Re: [RFC PATCH v3 2/2] selftests/x86: sysret_rip: Add more syscall tests with respect to `%rcx` and `%r11`

H. Peter Anvin
2023-01-24T21:02:47Z

On 1/24/23 02:09, Ammar Faizi wrote:
> From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
>
> Test that:
>
> - "syscall" in a FRED system doesn't clobber %rcx and %r11.
> - "syscall" in a non-FRED system sets %rcx=%rip and %r11=%rflags.
>
> Test them out with a trivial system call like __NR_getppid and friends
> which are extremely likely to return with SYSRET on an IDT system.
>
> Link: https://lore.kernel.org/lkml/25b96960-a07e-a952-5c23-786b55054126@zytor.com
> Co-developed-by: H. Peter Anvin (Intel) <hpa@zytor.com>
> Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
> Acked-by: H. Peter Anvin (Intel) <hpa@zytor.com>
> Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>

Add to the description that the purpose of this is to ensure that
various system calls are *consistent*, as per the comment immediately
below your code.

-hpa