sys/kern/sys_pipe.c

   1 /*-
   2  * Copyright (c) 1996 John S. Dyson
   3  * Copyright (c) 2012 Giovanni Trematerra
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice immediately at the beginning of the file, without modification,
  11  *    this list of conditions, and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Absolutely no warranty of function or purpose is made by the author
  16  *    John S. Dyson.
  17  * 4. Modifications may be freely made to this file if the above conditions
  18  *    are met.
  19  */
  20
  21 /*
  22  * This file contains a high-performance replacement for the socket-based
  23  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
  24  * all features of sockets, but does do everything that pipes normally
  25  * do.
  26  */
  27
  28 /*
  29  * This code has two modes of operation, a small write mode and a large
  30  * write mode.  The small write mode acts like conventional pipes with
  31  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
  32  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
  33  * and PIPE_SIZE in size, the sending process pins the underlying pages in
  34  * memory, and the receiving process copies directly from these pinned pages
  35  * in the sending process.
  36  *
  37  * If the sending process receives a signal, it is possible that it will
  38  * go away, and certainly its address space can change, because control
  39  * is returned back to the user-mode side.  In that case, the pipe code
  40  * arranges to copy the buffer supplied by the user process, to a pageable
  41  * kernel buffer, and the receiving process will grab the data from the
  42  * pageable kernel buffer.  Since signals don't happen all that often,
  43  * the copy operation is normally eliminated.
  44  *
  45  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
  46  * happen for small transfers so that the system will not spend all of
  47  * its time context switching.
  48  *
  49  * In order to limit the resource use of pipes, two sysctls exist:
  50  *
  51  * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
  52  * address space available to us in pipe_map. This value is normally
  53  * autotuned, but may also be loader tuned.
  54  *
  55  * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
  56  * memory in use by pipes.
  57  *
  58  * Based on how large pipekva is relative to maxpipekva, the following
  59  * will happen:
  60  *
  61  * 0% - 50%:
  62  *     New pipes are given 16K of memory backing, pipes may dynamically
  63  *     grow to as large as 64K where needed.
  64  * 50% - 75%:
  65  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
  66  *     existing pipes may NOT grow.
  67  * 75% - 100%:
  68  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
  69  *     existing pipes will be shrunk down to 4K whenever possible.
  70  *
  71  * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
  72  * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
  73  * resize which MUST occur for reverse-direction pipes when they are
  74  * first used.
  75  *
  76  * Additional information about the current state of pipes may be obtained
  77  * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
  78  * and kern.ipc.piperesizefail.
  79  *
  80  * Locking rules:  There are two locks present here:  A mutex, used via
  81  * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
  82  * the flag, as mutexes can not persist over uiomove.  The mutex
  83  * exists only to guard access to the flag, and is not in itself a
  84  * locking mechanism.  Also note that there is only a single mutex for
  85  * both directions of a pipe.
  86  *
  87  * As pipelock() may have to sleep before it can acquire the flag, it
  88  * is important to reread all data after a call to pipelock(); everything
  89  * in the structure may have changed.
  90  */
  91
  92 #include <sys/cdefs.h>
  93 __FBSDID("$FreeBSD$");
  94
  95 #include <sys/param.h>
  96 #include <sys/systm.h>
  97 #include <sys/conf.h>
  98 #include <sys/fcntl.h>
  99 #include <sys/file.h>
 100 #include <sys/filedesc.h>
 101 #include <sys/filio.h>
 102 #include <sys/kernel.h>
 103 #include <sys/lock.h>
 104 #include <sys/mutex.h>
 105 #include <sys/ttycom.h>
 106 #include <sys/stat.h>
 107 #include <sys/malloc.h>
 108 #include <sys/poll.h>
 109 #include <sys/selinfo.h>
 110 #include <sys/signalvar.h>
 111 #include <sys/syscallsubr.h>
 112 #include <sys/sysctl.h>
 113 #include <sys/sysproto.h>
 114 #include <sys/pipe.h>
 115 #include <sys/proc.h>
 116 #include <sys/vnode.h>
 117 #include <sys/uio.h>
 118 #include <sys/user.h>
 119 #include <sys/event.h>
 120
 121 #include <security/mac/mac_framework.h>
 122
 123 #include <vm/vm.h>
 124 #include <vm/vm_param.h>
 125 #include <vm/vm_object.h>
 126 #include <vm/vm_kern.h>
 127 #include <vm/vm_extern.h>
 128 #include <vm/pmap.h>
 129 #include <vm/vm_map.h>
 130 #include <vm/vm_page.h>
 131 #include <vm/uma.h>
 132
 133 /*
 134  * Use this define if you want to disable *fancy* VM things.  Expect an
 135  * approx 30% decrease in transfer rate.  This could be useful for
 136  * NetBSD or OpenBSD.
 137  */
 138 /* #define PIPE_NODIRECT */
 139
 140 #define PIPE_PEER(pipe) \
 141         (((pipe)->pipe_type & PIPE_TYPE_NAMED) ? (pipe) : ((pipe)->pipe_peer))
 142
 143 /*
 144  * interfaces to the outside world
 145  */
 146 static fo_rdwr_t        pipe_read;
 147 static fo_rdwr_t        pipe_write;
 148 static fo_truncate_t    pipe_truncate;
 149 static fo_ioctl_t       pipe_ioctl;
 150 static fo_poll_t        pipe_poll;
 151 static fo_kqfilter_t    pipe_kqfilter;
 152 static fo_stat_t        pipe_stat;
 153 static fo_close_t       pipe_close;
 154 static fo_chmod_t       pipe_chmod;
 155 static fo_chown_t       pipe_chown;
 156 static fo_fill_kinfo_t  pipe_fill_kinfo;
 157
 158 struct fileops pipeops = {
 159         .fo_read = pipe_read,
 160         .fo_write = pipe_write,
 161         .fo_truncate = pipe_truncate,
 162         .fo_ioctl = pipe_ioctl,
 163         .fo_poll = pipe_poll,
 164         .fo_kqfilter = pipe_kqfilter,
 165         .fo_stat = pipe_stat,
 166         .fo_close = pipe_close,
 167         .fo_chmod = pipe_chmod,
 168         .fo_chown = pipe_chown,
 169         .fo_sendfile = invfo_sendfile,
 170         .fo_fill_kinfo = pipe_fill_kinfo,
 171         .fo_flags = DFLAG_PASSABLE
 172 };
 173
 174 static void     filt_pipedetach(struct knote *kn);
 175 static void     filt_pipedetach_notsup(struct knote *kn);
 176 static int      filt_pipenotsup(struct knote *kn, long hint);
 177 static int      filt_piperead(struct knote *kn, long hint);
 178 static int      filt_pipewrite(struct knote *kn, long hint);
 179
 180 static struct filterops pipe_nfiltops = {
 181         .f_isfd = 1,
 182         .f_detach = filt_pipedetach_notsup,
 183         .f_event = filt_pipenotsup
 184 };
 185 static struct filterops pipe_rfiltops = {
 186         .f_isfd = 1,
 187         .f_detach = filt_pipedetach,
 188         .f_event = filt_piperead
 189 };
 190 static struct filterops pipe_wfiltops = {
 191         .f_isfd = 1,
 192         .f_detach = filt_pipedetach,
 193         .f_event = filt_pipewrite
 194 };
 195
 196 /*
 197  * Default pipe buffer size(s), this can be kind-of large now because pipe
 198  * space is pageable.  The pipe code will try to maintain locality of
 199  * reference for performance reasons, so small amounts of outstanding I/O
 200  * will not wipe the cache.
