On 28.09.2020 14:30, Jan Beulich wrote:
> Commit b586a81b7a90 ("x86/CET: Fix build following c/s 43b98e7190") had
> to introduce a number of #ifdef-s to make the build work with older tool
> chains. Introduce an assembler macro covering for tool chains not
> knowing of CET-SS, allowing some conditionals where just SETSSBSY is the
> problem to be dropped again.
>
> No change to generated code.
>
> Signed-off-by: Jan Beulich <jbeul...@suse.com>
> Reviewed-by: Roger Pau Monné <roger....@citrix.com>
> ---
> Now that I've done this I'm no longer sure which direction is better to
> follow: On one hand this introduces dead code (even if just NOPs) into
> CET-SS-disabled builds.
A possible compromise here might be to ...
> --- a/xen/include/asm-x86/asm-defns.h
> +++ b/xen/include/asm-x86/asm-defns.h
> @@ -7,3 +7,9 @@
> .byte 0x0f, 0x01, 0xcb
> .endm
> #endif
> +
> +#ifndef CONFIG_HAS_AS_CET_SS
> +.macro setssbsy
> + .byte 0xf3, 0x0f, 0x01, 0xe8
> +.endm
> +#endif
... comment out this macro's body. If we went this route, incssp
and wrssp could be dealt with in similar ways, to allow dropping
further #ifdef-s.
Jan
