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  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice immediately at the beginning of the file, without modification,
   10  *    this list of conditions, and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. Absolutely no warranty of function or purpose is made by the author
   15  *    John S. Dyson.
   16  * 4. Modifications may be freely made to this file if the above conditions
   17  *    are met.
   18  */
   19 
   20 /*
   21  * This file contains a high-performance replacement for the socket-based
   22  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
   23  * all features of sockets, but does do everything that pipes normally
   24  * do.
   25  */
   26 
   27 /*
   28  * This code has two modes of operation, a small write mode and a large
   29  * write mode.  The small write mode acts like conventional pipes with
   30  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
   31  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
   32  * and PIPE_SIZE in size, it is fully mapped and wired into the kernel, and
   33  * the receiving process can copy it directly from the pages in the sending
   34  * process.
   35  *
   36  * If the sending process receives a signal, it is possible that it will
   37  * go away, and certainly its address space can change, because control
   38  * is returned back to the user-mode side.  In that case, the pipe code
   39  * arranges to copy the buffer supplied by the user process, to a pageable
   40  * kernel buffer, and the receiving process will grab the data from the
   41  * pageable kernel buffer.  Since signals don't happen all that often,
   42  * the copy operation is normally eliminated.
   43  *
   44  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
   45  * happen for small transfers so that the system will not spend all of
   46  * its time context switching.
   47  *
   48  * In order to limit the resource use of pipes, two sysctls exist:
   49  *
   50  * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
   51  * address space available to us in pipe_map. This value is normally
   52  * autotuned, but may also be loader tuned.
   53  *
   54  * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
   55  * memory in use by pipes.
   56  *
   57  * Based on how large pipekva is relative to maxpipekva, the following
   58  * will happen:
   59  *
   60  * 0% - 50%:
   61  *     New pipes are given 16K of memory backing, pipes may dynamically
   62  *     grow to as large as 64K where needed.
   63  * 50% - 75%:
   64  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   65  *     existing pipes may NOT grow.
   66  * 75% - 100%:
   67  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   68  *     existing pipes will be shrunk down to 4K whenever possible.
   69  *
   70  * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
   71  * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
   72  * resize which MUST occur for reverse-direction pipes when they are
   73  * first used.
   74  *
   75  * Additional information about the current state of pipes may be obtained
   76  * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
   77  * and kern.ipc.piperesizefail.
   78  *
   79  * Locking rules:  There are two locks present here:  A mutex, used via
   80  * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
   81  * the flag, as mutexes can not persist over uiomove.  The mutex
   82  * exists only to guard access to the flag, and is not in itself a
   83  * locking mechanism.  Also note that there is only a single mutex for
   84  * both directions of a pipe.
   85  *
   86  * As pipelock() may have to sleep before it can acquire the flag, it
   87  * is important to reread all data after a call to pipelock(); everything
   88  * in the structure may have changed.
   89  */
   90 
   91 #include <sys/cdefs.h>
   92 __FBSDID("$FreeBSD: releng/8.3/sys/kern/sys_pipe.c 225585 2011-09-15 12:27:26Z attilio $");
   93 
   94 #include <sys/param.h>
   95 #include <sys/systm.h>
   96 #include <sys/fcntl.h>
   97 #include <sys/file.h>
   98 #include <sys/filedesc.h>
   99 #include <sys/filio.h>
  100 #include <sys/kernel.h>
  101 #include <sys/lock.h>
  102 #include <sys/mutex.h>
  103 #include <sys/ttycom.h>
  104 #include <sys/stat.h>
  105 #include <sys/malloc.h>
  106 #include <sys/poll.h>
  107 #include <sys/selinfo.h>
  108 #include <sys/signalvar.h>
  109 #include <sys/syscallsubr.h>
  110 #include <sys/sysctl.h>
  111 #include <sys/sysproto.h>
  112 #include <sys/pipe.h>
  113 #include <sys/proc.h>
  114 #include <sys/vnode.h>
  115 #include <sys/uio.h>
  116 #include <sys/event.h>
  117 
  118 #include <security/mac/mac_framework.h>
  119 
  120 #include <vm/vm.h>
  121 #include <vm/vm_param.h>
  122 #include <vm/vm_object.h>
  123 #include <vm/vm_kern.h>
  124 #include <vm/vm_extern.h>
  125 #include <vm/pmap.h>
  126 #include <vm/vm_map.h>
  127 #include <vm/vm_page.h>
  128 #include <vm/uma.h>
  129 
  130 /*
  131  * Use this define if you want to disable *fancy* VM things.  Expect an
  132  * approx 30% decrease in transfer rate.  This could be useful for
  133  * NetBSD or OpenBSD.
  134  */
  135 /* #define PIPE_NODIRECT */
  136 
  137 /*
  138  * interfaces to the outside world
  139  */
  140 static fo_rdwr_t        pipe_read;
  141 static fo_rdwr_t        pipe_write;
  142 static fo_truncate_t    pipe_truncate;
  143 static fo_ioctl_t       pipe_ioctl;
  144 static fo_poll_t        pipe_poll;
  145 static fo_kqfilter_t    pipe_kqfilter;
  146 static fo_stat_t        pipe_stat;
  147 static fo_close_t       pipe_close;
  148 
  149 static struct fileops pipeops = {
  150         .fo_read = pipe_read,
  151         .fo_write = pipe_write,
  152         .fo_truncate = pipe_truncate,
  153         .fo_ioctl = pipe_ioctl,
  154         .fo_poll = pipe_poll,
  155         .fo_kqfilter = pipe_kqfilter,
  156         .fo_stat = pipe_stat,
  157         .fo_close = pipe_close,
  158         .fo_flags = DFLAG_PASSABLE
  159 };
  160 
  161 static void     filt_pipedetach(struct knote *kn);
  162 static int      filt_piperead(struct knote *kn, long hint);
  163 static int      filt_pipewrite(struct knote *kn, long hint);
  164 
  165 static struct filterops pipe_rfiltops =
  166         { 1, NULL, filt_pipedetach, filt_piperead };
  167 static struct filterops pipe_wfiltops =
  168         { 1, NULL, filt_pipedetach, filt_pipewrite };
  169 
  170 /*
  171  * Default pipe buffer size(s), this can be kind-of large now because pipe
  172  * space is pageable.  The pipe code will try to maintain locality of
  173  * reference for performance reasons, so small amounts of outstanding I/O
  174  * will not wipe the cache.
