/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (c) 2018 The FreeBSD Foundation
 * Copyright (c) 1992 Terrence R. Lambert.
 * Copyright (c) 1982, 1987, 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * William Jolitz.
 *
 * Portions of this software were developed by A. Joseph Koshy under
 * sponsorship from the FreeBSD Foundation and Google, Inc.
 *
 * 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.
 */

#include <sys/cdefs.h>
#include "opt_cpu.h"
#include "opt_ddb.h"
#include "opt_kstack_pages.h"

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/exec.h>
#include <sys/imgact.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/linker.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/pcpu.h>
#include <sys/ptrace.h>
#include <sys/reg.h>
#include <sys/rwlock.h>
#include <sys/signalvar.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>
#include <sys/ucontext.h>
#include <sys/vmmeter.h>

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

#ifdef DDB
#ifndef KDB
#error KDB must be enabled in order for DDB to work!
#endif
#include <ddb/ddb.h>
#include <ddb/db_sym.h>
#endif

#include <machine/cpu.h>
#include <machine/cputypes.h>
#include <machine/md_var.h>
#include <machine/pcb.h>
#include <machine/pcb_ext.h>
#include <machine/proc.h>
#include <machine/sigframe.h>
#include <machine/specialreg.h>
#include <machine/sysarch.h>
#include <machine/trap.h>

static void fpstate_drop(struct thread *td);
static void get_fpcontext(struct thread *td, mcontext_t *mcp,
    char *xfpusave, size_t xfpusave_len);
static int  set_fpcontext(struct thread *td, mcontext_t *mcp,
    char *xfpustate, size_t xfpustate_len);
#ifdef COMPAT_43
static void osendsig(sig_t catcher, ksiginfo_t *, sigset_t *mask);
#endif
#ifdef COMPAT_FREEBSD4
static void freebsd4_sendsig(sig_t catcher, ksiginfo_t *, sigset_t *mask);
#endif

extern struct sysentvec elf32_freebsd_sysvec;

_Static_assert(sizeof(mcontext_t) == 640, "mcontext_t size incorrect");
_Static_assert(sizeof(ucontext_t) == 704, "ucontext_t size incorrect");
_Static_assert(sizeof(siginfo_t) == 64, "siginfo_t size incorrect");

/*
 * Send an interrupt to process.
 *
 * Stack is set up to allow sigcode stored at top to call routine,
 * followed by call to sigreturn routine below.  After sigreturn
 * resets the signal mask, the stack, and the frame pointer, it
 * returns to the user specified pc, psl.
 */
#ifdef COMPAT_43
static void
osendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
{
        struct osigframe sf, *fp;
        struct proc *p;
        struct thread *td;
        struct sigacts *psp;
        struct trapframe *regs;
        int sig;
        int oonstack;

        td = curthread;
        p = td->td_proc;
        PROC_LOCK_ASSERT(p, MA_OWNED);
        sig = ksi->ksi_signo;
        psp = p->p_sigacts;
        mtx_assert(&psp->ps_mtx, MA_OWNED);
        regs = td->td_frame;
        oonstack = sigonstack(regs->tf_esp);

        /* Allocate space for the signal handler context. */
        if ((td->td_pflags & TDP_ALTSTACK) && !oonstack &&
            SIGISMEMBER(psp->ps_sigonstack, sig)) {
                fp = (struct osigframe *)((uintptr_t)td->td_sigstk.ss_sp +
                    td->td_sigstk.ss_size - sizeof(struct osigframe));
#if defined(COMPAT_43)
                td->td_sigstk.ss_flags |= SS_ONSTACK;
#endif
        } else
                fp = (struct osigframe *)regs->tf_esp - 1;

        /* Build the argument list for the signal handler. */
        sf.sf_signum = sig;
        sf.sf_scp = (register_t)&fp->sf_siginfo.si_sc;
        bzero(&sf.sf_siginfo, sizeof(sf.sf_siginfo));
        if (SIGISMEMBER(psp->ps_siginfo, sig)) {
                /* Signal handler installed with SA_SIGINFO. */
                sf.sf_arg2 = (register_t)&fp->sf_siginfo;
                sf.sf_siginfo.si_signo = sig;
                sf.sf_siginfo.si_code = ksi->ksi_code;
                sf.sf_ahu.sf_action = (__osiginfohandler_t *)catcher;
                sf.sf_addr = 0;
        } else {
                /* Old FreeBSD-style arguments. */
                sf.sf_arg2 = ksi->ksi_code;
                sf.sf_addr = (register_t)ksi->ksi_addr;
                sf.sf_ahu.sf_handler = catcher;
        }
        mtx_unlock(&psp->ps_mtx);
        PROC_UNLOCK(p);

        /* Save most if not all of trap frame. */
        sf.sf_siginfo.si_sc.sc_eax = regs->tf_eax;
        sf.sf_siginfo.si_sc.sc_ebx = regs->tf_ebx;
        sf.sf_siginfo.si_sc.sc_ecx = regs->tf_ecx;
        sf.sf_siginfo.si_sc.sc_edx = regs->tf_edx;
        sf.sf_siginfo.si_sc.sc_esi = regs->tf_esi;
        sf.sf_siginfo.si_sc.sc_edi = regs->tf_edi;
        sf.sf_siginfo.si_sc.sc_cs = regs->tf_cs;
        sf.sf_siginfo.si_sc.sc_ds = regs->tf_ds;
        sf.sf_siginfo.si_sc.sc_ss = regs->tf_ss;
        sf.sf_siginfo.si_sc.sc_es = regs->tf_es;
        sf.sf_siginfo.si_sc.sc_fs = regs->tf_fs;
        sf.sf_siginfo.si_sc.sc_gs = rgs();
        sf.sf_siginfo.si_sc.sc_isp = regs->tf_isp;

        /* Build the signal context to be used by osigreturn(). */
        sf.sf_siginfo.si_sc.sc_onstack = (oonstack) ? 1 : 0;
        SIG2OSIG(*mask, sf.sf_siginfo.si_sc.sc_mask);
        sf.sf_siginfo.si_sc.sc_sp = regs->tf_esp;
        sf.sf_siginfo.si_sc.sc_fp = regs->tf_ebp;
        sf.sf_siginfo.si_sc.sc_pc = regs->tf_eip;
        sf.sf_siginfo.si_sc.sc_ps = regs->tf_eflags;
        sf.sf_siginfo.si_sc.sc_trapno = regs->tf_trapno;
        sf.sf_siginfo.si_sc.sc_err = regs->tf_err;

