xnu-792.tar.gz

[apple/xnu.git] / osfmk / vm / vm_kern.c

/*
 * Copyright (c) 2000-2005 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 */
/*
 *      File:   vm/vm_kern.c
 *      Author: Avadis Tevanian, Jr., Michael Wayne Young
 *      Date:   1985
 *
 *      Kernel memory management.
 */

#include <mach/kern_return.h>
#include <mach/vm_param.h>
#include <kern/assert.h>
#include <kern/lock.h>
#include <kern/thread.h>
#include <vm/vm_kern.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <kern/misc_protos.h>
#include <vm/cpm.h>

#include <string.h>
/*
 *      Variables exported by this module.
 */

vm_map_t        kernel_map;
vm_map_t        kernel_pageable_map;

/*
 * Forward declarations for internal functions.
 */
extern kern_return_t kmem_alloc_pages(
        register vm_object_t            object,
        register vm_object_offset_t     offset,
        register vm_object_size_t       size);

extern void kmem_remap_pages(
        register vm_object_t            object,
        register vm_object_offset_t     offset,
        register vm_offset_t            start,
        register vm_offset_t            end,
        vm_prot_t                       protection);

kern_return_t
kmem_alloc_contig(
        vm_map_t                map,
        vm_offset_t             *addrp,
        vm_size_t               size,
        vm_offset_t             mask,
        int                     flags)
{
        vm_object_t             object;
        vm_object_offset_t      offset;
        vm_map_offset_t         map_addr; 
        vm_map_offset_t         map_mask;
        vm_map_size_t           map_size, i;
        vm_map_entry_t          entry;
        vm_page_t               m, pages;
        kern_return_t           kr;

        if (map == VM_MAP_NULL || (flags && (flags ^ KMA_KOBJECT))) 
                return KERN_INVALID_ARGUMENT;
        
        if (size == 0) {
                *addrp = 0;
                return KERN_INVALID_ARGUMENT;
        }

        map_size = vm_map_round_page(size);
        map_mask = (vm_map_offset_t)mask;

        /*
         *      Allocate a new object (if necessary) and the reference we
         *      will be donating to the map entry.  We must do this before
         *      locking the map, or risk deadlock with the default pager.
         */
        if ((flags & KMA_KOBJECT) != 0) {
                object = kernel_object;
                vm_object_reference(object);
        } else {
                object = vm_object_allocate(map_size);
        }

        kr = vm_map_find_space(map, &map_addr, map_size, map_mask, &entry);
        if (KERN_SUCCESS != kr) {
                vm_object_deallocate(object);
                return kr;
        }

        entry->object.vm_object = object;
        entry->offset = offset = (object == kernel_object) ? 
                        map_addr - VM_MIN_KERNEL_ADDRESS : 0;

        /* Take an extra object ref in case the map entry gets deleted */
        vm_object_reference(object);
        vm_map_unlock(map);

        kr = cpm_allocate(CAST_DOWN(vm_size_t, map_size), &pages, FALSE);

        if (kr != KERN_SUCCESS) {
                vm_map_remove(map, vm_map_trunc_page(map_addr),
                              vm_map_round_page(map_addr + map_size), 0);
                vm_object_deallocate(object);
                *addrp = 0;
                return kr;
        }

        vm_object_lock(object);
        for (i = 0; i < map_size; i += PAGE_SIZE) {
                m = pages;
                pages = NEXT_PAGE(m);
                m->busy = FALSE;
                vm_page_insert(m, object, offset + i);
        }
        vm_object_unlock(object);

        if ((kr = vm_map_wire(map, vm_map_trunc_page(map_addr),
                              vm_map_round_page(map_addr + map_size), VM_PROT_DEFAULT, FALSE)) 
                != KERN_SUCCESS) {
                if (object == kernel_object) {
                        vm_object_lock(object);
                        vm_object_page_remove(object, offset, offset + map_size);
                        vm_object_unlock(object);
                }
                vm_map_remove(map, vm_map_trunc_page(map_addr), 
                              vm_map_round_page(map_addr + map_size), 0);
                vm_object_deallocate(object);
                return kr;
        }
        vm_object_deallocate(object);

        if (object == kernel_object)
                vm_map_simplify(map, map_addr);

