sys/kern/sys_pipe.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-4-Clause
   3  *
   4  * Copyright (c) 1996 John S. Dyson
   5  * Copyright (c) 2012 Giovanni Trematerra
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice immediately at the beginning of the file, without modification,
  13  *    this list of conditions, and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 3. Absolutely no warranty of function or purpose is made by the author
  18  *    John S. Dyson.
  19  * 4. Modifications may be freely made to this file if the above conditions
  20  *    are met.
  21  */
  22
  23 /*
  24  * This file contains a high-performance replacement for the socket-based
  25  * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
  26  * all features of sockets, but does do everything that pipes normally
  27  * do.
  28  */
  29
  30 /*
  31  * This code has two modes of operation, a small write mode and a large
  32  * write mode.  The small write mode acts like conventional pipes with
  33  * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
  34  * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
  35  * and PIPE_SIZE in size, the sending process pins the underlying pages in
  36  * memory, and the receiving process copies directly from these pinned pages
  37  * in the sending process.
  38  *
  39  * If the sending process receives a signal, it is possible that it will
  40  * go away, and certainly its address space can change, because control
  41  * is returned back to the user-mode side.  In that case, the pipe code
  42  * arranges to copy the buffer supplied by the user process, to a pageable
  43  * kernel buffer, and the receiving process will grab the data from the
  44  * pageable kernel buffer.  Since signals don't happen all that often,
  45  * the copy operation is normally eliminated.
  46  *
  47  * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
  48  * happen for small transfers so that the system will not spend all of
  49  * its time context switching.
  50  *
  51  * In order to limit the resource use of pipes, two sysctls exist:
  52  *
  53  * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
  54  * address space available to us in pipe_map. This value is normally
  55  * autotuned, but may also be loader tuned.
  56  *
  57  * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
  58  * memory in use by pipes.
  59  *
  60  * Based on how large pipekva is relative to maxpipekva, the following
  61  * will happen:
  62  *
  63  * 0% - 50%:
  64  *     New pipes are given 16K of memory backing, pipes may dynamically
  65  *     grow to as large as 64K where needed.
  66  * 50% - 75%:
  67  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
  68  *     existing pipes may NOT grow.
  69  * 75% - 100%:
  70  *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
  71  *     existing pipes will be shrunk down to 4K whenever possible.
  72  *
  73  * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
  74  * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
  75  * resize which MUST occur for reverse-direction pipes when they are
  76  * first used.
  77  *
  78  * Additional information about the current state of pipes may be obtained
  79  * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
  80  * and kern.ipc.piperesizefail.
  81  *
  82  * Locking rules:  There are two locks present here:  A mutex, used via
  83  * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
  84  * the flag, as mutexes can not persist over uiomove.  The mutex
  85  * exists only to guard access to the flag, and is not in itself a
  86  * locking mechanism.  Also note that there is only a single mutex for
  87  * both directions of a pipe.
  88  *
  89  * As pipelock() may have to sleep before it can acquire the flag, it
  90  * is important to reread all data after a call to pipelock(); everything
  91  * in the structure may have changed.
  92  */
  93
  94 #include <sys/cdefs.h>
  95 __FBSDID("$FreeBSD$");
  96
  97 #include <sys/param.h>
  98 #include <sys/systm.h>
  99 #include <sys/conf.h>
 100 #include <sys/fcntl.h>
 101 #include <sys/file.h>
 102 #include <sys/filedesc.h>
 103 #include <sys/filio.h>
 104 #include <sys/kernel.h>
 105 #include <sys/lock.h>
 106 #include <sys/mutex.h>
 107 #include <sys/ttycom.h>
 108 #include <sys/stat.h>
 109 #include <sys/malloc.h>
 110 #include <sys/poll.h>
 111 #include <sys/selinfo.h>
 112 #include <sys/signalvar.h>
 113 #include <sys/syscallsubr.h>
 114 #include <sys/sysctl.h>
 115 #include <sys/sysproto.h>
 116 #include <sys/pipe.h>
 117 #include <sys/proc.h>
 118 #include <sys/vnode.h>
 119 #include <sys/uio.h>
 120 #include <sys/user.h>
 121 #include <sys/event.h>
 122
 123 #include <security/mac/mac_framework.h>
 124
 125 #include <vm/vm.h>
 126 #include <vm/vm_param.h>
 127 #include <vm/vm_object.h>
 128 #include <vm/vm_kern.h>
 129 #include <vm/vm_extern.h>
 130 #include <vm/pmap.h>
 131 #include <vm/vm_map.h>
 132 #include <vm/vm_page.h>
 133 #include <vm/uma.h>
 134
 135 /*
 136  * Use this define if you want to disable *fancy* VM things.  Expect an
 137  * approx 30% decrease in transfer rate.  This could be useful for
 138  * NetBSD or OpenBSD.
 139  */
 140 /* #define PIPE_NODIRECT */
 141
 142 #define PIPE_PEER(pipe) \
 143         (((pipe)->pipe_type & PIPE_TYPE_NAMED) ? (pipe) : ((pipe)->pipe_peer))
 144
 145 /*
 146  * interfaces to the outside world
 147  */
 148 static fo_rdwr_t        pipe_read;
 149 static fo_rdwr_t        pipe_write;
 150 static fo_truncate_t    pipe_truncate;
 151 static fo_ioctl_t       pipe_ioctl;
 152 static fo_poll_t        pipe_poll;
 153 static fo_kqfilter_t    pipe_kqfilter;
 154 static fo_stat_t        pipe_stat;
 155 static fo_close_t       pipe_close;
 156 static fo_chmod_t       pipe_chmod;
 157 static fo_chown_t       pipe_chown;
 158 static fo_fill_kinfo_t  pipe_fill_kinfo;
 159
 160 struct fileops pipeops = {
 161         .fo_read = pipe_read,
 162         .fo_write = pipe_write,
 163         .fo_truncate = pipe_truncate,
 164         .fo_ioctl = pipe_ioctl,
 165         .fo_poll = pipe_poll,
 166         .fo_kqfilter = pipe_kqfilter,
 167         .fo_stat = pipe_stat,
 168         .fo_close = pipe_close,
 169         .fo_chmod = pipe_chmod,
 170         .fo_chown = pipe_chown,
 171         .fo_sendfile = invfo_sendfile,
 172         .fo_fill_kinfo = pipe_fill_kinfo,
 173         .fo_flags = DFLAG_PASSABLE
 174 };
 175
 176 static void     filt_pipedetach(struct knote *kn);
 177 static void     filt_pipedetach_notsup(struct knote *kn);
 178 static int      filt_pipenotsup(struct knote *kn, long hint);
 179 static int      filt_piperead(struct knote *kn, long hint);
 180 static int      filt_pipewrite(struct knote *kn, long hint);
 181
 182 static struct filterops pipe_nfiltops = {
 183         .f_isfd = 1,
 184         .f_detach = filt_pipedetach_notsup,
 185         .f_event = filt_pipenotsup
 186 };
 187 static struct filterops pipe_rfiltops = {
 188         .f_isfd = 1,
 189         .f_detach = filt_pipedetach,
 190         .f_event = filt_piperead
 191 };
 192 static struct filterops pipe_wfiltops = {
 193         .f_isfd = 1,
 194         .f_detach = filt_pipedetach,
 195         .f_event = filt_pipewrite
 196 };
 197
 198 /*
 199  * Default pipe buffer size(s), this can be kind-of large now because pipe
 200  * space is pageable.  The pipe code will try to maintain locality of
 201  * reference for performance reasons, so small amounts of outstanding I/O
 202  * will not wipe the cache.
