The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/sys_pipe.c

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    1 /*-
    2  * Copyright (c) 1996 John S. Dyson
    3  * Copyright (c) 2012 Giovanni Trematerra
    4  * All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice immediately at the beginning of the file, without modification,
   11  *    this list of conditions, and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Absolutely no warranty of function or purpose is made by the author
   16  *    John S. Dyson.
   17  * 4. Modifications may be freely made to this file if the above conditions
   18  *    are met.
   19  */
   20 
   21 /*
   22  * This file contains a high-performance replacement for the socket-based
   23  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
   24  * all features of sockets, but does do everything that pipes normally
   25  * do.
   26  */
   27 
   28 /*
   29  * This code has two modes of operation, a small write mode and a large
   30  * write mode.  The small write mode acts like conventional pipes with
   31  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
   32  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
   33  * and PIPE_SIZE in size, the sending process pins the underlying pages in
   34  * memory, and the receiving process copies directly from these pinned pages
   35  * in the sending process.
   36  *
   37  * If the sending process receives a signal, it is possible that it will
   38  * go away, and certainly its address space can change, because control
   39  * is returned back to the user-mode side.  In that case, the pipe code
   40  * arranges to copy the buffer supplied by the user process, to a pageable
   41  * kernel buffer, and the receiving process will grab the data from the
   42  * pageable kernel buffer.  Since signals don't happen all that often,
   43  * the copy operation is normally eliminated.
   44  *
   45  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
   46  * happen for small transfers so that the system will not spend all of
   47  * its time context switching.
   48  *
   49  * In order to limit the resource use of pipes, two sysctls exist:
   50  *
   51  * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
   52  * address space available to us in pipe_map. This value is normally
   53  * autotuned, but may also be loader tuned.
   54  *
   55  * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
   56  * memory in use by pipes.
   57  *
   58  * Based on how large pipekva is relative to maxpipekva, the following
   59  * will happen:
   60  *
   61  * 0% - 50%:
   62  *     New pipes are given 16K of memory backing, pipes may dynamically
   63  *     grow to as large as 64K where needed.
   64  * 50% - 75%:
   65  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   66  *     existing pipes may NOT grow.
   67  * 75% - 100%:
   68  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   69  *     existing pipes will be shrunk down to 4K whenever possible.
   70  *
   71  * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
   72  * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
   73  * resize which MUST occur for reverse-direction pipes when they are
   74  * first used.
   75  *
   76  * Additional information about the current state of pipes may be obtained
   77  * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
   78  * and kern.ipc.piperesizefail.
   79  *
   80  * Locking rules:  There are two locks present here:  A mutex, used via
   81  * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
   82  * the flag, as mutexes can not persist over uiomove.  The mutex
   83  * exists only to guard access to the flag, and is not in itself a
   84  * locking mechanism.  Also note that there is only a single mutex for
   85  * both directions of a pipe.
   86  *
   87  * As pipelock() may have to sleep before it can acquire the flag, it
   88  * is important to reread all data after a call to pipelock(); everything
   89  * in the structure may have changed.
   90  */
   91 
   92 #include <sys/cdefs.h>
   93 __FBSDID("$FreeBSD: stable/10/sys/kern/sys_pipe.c 321020 2017-07-15 17:25:40Z dchagin $");
   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 file *rf, *wf;
  407         struct pipe *rpipe, *wpipe;
  408         struct pipepair *pp;
  409         int fd, fflags, error;
  410 
  411         pipe_paircreate(td, &pp);
  412         rpipe = &pp->pp_rpipe;
  413         wpipe = &pp->pp_wpipe;
  414         error = falloc(td, &rf, &fd, flags);
  415         if (error) {
  416                 pipeclose(rpipe);
  417                 pipeclose(wpipe);
  418                 return (error);
  419         }
  420         /* An extra reference on `rf' has been held for us by falloc(). */
  421         fildes[0] = fd;
  422 
  423         fflags = FREAD | FWRITE;
  424         if ((flags & O_NONBLOCK) != 0)
  425                 fflags |= FNONBLOCK;
  426 
  427         /*
  428          * Warning: once we've gotten past allocation of the fd for the
  429          * read-side, we can only drop the read side via fdrop() in order
  430          * to avoid races against processes which manage to dup() the read
  431          * side while we are blocked trying to allocate the write side.
  432          */
  433         finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
  434         error = falloc(td, &wf, &fd, flags);
  435         if (error) {
  436                 fdclose(td, rf, fildes[0]);
  437                 fdrop(rf, td);
  438                 /* rpipe has been closed by fdrop(). */
  439                 pipeclose(wpipe);
  440                 return (error);
  441         }
  442         /* An extra reference on `wf' has been held for us by falloc(). */
  443         finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
  444         fdrop(wf, td);
  445         fildes[1] = fd;
  446         fdrop(rf, td);
  447 
  448         return (0);
  449 }
  450 
  451 /* ARGSUSED */
  452 int
  453 sys_pipe(struct thread *td, struct pipe_args *uap)
  454 {
  455         int error;
  456         int fildes[2];
  457 
  458         error = kern_pipe(td, fildes);
  459         if (error)
  460                 return (error);
  461 
  462         td->td_retval[0] = fildes[0];
  463         td->td_retval[1] = fildes[1];
  464 
  465         return (0);
  466 }
  467 
  468 int
  469 sys_pipe2(struct thread *td, struct pipe2_args *uap)
  470 {
  471         int error, fildes[2];
  472 
  473         if (uap->flags & ~(O_CLOEXEC | O_NONBLOCK))
  474                 return (EINVAL);
  475         error = kern_pipe2(td, fildes, uap->flags);
  476         if (error)
  477                 return (error);
  478         error = copyout(fildes, uap->fildes, 2 * sizeof(int));
  479         if (error) {
  480                 (void)kern_close(td, fildes[0]);
  481                 (void)kern_close(td, fildes[1]);
  482         }
  483         return (error);
  484 }
  485 
  486 /*
  487  * Allocate kva for pipe circular buffer, the space is pageable
  488  * This routine will 'realloc' the size of a pipe safely, if it fails
  489  * it will retain the old buffer.
  490  * If it fails it will return ENOMEM.
