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Message-ID: <6206.1247592126@redhat.com>
Date: Tue, 14 Jul 2009 18:22:06 +0100
From: David Howells <dhowells@...hat.com>
To: Mike Frysinger <vapier@...too.org>
Cc: dhowells@...hat.com, linux-kernel@...r.kernel.org,
uclinux-dist-devel@...ckfin.uclinux.org,
Bernd Schmidt <bernds_cb1@...nline.de>,
Bryan Wu <cooloney@...nel.org>
Subject: Re: [PATCH v2] NOMMU: add support for Memory Protection Units (MPU)
Mike Frysinger <vapier@...too.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
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