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[apple/xnu.git] / iokit / Kernel / IOBufferMemoryDescriptor.cpp
index c7a521d10f0894eebacb991386348b1c1630f583..563059600b59c1a31850aaf736144e55bde62402 100644 (file)
@@ -1,16 +1,19 @@
 /*
  * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
  *
- * @APPLE_LICENSE_HEADER_START@
- * 
- * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
  * This file contains Original Code and/or Modifications of Original Code
  * as defined in and that are subject to the Apple Public Source License
  * Version 2.0 (the 'License'). You may not use this file except in
- * compliance with the License. Please obtain a copy of the License at
- * http://www.opensource.apple.com/apsl/ and read it before using this
- * file.
+ * compliance with the License. The rights granted to you under the License
+ * may not be used to create, or enable the creation or redistribution of,
+ * unlawful or unlicensed copies of an Apple operating system, or to
+ * circumvent, violate, or enable the circumvention or violation of, any
+ * terms of an Apple operating system software license agreement.
+ * 
+ * Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this file.
  * 
  * The Original Code and all software distributed under the License are
  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  * Please see the License for the specific language governing rights and
  * limitations under the License.
  * 
- * @APPLE_LICENSE_HEADER_END@
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  */
+
+#define _IOMEMORYDESCRIPTOR_INTERNAL_
+
 #include <IOKit/assert.h>
 #include <IOKit/system.h>
 
 #include <IOKit/IOLib.h>
+#include <IOKit/IOMapper.h>
 #include <IOKit/IOBufferMemoryDescriptor.h>
+#include <libkern/OSDebug.h>
+
+#include "IOKitKernelInternal.h"
 
 __BEGIN_DECLS
 void ipc_port_release_send(ipc_port_t port);
 #include <vm/pmap.h>
 
-vm_map_t IOPageableMapForAddress( vm_address_t address );
 __END_DECLS
 
-#define super IOGeneralMemoryDescriptor
-OSDefineMetaClassAndStructors(IOBufferMemoryDescriptor,
-                               IOGeneralMemoryDescriptor);
-
-bool IOBufferMemoryDescriptor::initWithAddress(
-                                  void *      /* address       */ ,
-                                  IOByteCount /* withLength    */ ,
-                                  IODirection /* withDirection */ )
-{
-    return false;
-}
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
-bool IOBufferMemoryDescriptor::initWithAddress(
-                                  vm_address_t /* address       */ ,
-                                  IOByteCount  /* withLength    */ ,
-                                  IODirection  /* withDirection */ ,
-                                  task_t       /* withTask      */ )
+enum
 {
-    return false;
-}
+    kInternalFlagPhysical  = 0x00000001,
+    kInternalFlagPageSized = 0x00000002
+};
 
-bool IOBufferMemoryDescriptor::initWithPhysicalAddress(
-                                  IOPhysicalAddress /* address       */ ,
-                                  IOByteCount       /* withLength    */ ,
-                                  IODirection       /* withDirection */ )
-{
-    return false;
-}
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
-bool IOBufferMemoryDescriptor::initWithPhysicalRanges(
-                                  IOPhysicalRange * /* ranges        */ ,
-                                  UInt32            /* withCount     */ ,
-                                  IODirection       /* withDirection */ ,
-                                  bool              /* asReference   */ )
-{
-    return false;
-}
+#define super IOGeneralMemoryDescriptor
+OSDefineMetaClassAndStructors(IOBufferMemoryDescriptor,
+                               IOGeneralMemoryDescriptor);
 
-bool IOBufferMemoryDescriptor::initWithRanges(
-                                  IOVirtualRange * /* ranges        */ ,
-                                  UInt32           /* withCount     */ ,
-                                  IODirection      /* withDirection */ ,
-                                  task_t           /* withTask      */ ,
-                                  bool             /* asReference   */ )
-{
-    return false;
-}
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
+#ifndef __LP64__
 bool IOBufferMemoryDescriptor::initWithOptions(
                                IOOptionBits options,
                                vm_size_t    capacity,
                                vm_offset_t  alignment,
                               task_t       inTask)
 {
-    vm_map_t map = 0;
-    IOOptionBits iomdOptions = kIOMemoryAsReference | kIOMemoryTypeVirtual;
+    mach_vm_address_t physicalMask = 0;
+    return (initWithPhysicalMask(inTask, options, capacity, alignment, physicalMask));
+}
+#endif /* !__LP64__ */
+
+bool IOBufferMemoryDescriptor::initWithPhysicalMask(
+                               task_t            inTask,
+                               IOOptionBits      options,
+                               mach_vm_size_t    capacity,
+                               mach_vm_address_t alignment,
+                               mach_vm_address_t physicalMask)
+{
+    kern_return_t      kr;
+    task_t             mapTask = NULL;
+    vm_map_t           vmmap = NULL;
+    mach_vm_address_t   highestMask = 0;
+    IOOptionBits       iomdOptions = kIOMemoryTypeVirtual64 | kIOMemoryAsReference;
 
