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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 33B2CC47254 for ; Tue, 5 May 2020 16:12:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 001B3206A4 for ; Tue, 5 May 2020 16:12:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="bEGCIuuy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729747AbgEEQMY (ORCPT ); Tue, 5 May 2020 12:12:24 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:35586 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729171AbgEEQMX (ORCPT ); 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Tue, 05 May 2020 16:12:10 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 045G8Wnl016936; Tue, 5 May 2020 16:12:09 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3020.oracle.com with ESMTP id 30sjk01e4c-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 05 May 2020 16:12:09 +0000 Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 045GC2NH009468; Tue, 5 May 2020 16:12:02 GMT Received: from [10.39.218.134] (/10.39.218.134) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 05 May 2020 09:12:02 -0700 Subject: Re: [PATCH] xenbus: avoid stack overflow warning To: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= , Arnd Bergmann Cc: Stefano Stabellini , Yan Yankovskyi , Wei Liu , xen-devel , "linux-kernel@vger.kernel.org" , clang-built-linux References: <20200505141546.824573-1-arnd@arndb.de> <30d49e6d-570b-f6fd-3a6f-628abcc8b127@suse.com> <48893239-dde9-4e94-040d-859f4348816d@suse.com> From: Boris Ostrovsky Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <48893239-dde9-4e94-040d-859f4348816d@suse.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9612 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 mlxscore=0 phishscore=0 bulkscore=0 malwarescore=0 spamscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005050127 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9612 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 suspectscore=0 mlxscore=0 spamscore=0 clxscore=1011 priorityscore=1501 bulkscore=0 phishscore=0 impostorscore=0 malwarescore=0 lowpriorityscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005050126 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/5/20 12:02 PM, Jürgen Groß wrote: > On 05.05.20 17:01, Arnd Bergmann wrote: >> On Tue, May 5, 2020 at 4:34 PM Jürgen Groß wrote: >>> On 05.05.20 16:15, Arnd Bergmann wrote: >>>> The __xenbus_map_ring() function has two large arrays, 'map' and >>>> 'unmap' on its stack. When clang decides to inline it into its caller, >>>> xenbus_map_ring_valloc_hvm(), the total stack usage exceeds the >>>> warning >>>> limit for stack size on 32-bit architectures. >>>> >>>> drivers/xen/xenbus/xenbus_client.c:592:12: error: stack frame size >>>> of 1104 bytes in function 'xenbus_map_ring_valloc_hvm' >>>> [-Werror,-Wframe-larger-than=] >>>> >>>> As far as I can tell, other compilers don't inline it here, so we get >>>> no warning, but the stack usage is actually the same. It is possible >>>> for both arrays to use the same location on the stack, but the >>>> compiler >>>> cannot prove that this is safe because they get passed to external >>>> functions that may end up using them until they go out of scope. >>>> >>>> Move the two arrays into separate basic blocks to limit the scope >>>> and force them to occupy less stack in total, regardless of the >>>> inlining decision. >>> >>> Why don't you put both arrays into a union? >> >> I considered that as well, and don't really mind either way. I think >> it does >> get a bit ugly whatever we do. If you prefer the union, I can respin the >> patch that way. > > Hmm, thinking more about it I think the real