Re: http://www.smashguard.org

[Crispin Cowan <crispin@xxxxxxxxxxx>]

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/
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