The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/sys_pipe.c

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    1 /*-
    2  * Copyright (c) 1996 John S. Dyson
    3  * Copyright (c) 2012 Giovanni Trematerra
    4  * All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice immediately at the beginning of the file, without modification,
   11  *    this list of conditions, and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Absolutely no warranty of function or purpose is made by the author
   16  *    John S. Dyson.
   17  * 4. Modifications may be freely made to this file if the above conditions
   18  *    are met.
   19  */
   20 
   21 /*
   22  * This file contains a high-performance replacement for the socket-based
   23  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
   24  * all features of sockets, but does do everything that pipes normally
   25  * do.
   26  */
   27 
   28 /*
   29  * This code has two modes of operation, a small write mode and a large
   30  * write mode.  The small write mode acts like conventional pipes with
   31  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
   32  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
   33  * and PIPE_SIZE in size, the sending process pins the underlying pages in
   34  * memory, and the receiving process copies directly from these pinned pages
   35  * in the sending process.
   36  *
   37  * If the sending process receives a signal, it is possible that it will
   38  * go away, and certainly its address space can change, because control
   39  * is returned back to the user-mode side.  In that case, the pipe code
   40  * arranges to copy the buffer supplied by the user process, to a pageable
   41  * kernel buffer, and the receiving process will grab the data from the
   42  * pageable kernel buffer.  Since signals don't happen all that often,
   43  * the copy operation is normally eliminated.
   44  *
   45  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
   46  * happen for small transfers so that the system will not spend all of
   47  * its time context switching.
   48  *
   49  * In order to limit the resource use of pipes, two sysctls exist:
   50  *
   51  * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
   52  * address space available to us in pipe_map. This value is normally
   53  * autotuned, but may also be loader tuned.
   54  *
   55  * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
   56  * memory in use by pipes.
   57  *
   58  * Based on how large pipekva is relative to maxpipekva, the following
   59  * will happen:
   60  *
   61  * 0% - 50%:
   62  *     New pipes are given 16K of memory backing, pipes may dynamically
   63  *     grow to as large as 64K where needed.
   64  * 50% - 75%:
   65  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   66  *     existing pipes may NOT grow.
   67  * 75% - 100%:
   68  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   69  *     existing pipes will be shrunk down to 4K whenever possible.
   70  *
   71  * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
   72  * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
   73  * resize which MUST occur for reverse-direction pipes when they are
   74  * first used.
   75  *
   76  * Additional information about the current state of pipes may be obtained
   77  * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
   78  * and kern.ipc.piperesizefail.
   79  *
   80  * Locking rules:  There are two locks present here:  A mutex, used via
   81  * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
   82  * the flag, as mutexes can not persist over uiomove.  The mutex
   83  * exists only to guard access to the flag, and is not in itself a
   84  * locking mechanism.  Also note that there is only a single mutex for
   85  * both directions of a pipe.
   86  *
   87  * As pipelock() may have to sleep before it can acquire the flag, it
   88  * is important to reread all data after a call to pipelock(); everything
   89  * in the structure may have changed.
   90  */
   91 
   92 #include <sys/cdefs.h>
   93 __FBSDID("$FreeBSD: releng/10.3/sys/kern/sys_pipe.c 285971 2015-07-28 18:37:23Z cem $");
   94 
   95 #include <sys/param.h>
   96 #include <sys/systm.h>
   97 #include <sys/conf.h>
   98 #include <sys/fcntl.h>
   99 #include <sys/file.h>
  100 #include <sys/filedesc.h>
  101 #include <sys/filio.h>
  102 #include <sys/kernel.h>
  103 #include <sys/lock.h>
  104 #include <sys/mutex.h>
  105 #include <sys/ttycom.h>
  106 #include <sys/stat.h>
  107 #include <sys/malloc.h>
  108 #include <sys/poll.h>
  109 #include <sys/selinfo.h>
  110 #include <sys/signalvar.h>
  111 #include <sys/syscallsubr.h>
  112 #include <sys/sysctl.h>
  113 #include <sys/sysproto.h>
  114 #include <sys/pipe.h>
  115 #include <sys/proc.h>
  116 #include <sys/vnode.h>
  117 #include <sys/uio.h>
  118 #include <sys/event.h>
  119 
  120 #include <security/mac/mac_framework.h>
  121 
  122 #include <vm/vm.h>
  123 #include <vm/vm_param.h>
  124 #include <vm/vm_object.h>
  125 #include <vm/vm_kern.h>
  126 #include <vm/vm_extern.h>
  127 #include <vm/pmap.h>
  128 #include <vm/vm_map.h>
  129 #include <vm/vm_page.h>
  130 #include <vm/uma.h>
  131 
  132 /*
  133  * Use this define if you want to disable *fancy* VM things.  Expect an
  134  * approx 30% decrease in transfer rate.  This could be useful for
  135  * NetBSD or OpenBSD.
  136  */
  137 /* #define PIPE_NODIRECT */
  138 
  139 #define PIPE_PEER(pipe) \
  140         (((pipe)->pipe_state & PIPE_NAMED) ? (pipe) : ((pipe)->pipe_peer))
  141 
  142 /*
  143  * interfaces to the outside world
  144  */
  145 static fo_rdwr_t        pipe_read;
  146 static fo_rdwr_t        pipe_write;
  147 static fo_truncate_t    pipe_truncate;
  148 static fo_ioctl_t       pipe_ioctl;
  149 static fo_poll_t        pipe_poll;
  150 static fo_kqfilter_t    pipe_kqfilter;
  151 static fo_stat_t        pipe_stat;
  152 static fo_close_t       pipe_close;
  153 static fo_chmod_t       pipe_chmod;
  154 static fo_chown_t       pipe_chown;
  155 
  156 struct fileops pipeops = {
  157         .fo_read = pipe_read,
  158         .fo_write = pipe_write,
  159         .fo_truncate = pipe_truncate,
  160         .fo_ioctl = pipe_ioctl,
  161         .fo_poll = pipe_poll,
  162         .fo_kqfilter = pipe_kqfilter,
  163         .fo_stat = pipe_stat,
  164         .fo_close = pipe_close,
  165         .fo_chmod = pipe_chmod,
  166         .fo_chown = pipe_chown,
  167         .fo_sendfile = invfo_sendfile,
  168         .fo_flags = DFLAG_PASSABLE
  169 };
  170 
  171 static void     filt_pipedetach(struct knote *kn);
  172 static void     filt_pipedetach_notsup(struct knote *kn);
  173 static int      filt_pipenotsup(struct knote *kn, long hint);
  174 static int      filt_piperead(struct knote *kn, long hint);
  175 static int      filt_pipewrite(struct knote *kn, long hint);
  176 
  177 static struct filterops pipe_nfiltops = {
  178         .f_isfd = 1,
  179         .f_detach = filt_pipedetach_notsup,
  180         .f_event = filt_pipenotsup
  181 };
  182 static struct filterops pipe_rfiltops = {
  183         .f_isfd = 1,
  184         .f_detach = filt_pipedetach,
  185         .f_event = filt_piperead
  186 };
  187 static struct filterops pipe_wfiltops = {
  188         .f_isfd = 1,
  189         .f_detach = filt_pipedetach,
  190         .f_event = filt_pipewrite
  191 };
  192 
  193 /*
  194  * Default pipe buffer size(s), this can be kind-of large now because pipe
  195  * space is pageable.  The pipe code will try to maintain locality of
  196  * reference for performance reasons, so small amounts of outstanding I/O
  197  * will not wipe the cache.
