More multi-threaded support for virtualization. Move the save context

[dragonfly.git] / sys / platform / vkernel / i386 / cpu_regs.c

/*-
 * Copyright (c) 1992 Terrence R. Lambert.
 * Copyright (C) 1994, David Greenman
 * Copyright (c) 1982, 1987, 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * 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.
 *
 *      from: @(#)machdep.c     7.4 (Berkeley) 6/3/91
 * $FreeBSD: src/sys/i386/i386/machdep.c,v 1.385.2.30 2003/05/31 08:48:05 alc Exp $
 * $DragonFly: src/sys/platform/vkernel/i386/cpu_regs.c,v 1.17 2007/07/01 01:11:36 dillon Exp $
 */

#include "use_ether.h"
#include "use_npx.h"
#include "use_isa.h"
#include "opt_atalk.h"
#include "opt_compat.h"
#include "opt_ddb.h"
#include "opt_directio.h"
#include "opt_inet.h"
#include "opt_ipx.h"
#include "opt_msgbuf.h"
#include "opt_swap.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/signalvar.h>
#include <sys/kernel.h>
#include <sys/linker.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/buf.h>
#include <sys/reboot.h>
#include <sys/mbuf.h>
#include <sys/msgbuf.h>
#include <sys/sysent.h>
#include <sys/sysctl.h>
#include <sys/vmmeter.h>
#include <sys/bus.h>
#include <sys/upcall.h>
#include <sys/usched.h>
#include <sys/reg.h>

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

#include <sys/thread2.h>

#include <sys/user.h>
#include <sys/exec.h>
#include <sys/cons.h>

#include <ddb/ddb.h>

#include <machine/cpu.h>
#include <machine/clock.h>
#include <machine/specialreg.h>
#include <machine/md_var.h>
#include <machine/pcb_ext.h>            /* pcb.h included via sys/user.h */
#include <machine/globaldata.h>         /* CPU_prvspace */
#include <machine/smp.h>
#ifdef PERFMON
#include <machine/perfmon.h>
#endif
#include <machine/cputypes.h>

#include <bus/isa/rtc.h>
#include <machine/vm86.h>
#include <sys/random.h>
#include <sys/ptrace.h>
#include <machine/sigframe.h>

extern void dblfault_handler (void);

#ifndef CPU_DISABLE_SSE
static void set_fpregs_xmm (struct save87 *, struct savexmm *);
static void fill_fpregs_xmm (struct savexmm *, struct save87 *);
#endif /* CPU_DISABLE_SSE */
#ifdef DIRECTIO
extern void ffs_rawread_setup(void);
#endif /* DIRECTIO */

#ifdef SMP
int64_t tsc_offsets[MAXCPU];
#else
int64_t tsc_offsets[1];
#endif

#if defined(SWTCH_OPTIM_STATS)
extern int swtch_optim_stats;
SYSCTL_INT(_debug, OID_AUTO, swtch_optim_stats,
        CTLFLAG_RD, &swtch_optim_stats, 0, "");
SYSCTL_INT(_debug, OID_AUTO, tlb_flush_count,
        CTLFLAG_RD, &tlb_flush_count, 0, "");
#endif

static int
sysctl_hw_physmem(SYSCTL_HANDLER_ARGS)
{
        int error = sysctl_handle_int(oidp, 0, ctob((int)Maxmem), req);
        return (error);
}

SYSCTL_PROC(_hw, HW_PHYSMEM, physmem, CTLTYPE_INT|CTLFLAG_RD,
        0, 0, sysctl_hw_physmem, "IU", "");

static int
sysctl_hw_usermem(SYSCTL_HANDLER_ARGS)
{
        int error = sysctl_handle_int(oidp, 0,
                ctob((int)Maxmem - vmstats.v_wire_count), req);
        return (error);
}

SYSCTL_PROC(_hw, HW_USERMEM, usermem, CTLTYPE_INT|CTLFLAG_RD,
        0, 0, sysctl_hw_usermem, "IU", "");

SYSCTL_ULONG(_hw, OID_AUTO, availpages, CTLFLAG_RD, &Maxmem, NULL, "");

#if 0

static int
sysctl_machdep_msgbuf(SYSCTL_HANDLER_ARGS)
{
        int error;

