1/* Return backtrace of current program state.
2 Copyright (C) 2003-2021 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 <https://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#include <unwind-arch.h>
27
28struct trace_arg
29{
30 void **array;
31 _Unwind_Word cfa;
32 int cnt;
33 int size;
34};
35
36#ifdef SHARED
37static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
38static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
39static _Unwind_Word (*unwind_getcfa) (struct _Unwind_Context *);
40static void *libgcc_handle;
41
42
43/* Dummy version in case libgcc_s does not contain the real code. */
44static _Unwind_Word
45dummy_getcfa (struct _Unwind_Context *ctx __attribute__ ((unused)))
46{
47 return 0;
48}
49
50
51static void
52init (void)
53{
54 libgcc_handle = __libc_dlopen (LIBGCC_S_SO);
55
56 if (libgcc_handle == NULL)
57 return;
58
59 unwind_backtrace = __libc_dlsym (libgcc_handle, "_Unwind_Backtrace");
60 unwind_getip = __libc_dlsym (libgcc_handle, "_Unwind_GetIP");
61 if (unwind_getip == NULL)
62 unwind_backtrace = NULL;
63 unwind_getcfa = (__libc_dlsym (libgcc_handle, "_Unwind_GetCFA")
64 ?: dummy_getcfa);
65}
66#else
67# define unwind_backtrace _Unwind_Backtrace
68# define unwind_getip _Unwind_GetIP
69# define unwind_getcfa _Unwind_GetCFA
70#endif
71
72static _Unwind_Reason_Code
73backtrace_helper (struct _Unwind_Context *ctx, void *a)
74{
75 struct trace_arg *arg = a;
76
77 /* We are first called with address in the __backtrace function.
78 Skip it. */
79 if (arg->cnt != -1)
80 {
81 arg->array[arg->cnt] = (void *) unwind_getip (ctx);
82 if (arg->cnt > 0)
83 arg->array[arg->cnt]
84 = unwind_arch_adjustment (arg->array[arg->cnt - 1],
85 arg->array[arg->cnt]);
86
87 /* Check whether we make any progress. */
88 _Unwind_Word cfa = unwind_getcfa (ctx);
89
90 if (arg->cnt > 0 && arg->array[arg->cnt - 1] == arg->array[arg->cnt]
91 && cfa == arg->cfa)
92 return _URC_END_OF_STACK;
93 arg->cfa = cfa;
94 }
95 if (++arg->cnt == arg->size)
96 return _URC_END_OF_STACK;
97 return _URC_NO_REASON;
98}
99
100int
101__backtrace (void **array, int size)
102{
103 struct trace_arg arg = { .array = array, .cfa = 0, .size = size, .cnt = -1 };
104
105 if (size <= 0)
106 return 0;
107
108#ifdef SHARED
109 __libc_once_define (static, once);
110
111 __libc_once (once, init);
112 if (unwind_backtrace == NULL)
113 return 0;
114#endif
115
116 unwind_backtrace (backtrace_helper, &arg);
117
118 /* _Unwind_Backtrace seems to put NULL address above
119 _start. Fix it up here. */
120 if (arg.cnt > 1 && arg.array[arg.cnt - 1] == NULL)
121 --arg.cnt;
122 return arg.cnt != -1 ? arg.cnt : 0;
123}
124weak_alias (__backtrace, backtrace)
125libc_hidden_def (__backtrace)
126
127
128#ifdef SHARED
129/* Free all resources if necessary. */
130libc_freeres_fn (free_mem)
131{
132 unwind_backtrace = NULL;
133 if (libgcc_handle != NULL)
134 {
135 __libc_dlclose (libgcc_handle);
136 libgcc_handle = NULL;
137 }
138}
139#endif
140