[PATCH] arm: Add unwinding annotations for 64bit division functions

The unwinding fix should be simple (I haven't tested it yet):

8<-----------------------------
ARM: Ignore the unwinding information for the first instruction in a function

From: Catalin Marinas <catalin.marinas@arm.com>

When backtracing from the first instruction of a function, the prologue
has not been executed and the unwinding information is not valid. This
patch checks for this case and just assumes that the return address is
in LR.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm/kernel/unwind.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index d2cb0b3..946face 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c

@@ -293,6 +293,16 @@ int unwind_frame(struct stackframe *frame)
 		return -URC_FAILURE;
 	}
 
+	/*
+	 * Check for backtrace on the first instruction of a function. The
+	 * prologue has not been executed yet and the unwinding information is
+	 * not valid. Assume that the return address is in LR.
+	 */
+	if (idx.addr == frame->pc) {
+		frame->pc = frame->lr;
+		return URC_OK;
+	}
+
 	ctrl.vrs[FP] = frame->fp;
 	ctrl.vrs[SP] = frame->sp;
 	ctrl.vrs[LR] = frame->lr;