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


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

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    1 /*-
    2  * Copyright (c) 1996 John S. Dyson
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice immediately at the beginning of the file, without modification,
   10  *    this list of conditions, and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. Absolutely no warranty of function or purpose is made by the author
   15  *    John S. Dyson.
   16  * 4. Modifications may be freely made to this file if the above conditions
   17  *    are met.
   18  */
   19 
   20 /*
   21  * This file contains a high-performance replacement for the socket-based
   22  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
   23  * all features of sockets, but does do everything that pipes normally
   24  * do.
   25  */
   26 
   27 /*
   28  * This code has two modes of operation, a small write mode and a large
   29  * write mode.  The small write mode acts like conventional pipes with
   30  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
   31  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
   32  * and PIPE_SIZE in size, it is fully mapped and wired into the kernel, and
   33  * the receiving process can copy it directly from the pages in the sending
   34  * process.
   35  *
   36  * If the sending process receives a signal, it is possible that it will
   37  * go away, and certainly its address space can change, because control
   38  * is returned back to the user-mode side.  In that case, the pipe code
   39  * arranges to copy the buffer supplied by the user process, to a pageable
   40  * kernel buffer, and the receiving process will grab the data from the
   41  * pageable kernel buffer.  Since signals don't happen all that often,
   42  * the copy operation is normally eliminated.
   43  *
   44  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
   45  * happen for small transfers so that the system will not spend all of
   46  * its time context switching.
   47  *
   48  * In order to limit the resource use of pipes, two sysctls exist:
   49  *
   50  * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
   51  * address space available to us in pipe_map. This value is normally
   52  * autotuned, but may also be loader tuned.
   53  *
   54  * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
   55  * memory in use by pipes.
   56  *
   57  * Based on how large pipekva is relative to maxpipekva, the following
   58  * will happen:
   59  *
   60  * 0% - 50%:
   61  *     New pipes are given 16K of memory backing, pipes may dynamically
   62  *     grow to as large as 64K where needed.
   63  * 50% - 75%:
   64  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   65  *     existing pipes may NOT grow.
   66  * 75% - 100%:
   67  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   68  *     existing pipes will be shrunk down to 4K whenever possible.
   69  *
   70  * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
   71  * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
   72  * resize which MUST occur for reverse-direction pipes when they are
   73  * first used.
   74  *
   75  * Additional information about the current state of pipes may be obtained
   76  * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
   77  * and kern.ipc.piperesizefail.
   78  *
   79  * Locking rules:  There are two locks present here:  A mutex, used via
   80  * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
   81  * the flag, as mutexes can not persist over uiomove.  The mutex
   82  * exists only to guard access to the flag, and is not in itself a
   83  * locking mechanism.  Also note that there is only a single mutex for
   84  * both directions of a pipe.
   85  *
   86  * As pipelock() may have to sleep before it can acquire the flag, it
   87  * is important to reread all data after a call to pipelock(); everything
   88  * in the structure may have changed.
   89  */
   90 
   91 #include <sys/cdefs.h>
   92 __FBSDID("$FreeBSD: releng/6.0/sys/kern/sys_pipe.c 147730 2005-07-01 16:28:32Z ssouhlal $");
   93 
   94 #include "opt_mac.h"
   95 
   96 #include <sys/param.h>
   97 #include <sys/systm.h>
   98 #include <sys/fcntl.h>
   99 #include <sys/file.h>
  100 #include <sys/filedesc.h>
  101 #include <sys/filio.h>
  102 #include <sys/kernel.h>
  103 #include <sys/lock.h>
  104 #include <sys/mac.h>
  105 #include <sys/mutex.h>
  106 #include <sys/ttycom.h>
  107 #include <sys/stat.h>
  108 #include <sys/malloc.h>
  109 #include <sys/poll.h>
  110 #include <sys/selinfo.h>
  111 #include <sys/signalvar.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 <vm/vm.h>
  121 #include <vm/vm_param.h>
  122 #include <vm/vm_object.h>
  123 #include <vm/vm_kern.h>
  124 #include <vm/vm_extern.h>
  125 #include <vm/pmap.h>
  126 #include <vm/vm_map.h>
  127 #include <vm/vm_page.h>
  128 #include <vm/uma.h>
  129 
  130 /*
  131  * Use this define if you want to disable *fancy* VM things.  Expect an
  132  * approx 30% decrease in transfer rate.  This could be useful for
  133  * NetBSD or OpenBSD.
  134  */
  135 /* #define PIPE_NODIRECT */
  136 
  137 /*
  138  * interfaces to the outside world
  139  */
  140 static fo_rdwr_t        pipe_read;
  141 static fo_rdwr_t        pipe_write;
  142 static fo_ioctl_t       pipe_ioctl;
  143 static fo_poll_t        pipe_poll;
  144 static fo_kqfilter_t    pipe_kqfilter;
  145 static fo_stat_t        pipe_stat;
  146 static fo_close_t       pipe_close;
  147 
  148 static struct fileops pipeops = {
  149         .fo_read = pipe_read,
  150         .fo_write = pipe_write,
  151         .fo_ioctl = pipe_ioctl,
  152         .fo_poll = pipe_poll,
  153         .fo_kqfilter = pipe_kqfilter,
  154         .fo_stat = pipe_stat,
  155         .fo_close = pipe_close,
  156         .fo_flags = DFLAG_PASSABLE
  157 };
  158 
  159 static void     filt_pipedetach(struct knote *kn);
  160 static int      filt_piperead(struct knote *kn, long hint);
  161 static int      filt_pipewrite(struct knote *kn, long hint);
  162 
  163 static struct filterops pipe_rfiltops =
  164         { 1, NULL, filt_pipedetach, filt_piperead };
  165 static struct filterops pipe_wfiltops =
  166         { 1, NULL, filt_pipedetach, filt_pipewrite };
  167 
  168 /*
  169  * Default pipe buffer size(s), this can be kind-of large now because pipe
  170  * space is pageable.  The pipe code will try to maintain locality of
  171  * reference for performance reasons, so small amounts of outstanding I/O
  172  * will not wipe the cache.
