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, the sending process pins the underlying pages in
   33  * memory, and the receiving process copies directly from these pinned pages
   34  * in the sending 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/9.0/sys/kern/sys_pipe.c 226578 2011-10-20 18:54:05Z kib $");
   93 
   94 #include <sys/param.h>
   95 #include <sys/systm.h>
   96 #include <sys/conf.h>
   97 #include <sys/fcntl.h>
   98 #include <sys/file.h>
   99 #include <sys/filedesc.h>
  100 #include <sys/filio.h>
  101 #include <sys/kernel.h>
  102 #include <sys/lock.h>
  103 #include <sys/mutex.h>
  104 #include <sys/ttycom.h>
  105 #include <sys/stat.h>
  106 #include <sys/malloc.h>
  107 #include <sys/poll.h>
  108 #include <sys/selinfo.h>
  109 #include <sys/signalvar.h>
  110 #include <sys/syscallsubr.h>
  111 #include <sys/sysctl.h>
  112 #include <sys/sysproto.h>
  113 #include <sys/pipe.h>
  114 #include <sys/proc.h>
  115 #include <sys/vnode.h>
  116 #include <sys/uio.h>
  117 #include <sys/event.h>
  118 
  119 #include <security/mac/mac_framework.h>
  120 
  121 #include <vm/vm.h>
  122 #include <vm/vm_param.h>
  123 #include <vm/vm_object.h>
  124 #include <vm/vm_kern.h>
  125 #include <vm/vm_extern.h>
  126 #include <vm/pmap.h>
  127 #include <vm/vm_map.h>
  128 #include <vm/vm_page.h>
  129 #include <vm/uma.h>
  130 
  131 /*
  132  * Use this define if you want to disable *fancy* VM things.  Expect an
  133  * approx 30% decrease in transfer rate.  This could be useful for
  134  * NetBSD or OpenBSD.
  135  */
  136 /* #define PIPE_NODIRECT */
  137 
  138 /*
  139  * interfaces to the outside world
  140  */
  141 static fo_rdwr_t        pipe_read;
  142 static fo_rdwr_t        pipe_write;
  143 static fo_truncate_t    pipe_truncate;
  144 static fo_ioctl_t       pipe_ioctl;
  145 static fo_poll_t        pipe_poll;
  146 static fo_kqfilter_t    pipe_kqfilter;
  147 static fo_stat_t        pipe_stat;
  148 static fo_close_t       pipe_close;
  149 
  150 static struct fileops pipeops = {
  151         .fo_read = pipe_read,
  152         .fo_write = pipe_write,
  153         .fo_truncate = pipe_truncate,
  154         .fo_ioctl = pipe_ioctl,
  155         .fo_poll = pipe_poll,
  156         .fo_kqfilter = pipe_kqfilter,
  157         .fo_stat = pipe_stat,
  158         .fo_close = pipe_close,
  159         .fo_chmod = invfo_chmod,
  160         .fo_chown = invfo_chown,
  161         .fo_flags = DFLAG_PASSABLE
  162 };
  163 
  164 static void     filt_pipedetach(struct knote *kn);
  165 static int      filt_piperead(struct knote *kn, long hint);
  166 static int      filt_pipewrite(struct knote *kn, long hint);
  167 
  168 static struct filterops pipe_rfiltops = {
  169         .f_isfd = 1,
  170         .f_detach = filt_pipedetach,
  171         .f_event = filt_piperead
  172 };
  173 static struct filterops pipe_wfiltops = {
  174         .f_isfd = 1,
  175         .f_detach = filt_pipedetach,
  176         .f_event = filt_pipewrite
  177 };
  178 
  179 /*
  180  * Default pipe buffer size(s), this can be kind-of large now because pipe
  181  * space is pageable.  The pipe code will try to maintain locality of
  182  * reference for performance reasons, so small amounts of outstanding I/O
  183  * will not wipe the cache.
  184  */
  185 #define MINPIPESIZE (PIPE_SIZE/3)
  186 #define MAXPIPESIZE (2*PIPE_SIZE/3)
  187 
  188 static long amountpipekva;
  189 static int pipefragretry;
  190 static int pipeallocfail;
  191 static int piperesizefail;
  192 static int piperesizeallowed = 1;
  193 
  194 SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN,
  195            &maxpipekva, 0, "Pipe KVA limit");
  196 SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
  197            &amountpipekva, 0, "Pipe KVA usage");
  198 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
  199           &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
  200 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
  201           &pipeallocfail, 0, "Pipe allocation failures");
  202 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
  203           &piperesizefail, 0, "Pipe resize failures");
  204 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
  205           &piperesizeallowed, 0, "Pipe resizing allowed");
  206 
  207 static void pipeinit(void *dummy __unused);
  208 static void pipeclose(struct pipe *cpipe);
  209 static void pipe_free_kmem(struct pipe *cpipe);
  210 static int pipe_create(struct pipe *pipe, int backing);
  211 static __inline int pipelock(struct pipe *cpipe, int catch);
  212 static __inline void pipeunlock(struct pipe *cpipe);
  213 static __inline void pipeselwakeup(struct pipe *cpipe);
  214 #ifndef PIPE_NODIRECT
  215 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
  216 static void pipe_destroy_write_buffer(struct pipe *wpipe);
  217 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
  218 static void pipe_clone_write_buffer(struct pipe *wpipe);
  219 #endif
  220 static int pipespace(struct pipe *cpipe, int size);
  221 static int pipespace_new(struct pipe *cpipe, int size);
  222 
  223 static int      pipe_zone_ctor(void *mem, int size, void *arg, int flags);
  224 static int      pipe_zone_init(void *mem, int size, int flags);
  225 static void     pipe_zone_fini(void *mem, int size);
  226 
  227 static uma_zone_t pipe_zone;
  228 static struct unrhdr *pipeino_unr;
  229 static dev_t pipedev_ino;
  230 
  231 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
  232 
  233 static void
  234 pipeinit(void *dummy __unused)
  235 {
  236 
  237         pipe_zone = uma_zcreate("pipe", sizeof(struct pipepair),
  238             pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
  239             UMA_ALIGN_PTR, 0);
  240         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
  241         pipeino_unr = new_unrhdr(1, INT32_MAX, NULL);
  242         KASSERT(pipeino_unr != NULL, ("pipe fake inodes not initialized"));
  243         pipedev_ino = devfs_alloc_cdp_inode();
  244         KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
  245 }
  246 
  247 static int
  248 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
  249 {
  250         struct pipepair *pp;
  251         struct pipe *rpipe, *wpipe;
  252 
  253         KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
  254 
  255         pp = (struct pipepair *)mem;
  256 
  257         /*
  258          * We zero both pipe endpoints to make sure all the kmem pointers
  259          * are NULL, flag fields are zero'd, etc.  We timestamp both
  260          * endpoints with the same time.
