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  * $FreeBSD: releng/5.0/sys/kern/sys_pipe.c 105132 2002-10-14 21:15:04Z alfred $
   20  */
   21 
   22 /*
   23  * This file contains a high-performance replacement for the socket-based
   24  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
   25  * all features of sockets, but does do everything that pipes normally
   26  * do.
   27  */
   28 
   29 /*
   30  * This code has two modes of operation, a small write mode and a large
   31  * write mode.  The small write mode acts like conventional pipes with
   32  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
   33  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
   34  * and PIPE_SIZE in size, it is fully mapped and wired into the kernel, and
   35  * the receiving process can copy it directly from the pages in the sending
   36  * process.
   37  *
   38  * If the sending process receives a signal, it is possible that it will
   39  * go away, and certainly its address space can change, because control
   40  * is returned back to the user-mode side.  In that case, the pipe code
   41  * arranges to copy the buffer supplied by the user process, to a pageable
   42  * kernel buffer, and the receiving process will grab the data from the
   43  * pageable kernel buffer.  Since signals don't happen all that often,
   44  * the copy operation is normally eliminated.
   45  *
   46  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
   47  * happen for small transfers so that the system will not spend all of
   48  * its time context switching.  PIPE_SIZE is constrained by the
   49  * amount of kernel virtual memory.
   50  */
   51 
   52 #include "opt_mac.h"
   53 
   54 #include <sys/param.h>
   55 #include <sys/systm.h>
   56 #include <sys/fcntl.h>
   57 #include <sys/file.h>
   58 #include <sys/filedesc.h>
   59 #include <sys/filio.h>
   60 #include <sys/kernel.h>
   61 #include <sys/lock.h>
   62 #include <sys/mac.h>
   63 #include <sys/mutex.h>
   64 #include <sys/ttycom.h>
   65 #include <sys/stat.h>
   66 #include <sys/malloc.h>
   67 #include <sys/poll.h>
   68 #include <sys/selinfo.h>
   69 #include <sys/signalvar.h>
   70 #include <sys/sysproto.h>
   71 #include <sys/pipe.h>
   72 #include <sys/proc.h>
   73 #include <sys/vnode.h>
   74 #include <sys/uio.h>
   75 #include <sys/event.h>
   76 
   77 #include <vm/vm.h>
   78 #include <vm/vm_param.h>
   79 #include <vm/vm_object.h>
   80 #include <vm/vm_kern.h>
   81 #include <vm/vm_extern.h>
   82 #include <vm/pmap.h>
   83 #include <vm/vm_map.h>
   84 #include <vm/vm_page.h>
   85 #include <vm/uma.h>
   86 
   87 /*
   88  * Use this define if you want to disable *fancy* VM things.  Expect an
   89  * approx 30% decrease in transfer rate.  This could be useful for
   90  * NetBSD or OpenBSD.
   91  */
   92 /* #define PIPE_NODIRECT */
   93 
   94 /*
   95  * interfaces to the outside world
   96  */
   97 static int pipe_read(struct file *fp, struct uio *uio, 
   98                 struct ucred *active_cred, int flags, struct thread *td);
   99 static int pipe_write(struct file *fp, struct uio *uio, 
  100                 struct ucred *active_cred, int flags, struct thread *td);
  101 static int pipe_close(struct file *fp, struct thread *td);
  102 static int pipe_poll(struct file *fp, int events, struct ucred *active_cred,
  103                 struct thread *td);
  104 static int pipe_kqfilter(struct file *fp, struct knote *kn);
  105 static int pipe_stat(struct file *fp, struct stat *sb,
  106                 struct ucred *active_cred, struct thread *td);
  107 static int pipe_ioctl(struct file *fp, u_long cmd, void *data,
  108                 struct ucred *active_cred, struct thread *td);
  109 
  110 static struct fileops pipeops = {
  111         pipe_read, pipe_write, pipe_ioctl, pipe_poll, pipe_kqfilter,
  112         pipe_stat, pipe_close
  113 };
  114 
  115 static void     filt_pipedetach(struct knote *kn);
  116 static int      filt_piperead(struct knote *kn, long hint);
  117 static int      filt_pipewrite(struct knote *kn, long hint);
  118 
  119 static struct filterops pipe_rfiltops =
  120         { 1, NULL, filt_pipedetach, filt_piperead };
  121 static struct filterops pipe_wfiltops =
  122         { 1, NULL, filt_pipedetach, filt_pipewrite };
  123 
  124 #define PIPE_GET_GIANT(pipe)                                            \
  125         do {                                                            \
  126                 KASSERT(((pipe)->pipe_state & PIPE_LOCKFL) != 0,        \
  127                     ("%s:%d PIPE_GET_GIANT: line pipe not locked",      \
  128                      __FILE__, __LINE__));                              \
  129                 PIPE_UNLOCK(pipe);                                      \
  130                 mtx_lock(&Giant);                                       \
  131         } while (0)
  132 
  133 #define PIPE_DROP_GIANT(pipe)                                           \
  134         do {                                                            \
  135                 mtx_unlock(&Giant);                                     \
  136                 PIPE_LOCK(pipe);                                        \
  137         } while (0)
  138 
  139 /*
  140  * Default pipe buffer size(s), this can be kind-of large now because pipe
  141  * space is pageable.  The pipe code will try to maintain locality of
  142  * reference for performance reasons, so small amounts of outstanding I/O
  143  * will not wipe the cache.
  144  */
  145 #define MINPIPESIZE (PIPE_SIZE/3)
  146 #define MAXPIPESIZE (2*PIPE_SIZE/3)
  147 
  148 /*
  149  * Maximum amount of kva for pipes -- this is kind-of a soft limit, but
  150  * is there so that on large systems, we don't exhaust it.
  151  */
  152 #define MAXPIPEKVA (8*1024*1024)
  153 
  154 /*
  155  * Limit for direct transfers, we cannot, of course limit
  156  * the amount of kva for pipes in general though.
