Re: [PATCH 6/9] x86, pkeys: add pkey set/get syscalls

On Wed, Jul 13, 2016 at 12:56 AM, Ingo Molnar [off-list ref] wrote:

* Andy Lutomirski [off-list ref] wrote:

quoted

quoted

If we push a PKRU value into a thread between the rdpkru() and wrpkru(), we'll
lose the content of that "push".  I'm not sure there's any way to guarantee
this with a user-controlled register.

We could try to insist that user code uses some vsyscall helper that tracks
which bits are as-yet-unassigned.  That's quite messy, though.

Actually, if we turned the vDSO into something more like a minimal user-space
library with the ability to run at process startup as well to prepare stuff then
it's painful to get right only *once*, and there will be tons of other areas where
a proper per thread data storage on the user-space side would be immensely useful!

Doing this could be tricky: how exactly is the vDSO supposed to find
per-thread data without breaking existing glibc?

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