        /*
         * If we're a vm86 process, we want to save the segment registers.
         * We also change eflags to be our emulated eflags, not the actual
         * eflags.
         */
        if (regs->tf_eflags & PSL_VM) {
                /* XXX confusing names: `tf' isn't a trapframe; `regs' is. */
                struct trapframe_vm86 *tf = (struct trapframe_vm86 *)regs;
                struct vm86_kernel *vm86 = &td->td_pcb->pcb_ext->ext_vm86;

                sf.sf_siginfo.si_sc.sc_gs = tf->tf_vm86_gs;
                sf.sf_siginfo.si_sc.sc_fs = tf->tf_vm86_fs;
                sf.sf_siginfo.si_sc.sc_es = tf->tf_vm86_es;
                sf.sf_siginfo.si_sc.sc_ds = tf->tf_vm86_ds;

                if (vm86->vm86_has_vme == 0)
                        sf.sf_siginfo.si_sc.sc_ps =
                            (tf->tf_eflags & ~(PSL_VIF | PSL_VIP)) |
                            (vm86->vm86_eflags & (PSL_VIF | PSL_VIP));

                /* See sendsig() for comments. */
                tf->tf_eflags &= ~(PSL_VM | PSL_NT | PSL_VIF | PSL_VIP);
        }

        /*
         * Copy the sigframe out to the user's stack.
         */
        if (copyout(&sf, fp, sizeof(*fp)) != 0) {
                PROC_LOCK(p);
                sigexit(td, SIGILL);
        }

        regs->tf_esp = (int)fp;
        if (PROC_HAS_SHP(p)) {
                regs->tf_eip = PROC_SIGCODE(p) + szsigcode -
                    szosigcode;
        } else {
                /* a.out sysentvec does not use shared page */
                regs->tf_eip = PROC_PS_STRINGS(p) - szosigcode;
        }
        regs->tf_eflags &= ~(PSL_T | PSL_D);
        regs->tf_cs = _ucodesel;
        regs->tf_ds = _udatasel;
        regs->tf_es = _udatasel;
        regs->tf_fs = _udatasel;
        load_gs(_udatasel);
        regs->tf_ss = _udatasel;
        PROC_LOCK(p);
        mtx_lock(&psp->ps_mtx);
}
#endif /* COMPAT_43 */

#ifdef COMPAT_FREEBSD4
static void
freebsd4_sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
{
        struct freebsd4_sigframe sf, *sfp;
        struct proc *p;
        struct thread *td;
        struct sigacts *psp;
        struct trapframe *regs;
        int sig;
        int oonstack;

        td = curthread;
        p = td->td_proc;
        PROC_LOCK_ASSERT(p, MA_OWNED);
        sig = ksi->ksi_signo;
        psp = p->p_sigacts;
        mtx_assert(&psp->ps_mtx, MA_OWNED);
        regs = td->td_frame;
        oonstack = sigonstack(regs->tf_esp);

        /* Save user context. */
        bzero(&sf, sizeof(sf));
        sf.sf_uc.uc_sigmask = *mask;
        sf.sf_uc.uc_stack = td->td_sigstk;
        sf.sf_uc.uc_stack.ss_flags = (td->td_pflags & TDP_ALTSTACK)
            ? ((oonstack) ? SS_ONSTACK : 0) : SS_DISABLE;
        sf.sf_uc.uc_mcontext.mc_onstack = (oonstack) ? 1 : 0;
        sf.sf_uc.uc_mcontext.mc_gs = rgs();
        bcopy(regs, &sf.sf_uc.uc_mcontext.mc_fs, sizeof(*regs));
        bzero(sf.sf_uc.uc_mcontext.mc_fpregs,
            sizeof(sf.sf_uc.uc_mcontext.mc_fpregs));
        bzero(sf.sf_uc.uc_mcontext.__spare__,
            sizeof(sf.sf_uc.uc_mcontext.__spare__));
        bzero(sf.sf_uc.__spare__, sizeof(sf.sf_uc.__spare__));

        /* Allocate space for the signal handler context. */
        if ((td->td_pflags & TDP_ALTSTACK) != 0 && !oonstack &&
            SIGISMEMBER(psp->ps_sigonstack, sig)) {
                sfp = (struct freebsd4_sigframe *)((uintptr_t)td->td_sigstk.ss_sp +
                    td->td_sigstk.ss_size - sizeof(struct freebsd4_sigframe));
#if defined(COMPAT_43)
                td->td_sigstk.ss_flags |= SS_ONSTACK;
#endif
        } else
                sfp = (struct freebsd4_sigframe *)regs->tf_esp - 1;

        /* Build the argument list for the signal handler. */
        sf.sf_signum = sig;
        sf.sf_ucontext = (register_t)&sfp->sf_uc;
        bzero(&sf.sf_si, sizeof(sf.sf_si));
        if (SIGISMEMBER(psp->ps_siginfo, sig)) {
                /* Signal handler installed with SA_SIGINFO. */
                sf.sf_siginfo = (register_t)&sfp->sf_si;
                sf.sf_ahu.sf_action = (__siginfohandler_t *)catcher;

                /* Fill in POSIX parts */
                sf.sf_si.si_signo = sig;
                sf.sf_si.si_code = ksi->ksi_code;
                sf.sf_si.si_addr = ksi->ksi_addr;
        } else {
                /* Old FreeBSD-style arguments. */
                sf.sf_siginfo = ksi->ksi_code;
                sf.sf_addr = (register_t)ksi->ksi_addr;
                sf.sf_ahu.sf_handler = catcher;
        }
        mtx_unlock(&psp->ps_mtx);
        PROC_UNLOCK(p);

        /*
         * If we're a vm86 process, we want to save the segment registers.
         * We also change eflags to be our emulated eflags, not the actual
         * eflags.
         */
        if (regs->tf_eflags & PSL_VM) {
                struct trapframe_vm86 *tf = (struct trapframe_vm86 *)regs;
                struct vm86_kernel *vm86 = &td->td_pcb->pcb_ext->ext_vm86;

                sf.sf_uc.uc_mcontext.mc_gs = tf->tf_vm86_gs;
                sf.sf_uc.uc_mcontext.mc_fs = tf->tf_vm86_fs;
                sf.sf_uc.uc_mcontext.mc_es = tf->tf_vm86_es;
                sf.sf_uc.uc_mcontext.mc_ds = tf->tf_vm86_ds;

                if (vm86->vm86_has_vme == 0)
                        sf.sf_uc.uc_mcontext.mc_eflags =
                            (tf->tf_eflags & ~(PSL_VIF | PSL_VIP)) |
                            (vm86->vm86_eflags & (PSL_VIF | PSL_VIP));

                /*
                 * Clear PSL_NT to inhibit T_TSSFLT faults on return from
                 * syscalls made by the signal handler.  This just avoids
                 * wasting time for our lazy fixup of such faults.  PSL_NT
                 * does nothing in vm86 mode, but vm86 programs can set it
                 * almost legitimately in probes for old cpu types.
                 */
                tf->tf_eflags &= ~(PSL_VM | PSL_NT | PSL_VIF | PSL_VIP);
        }

