Messages in this thread | | | Date | Tue, 14 Jul 2009 22:59:52 +0100 | From | Bernd Schmidt <> | Subject | Re: [PATCH v2] NOMMU: add support for Memory Protection Units (MPU) |
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David Howells wrote: > Mike Frysinger <vapier@gentoo.org> 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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