  173  */
  174 #define MINPIPESIZE (PIPE_SIZE/3)
  175 #define MAXPIPESIZE (2*PIPE_SIZE/3)
  176 
  177 static int amountpipes;
  178 static int amountpipekva;
  179 static int pipefragretry;
  180 static int pipeallocfail;
  181 static int piperesizefail;
  182 static int piperesizeallowed = 1;
  183 
  184 SYSCTL_DECL(_kern_ipc);
  185 
  186 SYSCTL_INT(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN,
  187            &maxpipekva, 0, "Pipe KVA limit");
  188 SYSCTL_INT(_kern_ipc, OID_AUTO, pipes, CTLFLAG_RD,
  189            &amountpipes, 0, "Current # of pipes");
  190 SYSCTL_INT(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
  191            &amountpipekva, 0, "Pipe KVA usage");
  192 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
  193           &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
  194 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
  195           &pipeallocfail, 0, "Pipe allocation failures");
  196 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
  197           &piperesizefail, 0, "Pipe resize failures");
  198 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
  199           &piperesizeallowed, 0, "Pipe resizing allowed");
  200 
  201 static void pipeinit(void *dummy __unused);
  202 static void pipeclose(struct pipe *cpipe);
  203 static void pipe_free_kmem(struct pipe *cpipe);
  204 static int pipe_create(struct pipe *pipe, int backing);
  205 static __inline int pipelock(struct pipe *cpipe, int catch);
  206 static __inline void pipeunlock(struct pipe *cpipe);
  207 static __inline void pipeselwakeup(struct pipe *cpipe);
  208 #ifndef PIPE_NODIRECT
  209 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
  210 static void pipe_destroy_write_buffer(struct pipe *wpipe);
  211 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
  212 static void pipe_clone_write_buffer(struct pipe *wpipe);
  213 #endif
  214 static int pipespace(struct pipe *cpipe, int size);
  215 static int pipespace_new(struct pipe *cpipe, int size);
  216 
  217 static int      pipe_zone_ctor(void *mem, int size, void *arg, int flags);
  218 static void     pipe_zone_dtor(void *mem, int size, void *arg);
  219 static int      pipe_zone_init(void *mem, int size, int flags);
  220 static void     pipe_zone_fini(void *mem, int size);
  221 
  222 static uma_zone_t pipe_zone;
  223 
  224 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
  225 
  226 static void
  227 pipeinit(void *dummy __unused)
  228 {
  229 
  230         pipe_zone = uma_zcreate("PIPE", sizeof(struct pipepair),
  231             pipe_zone_ctor, pipe_zone_dtor, pipe_zone_init, pipe_zone_fini,
  232             UMA_ALIGN_PTR, 0);
  233         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
  234 }
  235 
  236 static int
  237 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
  238 {
  239         struct pipepair *pp;
  240         struct pipe *rpipe, *wpipe;
  241 
  242         KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
  243 
  244         pp = (struct pipepair *)mem;
  245 
  246         /*
  247          * We zero both pipe endpoints to make sure all the kmem pointers
  248          * are NULL, flag fields are zero'd, etc.  We timestamp both
  249          * endpoints with the same time.
  250          */
  251         rpipe = &pp->pp_rpipe;
  252         bzero(rpipe, sizeof(*rpipe));
  253         vfs_timestamp(&rpipe->pipe_ctime);
  254         rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
  255 
  256         wpipe = &pp->pp_wpipe;
  257         bzero(wpipe, sizeof(*wpipe));
  258         wpipe->pipe_ctime = rpipe->pipe_ctime;
  259         wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
  260 
  261         rpipe->pipe_peer = wpipe;
  262         rpipe->pipe_pair = pp;
  263         wpipe->pipe_peer = rpipe;
  264         wpipe->pipe_pair = pp;
  265 
  266         /*
  267          * Mark both endpoints as present; they will later get free'd
  268          * one at a time.  When both are free'd, then the whole pair
  269          * is released.
  270          */
  271         rpipe->pipe_present = 1;
  272         wpipe->pipe_present = 1;
  273 
  274         /*
  275          * Eventually, the MAC Framework may initialize the label
  276          * in ctor or init, but for now we do it elswhere to avoid
  277          * blocking in ctor or init.
  278          */
  279         pp->pp_label = NULL;
  280 
  281         atomic_add_int(&amountpipes, 2);
  282         return (0);
  283 }
  284 
  285 static void
  286 pipe_zone_dtor(void *mem, int size, void *arg)
  287 {
  288         struct pipepair *pp;
  289 
  290         KASSERT(size == sizeof(*pp), ("pipe_zone_dtor: wrong size"));
  291 
  292         pp = (struct pipepair *)mem;
  293 
  294         atomic_subtract_int(&amountpipes, 2);
  295 }
  296 
  297 static int
  298 pipe_zone_init(void *mem, int size, int flags)
  299 {
  300         struct pipepair *pp;
  301 
  302         KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
  303 
  304         pp = (struct pipepair *)mem;
  305 
  306         mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_RECURSE);
  307         return (0);
  308 }
  309 
  310 static void
  311 pipe_zone_fini(void *mem, int size)
  312 {
  313         struct pipepair *pp;
  314 
  315         KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
  316 
  317         pp = (struct pipepair *)mem;
  318 
  319         mtx_destroy(&pp->pp_mtx);
  320 }
  321 
  322 /*
  323  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail,
  324  * let the zone pick up the pieces via pipeclose().
  325  */
  326 
  327 /* ARGSUSED */
  328 int
  329 pipe(td, uap)
  330         struct thread *td;
  331         struct pipe_args /* {
  332                 int     dummy;
  333         } */ *uap;
  334 {
  335         struct filedesc *fdp = td->td_proc->p_fd;
  336         struct file *rf, *wf;
  337         struct pipepair *pp;
  338         struct pipe *rpipe, *wpipe;
  339         int fd, error;
  340 
  341         pp = uma_zalloc(pipe_zone, M_WAITOK);
  342 #ifdef MAC
  343         /*
  344          * The MAC label is shared between the connected endpoints.  As a
  345          * result mac_init_pipe() and mac_create_pipe() are called once
  346          * for the pair, and not on the endpoints.
  347          */
  348         mac_init_pipe(pp);
  349         mac_create_pipe(td->td_ucred, pp);
  350 #endif
  351         rpipe = &pp->pp_rpipe;
  352         wpipe = &pp->pp_wpipe;
  353 
  354         knlist_init(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe), NULL, NULL,
  355             NULL);
  356         knlist_init(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe), NULL, NULL,
  357             NULL);
  358 
  359         /* Only the forward direction pipe is backed by default */
  360         if (pipe_create(rpipe, 1) || pipe_create(wpipe, 0)) {
  361                 pipeclose(rpipe);
  362                 pipeclose(wpipe);
  363                 return (ENFILE);
  364         }
  365 
  366         rpipe->pipe_state |= PIPE_DIRECTOK;
  367         wpipe->pipe_state |= PIPE_DIRECTOK;
  368 
  369         error = falloc(td, &rf, &fd);
  370         if (error) {
  371                 pipeclose(rpipe);
  372                 pipeclose(wpipe);
  373                 return (error);
  374         }
  375         /* An extra reference on `rf' has been held for us by falloc(). */
  376         td->td_retval[0] = fd;
  377 
  378         /*
  379          * Warning: once we've gotten past allocation of the fd for the
  380          * read-side, we can only drop the read side via fdrop() in order
  381          * to avoid races against processes which manage to dup() the read
  382          * side while we are blocked trying to allocate the write side.
  383          */
  384         FILE_LOCK(rf);
  385         rf->f_flag = FREAD | FWRITE;
  386         rf->f_type = DTYPE_PIPE;
  387         rf->f_data = rpipe;
  388         rf->f_ops = &pipeops;
  389         FILE_UNLOCK(rf);
  390         error = falloc(td, &wf, &fd);
  391         if (error) {
  392                 fdclose(fdp, rf, td->td_retval[0], td);
  393                 fdrop(rf, td);
  394                 /* rpipe has been closed by fdrop(). */
  395                 pipeclose(wpipe);
  396                 return (error);
  397         }
  398         /* An extra reference on `wf' has been held for us by falloc(). */
  399         FILE_LOCK(wf);
  400         wf->f_flag = FREAD | FWRITE;
  401         wf->f_type = DTYPE_PIPE;
  402         wf->f_data = wpipe;
  403         wf->f_ops = &pipeops;
  404         FILE_UNLOCK(wf);
  405         fdrop(wf, td);
  406         td->td_retval[1] = fd;
  407         fdrop(rf, td);
  408 
  409         return (0);
  410 }
  411 
  412 /*
  413  * Allocate kva for pipe circular buffer, the space is pageable
  414  * This routine will 'realloc' the size of a pipe safely, if it fails
  415  * it will retain the old buffer.