        /*
         * Copy the sigframe out to the user's stack.
         */
        if (copyout(&sf, sfp, sizeof(*sfp)) != 0) {
                PROC_LOCK(p);
                sigexit(td, SIGILL);
        }

        regs->tf_esp = (int)sfp;
        regs->tf_eip = PROC_SIGCODE(p) + szsigcode -
            szfreebsd4_sigcode;
        regs->tf_eflags &= ~(PSL_T | PSL_D);
        regs->tf_cs = _ucodesel;
        regs->tf_ds = _udatasel;
        regs->tf_es = _udatasel;
        regs->tf_fs = _udatasel;
        regs->tf_ss = _udatasel;
        PROC_LOCK(p);
        mtx_lock(&psp->ps_mtx);
}
#endif  /* COMPAT_FREEBSD4 */

void
sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
{
        struct sigframe sf, *sfp;
        struct proc *p;
        struct thread *td;
        struct sigacts *psp;
        char *sp;
        struct trapframe *regs;
        struct segment_descriptor *sdp;
        char *xfpusave;
        size_t xfpusave_len;
        int sig;
        int oonstack;

        td = curthread;
        p = td->td_proc;
        PROC_LOCK_ASSERT(p, MA_OWNED);
        sig = ksi->ksi_signo;
        psp = p->p_sigacts;
        mtx_assert(&psp->ps_mtx, MA_OWNED);
#ifdef COMPAT_FREEBSD4
        if (SIGISMEMBER(psp->ps_freebsd4, sig)) {
                freebsd4_sendsig(catcher, ksi, mask);
                return;
        }
#endif
#ifdef COMPAT_43
        if (SIGISMEMBER(psp->ps_osigset, sig)) {
                osendsig(catcher, ksi, mask);
                return;
        }
#endif
        regs = td->td_frame;
        oonstack = sigonstack(regs->tf_esp);

        if (cpu_max_ext_state_size > sizeof(union savefpu) && use_xsave) {
                xfpusave_len = cpu_max_ext_state_size - sizeof(union savefpu);
                xfpusave = __builtin_alloca(xfpusave_len);
        } else {
                xfpusave_len = 0;
                xfpusave = NULL;
        }

        /* Save user context. */
        bzero(&sf, sizeof(sf));
        sf.sf_uc.uc_sigmask = *mask;
        sf.sf_uc.uc_stack = td->td_sigstk;
        sf.sf_uc.uc_stack.ss_flags = (td->td_pflags & TDP_ALTSTACK)
            ? ((oonstack) ? SS_ONSTACK : 0) : SS_DISABLE;
        sf.sf_uc.uc_mcontext.mc_onstack = (oonstack) ? 1 : 0;
        sf.sf_uc.uc_mcontext.mc_gs = rgs();
        bcopy(regs, &sf.sf_uc.uc_mcontext.mc_fs, sizeof(*regs));
        sf.sf_uc.uc_mcontext.mc_len = sizeof(sf.sf_uc.uc_mcontext); /* magic */
        get_fpcontext(td, &sf.sf_uc.uc_mcontext, xfpusave, xfpusave_len);
        fpstate_drop(td);
        /*
         * Unconditionally fill the fsbase and gsbase into the mcontext.
         */
        sdp = &td->td_pcb->pcb_fsd;
        sf.sf_uc.uc_mcontext.mc_fsbase = sdp->sd_hibase << 24 |
            sdp->sd_lobase;
        sdp = &td->td_pcb->pcb_gsd;
        sf.sf_uc.uc_mcontext.mc_gsbase = sdp->sd_hibase << 24 |
            sdp->sd_lobase;
        bzero(sf.sf_uc.uc_mcontext.mc_spare2,
            sizeof(sf.sf_uc.uc_mcontext.mc_spare2));

        /* Allocate space for the signal handler context. */
        if ((td->td_pflags & TDP_ALTSTACK) != 0 && !oonstack &&
            SIGISMEMBER(psp->ps_sigonstack, sig)) {
                sp = (char *)td->td_sigstk.ss_sp + td->td_sigstk.ss_size;
#if defined(COMPAT_43)
                td->td_sigstk.ss_flags |= SS_ONSTACK;
#endif
        } else
                sp = (char *)regs->tf_esp - 128;
        if (xfpusave != NULL) {
                sp -= xfpusave_len;
                sp = (char *)((unsigned int)sp & ~0x3F);
                sf.sf_uc.uc_mcontext.mc_xfpustate = (register_t)sp;
        }
        sp -= sizeof(struct sigframe);

        /* Align to 16 bytes. */
        sfp = (struct sigframe *)((unsigned int)sp & ~0xF);

        /* Build the argument list for the signal handler. */
        sf.sf_signum = sig;
        sf.sf_ucontext = (register_t)&sfp->sf_uc;
        bzero(&sf.sf_si, sizeof(sf.sf_si));
        if (SIGISMEMBER(psp->ps_siginfo, sig)) {
                /* Signal handler installed with SA_SIGINFO. */
                sf.sf_siginfo = (register_t)&sfp->sf_si;
                sf.sf_ahu.sf_action = (__siginfohandler_t *)catcher;

                /* Fill in POSIX parts */
                sf.sf_si = ksi->ksi_info;
                sf.sf_si.si_signo = sig; /* maybe a translated signal */
        } else {
                /* Old FreeBSD-style arguments. */
                sf.sf_siginfo = ksi->ksi_code;
                sf.sf_addr = (register_t)ksi->ksi_addr;
                sf.sf_ahu.sf_handler = catcher;
        }
        mtx_unlock(&psp->ps_mtx);
        PROC_UNLOCK(p);

        /*
         * If we're a vm86 process, we want to save the segment registers.
         * We also change eflags to be our emulated eflags, not the actual
         * eflags.
         */
        if (regs->tf_eflags & PSL_VM) {
                struct trapframe_vm86 *tf = (struct trapframe_vm86 *)regs;
                struct vm86_kernel *vm86 = &td->td_pcb->pcb_ext->ext_vm86;

                sf.sf_uc.uc_mcontext.mc_gs = tf->tf_vm86_gs;
                sf.sf_uc.uc_mcontext.mc_fs = tf->tf_vm86_fs;
                sf.sf_uc.uc_mcontext.mc_es = tf->tf_vm86_es;
                sf.sf_uc.uc_mcontext.mc_ds = tf->tf_vm86_ds;

                if (vm86->vm86_has_vme == 0)
                        sf.sf_uc.uc_mcontext.mc_eflags =
                            (tf->tf_eflags & ~(PSL_VIF | PSL_VIP)) |
                            (vm86->vm86_eflags & (PSL_VIF | PSL_VIP));

                /*
                 * Clear PSL_NT to inhibit T_TSSFLT faults on return from
                 * syscalls made by the signal handler.  This just avoids
                 * wasting time for our lazy fixup of such faults.  PSL_NT
                 * does nothing in vm86 mode, but vm86 programs can set it
                 * almost legitimately in probes for old cpu types.
                 */
                tf->tf_eflags &= ~(PSL_VM | PSL_NT | PSL_VIF | PSL_VIP);
        }