  261          */
  262         rpipe = &pp->pp_rpipe;
  263         bzero(rpipe, sizeof(*rpipe));
  264         vfs_timestamp(&rpipe->pipe_ctime);
  265         rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
  266 
  267         wpipe = &pp->pp_wpipe;
  268         bzero(wpipe, sizeof(*wpipe));
  269         wpipe->pipe_ctime = rpipe->pipe_ctime;
  270         wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
  271 
  272         rpipe->pipe_peer = wpipe;
  273         rpipe->pipe_pair = pp;
  274         wpipe->pipe_peer = rpipe;
  275         wpipe->pipe_pair = pp;
  276 
  277         /*
  278          * Mark both endpoints as present; they will later get free'd
  279          * one at a time.  When both are free'd, then the whole pair
  280          * is released.
  281          */
  282         rpipe->pipe_present = PIPE_ACTIVE;
  283         wpipe->pipe_present = PIPE_ACTIVE;
  284 
  285         /*
  286          * Eventually, the MAC Framework may initialize the label
  287          * in ctor or init, but for now we do it elswhere to avoid
  288          * blocking in ctor or init.
  289          */
  290         pp->pp_label = NULL;
  291 
  292         return (0);
  293 }
  294 
  295 static int
  296 pipe_zone_init(void *mem, int size, int flags)
  297 {
  298         struct pipepair *pp;
  299 
  300         KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
  301 
  302         pp = (struct pipepair *)mem;
  303 
  304         mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_RECURSE);
  305         return (0);
  306 }
  307 
  308 static void
  309 pipe_zone_fini(void *mem, int size)
  310 {
  311         struct pipepair *pp;
  312 
  313         KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
  314 
  315         pp = (struct pipepair *)mem;
  316 
  317         mtx_destroy(&pp->pp_mtx);
  318 }
  319 
  320 /*
  321  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
  322  * the zone pick up the pieces via pipeclose().
  323  */
  324 int
  325 kern_pipe(struct thread *td, int fildes[2])
  326 {
  327         struct filedesc *fdp = td->td_proc->p_fd;
  328         struct file *rf, *wf;
  329         struct pipepair *pp;
  330         struct pipe *rpipe, *wpipe;
  331         int fd, error;
  332 
  333         pp = uma_zalloc(pipe_zone, M_WAITOK);
  334 #ifdef MAC
  335         /*
  336          * The MAC label is shared between the connected endpoints.  As a
  337          * result mac_pipe_init() and mac_pipe_create() are called once
  338          * for the pair, and not on the endpoints.
  339          */
  340         mac_pipe_init(pp);
  341         mac_pipe_create(td->td_ucred, pp);
  342 #endif
  343         rpipe = &pp->pp_rpipe;
  344         wpipe = &pp->pp_wpipe;
  345 
  346         knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
  347         knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
  348 
  349         /* Only the forward direction pipe is backed by default */
  350         if ((error = pipe_create(rpipe, 1)) != 0 ||
  351             (error = pipe_create(wpipe, 0)) != 0) {
  352                 pipeclose(rpipe);
  353                 pipeclose(wpipe);
  354                 return (error);
  355         }
  356 
  357         rpipe->pipe_state |= PIPE_DIRECTOK;
  358         wpipe->pipe_state |= PIPE_DIRECTOK;
  359 
  360         error = falloc(td, &rf, &fd, 0);
  361         if (error) {
  362                 pipeclose(rpipe);
  363                 pipeclose(wpipe);
  364                 return (error);
  365         }
  366         /* An extra reference on `rf' has been held for us by falloc(). */
  367         fildes[0] = fd;
  368 
  369         /*
  370          * Warning: once we've gotten past allocation of the fd for the
  371          * read-side, we can only drop the read side via fdrop() in order
  372          * to avoid races against processes which manage to dup() the read
  373          * side while we are blocked trying to allocate the write side.
  374          */
  375         finit(rf, FREAD | FWRITE, DTYPE_PIPE, rpipe, &pipeops);
  376         error = falloc(td, &wf, &fd, 0);
  377         if (error) {
  378                 fdclose(fdp, rf, fildes[0], td);
  379                 fdrop(rf, td);
  380                 /* rpipe has been closed by fdrop(). */
  381                 pipeclose(wpipe);
  382                 return (error);
  383         }
  384         /* An extra reference on `wf' has been held for us by falloc(). */
  385         finit(wf, FREAD | FWRITE, DTYPE_PIPE, wpipe, &pipeops);
  386         fdrop(wf, td);
  387         fildes[1] = fd;
  388         fdrop(rf, td);
  389 
  390         return (0);
  391 }
  392 
  393 /* ARGSUSED */
  394 int
  395 sys_pipe(struct thread *td, struct pipe_args *uap)
  396 {
  397         int error;
  398         int fildes[2];
  399 
  400         error = kern_pipe(td, fildes);
  401         if (error)
  402                 return (error);
  403         
  404         td->td_retval[0] = fildes[0];
  405         td->td_retval[1] = fildes[1];
  406 
  407         return (0);
  408 }
  409 
  410 /*
  411  * Allocate kva for pipe circular buffer, the space is pageable
  412  * This routine will 'realloc' the size of a pipe safely, if it fails
  413  * it will retain the old buffer.
  414  * If it fails it will return ENOMEM.
  415  */
  416 static int
  417 pipespace_new(cpipe, size)
  418         struct pipe *cpipe;
  419         int size;
  420 {
  421         caddr_t buffer;
  422         int error, cnt, firstseg;
  423         static int curfail = 0;
  424         static struct timeval lastfail;
  425 
  426         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
  427         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
  428                 ("pipespace: resize of direct writes not allowed"));
  429 retry:
  430         cnt = cpipe->pipe_buffer.cnt;
  431         if (cnt > size)
  432                 size = cnt;
  433 
  434         size = round_page(size);
  435         buffer = (caddr_t) vm_map_min(pipe_map);
  436 
  437         error = vm_map_find(pipe_map, NULL, 0,
  438                 (vm_offset_t *) &buffer, size, 1,
  439                 VM_PROT_ALL, VM_PROT_ALL, 0);
  440         if (error != KERN_SUCCESS) {
  441                 if ((cpipe->pipe_buffer.buffer == NULL) &&
  442                         (size > SMALL_PIPE_SIZE)) {
  443                         size = SMALL_PIPE_SIZE;
  444                         pipefragretry++;
  445                         goto retry;
  446                 }
  447                 if (cpipe->pipe_buffer.buffer == NULL) {
  448                         pipeallocfail++;
  449                         if (ppsratecheck(&lastfail, &curfail, 1))
  450                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
  451                 } else {
  452                         piperesizefail++;
  453                 }
  454                 return (ENOMEM);
  455         }
  456 
  457         /* copy data, then free old resources if we're resizing */
  458         if (cnt > 0) {
  459                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
  460                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
  461                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  462                                 buffer, firstseg);
  463                         if ((cnt - firstseg) > 0)
  464                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
  465                                         cpipe->pipe_buffer.in);
  466                 } else {
  467                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  468                                 buffer, cnt);
  469                 }
  470         }
  471         pipe_free_kmem(cpipe);
  472         cpipe->pipe_buffer.buffer = buffer;
  473         cpipe->pipe_buffer.size = size;
  474         cpipe->pipe_buffer.in = cnt;
  475         cpipe->pipe_buffer.out = 0;
  476         cpipe->pipe_buffer.cnt = cnt;
  477         atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
  478         return (0);
  479 }
  480 
  481 /*
  482  * Wrapper for pipespace_new() that performs locking assertions.