  491  */
  492 static int
  493 pipespace_new(cpipe, size)
  494         struct pipe *cpipe;
  495         int size;
  496 {
  497         caddr_t buffer;
  498         int error, cnt, firstseg;
  499         static int curfail = 0;
  500         static struct timeval lastfail;
  501 
  502         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
  503         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
  504                 ("pipespace: resize of direct writes not allowed"));
  505 retry:
  506         cnt = cpipe->pipe_buffer.cnt;
  507         if (cnt > size)
  508                 size = cnt;
  509 
  510         size = round_page(size);
  511         buffer = (caddr_t) vm_map_min(pipe_map);
  512 
  513         error = vm_map_find(pipe_map, NULL, 0,
  514                 (vm_offset_t *) &buffer, size, 0, VMFS_ANY_SPACE,
  515                 VM_PROT_ALL, VM_PROT_ALL, 0);
  516         if (error != KERN_SUCCESS) {
  517                 if ((cpipe->pipe_buffer.buffer == NULL) &&
  518                         (size > SMALL_PIPE_SIZE)) {
  519                         size = SMALL_PIPE_SIZE;
  520                         pipefragretry++;
  521                         goto retry;
  522                 }
  523                 if (cpipe->pipe_buffer.buffer == NULL) {
  524                         pipeallocfail++;
  525                         if (ppsratecheck(&lastfail, &curfail, 1))
  526                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
  527                 } else {
  528                         piperesizefail++;
  529                 }
  530                 return (ENOMEM);
  531         }
  532 
  533         /* copy data, then free old resources if we're resizing */
  534         if (cnt > 0) {
  535                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
  536                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
  537                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  538                                 buffer, firstseg);
  539                         if ((cnt - firstseg) > 0)
  540                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
  541                                         cpipe->pipe_buffer.in);
  542                 } else {
  543                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  544                                 buffer, cnt);
  545                 }
  546         }
  547         pipe_free_kmem(cpipe);
  548         cpipe->pipe_buffer.buffer = buffer;
  549         cpipe->pipe_buffer.size = size;
  550         cpipe->pipe_buffer.in = cnt;
  551         cpipe->pipe_buffer.out = 0;
  552         cpipe->pipe_buffer.cnt = cnt;
  553         atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
  554         return (0);
  555 }
  556 
  557 /*
  558  * Wrapper for pipespace_new() that performs locking assertions.
  559  */
  560 static int
  561 pipespace(cpipe, size)
  562         struct pipe *cpipe;
  563         int size;
  564 {
  565 
  566         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  567                 ("Unlocked pipe passed to pipespace"));
  568         return (pipespace_new(cpipe, size));
  569 }
  570 
  571 /*
  572  * lock a pipe for I/O, blocking other access
  573  */
  574 static __inline int
  575 pipelock(cpipe, catch)
  576         struct pipe *cpipe;
  577         int catch;
  578 {
  579         int error;
  580 
  581         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  582         while (cpipe->pipe_state & PIPE_LOCKFL) {
  583                 cpipe->pipe_state |= PIPE_LWANT;
  584                 error = msleep(cpipe, PIPE_MTX(cpipe),
  585                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  586                     "pipelk", 0);
  587                 if (error != 0)
  588                         return (error);
  589         }
  590         cpipe->pipe_state |= PIPE_LOCKFL;
  591         return (0);
  592 }
  593 
  594 /*
  595  * unlock a pipe I/O lock
  596  */
  597 static __inline void
  598 pipeunlock(cpipe)
  599         struct pipe *cpipe;
  600 {
  601 
  602         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  603         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  604                 ("Unlocked pipe passed to pipeunlock"));
  605         cpipe->pipe_state &= ~PIPE_LOCKFL;
  606         if (cpipe->pipe_state & PIPE_LWANT) {
  607                 cpipe->pipe_state &= ~PIPE_LWANT;
  608                 wakeup(cpipe);
  609         }
  610 }
  611 
  612 void
  613 pipeselwakeup(cpipe)
  614         struct pipe *cpipe;
  615 {
  616 
  617         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  618         if (cpipe->pipe_state & PIPE_SEL) {
  619                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
  620                 if (!SEL_WAITING(&cpipe->pipe_sel))
  621                         cpipe->pipe_state &= ~PIPE_SEL;
  622         }
  623         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  624                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  625         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
  626 }
  627 
  628 /*
  629  * Initialize and allocate VM and memory for pipe.  The structure
  630  * will start out zero'd from the ctor, so we just manage the kmem.
  631  */
  632 static void
  633 pipe_create(pipe, backing)
  634         struct pipe *pipe;
  635         int backing;
  636 {
  637 
  638         if (backing) {
  639                 /*
  640                  * Note that these functions can fail if pipe map is exhausted
  641                  * (as a result of too many pipes created), but we ignore the
  642                  * error as it is not fatal and could be provoked by
  643                  * unprivileged users. The only consequence is worse performance
  644                  * with given pipe.
  645                  */
  646                 if (amountpipekva > maxpipekva / 2)
  647                         (void)pipespace_new(pipe, SMALL_PIPE_SIZE);
  648                 else
  649                         (void)pipespace_new(pipe, PIPE_SIZE);
  650         }
  651 
  652         pipe->pipe_ino = -1;
  653 }
  654 
  655 /* ARGSUSED */
  656 static int
  657 pipe_read(fp, uio, active_cred, flags, td)
  658         struct file *fp;
  659         struct uio *uio;
  660         struct ucred *active_cred;
  661         struct thread *td;
  662         int flags;
  663 {
  664         struct pipe *rpipe;
  665         int error;
  666         int nread = 0;
  667         int size;
  668 
  669         rpipe = fp->f_data;
  670         PIPE_LOCK(rpipe);
  671         ++rpipe->pipe_busy;
  672         error = pipelock(rpipe, 1);
  673         if (error)
  674                 goto unlocked_error;
  675 
  676 #ifdef MAC
  677         error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
  678         if (error)
  679                 goto locked_error;
  680 #endif
  681         if (amountpipekva > (3 * maxpipekva) / 4) {
  682                 if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
  683                         (rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
  684                         (rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
  685                         (piperesizeallowed == 1)) {
  686                         PIPE_UNLOCK(rpipe);
  687                         pipespace(rpipe, SMALL_PIPE_SIZE);
  688                         PIPE_LOCK(rpipe);
  689                 }
  690         }
  691 
  692         while (uio->uio_resid) {
  693                 /*
  694                  * normal pipe buffer receive
  695                  */
  696                 if (rpipe->pipe_buffer.cnt > 0) {
  697                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  698                         if (size > rpipe->pipe_buffer.cnt)
  699                                 size = rpipe->pipe_buffer.cnt;
  700                         if (size > uio->uio_resid)
  701                                 size = uio->uio_resid;
  702 
  703                         PIPE_UNLOCK(rpipe);
  704                         error = uiomove(
  705                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  706                             size, uio);
  707                         PIPE_LOCK(rpipe);
  708                         if (error)
  709                                 break;
  710 
  711                         rpipe->pipe_buffer.out += size;
  712                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  713                                 rpipe->pipe_buffer.out = 0;
  714 
  715                         rpipe->pipe_buffer.cnt -= size;
  716 
  717                         /*
  718                          * If there is no more to read in the pipe, reset
  719                          * its pointers to the beginning.  This improves
  720                          * cache hit stats.
