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 * $FreeBSD$ 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 40 extern int errno; 41 42 #define CACHE_LINE_SIZE 64 43 44 static int _thr_rtld_clr_flag(int); 45 static void *_thr_rtld_lock_create(void); 46 static void _thr_rtld_lock_destroy(void *); 47 static void _thr_rtld_lock_release(void *); 48 static void _thr_rtld_rlock_acquire(void *); 49 static int _thr_rtld_set_flag(int); 50 static void _thr_rtld_wlock_acquire(void *); 51 52 struct rtld_lock { 53 struct urwlock lock; 54 void *base; 55 }; 56 57 static void * 58 _thr_rtld_lock_create(void) 59 { 60 void *base; 61 char *p; 62 uintptr_t r; 63 struct rtld_lock *l; 64 size_t size; 65 66 size = CACHE_LINE_SIZE; 67 while (size < sizeof(struct rtld_lock)) 68 size <<= 1; 69 base = calloc(1, size); 70 p = (char *)base; 71 if ((uintptr_t)p % CACHE_LINE_SIZE != 0) { 72 free(base); 73 base = calloc(1, size + CACHE_LINE_SIZE); 74 p = (char *)base; 75 if ((r = (uintptr_t)p % CACHE_LINE_SIZE) != 0) 76 p += CACHE_LINE_SIZE - r; 77 } 78 l = (struct rtld_lock *)p; 79 l->lock.rw_flags = URWLOCK_PREFER_READER; 80 l->base = base; 81 return (l); 82 } 83 84 static void 85 _thr_rtld_lock_destroy(void *lock) 86 { 87 struct rtld_lock *l = (struct rtld_lock *)lock; 88 free(l->base); 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 } 104 105 static 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 } 121 122 static 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 } 138 139 static 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 } 161 162 static 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 } 171 172 static int 173 _thr_rtld_clr_flag(int mask __unused) 174 { 175 return (0); 176 } 177 178 void 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 } 207 208 void 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