about summary refs log tree commit diff
path: root/sysdeps/x86_64/backtrace.c
blob: e04407c516c2edb679361169376f52e086ae4dd5 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
/* Return backtrace of current program state.
   Copyright (C) 2003-2016 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <libc-lock.h>
#include <dlfcn.h>
#include <execinfo.h>
#include <stdlib.h>
#include <unwind.h>

struct trace_arg
{
  void **array;
  _Unwind_Word cfa;
  int cnt;
  int size;
};

#ifdef SHARED
static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
static _Unwind_Word (*unwind_getcfa) (struct _Unwind_Context *);
static void *libgcc_handle;


/* Dummy version in case libgcc_s does not contain the real code.  */
static _Unwind_Word
dummy_getcfa (struct _Unwind_Context *ctx __attribute__ ((unused)))
{
  return 0;
}


static void
init (void)
{
  libgcc_handle = __libc_dlopen ("libgcc_s.so.1");

  if (libgcc_handle == NULL)
    return;

  unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");
  unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP");
  if (unwind_getip == NULL)
    unwind_backtrace = NULL;
  unwind_getcfa = (__libc_dlsym (libgcc_handle, "_Unwind_GetCFA")
		  ?: dummy_getcfa);
}
#else
# define unwind_backtrace _Unwind_Backtrace
# define unwind_getip _Unwind_GetIP
# define unwind_getcfa _Unwind_GetCFA
#endif

static _Unwind_Reason_Code
backtrace_helper (struct _Unwind_Context *ctx, void *a)
{
  struct trace_arg *arg = a;

  /* We are first called with address in the __backtrace function.
     Skip it.  */
  if (arg->cnt != -1)
    {
      arg->array[arg->cnt] = (void *) unwind_getip (ctx);

      /* Check whether we make any progress.  */
      _Unwind_Word cfa = unwind_getcfa (ctx);

      if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt]
	 && cfa == arg->cfa)
       return _URC_END_OF_STACK;
      arg->cfa = cfa;
    }
  if (++arg->cnt == arg->size)
    return _URC_END_OF_STACK;
  return _URC_NO_REASON;
}

int
__backtrace (void **array, int size)
{
  struct trace_arg arg = { .array = array, .cfa = 0, .size = size, .cnt = -1 };

  if (size <= 0)
    return 0;

#ifdef SHARED
  __libc_once_define (static, once);

  __libc_once (once, init);
  if (unwind_backtrace == NULL)
    return 0;
#endif

  unwind_backtrace (backtrace_helper, &arg);

  /* _Unwind_Backtrace seems to put NULL address above
     _start.  Fix it up here.  */
  if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
    --arg.cnt;
  return arg.cnt != -1 ? arg.cnt : 0;
}
weak_alias (__backtrace, backtrace)
libc_hidden_def (__backtrace)


#ifdef SHARED
/* Free all resources if necessary.  */
libc_freeres_fn (free_mem)
{
  unwind_backtrace = NULL;
  if (libgcc_handle != NULL)
    {
      __libc_dlclose (libgcc_handle);
      libgcc_handle = NULL;
    }
}
#endif