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 <sys/mman.h> 35 #include <link.h> 36 #include <stdlib.h> 37 #include <string.h> 38 39 #include "rtld_lock.h" 40 #include "thr_private.h" 41 42 #undef errno 43 extern int errno; 44 45 static int _thr_rtld_clr_flag(int); 46 static void *_thr_rtld_lock_create(void); 47 static void _thr_rtld_lock_destroy(void *); 48 static void _thr_rtld_lock_release(void *); 49 static void _thr_rtld_rlock_acquire(void *); 50 static int _thr_rtld_set_flag(int); 51 static void _thr_rtld_wlock_acquire(void *); 52 53 struct rtld_lock { 54 struct urwlock lock; 55 char _pad[CACHE_LINE_SIZE - sizeof(struct urwlock)]; 56 }; 57 58 static struct rtld_lock lock_place[MAX_RTLD_LOCKS] __aligned(CACHE_LINE_SIZE); 59 static int busy_places; 60 61 static void * 62 _thr_rtld_lock_create(void) 63 { 64 int locki; 65 struct rtld_lock *l; 66 static const char fail[] = "_thr_rtld_lock_create failed\n"; 67 68 for (locki = 0; locki < MAX_RTLD_LOCKS; locki++) { 69 if ((busy_places & (1 << locki)) == 0) 70 break; 71 } 72 if (locki == MAX_RTLD_LOCKS) { 73 write(2, fail, sizeof(fail) - 1); 74 return (NULL); 75 } 76 busy_places |= (1 << locki); 77 78 l = &lock_place[locki]; 79 l->lock.rw_flags = URWLOCK_PREFER_READER; 80 return (l); 81 } 82 83 static void 84 _thr_rtld_lock_destroy(void *lock) 85 { 86 int locki; 87 size_t i; 88 89 locki = (struct rtld_lock *)lock - &lock_place[0]; 90 for (i = 0; i < sizeof(struct rtld_lock); ++i) 91 ((char *)lock)[i] = 0; 92 busy_places &= ~(1 << locki); 93 } 94 95 #define SAVE_ERRNO() { \ 96 if (curthread != _thr_initial) \ 97 errsave = curthread->error; \ 98 else \ 99 errsave = errno; \ 100 } 101 102 #define RESTORE_ERRNO() { \ 103 if (curthread != _thr_initial) \ 104 curthread->error = errsave; \ 105 else \ 106 errno = errsave; \ 107 } 108 109 static void 110 _thr_rtld_rlock_acquire(void *lock) 111 { 112 struct pthread *curthread; 113 struct rtld_lock *l; 114 int errsave; 115 116 curthread = _get_curthread(); 117 SAVE_ERRNO(); 118 l = (struct rtld_lock *)lock; 119 120 THR_CRITICAL_ENTER(curthread); 121 while (_thr_rwlock_rdlock(&l->lock, 0, NULL) != 0) 122 ; 123 curthread->rdlock_count++; 124 RESTORE_ERRNO(); 125 } 126 127 static void 128 _thr_rtld_wlock_acquire(void *lock) 129 { 130 struct pthread *curthread; 131 struct rtld_lock *l; 132 int errsave; 133 134 curthread = _get_curthread(); 135 SAVE_ERRNO(); 136 l = (struct rtld_lock *)lock; 137 138 THR_CRITICAL_ENTER(curthread); 139 while (_thr_rwlock_wrlock(&l->lock, NULL) != 0) 140 ; 141 RESTORE_ERRNO(); 142 } 143 144 static void 145 _thr_rtld_lock_release(void *lock) 146 { 147 struct pthread *curthread; 148 struct rtld_lock *l; 149 int32_t state; 150 int errsave; 151 152 curthread = _get_curthread(); 153 SAVE_ERRNO(); 154 l = (struct rtld_lock *)lock; 155 156 state = l->lock.rw_state; 157 if (_thr_rwlock_unlock(&l->lock) == 0) { 158 if ((state & URWLOCK_WRITE_OWNER) == 0) 159 curthread->rdlock_count--; 160 THR_CRITICAL_LEAVE(curthread); 161 } 162 RESTORE_ERRNO(); 163 } 164 165 static int 166 _thr_rtld_set_flag(int mask __unused) 167 { 168 /* 169 * The caller's code in rtld-elf is broken, it is not signal safe, 170 * just return zero to fool it. 171 */ 172 return (0); 173 } 174 175 static int 176 _thr_rtld_clr_flag(int mask __unused) 177 { 178 return (0); 179 } 180 181 void 182 _thr_rtld_init(void) 183 { 184 struct RtldLockInfo li; 185 struct pthread *curthread; 186 long dummy = -1; 187 188 curthread = _get_curthread(); 189 190 /* force to resolve _umtx_op PLT */ 191 _umtx_op_err((struct umtx *)&dummy, UMTX_OP_WAKE, 1, 0, 0); 192 193 /* force to resolve errno() PLT */ 194 __error(); 195 196 /* force to resolve memcpy PLT */ 197 memcpy(&dummy, &dummy, sizeof(dummy)); 198 199 mprotect(NULL, 0, 0); 200 _rtld_get_stack_prot(); 201 202 li.lock_create = _thr_rtld_lock_create; 203 li.lock_destroy = _thr_rtld_lock_destroy; 204 li.rlock_acquire = _thr_rtld_rlock_acquire; 205 li.wlock_acquire = _thr_rtld_wlock_acquire; 206 li.lock_release = _thr_rtld_lock_release; 207 li.thread_set_flag = _thr_rtld_set_flag; 208 li.thread_clr_flag = _thr_rtld_clr_flag; 209 li.at_fork = NULL; 210 211 /* mask signals, also force to resolve __sys_sigprocmask PLT */ 212 _thr_signal_block(curthread); 213 _rtld_thread_init(&li); 214 _thr_signal_unblock(curthread); 215 } 216