Re: [RFC PATCH v2 2/2] selftests/x86: sysret_rip: Add more syscall tests with respect to `%rcx` and `%r11`

[H. Peter Anvin]

On 1/23/23 18:27, Ammar Faizi wrote:
> From: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
>
> 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; check
> that it returns a nonnegative value and then save the result.

"Nonnegative" here should be "valid"; it is an implementation detail 
that the error value is -1.

However, you are not checking that you don't get a mix of REGS_SAVED and 
REGS_SYSRET, which is a major part of the point.

	-hpa