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/5.3/sys/kern/sys_pipe.c 136588 2004-10-16 08:43:07Z cvs2svn $");
   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         /* Only the forward direction pipe is backed by default */
  355         if (pipe_create(rpipe, 1) || pipe_create(wpipe, 0)) {
  356                 pipeclose(rpipe);
  357                 pipeclose(wpipe);
  358                 return (ENFILE);
  359         }
  360 
  361         rpipe->pipe_state |= PIPE_DIRECTOK;
  362         wpipe->pipe_state |= PIPE_DIRECTOK;
  363 
  364         error = falloc(td, &rf, &fd);
  365         if (error) {
  366                 pipeclose(rpipe);
  367                 pipeclose(wpipe);
  368                 return (error);
  369         }
  370         /* An extra reference on `rf' has been held for us by falloc(). */
  371         td->td_retval[0] = fd;
  372 
  373         /*
  374          * Warning: once we've gotten past allocation of the fd for the
  375          * read-side, we can only drop the read side via fdrop() in order
  376          * to avoid races against processes which manage to dup() the read
  377          * side while we are blocked trying to allocate the write side.
  378          */
  379         FILE_LOCK(rf);
  380         rf->f_flag = FREAD | FWRITE;
  381         rf->f_type = DTYPE_PIPE;
  382         rf->f_data = rpipe;
  383         rf->f_ops = &pipeops;
  384         FILE_UNLOCK(rf);
  385         error = falloc(td, &wf, &fd);
  386         if (error) {
  387                 FILEDESC_LOCK(fdp);
  388                 if (fdp->fd_ofiles[td->td_retval[0]] == rf) {
  389                         fdp->fd_ofiles[td->td_retval[0]] = NULL;
  390                         fdunused(fdp, td->td_retval[0]);
  391                         FILEDESC_UNLOCK(fdp);
  392                         fdrop(rf, td);
  393                 } else {
  394                         FILEDESC_UNLOCK(fdp);
  395                 }
  396                 fdrop(rf, td);
  397                 /* rpipe has been closed by fdrop(). */
  398                 pipeclose(wpipe);
  399                 return (error);
  400         }
  401         /* An extra reference on `wf' has been held for us by falloc(). */
  402         FILE_LOCK(wf);
  403         wf->f_flag = FREAD | FWRITE;
  404         wf->f_type = DTYPE_PIPE;
  405         wf->f_data = wpipe;
  406         wf->f_ops = &pipeops;
  407         FILE_UNLOCK(wf);
  408         fdrop(wf, td);
  409         td->td_retval[1] = fd;
  410         fdrop(rf, td);
  411 
  412         return (0);
  413 }
  414 
  415 /*
  416  * Allocate kva for pipe circular buffer, the space is pageable
  417  * This routine will 'realloc' the size of a pipe safely, if it fails
  418  * it will retain the old buffer.
  419  * If it fails it will return ENOMEM.
  420  */
  421 static int
  422 pipespace_new(cpipe, size)
  423         struct pipe *cpipe;
  424         int size;
  425 {
  426         caddr_t buffer;
  427         int error, cnt, firstseg;
  428         static int curfail = 0;
  429         static struct timeval lastfail;
  430 
  431         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
  432         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
  433                 ("pipespace: resize of direct writes not allowed"));
  434 retry:
  435         cnt = cpipe->pipe_buffer.cnt;
  436         if (cnt > size)
  437                 size = cnt;
  438 
  439         size = round_page(size);
  440         buffer = (caddr_t) vm_map_min(pipe_map);
  441 
  442         error = vm_map_find(pipe_map, NULL, 0,
  443                 (vm_offset_t *) &buffer, size, 1,
  444                 VM_PROT_ALL, VM_PROT_ALL, 0);
  445         if (error != KERN_SUCCESS) {
  446                 if ((cpipe->pipe_buffer.buffer == NULL) &&
  447                         (size > SMALL_PIPE_SIZE)) {
  448                         size = SMALL_PIPE_SIZE;
  449                         pipefragretry++;
  450                         goto retry;
  451                 }
  452                 if (cpipe->pipe_buffer.buffer == NULL) {
  453                         pipeallocfail++;
  454                         if (ppsratecheck(&lastfail, &curfail, 1))
  455                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
  456                 } else {
  457                         piperesizefail++;
  458                 }
  459                 return (ENOMEM);
  460         }
  461 
  462         /* copy data, then free old resources if we're resizing */
  463         if (cnt > 0) {
  464                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
  465                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
  466                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  467                                 buffer, firstseg);
  468                         if ((cnt - firstseg) > 0)
  469                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
  470                                         cpipe->pipe_buffer.in);
  471                 } else {
  472                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  473                                 buffer, cnt);
  474                 }
  475         }
  476         pipe_free_kmem(cpipe);
  477         cpipe->pipe_buffer.buffer = buffer;
  478         cpipe->pipe_buffer.size = size;
  479         cpipe->pipe_buffer.in = cnt;
  480         cpipe->pipe_buffer.out = 0;
  481         cpipe->pipe_buffer.cnt = cnt;
  482         atomic_add_int(&amountpipekva, cpipe->pipe_buffer.size);
  483         return (0);
  484 }
  485 
  486 /*
  487  * Wrapper for pipespace_new() that performs locking assertions.
