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         return (error);
 419 }
 420
 421 int
 422 pipe_named_ctor(struct pipe **ppipe, struct thread *td)
 423 {
 424         struct pipepair *pp;
 425         int error;
 426
 427         error = pipe_paircreate(td, &pp);
 428         if (error != 0)
 429                 return (error);
 430         pp->pp_rpipe.pipe_type |= PIPE_TYPE_NAMED;
 431         *ppipe = &pp->pp_rpipe;
 432         return (0);
 433 }
 434
 435 void
 436 pipe_dtor(struct pipe *dpipe)
 437 {
 438         struct pipe *peer;
 439
 440         peer = (dpipe->pipe_type & PIPE_TYPE_NAMED) != 0 ? dpipe->pipe_peer : NULL;
 441         funsetown(&dpipe->pipe_sigio);
 442         pipeclose(dpipe);
 443         if (peer != NULL) {
 444                 funsetown(&peer->pipe_sigio);
 445                 pipeclose(peer);
 446         }
 447 }
 448
 449 /*
 450  * Get a timestamp.
 451  *
 452  * This used to be vfs_timestamp but the higher precision is unnecessary and
 453  * can very negatively affect performance in virtualized environments (e.g., on
 454  * vms running on amd64 when using the rdtscp instruction).
 455  */
 456 static void
 457 pipe_timestamp(struct timespec *tsp)
 458 {
 459
 460         getnanotime(tsp);
 461 }
 462
 463 /*
 464  * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
 465  * the zone pick up the pieces via pipeclose().
 466  */
 467 int
 468 kern_pipe(struct thread *td, int fildes[2], int flags, struct filecaps *fcaps1,
 469     struct filecaps *fcaps2)
 470 {
 471         struct file *rf, *wf;
 472         struct pipe *rpipe, *wpipe;
 473         struct pipepair *pp;
 474         int fd, fflags, error;
 475
 476         error = pipe_paircreate(td, &pp);
 477         if (error != 0)
 478                 return (error);
 479         rpipe = &pp->pp_rpipe;
 480         wpipe = &pp->pp_wpipe;
 481         error = falloc_caps(td, &rf, &fd, flags, fcaps1);
 482         if (error) {
 483                 pipeclose(rpipe);
 484                 pipeclose(wpipe);
 485                 return (error);
 486         }
 487         /* An extra reference on `rf' has been held for us by falloc_caps(). */
 488         fildes[0] = fd;
 489
 490         fflags = FREAD | FWRITE;
 491         if ((flags & O_NONBLOCK) != 0)
 492                 fflags |= FNONBLOCK;
 493
 494         /*
 495          * Warning: once we've gotten past allocation of the fd for the
 496          * read-side, we can only drop the read side via fdrop() in order
 497          * to avoid races against processes which manage to dup() the read
 498          * side while we are blocked trying to allocate the write side.
 499          */
 500         finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
 501         error = falloc_caps(td, &wf, &fd, flags, fcaps2);
 502         if (error) {
 503                 fdclose(td, rf, fildes[0]);
 504                 fdrop(rf, td);
 505                 /* rpipe has been closed by fdrop(). */
 506                 pipeclose(wpipe);
 507                 return (error);
 508         }
 509         /* An extra reference on `wf' has been held for us by falloc_caps(). */
 510         finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
 511         fdrop(wf, td);
 512         fildes[1] = fd;
 513         fdrop(rf, td);
 514
 515         return (0);
 516 }
 517
 518 #ifdef COMPAT_FREEBSD10
 519 /* ARGSUSED */
 520 int
 521 freebsd10_pipe(struct thread *td, struct freebsd10_pipe_args *uap __unused)
 522 {
 523         int error;
 524         int fildes[2];
 525
 526         error = kern_pipe(td, fildes, 0, NULL, NULL);
 527         if (error)
 528                 return (error);
 529
 530         td->td_retval[0] = fildes[0];
 531         td->td_retval[1] = fildes[1];
 532
 533         return (0);
 534 }
 535 #endif
 536
 537 int
 538 sys_pipe2(struct thread *td, struct pipe2_args *uap)
 539 {
 540         int error, fildes[2];
 541
 542         if (uap->flags & ~(O_CLOEXEC | O_NONBLOCK))
 543                 return (EINVAL);
 544         error = kern_pipe(td, fildes, uap->flags, NULL, NULL);
 545         if (error)
 546                 return (error);
 547         error = copyout(fildes, uap->fildes, 2 * sizeof(int));
 548         if (error) {
 549                 (void)kern_close(td, fildes[0]);
 550                 (void)kern_close(td, fildes[1]);
 551         }
 552         return (error);
 553 }
 554
 555 /*
 556  * Allocate kva for pipe circular buffer, the space is pageable
 557  * This routine will 'realloc' the size of a pipe safely, if it fails
 558  * it will retain the old buffer.
 559  * If it fails it will return ENOMEM.