  483  */
  484 static int
  485 pipespace(cpipe, size)
  486         struct pipe *cpipe;
  487         int size;
  488 {
  489 
  490         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  491                 ("Unlocked pipe passed to pipespace"));
  492         return (pipespace_new(cpipe, size));
  493 }
  494 
  495 /*
  496  * lock a pipe for I/O, blocking other access
  497  */
  498 static __inline int
  499 pipelock(cpipe, catch)
  500         struct pipe *cpipe;
  501         int catch;
  502 {
  503         int error;
  504 
  505         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  506         while (cpipe->pipe_state & PIPE_LOCKFL) {
  507                 cpipe->pipe_state |= PIPE_LWANT;
  508                 error = msleep(cpipe, PIPE_MTX(cpipe),
  509                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  510                     "pipelk", 0);
  511                 if (error != 0)
  512                         return (error);
  513         }
  514         cpipe->pipe_state |= PIPE_LOCKFL;
  515         return (0);
  516 }
  517 
  518 /*
  519  * unlock a pipe I/O lock
  520  */
  521 static __inline void
  522 pipeunlock(cpipe)
  523         struct pipe *cpipe;
  524 {
  525 
  526         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  527         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  528                 ("Unlocked pipe passed to pipeunlock"));
  529         cpipe->pipe_state &= ~PIPE_LOCKFL;
  530         if (cpipe->pipe_state & PIPE_LWANT) {
  531                 cpipe->pipe_state &= ~PIPE_LWANT;
  532                 wakeup(cpipe);
  533         }
  534 }
  535 
  536 static __inline void
  537 pipeselwakeup(cpipe)
  538         struct pipe *cpipe;
  539 {
  540 
  541         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  542         if (cpipe->pipe_state & PIPE_SEL) {
  543                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
  544                 if (!SEL_WAITING(&cpipe->pipe_sel))
  545                         cpipe->pipe_state &= ~PIPE_SEL;
  546         }
  547         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  548                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  549         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
  550 }
  551 
  552 /*
  553  * Initialize and allocate VM and memory for pipe.  The structure
  554  * will start out zero'd from the ctor, so we just manage the kmem.
  555  */
  556 static int
  557 pipe_create(pipe, backing)
  558         struct pipe *pipe;
  559         int backing;
  560 {
  561         int error;
  562 
  563         if (backing) {
  564                 if (amountpipekva > maxpipekva / 2)
  565                         error = pipespace_new(pipe, SMALL_PIPE_SIZE);
  566                 else
  567                         error = pipespace_new(pipe, PIPE_SIZE);
  568         } else {
  569                 /* If we're not backing this pipe, no need to do anything. */
  570                 error = 0;
  571         }
  572         if (error == 0) {
  573                 pipe->pipe_ino = alloc_unr(pipeino_unr);
  574                 if (pipe->pipe_ino == -1)
  575                         /* pipeclose will clear allocated kva */
  576                         error = ENOMEM;
  577         }
  578         return (error);
  579 }
  580 
  581 /* ARGSUSED */
  582 static int
  583 pipe_read(fp, uio, active_cred, flags, td)
  584         struct file *fp;
  585         struct uio *uio;
  586         struct ucred *active_cred;
  587         struct thread *td;
  588         int flags;
  589 {
  590         struct pipe *rpipe = fp->f_data;
  591         int error;
  592         int nread = 0;
  593         u_int size;
  594 
  595         PIPE_LOCK(rpipe);
  596         ++rpipe->pipe_busy;
  597         error = pipelock(rpipe, 1);
  598         if (error)
  599                 goto unlocked_error;
  600 
  601 #ifdef MAC
  602         error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
  603         if (error)
  604                 goto locked_error;
  605 #endif
  606         if (amountpipekva > (3 * maxpipekva) / 4) {
  607                 if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
  608                         (rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
  609                         (rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
  610                         (piperesizeallowed == 1)) {
  611                         PIPE_UNLOCK(rpipe);
  612                         pipespace(rpipe, SMALL_PIPE_SIZE);
  613                         PIPE_LOCK(rpipe);
  614                 }
  615         }
  616 
  617         while (uio->uio_resid) {
  618                 /*
  619                  * normal pipe buffer receive
  620                  */
  621                 if (rpipe->pipe_buffer.cnt > 0) {
  622                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  623                         if (size > rpipe->pipe_buffer.cnt)
  624                                 size = rpipe->pipe_buffer.cnt;
  625                         if (size > (u_int) uio->uio_resid)
  626                                 size = (u_int) uio->uio_resid;
  627 
  628                         PIPE_UNLOCK(rpipe);
  629                         error = uiomove(
  630                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  631                             size, uio);
  632                         PIPE_LOCK(rpipe);
  633                         if (error)
  634                                 break;
  635 
  636                         rpipe->pipe_buffer.out += size;
  637                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  638                                 rpipe->pipe_buffer.out = 0;
  639 
  640                         rpipe->pipe_buffer.cnt -= size;
  641 
  642                         /*
  643                          * If there is no more to read in the pipe, reset
  644                          * its pointers to the beginning.  This improves
  645                          * cache hit stats.
  646                          */
  647                         if (rpipe->pipe_buffer.cnt == 0) {
  648                                 rpipe->pipe_buffer.in = 0;
  649                                 rpipe->pipe_buffer.out = 0;
  650                         }
  651                         nread += size;
  652 #ifndef PIPE_NODIRECT
  653                 /*
  654                  * Direct copy, bypassing a kernel buffer.
  655                  */
  656                 } else if ((size = rpipe->pipe_map.cnt) &&
  657                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  658                         if (size > (u_int) uio->uio_resid)
  659                                 size = (u_int) uio->uio_resid;
  660 
  661                         PIPE_UNLOCK(rpipe);
  662                         error = uiomove_fromphys(rpipe->pipe_map.ms,
  663                             rpipe->pipe_map.pos, size, uio);
  664                         PIPE_LOCK(rpipe);
  665                         if (error)
  666                                 break;
  667                         nread += size;
  668                         rpipe->pipe_map.pos += size;
  669                         rpipe->pipe_map.cnt -= size;
  670                         if (rpipe->pipe_map.cnt == 0) {
  671                                 rpipe->pipe_state &= ~PIPE_DIRECTW;
  672                                 wakeup(rpipe);
  673                         }
  674 #endif
  675                 } else {
  676                         /*
  677                          * detect EOF condition
  678                          * read returns 0 on EOF, no need to set error
  679                          */
  680                         if (rpipe->pipe_state & PIPE_EOF)
  681                                 break;
  682 
  683                         /*
  684                          * If the "write-side" has been blocked, wake it up now.
