Re: [PATCH 05/22] x86/fpu: Remove fpu->initialized usage in copy_fpstate_to_sigframe()

Oleg Nesterov
2019-01-22T16:15:59Z

On 01/22, Borislav Petkov wrote:
>
> On Mon, Jan 21, 2019 at 12:21:17PM +0100, Oleg Nesterov wrote:
> > 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.
>
> Well, we were just speculating whether doing that would simplify the
> code around get_sigframe() et al. But if that is an ABI, then we can't
> really touch it.
>
> Btw, where is that whole ABI deal about saving FPU regs on the user
> signal stack documented?

I don't know... tried to google, found nothing.

the comment in /usr/include/sys/ucontext.h mentions SysV/i386 ABI + historical
reasons, this didn't help.

Oleg.