 560  */
 561 static int
 562 pipespace_new(struct pipe *cpipe, int size)
 563 {
 564         caddr_t buffer;
 565         int error, cnt, firstseg;
 566         static int curfail = 0;
 567         static struct timeval lastfail;
 568
 569         KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
 570         KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
 571                 ("pipespace: resize of direct writes not allowed"));
 572 retry:
 573         cnt = cpipe->pipe_buffer.cnt;
 574         if (cnt > size)
 575                 size = cnt;
 576
 577         size = round_page(size);
 578         buffer = (caddr_t) vm_map_min(pipe_map);
 579
 580         error = vm_map_find(pipe_map, NULL, 0, (vm_offset_t *)&buffer, size, 0,
 581             VMFS_ANY_SPACE, VM_PROT_RW, VM_PROT_RW, 0);
 582         if (error != KERN_SUCCESS) {
 583                 if (cpipe->pipe_buffer.buffer == NULL &&
 584                     size > SMALL_PIPE_SIZE) {
 585                         size = SMALL_PIPE_SIZE;
 586                         pipefragretry++;
 587                         goto retry;
 588                 }
 589                 if (cpipe->pipe_buffer.buffer == NULL) {
 590                         pipeallocfail++;
 591                         if (ppsratecheck(&lastfail, &curfail, 1))
 592                                 printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
 593                 } else {
 594                         piperesizefail++;
 595                 }
 596                 return (ENOMEM);
 597         }
 598
 599         /* copy data, then free old resources if we're resizing */
 600         if (cnt > 0) {
 601                 if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
 602                         firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
 603                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
 604                                 buffer, firstseg);
 605                         if ((cnt - firstseg) > 0)
 606                                 bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
 607                                         cpipe->pipe_buffer.in);
 608                 } else {
 609                         bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
 610                                 buffer, cnt);
 611                 }
 612         }
 613         pipe_free_kmem(cpipe);
 614         cpipe->pipe_buffer.buffer = buffer;
 615         cpipe->pipe_buffer.size = size;
 616         cpipe->pipe_buffer.in = cnt;
 617         cpipe->pipe_buffer.out = 0;
 618         cpipe->pipe_buffer.cnt = cnt;
 619         atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
 620         return (0);
 621 }
 622
 623 /*
 624  * Wrapper for pipespace_new() that performs locking assertions.
 625  */
 626 static int
 627 pipespace(struct pipe *cpipe, int size)
 628 {
 629
 630         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
 631             ("Unlocked pipe passed to pipespace"));
 632         return (pipespace_new(cpipe, size));
 633 }
 634
 635 /*
 636  * lock a pipe for I/O, blocking other access
 637  */
 638 static __inline int
 639 pipelock(struct pipe *cpipe, int catch)
 640 {
 641         int error, prio;
 642
 643         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 644
 645         prio = PRIBIO;
 646         if (catch)
 647                 prio |= PCATCH;
 648         while (cpipe->pipe_state & PIPE_LOCKFL) {
 649                 KASSERT(cpipe->pipe_waiters >= 0,
 650                     ("%s: bad waiter count %d", __func__,
 651                     cpipe->pipe_waiters));
 652                 cpipe->pipe_waiters++;
 653                 error = msleep(cpipe, PIPE_MTX(cpipe),
 654                     prio, "pipelk", 0);
 655                 cpipe->pipe_waiters--;
 656                 if (error != 0)
 657                         return (error);
 658         }
 659         cpipe->pipe_state |= PIPE_LOCKFL;
 660         return (0);
 661 }
 662
 663 /*
 664  * unlock a pipe I/O lock
 665  */
 666 static __inline void
 667 pipeunlock(struct pipe *cpipe)
 668 {
 669
 670         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 671         KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
 672                 ("Unlocked pipe passed to pipeunlock"));
 673         KASSERT(cpipe->pipe_waiters >= 0,
 674             ("%s: bad waiter count %d", __func__,
 675             cpipe->pipe_waiters));
 676         cpipe->pipe_state &= ~PIPE_LOCKFL;
 677         if (cpipe->pipe_waiters > 0) {
 678                 wakeup_one(cpipe);
 679         }
 680 }
 681
 682 void
 683 pipeselwakeup(struct pipe *cpipe)
 684 {
 685
 686         PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
 687         if (cpipe->pipe_state & PIPE_SEL) {
 688                 selwakeuppri(&cpipe->pipe_sel, PSOCK);
 689                 if (!SEL_WAITING(&cpipe->pipe_sel))
 690                         cpipe->pipe_state &= ~PIPE_SEL;
 691         }
 692         if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
 693                 pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
 694         KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
 695 }
 696
 697 /*
 698  * Initialize and allocate VM and memory for pipe.  The structure
 699  * will start out zero'd from the ctor, so we just manage the kmem.
