/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (C) 1994, David Greenman
 * Copyright (c) 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the University of Utah, and William Jolitz.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * AMD64 Trap and System call handling
 */

#include "opt_atpic.h"
#include "opt_clock.h"
#include "opt_cpu.h"
#include "opt_hwpmc_hooks.h"
#include "opt_isa.h"
#include "opt_kdb.h"

#include <sys/param.h>
#include <sys/asan.h>
#include <sys/bus.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/ptrace.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/msan.h>
#include <sys/mutex.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/smp.h>
#include <sys/syscall.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/uio.h>
#include <sys/vmmeter.h>
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
PMC_SOFT_DEFINE( , , page_fault, all);
PMC_SOFT_DEFINE( , , page_fault, read);
PMC_SOFT_DEFINE( , , page_fault, write);
#endif

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_kern.h>
#include <vm/vm_map.h>
#include <vm/vm_page.h>
#include <vm/vm_extern.h>

#include <machine/cpu.h>
#include <machine/intr_machdep.h>
#include <x86/apicreg.h>
#include <x86/apicvar.h>
#include <x86/mca.h>
#include <machine/md_var.h>
#include <machine/pcb.h>
#include <machine/smp.h>
#include <machine/stack.h>
#include <machine/trap.h>
#include <machine/tss.h>
#include <x86/isa/icu.h>

#ifdef KDTRACE_HOOKS
#include <sys/dtrace_bsd.h>
#endif

extern inthand_t IDTVEC(bpt), IDTVEC(bpt_pti), IDTVEC(dbg),
    IDTVEC(fast_syscall), IDTVEC(fast_syscall_pti), IDTVEC(fast_syscall32),
    IDTVEC(int0x80_syscall_pti), IDTVEC(int0x80_syscall);

void __noinline trap(struct trapframe *frame);
void trap_check(struct trapframe *frame);
void dblfault_handler(struct trapframe *frame);

static int trap_pfault(struct trapframe *, bool, int *, int *);
static void trap_diag(struct trapframe *, vm_offset_t, const char *);
static void trap_fatal(struct trapframe *, vm_offset_t);
#ifdef KDTRACE_HOOKS
static bool trap_user_dtrace(struct trapframe *,
    int (**hook)(struct trapframe *));
#endif

static const char UNKNOWN[] = "unknown";
static const char *const trap_msg[] = {
        [0] =                   UNKNOWN,                        /* unused */
        [T_PRIVINFLT] =         "privileged instruction fault",
        [2] =                   UNKNOWN,                        /* unused */
        [T_BPTFLT] =            "breakpoint instruction fault",
        [4] =                   UNKNOWN,                        /* unused */
        [5] =                   UNKNOWN,                        /* unused */
        [T_ARITHTRAP] =         "arithmetic trap",
        [7] =                   UNKNOWN,                        /* unused */
        [8] =                   UNKNOWN,                        /* unused */
        [T_PROTFLT] =           "general protection fault",
        [T_TRCTRAP] =           "debug exception",
        [11] =                  UNKNOWN,                        /* unused */
        [T_PAGEFLT] =           "page fault",
        [13] =                  UNKNOWN,                        /* unused */
        [T_ALIGNFLT] =          "alignment fault",
        [15] =                  UNKNOWN,                        /* unused */
        [16] =                  UNKNOWN,                        /* unused */
        [17] =                  UNKNOWN,                        /* unused */
        [T_DIVIDE] =            "integer divide fault",
        [T_NMI] =               "non-maskable interrupt trap",
        [T_OFLOW] =             "overflow trap",
        [T_BOUND] =             "FPU bounds check fault",
        [T_DNA] =               "FPU device not available",
        [T_DOUBLEFLT] =         "double fault",
        [T_FPOPFLT] =           "FPU operand fetch fault",
        [T_TSSFLT] =            "invalid TSS fault",
        [T_SEGNPFLT] =          "segment not present fault",
        [T_STKFLT] =            "stack fault",
        [T_MCHK] =              "machine check trap",
        [T_XMMFLT] =            "SIMD floating-point exception",
        [T_RESERVED] =          "reserved (unknown) fault",
        [31] =                  UNKNOWN,                        /* reserved */
        [T_DTRACE_RET] =        "DTrace pid return trap",
};

static const char *
traptype_to_msg(u_int type)
{
        return (type < nitems(trap_msg) ? trap_msg[type] :
            "unknown/reserved trap");
}

static int uprintf_signal;
SYSCTL_INT(_machdep, OID_AUTO, uprintf_signal, CTLFLAG_RWTUN,
    &uprintf_signal, 0,
    "Print debugging information on trap signal to ctty");

u_long cnt_efirt_faults;
int print_efirt_faults = 1;

/*
 * Control L1D flush on return from NMI.
 *
 * Tunable  can be set to the following values:
 * 0 - only enable flush on return from NMI if required by vmm.ko (default)
 * >1 - always flush on return from NMI.
 *
 * Post-boot, the sysctl indicates if flushing is currently enabled.
 */
int nmi_flush_l1d_sw;
SYSCTL_INT(_machdep, OID_AUTO, nmi_flush_l1d_sw, CTLFLAG_RWTUN,
    &nmi_flush_l1d_sw, 0,
    "Flush L1 Data Cache on NMI exit, software bhyve L1TF mitigation assist");

static void
trap_uprintf_signal(struct thread *td, struct trapframe *frame, register_t addr,
    int signo, int ucode)
{
        struct proc *p;
        struct pcb *pcb;
        register_t fsbase, gsbase, r;

        if (!uprintf_signal)
                return;
        p = td->td_proc;
        pcb = td->td_pcb;
        if ((cpu_stdext_feature & CPUID_STDEXT_FSGSBASE) != 0) {
                r = intr_disable();
                if ((pcb->pcb_flags & PCB_FULL_IRET) == 0) {
                        fsbase = rdfsbase();
                        gsbase = rdmsr(MSR_KGSBASE);
                } else {
                        fsbase = pcb->pcb_fsbase;
                        gsbase = pcb->pcb_gsbase;
                }
                intr_restore(r);
        } else {
                fsbase = pcb->pcb_fsbase;
                gsbase = pcb->pcb_gsbase;
        }
        uprintf("pid %d comm %s: signal %d err %#lx code %d type %d "
            "addr %#lx rsp %#lx rip %#lx rax %#lx fsb %#lx gsb %#lx "
            "<%02x %02x %02x %02x %02x %02x %02x %02x>\n",
            p->p_pid, p->p_comm, signo, frame->tf_err, ucode, frame->tf_trapno,
            addr, frame->tf_rsp, frame->tf_rip, frame->tf_rax, fsbase, gsbase,
            fubyte((void *)(frame->tf_rip + 0)),
            fubyte((void *)(frame->tf_rip + 1)),
            fubyte((void *)(frame->tf_rip + 2)),
            fubyte((void *)(frame->tf_rip + 3)),
            fubyte((void *)(frame->tf_rip + 4)),
            fubyte((void *)(frame->tf_rip + 5)),
            fubyte((void *)(frame->tf_rip + 6)),
            fubyte((void *)(frame->tf_rip + 7)));
}

static bool
trap_check_pcb_onfault(struct thread *td, struct trapframe *frame)
{
        bool res = false;

        if (curpcb->pcb_onfault == NULL)
                return (res);

        if (__predict_false((td->td_pflags & TDP_EFIRT) != 0)) {
                /*
                 * Most likely, EFI RT faulted.  This check prevents
                 * kdb from handling breakpoints set on the BIOS text,
                 * if such option is ever needed.
                 */
                u_long cnt = atomic_fetchadd_long(&cnt_efirt_faults, 1);

                if ((print_efirt_faults == 1 && cnt == 0) ||
                    print_efirt_faults == 2) {
                        printf("EFI RT fault %s\n",
                            traptype_to_msg(frame->tf_trapno));
                        trap_diag(frame, 0, "EFI runtime");
                }
                res = true;
        } else if (frame->tf_trapno == T_PAGEFLT) {
                res = true;
        }
        if (res)
                frame->tf_rip = (register_t)curpcb->pcb_onfault;
        return (res);
}

static void
trap_clear_step(struct thread *td, struct trapframe *frame)
{
        PROC_LOCK(td->td_proc);
        if ((td->td_dbgflags & TDB_STEP) != 0) {
                td->td_frame->tf_rflags &= ~PSL_T;
                td->td_dbgflags &= ~TDB_STEP;
        }
        PROC_UNLOCK(td->td_proc);
}