     if (!capacity)
         return false;
 
-    _options             = options;
-    _capacity     = capacity;
-    _physAddrs    = 0;
-    _physSegCount = 0;
-    _buffer      = 0;
+    _options                 = options;
+    _capacity         = capacity;
+    _internalFlags    = 0;
+    _internalReserved = 0;
+    _buffer          = 0;
 
-    // Grab the direction and the Auto Prepare bits from the Buffer MD options
-    iomdOptions  |= options & (kIOMemoryDirectionMask | kIOMemoryAutoPrepare);
+    _ranges.v64 = IONew(IOAddressRange, 1);
+    if (!_ranges.v64)
+       return (false);
+    _ranges.v64->address = 0;
+    _ranges.v64->length  = 0;
 
-    if ((options & kIOMemorySharingTypeMask) && (alignment < page_size))
-        alignment = page_size;
+    // Grab IOMD bits from the Buffer MD options
+    iomdOptions  |= (options & kIOBufferDescriptorMemoryFlags);
 
-    if ((inTask != kernel_task) && !(options & kIOMemoryPageable))
-        return false;
+    if (physicalMask && (alignment <= 1))
+    {
+       alignment   = ((physicalMask ^ (-1ULL)) & (physicalMask - 1));
+       highestMask = (physicalMask | alignment);
+       alignment++;
+       if (alignment < page_size)
+            alignment = page_size;
+    }
+
+    if ((options & (kIOMemorySharingTypeMask | kIOMapCacheMask | kIOMemoryClearEncrypt)) && (alignment < page_size))
+       alignment = page_size;
+
+    if (alignment >= page_size)
+       capacity = round_page(capacity);
+
+    if (alignment > page_size)
+       options |= kIOMemoryPhysicallyContiguous;
 
     _alignment = alignment;
+
+    if ((inTask != kernel_task) && !(options & kIOMemoryPageable))
+       return false;
+
+    // set flags for entry + object create
+    vm_prot_t memEntryCacheMode = VM_PROT_READ | VM_PROT_WRITE;
+
+    // set memory entry cache mode
+    switch (options & kIOMapCacheMask)
+    {
+       case kIOMapInhibitCache:
+           SET_MAP_MEM(MAP_MEM_IO, memEntryCacheMode);
+           break;
+
+       case kIOMapWriteThruCache:
+           SET_MAP_MEM(MAP_MEM_WTHRU, memEntryCacheMode);
+           break;
+
+       case kIOMapWriteCombineCache:
+           SET_MAP_MEM(MAP_MEM_WCOMB, memEntryCacheMode);
+           break;
+
+       case kIOMapCopybackCache:
+           SET_MAP_MEM(MAP_MEM_COPYBACK, memEntryCacheMode);
+           break;
+
+       case kIOMapDefaultCache:
+       default:
+           SET_MAP_MEM(MAP_MEM_NOOP, memEntryCacheMode);
+           break;
+    }
+
     if (options & kIOMemoryPageable)
     {
-        iomdOptions |= kIOMemoryBufferPageable;
-       if (inTask == kernel_task)
-       {
-           /* Allocate some kernel address space. */
-           _buffer = IOMallocPageable(capacity, alignment);
-           if (_buffer)
-               map = IOPageableMapForAddress((vm_address_t) _buffer);
-       }
-       else
-       {
-           kern_return_t kr;
+       iomdOptions |= kIOMemoryBufferPageable;
 
-           if( !reserved) {
-               reserved = IONew( ExpansionData, 1 );
-               if( !reserved)
-                   return( false );
-           }
-           map = get_task_map(inTask);
-           vm_map_reference(map);
-           reserved->map = map;
-           kr = vm_allocate( map, (vm_address_t *) &_buffer, round_page_32(capacity),
-                               VM_FLAGS_ANYWHERE | VM_MAKE_TAG(VM_MEMORY_IOKIT) );
-           if( KERN_SUCCESS != kr)
-               return( false );
+       // must create the entry before any pages are allocated
 
