PIPE(2): Import from FreeBSD

2 files changed, 1831 insertions, 0 deletions

diff --git a/freebsd/sys/kern/sys_pipe.c b/freebsd/sys/kern/sys_pipe.c
new file mode 100644
index 00000000..5565c007
--- /dev/null
+++ b/freebsd/sys/kern/sys_pipe.c
@@ -0,0 +1,1689 @@
+#include <machine/rtems-bsd-kernel-space.h>
+
+/*-
+ * Copyright (c) 1996 John S. Dyson
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice immediately at the beginning of the file, without modification,
+ *    this list of conditions, and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Absolutely no warranty of function or purpose is made by the author
+ *    John S. Dyson.
+ * 4. Modifications may be freely made to this file if the above conditions
+ *    are met.
+ */
+
+/*
+ * This file contains a high-performance replacement for the socket-based
+ * pipes scheme originally used in FreeBSD/4.4Lite.  It does not support
+ * all features of sockets, but does do everything that pipes normally
+ * do.
+ */
+
+/*
+ * This code has two modes of operation, a small write mode and a large
+ * write mode.  The small write mode acts like conventional pipes with
+ * a kernel buffer.  If the buffer is less than PIPE_MINDIRECT, then the
+ * "normal" pipe buffering is done.  If the buffer is between PIPE_MINDIRECT
+ * and PIPE_SIZE in size, the sending process pins the underlying pages in
+ * memory, and the receiving process copies directly from these pinned pages
+ * in the sending process.
+ *
+ * If the sending process receives a signal, it is possible that it will
+ * go away, and certainly its address space can change, because control
+ * is returned back to the user-mode side.  In that case, the pipe code
+ * arranges to copy the buffer supplied by the user process, to a pageable
+ * kernel buffer, and the receiving process will grab the data from the
+ * pageable kernel buffer.  Since signals don't happen all that often,
+ * the copy operation is normally eliminated.
+ *
+ * The constant PIPE_MINDIRECT is chosen to make sure that buffering will
+ * happen for small transfers so that the system will not spend all of
+ * its time context switching.
+ *
+ * In order to limit the resource use of pipes, two sysctls exist:
+ *
+ * kern.ipc.maxpipekva - This is a hard limit on the amount of pageable
+ * address space available to us in pipe_map. This value is normally
+ * autotuned, but may also be loader tuned.
+ *
+ * kern.ipc.pipekva - This read-only sysctl tracks the current amount of
+ * memory in use by pipes.
+ *
+ * Based on how large pipekva is relative to maxpipekva, the following
+ * will happen:
+ *
+ * 0% - 50%:
+ *     New pipes are given 16K of memory backing, pipes may dynamically
+ *     grow to as large as 64K where needed.
+ * 50% - 75%:
+ *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
+ *     existing pipes may NOT grow.
+ * 75% - 100%:
+ *     New pipes are given 4K (or PAGE_SIZE) of memory backing,
+ *     existing pipes will be shrunk down to 4K whenever possible.
+ *
+ * Resizing may be disabled by setting kern.ipc.piperesizeallowed=0.  If
+ * that is set,  the only resize that will occur is the 0 -> SMALL_PIPE_SIZE
+ * resize which MUST occur for reverse-direction pipes when they are
+ * first used.
+ *
+ * Additional information about the current state of pipes may be obtained
+ * from kern.ipc.pipes, kern.ipc.pipefragretry, kern.ipc.pipeallocfail,
+ * and kern.ipc.piperesizefail.
+ *
+ * Locking rules:  There are two locks present here:  A mutex, used via
+ * PIPE_LOCK, and a flag, used via pipelock().  All locking is done via
+ * the flag, as mutexes can not persist over uiomove.  The mutex
+ * exists only to guard access to the flag, and is not in itself a
+ * locking mechanism.  Also note that there is only a single mutex for
+ * both directions of a pipe.
+ *
+ * As pipelock() may have to sleep before it can acquire the flag, it
+ * is important to reread all data after a call to pipelock(); everything
+ * in the structure may have changed.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <rtems/bsd/sys/param.h>
+#include <sys/systm.h>
+#include <sys/conf.h>
+#include <sys/fcntl.h>
+#include <sys/file.h>
+#include <sys/filedesc.h>
+#include <sys/filio.h>
+#include <sys/kernel.h>
+#include <rtems/bsd/sys/lock.h>
+#include <sys/mutex.h>
+#include <sys/ttycom.h>
+#include <sys/stat.h>
+#include <sys/malloc.h>
+#include <sys/poll.h>
+#include <sys/selinfo.h>
+#include <sys/signalvar.h>
+#include <sys/syscallsubr.h>
+#include <sys/sysctl.h>
+#include <sys/sysproto.h>
+#include <sys/pipe.h>
+#include <sys/proc.h>
+#include <sys/vnode.h>
+#include <sys/uio.h>
+#include <sys/event.h>
+
+#include <security/mac/mac_framework.h>
+
+#include <vm/vm.h>
+#include <vm/vm_param.h>
+#include <vm/vm_object.h>
+#include <vm/vm_kern.h>
+#include <vm/vm_extern.h>
+#include <vm/pmap.h>
+#include <vm/vm_map.h>
+#include <vm/vm_page.h>
+#include <vm/uma.h>
+
+/* XXX */
+int	do_pipe(struct thread *td, int fildes[2], int flags);
+
+/*
+ * Use this define if you want to disable *fancy* VM things.  Expect an
+ * approx 30% decrease in transfer rate.  This could be useful for
+ * NetBSD or OpenBSD.
+ */
+/* #define PIPE_NODIRECT */
+
+/*
+ * interfaces to the outside world
+ */
+static fo_rdwr_t	pipe_read;
+static fo_rdwr_t	pipe_write;
+static fo_truncate_t	pipe_truncate;
+static fo_ioctl_t	pipe_ioctl;
+static fo_poll_t	pipe_poll;
+static fo_kqfilter_t	pipe_kqfilter;
+static fo_stat_t	pipe_stat;
+static fo_close_t	pipe_close;
+
+static struct fileops pipeops = {
+	.fo_read = pipe_read,
+	.fo_write = pipe_write,
+	.fo_truncate = pipe_truncate,
+	.fo_ioctl = pipe_ioctl,
+	.fo_poll = pipe_poll,
+	.fo_kqfilter = pipe_kqfilter,
+	.fo_stat = pipe_stat,
+	.fo_close = pipe_close,
+	.fo_chmod = invfo_chmod,
+	.fo_chown = invfo_chown,
+	.fo_flags = DFLAG_PASSABLE
+};
+
+static void	filt_pipedetach(struct knote *kn);
+static int	filt_piperead(struct knote *kn, long hint);
+static int	filt_pipewrite(struct knote *kn, long hint);
+
+static struct filterops pipe_rfiltops = {
+	.f_isfd = 1,
+	.f_detach = filt_pipedetach,
+	.f_event = filt_piperead
+};
+static struct filterops pipe_wfiltops = {
+	.f_isfd = 1,
+	.f_detach = filt_pipedetach,
+	.f_event = filt_pipewrite
+};
+
+/*
+ * Default pipe buffer size(s), this can be kind-of large now because pipe
+ * space is pageable.  The pipe code will try to maintain locality of
+ * reference for performance reasons, so small amounts of outstanding I/O
+ * will not wipe the cache.
