From e1368d0c9edbc366e45216e7295fd61ae55c2b12 Mon Sep 17 00:00:00 2001 From: Vaibhav Jain Date: Sun, 4 Mar 2018 23:00:25 +0530 Subject: [PATCH] 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 Reviewed-by: Balbir Singh [mpe: Just printf directly, no need for static const char[]] Signed-off-by: Michael Ellerman --- arch/powerpc/xmon/xmon.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) 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; } } -- 2.7.4