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From
SubjectRe: 64bit port
Date
Followup to:  <Pine.LNX.4.10.9905011108010.2314-100000@tahallah.demon.co.uk>
By author: Alex Buell <alex.buell@tahallah.demon.co.uk>
In newsgroup: linux.dev.kernel
> On Sat, 1 May 1999, David Miller wrote:
>
> > When Jakub and I get the 64-bit userland bootstrapped, I'll start
> > running crashme to learn what the exact instruction sequences are so
> > we have a chance at coding a more suitable workaround than what
> > Solaris has chosen.
>
> How about a run-time mechanism for detecting illegal instructions and
> modifying them into harmless NOP sequences?
>
> Ie. on loading of a binary could quickly scan it for illegal sequences and
> overwrite with NOPs, then execute it. Of course, this doesn't cater for
> things that does J-I-T compilation & execution though.
>

No good... it's trivial for the malicious user to bypass the
simple-minded check. The general problem is uncomputable.

-hpa
--
"The user's computer downloads the ActiveX code and simulates a 'Blue
Screen' crash, a generally benign event most users are familiar with
and that would not necessarily arouse suspicions."
-- Security exploit description on http://www.zks.net/p3/how.asp

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