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

/*
 * Copyright (c) 2000-2004 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_OSREFERENCE_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.  The rights granted to you under the 
 * License may not be used to create, or enable the creation or 
 * redistribution of, unlawful or unlicensed copies of an Apple operating 
 * system, or to circumvent, violate, or enable the circumvention or 
 * violation of, any terms of an Apple operating system software license 
 * agreement.
 *
 * 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_OSREFERENCE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Copyright (c) 1990,1991,1992 The University of Utah and
 * the Center for Software Science (CSS).  All rights reserved.
 *
 * Permission to use, copy, modify and distribute this software is hereby
 * granted provided that (1) source code retains these copyright, permission,
 * and disclaimer notices, and (2) redistributions including binaries
 * reproduce the notices in supporting documentation, and (3) all advertising
 * materials mentioning features or use of this software display the following
 * acknowledgement: ``This product includes software developed by the Center
 * for Software Science at the University of Utah.''
 *
 * THE UNIVERSITY OF UTAH AND CSS ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS
 * IS" CONDITION.  THE UNIVERSITY OF UTAH AND CSS DISCLAIM ANY LIABILITY OF
 * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * CSS requests users of this software to return to css-dist@cs.utah.edu any
 * improvements that they make and grant CSS redistribution rights.
 *
 *      Utah $Hdr: pcb.c 1.23 92/06/27$
 */

#include <debug.h>

#include <types.h>

#include <mach/mach_types.h>
#include <mach/thread_status.h>

#include <kern/kern_types.h>
#include <kern/task.h>
#include <kern/thread.h>
#include <kern/misc_protos.h>
#include <kern/mach_param.h>
#include <kern/spl.h>

#include <vm/vm_map.h>
#include <vm/vm_kern.h>

#include <ppc/misc_protos.h>
#include <ppc/cpu_internal.h>
#include <ppc/exception.h>
#include <ppc/proc_reg.h>
#include <ppc/pmap.h>
#include <ppc/trap.h>
#include <ppc/mappings.h>
#include <ppc/savearea.h>
#include <ppc/Firmware.h>
#include <ppc/asm.h>
#include <ppc/thread.h>
#include <ppc/vmachmon.h>
#include <ppc/low_trace.h>
#include <ppc/lowglobals.h>

#include <sys/kdebug.h>

void    machine_act_terminate(thread_t);

/*
 * These constants are dumb. They should not be in asm.h!
 */

#define KF_SIZE         (FM_SIZE+ARG_SIZE+FM_REDZONE)

#if DEBUG
int   fpu_trap_count = 0;
int   fpu_switch_count = 0;
int   vec_trap_count = 0;
int   vec_switch_count = 0;
#endif

/*
 * consider_machine_collect: try to collect machine-dependent pages
 */
void
consider_machine_collect()
{
    /*
     * none currently available
     */
        return;
}

void
consider_machine_adjust()
{
        consider_mapping_adjust();
}

/*
 * switch_context: Switch from one thread to another, needed for
 *                 switching of space
 * 
 */
thread_t
machine_switch_context(
        thread_t                        old,
        thread_continue_t       continuation,
        thread_t                        new)
{
        register thread_t retval;
        pmap_t  new_pmap;
        facility_context *fowner;
        struct per_proc_info *ppinfo;

        if (old == new)
                panic("machine_switch_context");

        ppinfo = getPerProc();                                                          /* Get our processor block */

        ppinfo->old_thread = (unsigned int)old;
        ppinfo->cpu_flags &= ~traceBE;                                           /* disable branch tracing if on */
               
        /* Our context might wake up on another processor, so we must
         * not keep hot state in our FPU, it must go back to the pcb
         * so that it can be found by the other if needed
         */
        if(real_ncpus > 1) {                                                            /* This is potentially slow, so only do when actually SMP */
                fowner = ppinfo->FPU_owner;                                             /* Cache this because it may change */
                if(fowner) {                                                                    /* Is there any live context? */
                        if(fowner->facAct == old) {             /* Is it for us? */
                                fpu_save(fowner);                                               /* Yes, save it */
                        }
                }
                fowner = ppinfo->VMX_owner;                                             /* Cache this because it may change */
                if(fowner) {                                                                    /* Is there any live context? */
                        if(fowner->facAct == old) {             /* Is it for us? */
                                vec_save(fowner);                                               /* Yes, save it */
                        }
                }
        }

