1 | /* Return backtrace of current program state. |
2 | Copyright (C) 2003-2019 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 <gnu/lib-names.h> |
24 | #include <stdlib.h> |
25 | #include <unwind.h> |
26 | |
27 | struct trace_arg |
28 | { |
29 | void **array; |
30 | _Unwind_Word cfa; |
31 | int cnt; |
32 | int size; |
33 | }; |
34 | |
35 | #ifdef SHARED |
36 | static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *); |
37 | static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *); |
38 | static _Unwind_Word (*unwind_getcfa) (struct _Unwind_Context *); |
39 | static void *libgcc_handle; |
40 | |
41 | |
42 | /* Dummy version in case libgcc_s does not contain the real code. */ |
43 | static _Unwind_Word |
44 | dummy_getcfa (struct _Unwind_Context *ctx __attribute__ ((unused))) |
45 | { |
46 | return 0; |
47 | } |
48 | |
49 | |
50 | static void |
51 | init (void) |
52 | { |
53 | libgcc_handle = __libc_dlopen (LIBGCC_S_SO); |
54 | |
55 | if (libgcc_handle == NULL) |
56 | return; |
57 | |
58 | unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace" ); |
59 | unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP" ); |
60 | if (unwind_getip == NULL) |
61 | unwind_backtrace = NULL; |
62 | unwind_getcfa = (__libc_dlsym (libgcc_handle, "_Unwind_GetCFA" ) |
63 | ?: dummy_getcfa); |
64 | } |
65 | #else |
66 | # define unwind_backtrace _Unwind_Backtrace |
67 | # define unwind_getip _Unwind_GetIP |
68 | # define unwind_getcfa _Unwind_GetCFA |
69 | #endif |
70 | |
71 | static _Unwind_Reason_Code |
72 | backtrace_helper (struct _Unwind_Context *ctx, void *a) |
73 | { |
74 | struct trace_arg *arg = a; |
75 | |
76 | /* We are first called with address in the __backtrace function. |
77 | Skip it. */ |
78 | if (arg->cnt != -1) |
79 | { |
80 | arg->array[arg->cnt] = (void *) unwind_getip (ctx); |
81 | |
82 | /* Check whether we make any progress. */ |
83 | _Unwind_Word cfa = unwind_getcfa (ctx); |
84 | |
85 | if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt] |
86 | && cfa == arg->cfa) |
87 | return _URC_END_OF_STACK; |
88 | arg->cfa = cfa; |
89 | } |
90 | if (++arg->cnt == arg->size) |
91 | return _URC_END_OF_STACK; |
92 | return _URC_NO_REASON; |
93 | } |
94 | |
95 | int |
96 | __backtrace (void **array, int size) |
97 | { |
98 | struct trace_arg arg = { .array = array, .cfa = 0, .size = size, .cnt = -1 }; |
99 | |
100 | if (size <= 0) |
101 | return 0; |
102 | |
103 | #ifdef SHARED |
104 | __libc_once_define (static, once); |
105 | |
106 | __libc_once (once, init); |
107 | if (unwind_backtrace == NULL) |
108 | return 0; |
109 | #endif |
110 | |
111 | unwind_backtrace (backtrace_helper, &arg); |
112 | |
113 | /* _Unwind_Backtrace seems to put NULL address above |
114 | _start. Fix it up here. */ |
115 | if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL) |
116 | --arg.cnt; |
117 | return arg.cnt != -1 ? arg.cnt : 0; |
118 | } |
119 | weak_alias (__backtrace, backtrace) |
120 | libc_hidden_def (__backtrace) |
121 | |
122 | |
123 | #ifdef SHARED |
124 | /* Free all resources if necessary. */ |
125 | libc_freeres_fn (free_mem) |
126 | { |
127 | unwind_backtrace = NULL; |
128 | if (libgcc_handle != NULL) |
129 | { |
130 | __libc_dlclose (libgcc_handle); |
131 | libgcc_handle = NULL; |
132 | } |
133 | } |
134 | #endif |
135 | |