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_futex, unimplemented_clockswitch);
 121 LIN_SDT_PROBE_DEFINE1(futex, linux_futex, copyin_error, "int");
 122 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, invalid_cmp_requeue_use);
 123 LIN_SDT_PROBE_DEFINE3(futex, linux_futex, debug_wait, "uint32_t *",
 124     "uint32_t", "uint32_t");
 125 LIN_SDT_PROBE_DEFINE4(futex, linux_futex, debug_wait_value_neq,
 126     "uint32_t *", "uint32_t", "int", "uint32_t");
 127 LIN_SDT_PROBE_DEFINE3(futex, linux_futex, debug_wake, "uint32_t *",
 128     "uint32_t", "uint32_t");
 129 LIN_SDT_PROBE_DEFINE5(futex, linux_futex, debug_cmp_requeue, "uint32_t *",
 130     "uint32_t", "uint32_t", "uint32_t *", "struct l_timespec *");
 131 LIN_SDT_PROBE_DEFINE2(futex, linux_futex, debug_cmp_requeue_value_neq,
 132     "uint32_t", "int");
 133 LIN_SDT_PROBE_DEFINE5(futex, linux_futex, debug_wake_op, "uint32_t *",
 134     "int", "uint32_t", "uint32_t *", "uint32_t");
 135 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unhandled_efault);
 136 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_lock_pi);
 137 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_unlock_pi);
 138 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_trylock_pi);
 139 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, deprecated_requeue);
 140 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_wait_requeue_pi);
 141 LIN_SDT_PROBE_DEFINE0(futex, linux_futex, unimplemented_cmp_requeue_pi);
 142 LIN_SDT_PROBE_DEFINE1(futex, linux_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_wait(struct futex *, struct waiting_proc *, struct timespec *,
 219     uint32_t);
 220 static void futex_lock(struct futex *);
 221 static void futex_unlock(struct futex *);
 222 static int futex_atomic_op(struct thread *, int, uint32_t *);
 223 static int handle_futex_death(struct linux_emuldata *, uint32_t *,
 224     unsigned int);
 225 static int fetch_robust_entry(struct linux_robust_list **,
 226     struct linux_robust_list **, unsigned int *);
 227
 228 struct linux_futex_args {
 229         uint32_t        *uaddr;
 230         int32_t         op;
 231         uint32_t        val;
 232         struct timespec *ts;
 233         uint32_t        *uaddr2;
 234         uint32_t        val3;
 235         struct timespec kts;
 236 };
 237
 238 static int      linux_futex(struct thread *, struct linux_futex_args *);
 239
 240 static void
 241 futex_put(struct futex *f, struct waiting_proc *wp)
 242 {
 243
 244         if (wp != NULL) {
 245                 if ((wp->wp_flags & FUTEX_WP_REMOVED) == 0)
 246                         TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
 247                 free(wp, M_FUTEX_WP);
 248         }
 249
 250         FUTEXES_LOCK;
 251         if (--f->f_refcount == 0) {
 252                 LIST_REMOVE(f, f_list);
 253                 FUTEXES_UNLOCK;
 254                 if (FUTEX_LOCKED(f))
 255                         futex_unlock(f);
 256
 257                 LIN_SDT_PROBE3(futex, futex_put, destroy, f->f_uaddr,
 258                     f->f_refcount, f->f_key.shared);
 259                 LINUX_CTR3(sys_futex, "futex_put destroy uaddr %p ref %d "
 260                     "shared %d", f->f_uaddr, f->f_refcount, f->f_key.shared);
 261                 umtx_key_release(&f->f_key);
 262                 FUTEX_DESTROY(f);
 263                 free(f, M_FUTEX);
 264                 return;
 265         }
 266
 267         LIN_SDT_PROBE3(futex, futex_put, unlock, f->f_uaddr, f->f_refcount,
 268             f->f_key.shared);
 269         LINUX_CTR3(sys_futex, "futex_put uaddr %p ref %d shared %d",
 270             f->f_uaddr, f->f_refcount, f->f_key.shared);
 271         if (FUTEX_LOCKED(f))
 272                 futex_unlock(f);
 273         FUTEXES_UNLOCK;
 274 }
 275
 276 static int
 277 futex_get0(uint32_t *uaddr, struct futex **newf, uint32_t flags)
 278 {
 279         struct futex *f, *tmpf;
 280         struct umtx_key key;
 281         int error;
 282
 283         *newf = tmpf = NULL;
 284
 285         error = umtx_key_get(uaddr, TYPE_FUTEX, (flags & FUTEX_SHARED) ?