  175  */
  176 #define MINPIPESIZE (PIPE_SIZE/3)
  177 #define MAXPIPESIZE (2*PIPE_SIZE/3)
  178 
  179 static long amountpipekva;
  180 static int pipefragretry;
  181 static int pipeallocfail;
  182 static int piperesizefail;
  183 static int piperesizeallowed = 1;
  184 
  185 SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN,
  186            &maxpipekva, 0, "Pipe KVA limit");
  187 SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
  188            &amountpipekva, 0, "Pipe KVA usage");
  189 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
  190           &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
  191 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
  192           &pipeallocfail, 0, "Pipe allocation failures");
  193 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
  194           &piperesizefail, 0, "Pipe resize failures");
  195 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
  196           &piperesizeallowed, 0, "Pipe resizing allowed");
  197 
  198 static void pipeinit(void *dummy __unused);
  199 static void pipeclose(struct pipe *cpipe);
  200 static void pipe_free_kmem(struct pipe *cpipe);
  201 static int pipe_create(struct pipe *pipe, int backing);
  202 static __inline int pipelock(struct pipe *cpipe, int catch);
  203 static __inline void pipeunlock(struct pipe *cpipe);
  204 static __inline void pipeselwakeup(struct pipe *cpipe);
  205 #ifndef PIPE_NODIRECT
  206 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
  207 static void pipe_destroy_write_buffer(struct pipe *wpipe);
  208 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
  209 static void pipe_clone_write_buffer(struct pipe *wpipe);
  210 #endif
  211 static int pipespace(struct pipe *cpipe, int size);
  212 static int pipespace_new(struct pipe *cpipe, int size);
  213 
  214 static int      pipe_zone_ctor(void *mem, int size, void *arg, int flags);
  215 static int      pipe_zone_init(void *mem, int size, int flags);
  216 static void     pipe_zone_fini(void *mem, int size);
  217 
  218 static uma_zone_t pipe_zone;
  219 
  220 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
  221 
  222 static void
  223 pipeinit(void *dummy __unused)
  224 {
  225 
  226         pipe_zone = uma_zcreate("pipe", sizeof(struct pipepair),
  227             pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
  228             UMA_ALIGN_PTR, 0);
  229         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
  230 }
  231 
  232 static int
  233 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
  234 {
  235         struct pipepair *pp;
  236         struct pipe *rpipe, *wpipe;
  237 
  238         KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
  239 
  240         pp = (struct pipepair *)mem;
  241 
  242         /*
  243          * We zero both pipe endpoints to make sure all the kmem pointers
  244          * are NULL, flag fields are zero'd, etc.  We timestamp both
  245          * endpoints with the same time.
  246          */
  247         rpipe = &pp->pp_rpipe;
  248         bzero(rpipe, sizeof(*rpipe));
  249         vfs_timestamp(&rpipe->pipe_ctime);
  250         rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
  251 
  252         wpipe = &pp->pp_wpipe;
  253         bzero(wpipe, sizeof(*wpipe));
  254         wpipe->pipe_ctime = rpipe->pipe_ctime;
  255         wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
  256 
  257         rpipe->pipe_peer = wpipe;
  258         rpipe->pipe_pair = pp;
  259         wpipe->pipe_peer = rpipe;
  260         wpipe->pipe_pair = pp;
  261 
  262         /*
  263          * Mark both endpoints as present; they will later get free'd
  264          * one at a time.  When both are free'd, then the whole pair
  265          * is released.
  266          */
  267         rpipe->pipe_present = PIPE_ACTIVE;
  268         wpipe->pipe_present = PIPE_ACTIVE;
  269 
  270         /*
  271          * Eventually, the MAC Framework may initialize the label
  272          * in ctor or init, but for now we do it elswhere to avoid
  273          * blocking in ctor or init.
  274          */
  275         pp->pp_label = NULL;
  276 
  277         return (0);
  278 }
  279 
  280 static int
  281 pipe_zone_init(void *mem, int size, int flags)
  282 {
  283         struct pipepair *pp;
  284 
  285         KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
  286 
  287         pp = (struct pipepair *)mem;
  288 
  289         mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_RECURSE);
  290         return (0);
  291 }
  292 
  293 static void
  294 pipe_zone_fini(void *mem, int size)
  295 {
  296         struct pipepair *pp;
  297 
  298         KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
  299 
  300         pp = (struct pipepair *)mem;
  301 
  302         mtx_destroy(&pp->pp_mtx);
  303 }
  304 
  305 /*
  306  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
  307  * the zone pick up the pieces via pipeclose().
  308  */
  309 int
  310 kern_pipe(struct thread *td, int fildes[2])
  311 {
  312         struct filedesc *fdp = td->td_proc->p_fd;
  313         struct file *rf, *wf;
  314         struct pipepair *pp;
  315         struct pipe *rpipe, *wpipe;
  316         int fd, error;
  317 
  318         pp = uma_zalloc(pipe_zone, M_WAITOK);
  319 #ifdef MAC
  320         /*
  321          * The MAC label is shared between the connected endpoints.  As a
  322          * result mac_pipe_init() and mac_pipe_create() are called once
  323          * for the pair, and not on the endpoints.
  324          */
  325         mac_pipe_init(pp);
  326         mac_pipe_create(td->td_ucred, pp);
  327 #endif
  328         rpipe = &pp->pp_rpipe;
  329         wpipe = &pp->pp_wpipe;
  330 
  331         knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
  332         knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
  333 
  334         /* Only the forward direction pipe is backed by default */
  335         if ((error = pipe_create(rpipe, 1)) != 0 ||
  336             (error = pipe_create(wpipe, 0)) != 0) {
  337                 pipeclose(rpipe);
  338                 pipeclose(wpipe);
  339                 return (error);
  340         }
  341 
  342         rpipe->pipe_state |= PIPE_DIRECTOK;
  343         wpipe->pipe_state |= PIPE_DIRECTOK;
  344 
  345         error = falloc(td, &rf, &fd);
  346         if (error) {
  347                 pipeclose(rpipe);
  348                 pipeclose(wpipe);
  349                 return (error);
  350         }
  351         /* An extra reference on `rf' has been held for us by falloc(). */
  352         fildes[0] = fd;
  353 
  354         /*
  355          * Warning: once we've gotten past allocation of the fd for the
  356          * read-side, we can only drop the read side via fdrop() in order
  357          * to avoid races against processes which manage to dup() the read
  358          * side while we are blocked trying to allocate the write side.
  359          */
  360         finit(rf, FREAD | FWRITE, DTYPE_PIPE, rpipe, &pipeops);
  361         error = falloc(td, &wf, &fd);
  362         if (error) {
  363                 fdclose(fdp, rf, fildes[0], td);
  364                 fdrop(rf, td);
  365                 /* rpipe has been closed by fdrop(). */
  366                 pipeclose(wpipe);
  367                 return (error);
  368         }
  369         /* An extra reference on `wf' has been held for us by falloc(). */
  370         finit(wf, FREAD | FWRITE, DTYPE_PIPE, wpipe, &pipeops);
  371         fdrop(wf, td);
  372         fildes[1] = fd;
  373         fdrop(rf, td);
  374 
  375         return (0);
  376 }
  377 
  378 /* ARGSUSED */
  379 int
  380 pipe(struct thread *td, struct pipe_args *uap)
  381 {
  382         int error;
  383         int fildes[2];
  384 
  385         error = kern_pipe(td, fildes);
  386         if (error)
  387                 return (error);
  388         
  389         td->td_retval[0] = fildes[0];
  390         td->td_retval[1] = fildes[1];
  391 
  392         return (0);
  393 }
  394 
  395 /*
  396  * Allocate kva for pipe circular buffer, the space is pageable
  397  * This routine will 'realloc' the size of a pipe safely, if it fails
  398  * it will retain the old buffer.
  399  * If it fails it will return ENOMEM.
