IOMemoryMap

Inherits from
OSObject
Availability
Available in OS X v10.0 and later.
Declared in
IOMemoryDescriptor.h

Overview

A class defining common methods for describing a memory mapping.

The IOMemoryMap object represents a mapped range of memory, described by a IOMemoryDescriptor. The mapping may be in the kernel or a non-kernel task and has processor cache mode attributes. IOMemoryMap instances are created by IOMemoryDescriptor when it creates mappings in its map method, and returned to the caller.

Tasks

Miscellaneous

Instance Methods

getAddress()

Accessor to the length of the mapping.

inline mach_vm_address_t getAddress() __attribute__((always_inline));
Return Value

A byte count.

Discussion

This method returns the length of the mapping.

getAddress()

Accessor to the length of the mapping.

virtual mach_vm_address_t getAddress();
Return Value

A byte count.

Discussion

This method returns the length of the mapping.

getAddressTask

Accessor to the task of the mapping.

virtual task_t getAddressTask();
Return Value

A mach task_t.

Discussion

This method returns the mach task the mapping exists in.

getLength

Accessor to the length of the mapping.

virtual IOByteCount getLength();
Return Value

A byte count.

Discussion

This method returns the length of the mapping.

getMapOptions

Accessor to the options the mapping was created with.

virtual IOOptionBits getMapOptions();
Return Value

Options for the mapping, including cache settings.

Discussion

This method returns the options to IOMemoryDescriptor::map the mapping was created with.

getMemoryDescriptor

Accessor to the IOMemoryDescriptor the mapping was created from.

virtual IOMemoryDescriptor * getMemoryDescriptor();
Return Value

An IOMemoryDescriptor reference, which is valid while the IOMemoryMap object is retained. It should not be released by the caller.

Discussion

This method returns the IOMemoryDescriptor the mapping was created from.

getPhysicalAddress

Return the physical address of the first byte in the mapping.

IOPhysicalAddress getPhysicalAddress();
Return Value

A physical address.

Discussion

This method returns the physical address of the first byte in the mapping. It is most useful on mappings known to be physically contiguous.

getPhysicalSegment

Break a mapping into its physically contiguous segments.

#ifdef __LP64__ virtual IOPhysicalAddress getPhysicalSegment( IOByteCount offset, IOByteCount *length, IOOptionBits options = 0); #else /* !__LP64__ */ virtual IOPhysicalAddress getPhysicalSegment( IOByteCount offset, IOByteCount *length); #endif /* !__LP64__ */
Parameters
offset

A byte offset into the mapping whose physical address to return.

length

If non-zero, getPhysicalSegment will store here the length of the physically contiguous segement at the given offset.

Return Value

A physical address, or zero if the offset is beyond the length of the mapping.

Discussion

This method returns the physical address of the byte at the given offset into the mapping, and optionally the length of the physically contiguous segment from that offset. It functions similarly to IOMemoryDescriptor::getPhysicalSegment.

getSize()

Accessor to the length of the mapping.

inline mach_vm_address_t getAddress() __attribute__((always_inline));
Return Value

A byte count.

Discussion

This method returns the length of the mapping.

getSize()

Accessor to the length of the mapping.

virtual mach_vm_address_t getAddress();
Return Value

A byte count.

Discussion

This method returns the length of the mapping.

getVirtualAddress

Accessor to the virtual address of the first byte in the mapping.

virtual IOVirtualAddress getVirtualAddress();
Return Value

A virtual address.

Discussion

This method returns the virtual address of the first byte in the mapping. Since the IOVirtualAddress is only 32bit in 32bit kernels, the getAddress() method should be used for compatibility with 64bit task mappings.

redirect

Replace the memory mapped in a process with new backing memory.

#ifndef __LP64__ virtual IOReturn redirect( IOMemoryDescriptor *newBackingMemory, IOOptionBits options, IOByteCount offset = 0); #endif
Parameters
newBackingMemory

The IOMemoryDescriptor that represents the physical memory that is to be now mapped in the virtual range the IOMemoryMap represents. If newBackingMemory is NULL, any access to the mapping will hang (in vm_fault()) until access has been restored by a new call to redirect() with non-NULL newBackingMemory argument.

options

Mapping options are defined in IOTypes.h, and are documented in IOMemoryDescriptor::map()

offset

As with IOMemoryDescriptor::map(), a beginning offset into the IOMemoryDescriptor's memory where the mapping starts. Zero is the default.

Return Value

An IOReturn code.

Discussion

An IOMemoryMap created with the kIOMapUnique option to IOMemoryDescriptor::map() can remapped to a new IOMemoryDescriptor backing object. If the new IOMemoryDescriptor is specified as NULL, client access to the memory map is blocked until a new backing object has been set. By blocking access and copying data, the caller can create atomic copies of the memory while the client is potentially reading or writing the memory.

unmap

Force the IOMemoryMap to unmap, without destroying the object.

virtual IOReturn unmap();
Return Value

An IOReturn code.

Discussion

IOMemoryMap instances will unmap themselves upon free, ie. when the last client with a reference calls release. This method forces the IOMemoryMap to destroy the mapping it represents, regardless of the number of clients. It is not generally used.