minix/servers/vm/region.c

#include <minix/com.h>
#include <minix/callnr.h>
#include <minix/type.h>
#include <minix/config.h>
#include <minix/const.h>
#include <minix/sysutil.h>
#include <minix/syslib.h>
#include <minix/debug.h>
#include <minix/bitmap.h>
#include <minix/hash.h>
#include <machine/multiboot.h>

#include <sys/mman.h>

#include <limits.h>
#include <string.h>
#include <assert.h>
#include <stdint.h>
#include <sys/param.h>

#include "vm.h"
#include "proto.h"
#include "util.h"
#include "glo.h"
#include "region.h"
#include "sanitycheck.h"
#include "physravl.h"
#include "memlist.h"
#include "memtype.h"

/* LRU list. */
static yielded_t *lru_youngest = NULL, *lru_oldest = NULL;

static int map_ph_writept(struct vmproc *vmp, struct vir_region *vr,
	struct phys_region *pr);

static phys_bytes freeyieldednode(yielded_t *node, int freemem);

static struct vir_region *map_copy_region(struct vmproc *vmp, struct
	vir_region *vr);

#if SANITYCHECKS
static void lrucheck(void);
#endif

/* hash table of yielded blocks */
#define YIELD_HASHSIZE 65536
static yielded_avl vm_yielded_blocks[YIELD_HASHSIZE];

static int avl_inited = 0;

void map_region_init(void)
{
	int h;
	assert(!avl_inited);
	for(h = 0; h < YIELD_HASHSIZE; h++)
		yielded_init(&vm_yielded_blocks[h]);
	avl_inited = 1;
}

static yielded_avl *get_yielded_avl(block_id_t id)
{
	u32_t h;

	assert(avl_inited);

	hash_i_64(id.owner, id.id, h);
	h = h % YIELD_HASHSIZE;

	assert(h >= 0);
	assert(h < YIELD_HASHSIZE);

	return &vm_yielded_blocks[h];
}

void map_printregion(struct vmproc *vmp, struct vir_region *vr)
{
	physr_iter iter;
	struct phys_region *ph;
	printf("map_printmap: map_name: %s\n", vr->memtype->name);
	printf("\t%lx (len 0x%lx, %lukB), %p\n",
		vr->vaddr, vr->length, vr->length/1024, vr->memtype->name);
	printf("\t\tphysblocks:\n");
	physr_start_iter_least(vr->phys, &iter);
	while((ph = physr_get_iter(&iter))) {
		printf("\t\t@ %lx (refs %d): phys 0x%lx\n",
			(vr->vaddr + ph->offset),
			ph->ph->refcount, ph->ph->phys);
		physr_incr_iter(&iter);
	}
}

/*===========================================================================*
 *				map_printmap				     *
 *===========================================================================*/
void map_printmap(vmp)
struct vmproc *vmp;
{
	struct vir_region *vr;
	region_iter iter;

	printf("memory regions in process %d:\n", vmp->vm_endpoint);

	region_start_iter_least(&vmp->vm_regions_avl, &iter);
	while((vr = region_get_iter(&iter))) {
		map_printregion(vmp, vr);
		region_incr_iter(&iter);
	}
}

static struct vir_region *getnextvr(struct vir_region *vr)
{
	struct vir_region *nextvr;
	region_iter v_iter;
	SLABSANE(vr);
	region_start_iter(&vr->parent->vm_regions_avl, &v_iter, vr->vaddr, AVL_EQUAL);
	assert(region_get_iter(&v_iter));
	assert(region_get_iter(&v_iter) == vr);
	region_incr_iter(&v_iter);
	nextvr = region_get_iter(&v_iter);
	if(!nextvr) return NULL;
	SLABSANE(nextvr);
	assert(vr->parent == nextvr->parent);
	assert(vr->vaddr < nextvr->vaddr);
	assert(vr->vaddr + vr->length <= nextvr->vaddr);
	return nextvr;
}

int pr_writable(struct vir_region *vr, struct phys_region *pr)
{
	assert(vr->memtype->writable);
	return ((vr->flags & VR_WRITABLE) && vr->memtype->writable(pr));
}

#if SANITYCHECKS

/*===========================================================================*
 *				map_sanitycheck_pt			     *
 *===========================================================================*/
static int map_sanitycheck_pt(struct vmproc *vmp,
	struct vir_region *vr, struct phys_region *pr)
{
	struct phys_block *pb = pr->ph;
	int rw;
	int r;

	if(pr_writable(vr, pr))
		rw = PTF_WRITE;
	else
		rw = PTF_READ;

	r = pt_writemap(vmp, &vmp->vm_pt, vr->vaddr + pr->offset,
	  pb->phys, VM_PAGE_SIZE, PTF_PRESENT | PTF_USER | rw, WMF_VERIFY);

	if(r != OK) {
		printf("proc %d phys_region 0x%lx sanity check failed\n",
			vmp->vm_endpoint, pr->offset);
		map_printregion(vmp, vr);
	}

	return r;
}

/*===========================================================================*
 *				map_sanitycheck			     *
 *===========================================================================*/
void map_sanitycheck(char *file, int line)
{
	struct vmproc *vmp;

	lrucheck();

/* Macro for looping over all physical blocks of all regions of
 * all processes.
 */
#define ALLREGIONS(regioncode, physcode)			\
	for(vmp = vmproc; vmp < &vmproc[VMP_NR]; vmp++) {	\
		region_iter v_iter;				\
		struct vir_region *vr;				\
		if(!(vmp->vm_flags & VMF_INUSE))		\
			continue;				\
		region_start_iter_least(&vmp->vm_regions_avl, &v_iter);	\
		while((vr = region_get_iter(&v_iter))) {	\
			physr_iter iter;			\
			struct phys_region *pr;			\
			regioncode;				\
			physr_start_iter_least(vr->phys, &iter); \
			while((pr = physr_get_iter(&iter))) {	\
				physcode;			\
				physr_incr_iter(&iter);		\
			}					\
			region_incr_iter(&v_iter);		\
		}						\
	}

#define MYSLABSANE(s) MYASSERT(slabsane_f(__FILE__, __LINE__, s, sizeof(*(s))))
	/* Basic pointers check. */
	ALLREGIONS(MYSLABSANE(vr),MYSLABSANE(pr); MYSLABSANE(pr->ph);MYSLABSANE(pr->parent));
	ALLREGIONS(/* MYASSERT(vr->parent == vmp) */,MYASSERT(pr->parent == vr););

	/* Do counting for consistency check. */
	ALLREGIONS(;,USE(pr->ph, pr->ph->seencount = 0;););
	ALLREGIONS(;,USE(pr->ph, pr->ph->seencount++;);
		if(pr->ph->seencount == 1) {
			if(pr->parent->memtype->ev_sanitycheck)
				pr->parent->memtype->ev_sanitycheck(pr, file, line);
		}
	);

