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[netbsd-mini2440.git] / sys / uvm / uvm_map.c

/*      $NetBSD: uvm_map.c,v 1.285 2009/12/14 21:19:47 matt Exp $       */

/*
 * Copyright (c) 1997 Charles D. Cranor and Washington University.
 * Copyright (c) 1991, 1993, The Regents of the University of California.
 *
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * The Mach Operating System project at Carnegie-Mellon University.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Charles D. Cranor,
 *      Washington University, the University of California, Berkeley and
 *      its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)vm_map.c    8.3 (Berkeley) 1/12/94
 * from: Id: uvm_map.c,v 1.1.2.27 1998/02/07 01:16:54 chs Exp
 *
 *
 * Copyright (c) 1987, 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 the
 * rights to redistribute these changes.
 */

/*
 * uvm_map.c: uvm map operations
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_map.c,v 1.285 2009/12/14 21:19:47 matt Exp $");

#include "opt_ddb.h"
#include "opt_uvmhist.h"
#include "opt_uvm.h"
#include "opt_sysv.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mman.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/pool.h>
#include <sys/kernel.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/lockdebug.h>
#include <sys/atomic.h>

#ifdef SYSVSHM
#include <sys/shm.h>
#endif

#include <uvm/uvm.h>
#include <uvm/uvm_readahead.h>

#if defined(DDB) || defined(DEBUGPRINT)
#include <uvm/uvm_ddb.h>
#endif

#if !defined(UVMMAP_COUNTERS)

#define UVMMAP_EVCNT_DEFINE(name)       /* nothing */
#define UVMMAP_EVCNT_INCR(ev)           /* nothing */
#define UVMMAP_EVCNT_DECR(ev)           /* nothing */

#else /* defined(UVMMAP_NOCOUNTERS) */

#include <sys/evcnt.h>
#define UVMMAP_EVCNT_DEFINE(name) \
struct evcnt uvmmap_evcnt_##name = EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, \
    "uvmmap", #name); \
EVCNT_ATTACH_STATIC(uvmmap_evcnt_##name);
#define UVMMAP_EVCNT_INCR(ev)           uvmmap_evcnt_##ev.ev_count++
#define UVMMAP_EVCNT_DECR(ev)           uvmmap_evcnt_##ev.ev_count--

#endif /* defined(UVMMAP_NOCOUNTERS) */

UVMMAP_EVCNT_DEFINE(ubackmerge)
UVMMAP_EVCNT_DEFINE(uforwmerge)
UVMMAP_EVCNT_DEFINE(ubimerge)
UVMMAP_EVCNT_DEFINE(unomerge)
UVMMAP_EVCNT_DEFINE(kbackmerge)
UVMMAP_EVCNT_DEFINE(kforwmerge)
UVMMAP_EVCNT_DEFINE(kbimerge)
UVMMAP_EVCNT_DEFINE(knomerge)
UVMMAP_EVCNT_DEFINE(map_call)
UVMMAP_EVCNT_DEFINE(mlk_call)
UVMMAP_EVCNT_DEFINE(mlk_hint)
UVMMAP_EVCNT_DEFINE(mlk_list)
UVMMAP_EVCNT_DEFINE(mlk_tree)
UVMMAP_EVCNT_DEFINE(mlk_treeloop)
UVMMAP_EVCNT_DEFINE(mlk_listloop)

UVMMAP_EVCNT_DEFINE(uke_alloc)
UVMMAP_EVCNT_DEFINE(uke_free)
UVMMAP_EVCNT_DEFINE(ukh_alloc)
UVMMAP_EVCNT_DEFINE(ukh_free)

const char vmmapbsy[] = "vmmapbsy";

/*
 * cache for vmspace structures.
 */

static struct pool_cache uvm_vmspace_cache;

/*
 * cache for dynamically-allocated map entries.
 */

static struct pool_cache uvm_map_entry_cache;

MALLOC_DEFINE(M_VMMAP, "VM map", "VM map structures");
MALLOC_DEFINE(M_VMPMAP, "VM pmap", "VM pmap");

#ifdef PMAP_GROWKERNEL
/*
 * This global represents the end of the kernel virtual address
 * space.  If we want to exceed this, we must grow the kernel
 * virtual address space dynamically.
 *
 * Note, this variable is locked by kernel_map's lock.
 */
vaddr_t uvm_maxkaddr;
#endif

/*
 * macros
 */

/*
 * VM_MAP_USE_KMAPENT: determine if uvm_kmapent_alloc/free is used
 * for the vm_map.
 */
extern struct vm_map *pager_map; /* XXX */
#define VM_MAP_USE_KMAPENT_FLAGS(flags) \
        (((flags) & VM_MAP_INTRSAFE) != 0)
#define VM_MAP_USE_KMAPENT(map) \
        (VM_MAP_USE_KMAPENT_FLAGS((map)->flags) || (map) == kernel_map)

/*
 * UVM_ET_ISCOMPATIBLE: check some requirements for map entry merging
 */

#define UVM_ET_ISCOMPATIBLE(ent, type, uobj, meflags, \
    prot, maxprot, inh, adv, wire) \
        ((ent)->etype == (type) && \
        (((ent)->flags ^ (meflags)) & (UVM_MAP_NOMERGE | UVM_MAP_QUANTUM)) \
        == 0 && \
        (ent)->object.uvm_obj == (uobj) && \
        (ent)->protection == (prot) && \
        (ent)->max_protection == (maxprot) && \
        (ent)->inheritance == (inh) && \
        (ent)->advice == (adv) && \
        (ent)->wired_count == (wire))

/*
 * uvm_map_entry_link: insert entry into a map
 *
 * => map must be locked
 */
#define uvm_map_entry_link(map, after_where, entry) do { \
        uvm_mapent_check(entry); \
        (map)->nentries++; \
        (entry)->prev = (after_where); \
        (entry)->next = (after_where)->next; \
        (entry)->prev->next = (entry); \
        (entry)->next->prev = (entry); \
        uvm_rb_insert((map), (entry)); \
} while (/*CONSTCOND*/ 0)

/*
 * uvm_map_entry_unlink: remove entry from a map
 *
 * => map must be locked
 */
#define uvm_map_entry_unlink(map, entry) do { \
        KASSERT((entry) != (map)->first_free); \
        KASSERT((entry) != (map)->hint); \
        uvm_mapent_check(entry); \
        (map)->nentries--; \
        (entry)->next->prev = (entry)->prev; \
        (entry)->prev->next = (entry)->next; \
        uvm_rb_remove((map), (entry)); \
} while (/*CONSTCOND*/ 0)

/*
 * SAVE_HINT: saves the specified entry as the hint for future lookups.
 *
 * => map need not be locked.
 */
#define SAVE_HINT(map, check, value) do { \
        if ((map)->hint == (check)) \
                (map)->hint = (value); \
} while (/*CONSTCOND*/ 0)

/*
 * clear_hints: ensure that hints don't point to the entry.
 *
 * => map must be write-locked.
 */
static void
clear_hints(struct vm_map *map, struct vm_map_entry *ent)
{

        SAVE_HINT(map, ent, ent->prev);
        if (map->first_free == ent) {
                map->first_free = ent->prev;
        }
}

/*
 * VM_MAP_RANGE_CHECK: check and correct range
 *
 * => map must at least be read locked
 */

#define VM_MAP_RANGE_CHECK(map, start, end) do { \
        if (start < vm_map_min(map))            \
                start = vm_map_min(map);        \
        if (end > vm_map_max(map))              \
                end = vm_map_max(map);          \
        if (start > end)                        \
                start = end;                    \
} while (/*CONSTCOND*/ 0)

/*
 * local prototypes
 */

static struct vm_map_entry *
                uvm_mapent_alloc(struct vm_map *, int);
static struct vm_map_entry *
                uvm_mapent_alloc_split(struct vm_map *,
                    const struct vm_map_entry *, int,
                    struct uvm_mapent_reservation *);
static void     uvm_mapent_copy(struct vm_map_entry *, struct vm_map_entry *);
static void     uvm_mapent_free(struct vm_map_entry *);
#if defined(DEBUG)
static void     _uvm_mapent_check(const struct vm_map_entry *, const char *,
                    int);
#define uvm_mapent_check(map)   _uvm_mapent_check(map, __FILE__, __LINE__)
#else /* defined(DEBUG) */
#define uvm_mapent_check(e)     /* nothing */
#endif /* defined(DEBUG) */
static struct vm_map_entry *
                uvm_kmapent_alloc(struct vm_map *, int);
static void     uvm_kmapent_free(struct vm_map_entry *);
static vsize_t  uvm_kmapent_overhead(vsize_t);

static void     uvm_map_entry_unwire(struct vm_map *, struct vm_map_entry *);
static void     uvm_map_reference_amap(struct vm_map_entry *, int);
static int      uvm_map_space_avail(vaddr_t *, vsize_t, voff_t, vsize_t, int,
                    struct vm_map_entry *);
static void     uvm_map_unreference_amap(struct vm_map_entry *, int);

int _uvm_map_sanity(struct vm_map *);
int _uvm_tree_sanity(struct vm_map *);
static vsize_t uvm_rb_maxgap(const struct vm_map_entry *);

CTASSERT(offsetof(struct vm_map_entry, rb_node) == 0);
#define ROOT_ENTRY(map)         ((struct vm_map_entry *)(map)->rb_tree.rbt_root)
#define LEFT_ENTRY(entry)       ((struct vm_map_entry *)(entry)->rb_node.rb_left)
#define RIGHT_ENTRY(entry)      ((struct vm_map_entry *)(entry)->rb_node.rb_right)
#define PARENT_ENTRY(map, entry) \
        (ROOT_ENTRY(map) == (entry) \
            ? NULL \
            : (struct vm_map_entry *)RB_FATHER(&(entry)->rb_node))

static int
uvm_map_compare_nodes(const struct rb_node *nparent,
        const struct rb_node *nkey)
{
        const struct vm_map_entry *eparent = (const void *) nparent;
        const struct vm_map_entry *ekey = (const void *) nkey;

        KASSERT(eparent->start < ekey->start || eparent->start >= ekey->end);
        KASSERT(ekey->start < eparent->start || ekey->start >= eparent->end);

        if (ekey->start < eparent->start)
                return -1;
        if (ekey->start >= eparent->end)
                return 1;
        return 0;
}

static int
uvm_map_compare_key(const struct rb_node *nparent, const void *vkey)
{
        const struct vm_map_entry *eparent = (const void *) nparent;
        const vaddr_t va = *(const vaddr_t *) vkey;

        if (va < eparent->start)
                return -1;
        if (va >= eparent->end)
                return 1;
        return 0;
}

static const struct rb_tree_ops uvm_map_tree_ops = {
        .rbto_compare_nodes = uvm_map_compare_nodes,
        .rbto_compare_key = uvm_map_compare_key,
};

static inline vsize_t
uvm_rb_gap(const struct vm_map_entry *entry)
{
        KASSERT(entry->next != NULL);
        return entry->next->start - entry->end;
}

static vsize_t
uvm_rb_maxgap(const struct vm_map_entry *entry)
{
        struct vm_map_entry *child;
        vsize_t maxgap = entry->gap;

        /*
         * We need maxgap to be the largest gap of us or any of our
         * descendents.  Since each of our children's maxgap is the
         * cached value of their largest gap of themselves or their
         * descendents, we can just use that value and avoid recursing
         * down the tree to calculate it.
         */
        if ((child = LEFT_ENTRY(entry)) != NULL && maxgap < child->maxgap)
                maxgap = child->maxgap;

        if ((child = RIGHT_ENTRY(entry)) != NULL && maxgap < child->maxgap)
                maxgap = child->maxgap;

        return maxgap;
}

static void
uvm_rb_fixup(struct vm_map *map, struct vm_map_entry *entry)
{
        struct vm_map_entry *parent;

        KASSERT(entry->gap == uvm_rb_gap(entry));
        entry->maxgap = uvm_rb_maxgap(entry);

        while ((parent = PARENT_ENTRY(map, entry)) != NULL) {
                struct vm_map_entry *brother;
                vsize_t maxgap = parent->gap;

                KDASSERT(parent->gap == uvm_rb_gap(parent));
                if (maxgap < entry->maxgap)
                        maxgap = entry->maxgap;
                /*
                 * Since we work our towards the root, we know entry's maxgap
                 * value is ok but its brothers may now be out-of-date due
                 * rebalancing.  So refresh it.
                 */
                brother = (struct vm_map_entry *)parent->rb_node.rb_nodes[RB_POSITION(&entry->rb_node) ^ RB_DIR_OTHER];
                if (brother != NULL) {
                        KDASSERT(brother->gap == uvm_rb_gap(brother));
                        brother->maxgap = uvm_rb_maxgap(brother);
                        if (maxgap < brother->maxgap)
                                maxgap = brother->maxgap;
                }

                parent->maxgap = maxgap;
                entry = parent;
        }
}

static void
uvm_rb_insert(struct vm_map *map, struct vm_map_entry *entry)
{
        entry->gap = entry->maxgap = uvm_rb_gap(entry);
        if (entry->prev != &map->header)
                entry->prev->gap = uvm_rb_gap(entry->prev);

        if (!rb_tree_insert_node(&map->rb_tree, &entry->rb_node))
                panic("uvm_rb_insert: map %p: duplicate entry?", map);

        /*
         * If the previous entry is not our immediate left child, then it's an
         * ancestor and will be fixed up on the way to the root.  We don't
         * have to check entry->prev against &map->header since &map->header
         * will never be in the tree.
         */
        uvm_rb_fixup(map,
            LEFT_ENTRY(entry) == entry->prev ? entry->prev : entry);
}

static void
uvm_rb_remove(struct vm_map *map, struct vm_map_entry *entry)
{
        struct vm_map_entry *prev_parent = NULL, *next_parent = NULL;

        /*
         * If we are removing an interior node, then an adjacent node will
         * be used to replace its position in the tree.  Therefore we will
         * need to fixup the tree starting at the parent of the replacement
         * node.  So record their parents for later use.
         */
        if (entry->prev != &map->header)
                prev_parent = PARENT_ENTRY(map, entry->prev);
        if (entry->next != &map->header)
                next_parent = PARENT_ENTRY(map, entry->next);

        rb_tree_remove_node(&map->rb_tree, &entry->rb_node);

        /*
         * If the previous node has a new parent, fixup the tree starting
         * at the previous node's old parent.
         */
        if (entry->prev != &map->header) {
                /*
                 * Update the previous entry's gap due to our absence.
                 */
                entry->prev->gap = uvm_rb_gap(entry->prev);
                uvm_rb_fixup(map, entry->prev);
                if (prev_parent != NULL
                    && prev_parent != entry
                    && prev_parent != PARENT_ENTRY(map, entry->prev))
                        uvm_rb_fixup(map, prev_parent);
        }

        /*
         * If the next node has a new parent, fixup the tree starting
         * at the next node's old parent.
         */
        if (entry->next != &map->header) {
                uvm_rb_fixup(map, entry->next);
                if (next_parent != NULL
                    && next_parent != entry
                    && next_parent != PARENT_ENTRY(map, entry->next))
                        uvm_rb_fixup(map, next_parent);
        }
}

#if defined(DEBUG)
int uvm_debug_check_map = 0;
int uvm_debug_check_rbtree = 0;
#define uvm_map_check(map, name) \
        _uvm_map_check((map), (name), __FILE__, __LINE__)
static void
_uvm_map_check(struct vm_map *map, const char *name,
    const char *file, int line)
{

        if ((uvm_debug_check_map && _uvm_map_sanity(map)) ||
            (uvm_debug_check_rbtree && _uvm_tree_sanity(map))) {
                panic("uvm_map_check failed: \"%s\" map=%p (%s:%d)",
                    name, map, file, line);
        }
}
#else /* defined(DEBUG) */
#define uvm_map_check(map, name)        /* nothing */
#endif /* defined(DEBUG) */

#if defined(DEBUG) || defined(DDB)
int
_uvm_map_sanity(struct vm_map *map)
{
        bool first_free_found = false;
        bool hint_found = false;
        const struct vm_map_entry *e;
        struct vm_map_entry *hint = map->hint;

        e = &map->header; 
        for (;;) {
                if (map->first_free == e) {
                        first_free_found = true;
                } else if (!first_free_found && e->next->start > e->end) {
                        printf("first_free %p should be %p\n",
                            map->first_free, e);
                        return -1;
                }
                if (hint == e) {
                        hint_found = true;
                }

                e = e->next;
                if (e == &map->header) {
                        break;
                }
        }
        if (!first_free_found) {
                printf("stale first_free\n");
                return -1;
        }
        if (!hint_found) {
                printf("stale hint\n");
                return -1;
        }
        return 0;
}

int
_uvm_tree_sanity(struct vm_map *map)
{
        struct vm_map_entry *tmp, *trtmp;
        int n = 0, i = 1;

        for (tmp = map->header.next; tmp != &map->header; tmp = tmp->next) {
                if (tmp->gap != uvm_rb_gap(tmp)) {
                        printf("%d/%d gap %lx != %lx %s\n",
                            n + 1, map->nentries,
                            (ulong)tmp->gap, (ulong)uvm_rb_gap(tmp),
                            tmp->next == &map->header ? "(last)" : "");
                        goto error;
                }
                /*
                 * If any entries are out of order, tmp->gap will be unsigned
                 * and will likely exceed the size of the map.
                 */
                if (tmp->gap >= vm_map_max(map) - vm_map_min(map)) {
                        printf("too large gap %zu\n", (size_t)tmp->gap);
                        goto error;
                }
                n++;
        }

        if (n != map->nentries) {
                printf("nentries: %d vs %d\n", n, map->nentries);
                goto error;
        }

        trtmp = NULL;
        for (tmp = map->header.next; tmp != &map->header; tmp = tmp->next) {
                if (tmp->maxgap != uvm_rb_maxgap(tmp)) {
                        printf("maxgap %lx != %lx\n",
                            (ulong)tmp->maxgap,
                            (ulong)uvm_rb_maxgap(tmp));
                        goto error;
                }
                if (trtmp != NULL && trtmp->start >= tmp->start) {
                        printf("corrupt: 0x%"PRIxVADDR"x >= 0x%"PRIxVADDR"x\n",
                            trtmp->start, tmp->start);
                        goto error;
                }

                trtmp = tmp;
        }

        for (tmp = map->header.next; tmp != &map->header;
            tmp = tmp->next, i++) {
                trtmp = (void *) rb_tree_iterate(&map->rb_tree, &tmp->rb_node,
                    RB_DIR_LEFT);
                if (trtmp == NULL)
                        trtmp = &map->header;
                if (tmp->prev != trtmp) {
                        printf("lookup: %d: %p->prev=%p: %p\n",
                            i, tmp, tmp->prev, trtmp);
                        goto error;
                }
                trtmp = (void *) rb_tree_iterate(&map->rb_tree, &tmp->rb_node,
                    RB_DIR_RIGHT);
                if (trtmp == NULL)
                        trtmp = &map->header;
                if (tmp->next != trtmp) {
                        printf("lookup: %d: %p->next=%p: %p\n",
                            i, tmp, tmp->next, trtmp);
                        goto error;
                }
                trtmp = (void *)rb_tree_find_node(&map->rb_tree, &tmp->start);
                if (trtmp != tmp) {
                        printf("lookup: %d: %p - %p: %p\n", i, tmp, trtmp,
                            PARENT_ENTRY(map, tmp));
                        goto error;
                }
        }

        return (0);
 error:
        return (-1);
}
#endif /* defined(DEBUG) || defined(DDB) */

#ifdef DIAGNOSTIC
static struct vm_map *uvm_kmapent_map(struct vm_map_entry *);
#endif

