sys/kern/sys_pipe.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-4-Clause
   3  *
   4  * Copyright (c) 1996 John S. Dyson
   5  * Copyright (c) 2012 Giovanni Trematerra
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice immediately at the beginning of the file, without modification,
  13  *    this list of conditions, and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 3. Absolutely no warranty of function or purpose is made by the author
  18  *    John S. Dyson.
  19  * 4. Modifications may be freely made to this file if the above conditions
  20  *    are met.
  21  */
  22
  23 /*
  24  * This file contains a high-performance replacement for the socket-based
  25  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
  26  * all features of sockets, but does do everything that pipes normally
  27  * do.
  28  */
  29
  30 /*
  31  * This code has two modes of operation, a small write mode and a large
  32  * write mode.  The small write mode acts like conventional pipes with
  33  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
  34  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
  35  * and PIPE_SIZE in size, the sending process pins the underlying pages in
  36  * memory, and the receiving process copies directly from these pinned pages
  37  * in the sending process.
  38  *
  39  * If the sending process receives a signal, it is possible that it will
  40  * go away, and certainly its address space can change, because control
  41  * is returned back to the user-mode side.  In that case, the pipe code
  42  * arranges to copy the buffer supplied by the user process, to a pageable
  43  * kernel buffer, and the receiving process will grab the data from the
  44  * pageable kernel buffer.  Since signals don't happen all that often,
  45  * the copy operation is normally eliminated.
  46  *
  47  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
  48  * happen for small transfers so that the system will not spend all of
  49  * its time context switching.
  50  *
  51  * In order to limit the resource use of pipes, two sysctls exist:
  52  *
  53  * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
  54  * address space available to us in pipe_map. This value is normally
  55  * autotuned, but may also be loader tuned.
  56  *
  57  * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
  58  * memory in use by pipes.
  59  *
  60  * Based on how large pipekva is relative to maxpipekva, the following
  61  * will happen:
  62  *
  63  * 0% - 50%:
  64  *     New pipes are given 16K of memory backing, pipes may dynamically
  65  *     grow to as large as 64K where needed.
  66  * 50% - 75%:
  67  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
  68  *     existing pipes may NOT grow.
  69  * 75% - 100%:
  70  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
  71  *     existing pipes will be shrunk down to 4K whenever possible.
  72  *
  73  * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
  74  * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
  75  * resize which MUST occur for reverse-direction pipes when they are
  76  * first used.
  77  *
  78  * Additional information about the current state of pipes may be obtained
  79  * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
  80  * and kern.ipc.piperesizefail.
  81  *
  82  * Locking rules:  There are two locks present here:  A mutex, used via
  83  * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
  84  * the flag, as mutexes can not persist over uiomove.  The mutex
  85  * exists only to guard access to the flag, and is not in itself a
  86  * locking mechanism.  Also note that there is only a single mutex for
  87  * both directions of a pipe.
  88  *
  89  * As pipelock() may have to sleep before it can acquire the flag, it
  90  * is important to reread all data after a call to pipelock(); everything
  91  * in the structure may have changed.
  92  */
  93
  94 #include <sys/cdefs.h>
  95 __FBSDID("$FreeBSD$");
  96
  97 #include <sys/param.h>
  98 #include <sys/systm.h>
  99 #include <sys/conf.h>
 100 #include <sys/fcntl.h>
 101 #include <sys/file.h>
 102 #include <sys/filedesc.h>
 103 #include <sys/filio.h>
 104 #include <sys/kernel.h>
 105 #include <sys/lock.h>
 106 #include <sys/mutex.h>
 107 #include <sys/ttycom.h>
 108 #include <sys/stat.h>
 109 #include <sys/malloc.h>
 110 #include <sys/poll.h>
 111 #include <sys/selinfo.h>
 112 #include <sys/signalvar.h>
 113 #include <sys/syscallsubr.h>
 114 #include <sys/sysctl.h>
 115 #include <sys/sysproto.h>
 116 #include <sys/pipe.h>
 117 #include <sys/proc.h>
 118 #include <sys/vnode.h>
 119 #include <sys/uio.h>
 120 #include <sys/user.h>
 121 #include <sys/event.h>
 122
 123 #include <security/mac/mac_framework.h>
 124
 125 #include <vm/vm.h>
 126 #include <vm/vm_param.h>
 127 #include <vm/vm_object.h>
 128 #include <vm/vm_kern.h>
 129 #include <vm/vm_extern.h>
 130 #include <vm/pmap.h>
 131 #include <vm/vm_map.h>
 132 #include <vm/vm_page.h>
 133 #include <vm/uma.h>
 134
 135 /*
 136  * Use this define if you want to disable *fancy* VM things.  Expect an
 137  * approx 30% decrease in transfer rate.  This could be useful for
 138  * NetBSD or OpenBSD.
 139  */
 140 /* #define PIPE_NODIRECT */
 141
 142 #define PIPE_PEER(pipe) \
 143         (((pipe)->pipe_type & PIPE_TYPE_NAMED) ? (pipe) : ((pipe)->pipe_peer))
 144
 145 /*
 146  * interfaces to the outside world
 147  */
 148 static fo_rdwr_t        pipe_read;
 149 static fo_rdwr_t        pipe_write;
 150 static fo_truncate_t    pipe_truncate;
 151 static fo_ioctl_t       pipe_ioctl;
 152 static fo_poll_t        pipe_poll;
 153 static fo_kqfilter_t    pipe_kqfilter;
 154 static fo_stat_t        pipe_stat;
 155 static fo_close_t       pipe_close;
 156 static fo_chmod_t       pipe_chmod;
 157 static fo_chown_t       pipe_chown;
 158 static fo_fill_kinfo_t  pipe_fill_kinfo;
 159
 160 struct fileops pipeops = {
 161         .fo_read = pipe_read,
 162         .fo_write = pipe_write,
 163         .fo_truncate = pipe_truncate,
 164         .fo_ioctl = pipe_ioctl,
 165         .fo_poll = pipe_poll,
 166         .fo_kqfilter = pipe_kqfilter,
 167         .fo_stat = pipe_stat,
 168         .fo_close = pipe_close,
 169         .fo_chmod = pipe_chmod,
 170         .fo_chown = pipe_chown,
 171         .fo_sendfile = invfo_sendfile,
 172         .fo_fill_kinfo = pipe_fill_kinfo,
 173         .fo_flags = DFLAG_PASSABLE
 174 };
 175
 176 static void     filt_pipedetach(struct knote *kn);
 177 static void     filt_pipedetach_notsup(struct knote *kn);
 178 static int      filt_pipenotsup(struct knote *kn, long hint);
 179 static int      filt_piperead(struct knote *kn, long hint);
 180 static int      filt_pipewrite(struct knote *kn, long hint);
 181
 182 static struct filterops pipe_nfiltops = {
 183         .f_isfd = 1,
 184         .f_detach = filt_pipedetach_notsup,
 185         .f_event = filt_pipenotsup
 186 };
 187 static struct filterops pipe_rfiltops = {
 188         .f_isfd = 1,
 189         .f_detach = filt_pipedetach,
 190         .f_event = filt_piperead
 191 };
 192 static struct filterops pipe_wfiltops = {
 193         .f_isfd = 1,
 194         .f_detach = filt_pipedetach,
 195         .f_event = filt_pipewrite
 196 };
 197
 198 /*
 199  * Default pipe buffer size(s), this can be kind-of large now because pipe
 200  * space is pageable.  The pipe code will try to maintain locality of
 201  * reference for performance reasons, so small amounts of outstanding I/O
 202  * will not wipe the cache.
