/*      $NetBSD: uvm_map.c,v 1.431 2026/06/23 19:29:12 skrll 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. 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 1.431 2026/06/23 19:29:12 skrll Exp $");

#include "opt_ddb.h"
#include "opt_pax.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/pool.h>
#include <sys/kernel.h>
#include <sys/mount.h>
#include <sys/pax.h>
#include <sys/vnode.h>
#include <sys/filedesc.h>
#include <sys/lockdebug.h>
#include <sys/atomic.h>
#include <sys/sysctl.h>
#ifndef __USER_VA0_IS_SAFE
#include <sys/kauth.h>
#include "opt_user_va0_disable_default.h"
#endif

#include <sys/shm.h>

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

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

#ifdef UVMHIST
#ifndef UVMHIST_MAPHIST_SIZE
#define UVMHIST_MAPHIST_SIZE 100
#endif
static struct kern_history_ent maphistbuf[UVMHIST_MAPHIST_SIZE];
UVMHIST_DEFINE(maphist) = UVMHIST_INITIALIZER(maphist, maphistbuf);
#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_tree)
UVMMAP_EVCNT_DEFINE(mlk_treeloop)

const char vmmapbsy[] = "vmmapbsy";

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

static struct pool_cache uvm_map_entry_cache;

#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

#ifndef __USER_VA0_IS_SAFE
#ifndef __USER_VA0_DISABLE_DEFAULT
#define __USER_VA0_DISABLE_DEFAULT 1
#endif
#ifdef USER_VA0_DISABLE_DEFAULT /* kernel config option overrides */
#undef __USER_VA0_DISABLE_DEFAULT
#define __USER_VA0_DISABLE_DEFAULT USER_VA0_DISABLE_DEFAULT
#endif
int user_va0_disable = __USER_VA0_DISABLE_DEFAULT;
#endif

/*
 * macros
 */

/*
 * uvm_map_align_va: round down or up virtual address
 */
static __inline void
uvm_map_align_va(vaddr_t *vap, vsize_t align, int topdown)
{

        KASSERT(powerof2(align));

        if (align != 0 && (*vap & (align - 1)) != 0) {
                if (topdown)
                        *vap = rounddown2(*vap, align);
                else
                        *vap = roundup2(*vap, align);
        }
}

/*
 * UVM_ET_ISCOMPATIBLE: check some requirements for map entry merging
 */
extern struct vm_map *pager_map;

#define UVM_ET_ISCOMPATIBLE(ent, type, uobj, meflags, \
    prot, maxprot, inh, adv, wire) \
        ((ent)->etype == (type) && \
        (((ent)->flags ^ (meflags)) & (UVM_MAP_NOMERGE)) == 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 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 *, int);
#define uvm_mapent_check(map)   _uvm_mapent_check(map, __LINE__)
#else /* defined(DEBUG) */
#define uvm_mapent_check(e)     /* nothing */
#endif /* defined(DEBUG) */

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,
                    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 *);

/*
 * Tree iteration.  We violate the rbtree(9) abstraction for various
 * things here.  Entries are ascending left to right, so, provided the
 * child entry in question exists:
 *
 *      LEFT_ENTRY(entry)->end <= entry->start
 *      entry->end <= RIGHT_ENTRY(entry)->start
 */
__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))

/*
 * These get filled in if/when SYSVSHM shared memory code is loaded
 *
 * We do this with function pointers rather the #ifdef SYSVSHM so the
 * SYSVSHM code can be loaded and unloaded
 */
void (*uvm_shmexit)(struct vmspace *) = NULL;
void (*uvm_shmfork)(struct vmspace *, struct vmspace *) = NULL;

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

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

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

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

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

static const rb_tree_ops_t uvm_map_tree_ops = {
        .rbto_compare_nodes = uvm_map_compare_nodes,
        .rbto_compare_key = uvm_map_compare_key,
        .rbto_node_offset = offsetof(struct vm_map_entry, rb_node),
        .rbto_context = NULL
};

/*
 * uvm_rb_gap: return the gap size between our entry and next entry.
 */
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;
                unsigned int which;

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

        entry->gap = entry->maxgap = uvm_rb_gap(entry);
        if (entry->prev != &map->header)
                entry->prev->gap = uvm_rb_gap(entry->prev);

        ret = rb_tree_insert_node(&map->rb_tree, entry);
        KASSERTMSG(ret == entry,
            "uvm_rb_insert: map %p: duplicate entry %p", map, ret);

        /*
         * 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);

        /*
         * 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 = rb_tree_iterate(&map->rb_tree, tmp, 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 = rb_tree_iterate(&map->rb_tree, tmp, 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 = 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) */

/*
 * vm_map_lock: acquire an exclusive (write) lock on a map.
 *
 * => 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)
{

        for (;;) {
                rw_enter(&map->lock, RW_WRITER);
                if (map->busy == NULL || 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 (!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)
{

        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)
{

        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)
{

        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)
{

        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(__func__); UVMHIST_CALLED(maphist);

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

        UVMHIST_LOG(maphist, "<- new entry=%#jx [kentry=%jd]", (uintptr_t)me,
            (map == kernel_map), 0, 0);
        return me;
}

/*
 * uvm_mapent_free: free map entry
 */

static void
uvm_mapent_free(struct vm_map_entry *me)
{
        UVMHIST_FUNC(__func__);
        UVMHIST_CALLARGS(maphist,"<- freeing map entry=%#jx [flags=%#jx]",
                (uintptr_t)me, me->flags, 0, 0);
        pool_cache_put(&uvm_map_entry_cache, 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, sizeof(*dst));
        dst->flags = 0;
}

#if defined(DEBUG)
static void
_uvm_mapent_check(const struct vm_map_entry *entry, 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, line %d", __func__, entry, 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)
{
        /*
         * first, init logging system.
         */

        UVMHIST_FUNC(__func__);
        UVMHIST_LINK_STATIC(maphist);
        UVMHIST_LINK_STATIC(pdhist);
        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);
}

/*
 * uvm_map_init_caches: init mapping system caches.
 */
void
uvm_map_init_caches(void)
{
        /*
         * initialize caches.
         */

        pool_cache_bootstrap(&uvm_map_entry_cache, sizeof(struct vm_map_entry),
            coherency_unit, 0, PR_LARGECACHE, "vmmpepl", 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 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(map, 0);
        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 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(map, 0);
        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");
}

/*
 *   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((size & PAGE_MASK) == 0);
        KASSERT((flags & UVM_FLAG_FIXED) == 0 || align == 0);

        /*
         * for pager_map, allocate the new entry first to avoid sleeping
         * for memory while we have the map locked.
         */

        new_entry = NULL;
        if (map == pager_map) {
                new_entry = uvm_mapent_alloc(map, (flags & UVM_FLAG_NOWAIT));
                if (__predict_false(new_entry == NULL))
                        return ENOMEM;
        }
        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) && (flags & UVM_FLAG_NOWAIT) == 0) {
                uvm_km_check_empty(map, *startp, *startp + size);
        }
#endif /* defined(DEBUG) */

        return error;
}

/*
 * uvm_map_prepare:
 *
 * called with map unlocked.
 * on success, returns the map locked.
 */

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(__func__);
        UVMHIST_CALLARGS(maphist, "(map=%#jx, start=%#jx, size=%jx, flags=%#jx)",
            (uintptr_t)map, start, size, flags);
        UVMHIST_LOG(maphist, "  uobj/offset %#jx/%jd", (uintptr_t)uobj,
            uoffset,0,0);

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

        KASSERT(doing_shutdown || curlwp != NULL);

        /*
         * 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=%#jx, max=%#jx",
                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) {
                        return EAGAIN;
                }
                vm_map_lock(map); /* could sleep here */
        }
        if (flags & UVM_FLAG_UNMAP) {
                KASSERT(flags & UVM_FLAG_FIXED);
                KASSERT((flags & UVM_FLAG_NOWAIT) == 0);

