[apple/xnu.git] / osfmk / i386 / pcb.c

/*
 * Copyright (c) 2000-2004 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1991,1990 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */

#include <mach_rt.h>
#include <mach_debug.h>
#include <mach_ldebug.h>

#include <sys/kdebug.h>

#include <mach/kern_return.h>
#include <mach/thread_status.h>
#include <mach/vm_param.h>

#include <i386/cpu_data.h>
#include <i386/cpu_number.h>

#include <kern/counters.h>
#include <kern/kalloc.h>
#include <kern/mach_param.h>
#include <kern/processor.h>
#include <kern/cpu_data.h>
#include <kern/cpu_number.h>
#include <kern/task.h>
#include <kern/thread.h>
#include <kern/sched_prim.h>
#include <kern/misc_protos.h>
#include <kern/assert.h>
#include <kern/spl.h>
#include <kern/machine.h>
#include <ipc/ipc_port.h>
#include <vm/vm_kern.h>
#include <vm/vm_map.h>
#include <vm/pmap.h>
#include <vm/vm_protos.h>

#include <i386/thread.h>
#include <i386/eflags.h>
#include <i386/proc_reg.h>
#include <i386/seg.h>
#include <i386/tss.h>
#include <i386/user_ldt.h>
#include <i386/fpu.h>
#include <i386/iopb_entries.h>
#include <i386/mp_desc.h>
#include <i386/cpu_data.h>


/*
 * Maps state flavor to number of words in the state:
 */
__private_extern__
unsigned int _MachineStateCount[] = {
        /* FLAVOR_LIST */ 0,
        i386_NEW_THREAD_STATE_COUNT,
        i386_FLOAT_STATE_COUNT,
        i386_ISA_PORT_MAP_STATE_COUNT,
        i386_V86_ASSIST_STATE_COUNT,
        i386_REGS_SEGS_STATE_COUNT,
        i386_THREAD_SYSCALL_STATE_COUNT,
        /* THREAD_STATE_NONE */ 0,
        i386_SAVED_STATE_COUNT,
};

/* Forward */

void            act_machine_throughcall(thread_t thr_act);
user_addr_t     get_useraddr(void);
void            act_machine_return(int);
void            act_machine_sv_free(thread_t, int);

extern thread_t         Switch_context(
                                thread_t                        old,
                                thread_continue_t       cont,
                                thread_t                        new);
extern void             Thread_continue(void);
extern void             Load_context(
                                thread_t                        thread);

/*
 * consider_machine_collect:
 *
 *      Try to collect machine-dependent pages
 */
void
consider_machine_collect(void)
{
}

void
consider_machine_adjust(void)
{
}


// DEBUG
int     DEBUG_kldt = 0;
int     DEBUG_uldt = 0;

static void
act_machine_switch_pcb( thread_t new )
{
        pcb_t                   pcb = new->machine.pcb;
        int                     mycpu;
        register iopb_tss_t     tss = pcb->ims.io_tss;
        vm_offset_t             pcb_stack_top;
        register user_ldt_t     uldt = pcb->ims.ldt;

        assert(new->kernel_stack != 0);
        STACK_IEL(new->kernel_stack)->saved_state =
                &new->machine.pcb->iss;

        /*
         *      Save a pointer to the top of the "kernel" stack -
         *      actually the place in the PCB where a trap into
         *      kernel mode will push the registers.
         *      The location depends on V8086 mode.  If we are
         *      not in V8086 mode, then a trap into the kernel
         *      won`t save the v86 segments, so we leave room.
         */

        pcb_stack_top = (pcb->iss.efl & EFL_VM)
                        ? (int) (&pcb->iss + 1)
                        : (int) (&pcb->iss.v86_segs);

        mp_disable_preemption();
        mycpu = cpu_number();

        if (tss == 0) {
            /*
             *  No per-thread IO permissions.
             *  Use standard kernel TSS.
             */
            if (!(gdt_desc_p(KERNEL_TSS)->access & ACC_TSS_BUSY))
                set_tr(KERNEL_TSS);
            current_ktss()->esp0 = pcb_stack_top;
        }
        else {
            /*
             * Set the IO permissions.  Use this thread`s TSS.
             */
            *gdt_desc_p(USER_TSS)
                = *(struct real_descriptor *)tss->iopb_desc;
            tss->tss.esp0 = pcb_stack_top;
            set_tr(USER_TSS);
            gdt_desc_p(KERNEL_TSS)->access &= ~ ACC_TSS_BUSY;
        }

