1 /* $OpenBSD: atexit.c,v 1.20 2014/07/11 09:51:37 kettenis 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 "private/thread_private.h"
39
40 /* BEGIN android-changed */
41 #include "private/bionic_prctl.h"
42 /* END android-changed */
43
44 struct atexit {
45 struct atexit *next; /* next in list */
46 int ind; /* next index in this table */
47 int max; /* max entries >= ATEXIT_SIZE */
48 struct atexit_fn {
49 void (*fn_ptr)(void *);
50 void *fn_arg; /* argument for CXA callback */
51 void *fn_dso; /* shared module handle */
52 } fns[1]; /* the table itself */
53 };
54
55 static struct atexit *__atexit;
56 static int restartloop;
57
58 /* BEGIN android-changed: __unregister_atfork is used by __cxa_finalize */
59 extern void __unregister_atfork(void* dso);
60 /* END android-changed */
61
62 /*
63 * Function pointers are stored in a linked list of pages. The list
64 * is initially empty, and pages are allocated on demand. The first
65 * function pointer in the first allocated page (the last one in
66 * the linked list) is reserved for the cleanup function.
67 *
68 * Outside the following functions, all pages are mprotect()'ed
69 * to prevent unintentional/malicious corruption.
70 */
71
72 /*
73 * Register a function to be performed at exit or when a shared object
74 * with the given dso handle is unloaded dynamically. Also used as
75 * the backend for atexit(). For more info on this API, see:
76 *
77 * http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor
78 */
79 int
__cxa_atexit(void (* func)(void *),void * arg,void * dso)80 __cxa_atexit(void (*func)(void *), void *arg, void *dso)
81 {
82 struct atexit *p = __atexit;
83 struct atexit_fn *fnp;
84 size_t pgsize = getpagesize();
85 int ret = -1;
86
87 if (pgsize < sizeof(*p))
88 return (-1);
89 _ATEXIT_LOCK();
90 p = __atexit;
91 if (p != NULL) {
92 if (p->ind + 1 >= p->max)
93 p = NULL;
94 else if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
95 goto unlock;
96 }
97 if (p == NULL) {
98 p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
99 MAP_ANON | MAP_PRIVATE, -1, 0);
100 if (p == MAP_FAILED)
101 goto unlock;
102 /* BEGIN android-changed */
103 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, p, pgsize,
104 "atexit handlers");
105 /* END android-changed */
106 if (__atexit == NULL) {
107 memset(&p->fns[0], 0, sizeof(p->fns[0]));
108 p->ind = 1;
109 } else
110 p->ind = 0;
111 p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) /
112 sizeof(p->fns[0]);
113 p->next = __atexit;
114 __atexit = p;
115 }
116 fnp = &p->fns[p->ind++];
117 fnp->fn_ptr = func;
118 fnp->fn_arg = arg;
119 fnp->fn_dso = dso;
120 if (mprotect(p, pgsize, PROT_READ))
121 goto unlock;
122 restartloop = 1;
123 ret = 0;
124 unlock:
125 _ATEXIT_UNLOCK();
126 return (ret);
127 }
128
129 /*
130 * Call all handlers registered with __cxa_atexit() for the shared
131 * object owning 'dso'.
132 * Note: if 'dso' is NULL, then all remaining handlers are called.
133 */
134 void
__cxa_finalize(void * dso)135 __cxa_finalize(void *dso)
136 {
137 struct atexit *p, *q;
138 struct atexit_fn fn;
139 int n, pgsize = getpagesize();
140 static int call_depth;
141
142 _ATEXIT_LOCK();
143 call_depth++;
144
145 restart:
146 restartloop = 0;
147 for (p = __atexit; p != NULL; p = p->next) {
148 for (n = p->ind; --n >= 0;) {
149 if (p->fns[n].fn_ptr == NULL)
150 continue; /* already called */
151 if (dso != NULL && dso != p->fns[n].fn_dso)
152 continue; /* wrong DSO */
153
154 /*
155 * Mark handler as having been already called to avoid
156 * dupes and loops, then call the appropriate function.
157 */
158 fn = p->fns[n];
159 if (mprotect(p, pgsize, PROT_READ | PROT_WRITE) == 0) {
160 p->fns[n].fn_ptr = NULL;
161 mprotect(p, pgsize, PROT_READ);
162 }
163 _ATEXIT_UNLOCK();
164 (*fn.fn_ptr)(fn.fn_arg);
165 _ATEXIT_LOCK();
166 if (restartloop)
167 goto restart;
168 }
169 }
170
171 call_depth--;
172
173 /*
174 * If called via exit(), unmap the pages since we have now run
175 * all the handlers. We defer this until calldepth == 0 so that
176 * we don't unmap things prematurely if called recursively.
177 */
178 if (dso == NULL && call_depth == 0) {
179 for (p = __atexit; p != NULL; ) {
180 q = p;
181 p = p->next;
182 munmap(q, pgsize);
183 }
184 __atexit = NULL;
185 }
186 _ATEXIT_UNLOCK();
187
188 extern void __libc_stdio_cleanup(void);
189 __libc_stdio_cleanup();
190
191 /* BEGIN android-changed: call __unregister_atfork if dso is not null */
192 if (dso != NULL) {
193 __unregister_atfork(dso);
194 }
195 /* END android-changed */
196 }
197