  488  */
  489 static int
  490 pipespace(cpipe, size)
  491         struct pipe *cpipe;
  492         int size;
  493 {
  494 
  495         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  496                 ("Unlocked pipe passed to pipespace"));
  497         return (pipespace_new(cpipe, size));
  498 }
  499 
  500 /*
  501  * lock a pipe for I/O, blocking other access
  502  */
  503 static __inline int
  504 pipelock(cpipe, catch)
  505         struct pipe *cpipe;
  506         int catch;
  507 {
  508         int error;
  509 
  510         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  511         while (cpipe->pipe_state & PIPE_LOCKFL) {
  512                 cpipe->pipe_state |= PIPE_LWANT;
  513                 error = msleep(cpipe, PIPE_MTX(cpipe),
  514                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  515                     "pipelk", 0);
  516                 if (error != 0)
  517                         return (error);
  518         }
  519         cpipe->pipe_state |= PIPE_LOCKFL;
  520         return (0);
  521 }
  522 
  523 /*
  524  * unlock a pipe I/O lock
  525  */
  526 static __inline void
  527 pipeunlock(cpipe)
  528         struct pipe *cpipe;
  529 {
  530 
  531         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  532         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  533                 ("Unlocked pipe passed to pipeunlock"));
  534         cpipe->pipe_state &= ~PIPE_LOCKFL;
  535         if (cpipe->pipe_state & PIPE_LWANT) {
  536                 cpipe->pipe_state &= ~PIPE_LWANT;
  537                 wakeup(cpipe);
  538         }
  539 }
  540 
  541 static __inline void
  542 pipeselwakeup(cpipe)
  543         struct pipe *cpipe;
  544 {
  545 
  546         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  547         if (cpipe->pipe_state & PIPE_SEL) {
  548                 cpipe->pipe_state &= ~PIPE_SEL;
  549                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
  550         }
  551         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  552                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  553         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
  554 }
  555 
  556 /*
  557  * Initialize and allocate VM and memory for pipe.  The structure
  558  * will start out zero'd from the ctor, so we just manage the kmem.
  559  */
  560 static int
  561 pipe_create(pipe, backing)
  562         struct pipe *pipe;
  563         int backing;
  564 {
  565         int error;
  566 
  567         if (backing) {
  568                 if (amountpipekva > maxpipekva / 2)
  569                         error = pipespace_new(pipe, SMALL_PIPE_SIZE);
  570                 else
  571                         error = pipespace_new(pipe, PIPE_SIZE);
  572         } else {
  573                 /* If we're not backing this pipe, no need to do anything. */
  574                 error = 0;
  575         }
  576         knlist_init(&pipe->pipe_sel.si_note, PIPE_MTX(pipe));
  577         return (error);
  578 }
  579 
  580 /* ARGSUSED */
  581 static int
  582 pipe_read(fp, uio, active_cred, flags, td)
  583         struct file *fp;
  584         struct uio *uio;
  585         struct ucred *active_cred;
  586         struct thread *td;
  587         int flags;
  588 {
  589         struct pipe *rpipe = fp->f_data;
  590         int error;
  591         int nread = 0;
  592         u_int size;
  593 
  594         PIPE_LOCK(rpipe);
  595         ++rpipe->pipe_busy;
  596         error = pipelock(rpipe, 1);
  597         if (error)
  598                 goto unlocked_error;
  599 
  600 #ifdef MAC
  601         error = mac_check_pipe_read(active_cred, rpipe->pipe_pair);
  602         if (error)
  603                 goto locked_error;
  604 #endif
  605         if (amountpipekva > (3 * maxpipekva) / 4) {
  606                 if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
  607                         (rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
  608                         (rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
  609                         (piperesizeallowed == 1)) {
  610                         PIPE_UNLOCK(rpipe);
  611                         pipespace(rpipe, SMALL_PIPE_SIZE);
  612                         PIPE_LOCK(rpipe);
  613                 }
  614         }
  615 
  616         while (uio->uio_resid) {
  617                 /*
  618                  * normal pipe buffer receive
  619                  */
  620                 if (rpipe->pipe_buffer.cnt > 0) {
  621                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  622                         if (size > rpipe->pipe_buffer.cnt)
  623                                 size = rpipe->pipe_buffer.cnt;
  624                         if (size > (u_int) uio->uio_resid)
  625                                 size = (u_int) uio->uio_resid;
  626 
  627                         PIPE_UNLOCK(rpipe);
  628                         error = uiomove(
  629                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  630                             size, uio);
  631                         PIPE_LOCK(rpipe);
  632                         if (error)
  633                                 break;
  634 
  635                         rpipe->pipe_buffer.out += size;
  636                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  637                                 rpipe->pipe_buffer.out = 0;
  638 
  639                         rpipe->pipe_buffer.cnt -= size;
  640 
  641                         /*
  642                          * If there is no more to read in the pipe, reset
  643                          * its pointers to the beginning.  This improves
  644                          * cache hit stats.
  645                          */
  646                         if (rpipe->pipe_buffer.cnt == 0) {
  647                                 rpipe->pipe_buffer.in = 0;
  648                                 rpipe->pipe_buffer.out = 0;
  649                         }
  650                         nread += size;
  651 #ifndef PIPE_NODIRECT
  652                 /*
  653                  * Direct copy, bypassing a kernel buffer.
  654                  */
  655                 } else if ((size = rpipe->pipe_map.cnt) &&
  656                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  657                         if (size > (u_int) uio->uio_resid)
  658                                 size = (u_int) uio->uio_resid;
  659 
  660                         PIPE_UNLOCK(rpipe);
  661                         error = uiomove_fromphys(rpipe->pipe_map.ms,
  662                             rpipe->pipe_map.pos, size, uio);
  663                         PIPE_LOCK(rpipe);
  664                         if (error)
  665                                 break;
  666                         nread += size;
  667                         rpipe->pipe_map.pos += size;
  668                         rpipe->pipe_map.cnt -= size;
  669                         if (rpipe->pipe_map.cnt == 0) {
  670                                 rpipe->pipe_state &= ~PIPE_DIRECTW;
  671                                 wakeup(rpipe);
  672                         }
  673 #endif
  674                 } else {
  675                         /*
  676                          * detect EOF condition
  677                          * read returns 0 on EOF, no need to set error
  678                          */
  679                         if (rpipe->pipe_state & PIPE_EOF)
  680                                 break;
  681 
  682                         /*
  683                          * If the "write-side" has been blocked, wake it up now.
