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Subject[PATCH v2] powerpc/xmon: Also setup debugger hooks when single-stepping
Date
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.

Call force_enable_xmon when single-stepping in xmon to install the xmon
debug hooks.

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

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/xmon/xmon.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)

v2: calling force_enable_xmon in do_step is sufficient

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index a0842f1ff72c..252df9741d20 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -778,6 +778,16 @@ static int xmon_fault_handler(struct pt_regs *regs)
return 0;
}

+/* 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 struct bpt *at_breakpoint(unsigned long pc)
{
int i;
@@ -1094,6 +1104,7 @@ 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) {
@@ -1268,16 +1279,6 @@ 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"
--
2.13.6
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