  157  */
  158 #define LIMITPIPEKVA (16*1024*1024)
  159 
  160 /*
  161  * Limit the number of "big" pipes
  162  */
  163 #define LIMITBIGPIPES   32
  164 static int nbigpipe;
  165 
  166 static int amountpipekva;
  167 
  168 static void pipeinit(void *dummy __unused);
  169 static void pipeclose(struct pipe *cpipe);
  170 static void pipe_free_kmem(struct pipe *cpipe);
  171 static int pipe_create(struct pipe **cpipep);
  172 static __inline int pipelock(struct pipe *cpipe, int catch);
  173 static __inline void pipeunlock(struct pipe *cpipe);
  174 static __inline void pipeselwakeup(struct pipe *cpipe);
  175 #ifndef PIPE_NODIRECT
  176 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
  177 static void pipe_destroy_write_buffer(struct pipe *wpipe);
  178 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
  179 static void pipe_clone_write_buffer(struct pipe *wpipe);
  180 #endif
  181 static int pipespace(struct pipe *cpipe, int size);
  182 
  183 static uma_zone_t pipe_zone;
  184 
  185 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
  186 
  187 static void
  188 pipeinit(void *dummy __unused)
  189 {
  190         pipe_zone = uma_zcreate("PIPE", sizeof(struct pipe), NULL,
  191             NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
  192 }
  193 
  194 /*
  195  * The pipe system call for the DTYPE_PIPE type of pipes
  196  */
  197 
  198 /* ARGSUSED */
  199 int
  200 pipe(td, uap)
  201         struct thread *td;
  202         struct pipe_args /* {
  203                 int     dummy;
  204         } */ *uap;
  205 {
  206         struct filedesc *fdp = td->td_proc->p_fd;
  207         struct file *rf, *wf;
  208         struct pipe *rpipe, *wpipe;
  209         struct mtx *pmtx;
  210         int fd, error;
  211         
  212         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
  213 
  214         pmtx = malloc(sizeof(*pmtx), M_TEMP, M_WAITOK | M_ZERO);
  215         
  216         rpipe = wpipe = NULL;
  217         if (pipe_create(&rpipe) || pipe_create(&wpipe)) {
  218                 pipeclose(rpipe); 
  219                 pipeclose(wpipe); 
  220                 free(pmtx, M_TEMP);
  221                 return (ENFILE);
  222         }
  223         
  224         rpipe->pipe_state |= PIPE_DIRECTOK;
  225         wpipe->pipe_state |= PIPE_DIRECTOK;
  226 
  227         error = falloc(td, &rf, &fd);
  228         if (error) {
  229                 pipeclose(rpipe);
  230                 pipeclose(wpipe);
  231                 free(pmtx, M_TEMP);
  232                 return (error);
  233         }
  234         fhold(rf);
  235         td->td_retval[0] = fd;
  236 
  237         /*
  238          * Warning: once we've gotten past allocation of the fd for the
  239          * read-side, we can only drop the read side via fdrop() in order
  240          * to avoid races against processes which manage to dup() the read
  241          * side while we are blocked trying to allocate the write side.
  242          */
  243         FILE_LOCK(rf);
  244         rf->f_flag = FREAD | FWRITE;
  245         rf->f_type = DTYPE_PIPE;
  246         rf->f_data = rpipe;
  247         rf->f_ops = &pipeops;
  248         FILE_UNLOCK(rf);
  249         error = falloc(td, &wf, &fd);
  250         if (error) {
  251                 FILEDESC_LOCK(fdp);
  252                 if (fdp->fd_ofiles[td->td_retval[0]] == rf) {
  253                         fdp->fd_ofiles[td->td_retval[0]] = NULL;
  254                         FILEDESC_UNLOCK(fdp);
  255                         fdrop(rf, td);
  256                 } else
  257                         FILEDESC_UNLOCK(fdp);
  258                 fdrop(rf, td);
  259                 /* rpipe has been closed by fdrop(). */
  260                 pipeclose(wpipe);
  261                 free(pmtx, M_TEMP);
  262                 return (error);
  263         }
  264         FILE_LOCK(wf);
  265         wf->f_flag = FREAD | FWRITE;
  266         wf->f_type = DTYPE_PIPE;
  267         wf->f_data = wpipe;
  268         wf->f_ops = &pipeops;
  269         FILE_UNLOCK(wf);
  270         td->td_retval[1] = fd;
  271         rpipe->pipe_peer = wpipe;
  272         wpipe->pipe_peer = rpipe;
  273 #ifdef MAC
  274         /*
  275          * struct pipe represents a pipe endpoint.  The MAC label is shared
  276          * between the connected endpoints.  As a result mac_init_pipe() and
  277          * mac_create_pipe() should only be called on one of the endpoints
  278          * after they have been connected.
  279          */
  280         mac_init_pipe(rpipe);
  281         mac_create_pipe(td->td_ucred, rpipe);
  282 #endif
  283         mtx_init(pmtx, "pipe mutex", NULL, MTX_DEF | MTX_RECURSE);
  284         rpipe->pipe_mtxp = wpipe->pipe_mtxp = pmtx;
  285         fdrop(rf, td);
  286 
  287         return (0);
  288 }
  289 
  290 /*
  291  * Allocate kva for pipe circular buffer, the space is pageable
  292  * This routine will 'realloc' the size of a pipe safely, if it fails
  293  * it will retain the old buffer.
  294  * If it fails it will return ENOMEM.
  295  */
  296 static int
  297 pipespace(cpipe, size)
  298         struct pipe *cpipe;
  299         int size;
  300 {
  301         struct vm_object *object;
  302         caddr_t buffer;
  303         int npages, error;
  304 
  305         GIANT_REQUIRED;
  306         KASSERT(cpipe->pipe_mtxp == NULL || !mtx_owned(PIPE_MTX(cpipe)),
  307                ("pipespace: pipe mutex locked"));
  308 
  309         npages = round_page(size)/PAGE_SIZE;
  310         /*
  311          * Create an object, I don't like the idea of paging to/from
  312          * kernel_object.
  313          * XXX -- minor change needed here for NetBSD/OpenBSD VM systems.
  314          */
  315         object = vm_object_allocate(OBJT_DEFAULT, npages);
  316         buffer = (caddr_t) vm_map_min(kernel_map);
  317 
  318         /*
  319          * Insert the object into the kernel map, and allocate kva for it.
  320          * The map entry is, by default, pageable.
  321          * XXX -- minor change needed here for NetBSD/OpenBSD VM systems.