 203  */
 204 #define MINPIPESIZE (PIPE_SIZE/3)
 205 #define MAXPIPESIZE (2*PIPE_SIZE/3)
 206
 207 static long amountpipekva;
 208 static int pipefragretry;
 209 static int pipeallocfail;
 210 static int piperesizefail;
 211 static int piperesizeallowed = 1;
 212 static long pipe_mindirect = PIPE_MINDIRECT;
 213
 214 SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
 215            &maxpipekva, 0, "Pipe KVA limit");
 216 SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
 217            &amountpipekva, 0, "Pipe KVA usage");
 218 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
 219           &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
 220 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
 221           &pipeallocfail, 0, "Pipe allocation failures");
 222 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
 223           &piperesizefail, 0, "Pipe resize failures");
 224 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
 225           &piperesizeallowed, 0, "Pipe resizing allowed");
 226
 227 static void pipeinit(void *dummy __unused);
 228 static void pipeclose(struct pipe *cpipe);
 229 static void pipe_free_kmem(struct pipe *cpipe);
 230 static int pipe_create(struct pipe *pipe, bool backing);
 231 static int pipe_paircreate(struct thread *td, struct pipepair **p_pp);
 232 static __inline int pipelock(struct pipe *cpipe, int catch);
 233 static __inline void pipeunlock(struct pipe *cpipe);
 234 static void pipe_timestamp(struct timespec *tsp);
 235 #ifndef PIPE_NODIRECT
 236 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
 237 static void pipe_destroy_write_buffer(struct pipe *wpipe);
 238 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
 239 static void pipe_clone_write_buffer(struct pipe *wpipe);
 240 #endif
 241 static int pipespace(struct pipe *cpipe, int size);
 242 static int pipespace_new(struct pipe *cpipe, int size);
 243
 244 static int      pipe_zone_ctor(void *mem, int size, void *arg, int flags);
 245 static int      pipe_zone_init(void *mem, int size, int flags);
 246 static void     pipe_zone_fini(void *mem, int size);
 247
 248 static uma_zone_t pipe_zone;
 249 static struct unrhdr64 pipeino_unr;
 250 static dev_t pipedev_ino;
 251
 252 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
 253
 254 static void
 255 pipeinit(void *dummy __unused)
 256 {
 257
 258         pipe_zone = uma_zcreate("pipe", sizeof(struct pipepair),
 259             pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
 260             UMA_ALIGN_PTR, 0);
 261         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
 262         new_unrhdr64(&pipeino_unr, 1);
 263         pipedev_ino = devfs_alloc_cdp_inode();
 264         KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
 265 }
 266
 267 static int
 268 sysctl_handle_pipe_mindirect(SYSCTL_HANDLER_ARGS)
 269 {
 270         int error = 0;
 271         long tmp_pipe_mindirect = pipe_mindirect;
 272
 273         error = sysctl_handle_long(oidp, &tmp_pipe_mindirect, arg2, req);
 274         if (error != 0 || req->newptr == NULL)
 275                 return (error);
 276
 277         /*
 278          * Don't allow pipe_mindirect to be set so low that we violate
 279          * atomicity requirements.
 280          */
 281         if (tmp_pipe_mindirect <= PIPE_BUF)
 282                 return (EINVAL);
 283         pipe_mindirect = tmp_pipe_mindirect;
 284         return (0);
 285 }
 286 SYSCTL_OID(_kern_ipc, OID_AUTO, pipe_mindirect, CTLTYPE_LONG | CTLFLAG_RW,
 287     &pipe_mindirect, 0, sysctl_handle_pipe_mindirect, "L",
 288     "Minimum write size triggering VM optimization");
 289
 290 static int
 291 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
 292 {
 293         struct pipepair *pp;
 294         struct pipe *rpipe, *wpipe;
 295
 296         KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
 297
 298         pp = (struct pipepair *)mem;
 299
 300         /*
 301          * We zero both pipe endpoints to make sure all the kmem pointers
 302          * are NULL, flag fields are zero'd, etc.  We timestamp both
 303          * endpoints with the same time.
 304          */
 305         rpipe = &pp->pp_rpipe;
 306         bzero(rpipe, sizeof(*rpipe));
 307         pipe_timestamp(&rpipe->pipe_ctime);
 308         rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
 309
 310         wpipe = &pp->pp_wpipe;
 311         bzero(wpipe, sizeof(*wpipe));
 312         wpipe->pipe_ctime = rpipe->pipe_ctime;
 313         wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
 314
 315         rpipe->pipe_peer = wpipe;
 316         rpipe->pipe_pair = pp;
 317         wpipe->pipe_peer = rpipe;
 318         wpipe->pipe_pair = pp;
 319
 320         /*
 321          * Mark both endpoints as present; they will later get free'd
 322          * one at a time.  When both are free'd, then the whole pair
 323          * is released.
 324          */
 325         rpipe->pipe_present = PIPE_ACTIVE;
 326         wpipe->pipe_present = PIPE_ACTIVE;
 327
 328         /*
 329          * Eventually, the MAC Framework may initialize the label
 330          * in ctor or init, but for now we do it elswhere to avoid
 331          * blocking in ctor or init.
 332          */
 333         pp->pp_label = NULL;
 334
 335         return (0);
 336 }
 337
 338 static int
 339 pipe_zone_init(void *mem, int size, int flags)
 340 {
 341         struct pipepair *pp;
 342
 343         KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
 344
 345         pp = (struct pipepair *)mem;
 346
 347         mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_NEW);
 348         return (0);
 349 }
 350
 351 static void
 352 pipe_zone_fini(void *mem, int size)
 353 {
 354         struct pipepair *pp;
 355
 356         KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
 357
 358         pp = (struct pipepair *)mem;
 359
 360         mtx_destroy(&pp->pp_mtx);
 361 }
 362
 363 static int
 364 pipe_paircreate(struct thread *td, struct pipepair **p_pp)
 365 {
 366         struct pipepair *pp;
 367         struct pipe *rpipe, *wpipe;
 368         int error;
 369
 370         *p_pp = pp = uma_zalloc(pipe_zone, M_WAITOK);
 371 #ifdef MAC
 372         /*
 373          * The MAC label is shared between the connected endpoints.  As a
 374          * result mac_pipe_init() and mac_pipe_create() are called once
 375          * for the pair, and not on the endpoints.
 376          */
 377         mac_pipe_init(pp);
 378         mac_pipe_create(td->td_ucred, pp);
 379 #endif
 380         rpipe = &pp->pp_rpipe;
 381         wpipe = &pp->pp_wpipe;
 382
 383         knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
 384         knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
 385
 386         /*
 387          * Only the forward direction pipe is backed by big buffer by
 388          * default.
 389          */
 390         error = pipe_create(rpipe, true);
 391         if (error != 0)
 392                 goto fail;
 393         error = pipe_create(wpipe, false);
 394         if (error != 0) {
 395                 /*
 396                  * This cleanup leaves the pipe inode number for rpipe
 397                  * still allocated, but never used.  We do not free
 398                  * inode numbers for opened pipes, which is required
 399                  * for correctness because numbers must be unique.
 400                  * But also it avoids any memory use by the unr
 401                  * allocator, so stashing away the transient inode
 402                  * number is reasonable.
 403                  */
 404                 pipe_free_kmem(rpipe);
 405                 goto fail;
 406         }
 407
 408         rpipe->pipe_state |= PIPE_DIRECTOK;
 409         wpipe->pipe_state |= PIPE_DIRECTOK;
 410         return (0);
 411
 412 fail:
 413         knlist_destroy(&rpipe->pipe_sel.si_note);
 414         knlist_destroy(&wpipe->pipe_sel.si_note);
 415 #ifdef MAC
 416         mac_pipe_destroy(pp);
 417 #endif
 418         uma_zfree(pipe_zone, pp);
 419         return (error);
 420 }
 421
 422 int
 423 pipe_named_ctor(struct pipe **ppipe, struct thread *td)
 424 {
 425         struct pipepair *pp;
 426         int error;
 427
 428         error = pipe_paircreate(td, &pp);
 429         if (error != 0)
 430                 return (error);
 431         pp->pp_rpipe.pipe_type |= PIPE_TYPE_NAMED;
 432         *ppipe = &pp->pp_rpipe;
 433         return (0);
 434 }
 435
 436 void
 437 pipe_dtor(struct pipe *dpipe)
 438 {
 439         struct pipe *peer;
 440
 441         peer = (dpipe->pipe_type & PIPE_TYPE_NAMED) != 0 ? dpipe->pipe_peer : NULL;
 442         funsetown(&dpipe->pipe_sigio);
 443         pipeclose(dpipe);
 444         if (peer != NULL) {
 445                 funsetown(&peer->pipe_sigio);
 446                 pipeclose(peer);
 447         }
 448 }
 449
 450 /*
 451  * Get a timestamp.
 452  *
 453  * This used to be vfs_timestamp but the higher precision is unnecessary and
 454  * can very negatively affect performance in virtualized environments (e.g., on
 455  * vms running on amd64 when using the rdtscp instruction).
 456  */
 457 static void
 458 pipe_timestamp(struct timespec *tsp)
 459 {
 460
 461         getnanotime(tsp);
 462 }
 463
 464 /*
 465  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
 466  * the zone pick up the pieces via pipeclose().