  685                          */
  686                         if (rpipe->pipe_state & PIPE_WANTW) {
  687                                 rpipe->pipe_state &= ~PIPE_WANTW;
  688                                 wakeup(rpipe);
  689                         }
  690 
  691                         /*
  692                          * Break if some data was read.
  693                          */
  694                         if (nread > 0)
  695                                 break;
  696 
  697                         /*
  698                          * Unlock the pipe buffer for our remaining processing.
  699                          * We will either break out with an error or we will
  700                          * sleep and relock to loop.
  701                          */
  702                         pipeunlock(rpipe);
  703 
  704                         /*
  705                          * Handle non-blocking mode operation or
  706                          * wait for more data.
  707                          */
  708                         if (fp->f_flag & FNONBLOCK) {
  709                                 error = EAGAIN;
  710                         } else {
  711                                 rpipe->pipe_state |= PIPE_WANTR;
  712                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  713                                     PRIBIO | PCATCH,
  714                                     "piperd", 0)) == 0)
  715                                         error = pipelock(rpipe, 1);
  716                         }
  717                         if (error)
  718                                 goto unlocked_error;
  719                 }
  720         }
  721 #ifdef MAC
  722 locked_error:
  723 #endif
  724         pipeunlock(rpipe);
  725 
  726         /* XXX: should probably do this before getting any locks. */
  727         if (error == 0)
  728                 vfs_timestamp(&rpipe->pipe_atime);
  729 unlocked_error:
  730         --rpipe->pipe_busy;
  731 
  732         /*
  733          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  734          */
  735         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  736                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  737                 wakeup(rpipe);
  738         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  739                 /*
  740                  * Handle write blocking hysteresis.
  741                  */
  742                 if (rpipe->pipe_state & PIPE_WANTW) {
  743                         rpipe->pipe_state &= ~PIPE_WANTW;
  744                         wakeup(rpipe);
  745                 }
  746         }
  747 
  748         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  749                 pipeselwakeup(rpipe);
  750 
  751         PIPE_UNLOCK(rpipe);
  752         return (error);
  753 }
  754 
  755 #ifndef PIPE_NODIRECT
  756 /*
  757  * Map the sending processes' buffer into kernel space and wire it.
  758  * This is similar to a physical write operation.
  759  */
  760 static int
  761 pipe_build_write_buffer(wpipe, uio)
  762         struct pipe *wpipe;
  763         struct uio *uio;
  764 {
  765         u_int size;
  766         int i;
  767 
  768         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  769         KASSERT(wpipe->pipe_state & PIPE_DIRECTW,
  770                 ("Clone attempt on non-direct write pipe!"));
  771 
  772         size = (u_int) uio->uio_iov->iov_len;
  773         if (size > wpipe->pipe_buffer.size)
  774                 size = wpipe->pipe_buffer.size;
  775 
  776         if ((i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
  777             (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
  778             wpipe->pipe_map.ms, PIPENPAGES)) < 0)
  779                 return (EFAULT);
  780 
  781 /*
  782  * set up the control block
  783  */
  784         wpipe->pipe_map.npages = i;
  785         wpipe->pipe_map.pos =
  786             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  787         wpipe->pipe_map.cnt = size;
  788 
  789 /*
  790  * and update the uio data
  791  */
  792 
  793         uio->uio_iov->iov_len -= size;
  794         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  795         if (uio->uio_iov->iov_len == 0)
  796                 uio->uio_iov++;
  797         uio->uio_resid -= size;
  798         uio->uio_offset += size;
  799         return (0);
  800 }
  801 
  802 /*
  803  * unmap and unwire the process buffer
  804  */
  805 static void
  806 pipe_destroy_write_buffer(wpipe)
  807         struct pipe *wpipe;
  808 {
  809 
  810         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  811         vm_page_unhold_pages(wpipe->pipe_map.ms, wpipe->pipe_map.npages);
  812         wpipe->pipe_map.npages = 0;
  813 }
  814 
  815 /*
  816  * In the case of a signal, the writing process might go away.  This
  817  * code copies the data into the circular buffer so that the source
  818  * pages can be freed without loss of data.
  819  */
  820 static void
  821 pipe_clone_write_buffer(wpipe)
  822         struct pipe *wpipe;
  823 {
  824         struct uio uio;
  825         struct iovec iov;
  826         int size;
  827         int pos;
  828 
  829         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  830         size = wpipe->pipe_map.cnt;
  831         pos = wpipe->pipe_map.pos;
  832 
  833         wpipe->pipe_buffer.in = size;
  834         wpipe->pipe_buffer.out = 0;
  835         wpipe->pipe_buffer.cnt = size;
  836         wpipe->pipe_state &= ~PIPE_DIRECTW;
  837 
  838         PIPE_UNLOCK(wpipe);
  839         iov.iov_base = wpipe->pipe_buffer.buffer;
  840         iov.iov_len = size;
  841         uio.uio_iov = &iov;
  842         uio.uio_iovcnt = 1;
  843         uio.uio_offset = 0;
  844         uio.uio_resid = size;
  845         uio.uio_segflg = UIO_SYSSPACE;
  846         uio.uio_rw = UIO_READ;
  847         uio.uio_td = curthread;
  848         uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
  849         PIPE_LOCK(wpipe);
  850         pipe_destroy_write_buffer(wpipe);
  851 }
  852 
  853 /*
  854  * This implements the pipe buffer write mechanism.  Note that only
  855  * a direct write OR a normal pipe write can be pending at any given time.
  856  * If there are any characters in the pipe buffer, the direct write will
  857  * be deferred until the receiving process grabs all of the bytes from
  858  * the pipe buffer.  Then the direct mapping write is set-up.
