Mark up sysctl node with Li, like in sysctl(7).

[netbsd-mini2440.git] / sys / kern / kern_descrip.c

/*      $NetBSD: kern_descrip.c,v 1.189 2009/03/29 04:40:01 rmind Exp $ */

/*-
 * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Andrew Doran.
 *
 * 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, 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Copyright (c) 1982, 1986, 1989, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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, 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. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)kern_descrip.c      8.8 (Berkeley) 2/14/95
 */

/*
 * File descriptor management.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_descrip.c,v 1.189 2009/03/29 04:40:01 rmind Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/file.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/fcntl.h>
#include <sys/pool.h>
#include <sys/unistd.h>
#include <sys/resourcevar.h>
#include <sys/conf.h>
#include <sys/event.h>
#include <sys/kauth.h>
#include <sys/atomic.h>
#include <sys/syscallargs.h>
#include <sys/cpu.h>
#include <sys/kmem.h>
#include <sys/vnode.h>

static int      file_ctor(void *, void *, int);
static void     file_dtor(void *, void *);
static int      fdfile_ctor(void *, void *, int);
static void     fdfile_dtor(void *, void *);
static int      filedesc_ctor(void *, void *, int);
static void     filedesc_dtor(void *, void *);
static int      filedescopen(dev_t, int, int, lwp_t *);

kmutex_t        filelist_lock;  /* lock on filehead */
struct filelist filehead;       /* head of list of open files */
u_int           nfiles;         /* actual number of open files */

static pool_cache_t filedesc_cache;
static pool_cache_t file_cache;
static pool_cache_t fdfile_cache;

const struct cdevsw filedesc_cdevsw = {
        filedescopen, noclose, noread, nowrite, noioctl,
        nostop, notty, nopoll, nommap, nokqfilter, D_OTHER | D_MPSAFE,
};

/* For ease of reading. */
__strong_alias(fd_putvnode,fd_putfile)
__strong_alias(fd_putsock,fd_putfile)

/*
 * Initialize the descriptor system.
 */
void
fd_sys_init(void)
{

        mutex_init(&filelist_lock, MUTEX_DEFAULT, IPL_NONE);

        file_cache = pool_cache_init(sizeof(file_t), coherency_unit, 0,
            0, "file", NULL, IPL_NONE, file_ctor, file_dtor, NULL);
        KASSERT(file_cache != NULL);

        fdfile_cache = pool_cache_init(sizeof(fdfile_t), coherency_unit, 0,
            PR_LARGECACHE, "fdfile", NULL, IPL_NONE, fdfile_ctor, fdfile_dtor,
            NULL);
        KASSERT(fdfile_cache != NULL);

        filedesc_cache = pool_cache_init(sizeof(filedesc_t), coherency_unit,
            0, 0, "filedesc", NULL, IPL_NONE, filedesc_ctor, filedesc_dtor,
            NULL);
        KASSERT(filedesc_cache != NULL);
}

static int
fd_next_zero(filedesc_t *fdp, uint32_t *bitmap, int want, u_int bits)
{
        int i, off, maxoff;
        uint32_t sub;

        KASSERT(mutex_owned(&fdp->fd_lock));

        if (want > bits)
                return -1;

        off = want >> NDENTRYSHIFT;
        i = want & NDENTRYMASK;
        if (i) {
                sub = bitmap[off] | ((u_int)~0 >> (NDENTRIES - i));
                if (sub != ~0)
                        goto found;
                off++;
        }

        maxoff = NDLOSLOTS(bits);
        while (off < maxoff) {
                if ((sub = bitmap[off]) != ~0)
                        goto found;
                off++;
        }

        return (-1);

 found:
        return (off << NDENTRYSHIFT) + ffs(~sub) - 1;
}

static int
fd_last_set(filedesc_t *fd, int last)
{
        int off, i;
        fdfile_t **ofiles = fd->fd_ofiles;
        uint32_t *bitmap = fd->fd_lomap;

        KASSERT(mutex_owned(&fd->fd_lock));

        off = (last - 1) >> NDENTRYSHIFT;

        while (off >= 0 && !bitmap[off])
                off--;

        if (off < 0)
                return (-1);

        i = ((off + 1) << NDENTRYSHIFT) - 1;
        if (i >= last)
                i = last - 1;

        /* XXX should use bitmap */
        /* XXXAD does not work for fd_copy() */
        while (i > 0 && (ofiles[i] == NULL || !ofiles[i]->ff_allocated))
                i--;

        return (i);
}

void
fd_used(filedesc_t *fdp, unsigned fd)
{
        u_int off = fd >> NDENTRYSHIFT;
        fdfile_t *ff;

        ff = fdp->fd_ofiles[fd];

        KASSERT(mutex_owned(&fdp->fd_lock));
        KASSERT((fdp->fd_lomap[off] & (1 << (fd & NDENTRYMASK))) == 0);
        KASSERT(ff != NULL);
        KASSERT(ff->ff_file == NULL);
        KASSERT(!ff->ff_allocated);

        ff->ff_allocated = 1;
        fdp->fd_lomap[off] |= 1 << (fd & NDENTRYMASK);
        if (fdp->fd_lomap[off] == ~0) {
                KASSERT((fdp->fd_himap[off >> NDENTRYSHIFT] &
                    (1 << (off & NDENTRYMASK))) == 0);
                fdp->fd_himap[off >> NDENTRYSHIFT] |= 1 << (off & NDENTRYMASK);
        }

        if ((int)fd > fdp->fd_lastfile) {
                fdp->fd_lastfile = fd;
        }

        if (fd >= NDFDFILE) {
                fdp->fd_nused++;
        } else {
                KASSERT(ff == (fdfile_t *)fdp->fd_dfdfile[fd]);
        }
}

void
fd_unused(filedesc_t *fdp, unsigned fd)
{
        u_int off = fd >> NDENTRYSHIFT;
        fdfile_t *ff;

        ff = fdp->fd_ofiles[fd];

        /*
         * Don't assert the lock is held here, as we may be copying
         * the table during exec() and it is not needed there.
         * procfs and sysctl are locked out by proc::p_reflock.
         *
         * KASSERT(mutex_owned(&fdp->fd_lock));
         */
        KASSERT(ff != NULL);
        KASSERT(ff->ff_file == NULL);
        KASSERT(ff->ff_allocated);

        if (fd < fdp->fd_freefile) {
                fdp->fd_freefile = fd;
        }

        if (fdp->fd_lomap[off] == ~0) {
                KASSERT((fdp->fd_himap[off >> NDENTRYSHIFT] &
                    (1 << (off & NDENTRYMASK))) != 0);
                fdp->fd_himap[off >> NDENTRYSHIFT] &=
                    ~(1 << (off & NDENTRYMASK));
        }
        KASSERT((fdp->fd_lomap[off] & (1 << (fd & NDENTRYMASK))) != 0);
        fdp->fd_lomap[off] &= ~(1 << (fd & NDENTRYMASK));
        ff->ff_allocated = 0;