+ */
+#define MINPIPESIZE (PIPE_SIZE/3)
+#define MAXPIPESIZE (2*PIPE_SIZE/3)
+
+static long amountpipekva;
+static int pipefragretry;
+static int pipeallocfail;
+static int piperesizefail;
+static int piperesizeallowed = 1;
+
+SYSCTL_LONG(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RDTUN,
+	   &maxpipekva, 0, "Pipe KVA limit");
+SYSCTL_LONG(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
+	   &amountpipekva, 0, "Pipe KVA usage");
+SYSCTL_INT(_kern_ipc, OID_AUTO, pipefragretry, CTLFLAG_RD,
+	  &pipefragretry, 0, "Pipe allocation retries due to fragmentation");
+SYSCTL_INT(_kern_ipc, OID_AUTO, pipeallocfail, CTLFLAG_RD,
+	  &pipeallocfail, 0, "Pipe allocation failures");
+SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizefail, CTLFLAG_RD,
+	  &piperesizefail, 0, "Pipe resize failures");
+SYSCTL_INT(_kern_ipc, OID_AUTO, piperesizeallowed, CTLFLAG_RW,
+	  &piperesizeallowed, 0, "Pipe resizing allowed");
+
+static void pipeinit(void *dummy __unused);
+static void pipeclose(struct pipe *cpipe);
+static void pipe_free_kmem(struct pipe *cpipe);
+static int pipe_create(struct pipe *pipe, int backing);
+static __inline int pipelock(struct pipe *cpipe, int catch);
+static __inline void pipeunlock(struct pipe *cpipe);
+static __inline void pipeselwakeup(struct pipe *cpipe);
+#ifndef PIPE_NODIRECT
+static int pipe_build_write_buffer(struct pipe *wpipe, struct uio *uio);
+static void pipe_destroy_write_buffer(struct pipe *wpipe);
+static int pipe_direct_write(struct pipe *wpipe, struct uio *uio);
+static void pipe_clone_write_buffer(struct pipe *wpipe);
+#endif
+static int pipespace(struct pipe *cpipe, int size);
+static int pipespace_new(struct pipe *cpipe, int size);
+
+static int	pipe_zone_ctor(void *mem, int size, void *arg, int flags);
+static int	pipe_zone_init(void *mem, int size, int flags);
+static void	pipe_zone_fini(void *mem, int size);
+
+static uma_zone_t pipe_zone;
+static struct unrhdr *pipeino_unr;
+static dev_t pipedev_ino;
+
+SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);
+
+static void
+pipeinit(void *dummy __unused)
+{
+
+	pipe_zone = uma_zcreate("pipe", sizeof(struct pipepair),
+	    pipe_zone_ctor, NULL, pipe_zone_init, pipe_zone_fini,
+	    UMA_ALIGN_PTR, 0);
+	KASSERT(pipe_zone != NULL, ("pipe_zone not initialized"));
+	pipeino_unr = new_unrhdr(1, INT32_MAX, NULL);
+	KASSERT(pipeino_unr != NULL, ("pipe fake inodes not initialized"));
+	pipedev_ino = devfs_alloc_cdp_inode();
+	KASSERT(pipedev_ino > 0, ("pipe dev inode not initialized"));
+}
+
+static int
+pipe_zone_ctor(void *mem, int size, void *arg, int flags)
+{
+	struct pipepair *pp;
+	struct pipe *rpipe, *wpipe;
+
+	KASSERT(size == sizeof(*pp), ("pipe_zone_ctor: wrong size"));
+
+	pp = (struct pipepair *)mem;
+
+	/*
+	 * We zero both pipe endpoints to make sure all the kmem pointers
+	 * are NULL, flag fields are zero'd, etc.  We timestamp both
+	 * endpoints with the same time.
+	 */
+	rpipe = &pp->pp_rpipe;
+	bzero(rpipe, sizeof(*rpipe));
+	vfs_timestamp(&rpipe->pipe_ctime);
+	rpipe->pipe_atime = rpipe->pipe_mtime = rpipe->pipe_ctime;
+
+	wpipe = &pp->pp_wpipe;
+	bzero(wpipe, sizeof(*wpipe));
+	wpipe->pipe_ctime = rpipe->pipe_ctime;
+	wpipe->pipe_atime = wpipe->pipe_mtime = rpipe->pipe_ctime;
+
+	rpipe->pipe_peer = wpipe;
+	rpipe->pipe_pair = pp;
+	wpipe->pipe_peer = rpipe;
+	wpipe->pipe_pair = pp;
+
+	/*
+	 * Mark both endpoints as present; they will later get free'd
+	 * one at a time.  When both are free'd, then the whole pair
+	 * is released.
+	 */
+	rpipe->pipe_present = PIPE_ACTIVE;
+	wpipe->pipe_present = PIPE_ACTIVE;
+
+	/*
+	 * Eventually, the MAC Framework may initialize the label
+	 * in ctor or init, but for now we do it elswhere to avoid
+	 * blocking in ctor or init.
+	 */
+	pp->pp_label = NULL;
+
+	return (0);
+}
+
+static int
+pipe_zone_init(void *mem, int size, int flags)
+{
+	struct pipepair *pp;
+
+	KASSERT(size == sizeof(*pp), ("pipe_zone_init: wrong size"));
+
+	pp = (struct pipepair *)mem;
+
+	mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_RECURSE);
+	return (0);
+}
+
+static void
+pipe_zone_fini(void *mem, int size)
+{
+	struct pipepair *pp;
+
+	KASSERT(size == sizeof(*pp), ("pipe_zone_fini: wrong size"));
+
+	pp = (struct pipepair *)mem;
+
+	mtx_destroy(&pp->pp_mtx);
+}
+
+/*
+ * The pipe system call for the DTYPE_PIPE type of pipes.  If we fail, let
+ * the zone pick up the pieces via pipeclose().
+ */
+int
+kern_pipe(struct thread *td, int fildes[2])
+{
+
+	return (do_pipe(td, fildes, 0));
+}
+
+int
+do_pipe(struct thread *td, int fildes[2], int flags)
+{
+	struct filedesc *fdp = td->td_proc->p_fd;
+	struct file *rf, *wf;
+	struct pipepair *pp;
+	struct pipe *rpipe, *wpipe;
+	int fd, fflags, error;
+
+	pp = uma_zalloc(pipe_zone, M_WAITOK);
+#ifdef MAC
+	/*
+	 * The MAC label is shared between the connected endpoints.  As a
+	 * result mac_pipe_init() and mac_pipe_create() are called once
+	 * for the pair, and not on the endpoints.
+	 */
+	mac_pipe_init(pp);
+	mac_pipe_create(td->td_ucred, pp);
+#endif
+	rpipe = &pp->pp_rpipe;
+	wpipe = &pp->pp_wpipe;
+
+	knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
+	knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
+
+	/* Only the forward direction pipe is backed by default */
+	if ((error = pipe_create(rpipe, 1)) != 0 ||
+	    (error = pipe_create(wpipe, 0)) != 0) {
+		pipeclose(rpipe);
+		pipeclose(wpipe);
+		return (error);
+	}
+
+	rpipe->pipe_state |= PIPE_DIRECTOK;
+	wpipe->pipe_state |= PIPE_DIRECTOK;
+
+	error = falloc(td, &rf, &fd, flags);
+	if (error) {
+		pipeclose(rpipe);
+		pipeclose(wpipe);
+		return (error);
+	}
+	/* An extra reference on `rf' has been held for us by falloc(). */
+	fildes[0] = fd;
+
+	fflags = FREAD | FWRITE;
+	if ((flags & O_NONBLOCK) != 0)
+		fflags |= FNONBLOCK;
+
+	/*
+	 * Warning: once we've gotten past allocation of the fd for the
+	 * read-side, we can only drop the read side via fdrop() in order
+	 * to avoid races against processes which manage to dup() the read
+	 * side while we are blocked trying to allocate the write side.
+	 */
+	finit(rf, fflags, DTYPE_PIPE, rpipe, &pipeops);
+	error = falloc(td, &wf, &fd, flags);
+	if (error) {
+		fdclose(fdp, rf, fildes[0], td);
+		fdrop(rf, td);
+		/* rpipe has been closed by fdrop(). */
+		pipeclose(wpipe);
+		return (error);
+	}
+	/* An extra reference on `wf' has been held for us by falloc(). */
+	finit(wf, fflags, DTYPE_PIPE, wpipe, &pipeops);
+	fdrop(wf, td);
+	fildes[1] = fd;
+	fdrop(rf, td);
+
+	return (0);
+}
+
+/* ARGSUSED */
+int
+sys_pipe(struct thread *td, struct pipe_args *uap)
+{
+	int error;
+	int fildes[2];
+
+	error = kern_pipe(td, fildes);
+	if (error)
+		return (error);
+
+	td->td_retval[0] = fildes[0];
+	td->td_retval[1] = fildes[1];
+
+	return (0);
+}
+
+/*
+ * Allocate kva for pipe circular buffer, the space is pageable
+ * This routine will 'realloc' the size of a pipe safely, if it fails
+ * it will retain the old buffer.