  684                          */
  685                         if (rpipe->pipe_state & PIPE_WANTW) {
  686                                 rpipe->pipe_state &= ~PIPE_WANTW;
  687                                 wakeup(rpipe);
  688                         }
  689 
  690                         /*
  691                          * Break if some data was read.
  692                          */
  693                         if (nread > 0)
  694                                 break;
  695 
  696                         /*
  697                          * Unlock the pipe buffer for our remaining processing.
  698                          * We will either break out with an error or we will
  699                          * sleep and relock to loop.
  700                          */
  701                         pipeunlock(rpipe);
  702 
  703                         /*
  704                          * Handle non-blocking mode operation or
  705                          * wait for more data.
  706                          */
  707                         if (fp->f_flag & FNONBLOCK) {
  708                                 error = EAGAIN;
  709                         } else {
  710                                 rpipe->pipe_state |= PIPE_WANTR;
  711                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  712                                     PRIBIO | PCATCH,
  713                                     "piperd", 0)) == 0)
  714                                         error = pipelock(rpipe, 1);
  715                         }
  716                         if (error)
  717                                 goto unlocked_error;
  718                 }
  719         }
  720 #ifdef MAC
  721 locked_error:
  722 #endif
  723         pipeunlock(rpipe);
  724 
  725         /* XXX: should probably do this before getting any locks. */
  726         if (error == 0)
  727                 vfs_timestamp(&rpipe->pipe_atime);
  728 unlocked_error:
  729         --rpipe->pipe_busy;
  730 
  731         /*
  732          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  733          */
  734         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  735                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  736                 wakeup(rpipe);
  737         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  738                 /*
  739                  * Handle write blocking hysteresis.
  740                  */
  741                 if (rpipe->pipe_state & PIPE_WANTW) {
  742                         rpipe->pipe_state &= ~PIPE_WANTW;
  743                         wakeup(rpipe);
  744                 }
  745         }
  746 
  747         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  748                 pipeselwakeup(rpipe);
  749 
  750         PIPE_UNLOCK(rpipe);
  751         return (error);
  752 }
  753 
  754 #ifndef PIPE_NODIRECT
  755 /*
  756  * Map the sending processes' buffer into kernel space and wire it.
  757  * This is similar to a physical write operation.
  758  */
  759 static int
  760 pipe_build_write_buffer(wpipe, uio)
  761         struct pipe *wpipe;
  762         struct uio *uio;
  763 {
  764         pmap_t pmap;
  765         u_int size;
  766         int i, j;
  767         vm_offset_t addr, endaddr;
  768 
  769         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  770         KASSERT(wpipe->pipe_state & PIPE_DIRECTW,
  771                 ("Clone attempt on non-direct write pipe!"));
  772 
  773         size = (u_int) uio->uio_iov->iov_len;
  774         if (size > wpipe->pipe_buffer.size)
  775                 size = wpipe->pipe_buffer.size;
  776 
  777         pmap = vmspace_pmap(curproc->p_vmspace);
  778         endaddr = round_page((vm_offset_t)uio->uio_iov->iov_base + size);
  779         addr = trunc_page((vm_offset_t)uio->uio_iov->iov_base);
  780         for (i = 0; addr < endaddr; addr += PAGE_SIZE, i++) {
  781                 /*
  782                  * vm_fault_quick() can sleep.  Consequently,
  783                  * vm_page_lock_queue() and vm_page_unlock_queue()
  784                  * should not be performed outside of this loop.
  785                  */
  786         race:
  787                 if (vm_fault_quick((caddr_t)addr, VM_PROT_READ) < 0) {
  788                         vm_page_lock_queues();
  789                         for (j = 0; j < i; j++)
  790                                 vm_page_unhold(wpipe->pipe_map.ms[j]);
  791                         vm_page_unlock_queues();
  792                         return (EFAULT);
  793                 }
  794                 wpipe->pipe_map.ms[i] = pmap_extract_and_hold(pmap, addr,
  795                     VM_PROT_READ);
  796                 if (wpipe->pipe_map.ms[i] == NULL)
  797                         goto race;
  798         }
  799 
  800 /*
  801  * set up the control block
  802  */
  803         wpipe->pipe_map.npages = i;
  804         wpipe->pipe_map.pos =
  805             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  806         wpipe->pipe_map.cnt = size;
  807 
  808 /*
  809  * and update the uio data
  810  */
  811 
  812         uio->uio_iov->iov_len -= size;
  813         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  814         if (uio->uio_iov->iov_len == 0)
  815                 uio->uio_iov++;
  816         uio->uio_resid -= size;
  817         uio->uio_offset += size;
  818         return (0);
  819 }
  820 
  821 /*
  822  * unmap and unwire the process buffer
  823  */
  824 static void
  825 pipe_destroy_write_buffer(wpipe)
  826         struct pipe *wpipe;
  827 {
  828         int i;
  829 
  830         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  831         vm_page_lock_queues();
  832         for (i = 0; i < wpipe->pipe_map.npages; i++) {
  833                 vm_page_unhold(wpipe->pipe_map.ms[i]);
  834         }
  835         vm_page_unlock_queues();
  836         wpipe->pipe_map.npages = 0;
  837 }
  838 
  839 /*
  840  * In the case of a signal, the writing process might go away.  This
  841  * code copies the data into the circular buffer so that the source
  842  * pages can be freed without loss of data.