        /* Unwind the buffer, so that it's linear (possibly starting with
         * some initial nulls).
         */
        error=sysctl_handle_opaque(oidp,msgbufp->msg_ptr+msgbufp->msg_bufr,
                msgbufp->msg_size-msgbufp->msg_bufr,req);
        if(error) return(error);
        if(msgbufp->msg_bufr>0) {
                error=sysctl_handle_opaque(oidp,msgbufp->msg_ptr,
                        msgbufp->msg_bufr,req);
        }
        return(error);
}

SYSCTL_PROC(_machdep, OID_AUTO, msgbuf, CTLTYPE_STRING|CTLFLAG_RD,
        0, 0, sysctl_machdep_msgbuf, "A","Contents of kernel message buffer");

static int msgbuf_clear;

static int
sysctl_machdep_msgbuf_clear(SYSCTL_HANDLER_ARGS)
{
        int error;
        error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2,
                req);
        if (!error && req->newptr) {
                /* Clear the buffer and reset write pointer */
                bzero(msgbufp->msg_ptr,msgbufp->msg_size);
                msgbufp->msg_bufr=msgbufp->msg_bufx=0;
                msgbuf_clear=0;
        }
        return (error);
}

SYSCTL_PROC(_machdep, OID_AUTO, msgbuf_clear, CTLTYPE_INT|CTLFLAG_RW,
        &msgbuf_clear, 0, sysctl_machdep_msgbuf_clear, "I",
        "Clear kernel message buffer");

#endif

/*
 * Send an interrupt to process.
 *
 * Stack is set up to allow sigcode stored
 * at top to call routine, followed by kcall
 * to sigreturn routine below.  After sigreturn
 * resets the signal mask, the stack, and the
 * frame pointer, it returns to the user
 * specified pc, psl.
 */
void
sendsig(sig_t catcher, int sig, sigset_t *mask, u_long code)
{
        struct lwp *lp = curthread->td_lwp;
        struct proc *p = lp->lwp_proc;
        struct trapframe *regs;
        struct sigacts *psp = p->p_sigacts;
        struct sigframe sf, *sfp;
        int oonstack;

        regs = lp->lwp_md.md_regs;
        oonstack = (lp->lwp_sigstk.ss_flags & SS_ONSTACK) ? 1 : 0;

        /* save user context */
        bzero(&sf, sizeof(struct sigframe));
        sf.sf_uc.uc_sigmask = *mask;
        sf.sf_uc.uc_stack = lp->lwp_sigstk;
        sf.sf_uc.uc_mcontext.mc_onstack = oonstack;
        bcopy(regs, &sf.sf_uc.uc_mcontext.mc_gs, sizeof(struct trapframe));

        /* make the size of the saved context visible to userland */
        sf.sf_uc.uc_mcontext.mc_len = sizeof(sf.sf_uc.uc_mcontext); 

        /* save mailbox pending state for syscall interlock semantics */
        if (p->p_flag & P_MAILBOX)
                sf.sf_uc.uc_mcontext.mc_xflags |= PGEX_MAILBOX;


        /* Allocate and validate space for the signal handler context. */
        if ((lp->lwp_flag & LWP_ALTSTACK) != 0 && !oonstack &&
            SIGISMEMBER(psp->ps_sigonstack, sig)) {
                sfp = (struct sigframe *)(lp->lwp_sigstk.ss_sp +
                    lp->lwp_sigstk.ss_size - sizeof(struct sigframe));
                lp->lwp_sigstk.ss_flags |= SS_ONSTACK;
        }
        else
                sfp = (struct sigframe *)regs->tf_esp - 1;

        /* Translate the signal is appropriate */
        if (p->p_sysent->sv_sigtbl) {
                if (sig <= p->p_sysent->sv_sigsize)
                        sig = p->p_sysent->sv_sigtbl[_SIG_IDX(sig)];
        }

        /* Build the argument list for the signal handler. */
        sf.sf_signum = sig;
        sf.sf_ucontext = (register_t)&sfp->sf_uc;
        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 siginfo structure */
                sf.sf_si.si_signo = sig;
                sf.sf_si.si_code = code;
                sf.sf_si.si_addr = (void*)regs->tf_err;
        }
        else {
                /* Old FreeBSD-style arguments. */
                sf.sf_siginfo = code;
                sf.sf_addr = regs->tf_err;
                sf.sf_ahu.sf_handler = catcher;
        }

#if 0
        /*
         * 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 = &lp->lwp_thread->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);
        }
#endif