 700  */
 701 static int
 702 pipe_create(struct pipe *pipe, bool large_backing)
 703 {
 704         int error;
 705
 706         error = pipespace_new(pipe, !large_backing || amountpipekva >
 707             maxpipekva / 2 ? SMALL_PIPE_SIZE : PIPE_SIZE);
 708         if (error == 0)
 709                 pipe->pipe_ino = alloc_unr64(&pipeino_unr);
 710         return (error);
 711 }
 712
 713 /* ARGSUSED */
 714 static int
 715 pipe_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
 716     int flags, struct thread *td)
 717 {
 718         struct pipe *rpipe;
 719         int error;
 720         int nread = 0;
 721         int size;
 722
 723         rpipe = fp->f_data;
 724         PIPE_LOCK(rpipe);
 725         ++rpipe->pipe_busy;
 726         error = pipelock(rpipe, 1);
 727         if (error)
 728                 goto unlocked_error;
 729
 730 #ifdef MAC
 731         error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
 732         if (error)
 733                 goto locked_error;
 734 #endif
 735         if (amountpipekva > (3 * maxpipekva) / 4) {
 736                 if ((rpipe->pipe_state & PIPE_DIRECTW) == 0 &&
 737                     rpipe->pipe_buffer.size > SMALL_PIPE_SIZE &&
 738                     rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE &&
 739                     piperesizeallowed == 1) {
 740                         PIPE_UNLOCK(rpipe);
 741                         pipespace(rpipe, SMALL_PIPE_SIZE);
 742                         PIPE_LOCK(rpipe);
 743                 }
 744         }
 745
 746         while (uio->uio_resid) {
 747                 /*
 748                  * normal pipe buffer receive
 749                  */
 750                 if (rpipe->pipe_buffer.cnt > 0) {
 751                         size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
 752                         if (size > rpipe->pipe_buffer.cnt)
 753                                 size = rpipe->pipe_buffer.cnt;
 754                         if (size > uio->uio_resid)
 755                                 size = uio->uio_resid;
 756
 757                         PIPE_UNLOCK(rpipe);
 758                         error = uiomove(
 759                             &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
 760                             size, uio);
 761                         PIPE_LOCK(rpipe);
 762                         if (error)
 763                                 break;
 764
 765                         rpipe->pipe_buffer.out += size;
 766                         if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
 767                                 rpipe->pipe_buffer.out = 0;
 768
 769                         rpipe->pipe_buffer.cnt -= size;
 770
 771                         /*
 772                          * If there is no more to read in the pipe, reset
 773                          * its pointers to the beginning.  This improves
 774                          * cache hit stats.
 775                          */
 776                         if (rpipe->pipe_buffer.cnt == 0) {
 777                                 rpipe->pipe_buffer.in = 0;
 778                                 rpipe->pipe_buffer.out = 0;
 779                         }
 780                         nread += size;
 781 #ifndef PIPE_NODIRECT
 782                 /*
 783                  * Direct copy, bypassing a kernel buffer.
 784                  */
 785                 } else if ((size = rpipe->pipe_pages.cnt) != 0) {
 786                         if (size > uio->uio_resid)
 787                                 size = (u_int) uio->uio_resid;
 788                         PIPE_UNLOCK(rpipe);
 789                         error = uiomove_fromphys(rpipe->pipe_pages.ms,
 790                             rpipe->pipe_pages.pos, size, uio);
 791                         PIPE_LOCK(rpipe);
 792                         if (error)
 793                                 break;
 794                         nread += size;
 795                         rpipe->pipe_pages.pos += size;
 796                         rpipe->pipe_pages.cnt -= size;
 797                         if (rpipe->pipe_pages.cnt == 0) {
 798                                 rpipe->pipe_state &= ~PIPE_WANTW;
 799                                 wakeup(rpipe);
 800                         }
 801 #endif
 802                 } else {
 803                         /*
 804                          * detect EOF condition
 805                          * read returns 0 on EOF, no need to set error
 806                          */
 807                         if (rpipe->pipe_state & PIPE_EOF)
 808                                 break;
 809
 810                         /*
 811                          * If the "write-side" has been blocked, wake it up now.
 812                          */
 813                         if (rpipe->pipe_state & PIPE_WANTW) {
 814                                 rpipe->pipe_state &= ~PIPE_WANTW;
 815                                 wakeup(rpipe);
 816                         }
 817
 818                         /*
 819                          * Break if some data was read.
 820                          */
 821                         if (nread > 0)
 822                                 break;
 823
 824                         /*
 825                          * Unlock the pipe buffer for our remaining processing.
 826                          * We will either break out with an error or we will
 827                          * sleep and relock to loop.
 828                          */
 829                         pipeunlock(rpipe);
 830
 831                         /*
 832                          * Handle non-blocking mode operation or
 833                          * wait for more data.
 834                          */
 835                         if (fp->f_flag & FNONBLOCK) {
 836                                 error = EAGAIN;
 837                         } else {
 838                                 rpipe->pipe_state |= PIPE_WANTR;
 839                                 if ((error = msleep(rpipe, PIPE_MTX(rpipe),
 840                                     PRIBIO | PCATCH,
 841                                     "piperd", 0)) == 0)
 842                                         error = pipelock(rpipe, 1);
 843                         }
 844                         if (error)
 845                                 goto unlocked_error;
 846                 }
 847         }
 848 #ifdef MAC
 849 locked_error:
 850 #endif
 851         pipeunlock(rpipe);
 852
 853         /* XXX: should probably do this before getting any locks. */
 854         if (error == 0)
 855                 pipe_timestamp(&rpipe->pipe_atime);
 856 unlocked_error:
 857         --rpipe->pipe_busy;
 858
 859         /*
 860          * PIPE_WANT processing only makes sense if pipe_busy is 0.
 861          */
 862         if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
 863                 rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
 864                 wakeup(rpipe);
 865         } else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
 866                 /*
 867                  * Handle write blocking hysteresis.
 868                  */
 869                 if (rpipe->pipe_state & PIPE_WANTW) {
 870                         rpipe->pipe_state &= ~PIPE_WANTW;
 871                         wakeup(rpipe);
 872                 }
 873         }
 874
 875         /*
 876          * Only wake up writers if there was actually something read.
 877          * Otherwise, when calling read(2) at EOF, a spurious wakeup occurs.