        /*
         * Copy the sigframe out to the user's stack.
         */
        if (copyout(&sf, sfp, sizeof(*sfp)) != 0 ||
            (xfpusave != NULL && copyout(xfpusave,
            (void *)sf.sf_uc.uc_mcontext.mc_xfpustate, xfpusave_len)
            != 0)) {
                PROC_LOCK(p);
                sigexit(td, SIGILL);
        }

        regs->tf_esp = (int)sfp;
        regs->tf_eip = PROC_SIGCODE(p);
        if (regs->tf_eip == 0)
                regs->tf_eip = PROC_PS_STRINGS(p) - szsigcode;
        regs->tf_eflags &= ~(PSL_T | PSL_D);
        regs->tf_cs = _ucodesel;
        regs->tf_ds = _udatasel;
        regs->tf_es = _udatasel;
        regs->tf_fs = _udatasel;
        regs->tf_ss = _udatasel;
        PROC_LOCK(p);
        mtx_lock(&psp->ps_mtx);
}

/*
 * System call to cleanup state after a signal has been taken.  Reset
 * signal mask and stack state from context left by sendsig (above).
 * Return to previous pc and psl as specified by context left by
 * sendsig. Check carefully to make sure that the user has not
 * modified the state to gain improper privileges.
 */
#ifdef COMPAT_43
int
osigreturn(struct thread *td, struct osigreturn_args *uap)
{
        struct osigcontext sc;
        struct trapframe *regs;
        struct osigcontext *scp;
        int eflags, error;
        ksiginfo_t ksi;

        regs = td->td_frame;
        error = copyin(uap->sigcntxp, &sc, sizeof(sc));
        if (error != 0)
                return (error);
        scp = &sc;
        eflags = scp->sc_ps;
        if (eflags & PSL_VM) {
                struct trapframe_vm86 *tf = (struct trapframe_vm86 *)regs;
                struct vm86_kernel *vm86;

                /*
                 * if pcb_ext == 0 or vm86_inited == 0, the user hasn't
                 * set up the vm86 area, and we can't enter vm86 mode.
                 */
                if (td->td_pcb->pcb_ext == 0)
                        return (EINVAL);
                vm86 = &td->td_pcb->pcb_ext->ext_vm86;
                if (vm86->vm86_inited == 0)
                        return (EINVAL);

                /* Go back to user mode if both flags are set. */
                if ((eflags & PSL_VIP) && (eflags & PSL_VIF)) {
                        ksiginfo_init_trap(&ksi);
                        ksi.ksi_signo = SIGBUS;
                        ksi.ksi_code = BUS_OBJERR;
                        ksi.ksi_addr = (void *)regs->tf_eip;
                        trapsignal(td, &ksi);
                }

                if (vm86->vm86_has_vme) {
                        eflags = (tf->tf_eflags & ~VME_USERCHANGE) |
                            (eflags & VME_USERCHANGE) | PSL_VM;
                } else {
                        vm86->vm86_eflags = eflags;     /* save VIF, VIP */
                        eflags = (tf->tf_eflags & ~VM_USERCHANGE) |
                            (eflags & VM_USERCHANGE) | PSL_VM;
                }
                tf->tf_vm86_ds = scp->sc_ds;
                tf->tf_vm86_es = scp->sc_es;
                tf->tf_vm86_fs = scp->sc_fs;
                tf->tf_vm86_gs = scp->sc_gs;
                tf->tf_ds = _udatasel;
                tf->tf_es = _udatasel;
                tf->tf_fs = _udatasel;
        } else {
                /*
                 * Don't allow users to change privileged or reserved flags.
                 */
                if (!EFL_SECURE(eflags, regs->tf_eflags)) {
                        return (EINVAL);
                }

                /*
                 * Don't allow users to load a valid privileged %cs.  Let the
                 * hardware check for invalid selectors, excess privilege in
                 * other selectors, invalid %eip's and invalid %esp's.
                 */
                if (!CS_SECURE(scp->sc_cs)) {
                        ksiginfo_init_trap(&ksi);
                        ksi.ksi_signo = SIGBUS;
                        ksi.ksi_code = BUS_OBJERR;
                        ksi.ksi_trapno = T_PROTFLT;
                        ksi.ksi_addr = (void *)regs->tf_eip;
                        trapsignal(td, &ksi);
                        return (EINVAL);
                }
                regs->tf_ds = scp->sc_ds;
                regs->tf_es = scp->sc_es;
                regs->tf_fs = scp->sc_fs;
        }

        /* Restore remaining registers. */
        regs->tf_eax = scp->sc_eax;
        regs->tf_ebx = scp->sc_ebx;
        regs->tf_ecx = scp->sc_ecx;
        regs->tf_edx = scp->sc_edx;
        regs->tf_esi = scp->sc_esi;
        regs->tf_edi = scp->sc_edi;
        regs->tf_cs = scp->sc_cs;
        regs->tf_ss = scp->sc_ss;
        regs->tf_isp = scp->sc_isp;
        regs->tf_ebp = scp->sc_fp;
        regs->tf_esp = scp->sc_sp;
        regs->tf_eip = scp->sc_pc;
        regs->tf_eflags = eflags;
        regs->tf_trapno = T_RESERVED;

#if defined(COMPAT_43)
        if (scp->sc_onstack & 1)
                td->td_sigstk.ss_flags |= SS_ONSTACK;
        else
                td->td_sigstk.ss_flags &= ~SS_ONSTACK;
#endif
        kern_sigprocmask(td, SIG_SETMASK, (sigset_t *)&scp->sc_mask, NULL,
            SIGPROCMASK_OLD);
        return (EJUSTRETURN);
}
#endif /* COMPAT_43 */

#ifdef COMPAT_FREEBSD4
int
freebsd4_sigreturn(struct thread *td, struct freebsd4_sigreturn_args *uap)
{
        struct freebsd4_ucontext uc;
        struct trapframe *regs;
        struct freebsd4_ucontext *ucp;
        int cs, eflags, error;
        ksiginfo_t ksi;

        error = copyin(uap->sigcntxp, &uc, sizeof(uc));
        if (error != 0)
                return (error);
        ucp = &uc;
        regs = td->td_frame;
        eflags = ucp->uc_mcontext.mc_eflags;
        if (eflags & PSL_VM) {
                struct trapframe_vm86 *tf = (struct trapframe_vm86 *)regs;
                struct vm86_kernel *vm86;

                /*
                 * if pcb_ext == 0 or vm86_inited == 0, the user hasn't
                 * set up the vm86 area, and we can't enter vm86 mode.
                 */
                if (td->td_pcb->pcb_ext == 0)
                        return (EINVAL);
                vm86 = &td->td_pcb->pcb_ext->ext_vm86;
                if (vm86->vm86_inited == 0)
                        return (EINVAL);