        /*
         * Copy the sigframe out to the user's stack.
         */
        if (copyout(&sf, sfp, sizeof(struct sigframe)) != 0) {
                /*
                 * Something is wrong with the stack pointer.
                 * ...Kill the process.
                 */
                sigexit(p, SIGILL);
        }

        regs->tf_esp = (int)sfp;
        regs->tf_eip = PS_STRINGS - *(p->p_sysent->sv_szsigcode);
        regs->tf_eflags &= ~PSL_T;
        regs->tf_cs = _ucodesel;
        regs->tf_ds = _udatasel;
        regs->tf_es = _udatasel;
        if (regs->tf_trapno == T_PROTFLT) {
                regs->tf_fs = _udatasel;
                regs->tf_gs = _udatasel;
        }
        regs->tf_ss = _udatasel;
}

/*
 * Sanitize the trapframe for a virtual kernel passing control to a custom
 * VM context.
 *
 * Allow userland to set or maintain PSL_RF, the resume flag.  This flag
 * basically controls whether the return PC should skip the first instruction
 * (as in an explicit system call) or re-execute it (as in an exception).
 */
int
cpu_sanitize_frame(struct trapframe *frame)
{
        frame->tf_cs = _ucodesel;
        frame->tf_ds = _udatasel;
        frame->tf_es = _udatasel;
#if 0
        frame->tf_fs = _udatasel;
        frame->tf_gs = _udatasel;
#endif
        frame->tf_ss = _udatasel;
        frame->tf_eflags &= (PSL_RF | PSL_USERCHANGE);
        frame->tf_eflags |= PSL_RESERVED_DEFAULT | PSL_I;
        return(0);
}

int
cpu_sanitize_tls(struct savetls *tls)
{
         struct segment_descriptor *desc;
         int i;

         for (i = 0; i < NGTLS; ++i) {
                desc = &tls->tls[i];
                if (desc->sd_dpl == 0 && desc->sd_type == 0)
                        continue;
                if (desc->sd_def32 == 0)
                        return(ENXIO);
                if (desc->sd_type != SDT_MEMRWA)
                        return(ENXIO);
                if (desc->sd_dpl != SEL_UPL)
                        return(ENXIO);
                if (desc->sd_xx != 0 || desc->sd_p != 1)
                        return(ENXIO);
         }
         return(0);
}

/*
 * sigreturn(ucontext_t *sigcntxp)
 *
 * 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.
 */
#define EFL_SECURE(ef, oef)     ((((ef) ^ (oef)) & ~PSL_USERCHANGE) == 0)
#define CS_SECURE(cs)           (ISPL(cs) == SEL_UPL)

int
sys_sigreturn(struct sigreturn_args *uap)
{
        struct lwp *lp = curthread->td_lwp;
        struct proc *p = lp->lwp_proc;
        struct trapframe *regs;
        ucontext_t ucp;
        int cs;
        int eflags;
        int error;

        error = copyin(uap->sigcntxp, &ucp, sizeof(ucp));
        if (error)
                return (error);

        regs = lp->lwp_md.md_regs;
        eflags = ucp.uc_mcontext.mc_eflags;

#if 0
        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 (lp->lwp_thread->td_pcb->pcb_ext == 0)
                        return (EINVAL);
                vm86 = &lp->lwp_thread->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))
                        trapsignal(lp->lwp_proc, SIGBUS, 0);

                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_gs, 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 = tf->tf_gs;
                tf->tf_ds = _udatasel;
                tf->tf_es = _udatasel;
#if 0
                tf->tf_fs = _udatasel;
                tf->tf_gs = _udatasel;
#endif
        } else 
#endif
        {
                /*
                 * Don't allow users to change privileged or reserved flags.
                 */
                /*
                 * XXX do allow users to change the privileged flag PSL_RF.
                 * The cpu sets PSL_RF in tf_eflags for faults.  Debuggers
                 * should sometimes set it there too.  tf_eflags is kept in
                 * the signal context during signal handling and there is no
                 * other place to remember it, so the PSL_RF bit may be
                 * corrupted by the signal handler without us knowing.
                 * Corruption of the PSL_RF bit at worst causes one more or
                 * one less debugger trap, so allowing it is fairly harmless.
                 */
                if (!EFL_SECURE(eflags & ~PSL_RF, regs->tf_eflags & ~PSL_RF)) {
                        kprintf("sigreturn: eflags = 0x%x\n", 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)) {
                        kprintf("sigreturn: cs = 0x%x\n", cs);
                        trapsignal(lp, SIGBUS, T_PROTFLT);
                        return(EINVAL);
                }
                bcopy(&ucp.uc_mcontext.mc_gs, regs, sizeof(struct trapframe));
        }

