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


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

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    1 /*-
    2  * Copyright (c) 1996 John S. Dyson
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice immediately at the beginning of the file, without modification,
   10  *    this list of conditions, and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. Absolutely no warranty of function or purpose is made by the author
   15  *    John S. Dyson.
   16  * 4. Modifications may be freely made to this file if the above conditions
   17  *    are met.
   18  */
   19 
   20 /*
   21  * This file contains a high-performance replacement for the socket-based
   22  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
   23  * all features of sockets, but does do everything that pipes normally
   24  * do.
   25  */
   26 
   27 /*
   28  * This code has two modes of operation, a small write mode and a large
   29  * write mode.  The small write mode acts like conventional pipes with
   30  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
   31  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
   32  * and PIPE_SIZE in size, it is fully mapped and wired into the kernel, and
   33  * the receiving process can copy it directly from the pages in the sending
   34  * process.
   35  *
   36  * If the sending process receives a signal, it is possible that it will
   37  * go away, and certainly its address space can change, because control
   38  * is returned back to the user-mode side.  In that case, the pipe code
   39  * arranges to copy the buffer supplied by the user process, to a pageable
   40  * kernel buffer, and the receiving process will grab the data from the
   41  * pageable kernel buffer.  Since signals don't happen all that often,
   42  * the copy operation is normally eliminated.
   43  *
   44  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
   45  * happen for small transfers so that the system will not spend all of
   46  * its time context switching.
   47  *
   48  * In order to limit the resource use of pipes, two sysctls exist:
   49  *
   50  * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
   51  * address space available to us in pipe_map. This value is normally
   52  * autotuned, but may also be loader tuned.
   53  *
   54  * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
   55  * memory in use by pipes.
   56  *
   57  * Based on how large pipekva is relative to maxpipekva, the following
   58  * will happen:
   59  *
   60  * 0% - 50%:
   61  *     New pipes are given 16K of memory backing, pipes may dynamically
   62  *     grow to as large as 64K where needed.
   63  * 50% - 75%:
   64  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   65  *     existing pipes may NOT grow.
   66  * 75% - 100%:
   67  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
   68  *     existing pipes will be shrunk down to 4K whenever possible.
   69  *
   70  * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
   71  * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
   72  * resize which MUST occur for reverse-direction pipes when they are
   73  * first used.
   74  *
   75  * Additional information about the current state of pipes may be obtained
   76  * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
   77  * and kern.ipc.piperesizefail.
   78  *
   79  * Locking rules:  There are two locks present here:  A mutex, used via
   80  * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
   81  * the flag, as mutexes can not persist over uiomove.  The mutex
   82  * exists only to guard access to the flag, and is not in itself a
   83  * locking mechanism.  Also note that there is only a single mutex for
   84  * both directions of a pipe.
   85  *
   86  * As pipelock() may have to sleep before it can acquire the flag, it
   87  * is important to reread all data after a call to pipelock(); everything
   88  * in the structure may have changed.
   89  */
   90 
   91 #include <sys/cdefs.h>
   92 __FBSDID("$FreeBSD$");
   93 
   94 #include "opt_mac.h"
   95 
   96 #include <sys/param.h>
   97 #include <sys/systm.h>
   98 #include <sys/fcntl.h>
   99 #include <sys/file.h>
  100 #include <sys/filedesc.h>
  101 #include <sys/filio.h>
  102 #include <sys/kernel.h>
  103 #include <sys/lock.h>
  104 #include <sys/mac.h>
  105 #include <sys/mutex.h>
  106 #include <sys/ttycom.h>
  107 #include <sys/stat.h>
  108 #include <sys/malloc.h>
  109 #include <sys/poll.h>
  110 #include <sys/selinfo.h>
  111 #include <sys/signalvar.h>
  112 #include <sys/sysctl.h>
  113 #include <sys/sysproto.h>
  114 #include <sys/pipe.h>
  115 #include <sys/proc.h>
  116 #include <sys/vnode.h>
  117 #include <sys/uio.h>
  118 #include <sys/event.h>
  119 
  120 #include <vm/vm.h>
  121 #include <vm/vm_param.h>
  122 #include <vm/vm_object.h>
  123 #include <vm/vm_kern.h>
  124 #include <vm/vm_extern.h>
  125 #include <vm/pmap.h>
  126 #include <vm/vm_map.h>
  127 #include <vm/vm_page.h>
  128 #include <vm/uma.h>
  129 
  130 /*
  131  * Use this define if you want to disable *fancy* VM things.  Expect an
  132  * approx 30% decrease in transfer rate.  This could be useful for
  133  * NetBSD or OpenBSD.
  134  */
  135 /* #define PIPE_NODIRECT */
  136 
  137 /*
  138  * interfaces to the outside world
  139  */
  140 static fo_rdwr_t        pipe_read;
  141 static fo_rdwr_t        pipe_write;
  142 static fo_ioctl_t       pipe_ioctl;
  143 static fo_poll_t        pipe_poll;
  144 static fo_kqfilter_t    pipe_kqfilter;
  145 static fo_stat_t        pipe_stat;
  146 static fo_close_t       pipe_close;
  147 
  148 static struct fileops pipeops = {
  149         .fo_read = pipe_read,
  150         .fo_write = pipe_write,
  151         .fo_ioctl = pipe_ioctl,
  152         .fo_poll = pipe_poll,
  153         .fo_kqfilter = pipe_kqfilter,
  154         .fo_stat = pipe_stat,
  155         .fo_close = pipe_close,
  156         .fo_flags = DFLAG_PASSABLE
  157 };
  158 
  159 static void     filt_pipedetach(struct knote *kn);
  160 static int      filt_piperead(struct knote *kn, long hint);
  161 static int      filt_pipewrite(struct knote *kn, long hint);
  162 
  163 static struct filterops pipe_rfiltops =
  164         { 1, NULL, filt_pipedetach, filt_piperead };
  165 static struct filterops pipe_wfiltops =
  166         { 1, NULL, filt_pipedetach, filt_pipewrite };
  167 
  168 /*
  169  * Default pipe buffer size(s), this can be kind-of large now because pipe
  170  * space is pageable.  The pipe code will try to maintain locality of
  171  * reference for performance reasons, so small amounts of outstanding I/O
  172  * will not wipe the cache.
