linux-kernel - Re: [RFC PATCH v2 0/3] An alternative __vdso_sgx_enter_enclave() to allow enclave/host parameter passing using untrusted stack

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Message-ID: <f24c8440-2397-0015-745b-c338d9496a53@intel.com>
Date:   Thu, 11 Jul 2019 12:49:04 -0700
From:   "Xing, Cedric" <cedric.xing@...el.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-sgx@...r.kernel.org,
        akpm@...ux-foundation.org, dave.hansen@...el.com,
        sean.j.christopherson@...el.com, serge.ayoun@...el.com,
        shay.katz-zamir@...el.com, haitao.huang@...el.com,
        kai.svahn@...el.com, kai.huang@...el.com
Subject: Re: [RFC PATCH v2 0/3] An alternative __vdso_sgx_enter_enclave() to
 allow enclave/host parameter passing using untrusted stack

On 7/11/2019 2:36 AM, Jarkko Sakkinen wrote:
> On Wed, Jul 10, 2019 at 03:54:20PM -0700, Xing, Cedric wrote:
>> On 7/10/2019 3:46 PM, Jarkko Sakkinen wrote:
>>> On Wed, Jul 10, 2019 at 11:08:37AM -0700, Xing, Cedric wrote:
>>>>> With these conclusions I think the current vDSO API is sufficient for
>>>>> Linux.
>>>>
>>>> The new vDSO API is to support data exchange on stack. It has nothing to do
>>>> with debugging. BTW, the community has closed on this.
>>>
>>> And how that is useful?
>>
>> There is a lengthy discussion on its usefulness so I don't want to repeat.
>> In short, it allows using untrusted stack as a convenient method to exchange
>> data with the enclave. It is currently being used by Intel's SGX SDK for
>> e/o-calls parameters.
>>
>>>> The CFI directives are for stack unwinding. They don't affect what the code
>>>> does so you can just treat them as NOPs if you don't understand what they
>>>> do. However, they are useful to not only debuggers but also exception
>>>> handling code. libunwind also has a setjmp()/longjmp() implementation based
>>>> on CFI directives.
>>>
>>> Of course I won't merge code of which usefulness I don't understand.
>>
>> Sure.
>>
>> Any other questions I can help with?
> 
> I dissected my concerns in other email. We can merge this feature after
> v21 if it makes sense.

Sent out v3 of vDSO changes last night. I hope your concerns have been 
properly addressed.

The new vDSO API is a community consensus. I can help on whatever 
technical problems you may have but I don't see a reason you should 
reject it.

> /Jarkko
>