From patchwork Thu Jun 13 03:30:14 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ravi Bangoria X-Patchwork-Id: 1114934 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 45PTnK3m0kz9sBb for ; Thu, 13 Jun 2019 13:32:05 +1000 (AEST) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 45PTnK1dX3zDrB4 for ; Thu, 13 Jun 2019 13:32:05 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=linux.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=ravi.bangoria@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 (mx0b-001b2d01.pphosted.com [148.163.158.5]) (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 45PTlR1Jv7zDqlP for ; Thu, 13 Jun 2019 13:30:26 +1000 (AEST) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x5D3Rntb066366 for ; Wed, 12 Jun 2019 23:30:23 -0400 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0b-001b2d01.pphosted.com with ESMTP id 2t3aqyf73x-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 12 Jun 2019 23:30:23 -0400 Received: from localhost by e06smtp01.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) Thu, 13 Jun 2019 04:30:19 +0100 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5D3UHHR51445824 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 13 Jun 2019 03:30:17 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 81C5F52065; Thu, 13 Jun 2019 03:30:17 +0000 (GMT) Received: from bangoria.in.ibm.com (unknown [9.124.31.207]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 866F152052; Thu, 13 Jun 2019 03:30:15 +0000 (GMT) From: Ravi Bangoria To: mpe@ellerman.id.au Subject: [PATCH v2] Powerpc/Watchpoint: Restore nvgprs while returning from exception Date: Thu, 13 Jun 2019 09:00:14 +0530 X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 X-TM-AS-GCONF: 00 x-cbid: 19061303-4275-0000-0000-00000341DB39 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19061303-4276-0000-0000-00003851F339 Message-Id: <20190613033014.17496-1-ravi.bangoria@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-06-13_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-1906130025 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@linux.ibm.com, mikey@neuling.org, linux-kernel@vger.kernel.org, npiggin@gmail.com, paulus@samba.org, aneesh.kumar@linux.ibm.com, mahesh@linux.vnet.ibm.com, naveen.n.rao@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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->prev: # 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 List corruption happened because it uses 'load into non-volatile register' instruction: Snippet from __kthread_create_on_node: c000000000136be8: addis r29,r2,-19 c000000000136bec: ld r29,31424(r29) if (!__list_add_valid(new, prev, next)) c000000000136bf0: mr r3,r30 c000000000136bf4: mr r5,r28 c000000000136bf8: mr r4,r29 c000000000136bfc: bl c00000000059a2f8 <__list_add_valid+0x8> Register state from WARN_ON(): GPR00: c00000000059a3a0 c000007ff23afb50 c000000001344e00 0000000000000075 GPR04: 0000000000000000 0000000000000000 0000001852af8bc1 0000000000000000 GPR08: 0000000000000001 0000000000000007 0000000000000006 00000000000004aa GPR12: 0000000000000000 c000007ffffeb080 c000000000137038 c000005ff62aaa00 GPR16: 0000000000000000 0000000000000000 c000007fffbe7600 c000007fffbe7370 GPR20: c000007fffbe7320 c000007fffbe7300 c000000001373a00 0000000000000000 GPR24: fffffffffffffef7 c00000000012e320 c000007ff23afcb0 c000000000cb8628 GPR28: c00000000121c8b8 c000000001214e00 c000007fef5b17e8 c000007fef5b17c0 Watchpoint hit at 0xc000000000136bec. addis r29,r2,-19 => r29 = 0xc000000001344e00 + (-19 << 16) => r29 = 0xc000000001214e00 ld r29,31424(r29) => r29 = *(0xc000000001214e00 + 31424) => r29 = *(0xc00000000121c8c0) 0xc00000000121c8c0 is where we placed a watchpoint and thus this instruction was emulated by emulate_step. But because handle_dabr_fault did not restore emulated register state, r29 still contains stale value in above register state. Fixes: 5aae8a5370802 ("powerpc, hw_breakpoints: Implement hw_breakpoints for 64-bit server processors") Signed-off-by: Ravi Bangoria Cc: stable@vger.kernel.org # 2.6.36+ --- v1: https://lkml.org/lkml/2019/6/10/1058 v1->v2: Successful do_page_fault returns using ret_from_except_lite at the same place where handle_dabr_fault also returns. v1 messed up with do_page_fault return path. Fix that in v2. arch/powerpc/kernel/exceptions-64s.S | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 6b86055..2546427 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -1746,7 +1746,7 @@ handle_page_fault: addi r3,r1,STACK_FRAME_OVERHEAD bl do_page_fault cmpdi r3,0 - beq+ 12f + beq+ ret_from_except_lite bl save_nvgprs mr r5,r3 addi r3,r1,STACK_FRAME_OVERHEAD @@ -1761,7 +1761,12 @@ handle_dabr_fault: ld r5,_DSISR(r1) addi r3,r1,STACK_FRAME_OVERHEAD bl do_break -12: b ret_from_except_lite + /* + * do_break may have changed the nv-gprs while haldling + * breakpoint. If so, we need to restore them with their + * updated values. Don't use ret_from_except_lite here. + */ + b ret_from_except #ifdef CONFIG_PPC_BOOK3S_64