 201  */
 202 #define MINPIPESIZE (PIPE_SIZE/3)
 203 #define MAXPIPESIZE (2*PIPE_SIZE/3)
 204
 205 static long amountpipekva;
 206 static int pipefragretry;
 207 static int pipeallocfail;
 208 static int piperesizefail;
 209 static int piperesizeallowed = 1;
 210 static long pipe_mindirect = PIPE_MINDIRECT;
 211
 212 SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
 213            &maxpipekva, 0, "Pipe KVA limit");
 214 SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
 215            &amountpipekva, 0, "Pipe KVA usage");
 216 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
 217           &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
 218 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
 219           &pipeallocfail, 0, "Pipe allocation failures");
 220 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
 221           &piperesizefail, 0, "Pipe resize failures");
 222 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
 223           &piperesizeallowed, 0, "Pipe resizing allowed");
 224
 225 static void pipeinit(void *dummy __unused);
 226 static void pipeclose(struct pipe *cpipe);
 227 static void pipe_free_kmem(struct pipe *cpipe);
 228 static int pipe_create(struct pipe *pipe, bool backing);
 229 static int pipe_paircreate(struct thread *td, struct pipepair **p_pp);
 230 static __inline int pipelock(struct pipe *cpipe, int catch);
 231 static __inline void pipeunlock(struct pipe *cpipe);
 232 static void pipe_timestamp(struct timespec *tsp);
 233 #ifndef PIPE_NODIRECT
 234 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
 235 static void pipe_destroy_write_buffer(struct pipe *wpipe);
 236 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
 237 static void pipe_clone_write_buffer(struct pipe *wpipe);
 238 #endif
 239 static int pipespace(struct pipe *cpipe, int size);
 240 static int pipespace_new(struct pipe *cpipe, int size);
 241
 242 static int      pipe_zone_ctor(void *mem, int size, void *arg, int flags);
 243 static int      pipe_zone_init(void *mem, int size, int flags);
 244 static void     pipe_zone_fini(void *mem, int size);
 245
 246 static uma_zone_t pipe_zone;
 247 static struct unrhdr64 pipeino_unr;
 248 static dev_t pipedev_ino;
 249
 250 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
 251
 252 static void
 253 pipeinit(void *dummy __unused)
 254 {
 255
 256         pipe_zone = uma_zcreate("pipe", sizeof(struct pipepair),
 257             pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
 258             UMA_ALIGN_PTR, 0);
 259         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
 260         new_unrhdr64(&pipeino_unr, 1);
 261         pipedev_ino = devfs_alloc_cdp_inode();
 262         KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
 263 }
 264
 265 static int
 266 sysctl_handle_pipe_mindirect(SYSCTL_HANDLER_ARGS)
 267 {
 268         int error = 0;
 269         long tmp_pipe_mindirect = pipe_mindirect;
 270
 271         error = sysctl_handle_long(oidp, &tmp_pipe_mindirect, arg2, req);
 272         if (error != 0 || req->newptr == NULL)
 273                 return (error);
 274
 275         /*
 276          * Don't allow pipe_mindirect to be set so low that we violate
 277          * atomicity requirements.
 278          */
 279         if (tmp_pipe_mindirect <= PIPE_BUF)
 280                 return (EINVAL);
 281         pipe_mindirect = tmp_pipe_mindirect;
 282         return (0);
 283 }
 284 SYSCTL_OID(_kern_ipc, OID_AUTO, pipe_mindirect, CTLTYPE_LONG | CTLFLAG_RW,
 285     &pipe_mindirect, 0, sysctl_handle_pipe_mindirect, "L",
 286     "Minimum write size triggering VM optimization");
 287
 288 static int
 289 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
 290 {
 291         struct pipepair *pp;
 292         struct pipe *rpipe, *wpipe;
 293
 294         KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
 295
 296         pp = (struct pipepair *)mem;
 297
 298         /*
 299          * We zero both pipe endpoints to make sure all the kmem pointers
 300          * are NULL, flag fields are zero'd, etc.  We timestamp both
 301          * endpoints with the same time.
 302          */
 303         rpipe = &pp->pp_rpipe;
 304         bzero(rpipe, sizeof(*rpipe));
 305         pipe_timestamp(&rpipe->pipe_ctime);
 306         rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
 307
 308         wpipe = &pp->pp_wpipe;
 309         bzero(wpipe, sizeof(*wpipe));
 310         wpipe->pipe_ctime = rpipe->pipe_ctime;
 311         wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
 312
 313         rpipe->pipe_peer = wpipe;
 314         rpipe->pipe_pair = pp;
 315         wpipe->pipe_peer = rpipe;
 316         wpipe->pipe_pair = pp;
 317
 318         /*
 319          * Mark both endpoints as present; they will later get free'd
 320          * one at a time.  When both are free'd, then the whole pair
 321          * is released.
 322          */
 323         rpipe->pipe_present = PIPE_ACTIVE;
 324         wpipe->pipe_present = PIPE_ACTIVE;
 325
 326         /*
 327          * Eventually, the MAC Framework may initialize the label
 328          * in ctor or init, but for now we do it elswhere to avoid
 329          * blocking in ctor or init.
 330          */
 331         pp->pp_label = NULL;
 332
 333         return (0);
 334 }
 335
 336 static int
 337 pipe_zone_init(void *mem, int size, int flags)
 338 {
 339         struct pipepair *pp;
 340
 341         KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
 342
 343         pp = (struct pipepair *)mem;
 344
 345         mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_NEW);
 346         return (0);
 347 }
 348
 349 static void
 350 pipe_zone_fini(void *mem, int size)
 351 {
 352         struct pipepair *pp;
 353
 354         KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
 355
 356         pp = (struct pipepair *)mem;
 357
 358         mtx_destroy(&pp->pp_mtx);
 359 }
 360
 361 static int
 362 pipe_paircreate(struct thread *td, struct pipepair **p_pp)
 363 {
 364         struct pipepair *pp;
 365         struct pipe *rpipe, *wpipe;
 366         int error;
 367
 368         *p_pp = pp = uma_zalloc(pipe_zone, M_WAITOK);
 369 #ifdef MAC
 370         /*
 371          * The MAC label is shared between the connected endpoints.  As a
 372          * result mac_pipe_init() and mac_pipe_create() are called once
 373          * for the pair, and not on the endpoints.
 374          */
 375         mac_pipe_init(pp);
 376         mac_pipe_create(td->td_ucred, pp);
 377 #endif
 378         rpipe = &pp->pp_rpipe;
 379         wpipe = &pp->pp_wpipe;
 380
 381         knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
 382         knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
 383
 384         /*
 385          * Only the forward direction pipe is backed by big buffer by
 386          * default.
 387          */
 388         error = pipe_create(rpipe, true);
 389         if (error != 0)
 390                 goto fail;
 391         error = pipe_create(wpipe, false);
 392         if (error != 0) {
 393                 /*
 394                  * This cleanup leaves the pipe inode number for rpipe
 395                  * still allocated, but never used.  We do not free
 396                  * inode numbers for opened pipes, which is required
 397                  * for correctness because numbers must be unique.
 398                  * But also it avoids any memory use by the unr
 399                  * allocator, so stashing away the transient inode
 400                  * number is reasonable.
 401                  */
 402                 pipe_free_kmem(rpipe);
 403                 goto fail;
 404         }
 405
 406         rpipe->pipe_state |= PIPE_DIRECTOK;
 407         wpipe->pipe_state |= PIPE_DIRECTOK;
 408         return (0);
 409
 410 fail:
 411         knlist_destroy(&rpipe->pipe_sel.si_note);
 412         knlist_destroy(&wpipe->pipe_sel.si_note);
 413 #ifdef MAC
 414         mac_pipe_destroy(pp);
 415 #endif
 416         uma_zfree(pipe_zone, pp);
 417         return (error);
 418 }
 419
 420 int
 421 pipe_named_ctor(struct pipe **ppipe, struct thread *td)
 422 {
 423         struct pipepair *pp;
 424         int error;
 425
 426         error = pipe_paircreate(td, &pp);
 427         if (error != 0)
 428                 return (error);
 429         pp->pp_rpipe.pipe_type |= PIPE_TYPE_NAMED;
 430         *ppipe = &pp->pp_rpipe;
 431         return (0);
 432 }
 433
 434 void
 435 pipe_dtor(struct pipe *dpipe)
 436 {
 437         struct pipe *peer;
 438
 439         peer = (dpipe->pipe_type & PIPE_TYPE_NAMED) != 0 ? dpipe->pipe_peer : NULL;
 440         funsetown(&dpipe->pipe_sigio);
 441         pipeclose(dpipe);
 442         if (peer != NULL) {
 443                 funsetown(&peer->pipe_sigio);
 444                 pipeclose(peer);
 445         }
 446 }
 447
 448 /*
 449  * Get a timestamp.
 450  *
 451  * This used to be vfs_timestamp but the higher precision is unnecessary and
 452  * can very negatively affect performance in virtualized environments (e.g., on
 453  * vms running on amd64 when using the rdtscp instruction).
 454  */
 455 static void
 456 pipe_timestamp(struct timespec *tsp)
 457 {
 458
 459         getnanotime(tsp);
 460 }
 461
 462 /*
 463  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
 464  * the zone pick up the pieces via pipeclose().