/*
 * vm_map_lock: acquire an exclusive (write) lock on a map.
 *
 * => Note that "intrsafe" maps use only exclusive, spin locks.
 *
 * => The locking protocol provides for guaranteed upgrade from shared ->
 *    exclusive by whichever thread currently has the map marked busy.
 *    See "LOCKING PROTOCOL NOTES" in uvm_map.h.  This is horrible; among
 *    other problems, it defeats any fairness guarantees provided by RW
 *    locks.
 */

void
vm_map_lock(struct vm_map *map)
{

        if ((map->flags & VM_MAP_INTRSAFE) != 0) {
                mutex_spin_enter(&map->mutex);
                return;
        }

        for (;;) {
                rw_enter(&map->lock, RW_WRITER);
                if (map->busy == NULL)
                        break;
                if (map->busy == curlwp)
                        break;
                mutex_enter(&map->misc_lock);
                rw_exit(&map->lock);
                if (map->busy != NULL)
                        cv_wait(&map->cv, &map->misc_lock);
                mutex_exit(&map->misc_lock);
        }

        map->timestamp++;
}

/*
 * vm_map_lock_try: try to lock a map, failing if it is already locked.
 */

bool
vm_map_lock_try(struct vm_map *map)
{

        if ((map->flags & VM_MAP_INTRSAFE) != 0)
                return mutex_tryenter(&map->mutex);
        if (!rw_tryenter(&map->lock, RW_WRITER))
                return false;
        if (map->busy != NULL) {
                rw_exit(&map->lock);
                return false;
        }

        map->timestamp++;
        return true;
}

/*
 * vm_map_unlock: release an exclusive lock on a map.
 */

void
vm_map_unlock(struct vm_map *map)
{

        if ((map->flags & VM_MAP_INTRSAFE) != 0)
                mutex_spin_exit(&map->mutex);
        else {
                KASSERT(rw_write_held(&map->lock));
                KASSERT(map->busy == NULL || map->busy == curlwp);
                rw_exit(&map->lock);
        }
}

/*
 * vm_map_unbusy: mark the map as unbusy, and wake any waiters that
 *     want an exclusive lock.
 */

void
vm_map_unbusy(struct vm_map *map)
{

        KASSERT(map->busy == curlwp);

        /*
         * Safe to clear 'busy' and 'waiters' with only a read lock held:
         *
         * o they can only be set with a write lock held
         * o writers are blocked out with a read or write hold
         * o at any time, only one thread owns the set of values
         */
        mutex_enter(&map->misc_lock);
        map->busy = NULL;
        cv_broadcast(&map->cv);
        mutex_exit(&map->misc_lock);
}

/*
 * vm_map_lock_read: acquire a shared (read) lock on a map.
 */

void
vm_map_lock_read(struct vm_map *map)
{

        KASSERT((map->flags & VM_MAP_INTRSAFE) == 0);

        rw_enter(&map->lock, RW_READER);
}

/*
 * vm_map_unlock_read: release a shared lock on a map.
 */
 
void
vm_map_unlock_read(struct vm_map *map)
{

        KASSERT((map->flags & VM_MAP_INTRSAFE) == 0);

        rw_exit(&map->lock);
}

/*
 * vm_map_busy: mark a map as busy.
 *
 * => the caller must hold the map write locked
 */

void
vm_map_busy(struct vm_map *map)
{

        KASSERT(rw_write_held(&map->lock));
        KASSERT(map->busy == NULL);

        map->busy = curlwp;
}

/*
 * vm_map_locked_p: return true if the map is write locked.
 *
 * => only for debug purposes like KASSERTs.
 * => should not be used to verify that a map is not locked.
 */

bool
vm_map_locked_p(struct vm_map *map)
{

        if ((map->flags & VM_MAP_INTRSAFE) != 0) {
                return mutex_owned(&map->mutex);
        } else {
                return rw_write_held(&map->lock);
        }
}

/*
 * uvm_mapent_alloc: allocate a map entry
 */

static struct vm_map_entry *
uvm_mapent_alloc(struct vm_map *map, int flags)
{
        struct vm_map_entry *me;
        int pflags = (flags & UVM_FLAG_NOWAIT) ? PR_NOWAIT : PR_WAITOK;
        UVMHIST_FUNC("uvm_mapent_alloc"); UVMHIST_CALLED(maphist);

        if (VM_MAP_USE_KMAPENT(map)) {
                me = uvm_kmapent_alloc(map, flags);
        } else {
                me = pool_cache_get(&uvm_map_entry_cache, pflags);
                if (__predict_false(me == NULL))
                        return NULL;
                me->flags = 0;
        }

        UVMHIST_LOG(maphist, "<- new entry=0x%x [kentry=%d]", me,
            ((map->flags & VM_MAP_INTRSAFE) != 0 || map == kernel_map), 0, 0);
        return (me);
}

/*
 * uvm_mapent_alloc_split: allocate a map entry for clipping.
 *
 * => map must be locked by caller if UVM_MAP_QUANTUM is set.
 */

static struct vm_map_entry *
uvm_mapent_alloc_split(struct vm_map *map,
    const struct vm_map_entry *old_entry, int flags,
    struct uvm_mapent_reservation *umr)
{
        struct vm_map_entry *me;

        KASSERT(!VM_MAP_USE_KMAPENT(map) ||
            (old_entry->flags & UVM_MAP_QUANTUM) || !UMR_EMPTY(umr));

        if (old_entry->flags & UVM_MAP_QUANTUM) {
                struct vm_map_kernel *vmk = vm_map_to_kernel(map);

                KASSERT(vm_map_locked_p(map));
                me = vmk->vmk_merged_entries;
                KASSERT(me);
                vmk->vmk_merged_entries = me->next;
                KASSERT(me->flags & UVM_MAP_QUANTUM);
        } else {
                me = uvm_mapent_alloc(map, flags);
        }

        return me;
}

/*
 * uvm_mapent_free: free map entry
 */

static void
uvm_mapent_free(struct vm_map_entry *me)
{
        UVMHIST_FUNC("uvm_mapent_free"); UVMHIST_CALLED(maphist);

        UVMHIST_LOG(maphist,"<- freeing map entry=0x%x [flags=%d]",
                me, me->flags, 0, 0);
        if (me->flags & UVM_MAP_KERNEL) {
                uvm_kmapent_free(me);
        } else {
                pool_cache_put(&uvm_map_entry_cache, me);
        }
}

/*
 * uvm_mapent_free_merged: free merged map entry
 *
 * => keep the entry if needed.
 * => caller shouldn't hold map locked if VM_MAP_USE_KMAPENT(map) is true.
 * => map should be locked if UVM_MAP_QUANTUM is set.
 */

static void
uvm_mapent_free_merged(struct vm_map *map, struct vm_map_entry *me)
{

        KASSERT(!(me->flags & UVM_MAP_KERNEL) || uvm_kmapent_map(me) == map);

        if (me->flags & UVM_MAP_QUANTUM) {
                /*
                 * keep this entry for later splitting.
                 */
                struct vm_map_kernel *vmk;

                KASSERT(vm_map_locked_p(map));
                KASSERT(VM_MAP_IS_KERNEL(map));
                KASSERT(!VM_MAP_USE_KMAPENT(map) ||
                    (me->flags & UVM_MAP_KERNEL));

                vmk = vm_map_to_kernel(map);
                me->next = vmk->vmk_merged_entries;
                vmk->vmk_merged_entries = me;
        } else {
                uvm_mapent_free(me);
        }
}

/*
 * uvm_mapent_copy: copy a map entry, preserving flags
 */

static inline void
uvm_mapent_copy(struct vm_map_entry *src, struct vm_map_entry *dst)
{

        memcpy(dst, src, ((char *)&src->uvm_map_entry_stop_copy) -
            ((char *)src));
}

/*
 * uvm_mapent_overhead: calculate maximum kva overhead necessary for
 * map entries.
 *
 * => size and flags are the same as uvm_km_suballoc's ones.
 */

vsize_t
uvm_mapent_overhead(vsize_t size, int flags)
{

        if (VM_MAP_USE_KMAPENT_FLAGS(flags)) {
                return uvm_kmapent_overhead(size);
        }
        return 0;
}

#if defined(DEBUG)
static void
_uvm_mapent_check(const struct vm_map_entry *entry, const char *file, int line)
{

        if (entry->start >= entry->end) {
                goto bad;
        }
        if (UVM_ET_ISOBJ(entry)) {
                if (entry->object.uvm_obj == NULL) {
                        goto bad;
                }
        } else if (UVM_ET_ISSUBMAP(entry)) {
                if (entry->object.sub_map == NULL) {
                        goto bad;
                }
        } else {
                if (entry->object.uvm_obj != NULL ||
                    entry->object.sub_map != NULL) {
                        goto bad;
                }
        }
        if (!UVM_ET_ISOBJ(entry)) {
                if (entry->offset != 0) {
                        goto bad;
                }
        }

        return;

bad:
        panic("%s: bad entry %p (%s:%d)", __func__, entry, file, line);
}
#endif /* defined(DEBUG) */

/*
 * uvm_map_entry_unwire: unwire a map entry
 *
 * => map should be locked by caller
 */

static inline void
uvm_map_entry_unwire(struct vm_map *map, struct vm_map_entry *entry)
{

        entry->wired_count = 0;
        uvm_fault_unwire_locked(map, entry->start, entry->end);
}


/*
 * wrapper for calling amap_ref()
 */
static inline void
uvm_map_reference_amap(struct vm_map_entry *entry, int flags)
{

        amap_ref(entry->aref.ar_amap, entry->aref.ar_pageoff,
            (entry->end - entry->start) >> PAGE_SHIFT, flags);
}


/*
 * wrapper for calling amap_unref()
 */
static inline void
uvm_map_unreference_amap(struct vm_map_entry *entry, int flags)
{

        amap_unref(entry->aref.ar_amap, entry->aref.ar_pageoff,
            (entry->end - entry->start) >> PAGE_SHIFT, flags);
}


/*
 * uvm_map_init: init mapping system at boot time.
 */

void
uvm_map_init(void)
{
#if defined(UVMHIST)
        static struct uvm_history_ent maphistbuf[100];
        static struct uvm_history_ent pdhistbuf[100];
#endif

        /*
         * first, init logging system.
         */

        UVMHIST_FUNC("uvm_map_init");
        UVMHIST_INIT_STATIC(maphist, maphistbuf);
        UVMHIST_INIT_STATIC(pdhist, pdhistbuf);
        UVMHIST_CALLED(maphist);
        UVMHIST_LOG(maphist,"<starting uvm map system>", 0, 0, 0, 0);

        /*
         * initialize the global lock for kernel map entry.
         */

        mutex_init(&uvm_kentry_lock, MUTEX_DRIVER, IPL_VM);

        /*
         * initialize caches.
         */

        pool_cache_bootstrap(&uvm_map_entry_cache, sizeof(struct vm_map_entry),
            0, 0, 0, "vmmpepl", NULL, IPL_NONE, NULL, NULL, NULL);
        pool_cache_bootstrap(&uvm_vmspace_cache, sizeof(struct vmspace),
            0, 0, 0, "vmsppl", NULL, IPL_NONE, NULL, NULL, NULL);
}

/*
 * clippers
 */

/*
 * uvm_mapent_splitadj: adjust map entries for splitting, after uvm_mapent_copy.
 */

static void
uvm_mapent_splitadj(struct vm_map_entry *entry1, struct vm_map_entry *entry2,
    vaddr_t splitat)
{
        vaddr_t adj;

        KASSERT(entry1->start < splitat);
        KASSERT(splitat < entry1->end);

        adj = splitat - entry1->start;
        entry1->end = entry2->start = splitat;

        if (entry1->aref.ar_amap) {
                amap_splitref(&entry1->aref, &entry2->aref, adj);
        }
        if (UVM_ET_ISSUBMAP(entry1)) {
                /* ... unlikely to happen, but play it safe */
                 uvm_map_reference(entry1->object.sub_map);
        } else if (UVM_ET_ISOBJ(entry1)) {
                KASSERT(entry1->object.uvm_obj != NULL); /* suppress coverity */
                entry2->offset += adj;
                if (entry1->object.uvm_obj->pgops &&
                    entry1->object.uvm_obj->pgops->pgo_reference)
                        entry1->object.uvm_obj->pgops->pgo_reference(
                            entry1->object.uvm_obj);
        }
}

/*
 * uvm_map_clip_start: ensure that the entry begins at or after
 *      the starting address, if it doesn't we split the entry.
 *
 * => caller should use UVM_MAP_CLIP_START macro rather than calling
 *    this directly
 * => map must be locked by caller
 */

void
uvm_map_clip_start(struct vm_map *map, struct vm_map_entry *entry,
    vaddr_t start, struct uvm_mapent_reservation *umr)
{
        struct vm_map_entry *new_entry;

        /* uvm_map_simplify_entry(map, entry); */ /* XXX */

        uvm_map_check(map, "clip_start entry");
        uvm_mapent_check(entry);

        /*
         * Split off the front portion.  note that we must insert the new
         * entry BEFORE this one, so that this entry has the specified
         * starting address.
         */
        new_entry = uvm_mapent_alloc_split(map, entry, 0, umr);
        uvm_mapent_copy(entry, new_entry); /* entry -> new_entry */
        uvm_mapent_splitadj(new_entry, entry, start);
        uvm_map_entry_link(map, entry->prev, new_entry);

        uvm_map_check(map, "clip_start leave");
}

/*
 * uvm_map_clip_end: ensure that the entry ends at or before
 *      the ending address, if it does't we split the reference
 *
 * => caller should use UVM_MAP_CLIP_END macro rather than calling
 *    this directly
 * => map must be locked by caller
 */

void
uvm_map_clip_end(struct vm_map *map, struct vm_map_entry *entry, vaddr_t end,
    struct uvm_mapent_reservation *umr)
{
        struct vm_map_entry *new_entry;

        uvm_map_check(map, "clip_end entry");
        uvm_mapent_check(entry);

        /*
         *      Create a new entry and insert it
         *      AFTER the specified entry
         */
        new_entry = uvm_mapent_alloc_split(map, entry, 0, umr);
        uvm_mapent_copy(entry, new_entry); /* entry -> new_entry */
        uvm_mapent_splitadj(entry, new_entry, end);
        uvm_map_entry_link(map, entry, new_entry);

        uvm_map_check(map, "clip_end leave");
}

static void
vm_map_drain(struct vm_map *map, uvm_flag_t flags)
{

        if (!VM_MAP_IS_KERNEL(map)) {
                return;
        }

        uvm_km_va_drain(map, flags);
}

/*
 *   M A P   -   m a i n   e n t r y   p o i n t
 */
/*
 * uvm_map: establish a valid mapping in a map
 *
 * => assume startp is page aligned.
 * => assume size is a multiple of PAGE_SIZE.
 * => assume sys_mmap provides enough of a "hint" to have us skip
 *      over text/data/bss area.
 * => map must be unlocked (we will lock it)
 * => <uobj,uoffset> value meanings (4 cases):
 *       [1] <NULL,uoffset>             == uoffset is a hint for PMAP_PREFER
 *       [2] <NULL,UVM_UNKNOWN_OFFSET>  == don't PMAP_PREFER
 *       [3] <uobj,uoffset>             == normal mapping
 *       [4] <uobj,UVM_UNKNOWN_OFFSET>  == uvm_map finds offset based on VA
 *
 *    case [4] is for kernel mappings where we don't know the offset until
 *    we've found a virtual address.   note that kernel object offsets are
 *    always relative to vm_map_min(kernel_map).
 *
 * => if `align' is non-zero, we align the virtual address to the specified
 *      alignment.
 *      this is provided as a mechanism for large pages.
 *
 * => XXXCDC: need way to map in external amap?
 */

int
uvm_map(struct vm_map *map, vaddr_t *startp /* IN/OUT */, vsize_t size,
    struct uvm_object *uobj, voff_t uoffset, vsize_t align, uvm_flag_t flags)
{
        struct uvm_map_args args;
        struct vm_map_entry *new_entry;
        int error;

        KASSERT((flags & UVM_FLAG_QUANTUM) == 0 || VM_MAP_IS_KERNEL(map));
        KASSERT((size & PAGE_MASK) == 0);

        /*
         * for pager_map, allocate the new entry first to avoid sleeping
         * for memory while we have the map locked.
         *
         * Also, because we allocate entries for in-kernel maps
         * a bit differently (cf. uvm_kmapent_alloc/free), we need to
         * allocate them before locking the map.
         */

        new_entry = NULL;
        if (VM_MAP_USE_KMAPENT(map) || (flags & UVM_FLAG_QUANTUM) ||
            map == pager_map) {
                new_entry = uvm_mapent_alloc(map, (flags & UVM_FLAG_NOWAIT));
                if (__predict_false(new_entry == NULL))
                        return ENOMEM;
                if (flags & UVM_FLAG_QUANTUM)
                        new_entry->flags |= UVM_MAP_QUANTUM;
        }
        if (map == pager_map)
                flags |= UVM_FLAG_NOMERGE;

        error = uvm_map_prepare(map, *startp, size, uobj, uoffset, align,
            flags, &args);
        if (!error) {
                error = uvm_map_enter(map, &args, new_entry);
                *startp = args.uma_start;
        } else if (new_entry) {
                uvm_mapent_free(new_entry);
        }

#if defined(DEBUG)
        if (!error && VM_MAP_IS_KERNEL(map)) {
                uvm_km_check_empty(map, *startp, *startp + size);
        }
#endif /* defined(DEBUG) */

        return error;
}

int
uvm_map_prepare(struct vm_map *map, vaddr_t start, vsize_t size,
    struct uvm_object *uobj, voff_t uoffset, vsize_t align, uvm_flag_t flags,
    struct uvm_map_args *args)
{
        struct vm_map_entry *prev_entry;
        vm_prot_t prot = UVM_PROTECTION(flags);
        vm_prot_t maxprot = UVM_MAXPROTECTION(flags);

        UVMHIST_FUNC("uvm_map_prepare");
        UVMHIST_CALLED(maphist);

        UVMHIST_LOG(maphist, "(map=0x%x, start=0x%x, size=%d, flags=0x%x)",
            map, start, size, flags);
        UVMHIST_LOG(maphist, "  uobj/offset 0x%x/%d", uobj, uoffset,0,0);

        /*
         * detect a popular device driver bug.
         */

        KASSERT(doing_shutdown || curlwp != NULL ||
            (map->flags & VM_MAP_INTRSAFE));

        /*
         * zero-sized mapping doesn't make any sense.
         */
        KASSERT(size > 0);

        KASSERT((~flags & (UVM_FLAG_NOWAIT | UVM_FLAG_WAITVA)) != 0);

        uvm_map_check(map, "map entry");

        /*
         * check sanity of protection code
         */

        if ((prot & maxprot) != prot) {
                UVMHIST_LOG(maphist, "<- prot. failure:  prot=0x%x, max=0x%x",
                prot, maxprot,0,0);
                return EACCES;
        }

        /*
         * figure out where to put new VM range
         */

retry:
        if (vm_map_lock_try(map) == false) {
                if ((flags & UVM_FLAG_TRYLOCK) != 0 &&
                    (map->flags & VM_MAP_INTRSAFE) == 0) {
                        return EAGAIN;
                }
                vm_map_lock(map); /* could sleep here */
        }
        prev_entry = uvm_map_findspace(map, start, size, &start,
            uobj, uoffset, align, flags);
        if (prev_entry == NULL) {
                unsigned int timestamp;

                timestamp = map->timestamp;
                UVMHIST_LOG(maphist,"waiting va timestamp=0x%x",
                            timestamp,0,0,0);
                map->flags |= VM_MAP_WANTVA;
                vm_map_unlock(map);

                /*
                 * try to reclaim kva and wait until someone does unmap.
                 * fragile locking here, so we awaken every second to
                 * recheck the condition.
                 */

                vm_map_drain(map, flags);

                mutex_enter(&map->misc_lock);
                while ((map->flags & VM_MAP_WANTVA) != 0 &&
                   map->timestamp == timestamp) {
                        if ((flags & UVM_FLAG_WAITVA) == 0) {
                                mutex_exit(&map->misc_lock);
                                UVMHIST_LOG(maphist,
                                    "<- uvm_map_findspace failed!", 0,0,0,0);
                                return ENOMEM;
                        } else {
                                cv_timedwait(&map->cv, &map->misc_lock, hz);
                        }
                }
                mutex_exit(&map->misc_lock);
                goto retry;
        }

#ifdef PMAP_GROWKERNEL
        /*
         * If the kernel pmap can't map the requested space,
         * then allocate more resources for it.
         */
        if (map == kernel_map && uvm_maxkaddr < (start + size))
                uvm_maxkaddr = pmap_growkernel(start + size);
#endif

        UVMMAP_EVCNT_INCR(map_call);

