The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/sys_pipe.c

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    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: releng/12.0/sys/kern/sys_pipe.c 334486 2018-06-01 13:26:45Z emaste $");
   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_state & PIPE_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 
  213 SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
  214            &maxpipekva, 0, "Pipe KVA limit");
  215 SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
  216            &amountpipekva, 0, "Pipe KVA usage");
  217 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
  218           &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
  219 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
  220           &pipeallocfail, 0, "Pipe allocation failures");
  221 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
  222           &piperesizefail, 0, "Pipe resize failures");
  223 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
  224           &piperesizeallowed, 0, "Pipe resizing allowed");
  225 
  226 static void pipeinit(void *dummy __unused);
  227 static void pipeclose(struct pipe *cpipe);
  228 static void pipe_free_kmem(struct pipe *cpipe);
  229 static void pipe_create(struct pipe *pipe, int backing);
  230 static void pipe_paircreate(struct thread *td, struct pipepair **p_pp);
  231 static __inline int pipelock(struct pipe *cpipe, int catch);
  232 static __inline void pipeunlock(struct pipe *cpipe);
  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 unrhdr *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         pipeino_unr = new_unrhdr(1, INT32_MAX, NULL);
  261         KASSERT(pipeino_unr != NULL, ("pipe fake inodes not initialized"));
  262         pipedev_ino = devfs_alloc_cdp_inode();
  263         KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
  264 }
  265 
  266 static int
  267 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
  268 {
  269         struct pipepair *pp;
  270         struct pipe *rpipe, *wpipe;
  271 
  272         KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
  273 
  274         pp = (struct pipepair *)mem;
  275 
  276         /*
  277          * We zero both pipe endpoints to make sure all the kmem pointers
  278          * are NULL, flag fields are zero'd, etc.  We timestamp both
  279          * endpoints with the same time.
  280          */
  281         rpipe = &pp->pp_rpipe;
  282         bzero(rpipe, sizeof(*rpipe));
  283         vfs_timestamp(&rpipe->pipe_ctime);
  284         rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
  285 
  286         wpipe = &pp->pp_wpipe;
  287         bzero(wpipe, sizeof(*wpipe));
  288         wpipe->pipe_ctime = rpipe->pipe_ctime;
  289         wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
  290 
  291         rpipe->pipe_peer = wpipe;
  292         rpipe->pipe_pair = pp;
  293         wpipe->pipe_peer = rpipe;
  294         wpipe->pipe_pair = pp;
  295 
  296         /*
  297          * Mark both endpoints as present; they will later get free'd
  298          * one at a time.  When both are free'd, then the whole pair
  299          * is released.
  300          */
  301         rpipe->pipe_present = PIPE_ACTIVE;
  302         wpipe->pipe_present = PIPE_ACTIVE;
  303 
  304         /*
  305          * Eventually, the MAC Framework may initialize the label
  306          * in ctor or init, but for now we do it elswhere to avoid
  307          * blocking in ctor or init.
  308          */
  309         pp->pp_label = NULL;
  310 
  311         return (0);
  312 }
  313 
  314 static int
  315 pipe_zone_init(void *mem, int size, int flags)
  316 {
  317         struct pipepair *pp;
  318 
  319         KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
  320 
  321         pp = (struct pipepair *)mem;
  322 
  323         mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_NEW);
  324         return (0);
  325 }
  326 
  327 static void
  328 pipe_zone_fini(void *mem, int size)
  329 {
  330         struct pipepair *pp;
  331 
  332         KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
  333 
  334         pp = (struct pipepair *)mem;
  335 
  336         mtx_destroy(&pp->pp_mtx);
  337 }
  338 
  339 static void
  340 pipe_paircreate(struct thread *td, struct pipepair **p_pp)
  341 {
  342         struct pipepair *pp;
  343         struct pipe *rpipe, *wpipe;
  344 
  345         *p_pp = pp = uma_zalloc(pipe_zone, M_WAITOK);
  346 #ifdef MAC
  347         /*
  348          * The MAC label is shared between the connected endpoints.  As a
  349          * result mac_pipe_init() and mac_pipe_create() are called once
  350          * for the pair, and not on the endpoints.
  351          */
  352         mac_pipe_init(pp);
  353         mac_pipe_create(td->td_ucred, pp);
  354 #endif
  355         rpipe = &pp->pp_rpipe;
  356         wpipe = &pp->pp_wpipe;
  357 
  358         knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
  359         knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
  360 
  361         /* Only the forward direction pipe is backed by default */
  362         pipe_create(rpipe, 1);
  363         pipe_create(wpipe, 0);
  364 
  365         rpipe->pipe_state |= PIPE_DIRECTOK;
  366         wpipe->pipe_state |= PIPE_DIRECTOK;
  367 }
  368 
  369 void
  370 pipe_named_ctor(struct pipe **ppipe, struct thread *td)
  371 {
  372         struct pipepair *pp;
  373 
  374         pipe_paircreate(td, &pp);
  375         pp->pp_rpipe.pipe_state |= PIPE_NAMED;
  376         *ppipe = &pp->pp_rpipe;
  377 }
  378 
  379 void
  380 pipe_dtor(struct pipe *dpipe)
  381 {
  382         struct pipe *peer;
  383         ino_t ino;
  384 
  385         ino = dpipe->pipe_ino;
  386         peer = (dpipe->pipe_state & PIPE_NAMED) != 0 ? dpipe->pipe_peer : NULL;
  387         funsetown(&dpipe->pipe_sigio);
  388         pipeclose(dpipe);
  389         if (peer != NULL) {
  390                 funsetown(&peer->pipe_sigio);
  391                 pipeclose(peer);
  392         }
  393         if (ino != 0 && ino != (ino_t)-1)
  394                 free_unr(pipeino_unr, ino);
  395 }
  396 
  397 /*
  398  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
  399  * the zone pick up the pieces via pipeclose().
  400  */
  401 int
  402 kern_pipe(struct thread *td, int fildes[2], int flags, struct filecaps *fcaps1,
  403     struct filecaps *fcaps2)
  404 {
  405         struct file *rf, *wf;
  406         struct pipe *rpipe, *wpipe;
  407         struct pipepair *pp;
  408         int fd, fflags, error;
  409 
  410         pipe_paircreate(td, &pp);
  411         rpipe = &pp->pp_rpipe;
  412         wpipe = &pp->pp_wpipe;
  413         error = falloc_caps(td, &rf, &fd, flags, fcaps1);
  414         if (error) {
  415                 pipeclose(rpipe);
  416                 pipeclose(wpipe);
  417                 return (error);
  418         }
  419         /* An extra reference on `rf' has been held for us by falloc_caps(). */
  420         fildes[0] = fd;
  421 
  422         fflags = FREAD | FWRITE;
  423         if ((flags & O_NONBLOCK) != 0)
  424                 fflags |= FNONBLOCK;
  425 
  426         /*
  427          * Warning: once we've gotten past allocation of the fd for the
  428          * read-side, we can only drop the read side via fdrop() in order
  429          * to avoid races against processes which manage to dup() the read
  430          * side while we are blocked trying to allocate the write side.