 467  */
 468 int
 469 kern_pipe(struct thread *td, int fildes[2], int flags, struct filecaps *fcaps1,
 470     struct filecaps *fcaps2)
 471 {
 472         struct file *rf, *wf;
 473         struct pipe *rpipe, *wpipe;
 474         struct pipepair *pp;
 475         int fd, fflags, error;
 476
 477         error = pipe_paircreate(td, &pp);
 478         if (error != 0)
 479                 return (error);
 480         rpipe = &pp->pp_rpipe;
 481         wpipe = &pp->pp_wpipe;
 482         error = falloc_caps(td, &rf, &fd, flags, fcaps1);
 483         if (error) {
 484                 pipeclose(rpipe);
 485                 pipeclose(wpipe);
 486                 return (error);
 487         }
 488         /* An extra reference on `rf' has been held for us by falloc_caps(). */
 489         fildes[0] = fd;
 490
 491         fflags = FREAD | FWRITE;
 492         if ((flags & O_NONBLOCK) != 0)
 493                 fflags |= FNONBLOCK;
 494
 495         /*
 496          * Warning: once we've gotten past allocation of the fd for the
 497          * read-side, we can only drop the read side via fdrop() in order
 498          * to avoid races against processes which manage to dup() the read
 499          * side while we are blocked trying to allocate the write side.
 500          */
 501         finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
 502         error = falloc_caps(td, &wf, &fd, flags, fcaps2);
 503         if (error) {
 504                 fdclose(td, rf, fildes[0]);
 505                 fdrop(rf, td);
 506                 /* rpipe has been closed by fdrop(). */
 507                 pipeclose(wpipe);
 508                 return (error);
 509         }
 510         /* An extra reference on `wf' has been held for us by falloc_caps(). */
 511         finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
 512         fdrop(wf, td);
 513         fildes[1] = fd;
 514         fdrop(rf, td);
 515
 516         return (0);
 517 }
 518
 519 #ifdef COMPAT_FREEBSD10
 520 /* ARGSUSED */
 521 int
 522 freebsd10_pipe(struct thread *td, struct freebsd10_pipe_args *uap __unused)
 523 {
 524         int error;
 525         int fildes[2];
 526
 527         error = kern_pipe(td, fildes, 0, NULL, NULL);
 528         if (error)
 529                 return (error);
 530
 531         td->td_retval[0] = fildes[0];
 532         td->td_retval[1] = fildes[1];
 533
 534         return (0);
 535 }
 536 #endif
 537
 538 int
 539 sys_pipe2(struct thread *td, struct pipe2_args *uap)
 540 {
 541         int error, fildes[2];
 542
 543         if (uap->flags & ~(O_CLOEXEC | O_NONBLOCK))
 544                 return (EINVAL);
 545         error = kern_pipe(td, fildes, uap->flags, NULL, NULL);
 546         if (error)
 547                 return (error);
 548         error = copyout(fildes, uap->fildes, 2 * sizeof(int));
 549         if (error) {
 550                 (void)kern_close(td, fildes[0]);
 551                 (void)kern_close(td, fildes[1]);
 552         }
 553         return (error);
 554 }
 555
 556 /*
 557  * Allocate kva for pipe circular buffer, the space is pageable
 558  * This routine will 'realloc' the size of a pipe safely, if it fails
 559  * it will retain the old buffer.
 560  * If it fails it will return ENOMEM.
 561  */
 562 static int
 563 pipespace_new(struct pipe *cpipe, int size)
 564 {
 565         caddr_t buffer;
 566         int error, cnt, firstseg;
 567         static int curfail = 0;
 568         static struct timeval lastfail;
 569
 570         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
 571         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
 572                 ("pipespace: resize of direct writes not allowed"));
 573 retry:
 574         cnt = cpipe->pipe_buffer.cnt;
 575         if (cnt > size)
 576                 size = cnt;
 577
 578         size = round_page(size);
 579         buffer = (caddr_t) vm_map_min(pipe_map);
 580
 581         error = vm_map_find(pipe_map, NULL, 0, (vm_offset_t *)&buffer, size, 0,
 582             VMFS_ANY_SPACE, VM_PROT_RW, VM_PROT_RW, 0);
 583         if (error != KERN_SUCCESS) {
 584                 if (cpipe->pipe_buffer.buffer == NULL &&
 585                     size > SMALL_PIPE_SIZE) {
 586                         size = SMALL_PIPE_SIZE;
 587                         pipefragretry++;
 588                         goto retry;
 589                 }
 590                 if (cpipe->pipe_buffer.buffer == NULL) {
 591                         pipeallocfail++;
 592                         if (ppsratecheck(&lastfail, &curfail, 1))
 593                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
 594                 } else {
 595                         piperesizefail++;
 596                 }
 597                 return (ENOMEM);
 598         }
 599
 600         /* copy data, then free old resources if we're resizing */
 601         if (cnt > 0) {
 602                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
 603                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
 604                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
 605                                 buffer, firstseg);
 606                         if ((cnt - firstseg) > 0)
 607                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
 608                                         cpipe->pipe_buffer.in);
 609                 } else {
 610                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
 611                                 buffer, cnt);
 612                 }
 613         }
 614         pipe_free_kmem(cpipe);
 615         cpipe->pipe_buffer.buffer = buffer;
 616         cpipe->pipe_buffer.size = size;
 617         cpipe->pipe_buffer.in = cnt;
 618         cpipe->pipe_buffer.out = 0;
 619         cpipe->pipe_buffer.cnt = cnt;
 620         atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
 621         return (0);
 622 }
 623
 624 /*
 625  * Wrapper for pipespace_new() that performs locking assertions.
 626  */
 627 static int
 628 pipespace(struct pipe *cpipe, int size)
 629 {
 630
 631         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
 632             ("Unlocked pipe passed to pipespace"));
 633         return (pipespace_new(cpipe, size));
 634 }
 635
 636 /*
 637  * lock a pipe for I/O, blocking other access
 638  */
 639 static __inline int
 640 pipelock(struct pipe *cpipe, int catch)
 641 {
 642         int error, prio;
 643
 644         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 645
 646         prio = PRIBIO;
 647         if (catch)
 648                 prio |= PCATCH;
 649         while (cpipe->pipe_state & PIPE_LOCKFL) {
 650                 KASSERT(cpipe->pipe_waiters >= 0,
 651                     ("%s: bad waiter count %d", __func__,
 652                     cpipe->pipe_waiters));
 653                 cpipe->pipe_waiters++;
 654                 error = msleep(&cpipe->pipe_waiters, PIPE_MTX(cpipe), prio,
 655                     "pipelk", 0);
 656                 cpipe->pipe_waiters--;
 657                 if (error != 0)
 658                         return (error);
 659         }
 660         cpipe->pipe_state |= PIPE_LOCKFL;
 661         return (0);
 662 }
 663
 664 /*
 665  * unlock a pipe I/O lock
 666  */
 667 static __inline void
 668 pipeunlock(struct pipe *cpipe)
 669 {
 670
 671         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 672         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
 673                 ("Unlocked pipe passed to pipeunlock"));
 674         KASSERT(cpipe->pipe_waiters >= 0,
 675             ("%s: bad waiter count %d", __func__,
 676             cpipe->pipe_waiters));
 677         cpipe->pipe_state &= ~PIPE_LOCKFL;
 678         if (cpipe->pipe_waiters > 0)
 679                 wakeup_one(&cpipe->pipe_waiters);
 680 }
 681
 682 void
 683 pipeselwakeup(struct pipe *cpipe)
 684 {
 685
 686         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 687         if (cpipe->pipe_state & PIPE_SEL) {
 688                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
 689                 if (!SEL_WAITING(&cpipe->pipe_sel))
 690                         cpipe->pipe_state &= ~PIPE_SEL;
 691         }
 692         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
 693                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
 694         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
 695 }
 696
 697 /*
 698  * Initialize and allocate VM and memory for pipe.  The structure
 699  * will start out zero'd from the ctor, so we just manage the kmem.