	/* Do consistency check. */
	ALLREGIONS({ struct vir_region *nextvr = getnextvr(vr);
		if(nextvr) {
			MYASSERT(vr->vaddr < nextvr->vaddr);
			MYASSERT(vr->vaddr + vr->length <= nextvr->vaddr);
		}
		}
		MYASSERT(!(vr->vaddr % VM_PAGE_SIZE));,	
		if(pr->ph->refcount != pr->ph->seencount) {
			map_printmap(vmp);
			printf("ph in vr %p: 0x%lx  refcount %u "
				"but seencount %u\n", 
				vr, pr->offset,
				pr->ph->refcount, pr->ph->seencount);
		}
		{
			int n_others = 0;
			struct phys_region *others;
			if(pr->ph->refcount > 0) {
				MYASSERT(pr->ph->firstregion);
				if(pr->ph->refcount == 1) {
					MYASSERT(pr->ph->firstregion == pr);
				}
			} else {
				MYASSERT(!pr->ph->firstregion);
			}
			for(others = pr->ph->firstregion; others;
				others = others->next_ph_list) {
				MYSLABSANE(others);
				MYASSERT(others->ph == pr->ph);
				n_others++;
			}
			MYASSERT(pr->ph->refcount == n_others);
		}
		MYASSERT(pr->ph->refcount == pr->ph->seencount);
		MYASSERT(!(pr->offset % VM_PAGE_SIZE)););
	ALLREGIONS(,MYASSERT(map_sanitycheck_pt(vmp, vr, pr) == OK));
}

#define LRUCHECK lrucheck()

static void lrucheck(void)
{
	yielded_t *list;

	/* list is empty and ok if both ends point to null. */
	if(!lru_youngest && !lru_oldest)
		return;

	/* if not, both should point to something. */
	SLABSANE(lru_youngest);
	SLABSANE(lru_oldest);

	assert(!lru_youngest->younger);
	assert(!lru_oldest->older);

	for(list = lru_youngest; list; list = list->older) {
		SLABSANE(list);
		if(list->younger) {
			SLABSANE(list->younger);
			assert(list->younger->older == list);
		} else	assert(list == lru_youngest);
		if(list->older) {
			SLABSANE(list->older);
			assert(list->older->younger == list);
		} else	assert(list == lru_oldest);
	}
}

void blockstats(void)
{
	yielded_t *list;
	int blocks = 0;
	phys_bytes mem = 0;
	clock_t ticks;
	int s;

	s = getuptime(&ticks);

	assert(s == OK);

	LRUCHECK;

	for(list = lru_youngest; list; list = list->older) {
		mem += VM_PAGE_SIZE;
		blocks++;
	}

	if(blocks > 0)
		printf("%d blocks, %lukB; ", blocks, mem/1024);

	printmemstats();
}
#else
#define LRUCHECK 
#endif


/*=========================================================================*
 *				map_ph_writept				*
 *=========================================================================*/
static int map_ph_writept(struct vmproc *vmp, struct vir_region *vr,
	struct phys_region *pr)
{
	int rw;
	struct phys_block *pb = pr->ph;

	assert(vr);
	assert(pr);
	assert(pb);

	assert(!(vr->vaddr % VM_PAGE_SIZE));
	assert(!(pr->offset % VM_PAGE_SIZE));
	assert(pb->refcount > 0);

	if(pr_writable(vr, pr))
		rw = PTF_WRITE;
	else
		rw = PTF_READ;

	if(pt_writemap(vmp, &vmp->vm_pt, vr->vaddr + pr->offset,
	  pb->phys, VM_PAGE_SIZE, PTF_PRESENT | PTF_USER | rw,
#if SANITYCHECKS
	  	!pr->written ? 0 :
#endif
	  	WMF_OVERWRITE) != OK) {
	    printf("VM: map_writept: pt_writemap failed\n");
	    return ENOMEM;
	}

#if SANITYCHECKS
	USE(pr, pr->written = 1;);
#endif

	return OK;
}

#define SLOT_FAIL ((vir_bytes) -1)

/*===========================================================================*
 *				region_find_slot_range			     *
 *===========================================================================*/
static vir_bytes region_find_slot_range(struct vmproc *vmp,
		vir_bytes minv, vir_bytes maxv, vir_bytes length)
{
	struct vir_region *lastregion;
	vir_bytes startv = 0;
	int foundflag = 0;
	region_iter iter;

	SANITYCHECK(SCL_FUNCTIONS);

	/* Length must be reasonable. */
	assert(length > 0);

	/* Special case: allow caller to set maxv to 0 meaning 'I want
	 * it to be mapped in right here.'
	 */
        if(maxv == 0) {
                maxv = minv + length;

                /* Sanity check. */
                if(maxv <= minv) {
                        printf("region_find_slot: minv 0x%lx and bytes 0x%lx\n",
                                minv, length);
                        return SLOT_FAIL;
                }
        }

	/* Basic input sanity checks. */
	assert(!(length % VM_PAGE_SIZE));
	if(minv >= maxv) {
		printf("VM: 1 minv: 0x%lx maxv: 0x%lx length: 0x%lx\n",
			minv, maxv, length);
	}

	assert(minv < maxv);

	if(minv + length > maxv)
		return SLOT_FAIL;

#define FREEVRANGE_TRY(rangestart, rangeend) {		\
	vir_bytes frstart = (rangestart), frend = (rangeend);	\
	frstart = MAX(frstart, minv);				\
	frend   = MIN(frend, maxv);				\
	if(frend > frstart && (frend - frstart) >= length) {	\
		startv = frend-length;				\
		foundflag = 1;					\
	} }

#define FREEVRANGE(start, end) {					\
	assert(!foundflag);						\
	FREEVRANGE_TRY(((start)+VM_PAGE_SIZE), ((end)-VM_PAGE_SIZE));	\
	if(!foundflag) {						\
		FREEVRANGE_TRY((start), (end));				\
	}								\
}

	/* find region after maxv. */
	region_start_iter(&vmp->vm_regions_avl, &iter, maxv, AVL_GREATER_EQUAL);
	lastregion = region_get_iter(&iter);

	if(!lastregion) {
		/* This is the free virtual address space after the last region. */
		region_start_iter(&vmp->vm_regions_avl, &iter, maxv, AVL_LESS);
		lastregion = region_get_iter(&iter);
		FREEVRANGE(lastregion ?
			lastregion->vaddr+lastregion->length : 0, VM_DATATOP);
	}

	if(!foundflag) {
		struct vir_region *vr;
		while((vr = region_get_iter(&iter)) && !foundflag) {
			struct vir_region *nextvr;
			region_decr_iter(&iter);
			nextvr = region_get_iter(&iter);
			FREEVRANGE(nextvr ? nextvr->vaddr+nextvr->length : 0,
			  vr->vaddr);
		}
	}

	if(!foundflag) {
		return SLOT_FAIL;
	}

	/* However we got it, startv must be in the requested range. */
	assert(startv >= minv);
	assert(startv < maxv);
	assert(startv + length <= maxv);

