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

Dave Hansen
2019-01-18T21:43:20Z

On 1/18/19 1:37 PM, Sebastian Andrzej Siewior wrote:
> On 2019-01-18 13:17:28 [-0800], 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*.
>
> I missed that part. I will try to look it up and look see if says
> something about optional part.
> But ABI means we must keep doing it even if there are no users?

I'd bet a large sum of money there are users.

Google for 'uc_mcontext fpregs'.