  400  */
  401 static int
  402 pipespace_new(cpipe, size)
  403         struct pipe *cpipe;
  404         int size;
  405 {
  406         caddr_t buffer;
  407         int error, cnt, firstseg;
  408         static int curfail = 0;
  409         static struct timeval lastfail;
  410 
  411         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
  412         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
  413                 ("pipespace: resize of direct writes not allowed"));
  414 retry:
  415         cnt = cpipe->pipe_buffer.cnt;
  416         if (cnt > size)
  417                 size = cnt;
  418 
  419         size = round_page(size);
  420         buffer = (caddr_t) vm_map_min(pipe_map);
  421 
  422         error = vm_map_find(pipe_map, NULL, 0,
  423                 (vm_offset_t *) &buffer, size, 1,
  424                 VM_PROT_ALL, VM_PROT_ALL, 0);
  425         if (error != KERN_SUCCESS) {
  426                 if ((cpipe->pipe_buffer.buffer == NULL) &&
  427                         (size > SMALL_PIPE_SIZE)) {
  428                         size = SMALL_PIPE_SIZE;
  429                         pipefragretry++;
  430                         goto retry;
  431                 }
  432                 if (cpipe->pipe_buffer.buffer == NULL) {
  433                         pipeallocfail++;
  434                         if (ppsratecheck(&lastfail, &curfail, 1))
  435                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
  436                 } else {
  437                         piperesizefail++;
  438                 }
  439                 return (ENOMEM);
  440         }
  441 
  442         /* copy data, then free old resources if we're resizing */
  443         if (cnt > 0) {
  444                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
  445                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
  446                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  447                                 buffer, firstseg);
  448                         if ((cnt - firstseg) > 0)
  449                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
  450                                         cpipe->pipe_buffer.in);
  451                 } else {
  452                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  453                                 buffer, cnt);
  454                 }
  455         }
  456         pipe_free_kmem(cpipe);
  457         cpipe->pipe_buffer.buffer = buffer;
  458         cpipe->pipe_buffer.size = size;
  459         cpipe->pipe_buffer.in = cnt;
  460         cpipe->pipe_buffer.out = 0;
  461         cpipe->pipe_buffer.cnt = cnt;
  462         atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
  463         return (0);
  464 }
  465 
  466 /*
  467  * Wrapper for pipespace_new() that performs locking assertions.
  468  */
  469 static int
  470 pipespace(cpipe, size)
  471         struct pipe *cpipe;
  472         int size;
  473 {
  474 
  475         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  476                 ("Unlocked pipe passed to pipespace"));
  477         return (pipespace_new(cpipe, size));
  478 }
  479 
  480 /*
  481  * lock a pipe for I/O, blocking other access
  482  */
  483 static __inline int
  484 pipelock(cpipe, catch)
  485         struct pipe *cpipe;
  486         int catch;
  487 {
  488         int error;
  489 
  490         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  491         while (cpipe->pipe_state & PIPE_LOCKFL) {
  492                 cpipe->pipe_state |= PIPE_LWANT;
  493                 error = msleep(cpipe, PIPE_MTX(cpipe),
  494                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  495                     "pipelk", 0);
  496                 if (error != 0)
  497                         return (error);
  498         }
  499         cpipe->pipe_state |= PIPE_LOCKFL;
  500         return (0);
  501 }
  502 
  503 /*
  504  * unlock a pipe I/O lock
  505  */
  506 static __inline void
  507 pipeunlock(cpipe)
  508         struct pipe *cpipe;
  509 {
  510 
  511         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  512         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  513                 ("Unlocked pipe passed to pipeunlock"));
  514         cpipe->pipe_state &= ~PIPE_LOCKFL;
  515         if (cpipe->pipe_state & PIPE_LWANT) {
  516                 cpipe->pipe_state &= ~PIPE_LWANT;
  517                 wakeup(cpipe);
  518         }
  519 }
  520 
  521 static __inline void
  522 pipeselwakeup(cpipe)
  523         struct pipe *cpipe;
  524 {
  525 
  526         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  527         if (cpipe->pipe_state & PIPE_SEL) {
  528                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
  529                 if (!SEL_WAITING(&cpipe->pipe_sel))
  530                         cpipe->pipe_state &= ~PIPE_SEL;
  531         }
  532         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  533                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  534         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
  535 }
  536 
  537 /*
  538  * Initialize and allocate VM and memory for pipe.  The structure
  539  * will start out zero'd from the ctor, so we just manage the kmem.
  540  */
  541 static int
  542 pipe_create(pipe, backing)
  543         struct pipe *pipe;
  544         int backing;
  545 {
  546         int error;
  547 
  548         if (backing) {
  549                 if (amountpipekva > maxpipekva / 2)
  550                         error = pipespace_new(pipe, SMALL_PIPE_SIZE);
  551                 else
  552                         error = pipespace_new(pipe, PIPE_SIZE);
  553         } else {
  554                 /* If we're not backing this pipe, no need to do anything. */
  555                 error = 0;
  556         }
  557         return (error);
  558 }
  559 
  560 /* ARGSUSED */
  561 static int
  562 pipe_read(fp, uio, active_cred, flags, td)
  563         struct file *fp;
  564         struct uio *uio;
  565         struct ucred *active_cred;
  566         struct thread *td;
  567         int flags;
  568 {
  569         struct pipe *rpipe = fp->f_data;
  570         int error;
  571         int nread = 0;
  572         u_int size;
  573 
  574         PIPE_LOCK(rpipe);
  575         ++rpipe->pipe_busy;
  576         error = pipelock(rpipe, 1);
  577         if (error)
  578                 goto unlocked_error;
  579 
  580 #ifdef MAC
  581         error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
  582         if (error)
  583                 goto locked_error;
  584 #endif
  585         if (amountpipekva > (3 * maxpipekva) / 4) {
  586                 if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
  587                         (rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
  588                         (rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
  589                         (piperesizeallowed == 1)) {
  590                         PIPE_UNLOCK(rpipe);
  591                         pipespace(rpipe, SMALL_PIPE_SIZE);
  592                         PIPE_LOCK(rpipe);
  593                 }
  594         }
  595 
  596         while (uio->uio_resid) {
  597                 /*
  598                  * normal pipe buffer receive
  599                  */
  600                 if (rpipe->pipe_buffer.cnt > 0) {
  601                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  602                         if (size > rpipe->pipe_buffer.cnt)
  603                                 size = rpipe->pipe_buffer.cnt;
  604                         if (size > (u_int) uio->uio_resid)
  605                                 size = (u_int) uio->uio_resid;
  606 
  607                         PIPE_UNLOCK(rpipe);
  608                         error = uiomove(
  609                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  610                             size, uio);
  611                         PIPE_LOCK(rpipe);
  612                         if (error)
  613                                 break;
  614 
  615                         rpipe->pipe_buffer.out += size;
  616                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  617                                 rpipe->pipe_buffer.out = 0;
  618 
  619                         rpipe->pipe_buffer.cnt -= size;
  620 
  621                         /*
  622                          * If there is no more to read in the pipe, reset
  623                          * its pointers to the beginning.  This improves
  624                          * cache hit stats.
  625                          */
  626                         if (rpipe->pipe_buffer.cnt == 0) {
  627                                 rpipe->pipe_buffer.in = 0;
  628                                 rpipe->pipe_buffer.out = 0;
  629                         }
  630                         nread += size;
  631 #ifndef PIPE_NODIRECT
  632                 /*
  633                  * Direct copy, bypassing a kernel buffer.