/*
 * Warn with a message on the user's tty if application code has
 * disabled interrupts and then trapped.
 */
static void
trap_check_intr_user(struct thread *td, struct trapframe *frame)
{
        MPASS(TRAPF_USERMODE(frame));

        if (__predict_true((frame->tf_rflags & PSL_I) != 0))
                return;

        uprintf("pid %ld (%s): trap %d (%s) with interrupts disabled\n",
            (long)td->td_proc->p_pid, td->td_name, frame->tf_trapno,
            trap_msg[frame->tf_trapno]);
}

/*
 * Some exceptions can occur on kernel attempt to reload a corrupted
 * user context, which is done with interrupts enabled.  Interrupts
 * such as NMIs and debugging faults can be also taken in the kernel
 * while interrupts are disabled.  Other traps shouldn't occur with
 * interrupts disabled unless the kernel has a bug.  Re-enable
 * interrupts in case this occurs, unless the interrupted thread holds
 * a spin lock.
 */
static void
trap_check_intr_kernel(struct thread *td, struct trapframe *frame)
{
        MPASS(!TRAPF_USERMODE(frame));

        if (__predict_true((frame->tf_rflags & PSL_I) != 0))
                return;

        switch (frame->tf_trapno) {
        case T_NMI:
        case T_BPTFLT:
        case T_TRCTRAP:
        case T_PROTFLT:
        case T_SEGNPFLT:
        case T_STKFLT:
                break;
        default:
                printf("kernel trap %d with interrupts disabled\n",
                    frame->tf_trapno);

                /*
                 * We shouldn't enable interrupts while holding a
                 * spin lock.
                 */
                if (td->td_md.md_spinlock_count == 0)
                        enable_intr();
                break;
        }
}

/*
 * Table of handlers for various segment load faults.
 */
struct sfhandler {
        uintptr_t       faddr;
        uintptr_t       fhandler;
};

static const struct sfhandler sfhandlers[] = {
        {
                .faddr = (uintptr_t)ld_ds,
                .fhandler = (uintptr_t)ds_load_fault,
        },
        {
                .faddr = (uintptr_t)ld_es,
                .fhandler = (uintptr_t)es_load_fault,
        },
        {
                .faddr = (uintptr_t)ld_fs,
                .fhandler = (uintptr_t)fs_load_fault,
        },
        {
                .faddr = (uintptr_t)ld_gs,
                .fhandler = (uintptr_t)gs_load_fault,
        },
        {
                .faddr = (uintptr_t)ld_gsbase,
                .fhandler = (uintptr_t)gsbase_load_fault
        },
        {
                .faddr = (uintptr_t)ld_fsbase,
                .fhandler = (uintptr_t)fsbase_load_fault,
        },
};

/*
 * Exception, fault, and trap interface to the FreeBSD kernel.
 * This common code is called from assembly language IDT gate entry
 * routines that prepare a suitable stack frame, and restore this
 * frame after the exception has been processed.
 */

void
trap(struct trapframe *frame)
{
        ksiginfo_t ksi;
        struct thread *td;
        struct proc *p;
        register_t addr, dr6;
        size_t i;
        int pf, signo, ucode;
        u_int type;

        td = curthread;
        p = td->td_proc;
        dr6 = 0;

        kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
        kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);

        VM_CNT_INC(v_trap);
        type = frame->tf_trapno;

#ifdef KDB
        if (kdb_active) {
                kdb_reenter();
                return;
        }
#endif
        if (type == T_NMI) {
                nmi_handle_intr(frame);
                return;
        }

        if (type == T_RESERVED) {
                trap_fatal(frame, 0);
                return;
        }

        if (TRAPF_USERMODE(frame)) {
                /* user trap */
                trap_check_intr_user(td, frame);

                td->td_pticks = 0;
                td->td_frame = frame;
                addr = frame->tf_rip;
                if (td->td_cowgen != atomic_load_int(&p->p_cowgen))
                        thread_cow_update(td);

                switch (type) {
                case T_PRIVINFLT:       /* privileged instruction fault */
                        signo = SIGILL;
                        ucode = ILL_PRVOPC;
                        break;

                case T_BPTFLT:          /* bpt instruction fault */
#ifdef KDTRACE_HOOKS
                        if (trap_user_dtrace(frame, &dtrace_pid_probe_ptr))
                                return;
#else
                        enable_intr();
#endif
                        signo = SIGTRAP;
                        ucode = TRAP_BRKPT;
                        break;

                case T_TRCTRAP:         /* debug exception */
                        enable_intr();
                        signo = SIGTRAP;
                        ucode = TRAP_TRACE;
                        dr6 = rdr6();
                        if ((dr6 & DBREG_DR6_BS) != 0)
                                trap_clear_step(td, frame);
                        break;

                case T_ARITHTRAP:       /* arithmetic trap */
                        ucode = fputrap_x87();
                        if (ucode == -1)
                                return;
                        signo = SIGFPE;
                        break;

                case T_PROTFLT:         /* general protection fault */
                        signo = SIGBUS;
                        ucode = BUS_OBJERR;
                        break;
                case T_STKFLT:          /* stack fault */
                case T_SEGNPFLT:        /* segment not present fault */
                        signo = SIGBUS;
                        ucode = BUS_ADRERR;
                        break;
                case T_TSSFLT:          /* invalid TSS fault */
                        signo = SIGBUS;
                        ucode = BUS_OBJERR;
                        break;
                case T_ALIGNFLT:
                        signo = SIGBUS;
                        ucode = BUS_ADRALN;
                        break;
                case T_DOUBLEFLT:       /* double fault */
                default:
                        signo = SIGBUS;
                        ucode = BUS_OBJERR;
                        break;

                case T_PAGEFLT:         /* page fault */
                        /*
                         * Can emulator handle this trap?
                         */
                        if (*p->p_sysent->sv_trap != NULL &&
                            (*p->p_sysent->sv_trap)(td) == 0)
                                return;

                        pf = trap_pfault(frame, true, &signo, &ucode);
                        if (pf == -1)
                                return;
                        if (pf == 0)
                                goto userret;
                        addr = frame->tf_addr;
                        break;

                case T_DIVIDE:          /* integer divide fault */
                        ucode = FPE_INTDIV;
                        signo = SIGFPE;
                        break;

                case T_OFLOW:           /* integer overflow fault */
                        ucode = FPE_INTOVF;
                        signo = SIGFPE;
                        break;

                case T_BOUND:           /* bounds check fault */
                        ucode = FPE_FLTSUB;
                        signo = SIGFPE;
                        break;

                case T_DNA:
                        /* transparent fault (due to context switch "late") */
                        KASSERT(PCB_USER_FPU(td->td_pcb),
                            ("kernel FPU ctx has leaked"));
                        fpudna();
                        return;

                case T_FPOPFLT:         /* FPU operand fetch fault */
                        ucode = ILL_COPROC;
                        signo = SIGILL;
                        break;

                case T_XMMFLT:          /* SIMD floating-point exception */
                        ucode = fputrap_sse();
                        if (ucode == -1)
                                return;
                        signo = SIGFPE;
                        break;
#ifdef KDTRACE_HOOKS
                case T_DTRACE_RET:
                        (void)trap_user_dtrace(frame, &dtrace_return_probe_ptr);
                        return;
#endif
                }
        } else {
                /* kernel trap */
                trap_check_intr_kernel(td, frame);