  431          */
  432         finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
  433         error = falloc_caps(td, &wf, &fd, flags, fcaps2);
  434         if (error) {
  435                 fdclose(td, rf, fildes[0]);
  436                 fdrop(rf, td);
  437                 /* rpipe has been closed by fdrop(). */
  438                 pipeclose(wpipe);
  439                 return (error);
  440         }
  441         /* An extra reference on `wf' has been held for us by falloc_caps(). */
  442         finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
  443         fdrop(wf, td);
  444         fildes[1] = fd;
  445         fdrop(rf, td);
  446 
  447         return (0);
  448 }
  449 
  450 #ifdef COMPAT_FREEBSD10
  451 /* ARGSUSED */
  452 int
  453 freebsd10_pipe(struct thread *td, struct freebsd10_pipe_args *uap __unused)
  454 {
  455         int error;
  456         int fildes[2];
  457 
  458         error = kern_pipe(td, fildes, 0, NULL, NULL);
  459         if (error)
  460                 return (error);
  461 
  462         td->td_retval[0] = fildes[0];
  463         td->td_retval[1] = fildes[1];
  464 
  465         return (0);
  466 }
  467 #endif
  468 
  469 int
  470 sys_pipe2(struct thread *td, struct pipe2_args *uap)
  471 {
  472         int error, fildes[2];
  473 
  474         if (uap->flags & ~(O_CLOEXEC | O_NONBLOCK))
  475                 return (EINVAL);
  476         error = kern_pipe(td, fildes, uap->flags, NULL, NULL);
  477         if (error)
  478                 return (error);
  479         error = copyout(fildes, uap->fildes, 2 * sizeof(int));
  480         if (error) {
  481                 (void)kern_close(td, fildes[0]);
  482                 (void)kern_close(td, fildes[1]);
  483         }
  484         return (error);
  485 }
  486 
  487 /*
  488  * Allocate kva for pipe circular buffer, the space is pageable
  489  * This routine will 'realloc' the size of a pipe safely, if it fails
  490  * it will retain the old buffer.
  491  * If it fails it will return ENOMEM.
  492  */
  493 static int
  494 pipespace_new(struct pipe *cpipe, int size)
  495 {
  496         caddr_t buffer;
  497         int error, cnt, firstseg;
  498         static int curfail = 0;
  499         static struct timeval lastfail;
  500 
  501         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
  502         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
  503                 ("pipespace: resize of direct writes not allowed"));
  504 retry:
  505         cnt = cpipe->pipe_buffer.cnt;
  506         if (cnt > size)
  507                 size = cnt;
  508 
  509         size = round_page(size);
  510         buffer = (caddr_t) vm_map_min(pipe_map);
  511 
  512         error = vm_map_find(pipe_map, NULL, 0,
  513                 (vm_offset_t *) &buffer, size, 0, VMFS_ANY_SPACE,
  514                 VM_PROT_ALL, VM_PROT_ALL, 0);
  515         if (error != KERN_SUCCESS) {
  516                 if ((cpipe->pipe_buffer.buffer == NULL) &&
  517                         (size > SMALL_PIPE_SIZE)) {
  518                         size = SMALL_PIPE_SIZE;
  519                         pipefragretry++;
  520                         goto retry;
  521                 }
  522                 if (cpipe->pipe_buffer.buffer == NULL) {
  523                         pipeallocfail++;
  524                         if (ppsratecheck(&lastfail, &curfail, 1))
  525                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
  526                 } else {
  527                         piperesizefail++;
  528                 }
  529                 return (ENOMEM);
  530         }
  531 
  532         /* copy data, then free old resources if we're resizing */
  533         if (cnt > 0) {
  534                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
  535                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
  536                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  537                                 buffer, firstseg);
  538                         if ((cnt - firstseg) > 0)
  539                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
  540                                         cpipe->pipe_buffer.in);
  541                 } else {
  542                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  543                                 buffer, cnt);
  544                 }
  545         }
  546         pipe_free_kmem(cpipe);
  547         cpipe->pipe_buffer.buffer = buffer;
  548         cpipe->pipe_buffer.size = size;
  549         cpipe->pipe_buffer.in = cnt;
  550         cpipe->pipe_buffer.out = 0;
  551         cpipe->pipe_buffer.cnt = cnt;
  552         atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
  553         return (0);
  554 }
  555 
  556 /*
  557  * Wrapper for pipespace_new() that performs locking assertions.
  558  */
  559 static int
  560 pipespace(struct pipe *cpipe, int size)
  561 {
  562 
  563         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  564                 ("Unlocked pipe passed to pipespace"));
  565         return (pipespace_new(cpipe, size));
  566 }
  567 
  568 /*
  569  * lock a pipe for I/O, blocking other access
  570  */
  571 static __inline int
  572 pipelock(struct pipe *cpipe, int catch)
  573 {
  574         int error;
  575 
  576         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  577         while (cpipe->pipe_state & PIPE_LOCKFL) {
  578                 cpipe->pipe_state |= PIPE_LWANT;
  579                 error = msleep(cpipe, PIPE_MTX(cpipe),
  580                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  581                     "pipelk", 0);
  582                 if (error != 0)
  583                         return (error);
  584         }
  585         cpipe->pipe_state |= PIPE_LOCKFL;
  586         return (0);
  587 }
  588 
  589 /*
  590  * unlock a pipe I/O lock
  591  */
  592 static __inline void
  593 pipeunlock(struct pipe *cpipe)
  594 {
  595 
  596         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  597         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  598                 ("Unlocked pipe passed to pipeunlock"));
  599         cpipe->pipe_state &= ~PIPE_LOCKFL;
  600         if (cpipe->pipe_state & PIPE_LWANT) {
  601                 cpipe->pipe_state &= ~PIPE_LWANT;
  602                 wakeup(cpipe);
  603         }
  604 }
  605 
  606 void
  607 pipeselwakeup(struct pipe *cpipe)
  608 {
  609 
  610         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  611         if (cpipe->pipe_state & PIPE_SEL) {
  612                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
  613                 if (!SEL_WAITING(&cpipe->pipe_sel))
  614                         cpipe->pipe_state &= ~PIPE_SEL;
  615         }
  616         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  617                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  618         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
  619 }
  620 
  621 /*
  622  * Initialize and allocate VM and memory for pipe.  The structure
  623  * will start out zero'd from the ctor, so we just manage the kmem.
  624  */
  625 static void
  626 pipe_create(struct pipe *pipe, int backing)
  627 {
  628 
  629         if (backing) {
  630                 /*
  631                  * Note that these functions can fail if pipe map is exhausted
  632                  * (as a result of too many pipes created), but we ignore the
  633                  * error as it is not fatal and could be provoked by
  634                  * unprivileged users. The only consequence is worse performance
  635                  * with given pipe.
