xnu-792.6.76.tar.gz

[apple/xnu.git] / bsd / kern / sys_pipe.c

/*
 * 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.
 */
/*
 * Copyright (c) 2003-2004 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

/*
 * 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, it is fully mapped and wired into the kernel, and
 * the receiving process can copy it directly from the 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.  Whenever the amount in use
 * exceeds half of this value, all new pipes will be created with size
 * SMALL_PIPE_SIZE, rather than PIPE_SIZE.  Big pipe creation will be limited
 * as well.  This value is loader tunable only.
 *
 * kern.ipc.maxpipekvawired - This value limits the amount of memory that may
 * be wired in order to facilitate direct copies using page flipping.
 * Whenever this value is exceeded, pipes will fall back to using regular
 * copies.  This value is sysctl controllable at all times.
 *
 * These values are autotuned in subr_param.c.
 *
 * Memory usage may be monitored through the sysctls
 * kern.ipc.pipes, kern.ipc.pipekva and kern.ipc.pipekvawired.
 *
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/vnode.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/file_internal.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/fcntl.h>
#include <sys/malloc.h>
#include <sys/syslog.h>
#include <sys/unistd.h>
#include <sys/resourcevar.h>
#include <sys/aio_kern.h>
#include <sys/signalvar.h>
#include <sys/pipe.h>
#include <sys/sysproto.h>

#include <bsm/audit_kernel.h>

#include <sys/kdebug.h>

#include <kern/zalloc.h>
#include <vm/vm_kern.h>
#include <libkern/OSAtomic.h>

#define f_flag f_fglob->fg_flag
#define f_type f_fglob->fg_type
#define f_msgcount f_fglob->fg_msgcount
#define f_cred f_fglob->fg_cred
#define f_ops f_fglob->fg_ops
#define f_offset f_fglob->fg_offset
#define f_data f_fglob->fg_data
/*
 * 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.
 *
 * this needs to be ported to X and the performance measured
 * before committing to supporting it
 */
#define PIPE_NODIRECT  1

#ifndef PIPE_NODIRECT

#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>

#endif


/*
 * interfaces to the outside world
 */
static int pipe_read(struct fileproc *fp, struct uio *uio,
                kauth_cred_t cred, int flags, struct proc *p);

static int pipe_write(struct fileproc *fp, struct uio *uio,
                kauth_cred_t cred, int flags, struct proc *p);

static int pipe_close(struct fileglob *fg, struct proc *p);

static int pipe_select(struct fileproc *fp, int which, void * wql, struct proc *p);

static int pipe_kqfilter(struct fileproc *fp, struct knote *kn, struct proc *p);

static int pipe_ioctl(struct fileproc *fp, u_long cmd, caddr_t data, struct proc *p);


struct  fileops pipeops =
  { pipe_read,
    pipe_write,
    pipe_ioctl,
    pipe_select,
    pipe_close,
    pipe_kqfilter,
    0 };


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 =
        { 1, NULL, filt_pipedetach, filt_piperead };
static struct filterops pipe_wfiltops =
        { 1, NULL, filt_pipedetach, 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)

/*
 * Limit the number of "big" pipes
 */
#define LIMITBIGPIPES   32
static int nbigpipe;

static int amountpipes;
static int amountpipekva;

#ifndef PIPE_NODIRECT
static int amountpipekvawired;
#endif
int maxpipekva = 1024 * 1024 * 16;

#if PIPE_SYSCTLS
SYSCTL_DECL(_kern_ipc);

SYSCTL_INT(_kern_ipc, OID_AUTO, maxpipekva, CTLFLAG_RD,
           &maxpipekva, 0, "Pipe KVA limit");
SYSCTL_INT(_kern_ipc, OID_AUTO, maxpipekvawired, CTLFLAG_RW,
           &maxpipekvawired, 0, "Pipe KVA wired limit");
SYSCTL_INT(_kern_ipc, OID_AUTO, pipes, CTLFLAG_RD,
           &amountpipes, 0, "Current # of pipes");
SYSCTL_INT(_kern_ipc, OID_AUTO, bigpipes, CTLFLAG_RD,
           &nbigpipe, 0, "Current # of big pipes");
SYSCTL_INT(_kern_ipc, OID_AUTO, pipekva, CTLFLAG_RD,
           &amountpipekva, 0, "Pipe KVA usage");
SYSCTL_INT(_kern_ipc, OID_AUTO, pipekvawired, CTLFLAG_RD,
           &amountpipekvawired, 0, "Pipe wired KVA usage");
#endif

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 **cpipep);
static void pipeselwakeup(struct pipe *cpipe, struct pipe *spipe);
static __inline int pipelock(struct pipe *cpipe, int catch);
static __inline void pipeunlock(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

extern int postpipeevent(struct pipe *, int);
extern void evpipefree(struct pipe *cpipe);


static int pipespace(struct pipe *cpipe, int size);

static lck_grp_t        *pipe_mtx_grp;
static lck_attr_t       *pipe_mtx_attr;
static lck_grp_attr_t   *pipe_mtx_grp_attr;

static zone_t pipe_zone;

SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, pipeinit, NULL);

void
pipeinit(void *dummy __unused)
{
        pipe_zone = (zone_t)zinit(sizeof(struct pipe), 8192 * sizeof(struct pipe), 4096, "pipe zone");

        /*
         * allocate lock group attribute and group for pipe mutexes
         */
        pipe_mtx_grp_attr = lck_grp_attr_alloc_init();
        //lck_grp_attr_setstat(pipe_mtx_grp_attr);
        pipe_mtx_grp = lck_grp_alloc_init("pipe", pipe_mtx_grp_attr);

        /*
         * allocate the lock attribute for pipe mutexes
         */
        pipe_mtx_attr = lck_attr_alloc_init();
        //lck_attr_setdebug(pipe_mtx_attr);
}



/*
 * The pipe system call for the DTYPE_PIPE type of pipes
 */

/* ARGSUSED */
int
pipe(struct proc *p, __unused struct pipe_args *uap, register_t *retval)
{
        struct fileproc *rf, *wf;
        struct pipe *rpipe, *wpipe;
        lck_mtx_t   *pmtx;
        int fd, error;

        if ((pmtx = lck_mtx_alloc_init(pipe_mtx_grp, pipe_mtx_attr)) == NULL)
                return (ENOMEM);
        
        rpipe = wpipe = NULL;
        if (pipe_create(&rpipe) || pipe_create(&wpipe)) {
                error = ENFILE;
                goto freepipes;
        }
        /*
         * allocate the space for the normal I/O direction up
         * front... we'll delay the allocation for the other
         * direction until a write actually occurs (most
         * likely it won't)...
         *
         * Reduce to 1/4th pipe size if we're over our global max.
         */
        if (amountpipekva > maxpipekva / 2)
                error = pipespace(rpipe, SMALL_PIPE_SIZE);
        else
                error = pipespace(rpipe, PIPE_SIZE);
        if (error)
                goto freepipes;

#ifndef PIPE_NODIRECT
        rpipe->pipe_state |= PIPE_DIRECTOK;
        wpipe->pipe_state |= PIPE_DIRECTOK;
#endif
        TAILQ_INIT(&rpipe->pipe_evlist);
        TAILQ_INIT(&wpipe->pipe_evlist);

        error = falloc(p, &rf, &fd);
        if (error) {
                goto freepipes;
        }
        retval[0] = fd;

        /*
         * for now we'll create half-duplex
         * pipes... this is what we've always
         * supported..
         */
        rf->f_flag = FREAD;
        rf->f_type = DTYPE_PIPE;
        rf->f_data = (caddr_t)rpipe;
        rf->f_ops = &pipeops;

        error = falloc(p, &wf, &fd);
        if (error) {
                fp_free(p, retval[0], rf);
                goto freepipes;
        }
        wf->f_flag = FWRITE;
        wf->f_type = DTYPE_PIPE;
        wf->f_data = (caddr_t)wpipe;
        wf->f_ops = &pipeops;

        retval[1] = fd;
#ifdef MAC
        /*
         * XXXXXXXX SHOULD NOT HOLD FILE_LOCK() XXXXXXXXXXXX
         *
         * struct pipe represents a pipe endpoint.  The MAC label is shared
         * between the connected endpoints.  As a result mac_init_pipe() and
         * mac_create_pipe() should only be called on one of the endpoints
         * after they have been connected.
         */
        mac_init_pipe(rpipe);
        mac_create_pipe(td->td_ucred, rpipe);
#endif
        proc_fdlock(p);
        *fdflags(p, retval[0]) &= ~UF_RESERVED;
        *fdflags(p, retval[1]) &= ~UF_RESERVED;
        fp_drop(p, retval[0], rf, 1);
        fp_drop(p, retval[1], wf, 1);
        proc_fdunlock(p);

        rpipe->pipe_peer = wpipe;
        wpipe->pipe_peer = rpipe;

        rpipe->pipe_mtxp = wpipe->pipe_mtxp = pmtx;

        return (0);

freepipes:
        pipeclose(rpipe); 
        pipeclose(wpipe); 
        lck_mtx_free(pmtx, pipe_mtx_grp);

        return (error);
}


int
pipe_stat(struct pipe *cpipe, struct stat *ub)
{
#ifdef MAC
        int error;
#endif
        struct timeval now;

        if (cpipe == NULL)
                return (EBADF);
#ifdef MAC
        PIPE_LOCK(cpipe);
        error = mac_check_pipe_stat(active_cred, cpipe);
        PIPE_UNLOCK(cpipe);
        if (error)
                return (error);
#endif
        if (cpipe->pipe_buffer.buffer == 0) {
                /*
                 * must be stat'ing the write fd
                 */
                cpipe = cpipe->pipe_peer;

