return_address.c

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * arch/sh/kernel/return_address.c
 4 *
 5 * Copyright (C) 2009  Matt Fleming
 6 * Copyright (C) 2009  Paul Mundt
 7 */
 8#include <linux/kernel.h>
 9#include <linux/module.h>
10
11#include <asm/dwarf.h>
12#include <asm/ftrace.h>
13
14#ifdef CONFIG_DWARF_UNWINDER
15
16void *return_address(unsigned int depth)
17{
18	struct dwarf_frame *frame;
19	unsigned long ra;
20	int i;
21
22	for (i = 0, frame = NULL, ra = 0; i <= depth; i++) {
23		struct dwarf_frame *tmp;
24
25		tmp = dwarf_unwind_stack(ra, frame);
26		if (!tmp)
27			return NULL;
28
29		if (frame)
30			dwarf_free_frame(frame);
31
32		frame = tmp;
33
34		if (!frame || !frame->return_addr)
35			break;
36
37		ra = frame->return_addr;
38	}
39
40	/* Failed to unwind the stack to the specified depth. */
41	WARN_ON(i != depth + 1);
42
43	if (frame)
44		dwarf_free_frame(frame);
45
46	return (void *)ra;
47}
48
49#else
50
51void *return_address(unsigned int depth)
52{
53	return NULL;
54}
55
56#endif
57
58EXPORT_SYMBOL_GPL(return_address);