 700  */
 701 static int
 702 pipe_create(struct pipe *pipe, bool large_backing)
 703 {
 704         int error;
 705
 706         error = pipespace_new(pipe, !large_backing || amountpipekva >
 707             maxpipekva / 2 ? SMALL_PIPE_SIZE : PIPE_SIZE);
 708         if (error == 0)
 709                 pipe->pipe_ino = alloc_unr64(&pipeino_unr);
 710         return (error);
 711 }
 712
 713 /* ARGSUSED */
 714 static int
 715 pipe_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
 716     int flags, struct thread *td)
 717 {
 718         struct pipe *rpipe;
 719         int error;
 720         int nread = 0;
 721         int size;
 722
 723         rpipe = fp->f_data;
 724
 725         /*
 726          * Try to avoid locking the pipe if we have nothing to do.
 727          *
 728          * There are programs which share one pipe amongst multiple processes
 729          * and perform non-blocking reads in parallel, even if the pipe is
 730          * empty.  This in particular is the case with BSD make, which when
 731          * spawned with a high -j number can find itself with over half of the
 732          * calls failing to find anything.
 733          */
 734         if ((fp->f_flag & FNONBLOCK) != 0 && !mac_pipe_check_read_enabled()) {
 735                 if (__predict_false(uio->uio_resid == 0))
 736                         return (0);
 737                 if ((atomic_load_short(&rpipe->pipe_state) & PIPE_EOF) == 0 &&
 738                     atomic_load_int(&rpipe->pipe_buffer.cnt) == 0 &&
 739                     atomic_load_int(&rpipe->pipe_pages.cnt) == 0)
 740                         return (EAGAIN);
 741         }
 742
 743         PIPE_LOCK(rpipe);
 744         ++rpipe->pipe_busy;
 745         error = pipelock(rpipe, 1);
 746         if (error)
 747                 goto unlocked_error;
 748
 749 #ifdef MAC
 750         error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
 751         if (error)
 752                 goto locked_error;
 753 #endif
 754         if (amountpipekva > (3 * maxpipekva) / 4) {
 755                 if ((rpipe->pipe_state & PIPE_DIRECTW) == 0 &&
 756                     rpipe->pipe_buffer.size > SMALL_PIPE_SIZE &&
 757                     rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE &&
 758                     piperesizeallowed == 1) {
 759                         PIPE_UNLOCK(rpipe);
 760                         pipespace(rpipe, SMALL_PIPE_SIZE);
 761                         PIPE_LOCK(rpipe);
 762                 }
 763         }
 764
 765         while (uio->uio_resid) {
 766                 /*
 767                  * normal pipe buffer receive
 768                  */
 769                 if (rpipe->pipe_buffer.cnt > 0) {
 770                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
 771                         if (size > rpipe->pipe_buffer.cnt)
 772                                 size = rpipe->pipe_buffer.cnt;
 773                         if (size > uio->uio_resid)
 774                                 size = uio->uio_resid;
 775
 776                         PIPE_UNLOCK(rpipe);
 777                         error = uiomove(
 778                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
 779                             size, uio);
 780                         PIPE_LOCK(rpipe);
 781                         if (error)
 782                                 break;
 783
 784                         rpipe->pipe_buffer.out += size;
 785                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
 786                                 rpipe->pipe_buffer.out = 0;
 787
 788                         rpipe->pipe_buffer.cnt -= size;
 789
 790                         /*
 791                          * If there is no more to read in the pipe, reset
 792                          * its pointers to the beginning.  This improves
 793                          * cache hit stats.
 794                          */
 795                         if (rpipe->pipe_buffer.cnt == 0) {
 796                                 rpipe->pipe_buffer.in = 0;
 797                                 rpipe->pipe_buffer.out = 0;
 798                         }
 799                         nread += size;
 800 #ifndef PIPE_NODIRECT
 801                 /*
 802                  * Direct copy, bypassing a kernel buffer.
 803                  */
 804                 } else if ((size = rpipe->pipe_pages.cnt) != 0) {
 805                         if (size > uio->uio_resid)
 806                                 size = (u_int) uio->uio_resid;
 807                         PIPE_UNLOCK(rpipe);
 808                         error = uiomove_fromphys(rpipe->pipe_pages.ms,
 809                             rpipe->pipe_pages.pos, size, uio);
 810                         PIPE_LOCK(rpipe);
 811                         if (error)
 812                                 break;
 813                         nread += size;
 814                         rpipe->pipe_pages.pos += size;
 815                         rpipe->pipe_pages.cnt -= size;
 816                         if (rpipe->pipe_pages.cnt == 0) {
 817                                 rpipe->pipe_state &= ~PIPE_WANTW;
 818                                 wakeup(rpipe);
 819                         }
 820 #endif
 821                 } else {
 822                         /*
 823                          * detect EOF condition
 824                          * read returns 0 on EOF, no need to set error
 825                          */
 826                         if (rpipe->pipe_state & PIPE_EOF)
 827                                 break;
 828
 829                         /*
 830                          * If the "write-side" has been blocked, wake it up now.
 831                          */
 832                         if (rpipe->pipe_state & PIPE_WANTW) {
 833                                 rpipe->pipe_state &= ~PIPE_WANTW;
 834                                 wakeup(rpipe);
 835                         }
 836
 837                         /*
 838                          * Break if some data was read.
 839                          */
 840                         if (nread > 0)
 841                                 break;
 842
 843                         /*
 844                          * Unlock the pipe buffer for our remaining processing.
 845                          * We will either break out with an error or we will
 846                          * sleep and relock to loop.
 847                          */
 848                         pipeunlock(rpipe);
 849
 850                         /*
 851                          * Handle non-blocking mode operation or
 852                          * wait for more data.
 853                          */
 854                         if (fp->f_flag & FNONBLOCK) {
 855                                 error = EAGAIN;
 856                         } else {
 857                                 rpipe->pipe_state |= PIPE_WANTR;
 858                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
 859                                     PRIBIO | PCATCH,
 860                                     "piperd", 0)) == 0)
 861                                         error = pipelock(rpipe, 1);
 862                         }
 863                         if (error)
 864                                 goto unlocked_error;
 865                 }
 866         }
 867 #ifdef MAC
 868 locked_error:
 869 #endif
 870         pipeunlock(rpipe);
 871
 872         /* XXX: should probably do this before getting any locks. */
 873         if (error == 0)
 874                 pipe_timestamp(&rpipe->pipe_atime);
 875 unlocked_error:
 876         --rpipe->pipe_busy;
 877
 878         /*
 879          * PIPE_WANT processing only makes sense if pipe_busy is 0.
 880          */
 881         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
 882                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
 883                 wakeup(rpipe);
 884         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
 885                 /*
 886                  * Handle write blocking hysteresis.
 887                  */
 888                 if (rpipe->pipe_state & PIPE_WANTW) {
 889                         rpipe->pipe_state &= ~PIPE_WANTW;
 890                         wakeup(rpipe);
 891                 }
 892         }
 893
 894         /*
 895          * Only wake up writers if there was actually something read.
 896          * Otherwise, when calling read(2) at EOF, a spurious wakeup occurs.
 897          */
 898         if (nread > 0 &&
 899             rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt >= PIPE_BUF)
 900                 pipeselwakeup(rpipe);
 901
 902         PIPE_UNLOCK(rpipe);
 903         if (nread > 0)
 904                 td->td_ru.ru_msgrcv++;
 905         return (error);
 906 }
 907
 908 #ifndef PIPE_NODIRECT
 909 /*
 910  * Map the sending processes' buffer into kernel space and wire it.
 911  * This is similar to a physical write operation.
 912  */
 913 static int
 914 pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio)
 915 {
 916         u_int size;
 917         int i;
 918
 919         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 920         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
 921             ("%s: PIPE_DIRECTW set on %p", __func__, wpipe));
 922         KASSERT(wpipe->pipe_pages.cnt == 0,
 923             ("%s: pipe map for %p contains residual data", __func__, wpipe));
 924
 925         if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
 926                 size = wpipe->pipe_buffer.size;
 927         else
 928                 size = uio->uio_iov->iov_len;
 929
 930         wpipe->pipe_state |= PIPE_DIRECTW;
 931         PIPE_UNLOCK(wpipe);
 932         i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
 933             (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
 934             wpipe->pipe_pages.ms, PIPENPAGES);
 935         PIPE_LOCK(wpipe);
 936         if (i < 0) {
 937                 wpipe->pipe_state &= ~PIPE_DIRECTW;
 938                 return (EFAULT);
 939         }
 940
 941         wpipe->pipe_pages.npages = i;
 942         wpipe->pipe_pages.pos =
 943             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
 944         wpipe->pipe_pages.cnt = size;
 945
 946         uio->uio_iov->iov_len -= size;
 947         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
 948         if (uio->uio_iov->iov_len == 0)
 949                 uio->uio_iov++;
 950         uio->uio_resid -= size;
 951         uio->uio_offset += size;
 952         return (0);
 953 }
 954
 955 /*
 956  * Unwire the process buffer.
