Update compiler-rt to trunk r224034. This brings a number of new

[FreeBSD/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_capsicum.h"
#include "opt_compat.h"
#include "opt_ddb.h"
#include "opt_ktrace.h"

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

#include <sys/capsicum.h>
#include <sys/conf.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/mutex.h>
#include <sys/namei.h>
#include <sys/selinfo.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/protosw.h>
#include <sys/racct.h>
#include <sys/resourcevar.h>
#include <sys/sbuf.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/unistd.h>
#include <sys/user.h>
#include <sys/vnode.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif

#include <net/vnet.h>

#include <security/audit/audit.h>

#include <vm/uma.h>
#include <vm/vm.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");
MALLOC_DEFINE(M_FILECAPS, "filecaps", "descriptor capabilities");

MALLOC_DECLARE(M_FADVISE);

static uma_zone_t file_zone;
static uma_zone_t filedesc0_zone;

static int      closefp(struct filedesc *fdp, int fd, struct file *fp,
                    struct thread *td, int holdleaders);
static int      do_dup(struct thread *td, int flags, int old, int new);
static int      fd_first_free(struct filedesc *fdp, int low, int size);
static int      fd_last_used(struct filedesc *fdp, int size);
static void     fdgrowtable(struct filedesc *fdp, int nfd);
static void     fdgrowtable_exp(struct filedesc *fdp, int nfd);
static void     fdunused(struct filedesc *fdp, int fd);
static void     fdused(struct filedesc *fdp, int fd);
static int      getmaxfd(struct proc *p);

/* Flags for do_dup() */
#define DUP_FIXED       0x1     /* Force fixed allocation. */
#define DUP_FCNTL       0x2     /* fcntl()-style errors. */
#define DUP_CLOEXEC     0x4     /* Atomically set FD_CLOEXEC. */

/*
 * Each process has:
 *
 * - An array of open file descriptors (fd_ofiles)
 * - An array of file flags (fd_ofileflags)
 * - A bitmap recording which descriptors are in use (fd_map)
 *
 * A process starts out with NDFILE descriptors.  The value of NDFILE has
 * been selected based the historical limit of 20 open files, and an
 * assumption that the majority of processes, especially short-lived
 * processes like shells, will never need more.
 *
 * If this initial allocation is exhausted, a larger descriptor table and
 * map are allocated dynamically, and the pointers in the process's struct
 * filedesc are updated to point to those.  This is repeated every time
 * the process runs out of file descriptors (provided it hasn't hit its
 * resource limit).
 *
 * Since threads may hold references to individual descriptor table
 * entries, the tables are never freed.  Instead, they are placed on a
 * linked list and freed only when the struct filedesc is released.
 */
#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)

/*
 * SLIST entry used to keep track of ofiles which must be reclaimed when
 * the process exits.
 */
struct freetable {
        struct fdescenttbl *ft_table;
        SLIST_ENTRY(freetable) ft_next;
};

/*
 * Initial allocation: a filedesc structure + the head of SLIST used to
 * keep track of old ofiles + enough space for NDFILE descriptors.
 */

struct fdescenttbl0 {
        int     fdt_nfiles;
        struct  filedescent fdt_ofiles[NDFILE];
};

struct filedesc0 {
        struct filedesc fd_fd;
        SLIST_HEAD(, freetable) fd_free;
        struct  fdescenttbl0 fd_dfiles;
        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;

/*
 * If low >= size, just return low. Otherwise find the first zero bit in the
 * given bitmap, starting at low and not exceeding size - 1. Return size if
 * not found.
 */
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 0 and
 * not exceeding size - 1. Return -1 if not found.
 */
static int
fd_last_used(struct filedesc *fdp, int size)
{
        NDSLOTTYPE *map = fdp->fd_map;
        NDSLOTTYPE mask;
        int off, minoff;

        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(0); off >= minoff; --off)
                if (map[off] != 0)
                        return (off * NDENTRIES + flsl(map[off]) - 1);
        return (-1);
}

#ifdef INVARIANTS
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);
}
#endif

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

        KASSERT(!fdisused(fdp, fd), ("fd=%d is already used", fd));

        fdp->fd_map[NDSLOT(fd)] |= NDBIT(fd);
}

static void
fdused(struct filedesc *fdp, int fd)
{

        FILEDESC_XLOCK_ASSERT(fdp);

        fdused_init(fdp, 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=%d is already unused", fd));
        KASSERT(fdp->fd_ofiles[fd].fde_file == NULL,
            ("fd=%d is still in use", fd));

        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, fd);
}

/*
 * Free a file descriptor.
 *
 * Avoid some work if fdp is about to be destroyed.
 */
static inline void
fdefree_last(struct filedescent *fde)
{

        filecaps_free(&fde->fde_caps);
}

static inline void
fdfree(struct filedesc *fdp, int fd)
{
        struct filedescent *fde;

        fde = &fdp->fd_ofiles[fd];
#ifdef CAPABILITIES
        seq_write_begin(&fde->fde_seq);
#endif
        fdefree_last(fde);
        bzero(fde, fde_change_size);
        fdunused(fdp, fd);
#ifdef CAPABILITIES
        seq_write_end(&fde->fde_seq);
#endif
}

/*
 * System calls on descriptors.
 */
#ifndef _SYS_SYSPROTO_H_
struct getdtablesize_args {
        int     dummy;
};
#endif
/* ARGSUSED */
int
sys_getdtablesize(struct thread *td, struct getdtablesize_args *uap)
{
        struct proc *p = td->td_proc;
        uint64_t lim;

        PROC_LOCK(p);
        td->td_retval[0] =
            min((int)lim_cur(p, RLIMIT_NOFILE), maxfilesperproc);
        lim = racct_get_limit(td->td_proc, RACCT_NOFILE);
        PROC_UNLOCK(p);
        if (lim < td->td_retval[0])
                td->td_retval[0] = lim;
        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
sys_dup2(struct thread *td, struct dup2_args *uap)
{

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

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

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

/*
 * The file control system call.
 */
#ifndef _SYS_SYSPROTO_H_
struct fcntl_args {
        int     fd;
        int     cmd;
        long    arg;
};
#endif
/* ARGSUSED */
int
sys_fcntl(struct thread *td, struct fcntl_args *uap)
{

        return (kern_fcntl_freebsd(td, uap->fd, uap->cmd, uap->arg));
}

int
kern_fcntl_freebsd(struct thread *td, int fd, int cmd, long arg)
{
        struct flock fl;
        struct __oflock ofl;
        intptr_t arg1;
        int error;

        error = 0;
        switch (cmd) {
        case F_OGETLK:
        case F_OSETLK:
        case F_OSETLKW:
                /*
                 * Convert old flock structure to new.
                 */
                error = copyin((void *)(intptr_t)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 (cmd) {
                case F_OGETLK:
                    cmd = F_GETLK;
                    break;
                case F_OSETLK:
                    cmd = F_SETLK;
                    break;
                case F_OSETLKW:
                    cmd = F_SETLKW;
                    break;
                }
                arg1 = (intptr_t)&fl;
                break;
        case F_GETLK:
        case F_SETLK:
        case F_SETLKW:
        case F_SETLK_REMOTE:
                error = copyin((void *)(intptr_t)arg, &fl, sizeof(fl));
                arg1 = (intptr_t)&fl;
                break;
        default:
                arg1 = arg;
                break;
        }
        if (error)
                return (error);
        error = kern_fcntl(td, fd, cmd, arg1);
        if (error)
                return (error);
        if (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)arg, sizeof(ofl));
        } else if (cmd == F_GETLK) {
                error = copyout(&fl, (void *)(intptr_t)arg, sizeof(fl));
        }
        return (error);
}

int
kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
{
        struct filedesc *fdp;
        struct flock *flp;
        struct file *fp, *fp2;
        struct filedescent *fde;
        struct proc *p;
        struct vnode *vp;
        cap_rights_t rights;
        int error, flg, tmp;
        uint64_t bsize;
        off_t foffset;

        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);
                break;

        case F_DUPFD_CLOEXEC:
                tmp = arg;
                error = do_dup(td, DUP_FCNTL | DUP_CLOEXEC, fd, tmp);
                break;

