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Date: Thu, 29 Apr 2004 16:24:08 -0700 From: Crispin Cowan <crispin@...unix.com> To: Pavel Machek <pavel@....cz> Cc: Hilmi Ozdoganoglu <cyprian@...due.edu>, Dave Paris <dparis@...orks.com>, bugtraq@...urityfocus.com Subject: Re: http://www.smashguard.org Pavel Machek wrote: >>>The idea is not to create "custom CPUs" but to have our modification >>>picked up by major vendors. Clearly there is interest in applying >>>hardware to solve security issues based on the latest press releases >>> >>> >>>from AMD that AMD chips include buffer-overflow protection (see >> >> >>>Computer World, January 15, 2004). >>> >>> >>> >>As Theo said, the AMD buffer overflow "protection" is nothing more than >>sensible separation of R and X bits per page, fixing a glaring and >> >> > >Actually it is not "sensible", and it is not separation. > >You can have r--, r-x, but you can't have --x. > > But that is *exactly* what is meant by "separation" of R and X. I have no idea what you mean by it not being "sensible". Most every CPU I have ever seen does this except the x86. Someone apparently thought there was no value in separate R and X bits for the i386 back in the mid-80s. It was a false economy :) Crispin -- Crispin Cowan, Ph.D. http://immunix.com/~crispin/ CTO, Immunix http://immunix.com Immunix 7.3 http://www.immunix.com/shop/
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