 957  */
 958 static void
 959 pipe_destroy_write_buffer(struct pipe *wpipe)
 960 {
 961
 962         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 963         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
 964             ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
 965         KASSERT(wpipe->pipe_pages.cnt == 0,
 966             ("%s: pipe map for %p contains residual data", __func__, wpipe));
 967
 968         wpipe->pipe_state &= ~PIPE_DIRECTW;
 969         vm_page_unhold_pages(wpipe->pipe_pages.ms, wpipe->pipe_pages.npages);
 970         wpipe->pipe_pages.npages = 0;
 971 }
 972
 973 /*
 974  * In the case of a signal, the writing process might go away.  This
 975  * code copies the data into the circular buffer so that the source
 976  * pages can be freed without loss of data.
 977  */
 978 static void
 979 pipe_clone_write_buffer(struct pipe *wpipe)
 980 {
 981         struct uio uio;
 982         struct iovec iov;
 983         int size;
 984         int pos;
 985
 986         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 987         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
 988             ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
 989
 990         size = wpipe->pipe_pages.cnt;
 991         pos = wpipe->pipe_pages.pos;
 992         wpipe->pipe_pages.cnt = 0;
 993
 994         wpipe->pipe_buffer.in = size;
 995         wpipe->pipe_buffer.out = 0;
 996         wpipe->pipe_buffer.cnt = size;
 997
 998         PIPE_UNLOCK(wpipe);
 999         iov.iov_base = wpipe->pipe_buffer.buffer;
1000         iov.iov_len = size;
1001         uio.uio_iov = &iov;
1002         uio.uio_iovcnt = 1;
1003         uio.uio_offset = 0;
1004         uio.uio_resid = size;
1005         uio.uio_segflg = UIO_SYSSPACE;
1006         uio.uio_rw = UIO_READ;
1007         uio.uio_td = curthread;
1008         uiomove_fromphys(wpipe->pipe_pages.ms, pos, size, &uio);
1009         PIPE_LOCK(wpipe);
1010         pipe_destroy_write_buffer(wpipe);
1011 }
1012
1013 /*
1014  * This implements the pipe buffer write mechanism.  Note that only
1015  * a direct write OR a normal pipe write can be pending at any given time.
1016  * If there are any characters in the pipe buffer, the direct write will
1017  * be deferred until the receiving process grabs all of the bytes from
1018  * the pipe buffer.  Then the direct mapping write is set-up.
1019  */
1020 static int
1021 pipe_direct_write(struct pipe *wpipe, struct uio *uio)
1022 {
1023         int error;
1024
1025 retry:
1026         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
1027         if ((wpipe->pipe_state & PIPE_EOF) != 0) {
1028                 error = EPIPE;
1029                 goto error1;
1030         }
1031         if (wpipe->pipe_state & PIPE_DIRECTW) {
1032                 if (wpipe->pipe_state & PIPE_WANTR) {
1033                         wpipe->pipe_state &= ~PIPE_WANTR;
1034                         wakeup(wpipe);
1035                 }
1036                 pipeselwakeup(wpipe);
1037                 wpipe->pipe_state |= PIPE_WANTW;
1038                 pipeunlock(wpipe);
1039                 error = msleep(wpipe, PIPE_MTX(wpipe),
1040                     PRIBIO | PCATCH, "pipdww", 0);
1041                 pipelock(wpipe, 0);
1042                 if (error != 0)
1043                         goto error1;
1044                 goto retry;
1045         }
1046         if (wpipe->pipe_buffer.cnt > 0) {
1047                 if (wpipe->pipe_state & PIPE_WANTR) {
1048                         wpipe->pipe_state &= ~PIPE_WANTR;
1049                         wakeup(wpipe);
1050                 }
1051                 pipeselwakeup(wpipe);
1052                 wpipe->pipe_state |= PIPE_WANTW;
1053                 pipeunlock(wpipe);
1054                 error = msleep(wpipe, PIPE_MTX(wpipe),
1055                     PRIBIO | PCATCH, "pipdwc", 0);
1056                 pipelock(wpipe, 0);
1057                 if (error != 0)
1058                         goto error1;
1059                 goto retry;
1060         }
1061
1062         error = pipe_build_write_buffer(wpipe, uio);
1063         if (error) {
1064                 goto error1;
1065         }
1066
1067         while (wpipe->pipe_pages.cnt != 0 &&
1068             (wpipe->pipe_state & PIPE_EOF) == 0) {
1069                 if (wpipe->pipe_state & PIPE_WANTR) {
1070                         wpipe->pipe_state &= ~PIPE_WANTR;
1071                         wakeup(wpipe);
1072                 }
1073                 pipeselwakeup(wpipe);
1074                 wpipe->pipe_state |= PIPE_WANTW;
1075                 pipeunlock(wpipe);
1076                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
1077                     "pipdwt", 0);
1078                 pipelock(wpipe, 0);
1079                 if (error != 0)
1080                         break;
1081         }
1082
1083         if ((wpipe->pipe_state & PIPE_EOF) != 0) {
1084                 wpipe->pipe_pages.cnt = 0;
1085                 pipe_destroy_write_buffer(wpipe);
1086                 pipeselwakeup(wpipe);
1087                 error = EPIPE;
1088         } else if (error == EINTR || error == ERESTART) {
1089                 pipe_clone_write_buffer(wpipe);
1090         } else {
1091                 pipe_destroy_write_buffer(wpipe);
1092         }
1093         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
1094             ("pipe %p leaked PIPE_DIRECTW", wpipe));
1095         return (error);
1096
1097 error1:
1098         wakeup(wpipe);
1099         return (error);
1100 }
1101 #endif
1102
1103 static int
1104 pipe_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
1105     int flags, struct thread *td)
1106 {
1107         struct pipe *wpipe, *rpipe;
1108         ssize_t orig_resid;
1109         int desiredsize, error;
1110
1111         rpipe = fp->f_data;
1112         wpipe = PIPE_PEER(rpipe);
1113         PIPE_LOCK(rpipe);
1114         error = pipelock(wpipe, 1);
1115         if (error) {
1116                 PIPE_UNLOCK(rpipe);
1117                 return (error);
1118         }
1119         /*
1120          * detect loss of pipe read side, issue SIGPIPE if lost.
1121          */
1122         if (wpipe->pipe_present != PIPE_ACTIVE ||
1123             (wpipe->pipe_state & PIPE_EOF)) {
1124                 pipeunlock(wpipe);
1125                 PIPE_UNLOCK(rpipe);
1126                 return (EPIPE);
1127         }
1128 #ifdef MAC
1129         error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
1130         if (error) {
1131                 pipeunlock(wpipe);
1132                 PIPE_UNLOCK(rpipe);
1133                 return (error);
1134         }
1135 #endif
1136         ++wpipe->pipe_busy;
1137
1138         /* Choose a larger size if it's advantageous */
1139         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
1140         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
1141                 if (piperesizeallowed != 1)
1142                         break;
1143                 if (amountpipekva > maxpipekva / 2)
1144                         break;
1145                 if (desiredsize == BIG_PIPE_SIZE)
1146                         break;
1147                 desiredsize = desiredsize * 2;
1148         }
1149
1150         /* Choose a smaller size if we're in a OOM situation */
1151         if (amountpipekva > (3 * maxpipekva) / 4 &&
1152             wpipe->pipe_buffer.size > SMALL_PIPE_SIZE &&
1153             wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE &&
1154             piperesizeallowed == 1)
1155                 desiredsize = SMALL_PIPE_SIZE;
1156
1157         /* Resize if the above determined that a new size was necessary */
1158         if (desiredsize != wpipe->pipe_buffer.size &&
1159             (wpipe->pipe_state & PIPE_DIRECTW) == 0) {
1160                 PIPE_UNLOCK(wpipe);
1161                 pipespace(wpipe, desiredsize);
1162                 PIPE_LOCK(wpipe);
1163         }
1164         MPASS(wpipe->pipe_buffer.size != 0);
1165
1166         orig_resid = uio->uio_resid;
1167
1168         while (uio->uio_resid) {
1169                 int space;
1170
1171                 if (wpipe->pipe_state & PIPE_EOF) {
1172                         error = EPIPE;
1173                         break;
1174                 }
1175 #ifndef PIPE_NODIRECT
1176                 /*
1177                  * If the transfer is large, we can gain performance if
1178                  * we do process-to-process copies directly.
