linux-kernel - Re: [RFC PATCH v2 4/4] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions

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Message-Id: <85EE19AF-C085-4E17-A673-44242996AF75@amacapital.net>
Date:   Fri, 7 Dec 2018 10:50:08 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Jethro Beekman <jethro@...tanix.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "x86@...nel.org" <x86@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Josh Triplett <josh@...htriplett.org>,
        Haitao Huang <haitao.huang@...ux.intel.com>,
        "linux-sgx@...r.kernel.org" <linux-sgx@...r.kernel.org>,
        "Dr. Greg" <greg@...ellic.com>
Subject: Re: [RFC PATCH v2 4/4] x86/vdso: Add __vdso_sgx_enter_enclave() to wrap SGX enclave transitions



> On Dec 7, 2018, at 10:44 AM, Dave Hansen <dave.hansen@...el.com> wrote:
> 
>> 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.
> 
> 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 quite reasonable, but I don’t have a strong opinion.