  634                  */
  635                 } else if ((size = rpipe->pipe_map.cnt) &&
  636                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  637                         if (size > (u_int) uio->uio_resid)
  638                                 size = (u_int) uio->uio_resid;
  639 
  640                         PIPE_UNLOCK(rpipe);
  641                         error = uiomove_fromphys(rpipe->pipe_map.ms,
  642                             rpipe->pipe_map.pos, size, uio);
  643                         PIPE_LOCK(rpipe);
  644                         if (error)
  645                                 break;
  646                         nread += size;
  647                         rpipe->pipe_map.pos += size;
  648                         rpipe->pipe_map.cnt -= size;
  649                         if (rpipe->pipe_map.cnt == 0) {
  650                                 rpipe->pipe_state &= ~PIPE_DIRECTW;
  651                                 wakeup(rpipe);
  652                         }
  653 #endif
  654                 } else {
  655                         /*
  656                          * detect EOF condition
  657                          * read returns 0 on EOF, no need to set error
  658                          */
  659                         if (rpipe->pipe_state & PIPE_EOF)
  660                                 break;
  661 
  662                         /*
  663                          * If the "write-side" has been blocked, wake it up now.
  664                          */
  665                         if (rpipe->pipe_state & PIPE_WANTW) {
  666                                 rpipe->pipe_state &= ~PIPE_WANTW;
  667                                 wakeup(rpipe);
  668                         }
  669 
  670                         /*
  671                          * Break if some data was read.
  672                          */
  673                         if (nread > 0)
  674                                 break;
  675 
  676                         /*
  677                          * Unlock the pipe buffer for our remaining processing.
  678                          * We will either break out with an error or we will
  679                          * sleep and relock to loop.
  680                          */
  681                         pipeunlock(rpipe);
  682 
  683                         /*
  684                          * Handle non-blocking mode operation or
  685                          * wait for more data.
  686                          */
  687                         if (fp->f_flag & FNONBLOCK) {
  688                                 error = EAGAIN;
  689                         } else {
  690                                 rpipe->pipe_state |= PIPE_WANTR;
  691                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  692                                     PRIBIO | PCATCH,
  693                                     "piperd", 0)) == 0)
  694                                         error = pipelock(rpipe, 1);
  695                         }
  696                         if (error)
  697                                 goto unlocked_error;
  698                 }
  699         }
  700 #ifdef MAC
  701 locked_error:
  702 #endif
  703         pipeunlock(rpipe);
  704 
  705         /* XXX: should probably do this before getting any locks. */
  706         if (error == 0)
  707                 vfs_timestamp(&rpipe->pipe_atime);
  708 unlocked_error:
  709         --rpipe->pipe_busy;
  710 
  711         /*
  712          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  713          */
  714         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  715                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  716                 wakeup(rpipe);
  717         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  718                 /*
  719                  * Handle write blocking hysteresis.
  720                  */
  721                 if (rpipe->pipe_state & PIPE_WANTW) {
  722                         rpipe->pipe_state &= ~PIPE_WANTW;
  723                         wakeup(rpipe);
  724                 }
  725         }
  726 
  727         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  728                 pipeselwakeup(rpipe);
  729 
  730         PIPE_UNLOCK(rpipe);
  731         return (error);
  732 }
  733 
  734 #ifndef PIPE_NODIRECT
  735 /*
  736  * Map the sending processes' buffer into kernel space and wire it.
  737  * This is similar to a physical write operation.
  738  */
  739 static int
  740 pipe_build_write_buffer(wpipe, uio)
  741         struct pipe *wpipe;
  742         struct uio *uio;
  743 {
  744         pmap_t pmap;
  745         u_int size;
  746         int i, j;
  747         vm_offset_t addr, endaddr;
  748 
  749         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  750         KASSERT(wpipe->pipe_state & PIPE_DIRECTW,
  751                 ("Clone attempt on non-direct write pipe!"));
  752 
  753         size = (u_int) uio->uio_iov->iov_len;
  754         if (size > wpipe->pipe_buffer.size)
  755                 size = wpipe->pipe_buffer.size;
  756 
  757         pmap = vmspace_pmap(curproc->p_vmspace);
  758         endaddr = round_page((vm_offset_t)uio->uio_iov->iov_base + size);
  759         addr = trunc_page((vm_offset_t)uio->uio_iov->iov_base);
  760         if (endaddr < addr)
  761                 return (EFAULT);
  762         for (i = 0; addr < endaddr; addr += PAGE_SIZE, i++) {
  763                 /*
  764                  * vm_fault_quick() can sleep.  Consequently,
  765                  * vm_page_lock_queue() and vm_page_unlock_queue()
  766                  * should not be performed outside of this loop.
  767                  */
  768         race:
  769                 if (vm_fault_quick((caddr_t)addr, VM_PROT_READ) < 0) {
  770                         vm_page_lock_queues();
  771                         for (j = 0; j < i; j++)
  772                                 vm_page_unhold(wpipe->pipe_map.ms[j]);
  773                         vm_page_unlock_queues();
  774                         return (EFAULT);
  775                 }
  776                 wpipe->pipe_map.ms[i] = pmap_extract_and_hold(pmap, addr,
  777                     VM_PROT_READ);
  778                 if (wpipe->pipe_map.ms[i] == NULL)
  779                         goto race;
  780         }
  781 
  782 /*
  783  * set up the control block
  784  */
  785         wpipe->pipe_map.npages = i;
  786         wpipe->pipe_map.pos =
  787             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  788         wpipe->pipe_map.cnt = size;
  789 
  790 /*
  791  * and update the uio data
  792  */
  793 
  794         uio->uio_iov->iov_len -= size;
  795         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  796         if (uio->uio_iov->iov_len == 0)
  797                 uio->uio_iov++;
  798         uio->uio_resid -= size;
  799         uio->uio_offset += size;
  800         return (0);
  801 }
  802 
  803 /*
  804  * unmap and unwire the process buffer
  805  */
  806 static void
  807 pipe_destroy_write_buffer(wpipe)
  808         struct pipe *wpipe;
  809 {
  810         int i;
  811 
  812         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  813         vm_page_lock_queues();
  814         for (i = 0; i < wpipe->pipe_map.npages; i++) {
  815                 vm_page_unhold(wpipe->pipe_map.ms[i]);
  816         }
  817         vm_page_unlock_queues();
  818         wpipe->pipe_map.npages = 0;
  819 }
  820 
  821 /*
  822  * In the case of a signal, the writing process might go away.  This
  823  * code copies the data into the circular buffer so that the source
  824  * pages can be freed without loss of data.
  825  */
  826 static void
  827 pipe_clone_write_buffer(wpipe)
  828         struct pipe *wpipe;
  829 {
  830         struct uio uio;
  831         struct iovec iov;
  832         int size;
  833         int pos;
  834 
  835         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  836         size = wpipe->pipe_map.cnt;
  837         pos = wpipe->pipe_map.pos;
  838 
  839         wpipe->pipe_buffer.in = size;
  840         wpipe->pipe_buffer.out = 0;
  841         wpipe->pipe_buffer.cnt = size;
  842         wpipe->pipe_state &= ~PIPE_DIRECTW;
  843 
  844         PIPE_UNLOCK(wpipe);
  845         iov.iov_base = wpipe->pipe_buffer.buffer;
  846         iov.iov_len = size;
  847         uio.uio_iov = &iov;
  848         uio.uio_iovcnt = 1;
  849         uio.uio_offset = 0;
  850         uio.uio_resid = size;
  851         uio.uio_segflg = UIO_SYSSPACE;
  852         uio.uio_rw = UIO_READ;
  853         uio.uio_td = curthread;
  854         uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
  855         PIPE_LOCK(wpipe);
  856         pipe_destroy_write_buffer(wpipe);
  857 }
  858 
  859 /*
  860  * This implements the pipe buffer write mechanism.  Note that only
  861  * a direct write OR a normal pipe write can be pending at any given time.