  322          */
  323         error = vm_map_find(kernel_map, object, 0,
  324                 (vm_offset_t *) &buffer, size, 1,
  325                 VM_PROT_ALL, VM_PROT_ALL, 0);
  326 
  327         if (error != KERN_SUCCESS) {
  328                 vm_object_deallocate(object);
  329                 return (ENOMEM);
  330         }
  331 
  332         /* free old resources if we're resizing */
  333         pipe_free_kmem(cpipe);
  334         cpipe->pipe_buffer.object = object;
  335         cpipe->pipe_buffer.buffer = buffer;
  336         cpipe->pipe_buffer.size = size;
  337         cpipe->pipe_buffer.in = 0;
  338         cpipe->pipe_buffer.out = 0;
  339         cpipe->pipe_buffer.cnt = 0;
  340         amountpipekva += cpipe->pipe_buffer.size;
  341         return (0);
  342 }
  343 
  344 /*
  345  * initialize and allocate VM and memory for pipe
  346  */
  347 static int
  348 pipe_create(cpipep)
  349         struct pipe **cpipep;
  350 {
  351         struct pipe *cpipe;
  352         int error;
  353 
  354         *cpipep = uma_zalloc(pipe_zone, M_WAITOK);
  355         if (*cpipep == NULL)
  356                 return (ENOMEM);
  357 
  358         cpipe = *cpipep;
  359         
  360         /* so pipespace()->pipe_free_kmem() doesn't follow junk pointer */
  361         cpipe->pipe_buffer.object = NULL;
  362 #ifndef PIPE_NODIRECT
  363         cpipe->pipe_map.kva = 0;
  364 #endif
  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         error = pipespace(cpipe, PIPE_SIZE);
  387         if (error)
  388                 return (error);
  389 
  390         vfs_timestamp(&cpipe->pipe_ctime);
  391         cpipe->pipe_atime = cpipe->pipe_ctime;
  392         cpipe->pipe_mtime = cpipe->pipe_ctime;
  393 
  394         return (0);
  395 }
  396 
  397 
  398 /*
  399  * lock a pipe for I/O, blocking other access
  400  */
  401 static __inline int
  402 pipelock(cpipe, catch)
  403         struct pipe *cpipe;
  404         int catch;
  405 {
  406         int error;
  407 
  408         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  409         while (cpipe->pipe_state & PIPE_LOCKFL) {
  410                 cpipe->pipe_state |= PIPE_LWANT;
  411                 error = msleep(cpipe, PIPE_MTX(cpipe),
  412                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  413                     "pipelk", 0);
  414                 if (error != 0) 
  415                         return (error);
  416         }
  417         cpipe->pipe_state |= PIPE_LOCKFL;
  418         return (0);
  419 }
  420 
  421 /*
  422  * unlock a pipe I/O lock
  423  */
  424 static __inline void
  425 pipeunlock(cpipe)
  426         struct pipe *cpipe;
  427 {
  428 
  429         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  430         cpipe->pipe_state &= ~PIPE_LOCKFL;
  431         if (cpipe->pipe_state & PIPE_LWANT) {
  432                 cpipe->pipe_state &= ~PIPE_LWANT;
  433                 wakeup(cpipe);
  434         }
  435 }
  436 
  437 static __inline void
  438 pipeselwakeup(cpipe)
  439         struct pipe *cpipe;
  440 {
  441 
  442         if (cpipe->pipe_state & PIPE_SEL) {
  443                 cpipe->pipe_state &= ~PIPE_SEL;
  444                 selwakeup(&cpipe->pipe_sel);
  445         }
  446         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  447                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  448         KNOTE(&cpipe->pipe_sel.si_note, 0);
  449 }
  450 
  451 /* ARGSUSED */
  452 static int
  453 pipe_read(fp, uio, active_cred, flags, td)
  454         struct file *fp;
  455         struct uio *uio;
  456         struct ucred *active_cred;
  457         struct thread *td;
  458         int flags;
  459 {
  460         struct pipe *rpipe = (struct pipe *) fp->f_data;
  461         int error;
  462         int nread = 0;
  463         u_int size;
  464 
  465         PIPE_LOCK(rpipe);
  466         ++rpipe->pipe_busy;
  467         error = pipelock(rpipe, 1);
  468         if (error)
  469                 goto unlocked_error;
  470 
  471 #ifdef MAC
  472         error = mac_check_pipe_read(active_cred, rpipe);
  473         if (error)
  474                 goto locked_error;
  475 #endif
  476 
  477         while (uio->uio_resid) {
  478                 /*
  479                  * normal pipe buffer receive
  480                  */
  481                 if (rpipe->pipe_buffer.cnt > 0) {
  482                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  483                         if (size > rpipe->pipe_buffer.cnt)
  484                                 size = rpipe->pipe_buffer.cnt;
  485                         if (size > (u_int) uio->uio_resid)
  486                                 size = (u_int) uio->uio_resid;
  487 
  488                         PIPE_UNLOCK(rpipe);
  489                         error = uiomove(&rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  490                                         size, uio);
  491                         PIPE_LOCK(rpipe);
  492                         if (error)
  493                                 break;
  494 
  495                         rpipe->pipe_buffer.out += size;
  496                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  497                                 rpipe->pipe_buffer.out = 0;
  498 
  499                         rpipe->pipe_buffer.cnt -= size;
  500 
  501                         /*
  502                          * If there is no more to read in the pipe, reset
  503                          * its pointers to the beginning.  This improves
  504                          * cache hit stats.
  505                          */
  506                         if (rpipe->pipe_buffer.cnt == 0) {
  507                                 rpipe->pipe_buffer.in = 0;
  508                                 rpipe->pipe_buffer.out = 0;
  509                         }
  510                         nread += size;
  511 #ifndef PIPE_NODIRECT
  512                 /*
  513                  * Direct copy, bypassing a kernel buffer.
  514                  */
  515                 } else if ((size = rpipe->pipe_map.cnt) &&
  516                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  517                         caddr_t va;
  518                         if (size > (u_int) uio->uio_resid)
  519                                 size = (u_int) uio->uio_resid;
  520 
  521                         va = (caddr_t) rpipe->pipe_map.kva +
  522                             rpipe->pipe_map.pos;
  523                         PIPE_UNLOCK(rpipe);
  524                         error = uiomove(va, size, uio);
  525                         PIPE_LOCK(rpipe);
  526                         if (error)
  527                                 break;
  528                         nread += size;
  529                         rpipe->pipe_map.pos += size;
  530                         rpipe->pipe_map.cnt -= size;
  531                         if (rpipe->pipe_map.cnt == 0) {
  532                                 rpipe->pipe_state &= ~PIPE_DIRECTW;
  533                                 wakeup(rpipe);
  534                         }
  535 #endif
  536                 } else {
  537                         /*
  538                          * detect EOF condition
  539                          * read returns 0 on EOF, no need to set error
  540                          */
  541                         if (rpipe->pipe_state & PIPE_EOF)
  542                                 break;
  543 
  544                         /*
  545                          * If the "write-side" has been blocked, wake it up now.
  546                          */
  547                         if (rpipe->pipe_state & PIPE_WANTW) {
  548                                 rpipe->pipe_state &= ~PIPE_WANTW;
  549                                 wakeup(rpipe);
  550                         }
  551 
  552                         /*
  553                          * Break if some data was read.
  554                          */
  555                         if (nread > 0)
  556                                 break;
  557 
  558                         /*
  559                          * Unlock the pipe buffer for our remaining processing.  We
  560                          * will either break out with an error or we will sleep and
  561                          * relock to loop.
  562                          */
  563                         pipeunlock(rpipe);
  564 
  565                         /*
  566                          * Handle non-blocking mode operation or
  567                          * wait for more data.
  568                          */
  569                         if (fp->f_flag & FNONBLOCK) {
  570                                 error = EAGAIN;
  571                         } else {
  572                                 rpipe->pipe_state |= PIPE_WANTR;
  573                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  574                                     PRIBIO | PCATCH,
  575                                     "piperd", 0)) == 0)
  576                                         error = pipelock(rpipe, 1);
  577                         }
  578                         if (error)
  579                                 goto unlocked_error;
  580                 }
  581         }
  582 #ifdef MAC
  583 locked_error:
  584 #endif
  585         pipeunlock(rpipe);
  586 
  587         /* XXX: should probably do this before getting any locks. */
  588         if (error == 0)
  589                 vfs_timestamp(&rpipe->pipe_atime);
  590 unlocked_error:
  591         --rpipe->pipe_busy;
  592 
  593         /*
  594          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  595          */
  596         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  597                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  598                 wakeup(rpipe);
  599         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  600                 /*
  601                  * Handle write blocking hysteresis.