  721                          */
  722                         if (rpipe->pipe_buffer.cnt == 0) {
  723                                 rpipe->pipe_buffer.in = 0;
  724                                 rpipe->pipe_buffer.out = 0;
  725                         }
  726                         nread += size;
  727 #ifndef PIPE_NODIRECT
  728                 /*
  729                  * Direct copy, bypassing a kernel buffer.
  730                  */
  731                 } else if ((size = rpipe->pipe_map.cnt) &&
  732                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  733                         if (size > uio->uio_resid)
  734                                 size = (u_int) uio->uio_resid;
  735 
  736                         PIPE_UNLOCK(rpipe);
  737                         error = uiomove_fromphys(rpipe->pipe_map.ms,
  738                             rpipe->pipe_map.pos, size, uio);
  739                         PIPE_LOCK(rpipe);
  740                         if (error)
  741                                 break;
  742                         nread += size;
  743                         rpipe->pipe_map.pos += size;
  744                         rpipe->pipe_map.cnt -= size;
  745                         if (rpipe->pipe_map.cnt == 0) {
  746                                 rpipe->pipe_state &= ~(PIPE_DIRECTW|PIPE_WANTW);
  747                                 wakeup(rpipe);
  748                         }
  749 #endif
  750                 } else {
  751                         /*
  752                          * detect EOF condition
  753                          * read returns 0 on EOF, no need to set error
  754                          */
  755                         if (rpipe->pipe_state & PIPE_EOF)
  756                                 break;
  757 
  758                         /*
  759                          * If the "write-side" has been blocked, wake it up now.
  760                          */
  761                         if (rpipe->pipe_state & PIPE_WANTW) {
  762                                 rpipe->pipe_state &= ~PIPE_WANTW;
  763                                 wakeup(rpipe);
  764                         }
  765 
  766                         /*
  767                          * Break if some data was read.
  768                          */
  769                         if (nread > 0)
  770                                 break;
  771 
  772                         /*
  773                          * Unlock the pipe buffer for our remaining processing.
  774                          * We will either break out with an error or we will
  775                          * sleep and relock to loop.
  776                          */
  777                         pipeunlock(rpipe);
  778 
  779                         /*
  780                          * Handle non-blocking mode operation or
  781                          * wait for more data.
  782                          */
  783                         if (fp->f_flag & FNONBLOCK) {
  784                                 error = EAGAIN;
  785                         } else {
  786                                 rpipe->pipe_state |= PIPE_WANTR;
  787                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  788                                     PRIBIO | PCATCH,
  789                                     "piperd", 0)) == 0)
  790                                         error = pipelock(rpipe, 1);
  791                         }
  792                         if (error)
  793                                 goto unlocked_error;
  794                 }
  795         }
  796 #ifdef MAC
  797 locked_error:
  798 #endif
  799         pipeunlock(rpipe);
  800 
  801         /* XXX: should probably do this before getting any locks. */
  802         if (error == 0)
  803                 vfs_timestamp(&rpipe->pipe_atime);
  804 unlocked_error:
  805         --rpipe->pipe_busy;
  806 
  807         /*
  808          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  809          */
  810         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  811                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  812                 wakeup(rpipe);
  813         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  814                 /*
  815                  * Handle write blocking hysteresis.
  816                  */
  817                 if (rpipe->pipe_state & PIPE_WANTW) {
  818                         rpipe->pipe_state &= ~PIPE_WANTW;
  819                         wakeup(rpipe);
  820                 }
  821         }
  822 
  823         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  824                 pipeselwakeup(rpipe);
  825 
  826         PIPE_UNLOCK(rpipe);
  827         return (error);
  828 }
  829 
  830 #ifndef PIPE_NODIRECT
  831 /*
  832  * Map the sending processes' buffer into kernel space and wire it.
  833  * This is similar to a physical write operation.
  834  */
  835 static int
  836 pipe_build_write_buffer(wpipe, uio)
  837         struct pipe *wpipe;
  838         struct uio *uio;
  839 {
  840         u_int size;
  841         int i;
  842 
  843         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  844         KASSERT(wpipe->pipe_state & PIPE_DIRECTW,
  845                 ("Clone attempt on non-direct write pipe!"));
  846 
  847         if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
  848                 size = wpipe->pipe_buffer.size;
  849         else
  850                 size = uio->uio_iov->iov_len;
  851 
  852         if ((i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
  853             (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
  854             wpipe->pipe_map.ms, PIPENPAGES)) < 0)
  855                 return (EFAULT);
  856 
  857 /*
  858  * set up the control block
  859  */
  860         wpipe->pipe_map.npages = i;
  861         wpipe->pipe_map.pos =
  862             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  863         wpipe->pipe_map.cnt = size;
  864 
  865 /*
  866  * and update the uio data
  867  */
  868 
  869         uio->uio_iov->iov_len -= size;
  870         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  871         if (uio->uio_iov->iov_len == 0)
  872                 uio->uio_iov++;
  873         uio->uio_resid -= size;
  874         uio->uio_offset += size;
  875         return (0);
  876 }
  877 
  878 /*
  879  * unmap and unwire the process buffer
  880  */
  881 static void
  882 pipe_destroy_write_buffer(wpipe)
  883         struct pipe *wpipe;
  884 {
  885 
  886         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  887         vm_page_unhold_pages(wpipe->pipe_map.ms, wpipe->pipe_map.npages);
  888         wpipe->pipe_map.npages = 0;
  889 }
  890 
  891 /*
  892  * In the case of a signal, the writing process might go away.  This
  893  * code copies the data into the circular buffer so that the source
  894  * pages can be freed without loss of data.
  895  */
  896 static void
  897 pipe_clone_write_buffer(wpipe)
  898         struct pipe *wpipe;
  899 {
  900         struct uio uio;
  901         struct iovec iov;
  902         int size;
  903         int pos;
  904 
  905         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  906         size = wpipe->pipe_map.cnt;
  907         pos = wpipe->pipe_map.pos;
  908 
  909         wpipe->pipe_buffer.in = size;
  910         wpipe->pipe_buffer.out = 0;
  911         wpipe->pipe_buffer.cnt = size;
  912         wpipe->pipe_state &= ~PIPE_DIRECTW;
  913 
  914         PIPE_UNLOCK(wpipe);
  915         iov.iov_base = wpipe->pipe_buffer.buffer;
  916         iov.iov_len = size;
  917         uio.uio_iov = &iov;
  918         uio.uio_iovcnt = 1;
  919         uio.uio_offset = 0;
  920         uio.uio_resid = size;
  921         uio.uio_segflg = UIO_SYSSPACE;
  922         uio.uio_rw = UIO_READ;
  923         uio.uio_td = curthread;
  924         uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
  925         PIPE_LOCK(wpipe);
  926         pipe_destroy_write_buffer(wpipe);
  927 }
  928 
  929 /*
  930  * This implements the pipe buffer write mechanism.  Note that only
  931  * a direct write OR a normal pipe write can be pending at any given time.
