1 /* $OpenBSD: atexit.c,v 1.14 2007/09/05 20:47:47 chl Exp $ */
2 /*
3 * Copyright (c) 2002 Daniel Hartmeier
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * - Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * - Redistributions in binary form must reproduce the above
13 * copyright notice, this list of conditions and the following
14 * disclaimer in the documentation and/or other materials provided
15 * with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
20 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
21 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
23 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
25 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
27 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
28 * POSSIBILITY OF SUCH DAMAGE.
29 *
30 */
31
32 #include <sys/types.h>
33 #include <sys/mman.h>
34 #include <stdlib.h>
35 #include <string.h>
36 #include <unistd.h>
37 #include "atexit.h"
38 #include "thread_private.h"
39
40 int __atexit_invalid = 1;
41 struct atexit *__atexit;
42
43 /*
44 * Function pointers are stored in a linked list of pages. The list
45 * is initially empty, and pages are allocated on demand. The first
46 * function pointer in the first allocated page (the last one in
47 * the linked list) is reserved for the cleanup function.
48 *
49 * Outside the following functions, all pages are mprotect()'ed
50 * to prevent unintentional/malicious corruption.
51 */
52
53 /*
54 * Register a function to be performed at exit or when a shared object
55 * with the given dso handle is unloaded dynamically. Also used as
56 * the backend for atexit(). For more info on this API, see:
57 *
58 * http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor
59 */
60 int
__cxa_atexit(void (* func)(void *),void * arg,void * dso)61 __cxa_atexit(void (*func)(void *), void *arg, void *dso)
62 {
63 struct atexit *p = __atexit;
64 struct atexit_fn *fnp;
65 int pgsize = getpagesize();
66 int ret = -1;
67
68 if (pgsize < (int)sizeof(*p))
69 return (-1);
70 _ATEXIT_LOCK();
71 p = __atexit;
72 if (p != NULL) {
73 if (p->ind + 1 >= p->max)
74 p = NULL;
75 else if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
76 goto unlock;
77 }
78 if (p == NULL) {
79 p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
80 MAP_ANON | MAP_PRIVATE, -1, 0);
81 if (p == MAP_FAILED)
82 goto unlock;
83 if (__atexit == NULL) {
84 memset(&p->fns[0], 0, sizeof(p->fns[0]));
85 p->ind = 1;
86 } else
87 p->ind = 0;
88 p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) /
89 sizeof(p->fns[0]);
90 p->next = __atexit;
91 __atexit = p;
92 if (__atexit_invalid)
93 __atexit_invalid = 0;
94 }
95 fnp = &p->fns[p->ind++];
96 fnp->fn_ptr.cxa_func = func;
97 fnp->fn_arg = arg;
98 fnp->fn_dso = dso;
99 if (mprotect(p, pgsize, PROT_READ))
100 goto unlock;
101 ret = 0;
102 unlock:
103 _ATEXIT_UNLOCK();
104 return (ret);
105 }
106
107 #ifdef CRT_LEGACY_WORKAROUND
108 /*
109 * Register a function to be performed at exit.
110 */
111 int
atexit(void (* func)(void))112 atexit(void (*func)(void))
113 {
114 return (__cxa_atexit((void (*)(void *))func, NULL, NULL));
115 }
116 #endif
117
118 /*
119 * Call all handlers registered with __cxa_atexit() for the shared
120 * object owning 'dso'.
121 * Note: if 'dso' is NULL, then all remaining handlers are called.
122 */
123 void
__cxa_finalize(void * dso)124 __cxa_finalize(void *dso)
125 {
126 struct atexit *p, *q;
127 struct atexit_fn fn;
128 int n, pgsize = getpagesize();
129 static int call_depth;
130
131 if (__atexit_invalid)
132 return;
133
134 call_depth++;
135
136 for (p = __atexit; p != NULL; p = p->next) {
137 for (n = p->ind; --n >= 0;) {
138 if (p->fns[n].fn_ptr.cxa_func == NULL)
139 continue; /* already called */
140 if (dso != NULL && dso != p->fns[n].fn_dso)
141 continue; /* wrong DSO */
142
143 /*
144 * Mark handler as having been already called to avoid
145 * dupes and loops, then call the appropriate function.
146 */
147 fn = p->fns[n];
148 if (mprotect(p, pgsize, PROT_READ | PROT_WRITE) == 0) {
149 p->fns[n].fn_ptr.cxa_func = NULL;
150 mprotect(p, pgsize, PROT_READ);
151 }
152 #if ANDROID
153 /* it looks like we should always call the function
154 * with an argument, even if dso is not NULL. Otherwise
155 * static destructors will not be called properly on
156 * the ARM.
157 */
158 (*fn.fn_ptr.cxa_func)(fn.fn_arg);
159 #else /* !ANDROID */
160 if (dso != NULL)
161 (*fn.fn_ptr.cxa_func)(fn.fn_arg);
162 else
163 (*fn.fn_ptr.std_func)();
164 #endif /* !ANDROID */
165 }
166 }
167
168 /*
169 * If called via exit(), unmap the pages since we have now run
170 * all the handlers. We defer this until calldepth == 0 so that
171 * we don't unmap things prematurely if called recursively.
172 */
173 if (dso == NULL && --call_depth == 0) {
174 for (p = __atexit; p != NULL; ) {
175 q = p;
176 p = p->next;
177 munmap(q, pgsize);
178 }
179 __atexit = NULL;
180 }
181 }
182
183 /*
184 * Register the cleanup function
185 */
186 void
__atexit_register_cleanup(void (* func)(void))187 __atexit_register_cleanup(void (*func)(void))
188 {
189 struct atexit *p;
190 int pgsize = getpagesize();
191
192 if (pgsize < (int)sizeof(*p))
193 return;
194 _ATEXIT_LOCK();
195 p = __atexit;
196 while (p != NULL && p->next != NULL)
197 p = p->next;
198 if (p == NULL) {
199 p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
200 MAP_ANON | MAP_PRIVATE, -1, 0);
201 if (p == MAP_FAILED)
202 goto unlock;
203 p->ind = 1;
204 p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) /
205 sizeof(p->fns[0]);
206 p->next = NULL;
207 __atexit = p;
208 if (__atexit_invalid)
209 __atexit_invalid = 0;
210 } else {
211 if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
212 goto unlock;
213 }
214 p->fns[0].fn_ptr.std_func = func;
215 p->fns[0].fn_arg = NULL;
216 p->fns[0].fn_dso = NULL;
217 mprotect(p, pgsize, PROT_READ);
218 unlock:
219 _ATEXIT_UNLOCK();
220 }
221