        /*
         * Merge saved signal mailbox pending flag to maintain interlock
         * semantics against system calls.
         */
        if (ucp.uc_mcontext.mc_xflags & PGEX_MAILBOX)
                p->p_flag |= P_MAILBOX;

        if (ucp.uc_mcontext.mc_onstack & 1)
                lp->lwp_sigstk.ss_flags |= SS_ONSTACK;
        else
                lp->lwp_sigstk.ss_flags &= ~SS_ONSTACK;

        lp->lwp_sigmask = ucp.uc_sigmask;
        SIG_CANTMASK(lp->lwp_sigmask);
        return(EJUSTRETURN);
}

/*
 * Stack frame on entry to function.  %eax will contain the function vector,
 * %ecx will contain the function data.  flags, ecx, and eax will have 
 * already been pushed on the stack.
 */
struct upc_frame {
        register_t      eax;
        register_t      ecx;
        register_t      edx;
        register_t      flags;
        register_t      oldip;
};

void
sendupcall(struct vmupcall *vu, int morepending)
{
        struct lwp *lp = curthread->td_lwp;
        struct trapframe *regs;
        struct upcall upcall;
        struct upc_frame upc_frame;
        int     crit_count = 0;

        /*
         * If we are a virtual kernel running an emulated user process
         * context, switch back to the virtual kernel context before
         * trying to post the signal.
         */
        if (lp->lwp_vkernel && lp->lwp_vkernel->ve) {
                lp->lwp_md.md_regs->tf_trapno = 0;
                vkernel_trap(lp, lp->lwp_md.md_regs);
        }

        /*
         * Get the upcall data structure
         */
        if (copyin(lp->lwp_upcall, &upcall, sizeof(upcall)) ||
            copyin((char *)upcall.upc_uthread + upcall.upc_critoff, &crit_count, sizeof(int))
        ) {
                vu->vu_pending = 0;
                kprintf("bad upcall address\n");
                return;
        }

        /*
         * If the data structure is already marked pending or has a critical
         * section count, mark the data structure as pending and return 
         * without doing an upcall.  vu_pending is left set.
         */
        if (upcall.upc_pending || crit_count >= vu->vu_pending) {
                if (upcall.upc_pending < vu->vu_pending) {
                        upcall.upc_pending = vu->vu_pending;
                        copyout(&upcall.upc_pending, &lp->lwp_upcall->upc_pending,
                                sizeof(upcall.upc_pending));
                }
                return;
        }

        /*
         * We can run this upcall now, clear vu_pending.
         *
         * Bump our critical section count and set or clear the
         * user pending flag depending on whether more upcalls are
         * pending.  The user will be responsible for calling 
         * upc_dispatch(-1) to process remaining upcalls.
         */
        vu->vu_pending = 0;
        upcall.upc_pending = morepending;
        crit_count += TDPRI_CRIT;
        copyout(&upcall.upc_pending, &lp->lwp_upcall->upc_pending, 
                sizeof(upcall.upc_pending));
        copyout(&crit_count, (char *)upcall.upc_uthread + upcall.upc_critoff,
                sizeof(int));

        /*
         * Construct a stack frame and issue the upcall
         */
        regs = lp->lwp_md.md_regs;
        upc_frame.eax = regs->tf_eax;
        upc_frame.ecx = regs->tf_ecx;
        upc_frame.edx = regs->tf_edx;
        upc_frame.flags = regs->tf_eflags;
        upc_frame.oldip = regs->tf_eip;
        if (copyout(&upc_frame, (void *)(regs->tf_esp - sizeof(upc_frame)),
            sizeof(upc_frame)) != 0) {
                kprintf("bad stack on upcall\n");
        } else {
                regs->tf_eax = (register_t)vu->vu_func;
                regs->tf_ecx = (register_t)vu->vu_data;
                regs->tf_edx = (register_t)lp->lwp_upcall;
                regs->tf_eip = (register_t)vu->vu_ctx;
                regs->tf_esp -= sizeof(upc_frame);
        }
}