 465  */
 466 int
 467 kern_pipe(struct thread *td, int fildes[2], int flags, struct filecaps *fcaps1,
 468     struct filecaps *fcaps2)
 469 {
 470         struct file *rf, *wf;
 471         struct pipe *rpipe, *wpipe;
 472         struct pipepair *pp;
 473         int fd, fflags, error;
 474
 475         error = pipe_paircreate(td, &pp);
 476         if (error != 0)
 477                 return (error);
 478         rpipe = &pp->pp_rpipe;
 479         wpipe = &pp->pp_wpipe;
 480         error = falloc_caps(td, &rf, &fd, flags, fcaps1);
 481         if (error) {
 482                 pipeclose(rpipe);
 483                 pipeclose(wpipe);
 484                 return (error);
 485         }
 486         /* An extra reference on `rf' has been held for us by falloc_caps(). */
 487         fildes[0] = fd;
 488
 489         fflags = FREAD | FWRITE;
 490         if ((flags & O_NONBLOCK) != 0)
 491                 fflags |= FNONBLOCK;
 492
 493         /*
 494          * Warning: once we've gotten past allocation of the fd for the
 495          * read-side, we can only drop the read side via fdrop() in order
 496          * to avoid races against processes which manage to dup() the read
 497          * side while we are blocked trying to allocate the write side.
 498          */
 499         finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
 500         error = falloc_caps(td, &wf, &fd, flags, fcaps2);
 501         if (error) {
 502                 fdclose(td, rf, fildes[0]);
 503                 fdrop(rf, td);
 504                 /* rpipe has been closed by fdrop(). */
 505                 pipeclose(wpipe);
 506                 return (error);
 507         }
 508         /* An extra reference on `wf' has been held for us by falloc_caps(). */
 509         finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
 510         fdrop(wf, td);
 511         fildes[1] = fd;
 512         fdrop(rf, td);
 513
 514         return (0);
 515 }
 516
 517 #ifdef COMPAT_FREEBSD10
 518 /* ARGSUSED */
 519 int
 520 freebsd10_pipe(struct thread *td, struct freebsd10_pipe_args *uap __unused)
 521 {
 522         int error;
 523         int fildes[2];
 524
 525         error = kern_pipe(td, fildes, 0, NULL, NULL);
 526         if (error)
 527                 return (error);
 528
 529         td->td_retval[0] = fildes[0];
 530         td->td_retval[1] = fildes[1];
 531
 532         return (0);
 533 }
 534 #endif
 535
 536 int
 537 sys_pipe2(struct thread *td, struct pipe2_args *uap)
 538 {
 539         int error, fildes[2];
 540
 541         if (uap->flags & ~(O_CLOEXEC | O_NONBLOCK))
 542                 return (EINVAL);
 543         error = kern_pipe(td, fildes, uap->flags, NULL, NULL);
 544         if (error)
 545                 return (error);
 546         error = copyout(fildes, uap->fildes, 2 * sizeof(int));
 547         if (error) {
 548                 (void)kern_close(td, fildes[0]);
 549                 (void)kern_close(td, fildes[1]);
 550         }
 551         return (error);
 552 }
 553
 554 /*
 555  * Allocate kva for pipe circular buffer, the space is pageable
 556  * This routine will 'realloc' the size of a pipe safely, if it fails
 557  * it will retain the old buffer.
 558  * If it fails it will return ENOMEM.
 559  */
 560 static int
 561 pipespace_new(struct pipe *cpipe, int size)
 562 {
 563         caddr_t buffer;
 564         int error, cnt, firstseg;
 565         static int curfail = 0;
 566         static struct timeval lastfail;
 567
 568         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
 569         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
 570                 ("pipespace: resize of direct writes not allowed"));
 571 retry:
 572         cnt = cpipe->pipe_buffer.cnt;
 573         if (cnt > size)
 574                 size = cnt;
 575
 576         size = round_page(size);
 577         buffer = (caddr_t) vm_map_min(pipe_map);
 578
 579         error = vm_map_find(pipe_map, NULL, 0, (vm_offset_t *)&buffer, size, 0,
 580             VMFS_ANY_SPACE, VM_PROT_RW, VM_PROT_RW, 0);
 581         if (error != KERN_SUCCESS) {
 582                 if (cpipe->pipe_buffer.buffer == NULL &&
 583                     size > SMALL_PIPE_SIZE) {
 584                         size = SMALL_PIPE_SIZE;
 585                         pipefragretry++;
 586                         goto retry;
 587                 }
 588                 if (cpipe->pipe_buffer.buffer == NULL) {
 589                         pipeallocfail++;
 590                         if (ppsratecheck(&lastfail, &curfail, 1))
 591                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
 592                 } else {
 593                         piperesizefail++;
 594                 }
 595                 return (ENOMEM);
 596         }
 597
 598         /* copy data, then free old resources if we're resizing */
 599         if (cnt > 0) {
 600                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
 601                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
 602                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
 603                                 buffer, firstseg);
 604                         if ((cnt - firstseg) > 0)
 605                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
 606                                         cpipe->pipe_buffer.in);
 607                 } else {
 608                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
 609                                 buffer, cnt);
 610                 }
 611         }
 612         pipe_free_kmem(cpipe);
 613         cpipe->pipe_buffer.buffer = buffer;
 614         cpipe->pipe_buffer.size = size;
 615         cpipe->pipe_buffer.in = cnt;
 616         cpipe->pipe_buffer.out = 0;
 617         cpipe->pipe_buffer.cnt = cnt;
 618         atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
 619         return (0);
 620 }
 621
 622 /*
 623  * Wrapper for pipespace_new() that performs locking assertions.
 624  */
 625 static int
 626 pipespace(struct pipe *cpipe, int size)
 627 {
 628
 629         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
 630             ("Unlocked pipe passed to pipespace"));
 631         return (pipespace_new(cpipe, size));
 632 }
 633
 634 /*
 635  * lock a pipe for I/O, blocking other access
 636  */
 637 static __inline int
 638 pipelock(struct pipe *cpipe, int catch)
 639 {
 640         int error, prio;
 641
 642         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 643
 644         prio = PRIBIO;
 645         if (catch)
 646                 prio |= PCATCH;
 647         while (cpipe->pipe_state & PIPE_LOCKFL) {
 648                 KASSERT(cpipe->pipe_waiters >= 0,
 649                     ("%s: bad waiter count %d", __func__,
 650                     cpipe->pipe_waiters));
 651                 cpipe->pipe_waiters++;
 652                 error = msleep(&cpipe->pipe_waiters, PIPE_MTX(cpipe), prio,
 653                     "pipelk", 0);
 654                 cpipe->pipe_waiters--;
 655                 if (error != 0)
 656                         return (error);
 657         }
 658         cpipe->pipe_state |= PIPE_LOCKFL;
 659         return (0);
 660 }
 661
 662 /*
 663  * unlock a pipe I/O lock
 664  */
 665 static __inline void
 666 pipeunlock(struct pipe *cpipe)
 667 {
 668
 669         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 670         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
 671                 ("Unlocked pipe passed to pipeunlock"));
 672         KASSERT(cpipe->pipe_waiters >= 0,
 673             ("%s: bad waiter count %d", __func__,
 674             cpipe->pipe_waiters));
 675         cpipe->pipe_state &= ~PIPE_LOCKFL;
 676         if (cpipe->pipe_waiters > 0)
 677                 wakeup_one(&cpipe->pipe_waiters);
 678 }
 679
 680 void
 681 pipeselwakeup(struct pipe *cpipe)
 682 {
 683
 684         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 685         if (cpipe->pipe_state & PIPE_SEL) {
 686                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
 687                 if (!SEL_WAITING(&cpipe->pipe_sel))
 688                         cpipe->pipe_state &= ~PIPE_SEL;
 689         }
 690         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
 691                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
 692         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
 693 }
 694
 695 /*
 696  * Initialize and allocate VM and memory for pipe.  The structure
 697  * will start out zero'd from the ctor, so we just manage the kmem.