  173  */
  174 #define MINPIPESIZE (PIPE_SIZE/3)
  175 #define MAXPIPESIZE (2*PIPE_SIZE/3)
  176 
  177 static int amountpipes;
  178 static int amountpipekva;
  179 static int pipefragretry;
  180 static int pipeallocfail;
  181 static int piperesizefail;
  182 static int piperesizeallowed = 1;
  183 
  184 SYSCTL_DECL(_kern_ipc);
  185 
  186 SYSCTL_INT(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN,
  187            &maxpipekva, 0, "Pipe KVA limit");
  188 SYSCTL_INT(_kern_ipc, OID_AUTO, pipes, CTLFLAG_RD,
  189            &amountpipes, 0, "Current # of pipes");
  190 SYSCTL_INT(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
  191            &amountpipekva, 0, "Pipe KVA usage");
  192 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
  193           &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
  194 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
  195           &pipeallocfail, 0, "Pipe allocation failures");
  196 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
  197           &piperesizefail, 0, "Pipe resize failures");
  198 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
  199           &piperesizeallowed, 0, "Pipe resizing allowed");
  200 
  201 static void pipeinit(void *dummy __unused);
  202 static void pipeclose(struct pipe *cpipe);
  203 static void pipe_free_kmem(struct pipe *cpipe);
  204 static int pipe_create(struct pipe *pipe, int backing);
  205 static __inline int pipelock(struct pipe *cpipe, int catch);
  206 static __inline void pipeunlock(struct pipe *cpipe);
  207 static __inline void pipeselwakeup(struct pipe *cpipe);
  208 #ifndef PIPE_NODIRECT
  209 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
  210 static void pipe_destroy_write_buffer(struct pipe *wpipe);
  211 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
  212 static void pipe_clone_write_buffer(struct pipe *wpipe);
  213 #endif
  214 static int pipespace(struct pipe *cpipe, int size);
  215 static int pipespace_new(struct pipe *cpipe, int size);
  216 
  217 static int      pipe_zone_ctor(void *mem, int size, void *arg, int flags);
  218 static void     pipe_zone_dtor(void *mem, int size, void *arg);
  219 static int      pipe_zone_init(void *mem, int size, int flags);
  220 static void     pipe_zone_fini(void *mem, int size);
  221 
  222 static uma_zone_t pipe_zone;
  223 
  224 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
  225 
  226 static void
  227 pipeinit(void *dummy __unused)
  228 {
  229 
  230         pipe_zone = uma_zcreate("PIPE", sizeof(struct pipepair),
  231             pipe_zone_ctor, pipe_zone_dtor, pipe_zone_init, pipe_zone_fini,
  232             UMA_ALIGN_PTR, 0);
  233         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
  234 }
  235 
  236 static int
  237 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
  238 {
  239         struct pipepair *pp;
  240         struct pipe *rpipe, *wpipe;
  241 
  242         KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
  243 
  244         pp = (struct pipepair *)mem;
  245 
  246         /*
  247          * We zero both pipe endpoints to make sure all the kmem pointers
  248          * are NULL, flag fields are zero'd, etc.  We timestamp both
  249          * endpoints with the same time.
  250          */
  251         rpipe = &pp->pp_rpipe;
  252         bzero(rpipe, sizeof(*rpipe));
  253         vfs_timestamp(&rpipe->pipe_ctime);
  254         rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
  255 
  256         wpipe = &pp->pp_wpipe;
  257         bzero(wpipe, sizeof(*wpipe));
  258         wpipe->pipe_ctime = rpipe->pipe_ctime;
  259         wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
  260 
  261         rpipe->pipe_peer = wpipe;
  262         rpipe->pipe_pair = pp;
  263         wpipe->pipe_peer = rpipe;
  264         wpipe->pipe_pair = pp;
  265 
  266         /*
  267          * Mark both endpoints as present; they will later get free'd
  268          * one at a time.  When both are free'd, then the whole pair
  269          * is released.
  270          */
  271         rpipe->pipe_present = PIPE_ACTIVE;
  272         wpipe->pipe_present = PIPE_ACTIVE;
  273 
  274         /*
  275          * Eventually, the MAC Framework may initialize the label
  276          * in ctor or init, but for now we do it elswhere to avoid
  277          * blocking in ctor or init.
  278          */
  279         pp->pp_label = NULL;
  280 
  281         atomic_add_int(&amountpipes, 2);
  282         return (0);
  283 }
  284 
  285 static void
  286 pipe_zone_dtor(void *mem, int size, void *arg)
  287 {
  288         struct pipepair *pp;
  289 
  290         KASSERT(size == sizeof(*pp), ("pipe_zone_dtor: wrong size"));
  291 
  292         pp = (struct pipepair *)mem;
  293 
  294         atomic_subtract_int(&amountpipes, 2);
  295 }
  296 
  297 static int
  298 pipe_zone_init(void *mem, int size, int flags)
  299 {
  300         struct pipepair *pp;
  301 
  302         KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
  303 
  304         pp = (struct pipepair *)mem;
  305 
  306         mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_RECURSE);
  307         return (0);
  308 }
  309 
  310 static void
  311 pipe_zone_fini(void *mem, int size)
  312 {
  313         struct pipepair *pp;
  314 
  315         KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
  316 
  317         pp = (struct pipepair *)mem;
  318 
  319         mtx_destroy(&pp->pp_mtx);
  320 }
  321 
  322 /*
  323  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail,
  324  * let the zone pick up the pieces via pipeclose().
  325  */
  326 
  327 /* ARGSUSED */
  328 int
  329 pipe(td, uap)
  330         struct thread *td;
  331         struct pipe_args /* {
  332                 int     dummy;
  333         } */ *uap;
  334 {
  335         struct filedesc *fdp = td->td_proc->p_fd;
  336         struct file *rf, *wf;
  337         struct pipepair *pp;
  338         struct pipe *rpipe, *wpipe;
  339         int fd, error;
  340 
  341         pp = uma_zalloc(pipe_zone, M_WAITOK);
  342 #ifdef MAC
  343         /*
  344          * The MAC label is shared between the connected endpoints.  As a
  345          * result mac_init_pipe() and mac_create_pipe() are called once
  346          * for the pair, and not on the endpoints.
  347          */
  348         mac_init_pipe(pp);
  349         mac_create_pipe(td->td_ucred, pp);
  350 #endif
  351         rpipe = &pp->pp_rpipe;
  352         wpipe = &pp->pp_wpipe;
  353 
  354         knlist_init(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe), NULL, NULL,
  355             NULL);
  356         knlist_init(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe), NULL, NULL,
  357             NULL);
  358 
  359         /* Only the forward direction pipe is backed by default */
  360         if ((error = pipe_create(rpipe, 1)) != 0 ||
  361             (error = pipe_create(wpipe, 0)) != 0) {
  362                 pipeclose(rpipe);
  363                 pipeclose(wpipe);
  364                 return (error);
  365         }
  366 
  367         rpipe->pipe_state |= PIPE_DIRECTOK;
  368         wpipe->pipe_state |= PIPE_DIRECTOK;
  369 
  370         error = falloc(td, &rf, &fd);
  371         if (error) {
  372                 pipeclose(rpipe);
  373                 pipeclose(wpipe);
  374                 return (error);
  375         }
  376         /* An extra reference on `rf' has been held for us by falloc(). */
  377         td->td_retval[0] = fd;
  378 
  379         /*
  380          * Warning: once we've gotten past allocation of the fd for the
  381          * read-side, we can only drop the read side via fdrop() in order
  382          * to avoid races against processes which manage to dup() the read
  383          * side while we are blocked trying to allocate the write side.
  384          */
  385         FILE_LOCK(rf);
  386         rf->f_flag = FREAD | FWRITE;
  387         rf->f_type = DTYPE_PIPE;
  388         rf->f_data = rpipe;
  389         rf->f_ops = &pipeops;
  390         FILE_UNLOCK(rf);
  391         error = falloc(td, &wf, &fd);
  392         if (error) {
  393                 fdclose(fdp, rf, td->td_retval[0], td);
  394                 fdrop(rf, td);
  395                 /* rpipe has been closed by fdrop(). */
  396                 pipeclose(wpipe);
  397                 return (error);
  398         }
  399         /* An extra reference on `wf' has been held for us by falloc(). */
  400         FILE_LOCK(wf);
  401         wf->f_flag = FREAD | FWRITE;
  402         wf->f_type = DTYPE_PIPE;
  403         wf->f_data = wpipe;
  404         wf->f_ops = &pipeops;
  405         FILE_UNLOCK(wf);
  406         fdrop(wf, td);
  407         td->td_retval[1] = fd;
  408         fdrop(rf, td);
  409 
  410         return (0);
  411 }
  412 
  413 /*
  414  * Allocate kva for pipe circular buffer, the space is pageable
  415  * This routine will 'realloc' the size of a pipe safely, if it fails
  416  * it will retain the old buffer.
