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.  Whenever the amount in use
   52  * exceeds half of this value, all new pipes will be created with size
   53  * SMALL_PIPE_SIZE, rather than PIPE_SIZE.  Big pipe creation will be limited
   54  * as well.  This value is loader tunable only.
   55  *
   56  * kern.ipc.maxpipekvawired - This value limits the amount of memory that may
   57  * be wired in order to facilitate direct copies using page flipping.
   58  * Whenever this value is exceeded, pipes will fall back to using regular
   59  * copies.  This value is sysctl controllable at all times.
   60  *
   61  * These values are autotuned in subr_param.c.
   62  *
   63  * Memory usage may be monitored through the sysctls
   64  * kern.ipc.pipes, kern.ipc.pipekva and kern.ipc.pipekvawired.
   65  *
   66  */
   67 
   68 #include <sys/cdefs.h>
   69 __FBSDID("$FreeBSD: releng/5.2/sys/kern/sys_pipe.c 122352 2003-11-09 09:17:26Z tanimura $");
   70 
   71 #include "opt_mac.h"
   72 
   73 #include <sys/param.h>
   74 #include <sys/systm.h>
   75 #include <sys/fcntl.h>
   76 #include <sys/file.h>
   77 #include <sys/filedesc.h>
   78 #include <sys/filio.h>
   79 #include <sys/kernel.h>
   80 #include <sys/lock.h>
   81 #include <sys/mac.h>
   82 #include <sys/mutex.h>
   83 #include <sys/ttycom.h>
   84 #include <sys/stat.h>
   85 #include <sys/malloc.h>
   86 #include <sys/poll.h>
   87 #include <sys/selinfo.h>
   88 #include <sys/signalvar.h>
   89 #include <sys/sysctl.h>
   90 #include <sys/sysproto.h>
   91 #include <sys/pipe.h>
   92 #include <sys/proc.h>
   93 #include <sys/vnode.h>
   94 #include <sys/uio.h>
   95 #include <sys/event.h>
   96 
   97 #include <vm/vm.h>
   98 #include <vm/vm_param.h>
   99 #include <vm/vm_object.h>
  100 #include <vm/vm_kern.h>
  101 #include <vm/vm_extern.h>
  102 #include <vm/pmap.h>
  103 #include <vm/vm_map.h>
  104 #include <vm/vm_page.h>
  105 #include <vm/uma.h>
  106 
  107 /*
  108  * Use this define if you want to disable *fancy* VM things.  Expect an
  109  * approx 30% decrease in transfer rate.  This could be useful for
  110  * NetBSD or OpenBSD.
  111  */
  112 /* #define PIPE_NODIRECT */
  113 
  114 /*
  115  * interfaces to the outside world
  116  */
  117 static fo_rdwr_t        pipe_read;
  118 static fo_rdwr_t        pipe_write;
  119 static fo_ioctl_t       pipe_ioctl;
  120 static fo_poll_t        pipe_poll;
  121 static fo_kqfilter_t    pipe_kqfilter;
  122 static fo_stat_t        pipe_stat;
  123 static fo_close_t       pipe_close;
  124 
  125 static struct fileops pipeops = {
  126         .fo_read = pipe_read,
  127         .fo_write = pipe_write,
  128         .fo_ioctl = pipe_ioctl,
  129         .fo_poll = pipe_poll,
  130         .fo_kqfilter = pipe_kqfilter,
  131         .fo_stat = pipe_stat,
  132         .fo_close = pipe_close,
  133         .fo_flags = DFLAG_PASSABLE
  134 };
  135 
  136 static void     filt_pipedetach(struct knote *kn);
  137 static int      filt_piperead(struct knote *kn, long hint);
  138 static int      filt_pipewrite(struct knote *kn, long hint);
  139 
  140 static struct filterops pipe_rfiltops =
  141         { 1, NULL, filt_pipedetach, filt_piperead };
  142 static struct filterops pipe_wfiltops =
  143         { 1, NULL, filt_pipedetach, filt_pipewrite };
  144 
  145 /*
  146  * Default pipe buffer size(s), this can be kind-of large now because pipe
  147  * space is pageable.  The pipe code will try to maintain locality of
  148  * reference for performance reasons, so small amounts of outstanding I/O
  149  * will not wipe the cache.
  150  */
  151 #define MINPIPESIZE (PIPE_SIZE/3)
  152 #define MAXPIPESIZE (2*PIPE_SIZE/3)
  153 
  154 /*
  155  * Limit the number of "big" pipes
  156  */
  157 #define LIMITBIGPIPES   32
  158 static int nbigpipe;
  159 
  160 static int amountpipes;
  161 static int amountpipekva;
  162 static int amountpipekvawired;
  163 
  164 SYSCTL_DECL(_kern_ipc);
  165 
  166 SYSCTL_INT(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN,
  167            &maxpipekva, 0, "Pipe KVA limit");
  168 SYSCTL_INT(_kern_ipc, OID_AUTO, maxpipekvawired, CTLFLAG_RW,
  169            &maxpipekvawired, 0, "Pipe KVA wired limit");
  170 SYSCTL_INT(_kern_ipc, OID_AUTO, pipes, CTLFLAG_RD,
  171            &amountpipes, 0, "Current # of pipes");
  172 SYSCTL_INT(_kern_ipc, OID_AUTO, bigpipes, CTLFLAG_RD,
  173            &nbigpipe, 0, "Current # of big pipes");
  174 SYSCTL_INT(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
  175            &amountpipekva, 0, "Pipe KVA usage");
  176 SYSCTL_INT(_kern_ipc, OID_AUTO, pipekvawired, CTLFLAG_RD,
  177            &amountpipekvawired, 0, "Pipe wired KVA usage");
  178 
  179 static void pipeinit(void *dummy __unused);
  180 static void pipeclose(struct pipe *cpipe);
  181 static void pipe_free_kmem(struct pipe *cpipe);
  182 static int pipe_create(struct pipe **cpipep);
  183 static __inline int pipelock(struct pipe *cpipe, int catch);
  184 static __inline void pipeunlock(struct pipe *cpipe);
  185 static __inline void pipeselwakeup(struct pipe *cpipe);
  186 #ifndef PIPE_NODIRECT
  187 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
  188 static void pipe_destroy_write_buffer(struct pipe *wpipe);
  189 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
  190 static void pipe_clone_write_buffer(struct pipe *wpipe);
  191 #endif
  192 static int pipespace(struct pipe *cpipe, int size);
  193 
  194 static uma_zone_t pipe_zone;
  195 
  196 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
  197 
  198 static void
  199 pipeinit(void *dummy __unused)
  200 {
  201 
  202         pipe_zone = uma_zcreate("PIPE", sizeof(struct pipe), NULL,
  203             NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
  204         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
  205 }
  206 
  207 /*
  208  * The pipe system call for the DTYPE_PIPE type of pipes
  209  */
  210 
  211 /* ARGSUSED */
  212 int
  213 pipe(td, uap)
  214         struct thread *td;
  215         struct pipe_args /* {
  216                 int     dummy;
  217         } */ *uap;
  218 {
  219         struct filedesc *fdp = td->td_proc->p_fd;
  220         struct file *rf, *wf;
  221         struct pipe *rpipe, *wpipe;
  222         struct mtx *pmtx;
  223         int fd, error;
  224 
  225         rpipe = wpipe = NULL;
  226         if (pipe_create(&rpipe) || pipe_create(&wpipe)) {
  227                 pipeclose(rpipe); 
  228                 pipeclose(wpipe); 
  229                 return (ENFILE);
  230         }
  231         
  232         rpipe->pipe_state |= PIPE_DIRECTOK;
  233         wpipe->pipe_state |= PIPE_DIRECTOK;
  234 
  235         error = falloc(td, &rf, &fd);
  236         if (error) {
  237                 pipeclose(rpipe);
  238                 pipeclose(wpipe);
  239                 return (error);
  240         }
  241         /* An extra reference on `rf' has been held for us by falloc(). */
  242         td->td_retval[0] = fd;
  243 
  244         /*
  245          * Warning: once we've gotten past allocation of the fd for the
  246          * read-side, we can only drop the read side via fdrop() in order
  247          * to avoid races against processes which manage to dup() the read
  248          * side while we are blocked trying to allocate the write side.
