1/* $NetBSD: atexit.c,v 1.32 2017/11/06 14:26:03 joerg Exp $ */
2
3/*-
4 * Copyright (c) 2003 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe.
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 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32#include <sys/cdefs.h>
33#if defined(LIBC_SCCS) && !defined(lint)
34__RCSID("$NetBSD: atexit.c,v 1.32 2017/11/06 14:26:03 joerg Exp $");
35#endif /* LIBC_SCCS and not lint */
36
37#include "reentrant.h"
38
39#include <assert.h>
40#include <stdlib.h>
41
42#include "atexit.h"
43
44struct atexit_handler {
45 struct atexit_handler *ah_next;
46 union {
47 void (*fun_atexit)(void);
48 void (*fun_cxa_atexit)(void *);
49 } ah_fun;
50#define ah_atexit ah_fun.fun_atexit
51#define ah_cxa_atexit ah_fun.fun_cxa_atexit
52
53 void *ah_arg; /* argument for cxa_atexit handlers */
54 void *ah_dso; /* home DSO for cxa_atexit handlers */
55};
56
57/*
58 * There must be at least 32 to guarantee ANSI conformance, plus
59 * 3 additional ones for the benefit of the startup code, which
60 * may use them to register the dynamic loader's cleanup routine,
61 * the profiling cleanup routine, and the global destructor routine.
62 */
63#define NSTATIC_HANDLERS (32 + 3)
64static struct atexit_handler atexit_handler0[NSTATIC_HANDLERS];
65
66#define STATIC_HANDLER_P(ah) \
67 (ah >= &atexit_handler0[0] && ah < &atexit_handler0[NSTATIC_HANDLERS])
68
69/*
70 * Stack of atexit handlers. Handlers must be called in the opposite
71 * order they were registered.
72 */
73static struct atexit_handler *atexit_handler_stack;
74
75#ifdef _REENTRANT
76/* ..and a mutex to protect it all. */
77mutex_t __atexit_mutex;
78#endif /* _REENTRANT */
79
80void __libc_atexit_init(void) __attribute__ ((visibility("hidden")));
81
82/*
83 * Allocate an atexit handler descriptor. If "dso" is NULL, it indicates
84 * a normal atexit handler, which must be allocated from the static pool,
85 * if possible. cxa_atexit handlers are never allocated from the static
86 * pool.
87 *
88 * __atexit_mutex must be held.
89 */
90static struct atexit_handler *
91atexit_handler_alloc(void *dso)
92{
93 struct atexit_handler *ah;
94 int i;
95
96 if (dso == NULL) {
97 for (i = 0; i < NSTATIC_HANDLERS; i++) {
98 ah = &atexit_handler0[i];
99 if (ah->ah_atexit == NULL && ah->ah_next == NULL) {
100 /* Slot is free. */
101 return (ah);
102 }
103 }
104 }
105
106 /*
107 * Either no static slot was free, or this is a cxa_atexit
108 * handler. Allocate a new one. We keep the __atexit_mutex
109 * held to prevent handlers from being run while we (potentially)
110 * block in malloc().
111 */
112 ah = malloc(sizeof(*ah));
113 return (ah);
114}
115
116/*
117 * Initialize __atexit_mutex with the PTHREAD_MUTEX_RECURSIVE attribute.
118 * Note that __cxa_finalize may generate calls to __cxa_atexit.