-           // we have to make sure that these pages don't get copied on fork.
-           kr = vm_inherit( map, (vm_address_t) _buffer, round_page_32(capacity), VM_INHERIT_NONE);
-           if( KERN_SUCCESS != kr)
-               return( false );
-       }
+       // set flags for entry + object create
+       memEntryCacheMode |= MAP_MEM_NAMED_CREATE;
+
+       if (options & kIOMemoryPurgeable)
+           memEntryCacheMode |= MAP_MEM_PURGABLE;
     }
-    else 
+    else
     {
-        // @@@ gvdl: Need to remove this
-        // Buffer should never auto prepare they should be prepared explicitly
-        // But it never was enforced so what are you going to do?
-        iomdOptions |= kIOMemoryAutoPrepare;
+       memEntryCacheMode |= MAP_MEM_NAMED_REUSE;
+       vmmap = kernel_map;
+
+       // Buffer shouldn't auto prepare they should be prepared explicitly
+       // But it never was enforced so what are you going to do?
+       iomdOptions |= kIOMemoryAutoPrepare;
 
        /* Allocate a wired-down buffer inside kernel space. */
-       if (options & kIOMemoryPhysicallyContiguous)
-           _buffer = IOMallocContiguous(capacity, alignment, 0);
+
+       if ((options & kIOMemoryPhysicallyContiguous) || highestMask || (alignment > page_size))
+       {
+            _internalFlags |= kInternalFlagPhysical;
+            if (highestMask)
+            {
+                _internalFlags |= kInternalFlagPageSized;
+                capacity = round_page(capacity);
+            }
+            _buffer = (void *) IOKernelAllocateWithPhysicalRestrict(capacity, highestMask, alignment, 
+                                        (0 != (options & kIOMemoryPhysicallyContiguous)));
+       }
        else if (alignment > 1)
-           _buffer = IOMallocAligned(capacity, alignment);
+       {
+            _buffer = IOMallocAligned(capacity, alignment);
+       }
        else
-           _buffer = IOMalloc(capacity);
-    }
-
-    if (!_buffer)
-       return false;
+       {
+            _buffer = IOMalloc(capacity);
+       }
 
-    _singleRange.v.address = (vm_address_t) _buffer;
-    _singleRange.v.length  = capacity;
+       if (!_buffer)
+       {
+            return false;
+       }
+    }
 
-    if (!super::initWithOptions(&_singleRange.v, 1, 0,
-                               inTask, iomdOptions, /* System mapper */ 0))
-       return false;
+    if( (options & (kIOMemoryPageable | kIOMapCacheMask))) {
+       ipc_port_t      sharedMem;
+       vm_size_t       size = round_page(capacity);
 
-    if (options & kIOMemoryPageable) {
-        kern_return_t kr;
-        ipc_port_t sharedMem = (ipc_port_t) _memEntry;
-        vm_size_t size = round_page_32(_ranges.v[0].length);
+       kr = mach_make_memory_entry(vmmap,
+                                   &size, (vm_offset_t)_buffer,
+                                   memEntryCacheMode, &sharedMem,
+                                   NULL );
 
-        // must create the entry before any pages are allocated
-        if( 0 == sharedMem) {
+       if( (KERN_SUCCESS == kr) && (size != round_page(capacity))) {
+           ipc_port_release_send( sharedMem );
+           kr = kIOReturnVMError;
+       }
+       if( KERN_SUCCESS != kr)
+           return( false );
+
+       _memEntry = (void *) sharedMem;
+
+       if( options & kIOMemoryPageable) {
+#if IOALLOCDEBUG
+           debug_iomallocpageable_size += size;
+#endif
+           mapTask = inTask;
+           if (NULL == inTask)
+               inTask = kernel_task;
+       }
+       else if (options & kIOMapCacheMask)
+       {
+           // Prefetch each page to put entries into the pmap
+           volatile UInt8 *    startAddr = (UInt8 *)_buffer;
+           volatile UInt8 *    endAddr   = (UInt8 *)_buffer + capacity;
+
+           while (startAddr < endAddr)
+           {
+               *startAddr;
+               startAddr += page_size;
+           }
+       }
+    }
 