                KASSERT(cold || td->td_ucred != NULL,
                    ("kernel trap doesn't have ucred"));

                if (type != T_PAGEFLT && trap_check_pcb_onfault(td, frame))
                        return;

                switch (type) {
                case T_PAGEFLT:                 /* page fault */
                        (void)trap_pfault(frame, false, NULL, NULL);
                        return;

                case T_DNA:
                        if (PCB_USER_FPU(td->td_pcb))
                                panic("Unregistered use of FPU in kernel");
                        fpudna();
                        return;

                case T_ARITHTRAP:       /* arithmetic trap */
                case T_XMMFLT:          /* SIMD floating-point exception */
                case T_FPOPFLT:         /* FPU operand fetch fault */
                        /*
                         * For now, supporting kernel handler
                         * registration for FPU traps is overkill.
                         */
                        trap_fatal(frame, 0);
                        return;

                case T_STKFLT:          /* stack fault */
                case T_PROTFLT:         /* general protection fault */
                case T_SEGNPFLT:        /* segment not present fault */
                        if (td->td_intr_nesting_level != 0)
                                break;

                        /*
                         * Invalid segment selectors and out of bounds
                         * %rip's and %rsp's can be set up in user mode.
                         * This causes a fault in kernel mode when the
                         * kernel tries to return to user mode.  We want
                         * to get this fault so that we can fix the
                         * problem here and not have to check all the
                         * selectors and pointers when the user changes
                         * them.
                         *
                         * In case of PTI, the IRETQ faulted while the
                         * kernel used the pti stack, and exception
                         * frame records %rsp value pointing to that
                         * stack.  If we return normally to
                         * doreti_iret_fault, the trapframe is
                         * reconstructed on pti stack, and calltrap()
                         * called on it as well.  Due to the very
                         * limited pti stack size, kernel does not
                         * survive for too long.  Switch to the normal
                         * thread stack for the trap handling.
                         *
                         * Magic '5' is the number of qwords occupied by
                         * the hardware trap frame.
                         */
                        if (frame->tf_rip == (long)doreti_iret) {
                                KASSERT((read_rflags() & PSL_I) == 0,
                                    ("interrupts enabled"));
                                frame->tf_rip = (long)doreti_iret_fault;
                                if ((PCPU_GET(curpmap)->pm_ucr3 !=
                                    PMAP_NO_CR3) &&
                                    (frame->tf_rsp == (uintptr_t)PCPU_GET(
                                    pti_rsp0) - 5 * sizeof(register_t))) {
                                        frame->tf_rsp = PCPU_GET(rsp0) - 5 *
                                            sizeof(register_t);
                                }
                                return;
                        }

                        for (i = 0; i < nitems(sfhandlers); i++) {
                                if (frame->tf_rip == sfhandlers[i].faddr) {
                                        KASSERT((read_rflags() & PSL_I) == 0,
                                            ("interrupts enabled"));
                                        frame->tf_rip = sfhandlers[i].fhandler;
                                        return;
                                }
                        }

                        if (curpcb->pcb_onfault != NULL) {
                                frame->tf_rip = (long)curpcb->pcb_onfault;
                                return;
                        }
                        break;

                case T_TSSFLT:
                        /*
                         * PSL_NT can be set in user mode and isn't cleared
                         * automatically when the kernel is entered.  This
                         * causes a TSS fault when the kernel attempts to
                         * `iret' because the TSS link is uninitialized.  We
                         * want to get this fault so that we can fix the
                         * problem here and not every time the kernel is
                         * entered.
                         */
                        if (frame->tf_rflags & PSL_NT) {
                                frame->tf_rflags &= ~PSL_NT;
                                return;
                        }
                        break;

                case T_TRCTRAP:  /* debug exception */
                        /* Clear any pending debug events. */
                        dr6 = rdr6();
                        load_dr6(0);

                        /*
                         * Ignore debug register exceptions due to
                         * accesses in the user's address space, which
                         * can happen under several conditions such as
                         * if a user sets a watchpoint on a buffer and
                         * then passes that buffer to a system call.
                         * We still want to get TRCTRAPS for addresses
                         * in kernel space because that is useful when
                         * debugging the kernel.
                         */
                        if (user_dbreg_trap(dr6))
                                return;

                        /*
                         * Malicious user code can configure a debug
                         * register watchpoint to trap on data access
                         * to the top of stack and then execute 'pop
                         * %ss; int 3'.  Due to exception deferral for
                         * 'pop %ss', the CPU will not interrupt 'int
                         * 3' to raise the DB# exception for the debug
                         * register but will postpone the DB# until
                         * execution of the first instruction of the
                         * BP# handler (in kernel mode).  Normally the
                         * previous check would ignore DB# exceptions
                         * for watchpoints on user addresses raised in
                         * kernel mode.  However, some CPU errata
                         * include cases where DB# exceptions do not
                         * properly set bits in %dr6, e.g. Haswell
                         * HSD23 and Skylake-X SKZ24.
                         *
                         * A deferred DB# can also be raised on the
                         * first instructions of system call entry
                         * points or single-step traps via similar use
                         * of 'pop %ss' or 'mov xxx, %ss'.
                         */
                        if (pti) {
                                if (frame->tf_rip ==
                                    (uintptr_t)IDTVEC(fast_syscall_pti) ||
#ifdef COMPAT_FREEBSD32
                                    frame->tf_rip ==
                                    (uintptr_t)IDTVEC(int0x80_syscall_pti) ||
#endif
                                    frame->tf_rip == (uintptr_t)IDTVEC(bpt_pti))
                                        return;
                        } else {
                                if (frame->tf_rip ==
                                    (uintptr_t)IDTVEC(fast_syscall) ||
#ifdef COMPAT_FREEBSD32
                                    frame->tf_rip ==
                                    (uintptr_t)IDTVEC(int0x80_syscall) ||
#endif
                                    frame->tf_rip == (uintptr_t)IDTVEC(bpt))
                                        return;
                        }
                        if (frame->tf_rip == (uintptr_t)IDTVEC(dbg) ||
                            /* Needed for AMD. */
                            frame->tf_rip == (uintptr_t)IDTVEC(fast_syscall32))
                                return;
                        /*
                         * FALLTHROUGH (TRCTRAP kernel mode, kernel address)
                         */
                case T_BPTFLT:
                        /*
                         * If KDB is enabled, let it handle the debugger trap.
                         * Otherwise, debugger traps "can't happen".
                         */
#ifdef KDB
                        if (kdb_trap(type, dr6, frame))
                                return;
#endif
                        break;
                }

                trap_fatal(frame, 0);
                return;
        }

        ksiginfo_init_trap(&ksi);
        ksi.ksi_signo = signo;
        ksi.ksi_code = ucode;
        ksi.ksi_trapno = type;
        ksi.ksi_addr = (void *)addr;
        trap_uprintf_signal(td, frame, addr, signo, ucode);
        KASSERT((read_rflags() & PSL_I) != 0, ("interrupts disabled"));
        trapsignal(td, &ksi);

userret:
        userret(td, frame);
        KASSERT(PCB_USER_FPU(td->td_pcb),
            ("Return from trap with kernel FPU ctx leaked"));
}

/*
 * Ensure that we ignore any DTrace-induced faults. This function cannot
 * be instrumented, so it cannot generate such faults itself.
 */
void
trap_check(struct trapframe *frame)
{