 286             AUTO_SHARE : THREAD_SHARE, &key);
 287         if (error) {
 288                 LIN_SDT_PROBE1(futex, futex_get0, umtx_key_get_error, error);
 289                 return (error);
 290         }
 291 retry:
 292         FUTEXES_LOCK;
 293         LIST_FOREACH(f, &futex_list, f_list) {
 294                 if (umtx_key_match(&f->f_key, &key)) {
 295                         if (tmpf != NULL) {
 296                                 if (FUTEX_LOCKED(tmpf))
 297                                         futex_unlock(tmpf);
 298                                 FUTEX_DESTROY(tmpf);
 299                                 free(tmpf, M_FUTEX);
 300                         }
 301                         if (flags & FUTEX_DONTEXISTS) {
 302                                 FUTEXES_UNLOCK;
 303                                 umtx_key_release(&key);
 304
 305                                 return (EINVAL);
 306                         }
 307
 308                         /*
 309                          * Increment refcount of the found futex to
 310                          * prevent it from deallocation before FUTEX_LOCK()
 311                          */
 312                         ++f->f_refcount;
 313                         FUTEXES_UNLOCK;
 314                         umtx_key_release(&key);
 315
 316                         if ((flags & FUTEX_DONTLOCK) == 0)
 317                                 futex_lock(f);
 318                         *newf = f;
 319                         LIN_SDT_PROBE3(futex, futex_get0, shared, uaddr,
 320                             f->f_refcount, f->f_key.shared);
 321                         LINUX_CTR3(sys_futex, "futex_get uaddr %p ref %d shared %d",
 322                             uaddr, f->f_refcount, f->f_key.shared);
 323
 324                         return (0);
 325                 }
 326         }
 327
 328         if (flags & FUTEX_DONTCREATE) {
 329                 FUTEXES_UNLOCK;
 330                 umtx_key_release(&key);
 331                 LIN_SDT_PROBE1(futex, futex_get0, null, uaddr);
 332                 LINUX_CTR1(sys_futex, "futex_get uaddr %p null", uaddr);
 333
 334                 return (0);
 335         }
 336
 337         if (tmpf == NULL) {
 338                 FUTEXES_UNLOCK;
 339                 tmpf = malloc(sizeof(*tmpf), M_FUTEX, M_WAITOK | M_ZERO);
 340                 tmpf->f_uaddr = uaddr;
 341                 tmpf->f_key = key;
 342                 tmpf->f_refcount = 1;
 343                 tmpf->f_bitset = FUTEX_BITSET_MATCH_ANY;
 344                 FUTEX_INIT(tmpf);
 345                 TAILQ_INIT(&tmpf->f_waiting_proc);
 346
 347                 /*
 348                  * Lock the new futex before an insert into the futex_list
 349                  * to prevent futex usage by other.
 350                  */
 351                 if ((flags & FUTEX_DONTLOCK) == 0)
 352                         futex_lock(tmpf);
 353                 goto retry;
 354         }
 355
 356         LIST_INSERT_HEAD(&futex_list, tmpf, f_list);
 357         FUTEXES_UNLOCK;
 358
 359         LIN_SDT_PROBE3(futex, futex_get0, new, uaddr, tmpf->f_refcount,
 360             tmpf->f_key.shared);
 361         LINUX_CTR3(sys_futex, "futex_get uaddr %p ref %d shared %d new",
 362             uaddr, tmpf->f_refcount, tmpf->f_key.shared);
 363         *newf = tmpf;
 364
 365         return (0);
 366 }
 367
 368 static int
 369 futex_get(uint32_t *uaddr, struct waiting_proc **wp, struct futex **f,
 370     uint32_t flags)
 371 {
 372         int error;
 373
 374         if (flags & FUTEX_CREATE_WP) {
 375                 *wp = malloc(sizeof(struct waiting_proc), M_FUTEX_WP, M_WAITOK);
 376                 (*wp)->wp_flags = 0;
 377         }
 378         error = futex_get0(uaddr, f, flags);
 379         if (error) {
 380                 LIN_SDT_PROBE0(futex, futex_get, error);
 381
 382                 if (flags & FUTEX_CREATE_WP)
 383                         free(*wp, M_FUTEX_WP);
 384
 385                 return (error);
 386         }
 387         if (flags & FUTEX_CREATE_WP) {
 388                 TAILQ_INSERT_HEAD(&(*f)->f_waiting_proc, *wp, wp_list);
 389                 (*wp)->wp_futex = *f;
 390         }
 391
 392         return (error);
 393 }
 394
 395 static inline void
 396 futex_lock(struct futex *f)
 397 {
 398
 399         LINUX_CTR3(sys_futex, "futex_lock uaddr %p ref %d shared %d",
 400             f->f_uaddr, f->f_refcount, f->f_key.shared);
 401         FUTEX_ASSERT_UNLOCKED(f);
 402         FUTEX_LOCK(f);
 403 }
 404
 405 static inline void
 406 futex_unlock(struct futex *f)
 407 {
 408
 409         LINUX_CTR3(sys_futex, "futex_unlock uaddr %p ref %d shared %d",
 410             f->f_uaddr, f->f_refcount, f->f_key.shared);
 411         FUTEX_ASSERT_LOCKED(f);
 412         FUTEX_UNLOCK(f);
 413 }
 414
 415 static int
 416 futex_sleep(struct futex *f, struct waiting_proc *wp, struct timespec *ts)
 417 {
 418         sbintime_t sbt, prec, tmp;
 419         time_t over;