 203  */
 204 #define MINPIPESIZE (PIPE_SIZE/3)
 205 #define MAXPIPESIZE (2*PIPE_SIZE/3)
 206
 207 static long amountpipekva;
 208 static int pipefragretry;
 209 static int pipeallocfail;
 210 static int piperesizefail;
 211 static int piperesizeallowed = 1;
 212 static long pipe_mindirect = PIPE_MINDIRECT;
 213
 214 SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
 215            &maxpipekva, 0, "Pipe KVA limit");
 216 SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
 217            &amountpipekva, 0, "Pipe KVA usage");
 218 SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
 219           &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
 220 SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
 221           &pipeallocfail, 0, "Pipe allocation failures");
 222 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
 223           &piperesizefail, 0, "Pipe resize failures");
 224 SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
 225           &piperesizeallowed, 0, "Pipe resizing allowed");
 226
 227 static void pipeinit(void *dummy __unused);
 228 static void pipeclose(struct pipe *cpipe);
 229 static void pipe_free_kmem(struct pipe *cpipe);
 230 static int pipe_create(struct pipe *pipe, bool backing);
 231 static int pipe_paircreate(struct thread *td, struct pipepair **p_pp);
 232 static __inline int pipelock(struct pipe *cpipe, int catch);
 233 static __inline void pipeunlock(struct pipe *cpipe);
 234 static void pipe_timestamp(struct timespec *tsp);
 235 #ifndef PIPE_NODIRECT
 236 static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
 237 static void pipe_destroy_write_buffer(struct pipe *wpipe);
 238 static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
 239 static void pipe_clone_write_buffer(struct pipe *wpipe);
 240 #endif
 241 static int pipespace(struct pipe *cpipe, int size);
 242 static int pipespace_new(struct pipe *cpipe, int size);
 243
 244 static int      pipe_zone_ctor(void *mem, int size, void *arg, int flags);
 245 static int      pipe_zone_init(void *mem, int size, int flags);
 246 static void     pipe_zone_fini(void *mem, int size);
 247
 248 static uma_zone_t pipe_zone;
 249 static struct unrhdr64 pipeino_unr;
 250 static dev_t pipedev_ino;
 251
 252 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
 253
 254 static void
 255 pipeinit(void *dummy __unused)
 256 {
 257
 258         pipe_zone = uma_zcreate("pipe", sizeof(struct pipepair),
 259             pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
 260             UMA_ALIGN_PTR, 0);
 261         KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
 262         new_unrhdr64(&pipeino_unr, 1);
 263         pipedev_ino = devfs_alloc_cdp_inode();
 264         KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
 265 }
 266
 267 static int
 268 sysctl_handle_pipe_mindirect(SYSCTL_HANDLER_ARGS)
 269 {
 270         int error = 0;
 271         long tmp_pipe_mindirect = pipe_mindirect;
 272
 273         error = sysctl_handle_long(oidp, &tmp_pipe_mindirect, arg2, req);
 274         if (error != 0 || req->newptr == NULL)
 275                 return (error);
 276
 277         /*
 278          * Don't allow pipe_mindirect to be set so low that we violate
 279          * atomicity requirements.
 280          */
 281         if (tmp_pipe_mindirect <= PIPE_BUF)
 282                 return (EINVAL);
 283         pipe_mindirect = tmp_pipe_mindirect;
 284         return (0);
 285 }
 286 SYSCTL_OID(_kern_ipc, OID_AUTO, pipe_mindirect, CTLTYPE_LONG | CTLFLAG_RW,
 287     &pipe_mindirect, 0, sysctl_handle_pipe_mindirect, "L",
 288     "Minimum write size triggering VM optimization");
 289
 290 static int
 291 pipe_zone_ctor(void *mem, int size, void *arg, int flags)
 292 {
 293         struct pipepair *pp;
 294         struct pipe *rpipe, *wpipe;
 295
 296         KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
 297
 298         pp = (struct pipepair *)mem;
 299
 300         /*
 301          * We zero both pipe endpoints to make sure all the kmem pointers
 302          * are NULL, flag fields are zero'd, etc.  We timestamp both
 303          * endpoints with the same time.
 304          */
 305         rpipe = &pp->pp_rpipe;
 306         bzero(rpipe, sizeof(*rpipe));
 307         pipe_timestamp(&rpipe->pipe_ctime);
 308         rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
 309
 310         wpipe = &pp->pp_wpipe;
 311         bzero(wpipe, sizeof(*wpipe));
 312         wpipe->pipe_ctime = rpipe->pipe_ctime;
 313         wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
 314
 315         rpipe->pipe_peer = wpipe;
 316         rpipe->pipe_pair = pp;
 317         wpipe->pipe_peer = rpipe;
 318         wpipe->pipe_pair = pp;
 319
 320         /*
 321          * Mark both endpoints as present; they will later get free'd
 322          * one at a time.  When both are free'd, then the whole pair
 323          * is released.
 324          */
 325         rpipe->pipe_present = PIPE_ACTIVE;
 326         wpipe->pipe_present = PIPE_ACTIVE;
 327
 328         /*
 329          * Eventually, the MAC Framework may initialize the label
 330          * in ctor or init, but for now we do it elswhere to avoid
 331          * blocking in ctor or init.
 332          */
 333         pp->pp_label = NULL;
 334
 335         return (0);
 336 }
 337
 338 static int
 339 pipe_zone_init(void *mem, int size, int flags)
 340 {
 341         struct pipepair *pp;
 342
 343         KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
 344
 345         pp = (struct pipepair *)mem;
 346
 347         mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_NEW);
 348         return (0);
 349 }
 350
 351 static void
 352 pipe_zone_fini(void *mem, int size)
 353 {
 354         struct pipepair *pp;
 355
 356         KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
 357
 358         pp = (struct pipepair *)mem;
 359
 360         mtx_destroy(&pp->pp_mtx);
 361 }
 362
 363 static int
 364 pipe_paircreate(struct thread *td, struct pipepair **p_pp)
 365 {
 366         struct pipepair *pp;
 367         struct pipe *rpipe, *wpipe;
 368         int error;
 369
 370         *p_pp = pp = uma_zalloc(pipe_zone, M_WAITOK);
 371 #ifdef MAC
 372         /*
 373          * The MAC label is shared between the connected endpoints.  As a
 374          * result mac_pipe_init() and mac_pipe_create() are called once
 375          * for the pair, and not on the endpoints.
 376          */
 377         mac_pipe_init(pp);
 378         mac_pipe_create(td->td_ucred, pp);
 379 #endif
 380         rpipe = &pp->pp_rpipe;
 381         wpipe = &pp->pp_wpipe;
 382
 383         knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
 384         knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
 385
 386         /*
 387          * Only the forward direction pipe is backed by big buffer by
 388          * default.
 389          */
 390         error = pipe_create(rpipe, true);
 391         if (error != 0)
 392                 goto fail;
 393         error = pipe_create(wpipe, false);
 394         if (error != 0) {
 395                 /*
 396                  * This cleanup leaves the pipe inode number for rpipe
 397                  * still allocated, but never used.  We do not free
 398                  * inode numbers for opened pipes, which is required
 399                  * for correctness because numbers must be unique.
 400                  * But also it avoids any memory use by the unr
 401                  * allocator, so stashing away the transient inode
 402                  * number is reasonable.
 403                  */
 404                 pipe_free_kmem(rpipe);
 405                 goto fail;
 406         }
 407
 408         rpipe->pipe_state |= PIPE_DIRECTOK;
 409         wpipe->pipe_state |= PIPE_DIRECTOK;
 410         return (0);
 411
 412 fail:
 413         knlist_destroy(&rpipe->pipe_sel.si_note);
 414         knlist_destroy(&wpipe->pipe_sel.si_note);
 415 #ifdef MAC
 416         mac_pipe_destroy(pp);
 417 #endif
 418         uma_zfree(pipe_zone, pp);
 419         return (error);
 420 }
 421
 422 int
 423 pipe_named_ctor(struct pipe **ppipe, struct thread *td)
 424 {
 425         struct pipepair *pp;
 426         int error;
 427
 428         error = pipe_paircreate(td, &pp);
 429         if (error != 0)
 430                 return (error);
 431         pp->pp_rpipe.pipe_type |= PIPE_TYPE_NAMED;
 432         *ppipe = &pp->pp_rpipe;
 433         return (0);
 434 }
 435
 436 void
 437 pipe_dtor(struct pipe *dpipe)
 438 {
 439         struct pipe *peer;
 440
 441         peer = (dpipe->pipe_type & PIPE_TYPE_NAMED) != 0 ? dpipe->pipe_peer : NULL;
 442         funsetown(&dpipe->pipe_sigio);
 443         pipeclose(dpipe);
 444         if (peer != NULL) {
 445                 funsetown(&peer->pipe_sigio);
 446                 pipeclose(peer);
 447         }
 448 }
 449
 450 /*
 451  * Get a timestamp.