  859  */
  860 static int
  861 pipe_direct_write(wpipe, uio)
  862         struct pipe *wpipe;
  863         struct uio *uio;
  864 {
  865         int error;
  866 
  867 retry:
  868         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  869         error = pipelock(wpipe, 1);
  870         if (wpipe->pipe_state & PIPE_EOF)
  871                 error = EPIPE;
  872         if (error) {
  873                 pipeunlock(wpipe);
  874                 goto error1;
  875         }
  876         while (wpipe->pipe_state & PIPE_DIRECTW) {
  877                 if (wpipe->pipe_state & PIPE_WANTR) {
  878                         wpipe->pipe_state &= ~PIPE_WANTR;
  879                         wakeup(wpipe);
  880                 }
  881                 pipeselwakeup(wpipe);
  882                 wpipe->pipe_state |= PIPE_WANTW;
  883                 pipeunlock(wpipe);
  884                 error = msleep(wpipe, PIPE_MTX(wpipe),
  885                     PRIBIO | PCATCH, "pipdww", 0);
  886                 if (error)
  887                         goto error1;
  888                 else
  889                         goto retry;
  890         }
  891         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  892         if (wpipe->pipe_buffer.cnt > 0) {
  893                 if (wpipe->pipe_state & PIPE_WANTR) {
  894                         wpipe->pipe_state &= ~PIPE_WANTR;
  895                         wakeup(wpipe);
  896                 }
  897                 pipeselwakeup(wpipe);
  898                 wpipe->pipe_state |= PIPE_WANTW;
  899                 pipeunlock(wpipe);
  900                 error = msleep(wpipe, PIPE_MTX(wpipe),
  901                     PRIBIO | PCATCH, "pipdwc", 0);
  902                 if (error)
  903                         goto error1;
  904                 else
  905                         goto retry;
  906         }
  907 
  908         wpipe->pipe_state |= PIPE_DIRECTW;
  909 
  910         PIPE_UNLOCK(wpipe);
  911         error = pipe_build_write_buffer(wpipe, uio);
  912         PIPE_LOCK(wpipe);
  913         if (error) {
  914                 wpipe->pipe_state &= ~PIPE_DIRECTW;
  915                 pipeunlock(wpipe);
  916                 goto error1;
  917         }
  918 
  919         error = 0;
  920         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
  921                 if (wpipe->pipe_state & PIPE_EOF) {
  922                         pipe_destroy_write_buffer(wpipe);
  923                         pipeselwakeup(wpipe);
  924                         pipeunlock(wpipe);
  925                         error = EPIPE;
  926                         goto error1;
  927                 }
  928                 if (wpipe->pipe_state & PIPE_WANTR) {
  929                         wpipe->pipe_state &= ~PIPE_WANTR;
  930                         wakeup(wpipe);
  931                 }
  932                 pipeselwakeup(wpipe);
  933                 pipeunlock(wpipe);
  934                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
  935                     "pipdwt", 0);
  936                 pipelock(wpipe, 0);
  937         }
  938 
  939         if (wpipe->pipe_state & PIPE_EOF)
  940                 error = EPIPE;
  941         if (wpipe->pipe_state & PIPE_DIRECTW) {
  942                 /*
  943                  * this bit of trickery substitutes a kernel buffer for
  944                  * the process that might be going away.
  945                  */
  946                 pipe_clone_write_buffer(wpipe);
  947         } else {
  948                 pipe_destroy_write_buffer(wpipe);
  949         }
  950         pipeunlock(wpipe);
  951         return (error);
  952 
  953 error1:
  954         wakeup(wpipe);
  955         return (error);
  956 }
  957 #endif
  958 
  959 static int
  960 pipe_write(fp, uio, active_cred, flags, td)
  961         struct file *fp;
  962         struct uio *uio;
  963         struct ucred *active_cred;
  964         struct thread *td;
  965         int flags;
  966 {
  967         int error = 0;
  968         int desiredsize, orig_resid;
  969         struct pipe *wpipe, *rpipe;
  970 
  971         rpipe = fp->f_data;
  972         wpipe = rpipe->pipe_peer;
  973 
  974         PIPE_LOCK(rpipe);
  975         error = pipelock(wpipe, 1);
  976         if (error) {
  977                 PIPE_UNLOCK(rpipe);
  978                 return (error);
  979         }
  980         /*
  981          * detect loss of pipe read side, issue SIGPIPE if lost.
  982          */
  983         if (wpipe->pipe_present != PIPE_ACTIVE ||
  984             (wpipe->pipe_state & PIPE_EOF)) {
  985                 pipeunlock(wpipe);
  986                 PIPE_UNLOCK(rpipe);
  987                 return (EPIPE);
  988         }
  989 #ifdef MAC
  990         error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
  991         if (error) {
  992                 pipeunlock(wpipe);
  993                 PIPE_UNLOCK(rpipe);
  994                 return (error);
  995         }
  996 #endif
  997         ++wpipe->pipe_busy;
  998 
  999         /* Choose a larger size if it's advantageous */
 1000         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
 1001         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
 1002                 if (piperesizeallowed != 1)
 1003                         break;
 1004                 if (amountpipekva > maxpipekva / 2)
 1005                         break;
 1006                 if (desiredsize == BIG_PIPE_SIZE)
 1007                         break;
 1008                 desiredsize = desiredsize * 2;
 1009         }
 1010 
 1011         /* Choose a smaller size if we're in a OOM situation */
 1012         if ((amountpipekva > (3 * maxpipekva) / 4) &&
 1013                 (wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
 1014                 (wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
 1015                 (piperesizeallowed == 1))
 1016                 desiredsize = SMALL_PIPE_SIZE;
 1017 
 1018         /* Resize if the above determined that a new size was necessary */
 1019         if ((desiredsize != wpipe->pipe_buffer.size) &&
 1020                 ((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
 1021                 PIPE_UNLOCK(wpipe);
 1022                 pipespace(wpipe, desiredsize);
 1023                 PIPE_LOCK(wpipe);
 1024         }
 1025         if (wpipe->pipe_buffer.size == 0) {
 1026                 /*
 1027                  * This can only happen for reverse direction use of pipes
 1028                  * in a complete OOM situation.
 1029                  */
 1030                 error = ENOMEM;
 1031                 --wpipe->pipe_busy;
 1032                 pipeunlock(wpipe);
 1033                 PIPE_UNLOCK(wpipe);
 1034                 return (error);
 1035         }
 1036 
 1037         pipeunlock(wpipe);
 1038 
 1039         orig_resid = uio->uio_resid;
 1040 
 1041         while (uio->uio_resid) {
 1042                 int space;
 1043 
 1044                 pipelock(wpipe, 0);
 1045                 if (wpipe->pipe_state & PIPE_EOF) {
 1046                         pipeunlock(wpipe);
 1047                         error = EPIPE;
 1048                         break;
 1049                 }
 1050 #ifndef PIPE_NODIRECT
 1051                 /*
 1052                  * If the transfer is large, we can gain performance if
 1053                  * we do process-to-process copies directly.
 1054                  * If the write is non-blocking, we don't use the
 1055                  * direct write mechanism.
 1056                  *
 1057                  * The direct write mechanism will detect the reader going
 1058                  * away on us.
 1059                  */
 1060                 if (uio->uio_segflg == UIO_USERSPACE &&
 1061                     uio->uio_iov->iov_len >= PIPE_MINDIRECT &&
 1062                     wpipe->pipe_buffer.size >= PIPE_MINDIRECT &&
 1063                     (fp->f_flag & FNONBLOCK) == 0) {
 1064                         pipeunlock(wpipe);
 1065                         error = pipe_direct_write(wpipe, uio);
 1066                         if (error)
 1067                                 break;
 1068                         continue;
 1069                 }
 1070 #endif
 1071 
 1072                 /*
 1073                  * Pipe buffered writes cannot be coincidental with
 1074                  * direct writes.  We wait until the currently executing
 1075                  * direct write is completed before we start filling the
 1076                  * pipe buffer.  We break out if a signal occurs or the
 1077                  * reader goes away.
