fd: split fget_unlocked_seq depending on CAPABILITIES

[FreeBSD/FreeBSD.git] / sys / kern / kern_descrip.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1982, 1986, 1989, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)kern_descrip.c      8.6 (Berkeley) 4/19/94
 */

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

#include "opt_capsicum.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/poll.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/kdb.h>
#include <sys/smr.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>
#include <sys/ktrace.h>

#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_PWD, "pwd", "Descriptor table vnodes");
static MALLOC_DEFINE(M_PWDDESC, "pwddesc", "Pwd descriptors");
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 __read_mostly uma_zone_t file_zone;
static __read_mostly uma_zone_t filedesc0_zone;
__read_mostly uma_zone_t pwd_zone;
VFS_SMR_DECLARE;

static int      closefp(struct filedesc *fdp, int fd, struct file *fp,
                    struct thread *td, bool holdleaders, bool audit);
static void     export_file_to_kinfo(struct file *fp, int fd,
                    cap_rights_t *rightsp, struct kinfo_file *kif,
                    struct filedesc *fdp, int flags);
static int      fd_first_free(struct filedesc *fdp, int low, 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      fget_unlocked_seq(struct filedesc *fdp, int fd,
                    cap_rights_t *needrightsp, struct file **fpp, seqc_t *seqp);
static int      getmaxfd(struct thread *td);
static u_long   *filecaps_copy_prep(const struct filecaps *src);
static void     filecaps_copy_finish(const struct filecaps *src,
                    struct filecaps *dst, u_long *ioctls);
static u_long   *filecaps_free_prep(struct filecaps *fcaps);
static void     filecaps_free_finish(u_long *ioctls);

static struct pwd *pwd_alloc(void);

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

/*
 * 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 last used fd.
 *
 * Call this variant if fdp can't be modified by anyone else (e.g, during exec).
 * Otherwise use fdlastfile.
 */
int
fdlastfile_single(struct filedesc *fdp)
{
        NDSLOTTYPE *map = fdp->fd_map;
        int off, minoff;

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

int
fdlastfile(struct filedesc *fdp)
{

        FILEDESC_LOCK_ASSERT(fdp);
        return (fdlastfile_single(fdp));
}

static int
fdisused(struct filedesc *fdp, int fd)
{

        KASSERT(fd >= 0 && fd < fdp->fd_nfiles,
            ("file descriptor %d out of range (0, %d)", fd, fdp->fd_nfiles));

        return ((fdp->fd_map[NDSLOT(fd)] & NDBIT(fd)) != 0);
}

/*
 * Mark a file descriptor as used.
 */
static void
fdused_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_freefile)
                fdp->fd_freefile++;
}

/*
 * 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;
}

/*
 * 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;

        FILEDESC_XLOCK_ASSERT(fdp);
        fde = &fdp->fd_ofiles[fd];
#ifdef CAPABILITIES
        seqc_write_begin(&fde->fde_seqc);
#endif
        fde->fde_file = NULL;
#ifdef CAPABILITIES
        seqc_write_end(&fde->fde_seqc);
#endif
        fdefree_last(fde);
        fdunused(fdp, fd);
}

/*
 * 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)
{
#ifdef  RACCT
        uint64_t lim;
#endif

        td->td_retval[0] = getmaxfd(td);
#ifdef  RACCT
        PROC_LOCK(td->td_proc);
        lim = racct_get_limit(td->td_proc, RACCT_NOFILE);
        PROC_UNLOCK(td->td_proc);
        if (lim < td->td_retval[0])
                td->td_retval[0] = lim;
#endif
        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 (kern_dup(td, FDDUP_FIXED, 0, (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 (kern_dup(td, FDDUP_NORMAL, 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, newcmd;

        error = 0;
        newcmd = cmd;
        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:
                        newcmd = F_GETLK;
                        break;
                case F_OSETLK:
                        newcmd = F_SETLK;
                        break;
                case F_OSETLKW:
                        newcmd = 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, newcmd, 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;
        struct mount *mp;
        struct kinfo_file *kif;
        int error, flg, kif_sz, seals, tmp;
        uint64_t bsize;
        off_t foffset;

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

        AUDIT_ARG_FD(cmd);
        AUDIT_ARG_CMD(cmd);
        switch (cmd) {
        case F_DUPFD:
                tmp = arg;
                error = kern_dup(td, FDDUP_FCNTL, 0, fd, tmp);
                break;

        case F_DUPFD_CLOEXEC:
                tmp = arg;
                error = kern_dup(td, FDDUP_FCNTL, FDDUP_FLAG_CLOEXEC, fd, tmp);
                break;

        case F_DUP2FD:
                tmp = arg;
                error = kern_dup(td, FDDUP_FIXED, 0, fd, tmp);
                break;

        case F_DUP2FD_CLOEXEC:
                tmp = arg;
                error = kern_dup(td, FDDUP_FIXED, FDDUP_FLAG_CLOEXEC, fd, tmp);
                break;

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

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

        case F_GETFL:
                error = fget_fcntl(td, fd, &cap_fcntl_rights, F_GETFL, &fp);
                if (error != 0)
                        break;
                td->td_retval[0] = OFLAGS(fp->f_flag);
                fdrop(fp, td);
                break;

        case F_SETFL:
                error = fget_fcntl(td, fd, &cap_fcntl_rights, F_SETFL, &fp);
                if (error != 0)
                        break;
                if (fp->f_ops == &path_fileops) {
                        fdrop(fp, td);
                        error = EBADF;
                        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_fcntl(td, fd, &cap_fcntl_rights, F_GETOWN, &fp);
                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_fcntl(td, fd, &cap_fcntl_rights, F_SETOWN, &fp);
                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 != 0)
                        return (error);
                flg = F_REMOTE;
                goto do_setlk;

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

        case F_SETLK:
        do_setlk:
                flp = (struct flock *)arg;
                if ((flg & F_REMOTE) != 0 && flp->l_sysid == 0) {
                        error = EINVAL;
                        break;
                }

                error = fget_unlocked(fdp, fd, &cap_flock_rights, &fp);
                if (error != 0)
                        break;
                if (fp->f_type != DTYPE_VNODE || fp->f_ops == &path_fileops) {
                        error = EBADF;
                        fdrop(fp, td);
                        break;
                }

                if (flp->l_whence == SEEK_CUR) {
                        foffset = foffset_get(fp);
                        if (foffset < 0 ||
                            (flp->l_start > 0 &&
                             foffset > OFF_MAX - flp->l_start)) {
                                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;
                        }
                        if ((p->p_leader->p_flag & P_ADVLOCK) == 0) {
                                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;
                        }
                        if ((p->p_leader->p_flag & P_ADVLOCK) == 0) {
                                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:
                        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, &cap_no_rights, &fp2);
                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_flock_rights, &fp);
                if (error != 0)
                        break;
                if (fp->f_type != DTYPE_VNODE || fp->f_ops == &path_fileops) {
                        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)) {
                                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_ADD_SEALS:
                error = fget_unlocked(fdp, fd, &cap_no_rights, &fp);
                if (error != 0)
                        break;
                error = fo_add_seals(fp, arg);
                fdrop(fp, td);
                break;

        case F_GET_SEALS:
                error = fget_unlocked(fdp, fd, &cap_no_rights, &fp);
                if (error != 0)
                        break;
                if (fo_get_seals(fp, &seals) == 0)
                        td->td_retval[0] = seals;
                else
                        error = EINVAL;
                fdrop(fp, td);
                break;

        case F_RDAHEAD:
                arg = arg ? 128 * 1024: 0;
                /* FALLTHROUGH */
        case F_READAHEAD:
                error = fget_unlocked(fdp, fd, &cap_no_rights, &fp);
                if (error != 0)
                        break;
                if (fp->f_type != DTYPE_VNODE || fp->f_ops == &path_fileops) {
                        fdrop(fp, td);
                        error = EBADF;
                        break;
                }
                vp = fp->f_vnode;
                if (vp->v_type != VREG) {
                        fdrop(fp, td);
                        error = ENOTTY;
                        break;
                }

                /*
                 * 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;
                        arg = MIN(arg, INT_MAX - bsize + 1);
                        fp->f_seqcount[UIO_READ] = MIN(IO_SEQMAX,
                            (arg + bsize - 1) / bsize);
                        atomic_set_int(&fp->f_flag, FRDAHEAD);
                } else {
                        atomic_clear_int(&fp->f_flag, FRDAHEAD);
                }
                VOP_UNLOCK(vp);
                fdrop(fp, td);
                break;

        case F_ISUNIONSTACK:
                /*
                 * Check if the vnode is part of a union stack (either the
                 * "union" flag from mount(2) or unionfs).
                 *
                 * Prior to introduction of this op libc's readdir would call
                 * fstatfs(2), in effect unnecessarily copying kilobytes of
                 * data just to check fs name and a mount flag.
                 *
                 * Fixing the code to handle everything in the kernel instead
                 * is a non-trivial endeavor and has low priority, thus this
                 * horrible kludge facilitates the current behavior in a much
                 * cheaper manner until someone(tm) sorts this out.
                 */
                error = fget_unlocked(fdp, fd, &cap_no_rights, &fp);
                if (error != 0)
                        break;
                if (fp->f_type != DTYPE_VNODE) {
                        fdrop(fp, td);
                        error = EBADF;
                        break;
                }
                vp = fp->f_vnode;
                /*
                 * Since we don't prevent dooming the vnode even non-null mp
                 * found can become immediately stale. This is tolerable since
                 * mount points are type-stable (providing safe memory access)
                 * and any vfs op on this vnode going forward will return an
                 * error (meaning return value in this case is meaningless).
                 */
                mp = atomic_load_ptr(&vp->v_mount);
                if (__predict_false(mp == NULL)) {
                        fdrop(fp, td);
                        error = EBADF;
                        break;
                }
                td->td_retval[0] = 0;
                if (mp->mnt_kern_flag & MNTK_UNIONFS ||
                    mp->mnt_flag & MNT_UNION)
                        td->td_retval[0] = 1;
                fdrop(fp, td);
                break;

        case F_KINFO:
#ifdef CAPABILITY_MODE
                if (IN_CAPABILITY_MODE(td)) {
                        error = ECAPMODE;
                        break;
                }
#endif
                error = copyin((void *)arg, &kif_sz, sizeof(kif_sz));
                if (error != 0)
                        break;
                if (kif_sz != sizeof(*kif)) {
                        error = EINVAL;
                        break;
                }
                kif = malloc(sizeof(*kif), M_TEMP, M_WAITOK | M_ZERO);
                FILEDESC_SLOCK(fdp);
                error = fget_cap_locked(fdp, fd, &cap_fcntl_rights, &fp, NULL);
                if (error == 0 && fhold(fp)) {
                        export_file_to_kinfo(fp, fd, NULL, kif, fdp, 0);
                        FILEDESC_SUNLOCK(fdp);
                        fdrop(fp, td);
                        if ((kif->kf_status & KF_ATTR_VALID) != 0) {
                                kif->kf_structsize = sizeof(*kif);
                                error = copyout(kif, (void *)arg, sizeof(*kif));
                        } else {
                                error = EBADF;
                        }
                } else {
                        FILEDESC_SUNLOCK(fdp);
                        if (error == 0)
                                error = EBADF;
                }
                free(kif, M_TEMP);
                break;

