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 AB6CEC433E1 for ; Tue, 18 Aug 2020 14:52:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 94F9D2080C for ; Tue, 18 Aug 2020 14:52:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727828AbgHROwo (ORCPT ); Tue, 18 Aug 2020 10:52:44 -0400 Received: from mga02.intel.com ([134.134.136.20]:12236 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726145AbgHROwm (ORCPT ); Tue, 18 Aug 2020 10:52:42 -0400 IronPort-SDR: +jKtLePMzRQoO2k/6dt7ZuwZ179pMSLcm1NNYOm2jkTdZPaFNzPlsjA2ohgN4nZWdkiIvLHZo7 ckVWUsnk7JsA== X-IronPort-AV: E=McAfee;i="6000,8403,9716"; a="142742972" X-IronPort-AV: E=Sophos;i="5.76,327,1592895600"; d="scan'208";a="142742972" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Aug 2020 07:52:41 -0700 IronPort-SDR: d2buaeSk2jnkNjYsMBcotUV83mieA7rCG9w4EIOwKwdWB2GHnm5IFP348wPBzeCQJ6TG+wMbQU v+IBc1Q2f80A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,327,1592895600"; d="scan'208";a="497394912" Received: from ribnhajh-mobl.ger.corp.intel.com (HELO localhost) ([10.249.47.113]) by fmsmga005.fm.intel.com with ESMTP; 18 Aug 2020 07:52:35 -0700 Date: Tue, 18 Aug 2020 17:52:34 +0300 From: Jarkko Sakkinen To: Sean Christopherson Cc: Nathaniel McCallum , x86@kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, 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: <20200818145234.GC132200@linux.intel.com> References: <20200716135303.276442-1-jarkko.sakkinen@linux.intel.com> <20200716135303.276442-22-jarkko.sakkinen@linux.intel.com> <20200810222317.GG14724@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200810222317.GG14724@linux.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 10, 2020 at 03:23:17PM -0700, Sean Christopherson wrote: > > 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. > > What bits of the x86-64 ABI require writing the handler in assembly? There > are certainly restrictions on what the handler can do without needing an > assembly trampoline, but I was under the impression that vanilla C code is > compatible with the exit handler patch. Is Rust more picky about calling > convention? > > Side topic, the documentation for vdso_sgx_enter_enclave_t is wrong, it > states the EFLAGS.DF is not cleared before invoking the handler, but that's > a lie. If handler requires the use of setjmp/longjmp API for sudden exits, that is considered bad even with C++, as it is not compatible with stack unwinding. The handler has a lot of constraints for its environment, and is somewhat unappealing to use. That's why I started today thinking a possibility of using a bpf program as a middle-man. BPF programs can be used to execute code by the kernel in behalf of user in a domain defined sandbox. The execution context is just a buffer passed in R1 to the BPF interpreter. It can be defined by application. /Jarkko