  862  * If there are any characters in the pipe buffer, the direct write will
  863  * be deferred until the receiving process grabs all of the bytes from
  864  * the pipe buffer.  Then the direct mapping write is set-up.
  865  */
  866 static int
  867 pipe_direct_write(wpipe, uio)
  868         struct pipe *wpipe;
  869         struct uio *uio;
  870 {
  871         int error;
  872 
  873 retry:
  874         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  875         error = pipelock(wpipe, 1);
  876         if (wpipe->pipe_state & PIPE_EOF)
  877                 error = EPIPE;
  878         if (error) {
  879                 pipeunlock(wpipe);
  880                 goto error1;
  881         }
  882         while (wpipe->pipe_state & PIPE_DIRECTW) {
  883                 if (wpipe->pipe_state & PIPE_WANTR) {
  884                         wpipe->pipe_state &= ~PIPE_WANTR;
  885                         wakeup(wpipe);
  886                 }
  887                 pipeselwakeup(wpipe);
  888                 wpipe->pipe_state |= PIPE_WANTW;
  889                 pipeunlock(wpipe);
  890                 error = msleep(wpipe, PIPE_MTX(wpipe),
  891                     PRIBIO | PCATCH, "pipdww", 0);
  892                 if (error)
  893                         goto error1;
  894                 else
  895                         goto retry;
  896         }
  897         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  898         if (wpipe->pipe_buffer.cnt > 0) {
  899                 if (wpipe->pipe_state & PIPE_WANTR) {
  900                         wpipe->pipe_state &= ~PIPE_WANTR;
  901                         wakeup(wpipe);
  902                 }
  903                 pipeselwakeup(wpipe);
  904                 wpipe->pipe_state |= PIPE_WANTW;
  905                 pipeunlock(wpipe);
  906                 error = msleep(wpipe, PIPE_MTX(wpipe),
  907                     PRIBIO | PCATCH, "pipdwc", 0);
  908                 if (error)
  909                         goto error1;
  910                 else
  911                         goto retry;
  912         }
  913 
  914         wpipe->pipe_state |= PIPE_DIRECTW;
  915 
  916         PIPE_UNLOCK(wpipe);
  917         error = pipe_build_write_buffer(wpipe, uio);
  918         PIPE_LOCK(wpipe);
  919         if (error) {
  920                 wpipe->pipe_state &= ~PIPE_DIRECTW;
  921                 pipeunlock(wpipe);
  922                 goto error1;
  923         }
  924 
  925         error = 0;
  926         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
  927                 if (wpipe->pipe_state & PIPE_EOF) {
  928                         pipe_destroy_write_buffer(wpipe);
  929                         pipeselwakeup(wpipe);
  930                         pipeunlock(wpipe);
  931                         error = EPIPE;
  932                         goto error1;
  933                 }
  934                 if (wpipe->pipe_state & PIPE_WANTR) {
  935                         wpipe->pipe_state &= ~PIPE_WANTR;
  936                         wakeup(wpipe);
  937                 }
  938                 pipeselwakeup(wpipe);
  939                 pipeunlock(wpipe);
  940                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
  941                     "pipdwt", 0);
  942                 pipelock(wpipe, 0);
  943         }
  944 
  945         if (wpipe->pipe_state & PIPE_EOF)
  946                 error = EPIPE;
  947         if (wpipe->pipe_state & PIPE_DIRECTW) {
  948                 /*
  949                  * this bit of trickery substitutes a kernel buffer for
  950                  * the process that might be going away.
  951                  */
  952                 pipe_clone_write_buffer(wpipe);
  953         } else {
  954                 pipe_destroy_write_buffer(wpipe);
  955         }
  956         pipeunlock(wpipe);
  957         return (error);
  958 
  959 error1:
  960         wakeup(wpipe);
  961         return (error);
  962 }
  963 #endif
  964 
  965 static int
  966 pipe_write(fp, uio, active_cred, flags, td)
  967         struct file *fp;
  968         struct uio *uio;
  969         struct ucred *active_cred;
  970         struct thread *td;
  971         int flags;
  972 {
  973         int error = 0;
  974         int desiredsize, orig_resid;
  975         struct pipe *wpipe, *rpipe;
  976 
  977         rpipe = fp->f_data;
  978         wpipe = rpipe->pipe_peer;
  979 
  980         PIPE_LOCK(rpipe);
  981         error = pipelock(wpipe, 1);
  982         if (error) {
  983                 PIPE_UNLOCK(rpipe);
  984                 return (error);
  985         }
  986         /*
  987          * detect loss of pipe read side, issue SIGPIPE if lost.
  988          */
  989         if (wpipe->pipe_present != PIPE_ACTIVE ||
  990             (wpipe->pipe_state & PIPE_EOF)) {
  991                 pipeunlock(wpipe);
  992                 PIPE_UNLOCK(rpipe);
  993                 return (EPIPE);
  994         }
  995 #ifdef MAC
  996         error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
  997         if (error) {
  998                 pipeunlock(wpipe);
  999                 PIPE_UNLOCK(rpipe);
 1000                 return (error);
 1001         }
 1002 #endif
 1003         ++wpipe->pipe_busy;
 1004 
 1005         /* Choose a larger size if it's advantageous */
 1006         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
 1007         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
 1008                 if (piperesizeallowed != 1)
 1009                         break;
 1010                 if (amountpipekva > maxpipekva / 2)
 1011                         break;
 1012                 if (desiredsize == BIG_PIPE_SIZE)
 1013                         break;
 1014                 desiredsize = desiredsize * 2;
 1015         }
 1016 
 1017         /* Choose a smaller size if we're in a OOM situation */
 1018         if ((amountpipekva > (3 * maxpipekva) / 4) &&
 1019                 (wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
 1020                 (wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
 1021                 (piperesizeallowed == 1))
 1022                 desiredsize = SMALL_PIPE_SIZE;
 1023 
 1024         /* Resize if the above determined that a new size was necessary */
 1025         if ((desiredsize != wpipe->pipe_buffer.size) &&
 1026                 ((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
 1027                 PIPE_UNLOCK(wpipe);
 1028                 pipespace(wpipe, desiredsize);
 1029                 PIPE_LOCK(wpipe);
 1030         }
 1031         if (wpipe->pipe_buffer.size == 0) {
 1032                 /*
 1033                  * This can only happen for reverse direction use of pipes
 1034                  * in a complete OOM situation.