  249          */
  250         FILE_LOCK(rf);
  251         rf->f_flag = FREAD | FWRITE;
  252         rf->f_type = DTYPE_PIPE;
  253         rf->f_data = rpipe;
  254         rf->f_ops = &pipeops;
  255         FILE_UNLOCK(rf);
  256         error = falloc(td, &wf, &fd);
  257         if (error) {
  258                 FILEDESC_LOCK(fdp);
  259                 if (fdp->fd_ofiles[td->td_retval[0]] == rf) {
  260                         fdp->fd_ofiles[td->td_retval[0]] = NULL;
  261                         FILEDESC_UNLOCK(fdp);
  262                         fdrop(rf, td);
  263                 } else
  264                         FILEDESC_UNLOCK(fdp);
  265                 fdrop(rf, td);
  266                 /* rpipe has been closed by fdrop(). */
  267                 pipeclose(wpipe);
  268                 return (error);
  269         }
  270         /* An extra reference on `wf' has been held for us by falloc(). */
  271         FILE_LOCK(wf);
  272         wf->f_flag = FREAD | FWRITE;
  273         wf->f_type = DTYPE_PIPE;
  274         wf->f_data = wpipe;
  275         wf->f_ops = &pipeops;
  276         FILE_UNLOCK(wf);
  277         fdrop(wf, td);
  278         td->td_retval[1] = fd;
  279         rpipe->pipe_peer = wpipe;
  280         wpipe->pipe_peer = rpipe;
  281 #ifdef MAC
  282         /*
  283          * struct pipe represents a pipe endpoint.  The MAC label is shared
  284          * between the connected endpoints.  As a result mac_init_pipe() and
  285          * mac_create_pipe() should only be called on one of the endpoints
  286          * after they have been connected.
  287          */
  288         mac_init_pipe(rpipe);
  289         mac_create_pipe(td->td_ucred, rpipe);
  290 #endif
  291         pmtx = malloc(sizeof(*pmtx), M_TEMP, M_WAITOK | M_ZERO);
  292         mtx_init(pmtx, "pipe mutex", NULL, MTX_DEF | MTX_RECURSE);
  293         rpipe->pipe_mtxp = wpipe->pipe_mtxp = pmtx;
  294         fdrop(rf, td);
  295 
  296         return (0);
  297 }
  298 
  299 /*
  300  * Allocate kva for pipe circular buffer, the space is pageable
  301  * This routine will 'realloc' the size of a pipe safely, if it fails
  302  * it will retain the old buffer.
  303  * If it fails it will return ENOMEM.
  304  */
  305 static int
  306 pipespace(cpipe, size)
  307         struct pipe *cpipe;
  308         int size;
  309 {
  310         caddr_t buffer;
  311         int error;
  312         static int curfail = 0;
  313         static struct timeval lastfail;
  314 
  315         KASSERT(cpipe->pipe_mtxp == NULL || !mtx_owned(PIPE_MTX(cpipe)),
  316                ("pipespace: pipe mutex locked"));
  317 
  318         size = round_page(size);
  319         /*
  320          * XXX -- minor change needed here for NetBSD/OpenBSD VM systems.
  321          */
  322         buffer = (caddr_t) vm_map_min(pipe_map);
  323 
  324         /*
  325          * The map entry is, by default, pageable.
  326          * XXX -- minor change needed here for NetBSD/OpenBSD VM systems.
  327          */
  328         error = vm_map_find(pipe_map, NULL, 0,
  329                 (vm_offset_t *) &buffer, size, 1,
  330                 VM_PROT_ALL, VM_PROT_ALL, 0);
  331         if (error != KERN_SUCCESS) {
  332                 if (ppsratecheck(&lastfail, &curfail, 1))
  333                         printf("kern.maxpipekva exceeded, please see tuning(7).\n");
  334                 return (ENOMEM);
  335         }
  336 
  337         /* free old resources if we're resizing */
  338         pipe_free_kmem(cpipe);
  339         cpipe->pipe_buffer.buffer = buffer;
  340         cpipe->pipe_buffer.size = size;
  341         cpipe->pipe_buffer.in = 0;
  342         cpipe->pipe_buffer.out = 0;
  343         cpipe->pipe_buffer.cnt = 0;
  344         atomic_add_int(&amountpipes, 1);
  345         atomic_add_int(&amountpipekva, cpipe->pipe_buffer.size);
  346         return (0);
  347 }
  348 
  349 /*
  350  * initialize and allocate VM and memory for pipe
  351  */
  352 static int
  353 pipe_create(cpipep)
  354         struct pipe **cpipep;
  355 {
  356         struct pipe *cpipe;
  357         int error;
  358 
  359         *cpipep = uma_zalloc(pipe_zone, M_WAITOK);
  360         if (*cpipep == NULL)
  361                 return (ENOMEM);
  362 
  363         cpipe = *cpipep;
  364         
  365         /*
  366          * protect so pipeclose() doesn't follow a junk pointer
  367          * if pipespace() fails.
  368          */
  369         bzero(&cpipe->pipe_sel, sizeof(cpipe->pipe_sel));
  370         cpipe->pipe_state = 0;
  371         cpipe->pipe_peer = NULL;
  372         cpipe->pipe_busy = 0;
  373 
  374 #ifndef PIPE_NODIRECT
  375         /*
  376          * pipe data structure initializations to support direct pipe I/O
  377          */
  378         cpipe->pipe_map.cnt = 0;
  379         cpipe->pipe_map.kva = 0;
  380         cpipe->pipe_map.pos = 0;
  381         cpipe->pipe_map.npages = 0;
  382         /* cpipe->pipe_map.ms[] = invalid */
  383 #endif
  384 
  385         cpipe->pipe_mtxp = NULL;        /* avoid pipespace assertion */
  386         /*
  387          * Reduce to 1/4th pipe size if we're over our global max.