	/* remember this position as a hint for next time. */
	vmp->vm_region_top = startv + length;

	return startv;
}

/*===========================================================================*
 *				region_find_slot			     *
 *===========================================================================*/
static vir_bytes region_find_slot(struct vmproc *vmp,
		vir_bytes minv, vir_bytes maxv, vir_bytes length)
{
	vir_bytes v, hint = vmp->vm_region_top;

	/* use the top of the last inserted region as a minv hint if
	 * possible. remember that a zero maxv is a special case.
	 */

	if(maxv && hint < maxv && hint >= minv) {
		v = region_find_slot_range(vmp, minv, hint, length);

		if(v != SLOT_FAIL)
			return v;
	}

	return region_find_slot_range(vmp, minv, maxv, length);
}

struct vir_region *region_new(struct vmproc *vmp, vir_bytes startv, vir_bytes length,
	int flags, mem_type_t *memtype)
{
	physr_avl *phavl;
	struct vir_region *newregion;
	static u32_t id;

	if(!(SLABALLOC(newregion))) {
		printf("vm: region_new: could not allocate\n");
		return NULL;
	}

	/* Fill in node details. */
USE(newregion,
	memset(newregion, 0, sizeof(*newregion));
	newregion->vaddr = startv;
	newregion->length = length;
	newregion->flags = flags;
	newregion->memtype = memtype;
	newregion->remaps = 0;
	newregion->id = id++;
	newregion->lower = newregion->higher = NULL;
	newregion->parent = vmp;);

	SLABALLOC(phavl);
	if(!phavl) {
		printf("VM: region_new: allocating phys avl failed\n");
		SLABFREE(newregion);
		return NULL;
	}
	USE(newregion, newregion->phys = phavl;);
	physr_init(newregion->phys);

	return newregion;
}

/*===========================================================================*
 *				map_page_region				     *
 *===========================================================================*/
struct vir_region *map_page_region(vmp, minv, maxv, length,
	flags, mapflags, memtype)
struct vmproc *vmp;
vir_bytes minv;
vir_bytes maxv;
vir_bytes length;
u32_t flags;
int mapflags;
mem_type_t *memtype;
{
	struct vir_region *newregion;
	vir_bytes startv;

	assert(!(length % VM_PAGE_SIZE));

	SANITYCHECK(SCL_FUNCTIONS);

	startv = region_find_slot(vmp, minv, maxv, length);
	if (startv == SLOT_FAIL)
		return NULL;

	/* Now we want a new region. */
	if(!(newregion = region_new(vmp, startv, length, flags, memtype))) {
		printf("VM: map_page_region: allocating region failed\n");
		return NULL;
	}

	/* If a new event is specified, invoke it. */
	if(newregion->memtype->ev_new) {
		if(newregion->memtype->ev_new(newregion) != OK) {
			/* ev_new will have freed and removed the region */
			return NULL;
		}
	}

	if(mapflags & MF_PREALLOC) {
		if(map_handle_memory(vmp, newregion, 0, length, 1) != OK) {
			printf("VM: map_page_region: prealloc failed\n");
			USE(newregion,
				SLABFREE(newregion->phys););
			SLABFREE(newregion);
			return NULL;
		}
	}

	/* Pre-allocations should be uninitialized, but after that it's a
	 * different story.
	 */
	USE(newregion, newregion->flags &= ~VR_UNINITIALIZED;);

	/* Link it. */
	region_insert(&vmp->vm_regions_avl, newregion);

#if SANITYCHECKS
	assert(startv == newregion->vaddr);
	{
		struct vir_region *nextvr;
		if((nextvr = getnextvr(newregion))) {
			assert(newregion->vaddr < nextvr->vaddr);
		}
	}
#endif

	SANITYCHECK(SCL_FUNCTIONS);

	return newregion;
}

/*===========================================================================*
 *				map_subfree				     *
 *===========================================================================*/
static int map_subfree(struct vir_region *region, 
	vir_bytes start, vir_bytes len)
{
	struct phys_region *pr;
	physr_iter iter;
	vir_bytes end = start+len;

	int full = 0;

#if SANITYCHECKS
	{
	SLABSANE(region);
	SLABSANE(region->phys);
	physr_start_iter_least(region->phys, &iter);
	while((pr = physr_get_iter(&iter))) {
		struct phys_region *others;
		struct phys_block *pb;

		pb = pr->ph;

		for(others = pb->firstregion; others;
			others = others->next_ph_list) {
			assert(others->ph == pb);
		}
		physr_incr_iter(&iter);
	}
	}
#endif

	if(start == 0 && len == region->length)
		full = 1;

	physr_init_iter(&iter);
	physr_start_iter(region->phys, &iter, start, AVL_GREATER_EQUAL);
	while((pr = physr_get_iter(&iter))) {
		physr_incr_iter(&iter);
		if(pr->offset >= end)
			break;
		pb_unreferenced(region, pr, !full);
		if(!full) {
			physr_start_iter(region->phys, &iter,
				pr->offset, AVL_GREATER_EQUAL);
		}
		SLABFREE(pr);
	}

	if(full)
		physr_init(region->phys);

	return OK;
}

/*===========================================================================*
 *				map_free				     *
 *===========================================================================*/
int map_free(struct vir_region *region)
{
	int r;

	if((r=map_subfree(region, 0, region->length)) != OK) {
		printf("%d\n", __LINE__);
		return r;
	}

	if(region->memtype->ev_delete)
		region->memtype->ev_delete(region);

	USE(region,
		SLABFREE(region->phys););
	SLABFREE(region);

	return OK;
}

/*===========================================================================*
 *				yielded_block_cmp			     *
 *===========================================================================*/
int yielded_block_cmp(struct block_id *id1, struct block_id *id2)
{
	if(id1->owner < id2->owner)
		return -1;
	if(id1->owner > id2->owner)
		return 1;
	return cmp64(id1->id, id2->id);
}


/*===========================================================================*
 *				free_yielded_proc			     *
 *===========================================================================*/
static vir_bytes free_yielded_proc(struct vmproc *vmp)
{
	vir_bytes total = 0;
	int h;

	SANITYCHECK(SCL_FUNCTIONS);

	/* Free associated regions. */
	for(h = 0; h < YIELD_HASHSIZE && vmp->vm_yielded > 0; h++) {
		yielded_t *yb;
		yielded_iter iter;
		yielded_avl *avl = &vm_yielded_blocks[h];
		yielded_start_iter_least(avl, &iter);
		while((yb = yielded_get_iter(&iter))) {
			yielded_t *next_yb;
			SLABSANE(yb);
			yielded_incr_iter(&iter);
			if(yb->id.owner != vmp->vm_endpoint)
				continue;
			next_yb = yielded_get_iter(&iter); 
			total += freeyieldednode(yb, 1);
			/* the above removal invalidated our iter; restart it
			 * for the node we want to start at.
			 */
			if(!next_yb) break; 
			yielded_start_iter(avl, &iter, next_yb->id, AVL_EQUAL);
			assert(yielded_get_iter(&iter) == next_yb);
		}
	}

	return total;
}


static phys_bytes freeyieldednode(yielded_t *node, int freemem)
{
	yielded_t *older, *younger, *removed;
	yielded_avl *avl; 
	int p;