 1035                  */
 1036                 error = ENOMEM;
 1037                 --wpipe->pipe_busy;
 1038                 pipeunlock(wpipe);
 1039                 PIPE_UNLOCK(wpipe);
 1040                 return (error);
 1041         }
 1042 
 1043         pipeunlock(wpipe);
 1044 
 1045         orig_resid = uio->uio_resid;
 1046 
 1047         while (uio->uio_resid) {
 1048                 int space;
 1049 
 1050                 pipelock(wpipe, 0);
 1051                 if (wpipe->pipe_state & PIPE_EOF) {
 1052                         pipeunlock(wpipe);
 1053                         error = EPIPE;
 1054                         break;
 1055                 }
 1056 #ifndef PIPE_NODIRECT
 1057                 /*
 1058                  * If the transfer is large, we can gain performance if
 1059                  * we do process-to-process copies directly.
 1060                  * If the write is non-blocking, we don't use the
 1061                  * direct write mechanism.
 1062                  *
 1063                  * The direct write mechanism will detect the reader going
 1064                  * away on us.
 1065                  */
 1066                 if (uio->uio_segflg == UIO_USERSPACE &&
 1067                     uio->uio_iov->iov_len >= PIPE_MINDIRECT &&
 1068                     wpipe->pipe_buffer.size >= PIPE_MINDIRECT &&
 1069                     (fp->f_flag & FNONBLOCK) == 0) {
 1070                         pipeunlock(wpipe);
 1071                         error = pipe_direct_write(wpipe, uio);
 1072                         if (error)
 1073                                 break;
 1074                         continue;
 1075                 }
 1076 #endif
 1077 
 1078                 /*
 1079                  * Pipe buffered writes cannot be coincidental with
 1080                  * direct writes.  We wait until the currently executing
 1081                  * direct write is completed before we start filling the
 1082                  * pipe buffer.  We break out if a signal occurs or the
 1083                  * reader goes away.
 1084                  */
 1085                 if (wpipe->pipe_state & PIPE_DIRECTW) {
 1086                         if (wpipe->pipe_state & PIPE_WANTR) {
 1087                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1088                                 wakeup(wpipe);
 1089                         }
 1090                         pipeselwakeup(wpipe);
 1091                         wpipe->pipe_state |= PIPE_WANTW;
 1092                         pipeunlock(wpipe);
 1093                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
 1094                             "pipbww", 0);
 1095                         if (error)
 1096                                 break;
 1097                         else
 1098                                 continue;
 1099                 }
 1100 
 1101                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1102 
 1103                 /* Writes of size <= PIPE_BUF must be atomic. */
 1104                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 1105                         space = 0;
 1106 
 1107                 if (space > 0) {
 1108                         int size;       /* Transfer size */
 1109                         int segsize;    /* first segment to transfer */
 1110 
 1111                         /*
 1112                          * Transfer size is minimum of uio transfer
 1113                          * and free space in pipe buffer.
 1114                          */
 1115                         if (space > uio->uio_resid)
 1116                                 size = uio->uio_resid;
 1117                         else
 1118                                 size = space;
 1119                         /*
 1120                          * First segment to transfer is minimum of
 1121                          * transfer size and contiguous space in
 1122                          * pipe buffer.  If first segment to transfer
 1123                          * is less than the transfer size, we've got
 1124                          * a wraparound in the buffer.
 1125                          */
 1126                         segsize = wpipe->pipe_buffer.size -
 1127                                 wpipe->pipe_buffer.in;
 1128                         if (segsize > size)
 1129                                 segsize = size;
 1130 
 1131                         /* Transfer first segment */
 1132 
 1133                         PIPE_UNLOCK(rpipe);
 1134                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
 1135                                         segsize, uio);
 1136                         PIPE_LOCK(rpipe);
 1137 
 1138                         if (error == 0 && segsize < size) {
 1139                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
 1140                                         wpipe->pipe_buffer.size,
 1141                                         ("Pipe buffer wraparound disappeared"));
 1142                                 /*
 1143                                  * Transfer remaining part now, to
 1144                                  * support atomic writes.  Wraparound
 1145                                  * happened.
 1146                                  */
 1147 
 1148                                 PIPE_UNLOCK(rpipe);
 1149                                 error = uiomove(
 1150                                     &wpipe->pipe_buffer.buffer[0],
 1151                                     size - segsize, uio);
 1152                                 PIPE_LOCK(rpipe);
 1153                         }
 1154                         if (error == 0) {
 1155                                 wpipe->pipe_buffer.in += size;
 1156                                 if (wpipe->pipe_buffer.in >=
 1157                                     wpipe->pipe_buffer.size) {
 1158                                         KASSERT(wpipe->pipe_buffer.in ==
 1159                                                 size - segsize +
 1160                                                 wpipe->pipe_buffer.size,
 1161                                                 ("Expected wraparound bad"));
 1162                                         wpipe->pipe_buffer.in = size - segsize;
 1163                                 }
 1164 
 1165                                 wpipe->pipe_buffer.cnt += size;
 1166                                 KASSERT(wpipe->pipe_buffer.cnt <=
 1167                                         wpipe->pipe_buffer.size,
 1168                                         ("Pipe buffer overflow"));
 1169                         }
 1170                         pipeunlock(wpipe);
 1171                         if (error != 0)
 1172                                 break;
 1173                 } else {
 1174                         /*
 1175                          * If the "read-side" has been blocked, wake it up now.
 1176                          */
 1177                         if (wpipe->pipe_state & PIPE_WANTR) {
 1178                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1179                                 wakeup(wpipe);
 1180                         }
 1181 
 1182                         /*
 1183                          * don't block on non-blocking I/O
 1184                          */
 1185                         if (fp->f_flag & FNONBLOCK) {
 1186                                 error = EAGAIN;
 1187                                 pipeunlock(wpipe);
 1188                                 break;
 1189                         }
 1190 
 1191                         /*
 1192                          * We have no more space and have something to offer,
 1193                          * wake up select/poll.
 1194                          */
 1195                         pipeselwakeup(wpipe);
 1196 
 1197                         wpipe->pipe_state |= PIPE_WANTW;
 1198                         pipeunlock(wpipe);
 1199                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1200                             PRIBIO | PCATCH, "pipewr", 0);
 1201                         if (error != 0)
 1202                                 break;
 1203                 }
 1204         }
 1205 
 1206         pipelock(wpipe, 0);
 1207         --wpipe->pipe_busy;
 1208 
 1209         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1210                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1211                 wakeup(wpipe);
 1212         } else if (wpipe->pipe_buffer.cnt > 0) {
 1213                 /*
 1214                  * If we have put any characters in the buffer, we wake up
 1215                  * the reader.
 1216                  */
 1217                 if (wpipe->pipe_state & PIPE_WANTR) {
 1218                         wpipe->pipe_state &= ~PIPE_WANTR;
 1219                         wakeup(wpipe);
 1220                 }
 1221         }
 1222 
 1223         /*
 1224          * Don't return EPIPE if I/O was successful
 1225          */
 1226         if ((wpipe->pipe_buffer.cnt == 0) &&
 1227             (uio->uio_resid == 0) &&
 1228             (error == EPIPE)) {
 1229                 error = 0;
 1230         }
 1231 
 1232         if (error == 0)
 1233                 vfs_timestamp(&wpipe->pipe_mtime);
 1234 
 1235         /*
 1236          * We have something to offer,
 1237          * wake up select/poll.