  932  * If there are any characters in the pipe buffer, the direct write will
  933  * be deferred until the receiving process grabs all of the bytes from
  934  * the pipe buffer.  Then the direct mapping write is set-up.
  935  */
  936 static int
  937 pipe_direct_write(wpipe, uio)
  938         struct pipe *wpipe;
  939         struct uio *uio;
  940 {
  941         int error;
  942 
  943 retry:
  944         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  945         error = pipelock(wpipe, 1);
  946         if (error != 0)
  947                 goto error1;
  948         if ((wpipe->pipe_state & PIPE_EOF) != 0) {
  949                 error = EPIPE;
  950                 pipeunlock(wpipe);
  951                 goto error1;
  952         }
  953         while (wpipe->pipe_state & PIPE_DIRECTW) {
  954                 if (wpipe->pipe_state & PIPE_WANTR) {
  955                         wpipe->pipe_state &= ~PIPE_WANTR;
  956                         wakeup(wpipe);
  957                 }
  958                 pipeselwakeup(wpipe);
  959                 wpipe->pipe_state |= PIPE_WANTW;
  960                 pipeunlock(wpipe);
  961                 error = msleep(wpipe, PIPE_MTX(wpipe),
  962                     PRIBIO | PCATCH, "pipdww", 0);
  963                 if (error)
  964                         goto error1;
  965                 else
  966                         goto retry;
  967         }
  968         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  969         if (wpipe->pipe_buffer.cnt > 0) {
  970                 if (wpipe->pipe_state & PIPE_WANTR) {
  971                         wpipe->pipe_state &= ~PIPE_WANTR;
  972                         wakeup(wpipe);
  973                 }
  974                 pipeselwakeup(wpipe);
  975                 wpipe->pipe_state |= PIPE_WANTW;
  976                 pipeunlock(wpipe);
  977                 error = msleep(wpipe, PIPE_MTX(wpipe),
  978                     PRIBIO | PCATCH, "pipdwc", 0);
  979                 if (error)
  980                         goto error1;
  981                 else
  982                         goto retry;
  983         }
  984 
  985         wpipe->pipe_state |= PIPE_DIRECTW;
  986 
  987         PIPE_UNLOCK(wpipe);
  988         error = pipe_build_write_buffer(wpipe, uio);
  989         PIPE_LOCK(wpipe);
  990         if (error) {
  991                 wpipe->pipe_state &= ~PIPE_DIRECTW;
  992                 pipeunlock(wpipe);
  993                 goto error1;
  994         }
  995 
  996         error = 0;
  997         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
  998                 if (wpipe->pipe_state & PIPE_EOF) {
  999                         pipe_destroy_write_buffer(wpipe);
 1000                         pipeselwakeup(wpipe);
 1001                         pipeunlock(wpipe);
 1002                         error = EPIPE;
 1003                         goto error1;
 1004                 }
 1005                 if (wpipe->pipe_state & PIPE_WANTR) {
 1006                         wpipe->pipe_state &= ~PIPE_WANTR;
 1007                         wakeup(wpipe);
 1008                 }
 1009                 pipeselwakeup(wpipe);
 1010                 wpipe->pipe_state |= PIPE_WANTW;
 1011                 pipeunlock(wpipe);
 1012                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
 1013                     "pipdwt", 0);
 1014                 pipelock(wpipe, 0);
 1015         }
 1016 
 1017         if (wpipe->pipe_state & PIPE_EOF)
 1018                 error = EPIPE;
 1019         if (wpipe->pipe_state & PIPE_DIRECTW) {
 1020                 /*
 1021                  * this bit of trickery substitutes a kernel buffer for
 1022                  * the process that might be going away.
 1023                  */
 1024                 pipe_clone_write_buffer(wpipe);
 1025         } else {
 1026                 pipe_destroy_write_buffer(wpipe);
 1027         }
 1028         pipeunlock(wpipe);
 1029         return (error);
 1030 
 1031 error1:
 1032         wakeup(wpipe);
 1033         return (error);
 1034 }
 1035 #endif
 1036 
 1037 static int
 1038 pipe_write(fp, uio, active_cred, flags, td)
 1039         struct file *fp;
 1040         struct uio *uio;
 1041         struct ucred *active_cred;
 1042         struct thread *td;
 1043         int flags;
 1044 {
 1045         int error = 0;
 1046         int desiredsize;
 1047         ssize_t orig_resid;
 1048         struct pipe *wpipe, *rpipe;
 1049 
 1050         rpipe = fp->f_data;
 1051         wpipe = PIPE_PEER(rpipe);
 1052         PIPE_LOCK(rpipe);
 1053         error = pipelock(wpipe, 1);
 1054         if (error) {
 1055                 PIPE_UNLOCK(rpipe);
 1056                 return (error);
 1057         }
 1058         /*
 1059          * detect loss of pipe read side, issue SIGPIPE if lost.
 1060          */
 1061         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1062             (wpipe->pipe_state & PIPE_EOF)) {
 1063                 pipeunlock(wpipe);
 1064                 PIPE_UNLOCK(rpipe);
 1065                 return (EPIPE);
 1066         }
 1067 #ifdef MAC
 1068         error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
 1069         if (error) {
 1070                 pipeunlock(wpipe);
 1071                 PIPE_UNLOCK(rpipe);
 1072                 return (error);
 1073         }
 1074 #endif
 1075         ++wpipe->pipe_busy;
 1076 
 1077         /* Choose a larger size if it's advantageous */
 1078         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
 1079         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
 1080                 if (piperesizeallowed != 1)
 1081                         break;
 1082                 if (amountpipekva > maxpipekva / 2)
 1083                         break;
 1084                 if (desiredsize == BIG_PIPE_SIZE)
 1085                         break;
 1086                 desiredsize = desiredsize * 2;
 1087         }
 1088 
 1089         /* Choose a smaller size if we're in a OOM situation */
 1090         if ((amountpipekva > (3 * maxpipekva) / 4) &&
 1091                 (wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
 1092                 (wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
 1093                 (piperesizeallowed == 1))
 1094                 desiredsize = SMALL_PIPE_SIZE;
 1095 
 1096         /* Resize if the above determined that a new size was necessary */
 1097         if ((desiredsize != wpipe->pipe_buffer.size) &&
 1098                 ((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
 1099                 PIPE_UNLOCK(wpipe);
 1100                 pipespace(wpipe, desiredsize);
 1101                 PIPE_LOCK(wpipe);
 1102         }
 1103         if (wpipe->pipe_buffer.size == 0) {
 1104                 /*
 1105                  * This can only happen for reverse direction use of pipes
 1106                  * in a complete OOM situation.
