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Subject: Re: [RFC PATCH v2 4/4] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions
From:   Andy Lutomirski <luto@amacapital.net>
In-Reply-To: <59c989a1-e699-9665-780f-6dd263f41ce4@intel.com>
Date:   Fri, 7 Dec 2018 10:50:08 -0800
Cc:     Jethro Beekman <jethro@fortanix.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "x86@kernel.org" <x86@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Josh Triplett <josh@joshtriplett.org>,
        Haitao Huang <haitao.huang@linux.intel.com>,
        "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
        "Dr. Greg" <greg@enjellic.com>
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Message-Id: <85EE19AF-C085-4E17-A673-44242996AF75@amacapital.net>
References: <20181206221922.31012-1-sean.j.christopherson@intel.com> <20181206221922.31012-5-sean.j.christopherson@intel.com> <f2b7df05-20ef-ac16-fc99-258c39d84666@fortanix.com> <59c989a1-e699-9665-780f-6dd263f41ce4@intel.com>
To:     Dave Hansen <dave.hansen@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
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> On Dec 7, 2018, at 10:44 AM, Dave Hansen <dave.hansen@intel.com> wrote:
>=20
>> On 12/7/18 10:15 AM, Jethro Beekman wrote:
>> This is not sufficient to support the Fortanix SGX ABI calling
>> convention, which was designed to be mostly compatible with the SysV
>> 64-bit calling convention. The following registers need to be passed in
>> to an enclave from userspace: RDI, RSI, RDX, R8, R9, R10. The following
>> registers need to be passed out from an enclave to userspace: RDI, RSI,
>> RDX, R8, R9.
>=20
> Are you asking nicely to change the new Linux ABI to be consistent with
> your existing ABI?  Or, are you saying that the new ABI *must* be
> compatible with this previous out-of-tree implementation?

I think that allowing the enclave to return at least a few registers is quit=
e reasonable, but I don=E2=80=99t have a strong opinion.=