 698  */
 699 static int
 700 pipe_create(struct pipe *pipe, bool large_backing)
 701 {
 702         int error;
 703
 704         error = pipespace_new(pipe, !large_backing || amountpipekva >
 705             maxpipekva / 2 ? SMALL_PIPE_SIZE : PIPE_SIZE);
 706         if (error == 0)
 707                 pipe->pipe_ino = alloc_unr64(&pipeino_unr);
 708         return (error);
 709 }
 710
 711 /* ARGSUSED */
 712 static int
 713 pipe_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
 714     int flags, struct thread *td)
 715 {
 716         struct pipe *rpipe;
 717         int error;
 718         int nread = 0;
 719         int size;
 720
 721         rpipe = fp->f_data;
 722
 723         /*
 724          * Try to avoid locking the pipe if we have nothing to do.
 725          *
 726          * There are programs which share one pipe amongst multiple processes
 727          * and perform non-blocking reads in parallel, even if the pipe is
 728          * empty.  This in particular is the case with BSD make, which when
 729          * spawned with a high -j number can find itself with over half of the
 730          * calls failing to find anything.
 731          */
 732         if ((fp->f_flag & FNONBLOCK) != 0 && !mac_pipe_check_read_enabled()) {
 733                 if (__predict_false(uio->uio_resid == 0))
 734                         return (0);
 735                 if ((atomic_load_short(&rpipe->pipe_state) & PIPE_EOF) == 0 &&
 736                     atomic_load_int(&rpipe->pipe_buffer.cnt) == 0 &&
 737                     atomic_load_int(&rpipe->pipe_pages.cnt) == 0)
 738                         return (EAGAIN);
 739         }
 740
 741         PIPE_LOCK(rpipe);
 742         ++rpipe->pipe_busy;
 743         error = pipelock(rpipe, 1);
 744         if (error)
 745                 goto unlocked_error;
 746
 747 #ifdef MAC
 748         error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
 749         if (error)
 750                 goto locked_error;
 751 #endif
 752         if (amountpipekva > (3 * maxpipekva) / 4) {
 753                 if ((rpipe->pipe_state & PIPE_DIRECTW) == 0 &&
 754                     rpipe->pipe_buffer.size > SMALL_PIPE_SIZE &&
 755                     rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE &&
 756                     piperesizeallowed == 1) {
 757                         PIPE_UNLOCK(rpipe);
 758                         pipespace(rpipe, SMALL_PIPE_SIZE);
 759                         PIPE_LOCK(rpipe);
 760                 }
 761         }
 762
 763         while (uio->uio_resid) {
 764                 /*
 765                  * normal pipe buffer receive
 766                  */
 767                 if (rpipe->pipe_buffer.cnt > 0) {
 768                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
 769                         if (size > rpipe->pipe_buffer.cnt)
 770                                 size = rpipe->pipe_buffer.cnt;
 771                         if (size > uio->uio_resid)
 772                                 size = uio->uio_resid;
 773
 774                         PIPE_UNLOCK(rpipe);
 775                         error = uiomove(
 776                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
 777                             size, uio);
 778                         PIPE_LOCK(rpipe);
 779                         if (error)
 780                                 break;
 781
 782                         rpipe->pipe_buffer.out += size;
 783                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
 784                                 rpipe->pipe_buffer.out = 0;
 785
 786                         rpipe->pipe_buffer.cnt -= size;
 787
 788                         /*
 789                          * If there is no more to read in the pipe, reset
 790                          * its pointers to the beginning.  This improves
 791                          * cache hit stats.
 792                          */
 793                         if (rpipe->pipe_buffer.cnt == 0) {
 794                                 rpipe->pipe_buffer.in = 0;
 795                                 rpipe->pipe_buffer.out = 0;
 796                         }
 797                         nread += size;
 798 #ifndef PIPE_NODIRECT
 799                 /*
 800                  * Direct copy, bypassing a kernel buffer.
 801                  */
 802                 } else if ((size = rpipe->pipe_pages.cnt) != 0) {
 803                         if (size > uio->uio_resid)
 804                                 size = (u_int) uio->uio_resid;
 805                         PIPE_UNLOCK(rpipe);
 806                         error = uiomove_fromphys(rpipe->pipe_pages.ms,
 807                             rpipe->pipe_pages.pos, size, uio);
 808                         PIPE_LOCK(rpipe);
 809                         if (error)
 810                                 break;
 811                         nread += size;
 812                         rpipe->pipe_pages.pos += size;
 813                         rpipe->pipe_pages.cnt -= size;
 814                         if (rpipe->pipe_pages.cnt == 0) {
 815                                 rpipe->pipe_state &= ~PIPE_WANTW;
 816                                 wakeup(rpipe);
 817                         }
 818 #endif
 819                 } else {
 820                         /*
 821                          * detect EOF condition
 822                          * read returns 0 on EOF, no need to set error
 823                          */
 824                         if (rpipe->pipe_state & PIPE_EOF)
 825                                 break;
 826
 827                         /*
 828                          * If the "write-side" has been blocked, wake it up now.
 829                          */
 830                         if (rpipe->pipe_state & PIPE_WANTW) {
 831                                 rpipe->pipe_state &= ~PIPE_WANTW;
 832                                 wakeup(rpipe);
 833                         }
 834
 835                         /*
 836                          * Break if some data was read.
 837                          */
 838                         if (nread > 0)
 839                                 break;
 840
 841                         /*
 842                          * Unlock the pipe buffer for our remaining processing.
 843                          * We will either break out with an error or we will
 844                          * sleep and relock to loop.
 845                          */
 846                         pipeunlock(rpipe);
 847
 848                         /*
 849                          * Handle non-blocking mode operation or
 850                          * wait for more data.
 851                          */
 852                         if (fp->f_flag & FNONBLOCK) {
 853                                 error = EAGAIN;
 854                         } else {
 855                                 rpipe->pipe_state |= PIPE_WANTR;
 856                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
 857                                     PRIBIO | PCATCH,
 858                                     "piperd", 0)) == 0)
 859                                         error = pipelock(rpipe, 1);
 860                         }
 861                         if (error)
 862                                 goto unlocked_error;
 863                 }
 864         }
 865 #ifdef MAC
 866 locked_error:
 867 #endif
 868         pipeunlock(rpipe);
 869
 870         /* XXX: should probably do this before getting any locks. */
 871         if (error == 0)
 872                 pipe_timestamp(&rpipe->pipe_atime);
 873 unlocked_error:
 874         --rpipe->pipe_busy;
 875
 876         /*
 877          * PIPE_WANT processing only makes sense if pipe_busy is 0.
 878          */
 879         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
 880                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
 881                 wakeup(rpipe);
 882         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
 883                 /*
 884                  * Handle write blocking hysteresis.
 885                  */
 886                 if (rpipe->pipe_state & PIPE_WANTW) {
 887                         rpipe->pipe_state &= ~PIPE_WANTW;
 888                         wakeup(rpipe);
 889                 }
 890         }
 891
 892         /*
 893          * Only wake up writers if there was actually something read.
 894          * Otherwise, when calling read(2) at EOF, a spurious wakeup occurs.
 895          */
 896         if (nread > 0 &&
 897             rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt >= PIPE_BUF)
 898                 pipeselwakeup(rpipe);
 899
 900         PIPE_UNLOCK(rpipe);
 901         if (nread > 0)
 902                 td->td_ru.ru_msgrcv++;
 903         return (error);
 904 }
 905
 906 #ifndef PIPE_NODIRECT
 907 /*
 908  * Map the sending processes' buffer into kernel space and wire it.
 909  * This is similar to a physical write operation.
 910  */
 911 static int
 912 pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio)
 913 {
 914         u_int size;
 915         int i;
 916
 917         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 918         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
 919             ("%s: PIPE_DIRECTW set on %p", __func__, wpipe));
 920         KASSERT(wpipe->pipe_pages.cnt == 0,
 921             ("%s: pipe map for %p contains residual data", __func__, wpipe));
 922
 923         if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
 924                 size = wpipe->pipe_buffer.size;
 925         else
 926                 size = uio->uio_iov->iov_len;
 927
 928         wpipe->pipe_state |= PIPE_DIRECTW;
 929         PIPE_UNLOCK(wpipe);
 930         i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
 931             (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
 932             wpipe->pipe_pages.ms, PIPENPAGES);
 933         PIPE_LOCK(wpipe);
 934         if (i < 0) {
 935                 wpipe->pipe_state &= ~PIPE_DIRECTW;
 936                 return (EFAULT);
 937         }
 938
 939         wpipe->pipe_pages.npages = i;
 940         wpipe->pipe_pages.pos =
 941             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
 942         wpipe->pipe_pages.cnt = size;
 943
 944         uio->uio_iov->iov_len -= size;
 945         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
 946         if (uio->uio_iov->iov_len == 0)
 947                 uio->uio_iov++;
 948         uio->uio_resid -= size;
 949         uio->uio_offset += size;
 950         return (0);
 951 }
 952
 953 /*
 954  * Unwire the process buffer.