  417  * If it fails it will return ENOMEM.
  418  */
  419 static int
  420 pipespace_new(cpipe, size)
  421         struct pipe *cpipe;
  422         int size;
  423 {
  424         caddr_t buffer;
  425         int error, cnt, firstseg;
  426         static int curfail = 0;
  427         static struct timeval lastfail;
  428 
  429         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
  430         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
  431                 ("pipespace: resize of direct writes not allowed"));
  432 retry:
  433         cnt = cpipe->pipe_buffer.cnt;
  434         if (cnt > size)
  435                 size = cnt;
  436 
  437         size = round_page(size);
  438         buffer = (caddr_t) vm_map_min(pipe_map);
  439 
  440         error = vm_map_find(pipe_map, NULL, 0,
  441                 (vm_offset_t *) &buffer, size, 1,
  442                 VM_PROT_ALL, VM_PROT_ALL, 0);
  443         if (error != KERN_SUCCESS) {
  444                 if ((cpipe->pipe_buffer.buffer == NULL) &&
  445                         (size > SMALL_PIPE_SIZE)) {
  446                         size = SMALL_PIPE_SIZE;
  447                         pipefragretry++;
  448                         goto retry;
  449                 }
  450                 if (cpipe->pipe_buffer.buffer == NULL) {
  451                         pipeallocfail++;
  452                         if (ppsratecheck(&lastfail, &curfail, 1))
  453                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
  454                 } else {
  455                         piperesizefail++;
  456                 }
  457                 return (ENOMEM);
  458         }
  459 
  460         /* copy data, then free old resources if we're resizing */
  461         if (cnt > 0) {
  462                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
  463                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
  464                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  465                                 buffer, firstseg);
  466                         if ((cnt - firstseg) > 0)
  467                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
  468                                         cpipe->pipe_buffer.in);
  469                 } else {
  470                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
  471                                 buffer, cnt);
  472                 }
  473         }
  474         pipe_free_kmem(cpipe);
  475         cpipe->pipe_buffer.buffer = buffer;
  476         cpipe->pipe_buffer.size = size;
  477         cpipe->pipe_buffer.in = cnt;
  478         cpipe->pipe_buffer.out = 0;
  479         cpipe->pipe_buffer.cnt = cnt;
  480         atomic_add_int(&amountpipekva, cpipe->pipe_buffer.size);
  481         return (0);
  482 }
  483 
  484 /*
  485  * Wrapper for pipespace_new() that performs locking assertions.
  486  */
  487 static int
  488 pipespace(cpipe, size)
  489         struct pipe *cpipe;
  490         int size;
  491 {
  492 
  493         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  494                 ("Unlocked pipe passed to pipespace"));
  495         return (pipespace_new(cpipe, size));
  496 }
  497 
  498 /*
  499  * lock a pipe for I/O, blocking other access
  500  */
  501 static __inline int
  502 pipelock(cpipe, catch)
  503         struct pipe *cpipe;
  504         int catch;
  505 {
  506         int error;
  507 
  508         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  509         while (cpipe->pipe_state & PIPE_LOCKFL) {
  510                 cpipe->pipe_state |= PIPE_LWANT;
  511                 error = msleep(cpipe, PIPE_MTX(cpipe),
  512                     catch ? (PRIBIO | PCATCH) : PRIBIO,
  513                     "pipelk", 0);
  514                 if (error != 0)
  515                         return (error);
  516         }
  517         cpipe->pipe_state |= PIPE_LOCKFL;
  518         return (0);
  519 }
  520 
  521 /*
  522  * unlock a pipe I/O lock
  523  */
  524 static __inline void
  525 pipeunlock(cpipe)
  526         struct pipe *cpipe;
  527 {
  528 
  529         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  530         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
  531                 ("Unlocked pipe passed to pipeunlock"));
  532         cpipe->pipe_state &= ~PIPE_LOCKFL;
  533         if (cpipe->pipe_state & PIPE_LWANT) {
  534                 cpipe->pipe_state &= ~PIPE_LWANT;
  535                 wakeup(cpipe);
  536         }
  537 }
  538 
  539 static __inline void
  540 pipeselwakeup(cpipe)
  541         struct pipe *cpipe;
  542 {
  543 
  544         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
  545         if (cpipe->pipe_state & PIPE_SEL) {
  546                 cpipe->pipe_state &= ~PIPE_SEL;
  547                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
  548         }
  549         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
  550                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
  551         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
  552 }
  553 
  554 /*
  555  * Initialize and allocate VM and memory for pipe.  The structure
  556  * will start out zero'd from the ctor, so we just manage the kmem.
  557  */
  558 static int
  559 pipe_create(pipe, backing)
  560         struct pipe *pipe;
  561         int backing;
  562 {
  563         int error;
  564 
  565         if (backing) {
  566                 if (amountpipekva > maxpipekva / 2)
  567                         error = pipespace_new(pipe, SMALL_PIPE_SIZE);
  568                 else
  569                         error = pipespace_new(pipe, PIPE_SIZE);
  570         } else {
  571                 /* If we're not backing this pipe, no need to do anything. */
  572                 error = 0;
  573         }
  574         return (error);
  575 }
  576 
  577 /* ARGSUSED */
  578 static int
  579 pipe_read(fp, uio, active_cred, flags, td)
  580         struct file *fp;
  581         struct uio *uio;
  582         struct ucred *active_cred;
  583         struct thread *td;
  584         int flags;
  585 {
  586         struct pipe *rpipe = fp->f_data;
  587         int error;
  588         int nread = 0;
  589         u_int size;
  590 
  591         PIPE_LOCK(rpipe);
  592         ++rpipe->pipe_busy;
  593         error = pipelock(rpipe, 1);
  594         if (error)
  595                 goto unlocked_error;
  596 
  597 #ifdef MAC
  598         error = mac_check_pipe_read(active_cred, rpipe->pipe_pair);
  599         if (error)
  600                 goto locked_error;
  601 #endif
  602         if (amountpipekva > (3 * maxpipekva) / 4) {
  603                 if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
  604                         (rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
  605                         (rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
  606                         (piperesizeallowed == 1)) {
  607                         PIPE_UNLOCK(rpipe);
  608                         pipespace(rpipe, SMALL_PIPE_SIZE);
  609                         PIPE_LOCK(rpipe);
  610                 }
  611         }
  612 
  613         while (uio->uio_resid) {
  614                 /*
  615                  * normal pipe buffer receive
  616                  */
  617                 if (rpipe->pipe_buffer.cnt > 0) {
  618                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
  619                         if (size > rpipe->pipe_buffer.cnt)
  620                                 size = rpipe->pipe_buffer.cnt;
  621                         if (size > (u_int) uio->uio_resid)
  622                                 size = (u_int) uio->uio_resid;
  623 
  624                         PIPE_UNLOCK(rpipe);
  625                         error = uiomove(
  626                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
  627                             size, uio);
  628                         PIPE_LOCK(rpipe);
  629                         if (error)
  630                                 break;
  631 
  632                         rpipe->pipe_buffer.out += size;
  633                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
  634                                 rpipe->pipe_buffer.out = 0;
  635 
  636                         rpipe->pipe_buffer.cnt -= size;
  637 
  638                         /*
  639                          * If there is no more to read in the pipe, reset
  640                          * its pointers to the beginning.  This improves
  641                          * cache hit stats.
