Ignore machine-check MSRs

[freebsd-src/fkvm-freebsd.git] / sys / kern / kern_descrip.c

/*-
 * 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.
 * 4. 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      8.6 (Berkeley) 4/19/94
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_compat.h"
#include "opt_ddb.h"
#include "opt_ktrace.h"

#include <sys/param.h>
#include <sys/systm.h>

#include <sys/conf.h>
#include <sys/domain.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/filio.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/mqueue.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/protosw.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/socketvar.h>
#include <sys/stat.h>
#include <sys/sx.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/tty.h>
#include <sys/unistd.h>
#include <sys/user.h>
#include <sys/vnode.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif

#include <security/audit/audit.h>

#include <vm/uma.h>

#include <ddb/ddb.h>

static MALLOC_DEFINE(M_FILEDESC, "filedesc", "Open file descriptor table");
static MALLOC_DEFINE(M_FILEDESC_TO_LEADER, "filedesc_to_leader",
                     "file desc to leader structures");
static MALLOC_DEFINE(M_SIGIO, "sigio", "sigio structures");

static uma_zone_t file_zone;


/* Flags for do_dup() */
#define DUP_FIXED       0x1     /* Force fixed allocation */
#define DUP_FCNTL       0x2     /* fcntl()-style errors */

static int do_dup(struct thread *td, int flags, int old, int new,
    register_t *retval);
static int      fd_first_free(struct filedesc *, int, int);
static int      fd_last_used(struct filedesc *, int, int);
static void     fdgrowtable(struct filedesc *, int);
static void     fdunused(struct filedesc *fdp, int fd);
static void     fdused(struct filedesc *fdp, int fd);

/*
 * A process is initially started out with NDFILE descriptors stored within
 * this structure, selected to be enough for typical applications based on
 * the historical limit of 20 open files (and the usage of descriptors by
 * shells).  If these descriptors are exhausted, a larger descriptor table
 * may be allocated, up to a process' resource limit; the internal arrays
 * are then unused.
 */
#define NDFILE          20
#define NDSLOTSIZE      sizeof(NDSLOTTYPE)
#define NDENTRIES       (NDSLOTSIZE * __CHAR_BIT)
#define NDSLOT(x)       ((x) / NDENTRIES)
#define NDBIT(x)        ((NDSLOTTYPE)1 << ((x) % NDENTRIES))
#define NDSLOTS(x)      (((x) + NDENTRIES - 1) / NDENTRIES)

/*
 * Storage required per open file descriptor.
 */
#define OFILESIZE (sizeof(struct file *) + sizeof(char))

/*
 * Basic allocation of descriptors:
 * one of the above, plus arrays for NDFILE descriptors.
 */
struct filedesc0 {
        struct  filedesc fd_fd;
        /*
         * These arrays are used when the number of open files is
         * <= NDFILE, and are then pointed to by the pointers above.
         */
        struct  file *fd_dfiles[NDFILE];
        char    fd_dfileflags[NDFILE];
        NDSLOTTYPE fd_dmap[NDSLOTS(NDFILE)];
};

/*
 * Descriptor management.
 */
volatile int openfiles;                 /* actual number of open files */
struct mtx sigio_lock;          /* mtx to protect pointers to sigio */
void    (*mq_fdclose)(struct thread *td, int fd, struct file *fp);

/* A mutex to protect the association between a proc and filedesc. */
static struct mtx       fdesc_mtx;

/*
 * Find the first zero bit in the given bitmap, starting at low and not
 * exceeding size - 1.
 */
static int
fd_first_free(struct filedesc *fdp, int low, int size)
{
        NDSLOTTYPE *map = fdp->fd_map;
        NDSLOTTYPE mask;
        int off, maxoff;

        if (low >= size)
                return (low);

        off = NDSLOT(low);
        if (low % NDENTRIES) {
                mask = ~(~(NDSLOTTYPE)0 >> (NDENTRIES - (low % NDENTRIES)));
                if ((mask &= ~map[off]) != 0UL)
                        return (off * NDENTRIES + ffsl(mask) - 1);
                ++off;
        }
        for (maxoff = NDSLOTS(size); off < maxoff; ++off)
                if (map[off] != ~0UL)
                        return (off * NDENTRIES + ffsl(~map[off]) - 1);
        return (size);
}

/*
 * Find the highest non-zero bit in the given bitmap, starting at low and
 * not exceeding size - 1.
 */
static int
fd_last_used(struct filedesc *fdp, int low, int size)
{
        NDSLOTTYPE *map = fdp->fd_map;
        NDSLOTTYPE mask;
        int off, minoff;

        if (low >= size)
                return (-1);

        off = NDSLOT(size);
        if (size % NDENTRIES) {
                mask = ~(~(NDSLOTTYPE)0 << (size % NDENTRIES));
                if ((mask &= map[off]) != 0)
                        return (off * NDENTRIES + flsl(mask) - 1);
                --off;
        }
        for (minoff = NDSLOT(low); off >= minoff; --off)
                if (map[off] != 0)
                        return (off * NDENTRIES + flsl(map[off]) - 1);
        return (low - 1);
}

static int
fdisused(struct filedesc *fdp, int fd)
{
        KASSERT(fd >= 0 && fd < fdp->fd_nfiles,
            ("file descriptor %d out of range (0, %d)", fd, fdp->fd_nfiles));
        return ((fdp->fd_map[NDSLOT(fd)] & NDBIT(fd)) != 0);
}

/*
 * Mark a file descriptor as used.
 */
static void
fdused(struct filedesc *fdp, int fd)
{

        FILEDESC_XLOCK_ASSERT(fdp);
        KASSERT(!fdisused(fdp, fd),
            ("fd already used"));

        fdp->fd_map[NDSLOT(fd)] |= NDBIT(fd);
        if (fd > fdp->fd_lastfile)
                fdp->fd_lastfile = fd;
        if (fd == fdp->fd_freefile)
                fdp->fd_freefile = fd_first_free(fdp, fd, fdp->fd_nfiles);
}

/*
 * Mark a file descriptor as unused.
 */
static void
fdunused(struct filedesc *fdp, int fd)
{

        FILEDESC_XLOCK_ASSERT(fdp);
        KASSERT(fdisused(fdp, fd),
            ("fd is already unused"));
        KASSERT(fdp->fd_ofiles[fd] == NULL,
            ("fd is still in use"));

        fdp->fd_map[NDSLOT(fd)] &= ~NDBIT(fd);
        if (fd < fdp->fd_freefile)
                fdp->fd_freefile = fd;
        if (fd == fdp->fd_lastfile)
                fdp->fd_lastfile = fd_last_used(fdp, 0, fd);
}

/*
 * System calls on descriptors.
 */
#ifndef _SYS_SYSPROTO_H_
struct getdtablesize_args {
        int     dummy;
};
#endif
/* ARGSUSED */
int
getdtablesize(struct thread *td, struct getdtablesize_args *uap)
{
        struct proc *p = td->td_proc;

        PROC_LOCK(p);
        td->td_retval[0] =
            min((int)lim_cur(p, RLIMIT_NOFILE), maxfilesperproc);
        PROC_UNLOCK(p);
        return (0);
}

/*
 * Duplicate a file descriptor to a particular value.
 *
 * Note: keep in mind that a potential race condition exists when closing
 * descriptors from a shared descriptor table (via rfork).
 */
#ifndef _SYS_SYSPROTO_H_
struct dup2_args {
        u_int   from;
        u_int   to;
};
#endif
/* ARGSUSED */
int
dup2(struct thread *td, struct dup2_args *uap)
{

        return (do_dup(td, DUP_FIXED, (int)uap->from, (int)uap->to,
                    td->td_retval));
}

/*
 * Duplicate a file descriptor.
 */
#ifndef _SYS_SYSPROTO_H_
struct dup_args {
        u_int   fd;
};
#endif
/* ARGSUSED */
int
dup(struct thread *td, struct dup_args *uap)
{

        return (do_dup(td, 0, (int)uap->fd, 0, td->td_retval));
}

/*
 * The file control system call.
 */
#ifndef _SYS_SYSPROTO_H_
struct fcntl_args {
        int     fd;
        int     cmd;
        long    arg;
};
#endif
/* ARGSUSED */
int
fcntl(struct thread *td, struct fcntl_args *uap)
{
        struct flock fl;
        struct oflock ofl;
        intptr_t arg;
        int error;
        int cmd;

        error = 0;
        cmd = uap->cmd;
        switch (uap->cmd) {
        case F_OGETLK:
        case F_OSETLK:
        case F_OSETLKW:
                /*
                 * Convert old flock structure to new.
                 */
                error = copyin((void *)(intptr_t)uap->arg, &ofl, sizeof(ofl));
                fl.l_start = ofl.l_start;
                fl.l_len = ofl.l_len;
                fl.l_pid = ofl.l_pid;
                fl.l_type = ofl.l_type;
                fl.l_whence = ofl.l_whence;
                fl.l_sysid = 0;

                switch (uap->cmd) {
                case F_OGETLK:
                    cmd = F_GETLK;
                    break;
                case F_OSETLK:
                    cmd = F_SETLK;
                    break;
                case F_OSETLKW:
                    cmd = F_SETLKW;
                    break;
                }
                arg = (intptr_t)&fl;
                break;
        case F_GETLK:
        case F_SETLK:
        case F_SETLKW:
        case F_SETLK_REMOTE:
                error = copyin((void *)(intptr_t)uap->arg, &fl, sizeof(fl));
                arg = (intptr_t)&fl;
                break;
        default:
                arg = uap->arg;
                break;
        }
        if (error)
                return (error);
        error = kern_fcntl(td, uap->fd, cmd, arg);
        if (error)
                return (error);
        if (uap->cmd == F_OGETLK) {
                ofl.l_start = fl.l_start;
                ofl.l_len = fl.l_len;
                ofl.l_pid = fl.l_pid;
                ofl.l_type = fl.l_type;
                ofl.l_whence = fl.l_whence;
                error = copyout(&ofl, (void *)(intptr_t)uap->arg, sizeof(ofl));
        } else if (uap->cmd == F_GETLK) {
                error = copyout(&fl, (void *)(intptr_t)uap->arg, sizeof(fl));
        }
        return (error);
}

static inline struct file *
fdtofp(int fd, struct filedesc *fdp)
{
        struct file *fp;

