RE: [RFC PATCH v5 0/2] sysret_rip update for the Intel FRED architecture

["Li, Xin3" <xin3.li@intel.com>]

This version passes on FRED, thanks a lot for quickly fixing it.

  Xin

> From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
> 
> This is an RFC patchset v5. There are two patches in this series.
> 
> Xin Li reported that the sysret_rip test fails at:
> 
>         assert(ctx->uc_mcontext.gregs[REG_EFL] ==
>                ctx->uc_mcontext.gregs[REG_R11]);
> 
> on the Intel FRED architecture. Let's handle the FRED system scenario too. The
> 'syscall' instruction in a FRED system doesn't set %rcx=%rip and %r11=%rflags.
> 
> Syscall and sysenter in a FRED system are treated equivalently to software
> interrupts, e.g. INT 0x80. They do not modify any registers.
> 
> Link: https://lore.kernel.org/lkml/5d4ad3e3-034f-c7da-d141-
> 9c001c2343af@intel.com
> 
> #### Changelog v5:
> 
>    - Fix do_syscall() return value (Ammar).
> 
> #### Changelog v4:
> 
>    - Fix the assertion condition inside the SIGUSR1 handler (Xin Li).
> 
>    - Explain the purpose of patch #2 in the commit message (HPA).
> 
>    - Update commit message (Ammar).
> 
>    - Repeat test_syscall_rcx_r11_consistent() 32 times to be more sure
>      that the result is really consistent (Ammar).
> 
> #### Changelog v3:
> 
>    - Test that we don't get a mix of REGS_SAVED and REGS_SYSRET,
>      which is a major part of the point (HPA).
> 
> #### Changelog v2:
> 
>    - Use "+r"(rsp) as the right way to avoid redzone problems
>      per Andrew's comment (HPA).
> 
> 
> Co-developed-by: H. Peter Anvin (Intel) <hpa@zytor.com>
> Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
> Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
> ---
> 
> Ammar Faizi (2):
>   selftests/x86: sysret_rip: Handle syscall in a FRED system
>   selftests/x86: sysret_rip: Add more syscall tests with respect to `%rcx` and `%r11`
> 
>  tools/testing/selftests/x86/sysret_rip.c | 146 +++++++++++++++++++++--
>  1 file changed, 137 insertions(+), 9 deletions(-)
> 
> 
> base-commit: e12ad468c22065a2826b2fc4c11d2113a7975301
> --
> Ammar Faizi