  642                          */
  643                         if (rpipe->pipe_buffer.cnt == 0) {
  644                                 rpipe->pipe_buffer.in = 0;
  645                                 rpipe->pipe_buffer.out = 0;
  646                         }
  647                         nread += size;
  648 #ifndef PIPE_NODIRECT
  649                 /*
  650                  * Direct copy, bypassing a kernel buffer.
  651                  */
  652                 } else if ((size = rpipe->pipe_map.cnt) &&
  653                            (rpipe->pipe_state & PIPE_DIRECTW)) {
  654                         if (size > (u_int) uio->uio_resid)
  655                                 size = (u_int) uio->uio_resid;
  656 
  657                         PIPE_UNLOCK(rpipe);
  658                         error = uiomove_fromphys(rpipe->pipe_map.ms,
  659                             rpipe->pipe_map.pos, size, uio);
  660                         PIPE_LOCK(rpipe);
  661                         if (error)
  662                                 break;
  663                         nread += size;
  664                         rpipe->pipe_map.pos += size;
  665                         rpipe->pipe_map.cnt -= size;
  666                         if (rpipe->pipe_map.cnt == 0) {
  667                                 rpipe->pipe_state &= ~PIPE_DIRECTW;
  668                                 wakeup(rpipe);
  669                         }
  670 #endif
  671                 } else {
  672                         /*
  673                          * detect EOF condition
  674                          * read returns 0 on EOF, no need to set error
  675                          */
  676                         if (rpipe->pipe_state & PIPE_EOF)
  677                                 break;
  678 
  679                         /*
  680                          * If the "write-side" has been blocked, wake it up now.
  681                          */
  682                         if (rpipe->pipe_state & PIPE_WANTW) {
  683                                 rpipe->pipe_state &= ~PIPE_WANTW;
  684                                 wakeup(rpipe);
  685                         }
  686 
  687                         /*
  688                          * Break if some data was read.
  689                          */
  690                         if (nread > 0)
  691                                 break;
  692 
  693                         /*
  694                          * Unlock the pipe buffer for our remaining processing.
  695                          * We will either break out with an error or we will
  696                          * sleep and relock to loop.
  697                          */
  698                         pipeunlock(rpipe);
  699 
  700                         /*
  701                          * Handle non-blocking mode operation or
  702                          * wait for more data.
  703                          */
  704                         if (fp->f_flag & FNONBLOCK) {
  705                                 error = EAGAIN;
  706                         } else {
  707                                 rpipe->pipe_state |= PIPE_WANTR;
  708                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
  709                                     PRIBIO | PCATCH,
  710                                     "piperd", 0)) == 0)
  711                                         error = pipelock(rpipe, 1);
  712                         }
  713                         if (error)
  714                                 goto unlocked_error;
  715                 }
  716         }
  717 #ifdef MAC
  718 locked_error:
  719 #endif
  720         pipeunlock(rpipe);
  721 
  722         /* XXX: should probably do this before getting any locks. */
  723         if (error == 0)
  724                 vfs_timestamp(&rpipe->pipe_atime);
  725 unlocked_error:
  726         --rpipe->pipe_busy;
  727 
  728         /*
  729          * PIPE_WANT processing only makes sense if pipe_busy is 0.
  730          */
  731         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
  732                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
  733                 wakeup(rpipe);
  734         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
  735                 /*
  736                  * Handle write blocking hysteresis.
  737                  */
  738                 if (rpipe->pipe_state & PIPE_WANTW) {
  739                         rpipe->pipe_state &= ~PIPE_WANTW;
  740                         wakeup(rpipe);
  741                 }
  742         }
  743 
  744         if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
  745                 pipeselwakeup(rpipe);
  746 
  747         PIPE_UNLOCK(rpipe);
  748         return (error);
  749 }
  750 
  751 #ifndef PIPE_NODIRECT
  752 /*
  753  * Map the sending processes' buffer into kernel space and wire it.
  754  * This is similar to a physical write operation.
  755  */
  756 static int
  757 pipe_build_write_buffer(wpipe, uio)
  758         struct pipe *wpipe;
  759         struct uio *uio;
  760 {
  761         pmap_t pmap;
  762         u_int size;
  763         int i, j;
  764         vm_offset_t addr, endaddr;
  765 
  766         PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
  767         KASSERT(wpipe->pipe_state & PIPE_DIRECTW,
  768                 ("Clone attempt on non-direct write pipe!"));
  769 
  770         size = (u_int) uio->uio_iov->iov_len;
  771         if (size > wpipe->pipe_buffer.size)
  772                 size = wpipe->pipe_buffer.size;
  773 
  774         pmap = vmspace_pmap(curproc->p_vmspace);
  775         endaddr = round_page((vm_offset_t)uio->uio_iov->iov_base + size);
  776         addr = trunc_page((vm_offset_t)uio->uio_iov->iov_base);
  777         if (endaddr < addr)
  778                 return (EFAULT);
  779         for (i = 0; addr < endaddr; addr += PAGE_SIZE, i++) {
  780                 /*
  781                  * vm_fault_quick() can sleep.  Consequently,
  782                  * vm_page_lock_queue() and vm_page_unlock_queue()
  783                  * should not be performed outside of this loop.
  784                  */
  785         race:
  786                 if (vm_fault_quick((caddr_t)addr, VM_PROT_READ) < 0) {
  787                         vm_page_lock_queues();
  788                         for (j = 0; j < i; j++)
  789                                 vm_page_unhold(wpipe->pipe_map.ms[j]);
  790                         vm_page_unlock_queues();
  791                         return (EFAULT);
  792                 }
  793                 wpipe->pipe_map.ms[i] = pmap_extract_and_hold(pmap, addr,
  794                     VM_PROT_READ);
  795                 if (wpipe->pipe_map.ms[i] == NULL)
  796                         goto race;
  797         }
  798 
  799 /*
  800  * set up the control block
  801  */
  802         wpipe->pipe_map.npages = i;
  803         wpipe->pipe_map.pos =
  804             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
  805         wpipe->pipe_map.cnt = size;
  806 
  807 /*
  808  * and update the uio data
  809  */
  810 
  811         uio->uio_iov->iov_len -= size;
  812         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
  813         if (uio->uio_iov->iov_len == 0)
  814                 uio->uio_iov++;
  815         uio->uio_resid -= size;
  816         uio->uio_offset += size;
  817         return (0);
  818 }
  819 
  820 /*
  821  * unmap and unwire the process buffer
  822  */
  823 static void
  824 pipe_destroy_write_buffer(wpipe)
  825         struct pipe *wpipe;
  826 {
  827         int i;
  828 
  829         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  830         vm_page_lock_queues();
  831         for (i = 0; i < wpipe->pipe_map.npages; i++) {
  832                 vm_page_unhold(wpipe->pipe_map.ms[i]);
  833         }
  834         vm_page_unlock_queues();
  835         wpipe->pipe_map.npages = 0;
  836 }
  837 
  838 /*
  839  * In the case of a signal, the writing process might go away.  This
  840  * code copies the data into the circular buffer so that the source
  841  * pages can be freed without loss of data.
