ARM: 7676/1: fix a wrong value returned from CALLER_ADDRn

This makes return_address() return a correct value for CALLER_ADDRn.
To have a correct value from CALLER_ADDRn, we need to fix three points.

* The unwind_frame() does not update frame->lr but frame->pc for backtrace.
So frame->pc is meaningful for backtrace.

* data.level should be adjusted by adding 2 additional iteration levels.
With the current +1 level adjustment, the result of CALLER_ADDR1 will
be the same return address with CALLER_ADDR0.

* The initialization of data.addr to NULL is needed.
When unwind_fame() fails right after data.level reaches zero,
the routine returns data.addr which has uninitialized garbage value.
Signed-off-by: NSahara <keun-o.park@windriver.com>
Reviewed-by: NDave Martin <dave.martin@linaro.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/return_address.c

@@ -26,7 +26,7 @@ static int save_return_addr(struct stackframe *frame, void *d)
 	struct return_address_data *data = d;
 
 	if (!data->level) {
-		data->addr = (void *)frame->lr;
+		data->addr = (void *)frame->pc;
 
 		return 1;
 	} else {
@@ -41,7 +41,8 @@ void *return_address(unsigned int level)
 	struct stackframe frame;
 	register unsigned long current_sp asm ("sp");
 
-	data.level = level + 1;
+	data.level = level + 2;
+	data.addr = NULL;
 
 	frame.fp = (unsigned long)__builtin_frame_address(0);
 	frame.sp = current_sp;