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

        case F_DUP2FD_CLOEXEC:
                tmp = arg;
                error = do_dup(td, DUP_FIXED | DUP_CLOEXEC, fd, tmp);
                break;

        case F_GETFD:
                FILEDESC_SLOCK(fdp);
                if (fget_locked(fdp, fd) == NULL) {
                        FILEDESC_SUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                fde = &fdp->fd_ofiles[fd];
                td->td_retval[0] =
                    (fde->fde_flags & UF_EXCLOSE) ? FD_CLOEXEC : 0;
                FILEDESC_SUNLOCK(fdp);
                break;

        case F_SETFD:
                FILEDESC_XLOCK(fdp);
                if (fget_locked(fdp, fd) == NULL) {
                        FILEDESC_XUNLOCK(fdp);
                        error = EBADF;
                        break;
                }
                fde = &fdp->fd_ofiles[fd];
                fde->fde_flags = (fde->fde_flags & ~UF_EXCLOSE) |
                    (arg & FD_CLOEXEC ? UF_EXCLOSE : 0);
                FILEDESC_XUNLOCK(fdp);
                break;

        case F_GETFL:
                error = fget_unlocked(fdp, fd,
                    cap_rights_init(&rights, CAP_FCNTL), F_GETFL, &fp, NULL);
                if (error != 0)
                        break;
                td->td_retval[0] = OFLAGS(fp->f_flag);
                fdrop(fp, td);
                break;

        case F_SETFL:
                error = fget_unlocked(fdp, fd,
                    cap_rights_init(&rights, CAP_FCNTL), F_SETFL, &fp, NULL);
                if (error != 0)
                        break;
                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 != 0) {
                        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:
                error = fget_unlocked(fdp, fd,
                    cap_rights_init(&rights, CAP_FCNTL), F_GETOWN, &fp, NULL);
                if (error != 0)
                        break;
                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:
                error = fget_unlocked(fdp, fd,
                    cap_rights_init(&rights, CAP_FCNTL), F_SETOWN, &fp, NULL);
                if (error != 0)
                        break;
                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:
                cap_rights_init(&rights, CAP_FLOCK);
                error = fget_unlocked(fdp, fd, &rights, 0, &fp, NULL);
                if (error != 0)
                        break;
                if (fp->f_type != DTYPE_VNODE) {
                        error = EBADF;
                        fdrop(fp, td);
                        break;
                }

                flp = (struct flock *)arg;
                if (flp->l_whence == SEEK_CUR) {
                        foffset = foffset_get(fp);
                        if (foffset < 0 ||
                            (flp->l_start > 0 &&
                             foffset > OFF_MAX - flp->l_start)) {
                                FILEDESC_SUNLOCK(fdp);
                                error = EOVERFLOW;
                                fdrop(fp, td);
                                break;
                        }
                        flp->l_start += foffset;
                }

                vp = fp->f_vnode;
                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;
                }
                if (error != 0 || flp->l_type == F_UNLCK ||
                    flp->l_type == F_UNLCKSYS) {
                        fdrop(fp, td);
                        break;
                }

                /*
                 * Check for a race with close.
                 *
                 * The vnode is now advisory locked (or unlocked, but this case
                 * is not really important) as the caller requested.
                 * We had to drop the filedesc lock, so we need to recheck if
                 * the descriptor is still valid, because if it was closed
                 * in the meantime we need to remove advisory lock from the
                 * vnode - close on any descriptor leading to an advisory
                 * locked vnode, removes that lock.
                 * We will return 0 on purpose in that case, as the result of
                 * successful advisory lock might have been externally visible
                 * already. This is fine - effectively we pretend to the caller
                 * that the closing thread was a bit slower and that the
                 * advisory lock succeeded before the close.
                 */
                error = fget_unlocked(fdp, fd, &rights, 0, &fp2, NULL);
                if (error != 0) {
                        fdrop(fp, td);
                        break;
                }
                if (fp != fp2) {
                        flp->l_whence = SEEK_SET;
                        flp->l_start = 0;
                        flp->l_len = 0;
                        flp->l_type = F_UNLCK;
                        (void) VOP_ADVLOCK(vp, (caddr_t)p->p_leader,
                            F_UNLCK, flp, F_POSIX);
                }
                fdrop(fp, td);
                fdrop(fp2, td);
                break;

        case F_GETLK:
                error = fget_unlocked(fdp, fd,
                    cap_rights_init(&rights, CAP_FLOCK), 0, &fp, NULL);
                if (error != 0)
                        break;
                if (fp->f_type != DTYPE_VNODE) {
                        error = EBADF;
                        fdrop(fp, td);
                        break;
                }
                flp = (struct flock *)arg;
                if (flp->l_type != F_RDLCK && flp->l_type != F_WRLCK &&
                    flp->l_type != F_UNLCK) {
                        error = EINVAL;
                        fdrop(fp, td);
                        break;
                }
                if (flp->l_whence == SEEK_CUR) {
                        foffset = foffset_get(fp);
                        if ((flp->l_start > 0 &&
                            foffset > OFF_MAX - flp->l_start) ||
                            (flp->l_start < 0 &&
                             foffset < OFF_MIN - flp->l_start)) {
                                FILEDESC_SUNLOCK(fdp);
                                error = EOVERFLOW;
                                fdrop(fp, td);
                                break;
                        }
                        flp->l_start += foffset;
                }
                vp = fp->f_vnode;
                error = VOP_ADVLOCK(vp, (caddr_t)p->p_leader, F_GETLK, flp,
                    F_POSIX);
                fdrop(fp, td);
                break;

        case F_RDAHEAD:
                arg = arg ? 128 * 1024: 0;
                /* FALLTHROUGH */
        case F_READAHEAD:
                error = fget_unlocked(fdp, fd, NULL, 0, &fp, NULL);
                if (error != 0)
                        break;
                if (fp->f_type != DTYPE_VNODE) {
                        fdrop(fp, td);
                        error = EBADF;
                        break;
                }
                vp = fp->f_vnode;
                /*
                 * Exclusive lock synchronizes against f_seqcount reads and
                 * writes in sequential_heuristic().
                 */
                error = vn_lock(vp, LK_EXCLUSIVE);
                if (error != 0) {
                        fdrop(fp, td);
                        break;
                }
                if (arg >= 0) {
                        bsize = fp->f_vnode->v_mount->mnt_stat.f_iosize;
                        fp->f_seqcount = (arg + bsize - 1) / bsize;
                        atomic_set_int(&fp->f_flag, FRDAHEAD);
                } else {
                        atomic_clear_int(&fp->f_flag, FRDAHEAD);
                }
                VOP_UNLOCK(vp, 0);
                fdrop(fp, td);
                break;

        default:
                error = EINVAL;
                break;
        }
        return (error);
}

static int
getmaxfd(struct proc *p)
{
        int maxfd;

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

        return (maxfd);
}

/*
 * 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)
{
        struct filedesc *fdp;
        struct filedescent *oldfde, *newfde;
        struct proc *p;
        struct file *fp;
        struct file *delfp;
        int error, 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);
        maxfd = getmaxfd(p);
        if (new >= maxfd)
                return (flags & DUP_FCNTL ? EINVAL : EBADF);

        FILEDESC_XLOCK(fdp);
        if (fget_locked(fdp, old) == NULL) {
                FILEDESC_XUNLOCK(fdp);
                return (EBADF);
        }
        oldfde = &fdp->fd_ofiles[old];
        if (flags & DUP_FIXED && old == new) {
                td->td_retval[0] = new;
                if (flags & DUP_CLOEXEC)
                        fdp->fd_ofiles[new].fde_flags |= UF_EXCLOSE;
                FILEDESC_XUNLOCK(fdp);
                return (0);
        }
        fp = oldfde->fde_file;
        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.
         */
        if (flags & DUP_FIXED) {
                if (new >= fdp->fd_nfiles) {
                        /*
                         * The resource limits are here instead of e.g.
                         * fdalloc(), because the file descriptor table may be
                         * shared between processes, so we can't really use
                         * racct_add()/racct_sub().  Instead of counting the
                         * number of actually allocated descriptors, just put
                         * the limit on the size of the file descriptor table.
                         */
#ifdef RACCT
                        PROC_LOCK(p);
                        error = racct_set(p, RACCT_NOFILE, new + 1);
                        PROC_UNLOCK(p);
                        if (error != 0) {
                                FILEDESC_XUNLOCK(fdp);
                                fdrop(fp, td);
                                return (EMFILE);
                        }
#endif
                        fdgrowtable_exp(fdp, new + 1);
                        oldfde = &fdp->fd_ofiles[old];
                }
                newfde = &fdp->fd_ofiles[new];
                if (newfde->fde_file == NULL)
                        fdused(fdp, new);
        } else {
                if ((error = fdalloc(td, new, &new)) != 0) {
                        FILEDESC_XUNLOCK(fdp);
                        fdrop(fp, td);
                        return (error);
                }
                newfde = &fdp->fd_ofiles[new];
        }

        KASSERT(fp == oldfde->fde_file, ("old fd has been modified"));
        KASSERT(old != new, ("new fd is same as old"));

        delfp = newfde->fde_file;

        /*
         * Duplicate the source descriptor.
         */
#ifdef CAPABILITIES
        seq_write_begin(&newfde->fde_seq);
#endif
        filecaps_free(&newfde->fde_caps);
        memcpy(newfde, oldfde, fde_change_size);
        filecaps_copy(&oldfde->fde_caps, &newfde->fde_caps);
        if ((flags & DUP_CLOEXEC) != 0)
                newfde->fde_flags = oldfde->fde_flags | UF_EXCLOSE;
        else
                newfde->fde_flags = oldfde->fde_flags & ~UF_EXCLOSE;
#ifdef CAPABILITIES
        seq_write_end(&newfde->fde_seq);
#endif
        td->td_retval[0] = new;

        if (delfp != NULL) {
                (void) closefp(fdp, new, delfp, td, 1);
                /* closefp() drops the FILEDESC lock for us. */
        } 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. */
        sigio = malloc(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);
}

/*
 * Function drops the filedesc lock on return.
 */
static int
closefp(struct filedesc *fdp, int fd, struct file *fp, struct thread *td,
    int holdleaders)
{
        int error;

