sh: handle early calls to return_address() when using dwarf unwinder.
The dwarf unwinder ties in to an early initcall, but it's possible that
return_address() calls will be made prior to that. This implements some
additional error handling in to the dwarf unwinder as well as an exit
path in the return_address() case to bail out if the unwinder hasn't come
up yet.
This fixes a NULL pointer deref in early boot when mempool_alloc() blows
up on the not-yet-ready mempool via dwarf_unwind_stack().
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/kernel/return_address.c b/arch/sh/kernel/return_address.c
index cbf1dd5..5124aeb 100644
--- a/arch/sh/kernel/return_address.c
+++ b/arch/sh/kernel/return_address.c
@@ -24,6 +24,8 @@
struct dwarf_frame *tmp;
tmp = dwarf_unwind_stack(ra, frame);
+ if (!tmp)
+ return NULL;
if (frame)
dwarf_free_frame(frame);