  843  */
  844 static void
  845 pipe_clone_write_buffer(wpipe)
  846         struct pipe *wpipe;
  847 {
  848         struct uio uio;
  849         struct iovec iov;
  850         int size;
  851         int pos;
  852 
  853         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  854         size = wpipe->pipe_map.cnt;
  855         pos = wpipe->pipe_map.pos;
  856 
  857         wpipe->pipe_buffer.in = size;
  858         wpipe->pipe_buffer.out = 0;
  859         wpipe->pipe_buffer.cnt = size;
  860         wpipe->pipe_state &= ~PIPE_DIRECTW;
  861 
  862         PIPE_UNLOCK(wpipe);
  863         iov.iov_base = wpipe->pipe_buffer.buffer;
  864         iov.iov_len = size;
  865         uio.uio_iov = &iov;
  866         uio.uio_iovcnt = 1;
  867         uio.uio_offset = 0;
  868         uio.uio_resid = size;
  869         uio.uio_segflg = UIO_SYSSPACE;
  870         uio.uio_rw = UIO_READ;
  871         uio.uio_td = curthread;
  872         uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
  873         PIPE_LOCK(wpipe);
  874         pipe_destroy_write_buffer(wpipe);
  875 }
  876 
  877 /*
  878  * This implements the pipe buffer write mechanism.  Note that only
  879  * a direct write OR a normal pipe write can be pending at any given time.
  880  * If there are any characters in the pipe buffer, the direct write will
  881  * be deferred until the receiving process grabs all of the bytes from
  882  * the pipe buffer.  Then the direct mapping write is set-up.
  883  */
  884 static int
  885 pipe_direct_write(wpipe, uio)
  886         struct pipe *wpipe;
  887         struct uio *uio;
  888 {
  889         int error;
  890 
  891 retry:
  892         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  893         error = pipelock(wpipe, 1);
  894         if (wpipe->pipe_state & PIPE_EOF)
  895                 error = EPIPE;
  896         if (error) {
  897                 pipeunlock(wpipe);
  898                 goto error1;
  899         }
  900         while (wpipe->pipe_state & PIPE_DIRECTW) {
  901                 if (wpipe->pipe_state & PIPE_WANTR) {
  902                         wpipe->pipe_state &= ~PIPE_WANTR;
  903                         wakeup(wpipe);
  904                 }
  905                 wpipe->pipe_state |= PIPE_WANTW;
  906                 pipeunlock(wpipe);
  907                 error = msleep(wpipe, PIPE_MTX(wpipe),
  908                     PRIBIO | PCATCH, "pipdww", 0);
  909                 if (error)
  910                         goto error1;
  911                 else
  912                         goto retry;
  913         }
  914         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  915         if (wpipe->pipe_buffer.cnt > 0) {
  916                 if (wpipe->pipe_state & PIPE_WANTR) {
  917                         wpipe->pipe_state &= ~PIPE_WANTR;
  918                         wakeup(wpipe);
  919                 }
  920                 wpipe->pipe_state |= PIPE_WANTW;
  921                 pipeunlock(wpipe);
  922                 error = msleep(wpipe, PIPE_MTX(wpipe),
  923                     PRIBIO | PCATCH, "pipdwc", 0);
  924                 if (error)
  925                         goto error1;
  926                 else
  927                         goto retry;
  928         }
  929 
  930         wpipe->pipe_state |= PIPE_DIRECTW;
  931 
  932         PIPE_UNLOCK(wpipe);
  933         error = pipe_build_write_buffer(wpipe, uio);
  934         PIPE_LOCK(wpipe);
  935         if (error) {
  936                 wpipe->pipe_state &= ~PIPE_DIRECTW;
  937                 pipeunlock(wpipe);
  938                 goto error1;
  939         }
  940 
  941         error = 0;
  942         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
  943                 if (wpipe->pipe_state & PIPE_EOF) {
  944                         pipe_destroy_write_buffer(wpipe);
  945                         pipeselwakeup(wpipe);
  946                         pipeunlock(wpipe);
  947                         error = EPIPE;
  948                         goto error1;
  949                 }
  950                 if (wpipe->pipe_state & PIPE_WANTR) {
  951                         wpipe->pipe_state &= ~PIPE_WANTR;
  952                         wakeup(wpipe);
  953                 }
  954                 pipeselwakeup(wpipe);
  955                 pipeunlock(wpipe);
  956                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
  957                     "pipdwt", 0);
  958                 pipelock(wpipe, 0);
  959         }
  960 
  961         if (wpipe->pipe_state & PIPE_EOF)
  962                 error = EPIPE;
  963         if (wpipe->pipe_state & PIPE_DIRECTW) {
  964                 /*
  965                  * this bit of trickery substitutes a kernel buffer for
  966                  * the process that might be going away.
  967                  */
  968                 pipe_clone_write_buffer(wpipe);
  969         } else {
  970                 pipe_destroy_write_buffer(wpipe);
  971         }
  972         pipeunlock(wpipe);
  973         return (error);
  974 
  975 error1:
  976         wakeup(wpipe);
  977         return (error);
  978 }
  979 #endif
  980 
  981 static int
  982 pipe_write(fp, uio, active_cred, flags, td)
  983         struct file *fp;
  984         struct uio *uio;
  985         struct ucred *active_cred;
  986         struct thread *td;
  987         int flags;
  988 {
  989         int error = 0;
  990         int desiredsize, orig_resid;
  991         struct pipe *wpipe, *rpipe;
  992 
  993         rpipe = fp->f_data;
  994         wpipe = rpipe->pipe_peer;
  995 
  996         PIPE_LOCK(rpipe);
  997         error = pipelock(wpipe, 1);
  998         if (error) {
  999                 PIPE_UNLOCK(rpipe);
 1000                 return (error);
 1001         }
 1002         /*
 1003          * detect loss of pipe read side, issue SIGPIPE if lost.