                if (cpipe == NULL)
                        return (EBADF);
        }
        bzero(ub, sizeof(*ub));
        ub->st_mode = S_IFIFO | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP;
        ub->st_blksize = cpipe->pipe_buffer.size;
        ub->st_size = cpipe->pipe_buffer.cnt;
        ub->st_blocks = (ub->st_size + ub->st_blksize - 1) / ub->st_blksize;
        ub->st_nlink = 1;

        ub->st_uid = kauth_getuid();
        ub->st_gid = kauth_getgid();

        microtime(&now);
        ub->st_atimespec.tv_sec  = now.tv_sec;
        ub->st_atimespec.tv_nsec = now.tv_usec * 1000;

        ub->st_mtimespec.tv_sec  = now.tv_sec;
        ub->st_mtimespec.tv_nsec = now.tv_usec * 1000;

        ub->st_ctimespec.tv_sec  = now.tv_sec;
        ub->st_ctimespec.tv_nsec = now.tv_usec * 1000;

        /*
         * Left as 0: st_dev, st_ino, st_nlink, st_rdev, st_flags, st_gen, st_uid, st_gid.
         * XXX (st_dev, st_ino) should be unique.
         */
        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(struct pipe *cpipe, int size)
{
        vm_offset_t buffer;

        size = round_page(size);

        if (kmem_alloc(kernel_map, &buffer, size) != KERN_SUCCESS)
                return(ENOMEM);

        /* free old resources if we're resizing */
        pipe_free_kmem(cpipe);
        cpipe->pipe_buffer.buffer = (caddr_t)buffer;
        cpipe->pipe_buffer.size = size;
        cpipe->pipe_buffer.in = 0;
        cpipe->pipe_buffer.out = 0;
        cpipe->pipe_buffer.cnt = 0;

        OSAddAtomic(1, (SInt32 *)&amountpipes);
        OSAddAtomic(cpipe->pipe_buffer.size, (SInt32 *)&amountpipekva);

        return (0);
}

/*
 * initialize and allocate VM and memory for pipe
 */
static int
pipe_create(struct pipe **cpipep)
{
        struct pipe *cpipe;

        cpipe = (struct pipe *)zalloc(pipe_zone);

        if ((*cpipep = cpipe) == NULL)
                return (ENOMEM);

        /*
         * protect so pipespace or pipeclose don't follow a junk pointer
         * if pipespace() fails.
         */
        bzero(cpipe, sizeof *cpipe);

        return (0);
}


/*
 * lock a pipe for I/O, blocking other access
 */
static __inline int
pipelock(cpipe, catch)
        struct pipe *cpipe;
        int catch;
{
        int error;

        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;
{

        cpipe->pipe_state &= ~PIPE_LOCKFL;

        if (cpipe->pipe_state & PIPE_LWANT) {
                cpipe->pipe_state &= ~PIPE_LWANT;
                wakeup(cpipe);
        }
}

static void
pipeselwakeup(cpipe, spipe)
        struct pipe *cpipe;
        struct pipe *spipe;
{

        if (cpipe->pipe_state & PIPE_SEL) {
                cpipe->pipe_state &= ~PIPE_SEL;
                selwakeup(&cpipe->pipe_sel);
        }
        if (cpipe->pipe_state & PIPE_KNOTE) 
               KNOTE(&cpipe->pipe_sel.si_note, 1);

        postpipeevent(cpipe, EV_RWBYTES);

        if (spipe && (spipe->pipe_state & PIPE_ASYNC) && spipe->pipe_pgid) {
                struct proc *p;

                if (spipe->pipe_pgid < 0)
                        gsignal(-spipe->pipe_pgid, SIGIO);
                else if ((p = pfind(spipe->pipe_pgid)) != (struct proc *)0)
                        psignal(p, SIGIO);
        }
}

/* ARGSUSED */
static int
pipe_read(struct fileproc *fp, struct uio *uio, __unused kauth_cred_t active_cred, __unused int flags, __unused struct proc *p)
{
        struct pipe *rpipe = (struct pipe *)fp->f_data;
        int error;
        int nread = 0;
        u_int size;

        PIPE_LOCK(rpipe);
        ++rpipe->pipe_busy;

        error = pipelock(rpipe, 1);
        if (error)
                goto unlocked_error;

#ifdef MAC
        error = mac_check_pipe_read(active_cred, rpipe);
        if (error)
                goto locked_error;
#endif

        while (uio_resid(uio)) {
                /*
                 * 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;
                        // LP64todo - fix this!
                        if (size > (u_int) uio_resid(uio))
                                size = (u_int) uio_resid(uio);

                        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)) {
                        caddr_t va;
                        // LP64todo - fix this!
                        if (size > (u_int) uio_resid(uio))
                                size = (u_int) uio_resid(uio);

                        va = (caddr_t) rpipe->pipe_map.kva +
                            rpipe->pipe_map.pos;
                        PIPE_UNLOCK(rpipe);
                        error = uiomove(va, 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;

                                error = msleep(rpipe, PIPE_MTX(rpipe), PRIBIO | PCATCH, "piperd", 0);