        /*
         * Set the thread`s LDT or LDT entry.
         */
        if (uldt == 0) {
            struct real_descriptor *ldtp;
            /*
             * Use system LDT.
             */
            // Set up the tasks specific ldt entries if extant
            ldtp = (struct real_descriptor *)current_ldt();
            ldtp[sel_idx(USER_CTHREAD)] = pcb->cthread_desc;
            if (pcb->uldt_selector != 0)
                ldtp[sel_idx(pcb->uldt_selector)] = pcb->uldt_desc;
            set_ldt(KERNEL_LDT);
        }
        else {
            /*
             * Thread has its own LDT. // THIS SHOULD BE REMOVED!!!!
             */
            *gdt_desc_p(USER_LDT) = uldt->desc;
            set_ldt(USER_LDT);
            /*debug*/
            if ((DEBUG_uldt++ % 0x7fff) == 0)
                printf("KERNEL----> setting user ldt");
        
        }

        mp_enable_preemption();
        /*
         * Load the floating-point context, if necessary.
         */
        fpu_load_context(pcb);

}

/*
 * Switch to the first thread on a CPU.
 */
void
machine_load_context(
        thread_t                new)
{
        act_machine_switch_pcb(new);
        Load_context(new);
}

/*
 * Switch to a new thread.
 * Save the old thread`s kernel state or continuation,
 * and return it.
 */
thread_t
machine_switch_context(
        thread_t                        old,
        thread_continue_t       continuation,
        thread_t                        new)
{
#if MACH_RT
        assert(current_cpu_datap()->cpu_active_stack == old->kernel_stack);
#endif

        /*
         *      Save FP registers if in use.
         */
        fpu_save_context(old);

        /*
         *      Switch address maps if need be, even if not switching tasks.
         *      (A server activation may be "borrowing" a client map.)
         */
    {
        int     mycpu = cpu_number();

        PMAP_SWITCH_CONTEXT(old, new, mycpu)
    }

        /*
         *      Load the rest of the user state for the new thread
         */
        act_machine_switch_pcb(new);
        KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED,MACH_SCHED) | DBG_FUNC_NONE,
                     (int)old, (int)new, old->sched_pri, new->sched_pri, 0);
        old->continuation = NULL;
        return(Switch_context(old, continuation, new));
}

/*
 * act_machine_sv_free
 * release saveareas associated with an act. if flag is true, release
 * user level savearea(s) too, else don't
 */
void
act_machine_sv_free(__unused thread_t act, __unused int flag)
{
}


/*
 * This is where registers that are not normally specified by the mach-o
 * file on an execve would be nullified, perhaps to avoid a covert channel.
 */
kern_return_t
machine_thread_state_initialize(
        thread_t thread)
{
#pragma unused (thread)

    return  KERN_SUCCESS;
}
 
 
/*
 *      act_machine_set_state:
 *
 *      Set the status of the specified thread.
 */

kern_return_t
machine_thread_set_state(
        thread_t thr_act,
        thread_flavor_t flavor,
        thread_state_t tstate,
        mach_msg_type_number_t count)
{
        int kernel_act = 0;

        switch (flavor) {
            case THREAD_SYSCALL_STATE:
            {
                register struct thread_syscall_state *state;
                register struct i386_saved_state *saved_state = USER_REGS(thr_act);

                state = (struct thread_syscall_state *) tstate;
                saved_state->eax = state->eax;
                saved_state->edx = state->edx;
                if (kernel_act)
                        saved_state->efl = state->efl;
                else
                        saved_state->efl = (state->efl & ~EFL_USER_CLEAR) | EFL_USER_SET;
                saved_state->eip = state->eip;
                saved_state->uesp = state->esp;
                break;
            }

            case i386_SAVED_STATE:
            {
                register struct i386_saved_state        *state;
                register struct i386_saved_state        *saved_state;

                if (count < i386_SAVED_STATE_COUNT) {
                    return(KERN_INVALID_ARGUMENT);
                }

                state = (struct i386_saved_state *) tstate;

                /* Check segment selectors are safe */
                if (!kernel_act &&
                    !valid_user_segment_selectors(state->cs,
                                                  state->ss,
                                                  state->ds,
                                                  state->es,
                                                  state->fs,
                                                  state->gs))
                    return KERN_INVALID_ARGUMENT;
                
                saved_state = USER_REGS(thr_act);