                /*
                 * Set prev_entry to what it will need to be after any existing
                 * entries are removed later in uvm_map_enter().
                 */

                if (uvm_map_lookup_entry(map, start, &prev_entry)) {
                        if (start == prev_entry->start)
                                prev_entry = prev_entry->prev;
                        else
                                UVM_MAP_CLIP_END(map, prev_entry, start);
                        SAVE_HINT(map, map->hint, prev_entry);
                }
        } else {
                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=%#jx",
                            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.
                 */

                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;
}

/*
 * uvm_map_enter:
 *
 * called with map locked.
 * unlock the map before returning.
 */

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, *dead_entries = 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);

        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(__func__);
        UVMHIST_CALLARGS(maphist, "(map=%#jx, start=%#jx, size=%ju, flags=%#jx)",
            (uintptr_t)map, start, size, flags);
        UVMHIST_LOG(maphist, "  uobj/offset %#jx/%jd", (uintptr_t)uobj,
            uoffset,0,0);

        KASSERT(map->hint == prev_entry); /* bimerge case assumes this */
        KASSERT(vm_map_locked_p(map));
        KASSERT((flags & (UVM_FLAG_NOWAIT | UVM_FLAG_UNMAP)) !=
                (UVM_FLAG_NOWAIT | UVM_FLAG_UNMAP));

        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;
        }

        /*
         * For mappings with unmap, remove any old entries now.  Adding the new
         * entry cannot fail because that can only happen if UVM_FLAG_NOWAIT
         * is set, and we do not support nowait and unmap together.
         */

        if (flags & UVM_FLAG_UNMAP) {
                KASSERT(flags & UVM_FLAG_FIXED);
                uvm_unmap_remove(map, start, start + size, &dead_entries, 0);
#ifdef DEBUG
                struct vm_map_entry *tmp_entry __diagused;
                bool rv __diagused;

                rv = uvm_map_lookup_entry(map, start, &tmp_entry);
                KASSERT(!rv);
                KASSERTMSG(prev_entry == tmp_entry,
                           "args %p prev_entry %p tmp_entry %p",
                           args, prev_entry, tmp_entry);
#endif
                SAVE_HINT(map, map->hint, prev_entry);
        }

        /*
         * 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, 0,
            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, 0,
            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 (uobj && uobj->pgops->pgo_detach)
                        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:
        vm_map_unlock(map);

        if (new_entry) {
                uvm_mapent_free(new_entry);
        }
        if (dead) {
                KDASSERT(merged);
                uvm_mapent_free(dead);
        }
        if (dead_entries)
                uvm_unmap_detach(dead_entries, 0);

        return error;
}

/*
 * uvm_map_lookup_entry_bytree: lookup an entry in tree
 *
 * => map must at least be read-locked by caller.
 *
 * => If address lies in an entry, set *entry to it and return true;
 *    then (*entry)->start <= address < (*entry)->end.

 * => If address is below all entries in map, return false and set
 *    *entry to &map->header.
 *
 * => Otherwise, return false and set *entry to the highest entry below
 *    address, so (*entry)->end <= address, and if (*entry)->next is
 *    not &map->header, address < (*entry)->next->start.
 */

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);

        KASSERT(rw_lock_held(&map->lock));

        while (cur) {
                KASSERT(prev == &map->header || prev->end <= address);
                KASSERT(prev == &map->header || prev->end <= cur->start);
                UVMMAP_EVCNT_INCR(mlk_treeloop);
                if (address >= cur->start) {
                        if (address < cur->end) {
                                *entry = cur;
                                return true;
                        }
                        prev = cur;
                        KASSERT(prev->end <= address);
                        cur = RIGHT_ENTRY(cur);
                        KASSERT(cur == NULL || prev->end <= cur->start);
                } else
                        cur = LEFT_ENTRY(cur);
        }
        KASSERT(prev == &map->header || prev->end <= address);
        KASSERT(prev->next == &map->header || address < prev->next->start);
        *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.
 *
 * => If address lies in an entry, set *entry to it and return true;
 *    then (*entry)->start <= address < (*entry)->end.

 * => If address is below all entries in map, return false and set
 *    *entry to &map->header.
 *
 * => Otherwise, return false and set *entry to the highest entry below
 *    address, so (*entry)->end <= address, and if (*entry)->next is
 *    not &map->header, address < (*entry)->next->start.
 */

bool
uvm_map_lookup_entry(struct vm_map *map, vaddr_t address,
    struct vm_map_entry **entry /* OUT */)
{
        struct vm_map_entry *cur;
        UVMHIST_FUNC(__func__);
        UVMHIST_CALLARGS(maphist,"(map=%#jx,addr=%#jx,ent=%#jx)",
            (uintptr_t)map, address, (uintptr_t)entry, 0);

        KASSERT(rw_lock_held(&map->lock));

        /*
         * 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).
         */

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

        /*
         * lookup in the tree.
         */

        UVMMAP_EVCNT_INCR(mlk_tree);
        if (__predict_true(uvm_map_lookup_entry_bytree(map, address, entry))) {
                SAVE_HINT(map, map->hint, *entry);
                UVMHIST_LOG(maphist,"<- search got it (%#jx)",
                    (uintptr_t)cur, 0, 0, 0);
                KDASSERT((*entry)->start <= address);
                KDASSERT(address < (*entry)->end);
                uvm_mapent_check(*entry);
                return (true);
        }

        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 flags, int topdown, struct vm_map_entry *entry)
{
        vaddr_t orig_start = *start;
        vaddr_t end;

#define INVARIANTS()                                                          \
        KASSERTMSG((topdown                                                   \
                ? *start <= orig_start                                        \
                : *start >= orig_start),                                      \
            "[%s] *start=%"PRIxVADDR" orig_start=%"PRIxVADDR                  \
            " length=%"PRIxVSIZE" uoffset=%#llx align=%"PRIxVSIZE             \
            " flags=%x entry@%p=[%"PRIxVADDR",%"PRIxVADDR")"                  \
            " ncolors=%d colormask=%x",                                       \
            topdown ? "topdown" : "bottomup", *start, orig_start,             \
            length, (unsigned long long)uoffset, align,                       \
            flags, entry, entry->start, entry->end,                           \
            uvmexp.ncolors, uvmexp.colormask)

        INVARIANTS();

#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);
                INVARIANTS();
        }
#endif
        if ((flags & UVM_FLAG_COLORMATCH) != 0) {
                KASSERT(align < uvmexp.ncolors);
                if (uvmexp.ncolors > 1) {
                        const u_int colormask = uvmexp.colormask;
                        const u_int colorsize = colormask + 1;
                        vaddr_t hint = atop(*start);
                        const u_int color = hint & colormask;
                        if (color != align) {
                                hint -= color;  /* adjust to color boundary */
                                KASSERT((hint & colormask) == 0);
                                if (topdown) {
                                        if (align > color)
                                                hint -= colorsize;
                                } else {
                                        if (align < color)
                                                hint += colorsize;
                                }
                                *start = ptoa(hint + align); /* adjust to color */
                                INVARIANTS();
                        }
                }
        } else {
                KASSERT(powerof2(align));
                uvm_map_align_va(start, align, topdown);
                INVARIANTS();
                /*
                 * 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.
         *
         * XXX Should this use vm_map_max(map) as the max?
         */

        if (length > __type_max(vaddr_t) - *start)
                return (-1);
        end = *start + length;

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

        return (0);

