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 /*
108 * Call all handlers registered with __cxa_atexit() for the shared
109 * object owning 'dso'.
110 * Note: if 'dso' is NULL, then all remaining handlers are called.
111 */
112 void
__cxa_finalize(void * dso)113 __cxa_finalize(void *dso)
114 {
115 struct atexit *p, *q;
116 struct atexit_fn fn;
117 int n, pgsize = getpagesize();
118 static int call_depth;
119
120 if (__atexit_invalid)
121 return;
122
123 _ATEXIT_LOCK();
124 call_depth++;
125
126 for (p = __atexit; p != NULL; p = p->next) {
127 for (n = p->ind; --n >= 0;) {
128 if (p->fns[n].fn_ptr.cxa_func == NULL)
129 continue; /* already called */
130 if (dso != NULL && dso != p->fns[n].fn_dso)
131 continue; /* wrong DSO */
132
133 /*
134 * Mark handler as having been already called to avoid
135 * dupes and loops, then call the appropriate function.
136 */
137 fn = p->fns[n];
138 if (mprotect(p, pgsize, PROT_READ | PROT_WRITE) == 0) {
139 p->fns[n].fn_ptr.cxa_func = NULL;
140 mprotect(p, pgsize, PROT_READ);
141 }
142 _ATEXIT_UNLOCK();
143 #if ANDROID
144 /* it looks like we should always call the function
145 * with an argument, even if dso is not NULL. Otherwise
146 * static destructors will not be called properly on
147 * the ARM.
148 */
149 (*fn.fn_ptr.cxa_func)(fn.fn_arg);
150 #else /* !ANDROID */
151 if (dso != NULL)
152 (*fn.fn_ptr.cxa_func)(fn.fn_arg);
153 else
154 (*fn.fn_ptr.std_func)();
155 #endif /* !ANDROID */
156 _ATEXIT_LOCK();
157 }
158 }
159
160 /*
161 * If called via exit(), unmap the pages since we have now run
162 * all the handlers. We defer this until calldepth == 0 so that
163 * we don't unmap things prematurely if called recursively.
164 */
165 if (dso == NULL && --call_depth == 0) {
166 for (p = __atexit; p != NULL; ) {
167 q = p;
168 p = p->next;
169 munmap(q, pgsize);
170 }
171 __atexit = NULL;
172 }
173 _ATEXIT_UNLOCK();
174 }
175
176 /*
177 * Register the cleanup function
178 */
179 void
__atexit_register_cleanup(void (* func)(void))180 __atexit_register_cleanup(void (*func)(void))
181 {
182 struct atexit *p;
183 int pgsize = getpagesize();
184
185 if (pgsize < (int)sizeof(*p))
186 return;
187 _ATEXIT_LOCK();
188 p = __atexit;
189 while (p != NULL && p->next != NULL)
190 p = p->next;
191 if (p == NULL) {
192 p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
193 MAP_ANON | MAP_PRIVATE, -1, 0);
194 if (p == MAP_FAILED)
195 goto unlock;
196 p->ind = 1;
197 p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) /
198 sizeof(p->fns[0]);
199 p->next = NULL;
200 __atexit = p;
201 if (__atexit_invalid)
202 __atexit_invalid = 0;
203 } else {
204 if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
205 goto unlock;
206 }
207 p->fns[0].fn_ptr.std_func = func;
208 p->fns[0].fn_arg = NULL;
209 p->fns[0].fn_dso = NULL;
210 mprotect(p, pgsize, PROT_READ);
211 unlock:
212 _ATEXIT_UNLOCK();
213 }
214