        FILEDESC_XLOCK_ASSERT(fdp);

        if (holdleaders) {
                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++;
                } else {
                        holdleaders = 0;
                }
        }

        /*
         * 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);

        /*
         * We need to notify mqueue if the object is of type mqueue.
         */
        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);
}

/*
 * Close a file descriptor.
 */
#ifndef _SYS_SYSPROTO_H_
struct close_args {
        int     fd;
};
#endif
/* ARGSUSED */
int
sys_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;

        fdp = td->td_proc->p_fd;

        AUDIT_SYSCLOSE(td, fd);

        FILEDESC_XLOCK(fdp);
        if ((fp = fget_locked(fdp, fd)) == NULL) {
                FILEDESC_XUNLOCK(fdp);
                return (EBADF);
        }
        fdfree(fdp, fd);

        /* closefp() drops the FILEDESC lock for us. */
        return (closefp(fdp, fd, fp, td, 1));
}

/*
 * Close open file descriptors.
 */
#ifndef _SYS_SYSPROTO_H_
struct closefrom_args {
        int     lowfd;
};
#endif
/* ARGSUSED */
int
sys_closefrom(struct thread *td, struct closefrom_args *uap)
{
        struct filedesc *fdp;
        int fd;

        fdp = td->td_proc->p_fd;
        AUDIT_ARG_FD(uap->lowfd);

        /*
         * Treat negative starting file descriptor values identical to
         * closefrom(0) which closes all files.
         */
        if (uap->lowfd < 0)
                uap->lowfd = 0;
        FILEDESC_SLOCK(fdp);
        for (fd = uap->lowfd; fd <= fdp->fd_lastfile; fd++) {
                if (fdp->fd_ofiles[fd].fde_file != NULL) {
                        FILEDESC_SUNLOCK(fdp);
                        (void)kern_close(td, fd);
                        FILEDESC_SLOCK(fdp);
                }
        }
        FILEDESC_SUNLOCK(fdp);
        return (0);
}

#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
sys_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;
        cap_rights_t rights;
        int error;

        AUDIT_ARG_FD(fd);

        error = fget(td, fd, cap_rights_init(&rights, CAP_FSTAT), &fp);
        if (error != 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
sys_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
sys_fpathconf(struct thread *td, struct fpathconf_args *uap)
{
        struct file *fp;
        struct vnode *vp;
        cap_rights_t rights;
        int error;

        error = fget(td, uap->fd, cap_rights_init(&rights, CAP_FPATHCONF), &fp);
        if (error != 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) {
                vn_lock(vp, LK_SHARED | LK_RETRY);
                error = VOP_PATHCONF(vp, uap->name, td->td_retval);
                VOP_UNLOCK(vp, 0);
        } 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);
}

/*
 * Initialize filecaps structure.
 */
void
filecaps_init(struct filecaps *fcaps)
{

        bzero(fcaps, sizeof(*fcaps));
        fcaps->fc_nioctls = -1;
}

/*
 * Copy filecaps structure allocating memory for ioctls array if needed.
 */
void
filecaps_copy(const struct filecaps *src, struct filecaps *dst)
{
        size_t size;

        *dst = *src;
        if (src->fc_ioctls != NULL) {
                KASSERT(src->fc_nioctls > 0,
                    ("fc_ioctls != NULL, but fc_nioctls=%hd", src->fc_nioctls));

                size = sizeof(src->fc_ioctls[0]) * src->fc_nioctls;
                dst->fc_ioctls = malloc(size, M_FILECAPS, M_WAITOK);
                bcopy(src->fc_ioctls, dst->fc_ioctls, size);
        }
}

/*
 * Move filecaps structure to the new place and clear the old place.
 */
void
filecaps_move(struct filecaps *src, struct filecaps *dst)
{

        *dst = *src;
        bzero(src, sizeof(*src));
}

/*
 * Fill the given filecaps structure with full rights.
 */
static void
filecaps_fill(struct filecaps *fcaps)
{

        CAP_ALL(&fcaps->fc_rights);
        fcaps->fc_ioctls = NULL;
        fcaps->fc_nioctls = -1;
        fcaps->fc_fcntls = CAP_FCNTL_ALL;
}

/*
 * Free memory allocated within filecaps structure.
 */
void
filecaps_free(struct filecaps *fcaps)
{

        free(fcaps->fc_ioctls, M_FILECAPS);
        bzero(fcaps, sizeof(*fcaps));
}

/*
 * Validate the given filecaps structure.
 */
static void
filecaps_validate(const struct filecaps *fcaps, const char *func)
{

        KASSERT(cap_rights_is_valid(&fcaps->fc_rights),
            ("%s: invalid rights", func));
        KASSERT((fcaps->fc_fcntls & ~CAP_FCNTL_ALL) == 0,
            ("%s: invalid fcntls", func));
        KASSERT(fcaps->fc_fcntls == 0 ||
            cap_rights_is_set(&fcaps->fc_rights, CAP_FCNTL),
            ("%s: fcntls without CAP_FCNTL", func));
        KASSERT(fcaps->fc_ioctls != NULL ? fcaps->fc_nioctls > 0 :
            (fcaps->fc_nioctls == -1 || fcaps->fc_nioctls == 0),
            ("%s: invalid ioctls", func));
        KASSERT(fcaps->fc_nioctls == 0 ||
            cap_rights_is_set(&fcaps->fc_rights, CAP_IOCTL),
            ("%s: ioctls without CAP_IOCTL", func));
}

static void
fdgrowtable_exp(struct filedesc *fdp, int nfd)
{
        int nfd1;

        FILEDESC_XLOCK_ASSERT(fdp);

        nfd1 = fdp->fd_nfiles * 2;
        if (nfd1 < nfd)
                nfd1 = nfd;
        fdgrowtable(fdp, nfd1);
}

/*
 * Grow the file table to accomodate (at least) nfd descriptors.
 */
static void
fdgrowtable(struct filedesc *fdp, int nfd)
{
        struct filedesc0 *fdp0;
        struct freetable *ft;
        struct fdescenttbl *ntable;
        struct fdescenttbl *otable;
        int nnfiles, onfiles;
        NDSLOTTYPE *nmap, *omap;

        /*
         * If lastfile is -1 this struct filedesc was just allocated and we are
         * growing it to accomodate for the one we are going to copy from. There
         * is no need to have a lock on this one as it's not visible to anyone.
         */
        if (fdp->fd_lastfile != -1)
                FILEDESC_XLOCK_ASSERT(fdp);

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

        /* save old values */
        onfiles = fdp->fd_nfiles;
        otable = fdp->fd_files;
        omap = fdp->fd_map;

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

        /*
         * Allocate a new table.  We need enough space for the number of
         * entries, file entries themselves and the struct freetable we will use
         * when we decommission the table and place it on the freelist.
         * We place the struct freetable in the middle so we don't have
         * to worry about padding.
         */
        ntable = malloc(offsetof(struct fdescenttbl, fdt_ofiles) +
            nnfiles * sizeof(ntable->fdt_ofiles[0]) +
            sizeof(struct freetable),
            M_FILEDESC, M_ZERO | M_WAITOK);
        /* copy the old data */
        ntable->fdt_nfiles = nnfiles;
        memcpy(ntable->fdt_ofiles, otable->fdt_ofiles,
            onfiles * sizeof(ntable->fdt_ofiles[0]));

        /*
         * Allocate a new map only if the old is not large enough.  It will
         * grow at a slower rate than the table as it can map more
         * entries than the table can hold.
         */
        if (NDSLOTS(nnfiles) > NDSLOTS(onfiles)) {
                nmap = malloc(NDSLOTS(nnfiles) * NDSLOTSIZE, M_FILEDESC,
                    M_ZERO | M_WAITOK);
                /* copy over the old data and update the pointer */
                memcpy(nmap, omap, NDSLOTS(onfiles) * sizeof(*omap));
                fdp->fd_map = nmap;
        }

        /*
         * Make sure that ntable is correctly initialized before we replace
         * fd_files poiner. Otherwise fget_unlocked() may see inconsistent
         * data.
         */
        atomic_store_rel_ptr((volatile void *)&fdp->fd_files, (uintptr_t)ntable);

        /*
         * Do not free the old file table, as some threads may still
         * reference entries within it.  Instead, place it on a freelist
         * which will be processed when the struct filedesc is released.
         *
         * Note that if onfiles == NDFILE, we're dealing with the original
         * static allocation contained within (struct filedesc0 *)fdp,
         * which must not be freed.
         */
        if (onfiles > NDFILE) {
                ft = (struct freetable *)&otable->fdt_ofiles[onfiles];
                fdp0 = (struct filedesc0 *)fdp;
                ft->ft_table = otable;
                SLIST_INSERT_HEAD(&fdp0->fd_free, ft, ft_next);
        }
        /*
         * The map does not have the same possibility of threads still
         * holding references to it.  So always free it as long as it
         * does not reference the original static allocation.
         */
        if (NDSLOTS(onfiles) > NDSLOTS(NDFILE))
                free(omap, M_FILEDESC);
}

/*
 * 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, allocfd;
#ifdef RACCT
        int error;
#endif