1179                  * If the write is non-blocking, we don't use the
1180                  * direct write mechanism.
1181                  *
1182                  * The direct write mechanism will detect the reader going
1183                  * away on us.
1184                  */
1185                 if (uio->uio_segflg == UIO_USERSPACE &&
1186                     uio->uio_iov->iov_len >= pipe_mindirect &&
1187                     wpipe->pipe_buffer.size >= pipe_mindirect &&
1188                     (fp->f_flag & FNONBLOCK) == 0) {
1189                         error = pipe_direct_write(wpipe, uio);
1190                         if (error != 0)
1191                                 break;
1192                         continue;
1193                 }
1194 #endif
1195
1196                 /*
1197                  * Pipe buffered writes cannot be coincidental with
1198                  * direct writes.  We wait until the currently executing
1199                  * direct write is completed before we start filling the
1200                  * pipe buffer.  We break out if a signal occurs or the
1201                  * reader goes away.
1202                  */
1203                 if (wpipe->pipe_pages.cnt != 0) {
1204                         if (wpipe->pipe_state & PIPE_WANTR) {
1205                                 wpipe->pipe_state &= ~PIPE_WANTR;
1206                                 wakeup(wpipe);
1207                         }
1208                         pipeselwakeup(wpipe);
1209                         wpipe->pipe_state |= PIPE_WANTW;
1210                         pipeunlock(wpipe);
1211                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
1212                             "pipbww", 0);
1213                         pipelock(wpipe, 0);
1214                         if (error != 0)
1215                                 break;
1216                         continue;
1217                 }
1218
1219                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
1220
1221                 /* Writes of size <= PIPE_BUF must be atomic. */
1222                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
1223                         space = 0;
1224
1225                 if (space > 0) {
1226                         int size;       /* Transfer size */
1227                         int segsize;    /* first segment to transfer */
1228
1229                         /*
1230                          * Transfer size is minimum of uio transfer
1231                          * and free space in pipe buffer.
1232                          */
1233                         if (space > uio->uio_resid)
1234                                 size = uio->uio_resid;
1235                         else
1236                                 size = space;
1237                         /*
1238                          * First segment to transfer is minimum of
1239                          * transfer size and contiguous space in
1240                          * pipe buffer.  If first segment to transfer
1241                          * is less than the transfer size, we've got
1242                          * a wraparound in the buffer.
1243                          */
1244                         segsize = wpipe->pipe_buffer.size -
1245                                 wpipe->pipe_buffer.in;
1246                         if (segsize > size)
1247                                 segsize = size;
1248
1249                         /* Transfer first segment */
1250
1251                         PIPE_UNLOCK(rpipe);
1252                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
1253                                         segsize, uio);
1254                         PIPE_LOCK(rpipe);
1255
1256                         if (error == 0 && segsize < size) {
1257                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
1258                                         wpipe->pipe_buffer.size,
1259                                         ("Pipe buffer wraparound disappeared"));
1260                                 /*
1261                                  * Transfer remaining part now, to
1262                                  * support atomic writes.  Wraparound
1263                                  * happened.
1264                                  */
1265
1266                                 PIPE_UNLOCK(rpipe);
1267                                 error = uiomove(
1268                                     &wpipe->pipe_buffer.buffer[0],
1269                                     size - segsize, uio);
1270                                 PIPE_LOCK(rpipe);
1271                         }
1272                         if (error == 0) {
1273                                 wpipe->pipe_buffer.in += size;
1274                                 if (wpipe->pipe_buffer.in >=
1275                                     wpipe->pipe_buffer.size) {
1276                                         KASSERT(wpipe->pipe_buffer.in ==
1277                                                 size - segsize +
1278                                                 wpipe->pipe_buffer.size,
1279                                                 ("Expected wraparound bad"));
1280                                         wpipe->pipe_buffer.in = size - segsize;
1281                                 }
1282
1283                                 wpipe->pipe_buffer.cnt += size;
1284                                 KASSERT(wpipe->pipe_buffer.cnt <=
1285                                         wpipe->pipe_buffer.size,
1286                                         ("Pipe buffer overflow"));
1287                         }
1288                         if (error != 0)
1289                                 break;
1290                         continue;
1291                 } else {
1292                         /*
1293                          * If the "read-side" has been blocked, wake it up now.
1294                          */
1295                         if (wpipe->pipe_state & PIPE_WANTR) {
1296                                 wpipe->pipe_state &= ~PIPE_WANTR;
1297                                 wakeup(wpipe);
1298                         }
1299
1300                         /*
1301                          * don't block on non-blocking I/O
1302                          */
1303                         if (fp->f_flag & FNONBLOCK) {
1304                                 error = EAGAIN;
1305                                 break;
1306                         }
1307
1308                         /*
1309                          * We have no more space and have something to offer,
1310                          * wake up select/poll.
1311                          */
1312                         pipeselwakeup(wpipe);
1313
1314                         wpipe->pipe_state |= PIPE_WANTW;
1315                         pipeunlock(wpipe);
1316                         error = msleep(wpipe, PIPE_MTX(rpipe),
1317                             PRIBIO | PCATCH, "pipewr", 0);
1318                         pipelock(wpipe, 0);
1319                         if (error != 0)
1320                                 break;
1321                         continue;
1322                 }
1323         }
1324
1325         --wpipe->pipe_busy;
1326
1327         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
1328                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
1329                 wakeup(wpipe);
1330         } else if (wpipe->pipe_buffer.cnt > 0) {
1331                 /*
1332                  * If we have put any characters in the buffer, we wake up
1333                  * the reader.
1334                  */
1335                 if (wpipe->pipe_state & PIPE_WANTR) {
1336                         wpipe->pipe_state &= ~PIPE_WANTR;
1337                         wakeup(wpipe);
1338                 }
1339         }
1340
1341         /*
1342          * Don't return EPIPE if any byte was written.
1343          * EINTR and other interrupts are handled by generic I/O layer.
1344          * Do not pretend that I/O succeeded for obvious user error
1345          * like EFAULT.
1346          */
1347         if (uio->uio_resid != orig_resid && error == EPIPE)
1348                 error = 0;
1349
1350         if (error == 0)
1351                 pipe_timestamp(&wpipe->pipe_mtime);
1352
1353         /*
1354          * We have something to offer,
1355          * wake up select/poll.
1356          */
1357         if (wpipe->pipe_buffer.cnt)
1358                 pipeselwakeup(wpipe);
1359
1360         pipeunlock(wpipe);
1361         PIPE_UNLOCK(rpipe);
1362         if (uio->uio_resid != orig_resid)
1363                 td->td_ru.ru_msgsnd++;
1364         return (error);
1365 }
1366
1367 /* ARGSUSED */
1368 static int
1369 pipe_truncate(struct file *fp, off_t length, struct ucred *active_cred,
1370     struct thread *td)
1371 {
1372         struct pipe *cpipe;
1373         int error;
1374
1375         cpipe = fp->f_data;
1376         if (cpipe->pipe_type & PIPE_TYPE_NAMED)
1377                 error = vnops.fo_truncate(fp, length, active_cred, td);
1378         else
1379                 error = invfo_truncate(fp, length, active_cred, td);
1380         return (error);
1381 }
1382
1383 /*
1384  * we implement a very minimal set of ioctls for compatibility with sockets.
