Merge commit '4c28a617e3922d92a58e813a5b955eb526b9c386'

[unleashed.git] / arch / x86 / kernel / platform / i86pc / os / trap.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 1992, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*      Copyright (c) 1990, 1991 UNIX System Laboratories, Inc. */
/*      Copyright (c) 1984, 1986, 1987, 1988, 1989, 1990 AT&T   */
/*              All Rights Reserved                             */
/*                                                              */
/*      Copyright (c) 1987, 1988 Microsoft Corporation          */
/*              All Rights Reserved                             */
/*                                                              */

/*
 * Copyright 2018 Joyent, Inc.
 */

#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/param.h>
#include <sys/signal.h>
#include <sys/systm.h>
#include <sys/user.h>
#include <sys/proc.h>
#include <sys/disp.h>
#include <sys/class.h>
#include <sys/core.h>
#include <sys/syscall.h>
#include <sys/cpuvar.h>
#include <sys/vm.h>
#include <sys/sysinfo.h>
#include <sys/fault.h>
#include <sys/stack.h>
#include <sys/psw.h>
#include <sys/regset.h>
#include <sys/fp.h>
#include <sys/trap.h>
#include <sys/kmem.h>
#include <sys/vtrace.h>
#include <sys/cmn_err.h>
#include <sys/prsystm.h>
#include <sys/mutex_impl.h>
#include <sys/machsystm.h>
#include <sys/archsystm.h>
#include <sys/sdt.h>
#include <sys/avintr.h>
#include <sys/kobj.h>

#include <vm/hat.h>

#include <vm/seg_kmem.h>
#include <vm/as.h>
#include <vm/seg.h>
#include <vm/hat_pte.h>
#include <vm/hat_i86.h>

#include <sys/procfs.h>

#include <sys/reboot.h>
#include <sys/debug.h>
#include <sys/debugreg.h>
#include <sys/modctl.h>
#include <sys/aio_impl.h>
#include <sys/tnf.h>
#include <sys/tnf_probe.h>
#include <sys/cred.h>
#include <sys/mman.h>
#include <sys/x86_archext.h>
#include <sys/copyops.h>
#include <c2/audit.h>
#include <sys/ftrace.h>
#include <sys/panic.h>
#include <sys/traptrace.h>
#include <sys/ontrap.h>
#include <sys/cpc_impl.h>
#include <sys/bootconf.h>
#include <sys/bootinfo.h>
#include <sys/promif.h>
#include <sys/mach_mmu.h>
#include <sys/contract/process_impl.h>

#define USER    0x10000         /* user-mode flag added to trap type */

static const char *trap_type_mnemonic[] = {
        "de",   "db",   "2",    "bp",
        "of",   "br",   "ud",   "nm",
        "df",   "9",    "ts",   "np",
        "ss",   "gp",   "pf",   "15",
        "mf",   "ac",   "mc",   "xf"
};

static const char *trap_type[] = {
        "Divide error",                         /* trap id 0    */
        "Debug",                                /* trap id 1    */
        "NMI interrupt",                        /* trap id 2    */
        "Breakpoint",                           /* trap id 3    */
        "Overflow",                             /* trap id 4    */
        "BOUND range exceeded",                 /* trap id 5    */
        "Invalid opcode",                       /* trap id 6    */
        "Device not available",                 /* trap id 7    */
        "Double fault",                         /* trap id 8    */
        "Coprocessor segment overrun",          /* trap id 9    */
        "Invalid TSS",                          /* trap id 10   */
        "Segment not present",                  /* trap id 11   */
        "Stack segment fault",                  /* trap id 12   */
        "General protection",                   /* trap id 13   */
        "Page fault",                           /* trap id 14   */
        "Reserved",                             /* trap id 15   */
        "x87 floating point error",             /* trap id 16   */
        "Alignment check",                      /* trap id 17   */
        "Machine check",                        /* trap id 18   */
        "SIMD floating point exception",        /* trap id 19   */
};

#define TRAP_TYPES      (sizeof (trap_type) / sizeof (trap_type[0]))

#define SLOW_SCALL_SIZE 2
#define FAST_SCALL_SIZE 2

int tudebug = 0;
int tudebugbpt = 0;
int tudebugfpe = 0;
int tudebugsse = 0;

#if defined(TRAPDEBUG) || defined(lint)
int tdebug = 0;
int lodebug = 0;
int faultdebug = 0;
#else
#define tdebug  0
#define lodebug 0
#define faultdebug      0
#endif /* defined(TRAPDEBUG) || defined(lint) */

#if defined(TRAPTRACE)
/*
 * trap trace record for cpu0 is allocated here.
 * trap trace records for non-boot cpus are allocated in mp_startup_init().
 */
static trap_trace_rec_t trap_tr0[TRAPTR_NENT];
trap_trace_ctl_t trap_trace_ctl[NCPU] = {
        {
            (uintptr_t)trap_tr0,                        /* next record */
            (uintptr_t)trap_tr0,                        /* first record */
            (uintptr_t)(trap_tr0 + TRAPTR_NENT),        /* limit */
            (uintptr_t)0                                /* current */
        },
};

/*
 * default trap buffer size
 */
size_t trap_trace_bufsize = TRAPTR_NENT * sizeof (trap_trace_rec_t);
int trap_trace_freeze = 0;
int trap_trace_off = 0;

/*
 * A dummy TRAPTRACE entry to use after death.
 */
trap_trace_rec_t trap_trace_postmort;

static void dump_ttrace(void);
#endif  /* TRAPTRACE */
static void dumpregs(struct regs *);
static void showregs(uint_t, struct regs *, caddr_t);
static int kern_gpfault(struct regs *);

/*ARGSUSED*/
static int
die(uint_t type, struct regs *rp, caddr_t addr, processorid_t cpuid)
{
        struct panic_trap_info ti;
        const char *trap_name, *trap_mnemonic;

        if (type < TRAP_TYPES) {
                trap_name = trap_type[type];
                trap_mnemonic = trap_type_mnemonic[type];
        } else {
                trap_name = "trap";
                trap_mnemonic = "-";
        }

#ifdef TRAPTRACE
        TRAPTRACE_FREEZE;
#endif

        ti.trap_regs = rp;
        ti.trap_type = type & ~USER;
        ti.trap_addr = addr;

        curthread->t_panic_trap = &ti;

        if (type == T_PGFLT && addr < (caddr_t)kernelbase) {
                panic("BAD TRAP: type=%x (#%s %s) rp=%p addr=%p "
                    "occurred in module \"%s\" due to %s",
                    type, trap_mnemonic, trap_name, (void *)rp, (void *)addr,
                    mod_containing_pc((caddr_t)rp->r_pc),
                    addr < (caddr_t)PAGESIZE ?
                    "a NULL pointer dereference" :
                    "an illegal access to a user address");
        } else
                panic("BAD TRAP: type=%x (#%s %s) rp=%p addr=%p",
                    type, trap_mnemonic, trap_name, (void *)rp, (void *)addr);
        return (0);
}

/*
 * Rewrite the instruction at pc to be an int $T_SYSCALLINT instruction.
 *
 * int <vector> is two bytes: 0xCD <vector>
 */

static int
rewrite_syscall(caddr_t pc)
{
        uchar_t instr[SLOW_SCALL_SIZE] = { 0xCD, T_SYSCALLINT };

        if (uwrite(curthread->t_procp, instr, SLOW_SCALL_SIZE,
            (uintptr_t)pc) != 0)
                return (1);

        return (0);
}

/*
 * Test to see if the instruction at pc is sysenter or syscall. The second
 * argument should be the x86 feature flag corresponding to the expected
 * instruction.
 *
 * sysenter is two bytes: 0x0F 0x34
 * syscall is two bytes:  0x0F 0x05
 * int $T_SYSCALLINT is two bytes: 0xCD 0x91
 */

static int
instr_is_other_syscall(caddr_t pc, int which)
{
        uchar_t instr[FAST_SCALL_SIZE];

        ASSERT(which == X86FSET_SEP || which == X86FSET_ASYSC || which == 0xCD);

        if (copyin_nowatch(pc, (caddr_t)instr, FAST_SCALL_SIZE) != 0)
                return (0);

        switch (which) {
        case X86FSET_SEP:
                if (instr[0] == 0x0F && instr[1] == 0x34)
                        return (1);
                break;
        case X86FSET_ASYSC:
                if (instr[0] == 0x0F && instr[1] == 0x05)
                        return (1);
                break;
        case 0xCD:
                if (instr[0] == 0xCD && instr[1] == T_SYSCALLINT)
                        return (1);
                break;
        }

        return (0);
}

static const char *
syscall_insn_string(int syscall_insn)
{
        switch (syscall_insn) {
        case X86FSET_SEP:
                return ("sysenter");
        case X86FSET_ASYSC:
                return ("syscall");
        case 0xCD:
                return ("int");
        default:
                return ("Unknown");
        }
}

static int
ldt_rewrite_syscall(struct regs *rp, proc_t *p, int syscall_insn)
{
        caddr_t linearpc;
        int return_code = 0;

        mutex_enter(&p->p_ldtlock);     /* Must be held across linear_pc() */

        if (linear_pc(rp, p, &linearpc) == 0) {

                /*
                 * If another thread beat us here, it already changed
                 * this site to the slower (int) syscall instruction.
                 */
                if (instr_is_other_syscall(linearpc, 0xCD)) {
                        return_code = 1;
                } else if (instr_is_other_syscall(linearpc, syscall_insn)) {

                        if (rewrite_syscall(linearpc) == 0) {
                                return_code = 1;
                        }
#ifdef DEBUG
                        else
                                cmn_err(CE_WARN, "failed to rewrite %s "
                                    "instruction in process %d",
                                    syscall_insn_string(syscall_insn),
                                    p->p_pid);
#endif /* DEBUG */
                }
        }

        mutex_exit(&p->p_ldtlock);      /* Must be held across linear_pc() */

        return (return_code);
}

/*
 * Test to see if the instruction at pc is a system call instruction.
 *
 * The bytes of an lcall instruction used for the syscall trap.
 * static uchar_t lcall[7] = { 0x9a, 0, 0, 0, 0, 0x7, 0 };
 * static uchar_t lcallalt[7] = { 0x9a, 0, 0, 0, 0, 0x27, 0 };
 */