#ifdef KDTRACE_HOOKS
        if (dtrace_trap_func != NULL &&
            (*dtrace_trap_func)(frame, frame->tf_trapno) != 0)
                return;
#endif
        trap(frame);
}

static bool
trap_is_smap(struct trapframe *frame)
{

        /*
         * A page fault on a userspace address is classified as
         * SMAP-induced if:
         * - SMAP is supported;
         * - kernel mode accessed present data page;
         * - rflags.AC was cleared.
         * Kernel must never access user space with rflags.AC cleared
         * if SMAP is enabled.
         */
        return ((cpu_stdext_feature & CPUID_STDEXT_SMAP) != 0 &&
            (frame->tf_err & (PGEX_P | PGEX_U | PGEX_I | PGEX_RSV)) ==
            PGEX_P && (frame->tf_rflags & PSL_AC) == 0);
}

static bool
trap_is_pti(struct trapframe *frame)
{

        return (PCPU_GET(curpmap)->pm_ucr3 != PMAP_NO_CR3 &&
            pg_nx != 0 && (frame->tf_err & (PGEX_P | PGEX_W |
            PGEX_U | PGEX_I)) == (PGEX_P | PGEX_U | PGEX_I) &&
            (curpcb->pcb_saved_ucr3 & ~CR3_PCID_MASK) ==
            (PCPU_GET(curpmap)->pm_cr3 & ~CR3_PCID_MASK));
}

/*
 * Handle all details of a page fault.
 * Returns:
 * -1 if this fault was fatal, typically from kernel mode
 *    (cannot happen, but we need to return something).
 * 0  if this fault was handled by updating either the user or kernel
 *    page table, execution can continue.
 * 1  if this fault was from usermode and it was not handled, a synchronous
 *    signal should be delivered to the thread.  *signo returns the signal
 *    number, *ucode gives si_code.
 */
static int
trap_pfault(struct trapframe *frame, bool usermode, int *signo, int *ucode)
{
        struct thread *td;
        struct proc *p;
        vm_map_t map;
        vm_offset_t eva;
        int rv;
        vm_prot_t ftype;

        MPASS(!usermode || (signo != NULL && ucode != NULL));

        td = curthread;
        p = td->td_proc;
        eva = frame->tf_addr;

        if (__predict_false((td->td_pflags & TDP_NOFAULTING) != 0)) {
                /*
                 * Due to both processor errata and lazy TLB invalidation when
                 * access restrictions are removed from virtual pages, memory
                 * accesses that are allowed by the physical mapping layer may
                 * nonetheless cause one spurious page fault per virtual page.
                 * When the thread is executing a "no faulting" section that
                 * is bracketed by vm_fault_{disable,enable}_pagefaults(),
                 * every page fault is treated as a spurious page fault,
                 * unless it accesses the same virtual address as the most
                 * recent page fault within the same "no faulting" section.
                 */
                if (td->td_md.md_spurflt_addr != eva ||
                    (td->td_pflags & TDP_RESETSPUR) != 0) {
                        /*
                         * Do nothing to the TLB.  A stale TLB entry is
                         * flushed automatically by a page fault.
                         */
                        td->td_md.md_spurflt_addr = eva;
                        td->td_pflags &= ~TDP_RESETSPUR;
                        return (0);
                }
        } else {
                /*
                 * If we get a page fault while in a critical section, then
                 * it is most likely a fatal kernel page fault.  The kernel
                 * is already going to panic trying to get a sleep lock to
                 * do the VM lookup, so just consider it a fatal trap so the
                 * kernel can print out a useful trap message and even get
                 * to the debugger.
                 *
                 * If we get a page fault while holding a non-sleepable
                 * lock, then it is most likely a fatal kernel page fault.
                 * If WITNESS is enabled, then it's going to whine about
                 * bogus LORs with various VM locks, so just skip to the
                 * fatal trap handling directly.
                 */
                if (td->td_critnest != 0 ||
                    WITNESS_CHECK(WARN_SLEEPOK | WARN_GIANTOK, NULL,
                    "Kernel page fault") != 0) {
                        trap_fatal(frame, eva);
                        return (-1);
                }
        }
        if (eva >= kva_layout.km_low) {
                /*
                 * Don't allow user-mode faults in kernel address space.
                 */
                if (usermode) {
                        *signo = SIGSEGV;
                        *ucode = SEGV_MAPERR;
                        return (1);
                }

                map = kernel_map;
        } else {
                map = &p->p_vmspace->vm_map;

                /*
                 * When accessing a usermode address, kernel must be
                 * ready to accept the page fault, and provide a
                 * handling routine.  Since accessing the address
                 * without the handler is a bug, do not try to handle
                 * it normally, and panic immediately.
                 *
                 * If SMAP is enabled, filter SMAP faults also,
                 * because illegal access might occur to the mapped
                 * user address, causing infinite loop.
                 */
                if (!usermode && (td->td_intr_nesting_level != 0 ||
                    trap_is_smap(frame) || curpcb->pcb_onfault == NULL)) {
                        trap_fatal(frame, eva);
                        return (-1);
                }
        }

        /*
         * If the trap was caused by errant bits in the PTE then panic.
         */
        if (frame->tf_err & PGEX_RSV) {
                trap_fatal(frame, eva);
                return (-1);
        }

        /*
         * User-mode protection key violation (PKU).  May happen
         * either from usermode or from kernel if copyin accessed
         * key-protected mapping.
         */
        if ((frame->tf_err & PGEX_PK) != 0) {
                if (eva > VM_MAXUSER_ADDRESS) {
                        trap_fatal(frame, eva);
                        return (-1);
                }
                if (usermode) {
                        *signo = SIGSEGV;
                        *ucode = SEGV_PKUERR;
                        return (1);
                }
                goto after_vmfault;
        }

        /*
         * If nx protection of the usermode portion of kernel page
         * tables caused trap, panic.
         */
        if (usermode && trap_is_pti(frame))
                panic("PTI: pid %d comm %s tf_err %#lx", p->p_pid,
                    p->p_comm, frame->tf_err);

        /*
         * PGEX_I is defined only if the execute disable bit capability is
         * supported and enabled.
         */
        if (frame->tf_err & PGEX_W)
                ftype = VM_PROT_WRITE;
        else if ((frame->tf_err & PGEX_I) && pg_nx != 0)
                ftype = VM_PROT_EXECUTE;
        else
                ftype = VM_PROT_READ;

        /* Fault in the page. */
        rv = vm_fault_trap(map, eva, ftype, VM_FAULT_NORMAL, signo, ucode);
        if (rv == KERN_SUCCESS) {
#ifdef HWPMC_HOOKS
                if (ftype == VM_PROT_READ || ftype == VM_PROT_WRITE) {
                        PMC_SOFT_CALL_TF( , , page_fault, all, frame);
                        if (ftype == VM_PROT_READ)
                                PMC_SOFT_CALL_TF( , , page_fault, read,
                                    frame);
                        else
                                PMC_SOFT_CALL_TF( , , page_fault, write,
                                    frame);
                }
#endif
                return (0);
        }

        if (usermode)
                return (1);
after_vmfault:
        if (td->td_intr_nesting_level == 0 &&
            trap_check_pcb_onfault(td, frame))
                return (0);
        trap_fatal(frame, eva);
        return (-1);
}

static void
trap_diag(struct trapframe *frame, vm_offset_t eva, const char *type_str)
{
        int code;
        u_int type;

        code = frame->tf_err;
        type = frame->tf_trapno;