/*
 * fetchupcall occurs in the context of a system call, which means that
 * we have to return EJUSTRETURN in order to prevent eax and edx from
 * being overwritten by the syscall return value.
 *
 * if vu is not NULL we return the new context in %edx, the new data in %ecx,
 * and the function pointer in %eax.  
 */
int
fetchupcall (struct vmupcall *vu, int morepending, void *rsp)
{
        struct upc_frame upc_frame;
        struct lwp *lp = curthread->td_lwp;
        struct trapframe *regs;
        int error;
        struct upcall upcall;
        int crit_count;

        regs = lp->lwp_md.md_regs;

        error = copyout(&morepending, &lp->lwp_upcall->upc_pending, sizeof(int));
        if (error == 0) {
            if (vu) {
                /*
                 * This jumps us to the next ready context.
                 */
                vu->vu_pending = 0;
                error = copyin(lp->lwp_upcall, &upcall, sizeof(upcall));
                crit_count = 0;
                if (error == 0)
                        error = copyin((char *)upcall.upc_uthread + upcall.upc_critoff, &crit_count, sizeof(int));
                crit_count += TDPRI_CRIT;
                if (error == 0)
                        error = copyout(&crit_count, (char *)upcall.upc_uthread + upcall.upc_critoff, sizeof(int));
                regs->tf_eax = (register_t)vu->vu_func;
                regs->tf_ecx = (register_t)vu->vu_data;
                regs->tf_edx = (register_t)lp->lwp_upcall;
                regs->tf_eip = (register_t)vu->vu_ctx;
                regs->tf_esp = (register_t)rsp;
            } else {
                /*
                 * This returns us to the originally interrupted code.
                 */
                error = copyin(rsp, &upc_frame, sizeof(upc_frame));
                regs->tf_eax = upc_frame.eax;
                regs->tf_ecx = upc_frame.ecx;
                regs->tf_edx = upc_frame.edx;
                regs->tf_eflags = (regs->tf_eflags & ~PSL_USERCHANGE) |
                                (upc_frame.flags & PSL_USERCHANGE);
                regs->tf_eip = upc_frame.oldip;
                regs->tf_esp = (register_t)((char *)rsp + sizeof(upc_frame));
            }
        }
        if (error == 0)
                error = EJUSTRETURN;
        return(error);
}

/*
 * cpu_idle() represents the idle LWKT.  You cannot return from this function
 * (unless you want to blow things up!).  Instead we look for runnable threads
 * and loop or halt as appropriate.  Giant is not held on entry to the thread.
 *
 * The main loop is entered with a critical section held, we must release
 * the critical section before doing anything else.  lwkt_switch() will
 * check for pending interrupts due to entering and exiting its own 
 * critical section.
 *
 * Note on cpu_idle_hlt:  On an SMP system we rely on a scheduler IPI
 * to wake a HLTed cpu up.  However, there are cases where the idlethread
 * will be entered with the possibility that no IPI will occur and in such
 * cases lwkt_switch() sets TDF_IDLE_NOHLT.
 */
static int      cpu_idle_hlt = 1;
static int      cpu_idle_hltcnt;
static int      cpu_idle_spincnt;
SYSCTL_INT(_machdep, OID_AUTO, cpu_idle_hlt, CTLFLAG_RW,
    &cpu_idle_hlt, 0, "Idle loop HLT enable");
SYSCTL_INT(_machdep, OID_AUTO, cpu_idle_hltcnt, CTLFLAG_RW,
    &cpu_idle_hltcnt, 0, "Idle loop entry halts");
SYSCTL_INT(_machdep, OID_AUTO, cpu_idle_spincnt, CTLFLAG_RW,
    &cpu_idle_spincnt, 0, "Idle loop entry spins");

void
cpu_idle(void)
{
        struct thread *td = curthread;

        crit_exit();
        KKASSERT(td->td_pri < TDPRI_CRIT);
        for (;;) {
                /*
                 * See if there are any LWKTs ready to go.
                 */
                lwkt_switch();

