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