                /*
                 * General registers
                 */
                saved_state->edi = state->edi;
                saved_state->esi = state->esi;
                saved_state->ebp = state->ebp;
                saved_state->uesp = state->uesp;
                saved_state->ebx = state->ebx;
                saved_state->edx = state->edx;
                saved_state->ecx = state->ecx;
                saved_state->eax = state->eax;
                saved_state->eip = state->eip;
                if (kernel_act)
                        saved_state->efl = state->efl;
                else
                        saved_state->efl = (state->efl & ~EFL_USER_CLEAR)
                                                | EFL_USER_SET;

                /*
                 * Segment registers.  Set differently in V8086 mode.
                 */
                if (state->efl & EFL_VM) {
                    /*
                     * Set V8086 mode segment registers.
                     */
                    saved_state->cs = state->cs & 0xffff;
                    saved_state->ss = state->ss & 0xffff;
                    saved_state->v86_segs.v86_ds = state->ds & 0xffff;
                    saved_state->v86_segs.v86_es = state->es & 0xffff;
                    saved_state->v86_segs.v86_fs = state->fs & 0xffff;
                    saved_state->v86_segs.v86_gs = state->gs & 0xffff;

                    /*
                     * Zero protected mode segment registers.
                     */
                    saved_state->ds = 0;
                    saved_state->es = 0;
                    saved_state->fs = 0;
                    saved_state->gs = 0;

                    if (thr_act->machine.pcb->ims.v86s.int_table) {
                        /*
                         * Hardware assist on.
                         */
                        thr_act->machine.pcb->ims.v86s.flags =
                            state->efl & (EFL_TF | EFL_IF);
                    }
                }
                else if (kernel_act) {
                    /*
                     * 386 mode.  Set segment registers for flat
                     * 32-bit address space.
                     */
                  saved_state->cs = KERNEL_CS;
                  saved_state->ss = KERNEL_DS;
                  saved_state->ds = KERNEL_DS;
                  saved_state->es = KERNEL_DS;
                  saved_state->fs = KERNEL_DS;
                  saved_state->gs = CPU_DATA_GS;
                }
                else {
                    /*
                     * User setting segment registers.
                     * Code and stack selectors have already been
                     * checked.  Others will be reset by 'iret'
                     * if they are not valid.
                     */
                    saved_state->cs = state->cs;
                    saved_state->ss = state->ss;
                    saved_state->ds = state->ds;
                    saved_state->es = state->es;
                    saved_state->fs = state->fs;
                    saved_state->gs = state->gs;
                }
                break;
            }

            case i386_NEW_THREAD_STATE:
            case i386_REGS_SEGS_STATE:
            {
                register struct i386_new_thread_state   *state;
                register struct i386_saved_state        *saved_state;

                if (count < i386_NEW_THREAD_STATE_COUNT) {
                    return(KERN_INVALID_ARGUMENT);
                }

                state = (struct i386_new_thread_state *) tstate;

                if (flavor == i386_REGS_SEGS_STATE) {
                    /*
                     * Code and stack selectors must not be null,
                     * and must have user protection levels.
                     * Only the low 16 bits are valid.
                     */
                    state->cs &= 0xffff;
                    state->ss &= 0xffff;
                    state->ds &= 0xffff;
                    state->es &= 0xffff;
                    state->fs &= 0xffff;
                    state->gs &= 0xffff;

                    if (!kernel_act &&
                        !valid_user_segment_selectors(state->cs,
                                                      state->ss,
                                                      state->ds,
                                                      state->es,
                                                      state->fs,
                                                      state->gs))
                        return KERN_INVALID_ARGUMENT;
                }

                saved_state = USER_REGS(thr_act);

                /*
                 * General registers
                 */
                saved_state->edi = state->edi;
                saved_state->esi = state->esi;
                saved_state->ebp = state->ebp;
                saved_state->uesp = state->uesp;
                saved_state->ebx = state->ebx;
                saved_state->edx = state->edx;
                saved_state->ecx = state->ecx;
                saved_state->eax = state->eax;
                saved_state->eip = state->eip;
                if (kernel_act)
                        saved_state->efl = state->efl;
                else
                        saved_state->efl = (state->efl & ~EFL_USER_CLEAR)
                                                | EFL_USER_SET;