                /* Go back to user mode if both flags are set. */
                if ((eflags & PSL_VIP) && (eflags & PSL_VIF)) {
                        ksiginfo_init_trap(&ksi);
                        ksi.ksi_signo = SIGBUS;
                        ksi.ksi_code = BUS_OBJERR;
                        ksi.ksi_addr = (void *)regs->tf_eip;
                        trapsignal(td, &ksi);
                }
                if (vm86->vm86_has_vme) {
                        eflags = (tf->tf_eflags & ~VME_USERCHANGE) |
                            (eflags & VME_USERCHANGE) | PSL_VM;
                } else {
                        vm86->vm86_eflags = eflags;     /* save VIF, VIP */
                        eflags = (tf->tf_eflags & ~VM_USERCHANGE) |
                            (eflags & VM_USERCHANGE) | PSL_VM;
                }
                bcopy(&ucp->uc_mcontext.mc_fs, tf, sizeof(struct trapframe));
                tf->tf_eflags = eflags;
                tf->tf_vm86_ds = tf->tf_ds;
                tf->tf_vm86_es = tf->tf_es;
                tf->tf_vm86_fs = tf->tf_fs;
                tf->tf_vm86_gs = ucp->uc_mcontext.mc_gs;
                tf->tf_ds = _udatasel;
                tf->tf_es = _udatasel;
                tf->tf_fs = _udatasel;
        } else {
                /*
                 * Don't allow users to change privileged or reserved flags.
                 */
                if (!EFL_SECURE(eflags, regs->tf_eflags)) {
                        uprintf(
                            "pid %d (%s): freebsd4_sigreturn eflags = 0x%x\n",
                            td->td_proc->p_pid, td->td_name, eflags);
                        return (EINVAL);
                }

                /*
                 * Don't allow users to load a valid privileged %cs.  Let the
                 * hardware check for invalid selectors, excess privilege in
                 * other selectors, invalid %eip's and invalid %esp's.
                 */
                cs = ucp->uc_mcontext.mc_cs;
                if (!CS_SECURE(cs)) {
                        uprintf("pid %d (%s): freebsd4_sigreturn cs = 0x%x\n",
                            td->td_proc->p_pid, td->td_name, cs);
                        ksiginfo_init_trap(&ksi);
                        ksi.ksi_signo = SIGBUS;
                        ksi.ksi_code = BUS_OBJERR;
                        ksi.ksi_trapno = T_PROTFLT;
                        ksi.ksi_addr = (void *)regs->tf_eip;
                        trapsignal(td, &ksi);
                        return (EINVAL);
                }

                bcopy(&ucp->uc_mcontext.mc_fs, regs, sizeof(*regs));
        }
        regs->tf_trapno = T_RESERVED;

#if defined(COMPAT_43)
        if (ucp->uc_mcontext.mc_onstack & 1)
                td->td_sigstk.ss_flags |= SS_ONSTACK;
        else
                td->td_sigstk.ss_flags &= ~SS_ONSTACK;
#endif
        kern_sigprocmask(td, SIG_SETMASK, &ucp->uc_sigmask, NULL, 0);
        return (EJUSTRETURN);
}
#endif  /* COMPAT_FREEBSD4 */

int
sys_sigreturn(struct thread *td, struct sigreturn_args *uap)
{
        ucontext_t uc;
        struct proc *p;
        struct trapframe *regs;
        ucontext_t *ucp;
        char *xfpustate;
        size_t xfpustate_len;
        int cs, eflags, error, ret;
        ksiginfo_t ksi;

        p = td->td_proc;

        error = copyin(uap->sigcntxp, &uc, sizeof(uc));
        if (error != 0)
                return (error);
        ucp = &uc;
        if ((ucp->uc_mcontext.mc_flags & ~_MC_FLAG_MASK) != 0) {
                uprintf("pid %d (%s): sigreturn mc_flags %x\n", p->p_pid,
                    td->td_name, ucp->uc_mcontext.mc_flags);
                return (EINVAL);
        }
        regs = td->td_frame;
        eflags = ucp->uc_mcontext.mc_eflags;
        if (eflags & PSL_VM) {
                struct trapframe_vm86 *tf = (struct trapframe_vm86 *)regs;
                struct vm86_kernel *vm86;

                /*
                 * if pcb_ext == 0 or vm86_inited == 0, the user hasn't
                 * set up the vm86 area, and we can't enter vm86 mode.
                 */
                if (td->td_pcb->pcb_ext == 0)
                        return (EINVAL);
                vm86 = &td->td_pcb->pcb_ext->ext_vm86;
                if (vm86->vm86_inited == 0)
                        return (EINVAL);

                /* Go back to user mode if both flags are set. */
                if ((eflags & PSL_VIP) && (eflags & PSL_VIF)) {
                        ksiginfo_init_trap(&ksi);
                        ksi.ksi_signo = SIGBUS;
                        ksi.ksi_code = BUS_OBJERR;
                        ksi.ksi_addr = (void *)regs->tf_eip;
                        trapsignal(td, &ksi);
                }

                if (vm86->vm86_has_vme) {
                        eflags = (tf->tf_eflags & ~VME_USERCHANGE) |
                            (eflags & VME_USERCHANGE) | PSL_VM;
                } else {
                        vm86->vm86_eflags = eflags;     /* save VIF, VIP */
                        eflags = (tf->tf_eflags & ~VM_USERCHANGE) |
                            (eflags & VM_USERCHANGE) | PSL_VM;
                }
                bcopy(&ucp->uc_mcontext.mc_fs, tf, sizeof(struct trapframe));
                tf->tf_eflags = eflags;
                tf->tf_vm86_ds = tf->tf_ds;
                tf->tf_vm86_es = tf->tf_es;
                tf->tf_vm86_fs = tf->tf_fs;
                tf->tf_vm86_gs = ucp->uc_mcontext.mc_gs;
                tf->tf_ds = _udatasel;
                tf->tf_es = _udatasel;
                tf->tf_fs = _udatasel;
        } else {
                /*
                 * Don't allow users to change privileged or reserved flags.
                 */
                if (!EFL_SECURE(eflags, regs->tf_eflags)) {
                        uprintf("pid %d (%s): sigreturn eflags = 0x%x\n",
                            td->td_proc->p_pid, td->td_name, eflags);
                        return (EINVAL);
                }

                /*
                 * Don't allow users to load a valid privileged %cs.  Let the
                 * hardware check for invalid selectors, excess privilege in
                 * other selectors, invalid %eip's and invalid %esp's.
                 */
                cs = ucp->uc_mcontext.mc_cs;
                if (!CS_SECURE(cs)) {
                        uprintf("pid %d (%s): sigreturn cs = 0x%x\n",
                            td->td_proc->p_pid, td->td_name, cs);
                        ksiginfo_init_trap(&ksi);
                        ksi.ksi_signo = SIGBUS;
                        ksi.ksi_code = BUS_OBJERR;
                        ksi.ksi_trapno = T_PROTFLT;
                        ksi.ksi_addr = (void *)regs->tf_eip;
                        trapsignal(td, &ksi);
                        return (EINVAL);
                }

                if ((uc.uc_mcontext.mc_flags & _MC_HASFPXSTATE) != 0) {
                        xfpustate_len = uc.uc_mcontext.mc_xfpustate_len;
                        if (xfpustate_len > cpu_max_ext_state_size -
                            sizeof(union savefpu)) {
                                uprintf(
                            "pid %d (%s): sigreturn xfpusave_len = 0x%zx\n",
                                    p->p_pid, td->td_name, xfpustate_len);
                                return (EINVAL);
                        }
                        xfpustate = __builtin_alloca(xfpustate_len);
                        error = copyin(
                            (const void *)uc.uc_mcontext.mc_xfpustate,
                            xfpustate, xfpustate_len);
                        if (error != 0) {
                                uprintf(
        "pid %d (%s): sigreturn copying xfpustate failed\n",
                                    p->p_pid, td->td_name);
                                return (error);
                        }
                } else {
                        xfpustate = NULL;
                        xfpustate_len = 0;
                }
                ret = set_fpcontext(td, &ucp->uc_mcontext, xfpustate,
                    xfpustate_len);
                if (ret != 0)
                        return (ret);
                bcopy(&ucp->uc_mcontext.mc_fs, regs, sizeof(*regs));
        }
        regs->tf_trapno = T_RESERVED;