 1238          */
 1239         if (wpipe->pipe_buffer.cnt)
 1240                 pipeselwakeup(wpipe);
 1241 
 1242         pipeunlock(wpipe);
 1243         PIPE_UNLOCK(rpipe);
 1244         return (error);
 1245 }
 1246 
 1247 /* ARGSUSED */
 1248 static int
 1249 pipe_truncate(fp, length, active_cred, td)
 1250         struct file *fp;
 1251         off_t length;
 1252         struct ucred *active_cred;
 1253         struct thread *td;
 1254 {
 1255 
 1256         return (EINVAL);
 1257 }
 1258 
 1259 /*
 1260  * we implement a very minimal set of ioctls for compatibility with sockets.
 1261  */
 1262 static int
 1263 pipe_ioctl(fp, cmd, data, active_cred, td)
 1264         struct file *fp;
 1265         u_long cmd;
 1266         void *data;
 1267         struct ucred *active_cred;
 1268         struct thread *td;
 1269 {
 1270         struct pipe *mpipe = fp->f_data;
 1271         int error;
 1272 
 1273         PIPE_LOCK(mpipe);
 1274 
 1275 #ifdef MAC
 1276         error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
 1277         if (error) {
 1278                 PIPE_UNLOCK(mpipe);
 1279                 return (error);
 1280         }
 1281 #endif
 1282 
 1283         error = 0;
 1284         switch (cmd) {
 1285 
 1286         case FIONBIO:
 1287                 break;
 1288 
 1289         case FIOASYNC:
 1290                 if (*(int *)data) {
 1291                         mpipe->pipe_state |= PIPE_ASYNC;
 1292                 } else {
 1293                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1294                 }
 1295                 break;
 1296 
 1297         case FIONREAD:
 1298                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1299                         *(int *)data = mpipe->pipe_map.cnt;
 1300                 else
 1301                         *(int *)data = mpipe->pipe_buffer.cnt;
 1302                 break;
 1303 
 1304         case FIOSETOWN:
 1305                 PIPE_UNLOCK(mpipe);
 1306                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 1307                 goto out_unlocked;
 1308 
 1309         case FIOGETOWN:
 1310                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1311                 break;
 1312 
 1313         /* This is deprecated, FIOSETOWN should be used instead. */
 1314         case TIOCSPGRP:
 1315                 PIPE_UNLOCK(mpipe);
 1316                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 1317                 goto out_unlocked;
 1318 
 1319         /* This is deprecated, FIOGETOWN should be used instead. */
 1320         case TIOCGPGRP:
 1321                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1322                 break;
 1323 
 1324         default:
 1325                 error = ENOTTY;
 1326                 break;
 1327         }
 1328         PIPE_UNLOCK(mpipe);
 1329 out_unlocked:
 1330         return (error);
 1331 }
 1332 
 1333 static int
 1334 pipe_poll(fp, events, active_cred, td)
 1335         struct file *fp;
 1336         int events;
 1337         struct ucred *active_cred;
 1338         struct thread *td;
 1339 {
 1340         struct pipe *rpipe = fp->f_data;
 1341         struct pipe *wpipe;
 1342         int revents = 0;
 1343 #ifdef MAC
 1344         int error;
 1345 #endif
 1346 
 1347         wpipe = rpipe->pipe_peer;
 1348         PIPE_LOCK(rpipe);
 1349 #ifdef MAC
 1350         error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
 1351         if (error)
 1352                 goto locked_error;
 1353 #endif
 1354         if (events & (POLLIN | POLLRDNORM))
 1355                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1356                     (rpipe->pipe_buffer.cnt > 0))
 1357                         revents |= events & (POLLIN | POLLRDNORM);
 1358 
 1359         if (events & (POLLOUT | POLLWRNORM))
 1360                 if (wpipe->pipe_present != PIPE_ACTIVE ||
 1361                     (wpipe->pipe_state & PIPE_EOF) ||
 1362                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1363                      (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF))
 1364                         revents |= events & (POLLOUT | POLLWRNORM);
 1365 
 1366         if ((events & POLLINIGNEOF) == 0) {
 1367                 if (rpipe->pipe_state & PIPE_EOF) {
 1368                         revents |= (events & (POLLIN | POLLRDNORM));
 1369                         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1370                             (wpipe->pipe_state & PIPE_EOF))
 1371                                 revents |= POLLHUP;
 1372                 }
 1373         }
 1374 
 1375         if (revents == 0) {
 1376                 if (events & (POLLIN | POLLRDNORM)) {
 1377                         selrecord(td, &rpipe->pipe_sel);
 1378                         if (SEL_WAITING(&rpipe->pipe_sel))
 1379                                 rpipe->pipe_state |= PIPE_SEL;
 1380                 }
 1381 
 1382                 if (events & (POLLOUT | POLLWRNORM)) {
 1383                         selrecord(td, &wpipe->pipe_sel);
 1384                         if (SEL_WAITING(&wpipe->pipe_sel))
 1385                                 wpipe->pipe_state |= PIPE_SEL;
 1386                 }
 1387         }
 1388 #ifdef MAC
 1389 locked_error:
 1390 #endif
 1391         PIPE_UNLOCK(rpipe);
 1392 
 1393         return (revents);
 1394 }
 1395 
 1396 /*
 1397  * We shouldn't need locks here as we're doing a read and this should
 1398  * be a natural race.
 1399  */
 1400 static int
 1401 pipe_stat(fp, ub, active_cred, td)
 1402         struct file *fp;
 1403         struct stat *ub;
 1404         struct ucred *active_cred;
 1405         struct thread *td;
 1406 {
 1407         struct pipe *pipe = fp->f_data;
 1408 #ifdef MAC
 1409         int error;
 1410 
 1411         PIPE_LOCK(pipe);
 1412         error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
 1413         PIPE_UNLOCK(pipe);
 1414         if (error)
 1415                 return (error);
 1416 #endif
 1417         bzero(ub, sizeof(*ub));
 1418         ub->st_mode = S_IFIFO;
 1419         ub->st_blksize = PAGE_SIZE;
 1420         if (pipe->pipe_state & PIPE_DIRECTW)
 1421                 ub->st_size = pipe->pipe_map.cnt;
 1422         else
 1423                 ub->st_size = pipe->pipe_buffer.cnt;
 1424         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
 1425         ub->st_atimespec = pipe->pipe_atime;
 1426         ub->st_mtimespec = pipe->pipe_mtime;
 1427         ub->st_ctimespec = pipe->pipe_ctime;
 1428         ub->st_uid = fp->f_cred->cr_uid;
 1429         ub->st_gid = fp->f_cred->cr_gid;
 1430         /*
 1431          * Left as 0: st_dev, st_ino, st_nlink, st_rdev, st_flags, st_gen.
 1432          * XXX (st_dev, st_ino) should be unique.
