CSE 120 (Fall 2002) -- Nachos VM Worksheet
[16 pts] In Project #2, part 1, you need to create a page table
for a new address space, allocate physical memory for the address
space, and then load the program code and data segments into the
address space. This worksheet is intended to give you practice with
Nachos page tables so that you are comfortable implementing these
operations. The context of this worksheet is the AddrSpace
constructor (i.e., interpret references to variables in the context of
the AddrSpace constructor method).
For the purposes of this worksheet, assume that virtual addresses
are 32 bits, PageSize is 128 bytes, the program being loaded requires
4 pages, and physical memory has 8 pages. Assume that no stack is
necessary, and that you only need to load and map the code and data.
In the diagram below, we have assigned a set of physical pages (from
machine->mainMemory) to virtual pages (in pageTable).
- What is the value of the AddrSpace variable numPages?
- What is the value of size?
- What is the value of NumPhysPages?
- What are the values of the pageTable mappings?
- pageTable[0].virtualPage =
- pageTable[0].physicalPage =
- pageTable[1].virtualPage =
- pageTable[1].physicalPage =
- pageTable[2].virtualPage =
- pageTable[2].physicalPage =
- pageTable[3].virtualPage =
- pageTable[3].physicalPage =
- What is the virtual address of virtual page 3 (the start of virtual page 3 in the virtual address space)?
- What is the physical address of virtual page 3?
- What physical page does the virtual address 177 reside in?
- What is the offset of the virtual address 177?
- What is the physical address of the virtual address 177?
In the diagram below, we want to load the code (".text") and
initialized data (".rdata") segments from the executable file into the
virtual address space of the process. Assume that code.inFileAddr has
the value 0xD0 as an offset in the executable file, code.virtualAddr
is 0x00 in the virtual address space, and code.size is 0x144 bytes.
Also assume that initData.inFileAddr is 0x3C0 in the executable file,
initData.virtualAddr is 0x144 in the virtual address space, and
initData.size is 0x020 bytes.
- What is the physical address that corresponds to code.virtualAddr?
- What physical pages is the code loaded into?
- What is the physical address that corresponds to initData.virtualAddr?
- What physical page is the initialized data loaded into?
- At what virtual address does the initialized data end?
- Now assume that initData.size is 0x0A0 bytes. What additional
physical page is the initialized data loaded into?
- Now at what virtual address does the initialized data end?