  636                  */
  637                 if (amountpipekva > maxpipekva / 2)
  638                         (void)pipespace_new(pipe, SMALL_PIPE_SIZE);
  639                 else
  640                         (void)pipespace_new(pipe, PIPE_SIZE);
  641         }
  642 
  643         pipe->pipe_ino = -1;
  644 }
  645 
  646 /* ARGSUSED */
  647 static int
  648 pipe_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
  649     int flags, struct thread *td)
  650 {
  651         struct pipe *rpipe;
  652         int error;
  653         int nread = 0;
  654         int size;
  655 
  656         rpipe = fp->f_data;
  657         PIPE_LOCK(rpipe);
  658         ++rpipe->pipe_busy;
  659         error = pipelock(rpipe, 1);
  660         if (error)
  661                 goto unlocked_error;
  662 
  663 #ifdef MAC
  664         error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
  665         if (error)
  666                 goto locked_error;
  667 #endif
  668         if (amountpipekva > (3 * maxpipekva) / 4) {
  669                 if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
  670                         (rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
  671                         (rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
  672                         (piperesizeallowed == 1)) {
  673                         PIPE_UNLOCK(rpipe);
  674                         pipespace(rpipe, SMALL_PIPE_SIZE);
  675                         PIPE_LOCK(rpipe);
  676                 }
  677         }
  678 
  679         while (uio->uio_resid) {
  680                 /*
  681                  * normal pipe buffer receive
  682                  */
  683                 if (rpipe->pipe_buffer.cnt > 0) {
  684                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  685                         if (size > rpipe->pipe_buffer.cnt)
  686                                 size = rpipe->pipe_buffer.cnt;
  687                         if (size > uio->uio_resid)
  688                                 size = uio->uio_resid;
  689 
  690                         PIPE_UNLOCK(rpipe);
  691                         error = uiomove(
  692                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  693                             size, uio);
  694                         PIPE_LOCK(rpipe);
  695                         if (error)
  696                                 break;
  697 
  698                         rpipe->pipe_buffer.out += size;
  699                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  700                                 rpipe->pipe_buffer.out = 0;
  701 
  702                         rpipe->pipe_buffer.cnt -= size;
  703 
  704                         /*
  705                          * If there is no more to read in the pipe, reset
  706                          * its pointers to the beginning.  This improves
  707                          * cache hit stats.
  708                          */
  709                         if (rpipe->pipe_buffer.cnt == 0) {
  710                                 rpipe->pipe_buffer.in = 0;
  711                                 rpipe->pipe_buffer.out = 0;
  712                         }
  713                         nread += size;
  714 #ifndef PIPE_NODIRECT
  715                 /*
  716                  * Direct copy, bypassing a kernel buffer.
  717                  */
  718                 } else if ((size = rpipe->pipe_map.cnt) &&
  719                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  720                         if (size > uio->uio_resid)
  721                                 size = (u_int) uio->uio_resid;
  722 
  723                         PIPE_UNLOCK(rpipe);
  724                         error = uiomove_fromphys(rpipe->pipe_map.ms,
  725                             rpipe->pipe_map.pos, size, uio);
  726                         PIPE_LOCK(rpipe);
  727                         if (error)
  728                                 break;
  729                         nread += size;
  730                         rpipe->pipe_map.pos += size;
  731                         rpipe->pipe_map.cnt -= size;
  732                         if (rpipe->pipe_map.cnt == 0) {
  733                                 rpipe->pipe_state &= ~(PIPE_DIRECTW|PIPE_WANTW);
  734                                 wakeup(rpipe);
  735                         }
  736 #endif
  737                 } else {
  738                         /*
  739                          * detect EOF condition
  740                          * read returns 0 on EOF, no need to set error
  741                          */
  742                         if (rpipe->pipe_state & PIPE_EOF)
  743                                 break;
  744 
  745                         /*
  746                          * If the "write-side" has been blocked, wake it up now.
  747                          */
  748                         if (rpipe->pipe_state & PIPE_WANTW) {
  749                                 rpipe->pipe_state &= ~PIPE_WANTW;
  750                                 wakeup(rpipe);
  751                         }
  752 
  753                         /*
  754                          * Break if some data was read.
  755                          */
  756                         if (nread > 0)
  757                                 break;
  758 
  759                         /*
  760                          * Unlock the pipe buffer for our remaining processing.
  761                          * We will either break out with an error or we will
  762                          * sleep and relock to loop.
  763                          */
  764                         pipeunlock(rpipe);
  765 
  766                         /*
  767                          * Handle non-blocking mode operation or
  768                          * wait for more data.
  769                          */
  770                         if (fp->f_flag & FNONBLOCK) {
  771                                 error = EAGAIN;
  772                         } else {
  773                                 rpipe->pipe_state |= PIPE_WANTR;
  774                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  775                                     PRIBIO | PCATCH,
  776                                     "piperd", 0)) == 0)
  777                                         error = pipelock(rpipe, 1);
  778                         }
  779                         if (error)
  780                                 goto unlocked_error;
  781                 }
  782         }
  783 #ifdef MAC
  784 locked_error:
  785 #endif
  786         pipeunlock(rpipe);
  787 
  788         /* XXX: should probably do this before getting any locks. */
  789         if (error == 0)
  790                 vfs_timestamp(&rpipe->pipe_atime);
  791 unlocked_error:
  792         --rpipe->pipe_busy;
  793 
  794         /*
  795          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  796          */
  797         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  798                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  799                 wakeup(rpipe);
  800         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  801                 /*
  802                  * Handle write blocking hysteresis.
  803                  */
  804                 if (rpipe->pipe_state & PIPE_WANTW) {
  805                         rpipe->pipe_state &= ~PIPE_WANTW;
  806                         wakeup(rpipe);
  807                 }
  808         }
  809 
  810         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  811                 pipeselwakeup(rpipe);
  812 
  813         PIPE_UNLOCK(rpipe);
  814         return (error);
  815 }
  816 
  817 #ifndef PIPE_NODIRECT
  818 /*
  819  * Map the sending processes' buffer into kernel space and wire it.
  820  * This is similar to a physical write operation.
  821  */
  822 static int
  823 pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio)
  824 {
  825         u_int size;
  826         int i;
  827 
  828         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  829         KASSERT(wpipe->pipe_state & PIPE_DIRECTW,
  830                 ("Clone attempt on non-direct write pipe!"));
  831 
  832         if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
  833                 size = wpipe->pipe_buffer.size;
  834         else
  835                 size = uio->uio_iov->iov_len;
  836 
  837         if ((i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
  838             (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
  839             wpipe->pipe_map.ms, PIPENPAGES)) < 0)
  840                 return (EFAULT);
  841 
  842 /*
  843  * set up the control block
  844  */
  845         wpipe->pipe_map.npages = i;
  846         wpipe->pipe_map.pos =
  847             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  848         wpipe->pipe_map.cnt = size;
  849 
  850 /*
  851  * and update the uio data
  852  */
  853 
  854         uio->uio_iov->iov_len -= size;
  855         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  856         if (uio->uio_iov->iov_len == 0)
  857                 uio->uio_iov++;
  858         uio->uio_resid -= size;
  859         uio->uio_offset += size;
  860         return (0);
  861 }
  862 
  863 /*
  864  * unmap and unwire the process buffer
  865  */
  866 static void
  867 pipe_destroy_write_buffer(struct pipe *wpipe)
  868 {
  869 
  870         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  871         vm_page_unhold_pages(wpipe->pipe_map.ms, wpipe->pipe_map.npages);
  872         wpipe->pipe_map.npages = 0;
  873 }
  874 
  875 /*
  876  * In the case of a signal, the writing process might go away.  This
  877  * code copies the data into the circular buffer so that the source
  878  * pages can be freed without loss of data.