#define LCALLSIZE       7

static int
instr_is_lcall_syscall(caddr_t pc)
{
        uchar_t instr[LCALLSIZE];

        if (copyin_nowatch(pc, (caddr_t)instr, LCALLSIZE) == 0 &&
            instr[0] == 0x9a &&
            instr[1] == 0 &&
            instr[2] == 0 &&
            instr[3] == 0 &&
            instr[4] == 0 &&
            (instr[5] == 0x7 || instr[5] == 0x27) &&
            instr[6] == 0)
                return (1);

        return (0);
}

#ifdef __amd64

/*
 * In the first revisions of amd64 CPUs produced by AMD, the LAHF and
 * SAHF instructions were not implemented in 64-bit mode. Later revisions
 * did implement these instructions. An extension to the cpuid instruction
 * was added to check for the capability of executing these instructions
 * in 64-bit mode.
 *
 * Intel originally did not implement these instructions in EM64T either,
 * but added them in later revisions.
 *
 * So, there are different chip revisions by both vendors out there that
 * may or may not implement these instructions. The easy solution is to
 * just always emulate these instructions on demand.
 *
 * SAHF == store %ah in the lower 8 bits of %rflags (opcode 0x9e)
 * LAHF == load the lower 8 bits of %rflags into %ah (opcode 0x9f)
 */

#define LSAHFSIZE 1

static int
instr_is_lsahf(caddr_t pc, uchar_t *instr)
{
        if (copyin_nowatch(pc, (caddr_t)instr, LSAHFSIZE) == 0 &&
            (*instr == 0x9e || *instr == 0x9f))
                return (1);
        return (0);
}

/*
 * Emulate the LAHF and SAHF instructions. The reference manuals define
 * these instructions to always load/store bit 1 as a 1, and bits 3 and 5
 * as a 0. The other, defined, bits are copied (the PS_ICC bits and PS_P).
 *
 * Note that %ah is bits 8-15 of %rax.
 */
static void
emulate_lsahf(struct regs *rp, uchar_t instr)
{
        if (instr == 0x9e) {
                /* sahf. Copy bits from %ah to flags. */
                rp->r_ps = (rp->r_ps & ~0xff) |
                    ((rp->r_rax >> 8) & PSL_LSAHFMASK) | PS_MB1;
        } else {
                /* lahf. Copy bits from flags to %ah. */
                rp->r_rax = (rp->r_rax & ~0xff00) |
                    (((rp->r_ps & PSL_LSAHFMASK) | PS_MB1) << 8);
        }
        rp->r_pc += LSAHFSIZE;
}
#endif /* __amd64 */

#ifdef OPTERON_ERRATUM_91

/*
 * Test to see if the instruction at pc is a prefetch instruction.
 *
 * The first byte of prefetch instructions is always 0x0F.
 * The second byte is 0x18 for regular prefetch or 0x0D for AMD 3dnow prefetch.
 * The third byte (ModRM) contains the register field bits (bits 3-5).
 * These bits must be between 0 and 3 inclusive for regular prefetch and
 * 0 and 1 inclusive for AMD 3dnow prefetch.
 *
 * In 64-bit mode, there may be a one-byte REX prefex (0x40-0x4F).
 */

static int
cmp_to_prefetch(uchar_t *p)
{
#ifdef _LP64
        if ((p[0] & 0xF0) == 0x40)      /* 64-bit REX prefix */
                p++;
#endif
        return ((p[0] == 0x0F && p[1] == 0x18 && ((p[2] >> 3) & 7) <= 3) ||
            (p[0] == 0x0F && p[1] == 0x0D && ((p[2] >> 3) & 7) <= 1));
}

static int
instr_is_prefetch(caddr_t pc)
{
        uchar_t instr[4];       /* optional REX prefix plus 3-byte opcode */

        return (copyin_nowatch(pc, instr, sizeof (instr)) == 0 &&
            cmp_to_prefetch(instr));
}

#endif /* OPTERON_ERRATUM_91 */

/*
 * Called from the trap handler when a processor trap occurs.
 *
 * Note: All user-level traps that might call stop() must exit
 * trap() by 'goto out' or by falling through.
 * Note Also: trap() is usually called with interrupts enabled, (PS_IE == 1)
 * however, there are paths that arrive here with PS_IE == 0 so special care
 * must be taken in those cases.
 */
void
trap(struct regs *rp, caddr_t addr, processorid_t cpuid)
{
        kthread_t *ct = curthread;
        enum seg_rw rw;
        unsigned type;
        proc_t *p = ttoproc(ct);
        klwp_t *lwp = ttolwp(ct);
        uintptr_t lofault;
        label_t *onfault;
        faultcode_t pagefault(), res, errcode;
        enum fault_type fault_type;
        k_siginfo_t siginfo;
        uint_t fault = 0;
        int mstate;
        int sicode = 0;
        int watchcode;
        int watchpage;
        caddr_t vaddr;
        size_t sz;
        int ta;
#ifdef __amd64
        uchar_t instr;
#endif

        ASSERT_STACK_ALIGNED();

        type = rp->r_trapno;
        CPU_STATS_ADDQ(CPU, sys, trap, 1);

        if (type == T_PGFLT) {

                errcode = rp->r_err;
                if (errcode & PF_ERR_WRITE)
                        rw = S_WRITE;
                else if ((caddr_t)rp->r_pc == addr ||
                    (mmu.pt_nx != 0 && (errcode & PF_ERR_EXEC)))
                        rw = S_EXEC;
                else
                        rw = S_READ;

#if defined(__i386)
                /*
                 * Pentium Pro work-around
                 */
                if ((errcode & PF_ERR_PROT) && pentiumpro_bug4046376) {
                        uint_t  attr;
                        uint_t  priv_violation;
                        uint_t  access_violation;

                        if (hat_getattr(addr < (caddr_t)kernelbase ?
                            curproc->p_as->a_hat : kas.a_hat, addr, &attr)
                            == -1) {
                                errcode &= ~PF_ERR_PROT;
                        } else {
                                priv_violation = (errcode & PF_ERR_USER) &&
                                    !(attr & PROT_USER);
                                access_violation = (errcode & PF_ERR_WRITE) &&
                                    !(attr & PROT_WRITE);
                                if (!priv_violation && !access_violation)
                                        goto cleanup;
                        }
                }
#endif /* __i386 */

        } else if (type == T_SGLSTP && lwp != NULL)
                lwp->lwp_pcb.pcb_drstat = (uintptr_t)addr;

        if (tdebug)
                showregs(type, rp, addr);

        if (USERMODE(rp->r_cs)) {
                /*
                 * Set up the current cred to use during this trap. u_cred
                 * no longer exists.  t_cred is used instead.
                 * The current process credential applies to the thread for
                 * the entire trap.  If trapping from the kernel, this
                 * should already be set up.
                 */
                if (ct->t_cred != p->p_cred) {
                        cred_t *oldcred = ct->t_cred;
                        /*
                         * DTrace accesses t_cred in probe context.  t_cred
                         * must always be either NULL, or point to a valid,
                         * allocated cred structure.
                         */
                        ct->t_cred = crgetcred();
                        crfree(oldcred);
                }
                ASSERT(lwp != NULL);
                type |= USER;
                ASSERT(lwptoregs(lwp) == rp);
                lwp->lwp_state = LWP_SYS;

                switch (type) {
                case T_PGFLT + USER:
                        if ((caddr_t)rp->r_pc == addr)
                                mstate = LMS_TFAULT;
                        else
                                mstate = LMS_DFAULT;
                        break;
                default:
                        mstate = LMS_TRAP;
                        break;
                }

                mstate = new_mstate(ct, mstate);

                bzero(&siginfo, sizeof (siginfo));
        }

        switch (type) {
        case T_PGFLT + USER:
        case T_SGLSTP:
        case T_SGLSTP + USER:
        case T_BPTFLT + USER:
                break;

        default:
                FTRACE_2("trap(): type=0x%lx, regs=0x%lx",
                    (ulong_t)type, (ulong_t)rp);
                break;
        }

        switch (type) {
        case T_SIMDFPE:
                /* Make sure we enable interrupts before die()ing */
                sti();  /* The SIMD exception comes in via cmninttrap */
                /*FALLTHROUGH*/
        default:
                if (type & USER) {
                        if (tudebug)
                                showregs(type, rp, (caddr_t)0);
                        printf("trap: Unknown trap type %d in user mode\n",
                            type & ~USER);
                        siginfo.si_signo = SIGILL;
                        siginfo.si_code  = ILL_ILLTRP;
                        siginfo.si_addr  = (caddr_t)rp->r_pc;
                        siginfo.si_trapno = type & ~USER;
                        fault = FLTILL;
                } else {
                        (void) die(type, rp, addr, cpuid);
                        /*NOTREACHED*/
                }
                break;

        case T_PGFLT:           /* system page fault */
                /*
                 * If we're under on_trap() protection (see <sys/ontrap.h>),
                 * set ot_trap and bounce back to the on_trap() call site
                 * via the installed trampoline.
                 */
                if ((ct->t_ontrap != NULL) &&
                    (ct->t_ontrap->ot_prot & OT_DATA_ACCESS)) {
                        ct->t_ontrap->ot_trap |= OT_DATA_ACCESS;
                        rp->r_pc = ct->t_ontrap->ot_trampoline;
                        goto cleanup;
                }

                /*
                 * If we have an Instruction fault in kernel mode, then that
                 * means we've tried to execute a user page (SMEP) or both of
                 * PAE and NXE are enabled. In either case, given that it's a
                 * kernel fault, we should panic immediately and not try to make
                 * any more forward progress. This indicates a bug in the
                 * kernel, which if execution continued, could be exploited to
                 * wreak havoc on the system.
                 */
                if (errcode & PF_ERR_EXEC) {
                        (void) die(type, rp, addr, cpuid);
                }