 878          */
 879         if (nread > 0 &&
 880             rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt >= PIPE_BUF)
 881                 pipeselwakeup(rpipe);
 882
 883         PIPE_UNLOCK(rpipe);
 884         if (nread > 0)
 885                 td->td_ru.ru_msgrcv++;
 886         return (error);
 887 }
 888
 889 #ifndef PIPE_NODIRECT
 890 /*
 891  * Map the sending processes' buffer into kernel space and wire it.
 892  * This is similar to a physical write operation.
 893  */
 894 static int
 895 pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio)
 896 {
 897         u_int size;
 898         int i;
 899
 900         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 901         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
 902             ("%s: PIPE_DIRECTW set on %p", __func__, wpipe));
 903         KASSERT(wpipe->pipe_pages.cnt == 0,
 904             ("%s: pipe map for %p contains residual data", __func__, wpipe));
 905
 906         if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
 907                 size = wpipe->pipe_buffer.size;
 908         else
 909                 size = uio->uio_iov->iov_len;
 910
 911         wpipe->pipe_state |= PIPE_DIRECTW;
 912         PIPE_UNLOCK(wpipe);
 913         i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
 914             (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
 915             wpipe->pipe_pages.ms, PIPENPAGES);
 916         PIPE_LOCK(wpipe);
 917         if (i < 0) {
 918                 wpipe->pipe_state &= ~PIPE_DIRECTW;
 919                 return (EFAULT);
 920         }
 921
 922         wpipe->pipe_pages.npages = i;
 923         wpipe->pipe_pages.pos =
 924             ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
 925         wpipe->pipe_pages.cnt = size;
 926
 927         uio->uio_iov->iov_len -= size;
 928         uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
 929         if (uio->uio_iov->iov_len == 0)
 930                 uio->uio_iov++;
 931         uio->uio_resid -= size;
 932         uio->uio_offset += size;
 933         return (0);
 934 }
 935
 936 /*
 937  * Unwire the process buffer.
 938  */
 939 static void
 940 pipe_destroy_write_buffer(struct pipe *wpipe)
 941 {
 942
 943         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 944         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
 945             ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
 946         KASSERT(wpipe->pipe_pages.cnt == 0,
 947             ("%s: pipe map for %p contains residual data", __func__, wpipe));
 948
 949         wpipe->pipe_state &= ~PIPE_DIRECTW;
 950         vm_page_unhold_pages(wpipe->pipe_pages.ms, wpipe->pipe_pages.npages);
 951         wpipe->pipe_pages.npages = 0;
 952 }
 953
 954 /*
 955  * In the case of a signal, the writing process might go away.  This
 956  * code copies the data into the circular buffer so that the source
 957  * pages can be freed without loss of data.
 958  */
 959 static void
 960 pipe_clone_write_buffer(struct pipe *wpipe)
 961 {
 962         struct uio uio;
 963         struct iovec iov;
 964         int size;
 965         int pos;
 966
 967         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
 968         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) != 0,
 969             ("%s: PIPE_DIRECTW not set on %p", __func__, wpipe));
 970
 971         size = wpipe->pipe_pages.cnt;
 972         pos = wpipe->pipe_pages.pos;
 973         wpipe->pipe_pages.cnt = 0;
 974
 975         wpipe->pipe_buffer.in = size;
 976         wpipe->pipe_buffer.out = 0;
 977         wpipe->pipe_buffer.cnt = size;
 978
 979         PIPE_UNLOCK(wpipe);
 980         iov.iov_base = wpipe->pipe_buffer.buffer;
 981         iov.iov_len = size;
 982         uio.uio_iov = &iov;
 983         uio.uio_iovcnt = 1;
 984         uio.uio_offset = 0;
 985         uio.uio_resid = size;
 986         uio.uio_segflg = UIO_SYSSPACE;
 987         uio.uio_rw = UIO_READ;
 988         uio.uio_td = curthread;
 989         uiomove_fromphys(wpipe->pipe_pages.ms, pos, size, &uio);
 990         PIPE_LOCK(wpipe);
 991         pipe_destroy_write_buffer(wpipe);
 992 }
 993
 994 /*
 995  * This implements the pipe buffer write mechanism.  Note that only
 996  * a direct write OR a normal pipe write can be pending at any given time.
 997  * If there are any characters in the pipe buffer, the direct write will
 998  * be deferred until the receiving process grabs all of the bytes from
 999  * the pipe buffer.  Then the direct mapping write is set-up.
