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Date: Sun, 31 Aug 2003 19:15:44 +1000
From: Peter Jeremy <PeterJeremy@optushome.com.au>
To: "Pedro F. Giffuni" <giffunip@yahoo.com>
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Subject: Re: Non-executable mappings now in NetBSD too
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On Sun, Aug 31, 2003 at 12:06:28AM +0100, Pedro F. Giffuni wrote:
>> Emacs and perl both use traditional bytecode interpreters, as does the
>> Classic JVM.  I agree they will be unaffected.  This change will only
>> impact JIT JVMs.
>
>Well, we only have a JIT JVM for the i386, and on the particular case of the
>i386 we cannot enforce full protection anyways so there is probably a
>workaround if we do need it. 

Based on some recent BUGTRAQ postings, OpenBSD has a trick to support
full protection on the i386.  The text segment and executable part of
shared libraries are placed at low virtual addresses and CS is
restricted to only cover the low address space.  I don't know whether
it's worthwhile to implement something along these lines in FreeBSD.

Peter