 420         int error;
 421
 422         FUTEX_ASSERT_LOCKED(f);
 423         if (ts != NULL) {
 424                 if (ts->tv_sec > INT32_MAX / 2) {
 425                         over = ts->tv_sec - INT32_MAX / 2;
 426                         ts->tv_sec -= over;
 427                 }
 428                 tmp = tstosbt(*ts);
 429                 if (TIMESEL(&sbt, tmp))
 430                         sbt += tc_tick_sbt;
 431                 sbt += tmp;
 432                 prec = tmp;
 433                 prec >>= tc_precexp;
 434         } else {
 435                 sbt = 0;
 436                 prec = 0;
 437         }
 438         LINUX_CTR4(sys_futex, "futex_sleep enter uaddr %p wp %p timo %ld ref %d",
 439             f->f_uaddr, wp, sbt, f->f_refcount);
 440
 441         error = msleep_sbt(wp, &f->f_lck, PCATCH, "futex", sbt, prec, C_ABSOLUTE);
 442         if (wp->wp_flags & FUTEX_WP_REQUEUED) {
 443                 KASSERT(f != wp->wp_futex, ("futex != wp_futex"));
 444
 445                 if (error) {
 446                         LIN_SDT_PROBE5(futex, futex_sleep, requeue_error, error,
 447                             f->f_uaddr, wp, wp->wp_futex->f_uaddr,
 448                             wp->wp_futex->f_refcount);
 449                 }
 450
 451                 LINUX_CTR5(sys_futex, "futex_sleep out error %d uaddr %p wp"
 452                     " %p requeued uaddr %p ref %d",
 453                     error, f->f_uaddr, wp, wp->wp_futex->f_uaddr,
 454                     wp->wp_futex->f_refcount);
 455                 futex_put(f, NULL);
 456                 f = wp->wp_futex;
 457                 futex_lock(f);
 458         } else {
 459                 if (error) {
 460                         LIN_SDT_PROBE3(futex, futex_sleep, sleep_error, error,
 461                             f->f_uaddr, wp);
 462                 }
 463                 LINUX_CTR3(sys_futex, "futex_sleep out error %d uaddr %p wp %p",
 464                     error, f->f_uaddr, wp);
 465         }
 466
 467         futex_put(f, wp);
 468
 469         return (error);
 470 }
 471
 472 static int
 473 futex_wake(struct futex *f, int n, uint32_t bitset)
 474 {
 475         struct waiting_proc *wp, *wpt;
 476         int count = 0;
 477
 478         if (bitset == 0)
 479                 return (EINVAL);
 480
 481         FUTEX_ASSERT_LOCKED(f);
 482         TAILQ_FOREACH_SAFE(wp, &f->f_waiting_proc, wp_list, wpt) {
 483                 LIN_SDT_PROBE3(futex, futex_wake, iterate, f->f_uaddr, wp,
 484                     f->f_refcount);
 485                 LINUX_CTR3(sys_futex, "futex_wake uaddr %p wp %p ref %d",
 486                     f->f_uaddr, wp, f->f_refcount);
 487                 /*
 488                  * Unless we find a matching bit in
 489                  * the bitset, continue searching.
 490                  */
 491                 if (!(wp->wp_futex->f_bitset & bitset))
 492                         continue;
 493
 494                 wp->wp_flags |= FUTEX_WP_REMOVED;
 495                 TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
 496                 LIN_SDT_PROBE1(futex, futex_wake, wakeup, wp);
 497                 wakeup_one(wp);
 498                 if (++count == n)
 499                         break;
 500         }
 501
 502         return (count);
 503 }
 504
 505 static int
 506 futex_requeue(struct futex *f, int nrwake, struct futex *f2,
 507     int nrrequeue)
 508 {
 509         struct waiting_proc *wp, *wpt;
 510         int count = 0;
 511
 512         FUTEX_ASSERT_LOCKED(f);
 513         FUTEX_ASSERT_LOCKED(f2);
 514
 515         TAILQ_FOREACH_SAFE(wp, &f->f_waiting_proc, wp_list, wpt) {
 516                 if (++count <= nrwake) {
 517                         LINUX_CTR2(sys_futex, "futex_req_wake uaddr %p wp %p",
 518                             f->f_uaddr, wp);
 519                         wp->wp_flags |= FUTEX_WP_REMOVED;
 520                         TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
 521                         LIN_SDT_PROBE1(futex, futex_requeue, wakeup, wp);
 522                         wakeup_one(wp);
 523                 } else {
 524                         LIN_SDT_PROBE3(futex, futex_requeue, requeue,
 525                             f->f_uaddr, wp, f2->f_uaddr);
 526                         LINUX_CTR3(sys_futex, "futex_requeue uaddr %p wp %p to %p",
 527                             f->f_uaddr, wp, f2->f_uaddr);
 528                         wp->wp_flags |= FUTEX_WP_REQUEUED;
 529                         /* Move wp to wp_list of f2 futex */
 530                         TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
 531                         TAILQ_INSERT_HEAD(&f2->f_waiting_proc, wp, wp_list);
 532
 533                         /*
 534                          * Thread which sleeps on wp after waking should
 535                          * acquire f2 lock, so increment refcount of f2 to
 536                          * prevent it from premature deallocation.
