Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2314C7EE30 for ; Wed, 1 Mar 2023 22:33:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229801AbjCAWd2 (ORCPT ); Wed, 1 Mar 2023 17:33:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47268 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229700AbjCAWd0 (ORCPT ); Wed, 1 Mar 2023 17:33:26 -0500 Received: from mx0a-0031df01.pphosted.com (mx0a-0031df01.pphosted.com [205.220.168.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA2BC199E1; Wed, 1 Mar 2023 14:33:25 -0800 (PST) Received: from pps.filterd (m0279867.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 321JW1kQ027616; Wed, 1 Mar 2023 22:33:03 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; h=message-id : date : mime-version : subject : from : to : cc : references : in-reply-to : content-type : content-transfer-encoding; s=qcppdkim1; bh=o5ZIBNmF7KvdNDkYw4H/FsK4k1dZByMZQZMtrmciBHI=; b=fugEfDlUYGEpardpmqvt4hKGuPtjvzNAuyOGPJ7n3j+Vt9VpIt6out83vAuDAm90RA90 5xGh/2smAWoXM36mmFSTXloNX4lSK7xPFDxVbj13DHu2PdAiWfJKSHdlhPLCyPdXLZbM B0Ik8++c9VXXqN/G5f1VyRYleCJQut9TJ7ZEYRZ5/CeeZHKYUfwkxkvl9qddmDYLd2E8 n/fXJfIp83DV9lLLVYW2XczVRauV9JFipBGgylUJmZ5ztd6JLCJt5xLx7MMJOiOreMOh ilPAe6gH2sPnr1gJJ9P+jSXogKjQOpnBv1NcsbAIFkBpFmAWQKu8HEyUtpg2CzV2fbfl qA== Received: from nalasppmta05.qualcomm.com (Global_NAT1.qualcomm.com [129.46.96.20]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 3p2cx88cc2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 01 Mar 2023 22:33:03 +0000 Received: from nalasex01c.na.qualcomm.com (nalasex01c.na.qualcomm.com [10.47.97.35]) by NALASPPMTA05.qualcomm.com (8.17.1.5/8.17.1.5) with ESMTPS id 321MX2VK012100 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 1 Mar 2023 22:33:02 GMT Received: from [10.110.81.49] (10.80.80.8) by nalasex01c.na.qualcomm.com (10.47.97.35) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.41; Wed, 1 Mar 2023 14:33:01 -0800 Message-ID: Date: Wed, 1 Mar 2023 14:33:00 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [PATCH v2 0/2] Validating UAPI backwards compatibility Content-Language: en-US From: John Moon To: Nick Desaulniers CC: Masahiro Yamada , Nathan Chancellor , Nicolas Schier , , , , , "Greg Kroah-Hartman" , Randy Dunlap , Arnd Bergmann , Bjorn Andersson , Todd Kjos , Matthias Maennich , Giuliano Procida , , , Jordan Crouse , Trilok Soni , "Satya Durga Srinivasu Prabhala" , Elliot Berman References: <20230301075402.4578-1-quic_johmoo@quicinc.com> <41d287fa-3a0a-cac6-4595-ad47ef873d79@quicinc.com> <0c92e7b8-e415-8ad5-14e7-d94f18c3fa25@quicinc.com> In-Reply-To: <0c92e7b8-e415-8ad5-14e7-d94f18c3fa25@quicinc.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01a.na.qualcomm.com (10.52.223.231) To nalasex01c.na.qualcomm.com (10.47.97.35) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-GUID: ggUEQWr3qftnQ-SSJf0sFW0fKwwFRWx- X-Proofpoint-ORIG-GUID: ggUEQWr3qftnQ-SSJf0sFW0fKwwFRWx- X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-03-01_15,2023-03-01_03,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 priorityscore=1501 clxscore=1015 impostorscore=0 mlxscore=0 suspectscore=0 malwarescore=0 bulkscore=0 lowpriorityscore=0 adultscore=0 mlxlogscore=999 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2303010180 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/1/2023 11:24 AM, John Moon wrote: > On 3/1/2023 10:03 AM, John Moon wrote: >> On 3/1/2023 9:50 AM, Nick Desaulniers wrote: >>> On Tue, Feb 28, 2023 at 11:54 PM John Moon >>> wrote: >>>> >>>> Currently, the script works with gcc. It generates output like this >>>> when >>>> a backwards-incompatible change is made to a UAPI header: >>>> >>>>   !!! ABI differences detected in include/uapi/linux/acct.h >>>> (compared to >>>>   file at HEAD^1) !!! >>>> >>>>       [C] 'struct acct' changed: >>>>         type size changed from 512 to 544 (in bits) >>>>         1 data member insertion: >>>>           '__u32 new_val', at offset 512 (in bits) at acct.h:71:1 >>>> >>>>   0/1 UAPI header file changes are backwards compatible >>>>   UAPI header ABI check failed >>>> >>>> However, we have not had success with clang. It seems clang is more >>>> aggressive in optimizing dead code away (no matter which options we >>>> pass). Therefore, no ABI differences are found. >>> >>> Hi John, >>> Do you have the list of bugs you've filed upstream against clang wrt. >>> information missing when using `-fno-eliminate-unused-debug-types`? >>> >>> https://github.com/llvm/llvm-project/issues is the issue tracker. >>> >>> Seeing a strong participant in both the Android and LLVM ecosystems >>> supply scripts that lack clang support...raises eyebrows. >> >> We have not filed a bug with upstream clang since we're not sure it's >> *not* and issue on our end. Giuliano Procida (CC'd) has tested the >> script with clang 13 and 14 and GCC 10, 11 and 12 and got the expected >> diff. If it's convenient for anyone testing this script to give it a >> whirl with clang and report back, it could help us determine if >> there's a real issue with clang support. :) > > With some additional internal testing, we've found that clang does not > work with this script on Ubuntu 18.04, but does work on Ubuntu 20.04. > This is controlling for the clang version and different installation > sources. The same clang-15 binary run on an 18.04 host fails while > working on 20.04. > > We'll investigate some more internally and potentially file a bug with > upstream clang. With some additional help from Nick offline, we determined that the issue isn't with clang, but with libdw (from elfutils). You need at least libdw version 0.171 for the abidiff tool to work correctly with clang (in this particular case). Ubuntu 18.04 ships with version 0.170. If there's any interest, it'd be fairly easy to add a check for this condition under the check_deps() function in the script.