        KASSERT(fd <= fdp->fd_lastfile);
        if (fd == fdp->fd_lastfile) {
                fdp->fd_lastfile = fd_last_set(fdp, fd);
        }

        if (fd >= NDFDFILE) {
                KASSERT(fdp->fd_nused > 0);
                fdp->fd_nused--;
        } else {
                KASSERT(ff == (fdfile_t *)fdp->fd_dfdfile[fd]);
        }
}

/*
 * Custom version of fd_unused() for fd_copy(), where the descriptor
 * table is not yet fully initialized.
 */
static inline void
fd_zap(filedesc_t *fdp, unsigned fd)
{
        u_int off = fd >> NDENTRYSHIFT;

        if (fd < fdp->fd_freefile) {
                fdp->fd_freefile = fd;
        }

        if (fdp->fd_lomap[off] == ~0) {
                KASSERT((fdp->fd_himap[off >> NDENTRYSHIFT] &
                    (1 << (off & NDENTRYMASK))) != 0);
                fdp->fd_himap[off >> NDENTRYSHIFT] &=
                    ~(1 << (off & NDENTRYMASK));
        }
        KASSERT((fdp->fd_lomap[off] & (1 << (fd & NDENTRYMASK))) != 0);
        fdp->fd_lomap[off] &= ~(1 << (fd & NDENTRYMASK));
}

bool
fd_isused(filedesc_t *fdp, unsigned fd)
{
        u_int off = fd >> NDENTRYSHIFT;

        KASSERT(fd < fdp->fd_nfiles);

        return (fdp->fd_lomap[off] & (1 << (fd & NDENTRYMASK))) != 0;
}

/*
 * Look up the file structure corresponding to a file descriptor
 * and return the file, holding a reference on the descriptor.
 */
inline file_t *
fd_getfile(unsigned fd)
{
        filedesc_t *fdp;
        fdfile_t *ff;
        file_t *fp;

        fdp = curlwp->l_fd;

        /*
         * Look up the fdfile structure representing this descriptor.
         * Ensure that we see fd_nfiles before fd_ofiles since we
         * are doing this unlocked.  See fd_tryexpand().
         */
        if (__predict_false(fd >= fdp->fd_nfiles)) {
                return NULL;
        }
        membar_consumer();
        ff = fdp->fd_ofiles[fd];
        KASSERT(fd >= NDFDFILE || ff == (fdfile_t *)fdp->fd_dfdfile[fd]);
        if (__predict_false(ff == NULL)) {
                return NULL;
        }

        /*
         * Now get a reference to the descriptor.   Issue a memory
         * barrier to ensure that we acquire the file pointer _after_
         * adding a reference.  If no memory barrier, we could fetch
         * a stale pointer.
         */
        atomic_inc_uint(&ff->ff_refcnt);
#ifndef __HAVE_ATOMIC_AS_MEMBAR
        membar_enter();
#endif

        /*
         * If the file is not open or is being closed then put the
         * reference back.
         */
        fp = ff->ff_file;
        if (__predict_true(fp != NULL)) {
                return fp;
        }
        fd_putfile(fd);
        return NULL;
}

/*
 * Release a reference to a file descriptor acquired with fd_getfile().
 */
void
fd_putfile(unsigned fd)
{
        filedesc_t *fdp;
        fdfile_t *ff;
        u_int u, v;

        fdp = curlwp->l_fd;
        ff = fdp->fd_ofiles[fd];

        KASSERT(fd < fdp->fd_nfiles);
        KASSERT(ff != NULL);
        KASSERT((ff->ff_refcnt & FR_MASK) > 0);
        KASSERT(fd >= NDFDFILE || ff == (fdfile_t *)fdp->fd_dfdfile[fd]);

        /*
         * Ensure that any use of the file is complete and globally
         * visible before dropping the final reference.  If no membar,
         * the current CPU could still access memory associated with
         * the file after it has been freed or recycled by another
         * CPU.
         */
#ifndef __HAVE_ATOMIC_AS_MEMBAR
        membar_exit();
#endif

        /*
         * Be optimistic and start out with the assumption that no other
         * threads are trying to close the descriptor.  If the CAS fails,
         * we lost a race and/or it's being closed.
         */
        for (u = ff->ff_refcnt & FR_MASK;; u = v) {
                v = atomic_cas_uint(&ff->ff_refcnt, u, u - 1);
                if (__predict_true(u == v)) {
                        return;
                }
                if (__predict_false((v & FR_CLOSING) != 0)) {
                        break;
                }
        }

        /* Another thread is waiting to close the file: join it. */
        (void)fd_close(fd);
}

/*
 * Convenience wrapper around fd_getfile() that returns reference
 * to a vnode.
 */
int
fd_getvnode(unsigned fd, file_t **fpp)
{
        vnode_t *vp;
        file_t *fp;

        fp = fd_getfile(fd);
        if (__predict_false(fp == NULL)) {
                return EBADF;
        }
        if (__predict_false(fp->f_type != DTYPE_VNODE)) {
                fd_putfile(fd);
                return EINVAL;
        }
        vp = fp->f_data;
        if (__predict_false(vp->v_type == VBAD)) {
                /* XXX Is this case really necessary? */
                fd_putfile(fd);
                return EBADF;
        }
        *fpp = fp;
        return 0;
}

/*
 * Convenience wrapper around fd_getfile() that returns reference
 * to a socket.
 */
int
fd_getsock(unsigned fd, struct socket **sop)
{
        file_t *fp;

        fp = fd_getfile(fd);
        if (__predict_false(fp == NULL)) {
                return EBADF;
        }
        if (__predict_false(fp->f_type != DTYPE_SOCKET)) {
                fd_putfile(fd);
                return ENOTSOCK;
        }
        *sop = fp->f_data;
        return 0;
}