  842  */
  843 static void
  844 pipe_clone_write_buffer(wpipe)
  845         struct pipe *wpipe;
  846 {
  847         struct uio uio;
  848         struct iovec iov;
  849         int size;
  850         int pos;
  851 
  852         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  853         size = wpipe->pipe_map.cnt;
  854         pos = wpipe->pipe_map.pos;
  855 
  856         wpipe->pipe_buffer.in = size;
  857         wpipe->pipe_buffer.out = 0;
  858         wpipe->pipe_buffer.cnt = size;
  859         wpipe->pipe_state &= ~PIPE_DIRECTW;
  860 
  861         PIPE_UNLOCK(wpipe);
  862         iov.iov_base = wpipe->pipe_buffer.buffer;
  863         iov.iov_len = size;
  864         uio.uio_iov = &iov;
  865         uio.uio_iovcnt = 1;
  866         uio.uio_offset = 0;
  867         uio.uio_resid = size;
  868         uio.uio_segflg = UIO_SYSSPACE;
  869         uio.uio_rw = UIO_READ;
  870         uio.uio_td = curthread;
  871         uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
  872         PIPE_LOCK(wpipe);
  873         pipe_destroy_write_buffer(wpipe);
  874 }
  875 
  876 /*
  877  * This implements the pipe buffer write mechanism.  Note that only
  878  * a direct write OR a normal pipe write can be pending at any given time.
  879  * If there are any characters in the pipe buffer, the direct write will
  880  * be deferred until the receiving process grabs all of the bytes from
  881  * the pipe buffer.  Then the direct mapping write is set-up.
  882  */
  883 static int
  884 pipe_direct_write(wpipe, uio)
  885         struct pipe *wpipe;
  886         struct uio *uio;
  887 {
  888         int error;
  889 
  890 retry:
  891         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
  892         error = pipelock(wpipe, 1);
  893         if (wpipe->pipe_state & PIPE_EOF)
  894                 error = EPIPE;
  895         if (error) {
  896                 pipeunlock(wpipe);
  897                 goto error1;
  898         }
  899         while (wpipe->pipe_state & PIPE_DIRECTW) {
  900                 if (wpipe->pipe_state & PIPE_WANTR) {
  901                         wpipe->pipe_state &= ~PIPE_WANTR;
  902                         wakeup(wpipe);
  903                 }
  904                 pipeselwakeup(wpipe);
  905                 wpipe->pipe_state |= PIPE_WANTW;
  906                 pipeunlock(wpipe);
  907                 error = msleep(wpipe, PIPE_MTX(wpipe),
  908                     PRIBIO | PCATCH, "pipdww", 0);
  909                 if (error)
  910                         goto error1;
  911                 else
  912                         goto retry;
  913         }
  914         wpipe->pipe_map.cnt = 0;        /* transfer not ready yet */
  915         if (wpipe->pipe_buffer.cnt > 0) {
  916                 if (wpipe->pipe_state & PIPE_WANTR) {
  917                         wpipe->pipe_state &= ~PIPE_WANTR;
  918                         wakeup(wpipe);
  919                 }
  920                 pipeselwakeup(wpipe);
  921                 wpipe->pipe_state |= PIPE_WANTW;
  922                 pipeunlock(wpipe);
  923                 error = msleep(wpipe, PIPE_MTX(wpipe),
  924                     PRIBIO | PCATCH, "pipdwc", 0);
  925                 if (error)
  926                         goto error1;
  927                 else
  928                         goto retry;
  929         }
  930 
  931         wpipe->pipe_state |= PIPE_DIRECTW;
  932 
  933         PIPE_UNLOCK(wpipe);
  934         error = pipe_build_write_buffer(wpipe, uio);
  935         PIPE_LOCK(wpipe);
  936         if (error) {
  937                 wpipe->pipe_state &= ~PIPE_DIRECTW;
  938                 pipeunlock(wpipe);
  939                 goto error1;
  940         }
  941 
  942         error = 0;
  943         while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
  944                 if (wpipe->pipe_state & PIPE_EOF) {
  945                         pipe_destroy_write_buffer(wpipe);
  946                         pipeselwakeup(wpipe);
  947                         pipeunlock(wpipe);
  948                         error = EPIPE;
  949                         goto error1;
  950                 }
  951                 if (wpipe->pipe_state & PIPE_WANTR) {
  952                         wpipe->pipe_state &= ~PIPE_WANTR;
  953                         wakeup(wpipe);
  954                 }
  955                 pipeselwakeup(wpipe);
  956                 pipeunlock(wpipe);
  957                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
  958                     "pipdwt", 0);
  959                 pipelock(wpipe, 0);
  960         }
  961 
  962         if (wpipe->pipe_state & PIPE_EOF)
  963                 error = EPIPE;
  964         if (wpipe->pipe_state & PIPE_DIRECTW) {
  965                 /*
  966                  * this bit of trickery substitutes a kernel buffer for
  967                  * the process that might be going away.
  968                  */
  969                 pipe_clone_write_buffer(wpipe);
  970         } else {
  971                 pipe_destroy_write_buffer(wpipe);
  972         }
  973         pipeunlock(wpipe);
  974         return (error);
  975 
  976 error1:
  977         wakeup(wpipe);
  978         return (error);
  979 }
  980 #endif
  981 
  982 static int
  983 pipe_write(fp, uio, active_cred, flags, td)
  984         struct file *fp;
  985         struct uio *uio;
  986         struct ucred *active_cred;
  987         struct thread *td;
  988         int flags;
  989 {
  990         int error = 0;
  991         int desiredsize, orig_resid;
  992         struct pipe *wpipe, *rpipe;
  993 
  994         rpipe = fp->f_data;
  995         wpipe = rpipe->pipe_peer;
  996 
  997         PIPE_LOCK(rpipe);
  998         error = pipelock(wpipe, 1);
  999         if (error) {
 1000                 PIPE_UNLOCK(rpipe);
 1001                 return (error);
 1002         }
 1003         /*
 1004          * detect loss of pipe read side, issue SIGPIPE if lost.
 1005          */
 1006         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1007             (wpipe->pipe_state & PIPE_EOF)) {
 1008                 pipeunlock(wpipe);
 1009                 PIPE_UNLOCK(rpipe);
 1010                 return (EPIPE);
 1011         }
 1012 #ifdef MAC
 1013         error = mac_check_pipe_write(active_cred, wpipe->pipe_pair);
 1014         if (error) {
 1015                 pipeunlock(wpipe);
 1016                 PIPE_UNLOCK(rpipe);
 1017                 return (error);
 1018         }
 1019 #endif
 1020         ++wpipe->pipe_busy;
 1021 
 1022         /* Choose a larger size if it's advantageous */
 1023         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
 1024         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
 1025                 if (piperesizeallowed != 1)
 1026                         break;
 1027                 if (amountpipekva > maxpipekva / 2)
 1028                         break;
 1029                 if (desiredsize == BIG_PIPE_SIZE)
 1030                         break;
 1031                 desiredsize = desiredsize * 2;
 1032         }
 1033 
 1034         /* Choose a smaller size if we're in a OOM situation */
 1035         if ((amountpipekva > (3 * maxpipekva) / 4) &&
 1036                 (wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
 1037                 (wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
 1038                 (piperesizeallowed == 1))
 1039                 desiredsize = SMALL_PIPE_SIZE;
 1040 
 1041         /* Resize if the above determined that a new size was necessary */
 1042         if ((desiredsize != wpipe->pipe_buffer.size) &&
 1043                 ((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
 1044                 PIPE_UNLOCK(wpipe);
 1045                 pipespace(wpipe, desiredsize);
 1046                 PIPE_LOCK(wpipe);
 1047         }
 1048         if (wpipe->pipe_buffer.size == 0) {
 1049                 /*
 1050                  * This can only happen for reverse direction use of pipes
 1051                  * in a complete OOM situation.