 537                          */
 538                         wp->wp_futex = f2;
 539                         FUTEXES_LOCK;
 540                         ++f2->f_refcount;
 541                         FUTEXES_UNLOCK;
 542                         if (count - nrwake >= nrrequeue)
 543                                 break;
 544                 }
 545         }
 546
 547         return (count);
 548 }
 549
 550 static int
 551 futex_wait(struct futex *f, struct waiting_proc *wp, struct timespec *ts,
 552     uint32_t bitset)
 553 {
 554         int error;
 555
 556         if (bitset == 0) {
 557                 futex_put(f, wp);
 558                 return (EINVAL);
 559         }
 560
 561         f->f_bitset = bitset;
 562         error = futex_sleep(f, wp, ts);
 563         if (error)
 564                 LIN_SDT_PROBE1(futex, futex_wait, sleep_error, error);
 565         if (error == EWOULDBLOCK)
 566                 error = ETIMEDOUT;
 567
 568         return (error);
 569 }
 570
 571 static int
 572 futex_atomic_op(struct thread *td, int encoded_op, uint32_t *uaddr)
 573 {
 574         int op = (encoded_op >> 28) & 7;
 575         int cmp = (encoded_op >> 24) & 15;
 576         int oparg = (encoded_op << 8) >> 20;
 577         int cmparg = (encoded_op << 20) >> 20;
 578         int oldval = 0, ret;
 579
 580         if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
 581                 oparg = 1 << oparg;
 582
 583         LIN_SDT_PROBE4(futex, futex_atomic_op, decoded_op, op, cmp, oparg,
 584             cmparg);
 585
 586         /* XXX: Linux verifies access here and returns EFAULT */
 587         LIN_SDT_PROBE0(futex, futex_atomic_op, missing_access_check);
 588
 589         switch (op) {
 590         case FUTEX_OP_SET:
 591                 ret = futex_xchgl(oparg, uaddr, &oldval);
 592                 break;
 593         case FUTEX_OP_ADD:
 594                 ret = futex_addl(oparg, uaddr, &oldval);
 595                 break;
 596         case FUTEX_OP_OR:
 597                 ret = futex_orl(oparg, uaddr, &oldval);
 598                 break;
 599         case FUTEX_OP_ANDN:
 600                 ret = futex_andl(~oparg, uaddr, &oldval);
 601                 break;
 602         case FUTEX_OP_XOR:
 603                 ret = futex_xorl(oparg, uaddr, &oldval);
 604                 break;
 605         default:
 606                 LIN_SDT_PROBE1(futex, futex_atomic_op, unimplemented_op, op);
 607                 ret = -ENOSYS;
 608                 break;
 609         }
 610
 611         if (ret)
 612                 return (ret);
 613
 614         switch (cmp) {
 615         case FUTEX_OP_CMP_EQ:
 616                 ret = (oldval == cmparg);
 617                 break;
 618         case FUTEX_OP_CMP_NE:
 619                 ret = (oldval != cmparg);
 620                 break;
 621         case FUTEX_OP_CMP_LT:
 622                 ret = (oldval < cmparg);
 623                 break;
 624         case FUTEX_OP_CMP_GE:
 625                 ret = (oldval >= cmparg);
 626                 break;
 627         case FUTEX_OP_CMP_LE:
 628                 ret = (oldval <= cmparg);
 629                 break;
 630         case FUTEX_OP_CMP_GT:
 631                 ret = (oldval > cmparg);
 632                 break;
 633         default:
 634                 LIN_SDT_PROBE1(futex, futex_atomic_op, unimplemented_cmp, cmp);
 635                 ret = -ENOSYS;
 636         }
 637
 638         return (ret);
 639 }
 640
 641 static int
 642 linux_futex(struct thread *td, struct linux_futex_args *args)
 643 {
 644         int clockrt, nrwake, nrrequeue, op_ret, ret;
 645         struct linux_pemuldata *pem;
 646         struct waiting_proc *wp;
 647         struct futex *f, *f2;
 648         struct timespec kts;
 649         int error, save;
 650         uint32_t flags, val;
 651
 652         if (args->op & LINUX_FUTEX_PRIVATE_FLAG) {
 653                 flags = 0;
 654                 args->op &= ~LINUX_FUTEX_PRIVATE_FLAG;
 655         } else
 656                 flags = FUTEX_SHARED;
 657
 658         /*
 659          * Currently support for switching between CLOCK_MONOTONIC and
 660          * CLOCK_REALTIME is not present. However Linux forbids the use of
 661          * FUTEX_CLOCK_REALTIME with any op except FUTEX_WAIT_BITSET and
 662          * FUTEX_WAIT_REQUEUE_PI.
