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 <sys/cdefs.h>
39 #include "namespace.h"
40 #include <errno.h>
41 #include <link.h>
42 #include <stdbool.h>
43 #include <stddef.h>
44 #include <stdlib.h>
45 #include <unistd.h>
46 #include <pthread.h>
47 #include "atexit.h"
48 #include "un-namespace.h"
49 #include "block_abi.h"
50
51 #include "libc_private.h"
52
53 /**
54 * The _Block_copy() function is provided by the block runtime.
55 */
56 __attribute__((weak)) void*
57 _Block_copy(void*);
58
59 #define ATEXIT_FN_EMPTY 0
60 #define ATEXIT_FN_STD 1
61 #define ATEXIT_FN_CXA 2
62
63 static pthread_mutex_t atexit_mutex = PTHREAD_MUTEX_INITIALIZER;
64 static void *current_finalize_dso = NULL;
65 static bool call_finalize_again = false;
66
67 #define _MUTEX_LOCK(x) if (__isthreaded) _pthread_mutex_lock(x)
68 #define _MUTEX_UNLOCK(x) if (__isthreaded) _pthread_mutex_unlock(x)
69 #define _MUTEX_DESTROY(x) if (__isthreaded) _pthread_mutex_destroy(x)
70
71 struct atexit {
72 struct atexit *next; /* next in list */
73 int ind; /* next index in this table */
74 struct atexit_fn {
75 int fn_type; /* ATEXIT_? from above */
76 union {
77 void (*std_func)(void);
78 void (*cxa_func)(void *);
79 } fn_ptr; /* function pointer */
80 void *fn_arg; /* argument for CXA callback */
81 void *fn_dso; /* shared module handle */
82 } fns[ATEXIT_SIZE]; /* the table itself */
83 };
84
85 static struct atexit *__atexit; /* points to head of LIFO stack */
86 typedef DECLARE_BLOCK(void, atexit_block, void);
87
88 int atexit_b(atexit_block);
89 int __cxa_atexit(void (*)(void *), void *, void *);
90
91 /*
92 * Register the function described by 'fptr' to be called at application
93 * exit or owning shared object unload time. This is a helper function
94 * for atexit and __cxa_atexit.
95 */
96 static int
atexit_register(struct atexit_fn * fptr)97 atexit_register(struct atexit_fn *fptr)
98 {
99 static struct atexit __atexit0; /* one guaranteed table */
100 struct atexit *p;
101
102 _MUTEX_LOCK(&atexit_mutex);
103 if ((p = __atexit) == NULL)
104 __atexit = p = &__atexit0;
105 else while (p->ind >= ATEXIT_SIZE) {
106 struct atexit *old__atexit;
107 old__atexit = __atexit;
108 _MUTEX_UNLOCK(&atexit_mutex);
109 if ((p = (struct atexit *)malloc(sizeof(*p))) == NULL)
110 return (-1);
111 _MUTEX_LOCK(&atexit_mutex);
112 if (old__atexit != __atexit) {
113 /* Lost race, retry operation */
114 _MUTEX_UNLOCK(&atexit_mutex);
115 free(p);
116 _MUTEX_LOCK(&atexit_mutex);
117 p = __atexit;
118 continue;
119 }
120 p->ind = 0;
121 p->next = __atexit;
122 __atexit = p;
123 }
124 p->fns[p->ind++] = *fptr;
125 if (current_finalize_dso != NULL &&
126 current_finalize_dso == fptr->fn_dso)
127 call_finalize_again = true;
128 _MUTEX_UNLOCK(&atexit_mutex);
129 return 0;
130 }
131
132 /*
133 * Register a function to be performed at exit.
134 */
135 int
atexit(void (* func)(void))136 atexit(void (*func)(void))
137 {
138 struct atexit_fn fn;
139 int error;
140
141 fn.fn_type = ATEXIT_FN_STD;
142 fn.fn_ptr.std_func = func;
143 fn.fn_arg = NULL;
144 fn.fn_dso = NULL;
145
146 error = atexit_register(&fn);
147 return (error);
148 }
149 __weak_reference(atexit, __libc_atexit);
150
151 /**
152 * Register a block to be performed at exit.
