched_prim.h>
#include <kern/exception.h>
#include <kern/spl.h>
#include <kern/misc_protos.h>
#include <kern/debug.h>
#if CONFIG_TELEMETRY
#include <kern/telemetry.h>
#endif
#include <sys/kdebug.h>
#include <prng/random.h>

#include <string.h>

#include <i386/postcode.h>
#include <i386/mp_desc.h>
#include <i386/proc_reg.h>
#if CONFIG_MCA
#include <i386/machine_check.h>
#endif
#include <mach/i386/syscall_sw.h>

#include <libkern/OSDebug.h>
#include <i386/cpu_threads.h>
#include <machine/pal_routines.h>

extern void throttle_lowpri_io(int);
extern void kprint_state(x86_saved_state64_t *saved_state);

/*
 * Forward declarations
 */
static void user_page_fault_continue(kern_return_t kret);
static void panic_trap(x86_saved_state64_t *saved_state, uint32_t pl, kern_return_t fault_result);
static void set_recovery_ip(x86_saved_state64_t *saved_state, vm_offset_t ip);

#if CONFIG_DTRACE
/* See <rdar://problem/4613924> */
perfCallback tempDTraceTrapHook = NULL; /* Pointer to DTrace fbt trap hook routine */

extern boolean_t dtrace_tally_fault(user_addr_t);
#endif

extern boolean_t pmap_smep_enabled;
extern boolean_t pmap_smap_enabled;

__attribute__((noreturn))
void
thread_syscall_return(
        kern_return_t ret)
{
        thread_t        thr_act = current_thread();
        boolean_t       is_mach;
        int             code;

        pal_register_cache_state(thr_act, DIRTY);

        if (thread_is_64bit(thr_act)) {
                x86_saved_state64_t     *regs;
                
                regs = USER_REGS64(thr_act);

                code = (int) (regs->rax & SYSCALL_NUMBER_MASK);
                is_mach = (regs->rax & SYSCALL_CLASS_MASK)
                            == (SYSCALL_CLASS_MACH << SYSCALL_CLASS_SHIFT);
                if (kdebug_enable && is_mach) {
                        /* Mach trap */
                        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
                              MACHDBG_CODE(DBG_MACH_EXCP_SC,code)|DBG_FUNC_END,
                              ret, 0, 0, 0, 0);
                }
                regs->rax = ret;
#if DEBUG
                if (is_mach)
                        DEBUG_KPRINT_SYSCALL_MACH(
                                "thread_syscall_return: 64-bit mach ret=%u\n",
                                ret);
                else
                        DEBUG_KPRINT_SYSCALL_UNIX(
                                "thread_syscall_return: 64-bit unix ret=%u\n",
                                ret);
#endif
        } else {
                x86_saved_state32_t     *regs;
                
                regs = USER_REGS32(thr_act);

                code = ((int) regs->eax);
                is_mach = (code < 0);
                if (kdebug_enable && is_mach) {
                        /* Mach trap */
                        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
                              MACHDBG_CODE(DBG_MACH_EXCP_SC,-code)|DBG_FUNC_END,
                              ret, 0, 0, 0, 0);
                }
                regs->eax = ret;
#if DEBUG
                if (is_mach)
                        DEBUG_KPRINT_SYSCALL_MACH(
                                "thread_syscall_return: 32-bit mach ret=%u\n",
                                ret);
                else
                        DEBUG_KPRINT_SYSCALL_UNIX(
                                "thread_syscall_return: 32-bit unix ret=%u\n",
                                ret);
#endif
        }

#if DEBUG || DEVELOPMENT
        kern_allocation_name_t
        prior __assert_only = thread_get_kernel_state(thr_act)->allocation_name;
        assertf(prior == NULL, "thread_set_allocation_name(\"%s\") not cleared", kern_allocation_get_name(prior));
#endif /* DEBUG || DEVELOPMENT */

        throttle_lowpri_io(1);

        thread_exception_return();
        /*NOTREACHED*/
}


static inline void
user_page_fault_continue(
                         kern_return_t  kr)
{
        thread_t        thread = current_thread();
        user_addr_t     vaddr;

        if (thread_is_64bit(thread)) {
                x86_saved_state64_t     *uregs;

                uregs = USER_REGS64(thread);

                vaddr = (user_addr_t)uregs->cr2;
        } else {
                x86_saved_state32_t     *uregs;

                uregs = USER_REGS32(thread);

                vaddr = uregs->cr2;
        }


        /* PAL debug hook */
        pal_dbg_page_fault( thread, vaddr, kr );

        i386_exception(EXC_BAD_ACCESS, kr, vaddr);
        /*NOTREACHED*/
}

/*
 * Fault recovery in copyin/copyout routines.
 */
struct recovery {
        uintptr_t       fault_addr;
        uintptr_t       recover_addr;
};

extern struct recovery  recover_table[];
extern struct recovery  recover_table_end[];

const char *    trap_type[] = {TRAP_NAMES};
unsigned        TRAP_TYPES = sizeof(trap_type)/sizeof(trap_type[0]);

extern void     PE_incoming_interrupt(int interrupt);