 663          */
 664         clockrt = args->op & LINUX_FUTEX_CLOCK_REALTIME;
 665         args->op = args->op & ~LINUX_FUTEX_CLOCK_REALTIME;
 666         if (clockrt && args->op != LINUX_FUTEX_WAIT_BITSET &&
 667                 args->op != LINUX_FUTEX_WAIT_REQUEUE_PI) {
 668                 LIN_SDT_PROBE0(futex, linux_futex,
 669                     unimplemented_clockswitch);
 670                 return (ENOSYS);
 671         }
 672
 673         error = 0;
 674         f = f2 = NULL;
 675
 676         switch (args->op) {
 677         case LINUX_FUTEX_WAIT:
 678                 args->val3 = FUTEX_BITSET_MATCH_ANY;
 679                 /* FALLTHROUGH */
 680
 681         case LINUX_FUTEX_WAIT_BITSET:
 682                 LIN_SDT_PROBE3(futex, linux_futex, debug_wait, args->uaddr,
 683                     args->val, args->val3);
 684                 LINUX_CTR3(sys_futex, "WAIT uaddr %p val 0x%x bitset 0x%x",
 685                     args->uaddr, args->val, args->val3);
 686
 687                 if (args->ts != NULL) {
 688                         if (clockrt) {
 689                                 nanotime(&kts);
 690                                 timespecsub(args->ts, &kts, args->ts);
 691                         } else if (args->op == LINUX_FUTEX_WAIT_BITSET) {
 692                                 nanouptime(&kts);
 693                                 timespecsub(args->ts, &kts, args->ts);
 694                         }
 695                 }
 696
 697 retry0:
 698                 error = futex_get(args->uaddr, &wp, &f,
 699                     flags | FUTEX_CREATE_WP);
 700                 if (error)
 701                         return (error);
 702
 703                 error = copyin_nofault(args->uaddr, &val, sizeof(val));
 704                 if (error) {
 705                         futex_put(f, wp);
 706                         error = copyin(args->uaddr, &val, sizeof(val));
 707                         if (error == 0)
 708                                 goto retry0;
 709                         LIN_SDT_PROBE1(futex, linux_futex, copyin_error,
 710                             error);
 711                         LINUX_CTR1(sys_futex, "WAIT copyin failed %d",
 712                             error);
 713                         return (error);
 714                 }
 715                 if (val != args->val) {
 716                         LIN_SDT_PROBE4(futex, linux_futex,
 717                             debug_wait_value_neq, args->uaddr, args->val, val,
 718                             args->val3);
 719                         LINUX_CTR3(sys_futex,
 720                             "WAIT uaddr %p val 0x%x != uval 0x%x",
 721                             args->uaddr, args->val, val);
 722                         futex_put(f, wp);
 723                         return (EWOULDBLOCK);
 724                 }
 725
 726                 error = futex_wait(f, wp, args->ts, args->val3);
 727                 break;
 728
 729         case LINUX_FUTEX_WAKE:
 730                 args->val3 = FUTEX_BITSET_MATCH_ANY;
 731                 /* FALLTHROUGH */
 732
 733         case LINUX_FUTEX_WAKE_BITSET:
 734                 LIN_SDT_PROBE3(futex, linux_futex, debug_wake, args->uaddr,
 735                     args->val, args->val3);
 736                 LINUX_CTR3(sys_futex, "WAKE uaddr %p nrwake 0x%x bitset 0x%x",
 737                     args->uaddr, args->val, args->val3);
 738
 739                 error = futex_get(args->uaddr, NULL, &f,
 740                     flags | FUTEX_DONTCREATE);
 741                 if (error)
 742                         return (error);
 743
 744                 if (f == NULL) {
 745                         td->td_retval[0] = 0;
 746                         return (error);
 747                 }
 748                 td->td_retval[0] = futex_wake(f, args->val, args->val3);
 749                 futex_put(f, NULL);
 750                 break;
 751
 752         case LINUX_FUTEX_CMP_REQUEUE:
 753                 LIN_SDT_PROBE5(futex, linux_futex, debug_cmp_requeue,
 754                     args->uaddr, args->val, args->val3, args->uaddr2,
 755                     args->ts);
 756                 LINUX_CTR5(sys_futex, "CMP_REQUEUE uaddr %p "
 757                     "nrwake 0x%x uval 0x%x uaddr2 %p nrequeue 0x%x",
 758                     args->uaddr, args->val, args->val3, args->uaddr2,
 759                     args->ts);
 760
 761                 /*
 762                  * Linux allows this, we would not, it is an incorrect
 763                  * usage of declared ABI, so return EINVAL.
 764                  */
 765                 if (args->uaddr == args->uaddr2) {
 766                         LIN_SDT_PROBE0(futex, linux_futex,
 767                             invalid_cmp_requeue_use);
 768                         return (EINVAL);
 769                 }
 770
 771                 nrrequeue = (int)(unsigned long)args->ts;
 772                 nrwake = args->val;
 773                 /*
 774                  * Sanity check to prevent signed integer overflow,
 775                  * see Linux CVE-2018-6927
 776                  */
 777                 if (nrwake < 0 || nrrequeue < 0)
 778                         return (EINVAL);
 779
 780 retry1:
 781                 error = futex_get(args->uaddr, NULL, &f, flags | FUTEX_DONTLOCK);
 782                 if (error)
 783                         return (error);
 784
 785                 /*
 786                  * To avoid deadlocks return EINVAL if second futex
 787                  * exists at this time.
 788                  *
 789                  * Glibc fall back to FUTEX_WAKE in case of any error
 790                  * returned by FUTEX_CMP_REQUEUE.