                                if (error == 0)
                                        error = pipelock(rpipe, 1);
                        }
                        if (error)
                                goto unlocked_error;
                }
        }
#ifdef MAC
locked_error:
#endif
        pipeunlock(rpipe);

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, rpipe->pipe_peer);

        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;
{
        pmap_t pmap;
        u_int size;
        int i, j;
        vm_offset_t addr, endaddr;


        size = (u_int) uio->uio_iov->iov_len;
        if (size > wpipe->pipe_buffer.size)
                size = wpipe->pipe_buffer.size;

        pmap = vmspace_pmap(curproc->p_vmspace);
        endaddr = round_page((vm_offset_t)uio->uio_iov->iov_base + size);
        addr = trunc_page((vm_offset_t)uio->uio_iov->iov_base);
        for (i = 0; addr < endaddr; addr += PAGE_SIZE, i++) {
                /*
                 * vm_fault_quick() can sleep.  Consequently,
                 * vm_page_lock_queue() and vm_page_unlock_queue()
                 * should not be performed outside of this loop.
                 */
        race:
                if (vm_fault_quick((caddr_t)addr, VM_PROT_READ) < 0) {
                        vm_page_lock_queues();
                        for (j = 0; j < i; j++)
                                vm_page_unhold(wpipe->pipe_map.ms[j]);
                        vm_page_unlock_queues();
                        return (EFAULT);
                }
                wpipe->pipe_map.ms[i] = pmap_extract_and_hold(pmap, addr,
                    VM_PROT_READ);
                if (wpipe->pipe_map.ms[i] == NULL)
                        goto race;
        }

/*
 * 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 map the buffer
 */
        if (wpipe->pipe_map.kva == 0) {
                /*
                 * We need to allocate space for an extra page because the
                 * address range might (will) span pages at times.
                 */
                wpipe->pipe_map.kva = kmem_alloc_nofault(kernel_map,
                        wpipe->pipe_buffer.size + PAGE_SIZE);
                atomic_add_int(&amountpipekvawired,
                    wpipe->pipe_buffer.size + PAGE_SIZE);
        }
        pmap_qenter(wpipe->pipe_map.kva, wpipe->pipe_map.ms,
                wpipe->pipe_map.npages);

/*
 * 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_setresid(uio, (uio_resid(uio) - size));
        uio->uio_offset += size;
        return (0);
}

/*
 * unmap and unwire the process buffer
 */
static void
pipe_destroy_write_buffer(wpipe)
        struct pipe *wpipe;
{
        int i;

        if (wpipe->pipe_map.kva) {
                pmap_qremove(wpipe->pipe_map.kva, wpipe->pipe_map.npages);

                if (amountpipekvawired > maxpipekvawired / 2) {
                        /* Conserve address space */
                        vm_offset_t kva = wpipe->pipe_map.kva;
                        wpipe->pipe_map.kva = 0;
                        kmem_free(kernel_map, kva,
                            wpipe->pipe_buffer.size + PAGE_SIZE);
                        atomic_subtract_int(&amountpipekvawired,
                            wpipe->pipe_buffer.size + PAGE_SIZE);
                }
        }
        vm_page_lock_queues();
        for (i = 0; i < wpipe->pipe_map.npages; i++) {
                vm_page_unhold(wpipe->pipe_map.ms[i]);
        }
        vm_page_unlock_queues();
        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;
{
        int size;
        int pos;

        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);
        bcopy((caddr_t) wpipe->pipe_map.kva + pos,
            wpipe->pipe_buffer.buffer, size);
        pipe_destroy_write_buffer(wpipe);
        PIPE_LOCK(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:
        while (wpipe->pipe_state & PIPE_DIRECTW) {
                if (wpipe->pipe_state & PIPE_WANTR) {
                        wpipe->pipe_state &= ~PIPE_WANTR;
                        wakeup(wpipe);
                }
                wpipe->pipe_state |= PIPE_WANTW;
                error = msleep(wpipe, PIPE_MTX(wpipe),
                    PRIBIO | PCATCH, "pipdww", 0);
                if (error)
                        goto error1;
                if (wpipe->pipe_state & PIPE_EOF) {
                        error = EPIPE;
                        goto error1;
                }
        }
        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);
                }
                        
                wpipe->pipe_state |= PIPE_WANTW;
                error = msleep(wpipe, PIPE_MTX(wpipe),
                    PRIBIO | PCATCH, "pipdwc", 0);
                if (error)
                        goto error1;
                if (wpipe->pipe_state & PIPE_EOF) {
                        error = EPIPE;
                        goto error1;
                }
                goto retry;
        }

        wpipe->pipe_state |= PIPE_DIRECTW;

        pipelock(wpipe, 0);
        PIPE_UNLOCK(wpipe);
        error = pipe_build_write_buffer(wpipe, uio);
        PIPE_LOCK(wpipe);
        pipeunlock(wpipe);
        if (error) {
                wpipe->pipe_state &= ~PIPE_DIRECTW;
                goto error1;
        }

