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: releng/10.2/lib/libthr/thread/thr_rtld.c 267200 2014-06-07 02:45:24Z kib $ 27 * 28 */ 29 30 /* 31 * A lockless rwlock for rtld. 32 */ 33#include <sys/cdefs.h> 34#include <sys/mman.h> 35#include <sys/syscall.h> 36#include <link.h> 37#include <stdlib.h> 38#include <string.h> 39 40#include "libc_private.h" 41#include "rtld_lock.h" 42#include "thr_private.h" 43 44#undef errno 45extern int errno; 46 47static int _thr_rtld_clr_flag(int); 48static void *_thr_rtld_lock_create(void); 49static void _thr_rtld_lock_destroy(void *); 50static void _thr_rtld_lock_release(void *); 51static void _thr_rtld_rlock_acquire(void *); 52static int _thr_rtld_set_flag(int); 53static void _thr_rtld_wlock_acquire(void *); 54 55struct rtld_lock { 56 struct urwlock lock; 57 char _pad[CACHE_LINE_SIZE - sizeof(struct urwlock)]; 58}; 59 60static struct rtld_lock lock_place[MAX_RTLD_LOCKS] __aligned(CACHE_LINE_SIZE); 61static int busy_places; 62 63static void * 64_thr_rtld_lock_create(void) 65{ 66 int locki; 67 struct rtld_lock *l; 68 static const char fail[] = "_thr_rtld_lock_create failed\n"; 69 70 for (locki = 0; locki < MAX_RTLD_LOCKS; locki++) { 71 if ((busy_places & (1 << locki)) == 0) 72 break; 73 } 74 if (locki == MAX_RTLD_LOCKS) { 75 write(2, fail, sizeof(fail) - 1); 76 return (NULL); 77 } 78 busy_places |= (1 << locki); 79 80 l = &lock_place[locki]; 81 l->lock.rw_flags = URWLOCK_PREFER_READER; 82 return (l); 83} 84 85static void 86_thr_rtld_lock_destroy(void *lock) 87{ 88 int locki; 89 size_t i; 90 91 locki = (struct rtld_lock *)lock - &lock_place[0]; 92 for (i = 0; i < sizeof(struct rtld_lock); ++i) 93 ((char *)lock)[i] = 0; 94 busy_places &= ~(1 << locki); 95} 96 97#define SAVE_ERRNO() { \ 98 if (curthread != _thr_initial) \ 99 errsave = curthread->error; \ 100 else \ 101 errsave = errno; \ 102} 103 104#define RESTORE_ERRNO() { \ 105 if (curthread != _thr_initial) \ 106 curthread->error = errsave; \ 107 else \ 108 errno = errsave; \ 109} 110 111static void 112_thr_rtld_rlock_acquire(void *lock) 113{ 114 struct pthread *curthread; 115 struct rtld_lock *l; 116 int errsave; 117 118 curthread = _get_curthread(); 119 SAVE_ERRNO(); 120 l = (struct rtld_lock *)lock; 121 122 THR_CRITICAL_ENTER(curthread); 123 while (_thr_rwlock_rdlock(&l->lock, 0, NULL) != 0) 124 ; 125 curthread->rdlock_count++; 126 RESTORE_ERRNO(); 127} 128 129static void 130_thr_rtld_wlock_acquire(void *lock) 131{ 132 struct pthread *curthread; 133 struct rtld_lock *l; 134 int errsave; 135 136 curthread = _get_curthread(); 137 SAVE_ERRNO(); 138 l = (struct rtld_lock *)lock; 139 140 THR_CRITICAL_ENTER(curthread); 141 while (_thr_rwlock_wrlock(&l->lock, NULL) != 0) 142 ; 143 RESTORE_ERRNO(); 144} 145 146static void 147_thr_rtld_lock_release(void *lock) 148{ 149 struct pthread *curthread; 150 struct rtld_lock *l; 151 int32_t state; 152 int errsave; 153 154 curthread = _get_curthread(); 155 SAVE_ERRNO(); 156 l = (struct rtld_lock *)lock; 157 158 state = l->lock.rw_state; 159 if (_thr_rwlock_unlock(&l->lock) == 0) { 160 if ((state & URWLOCK_WRITE_OWNER) == 0) 161 curthread->rdlock_count--; 162 THR_CRITICAL_LEAVE(curthread); 163 } 164 RESTORE_ERRNO(); 165} 166 167static int 168_thr_rtld_set_flag(int mask __unused) 169{ 170 /* 171 * The caller's code in rtld-elf is broken, it is not signal safe, 172 * just return zero to fool it. 173 */ 174 return (0); 175} 176 177static int 178_thr_rtld_clr_flag(int mask __unused) 179{ 180 return (0); 181} 182 183void 184_thr_rtld_init(void) 185{ 186 struct RtldLockInfo li; 187 struct pthread *curthread; 188 long dummy = -1; 189 190 curthread = _get_curthread(); 191 192 /* force to resolve _umtx_op PLT */ 193 _umtx_op_err((struct umtx *)&dummy, UMTX_OP_WAKE, 1, 0, 0); 194 195 /* force to resolve errno() PLT */ 196 __error(); 197 198 /* force to resolve memcpy PLT */ 199 memcpy(&dummy, &dummy, sizeof(dummy)); 200 201 mprotect(NULL, 0, 0); 202 _rtld_get_stack_prot(); 203 204 li.lock_create = _thr_rtld_lock_create; 205 li.lock_destroy = _thr_rtld_lock_destroy; 206 li.rlock_acquire = _thr_rtld_rlock_acquire; 207 li.wlock_acquire = _thr_rtld_wlock_acquire; 208 li.lock_release = _thr_rtld_lock_release; 209 li.thread_set_flag = _thr_rtld_set_flag; 210 li.thread_clr_flag = _thr_rtld_clr_flag; 211 li.at_fork = NULL; 212 213 /* 214 * Preresolve the symbols needed for the fork interposer. We 215 * call _rtld_atfork_pre() and _rtld_atfork_post() with NULL 216 * argument to indicate that no actual locking inside the 217 * functions should happen. Neither rtld compat locks nor 218 * libthr rtld locks cannot work there: 219 * - compat locks do not handle the case of two locks taken 220 * in write mode (the signal mask for the thread is corrupted); 221 * - libthr locks would work, but locked rtld_bind_lock prevents 222 * symbol resolution for _rtld_atfork_post. 223 */ 224 _rtld_atfork_pre(NULL); 225 _rtld_atfork_post(NULL); 226 _malloc_prefork(); 227 _malloc_postfork(); 228 syscall(SYS_getpid); 229 230 /* mask signals, also force to resolve __sys_sigprocmask PLT */ 231 _thr_signal_block(curthread); 232 _rtld_thread_init(&li); 233 _thr_signal_unblock(curthread); 234} 235