+ * If it fails it will return ENOMEM.
+ */
+static int
+pipespace_new(cpipe, size)
+	struct pipe *cpipe;
+	int size;
+{
+	caddr_t buffer;
+	int error, cnt, firstseg;
+	static int curfail = 0;
+	static struct timeval lastfail;
+
+	KASSERT(!mtx_owned(PIPE_MTX(cpipe)), ("pipespace: pipe mutex locked"));
+	KASSERT(!(cpipe->pipe_state & PIPE_DIRECTW),
+		("pipespace: resize of direct writes not allowed"));
+retry:
+	cnt = cpipe->pipe_buffer.cnt;
+	if (cnt > size)
+		size = cnt;
+
+	size = round_page(size);
+	buffer = (caddr_t) vm_map_min(pipe_map);
+
+	error = vm_map_find(pipe_map, NULL, 0,
+		(vm_offset_t *) &buffer, size, 1,
+		VM_PROT_ALL, VM_PROT_ALL, 0);
+	if (error != KERN_SUCCESS) {
+		if ((cpipe->pipe_buffer.buffer == NULL) &&
+			(size > SMALL_PIPE_SIZE)) {
+			size = SMALL_PIPE_SIZE;
+			pipefragretry++;
+			goto retry;
+		}
+		if (cpipe->pipe_buffer.buffer == NULL) {
+			pipeallocfail++;
+			if (ppsratecheck(&lastfail, &curfail, 1))
+				printf("kern.ipc.maxpipekva exceeded; see tuning(7)\n");
+		} else {
+			piperesizefail++;
+		}
+		return (ENOMEM);
+	}
+
+	/* copy data, then free old resources if we're resizing */
+	if (cnt > 0) {
+		if (cpipe->pipe_buffer.in <= cpipe->pipe_buffer.out) {
+			firstseg = cpipe->pipe_buffer.size - cpipe->pipe_buffer.out;
+			bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
+				buffer, firstseg);
+			if ((cnt - firstseg) > 0)
+				bcopy(cpipe->pipe_buffer.buffer, &buffer[firstseg],
+					cpipe->pipe_buffer.in);
+		} else {
+			bcopy(&cpipe->pipe_buffer.buffer[cpipe->pipe_buffer.out],
+				buffer, cnt);
+		}
+	}
+	pipe_free_kmem(cpipe);
+	cpipe->pipe_buffer.buffer = buffer;
+	cpipe->pipe_buffer.size = size;
+	cpipe->pipe_buffer.in = cnt;
+	cpipe->pipe_buffer.out = 0;
+	cpipe->pipe_buffer.cnt = cnt;
+	atomic_add_long(&amountpipekva, cpipe->pipe_buffer.size);
+	return (0);
+}
+
+/*
+ * Wrapper for pipespace_new() that performs locking assertions.
+ */
+static int
+pipespace(cpipe, size)
+	struct pipe *cpipe;
+	int size;
+{
+
+	KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
+		("Unlocked pipe passed to pipespace"));
+	return (pipespace_new(cpipe, size));
+}
+
+/*
+ * lock a pipe for I/O, blocking other access
+ */
+static __inline int
+pipelock(cpipe, catch)
+	struct pipe *cpipe;
+	int catch;
+{
+	int error;
+
+	PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
+	while (cpipe->pipe_state & PIPE_LOCKFL) {
+		cpipe->pipe_state |= PIPE_LWANT;
+		error = msleep(cpipe, PIPE_MTX(cpipe),
+		    catch ? (PRIBIO | PCATCH) : PRIBIO,
+		    "pipelk", 0);
+		if (error != 0)
+			return (error);
+	}
+	cpipe->pipe_state |= PIPE_LOCKFL;
+	return (0);
+}
+
+/*
+ * unlock a pipe I/O lock
+ */
+static __inline void
+pipeunlock(cpipe)
+	struct pipe *cpipe;
+{
+
+	PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
+	KASSERT(cpipe->pipe_state & PIPE_LOCKFL,
+		("Unlocked pipe passed to pipeunlock"));
+	cpipe->pipe_state &= ~PIPE_LOCKFL;
+	if (cpipe->pipe_state & PIPE_LWANT) {
+		cpipe->pipe_state &= ~PIPE_LWANT;
+		wakeup(cpipe);
+	}
+}
+
+static __inline void
+pipeselwakeup(cpipe)
+	struct pipe *cpipe;
+{
+
+	PIPE_LOCK_ASSERT(cpipe, MA_OWNED);
+	if (cpipe->pipe_state & PIPE_SEL) {
+		selwakeuppri(&cpipe->pipe_sel, PSOCK);
+		if (!SEL_WAITING(&cpipe->pipe_sel))
+			cpipe->pipe_state &= ~PIPE_SEL;
+	}
+	if ((cpipe->pipe_state & PIPE_ASYNC) && cpipe->pipe_sigio)
+		pgsigio(&cpipe->pipe_sigio, SIGIO, 0);
+	KNOTE_LOCKED(&cpipe->pipe_sel.si_note, 0);
+}
+
+/*
+ * Initialize and allocate VM and memory for pipe.  The structure
+ * will start out zero'd from the ctor, so we just manage the kmem.
+ */
+static int
+pipe_create(pipe, backing)
+	struct pipe *pipe;
+	int backing;
+{
+	int error;
+
+	if (backing) {
+		if (amountpipekva > maxpipekva / 2)
+			error = pipespace_new(pipe, SMALL_PIPE_SIZE);
+		else
+			error = pipespace_new(pipe, PIPE_SIZE);
+	} else {
+		/* If we're not backing this pipe, no need to do anything. */
+		error = 0;
+	}
+	pipe->pipe_ino = -1;
+	return (error);
+}
+
+/* ARGSUSED */
+static int
+pipe_read(fp, uio, active_cred, flags, td)
+	struct file *fp;
+	struct uio *uio;
+	struct ucred *active_cred;
+	struct thread *td;
+	int flags;
+{
+	struct pipe *rpipe = fp->f_data;
+	int error;
+	int nread = 0;
+	int size;
+
+	PIPE_LOCK(rpipe);
+	++rpipe->pipe_busy;
+	error = pipelock(rpipe, 1);
+	if (error)
+		goto unlocked_error;
+
+#ifdef MAC
+	error = mac_pipe_check_read(active_cred, rpipe->pipe_pair);
+	if (error)
+		goto locked_error;
+#endif
+	if (amountpipekva > (3 * maxpipekva) / 4) {
+		if (!(rpipe->pipe_state & PIPE_DIRECTW) &&
+			(rpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
+			(rpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
+			(piperesizeallowed == 1)) {
+			PIPE_UNLOCK(rpipe);
+			pipespace(rpipe, SMALL_PIPE_SIZE);
+			PIPE_LOCK(rpipe);
+		}
+	}
+
+	while (uio->uio_resid) {
+		/*
+		 * normal pipe buffer receive
+		 */
+		if (rpipe->pipe_buffer.cnt > 0) {
+			size = rpipe->pipe_buffer.size - rpipe->pipe_buffer.out;
+			if (size > rpipe->pipe_buffer.cnt)
+				size = rpipe->pipe_buffer.cnt;
+			if (size > uio->uio_resid)
+				size = uio->uio_resid;
+
+			PIPE_UNLOCK(rpipe);
+			error = uiomove(
+			    &rpipe->pipe_buffer.buffer[rpipe->pipe_buffer.out],
+			    size, uio);
+			PIPE_LOCK(rpipe);
+			if (error)
+				break;
+
+			rpipe->pipe_buffer.out += size;
+			if (rpipe->pipe_buffer.out >= rpipe->pipe_buffer.size)
+				rpipe->pipe_buffer.out = 0;
+
+			rpipe->pipe_buffer.cnt -= size;
+
+			/*
+			 * If there is no more to read in the pipe, reset
+			 * its pointers to the beginning.  This improves
+			 * cache hit stats.