  602                  */
  603                 if (rpipe->pipe_state & PIPE_WANTW) {
  604                         rpipe->pipe_state &= ~PIPE_WANTW;
  605                         wakeup(rpipe);
  606                 }
  607         }
  608 
  609         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  610                 pipeselwakeup(rpipe);
  611 
  612         PIPE_UNLOCK(rpipe);
  613         return (error);
  614 }
  615 
  616 #ifndef PIPE_NODIRECT
  617 /*
  618  * Map the sending processes' buffer into kernel space and wire it.
  619  * This is similar to a physical write operation.
  620  */
  621 static int
  622 pipe_build_write_buffer(wpipe, uio)
  623         struct pipe *wpipe;
  624         struct uio *uio;
  625 {
  626         u_int size;
  627         int i;
  628         vm_offset_t addr, endaddr, paddr;
  629 
  630         GIANT_REQUIRED;
  631         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  632 
  633         size = (u_int) uio->uio_iov->iov_len;
  634         if (size > wpipe->pipe_buffer.size)
  635                 size = wpipe->pipe_buffer.size;
  636 
  637         endaddr = round_page((vm_offset_t)uio->uio_iov->iov_base + size);
  638         addr = trunc_page((vm_offset_t)uio->uio_iov->iov_base);
  639         for (i = 0; addr < endaddr; addr += PAGE_SIZE, i++) {
  640                 vm_page_t m;
  641 
  642                 /*
  643                  * vm_fault_quick() can sleep.  Consequently,
  644                  * vm_page_lock_queue() and vm_page_unlock_queue()
  645                  * should not be performed outside of this loop.
  646                  */
  647                 if (vm_fault_quick((caddr_t)addr, VM_PROT_READ) < 0 ||
  648                     (paddr = pmap_extract(vmspace_pmap(curproc->p_vmspace),
  649                      addr)) == 0) {
  650                         int j;
  651 
  652                         vm_page_lock_queues();
  653                         for (j = 0; j < i; j++)
  654                                 vm_page_unwire(wpipe->pipe_map.ms[j], 1);
  655                         vm_page_unlock_queues();
  656                         return (EFAULT);
  657                 }
  658 
  659                 m = PHYS_TO_VM_PAGE(paddr);
  660                 vm_page_lock_queues();
  661                 vm_page_wire(m);
  662                 vm_page_unlock_queues();
  663                 wpipe->pipe_map.ms[i] = m;
  664         }
  665 
  666 /*
  667  * set up the control block
  668  */
  669         wpipe->pipe_map.npages = i;
  670         wpipe->pipe_map.pos =
  671             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  672         wpipe->pipe_map.cnt = size;
  673 
  674 /*
  675  * and map the buffer
  676  */
  677         if (wpipe->pipe_map.kva == 0) {
  678                 /*
  679                  * We need to allocate space for an extra page because the
  680                  * address range might (will) span pages at times.
  681                  */
  682                 wpipe->pipe_map.kva = kmem_alloc_pageable(kernel_map,
  683                         wpipe->pipe_buffer.size + PAGE_SIZE);
  684                 amountpipekva += wpipe->pipe_buffer.size + PAGE_SIZE;
  685         }
  686         pmap_qenter(wpipe->pipe_map.kva, wpipe->pipe_map.ms,
  687                 wpipe->pipe_map.npages);
  688 
  689 /*
  690  * and update the uio data
  691  */
  692 
  693         uio->uio_iov->iov_len -= size;
  694         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  695         if (uio->uio_iov->iov_len == 0)
  696                 uio->uio_iov++;
  697         uio->uio_resid -= size;
  698         uio->uio_offset += size;
  699         return (0);
  700 }
  701 
  702 /*
  703  * unmap and unwire the process buffer
  704  */
  705 static void
  706 pipe_destroy_write_buffer(wpipe)
  707         struct pipe *wpipe;
  708 {
  709         int i;
  710 
  711         GIANT_REQUIRED;
  712         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  713 
  714         if (wpipe->pipe_map.kva) {
  715                 pmap_qremove(wpipe->pipe_map.kva, wpipe->pipe_map.npages);
  716 
  717                 if (amountpipekva > MAXPIPEKVA) {
  718                         vm_offset_t kva = wpipe->pipe_map.kva;
  719                         wpipe->pipe_map.kva = 0;
  720                         kmem_free(kernel_map, kva,
  721                                 wpipe->pipe_buffer.size + PAGE_SIZE);
  722                         amountpipekva -= wpipe->pipe_buffer.size + PAGE_SIZE;
  723                 }
  724         }
  725         vm_page_lock_queues();
  726         for (i = 0; i < wpipe->pipe_map.npages; i++)
  727                 vm_page_unwire(wpipe->pipe_map.ms[i], 1);
  728         vm_page_unlock_queues();
  729         wpipe->pipe_map.npages = 0;
  730 }
  731 
  732 /*
  733  * In the case of a signal, the writing process might go away.  This
  734  * code copies the data into the circular buffer so that the source
  735  * pages can be freed without loss of data.
  736  */
  737 static void
  738 pipe_clone_write_buffer(wpipe)
  739         struct pipe *wpipe;
  740 {
  741         int size;
  742         int pos;
  743 
  744         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  745         size = wpipe->pipe_map.cnt;
  746         pos = wpipe->pipe_map.pos;
  747 
  748         wpipe->pipe_buffer.in = size;
  749         wpipe->pipe_buffer.out = 0;
  750         wpipe->pipe_buffer.cnt = size;
  751         wpipe->pipe_state &= ~PIPE_DIRECTW;
  752 
  753         PIPE_GET_GIANT(wpipe);
  754         bcopy((caddr_t) wpipe->pipe_map.kva + pos,
  755             wpipe->pipe_buffer.buffer, size);
  756         pipe_destroy_write_buffer(wpipe);
  757         PIPE_DROP_GIANT(wpipe);
  758 }
  759 
  760 /*
  761  * This implements the pipe buffer write mechanism.  Note that only
  762  * a direct write OR a normal pipe write can be pending at any given time.
  763  * If there are any characters in the pipe buffer, the direct write will
  764  * be deferred until the receiving process grabs all of the bytes from
  765  * the pipe buffer.  Then the direct mapping write is set-up.
