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Subject[PATCH] xmon: Clear all breakpoints when xmon is disabled via debugfs
Date
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>
---
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 e9c7ec8f15f8..f43aacd74625 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -903,6 +903,27 @@ static void remove_bpts(void)
}
}

+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 void remove_cpu_bpts(void)
{
hw_breakpoint_disable();
@@ -3671,6 +3692,9 @@ 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;
}

--
2.14.3
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