                /*
                 * Segment registers.  Set differently in V8086 mode.
                 */
                if (state->efl & EFL_VM) {
                    /*
                     * Set V8086 mode segment registers.
                     */
                    saved_state->cs = state->cs & 0xffff;
                    saved_state->ss = state->ss & 0xffff;
                    saved_state->v86_segs.v86_ds = state->ds & 0xffff;
                    saved_state->v86_segs.v86_es = state->es & 0xffff;
                    saved_state->v86_segs.v86_fs = state->fs & 0xffff;
                    saved_state->v86_segs.v86_gs = state->gs & 0xffff;

                    /*
                     * Zero protected mode segment registers.
                     */
                    saved_state->ds = 0;
                    saved_state->es = 0;
                    saved_state->fs = 0;
                    saved_state->gs = 0;

                    if (thr_act->machine.pcb->ims.v86s.int_table) {
                        /*
                         * Hardware assist on.
                         */
                        thr_act->machine.pcb->ims.v86s.flags =
                            state->efl & (EFL_TF | EFL_IF);
                    }
                }
                else if (flavor == i386_NEW_THREAD_STATE && kernel_act) {
                    /*
                     * 386 mode.  Set segment registers for flat
                     * 32-bit address space.
                     */
                  saved_state->cs = KERNEL_CS;
                  saved_state->ss = KERNEL_DS;
                  saved_state->ds = KERNEL_DS;
                  saved_state->es = KERNEL_DS;
                  saved_state->fs = KERNEL_DS;
                  saved_state->gs = CPU_DATA_GS;
                }
                else {
                    /*
                     * User setting segment registers.
                     * Code and stack selectors have already been
                     * checked.  Others will be reset by 'iret'
                     * if they are not valid.
                     */
                    saved_state->cs = state->cs;
                    saved_state->ss = state->ss;
                    saved_state->ds = state->ds;
                    saved_state->es = state->es;
                    saved_state->fs = state->fs;
                    saved_state->gs = state->gs;
                }
                break;
            }

            case i386_FLOAT_STATE: {
                if (count < i386_old_FLOAT_STATE_COUNT)
                        return(KERN_INVALID_ARGUMENT);
                if (count < i386_FLOAT_STATE_COUNT)
                    return fpu_set_state(thr_act,(struct i386_float_state*)tstate);
                else return fpu_set_fxstate(thr_act,(struct i386_float_state*)tstate);
            }

            /*
             * Temporary - replace by i386_io_map
             */
            case i386_ISA_PORT_MAP_STATE: {
                if (count < i386_ISA_PORT_MAP_STATE_COUNT)
                        return(KERN_INVALID_ARGUMENT);

                break;
            }

            case i386_V86_ASSIST_STATE:
            {
                register struct i386_v86_assist_state *state;
                vm_offset_t     int_table;
                int             int_count;

                if (count < i386_V86_ASSIST_STATE_COUNT)
                    return KERN_INVALID_ARGUMENT;

                state = (struct i386_v86_assist_state *) tstate;
                int_table = state->int_table;
                int_count = state->int_count;

                if (int_table >= VM_MAX_ADDRESS ||
                    int_table +
                        int_count * sizeof(struct v86_interrupt_table)
                            > VM_MAX_ADDRESS)
                    return KERN_INVALID_ARGUMENT;

                thr_act->machine.pcb->ims.v86s.int_table = int_table;
                thr_act->machine.pcb->ims.v86s.int_count = int_count;

                thr_act->machine.pcb->ims.v86s.flags =
                        USER_REGS(thr_act)->efl & (EFL_TF | EFL_IF);
                break;
            }

        case i386_THREAD_STATE: {
                struct i386_saved_state *saved_state;
                i386_thread_state_t     *state25;

                saved_state = USER_REGS(thr_act);
                state25 = (i386_thread_state_t *)tstate;

                saved_state->eax = state25->eax;
                saved_state->ebx = state25->ebx;
                saved_state->ecx = state25->ecx;
                saved_state->edx = state25->edx;
                saved_state->edi = state25->edi;
                saved_state->esi = state25->esi;
                saved_state->ebp = state25->ebp;
                saved_state->uesp = state25->esp;
                saved_state->efl = (state25->eflags & ~EFL_USER_CLEAR)
                                                | EFL_USER_SET;
                saved_state->eip = state25->eip;
                saved_state->cs = USER_CS;      /* FIXME? */
                saved_state->ss = USER_DS;
                saved_state->ds = USER_DS;
                saved_state->es = USER_DS;
                saved_state->fs = state25->fs;
                saved_state->gs = state25->gs;
        }
                break;