153 */
154 int
atexit_b(atexit_block func)155 atexit_b(atexit_block func)
156 {
157 struct atexit_fn fn;
158 int error;
159 if (_Block_copy == 0) {
160 errno = ENOSYS;
161 return -1;
162 }
163 func = _Block_copy(func);
164
165 // Blocks are not C++ destructors, but they have the same signature (a
166 // single void* parameter), so we can pretend that they are.
167 fn.fn_type = ATEXIT_FN_CXA;
168 fn.fn_ptr.cxa_func = (void(*)(void*))GET_BLOCK_FUNCTION(func);
169 fn.fn_arg = func;
170 fn.fn_dso = NULL;
171
172 error = atexit_register(&fn);
173 return (error);
174 }
175
176 /*
177 * Register a function to be performed at exit or when an shared object
178 * with given dso handle is unloaded dynamically.
179 */
180 int
__cxa_atexit(void (* func)(void *),void * arg,void * dso)181 __cxa_atexit(void (*func)(void *), void *arg, void *dso)
182 {
183 struct atexit_fn fn;
184 int error;
185
186 fn.fn_type = ATEXIT_FN_CXA;
187 fn.fn_ptr.cxa_func = func;
188 fn.fn_arg = arg;
189 fn.fn_dso = dso;
190
191 error = atexit_register(&fn);
192 return (error);
193 }
194
195 #pragma weak __pthread_cxa_finalize
196 void __pthread_cxa_finalize(const struct dl_phdr_info *);
197
198 static int global_exit;
199
200 /*
201 * Call all handlers registered with __cxa_atexit for the shared
202 * object owning 'dso'. Note: if 'dso' is NULL, then all remaining
203 * handlers are called.
204 */
205 void
__cxa_finalize(void * dso)206 __cxa_finalize(void *dso)
207 {
208 struct dl_phdr_info phdr_info;
209 struct atexit *p;
210 struct atexit_fn fn;
211 int n, has_phdr;
212
213 if (dso != NULL) {
214 has_phdr = _rtld_addr_phdr(dso, &phdr_info);
215 } else {
216 has_phdr = 0;
217 global_exit = 1;
218 }
219
220 _MUTEX_LOCK(&atexit_mutex);
221 current_finalize_dso = dso;
222 do {
223 call_finalize_again = false;
224 for (p = __atexit; p; p = p->next) {
225 for (n = p->ind; --n >= 0;) {
226 if (p->fns[n].fn_type == ATEXIT_FN_EMPTY)
227 continue; /* already been called */
228 fn = p->fns[n];
229 if (dso != NULL && dso != fn.fn_dso) {
230 /* wrong DSO ? */
231 if (!has_phdr || global_exit ||
232 !__elf_phdr_match_addr(&phdr_info,
233 fn.fn_ptr.cxa_func))
234 continue;
235 }
236 /*
237 Mark entry to indicate that this particular
238 handler has already been called.
239 */
240 p->fns[n].fn_type = ATEXIT_FN_EMPTY;
241 _MUTEX_UNLOCK(&atexit_mutex);
242
243 /* Call the function of correct type. */
244 if (fn.fn_type == ATEXIT_FN_CXA)
245 fn.fn_ptr.cxa_func(fn.fn_arg);
246 else if (fn.fn_type == ATEXIT_FN_STD)
247 fn.fn_ptr.std_func();
248 _MUTEX_LOCK(&atexit_mutex);
249 }
250 }
251 } while (call_finalize_again);
252 current_finalize_dso = NULL;
253 _MUTEX_UNLOCK(&atexit_mutex);
254 if (dso == NULL)
255 _MUTEX_DESTROY(&atexit_mutex);
256
257 if (has_phdr && !global_exit && &__pthread_cxa_finalize != NULL)
258 __pthread_cxa_finalize(&phdr_info);
259 }
260