sys/compat/linux/linux_futex.c

   1 /*      $NetBSD: linux_futex.c,v 1.7 2006/07/24 19:01:49 manu Exp $ */
   2
   3 /*-
   4  * SPDX-License-Identifier: BSD-4-Clause
   5  *
   6  * Copyright (c) 2009-2016 Dmitry Chagin
   7  * Copyright (c) 2005 Emmanuel Dreyfus
   8  * All rights reserved.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. All advertising materials mentioning features or use of this software
  19  *    must display the following acknowledgement:
  20  *      This product includes software developed by Emmanuel Dreyfus
  21  * 4. The name of the author may not be used to endorse or promote
  22  *    products derived from this software without specific prior written
  23  *    permission.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE THE AUTHOR AND CONTRIBUTORS ``AS IS''
  26  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  27  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  28  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
  29  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  30  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  31  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  32  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  33  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  34  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  35  * POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include <sys/cdefs.h>
  39 __FBSDID("$FreeBSD$");
  40 #if 0
  41 __KERNEL_RCSID(1, "$NetBSD: linux_futex.c,v 1.7 2006/07/24 19:01:49 manu Exp $");
  42 #endif
  43
  44 #include "opt_compat.h"
  45
  46 #include <sys/param.h>
  47 #include <sys/systm.h>
  48 #include <sys/imgact.h>
  49 #include <sys/kernel.h>
  50 #include <sys/ktr.h>
  51 #include <sys/lock.h>
  52 #include <sys/malloc.h>
  53 #include <sys/mutex.h>
  54 #include <sys/priv.h>
  55 #include <sys/proc.h>
  56 #include <sys/queue.h>
  57 #include <sys/sched.h>
  58 #include <sys/sdt.h>
  59 #include <sys/umtx.h>
  60
  61 #include <vm/vm_extern.h>
  62
  63 #ifdef COMPAT_LINUX32
  64 #include <machine/../linux32/linux.h>
  65 #include <machine/../linux32/linux32_proto.h>
  66 #else
  67 #include <machine/../linux/linux.h>
  68 #include <machine/../linux/linux_proto.h>
  69 #endif
  70 #include <compat/linux/linux_dtrace.h>
  71 #include <compat/linux/linux_emul.h>
  72 #include <compat/linux/linux_futex.h>
  73 #include <compat/linux/linux_timer.h>
  74 #include <compat/linux/linux_util.h>
  75
  76 /* DTrace init */
  77 LIN_SDT_PROVIDER_DECLARE(LINUX_DTRACE);
  78
  79 /**
  80  * Futex part for the special DTrace module "locks".
  81  */
  82 LIN_SDT_PROBE_DEFINE1(locks, futex_mtx, locked, "struct mtx *");
  83 LIN_SDT_PROBE_DEFINE1(locks, futex_mtx, unlock, "struct mtx *");
  84
  85 /**
  86  * Per futex probes.
  87  */
  88 LIN_SDT_PROBE_DEFINE1(futex, futex, create, "struct sx *");
  89 LIN_SDT_PROBE_DEFINE1(futex, futex, destroy, "struct sx *");
  90
  91 /**
  92  * DTrace probes in this module.
  93  */
  94 LIN_SDT_PROBE_DEFINE3(futex, futex_put, destroy, "uint32_t *", "uint32_t",
  95     "int");
  96 LIN_SDT_PROBE_DEFINE3(futex, futex_put, unlock, "uint32_t *", "uint32_t",
  97     "int");
  98 LIN_SDT_PROBE_DEFINE1(futex, futex_get0, umtx_key_get_error, "int");
  99 LIN_SDT_PROBE_DEFINE3(futex, futex_get0, shared, "uint32_t *", "uint32_t",
 100     "int");
 101 LIN_SDT_PROBE_DEFINE1(futex, futex_get0, null, "uint32_t *");
 102 LIN_SDT_PROBE_DEFINE3(futex, futex_get0, new, "uint32_t *", "uint32_t", "int");
 103 LIN_SDT_PROBE_DEFINE0(futex, futex_get, error);
 104 LIN_SDT_PROBE_DEFINE5(futex, futex_sleep, requeue_error, "int", "uint32_t *",
 105     "struct waiting_proc *", "uint32_t *", "uint32_t");
 106 LIN_SDT_PROBE_DEFINE3(futex, futex_sleep, sleep_error, "int", "uint32_t *",
 107     "struct waiting_proc *");
 108 LIN_SDT_PROBE_DEFINE3(futex, futex_wake, iterate, "uint32_t",
 109     "struct waiting_proc *", "uint32_t");
 110 LIN_SDT_PROBE_DEFINE1(futex, futex_wake, wakeup, "struct waiting_proc *");
 111 LIN_SDT_PROBE_DEFINE1(futex, futex_requeue, wakeup, "struct waiting_proc *");
 112 LIN_SDT_PROBE_DEFINE3(futex, futex_requeue, requeue, "uint32_t *",
 113     "struct waiting_proc *", "uint32_t");
 114 LIN_SDT_PROBE_DEFINE1(futex, futex_wait, sleep_error, "int");
 115 LIN_SDT_PROBE_DEFINE4(futex, futex_atomic_op, decoded_op, "int", "int", "int",
 116     "int");
 117 LIN_SDT_PROBE_DEFINE0(futex, futex_atomic_op, missing_access_check);
 118 LIN_SDT_PROBE_DEFINE1(futex, futex_atomic_op, unimplemented_op, "int");
 119 LIN_SDT_PROBE_DEFINE1(futex, futex_atomic_op, unimplemented_cmp, "int");
 120 LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_clockswitch);
 121 LIN_SDT_PROBE_DEFINE1(futex, linux_sys_futex, copyin_error, "int");
 122 LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, invalid_cmp_requeue_use);