 1078                  */
 1079                 if (wpipe->pipe_state & PIPE_DIRECTW) {
 1080                         if (wpipe->pipe_state & PIPE_WANTR) {
 1081                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1082                                 wakeup(wpipe);
 1083                         }
 1084                         pipeselwakeup(wpipe);
 1085                         wpipe->pipe_state |= PIPE_WANTW;
 1086                         pipeunlock(wpipe);
 1087                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
 1088                             "pipbww", 0);
 1089                         if (error)
 1090                                 break;
 1091                         else
 1092                                 continue;
 1093                 }
 1094 
 1095                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1096 
 1097                 /* Writes of size <= PIPE_BUF must be atomic. */
 1098                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 1099                         space = 0;
 1100 
 1101                 if (space > 0) {
 1102                         int size;       /* Transfer size */
 1103                         int segsize;    /* first segment to transfer */
 1104 
 1105                         /*
 1106                          * Transfer size is minimum of uio transfer
 1107                          * and free space in pipe buffer.
 1108                          */
 1109                         if (space > uio->uio_resid)
 1110                                 size = uio->uio_resid;
 1111                         else
 1112                                 size = space;
 1113                         /*
 1114                          * First segment to transfer is minimum of
 1115                          * transfer size and contiguous space in
 1116                          * pipe buffer.  If first segment to transfer
 1117                          * is less than the transfer size, we've got
 1118                          * a wraparound in the buffer.
 1119                          */
 1120                         segsize = wpipe->pipe_buffer.size -
 1121                                 wpipe->pipe_buffer.in;
 1122                         if (segsize > size)
 1123                                 segsize = size;
 1124 
 1125                         /* Transfer first segment */
 1126 
 1127                         PIPE_UNLOCK(rpipe);
 1128                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
 1129                                         segsize, uio);
 1130                         PIPE_LOCK(rpipe);
 1131 
 1132                         if (error == 0 && segsize < size) {
 1133                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
 1134                                         wpipe->pipe_buffer.size,
 1135                                         ("Pipe buffer wraparound disappeared"));
 1136                                 /*
 1137                                  * Transfer remaining part now, to
 1138                                  * support atomic writes.  Wraparound
 1139                                  * happened.
 1140                                  */
 1141 
 1142                                 PIPE_UNLOCK(rpipe);
 1143                                 error = uiomove(
 1144                                     &wpipe->pipe_buffer.buffer[0],
 1145                                     size - segsize, uio);
 1146                                 PIPE_LOCK(rpipe);
 1147                         }
 1148                         if (error == 0) {
 1149                                 wpipe->pipe_buffer.in += size;
 1150                                 if (wpipe->pipe_buffer.in >=
 1151                                     wpipe->pipe_buffer.size) {
 1152                                         KASSERT(wpipe->pipe_buffer.in ==
 1153                                                 size - segsize +
 1154                                                 wpipe->pipe_buffer.size,
 1155                                                 ("Expected wraparound bad"));
 1156                                         wpipe->pipe_buffer.in = size - segsize;
 1157                                 }
 1158 
 1159                                 wpipe->pipe_buffer.cnt += size;
 1160                                 KASSERT(wpipe->pipe_buffer.cnt <=
 1161                                         wpipe->pipe_buffer.size,
 1162                                         ("Pipe buffer overflow"));
 1163                         }
 1164                         pipeunlock(wpipe);
 1165                         if (error != 0)
 1166                                 break;
 1167                 } else {
 1168                         /*
 1169                          * If the "read-side" has been blocked, wake it up now.
 1170                          */
 1171                         if (wpipe->pipe_state & PIPE_WANTR) {
 1172                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1173                                 wakeup(wpipe);
 1174                         }
 1175 
 1176                         /*
 1177                          * don't block on non-blocking I/O
 1178                          */
 1179                         if (fp->f_flag & FNONBLOCK) {
 1180                                 error = EAGAIN;
 1181                                 pipeunlock(wpipe);
 1182                                 break;
 1183                         }
 1184 
 1185                         /*
 1186                          * We have no more space and have something to offer,
 1187                          * wake up select/poll.
 1188                          */
 1189                         pipeselwakeup(wpipe);
 1190 
 1191                         wpipe->pipe_state |= PIPE_WANTW;
 1192                         pipeunlock(wpipe);
 1193                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1194                             PRIBIO | PCATCH, "pipewr", 0);
 1195                         if (error != 0)
 1196                                 break;
 1197                 }
 1198         }
 1199 
 1200         pipelock(wpipe, 0);
 1201         --wpipe->pipe_busy;
 1202 
 1203         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1204                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1205                 wakeup(wpipe);
 1206         } else if (wpipe->pipe_buffer.cnt > 0) {
 1207                 /*
 1208                  * If we have put any characters in the buffer, we wake up
 1209                  * the reader.
 1210                  */
 1211                 if (wpipe->pipe_state & PIPE_WANTR) {
 1212                         wpipe->pipe_state &= ~PIPE_WANTR;
 1213                         wakeup(wpipe);
 1214                 }
 1215         }
 1216 
 1217         /*
 1218          * Don't return EPIPE if I/O was successful
 1219          */
 1220         if ((wpipe->pipe_buffer.cnt == 0) &&
 1221             (uio->uio_resid == 0) &&
 1222             (error == EPIPE)) {
 1223                 error = 0;
 1224         }
 1225 
 1226         if (error == 0)
 1227                 vfs_timestamp(&wpipe->pipe_mtime);
 1228 
 1229         /*
 1230          * We have something to offer,
 1231          * wake up select/poll.
 1232          */
 1233         if (wpipe->pipe_buffer.cnt)
 1234                 pipeselwakeup(wpipe);
 1235 
 1236         pipeunlock(wpipe);
 1237         PIPE_UNLOCK(rpipe);
 1238         return (error);
 1239 }
 1240 
 1241 /* ARGSUSED */
 1242 static int
 1243 pipe_truncate(fp, length, active_cred, td)
 1244         struct file *fp;
 1245         off_t length;
 1246         struct ucred *active_cred;
 1247         struct thread *td;
 1248 {
 1249 
 1250         return (EINVAL);
 1251 }
 1252 
 1253 /*
 1254  * we implement a very minimal set of ioctls for compatibility with sockets.
