1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * arch/arm/kernel/return_address.c
4  *
5  * Copyright (C) 2009 Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>
6  * for Pengutronix
7  */
8 #include <linux/export.h>
9 #include <linux/ftrace.h>
10 #include <linux/sched.h>
11 
12 #include <asm/stacktrace.h>
13 
14 struct return_address_data {
15 	unsigned int level;
16 	void *addr;
17 };
18 
save_return_addr(void * d,unsigned long pc)19 static bool save_return_addr(void *d, unsigned long pc)
20 {
21 	struct return_address_data *data = d;
22 
23 	if (!data->level) {
24 		data->addr = (void *)pc;
25 
26 		return false;
27 	} else {
28 		--data->level;
29 		return true;
30 	}
31 }
32 
return_address(unsigned int level)33 void *return_address(unsigned int level)
34 {
35 	struct return_address_data data;
36 	struct stackframe frame;
37 
38 	data.level = level + 2;
39 	data.addr = NULL;
40 
41 	frame.fp = (unsigned long)__builtin_frame_address(0);
42 	frame.sp = current_stack_pointer;
43 	frame.lr = (unsigned long)__builtin_return_address(0);
44 here:
45 	frame.pc = (unsigned long)&&here;
46 #ifdef CONFIG_KRETPROBES
47 	frame.kr_cur = NULL;
48 	frame.tsk = current;
49 #endif
50 	frame.ex_frame = false;
51 
52 	walk_stackframe(&frame, save_return_addr, &data);
53 
54 	if (!data.level)
55 		return data.addr;
56 	else
57 		return NULL;
58 }
59 
60 EXPORT_SYMBOL_GPL(return_address);
61