                /*
                 * We need to check if SMAP is in play. If SMAP is in play, then
                 * any access to a user page will show up as a protection
                 * violation. To see if SMAP is enabled we first check if it's a
                 * user address and whether we have the feature flag set. If we
                 * do and the interrupted registers do not allow for user
                 * accesses (PS_ACHK is not enabled), then we need to die
                 * immediately.
                 */
                if (addr < (caddr_t)kernelbase &&
                    is_x86_feature(x86_featureset, X86FSET_SMAP) == B_TRUE &&
                    (rp->r_ps & PS_ACHK) == 0) {
                        (void) die(type, rp, addr, cpuid);
                }

                /*
                 * See if we can handle as pagefault. Save lofault and onfault
                 * across this. Here we assume that an address less than
                 * KERNELBASE is a user fault.  We can do this as copy.s
                 * routines verify that the starting address is less than
                 * KERNELBASE before starting and because we know that we
                 * always have KERNELBASE mapped as invalid to serve as a
                 * "barrier".
                 */
                lofault = ct->t_lofault;
                onfault = ct->t_onfault;
                ct->t_lofault = 0;

                mstate = new_mstate(ct, LMS_KFAULT);

                if (addr < (caddr_t)kernelbase) {
                        res = pagefault(addr,
                            (errcode & PF_ERR_PROT)? F_PROT: F_INVAL, rw, 0);
                        if (res == FC_NOMAP &&
                            addr < p->p_usrstack &&
                            grow(addr))
                                res = 0;
                } else {
                        res = pagefault(addr,
                            (errcode & PF_ERR_PROT)? F_PROT: F_INVAL, rw, 1);
                }
                (void) new_mstate(ct, mstate);

                /*
                 * Restore lofault and onfault. If we resolved the fault, exit.
                 * If we didn't and lofault wasn't set, die.
                 */
                ct->t_lofault = lofault;
                ct->t_onfault = onfault;
                if (res == 0)
                        goto cleanup;

#if defined(OPTERON_ERRATUM_93) && defined(_LP64)
                if (lofault == 0 && opteron_erratum_93) {
                        /*
                         * Workaround for Opteron Erratum 93. On return from
                         * a System Managment Interrupt at a HLT instruction
                         * the %rip might be truncated to a 32 bit value.
                         * BIOS is supposed to fix this, but some don't.
                         * If this occurs we simply restore the high order bits.
                         * The HLT instruction is 1 byte of 0xf4.
                         */
                        uintptr_t       rip = rp->r_pc;

                        if ((rip & 0xfffffffful) == rip) {
                                rip |= 0xfffffffful << 32;
                                if (hat_getpfnum(kas.a_hat, (caddr_t)rip) !=
                                    PFN_INVALID &&
                                    (*(uchar_t *)rip == 0xf4 ||
                                    *(uchar_t *)(rip - 1) == 0xf4)) {
                                        rp->r_pc = rip;
                                        goto cleanup;
                                }
                        }
                }
#endif /* OPTERON_ERRATUM_93 && _LP64 */

#ifdef OPTERON_ERRATUM_91
                if (lofault == 0 && opteron_erratum_91) {
                        /*
                         * Workaround for Opteron Erratum 91. Prefetches may
                         * generate a page fault (they're not supposed to do
                         * that!). If this occurs we simply return back to the
                         * instruction.
                         */
                        caddr_t         pc = (caddr_t)rp->r_pc;

                        /*
                         * If the faulting PC is not mapped, this is a
                         * legitimate kernel page fault that must result in a
                         * panic. If the faulting PC is mapped, it could contain
                         * a prefetch instruction. Check for that here.
                         */
                        if (hat_getpfnum(kas.a_hat, pc) != PFN_INVALID) {
                                if (cmp_to_prefetch((uchar_t *)pc)) {
#ifdef DEBUG
                                        cmn_err(CE_WARN, "Opteron erratum 91 "
                                            "occurred: kernel prefetch"
                                            " at %p generated a page fault!",
                                            (void *)rp->r_pc);
#endif /* DEBUG */
                                        goto cleanup;
                                }
                        }
                        (void) die(type, rp, addr, cpuid);
                }
#endif /* OPTERON_ERRATUM_91 */

                if (lofault == 0)
                        (void) die(type, rp, addr, cpuid);

                /*
                 * Cannot resolve fault.  Return to lofault.
                 */
                if (lodebug) {
                        showregs(type, rp, addr);
                        traceregs(rp);
                }
                if (FC_CODE(res) == FC_OBJERR)
                        res = FC_ERRNO(res);
                else
                        res = EFAULT;
                rp->r_r0 = res;
                rp->r_pc = ct->t_lofault;
                goto cleanup;

        case T_PGFLT + USER:    /* user page fault */
                if (faultdebug) {
                        char *fault_str;

                        switch (rw) {
                        case S_READ:
                                fault_str = "read";
                                break;
                        case S_WRITE:
                                fault_str = "write";
                                break;
                        case S_EXEC:
                                fault_str = "exec";
                                break;
                        default:
                                fault_str = "";
                                break;
                        }
                        printf("user %s fault:  addr=0x%lx errcode=0x%x\n",
                            fault_str, (uintptr_t)addr, errcode);
                }

#if defined(OPTERON_ERRATUM_100) && defined(_LP64)
                /*
                 * Workaround for AMD erratum 100
                 *
                 * A 32-bit process may receive a page fault on a non
                 * 32-bit address by mistake. The range of the faulting
                 * address will be
                 *
                 *      0xffffffff80000000 .. 0xffffffffffffffff or
                 *      0x0000000100000000 .. 0x000000017fffffff
                 *
                 * The fault is always due to an instruction fetch, however
                 * the value of r_pc should be correct (in 32 bit range),
                 * so we ignore the page fault on the bogus address.
                 */
                if (p->p_model == DATAMODEL_ILP32 &&
                    (0xffffffff80000000 <= (uintptr_t)addr ||
                    (0x100000000 <= (uintptr_t)addr &&
                    (uintptr_t)addr <= 0x17fffffff))) {
                        if (!opteron_erratum_100)
                                panic("unexpected erratum #100");
                        if (rp->r_pc <= 0xffffffff)
                                goto out;
                }
#endif /* OPTERON_ERRATUM_100 && _LP64 */

                ASSERT(!(curthread->t_flag & T_WATCHPT));
                watchpage = (pr_watch_active(p) && pr_is_watchpage(addr, rw));
#ifdef __i386
                /*
                 * In 32-bit mode, the lcall (system call) instruction fetches
                 * one word from the stack, at the stack pointer, because of the
                 * way the call gate is constructed.  This is a bogus
                 * read and should not be counted as a read watchpoint.
                 * We work around the problem here by testing to see if
                 * this situation applies and, if so, simply jumping to
                 * the code in locore.s that fields the system call trap.
                 * The registers on the stack are already set up properly
                 * due to the match between the call gate sequence and the
                 * trap gate sequence.  We just have to adjust the pc.
                 */
                if (watchpage && addr == (caddr_t)rp->r_sp &&
                    rw == S_READ && instr_is_lcall_syscall((caddr_t)rp->r_pc)) {
                        extern void watch_syscall(void);

                        rp->r_pc += LCALLSIZE;
                        watch_syscall();        /* never returns */
                        /* NOTREACHED */
                }
#endif /* __i386 */
                vaddr = addr;
                if (!watchpage || (sz = instr_size(rp, &vaddr, rw)) <= 0)
                        fault_type = (errcode & PF_ERR_PROT)? F_PROT: F_INVAL;
                else if ((watchcode = pr_is_watchpoint(&vaddr, &ta,
                    sz, NULL, rw)) != 0) {
                        if (ta) {
                                do_watch_step(vaddr, sz, rw,
                                    watchcode, rp->r_pc);
                                fault_type = F_INVAL;
                        } else {
                                bzero(&siginfo, sizeof (siginfo));
                                siginfo.si_signo = SIGTRAP;
                                siginfo.si_code = watchcode;
                                siginfo.si_addr = vaddr;
                                siginfo.si_trapafter = 0;
                                siginfo.si_pc = (caddr_t)rp->r_pc;
                                fault = FLTWATCH;
                                break;
                        }
                } else {
                        /* XXX pr_watch_emul() never succeeds (for now) */
                        if (rw != S_EXEC && pr_watch_emul(rp, vaddr, rw))
                                goto out;
                        do_watch_step(vaddr, sz, rw, 0, 0);
                        fault_type = F_INVAL;
                }

                res = pagefault(addr, fault_type, rw, 0);

                /*
                 * If pagefault() succeeded, ok.
                 * Otherwise attempt to grow the stack.
                 */
                if (res == 0 ||
                    (res == FC_NOMAP &&
                    addr < p->p_usrstack &&
                    grow(addr))) {
                        lwp->lwp_lastfault = FLTPAGE;
                        lwp->lwp_lastfaddr = addr;
                        if (prismember(&p->p_fltmask, FLTPAGE)) {
                                bzero(&siginfo, sizeof (siginfo));
                                siginfo.si_addr = addr;
                                (void) stop_on_fault(FLTPAGE, &siginfo);
                        }
                        goto out;
                } else if (res == FC_PROT && addr < p->p_usrstack &&
                    (mmu.pt_nx != 0 && (errcode & PF_ERR_EXEC))) {
                        report_stack_exec(p, addr);
                }