 1107                  */
 1108                 error = ENOMEM;
 1109                 --wpipe->pipe_busy;
 1110                 pipeunlock(wpipe);
 1111                 PIPE_UNLOCK(wpipe);
 1112                 return (error);
 1113         }
 1114 
 1115         pipeunlock(wpipe);
 1116 
 1117         orig_resid = uio->uio_resid;
 1118 
 1119         while (uio->uio_resid) {
 1120                 int space;
 1121 
 1122                 pipelock(wpipe, 0);
 1123                 if (wpipe->pipe_state & PIPE_EOF) {
 1124                         pipeunlock(wpipe);
 1125                         error = EPIPE;
 1126                         break;
 1127                 }
 1128 #ifndef PIPE_NODIRECT
 1129                 /*
 1130                  * If the transfer is large, we can gain performance if
 1131                  * we do process-to-process copies directly.
 1132                  * If the write is non-blocking, we don't use the
 1133                  * direct write mechanism.
 1134                  *
 1135                  * The direct write mechanism will detect the reader going
 1136                  * away on us.
 1137                  */
 1138                 if (uio->uio_segflg == UIO_USERSPACE &&
 1139                     uio->uio_iov->iov_len >= PIPE_MINDIRECT &&
 1140                     wpipe->pipe_buffer.size >= PIPE_MINDIRECT &&
 1141                     (fp->f_flag & FNONBLOCK) == 0) {
 1142                         pipeunlock(wpipe);
 1143                         error = pipe_direct_write(wpipe, uio);
 1144                         if (error)
 1145                                 break;
 1146                         continue;
 1147                 }
 1148 #endif
 1149 
 1150                 /*
 1151                  * Pipe buffered writes cannot be coincidental with
 1152                  * direct writes.  We wait until the currently executing
 1153                  * direct write is completed before we start filling the
 1154                  * pipe buffer.  We break out if a signal occurs or the
 1155                  * reader goes away.
 1156                  */
 1157                 if (wpipe->pipe_state & PIPE_DIRECTW) {
 1158                         if (wpipe->pipe_state & PIPE_WANTR) {
 1159                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1160                                 wakeup(wpipe);
 1161                         }
 1162                         pipeselwakeup(wpipe);
 1163                         wpipe->pipe_state |= PIPE_WANTW;
 1164                         pipeunlock(wpipe);
 1165                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
 1166                             "pipbww", 0);
 1167                         if (error)
 1168                                 break;
 1169                         else
 1170                                 continue;
 1171                 }
 1172 
 1173                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1174 
 1175                 /* Writes of size <= PIPE_BUF must be atomic. */
 1176                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 1177                         space = 0;
 1178 
 1179                 if (space > 0) {
 1180                         int size;       /* Transfer size */
 1181                         int segsize;    /* first segment to transfer */
 1182 
 1183                         /*
 1184                          * Transfer size is minimum of uio transfer
 1185                          * and free space in pipe buffer.
 1186                          */
 1187                         if (space > uio->uio_resid)
 1188                                 size = uio->uio_resid;
 1189                         else
 1190                                 size = space;
 1191                         /*
 1192                          * First segment to transfer is minimum of
 1193                          * transfer size and contiguous space in
 1194                          * pipe buffer.  If first segment to transfer
 1195                          * is less than the transfer size, we've got
 1196                          * a wraparound in the buffer.
 1197                          */
 1198                         segsize = wpipe->pipe_buffer.size -
 1199                                 wpipe->pipe_buffer.in;
 1200                         if (segsize > size)
 1201                                 segsize = size;
 1202 
 1203                         /* Transfer first segment */
 1204 
 1205                         PIPE_UNLOCK(rpipe);
 1206                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
 1207                                         segsize, uio);
 1208                         PIPE_LOCK(rpipe);
 1209 
 1210                         if (error == 0 && segsize < size) {
 1211                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
 1212                                         wpipe->pipe_buffer.size,
 1213                                         ("Pipe buffer wraparound disappeared"));
 1214                                 /*
 1215                                  * Transfer remaining part now, to
 1216                                  * support atomic writes.  Wraparound
 1217                                  * happened.
 1218                                  */
 1219 
 1220                                 PIPE_UNLOCK(rpipe);
 1221                                 error = uiomove(
 1222                                     &wpipe->pipe_buffer.buffer[0],
 1223                                     size - segsize, uio);
 1224                                 PIPE_LOCK(rpipe);
 1225                         }
 1226                         if (error == 0) {
 1227                                 wpipe->pipe_buffer.in += size;
 1228                                 if (wpipe->pipe_buffer.in >=
 1229                                     wpipe->pipe_buffer.size) {
 1230                                         KASSERT(wpipe->pipe_buffer.in ==
 1231                                                 size - segsize +
 1232                                                 wpipe->pipe_buffer.size,
 1233                                                 ("Expected wraparound bad"));
 1234                                         wpipe->pipe_buffer.in = size - segsize;
 1235                                 }
 1236 
 1237                                 wpipe->pipe_buffer.cnt += size;
 1238                                 KASSERT(wpipe->pipe_buffer.cnt <=
 1239                                         wpipe->pipe_buffer.size,
 1240                                         ("Pipe buffer overflow"));
 1241                         }
 1242                         pipeunlock(wpipe);
 1243                         if (error != 0)
 1244                                 break;
 1245                 } else {
 1246                         /*
 1247                          * If the "read-side" has been blocked, wake it up now.
 1248                          */
 1249                         if (wpipe->pipe_state & PIPE_WANTR) {
 1250                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1251                                 wakeup(wpipe);
 1252                         }
 1253 
 1254                         /*
 1255                          * don't block on non-blocking I/O
 1256                          */
 1257                         if (fp->f_flag & FNONBLOCK) {
 1258                                 error = EAGAIN;
 1259                                 pipeunlock(wpipe);
 1260                                 break;
 1261                         }
 1262 
 1263                         /*
 1264                          * We have no more space and have something to offer,
 1265                          * wake up select/poll.