                /*
                 * If we are going to halt call splz unconditionally after
                 * CLIing to catch any interrupt races.  Note that we are
                 * at SPL0 and interrupts are enabled.
                 *
                 * We must poll our mailbox signals prior to calling 
                 * sigpause() in order to properly interlock with them.
                 */
                if (cpu_idle_hlt && !lwkt_runnable() &&
                    (td->td_flags & TDF_IDLE_NOHLT) == 0) {
                        splz();
                        signalmailbox(NULL);
                        if (!lwkt_runnable()) {
                                sigpause(0);
                        }
#ifdef SMP
                        else {
                            __asm __volatile("pause");
                        }
#endif
                        ++cpu_idle_hltcnt;
                } else {
                        td->td_flags &= ~TDF_IDLE_NOHLT;
                        splz();
                        signalmailbox(NULL);
#ifdef SMP
                        /*__asm __volatile("sti; pause");*/
                        __asm __volatile("pause");
#else
                        /*__asm __volatile("sti");*/
#endif
                        ++cpu_idle_spincnt;
                }
        }
}

/*
 * Clear registers on exec
 */
void
exec_setregs(u_long entry, u_long stack, u_long ps_strings)
{
        struct thread *td = curthread;
        struct lwp *lp = td->td_lwp;
        struct trapframe *regs = lp->lwp_md.md_regs;
        struct pcb *pcb = lp->lwp_thread->td_pcb;

        /* was i386_user_cleanup() in NetBSD */
        user_ldt_free(pcb);
  
        bzero((char *)regs, sizeof(struct trapframe));
        regs->tf_eip = entry;
        regs->tf_esp = stack;
        regs->tf_eflags = PSL_USER | (regs->tf_eflags & PSL_T);
        regs->tf_ss = 0;
        regs->tf_ds = 0;
        regs->tf_es = 0;
        regs->tf_fs = 0;
        regs->tf_gs = 0;
        regs->tf_cs = 0;

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

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

        /*
         * Initialize the math emulator (if any) for the current process.
         * Actually, just clear the bit that says that the emulator has
         * been initialized.  Initialization is delayed until the process
         * traps to the emulator (if it is done at all) mainly because
         * emulators don't provide an entry point for initialization.
         */
        pcb->pcb_flags &= ~FP_SOFTFP;

        /*
         * note: do not set CR0_TS here.  npxinit() must do it after clearing
         * gd_npxthread.  Otherwise a preemptive interrupt thread may panic
         * in npxdna().
         */
        crit_enter();
#if 0
        load_cr0(rcr0() | CR0_MP);
#endif

#if NNPX > 0
        /* Initialize the npx (if any) for the current process. */
        npxinit(__INITIAL_NPXCW__);
#endif
        crit_exit();

        /*
         * note: linux emulator needs edx to be 0x0 on entry, which is
         * handled in execve simply by setting the 64 bit syscall
         * return value to 0.
         */
}

void
cpu_setregs(void)
{
#if 0
        unsigned int cr0;

        cr0 = rcr0();
        cr0 |= CR0_NE;                  /* Done by npxinit() */
        cr0 |= CR0_MP | CR0_TS;         /* Done at every execve() too. */
#ifdef I386_CPU
        if (cpu_class != CPUCLASS_386)
#endif
                cr0 |= CR0_WP | CR0_AM;
        load_cr0(cr0);
        load_gs(_udatasel);
#endif
}

static int
sysctl_machdep_adjkerntz(SYSCTL_HANDLER_ARGS)
{
        int error;
        error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2,
                req);
        if (!error && req->newptr)
                resettodr();
        return (error);
}

SYSCTL_PROC(_machdep, CPU_ADJKERNTZ, adjkerntz, CTLTYPE_INT|CTLFLAG_RW,
        &adjkerntz, 0, sysctl_machdep_adjkerntz, "I", "");

extern u_long bootdev;          /* not a cdev_t - encoding is different */
SYSCTL_ULONG(_machdep, OID_AUTO, guessed_bootdev,
        CTLFLAG_RD, &bootdev, 0, "Boot device (not in cdev_t format)");

/*
 * Initialize 386 and configure to run kernel
 */

/*
 * Initialize segments & interrupt table
 */

extern  struct user *proc0paddr;

#if 0

extern inthand_t
        IDTVEC(div), IDTVEC(dbg), IDTVEC(nmi), IDTVEC(bpt), IDTVEC(ofl),
        IDTVEC(bnd), IDTVEC(ill), IDTVEC(dna), IDTVEC(fpusegm),
        IDTVEC(tss), IDTVEC(missing), IDTVEC(stk), IDTVEC(prot),
        IDTVEC(page), IDTVEC(mchk), IDTVEC(fpu), IDTVEC(align),
        IDTVEC(xmm), IDTVEC(syscall),
        IDTVEC(rsvd0);
extern inthand_t
        IDTVEC(int0x80_syscall);