  416  * If it fails it will return ENOMEM.
  417  */
  418 static int
  419 pipespace_new(cpipe, size)
  420         struct pipe *cpipe;
  421         int size;
  422 {
  423         caddr_t buffer;
  424         int error, cnt, firstseg;
  425         static int curfail = 0;
  426         static struct timeval lastfail;
  427 
  428         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
  429         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
  430                 ("pipespace: resize of direct writes not allowed"));
  431 retry:
  432         cnt = cpipe->pipe_buffer.cnt;
  433         if (cnt > size)
  434                 size = cnt;
  435 
  436         size = round_page(size);
  437         buffer = (caddr_t) vm_map_min(pipe_map);
  438 
  439         error = vm_map_find(pipe_map, NULL, 0,
  440                 (vm_offset_t *) &buffer, size, 1,
  441                 VM_PROT_ALL, VM_PROT_ALL, 0);
  442         if (error != KERN_SUCCESS) {
  443                 if ((cpipe->pipe_buffer.buffer == NULL) &&
  444                         (size > SMALL_PIPE_SIZE)) {
  445                         size = SMALL_PIPE_SIZE;
  446                         pipefragretry++;
  447                         goto retry;
  448                 }
  449                 if (cpipe->pipe_buffer.buffer == NULL) {
  450                         pipeallocfail++;
  451                         if (ppsratecheck(&lastfail, &curfail, 1))
  452                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
  453                 } else {
  454                         piperesizefail++;
  455                 }
  456                 return (ENOMEM);
  457         }
  458 
  459         /* copy data, then free old resources if we're resizing */
  460         if (cnt > 0) {
  461                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
  462                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
  463                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  464                                 buffer, firstseg);
  465                         if ((cnt - firstseg) > 0)
  466                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
  467                                         cpipe->pipe_buffer.in);
  468                 } else {
  469                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  470                                 buffer, cnt);
  471                 }
  472         }
  473         pipe_free_kmem(cpipe);
  474         cpipe->pipe_buffer.buffer = buffer;
  475         cpipe->pipe_buffer.size = size;
  476         cpipe->pipe_buffer.in = cnt;
  477         cpipe->pipe_buffer.out = 0;
  478         cpipe->pipe_buffer.cnt = cnt;
  479         atomic_add_int(&amountpipekva, cpipe->pipe_buffer.size);
  480         return (0);
  481 }
  482 
  483 /*
  484  * Wrapper for pipespace_new() that performs locking assertions.
  485  */
  486 static int
  487 pipespace(cpipe, size)
  488         struct pipe *cpipe;
  489         int size;
  490 {
  491 
  492         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  493                 ("Unlocked pipe passed to pipespace"));
  494         return (pipespace_new(cpipe, size));
  495 }
  496 
  497 /*
  498  * lock a pipe for I/O, blocking other access
  499  */
  500 static __inline int
  501 pipelock(cpipe, catch)
  502         struct pipe *cpipe;
  503         int catch;
  504 {
  505         int error;
  506 
  507         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  508         while (cpipe->pipe_state & PIPE_LOCKFL) {
  509                 cpipe->pipe_state |= PIPE_LWANT;
  510                 error = msleep(cpipe, PIPE_MTX(cpipe),
  511                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  512                     "pipelk", 0);
  513                 if (error != 0)
  514                         return (error);
  515         }
  516         cpipe->pipe_state |= PIPE_LOCKFL;
  517         return (0);
  518 }
  519 
  520 /*
  521  * unlock a pipe I/O lock
  522  */
  523 static __inline void
  524 pipeunlock(cpipe)
  525         struct pipe *cpipe;
  526 {
  527 
  528         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  529         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  530                 ("Unlocked pipe passed to pipeunlock"));
  531         cpipe->pipe_state &= ~PIPE_LOCKFL;
  532         if (cpipe->pipe_state & PIPE_LWANT) {
  533                 cpipe->pipe_state &= ~PIPE_LWANT;
  534                 wakeup(cpipe);
  535         }
  536 }
  537 
  538 static __inline void
  539 pipeselwakeup(cpipe)
  540         struct pipe *cpipe;
  541 {
  542 
  543         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  544         if (cpipe->pipe_state & PIPE_SEL) {
  545                 cpipe->pipe_state &= ~PIPE_SEL;
  546                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
  547         }
  548         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  549                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  550         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
  551 }
  552 
  553 /*
  554  * Initialize and allocate VM and memory for pipe.  The structure
  555  * will start out zero'd from the ctor, so we just manage the kmem.
  556  */
  557 static int
  558 pipe_create(pipe, backing)
  559         struct pipe *pipe;
  560         int backing;
  561 {
  562         int error;
  563 
  564         if (backing) {
  565                 if (amountpipekva > maxpipekva / 2)
  566                         error = pipespace_new(pipe, SMALL_PIPE_SIZE);
  567                 else
  568                         error = pipespace_new(pipe, PIPE_SIZE);
  569         } else {
  570                 /* If we're not backing this pipe, no need to do anything. */
  571                 error = 0;
  572         }
  573         return (error);
  574 }
  575 
  576 /* ARGSUSED */
  577 static int
  578 pipe_read(fp, uio, active_cred, flags, td)
  579         struct file *fp;
  580         struct uio *uio;
  581         struct ucred *active_cred;
  582         struct thread *td;
  583         int flags;
  584 {
  585         struct pipe *rpipe = fp->f_data;
  586         int error;
  587         int nread = 0;
  588         u_int size;
  589 
  590         PIPE_LOCK(rpipe);
  591         ++rpipe->pipe_busy;
  592         error = pipelock(rpipe, 1);
  593         if (error)
  594                 goto unlocked_error;
  595 
  596 #ifdef MAC
  597         error = mac_check_pipe_read(active_cred, rpipe->pipe_pair);
  598         if (error)
  599                 goto locked_error;
  600 #endif
  601         if (amountpipekva > (3 * maxpipekva) / 4) {
  602                 if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
  603                         (rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
  604                         (rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
  605                         (piperesizeallowed == 1)) {
  606                         PIPE_UNLOCK(rpipe);
  607                         pipespace(rpipe, SMALL_PIPE_SIZE);
  608                         PIPE_LOCK(rpipe);
  609                 }
  610         }
  611 
  612         while (uio->uio_resid) {
  613                 /*
  614                  * normal pipe buffer receive
  615                  */
  616                 if (rpipe->pipe_buffer.cnt > 0) {
  617                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  618                         if (size > rpipe->pipe_buffer.cnt)
  619                                 size = rpipe->pipe_buffer.cnt;
  620                         if (size > (u_int) uio->uio_resid)
  621                                 size = (u_int) uio->uio_resid;
  622 
  623                         PIPE_UNLOCK(rpipe);
  624                         error = uiomove(
  625                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  626                             size, uio);
  627                         PIPE_LOCK(rpipe);
  628                         if (error)
  629                                 break;
  630 
  631                         rpipe->pipe_buffer.out += size;
  632                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  633                                 rpipe->pipe_buffer.out = 0;
  634 
  635                         rpipe->pipe_buffer.cnt -= size;
  636 
  637                         /*
  638                          * If there is no more to read in the pipe, reset
  639                          * its pointers to the beginning.  This improves
  640                          * cache hit stats.