	SLABSANE(node);

	LRUCHECK;

	/* Update LRU. */

	younger = node->younger;
	older = node->older;

	if(younger) {
		SLABSANE(younger);
		assert(younger->older == node);
		USE(younger, younger->older = node->older;);
	} else {
		assert(node == lru_youngest);
		lru_youngest = node->older;
	}

	if(older) {
		SLABSANE(older);
		assert(older->younger == node);
		USE(older, older->younger = node->younger;);
	} else {
		assert(node == lru_oldest);
		lru_oldest = node->younger;
	}

	LRUCHECK;

	/* Update AVL. */

	if(vm_isokendpt(node->id.owner, &p) != OK)
		panic("out of date owner of yielded block %d", node->id.owner);
	avl = get_yielded_avl(node->id);
	removed = yielded_remove(avl, node->id);
	assert(removed == node);
	assert(vmproc[p].vm_yielded > 0);
	vmproc[p].vm_yielded--;

	/* Free associated memory if requested. */

	if(freemem) {
		free_mem(ABS2CLICK(node->physaddr), node->pages);
	}

	/* Free node. */
	SLABFREE(node);

	return VM_PAGE_SIZE;
}

/*========================================================================*
 *				free_yielded				  *
 *========================================================================*/
vir_bytes free_yielded(vir_bytes max_bytes)
{

/* PRIVATE yielded_t *lru_youngest = NULL, *lru_oldest = NULL; */
	vir_bytes freed = 0;
	int blocks = 0;
	
	while(freed < max_bytes && lru_oldest) {
		SLABSANE(lru_oldest);
		freed += freeyieldednode(lru_oldest, 1);
		blocks++;
	}

	return freed;
}

/*========================================================================*
 *				map_free_proc				  *
 *========================================================================*/
int map_free_proc(vmp)
struct vmproc *vmp;
{
	struct vir_region *r;

	while((r = region_search_root(&vmp->vm_regions_avl))) {
		SANITYCHECK(SCL_DETAIL);
#if SANITYCHECKS
		nocheck++;
#endif
		region_remove(&vmp->vm_regions_avl, r->vaddr); /* For sanity checks. */
		map_free(r);
#if SANITYCHECKS
		nocheck--;
#endif
		SANITYCHECK(SCL_DETAIL);
	}

	region_init(&vmp->vm_regions_avl);

	/* Free associated yielded blocks. */
	free_yielded_proc(vmp);

	SANITYCHECK(SCL_FUNCTIONS);

	return OK;
}

/*===========================================================================*
 *				map_lookup				     *
 *===========================================================================*/
struct vir_region *map_lookup(vmp, offset, physr)
struct vmproc *vmp;
vir_bytes offset;
struct phys_region **physr;
{
	struct vir_region *r;

	SANITYCHECK(SCL_FUNCTIONS);

#if SANITYCHECKS
	if(!region_search_root(&vmp->vm_regions_avl))
		panic("process has no regions: %d", vmp->vm_endpoint);
#endif

	if((r = region_search(&vmp->vm_regions_avl, offset, AVL_LESS_EQUAL))) {
		vir_bytes ph;
		if(offset >= r->vaddr && offset < r->vaddr + r->length) {
			ph = offset - r->vaddr;
			if(physr) {
				*physr = physr_search(r->phys, ph, AVL_EQUAL);
				if(*physr) assert((*physr)->offset == ph);
			}
			return r;
		}
	}

	SANITYCHECK(SCL_FUNCTIONS);

	return NULL;
}

u32_t vrallocflags(u32_t flags)
{
	u32_t allocflags = 0;

	if(flags & VR_PHYS64K)
		allocflags |= PAF_ALIGN64K;
	if(flags & VR_LOWER16MB)
		allocflags |= PAF_LOWER16MB;
	if(flags & VR_LOWER1MB)
		allocflags |= PAF_LOWER1MB;
	if(flags & VR_CONTIG)
		allocflags |= PAF_CONTIG;
	if(!(flags & VR_UNINITIALIZED))
		allocflags |= PAF_CLEAR;

	return allocflags;
}

/*===========================================================================*
 *				map_clone_ph_block			     *
 *===========================================================================*/
struct phys_region *map_clone_ph_block(vmp, region, ph, iter)
struct vmproc *vmp;
struct vir_region *region;
struct phys_region *ph;
physr_iter *iter;
{
	vir_bytes offset;
	u32_t allocflags;
	phys_bytes physaddr;
	struct phys_region *newpr;
	int region_has_single_block;
	SANITYCHECK(SCL_FUNCTIONS);

	/* Warning: this function will free the passed
	 * phys_region *ph and replace it (in the same offset)
	 * with another! So both the pointer to it
	 * and any iterators over the phys_regions in the vir_region
	 * will be invalid on successful return. (Iterators over
	 * the vir_region could be invalid on unsuccessful return too.)
	 */

	/* This is only to be done if there is more than one copy. */
	assert(ph->ph->refcount > 1);

	/* This function takes a physical block, copies its contents
	 * into newly allocated memory, and replaces the single physical
	 * block by one or more physical blocks with refcount 1 with the
	 * same contents as the original. In other words, a fragmentable
	 * version of map_copy_ph_block().
	 */

	/* Remember where and how much. */
	offset = ph->offset;
	physaddr = ph->ph->phys;

	/* Now unlink the original physical block so we can replace
	 * it with new ones.
	 */

	SLABSANE(ph);
	SLABSANE(ph->ph);
	assert(ph->ph->refcount > 1);
	pb_unreferenced(region, ph, 1);
	SLABFREE(ph);

	SANITYCHECK(SCL_DETAIL);

	/* Put new free memory in. */
	allocflags = vrallocflags(region->flags | VR_UNINITIALIZED);
	region_has_single_block = (offset == 0 && region->length == VM_PAGE_SIZE);
	assert(region_has_single_block || !(allocflags & PAF_CONTIG));
	assert(!(allocflags & PAF_CLEAR));

	if(map_pf(vmp, region, offset, 1) != OK) {
		/* XXX original range now gone. */
		printf("VM: map_clone_ph_block: map_pf failed.\n");
		return NULL;
	}

	/* Copy the block to the new memory.
	 * Can only fail if map_new_physblock didn't do what we asked.
	 */
	if(copy_abs2region(physaddr, region, offset, VM_PAGE_SIZE) != OK)
		panic("copy_abs2region failed, no good reason for that");

	newpr = physr_search(region->phys, offset, AVL_EQUAL);
	assert(newpr);
	assert(newpr->offset == offset);

	if(iter) {
		physr_start_iter(region->phys, iter, offset, AVL_EQUAL);
		assert(physr_get_iter(iter) == newpr);
	}

	SANITYCHECK(SCL_FUNCTIONS);

	return newpr;
}


/*===========================================================================*
 *				map_pf			     *
 *===========================================================================*/
int map_pf(vmp, region, offset, write)
struct vmproc *vmp;
struct vir_region *region;
vir_bytes offset;
int write;
{
	struct phys_region *ph;
	int r = OK;

	offset -= offset % VM_PAGE_SIZE;

	assert(offset >= 0);
	assert(offset < region->length);

	assert(!(region->vaddr % VM_PAGE_SIZE));
	assert(!(write && !(region->flags & VR_WRITABLE)));