1000  */
1001 static int
1002 pipe_direct_write(struct pipe *wpipe, struct uio *uio)
1003 {
1004         int error;
1005
1006 retry:
1007         PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
1008         if ((wpipe->pipe_state & PIPE_EOF) != 0) {
1009                 error = EPIPE;
1010                 goto error1;
1011         }
1012         if (wpipe->pipe_state & PIPE_DIRECTW) {
1013                 if (wpipe->pipe_state & PIPE_WANTR) {
1014                         wpipe->pipe_state &= ~PIPE_WANTR;
1015                         wakeup(wpipe);
1016                 }
1017                 pipeselwakeup(wpipe);
1018                 wpipe->pipe_state |= PIPE_WANTW;
1019                 pipeunlock(wpipe);
1020                 error = msleep(wpipe, PIPE_MTX(wpipe),
1021                     PRIBIO | PCATCH, "pipdww", 0);
1022                 pipelock(wpipe, 0);
1023                 if (error != 0)
1024                         goto error1;
1025                 goto retry;
1026         }
1027         if (wpipe->pipe_buffer.cnt > 0) {
1028                 if (wpipe->pipe_state & PIPE_WANTR) {
1029                         wpipe->pipe_state &= ~PIPE_WANTR;
1030                         wakeup(wpipe);
1031                 }
1032                 pipeselwakeup(wpipe);
1033                 wpipe->pipe_state |= PIPE_WANTW;
1034                 pipeunlock(wpipe);
1035                 error = msleep(wpipe, PIPE_MTX(wpipe),
1036                     PRIBIO | PCATCH, "pipdwc", 0);
1037                 pipelock(wpipe, 0);
1038                 if (error != 0)
1039                         goto error1;
1040                 goto retry;
1041         }
1042
1043         error = pipe_build_write_buffer(wpipe, uio);
1044         if (error) {
1045                 goto error1;
1046         }
1047
1048         while (wpipe->pipe_pages.cnt != 0 &&
1049             (wpipe->pipe_state & PIPE_EOF) == 0) {
1050                 if (wpipe->pipe_state & PIPE_WANTR) {
1051                         wpipe->pipe_state &= ~PIPE_WANTR;
1052                         wakeup(wpipe);
1053                 }
1054                 pipeselwakeup(wpipe);
1055                 wpipe->pipe_state |= PIPE_WANTW;
1056                 pipeunlock(wpipe);
1057                 error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
1058                     "pipdwt", 0);
1059                 pipelock(wpipe, 0);
1060                 if (error != 0)
1061                         break;
1062         }
1063
1064         if ((wpipe->pipe_state & PIPE_EOF) != 0) {
1065                 wpipe->pipe_pages.cnt = 0;
1066                 pipe_destroy_write_buffer(wpipe);
1067                 pipeselwakeup(wpipe);
1068                 error = EPIPE;
1069         } else if (error == EINTR || error == ERESTART) {
1070                 pipe_clone_write_buffer(wpipe);
1071         } else {
1072                 pipe_destroy_write_buffer(wpipe);
1073         }
1074         KASSERT((wpipe->pipe_state & PIPE_DIRECTW) == 0,
1075             ("pipe %p leaked PIPE_DIRECTW", wpipe));
1076         return (error);
1077
1078 error1:
1079         wakeup(wpipe);
1080         return (error);
1081 }
1082 #endif
1083
1084 static int
1085 pipe_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
1086     int flags, struct thread *td)
1087 {
1088         struct pipe *wpipe, *rpipe;
1089         ssize_t orig_resid;
1090         int desiredsize, error;
1091
1092         rpipe = fp->f_data;
1093         wpipe = PIPE_PEER(rpipe);
1094         PIPE_LOCK(rpipe);
1095         error = pipelock(wpipe, 1);
1096         if (error) {
1097                 PIPE_UNLOCK(rpipe);
1098                 return (error);
1099         }
1100         /*
1101          * detect loss of pipe read side, issue SIGPIPE if lost.
1102          */
1103         if (wpipe->pipe_present != PIPE_ACTIVE ||
1104             (wpipe->pipe_state & PIPE_EOF)) {
1105                 pipeunlock(wpipe);
1106                 PIPE_UNLOCK(rpipe);
1107                 return (EPIPE);
1108         }
1109 #ifdef MAC
1110         error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
1111         if (error) {
1112                 pipeunlock(wpipe);
1113                 PIPE_UNLOCK(rpipe);
1114                 return (error);
1115         }
1116 #endif
1117         ++wpipe->pipe_busy;
1118
1119         /* Choose a larger size if it's advantageous */
1120         desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
1121         while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
1122                 if (piperesizeallowed != 1)
1123                         break;
1124                 if (amountpipekva > maxpipekva / 2)
1125                         break;
1126                 if (desiredsize == BIG_PIPE_SIZE)
1127                         break;
1128                 desiredsize = desiredsize * 2;
1129         }
1130
1131         /* Choose a smaller size if we're in a OOM situation */
1132         if (amountpipekva > (3 * maxpipekva) / 4 &&
1133             wpipe->pipe_buffer.size > SMALL_PIPE_SIZE &&
1134             wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE &&
1135             piperesizeallowed == 1)
1136                 desiredsize = SMALL_PIPE_SIZE;
1137
1138         /* Resize if the above determined that a new size was necessary */
1139         if (desiredsize != wpipe->pipe_buffer.size &&
1140             (wpipe->pipe_state & PIPE_DIRECTW) == 0) {
1141                 PIPE_UNLOCK(wpipe);
1142                 pipespace(wpipe, desiredsize);
1143                 PIPE_LOCK(wpipe);
1144         }
1145         MPASS(wpipe->pipe_buffer.size != 0);
1146
1147         orig_resid = uio->uio_resid;
1148
1149         while (uio->uio_resid) {
1150                 int space;
1151
1152                 if (wpipe->pipe_state & PIPE_EOF) {
1153                         error = EPIPE;
1154                         break;
1155                 }
1156 #ifndef PIPE_NODIRECT
1157                 /*
1158                  * If the transfer is large, we can gain performance if
1159                  * we do process-to-process copies directly.
1160                  * If the write is non-blocking, we don't use the
1161                  * direct write mechanism.
1162                  *
1163                  * The direct write mechanism will detect the reader going
1164                  * away on us.