        /*
         * if uobj is null, then uoffset is either a VAC hint for PMAP_PREFER
         * [typically from uvm_map_reserve] or it is UVM_UNKNOWN_OFFSET.   in
         * either case we want to zero it  before storing it in the map entry
         * (because it looks strange and confusing when debugging...)
         *
         * if uobj is not null
         *   if uoffset is not UVM_UNKNOWN_OFFSET then we have a normal mapping
         *      and we do not need to change uoffset.
         *   if uoffset is UVM_UNKNOWN_OFFSET then we need to find the offset
         *      now (based on the starting address of the map).   this case is
         *      for kernel object mappings where we don't know the offset until
         *      the virtual address is found (with uvm_map_findspace).   the
         *      offset is the distance we are from the start of the map.
         */

        if (uobj == NULL) {
                uoffset = 0;
        } else {
                if (uoffset == UVM_UNKNOWN_OFFSET) {
                        KASSERT(UVM_OBJ_IS_KERN_OBJECT(uobj));
                        uoffset = start - vm_map_min(kernel_map);
                }
        }

        args->uma_flags = flags;
        args->uma_prev = prev_entry;
        args->uma_start = start;
        args->uma_size = size;
        args->uma_uobj = uobj;
        args->uma_uoffset = uoffset;

        UVMHIST_LOG(maphist, "<- done!", 0,0,0,0);
        return 0;
}

int
uvm_map_enter(struct vm_map *map, const struct uvm_map_args *args,
    struct vm_map_entry *new_entry)
{
        struct vm_map_entry *prev_entry = args->uma_prev;
        struct vm_map_entry *dead = NULL;

        const uvm_flag_t flags = args->uma_flags;
        const vm_prot_t prot = UVM_PROTECTION(flags);
        const vm_prot_t maxprot = UVM_MAXPROTECTION(flags);
        const vm_inherit_t inherit = UVM_INHERIT(flags);
        const int amapwaitflag = (flags & UVM_FLAG_NOWAIT) ?
            AMAP_EXTEND_NOWAIT : 0;
        const int advice = UVM_ADVICE(flags);
        const int meflagval = (flags & UVM_FLAG_QUANTUM) ?
            UVM_MAP_QUANTUM : 0;

        vaddr_t start = args->uma_start;
        vsize_t size = args->uma_size;
        struct uvm_object *uobj = args->uma_uobj;
        voff_t uoffset = args->uma_uoffset;

        const int kmap = (vm_map_pmap(map) == pmap_kernel());
        int merged = 0;
        int error;
        int newetype;

        UVMHIST_FUNC("uvm_map_enter");
        UVMHIST_CALLED(maphist);

        UVMHIST_LOG(maphist, "(map=0x%x, start=0x%x, size=%d, flags=0x%x)",
            map, start, size, flags);
        UVMHIST_LOG(maphist, "  uobj/offset 0x%x/%d", uobj, uoffset,0,0);

        KASSERT(map->hint == prev_entry); /* bimerge case assumes this */

        if (flags & UVM_FLAG_QUANTUM) {
                KASSERT(new_entry);
                KASSERT(new_entry->flags & UVM_MAP_QUANTUM);
        }

        if (uobj)
                newetype = UVM_ET_OBJ;
        else
                newetype = 0;

        if (flags & UVM_FLAG_COPYONW) {
                newetype |= UVM_ET_COPYONWRITE;
                if ((flags & UVM_FLAG_OVERLAY) == 0)
                        newetype |= UVM_ET_NEEDSCOPY;
        }

        /*
         * try and insert in map by extending previous entry, if possible.
         * XXX: we don't try and pull back the next entry.   might be useful
         * for a stack, but we are currently allocating our stack in advance.
         */

        if (flags & UVM_FLAG_NOMERGE)
                goto nomerge;

        if (prev_entry->end == start &&
            prev_entry != &map->header &&
            UVM_ET_ISCOMPATIBLE(prev_entry, newetype, uobj, meflagval,
            prot, maxprot, inherit, advice, 0)) {

                if (uobj && prev_entry->offset +
                    (prev_entry->end - prev_entry->start) != uoffset)
                        goto forwardmerge;

                /*
                 * can't extend a shared amap.  note: no need to lock amap to
                 * look at refs since we don't care about its exact value.
                 * if it is one (i.e. we have only reference) it will stay there
                 */

                if (prev_entry->aref.ar_amap &&
                    amap_refs(prev_entry->aref.ar_amap) != 1) {
                        goto forwardmerge;
                }

                if (prev_entry->aref.ar_amap) {
                        error = amap_extend(prev_entry, size,
                            amapwaitflag | AMAP_EXTEND_FORWARDS);
                        if (error)
                                goto nomerge;
                }

                if (kmap) {
                        UVMMAP_EVCNT_INCR(kbackmerge);
                } else {
                        UVMMAP_EVCNT_INCR(ubackmerge);
                }
                UVMHIST_LOG(maphist,"  starting back merge", 0, 0, 0, 0);

                /*
                 * drop our reference to uobj since we are extending a reference
                 * that we already have (the ref count can not drop to zero).
                 */

                if (uobj && uobj->pgops->pgo_detach)
                        uobj->pgops->pgo_detach(uobj);

                /*
                 * Now that we've merged the entries, note that we've grown
                 * and our gap has shrunk.  Then fix the tree.
                 */
                prev_entry->end += size;
                prev_entry->gap -= size;
                uvm_rb_fixup(map, prev_entry);

                uvm_map_check(map, "map backmerged");

                UVMHIST_LOG(maphist,"<- done (via backmerge)!", 0, 0, 0, 0);
                merged++;
        }

forwardmerge:
        if (prev_entry->next->start == (start + size) &&
            prev_entry->next != &map->header &&
            UVM_ET_ISCOMPATIBLE(prev_entry->next, newetype, uobj, meflagval,
            prot, maxprot, inherit, advice, 0)) {

                if (uobj && prev_entry->next->offset != uoffset + size)
                        goto nomerge;

                /*
                 * can't extend a shared amap.  note: no need to lock amap to
                 * look at refs since we don't care about its exact value.
                 * if it is one (i.e. we have only reference) it will stay there.
                 *
                 * note that we also can't merge two amaps, so if we
                 * merged with the previous entry which has an amap,
                 * and the next entry also has an amap, we give up.
                 *
                 * Interesting cases:
                 * amap, new, amap -> give up second merge (single fwd extend)
                 * amap, new, none -> double forward extend (extend again here)
                 * none, new, amap -> double backward extend (done here)
                 * uobj, new, amap -> single backward extend (done here)
                 *
                 * XXX should we attempt to deal with someone refilling
                 * the deallocated region between two entries that are
                 * backed by the same amap (ie, arefs is 2, "prev" and
                 * "next" refer to it, and adding this allocation will
                 * close the hole, thus restoring arefs to 1 and
                 * deallocating the "next" vm_map_entry)?  -- @@@
                 */

                if (prev_entry->next->aref.ar_amap &&
                    (amap_refs(prev_entry->next->aref.ar_amap) != 1 ||
                     (merged && prev_entry->aref.ar_amap))) {
                        goto nomerge;
                }

                if (merged) {
                        /*
                         * Try to extend the amap of the previous entry to
                         * cover the next entry as well.  If it doesn't work
                         * just skip on, don't actually give up, since we've
                         * already completed the back merge.
                         */
                        if (prev_entry->aref.ar_amap) {
                                if (amap_extend(prev_entry,
                                    prev_entry->next->end -
                                    prev_entry->next->start,
                                    amapwaitflag | AMAP_EXTEND_FORWARDS))
                                        goto nomerge;
                        }

                        /*
                         * Try to extend the amap of the *next* entry
                         * back to cover the new allocation *and* the
                         * previous entry as well (the previous merge
                         * didn't have an amap already otherwise we
                         * wouldn't be checking here for an amap).  If
                         * it doesn't work just skip on, again, don't
                         * actually give up, since we've already
                         * completed the back merge.
                         */
                        else if (prev_entry->next->aref.ar_amap) {
                                if (amap_extend(prev_entry->next,
                                    prev_entry->end -
                                    prev_entry->start,
                                    amapwaitflag | AMAP_EXTEND_BACKWARDS))
                                        goto nomerge;
                        }
                } else {
                        /*
                         * Pull the next entry's amap backwards to cover this
                         * new allocation.
                         */
                        if (prev_entry->next->aref.ar_amap) {
                                error = amap_extend(prev_entry->next, size,
                                    amapwaitflag | AMAP_EXTEND_BACKWARDS);
                                if (error)
                                        goto nomerge;
                        }
                }

                if (merged) {
                        if (kmap) {
                                UVMMAP_EVCNT_DECR(kbackmerge);
                                UVMMAP_EVCNT_INCR(kbimerge);
                        } else {
                                UVMMAP_EVCNT_DECR(ubackmerge);
                                UVMMAP_EVCNT_INCR(ubimerge);
                        }
                } else {
                        if (kmap) {
                                UVMMAP_EVCNT_INCR(kforwmerge);
                        } else {
                                UVMMAP_EVCNT_INCR(uforwmerge);
                        }
                }
                UVMHIST_LOG(maphist,"  starting forward merge", 0, 0, 0, 0);

                /*
                 * drop our reference to uobj since we are extending a reference
                 * that we already have (the ref count can not drop to zero).
                 * (if merged, we've already detached)
                 */
                if (uobj && uobj->pgops->pgo_detach && !merged)
                        uobj->pgops->pgo_detach(uobj);

                if (merged) {
                        dead = prev_entry->next;
                        prev_entry->end = dead->end;
                        uvm_map_entry_unlink(map, dead);
                        if (dead->aref.ar_amap != NULL) {
                                prev_entry->aref = dead->aref;
                                dead->aref.ar_amap = NULL;
                        }
                } else {
                        prev_entry->next->start -= size;
                        if (prev_entry != &map->header) {
                                prev_entry->gap -= size;
                                KASSERT(prev_entry->gap == uvm_rb_gap(prev_entry));
                                uvm_rb_fixup(map, prev_entry);
                        }
                        if (uobj)
                                prev_entry->next->offset = uoffset;
                }

                uvm_map_check(map, "map forwardmerged");

                UVMHIST_LOG(maphist,"<- done forwardmerge", 0, 0, 0, 0);
                merged++;
        }

nomerge:
        if (!merged) {
                UVMHIST_LOG(maphist,"  allocating new map entry", 0, 0, 0, 0);
                if (kmap) {
                        UVMMAP_EVCNT_INCR(knomerge);
                } else {
                        UVMMAP_EVCNT_INCR(unomerge);
                }

                /*
                 * allocate new entry and link it in.
                 */

                if (new_entry == NULL) {
                        new_entry = uvm_mapent_alloc(map,
                                (flags & UVM_FLAG_NOWAIT));
                        if (__predict_false(new_entry == NULL)) {
                                error = ENOMEM;
                                goto done;
                        }
                }
                new_entry->start = start;
                new_entry->end = new_entry->start + size;
                new_entry->object.uvm_obj = uobj;
                new_entry->offset = uoffset;

                new_entry->etype = newetype;

                if (flags & UVM_FLAG_NOMERGE) {
                        new_entry->flags |= UVM_MAP_NOMERGE;
                }

                new_entry->protection = prot;
                new_entry->max_protection = maxprot;
                new_entry->inheritance = inherit;
                new_entry->wired_count = 0;
                new_entry->advice = advice;
                if (flags & UVM_FLAG_OVERLAY) {

                        /*
                         * to_add: for BSS we overallocate a little since we
                         * are likely to extend
                         */

                        vaddr_t to_add = (flags & UVM_FLAG_AMAPPAD) ?
                                UVM_AMAP_CHUNK << PAGE_SHIFT : 0;
                        struct vm_amap *amap = amap_alloc(size, to_add,
                            (flags & UVM_FLAG_NOWAIT));
                        if (__predict_false(amap == NULL)) {
                                error = ENOMEM;
                                goto done;
                        }
                        new_entry->aref.ar_pageoff = 0;
                        new_entry->aref.ar_amap = amap;
                } else {
                        new_entry->aref.ar_pageoff = 0;
                        new_entry->aref.ar_amap = NULL;
                }
                uvm_map_entry_link(map, prev_entry, new_entry);

                /*
                 * Update the free space hint
                 */

                if ((map->first_free == prev_entry) &&
                    (prev_entry->end >= new_entry->start))
                        map->first_free = new_entry;

                new_entry = NULL;
        }

        map->size += size;

        UVMHIST_LOG(maphist,"<- done!", 0, 0, 0, 0);

        error = 0;
done:
        if ((flags & UVM_FLAG_QUANTUM) == 0) {
                /*
                 * vmk_merged_entries is locked by the map's lock.
                 */
                vm_map_unlock(map);
        }
        if (new_entry && error == 0) {
                KDASSERT(merged);
                uvm_mapent_free_merged(map, new_entry);
                new_entry = NULL;
        }
        if (dead) {
                KDASSERT(merged);
                uvm_mapent_free_merged(map, dead);
        }
        if ((flags & UVM_FLAG_QUANTUM) != 0) {
                vm_map_unlock(map);
        }
        if (new_entry != NULL) {
                uvm_mapent_free(new_entry);
        }
        return error;
}

/*
 * uvm_map_lookup_entry_bytree: lookup an entry in tree
 */

static inline bool
uvm_map_lookup_entry_bytree(struct vm_map *map, vaddr_t address,
    struct vm_map_entry **entry /* OUT */)
{
        struct vm_map_entry *prev = &map->header;
        struct vm_map_entry *cur = ROOT_ENTRY(map);

        while (cur) {
                UVMMAP_EVCNT_INCR(mlk_treeloop);
                if (address >= cur->start) {
                        if (address < cur->end) {
                                *entry = cur;
                                return true;
                        }
                        prev = cur;
                        cur = RIGHT_ENTRY(cur);
                } else
                        cur = LEFT_ENTRY(cur);
        }
        *entry = prev;
        return false;
}

/*
 * uvm_map_lookup_entry: find map entry at or before an address
 *
 * => map must at least be read-locked by caller
 * => entry is returned in "entry"
 * => return value is true if address is in the returned entry
 */

bool
uvm_map_lookup_entry(struct vm_map *map, vaddr_t address,
    struct vm_map_entry **entry /* OUT */)
{
        struct vm_map_entry *cur;
        bool use_tree = false;
        UVMHIST_FUNC("uvm_map_lookup_entry");
        UVMHIST_CALLED(maphist);

        UVMHIST_LOG(maphist,"(map=0x%x,addr=0x%x,ent=0x%x)",
            map, address, entry, 0);

        /*
         * start looking either from the head of the
         * list, or from the hint.
         */

        cur = map->hint;

        if (cur == &map->header)
                cur = cur->next;

        UVMMAP_EVCNT_INCR(mlk_call);
        if (address >= cur->start) {

                /*
                 * go from hint to end of list.
                 *
                 * but first, make a quick check to see if
                 * we are already looking at the entry we
                 * want (which is usually the case).
                 * note also that we don't need to save the hint
                 * here... it is the same hint (unless we are
                 * at the header, in which case the hint didn't
                 * buy us anything anyway).
                 */

                if (cur != &map->header && cur->end > address) {
                        UVMMAP_EVCNT_INCR(mlk_hint);
                        *entry = cur;
                        UVMHIST_LOG(maphist,"<- got it via hint (0x%x)",
                            cur, 0, 0, 0);
                        uvm_mapent_check(*entry);
                        return (true);
                }

                if (map->nentries > 15)
                        use_tree = true;
        } else {

                /*
                 * invalid hint.  use tree.
                 */
                use_tree = true;
        }

        uvm_map_check(map, __func__);

        if (use_tree) {
                /*
                 * Simple lookup in the tree.  Happens when the hint is
                 * invalid, or nentries reach a threshold.
                 */
                UVMMAP_EVCNT_INCR(mlk_tree);
                if (uvm_map_lookup_entry_bytree(map, address, entry)) {
                        goto got;
                } else {
                        goto failed;
                }
        }

        /*
         * search linearly
         */

        UVMMAP_EVCNT_INCR(mlk_list);
        while (cur != &map->header) {
                UVMMAP_EVCNT_INCR(mlk_listloop);
                if (cur->end > address) {
                        if (address >= cur->start) {
                                /*
                                 * save this lookup for future
                                 * hints, and return
                                 */

                                *entry = cur;
got:
                                SAVE_HINT(map, map->hint, *entry);
                                UVMHIST_LOG(maphist,"<- search got it (0x%x)",
                                        cur, 0, 0, 0);
                                KDASSERT((*entry)->start <= address);
                                KDASSERT(address < (*entry)->end);
                                uvm_mapent_check(*entry);
                                return (true);
                        }
                        break;
                }
                cur = cur->next;
        }
        *entry = cur->prev;
failed:
        SAVE_HINT(map, map->hint, *entry);
        UVMHIST_LOG(maphist,"<- failed!",0,0,0,0);
        KDASSERT((*entry) == &map->header || (*entry)->end <= address);
        KDASSERT((*entry)->next == &map->header ||
            address < (*entry)->next->start);
        return (false);
}

/*
 * See if the range between start and start + length fits in the gap
 * entry->next->start and entry->end.  Returns 1 if fits, 0 if doesn't
 * fit, and -1 address wraps around.
 */
static int
uvm_map_space_avail(vaddr_t *start, vsize_t length, voff_t uoffset,
    vsize_t align, int topdown, struct vm_map_entry *entry)
{
        vaddr_t end;

#ifdef PMAP_PREFER
        /*
         * push start address forward as needed to avoid VAC alias problems.
         * we only do this if a valid offset is specified.
         */

        if (uoffset != UVM_UNKNOWN_OFFSET)
                PMAP_PREFER(uoffset, start, length, topdown);
#endif
        if (align != 0) {
                if ((*start & (align - 1)) != 0) {
                        if (topdown)
                                *start &= ~(align - 1);
                        else
                                *start = roundup(*start, align);
                }
                /*
                 * XXX Should we PMAP_PREFER() here again?
                 * eh...i think we're okay
                 */
        }

        /*
         * Find the end of the proposed new region.  Be sure we didn't
         * wrap around the address; if so, we lose.  Otherwise, if the
         * proposed new region fits before the next entry, we win.
         */

        end = *start + length;
        if (end < *start)
                return (-1);

        if (entry->next->start >= end && *start >= entry->end)
                return (1);

        return (0);
}

/*
 * uvm_map_findspace: find "length" sized space in "map".
 *
 * => "hint" is a hint about where we want it, unless UVM_FLAG_FIXED is
 *      set in "flags" (in which case we insist on using "hint").
 * => "result" is VA returned
 * => uobj/uoffset are to be used to handle VAC alignment, if required
 * => if "align" is non-zero, we attempt to align to that value.
 * => caller must at least have read-locked map
 * => returns NULL on failure, or pointer to prev. map entry if success
 * => note this is a cross between the old vm_map_findspace and vm_map_find
 */

struct vm_map_entry *
uvm_map_findspace(struct vm_map *map, vaddr_t hint, vsize_t length,
    vaddr_t *result /* OUT */, struct uvm_object *uobj, voff_t uoffset,
    vsize_t align, int flags)
{
        struct vm_map_entry *entry;
        struct vm_map_entry *child, *prev, *tmp;
        vaddr_t orig_hint;
        const int topdown = map->flags & VM_MAP_TOPDOWN;
        UVMHIST_FUNC("uvm_map_findspace");
        UVMHIST_CALLED(maphist);

        UVMHIST_LOG(maphist, "(map=0x%x, hint=0x%x, len=%d, flags=0x%x)",
            map, hint, length, flags);
        KASSERT((align & (align - 1)) == 0);
        KASSERT((flags & UVM_FLAG_FIXED) == 0 || align == 0);

        uvm_map_check(map, "map_findspace entry");

        /*
         * remember the original hint.  if we are aligning, then we
         * may have to try again with no alignment constraint if
         * we fail the first time.
         */

        orig_hint = hint;
        if (hint < vm_map_min(map)) {   /* check ranges ... */
                if (flags & UVM_FLAG_FIXED) {
                        UVMHIST_LOG(maphist,"<- VA below map range",0,0,0,0);
                        return (NULL);
                }
                hint = vm_map_min(map);
        }
        if (hint > vm_map_max(map)) {
                UVMHIST_LOG(maphist,"<- VA 0x%x > range [0x%x->0x%x]",
                    hint, vm_map_min(map), vm_map_max(map), 0);
                return (NULL);
        }