 123 LIN_SDT_PROBE_DEFINE3(futex, linux_sys_futex, debug_wait, "uint32_t *",
 124     "uint32_t", "uint32_t");
 125 LIN_SDT_PROBE_DEFINE4(futex, linux_sys_futex, debug_wait_value_neq,
 126     "uint32_t *", "uint32_t", "int", "uint32_t");
 127 LIN_SDT_PROBE_DEFINE3(futex, linux_sys_futex, debug_wake, "uint32_t *",
 128     "uint32_t", "uint32_t");
 129 LIN_SDT_PROBE_DEFINE5(futex, linux_sys_futex, debug_cmp_requeue, "uint32_t *",
 130     "uint32_t", "uint32_t", "uint32_t *", "struct l_timespec *");
 131 LIN_SDT_PROBE_DEFINE2(futex, linux_sys_futex, debug_cmp_requeue_value_neq,
 132     "uint32_t", "int");
 133 LIN_SDT_PROBE_DEFINE5(futex, linux_sys_futex, debug_wake_op, "uint32_t *",
 134     "int", "uint32_t", "uint32_t *", "uint32_t");
 135 LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unhandled_efault);
 136 LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_lock_pi);
 137 LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_unlock_pi);
 138 LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_trylock_pi);
 139 LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, deprecated_requeue);
 140 LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_wait_requeue_pi);
 141 LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_cmp_requeue_pi);
 142 LIN_SDT_PROBE_DEFINE1(futex, linux_sys_futex, unknown_operation, "int");
 143 LIN_SDT_PROBE_DEFINE0(futex, linux_set_robust_list, size_error);
 144 LIN_SDT_PROBE_DEFINE1(futex, linux_get_robust_list, copyout_error, "int");
 145 LIN_SDT_PROBE_DEFINE1(futex, handle_futex_death, copyin_error, "int");
 146 LIN_SDT_PROBE_DEFINE1(futex, fetch_robust_entry, copyin_error, "int");
 147 LIN_SDT_PROBE_DEFINE1(futex, release_futexes, copyin_error, "int");
 148
 149 struct futex;
 150
 151 struct waiting_proc {
 152         uint32_t        wp_flags;
 153         struct futex    *wp_futex;
 154         TAILQ_ENTRY(waiting_proc) wp_list;
 155 };
 156
 157 struct futex {
 158         struct mtx      f_lck;
 159         uint32_t        *f_uaddr;       /* user-supplied value, for debug */
 160         struct umtx_key f_key;
 161         uint32_t        f_refcount;
 162         uint32_t        f_bitset;
 163         LIST_ENTRY(futex) f_list;
 164         TAILQ_HEAD(lf_waiting_proc, waiting_proc) f_waiting_proc;
 165 };
 166
 167 #define FUTEX_LOCK(f)           mtx_lock(&(f)->f_lck)
 168 #define FUTEX_LOCKED(f)         mtx_owned(&(f)->f_lck)
 169 #define FUTEX_UNLOCK(f)         mtx_unlock(&(f)->f_lck)
 170 #define FUTEX_INIT(f)           do { \
 171                                     mtx_init(&(f)->f_lck, "ftlk", NULL, \
 172                                         MTX_DUPOK); \
 173                                     LIN_SDT_PROBE1(futex, futex, create, \
 174                                         &(f)->f_lck); \
 175                                 } while (0)
 176 #define FUTEX_DESTROY(f)        do { \
 177                                     LIN_SDT_PROBE1(futex, futex, destroy, \
 178                                         &(f)->f_lck); \
 179                                     mtx_destroy(&(f)->f_lck); \
 180                                 } while (0)
 181 #define FUTEX_ASSERT_LOCKED(f)  mtx_assert(&(f)->f_lck, MA_OWNED)
 182 #define FUTEX_ASSERT_UNLOCKED(f) mtx_assert(&(f)->f_lck, MA_NOTOWNED)
 183
 184 #define FUTEXES_LOCK            do { \
 185                                     mtx_lock(&futex_mtx); \
 186                                     LIN_SDT_PROBE1(locks, futex_mtx, \
 187                                         locked, &futex_mtx); \
 188                                 } while (0)
 189 #define FUTEXES_UNLOCK          do { \
 190                                     LIN_SDT_PROBE1(locks, futex_mtx, \
 191                                         unlock, &futex_mtx); \
 192                                     mtx_unlock(&futex_mtx); \
 193                                 } while (0)
 194
 195 /* flags for futex_get() */
 196 #define FUTEX_CREATE_WP         0x1     /* create waiting_proc */
 197 #define FUTEX_DONTCREATE        0x2     /* don't create futex if not exists */
 198 #define FUTEX_DONTEXISTS        0x4     /* return EINVAL if futex exists */
 199 #define FUTEX_SHARED            0x8     /* shared futex */
 200 #define FUTEX_DONTLOCK          0x10    /* don't lock futex */
 201
 202 /* wp_flags */
 203 #define FUTEX_WP_REQUEUED       0x1     /* wp requeued - wp moved from wp_list
 204                                          * of futex where thread sleep to wp_list
 205                                          * of another futex.
 206                                          */
 207 #define FUTEX_WP_REMOVED        0x2     /* wp is woken up and removed from futex
 208                                          * wp_list to prevent double wakeup.