#undef INVARIANTS
}

static void
uvm_findspace_invariants(struct vm_map *map, vaddr_t orig_hint, vaddr_t length,
    struct uvm_object *uobj, voff_t uoffset, vsize_t align, int flags,
    vaddr_t hint, struct vm_map_entry *entry, int line)
{
        const int topdown = map->flags & VM_MAP_TOPDOWN;
        const int hint_location_ok =
                topdown ? hint <= orig_hint
                        : hint >= orig_hint;

        KASSERTMSG(hint_location_ok,
            "%s map=%p hint=%#" PRIxVADDR " %s orig_hint=%#" PRIxVADDR
            " length=%#" PRIxVSIZE " uobj=%p uoffset=%#llx align=%" PRIxVSIZE
            " flags=%#x entry@%p=[%" PRIxVADDR ",%" PRIxVADDR ")"
            " entry->next@%p=[%" PRIxVADDR ",%" PRIxVADDR ")"
            " (uvm_map_findspace line %d)",
            topdown ? "topdown" : "bottomup",
            map, hint, topdown ? ">" : "<", orig_hint,
            length, uobj, (unsigned long long)uoffset, align,
            flags, entry, entry ? entry->start : 0, entry ? entry->end : 0,
            entry ? entry->next : NULL,
            entry && entry->next ? entry->next->start : 0,
            entry && entry->next ? entry->next->end : 0,
            line);
}

/*
 * 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)
{
#define INVARIANTS()                                                          \
        uvm_findspace_invariants(map, orig_hint, length, uobj, uoffset, align,\
            flags, hint, entry, __LINE__)
        struct vm_map_entry *entry = NULL;
        struct vm_map_entry *child, *prev, *tmp;
        vaddr_t orig_hint __diagused;
        const int topdown = map->flags & VM_MAP_TOPDOWN;
        int avail;
        UVMHIST_FUNC(__func__);
        UVMHIST_CALLARGS(maphist, "(map=%#jx, hint=%#jx, len=%ju, flags=%#jx...",
            (uintptr_t)map, hint, length, flags);
        UVMHIST_LOG(maphist, " uobj=%#jx, uoffset=%#jx, align=%#jx)",
            (uintptr_t)uobj, uoffset, align, 0);

        KASSERT((flags & UVM_FLAG_COLORMATCH) != 0 || powerof2(align));
        KASSERT((flags & UVM_FLAG_COLORMATCH) == 0 || align < uvmexp.ncolors);
        KASSERT((flags & UVM_FLAG_FIXED) == 0 || align == 0);

        uvm_map_check(map, "map_findspace entry");

        /*
         * Clamp the hint to the VM map's min/max address, and remmeber
         * the clamped original hint.  Remember the original hint,
         * clamped to the min/max address.  If we are aligning, then we
         * may have to try again with no alignment constraint if we
         * fail the first time.
         *
         * We use the original hint to verify later that the search has
         * been monotonic -- that is, nonincreasing or nondecreasing,
         * according to topdown or !topdown respectively.  But the
         * clamping is not monotonic.
         */
        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 %#jx > range [%#jx->%#jx]",
                    hint, vm_map_min(map), vm_map_max(map), 0);
                return (NULL);
        }
        orig_hint = hint;
        INVARIANTS();

        UVMHIST_LOG(maphist,"<- VA %#jx vs range [%#jx->%#jx]",
            hint, vm_map_min(map), vm_map_max(map), 0);

        /*
         * hint may not be aligned properly; we need round up or down it
         * before proceeding further.
         */
        if ((flags & UVM_FLAG_COLORMATCH) == 0) {
                uvm_map_align_va(&hint, align, topdown);
                INVARIANTS();
        }

        UVMHIST_LOG(maphist,"<- VA %#jx vs range [%#jx->%#jx]",
            hint, vm_map_min(map), vm_map_max(map), 0);
        /*
         * 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 == (topdown ? vm_map_max(map) : vm_map_min(map))) {
                /*
                 * The uvm_map_findspace algorithm is monotonic -- for
                 * topdown VM it starts with a high hint and returns a
                 * lower free address; for !topdown VM it starts with a
                 * low hint and returns a higher free address.  As an
                 * optimization, start with the first (highest for
                 * topdown, lowest for !topdown) free address.
                 *
                 * XXX This `optimization' probably doesn't actually do
                 * much in practice unless userland explicitly passes
                 * the VM map's minimum or maximum address, which
                 * varies from machine to machine (VM_MAX/MIN_ADDRESS,
                 * e.g. 0x7fbfdfeff000 on amd64 but 0xfffffffff000 on
                 * aarch64) and may vary according to other factors
                 * like sysctl vm.user_va0_disable.  In particular, if
                 * the user specifies 0 as a hint to mmap, then mmap
                 * will choose a default address which is usually _not_
                 * VM_MAX/MIN_ADDRESS but something else instead like
                 * VM_MAX_ADDRESS - stack size - guard page overhead,
                 * in which case this branch is never hit.
                 *
                 * In fact, this branch appears to have been broken for
                 * two decades between when topdown was introduced in
                 * ~2003 and when it was adapted to handle the topdown
                 * case without violating the monotonicity assertion in
                 * 2022.  Maybe Someone^TM should either ditch the
                 * optimization or find a better way to do it.
                 */
                entry = map->first_free;
        } else if (uvm_map_lookup_entry(map, hint, &entry)) {
                KASSERT(entry->start <= hint);
                KASSERT(hint < entry->end);
                /* "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 {
                KASSERT(entry == &map->header || entry->end <= hint);
                KASSERT(entry->next == &map->header ||
                    hint < entry->next->start);
                if (flags & UVM_FLAG_FIXED) {
                        if (entry->next->start >= hint &&
                            length <= entry->next->start - 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.
                         */
                        avail = uvm_map_space_avail(&hint, length,
                            uoffset, align, flags, topdown, entry);
                        INVARIANTS();
                        switch (avail) {
                        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 */
        if (topdown) {
                KASSERTMSG(entry->next->start >= vm_map_min(map),
                    "map=%p entry=%p entry->next=%p"
                    " entry->next->start=0x%"PRIxVADDR" min=0x%"PRIxVADDR,
                    map, entry, entry->next,
                    entry->next->start, vm_map_min(map));
                if (length > entry->next->start - vm_map_min(map))
                        hint = vm_map_min(map); /* XXX goto wraparound? */
                else
                        hint = MIN(orig_hint, entry->next->start - length);
                KASSERT(hint >= vm_map_min(map));
        } else {
                hint = entry->end;
        }
        INVARIANTS();
        avail = uvm_map_space_avail(&hint, length, uoffset, align, flags,
            topdown, entry);
        INVARIANTS();
        switch (avail) {
        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;
                }
                INVARIANTS();
                avail = uvm_map_space_avail(&hint, length, uoffset, align,
                    flags, topdown, tmp);
                INVARIANTS();
                switch (avail) {
                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;
        }
        INVARIANTS();
        avail = uvm_map_space_avail(&hint, length, uoffset, align,
            flags, topdown, prev);
        INVARIANTS();
        switch (avail) {
        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);
                KASSERTMSG(tmp->maxgap >= length,
                    "tmp->maxgap=0x%"PRIxVSIZE" length=0x%"PRIxVSIZE,
                    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;
        }
        INVARIANTS();
        avail = uvm_map_space_avail(&hint, length, uoffset, align,
            flags, topdown, tmp);
        INVARIANTS();
        switch (avail) {
        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
         */

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

                /* See if it fits. */
                avail = uvm_map_space_avail(&hint, length, uoffset, align,
                    flags, topdown, entry);
                INVARIANTS();
                switch (avail) {
                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=%#jx)", hint, 0,0,0);
        INVARIANTS();
        KASSERT(entry->end <= hint);
        KASSERT(hint <= entry->next->start);
        KASSERT(length <= entry->next->start - hint);
        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);
#undef INVARIANTS
}

