Re: [PATCH v2] NOMMU: add support for Memory Protection Units (MPU)

[David Howells <dhowells@redhat.com>]

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?

David