powerpc/xmon: Setup debugger hooks when first break-point is set
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 <vaibhav@linux.vnet.ibm.com>
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
[mpe: Just printf directly, no need for static const char[]]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 82e1a3e..ee4b6071 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -1273,6 +1273,16 @@ static long check_bp_loc(unsigned long addr)
return 1;
}
+/* Force enable xmon if not already enabled */
+static inline void force_enable_xmon(void)
+{
+ /* Enable xmon hooks if needed */
+ if (!xmon_on) {
+ printf("xmon: Enabling debugger hooks\n");
+ xmon_on = 1;
+ }
+}
+
static char *breakpoint_help_string =
"Breakpoint command usage:\n"
"b show breakpoints\n"
@@ -1315,6 +1325,8 @@ 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 +1347,7 @@ bpt_cmds(void)
if (bp != NULL) {
bp->enabled |= BP_CIABR;
iabr = bp;
+ force_enable_xmon();
}
break;
#endif
@@ -1399,8 +1412,10 @@ 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;
}
}