        FILEDESC_XLOCK_ASSERT(fdp);

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

        maxfd = getmaxfd(p);

        /*
         * Search the bitmap for a free descriptor starting at minfd.
         * If none is found, grow the file table.
         */
        fd = fd_first_free(fdp, minfd, fdp->fd_nfiles);
        if (fd >= maxfd)
                return (EMFILE);
        if (fd >= fdp->fd_nfiles) {
                allocfd = min(fd * 2, maxfd);
#ifdef RACCT
                PROC_LOCK(p);
                error = racct_set(p, RACCT_NOFILE, allocfd);
                PROC_UNLOCK(p);
                if (error != 0)
                        return (EMFILE);
#endif
                /*
                 * fd is already equal to first free descriptor >= minfd, so
                 * we only need to grow the table and we are done.
                 */
                fdgrowtable_exp(fdp, allocfd);
        }

        /*
         * Perform some sanity checks, then mark the file descriptor as
         * used and return it to the caller.
         */
        KASSERT(fd >= 0 && fd < min(maxfd, fdp->fd_nfiles),
            ("invalid descriptor %d", fd));
        KASSERT(!fdisused(fdp, fd),
            ("fd_first_free() returned non-free descriptor"));
        KASSERT(fdp->fd_ofiles[fd].fde_file == NULL,
            ("file descriptor isn't free"));
        KASSERT(fdp->fd_ofiles[fd].fde_flags == 0, ("file flags are set"));
        fdused(fdp, fd);
        *result = fd;
        return (0);
}

/*
 * Allocate n file descriptors for the process.
 */
int
fdallocn(struct thread *td, int minfd, int *fds, int n)
{
        struct proc *p = td->td_proc;
        struct filedesc *fdp = p->p_fd;
        int i;

        FILEDESC_XLOCK_ASSERT(fdp);

        for (i = 0; i < n; i++)
                if (fdalloc(td, 0, &fds[i]) != 0)
                        break;

        if (i < n) {
                for (i--; i >= 0; i--)
                        fdunused(fdp, fds[i]);
                return (EMFILE);
        }

        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, int flags)
{
        struct file *fp;
        int error, fd;

        error = falloc_noinstall(td, &fp);
        if (error)
                return (error);         /* no reference held on error */

        error = finstall(td, fp, &fd, flags, NULL);
        if (error) {
                fdrop(fp, td);          /* one reference (fp only) */
                return (error);
        }

        if (resultfp != NULL)
                *resultfp = fp;         /* copy out result */
        else
                fdrop(fp, td);          /* release local reference */

        if (resultfd != NULL)
                *resultfd = fd;

        return (0);
}

/*
 * Create a new open file structure without allocating a file descriptor.
 */
int
falloc_noinstall(struct thread *td, struct file **resultfp)
{
        struct file *fp;
        int maxuserfiles = maxfiles - (maxfiles / 20);
        static struct timeval lastfail;
        static int curfail;

        KASSERT(resultfp != NULL, ("%s: resultfp == NULL", __func__));

        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);
                }
                return (ENFILE);
        }
        atomic_add_int(&openfiles, 1);
        fp = uma_zalloc(file_zone, M_WAITOK | M_ZERO);
        refcount_init(&fp->f_count, 1);
        fp->f_cred = crhold(td->td_ucred);
        fp->f_ops = &badfileops;
        *resultfp = fp;
        return (0);
}

/*
 * Install a file in a file descriptor table.
 */
int
finstall(struct thread *td, struct file *fp, int *fd, int flags,
    struct filecaps *fcaps)
{
        struct filedesc *fdp = td->td_proc->p_fd;
        struct filedescent *fde;
        int error;

        KASSERT(fd != NULL, ("%s: fd == NULL", __func__));
        KASSERT(fp != NULL, ("%s: fp == NULL", __func__));
        if (fcaps != NULL)
                filecaps_validate(fcaps, __func__);

        FILEDESC_XLOCK(fdp);
        if ((error = fdalloc(td, 0, fd))) {
                FILEDESC_XUNLOCK(fdp);
                return (error);
        }
        fhold(fp);
        fde = &fdp->fd_ofiles[*fd];
#ifdef CAPABILITIES
        seq_write_begin(&fde->fde_seq);
#endif
        fde->fde_file = fp;
        if ((flags & O_CLOEXEC) != 0)
                fde->fde_flags |= UF_EXCLOSE;
        if (fcaps != NULL)
                filecaps_move(fcaps, &fde->fde_caps);
        else
                filecaps_fill(&fde->fde_caps);
#ifdef CAPABILITIES
        seq_write_end(&fde->fde_seq);
#endif
        FILEDESC_XUNLOCK(fdp);
        return (0);
}

/*
 * Build a new filedesc structure from another.
 * Copy the current, root, and jail root vnode references.
 *
 * If fdp is not NULL, return with it shared locked.
 */
struct filedesc *
fdinit(struct filedesc *fdp, bool prepfiles)
{
        struct filedesc0 *newfdp0;
        struct filedesc *newfdp;

        newfdp0 = uma_zalloc(filedesc0_zone, M_WAITOK | M_ZERO);
        newfdp = &newfdp0->fd_fd;

        /* Create the file descriptor table. */
        FILEDESC_LOCK_INIT(newfdp);
        newfdp->fd_refcnt = 1;
        newfdp->fd_holdcnt = 1;
        newfdp->fd_cmask = CMASK;
        newfdp->fd_map = newfdp0->fd_dmap;
        newfdp->fd_lastfile = -1;
        newfdp->fd_files = (struct fdescenttbl *)&newfdp0->fd_dfiles;
        newfdp->fd_files->fdt_nfiles = NDFILE;

        if (fdp == NULL)
                return (newfdp);

        if (prepfiles && fdp->fd_lastfile >= newfdp->fd_nfiles)
                fdgrowtable(newfdp, fdp->fd_lastfile + 1);

        FILEDESC_SLOCK(fdp);
        newfdp->fd_cdir = fdp->fd_cdir;
        if (newfdp->fd_cdir)
                VREF(newfdp->fd_cdir);
        newfdp->fd_rdir = fdp->fd_rdir;
        if (newfdp->fd_rdir)
                VREF(newfdp->fd_rdir);
        newfdp->fd_jdir = fdp->fd_jdir;
        if (newfdp->fd_jdir)
                VREF(newfdp->fd_jdir);

        if (!prepfiles) {
                FILEDESC_SUNLOCK(fdp);
        } else {
                while (fdp->fd_lastfile >= newfdp->fd_nfiles) {
                        FILEDESC_SUNLOCK(fdp);
                        fdgrowtable(newfdp, fdp->fd_lastfile + 1);
                        FILEDESC_SLOCK(fdp);
                }
        }

        return (newfdp);
}

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;

        if (fdp->fd_holdcnt > 1) {
                mtx_lock(&fdesc_mtx);
                i = --fdp->fd_holdcnt;
                mtx_unlock(&fdesc_mtx);
                if (i > 0)
                        return;
        }

        FILEDESC_LOCK_DESTROY(fdp);
        uma_zfree(filedesc0_zone, fdp);
}

/*
 * 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 thread *td)
{
        struct filedesc *tmp;
        struct proc *p = td->td_proc;

        if (p->p_fd->fd_refcnt == 1)
                return;

        tmp = fdcopy(p->p_fd);
        fdescfree(td);
        p->p_fd = tmp;
}

/*
 * 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;
        struct filedescent *nfde, *ofde;
        int i;

        MPASS(fdp != NULL);

        newfdp = fdinit(fdp, true);
        /* copy all passable descriptors (i.e. not kqueue) */
        newfdp->fd_freefile = -1;
        for (i = 0; i <= fdp->fd_lastfile; ++i) {
                ofde = &fdp->fd_ofiles[i];
                if (ofde->fde_file == NULL ||
                    (ofde->fde_file->f_ops->fo_flags & DFLAG_PASSABLE) == 0) {
                        if (newfdp->fd_freefile == -1)
                                newfdp->fd_freefile = i;
                        continue;
                }
                nfde = &newfdp->fd_ofiles[i];
                *nfde = *ofde;
                filecaps_copy(&ofde->fde_caps, &nfde->fde_caps);
                fhold(nfde->fde_file);
                fdused_init(newfdp, i);
                newfdp->fd_lastfile = i;
        }
        if (newfdp->fd_freefile == -1)
                newfdp->fd_freefile = i;
        newfdp->fd_cmask = fdp->fd_cmask;
        FILEDESC_SUNLOCK(fdp);
        return (newfdp);
}

