* Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > On Wed, Jul 13, 2016 at 12:56 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote: > > > > * Andy Lutomirski <luto@xxxxxxxxxxxxxx> 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>