Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: qQqHZTuE+Mh8J5CZiLIolE1apfst99fEJvZYTHcRNoZ9Fg7OknZritWrmZ1r9pB4BsydVdCELQ
 69FWBiJTjEGA==
IronPort-SDR: QixY2KCI8RuTaNZ15Zir8oirwhfamYYRxgCHUV/j7rw7sixYiquZlnGAPyr/EaVxinU2Cw6/Aq
 eMx/bicyDm6w==
Date:   Tue, 29 Sep 2020 00:36:25 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     "H.J. Lu" <hjl.tools@gmail.com>
Cc:     "Yu, Yu-cheng" <yu-cheng.yu@intel.com>,
        Andrew Cooper <andrew.cooper3@citrix.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        linux-sgx@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Jethro Beekman <jethro@fortanix.com>,
        Cedric Xing <cedric.xing@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        andriy.shevchenko@linux.intel.com, asapek@google.com,
        Borislav Petkov <bp@alien8.de>, chenalexchen@google.com,
        conradparker@google.com, cyhanish@google.com,
        Dave Hansen <dave.hansen@intel.com>,
        "Huang, Haitao" <haitao.huang@intel.com>, josh@joshtriplett.org,
        kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com,
        Christian Ludloff <ludloff@google.com>,
        Andy Lutomirski <luto@kernel.org>, nhorman@redhat.com,
        npmccallum@redhat.com, puiterwijk@redhat.com, rientjes@google.com,
        Thomas Gleixner <tglx@linutronix.de>, yaozhangx@google.com
Subject: Re: [PATCH v38 21/24] x86/vdso: Implement a vDSO for Intel SGX
 enclave call
Message-ID: <20200928213625.GC2705@linux.intel.com>
References: <20200915112842.897265-1-jarkko.sakkinen@linux.intel.com>
 <20200915112842.897265-22-jarkko.sakkinen@linux.intel.com>
 <721ca14e-21df-3df1-7bef-0b00d0ff90c3@citrix.com>
 <c1b0019d-d3cb-cc62-f47f-90c2550c22a4@intel.com>
 <CAMe9rOrVhQr9ad_4en2D5GTTqDsJGXqszBmscgenn_87mDxvUA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAMe9rOrVhQr9ad_4en2D5GTTqDsJGXqszBmscgenn_87mDxvUA@mail.gmail.com>
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
Precedence: bulk

On Mon, Sep 28, 2020 at 08:54:01AM -0700, H.J. Lu wrote:
> On Mon, Sep 28, 2020 at 8:43 AM Yu, Yu-cheng <yu-cheng.yu@intel.com> wrote:
> >
> > On 9/25/2020 11:23 AM, Andrew Cooper wrote:
> > > On 15/09/2020 12:28, Jarkko Sakkinen wrote:
> > >> diff --git a/arch/x86/entry/vdso/vsgx_enter_enclave.S b/arch/x86/entry/vdso/vsgx_enter_enclave.S
> > >> new file mode 100644
> > >> index 000000000000..adbd59d41517
> > >> --- /dev/null
> > >> +++ b/arch/x86/entry/vdso/vsgx_enter_enclave.S
> > >> @@ -0,0 +1,157 @@
> > >> +SYM_FUNC_START(__vdso_sgx_enter_enclave)
> > >> <snip>
> > >> +.Lretpoline:
> > >> +    call    2f
> > >> +1:  pause
> > >> +    lfence
> > >> +    jmp     1b
> > >> +2:  mov     %rax, (%rsp)
> > >> +    ret
> > >
> > > I hate to throw further spanners in the work, but this is not compatible
> > > with CET, and the user shadow stack work in progress.
> >
> > Hi Jarkko,
> >
> > These 1: and 2: targets are reached only from these few lines?  If they
> > are direct call/jmp targets, I think it is OK in terms of CET.  If they
> > are reached from an instruction like "jmp *%rax", then we need to put in
> > an "endbr64".
> >
> 
> This also isn't compatible with shadow stack.
> 
> -- 
> H.J.

I have the now full picture of the problem thanks to Andrew's response
[1]. And Dave Hansen just explained me in detail the context and
background with [2]. So I'd guess this will get sorted out soon.

If you don't mind I'll CC you to this commit when I send the next
version?

[1] https://lkml.org/lkml/2020/9/28/1153
[2] https://lkml.org/lkml/2020/9/25/1122

/Jarkko