        *addrp = map_addr;
        return KERN_SUCCESS;
}

/*
 * Master entry point for allocating kernel memory.
 * NOTE: this routine is _never_ interrupt safe.
 *
 * map          : map to allocate into
 * addrp        : pointer to start address of new memory
 * size         : size of memory requested
 * flags        : options
 *                KMA_HERE              *addrp is base address, else "anywhere"
 *                KMA_NOPAGEWAIT        don't wait for pages if unavailable
 *                KMA_KOBJECT           use kernel_object
 */

kern_return_t
kernel_memory_allocate(
        register vm_map_t       map,
        register vm_offset_t    *addrp,
        register vm_size_t      size,
        register vm_offset_t    mask,
        int                     flags)
{
        vm_object_t             object;
        vm_object_offset_t      offset;
        vm_map_entry_t          entry;
        vm_map_offset_t         map_addr;
        vm_map_offset_t         map_mask;
        vm_map_size_t           map_size;
        vm_map_size_t           i;
        kern_return_t           kr;

        if (size == 0) {
                *addrp = 0;
                return KERN_INVALID_ARGUMENT;
        }

        map_size = vm_map_round_page(size);
        map_mask = (vm_map_offset_t) mask;

        /*
         *      Allocate a new object (if necessary).  We must do this before
         *      locking the map, or risk deadlock with the default pager.
         */
        if ((flags & KMA_KOBJECT) != 0) {
                object = kernel_object;
                vm_object_reference(object);
        } else {
                object = vm_object_allocate(map_size);
        }

        kr = vm_map_find_space(map, &map_addr, map_size, map_mask, &entry);
        if (KERN_SUCCESS != kr) {
                vm_object_deallocate(object);
                return kr;
        }

        entry->object.vm_object = object;
        entry->offset = offset = (object == kernel_object) ? 
                        map_addr - VM_MIN_KERNEL_ADDRESS : 0;

        vm_object_reference(object);
        vm_map_unlock(map);

        vm_object_lock(object);
        for (i = 0; i < map_size; i += PAGE_SIZE) {
                vm_page_t       mem;

                while (VM_PAGE_NULL == 
                       (mem = vm_page_alloc(object, offset + i))) {
                        if (flags & KMA_NOPAGEWAIT) {
                                if (object == kernel_object)
                                        vm_object_page_remove(object, offset, offset + i);
                                vm_object_unlock(object);
                                vm_map_remove(map, map_addr, map_addr + map_size, 0);
                                vm_object_deallocate(object);
                                return KERN_RESOURCE_SHORTAGE;
                        }
                        vm_object_unlock(object);
                        VM_PAGE_WAIT();
                        vm_object_lock(object);
                }
                mem->busy = FALSE;
        }
        vm_object_unlock(object);

        if ((kr = vm_map_wire(map, map_addr, map_addr + map_size, VM_PROT_DEFAULT, FALSE)) 
                != KERN_SUCCESS) {
                if (object == kernel_object) {
                        vm_object_lock(object);
                        vm_object_page_remove(object, offset, offset + map_size);
                        vm_object_unlock(object);
                }
                vm_map_remove(map, map_addr, map_addr + map_size, 0);
                vm_object_deallocate(object);
                return (kr);
        }
        /* now that the page is wired, we no longer have to fear coalesce */
        vm_object_deallocate(object);
        if (object == kernel_object)
                vm_map_simplify(map, map_addr);

        /*
         *      Return the memory, not zeroed.
         */
        *addrp = CAST_DOWN(vm_offset_t, map_addr);
        return KERN_SUCCESS;
}