        error = 0;
        while (!error && (wpipe->pipe_state & PIPE_DIRECTW)) {
                if (wpipe->pipe_state & PIPE_EOF) {
                        pipelock(wpipe, 0);
                        PIPE_UNLOCK(wpipe);
                        pipe_destroy_write_buffer(wpipe);
                        PIPE_LOCK(wpipe);
                        pipeselwakeup(wpipe, wpipe);
                        pipeunlock(wpipe);
                        error = EPIPE;
                        goto error1;
                }
                if (wpipe->pipe_state & PIPE_WANTR) {
                        wpipe->pipe_state &= ~PIPE_WANTR;
                        wakeup(wpipe);
                }
                pipeselwakeup(wpipe, wpipe);
                error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH,
                    "pipdwt", 0);
        }

        pipelock(wpipe,0);
        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_UNLOCK(wpipe);
                pipe_destroy_write_buffer(wpipe);
                PIPE_LOCK(wpipe);
        }
        pipeunlock(wpipe);
        return (error);

error1:
        wakeup(wpipe);
        return (error);
}
#endif
        


static int
pipe_write(struct fileproc *fp, struct uio *uio, __unused kauth_cred_t active_cred, __unused int flags, __unused struct proc *p)
{
        int error = 0;
        int orig_resid;
        int pipe_size;
        struct pipe *wpipe, *rpipe;

        rpipe = (struct pipe *)fp->f_data;

        PIPE_LOCK(rpipe);
        wpipe = rpipe->pipe_peer;

        /*
         * detect loss of pipe read side, issue SIGPIPE if lost.
         */
        if (wpipe == NULL || (wpipe->pipe_state & PIPE_EOF)) {
                PIPE_UNLOCK(rpipe);
                return (EPIPE);
        }
#ifdef MAC
        error = mac_check_pipe_write(active_cred, wpipe);
        if (error) {
                PIPE_UNLOCK(rpipe);
                return (error);
        }
#endif
        ++wpipe->pipe_busy;

        pipe_size = 0;

        if (wpipe->pipe_buffer.buffer == 0) {
                /*
                 * need to allocate some storage... we delay the allocation
                 * until the first write on fd[0] to avoid allocating storage for both
                 * 'pipe ends'... most pipes are half-duplex with the writes targeting
                 * fd[1], so allocating space for both ends is a waste...
                 *
                 * Reduce to 1/4th pipe size if we're over our global max.
                 */
                if (amountpipekva > maxpipekva / 2)
                        pipe_size = SMALL_PIPE_SIZE;
                else
                        pipe_size = PIPE_SIZE;
        }

        /*
         * If it is advantageous to resize the pipe buffer, do
         * so.
         */
        if ((uio_resid(uio) > PIPE_SIZE) &&
                (wpipe->pipe_buffer.size <= PIPE_SIZE) &&
                (amountpipekva < maxpipekva / 2) &&
                (nbigpipe < LIMITBIGPIPES) &&
#ifndef PIPE_NODIRECT
                (wpipe->pipe_state & PIPE_DIRECTW) == 0 &&
#endif
                (wpipe->pipe_buffer.cnt == 0)) {

                pipe_size = BIG_PIPE_SIZE;

        }
        if (pipe_size) {
                /*
                 * need to do initial allocation or resizing of pipe
                 */
                if ((error = pipelock(wpipe, 1)) == 0) {
                        PIPE_UNLOCK(wpipe);
                        if (pipespace(wpipe, pipe_size) == 0)
                                OSAddAtomic(1, (SInt32 *)&nbigpipe);
                        PIPE_LOCK(wpipe);
                        pipeunlock(wpipe);

                        if (wpipe->pipe_buffer.buffer == 0) {
                                /*
                                 * initial allocation failed
                                 */
                                error = ENOMEM;
                        }
                }
                if (error) {
                        /*
                         * If an error occurred unbusy and return, waking up any pending
                         * readers.
                         */
                        --wpipe->pipe_busy;
                        if ((wpipe->pipe_busy == 0) && 
                            (wpipe->pipe_state & PIPE_WANT)) {
                                wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
                                wakeup(wpipe);
                        }
                        PIPE_UNLOCK(rpipe);
                        return(error);
                }
        }
        // LP64todo - fix this!
        orig_resid = uio_resid(uio);

        while (uio_resid(uio)) {
                int space;

#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_iov->iov_len >= PIPE_MINDIRECT) &&
                    (fp->f_flag & FNONBLOCK) == 0 &&
                    amountpipekvawired + uio->uio_resid < maxpipekvawired) { 
                        error = pipe_direct_write(wpipe, uio);
                        if (error)
                                break;
                        continue;
                }

                /*
                 * 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.
                 */
        retrywrite:
                while (wpipe->pipe_state & PIPE_DIRECTW) {
                        if (wpipe->pipe_state & PIPE_WANTR) {
                                wpipe->pipe_state &= ~PIPE_WANTR;
                                wakeup(wpipe);
                        }
                        error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH, "pipbww", 0);

