powerpc/xmon: Clear all breakpoints when xmon is disabled via debugfs

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>

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index ee4b607..3ddf9dd 100644 (file)
--- 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;
 }