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Subject[PATCH] powerpc/xmon: really enable xmon when a breakpoint is set
When single-stepping kernel code from xmon without a debug hook enabled
the kernel crashes. This can happen when kernel starts with xmon on
crash disabled but xmon is entered using sysrq.

Commit e1368d0c9edb ("powerpc/xmon: Setup debugger hooks when first
break-point is set") adds force_enable_xmon function that prints
"xmon: Enabling debugger hooks" but does not enable them.

Add the call to xmon_init to install the debugger hooks in
force_enable_xmon and also call force_enable_xmon when single-stepping
in xmon.

Fixes: e1368d0c9edb ("powerpc/xmon: Setup debugger hooks when first
break-point is set")

Signed-off-by: Michal Suchanek <>
arch/powerpc/xmon/xmon.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index a0842f1ff72c..504bd1c3d8b0 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -179,6 +179,9 @@ static const char *getvecname(unsigned long vec);

static int do_spu_cmd(void);

+static void xmon_init(int enable);
+static inline void force_enable_xmon(void);
#ifdef CONFIG_44x
static void dump_tlb_44x(void);
@@ -1094,6 +1097,7 @@ static int do_step(struct pt_regs *regs)
unsigned int instr;
int stepped;

+ force_enable_xmon();
/* check we are in 64-bit kernel mode, translation enabled */
if ((regs->msr & (MSR_64BIT|MSR_PR|MSR_IR)) == (MSR_64BIT|MSR_IR)) {
if (mread(regs->nip, &instr, 4) == 4) {
@@ -1275,6 +1279,7 @@ static inline void force_enable_xmon(void)
if (!xmon_on) {
printf("xmon: Enabling debugger hooks\n");
xmon_on = 1;
+ xmon_init(1);

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