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      1 /*
      2  * Copyright (c) 2005 David Xu <davidxu (at) freebsd.org>
      3  * Copyright (c) 2003 Daniel Eischen <deischen (at) freebsd.org>
      4  * All rights reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Neither the name of the author nor the names of any co-contributors
     12  *    may be used to endorse or promote products derived from this software
     13  *    without specific prior written permission.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     25  * SUCH DAMAGE.
     26  *
     27  * $FreeBSD: head/lib/libthr/thread/thr_fork.c 276630 2015-01-03 18:38:46Z kib $
     28  */
     29 
     30 /*
     31  * Copyright (c) 1995-1998 John Birrell <jb (at) cimlogic.com.au>
     32  * All rights reserved.
     33  *
     34  * Redistribution and use in source and binary forms, with or without
     35  * modification, are permitted provided that the following conditions
     36  * are met:
     37  * 1. Redistributions of source code must retain the above copyright
     38  *    notice, this list of conditions and the following disclaimer.
     39  * 2. Redistributions in binary form must reproduce the above copyright
     40  *    notice, this list of conditions and the following disclaimer in the
     41  *    documentation and/or other materials provided with the distribution.
     42  * 3. Neither the name of the author nor the names of any co-contributors
     43  *    may be used to endorse or promote products derived from this software
     44  *    without specific prior written permission.
     45  *
     46  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
     47  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     48  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     49  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     50  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     51  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     52  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     53  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     54  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     55  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     56  * SUCH DAMAGE.
     57  *
     58  */
     59 
     60 #include <sys/syscall.h>
     61 #include "namespace.h"
     62 #include <errno.h>
     63 #include <link.h>
     64 #include <string.h>
     65 #include <stdlib.h>
     66 #include <unistd.h>
     67 #include <pthread.h>
     68 #include <spinlock.h>
     69 #include "un-namespace.h"
     70 
     71 #include "libc_private.h"
     72 #include "rtld_lock.h"
     73 #include "thr_private.h"
     74 
     75 __weak_reference(_pthread_atfork, pthread_atfork);
     76 
     77 int
     78 _pthread_atfork(void (*prepare)(void), void (*parent)(void),
     79     void (*child)(void))
     80 {
     81 	struct pthread *curthread;
     82 	struct pthread_atfork *af;
     83 
     84 	_thr_check_init();
     85 
     86 	if ((af = malloc(sizeof(struct pthread_atfork))) == NULL)
     87 		return (ENOMEM);
     88 
     89 	curthread = _get_curthread();
     90 	af->prepare = prepare;
     91 	af->parent = parent;
     92 	af->child = child;
     93 	THR_CRITICAL_ENTER(curthread);
     94 	_thr_rwl_wrlock(&_thr_atfork_lock);
     95 	TAILQ_INSERT_TAIL(&_thr_atfork_list, af, qe);
     96 	_thr_rwl_unlock(&_thr_atfork_lock);
     97 	THR_CRITICAL_LEAVE(curthread);
     98 	return (0);
     99 }
    100 
    101 void
    102 __pthread_cxa_finalize(struct dl_phdr_info *phdr_info)
    103 {
    104 	atfork_head    temp_list = TAILQ_HEAD_INITIALIZER(temp_list);
    105 	struct pthread *curthread;
    106 	struct pthread_atfork *af, *af1;
    107 
    108 	_thr_check_init();
    109 
    110 	curthread = _get_curthread();
    111 	THR_CRITICAL_ENTER(curthread);
    112 	_thr_rwl_wrlock(&_thr_atfork_lock);
    113 	TAILQ_FOREACH_SAFE(af, &_thr_atfork_list, qe, af1) {
    114 		if (__elf_phdr_match_addr(phdr_info, af->prepare) ||
    115 		    __elf_phdr_match_addr(phdr_info, af->parent) ||
    116 		    __elf_phdr_match_addr(phdr_info, af->child)) {
    117 			TAILQ_REMOVE(&_thr_atfork_list, af, qe);
    118 			TAILQ_INSERT_TAIL(&temp_list, af, qe);
    119 		}
    120 	}
    121 	_thr_rwl_unlock(&_thr_atfork_lock);
    122 	THR_CRITICAL_LEAVE(curthread);
    123 	while ((af = TAILQ_FIRST(&temp_list)) != NULL) {
    124 		TAILQ_REMOVE(&temp_list, af, qe);
    125 		free(af);
    126 	}
    127 	_thr_tsd_unload(phdr_info);
    128 	_thr_sigact_unload(phdr_info);
    129 }
    130 
    131 __weak_reference(__thr_fork, _fork);
    132 
    133 pid_t
    134 __thr_fork(void)
    135 {
    136 	struct pthread *curthread;
    137 	struct pthread_atfork *af;
    138 	pid_t ret;
    139 	int errsave, cancelsave;
    140 	int was_threaded;
    141 	int rtld_locks[MAX_RTLD_LOCKS];
    142 
    143 	if (!_thr_is_inited())
    144 		return (__sys_fork());
    145 
    146 	curthread = _get_curthread();
    147 	cancelsave = curthread->no_cancel;
    148 	curthread->no_cancel = 1;
    149 	_thr_rwl_rdlock(&_thr_atfork_lock);
    150 
    151 	/* Run down atfork prepare handlers. */
    152 	TAILQ_FOREACH_REVERSE(af, &_thr_atfork_list, atfork_head, qe) {
    153 		if (af->prepare != NULL)
    154 			af->prepare();
    155 	}
    156 
    157 	/*
    158 	 * Block all signals until we reach a safe point.