1385  */
1386 static int
1387 pipe_ioctl(struct file *fp, u_long cmd, void *data, struct ucred *active_cred,
1388     struct thread *td)
1389 {
1390         struct pipe *mpipe = fp->f_data;
1391         int error;
1392
1393         PIPE_LOCK(mpipe);
1394
1395 #ifdef MAC
1396         error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
1397         if (error) {
1398                 PIPE_UNLOCK(mpipe);
1399                 return (error);
1400         }
1401 #endif
1402
1403         error = 0;
1404         switch (cmd) {
1405         case FIONBIO:
1406                 break;
1407
1408         case FIOASYNC:
1409                 if (*(int *)data) {
1410                         mpipe->pipe_state |= PIPE_ASYNC;
1411                 } else {
1412                         mpipe->pipe_state &= ~PIPE_ASYNC;
1413                 }
1414                 break;
1415
1416         case FIONREAD:
1417                 if (!(fp->f_flag & FREAD)) {
1418                         *(int *)data = 0;
1419                         PIPE_UNLOCK(mpipe);
1420                         return (0);
1421                 }
1422                 if (mpipe->pipe_pages.cnt != 0)
1423                         *(int *)data = mpipe->pipe_pages.cnt;
1424                 else
1425                         *(int *)data = mpipe->pipe_buffer.cnt;
1426                 break;
1427
1428         case FIOSETOWN:
1429                 PIPE_UNLOCK(mpipe);
1430                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
1431                 goto out_unlocked;
1432
1433         case FIOGETOWN:
1434                 *(int *)data = fgetown(&mpipe->pipe_sigio);
1435                 break;
1436
1437         /* This is deprecated, FIOSETOWN should be used instead. */
1438         case TIOCSPGRP:
1439                 PIPE_UNLOCK(mpipe);
1440                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
1441                 goto out_unlocked;
1442
1443         /* This is deprecated, FIOGETOWN should be used instead. */
1444         case TIOCGPGRP:
1445                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
1446                 break;
1447
1448         default:
1449                 error = ENOTTY;
1450                 break;
1451         }
1452         PIPE_UNLOCK(mpipe);
1453 out_unlocked:
1454         return (error);
1455 }
1456
1457 static int
1458 pipe_poll(struct file *fp, int events, struct ucred *active_cred,
1459     struct thread *td)
1460 {
1461         struct pipe *rpipe;
1462         struct pipe *wpipe;
1463         int levents, revents;
1464 #ifdef MAC
1465         int error;
1466 #endif
1467
1468         revents = 0;
1469         rpipe = fp->f_data;
1470         wpipe = PIPE_PEER(rpipe);
1471         PIPE_LOCK(rpipe);
1472 #ifdef MAC
1473         error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
1474         if (error)
1475                 goto locked_error;
1476 #endif
1477         if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM))
1478                 if (rpipe->pipe_pages.cnt > 0 || rpipe->pipe_buffer.cnt > 0)
1479                         revents |= events & (POLLIN | POLLRDNORM);
1480
1481         if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM))
1482                 if (wpipe->pipe_present != PIPE_ACTIVE ||
1483                     (wpipe->pipe_state & PIPE_EOF) ||
1484                     ((wpipe->pipe_state & PIPE_DIRECTW) == 0 &&
1485                      ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
1486                          wpipe->pipe_buffer.size == 0)))
1487                         revents |= events & (POLLOUT | POLLWRNORM);
1488
1489         levents = events &
1490             (POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
1491         if (rpipe->pipe_type & PIPE_TYPE_NAMED && fp->f_flag & FREAD && levents &&
1492             fp->f_pipegen == rpipe->pipe_wgen)
1493                 events |= POLLINIGNEOF;
1494
1495         if ((events & POLLINIGNEOF) == 0) {
1496                 if (rpipe->pipe_state & PIPE_EOF) {
1497                         if (fp->f_flag & FREAD)
1498                                 revents |= (events & (POLLIN | POLLRDNORM));
1499                         if (wpipe->pipe_present != PIPE_ACTIVE ||
1500                             (wpipe->pipe_state & PIPE_EOF))
1501                                 revents |= POLLHUP;
1502                 }
1503         }
1504
1505         if (revents == 0) {
1506                 /*
1507                  * Add ourselves regardless of eventmask as we have to return
1508                  * POLLHUP even if it was not asked for.
1509                  */
1510                 if ((fp->f_flag & FREAD) != 0) {
1511                         selrecord(td, &rpipe->pipe_sel);
1512                         if (SEL_WAITING(&rpipe->pipe_sel))
1513                                 rpipe->pipe_state |= PIPE_SEL;
1514                 }
1515
1516                 if ((fp->f_flag & FWRITE) != 0 &&
1517                     wpipe->pipe_present == PIPE_ACTIVE) {
1518                         selrecord(td, &wpipe->pipe_sel);
1519                         if (SEL_WAITING(&wpipe->pipe_sel))
1520                                 wpipe->pipe_state |= PIPE_SEL;
1521                 }
1522         }
1523 #ifdef MAC
1524 locked_error:
1525 #endif
1526         PIPE_UNLOCK(rpipe);
1527
1528         return (revents);
1529 }
1530
1531 /*
1532  * We shouldn't need locks here as we're doing a read and this should
1533  * be a natural race.
1534  */
1535 static int
1536 pipe_stat(struct file *fp, struct stat *ub, struct ucred *active_cred)
1537 {
1538         struct pipe *pipe;
1539 #ifdef MAC
1540         int error;
1541 #endif
1542
1543         pipe = fp->f_data;
1544 #ifdef MAC
1545         if (mac_pipe_check_stat_enabled()) {
1546                 PIPE_LOCK(pipe);
1547                 error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
1548                 PIPE_UNLOCK(pipe);
1549                 if (error) {
1550                         return (error);
1551                 }
1552         }
1553 #endif
1554
1555         /* For named pipes ask the underlying filesystem. */
1556         if (pipe->pipe_type & PIPE_TYPE_NAMED) {
1557                 return (vnops.fo_stat(fp, ub, active_cred));
1558         }
1559
1560         bzero(ub, sizeof(*ub));
1561         ub->st_mode = S_IFIFO;
1562         ub->st_blksize = PAGE_SIZE;
1563         if (pipe->pipe_pages.cnt != 0)
1564                 ub->st_size = pipe->pipe_pages.cnt;
1565         else
1566                 ub->st_size = pipe->pipe_buffer.cnt;
1567         ub->st_blocks = howmany(ub->st_size, ub->st_blksize);
1568         ub->st_atim = pipe->pipe_atime;
1569         ub->st_mtim = pipe->pipe_mtime;
1570         ub->st_ctim = pipe->pipe_ctime;
1571         ub->st_uid = fp->f_cred->cr_uid;
1572         ub->st_gid = fp->f_cred->cr_gid;
1573         ub->st_dev = pipedev_ino;
1574         ub->st_ino = pipe->pipe_ino;
1575         /*
1576          * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
1577          */
1578         return (0);
1579 }
1580
1581 /* ARGSUSED */
1582 static int
1583 pipe_close(struct file *fp, struct thread *td)
1584 {
1585
1586         if (fp->f_vnode != NULL)
1587                 return vnops.fo_close(fp, td);
1588         fp->f_ops = &badfileops;
1589         pipe_dtor(fp->f_data);
1590         fp->f_data = NULL;
1591         return (0);
1592 }
1593
1594 static int
1595 pipe_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, struct thread *td)
1596 {
1597         struct pipe *cpipe;
1598         int error;
1599
1600         cpipe = fp->f_data;
1601         if (cpipe->pipe_type & PIPE_TYPE_NAMED)
1602                 error = vn_chmod(fp, mode, active_cred, td);
1603         else
1604                 error = invfo_chmod(fp, mode, active_cred, td);
1605         return (error);
1606 }
1607
1608 static int
1609 pipe_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
1610     struct thread *td)
1611 {
1612         struct pipe *cpipe;
1613         int error;
1614
1615         cpipe = fp->f_data;
1616         if (cpipe->pipe_type & PIPE_TYPE_NAMED)
1617                 error = vn_chown(fp, uid, gid, active_cred, td);
1618         else
1619                 error = invfo_chown(fp, uid, gid, active_cred, td);
1620         return (error);
1621 }
1622
1623 static int
1624 pipe_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
1625 {
1626         struct pipe *pi;
1627
1628         if (fp->f_type == DTYPE_FIFO)
1629                 return (vn_fill_kinfo(fp, kif, fdp));
1630         kif->kf_type = KF_TYPE_PIPE;
1631         pi = fp->f_data;
1632         kif->kf_un.kf_pipe.kf_pipe_addr = (uintptr_t)pi;
1633         kif->kf_un.kf_pipe.kf_pipe_peer = (uintptr_t)pi->pipe_peer;
1634         kif->kf_un.kf_pipe.kf_pipe_buffer_cnt = pi->pipe_buffer.cnt;
1635         kif->kf_un.kf_pipe.kf_pipe_buffer_in = pi->pipe_buffer.in;
1636         kif->kf_un.kf_pipe.kf_pipe_buffer_out = pi->pipe_buffer.out;
1637         kif->kf_un.kf_pipe.kf_pipe_buffer_size = pi->pipe_buffer.size;
1638         return (0);
1639 }
1640
1641 static void
1642 pipe_free_kmem(struct pipe *cpipe)
1643 {
1644
1645         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
1646             ("pipe_free_kmem: pipe mutex locked"));
1647
1648         if (cpipe->pipe_buffer.buffer != NULL) {
1649                 atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
1650                 vm_map_remove(pipe_map,
1651                     (vm_offset_t)cpipe->pipe_buffer.buffer,
1652                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
1653                 cpipe->pipe_buffer.buffer = NULL;
1654         }
1655 #ifndef PIPE_NODIRECT
1656         {
1657                 cpipe->pipe_pages.cnt = 0;
1658                 cpipe->pipe_pages.pos = 0;
1659                 cpipe->pipe_pages.npages = 0;
1660         }
1661 #endif
1662 }
1663
1664 /*
1665  * shutdown the pipe
1666  */
1667 static void
1668 pipeclose(struct pipe *cpipe)
1669 {
1670 #ifdef MAC
1671         struct pipepair *pp;
1672 #endif
1673         struct pipe *ppipe;
1674
1675         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
1676
1677         PIPE_LOCK(cpipe);
1678         pipelock(cpipe, 0);
1679 #ifdef MAC
1680         pp = cpipe->pipe_pair;
1681 #endif
1682
1683         /*
1684          * If the other side is blocked, wake it up saying that
1685          * we want to close it down.