        /*
         * Look for the first possible address; if there's already
         * something at this address, we have to start after it.
         */

        /*
         * @@@: there are four, no, eight cases to consider.
         *
         * 0: found,     fixed,     bottom up -> fail
         * 1: found,     fixed,     top down  -> fail
         * 2: found,     not fixed, bottom up -> start after entry->end,
         *                                       loop up
         * 3: found,     not fixed, top down  -> start before entry->start,
         *                                       loop down
         * 4: not found, fixed,     bottom up -> check entry->next->start, fail
         * 5: not found, fixed,     top down  -> check entry->next->start, fail
         * 6: not found, not fixed, bottom up -> check entry->next->start,
         *                                       loop up
         * 7: not found, not fixed, top down  -> check entry->next->start,
         *                                       loop down
         *
         * as you can see, it reduces to roughly five cases, and that
         * adding top down mapping only adds one unique case (without
         * it, there would be four cases).
         */

        if ((flags & UVM_FLAG_FIXED) == 0 && hint == vm_map_min(map)) {
                entry = map->first_free;
        } else {
                if (uvm_map_lookup_entry(map, hint, &entry)) {
                        /* "hint" address already in use ... */
                        if (flags & UVM_FLAG_FIXED) {
                                UVMHIST_LOG(maphist, "<- fixed & VA in use",
                                    0, 0, 0, 0);
                                return (NULL);
                        }
                        if (topdown)
                                /* Start from lower gap. */
                                entry = entry->prev;
                } else if (flags & UVM_FLAG_FIXED) {
                        if (entry->next->start >= hint + length &&
                            hint + length > hint)
                                goto found;

                        /* "hint" address is gap but too small */
                        UVMHIST_LOG(maphist, "<- fixed mapping failed",
                            0, 0, 0, 0);
                        return (NULL); /* only one shot at it ... */
                } else {
                        /*
                         * See if given hint fits in this gap.
                         */
                        switch (uvm_map_space_avail(&hint, length,
                            uoffset, align, topdown, entry)) {
                        case 1:
                                goto found;
                        case -1:
                                goto wraparound;
                        }

                        if (topdown) {
                                /*
                                 * Still there is a chance to fit
                                 * if hint > entry->end.
                                 */
                        } else {
                                /* Start from higher gap. */
                                entry = entry->next;
                                if (entry == &map->header)
                                        goto notfound;
                                goto nextgap;
                        }
                }
        }

        /*
         * Note that all UVM_FLAGS_FIXED case is already handled.
         */
        KDASSERT((flags & UVM_FLAG_FIXED) == 0);

        /* Try to find the space in the red-black tree */

        /* Check slot before any entry */
        hint = topdown ? entry->next->start - length : entry->end;
        switch (uvm_map_space_avail(&hint, length, uoffset, align,
            topdown, entry)) {
        case 1:
                goto found;
        case -1:
                goto wraparound;
        }

nextgap:
        KDASSERT((flags & UVM_FLAG_FIXED) == 0);
        /* If there is not enough space in the whole tree, we fail */
        tmp = ROOT_ENTRY(map);
        if (tmp == NULL || tmp->maxgap < length)
                goto notfound;

        prev = NULL; /* previous candidate */

        /* Find an entry close to hint that has enough space */
        for (; tmp;) {
                KASSERT(tmp->next->start == tmp->end + tmp->gap);
                if (topdown) {
                        if (tmp->next->start < hint + length &&
                            (prev == NULL || tmp->end > prev->end)) {
                                if (tmp->gap >= length)
                                        prev = tmp;
                                else if ((child = LEFT_ENTRY(tmp)) != NULL
                                    && child->maxgap >= length)
                                        prev = tmp;
                        }
                } else {
                        if (tmp->end >= hint &&
                            (prev == NULL || tmp->end < prev->end)) {
                                if (tmp->gap >= length)
                                        prev = tmp;
                                else if ((child = RIGHT_ENTRY(tmp)) != NULL
                                    && child->maxgap >= length)
                                        prev = tmp;
                        }
                }
                if (tmp->next->start < hint + length)
                        child = RIGHT_ENTRY(tmp);
                else if (tmp->end > hint)
                        child = LEFT_ENTRY(tmp);
                else {
                        if (tmp->gap >= length)
                                break;
                        if (topdown)
                                child = LEFT_ENTRY(tmp);
                        else
                                child = RIGHT_ENTRY(tmp);
                }
                if (child == NULL || child->maxgap < length)
                        break;
                tmp = child;
        }

        if (tmp != NULL && tmp->start < hint && hint < tmp->next->start) {
                /*
                 * Check if the entry that we found satifies the
                 * space requirement
                 */
                if (topdown) {
                        if (hint > tmp->next->start - length)
                                hint = tmp->next->start - length;
                } else {
                        if (hint < tmp->end)
                                hint = tmp->end;
                }
                switch (uvm_map_space_avail(&hint, length, uoffset, align,
                    topdown, tmp)) {
                case 1:
                        entry = tmp;
                        goto found;
                case -1:
                        goto wraparound;
                }
                if (tmp->gap >= length)
                        goto listsearch;
        }
        if (prev == NULL)
                goto notfound;

        if (topdown) {
                KASSERT(orig_hint >= prev->next->start - length ||
                    prev->next->start - length > prev->next->start);
                hint = prev->next->start - length;
        } else {
                KASSERT(orig_hint <= prev->end);
                hint = prev->end;
        }
        switch (uvm_map_space_avail(&hint, length, uoffset, align,
            topdown, prev)) {
        case 1:
                entry = prev;
                goto found;
        case -1:
                goto wraparound;
        }
        if (prev->gap >= length)
                goto listsearch;

        if (topdown)
                tmp = LEFT_ENTRY(prev);
        else
                tmp = RIGHT_ENTRY(prev);
        for (;;) {
                KASSERT(tmp && tmp->maxgap >= length);
                if (topdown)
                        child = RIGHT_ENTRY(tmp);
                else
                        child = LEFT_ENTRY(tmp);
                if (child && child->maxgap >= length) {
                        tmp = child;
                        continue;
                }
                if (tmp->gap >= length)
                        break;
                if (topdown)
                        tmp = LEFT_ENTRY(tmp);
                else
                        tmp = RIGHT_ENTRY(tmp);
        }

        if (topdown) {
                KASSERT(orig_hint >= tmp->next->start - length ||
                    tmp->next->start - length > tmp->next->start);
                hint = tmp->next->start - length;
        } else {
                KASSERT(orig_hint <= tmp->end);
                hint = tmp->end;
        }
        switch (uvm_map_space_avail(&hint, length, uoffset, align,
            topdown, tmp)) {
        case 1:
                entry = tmp;
                goto found;
        case -1:
                goto wraparound;
        }

        /*
         * The tree fails to find an entry because of offset or alignment
         * restrictions.  Search the list instead.
         */
 listsearch:
        /*
         * Look through the rest of the map, trying to fit a new region in
         * the gap between existing regions, or after the very last region.
         * note: entry->end = base VA of current gap,
         *       entry->next->start = VA of end of current gap
         */

        for (;;) {
                /* Update hint for current gap. */
                hint = topdown ? entry->next->start - length : entry->end;

                /* See if it fits. */
                switch (uvm_map_space_avail(&hint, length, uoffset, align,
                    topdown, entry)) {
                case 1:
                        goto found;
                case -1:
                        goto wraparound;
                }

                /* Advance to next/previous gap */
                if (topdown) {
                        if (entry == &map->header) {
                                UVMHIST_LOG(maphist, "<- failed (off start)",
                                    0,0,0,0);
                                goto notfound;
                        }
                        entry = entry->prev;
                } else {
                        entry = entry->next;
                        if (entry == &map->header) {
                                UVMHIST_LOG(maphist, "<- failed (off end)",
                                    0,0,0,0);
                                goto notfound;
                        }
                }
        }

 found:
        SAVE_HINT(map, map->hint, entry);
        *result = hint;
        UVMHIST_LOG(maphist,"<- got it!  (result=0x%x)", hint, 0,0,0);
        KASSERT( topdown || hint >= orig_hint);
        KASSERT(!topdown || hint <= orig_hint);
        KASSERT(entry->end <= hint);
        KASSERT(hint + length <= entry->next->start);
        return (entry);

 wraparound:
        UVMHIST_LOG(maphist, "<- failed (wrap around)", 0,0,0,0);

        return (NULL);

 notfound:
        UVMHIST_LOG(maphist, "<- failed (notfound)", 0,0,0,0);

        return (NULL);
}

/*
 *   U N M A P   -   m a i n   h e l p e r   f u n c t i o n s
 */

/*
 * uvm_unmap_remove: remove mappings from a vm_map (from "start" up to "stop")
 *
 * => caller must check alignment and size
 * => map must be locked by caller
 * => we return a list of map entries that we've remove from the map
 *    in "entry_list"
 */

void
uvm_unmap_remove(struct vm_map *map, vaddr_t start, vaddr_t end,
    struct vm_map_entry **entry_list /* OUT */,
    struct uvm_mapent_reservation *umr, int flags)
{
        struct vm_map_entry *entry, *first_entry, *next;
        vaddr_t len;
        UVMHIST_FUNC("uvm_unmap_remove"); UVMHIST_CALLED(maphist);

        UVMHIST_LOG(maphist,"(map=0x%x, start=0x%x, end=0x%x)",
            map, start, end, 0);
        VM_MAP_RANGE_CHECK(map, start, end);

        uvm_map_check(map, "unmap_remove entry");

        /*
         * find first entry
         */

        if (uvm_map_lookup_entry(map, start, &first_entry) == true) {
                /* clip and go... */
                entry = first_entry;
                UVM_MAP_CLIP_START(map, entry, start, umr);
                /* critical!  prevents stale hint */
                SAVE_HINT(map, entry, entry->prev);
        } else {
                entry = first_entry->next;
        }

        /*
         * Save the free space hint
         */

        if (map->first_free != &map->header && map->first_free->start >= start)
                map->first_free = entry->prev;

        /*
         * note: we now re-use first_entry for a different task.  we remove
         * a number of map entries from the map and save them in a linked
         * list headed by "first_entry".  once we remove them from the map
         * the caller should unlock the map and drop the references to the
         * backing objects [c.f. uvm_unmap_detach].  the object is to
         * separate unmapping from reference dropping.  why?
         *   [1] the map has to be locked for unmapping
         *   [2] the map need not be locked for reference dropping
         *   [3] dropping references may trigger pager I/O, and if we hit
         *       a pager that does synchronous I/O we may have to wait for it.
         *   [4] we would like all waiting for I/O to occur with maps unlocked
         *       so that we don't block other threads.
         */

        first_entry = NULL;
        *entry_list = NULL;

        /*
         * break up the area into map entry sized regions and unmap.  note
         * that all mappings have to be removed before we can even consider
         * dropping references to amaps or VM objects (otherwise we could end
         * up with a mapping to a page on the free list which would be very bad)
         */

        while ((entry != &map->header) && (entry->start < end)) {
                KASSERT((entry->flags & UVM_MAP_FIRST) == 0);

                UVM_MAP_CLIP_END(map, entry, end, umr);
                next = entry->next;
                len = entry->end - entry->start;

                /*
                 * unwire before removing addresses from the pmap; otherwise
                 * unwiring will put the entries back into the pmap (XXX).
                 */

                if (VM_MAPENT_ISWIRED(entry)) {
                        uvm_map_entry_unwire(map, entry);
                }
                if (flags & UVM_FLAG_VAONLY) {

                        /* nothing */

                } else if ((map->flags & VM_MAP_PAGEABLE) == 0) {

                        /*
                         * if the map is non-pageable, any pages mapped there
                         * must be wired and entered with pmap_kenter_pa(),
                         * and we should free any such pages immediately.
                         * this is mostly used for kmem_map and mb_map.
                         */

                        if ((entry->flags & UVM_MAP_KMAPENT) == 0) {
                                uvm_km_pgremove_intrsafe(map, entry->start,
                                    entry->end);
                                pmap_kremove(entry->start, len);
                        }
                } else if (UVM_ET_ISOBJ(entry) &&
                           UVM_OBJ_IS_KERN_OBJECT(entry->object.uvm_obj)) {
                        KASSERT(vm_map_pmap(map) == pmap_kernel());

                        /*
                         * note: kernel object mappings are currently used in
                         * two ways:
                         *  [1] "normal" mappings of pages in the kernel object
                         *  [2] uvm_km_valloc'd allocations in which we
                         *      pmap_enter in some non-kernel-object page
                         *      (e.g. vmapbuf).
                         *
                         * for case [1], we need to remove the mapping from
                         * the pmap and then remove the page from the kernel
                         * object (because, once pages in a kernel object are
                         * unmapped they are no longer needed, unlike, say,
                         * a vnode where you might want the data to persist
                         * until flushed out of a queue).
                         *
                         * for case [2], we need to remove the mapping from
                         * the pmap.  there shouldn't be any pages at the
                         * specified offset in the kernel object [but it
                         * doesn't hurt to call uvm_km_pgremove just to be
                         * safe?]
                         *
                         * uvm_km_pgremove currently does the following:
                         *   for pages in the kernel object in range:
                         *     - drops the swap slot
                         *     - uvm_pagefree the page
                         */

                        /*
                         * remove mappings from pmap and drop the pages
                         * from the object.  offsets are always relative
                         * to vm_map_min(kernel_map).
                         */

                        pmap_remove(pmap_kernel(), entry->start,
                            entry->start + len);
                        uvm_km_pgremove(entry->start, entry->end);

                        /*
                         * null out kernel_object reference, we've just
                         * dropped it
                         */

                        entry->etype &= ~UVM_ET_OBJ;
                        entry->object.uvm_obj = NULL;
                } else if (UVM_ET_ISOBJ(entry) || entry->aref.ar_amap) {

                        /*
                         * remove mappings the standard way.
                         */

                        pmap_remove(map->pmap, entry->start, entry->end);
                }

#if defined(DEBUG)
                if ((entry->flags & UVM_MAP_KMAPENT) == 0) {

                        /*
                         * check if there's remaining mapping,
                         * which is a bug in caller.
                         */

                        vaddr_t va;
                        for (va = entry->start; va < entry->end;
                            va += PAGE_SIZE) {
                                if (pmap_extract(vm_map_pmap(map), va, NULL)) {
                                        panic("uvm_unmap_remove: has mapping");
                                }
                        }

                        if (VM_MAP_IS_KERNEL(map)) {
                                uvm_km_check_empty(map, entry->start,
                                    entry->end);
                        }
                }
#endif /* defined(DEBUG) */

                /*
                 * remove entry from map and put it on our list of entries
                 * that we've nuked.  then go to next entry.
                 */

                UVMHIST_LOG(maphist, "  removed map entry 0x%x", entry, 0, 0,0);

                /* critical!  prevents stale hint */
                SAVE_HINT(map, entry, entry->prev);

                uvm_map_entry_unlink(map, entry);
                KASSERT(map->size >= len);
                map->size -= len;
                entry->prev = NULL;
                entry->next = first_entry;
                first_entry = entry;
                entry = next;
        }
        if ((map->flags & VM_MAP_DYING) == 0) {
                pmap_update(vm_map_pmap(map));
        }

        uvm_map_check(map, "unmap_remove leave");

        /*
         * now we've cleaned up the map and are ready for the caller to drop
         * references to the mapped objects.
         */

        *entry_list = first_entry;
        UVMHIST_LOG(maphist,"<- done!", 0, 0, 0, 0);

        if (map->flags & VM_MAP_WANTVA) {
                mutex_enter(&map->misc_lock);
                map->flags &= ~VM_MAP_WANTVA;
                cv_broadcast(&map->cv);
                mutex_exit(&map->misc_lock);
        }
}

/*
 * uvm_unmap_detach: drop references in a chain of map entries
 *
 * => we will free the map entries as we traverse the list.
 */

void
uvm_unmap_detach(struct vm_map_entry *first_entry, int flags)
{
        struct vm_map_entry *next_entry;
        UVMHIST_FUNC("uvm_unmap_detach"); UVMHIST_CALLED(maphist);

        while (first_entry) {
                KASSERT(!VM_MAPENT_ISWIRED(first_entry));
                UVMHIST_LOG(maphist,
                    "  detach 0x%x: amap=0x%x, obj=0x%x, submap?=%d",
                    first_entry, first_entry->aref.ar_amap,
                    first_entry->object.uvm_obj,
                    UVM_ET_ISSUBMAP(first_entry));

                /*
                 * drop reference to amap, if we've got one
                 */

                if (first_entry->aref.ar_amap)
                        uvm_map_unreference_amap(first_entry, flags);

                /*
                 * drop reference to our backing object, if we've got one
                 */

                KASSERT(!UVM_ET_ISSUBMAP(first_entry));
                if (UVM_ET_ISOBJ(first_entry) &&
                    first_entry->object.uvm_obj->pgops->pgo_detach) {
                        (*first_entry->object.uvm_obj->pgops->pgo_detach)
                                (first_entry->object.uvm_obj);
                }
                next_entry = first_entry->next;
                uvm_mapent_free(first_entry);
                first_entry = next_entry;
        }
        UVMHIST_LOG(maphist, "<- done", 0,0,0,0);
}

/*
 *   E X T R A C T I O N   F U N C T I O N S
 */

/*
 * uvm_map_reserve: reserve space in a vm_map for future use.
 *
 * => we reserve space in a map by putting a dummy map entry in the
 *    map (dummy means obj=NULL, amap=NULL, prot=VM_PROT_NONE)
 * => map should be unlocked (we will write lock it)
 * => we return true if we were able to reserve space
 * => XXXCDC: should be inline?
 */

int
uvm_map_reserve(struct vm_map *map, vsize_t size,
    vaddr_t offset      /* hint for pmap_prefer */,
    vsize_t align       /* alignment */,
    vaddr_t *raddr      /* IN:hint, OUT: reserved VA */,
    uvm_flag_t flags    /* UVM_FLAG_FIXED or 0 */)
{
        UVMHIST_FUNC("uvm_map_reserve"); UVMHIST_CALLED(maphist);

        UVMHIST_LOG(maphist, "(map=0x%x, size=0x%x, offset=0x%x,addr=0x%x)",
            map,size,offset,raddr);

        size = round_page(size);

        /*
         * reserve some virtual space.
         */

        if (uvm_map(map, raddr, size, NULL, offset, align,
            UVM_MAPFLAG(UVM_PROT_NONE, UVM_PROT_NONE, UVM_INH_NONE,
            UVM_ADV_RANDOM, UVM_FLAG_NOMERGE|flags)) != 0) {
            UVMHIST_LOG(maphist, "<- done (no VM)", 0,0,0,0);
                return (false);
        }

        UVMHIST_LOG(maphist, "<- done (*raddr=0x%x)", *raddr,0,0,0);
        return (true);
}

/*
 * uvm_map_replace: replace a reserved (blank) area of memory with
 * real mappings.
 *
 * => caller must WRITE-LOCK the map
 * => we return true if replacement was a success
 * => we expect the newents chain to have nnewents entrys on it and
 *    we expect newents->prev to point to the last entry on the list
 * => note newents is allowed to be NULL
 */

static int
uvm_map_replace(struct vm_map *map, vaddr_t start, vaddr_t end,
    struct vm_map_entry *newents, int nnewents, vsize_t nsize,
    struct vm_map_entry **oldentryp)
{
        struct vm_map_entry *oldent, *last;

        uvm_map_check(map, "map_replace entry");

        /*
         * first find the blank map entry at the specified address
         */

        if (!uvm_map_lookup_entry(map, start, &oldent)) {
                return (false);
        }

        /*
         * check to make sure we have a proper blank entry
         */

        if (end < oldent->end && !VM_MAP_USE_KMAPENT(map)) {
                UVM_MAP_CLIP_END(map, oldent, end, NULL);
        }
        if (oldent->start != start || oldent->end != end ||
            oldent->object.uvm_obj != NULL || oldent->aref.ar_amap != NULL) {
                return (false);
        }