/*
 * Look up the file structure corresponding to a file descriptor
 * and return it with a reference held on the file, not the
 * descriptor.
 *
 * This is heavyweight and only used when accessing descriptors
 * from a foreign process.  The caller must ensure that `p' does
 * not exit or fork across this call.
 *
 * To release the file (not descriptor) reference, use closef().
 */
file_t *
fd_getfile2(proc_t *p, unsigned fd)
{
        filedesc_t *fdp;
        fdfile_t *ff;
        file_t *fp;

        fdp = p->p_fd;
        mutex_enter(&fdp->fd_lock);
        if (fd > fdp->fd_nfiles) {
                mutex_exit(&fdp->fd_lock);
                return NULL;
        }
        if ((ff = fdp->fd_ofiles[fd]) == NULL) {
                mutex_exit(&fdp->fd_lock);
                return NULL;
        }
        mutex_enter(&ff->ff_lock);
        if ((fp = ff->ff_file) == NULL) {
                mutex_exit(&ff->ff_lock);
                mutex_exit(&fdp->fd_lock);
                return NULL;
        }
        mutex_enter(&fp->f_lock);
        fp->f_count++;
        mutex_exit(&fp->f_lock);
        mutex_exit(&ff->ff_lock);
        mutex_exit(&fdp->fd_lock);

        return fp;
}

/*
 * Internal form of close.  Must be called with a reference to the
 * descriptor, and will drop the reference.  When all descriptor
 * references are dropped, releases the descriptor slot and a single
 * reference to the file structure.
 */
int
fd_close(unsigned fd)
{
        struct flock lf;
        filedesc_t *fdp;
        fdfile_t *ff;
        file_t *fp;
        proc_t *p;
        lwp_t *l;

        l = curlwp;
        p = l->l_proc;
        fdp = l->l_fd;
        ff = fdp->fd_ofiles[fd];

        KASSERT(fd >= NDFDFILE || ff == (fdfile_t *)fdp->fd_dfdfile[fd]);

        mutex_enter(&ff->ff_lock);
        KASSERT((ff->ff_refcnt & FR_MASK) > 0);
        if (ff->ff_file == NULL) {
                /*
                 * Another user of the file is already closing, and is
                 * waiting for other users of the file to drain.  Release
                 * our reference, and wake up the closer.
                 */
                atomic_dec_uint(&ff->ff_refcnt);
                cv_broadcast(&ff->ff_closing);
                mutex_exit(&ff->ff_lock);

                /*
                 * An application error, so pretend that the descriptor
                 * was already closed.  We can't safely wait for it to
                 * be closed without potentially deadlocking.
                 */
                return (EBADF);
        }
        KASSERT((ff->ff_refcnt & FR_CLOSING) == 0);

        /*
         * There may be multiple users of this file within the process.
         * Notify existing and new users that the file is closing.  This
         * will prevent them from adding additional uses to this file
         * while we are closing it.
         */
        fp = ff->ff_file;
        ff->ff_file = NULL;
        ff->ff_exclose = false;

        /*
         * We expect the caller to hold a descriptor reference - drop it.
         * The reference count may increase beyond zero at this point due
         * to an erroneous descriptor reference by an application, but
         * fd_getfile() will notice that the file is being closed and drop
         * the reference again.
         */
#ifndef __HAVE_ATOMIC_AS_MEMBAR
        membar_producer();
#endif
        if (__predict_false(atomic_dec_uint_nv(&ff->ff_refcnt) != 0)) {
                /*
                 * Wait for other references to drain.  This is typically
                 * an application error - the descriptor is being closed
                 * while still in use.
                 *
                 */
                atomic_or_uint(&ff->ff_refcnt, FR_CLOSING);

                /*
                 * Remove any knotes attached to the file.  A knote
                 * attached to the descriptor can hold references on it.
                 */
                mutex_exit(&ff->ff_lock);
                if (!SLIST_EMPTY(&ff->ff_knlist)) {
                        knote_fdclose(fd);
                }

                /* Try to drain out descriptor references. */
                (*fp->f_ops->fo_drain)(fp);
                mutex_enter(&ff->ff_lock);

                /*
                 * We need to see the count drop to zero at least once,
                 * in order to ensure that all pre-existing references
                 * have been drained.  New references past this point are
                 * of no interest.
                 */
                while ((ff->ff_refcnt & FR_MASK) != 0) {
                        cv_wait(&ff->ff_closing, &ff->ff_lock);
                }
                atomic_and_uint(&ff->ff_refcnt, ~FR_CLOSING);
        } else {
                /* If no references, there must be no knotes. */
                KASSERT(SLIST_EMPTY(&ff->ff_knlist));
        }
        mutex_exit(&ff->ff_lock);

        /*
         * POSIX record locking dictates that any close releases ALL
         * locks owned by this process.  This is handled by setting
         * a flag in the unlock to free ONLY locks obeying POSIX
         * semantics, and not to free BSD-style file locks.
         * If the descriptor was in a message, POSIX-style locks
         * aren't passed with the descriptor.
         */
        if ((p->p_flag & PK_ADVLOCK) != 0 && fp->f_type == DTYPE_VNODE) {
                lf.l_whence = SEEK_SET;
                lf.l_start = 0;
                lf.l_len = 0;
                lf.l_type = F_UNLCK;
                (void)VOP_ADVLOCK(fp->f_data, p, F_UNLCK, &lf, F_POSIX);
        }


        /* Free descriptor slot. */
        mutex_enter(&fdp->fd_lock);
        fd_unused(fdp, fd);
        mutex_exit(&fdp->fd_lock);

        /* Now drop reference to the file itself. */
        return closef(fp);
}

/*
 * Duplicate a file descriptor.
 */
int
fd_dup(file_t *fp, int minfd, int *newp, bool exclose)
{
        proc_t *p;
        int error;

        p = curproc;

        while ((error = fd_alloc(p, minfd, newp)) != 0) {
                if (error != ENOSPC) {
                        return error;
                }
                fd_tryexpand(p);
        }

        curlwp->l_fd->fd_ofiles[*newp]->ff_exclose = exclose;
        fd_affix(p, fp, *newp);
        return 0;
}

/*
 * dup2 operation.
 */
int
fd_dup2(file_t *fp, unsigned new)
{
        filedesc_t *fdp;
        fdfile_t *ff;

        fdp = curlwp->l_fd;

        /*
         * Ensure there are enough slots in the descriptor table,
         * and allocate an fdfile_t up front in case we need it.
         */
        while (new >= fdp->fd_nfiles) {
                fd_tryexpand(curproc);
        }
        ff = pool_cache_get(fdfile_cache, PR_WAITOK);