 1255  */
 1256 static int
 1257 pipe_ioctl(fp, cmd, data, active_cred, td)
 1258         struct file *fp;
 1259         u_long cmd;
 1260         void *data;
 1261         struct ucred *active_cred;
 1262         struct thread *td;
 1263 {
 1264         struct pipe *mpipe = fp->f_data;
 1265         int error;
 1266 
 1267         PIPE_LOCK(mpipe);
 1268 
 1269 #ifdef MAC
 1270         error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
 1271         if (error) {
 1272                 PIPE_UNLOCK(mpipe);
 1273                 return (error);
 1274         }
 1275 #endif
 1276 
 1277         error = 0;
 1278         switch (cmd) {
 1279 
 1280         case FIONBIO:
 1281                 break;
 1282 
 1283         case FIOASYNC:
 1284                 if (*(int *)data) {
 1285                         mpipe->pipe_state |= PIPE_ASYNC;
 1286                 } else {
 1287                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1288                 }
 1289                 break;
 1290 
 1291         case FIONREAD:
 1292                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1293                         *(int *)data = mpipe->pipe_map.cnt;
 1294                 else
 1295                         *(int *)data = mpipe->pipe_buffer.cnt;
 1296                 break;
 1297 
 1298         case FIOSETOWN:
 1299                 PIPE_UNLOCK(mpipe);
 1300                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 1301                 goto out_unlocked;
 1302 
 1303         case FIOGETOWN:
 1304                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1305                 break;
 1306 
 1307         /* This is deprecated, FIOSETOWN should be used instead. */
 1308         case TIOCSPGRP:
 1309                 PIPE_UNLOCK(mpipe);
 1310                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 1311                 goto out_unlocked;
 1312 
 1313         /* This is deprecated, FIOGETOWN should be used instead. */
 1314         case TIOCGPGRP:
 1315                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1316                 break;
 1317 
 1318         default:
 1319                 error = ENOTTY;
 1320                 break;
 1321         }
 1322         PIPE_UNLOCK(mpipe);
 1323 out_unlocked:
 1324         return (error);
 1325 }
 1326 
 1327 static int
 1328 pipe_poll(fp, events, active_cred, td)
 1329         struct file *fp;
 1330         int events;
 1331         struct ucred *active_cred;
 1332         struct thread *td;
 1333 {
 1334         struct pipe *rpipe = fp->f_data;
 1335         struct pipe *wpipe;
 1336         int revents = 0;
 1337 #ifdef MAC
 1338         int error;
 1339 #endif
 1340 
 1341         wpipe = rpipe->pipe_peer;
 1342         PIPE_LOCK(rpipe);
 1343 #ifdef MAC
 1344         error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
 1345         if (error)
 1346                 goto locked_error;
 1347 #endif
 1348         if (events & (POLLIN | POLLRDNORM))
 1349                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1350                     (rpipe->pipe_buffer.cnt > 0))
 1351                         revents |= events & (POLLIN | POLLRDNORM);
 1352 
 1353         if (events & (POLLOUT | POLLWRNORM))
 1354                 if (wpipe->pipe_present != PIPE_ACTIVE ||
 1355                     (wpipe->pipe_state & PIPE_EOF) ||
 1356                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1357                      (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF))
 1358                         revents |= events & (POLLOUT | POLLWRNORM);
 1359 
 1360         if ((events & POLLINIGNEOF) == 0) {
 1361                 if (rpipe->pipe_state & PIPE_EOF) {
 1362                         revents |= (events & (POLLIN | POLLRDNORM));
 1363                         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1364                             (wpipe->pipe_state & PIPE_EOF))
 1365                                 revents |= POLLHUP;
 1366                 }
 1367         }
 1368 
 1369         if (revents == 0) {
 1370                 if (events & (POLLIN | POLLRDNORM)) {
 1371                         selrecord(td, &rpipe->pipe_sel);
 1372                         if (SEL_WAITING(&rpipe->pipe_sel))
 1373                                 rpipe->pipe_state |= PIPE_SEL;
 1374                 }
 1375 
 1376                 if (events & (POLLOUT | POLLWRNORM)) {
 1377                         selrecord(td, &wpipe->pipe_sel);
 1378                         if (SEL_WAITING(&wpipe->pipe_sel))
 1379                                 wpipe->pipe_state |= PIPE_SEL;
 1380                 }
 1381         }
 1382 #ifdef MAC
 1383 locked_error:
 1384 #endif
 1385         PIPE_UNLOCK(rpipe);
 1386 
 1387         return (revents);
 1388 }
 1389 
 1390 /*
 1391  * We shouldn't need locks here as we're doing a read and this should
 1392  * be a natural race.
 1393  */
 1394 static int
 1395 pipe_stat(fp, ub, active_cred, td)
 1396         struct file *fp;
 1397         struct stat *ub;
 1398         struct ucred *active_cred;
 1399         struct thread *td;
 1400 {
 1401         struct pipe *pipe = fp->f_data;
 1402 #ifdef MAC
 1403         int error;
 1404 
 1405         PIPE_LOCK(pipe);
 1406         error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
 1407         PIPE_UNLOCK(pipe);
 1408         if (error)
 1409                 return (error);
 1410 #endif
 1411         bzero(ub, sizeof(*ub));
 1412         ub->st_mode = S_IFIFO;
 1413         ub->st_blksize = PAGE_SIZE;
 1414         if (pipe->pipe_state & PIPE_DIRECTW)
 1415                 ub->st_size = pipe->pipe_map.cnt;
 1416         else
 1417                 ub->st_size = pipe->pipe_buffer.cnt;
 1418         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
 1419         ub->st_atim = pipe->pipe_atime;
 1420         ub->st_mtim = pipe->pipe_mtime;
 1421         ub->st_ctim = pipe->pipe_ctime;
 1422         ub->st_uid = fp->f_cred->cr_uid;
 1423         ub->st_gid = fp->f_cred->cr_gid;
 1424         ub->st_dev = pipedev_ino;
 1425         ub->st_ino = pipe->pipe_ino;
 1426         /*
 1427          * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
 1428          */
 1429         return (0);
 1430 }
 1431 
 1432 /* ARGSUSED */
 1433 static int
 1434 pipe_close(fp, td)
 1435         struct file *fp;
 1436         struct thread *td;
 1437 {
 1438         struct pipe *cpipe = fp->f_data;
 1439 
 1440         fp->f_ops = &badfileops;
 1441         fp->f_data = NULL;
 1442         funsetown(&cpipe->pipe_sigio);
 1443         pipeclose(cpipe);
 1444         return (0);
 1445 }
 1446 
 1447 static void
 1448 pipe_free_kmem(cpipe)
 1449         struct pipe *cpipe;
 1450 {
 1451 
 1452         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
 1453             ("pipe_free_kmem: pipe mutex locked"));
 1454 
 1455         if (cpipe->pipe_buffer.buffer != NULL) {
 1456                 atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
 1457                 vm_map_remove(pipe_map,
 1458                     (vm_offset_t)cpipe->pipe_buffer.buffer,
 1459                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
 1460                 cpipe->pipe_buffer.buffer = NULL;
 1461         }
 1462 #ifndef PIPE_NODIRECT
 1463         {
 1464                 cpipe->pipe_map.cnt = 0;
 1465                 cpipe->pipe_map.pos = 0;
 1466                 cpipe->pipe_map.npages = 0;
 1467         }
 1468 #endif
 1469 }
 1470 
 1471 /*
 1472  * shutdown the pipe
 1473  */
 1474 static void
 1475 pipeclose(cpipe)
 1476         struct pipe *cpipe;
 1477 {
 1478         struct pipepair *pp;
 1479         struct pipe *ppipe;
 1480         ino_t ino;
 1481 
 1482         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
 1483 
 1484         PIPE_LOCK(cpipe);
 1485         pipelock(cpipe, 0);
 1486         pp = cpipe->pipe_pair;
 1487 
 1488         pipeselwakeup(cpipe);
 1489 
 1490         /*
 1491          * If the other side is blocked, wake it up saying that
 1492          * we want to close it down.