#if defined(__x86_64__) && DEBUG
void
kprint_state(x86_saved_state64_t        *saved_state)
{
        kprintf("current_cpu_datap() 0x%lx\n", (uintptr_t)current_cpu_datap());
        kprintf("Current GS base MSR 0x%llx\n", rdmsr64(MSR_IA32_GS_BASE));
        kprintf("Kernel  GS base MSR 0x%llx\n", rdmsr64(MSR_IA32_KERNEL_GS_BASE));
        kprintf("state at 0x%lx:\n", (uintptr_t) saved_state);

        kprintf("      rdi    0x%llx\n", saved_state->rdi);        
        kprintf("      rsi    0x%llx\n", saved_state->rsi);    
        kprintf("      rdx    0x%llx\n", saved_state->rdx);
        kprintf("      r10    0x%llx\n", saved_state->r10);
        kprintf("      r8     0x%llx\n", saved_state->r8);
        kprintf("      r9     0x%llx\n", saved_state->r9);     

        kprintf("      cr2    0x%llx\n", saved_state->cr2);
        kprintf("real  cr2    0x%lx\n", get_cr2());
        kprintf("      r15    0x%llx\n", saved_state->r15);
        kprintf("      r14    0x%llx\n", saved_state->r14);
        kprintf("      r13    0x%llx\n", saved_state->r13);
        kprintf("      r12    0x%llx\n", saved_state->r12);
        kprintf("      r11    0x%llx\n", saved_state->r11);
        kprintf("      rbp    0x%llx\n", saved_state->rbp);
        kprintf("      rbx    0x%llx\n", saved_state->rbx);
        kprintf("      rcx    0x%llx\n", saved_state->rcx);
        kprintf("      rax    0x%llx\n", saved_state->rax);

        kprintf("      gs     0x%x\n", saved_state->gs);
        kprintf("      fs     0x%x\n", saved_state->fs);

        kprintf("  isf.trapno 0x%x\n", saved_state->isf.trapno);
        kprintf("  isf._pad   0x%x\n", saved_state->isf._pad);
        kprintf("  isf.trapfn 0x%llx\n", saved_state->isf.trapfn);
        kprintf("  isf.err    0x%llx\n", saved_state->isf.err);
        kprintf("  isf.rip    0x%llx\n", saved_state->isf.rip);
        kprintf("  isf.cs     0x%llx\n", saved_state->isf.cs);
        kprintf("  isf.rflags 0x%llx\n", saved_state->isf.rflags);
        kprintf("  isf.rsp    0x%llx\n", saved_state->isf.rsp);
        kprintf("  isf.ss     0x%llx\n", saved_state->isf.ss);
}
#endif


/*
 * Non-zero indicates latency assert is enabled and capped at valued
 * absolute time units.
 */
   
uint64_t interrupt_latency_cap = 0;
boolean_t ilat_assert = FALSE;

void
interrupt_latency_tracker_setup(void) {
        uint32_t ilat_cap_us;
        if (PE_parse_boot_argn("interrupt_latency_cap_us", &ilat_cap_us, sizeof(ilat_cap_us))) {
                interrupt_latency_cap = ilat_cap_us * NSEC_PER_USEC;
                nanoseconds_to_absolutetime(interrupt_latency_cap, &interrupt_latency_cap);
        } else {
                interrupt_latency_cap = LockTimeOut;
        }
        PE_parse_boot_argn("-interrupt_latency_assert_enable", &ilat_assert, sizeof(ilat_assert));
}

void interrupt_reset_latency_stats(void) {
        uint32_t i;
        for (i = 0; i < real_ncpus; i++) {
                cpu_data_ptr[i]->cpu_max_observed_int_latency =
                    cpu_data_ptr[i]->cpu_max_observed_int_latency_vector = 0;
        }
}

void interrupt_populate_latency_stats(char *buf, unsigned bufsize) {
        uint32_t i, tcpu = ~0;
        uint64_t cur_max = 0;

        for (i = 0; i < real_ncpus; i++) {
                if (cur_max < cpu_data_ptr[i]->cpu_max_observed_int_latency) {
                        cur_max = cpu_data_ptr[i]->cpu_max_observed_int_latency;
                        tcpu = i;
                }
        }

        if (tcpu < real_ncpus)
                snprintf(buf, bufsize, "0x%x 0x%x 0x%llx", tcpu, cpu_data_ptr[tcpu]->cpu_max_observed_int_latency_vector, cpu_data_ptr[tcpu]->cpu_max_observed_int_latency);
}

uint32_t interrupt_timer_coalescing_enabled = 1;
uint64_t interrupt_coalesced_timers;

/*
 * Handle interrupts:
 *  - local APIC interrupts (IPIs, timers, etc) are handled by the kernel,
 *  - device interrupts go to the platform expert.
 */
void
interrupt(x86_saved_state_t *state)
{
        uint64_t        rip;
        uint64_t        rsp;
        int             interrupt_num;
        boolean_t       user_mode = FALSE;
        int             ipl;
        int             cnum = cpu_number();
        cpu_data_t      *cdp = cpu_data_ptr[cnum];
        int             itype = DBG_INTR_TYPE_UNKNOWN;

        x86_saved_state64_t     *state64 = saved_state64(state);
        rip = state64->isf.rip;
        rsp = state64->isf.rsp;
        interrupt_num = state64->isf.trapno;
        if(state64->isf.cs & 0x03)
                user_mode = TRUE;

        if (cpu_data_ptr[cnum]->lcpu.package->num_idle == topoParms.nLThreadsPerPackage)
                cpu_data_ptr[cnum]->cpu_hwIntpexits[interrupt_num]++;

        if (interrupt_num == (LAPIC_DEFAULT_INTERRUPT_BASE + LAPIC_INTERPROCESSOR_INTERRUPT))
                itype = DBG_INTR_TYPE_IPI;
        else if (interrupt_num == (LAPIC_DEFAULT_INTERRUPT_BASE + LAPIC_TIMER_INTERRUPT))
                itype = DBG_INTR_TYPE_TIMER;
        else
                itype = DBG_INTR_TYPE_OTHER;