  198  */
  199 #define MINPIPESIZE (PIPE_SIZE/3)
  200 #define MAXPIPESIZE (2*PIPE_SIZE/3)
  201 
  202 static long amountpipekva;
  203 static int pipefragretry;
  204 static int pipeallocfail;
  205 static int piperesizefail;
  206 static int piperesizeallowed = 1;
  207 
  208 SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN,
  209            &maxpipekva, 0, "Pipe KVA limit");
  210 SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
  211            &amountpipekva, 0, "Pipe KVA usage");
  212 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
  213           &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
  214 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
  215           &pipeallocfail, 0, "Pipe allocation failures");
  216 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
  217           &piperesizefail, 0, "Pipe resize failures");
  218 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
  219           &piperesizeallowed, 0, "Pipe resizing allowed");
  220 
  221 static void pipeinit(void *dummy __unused);
  222 static void pipeclose(struct pipe *cpipe);
  223 static void pipe_free_kmem(struct pipe *cpipe);
  224 static void pipe_create(struct pipe *pipe, int backing);
  225 static void pipe_paircreate(struct thread *td, struct pipepair **p_pp);
  226 static __inline int pipelock(struct pipe *cpipe, int catch);
  227 static __inline void pipeunlock(struct pipe *cpipe);
  228 #ifndef PIPE_NODIRECT
  229 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
  230 static void pipe_destroy_write_buffer(struct pipe *wpipe);
  231 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
  232 static void pipe_clone_write_buffer(struct pipe *wpipe);
  233 #endif
  234 static int pipespace(struct pipe *cpipe, int size);
  235 static int pipespace_new(struct pipe *cpipe, int size);
  236 
  237 static int      pipe_zone_ctor(void *mem, int size, void *arg, int flags);
  238 static int      pipe_zone_init(void *mem, int size, int flags);
  239 static void     pipe_zone_fini(void *mem, int size);
  240 
  241 static uma_zone_t pipe_zone;
  242 static struct unrhdr *pipeino_unr;
  243 static dev_t pipedev_ino;
  244 
  245 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
  246 
  247 static void
  248 pipeinit(void *dummy __unused)
  249 {
  250 
  251         pipe_zone = uma_zcreate("pipe", sizeof(struct pipepair),
  252             pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
  253             UMA_ALIGN_PTR, 0);
  254         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
  255         pipeino_unr = new_unrhdr(1, INT32_MAX, NULL);
  256         KASSERT(pipeino_unr != NULL, ("pipe fake inodes not initialized"));
  257         pipedev_ino = devfs_alloc_cdp_inode();
  258         KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
  259 }
  260 
  261 static int
  262 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
  263 {
  264         struct pipepair *pp;
  265         struct pipe *rpipe, *wpipe;
  266 
  267         KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
  268 
  269         pp = (struct pipepair *)mem;
  270 
  271         /*
  272          * We zero both pipe endpoints to make sure all the kmem pointers
  273          * are NULL, flag fields are zero'd, etc.  We timestamp both
  274          * endpoints with the same time.
  275          */
  276         rpipe = &pp->pp_rpipe;
  277         bzero(rpipe, sizeof(*rpipe));
  278         vfs_timestamp(&rpipe->pipe_ctime);
  279         rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
  280 
  281         wpipe = &pp->pp_wpipe;
  282         bzero(wpipe, sizeof(*wpipe));
  283         wpipe->pipe_ctime = rpipe->pipe_ctime;
  284         wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
  285 
  286         rpipe->pipe_peer = wpipe;
  287         rpipe->pipe_pair = pp;
  288         wpipe->pipe_peer = rpipe;
  289         wpipe->pipe_pair = pp;
  290 
  291         /*
  292          * Mark both endpoints as present; they will later get free'd
  293          * one at a time.  When both are free'd, then the whole pair
  294          * is released.
  295          */
  296         rpipe->pipe_present = PIPE_ACTIVE;
  297         wpipe->pipe_present = PIPE_ACTIVE;
  298 
  299         /*
  300          * Eventually, the MAC Framework may initialize the label
  301          * in ctor or init, but for now we do it elswhere to avoid
  302          * blocking in ctor or init.
  303          */
  304         pp->pp_label = NULL;
  305 
  306         return (0);
  307 }
  308 
  309 static int
  310 pipe_zone_init(void *mem, int size, int flags)
  311 {
  312         struct pipepair *pp;
  313 
  314         KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
  315 
  316         pp = (struct pipepair *)mem;
  317 
  318         mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF);
  319         return (0);
  320 }
  321 
  322 static void
  323 pipe_zone_fini(void *mem, int size)
  324 {
  325         struct pipepair *pp;
  326 
  327         KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
  328 
  329         pp = (struct pipepair *)mem;
  330 
  331         mtx_destroy(&pp->pp_mtx);
  332 }
  333 
  334 static void
  335 pipe_paircreate(struct thread *td, struct pipepair **p_pp)
  336 {
  337         struct pipepair *pp;
  338         struct pipe *rpipe, *wpipe;
  339 
  340         *p_pp = pp = uma_zalloc(pipe_zone, M_WAITOK);
  341 #ifdef MAC
  342         /*
  343          * The MAC label is shared between the connected endpoints.  As a
  344          * result mac_pipe_init() and mac_pipe_create() are called once
  345          * for the pair, and not on the endpoints.
  346          */
  347         mac_pipe_init(pp);
  348         mac_pipe_create(td->td_ucred, pp);
  349 #endif
  350         rpipe = &pp->pp_rpipe;
  351         wpipe = &pp->pp_wpipe;
  352 
  353         knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
  354         knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
  355 
  356         /* Only the forward direction pipe is backed by default */
  357         pipe_create(rpipe, 1);
  358         pipe_create(wpipe, 0);
  359 
  360         rpipe->pipe_state |= PIPE_DIRECTOK;
  361         wpipe->pipe_state |= PIPE_DIRECTOK;
  362 }
  363 
  364 void
  365 pipe_named_ctor(struct pipe **ppipe, struct thread *td)
  366 {
  367         struct pipepair *pp;
  368 
  369         pipe_paircreate(td, &pp);
  370         pp->pp_rpipe.pipe_state |= PIPE_NAMED;
  371         *ppipe = &pp->pp_rpipe;
  372 }
  373 
  374 void
  375 pipe_dtor(struct pipe *dpipe)
  376 {
  377         struct pipe *peer;
  378         ino_t ino;
  379 
  380         ino = dpipe->pipe_ino;
  381         peer = (dpipe->pipe_state & PIPE_NAMED) != 0 ? dpipe->pipe_peer : NULL;
  382         funsetown(&dpipe->pipe_sigio);
  383         pipeclose(dpipe);
  384         if (peer != NULL) {
  385                 funsetown(&peer->pipe_sigio);
  386                 pipeclose(peer);
  387         }
  388         if (ino != 0 && ino != (ino_t)-1)
  389                 free_unr(pipeino_unr, ino);
  390 }
  391 
  392 /*
  393  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
  394  * the zone pick up the pieces via pipeclose().
  395  */
  396 int
  397 kern_pipe(struct thread *td, int fildes[2])
  398 {
  399 
  400         return (kern_pipe2(td, fildes, 0));
  401 }
  402 
  403 int
  404 kern_pipe2(struct thread *td, int fildes[2], int flags)
  405 {
  406         struct filedesc *fdp; 
  407         struct file *rf, *wf;
  408         struct pipe *rpipe, *wpipe;
  409         struct pipepair *pp;
  410         int fd, fflags, error;
  411 
  412         fdp = td->td_proc->p_fd;
  413         pipe_paircreate(td, &pp);
  414         rpipe = &pp->pp_rpipe;
  415         wpipe = &pp->pp_wpipe;
  416         error = falloc(td, &rf, &fd, flags);
  417         if (error) {
  418                 pipeclose(rpipe);
  419                 pipeclose(wpipe);
  420                 return (error);
  421         }
  422         /* An extra reference on `rf' has been held for us by falloc(). */
  423         fildes[0] = fd;
  424 
  425         fflags = FREAD | FWRITE;
  426         if ((flags & O_NONBLOCK) != 0)
  427                 fflags |= FNONBLOCK;
  428 
  429         /*
  430          * Warning: once we've gotten past allocation of the fd for the
  431          * read-side, we can only drop the read side via fdrop() in order
  432          * to avoid races against processes which manage to dup() the read
  433          * side while we are blocked trying to allocate the write side.