  879  */
  880 static void
  881 pipe_clone_write_buffer(struct pipe *wpipe)
  882 {
  883         struct uio uio;
  884         struct iovec iov;
  885         int size;
  886         int pos;
  887 
  888         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  889         size = wpipe->pipe_map.cnt;
  890         pos = wpipe->pipe_map.pos;
  891 
  892         wpipe->pipe_buffer.in = size;
  893         wpipe->pipe_buffer.out = 0;
  894         wpipe->pipe_buffer.cnt = size;
  895         wpipe->pipe_state &= ~PIPE_DIRECTW;
  896 
  897         PIPE_UNLOCK(wpipe);
  898         iov.iov_base = wpipe->pipe_buffer.buffer;
  899         iov.iov_len = size;
  900         uio.uio_iov = &iov;
  901         uio.uio_iovcnt = 1;
  902         uio.uio_offset = 0;
  903         uio.uio_resid = size;
  904         uio.uio_segflg = UIO_SYSSPACE;
  905         uio.uio_rw = UIO_READ;
  906         uio.uio_td = curthread;
  907         uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
  908         PIPE_LOCK(wpipe);
  909         pipe_destroy_write_buffer(wpipe);
  910 }
  911 
  912 /*
  913  * This implements the pipe buffer write mechanism.  Note that only
  914  * a direct write OR a normal pipe write can be pending at any given time.
  915  * If there are any characters in the pipe buffer, the direct write will
  916  * be deferred until the receiving process grabs all of the bytes from
  917  * the pipe buffer.  Then the direct mapping write is set-up.
  918  */
  919 static int
  920 pipe_direct_write(struct pipe *wpipe, struct uio *uio)
  921 {
  922         int error;
  923 
  924 retry:
  925         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  926         error = pipelock(wpipe, 1);
  927         if (error != 0)
  928                 goto error1;
  929         if ((wpipe->pipe_state & PIPE_EOF) != 0) {
  930                 error = EPIPE;
  931                 pipeunlock(wpipe);
  932                 goto error1;
  933         }
  934         while (wpipe->pipe_state & PIPE_DIRECTW) {
  935                 if (wpipe->pipe_state & PIPE_WANTR) {
  936                         wpipe->pipe_state &= ~PIPE_WANTR;
  937                         wakeup(wpipe);
  938                 }
  939                 pipeselwakeup(wpipe);
  940                 wpipe->pipe_state |= PIPE_WANTW;
  941                 pipeunlock(wpipe);
  942                 error = msleep(wpipe, PIPE_MTX(wpipe),
  943                     PRIBIO | PCATCH, "pipdww", 0);
  944                 if (error)
  945                         goto error1;
  946                 else
  947                         goto retry;
  948         }
  949         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  950         if (wpipe->pipe_buffer.cnt > 0) {
  951                 if (wpipe->pipe_state & PIPE_WANTR) {
  952                         wpipe->pipe_state &= ~PIPE_WANTR;
  953                         wakeup(wpipe);
  954                 }
  955                 pipeselwakeup(wpipe);
  956                 wpipe->pipe_state |= PIPE_WANTW;
  957                 pipeunlock(wpipe);
  958                 error = msleep(wpipe, PIPE_MTX(wpipe),
  959                     PRIBIO | PCATCH, "pipdwc", 0);
  960                 if (error)
  961                         goto error1;
  962                 else
  963                         goto retry;
  964         }
  965 
  966         wpipe->pipe_state |= PIPE_DIRECTW;
  967 
  968         PIPE_UNLOCK(wpipe);
  969         error = pipe_build_write_buffer(wpipe, uio);
  970         PIPE_LOCK(wpipe);
  971         if (error) {
  972                 wpipe->pipe_state &= ~PIPE_DIRECTW;
  973                 pipeunlock(wpipe);
  974                 goto error1;
  975         }
  976 
  977         error = 0;
  978         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
  979                 if (wpipe->pipe_state & PIPE_EOF) {
  980                         pipe_destroy_write_buffer(wpipe);
  981                         pipeselwakeup(wpipe);
  982                         pipeunlock(wpipe);
  983                         error = EPIPE;
  984                         goto error1;
  985                 }
  986                 if (wpipe->pipe_state & PIPE_WANTR) {
  987                         wpipe->pipe_state &= ~PIPE_WANTR;
  988                         wakeup(wpipe);
  989                 }
  990                 pipeselwakeup(wpipe);
  991                 wpipe->pipe_state |= PIPE_WANTW;
  992                 pipeunlock(wpipe);
  993                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
  994                     "pipdwt", 0);
  995                 pipelock(wpipe, 0);
  996         }
  997 
  998         if (wpipe->pipe_state & PIPE_EOF)
  999                 error = EPIPE;
 1000         if (wpipe->pipe_state & PIPE_DIRECTW) {
 1001                 /*
 1002                  * this bit of trickery substitutes a kernel buffer for
 1003                  * the process that might be going away.
 1004                  */
 1005                 pipe_clone_write_buffer(wpipe);
 1006         } else {
 1007                 pipe_destroy_write_buffer(wpipe);
 1008         }
 1009         pipeunlock(wpipe);
 1010         return (error);
 1011 
 1012 error1:
 1013         wakeup(wpipe);
 1014         return (error);
 1015 }
 1016 #endif
 1017 
 1018 static int
 1019 pipe_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
 1020     int flags, struct thread *td)
 1021 {
 1022         int error = 0;
 1023         int desiredsize;
 1024         ssize_t orig_resid;
 1025         struct pipe *wpipe, *rpipe;
 1026 
 1027         rpipe = fp->f_data;
 1028         wpipe = PIPE_PEER(rpipe);
 1029         PIPE_LOCK(rpipe);
 1030         error = pipelock(wpipe, 1);
 1031         if (error) {
 1032                 PIPE_UNLOCK(rpipe);
 1033                 return (error);
 1034         }
 1035         /*
 1036          * detect loss of pipe read side, issue SIGPIPE if lost.