 209                                          */
 210
 211 static void futex_put(struct futex *, struct waiting_proc *);
 212 static int futex_get0(uint32_t *, struct futex **f, uint32_t);
 213 static int futex_get(uint32_t *, struct waiting_proc **, struct futex **,
 214     uint32_t);
 215 static int futex_sleep(struct futex *, struct waiting_proc *, struct timespec *);
 216 static int futex_wake(struct futex *, int, uint32_t);
 217 static int futex_requeue(struct futex *, int, struct futex *, int);
 218 static int futex_copyin_timeout(int, struct l_timespec *, int,
 219     struct timespec *);
 220 static int futex_wait(struct futex *, struct waiting_proc *, struct timespec *,
 221     uint32_t);
 222 static void futex_lock(struct futex *);
 223 static void futex_unlock(struct futex *);
 224 static int futex_atomic_op(struct thread *, int, uint32_t *);
 225 static int handle_futex_death(struct linux_emuldata *, uint32_t *,
 226     unsigned int);
 227 static int fetch_robust_entry(struct linux_robust_list **,
 228     struct linux_robust_list **, unsigned int *);
 229
 230 static int
 231 futex_copyin_timeout(int op, struct l_timespec *luts, int clockrt,
 232     struct timespec *ts)
 233 {
 234         struct l_timespec lts;
 235         struct timespec kts;
 236         int error;
 237
 238         error = copyin(luts, &lts, sizeof(lts));
 239         if (error)
 240                 return (error);
 241
 242         error = linux_to_native_timespec(ts, &lts);
 243         if (error)
 244                 return (error);
 245         if (clockrt) {
 246                 nanotime(&kts);
 247                 timespecsub(ts, &kts, ts);
 248         } else if (op == LINUX_FUTEX_WAIT_BITSET) {
 249                 nanouptime(&kts);
 250                 timespecsub(ts, &kts, ts);
 251         }
 252         return (error);
 253 }
 254
 255 static void
 256 futex_put(struct futex *f, struct waiting_proc *wp)
 257 {
 258
 259         if (wp != NULL) {
 260                 if ((wp->wp_flags & FUTEX_WP_REMOVED) == 0)
 261                         TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
 262                 free(wp, M_FUTEX_WP);
 263         }
 264
 265         FUTEXES_LOCK;
 266         if (--f->f_refcount == 0) {
 267                 LIST_REMOVE(f, f_list);
 268                 FUTEXES_UNLOCK;
 269                 if (FUTEX_LOCKED(f))
 270                         futex_unlock(f);
 271
 272                 LIN_SDT_PROBE3(futex, futex_put, destroy, f->f_uaddr,
 273                     f->f_refcount, f->f_key.shared);
 274                 LINUX_CTR3(sys_futex, "futex_put destroy uaddr %p ref %d "
 275                     "shared %d", f->f_uaddr, f->f_refcount, f->f_key.shared);
 276                 umtx_key_release(&f->f_key);
 277                 FUTEX_DESTROY(f);
 278                 free(f, M_FUTEX);
 279                 return;
 280         }
 281
 282         LIN_SDT_PROBE3(futex, futex_put, unlock, f->f_uaddr, f->f_refcount,
 283             f->f_key.shared);
 284         LINUX_CTR3(sys_futex, "futex_put uaddr %p ref %d shared %d",
 285             f->f_uaddr, f->f_refcount, f->f_key.shared);
 286         if (FUTEX_LOCKED(f))
 287                 futex_unlock(f);
 288         FUTEXES_UNLOCK;
 289 }
 290
 291 static int
 292 futex_get0(uint32_t *uaddr, struct futex **newf, uint32_t flags)
 293 {
 294         struct futex *f, *tmpf;
 295         struct umtx_key key;
 296         int error;
 297
 298         *newf = tmpf = NULL;
 299
 300         error = umtx_key_get(uaddr, TYPE_FUTEX, (flags & FUTEX_SHARED) ?
 301             AUTO_SHARE : THREAD_SHARE, &key);
 302         if (error) {
 303                 LIN_SDT_PROBE1(futex, futex_get0, umtx_key_get_error, error);
 304                 return (error);
 305         }
 306 retry:
 307         FUTEXES_LOCK;
 308         LIST_FOREACH(f, &futex_list, f_list) {
 309                 if (umtx_key_match(&f->f_key, &key)) {
 310                         if (tmpf != NULL) {
 311                                 if (FUTEX_LOCKED(tmpf))
 312                                         futex_unlock(tmpf);
 313                                 FUTEX_DESTROY(tmpf);
 314                                 free(tmpf, M_FUTEX);
 315                         }
 316                         if (flags & FUTEX_DONTEXISTS) {
 317                                 FUTEXES_UNLOCK;
 318                                 umtx_key_release(&key);
 319
 320                                 return (EINVAL);
 321                         }
 322
 323                         /*
 324                          * Increment refcount of the found futex to
 325                          * prevent it from deallocation before FUTEX_LOCK()
 326                          */
 327                         ++f->f_refcount;
 328                         FUTEXES_UNLOCK;
 329                         umtx_key_release(&key);
 330
 331                         if ((flags & FUTEX_DONTLOCK) == 0)
 332                                 futex_lock(f);
 333                         *newf = f;
 334                         LIN_SDT_PROBE3(futex, futex_get0, shared, uaddr,
 335                             f->f_refcount, f->f_key.shared);
 336                         LINUX_CTR3(sys_futex, "futex_get uaddr %p ref %d shared %d",
 337                             uaddr, f->f_refcount, f->f_key.shared);
 338
 339                         return (0);
 340                 }
 341         }
 342
 343         if (flags & FUTEX_DONTCREATE) {
 344                 FUTEXES_UNLOCK;
 345                 umtx_key_release(&key);
 346                 LIN_SDT_PROBE1(futex, futex_get0, null, uaddr);
 347                 LINUX_CTR1(sys_futex, "futex_get uaddr %p null", uaddr);
 348
 349                 return (0);
 350         }
 351
 352         if (tmpf == NULL) {
 353                 FUTEXES_UNLOCK;
 354                 tmpf = malloc(sizeof(*tmpf), M_FUTEX, M_WAITOK | M_ZERO);
 355                 tmpf->f_uaddr = uaddr;
 356                 tmpf->f_key = key;
 357                 tmpf->f_refcount = 1;
 358                 tmpf->f_bitset = FUTEX_BITSET_MATCH_ANY;
 359                 FUTEX_INIT(tmpf);
 360                 TAILQ_INIT(&tmpf->f_waiting_proc);
 361
 362                 /*
 363                  * Lock the new futex before an insert into the futex_list
 364                  * to prevent futex usage by other.