        /*
         * If there is already a file open, close it.  If the file is
         * half open, wait for it to be constructed before closing it.
         * XXX Potential for deadlock here?
         */
        mutex_enter(&fdp->fd_lock);
        while (fd_isused(fdp, new)) {
                mutex_exit(&fdp->fd_lock);
                if (fd_getfile(new) != NULL) {
                        (void)fd_close(new);
                } else {
                        /* XXX Crummy, but unlikely to happen. */
                        kpause("dup2", false, 1, NULL);
                }
                mutex_enter(&fdp->fd_lock);
        }
        if (fdp->fd_ofiles[new] == NULL) {
                KASSERT(new >= NDFDFILE);
                fdp->fd_ofiles[new] = ff;
                ff = NULL;
        }               
        fd_used(fdp, new);
        mutex_exit(&fdp->fd_lock);

        /* Slot is now allocated.  Insert copy of the file. */
        fd_affix(curproc, fp, new);
        if (ff != NULL) {
                pool_cache_put(fdfile_cache, ff);
        }
        return 0;
}

/*
 * Drop reference to a file structure.
 */
int
closef(file_t *fp)
{
        struct flock lf;
        int error;

        /*
         * Drop reference.  If referenced elsewhere it's still open
         * and we have nothing more to do.
         */
        mutex_enter(&fp->f_lock);
        KASSERT(fp->f_count > 0);
        if (--fp->f_count > 0) {
                mutex_exit(&fp->f_lock);
                return 0;
        }
        KASSERT(fp->f_count == 0);
        mutex_exit(&fp->f_lock);

        /* We held the last reference - release locks, close and free. */
        if ((fp->f_flag & FHASLOCK) && fp->f_type == DTYPE_VNODE) {
                lf.l_whence = SEEK_SET;
                lf.l_start = 0;
                lf.l_len = 0;
                lf.l_type = F_UNLCK;
                (void)VOP_ADVLOCK(fp->f_data, fp, F_UNLCK, &lf, F_FLOCK);
        }
        if (fp->f_ops != NULL) {
                error = (*fp->f_ops->fo_close)(fp);
        } else {
                error = 0;
        }
        ffree(fp);

        return error;
}

/*
 * Allocate a file descriptor for the process.
 */
int
fd_alloc(proc_t *p, int want, int *result)
{
        filedesc_t *fdp;
        int i, lim, last, error;
        u_int off, new;
        fdfile_t *ff;

        KASSERT(p == curproc || p == &proc0);

        fdp = p->p_fd;
        ff = pool_cache_get(fdfile_cache, PR_WAITOK);
        KASSERT(ff->ff_refcnt == 0);
        KASSERT(ff->ff_file == NULL);

        /*
         * Search for a free descriptor starting at the higher
         * of want or fd_freefile.
         */
        mutex_enter(&fdp->fd_lock);
        KASSERT(fdp->fd_ofiles[0] == (fdfile_t *)fdp->fd_dfdfile[0]);
        lim = min((int)p->p_rlimit[RLIMIT_NOFILE].rlim_cur, maxfiles);
        last = min(fdp->fd_nfiles, lim);
        for (;;) {
                if ((i = want) < fdp->fd_freefile)
                        i = fdp->fd_freefile;
                off = i >> NDENTRYSHIFT;
                new = fd_next_zero(fdp, fdp->fd_himap, off,
                    (last + NDENTRIES - 1) >> NDENTRYSHIFT);
                if (new == -1)
                        break;
                i = fd_next_zero(fdp, &fdp->fd_lomap[new],
                    new > off ? 0 : i & NDENTRYMASK, NDENTRIES);
                if (i == -1) {
                        /*
                         * Free file descriptor in this block was
                         * below want, try again with higher want.
                         */
                        want = (new + 1) << NDENTRYSHIFT;
                        continue;
                }
                i += (new << NDENTRYSHIFT);
                if (i >= last) {
                        break;
                }
                if (fdp->fd_ofiles[i] == NULL) {
                        KASSERT(i >= NDFDFILE);
                        fdp->fd_ofiles[i] = ff;
                } else {
                        pool_cache_put(fdfile_cache, ff);
                }
                KASSERT(fdp->fd_ofiles[i]->ff_file == NULL);
                fd_used(fdp, i);
                if (want <= fdp->fd_freefile) {
                        fdp->fd_freefile = i;
                }
                *result = i;
                mutex_exit(&fdp->fd_lock);
                KASSERT(i >= NDFDFILE ||
                    fdp->fd_ofiles[i] == (fdfile_t *)fdp->fd_dfdfile[i]);
                return 0;
        }

        /* No space in current array.  Let the caller expand and retry. */
        error = (fdp->fd_nfiles >= lim) ? EMFILE : ENOSPC;
        mutex_exit(&fdp->fd_lock);
        pool_cache_put(fdfile_cache, ff);
        return error;
}

/*
 * Allocate memory for the open files array.
 */
static fdfile_t **
fd_ofile_alloc(int n)
{
        uintptr_t *ptr, sz;

        KASSERT(n > NDFILE);

        sz = (n + 2) * sizeof(uintptr_t);
        ptr = kmem_alloc((size_t)sz, KM_SLEEP);
        ptr[1] = sz;

        return (fdfile_t **)(ptr + 2);
}

/*
 * Free an open files array.
 */
static void
fd_ofile_free(int n, fdfile_t **of)
{
        uintptr_t *ptr, sz;

        KASSERT(n > NDFILE);

        sz = (n + 2) * sizeof(uintptr_t);
        ptr = (uintptr_t *)of - 2;
        KASSERT(ptr[1] == sz);
        kmem_free(ptr, sz);
}

/*
 * Allocate descriptor bitmap.
 */
static void
fd_map_alloc(int n, uint32_t **lo, uint32_t **hi)
{
        uint8_t *ptr;
        size_t szlo, szhi;

        KASSERT(n > NDENTRIES);

        szlo = NDLOSLOTS(n) * sizeof(uint32_t);
        szhi = NDHISLOTS(n) * sizeof(uint32_t);
        ptr = kmem_alloc(szlo + szhi, KM_SLEEP);
        *lo = (uint32_t *)ptr;
        *hi = (uint32_t *)(ptr + szlo);
}

/*
 * Free descriptor bitmap.
 */
static void
fd_map_free(int n, uint32_t *lo, uint32_t *hi)
{
        size_t szlo, szhi;

        KASSERT(n > NDENTRIES);

        szlo = NDLOSLOTS(n) * sizeof(uint32_t);
        szhi = NDHISLOTS(n) * sizeof(uint32_t);
        KASSERT(hi == (uint32_t *)((uint8_t *)lo + szlo));
        kmem_free(lo, szlo + szhi);
}

