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32ebef01 | 1 | /* Return backtrace of current program state. |
2b778ceb | 2 | Copyright (C) 2013-2021 Free Software Foundation, Inc. |
32ebef01 AS |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, see | |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
32ebef01 | 18 | |
ec999b8e | 19 | #include <libc-lock.h> |
32ebef01 AS |
20 | #include <dlfcn.h> |
21 | #include <execinfo.h> | |
22 | #include <stdlib.h> | |
23 | #include <unwind.h> | |
24 | ||
25 | struct trace_arg | |
26 | { | |
27 | void **array; | |
28 | int cnt, size; | |
29 | void *lastfp, *lastsp; | |
30 | }; | |
31 | ||
32 | #ifdef SHARED | |
33 | static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *); | |
34 | static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *); | |
35 | static _Unwind_Ptr (*unwind_getcfa) (struct _Unwind_Context *); | |
36 | static _Unwind_Ptr (*unwind_getgr) (struct _Unwind_Context *, int); | |
37 | static void *libgcc_handle; | |
38 | ||
39 | static void | |
40 | init (void) | |
41 | { | |
42 | libgcc_handle = __libc_dlopen ("libgcc_s.so.2"); | |
43 | ||
44 | if (libgcc_handle == NULL) | |
45 | return; | |
46 | ||
47 | unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace"); | |
48 | unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP"); | |
49 | unwind_getcfa = __libc_dlsym (libgcc_handle, "_Unwind_GetCFA"); | |
50 | unwind_getgr = __libc_dlsym (libgcc_handle, "_Unwind_GetGR"); | |
51 | if (unwind_getip == NULL || unwind_getgr == NULL || unwind_getcfa == NULL) | |
52 | { | |
53 | unwind_backtrace = NULL; | |
54 | __libc_dlclose (libgcc_handle); | |
55 | libgcc_handle = NULL; | |
56 | } | |
57 | } | |
58 | #else | |
59 | # define unwind_backtrace _Unwind_Backtrace | |
60 | # define unwind_getip _Unwind_GetIP | |
61 | # define unwind_getcfa _Unwind_GetCFA | |
62 | # define unwind_getgr _Unwind_GetGR | |
63 | #endif | |
64 | ||
65 | static _Unwind_Reason_Code | |
66 | backtrace_helper (struct _Unwind_Context *ctx, void *a) | |
67 | { | |
68 | struct trace_arg *arg = a; | |
69 | ||
70 | /* We are first called with address in the __backtrace function. | |
71 | Skip it. */ | |
72 | if (arg->cnt != -1) | |
73 | arg->array[arg->cnt] = (void *) unwind_getip (ctx); | |
74 | if (++arg->cnt == arg->size) | |
75 | return _URC_END_OF_STACK; | |
76 | ||
77 | /* %fp is DWARF2 register 14 on M68K. */ | |
78 | arg->lastfp = (void *) unwind_getgr (ctx, 14); | |
79 | arg->lastsp = (void *) unwind_getcfa (ctx); | |
80 | return _URC_NO_REASON; | |
81 | } | |
82 | ||
83 | ||
84 | /* This is a global variable set at program start time. It marks the | |
85 | highest used stack address. */ | |
86 | extern void *__libc_stack_end; | |
87 | ||
88 | ||
89 | /* This is the stack layout we see with every stack frame | |
90 | if not compiled without frame pointer. | |
91 | ||
92 | +-----------------+ +-----------------+ | |
93 | %fp -> | %fp last frame--------> | %fp last frame--->... | |
94 | | | | | | |
95 | | return address | | return address | | |
96 | +-----------------+ +-----------------+ | |
97 | ||
98 | First try as far to get as far as possible using | |
99 | _Unwind_Backtrace which handles -fomit-frame-pointer | |
100 | as well, but requires .eh_frame info. Then fall back to | |
101 | walking the stack manually. */ | |
102 | ||
103 | struct layout | |
104 | { | |
105 | struct layout *fp; | |
106 | void *ret; | |
107 | }; | |
108 | ||
109 | ||
110 | int | |
111 | __backtrace (void **array, int size) | |
112 | { | |
113 | struct trace_arg arg = { .array = array, .size = size, .cnt = -1 }; | |
d5dff793 PP |
114 | |
115 | if (size <= 0) | |
116 | return 0; | |
117 | ||
32ebef01 AS |
118 | #ifdef SHARED |
119 | __libc_once_define (static, once); | |
120 | ||
121 | __libc_once (once, init); | |
122 | if (unwind_backtrace == NULL) | |
123 | return 0; | |
124 | #endif | |
125 | ||
d5dff793 | 126 | unwind_backtrace (backtrace_helper, &arg); |
32ebef01 AS |
127 | |
128 | if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL) | |
129 | --arg.cnt; | |
130 | else if (arg.cnt < size) | |
131 | { | |
132 | struct layout *fp = (struct layout *) arg.lastfp; | |
133 | ||
134 | while (arg.cnt < size) | |
135 | { | |
136 | /* Check for out of range. */ | |
137 | if ((void *) fp < arg.lastsp || (void *) fp > __libc_stack_end | |
138 | || ((long) fp & 1)) | |
139 | break; | |
140 | ||
141 | array[arg.cnt++] = fp->ret; | |
142 | fp = fp->fp; | |
143 | } | |
144 | } | |
145 | return arg.cnt != -1 ? arg.cnt : 0; | |
146 | } | |
147 | weak_alias (__backtrace, backtrace) | |
148 | libc_hidden_def (__backtrace) | |
149 | ||
150 | ||
151 | #ifdef SHARED | |
152 | /* Free all resources if necessary. */ | |
153 | libc_freeres_fn (free_mem) | |
154 | { | |
155 | unwind_backtrace = NULL; | |
156 | if (libgcc_handle != NULL) | |
157 | { | |
158 | __libc_dlclose (libgcc_handle); | |
159 | libgcc_handle = NULL; | |
160 | } | |
161 | } | |
162 | #endif |