        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
                MACHDBG_CODE(DBG_MACH_EXCP_INTR, 0) | DBG_FUNC_START,
                interrupt_num,
                (user_mode ? rip : VM_KERNEL_UNSLIDE(rip)),
                user_mode, itype, 0);

        SCHED_STATS_INTERRUPT(current_processor());

#if CONFIG_TELEMETRY
        if (telemetry_needs_record) {
                telemetry_mark_curthread(user_mode);
        }
#endif

        ipl = get_preemption_level();
        
        /*
         * Handle local APIC interrupts
         * else call platform expert for devices.
         */
        if (!lapic_interrupt(interrupt_num, state)) {
                PE_incoming_interrupt(interrupt_num);
        }

        if (__improbable(get_preemption_level() != ipl)) {
                panic("Preemption level altered by interrupt vector 0x%x: initial 0x%x, final: 0x%x\n", interrupt_num, ipl, get_preemption_level());
        }


        if (__improbable(cdp->cpu_nested_istack)) {
                cdp->cpu_nested_istack_events++;
        }
        else  {
                uint64_t ctime = mach_absolute_time();
                uint64_t int_latency = ctime - cdp->cpu_int_event_time;
                uint64_t esdeadline, ehdeadline;
                /* Attempt to process deferred timers in the context of
                 * this interrupt, unless interrupt time has already exceeded
                 * TCOAL_ILAT_THRESHOLD.
                 */
#define TCOAL_ILAT_THRESHOLD (30000ULL)

                if ((int_latency < TCOAL_ILAT_THRESHOLD) &&
                    interrupt_timer_coalescing_enabled) {
                        esdeadline = cdp->rtclock_timer.queue.earliest_soft_deadline;
                        ehdeadline = cdp->rtclock_timer.deadline;
                        if ((ctime >= esdeadline) && (ctime < ehdeadline)) {
                                interrupt_coalesced_timers++;
                                TCOAL_DEBUG(0x88880000 | DBG_FUNC_START, ctime, esdeadline, ehdeadline, interrupt_coalesced_timers, 0);
                                rtclock_intr(state);
                                TCOAL_DEBUG(0x88880000 | DBG_FUNC_END, ctime, esdeadline, interrupt_coalesced_timers, 0, 0);
                        } else {
                                TCOAL_DEBUG(0x77770000, ctime, cdp->rtclock_timer.queue.earliest_soft_deadline, cdp->rtclock_timer.deadline, interrupt_coalesced_timers, 0);
                        }
                }

                if (__improbable(ilat_assert && (int_latency > interrupt_latency_cap) && !machine_timeout_suspended())) {
                        panic("Interrupt vector 0x%x exceeded interrupt latency threshold, 0x%llx absolute time delta, prior signals: 0x%x, current signals: 0x%x", interrupt_num, int_latency, cdp->cpu_prior_signals, cdp->cpu_signals);
                }

                if (__improbable(int_latency > cdp->cpu_max_observed_int_latency)) {
                        cdp->cpu_max_observed_int_latency = int_latency;
                        cdp->cpu_max_observed_int_latency_vector = interrupt_num;
                }
        }

        /*
         * Having serviced the interrupt first, look at the interrupted stack depth.
         */
        if (!user_mode) {
                uint64_t depth = cdp->cpu_kernel_stack
                                 + sizeof(struct thread_kernel_state)
                                 + sizeof(struct i386_exception_link *)
                                 - rsp;
                if (__improbable(depth > kernel_stack_depth_max)) {
                        kernel_stack_depth_max = (vm_offset_t)depth;
                        KERNEL_DEBUG_CONSTANT(
                                MACHDBG_CODE(DBG_MACH_SCHED, MACH_STACK_DEPTH),
                                (long) depth, (long) VM_KERNEL_UNSLIDE(rip), 0, 0, 0);
                }
        }
        
        if (cnum == master_cpu)
                ml_entropy_collect();

        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
                MACHDBG_CODE(DBG_MACH_EXCP_INTR, 0) | DBG_FUNC_END,
                interrupt_num, 0, 0, 0, 0);

        assert(ml_get_interrupts_enabled() == FALSE);
}

static inline void
reset_dr7(void)
{
        long dr7 = 0x400; /* magic dr7 reset value; 32 bit on i386, 64 bit on x86_64 */
        __asm__ volatile("mov %0,%%dr7" : : "r" (dr7));
}
#if MACH_KDP
unsigned kdp_has_active_watchpoints = 0;
#define NO_WATCHPOINTS (!kdp_has_active_watchpoints)
#else
#define NO_WATCHPOINTS 1
#endif
/*
 * Trap from kernel mode.  Only page-fault errors are recoverable,
 * and then only in special circumstances.  All other errors are
 * fatal.  Return value indicates if trap was handled.
 */

void
kernel_trap(
        x86_saved_state_t       *state,
        uintptr_t *lo_spp)
{
        x86_saved_state64_t     *saved_state;
        int                     code;
        user_addr_t             vaddr;
        int                     type;
        vm_map_t                map = 0;        /* protected by T_PAGE_FAULT */
        kern_return_t           result = KERN_FAILURE;
        kern_return_t           fault_result = KERN_SUCCESS;
        thread_t                thread;
        boolean_t               intr;
        vm_prot_t               prot;
        struct recovery         *rp;
        vm_offset_t             kern_ip;
#if NCOPY_WINDOWS > 0
        int                     fault_in_copy_window = -1;
#endif
        int                     is_user;
        int                     trap_pl = get_preemption_level();

        thread = current_thread();

        if (__improbable(is_saved_state32(state)))
                panic("kernel_trap(%p) with 32-bit state", state);
        saved_state = saved_state64(state);

