Address space interfaces

AddressSpace.T provides the reservation of an address range, and mapping and unmapping of a memory object on the address space.

The Space.T is a subtype of AddressSpace.T. Thus, it supports all the services that AddressSpace.T provides. In addition to them, Space.T provides reading and writing on it.

AddressSpace.T

init(name: TEXT): T;

destroy();

Initializes and destroys the address space.

allocate(VAR pageNum: PageNumber; numPages: PageCount; anyWhere: BOOLEAN) RAISES {VMError.E};

deallocate(pageNum: PageNumber; numPages: PageCount) RAISES {VMError.E};

These methods reserve or unreserve the virtual address region without allocating memory. They are used to reserve a certain region for later use.

map(pageNum: PageNumber; numPages: PageCount; mObj: MemoryObject.T; mOff: PageNumber; lazy := FALSE) RAISES {VMError.E};

map maps the region mOff to mOff+numPages of the memory object mObj on the virtual address pageNum to pageNum + numPages. mOff, pageNum, and numPages are all specified in machine MMU page unit. On Alpha, the page size is 8192 bytes.

The region pageNum to pageNum + numPages must be reserved beforehand using allocate

foo         bar unmap(pageNum: PageNumber; numPages: PageCount) RAISES {VMError.E};

Undos the previous map.

clear() RAISES {VMError.E};

Unmaps all the memory objects mapped on the address space.

Space.T

PROCEDURE Create(): T;

PROCEDURE Destroy(space: T);

Create and destroy an address space.

PROCEDURE Duplicate(space: T): T RAISES {VMError.E};

Create a copy of the space

Note: no copy on write now. Everything is copied eagerly.

PROCEDURE Allocate(space: T; VAR addr: VirtAddr.Address; size: VirtAddr.Size; anywhere: BOOLEAN := FALSE): VirtAddr.T RAISES {VMError.E};

PROCEDURE Deallocate(space:T;v: VirtAddr.T := NIL; addr: VirtAddr.Address; size: VirtAddr.Size): VirtAddr.T RAISES {VMError.E};

These two allocates a memory on the specified region. Note that unlike AddressSpace.allocate, Allocate actually allocates a memory on the region.

PROCEDURE Read(space: T; fromaddr: VirtAddr.Address; VAR to: ARRAY OF CHAR; size := -1) RAISES {VMError.E};

PROCEDURE Write(space: T; READONLY from: ARRAY OF CHAR; to : VirtAddr.Address; size := -1) RAISES {VMError.E};

These procedures reads or writes the specified region. Page faults may happen. If size is ommitted, it is assumed to be NUMBER(to) or NUMBER(from).

PROCEDURE Protect(space: T; v: VirtAddr.T := NIL; addr: VirtAddr.Address; size: VirtAddr.Size; prot: Protection ) RAISES {VMError.E};

This procedure changes the protection mode.