  434          */
  435         finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
  436         error = falloc(td, &wf, &fd, flags);
  437         if (error) {
  438                 fdclose(fdp, rf, fildes[0], td);
  439                 fdrop(rf, td);
  440                 /* rpipe has been closed by fdrop(). */
  441                 pipeclose(wpipe);
  442                 return (error);
  443         }
  444         /* An extra reference on `wf' has been held for us by falloc(). */
  445         finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
  446         fdrop(wf, td);
  447         fildes[1] = fd;
  448         fdrop(rf, td);
  449 
  450         return (0);
  451 }
  452 
  453 /* ARGSUSED */
  454 int
  455 sys_pipe(struct thread *td, struct pipe_args *uap)
  456 {
  457         int error;
  458         int fildes[2];
  459 
  460         error = kern_pipe(td, fildes);
  461         if (error)
  462                 return (error);
  463 
  464         td->td_retval[0] = fildes[0];
  465         td->td_retval[1] = fildes[1];
  466 
  467         return (0);
  468 }
  469 
  470 int
  471 sys_pipe2(struct thread *td, struct pipe2_args *uap)
  472 {
  473         int error, fildes[2];
  474 
  475         if (uap->flags & ~(O_CLOEXEC | O_NONBLOCK))
  476                 return (EINVAL);
  477         error = kern_pipe2(td, fildes, uap->flags);
  478         if (error)
  479                 return (error);
  480         error = copyout(fildes, uap->fildes, 2 * sizeof(int));
  481         if (error) {
  482                 (void)kern_close(td, fildes[0]);
  483                 (void)kern_close(td, fildes[1]);
  484         }
  485         return (error);
  486 }
  487 
  488 /*
  489  * Allocate kva for pipe circular buffer, the space is pageable
  490  * This routine will 'realloc' the size of a pipe safely, if it fails
  491  * it will retain the old buffer.
  492  * If it fails it will return ENOMEM.
  493  */
  494 static int
  495 pipespace_new(cpipe, size)
  496         struct pipe *cpipe;
  497         int size;
  498 {
  499         caddr_t buffer;
  500         int error, cnt, firstseg;
  501         static int curfail = 0;
  502         static struct timeval lastfail;
  503 
  504         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
  505         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
  506                 ("pipespace: resize of direct writes not allowed"));
  507 retry:
  508         cnt = cpipe->pipe_buffer.cnt;
  509         if (cnt > size)
  510                 size = cnt;
  511 
  512         size = round_page(size);
  513         buffer = (caddr_t) vm_map_min(pipe_map);
  514 
  515         error = vm_map_find(pipe_map, NULL, 0,
  516                 (vm_offset_t *) &buffer, size, 0, VMFS_ANY_SPACE,
  517                 VM_PROT_ALL, VM_PROT_ALL, 0);
  518         if (error != KERN_SUCCESS) {
  519                 if ((cpipe->pipe_buffer.buffer == NULL) &&
  520                         (size > SMALL_PIPE_SIZE)) {
  521                         size = SMALL_PIPE_SIZE;
  522                         pipefragretry++;
  523                         goto retry;
  524                 }
  525                 if (cpipe->pipe_buffer.buffer == NULL) {
  526                         pipeallocfail++;
  527                         if (ppsratecheck(&lastfail, &curfail, 1))
  528                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
  529                 } else {
  530                         piperesizefail++;
  531                 }
  532                 return (ENOMEM);
  533         }
  534 
  535         /* copy data, then free old resources if we're resizing */
  536         if (cnt > 0) {
  537                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
  538                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
  539                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  540                                 buffer, firstseg);
  541                         if ((cnt - firstseg) > 0)
  542                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
  543                                         cpipe->pipe_buffer.in);
  544                 } else {
  545                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  546                                 buffer, cnt);
  547                 }
  548         }
  549         pipe_free_kmem(cpipe);
  550         cpipe->pipe_buffer.buffer = buffer;
  551         cpipe->pipe_buffer.size = size;
  552         cpipe->pipe_buffer.in = cnt;
  553         cpipe->pipe_buffer.out = 0;
  554         cpipe->pipe_buffer.cnt = cnt;
  555         atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
  556         return (0);
  557 }
  558 
  559 /*
  560  * Wrapper for pipespace_new() that performs locking assertions.
  561  */
  562 static int
  563 pipespace(cpipe, size)
  564         struct pipe *cpipe;
  565         int size;
  566 {
  567 
  568         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  569                 ("Unlocked pipe passed to pipespace"));
  570         return (pipespace_new(cpipe, size));
  571 }
  572 
  573 /*
  574  * lock a pipe for I/O, blocking other access
  575  */
  576 static __inline int
  577 pipelock(cpipe, catch)
  578         struct pipe *cpipe;
  579         int catch;
  580 {
  581         int error;
  582 
  583         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  584         while (cpipe->pipe_state & PIPE_LOCKFL) {
  585                 cpipe->pipe_state |= PIPE_LWANT;
  586                 error = msleep(cpipe, PIPE_MTX(cpipe),
  587                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  588                     "pipelk", 0);
  589                 if (error != 0)
  590                         return (error);
  591         }
  592         cpipe->pipe_state |= PIPE_LOCKFL;
  593         return (0);
  594 }
  595 
  596 /*
  597  * unlock a pipe I/O lock
  598  */
  599 static __inline void
  600 pipeunlock(cpipe)
  601         struct pipe *cpipe;
  602 {
  603 
  604         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  605         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  606                 ("Unlocked pipe passed to pipeunlock"));
  607         cpipe->pipe_state &= ~PIPE_LOCKFL;
  608         if (cpipe->pipe_state & PIPE_LWANT) {
  609                 cpipe->pipe_state &= ~PIPE_LWANT;
  610                 wakeup(cpipe);
  611         }
  612 }
  613 
  614 void
  615 pipeselwakeup(cpipe)
  616         struct pipe *cpipe;
  617 {
  618 
  619         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  620         if (cpipe->pipe_state & PIPE_SEL) {
  621                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
  622                 if (!SEL_WAITING(&cpipe->pipe_sel))
  623                         cpipe->pipe_state &= ~PIPE_SEL;
  624         }
  625         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  626                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  627         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
  628 }
  629 
  630 /*
  631  * Initialize and allocate VM and memory for pipe.  The structure
  632  * will start out zero'd from the ctor, so we just manage the kmem.
  633  */
  634 static void
  635 pipe_create(pipe, backing)
  636         struct pipe *pipe;
  637         int backing;
  638 {
  639 
  640         if (backing) {
  641                 /*
  642                  * Note that these functions can fail if pipe map is exhausted
  643                  * (as a result of too many pipes created), but we ignore the
  644                  * error as it is not fatal and could be provoked by
  645                  * unprivileged users. The only consequence is worse performance
  646                  * with given pipe.
  647                  */
  648                 if (amountpipekva > maxpipekva / 2)
  649                         (void)pipespace_new(pipe, SMALL_PIPE_SIZE);
  650                 else
  651                         (void)pipespace_new(pipe, PIPE_SIZE);
  652         }
  653 
  654         pipe->pipe_ino = -1;
  655 }
  656 
  657 /* ARGSUSED */
  658 static int
  659 pipe_read(fp, uio, active_cred, flags, td)
  660         struct file *fp;
  661         struct uio *uio;
  662         struct ucred *active_cred;
  663         struct thread *td;
  664         int flags;
  665 {
  666         struct pipe *rpipe;
  667         int error;
  668         int nread = 0;
  669         int size;
  670 
  671         rpipe = fp->f_data;
  672         PIPE_LOCK(rpipe);
  673         ++rpipe->pipe_busy;
  674         error = pipelock(rpipe, 1);
  675         if (error)
  676                 goto unlocked_error;
  677 
  678 #ifdef MAC
  679         error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
  680         if (error)
  681                 goto locked_error;
  682 #endif
  683         if (amountpipekva > (3 * maxpipekva) / 4) {
  684                 if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
  685                         (rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
  686                         (rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
  687                         (piperesizeallowed == 1)) {
  688                         PIPE_UNLOCK(rpipe);
  689                         pipespace(rpipe, SMALL_PIPE_SIZE);
  690                         PIPE_LOCK(rpipe);
  691                 }
  692         }
  693 
  694         while (uio->uio_resid) {
  695                 /*
  696                  * normal pipe buffer receive
  697                  */
  698                 if (rpipe->pipe_buffer.cnt > 0) {
  699                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  700                         if (size > rpipe->pipe_buffer.cnt)
  701                                 size = rpipe->pipe_buffer.cnt;
  702                         if (size > uio->uio_resid)
  703                                 size = uio->uio_resid;
  704 
  705                         PIPE_UNLOCK(rpipe);
  706                         error = uiomove(
  707                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  708                             size, uio);
  709                         PIPE_LOCK(rpipe);
  710                         if (error)
  711                                 break;
  712 
  713                         rpipe->pipe_buffer.out += size;
  714                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  715                                 rpipe->pipe_buffer.out = 0;
  716 
  717                         rpipe->pipe_buffer.cnt -= size;
  718 
  719                         /*
  720                          * If there is no more to read in the pipe, reset
  721                          * its pointers to the beginning.  This improves
  722                          * cache hit stats.
