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_HELO_NONE,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 CD9EDC28CC3 for ; Fri, 7 Jun 2019 03:18:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A2365208C3 for ; Fri, 7 Jun 2019 03:18:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726542AbfFGDSA (ORCPT ); Thu, 6 Jun 2019 23:18:00 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:39920 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726157AbfFGDSA (ORCPT ); Thu, 6 Jun 2019 23:18:00 -0400 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x5737P6Q018103 for ; Thu, 6 Jun 2019 23:17:58 -0400 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0b-001b2d01.pphosted.com with ESMTP id 2sybst8ke5-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 06 Jun 2019 23:17:58 -0400 Received: from localhost by e06smtp05.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, 7 Jun 2019 04:17:54 +0100 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x573HrZP43909258 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 7 Jun 2019 03:17:53 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4505AA4051; Fri, 7 Jun 2019 03:17:53 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C0BCFA404D; Fri, 7 Jun 2019 03:17:49 +0000 (GMT) Received: from [9.199.59.123] (unknown [9.199.59.123]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 7 Jun 2019 03:17:49 +0000 (GMT) Subject: Re: [PATCH] Powerpc/Watchpoint: Restore nvgprs while returning from exception To: Michael Neuling , mpe@ellerman.id.au Cc: benh@kernel.crashing.org, paulus@samba.org, npiggin@gmail.com, christophe.leroy@c-s.fr, mahesh@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Ravi Bangoria References: <20190606072951.32116-1-ravi.bangoria@linux.ibm.com> <80cfc8d7327d3bb744ea1f7e2843943a998d48de.camel@neuling.org> From: Ravi Bangoria Date: Fri, 7 Jun 2019 08:47:47 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <80cfc8d7327d3bb744ea1f7e2843943a998d48de.camel@neuling.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19060703-0020-0000-0000-00000347E8B6 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19060703-0021-0000-0000-0000219AFFBF Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-07_01:,, 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=1015 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-1906070021 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/7/19 6:20 AM, Michael Neuling wrote: > On Thu, 2019-06-06 at 12:59 +0530, Ravi Bangoria wrote: >> Powerpc hw triggers watchpoint before executing the instruction. >> To make trigger-after-execute behavior, kernel emulates the >> instruction. If the instruction is 'load something into non- >> volatile register', exception handler should restore emulated >> register state while returning back, otherwise there will be >> register state corruption. Ex, Adding a watchpoint on a list >> can corrput the list: >> >> # cat /proc/kallsyms | grep kthread_create_list >> c00000000121c8b8 d kthread_create_list >> >> Add watchpoint on kthread_create_list->next: >> >> # perf record -e mem:0xc00000000121c8c0 >> >> Run some workload such that new kthread gets invoked. Ex, I >> just logged out from console: >> >> list_add corruption. next->prev should be prev (c000000001214e00), \ >> but was c00000000121c8b8. (next=c00000000121c8b8). >> WARNING: CPU: 59 PID: 309 at lib/list_debug.c:25 __list_add_valid+0xb4/0xc0 >> CPU: 59 PID: 309 Comm: kworker/59:0 Kdump: loaded Not tainted 5.1.0-rc7+ #69 >> ... >> NIP __list_add_valid+0xb4/0xc0 >> LR __list_add_valid+0xb0/0xc0 >> Call Trace: >> __list_add_valid+0xb0/0xc0 (unreliable) >> __kthread_create_on_node+0xe0/0x260 >> kthread_create_on_node+0x34/0x50 >> create_worker+0xe8/0x260 >> worker_thread+0x444/0x560 >> kthread+0x160/0x1a0 >> ret_from_kernel_thread+0x5c/0x70 >> >> Signed-off-by: Ravi Bangoria > > How long has this been around? Should we be CCing stable? "bl .save_nvgprs" was added in the commit 5aae8a5370802 ("powerpc, hw_breakpoints: Implement hw_breakpoints for 64-bit server processors"), which was merged in v2.6.36.