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=-0.8 required=3.0 tests=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 D8A75C4332B for ; Fri, 20 Mar 2020 03:07:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B43152075E for ; Fri, 20 Mar 2020 03:07:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726596AbgCTDHE (ORCPT ); Thu, 19 Mar 2020 23:07:04 -0400 Received: from mga17.intel.com ([192.55.52.151]:20281 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726603AbgCTDHE (ORCPT ); Thu, 19 Mar 2020 23:07:04 -0400 IronPort-SDR: Q6vITU4waxPb+N5N5qgOzK3m47bxREcGhvyjIp32wF/nbbkxJoo1uRC+xzztNHpNAQonHpSVeX 9txT2ojEF3KQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Mar 2020 20:07:03 -0700 IronPort-SDR: L2Oz9ClVW2h098P8i84L5kQ3RBwFCGG2xrPmorBYCpwAVL4oSo+fDf9Gf04y+Ed3uJX+rq4Z2k GkNw+F7G8ajQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,283,1580803200"; d="scan'208";a="444821358" Received: from anakash-mobl2.ger.corp.intel.com (HELO localhost) ([10.251.183.74]) by fmsmga005.fm.intel.com with ESMTP; 19 Mar 2020 20:07:01 -0700 Date: Fri, 20 Mar 2020 05:07:00 +0200 From: Jarkko Sakkinen To: Sean Christopherson Cc: "Xing, Cedric" , Nathaniel McCallum , Jethro Beekman , Andy Lutomirski , linux-sgx@vger.kernel.org Subject: Re: [PATCH for_v29 3/8] x86/sgx: vdso: Make __vdso_sgx_enter_enclave() callable from C code Message-ID: <20200320030700.GF183331@linux.intel.com> References: <20200319011130.8556-1-sean.j.christopherson@intel.com> <20200319011130.8556-4-sean.j.christopherson@intel.com> <9a4878b9-bcad-b279-acd5-2eef03b13af8@intel.com> <20200319201144.GF11305@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200319201144.GF11305@linux.intel.com> 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, Mar 19, 2020 at 01:11:45PM -0700, Sean Christopherson wrote: > On Thu, Mar 19, 2020 at 01:03:41PM -0700, Xing, Cedric wrote: > > On 3/18/2020 6:11 PM, Sean Christopherson wrote: > > > #endif > > > SYM_FUNC_START(__vdso_sgx_enter_enclave) > > > /* Prolog */ > > >@@ -82,7 +84,9 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave) > > > .cfi_rel_offset %rbp, 0 > > > mov %rsp, %rbp > > > .cfi_def_cfa_register %rbp > > >+ push %rbx > > A CFI directive is needed here: > > > > .cfi_rel_offset %rbx, -8 > > Darn, I suspected as much, but wasn't 100% positive. Shouldn't have > hedged. :-) > > Is the rule of thumb for adding directives that one is needed any time > there is a new saved value of a register, or if the relative address of > the last saved value changes? Are CFI directives only used for > non-volatile registers? AFAIK the convention is just that if you push a register you need to offset it so that the FDE that is put into .eh_frame by GCC has the information from which locations of the stack the register values are copied. BTW, why use GCC-style ".L-mangled" label names instead of having more readable ones? /Jarkko