        /* Record cpu where state was captured */
        saved_state->isf.cpu = cpu_number();

        vaddr = (user_addr_t)saved_state->cr2;
        type  = saved_state->isf.trapno;
        code  = (int)(saved_state->isf.err & 0xffff);
        intr  = (saved_state->isf.rflags & EFL_IF) != 0;        /* state of ints at trap */
        kern_ip = (vm_offset_t)saved_state->isf.rip;

        is_user = (vaddr < VM_MAX_USER_PAGE_ADDRESS);

#if CONFIG_DTRACE
        /*
         * Is there a DTrace hook?
         */     
        if (__improbable(tempDTraceTrapHook != NULL)) {
                if (tempDTraceTrapHook(type, state, lo_spp, 0) == KERN_SUCCESS) {
                        /*
                         * If it succeeds, we are done...
                         */
                        return;
                }
        }
#endif /* CONFIG_DTRACE */

        /*
         * we come here with interrupts off as we don't want to recurse
         * on preemption below.  but we do want to re-enable interrupts
         * as soon we possibly can to hold latency down
         */
        if (__improbable(T_PREEMPT == type)) {
                ast_taken_kernel();

                KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
                        (MACHDBG_CODE(DBG_MACH_EXCP_KTRAP_x86, type)) | DBG_FUNC_NONE,
                        0, 0, 0, VM_KERNEL_UNSLIDE(kern_ip), 0);
                return;
        }

        user_addr_t     kd_vaddr = is_user ? vaddr : VM_KERNEL_UNSLIDE(vaddr);
        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE,
                (MACHDBG_CODE(DBG_MACH_EXCP_KTRAP_x86, type)) | DBG_FUNC_NONE,
                (unsigned)(kd_vaddr >> 32), (unsigned)kd_vaddr, is_user,
                VM_KERNEL_UNSLIDE(kern_ip), 0);


        if (T_PAGE_FAULT == type) {
                /*
                 * assume we're faulting in the kernel map
                 */
                map = kernel_map;

                if (__probable(thread != THREAD_NULL && thread->map != kernel_map)) {
#if NCOPY_WINDOWS > 0
                        vm_offset_t     copy_window_base;
                        vm_offset_t     kvaddr;
                        int             window_index;

                        kvaddr = (vm_offset_t)vaddr;
                        /*
                         * must determine if fault occurred in
                         * the copy window while pre-emption is
                         * disabled for this processor so that
                         * we only need to look at the window
                         * associated with this processor
                         */
                        copy_window_base = current_cpu_datap()->cpu_copywindow_base;

                        if (kvaddr >= copy_window_base && kvaddr < (copy_window_base + (NBPDE * NCOPY_WINDOWS)) ) {

                                window_index = (int)((kvaddr - copy_window_base) / NBPDE);

                                if (thread->machine.copy_window[window_index].user_base != (user_addr_t)-1) {

                                        kvaddr -= (copy_window_base + (NBPDE * window_index));
                                        vaddr = thread->machine.copy_window[window_index].user_base + kvaddr;

                                        map = thread->map;
                                        fault_in_copy_window = window_index;
                                }
                        }
#else
                        if (__probable(vaddr < VM_MAX_USER_PAGE_ADDRESS)) {
                                /* fault occurred in userspace */
                                map = thread->map;

                                /* Intercept a potential Supervisor Mode Execute
                                 * Protection fault. These criteria identify
                                 * both NX faults and SMEP faults, but both
                                 * are fatal. We avoid checking PTEs (racy).
                                 * (The VM could just redrive a SMEP fault, hence
                                 * the intercept).
                                 */
                                if (__improbable((code == (T_PF_PROT | T_PF_EXECUTE)) &&
                                        (pmap_smep_enabled) && (saved_state->isf.rip == vaddr))) {
                                        goto debugger_entry;
                                }

                                /*
                                 * Additionally check for SMAP faults...
                                 * which are characterized by page-present and
                                 * the AC bit unset (i.e. not from copyin/out path).
                                 */
                                if (__improbable(code & T_PF_PROT &&
                                                 pmap_smap_enabled &&
                                                 (saved_state->isf.rflags & EFL_AC) == 0)) {
                                        goto debugger_entry;
                                }

                                /*
                                 * If we're not sharing cr3 with the user
                                 * and we faulted in copyio,
                                 * then switch cr3 here and dismiss the fault.
                                 */
                                if (no_shared_cr3 &&
                                    (thread->machine.specFlags&CopyIOActive) &&
                                    map->pmap->pm_cr3 != get_cr3_base()) {
                                        pmap_assert(current_cpu_datap()->cpu_pmap_pcid_enabled == FALSE);
                                        set_cr3_raw(map->pmap->pm_cr3);
                                        return;
                                }
                                if (__improbable(vaddr < PAGE_SIZE) &&
                                    ((thread->machine.specFlags & CopyIOActive) == 0)) {
                                        goto debugger_entry;
                                }
                        }
#endif
                }
        }