1686          */
1687         cpipe->pipe_state |= PIPE_EOF;
1688         while (cpipe->pipe_busy) {
1689                 wakeup(cpipe);
1690                 cpipe->pipe_state |= PIPE_WANT;
1691                 pipeunlock(cpipe);
1692                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
1693                 pipelock(cpipe, 0);
1694         }
1695
1696         pipeselwakeup(cpipe);
1697
1698         /*
1699          * Disconnect from peer, if any.
1700          */
1701         ppipe = cpipe->pipe_peer;
1702         if (ppipe->pipe_present == PIPE_ACTIVE) {
1703                 ppipe->pipe_state |= PIPE_EOF;
1704                 wakeup(ppipe);
1705                 pipeselwakeup(ppipe);
1706         }
1707
1708         /*
1709          * Mark this endpoint as free.  Release kmem resources.  We
1710          * don't mark this endpoint as unused until we've finished
1711          * doing that, or the pipe might disappear out from under
1712          * us.
1713          */
1714         PIPE_UNLOCK(cpipe);
1715         pipe_free_kmem(cpipe);
1716         PIPE_LOCK(cpipe);
1717         cpipe->pipe_present = PIPE_CLOSING;
1718         pipeunlock(cpipe);
1719
1720         /*
1721          * knlist_clear() may sleep dropping the PIPE_MTX. Set the
1722          * PIPE_FINALIZED, that allows other end to free the
1723          * pipe_pair, only after the knotes are completely dismantled.
1724          */
1725         knlist_clear(&cpipe->pipe_sel.si_note, 1);
1726         cpipe->pipe_present = PIPE_FINALIZED;
1727         seldrain(&cpipe->pipe_sel);
1728         knlist_destroy(&cpipe->pipe_sel.si_note);
1729
1730         /*
1731          * If both endpoints are now closed, release the memory for the
1732          * pipe pair.  If not, unlock.
1733          */
1734         if (ppipe->pipe_present == PIPE_FINALIZED) {
1735                 PIPE_UNLOCK(cpipe);
1736 #ifdef MAC
1737                 mac_pipe_destroy(pp);
1738 #endif
1739                 uma_zfree(pipe_zone, cpipe->pipe_pair);
1740         } else
1741                 PIPE_UNLOCK(cpipe);
1742 }
1743
1744 /*ARGSUSED*/
1745 static int
1746 pipe_kqfilter(struct file *fp, struct knote *kn)
1747 {
1748         struct pipe *cpipe;
1749
1750         /*
1751          * If a filter is requested that is not supported by this file
1752          * descriptor, don't return an error, but also don't ever generate an
1753          * event.
1754          */
1755         if ((kn->kn_filter == EVFILT_READ) && !(fp->f_flag & FREAD)) {
1756                 kn->kn_fop = &pipe_nfiltops;
1757                 return (0);
1758         }
1759         if ((kn->kn_filter == EVFILT_WRITE) && !(fp->f_flag & FWRITE)) {
1760                 kn->kn_fop = &pipe_nfiltops;
1761                 return (0);
1762         }
1763         cpipe = fp->f_data;
1764         PIPE_LOCK(cpipe);
1765         switch (kn->kn_filter) {
1766         case EVFILT_READ:
1767                 kn->kn_fop = &pipe_rfiltops;
1768                 break;
1769         case EVFILT_WRITE:
1770                 kn->kn_fop = &pipe_wfiltops;
1771                 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
1772                         /* other end of pipe has been closed */
1773                         PIPE_UNLOCK(cpipe);
1774                         return (EPIPE);
1775                 }
1776                 cpipe = PIPE_PEER(cpipe);
1777                 break;
1778         default:
1779                 if ((cpipe->pipe_type & PIPE_TYPE_NAMED) != 0) {
1780                         PIPE_UNLOCK(cpipe);
1781                         return (vnops.fo_kqfilter(fp, kn));
1782                 }
1783                 PIPE_UNLOCK(cpipe);
1784                 return (EINVAL);
1785         }
1786
1787         kn->kn_hook = cpipe;
1788         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
1789         PIPE_UNLOCK(cpipe);
1790         return (0);
1791 }
1792
1793 static void
1794 filt_pipedetach(struct knote *kn)
1795 {
1796         struct pipe *cpipe = kn->kn_hook;
1797
1798         PIPE_LOCK(cpipe);
1799         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
1800         PIPE_UNLOCK(cpipe);
1801 }
1802
1803 /*ARGSUSED*/
1804 static int
1805 filt_piperead(struct knote *kn, long hint)
1806 {
1807         struct file *fp = kn->kn_fp;
1808         struct pipe *rpipe = kn->kn_hook;
1809
1810         PIPE_LOCK_ASSERT(rpipe, MA_OWNED);
1811         kn->kn_data = rpipe->pipe_buffer.cnt;
1812         if (kn->kn_data == 0)
1813                 kn->kn_data = rpipe->pipe_pages.cnt;
1814
1815         if ((rpipe->pipe_state & PIPE_EOF) != 0 &&
1816             ((rpipe->pipe_type & PIPE_TYPE_NAMED) == 0 ||
1817             fp->f_pipegen != rpipe->pipe_wgen)) {
1818                 kn->kn_flags |= EV_EOF;
1819                 return (1);
1820         }
1821         kn->kn_flags &= ~EV_EOF;
1822         return (kn->kn_data > 0);
1823 }
1824
1825 /*ARGSUSED*/
1826 static int
1827 filt_pipewrite(struct knote *kn, long hint)
1828 {
1829         struct pipe *wpipe = kn->kn_hook;
1830
1831         /*
1832          * If this end of the pipe is closed, the knote was removed from the
1833          * knlist and the list lock (i.e., the pipe lock) is therefore not held.
1834          */
1835         if (wpipe->pipe_present == PIPE_ACTIVE ||
1836             (wpipe->pipe_type & PIPE_TYPE_NAMED) != 0) {
1837                 PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
1838
1839                 if (wpipe->pipe_state & PIPE_DIRECTW) {
1840                         kn->kn_data = 0;
1841                 } else if (wpipe->pipe_buffer.size > 0) {
1842                         kn->kn_data = wpipe->pipe_buffer.size -
1843                             wpipe->pipe_buffer.cnt;
1844                 } else {
1845                         kn->kn_data = PIPE_BUF;
1846                 }
1847         }
1848
1849         if (wpipe->pipe_present != PIPE_ACTIVE ||
1850             (wpipe->pipe_state & PIPE_EOF)) {
1851                 kn->kn_flags |= EV_EOF;
1852                 return (1);
1853         }
1854         kn->kn_flags &= ~EV_EOF;
1855         return (kn->kn_data >= PIPE_BUF);
1856 }
1857
1858 static void
1859 filt_pipedetach_notsup(struct knote *kn)
1860 {
1861
1862 }
1863
1864 static int
1865 filt_pipenotsup(struct knote *kn, long hint)
1866 {
1867
1868         return (0);
1869 }