 1037          */
 1038         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1039             (wpipe->pipe_state & PIPE_EOF)) {
 1040                 pipeunlock(wpipe);
 1041                 PIPE_UNLOCK(rpipe);
 1042                 return (EPIPE);
 1043         }
 1044 #ifdef MAC
 1045         error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
 1046         if (error) {
 1047                 pipeunlock(wpipe);
 1048                 PIPE_UNLOCK(rpipe);
 1049                 return (error);
 1050         }
 1051 #endif
 1052         ++wpipe->pipe_busy;
 1053 
 1054         /* Choose a larger size if it's advantageous */
 1055         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
 1056         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
 1057                 if (piperesizeallowed != 1)
 1058                         break;
 1059                 if (amountpipekva > maxpipekva / 2)
 1060                         break;
 1061                 if (desiredsize == BIG_PIPE_SIZE)
 1062                         break;
 1063                 desiredsize = desiredsize * 2;
 1064         }
 1065 
 1066         /* Choose a smaller size if we're in a OOM situation */
 1067         if ((amountpipekva > (3 * maxpipekva) / 4) &&
 1068                 (wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
 1069                 (wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
 1070                 (piperesizeallowed == 1))
 1071                 desiredsize = SMALL_PIPE_SIZE;
 1072 
 1073         /* Resize if the above determined that a new size was necessary */
 1074         if ((desiredsize != wpipe->pipe_buffer.size) &&
 1075                 ((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
 1076                 PIPE_UNLOCK(wpipe);
 1077                 pipespace(wpipe, desiredsize);
 1078                 PIPE_LOCK(wpipe);
 1079         }
 1080         if (wpipe->pipe_buffer.size == 0) {
 1081                 /*
 1082                  * This can only happen for reverse direction use of pipes
 1083                  * in a complete OOM situation.
 1084                  */
 1085                 error = ENOMEM;
 1086                 --wpipe->pipe_busy;
 1087                 pipeunlock(wpipe);
 1088                 PIPE_UNLOCK(wpipe);
 1089                 return (error);
 1090         }
 1091 
 1092         pipeunlock(wpipe);
 1093 
 1094         orig_resid = uio->uio_resid;
 1095 
 1096         while (uio->uio_resid) {
 1097                 int space;
 1098 
 1099                 pipelock(wpipe, 0);
 1100                 if (wpipe->pipe_state & PIPE_EOF) {
 1101                         pipeunlock(wpipe);
 1102                         error = EPIPE;
 1103                         break;
 1104                 }
 1105 #ifndef PIPE_NODIRECT
 1106                 /*
 1107                  * If the transfer is large, we can gain performance if
 1108                  * we do process-to-process copies directly.
 1109                  * If the write is non-blocking, we don't use the
 1110                  * direct write mechanism.
 1111                  *
 1112                  * The direct write mechanism will detect the reader going
 1113                  * away on us.
 1114                  */
 1115                 if (uio->uio_segflg == UIO_USERSPACE &&
 1116                     uio->uio_iov->iov_len >= PIPE_MINDIRECT &&
 1117                     wpipe->pipe_buffer.size >= PIPE_MINDIRECT &&
 1118                     (fp->f_flag & FNONBLOCK) == 0) {
 1119                         pipeunlock(wpipe);
 1120                         error = pipe_direct_write(wpipe, uio);
 1121                         if (error)
 1122                                 break;
 1123                         continue;
 1124                 }
 1125 #endif
 1126 
 1127                 /*
 1128                  * Pipe buffered writes cannot be coincidental with
 1129                  * direct writes.  We wait until the currently executing
 1130                  * direct write is completed before we start filling the
 1131                  * pipe buffer.  We break out if a signal occurs or the
 1132                  * reader goes away.
 1133                  */
 1134                 if (wpipe->pipe_state & PIPE_DIRECTW) {
 1135                         if (wpipe->pipe_state & PIPE_WANTR) {
 1136                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1137                                 wakeup(wpipe);
 1138                         }
 1139                         pipeselwakeup(wpipe);
 1140                         wpipe->pipe_state |= PIPE_WANTW;
 1141                         pipeunlock(wpipe);
 1142                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
 1143                             "pipbww", 0);
 1144                         if (error)
 1145                                 break;
 1146                         else
 1147                                 continue;
 1148                 }
 1149 
 1150                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1151 
 1152                 /* Writes of size <= PIPE_BUF must be atomic. */
 1153                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 1154                         space = 0;
 1155 
 1156                 if (space > 0) {
 1157                         int size;       /* Transfer size */
 1158                         int segsize;    /* first segment to transfer */
 1159 
 1160                         /*
 1161                          * Transfer size is minimum of uio transfer
 1162                          * and free space in pipe buffer.
 1163                          */
 1164                         if (space > uio->uio_resid)
 1165                                 size = uio->uio_resid;
 1166                         else
 1167                                 size = space;
 1168                         /*
 1169                          * First segment to transfer is minimum of
 1170                          * transfer size and contiguous space in
 1171                          * pipe buffer.  If first segment to transfer
 1172                          * is less than the transfer size, we've got
 1173                          * a wraparound in the buffer.
 1174                          */
 1175                         segsize = wpipe->pipe_buffer.size -
 1176                                 wpipe->pipe_buffer.in;
 1177                         if (segsize > size)
 1178                                 segsize = size;
 1179 
 1180                         /* Transfer first segment */
 1181 
 1182                         PIPE_UNLOCK(rpipe);
 1183                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
 1184                                         segsize, uio);
 1185                         PIPE_LOCK(rpipe);
 1186 
 1187                         if (error == 0 && segsize < size) {
 1188                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
 1189                                         wpipe->pipe_buffer.size,
 1190                                         ("Pipe buffer wraparound disappeared"));
 1191                                 /*
 1192                                  * Transfer remaining part now, to
 1193                                  * support atomic writes.  Wraparound
 1194                                  * happened.
 1195                                  */
 1196 
 1197                                 PIPE_UNLOCK(rpipe);
 1198                                 error = uiomove(
 1199                                     &wpipe->pipe_buffer.buffer[0],
 1200                                     size - segsize, uio);
 1201                                 PIPE_LOCK(rpipe);
 1202                         }
 1203                         if (error == 0) {
 1204                                 wpipe->pipe_buffer.in += size;
 1205                                 if (wpipe->pipe_buffer.in >=
 1206                                     wpipe->pipe_buffer.size) {
 1207                                         KASSERT(wpipe->pipe_buffer.in ==
 1208                                                 size - segsize +
 1209                                                 wpipe->pipe_buffer.size,
 1210                                                 ("Expected wraparound bad"));
 1211                                         wpipe->pipe_buffer.in = size - segsize;
 1212                                 }
 1213 
 1214                                 wpipe->pipe_buffer.cnt += size;
 1215                                 KASSERT(wpipe->pipe_buffer.cnt <=
 1216                                         wpipe->pipe_buffer.size,
 1217                                         ("Pipe buffer overflow"));
 1218                         }
 1219                         pipeunlock(wpipe);
 1220                         if (error != 0)
 1221                                 break;
 1222                 } else {
 1223                         /*
 1224                          * If the "read-side" has been blocked, wake it up now.
