diff options
Diffstat (limited to 'libc/stdlib/atexit.c')
-rw-r--r-- | libc/stdlib/atexit.c | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/libc/stdlib/atexit.c b/libc/stdlib/atexit.c new file mode 100644 index 0000000..97eac4a --- /dev/null +++ b/libc/stdlib/atexit.c @@ -0,0 +1,133 @@ +/* $OpenBSD: atexit.c,v 1.12 2006/02/22 07:16:32 otto Exp $ */ +/* + * Copyright (c) 2002 Daniel Hartmeier + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * - Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * - Redistributions in binary form must reproduce the above + * copyright notice, this list of conditions and the following + * disclaimer in the documentation and/or other materials provided + * with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; + * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER + * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + */ + +#include <sys/types.h> +#include <sys/mman.h> +#include <stdlib.h> +#include <unistd.h> +#include "atexit.h" +#include "thread_private.h" + +int __atexit_invalid = 1; +struct atexit *__atexit; + +/* + * Function pointers are stored in a linked list of pages. The list + * is initially empty, and pages are allocated on demand. The first + * function pointer in the first allocated page (the last one in + * the linked list) is reserved for the cleanup function. + * + * Outside the following two functions, all pages are mprotect()'ed + * to prevent unintentional/malicious corruption. + */ + +/* + * Register a function to be performed at exit. + */ +int +atexit(void (*fn)(void)) +{ + struct atexit *p; + int pgsize = getpagesize(); + int ret = -1; + + if (pgsize < (int)sizeof(*p)) + return (-1); + _ATEXIT_LOCK(); + p = __atexit; + if (p != NULL) { + if (p->ind + 1 >= p->max) + p = NULL; + else if (mprotect(p, pgsize, PROT_READ | PROT_WRITE)) + goto unlock; + } + if (p == NULL) { + p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + if (p == MAP_FAILED) + goto unlock; + if (__atexit == NULL) { + p->fns[0] = NULL; + p->ind = 1; + } else + p->ind = 0; + p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) / + sizeof(p->fns[0]); + p->next = __atexit; + __atexit = p; + if (__atexit_invalid) + __atexit_invalid = 0; + } + p->fns[p->ind++] = fn; + if (mprotect(p, pgsize, PROT_READ)) + goto unlock; + ret = 0; +unlock: + _ATEXIT_UNLOCK(); + return (ret); +} + +/* + * Register the cleanup function + */ +void +__atexit_register_cleanup(void (*fn)(void)) +{ + struct atexit *p; + int pgsize = getpagesize(); + + if (pgsize < (int)sizeof(*p)) + return; + _ATEXIT_LOCK(); + p = __atexit; + while (p != NULL && p->next != NULL) + p = p->next; + if (p == NULL) { + p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + if (p == MAP_FAILED) + goto unlock; + p->ind = 1; + p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) / + sizeof(p->fns[0]); + p->next = NULL; + __atexit = p; + if (__atexit_invalid) + __atexit_invalid = 0; + } else { + if (mprotect(p, pgsize, PROT_READ | PROT_WRITE)) + goto unlock; + } + p->fns[0] = fn; + mprotect(p, pgsize, PROT_READ); +unlock: + _ATEXIT_UNLOCK(); +} |