  723                          */
  724                         if (rpipe->pipe_buffer.cnt == 0) {
  725                                 rpipe->pipe_buffer.in = 0;
  726                                 rpipe->pipe_buffer.out = 0;
  727                         }
  728                         nread += size;
  729 #ifndef PIPE_NODIRECT
  730                 /*
  731                  * Direct copy, bypassing a kernel buffer.
  732                  */
  733                 } else if ((size = rpipe->pipe_map.cnt) &&
  734                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  735                         if (size > uio->uio_resid)
  736                                 size = (u_int) uio->uio_resid;
  737 
  738                         PIPE_UNLOCK(rpipe);
  739                         error = uiomove_fromphys(rpipe->pipe_map.ms,
  740                             rpipe->pipe_map.pos, size, uio);
  741                         PIPE_LOCK(rpipe);
  742                         if (error)
  743                                 break;
  744                         nread += size;
  745                         rpipe->pipe_map.pos += size;
  746                         rpipe->pipe_map.cnt -= size;
  747                         if (rpipe->pipe_map.cnt == 0) {
  748                                 rpipe->pipe_state &= ~(PIPE_DIRECTW|PIPE_WANTW);
  749                                 wakeup(rpipe);
  750                         }
  751 #endif
  752                 } else {
  753                         /*
  754                          * detect EOF condition
  755                          * read returns 0 on EOF, no need to set error
  756                          */
  757                         if (rpipe->pipe_state & PIPE_EOF)
  758                                 break;
  759 
  760                         /*
  761                          * If the "write-side" has been blocked, wake it up now.
  762                          */
  763                         if (rpipe->pipe_state & PIPE_WANTW) {
  764                                 rpipe->pipe_state &= ~PIPE_WANTW;
  765                                 wakeup(rpipe);
  766                         }
  767 
  768                         /*
  769                          * Break if some data was read.
  770                          */
  771                         if (nread > 0)
  772                                 break;
  773 
  774                         /*
  775                          * Unlock the pipe buffer for our remaining processing.
  776                          * We will either break out with an error or we will
  777                          * sleep and relock to loop.
  778                          */
  779                         pipeunlock(rpipe);
  780 
  781                         /*
  782                          * Handle non-blocking mode operation or
  783                          * wait for more data.
  784                          */
  785                         if (fp->f_flag & FNONBLOCK) {
  786                                 error = EAGAIN;
  787                         } else {
  788                                 rpipe->pipe_state |= PIPE_WANTR;
  789                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  790                                     PRIBIO | PCATCH,
  791                                     "piperd", 0)) == 0)
  792                                         error = pipelock(rpipe, 1);
  793                         }
  794                         if (error)
  795                                 goto unlocked_error;
  796                 }
  797         }
  798 #ifdef MAC
  799 locked_error:
  800 #endif
  801         pipeunlock(rpipe);
  802 
  803         /* XXX: should probably do this before getting any locks. */
  804         if (error == 0)
  805                 vfs_timestamp(&rpipe->pipe_atime);
  806 unlocked_error:
  807         --rpipe->pipe_busy;
  808 
  809         /*
  810          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  811          */
  812         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  813                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  814                 wakeup(rpipe);
  815         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  816                 /*
  817                  * Handle write blocking hysteresis.
  818                  */
  819                 if (rpipe->pipe_state & PIPE_WANTW) {
  820                         rpipe->pipe_state &= ~PIPE_WANTW;
  821                         wakeup(rpipe);
  822                 }
  823         }
  824 
  825         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  826                 pipeselwakeup(rpipe);
  827 
  828         PIPE_UNLOCK(rpipe);
  829         return (error);
  830 }
  831 
  832 #ifndef PIPE_NODIRECT
  833 /*
  834  * Map the sending processes' buffer into kernel space and wire it.
  835  * This is similar to a physical write operation.
  836  */
  837 static int
  838 pipe_build_write_buffer(wpipe, uio)
  839         struct pipe *wpipe;
  840         struct uio *uio;
  841 {
  842         u_int size;
  843         int i;
  844 
  845         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  846         KASSERT(wpipe->pipe_state & PIPE_DIRECTW,
  847                 ("Clone attempt on non-direct write pipe!"));
  848 
  849         if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
  850                 size = wpipe->pipe_buffer.size;
  851         else
  852                 size = uio->uio_iov->iov_len;
  853 
  854         if ((i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
  855             (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
  856             wpipe->pipe_map.ms, PIPENPAGES)) < 0)
  857                 return (EFAULT);
  858 
  859 /*
  860  * set up the control block
  861  */
  862         wpipe->pipe_map.npages = i;
  863         wpipe->pipe_map.pos =
  864             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  865         wpipe->pipe_map.cnt = size;
  866 
  867 /*
  868  * and update the uio data
  869  */
  870 
  871         uio->uio_iov->iov_len -= size;
  872         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  873         if (uio->uio_iov->iov_len == 0)
  874                 uio->uio_iov++;
  875         uio->uio_resid -= size;
  876         uio->uio_offset += size;
  877         return (0);
  878 }
  879 
  880 /*
  881  * unmap and unwire the process buffer
  882  */
  883 static void
  884 pipe_destroy_write_buffer(wpipe)
  885         struct pipe *wpipe;
  886 {
  887 
  888         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  889         vm_page_unhold_pages(wpipe->pipe_map.ms, wpipe->pipe_map.npages);
  890         wpipe->pipe_map.npages = 0;
  891 }
  892 
  893 /*
  894  * In the case of a signal, the writing process might go away.  This
  895  * code copies the data into the circular buffer so that the source
  896  * pages can be freed without loss of data.
  897  */
  898 static void
  899 pipe_clone_write_buffer(wpipe)
  900         struct pipe *wpipe;
  901 {
  902         struct uio uio;
  903         struct iovec iov;
  904         int size;
  905         int pos;
  906 
  907         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  908         size = wpipe->pipe_map.cnt;
  909         pos = wpipe->pipe_map.pos;
  910 
  911         wpipe->pipe_buffer.in = size;
  912         wpipe->pipe_buffer.out = 0;
  913         wpipe->pipe_buffer.cnt = size;
  914         wpipe->pipe_state &= ~PIPE_DIRECTW;
  915 
  916         PIPE_UNLOCK(wpipe);
  917         iov.iov_base = wpipe->pipe_buffer.buffer;
  918         iov.iov_len = size;
  919         uio.uio_iov = &iov;
  920         uio.uio_iovcnt = 1;
  921         uio.uio_offset = 0;
  922         uio.uio_resid = size;
  923         uio.uio_segflg = UIO_SYSSPACE;
  924         uio.uio_rw = UIO_READ;
  925         uio.uio_td = curthread;
  926         uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
  927         PIPE_LOCK(wpipe);
  928         pipe_destroy_write_buffer(wpipe);
  929 }
  930 
  931 /*
  932  * This implements the pipe buffer write mechanism.  Note that only
  933  * a direct write OR a normal pipe write can be pending at any given time.
  934  * If there are any characters in the pipe buffer, the direct write will
  935  * be deferred until the receiving process grabs all of the bytes from
  936  * the pipe buffer.  Then the direct mapping write is set-up.