#ifdef DIAGNOSTIC

        /*
         * sanity check the newents chain
         */

        {
                struct vm_map_entry *tmpent = newents;
                int nent = 0;
                vsize_t sz = 0;
                vaddr_t cur = start;

                while (tmpent) {
                        nent++;
                        sz += tmpent->end - tmpent->start;
                        if (tmpent->start < cur)
                                panic("uvm_map_replace1");
                        if (tmpent->start >= tmpent->end || tmpent->end > end) {
                                panic("uvm_map_replace2: "
                                    "tmpent->start=0x%"PRIxVADDR
                                    ", tmpent->end=0x%"PRIxVADDR
                                    ", end=0x%"PRIxVADDR,
                                    tmpent->start, tmpent->end, end);
                        }
                        cur = tmpent->end;
                        if (tmpent->next) {
                                if (tmpent->next->prev != tmpent)
                                        panic("uvm_map_replace3");
                        } else {
                                if (newents->prev != tmpent)
                                        panic("uvm_map_replace4");
                        }
                        tmpent = tmpent->next;
                }
                if (nent != nnewents)
                        panic("uvm_map_replace5");
                if (sz != nsize)
                        panic("uvm_map_replace6");
        }
#endif

        /*
         * map entry is a valid blank!   replace it.   (this does all the
         * work of map entry link/unlink...).
         */

        if (newents) {
                last = newents->prev;

                /* critical: flush stale hints out of map */
                SAVE_HINT(map, map->hint, newents);
                if (map->first_free == oldent)
                        map->first_free = last;

                last->next = oldent->next;
                last->next->prev = last;

                /* Fix RB tree */
                uvm_rb_remove(map, oldent);

                newents->prev = oldent->prev;
                newents->prev->next = newents;
                map->nentries = map->nentries + (nnewents - 1);

                /* Fixup the RB tree */
                {
                        int i;
                        struct vm_map_entry *tmp;

                        tmp = newents;
                        for (i = 0; i < nnewents && tmp; i++) {
                                uvm_rb_insert(map, tmp);
                                tmp = tmp->next;
                        }
                }
        } else {
                /* NULL list of new entries: just remove the old one */
                clear_hints(map, oldent);
                uvm_map_entry_unlink(map, oldent);
        }
        map->size -= end - start - nsize;

        uvm_map_check(map, "map_replace leave");

        /*
         * now we can free the old blank entry and return.
         */

        *oldentryp = oldent;
        return (true);
}

/*
 * uvm_map_extract: extract a mapping from a map and put it somewhere
 *      (maybe removing the old mapping)
 *
 * => maps should be unlocked (we will write lock them)
 * => returns 0 on success, error code otherwise
 * => start must be page aligned
 * => len must be page sized
 * => flags:
 *      UVM_EXTRACT_REMOVE: remove mappings from srcmap
 *      UVM_EXTRACT_CONTIG: abort if unmapped area (advisory only)
 *      UVM_EXTRACT_QREF: for a temporary extraction do quick obj refs
 *      UVM_EXTRACT_FIXPROT: set prot to maxprot as we go
 *    >>>NOTE: if you set REMOVE, you are not allowed to use CONTIG or QREF!<<<
 *    >>>NOTE: QREF's must be unmapped via the QREF path, thus should only
 *             be used from within the kernel in a kernel level map <<<
 */

int
uvm_map_extract(struct vm_map *srcmap, vaddr_t start, vsize_t len,
    struct vm_map *dstmap, vaddr_t *dstaddrp, int flags)
{
        vaddr_t dstaddr, end, newend, oldoffset, fudge, orig_fudge;
        struct vm_map_entry *chain, *endchain, *entry, *orig_entry, *newentry,
            *deadentry, *oldentry;
        struct vm_map_entry *resentry = NULL; /* a dummy reservation entry */
        vsize_t elen;
        int nchain, error, copy_ok;
        vsize_t nsize;
        UVMHIST_FUNC("uvm_map_extract"); UVMHIST_CALLED(maphist);

        UVMHIST_LOG(maphist,"(srcmap=0x%x,start=0x%x, len=0x%x", srcmap, start,
            len,0);
        UVMHIST_LOG(maphist," ...,dstmap=0x%x, flags=0x%x)", dstmap,flags,0,0);

        /*
         * step 0: sanity check: start must be on a page boundary, length
         * must be page sized.  can't ask for CONTIG/QREF if you asked for
         * REMOVE.
         */

        KASSERT((start & PAGE_MASK) == 0 && (len & PAGE_MASK) == 0);
        KASSERT((flags & UVM_EXTRACT_REMOVE) == 0 ||
                (flags & (UVM_EXTRACT_CONTIG|UVM_EXTRACT_QREF)) == 0);

        /*
         * step 1: reserve space in the target map for the extracted area
         */

        if ((flags & UVM_EXTRACT_RESERVED) == 0) {
                dstaddr = vm_map_min(dstmap);
                if (!uvm_map_reserve(dstmap, len, start, 0, &dstaddr, 0))
                        return (ENOMEM);
                *dstaddrp = dstaddr;    /* pass address back to caller */
                UVMHIST_LOG(maphist, "  dstaddr=0x%x", dstaddr,0,0,0);
        } else {
                dstaddr = *dstaddrp;
        }

        /*
         * step 2: setup for the extraction process loop by init'ing the
         * map entry chain, locking src map, and looking up the first useful
         * entry in the map.
         */

        end = start + len;
        newend = dstaddr + len;
        chain = endchain = NULL;
        nchain = 0;
        nsize = 0;
        vm_map_lock(srcmap);

        if (uvm_map_lookup_entry(srcmap, start, &entry)) {

                /* "start" is within an entry */
                if (flags & UVM_EXTRACT_QREF) {

                        /*
                         * for quick references we don't clip the entry, so
                         * the entry may map space "before" the starting
                         * virtual address... this is the "fudge" factor
                         * (which can be non-zero only the first time
                         * through the "while" loop in step 3).
                         */

                        fudge = start - entry->start;
                } else {

                        /*
                         * normal reference: we clip the map to fit (thus
                         * fudge is zero)
                         */

                        UVM_MAP_CLIP_START(srcmap, entry, start, NULL);
                        SAVE_HINT(srcmap, srcmap->hint, entry->prev);
                        fudge = 0;
                }
        } else {

                /* "start" is not within an entry ... skip to next entry */
                if (flags & UVM_EXTRACT_CONTIG) {
                        error = EINVAL;
                        goto bad;    /* definite hole here ... */
                }

                entry = entry->next;
                fudge = 0;
        }

        /* save values from srcmap for step 6 */
        orig_entry = entry;
        orig_fudge = fudge;

        /*
         * step 3: now start looping through the map entries, extracting
         * as we go.
         */

        while (entry->start < end && entry != &srcmap->header) {

                /* if we are not doing a quick reference, clip it */
                if ((flags & UVM_EXTRACT_QREF) == 0)
                        UVM_MAP_CLIP_END(srcmap, entry, end, NULL);

                /* clear needs_copy (allow chunking) */
                if (UVM_ET_ISNEEDSCOPY(entry)) {
                        amap_copy(srcmap, entry,
                            AMAP_COPY_NOWAIT|AMAP_COPY_NOMERGE, start, end);
                        if (UVM_ET_ISNEEDSCOPY(entry)) {  /* failed? */
                                error = ENOMEM;
                                goto bad;
                        }

                        /* amap_copy could clip (during chunk)!  update fudge */
                        if (fudge) {
                                fudge = start - entry->start;
                                orig_fudge = fudge;
                        }
                }

                /* calculate the offset of this from "start" */
                oldoffset = (entry->start + fudge) - start;

                /* allocate a new map entry */
                newentry = uvm_mapent_alloc(dstmap, 0);
                if (newentry == NULL) {
                        error = ENOMEM;
                        goto bad;
                }

                /* set up new map entry */
                newentry->next = NULL;
                newentry->prev = endchain;
                newentry->start = dstaddr + oldoffset;
                newentry->end =
                    newentry->start + (entry->end - (entry->start + fudge));
                if (newentry->end > newend || newentry->end < newentry->start)
                        newentry->end = newend;
                newentry->object.uvm_obj = entry->object.uvm_obj;
                if (newentry->object.uvm_obj) {
                        if (newentry->object.uvm_obj->pgops->pgo_reference)
                                newentry->object.uvm_obj->pgops->
                                    pgo_reference(newentry->object.uvm_obj);
                                newentry->offset = entry->offset + fudge;
                } else {
                        newentry->offset = 0;
                }
                newentry->etype = entry->etype;
                newentry->protection = (flags & UVM_EXTRACT_FIXPROT) ?
                        entry->max_protection : entry->protection;
                newentry->max_protection = entry->max_protection;
                newentry->inheritance = entry->inheritance;
                newentry->wired_count = 0;
                newentry->aref.ar_amap = entry->aref.ar_amap;
                if (newentry->aref.ar_amap) {
                        newentry->aref.ar_pageoff =
                            entry->aref.ar_pageoff + (fudge >> PAGE_SHIFT);
                        uvm_map_reference_amap(newentry, AMAP_SHARED |
                            ((flags & UVM_EXTRACT_QREF) ? AMAP_REFALL : 0));
                } else {
                        newentry->aref.ar_pageoff = 0;
                }
                newentry->advice = entry->advice;
                if ((flags & UVM_EXTRACT_QREF) != 0) {
                        newentry->flags |= UVM_MAP_NOMERGE;
                }

                /* now link it on the chain */
                nchain++;
                nsize += newentry->end - newentry->start;
                if (endchain == NULL) {
                        chain = endchain = newentry;
                } else {
                        endchain->next = newentry;
                        endchain = newentry;
                }

                /* end of 'while' loop! */
                if ((flags & UVM_EXTRACT_CONTIG) && entry->end < end &&
                    (entry->next == &srcmap->header ||
                    entry->next->start != entry->end)) {
                        error = EINVAL;
                        goto bad;
                }
                entry = entry->next;
                fudge = 0;
        }

        /*
         * step 4: close off chain (in format expected by uvm_map_replace)
         */

        if (chain)
                chain->prev = endchain;

        /*
         * step 5: attempt to lock the dest map so we can pmap_copy.
         * note usage of copy_ok:
         *   1 => dstmap locked, pmap_copy ok, and we "replace" here (step 5)
         *   0 => dstmap unlocked, NO pmap_copy, and we will "replace" in step 7
         */

        if (srcmap == dstmap || vm_map_lock_try(dstmap) == true) {
                copy_ok = 1;
                if (!uvm_map_replace(dstmap, dstaddr, dstaddr+len, chain,
                    nchain, nsize, &resentry)) {
                        if (srcmap != dstmap)
                                vm_map_unlock(dstmap);
                        error = EIO;
                        goto bad;
                }
        } else {
                copy_ok = 0;
                /* replace defered until step 7 */
        }

        /*
         * step 6: traverse the srcmap a second time to do the following:
         *  - if we got a lock on the dstmap do pmap_copy
         *  - if UVM_EXTRACT_REMOVE remove the entries
         * we make use of orig_entry and orig_fudge (saved in step 2)
         */

        if (copy_ok || (flags & UVM_EXTRACT_REMOVE)) {

                /* purge possible stale hints from srcmap */
                if (flags & UVM_EXTRACT_REMOVE) {
                        SAVE_HINT(srcmap, srcmap->hint, orig_entry->prev);
                        if (srcmap->first_free != &srcmap->header &&
                            srcmap->first_free->start >= start)
                                srcmap->first_free = orig_entry->prev;
                }

                entry = orig_entry;
                fudge = orig_fudge;
                deadentry = NULL;       /* for UVM_EXTRACT_REMOVE */

                while (entry->start < end && entry != &srcmap->header) {
                        if (copy_ok) {
                                oldoffset = (entry->start + fudge) - start;
                                elen = MIN(end, entry->end) -
                                    (entry->start + fudge);
                                pmap_copy(dstmap->pmap, srcmap->pmap,
                                    dstaddr + oldoffset, elen,
                                    entry->start + fudge);
                        }

                        /* we advance "entry" in the following if statement */
                        if (flags & UVM_EXTRACT_REMOVE) {
                                pmap_remove(srcmap->pmap, entry->start,
                                                entry->end);
                                oldentry = entry;       /* save entry */
                                entry = entry->next;    /* advance */
                                uvm_map_entry_unlink(srcmap, oldentry);
                                                        /* add to dead list */
                                oldentry->next = deadentry;
                                deadentry = oldentry;
                        } else {
                                entry = entry->next;            /* advance */
                        }

                        /* end of 'while' loop */
                        fudge = 0;
                }
                pmap_update(srcmap->pmap);

                /*
                 * unlock dstmap.  we will dispose of deadentry in
                 * step 7 if needed
                 */

                if (copy_ok && srcmap != dstmap)
                        vm_map_unlock(dstmap);

        } else {
                deadentry = NULL;
        }

        /*
         * step 7: we are done with the source map, unlock.   if copy_ok
         * is 0 then we have not replaced the dummy mapping in dstmap yet
         * and we need to do so now.
         */

        vm_map_unlock(srcmap);
        if ((flags & UVM_EXTRACT_REMOVE) && deadentry)
                uvm_unmap_detach(deadentry, 0);   /* dispose of old entries */

        /* now do the replacement if we didn't do it in step 5 */
        if (copy_ok == 0) {
                vm_map_lock(dstmap);
                error = uvm_map_replace(dstmap, dstaddr, dstaddr+len, chain,
                    nchain, nsize, &resentry);
                vm_map_unlock(dstmap);

                if (error == false) {
                        error = EIO;
                        goto bad2;
                }
        }

        if (resentry != NULL)
                uvm_mapent_free(resentry);

        return (0);

        /*
         * bad: failure recovery
         */
bad:
        vm_map_unlock(srcmap);
bad2:                   /* src already unlocked */
        if (chain)
                uvm_unmap_detach(chain,
                    (flags & UVM_EXTRACT_QREF) ? AMAP_REFALL : 0);

        if (resentry != NULL)
                uvm_mapent_free(resentry);

        if ((flags & UVM_EXTRACT_RESERVED) == 0) {
                uvm_unmap(dstmap, dstaddr, dstaddr+len);   /* ??? */
        }
        return (error);
}

/* end of extraction functions */

/*
 * uvm_map_submap: punch down part of a map into a submap
 *
 * => only the kernel_map is allowed to be submapped
 * => the purpose of submapping is to break up the locking granularity
 *      of a larger map
 * => the range specified must have been mapped previously with a uvm_map()
 *      call [with uobj==NULL] to create a blank map entry in the main map.
 *      [And it had better still be blank!]
 * => maps which contain submaps should never be copied or forked.
 * => to remove a submap, use uvm_unmap() on the main map
 *      and then uvm_map_deallocate() the submap.
 * => main map must be unlocked.
 * => submap must have been init'd and have a zero reference count.
 *      [need not be locked as we don't actually reference it]
 */

int
uvm_map_submap(struct vm_map *map, vaddr_t start, vaddr_t end,
    struct vm_map *submap)
{
        struct vm_map_entry *entry;
        struct uvm_mapent_reservation umr;
        int error;

        uvm_mapent_reserve(map, &umr, 2, 0);

        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);

        if (uvm_map_lookup_entry(map, start, &entry)) {
                UVM_MAP_CLIP_START(map, entry, start, &umr);
                UVM_MAP_CLIP_END(map, entry, end, &umr);        /* to be safe */
        } else {
                entry = NULL;
        }

        if (entry != NULL &&
            entry->start == start && entry->end == end &&
            entry->object.uvm_obj == NULL && entry->aref.ar_amap == NULL &&
            !UVM_ET_ISCOPYONWRITE(entry) && !UVM_ET_ISNEEDSCOPY(entry)) {
                entry->etype |= UVM_ET_SUBMAP;
                entry->object.sub_map = submap;
                entry->offset = 0;
                uvm_map_reference(submap);
                error = 0;
        } else {
                error = EINVAL;
        }
        vm_map_unlock(map);

        uvm_mapent_unreserve(map, &umr);

        return error;
}

/*
 * uvm_map_setup_kernel: init in-kernel map
 *
 * => map must not be in service yet.
 */

void
uvm_map_setup_kernel(struct vm_map_kernel *map,
    vaddr_t vmin, vaddr_t vmax, int flags)
{

        uvm_map_setup(&map->vmk_map, vmin, vmax, flags);
        callback_head_init(&map->vmk_reclaim_callback, IPL_VM);
        LIST_INIT(&map->vmk_kentry_free);
        map->vmk_merged_entries = NULL;
}


/*
 * uvm_map_protect: change map protection
 *
 * => set_max means set max_protection.
 * => map must be unlocked.
 */

#define MASK(entry)     (UVM_ET_ISCOPYONWRITE(entry) ? \
                         ~VM_PROT_WRITE : VM_PROT_ALL)

int
uvm_map_protect(struct vm_map *map, vaddr_t start, vaddr_t end,
    vm_prot_t new_prot, bool set_max)
{
        struct vm_map_entry *current, *entry;
        int error = 0;
        UVMHIST_FUNC("uvm_map_protect"); UVMHIST_CALLED(maphist);
        UVMHIST_LOG(maphist,"(map=0x%x,start=0x%x,end=0x%x,new_prot=0x%x)",
                    map, start, end, new_prot);

        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (uvm_map_lookup_entry(map, start, &entry)) {
                UVM_MAP_CLIP_START(map, entry, start, NULL);
        } else {
                entry = entry->next;
        }

        /*
         * make a first pass to check for protection violations.
         */

        current = entry;
        while ((current != &map->header) && (current->start < end)) {
                if (UVM_ET_ISSUBMAP(current)) {
                        error = EINVAL;
                        goto out;
                }
                if ((new_prot & current->max_protection) != new_prot) {
                        error = EACCES;
                        goto out;
                }
                /*
                 * Don't allow VM_PROT_EXECUTE to be set on entries that
                 * point to vnodes that are associated with a NOEXEC file
                 * system.
                 */
                if (UVM_ET_ISOBJ(current) &&
                    UVM_OBJ_IS_VNODE(current->object.uvm_obj)) {
                        struct vnode *vp =
                            (struct vnode *) current->object.uvm_obj;

                        if ((new_prot & VM_PROT_EXECUTE) != 0 &&
                            (vp->v_mount->mnt_flag & MNT_NOEXEC) != 0) {
                                error = EACCES;
                                goto out;
                        }
                }

                current = current->next;
        }

        /* go back and fix up protections (no need to clip this time). */

        current = entry;
        while ((current != &map->header) && (current->start < end)) {
                vm_prot_t old_prot;

                UVM_MAP_CLIP_END(map, current, end, NULL);
                old_prot = current->protection;
                if (set_max)
                        current->protection =
                            (current->max_protection = new_prot) & old_prot;
                else
                        current->protection = new_prot;

                /*
                 * update physical map if necessary.  worry about copy-on-write
                 * here -- CHECK THIS XXX
                 */

                if (current->protection != old_prot) {
                        /* update pmap! */
                        pmap_protect(map->pmap, current->start, current->end,
                            current->protection & MASK(entry));

                        /*
                         * If this entry points at a vnode, and the
                         * protection includes VM_PROT_EXECUTE, mark
                         * the vnode as VEXECMAP.
                         */
                        if (UVM_ET_ISOBJ(current)) {
                                struct uvm_object *uobj =
                                    current->object.uvm_obj;

                                if (UVM_OBJ_IS_VNODE(uobj) &&
                                    (current->protection & VM_PROT_EXECUTE)) {
                                        vn_markexec((struct vnode *) uobj);
                                }
                        }
                }

                /*
                 * If the map is configured to lock any future mappings,
                 * wire this entry now if the old protection was VM_PROT_NONE
                 * and the new protection is not VM_PROT_NONE.
                 */

                if ((map->flags & VM_MAP_WIREFUTURE) != 0 &&
                    VM_MAPENT_ISWIRED(entry) == 0 &&
                    old_prot == VM_PROT_NONE &&
                    new_prot != VM_PROT_NONE) {
                        if (uvm_map_pageable(map, entry->start,
                            entry->end, false,
                            UVM_LK_ENTER|UVM_LK_EXIT) != 0) {

                                /*
                                 * If locking the entry fails, remember the
                                 * error if it's the first one.  Note we
                                 * still continue setting the protection in
                                 * the map, but will return the error
                                 * condition regardless.
                                 *
                                 * XXX Ignore what the actual error is,
                                 * XXX just call it a resource shortage
                                 * XXX so that it doesn't get confused
                                 * XXX what uvm_map_protect() itself would
                                 * XXX normally return.
                                 */

                                error = ENOMEM;
                        }
                }
                current = current->next;
        }
        pmap_update(map->pmap);

 out:
        vm_map_unlock(map);

