Re: [RFC][PATCH 08/24] x86/entry: Add C version of SWAPGS and SWAPGS_UNSAFE_STACK

[Andy Lutomirski]

On Mon, Nov 9, 2020 at 3:22 AM Alexandre Chartre
<alexandre.chartre@xxxxxxxxxx> wrote:
>
> SWAPGS and SWAPGS_UNSAFE_STACK are assembly macros. Add C versions
> of these macros (swapgs() and swapgs_unsafe_stack()).

This needs a very good justification.  It also needs some kind of
static verification that these helpers are only used by noinstr code,
and they need to be __always_inline.  And I cannot fathom how C code
could possibly use SWAPGS_UNSAFE_STACK in a meaningful way.