1/*
2 * arch/arm64/kernel/return_address.c
3 *
4 * Copyright (C) 2013 Linaro Limited
5 * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 */
11
12#include <linux/export.h>
13#include <linux/ftrace.h>
14
15#include <asm/stacktrace.h>
16
17struct return_address_data {
18	unsigned int level;
19	void *addr;
20};
21
22static int save_return_addr(struct stackframe *frame, void *d)
23{
24	struct return_address_data *data = d;
25
26	if (!data->level) {
27		data->addr = (void *)frame->pc;
28		return 1;
29	} else {
30		--data->level;
31		return 0;
32	}
33}
34
35void *return_address(unsigned int level)
36{
37	struct return_address_data data;
38	struct stackframe frame;
39
40	data.level = level + 2;
41	data.addr = NULL;
42
43	frame.fp = (unsigned long)__builtin_frame_address(0);
44	frame.sp = current_stack_pointer;
45	frame.pc = (unsigned long)return_address; /* dummy */
46
47	walk_stackframe(&frame, save_return_addr, &data);
48
49	if (!data.level)
50		return data.addr;
51	else
52		return NULL;
53}
54EXPORT_SYMBOL_GPL(return_address);
55