        /*
         * If old thread is running VM, save per proc userProtKey and FamVMmode spcFlags bits in the thread spcFlags
         * This bits can be modified in the per proc without updating the thread spcFlags
         */
        if(old->machine.specFlags & runningVM) {
                old->machine.specFlags &=  ~(userProtKey|FamVMmode);
                old->machine.specFlags |= (ppinfo->spcFlags) & (userProtKey|FamVMmode);
        }
        old->machine.specFlags &= ~OnProc;
        new->machine.specFlags |= OnProc;

        /*
         * We do not have to worry about the PMAP module, so switch.
         *
         * We must not use thread->map since this may not be the actual
         * task map, but the map being used for a klcopyin/out.
         */

        if(new->machine.specFlags & runningVM) {                        /* Is the new guy running a VM? */
                pmap_switch(new->machine.vmmCEntry->vmmPmap);   /* Switch to the VM's pmap */
                ppinfo->VMMareaPhys = new->machine.vmmCEntry->vmmContextPhys;
                ppinfo->VMMXAFlgs = new->machine.vmmCEntry->vmmXAFlgs;
                ppinfo->FAMintercept = new->machine.vmmCEntry->vmmFAMintercept;
        }
        else {                                                                                          /* otherwise, we use the task's pmap */
                new_pmap = new->task->map->pmap;
                if ((old->task->map->pmap != new_pmap) || (old->machine.specFlags & runningVM)) {
                        pmap_switch(new_pmap);                                          /* Switch if there is a change */
                }
        }

        if(old->machine.umwSpace != invalSpace) {                       /* Does our old guy have an active window? */
                old->machine.umwSpace |= umwSwitchAway;                 /* Show we switched away from this guy */
                hw_blow_seg(lowGlo.lgUMWvaddr);                                 /* Blow off the first segment */
                hw_blow_seg(lowGlo.lgUMWvaddr + 0x10000000ULL); /* Blow off the second segment */
        }

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

        retval = Switch_context(old, continuation, new);
        assert(retval != NULL);

        if (branch_tracing_enabled()) {
                ppinfo = getPerProc();                                                  /* Get our processor block */
                ppinfo->cpu_flags |= traceBE;                                   /* restore branch tracing */
        }

        /* We've returned from having switched context, so we should be
         * back in the original context.
         */

        return retval;
}

/*
 * Initialize the machine-dependent state for a new thread.
 */
kern_return_t
machine_thread_create(
        thread_t                thread,
        task_t                  task)
{
        savearea                *sv;                                                                    /* Pointer to newly allocated savearea */
        unsigned int    *CIsTooLimited, i;

        hw_atomic_add((uint32_t *)&saveanchor.savetarget, 4);   /* Account for the number of saveareas we think we "need"
                                                                                                                           for this activation */
        assert(thread->machine.pcb == (savearea *)0);                           /* Make sure there was no previous savearea */
        
        sv = save_alloc();                                                                              /* Go get us a savearea */
                
        bzero((char *)((unsigned int)sv + sizeof(savearea_comm)), (sizeof(savearea) - sizeof(savearea_comm)));  /* Clear it */
                
        sv->save_hdr.save_prev = 0;                                                             /* Clear the back pointer */
        sv->save_hdr.save_flags = (sv->save_hdr.save_flags & ~SAVtype) | (SAVgeneral << SAVtypeshft);   /* Mark as in use */
        sv->save_hdr.save_act = thread; /* Set who owns it */
        thread->machine.pcb = sv;                                                                       /* Point to the save area */
        thread->machine.curctx = &thread->machine.facctx;                       /* Initialize facility context */
        thread->machine.facctx.facAct = thread;                                         /* Initialize facility context pointer to activation */
        thread->machine.umwSpace = invalSpace;                                          /* Initialize user memory window space to invalid */
        thread->machine.preemption_count = 0;                                           /* Initialize preemption counter */