        UVMHIST_LOG(maphist, "<- done, error=%d",error,0,0,0);
        return error;
}

#undef  MASK

/*
 * uvm_map_inherit: set inheritance code for range of addrs in map.
 *
 * => map must be unlocked
 * => note that the inherit code is used during a "fork".  see fork
 *      code for details.
 */

int
uvm_map_inherit(struct vm_map *map, vaddr_t start, vaddr_t end,
    vm_inherit_t new_inheritance)
{
        struct vm_map_entry *entry, *temp_entry;
        UVMHIST_FUNC("uvm_map_inherit"); UVMHIST_CALLED(maphist);
        UVMHIST_LOG(maphist,"(map=0x%x,start=0x%x,end=0x%x,new_inh=0x%x)",
            map, start, end, new_inheritance);

        switch (new_inheritance) {
        case MAP_INHERIT_NONE:
        case MAP_INHERIT_COPY:
        case MAP_INHERIT_SHARE:
                break;
        default:
                UVMHIST_LOG(maphist,"<- done (INVALID ARG)",0,0,0,0);
                return EINVAL;
        }

        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (uvm_map_lookup_entry(map, start, &temp_entry)) {
                entry = temp_entry;
                UVM_MAP_CLIP_START(map, entry, start, NULL);
        }  else {
                entry = temp_entry->next;
        }
        while ((entry != &map->header) && (entry->start < end)) {
                UVM_MAP_CLIP_END(map, entry, end, NULL);
                entry->inheritance = new_inheritance;
                entry = entry->next;
        }
        vm_map_unlock(map);
        UVMHIST_LOG(maphist,"<- done (OK)",0,0,0,0);
        return 0;
}

/*
 * uvm_map_advice: set advice code for range of addrs in map.
 *
 * => map must be unlocked
 */

int
uvm_map_advice(struct vm_map *map, vaddr_t start, vaddr_t end, int new_advice)
{
        struct vm_map_entry *entry, *temp_entry;
        UVMHIST_FUNC("uvm_map_advice"); UVMHIST_CALLED(maphist);
        UVMHIST_LOG(maphist,"(map=0x%x,start=0x%x,end=0x%x,new_adv=0x%x)",
            map, start, end, new_advice);

        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (uvm_map_lookup_entry(map, start, &temp_entry)) {
                entry = temp_entry;
                UVM_MAP_CLIP_START(map, entry, start, NULL);
        } else {
                entry = temp_entry->next;
        }

        /*
         * XXXJRT: disallow holes?
         */

        while ((entry != &map->header) && (entry->start < end)) {
                UVM_MAP_CLIP_END(map, entry, end, NULL);

                switch (new_advice) {
                case MADV_NORMAL:
                case MADV_RANDOM:
                case MADV_SEQUENTIAL:
                        /* nothing special here */
                        break;

                default:
                        vm_map_unlock(map);
                        UVMHIST_LOG(maphist,"<- done (INVALID ARG)",0,0,0,0);
                        return EINVAL;
                }
                entry->advice = new_advice;
                entry = entry->next;
        }

        vm_map_unlock(map);
        UVMHIST_LOG(maphist,"<- done (OK)",0,0,0,0);
        return 0;
}

/*
 * uvm_map_willneed: apply MADV_WILLNEED
 */

int
uvm_map_willneed(struct vm_map *map, vaddr_t start, vaddr_t end)
{
        struct vm_map_entry *entry;
        UVMHIST_FUNC("uvm_map_willneed"); UVMHIST_CALLED(maphist);
        UVMHIST_LOG(maphist,"(map=0x%lx,start=0x%lx,end=0x%lx)",
            map, start, end, 0);

        vm_map_lock_read(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (!uvm_map_lookup_entry(map, start, &entry)) {
                entry = entry->next;
        }
        while (entry->start < end) {
                struct vm_amap * const amap = entry->aref.ar_amap;
                struct uvm_object * const uobj = entry->object.uvm_obj;

                KASSERT(entry != &map->header);
                KASSERT(start < entry->end);
                /*
                 * XXX IMPLEMENT ME.
                 * Should invent a "weak" mode for uvm_fault()
                 * which would only do the PGO_LOCKED pgo_get().
                 *
                 * for now, we handle only the easy but common case.
                 */
                if (UVM_ET_ISOBJ(entry) && amap == NULL && uobj != NULL) {
                        off_t offset;
                        off_t size;

                        offset = entry->offset;
                        if (start < entry->start) {
                                offset += entry->start - start;
                        }
                        size = entry->offset + (entry->end - entry->start);
                        if (entry->end < end) {
                                size -= end - entry->end;
                        }
                        uvm_readahead(uobj, offset, size);
                }
                entry = entry->next;
        }
        vm_map_unlock_read(map);
        UVMHIST_LOG(maphist,"<- done (OK)",0,0,0,0);
        return 0;
}

/*
 * uvm_map_pageable: sets the pageability of a range in a map.
 *
 * => wires map entries.  should not be used for transient page locking.
 *      for that, use uvm_fault_wire()/uvm_fault_unwire() (see uvm_vslock()).
 * => regions specified as not pageable require lock-down (wired) memory
 *      and page tables.
 * => map must never be read-locked
 * => if islocked is true, map is already write-locked
 * => we always unlock the map, since we must downgrade to a read-lock
 *      to call uvm_fault_wire()
 * => XXXCDC: check this and try and clean it up.
 */

int
uvm_map_pageable(struct vm_map *map, vaddr_t start, vaddr_t end,
    bool new_pageable, int lockflags)
{
        struct vm_map_entry *entry, *start_entry, *failed_entry;
        int rv;
#ifdef DIAGNOSTIC
        u_int timestamp_save;
#endif
        UVMHIST_FUNC("uvm_map_pageable"); UVMHIST_CALLED(maphist);
        UVMHIST_LOG(maphist,"(map=0x%x,start=0x%x,end=0x%x,new_pageable=0x%x)",
                    map, start, end, new_pageable);
        KASSERT(map->flags & VM_MAP_PAGEABLE);

        if ((lockflags & UVM_LK_ENTER) == 0)
                vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);

        /*
         * only one pageability change may take place at one time, since
         * uvm_fault_wire assumes it will be called only once for each
         * wiring/unwiring.  therefore, we have to make sure we're actually
         * changing the pageability for the entire region.  we do so before
         * making any changes.
         */

        if (uvm_map_lookup_entry(map, start, &start_entry) == false) {
                if ((lockflags & UVM_LK_EXIT) == 0)
                        vm_map_unlock(map);

                UVMHIST_LOG(maphist,"<- done (fault)",0,0,0,0);
                return EFAULT;
        }
        entry = start_entry;

        /*
         * handle wiring and unwiring separately.
         */

        if (new_pageable) {             /* unwire */
                UVM_MAP_CLIP_START(map, entry, start, NULL);

                /*
                 * unwiring.  first ensure that the range to be unwired is
                 * really wired down and that there are no holes.
                 */

                while ((entry != &map->header) && (entry->start < end)) {
                        if (entry->wired_count == 0 ||
                            (entry->end < end &&
                             (entry->next == &map->header ||
                              entry->next->start > entry->end))) {
                                if ((lockflags & UVM_LK_EXIT) == 0)
                                        vm_map_unlock(map);
                                UVMHIST_LOG(maphist, "<- done (INVAL)",0,0,0,0);
                                return EINVAL;
                        }
                        entry = entry->next;
                }

                /*
                 * POSIX 1003.1b - a single munlock call unlocks a region,
                 * regardless of the number of mlock calls made on that
                 * region.
                 */

                entry = start_entry;
                while ((entry != &map->header) && (entry->start < end)) {
                        UVM_MAP_CLIP_END(map, entry, end, NULL);
                        if (VM_MAPENT_ISWIRED(entry))
                                uvm_map_entry_unwire(map, entry);
                        entry = entry->next;
                }
                if ((lockflags & UVM_LK_EXIT) == 0)
                        vm_map_unlock(map);
                UVMHIST_LOG(maphist,"<- done (OK UNWIRE)",0,0,0,0);
                return 0;
        }

        /*
         * wire case: in two passes [XXXCDC: ugly block of code here]
         *
         * 1: holding the write lock, we create any anonymous maps that need
         *    to be created.  then we clip each map entry to the region to
         *    be wired and increment its wiring count.
         *
         * 2: we downgrade to a read lock, and call uvm_fault_wire to fault
         *    in the pages for any newly wired area (wired_count == 1).
         *
         *    downgrading to a read lock for uvm_fault_wire avoids a possible
         *    deadlock with another thread that may have faulted on one of
         *    the pages to be wired (it would mark the page busy, blocking
         *    us, then in turn block on the map lock that we hold).  because
         *    of problems in the recursive lock package, we cannot upgrade
         *    to a write lock in vm_map_lookup.  thus, any actions that
         *    require the write lock must be done beforehand.  because we
         *    keep the read lock on the map, the copy-on-write status of the
         *    entries we modify here cannot change.
         */

        while ((entry != &map->header) && (entry->start < end)) {
                if (VM_MAPENT_ISWIRED(entry) == 0) { /* not already wired? */

                        /*
                         * perform actions of vm_map_lookup that need the
                         * write lock on the map: create an anonymous map
                         * for a copy-on-write region, or an anonymous map
                         * for a zero-fill region.  (XXXCDC: submap case
                         * ok?)
                         */

                        if (!UVM_ET_ISSUBMAP(entry)) {  /* not submap */
                                if (UVM_ET_ISNEEDSCOPY(entry) &&
                                    ((entry->max_protection & VM_PROT_WRITE) ||
                                     (entry->object.uvm_obj == NULL))) {
                                        amap_copy(map, entry, 0, start, end);
                                        /* XXXCDC: wait OK? */
                                }
                        }
                }
                UVM_MAP_CLIP_START(map, entry, start, NULL);
                UVM_MAP_CLIP_END(map, entry, end, NULL);
                entry->wired_count++;

                /*
                 * Check for holes
                 */

                if (entry->protection == VM_PROT_NONE ||
                    (entry->end < end &&
                     (entry->next == &map->header ||
                      entry->next->start > entry->end))) {

                        /*
                         * found one.  amap creation actions do not need to
                         * be undone, but the wired counts need to be restored.
                         */

                        while (entry != &map->header && entry->end > start) {
                                entry->wired_count--;
                                entry = entry->prev;
                        }
                        if ((lockflags & UVM_LK_EXIT) == 0)
                                vm_map_unlock(map);
                        UVMHIST_LOG(maphist,"<- done (INVALID WIRE)",0,0,0,0);
                        return EINVAL;
                }
                entry = entry->next;
        }

        /*
         * Pass 2.
         */

#ifdef DIAGNOSTIC
        timestamp_save = map->timestamp;
#endif
        vm_map_busy(map);
        vm_map_unlock(map);

        rv = 0;
        entry = start_entry;
        while (entry != &map->header && entry->start < end) {
                if (entry->wired_count == 1) {
                        rv = uvm_fault_wire(map, entry->start, entry->end,
                            entry->max_protection, 1);
                        if (rv) {

                                /*
                                 * wiring failed.  break out of the loop.
                                 * we'll clean up the map below, once we
                                 * have a write lock again.
                                 */

                                break;
                        }
                }
                entry = entry->next;
        }

        if (rv) {       /* failed? */

                /*
                 * Get back to an exclusive (write) lock.
                 */

                vm_map_lock(map);
                vm_map_unbusy(map);

#ifdef DIAGNOSTIC
                if (timestamp_save + 1 != map->timestamp)
                        panic("uvm_map_pageable: stale map");
#endif

                /*
                 * first drop the wiring count on all the entries
                 * which haven't actually been wired yet.
                 */

                failed_entry = entry;
                while (entry != &map->header && entry->start < end) {
                        entry->wired_count--;
                        entry = entry->next;
                }

                /*
                 * now, unwire all the entries that were successfully
                 * wired above.
                 */

                entry = start_entry;
                while (entry != failed_entry) {
                        entry->wired_count--;
                        if (VM_MAPENT_ISWIRED(entry) == 0)
                                uvm_map_entry_unwire(map, entry);
                        entry = entry->next;
                }
                if ((lockflags & UVM_LK_EXIT) == 0)
                        vm_map_unlock(map);
                UVMHIST_LOG(maphist, "<- done (RV=%d)", rv,0,0,0);
                return (rv);
        }

        if ((lockflags & UVM_LK_EXIT) == 0) {
                vm_map_unbusy(map);
        } else {

                /*
                 * Get back to an exclusive (write) lock.
                 */

                vm_map_lock(map);
                vm_map_unbusy(map);
        }

        UVMHIST_LOG(maphist,"<- done (OK WIRE)",0,0,0,0);
        return 0;
}

/*
 * uvm_map_pageable_all: special case of uvm_map_pageable - affects
 * all mapped regions.
 *
 * => map must not be locked.
 * => if no flags are specified, all regions are unwired.
 * => XXXJRT: has some of the same problems as uvm_map_pageable() above.
 */

int
uvm_map_pageable_all(struct vm_map *map, int flags, vsize_t limit)
{
        struct vm_map_entry *entry, *failed_entry;
        vsize_t size;
        int rv;
#ifdef DIAGNOSTIC
        u_int timestamp_save;
#endif
        UVMHIST_FUNC("uvm_map_pageable_all"); UVMHIST_CALLED(maphist);
        UVMHIST_LOG(maphist,"(map=0x%x,flags=0x%x)", map, flags, 0, 0);

        KASSERT(map->flags & VM_MAP_PAGEABLE);

        vm_map_lock(map);

        /*
         * handle wiring and unwiring separately.
         */

        if (flags == 0) {                       /* unwire */

                /*
                 * POSIX 1003.1b -- munlockall unlocks all regions,
                 * regardless of how many times mlockall has been called.
                 */

                for (entry = map->header.next; entry != &map->header;
                     entry = entry->next) {
                        if (VM_MAPENT_ISWIRED(entry))
                                uvm_map_entry_unwire(map, entry);
                }
                map->flags &= ~VM_MAP_WIREFUTURE;
                vm_map_unlock(map);
                UVMHIST_LOG(maphist,"<- done (OK UNWIRE)",0,0,0,0);
                return 0;
        }

        if (flags & MCL_FUTURE) {

                /*
                 * must wire all future mappings; remember this.
                 */

                map->flags |= VM_MAP_WIREFUTURE;
        }

        if ((flags & MCL_CURRENT) == 0) {

                /*
                 * no more work to do!
                 */

                UVMHIST_LOG(maphist,"<- done (OK no wire)",0,0,0,0);
                vm_map_unlock(map);
                return 0;
        }

        /*
         * wire case: in three passes [XXXCDC: ugly block of code here]
         *
         * 1: holding the write lock, count all pages mapped by non-wired
         *    entries.  if this would cause us to go over our limit, we fail.
         *
         * 2: still holding the write lock, we create any anonymous maps that
         *    need to be created.  then we increment its wiring count.
         *
         * 3: we downgrade to a read lock, and call uvm_fault_wire to fault
         *    in the pages for any newly wired area (wired_count == 1).
         *
         *    downgrading to a read lock for uvm_fault_wire avoids a possible
         *    deadlock with another thread that may have faulted on one of
         *    the pages to be wired (it would mark the page busy, blocking
         *    us, then in turn block on the map lock that we hold).  because
         *    of problems in the recursive lock package, we cannot upgrade
         *    to a write lock in vm_map_lookup.  thus, any actions that
         *    require the write lock must be done beforehand.  because we
         *    keep the read lock on the map, the copy-on-write status of the
         *    entries we modify here cannot change.
         */

        for (size = 0, entry = map->header.next; entry != &map->header;
             entry = entry->next) {
                if (entry->protection != VM_PROT_NONE &&
                    VM_MAPENT_ISWIRED(entry) == 0) { /* not already wired? */
                        size += entry->end - entry->start;
                }
        }

        if (atop(size) + uvmexp.wired > uvmexp.wiredmax) {
                vm_map_unlock(map);
                return ENOMEM;
        }

        if (limit != 0 &&
            (size + ptoa(pmap_wired_count(vm_map_pmap(map))) > limit)) {
                vm_map_unlock(map);
                return ENOMEM;
        }

        /*
         * Pass 2.
         */

        for (entry = map->header.next; entry != &map->header;
             entry = entry->next) {
                if (entry->protection == VM_PROT_NONE)
                        continue;
                if (VM_MAPENT_ISWIRED(entry) == 0) { /* not already wired? */

                        /*
                         * perform actions of vm_map_lookup that need the
                         * write lock on the map: create an anonymous map
                         * for a copy-on-write region, or an anonymous map
                         * for a zero-fill region.  (XXXCDC: submap case
                         * ok?)
                         */

                        if (!UVM_ET_ISSUBMAP(entry)) {  /* not submap */
                                if (UVM_ET_ISNEEDSCOPY(entry) &&
                                    ((entry->max_protection & VM_PROT_WRITE) ||
                                     (entry->object.uvm_obj == NULL))) {
                                        amap_copy(map, entry, 0, entry->start,
                                            entry->end);
                                        /* XXXCDC: wait OK? */
                                }
                        }
                }
                entry->wired_count++;
        }

        /*
         * Pass 3.
         */

#ifdef DIAGNOSTIC
        timestamp_save = map->timestamp;
#endif
        vm_map_busy(map);
        vm_map_unlock(map);

        rv = 0;
        for (entry = map->header.next; entry != &map->header;
             entry = entry->next) {
                if (entry->wired_count == 1) {
                        rv = uvm_fault_wire(map, entry->start, entry->end,
                            entry->max_protection, 1);
                        if (rv) {

                                /*
                                 * wiring failed.  break out of the loop.
                                 * we'll clean up the map below, once we
                                 * have a write lock again.
                                 */

                                break;
                        }
                }
        }

        if (rv) {

                /*
                 * Get back an exclusive (write) lock.
                 */

                vm_map_lock(map);
                vm_map_unbusy(map);

#ifdef DIAGNOSTIC
                if (timestamp_save + 1 != map->timestamp)
                        panic("uvm_map_pageable_all: stale map");
#endif

                /*
                 * first drop the wiring count on all the entries
                 * which haven't actually been wired yet.
                 *
                 * Skip VM_PROT_NONE entries like we did above.
                 */

                failed_entry = entry;
                for (/* nothing */; entry != &map->header;
                     entry = entry->next) {
                        if (entry->protection == VM_PROT_NONE)
                                continue;
                        entry->wired_count--;
                }

                /*
                 * now, unwire all the entries that were successfully
                 * wired above.
                 *
                 * Skip VM_PROT_NONE entries like we did above.
                 */

                for (entry = map->header.next; entry != failed_entry;
                     entry = entry->next) {
                        if (entry->protection == VM_PROT_NONE)
                                continue;
                        entry->wired_count--;
                        if (VM_MAPENT_ISWIRED(entry))
                                uvm_map_entry_unwire(map, entry);
                }
                vm_map_unlock(map);
                UVMHIST_LOG(maphist,"<- done (RV=%d)", rv,0,0,0);
                return (rv);
        }

        vm_map_unbusy(map);

        UVMHIST_LOG(maphist,"<- done (OK WIRE)",0,0,0,0);
        return 0;
}

/*
 * uvm_map_clean: clean out a map range
 *
 * => valid flags:
 *   if (flags & PGO_CLEANIT): dirty pages are cleaned first
 *   if (flags & PGO_SYNCIO): dirty pages are written synchronously
 *   if (flags & PGO_DEACTIVATE): any cached pages are deactivated after clean
 *   if (flags & PGO_FREE): any cached pages are freed after clean
 * => returns an error if any part of the specified range isn't mapped
 * => never a need to flush amap layer since the anonymous memory has
 *      no permanent home, but may deactivate pages there
 * => called from sys_msync() and sys_madvise()
 * => caller must not write-lock map (read OK).
 * => we may sleep while cleaning if SYNCIO [with map read-locked]
 */

int
uvm_map_clean(struct vm_map *map, vaddr_t start, vaddr_t end, int flags)
{
        struct vm_map_entry *current, *entry;
        struct uvm_object *uobj;
        struct vm_amap *amap;
        struct vm_anon *anon;
        struct vm_page *pg;
        vaddr_t offset;
        vsize_t size;
        voff_t uoff;
        int error, refs;
        UVMHIST_FUNC("uvm_map_clean"); UVMHIST_CALLED(maphist);