#endif

#ifdef DEBUG_INTERRUPTS
extern inthand_t *Xrsvdary[256];
#endif

int
ptrace_set_pc(struct lwp *lp, unsigned long addr)
{
        lp->lwp_md.md_regs->tf_eip = addr;
        return (0);
}

int
ptrace_single_step(struct lwp *lp)
{
        lp->lwp_md.md_regs->tf_eflags |= PSL_T;
        return (0);
}

int
fill_regs(struct lwp *lp, struct reg *regs)
{
        struct trapframe *tp;

        tp = lp->lwp_md.md_regs;
        regs->r_gs = tp->tf_gs;
        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;
        return (0);
}

int
set_regs(struct lwp *lp, struct reg *regs)
{
        struct trapframe *tp;

        tp = lp->lwp_md.md_regs;
        if (!EFL_SECURE(regs->r_eflags, tp->tf_eflags) ||
            !CS_SECURE(regs->r_cs))
                return (EINVAL);
        tp->tf_gs = regs->r_gs;
        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;
        return (0);
}

#ifndef CPU_DISABLE_SSE
static void
fill_fpregs_xmm(struct savexmm *sv_xmm, struct save87 *sv_87)
{
        struct env87 *penv_87 = &sv_87->sv_env;
        struct envxmm *penv_xmm = &sv_xmm->sv_env;
        int i;

        /* FPU control/status */
        penv_87->en_cw = penv_xmm->en_cw;
        penv_87->en_sw = penv_xmm->en_sw;
        penv_87->en_tw = penv_xmm->en_tw;
        penv_87->en_fip = penv_xmm->en_fip;
        penv_87->en_fcs = penv_xmm->en_fcs;
        penv_87->en_opcode = penv_xmm->en_opcode;
        penv_87->en_foo = penv_xmm->en_foo;
        penv_87->en_fos = penv_xmm->en_fos;

        /* FPU registers */
        for (i = 0; i < 8; ++i)
                sv_87->sv_ac[i] = sv_xmm->sv_fp[i].fp_acc;

        sv_87->sv_ex_sw = sv_xmm->sv_ex_sw;
}

static void
set_fpregs_xmm(struct save87 *sv_87, struct savexmm *sv_xmm)
{
        struct env87 *penv_87 = &sv_87->sv_env;
        struct envxmm *penv_xmm = &sv_xmm->sv_env;
        int i;

        /* FPU control/status */
        penv_xmm->en_cw = penv_87->en_cw;
        penv_xmm->en_sw = penv_87->en_sw;
        penv_xmm->en_tw = penv_87->en_tw;
        penv_xmm->en_fip = penv_87->en_fip;
        penv_xmm->en_fcs = penv_87->en_fcs;
        penv_xmm->en_opcode = penv_87->en_opcode;
        penv_xmm->en_foo = penv_87->en_foo;
        penv_xmm->en_fos = penv_87->en_fos;

        /* FPU registers */
        for (i = 0; i < 8; ++i)
                sv_xmm->sv_fp[i].fp_acc = sv_87->sv_ac[i];

        sv_xmm->sv_ex_sw = sv_87->sv_ex_sw;
}
#endif /* CPU_DISABLE_SSE */

int
fill_fpregs(struct lwp *lp, struct fpreg *fpregs)
{
#ifndef CPU_DISABLE_SSE
        if (cpu_fxsr) {
                fill_fpregs_xmm(&lp->lwp_thread->td_pcb->pcb_save.sv_xmm,
                                (struct save87 *)fpregs);
                return (0);
        }
#endif /* CPU_DISABLE_SSE */
        bcopy(&lp->lwp_thread->td_pcb->pcb_save.sv_87, fpregs, sizeof *fpregs);
        return (0);
}

int
set_fpregs(struct lwp *lp, struct fpreg *fpregs)
{
#ifndef CPU_DISABLE_SSE
        if (cpu_fxsr) {
                set_fpregs_xmm((struct save87 *)fpregs,
                               &lp->lwp_thread->td_pcb->pcb_save.sv_xmm);
                return (0);
        }
#endif /* CPU_DISABLE_SSE */
        bcopy(fpregs, &lp->lwp_thread->td_pcb->pcb_save.sv_87, sizeof *fpregs);
        return (0);
}