-            // set memory entry cache
-            vm_prot_t memEntryCacheMode = VM_PROT_READ | VM_PROT_WRITE;
-            switch (options & kIOMapCacheMask)
-            {
-               case kIOMapInhibitCache:
-                    SET_MAP_MEM(MAP_MEM_IO, memEntryCacheMode);
-                    break;
-       
-               case kIOMapWriteThruCache:
-                    SET_MAP_MEM(MAP_MEM_WTHRU, memEntryCacheMode);
-                    break;
-
-               case kIOMapWriteCombineCache:
-                    SET_MAP_MEM(MAP_MEM_WCOMB, memEntryCacheMode);
-                    break;
-
-               case kIOMapCopybackCache:
-                    SET_MAP_MEM(MAP_MEM_COPYBACK, memEntryCacheMode);
-                    break;
-
-               case kIOMapDefaultCache:
-               default:
-                    SET_MAP_MEM(MAP_MEM_NOOP, memEntryCacheMode);
-                    break;
-            }
+    _ranges.v64->address = (mach_vm_address_t) _buffer;;
+    _ranges.v64->length  = _capacity;
 
-            kr = mach_make_memory_entry( map,
-                        &size, _ranges.v[0].address,
-                        memEntryCacheMode, &sharedMem,
-                        NULL );
+    if (!super::initWithOptions(_ranges.v64, 1, 0,
+                               inTask, iomdOptions, /* System mapper */ 0))
+       return false;
 
-            if( (KERN_SUCCESS == kr) && (size != round_page_32(_ranges.v[0].length))) {
-                ipc_port_release_send( sharedMem );
-                kr = kIOReturnVMError;
-            }
-            if( KERN_SUCCESS != kr)
-                sharedMem = 0;
-            _memEntry = (void *) sharedMem;
-        }
+    if (mapTask)
+    {
+       if (!reserved) {
+           reserved = IONew( ExpansionData, 1 );
+           if( !reserved)
+               return( false );
+       }
+       reserved->map = createMappingInTask(mapTask, 0, 
+                           kIOMapAnywhere | (options & kIOMapCacheMask), 0, 0);
+       if (!reserved->map)
+       {
+           _buffer = 0;
+           return( false );
+       }
+       release();          // map took a retain on this
+       reserved->map->retain();
+       removeMapping(reserved->map);
+       mach_vm_address_t buffer = reserved->map->getAddress();
+       _buffer = (void *) buffer;
+       if (kIOMemoryTypeVirtual64 == (kIOMemoryTypeMask & iomdOptions))
+           _ranges.v64->address = buffer;
     }
 
-    setLength(capacity);
-    
+    setLength(_capacity);
+
     return true;
 }
 
@@ -232,20 +286,38 @@ IOBufferMemoryDescriptor * IOBufferMemoryDescriptor::inTaskWithOptions(
 {
     IOBufferMemoryDescriptor *me = new IOBufferMemoryDescriptor;
     
-    if (me && !me->initWithOptions(options, capacity, alignment, inTask)) {
+    if (me && !me->initWithPhysicalMask(inTask, options, capacity, alignment, 0)) {
+       me->release();
+       me = 0;
+    }
+    return me;
+}
+
+IOBufferMemoryDescriptor * IOBufferMemoryDescriptor::inTaskWithPhysicalMask(
+                                           task_t            inTask,
+                                            IOOptionBits      options,
+                                            mach_vm_size_t    capacity,
+                                            mach_vm_address_t physicalMask)
+{
+    IOBufferMemoryDescriptor *me = new IOBufferMemoryDescriptor;
+    
+    if (me && !me->initWithPhysicalMask(inTask, options, capacity, 1, physicalMask))
+    {
        me->release();
        me = 0;
     }
     return me;
 }
 
+#ifndef __LP64__
 bool IOBufferMemoryDescriptor::initWithOptions(
                                IOOptionBits options,
                                vm_size_t    capacity,
                                vm_offset_t  alignment)
 {
-    return( initWithOptions(options, capacity, alignment, kernel_task) );
+    return (initWithPhysicalMask(kernel_task, options, capacity, alignment, (mach_vm_address_t)0));
 }
+#endif /* !__LP64__ */
 
