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

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