x86/fpu: Rename and sanitize fpu__save/copy()

x86/fpu: Rename and sanitize fpu__save/copy()

Both function names are a misnomer.

fpu__save() is actually about synchronizing the hardware register state
into the task's memory state so that either coredump or a math exception
handler can inspect the state at the time where the problem happens.

The function guarantees to preserve the register state, while "save" is a
common terminology for saving the current state so it can be modified and
restored later. This is clearly not the case here.

Rename it to fpu_sync_fpstate().

fpu__copy() is used to clone the current task's FPU state when duplicating
task_struct. While the register state is a copy the rest of the FPU state
is not.

Name it accordingly and remove the really pointless @src argument along
with the warning which comes along with it.

Nothing can ever copy the FPU state of a non-current task. It's clearly
just a consequence of arch_dup_task_struct(), but it makes no sense to
proliferate that further.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121455.196727450@linutronix.de