 1004          */
 1005         if ((!wpipe->pipe_present) || (wpipe->pipe_state & PIPE_EOF)) {
 1006                 pipeunlock(wpipe);
 1007                 PIPE_UNLOCK(rpipe);
 1008                 return (EPIPE);
 1009         }
 1010 #ifdef MAC
 1011         error = mac_check_pipe_write(active_cred, wpipe->pipe_pair);
 1012         if (error) {
 1013                 pipeunlock(wpipe);
 1014                 PIPE_UNLOCK(rpipe);
 1015                 return (error);
 1016         }
 1017 #endif
 1018         ++wpipe->pipe_busy;
 1019 
 1020         /* Choose a larger size if it's advantageous */
 1021         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
 1022         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
 1023                 if (piperesizeallowed != 1)
 1024                         break;
 1025                 if (amountpipekva > maxpipekva / 2)
 1026                         break;
 1027                 if (desiredsize == BIG_PIPE_SIZE)
 1028                         break;
 1029                 desiredsize = desiredsize * 2;
 1030         }
 1031 
 1032         /* Choose a smaller size if we're in a OOM situation */
 1033         if ((amountpipekva > (3 * maxpipekva) / 4) &&
 1034                 (wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
 1035                 (wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
 1036                 (piperesizeallowed == 1))
 1037                 desiredsize = SMALL_PIPE_SIZE;
 1038 
 1039         /* Resize if the above determined that a new size was necessary */
 1040         if ((desiredsize != wpipe->pipe_buffer.size) &&
 1041                 ((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
 1042                 PIPE_UNLOCK(wpipe);
 1043                 pipespace(wpipe, desiredsize);
 1044                 PIPE_LOCK(wpipe);
 1045         }
 1046         if (wpipe->pipe_buffer.size == 0) {
 1047                 /*
 1048                  * This can only happen for reverse direction use of pipes
 1049                  * in a complete OOM situation.
 1050                  */
 1051                 error = ENOMEM;
 1052                 --wpipe->pipe_busy;
 1053                 pipeunlock(wpipe);
 1054                 PIPE_UNLOCK(wpipe);
 1055                 return (error);
 1056         }
 1057 
 1058         pipeunlock(wpipe);
 1059 
 1060         orig_resid = uio->uio_resid;
 1061 
 1062         while (uio->uio_resid) {
 1063                 int space;
 1064 
 1065                 pipelock(wpipe, 0);
 1066                 if (wpipe->pipe_state & PIPE_EOF) {
 1067                         pipeunlock(wpipe);
 1068                         error = EPIPE;
 1069                         break;
 1070                 }
 1071 #ifndef PIPE_NODIRECT
 1072                 /*
 1073                  * If the transfer is large, we can gain performance if
 1074                  * we do process-to-process copies directly.
 1075                  * If the write is non-blocking, we don't use the
 1076                  * direct write mechanism.
 1077                  *
 1078                  * The direct write mechanism will detect the reader going
 1079                  * away on us.
 1080                  */
 1081                 if ((uio->uio_iov->iov_len >= PIPE_MINDIRECT) &&
 1082                     (wpipe->pipe_buffer.size >= PIPE_MINDIRECT) &&
 1083                     (fp->f_flag & FNONBLOCK) == 0) {
 1084                         pipeunlock(wpipe);
 1085                         error = pipe_direct_write(wpipe, uio);
 1086                         if (error)
 1087                                 break;
 1088                         continue;
 1089                 }
 1090 #endif
 1091 
 1092                 /*
 1093                  * Pipe buffered writes cannot be coincidental with
 1094                  * direct writes.  We wait until the currently executing
 1095                  * direct write is completed before we start filling the
 1096                  * pipe buffer.  We break out if a signal occurs or the
 1097                  * reader goes away.
 1098                  */
 1099                 if (wpipe->pipe_state & PIPE_DIRECTW) {
 1100                         if (wpipe->pipe_state & PIPE_WANTR) {
 1101                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1102                                 wakeup(wpipe);
 1103                         }
 1104                         pipeunlock(wpipe);
 1105                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
 1106                             "pipbww", 0);
 1107                         if (error)
 1108                                 break;
 1109                         else
 1110                                 continue;
 1111                 }
 1112 
 1113                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1114 
 1115                 /* Writes of size <= PIPE_BUF must be atomic. */
 1116                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 1117                         space = 0;
 1118 
 1119                 if (space > 0) {
 1120                         int size;       /* Transfer size */
 1121                         int segsize;    /* first segment to transfer */
 1122 
 1123                         /*
 1124                          * Transfer size is minimum of uio transfer
 1125                          * and free space in pipe buffer.
 1126                          */
 1127                         if (space > uio->uio_resid)
 1128                                 size = uio->uio_resid;
 1129                         else
 1130                                 size = space;
 1131                         /*
 1132                          * First segment to transfer is minimum of
 1133                          * transfer size and contiguous space in
 1134                          * pipe buffer.  If first segment to transfer
 1135                          * is less than the transfer size, we've got
 1136                          * a wraparound in the buffer.
 1137                          */
 1138                         segsize = wpipe->pipe_buffer.size -
 1139                                 wpipe->pipe_buffer.in;
 1140                         if (segsize > size)
 1141                                 segsize = size;
 1142 
 1143                         /* Transfer first segment */
 1144 
 1145                         PIPE_UNLOCK(rpipe);
 1146                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
 1147                                         segsize, uio);
 1148                         PIPE_LOCK(rpipe);
 1149 
 1150                         if (error == 0 && segsize < size) {
 1151                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
 1152                                         wpipe->pipe_buffer.size,
 1153                                         ("Pipe buffer wraparound disappeared"));
 1154                                 /*
 1155                                  * Transfer remaining part now, to
 1156                                  * support atomic writes.  Wraparound
 1157                                  * happened.