        (void) ml_set_interrupts_enabled(intr);

        switch (type) {

            case T_NO_FPU:
                fpnoextflt();
                return;

            case T_FPU_FAULT:
                fpextovrflt();
                return;

            case T_FLOATING_POINT_ERROR:
                fpexterrflt();
                return;

            case T_SSE_FLOAT_ERROR:
                fpSSEexterrflt();
                return;
            case T_DEBUG:
                    if ((saved_state->isf.rflags & EFL_TF) == 0 && NO_WATCHPOINTS)
                    {
                            /* We've somehow encountered a debug
                             * register match that does not belong
                             * to the kernel debugger.
                             * This isn't supposed to happen.
                             */
                            reset_dr7();
                            return;
                    }
                    goto debugger_entry;
#ifdef __x86_64__
            case T_INT3:
              goto debugger_entry;
#endif
            case T_PAGE_FAULT:

#if CONFIG_DTRACE
                if (thread != THREAD_NULL && thread->options & TH_OPT_DTRACE) { /* Executing under dtrace_probe? */
                        if (dtrace_tally_fault(vaddr)) { /* Should a fault under dtrace be ignored? */
                                /*
                                 * DTrace has "anticipated" the possibility of this fault, and has
                                 * established the suitable recovery state. Drop down now into the
                                 * recovery handling code in "case T_GENERAL_PROTECTION:". 
                                 */
                                goto FALL_THROUGH;
                        }
                }
#endif /* CONFIG_DTRACE */
                
                prot = VM_PROT_READ;

                if (code & T_PF_WRITE)
                        prot |= VM_PROT_WRITE;
                if (code & T_PF_EXECUTE)
                        prot |= VM_PROT_EXECUTE;

                fault_result = result = vm_fault(map,
                                  vaddr,
                                  prot,
                                  FALSE, VM_KERN_MEMORY_NONE,
                                  THREAD_UNINT, NULL, 0);

                if (result == KERN_SUCCESS) {
#if NCOPY_WINDOWS > 0
                        if (fault_in_copy_window != -1) {
                                ml_set_interrupts_enabled(FALSE);
                                copy_window_fault(thread, map,
                                                  fault_in_copy_window);
                                (void) ml_set_interrupts_enabled(intr);
                        }
#endif /* NCOPY_WINDOWS > 0 */
                        return;
                }
                /*
                 * fall through
                 */
#if CONFIG_DTRACE
FALL_THROUGH:
#endif /* CONFIG_DTRACE */

            case T_GENERAL_PROTECTION:
                /*
                 * If there is a failure recovery address
                 * for this fault, go there.
                 */
                for (rp = recover_table; rp < recover_table_end; rp++) {
                        if (kern_ip == rp->fault_addr) {
                                set_recovery_ip(saved_state, rp->recover_addr);
                                return;
                        }
                }

                /*
                 * Check thread recovery address also.
                 */
                if (thread != THREAD_NULL && thread->recover) {
                        set_recovery_ip(saved_state, thread->recover);
                        thread->recover = 0;
                        return;
                }
                /*
                 * Unanticipated page-fault errors in kernel
                 * should not happen.
                 *
                 * fall through...
                 */
            default:
                /*
                 * Exception 15 is reserved but some chips may generate it
                 * spuriously. Seen at startup on AMD Athlon-64.
                 */
                if (type == 15) {
                        kprintf("kernel_trap() ignoring spurious trap 15\n"); 
                        return;
                }
debugger_entry:
                /* Ensure that the i386_kernel_state at the base of the
                 * current thread's stack (if any) is synchronized with the
                 * context at the moment of the trap, to facilitate
                 * access through the debugger.
                 */
                sync_iss_to_iks(state);
#if  MACH_KDP
                if (kdp_i386_trap(type, saved_state, result, (vm_offset_t)vaddr))
                        return;
#endif
        }
        pal_cli();
        panic_trap(saved_state, trap_pl, fault_result);
        /*
         * NO RETURN
         */
}

static void
set_recovery_ip(x86_saved_state64_t  *saved_state, vm_offset_t ip)
{
        saved_state->isf.rip = ip;
}

static void
panic_trap(x86_saved_state64_t *regs, uint32_t pl, kern_return_t fault_result)
{
        const char      *trapname = "Unknown";
        pal_cr_t        cr0, cr2, cr3, cr4;
        boolean_t       potential_smep_fault = FALSE, potential_kernel_NX_fault = FALSE;
        boolean_t       potential_smap_fault = FALSE;

        pal_get_control_registers( &cr0, &cr2, &cr3, &cr4 );
        assert(ml_get_interrupts_enabled() == FALSE);
        current_cpu_datap()->cpu_fatal_trap_state = regs;
        /*
         * Issue an I/O port read if one has been requested - this is an
         * event logic analyzers can use as a trigger point.
         */
        panic_io_port_read();

        kprintf("CPU %d panic trap number 0x%x, rip 0x%016llx\n",
            cpu_number(), regs->isf.trapno, regs->isf.rip);
        kprintf("cr0 0x%016llx cr2 0x%016llx cr3 0x%016llx cr4 0x%016llx\n",
                cr0, cr2, cr3, cr4);

        if (regs->isf.trapno < TRAP_TYPES)
                trapname = trap_type[regs->isf.trapno];

        if ((regs->isf.trapno == T_PAGE_FAULT) && (regs->isf.err == (T_PF_PROT | T_PF_EXECUTE)) && (regs->isf.rip == regs->cr2)) {
                if (pmap_smep_enabled && (regs->isf.rip < VM_MAX_USER_PAGE_ADDRESS)) {
                        potential_smep_fault = TRUE;
                } else if (regs->isf.rip >= VM_MIN_KERNEL_AND_KEXT_ADDRESS) {
                        potential_kernel_NX_fault = TRUE;
                }
        } else if (pmap_smap_enabled &&
                   regs->isf.trapno == T_PAGE_FAULT &&
                   regs->isf.err & T_PF_PROT &&
                   regs->cr2 < VM_MAX_USER_PAGE_ADDRESS &&
                   regs->isf.rip >= VM_MIN_KERNEL_AND_KEXT_ADDRESS) {
                potential_smap_fault = TRUE;
        }