                        if (wpipe->pipe_state & PIPE_EOF)
                                break;
                        if (error)
                                break;
                }
#else
        retrywrite:
#endif
                space = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;

                /*
                 * Writes of size <= PIPE_BUF must be atomic.
                 */
                if ((space < uio_resid(uio)) && (orig_resid <= PIPE_BUF))
                        space = 0;

                if (space > 0) {

                        if ((error = pipelock(wpipe,1)) == 0) {
                                int size;       /* Transfer size */
                                int segsize;    /* first segment to transfer */

                                if (wpipe->pipe_state & PIPE_EOF) {
                                        pipeunlock(wpipe);
                                        error = EPIPE;
                                        break;
                                }
#ifndef PIPE_NODIRECT
                                /*
                                 * It is possible for a direct write to
                                 * slip in on us... handle it here...
                                 */
                                if (wpipe->pipe_state & PIPE_DIRECTW) {
                                        pipeunlock(wpipe);
                                        goto retrywrite;
                                }
#endif
                                /* 
                                 * If a process blocked in pipelock, our
                                 * value for space might be bad... the mutex
                                 * is dropped while we're blocked
                                 */
                                if (space > (int)(wpipe->pipe_buffer.size - 
                                    wpipe->pipe_buffer.cnt)) {
                                        pipeunlock(wpipe);
                                        goto retrywrite;
                                }

                                /*
                                 * Transfer size is minimum of uio transfer
                                 * and free space in pipe buffer.
                                 */
                                // LP64todo - fix this!
                                if (space > uio_resid(uio))
                                        size = uio_resid(uio);
                                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) {
                                        /* 
                                         * Transfer remaining part now, to
                                         * support atomic writes.  Wraparound
                                         * happened.
                                         */
                                        if (wpipe->pipe_buffer.in + segsize != 
                                            wpipe->pipe_buffer.size)
                                                panic("Expected pipe buffer "
                                                    "wraparound disappeared");
                                                
                                        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) {
                                                if (wpipe->pipe_buffer.in !=
                                                    size - segsize +
                                                    wpipe->pipe_buffer.size)
                                                        panic("Expected "
                                                            "wraparound bad");
                                                wpipe->pipe_buffer.in = size -
                                                    segsize;
                                        }
                                
                                        wpipe->pipe_buffer.cnt += size;
                                        if (wpipe->pipe_buffer.cnt >
                                            wpipe->pipe_buffer.size)
                                                panic("Pipe buffer overflow");
                                
                                }
                                pipeunlock(wpipe);
                        }
                        if (error)
                                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
                         * we'll do the pipeselwakeup on the way out
                         */
                        if (fp->f_flag & FNONBLOCK) {
                                error = EAGAIN;
                                break;
                        }
                        /*
                         * We have no more space and have something to offer,
                         * wake up select/poll.
                         */
                        pipeselwakeup(wpipe, wpipe);

                        wpipe->pipe_state |= PIPE_WANTW;

                        error = msleep(wpipe, PIPE_MTX(wpipe), PRIBIO | PCATCH, "pipewr", 0);

                        if (error != 0)
                                break;
                        /*
                         * If read side wants to go away, we just issue a signal
                         * to ourselves.
                         */
                        if (wpipe->pipe_state & PIPE_EOF) {
                                error = EPIPE;
                                break;
                        }       
                }
        }
        --wpipe->pipe_busy;

        if ((wpipe->pipe_busy == 0) && (wpipe->pipe_state & PIPE_WANT)) {
                wpipe->pipe_state &= ~(PIPE_WANT | PIPE_WANTR);
                wakeup(wpipe);
        }
        if (wpipe->pipe_buffer.cnt > 0) {
                /*
                 * If there are any characters in the buffer, we wake up
                 * the reader if it was blocked waiting for data.
                 */
                if (wpipe->pipe_state & PIPE_WANTR) {
                        wpipe->pipe_state &= ~PIPE_WANTR;
                        wakeup(wpipe);
                }
                /*
                 * wake up thread blocked in select/poll or post the notification
                 */
                pipeselwakeup(wpipe, wpipe);
        }
        PIPE_UNLOCK(rpipe);

        return (error);
}

/*
 * we implement a very minimal set of ioctls for compatibility with sockets.
 */
/* ARGSUSED 3 */
static int
pipe_ioctl(struct fileproc *fp, u_long cmd, caddr_t data, __unused struct proc *p)
{
        struct pipe *mpipe = (struct pipe *)fp->f_data;
#ifdef MAC
        int error;
#endif

        PIPE_LOCK(mpipe);