  388          */
  389         if (amountpipekva > maxpipekva / 2)
  390                 error = pipespace(cpipe, SMALL_PIPE_SIZE);
  391         else
  392                 error = pipespace(cpipe, PIPE_SIZE);
  393         if (error)
  394                 return (error);
  395 
  396         vfs_timestamp(&cpipe->pipe_ctime);
  397         cpipe->pipe_atime = cpipe->pipe_ctime;
  398         cpipe->pipe_mtime = cpipe->pipe_ctime;
  399 
  400         return (0);
  401 }
  402 
  403 
  404 /*
  405  * lock a pipe for I/O, blocking other access
  406  */
  407 static __inline int
  408 pipelock(cpipe, catch)
  409         struct pipe *cpipe;
  410         int catch;
  411 {
  412         int error;
  413 
  414         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  415         while (cpipe->pipe_state & PIPE_LOCKFL) {
  416                 cpipe->pipe_state |= PIPE_LWANT;
  417                 error = msleep(cpipe, PIPE_MTX(cpipe),
  418                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  419                     "pipelk", 0);
  420                 if (error != 0) 
  421                         return (error);
  422         }
  423         cpipe->pipe_state |= PIPE_LOCKFL;
  424         return (0);
  425 }
  426 
  427 /*
  428  * unlock a pipe I/O lock
  429  */
  430 static __inline void
  431 pipeunlock(cpipe)
  432         struct pipe *cpipe;
  433 {
  434 
  435         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  436         cpipe->pipe_state &= ~PIPE_LOCKFL;
  437         if (cpipe->pipe_state & PIPE_LWANT) {
  438                 cpipe->pipe_state &= ~PIPE_LWANT;
  439                 wakeup(cpipe);
  440         }
  441 }
  442 
  443 static __inline void
  444 pipeselwakeup(cpipe)
  445         struct pipe *cpipe;
  446 {
  447 
  448         if (cpipe->pipe_state & PIPE_SEL) {
  449                 cpipe->pipe_state &= ~PIPE_SEL;
  450                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
  451         }
  452         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  453                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  454         KNOTE(&cpipe->pipe_sel.si_note, 0);
  455 }
  456 
  457 /* ARGSUSED */
  458 static int
  459 pipe_read(fp, uio, active_cred, flags, td)
  460         struct file *fp;
  461         struct uio *uio;
  462         struct ucred *active_cred;
  463         struct thread *td;
  464         int flags;
  465 {
  466         struct pipe *rpipe = fp->f_data;
  467         int error;
  468         int nread = 0;
  469         u_int size;
  470 
  471         PIPE_LOCK(rpipe);
  472         ++rpipe->pipe_busy;
  473         error = pipelock(rpipe, 1);
  474         if (error)
  475                 goto unlocked_error;
  476 
  477 #ifdef MAC
  478         error = mac_check_pipe_read(active_cred, rpipe);
  479         if (error)
  480                 goto locked_error;
  481 #endif
  482 
  483         while (uio->uio_resid) {
  484                 /*
  485                  * normal pipe buffer receive
  486                  */
  487                 if (rpipe->pipe_buffer.cnt > 0) {
  488                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  489                         if (size > rpipe->pipe_buffer.cnt)
  490                                 size = rpipe->pipe_buffer.cnt;
  491                         if (size > (u_int) uio->uio_resid)
  492                                 size = (u_int) uio->uio_resid;
  493 
  494                         PIPE_UNLOCK(rpipe);
  495                         error = uiomove(
  496                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  497                             size, uio);
  498                         PIPE_LOCK(rpipe);
  499                         if (error)
  500                                 break;
  501 
  502                         rpipe->pipe_buffer.out += size;
  503                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  504                                 rpipe->pipe_buffer.out = 0;
  505 
  506                         rpipe->pipe_buffer.cnt -= size;
  507 
  508                         /*
  509                          * If there is no more to read in the pipe, reset
  510                          * its pointers to the beginning.  This improves
  511                          * cache hit stats.
  512                          */
  513                         if (rpipe->pipe_buffer.cnt == 0) {
  514                                 rpipe->pipe_buffer.in = 0;
  515                                 rpipe->pipe_buffer.out = 0;
  516                         }
  517                         nread += size;
  518 #ifndef PIPE_NODIRECT
  519                 /*
  520                  * Direct copy, bypassing a kernel buffer.
  521                  */
  522                 } else if ((size = rpipe->pipe_map.cnt) &&
  523                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  524                         caddr_t va;
  525                         if (size > (u_int) uio->uio_resid)
  526                                 size = (u_int) uio->uio_resid;
  527 
  528                         va = (caddr_t) rpipe->pipe_map.kva +
  529                             rpipe->pipe_map.pos;
  530                         PIPE_UNLOCK(rpipe);
  531                         error = uiomove(va, size, uio);
  532                         PIPE_LOCK(rpipe);
  533                         if (error)
  534                                 break;
  535                         nread += size;
  536                         rpipe->pipe_map.pos += size;
  537                         rpipe->pipe_map.cnt -= size;
  538                         if (rpipe->pipe_map.cnt == 0) {
  539                                 rpipe->pipe_state &= ~PIPE_DIRECTW;
  540                                 wakeup(rpipe);
  541                         }
  542 #endif
  543                 } else {
  544                         /*
  545                          * detect EOF condition
  546                          * read returns 0 on EOF, no need to set error
  547                          */
  548                         if (rpipe->pipe_state & PIPE_EOF)
  549                                 break;
  550 
  551                         /*
  552                          * If the "write-side" has been blocked, wake it up now.
  553                          */
  554                         if (rpipe->pipe_state & PIPE_WANTW) {
  555                                 rpipe->pipe_state &= ~PIPE_WANTW;
  556                                 wakeup(rpipe);
  557                         }
  558 
  559                         /*
  560                          * Break if some data was read.
  561                          */
  562                         if (nread > 0)
  563                                 break;
  564 
  565                         /*
  566                          * Unlock the pipe buffer for our remaining processing. 
  567                          * We will either break out with an error or we will
  568                          * sleep and relock to loop.
  569                          */
  570                         pipeunlock(rpipe);
  571 
  572                         /*
  573                          * Handle non-blocking mode operation or
  574                          * wait for more data.
  575                          */
  576                         if (fp->f_flag & FNONBLOCK) {
  577                                 error = EAGAIN;
  578                         } else {
  579                                 rpipe->pipe_state |= PIPE_WANTR;
  580                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  581                                     PRIBIO | PCATCH,
  582                                     "piperd", 0)) == 0)
  583                                         error = pipelock(rpipe, 1);
  584                         }
  585                         if (error)
  586                                 goto unlocked_error;
  587                 }
  588         }
  589 #ifdef MAC
  590 locked_error:
  591 #endif
  592         pipeunlock(rpipe);
  593 
  594         /* XXX: should probably do this before getting any locks. */
  595         if (error == 0)
  596                 vfs_timestamp(&rpipe->pipe_atime);
  597 unlocked_error:
  598         --rpipe->pipe_busy;
  599 
  600         /*
  601          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  602          */
  603         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  604                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  605                 wakeup(rpipe);
  606         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  607                 /*
  608                  * Handle write blocking hysteresis.