/*
 *   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 */, int flags)
{
        struct vm_map_entry *entry, *first_entry, *next;
        vaddr_t len;
        UVMHIST_FUNC(__func__);
        UVMHIST_CALLARGS(maphist,"(map=%#jx, start=%#jx, end=%#jx)",
            (uintptr_t)map, start, end, 0);
        VM_MAP_RANGE_CHECK(map, start, end);

        KASSERT(vm_map_locked_p(map));

        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);
                /* 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_STATIC) == 0);

                UVM_MAP_CLIP_END(map, entry, end);
                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.
                         */
                        KASSERT(vm_map_pmap(map) == pmap_kernel());

                        uvm_km_pgremove_intrsafe(map, entry->start, entry->end);
                } else if (UVM_ET_ISOBJ(entry) &&
                           UVM_OBJ_IS_KERN_OBJECT(entry->object.uvm_obj)) {
                        panic("%s: kernel object %p %p\n",
                            __func__, map, entry);
                } else if (UVM_ET_ISOBJ(entry) || entry->aref.ar_amap) {
                        /*
                         * remove mappings the standard way.  lock object
                         * and/or amap to ensure vm_page state does not
                         * change while in pmap_remove().
                         */

#ifdef __HAVE_UNLOCKED_PMAP /* XXX temporary */
                        uvm_map_lock_entry(entry, RW_WRITER);
#else
                        uvm_map_lock_entry(entry, RW_READER);
#endif
                        pmap_remove(map->pmap, entry->start, entry->end);

                        /*
                         * note: if map is dying, leave pmap_update() for
                         * later.  if the map is to be reused (exec) then
                         * pmap_update() will be called.  if the map is
                         * being disposed of (exit) then pmap_destroy()
                         * will be called.
                         */

                        if ((map->flags & VM_MAP_DYING) == 0) {
                                pmap_update(vm_map_pmap(map));
                        } else {
                                KASSERT(vm_map_pmap(map) != pmap_kernel());
                        }

                        uvm_map_unlock_entry(entry);
                }

#if defined(UVMDEBUG)
                /*
                 * 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("%s: %#"PRIxVADDR" has mapping",
                                    __func__, va);
                        }
                }

                if (VM_MAP_IS_KERNEL(map) && (flags & UVM_FLAG_NOWAIT) == 0) {
                        uvm_km_check_empty(map, entry->start, entry->end);
                }
#endif /* defined(UVMDEBUG) */

                /*
                 * 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 %#jx",
                    (uintptr_t)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;
        }

        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(__func__); UVMHIST_CALLED(maphist);

        while (first_entry) {
                KASSERT(!VM_MAPENT_ISWIRED(first_entry));
                UVMHIST_LOG(maphist,
                    "  detach %#jx: amap=%#jx, obj=%#jx, submap?=%jd",
                    (uintptr_t)first_entry,
                    (uintptr_t)first_entry->aref.ar_amap,
                    (uintptr_t)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 UVM_FLAG_COLORMATCH or 0 */)
{
        UVMHIST_FUNC(__func__);
        UVMHIST_CALLARGS(maphist, "(map=%#jx, size=%#jx, offset=%#jx, addr=%#jx)",
            (uintptr_t)map, size, offset, (uintptr_t)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=%#jx)", *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) {
                UVM_MAP_CLIP_END(map, oldent, end);
        }
        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=%#"PRIxVADDR
                                    ", tmpent->end=%#"PRIxVADDR
                                    ", end=%#"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
 *      UVM_EXTRACT_PROT_ALL: set prot to UVM_PROT_ALL 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 __unused;
        int nchain, error, copy_ok;
        vsize_t nsize;
        UVMHIST_FUNC(__func__);
        UVMHIST_CALLARGS(maphist,"(srcmap=%#jx,start=%#jx, len=%#jx",
            (uintptr_t)srcmap, start, len, 0);
        UVMHIST_LOG(maphist," ...,dstmap=%#jx, flags=%#jx)",
            (uintptr_t)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.
         */

        KASSERTMSG((start & PAGE_MASK) == 0, "start=0x%"PRIxVADDR, start);
        KASSERTMSG((len & PAGE_MASK) == 0, "len=0x%"PRIxVADDR, len);
        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,
                    atop(start) & uvmexp.colormask, &dstaddr,
                    UVM_FLAG_COLORMATCH))
                        return (ENOMEM);
                KASSERT((atop(start ^ dstaddr) & uvmexp.colormask) == 0);
                *dstaddrp = dstaddr;    /* pass address back to caller */
                UVMHIST_LOG(maphist, "  dstaddr=%#jx", 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);
                        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);

                /* 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;
                if (flags & UVM_EXTRACT_PROT_ALL) {
                        newentry->protection = newentry->max_protection =
                            UVM_PROT_ALL;
                } else {
                        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 deferred 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) {
#ifdef __HAVE_UNLOCKED_PMAP /* XXX temporary */
                                uvm_map_lock_entry(entry, RW_WRITER);
#else
                                uvm_map_lock_entry(entry, RW_READER);
#endif
                                pmap_remove(srcmap->pmap, entry->start,
                                                entry->end);
                                uvm_map_unlock_entry(entry);
                                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;
        int error;

        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);
                UVM_MAP_CLIP_END(map, entry, end);      /* 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);

        return error;
}

/*
 * uvm_map_protect_user: change map protection on behalf of the user.
 * Enforces PAX settings as necessary.
 */
int
uvm_map_protect_user(struct lwp *l, vaddr_t start, vaddr_t end,
    vm_prot_t new_prot)
{
        int error;

        if ((error = PAX_MPROTECT_VALIDATE(l, new_prot)))
                return error;

        return uvm_map_protect(&l->l_proc->p_vmspace->vm_map, start, end,
            new_prot, false);
}


/*
 * 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(__func__);
        UVMHIST_CALLARGS(maphist,"(map=%#jx,start=%#jx,end=%#jx,new_prot=%#jx)",
            (uintptr_t)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);
        } 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);
                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! */
#ifdef __HAVE_UNLOCKED_PMAP /* XXX temporary */
                        uvm_map_lock_entry(current, RW_WRITER);
#else
                        uvm_map_lock_entry(current, RW_READER);
#endif
                        pmap_protect(map->pmap, current->start, current->end,
                            current->protection & MASK(current));
                        uvm_map_unlock_entry(current);

                        /*
                         * 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(current) == 0 &&
                    old_prot == VM_PROT_NONE &&
                    new_prot != VM_PROT_NONE) {

                        /*
                         * We must call pmap_update() here because the
                         * pmap_protect() call above might have removed some
                         * pmap entries and uvm_map_pageable() might create
                         * some new pmap entries that rely on the prior
                         * removals being completely finished.
                         */

                        pmap_update(map->pmap);

                        if (uvm_map_pageable(map, current->start,
                            current->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=%jd",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(__func__);
        UVMHIST_CALLARGS(maphist,"(map=%#jx,start=%#jx,end=%#jx,new_inh=%#jx)",
            (uintptr_t)map, start, end, new_inheritance);

        switch (new_inheritance) {
        case MAP_INHERIT_NONE:
        case MAP_INHERIT_COPY:
        case MAP_INHERIT_SHARE:
        case MAP_INHERIT_ZERO:
                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);
        } else {
                entry = temp_entry->next;
        }
        while ((entry != &map->header) && (entry->start < end)) {
                UVM_MAP_CLIP_END(map, entry, end);
                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(__func__);
        UVMHIST_CALLARGS(maphist,"(map=%#jx,start=%#jx,end=%#jx,new_adv=%#jx)",
            (uintptr_t)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);
        } else {
                entry = temp_entry->next;
        }