+			 */
+			if (rpipe->pipe_buffer.cnt == 0) {
+				rpipe->pipe_buffer.in = 0;
+				rpipe->pipe_buffer.out = 0;
+			}
+			nread += size;
+#ifndef PIPE_NODIRECT
+		/*
+		 * Direct copy, bypassing a kernel buffer.
+		 */
+		} else if ((size = rpipe->pipe_map.cnt) &&
+			   (rpipe->pipe_state & PIPE_DIRECTW)) {
+			if (size > uio->uio_resid)
+				size = (u_int) uio->uio_resid;
+
+			PIPE_UNLOCK(rpipe);
+			error = uiomove_fromphys(rpipe->pipe_map.ms,
+			    rpipe->pipe_map.pos, size, uio);
+			PIPE_LOCK(rpipe);
+			if (error)
+				break;
+			nread += size;
+			rpipe->pipe_map.pos += size;
+			rpipe->pipe_map.cnt -= size;
+			if (rpipe->pipe_map.cnt == 0) {
+				rpipe->pipe_state &= ~PIPE_DIRECTW;
+				wakeup(rpipe);
+			}
+#endif
+		} else {
+			/*
+			 * detect EOF condition
+			 * read returns 0 on EOF, no need to set error
+			 */
+			if (rpipe->pipe_state & PIPE_EOF)
+				break;
+
+			/*
+			 * If the "write-side" has been blocked, wake it up now.
+			 */
+			if (rpipe->pipe_state & PIPE_WANTW) {
+				rpipe->pipe_state &= ~PIPE_WANTW;
+				wakeup(rpipe);
+			}
+
+			/*
+			 * Break if some data was read.
+			 */
+			if (nread > 0)
+				break;
+
+			/*
+			 * Unlock the pipe buffer for our remaining processing.
+			 * We will either break out with an error or we will
+			 * sleep and relock to loop.
+			 */
+			pipeunlock(rpipe);
+
+			/*
+			 * Handle non-blocking mode operation or
+			 * wait for more data.
+			 */
+			if (fp->f_flag & FNONBLOCK) {
+				error = EAGAIN;
+			} else {
+				rpipe->pipe_state |= PIPE_WANTR;
+				if ((error = msleep(rpipe, PIPE_MTX(rpipe),
+				    PRIBIO | PCATCH,
+				    "piperd", 0)) == 0)
+					error = pipelock(rpipe, 1);
+			}
+			if (error)
+				goto unlocked_error;
+		}
+	}
+#ifdef MAC
+locked_error:
+#endif
+	pipeunlock(rpipe);
+
+	/* XXX: should probably do this before getting any locks. */
+	if (error == 0)
+		vfs_timestamp(&rpipe->pipe_atime);
+unlocked_error:
+	--rpipe->pipe_busy;
+
+	/*
+	 * PIPE_WANT processing only makes sense if pipe_busy is 0.
+	 */
+	if ((rpipe->pipe_busy == 0) && (rpipe->pipe_state & PIPE_WANT)) {
+		rpipe->pipe_state &= ~(PIPE_WANT|PIPE_WANTW);
+		wakeup(rpipe);
+	} else if (rpipe->pipe_buffer.cnt < MINPIPESIZE) {
+		/*
+		 * Handle write blocking hysteresis.
+		 */
+		if (rpipe->pipe_state & PIPE_WANTW) {
+			rpipe->pipe_state &= ~PIPE_WANTW;
+			wakeup(rpipe);
+		}
+	}
+
+	if ((rpipe->pipe_buffer.size - rpipe->pipe_buffer.cnt) >= PIPE_BUF)
+		pipeselwakeup(rpipe);
+
+	PIPE_UNLOCK(rpipe);
+	return (error);
+}
+
+#ifndef PIPE_NODIRECT
+/*
+ * Map the sending processes' buffer into kernel space and wire it.
+ * This is similar to a physical write operation.
+ */
+static int
+pipe_build_write_buffer(wpipe, uio)
+	struct pipe *wpipe;
+	struct uio *uio;
+{
+	u_int size;
+	int i;
+
+	PIPE_LOCK_ASSERT(wpipe, MA_NOTOWNED);
+	KASSERT(wpipe->pipe_state & PIPE_DIRECTW,
+		("Clone attempt on non-direct write pipe!"));
+
+	if (uio->uio_iov->iov_len > wpipe->pipe_buffer.size)
+                size = wpipe->pipe_buffer.size;
+	else
+                size = uio->uio_iov->iov_len;
+
+	if ((i = vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
+	    (vm_offset_t)uio->uio_iov->iov_base, size, VM_PROT_READ,
+	    wpipe->pipe_map.ms, PIPENPAGES)) < 0)
+		return (EFAULT);
+
+/*
+ * set up the control block
+ */
+	wpipe->pipe_map.npages = i;
+	wpipe->pipe_map.pos =
+	    ((vm_offset_t) uio->uio_iov->iov_base) & PAGE_MASK;
+	wpipe->pipe_map.cnt = size;
+
+/*
+ * and update the uio data
+ */
+
+	uio->uio_iov->iov_len -= size;
+	uio->uio_iov->iov_base = (char *)uio->uio_iov->iov_base + size;
+	if (uio->uio_iov->iov_len == 0)
+		uio->uio_iov++;
+	uio->uio_resid -= size;
+	uio->uio_offset += size;
+	return (0);
+}
+
+/*
+ * unmap and unwire the process buffer
+ */
+static void
+pipe_destroy_write_buffer(wpipe)
+	struct pipe *wpipe;
+{
+
+	PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
+	vm_page_unhold_pages(wpipe->pipe_map.ms, wpipe->pipe_map.npages);
+	wpipe->pipe_map.npages = 0;
+}
+
+/*
+ * In the case of a signal, the writing process might go away.  This
+ * code copies the data into the circular buffer so that the source
+ * pages can be freed without loss of data.
+ */
+static void
+pipe_clone_write_buffer(wpipe)
+	struct pipe *wpipe;
+{
+	struct uio uio;
+	struct iovec iov;
+	int size;
+	int pos;
+
+	PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
+	size = wpipe->pipe_map.cnt;
+	pos = wpipe->pipe_map.pos;
+
+	wpipe->pipe_buffer.in = size;
+	wpipe->pipe_buffer.out = 0;
+	wpipe->pipe_buffer.cnt = size;
+	wpipe->pipe_state &= ~PIPE_DIRECTW;
+
+	PIPE_UNLOCK(wpipe);
+	iov.iov_base = wpipe->pipe_buffer.buffer;
+	iov.iov_len = size;
+	uio.uio_iov = &iov;
+	uio.uio_iovcnt = 1;
+	uio.uio_offset = 0;
+	uio.uio_resid = size;
+	uio.uio_segflg = UIO_SYSSPACE;
+	uio.uio_rw = UIO_READ;
+	uio.uio_td = curthread;
+	uiomove_fromphys(wpipe->pipe_map.ms, pos, size, &uio);
+	PIPE_LOCK(wpipe);
+	pipe_destroy_write_buffer(wpipe);
+}
+
+/*
+ * This implements the pipe buffer write mechanism.  Note that only
+ * a direct write OR a normal pipe write can be pending at any given time.
+ * If there are any characters in the pipe buffer, the direct write will
+ * be deferred until the receiving process grabs all of the bytes from
+ * the pipe buffer.  Then the direct mapping write is set-up.