 452  *
 453  * This used to be vfs_timestamp but the higher precision is unnecessary and
 454  * can very negatively affect performance in virtualized environments (e.g., on
 455  * vms running on amd64 when using the rdtscp instruction).
 456  */
 457 static void
 458 pipe_timestamp(struct timespec *tsp)
 459 {
 460
 461         getnanotime(tsp);
 462 }
 463
 464 /*
 465  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
 466  * the zone pick up the pieces via pipeclose().
 467  */
 468 int
 469 kern_pipe(struct thread *td, int fildes[2], int flags, struct filecaps *fcaps1,
 470     struct filecaps *fcaps2)
 471 {
 472         struct file *rf, *wf;
 473         struct pipe *rpipe, *wpipe;
 474         struct pipepair *pp;
 475         int fd, fflags, error;
 476
 477         error = pipe_paircreate(td, &pp);
 478         if (error != 0)
 479                 return (error);
 480         rpipe = &pp->pp_rpipe;
 481         wpipe = &pp->pp_wpipe;
 482         error = falloc_caps(td, &rf, &fd, flags, fcaps1);
 483         if (error) {
 484                 pipeclose(rpipe);
 485                 pipeclose(wpipe);
 486                 return (error);
 487         }
 488         /* An extra reference on `rf' has been held for us by falloc_caps(). */
 489         fildes[0] = fd;
 490
 491         fflags = FREAD | FWRITE;
 492         if ((flags & O_NONBLOCK) != 0)
 493                 fflags |= FNONBLOCK;
 494
 495         /*
 496          * Warning: once we've gotten past allocation of the fd for the
 497          * read-side, we can only drop the read side via fdrop() in order
 498          * to avoid races against processes which manage to dup() the read
 499          * side while we are blocked trying to allocate the write side.
 500          */
 501         finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
 502         error = falloc_caps(td, &wf, &fd, flags, fcaps2);
 503         if (error) {
 504                 fdclose(td, rf, fildes[0]);
 505                 fdrop(rf, td);
 506                 /* rpipe has been closed by fdrop(). */
 507                 pipeclose(wpipe);
 508                 return (error);
 509         }
 510         /* An extra reference on `wf' has been held for us by falloc_caps(). */
 511         finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
 512         fdrop(wf, td);
 513         fildes[1] = fd;
 514         fdrop(rf, td);
 515
 516         return (0);
 517 }
 518
 519 #ifdef COMPAT_FREEBSD10
 520 /* ARGSUSED */
 521 int
 522 freebsd10_pipe(struct thread *td, struct freebsd10_pipe_args *uap __unused)
 523 {
 524         int error;
 525         int fildes[2];
 526
 527         error = kern_pipe(td, fildes, 0, NULL, NULL);
 528         if (error)
 529                 return (error);
 530
 531         td->td_retval[0] = fildes[0];
 532         td->td_retval[1] = fildes[1];
 533
 534         return (0);
 535 }
 536 #endif
 537
 538 int
 539 sys_pipe2(struct thread *td, struct pipe2_args *uap)
 540 {
 541         int error, fildes[2];
 542
 543         if (uap->flags & ~(O_CLOEXEC | O_NONBLOCK))
 544                 return (EINVAL);
 545         error = kern_pipe(td, fildes, uap->flags, NULL, NULL);
 546         if (error)
 547                 return (error);
 548         error = copyout(fildes, uap->fildes, 2 * sizeof(int));
 549         if (error) {
 550                 (void)kern_close(td, fildes[0]);
 551                 (void)kern_close(td, fildes[1]);
 552         }
 553         return (error);
 554 }
 555
 556 /*
 557  * Allocate kva for pipe circular buffer, the space is pageable
 558  * This routine will 'realloc' the size of a pipe safely, if it fails
 559  * it will retain the old buffer.
 560  * If it fails it will return ENOMEM.
 561  */
 562 static int
 563 pipespace_new(struct pipe *cpipe, int size)
 564 {
 565         caddr_t buffer;
 566         int error, cnt, firstseg;
 567         static int curfail = 0;
 568         static struct timeval lastfail;
 569
 570         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
 571         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
 572                 ("pipespace: resize of direct writes not allowed"));
 573 retry:
 574         cnt = cpipe->pipe_buffer.cnt;
 575         if (cnt > size)
 576                 size = cnt;
 577
 578         size = round_page(size);
 579         buffer = (caddr_t) vm_map_min(pipe_map);
 580
 581         error = vm_map_find(pipe_map, NULL, 0, (vm_offset_t *)&buffer, size, 0,
 582             VMFS_ANY_SPACE, VM_PROT_RW, VM_PROT_RW, 0);
 583         if (error != KERN_SUCCESS) {
 584                 if (cpipe->pipe_buffer.buffer == NULL &&
 585                     size > SMALL_PIPE_SIZE) {
 586                         size = SMALL_PIPE_SIZE;
 587                         pipefragretry++;
 588                         goto retry;
 589                 }
 590                 if (cpipe->pipe_buffer.buffer == NULL) {
 591                         pipeallocfail++;
 592                         if (ppsratecheck(&lastfail, &curfail, 1))
 593                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
 594                 } else {
 595                         piperesizefail++;
 596                 }
 597                 return (ENOMEM);
 598         }
 599
 600         /* copy data, then free old resources if we're resizing */
 601         if (cnt > 0) {
 602                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
 603                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
 604                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
 605                                 buffer, firstseg);
 606                         if ((cnt - firstseg) > 0)
 607                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
 608                                         cpipe->pipe_buffer.in);
 609                 } else {
 610                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
 611                                 buffer, cnt);
 612                 }
 613         }
 614         pipe_free_kmem(cpipe);
 615         cpipe->pipe_buffer.buffer = buffer;
 616         cpipe->pipe_buffer.size = size;
 617         cpipe->pipe_buffer.in = cnt;
 618         cpipe->pipe_buffer.out = 0;
 619         cpipe->pipe_buffer.cnt = cnt;
 620         atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
 621         return (0);
 622 }
 623
 624 /*
 625  * Wrapper for pipespace_new() that performs locking assertions.
 626  */
 627 static int
 628 pipespace(struct pipe *cpipe, int size)
 629 {
 630
 631         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
 632             ("Unlocked pipe passed to pipespace"));
 633         return (pipespace_new(cpipe, size));
 634 }
 635
 636 /*
 637  * lock a pipe for I/O, blocking other access
 638  */
 639 static __inline int
 640 pipelock(struct pipe *cpipe, int catch)
 641 {
 642         int error, prio;
 643
 644         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 645
 646         prio = PRIBIO;
 647         if (catch)
 648                 prio |= PCATCH;
 649         while (cpipe->pipe_state & PIPE_LOCKFL) {
 650                 KASSERT(cpipe->pipe_waiters >= 0,
 651                     ("%s: bad waiter count %d", __func__,
 652                     cpipe->pipe_waiters));
 653                 cpipe->pipe_waiters++;
 654                 error = msleep(cpipe, PIPE_MTX(cpipe),
 655                     prio, "pipelk", 0);
 656                 cpipe->pipe_waiters--;
 657                 if (error != 0)
 658                         return (error);
 659         }
 660         cpipe->pipe_state |= PIPE_LOCKFL;
 661         return (0);
 662 }
 663
 664 /*
 665  * unlock a pipe I/O lock
 666  */
 667 static __inline void
 668 pipeunlock(struct pipe *cpipe)
 669 {
 670
 671         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 672         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
 673                 ("Unlocked pipe passed to pipeunlock"));
 674         KASSERT(cpipe->pipe_waiters >= 0,
 675             ("%s: bad waiter count %d", __func__,
 676             cpipe->pipe_waiters));
 677         cpipe->pipe_state &= ~PIPE_LOCKFL;
 678         if (cpipe->pipe_waiters > 0) {
 679                 wakeup_one(cpipe);
 680         }
 681 }
 682
 683 void
 684 pipeselwakeup(struct pipe *cpipe)
 685 {
 686
 687         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 688         if (cpipe->pipe_state & PIPE_SEL) {
 689                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
 690                 if (!SEL_WAITING(&cpipe->pipe_sel))
 691                         cpipe->pipe_state &= ~PIPE_SEL;
 692         }
 693         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
 694                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
 695         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
 696 }
 697
 698 /*
 699  * Initialize and allocate VM and memory for pipe.  The structure
 700  * will start out zero'd from the ctor, so we just manage the kmem.