        /*
         * XXXJRT: disallow holes?
         */

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

                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(__func__);
        UVMHIST_CALLARGS(maphist,"(map=%#jx,start=%#jx,end=%#jx)",
            (uintptr_t)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);
                /*
                 * For now, we handle only the easy but commonly-requested case.
                 * ie. start prefetching of backing uobj pages.
                 *
                 * XXX It might be useful to pmap_enter() the already-in-core
                 * pages by inventing a "weak" mode for uvm_fault() which would
                 * only do the PGO_LOCKED pgo_get().
                 */
                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(__func__);
        UVMHIST_CALLARGS(maphist,"(map=%#jx,start=%#jx,end=%#jx,new_pageable=%ju)",
            (uintptr_t)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;

        if (start == end) {             /* nothing required */
                if ((lockflags & UVM_LK_EXIT) == 0)
                        vm_map_unlock(map);

                UVMHIST_LOG(maphist,"<- done (nothing)",0,0,0,0);
                return 0;
        }

        /*
         * handle wiring and unwiring separately.
         */

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

                /*
                 * 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);
                        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);
                UVM_MAP_CLIP_END(map, entry, end);
                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=%jd)", 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(__func__);
        UVMHIST_CALLARGS(maphist,"(map=%#jx,flags=%#jx)", (uintptr_t)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=%jd)", 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 have map 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(__func__);
        UVMHIST_CALLARGS(maphist,"(map=%#jx,start=%#jx,end=%#jx,flags=%#jx)",
            (uintptr_t)map, start, end, flags);

        KASSERT((flags & (PGO_FREE|PGO_DEACTIVATE)) !=
                (PGO_FREE|PGO_DEACTIVATE));

        vm_map_lock(map);
        VM_MAP_RANGE_CHECK(map, start, end);
        if (!uvm_map_lookup_entry(map, start, &entry)) {
                vm_map_unlock(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(map);
                        return EINVAL;
                }
                if ((flags & PGO_FREE) != 0 && VM_MAPENT_ISWIRED(entry)) {
                        vm_map_unlock(map);
                        return EBUSY;
                }
                if (end <= current->end) {
                        break;
                }
                if (current->end != current->next->start) {
                        vm_map_unlock(map);
                        return EFAULT;
                }
        }

        vm_map_busy(map);
        vm_map_unlock(map);
        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;

                offset = start - current->start;
                size = MIN(end, current->end) - start;

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

                        KASSERT(anon->an_lock == amap->am_lock);
                        pg = anon->an_page;
                        if (pg == NULL) {
                                continue;
                        }
                        if (pg->flags & PG_BUSY) {
                                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.
                                 */

                                if (pg->loan_count != 0 ||
                                    pg->wire_count != 0) {
                                        continue;
                                }
                                KASSERT(pg->uanon == anon);
                                uvm_pagelock(pg);
                                uvm_pagedeactivate(pg);
                                uvm_pageunlock(pg);
                                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) {
                                        continue;
                                }
                                amap_unadd(&current->aref, offset);
                                refs = --anon->an_ref;
                                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) {
                        rw_enter(uobj->vmobjlock, RW_WRITER);
                        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_unbusy(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, bool topdown)
{
        struct vmspace *vm;
        UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);

        vm = kmem_alloc(sizeof(*vm), KM_SLEEP);
        uvmspace_init(vm, NULL, vmin, vmax, topdown);
        UVMHIST_LOG(maphist,"<- done (vm=%#jx)", (uintptr_t)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, bool topdown)
{
        UVMHIST_FUNC(__func__);
        UVMHIST_CALLARGS(maphist, "(vm=%#jx, pmap=%#jx, vmin=%#jx, vmax=%#jx",
            (uintptr_t)vm, (uintptr_t)pmap, vmin, vmax);
        UVMHIST_LOG(maphist, "   topdown=%ju)", topdown, 0, 0, 0);

        memset(vm, 0, sizeof(*vm));
        uvm_map_setup(&vm->vm_map, vmin, vmax, VM_MAP_PAGEABLE
            | (topdown ? VM_MAP_TOPDOWN : 0)
            );
        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, bool topdown)
{
        struct proc *p = l->l_proc;
        struct vmspace *nvm, *ovm = p->p_vmspace;
        struct vm_map *map;
        int flags;

        KASSERT(ovm != NULL);
#ifdef __HAVE_CPU_VMSPACE_EXEC
        cpu_vmspace_exec(l, start, end);
#endif

        /*
         * If p is the only process using the vmspace, we can safely
         * recycle it for the program that is being exec'd, rather than
         * allocate a new vmspace -- but we have to make sure it's
         * empty first.
         */
        map = &ovm->vm_map;
        if (ovm->vm_refcnt == 1 && map->nentries != 0) {
                /*
                 * SYSV SHM semantics require us to kill all segments on an exec
                 */
                if (uvm_shmexit && ovm->vm_shm)
                        (*uvm_shmexit)(ovm);

                /*
                 * 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.
                 *
                 * XXX set VM_MAP_DYING for the duration, so pmap_update()
                 * is not called until the pmap has been totally cleared out
                 * after pmap_remove_all(), or it can confuse some pmap
                 * implementations.  it would be nice to handle this by
                 * deferring the pmap_update() while it is known the address
                 * space is not visible to any user LWP other than curlwp,
                 * but there isn't an elegant way of inferring that right
                 * now.
                 */
                flags = pmap_remove_all(map->pmap) ? UVM_FLAG_VAONLY : 0;
                map->flags |= VM_MAP_DYING;
                uvm_unmap1(map, vm_map_min(map), vm_map_max(map), flags);
                map->flags &= ~VM_MAP_DYING;
                pmap_update(map->pmap);
                KASSERT(map->header.prev == &map->header);
                KASSERT(map->nentries == 0);
        }

        if (ovm->vm_refcnt == 1) {
                /*
                 * The vmspace is not shared and is empty (if it
                 * weren't, we would have emptied it above).
                 *
                 * Resize the map and set topdown as appropriate.
                 */
                KASSERT(map->nentries == 0);
                vm_map_setmin(map, start);
                vm_map_setmax(map, end);
                if (topdown) {
                        map->flags |= VM_MAP_TOPDOWN;
                } else {
                        map->flags &= ~VM_MAP_TOPDOWN;
                }
        } 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, topdown);

                /*
                 * 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 reference to a vmspace.
 */

void
uvmspace_addref(struct vmspace *vm)
{

        KASSERT((vm->vm_map.flags & VM_MAP_DYING) == 0);
        KASSERT(vm->vm_refcnt > 0);
        atomic_inc_uint(&vm->vm_refcnt);
}

/*
 * 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 flags;

        UVMHIST_FUNC(__func__);
        UVMHIST_CALLARGS(maphist,"(vm=%#jx) ref=%jd", (uintptr_t)vm,
            vm->vm_refcnt, 0, 0);

        membar_release();
        if (atomic_dec_uint_nv(&vm->vm_refcnt) > 0)
                return;
        membar_acquire();

        /*
         * 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;
        flags = pmap_remove_all(map->pmap) ? UVM_FLAG_VAONLY : 0;

        /* Get rid of any SYSV shared memory segments. */
        if (uvm_shmexit && vm->vm_shm != NULL)
                (*uvm_shmexit)(vm);

        if (map->nentries) {
                vm_map_lock(map);
                uvm_unmap_remove(map, vm_map_min(map), vm_map_max(map),
                    &dead_entries, flags);
                vm_map_unlock(map);
                if (dead_entries != NULL)
                        uvm_unmap_detach(dead_entries, 0);
        }
        KASSERT(map->nentries == 0);
        KASSERT(map->size == 0);

        mutex_destroy(&map->misc_lock);
        rw_destroy(&map->lock);
        cv_destroy(&map->cv);
        pmap_destroy(map->pmap);
        kmem_free(vm, sizeof(*vm));
}

static struct vm_map_entry *
uvm_mapent_clone(struct vm_map *new_map, struct vm_map_entry *old_entry,
    int flags)
{
        struct vm_map_entry *new_entry;