 1493          */
 1494         cpipe->pipe_state |= PIPE_EOF;
 1495         while (cpipe->pipe_busy) {
 1496                 wakeup(cpipe);
 1497                 cpipe->pipe_state |= PIPE_WANT;
 1498                 pipeunlock(cpipe);
 1499                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1500                 pipelock(cpipe, 0);
 1501         }
 1502 
 1503 
 1504         /*
 1505          * Disconnect from peer, if any.
 1506          */
 1507         ppipe = cpipe->pipe_peer;
 1508         if (ppipe->pipe_present == PIPE_ACTIVE) {
 1509                 pipeselwakeup(ppipe);
 1510 
 1511                 ppipe->pipe_state |= PIPE_EOF;
 1512                 wakeup(ppipe);
 1513                 KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
 1514         }
 1515 
 1516         /*
 1517          * Mark this endpoint as free.  Release kmem resources.  We
 1518          * don't mark this endpoint as unused until we've finished
 1519          * doing that, or the pipe might disappear out from under
 1520          * us.
 1521          */
 1522         PIPE_UNLOCK(cpipe);
 1523         pipe_free_kmem(cpipe);
 1524         PIPE_LOCK(cpipe);
 1525         cpipe->pipe_present = PIPE_CLOSING;
 1526         pipeunlock(cpipe);
 1527 
 1528         /*
 1529          * knlist_clear() may sleep dropping the PIPE_MTX. Set the
 1530          * PIPE_FINALIZED, that allows other end to free the
 1531          * pipe_pair, only after the knotes are completely dismantled.
 1532          */
 1533         knlist_clear(&cpipe->pipe_sel.si_note, 1);
 1534         cpipe->pipe_present = PIPE_FINALIZED;
 1535         seldrain(&cpipe->pipe_sel);
 1536         knlist_destroy(&cpipe->pipe_sel.si_note);
 1537 
 1538         /*
 1539          * Postpone the destroy of the fake inode number allocated for
 1540          * our end, until pipe mtx is unlocked.
 1541          */
 1542         ino = cpipe->pipe_ino;
 1543 
 1544         /*
 1545          * If both endpoints are now closed, release the memory for the
 1546          * pipe pair.  If not, unlock.
 1547          */
 1548         if (ppipe->pipe_present == PIPE_FINALIZED) {
 1549                 PIPE_UNLOCK(cpipe);
 1550 #ifdef MAC
 1551                 mac_pipe_destroy(pp);
 1552 #endif
 1553                 uma_zfree(pipe_zone, cpipe->pipe_pair);
 1554         } else
 1555                 PIPE_UNLOCK(cpipe);
 1556 
 1557         if (ino > 0)
 1558                 free_unr(pipeino_unr, cpipe->pipe_ino);
 1559 }
 1560 
 1561 /*ARGSUSED*/
 1562 static int
 1563 pipe_kqfilter(struct file *fp, struct knote *kn)
 1564 {
 1565         struct pipe *cpipe;
 1566 
 1567         cpipe = kn->kn_fp->f_data;
 1568         PIPE_LOCK(cpipe);
 1569         switch (kn->kn_filter) {
 1570         case EVFILT_READ:
 1571                 kn->kn_fop = &pipe_rfiltops;
 1572                 break;
 1573         case EVFILT_WRITE:
 1574                 kn->kn_fop = &pipe_wfiltops;
 1575                 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
 1576                         /* other end of pipe has been closed */
 1577                         PIPE_UNLOCK(cpipe);
 1578                         return (EPIPE);
 1579                 }
 1580                 cpipe = cpipe->pipe_peer;
 1581                 break;
 1582         default:
 1583                 PIPE_UNLOCK(cpipe);
 1584                 return (EINVAL);
 1585         }
 1586 
 1587         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
 1588         PIPE_UNLOCK(cpipe);
 1589         return (0);
 1590 }
 1591 
 1592 static void
 1593 filt_pipedetach(struct knote *kn)
 1594 {
 1595         struct pipe *cpipe = (struct pipe *)kn->kn_fp->f_data;
 1596 
 1597         PIPE_LOCK(cpipe);
 1598         if (kn->kn_filter == EVFILT_WRITE)
 1599                 cpipe = cpipe->pipe_peer;
 1600         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
 1601         PIPE_UNLOCK(cpipe);
 1602 }
 1603 
 1604 /*ARGSUSED*/
 1605 static int
 1606 filt_piperead(struct knote *kn, long hint)
 1607 {
 1608         struct pipe *rpipe = kn->kn_fp->f_data;
 1609         struct pipe *wpipe = rpipe->pipe_peer;
 1610         int ret;
 1611 
 1612         PIPE_LOCK(rpipe);
 1613         kn->kn_data = rpipe->pipe_buffer.cnt;
 1614         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1615                 kn->kn_data = rpipe->pipe_map.cnt;
 1616 
 1617         if ((rpipe->pipe_state & PIPE_EOF) ||
 1618             wpipe->pipe_present != PIPE_ACTIVE ||
 1619             (wpipe->pipe_state & PIPE_EOF)) {
 1620                 kn->kn_flags |= EV_EOF;
 1621                 PIPE_UNLOCK(rpipe);
 1622                 return (1);
 1623         }
 1624         ret = kn->kn_data > 0;
 1625         PIPE_UNLOCK(rpipe);
 1626         return ret;
 1627 }
 1628 
 1629 /*ARGSUSED*/
 1630 static int
 1631 filt_pipewrite(struct knote *kn, long hint)
 1632 {
 1633         struct pipe *rpipe = kn->kn_fp->f_data;
 1634         struct pipe *wpipe = rpipe->pipe_peer;
 1635 
 1636         PIPE_LOCK(rpipe);
 1637         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1638             (wpipe->pipe_state & PIPE_EOF)) {
 1639                 kn->kn_data = 0;
 1640                 kn->kn_flags |= EV_EOF;
 1641                 PIPE_UNLOCK(rpipe);
 1642                 return (1);
 1643         }
 1644         kn->kn_data = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1645         if (wpipe->pipe_state & PIPE_DIRECTW)
 1646                 kn->kn_data = 0;
 1647 
 1648         PIPE_UNLOCK(rpipe);
 1649         return (kn->kn_data >= PIPE_BUF);
 1650 }

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