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Fix PROT_NONE page permissions when !CPU_USE_DOMAINS

Benjamin Herrenschmidt linux-arm-kernel 1 version New

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  1. v1 Latest0 of 4 patches 0 repliesNew

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Cover letter [PATCH 0/4] Fix PROT_NONE page permissions when !CPU_USE_DOMAINS

On Thu, 2012-09-20 at 23:12 +0100, Russell King - ARM Linux wrote:

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That'll make the set_pte assembly more horrid, but I guess that's the price you pay for removing useful features which architecture folk don't like from CPUs... and it gets more horrid because you can't encode some of those bit patterns with the standard 8-bit and shift opcode representation.

Really fun bug, but it needs more thought about how to solve it.

Yeah, fun isn't it ? :-)

The x86 way to solve it is simple, though ugly ... They use a SW bit called "PROTNONE". A PROT_NONE page gets that instead of the HW valid bit and pte_present() test if any of them is set.

Cheers,
Ben.

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