        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, flags);

        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);

        return new_entry;
}

/*
 * share the mapping: this means we want the old and
 * new entries to share amaps and backing objects.
 */
static void
uvm_mapent_forkshared(struct vm_map *new_map, struct vm_map *old_map,
    struct vm_map_entry *old_entry)
{
        /*
         * 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??? */
        }

        uvm_mapent_clone(new_map, old_entry, AMAP_SHARED);
}


static void
uvm_mapent_forkcopy(struct vm_map *new_map, struct vm_map *old_map,
    struct vm_map_entry *old_entry)
{
        struct vm_map_entry *new_entry;

        /*
         * 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_clone(new_map, old_entry, 0);

        new_entry->etype |=
            (UVM_ET_COPYONWRITE|UVM_ET_NEEDSCOPY);

        /*
         * 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 referring 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) {
#ifdef __HAVE_UNLOCKED_PMAP /* XXX temporary */
                                uvm_map_lock_entry(old_entry, RW_WRITER);
#else
                                uvm_map_lock_entry(old_entry, RW_READER);
#endif
                                pmap_protect(old_map->pmap,
                                    old_entry->start, old_entry->end,
                                    old_entry->protection & ~VM_PROT_WRITE);
                                uvm_map_unlock_entry(old_entry);
                        }
                        old_entry->etype |= UVM_ET_NEEDSCOPY;
                }
        }
}

/*
 * zero the mapping: the new entry will be zero initialized
 */
static void
uvm_mapent_forkzero(struct vm_map *new_map, struct vm_map *old_map,
    struct vm_map_entry *old_entry)
{
        struct vm_map_entry *new_entry;

        new_entry = uvm_mapent_clone(new_map, old_entry, 0);

        new_entry->etype |=
            (UVM_ET_COPYONWRITE|UVM_ET_NEEDSCOPY);

        if (new_entry->aref.ar_amap) {
                uvm_map_unreference_amap(new_entry, 0);
                new_entry->aref.ar_pageoff = 0;
                new_entry->aref.ar_amap = NULL;
        }

        if (UVM_ET_ISOBJ(new_entry)) {
                if (new_entry->object.uvm_obj->pgops->pgo_detach)
                        new_entry->object.uvm_obj->pgops->pgo_detach(
                            new_entry->object.uvm_obj);
                new_entry->object.uvm_obj = NULL;
                new_entry->offset = 0;
                new_entry->etype &= ~UVM_ET_OBJ;
        }
}

/*
 *   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;
        UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);

        vm_map_lock(old_map);

        vm2 = uvmspace_alloc(vm_map_min(old_map), vm_map_max(old_map),
            vm1->vm_map.flags & VM_MAP_TOPDOWN);
        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:
                        uvm_mapent_forkshared(new_map, old_map, old_entry);
                        break;

                case MAP_INHERIT_COPY:
                        uvm_mapent_forkcopy(new_map, old_map, old_entry);
                        break;

                case MAP_INHERIT_ZERO:
                        uvm_mapent_forkzero(new_map, old_map, old_entry);
                        break;
                default:
                        KASSERT(0);
                        break;
                }
                old_entry = old_entry->next;
        }

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

        if (uvm_shmfork && vm1->vm_shm)
                (*uvm_shmfork)(vm1, vm2);

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

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


/*
 * 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 (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(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(prev);
                        merged++;
                }
        }

        return merged;
}

/*
 * 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)
{

        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;

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

/*
 *   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;
        UVMHIST_FUNC(__func__);
        UVMHIST_CALLARGS(maphist, "  (map=%#jx, start=%#jx, end=%#jx)",
            (uintptr_t)map, start, end, 0);

        KASSERTMSG(start < end,
            "%s: map %p: start %#jx < end %#jx", __func__, map,
            (uintmax_t)start, (uintmax_t)end);
        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...
         */
        vm_map_lock(map);
        uvm_unmap_remove(map, start, end, &dead_entries, flags);
        vm_map_unlock(map);

        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
 */

void
uvm_map_reference(struct vm_map *map)
{

        atomic_inc_uint(&map->ref_count);
}

void
uvm_map_lock_entry(struct vm_map_entry *entry, krw_t op)
{

        if (entry->aref.ar_amap != NULL) {
                amap_lock(entry->aref.ar_amap, op);
        }
        if (UVM_ET_ISOBJ(entry)) {
                rw_enter(entry->object.uvm_obj->vmobjlock, op);
        }
}

void
uvm_map_unlock_entry(struct vm_map_entry *entry)
{

        if (UVM_ET_ISOBJ(entry)) {
                rw_exit(entry->object.uvm_obj->vmobjlock);
        }
        if (entry->aref.ar_amap != NULL) {
                amap_unlock(entry->aref.ar_amap);
        }
}

#define UVM_VOADDR_TYPE_MASK    0x3UL
#define UVM_VOADDR_TYPE_UOBJ    0x1UL
#define UVM_VOADDR_TYPE_ANON    0x2UL
#define UVM_VOADDR_OBJECT_MASK  ~UVM_VOADDR_TYPE_MASK

#define UVM_VOADDR_GET_TYPE(voa)                                        \
        ((voa)->object & UVM_VOADDR_TYPE_MASK)
#define UVM_VOADDR_GET_OBJECT(voa)                                      \
        ((voa)->object & UVM_VOADDR_OBJECT_MASK)
#define UVM_VOADDR_SET_OBJECT(voa, obj, type)                           \
do {                                                                    \
        KASSERT(((uintptr_t)(obj) & UVM_VOADDR_TYPE_MASK) == 0);        \
        (voa)->object = ((uintptr_t)(obj)) | (type);                    \
} while (/*CONSTCOND*/0)

#define UVM_VOADDR_GET_UOBJ(voa)                                        \
        ((struct uvm_object *)UVM_VOADDR_GET_OBJECT(voa))
#define UVM_VOADDR_SET_UOBJ(voa, uobj)                                  \
        UVM_VOADDR_SET_OBJECT(voa, uobj, UVM_VOADDR_TYPE_UOBJ)

#define UVM_VOADDR_GET_ANON(voa)                                        \
        ((struct vm_anon *)UVM_VOADDR_GET_OBJECT(voa))
#define UVM_VOADDR_SET_ANON(voa, anon)                                  \
        UVM_VOADDR_SET_OBJECT(voa, anon, UVM_VOADDR_TYPE_ANON)

/*
 * uvm_voaddr_acquire: returns the virtual object address corresponding
 * to the specified virtual address.
 *
 * => resolves COW so the true page identity is tracked.
 *
 * => acquires a reference on the page's owner (uvm_object or vm_anon)
 */
bool
uvm_voaddr_acquire(struct vm_map * const map, vaddr_t const va,
    struct uvm_voaddr * const voaddr)
{
        struct vm_map_entry *entry;
        struct vm_anon *anon = NULL;
        bool result = false;
        bool exclusive = false;
        void (*unlock_fn)(struct vm_map *);

        UVMHIST_FUNC(__func__); UVMHIST_CALLED(maphist);
        UVMHIST_LOG(maphist,"(map=%#jx,va=%#jx)", (uintptr_t)map, va, 0, 0);

        const vaddr_t start = trunc_page(va);
        const vaddr_t end = round_page(va+1);

 lookup_again:
        if (__predict_false(exclusive)) {
                vm_map_lock(map);
                unlock_fn = vm_map_unlock;
        } else {
                vm_map_lock_read(map);
                unlock_fn = vm_map_unlock_read;
        }

        if (__predict_false(!uvm_map_lookup_entry(map, start, &entry))) {
                unlock_fn(map);
                UVMHIST_LOG(maphist,"<- done (no entry)",0,0,0,0);
                return false;
        }

        if (__predict_false(entry->protection == VM_PROT_NONE)) {
                unlock_fn(map);
                UVMHIST_LOG(maphist,"<- done (PROT_NONE)",0,0,0,0);
                return false;
        }

