Re: http://www.smashguard.org

[Theo de Raadt <deraadt () cvs openbsd org>]

> > > 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.

Oh for the record.  A few chips make it possible to have --x
permissions.

alpha (I am not positive)
sparc64 (I am not positive)

ia64
hppa
amd29k

m88k

The first two have software tlb refillers with a split tlb architecture,
but I am not sure if there is tlb "leak"

The next three have specific page table bits for kernel (r w x) and
user (r w x).

The last has a harvard-style split mmu (entirely different mmu for
code and data), and it should be possible to play games to do it...