 1158                                  */
 1159 
 1160                                 PIPE_UNLOCK(rpipe);
 1161                                 error = uiomove(
 1162                                     &wpipe->pipe_buffer.buffer[0],
 1163                                     size - segsize, uio);
 1164                                 PIPE_LOCK(rpipe);
 1165                         }
 1166                         if (error == 0) {
 1167                                 wpipe->pipe_buffer.in += size;
 1168                                 if (wpipe->pipe_buffer.in >=
 1169                                     wpipe->pipe_buffer.size) {
 1170                                         KASSERT(wpipe->pipe_buffer.in ==
 1171                                                 size - segsize +
 1172                                                 wpipe->pipe_buffer.size,
 1173                                                 ("Expected wraparound bad"));
 1174                                         wpipe->pipe_buffer.in = size - segsize;
 1175                                 }
 1176 
 1177                                 wpipe->pipe_buffer.cnt += size;
 1178                                 KASSERT(wpipe->pipe_buffer.cnt <=
 1179                                         wpipe->pipe_buffer.size,
 1180                                         ("Pipe buffer overflow"));
 1181                         }
 1182                         pipeunlock(wpipe);
 1183                 } else {
 1184                         /*
 1185                          * If the "read-side" has been blocked, wake it up now.
 1186                          */
 1187                         if (wpipe->pipe_state & PIPE_WANTR) {
 1188                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1189                                 wakeup(wpipe);
 1190                         }
 1191 
 1192                         /*
 1193                          * don't block on non-blocking I/O
 1194                          */
 1195                         if (fp->f_flag & FNONBLOCK) {
 1196                                 error = EAGAIN;
 1197                                 pipeunlock(wpipe);
 1198                                 break;
 1199                         }
 1200 
 1201                         /*
 1202                          * We have no more space and have something to offer,
 1203                          * wake up select/poll.
 1204                          */
 1205                         pipeselwakeup(wpipe);
 1206 
 1207                         wpipe->pipe_state |= PIPE_WANTW;
 1208                         pipeunlock(wpipe);
 1209                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1210                             PRIBIO | PCATCH, "pipewr", 0);
 1211                         if (error != 0)
 1212                                 break;
 1213                 }
 1214         }
 1215 
 1216         pipelock(wpipe, 0);
 1217         --wpipe->pipe_busy;
 1218 
 1219         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1220                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1221                 wakeup(wpipe);
 1222         } else if (wpipe->pipe_buffer.cnt > 0) {
 1223                 /*
 1224                  * If we have put any characters in the buffer, we wake up
 1225                  * the reader.
 1226                  */
 1227                 if (wpipe->pipe_state & PIPE_WANTR) {
 1228                         wpipe->pipe_state &= ~PIPE_WANTR;
 1229                         wakeup(wpipe);
 1230                 }
 1231         }
 1232 
 1233         /*
 1234          * Don't return EPIPE if I/O was successful
 1235          */
 1236         if ((wpipe->pipe_buffer.cnt == 0) &&
 1237             (uio->uio_resid == 0) &&
 1238             (error == EPIPE)) {
 1239                 error = 0;
 1240         }
 1241 
 1242         if (error == 0)
 1243                 vfs_timestamp(&wpipe->pipe_mtime);
 1244 
 1245         /*
 1246          * We have something to offer,
 1247          * wake up select/poll.
 1248          */
 1249         if (wpipe->pipe_buffer.cnt)
 1250                 pipeselwakeup(wpipe);
 1251 
 1252         pipeunlock(wpipe);
 1253         PIPE_UNLOCK(rpipe);
 1254         return (error);
 1255 }
 1256 
 1257 /*
 1258  * we implement a very minimal set of ioctls for compatibility with sockets.
 1259  */
 1260 static int
 1261 pipe_ioctl(fp, cmd, data, active_cred, td)
 1262         struct file *fp;
 1263         u_long cmd;
 1264         void *data;
 1265         struct ucred *active_cred;
 1266         struct thread *td;
 1267 {
 1268         struct pipe *mpipe = fp->f_data;
 1269 #ifdef MAC
 1270         int error;
 1271 #endif
 1272 
 1273         PIPE_LOCK(mpipe);
 1274 
 1275 #ifdef MAC
 1276         error = mac_check_pipe_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
 1277         if (error) {
 1278                 PIPE_UNLOCK(mpipe);
 1279                 return (error);
 1280         }
 1281 #endif
 1282 
 1283         switch (cmd) {
 1284 
 1285         case FIONBIO:
 1286                 PIPE_UNLOCK(mpipe);
 1287                 return (0);
 1288 
 1289         case FIOASYNC:
 1290                 if (*(int *)data) {
 1291                         mpipe->pipe_state |= PIPE_ASYNC;
 1292                 } else {
 1293                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1294                 }
 1295                 PIPE_UNLOCK(mpipe);
 1296                 return (0);
 1297 
 1298         case FIONREAD:
 1299                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1300                         *(int *)data = mpipe->pipe_map.cnt;
 1301                 else
 1302                         *(int *)data = mpipe->pipe_buffer.cnt;
 1303                 PIPE_UNLOCK(mpipe);
 1304                 return (0);
 1305 
 1306         case FIOSETOWN:
 1307                 PIPE_UNLOCK(mpipe);
 1308                 return (fsetown(*(int *)data, &mpipe->pipe_sigio));
 1309 
 1310         case FIOGETOWN:
 1311                 PIPE_UNLOCK(mpipe);