        FILEDESC_LOCK_ASSERT(fdp);
        if ((unsigned)fd >= fdp->fd_nfiles ||
            (fp = fdp->fd_ofiles[fd]) == NULL)
                return (NULL);
        return (fp);
}

int
kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
{
        struct filedesc *fdp;
        struct flock *flp;
        struct file *fp;
        struct proc *p;
        char *pop;
        struct vnode *vp;
        int error, flg, tmp;
        int vfslocked;

        vfslocked = 0;
        error = 0;
        flg = F_POSIX;
        p = td->td_proc;
        fdp = p->p_fd;

        switch (cmd) {
        case F_DUPFD:
                tmp = arg;
                error = do_dup(td, DUP_FCNTL, fd, tmp, td->td_retval);
                break;

        case F_DUP2FD:
                tmp = arg;
                error = do_dup(td, DUP_FIXED, fd, tmp, td->td_retval);
                break;

        case F_GETFD:
                FILEDESC_SLOCK(fdp);
                if ((fp = fdtofp(fd, fdp)) == NULL) {
                        FILEDESC_SUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                pop = &fdp->fd_ofileflags[fd];
                td->td_retval[0] = (*pop & UF_EXCLOSE) ? FD_CLOEXEC : 0;
                FILEDESC_SUNLOCK(fdp);
                break;

        case F_SETFD:
                FILEDESC_XLOCK(fdp);
                if ((fp = fdtofp(fd, fdp)) == NULL) {
                        FILEDESC_XUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                pop = &fdp->fd_ofileflags[fd];
                *pop = (*pop &~ UF_EXCLOSE) |
                    (arg & FD_CLOEXEC ? UF_EXCLOSE : 0);
                FILEDESC_XUNLOCK(fdp);
                break;

        case F_GETFL:
                FILEDESC_SLOCK(fdp);
                if ((fp = fdtofp(fd, fdp)) == NULL) {
                        FILEDESC_SUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                td->td_retval[0] = OFLAGS(fp->f_flag);
                FILEDESC_SUNLOCK(fdp);
                break;

        case F_SETFL:
                FILEDESC_SLOCK(fdp);
                if ((fp = fdtofp(fd, fdp)) == NULL) {
                        FILEDESC_SUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                fhold(fp);
                FILEDESC_SUNLOCK(fdp);
                do {
                        tmp = flg = fp->f_flag;
                        tmp &= ~FCNTLFLAGS;
                        tmp |= FFLAGS(arg & ~O_ACCMODE) & FCNTLFLAGS;
                } while(atomic_cmpset_int(&fp->f_flag, flg, tmp) == 0);
                tmp = fp->f_flag & FNONBLOCK;
                error = fo_ioctl(fp, FIONBIO, &tmp, td->td_ucred, td);
                if (error) {
                        fdrop(fp, td);
                        break;
                }
                tmp = fp->f_flag & FASYNC;
                error = fo_ioctl(fp, FIOASYNC, &tmp, td->td_ucred, td);
                if (error == 0) {
                        fdrop(fp, td);
                        break;
                }
                atomic_clear_int(&fp->f_flag, FNONBLOCK);
                tmp = 0;
                (void)fo_ioctl(fp, FIONBIO, &tmp, td->td_ucred, td);
                fdrop(fp, td);
                break;

        case F_GETOWN:
                FILEDESC_SLOCK(fdp);
                if ((fp = fdtofp(fd, fdp)) == NULL) {
                        FILEDESC_SUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                fhold(fp);
                FILEDESC_SUNLOCK(fdp);
                error = fo_ioctl(fp, FIOGETOWN, &tmp, td->td_ucred, td);
                if (error == 0)
                        td->td_retval[0] = tmp;
                fdrop(fp, td);
                break;

        case F_SETOWN:
                FILEDESC_SLOCK(fdp);
                if ((fp = fdtofp(fd, fdp)) == NULL) {
                        FILEDESC_SUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                fhold(fp);
                FILEDESC_SUNLOCK(fdp);
                tmp = arg;
                error = fo_ioctl(fp, FIOSETOWN, &tmp, td->td_ucred, td);
                fdrop(fp, td);
                break;

        case F_SETLK_REMOTE:
                error = priv_check(td, PRIV_NFS_LOCKD);
                if (error)
                        return (error);
                flg = F_REMOTE;
                goto do_setlk;

        case F_SETLKW:
                flg |= F_WAIT;
                /* FALLTHROUGH F_SETLK */

        case F_SETLK:
        do_setlk:
                FILEDESC_SLOCK(fdp);
                if ((fp = fdtofp(fd, fdp)) == NULL) {
                        FILEDESC_SUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                if (fp->f_type != DTYPE_VNODE) {
                        FILEDESC_SUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                flp = (struct flock *)arg;
                if (flp->l_whence == SEEK_CUR) {
                        if (fp->f_offset < 0 ||
                            (flp->l_start > 0 &&
                             fp->f_offset > OFF_MAX - flp->l_start)) {
                                FILEDESC_SUNLOCK(fdp);
                                error = EOVERFLOW;
                                break;
                        }
                        flp->l_start += fp->f_offset;
                }

                /*
                 * VOP_ADVLOCK() may block.
                 */
                fhold(fp);
                FILEDESC_SUNLOCK(fdp);
                vp = fp->f_vnode;
                vfslocked = VFS_LOCK_GIANT(vp->v_mount);
                switch (flp->l_type) {
                case F_RDLCK:
                        if ((fp->f_flag & FREAD) == 0) {
                                error = EBADF;
                                break;
                        }
                        PROC_LOCK(p->p_leader);
                        p->p_leader->p_flag |= P_ADVLOCK;
                        PROC_UNLOCK(p->p_leader);
                        error = VOP_ADVLOCK(vp, (caddr_t)p->p_leader, F_SETLK,
                            flp, flg);
                        break;
                case F_WRLCK:
                        if ((fp->f_flag & FWRITE) == 0) {
                                error = EBADF;
                                break;
                        }
                        PROC_LOCK(p->p_leader);
                        p->p_leader->p_flag |= P_ADVLOCK;
                        PROC_UNLOCK(p->p_leader);
                        error = VOP_ADVLOCK(vp, (caddr_t)p->p_leader, F_SETLK,
                            flp, flg);
                        break;
                case F_UNLCK:
                        error = VOP_ADVLOCK(vp, (caddr_t)p->p_leader, F_UNLCK,
                            flp, flg);
                        break;
                case F_UNLCKSYS:
                        /*
                         * Temporary api for testing remote lock
                         * infrastructure.
                         */
                        if (flg != F_REMOTE) {
                                error = EINVAL;
                                break;
                        }
                        error = VOP_ADVLOCK(vp, (caddr_t)p->p_leader,
                            F_UNLCKSYS, flp, flg);
                        break;
                default:
                        error = EINVAL;
                        break;
                }
                VFS_UNLOCK_GIANT(vfslocked);
                vfslocked = 0;
                /* Check for race with close */
                FILEDESC_SLOCK(fdp);
                if ((unsigned) fd >= fdp->fd_nfiles ||
                    fp != fdp->fd_ofiles[fd]) {
                        FILEDESC_SUNLOCK(fdp);
                        flp->l_whence = SEEK_SET;
                        flp->l_start = 0;
                        flp->l_len = 0;
                        flp->l_type = F_UNLCK;
                        vfslocked = VFS_LOCK_GIANT(vp->v_mount);
                        (void) VOP_ADVLOCK(vp, (caddr_t)p->p_leader,
                                           F_UNLCK, flp, F_POSIX);
                        VFS_UNLOCK_GIANT(vfslocked);
                        vfslocked = 0;
                } else
                        FILEDESC_SUNLOCK(fdp);
                fdrop(fp, td);
                break;

        case F_GETLK:
                FILEDESC_SLOCK(fdp);
                if ((fp = fdtofp(fd, fdp)) == NULL) {
                        FILEDESC_SUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                if (fp->f_type != DTYPE_VNODE) {
                        FILEDESC_SUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                flp = (struct flock *)arg;
                if (flp->l_type != F_RDLCK && flp->l_type != F_WRLCK &&
                    flp->l_type != F_UNLCK) {
                        FILEDESC_SUNLOCK(fdp);
                        error = EINVAL;
                        break;
                }
                if (flp->l_whence == SEEK_CUR) {
                        if ((flp->l_start > 0 &&
                            fp->f_offset > OFF_MAX - flp->l_start) ||
                            (flp->l_start < 0 &&
                             fp->f_offset < OFF_MIN - flp->l_start)) {
                                FILEDESC_SUNLOCK(fdp);
                                error = EOVERFLOW;
                                break;
                        }
                        flp->l_start += fp->f_offset;
                }
                /*
                 * VOP_ADVLOCK() may block.
                 */
                fhold(fp);
                FILEDESC_SUNLOCK(fdp);
                vp = fp->f_vnode;
                vfslocked = VFS_LOCK_GIANT(vp->v_mount);
                error = VOP_ADVLOCK(vp, (caddr_t)p->p_leader, F_GETLK, flp,
                    F_POSIX);
                VFS_UNLOCK_GIANT(vfslocked);
                vfslocked = 0;
                fdrop(fp, td);
                break;
        default:
                error = EINVAL;
                break;
        }
        VFS_UNLOCK_GIANT(vfslocked);
        return (error);
}

/*
 * Common code for dup, dup2, fcntl(F_DUPFD) and fcntl(F_DUP2FD).
 */
static int
do_dup(struct thread *td, int flags, int old, int new,
    register_t *retval)
{
        struct filedesc *fdp;
        struct proc *p;
        struct file *fp;
        struct file *delfp;
        int error, holdleaders, maxfd;

        p = td->td_proc;
        fdp = p->p_fd;

        /*
         * Verify we have a valid descriptor to dup from and possibly to
         * dup to. Unlike dup() and dup2(), fcntl()'s F_DUPFD should
         * return EINVAL when the new descriptor is out of bounds.
         */
        if (old < 0)
                return (EBADF);
        if (new < 0)
                return (flags & DUP_FCNTL ? EINVAL : EBADF);
        PROC_LOCK(p);
        maxfd = min((int)lim_cur(p, RLIMIT_NOFILE), maxfilesperproc);
        PROC_UNLOCK(p);
        if (new >= maxfd)
                return (flags & DUP_FCNTL ? EINVAL : EMFILE);

        FILEDESC_XLOCK(fdp);
        if (old >= fdp->fd_nfiles || fdp->fd_ofiles[old] == NULL) {
                FILEDESC_XUNLOCK(fdp);
                return (EBADF);
        }
        if (flags & DUP_FIXED && old == new) {
                *retval = new;
                FILEDESC_XUNLOCK(fdp);
                return (0);
        }
        fp = fdp->fd_ofiles[old];
        fhold(fp);

        /*
         * If the caller specified a file descriptor, make sure the file
         * table is large enough to hold it, and grab it.  Otherwise, just
         * allocate a new descriptor the usual way.  Since the filedesc
         * lock may be temporarily dropped in the process, we have to look
         * out for a race.
         */
        if (flags & DUP_FIXED) {
                if (new >= fdp->fd_nfiles)
                        fdgrowtable(fdp, new + 1);
                if (fdp->fd_ofiles[new] == NULL)
                        fdused(fdp, new);
        } else {
                if ((error = fdalloc(td, new, &new)) != 0) {
                        FILEDESC_XUNLOCK(fdp);
                        fdrop(fp, td);
                        return (error);
                }
        }

        /*
         * If the old file changed out from under us then treat it as a
         * bad file descriptor.  Userland should do its own locking to
         * avoid this case.
         */
        if (fdp->fd_ofiles[old] != fp) {
                /* we've allocated a descriptor which we won't use */
                if (fdp->fd_ofiles[new] == NULL)
                        fdunused(fdp, new);
                FILEDESC_XUNLOCK(fdp);
                fdrop(fp, td);
                return (EBADF);
        }
        KASSERT(old != new,
            ("new fd is same as old"));

        /*
         * Save info on the descriptor being overwritten.  We cannot close
         * it without introducing an ownership race for the slot, since we
         * need to drop the filedesc lock to call closef().
         *
         * XXX this duplicates parts of close().
         */
        delfp = fdp->fd_ofiles[new];
        holdleaders = 0;
        if (delfp != NULL) {
                if (td->td_proc->p_fdtol != NULL) {
                        /*
                         * Ask fdfree() to sleep to ensure that all relevant
                         * process leaders can be traversed in closef().
                         */
                        fdp->fd_holdleaderscount++;
                        holdleaders = 1;
                }
        }

        /*
         * Duplicate the source descriptor
         */
        fdp->fd_ofiles[new] = fp;
        fdp->fd_ofileflags[new] = fdp->fd_ofileflags[old] &~ UF_EXCLOSE;
        if (new > fdp->fd_lastfile)
                fdp->fd_lastfile = new;
        *retval = new;