	SANITYCHECK(SCL_FUNCTIONS);

	if(!(ph = physr_search(region->phys, offset, AVL_EQUAL))) {
		struct phys_block *pb;

		/* New block. */

		if(!(pb = pb_new(MAP_NONE))) {
			printf("map_pf: pb_new failed\n");
			return ENOMEM;
		}

		if(!(ph = pb_reference(pb, offset, region))) {
			printf("map_pf: pb_reference failed\n");
			pb_free(pb);
			return ENOMEM;
		}	
	}

	assert(ph);
	assert(ph->ph);

	/* If we're writing and the block is already
	 * writable, nothing to do.
	 */

	assert(region->memtype->writable);

	if(!write || !region->memtype->writable(ph)) {
		assert(region->memtype->ev_pagefault);
		assert(ph->ph);
		if((r = region->memtype->ev_pagefault(vmp,
			region, ph, write)) == SUSPEND) {
			panic("map_pf: memtype->ev_pagefault returned SUSPEND\n");
			return SUSPEND;
		}

		if(r != OK) {
			printf("map_pf: memtype->ev_pagefault failed\n");
			if(ph)
				pb_unreferenced(region, ph, 1);
			return r;
		}

		assert(ph);
		assert(ph->ph);
	}

	assert(ph->ph);

	if((r = map_ph_writept(vmp, region, ph)) != OK) {
		printf("map_pf: writept failed\n");
		return r;
	}

	SANITYCHECK(SCL_FUNCTIONS);

#if SANITYCHECKS
	if(OK != pt_checkrange(&vmp->vm_pt, region->vaddr+offset,
		VM_PAGE_SIZE, write)) {
		panic("map_pf: pt_checkrange failed: %d", r);
	}
#endif	

	return r;
}

int map_handle_memory(vmp, region, start_offset, length, write)
struct vmproc *vmp;
struct vir_region *region;
vir_bytes start_offset;
vir_bytes length;
int write;
{
	vir_bytes offset, lim;
	int r;

	assert(length > 0);
	lim = start_offset + length;
	assert(lim > start_offset);

	for(offset = start_offset; offset < lim; offset += VM_PAGE_SIZE)
		if((r = map_pf(vmp, region, offset, write)) != OK)
			return r;

	return OK;
}

/*===========================================================================*
 *				map_pin_memory      			     *
 *===========================================================================*/
int map_pin_memory(struct vmproc *vmp)
{
	struct vir_region *vr;
	int r;
	region_iter iter;
	region_start_iter_least(&vmp->vm_regions_avl, &iter);
	/* Scan all memory regions. */
	while((vr = region_get_iter(&iter))) {
		/* Make sure region is mapped to physical memory and writable.*/
		r = map_handle_memory(vmp, vr, 0, vr->length, 1);
		if(r != OK) {
		    panic("map_pin_memory: map_handle_memory failed: %d", r);
		}
		region_incr_iter(&iter);
	}
	return OK;
}

#if SANITYCHECKS
static int count_phys_regions(struct vir_region *vr)
{
	int n = 0;
	struct phys_region *ph;
	physr_iter iter;
	physr_start_iter_least(vr->phys, &iter);
	while((ph = physr_get_iter(&iter))) {
		n++;
		physr_incr_iter(&iter);
	}
	return n;
}
#endif

/*===========================================================================*
 *				map_copy_region			     	*
 *===========================================================================*/
static struct vir_region *map_copy_region(struct vmproc *vmp, struct vir_region *vr)
{
	/* map_copy_region creates a complete copy of the vir_region
	 * data structure, linking in the same phys_blocks directly,
	 * but all in limbo, i.e., the caller has to link the vir_region
	 * to a process. Therefore it doesn't increase the refcount in
	 * the phys_block; the caller has to do this once it's linked.
	 * The reason for this is to keep the sanity checks working
	 * within this function.
	 */
	struct vir_region *newvr;
	struct phys_region *ph;
	int r;
	physr_iter iter;
#if SANITYCHECKS
	int cr;
	cr = count_phys_regions(vr);
#endif

	if(!(newvr = region_new(vr->parent, vr->vaddr, vr->length, vr->flags, vr->memtype)))
		return NULL;

	if(vr->memtype->ev_copy && (r=vr->memtype->ev_copy(vr, newvr)) != OK) {
		map_free(newvr);
		printf("VM: memtype-specific copy failed (%d)\n", r);
		return NULL;
	}

	physr_start_iter_least(vr->phys, &iter);
	while((ph = physr_get_iter(&iter))) {
		struct phys_region *newph = pb_reference(ph->ph, ph->offset, newvr);

		if(!newph) { map_free(newvr); return NULL; }

#if SANITYCHECKS
		USE(newph, newph->written = 0;);
		assert(count_phys_regions(vr) == cr);
#endif
		physr_incr_iter(&iter);
	}

#if SANITYCHECKS
	assert(count_phys_regions(vr) == count_phys_regions(newvr));
#endif

	return newvr;
}

/*===========================================================================*
 *				copy_abs2region			     	*
 *===========================================================================*/
int copy_abs2region(phys_bytes abs, struct vir_region *destregion,
	phys_bytes offset, phys_bytes len)

{
	assert(destregion);
	assert(destregion->phys);
	while(len > 0) {
		phys_bytes sublen, suboffset;
		struct phys_region *ph;
		assert(destregion);
		assert(destregion->phys);
		if(!(ph = physr_search(destregion->phys, offset, AVL_LESS_EQUAL))) {
			printf("VM: copy_abs2region: no phys region found (1).\n");
			return EFAULT;
		}
		assert(ph->offset <= offset);
		if(ph->offset+VM_PAGE_SIZE <= offset) {
			printf("VM: copy_abs2region: no phys region found (2).\n");
			return EFAULT;
		}
		suboffset = offset - ph->offset;
		assert(suboffset < VM_PAGE_SIZE);
		sublen = len;
		if(sublen > VM_PAGE_SIZE - suboffset)
			sublen = VM_PAGE_SIZE - suboffset;
		assert(suboffset + sublen <= VM_PAGE_SIZE);
		if(ph->ph->refcount != 1) {
			printf("VM: copy_abs2region: refcount not 1.\n");
			return EFAULT;
		}

		if(sys_abscopy(abs, ph->ph->phys + suboffset, sublen) != OK) {
			printf("VM: copy_abs2region: abscopy failed.\n");
			return EFAULT;
		}
		abs += sublen;
		offset += sublen;
		len -= sublen;
	}

	return OK;
}

/*=========================================================================*
 *				map_writept				*
 *=========================================================================*/
int map_writept(struct vmproc *vmp)
{
	struct vir_region *vr;
	struct phys_region *ph;
	int r;
	region_iter v_iter;
	region_start_iter_least(&vmp->vm_regions_avl, &v_iter);