        printf("\n%s trap %d: %s while in %s mode\n", type_str, type,
            type < nitems(trap_msg) ? trap_msg[type] : UNKNOWN,
            TRAPF_USERMODE(frame) ? "user" : "kernel");
        /* Print these separately in case pcpu accesses trap. */
        printf("cpuid = %d; apic id = %02x\n", PCPU_GET(cpuid),
            PCPU_GET(apic_id));
        if (type == T_PAGEFLT) {
                printf("fault virtual address   = 0x%lx\n", eva);
                printf("fault code              = %s %s %s%s%s, %s\n",
                        code & PGEX_U ? "user" : "supervisor",
                        code & PGEX_W ? "write" : "read",
                        code & PGEX_I ? "instruction" : "data",
                        code & PGEX_PK ? " prot key" : "",
                        code & PGEX_SGX ? " SGX" : "",
                        code & PGEX_RSV ? "reserved bits in PTE" :
                        code & PGEX_P ? "protection violation" : "page not present");
        }
        printf("instruction pointer     = %#hx:%#lx\n",
               frame->tf_cs, frame->tf_rip);
        printf("stack pointer           = %#hx:%#lx\n", frame->tf_ss,
            frame->tf_rsp);
        printf("frame pointer           = %#hx:%#lx\n", frame->tf_ss,
            frame->tf_rbp);
        printf("processor eflags        = ");
        if (frame->tf_rflags & PSL_T)
                printf("trace trap, ");
        if (frame->tf_rflags & PSL_I)
                printf("interrupt enabled, ");
        if (frame->tf_rflags & PSL_NT)
                printf("nested task, ");
        if (frame->tf_rflags & PSL_RF)
                printf("resume, ");
        printf("IOPL = %ld\n", (frame->tf_rflags & PSL_IOPL) >> 12);
        printf("current thread          = %d/%d (%s/%s)\n",
            curproc->p_pid, curthread->td_tid, curproc->p_comm,
            curthread->td_name);

        printf("rdi: %016lx rsi: %016lx rdx: %016lx\n", frame->tf_rdi,
            frame->tf_rsi, frame->tf_rdx);
        printf("rcx: %016lx  r8: %016lx  r9: %016lx\n", frame->tf_rcx,
            frame->tf_r8, frame->tf_r9);
        printf("rax: %016lx rbx: %016lx rbp: %016lx\n", frame->tf_rax,
            frame->tf_rbx, frame->tf_rbp);
        printf("r10: %016lx r11: %016lx r12: %016lx\n", frame->tf_r10,
            frame->tf_r11, frame->tf_r12);
        printf("r13: %016lx r14: %016lx r15: %016lx\n", frame->tf_r13,
            frame->tf_r14, frame->tf_r15);
        if (fred) {
                struct trapframe_fred *f;

                f = __containerof(frame, struct trapframe_fred, tf_idt);
                printf("evdata %016lx evinfo1 %04x evinfo2 %08x\n",
                    f->tf_fred_evdata, frame->tf_fred_evinfo1,
                    frame->tf_fred_evinfo2);
        }
}

static void
trap_fatal(struct trapframe *frame, vm_offset_t eva)
{
        u_int type;

        type = frame->tf_trapno;
        trap_diag(frame, eva, "\nFatal");
#ifdef KDB
        if (debugger_on_trap) {
                bool handled;

                kdb_why = KDB_WHY_TRAP;
                handled = kdb_trap(type, 0, frame);
                kdb_why = KDB_WHY_UNSET;
                if (handled)
                        return;
        }
#endif
        panic("%s", traptype_to_msg(type));
}

#ifdef KDTRACE_HOOKS
/*
 * Invoke a userspace DTrace hook.  The hook pointer is cleared when no
 * userspace probes are enabled, so we must synchronize with DTrace to ensure
 * that a trapping thread is able to call the hook before it is cleared.
 */
static bool
trap_user_dtrace(struct trapframe *frame, int (**hookp)(struct trapframe *))
{
        int (*hook)(struct trapframe *);

        hook = atomic_load_ptr(hookp);
        enable_intr();
        if (hook != NULL)
                return ((hook)(frame) == 0);
        return (false);
}
#endif

/*
 * Double fault handler. Called when a fault occurs while writing
 * a frame for a trap/exception onto the stack. This usually occurs
 * when the stack overflows (such is the case with infinite recursion,
 * for example).
 */
void
dblfault_handler(struct trapframe *frame)
{
        kmsan_mark(frame, sizeof(*frame), KMSAN_STATE_INITED);
#ifdef KDTRACE_HOOKS
        if (dtrace_doubletrap_func != NULL)
                (*dtrace_doubletrap_func)();
#endif
        printf("\nFatal double fault\n"
            "rip %#lx rsp %#lx rbp %#lx\n"
            "rax %#lx rdx %#lx rbx %#lx\n"
            "rcx %#lx rsi %#lx rdi %#lx\n"
            "r8 %#lx r9 %#lx r10 %#lx\n"
            "r11 %#lx r12 %#lx r13 %#lx\n"
            "r14 %#lx r15 %#lx rflags %#lx\n"
            "cs %#hx ss %#hx ds %#hx es %#hx fs %#hx gs %#hx\n"
            "fsbase %#lx gsbase %#lx kgsbase %#lx\n",
            frame->tf_rip, frame->tf_rsp, frame->tf_rbp,
            frame->tf_rax, frame->tf_rdx, frame->tf_rbx,
            frame->tf_rcx, frame->tf_rdi, frame->tf_rsi,
            frame->tf_r8, frame->tf_r9, frame->tf_r10,
            frame->tf_r11, frame->tf_r12, frame->tf_r13,
            frame->tf_r14, frame->tf_r15, frame->tf_rflags,
            frame->tf_cs, frame->tf_ss, frame->tf_ds, frame->tf_es,
            frame->tf_fs, frame->tf_gs,
            rdmsr(MSR_FSBASE), rdmsr(MSR_GSBASE), rdmsr(MSR_KGSBASE));
        if (fred) {
                struct trapframe_fred *f;

                f = __containerof(frame, struct trapframe_fred, tf_idt);
                printf("evdata %016lx evinfo1 %04x evinfo2 %08x\n",
                    f->tf_fred_evdata, frame->tf_fred_evinfo1,
                    frame->tf_fred_evinfo2);
        }
        /* Print these separately in case pcpu accesses trap. */
        printf("cpuid = %d; apic id = %02x\n", PCPU_GET(cpuid),
            PCPU_GET(apic_id));
        panic("double fault");
}

static int __noinline
cpu_fetch_syscall_args_fallback(struct thread *td, struct syscall_args *sa)
{
        struct proc *p;
        struct trapframe *frame;
        syscallarg_t *argp;
        caddr_t params;
        int reg, regcnt, error;

        p = td->td_proc;
        frame = td->td_frame;
        reg = 0;
        regcnt = NARGREGS;

        if (sa->code == SYS_syscall || sa->code == SYS___syscall) {
                sa->code = frame->tf_rdi;
                reg++;
                regcnt--;
        }

        if (sa->code >= p->p_sysent->sv_size)
                sa->callp = &nosys_sysent;
        else
                sa->callp = &p->p_sysent->sv_table[sa->code];

        KASSERT(sa->callp->sy_narg <= nitems(sa->args),
            ("Too many syscall arguments!"));
        argp = &frame->tf_rdi;
        argp += reg;
        memcpy(sa->args, argp, sizeof(sa->args[0]) * NARGREGS);
        if (sa->callp->sy_narg > regcnt) {
                params = (caddr_t)frame->tf_rsp + sizeof(register_t);
                error = copyin(params, &sa->args[regcnt],
                    (sa->callp->sy_narg - regcnt) * sizeof(sa->args[0]));
                if (__predict_false(error != 0))
                        return (error);
        }

        td->td_retval[0] = 0;
        td->td_retval[1] = frame->tf_rdx;

        return (0);
}

int
cpu_fetch_syscall_args(struct thread *td)
{
        struct proc *p;
        struct trapframe *frame;
        struct syscall_args *sa;

        p = td->td_proc;
        frame = td->td_frame;
        sa = &td->td_sa;

        sa->code = frame->tf_rax;
        sa->original_code = sa->code;

        if (__predict_false(sa->code == SYS_syscall ||
            sa->code == SYS___syscall ||
            sa->code >= p->p_sysent->sv_size))
                return (cpu_fetch_syscall_args_fallback(td, sa));

        sa->callp = &p->p_sysent->sv_table[sa->code];
        KASSERT(sa->callp->sy_narg <= nitems(sa->args),
            ("Too many syscall arguments!"));

        if (__predict_false(sa->callp->sy_narg > NARGREGS))
                return (cpu_fetch_syscall_args_fallback(td, sa));

