1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * This code come from arch/arm64/kernel/return_address.c
4  *
5  * Copyright (C) 2023 SiFive.
6  */
7 
8 #include <linux/export.h>
9 #include <linux/kprobes.h>
10 #include <linux/stacktrace.h>
11 
12 struct return_address_data {
13 	unsigned int level;
14 	void *addr;
15 };
16 
save_return_addr(void * d,unsigned long pc)17 static bool save_return_addr(void *d, unsigned long pc)
18 {
19 	struct return_address_data *data = d;
20 
21 	if (!data->level) {
22 		data->addr = (void *)pc;
23 		return false;
24 	}
25 
26 	--data->level;
27 
28 	return true;
29 }
30 NOKPROBE_SYMBOL(save_return_addr);
31 
return_address(unsigned int level)32 noinline void *return_address(unsigned int level)
33 {
34 	struct return_address_data data;
35 
36 	data.level = level + 3;
37 	data.addr = NULL;
38 
39 	arch_stack_walk(save_return_addr, &data, current, NULL);
40 
41 	if (!data.level)
42 		return data.addr;
43 	else
44 		return NULL;
45 
46 }
47 EXPORT_SYMBOL_GPL(return_address);
48 NOKPROBE_SYMBOL(return_address);
49