Paging Can Do It All
If segmentation is eliminated and Paging is used, the Paging Unit can provide complete protection, as well as the paging capability described in the previous chapter. The Paging Unit provides the following checks on each memory access attempt:
A privilege check using the PTE's U/S bit.
Read/write permission checking using the PTE's R/W bit.
When a memory access is attempted, the Paging Unit deals with one of three cases:
The target page is currently in memory (P = 1 in the PTE). Assuming that the currently executing program has sufficient privilege to access the page and that it's not attempting to write to a read-only page, the access is permitted.
The target page isn't in memory (P = 0 in the PTE). This results in a Page ...
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