        memcpy(sa->args, &frame->tf_rdi, sizeof(sa->args[0]) * NARGREGS);

        td->td_retval[0] = 0;
        td->td_retval[1] = frame->tf_rdx;

        return (0);
}

#include "../../kern/subr_syscall.c"

static void (*syscall_ret_l1d_flush)(void);
int syscall_ret_l1d_flush_mode;

static void
flush_l1d_hw(void)
{

        wrmsr(MSR_IA32_FLUSH_CMD, IA32_FLUSH_CMD_L1D);
}

static void __noinline
amd64_syscall_ret_flush_l1d_check(int error)
{
        void (*p)(void);

        if (error != EEXIST && error != EAGAIN && error != EXDEV &&
            error != ENOENT && error != ENOTCONN && error != EINPROGRESS) {
                p = atomic_load_ptr(&syscall_ret_l1d_flush);
                if (p != NULL)
                        p();
        }
}

static void __inline
amd64_syscall_ret_flush_l1d_check_inline(int error)
{

        if (__predict_false(error != 0))
                amd64_syscall_ret_flush_l1d_check(error);
}

void
amd64_syscall_ret_flush_l1d(int error)
{

        amd64_syscall_ret_flush_l1d_check_inline(error);
}

void
amd64_syscall_ret_flush_l1d_recalc(void)
{
        bool l1d_hw;

        l1d_hw = (cpu_stdext_feature3 & CPUID_STDEXT3_L1D_FLUSH) != 0;
again:
        switch (syscall_ret_l1d_flush_mode) {
        case 0:
                syscall_ret_l1d_flush = NULL;
                break;
        case 1:
                syscall_ret_l1d_flush = l1d_hw ? flush_l1d_hw :
                    flush_l1d_sw_abi;
                break;
        case 2:
                syscall_ret_l1d_flush = l1d_hw ? flush_l1d_hw : NULL;
                break;
        case 3:
                syscall_ret_l1d_flush = flush_l1d_sw_abi;
                break;
        default:
                syscall_ret_l1d_flush_mode = 1;
                goto again;
        }
}

static int
machdep_syscall_ret_flush_l1d(SYSCTL_HANDLER_ARGS)
{
        int error, val;

        val = syscall_ret_l1d_flush_mode;
        error = sysctl_handle_int(oidp, &val, 0, req);
        if (error != 0 || req->newptr == NULL)
                return (error);
        syscall_ret_l1d_flush_mode = val;
        amd64_syscall_ret_flush_l1d_recalc();
        return (0);
}
SYSCTL_PROC(_machdep, OID_AUTO, syscall_ret_flush_l1d, CTLTYPE_INT |
    CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE, NULL, 0,
    machdep_syscall_ret_flush_l1d, "I",
    "Flush L1D on syscall return with error (0 - off, 1 - on, "
    "2 - use hw only, 3 - use sw only)");

/*
 * System call handler for native binaries.  The trap frame is already
 * set up by the assembler trampoline and a pointer to it is saved in
 * td_frame.
 */
void
amd64_syscall(struct thread *td, int traced)
{
        ksiginfo_t ksi;

        kmsan_mark(td->td_frame, sizeof(*td->td_frame), KMSAN_STATE_INITED);

        KASSERT(TRAPF_USERMODE(td->td_frame),
            ("%s: not from user mode", __func__));

        syscallenter(td);

        /*
         * Traced syscall.
         */
        if (__predict_false(traced)) {
                td->td_frame->tf_rflags &= ~PSL_T;
                ksiginfo_init_trap(&ksi);
                ksi.ksi_signo = SIGTRAP;
                ksi.ksi_code = TRAP_TRACE;
                ksi.ksi_addr = (void *)td->td_frame->tf_rip;
                trapsignal(td, &ksi);
        }

        KASSERT(PCB_USER_FPU(td->td_pcb),
            ("System call %s returning with kernel FPU ctx leaked",
             syscallname(td->td_proc, td->td_sa.code)));
        KASSERT(td->td_pcb->pcb_save == get_pcb_user_save_td(td),
            ("System call %s returning with mangled pcb_save",
             syscallname(td->td_proc, td->td_sa.code)));
        KASSERT(pmap_not_in_di(),
            ("System call %s returning with leaked invl_gen %lu",
            syscallname(td->td_proc, td->td_sa.code),
            td->td_md.md_invl_gen.gen));

        syscallret(td);

        /*
         * If the user-supplied value of %rip is not a canonical
         * address, then some CPUs will trigger a ring 0 #GP during
         * the sysret instruction.  However, the fault handler would
         * execute in ring 0 with the user's %gs and %rsp which would
         * not be safe.  Instead, use the full return path which
         * catches the problem safely.
         */
        if (__predict_false(td->td_frame->tf_rip >= (la57 ?
            VM_MAXUSER_ADDRESS_LA57 : VM_MAXUSER_ADDRESS_LA48)))
                set_pcb_flags(td->td_pcb, PCB_FULL_IRET);

        amd64_syscall_ret_flush_l1d_check_inline(td->td_errno);
}

static void
trap_fred_extint(struct trapframe_fred *frame, u_int vec)
{
        switch (vec) {
        case IPI_RENDEZVOUS:
#ifdef COUNT_IPIS
                ipi_rendezvous_counts[PCPU_GET(cpuid)]++;
#endif
                smp_rendezvous_action();
                lapic_eoi();
                break;
        case IPI_INVLOP:
                invlop_handler();
                lapic_eoi();
                break;
        case IPI_BITMAP_VECTOR:
                lapic_eoi();
                ipi_bitmap_handler(&frame->tf_idt);
                break;
        case IPI_STOP:
                lapic_eoi();
                cpustop_handler();
                break;
        case IPI_SUSPEND:
                cpususpend_handler();
                lapic_eoi();
                break;
        case IPI_SWI:
                lapic_eoi();
                ipi_swi_handler(&frame->tf_idt);
                break;
        case IPI_OFF:
                cpuoff_handler();
                lapic_eoi();
                break;
        case APIC_SPURIOUS_INT:
                break;
        case APIC_TIMER_INT:
                lapic_handle_timer(&frame->tf_idt);
                break;
        case APIC_CMC_INT:
                lapic_handle_cmc();
                break;
        case APIC_ERROR_INT:
                lapic_handle_error();
                break;
        case APIC_THERMAL_INT:
                lapic_handle_thermal();
                break;
#ifdef XENHVM
        case IDT_EVTCHN:
                xen_arch_intr_handle_upcall(&frame->tf_idt);
                break;
#endif
        default:
                if (vec >= IPI_DYN_FIRST && vec <= IPI_DYN_LAST) {
                        void (*fi)(struct trapframe *);

                        fi = fred_ipi_handlers[vec - IPI_DYN_FIRST];
                        if (fi != NULL) {
                                fi(&frame->tf_idt);
                                lapic_eoi();
                        } else {
                                panic("DYN IPI %d without FRED handler", vec);
                        }
                        break;
                }
#ifdef DEV_ISA
#ifdef DEV_ATPIC
                if (vec >= IDT_IO_INTS && vec < IDT_IO_INTS + NUM_ISA_IRQS) {
                        atpic_handle_intr(vec - IDT_IO_INTS, &frame->tf_idt);
                        break;
                }
#endif
#endif
                /* apic ioint */
                lapic_handle_intr(vec, &frame->tf_idt);
                break;
        }
}

void fred_out_of_nmi(void);