        /*
         * If we dup'd over a valid file, we now own the reference to it
         * and must dispose of it using closef() semantics (as if a
         * close() were performed on it).
         *
         * XXX this duplicates parts of close().
         */
        if (delfp != NULL) {
                knote_fdclose(td, new);
                if (delfp->f_type == DTYPE_MQUEUE)
                        mq_fdclose(td, new, delfp);
                FILEDESC_XUNLOCK(fdp);
                (void) closef(delfp, td);
                if (holdleaders) {
                        FILEDESC_XLOCK(fdp);
                        fdp->fd_holdleaderscount--;
                        if (fdp->fd_holdleaderscount == 0 &&
                            fdp->fd_holdleaderswakeup != 0) {
                                fdp->fd_holdleaderswakeup = 0;
                                wakeup(&fdp->fd_holdleaderscount);
                        }
                        FILEDESC_XUNLOCK(fdp);
                }
        } else {
                FILEDESC_XUNLOCK(fdp);
        }
        return (0);
}

/*
 * If sigio is on the list associated with a process or process group,
 * disable signalling from the device, remove sigio from the list and
 * free sigio.
 */
void
funsetown(struct sigio **sigiop)
{
        struct sigio *sigio;

        SIGIO_LOCK();
        sigio = *sigiop;
        if (sigio == NULL) {
                SIGIO_UNLOCK();
                return;
        }
        *(sigio->sio_myref) = NULL;
        if ((sigio)->sio_pgid < 0) {
                struct pgrp *pg = (sigio)->sio_pgrp;
                PGRP_LOCK(pg);
                SLIST_REMOVE(&sigio->sio_pgrp->pg_sigiolst, sigio,
                             sigio, sio_pgsigio);
                PGRP_UNLOCK(pg);
        } else {
                struct proc *p = (sigio)->sio_proc;
                PROC_LOCK(p);
                SLIST_REMOVE(&sigio->sio_proc->p_sigiolst, sigio,
                             sigio, sio_pgsigio);
                PROC_UNLOCK(p);
        }
        SIGIO_UNLOCK();
        crfree(sigio->sio_ucred);
        FREE(sigio, M_SIGIO);
}

/*
 * Free a list of sigio structures.
 * We only need to lock the SIGIO_LOCK because we have made ourselves
 * inaccessible to callers of fsetown and therefore do not need to lock
 * the proc or pgrp struct for the list manipulation.
 */
void
funsetownlst(struct sigiolst *sigiolst)
{
        struct proc *p;
        struct pgrp *pg;
        struct sigio *sigio;

        sigio = SLIST_FIRST(sigiolst);
        if (sigio == NULL)
                return;
        p = NULL;
        pg = NULL;

        /*
         * Every entry of the list should belong
         * to a single proc or pgrp.
         */
        if (sigio->sio_pgid < 0) {
                pg = sigio->sio_pgrp;
                PGRP_LOCK_ASSERT(pg, MA_NOTOWNED);
        } else /* if (sigio->sio_pgid > 0) */ {
                p = sigio->sio_proc;
                PROC_LOCK_ASSERT(p, MA_NOTOWNED);
        }

        SIGIO_LOCK();
        while ((sigio = SLIST_FIRST(sigiolst)) != NULL) {
                *(sigio->sio_myref) = NULL;
                if (pg != NULL) {
                        KASSERT(sigio->sio_pgid < 0,
                            ("Proc sigio in pgrp sigio list"));
                        KASSERT(sigio->sio_pgrp == pg,
                            ("Bogus pgrp in sigio list"));
                        PGRP_LOCK(pg);
                        SLIST_REMOVE(&pg->pg_sigiolst, sigio, sigio,
                            sio_pgsigio);
                        PGRP_UNLOCK(pg);
                } else /* if (p != NULL) */ {
                        KASSERT(sigio->sio_pgid > 0,
                            ("Pgrp sigio in proc sigio list"));
                        KASSERT(sigio->sio_proc == p,
                            ("Bogus proc in sigio list"));
                        PROC_LOCK(p);
                        SLIST_REMOVE(&p->p_sigiolst, sigio, sigio,
                            sio_pgsigio);
                        PROC_UNLOCK(p);
                }
                SIGIO_UNLOCK();
                crfree(sigio->sio_ucred);
                FREE(sigio, M_SIGIO);
                SIGIO_LOCK();
        }
        SIGIO_UNLOCK();
}

/*
 * This is common code for FIOSETOWN ioctl called by fcntl(fd, F_SETOWN, arg).
 *
 * After permission checking, add a sigio structure to the sigio list for
 * the process or process group.
 */
int
fsetown(pid_t pgid, struct sigio **sigiop)
{
        struct proc *proc;
        struct pgrp *pgrp;
        struct sigio *sigio;
        int ret;

        if (pgid == 0) {
                funsetown(sigiop);
                return (0);
        }

        ret = 0;

        /* Allocate and fill in the new sigio out of locks. */
        MALLOC(sigio, struct sigio *, sizeof(struct sigio), M_SIGIO, M_WAITOK);
        sigio->sio_pgid = pgid;
        sigio->sio_ucred = crhold(curthread->td_ucred);
        sigio->sio_myref = sigiop;

        sx_slock(&proctree_lock);
        if (pgid > 0) {
                proc = pfind(pgid);
                if (proc == NULL) {
                        ret = ESRCH;
                        goto fail;
                }

                /*
                 * Policy - Don't allow a process to FSETOWN a process
                 * in another session.
                 *
                 * Remove this test to allow maximum flexibility or
                 * restrict FSETOWN to the current process or process
                 * group for maximum safety.
                 */
                PROC_UNLOCK(proc);
                if (proc->p_session != curthread->td_proc->p_session) {
                        ret = EPERM;
                        goto fail;
                }

                pgrp = NULL;
        } else /* if (pgid < 0) */ {
                pgrp = pgfind(-pgid);
                if (pgrp == NULL) {
                        ret = ESRCH;
                        goto fail;
                }
                PGRP_UNLOCK(pgrp);

                /*
                 * Policy - Don't allow a process to FSETOWN a process
                 * in another session.
                 *
                 * Remove this test to allow maximum flexibility or
                 * restrict FSETOWN to the current process or process
                 * group for maximum safety.
                 */
                if (pgrp->pg_session != curthread->td_proc->p_session) {
                        ret = EPERM;
                        goto fail;
                }

                proc = NULL;
        }
        funsetown(sigiop);
        if (pgid > 0) {
                PROC_LOCK(proc);
                /*
                 * Since funsetownlst() is called without the proctree
                 * locked, we need to check for P_WEXIT.
                 * XXX: is ESRCH correct?
                 */
                if ((proc->p_flag & P_WEXIT) != 0) {
                        PROC_UNLOCK(proc);
                        ret = ESRCH;
                        goto fail;
                }
                SLIST_INSERT_HEAD(&proc->p_sigiolst, sigio, sio_pgsigio);
                sigio->sio_proc = proc;
                PROC_UNLOCK(proc);
        } else {
                PGRP_LOCK(pgrp);
                SLIST_INSERT_HEAD(&pgrp->pg_sigiolst, sigio, sio_pgsigio);
                sigio->sio_pgrp = pgrp;
                PGRP_UNLOCK(pgrp);
        }
        sx_sunlock(&proctree_lock);
        SIGIO_LOCK();
        *sigiop = sigio;
        SIGIO_UNLOCK();
        return (0);

fail:
        sx_sunlock(&proctree_lock);
        crfree(sigio->sio_ucred);
        FREE(sigio, M_SIGIO);
        return (ret);
}

/*
 * This is common code for FIOGETOWN ioctl called by fcntl(fd, F_GETOWN, arg).
 */
pid_t
fgetown(sigiop)
        struct sigio **sigiop;
{
        pid_t pgid;

        SIGIO_LOCK();
        pgid = (*sigiop != NULL) ? (*sigiop)->sio_pgid : 0;
        SIGIO_UNLOCK();
        return (pgid);
}

/*
 * Close a file descriptor.
 */
#ifndef _SYS_SYSPROTO_H_
struct close_args {
        int     fd;
};
#endif
/* ARGSUSED */
int
close(td, uap)
        struct thread *td;
        struct close_args *uap;
{

        return (kern_close(td, uap->fd));
}

int
kern_close(td, fd)
        struct thread *td;
        int fd;
{
        struct filedesc *fdp;
        struct file *fp;
        int error;
        int holdleaders;

        error = 0;
        holdleaders = 0;
        fdp = td->td_proc->p_fd;

        AUDIT_SYSCLOSE(td, fd);

        FILEDESC_XLOCK(fdp);
        if ((unsigned)fd >= fdp->fd_nfiles ||
            (fp = fdp->fd_ofiles[fd]) == NULL) {
                FILEDESC_XUNLOCK(fdp);
                return (EBADF);
        }
        fdp->fd_ofiles[fd] = NULL;
        fdp->fd_ofileflags[fd] = 0;
        fdunused(fdp, fd);
        if (td->td_proc->p_fdtol != NULL) {
                /*
                 * Ask fdfree() to sleep to ensure that all relevant
                 * process leaders can be traversed in closef().
                 */
                fdp->fd_holdleaderscount++;
                holdleaders = 1;
        }

        /*
         * We now hold the fp reference that used to be owned by the
         * descriptor array.  We have to unlock the FILEDESC *AFTER*
         * knote_fdclose to prevent a race of the fd getting opened, a knote
         * added, and deleteing a knote for the new fd.
         */
        knote_fdclose(td, fd);
        if (fp->f_type == DTYPE_MQUEUE)
                mq_fdclose(td, fd, fp);
        FILEDESC_XUNLOCK(fdp);

        error = closef(fp, td);
        if (holdleaders) {
                FILEDESC_XLOCK(fdp);
                fdp->fd_holdleaderscount--;
                if (fdp->fd_holdleaderscount == 0 &&
                    fdp->fd_holdleaderswakeup != 0) {
                        fdp->fd_holdleaderswakeup = 0;
                        wakeup(&fdp->fd_holdleaderscount);
                }
                FILEDESC_XUNLOCK(fdp);
        }
        return (error);
}

#if defined(COMPAT_43)
/*
 * Return status information about a file descriptor.
 */
#ifndef _SYS_SYSPROTO_H_
struct ofstat_args {
        int     fd;
        struct  ostat *sb;
};
#endif
/* ARGSUSED */
int
ofstat(struct thread *td, struct ofstat_args *uap)
{
        struct ostat oub;
        struct stat ub;
        int error;

        error = kern_fstat(td, uap->fd, &ub);
        if (error == 0) {
                cvtstat(&ub, &oub);
                error = copyout(&oub, uap->sb, sizeof(oub));
        }
        return (error);
}
#endif /* COMPAT_43 */

/*
 * Return status information about a file descriptor.
 */
#ifndef _SYS_SYSPROTO_H_
struct fstat_args {
        int     fd;
        struct  stat *sb;
};
#endif
/* ARGSUSED */
int
fstat(struct thread *td, struct fstat_args *uap)
{
        struct stat ub;
        int error;

        error = kern_fstat(td, uap->fd, &ub);
        if (error == 0)
                error = copyout(&ub, uap->sb, sizeof(ub));
        return (error);
}

int
kern_fstat(struct thread *td, int fd, struct stat *sbp)
{
        struct file *fp;
        int error;

        AUDIT_ARG(fd, fd);

        if ((error = fget(td, fd, &fp)) != 0)
                return (error);

        AUDIT_ARG(file, td->td_proc, fp);

        error = fo_stat(fp, sbp, td->td_ucred, td);
        fdrop(fp, td);
#ifdef KTRACE
        if (error == 0 && KTRPOINT(td, KTR_STRUCT))
                ktrstat(sbp);
#endif
        return (error);
}