        /*
         * We have a fast path for the common case of "no COW resolution
         * needed" whereby we have taken a read lock on the map and if
         * we don't encounter any need to create a vm_anon then great!
         * But if we do, we loop around again, instead taking an exclusive
         * lock so that we can perform the fault.
         *
         * In the event that we have to resolve the fault, we do nearly the
         * same work as uvm_map_pageable() does:
         *
         * 1: holding the write lock, we create any anonymous maps that need
         *    to be created.  however, we do NOT need to clip the map entries
         *    in this case.
         *
         * 2: we downgrade to a read lock, and call uvm_fault_wire to fault
         *    in the page (assuming the entry is not already wired).  this
         *    is done because we need the vm_anon to be present.
         */
        if (__predict_true(!VM_MAPENT_ISWIRED(entry))) {

                bool need_fault = false;

                /*
                 * perform the action 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.
                 */
                if (__predict_false(UVM_ET_ISSUBMAP(entry))) {
                        unlock_fn(map);
                        UVMHIST_LOG(maphist,"<- done (submap)",0,0,0,0);
                        return false;
                }
                if (__predict_false(UVM_ET_ISNEEDSCOPY(entry) &&
                    ((entry->max_protection & VM_PROT_WRITE) ||
                     (entry->object.uvm_obj == NULL)))) {
                        if (!exclusive) {
                                /* need to take the slow path */
                                KASSERT(unlock_fn == vm_map_unlock_read);
                                vm_map_unlock_read(map);
                                exclusive = true;
                                goto lookup_again;
                        }
                        need_fault = true;
                        amap_copy(map, entry, 0, start, end);
                        /* XXXCDC: wait OK? */
                }

                /*
                 * do a quick check to see if the fault has already
                 * been resolved to the upper layer.
                 */
                if (__predict_true(entry->aref.ar_amap != NULL &&
                                   need_fault == false)) {
                        amap_lock(entry->aref.ar_amap, RW_WRITER);
                        anon = amap_lookup(&entry->aref, start - entry->start);
                        if (__predict_true(anon != NULL)) {
                                /* amap unlocked below */
                                goto found_anon;
                        }
                        amap_unlock(entry->aref.ar_amap);
                        need_fault = true;
                }

                /*
                 * we predict this test as false because if we reach
                 * this point, then we are likely dealing with a
                 * shared memory region backed by a uvm_object, in
                 * which case a fault to create the vm_anon is not
                 * necessary.
                 */
                if (__predict_false(need_fault)) {
                        if (exclusive) {
                                vm_map_busy(map);
                                vm_map_unlock(map);
                                unlock_fn = vm_map_unbusy;
                        }

                        if (uvm_fault_wire(map, start, end,
                                           entry->max_protection, 1)) {
                                /* wiring failed */
                                unlock_fn(map);
                                UVMHIST_LOG(maphist,"<- done (wire failed)",
                                            0,0,0,0);
                                return false;
                        }

                        /*
                         * now that we have resolved the fault, we can unwire
                         * the page.
                         */
                        if (exclusive) {
                                vm_map_lock(map);
                                vm_map_unbusy(map);
                                unlock_fn = vm_map_unlock;
                        }

                        uvm_fault_unwire_locked(map, start, end);
                }
        }

        /* check the upper layer */
        if (entry->aref.ar_amap) {
                amap_lock(entry->aref.ar_amap, RW_WRITER);
                anon = amap_lookup(&entry->aref, start - entry->start);
                if (anon) {
 found_anon:            KASSERT(anon->an_lock == entry->aref.ar_amap->am_lock);
                        anon->an_ref++;
                        rw_obj_hold(anon->an_lock);
                        KASSERT(anon->an_ref != 0);
                        UVM_VOADDR_SET_ANON(voaddr, anon);
                        voaddr->offset = va & PAGE_MASK;
                        result = true;
                }
                amap_unlock(entry->aref.ar_amap);
        }

        /* check the lower layer */
        if (!result && UVM_ET_ISOBJ(entry)) {
                struct uvm_object *uobj = entry->object.uvm_obj;

                KASSERT(uobj != NULL);
                (*uobj->pgops->pgo_reference)(uobj);
                UVM_VOADDR_SET_UOBJ(voaddr, uobj);
                voaddr->offset = entry->offset + (va - entry->start);
                result = true;
        }

        unlock_fn(map);

        if (result) {
                UVMHIST_LOG(maphist,
                    "<- done OK (type=%jd,owner=%#jx,offset=%#jx)",
                    UVM_VOADDR_GET_TYPE(voaddr),
                    UVM_VOADDR_GET_OBJECT(voaddr),
                    voaddr->offset, 0);
        } else {
                UVMHIST_LOG(maphist,"<- done (failed)",0,0,0,0);
        }

        return result;
}

/*
 * uvm_voaddr_release: release the references held by the
 * virtual object address.
 */
void
uvm_voaddr_release(struct uvm_voaddr * const voaddr)
{

        switch (UVM_VOADDR_GET_TYPE(voaddr)) {
        case UVM_VOADDR_TYPE_UOBJ: {
                struct uvm_object * const uobj = UVM_VOADDR_GET_UOBJ(voaddr);

                KASSERT(uobj != NULL);
                KASSERT(uobj->pgops->pgo_detach != NULL);
                (*uobj->pgops->pgo_detach)(uobj);
                break;
            }
        case UVM_VOADDR_TYPE_ANON: {
                struct vm_anon * const anon = UVM_VOADDR_GET_ANON(voaddr);
                krwlock_t *lock;

                KASSERT(anon != NULL);
                rw_enter((lock = anon->an_lock), RW_WRITER);
                KASSERT(anon->an_ref > 0);
                if (--anon->an_ref == 0) {
                        uvm_anfree(anon);
                }
                rw_exit(lock);
                rw_obj_free(lock);
                break;
            }
        default:
                panic("uvm_voaddr_release: bad type");
        }
        memset(voaddr, 0, sizeof(*voaddr));
}

/*
 * uvm_voaddr_compare: compare two uvm_voaddr objects.
 *
 * => memcmp() semantics
 */
int
uvm_voaddr_compare(const struct uvm_voaddr * const voaddr1,
    const struct uvm_voaddr * const voaddr2)
{
        const uintptr_t type1 = UVM_VOADDR_GET_TYPE(voaddr1);
        const uintptr_t type2 = UVM_VOADDR_GET_TYPE(voaddr2);

        KASSERT(type1 == UVM_VOADDR_TYPE_UOBJ ||
                type1 == UVM_VOADDR_TYPE_ANON);

        KASSERT(type2 == UVM_VOADDR_TYPE_UOBJ ||
                type2 == UVM_VOADDR_TYPE_ANON);

        if (type1 < type2)
                return -1;
        if (type1 > type2)
                return 1;

        const uintptr_t addr1 = UVM_VOADDR_GET_OBJECT(voaddr1);
        const uintptr_t addr2 = UVM_VOADDR_GET_OBJECT(voaddr2);

        if (addr1 < addr2)
                return -1;
        if (addr1 > addr2)
                return 1;

        if (voaddr1->offset < voaddr2->offset)
                return -1;
        if (voaddr1->offset > voaddr2->offset)
                return 1;

        return 0;
}

#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: [%#lx->%#lx]\n", map, vm_map_min(map),
            vm_map_max(map));
        (*pr)("\t#ent=%d, sz=%d, ref=%d, version=%d, flags=%#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: %#lx->%#lx: obj=%p/%#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%s\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,
                    entry == map->first_free ? " (first_free)" : "");
        }
}