static const int fred_ev_to_trapno_table[] = {
        [IDT_DE] =      T_DIVIDE,
        [IDT_DB] =      T_TRCTRAP,
        [IDT_NMI] =     T_RESERVED,
        [IDT_BP] =      T_BPTFLT,
        [IDT_OF] =      T_OFLOW,
        [IDT_BR] =      T_BOUND,
        [IDT_UD] =      T_PRIVINFLT,
        [IDT_NM] =      T_DNA,
        [IDT_DF] =      T_DOUBLEFLT,
        [IDT_FPUGP] =   T_FPOPFLT,
        [IDT_TS] =      T_TSSFLT,
        [IDT_NP] =      T_SEGNPFLT,
        [IDT_SS] =      T_STKFLT,
        [IDT_GP] =      T_PROTFLT,
        [IDT_PF] =      T_PAGEFLT,
        [15] =          T_RESERVED,
        [IDT_MF] =      T_ARITHTRAP,
        [IDT_AC] =      T_ALIGNFLT,
        [IDT_MC] =      T_MCHK,
        [IDT_XF] =      T_XMMFLT,
        [20] =          T_RESERVED,
        [21] =          T_RESERVED,
        [22] =          T_RESERVED,
        [23] =          T_RESERVED,
        [24] =          T_RESERVED,
        [25] =          T_RESERVED,
        [26] =          T_RESERVED,
        [27] =          T_RESERVED,
        [28] =          T_RESERVED,
        [29] =          T_RESERVED,
        [30] =          T_RESERVED,
        [31] =          T_RESERVED,
};

static void
trap_fred_ev_to_trapno(struct trapframe_fred *frame, u_int exc)
{
        frame->tf_idt.tf_trapno = fred_ev_to_trapno_table[exc];
}

static void
trap_fred_handle_u_exc(struct thread *td, struct trapframe_fred *frame,
    u_int exc, ksiginfo_t *ksi, bool *do_trapsig)
{
        struct proc *p;
        register_t addr;
        int pf, signo, ucode;

        addr = frame->tf_idt.tf_rip;
        signo = 0;
        ucode = 0;
        frame->tf_idt.tf_addr = 0;
        trap_check_intr_user(td, &frame->tf_idt);

        switch (exc) {
        case IDT_DE:
                ucode = FPE_INTDIV;
                signo = SIGFPE;
                break;
        case IDT_DB:
                signo = SIGTRAP;
                ucode = TRAP_TRACE;
                if ((frame->tf_fred_evdata & TF_FRED_EVDATA_BS) != 0)
                        trap_clear_step(td, &frame->tf_idt);
                break;
        case IDT_BP:
#ifdef KDTRACE_HOOKS
                if (trap_user_dtrace(&frame->tf_idt, &dtrace_pid_probe_ptr))
                        return;
#endif
                signo = SIGTRAP;
                ucode = TRAP_BRKPT;
                break;
        case IDT_OF:
                ucode = FPE_INTOVF;
                signo = SIGFPE;
                break;
        case IDT_BR:
                ucode = FPE_FLTSUB;
                signo = SIGFPE;
                break;
        case IDT_UD:
                signo = SIGILL;
                ucode = ILL_PRVOPC;
                break;
        case IDT_NM:
                KASSERT(PCB_USER_FPU(td->td_pcb),
                    ("kernel FPU ctx has leaked"));
                fpudna();
                return;
        case IDT_DF:
                signo = SIGBUS;
                ucode = BUS_OBJERR;
                break;
        case IDT_FPUGP:
                ucode = ILL_COPROC;
                signo = SIGILL;
                break;
        case IDT_TS:
                signo = SIGBUS;
                ucode = BUS_OBJERR;
                break;
        case IDT_NP:
                signo = SIGBUS;
                ucode = BUS_ADRERR;
                break;
        case IDT_SS:
                signo = SIGBUS;
                ucode = BUS_ADRERR;
                break;
        case IDT_GP:
                signo = SIGBUS;
                ucode = BUS_OBJERR;
                break;
        case IDT_PF:
                p = td->td_proc;
                frame->tf_idt.tf_addr = addr = frame->tf_fred_evdata;
                if (*p->p_sysent->sv_trap != NULL &&
                    (*p->p_sysent->sv_trap)(td) == 0)
                        return;
                pf = trap_pfault(&frame->tf_idt, true, &signo, &ucode);
                if (pf == -1 || pf == 0)
                        return;
                break;
        case IDT_MF:
                ucode = fputrap_x87();
                if (ucode == -1)
                        return;
                signo = SIGFPE;
                break;
        case IDT_AC:
                signo = SIGBUS;
                ucode = BUS_ADRALN;
                break;
        case IDT_MC:
                mca_intr();
                return;
        case IDT_XF:
                ucode = fputrap_sse();
                if (ucode == -1)
                        return;
                signo = SIGFPE;
                break;
        default:
                panic("missed FRED handler for exception %d", exc);
        }

        ksiginfo_init_trap(ksi);
        ksi->ksi_signo = signo;
        ksi->ksi_code = ucode;
        ksi->ksi_trapno = frame->tf_idt.tf_trapno;
        ksi->ksi_addr = (void *)addr;
        trap_uprintf_signal(td, &frame->tf_idt, addr, signo, ucode);
        KASSERT((read_rflags() & PSL_I) != 0, ("interrupts disabled"));
        *do_trapsig = true;
}

static u_int
fred_inst_len(const struct trapframe_fred *frame)
{
        return ((frame->tf_idt.tf_fred_evinfo2 & TF_FRED_EVINFO2_INSTLENMASK) >>
            TF_FRED_EVINFO2_INSTLENSHIFT);
}

int fred_verbose_events;

void trap_fred_u(struct trapframe_fred *frame);
void
trap_fred_u(struct trapframe_fred *frame)
{
        struct thread *td;
        ksiginfo_t ksi;
        u_int type, vec;
        bool do_trapsig;

        td = curthread;
        type = frame->tf_idt.tf_fred_evinfo2 & TF_FRED_EVINFO2_TYPEMASK;
        vec = frame->tf_idt.tf_fred_evinfo2 & TF_FRED_EVINFO2_VECMASK;
        do_trapsig = false;
        if (fred_verbose_events) {
                printf("pid %d tid %d type %d vec %d rax %#lx\n",
                    td->td_proc->p_pid, td->td_tid,
                    (frame->tf_idt.tf_fred_evinfo2 &
                    TF_FRED_EVINFO2_TYPEMASK) >> 16,
                    vec, frame->tf_idt.tf_rax);
        }
        if (__predict_true((td->td_proc->p_sysent->sv_flags &
            (SV_ABI_MASK | SV_LP64)) == (SV_ABI_FREEBSD | SV_LP64) &&
            (type == TF_FRED_EVINFO2_TYPE_SYSCALL ||
            type == TF_FRED_EVINFO2_TYPE_EXTINT ||
            (type == TF_FRED_EVINFO2_TYPE_EXC && vec == IDT_PF))))
                clear_pcb_flags(td->td_pcb, PCB_FULL_IRET);
        else
                set_pcb_flags(td->td_pcb, PCB_FULL_IRET);
        switch (type) {
        case TF_FRED_EVINFO2_TYPE_EXTINT:
                trap_fred_extint(frame, vec);
                break;
        case TF_FRED_EVINFO2_TYPE_NMI:
                frame->tf_idt.tf_trapno = T_NMI;
                nmi_handle_intr(&frame->tf_idt);
#ifdef HWPMC_HOOKS
                if ((td->td_pflags & TDP_CALLCHAIN) != 0) {
                        int (*ph)(struct thread *, int, void *);