 955  */
 956 static void
 957 pipe_destroy_write_buffer(struct pipe *wpipe)
 958 {
 959
 960         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 961         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
 962             ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
 963         KASSERT(wpipe->pipe_pages.cnt == 0,
 964             ("%s: pipe map for %p contains residual data", __func__, wpipe));
 965
 966         wpipe->pipe_state &= ~PIPE_DIRECTW;
 967         vm_page_unhold_pages(wpipe->pipe_pages.ms, wpipe->pipe_pages.npages);
 968         wpipe->pipe_pages.npages = 0;
 969 }
 970
 971 /*
 972  * In the case of a signal, the writing process might go away.  This
 973  * code copies the data into the circular buffer so that the source
 974  * pages can be freed without loss of data.
 975  */
 976 static void
 977 pipe_clone_write_buffer(struct pipe *wpipe)
 978 {
 979         struct uio uio;
 980         struct iovec iov;
 981         int size;
 982         int pos;
 983
 984         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 985         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
 986             ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
 987
 988         size = wpipe->pipe_pages.cnt;
 989         pos = wpipe->pipe_pages.pos;
 990         wpipe->pipe_pages.cnt = 0;
 991
 992         wpipe->pipe_buffer.in = size;
 993         wpipe->pipe_buffer.out = 0;
 994         wpipe->pipe_buffer.cnt = size;
 995
 996         PIPE_UNLOCK(wpipe);
 997         iov.iov_base = wpipe->pipe_buffer.buffer;
 998         iov.iov_len = size;
 999         uio.uio_iov = &iov;
1000         uio.uio_iovcnt = 1;
1001         uio.uio_offset = 0;
1002         uio.uio_resid = size;
1003         uio.uio_segflg = UIO_SYSSPACE;
1004         uio.uio_rw = UIO_READ;
1005         uio.uio_td = curthread;
1006         uiomove_fromphys(wpipe->pipe_pages.ms, pos, size, &uio);
1007         PIPE_LOCK(wpipe);
1008         pipe_destroy_write_buffer(wpipe);
1009 }
1010
1011 /*
1012  * This implements the pipe buffer write mechanism.  Note that only
1013  * a direct write OR a normal pipe write can be pending at any given time.
1014  * If there are any characters in the pipe buffer, the direct write will
1015  * be deferred until the receiving process grabs all of the bytes from
1016  * the pipe buffer.  Then the direct mapping write is set-up.
1017  */
1018 static int
1019 pipe_direct_write(struct pipe *wpipe, struct uio *uio)
1020 {
1021         int error;
1022
1023 retry:
1024         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
1025         if ((wpipe->pipe_state & PIPE_EOF) != 0) {
1026                 error = EPIPE;
1027                 goto error1;
1028         }
1029         if (wpipe->pipe_state & PIPE_DIRECTW) {
1030                 if (wpipe->pipe_state & PIPE_WANTR) {
1031                         wpipe->pipe_state &= ~PIPE_WANTR;
1032                         wakeup(wpipe);
1033                 }
1034                 pipeselwakeup(wpipe);
1035                 wpipe->pipe_state |= PIPE_WANTW;
1036                 pipeunlock(wpipe);
1037                 error = msleep(wpipe, PIPE_MTX(wpipe),
1038                     PRIBIO | PCATCH, "pipdww", 0);
1039                 pipelock(wpipe, 0);
1040                 if (error != 0)
1041                         goto error1;
1042                 goto retry;
1043         }
1044         if (wpipe->pipe_buffer.cnt > 0) {
1045                 if (wpipe->pipe_state & PIPE_WANTR) {
1046                         wpipe->pipe_state &= ~PIPE_WANTR;
1047                         wakeup(wpipe);
1048                 }
1049                 pipeselwakeup(wpipe);
1050                 wpipe->pipe_state |= PIPE_WANTW;
1051                 pipeunlock(wpipe);
1052                 error = msleep(wpipe, PIPE_MTX(wpipe),
1053                     PRIBIO | PCATCH, "pipdwc", 0);
1054                 pipelock(wpipe, 0);
1055                 if (error != 0)
1056                         goto error1;
1057                 goto retry;
1058         }
1059
1060         error = pipe_build_write_buffer(wpipe, uio);
1061         if (error) {
1062                 goto error1;
1063         }
1064
1065         while (wpipe->pipe_pages.cnt != 0 &&
1066             (wpipe->pipe_state & PIPE_EOF) == 0) {
1067                 if (wpipe->pipe_state & PIPE_WANTR) {
1068                         wpipe->pipe_state &= ~PIPE_WANTR;
1069                         wakeup(wpipe);
1070                 }
1071                 pipeselwakeup(wpipe);
1072                 wpipe->pipe_state |= PIPE_WANTW;
1073                 pipeunlock(wpipe);
1074                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
1075                     "pipdwt", 0);
1076                 pipelock(wpipe, 0);
1077                 if (error != 0)
1078                         break;
1079         }
1080
1081         if ((wpipe->pipe_state & PIPE_EOF) != 0) {
1082                 wpipe->pipe_pages.cnt = 0;
1083                 pipe_destroy_write_buffer(wpipe);
1084                 pipeselwakeup(wpipe);
1085                 error = EPIPE;
1086         } else if (error == EINTR || error == ERESTART) {
1087                 pipe_clone_write_buffer(wpipe);
1088         } else {
1089                 pipe_destroy_write_buffer(wpipe);
1090         }
1091         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
1092             ("pipe %p leaked PIPE_DIRECTW", wpipe));
1093         return (error);
1094
1095 error1:
1096         wakeup(wpipe);
1097         return (error);
1098 }
1099 #endif
1100
1101 static int
1102 pipe_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
1103     int flags, struct thread *td)
1104 {
1105         struct pipe *wpipe, *rpipe;
1106         ssize_t orig_resid;
1107         int desiredsize, error;
1108
1109         rpipe = fp->f_data;
1110         wpipe = PIPE_PEER(rpipe);
1111         PIPE_LOCK(rpipe);
1112         error = pipelock(wpipe, 1);
1113         if (error) {
1114                 PIPE_UNLOCK(rpipe);
1115                 return (error);
1116         }
1117         /*
1118          * detect loss of pipe read side, issue SIGPIPE if lost.
1119          */
1120         if (wpipe->pipe_present != PIPE_ACTIVE ||
1121             (wpipe->pipe_state & PIPE_EOF)) {
1122                 pipeunlock(wpipe);
1123                 PIPE_UNLOCK(rpipe);
1124                 return (EPIPE);
1125         }
1126 #ifdef MAC
1127         error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
1128         if (error) {
1129                 pipeunlock(wpipe);
1130                 PIPE_UNLOCK(rpipe);
1131                 return (error);
1132         }
1133 #endif
1134         ++wpipe->pipe_busy;
1135
1136         /* Choose a larger size if it's advantageous */
1137         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
1138         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
1139                 if (piperesizeallowed != 1)
1140                         break;
1141                 if (amountpipekva > maxpipekva / 2)
1142                         break;
1143                 if (desiredsize == BIG_PIPE_SIZE)
1144                         break;
1145                 desiredsize = desiredsize * 2;
1146         }
1147
1148         /* Choose a smaller size if we're in a OOM situation */
1149         if (amountpipekva > (3 * maxpipekva) / 4 &&
1150             wpipe->pipe_buffer.size > SMALL_PIPE_SIZE &&
1151             wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE &&
1152             piperesizeallowed == 1)
1153                 desiredsize = SMALL_PIPE_SIZE;
1154
1155         /* Resize if the above determined that a new size was necessary */
1156         if (desiredsize != wpipe->pipe_buffer.size &&
1157             (wpipe->pipe_state & PIPE_DIRECTW) == 0) {
1158                 PIPE_UNLOCK(wpipe);
1159                 pipespace(wpipe, desiredsize);
1160                 PIPE_LOCK(wpipe);
1161         }
1162         MPASS(wpipe->pipe_buffer.size != 0);
1163
1164         orig_resid = uio->uio_resid;
1165
1166         while (uio->uio_resid) {
1167                 int space;
1168
1169                 if (wpipe->pipe_state & PIPE_EOF) {
1170                         error = EPIPE;
1171                         break;
1172                 }
1173 #ifndef PIPE_NODIRECT
1174                 /*
1175                  * If the transfer is large, we can gain performance if
1176                  * we do process-to-process copies directly.