  609                  */
  610                 if (rpipe->pipe_state & PIPE_WANTW) {
  611                         rpipe->pipe_state &= ~PIPE_WANTW;
  612                         wakeup(rpipe);
  613                 }
  614         }
  615 
  616         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  617                 pipeselwakeup(rpipe);
  618 
  619         PIPE_UNLOCK(rpipe);
  620         return (error);
  621 }
  622 
  623 #ifndef PIPE_NODIRECT
  624 /*
  625  * Map the sending processes' buffer into kernel space and wire it.
  626  * This is similar to a physical write operation.
  627  */
  628 static int
  629 pipe_build_write_buffer(wpipe, uio)
  630         struct pipe *wpipe;
  631         struct uio *uio;
  632 {
  633         pmap_t pmap;
  634         u_int size;
  635         int i, j;
  636         vm_offset_t addr, endaddr;
  637 
  638         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  639 
  640         size = (u_int) uio->uio_iov->iov_len;
  641         if (size > wpipe->pipe_buffer.size)
  642                 size = wpipe->pipe_buffer.size;
  643 
  644         pmap = vmspace_pmap(curproc->p_vmspace);
  645         endaddr = round_page((vm_offset_t)uio->uio_iov->iov_base + size);
  646         addr = trunc_page((vm_offset_t)uio->uio_iov->iov_base);
  647         for (i = 0; addr < endaddr; addr += PAGE_SIZE, i++) {
  648                 /*
  649                  * vm_fault_quick() can sleep.  Consequently,
  650                  * vm_page_lock_queue() and vm_page_unlock_queue()
  651                  * should not be performed outside of this loop.
  652                  */
  653         race:
  654                 if (vm_fault_quick((caddr_t)addr, VM_PROT_READ) < 0) {
  655                         vm_page_lock_queues();
  656                         for (j = 0; j < i; j++)
  657                                 vm_page_unhold(wpipe->pipe_map.ms[j]);
  658                         vm_page_unlock_queues();
  659                         return (EFAULT);
  660                 }
  661                 wpipe->pipe_map.ms[i] = pmap_extract_and_hold(pmap, addr,
  662                     VM_PROT_READ);
  663                 if (wpipe->pipe_map.ms[i] == NULL)
  664                         goto race;
  665         }
  666 
  667 /*
  668  * set up the control block
  669  */
  670         wpipe->pipe_map.npages = i;
  671         wpipe->pipe_map.pos =
  672             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  673         wpipe->pipe_map.cnt = size;
  674 
  675 /*
  676  * and map the buffer
  677  */
  678         if (wpipe->pipe_map.kva == 0) {
  679                 /*
  680                  * We need to allocate space for an extra page because the
  681                  * address range might (will) span pages at times.
  682                  */
  683                 wpipe->pipe_map.kva = kmem_alloc_nofault(kernel_map,
  684                         wpipe->pipe_buffer.size + PAGE_SIZE);
  685                 atomic_add_int(&amountpipekvawired,
  686                     wpipe->pipe_buffer.size + PAGE_SIZE);
  687         }
  688         pmap_qenter(wpipe->pipe_map.kva, wpipe->pipe_map.ms,
  689                 wpipe->pipe_map.npages);
  690 
  691 /*
  692  * and update the uio data
  693  */
  694 
  695         uio->uio_iov->iov_len -= size;
  696         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  697         if (uio->uio_iov->iov_len == 0)
  698                 uio->uio_iov++;
  699         uio->uio_resid -= size;
  700         uio->uio_offset += size;
  701         return (0);
  702 }
  703 
  704 /*
  705  * unmap and unwire the process buffer
  706  */
  707 static void
  708 pipe_destroy_write_buffer(wpipe)
  709         struct pipe *wpipe;
  710 {
  711         int i;
  712 
  713         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  714         if (wpipe->pipe_map.kva) {
  715                 pmap_qremove(wpipe->pipe_map.kva, wpipe->pipe_map.npages);
  716 
  717                 if (amountpipekvawired > maxpipekvawired / 2) {
  718                         /* Conserve address space */
  719                         vm_offset_t kva = wpipe->pipe_map.kva;
  720                         wpipe->pipe_map.kva = 0;
  721                         kmem_free(kernel_map, kva,
  722                             wpipe->pipe_buffer.size + PAGE_SIZE);
  723                         atomic_subtract_int(&amountpipekvawired,
  724                             wpipe->pipe_buffer.size + PAGE_SIZE);
  725                 }
  726         }
  727         vm_page_lock_queues();
  728         for (i = 0; i < wpipe->pipe_map.npages; i++) {
  729                 vm_page_unhold(wpipe->pipe_map.ms[i]);
  730         }
  731         vm_page_unlock_queues();
  732         wpipe->pipe_map.npages = 0;
  733 }
  734 
  735 /*
  736  * In the case of a signal, the writing process might go away.  This
  737  * code copies the data into the circular buffer so that the source
  738  * pages can be freed without loss of data.
  739  */
  740 static void
  741 pipe_clone_write_buffer(wpipe)
  742         struct pipe *wpipe;
  743 {
  744         int size;
  745         int pos;
  746 
  747         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  748         size = wpipe->pipe_map.cnt;
  749         pos = wpipe->pipe_map.pos;
  750 
  751         wpipe->pipe_buffer.in = size;
  752         wpipe->pipe_buffer.out = 0;
  753         wpipe->pipe_buffer.cnt = size;
  754         wpipe->pipe_state &= ~PIPE_DIRECTW;
  755 
  756         PIPE_UNLOCK(wpipe);
  757         bcopy((caddr_t) wpipe->pipe_map.kva + pos,
  758             wpipe->pipe_buffer.buffer, size);
  759         pipe_destroy_write_buffer(wpipe);
  760         PIPE_LOCK(wpipe);
  761 }
  762 
  763 /*
  764  * This implements the pipe buffer write mechanism.  Note that only
  765  * a direct write OR a normal pipe write can be pending at any given time.
  766  * If there are any characters in the pipe buffer, the direct write will
  767  * be deferred until the receiving process grabs all of the bytes from
  768  * the pipe buffer.  Then the direct mapping write is set-up.