 1225                          */
 1226                         if (wpipe->pipe_state & PIPE_WANTR) {
 1227                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1228                                 wakeup(wpipe);
 1229                         }
 1230 
 1231                         /*
 1232                          * don't block on non-blocking I/O
 1233                          */
 1234                         if (fp->f_flag & FNONBLOCK) {
 1235                                 error = EAGAIN;
 1236                                 pipeunlock(wpipe);
 1237                                 break;
 1238                         }
 1239 
 1240                         /*
 1241                          * We have no more space and have something to offer,
 1242                          * wake up select/poll.
 1243                          */
 1244                         pipeselwakeup(wpipe);
 1245 
 1246                         wpipe->pipe_state |= PIPE_WANTW;
 1247                         pipeunlock(wpipe);
 1248                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1249                             PRIBIO | PCATCH, "pipewr", 0);
 1250                         if (error != 0)
 1251                                 break;
 1252                 }
 1253         }
 1254 
 1255         pipelock(wpipe, 0);
 1256         --wpipe->pipe_busy;
 1257 
 1258         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1259                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1260                 wakeup(wpipe);
 1261         } else if (wpipe->pipe_buffer.cnt > 0) {
 1262                 /*
 1263                  * If we have put any characters in the buffer, we wake up
 1264                  * the reader.
 1265                  */
 1266                 if (wpipe->pipe_state & PIPE_WANTR) {
 1267                         wpipe->pipe_state &= ~PIPE_WANTR;
 1268                         wakeup(wpipe);
 1269                 }
 1270         }
 1271 
 1272         /*
 1273          * Don't return EPIPE if any byte was written.
 1274          * EINTR and other interrupts are handled by generic I/O layer.
 1275          * Do not pretend that I/O succeeded for obvious user error
 1276          * like EFAULT.
 1277          */
 1278         if (uio->uio_resid != orig_resid && error == EPIPE)
 1279                 error = 0;
 1280 
 1281         if (error == 0)
 1282                 vfs_timestamp(&wpipe->pipe_mtime);
 1283 
 1284         /*
 1285          * We have something to offer,
 1286          * wake up select/poll.
 1287          */
 1288         if (wpipe->pipe_buffer.cnt)
 1289                 pipeselwakeup(wpipe);
 1290 
 1291         pipeunlock(wpipe);
 1292         PIPE_UNLOCK(rpipe);
 1293         return (error);
 1294 }
 1295 
 1296 /* ARGSUSED */
 1297 static int
 1298 pipe_truncate(struct file *fp, off_t length, struct ucred *active_cred,
 1299     struct thread *td)
 1300 {
 1301         struct pipe *cpipe;
 1302         int error;
 1303 
 1304         cpipe = fp->f_data;
 1305         if (cpipe->pipe_state & PIPE_NAMED)
 1306                 error = vnops.fo_truncate(fp, length, active_cred, td);
 1307         else
 1308                 error = invfo_truncate(fp, length, active_cred, td);
 1309         return (error);
 1310 }
 1311 
 1312 /*
 1313  * we implement a very minimal set of ioctls for compatibility with sockets.
 1314  */
 1315 static int
 1316 pipe_ioctl(struct file *fp, u_long cmd, void *data, struct ucred *active_cred,
 1317     struct thread *td)
 1318 {
 1319         struct pipe *mpipe = fp->f_data;
 1320         int error;
 1321 
 1322         PIPE_LOCK(mpipe);
 1323 
 1324 #ifdef MAC
 1325         error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
 1326         if (error) {
 1327                 PIPE_UNLOCK(mpipe);
 1328                 return (error);
 1329         }
 1330 #endif
 1331 
 1332         error = 0;
 1333         switch (cmd) {
 1334 
 1335         case FIONBIO:
 1336                 break;
 1337 
 1338         case FIOASYNC:
 1339                 if (*(int *)data) {
 1340                         mpipe->pipe_state |= PIPE_ASYNC;
 1341                 } else {
 1342                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1343                 }
 1344                 break;
 1345 
 1346         case FIONREAD:
 1347                 if (!(fp->f_flag & FREAD)) {
 1348                         *(int *)data = 0;
 1349                         PIPE_UNLOCK(mpipe);
 1350                         return (0);
 1351                 }
 1352                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1353                         *(int *)data = mpipe->pipe_map.cnt;
 1354                 else
 1355                         *(int *)data = mpipe->pipe_buffer.cnt;
 1356                 break;
 1357 
 1358         case FIOSETOWN:
 1359                 PIPE_UNLOCK(mpipe);
 1360                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 1361                 goto out_unlocked;
 1362 
 1363         case FIOGETOWN:
 1364                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1365                 break;
 1366 
 1367         /* This is deprecated, FIOSETOWN should be used instead. */
 1368         case TIOCSPGRP:
 1369                 PIPE_UNLOCK(mpipe);
 1370                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 1371                 goto out_unlocked;
 1372 
 1373         /* This is deprecated, FIOGETOWN should be used instead. */
 1374         case TIOCGPGRP:
 1375                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1376                 break;
 1377 
 1378         default:
 1379                 error = ENOTTY;
 1380                 break;
 1381         }
 1382         PIPE_UNLOCK(mpipe);
 1383 out_unlocked:
 1384         return (error);
 1385 }
 1386 
 1387 static int
 1388 pipe_poll(struct file *fp, int events, struct ucred *active_cred,
 1389     struct thread *td)
 1390 {
 1391         struct pipe *rpipe;
 1392         struct pipe *wpipe;
 1393         int levents, revents;
 1394 #ifdef MAC
 1395         int error;
 1396 #endif
 1397 
 1398         revents = 0;
 1399         rpipe = fp->f_data;
 1400         wpipe = PIPE_PEER(rpipe);
 1401         PIPE_LOCK(rpipe);
 1402 #ifdef MAC
 1403         error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
 1404         if (error)
 1405                 goto locked_error;
 1406 #endif
 1407         if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM))
 1408                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1409                     (rpipe->pipe_buffer.cnt > 0))
 1410                         revents |= events & (POLLIN | POLLRDNORM);
 1411 
 1412         if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM))
 1413                 if (wpipe->pipe_present != PIPE_ACTIVE ||
 1414                     (wpipe->pipe_state & PIPE_EOF) ||
 1415                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1416                      ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
 1417                          wpipe->pipe_buffer.size == 0)))
 1418                         revents |= events & (POLLOUT | POLLWRNORM);
 1419 
 1420         levents = events &
 1421             (POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
 1422         if (rpipe->pipe_state & PIPE_NAMED && fp->f_flag & FREAD && levents &&
 1423             fp->f_seqcount == rpipe->pipe_wgen)
 1424                 events |= POLLINIGNEOF;
 1425 
 1426         if ((events & POLLINIGNEOF) == 0) {
 1427                 if (rpipe->pipe_state & PIPE_EOF) {
 1428                         revents |= (events & (POLLIN | POLLRDNORM));
 1429                         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1430                             (wpipe->pipe_state & PIPE_EOF))
 1431                                 revents |= POLLHUP;
 1432                 }
 1433         }
 1434 
 1435         if (revents == 0) {
 1436                 if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM)) {
 1437                         selrecord(td, &rpipe->pipe_sel);
 1438                         if (SEL_WAITING(&rpipe->pipe_sel))
 1439                                 rpipe->pipe_state |= PIPE_SEL;
 1440                 }
 1441 
 1442                 if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM)) {
 1443                         selrecord(td, &wpipe->pipe_sel);
 1444                         if (SEL_WAITING(&wpipe->pipe_sel))
 1445                                 wpipe->pipe_state |= PIPE_SEL;
 1446                 }
 1447         }
 1448 #ifdef MAC
 1449 locked_error:
 1450 #endif
 1451         PIPE_UNLOCK(rpipe);
 1452 
 1453         return (revents);
 1454 }
 1455 
 1456 /*
 1457  * We shouldn't need locks here as we're doing a read and this should
 1458  * be a natural race.