1177                  * If the write is non-blocking, we don't use the
1178                  * direct write mechanism.
1179                  *
1180                  * The direct write mechanism will detect the reader going
1181                  * away on us.
1182                  */
1183                 if (uio->uio_segflg == UIO_USERSPACE &&
1184                     uio->uio_iov->iov_len >= pipe_mindirect &&
1185                     wpipe->pipe_buffer.size >= pipe_mindirect &&
1186                     (fp->f_flag & FNONBLOCK) == 0) {
1187                         error = pipe_direct_write(wpipe, uio);
1188                         if (error != 0)
1189                                 break;
1190                         continue;
1191                 }
1192 #endif
1193
1194                 /*
1195                  * Pipe buffered writes cannot be coincidental with
1196                  * direct writes.  We wait until the currently executing
1197                  * direct write is completed before we start filling the
1198                  * pipe buffer.  We break out if a signal occurs or the
1199                  * reader goes away.
1200                  */
1201                 if (wpipe->pipe_pages.cnt != 0) {
1202                         if (wpipe->pipe_state & PIPE_WANTR) {
1203                                 wpipe->pipe_state &= ~PIPE_WANTR;
1204                                 wakeup(wpipe);
1205                         }
1206                         pipeselwakeup(wpipe);
1207                         wpipe->pipe_state |= PIPE_WANTW;
1208                         pipeunlock(wpipe);
1209                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
1210                             "pipbww", 0);
1211                         pipelock(wpipe, 0);
1212                         if (error != 0)
1213                                 break;
1214                         continue;
1215                 }
1216
1217                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
1218
1219                 /* Writes of size <= PIPE_BUF must be atomic. */
1220                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
1221                         space = 0;
1222
1223                 if (space > 0) {
1224                         int size;       /* Transfer size */
1225                         int segsize;    /* first segment to transfer */
1226
1227                         /*
1228                          * Transfer size is minimum of uio transfer
1229                          * and free space in pipe buffer.
1230                          */
1231                         if (space > uio->uio_resid)
1232                                 size = uio->uio_resid;
1233                         else
1234                                 size = space;
1235                         /*
1236                          * First segment to transfer is minimum of
1237                          * transfer size and contiguous space in
1238                          * pipe buffer.  If first segment to transfer
1239                          * is less than the transfer size, we've got
1240                          * a wraparound in the buffer.
1241                          */
1242                         segsize = wpipe->pipe_buffer.size -
1243                                 wpipe->pipe_buffer.in;
1244                         if (segsize > size)
1245                                 segsize = size;
1246
1247                         /* Transfer first segment */
1248
1249                         PIPE_UNLOCK(rpipe);
1250                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
1251                                         segsize, uio);
1252                         PIPE_LOCK(rpipe);
1253
1254                         if (error == 0 && segsize < size) {
1255                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
1256                                         wpipe->pipe_buffer.size,
1257                                         ("Pipe buffer wraparound disappeared"));
1258                                 /*
1259                                  * Transfer remaining part now, to
1260                                  * support atomic writes.  Wraparound
1261                                  * happened.
1262                                  */
1263
1264                                 PIPE_UNLOCK(rpipe);
1265                                 error = uiomove(
1266                                     &wpipe->pipe_buffer.buffer[0],
1267                                     size - segsize, uio);
1268                                 PIPE_LOCK(rpipe);
1269                         }
1270                         if (error == 0) {
1271                                 wpipe->pipe_buffer.in += size;
1272                                 if (wpipe->pipe_buffer.in >=
1273                                     wpipe->pipe_buffer.size) {
1274                                         KASSERT(wpipe->pipe_buffer.in ==
1275                                                 size - segsize +
1276                                                 wpipe->pipe_buffer.size,
1277                                                 ("Expected wraparound bad"));
1278                                         wpipe->pipe_buffer.in = size - segsize;
1279                                 }
1280
1281                                 wpipe->pipe_buffer.cnt += size;
1282                                 KASSERT(wpipe->pipe_buffer.cnt <=
1283                                         wpipe->pipe_buffer.size,
1284                                         ("Pipe buffer overflow"));
1285                         }
1286                         if (error != 0)
1287                                 break;
1288                         continue;
1289                 } else {
1290                         /*
1291                          * If the "read-side" has been blocked, wake it up now.
1292                          */
1293                         if (wpipe->pipe_state & PIPE_WANTR) {
1294                                 wpipe->pipe_state &= ~PIPE_WANTR;
1295                                 wakeup(wpipe);
1296                         }
1297
1298                         /*
1299                          * don't block on non-blocking I/O
1300                          */
1301                         if (fp->f_flag & FNONBLOCK) {
1302                                 error = EAGAIN;
1303                                 break;
1304                         }
1305
1306                         /*
1307                          * We have no more space and have something to offer,
1308                          * wake up select/poll.
1309                          */
1310                         pipeselwakeup(wpipe);
1311
1312                         wpipe->pipe_state |= PIPE_WANTW;
1313                         pipeunlock(wpipe);
1314                         error = msleep(wpipe, PIPE_MTX(rpipe),
1315                             PRIBIO | PCATCH, "pipewr", 0);
1316                         pipelock(wpipe, 0);
1317                         if (error != 0)
1318                                 break;
1319                         continue;
1320                 }
1321         }
1322
1323         --wpipe->pipe_busy;
1324
1325         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
1326                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
1327                 wakeup(wpipe);
1328         } else if (wpipe->pipe_buffer.cnt > 0) {
1329                 /*
1330                  * If we have put any characters in the buffer, we wake up
1331                  * the reader.
1332                  */
1333                 if (wpipe->pipe_state & PIPE_WANTR) {
1334                         wpipe->pipe_state &= ~PIPE_WANTR;
1335                         wakeup(wpipe);
1336                 }
1337         }
1338
1339         /*
1340          * Don't return EPIPE if any byte was written.
1341          * EINTR and other interrupts are handled by generic I/O layer.
1342          * Do not pretend that I/O succeeded for obvious user error
1343          * like EFAULT.
1344          */
1345         if (uio->uio_resid != orig_resid && error == EPIPE)
1346                 error = 0;
1347
1348         if (error == 0)
1349                 pipe_timestamp(&wpipe->pipe_mtime);
1350
1351         /*
1352          * We have something to offer,
1353          * wake up select/poll.
1354          */
1355         if (wpipe->pipe_buffer.cnt)
1356                 pipeselwakeup(wpipe);
1357
1358         pipeunlock(wpipe);
1359         PIPE_UNLOCK(rpipe);
1360         if (uio->uio_resid != orig_resid)
1361                 td->td_ru.ru_msgsnd++;
1362         return (error);
1363 }
1364
1365 /* ARGSUSED */
1366 static int
1367 pipe_truncate(struct file *fp, off_t length, struct ucred *active_cred,
1368     struct thread *td)
1369 {
1370         struct pipe *cpipe;
1371         int error;
1372
1373         cpipe = fp->f_data;
1374         if (cpipe->pipe_type & PIPE_TYPE_NAMED)
1375                 error = vnops.fo_truncate(fp, length, active_cred, td);
1376         else
1377                 error = invfo_truncate(fp, length, active_cred, td);
1378         return (error);
1379 }
1380
1381 /*
1382  * we implement a very minimal set of ioctls for compatibility with sockets.
