[RFC PATCH v3 0/2] selftests/x86: sysret_rip update for FRED system

[Ammar Faizi]

From: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>

This is an RFC patchset v3:
sysret_rip test update for Intel FRED architecture. 

Xin Li reported sysret_rip test fails at:

        assert(ctx->uc_mcontext.gregs[REG_EFL] ==
               ctx->uc_mcontext.gregs[REG_R11]);

in a FRED system. Let's handle the FRED system scenario too. The
'syscall' instruction in a FRED system doesn't set %r11=%rflags.

There are two patches in this series.

How to test this:

  $ make -C tools/testing/selftests/x86
  $ tools/testing/selftests/x86/sysret_rip_64

Link: https://lore.kernel.org/lkml/5d4ad3e3-034f-c7da-d141-9c001c2343af@xxxxxxxxx
Fixes: 660602140103 ("selftests/x86: Add a selftest for SYSRET to noncanonical addresses")
Link: https://lore.kernel.org/lkml/25b96960-a07e-a952-5c23-786b55054126@xxxxxxxxx
Reported-by: Xin Li <xin3.li@xxxxxxxxx>
Co-developed-by: H. Peter Anvin (Intel) <hpa@xxxxxxxxx>
Signed-off-by: H. Peter Anvin (Intel) <hpa@xxxxxxxxx>
Acked-by: H. Peter Anvin (Intel) <hpa@xxxxxxxxx>
Signed-off-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
---

## 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).
     (Ref: https://lore.kernel.org/lkml/8f5c24df-514d-5d89-f58f-ec8c3eb1e049@xxxxxxxxx )

---

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 | 120 ++++++++++++++++++++++-
 1 file changed, 119 insertions(+), 1 deletion(-)


base-commit: e12ad468c22065a2826b2fc4c11d2113a7975301
-- 
Ammar Faizi