  769  */
  770 static int
  771 pipe_direct_write(wpipe, uio)
  772         struct pipe *wpipe;
  773         struct uio *uio;
  774 {
  775         int error;
  776 
  777 retry:
  778         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  779         while (wpipe->pipe_state & PIPE_DIRECTW) {
  780                 if (wpipe->pipe_state & PIPE_WANTR) {
  781                         wpipe->pipe_state &= ~PIPE_WANTR;
  782                         wakeup(wpipe);
  783                 }
  784                 wpipe->pipe_state |= PIPE_WANTW;
  785                 error = msleep(wpipe, PIPE_MTX(wpipe),
  786                     PRIBIO | PCATCH, "pipdww", 0);
  787                 if (error)
  788                         goto error1;
  789                 if (wpipe->pipe_state & PIPE_EOF) {
  790                         error = EPIPE;
  791                         goto error1;
  792                 }
  793         }
  794         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  795         if (wpipe->pipe_buffer.cnt > 0) {
  796                 if (wpipe->pipe_state & PIPE_WANTR) {
  797                         wpipe->pipe_state &= ~PIPE_WANTR;
  798                         wakeup(wpipe);
  799                 }
  800                         
  801                 wpipe->pipe_state |= PIPE_WANTW;
  802                 error = msleep(wpipe, PIPE_MTX(wpipe),
  803                     PRIBIO | PCATCH, "pipdwc", 0);
  804                 if (error)
  805                         goto error1;
  806                 if (wpipe->pipe_state & PIPE_EOF) {
  807                         error = EPIPE;
  808                         goto error1;
  809                 }
  810                 goto retry;
  811         }
  812 
  813         wpipe->pipe_state |= PIPE_DIRECTW;
  814 
  815         pipelock(wpipe, 0);
  816         PIPE_UNLOCK(wpipe);
  817         error = pipe_build_write_buffer(wpipe, uio);
  818         PIPE_LOCK(wpipe);
  819         pipeunlock(wpipe);
  820         if (error) {
  821                 wpipe->pipe_state &= ~PIPE_DIRECTW;
  822                 goto error1;
  823         }
  824 
  825         error = 0;
  826         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
  827                 if (wpipe->pipe_state & PIPE_EOF) {
  828                         pipelock(wpipe, 0);
  829                         PIPE_UNLOCK(wpipe);
  830                         pipe_destroy_write_buffer(wpipe);
  831                         PIPE_LOCK(wpipe);
  832                         pipeselwakeup(wpipe);
  833                         pipeunlock(wpipe);
  834                         error = EPIPE;
  835                         goto error1;
  836                 }
  837                 if (wpipe->pipe_state & PIPE_WANTR) {
  838                         wpipe->pipe_state &= ~PIPE_WANTR;
  839                         wakeup(wpipe);
  840                 }
  841                 pipeselwakeup(wpipe);
  842                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
  843                     "pipdwt", 0);
  844         }
  845 
  846         pipelock(wpipe,0);
  847         if (wpipe->pipe_state & PIPE_DIRECTW) {
  848                 /*
  849                  * this bit of trickery substitutes a kernel buffer for
  850                  * the process that might be going away.
  851                  */
  852                 pipe_clone_write_buffer(wpipe);
  853         } else {
  854                 PIPE_UNLOCK(wpipe);
  855                 pipe_destroy_write_buffer(wpipe);
  856                 PIPE_LOCK(wpipe);
  857         }
  858         pipeunlock(wpipe);
  859         return (error);
  860 
  861 error1:
  862         wakeup(wpipe);
  863         return (error);
  864 }
  865 #endif
  866         
  867 static int
  868 pipe_write(fp, uio, active_cred, flags, td)
  869         struct file *fp;
  870         struct uio *uio;
  871         struct ucred *active_cred;
  872         struct thread *td;
  873         int flags;
  874 {
  875         int error = 0;
  876         int orig_resid;
  877         struct pipe *wpipe, *rpipe;
  878 
  879         rpipe = fp->f_data;
  880         wpipe = rpipe->pipe_peer;
  881 
  882         PIPE_LOCK(rpipe);
  883         /*
  884          * detect loss of pipe read side, issue SIGPIPE if lost.
  885          */
  886         if ((wpipe == NULL) || (wpipe->pipe_state & PIPE_EOF)) {
  887                 PIPE_UNLOCK(rpipe);
  888                 return (EPIPE);
  889         }
  890 #ifdef MAC
  891         error = mac_check_pipe_write(active_cred, wpipe);
  892         if (error) {
  893                 PIPE_UNLOCK(rpipe);
  894                 return (error);
  895         }
  896 #endif
  897         ++wpipe->pipe_busy;
  898 
  899         /*
  900          * If it is advantageous to resize the pipe buffer, do
  901          * so.
  902          */
  903         if ((uio->uio_resid > PIPE_SIZE) &&
  904                 (amountpipekva < maxpipekva / 2) &&
  905                 (nbigpipe < LIMITBIGPIPES) &&
  906                 (wpipe->pipe_state & PIPE_DIRECTW) == 0 &&
  907                 (wpipe->pipe_buffer.size <= PIPE_SIZE) &&
  908                 (wpipe->pipe_buffer.cnt == 0)) {
  909 
  910                 if ((error = pipelock(wpipe, 1)) == 0) {
  911                         PIPE_UNLOCK(wpipe);
  912                         if (pipespace(wpipe, BIG_PIPE_SIZE) == 0)
  913                                 atomic_add_int(&nbigpipe, 1);
  914                         PIPE_LOCK(wpipe);
  915                         pipeunlock(wpipe);
  916                 }
  917         }
  918 
  919         /*
  920          * If an early error occured unbusy and return, waking up any pending
  921          * readers.
  922          */
  923         if (error) {
  924                 --wpipe->pipe_busy;
  925                 if ((wpipe->pipe_busy == 0) && 
  926                     (wpipe->pipe_state & PIPE_WANT)) {
  927                         wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
  928                         wakeup(wpipe);
  929                 }
  930                 PIPE_UNLOCK(rpipe);
  931                 return(error);
  932         }
  933                 
  934         orig_resid = uio->uio_resid;
  935 
  936         while (uio->uio_resid) {
  937                 int space;
  938 
  939 #ifndef PIPE_NODIRECT
  940                 /*
  941                  * If the transfer is large, we can gain performance if
  942                  * we do process-to-process copies directly.
  943                  * If the write is non-blocking, we don't use the
  944                  * direct write mechanism.
  945                  *
  946                  * The direct write mechanism will detect the reader going
  947                  * away on us.
  948                  */
  949                 if ((uio->uio_iov->iov_len >= PIPE_MINDIRECT) &&
  950                     (fp->f_flag & FNONBLOCK) == 0 &&
  951                     amountpipekvawired + uio->uio_resid < maxpipekvawired) { 
  952                         error = pipe_direct_write(wpipe, uio);
  953                         if (error)
  954                                 break;
  955                         continue;
  956                 }
  957 #endif
  958 
  959                 /*
  960                  * Pipe buffered writes cannot be coincidental with
  961                  * direct writes.  We wait until the currently executing
  962                  * direct write is completed before we start filling the
  963                  * pipe buffer.  We break out if a signal occurs or the
  964                  * reader goes away.