/*
 * Expand a process' descriptor table.
 */
void
fd_tryexpand(proc_t *p)
{
        filedesc_t *fdp;
        int i, numfiles, oldnfiles;
        fdfile_t **newofile;
        uint32_t *newhimap, *newlomap;

        KASSERT(p == curproc || p == &proc0);

        fdp = p->p_fd;
        newhimap = NULL;
        newlomap = NULL;
        oldnfiles = fdp->fd_nfiles;

        if (oldnfiles < NDEXTENT)
                numfiles = NDEXTENT;
        else
                numfiles = 2 * oldnfiles;

        newofile = fd_ofile_alloc(numfiles);
        if (NDHISLOTS(numfiles) > NDHISLOTS(oldnfiles)) {
                fd_map_alloc(numfiles, &newlomap, &newhimap);
        }

        mutex_enter(&fdp->fd_lock);
        KASSERT(fdp->fd_ofiles[0] == (fdfile_t *)fdp->fd_dfdfile[0]);
        if (fdp->fd_nfiles != oldnfiles) {
                /* fdp changed; caller must retry */
                mutex_exit(&fdp->fd_lock);
                fd_ofile_free(numfiles, newofile);
                if (NDHISLOTS(numfiles) > NDHISLOTS(oldnfiles)) {
                        fd_map_free(numfiles, newlomap, newhimap);
                }
                return;
        }

        /* Copy the existing ofile array and zero the new portion. */
        i = sizeof(fdfile_t *) * fdp->fd_nfiles;
        memcpy(newofile, fdp->fd_ofiles, i);
        memset((uint8_t *)newofile + i, 0, numfiles * sizeof(fdfile_t *) - i);

        /*
         * Link old ofiles array into list to be discarded.  We defer
         * freeing until process exit if the descriptor table is visble
         * to other threads.
         */
        if (oldnfiles > NDFILE) {
                if ((fdp->fd_refcnt | p->p_nlwps) > 1) {
                        fdp->fd_ofiles[-2] = (void *)fdp->fd_discard;
                        fdp->fd_discard = fdp->fd_ofiles - 2;
                } else {
                        fd_ofile_free(oldnfiles, fdp->fd_ofiles);
                }
        }

        if (NDHISLOTS(numfiles) > NDHISLOTS(oldnfiles)) {
                i = NDHISLOTS(oldnfiles) * sizeof(uint32_t);
                memcpy(newhimap, fdp->fd_himap, i);
                memset((uint8_t *)newhimap + i, 0,
                    NDHISLOTS(numfiles) * sizeof(uint32_t) - i);

                i = NDLOSLOTS(oldnfiles) * sizeof(uint32_t);
                memcpy(newlomap, fdp->fd_lomap, i);
                memset((uint8_t *)newlomap + i, 0,
                    NDLOSLOTS(numfiles) * sizeof(uint32_t) - i);

                if (NDHISLOTS(oldnfiles) > NDHISLOTS(NDFILE)) {
                        fd_map_free(oldnfiles, fdp->fd_lomap, fdp->fd_himap);
                }
                fdp->fd_himap = newhimap;
                fdp->fd_lomap = newlomap;
        }

        /*
         * All other modifications must become globally visible before
         * the change to fd_nfiles.  See fd_getfile().
         */
        fdp->fd_ofiles = newofile;
        membar_producer();
        fdp->fd_nfiles = numfiles;
        mutex_exit(&fdp->fd_lock);

        KASSERT(fdp->fd_ofiles[0] == (fdfile_t *)fdp->fd_dfdfile[0]);
}

/*
 * Create a new open file structure and allocate a file descriptor
 * for the current process.
 */
int
fd_allocfile(file_t **resultfp, int *resultfd)
{
        file_t *fp;
        proc_t *p;
        int error;

        p = curproc;

        while ((error = fd_alloc(p, 0, resultfd)) != 0) {
                if (error != ENOSPC) {
                        return error;
                }
                fd_tryexpand(p);
        }

        fp = pool_cache_get(file_cache, PR_WAITOK);
        KASSERT(fp->f_count == 0);
        KASSERT(fp->f_msgcount == 0);
        KASSERT(fp->f_unpcount == 0);
        fp->f_cred = kauth_cred_get();
        kauth_cred_hold(fp->f_cred);

        if (__predict_false(atomic_inc_uint_nv(&nfiles) >= maxfiles)) {
                fd_abort(p, fp, *resultfd);
                tablefull("file", "increase kern.maxfiles or MAXFILES");
                return ENFILE;
        }

        /*
         * Don't allow recycled files to be scanned.
         */
        if ((fp->f_flag & FSCAN) != 0) {
                mutex_enter(&fp->f_lock);
                atomic_and_uint(&fp->f_flag, ~FSCAN);
                mutex_exit(&fp->f_lock);
        }

        fp->f_advice = 0;
        fp->f_msgcount = 0;
        fp->f_offset = 0;
        *resultfp = fp;

        return 0;
}

/*
 * Successful creation of a new descriptor: make visible to the process.
 */
void
fd_affix(proc_t *p, file_t *fp, unsigned fd)
{
        fdfile_t *ff;
        filedesc_t *fdp;

        KASSERT(p == curproc || p == &proc0);

        /* Add a reference to the file structure. */
        mutex_enter(&fp->f_lock);
        fp->f_count++;
        mutex_exit(&fp->f_lock);

        /*
         * Insert the new file into the descriptor slot.
         *
         * The memory barriers provided by lock activity in this routine
         * ensure that any updates to the file structure become globally
         * visible before the file becomes visible to other LWPs in the
         * current process.
         */
        fdp = p->p_fd;
        ff = fdp->fd_ofiles[fd];

        KASSERT(ff != NULL);
        KASSERT(ff->ff_file == NULL);
        KASSERT(ff->ff_allocated);
        KASSERT(fd_isused(fdp, fd));
        KASSERT(fd >= NDFDFILE ||
            fdp->fd_ofiles[fd] == (fdfile_t *)fdp->fd_dfdfile[fd]);

        /* No need to lock in order to make file initially visible. */
        ff->ff_file = fp;
}

/*
 * Abort creation of a new descriptor: free descriptor slot and file.
 */
void
fd_abort(proc_t *p, file_t *fp, unsigned fd)
{
        filedesc_t *fdp;
        fdfile_t *ff;

        KASSERT(p == curproc || p == &proc0);

        fdp = p->p_fd;
        ff = fdp->fd_ofiles[fd];