1165                  */
1166                 if (uio->uio_segflg == UIO_USERSPACE &&
1167                     uio->uio_iov->iov_len >= pipe_mindirect &&
1168                     wpipe->pipe_buffer.size >= pipe_mindirect &&
1169                     (fp->f_flag & FNONBLOCK) == 0) {
1170                         error = pipe_direct_write(wpipe, uio);
1171                         if (error != 0)
1172                                 break;
1173                         continue;
1174                 }
1175 #endif
1176
1177                 /*
1178                  * Pipe buffered writes cannot be coincidental with
1179                  * direct writes.  We wait until the currently executing
1180                  * direct write is completed before we start filling the
1181                  * pipe buffer.  We break out if a signal occurs or the
1182                  * reader goes away.
1183                  */
1184                 if (wpipe->pipe_pages.cnt != 0) {
1185                         if (wpipe->pipe_state & PIPE_WANTR) {
1186                                 wpipe->pipe_state &= ~PIPE_WANTR;
1187                                 wakeup(wpipe);
1188                         }
1189                         pipeselwakeup(wpipe);
1190                         wpipe->pipe_state |= PIPE_WANTW;
1191                         pipeunlock(wpipe);
1192                         error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
1193                             "pipbww", 0);
1194                         pipelock(wpipe, 0);
1195                         if (error != 0)
1196                                 break;
1197                         continue;
1198                 }
1199
1200                 space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
1201
1202                 /* Writes of size <= PIPE_BUF must be atomic. */
1203                 if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
1204                         space = 0;
1205
1206                 if (space > 0) {
1207                         int size;       /* Transfer size */
1208                         int segsize;    /* first segment to transfer */
1209
1210                         /*
1211                          * Transfer size is minimum of uio transfer
1212                          * and free space in pipe buffer.
1213                          */
1214                         if (space > uio->uio_resid)
1215                                 size = uio->uio_resid;
1216                         else
1217                                 size = space;
1218                         /*
1219                          * First segment to transfer is minimum of
1220                          * transfer size and contiguous space in
1221                          * pipe buffer.  If first segment to transfer
1222                          * is less than the transfer size, we've got
1223                          * a wraparound in the buffer.
1224                          */
1225                         segsize = wpipe->pipe_buffer.size -
1226                                 wpipe->pipe_buffer.in;
1227                         if (segsize > size)
1228                                 segsize = size;
1229
1230                         /* Transfer first segment */
1231
1232                         PIPE_UNLOCK(rpipe);
1233                         error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
1234                                         segsize, uio);
1235                         PIPE_LOCK(rpipe);
1236
1237                         if (error == 0 && segsize < size) {
1238                                 KASSERT(wpipe->pipe_buffer.in + segsize ==
1239                                         wpipe->pipe_buffer.size,
1240                                         ("Pipe buffer wraparound disappeared"));
1241                                 /*
1242                                  * Transfer remaining part now, to
1243                                  * support atomic writes.  Wraparound
1244                                  * happened.
1245                                  */
1246
1247                                 PIPE_UNLOCK(rpipe);
1248                                 error = uiomove(
1249                                     &wpipe->pipe_buffer.buffer[0],
1250                                     size - segsize, uio);
1251                                 PIPE_LOCK(rpipe);
1252                         }
1253                         if (error == 0) {
1254                                 wpipe->pipe_buffer.in += size;
1255                                 if (wpipe->pipe_buffer.in >=
1256                                     wpipe->pipe_buffer.size) {
1257                                         KASSERT(wpipe->pipe_buffer.in ==
1258                                                 size - segsize +
1259                                                 wpipe->pipe_buffer.size,
1260                                                 ("Expected wraparound bad"));
1261                                         wpipe->pipe_buffer.in = size - segsize;
1262                                 }
1263
1264                                 wpipe->pipe_buffer.cnt += size;
1265                                 KASSERT(wpipe->pipe_buffer.cnt <=
1266                                         wpipe->pipe_buffer.size,
1267                                         ("Pipe buffer overflow"));
1268                         }
1269                         if (error != 0)
1270                                 break;
1271                         continue;
1272                 } else {
1273                         /*
1274                          * If the "read-side" has been blocked, wake it up now.
1275                          */
1276                         if (wpipe->pipe_state & PIPE_WANTR) {
1277                                 wpipe->pipe_state &= ~PIPE_WANTR;
1278                                 wakeup(wpipe);
1279                         }
1280
1281                         /*
1282                          * don't block on non-blocking I/O
1283                          */
1284                         if (fp->f_flag & FNONBLOCK) {
1285                                 error = EAGAIN;
1286                                 break;
1287                         }
1288
1289                         /*
1290                          * We have no more space and have something to offer,
1291                          * wake up select/poll.
1292                          */
1293                         pipeselwakeup(wpipe);
1294
1295                         wpipe->pipe_state |= PIPE_WANTW;
1296                         pipeunlock(wpipe);
1297                         error = msleep(wpipe, PIPE_MTX(rpipe),
1298                             PRIBIO | PCATCH, "pipewr", 0);
1299                         pipelock(wpipe, 0);
1300                         if (error != 0)
1301                                 break;
1302                         continue;
1303                 }
1304         }
1305
1306         --wpipe->pipe_busy;
1307
1308         if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
1309                 wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
1310                 wakeup(wpipe);
1311         } else if (wpipe->pipe_buffer.cnt > 0) {
1312                 /*
1313                  * If we have put any characters in the buffer, we wake up
1314                  * the reader.