/*
 *      kmem_alloc:
 *
 *      Allocate wired-down memory in the kernel's address map
 *      or a submap.  The memory is not zero-filled.
 */

kern_return_t
kmem_alloc(
        vm_map_t        map,
        vm_offset_t     *addrp,
        vm_size_t       size)
{
        return kernel_memory_allocate(map, addrp, size, 0, 0);
}

/*
 *      kmem_realloc:
 *
 *      Reallocate wired-down memory in the kernel's address map
 *      or a submap.  Newly allocated pages are not zeroed.
 *      This can only be used on regions allocated with kmem_alloc.
 *
 *      If successful, the pages in the old region are mapped twice.
 *      The old region is unchanged.  Use kmem_free to get rid of it.
 */
kern_return_t
kmem_realloc(
        vm_map_t                map,
        vm_offset_t             oldaddr,
        vm_size_t               oldsize,
        vm_offset_t             *newaddrp,
        vm_size_t               newsize)
{
        vm_object_t             object;
        vm_object_offset_t      offset;
        vm_map_offset_t         oldmapmin;
        vm_map_offset_t         oldmapmax;
        vm_map_offset_t         newmapaddr;
        vm_map_size_t           oldmapsize;
        vm_map_size_t           newmapsize;
        vm_map_entry_t          oldentry;
        vm_map_entry_t          newentry;
        vm_page_t               mem;
        kern_return_t           kr;

        oldmapmin = vm_map_trunc_page(oldaddr);
        oldmapmax = vm_map_round_page(oldaddr + oldsize);
        oldmapsize = oldmapmax - oldmapmin;
        newmapsize = vm_map_round_page(newsize);


        /*
         *      Find the VM object backing the old region.
         */

        vm_map_lock(map);

        if (!vm_map_lookup_entry(map, oldmapmin, &oldentry))
                panic("kmem_realloc");
        object = oldentry->object.vm_object;

        /*
         *      Increase the size of the object and
         *      fill in the new region.
         */

        vm_object_reference(object);
        /* by grabbing the object lock before unlocking the map */
        /* we guarantee that we will panic if more than one     */
        /* attempt is made to realloc a kmem_alloc'd area       */
        vm_object_lock(object);
        vm_map_unlock(map);
        if (object->size != oldmapsize)
                panic("kmem_realloc");
        object->size = newmapsize;
        vm_object_unlock(object);

        /* allocate the new pages while expanded portion of the */
        /* object is still not mapped */
        kmem_alloc_pages(object, vm_object_round_page(oldmapsize),
                         vm_object_round_page(newmapsize-oldmapsize));

        /*
         *      Find space for the new region.
         */

        kr = vm_map_find_space(map, &newmapaddr, newmapsize,
                               (vm_map_offset_t) 0, &newentry);
        if (kr != KERN_SUCCESS) {
                vm_object_lock(object);
                for(offset = oldmapsize; 
                    offset < newmapsize; offset += PAGE_SIZE) {
                        if ((mem = vm_page_lookup(object, offset)) != VM_PAGE_NULL) {
                                vm_page_lock_queues();
                                vm_page_free(mem);
                                vm_page_unlock_queues();
                        }
                }
                object->size = oldmapsize;
                vm_object_unlock(object);
                vm_object_deallocate(object);
                return kr;
        }
        newentry->object.vm_object = object;
        newentry->offset = 0;
        assert (newentry->wired_count == 0);

        
        /* add an extra reference in case we have someone doing an */
        /* unexpected deallocate */
        vm_object_reference(object);
        vm_map_unlock(map);

        kr = vm_map_wire(map, newmapaddr, newmapaddr + newmapsize, VM_PROT_DEFAULT, FALSE);
        if (KERN_SUCCESS != kr) {
                vm_map_remove(map, newmapaddr, newmapaddr + newmapsize, 0);
                vm_object_lock(object);
                for(offset = oldsize; offset < newmapsize; offset += PAGE_SIZE) {
                        if ((mem = vm_page_lookup(object, offset)) != VM_PAGE_NULL) {
                                vm_page_lock_queues();
                                vm_page_free(mem);
                                vm_page_unlock_queues();
                        }
                }
                object->size = oldmapsize;
                vm_object_unlock(object);
                vm_object_deallocate(object);
                return (kr);
        }
        vm_object_deallocate(object);