/*
 * Return status information about a file descriptor.
 */
#ifndef _SYS_SYSPROTO_H_
struct nfstat_args {
        int     fd;
        struct  nstat *sb;
};
#endif
/* ARGSUSED */
int
nfstat(struct thread *td, struct nfstat_args *uap)
{
        struct nstat nub;
        struct stat ub;
        int error;

        error = kern_fstat(td, uap->fd, &ub);
        if (error == 0) {
                cvtnstat(&ub, &nub);
                error = copyout(&nub, uap->sb, sizeof(nub));
        }
        return (error);
}

/*
 * Return pathconf information about a file descriptor.
 */
#ifndef _SYS_SYSPROTO_H_
struct fpathconf_args {
        int     fd;
        int     name;
};
#endif
/* ARGSUSED */
int
fpathconf(struct thread *td, struct fpathconf_args *uap)
{
        struct file *fp;
        struct vnode *vp;
        int error;

        if ((error = fget(td, uap->fd, &fp)) != 0)
                return (error);

        /* If asynchronous I/O is available, it works for all descriptors. */
        if (uap->name == _PC_ASYNC_IO) {
                td->td_retval[0] = async_io_version;
                goto out;
        }
        vp = fp->f_vnode;
        if (vp != NULL) {
                int vfslocked;
                vfslocked = VFS_LOCK_GIANT(vp->v_mount);
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                error = VOP_PATHCONF(vp, uap->name, td->td_retval);
                VOP_UNLOCK(vp, 0);
                VFS_UNLOCK_GIANT(vfslocked);
        } else if (fp->f_type == DTYPE_PIPE || fp->f_type == DTYPE_SOCKET) {
                if (uap->name != _PC_PIPE_BUF) {
                        error = EINVAL;
                } else {
                        td->td_retval[0] = PIPE_BUF;
                error = 0;
                }
        } else {
                error = EOPNOTSUPP;
        }
out:
        fdrop(fp, td);
        return (error);
}

/*
 * Grow the file table to accomodate (at least) nfd descriptors.  This may
 * block and drop the filedesc lock, but it will reacquire it before
 * returning.
 */
static void
fdgrowtable(struct filedesc *fdp, int nfd)
{
        struct file **ntable;
        char *nfileflags;
        int nnfiles, onfiles;
        NDSLOTTYPE *nmap;

        FILEDESC_XLOCK_ASSERT(fdp);

        KASSERT(fdp->fd_nfiles > 0,
            ("zero-length file table"));

        /* compute the size of the new table */
        onfiles = fdp->fd_nfiles;
        nnfiles = NDSLOTS(nfd) * NDENTRIES; /* round up */
        if (nnfiles <= onfiles)
                /* the table is already large enough */
                return;

        /* allocate a new table and (if required) new bitmaps */
        FILEDESC_XUNLOCK(fdp);
        MALLOC(ntable, struct file **, nnfiles * OFILESIZE,
            M_FILEDESC, M_ZERO | M_WAITOK);
        nfileflags = (char *)&ntable[nnfiles];
        if (NDSLOTS(nnfiles) > NDSLOTS(onfiles))
                MALLOC(nmap, NDSLOTTYPE *, NDSLOTS(nnfiles) * NDSLOTSIZE,
                    M_FILEDESC, M_ZERO | M_WAITOK);
        else
                nmap = NULL;
        FILEDESC_XLOCK(fdp);

        /*
         * We now have new tables ready to go.  Since we dropped the
         * filedesc lock to call malloc(), watch out for a race.
         */
        onfiles = fdp->fd_nfiles;
        if (onfiles >= nnfiles) {
                /* we lost the race, but that's OK */
                free(ntable, M_FILEDESC);
                if (nmap != NULL)
                        free(nmap, M_FILEDESC);
                return;
        }
        bcopy(fdp->fd_ofiles, ntable, onfiles * sizeof(*ntable));
        bcopy(fdp->fd_ofileflags, nfileflags, onfiles);
        if (onfiles > NDFILE)
                free(fdp->fd_ofiles, M_FILEDESC);
        fdp->fd_ofiles = ntable;
        fdp->fd_ofileflags = nfileflags;
        if (NDSLOTS(nnfiles) > NDSLOTS(onfiles)) {
                bcopy(fdp->fd_map, nmap, NDSLOTS(onfiles) * sizeof(*nmap));
                if (NDSLOTS(onfiles) > NDSLOTS(NDFILE))
                        free(fdp->fd_map, M_FILEDESC);
                fdp->fd_map = nmap;
        }
        fdp->fd_nfiles = nnfiles;
}

/*
 * Allocate a file descriptor for the process.
 */
int
fdalloc(struct thread *td, int minfd, int *result)
{
        struct proc *p = td->td_proc;
        struct filedesc *fdp = p->p_fd;
        int fd = -1, maxfd;

        FILEDESC_XLOCK_ASSERT(fdp);

        if (fdp->fd_freefile > minfd)
                minfd = fdp->fd_freefile;          

        PROC_LOCK(p);
        maxfd = min((int)lim_cur(p, RLIMIT_NOFILE), maxfilesperproc);
        PROC_UNLOCK(p);

        /*
         * Search the bitmap for a free descriptor.  If none is found, try
         * to grow the file table.  Keep at it until we either get a file
         * descriptor or run into process or system limits; fdgrowtable()
         * may drop the filedesc lock, so we're in a race.
         */
        for (;;) {
                fd = fd_first_free(fdp, minfd, fdp->fd_nfiles);
                if (fd >= maxfd)
                        return (EMFILE);
                if (fd < fdp->fd_nfiles)
                        break;
                fdgrowtable(fdp, min(fdp->fd_nfiles * 2, maxfd));
        }

        /*
         * Perform some sanity checks, then mark the file descriptor as
         * used and return it to the caller.
         */
        KASSERT(!fdisused(fdp, fd),
            ("fd_first_free() returned non-free descriptor"));
        KASSERT(fdp->fd_ofiles[fd] == NULL,
            ("free descriptor isn't"));
        fdp->fd_ofileflags[fd] = 0; /* XXX needed? */
        fdused(fdp, fd);
        *result = fd;
        return (0);
}

/*
 * Check to see whether n user file descriptors are available to the process
 * p.
 */
int
fdavail(struct thread *td, int n)
{
        struct proc *p = td->td_proc;
        struct filedesc *fdp = td->td_proc->p_fd;
        struct file **fpp;
        int i, lim, last;

        FILEDESC_LOCK_ASSERT(fdp);

        PROC_LOCK(p);
        lim = min((int)lim_cur(p, RLIMIT_NOFILE), maxfilesperproc);
        PROC_UNLOCK(p);
        if ((i = lim - fdp->fd_nfiles) > 0 && (n -= i) <= 0)
                return (1);
        last = min(fdp->fd_nfiles, lim);
        fpp = &fdp->fd_ofiles[fdp->fd_freefile];
        for (i = last - fdp->fd_freefile; --i >= 0; fpp++) {
                if (*fpp == NULL && --n <= 0)
                        return (1);
        }
        return (0);
}

/*
 * Create a new open file structure and allocate a file decriptor for the
 * process that refers to it.  We add one reference to the file for the
 * descriptor table and one reference for resultfp. This is to prevent us
 * being preempted and the entry in the descriptor table closed after we
 * release the FILEDESC lock.
 */
int
falloc(struct thread *td, struct file **resultfp, int *resultfd)
{
        struct proc *p = td->td_proc;
        struct file *fp;
        int error, i;
        int maxuserfiles = maxfiles - (maxfiles / 20);
        static struct timeval lastfail;
        static int curfail;

        fp = uma_zalloc(file_zone, M_WAITOK | M_ZERO);
        if ((openfiles >= maxuserfiles &&
            priv_check(td, PRIV_MAXFILES) != 0) ||
            openfiles >= maxfiles) {
                if (ppsratecheck(&lastfail, &curfail, 1)) {
                        printf("kern.maxfiles limit exceeded by uid %i, please see tuning(7).\n",
                                td->td_ucred->cr_ruid);
                }
                uma_zfree(file_zone, fp);
                return (ENFILE);
        }
        atomic_add_int(&openfiles, 1);

        /*
         * If the process has file descriptor zero open, add the new file
         * descriptor to the list of open files at that point, otherwise
         * put it at the front of the list of open files.
         */
        refcount_init(&fp->f_count, 1);
        if (resultfp)
                fhold(fp);
        fp->f_cred = crhold(td->td_ucred);
        fp->f_ops = &badfileops;
        fp->f_data = NULL;
        fp->f_vnode = NULL;
        FILEDESC_XLOCK(p->p_fd);
        if ((error = fdalloc(td, 0, &i))) {
                FILEDESC_XUNLOCK(p->p_fd);
                fdrop(fp, td);
                if (resultfp)
                        fdrop(fp, td);
                return (error);
        }
        p->p_fd->fd_ofiles[i] = fp;
        FILEDESC_XUNLOCK(p->p_fd);
        if (resultfp)
                *resultfp = fp;
        if (resultfd)
                *resultfd = i;
        return (0);
}

/*
 * Build a new filedesc structure from another.
 * Copy the current, root, and jail root vnode references.
 */
struct filedesc *
fdinit(struct filedesc *fdp)
{
        struct filedesc0 *newfdp;

        newfdp = malloc(sizeof *newfdp, M_FILEDESC, M_WAITOK | M_ZERO);
        FILEDESC_LOCK_INIT(&newfdp->fd_fd);
        if (fdp != NULL) {
                FILEDESC_XLOCK(fdp);
                newfdp->fd_fd.fd_cdir = fdp->fd_cdir;
                if (newfdp->fd_fd.fd_cdir)
                        VREF(newfdp->fd_fd.fd_cdir);
                newfdp->fd_fd.fd_rdir = fdp->fd_rdir;
                if (newfdp->fd_fd.fd_rdir)
                        VREF(newfdp->fd_fd.fd_rdir);
                newfdp->fd_fd.fd_jdir = fdp->fd_jdir;
                if (newfdp->fd_fd.fd_jdir)
                        VREF(newfdp->fd_fd.fd_jdir);
                FILEDESC_XUNLOCK(fdp);
        }

        /* Create the file descriptor table. */
        newfdp->fd_fd.fd_refcnt = 1;
        newfdp->fd_fd.fd_holdcnt = 1;
        newfdp->fd_fd.fd_cmask = CMASK;
        newfdp->fd_fd.fd_ofiles = newfdp->fd_dfiles;
        newfdp->fd_fd.fd_ofileflags = newfdp->fd_dfileflags;
        newfdp->fd_fd.fd_nfiles = NDFILE;
        newfdp->fd_fd.fd_map = newfdp->fd_dmap;
        newfdp->fd_fd.fd_lastfile = -1;
        return (&newfdp->fd_fd);
}

static struct filedesc *
fdhold(struct proc *p)
{
        struct filedesc *fdp;

        mtx_lock(&fdesc_mtx);
        fdp = p->p_fd;
        if (fdp != NULL)
                fdp->fd_holdcnt++;
        mtx_unlock(&fdesc_mtx);
        return (fdp);
}

static void
fddrop(struct filedesc *fdp)
{
        int i;

        mtx_lock(&fdesc_mtx);
        i = --fdp->fd_holdcnt;
        mtx_unlock(&fdesc_mtx);
        if (i > 0)
                return;

        FILEDESC_LOCK_DESTROY(fdp);
        FREE(fdp, M_FILEDESC);
}

/*
 * Share a filedesc structure.
 */
struct filedesc *
fdshare(struct filedesc *fdp)
{

        FILEDESC_XLOCK(fdp);
        fdp->fd_refcnt++;
        FILEDESC_XUNLOCK(fdp);
        return (fdp);
}