        /*
         * User threads will pull their context from the pcb when first
         * returning to user mode, so fill in all the necessary values.
         * Kernel threads are initialized from the save state structure 
         * at the base of the kernel stack (see stack_attach()).
         */

        thread->machine.upcb = sv;                                                              /* Set user pcb */
        sv->save_srr1 = (uint64_t)MSR_EXPORT_MASK_SET;                  /* Set the default user MSR */
        if(task_has_64BitAddr(task)) sv->save_srr1 |= (uint64_t)MASK32(MSR_SF) << 32;   /* If 64-bit task, force 64-bit mode */
        sv->save_fpscr = 0;                                                                             /* Clear all floating point exceptions */
        sv->save_vrsave = 0;                                                                    /* Set the vector save state */
        sv->save_vscr[0] = 0x00000000;                                  
        sv->save_vscr[1] = 0x00000000;                                  
        sv->save_vscr[2] = 0x00000000;                                  
        sv->save_vscr[3] = 0x00010000;                                                  /* Disable java mode and clear saturated */
        
    return(KERN_SUCCESS);
}

/*
 * Machine-dependent cleanup prior to destroying a thread
 */
void
machine_thread_destroy(
        thread_t                thread)
{
        register savearea *pcb, *ppsv;
        register savearea_vec *vsv, *vpsv;
        register savearea_fpu *fsv, *fpsv;
        register savearea *svp;
        register int i;
        boolean_t intr;

/*
 *      This function will release all context.
 */

        machine_act_terminate(thread);                                                  /* Make sure all virtual machines are dead first */
 
/*
 *
 *      Walk through and release all floating point and vector contexts. Also kill live context.
 *
 */

        intr = ml_set_interrupts_enabled(FALSE);                                /* Disable for interruptions */
 
        toss_live_vec(thread->machine.curctx);                                  /* Dump live vectors */

        vsv = thread->machine.curctx->VMXsave;                                  /* Get the top vector savearea */
        
        while(vsv) {                                                                                    /* Any VMX saved state? */
                vpsv = vsv;                                                                                     /* Remember so we can toss this */
                vsv = CAST_DOWN(savearea_vec *, vsv->save_hdr.save_prev);  /* Get one underneath our's */
                save_release((savearea *)vpsv);                                         /* Release it */
        }
        
        thread->machine.curctx->VMXsave = 0;                                    /* Kill chain */
 
        toss_live_fpu(thread->machine.curctx);                                  /* Dump live float */

        fsv = thread->machine.curctx->FPUsave;                                  /* Get the top float savearea */
        
        while(fsv) {                                                                                    /* Any float saved state? */
                fpsv = fsv;                                                                                     /* Remember so we can toss this */
                fsv = CAST_DOWN(savearea_fpu *, fsv->save_hdr.save_prev);   /* Get one underneath our's */
                save_release((savearea *)fpsv);                                         /* Release it */
        }
        
        thread->machine.curctx->FPUsave = 0;                                    /* Kill chain */

/*
 * free all regular saveareas.
 */

        pcb = thread->machine.pcb;                                                              /* Get the general savearea */
        
        while(pcb) {                                                                                    /* Any float saved state? */
                ppsv = pcb;                                                                                     /* Remember so we can toss this */
                pcb = CAST_DOWN(savearea *, pcb->save_hdr.save_prev);  /* Get one underneath our's */ 
                save_release(ppsv);                                                                     /* Release it */
        }
        
        hw_atomic_sub((uint32_t *)&saveanchor.savetarget, 4);   /* Unaccount for the number of saveareas we think we "need" */

        (void) ml_set_interrupts_enabled(intr);                                 /* Restore interrupts if enabled */

