1 /*-
2 * Copyright (c) 2016 Mahdi Mokhtari <mokhi64@gmail.com>
3 * Copyright (c) 2016, 2017 The FreeBSD Foundation
4 * All rights reserved.
5 *
6 * Portions of this software were developed by Konstantin Belousov
7 * under sponsorship from the FreeBSD Foundation.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31 #include <sys/queue.h>
32 #include "namespace.h"
33 #include <errno.h>
34 #include <link.h>
35 #include <pthread.h>
36 #include <stddef.h>
37 #include <stdlib.h>
38 #include <stdio.h>
39 #include "un-namespace.h"
40 #include "libc_private.h"
41
42 /*
43 * C++11 introduces the thread_local scope (like __thread with some
44 * additions). As a key-feature it should support non-trivial
45 * destructors, registered with __cxa_thread_atexit() to be executed
46 * at the thread termination.
47 *
48 * The implemention keeps a _Thread_local list of destructors per each
49 * thread, and calls __cxa_thread_call_dtors() on each thread's exit
50 * to do cleanup. For a thread calling exit(3), in particular, for
51 * the initial thread returning from main(), we call
52 * __cxa_thread_call_dtors() inside exit().
53 *
54 * It could be possible that a dynamically loaded library, use
55 * thread_local variable but is dlclose()'d before thread exit. The
56 * destructor of this variable will then try to access the address,
57 * for calling it but it's unloaded, so it'll crash. We're using
58 * __elf_phdr_match_addr() to detect and prevent such cases and so
59 * prevent the crash.
60 */
61
62 #define CXA_DTORS_ITERATIONS 4
63
64 struct cxa_thread_dtor {
65 void *obj;
66 void (*func)(void *);
67 void *dso;
68 LIST_ENTRY(cxa_thread_dtor) entry;
69 };
70 static _Thread_local LIST_HEAD(dtor_list, cxa_thread_dtor) dtors =
71 LIST_HEAD_INITIALIZER(dtors);
72
73 int
__cxa_thread_atexit_impl(void (* dtor_func)(void *),void * obj,void * dso_symbol)74 __cxa_thread_atexit_impl(void (*dtor_func)(void *), void *obj,
75 void *dso_symbol)
76 {
77
78 return (__cxa_thread_atexit_hidden(dtor_func, obj, dso_symbol));
79 }
80
81 int
__cxa_thread_atexit_hidden(void (* dtor_func)(void *),void * obj,void * dso_symbol)82 __cxa_thread_atexit_hidden(void (*dtor_func)(void *), void *obj,
83 void *dso_symbol)
84 {
85 struct cxa_thread_dtor *new_dtor;
86
87 new_dtor = malloc(sizeof(*new_dtor));
88 if (new_dtor == NULL) {
89 errno = ENOMEM; /* forcibly override malloc(3) error */
90 return (-1);
91 }
92
93 new_dtor->obj = obj;
94 new_dtor->func = dtor_func;
95 new_dtor->dso = dso_symbol;
96 LIST_INSERT_HEAD(&dtors, new_dtor, entry);
97 return (0);
98 }
99
100 static void
walk_cb_call(struct cxa_thread_dtor * dtor)101 walk_cb_call(struct cxa_thread_dtor *dtor)
102 {
103 struct dl_phdr_info phdr_info;
104
105 if (_rtld_addr_phdr(dtor->func, &phdr_info) &&
106 __elf_phdr_match_addr(&phdr_info, dtor->func))
107 dtor->func(dtor->obj);
108 else
109 fprintf(stderr,
110 "__cxa_thread_call_dtors: dtr %p from unloaded dso, skipping\n",
111 (void *)(dtor->func));
112 }
113
114 static void
walk_cb_nocall(struct cxa_thread_dtor * dtor __unused)115 walk_cb_nocall(struct cxa_thread_dtor *dtor __unused)
116 {
117 }
118
119 static void
cxa_thread_walk(void (* cb)(struct cxa_thread_dtor *))120 cxa_thread_walk(void (*cb)(struct cxa_thread_dtor *))
121 {
122 struct cxa_thread_dtor *dtor, *tdtor;
123
124 LIST_FOREACH_SAFE(dtor, &dtors, entry, tdtor) {
125 LIST_REMOVE(dtor, entry);
126 cb(dtor);
127 free(dtor);
128 }
129 }
130
131 /*
132 * This is the callback function we use to call destructors, once for
133 * each thread. It is called in exit(3) in libc/stdlib/exit.c and
134 * before exit_thread() in libthr/thread/thr_exit.c.
135 */
136 void
__cxa_thread_call_dtors(void)137 __cxa_thread_call_dtors(void)
138 {
139 int i;
140
141 for (i = 0; i < CXA_DTORS_ITERATIONS && !LIST_EMPTY(&dtors); i++)
142 cxa_thread_walk(walk_cb_call);
143
144 if (!LIST_EMPTY(&dtors)) {
145 fprintf(stderr, "Thread %p is exiting with more "
146 "thread-specific dtors created after %d iterations "
147 "of destructor calls\n",
148 _pthread_self(), i);
149 cxa_thread_walk(walk_cb_nocall);
150 }
151 }
152