atexit.c revision 211704 
1/*-
2 * Copyright (c) 1990, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 4. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)atexit.c	8.2 (Berkeley) 7/3/94";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: head/lib/libc/stdlib/atexit.c 211704 2010-08-23 15:18:35Z kib $");
38
39#include "namespace.h"
40#include <stddef.h>
41#include <stdlib.h>
42#include <unistd.h>
43#include <pthread.h>
44#include "atexit.h"
45#include "un-namespace.h"
46
47#include "libc_private.h"
48
49#define	ATEXIT_FN_EMPTY	0
50#define	ATEXIT_FN_STD	1
51#define	ATEXIT_FN_CXA	2
52
53static pthread_mutex_t atexit_mutex = PTHREAD_MUTEX_INITIALIZER;
54
55#define _MUTEX_LOCK(x)		if (__isthreaded) _pthread_mutex_lock(x)
56#define _MUTEX_UNLOCK(x)	if (__isthreaded) _pthread_mutex_unlock(x)
57#define _MUTEX_DESTROY(x)	if (__isthreaded) _pthread_mutex_destroy(x)
58
59struct atexit {
60	struct atexit *next;			/* next in list */
61	int ind;				/* next index in this table */
62	struct atexit_fn {
63		int fn_type;			/* ATEXIT_? from above */
64		union {
65			void (*std_func)(void);
66			void (*cxa_func)(void *);
67		} fn_ptr;			/* function pointer */
68		void *fn_arg;			/* argument for CXA callback */
69		void *fn_dso;			/* shared module handle */
70	} fns[ATEXIT_SIZE];			/* the table itself */
71};
72
73static struct atexit *__atexit;		/* points to head of LIFO stack */
74
75/*
76 * Register the function described by 'fptr' to be called at application
77 * exit or owning shared object unload time. This is a helper function
78 * for atexit and __cxa_atexit.
79 */
80static int
81atexit_register(struct atexit_fn *fptr)
82{
83	static struct atexit __atexit0;	/* one guaranteed table */
84	struct atexit *p;
85
86	_MUTEX_LOCK(&atexit_mutex);
87	if ((p = __atexit) == NULL)
88		__atexit = p = &__atexit0;
89	else while (p->ind >= ATEXIT_SIZE) {
90		struct atexit *old__atexit;
91		old__atexit = __atexit;
92	        _MUTEX_UNLOCK(&atexit_mutex);
93		if ((p = (struct atexit *)malloc(sizeof(*p))) == NULL)
94			return (-1);
95		_MUTEX_LOCK(&atexit_mutex);
96		if (old__atexit != __atexit) {
97			/* Lost race, retry operation */
98			_MUTEX_UNLOCK(&atexit_mutex);
99			free(p);
100			_MUTEX_LOCK(&atexit_mutex);
101			p = __atexit;
102			continue;
103		}
104		p->ind = 0;
105		p->next = __atexit;
106		__atexit = p;
107	}
108	p->fns[p->ind++] = *fptr;
109	_MUTEX_UNLOCK(&atexit_mutex);
110	return 0;
111}
112
113/*
114 * Register a function to be performed at exit.
115 */
116int
117atexit(void (*func)(void))
118{
119	struct atexit_fn fn;
120	int error;
121
122	fn.fn_type = ATEXIT_FN_STD;
123	fn.fn_ptr.std_func = func;
124	fn.fn_arg = NULL;
125	fn.fn_dso = NULL;
126
127 	error = atexit_register(&fn);
128	return (error);
129}
130
131/*
132 * Register a function to be performed at exit or when an shared object
133 * with given dso handle is unloaded dynamically.
134 */
135int
136__cxa_atexit(void (*func)(void *), void *arg, void *dso)
137{
138	struct atexit_fn fn;
139	int error;
140
141	fn.fn_type = ATEXIT_FN_CXA;
142	fn.fn_ptr.cxa_func = func;
143	fn.fn_arg = arg;
144	fn.fn_dso = dso;
145
146 	error = atexit_register(&fn);
147	return (error);
148}
149
150/*
151 * Call all handlers registered with __cxa_atexit for the shared
152 * object owning 'dso'.  Note: if 'dso' is NULL, then all remaining
153 * handlers are called.
154 */
155void
156__cxa_finalize(void *dso)
157{
158	struct atexit *p;
159	struct atexit_fn fn;
160	int n;
161
162	_MUTEX_LOCK(&atexit_mutex);
163	for (p = __atexit; p; p = p->next) {
164		for (n = p->ind; --n >= 0;) {
165			if (p->fns[n].fn_type == ATEXIT_FN_EMPTY)
166				continue; /* already been called */
167			if (dso != NULL && dso != p->fns[n].fn_dso)
168				continue; /* wrong DSO */
169			fn = p->fns[n];
170			/*
171			  Mark entry to indicate that this particular handler
172			  has already been called.
173			*/
174			p->fns[n].fn_type = ATEXIT_FN_EMPTY;
175		        _MUTEX_UNLOCK(&atexit_mutex);
176
177			/* Call the function of correct type. */
178			if (fn.fn_type == ATEXIT_FN_CXA)
179				fn.fn_ptr.cxa_func(fn.fn_arg);
180			else if (fn.fn_type == ATEXIT_FN_STD)
181				fn.fn_ptr.std_func();
182			_MUTEX_LOCK(&atexit_mutex);
183		}
184	}
185	_MUTEX_UNLOCK(&atexit_mutex);
186	if (dso == NULL)
187		_MUTEX_DESTROY(&atexit_mutex);
188}
189