From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751973AbeCDRbb (ORCPT ); Sun, 4 Mar 2018 12:31:31 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:39874 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751878AbeCDRb2 (ORCPT ); Sun, 4 Mar 2018 12:31:28 -0500 From: Vaibhav Jain To: Michael Ellerman , Balbir Singh Cc: Vaibhav Jain , Frederic Barrat , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Benjamin Herrenschmidt , Paul Mackerras , Nicholas Piggin , Douglas Miller Subject: [PATCH v2] xmon: Setup xmon debugger hooks when first break-point is set Date: Sun, 4 Mar 2018 23:00:25 +0530 X-Mailer: git-send-email 2.14.3 X-TM-AS-GCONF: 00 x-cbid: 18030417-0012-0000-0000-000005B893A5 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18030417-0013-0000-0000-00001934A27E Message-Id: <20180304173025.19520-1-vaibhav@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-03-04_09:,, 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 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1803040227 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Presently sysrq key for xmon('x') is registered during kernel init irrespective of the value of kernel param 'xmon'. Thus xmon is enabled even if 'xmon=off' is passed on the kernel command line. However this doesn't enable the kernel debugger hooks needed for instruction or data breakpoints. Thus when a break-point is hit with xmon=off a kernel oops of the form below is reported: Oops: Exception in kernel mode, sig: 5 [#1] < snip > Trace/breakpoint trap To fix this the patch checks and enables debugger hooks when an instruction or data break-point is set via xmon console. Signed-off-by: Vaibhav Jain --- Change-log: v2 -> Moved the code that was force enabling xmon to a separate inline function (Balbir) The change related to clearing all breakpoints when xmon is disabled via debugfs will be respinned as a separate patch. (Mpe) --- arch/powerpc/xmon/xmon.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index 82e1a3ee6e0f..e9c7ec8f15f8 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -1273,6 +1273,18 @@ static long check_bp_loc(unsigned long addr) return 1; } +/* Force enable xmon if not already enabled */ +static inline void force_enable_xmon(void) +{ + static const char warnxmon[] = "xmon: Enabling debugger hooks\n"; + + /* Enable xmon hooks if needed */ + if (!xmon_on) { + printf(warnxmon); + xmon_on = 1; + } +} + static char *breakpoint_help_string = "Breakpoint command usage:\n" "b show breakpoints\n" @@ -1315,6 +1327,8 @@ bpt_cmds(void) dabr.address &= ~HW_BRK_TYPE_DABR; dabr.enabled = mode | BP_DABR; } + + force_enable_xmon(); break; case 'i': /* bi - hardware instr breakpoint */ @@ -1335,6 +1349,7 @@ bpt_cmds(void) if (bp != NULL) { bp->enabled |= BP_CIABR; iabr = bp; + force_enable_xmon(); } break; #endif @@ -1399,8 +1414,10 @@ bpt_cmds(void) if (!check_bp_loc(a)) break; bp = new_breakpoint(a); - if (bp != NULL) + if (bp != NULL) { bp->enabled |= BP_TRAP; + force_enable_xmon(); + } break; } } -- 2.14.3