 1052                  */
 1053                 error = ENOMEM;
 1054                 --wpipe->pipe_busy;
 1055                 pipeunlock(wpipe);
 1056                 PIPE_UNLOCK(wpipe);
 1057                 return (error);
 1058         }
 1059 
 1060         pipeunlock(wpipe);
 1061 
 1062         orig_resid = uio->uio_resid;
 1063 
 1064         while (uio->uio_resid) {
 1065                 int space;
 1066 
 1067                 pipelock(wpipe, 0);
 1068                 if (wpipe->pipe_state & PIPE_EOF) {
 1069                         pipeunlock(wpipe);
 1070                         error = EPIPE;
 1071                         break;
 1072                 }
 1073 #ifndef PIPE_NODIRECT
 1074                 /*
 1075                  * If the transfer is large, we can gain performance if
 1076                  * we do process-to-process copies directly.
 1077                  * If the write is non-blocking, we don't use the
 1078                  * direct write mechanism.
 1079                  *
 1080                  * The direct write mechanism will detect the reader going
 1081                  * away on us.
 1082                  */
 1083                 if ((uio->uio_iov->iov_len >= PIPE_MINDIRECT) &&
 1084                     (wpipe->pipe_buffer.size >= PIPE_MINDIRECT) &&
 1085                     (fp->f_flag & FNONBLOCK) == 0) {
 1086                         pipeunlock(wpipe);
 1087                         error = pipe_direct_write(wpipe, uio);
 1088                         if (error)
 1089                                 break;
 1090                         continue;
 1091                 }
 1092 #endif
 1093 
 1094                 /*
 1095                  * Pipe buffered writes cannot be coincidental with
 1096                  * direct writes.  We wait until the currently executing
 1097                  * direct write is completed before we start filling the
 1098                  * pipe buffer.  We break out if a signal occurs or the
 1099                  * reader goes away.
 1100                  */
 1101                 if (wpipe->pipe_state & PIPE_DIRECTW) {
 1102                         if (wpipe->pipe_state & PIPE_WANTR) {
 1103                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1104                                 wakeup(wpipe);
 1105                         }
 1106                         pipeselwakeup(wpipe);
 1107                         wpipe->pipe_state |= PIPE_WANTW;
 1108                         pipeunlock(wpipe);
 1109                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
 1110                             "pipbww", 0);
 1111                         if (error)
 1112                                 break;
 1113                         else
 1114                                 continue;
 1115                 }
 1116 
 1117                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1118 
 1119                 /* Writes of size <= PIPE_BUF must be atomic. */
 1120                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
 1121                         space = 0;
 1122 
 1123                 if (space > 0) {
 1124                         int size;       /* Transfer size */
 1125                         int segsize;    /* first segment to transfer */
 1126 
 1127                         /*
 1128                          * Transfer size is minimum of uio transfer
 1129                          * and free space in pipe buffer.
 1130                          */
 1131                         if (space > uio->uio_resid)
 1132                                 size = uio->uio_resid;
 1133                         else
 1134                                 size = space;
 1135                         /*
 1136                          * First segment to transfer is minimum of
 1137                          * transfer size and contiguous space in
 1138                          * pipe buffer.  If first segment to transfer
 1139                          * is less than the transfer size, we've got
 1140                          * a wraparound in the buffer.
 1141                          */
 1142                         segsize = wpipe->pipe_buffer.size -
 1143                                 wpipe->pipe_buffer.in;
 1144                         if (segsize > size)
 1145                                 segsize = size;
 1146 
 1147                         /* Transfer first segment */
 1148 
 1149                         PIPE_UNLOCK(rpipe);
 1150                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
 1151                                         segsize, uio);
 1152                         PIPE_LOCK(rpipe);
 1153 
 1154                         if (error == 0 && segsize < size) {
 1155                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
 1156                                         wpipe->pipe_buffer.size,
 1157                                         ("Pipe buffer wraparound disappeared"));
 1158                                 /*
 1159                                  * Transfer remaining part now, to
 1160                                  * support atomic writes.  Wraparound
 1161                                  * happened.
 1162                                  */
 1163 
 1164                                 PIPE_UNLOCK(rpipe);
 1165                                 error = uiomove(
 1166                                     &wpipe->pipe_buffer.buffer[0],
 1167                                     size - segsize, uio);
 1168                                 PIPE_LOCK(rpipe);
 1169                         }
 1170                         if (error == 0) {
 1171                                 wpipe->pipe_buffer.in += size;
 1172                                 if (wpipe->pipe_buffer.in >=
 1173                                     wpipe->pipe_buffer.size) {
 1174                                         KASSERT(wpipe->pipe_buffer.in ==
 1175                                                 size - segsize +
 1176                                                 wpipe->pipe_buffer.size,
 1177                                                 ("Expected wraparound bad"));
 1178                                         wpipe->pipe_buffer.in = size - segsize;
 1179                                 }
 1180 
 1181                                 wpipe->pipe_buffer.cnt += size;
 1182                                 KASSERT(wpipe->pipe_buffer.cnt <=
 1183                                         wpipe->pipe_buffer.size,
 1184                                         ("Pipe buffer overflow"));
 1185                         }
 1186                         pipeunlock(wpipe);
 1187                         if (error != 0)
 1188                                 break;
 1189                 } else {
 1190                         /*
 1191                          * If the "read-side" has been blocked, wake it up now.
 1192                          */
 1193                         if (wpipe->pipe_state & PIPE_WANTR) {
 1194                                 wpipe->pipe_state &= ~PIPE_WANTR;
 1195                                 wakeup(wpipe);
 1196                         }
 1197 
 1198                         /*
 1199                          * don't block on non-blocking I/O
 1200                          */
 1201                         if (fp->f_flag & FNONBLOCK) {
 1202                                 error = EAGAIN;
 1203                                 pipeunlock(wpipe);
 1204                                 break;
 1205                         }
 1206 
 1207                         /*
 1208                          * We have no more space and have something to offer,
 1209                          * wake up select/poll.
 1210                          */
 1211                         pipeselwakeup(wpipe);
 1212 
 1213                         wpipe->pipe_state |= PIPE_WANTW;
 1214                         pipeunlock(wpipe);
 1215                         error = msleep(wpipe, PIPE_MTX(rpipe),
 1216                             PRIBIO | PCATCH, "pipewr", 0);
 1217                         if (error != 0)
 1218                                 break;
 1219                 }
 1220         }
 1221 
 1222         pipelock(wpipe, 0);
 1223         --wpipe->pipe_busy;
 1224 
 1225         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
 1226                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
 1227                 wakeup(wpipe);
 1228         } else if (wpipe->pipe_buffer.cnt > 0) {
 1229                 /*
 1230                  * If we have put any characters in the buffer, we wake up
 1231                  * the reader.
 1232                  */
 1233                 if (wpipe->pipe_state & PIPE_WANTR) {
 1234                         wpipe->pipe_state &= ~PIPE_WANTR;
 1235                         wakeup(wpipe);
 1236                 }
 1237         }
 1238 
 1239         /*
 1240          * Don't return EPIPE if I/O was successful
 1241          */
 1242         if ((wpipe->pipe_buffer.cnt == 0) &&
 1243             (uio->uio_resid == 0) &&
 1244             (error == EPIPE)) {
 1245                 error = 0;
 1246         }
 1247 
 1248         if (error == 0)
 1249                 vfs_timestamp(&wpipe->pipe_mtime);
 1250 
 1251         /*
 1252          * We have something to offer,
 1253          * wake up select/poll.
