This fault was detected using the kgdb test suite on boot and it
crashes recursively due to the fact that CONFIG_KPROBES on mips adds
an extra die notifier in the page fault handler. The crash signature
looks like this:
kgdbts:RUN bad memory access test
KGDB: re-enter exception: ALL breakpoints killed
Call Trace:
[<807b7548>] dump_stack+0x20/0x54
[<807b7548>] dump_stack+0x20/0x54
The fix for now is to have kgdb return immediately if the fault type
is DIE_PAGE_FAULT and allow the kprobe code to decide what is supposed
to happen.
Cc: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
Cc: David S. Miller <da...@davemloft.net>
Signed-off-by: Jason Wessel <jason.wes...@windriver.com>
---
arch/mips/kernel/kgdb.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/mips/kernel/kgdb.c b/arch/mips/kernel/kgdb.c
index f4546e9..23817a6 100644
--- a/arch/mips/kernel/kgdb.c
+++ b/arch/mips/kernel/kgdb.c
@@ -283,6 +283,15 @@ static int kgdb_mips_notify(struct notifier_block *self,
unsigned long cmd,
struct pt_regs *regs = args->regs;
int trap = (regs->cp0_cause & 0x7c) >> 2;
+#ifdef CONFIG_KPROBES
+ /*
+ * Return immediately if the kprobes fault notifier has set
+ * DIE_PAGE_FAULT.
+ */
+ if (cmd == DIE_PAGE_FAULT)
+ return NOTIFY_DONE;
+#endif /* CONFIG_KPROBES */
+
/* Userspace events, ignore. */
if (user_mode(regs))
return NOTIFY_DONE;
--
1.7.9.5
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