| 1 | /*- |
| 2 | * Copyright 1999, 2000 John D. Polstra. |
| 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, this list of conditions and the following disclaimer. |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright |
| 11 | * notice, this list of conditions and the following disclaimer in the |
| 12 | * documentation and/or other materials provided with the distribution. |
| 13 | * |
| 14 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| 15 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| 16 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 17 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 18 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| 19 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 20 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 21 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 22 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 23 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 24 | * |
| 25 | * from: FreeBSD: src/libexec/rtld-elf/sparc64/lockdflt.c,v 1.3 2002/10/09 |
| 26 | * $FreeBSD$ |
| 27 | */ |
| 28 | |
| 29 | /* |
| 30 | * Thread locking implementation for the dynamic linker. |
| 31 | * |
| 32 | * We use the "simple, non-scalable reader-preference lock" from: |
| 33 | * |
| 34 | * J. M. Mellor-Crummey and M. L. Scott. "Scalable Reader-Writer |
| 35 | * Synchronization for Shared-Memory Multiprocessors." 3rd ACM Symp. on |
| 36 | * Principles and Practice of Parallel Programming, April 1991. |
| 37 | * |
| 38 | * In this algorithm the lock is a single word. Its low-order bit is |
| 39 | * set when a writer holds the lock. The remaining high-order bits |
| 40 | * contain a count of readers desiring the lock. The algorithm requires |
| 41 | * atomic "compare_and_store" and "add" operations, which we implement |
| 42 | * using assembly language sequences in "rtld_start.S". |
| 43 | */ |
| 44 | |
| 45 | #include <sys/param.h> |
| 46 | #include <signal.h> |
| 47 | #include <stdlib.h> |
| 48 | #include <time.h> |
| 49 | |
| 50 | #include "debug.h" |
| 51 | #include "rtld.h" |
| 52 | #include "rtld_machdep.h" |
| 53 | |
| 54 | #define WAFLAG 0x1 /* A writer holds the lock */ |
| 55 | #define RC_INCR 0x2 /* Adjusts count of readers desiring lock */ |
| 56 | |
| 57 | typedef struct Struct_Lock { |
| 58 | volatile u_int lock; |
| 59 | void *base; |
| 60 | } Lock; |
| 61 | |
| 62 | static sigset_t fullsigmask, oldsigmask; |
| 63 | static int thread_flag; |
| 64 | |
| 65 | static void * |
| 66 | def_lock_create(void) |
| 67 | { |
| 68 | void *base; |
| 69 | char *p; |
| 70 | uintptr_t r; |
| 71 | Lock *l; |
| 72 | |
| 73 | /* |
| 74 | * Arrange for the lock to occupy its own cache line. First, we |
| 75 | * optimistically allocate just a cache line, hoping that malloc |
| 76 | * will give us a well-aligned block of memory. If that doesn't |
| 77 | * work, we allocate a larger block and take a well-aligned cache |
| 78 | * line from it. |
| 79 | */ |
| 80 | base = xmalloc(CACHE_LINE_SIZE); |
| 81 | p = (char *)base; |
| 82 | if ((uintptr_t)p % CACHE_LINE_SIZE != 0) { |
| 83 | free(base); |
| 84 | base = xmalloc(2 * CACHE_LINE_SIZE); |
| 85 | p = (char *)base; |
| 86 | if ((r = (uintptr_t)p % CACHE_LINE_SIZE) != 0) |
| 87 | p += CACHE_LINE_SIZE - r; |
| 88 | } |
| 89 | l = (Lock *)p; |
| 90 | l->base = base; |
| 91 | l->lock = 0; |
| 92 | return l; |
| 93 | } |
| 94 | |
| 95 | static void |
| 96 | def_lock_destroy(void *lock) |
| 97 | { |
| 98 | Lock *l = (Lock *)lock; |
| 99 | |
| 100 | free(l->base); |
| 101 | } |
| 102 | |
| 103 | static void |
| 104 | def_rlock_acquire(void *lock) |
| 105 | { |
| 106 | Lock *l = (Lock *)lock; |
| 107 | |
| 108 | atomic_add_acq_int(&l->lock, RC_INCR); |
| 109 | while (l->lock & WAFLAG) |
| 110 | ; /* Spin */ |
| 111 | } |
| 112 | |