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

static int
getmaxfd(struct thread *td)
{

        return (min((int)lim_cur(td, RLIMIT_NOFILE), maxfilesperproc));
}

/*
 * Common code for dup, dup2, fcntl(F_DUPFD) and fcntl(F_DUP2FD).
 */
int
kern_dup(struct thread *td, u_int mode, int flags, int old, int new)
{
        struct filedesc *fdp;
        struct filedescent *oldfde, *newfde;
        struct proc *p;
        struct file *delfp, *oldfp;
        u_long *oioctls, *nioctls;
        int error, maxfd;

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

        MPASS((flags & ~(FDDUP_FLAG_CLOEXEC)) == 0);
        MPASS(mode < FDDUP_LASTMODE);

        AUDIT_ARG_FD(old);
        /* XXXRW: if (flags & FDDUP_FIXED) AUDIT_ARG_FD2(new); */

        /*
         * 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 (mode == FDDUP_FCNTL ? EINVAL : EBADF);
        maxfd = getmaxfd(td);
        if (new >= maxfd)
                return (mode == FDDUP_FCNTL ? EINVAL : EBADF);

        error = EBADF;
        FILEDESC_XLOCK(fdp);
        if (fget_locked(fdp, old) == NULL)
                goto unlock;
        if (mode == FDDUP_FIXED && old == new) {
                td->td_retval[0] = new;
                if (flags & FDDUP_FLAG_CLOEXEC)
                        fdp->fd_ofiles[new].fde_flags |= UF_EXCLOSE;
                error = 0;
                goto unlock;
        }

        oldfde = &fdp->fd_ofiles[old];
        oldfp = oldfde->fde_file;
        if (!fhold(oldfp))
                goto unlock;

        /*
         * 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.
         */
        switch (mode) {
        case FDDUP_NORMAL:
        case FDDUP_FCNTL:
                if ((error = fdalloc(td, new, &new)) != 0) {
                        fdrop(oldfp, td);
                        goto unlock;
                }
                break;
        case FDDUP_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
                        if (RACCT_ENABLED()) {
                                error = racct_set_unlocked(p, RACCT_NOFILE, new + 1);
                                if (error != 0) {
                                        error = EMFILE;
                                        fdrop(oldfp, td);
                                        goto unlock;
                                }
                        }
#endif
                        fdgrowtable_exp(fdp, new + 1);
                }
                if (!fdisused(fdp, new))
                        fdused(fdp, new);
                break;
        default:
                KASSERT(0, ("%s unsupported mode %d", __func__, mode));
        }

        KASSERT(old != new, ("new fd is same as old"));

        /* Refetch oldfde because the table may have grown and old one freed. */
        oldfde = &fdp->fd_ofiles[old];
        KASSERT(oldfp == oldfde->fde_file,
            ("fdt_ofiles shift from growth observed at fd %d",
            old));

        newfde = &fdp->fd_ofiles[new];
        delfp = newfde->fde_file;

        nioctls = filecaps_copy_prep(&oldfde->fde_caps);

        /*
         * Duplicate the source descriptor.
         */
#ifdef CAPABILITIES
        seqc_write_begin(&newfde->fde_seqc);
#endif
        oioctls = filecaps_free_prep(&newfde->fde_caps);
        memcpy(newfde, oldfde, fde_change_size);
        filecaps_copy_finish(&oldfde->fde_caps, &newfde->fde_caps,
            nioctls);
        if ((flags & FDDUP_FLAG_CLOEXEC) != 0)
                newfde->fde_flags = oldfde->fde_flags | UF_EXCLOSE;
        else
                newfde->fde_flags = oldfde->fde_flags & ~UF_EXCLOSE;
#ifdef CAPABILITIES
        seqc_write_end(&newfde->fde_seqc);
#endif
        td->td_retval[0] = new;

        error = 0;

        if (delfp != NULL) {
                (void) closefp(fdp, new, delfp, td, true, false);
                FILEDESC_UNLOCK_ASSERT(fdp);
        } else {
unlock:
                FILEDESC_XUNLOCK(fdp);
        }

        filecaps_free_finish(oioctls);
        return (error);
}

static void
sigiofree(struct sigio *sigio)
{
        crfree(sigio->sio_ucred);
        free(sigio, M_SIGIO);
}

static struct sigio *
funsetown_locked(struct sigio *sigio)
{
        struct proc *p;
        struct pgrp *pg;

        SIGIO_ASSERT_LOCKED();

        if (sigio == NULL)
                return (NULL);
        *sigio->sio_myref = NULL;
        if (sigio->sio_pgid < 0) {
                pg = sigio->sio_pgrp;
                PGRP_LOCK(pg);
                SLIST_REMOVE(&pg->pg_sigiolst, sigio, sigio, sio_pgsigio);
                PGRP_UNLOCK(pg);
        } else {
                p = sigio->sio_proc;
                PROC_LOCK(p);
                SLIST_REMOVE(&p->p_sigiolst, sigio, sigio, sio_pgsigio);
                PROC_UNLOCK(p);
        }
        return (sigio);
}

/*
 * 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;

        /* Racy check, consumers must provide synchronization. */
        if (*sigiop == NULL)
                return;

        SIGIO_LOCK();
        sigio = funsetown_locked(*sigiop);
        SIGIO_UNLOCK();
        if (sigio != NULL)
                sigiofree(sigio);
}

/*
 * Free a list of sigio structures.  The caller must ensure that new sigio
 * structures cannot be added after this point.  For process groups this is
 * guaranteed using the proctree lock; for processes, the P_WEXIT flag serves
 * as an interlock.
 */
void
funsetownlst(struct sigiolst *sigiolst)
{
        struct proc *p;
        struct pgrp *pg;
        struct sigio *sigio, *tmp;

        /* Racy check. */
        sigio = SLIST_FIRST(sigiolst);
        if (sigio == NULL)
                return;

        p = NULL;
        pg = NULL;

        SIGIO_LOCK();
        sigio = SLIST_FIRST(sigiolst);
        if (sigio == NULL) {
                SIGIO_UNLOCK();
                return;
        }

        /*
         * Every entry of the list should belong to a single proc or pgrp.
         */
        if (sigio->sio_pgid < 0) {
                pg = sigio->sio_pgrp;
                sx_assert(&proctree_lock, SX_XLOCKED);
                PGRP_LOCK(pg);
        } else /* if (sigio->sio_pgid > 0) */ {
                p = sigio->sio_proc;
                PROC_LOCK(p);
                KASSERT((p->p_flag & P_WEXIT) != 0,
                    ("%s: process %p is not exiting", __func__, p));
        }

        SLIST_FOREACH(sigio, sigiolst, sio_pgsigio) {
                *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"));
                } 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"));
                }
        }

        if (pg != NULL)
                PGRP_UNLOCK(pg);
        else
                PROC_UNLOCK(p);
        SIGIO_UNLOCK();

        SLIST_FOREACH_SAFE(sigio, sigiolst, sio_pgsigio, tmp)
                sigiofree(sigio);
}

/*
 * 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 *osigio, *sigio;
        int ret;

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

        sigio = malloc(sizeof(struct sigio), M_SIGIO, M_WAITOK);
        sigio->sio_pgid = pgid;
        sigio->sio_ucred = crhold(curthread->td_ucred);
        sigio->sio_myref = sigiop;

        ret = 0;
        if (pgid > 0) {
                ret = pget(pgid, PGET_NOTWEXIT | PGET_NOTID | PGET_HOLD, &proc);
                SIGIO_LOCK();
                osigio = funsetown_locked(*sigiop);
                if (ret == 0) {
                        PROC_LOCK(proc);
                        _PRELE(proc);
                        if ((proc->p_flag & P_WEXIT) != 0) {
                                ret = ESRCH;
                        } else if (proc->p_session !=
                            curthread->td_proc->p_session) {
                                /*
                                 * 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.
                                 */
                                ret = EPERM;
                        } else {
                                sigio->sio_proc = proc;
                                SLIST_INSERT_HEAD(&proc->p_sigiolst, sigio,
                                    sio_pgsigio);
                        }
                        PROC_UNLOCK(proc);
                }
        } else /* if (pgid < 0) */ {
                sx_slock(&proctree_lock);
                SIGIO_LOCK();
                osigio = funsetown_locked(*sigiop);
                pgrp = pgfind(-pgid);
                if (pgrp == NULL) {
                        ret = ESRCH;
                } else {
                        if (pgrp->pg_session != curthread->td_proc->p_session) {
                                /*
                                 * 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.
                                 */
                                ret = EPERM;
                        } else {
                                sigio->sio_pgrp = pgrp;
                                SLIST_INSERT_HEAD(&pgrp->pg_sigiolst, sigio,
                                    sio_pgsigio);
                        }
                        PGRP_UNLOCK(pgrp);
                }
                sx_sunlock(&proctree_lock);
        }
        if (ret == 0)
                *sigiop = sigio;
        SIGIO_UNLOCK();
        if (osigio != NULL)
                sigiofree(osigio);
        return (ret);
}

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

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

static int
closefp_impl(struct filedesc *fdp, int fd, struct file *fp, struct thread *td,
    bool audit)
{
        int error;

        FILEDESC_XLOCK_ASSERT(fdp);

        /*
         * 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.
         */
        if (__predict_false(!TAILQ_EMPTY(&fdp->fd_kqlist)))
                knote_fdclose(td, fd);

        /*
         * We need to notify mqueue if the object is of type mqueue.
         */
        if (__predict_false(fp->f_type == DTYPE_MQUEUE))
                mq_fdclose(td, fd, fp);
        FILEDESC_XUNLOCK(fdp);

#ifdef AUDIT
        if (AUDITING_TD(td) && audit)
                audit_sysclose(td, fd, fp);
#endif
        error = closef(fp, td);

        /*
         * All paths leading up to closefp() will have already removed or
         * replaced the fd in the filedesc table, so a restart would not
         * operate on the same file.
         */
        if (error == ERESTART)
                error = EINTR;

        return (error);
}

static int
closefp_hl(struct filedesc *fdp, int fd, struct file *fp, struct thread *td,
    bool holdleaders, bool audit)
{
        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 = false;
                }
        }

        error = closefp_impl(fdp, fd, fp, td, audit);
        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);
}

static int
closefp(struct filedesc *fdp, int fd, struct file *fp, struct thread *td,
    bool holdleaders, bool audit)
{

        FILEDESC_XLOCK_ASSERT(fdp);

        if (__predict_false(td->td_proc->p_fdtol != NULL)) {
                return (closefp_hl(fdp, fd, fp, td, holdleaders, audit));
        } else {
                return (closefp_impl(fdp, fd, fp, td, audit));
        }
}

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

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

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

        fdp = td->td_proc->p_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, true, true));
}

int
kern_close_range(struct thread *td, u_int lowfd, u_int highfd)
{
        struct filedesc *fdp;
        const struct fdescenttbl *fdt;
        struct file *fp;
        int fd;

