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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [RFC][PATCH] x86: CS limit checks
Date: Thu, 17 Jul 2008 18:45:44 +0100
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To: qemu-devel@nongnu.org
Cc: Jan Kiszka <jan.kiszka@siemens.com>

> To me it looks like as if the generator can so far raise a PF
> prematurely when it steps on an invalid code address while building a
> new TB. This probably has to fix the same way as the limit check is
> realized: by injecting an exception (PF or GP) into the generated code
> at the correct PC. Hmm, the PF-during-translation issue is probably not
> just limited to x86...

Alpha, PPC, SPARC, SH and ARM avoid the problem by having fixed length word 
aligned instructions. Thumb-1 has special handling for the cross-boundary 
case (Instructions aren't really variable length, we just treat them that way 
as an optimisation).

Thumb-2, m68k, cris and x86 all look like they may incorrectly fetch code from 
the next page.

Paul