            default:
                return(KERN_INVALID_ARGUMENT);
        }

        return(KERN_SUCCESS);
}

/*
 *      thread_getstatus:
 *
 *      Get the status of the specified thread.
 */


kern_return_t
machine_thread_get_state(
        thread_t thr_act,
        thread_flavor_t flavor,
        thread_state_t tstate,
        mach_msg_type_number_t *count)
{
        switch (flavor)  {

            case i386_SAVED_STATE:
            {
                register struct i386_saved_state        *state;
                register struct i386_saved_state        *saved_state;

                if (*count < i386_SAVED_STATE_COUNT)
                    return(KERN_INVALID_ARGUMENT);

                state = (struct i386_saved_state *) tstate;
                saved_state = USER_REGS(thr_act);

                /*
                 * First, copy everything:
                 */
                *state = *saved_state;

                if (saved_state->efl & EFL_VM) {
                    /*
                     * V8086 mode.
                     */
                    state->ds = saved_state->v86_segs.v86_ds & 0xffff;
                    state->es = saved_state->v86_segs.v86_es & 0xffff;
                    state->fs = saved_state->v86_segs.v86_fs & 0xffff;
                    state->gs = saved_state->v86_segs.v86_gs & 0xffff;

                    if (thr_act->machine.pcb->ims.v86s.int_table) {
                        /*
                         * Hardware assist on
                         */
                        if ((thr_act->machine.pcb->ims.v86s.flags &
                                        (EFL_IF|V86_IF_PENDING)) == 0)
                            state->efl &= ~EFL_IF;
                    }
                }
                else {
                    /*
                     * 386 mode.
                     */
                    state->ds = saved_state->ds & 0xffff;
                    state->es = saved_state->es & 0xffff;
                    state->fs = saved_state->fs & 0xffff;
                    state->gs = saved_state->gs & 0xffff;
                }
                *count = i386_SAVED_STATE_COUNT;
                break;
            }

            case i386_NEW_THREAD_STATE:
            case i386_REGS_SEGS_STATE:
            {
                register struct i386_new_thread_state   *state;
                register struct i386_saved_state        *saved_state;

                if (*count < i386_NEW_THREAD_STATE_COUNT)
                    return(KERN_INVALID_ARGUMENT);

                state = (struct i386_new_thread_state *) tstate;
                saved_state = USER_REGS(thr_act);

                /*
                 * General registers.
                 */
                state->edi = saved_state->edi;
                state->esi = saved_state->esi;
                state->ebp = saved_state->ebp;
                state->ebx = saved_state->ebx;
                state->edx = saved_state->edx;
                state->ecx = saved_state->ecx;
                state->eax = saved_state->eax;
                state->eip = saved_state->eip;
                state->efl = saved_state->efl;
                state->uesp = saved_state->uesp;

                state->cs = saved_state->cs;
                state->ss = saved_state->ss;
                if (saved_state->efl & EFL_VM) {
                    /*
                     * V8086 mode.
                     */
                    state->ds = saved_state->v86_segs.v86_ds & 0xffff;
                    state->es = saved_state->v86_segs.v86_es & 0xffff;
                    state->fs = saved_state->v86_segs.v86_fs & 0xffff;
                    state->gs = saved_state->v86_segs.v86_gs & 0xffff;

                    if (thr_act->machine.pcb->ims.v86s.int_table) {
                        /*
                         * Hardware assist on
                         */
                        if ((thr_act->machine.pcb->ims.v86s.flags &
                                        (EFL_IF|V86_IF_PENDING)) == 0)
                            state->efl &= ~EFL_IF;
                    }
                }
                else {
                    /*
                     * 386 mode.
                     */
                    state->ds = saved_state->ds & 0xffff;
                    state->es = saved_state->es & 0xffff;
                    state->fs = saved_state->fs & 0xffff;
                    state->gs = saved_state->gs & 0xffff;
                }
                *count = i386_NEW_THREAD_STATE_COUNT;
                break;
            }

            case THREAD_SYSCALL_STATE:
            {
                register struct thread_syscall_state *state;
                register struct i386_saved_state *saved_state = USER_REGS(thr_act);

                state = (struct thread_syscall_state *) tstate;
                state->eax = saved_state->eax;
                state->edx = saved_state->edx;
                state->efl = saved_state->efl;
                state->eip = saved_state->eip;
                state->esp = saved_state->uesp;
                *count = i386_THREAD_SYSCALL_STATE_COUNT;
                break;
            }