#ifdef OPTERON_ERRATUM_91
                /*
                 * Workaround for Opteron Erratum 91. Prefetches may generate a
                 * page fault (they're not supposed to do that!). If this
                 * occurs we simply return back to the instruction.
                 *
                 * We rely on copyin to properly fault in the page with r_pc.
                 */
                if (opteron_erratum_91 &&
                    addr != (caddr_t)rp->r_pc &&
                    instr_is_prefetch((caddr_t)rp->r_pc)) {
#ifdef DEBUG
                        cmn_err(CE_WARN, "Opteron erratum 91 occurred: "
                            "prefetch at %p in pid %d generated a trap!",
                            (void *)rp->r_pc, p->p_pid);
#endif /* DEBUG */
                        goto out;
                }
#endif /* OPTERON_ERRATUM_91 */

                if (tudebug)
                        showregs(type, rp, addr);
                /*
                 * In the case where both pagefault and grow fail,
                 * set the code to the value provided by pagefault.
                 * We map all errors returned from pagefault() to SIGSEGV.
                 */
                bzero(&siginfo, sizeof (siginfo));
                siginfo.si_addr = addr;
                switch (FC_CODE(res)) {
                case FC_HWERR:
                case FC_NOSUPPORT:
                        siginfo.si_signo = SIGBUS;
                        siginfo.si_code = BUS_ADRERR;
                        fault = FLTACCESS;
                        break;
                case FC_ALIGN:
                        siginfo.si_signo = SIGBUS;
                        siginfo.si_code = BUS_ADRALN;
                        fault = FLTACCESS;
                        break;
                case FC_OBJERR:
                        if ((siginfo.si_errno = FC_ERRNO(res)) != EINTR) {
                                siginfo.si_signo = SIGBUS;
                                siginfo.si_code = BUS_OBJERR;
                                fault = FLTACCESS;
                        }
                        break;
                default:        /* FC_NOMAP or FC_PROT */
                        siginfo.si_signo = SIGSEGV;
                        siginfo.si_code =
                            (res == FC_NOMAP)? SEGV_MAPERR : SEGV_ACCERR;
                        fault = FLTBOUNDS;
                        break;
                }
                break;

        case T_ILLINST + USER:  /* invalid opcode fault */
                /*
                 * If the syscall instruction is disabled due to LDT usage, a
                 * user program that attempts to execute it will trigger a #ud
                 * trap. Check for that case here. If this occurs on a CPU which
                 * doesn't even support syscall, the result of all of this will
                 * be to emulate that particular instruction.
                 */
                if (p->p_ldt != NULL &&
                    ldt_rewrite_syscall(rp, p, X86FSET_ASYSC))
                        goto out;

#ifdef __amd64
                /*
                 * Emulate the LAHF and SAHF instructions if needed.
                 * See the instr_is_lsahf function for details.
                 */
                if (p->p_model == DATAMODEL_LP64 &&
                    instr_is_lsahf((caddr_t)rp->r_pc, &instr)) {
                        emulate_lsahf(rp, instr);
                        goto out;
                }
#endif

                /*FALLTHROUGH*/

                if (tudebug)
                        showregs(type, rp, (caddr_t)0);
                siginfo.si_signo = SIGILL;
                siginfo.si_code  = ILL_ILLOPC;
                siginfo.si_addr  = (caddr_t)rp->r_pc;
                fault = FLTILL;
                break;

        case T_ZERODIV + USER:          /* integer divide by zero */
                if (tudebug && tudebugfpe)
                        showregs(type, rp, (caddr_t)0);
                siginfo.si_signo = SIGFPE;
                siginfo.si_code  = FPE_INTDIV;
                siginfo.si_addr  = (caddr_t)rp->r_pc;
                fault = FLTIZDIV;
                break;

        case T_OVFLW + USER:    /* integer overflow */
                if (tudebug && tudebugfpe)
                        showregs(type, rp, (caddr_t)0);
                siginfo.si_signo = SIGFPE;
                siginfo.si_code  = FPE_INTOVF;
                siginfo.si_addr  = (caddr_t)rp->r_pc;
                fault = FLTIOVF;
                break;

        /*
         * When using an eager FPU on x86, the #NM trap is no longer meaningful.
         * Userland should not be able to trigger it. Anything that does
         * represents a fatal error in the kernel and likely in the register
         * state of the system. User FPU state should always be valid.
         */
        case T_NOEXTFLT + USER: /* math coprocessor not available */
        case T_NOEXTFLT:
                (void) die(type, rp, addr, cpuid);
                break;

        /*
         * Kernel threads leveraging floating point need to mask the exceptions
         * or ensure that they cannot happen. There is no recovery from this.
         */
        case T_EXTERRFLT:       /* x87 floating point exception pending */
                sti(); /* T_EXTERRFLT comes in via cmninttrap */
                (void) die(type, rp, addr, cpuid);
                break;

        case T_EXTERRFLT + USER: /* x87 floating point exception pending */
                if (tudebug && tudebugfpe)
                        showregs(type, rp, addr);
                if (sicode = fpexterrflt(rp)) {
                        siginfo.si_signo = SIGFPE;
                        siginfo.si_code  = sicode;
                        siginfo.si_addr  = (caddr_t)rp->r_pc;
                        fault = FLTFPE;
                }
                break;

        case T_SIMDFPE + USER:          /* SSE and SSE2 exceptions */
                if (tudebug && tudebugsse)
                        showregs(type, rp, addr);
                if (!is_x86_feature(x86_featureset, X86FSET_SSE) &&
                    !is_x86_feature(x86_featureset, X86FSET_SSE2)) {
                        /*
                         * There are rumours that some user instructions
                         * on older CPUs can cause this trap to occur; in
                         * which case send a SIGILL instead of a SIGFPE.
                         */
                        siginfo.si_signo = SIGILL;
                        siginfo.si_code  = ILL_ILLTRP;
                        siginfo.si_addr  = (caddr_t)rp->r_pc;
                        siginfo.si_trapno = type & ~USER;
                        fault = FLTILL;
                } else if ((sicode = fpsimderrflt(rp)) != 0) {
                        siginfo.si_signo = SIGFPE;
                        siginfo.si_code = sicode;
                        siginfo.si_addr = (caddr_t)rp->r_pc;
                        fault = FLTFPE;
                }

                sti();  /* The SIMD exception comes in via cmninttrap */
                break;

        case T_BPTFLT:  /* breakpoint trap */
                /*
                 * Kernel breakpoint traps should only happen when kmdb is
                 * active, and even then, it'll have interposed on the IDT, so
                 * control won't get here.  If it does, we've hit a breakpoint
                 * without the debugger, which is very strange, and very
                 * fatal.
                 */
                if (tudebug && tudebugbpt)
                        showregs(type, rp, (caddr_t)0);

                (void) die(type, rp, addr, cpuid);
                break;

        case T_SGLSTP: /* single step/hw breakpoint exception */

#if !defined(__xpv)
                /*
                 * We'd never normally get here, as kmdb handles its own single
                 * step traps.  There is one nasty exception though, as
                 * described in more detail in sys_sysenter().  Note that
                 * checking for all four locations covers both the KPTI and the
                 * non-KPTI cases correctly: the former will never be found at
                 * (brand_)sys_sysenter, and vice versa.
                 */
                if (lwp != NULL && (lwp->lwp_pcb.pcb_drstat & DR_SINGLESTEP)) {
                        if (rp->r_pc == (greg_t)brand_sys_sysenter ||
                            rp->r_pc == (greg_t)sys_sysenter ||
                            rp->r_pc == (greg_t)tr_brand_sys_sysenter ||
                            rp->r_pc == (greg_t)tr_sys_sysenter) {

                                rp->r_pc += 0x3; /* sizeof (swapgs) */

                                rp->r_ps &= ~PS_T; /* turn off trace */
                                lwp->lwp_pcb.pcb_flags |= DEBUG_PENDING;
                                ct->t_post_sys = 1;
                                aston(curthread);
                                goto cleanup;
                        } else {
                                if (tudebug && tudebugbpt)
                                        showregs(type, rp, (caddr_t)0);
                        }
                }
#endif /* !__xpv */

                if (boothowto & RB_DEBUG)
                        debug_enter(NULL);
                else
                        (void) die(type, rp, addr, cpuid);
                break;

        case T_NMIFLT:  /* NMI interrupt */
                printf("Unexpected NMI in system mode\n");
                goto cleanup;

        case T_NMIFLT + USER:   /* NMI interrupt */
                printf("Unexpected NMI in user mode\n");
                break;

        case T_GPFLT:   /* general protection violation */
                /*
                 * Any #GP that occurs during an on_trap .. no_trap bracket
                 * with OT_DATA_ACCESS or OT_SEGMENT_ACCESS protection,
                 * or in a on_fault .. no_fault bracket, is forgiven
                 * and we trampoline.  This protection is given regardless
                 * of whether we are 32/64 bit etc - if a distinction is
                 * required then define new on_trap protection types.
                 *
                 * On amd64, we can get a #gp from referencing addresses
                 * in the virtual address hole e.g. from a copyin or in
                 * update_sregs while updating user segment registers.
                 *
                 * On the 32-bit hypervisor we could also generate one in
                 * mfn_to_pfn by reaching around or into where the hypervisor
                 * lives which is protected by segmentation.
                 */

                /*
                 * If we're under on_trap() protection (see <sys/ontrap.h>),
                 * set ot_trap and trampoline back to the on_trap() call site
                 * for OT_DATA_ACCESS or OT_SEGMENT_ACCESS.
                 */
                if (ct->t_ontrap != NULL) {
                        int ttype =  ct->t_ontrap->ot_prot &
                            (OT_DATA_ACCESS | OT_SEGMENT_ACCESS);

                        if (ttype != 0) {
                                ct->t_ontrap->ot_trap |= ttype;
                                if (tudebug)
                                        showregs(type, rp, (caddr_t)0);
                                rp->r_pc = ct->t_ontrap->ot_trampoline;
                                goto cleanup;
                        }
                }

                /*
                 * If we're under lofault protection (copyin etc.),
                 * longjmp back to lofault with an EFAULT.
                 */
                if (ct->t_lofault) {
                        /*
                         * Fault is not resolvable, so just return to lofault
                         */
                        if (lodebug) {
                                showregs(type, rp, addr);
                                traceregs(rp);
                        }
                        rp->r_r0 = EFAULT;
                        rp->r_pc = ct->t_lofault;
                        goto cleanup;
                }

