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/stack_pointer.h>
16 #include <asm/stacktrace.h>
17 
18 struct return_address_data {
19 	unsigned int level;
20 	void *addr;
21 };
22 
23 static int save_return_addr(struct stackframe *frame, void *d)
24 {
25 	struct return_address_data *data = d;
26 
27 	if (!data->level) {
28 		data->addr = (void *)frame->pc;
29 		return 1;
30 	} else {
31 		--data->level;
32 		return 0;
33 	}
34 }
35 
36 void *return_address(unsigned int level)
37 {
38 	struct return_address_data data;
39 	struct stackframe frame;
40 
41 	data.level = level + 2;
42 	data.addr = NULL;
43 
44 	frame.fp = (unsigned long)__builtin_frame_address(0);
45 	frame.pc = (unsigned long)return_address; /* dummy */
46 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
47 	frame.graph = current->curr_ret_stack;
48 #endif
49 
50 	walk_stackframe(current, &frame, save_return_addr, &data);
51 
52 	if (!data.level)
53 		return data.addr;
54 	else
55 		return NULL;
56 }
57 EXPORT_SYMBOL_GPL(return_address);
58