/*
 * Clear POSIX style locks. This is only used when fdp looses a reference (i.e.
 * one of processes using it exits) and the table used to be shared.
 */
static void
fdclearlocks(struct thread *td)
{
        struct filedesc *fdp;
        struct filedesc_to_leader *fdtol;
        struct flock lf;
        struct file *fp;
        struct proc *p;
        struct vnode *vp;
        int i;

        p = td->td_proc;
        fdp = p->p_fd;
        fdtol = p->p_fdtol;
        MPASS(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 &&
            (p->p_leader->p_flag & P_ADVLOCK) != 0) {
                for (i = 0; i <= fdp->fd_lastfile; i++) {
                        fp = fdp->fd_ofiles[i].fde_file;
                        if (fp == NULL || fp->f_type != DTYPE_VNODE)
                                continue;
                        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;
                        (void) VOP_ADVLOCK(vp,
                            (caddr_t)p->p_leader, F_UNLCK,
                            &lf, F_POSIX);
                        FILEDESC_XLOCK(fdp);
                        fdrop(fp, td);
                }
        }
retry:
        if (fdtol->fdl_refcount == 1) {
                if (fdp->fd_holdleaderscount > 0 &&
                    (p->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;
        p->p_fdtol = NULL;
        FILEDESC_XUNLOCK(fdp);
        if (fdtol != NULL)
                free(fdtol, M_FILEDESC_TO_LEADER);
}

/*
 * Release a filedesc structure.
 */
void
fdescfree(struct thread *td)
{
        struct filedesc0 *fdp0;
        struct filedesc *fdp;
        struct freetable *ft, *tft;
        struct filedescent *fde;
        struct file *fp;
        struct vnode *cdir, *jdir, *rdir;
        int i;

        fdp = td->td_proc->p_fd;
        MPASS(fdp != NULL);

#ifdef RACCT
        PROC_LOCK(td->td_proc);
        racct_set(td->td_proc, RACCT_NOFILE, 0);
        PROC_UNLOCK(td->td_proc);
#endif

        if (td->td_proc->p_fdtol != NULL)
                fdclearlocks(td);

        mtx_lock(&fdesc_mtx);
        td->td_proc->p_fd = NULL;
        mtx_unlock(&fdesc_mtx);

        FILEDESC_XLOCK(fdp);
        i = --fdp->fd_refcnt;
        if (i > 0) {
                FILEDESC_XUNLOCK(fdp);
                return;
        }

        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);

        for (i = 0; i <= fdp->fd_lastfile; i++) {
                fde = &fdp->fd_ofiles[i];
                fp = fde->fde_file;
                if (fp != NULL) {
                        fdefree_last(fde);
                        (void) closef(fp, td);
                }
        }

        if (NDSLOTS(fdp->fd_nfiles) > NDSLOTS(NDFILE))
                free(fdp->fd_map, M_FILEDESC);
        if (fdp->fd_nfiles > NDFILE)
                free(fdp->fd_files, M_FILEDESC);

        fdp0 = (struct filedesc0 *)fdp;
        SLIST_FOREACH_SAFE(ft, &fdp0->fd_free, ft_next, tft)
                free(ft->ft_table, M_FILEDESC);

        if (cdir != NULL)
                vrele(cdir);
        if (rdir != NULL)
                vrele(rdir);
        if (jdir != NULL)
                vrele(jdir);

        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 fdsetugidsafety 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 bool
is_unsafe(struct file *fp)
{
        struct vnode *vp;

        if (fp->f_type != DTYPE_VNODE)
                return (false);

        vp = fp->f_vnode;
        return ((vp->v_vflag & VV_PROCDEP) != 0);
}

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

        fdp = td->td_proc->p_fd;
        KASSERT(fdp->fd_refcnt == 1, ("the fdtable should not be shared"));
        MPASS(fdp->fd_nfiles >= 3);
        for (i = 0; i <= 2; i++) {
                fp = fdp->fd_ofiles[i].fde_file;
                if (fp != NULL && is_unsafe(fp)) {
                        FILEDESC_XLOCK(fdp);
                        knote_fdclose(td, i);
                        /*
                         * NULL-out descriptor prior to close to avoid
                         * a race while close blocks.
                         */
                        fdfree(fdp, i);
                        FILEDESC_XUNLOCK(fdp);
                        (void) closef(fp, td);
                }
        }
}

/*
 * 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].fde_file == fp) {
                fdfree(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;
        struct filedescent *fde;
        struct file *fp;
        int i;

        fdp = td->td_proc->p_fd;
        KASSERT(fdp->fd_refcnt == 1, ("the fdtable should not be shared"));
        for (i = 0; i <= fdp->fd_lastfile; i++) {
                fde = &fdp->fd_ofiles[i];
                fp = fde->fde_file;
                if (fp != NULL && (fp->f_type == DTYPE_MQUEUE ||
                    (fde->fde_flags & UF_EXCLOSE))) {
                        FILEDESC_XLOCK(fdp);
                        fdfree(fdp, i);
                        (void) closefp(fdp, i, fp, td, 0);
                        /* closefp() drops the FILEDESC lock. */
                }
        }
}

/*
 * 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 save;
        int i, error, devnull;

        fdp = td->td_proc->p_fd;
        KASSERT(fdp->fd_refcnt == 1, ("the fdtable should not be shared"));
        MPASS(fdp->fd_nfiles >= 3);
        devnull = -1;
        for (i = 0; i <= 2; i++) {
                if (fdp->fd_ofiles[i].fde_file != NULL)
                        continue;

                save = td->td_retval[0];
                if (devnull != -1) {
                        error = do_dup(td, DUP_FIXED, devnull, i);
                } else {
                        error = kern_openat(td, AT_FDCWD, "/dev/null",
                            UIO_SYSSPACE, O_RDWR, 0);
                        if (error == 0) {
                                devnull = td->td_retval[0];
                                KASSERT(devnull == i, ("we didn't get our fd"));
                        }
                }
                td->td_retval[0] = save;
                if (error != 0)
                        return (error);
        }
        return (0);
}

/*
 * 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) {
                vp = fp->f_vnode;
                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);
                }
        }
        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);
}

int
fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
    int needfcntl, struct file **fpp, cap_rights_t *haverightsp)
{
#ifdef CAPABILITIES
        struct filedescent fde;
#endif
        struct fdescenttbl *fdt;
        struct file *fp;
        u_int count;
#ifdef CAPABILITIES
        seq_t seq;
        cap_rights_t haverights;
        int error;
#endif

        fdt = fdp->fd_files;
        if (fd < 0 || fd >= fdt->fdt_nfiles)
                return (EBADF);
        /*
         * Fetch the descriptor locklessly.  We avoid fdrop() races by
         * never raising a refcount above 0.  To accomplish this we have
         * to use a cmpset loop rather than an atomic_add.  The descriptor
         * must be re-verified once we acquire a reference to be certain
         * that the identity is still correct and we did not lose a race
         * due to preemption.
         */
        for (;;) {
#ifdef CAPABILITIES
                seq = seq_read(fd_seq(fdt, fd));
                fde = fdt->fdt_ofiles[fd];
                if (!seq_consistent(fd_seq(fdt, fd), seq)) {
                        cpu_spinwait();
                        continue;
                }
                fp = fde.fde_file;
#else
                fp = fdt->fdt_ofiles[fd].fde_file;
#endif
                if (fp == NULL)
                        return (EBADF);
#ifdef CAPABILITIES
                haverights = *cap_rights_fde(&fde);
                if (needrightsp != NULL) {
                        error = cap_check(&haverights, needrightsp);
                        if (error != 0)
                                return (error);
                        if (cap_rights_is_set(needrightsp, CAP_FCNTL)) {
                                error = cap_fcntl_check_fde(&fde, needfcntl);
                                if (error != 0)
                                        return (error);
                        }
                }
#endif
        retry:
                count = fp->f_count;
                if (count == 0) {
                        /*
                         * Force a reload. Other thread could reallocate the
                         * table before this fd was closed, so it possible that
                         * there is a stale fp pointer in cached version.
                         */
                        fdt = *(struct fdescenttbl * volatile *)&(fdp->fd_files);
                        continue;
                }
                /*
                 * Use an acquire barrier to force re-reading of fdt so it is
                 * refreshed for verification.
                 */
                if (atomic_cmpset_acq_int(&fp->f_count, count, count + 1) == 0)
                        goto retry;
                fdt = fdp->fd_files;
#ifdef  CAPABILITIES
                if (seq_consistent_nomb(fd_seq(fdt, fd), seq))
#else
                if (fp == fdt->fdt_ofiles[fd].fde_file)
#endif
                        break;
                fdrop(fp, curthread);
        }
        *fpp = fp;
        if (haverightsp != NULL) {
#ifdef CAPABILITIES
                *haverightsp = haverights;
#else
                CAP_ALL(haverightsp);
#endif
        }
        return (0);
}

/*
 * Extract the file pointer associated with the specified descriptor for the
 * current user process.
 *
 * If the descriptor doesn't exist or doesn't match 'flags', EBADF is
 * returned.
 *
 * File's rights will be checked against the capability rights mask.
 *
 * If an error occured the non-zero error is returned and *fpp is set to
 * NULL.  Otherwise *fpp is held and set and zero is returned.  Caller is
 * responsible for fdrop().
 */
static __inline int
_fget(struct thread *td, int fd, struct file **fpp, int flags,
    cap_rights_t *needrightsp, u_char *maxprotp)
{
        struct filedesc *fdp;
        struct file *fp;
        cap_rights_t haverights, needrights;
        int error;

