aboutsummaryrefslogtreecommitdiff
path: root/lib/libthr/thread/thr_fork.c
blob: 9861e93c427df930604714dc077eda31a6fa9150 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
/*
 * Copyright (c) 2005 David Xu <davidxu@freebsd.org>
 * Copyright (c) 2003 Daniel Eischen <deischen@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Neither the name of the author nor the names of any co-contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of the author nor the names of any co-contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL 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 AUTHOR 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/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/syscall.h>
#include "namespace.h"
#include <errno.h>
#include <link.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <spinlock.h>
#include "un-namespace.h"

#include "libc_private.h"
#include "rtld_lock.h"
#include "thr_private.h"

__weak_reference(_thr_atfork, _pthread_atfork);
__weak_reference(_thr_atfork, pthread_atfork);

int
_thr_atfork(void (*prepare)(void), void (*parent)(void),
    void (*child)(void))
{
	struct pthread *curthread;
	struct pthread_atfork *af;

	_thr_check_init();

	if ((af = malloc(sizeof(struct pthread_atfork))) == NULL)
		return (ENOMEM);

	curthread = _get_curthread();
	af->prepare = prepare;
	af->parent = parent;
	af->child = child;
	THR_CRITICAL_ENTER(curthread);
	_thr_rwl_wrlock(&_thr_atfork_lock);
	TAILQ_INSERT_TAIL(&_thr_atfork_list, af, qe);
	_thr_rwl_unlock(&_thr_atfork_lock);
	THR_CRITICAL_LEAVE(curthread);
	return (0);
}

void
__pthread_cxa_finalize(struct dl_phdr_info *phdr_info)
{
	atfork_head    temp_list = TAILQ_HEAD_INITIALIZER(temp_list);
	struct pthread *curthread;
	struct pthread_atfork *af, *af1;

	_thr_check_init();

	curthread = _get_curthread();
	THR_CRITICAL_ENTER(curthread);
	_thr_rwl_wrlock(&_thr_atfork_lock);
	TAILQ_FOREACH_SAFE(af, &_thr_atfork_list, qe, af1) {
		if (__elf_phdr_match_addr(phdr_info, af->prepare) ||
		    __elf_phdr_match_addr(phdr_info, af->parent) ||
		    __elf_phdr_match_addr(phdr_info, af->child)) {
			TAILQ_REMOVE(&_thr_atfork_list, af, qe);
			TAILQ_INSERT_TAIL(&temp_list, af, qe);
		}
	}
	_thr_rwl_unlock(&_thr_atfork_lock);
	THR_CRITICAL_LEAVE(curthread);
	while ((af = TAILQ_FIRST(&temp_list)) != NULL) {
		TAILQ_REMOVE(&temp_list, af, qe);
		free(af);
	}
	_thr_tsd_unload(phdr_info);
	_thr_sigact_unload(phdr_info);
}

enum thr_fork_mode {
	MODE_FORK,
	MODE_PDFORK,
};

struct thr_fork_args {
	enum thr_fork_mode mode;
	void *fdp;
	int flags;
};

static pid_t
thr_fork_impl(const struct thr_fork_args *a)
{
	struct pthread *curthread;
	struct pthread_atfork *af;
	pid_t ret;
	int errsave, cancelsave;
	int was_threaded;
	int rtld_locks[MAX_RTLD_LOCKS];

	if (!_thr_is_inited()) {
		switch (a->mode) {
		case MODE_FORK:
			return (__sys_fork());
		case MODE_PDFORK:
			return (__sys_pdfork(a->fdp, a->flags));
		default:
			errno = EDOOFUS;
			return (-1);
		}
	}

	curthread = _get_curthread();
	cancelsave = curthread->no_cancel;
	curthread->no_cancel = 1;
	_thr_rwl_rdlock(&_thr_atfork_lock);

	/* Run down atfork prepare handlers. */
	TAILQ_FOREACH_REVERSE(af, &_thr_atfork_list, atfork_head, qe) {
		if (af->prepare != NULL)
			af->prepare();
	}