	while((vr = region_get_iter(&v_iter))) {
		physr_iter ph_iter;
		physr_start_iter_least(vr->phys, &ph_iter);

		while((ph = physr_get_iter(&ph_iter))) {
			physr_incr_iter(&ph_iter);

			if((r=map_ph_writept(vmp, vr, ph)) != OK) {
				printf("VM: map_writept: failed\n");
				return r;
			}
		}
		region_incr_iter(&v_iter);
	}

	return OK;
}

/*========================================================================*
 *			       map_proc_copy			     	  *
 *========================================================================*/
int map_proc_copy(dst, src)
struct vmproc *dst;
struct vmproc *src;
{
/* Copy all the memory regions from the src process to the dst process. */
	region_init(&dst->vm_regions_avl);

	return map_proc_copy_from(dst, src, NULL);
}

/*========================================================================*
 *			     map_proc_copy_from			     	  *
 *========================================================================*/
int map_proc_copy_from(dst, src, start_src_vr)
struct vmproc *dst;
struct vmproc *src;
struct vir_region *start_src_vr;
{
	struct vir_region *vr;
	region_iter v_iter;

	if(!start_src_vr)
		start_src_vr = region_search_least(&src->vm_regions_avl);

	assert(start_src_vr);
	assert(start_src_vr->parent == src);
	region_start_iter(&src->vm_regions_avl, &v_iter,
		start_src_vr->vaddr, AVL_EQUAL);
	assert(region_get_iter(&v_iter) == start_src_vr);

	/* Copy source regions after the destination's last region (if any). */

	SANITYCHECK(SCL_FUNCTIONS);

	while((vr = region_get_iter(&v_iter))) {
		physr_iter iter_orig, iter_new;
		struct vir_region *newvr;
		struct phys_region *orig_ph, *new_ph;
		if(!(newvr = map_copy_region(dst, vr))) {
			map_free_proc(dst);
			return ENOMEM;
		}
		USE(newvr, newvr->parent = dst;);
		region_insert(&dst->vm_regions_avl, newvr);
		physr_start_iter_least(vr->phys, &iter_orig);
		physr_start_iter_least(newvr->phys, &iter_new);
		while((orig_ph = physr_get_iter(&iter_orig))) {
			struct phys_block *pb;
			new_ph = physr_get_iter(&iter_new);
			/* Check two physregions both are nonnull,
			 * are different, and match physblocks.
			 */
			assert(new_ph);
			assert(orig_ph);
			assert(orig_ph != new_ph);
			pb = orig_ph->ph;
			assert(orig_ph->ph == new_ph->ph);

			/* Get next new physregion */
			physr_incr_iter(&iter_orig);
			physr_incr_iter(&iter_new);
		}
		assert(!physr_get_iter(&iter_new));
		region_incr_iter(&v_iter);
	}

	map_writept(src);
	map_writept(dst);

	SANITYCHECK(SCL_FUNCTIONS);
	return OK;
}

int map_region_extend_upto_v(struct vmproc *vmp, vir_bytes v)
{
	vir_bytes offset = v;
	struct vir_region *vr, *nextvr;

	offset = roundup(offset, VM_PAGE_SIZE);

	if(!(vr = region_search(&vmp->vm_regions_avl, offset, AVL_LESS))) {
		printf("VM: nothing to extend\n");
		return ENOMEM;
	}

	assert(vr->vaddr <= offset);
	if((nextvr = getnextvr(vr))) {
		assert(offset <= nextvr->vaddr);
	}

	if(nextvr && nextvr->vaddr < offset) {
		printf("VM: can't grow into next region\n");
		return ENOMEM;
	}

	if(!vr->memtype->ev_resize) {
		printf("VM: can't resize this type of memory\n");
		return ENOMEM;
	}

	return vr->memtype->ev_resize(vmp, vr, offset - vr->vaddr);
}

/*========================================================================*
 *				map_unmap_region	     	  	*
 *========================================================================*/
int map_unmap_region(struct vmproc *vmp, struct vir_region *r,
	vir_bytes offset, vir_bytes len)
{
/* Shrink the region by 'len' bytes, from the start. Unreference
 * memory it used to reference if any.
 */
	vir_bytes regionstart;

	SANITYCHECK(SCL_FUNCTIONS);

	if(offset+len > r->length || (len % VM_PAGE_SIZE)) {
		printf("VM: bogus length 0x%lx\n", len);
		return EINVAL;
	}

	regionstart = r->vaddr + offset;

	/* unreference its memory */
	map_subfree(r, offset, len);

	/* if unmap was at start/end of this region, it actually shrinks */
	if(offset == 0) {
		struct phys_region *pr;
		physr_iter iter;

		region_remove(&vmp->vm_regions_avl, r->vaddr);

		USE(r,
		r->vaddr += len;
		r->length -= len;);

		region_insert(&vmp->vm_regions_avl, r);

		/* vaddr has increased; to make all the phys_regions
		 * point to the same addresses, make them shrink by the
		 * same amount.
		 */
		physr_init_iter(&iter);
        	physr_start_iter(r->phys, &iter, offset, AVL_GREATER_EQUAL);

		while((pr = physr_get_iter(&iter))) {
			assert(pr->offset >= offset);
			USE(pr, pr->offset -= len;);
			physr_incr_iter(&iter);
		}
	} else if(offset + len == r->length) {
		assert(len <= r->length);
		r->length -= len;
	}

	if(r->length == 0) {
		/* Whole region disappears. Unlink and free it. */
		region_remove(&vmp->vm_regions_avl, r->vaddr);
		map_free(r);
	}

	SANITYCHECK(SCL_DETAIL);

	if(pt_writemap(vmp, &vmp->vm_pt, regionstart,
	  MAP_NONE, len, 0, WMF_OVERWRITE) != OK) {
	    printf("VM: map_unmap_region: pt_writemap failed\n");
	    return ENOMEM;
	}

	SANITYCHECK(SCL_FUNCTIONS);

	return OK;
}

/*========================================================================*
 *				map_get_phys				  *
 *========================================================================*/
int map_get_phys(struct vmproc *vmp, vir_bytes addr, phys_bytes *r)
{
	struct vir_region *vr;

	if (!(vr = map_lookup(vmp, addr, NULL)) ||
		(vr->vaddr != addr))
		return EINVAL;

	if (!vr->memtype->regionid)
		return EINVAL;

	if(r)
		*r = vr->memtype->regionid(vr);

	return OK;
}

/*========================================================================*
 *				map_get_ref				  *
 *========================================================================*/
int map_get_ref(struct vmproc *vmp, vir_bytes addr, u8_t *cnt)
{
	struct vir_region *vr;

	if (!(vr = map_lookup(vmp, addr, NULL)) ||
		(vr->vaddr != addr) || !vr->memtype->refcount)
		return EINVAL;

	if (cnt)
		*cnt = vr->memtype->refcount(vr);

	return OK;
}

/*========================================================================*
 *				get_stats_info				  *
 *========================================================================*/
void get_stats_info(struct vm_stats_info *vsi)
{
	yielded_t *yb;

	vsi->vsi_cached = 0L;

	for(yb = lru_youngest; yb; yb = yb->older)
		vsi->vsi_cached++;
}

void get_usage_info_kernel(struct vm_usage_info *vui)
{
	memset(vui, 0, sizeof(*vui));
	vui->vui_total = kernel_boot_info.kernel_allocated_bytes;
}

static void get_usage_info_vm(struct vm_usage_info *vui)
{
	memset(vui, 0, sizeof(*vui));
	vui->vui_total = kernel_boot_info.vm_allocated_bytes +
		get_vm_self_pages() * VM_PAGE_SIZE;
}