#undef panic
        panic("Kernel trap at 0x%016llx, type %d=%s, registers:\n"
              "CR0: 0x%016llx, CR2: 0x%016llx, CR3: 0x%016llx, CR4: 0x%016llx\n"
              "RAX: 0x%016llx, RBX: 0x%016llx, RCX: 0x%016llx, RDX: 0x%016llx\n"
              "RSP: 0x%016llx, RBP: 0x%016llx, RSI: 0x%016llx, RDI: 0x%016llx\n"
              "R8:  0x%016llx, R9:  0x%016llx, R10: 0x%016llx, R11: 0x%016llx\n"
              "R12: 0x%016llx, R13: 0x%016llx, R14: 0x%016llx, R15: 0x%016llx\n"
              "RFL: 0x%016llx, RIP: 0x%016llx, CS:  0x%016llx, SS:  0x%016llx\n"
              "Fault CR2: 0x%016llx, Error code: 0x%016llx, Fault CPU: 0x%x%s%s%s%s, PL: %d, VF: %d\n",
              regs->isf.rip, regs->isf.trapno, trapname,
              cr0, cr2, cr3, cr4,
              regs->rax, regs->rbx, regs->rcx, regs->rdx,
              regs->isf.rsp, regs->rbp, regs->rsi, regs->rdi,
              regs->r8,  regs->r9,  regs->r10, regs->r11,
              regs->r12, regs->r13, regs->r14, regs->r15,
              regs->isf.rflags, regs->isf.rip, regs->isf.cs & 0xFFFF,
              regs->isf.ss & 0xFFFF,regs->cr2, regs->isf.err, regs->isf.cpu,
              virtualized ? " VMM" : "",
              potential_kernel_NX_fault ? " Kernel NX fault" : "",
              potential_smep_fault ? " SMEP/User NX fault" : "",
              potential_smap_fault ? " SMAP fault" : "",
              pl,
              fault_result);
        /*
         * This next statement is not executed,
         * but it's needed to stop the compiler using tail call optimization
         * for the panic call - which confuses the subsequent backtrace.
         */
        cr0 = 0;
}

#if CONFIG_DTRACE
extern kern_return_t dtrace_user_probe(x86_saved_state_t *);
#endif

/*
 *      Trap from user mode.
 */
void
user_trap(
        x86_saved_state_t *saved_state)
{
        int                     exc;
        int                     err;
        mach_exception_code_t   code;
        mach_exception_subcode_t subcode;
        int                     type;
        user_addr_t             vaddr;
        vm_prot_t               prot;
        thread_t                thread = current_thread();
        kern_return_t           kret;
        user_addr_t             rip;
        unsigned long           dr6 = 0; /* 32 bit for i386, 64 bit for x86_64 */

        assert((is_saved_state32(saved_state) && !thread_is_64bit(thread)) ||
               (is_saved_state64(saved_state) &&  thread_is_64bit(thread)));

        if (is_saved_state64(saved_state)) {
                x86_saved_state64_t     *regs;

                regs = saved_state64(saved_state);

                /* Record cpu where state was captured */
                regs->isf.cpu = cpu_number();

                type = regs->isf.trapno;
                err  = (int)regs->isf.err & 0xffff;
                vaddr = (user_addr_t)regs->cr2;
                rip   = (user_addr_t)regs->isf.rip;
        } else {
                x86_saved_state32_t     *regs;

                regs = saved_state32(saved_state);

                /* Record cpu where state was captured */
                regs->cpu = cpu_number();

                type  = regs->trapno;
                err   = regs->err & 0xffff;
                vaddr = (user_addr_t)regs->cr2;
                rip   = (user_addr_t)regs->eip;
        }

        if ((type == T_DEBUG) && thread->machine.ids) {
                unsigned long clear = 0;
                /* Stash and clear this processor's DR6 value, in the event
                 * this was a debug register match
                 */
                __asm__ volatile ("mov %%db6, %0" : "=r" (dr6)); 
                __asm__ volatile ("mov %0, %%db6" : : "r" (clear));
        }

        pal_sti();

        KERNEL_DEBUG_CONSTANT_IST(KDEBUG_TRACE, 
                (MACHDBG_CODE(DBG_MACH_EXCP_UTRAP_x86, type)) | DBG_FUNC_NONE,
                (unsigned)(vaddr>>32), (unsigned)vaddr,
                (unsigned)(rip>>32), (unsigned)rip, 0);

        code = 0;
        subcode = 0;
        exc = 0;

#if CONFIG_DTRACE
        /*
         * DTrace does not consume all user traps, only INT_3's for now.
         * Avoid needlessly calling tempDTraceTrapHook here, and let the
         * INT_3 case handle them.
         */
#endif
        
