linux-kernel - Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call

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Message-ID: <bf65f1f7-f91b-721c-90c5-064df152f710@fortanix.com>
Date:   Fri, 25 Sep 2020 10:39:58 +0200
From:   Jethro Beekman <jethro@...tanix.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Andy Lutomirski <luto@...capital.net>,
        Cedric Xing <cedric.xing@...el.com>, akpm@...ux-foundation.org,
        andriy.shevchenko@...ux.intel.com, asapek@...gle.com,
        chenalexchen@...gle.com, conradparker@...gle.com,
        cyhanish@...gle.com, dave.hansen@...el.com, haitao.huang@...el.com,
        josh@...htriplett.org, kai.huang@...el.com, kai.svahn@...el.com,
        kmoy@...gle.com, ludloff@...gle.com, luto@...nel.org,
        nhorman@...hat.com, npmccallum@...hat.com, puiterwijk@...hat.com,
        rientjes@...gle.com, tglx@...utronix.de, yaozhangx@...gle.com
Subject: Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX
 enclave call

On 2020-09-25 03:00, Jarkko Sakkinen wrote:
> End result:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-sgx.git/tree/arch/x86/include/uapi/asm/sgx.h
> 
> I'm wondering this sentence:
> 
> "The calling convention is custom and does not follow System V x86-64 ABI."
> 
> AFAIK, now the vDSO is fully C-callable but waiting for feedback before
> removing it.

It's C-callable *iff your enclave follows the System V x86-64 ABI*. In addition, all registers not clobbered by the SGX ISA are passed to the enclave, not just those specified as parameter passing registers in the ABI. This is intentional to make the vDSO function usable in applications that use the current flexibility of ENCLU.

--
Jethro Beekman | Fortanix



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