 1312                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1313                 return (0);
 1314 
 1315         /* This is deprecated, FIOSETOWN should be used instead. */
 1316         case TIOCSPGRP:
 1317                 PIPE_UNLOCK(mpipe);
 1318                 return (fsetown(-(*(int *)data), &mpipe->pipe_sigio));
 1319 
 1320         /* This is deprecated, FIOGETOWN should be used instead. */
 1321         case TIOCGPGRP:
 1322                 PIPE_UNLOCK(mpipe);
 1323                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1324                 return (0);
 1325 
 1326         }
 1327         PIPE_UNLOCK(mpipe);
 1328         return (ENOTTY);
 1329 }
 1330 
 1331 static int
 1332 pipe_poll(fp, events, active_cred, td)
 1333         struct file *fp;
 1334         int events;
 1335         struct ucred *active_cred;
 1336         struct thread *td;
 1337 {
 1338         struct pipe *rpipe = fp->f_data;
 1339         struct pipe *wpipe;
 1340         int revents = 0;
 1341 #ifdef MAC
 1342         int error;
 1343 #endif
 1344 
 1345         wpipe = rpipe->pipe_peer;
 1346         PIPE_LOCK(rpipe);
 1347 #ifdef MAC
 1348         error = mac_check_pipe_poll(active_cred, rpipe->pipe_pair);
 1349         if (error)
 1350                 goto locked_error;
 1351 #endif
 1352         if (events & (POLLIN | POLLRDNORM))
 1353                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1354                     (rpipe->pipe_buffer.cnt > 0) ||
 1355                     (rpipe->pipe_state & PIPE_EOF))
 1356                         revents |= events & (POLLIN | POLLRDNORM);
 1357 
 1358         if (events & (POLLOUT | POLLWRNORM))
 1359                 if (!wpipe->pipe_present || (wpipe->pipe_state & PIPE_EOF) ||
 1360                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1361                      (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF))
 1362                         revents |= events & (POLLOUT | POLLWRNORM);
 1363 
 1364         if ((rpipe->pipe_state & PIPE_EOF) ||
 1365             (!wpipe->pipe_present) ||
 1366             (wpipe->pipe_state & PIPE_EOF))
 1367                 revents |= POLLHUP;
 1368 
 1369         if (revents == 0) {
 1370                 if (events & (POLLIN | POLLRDNORM)) {
 1371                         selrecord(td, &rpipe->pipe_sel);
 1372                         rpipe->pipe_state |= PIPE_SEL;
 1373                 }
 1374 
 1375                 if (events & (POLLOUT | POLLWRNORM)) {
 1376                         selrecord(td, &wpipe->pipe_sel);
 1377                         wpipe->pipe_state |= PIPE_SEL;
 1378                 }
 1379         }
 1380 #ifdef MAC
 1381 locked_error:
 1382 #endif
 1383         PIPE_UNLOCK(rpipe);
 1384 
 1385         return (revents);
 1386 }
 1387 
 1388 /*
 1389  * We shouldn't need locks here as we're doing a read and this should
 1390  * be a natural race.
 1391  */
 1392 static int
 1393 pipe_stat(fp, ub, active_cred, td)
 1394         struct file *fp;
 1395         struct stat *ub;
 1396         struct ucred *active_cred;
 1397         struct thread *td;
 1398 {
 1399         struct pipe *pipe = fp->f_data;
 1400 #ifdef MAC
 1401         int error;
 1402 
 1403         PIPE_LOCK(pipe);
 1404         error = mac_check_pipe_stat(active_cred, pipe->pipe_pair);
 1405         PIPE_UNLOCK(pipe);
 1406         if (error)
 1407                 return (error);
 1408 #endif
 1409         bzero(ub, sizeof(*ub));
 1410         ub->st_mode = S_IFIFO;
 1411         ub->st_blksize = PAGE_SIZE;
 1412         if (pipe->pipe_state & PIPE_DIRECTW)
 1413                 ub->st_size = pipe->pipe_map.cnt;
 1414         else
 1415                 ub->st_size = pipe->pipe_buffer.cnt;
 1416         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
 1417         ub->st_atimespec = pipe->pipe_atime;
 1418         ub->st_mtimespec = pipe->pipe_mtime;
 1419         ub->st_ctimespec = pipe->pipe_ctime;
 1420         ub->st_uid = fp->f_cred->cr_uid;
 1421         ub->st_gid = fp->f_cred->cr_gid;
 1422         /*
 1423          * Left as 0: st_dev, st_ino, st_nlink, st_rdev, st_flags, st_gen.
 1424          * XXX (st_dev, st_ino) should be unique.
 1425          */
 1426         return (0);
 1427 }
 1428 
 1429 /* ARGSUSED */
 1430 static int
 1431 pipe_close(fp, td)
 1432         struct file *fp;
 1433         struct thread *td;
 1434 {
 1435         struct pipe *cpipe = fp->f_data;
 1436 
 1437         fp->f_ops = &badfileops;
 1438         fp->f_data = NULL;
 1439         funsetown(&cpipe->pipe_sigio);
 1440         pipeclose(cpipe);
 1441         return (0);
 1442 }
 1443 
 1444 static void
 1445 pipe_free_kmem(cpipe)
 1446         struct pipe *cpipe;
 1447 {
 1448 
 1449         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
 1450             ("pipe_free_kmem: pipe mutex locked"));
 1451 
 1452         if (cpipe->pipe_buffer.buffer != NULL) {
 1453                 atomic_subtract_int(&amountpipekva, cpipe->pipe_buffer.size);
 1454                 vm_map_remove(pipe_map,
 1455                     (vm_offset_t)cpipe->pipe_buffer.buffer,
 1456                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
 1457                 cpipe->pipe_buffer.buffer = NULL;
 1458         }
 1459 #ifndef PIPE_NODIRECT
 1460         {
 1461                 cpipe->pipe_map.cnt = 0;
 1462                 cpipe->pipe_map.pos = 0;
 1463                 cpipe->pipe_map.npages = 0;
 1464         }
 1465 #endif
 1466 }
 1467 
 1468 /*
 1469  * shutdown the pipe
 1470  */
 1471 static void
 1472 pipeclose(cpipe)
 1473         struct pipe *cpipe;
 1474 {
 1475         struct pipepair *pp;
 1476         struct pipe *ppipe;
 1477 
 1478         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
 1479 
 1480         PIPE_LOCK(cpipe);
 1481         pipelock(cpipe, 0);
 1482         pp = cpipe->pipe_pair;
 1483 
 1484         pipeselwakeup(cpipe);
 1485 
 1486         /*
 1487          * If the other side is blocked, wake it up saying that
 1488          * we want to close it down.