 365                  */
 366                 if ((flags & FUTEX_DONTLOCK) == 0)
 367                         futex_lock(tmpf);
 368                 goto retry;
 369         }
 370
 371         LIST_INSERT_HEAD(&futex_list, tmpf, f_list);
 372         FUTEXES_UNLOCK;
 373
 374         LIN_SDT_PROBE3(futex, futex_get0, new, uaddr, tmpf->f_refcount,
 375             tmpf->f_key.shared);
 376         LINUX_CTR3(sys_futex, "futex_get uaddr %p ref %d shared %d new",
 377             uaddr, tmpf->f_refcount, tmpf->f_key.shared);
 378         *newf = tmpf;
 379
 380         return (0);
 381 }
 382
 383 static int
 384 futex_get(uint32_t *uaddr, struct waiting_proc **wp, struct futex **f,
 385     uint32_t flags)
 386 {
 387         int error;
 388
 389         if (flags & FUTEX_CREATE_WP) {
 390                 *wp = malloc(sizeof(struct waiting_proc), M_FUTEX_WP, M_WAITOK);
 391                 (*wp)->wp_flags = 0;
 392         }
 393         error = futex_get0(uaddr, f, flags);
 394         if (error) {
 395                 LIN_SDT_PROBE0(futex, futex_get, error);
 396
 397                 if (flags & FUTEX_CREATE_WP)
 398                         free(*wp, M_FUTEX_WP);
 399
 400                 return (error);
 401         }
 402         if (flags & FUTEX_CREATE_WP) {
 403                 TAILQ_INSERT_HEAD(&(*f)->f_waiting_proc, *wp, wp_list);
 404                 (*wp)->wp_futex = *f;
 405         }
 406
 407         return (error);
 408 }
 409
 410 static inline void
 411 futex_lock(struct futex *f)
 412 {
 413
 414         LINUX_CTR3(sys_futex, "futex_lock uaddr %p ref %d shared %d",
 415             f->f_uaddr, f->f_refcount, f->f_key.shared);
 416         FUTEX_ASSERT_UNLOCKED(f);
 417         FUTEX_LOCK(f);
 418 }
 419
 420 static inline void
 421 futex_unlock(struct futex *f)
 422 {
 423
 424         LINUX_CTR3(sys_futex, "futex_unlock uaddr %p ref %d shared %d",
 425             f->f_uaddr, f->f_refcount, f->f_key.shared);
 426         FUTEX_ASSERT_LOCKED(f);
 427         FUTEX_UNLOCK(f);
 428 }
 429
 430 static int
 431 futex_sleep(struct futex *f, struct waiting_proc *wp, struct timespec *ts)
 432 {
 433         struct timespec uts;
 434         sbintime_t sbt, prec, tmp;
 435         time_t over;
 436         int error;
 437
 438         FUTEX_ASSERT_LOCKED(f);
 439         if (ts != NULL) {
 440                 uts = *ts;
 441                 if (uts.tv_sec > INT32_MAX / 2) {
 442                         over = uts.tv_sec - INT32_MAX / 2;
 443                         uts.tv_sec -= over;
 444                 }
 445                 tmp = tstosbt(uts);
 446                 if (TIMESEL(&sbt, tmp))
 447                         sbt += tc_tick_sbt;
 448                 sbt += tmp;
 449                 prec = tmp;
 450                 prec >>= tc_precexp;
 451         } else {
 452                 sbt = 0;
 453                 prec = 0;
 454         }
 455         LINUX_CTR4(sys_futex, "futex_sleep enter uaddr %p wp %p timo %ld ref %d",
 456             f->f_uaddr, wp, sbt, f->f_refcount);
 457
 458         error = msleep_sbt(wp, &f->f_lck, PCATCH, "futex", sbt, prec, C_ABSOLUTE);
 459         if (wp->wp_flags & FUTEX_WP_REQUEUED) {
 460                 KASSERT(f != wp->wp_futex, ("futex != wp_futex"));
 461
 462                 if (error) {
 463                         LIN_SDT_PROBE5(futex, futex_sleep, requeue_error, error,
 464                             f->f_uaddr, wp, wp->wp_futex->f_uaddr,
 465                             wp->wp_futex->f_refcount);
 466                 }
 467
 468                 LINUX_CTR5(sys_futex, "futex_sleep out error %d uaddr %p wp"
 469                     " %p requeued uaddr %p ref %d",
 470                     error, f->f_uaddr, wp, wp->wp_futex->f_uaddr,
 471                     wp->wp_futex->f_refcount);
 472                 futex_put(f, NULL);
 473                 f = wp->wp_futex;
 474                 futex_lock(f);
 475         } else {
 476                 if (error) {
 477                         LIN_SDT_PROBE3(futex, futex_sleep, sleep_error, error,
 478                             f->f_uaddr, wp);
 479                 }
 480                 LINUX_CTR3(sys_futex, "futex_sleep out error %d uaddr %p wp %p",
 481                     error, f->f_uaddr, wp);
 482         }
 483
 484         futex_put(f, wp);
 485
 486         return (error);
 487 }
 488
 489 static int
 490 futex_wake(struct futex *f, int n, uint32_t bitset)
 491 {
 492         struct waiting_proc *wp, *wpt;
 493         int count = 0;
 494
 495         if (bitset == 0)
 496                 return (EINVAL);
 497
 498         FUTEX_ASSERT_LOCKED(f);
 499         TAILQ_FOREACH_SAFE(wp, &f->f_waiting_proc, wp_list, wpt) {
 500                 LIN_SDT_PROBE3(futex, futex_wake, iterate, f->f_uaddr, wp,
 501                     f->f_refcount);
 502                 LINUX_CTR3(sys_futex, "futex_wake uaddr %p wp %p ref %d",
 503                     f->f_uaddr, wp, f->f_refcount);
 504                 /*
 505                  * Unless we find a matching bit in
 506                  * the bitset, continue searching.
 507                  */
 508                 if (!(wp->wp_futex->f_bitset & bitset))
 509                         continue;
 510
 511                 wp->wp_flags |= FUTEX_WP_REMOVED;
 512                 TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
 513                 LIN_SDT_PROBE1(futex, futex_wake, wakeup, wp);
 514                 wakeup_one(wp);
 515                 if (++count == n)
 516                         break;
 517         }
 518
 519         return (count);
 520 }
 521
 522 static int
 523 futex_requeue(struct futex *f, int n, struct futex *f2, int n2)
 524 {
 525         struct waiting_proc *wp, *wpt;
 526         int count = 0;
 527
 528         FUTEX_ASSERT_LOCKED(f);
 529         FUTEX_ASSERT_LOCKED(f2);
 530
 531         TAILQ_FOREACH_SAFE(wp, &f->f_waiting_proc, wp_list, wpt) {
 532                 if (++count <= n) {
 533                         LINUX_CTR2(sys_futex, "futex_req_wake uaddr %p wp %p",
 534                             f->f_uaddr, wp);
 535                         wp->wp_flags |= FUTEX_WP_REMOVED;
 536                         TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
 537                         LIN_SDT_PROBE1(futex, futex_requeue, wakeup, wp);
 538                         wakeup_one(wp);
 539                 } else {
 540                         LIN_SDT_PROBE3(futex, futex_requeue, requeue,
 541                             f->f_uaddr, wp, f2->f_uaddr);
 542                         LINUX_CTR3(sys_futex, "futex_requeue uaddr %p wp %p to %p",
 543                             f->f_uaddr, wp, f2->f_uaddr);
 544                         wp->wp_flags |= FUTEX_WP_REQUEUED;
 545                         /* Move wp to wp_list of f2 futex */
 546                         TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
 547                         TAILQ_INSERT_HEAD(&f2->f_waiting_proc, wp, wp_list);
 548
 549                         /*
 550                          * Thread which sleeps on wp after waking should
 551                          * acquire f2 lock, so increment refcount of f2 to
 552                          * prevent it from premature deallocation.