 1254          */
 1255         if (wpipe->pipe_buffer.cnt)
 1256                 pipeselwakeup(wpipe);
 1257 
 1258         pipeunlock(wpipe);
 1259         PIPE_UNLOCK(rpipe);
 1260         return (error);
 1261 }
 1262 
 1263 /*
 1264  * we implement a very minimal set of ioctls for compatibility with sockets.
 1265  */
 1266 static int
 1267 pipe_ioctl(fp, cmd, data, active_cred, td)
 1268         struct file *fp;
 1269         u_long cmd;
 1270         void *data;
 1271         struct ucred *active_cred;
 1272         struct thread *td;
 1273 {
 1274         struct pipe *mpipe = fp->f_data;
 1275         int error;
 1276 
 1277         PIPE_LOCK(mpipe);
 1278 
 1279 #ifdef MAC
 1280         error = mac_check_pipe_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
 1281         if (error) {
 1282                 PIPE_UNLOCK(mpipe);
 1283                 return (error);
 1284         }
 1285 #endif
 1286 
 1287         error = 0;
 1288         switch (cmd) {
 1289 
 1290         case FIONBIO:
 1291                 break;
 1292 
 1293         case FIOASYNC:
 1294                 if (*(int *)data) {
 1295                         mpipe->pipe_state |= PIPE_ASYNC;
 1296                 } else {
 1297                         mpipe->pipe_state &= ~PIPE_ASYNC;
 1298                 }
 1299                 break;
 1300 
 1301         case FIONREAD:
 1302                 if (mpipe->pipe_state & PIPE_DIRECTW)
 1303                         *(int *)data = mpipe->pipe_map.cnt;
 1304                 else
 1305                         *(int *)data = mpipe->pipe_buffer.cnt;
 1306                 break;
 1307 
 1308         case FIOSETOWN:
 1309                 PIPE_UNLOCK(mpipe);
 1310                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
 1311                 goto out_unlocked;
 1312 
 1313         case FIOGETOWN:
 1314                 *(int *)data = fgetown(&mpipe->pipe_sigio);
 1315                 break;
 1316 
 1317         /* This is deprecated, FIOSETOWN should be used instead. */
 1318         case TIOCSPGRP:
 1319                 PIPE_UNLOCK(mpipe);
 1320                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
 1321                 goto out_unlocked;
 1322 
 1323         /* This is deprecated, FIOGETOWN should be used instead. */
 1324         case TIOCGPGRP:
 1325                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
 1326                 break;
 1327 
 1328         default:
 1329                 error = ENOTTY;
 1330                 break;
 1331         }
 1332         PIPE_UNLOCK(mpipe);
 1333 out_unlocked:
 1334         return (error);
 1335 }
 1336 
 1337 static int
 1338 pipe_poll(fp, events, active_cred, td)
 1339         struct file *fp;
 1340         int events;
 1341         struct ucred *active_cred;
 1342         struct thread *td;
 1343 {
 1344         struct pipe *rpipe = fp->f_data;
 1345         struct pipe *wpipe;
 1346         int revents = 0;
 1347 #ifdef MAC
 1348         int error;
 1349 #endif
 1350 
 1351         wpipe = rpipe->pipe_peer;
 1352         PIPE_LOCK(rpipe);
 1353 #ifdef MAC
 1354         error = mac_check_pipe_poll(active_cred, rpipe->pipe_pair);
 1355         if (error)
 1356                 goto locked_error;
 1357 #endif
 1358         if (events & (POLLIN | POLLRDNORM))
 1359                 if ((rpipe->pipe_state & PIPE_DIRECTW) ||
 1360                     (rpipe->pipe_buffer.cnt > 0) ||
 1361                     (rpipe->pipe_state & PIPE_EOF))
 1362                         revents |= events & (POLLIN | POLLRDNORM);
 1363 
 1364         if (events & (POLLOUT | POLLWRNORM))
 1365                 if (wpipe->pipe_present != PIPE_ACTIVE ||
 1366                     (wpipe->pipe_state & PIPE_EOF) ||
 1367                     (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
 1368                      (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF))
 1369                         revents |= events & (POLLOUT | POLLWRNORM);
 1370 
 1371         if ((rpipe->pipe_state & PIPE_EOF) ||
 1372             wpipe->pipe_present != PIPE_ACTIVE ||
 1373             (wpipe->pipe_state & PIPE_EOF))
 1374                 revents |= POLLHUP;
 1375 
 1376         if (revents == 0) {
 1377                 if (events & (POLLIN | POLLRDNORM)) {
 1378                         selrecord(td, &rpipe->pipe_sel);
 1379                         rpipe->pipe_state |= PIPE_SEL;
 1380                 }
 1381 
 1382                 if (events & (POLLOUT | POLLWRNORM)) {
 1383                         selrecord(td, &wpipe->pipe_sel);
 1384                         wpipe->pipe_state |= PIPE_SEL;
 1385                 }
 1386         }
 1387 #ifdef MAC
 1388 locked_error:
 1389 #endif
 1390         PIPE_UNLOCK(rpipe);
 1391 
 1392         return (revents);
 1393 }
 1394 
 1395 /*
 1396  * We shouldn't need locks here as we're doing a read and this should
 1397  * be a natural race.
 1398  */
 1399 static int
 1400 pipe_stat(fp, ub, active_cred, td)
 1401         struct file *fp;
 1402         struct stat *ub;
 1403         struct ucred *active_cred;
 1404         struct thread *td;
 1405 {
 1406         struct pipe *pipe = fp->f_data;
 1407 #ifdef MAC
 1408         int error;
 1409 
 1410         PIPE_LOCK(pipe);
 1411         error = mac_check_pipe_stat(active_cred, pipe->pipe_pair);
 1412         PIPE_UNLOCK(pipe);
 1413         if (error)
 1414                 return (error);
 1415 #endif
 1416         bzero(ub, sizeof(*ub));
 1417         ub->st_mode = S_IFIFO;
 1418         ub->st_blksize = PAGE_SIZE;
 1419         if (pipe->pipe_state & PIPE_DIRECTW)
 1420                 ub->st_size = pipe->pipe_map.cnt;
 1421         else
 1422                 ub->st_size = pipe->pipe_buffer.cnt;
 1423         ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
 1424         ub->st_atimespec = pipe->pipe_atime;
 1425         ub->st_mtimespec = pipe->pipe_mtime;
 1426         ub->st_ctimespec = pipe->pipe_ctime;
 1427         ub->st_uid = fp->f_cred->cr_uid;
 1428         ub->st_gid = fp->f_cred->cr_gid;
 1429         /*
 1430          * Left as 0: st_dev, st_ino, st_nlink, st_rdev, st_flags, st_gen.
 1431          * XXX (st_dev, st_ino) should be unique.