                /*
                 * We fall through to the next case, which repeats
                 * the OT_SEGMENT_ACCESS check which we've already
                 * done, so we'll always fall through to the
                 * T_STKFLT case.
                 */
                /*FALLTHROUGH*/
        case T_SEGFLT:  /* segment not present fault */
                /*
                 * One example of this is #NP in update_sregs while
                 * attempting to update a user segment register
                 * that points to a descriptor that is marked not
                 * present.
                 */
                if (ct->t_ontrap != NULL &&
                    ct->t_ontrap->ot_prot & OT_SEGMENT_ACCESS) {
                        ct->t_ontrap->ot_trap |= OT_SEGMENT_ACCESS;
                        if (tudebug)
                                showregs(type, rp, (caddr_t)0);
                        rp->r_pc = ct->t_ontrap->ot_trampoline;
                        goto cleanup;
                }
                /*FALLTHROUGH*/
        case T_STKFLT:  /* stack fault */
        case T_TSSFLT:  /* invalid TSS fault */
                if (tudebug)
                        showregs(type, rp, (caddr_t)0);
                if (kern_gpfault(rp))
                        (void) die(type, rp, addr, cpuid);
                goto cleanup;

        /*
         * ONLY 32-bit PROCESSES can USE a PRIVATE LDT! 64-bit apps
         * should have no need for them, so we put a stop to it here.
         *
         * So: not-present fault is ONLY valid for 32-bit processes with
         * a private LDT trying to do a system call. Emulate it.
         *
         * #gp fault is ONLY valid for 32-bit processes also, which DO NOT
         * have a private LDT, and are trying to do a system call. Emulate it.
         */

        case T_SEGFLT + USER:   /* segment not present fault */
        case T_GPFLT + USER:    /* general protection violation */
#ifdef _SYSCALL32_IMPL
                if (p->p_model != DATAMODEL_NATIVE) {
#endif /* _SYSCALL32_IMPL */
                if (instr_is_lcall_syscall((caddr_t)rp->r_pc)) {
                        if (type == T_SEGFLT + USER)
                                ASSERT(p->p_ldt != NULL);

                        if ((p->p_ldt == NULL && type == T_GPFLT + USER) ||
                            type == T_SEGFLT + USER) {

                        /*
                         * The user attempted a system call via the obsolete
                         * call gate mechanism. Because the process doesn't have
                         * an LDT (i.e. the ldtr contains 0), a #gp results.
                         * Emulate the syscall here, just as we do above for a
                         * #np trap.
                         */

                        /*
                         * Since this is a not-present trap, rp->r_pc points to
                         * the trapping lcall instruction. We need to bump it
                         * to the next insn so the app can continue on.
                         */
                        rp->r_pc += LCALLSIZE;
                        lwp->lwp_regs = rp;

                        /*
                         * Normally the microstate of the LWP is forced back to
                         * LMS_USER by the syscall handlers. Emulate that
                         * behavior here.
                         */
                        mstate = LMS_USER;

                        dosyscall();
                        goto out;
                        }
                }
#ifdef _SYSCALL32_IMPL
                }
#endif /* _SYSCALL32_IMPL */
                /*
                 * If the current process is using a private LDT and the
                 * trapping instruction is sysenter, the sysenter instruction
                 * has been disabled on the CPU because it destroys segment
                 * registers. If this is the case, rewrite the instruction to
                 * be a safe system call and retry it. If this occurs on a CPU
                 * which doesn't even support sysenter, the result of all of
                 * this will be to emulate that particular instruction.
                 */
                if (p->p_ldt != NULL &&
                    ldt_rewrite_syscall(rp, p, X86FSET_SEP))
                        goto out;

                /*FALLTHROUGH*/

        case T_BOUNDFLT + USER: /* bound fault */
        case T_STKFLT + USER:   /* stack fault */
        case T_TSSFLT + USER:   /* invalid TSS fault */
                if (tudebug)
                        showregs(type, rp, (caddr_t)0);
                siginfo.si_signo = SIGSEGV;
                siginfo.si_code  = SEGV_MAPERR;
                siginfo.si_addr  = (caddr_t)rp->r_pc;
                fault = FLTBOUNDS;
                break;

        case T_ALIGNMENT + USER:        /* user alignment error (486) */
                if (tudebug)
                        showregs(type, rp, (caddr_t)0);
                bzero(&siginfo, sizeof (siginfo));
                siginfo.si_signo = SIGBUS;
                siginfo.si_code = BUS_ADRALN;
                siginfo.si_addr = (caddr_t)rp->r_pc;
                fault = FLTACCESS;
                break;

        case T_SGLSTP + USER: /* single step/hw breakpoint exception */
                if (tudebug && tudebugbpt)
                        showregs(type, rp, (caddr_t)0);

                /* Was it single-stepping? */
                if (lwp->lwp_pcb.pcb_drstat & DR_SINGLESTEP) {
                        pcb_t *pcb = &lwp->lwp_pcb;

                        rp->r_ps &= ~PS_T;
                        /*
                         * If both NORMAL_STEP and WATCH_STEP are in effect,
                         * give precedence to WATCH_STEP.  If neither is set,
                         * user must have set the PS_T bit in %efl; treat this
                         * as NORMAL_STEP.
                         */
                        if ((fault = undo_watch_step(&siginfo)) == 0 &&
                            ((pcb->pcb_flags & NORMAL_STEP) ||
                            !(pcb->pcb_flags & WATCH_STEP))) {
                                siginfo.si_signo = SIGTRAP;
                                siginfo.si_code = TRAP_TRACE;
                                siginfo.si_addr = (caddr_t)rp->r_pc;
                                fault = FLTTRACE;
                        }
                        pcb->pcb_flags &= ~(NORMAL_STEP|WATCH_STEP);
                }
                break;

        case T_BPTFLT + USER:   /* breakpoint trap */
                if (tudebug && tudebugbpt)
                        showregs(type, rp, (caddr_t)0);
                /*
                 * int 3 (the breakpoint instruction) leaves the pc referring
                 * to the address one byte after the breakpointed address.
                 * If the P_PR_BPTADJ flag has been set via /proc, We adjust
                 * it back so it refers to the breakpointed address.
                 */
                if (p->p_proc_flag & P_PR_BPTADJ)
                        rp->r_pc--;
                siginfo.si_signo = SIGTRAP;
                siginfo.si_code  = TRAP_BRKPT;
                siginfo.si_addr  = (caddr_t)rp->r_pc;
                fault = FLTBPT;
                break;

        case T_AST:
                /*
                 * This occurs only after the cs register has been made to
                 * look like a kernel selector, either through debugging or
                 * possibly by functions like setcontext().  The thread is
                 * about to cause a general protection fault at common_iret()
                 * in locore.  We let that happen immediately instead of
                 * doing the T_AST processing.
                 */
                goto cleanup;

        case T_AST + USER:      /* profiling, resched, h/w error pseudo trap */
                if (lwp->lwp_pcb.pcb_flags & ASYNC_HWERR) {
                        proc_t *p = ttoproc(curthread);
                        extern void print_msg_hwerr(ctid_t ct_id, proc_t *p);

                        lwp->lwp_pcb.pcb_flags &= ~ASYNC_HWERR;
                        print_msg_hwerr(p->p_ct_process->conp_contract.ct_id,
                            p);
                        contract_process_hwerr(p->p_ct_process, p);
                        siginfo.si_signo = SIGKILL;
                        siginfo.si_code = SI_NOINFO;
                } else if (lwp->lwp_pcb.pcb_flags & CPC_OVERFLOW) {
                        lwp->lwp_pcb.pcb_flags &= ~CPC_OVERFLOW;
                        if (kcpc_overflow_ast()) {
                                /*
                                 * Signal performance counter overflow
                                 */
                                if (tudebug)
                                        showregs(type, rp, (caddr_t)0);
                                bzero(&siginfo, sizeof (siginfo));
                                siginfo.si_signo = SIGEMT;
                                siginfo.si_code = EMT_CPCOVF;
                                siginfo.si_addr = (caddr_t)rp->r_pc;
                                fault = FLTCPCOVF;
                        }
                }

                break;
        }

        /*
         * We can't get here from a system trap
         */
        ASSERT(type & USER);

        if (fault) {
                /* We took a fault so abort single step. */
                lwp->lwp_pcb.pcb_flags &= ~(NORMAL_STEP|WATCH_STEP);
                /*
                 * Remember the fault and fault adddress
                 * for real-time (SIGPROF) profiling.
                 */
                lwp->lwp_lastfault = fault;
                lwp->lwp_lastfaddr = siginfo.si_addr;

                DTRACE_PROC2(fault, int, fault, ksiginfo_t *, &siginfo);

                /*
                 * If a debugger has declared this fault to be an
                 * event of interest, stop the lwp.  Otherwise just
                 * deliver the associated signal.
                 */
                if (siginfo.si_signo != SIGKILL &&
                    prismember(&p->p_fltmask, fault) &&
                    stop_on_fault(fault, &siginfo) == 0)
                        siginfo.si_signo = 0;
        }

        if (siginfo.si_signo)
                trapsig(&siginfo, (fault != FLTFPE && fault != FLTCPCOVF));

        if (lwp->lwp_oweupc)
                profil_tick(rp->r_pc);

        if (ct->t_astflag | ct->t_sig_check) {
                /*
                 * Turn off the AST flag before checking all the conditions that
                 * may have caused an AST.  This flag is on whenever a signal or
                 * unusual condition should be handled after the next trap or
                 * syscall.
                 */
                astoff(ct);
                /*
                 * If a single-step trap occurred on a syscall (see above)
                 * recognize it now.  Do this before checking for signals
                 * because deferred_singlestep_trap() may generate a SIGTRAP to
                 * the LWP or may otherwise mark the LWP to call issig(FORREAL).
                 */
                if (lwp->lwp_pcb.pcb_flags & DEBUG_PENDING)
                        deferred_singlestep_trap((caddr_t)rp->r_pc);

                ct->t_sig_check = 0;

                /*
                 * As in other code paths that check against TP_CHANGEBIND,
                 * we perform the check first without p_lock held -- only
                 * acquiring p_lock in the unlikely event that it is indeed
                 * set.  This is safe because we are doing this after the
                 * astoff(); if we are racing another thread setting
                 * TP_CHANGEBIND on us, we will pick it up on a subsequent
                 * lap through.
                 */
                if (curthread->t_proc_flag & TP_CHANGEBIND) {
                        mutex_enter(&p->p_lock);
                        if (curthread->t_proc_flag & TP_CHANGEBIND) {
                                timer_lwpbind();
                                curthread->t_proc_flag &= ~TP_CHANGEBIND;
                        }
                        mutex_exit(&p->p_lock);
                }