        DEBUG_KPRINT_SYSCALL_MASK(1,
                "user_trap: type=0x%x(%s) err=0x%x cr2=%p rip=%p\n",
                type, trap_type[type], err, (void *)(long) vaddr, (void *)(long) rip);
        
        switch (type) {

            case T_DIVIDE_ERROR:
                exc = EXC_ARITHMETIC;
                code = EXC_I386_DIV;
                break;

            case T_DEBUG:
                {
                        pcb_t   pcb;
                        /*
                         * Update the PCB with this processor's DR6 value
                         * in the event this was a debug register match.
                         */
                        pcb = THREAD_TO_PCB(thread);
                        if (pcb->ids) {
                                /*
                                 * We can get and set the status register
                                 * in 32-bit mode even on a 64-bit thread
                                 * because the high order bits are not
                                 * used on x86_64
                                 */
                                if (thread_is_64bit(thread)) {
                                        x86_debug_state64_t *ids = pcb->ids;
                                        ids->dr6 = dr6;
                                } else { /* 32 bit thread */
                                        x86_debug_state32_t *ids = pcb->ids;
                                        ids->dr6 = (uint32_t) dr6;
                                }
                        }
                        exc = EXC_BREAKPOINT;
                        code = EXC_I386_SGL;
                        break;
                }
            case T_INT3:
#if CONFIG_DTRACE
                if (dtrace_user_probe(saved_state) == KERN_SUCCESS)
                        return; /* If it succeeds, we are done... */
#endif
                exc = EXC_BREAKPOINT;
                code = EXC_I386_BPT;
                break;

            case T_OVERFLOW:
                exc = EXC_ARITHMETIC;
                code = EXC_I386_INTO;
                break;

            case T_OUT_OF_BOUNDS:
                exc = EXC_SOFTWARE;
                code = EXC_I386_BOUND;
                break;

            case T_INVALID_OPCODE:
#if !defined(RC_HIDE_XNU_J137)
                fpUDflt(rip);   /* May return from exception directly */
#endif
                exc = EXC_BAD_INSTRUCTION;
                code = EXC_I386_INVOP;
                break;

            case T_NO_FPU:
                fpnoextflt();
                return;

            case T_FPU_FAULT:
                fpextovrflt(); /* Propagates exception directly, doesn't return */
                return;

            case T_INVALID_TSS: /* invalid TSS == iret with NT flag set */
                exc = EXC_BAD_INSTRUCTION;
                code = EXC_I386_INVTSSFLT;
                subcode = err;
                break;

            case T_SEGMENT_NOT_PRESENT:
                exc = EXC_BAD_INSTRUCTION;
                code = EXC_I386_SEGNPFLT;
                subcode = err;
                break;

            case T_STACK_FAULT:
                exc = EXC_BAD_INSTRUCTION;
                code = EXC_I386_STKFLT;
                subcode = err;
                break;

            case T_GENERAL_PROTECTION:
                /*
                 * There's a wide range of circumstances which generate this
                 * class of exception. From user-space, many involve bad
                 * addresses (such as a non-canonical 64-bit address).
                 * So we map this to EXC_BAD_ACCESS (and thereby SIGSEGV).
                 * The trouble is cr2 doesn't contain the faulting address;
                 * we'd need to decode the faulting instruction to really
                 * determine this. We'll leave that to debuggers.
                 * However, attempted execution of privileged instructions
                 * (e.g. cli) also generate GP faults and so we map these to
                 * to EXC_BAD_ACCESS (and thence SIGSEGV) also - rather than
                 * EXC_BAD_INSTRUCTION which is more accurate. We just can't
                 * win!
                 */ 
                exc = EXC_BAD_ACCESS;
                code = EXC_I386_GPFLT;
                subcode = err;
                break;

            case T_PAGE_FAULT:
            {
                    prot = VM_PROT_READ;

                if (err & T_PF_WRITE)
                        prot |= VM_PROT_WRITE;
                if (__improbable(err & T_PF_EXECUTE))
                        prot |= VM_PROT_EXECUTE;
                kret = vm_fault(thread->map,
                                vaddr,
                                prot, FALSE, VM_KERN_MEMORY_NONE,
                                THREAD_ABORTSAFE, NULL, 0);

                if (__probable((kret == KERN_SUCCESS) || (kret == KERN_ABORTED))) {
                        thread_exception_return();
                        /*NOTREACHED*/
                }

                user_page_fault_continue(kret);
            }   /* NOTREACHED */
                break;

            case T_SSE_FLOAT_ERROR:
                fpSSEexterrflt(); /* Propagates exception directly, doesn't return */
                return;


            case T_FLOATING_POINT_ERROR:
                fpexterrflt(); /* Propagates exception directly, doesn't return */
                return;

            case T_DTRACE_RET:
#if CONFIG_DTRACE
                if (dtrace_user_probe(saved_state) == KERN_SUCCESS)
                        return; /* If it succeeds, we are done... */
#endif
                /*
                 * If we get an INT 0x7f when we do not expect to,
                 * treat it as an illegal instruction
                 */
                exc = EXC_BAD_INSTRUCTION;
                code = EXC_I386_INVOP;
                break;

            default:
                panic("Unexpected user trap, type %d", type);
                return;
        }
        /* Note: Codepaths that directly return from user_trap() have pending
         * ASTs processed in locore
         */
        i386_exception(exc, code, subcode);
        /* NOTREACHED */
}

