Linux Kernel  3.7.1
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return_address.c
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1 /*
2  * arch/arm/kernel/return_address.c
3  *
4  * Copyright (C) 2009 Uwe Kleine-Koenig <[email protected]>
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 
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->lr;
30 
31  return 1;
32  } else {
33  --data->level;
34  return 0;
35  }
36 }
37 
38 void *return_address(unsigned int level)
39 {
40  struct return_address_data data;
41  struct stackframe frame;
42  register unsigned long current_sp asm ("sp");
43 
44  data.level = level + 1;
45 
46  frame.fp = (unsigned long)__builtin_frame_address(0);
47  frame.sp = current_sp;
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 #else /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) */
60 
61 #if defined(CONFIG_ARM_UNWIND)
62 #warning "TODO: return_address should use unwind tables"
63 #endif
64 
65 void *return_address(unsigned int level)
66 {
67  return NULL;
68 }
69 
70 #endif /* if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND) / else */
71