 701  */
 702 static int
 703 pipe_create(struct pipe *pipe, bool large_backing)
 704 {
 705         int error;
 706
 707         error = pipespace_new(pipe, !large_backing || amountpipekva >
 708             maxpipekva / 2 ? SMALL_PIPE_SIZE : PIPE_SIZE);
 709         if (error == 0)
 710                 pipe->pipe_ino = alloc_unr64(&pipeino_unr);
 711         return (error);
 712 }
 713
 714 /* ARGSUSED */
 715 static int
 716 pipe_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
 717     int flags, struct thread *td)
 718 {
 719         struct pipe *rpipe;
 720         int error;
 721         int nread = 0;
 722         int size;
 723
 724         rpipe = fp->f_data;
 725         PIPE_LOCK(rpipe);
 726         ++rpipe->pipe_busy;
 727         error = pipelock(rpipe, 1);
 728         if (error)
 729                 goto unlocked_error;
 730
 731 #ifdef MAC
 732         error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
 733         if (error)
 734                 goto locked_error;
 735 #endif
 736         if (amountpipekva > (3 * maxpipekva) / 4) {
 737                 if ((rpipe->pipe_state & PIPE_DIRECTW) == 0 &&
 738                     rpipe->pipe_buffer.size > SMALL_PIPE_SIZE &&
 739                     rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE &&
 740                     piperesizeallowed == 1) {
 741                         PIPE_UNLOCK(rpipe);
 742                         pipespace(rpipe, SMALL_PIPE_SIZE);
 743                         PIPE_LOCK(rpipe);
 744                 }
 745         }
 746
 747         while (uio->uio_resid) {
 748                 /*
 749                  * normal pipe buffer receive
 750                  */
 751                 if (rpipe->pipe_buffer.cnt > 0) {
 752                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
 753                         if (size > rpipe->pipe_buffer.cnt)
 754                                 size = rpipe->pipe_buffer.cnt;
 755                         if (size > uio->uio_resid)
 756                                 size = uio->uio_resid;
 757
 758                         PIPE_UNLOCK(rpipe);
 759                         error = uiomove(
 760                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
 761                             size, uio);
 762                         PIPE_LOCK(rpipe);
 763                         if (error)
 764                                 break;
 765
 766                         rpipe->pipe_buffer.out += size;
 767                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
 768                                 rpipe->pipe_buffer.out = 0;
 769
 770                         rpipe->pipe_buffer.cnt -= size;
 771
 772                         /*
 773                          * If there is no more to read in the pipe, reset
 774                          * its pointers to the beginning.  This improves
 775                          * cache hit stats.
 776                          */
 777                         if (rpipe->pipe_buffer.cnt == 0) {
 778                                 rpipe->pipe_buffer.in = 0;
 779                                 rpipe->pipe_buffer.out = 0;
 780                         }
 781                         nread += size;
 782 #ifndef PIPE_NODIRECT
 783                 /*
 784                  * Direct copy, bypassing a kernel buffer.
 785                  */
 786                 } else if ((size = rpipe->pipe_pages.cnt) != 0) {
 787                         if (size > uio->uio_resid)
 788                                 size = (u_int) uio->uio_resid;
 789                         PIPE_UNLOCK(rpipe);
 790                         error = uiomove_fromphys(rpipe->pipe_pages.ms,
 791                             rpipe->pipe_pages.pos, size, uio);
 792                         PIPE_LOCK(rpipe);
 793                         if (error)
 794                                 break;
 795                         nread += size;
 796                         rpipe->pipe_pages.pos += size;
 797                         rpipe->pipe_pages.cnt -= size;
 798                         if (rpipe->pipe_pages.cnt == 0) {
 799                                 rpipe->pipe_state &= ~PIPE_WANTW;
 800                                 wakeup(rpipe);
 801                         }
 802 #endif
 803                 } else {
 804                         /*
 805                          * detect EOF condition
 806                          * read returns 0 on EOF, no need to set error
 807                          */
 808                         if (rpipe->pipe_state & PIPE_EOF)
 809                                 break;
 810
 811                         /*
 812                          * If the "write-side" has been blocked, wake it up now.
 813                          */
 814                         if (rpipe->pipe_state & PIPE_WANTW) {
 815                                 rpipe->pipe_state &= ~PIPE_WANTW;
 816                                 wakeup(rpipe);
 817                         }
 818
 819                         /*
 820                          * Break if some data was read.
 821                          */
 822                         if (nread > 0)
 823                                 break;
 824
 825                         /*
 826                          * Unlock the pipe buffer for our remaining processing.
 827                          * We will either break out with an error or we will
 828                          * sleep and relock to loop.
 829                          */
 830                         pipeunlock(rpipe);
 831
 832                         /*
 833                          * Handle non-blocking mode operation or
 834                          * wait for more data.
 835                          */
 836                         if (fp->f_flag & FNONBLOCK) {
 837                                 error = EAGAIN;
 838                         } else {
 839                                 rpipe->pipe_state |= PIPE_WANTR;
 840                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
 841                                     PRIBIO | PCATCH,
 842                                     "piperd", 0)) == 0)
 843                                         error = pipelock(rpipe, 1);
 844                         }
 845                         if (error)
 846                                 goto unlocked_error;
 847                 }
 848         }
 849 #ifdef MAC
 850 locked_error:
 851 #endif
 852         pipeunlock(rpipe);
 853
 854         /* XXX: should probably do this before getting any locks. */
 855         if (error == 0)
 856                 pipe_timestamp(&rpipe->pipe_atime);
 857 unlocked_error:
 858         --rpipe->pipe_busy;
 859
 860         /*
 861          * PIPE_WANT processing only makes sense if pipe_busy is 0.
 862          */
 863         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
 864                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
 865                 wakeup(rpipe);
 866         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
 867                 /*
 868                  * Handle write blocking hysteresis.
 869                  */
 870                 if (rpipe->pipe_state & PIPE_WANTW) {
 871                         rpipe->pipe_state &= ~PIPE_WANTW;
 872                         wakeup(rpipe);
 873                 }
 874         }
 875
 876         /*
 877          * Only wake up writers if there was actually something read.
 878          * Otherwise, when calling read(2) at EOF, a spurious wakeup occurs.
 879          */
 880         if (nread > 0 &&
 881             rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt >= PIPE_BUF)
 882                 pipeselwakeup(rpipe);
 883
 884         PIPE_UNLOCK(rpipe);
 885         if (nread > 0)
 886                 td->td_ru.ru_msgrcv++;
 887         return (error);
 888 }
 889
 890 #ifndef PIPE_NODIRECT
 891 /*
 892  * Map the sending processes' buffer into kernel space and wire it.
 893  * This is similar to a physical write operation.
 894  */
 895 static int
 896 pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio)
 897 {
 898         u_int size;
 899         int i;
 900
 901         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 902         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
 903             ("%s: PIPE_DIRECTW set on %p", __func__, wpipe));
 904         KASSERT(wpipe->pipe_pages.cnt == 0,
 905             ("%s: pipe map for %p contains residual data", __func__, wpipe));
 906
 907         if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
 908                 size = wpipe->pipe_buffer.size;
 909         else
 910                 size = uio->uio_iov->iov_len;
 911
 912         wpipe->pipe_state |= PIPE_DIRECTW;
 913         PIPE_UNLOCK(wpipe);
 914         i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
 915             (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
 916             wpipe->pipe_pages.ms, PIPENPAGES);
 917         PIPE_LOCK(wpipe);
 918         if (i < 0) {
 919                 wpipe->pipe_state &= ~PIPE_DIRECTW;
 920                 return (EFAULT);
 921         }
 922
 923         wpipe->pipe_pages.npages = i;
 924         wpipe->pipe_pages.pos =
 925             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
 926         wpipe->pipe_pages.cnt = size;
 927
 928         uio->uio_iov->iov_len -= size;
 929         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
 930         if (uio->uio_iov->iov_len == 0)
 931                 uio->uio_iov++;
 932         uio->uio_resid -= size;
 933         uio->uio_offset += size;
 934         return (0);
 935 }
 936
 937 /*
 938  * Unwire the process buffer.