 553                          */
 554                         wp->wp_futex = f2;
 555                         FUTEXES_LOCK;
 556                         ++f2->f_refcount;
 557                         FUTEXES_UNLOCK;
 558                         if (count - n >= n2)
 559                                 break;
 560                 }
 561         }
 562
 563         return (count);
 564 }
 565
 566 static int
 567 futex_wait(struct futex *f, struct waiting_proc *wp, struct timespec *ts,
 568     uint32_t bitset)
 569 {
 570         int error;
 571
 572         if (bitset == 0) {
 573                 futex_put(f, wp);
 574                 return (EINVAL);
 575         }
 576
 577         f->f_bitset = bitset;
 578         error = futex_sleep(f, wp, ts);
 579         if (error)
 580                 LIN_SDT_PROBE1(futex, futex_wait, sleep_error, error);
 581         if (error == EWOULDBLOCK)
 582                 error = ETIMEDOUT;
 583
 584         return (error);
 585 }
 586
 587 static int
 588 futex_atomic_op(struct thread *td, int encoded_op, uint32_t *uaddr)
 589 {
 590         int op = (encoded_op >> 28) & 7;
 591         int cmp = (encoded_op >> 24) & 15;
 592         int oparg = (encoded_op << 8) >> 20;
 593         int cmparg = (encoded_op << 20) >> 20;
 594         int oldval = 0, ret;
 595
 596         if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
 597                 oparg = 1 << oparg;
 598
 599         LIN_SDT_PROBE4(futex, futex_atomic_op, decoded_op, op, cmp, oparg,
 600             cmparg);
 601
 602         /* XXX: Linux verifies access here and returns EFAULT */
 603         LIN_SDT_PROBE0(futex, futex_atomic_op, missing_access_check);
 604
 605         switch (op) {
 606         case FUTEX_OP_SET:
 607                 ret = futex_xchgl(oparg, uaddr, &oldval);
 608                 break;
 609         case FUTEX_OP_ADD:
 610                 ret = futex_addl(oparg, uaddr, &oldval);
 611                 break;
 612         case FUTEX_OP_OR:
 613                 ret = futex_orl(oparg, uaddr, &oldval);
 614                 break;
 615         case FUTEX_OP_ANDN:
 616                 ret = futex_andl(~oparg, uaddr, &oldval);
 617                 break;
 618         case FUTEX_OP_XOR:
 619                 ret = futex_xorl(oparg, uaddr, &oldval);
 620                 break;
 621         default:
 622                 LIN_SDT_PROBE1(futex, futex_atomic_op, unimplemented_op, op);
 623                 ret = -ENOSYS;
 624                 break;
 625         }
 626
 627         if (ret)
 628                 return (ret);
 629
 630         switch (cmp) {
 631         case FUTEX_OP_CMP_EQ:
 632                 ret = (oldval == cmparg);
 633                 break;
 634         case FUTEX_OP_CMP_NE:
 635                 ret = (oldval != cmparg);
 636                 break;
 637         case FUTEX_OP_CMP_LT:
 638                 ret = (oldval < cmparg);
 639                 break;
 640         case FUTEX_OP_CMP_GE:
 641                 ret = (oldval >= cmparg);
 642                 break;
 643         case FUTEX_OP_CMP_LE:
 644                 ret = (oldval <= cmparg);
 645                 break;
 646         case FUTEX_OP_CMP_GT:
 647                 ret = (oldval > cmparg);
 648                 break;
 649         default:
 650                 LIN_SDT_PROBE1(futex, futex_atomic_op, unimplemented_cmp, cmp);
 651                 ret = -ENOSYS;
 652         }
 653
 654         return (ret);
 655 }
 656
 657 int
 658 linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
 659 {
 660         int clockrt, nrwake, op_ret, ret;
 661         struct linux_pemuldata *pem;
 662         struct waiting_proc *wp;
 663         struct futex *f, *f2;
 664         struct timespec uts, *ts;
 665         int error, save;
 666         uint32_t flags, val;
 667
 668         if (args->op & LINUX_FUTEX_PRIVATE_FLAG) {
 669                 flags = 0;
 670                 args->op &= ~LINUX_FUTEX_PRIVATE_FLAG;
 671         } else
 672                 flags = FUTEX_SHARED;
 673
 674         /*
 675          * Currently support for switching between CLOCK_MONOTONIC and
 676          * CLOCK_REALTIME is not present. However Linux forbids the use of
 677          * FUTEX_CLOCK_REALTIME with any op except FUTEX_WAIT_BITSET and
 678          * FUTEX_WAIT_REQUEUE_PI.