  766  */
  767 static int
  768 pipe_direct_write(wpipe, uio)
  769         struct pipe *wpipe;
  770         struct uio *uio;
  771 {
  772         int error;
  773 
  774 retry:
  775         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  776         while (wpipe->pipe_state & PIPE_DIRECTW) {
  777                 if (wpipe->pipe_state & PIPE_WANTR) {
  778                         wpipe->pipe_state &= ~PIPE_WANTR;
  779                         wakeup(wpipe);
  780                 }
  781                 wpipe->pipe_state |= PIPE_WANTW;
  782                 error = msleep(wpipe, PIPE_MTX(wpipe),
  783                     PRIBIO | PCATCH, "pipdww", 0);
  784                 if (error)
  785                         goto error1;
  786                 if (wpipe->pipe_state & PIPE_EOF) {
  787                         error = EPIPE;
  788                         goto error1;
  789                 }
  790         }
  791         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  792         if (wpipe->pipe_buffer.cnt > 0) {
  793                 if (wpipe->pipe_state & PIPE_WANTR) {
  794                         wpipe->pipe_state &= ~PIPE_WANTR;
  795                         wakeup(wpipe);
  796                 }
  797                         
  798                 wpipe->pipe_state |= PIPE_WANTW;
  799                 error = msleep(wpipe, PIPE_MTX(wpipe),
  800                     PRIBIO | PCATCH, "pipdwc", 0);
  801                 if (error)
  802                         goto error1;
  803                 if (wpipe->pipe_state & PIPE_EOF) {
  804                         error = EPIPE;
  805                         goto error1;
  806                 }
  807                 goto retry;
  808         }
  809 
  810         wpipe->pipe_state |= PIPE_DIRECTW;
  811 
  812         pipelock(wpipe, 0);
  813         PIPE_GET_GIANT(wpipe);
  814         error = pipe_build_write_buffer(wpipe, uio);
  815         PIPE_DROP_GIANT(wpipe);
  816         pipeunlock(wpipe);
  817         if (error) {
  818                 wpipe->pipe_state &= ~PIPE_DIRECTW;
  819                 goto error1;
  820         }
  821 
  822         error = 0;
  823         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
  824                 if (wpipe->pipe_state & PIPE_EOF) {
  825                         pipelock(wpipe, 0);
  826                         PIPE_GET_GIANT(wpipe);
  827                         pipe_destroy_write_buffer(wpipe);
  828                         PIPE_DROP_GIANT(wpipe);
  829                         pipeunlock(wpipe);
  830                         pipeselwakeup(wpipe);
  831                         error = EPIPE;
  832                         goto error1;
  833                 }
  834                 if (wpipe->pipe_state & PIPE_WANTR) {
  835                         wpipe->pipe_state &= ~PIPE_WANTR;
  836                         wakeup(wpipe);
  837                 }
  838                 pipeselwakeup(wpipe);
  839                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
  840                     "pipdwt", 0);
  841         }
  842 
  843         pipelock(wpipe,0);
  844         if (wpipe->pipe_state & PIPE_DIRECTW) {
  845                 /*
  846                  * this bit of trickery substitutes a kernel buffer for
  847                  * the process that might be going away.
  848                  */
  849                 pipe_clone_write_buffer(wpipe);
  850         } else {
  851                 PIPE_GET_GIANT(wpipe);
  852                 pipe_destroy_write_buffer(wpipe);
  853                 PIPE_DROP_GIANT(wpipe);
  854         }
  855         pipeunlock(wpipe);
  856         return (error);
  857 
  858 error1:
  859         wakeup(wpipe);
  860         return (error);
  861 }
  862 #endif
  863         
  864 static int
  865 pipe_write(fp, uio, active_cred, flags, td)
  866         struct file *fp;
  867         struct uio *uio;
  868         struct ucred *active_cred;
  869         struct thread *td;
  870         int flags;
  871 {
  872         int error = 0;
  873         int orig_resid;
  874         struct pipe *wpipe, *rpipe;
  875 
  876         rpipe = (struct pipe *) fp->f_data;
  877         wpipe = rpipe->pipe_peer;
  878 
  879         PIPE_LOCK(rpipe);
  880         /*
  881          * detect loss of pipe read side, issue SIGPIPE if lost.
  882          */
  883         if ((wpipe == NULL) || (wpipe->pipe_state & PIPE_EOF)) {
  884                 PIPE_UNLOCK(rpipe);
  885                 return (EPIPE);
  886         }
  887 #ifdef MAC
  888         error = mac_check_pipe_write(active_cred, wpipe);
  889         if (error) {
  890                 PIPE_UNLOCK(rpipe);
  891                 return (error);
  892         }
  893 #endif
  894         ++wpipe->pipe_busy;
  895 
  896         /*
  897          * If it is advantageous to resize the pipe buffer, do
  898          * so.
  899          */
  900         if ((uio->uio_resid > PIPE_SIZE) &&
  901                 (nbigpipe < LIMITBIGPIPES) &&
  902                 (wpipe->pipe_state & PIPE_DIRECTW) == 0 &&
  903                 (wpipe->pipe_buffer.size <= PIPE_SIZE) &&
  904                 (wpipe->pipe_buffer.cnt == 0)) {
  905 
  906                 if ((error = pipelock(wpipe, 1)) == 0) {
  907                         PIPE_GET_GIANT(wpipe);
  908                         if (pipespace(wpipe, BIG_PIPE_SIZE) == 0)
  909                                 nbigpipe++;
  910                         PIPE_DROP_GIANT(wpipe);
  911                         pipeunlock(wpipe);
  912                 }
  913         }
  914 
  915         /*
  916          * If an early error occured unbusy and return, waking up any pending
  917          * readers.
  918          */
  919         if (error) {
  920                 --wpipe->pipe_busy;
  921                 if ((wpipe->pipe_busy == 0) && 
  922                     (wpipe->pipe_state & PIPE_WANT)) {
  923                         wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
  924                         wakeup(wpipe);
  925                 }
  926                 PIPE_UNLOCK(rpipe);
  927                 return(error);
  928         }
  929                 
  930         orig_resid = uio->uio_resid;
  931 
  932         while (uio->uio_resid) {
  933                 int space;
  934 
  935 #ifndef PIPE_NODIRECT
  936                 /*
  937                  * If the transfer is large, we can gain performance if
  938                  * we do process-to-process copies directly.
  939                  * If the write is non-blocking, we don't use the
  940                  * direct write mechanism.
  941                  *
  942                  * The direct write mechanism will detect the reader going
  943                  * away on us.
  944                  */
  945                 if ((uio->uio_iov->iov_len >= PIPE_MINDIRECT) &&
  946                     (fp->f_flag & FNONBLOCK) == 0 &&
  947                         (wpipe->pipe_map.kva || (amountpipekva < LIMITPIPEKVA)) &&
  948                         (uio->uio_iov->iov_len >= PIPE_MINDIRECT)) {
  949                         error = pipe_direct_write(wpipe, uio);
  950                         if (error)
  951                                 break;
  952                         continue;
  953                 }
  954 #endif
  955 
  956                 /*
  957                  * Pipe buffered writes cannot be coincidental with
  958                  * direct writes.  We wait until the currently executing
  959                  * direct write is completed before we start filling the
  960                  * pipe buffer.  We break out if a signal occurs or the
  961                  * reader goes away.