                        fred_out_of_nmi();
                        ph = atomic_load_ptr(&pmc_hook);
                        if (ph != NULL) {
                                enable_intr();
                                ph(td, PMC_FN_USER_CALLCHAIN, &frame->tf_idt);
                        }
                }
#endif
                break;
        case TF_FRED_EVINFO2_TYPE_INT1:
        case TF_FRED_EVINFO2_TYPE_INT3:
        case TF_FRED_EVINFO2_TYPE_EXC:
                enable_intr();
                trap_fred_ev_to_trapno(frame, vec);
#ifdef KDTRACE_HOOKS
                if (dtrace_trap_func != NULL && (*dtrace_trap_func)(
                    &frame->tf_idt, frame->tf_idt.tf_trapno) != 0)
                        return;
#endif
                td->td_pticks = 0;
                td->td_frame = &frame->tf_idt;
                if (td->td_cowgen != atomic_load_int(&td->td_proc->p_cowgen))
                        thread_cow_update(td);
                trap_fred_handle_u_exc(td, frame, vec, &ksi, &do_trapsig);
                break;
        case TF_FRED_EVINFO2_TYPE_INTn:
                enable_intr();
#ifdef COMPAT_FREEBSD32
                if (vec == IDT_SYSCALL) {
                        frame->tf_idt.tf_err = fred_inst_len(frame);
                        ia32_syscall(&frame->tf_idt);
                        break;
                }
#endif
                frame->tf_idt.tf_trapno = vec;
                ksiginfo_init_trap(&ksi);
                ksi.ksi_signo = SIGBUS;
                ksi.ksi_code = BUS_OBJERR;
                ksi.ksi_trapno = frame->tf_idt.tf_trapno;
                ksi.ksi_addr = (void *)frame->tf_idt.tf_rip;
                do_trapsig = true;
                break;
        case TF_FRED_EVINFO2_TYPE_SYSCALL:
                /* Excessive */
                enable_intr();
                if (vec == TF_FRED_EVINFO2_VEC_SYSCALL) {
                        frame->tf_idt.tf_err = fred_inst_len(frame);
                        td->td_frame = &frame->tf_idt;
                        amd64_syscall(td, (frame->tf_idt.tf_rflags & PSL_T) !=
                            0);
                } else {
                        /* SYSENTER returns without action */
                }
                break;
        default:
                __unreachable();
        }
        if (do_trapsig)
                trapsignal(td, &ksi);
        userret(td, &frame->tf_idt);
        KASSERT(PCB_USER_FPU(td->td_pcb),
            ("Return from trap with kernel FPU ctx leaked"));
}

extern const char fred_ld_fs[];
extern const char fred_ld_fs_fault[];
extern const char fred_ld_fsbase[];
extern const char fred_ld_fsbase_fault[];
extern const char fred_lkgs[];
extern const char fred_lkgs_fault[];
extern const char fred_ld_kgsbase[];
extern const char fred_ld_kgsbase_fault[];
extern const char fred_ld_es[];
extern const char fred_ld_es_fault[];
extern const char fred_ld_ds[];
extern const char fred_ld_ds_fault[];
extern const char fred_eretu[];
extern const char fred_syscall_eretu[];
extern const char fred_eretu_fault[];

static const struct sfhandler fred_sfhandlers[] = {
        {
                .faddr = (uintptr_t)fred_ld_fs,
                .fhandler = (uintptr_t)fred_ld_fs_fault,
        },
        {
                .faddr = (uintptr_t)fred_ld_fsbase,
                .fhandler = (uintptr_t)fred_ld_fsbase_fault,
        },
        {
                .faddr = (uintptr_t)fred_lkgs,
                .fhandler = (uintptr_t)fred_lkgs_fault,
        },
        {
                .faddr = (uintptr_t)fred_ld_kgsbase,
                .fhandler = (uintptr_t)fred_ld_kgsbase_fault,
        },
        {
                .faddr = (uintptr_t)fred_ld_es,
                .fhandler = (uintptr_t)fred_ld_es_fault,
        },
        {
                .faddr = (uintptr_t)fred_ld_ds,
                .fhandler = (uintptr_t)fred_ld_ds_fault,
        },
        {
                .faddr = (uintptr_t)fred_eretu,
                .fhandler = (uintptr_t)fred_eretu_fault,
        },
        {
                .faddr = (uintptr_t)fred_syscall_eretu,
                .fhandler = (uintptr_t)fred_eretu_fault,
        },
};

static void
trap_fred_handle_k_exc(struct thread *td, struct trapframe_fred *frame,
    u_int exc)
{
        register_t addr;
        int i;

        addr = frame->tf_idt.tf_rip;
        frame->tf_idt.tf_addr = 0;
        KASSERT(cold || td->td_ucred != NULL,
            ("kernel trap doesn't have ucred"));

        /*
         * FRED exception handler runs with the interrupts disabled,
         * unlike the IDT case.  Only for page faults the interrupts
         * are enabled, since this is the only legitimate exception
         * from the kernel mode.  Anything else results in panic, so
         * there is no sense to enable interrupts.
         */

        if (exc != IDT_PF && trap_check_pcb_onfault(td, &frame->tf_idt))
                return;

        switch (exc) {
        case IDT_DE:
                break;
        case IDT_DB:
                if (user_dbreg_trap(frame->tf_fred_evdata))
                        return;
                /* FALLTHROUGH */
        case IDT_BP:
#ifdef KDB
                if (kdb_trap(frame->tf_idt.tf_trapno, frame->tf_fred_evdata,
                    &frame->tf_idt))
                        return;
#endif
                break;
        case IDT_OF:
                break;
        case IDT_BR:
                break;
        case IDT_UD:
                break;
        case IDT_NM:
                if (PCB_USER_FPU(td->td_pcb))
                        panic("Unregistered use of FPU in kernel");
                fpudna();
                return;
        case IDT_DF:
                dblfault_handler(&frame->tf_idt);
                break;
        case IDT_FPUGP:
                break;
        case IDT_TS:
                /*
                 * PSL_NT is cleared automatically by FRED entry.
                 */
                break;
        case IDT_NP:
        case IDT_SS:
        case IDT_GP:
                if (td->td_intr_nesting_level != 0)
                        break;
                for (i = 0; i < nitems(fred_sfhandlers); i++) {
                        if (frame->tf_idt.tf_rip == fred_sfhandlers[i].faddr) {
                                KASSERT((read_rflags() & PSL_I) == 0,
                                    ("interrupts enabled"));
                                frame->tf_idt.tf_rip = fred_sfhandlers[i].
                                    fhandler;
                                return;
                        }
                }
                if (curpcb->pcb_onfault != NULL) {
                        frame->tf_idt.tf_rip = (long)curpcb->pcb_onfault;
                        return;
                }
                break;
        case IDT_PF:
                frame->tf_idt.tf_addr = addr = frame->tf_fred_evdata;
                if ((frame->tf_idt.tf_rflags & PSL_I) != 0)
                        enable_intr();
                trap_pfault(&frame->tf_idt, false, NULL, NULL);
                return;
        case IDT_MF:
                break;
        case IDT_AC:
                break;
        case IDT_MC:
                mca_intr();
                return;
        case IDT_XF:
                break;
        default:
                printf("Missing FRED handler for exception %d", exc);
                trap_fatal(&frame->tf_idt, 0);
        }
        trap_fatal(&frame->tf_idt, 0);
}

void trap_fred_k(struct trapframe_fred *frame);
void
trap_fred_k(struct trapframe_fred *frame)
{
        struct thread *td;
        u_int vec;

        td = curthread;
        vec = frame->tf_idt.tf_fred_evinfo2 & TF_FRED_EVINFO2_VECMASK;
        switch (frame->tf_idt.tf_fred_evinfo2 & TF_FRED_EVINFO2_TYPEMASK) {
        case TF_FRED_EVINFO2_TYPE_EXTINT:
                trap_fred_extint(frame, vec);
                break;
        case TF_FRED_EVINFO2_TYPE_NMI:
                frame->tf_idt.tf_trapno = T_NMI;
                nmi_handle_intr(&frame->tf_idt);
                break;
        case TF_FRED_EVINFO2_TYPE_INT1:
        case TF_FRED_EVINFO2_TYPE_INT3:
        case TF_FRED_EVINFO2_TYPE_EXC:
                trap_fred_ev_to_trapno(frame, vec);
                trap_fred_handle_k_exc(td, frame, vec);
                break;
        case TF_FRED_EVINFO2_TYPE_INTn:
                panic("INT%d from kernel", vec);
                break;
        case TF_FRED_EVINFO2_TYPE_SYSCALL:
                panic("syscall from kernel");
                break;
        default:
                __unreachable();
        }
}