 1432          */
 1433         return (0);
 1434 }
 1435 
 1436 /* ARGSUSED */
 1437 static int
 1438 pipe_close(fp, td)
 1439         struct file *fp;
 1440         struct thread *td;
 1441 {
 1442         struct pipe *cpipe = fp->f_data;
 1443 
 1444         fp->f_ops = &badfileops;
 1445         fp->f_data = NULL;
 1446         funsetown(&cpipe->pipe_sigio);
 1447         pipeclose(cpipe);
 1448         return (0);
 1449 }
 1450 
 1451 static void
 1452 pipe_free_kmem(cpipe)
 1453         struct pipe *cpipe;
 1454 {
 1455 
 1456         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
 1457             ("pipe_free_kmem: pipe mutex locked"));
 1458 
 1459         if (cpipe->pipe_buffer.buffer != NULL) {
 1460                 atomic_subtract_int(&amountpipekva, cpipe->pipe_buffer.size);
 1461                 vm_map_remove(pipe_map,
 1462                     (vm_offset_t)cpipe->pipe_buffer.buffer,
 1463                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
 1464                 cpipe->pipe_buffer.buffer = NULL;
 1465         }
 1466 #ifndef PIPE_NODIRECT
 1467         {
 1468                 cpipe->pipe_map.cnt = 0;
 1469                 cpipe->pipe_map.pos = 0;
 1470                 cpipe->pipe_map.npages = 0;
 1471         }
 1472 #endif
 1473 }
 1474 
 1475 /*
 1476  * shutdown the pipe
 1477  */
 1478 static void
 1479 pipeclose(cpipe)
 1480         struct pipe *cpipe;
 1481 {
 1482         struct pipepair *pp;
 1483         struct pipe *ppipe;
 1484 
 1485         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
 1486 
 1487         PIPE_LOCK(cpipe);
 1488         pipelock(cpipe, 0);
 1489         pp = cpipe->pipe_pair;
 1490 
 1491         pipeselwakeup(cpipe);
 1492 
 1493         /*
 1494          * If the other side is blocked, wake it up saying that
 1495          * we want to close it down.
 1496          */
 1497         cpipe->pipe_state |= PIPE_EOF;
 1498         while (cpipe->pipe_busy) {
 1499                 wakeup(cpipe);
 1500                 cpipe->pipe_state |= PIPE_WANT;
 1501                 pipeunlock(cpipe);
 1502                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
 1503                 pipelock(cpipe, 0);
 1504         }
 1505 
 1506 
 1507         /*
 1508          * Disconnect from peer, if any.
 1509          */
 1510         ppipe = cpipe->pipe_peer;
 1511         if (ppipe->pipe_present == PIPE_ACTIVE) {
 1512                 pipeselwakeup(ppipe);
 1513 
 1514                 ppipe->pipe_state |= PIPE_EOF;
 1515                 wakeup(ppipe);
 1516                 KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
 1517         }
 1518 
 1519         /*
 1520          * Mark this endpoint as free.  Release kmem resources.  We
 1521          * don't mark this endpoint as unused until we've finished
 1522          * doing that, or the pipe might disappear out from under
 1523          * us.
 1524          */
 1525         PIPE_UNLOCK(cpipe);
 1526         pipe_free_kmem(cpipe);
 1527         PIPE_LOCK(cpipe);
 1528         cpipe->pipe_present = PIPE_CLOSING;
 1529         pipeunlock(cpipe);
 1530 
 1531         /*
 1532          * knlist_clear() may sleep dropping the PIPE_MTX. Set the
 1533          * PIPE_FINALIZED, that allows other end to free the
 1534          * pipe_pair, only after the knotes are completely dismantled.
 1535          */
 1536         knlist_clear(&cpipe->pipe_sel.si_note, 1);
 1537         cpipe->pipe_present = PIPE_FINALIZED;
 1538         knlist_destroy(&cpipe->pipe_sel.si_note);
 1539 
 1540         /*
 1541          * If both endpoints are now closed, release the memory for the
 1542          * pipe pair.  If not, unlock.
 1543          */
 1544         if (ppipe->pipe_present == PIPE_FINALIZED) {
 1545                 PIPE_UNLOCK(cpipe);
 1546 #ifdef MAC
 1547                 mac_destroy_pipe(pp);
 1548 #endif
 1549                 uma_zfree(pipe_zone, cpipe->pipe_pair);
 1550         } else
 1551                 PIPE_UNLOCK(cpipe);
 1552 }
 1553 
 1554 /*ARGSUSED*/
 1555 static int
 1556 pipe_kqfilter(struct file *fp, struct knote *kn)
 1557 {
 1558         struct pipe *cpipe;
 1559 
 1560         cpipe = kn->kn_fp->f_data;
 1561         PIPE_LOCK(cpipe);
 1562         switch (kn->kn_filter) {
 1563         case EVFILT_READ:
 1564                 kn->kn_fop = &pipe_rfiltops;
 1565                 break;
 1566         case EVFILT_WRITE:
 1567                 kn->kn_fop = &pipe_wfiltops;
 1568                 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
 1569                         /* other end of pipe has been closed */
 1570                         PIPE_UNLOCK(cpipe);
 1571                         return (EPIPE);
 1572                 }
 1573                 cpipe = cpipe->pipe_peer;
 1574                 break;
 1575         default:
 1576                 PIPE_UNLOCK(cpipe);
 1577                 return (EINVAL);
 1578         }
 1579 
 1580         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
 1581         PIPE_UNLOCK(cpipe);
 1582         return (0);
 1583 }
 1584 
 1585 static void
 1586 filt_pipedetach(struct knote *kn)
 1587 {
 1588         struct pipe *cpipe = (struct pipe *)kn->kn_fp->f_data;
 1589 
 1590         PIPE_LOCK(cpipe);
 1591         if (kn->kn_filter == EVFILT_WRITE)
 1592                 cpipe = cpipe->pipe_peer;
 1593         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
 1594         PIPE_UNLOCK(cpipe);
 1595 }
 1596 
 1597 /*ARGSUSED*/
 1598 static int
 1599 filt_piperead(struct knote *kn, long hint)
 1600 {
 1601         struct pipe *rpipe = kn->kn_fp->f_data;
 1602         struct pipe *wpipe = rpipe->pipe_peer;
 1603         int ret;
 1604 
 1605         PIPE_LOCK(rpipe);
 1606         kn->kn_data = rpipe->pipe_buffer.cnt;
 1607         if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
 1608                 kn->kn_data = rpipe->pipe_map.cnt;
 1609 
 1610         if ((rpipe->pipe_state & PIPE_EOF) ||
 1611             wpipe->pipe_present != PIPE_ACTIVE ||
 1612             (wpipe->pipe_state & PIPE_EOF)) {
 1613                 kn->kn_flags |= EV_EOF;
 1614                 PIPE_UNLOCK(rpipe);
 1615                 return (1);
 1616         }
 1617         ret = kn->kn_data > 0;
 1618         PIPE_UNLOCK(rpipe);
 1619         return ret;
 1620 }
 1621 
 1622 /*ARGSUSED*/
 1623 static int
 1624 filt_pipewrite(struct knote *kn, long hint)
 1625 {
 1626         struct pipe *rpipe = kn->kn_fp->f_data;
 1627         struct pipe *wpipe = rpipe->pipe_peer;
 1628 
 1629         PIPE_LOCK(rpipe);
 1630         if (wpipe->pipe_present != PIPE_ACTIVE ||
 1631             (wpipe->pipe_state & PIPE_EOF)) {
 1632                 kn->kn_data = 0;
 1633                 kn->kn_flags |= EV_EOF;
 1634                 PIPE_UNLOCK(rpipe);
 1635                 return (1);
 1636         }
 1637         kn->kn_data = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
 1638         if (wpipe->pipe_state & PIPE_DIRECTW)
 1639                 kn->kn_data = 0;
 1640 
 1641         PIPE_UNLOCK(rpipe);
 1642         return (kn->kn_data >= PIPE_BUF);
 1643 }

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