        *fpp = NULL;
        if (td == NULL || (fdp = td->td_proc->p_fd) == NULL)
                return (EBADF);
        if (needrightsp != NULL)
                needrights = *needrightsp;
        else
                cap_rights_init(&needrights);
        if (maxprotp != NULL)
                cap_rights_set(&needrights, CAP_MMAP);
        error = fget_unlocked(fdp, fd, &needrights, 0, &fp, &haverights);
        if (error != 0)
                return (error);
        if (fp->f_ops == &badfileops) {
                fdrop(fp, td);
                return (EBADF);
        }

#ifdef CAPABILITIES
        /*
         * If requested, convert capability rights to access flags.
         */
        if (maxprotp != NULL)
                *maxprotp = cap_rights_to_vmprot(&haverights);
#else /* !CAPABILITIES */
        if (maxprotp != NULL)
                *maxprotp = VM_PROT_ALL;
#endif /* CAPABILITIES */

        /*
         * FREAD and FWRITE failure return EBADF as per POSIX.
         */
        error = 0;
        switch (flags) {
        case FREAD:
        case FWRITE:
                if ((fp->f_flag & flags) == 0)
                        error = EBADF;
                break;
        case FEXEC:
                if ((fp->f_flag & (FREAD | FEXEC)) == 0 ||
                    ((fp->f_flag & FWRITE) != 0))
                        error = EBADF;
                break;
        case 0:
                break;
        default:
                KASSERT(0, ("wrong flags"));
        }

        if (error != 0) {
                fdrop(fp, td);
                return (error);
        }

        *fpp = fp;
        return (0);
}

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

        return(_fget(td, fd, fpp, 0, rightsp, NULL));
}

int
fget_mmap(struct thread *td, int fd, cap_rights_t *rightsp, u_char *maxprotp,
    struct file **fpp)
{

        return (_fget(td, fd, fpp, 0, rightsp, maxprotp));
}

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

        return(_fget(td, fd, fpp, FREAD, rightsp, NULL));
}

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

        return (_fget(td, fd, fpp, FWRITE, rightsp, NULL));
}

/*
 * 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, int flags, cap_rights_t *needrightsp,
    struct vnode **vpp)
{
        struct file *fp;
        int error;

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

        return (error);
}

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

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

int
fgetvp_rights(struct thread *td, int fd, cap_rights_t *needrightsp,
    struct filecaps *havecaps, struct vnode **vpp)
{
        struct filedesc *fdp;
        struct file *fp;
#ifdef CAPABILITIES
        int error;
#endif

        fdp = td->td_proc->p_fd;
        fp = fget_locked(fdp, fd);
        if (fp == NULL || fp->f_ops == &badfileops)
                return (EBADF);

#ifdef CAPABILITIES
        if (needrightsp != NULL) {
                error = cap_check(cap_rights(fdp, fd), needrightsp);
                if (error != 0)
                        return (error);
        }
#endif

        if (fp->f_vnode == NULL)
                return (EINVAL);

        *vpp = fp->f_vnode;
        vref(*vpp);
        filecaps_copy(&fdp->fd_ofiles[fd].fde_caps, havecaps);

        return (0);
}

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

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

int
fgetvp_exec(struct thread *td, int fd, cap_rights_t *rightsp, struct vnode **vpp)
{

        return (_fgetvp(td, fd, FEXEC, rightsp, vpp));
}

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

        return (_fgetvp(td, fd, FWRITE, rightsp, vpp));
}
#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.
 *
 * Note: 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, cap_rights_t *rightsp, 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, rightsp, NULL)) != 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);
        }
        fdrop(fp, td);

        return (error);
}

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

        ACCEPT_LOCK();
        SOCK_LOCK(so);
        CURVNET_SET(so->so_vnet);
        sorele(so);
        CURVNET_RESTORE();
}

/*
 * 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);
        atomic_subtract_int(&openfiles, 1);
        crfree(fp->f_cred);
        free(fp->f_advice, M_FADVISE);
        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
sys_flock(struct thread *td, struct flock_args *uap)
{
        struct file *fp;
        struct vnode *vp;
        struct flock lf;
        cap_rights_t rights;
        int error;

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

        vp = fp->f_vnode;
        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);
        return (error);
}
/*
 * Duplicate the specified descriptor to a free descriptor.
 */
int
dupfdopen(struct thread *td, struct filedesc *fdp, int dfd, int mode,
    int openerror, int *indxp)
{
        struct filedescent *newfde, *oldfde;
        struct file *fp;
        int error, indx;

        KASSERT(openerror == ENODEV || openerror == ENXIO,
            ("unexpected error %d in %s", openerror, __func__));

        /*
         * 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 ((fp = fget_locked(fdp, dfd)) == NULL) {
                FILEDESC_XUNLOCK(fdp);
                return (EBADF);
        }

        error = fdalloc(td, 0, &indx);
        if (error != 0) {
                FILEDESC_XUNLOCK(fdp);
                return (error);
        }

        /*
         * 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.
         */
        switch (openerror) {
        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)) | fp->f_flag) != fp->f_flag) {
                        fdunused(fdp, indx);
                        FILEDESC_XUNLOCK(fdp);
                        return (EACCES);
                }
                fhold(fp);
                newfde = &fdp->fd_ofiles[indx];
                oldfde = &fdp->fd_ofiles[dfd];
#ifdef CAPABILITIES
                seq_write_begin(&newfde->fde_seq);
#endif
                memcpy(newfde, oldfde, fde_change_size);
                filecaps_copy(&oldfde->fde_caps, &newfde->fde_caps);
#ifdef CAPABILITIES
                seq_write_end(&newfde->fde_seq);
#endif
                break;
        case ENXIO:
                /*
                 * Steal away the file pointer from dfd and stuff it into indx.
                 */
                newfde = &fdp->fd_ofiles[indx];
                oldfde = &fdp->fd_ofiles[dfd];
#ifdef CAPABILITIES
                seq_write_begin(&newfde->fde_seq);
#endif
                memcpy(newfde, oldfde, fde_change_size);
                bzero(oldfde, fde_change_size);
                fdunused(fdp, dfd);
#ifdef CAPABILITIES
                seq_write_end(&newfde->fde_seq);
#endif
                break;
        }
        FILEDESC_XUNLOCK(fdp);
        *indxp = indx;
        return (0);
}

/*
 * Scan all active processes and prisons 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 prison *pr;
        struct proc *p;
        int nrele;

        if (vrefcnt(olddp) == 1)
                return;
        nrele = 0;
        sx_slock(&allproc_lock);
        FOREACH_PROC_IN_SYSTEM(p) {
                fdp = fdhold(p);
                if (fdp == NULL)
                        continue;
                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++;
                }
                if (fdp->fd_jdir == olddp) {
                        vref(newdp);
                        fdp->fd_jdir = newdp;
                        nrele++;
                }
                FILEDESC_XUNLOCK(fdp);
                fddrop(fdp);
        }
        sx_sunlock(&allproc_lock);
        if (rootvnode == olddp) {
                vref(newdp);
                rootvnode = newdp;
                nrele++;
        }
        mtx_lock(&prison0.pr_mtx);
        if (prison0.pr_root == olddp) {
                vref(newdp);
                prison0.pr_root = newdp;
                nrele++;
        }
        mtx_unlock(&prison0.pr_mtx);
        sx_slock(&allprison_lock);
        TAILQ_FOREACH(pr, &allprison, pr_list) {
                mtx_lock(&pr->pr_mtx);
                if (pr->pr_root == olddp) {
                        vref(newdp);
                        pr->pr_root = newdp;
                        nrele++;
                }
                mtx_unlock(&pr->pr_mtx);
        }
        sx_sunlock(&allprison_lock);
        while (nrele--)
                vrele(olddp);
}

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

        fdtol = malloc(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) {
                PROC_LOCK(p);
                if (p->p_state == PRS_NEW) {
                        PROC_UNLOCK(p);
                        continue;
                }
                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_lastfile; ++n) {
                        if ((fp = fdp->fd_ofiles[n].fde_file) == 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 = foffset_get(fp);
                        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|CTLFLAG_MPSAFE,
    0, 0, sysctl_kern_file, "S,xfile", "Entire file table");

#ifdef KINFO_FILE_SIZE
CTASSERT(sizeof(struct kinfo_file) == KINFO_FILE_SIZE);
#endif

static int
xlate_fflags(int fflags)
{
        static const struct {
                int     fflag;
                int     kf_fflag;
        } fflags_table[] = {
                { FAPPEND, KF_FLAG_APPEND },
                { FASYNC, KF_FLAG_ASYNC },
                { FFSYNC, KF_FLAG_FSYNC },
                { FHASLOCK, KF_FLAG_HASLOCK },
                { FNONBLOCK, KF_FLAG_NONBLOCK },
                { FREAD, KF_FLAG_READ },
                { FWRITE, KF_FLAG_WRITE },
                { O_CREAT, KF_FLAG_CREAT },
                { O_DIRECT, KF_FLAG_DIRECT },
                { O_EXCL, KF_FLAG_EXCL },
                { O_EXEC, KF_FLAG_EXEC },
                { O_EXLOCK, KF_FLAG_EXLOCK },
                { O_NOFOLLOW, KF_FLAG_NOFOLLOW },
                { O_SHLOCK, KF_FLAG_SHLOCK },
                { O_TRUNC, KF_FLAG_TRUNC }
        };
        unsigned int i;
        int kflags;

        kflags = 0;
        for (i = 0; i < nitems(fflags_table); i++)
                if (fflags & fflags_table[i].fflag)
                        kflags |=  fflags_table[i].kf_fflag;
        return (kflags);
}