  965                  */
  966         retrywrite:
  967                 while (wpipe->pipe_state & PIPE_DIRECTW) {
  968                         if (wpipe->pipe_state & PIPE_WANTR) {
  969                                 wpipe->pipe_state &= ~PIPE_WANTR;
  970                                 wakeup(wpipe);
  971                         }
  972                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
  973                             "pipbww", 0);
  974                         if (wpipe->pipe_state & PIPE_EOF)
  975                                 break;
  976                         if (error)
  977                                 break;
  978                 }
  979                 if (wpipe->pipe_state & PIPE_EOF) {
  980                         error = EPIPE;
  981                         break;
  982                 }
  983 
  984                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
  985 
  986                 /* Writes of size <= PIPE_BUF must be atomic. */
  987                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
  988                         space = 0;
  989 
  990                 if (space > 0) {
  991                         if ((error = pipelock(wpipe,1)) == 0) {
  992                                 int size;       /* Transfer size */
  993                                 int segsize;    /* first segment to transfer */
  994 
  995                                 /*
  996                                  * It is possible for a direct write to
  997                                  * slip in on us... handle it here...
  998                                  */
  999                                 if (wpipe->pipe_state & PIPE_DIRECTW) {
 1000                                         pipeunlock(wpipe);
 1001                                         goto retrywrite;
 1002                                 }
 1003                                 /* 
 1004                                  * If a process blocked in uiomove, our
 1005                                  * value for space might be bad.
 1006                                  *
 1007                                  * XXX will we be ok if the reader has gone
 1008                                  * away here?
 1009                                  */
 1010                                 if (space > wpipe->pipe_buffer.size - 
 1011                                     wpipe->pipe_buffer.cnt) {
 1012                                         pipeunlock(wpipe);
 1013                                         goto retrywrite;
 1014                                 }
 1015 
 1016                                 /*
 1017                                  * Transfer size is minimum of uio transfer
 1018                                  * and free space in pipe buffer.
 1019                                  */
 1020                                 if (space > uio->uio_resid)
 1021                                         size = uio->uio_resid;
 1022                                 else
 1023                                         size = space;
 1024                                 /*
 1025                                  * First segment to transfer is minimum of 
 1026                                  * transfer size and contiguous space in
 1027                                  * pipe buffer.  If first segment to transfer
 1028                                  * is less than the transfer size, we've got
 1029                                  * a wraparound in the buffer.
 1030                                  */
 1031                                 segsize = wpipe->pipe_buffer.size - 
 1032                                         wpipe->pipe_buffer.in;
 1033                                 if (segsize > size)
 1034                                         segsize = size;
 1035                                 
 1036                                 /* Transfer first segment */
 1037 
 1038                                 PIPE_UNLOCK(rpipe);
 1039                                 error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in], 
 1040                                                 segsize, uio);
 1041                                 PIPE_LOCK(rpipe);
 1042                                 
 1043                                 if (error == 0 && segsize < size) {
 1044                                         /* 
 1045                                          * Transfer remaining part now, to
 1046                                          * support atomic writes.  Wraparound
 1047                                          * happened.
 1048                                          */
 1049                                         if (wpipe->pipe_buffer.in + segsize != 
 1050                                             wpipe->pipe_buffer.size)
 1051                                                 panic("Expected pipe buffer "
 1052                                                     "wraparound disappeared");
 1053                                                 
 1054                                         PIPE_UNLOCK(rpipe);
 1055                                         error = uiomove(
 1056                                             &wpipe->pipe_buffer.buffer[0],
 1057                                             size - segsize, uio);
 1058                                         PIPE_LOCK(rpipe);
 1059                                 }
 1060                                 if (error == 0) {
 1061                                         wpipe->pipe_buffer.in += size;
 1062                                         if (wpipe->pipe_buffer.in >=
 1063                                             wpipe->pipe_buffer.size) {
 1064                                                 if (wpipe->pipe_buffer.in !=
 1065                                                     size - segsize +
 1066                                                     wpipe->pipe_buffer.size)
 1067                                                         panic("Expected "
 1068                                                             "wraparound bad");
 1069                                                 wpipe->pipe_buffer.in = size -
 1070                                                     segsize;
 1071                                         }
 1072                                 
 1073                                         wpipe->pipe_buffer.cnt += size;
 1074                                         if (wpipe->pipe_buffer.cnt >
 1075                                             wpipe->pipe_buffer.size)
 1076                                                 panic("Pipe buffer overflow");
 1077                                 
 1078                                 }
 1079                                 pipeunlock(wpipe);
 1080                         }
 1081                         if (error)
 1082                                 break;
 1083 
 1084                 } else {
 1085                         /*
 1086                          * If the "read-side" has been blocked, wake it up now.
 1087                          */
 1088                         if (wpipe->pipe_state & PIPE_WANTR) {
 1089                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1090                                 wakeup(wpipe);
 1091                         }
 1092 
 1093                         /*
 1094                          * don't block on non-blocking I/O
 1095                          */
 1096                         if (fp->f_flag & FNONBLOCK) {
 1097                                 error = EAGAIN;
 1098                                 break;
 1099                         }
 1100 
 1101                         /*
 1102                          * We have no more space and have something to offer,
 1103                          * wake up select/poll.
 1104                          */
 1105                         pipeselwakeup(wpipe);
 1106 
 1107                         wpipe->pipe_state |= PIPE_WANTW;
 1108                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1109                             PRIBIO | PCATCH, "pipewr", 0);
 1110                         if (error != 0)
 1111                                 break;
 1112                         /*
 1113                          * If read side wants to go away, we just issue a signal
 1114                          * to ourselves.
 1115                          */
 1116                         if (wpipe->pipe_state & PIPE_EOF) {
 1117                                 error = EPIPE;
 1118                                 break;
 1119                         }       
 1120                 }
 1121         }
 1122 
 1123         --wpipe->pipe_busy;
 1124 
 1125         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1126                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1127                 wakeup(wpipe);
 1128         } else if (wpipe->pipe_buffer.cnt > 0) {
 1129                 /*
 1130                  * If we have put any characters in the buffer, we wake up
 1131                  * the reader.
 1132                  */
 1133                 if (wpipe->pipe_state & PIPE_WANTR) {
 1134                         wpipe->pipe_state &= ~PIPE_WANTR;
 1135                         wakeup(wpipe);
 1136                 }
 1137         }
 1138 
 1139         /*
 1140          * Don't return EPIPE if I/O was successful
 1141          */
 1142         if ((wpipe->pipe_buffer.cnt == 0) &&
 1143             (uio->uio_resid == 0) &&
 1144             (error == EPIPE)) {
 1145                 error = 0;
 1146         }
 1147 
 1148         if (error == 0)
 1149                 vfs_timestamp(&wpipe->pipe_mtime);
 1150 
 1151         /*
 1152          * We have something to offer,
 1153          * wake up select/poll.
 1154          */
 1155         if (wpipe->pipe_buffer.cnt)
 1156                 pipeselwakeup(wpipe);
 1157 
 1158         PIPE_UNLOCK(rpipe);
 1159         return (error);
 1160 }
 1161 
 1162 /*
 1163  * we implement a very minimal set of ioctls for compatibility with sockets.