 679          */
 680         clockrt = args->op & LINUX_FUTEX_CLOCK_REALTIME;
 681         args->op = args->op & ~LINUX_FUTEX_CLOCK_REALTIME;
 682         if (clockrt && args->op != LINUX_FUTEX_WAIT_BITSET &&
 683                 args->op != LINUX_FUTEX_WAIT_REQUEUE_PI) {
 684                 LIN_SDT_PROBE0(futex, linux_sys_futex,
 685                     unimplemented_clockswitch);
 686                 return (ENOSYS);
 687         }
 688
 689         error = 0;
 690         f = f2 = NULL;
 691
 692         switch (args->op) {
 693         case LINUX_FUTEX_WAIT:
 694                 args->val3 = FUTEX_BITSET_MATCH_ANY;
 695                 /* FALLTHROUGH */
 696
 697         case LINUX_FUTEX_WAIT_BITSET:
 698                 LIN_SDT_PROBE3(futex, linux_sys_futex, debug_wait, args->uaddr,
 699                     args->val, args->val3);
 700                 LINUX_CTR3(sys_futex, "WAIT uaddr %p val 0x%x bitset 0x%x",
 701                     args->uaddr, args->val, args->val3);
 702
 703                 if (args->timeout != NULL) {
 704                         error = futex_copyin_timeout(args->op, args->timeout,
 705                             clockrt, &uts);
 706                         if (error) {
 707                                 LIN_SDT_PROBE1(futex, linux_sys_futex, copyin_error,
 708                                     error);
 709                                 return (error);
 710                         }
 711                         ts = &uts;
 712                 } else
 713                         ts = NULL;
 714
 715 retry0:
 716                 error = futex_get(args->uaddr, &wp, &f,
 717                     flags | FUTEX_CREATE_WP);
 718                 if (error)
 719                         return (error);
 720
 721                 error = copyin_nofault(args->uaddr, &val, sizeof(val));
 722                 if (error) {
 723                         futex_put(f, wp);
 724                         error = copyin(args->uaddr, &val, sizeof(val));
 725                         if (error == 0)
 726                                 goto retry0;
 727                         LIN_SDT_PROBE1(futex, linux_sys_futex, copyin_error,
 728                             error);
 729                         LINUX_CTR1(sys_futex, "WAIT copyin failed %d",
 730                             error);
 731                         return (error);
 732                 }
 733                 if (val != args->val) {
 734                         LIN_SDT_PROBE4(futex, linux_sys_futex,
 735                             debug_wait_value_neq, args->uaddr, args->val, val,
 736                             args->val3);
 737                         LINUX_CTR3(sys_futex,
 738                             "WAIT uaddr %p val 0x%x != uval 0x%x",
 739                             args->uaddr, args->val, val);
 740                         futex_put(f, wp);
 741                         return (EWOULDBLOCK);
 742                 }
 743
 744                 error = futex_wait(f, wp, ts, args->val3);
 745                 break;
 746
 747         case LINUX_FUTEX_WAKE:
 748                 args->val3 = FUTEX_BITSET_MATCH_ANY;
 749                 /* FALLTHROUGH */
 750
 751         case LINUX_FUTEX_WAKE_BITSET:
 752                 LIN_SDT_PROBE3(futex, linux_sys_futex, debug_wake, args->uaddr,
 753                     args->val, args->val3);
 754                 LINUX_CTR3(sys_futex, "WAKE uaddr %p nrwake 0x%x bitset 0x%x",
 755                     args->uaddr, args->val, args->val3);
 756
 757                 error = futex_get(args->uaddr, NULL, &f,
 758                     flags | FUTEX_DONTCREATE);
 759                 if (error)
 760                         return (error);
 761
 762                 if (f == NULL) {
 763                         td->td_retval[0] = 0;
 764                         return (error);
 765                 }
 766                 td->td_retval[0] = futex_wake(f, args->val, args->val3);
 767                 futex_put(f, NULL);
 768                 break;
 769
 770         case LINUX_FUTEX_CMP_REQUEUE:
 771                 LIN_SDT_PROBE5(futex, linux_sys_futex, debug_cmp_requeue,
 772                     args->uaddr, args->val, args->val3, args->uaddr2,
 773                     args->timeout);
 774                 LINUX_CTR5(sys_futex, "CMP_REQUEUE uaddr %p "
 775                     "nrwake 0x%x uval 0x%x uaddr2 %p nrequeue 0x%x",
 776                     args->uaddr, args->val, args->val3, args->uaddr2,
 777                     args->timeout);
 778
 779                 /*
 780                  * Linux allows this, we would not, it is an incorrect
 781                  * usage of declared ABI, so return EINVAL.
 782                  */
 783                 if (args->uaddr == args->uaddr2) {
 784                         LIN_SDT_PROBE0(futex, linux_sys_futex,
 785                             invalid_cmp_requeue_use);
 786                         return (EINVAL);
 787                 }
 788
 789 retry1:
 790                 error = futex_get(args->uaddr, NULL, &f, flags | FUTEX_DONTLOCK);
 791                 if (error)
 792                         return (error);
 793
 794                 /*
 795                  * To avoid deadlocks return EINVAL if second futex
 796                  * exists at this time.
 797                  *
 798                  * Glibc fall back to FUTEX_WAKE in case of any error
 799                  * returned by FUTEX_CMP_REQUEUE.
