Re: Preventing Pentium Deaths
ralf@hotel.uni-koblenz.de
Wed, 12 Nov 1997 10:50:12 +0100
On Tue, Nov 11, 1997 at 04:22:39PM +0100, Alexander Kjeldaas wrote:
> Loooking through the arch-directories it seems that alpha might be the
> _only_ architecture linux runs on that is designed "correctly".
>
> PowerPC has the no-exec bit set in the segment descriptor and two bits
> indicating read/write in the PTE,
>
> MIPS seems to be similar to PowerPC (two bits in PTE). m68k (according to
> "the source") is also in this league.
Correct for all MIPS. The m68k case is more complicated as m68k CPUs
have several different types of MMUs. The one in the mc68851 and the
68030 can enable an additional level of lookups for the pagetable tree.
This first level is being indexed with the function code. Using it
would even allow different translations for code, data.The cost in
terms of performance and memory for the increased size of the page
table would however be unacceptable.
Ralf