+ */
+static int
+pipe_direct_write(wpipe, uio)
+	struct pipe *wpipe;
+	struct uio *uio;
+{
+	int error;
+
+retry:
+	PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
+	error = pipelock(wpipe, 1);
+	if (wpipe->pipe_state & PIPE_EOF)
+		error = EPIPE;
+	if (error) {
+		pipeunlock(wpipe);
+		goto error1;
+	}
+	while (wpipe->pipe_state & PIPE_DIRECTW) {
+		if (wpipe->pipe_state & PIPE_WANTR) {
+			wpipe->pipe_state &= ~PIPE_WANTR;
+			wakeup(wpipe);
+		}
+		pipeselwakeup(wpipe);
+		wpipe->pipe_state |= PIPE_WANTW;
+		pipeunlock(wpipe);
+		error = msleep(wpipe, PIPE_MTX(wpipe),
+		    PRIBIO | PCATCH, "pipdww", 0);
+		if (error)
+			goto error1;
+		else
+			goto retry;
+	}
+	wpipe->pipe_map.cnt = 0;	/* transfer not ready yet */
+	if (wpipe->pipe_buffer.cnt > 0) {
+		if (wpipe->pipe_state & PIPE_WANTR) {
+			wpipe->pipe_state &= ~PIPE_WANTR;
+			wakeup(wpipe);
+		}
+		pipeselwakeup(wpipe);
+		wpipe->pipe_state |= PIPE_WANTW;
+		pipeunlock(wpipe);
+		error = msleep(wpipe, PIPE_MTX(wpipe),
+		    PRIBIO | PCATCH, "pipdwc", 0);
+		if (error)
+			goto error1;
+		else
+			goto retry;
+	}
+
+	wpipe->pipe_state |= PIPE_DIRECTW;
+
+	PIPE_UNLOCK(wpipe);
+	error = pipe_build_write_buffer(wpipe, uio);
+	PIPE_LOCK(wpipe);
+	if (error) {
+		wpipe->pipe_state &= ~PIPE_DIRECTW;
+		pipeunlock(wpipe);
+		goto error1;
+	}
+
+	error = 0;
+	while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
+		if (wpipe->pipe_state & PIPE_EOF) {
+			pipe_destroy_write_buffer(wpipe);
+			pipeselwakeup(wpipe);
+			pipeunlock(wpipe);
+			error = EPIPE;
+			goto error1;
+		}
+		if (wpipe->pipe_state & PIPE_WANTR) {
+			wpipe->pipe_state &= ~PIPE_WANTR;
+			wakeup(wpipe);
+		}
+		pipeselwakeup(wpipe);
+		pipeunlock(wpipe);
+		error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
+		    "pipdwt", 0);
+		pipelock(wpipe, 0);
+	}
+
+	if (wpipe->pipe_state & PIPE_EOF)
+		error = EPIPE;
+	if (wpipe->pipe_state & PIPE_DIRECTW) {
+		/*
+		 * this bit of trickery substitutes a kernel buffer for
+		 * the process that might be going away.
+		 */
+		pipe_clone_write_buffer(wpipe);
+	} else {
+		pipe_destroy_write_buffer(wpipe);
+	}
+	pipeunlock(wpipe);
+	return (error);
+
+error1:
+	wakeup(wpipe);
+	return (error);
+}
+#endif
+
+static int
+pipe_write(fp, uio, active_cred, flags, td)
+	struct file *fp;
+	struct uio *uio;
+	struct ucred *active_cred;
+	struct thread *td;
+	int flags;
+{
+	int error = 0;
+	int desiredsize;
+	ssize_t orig_resid;
+	struct pipe *wpipe, *rpipe;
+
+	rpipe = fp->f_data;
+	wpipe = rpipe->pipe_peer;
+
+	PIPE_LOCK(rpipe);
+	error = pipelock(wpipe, 1);
+	if (error) {
+		PIPE_UNLOCK(rpipe);
+		return (error);
+	}
+	/*
+	 * detect loss of pipe read side, issue SIGPIPE if lost.
+	 */
+	if (wpipe->pipe_present != PIPE_ACTIVE ||
+	    (wpipe->pipe_state & PIPE_EOF)) {
+		pipeunlock(wpipe);
+		PIPE_UNLOCK(rpipe);
+		return (EPIPE);
+	}
+#ifdef MAC
+	error = mac_pipe_check_write(active_cred, wpipe->pipe_pair);
+	if (error) {
+		pipeunlock(wpipe);
+		PIPE_UNLOCK(rpipe);
+		return (error);
+	}
+#endif
+	++wpipe->pipe_busy;
+
+	/* Choose a larger size if it's advantageous */
+	desiredsize = max(SMALL_PIPE_SIZE, wpipe->pipe_buffer.size);
+	while (desiredsize < wpipe->pipe_buffer.cnt + uio->uio_resid) {
+		if (piperesizeallowed != 1)
+			break;
+		if (amountpipekva > maxpipekva / 2)
+			break;
+		if (desiredsize == BIG_PIPE_SIZE)
+			break;
+		desiredsize = desiredsize * 2;
+	}
+
+	/* Choose a smaller size if we're in a OOM situation */
+	if ((amountpipekva > (3 * maxpipekva) / 4) &&
+		(wpipe->pipe_buffer.size > SMALL_PIPE_SIZE) &&
+		(wpipe->pipe_buffer.cnt <= SMALL_PIPE_SIZE) &&
+		(piperesizeallowed == 1))
+		desiredsize = SMALL_PIPE_SIZE;
+
+	/* Resize if the above determined that a new size was necessary */
+	if ((desiredsize != wpipe->pipe_buffer.size) &&
+		((wpipe->pipe_state & PIPE_DIRECTW) == 0)) {
+		PIPE_UNLOCK(wpipe);
+		pipespace(wpipe, desiredsize);
+		PIPE_LOCK(wpipe);
+	}
+	if (wpipe->pipe_buffer.size == 0) {
+		/*
+		 * This can only happen for reverse direction use of pipes
+		 * in a complete OOM situation.
+		 */
+		error = ENOMEM;
+		--wpipe->pipe_busy;
+		pipeunlock(wpipe);
+		PIPE_UNLOCK(wpipe);
+		return (error);
+	}
+
+	pipeunlock(wpipe);
+
+	orig_resid = uio->uio_resid;
+
+	while (uio->uio_resid) {
+		int space;
+
+		pipelock(wpipe, 0);
+		if (wpipe->pipe_state & PIPE_EOF) {
+			pipeunlock(wpipe);
+			error = EPIPE;
+			break;
+		}
+#ifndef PIPE_NODIRECT
+		/*
+		 * If the transfer is large, we can gain performance if
+		 * we do process-to-process copies directly.
+		 * If the write is non-blocking, we don't use the
+		 * direct write mechanism.
+		 *
+		 * The direct write mechanism will detect the reader going
+		 * away on us.
+		 */
+		if (uio->uio_segflg == UIO_USERSPACE &&
+		    uio->uio_iov->iov_len >= PIPE_MINDIRECT &&
+		    wpipe->pipe_buffer.size >= PIPE_MINDIRECT &&
+		    (fp->f_flag & FNONBLOCK) == 0) {
+			pipeunlock(wpipe);
+			error = pipe_direct_write(wpipe, uio);
+			if (error)
+				break;
+			continue;
+		}
+#endif
+
+		/*
+		 * Pipe buffered writes cannot be coincidental with
+		 * direct writes.  We wait until the currently executing
+		 * direct write is completed before we start filling the
+		 * pipe buffer.  We break out if a signal occurs or the
+		 * reader goes away.
+		 */
+		if (wpipe->pipe_state & PIPE_DIRECTW) {
+			if (wpipe->pipe_state & PIPE_WANTR) {
+				wpipe->pipe_state &= ~PIPE_WANTR;
+				wakeup(wpipe);
+			}
+			pipeselwakeup(wpipe);
+			wpipe->pipe_state |= PIPE_WANTW;
+			pipeunlock(wpipe);
+			error = msleep(wpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH,
+			    "pipbww", 0);
+			if (error)
+				break;
+			else
+				continue;
+		}
+
+		space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;
+
+		/* Writes of size <= PIPE_BUF must be atomic. */
+		if ((space < uio->uio_resid) && (orig_resid <= PIPE_BUF))
+			space = 0;
+
+		if (space > 0) {
+			int size;	/* Transfer size */
+			int segsize;	/* first segment to transfer */
+
+			/*
+			 * Transfer size is minimum of uio transfer
+			 * and free space in pipe buffer.
+			 */
+			if (space > uio->uio_resid)
+				size = uio->uio_resid;
+			else
+				size = space;
+			/*
+			 * First segment to transfer is minimum of
+			 * transfer size and contiguous space in
+			 * pipe buffer.  If first segment to transfer
+			 * is less than the transfer size, we've got
+			 * a wraparound in the buffer.