 791                  */
 792                 error = futex_get(args->uaddr2, NULL, &f2,
 793                     flags | FUTEX_DONTEXISTS | FUTEX_DONTLOCK);
 794                 if (error) {
 795                         futex_put(f, NULL);
 796                         return (error);
 797                 }
 798                 futex_lock(f);
 799                 futex_lock(f2);
 800                 error = copyin_nofault(args->uaddr, &val, sizeof(val));
 801                 if (error) {
 802                         futex_put(f2, NULL);
 803                         futex_put(f, NULL);
 804                         error = copyin(args->uaddr, &val, sizeof(val));
 805                         if (error == 0)
 806                                 goto retry1;
 807                         LIN_SDT_PROBE1(futex, linux_futex, copyin_error,
 808                             error);
 809                         LINUX_CTR1(sys_futex, "CMP_REQUEUE copyin failed %d",
 810                             error);
 811                         return (error);
 812                 }
 813                 if (val != args->val3) {
 814                         LIN_SDT_PROBE2(futex, linux_futex,
 815                             debug_cmp_requeue_value_neq, args->val, val);
 816                         LINUX_CTR2(sys_futex, "CMP_REQUEUE val 0x%x != uval 0x%x",
 817                             args->val, val);
 818                         futex_put(f2, NULL);
 819                         futex_put(f, NULL);
 820                         return (EAGAIN);
 821                 }
 822
 823                 td->td_retval[0] = futex_requeue(f, nrwake, f2, nrrequeue);
 824                 futex_put(f2, NULL);
 825                 futex_put(f, NULL);
 826                 break;
 827
 828         case LINUX_FUTEX_WAKE_OP:
 829                 LIN_SDT_PROBE5(futex, linux_futex, debug_wake_op,
 830                     args->uaddr, args->op, args->val, args->uaddr2, args->val3);
 831                 LINUX_CTR5(sys_futex, "WAKE_OP "
 832                     "uaddr %p nrwake 0x%x uaddr2 %p op 0x%x nrwake2 0x%x",
 833                     args->uaddr, args->val, args->uaddr2, args->val3,
 834                     args->ts);
 835
 836                 if (args->uaddr == args->uaddr2)
 837                         return (EINVAL);
 838
 839 retry2:
 840                 error = futex_get(args->uaddr, NULL, &f, flags | FUTEX_DONTLOCK);
 841                 if (error)
 842                         return (error);
 843
 844                 error = futex_get(args->uaddr2, NULL, &f2, flags | FUTEX_DONTLOCK);
 845                 if (error) {
 846                         futex_put(f, NULL);
 847                         return (error);
 848                 }
 849                 futex_lock(f);
 850                 futex_lock(f2);
 851
 852                 /*
 853                  * This function returns positive number as results and
 854                  * negative as errors
 855                  */
 856                 save = vm_fault_disable_pagefaults();
 857                 op_ret = futex_atomic_op(td, args->val3, args->uaddr2);
 858                 vm_fault_enable_pagefaults(save);
 859
 860                 LINUX_CTR2(sys_futex, "WAKE_OP atomic_op uaddr %p ret 0x%x",
 861                     args->uaddr, op_ret);
 862
 863                 if (op_ret < 0) {
 864                         if (f2 != NULL)
 865                                 futex_put(f2, NULL);
 866                         futex_put(f, NULL);
 867                         error = copyin(args->uaddr2, &val, sizeof(val));
 868                         if (error == 0)
 869                                 goto retry2;
 870                         return (error);
 871                 }
 872
 873                 ret = futex_wake(f, args->val, args->val3);
 874
 875                 if (op_ret > 0) {
 876                         op_ret = 0;
 877                         nrwake = (int)(unsigned long)args->ts;
 878
 879                         if (f2 != NULL)
 880                                 op_ret += futex_wake(f2, nrwake, args->val3);
 881                         else
 882                                 op_ret += futex_wake(f, nrwake, args->val3);
 883                         ret += op_ret;
 884                 }
 885                 if (f2 != NULL)
 886                         futex_put(f2, NULL);
 887                 futex_put(f, NULL);
 888                 td->td_retval[0] = ret;
 889                 break;
 890
 891         case LINUX_FUTEX_LOCK_PI:
 892                 /* not yet implemented */
 893                 pem = pem_find(td->td_proc);
 894                 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
 895                         linux_msg(td, "unsupported FUTEX_LOCK_PI");
 896                         pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
 897                         LIN_SDT_PROBE0(futex, linux_futex,
 898                             unimplemented_lock_pi);
 899                 }
 900                 return (ENOSYS);
 901
 902         case LINUX_FUTEX_UNLOCK_PI:
 903                 /* not yet implemented */
 904                 pem = pem_find(td->td_proc);
 905                 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
 906                         linux_msg(td, "unsupported FUTEX_UNLOCK_PI");
 907                         pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
 908                         LIN_SDT_PROBE0(futex, linux_futex,
 909                             unimplemented_unlock_pi);
 910                 }
 911                 return (ENOSYS);
 912
 913         case LINUX_FUTEX_TRYLOCK_PI:
 914                 /* not yet implemented */
 915                 pem = pem_find(td->td_proc);
 916                 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
 917                         linux_msg(td, "unsupported FUTEX_TRYLOCK_PI");
 918                         pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
 919                         LIN_SDT_PROBE0(futex, linux_futex,
 920                             unimplemented_trylock_pi);
 921                 }
 922                 return (ENOSYS);
 923
 924         case LINUX_FUTEX_REQUEUE:
 925                 /*
 926                  * Glibc does not use this operation since version 2.3.3,
 927                  * as it is racy and replaced by FUTEX_CMP_REQUEUE operation.
 928                  * Glibc versions prior to 2.3.3 fall back to FUTEX_WAKE when
 929                  * FUTEX_REQUEUE returned EINVAL.