 1489          */
 1490         cpipe->pipe_state |= PIPE_EOF;
 1491         while (cpipe->pipe_busy) {
 1492                 wakeup(cpipe);
 1493                 cpipe->pipe_state |= PIPE_WANT;
 1494                 pipeunlock(cpipe);
 1495                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1496                 pipelock(cpipe, 0);
 1497         }
 1498 
 1499 
 1500         /*
 1501          * Disconnect from peer, if any.
 1502          */
 1503         ppipe = cpipe->pipe_peer;
 1504         if (ppipe->pipe_present != 0) {
 1505                 pipeselwakeup(ppipe);
 1506 
 1507                 ppipe->pipe_state |= PIPE_EOF;
 1508                 wakeup(ppipe);
 1509                 KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
 1510         }
 1511 
 1512         /*
 1513          * Mark this endpoint as free.  Release kmem resources.  We
 1514          * don't mark this endpoint as unused until we've finished
 1515          * doing that, or the pipe might disappear out from under
 1516          * us.
 1517          */
 1518         PIPE_UNLOCK(cpipe);
 1519         pipe_free_kmem(cpipe);
 1520         PIPE_LOCK(cpipe);
 1521         cpipe->pipe_present = 0;
 1522         pipeunlock(cpipe);
 1523         knlist_clear(&cpipe->pipe_sel.si_note, 1);
 1524         knlist_destroy(&cpipe->pipe_sel.si_note);
 1525 
 1526         /*
 1527          * If both endpoints are now closed, release the memory for the
 1528          * pipe pair.  If not, unlock.
 1529          */
 1530         if (ppipe->pipe_present == 0) {
 1531                 PIPE_UNLOCK(cpipe);
 1532 #ifdef MAC
 1533                 mac_destroy_pipe(pp);
 1534 #endif
 1535                 uma_zfree(pipe_zone, cpipe->pipe_pair);
 1536         } else
 1537                 PIPE_UNLOCK(cpipe);
 1538 }
 1539 
 1540 /*ARGSUSED*/
 1541 static int
 1542 pipe_kqfilter(struct file *fp, struct knote *kn)
 1543 {
 1544         struct pipe *cpipe;
 1545 
 1546         cpipe = kn->kn_fp->f_data;
 1547         PIPE_LOCK(cpipe);
 1548         switch (kn->kn_filter) {
 1549         case EVFILT_READ:
 1550                 kn->kn_fop = &pipe_rfiltops;
 1551                 break;
 1552         case EVFILT_WRITE:
 1553                 kn->kn_fop = &pipe_wfiltops;
 1554                 if (!cpipe->pipe_peer->pipe_present) {
 1555                         /* other end of pipe has been closed */
 1556                         PIPE_UNLOCK(cpipe);
 1557                         return (EPIPE);
 1558                 }
 1559                 cpipe = cpipe->pipe_peer;
 1560                 break;
 1561         default:
 1562                 PIPE_UNLOCK(cpipe);
 1563                 return (EINVAL);
 1564         }
 1565 
 1566         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
 1567         PIPE_UNLOCK(cpipe);
 1568         return (0);
 1569 }
 1570 
 1571 static void
 1572 filt_pipedetach(struct knote *kn)
 1573 {
 1574         struct pipe *cpipe = (struct pipe *)kn->kn_fp->f_data;
 1575 
 1576         PIPE_LOCK(cpipe);
 1577         if (kn->kn_filter == EVFILT_WRITE) {
 1578                 if (!cpipe->pipe_peer->pipe_present) {
 1579                         PIPE_UNLOCK(cpipe);
 1580                         return;
 1581                 }
 1582                 cpipe = cpipe->pipe_peer;
 1583         }
 1584         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
 1585         PIPE_UNLOCK(cpipe);
 1586 }
 1587 
 1588 /*ARGSUSED*/
 1589 static int
 1590 filt_piperead(struct knote *kn, long hint)
 1591 {
 1592         struct pipe *rpipe = kn->kn_fp->f_data;
 1593         struct pipe *wpipe = rpipe->pipe_peer;
 1594         int ret;
 1595 
 1596         PIPE_LOCK(rpipe);
 1597         kn->kn_data = rpipe->pipe_buffer.cnt;
 1598         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1599                 kn->kn_data = rpipe->pipe_map.cnt;
 1600 
 1601         if ((rpipe->pipe_state & PIPE_EOF) ||
 1602             (!wpipe->pipe_present) || (wpipe->pipe_state & PIPE_EOF)) {
 1603                 kn->kn_flags |= EV_EOF;
 1604                 PIPE_UNLOCK(rpipe);
 1605                 return (1);
 1606         }
 1607         ret = kn->kn_data > 0;
 1608         PIPE_UNLOCK(rpipe);
 1609         return ret;
 1610 }
 1611 
 1612 /*ARGSUSED*/
 1613 static int
 1614 filt_pipewrite(struct knote *kn, long hint)
 1615 {
 1616         struct pipe *rpipe = kn->kn_fp->f_data;
 1617         struct pipe *wpipe = rpipe->pipe_peer;
 1618 
 1619         PIPE_LOCK(rpipe);
 1620         if ((!wpipe->pipe_present) || (wpipe->pipe_state & PIPE_EOF)) {
 1621                 kn->kn_data = 0;
 1622                 kn->kn_flags |= EV_EOF;
 1623                 PIPE_UNLOCK(rpipe);
 1624                 return (1);
 1625         }
 1626         kn->kn_data = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1627         if (wpipe->pipe_state & PIPE_DIRECTW)
 1628                 kn->kn_data = 0;
 1629 
 1630         PIPE_UNLOCK(rpipe);
 1631         return (kn->kn_data >= PIPE_BUF);
 1632 }

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