        /*
         * Check this prior to clamping; closefrom(3) with only fd 0, 1, and 2
         * open should not be a usage error.  From a close_range() perspective,
         * close_range(3, ~0U, 0) in the same scenario should also likely not
         * be a usage error as all fd above 3 are in-fact already closed.
         */
        if (highfd < lowfd) {
                return (EINVAL);
        }

        fdp = td->td_proc->p_fd;
        FILEDESC_XLOCK(fdp);
        fdt = atomic_load_ptr(&fdp->fd_files);
        highfd = MIN(highfd, fdt->fdt_nfiles - 1);
        fd = lowfd;
        if (__predict_false(fd > highfd)) {
                goto out_locked;
        }
        for (;;) {
                fp = fdt->fdt_ofiles[fd].fde_file;
                if (fp == NULL) {
                        if (fd == highfd)
                                goto out_locked;
                } else {
                        fdfree(fdp, fd);
                        (void) closefp(fdp, fd, fp, td, true, true);
                        if (fd == highfd)
                                goto out_unlocked;
                        FILEDESC_XLOCK(fdp);
                        fdt = atomic_load_ptr(&fdp->fd_files);
                }
                fd++;
        }
out_locked:
        FILEDESC_XUNLOCK(fdp);
out_unlocked:
        return (0);
}

#ifndef _SYS_SYSPROTO_H_
struct close_range_args {
        u_int   lowfd;
        u_int   highfd;
        int     flags;
};
#endif
int
sys_close_range(struct thread *td, struct close_range_args *uap)
{

        AUDIT_ARG_FD(uap->lowfd);
        AUDIT_ARG_CMD(uap->highfd);
        AUDIT_ARG_FFLAGS(uap->flags);

        /* No flags currently defined */
        if (uap->flags != 0)
                return (EINVAL);
        return (kern_close_range(td, uap->lowfd, uap->highfd));
}

#ifdef COMPAT_FREEBSD12
/*
 * Close open file descriptors.
 */
#ifndef _SYS_SYSPROTO_H_
struct freebsd12_closefrom_args {
        int     lowfd;
};
#endif
/* ARGSUSED */
int
freebsd12_closefrom(struct thread *td, struct freebsd12_closefrom_args *uap)
{
        u_int lowfd;

        AUDIT_ARG_FD(uap->lowfd);

        /*
         * Treat negative starting file descriptor values identical to
         * closefrom(0) which closes all files.
         */
        lowfd = MAX(0, uap->lowfd);
        return (kern_close_range(td, lowfd, ~0U));
}
#endif  /* COMPAT_FREEBSD12 */

#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 */

#if defined(COMPAT_FREEBSD11)
int
freebsd11_fstat(struct thread *td, struct freebsd11_fstat_args *uap)
{
        struct stat sb;
        struct freebsd11_stat osb;
        int error;

        error = kern_fstat(td, uap->fd, &sb);
        if (error != 0)
                return (error);
        error = freebsd11_cvtstat(&sb, &osb);
        if (error == 0)
                error = copyout(&osb, uap->sb, sizeof(osb));
        return (error);
}
#endif  /* COMPAT_FREEBSD11 */

/*
 * 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;
        int error;

        AUDIT_ARG_FD(fd);

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

        AUDIT_ARG_FILE(td->td_proc, fp);

        error = fo_stat(fp, sbp, td->td_ucred);
        fdrop(fp, td);
#ifdef __STAT_TIME_T_EXT
        sbp->st_atim_ext = 0;
        sbp->st_mtim_ext = 0;
        sbp->st_ctim_ext = 0;
        sbp->st_btim_ext = 0;
#endif
#ifdef KTRACE
        if (KTRPOINT(td, KTR_STRUCT))
                ktrstat_error(sbp, error);
#endif
        return (error);
}

#if defined(COMPAT_FREEBSD11)
/*
 * Return status information about a file descriptor.
 */
#ifndef _SYS_SYSPROTO_H_
struct freebsd11_nfstat_args {
        int     fd;
        struct  nstat *sb;
};
#endif
/* ARGSUSED */
int
freebsd11_nfstat(struct thread *td, struct freebsd11_nfstat_args *uap)
{
        struct nstat nub;
        struct stat ub;
        int error;

        error = kern_fstat(td, uap->fd, &ub);
        if (error != 0)
                return (error);
        error = freebsd11_cvtnstat(&ub, &nub);
        if (error != 0)
                error = copyout(&nub, uap->sb, sizeof(nub));
        return (error);
}
#endif /* COMPAT_FREEBSD11 */

/*
 * 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)
{
        long value;
        int error;

        error = kern_fpathconf(td, uap->fd, uap->name, &value);
        if (error == 0)
                td->td_retval[0] = value;
        return (error);
}

int
kern_fpathconf(struct thread *td, int fd, int name, long *valuep)
{
        struct file *fp;
        struct vnode *vp;
        int error;

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

        if (name == _PC_ASYNC_IO) {
                *valuep = _POSIX_ASYNCHRONOUS_IO;
                goto out;
        }
        vp = fp->f_vnode;
        if (vp != NULL) {
                vn_lock(vp, LK_SHARED | LK_RETRY);
                error = VOP_PATHCONF(vp, name, valuep);
                VOP_UNLOCK(vp);
        } else if (fp->f_type == DTYPE_PIPE || fp->f_type == DTYPE_SOCKET) {
                if (name != _PC_PIPE_BUF) {
                        error = EINVAL;
                } else {
                        *valuep = PIPE_BUF;
                        error = 0;
                }
        } else {
                error = EOPNOTSUPP;
        }
out:
        fdrop(fp, td);
        return (error);
}

/*
 * Copy filecaps structure allocating memory for ioctls array if needed.
 *
 * The last parameter indicates whether the fdtable is locked. If it is not and
 * ioctls are encountered, copying fails and the caller must lock the table.
 *
 * Note that if the table was not locked, the caller has to check the relevant
 * sequence counter to determine whether the operation was successful.
 */
bool
filecaps_copy(const struct filecaps *src, struct filecaps *dst, bool locked)
{
        size_t size;

        if (src->fc_ioctls != NULL && !locked)
                return (false);
        memcpy(dst, src, sizeof(*src));
        if (src->fc_ioctls == NULL)
                return (true);

        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);
        memcpy(dst->fc_ioctls, src->fc_ioctls, size);
        return (true);
}

static u_long *
filecaps_copy_prep(const struct filecaps *src)
{
        u_long *ioctls;
        size_t size;

        if (__predict_true(src->fc_ioctls == NULL))
                return (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;
        ioctls = malloc(size, M_FILECAPS, M_WAITOK);
        return (ioctls);
}

static void
filecaps_copy_finish(const struct filecaps *src, struct filecaps *dst,
    u_long *ioctls)
{
        size_t size;

        *dst = *src;
        if (__predict_true(src->fc_ioctls == NULL)) {
                MPASS(ioctls == NULL);
                return;
        }

        size = sizeof(src->fc_ioctls[0]) * src->fc_nioctls;
        dst->fc_ioctls = ioctls;
        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));
}

static u_long *
filecaps_free_prep(struct filecaps *fcaps)
{
        u_long *ioctls;

        ioctls = fcaps->fc_ioctls;
        bzero(fcaps, sizeof(*fcaps));
        return (ioctls);
}

static void
filecaps_free_finish(u_long *ioctls)
{

        free(ioctls, M_FILECAPS);
}

/*
 * 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 accommodate (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;

        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);

        /*
         * Free the old file table when not shared by other threads or processes.
         * The old file table is considered to be shared when either are true:
         * - The process has more than one thread.
         * - The file descriptor table has been shared via fdshare().
         *
         * When shared, the old file table will be placed 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) {
                /*
                 * Note we may be called here from fdinit while allocating a
                 * table for a new process in which case ->p_fd points
                 * elsewhere.
                 */
                if (curproc->p_fd != fdp || FILEDESC_IS_ONLY_USER(fdp)) {
                        free(otable, M_FILEDESC);
                } else {
                        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, maxfd, allocfd;
#ifdef RACCT
        int error;
#endif

        FILEDESC_XLOCK_ASSERT(fdp);

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

        maxfd = getmaxfd(td);

        /*
         * 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 (__predict_false(fd >= maxfd))
                return (EMFILE);
        if (__predict_false(fd >= fdp->fd_nfiles)) {
                allocfd = min(fd * 2, maxfd);
#ifdef RACCT
                if (RACCT_ENABLED()) {
                        error = racct_set_unlocked(p, RACCT_NOFILE, allocfd);
                        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"));
        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 descriptor 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_caps(struct thread *td, struct file **resultfp, int *resultfd, int flags,
    struct filecaps *fcaps)
{
        struct file *fp;
        int error, fd;

        MPASS(resultfp != NULL);
        MPASS(resultfd != NULL);

        error = _falloc_noinstall(td, &fp, 2);
        if (__predict_false(error != 0)) {
                return (error);
        }

        error = finstall_refed(td, fp, &fd, flags, fcaps);
        if (__predict_false(error != 0)) {
                falloc_abort(td, fp);
                return (error);
        }

        *resultfp = fp;
        *resultfd = fd;

        return (0);
}

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

        KASSERT(resultfp != NULL, ("%s: resultfp == NULL", __func__));
        MPASS(n > 0);

        openfiles_new = atomic_fetchadd_int(&openfiles, 1) + 1;
        if ((openfiles_new >= maxuserfiles &&
            priv_check(td, PRIV_MAXFILES) != 0) ||
            openfiles_new >= maxfiles) {
                atomic_subtract_int(&openfiles, 1);
                if (ppsratecheck(&lastfail, &curfail, 1)) {
                        printf("kern.maxfiles limit exceeded by uid %i, (%s) "
                            "please see tuning(7).\n", td->td_ucred->cr_ruid, td->td_proc->p_comm);
                }
                return (ENFILE);
        }
        fp = uma_zalloc(file_zone, M_WAITOK);
        bzero(fp, sizeof(*fp));
        refcount_init(&fp->f_count, n);
        fp->f_cred = crhold(td->td_ucred);
        fp->f_ops = &badfileops;
        *resultfp = fp;
        return (0);
}

void
falloc_abort(struct thread *td, struct file *fp)
{

        /*
         * For assertion purposes.
         */
        refcount_init(&fp->f_count, 0);
        _fdrop(fp, td);
}

/*
 * Install a file in a file descriptor table.
 */
void
_finstall(struct filedesc *fdp, struct file *fp, int fd, int flags,
    struct filecaps *fcaps)
{
        struct filedescent *fde;

        MPASS(fp != NULL);
        if (fcaps != NULL)
                filecaps_validate(fcaps, __func__);
        FILEDESC_XLOCK_ASSERT(fdp);

        fde = &fdp->fd_ofiles[fd];
#ifdef CAPABILITIES
        seqc_write_begin(&fde->fde_seqc);
#endif
        fde->fde_file = fp;
        fde->fde_flags = (flags & O_CLOEXEC) != 0 ? UF_EXCLOSE : 0;
        if (fcaps != NULL)
                filecaps_move(fcaps, &fde->fde_caps);
        else
                filecaps_fill(&fde->fde_caps);
#ifdef CAPABILITIES
        seqc_write_end(&fde->fde_seqc);
#endif
}

int
finstall_refed(struct thread *td, struct file *fp, int *fd, int flags,
    struct filecaps *fcaps)
{
        struct filedesc *fdp = td->td_proc->p_fd;
        int error;