 930                  */
 931                 pem = pem_find(td->td_proc);
 932                 if ((pem->flags & LINUX_XDEPR_REQUEUEOP) == 0) {
 933                         linux_msg(td, "unsupported FUTEX_REQUEUE");
 934                         pem->flags |= LINUX_XDEPR_REQUEUEOP;
 935                         LIN_SDT_PROBE0(futex, linux_futex,
 936                             deprecated_requeue);
 937                 }
 938                 return (EINVAL);
 939
 940         case LINUX_FUTEX_WAIT_REQUEUE_PI:
 941                 /* not yet implemented */
 942                 pem = pem_find(td->td_proc);
 943                 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
 944                         linux_msg(td, "unsupported FUTEX_WAIT_REQUEUE_PI");
 945                         pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
 946                         LIN_SDT_PROBE0(futex, linux_futex,
 947                             unimplemented_wait_requeue_pi);
 948                 }
 949                 return (ENOSYS);
 950
 951         case LINUX_FUTEX_CMP_REQUEUE_PI:
 952                 /* not yet implemented */
 953                 pem = pem_find(td->td_proc);
 954                 if ((pem->flags & LINUX_XUNSUP_FUTEXPIOP) == 0) {
 955                         linux_msg(td, "unsupported FUTEX_CMP_REQUEUE_PI");
 956                         pem->flags |= LINUX_XUNSUP_FUTEXPIOP;
 957                         LIN_SDT_PROBE0(futex, linux_futex,
 958                             unimplemented_cmp_requeue_pi);
 959                 }
 960                 return (ENOSYS);
 961
 962         default:
 963                 linux_msg(td, "unsupported futex op %d", args->op);
 964                 LIN_SDT_PROBE1(futex, linux_futex, unknown_operation,
 965                     args->op);
 966                 return (ENOSYS);
 967         }
 968
 969         return (error);
 970 }
 971
 972 int
 973 linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
 974 {
 975         struct linux_futex_args fargs = {
 976                 .uaddr = args->uaddr,
 977                 .op = args->op,
 978                 .val = args->val,
 979                 .ts = NULL,
 980                 .uaddr2 = args->uaddr2,
 981                 .val3 = args->val3,
 982         };
 983         struct l_timespec lts;
 984         int error;
 985
 986         switch (args->op & LINUX_FUTEX_CMD_MASK) {
 987         case LINUX_FUTEX_WAIT:
 988         case LINUX_FUTEX_WAIT_BITSET:
 989                 if (args->timeout != NULL) {
 990                         error = copyin(args->timeout, &lts, sizeof(lts));
 991                         if (error != 0)
 992                                 return (error);
 993                         error = linux_to_native_timespec(&fargs.kts, &lts);
 994                         if (error != 0)
 995                                 return (error);
 996                         fargs.ts = &fargs.kts;
 997                 }
 998                 break;
 999         default:
1000                 fargs.ts = PTRIN(args->timeout);
1001         }
1002         return (linux_futex(td, &fargs));
1003 }
1004
1005 #if defined(__i386__) || (defined(__amd64__) && defined(COMPAT_LINUX32))
1006 int
1007 linux_sys_futex_time64(struct thread *td,
1008     struct linux_sys_futex_time64_args *args)
1009 {
1010         struct linux_futex_args fargs = {
1011                 .uaddr = args->uaddr,
1012                 .op = args->op,
1013                 .val = args->val,
1014                 .ts = NULL,
1015                 .uaddr2 = args->uaddr2,
1016                 .val3 = args->val3,
1017         };
1018         struct l_timespec64 lts;
1019         int error;
1020
1021         switch (args->op & LINUX_FUTEX_CMD_MASK) {
1022         case LINUX_FUTEX_WAIT:
1023         case LINUX_FUTEX_WAIT_BITSET:
1024                 if (args->timeout != NULL) {
1025                         error = copyin(args->timeout, &lts, sizeof(lts));
1026                         if (error != 0)
1027                                 return (error);
1028                         error = linux_to_native_timespec64(&fargs.kts, &lts);
1029                         if (error != 0)
1030                                 return (error);
1031                         fargs.ts = &fargs.kts;
1032                 }
1033                 break;
1034         default:
1035                 fargs.ts = PTRIN(args->timeout);
1036         }
1037         return (linux_futex(td, &fargs));
1038 }
1039 #endif
1040
1041 int
1042 linux_set_robust_list(struct thread *td, struct linux_set_robust_list_args *args)
1043 {
1044         struct linux_emuldata *em;
1045
1046         if (args->len != sizeof(struct linux_robust_list_head)) {
1047                 LIN_SDT_PROBE0(futex, linux_set_robust_list, size_error);
1048                 return (EINVAL);
1049         }
1050
1051         em = em_find(td);
1052         em->robust_futexes = args->head;
1053
1054         return (0);
1055 }
1056
1057 int
1058 linux_get_robust_list(struct thread *td, struct linux_get_robust_list_args *args)
1059 {
1060         struct linux_emuldata *em;
1061         struct linux_robust_list_head *head;
1062         l_size_t len = sizeof(struct linux_robust_list_head);
1063         struct thread *td2;
1064         int error = 0;
1065
1066         if (!args->pid) {
1067                 em = em_find(td);