  641                          */
  642                         if (rpipe->pipe_buffer.cnt == 0) {
  643                                 rpipe->pipe_buffer.in = 0;
  644                                 rpipe->pipe_buffer.out = 0;
  645                         }
  646                         nread += size;
  647 #ifndef PIPE_NODIRECT
  648                 /*
  649                  * Direct copy, bypassing a kernel buffer.
  650                  */
  651                 } else if ((size = rpipe->pipe_map.cnt) &&
  652                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  653                         if (size > (u_int) uio->uio_resid)
  654                                 size = (u_int) uio->uio_resid;
  655 
  656                         PIPE_UNLOCK(rpipe);
  657                         error = uiomove_fromphys(rpipe->pipe_map.ms,
  658                             rpipe->pipe_map.pos, size, uio);
  659                         PIPE_LOCK(rpipe);
  660                         if (error)
  661                                 break;
  662                         nread += size;
  663                         rpipe->pipe_map.pos += size;
  664                         rpipe->pipe_map.cnt -= size;
  665                         if (rpipe->pipe_map.cnt == 0) {
  666                                 rpipe->pipe_state &= ~PIPE_DIRECTW;
  667                                 wakeup(rpipe);
  668                         }
  669 #endif
  670                 } else {
  671                         /*
  672                          * detect EOF condition
  673                          * read returns 0 on EOF, no need to set error
  674                          */
  675                         if (rpipe->pipe_state & PIPE_EOF)
  676                                 break;
  677 
  678                         /*
  679                          * If the "write-side" has been blocked, wake it up now.
  680                          */
  681                         if (rpipe->pipe_state & PIPE_WANTW) {
  682                                 rpipe->pipe_state &= ~PIPE_WANTW;
  683                                 wakeup(rpipe);
  684                         }
  685 
  686                         /*
  687                          * Break if some data was read.
  688                          */
  689                         if (nread > 0)
  690                                 break;
  691 
  692                         /*
  693                          * Unlock the pipe buffer for our remaining processing.
  694                          * We will either break out with an error or we will
  695                          * sleep and relock to loop.
  696                          */
  697                         pipeunlock(rpipe);
  698 
  699                         /*
  700                          * Handle non-blocking mode operation or
  701                          * wait for more data.
  702                          */
  703                         if (fp->f_flag & FNONBLOCK) {
  704                                 error = EAGAIN;
  705                         } else {
  706                                 rpipe->pipe_state |= PIPE_WANTR;
  707                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  708                                     PRIBIO | PCATCH,
  709                                     "piperd", 0)) == 0)
  710                                         error = pipelock(rpipe, 1);
  711                         }
  712                         if (error)
  713                                 goto unlocked_error;
  714                 }
  715         }
  716 #ifdef MAC
  717 locked_error:
  718 #endif
  719         pipeunlock(rpipe);
  720 
  721         /* XXX: should probably do this before getting any locks. */
  722         if (error == 0)
  723                 vfs_timestamp(&rpipe->pipe_atime);
  724 unlocked_error:
  725         --rpipe->pipe_busy;
  726 
  727         /*
  728          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  729          */
  730         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  731                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  732                 wakeup(rpipe);
  733         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  734                 /*
  735                  * Handle write blocking hysteresis.
  736                  */
  737                 if (rpipe->pipe_state & PIPE_WANTW) {
  738                         rpipe->pipe_state &= ~PIPE_WANTW;
  739                         wakeup(rpipe);
  740                 }
  741         }
  742 
  743         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  744                 pipeselwakeup(rpipe);
  745 
  746         PIPE_UNLOCK(rpipe);
  747         return (error);
  748 }
  749 
  750 #ifndef PIPE_NODIRECT
  751 /*
  752  * Map the sending processes' buffer into kernel space and wire it.
  753  * This is similar to a physical write operation.
  754  */
  755 static int
  756 pipe_build_write_buffer(wpipe, uio)
  757         struct pipe *wpipe;
  758         struct uio *uio;
  759 {
  760         pmap_t pmap;
  761         u_int size;
  762         int i, j;
  763         vm_offset_t addr, endaddr;
  764 
  765         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  766         KASSERT(wpipe->pipe_state & PIPE_DIRECTW,
  767                 ("Clone attempt on non-direct write pipe!"));
  768 
  769         size = (u_int) uio->uio_iov->iov_len;
  770         if (size > wpipe->pipe_buffer.size)
  771                 size = wpipe->pipe_buffer.size;
  772 
  773         pmap = vmspace_pmap(curproc->p_vmspace);
  774         endaddr = round_page((vm_offset_t)uio->uio_iov->iov_base + size);
  775         addr = trunc_page((vm_offset_t)uio->uio_iov->iov_base);
  776         for (i = 0; addr < endaddr; addr += PAGE_SIZE, i++) {
  777                 /*
  778                  * vm_fault_quick() can sleep.  Consequently,
  779                  * vm_page_lock_queue() and vm_page_unlock_queue()
  780                  * should not be performed outside of this loop.
  781                  */
  782         race:
  783                 if (vm_fault_quick((caddr_t)addr, VM_PROT_READ) < 0) {
  784                         vm_page_lock_queues();
  785                         for (j = 0; j < i; j++)
  786                                 vm_page_unhold(wpipe->pipe_map.ms[j]);
  787                         vm_page_unlock_queues();
  788                         return (EFAULT);
  789                 }
  790                 wpipe->pipe_map.ms[i] = pmap_extract_and_hold(pmap, addr,
  791                     VM_PROT_READ);
  792                 if (wpipe->pipe_map.ms[i] == NULL)
  793                         goto race;
  794         }
  795 
  796 /*
  797  * set up the control block
  798  */
  799         wpipe->pipe_map.npages = i;
  800         wpipe->pipe_map.pos =
  801             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  802         wpipe->pipe_map.cnt = size;
  803 
  804 /*
  805  * and update the uio data
  806  */
  807 
  808         uio->uio_iov->iov_len -= size;
  809         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  810         if (uio->uio_iov->iov_len == 0)
  811                 uio->uio_iov++;
  812         uio->uio_resid -= size;
  813         uio->uio_offset += size;
  814         return (0);
  815 }
  816 
  817 /*
  818  * unmap and unwire the process buffer
  819  */
  820 static void
  821 pipe_destroy_write_buffer(wpipe)
  822         struct pipe *wpipe;
  823 {
  824         int i;
  825 
  826         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  827         vm_page_lock_queues();
  828         for (i = 0; i < wpipe->pipe_map.npages; i++) {
  829                 vm_page_unhold(wpipe->pipe_map.ms[i]);
  830         }
  831         vm_page_unlock_queues();
  832         wpipe->pipe_map.npages = 0;
  833 }
  834 
  835 /*
  836  * In the case of a signal, the writing process might go away.  This
  837  * code copies the data into the circular buffer so that the source
  838  * pages can be freed without loss of data.