#if defined(COMPAT_43)
        if (ucp->uc_mcontext.mc_onstack & 1)
                td->td_sigstk.ss_flags |= SS_ONSTACK;
        else
                td->td_sigstk.ss_flags &= ~SS_ONSTACK;
#endif

        kern_sigprocmask(td, SIG_SETMASK, &ucp->uc_sigmask, NULL, 0);
        return (EJUSTRETURN);
}

/*
 * Reset the hardware debug registers if they were in use.
 * They won't have any meaning for the newly exec'd process.
 */
void
x86_clear_dbregs(struct pcb *pcb)
{
        if ((pcb->pcb_flags & PCB_DBREGS) == 0)
                return;

        pcb->pcb_dr0 = 0;
        pcb->pcb_dr1 = 0;
        pcb->pcb_dr2 = 0;
        pcb->pcb_dr3 = 0;
        pcb->pcb_dr6 = 0;
        pcb->pcb_dr7 = 0;

        if (pcb == curpcb) {
                /*
                 * Clear the debug registers on the running CPU,
                 * otherwise they will end up affecting the next
                 * process we switch to.
                 */
                reset_dbregs();
        }
        pcb->pcb_flags &= ~PCB_DBREGS;
}

#ifdef COMPAT_43
static void
setup_priv_lcall_gate(struct proc *p)
{
        struct i386_ldt_args uap;
        union descriptor desc;
        u_int lcall_addr;

        bzero(&uap, sizeof(uap));
        uap.start = 0;
        uap.num = 1;
        lcall_addr = p->p_sysent->sv_psstrings - sz_lcall_tramp;
        bzero(&desc, sizeof(desc));
        desc.sd.sd_type = SDT_MEMERA;
        desc.sd.sd_dpl = SEL_UPL;
        desc.sd.sd_p = 1;
        desc.sd.sd_def32 = 1;
        desc.sd.sd_gran = 1;
        desc.sd.sd_lolimit = 0xffff;
        desc.sd.sd_hilimit = 0xf;
        desc.sd.sd_lobase = lcall_addr;
        desc.sd.sd_hibase = lcall_addr >> 24;
        i386_set_ldt(curthread, &uap, &desc);
}
#endif

/*
 * Reset registers to default values on exec.
 */
void
exec_setregs(struct thread *td, struct image_params *imgp, uintptr_t stack)
{
        struct trapframe *regs;
        struct pcb *pcb;
        register_t saved_eflags;

        regs = td->td_frame;
        pcb = td->td_pcb;

        /* Reset pc->pcb_gs and %gs before possibly invalidating it. */
        pcb->pcb_gs = _udatasel;
        load_gs(_udatasel);

        mtx_lock_spin(&dt_lock);
        if (td->td_proc->p_md.md_ldt != NULL)
                user_ldt_free(td);
        else
                mtx_unlock_spin(&dt_lock);

#ifdef COMPAT_43
        if (td->td_proc->p_sysent->sv_psstrings !=
            elf32_freebsd_sysvec.sv_psstrings)
                setup_priv_lcall_gate(td->td_proc);
#endif

        /*
         * Reset the fs and gs bases.  The values from the old address
         * space do not make sense for the new program.  In particular,
         * gsbase might be the TLS base for the old program but the new
         * program has no TLS now.
         */
        set_fsbase(td, 0);
        set_gsbase(td, 0);

        /* Make sure edx is 0x0 on entry. Linux binaries depend on it. */
        saved_eflags = regs->tf_eflags & PSL_T;
        bzero((char *)regs, sizeof(struct trapframe));
        regs->tf_eip = imgp->entry_addr;
        regs->tf_esp = stack;
        regs->tf_eflags = PSL_USER | saved_eflags;
        regs->tf_ss = _udatasel;
        regs->tf_ds = _udatasel;
        regs->tf_es = _udatasel;
        regs->tf_fs = _udatasel;
        regs->tf_cs = _ucodesel;

        /* PS_STRINGS value for BSD/OS binaries.  It is 0 for non-BSD/OS. */
        regs->tf_ebx = (register_t)imgp->ps_strings;

        x86_clear_dbregs(pcb);

        pcb->pcb_initial_npxcw = __INITIAL_NPXCW__;

        /*
         * Drop the FP state if we hold it, so that the process gets a
         * clean FP state if it uses the FPU again.
         */
        fpstate_drop(td);
}

int
fill_regs(struct thread *td, struct reg *regs)
{
        struct pcb *pcb;
        struct trapframe *tp;

        tp = td->td_frame;
        pcb = td->td_pcb;
        regs->r_gs = pcb->pcb_gs;
        return (fill_frame_regs(tp, regs));
}

int
fill_frame_regs(struct trapframe *tp, struct reg *regs)
{

        regs->r_fs = tp->tf_fs;
        regs->r_es = tp->tf_es;
        regs->r_ds = tp->tf_ds;
        regs->r_edi = tp->tf_edi;
        regs->r_esi = tp->tf_esi;
        regs->r_ebp = tp->tf_ebp;
        regs->r_ebx = tp->tf_ebx;
        regs->r_edx = tp->tf_edx;
        regs->r_ecx = tp->tf_ecx;
        regs->r_eax = tp->tf_eax;
        regs->r_eip = tp->tf_eip;
        regs->r_cs = tp->tf_cs;
        regs->r_eflags = tp->tf_eflags;
        regs->r_esp = tp->tf_esp;
        regs->r_ss = tp->tf_ss;
        regs->r_err = 0;
        regs->r_trapno = 0;
        return (0);
}

int
set_regs(struct thread *td, struct reg *regs)
{
        struct pcb *pcb;
        struct trapframe *tp;

        tp = td->td_frame;
        if (!EFL_SECURE(regs->r_eflags, tp->tf_eflags) ||
            !CS_SECURE(regs->r_cs))
                return (EINVAL);
        pcb = td->td_pcb;
        tp->tf_fs = regs->r_fs;
        tp->tf_es = regs->r_es;
        tp->tf_ds = regs->r_ds;
        tp->tf_edi = regs->r_edi;
        tp->tf_esi = regs->r_esi;
        tp->tf_ebp = regs->r_ebp;
        tp->tf_ebx = regs->r_ebx;
        tp->tf_edx = regs->r_edx;
        tp->tf_ecx = regs->r_ecx;
        tp->tf_eax = regs->r_eax;
        tp->tf_eip = regs->r_eip;
        tp->tf_cs = regs->r_cs;
        tp->tf_eflags = regs->r_eflags;
        tp->tf_esp = regs->r_esp;
        tp->tf_ss = regs->r_ss;
        pcb->pcb_gs = regs->r_gs;
        return (0);
}

