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 struct atexit { 41 struct atexit *next; /* next in list */ 42 int ind; /* next index in this table */ 43 int max; /* max entries >= ATEXIT_SIZE */ 44 struct atexit_fn { 45 void (*fn_ptr)(void *); 46 void *fn_arg; /* argument for CXA callback */ 47 void *fn_dso; /* shared module handle */ 48 } fns[1]; /* the table itself */ 49 }; 50 51 static struct atexit *__atexit; 52 static int restartloop; 53 54 /* BEGIN android-changed: __unregister_atfork is used by __cxa_finalize */ 55 extern void __unregister_atfork(void* dso); 56 /* END android-changed */ 57 58 /* 59 * Function pointers are stored in a linked list of pages. The list 60 * is initially empty, and pages are allocated on demand. The first 61 * function pointer in the first allocated page (the last one in 62 * the linked list) is reserved for the cleanup function. 63 * 64 * Outside the following functions, all pages are mprotect()'ed 65 * to prevent unintentional/malicious corruption. 66 */ 67 68 /* 69 * Register a function to be performed at exit or when a shared object 70 * with the given dso handle is unloaded dynamically. Also used as 71 * the backend for atexit(). For more info on this API, see: 72 * 73 * http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor 74 */ 75 int 76 __cxa_atexit(void (*func)(void *), void *arg, void *dso) 77 { 78 struct atexit *p = __atexit; 79 struct atexit_fn *fnp; 80 size_t pgsize = getpagesize(); 81 int ret = -1; 82 83 if (pgsize < sizeof(*p)) 84 return (-1); 85 _ATEXIT_LOCK(); 86 p = __atexit; 87 if (p != NULL) { 88 if (p->ind + 1 >= p->max) 89 p = NULL; 90 else if (mprotect(p, pgsize, PROT_READ | PROT_WRITE)) 91 goto unlock; 92 } 93 if (p == NULL) { 94 p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE, 95 MAP_ANON | MAP_PRIVATE, -1, 0); 96 if (p == MAP_FAILED) 97 goto unlock; 98 if (__atexit == NULL) { 99 memset(&p->fns[0], 0, sizeof(p->fns[0])); 100 p->ind = 1; 101 } else 102 p->ind = 0; 103 p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) / 104 sizeof(p->fns[0]); 105 p->next = __atexit; 106 __atexit = p; 107 } 108 fnp = &p->fns[p->ind++]; 109 fnp->fn_ptr = func; 110 fnp->fn_arg = arg; 111 fnp->fn_dso = dso; 112 if (mprotect(p, pgsize, PROT_READ)) 113 goto unlock; 114 restartloop = 1; 115 ret = 0; 116 unlock: 117 _ATEXIT_UNLOCK(); 118 return (ret); 119 } 120 121 /* 122 * Call all handlers registered with __cxa_atexit() for the shared 123 * object owning 'dso'. 124 * Note: if 'dso' is NULL, then all remaining handlers are called. 125 */ 126 void 127 __cxa_finalize(void *dso) 128 { 129 struct atexit *p, *q; 130 struct atexit_fn fn; 131 int n, pgsize = getpagesize(); 132 static int call_depth; 133 134 _ATEXIT_LOCK(); 135 call_depth++; 136 137 restart: 138 restartloop = 0; 139 for (p = __atexit; p != NULL; p = p->next) { 140 for (n = p->ind; --n >= 0;) { 141 if (p->fns[n].fn_ptr == NULL) 142 continue; /* already called */ 143 if (dso != NULL && dso != p->fns[n].fn_dso) 144 continue; /* wrong DSO */ 145 146 /* 147 * Mark handler as having been already called to avoid 148 * dupes and loops, then call the appropriate function. 149 */ 150 fn = p->fns[n]; 151 if (mprotect(p, pgsize, PROT_READ | PROT_WRITE) == 0) { 152 p->fns[n].fn_ptr = NULL; 153 mprotect(p, pgsize, PROT_READ); 154 } 155 _ATEXIT_UNLOCK(); 156 (*fn.fn_ptr)(fn.fn_arg); 157 _ATEXIT_LOCK(); 158 if (restartloop) 159 goto restart; 160 } 161 } 162 163 call_depth--; 164 165 /* 166 * If called via exit(), unmap the pages since we have now run 167 * all the handlers. We defer this until calldepth == 0 so that 168 * we don't unmap things prematurely if called recursively. 169 */ 170 if (dso == NULL && call_depth == 0) { 171 for (p = __atexit; p != NULL; ) { 172 q = p; 173 p = p->next; 174 munmap(q, pgsize); 175 } 176 __atexit = NULL; 177 } 178 _ATEXIT_UNLOCK(); 179 180 /* BEGIN android-changed: call __unregister_atfork if dso is not null */ 181 if (dso != NULL) { 182 __unregister_atfork(dso); 183 } 184 /* END android-changed */ 185 } 186 187 /* 188 * Register the cleanup function 189 */ 190 void 191 __atexit_register_cleanup(void (*func)(void)) 192 { 193 struct atexit *p; 194 size_t pgsize = getpagesize(); 195 196 if (pgsize < sizeof(*p)) 197 return; 198 _ATEXIT_LOCK(); 199 p = __atexit; 200 while (p != NULL && p->next != NULL) 201 p = p->next; 202 if (p == NULL) { 203 p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE, 204 MAP_ANON | MAP_PRIVATE, -1, 0); 205 if (p == MAP_FAILED) 206 goto unlock; 207 p->ind = 1; 208 p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) / 209 sizeof(p->fns[0]); 210 p->next = NULL; 211 __atexit = p; 212 } else { 213 if (mprotect(p, pgsize, PROT_READ | PROT_WRITE)) 214 goto unlock; 215 } 216 p->fns[0].fn_ptr = (void (*)(void *))func; 217 p->fns[0].fn_arg = NULL; 218 p->fns[0].fn_dso = NULL; 219 mprotect(p, pgsize, PROT_READ); 220 restartloop = 1; 221 unlock: 222 _ATEXIT_UNLOCK(); 223 } 224