  839  */
  840 static void
  841 pipe_clone_write_buffer(wpipe)
  842         struct pipe *wpipe;
  843 {
  844         struct uio uio;
  845         struct iovec iov;
  846         int size;
  847         int pos;
  848 
  849         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  850         size = wpipe->pipe_map.cnt;
  851         pos = wpipe->pipe_map.pos;
  852 
  853         wpipe->pipe_buffer.in = size;
  854         wpipe->pipe_buffer.out = 0;
  855         wpipe->pipe_buffer.cnt = size;
  856         wpipe->pipe_state &= ~PIPE_DIRECTW;
  857 
  858         PIPE_UNLOCK(wpipe);
  859         iov.iov_base = wpipe->pipe_buffer.buffer;
  860         iov.iov_len = size;
  861         uio.uio_iov = &iov;
  862         uio.uio_iovcnt = 1;
  863         uio.uio_offset = 0;
  864         uio.uio_resid = size;
  865         uio.uio_segflg = UIO_SYSSPACE;
  866         uio.uio_rw = UIO_READ;
  867         uio.uio_td = curthread;
  868         uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
  869         PIPE_LOCK(wpipe);
  870         pipe_destroy_write_buffer(wpipe);
  871 }
  872 
  873 /*
  874  * This implements the pipe buffer write mechanism.  Note that only
  875  * a direct write OR a normal pipe write can be pending at any given time.
  876  * If there are any characters in the pipe buffer, the direct write will
  877  * be deferred until the receiving process grabs all of the bytes from
  878  * the pipe buffer.  Then the direct mapping write is set-up.
  879  */
  880 static int
  881 pipe_direct_write(wpipe, uio)
  882         struct pipe *wpipe;
  883         struct uio *uio;
  884 {
  885         int error;
  886 
  887 retry:
  888         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  889         error = pipelock(wpipe, 1);
  890         if (wpipe->pipe_state & PIPE_EOF)
  891                 error = EPIPE;
  892         if (error) {
  893                 pipeunlock(wpipe);
  894                 goto error1;
  895         }
  896         while (wpipe->pipe_state & PIPE_DIRECTW) {
  897                 if (wpipe->pipe_state & PIPE_WANTR) {
  898                         wpipe->pipe_state &= ~PIPE_WANTR;
  899                         wakeup(wpipe);
  900                 }
  901                 wpipe->pipe_state |= PIPE_WANTW;
  902                 pipeunlock(wpipe);
  903                 error = msleep(wpipe, PIPE_MTX(wpipe),
  904                     PRIBIO | PCATCH, "pipdww", 0);
  905                 if (error)
  906                         goto error1;
  907                 else
  908                         goto retry;
  909         }
  910         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  911         if (wpipe->pipe_buffer.cnt > 0) {
  912                 if (wpipe->pipe_state & PIPE_WANTR) {
  913                         wpipe->pipe_state &= ~PIPE_WANTR;
  914                         wakeup(wpipe);
  915                 }
  916                 wpipe->pipe_state |= PIPE_WANTW;
  917                 pipeunlock(wpipe);
  918                 error = msleep(wpipe, PIPE_MTX(wpipe),
  919                     PRIBIO | PCATCH, "pipdwc", 0);
  920                 if (error)
  921                         goto error1;
  922                 else
  923                         goto retry;
  924         }
  925 
  926         wpipe->pipe_state |= PIPE_DIRECTW;
  927 
  928         PIPE_UNLOCK(wpipe);
  929         error = pipe_build_write_buffer(wpipe, uio);
  930         PIPE_LOCK(wpipe);
  931         if (error) {
  932                 wpipe->pipe_state &= ~PIPE_DIRECTW;
  933                 pipeunlock(wpipe);
  934                 goto error1;
  935         }
  936 
  937         error = 0;
  938         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
  939                 if (wpipe->pipe_state & PIPE_EOF) {
  940                         pipe_destroy_write_buffer(wpipe);
  941                         pipeselwakeup(wpipe);
  942                         pipeunlock(wpipe);
  943                         error = EPIPE;
  944                         goto error1;
  945                 }
  946                 if (wpipe->pipe_state & PIPE_WANTR) {
  947                         wpipe->pipe_state &= ~PIPE_WANTR;
  948                         wakeup(wpipe);
  949                 }
  950                 pipeselwakeup(wpipe);
  951                 pipeunlock(wpipe);
  952                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
  953                     "pipdwt", 0);
  954                 pipelock(wpipe, 0);
  955         }
  956 
  957         if (wpipe->pipe_state & PIPE_EOF)
  958                 error = EPIPE;
  959         if (wpipe->pipe_state & PIPE_DIRECTW) {
  960                 /*
  961                  * this bit of trickery substitutes a kernel buffer for
  962                  * the process that might be going away.
  963                  */
  964                 pipe_clone_write_buffer(wpipe);
  965         } else {
  966                 pipe_destroy_write_buffer(wpipe);
  967         }
  968         pipeunlock(wpipe);
  969         return (error);
  970 
  971 error1:
  972         wakeup(wpipe);
  973         return (error);
  974 }
  975 #endif
  976 
  977 static int
  978 pipe_write(fp, uio, active_cred, flags, td)
  979         struct file *fp;
  980         struct uio *uio;
  981         struct ucred *active_cred;
  982         struct thread *td;
  983         int flags;
  984 {
  985         int error = 0;
  986         int desiredsize, orig_resid;
  987         struct pipe *wpipe, *rpipe;
  988 
  989         rpipe = fp->f_data;
  990         wpipe = rpipe->pipe_peer;
  991 
  992         PIPE_LOCK(rpipe);
  993         error = pipelock(wpipe, 1);
  994         if (error) {
  995                 PIPE_UNLOCK(rpipe);
  996                 return (error);
  997         }
  998         /*
  999          * detect loss of pipe read side, issue SIGPIPE if lost.
 1000          */
 1001         if ((!wpipe->pipe_present) || (wpipe->pipe_state & PIPE_EOF)) {
 1002                 pipeunlock(wpipe);
 1003                 PIPE_UNLOCK(rpipe);
 1004                 return (EPIPE);
 1005         }
 1006 #ifdef MAC
 1007         error = mac_check_pipe_write(active_cred, wpipe->pipe_pair);
 1008         if (error) {
 1009                 pipeunlock(wpipe);
 1010                 PIPE_UNLOCK(rpipe);
 1011                 return (error);
 1012         }
 1013 #endif
 1014         ++wpipe->pipe_busy;
 1015 
 1016         /* Choose a larger size if it's advantageous */
 1017         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
 1018         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
 1019                 if (piperesizeallowed != 1)
 1020                         break;
 1021                 if (amountpipekva > maxpipekva / 2)
 1022                         break;
 1023                 if (desiredsize == BIG_PIPE_SIZE)
 1024                         break;
 1025                 desiredsize = desiredsize * 2;
 1026         }
 1027 
 1028         /* Choose a smaller size if we're in a OOM situation */
 1029         if ((amountpipekva > (3 * maxpipekva) / 4) &&
 1030                 (wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
 1031                 (wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
 1032                 (piperesizeallowed == 1))
 1033                 desiredsize = SMALL_PIPE_SIZE;
 1034 
 1035         /* Resize if the above determined that a new size was necessary */
 1036         if ((desiredsize != wpipe->pipe_buffer.size) &&
 1037                 ((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
 1038                 PIPE_UNLOCK(wpipe);
 1039                 pipespace(wpipe, desiredsize);
 1040                 PIPE_LOCK(wpipe);
 1041         }
 1042         if (wpipe->pipe_buffer.size == 0) {
 1043                 /*
 1044                  * This can only happen for reverse direction use of pipes
 1045                  * in a complete OOM situation.
