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Date: Fri, 30 Aug 2002 01:22:33 +0200
From: Pavel Machek <pavel@suse.cz>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Pavel Machek <pavel@suse.cz>, Luca Barbieri <ldb@ldb.ods.org>,
       Linux-Kernel ML <linux-kernel@vger.kernel.org>,
       Linus Torvalds <torvalds@transmeta.com>
Subject: Re: [PATCH 1 / ...] i386 dynamic fixup/self modifying code
Message-ID: <20020829232233.GA18573@atrey.karlin.mff.cuni.cz>
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Hi!


> > > Unfortunately with this patch executing invalid code will cause the
> > > processor to enter an infinite exception loop rather than panic. Fixing
> > > this is not trivial for SMP+preempt so it's not done at the moment.
> > 
> > Using 0xcc for everything should fix that, right?
> 
> Except you can't do the fixup on SMP without risking hitting the CPU
> errata. You also break debugging tools that map kernel code pages r/o
> and people who ROM it.
> 
> The latter aren't a big problem (they can compile without runtime
> fixups). For the other fixups though you -have- to do them before you
> run the code. That isnt hard (eg sparc btfixup). You generate a list of
> the addresses in a segment, patch them all and let the init freeup blow 
> the table away

Aha, making a list and just patching early at boot is even simpler
than method I was thinking about.... Why not do it that way?
								Pavel
-- 
Casualities in World Trade Center: ~3k dead inside the building,
cryptography in U.S.A. and free speech in Czech Republic.
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