        MPASS(fd != NULL);

        FILEDESC_XLOCK(fdp);
        error = fdalloc(td, 0, fd);
        if (__predict_true(error == 0)) {
                _finstall(fdp, fp, *fd, flags, fcaps);
        }
        FILEDESC_XUNLOCK(fdp);
        return (error);
}

int
finstall(struct thread *td, struct file *fp, int *fd, int flags,
    struct filecaps *fcaps)
{
        int error;

        MPASS(fd != NULL);

        if (!fhold(fp))
                return (EBADF);
        error = finstall_refed(td, fp, fd, flags, fcaps);
        if (__predict_false(error != 0)) {
                fdrop(fp, td);
        }
        return (error);
}

/*
 * Build a new filedesc structure from another.
 *
 * If fdp is not NULL, return with it shared locked.
 */
struct filedesc *
fdinit(struct filedesc *fdp, bool prepfiles, int *lastfile)
{
        struct filedesc0 *newfdp0;
        struct filedesc *newfdp;

        if (prepfiles)
                MPASS(lastfile != NULL);
        else
                MPASS(lastfile == NULL);

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

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

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

        FILEDESC_SLOCK(fdp);
        if (!prepfiles) {
                FILEDESC_SUNLOCK(fdp);
                return (newfdp);
        }

        for (;;) {
                *lastfile = fdlastfile(fdp);
                if (*lastfile < newfdp->fd_nfiles)
                        break;
                FILEDESC_SUNLOCK(fdp);
                fdgrowtable(newfdp, *lastfile + 1);
                FILEDESC_SLOCK(fdp);
        }

        return (newfdp);
}

/*
 * Build a pwddesc structure from another.
 * Copy the current, root, and jail root vnode references.
 *
 * If pdp is not NULL, return with it shared locked.
 */
struct pwddesc *
pdinit(struct pwddesc *pdp, bool keeplock)
{
        struct pwddesc *newpdp;
        struct pwd *newpwd;

        newpdp = malloc(sizeof(*newpdp), M_PWDDESC, M_WAITOK | M_ZERO);

        PWDDESC_LOCK_INIT(newpdp);
        refcount_init(&newpdp->pd_refcount, 1);
        newpdp->pd_cmask = CMASK;

        if (pdp == NULL) {
                newpwd = pwd_alloc();
                smr_serialized_store(&newpdp->pd_pwd, newpwd, true);
                return (newpdp);
        }

        PWDDESC_XLOCK(pdp);
        newpwd = pwd_hold_pwddesc(pdp);
        smr_serialized_store(&newpdp->pd_pwd, newpwd, true);
        if (!keeplock)
                PWDDESC_XUNLOCK(pdp);
        return (newpdp);
}

/*
 * Hold either filedesc or pwddesc of the passed process.
 *
 * The process lock is used to synchronize against the target exiting and
 * freeing the data.
 *
 * Clearing can be ilustrated in 3 steps:
 * 1. set the pointer to NULL. Either routine can race against it, hence
 *   atomic_load_ptr.
 * 2. observe the process lock as not taken. Until then fdhold/pdhold can
 *   race to either still see the pointer or find NULL. It is still safe to
 *   grab a reference as clearing is stalled.
 * 3. after the lock is observed as not taken, any fdhold/pdhold calls are
 *   guaranteed to see NULL, making it safe to finish clearing
 */
static struct filedesc *
fdhold(struct proc *p)
{
        struct filedesc *fdp;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        fdp = atomic_load_ptr(&p->p_fd);
        if (fdp != NULL)
                refcount_acquire(&fdp->fd_holdcnt);
        return (fdp);
}

static struct pwddesc *
pdhold(struct proc *p)
{
        struct pwddesc *pdp;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        pdp = atomic_load_ptr(&p->p_pd);
        if (pdp != NULL)
                refcount_acquire(&pdp->pd_refcount);
        return (pdp);
}

static void
fddrop(struct filedesc *fdp)
{

        if (refcount_load(&fdp->fd_holdcnt) > 1) {
                if (refcount_release(&fdp->fd_holdcnt) == 0)
                        return;
        }

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

static void
pddrop(struct pwddesc *pdp)
{
        struct pwd *pwd;

        if (refcount_release_if_not_last(&pdp->pd_refcount))
                return;

        PWDDESC_XLOCK(pdp);
        if (refcount_release(&pdp->pd_refcount) == 0) {
                PWDDESC_XUNLOCK(pdp);
                return;
        }
        pwd = PWDDESC_XLOCKED_LOAD_PWD(pdp);
        pwd_set(pdp, NULL);
        PWDDESC_XUNLOCK(pdp);
        pwd_drop(pwd);

        PWDDESC_LOCK_DESTROY(pdp);
        free(pdp, M_PWDDESC);
}

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

        refcount_acquire(&fdp->fd_refcnt);
        return (fdp);
}

/*
 * Share a pwddesc structure.
 */
struct pwddesc *
pdshare(struct pwddesc *pdp)
{
        refcount_acquire(&pdp->pd_refcount);
        return (pdp);
}

/*
 * 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 (refcount_load(&p->p_fd->fd_refcnt) == 1)
                return;

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

/*
 * Unshare a pwddesc structure.
 */
void
pdunshare(struct thread *td)
{
        struct pwddesc *pdp;
        struct proc *p;

        p = td->td_proc;
        /* Not shared. */
        if (p->p_pd->pd_refcount == 1)
                return;

        pdp = pdcopy(p->p_pd);
        pdescfree(td);
        p->p_pd = pdp;
}

/*
 * 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, lastfile;

        MPASS(fdp != NULL);

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

/*
 * Copy a pwddesc structure.
 */
struct pwddesc *
pdcopy(struct pwddesc *pdp)
{
        struct pwddesc *newpdp;

        MPASS(pdp != NULL);

        newpdp = pdinit(pdp, true);
        newpdp->pd_cmask = pdp->pd_cmask;
        PWDDESC_XUNLOCK(pdp);
        return (newpdp);
}

/*
 * 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, lastfile;

        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) {
                lastfile = fdlastfile(fdp);
                for (i = 0; i <= lastfile; i++) {
                        fp = fdp->fd_ofiles[i].fde_file;
                        if (fp == NULL || fp->f_type != DTYPE_VNODE ||
                            !fhold(fp))
                                continue;
                        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 kern_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.
 */
static void
fdescfree_fds(struct thread *td, struct filedesc *fdp)
{
        struct filedesc0 *fdp0;
        struct freetable *ft, *tft;
        struct filedescent *fde;
        struct file *fp;
        int i, lastfile;

        KASSERT(refcount_load(&fdp->fd_refcnt) == 0,
            ("%s: fd table %p carries references", __func__, fdp));

        /*
         * Serialize with threads iterating over the table, if any.
         */
        if (refcount_load(&fdp->fd_holdcnt) > 1) {
                FILEDESC_XLOCK(fdp);
                FILEDESC_XUNLOCK(fdp);
        }

        lastfile = fdlastfile_single(fdp);
        for (i = 0; i <= 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);

        fddrop(fdp);
}

void
fdescfree(struct thread *td)
{
        struct proc *p;
        struct filedesc *fdp;

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

#ifdef RACCT
        if (RACCT_ENABLED())
                racct_set_unlocked(p, RACCT_NOFILE, 0);
#endif

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

        /*
         * Check fdhold for an explanation.
         */
        atomic_store_ptr(&p->p_fd, NULL);
        atomic_thread_fence_seq_cst();
        PROC_WAIT_UNLOCKED(p);

        if (refcount_release(&fdp->fd_refcnt) == 0)
                return;

        fdescfree_fds(td, fdp);
}

void
pdescfree(struct thread *td)
{
        struct proc *p;
        struct pwddesc *pdp;

        p = td->td_proc;
        pdp = p->p_pd;
        MPASS(pdp != NULL);

        /*
         * Check pdhold for an explanation.
         */
        atomic_store_ptr(&p->p_pd, NULL);
        atomic_thread_fence_seq_cst();
        PROC_WAIT_UNLOCKED(p);

        pddrop(pdp);
}

/*
 * 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(refcount_load(&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 thread *td, struct file *fp, int idx)
{
        struct filedesc *fdp = td->td_proc->p_fd;

        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, lastfile;

        fdp = td->td_proc->p_fd;
        KASSERT(refcount_load(&fdp->fd_refcnt) == 1,
            ("the fdtable should not be shared"));
        lastfile = fdlastfile_single(fdp);
        for (i = 0; i <= 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, false, false);
                        FILEDESC_UNLOCK_ASSERT(fdp);
                }
        }
}

/*
 * It is unsafe for set[ug]id processes to be started with file
 * descriptors 0..2 closed, as these descriptors are given implicit
 * significance in the Standard C library.  fdcheckstd() will create a
 * descriptor referencing /dev/null for each of stdin, stdout, and
 * stderr that is not already open.
 */
int
fdcheckstd(struct thread *td)
{
        struct filedesc *fdp;
        register_t save;
        int i, error, devnull;

        fdp = td->td_proc->p_fd;
        KASSERT(refcount_load(&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 = kern_dup(td, FDDUP_FIXED, 0, 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.
 */
int
closef(struct file *fp, struct thread *td)
{
        struct vnode *vp;
        struct flock lf;
        struct filedesc_to_leader *fdtol;
        struct filedesc *fdp;

        MPASS(td != NULL);

        /*
         * 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) {
                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_close(fp, td));
}

/*
 * Hack for file descriptor passing code.
 */
void
closef_nothread(struct file *fp)
{

        fdrop(fp, NULL);
}

/*
 * 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);
}

void
finit_vnode(struct file *fp, u_int flag, void *data, struct fileops *ops)
{
        fp->f_seqcount[UIO_READ] = 1;
        fp->f_seqcount[UIO_WRITE] = 1;
        finit(fp, (flag & FMASK) | (fp->f_flag & FHASLOCK), DTYPE_VNODE,
            data, ops);
}

int
fget_cap_locked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
    struct file **fpp, struct filecaps *havecapsp)
{
        struct filedescent *fde;
        int error;

        FILEDESC_LOCK_ASSERT(fdp);

        *fpp = NULL;
        fde = fdeget_locked(fdp, fd);
        if (fde == NULL) {
                error = EBADF;
                goto out;
        }

#ifdef CAPABILITIES
        error = cap_check(cap_rights_fde_inline(fde), needrightsp);
        if (error != 0)
                goto out;
#endif

        if (havecapsp != NULL)
                filecaps_copy(&fde->fde_caps, havecapsp, true);

        *fpp = fde->fde_file;

        error = 0;
out:
        return (error);
}

#ifdef CAPABILITIES
int
fget_cap(struct thread *td, int fd, cap_rights_t *needrightsp,
    struct file **fpp, struct filecaps *havecapsp)
{
        struct filedesc *fdp = td->td_proc->p_fd;
        int error;
        struct file *fp;
        seqc_t seq;