 1266                          */
 1267                         pipeselwakeup(wpipe);
 1268 
 1269                         wpipe->pipe_state |= PIPE_WANTW;
 1270                         pipeunlock(wpipe);
 1271                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1272                             PRIBIO | PCATCH, "pipewr", 0);
 1273                         if (error != 0)
 1274                                 break;
 1275                 }
 1276         }
 1277 
 1278         pipelock(wpipe, 0);
 1279         --wpipe->pipe_busy;
 1280 
 1281         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1282                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1283                 wakeup(wpipe);
 1284         } else if (wpipe->pipe_buffer.cnt > 0) {
 1285                 /*
 1286                  * If we have put any characters in the buffer, we wake up
 1287                  * the reader.
 1288                  */
 1289                 if (wpipe->pipe_state & PIPE_WANTR) {
 1290                         wpipe->pipe_state &= ~PIPE_WANTR;
 1291                         wakeup(wpipe);
 1292                 }
 1293         }
 1294 
 1295         /*
 1296          * Don't return EPIPE if any byte was written.
 1297          * EINTR and other interrupts are handled by generic I/O layer.
 1298          * Do not pretend that I/O succeeded for obvious user error
 1299          * like EFAULT.
 1300          */
 1301         if (uio->uio_resid != orig_resid && error == EPIPE)
 1302                 error = 0;
 1303 
 1304         if (error == 0)
 1305                 vfs_timestamp(&wpipe->pipe_mtime);
 1306 
 1307         /*
 1308          * We have something to offer,
 1309          * wake up select/poll.
 1310          */
 1311         if (wpipe->pipe_buffer.cnt)
 1312                 pipeselwakeup(wpipe);
 1313 
 1314         pipeunlock(wpipe);
 1315         PIPE_UNLOCK(rpipe);
 1316         return (error);
 1317 }
 1318 
 1319 /* ARGSUSED */
 1320 static int
 1321 pipe_truncate(fp, length, active_cred, td)
 1322         struct file *fp;
 1323         off_t length;
 1324         struct ucred *active_cred;
 1325         struct thread *td;
 1326 {
 1327 
 1328         /* For named pipes call the vnode operation. */
 1329         if (fp->f_vnode != NULL)
 1330                 return (vnops.fo_truncate(fp, length, active_cred, td));
 1331         return (EINVAL);
 1332 }
 1333 
 1334 /*
 1335  * we implement a very minimal set of ioctls for compatibility with sockets.
 1336  */
 1337 static int
 1338 pipe_ioctl(fp, cmd, data, active_cred, td)
 1339         struct file *fp;
 1340         u_long cmd;
 1341         void *data;
 1342         struct ucred *active_cred;
 1343         struct thread *td;
 1344 {
 1345         struct pipe *mpipe = fp->f_data;
 1346         int error;
 1347 
 1348         PIPE_LOCK(mpipe);
 1349 
 1350 #ifdef MAC
 1351         error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
 1352         if (error) {
 1353                 PIPE_UNLOCK(mpipe);
 1354                 return (error);
 1355         }
 1356 #endif
 1357 
 1358         error = 0;
 1359         switch (cmd) {
 1360 
 1361         case FIONBIO:
 1362                 break;
 1363 
 1364         case FIOASYNC:
 1365                 if (*(int *)data) {
 1366                         mpipe->pipe_state |= PIPE_ASYNC;
 1367                 } else {
 1368                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1369                 }
 1370                 break;
 1371 
 1372         case FIONREAD:
 1373                 if (!(fp->f_flag & FREAD)) {
 1374                         *(int *)data = 0;
 1375                         PIPE_UNLOCK(mpipe);
 1376                         return (0);
 1377                 }
 1378                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1379                         *(int *)data = mpipe->pipe_map.cnt;
 1380                 else
 1381                         *(int *)data = mpipe->pipe_buffer.cnt;
 1382                 break;
 1383 
 1384         case FIOSETOWN:
 1385                 PIPE_UNLOCK(mpipe);
 1386                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 1387                 goto out_unlocked;
 1388 
 1389         case FIOGETOWN:
 1390                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1391                 break;
 1392 
 1393         /* This is deprecated, FIOSETOWN should be used instead. */
 1394         case TIOCSPGRP:
 1395                 PIPE_UNLOCK(mpipe);
 1396                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 1397                 goto out_unlocked;
 1398 
 1399         /* This is deprecated, FIOGETOWN should be used instead. */
 1400         case TIOCGPGRP:
 1401                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1402                 break;
 1403 
 1404         default:
 1405                 error = ENOTTY;
 1406                 break;
 1407         }
 1408         PIPE_UNLOCK(mpipe);
 1409 out_unlocked:
 1410         return (error);
 1411 }
 1412 
 1413 static int
 1414 pipe_poll(fp, events, active_cred, td)
 1415         struct file *fp;
 1416         int events;
 1417         struct ucred *active_cred;
 1418         struct thread *td;
 1419 {
 1420         struct pipe *rpipe;
 1421         struct pipe *wpipe;
 1422         int levents, revents;
 1423 #ifdef MAC
 1424         int error;
 1425 #endif
 1426 
 1427         revents = 0;
 1428         rpipe = fp->f_data;
 1429         wpipe = PIPE_PEER(rpipe);
 1430         PIPE_LOCK(rpipe);
 1431 #ifdef MAC
 1432         error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
 1433         if (error)
 1434                 goto locked_error;
 1435 #endif
 1436         if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM))
 1437                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1438                     (rpipe->pipe_buffer.cnt > 0))
 1439                         revents |= events & (POLLIN | POLLRDNORM);
 1440 
 1441         if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM))
 1442                 if (wpipe->pipe_present != PIPE_ACTIVE ||
 1443                     (wpipe->pipe_state & PIPE_EOF) ||
 1444                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1445                      ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
 1446                          wpipe->pipe_buffer.size == 0)))
 1447                         revents |= events & (POLLOUT | POLLWRNORM);
 1448 
 1449         levents = events &
 1450             (POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
 1451         if (rpipe->pipe_state & PIPE_NAMED && fp->f_flag & FREAD && levents &&
 1452             fp->f_seqcount == rpipe->pipe_wgen)
 1453                 events |= POLLINIGNEOF;
 1454 
 1455         if ((events & POLLINIGNEOF) == 0) {
 1456                 if (rpipe->pipe_state & PIPE_EOF) {
 1457                         revents |= (events & (POLLIN | POLLRDNORM));
 1458                         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1459                             (wpipe->pipe_state & PIPE_EOF))
 1460                                 revents |= POLLHUP;
 1461                 }
 1462         }
 1463 
 1464         if (revents == 0) {
 1465                 if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM)) {
 1466                         selrecord(td, &rpipe->pipe_sel);
 1467                         if (SEL_WAITING(&rpipe->pipe_sel))
 1468                                 rpipe->pipe_state |= PIPE_SEL;
 1469                 }
 1470 
 1471                 if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM)) {
 1472                         selrecord(td, &wpipe->pipe_sel);
 1473                         if (SEL_WAITING(&wpipe->pipe_sel))
 1474                                 wpipe->pipe_state |= PIPE_SEL;
 1475                 }
 1476         }
 1477 #ifdef MAC
 1478 locked_error:
 1479 #endif
 1480         PIPE_UNLOCK(rpipe);
 1481 
 1482         return (revents);
 1483 }
 1484 
 1485 /*
 1486  * We shouldn't need locks here as we're doing a read and this should
 1487  * be a natural race.