clean solution would be to > extend struct map_ring_valloc_hvm to cover the pv case, too, to add the > map and unmap arrays (possibly as a union) to it and to allocate it > dynamically instead of having it on the stack. > > Would you be fine doing this? Another option might be to factor out/modify code from  xenbus_unmap_ring() and call the resulting code from __xenbus_map_ring()'s fail path. -boris 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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 CC460C47257 for ; Tue, 5 May 2020 16:12:34 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9D91C206A4 for ; Tue, 5 May 2020 16:12:34 +0000 (UTC) Authentication-Results: mail.kernel.org; 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Tue, 5 May 2020 16:12:09 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3020.oracle.com with ESMTP id 30sjk01e4c-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 05 May 2020 16:12:09 +0000 Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 045GC2NH009468; Tue, 5 May 2020 16:12:02 GMT Received: from [10.39.218.134] (/10.39.218.134) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 05 May 2020 09:12:02 -0700 Subject: Re: [PATCH] xenbus: avoid stack overflow warning To: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= , Arnd Bergmann References: <20200505141546.824573-1-arnd@arndb.de> <30d49e6d-570b-f6fd-3a6f-628abcc8b127@suse.com> <48893239-dde9-4e94-040d-859f4348816d@suse.com> From: Boris Ostrovsky Autocrypt: addr=boris.ostrovsky@oracle.com; keydata= xsFNBFH8CgsBEAC0KiOi9siOvlXatK2xX99e/J3OvApoYWjieVQ9232Eb7GzCWrItCzP8FUV PQg8rMsSd0OzIvvjbEAvaWLlbs8wa3MtVLysHY/DfqRK9Zvr/RgrsYC6ukOB7igy2PGqZd+M MDnSmVzik0sPvB6xPV7QyFsykEgpnHbvdZAUy/vyys8xgT0PVYR5hyvhyf6VIfGuvqIsvJw5 C8+P71CHI+U/IhsKrLrsiYHpAhQkw+Zvyeml6XSi5w4LXDbF+3oholKYCkPwxmGdK8MUIdkM d7iYdKqiP4W6FKQou/lC3jvOceGupEoDV9botSWEIIlKdtm6C4GfL45RD8V4B9iy24JHPlom woVWc0xBZboQguhauQqrBFooHO3roEeM1pxXjLUbDtH4t3SAI3gt4dpSyT3EvzhyNQVVIxj2 FXnIChrYxR6S0ijSqUKO0cAduenhBrpYbz9qFcB/GyxD+ZWY7OgQKHUZMWapx5bHGQ8bUZz2 SfjZwK+GETGhfkvNMf6zXbZkDq4kKB/ywaKvVPodS1Poa44+B9sxbUp1jMfFtlOJ3AYB0WDS Op3d7F2ry20CIf1Ifh0nIxkQPkTX7aX5rI92oZeu5u038dHUu/dO2EcuCjl1eDMGm5PLHDSP 0QUw5xzk1Y8MG1JQ56PtqReO33inBXG63yTIikJmUXFTw6lLJwARAQABzTNCb3JpcyBPc3Ry b3Zza3kgKFdvcmspIDxib3Jpcy5vc3Ryb3Zza3lAb3JhY2xlLmNvbT7CwXgEEwECACIFAlH8 CgsCGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEIredpCGysGyasEP/j5xApopUf4g 9Fl3UxZuBx+oduuw3JHqgbGZ2siA3EA4bKwtKq8eT7ekpApn4c0HA8TWTDtgZtLSV5IdH+9z JimBDrhLkDI3Zsx2CafL4pMJvpUavhc5mEU8myp4dWCuIylHiWG65agvUeFZYK4P33fGqoaS VGx3tsQIAr7MsQxilMfRiTEoYH0WWthhE0YVQzV6kx4wj4yLGYPPBtFqnrapKKC8yFTpgjaK jImqWhU9CSUAXdNEs/oKVR1XlkDpMCFDl88vKAuJwugnixjbPFTVPyoC7+4Bm/FnL3iwlJVE qIGQRspt09r+datFzPqSbp5Fo/9m4JSvgtPp2X2+gIGgLPWp2ft1NXHHVWP19sPgEsEJXSr9 tskM8ScxEkqAUuDs6+x/ISX8wa5Pvmo65drN+JWA8EqKOHQG6LUsUdJolFM2i4Z0k40BnFU/ kjTARjrXW94LwokVy4x+ZYgImrnKWeKac6fMfMwH2aKpCQLlVxdO4qvJkv92SzZz4538az1T m+3ekJAimou89cXwXHCFb5WqJcyjDfdQF857vTn1z4qu7udYCuuV/4xDEhslUq1+GcNDjAhB nNYPzD+SvhWEsrjuXv+fDONdJtmLUpKs4Jtak3smGGhZsqpcNv8nQzUGDQZjuCSmDqW8vn2o hWwveNeRTkxh+2x1Qb3GT46uzsFNBFH8CgsBEADGC/yx5ctcLQlB9hbq7KNqCDyZNoYu1HAB Hal3MuxPfoGKObEktawQPQaSTB5vNlDxKihezLnlT/PKjcXC2R1OjSDinlu5XNGc6mnky03q yymUPyiMtWhBBftezTRxWRslPaFWlg/h/Y1iDuOcklhpr7K1h1jRPCrf1yIoxbIpDbffnuyz kuto4AahRvBU4Js4sU7f/btU+h+e0AcLVzIhTVPIz7PM+Gk2LNzZ3/on4dnEc/qd+ZZFlOQ4 KDN/hPqlwA/YJsKzAPX51L6Vv344pqTm6Z0f9M7YALB/11FO2nBB7zw7HAUYqJeHutCwxm7i BDNt0g9fhviNcJzagqJ1R7aPjtjBoYvKkbwNu5sWDpQ4idnsnck4YT6ctzN4I+6lfkU8zMzC gM2R4qqUXmxFIS4Bee+gnJi0Pc3KcBYBZsDK44FtM//5Cp9DrxRQOh19kNHBlxkmEb8kL/pw XIDcEq8MXzPBbxwHKJ3QRWRe5jPNpf8HCjnZz0XyJV0/4M1JvOua7IZftOttQ6KnM4m6WNIZ 