FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_descrip.c

     /*      $NetBSD: kern_descrip.c,v 1.182.6.6 2009/04/04 23:36:27 snj 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 1.182.6.6 2009/04/04 23:36:27 snj Exp $");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/filedesc.h>
    #include <sys/kernel.h>
    #include <sys/vnode.h>
    #include <sys/proc.h>
    #include <sys/file.h>
    #include <sys/namei.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/syslog.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/mount.h>
    #include <sys/syscallargs.h>
    #include <sys/cpu.h>
    
   static int      cwdi_ctor(void *, void *, int);
   static void     cwdi_dtor(void *, void *);
   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 cwdi_cache;
   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);
   
           cwdi_cache = pool_cache_init(sizeof(struct cwdinfo), coherency_unit,
               0, 0, "cwdi", NULL, IPL_NONE, cwdi_ctor, cwdi_dtor, NULL);
           KASSERT(cwdi_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);
  }
  
  /*
   * Create an initial cwdinfo structure, using the same current and root
   * directories as curproc.
   */
  struct cwdinfo *
  cwdinit(void)
  {
          struct cwdinfo *cwdi;
          struct cwdinfo *copy;
  
          cwdi = pool_cache_get(cwdi_cache, PR_WAITOK);
          copy = curproc->p_cwdi;
  
          rw_enter(&copy->cwdi_lock, RW_READER);
          cwdi->cwdi_cdir = copy->cwdi_cdir;
          if (cwdi->cwdi_cdir)
                  VREF(cwdi->cwdi_cdir);
          cwdi->cwdi_rdir = copy->cwdi_rdir;
          if (cwdi->cwdi_rdir)
                  VREF(cwdi->cwdi_rdir);
          cwdi->cwdi_edir = copy->cwdi_edir;
          if (cwdi->cwdi_edir)
                  VREF(cwdi->cwdi_edir);
          cwdi->cwdi_cmask =  copy->cwdi_cmask;
          cwdi->cwdi_refcnt = 1;
          rw_exit(&copy->cwdi_lock);
  
          return (cwdi);
  }
  
  static int
  cwdi_ctor(void *arg, void *obj, int flags)
  {
          struct cwdinfo *cwdi = obj;
  
          rw_init(&cwdi->cwdi_lock);
  
          return 0;
  }
  
  static void
  cwdi_dtor(void *arg, void *obj)
  {
          struct cwdinfo *cwdi = obj;
  
          rw_destroy(&cwdi->cwdi_lock);
  }
  
  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));
  }
  
  /*
   * Make p2 share p1's cwdinfo.
   */
  void
  cwdshare(struct proc *p2)
  {
          struct cwdinfo *cwdi;
  
          cwdi = curproc->p_cwdi;
  
          atomic_inc_uint(&cwdi->cwdi_refcnt);
          p2->p_cwdi = cwdi;
  }
  
  /*
   * Release a cwdinfo structure.
   */
  void
  cwdfree(struct cwdinfo *cwdi)
  {
  
          if (atomic_dec_uint_nv(&cwdi->cwdi_refcnt) > 0)
                  return;
  
          vrele(cwdi->cwdi_cdir);
          if (cwdi->cwdi_rdir)
                  vrele(cwdi->cwdi_rdir);
          if (cwdi->cwdi_edir)
                  vrele(cwdi->cwdi_edir);
          pool_cache_put(cwdi_cache, cwdi);
  }
  
