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    SubjectRe: [PATCH v2] NOMMU: add support for Memory Protection Units (MPU)
    David Howells wrote:
    > Mike Frysinger <> wrote:
    >> Some architectures (like the Blackfin arch) implement some of the
    >> "simpler" features that one would expect out of a MMU such as memory
    >> protection. In our case, we actually get read/write/exec protection
    >> down to the page boundary so processes can't stomp on each other let
    >> alone the kernel. There is a performance decrease (which depends greatly
    >> on the workload) however as the hardware/software interaction was not
    >> optimized at design time.
    > It occurs to me that I could probably test this on FRV by using the MMU in a
    > limited way. How do you actually keep track of the protections applied? Do
    > you have a single global page table that is managed by the mmap code on a
    > per-VMA basis?

    No page table, just three bitmaps (r/w/x), with one bit per page, per mm.

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