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To: Bruce Evans <bde@zeta.org.au>
cc: freebsd-hackers@FreeBSD.org
Subject: Re: Commerical applications (was: Development and validation 
In-reply-to: Your message of "Wed, 22 Jan 1997 15:29:20 +1100."
             <199701220429.PAA01813@godzilla.zeta.org.au> 
References: <199701220429.PAA01813@godzilla.zeta.org.au> 
Date: Tue, 21 Jan 1997 20:37:24 -0800
From: John Polstra <jdp@polstra.com>
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[double mapping the boundary page]

> Isn't this just wasteful on (flat model) i386's?  It provides no
> protection against writing the text in the boundary page via the
> data mapping, and isn't necessary for execution because the i386
> doesn't have an execution bit in its page tables.

Yes, I think you're right.  The double mapping has to take place, though,
because the linker has relocated addresses based on the assumption that
it will take place.  The linker could be changed not to do that, but
then it wouldn't be ELF any more.

John