  937  */
  938 static int
  939 pipe_direct_write(wpipe, uio)
  940         struct pipe *wpipe;
  941         struct uio *uio;
  942 {
  943         int error;
  944 
  945 retry:
  946         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  947         error = pipelock(wpipe, 1);
  948         if (error != 0)
  949                 goto error1;
  950         if ((wpipe->pipe_state & PIPE_EOF) != 0) {
  951                 error = EPIPE;
  952                 pipeunlock(wpipe);
  953                 goto error1;
  954         }
  955         while (wpipe->pipe_state & PIPE_DIRECTW) {
  956                 if (wpipe->pipe_state & PIPE_WANTR) {
  957                         wpipe->pipe_state &= ~PIPE_WANTR;
  958                         wakeup(wpipe);
  959                 }
  960                 pipeselwakeup(wpipe);
  961                 wpipe->pipe_state |= PIPE_WANTW;
  962                 pipeunlock(wpipe);
  963                 error = msleep(wpipe, PIPE_MTX(wpipe),
  964                     PRIBIO | PCATCH, "pipdww", 0);
  965                 if (error)
  966                         goto error1;
  967                 else
  968                         goto retry;
  969         }
  970         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  971         if (wpipe->pipe_buffer.cnt > 0) {
  972                 if (wpipe->pipe_state & PIPE_WANTR) {
  973                         wpipe->pipe_state &= ~PIPE_WANTR;
  974                         wakeup(wpipe);
  975                 }
  976                 pipeselwakeup(wpipe);
  977                 wpipe->pipe_state |= PIPE_WANTW;
  978                 pipeunlock(wpipe);
  979                 error = msleep(wpipe, PIPE_MTX(wpipe),
  980                     PRIBIO | PCATCH, "pipdwc", 0);
  981                 if (error)
  982                         goto error1;
  983                 else
  984                         goto retry;
  985         }
  986 
  987         wpipe->pipe_state |= PIPE_DIRECTW;
  988 
  989         PIPE_UNLOCK(wpipe);
  990         error = pipe_build_write_buffer(wpipe, uio);
  991         PIPE_LOCK(wpipe);
  992         if (error) {
  993                 wpipe->pipe_state &= ~PIPE_DIRECTW;
  994                 pipeunlock(wpipe);
  995                 goto error1;
  996         }
  997 
  998         error = 0;
  999         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
 1000                 if (wpipe->pipe_state & PIPE_EOF) {
 1001                         pipe_destroy_write_buffer(wpipe);
 1002                         pipeselwakeup(wpipe);
 1003                         pipeunlock(wpipe);
 1004                         error = EPIPE;
 1005                         goto error1;
 1006                 }
 1007                 if (wpipe->pipe_state & PIPE_WANTR) {
 1008                         wpipe->pipe_state &= ~PIPE_WANTR;
 1009                         wakeup(wpipe);
 1010                 }
 1011                 pipeselwakeup(wpipe);
 1012                 wpipe->pipe_state |= PIPE_WANTW;
 1013                 pipeunlock(wpipe);
 1014                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
 1015                     "pipdwt", 0);
 1016                 pipelock(wpipe, 0);
 1017         }
 1018 
 1019         if (wpipe->pipe_state & PIPE_EOF)
 1020                 error = EPIPE;
 1021         if (wpipe->pipe_state & PIPE_DIRECTW) {
 1022                 /*
 1023                  * this bit of trickery substitutes a kernel buffer for
 1024                  * the process that might be going away.
 1025                  */
 1026                 pipe_clone_write_buffer(wpipe);
 1027         } else {
 1028                 pipe_destroy_write_buffer(wpipe);
 1029         }
 1030         pipeunlock(wpipe);
 1031         return (error);
 1032 
 1033 error1:
 1034         wakeup(wpipe);
 1035         return (error);
 1036 }
 1037 #endif
 1038 
 1039 static int
 1040 pipe_write(fp, uio, active_cred, flags, td)
 1041         struct file *fp;
 1042         struct uio *uio;
 1043         struct ucred *active_cred;
 1044         struct thread *td;
 1045         int flags;
 1046 {
 1047         int error = 0;
 1048         int desiredsize;
 1049         ssize_t orig_resid;
 1050         struct pipe *wpipe, *rpipe;
 1051 
 1052         rpipe = fp->f_data;
 1053         wpipe = PIPE_PEER(rpipe);
 1054         PIPE_LOCK(rpipe);
 1055         error = pipelock(wpipe, 1);
 1056         if (error) {
 1057                 PIPE_UNLOCK(rpipe);
 1058                 return (error);
 1059         }
 1060         /*
 1061          * detect loss of pipe read side, issue SIGPIPE if lost.
 1062          */
 1063         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1064             (wpipe->pipe_state & PIPE_EOF)) {
 1065                 pipeunlock(wpipe);
 1066                 PIPE_UNLOCK(rpipe);
 1067                 return (EPIPE);
 1068         }
 1069 #ifdef MAC
 1070         error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
 1071         if (error) {
 1072                 pipeunlock(wpipe);
 1073                 PIPE_UNLOCK(rpipe);
 1074                 return (error);
 1075         }
 1076 #endif
 1077         ++wpipe->pipe_busy;
 1078 
 1079         /* Choose a larger size if it's advantageous */
 1080         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
 1081         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
 1082                 if (piperesizeallowed != 1)
 1083                         break;
 1084                 if (amountpipekva > maxpipekva / 2)
 1085                         break;
 1086                 if (desiredsize == BIG_PIPE_SIZE)
 1087                         break;
 1088                 desiredsize = desiredsize * 2;
 1089         }
 1090 
 1091         /* Choose a smaller size if we're in a OOM situation */
 1092         if ((amountpipekva > (3 * maxpipekva) / 4) &&
 1093                 (wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
 1094                 (wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
 1095                 (piperesizeallowed == 1))
 1096                 desiredsize = SMALL_PIPE_SIZE;
 1097 
 1098         /* Resize if the above determined that a new size was necessary */
 1099         if ((desiredsize != wpipe->pipe_buffer.size) &&
 1100                 ((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
 1101                 PIPE_UNLOCK(wpipe);
 1102                 pipespace(wpipe, desiredsize);
 1103                 PIPE_LOCK(wpipe);
 1104         }
 1105         if (wpipe->pipe_buffer.size == 0) {
 1106                 /*
 1107                  * This can only happen for reverse direction use of pipes
 1108                  * in a complete OOM situation.
 1109                  */
 1110                 error = ENOMEM;
 1111                 --wpipe->pipe_busy;
 1112                 pipeunlock(wpipe);
 1113                 PIPE_UNLOCK(wpipe);
 1114                 return (error);
 1115         }
 1116 
 1117         pipeunlock(wpipe);
 1118 
 1119         orig_resid = uio->uio_resid;
 1120 
 1121         while (uio->uio_resid) {
 1122                 int space;
 1123 
 1124                 pipelock(wpipe, 0);
 1125                 if (wpipe->pipe_state & PIPE_EOF) {
 1126                         pipeunlock(wpipe);
 1127                         error = EPIPE;
 1128                         break;
 1129                 }
 1130 #ifndef PIPE_NODIRECT
 1131                 /*
 1132                  * If the transfer is large, we can gain performance if
 1133                  * we do process-to-process copies directly.
 1134                  * If the write is non-blocking, we don't use the
 1135                  * direct write mechanism.
 1136                  *
 1137                  * The direct write mechanism will detect the reader going
 1138                  * away on us.
 1139                  */
 1140                 if (uio->uio_segflg == UIO_USERSPACE &&
 1141                     uio->uio_iov->iov_len >= PIPE_MINDIRECT &&
 1142                     wpipe->pipe_buffer.size >= PIPE_MINDIRECT &&
 1143                     (fp->f_flag & FNONBLOCK) == 0) {
 1144                         pipeunlock(wpipe);
 1145                         error = pipe_direct_write(wpipe, uio);
 1146                         if (error)
 1147                                 break;
 1148                         continue;
 1149                 }
 1150 #endif
 1151 
 1152                 /*
 1153                  * Pipe buffered writes cannot be coincidental with
 1154                  * direct writes.  We wait until the currently executing
 1155                  * direct write is completed before we start filling the
 1156                  * pipe buffer.  We break out if a signal occurs or the
 1157                  * reader goes away.