#ifdef MAC
        error = mac_check_pipe_ioctl(active_cred, mpipe, cmd, data);
        if (error) {
                PIPE_UNLOCK(mpipe);

                return (error);
        }
#endif

        switch (cmd) {

        case FIONBIO:
                PIPE_UNLOCK(mpipe);
                return (0);

        case FIOASYNC:
                if (*(int *)data) {
                        mpipe->pipe_state |= PIPE_ASYNC;
                } else {
                        mpipe->pipe_state &= ~PIPE_ASYNC;
                }
                PIPE_UNLOCK(mpipe);
                return (0);

        case FIONREAD:
#ifndef PIPE_NODIRECT
                if (mpipe->pipe_state & PIPE_DIRECTW)
                        *(int *)data = mpipe->pipe_map.cnt;
                else
#endif
                        *(int *)data = mpipe->pipe_buffer.cnt;
                PIPE_UNLOCK(mpipe);
                return (0);

        case TIOCSPGRP:
                mpipe->pipe_pgid = *(int *)data;

                PIPE_UNLOCK(mpipe);
                return (0);

        case TIOCGPGRP:
                *(int *)data = mpipe->pipe_pgid;

                PIPE_UNLOCK(mpipe);
                return (0);

        }
        PIPE_UNLOCK(mpipe);
        return (ENOTTY);
}


static int
pipe_select(struct fileproc *fp, int which, void *wql, struct proc *p)
{
        struct pipe *rpipe = (struct pipe *)fp->f_data;
        struct pipe *wpipe;
        int    retnum = 0;

        if (rpipe == NULL || rpipe == (struct pipe *)-1)
                return (retnum);

        PIPE_LOCK(rpipe);

        wpipe = rpipe->pipe_peer;

        switch (which) {

        case FREAD:
                if ((rpipe->pipe_state & PIPE_DIRECTW) ||
                    (rpipe->pipe_buffer.cnt > 0) ||
                    (rpipe->pipe_state & PIPE_EOF)) {

                        retnum = 1;
                } else {
                        rpipe->pipe_state |= PIPE_SEL;
                        selrecord(p, &rpipe->pipe_sel, wql);
                }
                break;

        case FWRITE:
                if (wpipe == NULL || (wpipe->pipe_state & PIPE_EOF) ||
                    (((wpipe->pipe_state & PIPE_DIRECTW) == 0) &&
                     (wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt) >= PIPE_BUF)) {

                        retnum = 1;
                } else {
                        wpipe->pipe_state |= PIPE_SEL;
                        selrecord(p, &wpipe->pipe_sel, wql);
                }
                break;
        case 0:
                rpipe->pipe_state |= PIPE_SEL;
                selrecord(p, &rpipe->pipe_sel, wql);
                break;
        }
        PIPE_UNLOCK(rpipe);

        return (retnum);
}


/* ARGSUSED 1 */
static int
pipe_close(struct fileglob *fg, __unused struct proc *p)
{
        struct pipe *cpipe;

        proc_fdlock(p);
        cpipe = (struct pipe *)fg->fg_data;
        fg->fg_data = NULL;
        proc_fdunlock(p);

        if (cpipe)
                pipeclose(cpipe);

        return (0);
}

static void
pipe_free_kmem(struct pipe *cpipe)
{

        if (cpipe->pipe_buffer.buffer != NULL) {
                if (cpipe->pipe_buffer.size > PIPE_SIZE)
                        OSAddAtomic(-1, (SInt32 *)&nbigpipe);
                OSAddAtomic(cpipe->pipe_buffer.size, (SInt32 *)&amountpipekva);
                OSAddAtomic(-1, (SInt32 *)&amountpipes);

                kmem_free(kernel_map, (vm_offset_t)cpipe->pipe_buffer.buffer,
                          cpipe->pipe_buffer.size);
                cpipe->pipe_buffer.buffer = NULL;
        }
#ifndef PIPE_NODIRECT
        if (cpipe->pipe_map.kva != 0) {
                atomic_subtract_int(&amountpipekvawired,
                    cpipe->pipe_buffer.size + PAGE_SIZE);
                kmem_free(kernel_map,
                        cpipe->pipe_map.kva,
                        cpipe->pipe_buffer.size + PAGE_SIZE);
                cpipe->pipe_map.cnt = 0;
                cpipe->pipe_map.kva = 0;
                cpipe->pipe_map.pos = 0;
                cpipe->pipe_map.npages = 0;
        }
#endif
}

/*
 * shutdown the pipe
 */
static void
pipeclose(struct pipe *cpipe)
{
        struct pipe *ppipe;

        if (cpipe == NULL)
                return;

        /* partially created pipes won't have a valid mutex. */
        if (PIPE_MTX(cpipe) != NULL)
                PIPE_LOCK(cpipe);
                
        pipeselwakeup(cpipe, cpipe);

        /*
         * If the other side is blocked, wake it up saying that
         * we want to close it down.
         */
        while (cpipe->pipe_busy) {
                cpipe->pipe_state |= PIPE_WANT | PIPE_EOF;

                wakeup(cpipe);

                msleep(cpipe, PIPE_MTX(cpipe), PRIBIO, "pipecl", 0);
        }

#ifdef MAC
        if (cpipe->pipe_label != NULL && cpipe->pipe_peer == NULL)
                mac_destroy_pipe(cpipe);
#endif

