Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751626AbdISGRV (ORCPT ); Tue, 19 Sep 2017 02:17:21 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:36977 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751605AbdISGRU (ORCPT ); Tue, 19 Sep 2017 02:17:20 -0400 From: Ravi Bangoria To: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org Cc: benh@kernel.crashing.org, paulus@samba.org, maddy@linux.vnet.ibm.com, tglx@linutronix.de, mingo@kernel.org, kan.liang@intel.com, linux-kernel@vger.kernel.org, Ravi Bangoria Subject: [PATCH] powerpc/sysrq: Fix oops whem ppmu is not registered Date: Tue, 19 Sep 2017 11:47:06 +0530 X-Mailer: git-send-email 2.1.4 X-TM-AS-MML: disable x-cbid: 17091906-1617-0000-0000-000002000802 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17091906-1618-0000-0000-0000484F3460 Message-Id: <1505801826-12396-1-git-send-email-ravi.bangoria@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-09-19_04:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1707230000 definitions=main-1709190091 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1226 Lines: 42 Kernel crashes if power pmu is not registered and user tries to dump regs with 'echo p > /proc/sysrq-trigger'. Sample log: Unable to handle kernel paging request for data at address 0x00000008 Faulting instruction address: 0xc0000000000d52f0 NIP [c0000000000d52f0] perf_event_print_debug+0x10/0x230 LR [c00000000058a938] sysrq_handle_showregs+0x38/0x50 Call Trace: printk+0x38/0x4c (unreliable) __handle_sysrq+0xe4/0x270 write_sysrq_trigger+0x64/0x80 proc_reg_write+0x80/0xd0 __vfs_write+0x40/0x200 vfs_write+0xc8/0x240 SyS_write+0x60/0x110 system_call+0x58/0x6c Signed-off-by: Ravi Bangoria Reviewed-by: Kamalesh Babulal --- arch/powerpc/perf/core-book3s.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c index 2e3eb74..9e3da16 100644 --- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -793,6 +793,11 @@ void perf_event_print_debug(void) u32 pmcs[MAX_HWEVENTS]; int i; + if (!ppmu) { + pr_info("Performance monitor hardware not registered.\n"); + return; + } + if (!ppmu->n_counter) return; -- 1.8.3.1