 1158                  */
 1159                 if (wpipe->pipe_state & PIPE_DIRECTW) {
 1160                         if (wpipe->pipe_state & PIPE_WANTR) {
 1161                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1162                                 wakeup(wpipe);
 1163                         }
 1164                         pipeselwakeup(wpipe);
 1165                         wpipe->pipe_state |= PIPE_WANTW;
 1166                         pipeunlock(wpipe);
 1167                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
 1168                             "pipbww", 0);
 1169                         if (error)
 1170                                 break;
 1171                         else
 1172                                 continue;
 1173                 }
 1174 
 1175                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1176 
 1177                 /* Writes of size <= PIPE_BUF must be atomic. */
 1178                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 1179                         space = 0;
 1180 
 1181                 if (space > 0) {
 1182                         int size;       /* Transfer size */
 1183                         int segsize;    /* first segment to transfer */
 1184 
 1185                         /*
 1186                          * Transfer size is minimum of uio transfer
 1187                          * and free space in pipe buffer.
 1188                          */
 1189                         if (space > uio->uio_resid)
 1190                                 size = uio->uio_resid;
 1191                         else
 1192                                 size = space;
 1193                         /*
 1194                          * First segment to transfer is minimum of
 1195                          * transfer size and contiguous space in
 1196                          * pipe buffer.  If first segment to transfer
 1197                          * is less than the transfer size, we've got
 1198                          * a wraparound in the buffer.
 1199                          */
 1200                         segsize = wpipe->pipe_buffer.size -
 1201                                 wpipe->pipe_buffer.in;
 1202                         if (segsize > size)
 1203                                 segsize = size;
 1204 
 1205                         /* Transfer first segment */
 1206 
 1207                         PIPE_UNLOCK(rpipe);
 1208                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
 1209                                         segsize, uio);
 1210                         PIPE_LOCK(rpipe);
 1211 
 1212                         if (error == 0 && segsize < size) {
 1213                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
 1214                                         wpipe->pipe_buffer.size,
 1215                                         ("Pipe buffer wraparound disappeared"));
 1216                                 /*
 1217                                  * Transfer remaining part now, to
 1218                                  * support atomic writes.  Wraparound
 1219                                  * happened.
 1220                                  */
 1221 
 1222                                 PIPE_UNLOCK(rpipe);
 1223                                 error = uiomove(
 1224                                     &wpipe->pipe_buffer.buffer[0],
 1225                                     size - segsize, uio);
 1226                                 PIPE_LOCK(rpipe);
 1227                         }
 1228                         if (error == 0) {
 1229                                 wpipe->pipe_buffer.in += size;
 1230                                 if (wpipe->pipe_buffer.in >=
 1231                                     wpipe->pipe_buffer.size) {
 1232                                         KASSERT(wpipe->pipe_buffer.in ==
 1233                                                 size - segsize +
 1234                                                 wpipe->pipe_buffer.size,
 1235                                                 ("Expected wraparound bad"));
 1236                                         wpipe->pipe_buffer.in = size - segsize;
 1237                                 }
 1238 
 1239                                 wpipe->pipe_buffer.cnt += size;
 1240                                 KASSERT(wpipe->pipe_buffer.cnt <=
 1241                                         wpipe->pipe_buffer.size,
 1242                                         ("Pipe buffer overflow"));
 1243                         }
 1244                         pipeunlock(wpipe);
 1245                         if (error != 0)
 1246                                 break;
 1247                 } else {
 1248                         /*
 1249                          * If the "read-side" has been blocked, wake it up now.
 1250                          */
 1251                         if (wpipe->pipe_state & PIPE_WANTR) {
 1252                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1253                                 wakeup(wpipe);
 1254                         }
 1255 
 1256                         /*
 1257                          * don't block on non-blocking I/O
 1258                          */
 1259                         if (fp->f_flag & FNONBLOCK) {
 1260                                 error = EAGAIN;
 1261                                 pipeunlock(wpipe);
 1262                                 break;
 1263                         }
 1264 
 1265                         /*
 1266                          * We have no more space and have something to offer,
 1267                          * wake up select/poll.
 1268                          */
 1269                         pipeselwakeup(wpipe);
 1270 
 1271                         wpipe->pipe_state |= PIPE_WANTW;
 1272                         pipeunlock(wpipe);
 1273                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1274                             PRIBIO | PCATCH, "pipewr", 0);
 1275                         if (error != 0)
 1276                                 break;
 1277                 }
 1278         }
 1279 
 1280         pipelock(wpipe, 0);
 1281         --wpipe->pipe_busy;
 1282 
 1283         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1284                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1285                 wakeup(wpipe);
 1286         } else if (wpipe->pipe_buffer.cnt > 0) {
 1287                 /*
 1288                  * If we have put any characters in the buffer, we wake up
 1289                  * the reader.
 1290                  */
 1291                 if (wpipe->pipe_state & PIPE_WANTR) {
 1292                         wpipe->pipe_state &= ~PIPE_WANTR;
 1293                         wakeup(wpipe);
 1294                 }
 1295         }
 1296 
 1297         /*
 1298          * Don't return EPIPE if any byte was written.
 1299          * EINTR and other interrupts are handled by generic I/O layer.
 1300          * Do not pretend that I/O succeeded for obvious user error
 1301          * like EFAULT.
 1302          */
 1303         if (uio->uio_resid != orig_resid && error == EPIPE)
 1304                 error = 0;
 1305 
 1306         if (error == 0)
 1307                 vfs_timestamp(&wpipe->pipe_mtime);
 1308 
 1309         /*
 1310          * We have something to offer,
 1311          * wake up select/poll.
 1312          */
 1313         if (wpipe->pipe_buffer.cnt)
 1314                 pipeselwakeup(wpipe);
 1315 
 1316         pipeunlock(wpipe);
 1317         PIPE_UNLOCK(rpipe);
 1318         return (error);
 1319 }
 1320 
 1321 /* ARGSUSED */
 1322 static int
 1323 pipe_truncate(fp, length, active_cred, td)
 1324         struct file *fp;
 1325         off_t length;
 1326         struct ucred *active_cred;
 1327         struct thread *td;
 1328 {
 1329 
 1330         /* For named pipes call the vnode operation. */
 1331         if (fp->f_vnode != NULL)
 1332                 return (vnops.fo_truncate(fp, length, active_cred, td));
 1333         return (EINVAL);
 1334 }
 1335 
 1336 /*
 1337  * we implement a very minimal set of ioctls for compatibility with sockets.
