From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A517C32789 for ; Tue, 6 Nov 2018 23:17:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 681E0204FD for ; Tue, 6 Nov 2018 23:17:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 681E0204FD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=libc.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-sgx-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727324AbeKGIp2 (ORCPT ); Wed, 7 Nov 2018 03:45:28 -0500 Received: from 216-12-86-13.cv.mvl.ntelos.net ([216.12.86.13]:58144 "EHLO brightrain.aerifal.cx" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726403AbeKGIp2 (ORCPT ); Wed, 7 Nov 2018 03:45:28 -0500 Received: from dalias by brightrain.aerifal.cx with local (Exim 3.15 #2) id 1gKAbC-0005m3-00; Tue, 06 Nov 2018 23:17:30 +0000 Date: Tue, 6 Nov 2018 18:17:30 -0500 From: Rich Felker To: Andy Lutomirski Cc: Dave Hansen , "Christopherson, Sean J" , Jann Horn , Linus Torvalds , Dave Hansen , Jethro Beekman , Jarkko Sakkinen , Florian Weimer , Linux API , X86 ML , linux-arch , LKML , Peter Zijlstra , nhorman@redhat.com, npmccallum@redhat.com, "Ayoun, Serge" , shay.katz-zamir@intel.com, linux-sgx@vger.kernel.org, Andy Shevchenko , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Carlos O'Donell , adhemerval.zanella@linaro.org Subject: Re: RFC: userspace exception fixups Message-ID: <20181106231730.GR5150@brightrain.aerifal.cx> References: <20181102220437.GI7393@linux.intel.com> <1541518670.7839.31.camel@intel.com> <1541524750.7839.51.camel@intel.com> <22596E35-F5D1-4935-86AB-B510DCA0FABE@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-sgx-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org Message-ID: <20181106231730.yOTPUK0Oauk4DA9hsYWDacuBYsq6A3OTrM2n2RZS1NQ@z> On Tue, Nov 06, 2018 at 11:02:11AM -0800, Andy Lutomirski wrote: > On Tue, Nov 6, 2018 at 10:41 AM Dave Hansen wrote: > > > > On 11/6/18 10:20 AM, Andy Lutomirski wrote: > > > I almost feel like the right solution is to call into SGX on its own > > > private stack or maybe even its own private address space. > > > > Yeah, I had the same gut feeling. Couldn't the debugger even treat the > > enclave like its own "thread" with its own stack and its own set of > > registers and context? That seems like a much more workable model than > > trying to weave it together with the EENTER context. > > So maybe the API should be, roughly > > sgx_exit_reason_t sgx_enter_enclave(pointer_to_enclave, struct > host_state *state); > sgx_exit_reason_t sgx_resume_enclave(same args); > > where host_state is something like: > > struct host_state { > unsigned long bp, sp, ax, bx, cx, dx, si, di; > }; > > and the values in host_state explicitly have nothing to do with the > actual host registers. So, if you want to use the outcall mechanism, > you'd allocate some memory, point sp to that memory, call > sgx_enter_enclave(), and then read that memory to do the outcall. > > Actually implementing this would be distinctly nontrivial, and would > almost certainly need some degree of kernel help to avoid an explosion > when a signal gets delivered while we have host_state.sp loaded into > the actual SP register. Maybe rseq could help with this? > > The ISA here is IMO not well thought through. Maybe I'm mistaken about some fundamentals here, but my understanding of SGX is that the whole point is that the host application and the code running in the enclave are mutually adversarial towards one another. Do any or all of the proposed protocols here account for this and fully protect the host application from malicious code in the enclave? It seems that having control over the register file on exit from the enclave is fundamentally problematic but I assume there must be some way I'm missing that this is fixed up. Rich