/*========================================================================*
 *				get_usage_info				  *
 *========================================================================*/
void get_usage_info(struct vmproc *vmp, struct vm_usage_info *vui)
{
	struct vir_region *vr;
	physr_iter iter;
	struct phys_region *ph;
	region_iter v_iter;
	region_start_iter_least(&vmp->vm_regions_avl, &v_iter);

	memset(vui, 0, sizeof(*vui));

	if(vmp->vm_endpoint == VM_PROC_NR) {
		get_usage_info_vm(vui);
		return;
	}

	if(vmp->vm_endpoint < 0) {
		get_usage_info_kernel(vui);
		return;
	}

	while((vr = region_get_iter(&v_iter))) {
		physr_start_iter_least(vr->phys, &iter);
		while((ph = physr_get_iter(&iter))) {
			/* All present pages are counted towards the total. */
			vui->vui_total += VM_PAGE_SIZE;

			if (ph->ph->refcount > 1) {
				/* Any page with a refcount > 1 is common. */
				vui->vui_common += VM_PAGE_SIZE;
	
				/* Any common, non-COW page is shared. */
				if (vr->flags & VR_SHARED)
					vui->vui_shared += VM_PAGE_SIZE;
			}
			physr_incr_iter(&iter);
		}
		region_incr_iter(&v_iter);
	}
}

/*===========================================================================*
 *				get_region_info				     *
 *===========================================================================*/
int get_region_info(struct vmproc *vmp, struct vm_region_info *vri,
	int max, vir_bytes *nextp)
{
	struct vir_region *vr;
	vir_bytes next;
	int count;
	region_iter v_iter;

	next = *nextp;

	if (!max) return 0;

	region_start_iter(&vmp->vm_regions_avl, &v_iter, next, AVL_GREATER_EQUAL);
	if(!(vr = region_get_iter(&v_iter))) return 0;

	for(count = 0; (vr = region_get_iter(&v_iter)) && count < max; count++, vri++) {
		struct phys_region *ph1, *ph2;

		/* Report part of the region that's actually in use. */

		/* Get first and last phys_regions, if any */
		ph1 = physr_search_least(vr->phys);
		ph2 = physr_search_greatest(vr->phys);
		if(!ph1 || !ph2) { assert(!ph1 && !ph2); continue; }

		/* Report start+length of region starting from lowest use. */
		vri->vri_addr = vr->vaddr + ph1->offset;
		vri->vri_prot = 0;
		vri->vri_length = ph2->offset + VM_PAGE_SIZE - ph1->offset;

		/* "AND" the provided protection with per-page protection. */
		if (!(vr->flags & VR_WRITABLE))
			vri->vri_prot &= ~PROT_WRITE;

		next = vr->vaddr + vr->length;
		region_incr_iter(&v_iter);
	}

	*nextp = next;
	return count;
}

/*========================================================================*
 *				regionprintstats			  *
 *========================================================================*/
void printregionstats(struct vmproc *vmp)
{
	struct vir_region *vr;
	struct phys_region *pr;
	physr_iter iter;
	vir_bytes used = 0, weighted = 0;
	region_iter v_iter;
	region_start_iter_least(&vmp->vm_regions_avl, &v_iter);

	while((vr = region_get_iter(&v_iter))) {
		region_incr_iter(&v_iter);
		if(vr->flags & VR_DIRECT)
			continue;
		physr_start_iter_least(vr->phys, &iter);
		while((pr = physr_get_iter(&iter))) {
			physr_incr_iter(&iter);
			used += VM_PAGE_SIZE;
			weighted += VM_PAGE_SIZE / pr->ph->refcount;
		}
	}

	printf("%6lukB  %6lukB\n", used/1024, weighted/1024);

	return;
}

/*===========================================================================*
 *				get_clean_phys_region			     *
 *===========================================================================*/
static struct phys_region *
get_clean_phys_region(struct vmproc *vmp, vir_bytes vaddr, struct vir_region **ret_region)
{
	struct vir_region *region;
	vir_bytes mapaddr;
	struct phys_region *ph;

	mapaddr = vaddr;

        if(!(region = map_lookup(vmp, mapaddr, &ph)) || !ph) {
		printf("VM: get_clean_phys_region: 0x%lx not found\n", vaddr);
		return NULL;
	}

	assert(mapaddr >= region->vaddr);
	assert(mapaddr < region->vaddr + region->length);

	/* If it's mapped more than once, make a copy. */
	assert(ph->ph->refcount > 0);
	if(ph->ph->refcount > 1) {
		if(!(ph = map_clone_ph_block(vmp, region,
			ph, NULL))) {
			printf("VM: get_clean_phys_region: ph copy failed\n");
			return NULL;
		}
	}

	assert(ph->ph->refcount == 1);

	*ret_region = region;

	return ph;
}

static int getblock(struct vmproc *vmp, u64_t id, vir_bytes vaddr, int pages)
{
	yielded_t *yb;
	struct phys_region *ph;
	struct vir_region *region;
	yielded_avl *avl;
	block_id_t blockid;
	phys_bytes phaddr;
	int p;

	/* Try to get the yielded block */
	blockid.owner = vmp->vm_endpoint;
	blockid.id = id;
	avl = get_yielded_avl(blockid);
	if(!(yb = yielded_search(avl, blockid, AVL_EQUAL))) {
		return ESRCH;
	}

	if(yb->pages != pages) {
		printf("VM: getblock: length mismatch (%d != %d)\n",
			pages, yb->pages);
		return EFAULT;
	}

	phaddr = yb->physaddr;

	for(p = 0; p < pages; p++) {
		/* Get the intended phys region, make sure refcount is 1. */
		if(!(ph = get_clean_phys_region(vmp, vaddr, &region))) {
			printf("VM: getblock: not found for %d\n", vmp->vm_endpoint);
			return EINVAL;
		}

		assert(ph->ph->refcount == 1);

		/* Free the block that is currently there. */
		free_mem(ABS2CLICK(ph->ph->phys), 1);