                /*
                 * for kaio requests that are on the per-process poll queue,
                 * aiop->aio_pollq, they're AIO_POLL bit is set, the kernel
                 * should copyout their result_t to user memory. by copying
                 * out the result_t, the user can poll on memory waiting
                 * for the kaio request to complete.
                 */
                if (p->p_aio)
                        aio_cleanup(0);
                /*
                 * If this LWP was asked to hold, call holdlwp(), which will
                 * stop.  holdlwps() sets this up and calls pokelwps() which
                 * sets the AST flag.
                 *
                 * Also check TP_EXITLWP, since this is used by fresh new LWPs
                 * through lwp_rtt().  That flag is set if the lwp_create(2)
                 * syscall failed after creating the LWP.
                 */
                if (ISHOLD(p))
                        holdlwp();

                /*
                 * All code that sets signals and makes ISSIG evaluate true must
                 * set t_astflag afterwards.
                 */
                if (ISSIG_PENDING(ct, lwp, p)) {
                        if (issig(FORREAL))
                                psig();
                        ct->t_sig_check = 1;
                }

                if (ct->t_rprof != NULL) {
                        realsigprof(0, 0, 0);
                        ct->t_sig_check = 1;
                }

                /*
                 * /proc can't enable/disable the trace bit itself
                 * because that could race with the call gate used by
                 * system calls via "lcall". If that happened, an
                 * invalid EFLAGS would result. prstep()/prnostep()
                 * therefore schedule an AST for the purpose.
                 */
                if (lwp->lwp_pcb.pcb_flags & REQUEST_STEP) {
                        lwp->lwp_pcb.pcb_flags &= ~REQUEST_STEP;
                        rp->r_ps |= PS_T;
                }
                if (lwp->lwp_pcb.pcb_flags & REQUEST_NOSTEP) {
                        lwp->lwp_pcb.pcb_flags &= ~REQUEST_NOSTEP;
                        rp->r_ps &= ~PS_T;
                }
        }

out:    /* We can't get here from a system trap */
        ASSERT(type & USER);

        if (ISHOLD(p))
                holdlwp();

        /*
         * Set state to LWP_USER here so preempt won't give us a kernel
         * priority if it occurs after this point.  Call CL_TRAPRET() to
         * restore the user-level priority.
         *
         * It is important that no locks (other than spinlocks) be entered
         * after this point before returning to user mode (unless lwp_state
         * is set back to LWP_SYS).
         */
        lwp->lwp_state = LWP_USER;

        if (ct->t_trapret) {
                ct->t_trapret = 0;
                thread_lock(ct);
                CL_TRAPRET(ct);
                thread_unlock(ct);
        }
        if (CPU->cpu_runrun || curthread->t_schedflag & TS_ANYWAITQ)
                preempt();
        prunstop();
        (void) new_mstate(ct, mstate);

        return;

cleanup:        /* system traps end up here */
        ASSERT(!(type & USER));
}

/*
 * Patch non-zero to disable preemption of threads in the kernel.
 */
int IGNORE_KERNEL_PREEMPTION = 0;       /* XXX - delete this someday */

struct kpreempt_cnts {          /* kernel preemption statistics */
        int     kpc_idle;       /* executing idle thread */
        int     kpc_intr;       /* executing interrupt thread */
        int     kpc_clock;      /* executing clock thread */
        int     kpc_blocked;    /* thread has blocked preemption (t_preempt) */
        int     kpc_notonproc;  /* thread is surrendering processor */
        int     kpc_inswtch;    /* thread has ratified scheduling decision */
        int     kpc_prilevel;   /* processor interrupt level is too high */
        int     kpc_apreempt;   /* asynchronous preemption */
        int     kpc_spreempt;   /* synchronous preemption */
} kpreempt_cnts;

/*
 * kernel preemption: forced rescheduling, preempt the running kernel thread.
 *      the argument is old PIL for an interrupt,
 *      or the distingished value KPREEMPT_SYNC.
 */
void
kpreempt(int asyncspl)
{
        kthread_t *ct = curthread;

        if (IGNORE_KERNEL_PREEMPTION) {
                aston(CPU->cpu_dispthread);
                return;
        }

        /*
         * Check that conditions are right for kernel preemption
         */
        do {
                if (ct->t_preempt) {
                        /*
                         * either a privileged thread (idle, panic, interrupt)
                         * or will check when t_preempt is lowered
                         * We need to specifically handle the case where
                         * the thread is in the middle of swtch (resume has
                         * been called) and has its t_preempt set
                         * [idle thread and a thread which is in kpreempt
                         * already] and then a high priority thread is
                         * available in the local dispatch queue.
                         * In this case the resumed thread needs to take a
                         * trap so that it can call kpreempt. We achieve
                         * this by using siron().
                         * How do we detect this condition:
                         * idle thread is running and is in the midst of
                         * resume: curthread->t_pri == -1 && CPU->dispthread
                         * != CPU->thread
                         * Need to ensure that this happens only at high pil
                         * resume is called at high pil
                         * Only in resume_from_idle is the pil changed.
                         */
                        if (ct->t_pri < 0) {
                                kpreempt_cnts.kpc_idle++;
                                if (CPU->cpu_dispthread != CPU->cpu_thread)
                                        siron();
                        } else if (ct->t_flag & T_INTR_THREAD) {
                                kpreempt_cnts.kpc_intr++;
                                if (ct->t_pil == CLOCK_LEVEL)
                                        kpreempt_cnts.kpc_clock++;
                        } else {
                                kpreempt_cnts.kpc_blocked++;
                                if (CPU->cpu_dispthread != CPU->cpu_thread)
                                        siron();
                        }
                        aston(CPU->cpu_dispthread);
                        return;
                }
                if (ct->t_state != TS_ONPROC ||
                    ct->t_disp_queue != CPU->cpu_disp) {
                        /* this thread will be calling swtch() shortly */
                        kpreempt_cnts.kpc_notonproc++;
                        if (CPU->cpu_thread != CPU->cpu_dispthread) {
                                /* already in swtch(), force another */
                                kpreempt_cnts.kpc_inswtch++;
                                siron();
                        }
                        return;
                }
                if (getpil() >= DISP_LEVEL) {
                        /*
                         * We can't preempt this thread if it is at
                         * a PIL >= DISP_LEVEL since it may be holding
                         * a spin lock (like sched_lock).
                         */
                        siron();        /* check back later */
                        kpreempt_cnts.kpc_prilevel++;
                        return;
                }
                if (!interrupts_enabled()) {
                        /*
                         * Can't preempt while running with ints disabled
                         */
                        kpreempt_cnts.kpc_prilevel++;
                        return;
                }
                if (asyncspl != KPREEMPT_SYNC)
                        kpreempt_cnts.kpc_apreempt++;
                else
                        kpreempt_cnts.kpc_spreempt++;

                ct->t_preempt++;
                preempt();
                ct->t_preempt--;
        } while (CPU->cpu_kprunrun);
}

/*
 * Print out debugging info.
 */
static void
showregs(uint_t type, struct regs *rp, caddr_t addr)
{
        int s;

        s = spl7();
        type &= ~USER;
        if (PTOU(curproc)->u_comm[0])
                printf("%s: ", PTOU(curproc)->u_comm);
        if (type < TRAP_TYPES)
                printf("#%s %s\n", trap_type_mnemonic[type], trap_type[type]);
        else
                switch (type) {
                case T_SYSCALL:
                        printf("Syscall Trap:\n");
                        break;
                case T_AST:
                        printf("AST\n");
                        break;
                default:
                        printf("Bad Trap = %d\n", type);
                        break;
                }
        if (type == T_PGFLT) {
                printf("Bad %s fault at addr=0x%lx\n",
                    USERMODE(rp->r_cs) ? "user": "kernel", (uintptr_t)addr);
        } else if (addr) {
                printf("addr=0x%lx\n", (uintptr_t)addr);
        }

        printf("pid=%d, pc=0x%lx, sp=0x%lx, eflags=0x%lx\n",
            (ttoproc(curthread) && ttoproc(curthread)->p_pidp) ?
            ttoproc(curthread)->p_pid : 0, rp->r_pc, rp->r_sp, rp->r_ps);

        printf("cr0: %b  cr4: %b\n",
            (uint_t)getcr0(), FMT_CR0, (uint_t)getcr4(), FMT_CR4);

        printf("cr2: %lx  ", getcr2());
        printf("cr3: %lx  ", getcr3());
#if defined(__amd64)
        printf("cr8: %lx\n", getcr8());
#endif
        printf("\n");

        dumpregs(rp);
        splx(s);
}

static void
dumpregs(struct regs *rp)
{
#if defined(__amd64)
        const char fmt[] = "\t%3s: %16lx %3s: %16lx %3s: %16lx\n";

        printf(fmt, "rdi", rp->r_rdi, "rsi", rp->r_rsi, "rdx", rp->r_rdx);
        printf(fmt, "rcx", rp->r_rcx, " r8", rp->r_r8, " r9", rp->r_r9);
        printf(fmt, "rax", rp->r_rax, "rbx", rp->r_rbx, "rbp", rp->r_rbp);
        printf(fmt, "r10", rp->r_r10, "r11", rp->r_r11, "r12", rp->r_r12);
        printf(fmt, "r13", rp->r_r13, "r14", rp->r_r14, "r15", rp->r_r15);

        printf(fmt, "fsb", rdmsr(MSR_AMD_FSBASE), "gsb", rdmsr(MSR_AMD_GSBASE),
            " ds", rp->r_ds);
        printf(fmt, " es", rp->r_es, " fs", rp->r_fs, " gs", rp->r_gs);

        printf(fmt, "trp", rp->r_trapno, "err", rp->r_err, "rip", rp->r_rip);
        printf(fmt, " cs", rp->r_cs, "rfl", rp->r_rfl, "rsp", rp->r_rsp);

        printf("\t%3s: %16lx\n", " ss", rp->r_ss);