 800                  */
 801                 error = futex_get(args->uaddr2, NULL, &f2,
 802                     flags | FUTEX_DONTEXISTS | FUTEX_DONTLOCK);
 803                 if (error) {
 804                         futex_put(f, NULL);
 805                         return (error);
 806                 }
 807                 futex_lock(f);
 808                 futex_lock(f2);
 809                 error = copyin_nofault(args->uaddr, &val, sizeof(val));
 810                 if (error) {
 811                         futex_put(f2, NULL);
 812                         futex_put(f, NULL);
 813                         error = copyin(args->uaddr, &val, sizeof(val));
 814                         if (error == 0)
 815                                 goto retry1;
 816                         LIN_SDT_PROBE1(futex, linux_sys_futex, copyin_error,
 817                             error);
 818                         LINUX_CTR1(sys_futex, "CMP_REQUEUE copyin failed %d",
 819                             error);
 820                         return (error);
 821                 }
 822                 if (val != args->val3) {
 823                         LIN_SDT_PROBE2(futex, linux_sys_futex,
 824                             debug_cmp_requeue_value_neq, args->val, val);
 825                         LINUX_CTR2(sys_futex, "CMP_REQUEUE val 0x%x != uval 0x%x",
 826                             args->val, val);
 827                         futex_put(f2, NULL);
 828                         futex_put(f, NULL);
 829                         return (EAGAIN);
 830                 }
 831
 832                 nrwake = (int)(unsigned long)args->timeout;
 833                 td->td_retval[0] = futex_requeue(f, args->val, f2, nrwake);
 834                 futex_put(f2, NULL);
 835                 futex_put(f, NULL);
 836                 break;
 837
 838         case LINUX_FUTEX_WAKE_OP:
 839                 LIN_SDT_PROBE5(futex, linux_sys_futex, debug_wake_op,
 840                     args->uaddr, args->op, args->val, args->uaddr2, args->val3);
 841                 LINUX_CTR5(sys_futex, "WAKE_OP "
 842                     "uaddr %p nrwake 0x%x uaddr2 %p op 0x%x nrwake2 0x%x",
 843                     args->uaddr, args->val, args->uaddr2, args->val3,
 844                     args->timeout);
 845
 846                 if (args->uaddr == args->uaddr2)
 847                         return (EINVAL);
 848
 849 retry2:
 850                 error = futex_get(args->uaddr, NULL, &f, flags | FUTEX_DONTLOCK);
 851                 if (error)
 852                         return (error);
 853
 854                 error = futex_get(args->uaddr2, NULL, &f2, flags | FUTEX_DONTLOCK);
 855                 if (error) {
 856                         futex_put(f, NULL);
 857                         return (error);
 858                 }
 859                 futex_lock(f);
 860                 futex_lock(f2);
 861
 862                 /*
 863                  * This function returns positive number as results and
 864                  * negative as errors
 865                  */
 866                 save = vm_fault_disable_pagefaults();
 867                 op_ret = futex_atomic_op(td, args->val3, args->uaddr2);
 868                 vm_fault_enable_pagefaults(save);
 869
 870                 LINUX_CTR2(sys_futex, "WAKE_OP atomic_op uaddr %p ret 0x%x",
 871                     args->uaddr, op_ret);
 872
 873                 if (op_ret < 0) {
 874                         if (f2 != NULL)
 875                                 futex_put(f2, NULL);
 876                         futex_put(f, NULL);
 877                         error = copyin(args->uaddr2, &val, sizeof(val));
 878                         if (error == 0)
 879                                 goto retry2;
 880                         return (error);
 881                 }
 882
 883                 ret = futex_wake(f, args->val, args->val3);
 884
 885                 if (op_ret > 0) {
 886                         op_ret = 0;
 887                         nrwake = (int)(unsigned long)args->timeout;
 888
 889                         if (f2 != NULL)
 890                                 op_ret += futex_wake(f2, nrwake, args->val3);
 891                         else
 892                                 op_ret += futex_wake(f, nrwake, args->val3);
 893                         ret += op_ret;
 894                 }
 895                 if (f2 != NULL)
 896                         futex_put(f2, NULL);
 897                 futex_put(f, NULL);
 898                 td->td_retval[0] = ret;
 899                 break;
 900
 901         case LINUX_FUTEX_LOCK_PI:
 902                 /* not yet implemented */
 903                 pem = pem_find(td->td_proc);
 904                 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
 905                         linux_msg(td, "unsupported FUTEX_LOCK_PI");
 906                         pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
 907                         LIN_SDT_PROBE0(futex, linux_sys_futex,
 908                             unimplemented_lock_pi);
 909                 }
 910                 return (ENOSYS);
 911
 912         case LINUX_FUTEX_UNLOCK_PI:
 913                 /* not yet implemented */
 914                 pem = pem_find(td->td_proc);
 915                 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
 916                         linux_msg(td, "unsupported FUTEX_UNLOCK_PI");
 917                         pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
 918                         LIN_SDT_PROBE0(futex, linux_sys_futex,
 919                             unimplemented_unlock_pi);
 920                 }
 921                 return (ENOSYS);
 922
 923         case LINUX_FUTEX_TRYLOCK_PI:
 924                 /* not yet implemented */
 925                 pem = pem_find(td->td_proc);
 926                 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
 927                         linux_msg(td, "unsupported FUTEX_TRYLOCK_PI");
 928                         pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
 929                         LIN_SDT_PROBE0(futex, linux_sys_futex,
 930                             unimplemented_trylock_pi);
 931                 }
 932                 return (ENOSYS);
 933
 934         case LINUX_FUTEX_REQUEUE:
 935                 /*
 936                  * Glibc does not use this operation since version 2.3.3,
 937                  * as it is racy and replaced by FUTEX_CMP_REQUEUE operation.
 938                  * Glibc versions prior to 2.3.3 fall back to FUTEX_WAKE when
 939                  * FUTEX_REQUEUE returned EINVAL.