/*
 * Unshare a filedesc structure, if necessary by making a copy
 */
void
fdunshare(struct proc *p, struct thread *td)
{

        FILEDESC_XLOCK(p->p_fd);
        if (p->p_fd->fd_refcnt > 1) {
                struct filedesc *tmp;

                FILEDESC_XUNLOCK(p->p_fd);
                tmp = fdcopy(p->p_fd);
                fdfree(td);
                p->p_fd = tmp;
        } else
                FILEDESC_XUNLOCK(p->p_fd);
}

/*
 * Copy a filedesc structure.  A NULL pointer in returns a NULL reference,
 * this is to ease callers, not catch errors.
 */
struct filedesc *
fdcopy(struct filedesc *fdp)
{
        struct filedesc *newfdp;
        int i;

        /* Certain daemons might not have file descriptors. */
        if (fdp == NULL)
                return (NULL);

        newfdp = fdinit(fdp);
        FILEDESC_SLOCK(fdp);
        while (fdp->fd_lastfile >= newfdp->fd_nfiles) {
                FILEDESC_SUNLOCK(fdp);
                FILEDESC_XLOCK(newfdp);
                fdgrowtable(newfdp, fdp->fd_lastfile + 1);
                FILEDESC_XUNLOCK(newfdp);
                FILEDESC_SLOCK(fdp);
        }
        /* copy everything except kqueue descriptors */
        newfdp->fd_freefile = -1;
        for (i = 0; i <= fdp->fd_lastfile; ++i) {
                if (fdisused(fdp, i) &&
                    fdp->fd_ofiles[i]->f_type != DTYPE_KQUEUE) {
                        newfdp->fd_ofiles[i] = fdp->fd_ofiles[i];
                        newfdp->fd_ofileflags[i] = fdp->fd_ofileflags[i];
                        fhold(newfdp->fd_ofiles[i]);
                        newfdp->fd_lastfile = i;
                } else {
                        if (newfdp->fd_freefile == -1)
                                newfdp->fd_freefile = i;
                }
        }
        FILEDESC_SUNLOCK(fdp);
        FILEDESC_XLOCK(newfdp);
        for (i = 0; i <= newfdp->fd_lastfile; ++i)
                if (newfdp->fd_ofiles[i] != NULL)
                        fdused(newfdp, i);
        FILEDESC_XUNLOCK(newfdp);
        FILEDESC_SLOCK(fdp);
        if (newfdp->fd_freefile == -1)
                newfdp->fd_freefile = i;
        newfdp->fd_cmask = fdp->fd_cmask;
        FILEDESC_SUNLOCK(fdp);
        return (newfdp);
}

/*
 * Release a filedesc structure.
 */
void
fdfree(struct thread *td)
{
        struct filedesc *fdp;
        struct file **fpp;
        int i, locked;
        struct filedesc_to_leader *fdtol;
        struct file *fp;
        struct vnode *cdir, *jdir, *rdir, *vp;
        struct flock lf;

        /* Certain daemons might not have file descriptors. */
        fdp = td->td_proc->p_fd;
        if (fdp == NULL)
                return;

        /* Check for special need to clear POSIX style locks */
        fdtol = td->td_proc->p_fdtol;
        if (fdtol != NULL) {
                FILEDESC_XLOCK(fdp);
                KASSERT(fdtol->fdl_refcount > 0,
                        ("filedesc_to_refcount botch: fdl_refcount=%d",
                         fdtol->fdl_refcount));
                if (fdtol->fdl_refcount == 1 &&
                    (td->td_proc->p_leader->p_flag & P_ADVLOCK) != 0) {
                        for (i = 0, fpp = fdp->fd_ofiles;
                             i <= fdp->fd_lastfile;
                             i++, fpp++) {
                                if (*fpp == NULL ||
                                    (*fpp)->f_type != DTYPE_VNODE)
                                        continue;
                                fp = *fpp;
                                fhold(fp);
                                FILEDESC_XUNLOCK(fdp);
                                lf.l_whence = SEEK_SET;
                                lf.l_start = 0;
                                lf.l_len = 0;
                                lf.l_type = F_UNLCK;
                                vp = fp->f_vnode;
                                locked = VFS_LOCK_GIANT(vp->v_mount);
                                (void) VOP_ADVLOCK(vp,
                                                   (caddr_t)td->td_proc->
                                                   p_leader,
                                                   F_UNLCK,
                                                   &lf,
                                                   F_POSIX);
                                VFS_UNLOCK_GIANT(locked);
                                FILEDESC_XLOCK(fdp);
                                fdrop(fp, td);
                                fpp = fdp->fd_ofiles + i;
                        }
                }
        retry:
                if (fdtol->fdl_refcount == 1) {
                        if (fdp->fd_holdleaderscount > 0 &&
                            (td->td_proc->p_leader->p_flag & P_ADVLOCK) != 0) {
                                /*
                                 * close() or do_dup() has cleared a reference
                                 * in a shared file descriptor table.
                                 */
                                fdp->fd_holdleaderswakeup = 1;
                                sx_sleep(&fdp->fd_holdleaderscount,
                                    FILEDESC_LOCK(fdp), PLOCK, "fdlhold", 0);
                                goto retry;
                        }
                        if (fdtol->fdl_holdcount > 0) {
                                /*
                                 * Ensure that fdtol->fdl_leader remains
                                 * valid in closef().
                                 */
                                fdtol->fdl_wakeup = 1;
                                sx_sleep(fdtol, FILEDESC_LOCK(fdp), PLOCK,
                                    "fdlhold", 0);
                                goto retry;
                        }
                }
                fdtol->fdl_refcount--;
                if (fdtol->fdl_refcount == 0 &&
                    fdtol->fdl_holdcount == 0) {
                        fdtol->fdl_next->fdl_prev = fdtol->fdl_prev;
                        fdtol->fdl_prev->fdl_next = fdtol->fdl_next;
                } else
                        fdtol = NULL;
                td->td_proc->p_fdtol = NULL;
                FILEDESC_XUNLOCK(fdp);
                if (fdtol != NULL)
                        FREE(fdtol, M_FILEDESC_TO_LEADER);
        }
        FILEDESC_XLOCK(fdp);
        i = --fdp->fd_refcnt;
        FILEDESC_XUNLOCK(fdp);
        if (i > 0)
                return;
        /*
         * We are the last reference to the structure, so we can
         * safely assume it will not change out from under us.
         */
        fpp = fdp->fd_ofiles;
        for (i = fdp->fd_lastfile; i-- >= 0; fpp++) {
                if (*fpp)
                        (void) closef(*fpp, td);
        }
        FILEDESC_XLOCK(fdp);

        /* XXX This should happen earlier. */
        mtx_lock(&fdesc_mtx);
        td->td_proc->p_fd = NULL;
        mtx_unlock(&fdesc_mtx);

        if (fdp->fd_nfiles > NDFILE)
                FREE(fdp->fd_ofiles, M_FILEDESC);
        if (NDSLOTS(fdp->fd_nfiles) > NDSLOTS(NDFILE))
                FREE(fdp->fd_map, M_FILEDESC);

        fdp->fd_nfiles = 0;

        cdir = fdp->fd_cdir;
        fdp->fd_cdir = NULL;
        rdir = fdp->fd_rdir;
        fdp->fd_rdir = NULL;
        jdir = fdp->fd_jdir;
        fdp->fd_jdir = NULL;
        FILEDESC_XUNLOCK(fdp);

        if (cdir) {
                locked = VFS_LOCK_GIANT(cdir->v_mount);
                vrele(cdir);
                VFS_UNLOCK_GIANT(locked);
        }
        if (rdir) {
                locked = VFS_LOCK_GIANT(rdir->v_mount);
                vrele(rdir);
                VFS_UNLOCK_GIANT(locked);
        }
        if (jdir) {
                locked = VFS_LOCK_GIANT(jdir->v_mount);
                vrele(jdir);
                VFS_UNLOCK_GIANT(locked);
        }

        fddrop(fdp);
}

/*
 * For setugid programs, we don't want to people to use that setugidness
 * to generate error messages which write to a file which otherwise would
 * otherwise be off-limits to the process.  We check for filesystems where
 * the vnode can change out from under us after execve (like [lin]procfs).
 *
 * Since setugidsafety calls this only for fd 0, 1 and 2, this check is
 * sufficient.  We also don't check for setugidness since we know we are.
 */
static int
is_unsafe(struct file *fp)
{
        if (fp->f_type == DTYPE_VNODE) {
                struct vnode *vp = fp->f_vnode;

                if ((vp->v_vflag & VV_PROCDEP) != 0)
                        return (1);
        }
        return (0);
}

/*
 * Make this setguid thing safe, if at all possible.
 */
void
setugidsafety(struct thread *td)
{
        struct filedesc *fdp;
        int i;

        /* Certain daemons might not have file descriptors. */
        fdp = td->td_proc->p_fd;
        if (fdp == NULL)
                return;

        /*
         * Note: fdp->fd_ofiles may be reallocated out from under us while
         * we are blocked in a close.  Be careful!
         */
        FILEDESC_XLOCK(fdp);
        for (i = 0; i <= fdp->fd_lastfile; i++) {
                if (i > 2)
                        break;
                if (fdp->fd_ofiles[i] && is_unsafe(fdp->fd_ofiles[i])) {
                        struct file *fp;

                        knote_fdclose(td, i);
                        /*
                         * NULL-out descriptor prior to close to avoid
                         * a race while close blocks.
                         */
                        fp = fdp->fd_ofiles[i];
                        fdp->fd_ofiles[i] = NULL;
                        fdp->fd_ofileflags[i] = 0;
                        fdunused(fdp, i);
                        FILEDESC_XUNLOCK(fdp);
                        (void) closef(fp, td);
                        FILEDESC_XLOCK(fdp);
                }
        }
        FILEDESC_XUNLOCK(fdp);
}

/*
 * If a specific file object occupies a specific file descriptor, close the
 * file descriptor entry and drop a reference on the file object.  This is a
 * convenience function to handle a subsequent error in a function that calls
 * falloc() that handles the race that another thread might have closed the
 * file descriptor out from under the thread creating the file object.
 */
void
fdclose(struct filedesc *fdp, struct file *fp, int idx, struct thread *td)
{

        FILEDESC_XLOCK(fdp);
        if (fdp->fd_ofiles[idx] == fp) {
                fdp->fd_ofiles[idx] = NULL;
                fdunused(fdp, idx);
                FILEDESC_XUNLOCK(fdp);
                fdrop(fp, td);
        } else
                FILEDESC_XUNLOCK(fdp);
}

/*
 * Close any files on exec?
 */
void
fdcloseexec(struct thread *td)
{
        struct filedesc *fdp;
        int i;

        /* Certain daemons might not have file descriptors. */
        fdp = td->td_proc->p_fd;
        if (fdp == NULL)
                return;

        FILEDESC_XLOCK(fdp);

        /*
         * We cannot cache fd_ofiles or fd_ofileflags since operations
         * may block and rip them out from under us.
         */
        for (i = 0; i <= fdp->fd_lastfile; i++) {
                if (fdp->fd_ofiles[i] != NULL &&
                    (fdp->fd_ofiles[i]->f_type == DTYPE_MQUEUE ||
                    (fdp->fd_ofileflags[i] & UF_EXCLOSE))) {
                        struct file *fp;