        *fpp = NULL;
        for (;;) {
                error = fget_unlocked_seq(fdp, fd, needrightsp, &fp, &seq);
                if (error != 0)
                        return (error);

                if (havecapsp != NULL) {
                        if (!filecaps_copy(&fdp->fd_ofiles[fd].fde_caps,
                            havecapsp, false)) {
                                fdrop(fp, td);
                                goto get_locked;
                        }
                }

                if (!fd_modified(fdp, fd, seq))
                        break;
                fdrop(fp, td);
        }

        *fpp = fp;
        return (0);

get_locked:
        FILEDESC_SLOCK(fdp);
        error = fget_cap_locked(fdp, fd, needrightsp, fpp, havecapsp);
        if (error == 0 && !fhold(*fpp))
                error = EBADF;
        FILEDESC_SUNLOCK(fdp);
        return (error);
}
#else
int
fget_cap(struct thread *td, int fd, cap_rights_t *needrightsp,
    struct file **fpp, struct filecaps *havecapsp)
{
        struct filedesc *fdp = td->td_proc->p_fd;
        int error;

        error = fget_unlocked(fdp, fd, needrightsp, fpp);
        if (havecapsp != NULL && error == 0)
                filecaps_fill(havecapsp);

        return (error);
}
#endif

#ifdef CAPABILITIES
int
fgetvp_lookup_smr(int fd, struct nameidata *ndp, struct vnode **vpp, bool *fsearch)
{
        const struct filedescent *fde;
        const struct fdescenttbl *fdt;
        struct filedesc *fdp;
        struct file *fp;
        struct vnode *vp;
        const cap_rights_t *haverights;
        cap_rights_t rights;
        seqc_t seq;

        VFS_SMR_ASSERT_ENTERED();

        rights = *ndp->ni_rightsneeded;
        cap_rights_set_one(&rights, CAP_LOOKUP);

        fdp = curproc->p_fd;
        fdt = fdp->fd_files;
        if (__predict_false((u_int)fd >= fdt->fdt_nfiles))
                return (EBADF);
        seq = seqc_read_notmodify(fd_seqc(fdt, fd));
        fde = &fdt->fdt_ofiles[fd];
        haverights = cap_rights_fde_inline(fde);
        fp = fde->fde_file;
        if (__predict_false(fp == NULL))
                return (EAGAIN);
        if (__predict_false(cap_check_inline_transient(haverights, &rights)))
                return (EAGAIN);
        *fsearch = ((fp->f_flag & FSEARCH) != 0);
        vp = fp->f_vnode;
        if (__predict_false(vp == NULL)) {
                return (EAGAIN);
        }
        if (!filecaps_copy(&fde->fde_caps, &ndp->ni_filecaps, false)) {
                return (EAGAIN);
        }
        /*
         * Use an acquire barrier to force re-reading of fdt so it is
         * refreshed for verification.
         */
        atomic_thread_fence_acq();
        fdt = fdp->fd_files;
        if (__predict_false(!seqc_consistent_nomb(fd_seqc(fdt, fd), seq)))
                return (EAGAIN);
        /*
         * If file descriptor doesn't have all rights,
         * all lookups relative to it must also be
         * strictly relative.
         *
         * Not yet supported by fast path.
         */
        CAP_ALL(&rights);
        if (!cap_rights_contains(&ndp->ni_filecaps.fc_rights, &rights) ||
            ndp->ni_filecaps.fc_fcntls != CAP_FCNTL_ALL ||
            ndp->ni_filecaps.fc_nioctls != -1) {
#ifdef notyet
                ndp->ni_lcf |= NI_LCF_STRICTRELATIVE;
#else
                return (EAGAIN);
#endif
        }
        *vpp = vp;
        return (0);
}
#else
int
fgetvp_lookup_smr(int fd, struct nameidata *ndp, struct vnode **vpp, bool *fsearch)
{
        const struct fdescenttbl *fdt;
        struct filedesc *fdp;
        struct file *fp;
        struct vnode *vp;

        VFS_SMR_ASSERT_ENTERED();

        fdp = curproc->p_fd;
        fdt = fdp->fd_files;
        if (__predict_false((u_int)fd >= fdt->fdt_nfiles))
                return (EBADF);
        fp = fdt->fdt_ofiles[fd].fde_file;
        if (__predict_false(fp == NULL))
                return (EAGAIN);
        *fsearch = ((fp->f_flag & FSEARCH) != 0);
        vp = fp->f_vnode;
        if (__predict_false(vp == NULL || vp->v_type != VDIR)) {
                return (EAGAIN);
        }
        /*
         * Use an acquire barrier to force re-reading of fdt so it is
         * refreshed for verification.
         */
        atomic_thread_fence_acq();
        fdt = fdp->fd_files;
        if (__predict_false(fp != fdt->fdt_ofiles[fd].fde_file))
                return (EAGAIN);
        filecaps_fill(&ndp->ni_filecaps);
        *vpp = vp;
        return (0);
}
#endif

/*
 * 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.
 *
 * Force a reload of fdt when looping. Another thread could reallocate
 * the table before this fd was closed, so it is possible that there is
 * a stale fp pointer in cached version.
 */
#ifdef CAPABILITIES
static int
fget_unlocked_seq(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
    struct file **fpp, seqc_t *seqp)
{
        const struct filedescent *fde;
        const struct fdescenttbl *fdt;
        struct file *fp;
        seqc_t seq;
        cap_rights_t haverights;
        int error;

        fdt = fdp->fd_files;
        if (__predict_false((u_int)fd >= fdt->fdt_nfiles))
                return (EBADF);

        for (;;) {
                seq = seqc_read_notmodify(fd_seqc(fdt, fd));
                fde = &fdt->fdt_ofiles[fd];
                haverights = *cap_rights_fde_inline(fde);
                fp = fde->fde_file;
                if (!seqc_consistent(fd_seqc(fdt, fd), seq))
                        continue;
                if (__predict_false(fp == NULL))
                        return (EBADF);
                error = cap_check_inline(&haverights, needrightsp);
                if (__predict_false(error != 0))
                        return (error);
                if (__predict_false(!refcount_acquire_if_not_zero(&fp->f_count))) {
                        fdt = atomic_load_ptr(&fdp->fd_files);
                        continue;
                }
                /*
                 * Use an acquire barrier to force re-reading of fdt so it is
                 * refreshed for verification.
                 */
                atomic_thread_fence_acq();
                fdt = fdp->fd_files;
                if (seqc_consistent_nomb(fd_seqc(fdt, fd), seq))
                        break;
                fdrop(fp, curthread);
        }
        *fpp = fp;
        if (seqp != NULL) {
                *seqp = seq;
        }
        return (0);
}
#else
static int
fget_unlocked_seq(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
    struct file **fpp, seqc_t *seqp __unused)
{
        const struct fdescenttbl *fdt;
        struct file *fp;

        fdt = fdp->fd_files;
        if (__predict_false((u_int)fd >= fdt->fdt_nfiles))
                return (EBADF);

        for (;;) {
                fp = fdt->fdt_ofiles[fd].fde_file;
                if (__predict_false(fp == NULL))
                        return (EBADF);
                if (__predict_false(!refcount_acquire_if_not_zero(&fp->f_count))) {
                        fdt = atomic_load_ptr(&fdp->fd_files);
                        continue;
                }
                /*
                 * Use an acquire barrier to force re-reading of fdt so it is
                 * refreshed for verification.
                 */
                atomic_thread_fence_acq();
                fdt = fdp->fd_files;
                if (__predict_true(fp == fdt->fdt_ofiles[fd].fde_file))
                        break;
                fdrop(fp, curthread);
        }
        *fpp = fp;
        return (0);
}
#endif

/*
 * See the comments in fget_unlocked_seq for an explanation of how this works.
 *
 * This is a simplified variant which bails out to the aforementioned routine
 * if anything goes wrong. In practice this only happens when userspace is
 * racing with itself.
 */
int
fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
    struct file **fpp)
{
#ifdef CAPABILITIES
        const struct filedescent *fde;
#endif
        const struct fdescenttbl *fdt;
        struct file *fp;
#ifdef CAPABILITIES
        seqc_t seq;
        const cap_rights_t *haverights;
#endif

        fdt = fdp->fd_files;
        if (__predict_false((u_int)fd >= fdt->fdt_nfiles)) {
                *fpp = NULL;
                return (EBADF);
        }
#ifdef CAPABILITIES
        seq = seqc_read_notmodify(fd_seqc(fdt, fd));
        fde = &fdt->fdt_ofiles[fd];
        haverights = cap_rights_fde_inline(fde);
        fp = fde->fde_file;
#else
        fp = fdt->fdt_ofiles[fd].fde_file;
#endif
        if (__predict_false(fp == NULL))
                goto out_fallback;
#ifdef CAPABILITIES
        if (__predict_false(cap_check_inline_transient(haverights, needrightsp)))
                goto out_fallback;
#endif
        if (__predict_false(!refcount_acquire_if_not_zero(&fp->f_count)))
                goto out_fallback;

        /*
         * Use an acquire barrier to force re-reading of fdt so it is
         * refreshed for verification.
         */
        atomic_thread_fence_acq();
        fdt = fdp->fd_files;
#ifdef  CAPABILITIES
        if (__predict_false(!seqc_consistent_nomb(fd_seqc(fdt, fd), seq)))
#else
        if (__predict_false(fp != fdt->fdt_ofiles[fd].fde_file))
#endif
                goto out_fdrop;
        *fpp = fp;
        return (0);
out_fdrop:
        fdrop(fp, curthread);
out_fallback:
        *fpp = NULL;
        return (fget_unlocked_seq(fdp, fd, needrightsp, fpp, NULL));
}

/*
 * Translate fd -> file when the caller guarantees the file descriptor table
 * can't be changed by others.
 *
 * Note this does not mean the file object itself is only visible to the caller,
 * merely that it wont disappear without having to be referenced.
 *
 * Must be paired with fput_only_user.
 */
#ifdef  CAPABILITIES
int
fget_only_user(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
    struct file **fpp)
{
        const struct filedescent *fde;
        const struct fdescenttbl *fdt;
        const cap_rights_t *haverights;
        struct file *fp;
        int error;

        MPASS(FILEDESC_IS_ONLY_USER(fdp));

        *fpp = NULL;
        if (__predict_false(fd >= fdp->fd_nfiles))
                return (EBADF);

        fdt = fdp->fd_files;
        fde = &fdt->fdt_ofiles[fd];
        fp = fde->fde_file;
        if (__predict_false(fp == NULL))
                return (EBADF);
        MPASS(refcount_load(&fp->f_count) > 0);
        haverights = cap_rights_fde_inline(fde);
        error = cap_check_inline(haverights, needrightsp);
        if (__predict_false(error != 0))
                return (error);
        *fpp = fp;
        return (0);
}
#else
int
fget_only_user(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
    struct file **fpp)
{
        struct file *fp;

        MPASS(FILEDESC_IS_ONLY_USER(fdp));