/*
 * Handle exceptions for i386.
 *
 * If we are an AT bus machine, we must turn off the AST for a
 * delayed floating-point exception.
 *
 * If we are providing floating-point emulation, we may have
 * to retrieve the real register values from the floating point
 * emulator.
 */
void
i386_exception(
        int     exc,
        mach_exception_code_t code,
        mach_exception_subcode_t subcode)
{
        mach_exception_data_type_t   codes[EXCEPTION_CODE_MAX];

        DEBUG_KPRINT_SYSCALL_MACH("i386_exception: exc=%d code=0x%llx subcode=0x%llx\n",
                                                          exc, code, subcode);
        codes[0] = code;                /* new exception interface */
        codes[1] = subcode;
        exception_triage(exc, codes, 2);
        /*NOTREACHED*/
}


/* Synchronize a thread's x86_kernel_state (if any) with the given
 * x86_saved_state_t obtained from the trap/IPI handler; called in
 * kernel_trap() prior to entering the debugger, and when receiving
 * an "MP_KDP" IPI. Called with null saved_state if an incoming IPI
 * was detected from the kernel while spinning with interrupts masked.
 */
  
void
sync_iss_to_iks(x86_saved_state_t *saved_state)
{
        struct x86_kernel_state *iks = NULL;
        vm_offset_t kstack;
        boolean_t record_active_regs = FALSE;

        /* The PAL may have a special way to sync registers */
        if (saved_state && saved_state->flavor == THREAD_STATE_NONE)
                pal_get_kern_regs( saved_state );

        if (current_thread() != NULL && 
            (kstack = current_thread()->kernel_stack) != 0) {
                x86_saved_state64_t     *regs = saved_state64(saved_state);

                iks = STACK_IKS(kstack);

                /* Did we take the trap/interrupt in kernel mode? */
                if (saved_state == NULL || /* NULL => polling in kernel */
                    regs == USER_REGS64(current_thread()))
                        record_active_regs = TRUE;
                else {
                        iks->k_rbx = regs->rbx;
                        iks->k_rsp = regs->isf.rsp;
                        iks->k_rbp = regs->rbp;
                        iks->k_r12 = regs->r12;
                        iks->k_r13 = regs->r13;
                        iks->k_r14 = regs->r14;
                        iks->k_r15 = regs->r15;
                        iks->k_rip = regs->isf.rip;
                }
        }

        if (record_active_regs == TRUE) {
                /* Show the trap handler path */
                __asm__ volatile("movq %%rbx, %0" : "=m" (iks->k_rbx));
                __asm__ volatile("movq %%rsp, %0" : "=m" (iks->k_rsp));
                __asm__ volatile("movq %%rbp, %0" : "=m" (iks->k_rbp));
                __asm__ volatile("movq %%r12, %0" : "=m" (iks->k_r12));
                __asm__ volatile("movq %%r13, %0" : "=m" (iks->k_r13));
                __asm__ volatile("movq %%r14, %0" : "=m" (iks->k_r14));
                __asm__ volatile("movq %%r15, %0" : "=m" (iks->k_r15));
                /* "Current" instruction pointer */
                __asm__ volatile("leaq 1f(%%rip), %%rax; mov %%rax, %0\n1:"
                                 : "=m" (iks->k_rip)
                                 :
                                 : "rax");
        }
}

/*
 * This is used by the NMI interrupt handler (from mp.c) to
 * uncondtionally sync the trap handler context to the IKS
 * irrespective of whether the NMI was fielded in kernel
 * or user space.
 */
void
sync_iss_to_iks_unconditionally(__unused x86_saved_state_t *saved_state) {
        struct x86_kernel_state *iks;
        vm_offset_t kstack;

        if ((kstack = current_thread()->kernel_stack) != 0) {
                iks = STACK_IKS(kstack);
                /* Display the trap handler path */
                __asm__ volatile("movq %%rbx, %0" : "=m" (iks->k_rbx));
                __asm__ volatile("movq %%rsp, %0" : "=m" (iks->k_rsp));
                __asm__ volatile("movq %%rbp, %0" : "=m" (iks->k_rbp));
                __asm__ volatile("movq %%r12, %0" : "=m" (iks->k_r12));
                __asm__ volatile("movq %%r13, %0" : "=m" (iks->k_r13));
                __asm__ volatile("movq %%r14, %0" : "=m" (iks->k_r14));
                __asm__ volatile("movq %%r15, %0" : "=m" (iks->k_r15));
                /* "Current" instruction pointer */
                __asm__ volatile("leaq 1f(%%rip), %%rax; mov %%rax, %0\n1:" : "=m" (iks->k_rip)::"rax");
        }
}

#if DEBUG
#define TERI 1
#endif

#if TERI
extern void     thread_exception_return_internal(void) __dead2;

void thread_exception_return(void) {
        thread_t thread = current_thread();
        ml_set_interrupts_enabled(FALSE);
        if (thread_is_64bit(thread) != task_has_64BitAddr(thread->task)) {
                panic("Task/thread bitness mismatch %p %p, task: %d, thread: %d", thread, thread->task, thread_is_64bit(thread),  task_has_64BitAddr(thread->task));
        }

        if (thread_is_64bit(thread)) {
                if ((gdt_desc_p(USER64_CS)->access & ACC_PL_U) == 0) {
                        panic("64-GDT mismatch %p, descriptor: %p", thread, gdt_desc_p(USER64_CS));
                }
        } else {
                        if ((gdt_desc_p(USER_CS)->access & ACC_PL_U) == 0) {
                                panic("32-GDT mismatch %p, descriptor: %p", thread, gdt_desc_p(USER_CS));

                }
        }
        thread_exception_return_internal();
}
#endif