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 #include <string.h> 36 37 #include "rtld_lock.h" 38 #include "thr_private.h" 39 40 #undef errno 41 extern int errno; 42 43 static int _thr_rtld_clr_flag(int); 44 static void *_thr_rtld_lock_create(void); 45 static void _thr_rtld_lock_destroy(void *); 46 static void _thr_rtld_lock_release(void *); 47 static void _thr_rtld_rlock_acquire(void *); 48 static int _thr_rtld_set_flag(int); 49 static void _thr_rtld_wlock_acquire(void *); 50 51 struct rtld_lock { 52 struct urwlock lock; 53 char _pad[CACHE_LINE_SIZE - sizeof(struct urwlock)]; 54 }; 55 56 static struct rtld_lock lock_place[MAX_RTLD_LOCKS] __aligned(CACHE_LINE_SIZE); 57 static int busy_places; 58 59 static void * 60 _thr_rtld_lock_create(void) 61 { 62 int locki; 63 struct rtld_lock *l; 64 static const char fail[] = "_thr_rtld_lock_create failed\n"; 65 66 for (locki = 0; locki < MAX_RTLD_LOCKS; locki++) { 67 if ((busy_places & (1 << locki)) == 0) 68 break; 69 } 70 if (locki == MAX_RTLD_LOCKS) { 71 write(2, fail, sizeof(fail) - 1); 72 return (NULL); 73 } 74 busy_places |= (1 << locki); 75 76 l = &lock_place[locki]; 77 l->lock.rw_flags = URWLOCK_PREFER_READER; 78 return (l); 79 } 80 81 static void 82 _thr_rtld_lock_destroy(void *lock) 83 { 84 int locki; 85 size_t i; 86 87 locki = (struct rtld_lock *)lock - &lock_place[0]; 88 for (i = 0; i < sizeof(struct rtld_lock); ++i) 89 ((char *)lock)[i] = 0; 90 busy_places &= ~(1 << locki); 91 } 92 93 #define SAVE_ERRNO() { \ 94 if (curthread != _thr_initial) \ 95 errsave = curthread->error; \ 96 else \ 97 errsave = errno; \ 98 } 99 100 #define RESTORE_ERRNO() { \ 101 if (curthread != _thr_initial) \ 102 curthread->error = errsave; \ 103 else \ 104 errno = errsave; \ 105 } 106 107 static void 108 _thr_rtld_rlock_acquire(void *lock) 109 { 110 struct pthread *curthread; 111 struct rtld_lock *l; 112 int errsave; 113 114 curthread = _get_curthread(); 115 SAVE_ERRNO(); 116 l = (struct rtld_lock *)lock; 117 118 THR_CRITICAL_ENTER(curthread); 119 while (_thr_rwlock_rdlock(&l->lock, 0, NULL) != 0) 120 ; 121 curthread->rdlock_count++; 122 RESTORE_ERRNO(); 123 } 124 125 static void 126 _thr_rtld_wlock_acquire(void *lock) 127 { 128 struct pthread *curthread; 129 struct rtld_lock *l; 130 int errsave; 131 132 curthread = _get_curthread(); 133 SAVE_ERRNO(); 134 l = (struct rtld_lock *)lock; 135 136 THR_CRITICAL_ENTER(curthread); 137 while (_thr_rwlock_wrlock(&l->lock, NULL) != 0) 138 ; 139 RESTORE_ERRNO(); 140 } 141 142 static void 143 _thr_rtld_lock_release(void *lock) 144 { 145 struct pthread *curthread; 146 struct rtld_lock *l; 147 int32_t state; 148 int errsave; 149 150 curthread = _get_curthread(); 151 SAVE_ERRNO(); 152 l = (struct rtld_lock *)lock; 153 154 state = l->lock.rw_state; 155 if (_thr_rwlock_unlock(&l->lock) == 0) { 156 if ((state & URWLOCK_WRITE_OWNER) == 0) 157 curthread->rdlock_count--; 158 THR_CRITICAL_LEAVE(curthread); 159 } 160 RESTORE_ERRNO(); 161 } 162 163 static int 164 _thr_rtld_set_flag(int mask __unused) 165 { 166 /* 167 * The caller's code in rtld-elf is broken, it is not signal safe, 168 * just return zero to fool it. 169 */ 170 return (0); 171 } 172 173 static int 174 _thr_rtld_clr_flag(int mask __unused) 175 { 176 return (0); 177 } 178 179 void 180 _thr_rtld_init(void) 181 { 182 struct RtldLockInfo li; 183 struct pthread *curthread; 184 long dummy = -1; 185 186 curthread = _get_curthread(); 187 188 /* force to resolve _umtx_op PLT */ 189 _umtx_op_err((struct umtx *)&dummy, UMTX_OP_WAKE, 1, 0, 0); 190 191 /* force to resolve errno() PLT */ 192 __error(); 193 194 /* force to resolve memcpy PLT */ 195 memcpy(&dummy, &dummy, sizeof(dummy)); 196 197 li.lock_create = _thr_rtld_lock_create; 198 li.lock_destroy = _thr_rtld_lock_destroy; 199 li.rlock_acquire = _thr_rtld_rlock_acquire; 200 li.wlock_acquire = _thr_rtld_wlock_acquire; 201 li.lock_release = _thr_rtld_lock_release; 202 li.thread_set_flag = _thr_rtld_set_flag; 203 li.thread_clr_flag = _thr_rtld_clr_flag; 204 li.at_fork = NULL; 205 206 /* mask signals, also force to resolve __sys_sigprocmask PLT */ 207 _thr_signal_block(curthread); 208 _rtld_thread_init(&li); 209 _thr_signal_unblock(curthread); 210 } 211 212 void 213 _thr_rtld_fini(void) 214 { 215 struct pthread *curthread; 216 217 curthread = _get_curthread(); 218 _thr_signal_block(curthread); 219 _rtld_thread_init(NULL); 220 _thr_signal_unblock(curthread); 221 } 222