  962                  */
  963         retrywrite:
  964                 while (wpipe->pipe_state & PIPE_DIRECTW) {
  965                         if (wpipe->pipe_state & PIPE_WANTR) {
  966                                 wpipe->pipe_state &= ~PIPE_WANTR;
  967                                 wakeup(wpipe);
  968                         }
  969                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
  970                             "pipbww", 0);
  971                         if (wpipe->pipe_state & PIPE_EOF)
  972                                 break;
  973                         if (error)
  974                                 break;
  975                 }
  976                 if (wpipe->pipe_state & PIPE_EOF) {
  977                         error = EPIPE;
  978                         break;
  979                 }
  980 
  981                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
  982 
  983                 /* Writes of size <= PIPE_BUF must be atomic. */
  984                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
  985                         space = 0;
  986 
  987                 if (space > 0 && (wpipe->pipe_buffer.cnt < PIPE_SIZE)) {
  988                         if ((error = pipelock(wpipe,1)) == 0) {
  989                                 int size;       /* Transfer size */
  990                                 int segsize;    /* first segment to transfer */
  991 
  992                                 /*
  993                                  * It is possible for a direct write to
  994                                  * slip in on us... handle it here...
  995                                  */
  996                                 if (wpipe->pipe_state & PIPE_DIRECTW) {
  997                                         pipeunlock(wpipe);
  998                                         goto retrywrite;
  999                                 }
 1000                                 /* 
 1001                                  * If a process blocked in uiomove, our
 1002                                  * value for space might be bad.
 1003                                  *
 1004                                  * XXX will we be ok if the reader has gone
 1005                                  * away here?
 1006                                  */
 1007                                 if (space > wpipe->pipe_buffer.size - 
 1008                                     wpipe->pipe_buffer.cnt) {
 1009                                         pipeunlock(wpipe);
 1010                                         goto retrywrite;
 1011                                 }
 1012 
 1013                                 /*
 1014                                  * Transfer size is minimum of uio transfer
 1015                                  * and free space in pipe buffer.
 1016                                  */
 1017                                 if (space > uio->uio_resid)
 1018                                         size = uio->uio_resid;
 1019                                 else
 1020                                         size = space;
 1021                                 /*
 1022                                  * First segment to transfer is minimum of 
 1023                                  * transfer size and contiguous space in
 1024                                  * pipe buffer.  If first segment to transfer
 1025                                  * is less than the transfer size, we've got
 1026                                  * a wraparound in the buffer.
 1027                                  */
 1028                                 segsize = wpipe->pipe_buffer.size - 
 1029                                         wpipe->pipe_buffer.in;
 1030                                 if (segsize > size)
 1031                                         segsize = size;
 1032                                 
 1033                                 /* Transfer first segment */
 1034 
 1035                                 PIPE_UNLOCK(rpipe);
 1036                                 error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in], 
 1037                                                 segsize, uio);
 1038                                 PIPE_LOCK(rpipe);
 1039                                 
 1040                                 if (error == 0 && segsize < size) {
 1041                                         /* 
 1042                                          * Transfer remaining part now, to
 1043                                          * support atomic writes.  Wraparound
 1044                                          * happened.
 1045                                          */
 1046                                         if (wpipe->pipe_buffer.in + segsize != 
 1047                                             wpipe->pipe_buffer.size)
 1048                                                 panic("Expected pipe buffer wraparound disappeared");
 1049                                                 
 1050                                         PIPE_UNLOCK(rpipe);
 1051                                         error = uiomove(&wpipe->pipe_buffer.buffer[0],
 1052                                                         size - segsize, uio);
 1053                                         PIPE_LOCK(rpipe);
 1054                                 }
 1055                                 if (error == 0) {
 1056                                         wpipe->pipe_buffer.in += size;
 1057                                         if (wpipe->pipe_buffer.in >=
 1058                                             wpipe->pipe_buffer.size) {
 1059                                                 if (wpipe->pipe_buffer.in != size - segsize + wpipe->pipe_buffer.size)
 1060                                                         panic("Expected wraparound bad");
 1061                                                 wpipe->pipe_buffer.in = size - segsize;
 1062                                         }
 1063                                 
 1064                                         wpipe->pipe_buffer.cnt += size;
 1065                                         if (wpipe->pipe_buffer.cnt > wpipe->pipe_buffer.size)
 1066                                                 panic("Pipe buffer overflow");
 1067                                 
 1068                                 }
 1069                                 pipeunlock(wpipe);
 1070                         }
 1071                         if (error)
 1072                                 break;
 1073 
 1074                 } else {
 1075                         /*
 1076                          * If the "read-side" has been blocked, wake it up now.
 1077                          */
 1078                         if (wpipe->pipe_state & PIPE_WANTR) {
 1079                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1080                                 wakeup(wpipe);
 1081                         }
 1082 
 1083                         /*
 1084                          * don't block on non-blocking I/O
 1085                          */
 1086                         if (fp->f_flag & FNONBLOCK) {
 1087                                 error = EAGAIN;
 1088                                 break;
 1089                         }
 1090 
 1091                         /*
 1092                          * We have no more space and have something to offer,
 1093                          * wake up select/poll.
 1094                          */
 1095                         pipeselwakeup(wpipe);
 1096 
 1097                         wpipe->pipe_state |= PIPE_WANTW;
 1098                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1099                             PRIBIO | PCATCH, "pipewr", 0);
 1100                         if (error != 0)
 1101                                 break;
 1102                         /*
 1103                          * If read side wants to go away, we just issue a signal
 1104                          * to ourselves.
 1105                          */
 1106                         if (wpipe->pipe_state & PIPE_EOF) {
 1107                                 error = EPIPE;
 1108                                 break;
 1109                         }       
 1110                 }
 1111         }
 1112 
 1113         --wpipe->pipe_busy;
 1114 
 1115         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1116                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1117                 wakeup(wpipe);
 1118         } else if (wpipe->pipe_buffer.cnt > 0) {
 1119                 /*
 1120                  * If we have put any characters in the buffer, we wake up
 1121                  * the reader.
 1122                  */
 1123                 if (wpipe->pipe_state & PIPE_WANTR) {
 1124                         wpipe->pipe_state &= ~PIPE_WANTR;
 1125                         wakeup(wpipe);
 1126                 }
 1127         }
 1128 
 1129         /*
 1130          * Don't return EPIPE if I/O was successful
 1131          */
 1132         if ((wpipe->pipe_buffer.cnt == 0) &&
 1133             (uio->uio_resid == 0) &&
 1134             (error == EPIPE)) {
 1135                 error = 0;
 1136         }
 1137 
 1138         if (error == 0)
 1139                 vfs_timestamp(&wpipe->pipe_mtime);
 1140 
 1141         /*
 1142          * We have something to offer,
 1143          * wake up select/poll.
 1144          */
 1145         if (wpipe->pipe_buffer.cnt)
 1146                 pipeselwakeup(wpipe);
 1147 
 1148         PIPE_UNLOCK(rpipe);
 1149         return (error);
 1150 }
 1151 
 1152 /*
 1153  * we implement a very minimal set of ioctls for compatibility with sockets.
