Re: Do x86 NX and AMD prefetch check cause page fault infinite loop?

[Jamie Lokier <jamie@shareable.org>]

On x86 and x86-64 with NX, is a fault due to non-exec permission
distinguishable from a fault due to lack of read/write permissions?

I.e. does the flags word have a different bit set?

If so, the solution is simple: don't just return if it's a non-exec fault.

(It's possible that won't work if the CPU is very speculative and
generates data faults from prefetches despite them being in non-exec
area -- i.e. if the buggy data fault gets precedence over the non-exec
fault or segment.  But I'd hope that's not the case).

-- Jamie