            case THREAD_STATE_FLAVOR_LIST:
                if (*count < 5)
                    return (KERN_INVALID_ARGUMENT);
                tstate[0] = i386_NEW_THREAD_STATE;
                tstate[1] = i386_FLOAT_STATE;
                tstate[2] = i386_ISA_PORT_MAP_STATE;
                tstate[3] = i386_V86_ASSIST_STATE;
                tstate[4] = THREAD_SYSCALL_STATE;
                *count = 5;
                break;

            case i386_FLOAT_STATE: {
                if (*count < i386_old_FLOAT_STATE_COUNT)
                        return(KERN_INVALID_ARGUMENT);
                if (*count< i386_FLOAT_STATE_COUNT) {
                    *count = i386_old_FLOAT_STATE_COUNT;
                    return fpu_get_state(thr_act,(struct i386_float_state *)tstate);
                } else {
                    *count = i386_FLOAT_STATE_COUNT;
                    return fpu_get_fxstate(thr_act,(struct i386_float_state *)tstate);
                }
            }

            /*
             * Temporary - replace by i386_io_map
             */
            case i386_ISA_PORT_MAP_STATE: {
                register struct i386_isa_port_map_state *state;
                register iopb_tss_t tss;

                if (*count < i386_ISA_PORT_MAP_STATE_COUNT)
                        return(KERN_INVALID_ARGUMENT);

                state = (struct i386_isa_port_map_state *) tstate;
                tss = thr_act->machine.pcb->ims.io_tss;

                if (tss == 0) {
                    unsigned int i;

                    /*
                     *  The thread has no ktss, so no IO permissions.
                     */

                    for (i = 0; i < sizeof state->pm; i++)
                        state->pm[i] = 0xff;
                } else {
                    /*
                     *  The thread has its own ktss.
                     */

                    bcopy((char *) tss->bitmap,
                          (char *) state->pm,
                          sizeof state->pm);
                }

                *count = i386_ISA_PORT_MAP_STATE_COUNT;
                break;
            }

            case i386_V86_ASSIST_STATE:
            {
                register struct i386_v86_assist_state *state;

                if (*count < i386_V86_ASSIST_STATE_COUNT)
                    return KERN_INVALID_ARGUMENT;

                state = (struct i386_v86_assist_state *) tstate;
                state->int_table = thr_act->machine.pcb->ims.v86s.int_table;
                state->int_count = thr_act->machine.pcb->ims.v86s.int_count;

                *count = i386_V86_ASSIST_STATE_COUNT;
                break;
            }

        case i386_THREAD_STATE: {
                struct i386_saved_state *saved_state;
                i386_thread_state_t     *state;

                saved_state = USER_REGS(thr_act);
                state = (i386_thread_state_t *)tstate;

                state->eax = saved_state->eax;
                state->ebx = saved_state->ebx;
                state->ecx = saved_state->ecx;
                state->edx = saved_state->edx;
                state->edi = saved_state->edi;
                state->esi = saved_state->esi;
                state->ebp = saved_state->ebp;
                state->esp = saved_state->uesp;
                state->eflags = saved_state->efl;
                state->eip = saved_state->eip;
                state->cs = saved_state->cs;
                state->ss = saved_state->ss;
                state->ds = saved_state->ds;
                state->es = saved_state->es;
                state->fs = saved_state->fs;
                state->gs = saved_state->gs;
                break;
        }

            default:
                return(KERN_INVALID_ARGUMENT);
        }

        return(KERN_SUCCESS);
}

/*
 * Initialize the machine-dependent state for a new thread.
 */
kern_return_t
machine_thread_create(
        thread_t                thread,
        __unused task_t         task)
{
        pcb_t   pcb = &thread->machine.xxx_pcb;

        thread->machine.pcb = pcb;

        simple_lock_init(&pcb->lock, 0);

        /*
         *      Guarantee that the bootstrapped thread will be in user
         *      mode.
         */
        pcb->iss.cs = USER_CS;
        pcb->iss.ss = USER_DS;
        pcb->iss.ds = USER_DS;
        pcb->iss.es = USER_DS;
        pcb->iss.fs = USER_DS;
        pcb->iss.gs = USER_DS;
        pcb->iss.efl = EFL_USER_SET;
        {
          struct real_descriptor *ldtp;
          ldtp = (struct real_descriptor *)ldt;
          pcb->cthread_desc = ldtp[sel_idx(USER_DS)];
          pcb->uldt_desc = ldtp[sel_idx(USER_DS)];
          pcb->uldt_selector = 0;
        }