 1046                  */
 1047                 error = ENOMEM;
 1048                 --wpipe->pipe_busy;
 1049                 pipeunlock(wpipe);
 1050                 PIPE_UNLOCK(wpipe);
 1051                 return (error);
 1052         }
 1053 
 1054         pipeunlock(wpipe);
 1055 
 1056         orig_resid = uio->uio_resid;
 1057 
 1058         while (uio->uio_resid) {
 1059                 int space;
 1060 
 1061                 pipelock(wpipe, 0);
 1062                 if (wpipe->pipe_state & PIPE_EOF) {
 1063                         pipeunlock(wpipe);
 1064                         error = EPIPE;
 1065                         break;
 1066                 }
 1067 #ifndef PIPE_NODIRECT
 1068                 /*
 1069                  * If the transfer is large, we can gain performance if
 1070                  * we do process-to-process copies directly.
 1071                  * If the write is non-blocking, we don't use the
 1072                  * direct write mechanism.
 1073                  *
 1074                  * The direct write mechanism will detect the reader going
 1075                  * away on us.
 1076                  */
 1077                 if ((uio->uio_iov->iov_len >= PIPE_MINDIRECT) &&
 1078                     (wpipe->pipe_buffer.size >= PIPE_MINDIRECT) &&
 1079                     (fp->f_flag & FNONBLOCK) == 0) {
 1080                         pipeunlock(wpipe);
 1081                         error = pipe_direct_write(wpipe, uio);
 1082                         if (error)
 1083                                 break;
 1084                         continue;
 1085                 }
 1086 #endif
 1087 
 1088                 /*
 1089                  * Pipe buffered writes cannot be coincidental with
 1090                  * direct writes.  We wait until the currently executing
 1091                  * direct write is completed before we start filling the
 1092                  * pipe buffer.  We break out if a signal occurs or the
 1093                  * reader goes away.
 1094                  */
 1095                 if (wpipe->pipe_state & PIPE_DIRECTW) {
 1096                         if (wpipe->pipe_state & PIPE_WANTR) {
 1097                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1098                                 wakeup(wpipe);
 1099                         }
 1100                         pipeunlock(wpipe);
 1101                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
 1102                             "pipbww", 0);
 1103                         if (error)
 1104                                 break;
 1105                         else
 1106                                 continue;
 1107                 }
 1108 
 1109                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1110 
 1111                 /* Writes of size <= PIPE_BUF must be atomic. */
 1112                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 1113                         space = 0;
 1114 
 1115                 if (space > 0) {
 1116                         int size;       /* Transfer size */
 1117                         int segsize;    /* first segment to transfer */
 1118 
 1119                         /*
 1120                          * Transfer size is minimum of uio transfer
 1121                          * and free space in pipe buffer.
 1122                          */
 1123                         if (space > uio->uio_resid)
 1124                                 size = uio->uio_resid;
 1125                         else
 1126                                 size = space;
 1127                         /*
 1128                          * First segment to transfer is minimum of
 1129                          * transfer size and contiguous space in
 1130                          * pipe buffer.  If first segment to transfer
 1131                          * is less than the transfer size, we've got
 1132                          * a wraparound in the buffer.
 1133                          */
 1134                         segsize = wpipe->pipe_buffer.size -
 1135                                 wpipe->pipe_buffer.in;
 1136                         if (segsize > size)
 1137                                 segsize = size;
 1138 
 1139                         /* Transfer first segment */
 1140 
 1141                         PIPE_UNLOCK(rpipe);
 1142                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
 1143                                         segsize, uio);
 1144                         PIPE_LOCK(rpipe);
 1145 
 1146                         if (error == 0 && segsize < size) {
 1147                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
 1148                                         wpipe->pipe_buffer.size,
 1149                                         ("Pipe buffer wraparound disappeared"));
 1150                                 /*
 1151                                  * Transfer remaining part now, to
 1152                                  * support atomic writes.  Wraparound
 1153                                  * happened.
 1154                                  */
 1155 
 1156                                 PIPE_UNLOCK(rpipe);
 1157                                 error = uiomove(
 1158                                     &wpipe->pipe_buffer.buffer[0],
 1159                                     size - segsize, uio);
 1160                                 PIPE_LOCK(rpipe);
 1161                         }
 1162                         if (error == 0) {
 1163                                 wpipe->pipe_buffer.in += size;
 1164                                 if (wpipe->pipe_buffer.in >=
 1165                                     wpipe->pipe_buffer.size) {
 1166                                         KASSERT(wpipe->pipe_buffer.in ==
 1167                                                 size - segsize +
 1168                                                 wpipe->pipe_buffer.size,
 1169                                                 ("Expected wraparound bad"));
 1170                                         wpipe->pipe_buffer.in = size - segsize;
 1171                                 }
 1172 
 1173                                 wpipe->pipe_buffer.cnt += size;
 1174                                 KASSERT(wpipe->pipe_buffer.cnt <=
 1175                                         wpipe->pipe_buffer.size,
 1176                                         ("Pipe buffer overflow"));
 1177                         }
 1178                         pipeunlock(wpipe);
 1179                 } else {
 1180                         /*
 1181                          * If the "read-side" has been blocked, wake it up now.
 1182                          */
 1183                         if (wpipe->pipe_state & PIPE_WANTR) {
 1184                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1185                                 wakeup(wpipe);
 1186                         }
 1187 
 1188                         /*
 1189                          * don't block on non-blocking I/O
 1190                          */
 1191                         if (fp->f_flag & FNONBLOCK) {
 1192                                 error = EAGAIN;
 1193                                 pipeunlock(wpipe);
 1194                                 break;
 1195                         }
 1196 
 1197                         /*
 1198                          * We have no more space and have something to offer,
 1199                          * wake up select/poll.
 1200                          */
 1201                         pipeselwakeup(wpipe);
 1202 
 1203                         wpipe->pipe_state |= PIPE_WANTW;
 1204                         pipeunlock(wpipe);
 1205                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1206                             PRIBIO | PCATCH, "pipewr", 0);
 1207                         if (error != 0)
 1208                                 break;
 1209                 }
 1210         }
 1211 
 1212         pipelock(wpipe, 0);
 1213         --wpipe->pipe_busy;
 1214 
 1215         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1216                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1217                 wakeup(wpipe);
 1218         } else if (wpipe->pipe_buffer.cnt > 0) {
 1219                 /*
 1220                  * If we have put any characters in the buffer, we wake up
 1221                  * the reader.
 1222                  */
 1223                 if (wpipe->pipe_state & PIPE_WANTR) {
 1224                         wpipe->pipe_state &= ~PIPE_WANTR;
 1225                         wakeup(wpipe);
 1226                 }
 1227         }
 1228 
 1229         /*
 1230          * Don't return EPIPE if I/O was successful
 1231          */
 1232         if ((wpipe->pipe_buffer.cnt == 0) &&
 1233             (uio->uio_resid == 0) &&
 1234             (error == EPIPE)) {
 1235                 error = 0;
 1236         }
 1237 
 1238         if (error == 0)
 1239                 vfs_timestamp(&wpipe->pipe_mtime);
 1240 
 1241         /*
 1242          * We have something to offer,
 1243          * wake up select/poll.
