From 1ff3b404019adf9d605224e1dce0677a0375d274 Mon Sep 17 00:00:00 2001
From: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Date: Sun, 4 Mar 2018 23:01:32 +0530
Subject: [PATCH] powerpc/xmon: Clear all breakpoints when xmon is disabled via
 debugfs

References: bsc#1072829
Patch-mainline: v4.17-rc1
Git-commit: 1ff3b404019adf9d605224e1dce0677a0375d274

Presently when xmon is disabled by debugfs any existing
instruction/data-access breakpoints set are not disabled. This may
lead to kernel oops when those breakpoints are hit as the necessary
debugger hooks aren't installed.

Hence this patch introduces a new function named clear_all_bpt() which
is called when xmon is disabled via debugfs. The function will
unpatch/clear all the trap and ciabr/dab based breakpoints.

Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
[mpe: Fix build break when CONFIG_DEBUG_FS=n]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/xmon/xmon.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index ee4b6071007d..3ddf9dd9a55f 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -3664,11 +3664,35 @@ device_initcall(setup_xmon_sysrq);
 #endif /* CONFIG_MAGIC_SYSRQ */
 
 #ifdef CONFIG_DEBUG_FS
+static void clear_all_bpt(void)
+{
+	int i;
+
+	/* clear/unpatch all breakpoints */
+	remove_bpts();
+	remove_cpu_bpts();
+
+	/* Disable all breakpoints */
+	for (i = 0; i < NBPTS; ++i)
+		bpts[i].enabled = 0;
+
+	/* Clear any data or iabr breakpoints */
+	if (iabr || dabr.enabled) {
+		iabr = NULL;
+		dabr.enabled = 0;
+	}
+
+	printf("xmon: All breakpoints cleared\n");
+}
+
 static int xmon_dbgfs_set(void *data, u64 val)
 {
 	xmon_on = !!val;
 	xmon_init(xmon_on);
 
+	/* make sure all breakpoints removed when disabling */
+	if (!xmon_on)
+		clear_all_bpt();
 	return 0;
 }
 
-- 
2.13.6