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Date:   Fri, 22 Mar 2019 14:20:15 -0700
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     "Xing, Cedric" <cedric.xing@intel.com>
Cc:     Andy Lutomirski <luto@kernel.org>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>,
        "linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "Hansen, Dave" <dave.hansen@intel.com>,
        "nhorman@redhat.com" <nhorman@redhat.com>,
        "npmccallum@redhat.com" <npmccallum@redhat.com>,
        "Ayoun, Serge" <serge.ayoun@intel.com>,
        "Katz-zamir, Shay" <shay.katz-zamir@intel.com>,
        "Huang, Haitao" <haitao.huang@intel.com>,
        "andriy.shevchenko@linux.intel.com" 
        <andriy.shevchenko@linux.intel.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "Svahn, Kai" <kai.svahn@intel.com>, "bp@alien8.de" <bp@alien8.de>,
        "josh@joshtriplett.org" <josh@joshtriplett.org>,
        "Huang, Kai" <kai.huang@intel.com>,
        "rientjes@google.com" <rientjes@google.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Haitao Huang <haitao.huang@linux.intel.com>,
        Jethro Beekman <jethro@fortanix.com>,
        "Dr . Greg Wettstein" <greg@enjellic.com>
Subject: Re: [PATCH v19,RESEND 24/27] x86/vdso: Add
 __vdso_sgx_enter_enclave() to wrap SGX enclave transitions
Message-ID: <20190322212011.GD12666@linux.intel.com>
References: <20190320162119.4469-1-jarkko.sakkinen@linux.intel.com>
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 <CALCETrVKAUK-jZ7Knp7RetTL055p3iK1D8Wyr6=hPq5HkePkFg@mail.gmail.com>
 <960B34DE67B9E140824F1DCDEC400C0F4E85C53D@ORSMSX116.amr.corp.intel.com>
 <20190320210313.GJ30469@linux.intel.com>
 <960B34DE67B9E140824F1DCDEC400C0F4E85C6B5@ORSMSX116.amr.corp.intel.com>
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On Wed, Mar 20, 2019 at 05:17:53PM -0700, Xing, Cedric wrote:
> > On Wed, Mar 20, 2019 at 12:57:52PM -0700, Xing, Cedric wrote:
> > > > Using the untrusted stack as a way to exchange data is very
> > > > convenient, but that doesn't mean it's a good idea.  Here are some
> > > > problems it
> > > > causes:
> > > >
> > > >  - It prevents using a normal function to wrap enclave entry (as
> > > > we're seeing with this patch set).
> > >
> > > It doesn't prevent.
> > 
> > Yes it does, keyword being "normal".  Though I guess we could do a bit
> > of bikeshedding on the definition of normal...
> 
> I don't understand what you mean by "normal".

My apologies, I missed the code snippet in your original code, I was
thinking of a previous idea involving a JMP %rbp.  Please ignore this
bit of discussion.