        *newaddrp = CAST_DOWN(vm_offset_t, newmapaddr);
        return KERN_SUCCESS;
}

/*
 *      kmem_alloc_wired:
 *
 *      Allocate wired-down memory in the kernel's address map
 *      or a submap.  The memory is not zero-filled.
 *
 *      The memory is allocated in the kernel_object.
 *      It may not be copied with vm_map_copy, and
 *      it may not be reallocated with kmem_realloc.
 */

kern_return_t
kmem_alloc_wired(
        vm_map_t        map,
        vm_offset_t     *addrp,
        vm_size_t       size)
{
        return kernel_memory_allocate(map, addrp, size, 0, KMA_KOBJECT);
}

/*
 *      kmem_alloc_aligned:
 *
 *      Like kmem_alloc_wired, except that the memory is aligned.
 *      The size should be a power-of-2.
 */

kern_return_t
kmem_alloc_aligned(
        vm_map_t        map,
        vm_offset_t     *addrp,
        vm_size_t       size)
{
        if ((size & (size - 1)) != 0)
                panic("kmem_alloc_aligned: size not aligned");
        return kernel_memory_allocate(map, addrp, size, size - 1, KMA_KOBJECT);
}

/*
 *      kmem_alloc_pageable:
 *
 *      Allocate pageable memory in the kernel's address map.
 */

kern_return_t
kmem_alloc_pageable(
        vm_map_t        map,
        vm_offset_t     *addrp,
        vm_size_t       size)
{
        vm_map_offset_t map_addr;
        vm_map_size_t   map_size;
        kern_return_t kr;

#ifndef normal
        map_addr = (vm_map_min(map)) + 0x1000;
#else
        map_addr = vm_map_min(map);
#endif
        map_size = vm_map_round_page(size);

        kr = vm_map_enter(map, &map_addr, map_size,
                          (vm_map_offset_t) 0, VM_FLAGS_ANYWHERE,
                          VM_OBJECT_NULL, (vm_object_offset_t) 0, FALSE,
                          VM_PROT_DEFAULT, VM_PROT_ALL, VM_INHERIT_DEFAULT);

        if (kr != KERN_SUCCESS)
                return kr;

        *addrp = CAST_DOWN(vm_offset_t, map_addr);
        return KERN_SUCCESS;
}

/*
 *      kmem_free:
 *
 *      Release a region of kernel virtual memory allocated
 *      with kmem_alloc, kmem_alloc_wired, or kmem_alloc_pageable,
 *      and return the physical pages associated with that region.
 */

void
kmem_free(
        vm_map_t        map,
        vm_offset_t     addr,
        vm_size_t       size)
{
        kern_return_t kr;

        kr = vm_map_remove(map, vm_map_trunc_page(addr),
                                vm_map_round_page(addr + size), 
                                VM_MAP_REMOVE_KUNWIRE);
        if (kr != KERN_SUCCESS)
                panic("kmem_free");
}

/*
 *      Allocate new pages in an object.
 */

kern_return_t
kmem_alloc_pages(
        register vm_object_t            object,
        register vm_object_offset_t     offset,
        register vm_object_size_t       size)
{
        vm_object_size_t                alloc_size;

        alloc_size = vm_object_round_page(size);
        vm_object_lock(object);
        while (alloc_size) {
            register vm_page_t  mem;


            /*
             *  Allocate a page
             */
            while (VM_PAGE_NULL == 
                  (mem = vm_page_alloc(object, offset))) {
                vm_object_unlock(object);
                VM_PAGE_WAIT();
                vm_object_lock(object);
            }
            mem->busy = FALSE;

            alloc_size -= PAGE_SIZE;
            offset += PAGE_SIZE;
        }
        vm_object_unlock(object);
        return KERN_SUCCESS;
}