int
fill_fpregs(struct thread *td, struct fpreg *fpregs)
{

        KASSERT(td == curthread || TD_IS_SUSPENDED(td) ||
            P_SHOULDSTOP(td->td_proc),
            ("not suspended thread %p", td));
        npxgetregs(td);
        if (cpu_fxsr)
                npx_fill_fpregs_xmm(&get_pcb_user_save_td(td)->sv_xmm,
                    (struct save87 *)fpregs);
        else
                bcopy(&get_pcb_user_save_td(td)->sv_87, fpregs,
                    sizeof(*fpregs));
        return (0);
}

int
set_fpregs(struct thread *td, struct fpreg *fpregs)
{

        critical_enter();
        if (cpu_fxsr)
                npx_set_fpregs_xmm((struct save87 *)fpregs,
                    &get_pcb_user_save_td(td)->sv_xmm);
        else
                bcopy(fpregs, &get_pcb_user_save_td(td)->sv_87,
                    sizeof(*fpregs));
        npxuserinited(td);
        critical_exit();
        return (0);
}

/*
 * Get machine context.
 */
int
get_mcontext(struct thread *td, mcontext_t *mcp, int flags)
{
        struct trapframe *tp;
        struct segment_descriptor *sdp;

        tp = td->td_frame;

        PROC_LOCK(curthread->td_proc);
        mcp->mc_onstack = sigonstack(tp->tf_esp);
        PROC_UNLOCK(curthread->td_proc);
        mcp->mc_gs = td->td_pcb->pcb_gs;
        mcp->mc_fs = tp->tf_fs;
        mcp->mc_es = tp->tf_es;
        mcp->mc_ds = tp->tf_ds;
        mcp->mc_edi = tp->tf_edi;
        mcp->mc_esi = tp->tf_esi;
        mcp->mc_ebp = tp->tf_ebp;
        mcp->mc_isp = tp->tf_isp;
        mcp->mc_eflags = tp->tf_eflags;
        if (flags & GET_MC_CLEAR_RET) {
                mcp->mc_eax = 0;
                mcp->mc_edx = 0;
                mcp->mc_eflags &= ~PSL_C;
        } else {
                mcp->mc_eax = tp->tf_eax;
                mcp->mc_edx = tp->tf_edx;
        }
        mcp->mc_ebx = tp->tf_ebx;
        mcp->mc_ecx = tp->tf_ecx;
        mcp->mc_eip = tp->tf_eip;
        mcp->mc_cs = tp->tf_cs;
        mcp->mc_esp = tp->tf_esp;
        mcp->mc_ss = tp->tf_ss;
        mcp->mc_len = sizeof(*mcp);
        get_fpcontext(td, mcp, NULL, 0);
        sdp = &td->td_pcb->pcb_fsd;
        mcp->mc_fsbase = sdp->sd_hibase << 24 | sdp->sd_lobase;
        sdp = &td->td_pcb->pcb_gsd;
        mcp->mc_gsbase = sdp->sd_hibase << 24 | sdp->sd_lobase;
        mcp->mc_flags = 0;
        mcp->mc_xfpustate = 0;
        mcp->mc_xfpustate_len = 0;
        bzero(mcp->mc_spare2, sizeof(mcp->mc_spare2));
        return (0);
}

/*
 * Set machine context.
 *
 * However, we don't set any but the user modifiable flags, and we won't
 * touch the cs selector.
 */
int
set_mcontext(struct thread *td, mcontext_t *mcp)
{
        struct trapframe *tp;
        char *xfpustate;
        int eflags, ret;

        tp = td->td_frame;
        if (mcp->mc_len != sizeof(*mcp) ||
            (mcp->mc_flags & ~_MC_FLAG_MASK) != 0)
                return (EINVAL);
        eflags = (mcp->mc_eflags & PSL_USERCHANGE) |
            (tp->tf_eflags & ~PSL_USERCHANGE);
        if (mcp->mc_flags & _MC_HASFPXSTATE) {
                if (mcp->mc_xfpustate_len > cpu_max_ext_state_size -
                    sizeof(union savefpu))
                        return (EINVAL);
                xfpustate = __builtin_alloca(mcp->mc_xfpustate_len);
                ret = copyin((void *)mcp->mc_xfpustate, xfpustate,
                    mcp->mc_xfpustate_len);
                if (ret != 0)
                        return (ret);
        } else
                xfpustate = NULL;
        ret = set_fpcontext(td, mcp, xfpustate, mcp->mc_xfpustate_len);
        if (ret != 0)
                return (ret);
        tp->tf_fs = mcp->mc_fs;
        tp->tf_es = mcp->mc_es;
        tp->tf_ds = mcp->mc_ds;
        tp->tf_edi = mcp->mc_edi;
        tp->tf_esi = mcp->mc_esi;
        tp->tf_ebp = mcp->mc_ebp;
        tp->tf_ebx = mcp->mc_ebx;
        tp->tf_edx = mcp->mc_edx;
        tp->tf_ecx = mcp->mc_ecx;
        tp->tf_eax = mcp->mc_eax;
        tp->tf_eip = mcp->mc_eip;
        tp->tf_eflags = eflags;
        tp->tf_esp = mcp->mc_esp;
        tp->tf_ss = mcp->mc_ss;
        td->td_pcb->pcb_gs = mcp->mc_gs;
        return (0);
}

static void
get_fpcontext(struct thread *td, mcontext_t *mcp, char *xfpusave,
    size_t xfpusave_len)
{
        size_t max_len, len;

        mcp->mc_ownedfp = npxgetregs(td);
        bcopy(get_pcb_user_save_td(td), &mcp->mc_fpstate[0],
            sizeof(mcp->mc_fpstate));
        mcp->mc_fpformat = npxformat();
        if (!use_xsave || xfpusave_len == 0)
                return;
        max_len = cpu_max_ext_state_size - sizeof(union savefpu);
        len = xfpusave_len;
        if (len > max_len) {
                len = max_len;
                bzero(xfpusave + max_len, len - max_len);
        }
        mcp->mc_flags |= _MC_HASFPXSTATE;
        mcp->mc_xfpustate_len = len;
        bcopy(get_pcb_user_save_td(td) + 1, xfpusave, len);
}

static int
set_fpcontext(struct thread *td, mcontext_t *mcp, char *xfpustate,
    size_t xfpustate_len)
{
        int error;

