1 /*
2  * arch/arm/kernel/return_address.c
3  *
4  * Copyright (C) 2009 Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>
5  * for Pengutronix
6  *
7  * This program is free software; you can redistribute it and/or modify it
8  * under the terms of the GNU General Public License version 2 as published by
9  * the Free Software Foundation.
10  */
11 #include <linux/export.h>
12 #include <linux/ftrace.h>
13 
14 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
15 #include <linux/sched.h>
16 
17 #include <asm/stacktrace.h>
18 
19 struct return_address_data {
20 	unsigned int level;
21 	void *addr;
22 };
23 
save_return_addr(struct stackframe * frame,void * d)24 static int save_return_addr(struct stackframe *frame, void *d)
25 {
26 	struct return_address_data *data = d;
27 
28 	if (!data->level) {
29 		data->addr = (void *)frame->pc;
30 
31 		return 1;
32 	} else {
33 		--data->level;
34 		return 0;
35 	}
36 }
37 
return_address(unsigned int level)38 void *return_address(unsigned int level)
39 {
40 	struct return_address_data data;
41 	struct stackframe frame;
42 
43 	data.level = level + 2;
44 	data.addr = NULL;
45 
46 	frame.fp = (unsigned long)__builtin_frame_address(0);
47 	frame.sp = current_stack_pointer;
48 	frame.lr = (unsigned long)__builtin_return_address(0);
49 	frame.pc = (unsigned long)return_address;
50 
51 	walk_stackframe(&frame, save_return_addr, &data);
52 
53 	if (!data.level)
54 		return data.addr;
55 	else
56 		return NULL;
57 }
58 
59 #endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */
60 
61 EXPORT_SYMBOL_GPL(return_address);
62