}

/*
 * act_machine_sv_free
 * release saveareas associated with an act. if flag is true, release
 * user level savearea(s) too, else don't
 *
 * This code must run with interruptions disabled because an interrupt handler could use
 * floating point and/or vectors.  If this happens and the thread we are blowing off owns
 * the facility, we can deadlock.
 */
void
act_machine_sv_free(thread_t act)
{
        register savearea *pcb, *userpcb;
        register savearea_vec *vsv, *vpst, *vsvt;
        register savearea_fpu *fsv, *fpst, *fsvt;
        register savearea *svp;
        register int i;
        boolean_t intr;

/*
 *      This function will release all non-user state context.
 */
 
/*
 *
 *      Walk through and release all floating point and vector contexts that are not
 *      user state.  We will also blow away live context if it belongs to non-user state.
 *      Note that the level can not change while we are in this code.  Nor can another
 *      context be pushed on the stack.
 *
 *      We do nothing here if the current level is user.  Otherwise,
 *      the live context is cleared.  Then we find the user saved context.
 *      Next,  we take the sync lock (to keep us from munging things in *_switch).
 *      The level is set to 0 and all stacked context other than user is dequeued.
 *      Then we unlock.  Next, all of the old kernel contexts are released.
 *
 */

        intr = ml_set_interrupts_enabled(FALSE);                                /* Disable for interruptions */

        if(act->machine.curctx->VMXlevel) {                                             /* Is the current level user state? */
                
                toss_live_vec(act->machine.curctx);                                     /* Dump live vectors if is not user */
                
                if(!hw_lock_to((hw_lock_t)&act->machine.curctx->VMXsync, LockTimeOut)) {        /* Get the sync lock */ 
                        panic("act_machine_sv_free - timeout getting VMX sync lock\n"); /* Tell all and die */
                }
        
                vsv = act->machine.curctx->VMXsave;                                     /* Get the top vector savearea */
                while(vsv && vsv->save_hdr.save_level) vsv = (savearea_vec *)vsv->save_hdr.save_prev;   /* Find user context if any */
                
                vsvt = act->machine.curctx->VMXsave;                            /* Get the top of the chain */
                act->machine.curctx->VMXsave = vsv;                                     /* Point to the user context */
                act->machine.curctx->VMXlevel = 0;                                      /* Set the level to user */
                hw_lock_unlock((hw_lock_t)&act->machine.curctx->VMXsync);       /* Unlock */
                
                while(vsvt) {                                                                           /* Clear any VMX saved state */
                        if (vsvt == vsv) break;                                                 /* Done when hit user if any */
                        vpst = vsvt;                                                                    /* Remember so we can toss this */
                        vsvt = (savearea_vec *)vsvt->save_hdr.save_prev;        /* Get one underneath our's */          
                        save_ret((savearea *)vpst);                                             /* Release it */
                }
                
        }
 
        if(act->machine.curctx->FPUlevel) {                                             /* Is the current level user state? */
                
                toss_live_fpu(act->machine.curctx);                                     /* Dump live floats if is not user */

                if(!hw_lock_to((hw_lock_t)&act->machine.curctx->FPUsync, LockTimeOut)) {        /* Get the sync lock */ 
                        panic("act_machine_sv_free - timeout getting FPU sync lock\n"); /* Tell all and die */
                }
                
                fsv = act->machine.curctx->FPUsave;                                     /* Get the top floats savearea */
                while(fsv && fsv->save_hdr.save_level) fsv = (savearea_fpu *)fsv->save_hdr.save_prev;   /* Find user context if any */
                
                fsvt = act->machine.curctx->FPUsave;                            /* Get the top of the chain */
                act->machine.curctx->FPUsave = fsv;                                     /* Point to the user context */
                act->machine.curctx->FPUlevel = 0;                                      /* Set the level to user */
                hw_lock_unlock((hw_lock_t)&act->machine.curctx->FPUsync);       /* Unlock */
                
                while(fsvt) {                                                                           /* Clear any VMX saved state */
                        if (fsvt == fsv) break;                                                 /* Done when hit user if any */
                        fpst = fsvt;                                                                    /* Remember so we can toss this */
                        fsvt = (savearea_fpu *)fsvt->save_hdr.save_prev;        /* Get one underneath our's */          
                        save_ret((savearea *)fpst);                                             /* Release it */
                }
                