 939  */
 940 static void
 941 pipe_destroy_write_buffer(struct pipe *wpipe)
 942 {
 943
 944         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 945         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
 946             ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
 947         KASSERT(wpipe->pipe_pages.cnt == 0,
 948             ("%s: pipe map for %p contains residual data", __func__, wpipe));
 949
 950         wpipe->pipe_state &= ~PIPE_DIRECTW;
 951         vm_page_unhold_pages(wpipe->pipe_pages.ms, wpipe->pipe_pages.npages);
 952         wpipe->pipe_pages.npages = 0;
 953 }
 954
 955 /*
 956  * In the case of a signal, the writing process might go away.  This
 957  * code copies the data into the circular buffer so that the source
 958  * pages can be freed without loss of data.
 959  */
 960 static void
 961 pipe_clone_write_buffer(struct pipe *wpipe)
 962 {
 963         struct uio uio;
 964         struct iovec iov;
 965         int size;
 966         int pos;
 967
 968         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 969         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
 970             ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
 971
 972         size = wpipe->pipe_pages.cnt;
 973         pos = wpipe->pipe_pages.pos;
 974         wpipe->pipe_pages.cnt = 0;
 975
 976         wpipe->pipe_buffer.in = size;
 977         wpipe->pipe_buffer.out = 0;
 978         wpipe->pipe_buffer.cnt = size;
 979
 980         PIPE_UNLOCK(wpipe);
 981         iov.iov_base = wpipe->pipe_buffer.buffer;
 982         iov.iov_len = size;
 983         uio.uio_iov = &iov;
 984         uio.uio_iovcnt = 1;
 985         uio.uio_offset = 0;
 986         uio.uio_resid = size;
 987         uio.uio_segflg = UIO_SYSSPACE;
 988         uio.uio_rw = UIO_READ;
 989         uio.uio_td = curthread;
 990         uiomove_fromphys(wpipe->pipe_pages.ms, pos, size, &uio);
 991         PIPE_LOCK(wpipe);
 992         pipe_destroy_write_buffer(wpipe);
 993 }
 994
 995 /*
 996  * This implements the pipe buffer write mechanism.  Note that only
 997  * a direct write OR a normal pipe write can be pending at any given time.
 998  * If there are any characters in the pipe buffer, the direct write will
 999  * be deferred until the receiving process grabs all of the bytes from
1000  * the pipe buffer.  Then the direct mapping write is set-up.
1001  */
1002 static int
1003 pipe_direct_write(struct pipe *wpipe, struct uio *uio)
1004 {
1005         int error;
1006
1007 retry:
1008         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
1009         if ((wpipe->pipe_state & PIPE_EOF) != 0) {
1010                 error = EPIPE;
1011                 goto error1;
1012         }
1013         if (wpipe->pipe_state & PIPE_DIRECTW) {
1014                 if (wpipe->pipe_state & PIPE_WANTR) {
1015                         wpipe->pipe_state &= ~PIPE_WANTR;
1016                         wakeup(wpipe);
1017                 }
1018                 pipeselwakeup(wpipe);
1019                 wpipe->pipe_state |= PIPE_WANTW;
1020                 pipeunlock(wpipe);
1021                 error = msleep(wpipe, PIPE_MTX(wpipe),
1022                     PRIBIO | PCATCH, "pipdww", 0);
1023                 pipelock(wpipe, 0);
1024                 if (error != 0)
1025                         goto error1;
1026                 goto retry;
1027         }
1028         if (wpipe->pipe_buffer.cnt > 0) {
1029                 if (wpipe->pipe_state & PIPE_WANTR) {
1030                         wpipe->pipe_state &= ~PIPE_WANTR;
1031                         wakeup(wpipe);
1032                 }
1033                 pipeselwakeup(wpipe);
1034                 wpipe->pipe_state |= PIPE_WANTW;
1035                 pipeunlock(wpipe);
1036                 error = msleep(wpipe, PIPE_MTX(wpipe),
1037                     PRIBIO | PCATCH, "pipdwc", 0);
1038                 pipelock(wpipe, 0);
1039                 if (error != 0)
1040                         goto error1;
1041                 goto retry;
1042         }
1043
1044         error = pipe_build_write_buffer(wpipe, uio);
1045         if (error) {
1046                 goto error1;
1047         }
1048
1049         while (wpipe->pipe_pages.cnt != 0 &&
1050             (wpipe->pipe_state & PIPE_EOF) == 0) {
1051                 if (wpipe->pipe_state & PIPE_WANTR) {
1052                         wpipe->pipe_state &= ~PIPE_WANTR;
1053                         wakeup(wpipe);
1054                 }
1055                 pipeselwakeup(wpipe);
1056                 wpipe->pipe_state |= PIPE_WANTW;
1057                 pipeunlock(wpipe);
1058                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
1059                     "pipdwt", 0);
1060                 pipelock(wpipe, 0);
1061                 if (error != 0)
1062                         break;
1063         }
1064
1065         if ((wpipe->pipe_state & PIPE_EOF) != 0) {
1066                 wpipe->pipe_pages.cnt = 0;
1067                 pipe_destroy_write_buffer(wpipe);
1068                 pipeselwakeup(wpipe);
1069                 error = EPIPE;
1070         } else if (error == EINTR || error == ERESTART) {
1071                 pipe_clone_write_buffer(wpipe);
1072         } else {
1073                 pipe_destroy_write_buffer(wpipe);
1074         }
1075         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
1076             ("pipe %p leaked PIPE_DIRECTW", wpipe));
1077         return (error);
1078
1079 error1:
1080         wakeup(wpipe);
1081         return (error);
1082 }
1083 #endif
1084
1085 static int
1086 pipe_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
1087     int flags, struct thread *td)
1088 {
1089         struct pipe *wpipe, *rpipe;
1090         ssize_t orig_resid;
1091         int desiredsize, error;
1092
1093         rpipe = fp->f_data;
1094         wpipe = PIPE_PEER(rpipe);
1095         PIPE_LOCK(rpipe);
1096         error = pipelock(wpipe, 1);
1097         if (error) {
1098                 PIPE_UNLOCK(rpipe);
1099                 return (error);
1100         }
1101         /*
1102          * detect loss of pipe read side, issue SIGPIPE if lost.
1103          */
1104         if (wpipe->pipe_present != PIPE_ACTIVE ||
1105             (wpipe->pipe_state & PIPE_EOF)) {
1106                 pipeunlock(wpipe);
1107                 PIPE_UNLOCK(rpipe);
1108                 return (EPIPE);
1109         }
1110 #ifdef MAC
1111         error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
1112         if (error) {
1113                 pipeunlock(wpipe);
1114                 PIPE_UNLOCK(rpipe);
1115                 return (error);
1116         }
1117 #endif
1118         ++wpipe->pipe_busy;
1119
1120         /* Choose a larger size if it's advantageous */
1121         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
1122         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
1123                 if (piperesizeallowed != 1)
1124                         break;
1125                 if (amountpipekva > maxpipekva / 2)
1126                         break;
1127                 if (desiredsize == BIG_PIPE_SIZE)
1128                         break;
1129                 desiredsize = desiredsize * 2;
1130         }
1131
1132         /* Choose a smaller size if we're in a OOM situation */
1133         if (amountpipekva > (3 * maxpipekva) / 4 &&
1134             wpipe->pipe_buffer.size > SMALL_PIPE_SIZE &&
1135             wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE &&
1136             piperesizeallowed == 1)
1137                 desiredsize = SMALL_PIPE_SIZE;
1138
1139         /* Resize if the above determined that a new size was necessary */
1140         if (desiredsize != wpipe->pipe_buffer.size &&
1141             (wpipe->pipe_state & PIPE_DIRECTW) == 0) {
1142                 PIPE_UNLOCK(wpipe);
1143                 pipespace(wpipe, desiredsize);
1144                 PIPE_LOCK(wpipe);
1145         }
1146         MPASS(wpipe->pipe_buffer.size != 0);
1147
1148         orig_resid = uio->uio_resid;
1149
1150         while (uio->uio_resid) {
1151                 int space;
1152
1153                 if (wpipe->pipe_state & PIPE_EOF) {
1154                         error = EPIPE;
1155                         break;
1156                 }
1157 #ifndef PIPE_NODIRECT
1158                 /*
1159                  * If the transfer is large, we can gain performance if
1160                  * we do process-to-process copies directly.
