On Wed, Jul 13, 2016 at 12:56 AM, Ingo Molnar <mi...@kernel.org> wrote: > > * Andy Lutomirski <l...@amacapital.net> wrote: > >> > 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?
