xref: /freebsd/sys/i386/i386/exec_machdep.c (revision 29363fb4)

/*-
 * 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);
}