+			 */
+			segsize = wpipe->pipe_buffer.size -
+				wpipe->pipe_buffer.in;
+			if (segsize > size)
+				segsize = size;
+
+			/* Transfer first segment */
+
+			PIPE_UNLOCK(rpipe);
+			error = uiomove(&wpipe->pipe_buffer.buffer[wpipe->pipe_buffer.in],
+					segsize, uio);
+			PIPE_LOCK(rpipe);
+
+			if (error == 0 && segsize < size) {
+				KASSERT(wpipe->pipe_buffer.in + segsize ==
+					wpipe->pipe_buffer.size,
+					("Pipe buffer wraparound disappeared"));
+				/*
+				 * Transfer remaining part now, to
+				 * support atomic writes.  Wraparound
+				 * happened.
+				 */
+
+				PIPE_UNLOCK(rpipe);
+				error = uiomove(
+				    &wpipe->pipe_buffer.buffer[0],
+				    size - segsize, uio);
+				PIPE_LOCK(rpipe);
+			}
+			if (error == 0) {
+				wpipe->pipe_buffer.in += size;
+				if (wpipe->pipe_buffer.in >=
+				    wpipe->pipe_buffer.size) {
+					KASSERT(wpipe->pipe_buffer.in ==
+						size - segsize +
+						wpipe->pipe_buffer.size,
+						("Expected wraparound bad"));
+					wpipe->pipe_buffer.in = size - segsize;
+				}
+
+				wpipe->pipe_buffer.cnt += size;
+				KASSERT(wpipe->pipe_buffer.cnt <=
+					wpipe->pipe_buffer.size,
+					("Pipe buffer overflow"));
+			}
+			pipeunlock(wpipe);
+			if (error != 0)
+				break;
+		} else {
+			/*
+			 * If the "read-side" has been blocked, wake it up now.
+			 */
+			if (wpipe->pipe_state & PIPE_WANTR) {
+				wpipe->pipe_state &= ~PIPE_WANTR;
+				wakeup(wpipe);
+			}
+
+			/*
+			 * don't block on non-blocking I/O
+			 */
+			if (fp->f_flag & FNONBLOCK) {
+				error = EAGAIN;
+				pipeunlock(wpipe);
+				break;
+			}
+
+			/*
+			 * We have no more space and have something to offer,
+			 * wake up select/poll.
+			 */
+			pipeselwakeup(wpipe);
+
+			wpipe->pipe_state |= PIPE_WANTW;
+			pipeunlock(wpipe);
+			error = msleep(wpipe, PIPE_MTX(rpipe),
+			    PRIBIO | PCATCH, "pipewr", 0);
+			if (error != 0)
+				break;
+		}
+	}
+
+	pipelock(wpipe, 0);
+	--wpipe->pipe_busy;
+
+	if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
+		wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
+		wakeup(wpipe);
+	} else if (wpipe->pipe_buffer.cnt > 0) {
+		/*
+		 * If we have put any characters in the buffer, we wake up
+		 * the reader.
+		 */
+		if (wpipe->pipe_state & PIPE_WANTR) {
+			wpipe->pipe_state &= ~PIPE_WANTR;
+			wakeup(wpipe);
+		}
+	}
+
+	/*
+	 * Don't return EPIPE if I/O was successful
+	 */
+	if ((wpipe->pipe_buffer.cnt == 0) &&
+	    (uio->uio_resid == 0) &&
+	    (error == EPIPE)) {
+		error = 0;
+	}
+
+	if (error == 0)
+		vfs_timestamp(&wpipe->pipe_mtime);
+
+	/*
+	 * We have something to offer,
+	 * wake up select/poll.
+	 */
+	if (wpipe->pipe_buffer.cnt)
+		pipeselwakeup(wpipe);
+
+	pipeunlock(wpipe);
+	PIPE_UNLOCK(rpipe);
+	return (error);
+}
+
+/* ARGSUSED */
+static int
+pipe_truncate(fp, length, active_cred, td)
+	struct file *fp;
+	off_t length;
+	struct ucred *active_cred;
+	struct thread *td;
+{
+
+	return (EINVAL);
+}
+
+/*
+ * we implement a very minimal set of ioctls for compatibility with sockets.
+ */
+static int
+pipe_ioctl(fp, cmd, data, active_cred, td)
+	struct file *fp;
+	u_long cmd;
+	void *data;
+	struct ucred *active_cred;
+	struct thread *td;
+{
+	struct pipe *mpipe = fp->f_data;
+	int error;
+
+	PIPE_LOCK(mpipe);
+
+#ifdef MAC
+	error = mac_pipe_check_ioctl(active_cred, mpipe->pipe_pair, cmd, data);
+	if (error) {
+		PIPE_UNLOCK(mpipe);
+		return (error);
+	}
+#endif
+
+	error = 0;
+	switch (cmd) {
+
+	case FIONBIO:
+		break;
+
+	case FIOASYNC:
+		if (*(int *)data) {
+			mpipe->pipe_state |= PIPE_ASYNC;
+		} else {
+			mpipe->pipe_state &= ~PIPE_ASYNC;
+		}
+		break;
+
+	case FIONREAD:
+		if (mpipe->pipe_state & PIPE_DIRECTW)
+			*(int *)data = mpipe->pipe_map.cnt;
+		else
+			*(int *)data = mpipe->pipe_buffer.cnt;
+		break;
+
+	case FIOSETOWN:
+		PIPE_UNLOCK(mpipe);
+		error = fsetown(*(int *)data, &mpipe->pipe_sigio);
+		goto out_unlocked;
+
+	case FIOGETOWN:
+		*(int *)data = fgetown(&mpipe->pipe_sigio);
+		break;
+
+	/* This is deprecated, FIOSETOWN should be used instead. */
+	case TIOCSPGRP:
+		PIPE_UNLOCK(mpipe);
+		error = fsetown(-(*(int *)data), &mpipe->pipe_sigio);
+		goto out_unlocked;
+
+	/* This is deprecated, FIOGETOWN should be used instead. */
+	case TIOCGPGRP:
+		*(int *)data = -fgetown(&mpipe->pipe_sigio);
+		break;
+
+	default:
+		error = ENOTTY;
+		break;
+	}
+	PIPE_UNLOCK(mpipe);
+out_unlocked:
+	return (error);
+}
+
+static int
+pipe_poll(fp, events, active_cred, td)
+	struct file *fp;
+	int events;
+	struct ucred *active_cred;
+	struct thread *td;
+{
+	struct pipe *rpipe = fp->f_data;
+	struct pipe *wpipe;
+	int revents = 0;
+#ifdef MAC
+	int error;
+#endif
+
+	wpipe = rpipe->pipe_peer;
+	PIPE_LOCK(rpipe);
+#ifdef MAC
+	error = mac_pipe_check_poll(active_cred, rpipe->pipe_pair);
+	if (error)
+		goto locked_error;
+#endif
+	if (events & (POLLIN | POLLRDNORM))
+		if ((rpipe->pipe_state & PIPE_DIRECTW) ||
+		    (rpipe->pipe_buffer.cnt > 0))
+			revents |= events & (POLLIN | POLLRDNORM);
+
+	if (events & (POLLOUT | POLLWRNORM))
+		if (wpipe->pipe_present != PIPE_ACTIVE ||
+		    (wpipe->pipe_state & PIPE_EOF) ||
+		    (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
+		     ((wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF ||
+			 wpipe->pipe_buffer.size == 0)))
+			revents |= events & (POLLOUT | POLLWRNORM);
+
+	if ((events & POLLINIGNEOF) == 0) {
+		if (rpipe->pipe_state & PIPE_EOF) {
+			revents |= (events & (POLLIN | POLLRDNORM));
+			if (wpipe->pipe_present != PIPE_ACTIVE ||
+			    (wpipe->pipe_state & PIPE_EOF))
+				revents |= POLLHUP;
+		}
+	}
+
+	if (revents == 0) {
+		if (events & (POLLIN | POLLRDNORM)) {
+			selrecord(td, &rpipe->pipe_sel);
+			if (SEL_WAITING(&rpipe->pipe_sel))
+				rpipe->pipe_state |= PIPE_SEL;
+		}
+
+		if (events & (POLLOUT | POLLWRNORM)) {
+			selrecord(td, &wpipe->pipe_sel);
+			if (SEL_WAITING(&wpipe->pipe_sel))
+				wpipe->pipe_state |= PIPE_SEL;
+		}
+	}
+#ifdef MAC
+locked_error:
+#endif
+	PIPE_UNLOCK(rpipe);
+
+	return (revents);
+}
+
+/*
+ * We shouldn't need locks here as we're doing a read and this should
+ * be a natural race.