 1154  */
 1155 static int
 1156 pipe_ioctl(fp, cmd, data, active_cred, td)
 1157         struct file *fp;
 1158         u_long cmd;
 1159         void *data;
 1160         struct ucred *active_cred;
 1161         struct thread *td;
 1162 {
 1163         struct pipe *mpipe = (struct pipe *)fp->f_data;
 1164 #ifdef MAC
 1165         int error;
 1166 #endif
 1167 
 1168         PIPE_LOCK(mpipe);
 1169 
 1170 #ifdef MAC
 1171         error = mac_check_pipe_ioctl(active_cred, mpipe, cmd, data);
 1172         if (error)
 1173                 return (error);
 1174 #endif
 1175 
 1176         switch (cmd) {
 1177 
 1178         case FIONBIO:
 1179                 PIPE_UNLOCK(mpipe);
 1180                 return (0);
 1181 
 1182         case FIOASYNC:
 1183                 if (*(int *)data) {
 1184                         mpipe->pipe_state |= PIPE_ASYNC;
 1185                 } else {
 1186                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1187                 }
 1188                 PIPE_UNLOCK(mpipe);
 1189                 return (0);
 1190 
 1191         case FIONREAD:
 1192                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1193                         *(int *)data = mpipe->pipe_map.cnt;
 1194                 else
 1195                         *(int *)data = mpipe->pipe_buffer.cnt;
 1196                 PIPE_UNLOCK(mpipe);
 1197                 return (0);
 1198 
 1199         case FIOSETOWN:
 1200                 PIPE_UNLOCK(mpipe);
 1201                 return (fsetown(*(int *)data, &mpipe->pipe_sigio));
 1202 
 1203         case FIOGETOWN:
 1204                 PIPE_UNLOCK(mpipe);
 1205                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1206                 return (0);
 1207 
 1208         /* This is deprecated, FIOSETOWN should be used instead. */
 1209         case TIOCSPGRP:
 1210                 PIPE_UNLOCK(mpipe);
 1211                 return (fsetown(-(*(int *)data), &mpipe->pipe_sigio));
 1212 
 1213         /* This is deprecated, FIOGETOWN should be used instead. */
 1214         case TIOCGPGRP:
 1215                 PIPE_UNLOCK(mpipe);
 1216                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1217                 return (0);
 1218 
 1219         }
 1220         PIPE_UNLOCK(mpipe);
 1221         return (ENOTTY);
 1222 }
 1223 
 1224 static int
 1225 pipe_poll(fp, events, active_cred, td)
 1226         struct file *fp;
 1227         int events;
 1228         struct ucred *active_cred;
 1229         struct thread *td;
 1230 {
 1231         struct pipe *rpipe = (struct pipe *)fp->f_data;
 1232         struct pipe *wpipe;
 1233         int revents = 0;
 1234 #ifdef MAC
 1235         int error;
 1236 #endif
 1237 
 1238         wpipe = rpipe->pipe_peer;
 1239         PIPE_LOCK(rpipe);
 1240 #ifdef MAC
 1241         error = mac_check_pipe_poll(active_cred, rpipe);
 1242         if (error)
 1243                 goto locked_error;
 1244 #endif
 1245         if (events & (POLLIN | POLLRDNORM))
 1246                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1247                     (rpipe->pipe_buffer.cnt > 0) ||
 1248                     (rpipe->pipe_state & PIPE_EOF))
 1249                         revents |= events & (POLLIN | POLLRDNORM);
 1250 
 1251         if (events & (POLLOUT | POLLWRNORM))
 1252                 if (wpipe == NULL || (wpipe->pipe_state & PIPE_EOF) ||
 1253                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1254                      (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF))
 1255                         revents |= events & (POLLOUT | POLLWRNORM);
 1256 
 1257         if ((rpipe->pipe_state & PIPE_EOF) ||
 1258             (wpipe == NULL) ||
 1259             (wpipe->pipe_state & PIPE_EOF))
 1260                 revents |= POLLHUP;
 1261 
 1262         if (revents == 0) {
 1263                 if (events & (POLLIN | POLLRDNORM)) {
 1264                         selrecord(td, &rpipe->pipe_sel);
 1265                         rpipe->pipe_state |= PIPE_SEL;
 1266                 }
 1267 
 1268                 if (events & (POLLOUT | POLLWRNORM)) {
 1269                         selrecord(td, &wpipe->pipe_sel);
 1270                         wpipe->pipe_state |= PIPE_SEL;
 1271                 }
 1272         }
 1273 #ifdef MAC
 1274 locked_error:
 1275 #endif
 1276         PIPE_UNLOCK(rpipe);
 1277 
 1278         return (revents);
 1279 }
 1280 
 1281 /*
 1282  * We shouldn't need locks here as we're doing a read and this should
 1283  * be a natural race.
 1284  */
 1285 static int
 1286 pipe_stat(fp, ub, active_cred, td)
 1287         struct file *fp;
 1288         struct stat *ub;
 1289         struct ucred *active_cred;
 1290         struct thread *td;
 1291 {
 1292         struct pipe *pipe = (struct pipe *)fp->f_data;
 1293 #ifdef MAC
 1294         int error;
 1295 
 1296         PIPE_LOCK(pipe);
 1297         error = mac_check_pipe_stat(active_cred, pipe);
 1298         PIPE_UNLOCK(pipe);
 1299         if (error)
 1300                 return (error);
 1301 #endif
 1302         bzero(ub, sizeof(*ub));
 1303         ub->st_mode = S_IFIFO;
 1304         ub->st_blksize = pipe->pipe_buffer.size;
 1305         ub->st_size = pipe->pipe_buffer.cnt;
 1306         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
 1307         ub->st_atimespec = pipe->pipe_atime;
 1308         ub->st_mtimespec = pipe->pipe_mtime;
 1309         ub->st_ctimespec = pipe->pipe_ctime;
 1310         ub->st_uid = fp->f_cred->cr_uid;
 1311         ub->st_gid = fp->f_cred->cr_gid;
 1312         /*
 1313          * Left as 0: st_dev, st_ino, st_nlink, st_rdev, st_flags, st_gen.
 1314          * XXX (st_dev, st_ino) should be unique.