 1338  */
 1339 static int
 1340 pipe_ioctl(fp, cmd, data, active_cred, td)
 1341         struct file *fp;
 1342         u_long cmd;
 1343         void *data;
 1344         struct ucred *active_cred;
 1345         struct thread *td;
 1346 {
 1347         struct pipe *mpipe = fp->f_data;
 1348         int error;
 1349 
 1350         PIPE_LOCK(mpipe);
 1351 
 1352 #ifdef MAC
 1353         error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
 1354         if (error) {
 1355                 PIPE_UNLOCK(mpipe);
 1356                 return (error);
 1357         }
 1358 #endif
 1359 
 1360         error = 0;
 1361         switch (cmd) {
 1362 
 1363         case FIONBIO:
 1364                 break;
 1365 
 1366         case FIOASYNC:
 1367                 if (*(int *)data) {
 1368                         mpipe->pipe_state |= PIPE_ASYNC;
 1369                 } else {
 1370                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1371                 }
 1372                 break;
 1373 
 1374         case FIONREAD:
 1375                 if (!(fp->f_flag & FREAD)) {
 1376                         *(int *)data = 0;
 1377                         PIPE_UNLOCK(mpipe);
 1378                         return (0);
 1379                 }
 1380                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1381                         *(int *)data = mpipe->pipe_map.cnt;
 1382                 else
 1383                         *(int *)data = mpipe->pipe_buffer.cnt;
 1384                 break;
 1385 
 1386         case FIOSETOWN:
 1387                 PIPE_UNLOCK(mpipe);
 1388                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 1389                 goto out_unlocked;
 1390 
 1391         case FIOGETOWN:
 1392                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1393                 break;
 1394 
 1395         /* This is deprecated, FIOSETOWN should be used instead. */
 1396         case TIOCSPGRP:
 1397                 PIPE_UNLOCK(mpipe);
 1398                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 1399                 goto out_unlocked;
 1400 
 1401         /* This is deprecated, FIOGETOWN should be used instead. */
 1402         case TIOCGPGRP:
 1403                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1404                 break;
 1405 
 1406         default:
 1407                 error = ENOTTY;
 1408                 break;
 1409         }
 1410         PIPE_UNLOCK(mpipe);
 1411 out_unlocked:
 1412         return (error);
 1413 }
 1414 
 1415 static int
 1416 pipe_poll(fp, events, active_cred, td)
 1417         struct file *fp;
 1418         int events;
 1419         struct ucred *active_cred;
 1420         struct thread *td;
 1421 {
 1422         struct pipe *rpipe;
 1423         struct pipe *wpipe;
 1424         int levents, revents;
 1425 #ifdef MAC
 1426         int error;
 1427 #endif
 1428 
 1429         revents = 0;
 1430         rpipe = fp->f_data;
 1431         wpipe = PIPE_PEER(rpipe);
 1432         PIPE_LOCK(rpipe);
 1433 #ifdef MAC
 1434         error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
 1435         if (error)
 1436                 goto locked_error;
 1437 #endif
 1438         if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM))
 1439                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1440                     (rpipe->pipe_buffer.cnt > 0))
 1441                         revents |= events & (POLLIN | POLLRDNORM);
 1442 
 1443         if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM))
 1444                 if (wpipe->pipe_present != PIPE_ACTIVE ||
 1445                     (wpipe->pipe_state & PIPE_EOF) ||
 1446                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1447                      ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
 1448                          wpipe->pipe_buffer.size == 0)))
 1449                         revents |= events & (POLLOUT | POLLWRNORM);
 1450 
 1451         levents = events &
 1452             (POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
 1453         if (rpipe->pipe_state & PIPE_NAMED && fp->f_flag & FREAD && levents &&
 1454             fp->f_seqcount == rpipe->pipe_wgen)
 1455                 events |= POLLINIGNEOF;
 1456 
 1457         if ((events & POLLINIGNEOF) == 0) {
 1458                 if (rpipe->pipe_state & PIPE_EOF) {
 1459                         revents |= (events & (POLLIN | POLLRDNORM));
 1460                         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1461                             (wpipe->pipe_state & PIPE_EOF))
 1462                                 revents |= POLLHUP;
 1463                 }
 1464         }
 1465 
 1466         if (revents == 0) {
 1467                 if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM)) {
 1468                         selrecord(td, &rpipe->pipe_sel);
 1469                         if (SEL_WAITING(&rpipe->pipe_sel))
 1470                                 rpipe->pipe_state |= PIPE_SEL;
 1471                 }
 1472 
 1473                 if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM)) {
 1474                         selrecord(td, &wpipe->pipe_sel);
 1475                         if (SEL_WAITING(&wpipe->pipe_sel))
 1476                                 wpipe->pipe_state |= PIPE_SEL;
 1477                 }
 1478         }
 1479 #ifdef MAC
 1480 locked_error:
 1481 #endif
 1482         PIPE_UNLOCK(rpipe);
 1483 
 1484         return (revents);
 1485 }
 1486 
 1487 /*
 1488  * We shouldn't need locks here as we're doing a read and this should
 1489  * be a natural race.
 1490  */
 1491 static int
 1492 pipe_stat(fp, ub, active_cred, td)
 1493         struct file *fp;
 1494         struct stat *ub;
 1495         struct ucred *active_cred;
 1496         struct thread *td;
 1497 {
 1498         struct pipe *pipe;
 1499         int new_unr;
 1500 #ifdef MAC
 1501         int error;
 1502 #endif
 1503 
 1504         pipe = fp->f_data;
 1505         PIPE_LOCK(pipe);
 1506 #ifdef MAC
 1507         error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
 1508         if (error) {
 1509                 PIPE_UNLOCK(pipe);
 1510                 return (error);
 1511         }
 1512 #endif
 1513 
 1514         /* For named pipes ask the underlying filesystem. */
 1515         if (pipe->pipe_state & PIPE_NAMED) {
 1516                 PIPE_UNLOCK(pipe);
 1517                 return (vnops.fo_stat(fp, ub, active_cred, td));
 1518         }
 1519 
 1520         /*
 1521          * Lazily allocate an inode number for the pipe.  Most pipe
 1522          * users do not call fstat(2) on the pipe, which means that
 1523          * postponing the inode allocation until it is must be
 1524          * returned to userland is useful.  If alloc_unr failed,
 1525          * assign st_ino zero instead of returning an error.
 1526          * Special pipe_ino values:
 1527          *  -1 - not yet initialized;
 1528          *  0  - alloc_unr failed, return 0 as st_ino forever.
 1529          */
 1530         if (pipe->pipe_ino == (ino_t)-1) {
 1531                 new_unr = alloc_unr(pipeino_unr);
 1532                 if (new_unr != -1)
 1533                         pipe->pipe_ino = new_unr;
 1534                 else
 1535                         pipe->pipe_ino = 0;
 1536         }
 1537         PIPE_UNLOCK(pipe);
 1538 
 1539         bzero(ub, sizeof(*ub));
 1540         ub->st_mode = S_IFIFO;
 1541         ub->st_blksize = PAGE_SIZE;
 1542         if (pipe->pipe_state & PIPE_DIRECTW)
 1543                 ub->st_size = pipe->pipe_map.cnt;
 1544         else
 1545                 ub->st_size = pipe->pipe_buffer.cnt;
 1546         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
 1547         ub->st_atim = pipe->pipe_atime;
 1548         ub->st_mtim = pipe->pipe_mtime;
 1549         ub->st_ctim = pipe->pipe_ctime;
 1550         ub->st_uid = fp->f_cred->cr_uid;
 1551         ub->st_gid = fp->f_cred->cr_gid;
 1552         ub->st_dev = pipedev_ino;
 1553         ub->st_ino = pipe->pipe_ino;
 1554         /*
 1555          * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
 1556          */
 1557         return (0);
 1558 }
 1559 
 1560 /* ARGSUSED */
 1561 static int
 1562 pipe_close(fp, td)
 1563         struct file *fp;
 1564         struct thread *td;
 1565 {
 1566 
 1567         if (fp->f_vnode != NULL) 
 1568                 return vnops.fo_close(fp, td);
 1569         fp->f_ops = &badfileops;
 1570         pipe_dtor(fp->f_data);
 1571         fp->f_data = NULL;
 1572         return (0);
 1573 }
 1574 
 1575 static int
 1576 pipe_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, struct thread *td)
 1577 {
 1578         struct pipe *cpipe;
 1579         int error;
 1580 
 1581         cpipe = fp->f_data;
 1582         if (cpipe->pipe_state & PIPE_NAMED)
 1583                 error = vn_chmod(fp, mode, active_cred, td);
 1584         else
 1585                 error = invfo_chmod(fp, mode, active_cred, td);
 1586         return (error);
 1587 }
 1588 
 1589 static int
 1590 pipe_chown(fp, uid, gid, active_cred, td)
 1591         struct file *fp;
 1592         uid_t uid;
 1593         gid_t gid;
 1594         struct ucred *active_cred;
 1595         struct thread *td;
 1596 {
 1597         struct pipe *cpipe;
 1598         int error;
 1599 
 1600         cpipe = fp->f_data;
 1601         if (cpipe->pipe_state & PIPE_NAMED)
 1602                 error = vn_chown(fp, uid, gid, active_cred, td);
 1603         else
 1604                 error = invfo_chown(fp, uid, gid, active_cred, td);
 1605         return (error);
 1606 }
 1607 
 1608 static void
 1609 pipe_free_kmem(cpipe)
 1610         struct pipe *cpipe;
 1611 {
 1612 
 1613         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
 1614             ("pipe_free_kmem: pipe mutex locked"));
 1615 
 1616         if (cpipe->pipe_buffer.buffer != NULL) {
 1617                 atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
 1618                 vm_map_remove(pipe_map,
 1619                     (vm_offset_t)cpipe->pipe_buffer.buffer,
 1620                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
 1621                 cpipe->pipe_buffer.buffer = NULL;
 1622         }
 1623 #ifndef PIPE_NODIRECT
 1624         {
 1625                 cpipe->pipe_map.cnt = 0;
 1626                 cpipe->pipe_map.pos = 0;
 1627                 cpipe->pipe_map.npages = 0;
 1628         }
 1629 #endif
 1630 }
 1631 
 1632 /*
 1633  * shutdown the pipe
 1634  */
 1635 static void
 1636 pipeclose(cpipe)
 1637         struct pipe *cpipe;
 1638 {
 1639         struct pipepair *pp;
 1640         struct pipe *ppipe;
 1641 
 1642         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
 1643 
 1644         PIPE_LOCK(cpipe);
 1645         pipelock(cpipe, 0);
 1646         pp = cpipe->pipe_pair;
 1647 
 1648         pipeselwakeup(cpipe);
 1649 
 1650         /*
 1651          * If the other side is blocked, wake it up saying that
 1652          * we want to close it down.
