From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 3zvVSz1JMhzF09j for ; Mon, 5 Mar 2018 04:31:30 +1100 (AEDT) Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w24HTLl1138317 for ; Sun, 4 Mar 2018 12:31:28 -0500 Received: from e06smtp13.uk.ibm.com (e06smtp13.uk.ibm.com [195.75.94.109]) by mx0a-001b2d01.pphosted.com with ESMTP id 2gga78r3mc-1 (version=TLSv1.2 cipher=AES256-SHA256 bits=256 verify=NOT) for ; Sun, 04 Mar 2018 12:31:28 -0500 Received: from localhost by e06smtp13.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sun, 4 Mar 2018 17:31:26 -0000 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 Message-Id: <20180304173025.19520-1-vaibhav@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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