                        knote_fdclose(td, i);
                        /*
                         * NULL-out descriptor prior to close to avoid
                         * a race while close blocks.
                         */
                        fp = fdp->fd_ofiles[i];
                        fdp->fd_ofiles[i] = NULL;
                        fdp->fd_ofileflags[i] = 0;
                        fdunused(fdp, i);
                        if (fp->f_type == DTYPE_MQUEUE)
                                mq_fdclose(td, i, fp);
                        FILEDESC_XUNLOCK(fdp);
                        (void) closef(fp, td);
                        FILEDESC_XLOCK(fdp);
                }
        }
        FILEDESC_XUNLOCK(fdp);
}

/*
 * 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.
 */
int
fdcheckstd(struct thread *td)
{
        struct filedesc *fdp;
        register_t retval, save;
        int i, error, devnull;

        fdp = td->td_proc->p_fd;
        if (fdp == NULL)
                return (0);
        KASSERT(fdp->fd_refcnt == 1, ("the fdtable should not be shared"));
        devnull = -1;
        error = 0;
        for (i = 0; i < 3; i++) {
                if (fdp->fd_ofiles[i] != NULL)
                        continue;
                if (devnull < 0) {
                        save = td->td_retval[0];
                        error = kern_open(td, "/dev/null", UIO_SYSSPACE,
                            O_RDWR, 0);
                        devnull = td->td_retval[0];
                        KASSERT(devnull == i, ("oof, we didn't get our fd"));
                        td->td_retval[0] = save;
                        if (error)
                                break;
                } else {
                        error = do_dup(td, DUP_FIXED, devnull, i, &retval);
                        if (error != 0)
                                break;
                }
        }
        return (error);
}

/*
 * Internal form of close.  Decrement reference count on file structure.
 * Note: td may be NULL when closing a file that was being passed in a
 * message.
 *
 * XXXRW: Giant is not required for the caller, but often will be held; this
 * makes it moderately likely the Giant will be recursed in the VFS case.
 */
int
closef(struct file *fp, struct thread *td)
{
        struct vnode *vp;
        struct flock lf;
        struct filedesc_to_leader *fdtol;
        struct filedesc *fdp;

        /*
         * 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, and the thread pointer
         * will be NULL.  Callers should be careful only to pass a
         * NULL thread pointer when there really is no owning
         * context that might have locks, or the locks will be
         * leaked.
         */
        if (fp->f_type == DTYPE_VNODE && td != NULL) {
                int vfslocked;

                vp = fp->f_vnode;
                vfslocked = VFS_LOCK_GIANT(vp->v_mount);
                if ((td->td_proc->p_leader->p_flag & P_ADVLOCK) != 0) {
                        lf.l_whence = SEEK_SET;
                        lf.l_start = 0;
                        lf.l_len = 0;
                        lf.l_type = F_UNLCK;
                        (void) VOP_ADVLOCK(vp, (caddr_t)td->td_proc->p_leader,
                                           F_UNLCK, &lf, F_POSIX);
                }
                fdtol = td->td_proc->p_fdtol;
                if (fdtol != NULL) {
                        /*
                         * Handle special case where file descriptor table is
                         * shared between multiple process leaders.
                         */
                        fdp = td->td_proc->p_fd;
                        FILEDESC_XLOCK(fdp);
                        for (fdtol = fdtol->fdl_next;
                             fdtol != td->td_proc->p_fdtol;
                             fdtol = fdtol->fdl_next) {
                                if ((fdtol->fdl_leader->p_flag &
                                     P_ADVLOCK) == 0)
                                        continue;
                                fdtol->fdl_holdcount++;
                                FILEDESC_XUNLOCK(fdp);
                                lf.l_whence = SEEK_SET;
                                lf.l_start = 0;
                                lf.l_len = 0;
                                lf.l_type = F_UNLCK;
                                vp = fp->f_vnode;
                                (void) VOP_ADVLOCK(vp,
                                                   (caddr_t)fdtol->fdl_leader,
                                                   F_UNLCK, &lf, F_POSIX);
                                FILEDESC_XLOCK(fdp);
                                fdtol->fdl_holdcount--;
                                if (fdtol->fdl_holdcount == 0 &&
                                    fdtol->fdl_wakeup != 0) {
                                        fdtol->fdl_wakeup = 0;
                                        wakeup(fdtol);
                                }
                        }
                        FILEDESC_XUNLOCK(fdp);
                }
                VFS_UNLOCK_GIANT(vfslocked);
        }
        return (fdrop(fp, td));
}

/*
 * Initialize the file pointer with the specified properties.
 * 
 * The ops are set with release semantics to be certain that the flags, type,
 * and data are visible when ops is.  This is to prevent ops methods from being
 * called with bad data.
 */
void
finit(struct file *fp, u_int flag, short type, void *data, struct fileops *ops)
{
        fp->f_data = data;
        fp->f_flag = flag;
        fp->f_type = type;
        atomic_store_rel_ptr((volatile uintptr_t *)&fp->f_ops, (uintptr_t)ops);
}


/*
 * Extract the file pointer associated with the specified descriptor for the
 * current user process.
 *
 * If the descriptor doesn't exist, EBADF is returned.
 *
 * If the descriptor exists but doesn't match 'flags' then return EBADF for
 * read attempts and EINVAL for write attempts.
 *
 * If 'hold' is set (non-zero) the file's refcount will be bumped on return.
 * It should be dropped with fdrop().  If it is not set, then the refcount
 * will not be bumped however the thread's filedesc struct will be returned
 * locked (for fgetsock).
 *
 * If an error occured the non-zero error is returned and *fpp is set to
 * NULL.  Otherwise *fpp is set and zero is returned.
 */
static __inline int
_fget(struct thread *td, int fd, struct file **fpp, int flags, int hold)
{
        struct filedesc *fdp;
        struct file *fp;

        *fpp = NULL;
        if (td == NULL || (fdp = td->td_proc->p_fd) == NULL)
                return (EBADF);
        FILEDESC_SLOCK(fdp);
        if ((fp = fget_locked(fdp, fd)) == NULL || fp->f_ops == &badfileops) {
                FILEDESC_SUNLOCK(fdp);
                return (EBADF);
        }

        /*
         * FREAD and FWRITE failure return EBADF as per POSIX.
         *
         * Only one flag, or 0, may be specified.
         */
        if (flags == FREAD && (fp->f_flag & FREAD) == 0) {
                FILEDESC_SUNLOCK(fdp);
                return (EBADF);
        }
        if (flags == FWRITE && (fp->f_flag & FWRITE) == 0) {
                FILEDESC_SUNLOCK(fdp);
                return (EBADF);
        }
        if (hold) {
                fhold(fp);
                FILEDESC_SUNLOCK(fdp);
        }
        *fpp = fp;
        return (0);
}

int
fget(struct thread *td, int fd, struct file **fpp)
{

        return(_fget(td, fd, fpp, 0, 1));
}

int
fget_read(struct thread *td, int fd, struct file **fpp)
{

        return(_fget(td, fd, fpp, FREAD, 1));
}

int
fget_write(struct thread *td, int fd, struct file **fpp)
{

        return(_fget(td, fd, fpp, FWRITE, 1));
}

/*
 * Like fget() but loads the underlying vnode, or returns an error if the
 * descriptor does not represent a vnode.  Note that pipes use vnodes but
 * never have VM objects.  The returned vnode will be vref()'d.
 *
 * XXX: what about the unused flags ?
 */
static __inline int
_fgetvp(struct thread *td, int fd, struct vnode **vpp, int flags)
{
        struct file *fp;
        int error;

        *vpp = NULL;
        if ((error = _fget(td, fd, &fp, flags, 0)) != 0)
                return (error);
        if (fp->f_vnode == NULL) {
                error = EINVAL;
        } else {
                *vpp = fp->f_vnode;
                vref(*vpp);
        }
        FILEDESC_SUNLOCK(td->td_proc->p_fd);
        return (error);
}

int
fgetvp(struct thread *td, int fd, struct vnode **vpp)
{

        return (_fgetvp(td, fd, vpp, 0));
}

int
fgetvp_read(struct thread *td, int fd, struct vnode **vpp)
{

        return (_fgetvp(td, fd, vpp, FREAD));
}

#ifdef notyet
int
fgetvp_write(struct thread *td, int fd, struct vnode **vpp)
{

        return (_fgetvp(td, fd, vpp, FWRITE));
}
#endif

/*
 * Like fget() but loads the underlying socket, or returns an error if the
 * descriptor does not represent a socket.
 *
 * We bump the ref count on the returned socket.  XXX Also obtain the SX lock
 * in the future.
 *
 * XXXRW: fgetsock() and fputsock() are deprecated, as consumers should rely
 * on their file descriptor reference to prevent the socket from being free'd
 * during use.
 */
int
fgetsock(struct thread *td, int fd, struct socket **spp, u_int *fflagp)
{
        struct file *fp;
        int error;

        *spp = NULL;
        if (fflagp != NULL)
                *fflagp = 0;
        if ((error = _fget(td, fd, &fp, 0, 0)) != 0)
                return (error);
        if (fp->f_type != DTYPE_SOCKET) {
                error = ENOTSOCK;
        } else {
                *spp = fp->f_data;
                if (fflagp)
                        *fflagp = fp->f_flag;
                SOCK_LOCK(*spp);
                soref(*spp);
                SOCK_UNLOCK(*spp);
        }
        FILEDESC_SUNLOCK(td->td_proc->p_fd);
        return (error);
}

/*
 * Drop the reference count on the socket and XXX release the SX lock in the
 * future.  The last reference closes the socket.
 *
 * XXXRW: fputsock() is deprecated, see comment for fgetsock().
 */
void
fputsock(struct socket *so)
{

        ACCEPT_LOCK();
        SOCK_LOCK(so);
        sorele(so);
}

/*
 * Handle the last reference to a file being closed.
 */
int
_fdrop(struct file *fp, struct thread *td)
{
        int error;

        error = 0;
        if (fp->f_count != 0)
                panic("fdrop: count %d", fp->f_count);
        if (fp->f_ops != &badfileops)
                error = fo_close(fp, td);
        /*
         * The f_cdevpriv cannot be assigned non-NULL value while we
         * are destroying the file.
         */
        if (fp->f_cdevpriv != NULL)
                devfs_fpdrop(fp);
        atomic_subtract_int(&openfiles, 1);
        crfree(fp->f_cred);
        uma_zfree(file_zone, fp);

        return (error);
}

/*
 * Apply an advisory lock on a file descriptor.
 *
 * Just attempt to get a record lock of the requested type on the entire file
 * (l_whence = SEEK_SET, l_start = 0, l_len = 0).
 */
#ifndef _SYS_SYSPROTO_H_
struct flock_args {
        int     fd;
        int     how;
};
#endif
/* ARGSUSED */
int
flock(struct thread *td, struct flock_args *uap)
{
        struct file *fp;
        struct vnode *vp;
        struct flock lf;
        int vfslocked;
        int error;

        if ((error = fget(td, uap->fd, &fp)) != 0)
                return (error);
        if (fp->f_type != DTYPE_VNODE) {
                fdrop(fp, td);
                return (EOPNOTSUPP);
        }

        vp = fp->f_vnode;
        vfslocked = VFS_LOCK_GIANT(vp->v_mount);
        lf.l_whence = SEEK_SET;
        lf.l_start = 0;
        lf.l_len = 0;
        if (uap->how & LOCK_UN) {
                lf.l_type = F_UNLCK;
                atomic_clear_int(&fp->f_flag, FHASLOCK);
                error = VOP_ADVLOCK(vp, (caddr_t)fp, F_UNLCK, &lf, F_FLOCK);
                goto done2;
        }
        if (uap->how & LOCK_EX)
                lf.l_type = F_WRLCK;
        else if (uap->how & LOCK_SH)
                lf.l_type = F_RDLCK;
        else {
                error = EBADF;
                goto done2;
        }
        atomic_set_int(&fp->f_flag, FHASLOCK);
        error = VOP_ADVLOCK(vp, (caddr_t)fp, F_SETLK, &lf,
            (uap->how & LOCK_NB) ? F_FLOCK : F_FLOCK | F_WAIT);
done2:
        fdrop(fp, td);
        VFS_UNLOCK_GIANT(vfslocked);
        return (error);
}
/*
 * Duplicate the specified descriptor to a free descriptor.
 */
int
dupfdopen(struct thread *td, struct filedesc *fdp, int indx, int dfd, int mode, int error)
{
        struct file *wfp;
        struct file *fp;

