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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham 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 5D9DDC43441 for ; Fri, 16 Nov 2018 09:52:10 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 DE5B320892 for ; Fri, 16 Nov 2018 09:52:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DE5B320892 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 42xD6H5BlVzF3kP for ; Fri, 16 Nov 2018 20:52:07 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=sandipan@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 42xD4C6kXszF3jl for ; Fri, 16 Nov 2018 20:50:16 +1100 (AEDT) Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wAG9iDwo117644 for ; Fri, 16 Nov 2018 04:50:14 -0500 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2nst9akgxk-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 16 Nov 2018 04:50:13 -0500 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 16 Nov 2018 09:50:10 -0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id wAG9o9GI10617144 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 16 Nov 2018 09:50:09 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 694BEAE045; Fri, 16 Nov 2018 09:50:09 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AC1FAAE055; Fri, 16 Nov 2018 09:50:08 +0000 (GMT) Received: from [9.124.31.81] (unknown [9.124.31.81]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 16 Nov 2018 09:50:08 +0000 (GMT) Subject: Re: [PATCH] powerpc/64: Fix kernel stack 16-byte alignment To: Nicholas Piggin References: <20181115023427.31033-1-npiggin@gmail.com> From: Sandipan Das Date: Fri, 16 Nov 2018 15:20:07 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <20181115023427.31033-1-npiggin@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 18111609-0008-0000-0000-00000293B6BB X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18111609-0009-0000-0000-000021FDD51A Message-Id: <6627fcee-17c9-4e04-35c8-898663aac85c@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2018-11-16_05:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1811160089 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Ravi Bangoria , "Naveen N. Rao" , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 15/11/18 8:04 AM, Nicholas Piggin wrote: > Commit 4c2de74cc869 ("powerpc/64: Interrupts save PPR on stack rather > than thread_struct") changed sizeof(struct pt_regs) % 16 from 0 to 8, > which causes the interrupt frame allocation on kernel entry to put the > kernel stack out of alignment. > > Add a pad field to fix alignment, and add a BUILD_BUG_ON to catch this > in future. > > Fixes: 4c2de74cc869 ("powerpc/64: Interrupts save PPR on stack rather > than thread_struct") > Signed-off-by: Nicholas Piggin > [...] Thanks for fixing this. Commit 4c2de74cc869 ("powerpc/64: Interrupts save PPR on stack rather than thread_struct") was also leading to incorrect kernel stack traces. E.g. If you are using `perf record -g` and expect to see a stack trace like this: c0000000002b19a0 bpf_check+0x1910 (/usr/lib/debug/lib/modules/4.18.17-200.fc28.ppc64le/vmlinux) c0000000002a5554 bpf_prog_load+0x684 (/usr/lib/debug/lib/modules/4.18.17-200.fc28.ppc64le/vmlinux) c0000000002a6938 sys_bpf+0xaf8 (/usr/lib/debug/lib/modules/4.18.17-200.fc28.ppc64le/vmlinux) c00000000000b9e4 system_call+0x5c (/usr/lib/debug/lib/modules/4.18.17-200.fc28.ppc64le/vmlinux) 7fff815bca90 syscall+0x50 (/usr/lib64/libc-2.27.so) 7fff7d96ee0c bpf_prog_load+0x16c (/usr/lib64/libbcc.so.0.7.0) [...] you would instead see something like this: c0000000002bdb88 bpf_check+0xb88 (/lib/modules/4.20.0-rc1+/build/vmlinux) c0000000002bdb60 bpf_check+0xb60 (/lib/modules/4.20.0-rc1+/build/vmlinux) 3fff8f350a90 syscall+0x50 (/usr/lib64/libc-2.27.so) 3fff8b788e0c bpf_prog_load+0x16c (/usr/lib64/libbcc.so.0.7.0) [...] -- With Regards, Sandipan