Re: [RFC PATCH v2 1/2] selftests/x86: sysret_rip: Handle syscall in a FRED system

H. Peter Anvin
2023-01-24T05:49:10Z

On 1/23/23 18:27, Ammar Faizi wrote:
> From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
>
> The current selftest asserts %r11 == %rflags after the 'syscall'
> returns to user. Such an assertion doesn't apply to a FRED system
> because in a FRED system the 'syscall' instruction does not set
> %r11=%rflags and %rcx=%rip.
>
> Handle the FRED case. Now, 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.
>
> The 'raise()' function from libc can't be used to control those
> registers. Therefore, create a syscall wrapper in inline Assembly to
> fully control them.
>
> Fixes: 660602140103 ("selftests/x86: Add a selftest for SYSRET to noncanonical addresses")
> Link: https://lore.kernel.org/lkml/25b96960-a07e-a952-5c23-786b55054126@zytor.com
> Reported-by: Xin Li <xin3.li@intel.com>
> Co-developed-by: "H. Peter Anvin" <hpa@zytor.com>
> Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
> ---
>
> Need hpa's sign off.
>

For both patches:

Acked-by: H. Peter Anvin (Intel) <hpa@zytor.com>