1383  */
1384 static int
1385 pipe_ioctl(struct file *fp, u_long cmd, void *data, struct ucred *active_cred,
1386     struct thread *td)
1387 {
1388         struct pipe *mpipe = fp->f_data;
1389         int error;
1390
1391         PIPE_LOCK(mpipe);
1392
1393 #ifdef MAC
1394         error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
1395         if (error) {
1396                 PIPE_UNLOCK(mpipe);
1397                 return (error);
1398         }
1399 #endif
1400
1401         error = 0;
1402         switch (cmd) {
1403         case FIONBIO:
1404                 break;
1405
1406         case FIOASYNC:
1407                 if (*(int *)data) {
1408                         mpipe->pipe_state |= PIPE_ASYNC;
1409                 } else {
1410                         mpipe->pipe_state &= ~PIPE_ASYNC;
1411                 }
1412                 break;
1413
1414         case FIONREAD:
1415                 if (!(fp->f_flag & FREAD)) {
1416                         *(int *)data = 0;
1417                         PIPE_UNLOCK(mpipe);
1418                         return (0);
1419                 }
1420                 if (mpipe->pipe_pages.cnt != 0)
1421                         *(int *)data = mpipe->pipe_pages.cnt;
1422                 else
1423                         *(int *)data = mpipe->pipe_buffer.cnt;
1424                 break;
1425
1426         case FIOSETOWN:
1427                 PIPE_UNLOCK(mpipe);
1428                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
1429                 goto out_unlocked;
1430
1431         case FIOGETOWN:
1432                 *(int *)data = fgetown(&mpipe->pipe_sigio);
1433                 break;
1434
1435         /* This is deprecated, FIOSETOWN should be used instead. */
1436         case TIOCSPGRP:
1437                 PIPE_UNLOCK(mpipe);
1438                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
1439                 goto out_unlocked;
1440
1441         /* This is deprecated, FIOGETOWN should be used instead. */
1442         case TIOCGPGRP:
1443                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
1444                 break;
1445
1446         default:
1447                 error = ENOTTY;
1448                 break;
1449         }
1450         PIPE_UNLOCK(mpipe);
1451 out_unlocked:
1452         return (error);
1453 }
1454
1455 static int
1456 pipe_poll(struct file *fp, int events, struct ucred *active_cred,
1457     struct thread *td)
1458 {
1459         struct pipe *rpipe;
1460         struct pipe *wpipe;
1461         int levents, revents;
1462 #ifdef MAC
1463         int error;
1464 #endif
1465
1466         revents = 0;
1467         rpipe = fp->f_data;
1468         wpipe = PIPE_PEER(rpipe);
1469         PIPE_LOCK(rpipe);
1470 #ifdef MAC
1471         error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
1472         if (error)
1473                 goto locked_error;
1474 #endif
1475         if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM))
1476                 if (rpipe->pipe_pages.cnt > 0 || rpipe->pipe_buffer.cnt > 0)
1477                         revents |= events & (POLLIN | POLLRDNORM);
1478
1479         if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM))
1480                 if (wpipe->pipe_present != PIPE_ACTIVE ||
1481                     (wpipe->pipe_state & PIPE_EOF) ||
1482                     ((wpipe->pipe_state & PIPE_DIRECTW) == 0 &&
1483                      ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
1484                          wpipe->pipe_buffer.size == 0)))
1485                         revents |= events & (POLLOUT | POLLWRNORM);
1486
1487         levents = events &
1488             (POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
1489         if (rpipe->pipe_type & PIPE_TYPE_NAMED && fp->f_flag & FREAD && levents &&
1490             fp->f_pipegen == rpipe->pipe_wgen)
1491                 events |= POLLINIGNEOF;
1492
1493         if ((events & POLLINIGNEOF) == 0) {
1494                 if (rpipe->pipe_state & PIPE_EOF) {
1495                         if (fp->f_flag & FREAD)
1496                                 revents |= (events & (POLLIN | POLLRDNORM));
1497                         if (wpipe->pipe_present != PIPE_ACTIVE ||
1498                             (wpipe->pipe_state & PIPE_EOF))
1499                                 revents |= POLLHUP;
1500                 }
1501         }
1502
1503         if (revents == 0) {
1504                 /*
1505                  * Add ourselves regardless of eventmask as we have to return
1506                  * POLLHUP even if it was not asked for.
1507                  */
1508                 if ((fp->f_flag & FREAD) != 0) {
1509                         selrecord(td, &rpipe->pipe_sel);
1510                         if (SEL_WAITING(&rpipe->pipe_sel))
1511                                 rpipe->pipe_state |= PIPE_SEL;
1512                 }
1513
1514                 if ((fp->f_flag & FWRITE) != 0 &&
1515                     wpipe->pipe_present == PIPE_ACTIVE) {
1516                         selrecord(td, &wpipe->pipe_sel);
1517                         if (SEL_WAITING(&wpipe->pipe_sel))
1518                                 wpipe->pipe_state |= PIPE_SEL;
1519                 }
1520         }
1521 #ifdef MAC
1522 locked_error:
1523 #endif
1524         PIPE_UNLOCK(rpipe);
1525
1526         return (revents);
1527 }
1528
1529 /*
1530  * We shouldn't need locks here as we're doing a read and this should
1531  * be a natural race.
1532  */
1533 static int
1534 pipe_stat(struct file *fp, struct stat *ub, struct ucred *active_cred)
1535 {
1536         struct pipe *pipe;
1537 #ifdef MAC
1538         int error;
1539 #endif
1540
1541         pipe = fp->f_data;
1542 #ifdef MAC
1543         if (mac_pipe_check_stat_enabled()) {
1544                 PIPE_LOCK(pipe);
1545                 error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
1546                 PIPE_UNLOCK(pipe);
1547                 if (error) {
1548                         return (error);
1549                 }
1550         }
1551 #endif
1552
1553         /* For named pipes ask the underlying filesystem. */
1554         if (pipe->pipe_type & PIPE_TYPE_NAMED) {
1555                 return (vnops.fo_stat(fp, ub, active_cred));
1556         }
1557
1558         bzero(ub, sizeof(*ub));
1559         ub->st_mode = S_IFIFO;
1560         ub->st_blksize = PAGE_SIZE;
1561         if (pipe->pipe_pages.cnt != 0)
1562                 ub->st_size = pipe->pipe_pages.cnt;
1563         else
1564                 ub->st_size = pipe->pipe_buffer.cnt;
1565         ub->st_blocks = howmany(ub->st_size, ub->st_blksize);
1566         ub->st_atim = pipe->pipe_atime;
1567         ub->st_mtim = pipe->pipe_mtime;
1568         ub->st_ctim = pipe->pipe_ctime;
1569         ub->st_uid = fp->f_cred->cr_uid;
1570         ub->st_gid = fp->f_cred->cr_gid;
1571         ub->st_dev = pipedev_ino;
1572         ub->st_ino = pipe->pipe_ino;
1573         /*
1574          * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
1575          */
1576         return (0);
1577 }
1578
1579 /* ARGSUSED */
1580 static int
1581 pipe_close(struct file *fp, struct thread *td)
1582 {
1583
1584         if (fp->f_vnode != NULL)
1585                 return vnops.fo_close(fp, td);
1586         fp->f_ops = &badfileops;
1587         pipe_dtor(fp->f_data);
1588         fp->f_data = NULL;
1589         return (0);
1590 }
1591
1592 static int
1593 pipe_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, struct thread *td)
1594 {
1595         struct pipe *cpipe;
1596         int error;
1597
1598         cpipe = fp->f_data;
1599         if (cpipe->pipe_type & PIPE_TYPE_NAMED)
1600                 error = vn_chmod(fp, mode, active_cred, td);
1601         else
1602                 error = invfo_chmod(fp, mode, active_cred, td);
1603         return (error);
1604 }
1605
1606 static int
1607 pipe_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
1608     struct thread *td)
1609 {
1610         struct pipe *cpipe;
1611         int error;
1612
1613         cpipe = fp->f_data;
1614         if (cpipe->pipe_type & PIPE_TYPE_NAMED)
1615                 error = vn_chown(fp, uid, gid, active_cred, td);
1616         else
1617                 error = invfo_chown(fp, uid, gid, active_cred, td);
1618         return (error);
1619 }
1620
1621 static int
1622 pipe_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
1623 {
1624         struct pipe *pi;
1625
1626         if (fp->f_type == DTYPE_FIFO)
1627                 return (vn_fill_kinfo(fp, kif, fdp));
1628         kif->kf_type = KF_TYPE_PIPE;
1629         pi = fp->f_data;
1630         kif->kf_un.kf_pipe.kf_pipe_addr = (uintptr_t)pi;
1631         kif->kf_un.kf_pipe.kf_pipe_peer = (uintptr_t)pi->pipe_peer;
1632         kif->kf_un.kf_pipe.kf_pipe_buffer_cnt = pi->pipe_buffer.cnt;
1633         kif->kf_un.kf_pipe.kf_pipe_buffer_in = pi->pipe_buffer.in;
1634         kif->kf_un.kf_pipe.kf_pipe_buffer_out = pi->pipe_buffer.out;
1635         kif->kf_un.kf_pipe.kf_pipe_buffer_size = pi->pipe_buffer.size;
1636         return (0);
1637 }
1638
1639 static void
1640 pipe_free_kmem(struct pipe *cpipe)
1641 {
1642
1643         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
1644             ("pipe_free_kmem: pipe mutex locked"));
1645
1646         if (cpipe->pipe_buffer.buffer != NULL) {
1647                 atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
1648                 vm_map_remove(pipe_map,
1649                     (vm_offset_t)cpipe->pipe_buffer.buffer,
1650                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
1651                 cpipe->pipe_buffer.buffer = NULL;
1652         }
1653 #ifndef PIPE_NODIRECT
1654         {
1655                 cpipe->pipe_pages.cnt = 0;
1656                 cpipe->pipe_pages.pos = 0;
1657                 cpipe->pipe_pages.npages = 0;
1658         }
1659 #endif
1660 }
1661
1662 /*
1663  * shutdown the pipe
1664  */
1665 static void
1666 pipeclose(struct pipe *cpipe)
1667 {
1668 #ifdef MAC
1669         struct pipepair *pp;
1670 #endif
1671         struct pipe *ppipe;
1672
1673         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
1674
1675         PIPE_LOCK(cpipe);
1676         pipelock(cpipe, 0);
1677 #ifdef MAC
1678         pp = cpipe->pipe_pair;
1679 #endif
1680
1681         /*
1682          * If the other side is blocked, wake it up saying that
1683          * we want to close it down.