1161                  * If the write is non-blocking, we don't use the
1162                  * direct write mechanism.
1163                  *
1164                  * The direct write mechanism will detect the reader going
1165                  * away on us.
1166                  */
1167                 if (uio->uio_segflg == UIO_USERSPACE &&
1168                     uio->uio_iov->iov_len >= pipe_mindirect &&
1169                     wpipe->pipe_buffer.size >= pipe_mindirect &&
1170                     (fp->f_flag & FNONBLOCK) == 0) {
1171                         error = pipe_direct_write(wpipe, uio);
1172                         if (error != 0)
1173                                 break;
1174                         continue;
1175                 }
1176 #endif
1177
1178                 /*
1179                  * Pipe buffered writes cannot be coincidental with
1180                  * direct writes.  We wait until the currently executing
1181                  * direct write is completed before we start filling the
1182                  * pipe buffer.  We break out if a signal occurs or the
1183                  * reader goes away.
1184                  */
1185                 if (wpipe->pipe_pages.cnt != 0) {
1186                         if (wpipe->pipe_state & PIPE_WANTR) {
1187                                 wpipe->pipe_state &= ~PIPE_WANTR;
1188                                 wakeup(wpipe);
1189                         }
1190                         pipeselwakeup(wpipe);
1191                         wpipe->pipe_state |= PIPE_WANTW;
1192                         pipeunlock(wpipe);
1193                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
1194                             "pipbww", 0);
1195                         pipelock(wpipe, 0);
1196                         if (error != 0)
1197                                 break;
1198                         continue;
1199                 }
1200
1201                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
1202
1203                 /* Writes of size <= PIPE_BUF must be atomic. */
1204                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
1205                         space = 0;
1206
1207                 if (space > 0) {
1208                         int size;       /* Transfer size */
1209                         int segsize;    /* first segment to transfer */
1210
1211                         /*
1212                          * Transfer size is minimum of uio transfer
1213                          * and free space in pipe buffer.
1214                          */
1215                         if (space > uio->uio_resid)
1216                                 size = uio->uio_resid;
1217                         else
1218                                 size = space;
1219                         /*
1220                          * First segment to transfer is minimum of
1221                          * transfer size and contiguous space in
1222                          * pipe buffer.  If first segment to transfer
1223                          * is less than the transfer size, we've got
1224                          * a wraparound in the buffer.
1225                          */
1226                         segsize = wpipe->pipe_buffer.size -
1227                                 wpipe->pipe_buffer.in;
1228                         if (segsize > size)
1229                                 segsize = size;
1230
1231                         /* Transfer first segment */
1232
1233                         PIPE_UNLOCK(rpipe);
1234                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
1235                                         segsize, uio);
1236                         PIPE_LOCK(rpipe);
1237
1238                         if (error == 0 && segsize < size) {
1239                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
1240                                         wpipe->pipe_buffer.size,
1241                                         ("Pipe buffer wraparound disappeared"));
1242                                 /*
1243                                  * Transfer remaining part now, to
1244                                  * support atomic writes.  Wraparound
1245                                  * happened.
1246                                  */
1247
1248                                 PIPE_UNLOCK(rpipe);
1249                                 error = uiomove(
1250                                     &wpipe->pipe_buffer.buffer[0],
1251                                     size - segsize, uio);
1252                                 PIPE_LOCK(rpipe);
1253                         }
1254                         if (error == 0) {
1255                                 wpipe->pipe_buffer.in += size;
1256                                 if (wpipe->pipe_buffer.in >=
1257                                     wpipe->pipe_buffer.size) {
1258                                         KASSERT(wpipe->pipe_buffer.in ==
1259                                                 size - segsize +
1260                                                 wpipe->pipe_buffer.size,
1261                                                 ("Expected wraparound bad"));
1262                                         wpipe->pipe_buffer.in = size - segsize;
1263                                 }
1264
1265                                 wpipe->pipe_buffer.cnt += size;
1266                                 KASSERT(wpipe->pipe_buffer.cnt <=
1267                                         wpipe->pipe_buffer.size,
1268                                         ("Pipe buffer overflow"));
1269                         }
1270                         if (error != 0)
1271                                 break;
1272                         continue;
1273                 } else {
1274                         /*
1275                          * If the "read-side" has been blocked, wake it up now.
1276                          */
1277                         if (wpipe->pipe_state & PIPE_WANTR) {
1278                                 wpipe->pipe_state &= ~PIPE_WANTR;
1279                                 wakeup(wpipe);
1280                         }
1281
1282                         /*
1283                          * don't block on non-blocking I/O
1284                          */
1285                         if (fp->f_flag & FNONBLOCK) {
1286                                 error = EAGAIN;
1287                                 break;
1288                         }
1289
1290                         /*
1291                          * We have no more space and have something to offer,
1292                          * wake up select/poll.
1293                          */
1294                         pipeselwakeup(wpipe);
1295
1296                         wpipe->pipe_state |= PIPE_WANTW;
1297                         pipeunlock(wpipe);
1298                         error = msleep(wpipe, PIPE_MTX(rpipe),
1299                             PRIBIO | PCATCH, "pipewr", 0);
1300                         pipelock(wpipe, 0);
1301                         if (error != 0)
1302                                 break;
1303                         continue;
1304                 }
1305         }
1306
1307         --wpipe->pipe_busy;
1308
1309         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
1310                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
1311                 wakeup(wpipe);
1312         } else if (wpipe->pipe_buffer.cnt > 0) {
1313                 /*
1314                  * If we have put any characters in the buffer, we wake up
1315                  * the reader.
1316                  */
1317                 if (wpipe->pipe_state & PIPE_WANTR) {
1318                         wpipe->pipe_state &= ~PIPE_WANTR;
1319                         wakeup(wpipe);
1320                 }
1321         }
1322
1323         /*
1324          * Don't return EPIPE if any byte was written.
1325          * EINTR and other interrupts are handled by generic I/O layer.
1326          * Do not pretend that I/O succeeded for obvious user error
1327          * like EFAULT.
1328          */
1329         if (uio->uio_resid != orig_resid && error == EPIPE)
1330                 error = 0;
1331
1332         if (error == 0)
1333                 pipe_timestamp(&wpipe->pipe_mtime);
1334
1335         /*
1336          * We have something to offer,
1337          * wake up select/poll.
1338          */
1339         if (wpipe->pipe_buffer.cnt)
1340                 pipeselwakeup(wpipe);
1341
1342         pipeunlock(wpipe);
1343         PIPE_UNLOCK(rpipe);
1344         if (uio->uio_resid != orig_resid)
1345                 td->td_ru.ru_msgsnd++;
1346         return (error);
1347 }
1348
1349 /* ARGSUSED */
1350 static int
1351 pipe_truncate(struct file *fp, off_t length, struct ucred *active_cred,
1352     struct thread *td)
1353 {
1354         struct pipe *cpipe;
1355         int error;
1356
1357         cpipe = fp->f_data;
1358         if (cpipe->pipe_type & PIPE_TYPE_NAMED)
1359                 error = vnops.fo_truncate(fp, length, active_cred, td);
1360         else
1361                 error = invfo_truncate(fp, length, active_cred, td);
1362         return (error);
1363 }
1364
1365 /*
1366  * we implement a very minimal set of ioctls for compatibility with sockets.