	/*
	 * Block all signals until we reach a safe point.
	 */
	_thr_signal_block(curthread);
	_thr_signal_prefork();

	/*
	 * All bets are off as to what should happen soon if the parent
	 * process was not so kindly as to set up pthread fork hooks to
	 * relinquish all running threads.
	 */
	if (_thr_isthreaded() != 0) {
		was_threaded = 1;
		__thr_malloc_prefork(curthread);
		_malloc_prefork();
		__thr_pshared_atfork_pre();
		_rtld_atfork_pre(rtld_locks);
	} else {
		was_threaded = 0;
	}

	/*
	 * Fork a new process.
	 * There is no easy way to pre-resolve the __sys_fork symbol
	 * without performing the fork.  Use the syscall(2)
	 * indirection, the syscall symbol is resolved in
	 * _thr_rtld_init() with side-effect free call.
	 */
	switch (a->mode) {
	case MODE_FORK:
		ret = syscall(SYS_fork);
		break;
	case MODE_PDFORK:
		ret = syscall(SYS_pdfork, a->fdp, a->flags);
		break;
	default:
		ret = -1;
		errno = EDOOFUS;
		break;
	}

	if (ret == 0) {
		/* Child process */
		errsave = errno;
		curthread->cancel_pending = 0;
		curthread->flags &= ~(THR_FLAGS_NEED_SUSPEND|THR_FLAGS_DETACHED);

		/*
		 * Thread list will be reinitialized, and later we call
		 * _libpthread_init(), it will add us back to list.
		 */
		curthread->tlflags &= ~TLFLAGS_IN_TDLIST;

		/* before thr_self() */
		if (was_threaded)
			__thr_malloc_postfork(curthread);

		/* child is a new kernel thread. */
		thr_self(&curthread->tid);

		/* clear other threads locked us. */
		_thr_umutex_init(&curthread->lock);
		_mutex_fork(curthread);

		_thr_signal_postfork_child();

		if (was_threaded) {
			_rtld_atfork_post(rtld_locks);
			__thr_pshared_atfork_post();
		}
		_thr_setthreaded(0);

		/* reinitalize library. */
		_libpthread_init(curthread);

		/* atfork is reinitialized by _libpthread_init()! */
		_thr_rwl_rdlock(&_thr_atfork_lock);

		if (was_threaded) {
			_thr_setthreaded(1);
			_malloc_postfork();
			_thr_setthreaded(0);
		}

		/* Ready to continue, unblock signals. */ 
		_thr_signal_unblock(curthread);

		/* Run down atfork child handlers. */
		TAILQ_FOREACH(af, &_thr_atfork_list, qe) {
			if (af->child != NULL)
				af->child();
		}
		_thr_rwlock_unlock(&_thr_atfork_lock);
		curthread->no_cancel = cancelsave;
	} else {
		/* Parent process */
		errsave = errno;

		_thr_signal_postfork();

		if (was_threaded) {
			__thr_malloc_postfork(curthread);
			_rtld_atfork_post(rtld_locks);
			__thr_pshared_atfork_post();
			_malloc_postfork();
		}

		/* Ready to continue, unblock signals. */ 
		_thr_signal_unblock(curthread);

		/* Run down atfork parent handlers. */
		TAILQ_FOREACH(af, &_thr_atfork_list, qe) {
			if (af->parent != NULL)
				af->parent();
		}

		_thr_rwlock_unlock(&_thr_atfork_lock);
		curthread->no_cancel = cancelsave;
		/* test async cancel */
		if (curthread->cancel_async)
			_thr_testcancel(curthread);
	}
	errno = errsave;

	return (ret);
}

__weak_reference(__thr_fork, _fork);

pid_t
__thr_fork(void)
{
	struct thr_fork_args a;

	a.mode = MODE_FORK;
	return (thr_fork_impl(&a));
}

pid_t
__thr_pdfork(int *fdp, int flags)
{
	struct thr_fork_args a;

	a.mode = MODE_PDFORK;
	a.fdp = fdp;
	a.flags = flags;
	return (thr_fork_impl(&a));
}