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 58762C433E0 for ; Wed, 3 Feb 2021 22:28:54 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BE00B64E4D for ; Wed, 3 Feb 2021 22:28:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BE00B64E4D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 013906B006E; Wed, 3 Feb 2021 17:28:53 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id EDF126B0072; Wed, 3 Feb 2021 17:28:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DA66D6B007B; Wed, 3 Feb 2021 17:28:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0233.hostedemail.com [216.40.44.233]) by kanga.kvack.org (Postfix) with ESMTP id C270E6B006E for ; Wed, 3 Feb 2021 17:28:52 -0500 (EST) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 840F1180AD81A for ; Wed, 3 Feb 2021 22:28:52 +0000 (UTC) X-FDA: 77778397704.15.cap18_5e08248275d7 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin15.hostedemail.com (Postfix) with ESMTP id 687731814B0C1 for ; Wed, 3 Feb 2021 22:28:52 +0000 (UTC) X-HE-Tag: cap18_5e08248275d7 X-Filterd-Recvd-Size: 4765 Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by imf46.hostedemail.com (Postfix) with ESMTP for ; Wed, 3 Feb 2021 22:28:50 +0000 (UTC) IronPort-SDR: 2ODoejMejvuzDLkE/iZoECjI6aBTmREwtHqzE/mqdNi8DmHCY2LMNnpcd1P72aDeU60NGX+xwf DJJCTju1MXcQ== X-IronPort-AV: E=McAfee;i="6000,8403,9884"; a="160294931" X-IronPort-AV: E=Sophos;i="5.79,399,1602572400"; d="scan'208";a="160294931" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga106.fm.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: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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: >>>>> +=C2=A0=C2=A0=C2=A0 if (!IS_ENABLED(CONFIG_X86_CET)) >>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return -EOPNOTSUPP; >>>> >>>> Let's ignore glibc for a moment.=C2=A0 What error code *should* the = kernel be >>>> returning here?=C2=A0 errno(3) says: >>>> >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 EOPNOTSUPP=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 Operation not supported on socket (POSIX.1) >>>> ... >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ENOTSUP=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Operation not supported (POSIX.1) >>>> >>> >>> Yeah, other places in kernel use ENOTSUPP.=C2=A0 This seems to be out= of >>> line.=C2=A0 And since the issue is long-existing, applications alread= y know >>> how to deal with it.=C2=A0 I should have made that argument.=C2=A0 Ch= ange 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: >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return -ENOTSUPP; >> >> Do we want to reconsider? >=20 > 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. >=20 > ENOTSUPP does seem less popular lately: >=20 >> $ 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; >=20 > but far from unused. That might be due to checkpatch spew more than > anything. >=20 Maybe I will keep it ENOTSUPP for now. If any logical reason should=20 come up, I will be happy to change it again. Thanks! -- Yu-cheng