 IOBufferMemoryDescriptor * IOBufferMemoryDescriptor::withOptions(
                                             IOOptionBits options,
@@ -254,7 +326,7 @@ IOBufferMemoryDescriptor * IOBufferMemoryDescriptor::withOptions(
 {
     IOBufferMemoryDescriptor *me = new IOBufferMemoryDescriptor;
     
-    if (me && !me->initWithOptions(options, capacity, alignment, kernel_task)) {
+    if (me && !me->initWithPhysicalMask(kernel_task, options, capacity, alignment, 0)) {
        me->release();
        me = 0;
     }
@@ -279,6 +351,7 @@ IOBufferMemoryDescriptor::withCapacity(vm_size_t   inCapacity,
                inCapacity, inContiguous ? inCapacity : 1 ));
 }
 
+#ifndef __LP64__
 /*
  * initWithBytes:
  *
@@ -290,10 +363,9 @@ bool IOBufferMemoryDescriptor::initWithBytes(const void * inBytes,
                                              IODirection  inDirection,
                                              bool         inContiguous)
 {
-    if (!initWithOptions(
-               inDirection | kIOMemoryUnshared
-                | (inContiguous ? kIOMemoryPhysicallyContiguous : 0),
-               inLength, inLength ))
+    if (!initWithPhysicalMask(kernel_task, inDirection | kIOMemoryUnshared
+                             | (inContiguous ? kIOMemoryPhysicallyContiguous : 0),
+                             inLength, inLength, (mach_vm_address_t)0))
         return false;
 
     // start out with no data
@@ -304,6 +376,7 @@ bool IOBufferMemoryDescriptor::initWithBytes(const void * inBytes,
 
     return true;
 }
+#endif /* !__LP64__ */
 
 /*
  * withBytes:
@@ -319,9 +392,25 @@ IOBufferMemoryDescriptor::withBytes(const void * inBytes,
 {
     IOBufferMemoryDescriptor *me = new IOBufferMemoryDescriptor;
 
-    if (me && !me->initWithBytes(inBytes, inLength, inDirection, inContiguous)){
-        me->release();
-        me = 0;
+    if (me && !me->initWithPhysicalMask(
+               kernel_task, inDirection | kIOMemoryUnshared
+                | (inContiguous ? kIOMemoryPhysicallyContiguous : 0),
+               inLength, inLength, 0 ))
+    {
+       me->release();
+       me = 0;
+    }
+
+    if (me)
+    {
+       // start out with no data
+       me->setLength(0);
+
+       if (!me->appendBytes(inBytes, inLength))
+       {
+           me->release();
+           me = 0;
+       }
     }
     return me;
 }
@@ -335,42 +424,50 @@ void IOBufferMemoryDescriptor::free()
 {
     // Cache all of the relevant information on the stack for use
     // after we call super::free()!
-    IOOptionBits options   = _options;
-    vm_size_t    size     = _capacity;
-    void *       buffer           = _buffer;
-    vm_map_t    map       = 0;
-    vm_offset_t  alignment = _alignment;
+    IOOptionBits     flags         = _flags;
+    IOOptionBits     internalFlags = _internalFlags;
+    IOOptionBits     options   = _options;
+    vm_size_t        size      = _capacity;
+    void *           buffer    = _buffer;
+    IOMemoryMap *    map       = 0;
+    IOAddressRange * range     = _ranges.v64;
+    vm_offset_t      alignment = _alignment;
+
+    if (alignment >= page_size)
+       size = round_page(size);
 
     if (reserved)
     {
        map = reserved->map;
         IODelete( reserved, ExpansionData, 1 );
+       if (map)
+           map->release();
     }
 
     /* super::free may unwire - deallocate buffer afterwards */
     super::free();
 
-    if (buffer)
+    if (options & kIOMemoryPageable)
     {
-        if (options & kIOMemoryPageable)
-       {
-           if (map)
-               vm_deallocate(map, (vm_address_t) buffer, round_page_32(size));
-           else
-              IOFreePageable(buffer, size);
-       }
-        else
-       {
-            if (options & kIOMemoryPhysicallyContiguous)
-                IOFreeContiguous(buffer, size);
-            else if (alignment > 1)
-                IOFreeAligned(buffer, size);
-            else
-                IOFree(buffer, size);
+#if IOALLOCDEBUG
+       debug_iomallocpageable_size -= round_page(size);
+#endif
+    }
+    else if (buffer)
+    {
+        if (internalFlags & kInternalFlagPhysical)
+        {
+            if (kInternalFlagPageSized & internalFlags)
+                size = round_page(size);
+            IOKernelFreePhysical((mach_vm_address_t) buffer, size);
         }
+        else if (alignment > 1)
+            IOFreeAligned(buffer, size);
+        else
+            IOFree(buffer, size);
     }
-    if (map)
-       vm_map_deallocate(map);
+    if (range && (kIOMemoryAsReference & flags))
+       IODelete(range, IOAddressRange, 1);
 }
 