| 113 | static void |
| 114 | def_wlock_acquire(void *lock) |
| 115 | { |
| 116 | Lock *l = (Lock *)lock; |
| 117 | sigset_t tmp_oldsigmask; |
| 118 | |
| 119 | for ( ; ; ) { |
| 120 | sigprocmask(SIG_BLOCK, &fullsigmask, &tmp_oldsigmask); |
| 121 | if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG)) |
| 122 | break; |
| 123 | sigprocmask(SIG_SETMASK, &tmp_oldsigmask, NULL); |
| 124 | } |
| 125 | oldsigmask = tmp_oldsigmask; |
| 126 | } |
| 127 | |
| 128 | static void |
| 129 | def_lock_release(void *lock) |
| 130 | { |
| 131 | Lock *l = (Lock *)lock; |
| 132 | |
| 133 | if ((l->lock & WAFLAG) == 0) |
| 134 | atomic_add_rel_int(&l->lock, -RC_INCR); |
| 135 | else { |
| 136 | atomic_add_rel_int(&l->lock, -WAFLAG); |
| 137 | sigprocmask(SIG_SETMASK, &oldsigmask, NULL); |
| 138 | } |
| 139 | } |
| 140 | |
| 141 | static int |
| 142 | def_thread_set_flag(int mask) |
| 143 | { |
| 144 | int old_val = thread_flag; |
| 145 | thread_flag |= mask; |
| 146 | return (old_val); |
| 147 | } |
| 148 | |
| 149 | static int |
| 150 | def_thread_clr_flag(int mask) |
| 151 | { |
| 152 | int old_val = thread_flag; |
| 153 | thread_flag &= ~mask; |
| 154 | return (old_val); |
| 155 | } |
| 156 | |
| 157 | /* |
| 158 | * Public interface exposed to the rest of the dynamic linker. |
| 159 | */ |
| 160 | static struct RtldLockInfo lockinfo; |
| 161 | static struct RtldLockInfo deflockinfo; |
| 162 | |
| 163 | static __inline int |
| 164 | thread_mask_set(int mask) |
| 165 | { |
| 166 | return lockinfo.thread_set_flag(mask); |
| 167 | } |
| 168 | |
| 169 | static __inline void |
| 170 | thread_mask_clear(int mask) |
| 171 | { |
| 172 | lockinfo.thread_clr_flag(mask); |
| 173 | } |
| 174 | |
| 175 | #define RTLD_LOCK_CNT 3 |
| 176 | struct rtld_lock { |
| 177 | void *handle; |
| 178 | int mask; |
| 179 | } rtld_locks[RTLD_LOCK_CNT]; |
| 180 | |
| 181 | rtld_lock_t rtld_bind_lock = &rtld_locks[0]; |
| 182 | rtld_lock_t rtld_libc_lock = &rtld_locks[1]; |
| 183 | rtld_lock_t rtld_phdr_lock = &rtld_locks[2]; |
| 184 | |
| 185 | void |
| 186 | rlock_acquire(rtld_lock_t lock, RtldLockState *lockstate) |
| 187 | { |
| 188 | |
| 189 | if (lockstate == NULL) |
| 190 | return; |
| 191 | |
| 192 | if (thread_mask_set(lock->mask) & lock->mask) { |
| 193 | dbg("rlock_acquire: recursed"); |
| 194 | lockstate->lockstate = RTLD_LOCK_UNLOCKED; |
| 195 | return; |
| 196 | } |
| 197 | lockinfo.rlock_acquire(lock->handle); |
| 198 | lockstate->lockstate = RTLD_LOCK_RLOCKED; |
| 199 | } |
| 200 | |
| 201 | void |
| 202 | wlock_acquire(rtld_lock_t lock, RtldLockState *lockstate) |
| 203 | { |
| 204 | |
| 205 | if (lockstate == NULL) |
| 206 | return; |
| 207 | |
| 208 | if (thread_mask_set(lock->mask) & lock->mask) { |
| 209 | dbg("wlock_acquire: recursed"); |
| 210 | lockstate->lockstate = RTLD_LOCK_UNLOCKED; |
| 211 | return; |
| 212 | } |
| 213 | lockinfo.wlock_acquire(lock->handle); |
| 214 | lockstate->lockstate = RTLD_LOCK_WLOCKED; |
| 215 | } |
| 216 | |
| 217 | void |
| 218 | lock_release(rtld_lock_t lock, RtldLockState *lockstate) |
| 219 | { |
| 220 | |
| 221 | if (lockstate == NULL) |
| 222 | return; |
| 223 | |
| 224 | switch (lockstate->lockstate) { |
| 225 | case RTLD_LOCK_UNLOCKED: |
| 226 | break; |
| 227 | case RTLD_LOCK_RLOCKED: |
| 228 | case RTLD_LOCK_WLOCKED: |
| 229 | thread_mask_clear(lock->mask); |
| 230 | lockinfo.lock_release(lock->handle); |
| 231 | break; |
| 232 | default: |
| 233 | assert(0); |
| 234 | } |
| 235 | } |
| 236 | |
| 237 | void |
| 238 | lock_upgrade(rtld_lock_t lock, RtldLockState *lockstate) |
| 239 | { |
| 240 | |
| 241 | if (lockstate == NULL) |
| 242 | return; |
| 243 | |
| 244 | lock_release(lock, lockstate); |
| 245 | wlock_acquire(lock, lockstate); |
| 246 | } |
| 247 | |
| 248 | void |
| 249 | lock_restart_for_upgrade(RtldLockState *lockstate) |