 1433          */
 1434         return (0);
 1435 }
 1436 
 1437 /* ARGSUSED */
 1438 static int
 1439 pipe_close(fp, td)
 1440         struct file *fp;
 1441         struct thread *td;
 1442 {
 1443         struct pipe *cpipe = fp->f_data;
 1444 
 1445         fp->f_ops = &badfileops;
 1446         fp->f_data = NULL;
 1447         funsetown(&cpipe->pipe_sigio);
 1448         pipeclose(cpipe);
 1449         return (0);
 1450 }
 1451 
 1452 static void
 1453 pipe_free_kmem(cpipe)
 1454         struct pipe *cpipe;
 1455 {
 1456 
 1457         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
 1458             ("pipe_free_kmem: pipe mutex locked"));
 1459 
 1460         if (cpipe->pipe_buffer.buffer != NULL) {
 1461                 atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
 1462                 vm_map_remove(pipe_map,
 1463                     (vm_offset_t)cpipe->pipe_buffer.buffer,
 1464                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
 1465                 cpipe->pipe_buffer.buffer = NULL;
 1466         }
 1467 #ifndef PIPE_NODIRECT
 1468         {
 1469                 cpipe->pipe_map.cnt = 0;
 1470                 cpipe->pipe_map.pos = 0;
 1471                 cpipe->pipe_map.npages = 0;
 1472         }
 1473 #endif
 1474 }
 1475 
 1476 /*
 1477  * shutdown the pipe
 1478  */
 1479 static void
 1480 pipeclose(cpipe)
 1481         struct pipe *cpipe;
 1482 {
 1483         struct pipepair *pp;
 1484         struct pipe *ppipe;
 1485 
 1486         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
 1487 
 1488         PIPE_LOCK(cpipe);
 1489         pipelock(cpipe, 0);
 1490         pp = cpipe->pipe_pair;
 1491 
 1492         pipeselwakeup(cpipe);
 1493 
 1494         /*
 1495          * If the other side is blocked, wake it up saying that
 1496          * we want to close it down.
 1497          */
 1498         cpipe->pipe_state |= PIPE_EOF;
 1499         while (cpipe->pipe_busy) {
 1500                 wakeup(cpipe);
 1501                 cpipe->pipe_state |= PIPE_WANT;
 1502                 pipeunlock(cpipe);
 1503                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1504                 pipelock(cpipe, 0);
 1505         }
 1506 
 1507 
 1508         /*
 1509          * Disconnect from peer, if any.
 1510          */
 1511         ppipe = cpipe->pipe_peer;
 1512         if (ppipe->pipe_present == PIPE_ACTIVE) {
 1513                 pipeselwakeup(ppipe);
 1514 
 1515                 ppipe->pipe_state |= PIPE_EOF;
 1516                 wakeup(ppipe);
 1517                 KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
 1518         }
 1519 
 1520         /*
 1521          * Mark this endpoint as free.  Release kmem resources.  We
 1522          * don't mark this endpoint as unused until we've finished
 1523          * doing that, or the pipe might disappear out from under
 1524          * us.
 1525          */
 1526         PIPE_UNLOCK(cpipe);
 1527         pipe_free_kmem(cpipe);
 1528         PIPE_LOCK(cpipe);
 1529         cpipe->pipe_present = PIPE_CLOSING;
 1530         pipeunlock(cpipe);
 1531 
 1532         /*
 1533          * knlist_clear() may sleep dropping the PIPE_MTX. Set the
 1534          * PIPE_FINALIZED, that allows other end to free the
 1535          * pipe_pair, only after the knotes are completely dismantled.
 1536          */
 1537         knlist_clear(&cpipe->pipe_sel.si_note, 1);
 1538         cpipe->pipe_present = PIPE_FINALIZED;
 1539         seldrain(&cpipe->pipe_sel);
 1540         knlist_destroy(&cpipe->pipe_sel.si_note);
 1541 
 1542         /*
 1543          * If both endpoints are now closed, release the memory for the
 1544          * pipe pair.  If not, unlock.
 1545          */
 1546         if (ppipe->pipe_present == PIPE_FINALIZED) {
 1547                 PIPE_UNLOCK(cpipe);
 1548 #ifdef MAC
 1549                 mac_pipe_destroy(pp);
 1550 #endif
 1551                 uma_zfree(pipe_zone, cpipe->pipe_pair);
 1552         } else
 1553                 PIPE_UNLOCK(cpipe);
 1554 }
 1555 
 1556 /*ARGSUSED*/
 1557 static int
 1558 pipe_kqfilter(struct file *fp, struct knote *kn)
 1559 {
 1560         struct pipe *cpipe;
 1561 
 1562         cpipe = kn->kn_fp->f_data;
 1563         PIPE_LOCK(cpipe);
 1564         switch (kn->kn_filter) {
 1565         case EVFILT_READ:
 1566                 kn->kn_fop = &pipe_rfiltops;
 1567                 break;
 1568         case EVFILT_WRITE:
 1569                 kn->kn_fop = &pipe_wfiltops;
 1570                 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
 1571                         /* other end of pipe has been closed */
 1572                         PIPE_UNLOCK(cpipe);
 1573                         return (EPIPE);
 1574                 }
 1575                 cpipe = cpipe->pipe_peer;
 1576                 break;
 1577         default:
 1578                 PIPE_UNLOCK(cpipe);
 1579                 return (EINVAL);
 1580         }
 1581 
 1582         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
 1583         PIPE_UNLOCK(cpipe);
 1584         return (0);
 1585 }
 1586 
 1587 static void
 1588 filt_pipedetach(struct knote *kn)
 1589 {
 1590         struct pipe *cpipe = (struct pipe *)kn->kn_fp->f_data;
 1591 
 1592         PIPE_LOCK(cpipe);
 1593         if (kn->kn_filter == EVFILT_WRITE)
 1594                 cpipe = cpipe->pipe_peer;
 1595         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
 1596         PIPE_UNLOCK(cpipe);
 1597 }
 1598 
 1599 /*ARGSUSED*/
 1600 static int
 1601 filt_piperead(struct knote *kn, long hint)
 1602 {
 1603         struct pipe *rpipe = kn->kn_fp->f_data;
 1604         struct pipe *wpipe = rpipe->pipe_peer;
 1605         int ret;
 1606 
 1607         PIPE_LOCK(rpipe);
 1608         kn->kn_data = rpipe->pipe_buffer.cnt;
 1609         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1610                 kn->kn_data = rpipe->pipe_map.cnt;
 1611 
 1612         if ((rpipe->pipe_state & PIPE_EOF) ||
 1613             wpipe->pipe_present != PIPE_ACTIVE ||
 1614             (wpipe->pipe_state & PIPE_EOF)) {
 1615                 kn->kn_flags |= EV_EOF;
 1616                 PIPE_UNLOCK(rpipe);
 1617                 return (1);
 1618         }
 1619         ret = kn->kn_data > 0;
 1620         PIPE_UNLOCK(rpipe);
 1621         return ret;
 1622 }
 1623 
 1624 /*ARGSUSED*/
 1625 static int
 1626 filt_pipewrite(struct knote *kn, long hint)
 1627 {
 1628         struct pipe *rpipe = kn->kn_fp->f_data;
 1629         struct pipe *wpipe = rpipe->pipe_peer;
 1630 
 1631         PIPE_LOCK(rpipe);
 1632         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1633             (wpipe->pipe_state & PIPE_EOF)) {
 1634                 kn->kn_data = 0;
 1635                 kn->kn_flags |= EV_EOF;
 1636                 PIPE_UNLOCK(rpipe);
 1637                 return (1);
 1638         }
 1639         kn->kn_data = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1640         if (wpipe->pipe_state & PIPE_DIRECTW)
 1641                 kn->kn_data = 0;
 1642 
 1643         PIPE_UNLOCK(rpipe);
 1644         return (kn->kn_data >= PIPE_BUF);
 1645 }

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