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assemblymemory-managementcomputer-sciencecpu-architecturelow-level

Address space map R/W

What results are returned when Reading / Writing to space, where no memory is mapped? What is inside this "Nothing" areas?

EDIT 1

In context of x86

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Solution

  • In general, the sequence the processor goes through if you access a memory location (page) is:

    1. Is there are page table entry for the address? If not, access violation (i.e. nothing in your example).

    2. Is there the page table entry marked as having a mapping? If no, access violation (a nothing area).

    3. Is the currently page mapped to a physical page frame? If no, PAGE FAULT.

    4. Does the process have access to the page in its current mode? If no, access violation (Not a "nothing area")

    The nothings then either have no corresponding page table entry or the page table entry has no mapping.