Messages in this thread | | | From | Andy Lutomirski <> | Date | Wed, 17 Feb 2016 16:46:39 -0800 | Subject | Re: [PATCH 33/33] x86, pkeys: execute-only support |
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On Wed, Feb 17, 2016 at 2:53 PM, Dave Hansen <dave@sr71.net> wrote: > On 02/17/2016 02:17 PM, Andy Lutomirski wrote: >>> > Is there a way to detect this feature's availability without userspace >>> > having to set up a segv handler and attempting to read a >>> > PROT_EXEC-only region? (i.e. cpu flag for protection keys, or a way to >>> > check the protection to see if PROT_READ got added automatically, >>> > etc?) >>> > >> We could add an HWCAP. > > I'll bite. What's an HWCAP?
It's a CPU capability vector that's passed to every program as an auxv entry. On x86, ELF_HWCAP is useless (it's already fully used up for pointless purposes for CPUID stuff), but ELF_HWCAP2 could be added and a bit could be defined like HWCAP2_PROT_EXEC_ONLY.
Some day, WRFSBASE, etc will be advertised via ELF_HWCAP2, I suspect.
--Andy
-- Andy Lutomirski AMA Capital Management, LLC
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