Date:   Tue, 24 Jan 2023 13:37:43 -0800
From:   "H. Peter Anvin" <hpa@zytor.com>
To:     "Li, Xin3" <xin3.li@intel.com>,
        Ammar Faizi <ammarfaizi2@gnuweeb.org>,
        x86 Mailing List <x86@kernel.org>
CC:     "Hansen, Dave" <dave.hansen@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>,
        Brian Gerst <brgerst@gmail.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Shuah Khan <shuah@kernel.org>, Ingo Molnar <mingo@kernel.org>,
        "Lutomirski, Andy" <luto@kernel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Linux Kselftest Mailing List 
        <linux-kselftest@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: =?US-ASCII?Q?RE=3A_=5BRFC_PATCH_v3_0/2=5D_selftests/x8?= =?US-ASCII?Q?6=3A_sysret=5Frip_update_for_FRED_system?=
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On January 24, 2023 1:32:14 PM PST, "Li, Xin3" <xin3=2Eli@intel=2Ecom> wrot=
e:
>> From: Ammar Faizi <ammarfaizi2@gnuweeb=2Eorg>
>>=20
>> This is an RFC patchset v3:
>> sysret_rip test update for Intel FRED architecture=2E
>>=20
>> Xin Li reported sysret_rip test fails at:
>>=20
>>         assert(ctx->uc_mcontext=2Egregs[REG_EFL] =3D=3D
>>                ctx->uc_mcontext=2Egregs[REG_R11]);
>
>On FRED systems, flags is 0x200a93 and r11 is 0xfeedfacedeadbeef here=2E
>
>We need to remove or change this assertion, maybe:
>  assert(ctx->uc_mcontext=2Egregs[REG_EFL] =3D=3D ctx->uc_mcontext=2Egreg=
s[REG_R11] ||
>         r11_sentinel =3D=3D ctx->uc_mcontext=2Egregs[REG_R11]);
>
>>=20
>> in a FRED system=2E Let's handle the FRED system scenario too=2E The 's=
yscall'
>> instruction in a FRED system doesn't set %r11=3D%rflags=2E
>>=20
>> There are two patches in this series=2E
>>=20
>> How to test this:
>>=20
>>   $ make -C tools/testing/selftests/x86
>>   $ tools/testing/selftests/x86/sysret_rip_64
>>=20
>> Link: https://lore=2Ekernel=2Eorg/lkml/5d4ad3e3-034f-c7da-d141-
>> 9c001c2343af@intel=2Ecom
>> Fixes: 660602140103 ("selftests/x86: Add a selftest for SYSRET to nonca=
nonical
>> addresses")
>> Link: https://lore=2Ekernel=2Eorg/lkml/25b96960-a07e-a952-5c23-
>> 786b55054126@zytor=2Ecom
>> Reported-by: Xin Li <xin3=2Eli@intel=2Ecom>
>> Co-developed-by: H=2E Peter Anvin (Intel) <hpa@zytor=2Ecom>
>> Signed-off-by: H=2E Peter Anvin (Intel) <hpa@zytor=2Ecom>
>> Acked-by: H=2E Peter Anvin (Intel) <hpa@zytor=2Ecom>
>> Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb=2Eorg>
>> ---
>>=20
>> ## Changelog v3:
>>=20
>>    - Test that we don't get a mix of REGS_SAVED and REGS_SYSRET,
>>      which is a major part of the point (hpa)=2E
>>=20
>> ## Changelog v2:
>>=20
>>    - Use "+r"(rsp) as the right way to avoid redzone problems
>>      per Andrew's comment (hpa)=2E
>>      (Ref: https://lore=2Ekernel=2Eorg/lkml/8f5c24df-514d-5d89-f58f-
>> ec8c3eb1e049@zytor=2Ecom )
>>=20
>> ---
>>=20
>> Ammar Faizi (2):
>>   selftests/x86: sysret_rip: Handle syscall in a FRED system
>>   selftests/x86: sysret_rip: Add more syscall tests with respect to `%r=
cx` and `%r11`
>>=20
>>  tools/testing/selftests/x86/sysret_rip=2Ec | 120 +++++++++++++++++++++=
+-
>>  1 file changed, 119 insertions(+), 1 deletion(-)
>>=20
>>=20
>> base-commit: e12ad468c22065a2826b2fc4c11d2113a7975301
>> --
>> Ammar Faizi
>
>

This should use check_regs_result() =E2=80=93 which is exactly the reason =
I made that a separate function=2E