1068                 KASSERT(em != NULL, ("get_robust_list: emuldata notfound.\n"));
1069                 head = em->robust_futexes;
1070         } else {
1071                 td2 = tdfind(args->pid, -1);
1072                 if (td2 == NULL)
1073                         return (ESRCH);
1074                 if (SV_PROC_ABI(td2->td_proc) != SV_ABI_LINUX) {
1075                         PROC_UNLOCK(td2->td_proc);
1076                         return (EPERM);
1077                 }
1078
1079                 em = em_find(td2);
1080                 KASSERT(em != NULL, ("get_robust_list: emuldata notfound.\n"));
1081                 /* XXX: ptrace? */
1082                 if (priv_check(td, PRIV_CRED_SETUID) ||
1083                     priv_check(td, PRIV_CRED_SETEUID) ||
1084                     p_candebug(td, td2->td_proc)) {
1085                         PROC_UNLOCK(td2->td_proc);
1086                         return (EPERM);
1087                 }
1088                 head = em->robust_futexes;
1089
1090                 PROC_UNLOCK(td2->td_proc);
1091         }
1092
1093         error = copyout(&len, args->len, sizeof(l_size_t));
1094         if (error) {
1095                 LIN_SDT_PROBE1(futex, linux_get_robust_list, copyout_error,
1096                     error);
1097                 return (EFAULT);
1098         }
1099
1100         error = copyout(&head, args->head, sizeof(head));
1101         if (error) {
1102                 LIN_SDT_PROBE1(futex, linux_get_robust_list, copyout_error,
1103                     error);
1104         }
1105
1106         return (error);
1107 }
1108
1109 static int
1110 handle_futex_death(struct linux_emuldata *em, uint32_t *uaddr,
1111     unsigned int pi)
1112 {
1113         uint32_t uval, nval, mval;
1114         struct futex *f;
1115         int error;
1116
1117 retry:
1118         error = copyin(uaddr, &uval, 4);
1119         if (error) {
1120                 LIN_SDT_PROBE1(futex, handle_futex_death, copyin_error, error);
1121                 return (EFAULT);
1122         }
1123         if ((uval & FUTEX_TID_MASK) == em->em_tid) {
1124                 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
1125                 nval = casuword32(uaddr, uval, mval);
1126
1127                 if (nval == -1)
1128                         return (EFAULT);
1129
1130                 if (nval != uval)
1131                         goto retry;
1132
1133                 if (!pi && (uval & FUTEX_WAITERS)) {
1134                         error = futex_get(uaddr, NULL, &f,
1135                             FUTEX_DONTCREATE | FUTEX_SHARED);
1136                         if (error)
1137                                 return (error);
1138                         if (f != NULL) {
1139                                 futex_wake(f, 1, FUTEX_BITSET_MATCH_ANY);
1140                                 futex_put(f, NULL);
1141                         }
1142                 }
1143         }
1144
1145         return (0);
1146 }
1147
1148 static int
1149 fetch_robust_entry(struct linux_robust_list **entry,
1150     struct linux_robust_list **head, unsigned int *pi)
1151 {
1152         l_ulong uentry;
1153         int error;
1154
1155         error = copyin((const void *)head, &uentry, sizeof(l_ulong));
1156         if (error) {
1157                 LIN_SDT_PROBE1(futex, fetch_robust_entry, copyin_error, error);
1158                 return (EFAULT);
1159         }
1160
1161         *entry = (void *)(uentry & ~1UL);
1162         *pi = uentry & 1;
1163
1164         return (0);
1165 }
1166
1167 /* This walks the list of robust futexes releasing them. */
1168 void
1169 release_futexes(struct thread *td, struct linux_emuldata *em)
1170 {
1171         struct linux_robust_list_head *head = NULL;
1172         struct linux_robust_list *entry, *next_entry, *pending;
1173         unsigned int limit = 2048, pi, next_pi, pip;
1174         l_long futex_offset;
1175         int rc, error;
1176
1177         head = em->robust_futexes;
1178
1179         if (head == NULL)
1180                 return;
1181
1182         if (fetch_robust_entry(&entry, PTRIN(&head->list.next), &pi))
1183                 return;
1184
1185         error = copyin(&head->futex_offset, &futex_offset,
1186             sizeof(futex_offset));
1187         if (error) {
1188                 LIN_SDT_PROBE1(futex, release_futexes, copyin_error, error);
1189                 return;
1190         }
1191
1192         if (fetch_robust_entry(&pending, PTRIN(&head->pending_list), &pip))
1193                 return;
1194
1195         while (entry != &head->list) {
1196                 rc = fetch_robust_entry(&next_entry, PTRIN(&entry->next), &next_pi);
1197
1198                 if (entry != pending)
1199                         if (handle_futex_death(em,
1200                             (uint32_t *)((caddr_t)entry + futex_offset), pi)) {
1201                                 return;
1202                         }
1203                 if (rc)
1204                         return;
1205
1206                 entry = next_entry;
1207                 pi = next_pi;
1208
1209                 if (!--limit)
1210                         break;
1211
1212                 sched_relinquish(curthread);
1213         }
1214
1215         if (pending)
1216                 handle_futex_death(em, (uint32_t *)((caddr_t)pending + futex_offset), pip);
1217 }