        UVMHIST_LOG(maphist,"(map=0x%x,start=0x%x,end=0x%x,flags=0x%x)",
                    map, start, end, flags);
        KASSERT((flags & (PGO_FREE|PGO_DEACTIVATE)) !=
                (PGO_FREE|PGO_DEACTIVATE));

        vm_map_lock_read(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (uvm_map_lookup_entry(map, start, &entry) == false) {
                vm_map_unlock_read(map);
                return EFAULT;
        }

        /*
         * Make a first pass to check for holes and wiring problems.
         */

        for (current = entry; current->start < end; current = current->next) {
                if (UVM_ET_ISSUBMAP(current)) {
                        vm_map_unlock_read(map);
                        return EINVAL;
                }
                if ((flags & PGO_FREE) != 0 && VM_MAPENT_ISWIRED(entry)) {
                        vm_map_unlock_read(map);
                        return EBUSY;
                }
                if (end <= current->end) {
                        break;
                }
                if (current->end != current->next->start) {
                        vm_map_unlock_read(map);
                        return EFAULT;
                }
        }

        error = 0;
        for (current = entry; start < end; current = current->next) {
                amap = current->aref.ar_amap;   /* upper layer */
                uobj = current->object.uvm_obj; /* lower layer */
                KASSERT(start >= current->start);

                /*
                 * No amap cleaning necessary if:
                 *
                 *      (1) There's no amap.
                 *
                 *      (2) We're not deactivating or freeing pages.
                 */

                if (amap == NULL || (flags & (PGO_DEACTIVATE|PGO_FREE)) == 0)
                        goto flush_object;

                amap_lock(amap);
                offset = start - current->start;
                size = MIN(end, current->end) - start;
                for ( ; size != 0; size -= PAGE_SIZE, offset += PAGE_SIZE) {
                        anon = amap_lookup(&current->aref, offset);
                        if (anon == NULL)
                                continue;

                        mutex_enter(&anon->an_lock);
                        pg = anon->an_page;
                        if (pg == NULL) {
                                mutex_exit(&anon->an_lock);
                                continue;
                        }

                        switch (flags & (PGO_CLEANIT|PGO_FREE|PGO_DEACTIVATE)) {

                        /*
                         * In these first 3 cases, we just deactivate the page.
                         */

                        case PGO_CLEANIT|PGO_FREE:
                        case PGO_CLEANIT|PGO_DEACTIVATE:
                        case PGO_DEACTIVATE:
 deactivate_it:
                                /*
                                 * skip the page if it's loaned or wired,
                                 * since it shouldn't be on a paging queue
                                 * at all in these cases.
                                 */

                                mutex_enter(&uvm_pageqlock);
                                if (pg->loan_count != 0 ||
                                    pg->wire_count != 0) {
                                        mutex_exit(&uvm_pageqlock);
                                        mutex_exit(&anon->an_lock);
                                        continue;
                                }
                                KASSERT(pg->uanon == anon);
                                uvm_pagedeactivate(pg);
                                mutex_exit(&uvm_pageqlock);
                                mutex_exit(&anon->an_lock);
                                continue;

                        case PGO_FREE:

                                /*
                                 * If there are multiple references to
                                 * the amap, just deactivate the page.
                                 */

                                if (amap_refs(amap) > 1)
                                        goto deactivate_it;

                                /* skip the page if it's wired */
                                if (pg->wire_count != 0) {
                                        mutex_exit(&anon->an_lock);
                                        continue;
                                }
                                amap_unadd(&current->aref, offset);
                                refs = --anon->an_ref;
                                mutex_exit(&anon->an_lock);
                                if (refs == 0)
                                        uvm_anfree(anon);
                                continue;
                        }
                }
                amap_unlock(amap);

 flush_object:
                /*
                 * flush pages if we've got a valid backing object.
                 * note that we must always clean object pages before
                 * freeing them since otherwise we could reveal stale
                 * data from files.
                 */

                uoff = current->offset + (start - current->start);
                size = MIN(end, current->end) - start;
                if (uobj != NULL) {
                        mutex_enter(&uobj->vmobjlock);
                        if (uobj->pgops->pgo_put != NULL)
                                error = (uobj->pgops->pgo_put)(uobj, uoff,
                                    uoff + size, flags | PGO_CLEANIT);
                        else
                                error = 0;
                }
                start += size;
        }
        vm_map_unlock_read(map);
        return (error);
}


/*
 * uvm_map_checkprot: check protection in map
 *
 * => must allow specified protection in a fully allocated region.
 * => map must be read or write locked by caller.
 */

bool
uvm_map_checkprot(struct vm_map *map, vaddr_t start, vaddr_t end,
    vm_prot_t protection)
{
        struct vm_map_entry *entry;
        struct vm_map_entry *tmp_entry;

        if (!uvm_map_lookup_entry(map, start, &tmp_entry)) {
                return (false);
        }
        entry = tmp_entry;
        while (start < end) {
                if (entry == &map->header) {
                        return (false);
                }

                /*
                 * no holes allowed
                 */

                if (start < entry->start) {
                        return (false);
                }

                /*
                 * check protection associated with entry
                 */

                if ((entry->protection & protection) != protection) {
                        return (false);
                }
                start = entry->end;
                entry = entry->next;
        }
        return (true);
}

/*
 * uvmspace_alloc: allocate a vmspace structure.
 *
 * - structure includes vm_map and pmap
 * - XXX: no locking on this structure
 * - refcnt set to 1, rest must be init'd by caller
 */
struct vmspace *
uvmspace_alloc(vaddr_t vmin, vaddr_t vmax)
{
        struct vmspace *vm;
        UVMHIST_FUNC("uvmspace_alloc"); UVMHIST_CALLED(maphist);

        vm = pool_cache_get(&uvm_vmspace_cache, PR_WAITOK);
        uvmspace_init(vm, NULL, vmin, vmax);
        UVMHIST_LOG(maphist,"<- done (vm=0x%x)", vm,0,0,0);
        return (vm);
}

/*
 * uvmspace_init: initialize a vmspace structure.
 *
 * - XXX: no locking on this structure
 * - refcnt set to 1, rest must be init'd by caller
 */
void
uvmspace_init(struct vmspace *vm, struct pmap *pmap, vaddr_t vmin, vaddr_t vmax)
{
        UVMHIST_FUNC("uvmspace_init"); UVMHIST_CALLED(maphist);

        memset(vm, 0, sizeof(*vm));
        uvm_map_setup(&vm->vm_map, vmin, vmax, VM_MAP_PAGEABLE
#ifdef __USING_TOPDOWN_VM
            | VM_MAP_TOPDOWN
#endif
            );
        if (pmap)
                pmap_reference(pmap);
        else
                pmap = pmap_create();
        vm->vm_map.pmap = pmap;
        vm->vm_refcnt = 1;
        UVMHIST_LOG(maphist,"<- done",0,0,0,0);
}

/*
 * uvmspace_share: share a vmspace between two processes
 *
 * - used for vfork, threads(?)
 */

void
uvmspace_share(struct proc *p1, struct proc *p2)
{

        uvmspace_addref(p1->p_vmspace);
        p2->p_vmspace = p1->p_vmspace;
}

#if 0

/*
 * uvmspace_unshare: ensure that process "p" has its own, unshared, vmspace
 *
 * - XXX: no locking on vmspace
 */

void
uvmspace_unshare(struct lwp *l)
{
        struct proc *p = l->l_proc;
        struct vmspace *nvm, *ovm = p->p_vmspace;

        if (ovm->vm_refcnt == 1)
                /* nothing to do: vmspace isn't shared in the first place */
                return;

        /* make a new vmspace, still holding old one */
        nvm = uvmspace_fork(ovm);

        kpreempt_disable();
        pmap_deactivate(l);             /* unbind old vmspace */
        p->p_vmspace = nvm;
        pmap_activate(l);               /* switch to new vmspace */
        kpreempt_enable();

        uvmspace_free(ovm);             /* drop reference to old vmspace */
}

#endif

/*
 * uvmspace_exec: the process wants to exec a new program
 */

void
uvmspace_exec(struct lwp *l, vaddr_t start, vaddr_t end)
{
        struct proc *p = l->l_proc;
        struct vmspace *nvm, *ovm = p->p_vmspace;
        struct vm_map *map = &ovm->vm_map;

#ifdef __sparc__
        /* XXX cgd 960926: the sparc #ifdef should be a MD hook */
        kill_user_windows(l);   /* before stack addresses go away */
#endif

        /*
         * see if more than one process is using this vmspace...
         */

        if (ovm->vm_refcnt == 1) {

                /*
                 * if p is the only process using its vmspace then we can safely
                 * recycle that vmspace for the program that is being exec'd.
                 */

#ifdef SYSVSHM
                /*
                 * SYSV SHM semantics require us to kill all segments on an exec
                 */

                if (ovm->vm_shm)
                        shmexit(ovm);
#endif

                /*
                 * POSIX 1003.1b -- "lock future mappings" is revoked
                 * when a process execs another program image.
                 */

                map->flags &= ~VM_MAP_WIREFUTURE;

                /*
                 * now unmap the old program
                 */

                pmap_remove_all(map->pmap);
                uvm_unmap(map, vm_map_min(map), vm_map_max(map));
                KASSERT(map->header.prev == &map->header);
                KASSERT(map->nentries == 0);

                /*
                 * resize the map
                 */

                vm_map_setmin(map, start);
                vm_map_setmax(map, end);
        } else {

                /*
                 * p's vmspace is being shared, so we can't reuse it for p since
                 * it is still being used for others.   allocate a new vmspace
                 * for p
                 */

                nvm = uvmspace_alloc(start, end);

                /*
                 * install new vmspace and drop our ref to the old one.
                 */

                kpreempt_disable();
                pmap_deactivate(l);
                p->p_vmspace = nvm;
                pmap_activate(l);
                kpreempt_enable();

                uvmspace_free(ovm);
        }
}

/*
 * uvmspace_addref: add a referece to a vmspace.
 */

void
uvmspace_addref(struct vmspace *vm)
{
        struct vm_map *map = &vm->vm_map;

        KASSERT((map->flags & VM_MAP_DYING) == 0);

        mutex_enter(&map->misc_lock);
        KASSERT(vm->vm_refcnt > 0);
        vm->vm_refcnt++;
        mutex_exit(&map->misc_lock);
}

/*
 * uvmspace_free: free a vmspace data structure
 */

void
uvmspace_free(struct vmspace *vm)
{
        struct vm_map_entry *dead_entries;
        struct vm_map *map = &vm->vm_map;
        int n;

        UVMHIST_FUNC("uvmspace_free"); UVMHIST_CALLED(maphist);

        UVMHIST_LOG(maphist,"(vm=0x%x) ref=%d", vm, vm->vm_refcnt,0,0);
        mutex_enter(&map->misc_lock);
        n = --vm->vm_refcnt;
        mutex_exit(&map->misc_lock);
        if (n > 0)
                return;

        /*
         * at this point, there should be no other references to the map.
         * delete all of the mappings, then destroy the pmap.
         */

        map->flags |= VM_MAP_DYING;
        pmap_remove_all(map->pmap);
#ifdef SYSVSHM
        /* Get rid of any SYSV shared memory segments. */
        if (vm->vm_shm != NULL)
                shmexit(vm);
#endif
        if (map->nentries) {
                uvm_unmap_remove(map, vm_map_min(map), vm_map_max(map),
                    &dead_entries, NULL, 0);
                if (dead_entries != NULL)
                        uvm_unmap_detach(dead_entries, 0);
        }
        KASSERT(map->nentries == 0);
        KASSERT(map->size == 0);
        mutex_destroy(&map->misc_lock);
        mutex_destroy(&map->mutex);
        rw_destroy(&map->lock);
        cv_destroy(&map->cv);
        pmap_destroy(map->pmap);
        pool_cache_put(&uvm_vmspace_cache, vm);
}

/*
 *   F O R K   -   m a i n   e n t r y   p o i n t
 */
/*
 * uvmspace_fork: fork a process' main map
 *
 * => create a new vmspace for child process from parent.
 * => parent's map must not be locked.
 */

struct vmspace *
uvmspace_fork(struct vmspace *vm1)
{
        struct vmspace *vm2;
        struct vm_map *old_map = &vm1->vm_map;
        struct vm_map *new_map;
        struct vm_map_entry *old_entry;
        struct vm_map_entry *new_entry;
        UVMHIST_FUNC("uvmspace_fork"); UVMHIST_CALLED(maphist);

        vm_map_lock(old_map);

        vm2 = uvmspace_alloc(vm_map_min(old_map), vm_map_max(old_map));
        memcpy(&vm2->vm_startcopy, &vm1->vm_startcopy,
            (char *) (vm1 + 1) - (char *) &vm1->vm_startcopy);
        new_map = &vm2->vm_map;           /* XXX */

        old_entry = old_map->header.next;
        new_map->size = old_map->size;

        /*
         * go entry-by-entry
         */

        while (old_entry != &old_map->header) {

                /*
                 * first, some sanity checks on the old entry
                 */

                KASSERT(!UVM_ET_ISSUBMAP(old_entry));
                KASSERT(UVM_ET_ISCOPYONWRITE(old_entry) ||
                        !UVM_ET_ISNEEDSCOPY(old_entry));

                switch (old_entry->inheritance) {
                case MAP_INHERIT_NONE:

                        /*
                         * drop the mapping, modify size
                         */
                        new_map->size -= old_entry->end - old_entry->start;
                        break;

                case MAP_INHERIT_SHARE:

                        /*
                         * share the mapping: this means we want the old and
                         * new entries to share amaps and backing objects.
                         */
                        /*
                         * if the old_entry needs a new amap (due to prev fork)
                         * then we need to allocate it now so that we have
                         * something we own to share with the new_entry.   [in
                         * other words, we need to clear needs_copy]
                         */

                        if (UVM_ET_ISNEEDSCOPY(old_entry)) {
                                /* get our own amap, clears needs_copy */
                                amap_copy(old_map, old_entry, AMAP_COPY_NOCHUNK,
                                    0, 0);
                                /* XXXCDC: WAITOK??? */
                        }

                        new_entry = uvm_mapent_alloc(new_map, 0);
                        /* old_entry -> new_entry */
                        uvm_mapent_copy(old_entry, new_entry);

                        /* new pmap has nothing wired in it */
                        new_entry->wired_count = 0;

                        /*
                         * gain reference to object backing the map (can't
                         * be a submap, already checked this case).
                         */

                        if (new_entry->aref.ar_amap)
                                uvm_map_reference_amap(new_entry, AMAP_SHARED);

                        if (new_entry->object.uvm_obj &&
                            new_entry->object.uvm_obj->pgops->pgo_reference)
                                new_entry->object.uvm_obj->
                                    pgops->pgo_reference(
                                        new_entry->object.uvm_obj);

                        /* insert entry at end of new_map's entry list */
                        uvm_map_entry_link(new_map, new_map->header.prev,
                            new_entry);

                        break;

                case MAP_INHERIT_COPY:

                        /*
                         * copy-on-write the mapping (using mmap's
                         * MAP_PRIVATE semantics)
                         *
                         * allocate new_entry, adjust reference counts.
                         * (note that new references are read-only).
                         */

                        new_entry = uvm_mapent_alloc(new_map, 0);
                        /* old_entry -> new_entry */
                        uvm_mapent_copy(old_entry, new_entry);

                        if (new_entry->aref.ar_amap)
                                uvm_map_reference_amap(new_entry, 0);

                        if (new_entry->object.uvm_obj &&
                            new_entry->object.uvm_obj->pgops->pgo_reference)
                                new_entry->object.uvm_obj->pgops->pgo_reference
                                    (new_entry->object.uvm_obj);

                        /* new pmap has nothing wired in it */
                        new_entry->wired_count = 0;

                        new_entry->etype |=
                            (UVM_ET_COPYONWRITE|UVM_ET_NEEDSCOPY);
                        uvm_map_entry_link(new_map, new_map->header.prev,
                            new_entry);

                        /*
                         * the new entry will need an amap.  it will either
                         * need to be copied from the old entry or created
                         * from scratch (if the old entry does not have an
                         * amap).  can we defer this process until later
                         * (by setting "needs_copy") or do we need to copy
                         * the amap now?
                         *
                         * we must copy the amap now if any of the following
                         * conditions hold:
                         * 1. the old entry has an amap and that amap is
                         *    being shared.  this means that the old (parent)
                         *    process is sharing the amap with another
                         *    process.  if we do not clear needs_copy here
                         *    we will end up in a situation where both the
                         *    parent and child process are refering to the
                         *    same amap with "needs_copy" set.  if the
                         *    parent write-faults, the fault routine will
                         *    clear "needs_copy" in the parent by allocating
                         *    a new amap.   this is wrong because the
                         *    parent is supposed to be sharing the old amap
                         *    and the new amap will break that.
                         *
                         * 2. if the old entry has an amap and a non-zero
                         *    wire count then we are going to have to call
                         *    amap_cow_now to avoid page faults in the
                         *    parent process.   since amap_cow_now requires
                         *    "needs_copy" to be clear we might as well
                         *    clear it here as well.
                         *
                         */

                        if (old_entry->aref.ar_amap != NULL) {
                                if ((amap_flags(old_entry->aref.ar_amap) &
                                     AMAP_SHARED) != 0 ||
                                    VM_MAPENT_ISWIRED(old_entry)) {

                                        amap_copy(new_map, new_entry,
                                            AMAP_COPY_NOCHUNK, 0, 0);
                                        /* XXXCDC: M_WAITOK ... ok? */
                                }
                        }

                        /*
                         * if the parent's entry is wired down, then the
                         * parent process does not want page faults on
                         * access to that memory.  this means that we
                         * cannot do copy-on-write because we can't write
                         * protect the old entry.   in this case we
                         * resolve all copy-on-write faults now, using
                         * amap_cow_now.   note that we have already
                         * allocated any needed amap (above).
                         */

                        if (VM_MAPENT_ISWIRED(old_entry)) {

                          /*
                           * resolve all copy-on-write faults now
                           * (note that there is nothing to do if
                           * the old mapping does not have an amap).
                           */
                          if (old_entry->aref.ar_amap)
                            amap_cow_now(new_map, new_entry);

                        } else {

                          /*
                           * setup mappings to trigger copy-on-write faults
                           * we must write-protect the parent if it has
                           * an amap and it is not already "needs_copy"...
                           * if it is already "needs_copy" then the parent
                           * has already been write-protected by a previous
                           * fork operation.
                           */

                          if (old_entry->aref.ar_amap &&
                              !UVM_ET_ISNEEDSCOPY(old_entry)) {
                              if (old_entry->max_protection & VM_PROT_WRITE) {
                                pmap_protect(old_map->pmap,
                                             old_entry->start,
                                             old_entry->end,
                                             old_entry->protection &
                                             ~VM_PROT_WRITE);
                              }
                              old_entry->etype |= UVM_ET_NEEDSCOPY;
                          }
                        }
                        break;
                }  /* end of switch statement */
                old_entry = old_entry->next;
        }

        pmap_update(old_map->pmap);
        vm_map_unlock(old_map);

#ifdef SYSVSHM
        if (vm1->vm_shm)
                shmfork(vm1, vm2);
#endif

#ifdef PMAP_FORK
        pmap_fork(vm1->vm_map.pmap, vm2->vm_map.pmap);
#endif

        UVMHIST_LOG(maphist,"<- done",0,0,0,0);
        return (vm2);
}


/*
 * in-kernel map entry allocation.
 */

struct uvm_kmapent_hdr {
        LIST_ENTRY(uvm_kmapent_hdr) ukh_listq;
        int ukh_nused;
        struct vm_map_entry *ukh_freelist;
        struct vm_map *ukh_map;
        struct vm_map_entry ukh_entries[0];
};

#define UVM_KMAPENT_CHUNK                               \
        ((PAGE_SIZE - sizeof(struct uvm_kmapent_hdr))   \
        / sizeof(struct vm_map_entry))

#define UVM_KHDR_FIND(entry)    \
        ((struct uvm_kmapent_hdr *)(((vaddr_t)entry) & ~PAGE_MASK))