 1459  */
 1460 static int
 1461 pipe_stat(struct file *fp, struct stat *ub, struct ucred *active_cred,
 1462     struct thread *td)
 1463 {
 1464         struct pipe *pipe;
 1465         int new_unr;
 1466 #ifdef MAC
 1467         int error;
 1468 #endif
 1469 
 1470         pipe = fp->f_data;
 1471         PIPE_LOCK(pipe);
 1472 #ifdef MAC
 1473         error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
 1474         if (error) {
 1475                 PIPE_UNLOCK(pipe);
 1476                 return (error);
 1477         }
 1478 #endif
 1479 
 1480         /* For named pipes ask the underlying filesystem. */
 1481         if (pipe->pipe_state & PIPE_NAMED) {
 1482                 PIPE_UNLOCK(pipe);
 1483                 return (vnops.fo_stat(fp, ub, active_cred, td));
 1484         }
 1485 
 1486         /*
 1487          * Lazily allocate an inode number for the pipe.  Most pipe
 1488          * users do not call fstat(2) on the pipe, which means that
 1489          * postponing the inode allocation until it is must be
 1490          * returned to userland is useful.  If alloc_unr failed,
 1491          * assign st_ino zero instead of returning an error.
 1492          * Special pipe_ino values:
 1493          *  -1 - not yet initialized;
 1494          *  0  - alloc_unr failed, return 0 as st_ino forever.
 1495          */
 1496         if (pipe->pipe_ino == (ino_t)-1) {
 1497                 new_unr = alloc_unr(pipeino_unr);
 1498                 if (new_unr != -1)
 1499                         pipe->pipe_ino = new_unr;
 1500                 else
 1501                         pipe->pipe_ino = 0;
 1502         }
 1503         PIPE_UNLOCK(pipe);
 1504 
 1505         bzero(ub, sizeof(*ub));
 1506         ub->st_mode = S_IFIFO;
 1507         ub->st_blksize = PAGE_SIZE;
 1508         if (pipe->pipe_state & PIPE_DIRECTW)
 1509                 ub->st_size = pipe->pipe_map.cnt;
 1510         else
 1511                 ub->st_size = pipe->pipe_buffer.cnt;
 1512         ub->st_blocks = howmany(ub->st_size, ub->st_blksize);
 1513         ub->st_atim = pipe->pipe_atime;
 1514         ub->st_mtim = pipe->pipe_mtime;
 1515         ub->st_ctim = pipe->pipe_ctime;
 1516         ub->st_uid = fp->f_cred->cr_uid;
 1517         ub->st_gid = fp->f_cred->cr_gid;
 1518         ub->st_dev = pipedev_ino;
 1519         ub->st_ino = pipe->pipe_ino;
 1520         /*
 1521          * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
 1522          */
 1523         return (0);
 1524 }
 1525 
 1526 /* ARGSUSED */
 1527 static int
 1528 pipe_close(struct file *fp, struct thread *td)
 1529 {
 1530 
 1531         if (fp->f_vnode != NULL) 
 1532                 return vnops.fo_close(fp, td);
 1533         fp->f_ops = &badfileops;
 1534         pipe_dtor(fp->f_data);
 1535         fp->f_data = NULL;
 1536         return (0);
 1537 }
 1538 
 1539 static int
 1540 pipe_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, struct thread *td)
 1541 {
 1542         struct pipe *cpipe;
 1543         int error;
 1544 
 1545         cpipe = fp->f_data;
 1546         if (cpipe->pipe_state & PIPE_NAMED)
 1547                 error = vn_chmod(fp, mode, active_cred, td);
 1548         else
 1549                 error = invfo_chmod(fp, mode, active_cred, td);
 1550         return (error);
 1551 }
 1552 
 1553 static int
 1554 pipe_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
 1555     struct thread *td)
 1556 {
 1557         struct pipe *cpipe;
 1558         int error;
 1559 
 1560         cpipe = fp->f_data;
 1561         if (cpipe->pipe_state & PIPE_NAMED)
 1562                 error = vn_chown(fp, uid, gid, active_cred, td);
 1563         else
 1564                 error = invfo_chown(fp, uid, gid, active_cred, td);
 1565         return (error);
 1566 }
 1567 
 1568 static int
 1569 pipe_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
 1570 {
 1571         struct pipe *pi;
 1572 
 1573         if (fp->f_type == DTYPE_FIFO)
 1574                 return (vn_fill_kinfo(fp, kif, fdp));
 1575         kif->kf_type = KF_TYPE_PIPE;
 1576         pi = fp->f_data;
 1577         kif->kf_un.kf_pipe.kf_pipe_addr = (uintptr_t)pi;
 1578         kif->kf_un.kf_pipe.kf_pipe_peer = (uintptr_t)pi->pipe_peer;
 1579         kif->kf_un.kf_pipe.kf_pipe_buffer_cnt = pi->pipe_buffer.cnt;
 1580         return (0);
 1581 }
 1582 
 1583 static void
 1584 pipe_free_kmem(struct pipe *cpipe)
 1585 {
 1586 
 1587         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
 1588             ("pipe_free_kmem: pipe mutex locked"));
 1589 
 1590         if (cpipe->pipe_buffer.buffer != NULL) {
 1591                 atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
 1592                 vm_map_remove(pipe_map,
 1593                     (vm_offset_t)cpipe->pipe_buffer.buffer,
 1594                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
 1595                 cpipe->pipe_buffer.buffer = NULL;
 1596         }
 1597 #ifndef PIPE_NODIRECT
 1598         {
 1599                 cpipe->pipe_map.cnt = 0;
 1600                 cpipe->pipe_map.pos = 0;
 1601                 cpipe->pipe_map.npages = 0;
 1602         }
 1603 #endif
 1604 }
 1605 
 1606 /*
 1607  * shutdown the pipe
 1608  */
 1609 static void
 1610 pipeclose(struct pipe *cpipe)
 1611 {
 1612         struct pipepair *pp;
 1613         struct pipe *ppipe;
 1614 
 1615         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
 1616 
 1617         PIPE_LOCK(cpipe);
 1618         pipelock(cpipe, 0);
 1619         pp = cpipe->pipe_pair;
 1620 
 1621         pipeselwakeup(cpipe);
 1622 
 1623         /*
 1624          * If the other side is blocked, wake it up saying that
 1625          * we want to close it down.
