AddressSpace

The VM extension provides two types of address spaces, "AddressSpace.T" and "Space.T".

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

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.

INTERFACE AddressSpace;

IMPORT Translation, MemoryObject, AddressMap;
IMPORT VMError;
IMPORT VMTypes;

TYPE
  T <: Public;
  Public = Translation.T OBJECT
  METHODS
    init(name: TEXT): T;
    This is the constructor. name is used only for debugging purposes.

destroy();
Frees up all the resources held by the address space.

    allocate(VAR pageNum: VMTypes.PageNumber;
             numPages: VMTypes.PageCount; anyWhere: BOOLEAN)
             RAISES {VMError.E};
    deallocate(pageNum: VMTypes.PageNumber; numPages: VMTypes.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. If anyWhere is true, then allocate first tries the address pageNum. If it is occupied, then it chooses a free region by its own. If anyWhere is false and the address pageNum is occupied, then allocate raises an exception.
Note: The semantics of when "anyWhere" is false is different from UNIX "mmap". This has to be fixed soon!
pageNum and numPages are counted in the MMU page size unit.

    map(pageNum: VMTypes.PageNumber; numPages: VMTypes.PageCount;
        mObj: MemoryObject.T;
        mOff: VMTypes.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.
If lazy is true, then the pages is the region is not immediately paged in. Instead, they are brought in as the user app page faults in the region. If lazy is false, then the pages are eager copied.

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

     Unmaps the memory object mapped on the space. Currently, the region pageNum .. pageNum+numPages must be exactly same as the region specified in previous "mmap" call. In other words, you can not unmap a subregion(or superregion) of a region created by mmap.

    clear() RAISES {VMError.E};
    print(): TEXT;
    iterate(): Iterator;
  END;
  Iterator = AddressMap.Iterator;

CONST
Brand = "AddressSpace-1.1";

PROCEDURE Equal(as1, as2: T): BOOLEAN;
PROCEDURE Hash(as: T): CARDINAL;
PROCEDURE Compare(as1, as2: T): [-1..1];

END AddressSpace.

Last updated: Sun Oct 13 16:36:48 PDT 1996

Stefan Savage (savage@cs.washington.edu)