1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)atexit.c 8.2 (Berkeley) 7/3/94";
37 #endif /* LIBC_SCCS and not lint */
38 #include "namespace.h"
39 #include <errno.h>
40 #include <link.h>
41 #include <stdbool.h>
42 #include <stddef.h>
43 #include <stdlib.h>
44 #include <unistd.h>
45 #include <pthread.h>
46 #include "atexit.h"
47 #include "un-namespace.h"
48 #include "block_abi.h"
49
50 #include "libc_private.h"
51
52 /**
53 * The _Block_copy() function is provided by the block runtime.
54 */
55 __attribute__((weak)) void*
56 _Block_copy(void*);
57
58 #define ATEXIT_FN_EMPTY 0
59 #define ATEXIT_FN_STD 1
60 #define ATEXIT_FN_CXA 2
61
62 static pthread_mutex_t atexit_mutex = PTHREAD_MUTEX_INITIALIZER;
63 static void *current_finalize_dso = NULL;
64 static bool call_finalize_again = false;
65
66 #define _MUTEX_LOCK(x) if (__isthreaded) _pthread_mutex_lock(x)
67 #define _MUTEX_UNLOCK(x) if (__isthreaded) _pthread_mutex_unlock(x)
68 #define _MUTEX_DESTROY(x) if (__isthreaded) _pthread_mutex_destroy(x)
69
70 struct atexit {
71 struct atexit *next; /* next in list */
72 int ind; /* next index in this table */
73 struct atexit_fn {
74 int fn_type; /* ATEXIT_? from above */
75 union {
76 void (*std_func)(void);
77 void (*cxa_func)(void *);
78 } fn_ptr; /* function pointer */
79 void *fn_arg; /* argument for CXA callback */
80 void *fn_dso; /* shared module handle */
81 } fns[ATEXIT_SIZE]; /* the table itself */
82 };
83
84 static struct atexit *__atexit; /* points to head of LIFO stack */
85 typedef DECLARE_BLOCK(void, atexit_block, void);
86
87 int atexit_b(atexit_block);
88 int __cxa_atexit(void (*)(void *), void *, void *);
89
90 /*
91 * Register the function described by 'fptr' to be called at application
92 * exit or owning shared object unload time. This is a helper function
93 * for atexit and __cxa_atexit.
94 */
95 static int
atexit_register(struct atexit_fn * fptr)96 atexit_register(struct atexit_fn *fptr)
97 {
98 static struct atexit __atexit0; /* one guaranteed table */
99 struct atexit *p;
100
101 _MUTEX_LOCK(&atexit_mutex);
102 if ((p = __atexit) == NULL)
103 __atexit = p = &__atexit0;
104 else while (p->ind >= ATEXIT_SIZE) {
105 struct atexit *old__atexit;
106 old__atexit = __atexit;
107 _MUTEX_UNLOCK(&atexit_mutex);
108 if ((p = (struct atexit *)malloc(sizeof(*p))) == NULL)
109 return (-1);
110 _MUTEX_LOCK(&atexit_mutex);
111 if (old__atexit != __atexit) {
112 /* Lost race, retry operation */
113 _MUTEX_UNLOCK(&atexit_mutex);
114 free(p);
115 _MUTEX_LOCK(&atexit_mutex);
116 p = __atexit;
117 continue;
118 }
119 p->ind = 0;
120 p->next = __atexit;
121 __atexit = p;
122 }
123 p->fns[p->ind++] = *fptr;
124 if (current_finalize_dso != NULL &&
125 current_finalize_dso == fptr->fn_dso)
126 call_finalize_again = true;
127 _MUTEX_UNLOCK(&atexit_mutex);
128 return 0;
129 }
130
131 /*
132 * Register a function to be performed at exit.
133 */
134 int
atexit(void (* func)(void))135 atexit(void (*func)(void))
136 {
137 struct atexit_fn fn;
138 int error;
139
140 fn.fn_type = ATEXIT_FN_STD;
141 fn.fn_ptr.std_func = func;
142 fn.fn_arg = NULL;
143 fn.fn_dso = NULL;
144
145 error = atexit_register(&fn);
146 return (error);
147 }
148 __weak_reference(atexit, __libc_atexit);
149
150 /**
151 * Register a block to be performed at exit.