        *fpp = NULL;
        if (__predict_false(fd >= fdp->fd_nfiles))
                return (EBADF);

        fp = fdp->fd_ofiles[fd].fde_file;
        if (__predict_false(fp == NULL))
                return (EBADF);

        MPASS(refcount_load(&fp->f_count) > 0);
        *fpp = fp;
        return (0);
}
#endif

/*
 * 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 occurred 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)
{
        struct filedesc *fdp;
        struct file *fp;
        int error;

        *fpp = NULL;
        fdp = td->td_proc->p_fd;
        error = fget_unlocked(fdp, fd, needrightsp, &fp);
        if (__predict_false(error != 0))
                return (error);
        if (__predict_false(fp->f_ops == &badfileops)) {
                fdrop(fp, td);
                return (EBADF);
        }

        /*
         * 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_ops != &path_fileops &&
                    ((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));
}

int
fget_mmap(struct thread *td, int fd, cap_rights_t *rightsp, vm_prot_t *maxprotp,
    struct file **fpp)
{
        int error;
#ifndef CAPABILITIES
        error = _fget(td, fd, fpp, 0, rightsp);
        if (maxprotp != NULL)
                *maxprotp = VM_PROT_ALL;
        return (error);
#else
        cap_rights_t fdrights;
        struct filedesc *fdp;
        struct file *fp;
        seqc_t seq;

        *fpp = NULL;
        fdp = td->td_proc->p_fd;
        MPASS(cap_rights_is_set(rightsp, CAP_MMAP));
        for (;;) {
                error = fget_unlocked_seq(fdp, fd, rightsp, &fp, &seq);
                if (__predict_false(error != 0))
                        return (error);
                if (__predict_false(fp->f_ops == &badfileops)) {
                        fdrop(fp, td);
                        return (EBADF);
                }
                if (maxprotp != NULL)
                        fdrights = *cap_rights(fdp, fd);
                if (!fd_modified(fdp, fd, seq))
                        break;
                fdrop(fp, td);
        }

        /*
         * If requested, convert capability rights to access flags.
         */
        if (maxprotp != NULL)
                *maxprotp = cap_rights_to_vmprot(&fdrights);
        *fpp = fp;
        return (0);
#endif
}

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

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

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

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

int
fget_fcntl(struct thread *td, int fd, cap_rights_t *rightsp, int needfcntl,
    struct file **fpp)
{
        struct filedesc *fdp = td->td_proc->p_fd;
#ifndef CAPABILITIES
        return (fget_unlocked(fdp, fd, rightsp, fpp));
#else
        struct file *fp;
        int error;
        seqc_t seq;

        *fpp = NULL;
        MPASS(cap_rights_is_set(rightsp, CAP_FCNTL));
        for (;;) {
                error = fget_unlocked_seq(fdp, fd, rightsp, &fp, &seq);
                if (error != 0)
                        return (error);
                error = cap_fcntl_check(fdp, fd, needfcntl);
                if (!fd_modified(fdp, fd, seq))
                        break;
                fdrop(fp, td);
        }
        if (error != 0) {
                fdrop(fp, td);
                return (error);
        }
        *fpp = fp;
        return (0);
#endif
}

/*
 * 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);
        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 filecaps caps;
        struct file *fp;
        int error;

        error = fget_cap(td, fd, needrightsp, &fp, &caps);
        if (error != 0)
                return (error);
        if (fp->f_ops == &badfileops) {
                error = EBADF;
                goto out;
        }
        if (fp->f_vnode == NULL) {
                error = EINVAL;
                goto out;
        }

        *havecaps = caps;
        *vpp = fp->f_vnode;
        vref(*vpp);
        fdrop(fp, td);

        return (0);
out:
        filecaps_free(&caps);
        fdrop(fp, td);
        return (error);
}

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

/*
 * Handle the last reference to a file being closed.
 *
 * Without the noinline attribute clang keeps inlining the func thorough this
 * file when fdrop is used.
 */
int __noinline
_fdrop(struct file *fp, struct thread *td)
{
        int error;
#ifdef INVARIANTS
        int count;

        count = refcount_load(&fp->f_count);
        if (count != 0)
                panic("fdrop: fp %p count %d", fp, count);
#endif
        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;
        int error;

        error = fget(td, uap->fd, &cap_flock_rights, &fp);
        if (error != 0)
                return (error);
        error = EOPNOTSUPP;
        if (fp->f_type != DTYPE_VNODE && fp->f_type != DTYPE_FIFO) {
                goto done;
        }
        if (fp->f_ops == &path_fileops) {
                goto done;
        }

        error = 0;
        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 done;
        }
        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 done;
        }
        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);
done:
        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;
        u_long *ioctls;
        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);
                }
                if (!fhold(fp)) {
                        fdunused(fdp, indx);
                        FILEDESC_XUNLOCK(fdp);
                        return (EBADF);
                }
                newfde = &fdp->fd_ofiles[indx];
                oldfde = &fdp->fd_ofiles[dfd];
                ioctls = filecaps_copy_prep(&oldfde->fde_caps);
#ifdef CAPABILITIES
                seqc_write_begin(&newfde->fde_seqc);
#endif
                memcpy(newfde, oldfde, fde_change_size);
                filecaps_copy_finish(&oldfde->fde_caps, &newfde->fde_caps,
                    ioctls);
#ifdef CAPABILITIES
                seqc_write_end(&newfde->fde_seqc);
#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
                seqc_write_begin(&newfde->fde_seqc);
#endif
                memcpy(newfde, oldfde, fde_change_size);
                oldfde->fde_file = NULL;
                fdunused(fdp, dfd);
#ifdef CAPABILITIES
                seqc_write_end(&newfde->fde_seqc);
#endif
                break;
        }
        FILEDESC_XUNLOCK(fdp);
        *indxp = indx;
        return (0);
}

/*
 * This sysctl determines if we will allow a process to chroot(2) if it
 * has a directory open:
 *      0: disallowed for all processes.
 *      1: allowed for processes that were not already chroot(2)'ed.
 *      2: allowed for all processes.
 */

static int chroot_allow_open_directories = 1;

SYSCTL_INT(_kern, OID_AUTO, chroot_allow_open_directories, CTLFLAG_RW,
    &chroot_allow_open_directories, 0,
    "Allow a process to chroot(2) if it has a directory open");

/*
 * Helper function for raised chroot(2) security function:  Refuse if
 * any filedescriptors are open directories.
 */
static int
chroot_refuse_vdir_fds(struct filedesc *fdp)
{
        struct vnode *vp;
        struct file *fp;
        int fd, lastfile;

        FILEDESC_LOCK_ASSERT(fdp);

        lastfile = fdlastfile(fdp);
        for (fd = 0; fd <= lastfile; fd++) {
                fp = fget_locked(fdp, fd);
                if (fp == NULL)
                        continue;
                if (fp->f_type == DTYPE_VNODE) {
                        vp = fp->f_vnode;
                        if (vp->v_type == VDIR)
                                return (EPERM);
                }
        }
        return (0);
}

static void
pwd_fill(struct pwd *oldpwd, struct pwd *newpwd)
{

        if (newpwd->pwd_cdir == NULL && oldpwd->pwd_cdir != NULL) {
                vrefact(oldpwd->pwd_cdir);
                newpwd->pwd_cdir = oldpwd->pwd_cdir;
        }

        if (newpwd->pwd_rdir == NULL && oldpwd->pwd_rdir != NULL) {
                vrefact(oldpwd->pwd_rdir);
                newpwd->pwd_rdir = oldpwd->pwd_rdir;
        }

        if (newpwd->pwd_jdir == NULL && oldpwd->pwd_jdir != NULL) {
                vrefact(oldpwd->pwd_jdir);
                newpwd->pwd_jdir = oldpwd->pwd_jdir;
        }
}

struct pwd *
pwd_hold_pwddesc(struct pwddesc *pdp)
{
        struct pwd *pwd;

        PWDDESC_ASSERT_XLOCKED(pdp);
        pwd = PWDDESC_XLOCKED_LOAD_PWD(pdp);
        if (pwd != NULL)
                refcount_acquire(&pwd->pwd_refcount);
        return (pwd);
}

bool
pwd_hold_smr(struct pwd *pwd)
{

        MPASS(pwd != NULL);
        if (__predict_true(refcount_acquire_if_not_zero(&pwd->pwd_refcount))) {
                return (true);
        }
        return (false);
}

struct pwd *
pwd_hold(struct thread *td)
{
        struct pwddesc *pdp;
        struct pwd *pwd;

        pdp = td->td_proc->p_pd;

        vfs_smr_enter();
        pwd = vfs_smr_entered_load(&pdp->pd_pwd);
        if (pwd_hold_smr(pwd)) {
                vfs_smr_exit();
                return (pwd);
        }
        vfs_smr_exit();
        PWDDESC_XLOCK(pdp);
        pwd = pwd_hold_pwddesc(pdp);
        MPASS(pwd != NULL);
        PWDDESC_XUNLOCK(pdp);
        return (pwd);
}

struct pwd *
pwd_hold_proc(struct proc *p)
{
        struct pwddesc *pdp;
        struct pwd *pwd;

        PROC_ASSERT_HELD(p);
        PROC_LOCK(p);
        pdp = pdhold(p);
        MPASS(pdp != NULL);
        PROC_UNLOCK(p);

        PWDDESC_XLOCK(pdp);
        pwd = pwd_hold_pwddesc(pdp);
        MPASS(pwd != NULL);
        PWDDESC_XUNLOCK(pdp);
        pddrop(pdp);
        return (pwd);
}

static struct pwd *
pwd_alloc(void)
{
        struct pwd *pwd;

        pwd = uma_zalloc_smr(pwd_zone, M_WAITOK);
        bzero(pwd, sizeof(*pwd));
        refcount_init(&pwd->pwd_refcount, 1);
        return (pwd);
}

void
pwd_drop(struct pwd *pwd)
{

        if (!refcount_release(&pwd->pwd_refcount))
                return;

        if (pwd->pwd_cdir != NULL)
                vrele(pwd->pwd_cdir);
        if (pwd->pwd_rdir != NULL)
                vrele(pwd->pwd_rdir);
        if (pwd->pwd_jdir != NULL)
                vrele(pwd->pwd_jdir);
        uma_zfree_smr(pwd_zone, pwd);
}

/*
* The caller is responsible for invoking priv_check() and
* mac_vnode_check_chroot() to authorize this operation.
*/
int
pwd_chroot(struct thread *td, struct vnode *vp)
{
        struct pwddesc *pdp;
        struct filedesc *fdp;
        struct pwd *newpwd, *oldpwd;
        int error;

        fdp = td->td_proc->p_fd;
        pdp = td->td_proc->p_pd;
        newpwd = pwd_alloc();
        FILEDESC_SLOCK(fdp);
        PWDDESC_XLOCK(pdp);
        oldpwd = PWDDESC_XLOCKED_LOAD_PWD(pdp);
        if (chroot_allow_open_directories == 0 ||
            (chroot_allow_open_directories == 1 &&
            oldpwd->pwd_rdir != rootvnode)) {
                error = chroot_refuse_vdir_fds(fdp);
                FILEDESC_SUNLOCK(fdp);
                if (error != 0) {
                        PWDDESC_XUNLOCK(pdp);
                        pwd_drop(newpwd);
                        return (error);
                }
        } else {
                FILEDESC_SUNLOCK(fdp);
        }

        vrefact(vp);
        newpwd->pwd_rdir = vp;
        if (oldpwd->pwd_jdir == NULL) {
                vrefact(vp);
                newpwd->pwd_jdir = vp;
        }
        pwd_fill(oldpwd, newpwd);
        pwd_set(pdp, newpwd);
        PWDDESC_XUNLOCK(pdp);
        pwd_drop(oldpwd);
        return (0);
}

void
pwd_chdir(struct thread *td, struct vnode *vp)
{
        struct pwddesc *pdp;
        struct pwd *newpwd, *oldpwd;