        /*
         * If the to-be-dup'd fd number is greater than the allowed number
         * of file descriptors, or the fd to be dup'd has already been
         * closed, then reject.
         */
        FILEDESC_XLOCK(fdp);
        if (dfd < 0 || dfd >= fdp->fd_nfiles ||
            (wfp = fdp->fd_ofiles[dfd]) == NULL) {
                FILEDESC_XUNLOCK(fdp);
                return (EBADF);
        }

        /*
         * There are two cases of interest here.
         *
         * For ENODEV simply dup (dfd) to file descriptor (indx) and return.
         *
         * For ENXIO 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 ENODEV:
                /*
                 * Check that the mode the file is being opened for is a
                 * subset of the mode of the existing descriptor.
                 */
                if (((mode & (FREAD|FWRITE)) | wfp->f_flag) != wfp->f_flag) {
                        FILEDESC_XUNLOCK(fdp);
                        return (EACCES);
                }
                fp = fdp->fd_ofiles[indx];
                fdp->fd_ofiles[indx] = wfp;
                fdp->fd_ofileflags[indx] = fdp->fd_ofileflags[dfd];
                if (fp == NULL)
                        fdused(fdp, indx);
                fhold(wfp);
                FILEDESC_XUNLOCK(fdp);
                if (fp != NULL)
                        /*
                         * We now own the reference to fp that the ofiles[]
                         * array used to own.  Release it.
                         */
                        fdrop(fp, td);
                return (0);

        case ENXIO:
                /*
                 * Steal away the file pointer from dfd and stuff it into indx.
                 */
                fp = fdp->fd_ofiles[indx];
                fdp->fd_ofiles[indx] = fdp->fd_ofiles[dfd];
                fdp->fd_ofiles[dfd] = NULL;
                fdp->fd_ofileflags[indx] = fdp->fd_ofileflags[dfd];
                fdp->fd_ofileflags[dfd] = 0;
                fdunused(fdp, dfd);
                if (fp == NULL)
                        fdused(fdp, indx);
                FILEDESC_XUNLOCK(fdp);

                /*
                 * We now own the reference to fp that the ofiles[] array
                 * used to own.  Release it.
                 */
                if (fp != NULL)
                        fdrop(fp, td);
                return (0);

        default:
                FILEDESC_XUNLOCK(fdp);
                return (error);
        }
        /* NOTREACHED */
}

/*
 * Scan all active processes to see if any of them have a current or root
 * directory of `olddp'. If so, replace them with the new mount point.
 */
void
mountcheckdirs(struct vnode *olddp, struct vnode *newdp)
{
        struct filedesc *fdp;
        struct proc *p;
        int nrele;

        if (vrefcnt(olddp) == 1)
                return;
        sx_slock(&allproc_lock);
        FOREACH_PROC_IN_SYSTEM(p) {
                fdp = fdhold(p);
                if (fdp == NULL)
                        continue;
                nrele = 0;
                FILEDESC_XLOCK(fdp);
                if (fdp->fd_cdir == olddp) {
                        vref(newdp);
                        fdp->fd_cdir = newdp;
                        nrele++;
                }
                if (fdp->fd_rdir == olddp) {
                        vref(newdp);
                        fdp->fd_rdir = newdp;
                        nrele++;
                }
                FILEDESC_XUNLOCK(fdp);
                fddrop(fdp);
                while (nrele--)
                        vrele(olddp);
        }
        sx_sunlock(&allproc_lock);
        if (rootvnode == olddp) {
                vrele(rootvnode);
                vref(newdp);
                rootvnode = newdp;
        }
}

struct filedesc_to_leader *
filedesc_to_leader_alloc(struct filedesc_to_leader *old, struct filedesc *fdp, struct proc *leader)
{
        struct filedesc_to_leader *fdtol;

        MALLOC(fdtol, struct filedesc_to_leader *,
               sizeof(struct filedesc_to_leader),
               M_FILEDESC_TO_LEADER,
               M_WAITOK);
        fdtol->fdl_refcount = 1;
        fdtol->fdl_holdcount = 0;
        fdtol->fdl_wakeup = 0;
        fdtol->fdl_leader = leader;
        if (old != NULL) {
                FILEDESC_XLOCK(fdp);
                fdtol->fdl_next = old->fdl_next;
                fdtol->fdl_prev = old;
                old->fdl_next = fdtol;
                fdtol->fdl_next->fdl_prev = fdtol;
                FILEDESC_XUNLOCK(fdp);
        } else {
                fdtol->fdl_next = fdtol;
                fdtol->fdl_prev = fdtol;
        }
        return (fdtol);
}

/*
 * Get file structures globally.
 */
static int
sysctl_kern_file(SYSCTL_HANDLER_ARGS)
{
        struct xfile xf;
        struct filedesc *fdp;
        struct file *fp;
        struct proc *p;
        int error, n;

        error = sysctl_wire_old_buffer(req, 0);
        if (error != 0)
                return (error);
        if (req->oldptr == NULL) {
                n = 0;
                sx_slock(&allproc_lock);
                FOREACH_PROC_IN_SYSTEM(p) {
                        if (p->p_state == PRS_NEW)
                                continue;
                        fdp = fdhold(p);
                        if (fdp == NULL)
                                continue;
                        /* overestimates sparse tables. */
                        if (fdp->fd_lastfile > 0)
                                n += fdp->fd_lastfile;
                        fddrop(fdp);
                }
                sx_sunlock(&allproc_lock);
                return (SYSCTL_OUT(req, 0, n * sizeof(xf)));
        }
        error = 0;
        bzero(&xf, sizeof(xf));
        xf.xf_size = sizeof(xf);
        sx_slock(&allproc_lock);
        FOREACH_PROC_IN_SYSTEM(p) {
                if (p->p_state == PRS_NEW)
                        continue;
                PROC_LOCK(p);
                if (p_cansee(req->td, p) != 0) {
                        PROC_UNLOCK(p);
                        continue;
                }
                xf.xf_pid = p->p_pid;
                xf.xf_uid = p->p_ucred->cr_uid;
                PROC_UNLOCK(p);
                fdp = fdhold(p);
                if (fdp == NULL)
                        continue;
                FILEDESC_SLOCK(fdp);
                for (n = 0; fdp->fd_refcnt > 0 && n < fdp->fd_nfiles; ++n) {
                        if ((fp = fdp->fd_ofiles[n]) == NULL)
                                continue;
                        xf.xf_fd = n;
                        xf.xf_file = fp;
                        xf.xf_data = fp->f_data;
                        xf.xf_vnode = fp->f_vnode;
                        xf.xf_type = fp->f_type;
                        xf.xf_count = fp->f_count;
                        xf.xf_msgcount = 0;
                        xf.xf_offset = fp->f_offset;
                        xf.xf_flag = fp->f_flag;
                        error = SYSCTL_OUT(req, &xf, sizeof(xf));
                        if (error)
                                break;
                }
                FILEDESC_SUNLOCK(fdp);
                fddrop(fdp);
                if (error)
                        break;
        }
        sx_sunlock(&allproc_lock);
        return (error);
}

SYSCTL_PROC(_kern, KERN_FILE, file, CTLTYPE_OPAQUE|CTLFLAG_RD,
    0, 0, sysctl_kern_file, "S,xfile", "Entire file table");

static int
export_vnode_for_sysctl(struct vnode *vp, int type,
    struct kinfo_file *kif, struct filedesc *fdp, struct sysctl_req *req)
{
        int error;
        char *fullpath, *freepath;
        int vfslocked;

        bzero(kif, sizeof(*kif));
        kif->kf_structsize = sizeof(*kif);

        vref(vp);
        kif->kf_fd = type;
        kif->kf_type = KF_TYPE_VNODE;
        /* This function only handles directories. */
        KASSERT(vp->v_type == VDIR, ("export_vnode_for_sysctl: vnode not directory"));
        kif->kf_vnode_type = KF_VTYPE_VDIR;

        /*
         * This is not a true file descriptor, so we set a bogus refcount
         * and offset to indicate these fields should be ignored.
         */
        kif->kf_ref_count = -1;
        kif->kf_offset = -1;

        freepath = NULL;
        fullpath = "-";
        FILEDESC_SUNLOCK(fdp);
        vfslocked = VFS_LOCK_GIANT(vp->v_mount);
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
        vn_fullpath(curthread, vp, &fullpath, &freepath);
        vput(vp);
        VFS_UNLOCK_GIANT(vfslocked);
        strlcpy(kif->kf_path, fullpath, sizeof(kif->kf_path));
        if (freepath != NULL)
                free(freepath, M_TEMP);
        error = SYSCTL_OUT(req, kif, sizeof(*kif));
        FILEDESC_SLOCK(fdp);
        return (error);
}

/*
 * Get per-process file descriptors for use by procstat(1), et al.
 */
static int
sysctl_kern_proc_filedesc(SYSCTL_HANDLER_ARGS)
{
        char *fullpath, *freepath;
        struct kinfo_file *kif;
        struct filedesc *fdp;
        int error, i, *name;
        struct socket *so;
        struct vnode *vp;
        struct file *fp;
        struct proc *p;
        struct tty *tp;
        int vfslocked;

        name = (int *)arg1;
        if ((p = pfind((pid_t)name[0])) == NULL)
                return (ESRCH);
        if ((error = p_candebug(curthread, p))) {
                PROC_UNLOCK(p);
                return (error);
        }
        fdp = fdhold(p);
        PROC_UNLOCK(p);
        if (fdp == NULL)
                return (ENOENT);
        kif = malloc(sizeof(*kif), M_TEMP, M_WAITOK);
        FILEDESC_SLOCK(fdp);
        if (fdp->fd_cdir != NULL)
                export_vnode_for_sysctl(fdp->fd_cdir, KF_FD_TYPE_CWD, kif,
                                fdp, req);
        if (fdp->fd_rdir != NULL)
                export_vnode_for_sysctl(fdp->fd_rdir, KF_FD_TYPE_ROOT, kif,
                                fdp, req);
        if (fdp->fd_jdir != NULL)
                export_vnode_for_sysctl(fdp->fd_jdir, KF_FD_TYPE_JAIL, kif,
                                fdp, req);
        for (i = 0; i < fdp->fd_nfiles; i++) {
                if ((fp = fdp->fd_ofiles[i]) == NULL)
                        continue;
                bzero(kif, sizeof(*kif));
                kif->kf_structsize = sizeof(*kif);
                vp = NULL;
                so = NULL;
                tp = NULL;
                kif->kf_fd = i;
                switch (fp->f_type) {
                case DTYPE_VNODE:
                        kif->kf_type = KF_TYPE_VNODE;
                        vp = fp->f_vnode;
                        break;

                case DTYPE_SOCKET:
                        kif->kf_type = KF_TYPE_SOCKET;
                        so = fp->f_data;
                        break;

                case DTYPE_PIPE:
                        kif->kf_type = KF_TYPE_PIPE;
                        break;

                case DTYPE_FIFO:
                        kif->kf_type = KF_TYPE_FIFO;
                        vp = fp->f_vnode;
                        vref(vp);
                        break;

