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=-5.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 06883C433DB for ; Wed, 3 Feb 2021 22:29:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C12A364F6B for ; Wed, 3 Feb 2021 22:29:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232392AbhBCW3d (ORCPT ); Wed, 3 Feb 2021 17:29:33 -0500 Received: from mga18.intel.com ([134.134.136.126]:44941 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232201AbhBCW3c (ORCPT ); Wed, 3 Feb 2021 17:29:32 -0500 IronPort-SDR: qCnO0xfovv3BelUrCDlUnNmfqHusXdVcXEQsOE7kbiDRIjlXTDZ8+wNahfWg/PBR4Bm0s+gcgb ogZYZMEI+Rag== X-IronPort-AV: E=McAfee;i="6000,8403,9884"; a="168811528" X-IronPort-AV: E=Sophos;i="5.79,399,1602572400"; d="scan'208";a="168811528" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Feb 2021 14:28:48 -0800 IronPort-SDR: teAHso16AhsuO/DSh9wwnpQvwEfuXc8bhQHU+KbBseRyIWT4j15au9I7BKs1vITYb4rh6MgfvA BREiF+xDa61g== X-IronPort-AV: E=Sophos;i="5.79,399,1602572400"; d="scan'208";a="356920008" Received: from yyu32-mobl1.amr.corp.intel.com (HELO [10.212.43.162]) ([10.212.43.162]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Feb 2021 14:28:46 -0800 Subject: Re: [PATCH v18 24/25] x86/cet/shstk: Add arch_prctl functions for shadow stack To: Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu References: <20210127212524.10188-1-yu-cheng.yu@intel.com> <20210127212524.10188-25-yu-cheng.yu@intel.com> <761ae8ce-0560-24cc-e6f7-684475cb3708@intel.com> <6720b1a9-f785-dbbd-1f0e-8c9090be2069@intel.com> From: "Yu, Yu-cheng" Message-ID: Date: Wed, 3 Feb 2021 14:28:45 -0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On 2/3/2021 2:11 PM, Dave Hansen wrote: > On 2/3/21 1:54 PM, Yu, Yu-cheng wrote: >> On 1/29/2021 10:56 AM, Yu, Yu-cheng wrote: >>> On 1/29/2021 9:07 AM, Dave Hansen wrote: >>>> On 1/27/21 1:25 PM, Yu-cheng Yu wrote: >>>>> +    if (!IS_ENABLED(CONFIG_X86_CET)) >>>>> +        return -EOPNOTSUPP; >>>> >>>> Let's ignore glibc for a moment.  What error code *should* the kernel be >>>> returning here?  errno(3) says: >>>> >>>>         EOPNOTSUPP      Operation not supported on socket (POSIX.1) >>>> ... >>>>         ENOTSUP         Operation not supported (POSIX.1) >>>> >>> >>> Yeah, other places in kernel use ENOTSUPP.  This seems to be out of >>> line.  And since the issue is long-existing, applications already know >>> how to deal with it.  I should have made that argument.  Change it to >>> ENOTSUPP. >> >> When I make the change, checkpatch says... >> >> WARNING: ENOTSUPP is not a SUSV4 error code, prefer EOPNOTSUPP >> #128: FILE: arch/x86/kernel/cet_prctl.c:33: >> +        return -ENOTSUPP; >> >> Do we want to reconsider? > > I'm not sure I trust checkpatch over manpages. I had to google "SUSV4". > I'm not sure it matters at *all* for a 100% Linux-specific interface. > > ENOTSUPP does seem less popular lately: > >> $ git diff v5.0.. kernel/ arch/ drivers/ | grep ^+.*return.*E.*NO.*SUP.*\; | grep -o -- -E.*\; | sort | uniq -c | sort -n >> ... noise >> 61 -EOPNOTSUPP); >> 260 -ENOTSUPP; >> 1577 -EOPNOTSUPP; > > but far from unused. That might be due to checkpatch spew more than > anything. > Maybe I will keep it ENOTSUPP for now. If any logical reason should come up, I will be happy to change it again. Thanks! -- Yu-cheng