 1315          */
 1316         return (0);
 1317 }
 1318 
 1319 /* ARGSUSED */
 1320 static int
 1321 pipe_close(fp, td)
 1322         struct file *fp;
 1323         struct thread *td;
 1324 {
 1325         struct pipe *cpipe = (struct pipe *)fp->f_data;
 1326 
 1327         fp->f_ops = &badfileops;
 1328         fp->f_data = NULL;
 1329         funsetown(&cpipe->pipe_sigio);
 1330         pipeclose(cpipe);
 1331         return (0);
 1332 }
 1333 
 1334 static void
 1335 pipe_free_kmem(cpipe)
 1336         struct pipe *cpipe;
 1337 {
 1338 
 1339         GIANT_REQUIRED;
 1340         KASSERT(cpipe->pipe_mtxp == NULL || !mtx_owned(PIPE_MTX(cpipe)),
 1341                ("pipespace: pipe mutex locked"));
 1342 
 1343         if (cpipe->pipe_buffer.buffer != NULL) {
 1344                 if (cpipe->pipe_buffer.size > PIPE_SIZE)
 1345                         --nbigpipe;
 1346                 amountpipekva -= cpipe->pipe_buffer.size;
 1347                 kmem_free(kernel_map,
 1348                         (vm_offset_t)cpipe->pipe_buffer.buffer,
 1349                         cpipe->pipe_buffer.size);
 1350                 cpipe->pipe_buffer.buffer = NULL;
 1351         }
 1352 #ifndef PIPE_NODIRECT
 1353         if (cpipe->pipe_map.kva != 0) {
 1354                 amountpipekva -= cpipe->pipe_buffer.size + PAGE_SIZE;
 1355                 kmem_free(kernel_map,
 1356                         cpipe->pipe_map.kva,
 1357                         cpipe->pipe_buffer.size + PAGE_SIZE);
 1358                 cpipe->pipe_map.cnt = 0;
 1359                 cpipe->pipe_map.kva = 0;
 1360                 cpipe->pipe_map.pos = 0;
 1361                 cpipe->pipe_map.npages = 0;
 1362         }
 1363 #endif
 1364 }
 1365 
 1366 /*
 1367  * shutdown the pipe
 1368  */
 1369 static void
 1370 pipeclose(cpipe)
 1371         struct pipe *cpipe;
 1372 {
 1373         struct pipe *ppipe;
 1374         int hadpeer;
 1375 
 1376         if (cpipe == NULL)
 1377                 return;
 1378 
 1379         hadpeer = 0;
 1380 
 1381         /* partially created pipes won't have a valid mutex. */
 1382         if (PIPE_MTX(cpipe) != NULL)
 1383                 PIPE_LOCK(cpipe);
 1384                 
 1385         pipeselwakeup(cpipe);
 1386 
 1387         /*
 1388          * If the other side is blocked, wake it up saying that
 1389          * we want to close it down.
 1390          */
 1391         while (cpipe->pipe_busy) {
 1392                 wakeup(cpipe);
 1393                 cpipe->pipe_state |= PIPE_WANT | PIPE_EOF;
 1394                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1395         }
 1396 
 1397 #ifdef MAC
 1398         if (cpipe->pipe_label != NULL && cpipe->pipe_peer == NULL)
 1399                 mac_destroy_pipe(cpipe);
 1400 #endif
 1401 
 1402         /*
 1403          * Disconnect from peer
 1404          */
 1405         if ((ppipe = cpipe->pipe_peer) != NULL) {
 1406                 hadpeer++;
 1407                 pipeselwakeup(ppipe);
 1408 
 1409                 ppipe->pipe_state |= PIPE_EOF;
 1410                 wakeup(ppipe);
 1411                 KNOTE(&ppipe->pipe_sel.si_note, 0);
 1412                 ppipe->pipe_peer = NULL;
 1413         }
 1414         /*
 1415          * free resources
 1416          */
 1417         if (PIPE_MTX(cpipe) != NULL) {
 1418                 PIPE_UNLOCK(cpipe);
 1419                 if (!hadpeer) {
 1420                         mtx_destroy(PIPE_MTX(cpipe));
 1421                         free(PIPE_MTX(cpipe), M_TEMP);
 1422                 }
 1423         }
 1424         mtx_lock(&Giant);
 1425         pipe_free_kmem(cpipe);
 1426         uma_zfree(pipe_zone, cpipe);
 1427         mtx_unlock(&Giant);
 1428 }
 1429 
 1430 /*ARGSUSED*/
 1431 static int
 1432 pipe_kqfilter(struct file *fp, struct knote *kn)
 1433 {
 1434         struct pipe *cpipe;
 1435 
 1436         cpipe = (struct pipe *)kn->kn_fp->f_data;
 1437         switch (kn->kn_filter) {
 1438         case EVFILT_READ:
 1439                 kn->kn_fop = &pipe_rfiltops;
 1440                 break;
 1441         case EVFILT_WRITE:
 1442                 kn->kn_fop = &pipe_wfiltops;
 1443                 cpipe = cpipe->pipe_peer;
 1444                 if (cpipe == NULL)
 1445                         /* other end of pipe has been closed */
 1446                         return (EBADF);
 1447                 break;
 1448         default:
 1449                 return (1);
 1450         }
 1451         kn->kn_hook = cpipe;
 1452 
 1453         PIPE_LOCK(cpipe);
 1454         SLIST_INSERT_HEAD(&cpipe->pipe_sel.si_note, kn, kn_selnext);
 1455         PIPE_UNLOCK(cpipe);
 1456         return (0);
 1457 }
 1458 
 1459 static void
 1460 filt_pipedetach(struct knote *kn)
 1461 {
 1462         struct pipe *cpipe = (struct pipe *)kn->kn_hook;
 1463 
 1464         PIPE_LOCK(cpipe);
 1465         SLIST_REMOVE(&cpipe->pipe_sel.si_note, kn, knote, kn_selnext);
 1466         PIPE_UNLOCK(cpipe);
 1467 }
 1468 
 1469 /*ARGSUSED*/
 1470 static int
 1471 filt_piperead(struct knote *kn, long hint)
 1472 {
 1473         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
 1474         struct pipe *wpipe = rpipe->pipe_peer;
 1475 
 1476         PIPE_LOCK(rpipe);
 1477         kn->kn_data = rpipe->pipe_buffer.cnt;
 1478         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1479                 kn->kn_data = rpipe->pipe_map.cnt;
 1480 
 1481         if ((rpipe->pipe_state & PIPE_EOF) ||
 1482             (wpipe == NULL) || (wpipe->pipe_state & PIPE_EOF)) {
 1483                 kn->kn_flags |= EV_EOF;
 1484                 PIPE_UNLOCK(rpipe);
 1485                 return (1);
 1486         }
 1487         PIPE_UNLOCK(rpipe);
 1488         return (kn->kn_data > 0);
 1489 }
 1490 
 1491 /*ARGSUSED*/
 1492 static int
 1493 filt_pipewrite(struct knote *kn, long hint)
 1494 {
 1495         struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
 1496         struct pipe *wpipe = rpipe->pipe_peer;
 1497 
 1498         PIPE_LOCK(rpipe);
 1499         if ((wpipe == NULL) || (wpipe->pipe_state & PIPE_EOF)) {
 1500                 kn->kn_data = 0;
 1501                 kn->kn_flags |= EV_EOF; 
 1502                 PIPE_UNLOCK(rpipe);
 1503                 return (1);
 1504         }
 1505         kn->kn_data = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1506         if (wpipe->pipe_state & PIPE_DIRECTW)
 1507                 kn->kn_data = 0;
 1508 
 1509         PIPE_UNLOCK(rpipe);
 1510         return (kn->kn_data >= PIPE_BUF);
 1511 }

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