                case DTYPE_KQUEUE:
                        kif->kf_type = KF_TYPE_KQUEUE;
                        break;

                case DTYPE_CRYPTO:
                        kif->kf_type = KF_TYPE_CRYPTO;
                        break;

                case DTYPE_MQUEUE:
                        kif->kf_type = KF_TYPE_MQUEUE;
                        break;

                case DTYPE_SHM:
                        kif->kf_type = KF_TYPE_SHM;
                        break;

                case DTYPE_SEM:
                        kif->kf_type = KF_TYPE_SEM;
                        break;

                case DTYPE_PTS:
                        kif->kf_type = KF_TYPE_PTS;
                        tp = fp->f_data;
                        break;

                default:
                        kif->kf_type = KF_TYPE_UNKNOWN;
                        break;
                }
                kif->kf_ref_count = fp->f_count;
                if (fp->f_flag & FREAD)
                        kif->kf_flags |= KF_FLAG_READ;
                if (fp->f_flag & FWRITE)
                        kif->kf_flags |= KF_FLAG_WRITE;
                if (fp->f_flag & FAPPEND)
                        kif->kf_flags |= KF_FLAG_APPEND;
                if (fp->f_flag & FASYNC)
                        kif->kf_flags |= KF_FLAG_ASYNC;
                if (fp->f_flag & FFSYNC)
                        kif->kf_flags |= KF_FLAG_FSYNC;
                if (fp->f_flag & FNONBLOCK)
                        kif->kf_flags |= KF_FLAG_NONBLOCK;
                if (fp->f_flag & O_DIRECT)
                        kif->kf_flags |= KF_FLAG_DIRECT;
                if (fp->f_flag & FHASLOCK)
                        kif->kf_flags |= KF_FLAG_HASLOCK;
                kif->kf_offset = fp->f_offset;
                if (vp != NULL) {
                        vref(vp);
                        switch (vp->v_type) {
                        case VNON:
                                kif->kf_vnode_type = KF_VTYPE_VNON;
                                break;
                        case VREG:
                                kif->kf_vnode_type = KF_VTYPE_VREG;
                                break;
                        case VDIR:
                                kif->kf_vnode_type = KF_VTYPE_VDIR;
                                break;
                        case VBLK:
                                kif->kf_vnode_type = KF_VTYPE_VBLK;
                                break;
                        case VCHR:
                                kif->kf_vnode_type = KF_VTYPE_VCHR;
                                break;
                        case VLNK:
                                kif->kf_vnode_type = KF_VTYPE_VLNK;
                                break;
                        case VSOCK:
                                kif->kf_vnode_type = KF_VTYPE_VSOCK;
                                break;
                        case VFIFO:
                                kif->kf_vnode_type = KF_VTYPE_VFIFO;
                                break;
                        case VBAD:
                                kif->kf_vnode_type = KF_VTYPE_VBAD;
                                break;
                        default:
                                kif->kf_vnode_type = KF_VTYPE_UNKNOWN;
                                break;
                        }
                        /*
                         * It is OK to drop the filedesc lock here as we will
                         * re-validate and re-evaluate its properties when
                         * the loop continues.
                         */
                        freepath = NULL;
                        fullpath = "-";
                        FILEDESC_SUNLOCK(fdp);
                        vfslocked = VFS_LOCK_GIANT(vp->v_mount);
                        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                        vn_fullpath(curthread, vp, &fullpath, &freepath);
                        vput(vp);
                        VFS_UNLOCK_GIANT(vfslocked);
                        strlcpy(kif->kf_path, fullpath,
                            sizeof(kif->kf_path));
                        if (freepath != NULL)
                                free(freepath, M_TEMP);
                        FILEDESC_SLOCK(fdp);
                }
                if (so != NULL) {
                        struct sockaddr *sa;

                        if (so->so_proto->pr_usrreqs->pru_sockaddr(so, &sa)
                            == 0 && sa->sa_len <= sizeof(kif->kf_sa_local)) {
                                bcopy(sa, &kif->kf_sa_local, sa->sa_len);
                                free(sa, M_SONAME);
                        }
                        if (so->so_proto->pr_usrreqs->pru_peeraddr(so, &sa)
                            == 00 && sa->sa_len <= sizeof(kif->kf_sa_peer)) {
                                bcopy(sa, &kif->kf_sa_peer, sa->sa_len);
                                free(sa, M_SONAME);
                        }
                        kif->kf_sock_domain =
                            so->so_proto->pr_domain->dom_family;
                        kif->kf_sock_type = so->so_type;
                        kif->kf_sock_protocol = so->so_proto->pr_protocol;
                }
                if (tp != NULL) {
                        strlcpy(kif->kf_path, tty_devname(tp),
                            sizeof(kif->kf_path));
                }
                error = SYSCTL_OUT(req, kif, sizeof(*kif));
                if (error)
                        break;
        }
        FILEDESC_SUNLOCK(fdp);
        fddrop(fdp);
        free(kif, M_TEMP);
        return (0);
}

static SYSCTL_NODE(_kern_proc, KERN_PROC_FILEDESC, filedesc, CTLFLAG_RD,
    sysctl_kern_proc_filedesc, "Process filedesc entries");

#ifdef DDB
/*
 * For the purposes of debugging, generate a human-readable string for the
 * file type.
 */
static const char *
file_type_to_name(short type)
{

        switch (type) {
        case 0:
                return ("zero");
        case DTYPE_VNODE:
                return ("vnod");
        case DTYPE_SOCKET:
                return ("sock");
        case DTYPE_PIPE:
                return ("pipe");
        case DTYPE_FIFO:
                return ("fifo");
        case DTYPE_KQUEUE:
                return ("kque");
        case DTYPE_CRYPTO:
                return ("crpt");
        case DTYPE_MQUEUE:
                return ("mque");
        case DTYPE_SHM:
                return ("shm");
        case DTYPE_SEM:
                return ("ksem");
        default:
                return ("unkn");
        }
}

/*
 * For the purposes of debugging, identify a process (if any, perhaps one of
 * many) that references the passed file in its file descriptor array. Return
 * NULL if none.
 */
static struct proc *
file_to_first_proc(struct file *fp)
{
        struct filedesc *fdp;
        struct proc *p;
        int n;

        FOREACH_PROC_IN_SYSTEM(p) {
                if (p->p_state == PRS_NEW)
                        continue;
                fdp = p->p_fd;
                if (fdp == NULL)
                        continue;
                for (n = 0; n < fdp->fd_nfiles; n++) {
                        if (fp == fdp->fd_ofiles[n])
                                return (p);
                }
        }
        return (NULL);
}

static void
db_print_file(struct file *fp, int header)
{
        struct proc *p;

        if (header)
                db_printf("%8s %4s %8s %8s %4s %5s %6s %8s %5s %12s\n",
                    "File", "Type", "Data", "Flag", "GCFl", "Count",
                    "MCount", "Vnode", "FPID", "FCmd");
        p = file_to_first_proc(fp);
        db_printf("%8p %4s %8p %08x %04x %5d %6d %8p %5d %12s\n", fp,
            file_type_to_name(fp->f_type), fp->f_data, fp->f_flag,
            0, fp->f_count, 0, fp->f_vnode,
            p != NULL ? p->p_pid : -1, p != NULL ? p->p_comm : "-");
}

DB_SHOW_COMMAND(file, db_show_file)
{
        struct file *fp;

        if (!have_addr) {
                db_printf("usage: show file <addr>\n");
                return;
        }
        fp = (struct file *)addr;
        db_print_file(fp, 1);
}

DB_SHOW_COMMAND(files, db_show_files)
{
        struct filedesc *fdp;
        struct file *fp;
        struct proc *p;
        int header;
        int n;

        header = 1;
        FOREACH_PROC_IN_SYSTEM(p) {
                if (p->p_state == PRS_NEW)
                        continue;
                if ((fdp = p->p_fd) == NULL)
                        continue;
                for (n = 0; n < fdp->fd_nfiles; ++n) {
                        if ((fp = fdp->fd_ofiles[n]) == NULL)
                                continue;
                        db_print_file(fp, header);
                        header = 0;
                }
        }
}
#endif

SYSCTL_INT(_kern, KERN_MAXFILESPERPROC, maxfilesperproc, CTLFLAG_RW,
    &maxfilesperproc, 0, "Maximum files allowed open per process");

SYSCTL_INT(_kern, KERN_MAXFILES, maxfiles, CTLFLAG_RW,
    &maxfiles, 0, "Maximum number of files");

SYSCTL_INT(_kern, OID_AUTO, openfiles, CTLFLAG_RD,
    __DEVOLATILE(int *, &openfiles), 0, "System-wide number of open files");

/* ARGSUSED*/
static void
filelistinit(void *dummy)
{

        file_zone = uma_zcreate("Files", sizeof(struct file), NULL, NULL,
            NULL, NULL, UMA_ALIGN_PTR, 0);
        mtx_init(&sigio_lock, "sigio lock", NULL, MTX_DEF);
        mtx_init(&fdesc_mtx, "fdesc", NULL, MTX_DEF);
}
SYSINIT(select, SI_SUB_LOCK, SI_ORDER_FIRST, filelistinit, NULL);

/*-------------------------------------------------------------------*/

static int
badfo_readwrite(struct file *fp, struct uio *uio, struct ucred *active_cred, int flags, struct thread *td)
{

        return (EBADF);
}

static int
badfo_truncate(struct file *fp, off_t length, struct ucred *active_cred, struct thread *td)
{

        return (EINVAL);
}

static int
badfo_ioctl(struct file *fp, u_long com, void *data, struct ucred *active_cred, struct thread *td)
{

        return (EBADF);
}

static int
badfo_poll(struct file *fp, int events, struct ucred *active_cred, struct thread *td)
{

        return (0);
}

static int
badfo_kqfilter(struct file *fp, struct knote *kn)
{

        return (EBADF);
}

static int
badfo_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, struct thread *td)
{

        return (EBADF);
}

static int
badfo_close(struct file *fp, struct thread *td)
{

        return (EBADF);
}

struct fileops badfileops = {
        .fo_read = badfo_readwrite,
        .fo_write = badfo_readwrite,
        .fo_truncate = badfo_truncate,
        .fo_ioctl = badfo_ioctl,
        .fo_poll = badfo_poll,
        .fo_kqfilter = badfo_kqfilter,
        .fo_stat = badfo_stat,
        .fo_close = badfo_close,
};


/*-------------------------------------------------------------------*/

/*
 * 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.
 *
 * XXX: we could give this one a cloning event handler if necessary.
 */

/* ARGSUSED */
static int
fdopen(struct cdev *dev, int mode, int type, struct thread *td)
{

        /*
         * XXX Kludge: set curthread->td_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.
         */
        td->td_dupfd = dev2unit(dev);
        return (ENODEV);
}

static struct cdevsw fildesc_cdevsw = {
        .d_version =    D_VERSION,
        .d_open =       fdopen,
        .d_name =       "FD",
};

static void
fildesc_drvinit(void *unused)
{
        struct cdev *dev;

        dev = make_dev(&fildesc_cdevsw, 0, UID_ROOT, GID_WHEEL, 0666, "fd/0");
        make_dev_alias(dev, "stdin");
        dev = make_dev(&fildesc_cdevsw, 1, UID_ROOT, GID_WHEEL, 0666, "fd/1");
        make_dev_alias(dev, "stdout");
        dev = make_dev(&fildesc_cdevsw, 2, UID_ROOT, GID_WHEEL, 0666, "fd/2");
        make_dev_alias(dev, "stderr");
}

SYSINIT(fildescdev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, fildesc_drvinit, NULL);