 1164  */
 1165 static int
 1166 pipe_ioctl(fp, cmd, data, active_cred, td)
 1167         struct file *fp;
 1168         u_long cmd;
 1169         void *data;
 1170         struct ucred *active_cred;
 1171         struct thread *td;
 1172 {
 1173         struct pipe *mpipe = fp->f_data;
 1174 #ifdef MAC
 1175         int error;
 1176 #endif
 1177 
 1178         PIPE_LOCK(mpipe);
 1179 
 1180 #ifdef MAC
 1181         error = mac_check_pipe_ioctl(active_cred, mpipe, cmd, data);
 1182         if (error) {
 1183                 PIPE_UNLOCK(mpipe);
 1184                 return (error);
 1185         }
 1186 #endif
 1187 
 1188         switch (cmd) {
 1189 
 1190         case FIONBIO:
 1191                 PIPE_UNLOCK(mpipe);
 1192                 return (0);
 1193 
 1194         case FIOASYNC:
 1195                 if (*(int *)data) {
 1196                         mpipe->pipe_state |= PIPE_ASYNC;
 1197                 } else {
 1198                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1199                 }
 1200                 PIPE_UNLOCK(mpipe);
 1201                 return (0);
 1202 
 1203         case FIONREAD:
 1204                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1205                         *(int *)data = mpipe->pipe_map.cnt;
 1206                 else
 1207                         *(int *)data = mpipe->pipe_buffer.cnt;
 1208                 PIPE_UNLOCK(mpipe);
 1209                 return (0);
 1210 
 1211         case FIOSETOWN:
 1212                 PIPE_UNLOCK(mpipe);
 1213                 return (fsetown(*(int *)data, &mpipe->pipe_sigio));
 1214 
 1215         case FIOGETOWN:
 1216                 PIPE_UNLOCK(mpipe);
 1217                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1218                 return (0);
 1219 
 1220         /* This is deprecated, FIOSETOWN should be used instead. */
 1221         case TIOCSPGRP:
 1222                 PIPE_UNLOCK(mpipe);
 1223                 return (fsetown(-(*(int *)data), &mpipe->pipe_sigio));
 1224 
 1225         /* This is deprecated, FIOGETOWN should be used instead. */
 1226         case TIOCGPGRP:
 1227                 PIPE_UNLOCK(mpipe);
 1228                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1229                 return (0);
 1230 
 1231         }
 1232         PIPE_UNLOCK(mpipe);
 1233         return (ENOTTY);
 1234 }
 1235 
 1236 static int
 1237 pipe_poll(fp, events, active_cred, td)
 1238         struct file *fp;
 1239         int events;
 1240         struct ucred *active_cred;
 1241         struct thread *td;
 1242 {
 1243         struct pipe *rpipe = fp->f_data;
 1244         struct pipe *wpipe;
 1245         int revents = 0;
 1246 #ifdef MAC
 1247         int error;
 1248 #endif
 1249 
 1250         wpipe = rpipe->pipe_peer;
 1251         PIPE_LOCK(rpipe);
 1252 #ifdef MAC
 1253         error = mac_check_pipe_poll(active_cred, rpipe);
 1254         if (error)
 1255                 goto locked_error;
 1256 #endif
 1257         if (events & (POLLIN | POLLRDNORM))
 1258                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1259                     (rpipe->pipe_buffer.cnt > 0) ||
 1260                     (rpipe->pipe_state & PIPE_EOF))
 1261                         revents |= events & (POLLIN | POLLRDNORM);
 1262 
 1263         if (events & (POLLOUT | POLLWRNORM))
 1264                 if (wpipe == NULL || (wpipe->pipe_state & PIPE_EOF) ||
 1265                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1266                      (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF))
 1267                         revents |= events & (POLLOUT | POLLWRNORM);
 1268 
 1269         if ((rpipe->pipe_state & PIPE_EOF) ||
 1270             (wpipe == NULL) ||
 1271             (wpipe->pipe_state & PIPE_EOF))
 1272                 revents |= POLLHUP;
 1273 
 1274         if (revents == 0) {
 1275                 if (events & (POLLIN | POLLRDNORM)) {
 1276                         selrecord(td, &rpipe->pipe_sel);
 1277                         rpipe->pipe_state |= PIPE_SEL;
 1278                 }
 1279 
 1280                 if (events & (POLLOUT | POLLWRNORM)) {
 1281                         selrecord(td, &wpipe->pipe_sel);
 1282                         wpipe->pipe_state |= PIPE_SEL;
 1283                 }
 1284         }
 1285 #ifdef MAC
 1286 locked_error:
 1287 #endif
 1288         PIPE_UNLOCK(rpipe);
 1289 
 1290         return (revents);
 1291 }
 1292 
 1293 /*
 1294  * We shouldn't need locks here as we're doing a read and this should
 1295  * be a natural race.
 1296  */
 1297 static int
 1298 pipe_stat(fp, ub, active_cred, td)
 1299         struct file *fp;
 1300         struct stat *ub;
 1301         struct ucred *active_cred;
 1302         struct thread *td;
 1303 {
 1304         struct pipe *pipe = fp->f_data;
 1305 #ifdef MAC
 1306         int error;
 1307 
 1308         PIPE_LOCK(pipe);
 1309         error = mac_check_pipe_stat(active_cred, pipe);
 1310         PIPE_UNLOCK(pipe);
 1311         if (error)
 1312                 return (error);
 1313 #endif
 1314         bzero(ub, sizeof(*ub));
 1315         ub->st_mode = S_IFIFO;
 1316         ub->st_blksize = pipe->pipe_buffer.size;
 1317         ub->st_size = pipe->pipe_buffer.cnt;
 1318         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
 1319         ub->st_atimespec = pipe->pipe_atime;
 1320         ub->st_mtimespec = pipe->pipe_mtime;
 1321         ub->st_ctimespec = pipe->pipe_ctime;
 1322         ub->st_uid = fp->f_cred->cr_uid;
 1323         ub->st_gid = fp->f_cred->cr_gid;
 1324         /*
 1325          * Left as 0: st_dev, st_ino, st_nlink, st_rdev, st_flags, st_gen.
 1326          * XXX (st_dev, st_ino) should be unique.
