Messages in this thread | | | Subject | AMD / Memory Protection Keys | From | Dave Hansen <> | Date | Wed, 29 Apr 2020 12:18:06 -0700 |
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The docs for AMD's implementation of protection keys showed up[1]. Welcome to the party!
It all looks fine, except for this nugget:
The MPK mechanism is ignored in the following cases: ... for pages marked in the paging structures as read-only (R/W=0) or as supervisor addresses (U/S=0)
That R/W=0 would mean that you can't access-disable read-only pages, which seems a bit goofy. It's certainly a feature that I could imagine folks wanting to have. Read-only pages might happen in unexpected places for things like mmap(PROT_WRITE)'d files or even CoW pages after fork().
Is this an error in the docs?
1. https://www.amd.com/system/files/TechDocs/24593.pdf
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