#elif defined(__i386)
        const char fmt[] = "\t%3s: %8lx %3s: %8lx %3s: %8lx %3s: %8lx\n";

        printf(fmt, " gs", rp->r_gs, " fs", rp->r_fs,
            " es", rp->r_es, " ds", rp->r_ds);
        printf(fmt, "edi", rp->r_edi, "esi", rp->r_esi,
            "ebp", rp->r_ebp, "esp", rp->r_esp);
        printf(fmt, "ebx", rp->r_ebx, "edx", rp->r_edx,
            "ecx", rp->r_ecx, "eax", rp->r_eax);
        printf(fmt, "trp", rp->r_trapno, "err", rp->r_err,
            "eip", rp->r_eip, " cs", rp->r_cs);
        printf("\t%3s: %8lx %3s: %8lx %3s: %8lx\n",
            "efl", rp->r_efl, "usp", rp->r_uesp, " ss", rp->r_ss);

#endif  /* __i386 */
}

/*
 * Test to see if the instruction is iret on i386 or iretq on amd64.
 *
 * On the hypervisor we can only test for nopop_sys_rtt_syscall. If true
 * then we are in the context of hypervisor's failsafe handler because it
 * tried to iret and failed due to a bad selector. See xen_failsafe_callback.
 */
static int
instr_is_iret(caddr_t pc)
{


#if defined(__amd64)
        static const uint8_t iret_insn[2] = { 0x48, 0xcf };     /* iretq */

#elif defined(__i386)
        static const uint8_t iret_insn[1] = { 0xcf };           /* iret */
#endif  /* __i386 */
        return (bcmp(pc, iret_insn, sizeof (iret_insn)) == 0);

}

#if defined(__i386)

/*
 * Test to see if the instruction is part of __SEGREGS_POP
 *
 * Note carefully the appallingly awful dependency between
 * the instruction sequence used in __SEGREGS_POP and these
 * instructions encoded here.
 */
static int
instr_is_segregs_pop(caddr_t pc)
{
        static const uint8_t movw_0_esp_gs[4] = { 0x8e, 0x6c, 0x24, 0x0 };
        static const uint8_t movw_4_esp_fs[4] = { 0x8e, 0x64, 0x24, 0x4 };
        static const uint8_t movw_8_esp_es[4] = { 0x8e, 0x44, 0x24, 0x8 };
        static const uint8_t movw_c_esp_ds[4] = { 0x8e, 0x5c, 0x24, 0xc };

        if (bcmp(pc, movw_0_esp_gs, sizeof (movw_0_esp_gs)) == 0 ||
            bcmp(pc, movw_4_esp_fs, sizeof (movw_4_esp_fs)) == 0 ||
            bcmp(pc, movw_8_esp_es, sizeof (movw_8_esp_es)) == 0 ||
            bcmp(pc, movw_c_esp_ds, sizeof (movw_c_esp_ds)) == 0)
                return (1);

        return (0);
}

#endif  /* __i386 */

/*
 * Test to see if the instruction is part of _sys_rtt (or the KPTI trampolines
 * which are used by _sys_rtt).
 *
 * Again on the hypervisor if we try to IRET to user land with a bad code
 * or stack selector we will get vectored through xen_failsafe_callback.
 * In which case we assume we got here via _sys_rtt since we only allow
 * IRET to user land to take place in _sys_rtt.
 */
static int
instr_is_sys_rtt(caddr_t pc)
{
        extern void _sys_rtt(), _sys_rtt_end();

#if !defined(__xpv)
        extern void tr_sysc_ret_start(), tr_sysc_ret_end();
        extern void tr_intr_ret_start(), tr_intr_ret_end();

        if ((uintptr_t)pc >= (uintptr_t)tr_sysc_ret_start &&
            (uintptr_t)pc <= (uintptr_t)tr_sysc_ret_end)
                return (1);

        if ((uintptr_t)pc >= (uintptr_t)tr_intr_ret_start &&
            (uintptr_t)pc <= (uintptr_t)tr_intr_ret_end)
                return (1);
#endif

        if ((uintptr_t)pc < (uintptr_t)_sys_rtt ||
            (uintptr_t)pc > (uintptr_t)_sys_rtt_end)
                return (0);

        return (1);
}

/*
 * Handle #gp faults in kernel mode.
 *
 * One legitimate way this can happen is if we attempt to update segment
 * registers to naughty values on the way out of the kernel.
 *
 * This can happen in a couple of ways: someone - either accidentally or
 * on purpose - creates (setcontext(2), lwp_create(2)) or modifies
 * (signal(2)) a ucontext that contains silly segment register values.
 * Or someone - either accidentally or on purpose - modifies the prgregset_t
 * of a subject process via /proc to contain silly segment register values.
 *
 * (The unfortunate part is that we can end up discovering the bad segment
 * register value in the middle of an 'iret' after we've popped most of the
 * stack.  So it becomes quite difficult to associate an accurate ucontext
 * with the lwp, because the act of taking the #gp trap overwrites most of
 * what we were going to send the lwp.)
 *
 * OTOH if it turns out that's -not- the problem, and we're -not- an lwp
 * trying to return to user mode and we get a #gp fault, then we need
 * to die() -- which will happen if we return non-zero from this routine.
 */
static int
kern_gpfault(struct regs *rp)
{
        kthread_t *t = curthread;
        proc_t *p = ttoproc(t);
        klwp_t *lwp = ttolwp(t);
        struct regs tmpregs, *trp = NULL;
        caddr_t pc = (caddr_t)rp->r_pc;
        int v;
        uint32_t auditing = AU_AUDITING();

        /*
         * if we're not an lwp, or in the case of running native the
         * pc range is outside _sys_rtt, then we should immediately
         * be die()ing horribly.
         */
        if (lwp == NULL || !instr_is_sys_rtt(pc))
                return (1);

        /*
         * So at least we're in the right part of the kernel.
         *
         * Disassemble the instruction at the faulting pc.
         * Once we know what it is, we carefully reconstruct the stack
         * based on the order in which the stack is deconstructed in
         * _sys_rtt. Ew.
         */
        if (instr_is_iret(pc)) {
                /*
                 * We took the #gp while trying to perform the IRET.
                 * This means that either %cs or %ss are bad.
                 * All we know for sure is that most of the general
                 * registers have been restored, including the
                 * segment registers, and all we have left on the
                 * topmost part of the lwp's stack are the
                 * registers that the iretq was unable to consume.
                 *
                 * All the rest of the state was crushed by the #gp
                 * which pushed -its- registers atop our old save area
                 * (because we had to decrement the stack pointer, sigh) so
                 * all that we can try and do is to reconstruct the
                 * crushed frame from the #gp trap frame itself.
                 */
                trp = &tmpregs;
                trp->r_ss = lwptoregs(lwp)->r_ss;
                trp->r_sp = lwptoregs(lwp)->r_sp;
                trp->r_ps = lwptoregs(lwp)->r_ps;
                trp->r_cs = lwptoregs(lwp)->r_cs;
                trp->r_pc = lwptoregs(lwp)->r_pc;
                bcopy(rp, trp, offsetof(struct regs, r_pc));

                /*
                 * Validate simple math
                 */
                ASSERT(trp->r_pc == lwptoregs(lwp)->r_pc);
                ASSERT(trp->r_err == rp->r_err);



        }

#if defined(__amd64)
        if (trp == NULL && PCB_NEED_UPDATE_SEGS(&lwp->lwp_pcb)) {

                /*
                 * This is the common case -- we're trying to load
                 * a bad segment register value in the only section
                 * of kernel code that ever loads segment registers.
                 *
                 * We don't need to do anything at this point because
                 * the pcb contains all the pending segment register
                 * state, and the regs are still intact because we
                 * didn't adjust the stack pointer yet.  Given the fidelity
                 * of all this, we could conceivably send a signal
                 * to the lwp, rather than core-ing.
                 */
                trp = lwptoregs(lwp);
                ASSERT((caddr_t)trp == (caddr_t)rp->r_sp);
        }

#elif defined(__i386)

        if (trp == NULL && instr_is_segregs_pop(pc))
                trp = lwptoregs(lwp);

#endif  /* __i386 */

        if (trp == NULL)
                return (1);

        /*
         * If we get to here, we're reasonably confident that we've
         * correctly decoded what happened on the way out of the kernel.
         * Rewrite the lwp's registers so that we can create a core dump
         * the (at least vaguely) represents the mcontext we were
         * being asked to restore when things went so terribly wrong.
         */

        /*
         * Make sure that we have a meaningful %trapno and %err.
         */
        trp->r_trapno = rp->r_trapno;
        trp->r_err = rp->r_err;

        if ((caddr_t)trp != (caddr_t)lwptoregs(lwp))
                bcopy(trp, lwptoregs(lwp), sizeof (*trp));


        mutex_enter(&p->p_lock);
        lwp->lwp_cursig = SIGSEGV;
        mutex_exit(&p->p_lock);

        /*
         * Terminate all LWPs but don't discard them.  If another lwp beat
         * us to the punch by calling exit(), evaporate now.
         */
        proc_is_exiting(p);
        if (exitlwps(1) != 0) {
                mutex_enter(&p->p_lock);
                lwp_exit();
        }

        if (auditing)           /* audit core dump */
                audit_core_start(SIGSEGV);
        v = core(SIGSEGV, B_FALSE);
        if (auditing)           /* audit core dump */
                audit_core_finish(v ? CLD_KILLED : CLD_DUMPED);
        exit(v ? CLD_KILLED : CLD_DUMPED, SIGSEGV);
        return (0);
}

/*
 * dump_tss() - Display the TSS structure
 */

#if defined(__amd64)

static void
dump_tss(void)
{
        const char tss_fmt[] = "tss.%s:\t0x%p\n";  /* Format string */
        tss_t *tss = CPU->cpu_tss;

        printf(tss_fmt, "tss_rsp0", (void *)tss->tss_rsp0);
        printf(tss_fmt, "tss_rsp1", (void *)tss->tss_rsp1);
        printf(tss_fmt, "tss_rsp2", (void *)tss->tss_rsp2);

        printf(tss_fmt, "tss_ist1", (void *)tss->tss_ist1);
        printf(tss_fmt, "tss_ist2", (void *)tss->tss_ist2);
        printf(tss_fmt, "tss_ist3", (void *)tss->tss_ist3);
        printf(tss_fmt, "tss_ist4", (void *)tss->tss_ist4);
        printf(tss_fmt, "tss_ist5", (void *)tss->tss_ist5);
        printf(tss_fmt, "tss_ist6", (void *)tss->tss_ist6);
        printf(tss_fmt, "tss_ist7", (void *)tss->tss_ist7);
}

