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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 CC029C433E1 for ; Tue, 18 Aug 2020 14:26:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A8FBA20786 for ; Tue, 18 Aug 2020 14:26:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727023AbgHRO0e (ORCPT ); Tue, 18 Aug 2020 10:26:34 -0400 Received: from mga17.intel.com ([192.55.52.151]:49348 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727040AbgHRO0d (ORCPT ); Tue, 18 Aug 2020 10:26:33 -0400 IronPort-SDR: LOf5ZthRJlyv6JmDDA9awHUuWGHWJfUnUybI/0bw/ZiwPziWcYyPG/2eRJYGHXs+/4UF9QFIx3 2e2AlTESHlkw== X-IronPort-AV: E=McAfee;i="6000,8403,9716"; a="134968974" X-IronPort-AV: E=Sophos;i="5.76,327,1592895600"; d="scan'208";a="134968974" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Aug 2020 07:26:32 -0700 IronPort-SDR: 6k2SbS6PyYJK8VDtr8rqyNjsVTFPQAc2p72UKWyp5AmkJ4gsKFaDYDiptWZFwNIwDgboNTydOs EjFziqeP3Idg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,327,1592895600"; d="scan'208";a="334385459" Received: from ribnhajh-mobl.ger.corp.intel.com (HELO localhost) ([10.249.47.113]) by FMSMGA003.fm.intel.com with ESMTP; 18 Aug 2020 07:26:26 -0700 Date: Tue, 18 Aug 2020 17:26:25 +0300 From: Jarkko Sakkinen To: Nathaniel McCallum Cc: x86@kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, Sean Christopherson , Andy Lutomirski , Jethro Beekman , Cedric Xing , akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com, asapek@google.com, bp@alien8.de, chenalexchen@google.com, conradparker@google.com, cyhanish@google.com, dave.hansen@intel.com, "Huang, Haitao" , Josh Triplett , kai.huang@intel.com, "Svahn, Kai" , kmoy@google.com, ludloff@google.com, luto@kernel.org, Neil Horman , Patrick Uiterwijk , David Rientjes , Thomas Gleixner , yaozhangx@google.com Subject: Re: [PATCH v36 21/24] x86/vdso: Implement a vDSO for Intel SGX enclave call Message-ID: <20200818142625.GB132200@linux.intel.com> References: <20200716135303.276442-1-jarkko.sakkinen@linux.intel.com> <20200716135303.276442-22-jarkko.sakkinen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-sgx-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org On Thu, Aug 06, 2020 at 10:55:43AM -0400, Nathaniel McCallum wrote: > In a past revision of this patch, I had requested a void *misc > parameter that could be passed through vdso_sgx_enter_enclave_t into > sgx_enclave_exit_handler_t. This request encountered some push back > and I dropped the issue. However, I'd like to revisit it or something > similar. > > One way to create a generic interface to SGX is to pass a structure > that captures the relevant CPU state from the handler so that it can > be evaluated in C code before reentry. Precedent for this approach can > be found in struct kvm_run[0]. Currently, however, there is no way to > pass a pointer to such a structure directly into the handler. > > This can be done implicitly by wrapping the struct > sgx_enclave_exception in another structure and then using techniques > like container_of() to find another field. However, this is made more > difficult by the fact that the sgx_enclave_exit_handler_t is not > really using the x86_64 sysv calling convention. Therefore, the > sgx_enclave_exit_handler_t MUST be written in assembly. This also > implies that we can't use techniques like container_of() and must > calculate all the offsets manually, which is tedious, error prone and > fragile. If instead of having a callback, kernel would run an optional bpf program, then a state structure could passed by the kernel to the execution context of the bpf program. That would also sort out difficulty of writing exit handlers. /Jarkko