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/* $OpenBSD: atexit.c,v 1.21 2015/04/07 01:27:07 guenther 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 <string.h>
#include <unistd.h>
#include "atexit.h"
#include "atfork.h"
#include "thread_private.h"
struct atexit *__atexit;
static int restartloop;
/*
* 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 functions, all pages are mprotect()'ed
* to prevent unintentional/malicious corruption.
*/
/*
* Register a function to be performed at exit or when a shared object
* with the given dso handle is unloaded dynamically. Also used as
* the backend for atexit(). For more info on this API, see:
*
* http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor
*/
int
__cxa_atexit(void (*func)(void *), void *arg, void *dso)
{
struct atexit *p = __atexit;
struct atexit_fn *fnp;
int pgsize = getpagesize();
int ret = -1;
if (pgsize < 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_ANON | MAP_PRIVATE, -1, 0);
if (p == MAP_FAILED)
goto unlock;
if (__atexit == NULL) {
memset(&p->fns[0], 0, sizeof(p->fns[0]));
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;
}
fnp = &p->fns[p->ind++];
fnp->fn_ptr = func;
fnp->fn_arg = arg;
fnp->fn_dso = dso;
if (mprotect(p, pgsize, PROT_READ))
goto unlock;
restartloop = 1;
ret = 0;
unlock:
_ATEXIT_UNLOCK();
return (ret);
}
/*
* Call all handlers registered with __cxa_atexit() for the shared
* object owning 'dso'.
* Note: if 'dso' is NULL, then all remaining handlers are called.
*/
void
__cxa_finalize(void *dso)
{
struct atexit *p, *q;
struct atexit_fn fn;
int n, pgsize = getpagesize();
static int call_depth;
_ATEXIT_LOCK();
call_depth++;
restart:
restartloop = 0;
for (p = __atexit; p != NULL; p = p->next) {
for (n = p->ind; --n >= 0;) {
if (p->fns[n].fn_ptr == NULL)
continue; /* already called */
if (dso != NULL && dso != p->fns[n].fn_dso)
continue; /* wrong DSO */
/*
* Mark handler as having been already called to avoid
* dupes and loops, then call the appropriate function.
*/
fn = p->fns[n];
if (mprotect(p, pgsize, PROT_READ | PROT_WRITE) == 0) {
p->fns[n].fn_ptr = NULL;
mprotect(p, pgsize, PROT_READ);
}
_ATEXIT_UNLOCK();
(*fn.fn_ptr)(fn.fn_arg);
_ATEXIT_LOCK();
if (restartloop)
goto restart;
}
}
call_depth--;
/*
* If called via exit(), unmap the pages since we have now run
* all the handlers. We defer this until calldepth == 0 so that
* we don't unmap things prematurely if called recursively.
*/
if (dso == NULL && call_depth == 0) {
for (p = __atexit; p != NULL; ) {
q = p;
p = p->next;
munmap(q, pgsize);
}
__atexit = NULL;
}
_ATEXIT_UNLOCK();
/*
* If unloading a DSO, unregister any atfork handlers registered
* by it. Skip the locking if the list is currently empty.
*/
if (dso != NULL && TAILQ_FIRST(&_atfork_list) != NULL) {
struct atfork_fn *af, *afnext;
_ATFORK_LOCK();
TAILQ_FOREACH_SAFE(af, &_atfork_list, fn_next, afnext)
if (af->fn_dso == dso) {
TAILQ_REMOVE(&_atfork_list, af, fn_next);
free(af);
}
_ATFORK_UNLOCK();
}
}
/*
* Register the cleanup function
*/
void
__atexit_register_cleanup(void (*func)(void))
{
struct atexit *p;
int pgsize = getpagesize();
if (pgsize < 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_ANON | 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;
} else {
if (mprotect(p, pgsize, PROT_READ | PROT_WRITE))
goto unlock;
}
p->fns[0].fn_ptr = (void (*)(void *))func;
p->fns[0].fn_arg = NULL;
p->fns[0].fn_dso = NULL;
mprotect(p, pgsize, PROT_READ);
restartloop = 1;
unlock:
_ATEXIT_UNLOCK();
}
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