+ */
+static int
+pipe_stat(fp, ub, active_cred, td)
+	struct file *fp;
+	struct stat *ub;
+	struct ucred *active_cred;
+	struct thread *td;
+{
+	struct pipe *pipe;
+	int new_unr;
+#ifdef MAC
+	int error;
+#endif
+
+	pipe = fp->f_data;
+	PIPE_LOCK(pipe);
+#ifdef MAC
+	error = mac_pipe_check_stat(active_cred, pipe->pipe_pair);
+	if (error) {
+		PIPE_UNLOCK(pipe);
+		return (error);
+	}
+#endif
+	/*
+	 * Lazily allocate an inode number for the pipe.  Most pipe
+	 * users do not call fstat(2) on the pipe, which means that
+	 * postponing the inode allocation until it is must be
+	 * returned to userland is useful.  If alloc_unr failed,
+	 * assign st_ino zero instead of returning an error.
+	 * Special pipe_ino values:
+	 *  -1 - not yet initialized;
+	 *  0  - alloc_unr failed, return 0 as st_ino forever.
+	 */
+	if (pipe->pipe_ino == (ino_t)-1) {
+		new_unr = alloc_unr(pipeino_unr);
+		if (new_unr != -1)
+			pipe->pipe_ino = new_unr;
+		else
+			pipe->pipe_ino = 0;
+	}
+	PIPE_UNLOCK(pipe);
+
+	bzero(ub, sizeof(*ub));
+	ub->st_mode = S_IFIFO;
+	ub->st_blksize = PAGE_SIZE;
+	if (pipe->pipe_state & PIPE_DIRECTW)
+		ub->st_size = pipe->pipe_map.cnt;
+	else
+		ub->st_size = pipe->pipe_buffer.cnt;
+	ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
+	ub->st_atim = pipe->pipe_atime;
+	ub->st_mtim = pipe->pipe_mtime;
+	ub->st_ctim = pipe->pipe_ctime;
+	ub->st_uid = fp->f_cred->cr_uid;
+	ub->st_gid = fp->f_cred->cr_gid;
+	ub->st_dev = pipedev_ino;
+	ub->st_ino = pipe->pipe_ino;
+	/*
+	 * Left as 0: st_nlink, st_rdev, st_flags, st_gen.
+	 */
+	return (0);
+}
+
+/* ARGSUSED */
+static int
+pipe_close(fp, td)
+	struct file *fp;
+	struct thread *td;
+{
+	struct pipe *cpipe = fp->f_data;
+
+	fp->f_ops = &badfileops;
+	fp->f_data = NULL;
+	funsetown(&cpipe->pipe_sigio);
+	pipeclose(cpipe);
+	return (0);
+}
+
+static void
+pipe_free_kmem(cpipe)
+	struct pipe *cpipe;
+{
+
+	KASSERT(!mtx_owned(PIPE_MTX(cpipe)),
+	    ("pipe_free_kmem: pipe mutex locked"));
+
+	if (cpipe->pipe_buffer.buffer != NULL) {
+		atomic_subtract_long(&amountpipekva, cpipe->pipe_buffer.size);
+		vm_map_remove(pipe_map,
+		    (vm_offset_t)cpipe->pipe_buffer.buffer,
+		    (vm_offset_t)cpipe->pipe_buffer.buffer + cpipe->pipe_buffer.size);
+		cpipe->pipe_buffer.buffer = NULL;
+	}
+#ifndef PIPE_NODIRECT
+	{
+		cpipe->pipe_map.cnt = 0;
+		cpipe->pipe_map.pos = 0;
+		cpipe->pipe_map.npages = 0;
+	}
+#endif
+}
+
+/*
+ * shutdown the pipe
+ */
+static void
+pipeclose(cpipe)
+	struct pipe *cpipe;
+{
+	struct pipepair *pp;
+	struct pipe *ppipe;
+	ino_t ino;
+
+	KASSERT(cpipe != NULL, ("pipeclose: cpipe == NULL"));
+
+	PIPE_LOCK(cpipe);
+	pipelock(cpipe, 0);
+	pp = cpipe->pipe_pair;
+
+	pipeselwakeup(cpipe);
+
+	/*
+	 * If the other side is blocked, wake it up saying that
+	 * we want to close it down.
+	 */
+	cpipe->pipe_state |= PIPE_EOF;
+	while (cpipe->pipe_busy) {
+		wakeup(cpipe);
+		cpipe->pipe_state |= PIPE_WANT;
+		pipeunlock(cpipe);
+		msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
+		pipelock(cpipe, 0);
+	}
+
+
+	/*
+	 * Disconnect from peer, if any.
+	 */
+	ppipe = cpipe->pipe_peer;
+	if (ppipe->pipe_present == PIPE_ACTIVE) {
+		pipeselwakeup(ppipe);
+
+		ppipe->pipe_state |= PIPE_EOF;
+		wakeup(ppipe);
+		KNOTE_LOCKED(&ppipe->pipe_sel.si_note, 0);
+	}
+
+	/*
+	 * Mark this endpoint as free.  Release kmem resources.  We
+	 * don't mark this endpoint as unused until we've finished
+	 * doing that, or the pipe might disappear out from under
+	 * us.
+	 */
+	PIPE_UNLOCK(cpipe);
+	pipe_free_kmem(cpipe);
+	PIPE_LOCK(cpipe);
+	cpipe->pipe_present = PIPE_CLOSING;
+	pipeunlock(cpipe);
+
+	/*
+	 * knlist_clear() may sleep dropping the PIPE_MTX. Set the
+	 * PIPE_FINALIZED, that allows other end to free the
+	 * pipe_pair, only after the knotes are completely dismantled.
+	 */
+	knlist_clear(&cpipe->pipe_sel.si_note, 1);
+	cpipe->pipe_present = PIPE_FINALIZED;
+	seldrain(&cpipe->pipe_sel);
+	knlist_destroy(&cpipe->pipe_sel.si_note);
+
+	/*
+	 * Postpone the destroy of the fake inode number allocated for
+	 * our end, until pipe mtx is unlocked.
+	 */
+	ino = cpipe->pipe_ino;
+
+	/*
+	 * If both endpoints are now closed, release the memory for the
+	 * pipe pair.  If not, unlock.
