Re: [PATCH 5/6] x86/fpu/xstate: Define new functions for clearing fpregs and xstates

From: Borislav Petkov
Date: Wed Oct 09 2019 - 13:28:16 EST

On Wed, Sep 25, 2019 at 08:10:21AM -0700, Yu-cheng Yu wrote:
> From: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> Currently, fpu__clear() clears all fpregs and xstates. Once XSAVES
> supervisor states are introduced, supervisor settings must remain active
> for signals;

I could very well use an example here: for signal handling supervisor
states, I'm guessing this would be something CET-related so some text
about a usage scenario would be very helpful here.

> it is necessary to have separate functions:
> - Create fpu__clear_user_states(): clear only user settings for signals;
> - Create fpu__clear_all(): clear both user and supervisor settings in
> flush_thread().
> Also modify copy_init_fpstate_to_fpregs() to take a mask from above two
> functions.
> Co-developed-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
> Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>

As before...