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 */

#ifndef __USER_VA0_IS_SAFE
static int
sysctl_user_va0_disable(SYSCTLFN_ARGS)
{
        struct sysctlnode node;
        int t, error;

        node = *rnode;
        node.sysctl_data = &t;
        t = user_va0_disable;
        error = sysctl_lookup(SYSCTLFN_CALL(&node));
        if (error || newp == NULL)
                return (error);

        if (!t && user_va0_disable &&
            kauth_authorize_system(l->l_cred, KAUTH_SYSTEM_MAP_VA_ZERO, 0,
            NULL, NULL, NULL))
                return EPERM;

        user_va0_disable = !!t;
        return 0;
}
#endif

static int
fill_vmentry(struct lwp *l, struct proc *p, struct kinfo_vmentry *kve,
    struct vm_map *m, struct vm_map_entry *e)
{
#ifndef _RUMPKERNEL
        int error;

        memset(kve, 0, sizeof(*kve));
        KASSERT(e != NULL);
        if (UVM_ET_ISOBJ(e)) {
                struct uvm_object *uobj = e->object.uvm_obj;
                KASSERT(uobj != NULL);
                kve->kve_ref_count = uobj->uo_refs;
                kve->kve_count = uobj->uo_npages;
                if (UVM_OBJ_IS_VNODE(uobj)) {
                        struct vattr va;
                        struct vnode *vp = (struct vnode *)uobj;
                        vn_lock(vp, LK_SHARED | LK_RETRY);
                        error = VOP_GETATTR(vp, &va, l->l_cred);
                        VOP_UNLOCK(vp);
                        kve->kve_type = KVME_TYPE_VNODE;
                        if (error == 0) {
                                kve->kve_vn_size = vp->v_size;
                                kve->kve_vn_type = (int)vp->v_type;
                                kve->kve_vn_mode = va.va_mode;
                                kve->kve_vn_rdev = va.va_rdev;
                                kve->kve_vn_fileid = va.va_fileid;
                                kve->kve_vn_fsid = va.va_fsid;
                                error = vnode_to_path(kve->kve_path,
                                    sizeof(kve->kve_path) / 2, vp, l, p);
                        }
                } else if (UVM_OBJ_IS_KERN_OBJECT(uobj)) {
                        kve->kve_type = KVME_TYPE_KERN;
                } else if (UVM_OBJ_IS_DEVICE(uobj)) {
                        kve->kve_type = KVME_TYPE_DEVICE;
                } else if (UVM_OBJ_IS_AOBJ(uobj)) {
                        kve->kve_type = KVME_TYPE_ANON;
                } else {
                        kve->kve_type = KVME_TYPE_OBJECT;
                }
        } else if (UVM_ET_ISSUBMAP(e)) {
                struct vm_map *map = e->object.sub_map;
                KASSERT(map != NULL);
                kve->kve_ref_count = map->ref_count;
                kve->kve_count = map->nentries;
                kve->kve_type = KVME_TYPE_SUBMAP;
        } else
                kve->kve_type = KVME_TYPE_UNKNOWN;

        kve->kve_start = e->start;
        kve->kve_end = e->end;
        kve->kve_offset = e->offset;
        kve->kve_wired_count = e->wired_count;
        kve->kve_inheritance = e->inheritance;
        kve->kve_attributes = 0; /* unused */
        kve->kve_advice = e->advice;
#define PROT(p) (((p) & VM_PROT_READ) ? KVME_PROT_READ : 0) | \
        (((p) & VM_PROT_WRITE) ? KVME_PROT_WRITE : 0) | \
        (((p) & VM_PROT_EXECUTE) ? KVME_PROT_EXEC : 0)
        kve->kve_protection = PROT(e->protection);
        kve->kve_max_protection = PROT(e->max_protection);
        kve->kve_flags |= (e->etype & UVM_ET_COPYONWRITE)
            ? KVME_FLAG_COW : 0;
        kve->kve_flags |= (e->etype & UVM_ET_NEEDSCOPY)
            ? KVME_FLAG_NEEDS_COPY : 0;
        kve->kve_flags |= (m->flags & VM_MAP_TOPDOWN)
            ? KVME_FLAG_GROWS_DOWN : KVME_FLAG_GROWS_UP;
        kve->kve_flags |= (m->flags & VM_MAP_PAGEABLE)
            ? KVME_FLAG_PAGEABLE : 0;
#endif
        return 0;
}

static int
fill_vmentries(struct lwp *l, pid_t pid, u_int elem_size, void *oldp,
    size_t *oldlenp)
{
        int error;
        struct proc *p;
        struct kinfo_vmentry *vme;
        struct vmspace *vm;
        struct vm_map *map;
        struct vm_map_entry *entry;
        char *dp;
        size_t count, vmesize;

        if (elem_size == 0 || elem_size > 2 * sizeof(*vme))
                return EINVAL;

        if (oldp) {
                if (*oldlenp > 10UL * 1024UL * 1024UL)
                        return E2BIG;
                count = *oldlenp / elem_size;
                if (count == 0)
                        return ENOMEM;
                vmesize = count * sizeof(*vme);
        } else
                vmesize = 0;

        if ((error = proc_find_locked(l, &p, pid)) != 0)
                return error;

        vme = NULL;
        count = 0;

        if ((error = proc_vmspace_getref(p, &vm)) != 0)
                goto out;

        map = &vm->vm_map;
        vm_map_lock_read(map);

        dp = oldp;
        if (oldp)
                vme = kmem_alloc(vmesize, KM_SLEEP);
        for (entry = map->header.next; entry != &map->header;
            entry = entry->next) {
                if (oldp && (dp - (char *)oldp) < vmesize) {
                        error = fill_vmentry(l, p, &vme[count], map, entry);
                        if (error)
                                goto out;
                        dp += elem_size;
                }
                count++;
        }
        vm_map_unlock_read(map);
        uvmspace_free(vm);

out:
        if (pid != -1)
                mutex_exit(p->p_lock);
        if (error == 0) {
                const u_int esize = uimin(sizeof(*vme), elem_size);
                dp = oldp;
                for (size_t i = 0; i < count; i++) {
                        if (oldp && (dp - (char *)oldp) < vmesize) {
                                error = sysctl_copyout(l, &vme[i], dp, esize);
                                if (error)
                                        break;
                                dp += elem_size;
                        } else
                                break;
                }
                count *= elem_size;
                if (oldp != NULL && *oldlenp < count)
                        error = ENOSPC;
                *oldlenp = count;
        }
        if (vme)
                kmem_free(vme, vmesize);
        return error;
}

static int
sysctl_vmproc(SYSCTLFN_ARGS)
{
        int error;

        if (namelen == 1 && name[0] == CTL_QUERY)
                return (sysctl_query(SYSCTLFN_CALL(rnode)));

        if (namelen == 0)
                return EINVAL;

        switch (name[0]) {
        case VM_PROC_MAP:
                if (namelen != 3)
                        return EINVAL;
                sysctl_unlock();
                error = fill_vmentries(l, name[1], name[2], oldp, oldlenp);
                sysctl_relock();
                return error;
        default:
                return EINVAL;
        }
}

SYSCTL_SETUP(sysctl_uvmmap_setup, "sysctl uvmmap setup")
{

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_STRUCT, "proc",
                       SYSCTL_DESCR("Process vm information"),
                       sysctl_vmproc, 0, NULL, 0,
                       CTL_VM, VM_PROC, CTL_EOL);
#ifndef __USER_VA0_IS_SAFE
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "user_va0_disable",
                       SYSCTL_DESCR("Disable VA 0"),
                       sysctl_user_va0_disable, 0, &user_va0_disable, 0,
                       CTL_VM, CTL_CREATE, CTL_EOL);
#endif
}