Commit e1368d0c authored Mar 04, 2018 by Vaibhav Jain Committed by Michael Ellerman Mar 13, 2018

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>

parent b395e55b

arch/powerpc/xmon/xmon.c

+16 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}
		}