        }

/*
 * free all regular saveareas except a user savearea, if any
 */

        pcb = act->machine.pcb;                                                                 /* Get the general savearea */
        userpcb = 0;                                                                                    /* Assume no user context for now */
        
        while(pcb) {                                                                                    /* Any float saved state? */
                if (pcb->save_srr1 & MASK(MSR_PR)) {                            /* Is this a user savearea? */
                        userpcb = pcb;                                                                  /* Remember so we can toss this */
                        break;
                }
                svp = pcb;                                                                                      /* Remember this */
                pcb = CAST_DOWN(savearea *, pcb->save_hdr.save_prev);  /* Get one underneath our's */ 
                save_ret(svp);                                                                          /* Release it */
        }
        
        act->machine.pcb = userpcb;                                                             /* Chain in the user if there is one, or 0 if not */
        (void) ml_set_interrupts_enabled(intr);                                 /* Restore interrupts if enabled */

}

void
machine_act_terminate(
        thread_t        act)
{
        if(act->machine.bbDescAddr) {                                                   /* Check if the Blue box assist is active */
                disable_bluebox_internal(act);                                          /* Kill off bluebox */
        }
        
        if(act->machine.vmmControl) {                                                   /* Check if VMM is active */
                vmm_tear_down_all(act);                                                         /* Kill off all VMM contexts */
        }
}

void
machine_thread_terminate_self(void)
{
        machine_act_terminate(current_thread());
}

void
machine_thread_init(void)
{
#ifdef  MACHINE_STACK
#if KERNEL_STACK_SIZE > PPC_PGBYTES
        panic("KERNEL_STACK_SIZE can't be greater than PPC_PGBYTES\n");
#endif
#endif
}

#if MACH_ASSERT

void
dump_thread(thread_t th)
{
        printf(" thread @ 0x%x:\n", th);
}

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=%x active=%x\n",
           thr_act->suspend_count, thr_act->active);

    return((int)thr_act);
}

#endif

user_addr_t 
get_useraddr()
{
        return(current_thread()->machine.upcb->save_srr0);
}

/*
 * 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);

  act_machine_sv_free(thread);

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

/*
 * attach a kernel stack to a thread and initialize it
 *
 * attaches a stack to a thread. if there is no save
 * area we allocate one.  the top save area is then
 * loaded with the pc (continuation address), the initial
 * stack pointer, and a std kernel MSR. if the top
 * save area is the user save area bad things will 
 * happen
 *
 */

void
machine_stack_attach(
        thread_t                thread,
        vm_offset_t             stack)
{
  unsigned int *kss;
  struct savearea *sv;

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

  assert(stack);
  kss = (unsigned int *)STACK_IKS(stack);
  thread->kernel_stack = stack;

  /* during initialization we sometimes do not have an
     activation. in that case do not do anything */
  sv = save_get();  /* cannot block */
  sv->save_hdr.save_flags = (sv->save_hdr.save_flags & ~SAVtype) | (SAVgeneral << SAVtypeshft); /* Mark as in use */
  sv->save_hdr.save_act = thread;
  sv->save_hdr.save_prev = (addr64_t)((uintptr_t)thread->machine.pcb);
  thread->machine.pcb = sv;

  sv->save_srr0 = (unsigned int)thread_continue;
  /* sv->save_r3 = ARG ? */
  sv->save_r1 = (vm_offset_t)((int)kss - KF_SIZE);
  sv->save_srr1 = MSR_SUPERVISOR_INT_OFF;
  sv->save_fpscr = 0;                                                                   /* Clear all floating point exceptions */
  sv->save_vrsave = 0;                                                          /* Set the vector save state */
  sv->save_vscr[3] = 0x00010000;                                                /* Supress java mode */
  *(CAST_DOWN(int *, sv->save_r1)) = 0;

  thread->machine.ksp = 0;                            
}

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

void
machine_stack_handoff(
        thread_t                old,
        thread_t                new)
{

        vm_offset_t stack;
        pmap_t new_pmap;
        facility_context *fowner;
        mapping_t *mp;
        struct per_proc_info *ppinfo;
        