| 250 | { |
| 251 | |
| 252 | if (lockstate == NULL) |
| 253 | return; |
| 254 | |
| 255 | switch (lockstate->lockstate) { |
| 256 | case RTLD_LOCK_UNLOCKED: |
| 257 | case RTLD_LOCK_WLOCKED: |
| 258 | break; |
| 259 | case RTLD_LOCK_RLOCKED: |
| 260 | siglongjmp(lockstate->env, 1); |
| 261 | break; |
| 262 | default: |
| 263 | assert(0); |
| 264 | } |
| 265 | } |
| 266 | |
| 267 | void |
| 268 | lockdflt_init(void) |
| 269 | { |
| 270 | int i; |
| 271 | |
| 272 | deflockinfo.rtli_version = RTLI_VERSION; |
| 273 | deflockinfo.lock_create = def_lock_create; |
| 274 | deflockinfo.lock_destroy = def_lock_destroy; |
| 275 | deflockinfo.rlock_acquire = def_rlock_acquire; |
| 276 | deflockinfo.wlock_acquire = def_wlock_acquire; |
| 277 | deflockinfo.lock_release = def_lock_release; |
| 278 | deflockinfo.thread_set_flag = def_thread_set_flag; |
| 279 | deflockinfo.thread_clr_flag = def_thread_clr_flag; |
| 280 | deflockinfo.at_fork = NULL; |
| 281 | |
| 282 | for (i = 0; i < RTLD_LOCK_CNT; i++) { |
| 283 | rtld_locks[i].mask = (1 << i); |
| 284 | rtld_locks[i].handle = NULL; |
| 285 | } |
| 286 | |
| 287 | memcpy(&lockinfo, &deflockinfo, sizeof(lockinfo)); |
| 288 | _rtld_thread_init(NULL); |
| 289 | /* |
| 290 | * Construct a mask to block all signals except traps which might |
| 291 | * conceivably be generated within the dynamic linker itself. |
| 292 | */ |
| 293 | sigfillset(&fullsigmask); |
| 294 | sigdelset(&fullsigmask, SIGILL); |
| 295 | sigdelset(&fullsigmask, SIGTRAP); |
| 296 | sigdelset(&fullsigmask, SIGABRT); |
| 297 | sigdelset(&fullsigmask, SIGEMT); |
| 298 | sigdelset(&fullsigmask, SIGFPE); |
| 299 | sigdelset(&fullsigmask, SIGBUS); |
| 300 | sigdelset(&fullsigmask, SIGSEGV); |
| 301 | sigdelset(&fullsigmask, SIGSYS); |
| 302 | } |
| 303 | |
| 304 | /* |
| 305 | * Callback function to allow threads implementation to |
| 306 | * register their own locking primitives if the default |
| 307 | * one is not suitable. |
| 308 | * The current context should be the only context |
| 309 | * executing at the invocation time. |
| 310 | */ |
| 311 | void |
| 312 | _rtld_thread_init(struct RtldLockInfo *pli) |
| 313 | { |
| 314 | int flags, i; |
| 315 | void *locks[RTLD_LOCK_CNT]; |
| 316 | |
| 317 | /* disable all locking while this function is running */ |
| 318 | flags = thread_mask_set(~0); |
| 319 | |
| 320 | if (pli == NULL) |
| 321 | pli = &deflockinfo; |
| 322 | |
| 323 | |
| 324 | for (i = 0; i < RTLD_LOCK_CNT; i++) |
| 325 | if ((locks[i] = pli->lock_create()) == NULL) |
| 326 | break; |
| 327 | |
| 328 | if (i < RTLD_LOCK_CNT) { |
| 329 | while (--i >= 0) |
| 330 | pli->lock_destroy(locks[i]); |
| 331 | abort(); |
| 332 | } |
| 333 | |
| 334 | for (i = 0; i < RTLD_LOCK_CNT; i++) { |
| 335 | if (rtld_locks[i].handle == NULL) |
| 336 | continue; |
| 337 | if (flags & rtld_locks[i].mask) |
| 338 | lockinfo.lock_release(rtld_locks[i].handle); |
| 339 | lockinfo.lock_destroy(rtld_locks[i].handle); |
| 340 | } |
| 341 | |
| 342 | for (i = 0; i < RTLD_LOCK_CNT; i++) { |
| 343 | rtld_locks[i].handle = locks[i]; |
| 344 | if (flags & rtld_locks[i].mask) |
| 345 | pli->wlock_acquire(rtld_locks[i].handle); |
| 346 | } |
| 347 | |
| 348 | lockinfo.lock_create = pli->lock_create; |
| 349 | lockinfo.lock_destroy = pli->lock_destroy; |
| 350 | lockinfo.rlock_acquire = pli->rlock_acquire; |
| 351 | lockinfo.wlock_acquire = pli->wlock_acquire; |
| 352 | lockinfo.lock_release = pli->lock_release; |
| 353 | lockinfo.thread_set_flag = pli->thread_set_flag; |
| 354 | lockinfo.thread_clr_flag = pli->thread_clr_flag; |
| 355 | lockinfo.at_fork = pli->at_fork; |
| 356 | |
| 357 | /* restore thread locking state, this time with new locks */ |
| 358 | thread_mask_clear(~0); |
| 359 | thread_mask_set(flags); |
| 360 | dbg("_rtld_thread_init: done"); |
| 361 | } |