/*
 *      Remap wired pages in an object into a new region.
 *      The object is assumed to be mapped into the kernel map or
 *      a submap.
 */
void
kmem_remap_pages(
        register vm_object_t            object,
        register vm_object_offset_t     offset,
        register vm_offset_t            start,
        register vm_offset_t            end,
        vm_prot_t                       protection)
{

        vm_map_offset_t                 map_start;
        vm_map_offset_t                 map_end;

        /*
         *      Mark the pmap region as not pageable.
         */
        map_start = vm_map_trunc_page(start);
        map_end = vm_map_round_page(end);

        pmap_pageable(kernel_pmap, map_start, map_end, FALSE);

        while (map_start < map_end) {
            register vm_page_t  mem;

            vm_object_lock(object);

            /*
             *  Find a page
             */
            if ((mem = vm_page_lookup(object, offset)) == VM_PAGE_NULL)
                panic("kmem_remap_pages");

            /*
             *  Wire it down (again)
             */
            vm_page_lock_queues();
            vm_page_wire(mem);
            vm_page_unlock_queues();
            vm_object_unlock(object);

            /*
             * ENCRYPTED SWAP:
             * The page is supposed to be wired now, so it
             * shouldn't be encrypted at this point.  It can
             * safely be entered in the page table.
             */
            ASSERT_PAGE_DECRYPTED(mem);

            /*
             *  Enter it in the kernel pmap.  The page isn't busy,
             *  but this shouldn't be a problem because it is wired.
             */
            PMAP_ENTER(kernel_pmap, map_start, mem, protection, 
                        ((unsigned int)(mem->object->wimg_bits))
                                        & VM_WIMG_MASK,
                        TRUE);

            map_start += PAGE_SIZE;
            offset += PAGE_SIZE;
        }
}

/*
 *      kmem_suballoc:
 *
 *      Allocates a map to manage a subrange
 *      of the kernel virtual address space.
 *
 *      Arguments are as follows:
 *
 *      parent          Map to take range from
 *      addr            Address of start of range (IN/OUT)
 *      size            Size of range to find
 *      pageable        Can region be paged
 *      anywhere        Can region be located anywhere in map
 *      new_map         Pointer to new submap
 */
kern_return_t
kmem_suballoc(
        vm_map_t        parent,
        vm_offset_t     *addr,
        vm_size_t       size,
        boolean_t       pageable,
        int             flags,
        vm_map_t        *new_map)
{
        vm_map_t        map;
        vm_map_offset_t map_addr;
        vm_map_size_t   map_size;
        kern_return_t   kr;

        map_size = vm_map_round_page(size);

        /*
         *      Need reference on submap object because it is internal
         *      to the vm_system.  vm_object_enter will never be called
         *      on it (usual source of reference for vm_map_enter).
         */
        vm_object_reference(vm_submap_object);

        map_addr = (flags & VM_FLAGS_ANYWHERE) ?
                   vm_map_min(parent) : vm_map_trunc_page(*addr);

        kr = vm_map_enter(parent, &map_addr, map_size,
                          (vm_map_offset_t) 0, flags,
                          vm_submap_object, (vm_object_offset_t) 0, FALSE,
                          VM_PROT_DEFAULT, VM_PROT_ALL, VM_INHERIT_DEFAULT);
        if (kr != KERN_SUCCESS) {
                vm_object_deallocate(vm_submap_object);
                return (kr);
        }

        pmap_reference(vm_map_pmap(parent));
        map = vm_map_create(vm_map_pmap(parent), map_addr, map_addr + map_size, pageable);
        if (map == VM_MAP_NULL)
                panic("kmem_suballoc: vm_map_create failed");   /* "can't happen" */

        kr = vm_map_submap(parent, map_addr, map_addr + map_size, map, map_addr, FALSE);
        if (kr != KERN_SUCCESS) {
                /*
                 * See comment preceding vm_map_submap().
                 */
                vm_map_remove(parent, map_addr, map_addr + map_size, VM_MAP_NO_FLAGS);
                vm_map_deallocate(map); /* also removes ref to pmap */
                vm_object_deallocate(vm_submap_object);
                return (kr);
        }
        *addr = CAST_DOWN(vm_offset_t, map_addr);
        *new_map = map;
        return (KERN_SUCCESS);
}