 1244          */
 1245         if (wpipe->pipe_buffer.cnt)
 1246                 pipeselwakeup(wpipe);
 1247 
 1248         pipeunlock(wpipe);
 1249         PIPE_UNLOCK(rpipe);
 1250         return (error);
 1251 }
 1252 
 1253 /*
 1254  * we implement a very minimal set of ioctls for compatibility with sockets.
 1255  */
 1256 static int
 1257 pipe_ioctl(fp, cmd, data, active_cred, td)
 1258         struct file *fp;
 1259         u_long cmd;
 1260         void *data;
 1261         struct ucred *active_cred;
 1262         struct thread *td;
 1263 {
 1264         struct pipe *mpipe = fp->f_data;
 1265         int error;
 1266 
 1267         PIPE_LOCK(mpipe);
 1268 
 1269 #ifdef MAC
 1270         error = mac_check_pipe_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
 1271         if (error) {
 1272                 PIPE_UNLOCK(mpipe);
 1273                 return (error);
 1274         }
 1275 #endif
 1276 
 1277         error = 0;
 1278         switch (cmd) {
 1279 
 1280         case FIONBIO:
 1281                 break;
 1282 
 1283         case FIOASYNC:
 1284                 if (*(int *)data) {
 1285                         mpipe->pipe_state |= PIPE_ASYNC;
 1286                 } else {
 1287                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1288                 }
 1289                 break;
 1290 
 1291         case FIONREAD:
 1292                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1293                         *(int *)data = mpipe->pipe_map.cnt;
 1294                 else
 1295                         *(int *)data = mpipe->pipe_buffer.cnt;
 1296                 break;
 1297 
 1298         case FIOSETOWN:
 1299                 PIPE_UNLOCK(mpipe);
 1300                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 1301                 goto out_unlocked;
 1302 
 1303         case FIOGETOWN:
 1304                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1305                 break;
 1306 
 1307         /* This is deprecated, FIOSETOWN should be used instead. */
 1308         case TIOCSPGRP:
 1309                 PIPE_UNLOCK(mpipe);
 1310                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 1311                 goto out_unlocked;
 1312 
 1313         /* This is deprecated, FIOGETOWN should be used instead. */
 1314         case TIOCGPGRP:
 1315                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1316                 break;
 1317 
 1318         default:
 1319                 error = ENOTTY;
 1320                 break;
 1321         }
 1322         PIPE_UNLOCK(mpipe);
 1323 out_unlocked:
 1324         return (error);
 1325 }
 1326 
 1327 static int
 1328 pipe_poll(fp, events, active_cred, td)
 1329         struct file *fp;
 1330         int events;
 1331         struct ucred *active_cred;
 1332         struct thread *td;
 1333 {
 1334         struct pipe *rpipe = fp->f_data;
 1335         struct pipe *wpipe;
 1336         int revents = 0;
 1337 #ifdef MAC
 1338         int error;
 1339 #endif
 1340 
 1341         wpipe = rpipe->pipe_peer;
 1342         PIPE_LOCK(rpipe);
 1343 #ifdef MAC
 1344         error = mac_check_pipe_poll(active_cred, rpipe->pipe_pair);
 1345         if (error)
 1346                 goto locked_error;
 1347 #endif
 1348         if (events & (POLLIN | POLLRDNORM))
 1349                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1350                     (rpipe->pipe_buffer.cnt > 0) ||
 1351                     (rpipe->pipe_state & PIPE_EOF))
 1352                         revents |= events & (POLLIN | POLLRDNORM);
 1353 
 1354         if (events & (POLLOUT | POLLWRNORM))
 1355                 if (!wpipe->pipe_present || (wpipe->pipe_state & PIPE_EOF) ||
 1356                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1357                      (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF))
 1358                         revents |= events & (POLLOUT | POLLWRNORM);
 1359 
 1360         if ((rpipe->pipe_state & PIPE_EOF) ||
 1361             (!wpipe->pipe_present) ||
 1362             (wpipe->pipe_state & PIPE_EOF))
 1363                 revents |= POLLHUP;
 1364 
 1365         if (revents == 0) {
 1366                 if (events & (POLLIN | POLLRDNORM)) {
 1367                         selrecord(td, &rpipe->pipe_sel);
 1368                         rpipe->pipe_state |= PIPE_SEL;
 1369                 }
 1370 
 1371                 if (events & (POLLOUT | POLLWRNORM)) {
 1372                         selrecord(td, &wpipe->pipe_sel);
 1373                         wpipe->pipe_state |= PIPE_SEL;
 1374                 }
 1375         }
 1376 #ifdef MAC
 1377 locked_error:
 1378 #endif
 1379         PIPE_UNLOCK(rpipe);
 1380 
 1381         return (revents);
 1382 }
 1383 
 1384 /*
 1385  * We shouldn't need locks here as we're doing a read and this should
 1386  * be a natural race.
 1387  */
 1388 static int
 1389 pipe_stat(fp, ub, active_cred, td)
 1390         struct file *fp;
 1391         struct stat *ub;
 1392         struct ucred *active_cred;
 1393         struct thread *td;
 1394 {
 1395         struct pipe *pipe = fp->f_data;
 1396 #ifdef MAC
 1397         int error;
 1398 
 1399         PIPE_LOCK(pipe);
 1400         error = mac_check_pipe_stat(active_cred, pipe->pipe_pair);
 1401         PIPE_UNLOCK(pipe);
 1402         if (error)
 1403                 return (error);
 1404 #endif
 1405         bzero(ub, sizeof(*ub));
 1406         ub->st_mode = S_IFIFO;
 1407         ub->st_blksize = PAGE_SIZE;
 1408         if (pipe->pipe_state & PIPE_DIRECTW)
 1409                 ub->st_size = pipe->pipe_map.cnt;
 1410         else
 1411                 ub->st_size = pipe->pipe_buffer.cnt;
 1412         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
 1413         ub->st_atimespec = pipe->pipe_atime;
 1414         ub->st_mtimespec = pipe->pipe_mtime;
 1415         ub->st_ctimespec = pipe->pipe_ctime;
 1416         ub->st_uid = fp->f_cred->cr_uid;
 1417         ub->st_gid = fp->f_cred->cr_gid;
 1418         /*
 1419          * Left as 0: st_dev, st_ino, st_nlink, st_rdev, st_flags, st_gen.
 1420          * XXX (st_dev, st_ino) should be unique.