        KASSERT(fd >= NDFDFILE ||
            fdp->fd_ofiles[fd] == (fdfile_t *)fdp->fd_dfdfile[fd]);

        mutex_enter(&fdp->fd_lock);
        KASSERT(fd_isused(fdp, fd));
        fd_unused(fdp, fd);
        mutex_exit(&fdp->fd_lock);

        if (fp != NULL) {
                ffree(fp);
        }
}

/*
 * Free a file descriptor.
 */
void
ffree(file_t *fp)
{

        KASSERT(fp->f_count == 0);

        atomic_dec_uint(&nfiles);
        kauth_cred_free(fp->f_cred);
        pool_cache_put(file_cache, fp);
}

static int
file_ctor(void *arg, void *obj, int flags)
{
        file_t *fp = obj;

        memset(fp, 0, sizeof(*fp));
        mutex_init(&fp->f_lock, MUTEX_DEFAULT, IPL_NONE);

        mutex_enter(&filelist_lock);
        LIST_INSERT_HEAD(&filehead, fp, f_list);
        mutex_exit(&filelist_lock);

        return 0;
}

static void
file_dtor(void *arg, void *obj)
{
        file_t *fp = obj;

        mutex_enter(&filelist_lock);
        LIST_REMOVE(fp, f_list);
        mutex_exit(&filelist_lock);

        mutex_destroy(&fp->f_lock);
}

static int
fdfile_ctor(void *arg, void *obj, int flags)
{
        fdfile_t *ff = obj;

        memset(ff, 0, sizeof(*ff));
        mutex_init(&ff->ff_lock, MUTEX_DEFAULT, IPL_NONE);
        cv_init(&ff->ff_closing, "fdclose");

        return 0;
}

static void
fdfile_dtor(void *arg, void *obj)
{
        fdfile_t *ff = obj;

        mutex_destroy(&ff->ff_lock);
        cv_destroy(&ff->ff_closing);
}

file_t *
fgetdummy(void)
{
        file_t *fp;

        fp = kmem_alloc(sizeof(*fp), KM_SLEEP);
        if (fp != NULL) {
                memset(fp, 0, sizeof(*fp));
                mutex_init(&fp->f_lock, MUTEX_DEFAULT, IPL_NONE);
        }
        return fp;
}

void
fputdummy(file_t *fp)
{

        mutex_destroy(&fp->f_lock);
        kmem_free(fp, sizeof(*fp));
}

/*
 * Create an initial filedesc structure.
 */
filedesc_t *
fd_init(filedesc_t *fdp)
{
        unsigned fd;

        if (fdp == NULL) {
                fdp = pool_cache_get(filedesc_cache, PR_WAITOK);
        } else {
                filedesc_ctor(NULL, fdp, PR_WAITOK);
        }

        fdp->fd_refcnt = 1;
        fdp->fd_ofiles = fdp->fd_dfiles;
        fdp->fd_nfiles = NDFILE;
        fdp->fd_himap = fdp->fd_dhimap;
        fdp->fd_lomap = fdp->fd_dlomap;
        KASSERT(fdp->fd_lastfile == -1);
        KASSERT(fdp->fd_lastkqfile == -1);
        KASSERT(fdp->fd_knhash == NULL);

        memset(&fdp->fd_startzero, 0, sizeof(*fdp) -
            offsetof(filedesc_t, fd_startzero));
        for (fd = 0; fd < NDFDFILE; fd++) {
                fdp->fd_ofiles[fd] = (fdfile_t *)fdp->fd_dfdfile[fd];
        }

        return fdp;
}

/*
 * Initialize a file descriptor table.
 */
static int
filedesc_ctor(void *arg, void *obj, int flag)
{
        filedesc_t *fdp = obj;
        int i;

        memset(fdp, 0, sizeof(*fdp));
        mutex_init(&fdp->fd_lock, MUTEX_DEFAULT, IPL_NONE);
        fdp->fd_lastfile = -1;
        fdp->fd_lastkqfile = -1;

        CTASSERT(sizeof(fdp->fd_dfdfile[0]) >= sizeof(fdfile_t));
        for (i = 0; i < NDFDFILE; i++) {
                fdfile_ctor(NULL, fdp->fd_dfdfile[i], PR_WAITOK);
        }

        return 0;
}

static void
filedesc_dtor(void *arg, void *obj)
{
        filedesc_t *fdp = obj;
        int i;

        for (i = 0; i < NDFDFILE; i++) {
                fdfile_dtor(NULL, fdp->fd_dfdfile[i]);
        }

        mutex_destroy(&fdp->fd_lock);
}

/*
 * Make p2 share p1's filedesc structure.
 */
void
fd_share(struct proc *p2)
{
        filedesc_t *fdp;

        fdp = curlwp->l_fd;
        p2->p_fd = fdp;
        atomic_inc_uint(&fdp->fd_refcnt);
}

/*
 * Copy a filedesc structure.
 */
filedesc_t *
fd_copy(void)
{
        filedesc_t *newfdp, *fdp;
        fdfile_t *ff, *fflist, **ffp, **nffp, *ff2;
        int i, nused, numfiles, lastfile, j, newlast;
        file_t *fp;

        fdp = curproc->p_fd;
        newfdp = pool_cache_get(filedesc_cache, PR_WAITOK);
        newfdp->fd_refcnt = 1;

        KASSERT(newfdp->fd_knhash == NULL);
        KASSERT(newfdp->fd_knhashmask == 0);
        KASSERT(newfdp->fd_discard == NULL);

        for (;;) {
                numfiles = fdp->fd_nfiles;
                lastfile = fdp->fd_lastfile;

                /*
                 * If the number of open files fits in the internal arrays
                 * of the open file structure, use them, otherwise allocate
                 * additional memory for the number of descriptors currently
                 * in use.
                 */
                if (lastfile < NDFILE) {
                        i = NDFILE;
                        newfdp->fd_ofiles = newfdp->fd_dfiles;
                } else {
                        /*
                         * Compute the smallest multiple of NDEXTENT needed
                         * for the file descriptors currently in use,
                         * allowing the table to shrink.
                         */
                        i = numfiles;
                        while (i >= 2 * NDEXTENT && i > lastfile * 2) {
                                i /= 2;
                        }
                        newfdp->fd_ofiles = fd_ofile_alloc(i);
                        KASSERT(i > NDFILE);
                }
                if (NDHISLOTS(i) <= NDHISLOTS(NDFILE)) {
                        newfdp->fd_himap = newfdp->fd_dhimap;
                        newfdp->fd_lomap = newfdp->fd_dlomap;
                } else {
                        fd_map_alloc(i, &newfdp->fd_lomap,
                            &newfdp->fd_himap);
                }

