From:   Ammar Faizi <ammarfaizi2@gnuweeb.org>
To:     "H. Peter Anvin" <hpa@zytor.com>, Xin Li <xin3.li@intel.com>
Cc:     Dave Hansen <dave.hansen@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andrew Cooper <Andrew.Cooper3@citrix.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Brian Gerst <brgerst@gmail.com>,
        Borislav Petkov <bp@alien8.de>, Shuah Khan <shuah@kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        x86 Mailing List <x86@kernel.org>,
        Linux Kselftest Mailing List 
        <linux-kselftest@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [RFC PATCH v7 0/3] sysret_rip update for the Intel FRED architecture
Date:   Thu, 26 Jan 2023 06:24:12 +0700
Message-Id: <20230125232415.860397-1-ammarfaizi2@gnuweeb.org>
In-Reply-To: <Y8+hGxVpgFVcm15g@biznet-home.integral.gnuweeb.org>
References: <b6e36a5c-6f5e-eda6-54ad-a0c20eb00402@intel.com> <25b96960-a07e-a952-5c23-786b55054126@zytor.com> <fb1cab9f-a373-38e6-92e6-456332010653@gnuweeb.org> <6cd0db14-c9e2-3598-fd10-4b473d78c373@citrix.com> <5ecc383c-621b-57d9-7f6d-d63496fca3b3@zytor.com> <20230124022729.596997-1-ammarfaizi2@gnuweeb.org> <20230124022729.596997-3-ammarfaizi2@gnuweeb.org> <ce25e53f-91d4-d793-42a5-036d6bce0b4c@zytor.com> <Y899kHYbz32H1S6a@biznet-home.integral.gnuweeb.org> <BC632CA8-D2CB-4781-82E5-9810347293B0@zytor.com> <Y8+hGxVpgFVcm15g@biznet-home.integral.gnuweeb.org>
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From: Ammar Faizi <ammarfaizi2@gnuweeb.org>

Hi,

This is an RFC patchset v7. There are three 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 v7:

   - Fix comment, REGS_ERROR no longer exists in the enum (Ammar).

   - Update commit message (Ammar).

## Changelog v6:

   - Move the check-regs assertion in sigusr1() to check_regs_result()
     (HPA).

   - Add a new test just like sigusr1(), but don't modify REG_RCX and
     REG_R11. This is used to test SYSRET behavior consistency (HPA).

## 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 (3):
  selftests/x86: sysret_rip: Handle syscall in a FRED system
  selftests/x86: sysret_rip: Add more syscall tests with respect to `%rcx` and `%r11`
  selftests/x86: sysret_rip: Test SYSRET with a signal handler

 tools/testing/selftests/x86/sysret_rip.c | 171 +++++++++++++++++++++--
 1 file changed, 162 insertions(+), 9 deletions(-)


base-commit: e12ad468c22065a2826b2fc4c11d2113a7975301
-- 
Ammar Faizi