/*
 *      kmem_init:
 *
 *      Initialize the kernel's virtual memory map, taking
 *      into account all memory allocated up to this time.
 */
void
kmem_init(
        vm_offset_t     start,
        vm_offset_t     end)
{
        vm_map_offset_t map_start;
        vm_map_offset_t map_end;

        map_start = vm_map_trunc_page(start);
        map_end = vm_map_round_page(end);

        kernel_map = vm_map_create(pmap_kernel(),VM_MIN_KERNEL_ADDRESS,
                                   map_end, FALSE);

        /*
         *      Reserve virtual memory allocated up to this time.
         */

        if (start != VM_MIN_KERNEL_ADDRESS) {
                vm_map_offset_t map_addr;

                map_addr = VM_MIN_KERNEL_ADDRESS;
                (void) vm_map_enter(kernel_map,
                                    &map_addr, 
                                    (vm_map_size_t)(map_start - VM_MIN_KERNEL_ADDRESS),
                                    (vm_map_offset_t) 0,
                                    VM_FLAGS_ANYWHERE | VM_FLAGS_NO_PMAP_CHECK,
                                    VM_OBJECT_NULL, 
                                    (vm_object_offset_t) 0, FALSE,
                                    VM_PROT_DEFAULT, VM_PROT_ALL,
                                    VM_INHERIT_DEFAULT);
        }

        /*
         * Account for kernel memory (text, data, bss, vm shenanigans).
         * This may include inaccessible "holes" as determined by what
         * the machine-dependent init code includes in max_mem.
         */
        vm_page_wire_count = (atop_64(max_mem) - (vm_page_free_count
                                                + vm_page_active_count
                                                + vm_page_inactive_count));
}


/*
 *      Routine:        copyinmap
 *      Purpose:
 *              Like copyin, except that fromaddr is an address
 *              in the specified VM map.  This implementation
 *              is incomplete; it handles the current user map
 *              and the kernel map/submaps.
 */
kern_return_t
copyinmap(
        vm_map_t                map,
        vm_map_offset_t         fromaddr,
        void                    *todata,
        vm_size_t               length)
{
        kern_return_t   kr = KERN_SUCCESS;
        vm_map_t oldmap;

        if (vm_map_pmap(map) == pmap_kernel())
        {
                /* assume a correct copy */
                memcpy(todata, CAST_DOWN(void *, fromaddr), length);
        } 
        else if (current_map() == map)
        {
                if (copyin(fromaddr, todata, length) != 0)
                        kr = KERN_INVALID_ADDRESS;
        }
        else
        {
                vm_map_reference(map);
                oldmap = vm_map_switch(map);
                if (copyin(fromaddr, todata, length) != 0)
                        kr = KERN_INVALID_ADDRESS;
                vm_map_switch(oldmap);
                vm_map_deallocate(map);
        }
        return kr;
}

/*
 *      Routine:        copyoutmap
 *      Purpose:
 *              Like copyout, except that toaddr is an address
 *              in the specified VM map.  This implementation
 *              is incomplete; it handles the current user map
 *              and the kernel map/submaps.
 */
kern_return_t
copyoutmap(
        vm_map_t                map,
        void                    *fromdata,
        vm_map_address_t        toaddr,
        vm_size_t               length)
{
        if (vm_map_pmap(map) == pmap_kernel()) {
                /* assume a correct copy */
                memcpy(CAST_DOWN(void *, toaddr), fromdata, length);
                return KERN_SUCCESS;
        }

