thr_rtld.c revision 185558 
1/*
2 * Copyright (c) 2006, David Xu <davidxu@freebsd.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice unmodified, this list of conditions, and the following
10 *    disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 * $FreeBSD: head/lib/libthr/thread/thr_rtld.c 185558 2008-12-02 11:58:31Z kib $
27 *
28 */
29
30 /*
31  * A lockless rwlock for rtld.
32  */
33#include <sys/cdefs.h>
34#include <stdlib.h>
35
36#include "rtld_lock.h"
37#include "thr_private.h"
38
39#undef errno
40extern int errno;
41
42#define CACHE_LINE_SIZE		64
43
44static int	_thr_rtld_clr_flag(int);
45static void	*_thr_rtld_lock_create(void);
46static void	_thr_rtld_lock_destroy(void *);
47static void	_thr_rtld_lock_release(void *);
48static void	_thr_rtld_rlock_acquire(void *);
49static int	_thr_rtld_set_flag(int);
50static void	_thr_rtld_wlock_acquire(void *);
51
52struct rtld_lock {
53	struct	urwlock	lock;
54	char		_pad[CACHE_LINE_SIZE - sizeof(struct urwlock)];
55};
56
57static struct rtld_lock lock_place[MAX_RTLD_LOCKS] __aligned(CACHE_LINE_SIZE);
58static int busy_places;
59
60static void *
61_thr_rtld_lock_create(void)
62{
63	int locki;
64	struct rtld_lock *l;
65	static const char fail[] = "_thr_rtld_lock_create failed\n";
66
67	for (locki = 0; locki < MAX_RTLD_LOCKS; locki++) {
68		if ((busy_places & (1 << locki)) == 0)
69			break;
70	}
71	if (locki == MAX_RTLD_LOCKS) {
72		write(2, fail, sizeof(fail) - 1);
73		return (NULL);
74	}
75	busy_places |= (1 << locki);
76
77	l = &lock_place[locki];
78	l->lock.rw_flags = URWLOCK_PREFER_READER;
79	return (l);
80}
81
82static void
83_thr_rtld_lock_destroy(void *lock)
84{
85	int locki;
86
87	locki = (struct rtld_lock *)lock - &lock_place[0];
88	busy_places &= ~(1 << locki);
89}
90
91#define SAVE_ERRNO()	{			\
92	if (curthread != _thr_initial)		\
93		errsave = curthread->error;	\
94	else					\
95		errsave = errno;		\
96}
97
98#define RESTORE_ERRNO()	{ 			\
99	if (curthread != _thr_initial)  	\
100		curthread->error = errsave;	\
101	else					\
102		errno = errsave;		\
103}
104
105static void
106_thr_rtld_rlock_acquire(void *lock)
107{
108	struct pthread		*curthread;
109	struct rtld_lock	*l;
110	int			errsave;
111
112	curthread = _get_curthread();
113	SAVE_ERRNO();
114	l = (struct rtld_lock *)lock;
115
116	THR_CRITICAL_ENTER(curthread);
117	while (_thr_rwlock_rdlock(&l->lock, 0, NULL) != 0)
118		;
119	RESTORE_ERRNO();
120}
121
122static void
123_thr_rtld_wlock_acquire(void *lock)
124{
125	struct pthread		*curthread;
126	struct rtld_lock	*l;
127	int			errsave;
128
129	curthread = _get_curthread();
130	SAVE_ERRNO();
131	l = (struct rtld_lock *)lock;
132
133	_thr_signal_block(curthread);
134	while (_thr_rwlock_wrlock(&l->lock, NULL) != 0)
135		;
136	RESTORE_ERRNO();
137}
138
139static void
140_thr_rtld_lock_release(void *lock)
141{
142	struct pthread		*curthread;
143	struct rtld_lock	*l;
144	int32_t			state;
145	int			errsave;
146
147	curthread = _get_curthread();
148	SAVE_ERRNO();
149	l = (struct rtld_lock *)lock;
150
151	state = l->lock.rw_state;
152	if (_thr_rwlock_unlock(&l->lock) == 0) {
153		if ((state & URWLOCK_WRITE_OWNER) == 0) {
154			THR_CRITICAL_LEAVE(curthread);
155		} else {
156			_thr_signal_unblock(curthread);
157		}
158	}
159	RESTORE_ERRNO();
160}
161
162static int
163_thr_rtld_set_flag(int mask __unused)
164{
165	/*
166	 * The caller's code in rtld-elf is broken, it is not signal safe,
167	 * just return zero to fool it.
168	 */
169	return (0);
170}
171
172static int
173_thr_rtld_clr_flag(int mask __unused)
174{
175	return (0);
176}
177
178void
179_thr_rtld_init(void)
180{
181	struct RtldLockInfo	li;
182	struct pthread		*curthread;
183	long dummy;
184
185	curthread = _get_curthread();
186
187	/* force to resolve _umtx_op PLT */
188	_umtx_op_err((struct umtx *)&dummy, UMTX_OP_WAKE, 1, 0, 0);
189
190	/* force to resolve errno() PLT */
191	__error();
192
193	li.lock_create  = _thr_rtld_lock_create;
194	li.lock_destroy = _thr_rtld_lock_destroy;
195	li.rlock_acquire = _thr_rtld_rlock_acquire;
196	li.wlock_acquire = _thr_rtld_wlock_acquire;
197	li.lock_release  = _thr_rtld_lock_release;
198	li.thread_set_flag = _thr_rtld_set_flag;
199	li.thread_clr_flag = _thr_rtld_clr_flag;
200	li.at_fork = NULL;
201
202	/* mask signals, also force to resolve __sys_sigprocmask PLT */
203	_thr_signal_block(curthread);
204	_rtld_thread_init(&li);
205	_thr_signal_unblock(curthread);
206}
207
208void
209_thr_rtld_fini(void)
210{
211	struct pthread	*curthread;
212
213	curthread = _get_curthread();
214	_thr_signal_block(curthread);
215	_rtld_thread_init(NULL);
216	_thr_signal_unblock(curthread);
217}
218