/* Trim unused data from kf_path by truncating the structure size. */
static void
pack_kinfo(struct kinfo_file *kif)
{

        kif->kf_structsize = offsetof(struct kinfo_file, kf_path) +
            strlen(kif->kf_path) + 1;
        kif->kf_structsize = roundup(kif->kf_structsize, sizeof(uint64_t));
}

static void
export_file_to_kinfo(struct file *fp, int fd, cap_rights_t *rightsp,
    struct kinfo_file *kif, struct filedesc *fdp)
{
        int error;

        bzero(kif, sizeof(*kif));

        /* Set a default type to allow for empty fill_kinfo() methods. */
        kif->kf_type = KF_TYPE_UNKNOWN;
        kif->kf_flags = xlate_fflags(fp->f_flag);
        if (rightsp != NULL)
                kif->kf_cap_rights = *rightsp;
        else
                cap_rights_init(&kif->kf_cap_rights);
        kif->kf_fd = fd;
        kif->kf_ref_count = fp->f_count;
        kif->kf_offset = foffset_get(fp);

        /*
         * This may drop the filedesc lock, so the 'fp' cannot be
         * accessed after this call.
         */
        error = fo_fill_kinfo(fp, kif, fdp);
        if (error == 0)
                kif->kf_status |= KF_ATTR_VALID;
        pack_kinfo(kif);
}

static void
export_vnode_to_kinfo(struct vnode *vp, int fd, int fflags,
    struct kinfo_file *kif)
{
        int error;

        bzero(kif, sizeof(*kif));

        kif->kf_type = KF_TYPE_VNODE;
        error = vn_fill_kinfo_vnode(vp, kif);
        if (error == 0)
                kif->kf_status |= KF_ATTR_VALID;
        kif->kf_flags = xlate_fflags(fflags);
        cap_rights_init(&kif->kf_cap_rights);
        kif->kf_fd = fd;
        kif->kf_ref_count = -1;
        kif->kf_offset = -1;
        pack_kinfo(kif);
        vrele(vp);
}

struct export_fd_buf {
        struct filedesc         *fdp;
        struct sbuf             *sb;
        ssize_t                 remainder;
        struct kinfo_file       kif;
};

static int
export_kinfo_to_sb(struct export_fd_buf *efbuf)
{
        struct kinfo_file *kif;

        kif = &efbuf->kif;
        if (efbuf->remainder != -1) {
                if (efbuf->remainder < kif->kf_structsize) {
                        /* Terminate export. */
                        efbuf->remainder = 0;
                        return (0);
                }
                efbuf->remainder -= kif->kf_structsize;
        }
        return (sbuf_bcat(efbuf->sb, kif, kif->kf_structsize) == 0 ? 0 : ENOMEM);
}

static int
export_file_to_sb(struct file *fp, int fd, cap_rights_t *rightsp,
    struct export_fd_buf *efbuf)
{
        int error;

        if (efbuf->remainder == 0)
                return (0);
        export_file_to_kinfo(fp, fd, rightsp, &efbuf->kif, efbuf->fdp);
        FILEDESC_SUNLOCK(efbuf->fdp);
        error = export_kinfo_to_sb(efbuf);
        FILEDESC_SLOCK(efbuf->fdp);
        return (error);
}

static int
export_vnode_to_sb(struct vnode *vp, int fd, int fflags,
    struct export_fd_buf *efbuf)
{
        int error;

        if (efbuf->remainder == 0)
                return (0);
        if (efbuf->fdp != NULL)
                FILEDESC_SUNLOCK(efbuf->fdp);
        export_vnode_to_kinfo(vp, fd, fflags, &efbuf->kif);
        error = export_kinfo_to_sb(efbuf);
        if (efbuf->fdp != NULL)
                FILEDESC_SLOCK(efbuf->fdp);
        return (error);
}

/*
 * Store a process file descriptor information to sbuf.
 *
 * Takes a locked proc as argument, and returns with the proc unlocked.
 */
int
kern_proc_filedesc_out(struct proc *p,  struct sbuf *sb, ssize_t maxlen)
{
        struct file *fp;
        struct filedesc *fdp;
        struct export_fd_buf *efbuf;
        struct vnode *cttyvp, *textvp, *tracevp;
        int error, i;
        cap_rights_t rights;

        PROC_LOCK_ASSERT(p, MA_OWNED);

        /* ktrace vnode */
        tracevp = p->p_tracevp;
        if (tracevp != NULL)
                vref(tracevp);
        /* text vnode */
        textvp = p->p_textvp;
        if (textvp != NULL)
                vref(textvp);
        /* Controlling tty. */
        cttyvp = NULL;
        if (p->p_pgrp != NULL && p->p_pgrp->pg_session != NULL) {
                cttyvp = p->p_pgrp->pg_session->s_ttyvp;
                if (cttyvp != NULL)
                        vref(cttyvp);
        }
        fdp = fdhold(p);
        PROC_UNLOCK(p);
        efbuf = malloc(sizeof(*efbuf), M_TEMP, M_WAITOK);
        efbuf->fdp = NULL;
        efbuf->sb = sb;
        efbuf->remainder = maxlen;
        if (tracevp != NULL)
                export_vnode_to_sb(tracevp, KF_FD_TYPE_TRACE, FREAD | FWRITE,
                    efbuf);
        if (textvp != NULL)
                export_vnode_to_sb(textvp, KF_FD_TYPE_TEXT, FREAD, efbuf);
        if (cttyvp != NULL)
                export_vnode_to_sb(cttyvp, KF_FD_TYPE_CTTY, FREAD | FWRITE,
                    efbuf);
        error = 0;
        if (fdp == NULL)
                goto fail;
        efbuf->fdp = fdp;
        FILEDESC_SLOCK(fdp);
        /* working directory */
        if (fdp->fd_cdir != NULL) {
                vref(fdp->fd_cdir);
                export_vnode_to_sb(fdp->fd_cdir, KF_FD_TYPE_CWD, FREAD, efbuf);
        }
        /* root directory */
        if (fdp->fd_rdir != NULL) {
                vref(fdp->fd_rdir);
                export_vnode_to_sb(fdp->fd_rdir, KF_FD_TYPE_ROOT, FREAD, efbuf);
        }
        /* jail directory */
        if (fdp->fd_jdir != NULL) {
                vref(fdp->fd_jdir);
                export_vnode_to_sb(fdp->fd_jdir, KF_FD_TYPE_JAIL, FREAD, efbuf);
        }
        for (i = 0; fdp->fd_refcnt > 0 && i <= fdp->fd_lastfile; i++) {
                if ((fp = fdp->fd_ofiles[i].fde_file) == NULL)
                        continue;
#ifdef CAPABILITIES
                rights = *cap_rights(fdp, i);
#else /* !CAPABILITIES */
                cap_rights_init(&rights);
#endif
                /*
                 * Create sysctl entry.  It is OK to drop the filedesc
                 * lock inside of export_file_to_sb() as we will
                 * re-validate and re-evaluate its properties when the
                 * loop continues.
                 */
                error = export_file_to_sb(fp, i, &rights, efbuf);
                if (error != 0 || efbuf->remainder == 0)
                        break;
        }
        FILEDESC_SUNLOCK(fdp);
        fddrop(fdp);
fail:
        free(efbuf, M_TEMP);
        return (error);
}

#define FILEDESC_SBUF_SIZE      (sizeof(struct kinfo_file) * 5)

/*
 * Get per-process file descriptors for use by procstat(1), et al.
 */
static int
sysctl_kern_proc_filedesc(SYSCTL_HANDLER_ARGS)
{
        struct sbuf sb;
        struct proc *p;
        ssize_t maxlen;
        int error, error2, *name;

        name = (int *)arg1;

        sbuf_new_for_sysctl(&sb, NULL, FILEDESC_SBUF_SIZE, req);
        error = pget((pid_t)name[0], PGET_CANDEBUG | PGET_NOTWEXIT, &p);
        if (error != 0) {
                sbuf_delete(&sb);
                return (error);
        }
        maxlen = req->oldptr != NULL ? req->oldlen : -1;
        error = kern_proc_filedesc_out(p, &sb, maxlen);
        error2 = sbuf_finish(&sb);
        sbuf_delete(&sb);
        return (error != 0 ? error : error2);
}

#ifdef KINFO_OFILE_SIZE
CTASSERT(sizeof(struct kinfo_ofile) == KINFO_OFILE_SIZE);
#endif

