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