        /*
         *      Allocate a kernel stack per thread.
         */
        stack_alloc(thread);

        return(KERN_SUCCESS);
}

/*
 * Machine-dependent cleanup prior to destroying a thread
 */
void
machine_thread_destroy(
        thread_t                thread)
{
        register pcb_t  pcb = thread->machine.pcb;

        assert(pcb);
        
        if (pcb->ims.io_tss != 0)
                iopb_destroy(pcb->ims.io_tss);
        if (pcb->ims.ifps != 0)
                fpu_free(pcb->ims.ifps);
        if (pcb->ims.ldt != 0)
                user_ldt_free(pcb->ims.ldt);
        thread->machine.pcb = (pcb_t)0;
}

/*
 * This is used to set the current thr_act/thread
 * when starting up a new processor
 */
void
machine_set_current_thread( thread_t thread )
{
        mp_disable_preemption();

        current_cpu_datap()->cpu_active_thread = thread;
        current_cpu_datap()->cpu_active_kloaded = THREAD_NULL;

        mp_enable_preemption();
}

void
machine_thread_terminate_self(void)
{
}

void
act_machine_return(int code)
{
        /*
         * This code is called with nothing locked.
         * It also returns with nothing locked, if it returns.
         *
         * This routine terminates the current thread activation.
         * If this is the only activation associated with its
         * thread shuttle, then the entire thread (shuttle plus
         * activation) is terminated.
         */
        assert( code == KERN_TERMINATED );

        thread_terminate_self();

        /*NOTREACHED*/

        panic("act_machine_return(%d): TALKING ZOMBIE! (1)", code);
}


/*
 * Perform machine-dependent per-thread initializations
 */
void
machine_thread_init(void)
{
        fpu_module_init();
        iopb_init();
}

/*
 * Some routines for debugging activation code
 */
static void     dump_handlers(thread_t);
void            dump_regs(thread_t);
int             dump_act(thread_t thr_act);

static void
dump_handlers(thread_t thr_act)
{
    ReturnHandler *rhp = thr_act->handlers;
    int counter = 0;

    printf("\t");
    while (rhp) {
        if (rhp == &thr_act->special_handler){
            if (rhp->next)
                printf("[NON-Zero next ptr(%x)]", rhp->next);
            printf("special_handler()->");
            break;
        }
        printf("hdlr_%d(%x)->",counter,rhp->handler);
        rhp = rhp->next;
        if (++counter > 32) {
                printf("Aborting: HUGE handler chain\n");
                break;
        }
    }
    printf("HLDR_NULL\n");
}

void
dump_regs(thread_t thr_act)
{
        if (thr_act->machine.pcb) {
                register struct i386_saved_state *ssp = USER_REGS(thr_act);
                /* Print out user register state */
                printf("\tRegs:\tedi=%x esi=%x ebp=%x ebx=%x edx=%x\n",
                    ssp->edi, ssp->esi, ssp->ebp, ssp->ebx, ssp->edx);
                printf("\t\tecx=%x eax=%x eip=%x efl=%x uesp=%x\n",
                    ssp->ecx, ssp->eax, ssp->eip, ssp->efl, ssp->uesp);
                printf("\t\tcs=%x ss=%x\n", ssp->cs, ssp->ss);
        }
}

int
dump_act(thread_t thr_act)
{
        if (!thr_act)
                return(0);

        printf("thread(0x%x)(%d): task=%x(%d)\n",
               thr_act, thr_act->ref_count,
               thr_act->task,   thr_act->task   ? thr_act->task->ref_count : 0);

        printf("\tsusp=%d user_stop=%d active=%x ast=%x\n",
                       thr_act->suspend_count, thr_act->user_stop_count,
                       thr_act->active, thr_act->ast);
        printf("\tpcb=%x\n", thr_act->machine.pcb);

        if (thr_act->kernel_stack) {
            vm_offset_t stack = thr_act->kernel_stack;

            printf("\tk_stk %x  eip %x ebx %x esp %x iss %x\n",
                stack, STACK_IKS(stack)->k_eip, STACK_IKS(stack)->k_ebx,
                STACK_IKS(stack)->k_esp, STACK_IEL(stack)->saved_state);
        }

        dump_handlers(thr_act);
        dump_regs(thr_act);
        return((int)thr_act);
}

user_addr_t
get_useraddr(void)
{
  
        thread_t thr_act = current_thread();
 
        if (thr_act->machine.pcb) 
                return(thr_act->machine.pcb->iss.eip);
        else 
                return(0);