  /*
   * 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;
  }
  
  /*
   * Close open files on exec.
   */
  void
  fd_closeexec(void)
  {
          struct cwdinfo *cwdi;
          proc_t *p;
          filedesc_t *fdp;
          fdfile_t *ff;
          lwp_t *l;
          int fd;
  
          l = curlwp;
          p = l->l_proc;
          fdp = p->p_fd;
          cwdi = p->p_cwdi;
  
          if (cwdi->cwdi_refcnt > 1) {
                  cwdi = cwdinit();
                  cwdfree(p->p_cwdi);
                  p->p_cwdi = cwdi;
          }
          if (p->p_cwdi->cwdi_edir) {
                  vrele(p->p_cwdi->cwdi_edir);
          }
  
          if (fdp->fd_refcnt > 1) {
                  fdp = fd_copy();
                  fd_free();
                  p->p_fd = fdp;
                  l->l_fd = fdp;
          }
          if (!fdp->fd_exclose) {
                  return;
          }
          fdp->fd_exclose = false;
  
          for (fd = 0; fd <= fdp->fd_lastfile; fd++) {
                  if ((ff = fdp->fd_ofiles[fd]) == NULL) {
                          KASSERT(fd >= NDFDFILE);
                          continue;
                  }
                  KASSERT(fd >= NDFDFILE ||
                      ff == (fdfile_t *)fdp->fd_dfdfile[fd]);
                  if (ff->ff_file == NULL)
                          continue;
                  if (ff->ff_exclose) {
                          /*
                           * We need a reference to close the file.
                           * No other threads can see the fdfile_t at
                           * this point, so don't bother locking.
                           */
                          KASSERT((ff->ff_refcnt & FR_CLOSING) == 0);
                          ff->ff_refcnt++;
                          fd_close(fd);
                  }
          }
  }
  
  /*
   * It is unsafe for set[ug]id processes to be started with file
   * descriptors 0..2 closed, as these descriptors are given implicit
   * significance in the Standard C library.  fdcheckstd() will create a
   * descriptor referencing /dev/null for each of stdin, stdout, and
   * stderr that is not already open.
   */
  #define CHECK_UPTO 3
  int
  fd_checkstd(void)
  {
          struct proc *p;
          struct nameidata nd;
          filedesc_t *fdp;
          file_t *fp;
          struct proc *pp;
          int fd, i, error, flags = FREAD|FWRITE;
          char closed[CHECK_UPTO * 3 + 1], which[3 + 1];
  
          p = curproc;
          closed[0] = '\0';
          if ((fdp = p->p_fd) == NULL)
                  return (0);
          for (i = 0; i < CHECK_UPTO; i++) {
                  KASSERT(i >= NDFDFILE ||
                      fdp->fd_ofiles[i] == (fdfile_t *)fdp->fd_dfdfile[i]);
                  if (fdp->fd_ofiles[i]->ff_file != NULL)
                          continue;
                  snprintf(which, sizeof(which), ",%d", i);
                  strlcat(closed, which, sizeof(closed));
                  if ((error = fd_allocfile(&fp, &fd)) != 0)
                          return (error);
                  KASSERT(fd < CHECK_UPTO);
                  NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, "/dev/null");
                  if ((error = vn_open(&nd, flags, 0)) != 0) {
                          fd_abort(p, fp, fd);
                          return (error);
                  }
                  fp->f_data = nd.ni_vp;
                  fp->f_flag = flags;
                  fp->f_ops = &vnops;
                  fp->f_type = DTYPE_VNODE;
                  VOP_UNLOCK(nd.ni_vp, 0);
                  fd_affix(p, fp, fd);
          }
          if (closed[0] != '\0') {
                  mutex_enter(proc_lock);
                  pp = p->p_pptr;
                  mutex_enter(pp->p_lock);
                  log(LOG_WARNING, "set{u,g}id pid %d (%s) "
                      "was invoked by uid %d ppid %d (%s) "
                      "with fd %s closed\n",
                      p->p_pid, p->p_comm, kauth_cred_geteuid(pp->p_cred),
                      pp->p_pid, pp->p_comm, &closed[1]);
                  mutex_exit(pp->p_lock);
                  mutex_exit(proc_lock);
          }
          return (0);
  }
  #undef CHECK_UPTO
  
  /*
   * 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;
  }

Cache object: c5fa7bda68f354837fbcdfa166158e41