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

On Tue, Jan 24, 2023 at 12:59:23PM -0800, H. Peter Anvin wrote:

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.

Added in v4.