1367  */
1368 static int
1369 pipe_ioctl(struct file *fp, u_long cmd, void *data, struct ucred *active_cred,
1370     struct thread *td)
1371 {
1372         struct pipe *mpipe = fp->f_data;
1373         int error;
1374
1375         PIPE_LOCK(mpipe);
1376
1377 #ifdef MAC
1378         error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
1379         if (error) {
1380                 PIPE_UNLOCK(mpipe);
1381                 return (error);
1382         }
1383 #endif
1384
1385         error = 0;
1386         switch (cmd) {
1387         case FIONBIO:
1388                 break;
1389
1390         case FIOASYNC:
1391                 if (*(int *)data) {
1392                         mpipe->pipe_state |= PIPE_ASYNC;
1393                 } else {
1394                         mpipe->pipe_state &= ~PIPE_ASYNC;
1395                 }
1396                 break;
1397
1398         case FIONREAD:
1399                 if (!(fp->f_flag & FREAD)) {
1400                         *(int *)data = 0;
1401                         PIPE_UNLOCK(mpipe);
1402                         return (0);
1403                 }
1404                 if (mpipe->pipe_pages.cnt != 0)
1405                         *(int *)data = mpipe->pipe_pages.cnt;
1406                 else
1407                         *(int *)data = mpipe->pipe_buffer.cnt;
1408                 break;
1409
1410         case FIOSETOWN:
1411                 PIPE_UNLOCK(mpipe);
1412                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
1413                 goto out_unlocked;
1414
1415         case FIOGETOWN:
1416                 *(int *)data = fgetown(&mpipe->pipe_sigio);
1417                 break;
1418
1419         /* This is deprecated, FIOSETOWN should be used instead. */
1420         case TIOCSPGRP:
1421                 PIPE_UNLOCK(mpipe);
1422                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
1423                 goto out_unlocked;
1424
1425         /* This is deprecated, FIOGETOWN should be used instead. */
1426         case TIOCGPGRP:
1427                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
1428                 break;
1429
1430         default:
1431                 error = ENOTTY;
1432                 break;
1433         }
1434         PIPE_UNLOCK(mpipe);
1435 out_unlocked:
1436         return (error);
1437 }
1438
1439 static int
1440 pipe_poll(struct file *fp, int events, struct ucred *active_cred,
1441     struct thread *td)
1442 {
1443         struct pipe *rpipe;
1444         struct pipe *wpipe;
1445         int levents, revents;
1446 #ifdef MAC
1447         int error;
1448 #endif
1449
1450         revents = 0;
1451         rpipe = fp->f_data;
1452         wpipe = PIPE_PEER(rpipe);
1453         PIPE_LOCK(rpipe);
1454 #ifdef MAC
1455         error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
1456         if (error)
1457                 goto locked_error;
1458 #endif
1459         if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM))
1460                 if (rpipe->pipe_pages.cnt > 0 || rpipe->pipe_buffer.cnt > 0)
1461                         revents |= events & (POLLIN | POLLRDNORM);
1462
1463         if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM))
1464                 if (wpipe->pipe_present != PIPE_ACTIVE ||
1465                     (wpipe->pipe_state & PIPE_EOF) ||
1466                     ((wpipe->pipe_state & PIPE_DIRECTW) == 0 &&
1467                      ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
1468                          wpipe->pipe_buffer.size == 0)))
1469                         revents |= events & (POLLOUT | POLLWRNORM);
1470
1471         levents = events &
1472             (POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
1473         if (rpipe->pipe_type & PIPE_TYPE_NAMED && fp->f_flag & FREAD && levents &&
1474             fp->f_pipegen == rpipe->pipe_wgen)
1475                 events |= POLLINIGNEOF;
1476
1477         if ((events & POLLINIGNEOF) == 0) {
1478                 if (rpipe->pipe_state & PIPE_EOF) {
1479                         if (fp->f_flag & FREAD)
1480                                 revents |= (events & (POLLIN | POLLRDNORM));
1481                         if (wpipe->pipe_present != PIPE_ACTIVE ||
1482                             (wpipe->pipe_state & PIPE_EOF))
1483                                 revents |= POLLHUP;
1484                 }
1485         }
1486
1487         if (revents == 0) {
1488                 /*
1489                  * Add ourselves regardless of eventmask as we have to return
1490                  * POLLHUP even if it was not asked for.
1491                  */
1492                 if ((fp->f_flag & FREAD) != 0) {
1493                         selrecord(td, &rpipe->pipe_sel);
1494                         if (SEL_WAITING(&rpipe->pipe_sel))
1495                                 rpipe->pipe_state |= PIPE_SEL;
1496                 }
1497
1498                 if ((fp->f_flag & FWRITE) != 0 &&
1499                     wpipe->pipe_present == PIPE_ACTIVE) {
1500                         selrecord(td, &wpipe->pipe_sel);
1501                         if (SEL_WAITING(&wpipe->pipe_sel))
1502                                 wpipe->pipe_state |= PIPE_SEL;
1503                 }
1504         }
1505 #ifdef MAC
1506 locked_error:
1507 #endif
1508         PIPE_UNLOCK(rpipe);
1509
1510         return (revents);
1511 }
1512
1513 /*
1514  * We shouldn't need locks here as we're doing a read and this should
1515  * be a natural race.
1516  */
1517 static int
1518 pipe_stat(struct file *fp, struct stat *ub, struct ucred *active_cred)
1519 {
1520         struct pipe *pipe;
1521 #ifdef MAC
1522         int error;
1523 #endif
1524
1525         pipe = fp->f_data;
1526 #ifdef MAC
1527         if (mac_pipe_check_stat_enabled()) {
1528                 PIPE_LOCK(pipe);
1529                 error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
1530                 PIPE_UNLOCK(pipe);
1531                 if (error) {
1532                         return (error);
1533                 }
1534         }
1535 #endif
1536
1537         /* For named pipes ask the underlying filesystem. */
1538         if (pipe->pipe_type & PIPE_TYPE_NAMED) {
1539                 return (vnops.fo_stat(fp, ub, active_cred));
1540         }
1541
1542         bzero(ub, sizeof(*ub));
1543         ub->st_mode = S_IFIFO;
1544         ub->st_blksize = PAGE_SIZE;
1545         if (pipe->pipe_pages.cnt != 0)
1546                 ub->st_size = pipe->pipe_pages.cnt;
1547         else
1548                 ub->st_size = pipe->pipe_buffer.cnt;
1549         ub->st_blocks = howmany(ub->st_size, ub->st_blksize);
1550         ub->st_atim = pipe->pipe_atime;
1551         ub->st_mtim = pipe->pipe_mtime;
1552         ub->st_ctim = pipe->pipe_ctime;
1553         ub->st_uid = fp->f_cred->cr_uid;
1554         ub->st_gid = fp->f_cred->cr_gid;
1555         ub->st_dev = pipedev_ino;
1556         ub->st_ino = pipe->pipe_ino;
1557         /*
1558          * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
1559          */
1560         return (0);
1561 }
1562
1563 /* ARGSUSED */
1564 static int
1565 pipe_close(struct file *fp, struct thread *td)
1566 {
1567
1568         if (fp->f_vnode != NULL)
1569                 return vnops.fo_close(fp, td);
1570         fp->f_ops = &badfileops;
1571         pipe_dtor(fp->f_data);
1572         fp->f_data = NULL;
1573         return (0);
1574 }
1575
1576 static int
1577 pipe_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, struct thread *td)
1578 {
1579         struct pipe *cpipe;
1580         int error;
1581
1582         cpipe = fp->f_data;
1583         if (cpipe->pipe_type & PIPE_TYPE_NAMED)
1584                 error = vn_chmod(fp, mode, active_cred, td);
1585         else
1586                 error = invfo_chmod(fp, mode, active_cred, td);
1587         return (error);
1588 }
1589
1590 static int
1591 pipe_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
1592     struct thread *td)
1593 {
1594         struct pipe *cpipe;
1595         int error;
1596
1597         cpipe = fp->f_data;
1598         if (cpipe->pipe_type & PIPE_TYPE_NAMED)
1599                 error = vn_chown(fp, uid, gid, active_cred, td);
1600         else
1601                 error = invfo_chown(fp, uid, gid, active_cred, td);
1602         return (error);
1603 }
1604
1605 static int
1606 pipe_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
1607 {
1608         struct pipe *pi;
1609
1610         if (fp->f_type == DTYPE_FIFO)
1611                 return (vn_fill_kinfo(fp, kif, fdp));
1612         kif->kf_type = KF_TYPE_PIPE;
1613         pi = fp->f_data;
1614         kif->kf_un.kf_pipe.kf_pipe_addr = (uintptr_t)pi;
1615         kif->kf_un.kf_pipe.kf_pipe_peer = (uintptr_t)pi->pipe_peer;
1616         kif->kf_un.kf_pipe.kf_pipe_buffer_cnt = pi->pipe_buffer.cnt;
1617         return (0);
1618 }
1619
1620 static void
1621 pipe_free_kmem(struct pipe *cpipe)
1622 {
1623
1624         KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
1625             ("pipe_free_kmem: pipe mutex locked"));
1626
1627         if (cpipe->pipe_buffer.buffer != NULL) {
1628                 atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
1629                 vm_map_remove(pipe_map,
1630                     (vm_offset_t)cpipe->pipe_buffer.buffer,
1631                     (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
1632                 cpipe->pipe_buffer.buffer = NULL;
1633         }
1634 #ifndef PIPE_NODIRECT
1635         {
1636                 cpipe->pipe_pages.cnt = 0;
1637                 cpipe->pipe_pages.pos = 0;
1638                 cpipe->pipe_pages.npages = 0;
1639         }
1640 #endif
1641 }
1642
1643 /*
1644  * shutdown the pipe
1645  */
1646 static void
1647 pipeclose(struct pipe *cpipe)
1648 {
1649         struct pipepair *pp;
1650         struct pipe *ppipe;
1651
1652         KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
1653
1654         PIPE_LOCK(cpipe);
1655         pipelock(cpipe, 0);
1656         pp = cpipe->pipe_pair;
1657
1658         /*
1659          * If the other side is blocked, wake it up saying that
1660          * we want to close it down.
