1 | /* Return backtrace of current program state. |
2 | Copyright (C) 2003-2016 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | Contributed by Jakub Jelinek <jakub@redhat.com>, 2003. |
5 | |
6 | The GNU C Library is free software; you can redistribute it and/or |
7 | modify it under the terms of the GNU Lesser General Public |
8 | License as published by the Free Software Foundation; either |
9 | version 2.1 of the License, or (at your option) any later version. |
10 | |
11 | The GNU C Library is distributed in the hope that it will be useful, |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
14 | Lesser General Public License for more details. |
15 | |
16 | You should have received a copy of the GNU Lesser General Public |
17 | License along with the GNU C Library; if not, see |
18 | <http://www.gnu.org/licenses/>. */ |
19 | |
20 | #include <libc-lock.h> |
21 | #include <dlfcn.h> |
22 | #include <execinfo.h> |
23 | #include <stdlib.h> |
24 | #include <unwind.h> |
25 | |
26 | struct trace_arg |
27 | { |
28 | void **array; |
29 | _Unwind_Word cfa; |
30 | int cnt; |
31 | int size; |
32 | }; |
33 | |
34 | #ifdef SHARED |
35 | static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *); |
36 | static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *); |
37 | static _Unwind_Word (*unwind_getcfa) (struct _Unwind_Context *); |
38 | static void *libgcc_handle; |
39 | |
40 | |
41 | /* Dummy version in case libgcc_s does not contain the real code. */ |
42 | static _Unwind_Word |
43 | dummy_getcfa (struct _Unwind_Context *ctx __attribute__ ((unused))) |
44 | { |
45 | return 0; |
46 | } |
47 | |
48 | |
49 | static void |
50 | init (void) |
51 | { |
52 | libgcc_handle = __libc_dlopen ("libgcc_s.so.1" ); |
53 | |
54 | if (libgcc_handle == NULL) |
55 | return; |
56 | |
57 | unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace" ); |
58 | unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP" ); |
59 | if (unwind_getip == NULL) |
60 | unwind_backtrace = NULL; |
61 | unwind_getcfa = (__libc_dlsym (libgcc_handle, "_Unwind_GetCFA" ) |
62 | ?: dummy_getcfa); |
63 | } |
64 | #else |
65 | # define unwind_backtrace _Unwind_Backtrace |
66 | # define unwind_getip _Unwind_GetIP |
67 | # define unwind_getcfa _Unwind_GetCFA |
68 | #endif |
69 | |
70 | static _Unwind_Reason_Code |
71 | backtrace_helper (struct _Unwind_Context *ctx, void *a) |
72 | { |
73 | struct trace_arg *arg = a; |
74 | |
75 | /* We are first called with address in the __backtrace function. |
76 | Skip it. */ |
77 | if (arg->cnt != -1) |
78 | { |
79 | arg->array[arg->cnt] = (void *) unwind_getip (ctx); |
80 | |
81 | /* Check whether we make any progress. */ |
82 | _Unwind_Word cfa = unwind_getcfa (ctx); |
83 | |
84 | if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt] |
85 | && cfa == arg->cfa) |
86 | return _URC_END_OF_STACK; |
87 | arg->cfa = cfa; |
88 | } |
89 | if (++arg->cnt == arg->size) |
90 | return _URC_END_OF_STACK; |
91 | return _URC_NO_REASON; |
92 | } |
93 | |
94 | int |
95 | __backtrace (void **array, int size) |
96 | { |
97 | struct trace_arg arg = { .array = array, .cfa = 0, .size = size, .cnt = -1 }; |
98 | |
99 | if (size <= 0) |
100 | return 0; |
101 | |
102 | #ifdef SHARED |
103 | __libc_once_define (static, once); |
104 | |
105 | __libc_once (once, init); |
106 | if (unwind_backtrace == NULL) |
107 | return 0; |
108 | #endif |
109 | |
110 | unwind_backtrace (backtrace_helper, &arg); |
111 | |
112 | /* _Unwind_Backtrace seems to put NULL address above |
113 | _start. Fix it up here. */ |
114 | if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL) |
115 | --arg.cnt; |
116 | return arg.cnt != -1 ? arg.cnt : 0; |
117 | } |
118 | weak_alias (__backtrace, backtrace) |
119 | libc_hidden_def (__backtrace) |
120 | |
121 | |
122 | #ifdef SHARED |
123 | /* Free all resources if necessary. */ |
124 | libc_freeres_fn (free_mem) |
125 | { |
126 | unwind_backtrace = NULL; |
127 | if (libgcc_handle != NULL) |
128 | { |
129 | __libc_dlclose (libgcc_handle); |
130 | libgcc_handle = NULL; |
131 | } |
132 | } |
133 | #endif |
134 | |