#elif defined(__i386)

static void
dump_tss(void)
{
        const char tss_fmt[] = "tss.%s:\t0x%p\n";  /* Format string */
        tss_t *tss = CPU->cpu_tss;

        printf(tss_fmt, "tss_link", (void *)(uintptr_t)tss->tss_link);
        printf(tss_fmt, "tss_esp0", (void *)(uintptr_t)tss->tss_esp0);
        printf(tss_fmt, "tss_ss0", (void *)(uintptr_t)tss->tss_ss0);
        printf(tss_fmt, "tss_esp1", (void *)(uintptr_t)tss->tss_esp1);
        printf(tss_fmt, "tss_ss1", (void *)(uintptr_t)tss->tss_ss1);
        printf(tss_fmt, "tss_esp2", (void *)(uintptr_t)tss->tss_esp2);
        printf(tss_fmt, "tss_ss2", (void *)(uintptr_t)tss->tss_ss2);
        printf(tss_fmt, "tss_cr3", (void *)(uintptr_t)tss->tss_cr3);
        printf(tss_fmt, "tss_eip", (void *)(uintptr_t)tss->tss_eip);
        printf(tss_fmt, "tss_eflags", (void *)(uintptr_t)tss->tss_eflags);
        printf(tss_fmt, "tss_eax", (void *)(uintptr_t)tss->tss_eax);
        printf(tss_fmt, "tss_ebx", (void *)(uintptr_t)tss->tss_ebx);
        printf(tss_fmt, "tss_ecx", (void *)(uintptr_t)tss->tss_ecx);
        printf(tss_fmt, "tss_edx", (void *)(uintptr_t)tss->tss_edx);
        printf(tss_fmt, "tss_esp", (void *)(uintptr_t)tss->tss_esp);
}

#endif  /* __amd64 */

#if defined(TRAPTRACE)

int ttrace_nrec = 10;           /* number of records to dump out */
int ttrace_dump_nregs = 0;      /* dump out this many records with regs too */

/*
 * Dump out the last ttrace_nrec traptrace records on each CPU
 */
static void
dump_ttrace(void)
{
        trap_trace_ctl_t *ttc;
        trap_trace_rec_t *rec;
        uintptr_t current;
        int i, j, k;
        int n = NCPU;
#if defined(__amd64)
        const char banner[] =
            "CPU          ADDRESS    TIMESTAMP TYPE  VC HANDLER          PC\n";
        /* Define format for the CPU, ADDRESS, and TIMESTAMP fields */
        const char fmt1[] = "%3d %016lx %12llx";
        char data1[34]; /* length of string formatted by fmt1 + 1 */
#elif defined(__i386)
        const char banner[] =
            "CPU  ADDRESS     TIMESTAMP TYPE  VC HANDLER          PC\n";
        /* Define format for the CPU, ADDRESS, and TIMESTAMP fields */
        const char fmt1[] = "%3d %08lx %12llx";
        char data1[26]; /* length of string formatted by fmt1 + 1 */
#endif
        /* Define format for the TYPE and VC fields */
        const char fmt2[] = "%4s %3x";
        char data2[9];  /* length of string formatted by fmt2 + 1 */
        /*
         * Define format for the HANDLER field. Width is arbitrary, but should
         * be enough for common handler's names, and leave enough space for
         * the PC field, especially when we are in kmdb.
         */
        const char fmt3h[] = "#%-15s";
        const char fmt3p[] = "%-16p";
        const char fmt3s[] = "%-16s";
        char data3[17]; /* length of string formatted by fmt3* + 1 */

        if (ttrace_nrec == 0)
                return;

        printf("\n");
        printf(banner);

        for (i = 0; i < n; i++) {
                ttc = &trap_trace_ctl[i];
                if (ttc->ttc_first == (uintptr_t)NULL)
                        continue;

                current = ttc->ttc_next - sizeof (trap_trace_rec_t);
                for (j = 0; j < ttrace_nrec; j++) {
                        struct sysent   *sys;
                        struct autovec  *vec;
                        extern struct av_head autovect[];
                        int type;
                        ulong_t off;
                        char *sym, *stype;

                        if (current < ttc->ttc_first)
                                current =
                                    ttc->ttc_limit - sizeof (trap_trace_rec_t);

                        if (current == (uintptr_t)NULL)
                                continue;

                        rec = (trap_trace_rec_t *)current;

                        if (rec->ttr_stamp == 0)
                                break;

                        (void) snprintf(data1, sizeof (data1), fmt1, i,
                            (uintptr_t)rec, rec->ttr_stamp);

                        switch (rec->ttr_marker) {
                        case TT_SYSCALL:
                        case TT_SYSENTER:
                        case TT_SYSC:
                        case TT_SYSC64:
                                sys = &sysent32[rec->ttr_sysnum];
                                switch (rec->ttr_marker) {
                                case TT_SYSC64:
                                        sys = &sysent[rec->ttr_sysnum];
                                        /* FALLTHROUGH */
                                case TT_SYSC:
                                        stype = "sysc"; /* syscall */
                                        break;
                                case TT_SYSCALL:
                                        stype = "lcal"; /* lcall */
                                        break;
                                case TT_SYSENTER:
                                        stype = "syse"; /* sysenter */
                                        break;
                                default:
                                        break;
                                }
                                (void) snprintf(data2, sizeof (data2), fmt2,
                                    stype, rec->ttr_sysnum);
                                if (sys != NULL) {
                                        sym = kobj_getsymname(
                                            (uintptr_t)sys->sy_callc,
                                            &off);
                                        if (sym != NULL) {
                                                (void) snprintf(data3,
                                                    sizeof (data3), fmt3s, sym);
                                        } else {
                                                (void) snprintf(data3,
                                                    sizeof (data3), fmt3p,
                                                    sys->sy_callc);
                                        }
                                } else {
                                        (void) snprintf(data3, sizeof (data3),
                                            fmt3s, "unknown");
                                }
                                break;

                        case TT_INTERRUPT:
                                (void) snprintf(data2, sizeof (data2), fmt2,
                                    "intr", rec->ttr_vector);
                                if (get_intr_handler != NULL)
                                        vec = (struct autovec *)
                                            (*get_intr_handler)
                                            (rec->ttr_cpuid, rec->ttr_vector);
                                else
                                        vec =
                                            autovect[rec->ttr_vector].avh_link;

                                if (vec != NULL) {
                                        sym = kobj_getsymname(
                                            (uintptr_t)vec->av_vector, &off);
                                        if (sym != NULL) {
                                                (void) snprintf(data3,
                                                    sizeof (data3), fmt3s, sym);
                                        } else {
                                                (void) snprintf(data3,
                                                    sizeof (data3), fmt3p,
                                                    vec->av_vector);
                                        }
                                } else {
                                        (void) snprintf(data3, sizeof (data3),
                                            fmt3s, "unknown");
                                }
                                break;

                        case TT_TRAP:
                        case TT_EVENT:
                                type = rec->ttr_regs.r_trapno;
                                (void) snprintf(data2, sizeof (data2), fmt2,
                                    "trap", type);
                                if (type < TRAP_TYPES) {
                                        (void) snprintf(data3, sizeof (data3),
                                            fmt3h, trap_type_mnemonic[type]);
                                } else {
                                        switch (type) {
                                        case T_AST:
                                                (void) snprintf(data3,
                                                    sizeof (data3), fmt3s,
                                                    "ast");
                                                break;
                                        default:
                                                (void) snprintf(data3,
                                                    sizeof (data3), fmt3s, "");
                                                break;
                                        }
                                }
                                break;

                        default:
                                break;
                        }

                        sym = kobj_getsymname(rec->ttr_regs.r_pc, &off);
                        if (sym != NULL) {
                                printf("%s %s %s %s+%lx\n", data1, data2, data3,
                                    sym, off);
                        } else {
                                printf("%s %s %s %lx\n", data1, data2, data3,
                                    rec->ttr_regs.r_pc);
                        }

                        if (ttrace_dump_nregs-- > 0) {
                                int s;

                                if (rec->ttr_marker == TT_INTERRUPT)
                                        printf(
                                            "\t\tipl %x spl %x pri %x\n",
                                            rec->ttr_ipl,
                                            rec->ttr_spl,
                                            rec->ttr_pri);

                                dumpregs(&rec->ttr_regs);

                                printf("\t%3s: %p\n\n", " ct",
                                    (void *)rec->ttr_curthread);

                                /*
                                 * print out the pc stack that we recorded
                                 * at trap time (if any)
                                 */
                                for (s = 0; s < rec->ttr_sdepth; s++) {
                                        uintptr_t fullpc;

                                        if (s >= TTR_STACK_DEPTH) {
                                                printf("ttr_sdepth corrupt\n");
                                                break;
                                        }

                                        fullpc = (uintptr_t)rec->ttr_stack[s];

                                        sym = kobj_getsymname(fullpc, &off);
                                        if (sym != NULL)
                                                printf("-> %s+0x%lx()\n",
                                                    sym, off);
                                        else
                                                printf("-> 0x%lx()\n", fullpc);
                                }
                                printf("\n");
                        }
                        current -= sizeof (trap_trace_rec_t);
                }
        }
}

#endif  /* TRAPTRACE */

void
panic_showtrap(struct panic_trap_info *tip)
{
        showregs(tip->trap_type, tip->trap_regs, tip->trap_addr);

#if defined(TRAPTRACE)
        dump_ttrace();
#endif

        if (tip->trap_type == T_DBLFLT)
                dump_tss();
}

void
panic_savetrap(panic_data_t *pdp, struct panic_trap_info *tip)
{
        panic_saveregs(pdp, tip->trap_regs);
}