152 */
153 int
atexit_b(atexit_block func)154 atexit_b(atexit_block func)
155 {
156 struct atexit_fn fn;
157 int error;
158 if (_Block_copy == 0) {
159 errno = ENOSYS;
160 return -1;
161 }
162 func = _Block_copy(func);
163
164 // Blocks are not C++ destructors, but they have the same signature (a
165 // single void* parameter), so we can pretend that they are.
166 fn.fn_type = ATEXIT_FN_CXA;
167 fn.fn_ptr.cxa_func = (void(*)(void*))GET_BLOCK_FUNCTION(func);
168 fn.fn_arg = func;
169 fn.fn_dso = NULL;
170
171 error = atexit_register(&fn);
172 return (error);
173 }
174
175 /*
176 * Register a function to be performed at exit or when an shared object
177 * with given dso handle is unloaded dynamically.
178 */
179 int
__cxa_atexit(void (* func)(void *),void * arg,void * dso)180 __cxa_atexit(void (*func)(void *), void *arg, void *dso)
181 {
182 struct atexit_fn fn;
183 int error;
184
185 fn.fn_type = ATEXIT_FN_CXA;
186 fn.fn_ptr.cxa_func = func;
187 fn.fn_arg = arg;
188 fn.fn_dso = dso;
189
190 error = atexit_register(&fn);
191 return (error);
192 }
193
194 #pragma weak __pthread_cxa_finalize
195 void __pthread_cxa_finalize(const struct dl_phdr_info *);
196
197 static int global_exit;
198
199 /*
200 * Call all handlers registered with __cxa_atexit for the shared
201 * object owning 'dso'. Note: if 'dso' is NULL, then all remaining
202 * handlers are called.
203 */
204 void
__cxa_finalize(void * dso)205 __cxa_finalize(void *dso)
206 {
207 struct dl_phdr_info phdr_info;
208 struct atexit *p;
209 struct atexit_fn fn;
210 int n, has_phdr;
211
212 if (dso != NULL) {
213 has_phdr = _rtld_addr_phdr(dso, &phdr_info);
214 } else {
215 has_phdr = 0;
216 global_exit = 1;
217 }
218
219 _MUTEX_LOCK(&atexit_mutex);
220 current_finalize_dso = dso;
221 do {
222 call_finalize_again = false;
223 for (p = __atexit; p; p = p->next) {
224 for (n = p->ind; --n >= 0;) {
225 if (p->fns[n].fn_type == ATEXIT_FN_EMPTY)
226 continue; /* already been called */
227 fn = p->fns[n];
228 if (dso != NULL && dso != fn.fn_dso) {
229 /* wrong DSO ? */
230 if (!has_phdr || global_exit ||
231 !__elf_phdr_match_addr(&phdr_info,
232 fn.fn_ptr.cxa_func))
233 continue;
234 }
235 /*
236 Mark entry to indicate that this particular
237 handler has already been called.
238 */
239 p->fns[n].fn_type = ATEXIT_FN_EMPTY;
240 _MUTEX_UNLOCK(&atexit_mutex);
241
242 /* Call the function of correct type. */
243 if (fn.fn_type == ATEXIT_FN_CXA)
244 fn.fn_ptr.cxa_func(fn.fn_arg);
245 else if (fn.fn_type == ATEXIT_FN_STD)
246 fn.fn_ptr.std_func();
247 _MUTEX_LOCK(&atexit_mutex);
248 }
249 }
250 } while (call_finalize_again);
251 current_finalize_dso = NULL;
252 _MUTEX_UNLOCK(&atexit_mutex);
253 if (dso == NULL)
254 _MUTEX_DESTROY(&atexit_mutex);
255
256 if (has_phdr && !global_exit && &__pthread_cxa_finalize != NULL)
257 __pthread_cxa_finalize(&phdr_info);
258 }
259