#ifdef DIAGNOSTIC
static struct vm_map *
uvm_kmapent_map(struct vm_map_entry *entry)
{
        const struct uvm_kmapent_hdr *ukh;

        ukh = UVM_KHDR_FIND(entry);
        return ukh->ukh_map;
}
#endif

static inline struct vm_map_entry *
uvm_kmapent_get(struct uvm_kmapent_hdr *ukh)
{
        struct vm_map_entry *entry;

        KASSERT(ukh->ukh_nused <= UVM_KMAPENT_CHUNK);
        KASSERT(ukh->ukh_nused >= 0);

        entry = ukh->ukh_freelist;
        if (entry) {
                KASSERT((entry->flags & (UVM_MAP_KERNEL | UVM_MAP_KMAPENT))
                    == UVM_MAP_KERNEL);
                ukh->ukh_freelist = entry->next;
                ukh->ukh_nused++;
                KASSERT(ukh->ukh_nused <= UVM_KMAPENT_CHUNK);
        } else {
                KASSERT(ukh->ukh_nused == UVM_KMAPENT_CHUNK);
        }

        return entry;
}

static inline void
uvm_kmapent_put(struct uvm_kmapent_hdr *ukh, struct vm_map_entry *entry)
{

        KASSERT((entry->flags & (UVM_MAP_KERNEL | UVM_MAP_KMAPENT))
            == UVM_MAP_KERNEL);
        KASSERT(ukh->ukh_nused <= UVM_KMAPENT_CHUNK);
        KASSERT(ukh->ukh_nused > 0);
        KASSERT(ukh->ukh_freelist != NULL ||
            ukh->ukh_nused == UVM_KMAPENT_CHUNK);
        KASSERT(ukh->ukh_freelist == NULL ||
            ukh->ukh_nused < UVM_KMAPENT_CHUNK);

        ukh->ukh_nused--;
        entry->next = ukh->ukh_freelist;
        ukh->ukh_freelist = entry;
}

/*
 * uvm_kmapent_alloc: allocate a map entry for in-kernel map
 */

static struct vm_map_entry *
uvm_kmapent_alloc(struct vm_map *map, int flags)
{
        struct vm_page *pg;
        struct uvm_kmapent_hdr *ukh;
        struct vm_map_entry *entry;
#ifndef PMAP_MAP_POOLPAGE
        struct uvm_map_args args;
        uvm_flag_t mapflags = UVM_MAPFLAG(UVM_PROT_ALL, UVM_PROT_ALL,
            UVM_INH_NONE, UVM_ADV_RANDOM, flags | UVM_FLAG_NOMERGE);
        int error;
#endif
        vaddr_t va;
        int i;

        KDASSERT(UVM_KMAPENT_CHUNK > 2);
        KDASSERT(kernel_map != NULL);
        KASSERT(vm_map_pmap(map) == pmap_kernel());

        UVMMAP_EVCNT_INCR(uke_alloc);
        entry = NULL;
again:
        /*
         * try to grab an entry from freelist.
         */
        mutex_spin_enter(&uvm_kentry_lock);
        ukh = LIST_FIRST(&vm_map_to_kernel(map)->vmk_kentry_free);
        if (ukh) {
                entry = uvm_kmapent_get(ukh);
                if (ukh->ukh_nused == UVM_KMAPENT_CHUNK)
                        LIST_REMOVE(ukh, ukh_listq);
        }
        mutex_spin_exit(&uvm_kentry_lock);

        if (entry)
                return entry;

        /*
         * there's no free entry for this vm_map.
         * now we need to allocate some vm_map_entry.
         * for simplicity, always allocate one page chunk of them at once.
         */

        pg = uvm_pagealloc(NULL, 0, NULL,
            (flags & UVM_KMF_NOWAIT) != 0 ? UVM_PGA_USERESERVE : 0);
        if (__predict_false(pg == NULL)) {
                if (flags & UVM_FLAG_NOWAIT)
                        return NULL;
                uvm_wait("kme_alloc");
                goto again;
        }

#ifdef PMAP_MAP_POOLPAGE
        va = PMAP_MAP_POOLPAGE(VM_PAGE_TO_PHYS(pg));
        KASSERT(va != 0);
#else
        error = uvm_map_prepare(map, 0, PAGE_SIZE, NULL, UVM_UNKNOWN_OFFSET,
            0, mapflags, &args);
        if (error) {
                uvm_pagefree(pg);
                return NULL;
        }

        va = args.uma_start;

        pmap_kenter_pa(va, VM_PAGE_TO_PHYS(pg),
            VM_PROT_READ|VM_PROT_WRITE|PMAP_KMPAGE, 0);
        pmap_update(vm_map_pmap(map));

#endif
        ukh = (void *)va;

        /*
         * use the last entry for ukh itsself.
         */

        i = UVM_KMAPENT_CHUNK - 1;
#ifndef PMAP_MAP_POOLPAGE
        entry = &ukh->ukh_entries[i--];
        entry->flags = UVM_MAP_KERNEL | UVM_MAP_KMAPENT;
        error = uvm_map_enter(map, &args, entry);
        KASSERT(error == 0);
#endif

        ukh->ukh_nused = UVM_KMAPENT_CHUNK;
        ukh->ukh_map = map;
        ukh->ukh_freelist = NULL;
        for (; i >= 1; i--) {
                struct vm_map_entry *xentry = &ukh->ukh_entries[i];

                xentry->flags = UVM_MAP_KERNEL;
                uvm_kmapent_put(ukh, xentry);
        }
#ifdef PMAP_MAP_POOLPAGE
        KASSERT(ukh->ukh_nused == 1);
#else
        KASSERT(ukh->ukh_nused == 2);
#endif

        mutex_spin_enter(&uvm_kentry_lock);
        LIST_INSERT_HEAD(&vm_map_to_kernel(map)->vmk_kentry_free,
            ukh, ukh_listq);
        mutex_spin_exit(&uvm_kentry_lock);

        /*
         * return first entry.
         */

        entry = &ukh->ukh_entries[0];
        entry->flags = UVM_MAP_KERNEL;
        UVMMAP_EVCNT_INCR(ukh_alloc);

        return entry;
}

/*
 * uvm_mapent_free: free map entry for in-kernel map
 */

static void
uvm_kmapent_free(struct vm_map_entry *entry)
{
        struct uvm_kmapent_hdr *ukh;
        struct vm_page *pg;
        struct vm_map *map;
#ifndef PMAP_UNMAP_POOLPAGE
        struct pmap *pmap;
        struct vm_map_entry *deadentry;
#endif
        vaddr_t va;
        paddr_t pa;

        UVMMAP_EVCNT_INCR(uke_free);
        ukh = UVM_KHDR_FIND(entry);
        map = ukh->ukh_map;

        mutex_spin_enter(&uvm_kentry_lock);
        uvm_kmapent_put(ukh, entry);
#ifdef PMAP_UNMAP_POOLPAGE
        if (ukh->ukh_nused > 0) {
#else
        if (ukh->ukh_nused > 1) {
#endif
                if (ukh->ukh_nused == UVM_KMAPENT_CHUNK - 1)
                        LIST_INSERT_HEAD(
                            &vm_map_to_kernel(map)->vmk_kentry_free,
                            ukh, ukh_listq);
                mutex_spin_exit(&uvm_kentry_lock);
                return;
        }

        /*
         * now we can free this ukh.
         *
         * however, keep an empty ukh to avoid ping-pong.
         */

        if (LIST_FIRST(&vm_map_to_kernel(map)->vmk_kentry_free) == ukh &&
            LIST_NEXT(ukh, ukh_listq) == NULL) {
                mutex_spin_exit(&uvm_kentry_lock);
                return;
        }
        LIST_REMOVE(ukh, ukh_listq);
        mutex_spin_exit(&uvm_kentry_lock);

        va = (vaddr_t)ukh;

#ifdef PMAP_UNMAP_POOLPAGE
        KASSERT(ukh->ukh_nused == 0);
        pa = PMAP_UNMAP_POOLPAGE(va);
        KASSERT(pa != 0);
#else
        KASSERT(ukh->ukh_nused == 1);

        /*
         * remove map entry for ukh itsself.
         */

        KASSERT((va & PAGE_MASK) == 0);
        vm_map_lock(map);
        uvm_unmap_remove(map, va, va + PAGE_SIZE, &deadentry, NULL, 0);
        KASSERT(deadentry->flags & UVM_MAP_KERNEL);
        KASSERT(deadentry->flags & UVM_MAP_KMAPENT);
        KASSERT(deadentry->next == NULL);
        KASSERT(deadentry == &ukh->ukh_entries[UVM_KMAPENT_CHUNK - 1]);

        /*
         * unmap the page from pmap and free it.
         */

        pmap = vm_map_pmap(map);
        KASSERT(pmap == pmap_kernel());
        if (!pmap_extract(pmap, va, &pa))
                panic("%s: no mapping", __func__);
        pmap_kremove(va, PAGE_SIZE);
        pmap_update(vm_map_pmap(map));
        vm_map_unlock(map);
#endif /* !PMAP_UNMAP_POOLPAGE */
        pg = PHYS_TO_VM_PAGE(pa);
        uvm_pagefree(pg);
        UVMMAP_EVCNT_INCR(ukh_free);
}

static vsize_t
uvm_kmapent_overhead(vsize_t size)
{

        /*
         * - the max number of unmerged entries is howmany(size, PAGE_SIZE)
         *   as the min allocation unit is PAGE_SIZE.
         * - UVM_KMAPENT_CHUNK "kmapent"s are allocated from a page.
         *   one of them are used to map the page itself.
         */

        return howmany(howmany(size, PAGE_SIZE), (UVM_KMAPENT_CHUNK - 1)) *
            PAGE_SIZE;
}

/*
 * map entry reservation
 */

/*
 * uvm_mapent_reserve: reserve map entries for clipping before locking map.
 *
 * => needed when unmapping entries allocated without UVM_FLAG_QUANTUM.
 * => caller shouldn't hold map locked.
 */
int
uvm_mapent_reserve(struct vm_map *map, struct uvm_mapent_reservation *umr,
    int nentries, int flags)
{

        umr->umr_nentries = 0;

        if ((flags & UVM_FLAG_QUANTUM) != 0)
                return 0;

        if (!VM_MAP_USE_KMAPENT(map))
                return 0;

        while (nentries--) {
                struct vm_map_entry *ent;
                ent = uvm_kmapent_alloc(map, flags);
                if (!ent) {
                        uvm_mapent_unreserve(map, umr);
                        return ENOMEM;
                }
                UMR_PUTENTRY(umr, ent);
        }

        return 0;
}

/*
 * uvm_mapent_unreserve:
 *
 * => caller shouldn't hold map locked.
 * => never fail or sleep.
 */
void
uvm_mapent_unreserve(struct vm_map *map, struct uvm_mapent_reservation *umr)
{

        while (!UMR_EMPTY(umr))
                uvm_kmapent_free(UMR_GETENTRY(umr));
}

/*
 * uvm_mapent_trymerge: try to merge an entry with its neighbors.
 *
 * => called with map locked.
 * => return non zero if successfully merged.
 */

int
uvm_mapent_trymerge(struct vm_map *map, struct vm_map_entry *entry, int flags)
{
        struct uvm_object *uobj;
        struct vm_map_entry *next;
        struct vm_map_entry *prev;
        vsize_t size;
        int merged = 0;
        bool copying;
        int newetype;

        if (VM_MAP_USE_KMAPENT(map)) {
                return 0;
        }
        if (entry->aref.ar_amap != NULL) {
                return 0;
        }
        if ((entry->flags & UVM_MAP_NOMERGE) != 0) {
                return 0;
        }

        uobj = entry->object.uvm_obj;
        size = entry->end - entry->start;
        copying = (flags & UVM_MERGE_COPYING) != 0;
        newetype = copying ? (entry->etype & ~UVM_ET_NEEDSCOPY) : entry->etype;

        next = entry->next;
        if (next != &map->header &&
            next->start == entry->end &&
            ((copying && next->aref.ar_amap != NULL &&
            amap_refs(next->aref.ar_amap) == 1) ||
            (!copying && next->aref.ar_amap == NULL)) &&
            UVM_ET_ISCOMPATIBLE(next, newetype,
            uobj, entry->flags, entry->protection,
            entry->max_protection, entry->inheritance, entry->advice,
            entry->wired_count) &&
            (uobj == NULL || entry->offset + size == next->offset)) {
                int error;

                if (copying) {
                        error = amap_extend(next, size,
                            AMAP_EXTEND_NOWAIT|AMAP_EXTEND_BACKWARDS);
                } else {
                        error = 0;
                }
                if (error == 0) {
                        if (uobj) {
                                if (uobj->pgops->pgo_detach) {
                                        uobj->pgops->pgo_detach(uobj);
                                }
                        }

                        entry->end = next->end;
                        clear_hints(map, next);
                        uvm_map_entry_unlink(map, next);
                        if (copying) {
                                entry->aref = next->aref;
                                entry->etype &= ~UVM_ET_NEEDSCOPY;
                        }
                        uvm_map_check(map, "trymerge forwardmerge");
                        uvm_mapent_free_merged(map, next);
                        merged++;
                }
        }

        prev = entry->prev;
        if (prev != &map->header &&
            prev->end == entry->start &&
            ((copying && !merged && prev->aref.ar_amap != NULL &&
            amap_refs(prev->aref.ar_amap) == 1) ||
            (!copying && prev->aref.ar_amap == NULL)) &&
            UVM_ET_ISCOMPATIBLE(prev, newetype,
            uobj, entry->flags, entry->protection,
            entry->max_protection, entry->inheritance, entry->advice,
            entry->wired_count) &&
            (uobj == NULL ||
            prev->offset + prev->end - prev->start == entry->offset)) {
                int error;

                if (copying) {
                        error = amap_extend(prev, size,
                            AMAP_EXTEND_NOWAIT|AMAP_EXTEND_FORWARDS);
                } else {
                        error = 0;
                }
                if (error == 0) {
                        if (uobj) {
                                if (uobj->pgops->pgo_detach) {
                                        uobj->pgops->pgo_detach(uobj);
                                }
                                entry->offset = prev->offset;
                        }

                        entry->start = prev->start;
                        clear_hints(map, prev);
                        uvm_map_entry_unlink(map, prev);
                        if (copying) {
                                entry->aref = prev->aref;
                                entry->etype &= ~UVM_ET_NEEDSCOPY;
                        }
                        uvm_map_check(map, "trymerge backmerge");
                        uvm_mapent_free_merged(map, prev);
                        merged++;
                }
        }

        return merged;
}

/*
 * uvm_map_create: create map
 */

struct vm_map *
uvm_map_create(pmap_t pmap, vaddr_t vmin, vaddr_t vmax, int flags)
{
        struct vm_map *result;

        result = malloc(sizeof(struct vm_map), M_VMMAP, M_WAITOK);
        uvm_map_setup(result, vmin, vmax, flags);
        result->pmap = pmap;
        return(result);
}

/*
 * uvm_map_setup: init map
 *
 * => map must not be in service yet.
 */

void
uvm_map_setup(struct vm_map *map, vaddr_t vmin, vaddr_t vmax, int flags)
{
        int ipl;

        rb_tree_init(&map->rb_tree, &uvm_map_tree_ops);
        map->header.next = map->header.prev = &map->header;
        map->nentries = 0;
        map->size = 0;
        map->ref_count = 1;
        vm_map_setmin(map, vmin);
        vm_map_setmax(map, vmax);
        map->flags = flags;
        map->first_free = &map->header;
        map->hint = &map->header;
        map->timestamp = 0;
        map->busy = NULL;

        if ((flags & VM_MAP_INTRSAFE) != 0) {
                ipl = IPL_VM;
        } else {
                ipl = IPL_NONE;
        }

        rw_init(&map->lock);
        cv_init(&map->cv, "vm_map");
        mutex_init(&map->misc_lock, MUTEX_DRIVER, ipl);
        mutex_init(&map->mutex, MUTEX_DRIVER, ipl);
}


/*
 *   U N M A P   -   m a i n   e n t r y   p o i n t
 */

/*
 * uvm_unmap1: remove mappings from a vm_map (from "start" up to "stop")
 *
 * => caller must check alignment and size
 * => map must be unlocked (we will lock it)
 * => flags is UVM_FLAG_QUANTUM or 0.
 */

void
uvm_unmap1(struct vm_map *map, vaddr_t start, vaddr_t end, int flags)
{
        struct vm_map_entry *dead_entries;
        struct uvm_mapent_reservation umr;
        UVMHIST_FUNC("uvm_unmap"); UVMHIST_CALLED(maphist);

        UVMHIST_LOG(maphist, "  (map=0x%x, start=0x%x, end=0x%x)",
            map, start, end, 0);
        if (map == kernel_map) {
                LOCKDEBUG_MEM_CHECK((void *)start, end - start);
        }
        /*
         * work now done by helper functions.   wipe the pmap's and then
         * detach from the dead entries...
         */
        uvm_mapent_reserve(map, &umr, 2, flags);
        vm_map_lock(map);
        uvm_unmap_remove(map, start, end, &dead_entries, &umr, flags);
        vm_map_unlock(map);
        uvm_mapent_unreserve(map, &umr);

        if (dead_entries != NULL)
                uvm_unmap_detach(dead_entries, 0);

        UVMHIST_LOG(maphist, "<- done", 0,0,0,0);
}


/*
 * uvm_map_reference: add reference to a map
 *
 * => map need not be locked (we use misc_lock).
 */

void
uvm_map_reference(struct vm_map *map)
{
        mutex_enter(&map->misc_lock);
        map->ref_count++;
        mutex_exit(&map->misc_lock);
}

struct vm_map_kernel *
vm_map_to_kernel(struct vm_map *map)
{

        KASSERT(VM_MAP_IS_KERNEL(map));

        return (struct vm_map_kernel *)map;
}

bool
vm_map_starved_p(struct vm_map *map)
{

        if ((map->flags & VM_MAP_WANTVA) != 0) {
                return true;
        }
        /* XXX */
        if ((vm_map_max(map) - vm_map_min(map)) / 16 * 15 < map->size) {
                return true;
        }
        return false;
}

#if defined(DDB) || defined(DEBUGPRINT)

/*
 * uvm_map_printit: actually prints the map
 */

void
uvm_map_printit(struct vm_map *map, bool full,
    void (*pr)(const char *, ...))
{
        struct vm_map_entry *entry;

        (*pr)("MAP %p: [0x%lx->0x%lx]\n", map, vm_map_min(map),
            vm_map_max(map));
        (*pr)("\t#ent=%d, sz=%d, ref=%d, version=%d, flags=0x%x\n",
            map->nentries, map->size, map->ref_count, map->timestamp,
            map->flags);
        (*pr)("\tpmap=%p(resident=%ld, wired=%ld)\n", map->pmap,
            pmap_resident_count(map->pmap), pmap_wired_count(map->pmap));
        if (!full)
                return;
        for (entry = map->header.next; entry != &map->header;
            entry = entry->next) {
                (*pr)(" - %p: 0x%lx->0x%lx: obj=%p/0x%llx, amap=%p/%d\n",
                    entry, entry->start, entry->end, entry->object.uvm_obj,
                    (long long)entry->offset, entry->aref.ar_amap,
                    entry->aref.ar_pageoff);
                (*pr)(
                    "\tsubmap=%c, cow=%c, nc=%c, prot(max)=%d/%d, inh=%d, "
                    "wc=%d, adv=%d\n",
                    (entry->etype & UVM_ET_SUBMAP) ? 'T' : 'F',
                    (entry->etype & UVM_ET_COPYONWRITE) ? 'T' : 'F',
                    (entry->etype & UVM_ET_NEEDSCOPY) ? 'T' : 'F',
                    entry->protection, entry->max_protection,
                    entry->inheritance, entry->wired_count, entry->advice);
        }
}

void
uvm_whatis(uintptr_t addr, void (*pr)(const char *, ...))
{
        struct vm_map *map;

        for (map = kernel_map;;) {
                struct vm_map_entry *entry;

                if (!uvm_map_lookup_entry_bytree(map, (vaddr_t)addr, &entry)) {
                        break;
                }
                (*pr)("%p is %p+%zu from VMMAP %p\n",
                    (void *)addr, (void *)entry->start,
                    (size_t)(addr - (uintptr_t)entry->start), map);
                if (!UVM_ET_ISSUBMAP(entry)) {
                        break;
                }
                map = entry->object.sub_map;
        }
}

#endif /* DDB || DEBUGPRINT */