}

/*
 * detach and return a kernel stack from a thread
 */

vm_offset_t
machine_stack_detach(thread_t thread)
{
  vm_offset_t stack;

                KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_SCHED,MACH_STACK_DETACH),
                        thread, thread->priority,
                        thread->sched_pri, 0,
                        0);

  stack = thread->kernel_stack;
  thread->kernel_stack = 0;
  return(stack);
}

/*
 * attach a kernel stack to a thread and initialize it
 */

void
machine_stack_attach(
        thread_t                thread,
        vm_offset_t             stack)
{
  struct i386_kernel_state *statep;

                KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_SCHED,MACH_STACK_ATTACH),
                        thread, thread->priority,
                        thread->sched_pri, 0, 0);

  assert(stack);
  statep = STACK_IKS(stack);
  thread->kernel_stack = stack;

  statep->k_eip = (unsigned long) Thread_continue;
  statep->k_ebx = (unsigned long) thread_continue;
  statep->k_esp = (unsigned long) STACK_IEL(stack);

  STACK_IEL(stack)->saved_state = &thread->machine.pcb->iss;

  return;
}

/*
 * move a stack from old to new thread
 */

void
machine_stack_handoff(thread_t old,
              thread_t new)
{
  vm_offset_t stack;

                KERNEL_DEBUG(MACHDBG_CODE(DBG_MACH_SCHED,MACH_STACK_HANDOFF),
                        thread, thread->priority,
                        thread->sched_pri, 0, 0);

  assert(new);
  assert(old);

  stack = machine_stack_detach(old);
  machine_stack_attach(new, stack);

  PMAP_SWITCH_CONTEXT(old->task, new->task, cpu_number());

  KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SCHED,MACH_STACK_HANDOFF) | DBG_FUNC_NONE,
                     (int)old, (int)new, old->sched_pri, new->sched_pri, 0);

  machine_set_current_thread(new);

  current_cpu_datap()->cpu_active_stack = new->kernel_stack;

  return;
}

struct i386_act_context {
        struct i386_saved_state ss;
        struct i386_float_state fs;
};

void *
act_thread_csave(void)
{
struct i386_act_context *ic;
kern_return_t kret;
int val;

                ic = (struct i386_act_context *)kalloc(sizeof(struct i386_act_context));

                if (ic == (struct i386_act_context *)NULL)
                                return((void *)0);

                val = i386_SAVED_STATE_COUNT; 
                kret = machine_thread_get_state(current_thread(),
                                                i386_SAVED_STATE,
                                                (thread_state_t) &ic->ss,
                                                &val);
                if (kret != KERN_SUCCESS) {
                                kfree(ic,sizeof(struct i386_act_context));
                                return((void *)0);
                }
                val = i386_FLOAT_STATE_COUNT; 
                kret = machine_thread_get_state(current_thread(),
                                                i386_FLOAT_STATE,
                                                (thread_state_t) &ic->fs,
                                                &val);
                if (kret != KERN_SUCCESS) {
                                kfree(ic,sizeof(struct i386_act_context));
                                return((void *)0);
                }
                return(ic);
}
void 
act_thread_catt(void *ctx)
{
struct i386_act_context *ic;
kern_return_t kret;

                ic = (struct i386_act_context *)ctx;

                if (ic == (struct i386_act_context *)NULL)
                                return;

                kret = machine_thread_set_state(current_thread(),
                                                i386_SAVED_STATE,
                                                (thread_state_t) &ic->ss,
                                                i386_SAVED_STATE_COUNT);
                if (kret != KERN_SUCCESS) 
                                goto out;

                kret = machine_thread_set_state(current_thread(),
                                                i386_FLOAT_STATE,
                                                (thread_state_t) &ic->fs,
                                                i386_FLOAT_STATE_COUNT);
                if (kret != KERN_SUCCESS)
                                goto out;
out:
        kfree(ic,sizeof(struct i386_act_context));              
}

void act_thread_cfree(void *ctx)
{
        kfree(ctx,sizeof(struct i386_act_context));             
}