 1653          */
 1654         cpipe->pipe_state |= PIPE_EOF;
 1655         while (cpipe->pipe_busy) {
 1656                 wakeup(cpipe);
 1657                 cpipe->pipe_state |= PIPE_WANT;
 1658                 pipeunlock(cpipe);
 1659                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1660                 pipelock(cpipe, 0);
 1661         }
 1662 
 1663 
 1664         /*
 1665          * Disconnect from peer, if any.
 1666          */
 1667         ppipe = cpipe->pipe_peer;
 1668         if (ppipe->pipe_present == PIPE_ACTIVE) {
 1669                 pipeselwakeup(ppipe);
 1670 
 1671                 ppipe->pipe_state |= PIPE_EOF;
 1672                 wakeup(ppipe);
 1673                 KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
 1674         }
 1675 
 1676         /*
 1677          * Mark this endpoint as free.  Release kmem resources.  We
 1678          * don't mark this endpoint as unused until we've finished
 1679          * doing that, or the pipe might disappear out from under
 1680          * us.
 1681          */
 1682         PIPE_UNLOCK(cpipe);
 1683         pipe_free_kmem(cpipe);
 1684         PIPE_LOCK(cpipe);
 1685         cpipe->pipe_present = PIPE_CLOSING;
 1686         pipeunlock(cpipe);
 1687 
 1688         /*
 1689          * knlist_clear() may sleep dropping the PIPE_MTX. Set the
 1690          * PIPE_FINALIZED, that allows other end to free the
 1691          * pipe_pair, only after the knotes are completely dismantled.
 1692          */
 1693         knlist_clear(&cpipe->pipe_sel.si_note, 1);
 1694         cpipe->pipe_present = PIPE_FINALIZED;
 1695         seldrain(&cpipe->pipe_sel);
 1696         knlist_destroy(&cpipe->pipe_sel.si_note);
 1697 
 1698         /*
 1699          * If both endpoints are now closed, release the memory for the
 1700          * pipe pair.  If not, unlock.
 1701          */
 1702         if (ppipe->pipe_present == PIPE_FINALIZED) {
 1703                 PIPE_UNLOCK(cpipe);
 1704 #ifdef MAC
 1705                 mac_pipe_destroy(pp);
 1706 #endif
 1707                 uma_zfree(pipe_zone, cpipe->pipe_pair);
 1708         } else
 1709                 PIPE_UNLOCK(cpipe);
 1710 }
 1711 
 1712 /*ARGSUSED*/
 1713 static int
 1714 pipe_kqfilter(struct file *fp, struct knote *kn)
 1715 {
 1716         struct pipe *cpipe;
 1717 
 1718         /*
 1719          * If a filter is requested that is not supported by this file
 1720          * descriptor, don't return an error, but also don't ever generate an
 1721          * event.
 1722          */
 1723         if ((kn->kn_filter == EVFILT_READ) && !(fp->f_flag & FREAD)) {
 1724                 kn->kn_fop = &pipe_nfiltops;
 1725                 return (0);
 1726         }
 1727         if ((kn->kn_filter == EVFILT_WRITE) && !(fp->f_flag & FWRITE)) {
 1728                 kn->kn_fop = &pipe_nfiltops;
 1729                 return (0);
 1730         }
 1731         cpipe = fp->f_data;
 1732         PIPE_LOCK(cpipe);
 1733         switch (kn->kn_filter) {
 1734         case EVFILT_READ:
 1735                 kn->kn_fop = &pipe_rfiltops;
 1736                 break;
 1737         case EVFILT_WRITE:
 1738                 kn->kn_fop = &pipe_wfiltops;
 1739                 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
 1740                         /* other end of pipe has been closed */
 1741                         PIPE_UNLOCK(cpipe);
 1742                         return (EPIPE);
 1743                 }
 1744                 cpipe = PIPE_PEER(cpipe);
 1745                 break;
 1746         default:
 1747                 PIPE_UNLOCK(cpipe);
 1748                 return (EINVAL);
 1749         }
 1750 
 1751         kn->kn_hook = cpipe; 
 1752         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
 1753         PIPE_UNLOCK(cpipe);
 1754         return (0);
 1755 }
 1756 
 1757 static void
 1758 filt_pipedetach(struct knote *kn)
 1759 {
 1760         struct pipe *cpipe = kn->kn_hook;
 1761 
 1762         PIPE_LOCK(cpipe);
 1763         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
 1764         PIPE_UNLOCK(cpipe);
 1765 }
 1766 
 1767 /*ARGSUSED*/
 1768 static int
 1769 filt_piperead(struct knote *kn, long hint)
 1770 {
 1771         struct pipe *rpipe = kn->kn_hook;
 1772         struct pipe *wpipe = rpipe->pipe_peer;
 1773         int ret;
 1774 
 1775         PIPE_LOCK_ASSERT(rpipe, MA_OWNED);
 1776         kn->kn_data = rpipe->pipe_buffer.cnt;
 1777         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1778                 kn->kn_data = rpipe->pipe_map.cnt;
 1779 
 1780         if ((rpipe->pipe_state & PIPE_EOF) ||
 1781             wpipe->pipe_present != PIPE_ACTIVE ||
 1782             (wpipe->pipe_state & PIPE_EOF)) {
 1783                 kn->kn_flags |= EV_EOF;
 1784                 return (1);
 1785         }
 1786         ret = kn->kn_data > 0;
 1787         return ret;
 1788 }
 1789 
 1790 /*ARGSUSED*/
 1791 static int
 1792 filt_pipewrite(struct knote *kn, long hint)
 1793 {
 1794         struct pipe *wpipe;
 1795    
 1796         wpipe = kn->kn_hook;
 1797         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 1798         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1799             (wpipe->pipe_state & PIPE_EOF)) {
 1800                 kn->kn_data = 0;
 1801                 kn->kn_flags |= EV_EOF;
 1802                 return (1);
 1803         }
 1804         kn->kn_data = (wpipe->pipe_buffer.size > 0) ?
 1805             (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) : PIPE_BUF;
 1806         if (wpipe->pipe_state & PIPE_DIRECTW)
 1807                 kn->kn_data = 0;
 1808 
 1809         return (kn->kn_data >= PIPE_BUF);
 1810 }
 1811 
 1812 static void
 1813 filt_pipedetach_notsup(struct knote *kn)
 1814 {
 1815 
 1816 }
 1817 
 1818 static int
 1819 filt_pipenotsup(struct knote *kn, long hint)
 1820 {
 1821 
 1822         return (0);
 1823 }

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