1661          */
1662         cpipe->pipe_state |= PIPE_EOF;
1663         while (cpipe->pipe_busy) {
1664                 wakeup(cpipe);
1665                 cpipe->pipe_state |= PIPE_WANT;
1666                 pipeunlock(cpipe);
1667                 msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
1668                 pipelock(cpipe, 0);
1669         }
1670
1671         pipeselwakeup(cpipe);
1672
1673         /*
1674          * Disconnect from peer, if any.
1675          */
1676         ppipe = cpipe->pipe_peer;
1677         if (ppipe->pipe_present == PIPE_ACTIVE) {
1678                 ppipe->pipe_state |= PIPE_EOF;
1679                 wakeup(ppipe);
1680                 pipeselwakeup(ppipe);
1681         }
1682
1683         /*
1684          * Mark this endpoint as free.  Release kmem resources.  We
1685          * don't mark this endpoint as unused until we've finished
1686          * doing that, or the pipe might disappear out from under
1687          * us.
1688          */
1689         PIPE_UNLOCK(cpipe);
1690         pipe_free_kmem(cpipe);
1691         PIPE_LOCK(cpipe);
1692         cpipe->pipe_present = PIPE_CLOSING;
1693         pipeunlock(cpipe);
1694
1695         /*
1696          * knlist_clear() may sleep dropping the PIPE_MTX. Set the
1697          * PIPE_FINALIZED, that allows other end to free the
1698          * pipe_pair, only after the knotes are completely dismantled.
1699          */
1700         knlist_clear(&cpipe->pipe_sel.si_note, 1);
1701         cpipe->pipe_present = PIPE_FINALIZED;
1702         seldrain(&cpipe->pipe_sel);
1703         knlist_destroy(&cpipe->pipe_sel.si_note);
1704
1705         /*
1706          * If both endpoints are now closed, release the memory for the
1707          * pipe pair.  If not, unlock.
1708          */
1709         if (ppipe->pipe_present == PIPE_FINALIZED) {
1710                 PIPE_UNLOCK(cpipe);
1711 #ifdef MAC
1712                 mac_pipe_destroy(pp);
1713 #endif
1714                 uma_zfree(pipe_zone, cpipe->pipe_pair);
1715         } else
1716                 PIPE_UNLOCK(cpipe);
1717 }
1718
1719 /*ARGSUSED*/
1720 static int
1721 pipe_kqfilter(struct file *fp, struct knote *kn)
1722 {
1723         struct pipe *cpipe;
1724
1725         /*
1726          * If a filter is requested that is not supported by this file
1727          * descriptor, don't return an error, but also don't ever generate an
1728          * event.
1729          */
1730         if ((kn->kn_filter == EVFILT_READ) && !(fp->f_flag & FREAD)) {
1731                 kn->kn_fop = &pipe_nfiltops;
1732                 return (0);
1733         }
1734         if ((kn->kn_filter == EVFILT_WRITE) && !(fp->f_flag & FWRITE)) {
1735                 kn->kn_fop = &pipe_nfiltops;
1736                 return (0);
1737         }
1738         cpipe = fp->f_data;
1739         PIPE_LOCK(cpipe);
1740         switch (kn->kn_filter) {
1741         case EVFILT_READ:
1742                 kn->kn_fop = &pipe_rfiltops;
1743                 break;
1744         case EVFILT_WRITE:
1745                 kn->kn_fop = &pipe_wfiltops;
1746                 if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
1747                         /* other end of pipe has been closed */
1748                         PIPE_UNLOCK(cpipe);
1749                         return (EPIPE);
1750                 }
1751                 cpipe = PIPE_PEER(cpipe);
1752                 break;
1753         default:
1754                 if ((cpipe->pipe_type & PIPE_TYPE_NAMED) != 0) {
1755                         PIPE_UNLOCK(cpipe);
1756                         return (vnops.fo_kqfilter(fp, kn));
1757                 }
1758                 PIPE_UNLOCK(cpipe);
1759                 return (EINVAL);
1760         }
1761
1762         kn->kn_hook = cpipe;
1763         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
1764         PIPE_UNLOCK(cpipe);
1765         return (0);
1766 }
1767
1768 static void
1769 filt_pipedetach(struct knote *kn)
1770 {
1771         struct pipe *cpipe = kn->kn_hook;
1772
1773         PIPE_LOCK(cpipe);
1774         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
1775         PIPE_UNLOCK(cpipe);
1776 }
1777
1778 /*ARGSUSED*/
1779 static int
1780 filt_piperead(struct knote *kn, long hint)
1781 {
1782         struct file *fp = kn->kn_fp;
1783         struct pipe *rpipe = kn->kn_hook;
1784
1785         PIPE_LOCK_ASSERT(rpipe, MA_OWNED);
1786         kn->kn_data = rpipe->pipe_buffer.cnt;
1787         if (kn->kn_data == 0)
1788                 kn->kn_data = rpipe->pipe_pages.cnt;
1789
1790         if ((rpipe->pipe_state & PIPE_EOF) != 0 &&
1791             ((rpipe->pipe_type & PIPE_TYPE_NAMED) == 0 ||
1792             fp->f_pipegen != rpipe->pipe_wgen)) {
1793                 kn->kn_flags |= EV_EOF;
1794                 return (1);
1795         }
1796         kn->kn_flags &= ~EV_EOF;
1797         return (kn->kn_data > 0);
1798 }
1799
1800 /*ARGSUSED*/
1801 static int
1802 filt_pipewrite(struct knote *kn, long hint)
1803 {
1804         struct pipe *wpipe = kn->kn_hook;
1805
1806         /*
1807          * If this end of the pipe is closed, the knote was removed from the
1808          * knlist and the list lock (i.e., the pipe lock) is therefore not held.
1809          */
1810         if (wpipe->pipe_present == PIPE_ACTIVE ||
1811             (wpipe->pipe_type & PIPE_TYPE_NAMED) != 0) {
1812                 PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
1813
1814                 if (wpipe->pipe_state & PIPE_DIRECTW) {
1815                         kn->kn_data = 0;
1816                 } else if (wpipe->pipe_buffer.size > 0) {
1817                         kn->kn_data = wpipe->pipe_buffer.size -
1818                             wpipe->pipe_buffer.cnt;
1819                 } else {
1820                         kn->kn_data = PIPE_BUF;
1821                 }
1822         }
1823
1824         if (wpipe->pipe_present != PIPE_ACTIVE ||
1825             (wpipe->pipe_state & PIPE_EOF)) {
1826                 kn->kn_flags |= EV_EOF;
1827                 return (1);
1828         }
1829         kn->kn_flags &= ~EV_EOF;
1830         return (kn->kn_data >= PIPE_BUF);
1831 }
1832
1833 static void
1834 filt_pipedetach_notsup(struct knote *kn)
1835 {
1836
1837 }
1838
1839 static int
1840 filt_pipenotsup(struct knote *kn, long hint)
1841 {
1842
1843         return (0);
1844 }