 940                  */
 941                 pem = pem_find(td->td_proc);
 942                 if ((pem->flags & LINUX_XDEPR_REQUEUEOP) == 0) {
 943                         linux_msg(td, "unsupported FUTEX_REQUEUE");
 944                         pem->flags |= LINUX_XDEPR_REQUEUEOP;
 945                         LIN_SDT_PROBE0(futex, linux_sys_futex,
 946                             deprecated_requeue);
 947                 }
 948                 return (EINVAL);
 949
 950         case LINUX_FUTEX_WAIT_REQUEUE_PI:
 951                 /* not yet implemented */
 952                 pem = pem_find(td->td_proc);
 953                 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
 954                         linux_msg(td, "unsupported FUTEX_WAIT_REQUEUE_PI");
 955                         pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
 956                         LIN_SDT_PROBE0(futex, linux_sys_futex,
 957                             unimplemented_wait_requeue_pi);
 958                 }
 959                 return (ENOSYS);
 960
 961         case LINUX_FUTEX_CMP_REQUEUE_PI:
 962                 /* not yet implemented */
 963                 pem = pem_find(td->td_proc);
 964                 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
 965                         linux_msg(td, "unsupported FUTEX_CMP_REQUEUE_PI");
 966                         pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
 967                         LIN_SDT_PROBE0(futex, linux_sys_futex,
 968                             unimplemented_cmp_requeue_pi);
 969                 }
 970                 return (ENOSYS);
 971
 972         default:
 973                 linux_msg(td, "unsupported futex op %d", args->op);
 974                 LIN_SDT_PROBE1(futex, linux_sys_futex, unknown_operation,
 975                     args->op);
 976                 return (ENOSYS);
 977         }
 978
 979         return (error);
 980 }
 981
 982 int
 983 linux_set_robust_list(struct thread *td, struct linux_set_robust_list_args *args)
 984 {
 985         struct linux_emuldata *em;
 986
 987         if (args->len != sizeof(struct linux_robust_list_head)) {
 988                 LIN_SDT_PROBE0(futex, linux_set_robust_list, size_error);
 989                 return (EINVAL);
 990         }
 991
 992         em = em_find(td);
 993         em->robust_futexes = args->head;
 994
 995         return (0);
 996 }
 997
 998 int
 999 linux_get_robust_list(struct thread *td, struct linux_get_robust_list_args *args)
1000 {
1001         struct linux_emuldata *em;
1002         struct linux_robust_list_head *head;
1003         l_size_t len = sizeof(struct linux_robust_list_head);
1004         struct thread *td2;
1005         int error = 0;
1006
1007         if (!args->pid) {
1008                 em = em_find(td);
1009                 KASSERT(em != NULL, ("get_robust_list: emuldata notfound.\n"));
1010                 head = em->robust_futexes;
1011         } else {
1012                 td2 = tdfind(args->pid, -1);
1013                 if (td2 == NULL)
1014                         return (ESRCH);
1015                 if (SV_PROC_ABI(td2->td_proc) != SV_ABI_LINUX) {
1016                         PROC_UNLOCK(td2->td_proc);
1017                         return (EPERM);
1018                 }
1019
1020                 em = em_find(td2);
1021                 KASSERT(em != NULL, ("get_robust_list: emuldata notfound.\n"));
1022                 /* XXX: ptrace? */
1023                 if (priv_check(td, PRIV_CRED_SETUID) ||
1024                     priv_check(td, PRIV_CRED_SETEUID) ||
1025                     p_candebug(td, td2->td_proc)) {
1026                         PROC_UNLOCK(td2->td_proc);
1027                         return (EPERM);
1028                 }
1029                 head = em->robust_futexes;
1030
1031                 PROC_UNLOCK(td2->td_proc);
1032         }
1033
1034         error = copyout(&len, args->len, sizeof(l_size_t));
1035         if (error) {
1036                 LIN_SDT_PROBE1(futex, linux_get_robust_list, copyout_error,
1037                     error);
1038                 return (EFAULT);
1039         }
1040
1041         error = copyout(&head, args->head, sizeof(head));
1042         if (error) {
1043                 LIN_SDT_PROBE1(futex, linux_get_robust_list, copyout_error,
1044                     error);
1045         }
1046
1047         return (error);
1048 }
1049
1050 static int
1051 handle_futex_death(struct linux_emuldata *em, uint32_t *uaddr,
1052     unsigned int pi)
1053 {
1054         uint32_t uval, nval, mval;
1055         struct futex *f;
1056         int error;
1057
1058 retry:
1059         error = copyin(uaddr, &uval, 4);
1060         if (error) {
1061                 LIN_SDT_PROBE1(futex, handle_futex_death, copyin_error, error);
1062                 return (EFAULT);
1063         }
1064         if ((uval & FUTEX_TID_MASK) == em->em_tid) {
1065                 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
1066                 nval = casuword32(uaddr, uval, mval);
1067
1068                 if (nval == -1)
1069                         return (EFAULT);
1070
1071                 if (nval != uval)
1072                         goto retry;
1073
1074                 if (!pi && (uval & FUTEX_WAITERS)) {
1075                         error = futex_get(uaddr, NULL, &f,
1076                             FUTEX_DONTCREATE | FUTEX_SHARED);
1077                         if (error)
1078                                 return (error);
1079                         if (f != NULL) {
1080                                 futex_wake(f, 1, FUTEX_BITSET_MATCH_ANY);
1081                                 futex_put(f, NULL);
1082                         }
1083                 }
1084         }
1085
1086         return (0);
1087 }
1088
1089 static int
1090 fetch_robust_entry(struct linux_robust_list **entry,
1091     struct linux_robust_list **head, unsigned int *pi)
1092 {
1093         l_ulong uentry;
1094         int error;
1095
1096         error = copyin((const void *)head, &uentry, sizeof(l_ulong));
1097         if (error) {
1098                 LIN_SDT_PROBE1(futex, fetch_robust_entry, copyin_error, error);
1099                 return (EFAULT);
1100         }
1101
1102         *entry = (void *)(uentry & ~1UL);
1103         *pi = uentry & 1;
1104
1105         return (0);
1106 }
1107
1108 /* This walks the list of robust futexes releasing them. */
1109 void
1110 release_futexes(struct thread *td, struct linux_emuldata *em)
1111 {
1112         struct linux_robust_list_head *head = NULL;
1113         struct linux_robust_list *entry, *next_entry, *pending;
1114         unsigned int limit = 2048, pi, next_pi, pip;
1115         l_long futex_offset;
1116         int rc, error;
1117
1118         head = em->robust_futexes;
1119
1120         if (head == NULL)
1121                 return;
1122
1123         if (fetch_robust_entry(&entry, PTRIN(&head->list.next), &pi))
1124                 return;
1125
1126         error = copyin(&head->futex_offset, &futex_offset,
1127             sizeof(futex_offset));
1128         if (error) {
1129                 LIN_SDT_PROBE1(futex, release_futexes, copyin_error, error);
1130                 return;
1131         }
1132
1133         if (fetch_robust_entry(&pending, PTRIN(&head->pending_list), &pip))
1134                 return;
1135
1136         while (entry != &head->list) {
1137                 rc = fetch_robust_entry(&next_entry, PTRIN(&entry->next), &next_pi);
1138
1139                 if (entry != pending)
1140                         if (handle_futex_death(em,
1141                             (uint32_t *)((caddr_t)entry + futex_offset), pi)) {
1142                                 return;
1143                         }
1144                 if (rc)
1145                         return;
1146
1147                 entry = next_entry;
1148                 pi = next_pi;
1149
1150                 if (!--limit)
1151                         break;
1152
1153                 sched_relinquish(curthread);
1154         }
1155
1156         if (pending)
1157                 handle_futex_death(em, (uint32_t *)((caddr_t)pending + futex_offset), pip);
1158 }