        VNPASS(vp->v_usecount > 0, vp);

        newpwd = pwd_alloc();
        pdp = td->td_proc->p_pd;
        PWDDESC_XLOCK(pdp);
        oldpwd = PWDDESC_XLOCKED_LOAD_PWD(pdp);
        newpwd->pwd_cdir = vp;
        pwd_fill(oldpwd, newpwd);
        pwd_set(pdp, newpwd);
        PWDDESC_XUNLOCK(pdp);
        pwd_drop(oldpwd);
}

/*
 * jail_attach(2) changes both root and working directories.
 */
int
pwd_chroot_chdir(struct thread *td, struct vnode *vp)
{
        struct pwddesc *pdp;
        struct filedesc *fdp;
        struct pwd *newpwd, *oldpwd;
        int error;

        fdp = td->td_proc->p_fd;
        pdp = td->td_proc->p_pd;
        newpwd = pwd_alloc();
        FILEDESC_SLOCK(fdp);
        PWDDESC_XLOCK(pdp);
        oldpwd = PWDDESC_XLOCKED_LOAD_PWD(pdp);
        error = chroot_refuse_vdir_fds(fdp);
        FILEDESC_SUNLOCK(fdp);
        if (error != 0) {
                PWDDESC_XUNLOCK(pdp);
                pwd_drop(newpwd);
                return (error);
        }

        vrefact(vp);
        newpwd->pwd_rdir = vp;
        vrefact(vp);
        newpwd->pwd_cdir = vp;
        if (oldpwd->pwd_jdir == NULL) {
                vrefact(vp);
                newpwd->pwd_jdir = vp;
        }
        pwd_fill(oldpwd, newpwd);
        pwd_set(pdp, newpwd);
        PWDDESC_XUNLOCK(pdp);
        pwd_drop(oldpwd);
        return (0);
}

void
pwd_ensure_dirs(void)
{
        struct pwddesc *pdp;
        struct pwd *oldpwd, *newpwd;

        pdp = curproc->p_pd;
        PWDDESC_XLOCK(pdp);
        oldpwd = PWDDESC_XLOCKED_LOAD_PWD(pdp);
        if (oldpwd->pwd_cdir != NULL && oldpwd->pwd_rdir != NULL) {
                PWDDESC_XUNLOCK(pdp);
                return;
        }
        PWDDESC_XUNLOCK(pdp);

        newpwd = pwd_alloc();
        PWDDESC_XLOCK(pdp);
        oldpwd = PWDDESC_XLOCKED_LOAD_PWD(pdp);
        pwd_fill(oldpwd, newpwd);
        if (newpwd->pwd_cdir == NULL) {
                vrefact(rootvnode);
                newpwd->pwd_cdir = rootvnode;
        }
        if (newpwd->pwd_rdir == NULL) {
                vrefact(rootvnode);
                newpwd->pwd_rdir = rootvnode;
        }
        pwd_set(pdp, newpwd);
        PWDDESC_XUNLOCK(pdp);
        pwd_drop(oldpwd);
}

void
pwd_set_rootvnode(void)
{
        struct pwddesc *pdp;
        struct pwd *oldpwd, *newpwd;

        pdp = curproc->p_pd;

        newpwd = pwd_alloc();
        PWDDESC_XLOCK(pdp);
        oldpwd = PWDDESC_XLOCKED_LOAD_PWD(pdp);
        vrefact(rootvnode);
        newpwd->pwd_cdir = rootvnode;
        vrefact(rootvnode);
        newpwd->pwd_rdir = rootvnode;
        pwd_fill(oldpwd, newpwd);
        pwd_set(pdp, newpwd);
        PWDDESC_XUNLOCK(pdp);
        pwd_drop(oldpwd);
}

/*
 * 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 pwddesc *pdp;
        struct pwd *newpwd, *oldpwd;
        struct prison *pr;
        struct proc *p;
        int nrele;

        if (vrefcnt(olddp) == 1)
                return;
        nrele = 0;
        newpwd = pwd_alloc();
        sx_slock(&allproc_lock);
        FOREACH_PROC_IN_SYSTEM(p) {
                PROC_LOCK(p);
                pdp = pdhold(p);
                PROC_UNLOCK(p);
                if (pdp == NULL)
                        continue;
                PWDDESC_XLOCK(pdp);
                oldpwd = PWDDESC_XLOCKED_LOAD_PWD(pdp);
                if (oldpwd == NULL ||
                    (oldpwd->pwd_cdir != olddp &&
                    oldpwd->pwd_rdir != olddp &&
                    oldpwd->pwd_jdir != olddp)) {
                        PWDDESC_XUNLOCK(pdp);
                        pddrop(pdp);
                        continue;
                }
                if (oldpwd->pwd_cdir == olddp) {
                        vrefact(newdp);
                        newpwd->pwd_cdir = newdp;
                }
                if (oldpwd->pwd_rdir == olddp) {
                        vrefact(newdp);
                        newpwd->pwd_rdir = newdp;
                }
                if (oldpwd->pwd_jdir == olddp) {
                        vrefact(newdp);
                        newpwd->pwd_jdir = newdp;
                }
                pwd_fill(oldpwd, newpwd);
                pwd_set(pdp, newpwd);
                PWDDESC_XUNLOCK(pdp);
                pwd_drop(oldpwd);
                pddrop(pdp);
                newpwd = pwd_alloc();
        }
        sx_sunlock(&allproc_lock);
        pwd_drop(newpwd);
        if (rootvnode == olddp) {
                vrefact(newdp);
                rootvnode = newdp;
                nrele++;
        }
        mtx_lock(&prison0.pr_mtx);
        if (prison0.pr_root == olddp) {
                vrefact(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) {
                        vrefact(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);
}

static int
sysctl_kern_proc_nfds(SYSCTL_HANDLER_ARGS)
{
        NDSLOTTYPE *map;
        struct filedesc *fdp;
        u_int namelen;
        int count, off, minoff;

        namelen = arg2;
        if (namelen != 1)
                return (EINVAL);

        if (*(int *)arg1 != 0)
                return (EINVAL);

        fdp = curproc->p_fd;
        count = 0;
        FILEDESC_SLOCK(fdp);
        map = fdp->fd_map;
        off = NDSLOT(fdp->fd_nfiles - 1);
        for (minoff = NDSLOT(0); off >= minoff; --off)
                count += bitcountl(map[off]);
        FILEDESC_SUNLOCK(fdp);

        return (SYSCTL_OUT(req, &count, sizeof(count)));
}

static SYSCTL_NODE(_kern_proc, KERN_PROC_NFDS, nfds,
    CTLFLAG_RD|CTLFLAG_CAPRD|CTLFLAG_MPSAFE, sysctl_kern_proc_nfds,
    "Number of open file descriptors");

/*
 * 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, lastfile;

        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) {
                        PROC_LOCK(p);
                        if (p->p_state == PRS_NEW) {
                                PROC_UNLOCK(p);
                                continue;
                        }
                        fdp = fdhold(p);
                        PROC_UNLOCK(p);
                        if (fdp == NULL)
                                continue;
                        /* overestimates sparse tables. */
                        n += fdp->fd_nfiles;
                        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;
                fdp = fdhold(p);
                PROC_UNLOCK(p);
                if (fdp == NULL)
                        continue;
                FILEDESC_SLOCK(fdp);
                lastfile = fdlastfile(fdp);
                for (n = 0; refcount_load(&fdp->fd_refcnt) > 0 && n <= lastfile;
                    n++) {
                        if ((fp = fdp->fd_ofiles[n].fde_file) == NULL)
                                continue;
                        xf.xf_fd = n;
                        xf.xf_file = (uintptr_t)fp;
                        xf.xf_data = (uintptr_t)fp->f_data;
                        xf.xf_vnode = (uintptr_t)fp->f_vnode;
                        xf.xf_type = (uintptr_t)fp->f_type;
                        xf.xf_count = refcount_load(&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. */
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 flags)
{
        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_zero(&kif->kf_cap_rights);
        kif->kf_fd = fd;
        kif->kf_ref_count = refcount_load(&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;
        if ((flags & KERN_FILEDESC_PACK_KINFO) != 0)
                pack_kinfo(kif);
        else
                kif->kf_structsize = roundup2(sizeof(*kif), sizeof(uint64_t));
}

static void
export_vnode_to_kinfo(struct vnode *vp, int fd, int fflags,
    struct kinfo_file *kif, int flags)
{
        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_zero(&kif->kf_cap_rights);
        kif->kf_fd = fd;
        kif->kf_ref_count = -1;
        kif->kf_offset = -1;
        if ((flags & KERN_FILEDESC_PACK_KINFO) != 0)
                pack_kinfo(kif);
        else
                kif->kf_structsize = roundup2(sizeof(*kif), sizeof(uint64_t));
        vrele(vp);
}

struct export_fd_buf {
        struct filedesc         *fdp;
        struct pwddesc  *pdp;
        struct sbuf             *sb;
        ssize_t                 remainder;
        struct kinfo_file       kif;
        int                     flags;
};

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)
                        return (ENOMEM);
                efbuf->remainder -= kif->kf_structsize;
        }
        if (sbuf_bcat(efbuf->sb, kif, kif->kf_structsize) != 0)
                return (sbuf_error(efbuf->sb));
        return (0);
}

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 (ENOMEM);
        export_file_to_kinfo(fp, fd, rightsp, &efbuf->kif, efbuf->fdp,
            efbuf->flags);
        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 (ENOMEM);
        if (efbuf->pdp != NULL)
                PWDDESC_XUNLOCK(efbuf->pdp);
        export_vnode_to_kinfo(vp, fd, fflags, &efbuf->kif, efbuf->flags);
        error = export_kinfo_to_sb(efbuf);
        if (efbuf->pdp != NULL)
                PWDDESC_XLOCK(efbuf->pdp);
        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,
    int flags)
{
        struct file *fp;
        struct filedesc *fdp;
        struct pwddesc *pdp;
        struct export_fd_buf *efbuf;
        struct vnode *cttyvp, *textvp, *tracevp;
        struct pwd *pwd;
        int error, i, lastfile;
        cap_rights_t rights;

        PROC_LOCK_ASSERT(p, MA_OWNED);

        /* ktrace vnode */
        tracevp = ktr_get_tracevp(p, true);
        /* text vnode */
        textvp = p->p_textvp;
        if (textvp != NULL)
                vrefact(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)
                        vrefact(cttyvp);
        }
        fdp = fdhold(p);
        pdp = pdhold(p);
        PROC_UNLOCK(p);