 /*
@@ -398,7 +495,7 @@ void IOBufferMemoryDescriptor::setLength(vm_size_t length)
     assert(length <= _capacity);
 
     _length = length;
-    _singleRange.v.length = length;
+    _ranges.v64->length = length;
 }
 
 /*
@@ -410,7 +507,10 @@ void IOBufferMemoryDescriptor::setLength(vm_size_t length)
  */
 void IOBufferMemoryDescriptor::setDirection(IODirection direction)
 {
-    _direction = direction;
+    _flags = (_flags & ~kIOMemoryDirectionMask) | direction;
+#ifndef __LP64__
+    _direction = (IODirection) (_flags & kIOMemoryDirectionMask);
+#endif /* !__LP64__ */
 }
 
 /*
@@ -423,13 +523,20 @@ void IOBufferMemoryDescriptor::setDirection(IODirection direction)
 bool
 IOBufferMemoryDescriptor::appendBytes(const void * bytes, vm_size_t withLength)
 {
-    vm_size_t actualBytesToCopy = min(withLength, _capacity - _length);
+    vm_size_t   actualBytesToCopy = min(withLength, _capacity - _length);
+    IOByteCount offset;
 
     assert(_length <= _capacity);
-    bcopy(/* from */ bytes, (void *)(_singleRange.v.address + _length),
-          actualBytesToCopy);
+
+    offset = _length;
     _length += actualBytesToCopy;
-    _singleRange.v.length += actualBytesToCopy;
+    _ranges.v64->length += actualBytesToCopy;
+
+    if (_task == kernel_task)
+       bcopy(/* from */ bytes, (void *)(_ranges.v64->address + offset),
+             actualBytesToCopy);
+    else
+       writeBytes(offset, bytes, actualBytesToCopy);
 
     return true;
 }
@@ -441,9 +548,13 @@ IOBufferMemoryDescriptor::appendBytes(const void * bytes, vm_size_t withLength)
  */
 void * IOBufferMemoryDescriptor::getBytesNoCopy()
 {
-    return (void *)_singleRange.v.address;
+    if (kIOMemoryTypePhysical64 == (_flags & kIOMemoryTypeMask))
+       return _buffer;
+    else
+       return (void *)_ranges.v64->address;
 }
 
+
 /*
  * getBytesNoCopy:
  *
@@ -452,13 +563,37 @@ void * IOBufferMemoryDescriptor::getBytesNoCopy()
 void *
 IOBufferMemoryDescriptor::getBytesNoCopy(vm_size_t start, vm_size_t withLength)
 {
-    if (start < _length && (start + withLength) <= _length)
-        return (void *)(_singleRange.v.address + start);
+    IOVirtualAddress address;
+    if (kIOMemoryTypePhysical64 == (_flags & kIOMemoryTypeMask))
+       address = (IOVirtualAddress) _buffer;
+    else
+       address = _ranges.v64->address;
+
+   if (start < _length && (start + withLength) <= _length)
+        return (void *)(address + start);
     return 0;
 }
 
-OSMetaClassDefineReservedUsed(IOBufferMemoryDescriptor, 0);
+#ifndef __LP64__
+void * IOBufferMemoryDescriptor::getVirtualSegment(IOByteCount offset,
+                                                       IOByteCount * lengthOfSegment)
+{
+    void * bytes = getBytesNoCopy(offset, 0);
+    
+    if (bytes && lengthOfSegment)
+       *lengthOfSegment = _length - offset;
+
+    return bytes;
+}
+#endif /* !__LP64__ */
+
+#ifdef __LP64__
+OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 0);
 OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 1);
+#else /* !__LP64__ */
+OSMetaClassDefineReservedUsed(IOBufferMemoryDescriptor, 0);
+OSMetaClassDefineReservedUsed(IOBufferMemoryDescriptor, 1);
+#endif /* !__LP64__ */
 OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 2);
 OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 3);
 OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 4);