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

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