 1327          */
 1328         return (0);
 1329 }
 1330 
 1331 /* ARGSUSED */
 1332 static int
 1333 pipe_close(fp, td)
 1334         struct file *fp;
 1335         struct thread *td;
 1336 {
 1337         struct pipe *cpipe = fp->f_data;
 1338 
 1339         fp->f_ops = &badfileops;
 1340         fp->f_data = NULL;
 1341         funsetown(&cpipe->pipe_sigio);
 1342         pipeclose(cpipe);
 1343         return (0);
 1344 }
 1345 
 1346 static void
 1347 pipe_free_kmem(cpipe)
 1348         struct pipe *cpipe;
 1349 {
 1350 
 1351         KASSERT(cpipe->pipe_mtxp == NULL || !mtx_owned(PIPE_MTX(cpipe)),
 1352                ("pipespace: pipe mutex locked"));
 1353 
 1354         if (cpipe->pipe_buffer.buffer != NULL) {
 1355                 if (cpipe->pipe_buffer.size > PIPE_SIZE)
 1356                         atomic_subtract_int(&nbigpipe, 1);
 1357                 atomic_subtract_int(&amountpipekva, cpipe->pipe_buffer.size);
 1358                 atomic_subtract_int(&amountpipes, 1);
 1359                 vm_map_remove(pipe_map,
 1360                     (vm_offset_t)cpipe->pipe_buffer.buffer,
 1361                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
 1362                 cpipe->pipe_buffer.buffer = NULL;
 1363         }
 1364 #ifndef PIPE_NODIRECT
 1365         if (cpipe->pipe_map.kva != 0) {
 1366                 atomic_subtract_int(&amountpipekvawired,
 1367                     cpipe->pipe_buffer.size + PAGE_SIZE);
 1368                 kmem_free(kernel_map,
 1369                         cpipe->pipe_map.kva,
 1370                         cpipe->pipe_buffer.size + PAGE_SIZE);
 1371                 cpipe->pipe_map.cnt = 0;
 1372                 cpipe->pipe_map.kva = 0;
 1373                 cpipe->pipe_map.pos = 0;
 1374                 cpipe->pipe_map.npages = 0;
 1375         }
 1376 #endif
 1377 }
 1378 
 1379 /*
 1380  * shutdown the pipe
 1381  */
 1382 static void
 1383 pipeclose(cpipe)
 1384         struct pipe *cpipe;
 1385 {
 1386         struct pipe *ppipe;
 1387         int hadpeer;
 1388 
 1389         if (cpipe == NULL)
 1390                 return;
 1391 
 1392         hadpeer = 0;
 1393 
 1394         /* partially created pipes won't have a valid mutex. */
 1395         if (PIPE_MTX(cpipe) != NULL)
 1396                 PIPE_LOCK(cpipe);
 1397                 
 1398         pipeselwakeup(cpipe);
 1399 
 1400         /*
 1401          * If the other side is blocked, wake it up saying that
 1402          * we want to close it down.
 1403          */
 1404         while (cpipe->pipe_busy) {
 1405                 wakeup(cpipe);
 1406                 cpipe->pipe_state |= PIPE_WANT | PIPE_EOF;
 1407                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1408         }
 1409 
 1410 #ifdef MAC
 1411         if (cpipe->pipe_label != NULL && cpipe->pipe_peer == NULL)
 1412                 mac_destroy_pipe(cpipe);
 1413 #endif
 1414 
 1415         /*
 1416          * Disconnect from peer
 1417          */
 1418         if ((ppipe = cpipe->pipe_peer) != NULL) {
 1419                 hadpeer++;
 1420                 pipeselwakeup(ppipe);
 1421 
 1422                 ppipe->pipe_state |= PIPE_EOF;
 1423                 wakeup(ppipe);
 1424                 KNOTE(&ppipe->pipe_sel.si_note, 0);
 1425                 ppipe->pipe_peer = NULL;
 1426         }
 1427         /*
 1428          * free resources
 1429          */
 1430         if (PIPE_MTX(cpipe) != NULL) {
 1431                 PIPE_UNLOCK(cpipe);
 1432                 if (!hadpeer) {
 1433                         mtx_destroy(PIPE_MTX(cpipe));
 1434                         free(PIPE_MTX(cpipe), M_TEMP);
 1435                 }
 1436         }
 1437         pipe_free_kmem(cpipe);
 1438         uma_zfree(pipe_zone, cpipe);
 1439 }
 1440 
 1441 /*ARGSUSED*/
 1442 static int
 1443 pipe_kqfilter(struct file *fp, struct knote *kn)
 1444 {
 1445         struct pipe *cpipe;
 1446 
 1447         cpipe = kn->kn_fp->f_data;
 1448         switch (kn->kn_filter) {
 1449         case EVFILT_READ:
 1450                 kn->kn_fop = &pipe_rfiltops;
 1451                 break;
 1452         case EVFILT_WRITE:
 1453                 kn->kn_fop = &pipe_wfiltops;
 1454                 cpipe = cpipe->pipe_peer;
 1455                 if (cpipe == NULL)
 1456                         /* other end of pipe has been closed */
 1457                         return (EPIPE);
 1458                 break;
 1459         default:
 1460                 return (1);
 1461         }
 1462 
 1463         PIPE_LOCK(cpipe);
 1464         SLIST_INSERT_HEAD(&cpipe->pipe_sel.si_note, kn, kn_selnext);
 1465         PIPE_UNLOCK(cpipe);
 1466         return (0);
 1467 }
 1468 
 1469 static void
 1470 filt_pipedetach(struct knote *kn)
 1471 {
 1472         struct pipe *cpipe = (struct pipe *)kn->kn_fp->f_data;
 1473 
 1474         if (kn->kn_filter == EVFILT_WRITE) {
 1475                 if (cpipe->pipe_peer == NULL)
 1476                         return;
 1477                 cpipe = cpipe->pipe_peer;
 1478         }
 1479 
 1480         PIPE_LOCK(cpipe);
 1481         SLIST_REMOVE(&cpipe->pipe_sel.si_note, kn, knote, kn_selnext);
 1482         PIPE_UNLOCK(cpipe);
 1483 }
 1484 
 1485 /*ARGSUSED*/
 1486 static int
 1487 filt_piperead(struct knote *kn, long hint)
 1488 {
 1489         struct pipe *rpipe = kn->kn_fp->f_data;
 1490         struct pipe *wpipe = rpipe->pipe_peer;
 1491 
 1492         PIPE_LOCK(rpipe);
 1493         kn->kn_data = rpipe->pipe_buffer.cnt;
 1494         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1495                 kn->kn_data = rpipe->pipe_map.cnt;
 1496 
 1497         if ((rpipe->pipe_state & PIPE_EOF) ||
 1498             (wpipe == NULL) || (wpipe->pipe_state & PIPE_EOF)) {
 1499                 kn->kn_flags |= EV_EOF;
 1500                 PIPE_UNLOCK(rpipe);
 1501                 return (1);
 1502         }
 1503         PIPE_UNLOCK(rpipe);
 1504         return (kn->kn_data > 0);
 1505 }
 1506 
 1507 /*ARGSUSED*/
 1508 static int
 1509 filt_pipewrite(struct knote *kn, long hint)
 1510 {
 1511         struct pipe *rpipe = kn->kn_fp->f_data;
 1512         struct pipe *wpipe = rpipe->pipe_peer;
 1513 
 1514         PIPE_LOCK(rpipe);
 1515         if ((wpipe == NULL) || (wpipe->pipe_state & PIPE_EOF)) {
 1516                 kn->kn_data = 0;
 1517                 kn->kn_flags |= EV_EOF; 
 1518                 PIPE_UNLOCK(rpipe);
 1519                 return (1);
 1520         }
 1521         kn->kn_data = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1522         if (wpipe->pipe_state & PIPE_DIRECTW)
 1523                 kn->kn_data = 0;
 1524 
 1525         PIPE_UNLOCK(rpipe);
 1526         return (kn->kn_data >= PIPE_BUF);
 1527 }

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