        /*
         * Disconnect from peer
         */
        if ((ppipe = cpipe->pipe_peer) != NULL) {

                ppipe->pipe_state |= PIPE_EOF;

                pipeselwakeup(ppipe, ppipe);
                wakeup(ppipe);

                if (cpipe->pipe_state & PIPE_KNOTE)
                        KNOTE(&ppipe->pipe_sel.si_note, 1);

                postpipeevent(ppipe, EV_RCLOSED);

                ppipe->pipe_peer = NULL;
        }
        evpipefree(cpipe);

        /*
         * free resources
         */
        if (PIPE_MTX(cpipe) != NULL) {
                if (ppipe != NULL) {
                        /*
                         * since the mutex is shared and the peer is still
                         * alive, we need to release the mutex, not free it
                         */
                        PIPE_UNLOCK(cpipe);
                } else {
                        /*
                         * peer is gone, so we're the sole party left with
                         * interest in this mutex... we can just free it
                         */
                        lck_mtx_free(PIPE_MTX(cpipe), pipe_mtx_grp);
                }
        }
        pipe_free_kmem(cpipe);

        zfree(pipe_zone, cpipe);
}


/*ARGSUSED*/
static int
pipe_kqfilter(__unused struct fileproc *fp, struct knote *kn, __unused struct proc *p)
{
        struct pipe *cpipe;

        cpipe = (struct pipe *)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 == NULL) {
                        /*
                         * other end of pipe has been closed
                         */
                        PIPE_UNLOCK(cpipe);
                        return (EPIPE);
                }
                cpipe = cpipe->pipe_peer;
                break;
        default:
                PIPE_UNLOCK(cpipe);
                return (1);
        }

        if (KNOTE_ATTACH(&cpipe->pipe_sel.si_note, kn))
                cpipe->pipe_state |= PIPE_KNOTE;

        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) {
                if (cpipe->pipe_peer == NULL) {
                        PIPE_UNLOCK(cpipe);
                        return;
                }
                cpipe = cpipe->pipe_peer;
        }
        if (cpipe->pipe_state & PIPE_KNOTE) {
                if (KNOTE_DETACH(&cpipe->pipe_sel.si_note, kn))
                        cpipe->pipe_state &= ~PIPE_KNOTE;
        }
        PIPE_UNLOCK(cpipe);
}

/*ARGSUSED*/
static int
filt_piperead(struct knote *kn, long hint)
{
        struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
        struct pipe *wpipe;
        int    retval;

        /*
         * if hint == 0, then we've been called from the kevent
         * world directly and do not currently hold the pipe mutex...
         * if hint == 1, we're being called back via the KNOTE post
         * we made in pipeselwakeup, and we already hold the mutex...
         */
        if (hint == 0)
                PIPE_LOCK(rpipe);

        wpipe = rpipe->pipe_peer;
        kn->kn_data = rpipe->pipe_buffer.cnt;

#ifndef PIPE_NODIRECT
        if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
                kn->kn_data = rpipe->pipe_map.cnt;
#endif
        if ((rpipe->pipe_state & PIPE_EOF) ||
            (wpipe == NULL) || (wpipe->pipe_state & PIPE_EOF)) {
                kn->kn_flags |= EV_EOF;
                retval = 1;
        } else
                retval = (kn->kn_sfflags & NOTE_LOWAT) ?
                         (kn->kn_data >= kn->kn_sdata) : (kn->kn_data > 0);

        if (hint == 0)
                PIPE_UNLOCK(rpipe);

        return (retval);
}

/*ARGSUSED*/
static int
filt_pipewrite(struct knote *kn, long hint)
{
        struct pipe *rpipe = (struct pipe *)kn->kn_fp->f_data;
        struct pipe *wpipe;

        /*
         * if hint == 0, then we've been called from the kevent
         * world directly and do not currently hold the pipe mutex...
         * if hint == 1, we're being called back via the KNOTE post
         * we made in pipeselwakeup, and we already hold the mutex...
         */
        if (hint == 0)
                PIPE_LOCK(rpipe);

        wpipe = rpipe->pipe_peer;

        if ((wpipe == NULL) || (wpipe->pipe_state & PIPE_EOF)) {
                kn->kn_data = 0;
                kn->kn_flags |= EV_EOF; 

                if (hint == 0)
                        PIPE_UNLOCK(rpipe);
                return (1);
        }
        kn->kn_data = wpipe->pipe_buffer.size - wpipe->pipe_buffer.cnt;

#ifndef PIPE_NODIRECT
        if (wpipe->pipe_state & PIPE_DIRECTW)
                kn->kn_data = 0;
#endif
        if (hint == 0)
                PIPE_UNLOCK(rpipe);

        return (kn->kn_data >= ((kn->kn_sfflags & NOTE_LOWAT) ?
                                 kn->kn_sdata : PIPE_BUF));
}