 1626          */
 1627         cpipe->pipe_state |= PIPE_EOF;
 1628         while (cpipe->pipe_busy) {
 1629                 wakeup(cpipe);
 1630                 cpipe->pipe_state |= PIPE_WANT;
 1631                 pipeunlock(cpipe);
 1632                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1633                 pipelock(cpipe, 0);
 1634         }
 1635 
 1636 
 1637         /*
 1638          * Disconnect from peer, if any.
 1639          */
 1640         ppipe = cpipe->pipe_peer;
 1641         if (ppipe->pipe_present == PIPE_ACTIVE) {
 1642                 pipeselwakeup(ppipe);
 1643 
 1644                 ppipe->pipe_state |= PIPE_EOF;
 1645                 wakeup(ppipe);
 1646                 KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
 1647         }
 1648 
 1649         /*
 1650          * Mark this endpoint as free.  Release kmem resources.  We
 1651          * don't mark this endpoint as unused until we've finished
 1652          * doing that, or the pipe might disappear out from under
 1653          * us.
 1654          */
 1655         PIPE_UNLOCK(cpipe);
 1656         pipe_free_kmem(cpipe);
 1657         PIPE_LOCK(cpipe);
 1658         cpipe->pipe_present = PIPE_CLOSING;
 1659         pipeunlock(cpipe);
 1660 
 1661         /*
 1662          * knlist_clear() may sleep dropping the PIPE_MTX. Set the
 1663          * PIPE_FINALIZED, that allows other end to free the
 1664          * pipe_pair, only after the knotes are completely dismantled.
 1665          */
 1666         knlist_clear(&cpipe->pipe_sel.si_note, 1);
 1667         cpipe->pipe_present = PIPE_FINALIZED;
 1668         seldrain(&cpipe->pipe_sel);
 1669         knlist_destroy(&cpipe->pipe_sel.si_note);
 1670 
 1671         /*
 1672          * If both endpoints are now closed, release the memory for the
 1673          * pipe pair.  If not, unlock.
 1674          */
 1675         if (ppipe->pipe_present == PIPE_FINALIZED) {
 1676                 PIPE_UNLOCK(cpipe);
 1677 #ifdef MAC
 1678                 mac_pipe_destroy(pp);
 1679 #endif
 1680                 uma_zfree(pipe_zone, cpipe->pipe_pair);
 1681         } else
 1682                 PIPE_UNLOCK(cpipe);
 1683 }
 1684 
 1685 /*ARGSUSED*/
 1686 static int
 1687 pipe_kqfilter(struct file *fp, struct knote *kn)
 1688 {
 1689         struct pipe *cpipe;
 1690 
 1691         /*
 1692          * If a filter is requested that is not supported by this file
 1693          * descriptor, don't return an error, but also don't ever generate an
 1694          * event.
 1695          */
 1696         if ((kn->kn_filter == EVFILT_READ) && !(fp->f_flag & FREAD)) {
 1697                 kn->kn_fop = &pipe_nfiltops;
 1698                 return (0);
 1699         }
 1700         if ((kn->kn_filter == EVFILT_WRITE) && !(fp->f_flag & FWRITE)) {
 1701                 kn->kn_fop = &pipe_nfiltops;
 1702                 return (0);
 1703         }
 1704         cpipe = fp->f_data;
 1705         PIPE_LOCK(cpipe);
 1706         switch (kn->kn_filter) {
 1707         case EVFILT_READ:
 1708                 kn->kn_fop = &pipe_rfiltops;
 1709                 break;
 1710         case EVFILT_WRITE:
 1711                 kn->kn_fop = &pipe_wfiltops;
 1712                 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
 1713                         /* other end of pipe has been closed */
 1714                         PIPE_UNLOCK(cpipe);
 1715                         return (EPIPE);
 1716                 }
 1717                 cpipe = PIPE_PEER(cpipe);
 1718                 break;
 1719         default:
 1720                 PIPE_UNLOCK(cpipe);
 1721                 return (EINVAL);
 1722         }
 1723 
 1724         kn->kn_hook = cpipe; 
 1725         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
 1726         PIPE_UNLOCK(cpipe);
 1727         return (0);
 1728 }
 1729 
 1730 static void
 1731 filt_pipedetach(struct knote *kn)
 1732 {
 1733         struct pipe *cpipe = kn->kn_hook;
 1734 
 1735         PIPE_LOCK(cpipe);
 1736         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
 1737         PIPE_UNLOCK(cpipe);
 1738 }
 1739 
 1740 /*ARGSUSED*/
 1741 static int
 1742 filt_piperead(struct knote *kn, long hint)
 1743 {
 1744         struct pipe *rpipe = kn->kn_hook;
 1745         struct pipe *wpipe = rpipe->pipe_peer;
 1746         int ret;
 1747 
 1748         PIPE_LOCK_ASSERT(rpipe, MA_OWNED);
 1749         kn->kn_data = rpipe->pipe_buffer.cnt;
 1750         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1751                 kn->kn_data = rpipe->pipe_map.cnt;
 1752 
 1753         if ((rpipe->pipe_state & PIPE_EOF) ||
 1754             wpipe->pipe_present != PIPE_ACTIVE ||
 1755             (wpipe->pipe_state & PIPE_EOF)) {
 1756                 kn->kn_flags |= EV_EOF;
 1757                 return (1);
 1758         }
 1759         ret = kn->kn_data > 0;
 1760         return ret;
 1761 }
 1762 
 1763 /*ARGSUSED*/
 1764 static int
 1765 filt_pipewrite(struct knote *kn, long hint)
 1766 {
 1767         struct pipe *wpipe;
 1768    
 1769         wpipe = kn->kn_hook;
 1770         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 1771         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1772             (wpipe->pipe_state & PIPE_EOF)) {
 1773                 kn->kn_data = 0;
 1774                 kn->kn_flags |= EV_EOF;
 1775                 return (1);
 1776         }
 1777         kn->kn_data = (wpipe->pipe_buffer.size > 0) ?
 1778             (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) : PIPE_BUF;
 1779         if (wpipe->pipe_state & PIPE_DIRECTW)
 1780                 kn->kn_data = 0;
 1781 
 1782         return (kn->kn_data >= PIPE_BUF);
 1783 }
 1784 
 1785 static void
 1786 filt_pipedetach_notsup(struct knote *kn)
 1787 {
 1788 
 1789 }
 1790 
 1791 static int
 1792 filt_pipenotsup(struct knote *kn, long hint)
 1793 {
 1794 
 1795         return (0);
 1796 }

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