 1421          */
 1422         return (0);
 1423 }
 1424 
 1425 /* ARGSUSED */
 1426 static int
 1427 pipe_close(fp, td)
 1428         struct file *fp;
 1429         struct thread *td;
 1430 {
 1431         struct pipe *cpipe = fp->f_data;
 1432 
 1433         fp->f_ops = &badfileops;
 1434         fp->f_data = NULL;
 1435         funsetown(&cpipe->pipe_sigio);
 1436         pipeclose(cpipe);
 1437         return (0);
 1438 }
 1439 
 1440 static void
 1441 pipe_free_kmem(cpipe)
 1442         struct pipe *cpipe;
 1443 {
 1444 
 1445         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
 1446             ("pipe_free_kmem: pipe mutex locked"));
 1447 
 1448         if (cpipe->pipe_buffer.buffer != NULL) {
 1449                 atomic_subtract_int(&amountpipekva, cpipe->pipe_buffer.size);
 1450                 vm_map_remove(pipe_map,
 1451                     (vm_offset_t)cpipe->pipe_buffer.buffer,
 1452                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
 1453                 cpipe->pipe_buffer.buffer = NULL;
 1454         }
 1455 #ifndef PIPE_NODIRECT
 1456         {
 1457                 cpipe->pipe_map.cnt = 0;
 1458                 cpipe->pipe_map.pos = 0;
 1459                 cpipe->pipe_map.npages = 0;
 1460         }
 1461 #endif
 1462 }
 1463 
 1464 /*
 1465  * shutdown the pipe
 1466  */
 1467 static void
 1468 pipeclose(cpipe)
 1469         struct pipe *cpipe;
 1470 {
 1471         struct pipepair *pp;
 1472         struct pipe *ppipe;
 1473 
 1474         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
 1475 
 1476         PIPE_LOCK(cpipe);
 1477         pipelock(cpipe, 0);
 1478         pp = cpipe->pipe_pair;
 1479 
 1480         pipeselwakeup(cpipe);
 1481 
 1482         /*
 1483          * If the other side is blocked, wake it up saying that
 1484          * we want to close it down.
 1485          */
 1486         cpipe->pipe_state |= PIPE_EOF;
 1487         while (cpipe->pipe_busy) {
 1488                 wakeup(cpipe);
 1489                 cpipe->pipe_state |= PIPE_WANT;
 1490                 pipeunlock(cpipe);
 1491                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1492                 pipelock(cpipe, 0);
 1493         }
 1494 
 1495 
 1496         /*
 1497          * Disconnect from peer, if any.
 1498          */
 1499         ppipe = cpipe->pipe_peer;
 1500         if (ppipe->pipe_present != 0) {
 1501                 pipeselwakeup(ppipe);
 1502 
 1503                 ppipe->pipe_state |= PIPE_EOF;
 1504                 wakeup(ppipe);
 1505                 KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
 1506         }
 1507 
 1508         /*
 1509          * Mark this endpoint as free.  Release kmem resources.  We
 1510          * don't mark this endpoint as unused until we've finished
 1511          * doing that, or the pipe might disappear out from under
 1512          * us.
 1513          */
 1514         PIPE_UNLOCK(cpipe);
 1515         pipe_free_kmem(cpipe);
 1516         PIPE_LOCK(cpipe);
 1517         cpipe->pipe_present = 0;
 1518         pipeunlock(cpipe);
 1519         knlist_clear(&cpipe->pipe_sel.si_note, 1);
 1520         knlist_destroy(&cpipe->pipe_sel.si_note);
 1521 
 1522         /*
 1523          * If both endpoints are now closed, release the memory for the
 1524          * pipe pair.  If not, unlock.
 1525          */
 1526         if (ppipe->pipe_present == 0) {
 1527                 PIPE_UNLOCK(cpipe);
 1528 #ifdef MAC
 1529                 mac_destroy_pipe(pp);
 1530 #endif
 1531                 uma_zfree(pipe_zone, cpipe->pipe_pair);
 1532         } else
 1533                 PIPE_UNLOCK(cpipe);
 1534 }
 1535 
 1536 /*ARGSUSED*/
 1537 static int
 1538 pipe_kqfilter(struct file *fp, struct knote *kn)
 1539 {
 1540         struct pipe *cpipe;
 1541 
 1542         cpipe = kn->kn_fp->f_data;
 1543         PIPE_LOCK(cpipe);
 1544         switch (kn->kn_filter) {
 1545         case EVFILT_READ:
 1546                 kn->kn_fop = &pipe_rfiltops;
 1547                 break;
 1548         case EVFILT_WRITE:
 1549                 kn->kn_fop = &pipe_wfiltops;
 1550                 if (!cpipe->pipe_peer->pipe_present) {
 1551                         /* other end of pipe has been closed */
 1552                         PIPE_UNLOCK(cpipe);
 1553                         return (EPIPE);
 1554                 }
 1555                 cpipe = cpipe->pipe_peer;
 1556                 break;
 1557         default:
 1558                 PIPE_UNLOCK(cpipe);
 1559                 return (EINVAL);
 1560         }
 1561 
 1562         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
 1563         PIPE_UNLOCK(cpipe);
 1564         return (0);
 1565 }
 1566 
 1567 static void
 1568 filt_pipedetach(struct knote *kn)
 1569 {
 1570         struct pipe *cpipe = (struct pipe *)kn->kn_fp->f_data;
 1571 
 1572         PIPE_LOCK(cpipe);
 1573         if (kn->kn_filter == EVFILT_WRITE) {
 1574                 if (!cpipe->pipe_peer->pipe_present) {
 1575                         PIPE_UNLOCK(cpipe);
 1576                         return;
 1577                 }
 1578                 cpipe = cpipe->pipe_peer;
 1579         }
 1580         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
 1581         PIPE_UNLOCK(cpipe);
 1582 }
 1583 
 1584 /*ARGSUSED*/
 1585 static int
 1586 filt_piperead(struct knote *kn, long hint)
 1587 {
 1588         struct pipe *rpipe = kn->kn_fp->f_data;
 1589         struct pipe *wpipe = rpipe->pipe_peer;
 1590         int ret;
 1591 
 1592         PIPE_LOCK(rpipe);
 1593         kn->kn_data = rpipe->pipe_buffer.cnt;
 1594         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1595                 kn->kn_data = rpipe->pipe_map.cnt;
 1596 
 1597         if ((rpipe->pipe_state & PIPE_EOF) ||
 1598             (!wpipe->pipe_present) || (wpipe->pipe_state & PIPE_EOF)) {
 1599                 kn->kn_flags |= EV_EOF;
 1600                 PIPE_UNLOCK(rpipe);
 1601                 return (1);
 1602         }
 1603         ret = kn->kn_data > 0;
 1604         PIPE_UNLOCK(rpipe);
 1605         return ret;
 1606 }
 1607 
 1608 /*ARGSUSED*/
 1609 static int
 1610 filt_pipewrite(struct knote *kn, long hint)
 1611 {
 1612         struct pipe *rpipe = kn->kn_fp->f_data;
 1613         struct pipe *wpipe = rpipe->pipe_peer;
 1614 
 1615         PIPE_LOCK(rpipe);
 1616         if ((!wpipe->pipe_present) || (wpipe->pipe_state & PIPE_EOF)) {
 1617                 kn->kn_data = 0;
 1618                 kn->kn_flags |= EV_EOF;
 1619                 PIPE_UNLOCK(rpipe);
 1620                 return (1);
 1621         }
 1622         kn->kn_data = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1623         if (wpipe->pipe_state & PIPE_DIRECTW)
 1624                 kn->kn_data = 0;
 1625 
 1626         PIPE_UNLOCK(rpipe);
 1627         return (kn->kn_data >= PIPE_BUF);
 1628 }

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