                /*
                 * Allocate and string together fdfile structures.
                 * We abuse fdfile_t::ff_file here, but it will be
                 * cleared before this routine returns.
                 */
                nused = fdp->fd_nused;
                fflist = NULL;
                for (j = nused; j != 0; j--) {
                        ff = pool_cache_get(fdfile_cache, PR_WAITOK);
                        ff->ff_file = (void *)fflist;
                        fflist = ff;
                }

                mutex_enter(&fdp->fd_lock);
                if (numfiles == fdp->fd_nfiles && nused == fdp->fd_nused &&
                    lastfile == fdp->fd_lastfile) {
                        break;
                }
                mutex_exit(&fdp->fd_lock);
                if (i > NDFILE) {
                        fd_ofile_free(i, newfdp->fd_ofiles);
                }
                if (NDHISLOTS(i) > NDHISLOTS(NDFILE)) {
                        fd_map_free(i, newfdp->fd_lomap, newfdp->fd_himap);
                }
                while (fflist != NULL) {
                        ff = fflist;
                        fflist = (void *)ff->ff_file;
                        ff->ff_file = NULL;
                        pool_cache_put(fdfile_cache, ff);
                }
        }

        newfdp->fd_nfiles = i;
        newfdp->fd_freefile = fdp->fd_freefile;
        newfdp->fd_exclose = fdp->fd_exclose;

        /*
         * Clear the entries that will not be copied over.
         * Avoid calling memset with 0 size.
         */
        if (lastfile < (i-1)) {
                memset(newfdp->fd_ofiles + lastfile + 1, 0,
                    (i - lastfile - 1) * sizeof(file_t **));
        }
        if (i < NDENTRIES * NDENTRIES) {
                i = NDENTRIES * NDENTRIES; /* size of inlined bitmaps */
        }
        memcpy(newfdp->fd_himap, fdp->fd_himap, NDHISLOTS(i)*sizeof(uint32_t));
        memcpy(newfdp->fd_lomap, fdp->fd_lomap, NDLOSLOTS(i)*sizeof(uint32_t));

        ffp = fdp->fd_ofiles;
        nffp = newfdp->fd_ofiles;
        j = imax(lastfile, (NDFDFILE - 1));
        newlast = -1;
        KASSERT(j < fdp->fd_nfiles);
        for (i = 0; i <= j; i++, ffp++, *nffp++ = ff2) {
                ff = *ffp;
                /* Install built-in fdfiles even if unused here. */
                if (i < NDFDFILE) {
                        ff2 = (fdfile_t *)newfdp->fd_dfdfile[i];
                } else {
                        ff2 = NULL;
                }
                /* Determine if descriptor is active in parent. */
                if (ff == NULL || !fd_isused(fdp, i)) {
                        KASSERT(ff != NULL || i >= NDFDFILE);
                        continue;
                }
                mutex_enter(&ff->ff_lock);
                fp = ff->ff_file;
                if (fp == NULL) {
                        /* Descriptor is half-open: free slot. */
                        fd_zap(newfdp, i);
                        mutex_exit(&ff->ff_lock);
                        continue;
                }
                if (fp->f_type == DTYPE_KQUEUE) {
                        /* kqueue descriptors cannot be copied. */
                        fd_zap(newfdp, i);
                        mutex_exit(&ff->ff_lock);
                        continue;
                }
                /* It's active: add a reference to the file. */
                mutex_enter(&fp->f_lock);
                fp->f_count++;
                mutex_exit(&fp->f_lock);
                /* Consume one fdfile_t to represent it. */
                if (i >= NDFDFILE) {
                        ff2 = fflist;
                        fflist = (void *)ff2->ff_file;
                }
                ff2->ff_file = fp;
                ff2->ff_exclose = ff->ff_exclose;
                ff2->ff_allocated = true;
                mutex_exit(&ff->ff_lock);
                if (i > newlast) {
                        newlast = i;
                }
        }
        mutex_exit(&fdp->fd_lock);

        /* Discard unused fdfile_t structures. */
        while (__predict_false(fflist != NULL)) {
                ff = fflist;
                fflist = (void *)ff->ff_file;
                ff->ff_file = NULL;
                pool_cache_put(fdfile_cache, ff);
                nused--;
        }
        KASSERT(nused >= 0);
        KASSERT(newfdp->fd_ofiles[0] == (fdfile_t *)newfdp->fd_dfdfile[0]);

        newfdp->fd_nused = nused;
        newfdp->fd_lastfile = newlast;

        return (newfdp);
}

/*
 * Release a filedesc structure.
 */
void
fd_free(void)
{
        filedesc_t *fdp;
        fdfile_t *ff;
        file_t *fp;
        int fd, lastfd;
        void **discard;

        fdp = curlwp->l_fd;

        KASSERT(fdp->fd_ofiles[0] == (fdfile_t *)fdp->fd_dfdfile[0]);

        if (atomic_dec_uint_nv(&fdp->fd_refcnt) > 0)
                return;

        /*
         * Close any files that the process holds open.
         */
        for (fd = 0, lastfd = fdp->fd_nfiles - 1; fd <= lastfd; fd++) {
                ff = fdp->fd_ofiles[fd];
                KASSERT(fd >= NDFDFILE ||
                    ff == (fdfile_t *)fdp->fd_dfdfile[fd]);
                if ((ff = fdp->fd_ofiles[fd]) == NULL)
                        continue;
                if ((fp = ff->ff_file) != NULL) {
                        /*
                         * Must use fd_close() here as kqueue holds
                         * long term references to descriptors.
                         */
                        ff->ff_refcnt++;
                        fd_close(fd);
                }
                KASSERT(ff->ff_refcnt == 0);
                KASSERT(ff->ff_file == NULL);
                KASSERT(!ff->ff_exclose);
                KASSERT(!ff->ff_allocated);
                if (fd >= NDFDFILE) {
                        pool_cache_put(fdfile_cache, ff);
                }
        }