1684          */
1685         cpipe->pipe_state |= PIPE_EOF;
1686         while (cpipe->pipe_busy) {
1687                 wakeup(cpipe);
1688                 cpipe->pipe_state |= PIPE_WANT;
1689                 pipeunlock(cpipe);
1690                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
1691                 pipelock(cpipe, 0);
1692         }
1693
1694         pipeselwakeup(cpipe);
1695
1696         /*
1697          * Disconnect from peer, if any.
1698          */
1699         ppipe = cpipe->pipe_peer;
1700         if (ppipe->pipe_present == PIPE_ACTIVE) {
1701                 ppipe->pipe_state |= PIPE_EOF;
1702                 wakeup(ppipe);
1703                 pipeselwakeup(ppipe);
1704         }
1705
1706         /*
1707          * Mark this endpoint as free.  Release kmem resources.  We
1708          * don't mark this endpoint as unused until we've finished
1709          * doing that, or the pipe might disappear out from under
1710          * us.
1711          */
1712         PIPE_UNLOCK(cpipe);
1713         pipe_free_kmem(cpipe);
1714         PIPE_LOCK(cpipe);
1715         cpipe->pipe_present = PIPE_CLOSING;
1716         pipeunlock(cpipe);
1717
1718         /*
1719          * knlist_clear() may sleep dropping the PIPE_MTX. Set the
1720          * PIPE_FINALIZED, that allows other end to free the
1721          * pipe_pair, only after the knotes are completely dismantled.
1722          */
1723         knlist_clear(&cpipe->pipe_sel.si_note, 1);
1724         cpipe->pipe_present = PIPE_FINALIZED;
1725         seldrain(&cpipe->pipe_sel);
1726         knlist_destroy(&cpipe->pipe_sel.si_note);
1727
1728         /*
1729          * If both endpoints are now closed, release the memory for the
1730          * pipe pair.  If not, unlock.
1731          */
1732         if (ppipe->pipe_present == PIPE_FINALIZED) {
1733                 PIPE_UNLOCK(cpipe);
1734 #ifdef MAC
1735                 mac_pipe_destroy(pp);
1736 #endif
1737                 uma_zfree(pipe_zone, cpipe->pipe_pair);
1738         } else
1739                 PIPE_UNLOCK(cpipe);
1740 }
1741
1742 /*ARGSUSED*/
1743 static int
1744 pipe_kqfilter(struct file *fp, struct knote *kn)
1745 {
1746         struct pipe *cpipe;
1747
1748         /*
1749          * If a filter is requested that is not supported by this file
1750          * descriptor, don't return an error, but also don't ever generate an
1751          * event.
1752          */
1753         if ((kn->kn_filter == EVFILT_READ) && !(fp->f_flag & FREAD)) {
1754                 kn->kn_fop = &pipe_nfiltops;
1755                 return (0);
1756         }
1757         if ((kn->kn_filter == EVFILT_WRITE) && !(fp->f_flag & FWRITE)) {
1758                 kn->kn_fop = &pipe_nfiltops;
1759                 return (0);
1760         }
1761         cpipe = fp->f_data;
1762         PIPE_LOCK(cpipe);
1763         switch (kn->kn_filter) {
1764         case EVFILT_READ:
1765                 kn->kn_fop = &pipe_rfiltops;
1766                 break;
1767         case EVFILT_WRITE:
1768                 kn->kn_fop = &pipe_wfiltops;
1769                 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
1770                         /* other end of pipe has been closed */
1771                         PIPE_UNLOCK(cpipe);
1772                         return (EPIPE);
1773                 }
1774                 cpipe = PIPE_PEER(cpipe);
1775                 break;
1776         default:
1777                 if ((cpipe->pipe_type & PIPE_TYPE_NAMED) != 0) {
1778                         PIPE_UNLOCK(cpipe);
1779                         return (vnops.fo_kqfilter(fp, kn));
1780                 }
1781                 PIPE_UNLOCK(cpipe);
1782                 return (EINVAL);
1783         }
1784
1785         kn->kn_hook = cpipe;
1786         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
1787         PIPE_UNLOCK(cpipe);
1788         return (0);
1789 }
1790
1791 static void
1792 filt_pipedetach(struct knote *kn)
1793 {
1794         struct pipe *cpipe = kn->kn_hook;
1795
1796         PIPE_LOCK(cpipe);
1797         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
1798         PIPE_UNLOCK(cpipe);
1799 }
1800
1801 /*ARGSUSED*/
1802 static int
1803 filt_piperead(struct knote *kn, long hint)
1804 {
1805         struct file *fp = kn->kn_fp;
1806         struct pipe *rpipe = kn->kn_hook;
1807
1808         PIPE_LOCK_ASSERT(rpipe, MA_OWNED);
1809         kn->kn_data = rpipe->pipe_buffer.cnt;
1810         if (kn->kn_data == 0)
1811                 kn->kn_data = rpipe->pipe_pages.cnt;
1812
1813         if ((rpipe->pipe_state & PIPE_EOF) != 0 &&
1814             ((rpipe->pipe_type & PIPE_TYPE_NAMED) == 0 ||
1815             fp->f_pipegen != rpipe->pipe_wgen)) {
1816                 kn->kn_flags |= EV_EOF;
1817                 return (1);
1818         }
1819         kn->kn_flags &= ~EV_EOF;
1820         return (kn->kn_data > 0);
1821 }
1822
1823 /*ARGSUSED*/
1824 static int
1825 filt_pipewrite(struct knote *kn, long hint)
1826 {
1827         struct pipe *wpipe = kn->kn_hook;
1828
1829         /*
1830          * If this end of the pipe is closed, the knote was removed from the
1831          * knlist and the list lock (i.e., the pipe lock) is therefore not held.
1832          */
1833         if (wpipe->pipe_present == PIPE_ACTIVE ||
1834             (wpipe->pipe_type & PIPE_TYPE_NAMED) != 0) {
1835                 PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
1836
1837                 if (wpipe->pipe_state & PIPE_DIRECTW) {
1838                         kn->kn_data = 0;
1839                 } else if (wpipe->pipe_buffer.size > 0) {
1840                         kn->kn_data = wpipe->pipe_buffer.size -
1841                             wpipe->pipe_buffer.cnt;
1842                 } else {
1843                         kn->kn_data = PIPE_BUF;
1844                 }
1845         }
1846
1847         if (wpipe->pipe_present != PIPE_ACTIVE ||
1848             (wpipe->pipe_state & PIPE_EOF)) {
1849                 kn->kn_flags |= EV_EOF;
1850                 return (1);
1851         }
1852         kn->kn_flags &= ~EV_EOF;
1853         return (kn->kn_data >= PIPE_BUF);
1854 }
1855
1856 static void
1857 filt_pipedetach_notsup(struct knote *kn)
1858 {
1859
1860 }
1861
1862 static int
1863 filt_pipenotsup(struct knote *kn, long hint)
1864 {
1865
1866         return (0);
1867 }