        assert(new);
        assert(old);

        if (old == new)
                panic("machine_stack_handoff");
        
        stack = machine_stack_detach(old);
        new->kernel_stack = stack;
        if (stack == old->reserved_stack) {
                assert(new->reserved_stack);
                old->reserved_stack = new->reserved_stack;
                new->reserved_stack = stack;
        }

        ppinfo = getPerProc();                                                          /* Get our processor block */

        ppinfo->cpu_flags &= ~traceBE;                                          /* Turn off special branch trace */

        if(real_ncpus > 1) {                                                            /* This is potentially slow, so only do when actually SMP */
                fowner = ppinfo->FPU_owner;                                             /* Cache this because it may change */
                if(fowner) {                                                                    /* Is there any live context? */
                        if(fowner->facAct == old) {             /* Is it for us? */
                                fpu_save(fowner);                                               /* Yes, save it */
                        }
                }
                fowner = ppinfo->VMX_owner;                                             /* Cache this because it may change */
                if(fowner) {                                                                    /* Is there any live context? */
                        if(fowner->facAct == old) {             /* Is it for us? */
                                vec_save(fowner);                                               /* Yes, save it */
                        }
                }
        }

        /*
         * If old thread is running VM, save per proc userProtKey and FamVMmode spcFlags bits in the thread spcFlags
         * This bits can be modified in the per proc without updating the thread spcFlags
         */
        if(old->machine.specFlags & runningVM) {                        /* Is the current thread running a VM? */
                old->machine.specFlags &= ~(userProtKey|FamVMmode);
                old->machine.specFlags |= (ppinfo->spcFlags) & (userProtKey|FamVMmode);
        }
        old->machine.specFlags &= ~OnProc;
        new->machine.specFlags |= OnProc;

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


        if(new->machine.specFlags & runningVM) {        /* Is the new guy running a VM? */
                pmap_switch(new->machine.vmmCEntry->vmmPmap);   /* Switch to the VM's pmap */
                ppinfo->VMMareaPhys = new->machine.vmmCEntry->vmmContextPhys;
                ppinfo->VMMXAFlgs = new->machine.vmmCEntry->vmmXAFlgs;
                ppinfo->FAMintercept = new->machine.vmmCEntry->vmmFAMintercept;
        }
        else {                                                                                  /* otherwise, we use the task's pmap */
                new_pmap = new->task->map->pmap;
                if ((old->task->map->pmap != new_pmap) || (old->machine.specFlags & runningVM)) {
                        pmap_switch(new_pmap);
                }
        }

        machine_set_current_thread(new);
        ppinfo->Uassist = new->machine.cthread_self;

        ppinfo->ppbbTaskEnv = new->machine.bbTaskEnv;
        ppinfo->spcFlags = new->machine.specFlags;
        
        old->machine.umwSpace |= umwSwitchAway;                 /* Show we switched away from this guy */
        mp = (mapping_t *)&ppinfo->ppUMWmp;
        mp->mpSpace = invalSpace;                                               /* Since we can't handoff in the middle of copy in/out, just invalidate */

        if (branch_tracing_enabled()) 
                ppinfo->cpu_flags |= traceBE;
    
        if(trcWork.traceMask) dbgTrace(0x9903, (unsigned int)old, (unsigned int)new, 0, 0);     /* Cut trace entry if tracing */    
    
  return;
}

/*
 * clean and initialize the current kernel stack and go to
 * the given continuation routine
 */

void
call_continuation(
        thread_continue_t       continuation,
        void                            *parameter,
        wait_result_t           wresult)
{
        thread_t                self = current_thread();
        unsigned int    *kss;
        vm_offset_t             tsp;

        assert(self->kernel_stack);
        kss = (unsigned int *)STACK_IKS(self->kernel_stack);
        assert(continuation);

        tsp = (vm_offset_t)((int)kss - KF_SIZE);
        assert(tsp);
        *((int *)tsp) = 0;

        Call_continuation(continuation, parameter, wresult, tsp);
}