1315                  */
1316                 if (wpipe->pipe_state & PIPE_WANTR) {
1317                         wpipe->pipe_state &= ~PIPE_WANTR;
1318                         wakeup(wpipe);
1319                 }
1320         }
1321
1322         /*
1323          * Don't return EPIPE if any byte was written.
1324          * EINTR and other interrupts are handled by generic I/O layer.
1325          * Do not pretend that I/O succeeded for obvious user error
1326          * like EFAULT.
1327          */
1328         if (uio->uio_resid != orig_resid && error == EPIPE)
1329                 error = 0;
1330
1331         if (error == 0)
1332                 pipe_timestamp(&wpipe->pipe_mtime);
1333
1334         /*
1335          * We have something to offer,
1336          * wake up select/poll.
1337          */
1338         if (wpipe->pipe_buffer.cnt)
1339                 pipeselwakeup(wpipe);
1340
1341         pipeunlock(wpipe);
1342         PIPE_UNLOCK(rpipe);
1343         if (uio->uio_resid != orig_resid)
1344                 td->td_ru.ru_msgsnd++;
1345         return (error);
1346 }
1347
1348 /* ARGSUSED */
1349 static int
1350 pipe_truncate(struct file *fp, off_t length, struct ucred *active_cred,
1351     struct thread *td)
1352 {
1353         struct pipe *cpipe;
1354         int error;
1355
1356         cpipe = fp->f_data;
1357         if (cpipe->pipe_type & PIPE_TYPE_NAMED)
1358                 error = vnops.fo_truncate(fp, length, active_cred, td);
1359         else
1360                 error = invfo_truncate(fp, length, active_cred, td);
1361         return (error);
1362 }
1363
1364 /*
1365  * we implement a very minimal set of ioctls for compatibility with sockets.
1366  */
1367 static int
1368 pipe_ioctl(struct file *fp, u_long cmd, void *data, struct ucred *active_cred,
1369     struct thread *td)
1370 {
1371         struct pipe *mpipe = fp->f_data;
1372         int error;
1373
1374         PIPE_LOCK(mpipe);
1375
1376 #ifdef MAC
1377         error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
1378         if (error) {
1379                 PIPE_UNLOCK(mpipe);
1380                 return (error);
1381         }
1382 #endif
1383
1384         error = 0;
1385         switch (cmd) {
1386         case FIONBIO:
1387                 break;
1388
1389         case FIOASYNC:
1390                 if (*(int *)data) {
1391                         mpipe->pipe_state |= PIPE_ASYNC;
1392                 } else {
1393                         mpipe->pipe_state &= ~PIPE_ASYNC;
1394                 }
1395                 break;
1396
1397         case FIONREAD:
1398                 if (!(fp->f_flag & FREAD)) {
1399                         *(int *)data = 0;
1400                         PIPE_UNLOCK(mpipe);
1401                         return (0);
1402                 }
1403                 if (mpipe->pipe_pages.cnt != 0)
1404                         *(int *)data = mpipe->pipe_pages.cnt;
1405                 else
1406                         *(int *)data = mpipe->pipe_buffer.cnt;
1407                 break;
1408
1409         case FIOSETOWN:
1410                 PIPE_UNLOCK(mpipe);
1411                 error = fsetown(*(int *)data, &mpipe->pipe_sigio);
1412                 goto out_unlocked;
1413
1414         case FIOGETOWN:
1415                 *(int *)data = fgetown(&mpipe->pipe_sigio);
1416                 break;
1417
1418         /* This is deprecated, FIOSETOWN should be used instead. */
1419         case TIOCSPGRP:
1420                 PIPE_UNLOCK(mpipe);
1421                 error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
1422                 goto out_unlocked;
1423
1424         /* This is deprecated, FIOGETOWN should be used instead. */
1425         case TIOCGPGRP:
1426                 *(int *)data = -fgetown(&mpipe->pipe_sigio);
1427                 break;
1428
1429         default:
1430                 error = ENOTTY;
1431                 break;
1432         }
1433         PIPE_UNLOCK(mpipe);
1434 out_unlocked:
1435         return (error);
1436 }
1437
1438 static int
1439 pipe_poll(struct file *fp, int events, struct ucred *active_cred,
1440     struct thread *td)
1441 {
1442         struct pipe *rpipe;
1443         struct pipe *wpipe;
1444         int levents, revents;
1445 #ifdef MAC
1446         int error;
1447 #endif
1448
1449         revents = 0;
1450         rpipe = fp->f_data;
1451         wpipe = PIPE_PEER(rpipe);
1452         PIPE_LOCK(rpipe);
1453 #ifdef MAC
1454         error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
1455         if (error)
1456                 goto locked_error;
1457 #endif
1458         if (fp->f_flag & FREAD && events & (POLLIN | POLLRDNORM))
1459                 if (rpipe->pipe_pages.cnt > 0 || rpipe->pipe_buffer.cnt > 0)
1460                         revents |= events & (POLLIN | POLLRDNORM);
1461
1462         if (fp->f_flag & FWRITE && events & (POLLOUT | POLLWRNORM))
1463                 if (wpipe->pipe_present != PIPE_ACTIVE ||
1464                     (wpipe->pipe_state & PIPE_EOF) ||
1465                     ((wpipe->pipe_state & PIPE_DIRECTW) == 0 &&
1466                      ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
1467                          wpipe->pipe_buffer.size == 0)))
1468                         revents |= events & (POLLOUT | POLLWRNORM);
1469
1470         levents = events &
1471             (POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
1472         if (rpipe->pipe_type & PIPE_TYPE_NAMED && fp->f_flag & FREAD && levents &&
1473             fp->f_pipegen == rpipe->pipe_wgen)
1474                 events |= POLLINIGNEOF;
1475
1476         if ((events & POLLINIGNEOF) == 0) {
1477                 if (rpipe->pipe_state & PIPE_EOF) {
1478                         if (fp->f_flag & FREAD)
1479                                 revents |= (events & (POLLIN | POLLRDNORM));
1480                         if (wpipe->pipe_present != PIPE_ACTIVE ||
1481                             (wpipe->pipe_state & PIPE_EOF))
1482                                 revents |= POLLHUP;
1483                 }
1484         }
1485
1486         if (revents == 0) {
1487                 /*
1488                  * Add ourselves regardless of eventmask as we have to return
1489                  * POLLHUP even if it was not asked for.
