1 /* $OpenBSD: atexit.c,v 1.12 2006/02/22 07:16:32 otto 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 <unistd.h> 36 #include "atexit.h" 37 #include "thread_private.h" 38 39 int __atexit_invalid = 1; 40 struct atexit *__atexit; 41 42 /* 43 * Function pointers are stored in a linked list of pages. The list 44 * is initially empty, and pages are allocated on demand. The first 45 * function pointer in the first allocated page (the last one in 46 * the linked list) is reserved for the cleanup function. 47 * 48 * Outside the following two functions, all pages are mprotect()'ed 49 * to prevent unintentional/malicious corruption. 50 */ 51 52 /* 53 * Register a function to be performed at exit. 54 */ 55 int 56 atexit(void (*fn)(void)) 57 { 58 struct atexit *p; 59 int pgsize = getpagesize(); 60 int ret = -1; 61 62 if (pgsize < sizeof(*p)) 63 return (-1); 64 _ATEXIT_LOCK(); 65 p = __atexit; 66 if (p != NULL) { 67 if (p->ind + 1 >= p->max) 68 p = NULL; 69 else if (mprotect(p, pgsize, PROT_READ | PROT_WRITE)) 70 goto unlock; 71 } 72 if (p == NULL) { 73 p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE, 74 MAP_ANON | MAP_PRIVATE, -1, 0); 75 if (p == MAP_FAILED) 76 goto unlock; 77 if (__atexit == NULL) { 78 p->fns[0] = NULL; 79 p->ind = 1; 80 } else 81 p->ind = 0; 82 p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) / 83 sizeof(p->fns[0]); 84 p->next = __atexit; 85 __atexit = p; 86 if (__atexit_invalid) 87 __atexit_invalid = 0; 88 } 89 p->fns[p->ind++] = fn; 90 if (mprotect(p, pgsize, PROT_READ)) 91 goto unlock; 92 ret = 0; 93 unlock: 94 _ATEXIT_UNLOCK(); 95 return (ret); 96 } 97 98 /* 99 * Register the cleanup function 100 */ 101 void 102 __atexit_register_cleanup(void (*fn)(void)) 103 { 104 struct atexit *p; 105 int pgsize = getpagesize(); 106 107 if (pgsize < sizeof(*p)) 108 return; 109 _ATEXIT_LOCK(); 110 p = __atexit; 111 while (p != NULL && p->next != NULL) 112 p = p->next; 113 if (p == NULL) { 114 p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE, 115 MAP_ANON | MAP_PRIVATE, -1, 0); 116 if (p == MAP_FAILED) 117 goto unlock; 118 p->ind = 1; 119 p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) / 120 sizeof(p->fns[0]); 121 p->next = NULL; 122 __atexit = p; 123 if (__atexit_invalid) 124 __atexit_invalid = 0; 125 } else { 126 if (mprotect(p, pgsize, PROT_READ | PROT_WRITE)) 127 goto unlock; 128 } 129 p->fns[0] = fn; 130 mprotect(p, pgsize, PROT_READ); 131 unlock: 132 _ATEXIT_UNLOCK(); 133 } 134