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 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 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 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
