On 01/18, Dave Hansen wrote: > > On 1/18/19 1:14 PM, Sebastian Andrzej Siewior wrote: > > The kernel saves task's FPU registers on user's signal stack before > > entering the signal handler. Can we avoid that and have in-kernel memory > > for that? Does someone rely on the FPU registers from the task in the > > signal handler? > > This is part of our ABI for *sure*. Inspecting that state is how > userspace makes sense of MPX or protection keys faults. We even use > this in selftests/. Yes. And in any case I do not understand the idea to use the second in-kernel struct fpu. A signal handler can be interrupted by another signal, this will need to save/restore the FPU state again. Oleg.