#ifdef COMPAT_FREEBSD7
static void
kinfo_to_okinfo(struct kinfo_file *kif, struct kinfo_ofile *okif)
{

        okif->kf_structsize = sizeof(*okif);
        okif->kf_type = kif->kf_type;
        okif->kf_fd = kif->kf_fd;
        okif->kf_ref_count = kif->kf_ref_count;
        okif->kf_flags = kif->kf_flags & (KF_FLAG_READ | KF_FLAG_WRITE |
            KF_FLAG_APPEND | KF_FLAG_ASYNC | KF_FLAG_FSYNC | KF_FLAG_NONBLOCK |
            KF_FLAG_DIRECT | KF_FLAG_HASLOCK);
        okif->kf_offset = kif->kf_offset;
        okif->kf_vnode_type = kif->kf_vnode_type;
        okif->kf_sock_domain = kif->kf_sock_domain;
        okif->kf_sock_type = kif->kf_sock_type;
        okif->kf_sock_protocol = kif->kf_sock_protocol;
        strlcpy(okif->kf_path, kif->kf_path, sizeof(okif->kf_path));
        okif->kf_sa_local = kif->kf_sa_local;
        okif->kf_sa_peer = kif->kf_sa_peer;
}

static int
export_vnode_for_osysctl(struct vnode *vp, int type, struct kinfo_file *kif,
    struct kinfo_ofile *okif, struct filedesc *fdp, struct sysctl_req *req)
{
        int error;

        vref(vp);
        FILEDESC_SUNLOCK(fdp);
        export_vnode_to_kinfo(vp, type, 0, kif);
        kinfo_to_okinfo(kif, okif);
        error = SYSCTL_OUT(req, okif, sizeof(*okif));
        FILEDESC_SLOCK(fdp);
        return (error);
}

/*
 * Get per-process file descriptors for use by procstat(1), et al.
 */
static int
sysctl_kern_proc_ofiledesc(SYSCTL_HANDLER_ARGS)
{
        struct kinfo_ofile *okif;
        struct kinfo_file *kif;
        struct filedesc *fdp;
        int error, i, *name;
        struct file *fp;
        struct proc *p;

        name = (int *)arg1;
        error = pget((pid_t)name[0], PGET_CANDEBUG | PGET_NOTWEXIT, &p);
        if (error != 0)
                return (error);
        fdp = fdhold(p);
        PROC_UNLOCK(p);
        if (fdp == NULL)
                return (ENOENT);
        kif = malloc(sizeof(*kif), M_TEMP, M_WAITOK);
        okif = malloc(sizeof(*okif), M_TEMP, M_WAITOK);
        FILEDESC_SLOCK(fdp);
        if (fdp->fd_cdir != NULL)
                export_vnode_for_osysctl(fdp->fd_cdir, KF_FD_TYPE_CWD, kif,
                    okif, fdp, req);
        if (fdp->fd_rdir != NULL)
                export_vnode_for_osysctl(fdp->fd_rdir, KF_FD_TYPE_ROOT, kif,
                    okif, fdp, req);
        if (fdp->fd_jdir != NULL)
                export_vnode_for_osysctl(fdp->fd_jdir, KF_FD_TYPE_JAIL, kif,
                    okif, fdp, req);
        for (i = 0; fdp->fd_refcnt > 0 && i <= fdp->fd_lastfile; i++) {
                if ((fp = fdp->fd_ofiles[i].fde_file) == NULL)
                        continue;
                export_file_to_kinfo(fp, i, NULL, kif, fdp);
                FILEDESC_SUNLOCK(fdp);
                kinfo_to_okinfo(kif, okif);
                error = SYSCTL_OUT(req, okif, sizeof(*okif));
                FILEDESC_SLOCK(fdp);
                if (error)
                        break;
        }
        FILEDESC_SUNLOCK(fdp);
        fddrop(fdp);
        free(kif, M_TEMP);
        free(okif, M_TEMP);
        return (0);
}

static SYSCTL_NODE(_kern_proc, KERN_PROC_OFILEDESC, ofiledesc,
    CTLFLAG_RD|CTLFLAG_MPSAFE, sysctl_kern_proc_ofiledesc,
    "Process ofiledesc entries");
#endif  /* COMPAT_FREEBSD7 */

int
vntype_to_kinfo(int vtype)
{
        struct {
                int     vtype;
                int     kf_vtype;
        } vtypes_table[] = {
                { VBAD, KF_VTYPE_VBAD },
                { VBLK, KF_VTYPE_VBLK },
                { VCHR, KF_VTYPE_VCHR },
                { VDIR, KF_VTYPE_VDIR },
                { VFIFO, KF_VTYPE_VFIFO },
                { VLNK, KF_VTYPE_VLNK },
                { VNON, KF_VTYPE_VNON },
                { VREG, KF_VTYPE_VREG },
                { VSOCK, KF_VTYPE_VSOCK }
        };
        unsigned int i;

        /*
         * Perform vtype translation.
         */
        for (i = 0; i < nitems(vtypes_table); i++)
                if (vtypes_table[i].vtype == vtype)
                        return (vtypes_table[i].kf_vtype);

        return (KF_VTYPE_UNKNOWN);
}

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

/*
 * Store a process current working directory information to sbuf.
 *
 * Takes a locked proc as argument, and returns with the proc unlocked.
 */
int
kern_proc_cwd_out(struct proc *p,  struct sbuf *sb, ssize_t maxlen)
{
        struct filedesc *fdp;
        struct export_fd_buf *efbuf;
        int error;

        PROC_LOCK_ASSERT(p, MA_OWNED);

        fdp = fdhold(p);
        PROC_UNLOCK(p);
        if (fdp == NULL)
                return (EINVAL);

        efbuf = malloc(sizeof(*efbuf), M_TEMP, M_WAITOK);
        efbuf->fdp = fdp;
        efbuf->sb = sb;
        efbuf->remainder = maxlen;

        FILEDESC_SLOCK(fdp);
        if (fdp->fd_cdir == NULL)
                error = EINVAL;
        else {
                vref(fdp->fd_cdir);
                error = export_vnode_to_sb(fdp->fd_cdir, KF_FD_TYPE_CWD,
                    FREAD, efbuf);
        }
        FILEDESC_SUNLOCK(fdp);
        fddrop(fdp);
        free(efbuf, M_TEMP);
        return (error);
}

/*
 * Get per-process current working directory.
 */
static int
sysctl_kern_proc_cwd(SYSCTL_HANDLER_ARGS)
{
        struct sbuf sb;
        struct proc *p;
        ssize_t maxlen;
        int error, error2, *name;

        name = (int *)arg1;

        sbuf_new_for_sysctl(&sb, NULL, sizeof(struct kinfo_file), req);
        error = pget((pid_t)name[0], PGET_CANDEBUG | PGET_NOTWEXIT, &p);
        if (error != 0) {
                sbuf_delete(&sb);
                return (error);
        }
        maxlen = req->oldptr != NULL ? req->oldlen : -1;
        error = kern_proc_cwd_out(p, &sb, maxlen);
        error2 = sbuf_finish(&sb);
        sbuf_delete(&sb);
        return (error != 0 ? error : error2);
}

static SYSCTL_NODE(_kern_proc, KERN_PROC_CWD, cwd, CTLFLAG_RD|CTLFLAG_MPSAFE,
    sysctl_kern_proc_cwd, "Process current working directory");

#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_lastfile; n++) {
                        if (fp == fdp->fd_ofiles[n].fde_file)
                                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_lastfile; ++n) {
                        if ((fp = fdp->fd_ofiles[n].fde_file) == 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, UMA_ZONE_NOFREE);
        filedesc0_zone = uma_zcreate("filedesc0", sizeof(struct filedesc0),
            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);
}

static int
badfo_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
    struct thread *td)
{

        return (EBADF);
}

static int
badfo_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
    struct thread *td)
{

        return (EBADF);
}

static int
badfo_sendfile(struct file *fp, int sockfd, struct uio *hdr_uio,
    struct uio *trl_uio, off_t offset, size_t nbytes, off_t *sent, int flags,
    int kflags, struct thread *td)
{

        return (EBADF);
}

static int
badfo_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
{

        return (0);
}

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,
        .fo_chmod = badfo_chmod,
        .fo_chown = badfo_chown,
        .fo_sendfile = badfo_sendfile,
        .fo_fill_kinfo = badfo_fill_kinfo,
};

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

        return (EOPNOTSUPP);
}

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

        return (EINVAL);
}

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

        return (ENOTTY);
}

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

        return (poll_no_poll(events));
}

int
invfo_kqfilter(struct file *fp, struct knote *kn)
{

        return (EINVAL);
}

int
invfo_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
    struct thread *td)
{

        return (EINVAL);
}

int
invfo_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
    struct thread *td)
{

        return (EINVAL);
}

int
invfo_sendfile(struct file *fp, int sockfd, struct uio *hdr_uio,
    struct uio *trl_uio, off_t offset, size_t nbytes, off_t *sent, int flags,
    int kflags, struct thread *td)
{

        return (EINVAL);
}

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

/*
 * 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_credf(MAKEDEV_ETERNAL, &fildesc_cdevsw, 0, NULL,
            UID_ROOT, GID_WHEEL, 0666, "fd/0");
        make_dev_alias(dev, "stdin");
        dev = make_dev_credf(MAKEDEV_ETERNAL, &fildesc_cdevsw, 1, NULL,
            UID_ROOT, GID_WHEEL, 0666, "fd/1");
        make_dev_alias(dev, "stdout");
        dev = make_dev_credf(MAKEDEV_ETERNAL, &fildesc_cdevsw, 2, NULL,
            UID_ROOT, GID_WHEEL, 0666, "fd/2");
        make_dev_alias(dev, "stderr");
}

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