int
fill_dbregs(struct lwp *lp, struct dbreg *dbregs)
{
        if (lp == NULL) {
                dbregs->dr0 = rdr0();
                dbregs->dr1 = rdr1();
                dbregs->dr2 = rdr2();
                dbregs->dr3 = rdr3();
                dbregs->dr4 = rdr4();
                dbregs->dr5 = rdr5();
                dbregs->dr6 = rdr6();
                dbregs->dr7 = rdr7();
        } else {
                struct pcb *pcb;

                pcb = lp->lwp_thread->td_pcb;
                dbregs->dr0 = pcb->pcb_dr0;
                dbregs->dr1 = pcb->pcb_dr1;
                dbregs->dr2 = pcb->pcb_dr2;
                dbregs->dr3 = pcb->pcb_dr3;
                dbregs->dr4 = 0;
                dbregs->dr5 = 0;
                dbregs->dr6 = pcb->pcb_dr6;
                dbregs->dr7 = pcb->pcb_dr7;
        }
        return (0);
}

int
set_dbregs(struct lwp *lp, struct dbreg *dbregs)
{
        if (lp == NULL) {
                load_dr0(dbregs->dr0);
                load_dr1(dbregs->dr1);
                load_dr2(dbregs->dr2);
                load_dr3(dbregs->dr3);
                load_dr4(dbregs->dr4);
                load_dr5(dbregs->dr5);
                load_dr6(dbregs->dr6);
                load_dr7(dbregs->dr7);
        } else {
                struct pcb *pcb;
                struct ucred *ucred;
                int i;
                uint32_t mask1, mask2;

                /*
                 * 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, mask1 = 0x3<<16, mask2 = 0x2<<16; i < 8; 
                     i++, mask1 <<= 2, mask2 <<= 2)
                        if ((dbregs->dr7 & mask1) == mask2)
                                return (EINVAL);
                
                pcb = lp->lwp_thread->td_pcb;
                ucred = lp->lwp_proc->p_ucred;

                /*
                 * 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, unless, perhaps, we were called by
                 * uid 0.
                 *
                 * 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 (suser_cred(ucred, 0) != 0) {
                        if (dbregs->dr7 & 0x3) {
                                /* dr0 is enabled */
                                if (dbregs->dr0 >= VM_MAX_USER_ADDRESS)
                                        return (EINVAL);
                        }

                        if (dbregs->dr7 & (0x3<<2)) {
                                /* dr1 is enabled */
                                if (dbregs->dr1 >= VM_MAX_USER_ADDRESS)
                                        return (EINVAL);
                        }

                        if (dbregs->dr7 & (0x3<<4)) {
                                /* dr2 is enabled */
                                if (dbregs->dr2 >= VM_MAX_USER_ADDRESS)
                                        return (EINVAL);
                        }

                        if (dbregs->dr7 & (0x3<<6)) {
                                /* dr3 is enabled */
                                if (dbregs->dr3 >= VM_MAX_USER_ADDRESS)
                                        return (EINVAL);
                        }
                }

                pcb->pcb_dr0 = dbregs->dr0;
                pcb->pcb_dr1 = dbregs->dr1;
                pcb->pcb_dr2 = dbregs->dr2;
                pcb->pcb_dr3 = dbregs->dr3;
                pcb->pcb_dr6 = dbregs->dr6;
                pcb->pcb_dr7 = dbregs->dr7;

                pcb->pcb_flags |= PCB_DBREGS;
        }

        return (0);
}

#if 0
/*
 * Return > 0 if a hardware breakpoint has been hit, and the
 * breakpoint was in user space.  Return 0, otherwise.
 */
int
user_dbreg_trap(void)
{
        u_int32_t dr7, dr6; /* debug registers dr6 and 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;
        
        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;
        dr6 = rdr6();
        bp = dr6 & 0x0000000f;

        if (!bp) {
                /*
                 * None of the breakpoint bits are set meaning this
                 * trap was not caused by any of the debug registers
                 */
                return 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_MAX_USER_ADDRESS) {
                        /*
                         * addr[i] is in user space
                         */
                        return nbp;
                }
        }

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

#endif


#ifndef DDB
void
Debugger(const char *msg)
{
        kprintf("Debugger(\"%s\") called.\n", msg);
}
#endif /* no DDB */