		/* Set the phys block to new addr and update pagetable. */
		USE(ph->ph, ph->ph->phys = phaddr;);
		if(map_ph_writept(vmp, region, ph) != OK) {
			/* Presumably it was mapped, so there is no reason
			 * updating should fail.
			 */
			panic("do_get_block: couldn't write pt");
		}
		
		vaddr += VM_PAGE_SIZE;
		phaddr += VM_PAGE_SIZE;
	}
	
	/* Forget about the yielded block and free the struct. */
	freeyieldednode(yb, 0);

	return OK;
}

static int yieldblock(struct vmproc *vmp, u64_t id,
	vir_bytes vaddr, yielded_t **retyb, int pages)
{
	yielded_t *newyb;
	vir_bytes mem_clicks, v, p, new_phaddr;
	struct vir_region *region;
	struct phys_region *ph = NULL, *prev_ph = NULL, *first_ph = NULL;
	yielded_avl *avl;
	block_id_t blockid;

	/* Makes no sense if yielded block ID already exists, and
	 * is likely a serious bug in the caller.
	 */
	blockid.id = id;
	blockid.owner = vmp->vm_endpoint;
	avl = get_yielded_avl(blockid);
	if(yielded_search(avl, blockid, AVL_EQUAL)) {
		printf("!");
		return EINVAL;
	}

	if((vaddr % VM_PAGE_SIZE) || pages < 1) return EFAULT;

	v = vaddr;
	for(p = 0; p < pages; p++) {
	        if(!(region = map_lookup(vmp, v, &ph)) || !ph) {
			printf("VM: do_yield_block: not found for %d\n",
				vmp->vm_endpoint);
			return EINVAL;
		}
		if(!(region->flags & VR_ANON)) {
			printf("VM: yieldblock: non-anon 0x%lx\n", v);
			return EFAULT;
		}
		if(ph->ph->refcount != 1) {
			printf("VM: do_yield_block: mapped not once for %d\n",
				vmp->vm_endpoint);
			return EFAULT;
		}
		if(prev_ph) {
			if(ph->ph->phys != prev_ph->ph->phys + VM_PAGE_SIZE) {
				printf("VM: physically discontiguous yield\n");
				return EINVAL;
			}
		}
		prev_ph = ph;
		if(!first_ph) first_ph = ph;
		v += VM_PAGE_SIZE;
	}

	/* Make a new block to record the yielding in. */
	if(!SLABALLOC(newyb)) {
		return ENOMEM;
	}

	assert(!(ph->ph->phys % VM_PAGE_SIZE));

	if((mem_clicks = alloc_mem(pages, PAF_CLEAR)) == NO_MEM) {
		SLABFREE(newyb);
		return ENOMEM;
	}

	/* Update yielded block info. */
	USE(newyb,
		newyb->id = blockid;
		newyb->physaddr = first_ph->ph->phys;
		newyb->pages = pages;
		newyb->younger = NULL;);

	new_phaddr = CLICK2ABS(mem_clicks);

	/* Set new phys block to new addr and update pagetable. */
	v = vaddr;
	for(p = 0; p < pages; p++) {
	        region = map_lookup(vmp, v, &ph);
		assert(region && ph);
		assert(ph->ph->refcount == 1);
		USE(ph->ph,
			ph->ph->phys = new_phaddr;);
		if(map_ph_writept(vmp, region, ph) != OK) {
			/* Presumably it was mapped, so there is no reason
			 * updating should fail.
			 */
			panic("yield_block: couldn't write pt");
		}
		v += VM_PAGE_SIZE;
		new_phaddr += VM_PAGE_SIZE;
	}

	/* Remember yielded block. */

	yielded_insert(avl, newyb);
	vmp->vm_yielded++;

	/* Add to LRU list too. It's the youngest block. */
	LRUCHECK;

	if(lru_youngest) {
		USE(lru_youngest,
			lru_youngest->younger = newyb;);
	} else {
		lru_oldest = newyb;
	}

	USE(newyb,
		newyb->older = lru_youngest;);

	lru_youngest = newyb;

	LRUCHECK;

	if(retyb)
		*retyb = newyb;

	return OK;
}

/*===========================================================================*
 *				do_forgetblocks				     *
 *===========================================================================*/
int do_forgetblocks(message *m)
{
	int n;
	struct vmproc *vmp;
	endpoint_t caller = m->m_source;

	if(vm_isokendpt(caller, &n) != OK)
		panic("do_yield_block: message from strange source: %d",
			m->m_source);

	vmp = &vmproc[n];

	free_yielded_proc(vmp);

	return OK;
}

/*===========================================================================*
 *				do_forgetblock				     *
 *===========================================================================*/
int do_forgetblock(message *m)
{
	int n;
	struct vmproc *vmp;
	endpoint_t caller = m->m_source;
	yielded_t *yb;
	u64_t id;
	block_id_t blockid;
	yielded_avl *avl;

	if(vm_isokendpt(caller, &n) != OK)
		panic("do_yield_block: message from strange source: %d",
			m->m_source);

	vmp = &vmproc[n];

	id = make64(m->VMFB_IDLO, m->VMFB_IDHI);

	blockid.id = id;
	blockid.owner = vmp->vm_endpoint;
	avl = get_yielded_avl(blockid);
	if((yb = yielded_search(avl, blockid, AVL_EQUAL))) {
		freeyieldednode(yb, 1);
	}

	return OK;
}

/*===========================================================================*
 *				do_yieldblockgetblock			     *
 *===========================================================================*/
int do_yieldblockgetblock(message *m)
{
	u64_t yieldid, getid;
	int n;
	endpoint_t caller = m->m_source;
	struct vmproc *vmp;
	yielded_t *yb = NULL;
	int r = ESRCH;
	int pages;

	if(vm_isokendpt(caller, &n) != OK)
		panic("do_yieldblockgetblock: message from strange source: %d",
			m->m_source);

	vmp = &vmproc[n];

	pages = m->VMYBGB_LEN / VM_PAGE_SIZE;

	if((m->VMYBGB_LEN % VM_PAGE_SIZE) || pages < 1) {
		static int printed;
		if(!printed) {
			printed = 1;
			printf("vm: non-page-aligned or short block length\n");
		}
		return EFAULT;
	}

	yieldid = make64(m->VMYBGB_YIELDIDLO, m->VMYBGB_YIELDIDHI);
	getid = make64(m->VMYBGB_GETIDLO, m->VMYBGB_GETIDHI);

	if(cmp64(yieldid, VM_BLOCKID_NONE) != 0) {
		/* A block was given to yield. */
		yieldblock(vmp, yieldid, (vir_bytes) m->VMYBGB_VADDR, &yb,
			pages);
	}

	if(cmp64(getid, VM_BLOCKID_NONE) != 0) {
		/* A block was given to get. */
		r = getblock(vmp, getid, (vir_bytes) m->VMYBGB_VADDR, pages);
	}

	return r;
}

void map_setparent(struct vmproc *vmp)
{
	region_iter iter;
	struct vir_region *vr;
        region_start_iter_least(&vmp->vm_regions_avl, &iter);
        while((vr = region_get_iter(&iter))) {
                USE(vr, vr->parent = vmp;);
                region_incr_iter(&iter);
        }
}

int physregions(struct vir_region *vr)
{
	int n =  0;
	physr_iter iter;
	physr_start_iter_least(vr->phys, &iter);
	while(physr_get_iter(&iter)) {
		n++;
		physr_incr_iter(&iter);
	}
	return n;
}