    159 	 */
    160 	_thr_signal_block(curthread);
    161 	_thr_signal_prefork();
    162 
    163 	/*
    164 	 * All bets are off as to what should happen soon if the parent
    165 	 * process was not so kindly as to set up pthread fork hooks to
    166 	 * relinquish all running threads.
    167 	 */
    168 	if (_thr_isthreaded() != 0) {
    169 		was_threaded = 1;
    170 		_malloc_prefork();
    171 		_rtld_atfork_pre(rtld_locks);
    172 	} else {
    173 		was_threaded = 0;
    174 	}
    175 
    176 	/*
    177 	 * Fork a new process.
    178 	 * There is no easy way to pre-resolve the __sys_fork symbol
    179 	 * without performing the fork.  Use the syscall(2)
    180 	 * indirection, the syscall symbol is resolved in
    181 	 * _thr_rtld_init() with side-effect free call.
    182 	 */
    183 	ret = syscall(SYS_fork);
    184 	if (ret == 0) {
    185 		/* Child process */
    186 		errsave = errno;
    187 		curthread->cancel_pending = 0;
    188 		curthread->flags &= ~(THR_FLAGS_NEED_SUSPEND|THR_FLAGS_DETACHED);
    189 
    190 		/*
    191 		 * Thread list will be reinitialized, and later we call
    192 		 * _libpthread_init(), it will add us back to list.
    193 		 */
    194 		curthread->tlflags &= ~TLFLAGS_IN_TDLIST;
    195 
    196 		/* child is a new kernel thread. */
    197 		thr_self(&curthread->tid);
    198 
    199 		/* clear other threads locked us. */
    200 		_thr_umutex_init(&curthread->lock);
    201 		_mutex_fork(curthread);
    202 
    203 		_thr_signal_postfork_child();
    204 
    205 		if (was_threaded)
    206 			_rtld_atfork_post(rtld_locks);
    207 		_thr_setthreaded(0);
    208 
    209 		/* reinitalize library. */
    210 		_libpthread_init(curthread);
    211 
    212 		/* atfork is reinitializeded by _libpthread_init()! */
    213 		_thr_rwl_rdlock(&_thr_atfork_lock);
    214 
    215 		if (was_threaded) {
    216 			__isthreaded = 1;
    217 			_malloc_postfork();
    218 			__isthreaded = 0;
    219 		}
    220 
    221 		/* Ready to continue, unblock signals. */
    222 		_thr_signal_unblock(curthread);
    223 
    224 		/* Run down atfork child handlers. */
    225 		TAILQ_FOREACH(af, &_thr_atfork_list, qe) {
    226 			if (af->child != NULL)
    227 				af->child();
    228 		}
    229 		_thr_rwlock_unlock(&_thr_atfork_lock);
    230 		curthread->no_cancel = cancelsave;
    231 	} else {
    232 		/* Parent process */
    233 		errsave = errno;
    234 
    235 		_thr_signal_postfork();
    236 
    237 		if (was_threaded) {
    238 			_rtld_atfork_post(rtld_locks);
    239 			_malloc_postfork();
    240 		}
    241 
    242 		/* Ready to continue, unblock signals. */
    243 		_thr_signal_unblock(curthread);
    244 
    245 		/* Run down atfork parent handlers. */
    246 		TAILQ_FOREACH(af, &_thr_atfork_list, qe) {
    247 			if (af->parent != NULL)
    248 				af->parent();
    249 		}
    250 
    251 		_thr_rwlock_unlock(&_thr_atfork_lock);
    252 		curthread->no_cancel = cancelsave;
    253 		/* test async cancel */
    254 		if (curthread->cancel_async)
    255 			_thr_testcancel(curthread);
    256 	}
    257 	errno = errsave;
    258 
    259 	return (ret);
    260 }
    261