Re: [RFC v5 00/38] powerpc: Memory Protection Keys
From: Michal Hocko <mhocko@kernel.org>
Date: 2017-07-12 07:39:54
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On Wed 12-07-17 09:23:37, Michal Hocko wrote:
On Tue 11-07-17 12:32:57, Ram Pai wrote:
[...]
quoted
Ideally the MMU looks at the PTE for keys, in order to enforce protection. This is the case with x86 and is the case with power9 Radix page table. Hence the keys have to be programmed into the PTE.But x86 doesn't update ptes for PKEYs, that would be just too expensive. You could use standard mprotect to do the same...
OK, this seems to be a misunderstanding and confusion on my end. do_mprotect_pkey does mprotect_fixup even for the pkey path which is quite surprising to me. I guess my misunderstanding comes from Documentation/x86/protection-keys.txt " Memory Protection Keys provides a mechanism for enforcing page-based protections, but without requiring modification of the page tables when an application changes protection domains. It works by dedicating 4 previously ignored bits in each page table entry to a "protection key", giving 16 possible keys. " So please disregard my previous comments about page tables and sorry about the confusion. -- Michal Hocko SUSE Labs