* Andy Lutomirski <[email protected]> wrote:
> On Wed, Jul 13, 2016 at 12:56 AM, Ingo Molnar <[email protected]> wrote:
> >
> > * Andy Lutomirski <[email protected]> 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?
So I think the way this could be done is by allocating it itself. The vDSO vma
itself is 'external' to glibc as well to begin with - this would be a small
extension to that concept.
Thanks,
Ingo
