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/* $OpenBSD: atexit.c,v 1.10 2005/08/08 08:05:36 espie 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"
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.
*
* The free(malloc(1)) is a workaround causing malloc_init() to
* ensure that malloc.c gets the first mmap() call for its sbrk()
* games.
*/
/*
* Register a function to be performed at exit.
*/
int
atexit(void (*fn)(void))
{
struct atexit *p = __atexit;
int pgsize = getpagesize();
if (pgsize < sizeof(*p))
return (-1);
if (p != NULL) {
if (p->ind + 1 >= p->max)
p = NULL;
else if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
return (-1);
}
if (p == NULL) {
p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
MAP_ANON | MAP_PRIVATE, -1, 0);
if (p == MAP_FAILED)
return (-1);
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))
return (-1);
return (0);
}
/*
* Register the cleanup function
*/
void
__atexit_register_cleanup(void (*fn)(void))
{
struct atexit *p = __atexit;
int pgsize = getpagesize();
if (pgsize < sizeof(*p))
return;
while (p != NULL && p->next != NULL)
p = p->next;
if (p == NULL) {
p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE,
MAP_ANON | MAP_PRIVATE, -1, 0);
if (p == MAP_FAILED)
return;
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))
return;
}
p->fns[0] = fn;
mprotect(p, pgsize, PROT_READ);
}
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