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

        error = 0;
        if (tracevp != NULL)
                error = export_vnode_to_sb(tracevp, KF_FD_TYPE_TRACE,
                    FREAD | FWRITE, efbuf);
        if (error == 0 && textvp != NULL)
                error = export_vnode_to_sb(textvp, KF_FD_TYPE_TEXT, FREAD,
                    efbuf);
        if (error == 0 && cttyvp != NULL)
                error = export_vnode_to_sb(cttyvp, KF_FD_TYPE_CTTY,
                    FREAD | FWRITE, efbuf);
        if (error != 0 || pdp == NULL || fdp == NULL)
                goto fail;
        efbuf->fdp = fdp;
        efbuf->pdp = pdp;
        PWDDESC_XLOCK(pdp);
        pwd = pwd_hold_pwddesc(pdp);
        if (pwd != NULL) {
                /* working directory */
                if (pwd->pwd_cdir != NULL) {
                        vrefact(pwd->pwd_cdir);
                        error = export_vnode_to_sb(pwd->pwd_cdir,
                            KF_FD_TYPE_CWD, FREAD, efbuf);
                }
                /* root directory */
                if (error == 0 && pwd->pwd_rdir != NULL) {
                        vrefact(pwd->pwd_rdir);
                        error = export_vnode_to_sb(pwd->pwd_rdir,
                            KF_FD_TYPE_ROOT, FREAD, efbuf);
                }
                /* jail directory */
                if (error == 0 && pwd->pwd_jdir != NULL) {
                        vrefact(pwd->pwd_jdir);
                        error = export_vnode_to_sb(pwd->pwd_jdir,
                            KF_FD_TYPE_JAIL, FREAD, efbuf);
                }
        }
        PWDDESC_XUNLOCK(pdp);
        if (error != 0)
                goto fail;
        if (pwd != NULL)
                pwd_drop(pwd);
        FILEDESC_SLOCK(fdp);
        lastfile = fdlastfile(fdp);
        for (i = 0; refcount_load(&fdp->fd_refcnt) > 0 && i <= lastfile; i++) {
                if ((fp = fdp->fd_ofiles[i].fde_file) == NULL)
                        continue;
#ifdef CAPABILITIES
                rights = *cap_rights(fdp, i);
#else /* !CAPABILITIES */
                rights = cap_no_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)
                        break;
        }
        FILEDESC_SUNLOCK(fdp);
fail:
        if (fdp != NULL)
                fddrop(fdp);
        if (pdp != NULL)
                pddrop(pdp);
        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;
        u_int namelen;
        int error, error2, *name;

        namelen = arg2;
        if (namelen != 1)
                return (EINVAL);

        name = (int *)arg1;

        sbuf_new_for_sysctl(&sb, NULL, FILEDESC_SBUF_SIZE, req);
        sbuf_clear_flags(&sb, SBUF_INCLUDENUL);
        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,
            KERN_FILEDESC_PACK_KINFO);
        error2 = sbuf_finish(&sb);
        sbuf_delete(&sb);
        return (error != 0 ? error : error2);
}

#ifdef COMPAT_FREEBSD7
#ifdef KINFO_OFILE_SIZE
CTASSERT(sizeof(struct kinfo_ofile) == KINFO_OFILE_SIZE);
#endif

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;
        if (kif->kf_type == KF_TYPE_VNODE)
                okif->kf_vnode_type = kif->kf_un.kf_file.kf_file_type;
        else
                okif->kf_vnode_type = KF_VTYPE_VNON;
        strlcpy(okif->kf_path, kif->kf_path, sizeof(okif->kf_path));
        if (kif->kf_type == KF_TYPE_SOCKET) {
                okif->kf_sock_domain = kif->kf_un.kf_sock.kf_sock_domain0;
                okif->kf_sock_type = kif->kf_un.kf_sock.kf_sock_type0;
                okif->kf_sock_protocol = kif->kf_un.kf_sock.kf_sock_protocol0;
                okif->kf_sa_local = kif->kf_un.kf_sock.kf_sa_local;
                okif->kf_sa_peer = kif->kf_un.kf_sock.kf_sa_peer;
        } else {
                okif->kf_sa_local.ss_family = AF_UNSPEC;
                okif->kf_sa_peer.ss_family = AF_UNSPEC;
        }
}

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

        vrefact(vp);
        PWDDESC_XUNLOCK(pdp);
        export_vnode_to_kinfo(vp, type, 0, kif, KERN_FILEDESC_PACK_KINFO);
        kinfo_to_okinfo(kif, okif);
        error = SYSCTL_OUT(req, okif, sizeof(*okif));
        PWDDESC_XLOCK(pdp);
        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;
        struct pwddesc *pdp;
        struct pwd *pwd;
        u_int namelen;
        int error, i, lastfile, *name;
        struct file *fp;
        struct proc *p;

        namelen = arg2;
        if (namelen != 1)
                return (EINVAL);

        name = (int *)arg1;
        error = pget((pid_t)name[0], PGET_CANDEBUG | PGET_NOTWEXIT, &p);
        if (error != 0)
                return (error);
        fdp = fdhold(p);
        if (fdp != NULL)
                pdp = pdhold(p);
        PROC_UNLOCK(p);
        if (fdp == NULL || pdp == NULL) {
                if (fdp != NULL)
                        fddrop(fdp);
                return (ENOENT);
        }
        kif = malloc(sizeof(*kif), M_TEMP, M_WAITOK);
        okif = malloc(sizeof(*okif), M_TEMP, M_WAITOK);
        PWDDESC_XLOCK(pdp);
        pwd = pwd_hold_pwddesc(pdp);
        if (pwd != NULL) {
                if (pwd->pwd_cdir != NULL)
                        export_vnode_for_osysctl(pwd->pwd_cdir, KF_FD_TYPE_CWD, kif,
                            okif, pdp, req);
                if (pwd->pwd_rdir != NULL)
                        export_vnode_for_osysctl(pwd->pwd_rdir, KF_FD_TYPE_ROOT, kif,
                            okif, pdp, req);
                if (pwd->pwd_jdir != NULL)
                        export_vnode_for_osysctl(pwd->pwd_jdir, KF_FD_TYPE_JAIL, kif,
                            okif, pdp, req);
        }
        PWDDESC_XUNLOCK(pdp);
        if (pwd != NULL)
                pwd_drop(pwd);
        FILEDESC_SLOCK(fdp);
        lastfile = fdlastfile(fdp);
        for (i = 0; refcount_load(&fdp->fd_refcnt) > 0 && i <= lastfile; i++) {
                if ((fp = fdp->fd_ofiles[i].fde_file) == NULL)
                        continue;
                export_file_to_kinfo(fp, i, NULL, kif, fdp,
                    KERN_FILEDESC_PACK_KINFO);
                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);
        pddrop(pdp);
        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 pwddesc *pdp;
        struct pwd *pwd;
        struct export_fd_buf *efbuf;
        struct vnode *cdir;
        int error;

        PROC_LOCK_ASSERT(p, MA_OWNED);

        pdp = pdhold(p);
        PROC_UNLOCK(p);
        if (pdp == NULL)
                return (EINVAL);

        efbuf = malloc(sizeof(*efbuf), M_TEMP, M_WAITOK);
        efbuf->fdp = NULL;
        efbuf->pdp = pdp;
        efbuf->sb = sb;
        efbuf->remainder = maxlen;
        efbuf->flags = 0;

        PWDDESC_XLOCK(pdp);
        pwd = PWDDESC_XLOCKED_LOAD_PWD(pdp);
        cdir = pwd->pwd_cdir;
        if (cdir == NULL) {
                error = EINVAL;
        } else {
                vrefact(cdir);
                error = export_vnode_to_sb(cdir, KF_FD_TYPE_CWD, FREAD, efbuf);
        }
        PWDDESC_XUNLOCK(pdp);
        pddrop(pdp);
        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;
        u_int namelen;
        int error, error2, *name;

        namelen = arg2;
        if (namelen != 1)
                return (EINVAL);

        name = (int *)arg1;

        sbuf_new_for_sysctl(&sb, NULL, sizeof(struct kinfo_file), req);
        sbuf_clear_flags(&sb, SBUF_INCLUDENUL);
        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 ("vnode");
        case DTYPE_SOCKET:
                return ("socket");
        case DTYPE_PIPE:
                return ("pipe");
        case DTYPE_FIFO:
                return ("fifo");
        case DTYPE_KQUEUE:
                return ("kqueue");
        case DTYPE_CRYPTO:
                return ("crypto");
        case DTYPE_MQUEUE:
                return ("mqueue");
        case DTYPE_SHM:
                return ("shm");
        case DTYPE_SEM:
                return ("ksem");
        case DTYPE_PTS:
                return ("pts");
        case DTYPE_DEV:
                return ("dev");
        case DTYPE_PROCDESC:
                return ("proc");
        case DTYPE_EVENTFD:
                return ("eventfd");
        case DTYPE_LINUXTFD:
                return ("ltimer");
        default:
                return ("unkn");
        }
}

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

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

static void
db_print_file(struct file *fp, int header)
{
#define XPTRWIDTH ((int)howmany(sizeof(void *) * NBBY, 4))
        struct proc *p;

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

#undef XPTRWIDTH
}

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

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

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

        header = 1;
        FOREACH_PROC_IN_SYSTEM(p) {
                if (p->p_state == PRS_NEW)
                        continue;
                if ((fdp = p->p_fd) == NULL)
                        continue;
                for (n = 0; n < fdp->fd_nfiles; ++n) {
                        if ((fp = fdp->fd_ofiles[n].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,
    &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);
        pwd_zone = uma_zcreate("PWD", sizeof(struct pwd), NULL, NULL,
            NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_SMR);
        /*
         * XXXMJG this is a temporary hack due to boot ordering issues against
         * the vnode zone.
         */
        vfs_smr = uma_zone_get_smr(pwd_zone);
        mtx_init(&sigio_lock, "sigio lock", 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)
{

        return (EBADF);
}

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

        return (0);
}

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,
    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,
};

static int
path_poll(struct file *fp, int events, struct ucred *active_cred,
    struct thread *td)
{
        return (POLLNVAL);
}

static int
path_close(struct file *fp, struct thread *td)
{
        MPASS(fp->f_type == DTYPE_VNODE);
        fp->f_ops = &badfileops;
        vdrop(fp->f_vnode);
        return (0);
}

struct fileops path_fileops = {
        .fo_read = badfo_readwrite,
        .fo_write = badfo_readwrite,
        .fo_truncate = badfo_truncate,
        .fo_ioctl = badfo_ioctl,
        .fo_poll = path_poll,
        .fo_kqfilter = vn_kqfilter_opath,
        .fo_stat = vn_statfile,
        .fo_close = path_close,
        .fo_chmod = badfo_chmod,
        .fo_chown = badfo_chown,
        .fo_sendfile = badfo_sendfile,
        .fo_fill_kinfo = vn_fill_kinfo,
        .fo_flags = DFLAG_PASSABLE,
};

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,
    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);