        if (mcp->mc_fpformat == _MC_FPFMT_NODEV)
                return (0);
        else if (mcp->mc_fpformat != _MC_FPFMT_387 &&
            mcp->mc_fpformat != _MC_FPFMT_XMM)
                return (EINVAL);
        else if (mcp->mc_ownedfp == _MC_FPOWNED_NONE) {
                /* We don't care what state is left in the FPU or PCB. */
                fpstate_drop(td);
                error = 0;
        } else if (mcp->mc_ownedfp == _MC_FPOWNED_FPU ||
            mcp->mc_ownedfp == _MC_FPOWNED_PCB) {
                error = npxsetregs(td, (union savefpu *)&mcp->mc_fpstate,
                    xfpustate, xfpustate_len);
        } else
                return (EINVAL);
        return (error);
}

static void
fpstate_drop(struct thread *td)
{

        KASSERT(PCB_USER_FPU(td->td_pcb), ("fpstate_drop: kernel-owned fpu"));
        critical_enter();
        if (PCPU_GET(fpcurthread) == td)
                npxdrop();
        /*
         * XXX force a full drop of the npx.  The above only drops it if we
         * owned it.  npxgetregs() has the same bug in the !cpu_fxsr case.
         *
         * XXX I don't much like npxgetregs()'s semantics of doing a full
         * drop.  Dropping only to the pcb matches fnsave's behaviour.
         * We only need to drop to !PCB_INITDONE in sendsig().  But
         * sendsig() is the only caller of npxgetregs()... perhaps we just
         * have too many layers.
         */
        curthread->td_pcb->pcb_flags &= ~(PCB_NPXINITDONE |
            PCB_NPXUSERINITDONE);
        critical_exit();
}

int
fill_dbregs(struct thread *td, struct dbreg *dbregs)
{
        struct pcb *pcb;

        if (td == NULL) {
                dbregs->dr[0] = rdr0();
                dbregs->dr[1] = rdr1();
                dbregs->dr[2] = rdr2();
                dbregs->dr[3] = rdr3();
                dbregs->dr[6] = rdr6();
                dbregs->dr[7] = rdr7();
        } else {
                pcb = td->td_pcb;
                dbregs->dr[0] = pcb->pcb_dr0;
                dbregs->dr[1] = pcb->pcb_dr1;
                dbregs->dr[2] = pcb->pcb_dr2;
                dbregs->dr[3] = pcb->pcb_dr3;
                dbregs->dr[6] = pcb->pcb_dr6;
                dbregs->dr[7] = pcb->pcb_dr7;
        }
        dbregs->dr[4] = 0;
        dbregs->dr[5] = 0;
        return (0);
}

int
set_dbregs(struct thread *td, struct dbreg *dbregs)
{
        struct pcb *pcb;
        int i;

        if (td == NULL) {
                load_dr0(dbregs->dr[0]);
                load_dr1(dbregs->dr[1]);
                load_dr2(dbregs->dr[2]);
                load_dr3(dbregs->dr[3]);
                load_dr6(dbregs->dr[6]);
                load_dr7(dbregs->dr[7]);
        } else {
                /*
                 * Don't let an illegal value for dr7 get set.  Specifically,
                 * check for undefined settings.  Setting these bit patterns
                 * result in undefined behaviour and can lead to an unexpected
                 * TRCTRAP.
                 */
                for (i = 0; i < 4; i++) {
                        if (DBREG_DR7_ACCESS(dbregs->dr[7], i) == 0x02)
                                return (EINVAL);
                        if (DBREG_DR7_LEN(dbregs->dr[7], i) == 0x02)
                                return (EINVAL);
                }

                pcb = td->td_pcb;

                /*
                 * Don't let a process set a breakpoint that is not within the
                 * process's address space.  If a process could do this, it
                 * could halt the system by setting a breakpoint in the kernel
                 * (if ddb was enabled).  Thus, we need to check to make sure
                 * that no breakpoints are being enabled for addresses outside
                 * process's address space.
                 *
                 * XXX - what about when the watched area of the user's
                 * address space is written into from within the kernel
                 * ... wouldn't that still cause a breakpoint to be generated
                 * from within kernel mode?
                 */

                if (DBREG_DR7_ENABLED(dbregs->dr[7], 0)) {
                        /* dr0 is enabled */
                        if (dbregs->dr[0] >= VM_MAXUSER_ADDRESS)
                                return (EINVAL);
                }

                if (DBREG_DR7_ENABLED(dbregs->dr[7], 1)) {
                        /* dr1 is enabled */
                        if (dbregs->dr[1] >= VM_MAXUSER_ADDRESS)
                                return (EINVAL);
                }

                if (DBREG_DR7_ENABLED(dbregs->dr[7], 2)) {
                        /* dr2 is enabled */
                        if (dbregs->dr[2] >= VM_MAXUSER_ADDRESS)
                                return (EINVAL);
                }

                if (DBREG_DR7_ENABLED(dbregs->dr[7], 3)) {
                        /* dr3 is enabled */
                        if (dbregs->dr[3] >= VM_MAXUSER_ADDRESS)
                                return (EINVAL);
                }

                pcb->pcb_dr0 = dbregs->dr[0];
                pcb->pcb_dr1 = dbregs->dr[1];
                pcb->pcb_dr2 = dbregs->dr[2];
                pcb->pcb_dr3 = dbregs->dr[3];
                pcb->pcb_dr6 = dbregs->dr[6];
                pcb->pcb_dr7 = dbregs->dr[7];

                pcb->pcb_flags |= PCB_DBREGS;
        }

        return (0);
}

/*
 * Return > 0 if a hardware breakpoint has been hit, and the
 * breakpoint was in user space.  Return 0, otherwise.
 */
int
user_dbreg_trap(register_t dr6)
{
        u_int32_t dr7;
        u_int32_t bp;       /* breakpoint bits extracted from dr6 */
        int nbp;            /* number of breakpoints that triggered */
        caddr_t addr[4];    /* breakpoint addresses */
        int i;

        bp = dr6 & DBREG_DR6_BMASK;
        if (bp == 0) {
                /*
                 * None of the breakpoint bits are set meaning this
                 * trap was not caused by any of the debug registers
                 */
                return (0);
        }

        dr7 = rdr7();
        if ((dr7 & 0x000000ff) == 0) {
                /*
                 * all GE and LE bits in the dr7 register are zero,
                 * thus the trap couldn't have been caused by the
                 * hardware debug registers
                 */
                return (0);
        }

        nbp = 0;

        /*
         * at least one of the breakpoints were hit, check to see
         * which ones and if any of them are user space addresses
         */

        if (bp & 0x01) {
                addr[nbp++] = (caddr_t)rdr0();
        }
        if (bp & 0x02) {
                addr[nbp++] = (caddr_t)rdr1();
        }
        if (bp & 0x04) {
                addr[nbp++] = (caddr_t)rdr2();
        }
        if (bp & 0x08) {
                addr[nbp++] = (caddr_t)rdr3();
        }

        for (i = 0; i < nbp; i++) {
                if (addr[i] < (caddr_t)VM_MAXUSER_ADDRESS) {
                        /*
                         * addr[i] is in user space
                         */
                        return (nbp);
                }
        }

        /*
         * None of the breakpoints are in user space.
         */
        return (0);
}