119 */
120void __section(".text.startup")
121__libc_atexit_init(void)
122{
123#ifdef _REENTRANT
124 mutexattr_t atexit_mutex_attr;
125 mutexattr_init(&atexit_mutex_attr);
126 mutexattr_settype(&atexit_mutex_attr, PTHREAD_MUTEX_RECURSIVE);
127 mutex_init(&__atexit_mutex, &atexit_mutex_attr);
128#endif
129}
130
131/*
132 * Register an atexit routine. This is suitable either for a cxa_atexit
133 * or normal atexit type handler. The __cxa_atexit() name and arguments
134 * are specified by the C++ ABI. See:
135 *
136 * http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor
137 */
138#if defined(__ARM_EABI__) && !defined(lint)
139int
140__aeabi_atexit(void *arg, void (*func)(void *), void *dso);
141
142int
143__aeabi_atexit(void *arg, void (*func)(void *), void *dso)
144{
145 return (__cxa_atexit(func, arg, dso));
146}
147#endif
148
149static int
150__cxa_atexit_internal(void (*func)(void *), void *arg, void *dso)
151{
152 struct atexit_handler *ah;
153
154 _DIAGASSERT(func != NULL);
155
156 mutex_lock(&__atexit_mutex);
157
158 ah = atexit_handler_alloc(dso);
159 if (ah == NULL) {
160 mutex_unlock(&__atexit_mutex);
161 return (-1);
162 }
163
164 ah->ah_cxa_atexit = func;
165 ah->ah_arg = arg;
166 ah->ah_dso = dso;
167
168 ah->ah_next = atexit_handler_stack;
169 atexit_handler_stack = ah;
170
171 mutex_unlock(&__atexit_mutex);
172 return (0);
173}
174
175int
176__cxa_atexit(void (*func)(void *), void *arg, void *dso)
177{
178 _DIAGASSERT(dso != NULL);
179 return (__cxa_atexit_internal(func, arg, dso));
180}
181
182/*
183 * Run the list of atexit handlers. If dso is NULL, run all of them,
184 * otherwise run only those matching the specified dso.
185 *
186 * Note that we can be recursively invoked; rtld cleanup is via an
187 * atexit handler, and rtld cleanup invokes _fini() for DSOs, which
188 * in turn invokes __cxa_finalize() for the DSO.
189 */
190void
191__cxa_finalize(void *dso)
192{
193 static u_int call_depth;
194 struct atexit_handler *ah, *dead_handlers = NULL, **prevp;
195 void (*cxa_func)(void *);
196 void (*atexit_func)(void);
197
198 mutex_lock(&__atexit_mutex);
199 call_depth++;
200
201 /*
202 * If we are at call depth 1 (which is usually the "do everything"
203 * call from exit(3)), we go ahead and remove elements from the
204 * list as we call them. This will prevent any nested calls from
205 * having to traverse elements we've already processed. If we are
206 * at call depth > 1, we simply mark elements we process as unused.
207 * When the depth 1 caller sees those, it will simply unlink them
208 * for us.
209 */
210again:
211 for (prevp = &atexit_handler_stack; (ah = (*prevp)) != NULL;) {
212 if (dso == NULL || dso == ah->ah_dso || ah->ah_atexit == NULL) {
213 if (ah->ah_atexit != NULL) {
214 void *p = atexit_handler_stack;
215 if (ah->ah_dso != NULL) {
216 cxa_func = ah->ah_cxa_atexit;
217 ah->ah_cxa_atexit = NULL;
218 (*cxa_func)(ah->ah_arg);
219 } else {
220 atexit_func = ah->ah_atexit;
221 ah->ah_atexit = NULL;
222 (*atexit_func)();
223 }
224 /* Restart if new atexit handler was added. */
225 if (p != atexit_handler_stack)
226 goto again;
227 }
228
229 if (call_depth == 1) {
230 *prevp = ah->ah_next;
231 if (STATIC_HANDLER_P(ah))
232 ah->ah_next = NULL;
233 else {
234 ah->ah_next = dead_handlers;
235 dead_handlers = ah;
236 }
237 } else
238 prevp = &ah->ah_next;
239 } else
240 prevp = &ah->ah_next;
241 }
242 call_depth--;
243 mutex_unlock(&__atexit_mutex);
244
245 if (call_depth > 0)
246 return;
247
248 /*
249 * Now free any dead handlers. Do this even if we're about to
250 * exit, in case a leak-detecting malloc is being used.
251 */
252 while ((ah = dead_handlers) != NULL) {
253 dead_handlers = ah->ah_next;
254 free(ah);
255 }
256}
257
258/*
259 * Register a function to be performed at exit.
260 */
261int
262atexit(void (*func)(void))
263{
264
265 return (__cxa_atexit_internal((void (*)(void *))func, NULL, NULL));
266}
267