+	 */
+	if (ppipe->pipe_present == PIPE_FINALIZED) {
+		PIPE_UNLOCK(cpipe);
+#ifdef MAC
+		mac_pipe_destroy(pp);
+#endif
+		uma_zfree(pipe_zone, cpipe->pipe_pair);
+	} else
+		PIPE_UNLOCK(cpipe);
+
+	if (ino != 0 && ino != (ino_t)-1)
+		free_unr(pipeino_unr, ino);
+}
+
+/*ARGSUSED*/
+static int
+pipe_kqfilter(struct file *fp, struct knote *kn)
+{
+	struct pipe *cpipe;
+
+	cpipe = kn->kn_fp->f_data;
+	PIPE_LOCK(cpipe);
+	switch (kn->kn_filter) {
+	case EVFILT_READ:
+		kn->kn_fop = &pipe_rfiltops;
+		break;
+	case EVFILT_WRITE:
+		kn->kn_fop = &pipe_wfiltops;
+		if (cpipe->pipe_peer->pipe_present != PIPE_ACTIVE) {
+			/* other end of pipe has been closed */
+			PIPE_UNLOCK(cpipe);
+			return (EPIPE);
+		}
+		cpipe = cpipe->pipe_peer;
+		break;
+	default:
+		PIPE_UNLOCK(cpipe);
+		return (EINVAL);
+	}
+
+	knlist_add(&cpipe->pipe_sel.si_note, kn, 1);
+	PIPE_UNLOCK(cpipe);
+	return (0);
+}
+
+static void
+filt_pipedetach(struct knote *kn)
+{
+	struct pipe *cpipe = (struct pipe *)kn->kn_fp->f_data;
+
+	PIPE_LOCK(cpipe);
+	if (kn->kn_filter == EVFILT_WRITE)
+		cpipe = cpipe->pipe_peer;
+	knlist_remove(&cpipe->pipe_sel.si_note, kn, 1);
+	PIPE_UNLOCK(cpipe);
+}
+
+/*ARGSUSED*/
+static int
+filt_piperead(struct knote *kn, long hint)
+{
+	struct pipe *rpipe = kn->kn_fp->f_data;
+	struct pipe *wpipe = rpipe->pipe_peer;
+	int ret;
+
+	PIPE_LOCK(rpipe);
+	kn->kn_data = rpipe->pipe_buffer.cnt;
+	if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
+		kn->kn_data = rpipe->pipe_map.cnt;
+
+	if ((rpipe->pipe_state & PIPE_EOF) ||
+	    wpipe->pipe_present != PIPE_ACTIVE ||
+	    (wpipe->pipe_state & PIPE_EOF)) {
+		kn->kn_flags |= EV_EOF;
+		PIPE_UNLOCK(rpipe);
+		return (1);
+	}
+	ret = kn->kn_data > 0;
+	PIPE_UNLOCK(rpipe);
+	return ret;
+}
+
+/*ARGSUSED*/
+static int
+filt_pipewrite(struct knote *kn, long hint)
+{
+	struct pipe *rpipe = kn->kn_fp->f_data;
+	struct pipe *wpipe = rpipe->pipe_peer;
+
+	PIPE_LOCK(rpipe);
+	if (wpipe->pipe_present != PIPE_ACTIVE ||
+	    (wpipe->pipe_state & PIPE_EOF)) {
+		kn->kn_data = 0;
+		kn->kn_flags |= EV_EOF;
+		PIPE_UNLOCK(rpipe);
+		return (1);
+	}
+	kn->kn_data = (wpipe->pipe_buffer.size > 0) ?
+	    (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) : PIPE_BUF;
+	if (wpipe->pipe_state & PIPE_DIRECTW)
+		kn->kn_data = 0;
+
+	PIPE_UNLOCK(rpipe);
+	return (kn->kn_data >= PIPE_BUF);
+}
diff --git a/freebsd/sys/sys/pipe.h b/freebsd/sys/sys/pipe.h
new file mode 100644
index 00000000..444c8fbe
--- /dev/null
+++ b/freebsd/sys/sys/pipe.h
@@ -0,0 +1,142 @@
+/*-
+ * Copyright (c) 1996 John S. Dyson
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice immediately at the beginning of the file, without modification,
+ *    this list of conditions, and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Absolutely no warranty of function or purpose is made by the author
+ *    John S. Dyson.
+ * 4. This work was done expressly for inclusion into FreeBSD.  Other use
+ *    is allowed if this notation is included.
+ * 5. Modifications may be freely made to this file if the above conditions
+ *    are met.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _SYS_PIPE_H_
+#define _SYS_PIPE_H_
+
+#ifndef _KERNEL
+#error "no user-servicable parts inside"
+#endif
+
+/*
+ * Pipe buffer size, keep moderate in value, pipes take kva space.
+ */
+#ifndef PIPE_SIZE
+#define PIPE_SIZE	16384
+#endif
+
+#ifndef BIG_PIPE_SIZE
+#define BIG_PIPE_SIZE	(64*1024)
+#endif
+
+#ifndef SMALL_PIPE_SIZE
+#define SMALL_PIPE_SIZE	PAGE_SIZE
+#endif
+
+/*
+ * PIPE_MINDIRECT MUST be smaller than PIPE_SIZE and MUST be bigger
+ * than PIPE_BUF.
+ */
+#ifndef PIPE_MINDIRECT
+#define PIPE_MINDIRECT	8192
+#endif
+
+#define PIPENPAGES	(BIG_PIPE_SIZE / PAGE_SIZE + 1)
+
+/*
+ * See sys_pipe.c for info on what these limits mean.
+ */
+extern long	maxpipekva;
+
+/*
+ * Pipe buffer information.
+ * Separate in, out, cnt are used to simplify calculations.
+ * Buffered write is active when the buffer.cnt field is set.
+ */
+struct pipebuf {
+	u_int	cnt;		/* number of chars currently in buffer */
+	u_int	in;		/* in pointer */
+	u_int	out;		/* out pointer */
+	u_int	size;		/* size of buffer */
+	caddr_t	buffer;		/* kva of buffer */
+};
+
+/*
+ * Information to support direct transfers between processes for pipes.
+ */
+struct pipemapping {
+	vm_size_t	cnt;		/* number of chars in buffer */
+	vm_size_t	pos;		/* current position of transfer */
+	int		npages;		/* number of pages */
+	vm_page_t	ms[PIPENPAGES];	/* pages in source process */
+};
+
+/*
+ * Bits in pipe_state.
+ */
+#define PIPE_ASYNC	0x004	/* Async? I/O. */
+#define PIPE_WANTR	0x008	/* Reader wants some characters. */
+#define PIPE_WANTW	0x010	/* Writer wants space to put characters. */
+#define PIPE_WANT	0x020	/* Pipe is wanted to be run-down. */
+#define PIPE_SEL	0x040	/* Pipe has a select active. */
+#define PIPE_EOF	0x080	/* Pipe is in EOF condition. */
+#define PIPE_LOCKFL	0x100	/* Process has exclusive access to pointers/data. */
+#define PIPE_LWANT	0x200	/* Process wants exclusive access to pointers/data. */
+#define PIPE_DIRECTW	0x400	/* Pipe direct write active. */
+#define PIPE_DIRECTOK	0x800	/* Direct mode ok. */
+
+/*
+ * Per-pipe data structure.
+ * Two of these are linked together to produce bi-directional pipes.
+ */
+struct pipe {
+	struct	pipebuf pipe_buffer;	/* data storage */
+	struct	pipemapping pipe_map;	/* pipe mapping for direct I/O */
+	struct	selinfo pipe_sel;	/* for compat with select */
+	struct	timespec pipe_atime;	/* time of last access */
+	struct	timespec pipe_mtime;	/* time of last modify */
+	struct	timespec pipe_ctime;	/* time of status change */
+	struct	sigio *pipe_sigio;	/* information for async I/O */
+	struct	pipe *pipe_peer;	/* link with other direction */
+	struct	pipepair *pipe_pair;	/* container structure pointer */
+	u_int	pipe_state;		/* pipe status info */
+	int	pipe_busy;		/* busy flag, mostly to handle rundown sanely */
+	int	pipe_present;		/* still present? */
+	ino_t	pipe_ino;		/* fake inode for stat(2) */
+};
+
+/*
+ * Values for the pipe_present.
+ */
+#define PIPE_ACTIVE		1
+#define	PIPE_CLOSING		2
+#define	PIPE_FINALIZED		3
+
+/*
+ * Container structure to hold the two pipe endpoints, mutex, and label
+ * pointer.
+ */
+struct pipepair {
+	struct pipe	pp_rpipe;
+	struct pipe	pp_wpipe;
+	struct mtx	pp_mtx;
+	struct label	*pp_label;
+};
+
+#define PIPE_MTX(pipe)		(&(pipe)->pipe_pair->pp_mtx)
+#define PIPE_LOCK(pipe)		mtx_lock(PIPE_MTX(pipe))
+#define PIPE_UNLOCK(pipe)	mtx_unlock(PIPE_MTX(pipe))
+#define PIPE_LOCK_ASSERT(pipe, type)  mtx_assert(PIPE_MTX(pipe), (type))
+
+
+#endif /* !_SYS_PIPE_H_ */