 1488  */
 1489 static int
 1490 pipe_stat(fp, ub, active_cred, td)
 1491         struct file *fp;
 1492         struct stat *ub;
 1493         struct ucred *active_cred;
 1494         struct thread *td;
 1495 {
 1496         struct pipe *pipe;
 1497         int new_unr;
 1498 #ifdef MAC
 1499         int error;
 1500 #endif
 1501 
 1502         pipe = fp->f_data;
 1503         PIPE_LOCK(pipe);
 1504 #ifdef MAC
 1505         error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
 1506         if (error) {
 1507                 PIPE_UNLOCK(pipe);
 1508                 return (error);
 1509         }
 1510 #endif
 1511 
 1512         /* For named pipes ask the underlying filesystem. */
 1513         if (pipe->pipe_state & PIPE_NAMED) {
 1514                 PIPE_UNLOCK(pipe);
 1515                 return (vnops.fo_stat(fp, ub, active_cred, td));
 1516         }
 1517 
 1518         /*
 1519          * Lazily allocate an inode number for the pipe.  Most pipe
 1520          * users do not call fstat(2) on the pipe, which means that
 1521          * postponing the inode allocation until it is must be
 1522          * returned to userland is useful.  If alloc_unr failed,
 1523          * assign st_ino zero instead of returning an error.
 1524          * Special pipe_ino values:
 1525          *  -1 - not yet initialized;
 1526          *  0  - alloc_unr failed, return 0 as st_ino forever.
 1527          */
 1528         if (pipe->pipe_ino == (ino_t)-1) {
 1529                 new_unr = alloc_unr(pipeino_unr);
 1530                 if (new_unr != -1)
 1531                         pipe->pipe_ino = new_unr;
 1532                 else
 1533                         pipe->pipe_ino = 0;
 1534         }
 1535         PIPE_UNLOCK(pipe);
 1536 
 1537         bzero(ub, sizeof(*ub));
 1538         ub->st_mode = S_IFIFO;
 1539         ub->st_blksize = PAGE_SIZE;
 1540         if (pipe->pipe_state & PIPE_DIRECTW)
 1541                 ub->st_size = pipe->pipe_map.cnt;
 1542         else
 1543                 ub->st_size = pipe->pipe_buffer.cnt;
 1544         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
 1545         ub->st_atim = pipe->pipe_atime;
 1546         ub->st_mtim = pipe->pipe_mtime;
 1547         ub->st_ctim = pipe->pipe_ctime;
 1548         ub->st_uid = fp->f_cred->cr_uid;
 1549         ub->st_gid = fp->f_cred->cr_gid;
 1550         ub->st_dev = pipedev_ino;
 1551         ub->st_ino = pipe->pipe_ino;
 1552         /*
 1553          * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
 1554          */
 1555         return (0);
 1556 }
 1557 
 1558 /* ARGSUSED */
 1559 static int
 1560 pipe_close(fp, td)
 1561         struct file *fp;
 1562         struct thread *td;
 1563 {
 1564 
 1565         if (fp->f_vnode != NULL) 
 1566                 return vnops.fo_close(fp, td);
 1567         fp->f_ops = &badfileops;
 1568         pipe_dtor(fp->f_data);
 1569         fp->f_data = NULL;
 1570         return (0);
 1571 }
 1572 
 1573 static int
 1574 pipe_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, struct thread *td)
 1575 {
 1576         struct pipe *cpipe;
 1577         int error;
 1578 
 1579         cpipe = fp->f_data;
 1580         if (cpipe->pipe_state & PIPE_NAMED)
 1581                 error = vn_chmod(fp, mode, active_cred, td);
 1582         else
 1583                 error = invfo_chmod(fp, mode, active_cred, td);
 1584         return (error);
 1585 }
 1586 
 1587 static int
 1588 pipe_chown(fp, uid, gid, active_cred, td)
 1589         struct file *fp;
 1590         uid_t uid;
 1591         gid_t gid;
 1592         struct ucred *active_cred;
 1593         struct thread *td;
 1594 {
 1595         struct pipe *cpipe;
 1596         int error;
 1597 
 1598         cpipe = fp->f_data;
 1599         if (cpipe->pipe_state & PIPE_NAMED)
 1600                 error = vn_chown(fp, uid, gid, active_cred, td);
 1601         else
 1602                 error = invfo_chown(fp, uid, gid, active_cred, td);
 1603         return (error);
 1604 }
 1605 
 1606 static void
 1607 pipe_free_kmem(cpipe)
 1608         struct pipe *cpipe;
 1609 {
 1610 
 1611         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
 1612             ("pipe_free_kmem: pipe mutex locked"));
 1613 
 1614         if (cpipe->pipe_buffer.buffer != NULL) {
 1615                 atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
 1616                 vm_map_remove(pipe_map,
 1617                     (vm_offset_t)cpipe->pipe_buffer.buffer,
 1618                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
 1619                 cpipe->pipe_buffer.buffer = NULL;
 1620         }
 1621 #ifndef PIPE_NODIRECT
 1622         {
 1623                 cpipe->pipe_map.cnt = 0;
 1624                 cpipe->pipe_map.pos = 0;
 1625                 cpipe->pipe_map.npages = 0;
 1626         }
 1627 #endif
 1628 }
 1629 
 1630 /*
 1631  * shutdown the pipe
 1632  */
 1633 static void
 1634 pipeclose(cpipe)
 1635         struct pipe *cpipe;
 1636 {
 1637         struct pipepair *pp;
 1638         struct pipe *ppipe;
 1639 
 1640         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
 1641 
 1642         PIPE_LOCK(cpipe);
 1643         pipelock(cpipe, 0);
 1644         pp = cpipe->pipe_pair;
 1645 
 1646         pipeselwakeup(cpipe);
 1647 
 1648         /*
 1649          * If the other side is blocked, wake it up saying that
 1650          * we want to close it down.