2ydg7dBhDa6iv1oKdL7wdp/rCulVWn8R7+3cRK95SnWiJ0qKDlMbIN8oGMhHdin8cSRYdmHK kTnvSGJNlkis5a+048o0C6jI3LozQYD/W9wq7MvgChgVQw1iEOB4u/3FXDEGulRVko6xCBU4 SQARAQABwsFfBBgBAgAJBQJR/AoLAhsMAAoJEIredpCGysGyfvMQAIywR6jTqix6/fL0Ip8G jpt3uk//QNxGJE3ZkUNLX6N786vnEJvc1beCu6EwqD1ezG9fJKMl7F3SEgpYaiKEcHfoKGdh 30B3Hsq44vOoxR6zxw2B/giADjhmWTP5tWQ9548N4VhIZMYQMQCkdqaueSL+8asp8tBNP+TJ PAIIANYvJaD8xA7sYUXGTzOXDh2THWSvmEWWmzok8er/u6ZKdS1YmZkUy8cfzrll/9hiGCTj u3qcaOM6i/m4hqtvsI1cOORMVwjJF4+IkC5ZBoeRs/xW5zIBdSUoC8L+OCyj5JETWTt40+lu qoqAF/AEGsNZTrwHJYu9rbHH260C0KYCNqmxDdcROUqIzJdzDKOrDmebkEVnxVeLJBIhYZUd t3Iq9hdjpU50TA6sQ3mZxzBdfRgg+vaj2DsJqI5Xla9QGKD+xNT6v14cZuIMZzO7w0DoojM4 ByrabFsOQxGvE0w9Dch2BDSI2Xyk1zjPKxG1VNBQVx3flH37QDWpL2zlJikW29Ws86PHdthh Fm5PY8YtX576DchSP6qJC57/eAAe/9ztZdVAdesQwGb9hZHJc75B+VNm4xrh/PJO6c1THqdQ 19WVJ+7rDx3PhVncGlbAOiiiE3NOFPJ1OQYxPKtpBUukAlOTnkKE6QcA4zckFepUkfmBV1wM Jg6OxFYd01z+a+oL Message-ID: <656d0dc4-6c4f-29df-be7b-4cb70c2c0a5e@oracle.com> Date: Tue, 5 May 2020 12:12:00 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <48893239-dde9-4e94-040d-859f4348816d@suse.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9612 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 mlxscore=0 phishscore=0 bulkscore=0 malwarescore=0 spamscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005050127 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9612 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 suspectscore=0 mlxscore=0 spamscore=0 clxscore=1011 priorityscore=1501 bulkscore=0 phishscore=0 impostorscore=0 malwarescore=0 lowpriorityscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005050126 X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Stefano Stabellini , Wei Liu , Yan Yankovskyi , "linux-kernel@vger.kernel.org" , clang-built-linux , xen-devel Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 5/5/20 12:02 PM, Jürgen Groß wrote: > On 05.05.20 17:01, Arnd Bergmann wrote: >> On Tue, May 5, 2020 at 4:34 PM Jürgen Groß wrote: >>> On 05.05.20 16:15, Arnd Bergmann wrote: >>>> The __xenbus_map_ring() function has two large arrays, 'map' and >>>> 'unmap' on its stack. When clang decides to inline it into its caller, >>>> xenbus_map_ring_valloc_hvm(), the total stack usage exceeds the >>>> warning >>>> limit for stack size on 32-bit architectures. >>>> >>>> drivers/xen/xenbus/xenbus_client.c:592:12: error: stack frame size >>>> of 1104 bytes in function 'xenbus_map_ring_valloc_hvm' >>>> [-Werror,-Wframe-larger-than=] >>>> >>>> As far as I can tell, other compilers don't inline it here, so we get >>>> no warning, but the stack usage is actually the same. It is possible >>>> for both arrays to use the same location on the stack, but the >>>> compiler >>>> cannot prove that this is safe because they get passed to external >>>> functions that may end up using them until they go out of scope. >>>> >>>> Move the two arrays into separate basic blocks to limit the scope >>>> and force them to occupy less stack in total, regardless of the >>>> inlining decision. >>> >>> Why don't you put both arrays into a union? >> >> I considered that as well, and don't really mind either way. I think >> it does >> get a bit ugly whatever we do. If you prefer the union, I can respin the >> patch that way. > > Hmm, thinking more about it I think the real clean solution would be to > extend struct map_ring_valloc_hvm to cover the pv case, too, to add the > map and unmap arrays (possibly as a union) to it and to allocate it > dynamically instead of having it on the stack. > > Would you be fine doing this? Another option might be to factor out/modify code from  xenbus_unmap_ring() and call the resulting code from __xenbus_map_ring()'s fail path. -boris