1490                  */
1491                 if ((fp->f_flag & FREAD) != 0) {
1492                         selrecord(td, &rpipe->pipe_sel);
1493                         if (SEL_WAITING(&rpipe->pipe_sel))
1494                                 rpipe->pipe_state |= PIPE_SEL;
1495                 }
1496
1497                 if ((fp->f_flag & FWRITE) != 0 &&
1498                     wpipe->pipe_present == PIPE_ACTIVE) {
1499                         selrecord(td, &wpipe->pipe_sel);
1500                         if (SEL_WAITING(&wpipe->pipe_sel))
1501                                 wpipe->pipe_state |= PIPE_SEL;
1502                 }
1503         }
1504 #ifdef MAC
1505 locked_error:
1506 #endif
1507         PIPE_UNLOCK(rpipe);
1508
1509         return (revents);
1510 }
1511
1512 /*
1513  * We shouldn't need locks here as we're doing a read and this should
1514  * be a natural race.
1515  */
1516 static int
1517 pipe_stat(struct file *fp, struct stat *ub, struct ucred *active_cred,
1518     struct thread *td)
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, td));
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                 PIPE_UNLOCK(cpipe);
1755                 return (EINVAL);
1756         }
1757
1758         kn->kn_hook = cpipe;
1759         knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
1760         PIPE_UNLOCK(cpipe);
1761         return (0);
1762 }
1763
1764 static void
1765 filt_pipedetach(struct knote *kn)
1766 {
1767         struct pipe *cpipe = kn->kn_hook;
1768
1769         PIPE_LOCK(cpipe);
1770         knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
1771         PIPE_UNLOCK(cpipe);
1772 }
1773
1774 /*ARGSUSED*/
1775 static int
1776 filt_piperead(struct knote *kn, long hint)
1777 {
1778         struct file *fp = kn->kn_fp;
1779         struct pipe *rpipe = kn->kn_hook;
1780
1781         PIPE_LOCK_ASSERT(rpipe, MA_OWNED);
1782         kn->kn_data = rpipe->pipe_buffer.cnt;
1783         if (kn->kn_data == 0)
1784                 kn->kn_data = rpipe->pipe_pages.cnt;
1785
1786         if ((rpipe->pipe_state & PIPE_EOF) != 0 &&
1787             ((rpipe->pipe_type & PIPE_TYPE_NAMED) == 0 ||
1788             fp->f_pipegen != rpipe->pipe_wgen)) {
1789                 kn->kn_flags |= EV_EOF;
1790                 return (1);
1791         }
1792         kn->kn_flags &= ~EV_EOF;
1793         return (kn->kn_data > 0);
1794 }
1795
1796 /*ARGSUSED*/
1797 static int
1798 filt_pipewrite(struct knote *kn, long hint)
1799 {
1800         struct pipe *wpipe = kn->kn_hook;
1801
1802         /*
1803          * If this end of the pipe is closed, the knote was removed from the
1804          * knlist and the list lock (i.e., the pipe lock) is therefore not held.
1805          */
1806         if (wpipe->pipe_present == PIPE_ACTIVE ||
1807             (wpipe->pipe_type & PIPE_TYPE_NAMED) != 0) {
1808                 PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
1809
1810                 if (wpipe->pipe_state & PIPE_DIRECTW) {
1811                         kn->kn_data = 0;
1812                 } else if (wpipe->pipe_buffer.size > 0) {
1813                         kn->kn_data = wpipe->pipe_buffer.size -
1814                             wpipe->pipe_buffer.cnt;
1815                 } else {
1816                         kn->kn_data = PIPE_BUF;
1817                 }
1818         }
1819
1820         if (wpipe->pipe_present != PIPE_ACTIVE ||
1821             (wpipe->pipe_state & PIPE_EOF)) {
1822                 kn->kn_flags |= EV_EOF;
1823                 return (1);
1824         }
1825         kn->kn_flags &= ~EV_EOF;
1826         return (kn->kn_data >= PIPE_BUF);
1827 }
1828
1829 static void
1830 filt_pipedetach_notsup(struct knote *kn)
1831 {
1832
1833 }
1834
1835 static int
1836 filt_pipenotsup(struct knote *kn, long hint)
1837 {
1838
1839         return (0);
1840 }