        /*
         * Clean out the descriptor table for the next user and return
         * to the cache.
         */
        while ((discard = fdp->fd_discard) != NULL) {
                fdp->fd_discard = discard[0];
                kmem_free(discard, (uintptr_t)discard[1]);
        }
        if (NDHISLOTS(fdp->fd_nfiles) > NDHISLOTS(NDFILE)) {
                KASSERT(fdp->fd_himap != fdp->fd_dhimap);
                KASSERT(fdp->fd_lomap != fdp->fd_dlomap);
                fd_map_free(fdp->fd_nfiles, fdp->fd_lomap, fdp->fd_himap);
        }
        if (fdp->fd_nfiles > NDFILE) {
                KASSERT(fdp->fd_ofiles != fdp->fd_dfiles);
                fd_ofile_free(fdp->fd_nfiles, fdp->fd_ofiles);
        }
        if (fdp->fd_knhash != NULL) {
                hashdone(fdp->fd_knhash, HASH_LIST, fdp->fd_knhashmask);
                fdp->fd_knhash = NULL;
                fdp->fd_knhashmask = 0;
        } else {
                KASSERT(fdp->fd_knhashmask == 0);
        }
        fdp->fd_lastkqfile = -1;
        pool_cache_put(filedesc_cache, fdp);
}

/*
 * File Descriptor pseudo-device driver (/dev/fd/).
 *
 * Opening minor device N dup()s the file (if any) connected to file
 * descriptor N belonging to the calling process.  Note that this driver
 * consists of only the ``open()'' routine, because all subsequent
 * references to this file will be direct to the other driver.
 */
static int
filedescopen(dev_t dev, int mode, int type, lwp_t *l)
{

        /*
         * XXX Kludge: set dupfd to contain the value of the
         * the file descriptor being sought for duplication. The error
         * return ensures that the vnode for this device will be released
         * by vn_open. Open will detect this special error and take the
         * actions in dupfdopen below. Other callers of vn_open or VOP_OPEN
         * will simply report the error.
         */
        l->l_dupfd = minor(dev);        /* XXX */
        return EDUPFD;
}

/*
 * Duplicate the specified descriptor to a free descriptor.
 */
int
fd_dupopen(int old, int *new, int mode, int error)
{
        filedesc_t *fdp;
        fdfile_t *ff;
        file_t *fp;

        if ((fp = fd_getfile(old)) == NULL) {
                return EBADF;
        }
        fdp = curlwp->l_fd;
        ff = fdp->fd_ofiles[old];

        /*
         * There are two cases of interest here.
         *
         * For EDUPFD simply dup (dfd) to file descriptor
         * (indx) and return.
         *
         * For EMOVEFD steal away the file structure from (dfd) and
         * store it in (indx).  (dfd) is effectively closed by
         * this operation.
         *
         * Any other error code is just returned.
         */
        switch (error) {
        case EDUPFD:
                /*
                 * Check that the mode the file is being opened for is a
                 * subset of the mode of the existing descriptor.
                 */
                if (((mode & (FREAD|FWRITE)) | fp->f_flag) != fp->f_flag) {
                        error = EACCES;
                        break;
                }

                /* Copy it. */
                error = fd_dup(fp, 0, new, fdp->fd_ofiles[old]->ff_exclose);
                break;

        case EMOVEFD:
                /* Copy it. */
                error = fd_dup(fp, 0, new, fdp->fd_ofiles[old]->ff_exclose);
                if (error != 0) {
                        break;
                }

                /* Steal away the file pointer from 'old'. */
                (void)fd_close(old);
                return 0;
        }

        fd_putfile(old);
        return error;
}

/*
 * Sets descriptor owner. If the owner is a process, 'pgid'
 * is set to positive value, process ID. If the owner is process group,
 * 'pgid' is set to -pg_id.
 */
int
fsetown(pid_t *pgid, u_long cmd, const void *data)
{
        int id = *(const int *)data;
        int error;

        switch (cmd) {
        case TIOCSPGRP:
                if (id < 0)
                        return (EINVAL);
                id = -id;
                break;
        default:
                break;
        }

        if (id > 0 && !pfind(id))
                return (ESRCH);
        else if (id < 0 && (error = pgid_in_session(curproc, -id)))
                return (error);

        *pgid = id;
        return (0);
}

/*
 * Return descriptor owner information. If the value is positive,
 * it's process ID. If it's negative, it's process group ID and
 * needs the sign removed before use.
 */
int
fgetown(pid_t pgid, u_long cmd, void *data)
{

        switch (cmd) {
        case TIOCGPGRP:
                *(int *)data = -pgid;
                break;
        default:
                *(int *)data = pgid;
                break;
        }
        return (0);
}

/*
 * Send signal to descriptor owner, either process or process group.
 */
void
fownsignal(pid_t pgid, int signo, int code, int band, void *fdescdata)
{
        ksiginfo_t ksi;

        KASSERT(!cpu_intr_p());

        if (pgid == 0) {
                return;
        }

        KSI_INIT(&ksi);
        ksi.ksi_signo = signo;
        ksi.ksi_code = code;
        ksi.ksi_band = band;

        mutex_enter(proc_lock);
        if (pgid > 0) {
                struct proc *p1;

                p1 = p_find(pgid, PFIND_LOCKED);
                if (p1 != NULL) {
                        kpsignal(p1, &ksi, fdescdata);
                }
        } else {
                struct pgrp *pgrp;

                KASSERT(pgid < 0);
                pgrp = pg_find(-pgid, PFIND_LOCKED);
                if (pgrp != NULL) {
                        kpgsignal(pgrp, &ksi, fdescdata, 0);
                }
        }
        mutex_exit(proc_lock);
}

int
fd_clone(file_t *fp, unsigned fd, int flag, const struct fileops *fops,
         void *data)
{

        fp->f_flag = flag;
        fp->f_type = DTYPE_MISC;
        fp->f_ops = fops;
        fp->f_data = data;
        curlwp->l_dupfd = fd;
        fd_affix(curproc, fp, fd);

        return EMOVEFD;
}

int
fnullop_fcntl(file_t *fp, u_int cmd, void *data)
{

        if (cmd == F_SETFL)
                return 0;

        return EOPNOTSUPP;
}

int
fnullop_poll(file_t *fp, int which)
{

        return 0;
}

int
fnullop_kqfilter(file_t *fp, struct knote *kn)
{

        return 0;
}

void
fnullop_drain(file_t *fp)
{

}

int
fbadop_read(file_t *fp, off_t *offset, struct uio *uio,
            kauth_cred_t cred, int flags)
{

        return EOPNOTSUPP;
}

int
fbadop_write(file_t *fp, off_t *offset, struct uio *uio,
             kauth_cred_t cred, int flags)
{

        return EOPNOTSUPP;
}

int
fbadop_ioctl(file_t *fp, u_long com, void *data)
{

        return EOPNOTSUPP;
}

int
fbadop_stat(file_t *fp, struct stat *sb)
{

        return EOPNOTSUPP;
}

int
fbadop_close(file_t *fp)
{

        return EOPNOTSUPP;
}