 1651          */
 1652         cpipe->pipe_state |= PIPE_EOF;
 1653         while (cpipe->pipe_busy) {
 1654                 wakeup(cpipe);
 1655                 cpipe->pipe_state |= PIPE_WANT;
 1656                 pipeunlock(cpipe);
 1657                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1658                 pipelock(cpipe, 0);
 1659         }
 1660 
 1661 
 1662         /*
 1663          * Disconnect from peer, if any.
 1664          */
 1665         ppipe = cpipe->pipe_peer;
 1666         if (ppipe->pipe_present == PIPE_ACTIVE) {
 1667                 pipeselwakeup(ppipe);
 1668 
 1669                 ppipe->pipe_state |= PIPE_EOF;
 1670                 wakeup(ppipe);
 1671                 KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
 1672         }
 1673 
 1674         /*
 1675          * Mark this endpoint as free.  Release kmem resources.  We
 1676          * don't mark this endpoint as unused until we've finished
 1677          * doing that, or the pipe might disappear out from under
 1678          * us.
 1679          */
 1680         PIPE_UNLOCK(cpipe);
 1681         pipe_free_kmem(cpipe);
 1682         PIPE_LOCK(cpipe);
 1683         cpipe->pipe_present = PIPE_CLOSING;
 1684         pipeunlock(cpipe);
 1685 
 1686         /*
 1687          * knlist_clear() may sleep dropping the PIPE_MTX. Set the
 1688          * PIPE_FINALIZED, that allows other end to free the
 1689          * pipe_pair, only after the knotes are completely dismantled.
 1690          */
 1691         knlist_clear(&cpipe->pipe_sel.si_note, 1);
 1692         cpipe->pipe_present = PIPE_FINALIZED;
 1693         seldrain(&cpipe->pipe_sel);
 1694         knlist_destroy(&cpipe->pipe_sel.si_note);
 1695 
 1696         /*
 1697          * If both endpoints are now closed, release the memory for the
 1698          * pipe pair.  If not, unlock.
 1699          */
 1700         if (ppipe->pipe_present == PIPE_FINALIZED) {
 1701                 PIPE_UNLOCK(cpipe);
 1702 #ifdef MAC
 1703                 mac_pipe_destroy(pp);
 1704 #endif
 1705                 uma_zfree(pipe_zone, cpipe->pipe_pair);
 1706         } else
 1707                 PIPE_UNLOCK(cpipe);
 1708 }
 1709 
 1710 /*ARGSUSED*/
 1711 static int
 1712 pipe_kqfilter(struct file *fp, struct knote *kn)
 1713 {
 1714         struct pipe *cpipe;
 1715 
 1716         /*
 1717          * If a filter is requested that is not supported by this file
 1718          * descriptor, don't return an error, but also don't ever generate an
 1719          * event.
 1720          */
 1721         if ((kn->kn_filter == EVFILT_READ) && !(fp->f_flag & FREAD)) {
 1722                 kn->kn_fop = &pipe_nfiltops;
 1723                 return (0);
 1724         }
 1725         if ((kn->kn_filter == EVFILT_WRITE) && !(fp->f_flag & FWRITE)) {
 1726                 kn->kn_fop = &pipe_nfiltops;
 1727                 return (0);
 1728         }
 1729         cpipe = fp->f_data;
 1730         PIPE_LOCK(cpipe);
 1731         switch (kn->kn_filter) {
 1732         case EVFILT_READ:
 1733                 kn->kn_fop = &pipe_rfiltops;
 1734                 break;
 1735         case EVFILT_WRITE:
 1736                 kn->kn_fop = &pipe_wfiltops;
 1737                 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
 1738                         /* other end of pipe has been closed */
 1739                         PIPE_UNLOCK(cpipe);
 1740                         return (EPIPE);
 1741                 }
 1742                 cpipe = PIPE_PEER(cpipe);
 1743                 break;
 1744         default:
 1745                 PIPE_UNLOCK(cpipe);
 1746                 return (EINVAL);
 1747         }
 1748 
 1749         kn->kn_hook = cpipe; 
 1750         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
 1751         PIPE_UNLOCK(cpipe);
 1752         return (0);
 1753 }
 1754 
 1755 static void
 1756 filt_pipedetach(struct knote *kn)
 1757 {
 1758         struct pipe *cpipe = kn->kn_hook;
 1759 
 1760         PIPE_LOCK(cpipe);
 1761         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
 1762         PIPE_UNLOCK(cpipe);
 1763 }
 1764 
 1765 /*ARGSUSED*/
 1766 static int
 1767 filt_piperead(struct knote *kn, long hint)
 1768 {
 1769         struct pipe *rpipe = kn->kn_hook;
 1770         struct pipe *wpipe = rpipe->pipe_peer;
 1771         int ret;
 1772 
 1773         PIPE_LOCK_ASSERT(rpipe, MA_OWNED);
 1774         kn->kn_data = rpipe->pipe_buffer.cnt;
 1775         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1776                 kn->kn_data = rpipe->pipe_map.cnt;
 1777 
 1778         if ((rpipe->pipe_state & PIPE_EOF) ||
 1779             wpipe->pipe_present != PIPE_ACTIVE ||
 1780             (wpipe->pipe_state & PIPE_EOF)) {
 1781                 kn->kn_flags |= EV_EOF;
 1782                 return (1);
 1783         }
 1784         ret = kn->kn_data > 0;
 1785         return ret;
 1786 }
 1787 
 1788 /*ARGSUSED*/
 1789 static int
 1790 filt_pipewrite(struct knote *kn, long hint)
 1791 {
 1792         struct pipe *wpipe;
 1793    
 1794         wpipe = kn->kn_hook;
 1795         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 1796         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1797             (wpipe->pipe_state & PIPE_EOF)) {
 1798                 kn->kn_data = 0;
 1799                 kn->kn_flags |= EV_EOF;
 1800                 return (1);
 1801         }
 1802         kn->kn_data = (wpipe->pipe_buffer.size > 0) ?
 1803             (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) : PIPE_BUF;
 1804         if (wpipe->pipe_state & PIPE_DIRECTW)
 1805                 kn->kn_data = 0;
 1806 
 1807         return (kn->kn_data >= PIPE_BUF);
 1808 }
 1809 
 1810 static void
 1811 filt_pipedetach_notsup(struct knote *kn)
 1812 {
 1813 
 1814 }
 1815 
 1816 static int
 1817 filt_pipenotsup(struct knote *kn, long hint)
 1818 {
 1819 
 1820         return (0);
 1821 }

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