Re: A question about PROT_NONE on Sparc and Sparc64

[Jakub Jelinek]

On Wed, Jun 30, 2004 at 04:05:03AM +0100, Jamie Lokier wrote:
> I'm doing a survey of the different architectural implementations of
> PROT_* flags for mmap() and mprotect().  I'm looking at linux-2.6.5.
> 
> The Sparc and Sparc64 implementations are very similar to plain x86:
> read implies exec, exec implies read and write implies read.
> 
> (Aside: A comment in include/asm-sparc/pgtsrmmu.h says that finer-grained
> access is possible.  Quite a few other architectures do implement
> finer-grained access, and even x86 is getting it now, so you may want
> to revisit that.  The code is already available, and tested, if you
> cut that part out of the PaX security patch).

I believe R!X and X!R pages ought to be possible on sparc64 too, just use a
different bit as "read" in the fast ITLB miss handler from the one fast DTLB
miss uses.

	Jakub
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