        if (current_map() != map)
                return KERN_NOT_SUPPORTED;

        if (copyout(fromdata, toaddr, length) != 0)
                return KERN_INVALID_ADDRESS;

        return KERN_SUCCESS;
}


kern_return_t
vm_conflict_check(
        vm_map_t                map,
        vm_map_offset_t off,
        vm_map_size_t           len,
        memory_object_t pager,
        vm_object_offset_t      file_off)
{
        vm_map_entry_t          entry;
        vm_object_t             obj;
        vm_object_offset_t      obj_off;
        vm_map_t                base_map;
        vm_map_offset_t         base_offset;
        vm_map_offset_t         original_offset;
        kern_return_t           kr;
        vm_map_size_t           local_len;

        base_map = map;
        base_offset = off;
        original_offset = off;
        kr = KERN_SUCCESS;
        vm_map_lock(map);
        while(vm_map_lookup_entry(map, off, &entry)) {
                local_len = len;

                if (entry->object.vm_object == VM_OBJECT_NULL) {
                        vm_map_unlock(map);
                        return KERN_SUCCESS;
                }
                if (entry->is_sub_map) {
                        vm_map_t        old_map;

                        old_map = map;
                        vm_map_lock(entry->object.sub_map);
                        map = entry->object.sub_map;
                        off = entry->offset + (off - entry->vme_start);
                        vm_map_unlock(old_map);
                        continue;
                }
                obj = entry->object.vm_object;
                obj_off = (off - entry->vme_start) + entry->offset;
                while(obj->shadow) {
                        obj_off += obj->shadow_offset;
                        obj = obj->shadow;
                }
                if((obj->pager_created) && (obj->pager == pager)) {
                        if(((obj->paging_offset) + obj_off) == file_off) {
                                if(off != base_offset) {
                                        vm_map_unlock(map);
                                        return KERN_FAILURE;
                                }
                                kr = KERN_ALREADY_WAITING;
                        } else {
                                vm_object_offset_t      obj_off_aligned;
                                vm_object_offset_t      file_off_aligned;

                                obj_off_aligned = obj_off & ~PAGE_MASK;
                                file_off_aligned = file_off & ~PAGE_MASK;

                                if (file_off_aligned == (obj->paging_offset + obj_off_aligned)) {
                                        /*
                                         * the target map and the file offset start in the same page
                                         * but are not identical... 
                                         */
                                        vm_map_unlock(map);
                                        return KERN_FAILURE;
                                }
                                if ((file_off < (obj->paging_offset + obj_off_aligned)) &&
                                    ((file_off + len) > (obj->paging_offset + obj_off_aligned))) {
                                        /*
                                         * some portion of the tail of the I/O will fall
                                         * within the encompass of the target map
                                         */
                                        vm_map_unlock(map);
                                        return KERN_FAILURE;
                                }
                                if ((file_off_aligned > (obj->paging_offset + obj_off)) &&
                                    (file_off_aligned < (obj->paging_offset + obj_off) + len)) {
                                        /*
                                         * the beginning page of the file offset falls within
                                         * the target map's encompass
                                         */
                                        vm_map_unlock(map);
                                        return KERN_FAILURE;
                                }
                        }
                } else if(kr != KERN_SUCCESS) {
                        vm_map_unlock(map);
                        return KERN_FAILURE;
                }

                if(len <= ((entry->vme_end - entry->vme_start) -
                                                (off - entry->vme_start))) {
                        vm_map_unlock(map);
                        return kr;
                } else {
                        len -= (entry->vme_end - entry->vme_start) -
                                                (off - entry->vme_start);
                }
                base_offset = base_offset + (local_len - len);
                file_off = file_off + (local_len - len);
                off = base_offset;
                if(map != base_map) {
                        vm_map_unlock(map);
                        vm_map_lock(base_map);
                        map = base_map;
                }
        }

        vm_map_unlock(map);
        return kr;
}