VM MODULE ON DEC UNIX
design.mps.vmo1
incomplete doc
drj 1997-03-25
INTRODUCTION
.readership: Any MPS developer.
.intro: This is the design of the VM Module for DEC UNIX (aka OSF/1 os.o1). In
general aspects (including interface) the design is as for design.mps.vm.
DETAILS
Functions
.fun.unmap:
VMUnmap
It "unmaps" a region by replacing the existing mapping with a mapping using the
vm->none_fd file descriptor (see mumble mumble, VMCreate), and protection set
to PROT_NONE (ie no access). .fun.unmap.justify: Replacing the mapping in this
way means that the address space is still reserved and will not be used by
calls to mmap (perhaps in other libraries) which specify MAP_VARIABLE.
.fun.unmap.offset: The offset for this mapping is the offset of the region
being unmapped in the VM; this gives the same effect as if there was one
mapping of the vm->none_fd from the base to the limit of the VM (but "behind"
all the other mappings that have been created). .fun.unmap.offset.justify: If
this is not done (if for example the offset is always specified as 0) then the
VM will cause the kernel to create a new file reference for each mapping
created with VMUnmap; eventually the kernel refuses the mmap call because it
can't create a new file reference.
A. References
B. Document History
| 2002-06-07 | RB | Converted from MMInfo database design document. |
C. Copyright and License
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