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/cdefs.h> 32 __FBSDID("$FreeBSD$"); 33 34 #include <sys/queue.h> 35 #include "namespace.h" 36 #include <errno.h> 37 #include <link.h> 38 #include <pthread.h> 39 #include <stddef.h> 40 #include <stdlib.h> 41 #include <stdio.h> 42 #include "un-namespace.h" 43 #include "libc_private.h" 44 45 /* 46 * C++11 introduces the thread_local scope (like __thread with some 47 * additions). As a key-feature it should support non-trivial 48 * destructors, registered with __cxa_thread_atexit() to be executed 49 * at the thread termination. 50 * 51 * The implemention keeps a _Thread_local list of destructors per each 52 * thread, and calls __cxa_thread_call_dtors() on each thread's exit 53 * to do cleanup. For a thread calling exit(3), in particular, for 54 * the initial thread returning from main(), we call 55 * __cxa_thread_call_dtors() inside exit(). 56 * 57 * It could be possible that a dynamically loaded library, use 58 * thread_local variable but is dlclose()'d before thread exit. The 59 * destructor of this variable will then try to access the address, 60 * for calling it but it's unloaded, so it'll crash. We're using 61 * __elf_phdr_match_addr() to detect and prevent such cases and so 62 * prevent the crash. 63 */ 64 65 #define CXA_DTORS_ITERATIONS 4 66 67 struct cxa_thread_dtor { 68 void *obj; 69 void (*func)(void *); 70 void *dso; 71 LIST_ENTRY(cxa_thread_dtor) entry; 72 }; 73 static _Thread_local LIST_HEAD(dtor_list, cxa_thread_dtor) dtors = 74 LIST_HEAD_INITIALIZER(dtors); 75 76 int 77 __cxa_thread_atexit_impl(void (*dtor_func)(void *), void *obj, 78 void *dso_symbol) 79 { 80 81 return (__cxa_thread_atexit_hidden(dtor_func, obj, dso_symbol)); 82 } 83 84 int 85 __cxa_thread_atexit_hidden(void (*dtor_func)(void *), void *obj, 86 void *dso_symbol) 87 { 88 struct cxa_thread_dtor *new_dtor; 89 90 new_dtor = malloc(sizeof(*new_dtor)); 91 if (new_dtor == NULL) { 92 errno = ENOMEM; /* forcibly override malloc(3) error */ 93 return (-1); 94 } 95 96 new_dtor->obj = obj; 97 new_dtor->func = dtor_func; 98 new_dtor->dso = dso_symbol; 99 LIST_INSERT_HEAD(&dtors, new_dtor, entry); 100 return (0); 101 } 102 103 static void 104 walk_cb_call(struct cxa_thread_dtor *dtor) 105 { 106 struct dl_phdr_info phdr_info; 107 108 if (_rtld_addr_phdr(dtor->dso, &phdr_info) && 109 __elf_phdr_match_addr(&phdr_info, dtor->func)) 110 dtor->func(dtor->obj); 111 else 112 fprintf(stderr, "__cxa_thread_call_dtors: dtr %p from " 113 "unloaded dso, skipping\n", (void *)(dtor->func)); 114 } 115 116 static void 117 walk_cb_nocall(struct cxa_thread_dtor *dtor __unused) 118 { 119 } 120 121 static void 122 cxa_thread_walk(void (*cb)(struct cxa_thread_dtor *)) 123 { 124 struct cxa_thread_dtor *dtor, *tdtor; 125 126 LIST_FOREACH_SAFE(dtor, &dtors, entry, tdtor) { 127 LIST_REMOVE(dtor, entry); 128 cb(dtor); 129 free(dtor); 130 } 131 } 132 133 /* 134 * This is the callback function we use to call destructors, once for 135 * each thread. It is called in exit(3) in libc/stdlib/exit.c and 136 * before exit_thread() in libthr/thread/thr_exit.c. 137 */ 138 void 139 __cxa_thread_call_dtors(void) 140 { 141 int i; 142 143 for (i = 0; i < CXA_DTORS_ITERATIONS && !LIST_EMPTY(&dtors); i++) 144 cxa_thread_walk(walk_cb_call); 145 146 if (!LIST_EMPTY(&dtors)) { 147 fprintf(stderr, "Thread %p is exiting with more " 148 "thread-specific dtors created after %d iterations " 149 "of destructor calls\n", 150 _pthread_self(), i); 151 cxa_thread_walk(walk_cb_nocall); 152 } 153 } 154