/*      $OpenBSD: kern_descrip.c,v 1.213 2026/03/08 16:41:21 deraadt Exp $      */
/*      $NetBSD: kern_descrip.c,v 1.42 1996/03/30 22:24:38 christos Exp $       */

/*
 * 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/param.h>
#include <sys/systm.h>
#include <sys/atomic.h>
#include <sys/filedesc.h>
#include <sys/vnode.h>
#include <sys/proc.h>
#include <sys/file.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/fcntl.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/ucred.h>
#include <sys/unistd.h>
#include <sys/resourcevar.h>
#include <sys/mount.h>
#include <sys/syscallargs.h>
#include <sys/event.h>
#include <sys/pool.h>
#include <sys/ktrace.h>
#include <sys/pledge.h>

/*
 * Descriptor management.
 *
 * We need to block interrupts as long as `fhdlk' is being taken
 * with and without the KERNEL_LOCK().
 */
struct mutex fhdlk = MUTEX_INITIALIZER(IPL_MPFLOOR);
struct filelist filehead;       /* head of list of open files */
int numfiles;                   /* actual number of open files */

static __inline void fd_used(struct filedesc *, int);
static __inline void fd_unused(struct filedesc *, int);
static __inline int find_next_zero(u_int *, int, u_int);
static __inline int fd_inuse(struct filedesc *, int);
int finishdup(struct proc *, struct file *, int, int, register_t *, int);
int find_last_set(struct filedesc *, int);
int dodup3(struct proc *, int, int, int, register_t *);

#define DUPF_CLOEXEC    0x01
#define DUPF_DUP2       0x02
#define DUPF_CLOFORK    0x04

struct pool file_pool;
struct pool fdesc_pool;

void
filedesc_init(void)
{
        pool_init(&file_pool, sizeof(struct file), 0, IPL_MPFLOOR,
            PR_WAITOK, "filepl", NULL);
        pool_init(&fdesc_pool, sizeof(struct filedesc0), 0, IPL_NONE,
            PR_WAITOK, "fdescpl", NULL);
        LIST_INIT(&filehead);
}

static __inline int
find_next_zero(u_int *bitmap, int want, u_int bits)
{
        int i, off, maxoff;
        u_int sub;

        if (want > bits)
                return -1;

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

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

        return -1;

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

int
find_last_set(struct filedesc *fd, int last)
{
        int off, i;
        u_int *bitmap = fd->fd_lomap;

        off = (last - 1) >> NDENTRYSHIFT;

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

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

        while (i > 0 && !fd_inuse(fd, i))
                i--;
        return i;
}

static __inline int
fd_inuse(struct filedesc *fdp, int fd)
{
        u_int off = fd >> NDENTRYSHIFT;

        if (fdp->fd_lomap[off] & (1U << (fd & NDENTRYMASK)))
                return 1;

        return 0;
}

static __inline void
fd_used(struct filedesc *fdp, int fd)
{
        u_int off = fd >> NDENTRYSHIFT;

        fdp->fd_lomap[off] |= 1U << (fd & NDENTRYMASK);
        if (fdp->fd_lomap[off] == ~0)
                fdp->fd_himap[off >> NDENTRYSHIFT] |= 1U << (off & NDENTRYMASK);

        if (fd > fdp->fd_lastfile)
                fdp->fd_lastfile = fd;
        fdp->fd_openfd++;
}

static __inline void
fd_unused(struct filedesc *fdp, int fd)
{
        u_int off = fd >> NDENTRYSHIFT;

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

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

#ifdef DIAGNOSTIC
        if (fd > fdp->fd_lastfile)
                panic("fd_unused: fd_lastfile inconsistent");
#endif
        if (fd == fdp->fd_lastfile)
                fdp->fd_lastfile = find_last_set(fdp, fd);
        fdp->fd_openfd--;
}

struct file *
fd_iterfile(struct file *fp, struct proc *p)
{
        struct file *nfp;
        unsigned int count;

        mtx_enter(&fhdlk);
        if (fp == NULL)
                nfp = LIST_FIRST(&filehead);
        else
                nfp = LIST_NEXT(fp, f_list);

        /* don't refcount when f_count == 0 to avoid race in fdrop() */
        while (nfp != NULL) {
                count = nfp->f_count;
                if (count == 0) {
                        nfp = LIST_NEXT(nfp, f_list);
                        continue;
                }
                if (atomic_cas_uint(&nfp->f_count, count, count + 1) == count)
                        break;
        }
        mtx_leave(&fhdlk);

        if (fp != NULL)
                FRELE(fp, p);

        return nfp;
}

struct file *
fd_getfile(struct filedesc *fdp, int fd)
{
        struct file *fp;

        vfs_stall_barrier();

        if ((u_int)fd >= fdp->fd_nfiles)
                return (NULL);

        mtx_enter(&fdp->fd_fplock);
        fp = fdp->fd_ofiles[fd];
        if (fp != NULL)
                atomic_inc_int(&fp->f_count);
        mtx_leave(&fdp->fd_fplock);

        return (fp);
}

struct file *
fd_getfile_mode(struct filedesc *fdp, int fd, int mode)
{
        struct file *fp;

        KASSERT(mode != 0);

        fp = fd_getfile(fdp, fd);
        if (fp == NULL)
                return (NULL);

        if ((fp->f_flag & mode) == 0) {
                FRELE(fp, curproc);
                return (NULL);
        }

        return (fp);
}

int
fd_checkclosed(struct filedesc *fdp, int fd, struct file *fp)
{
        int closed;

        mtx_enter(&fdp->fd_fplock);
        KASSERT(fd < fdp->fd_nfiles);
        closed = (fdp->fd_ofiles[fd] != fp);
        mtx_leave(&fdp->fd_fplock);
        return (closed);
}

/*
 * System calls on descriptors.
 */

/*
 * Duplicate a file descriptor.
 */
int
sys_dup(struct proc *p, void *v, register_t *retval)
{
        struct sys_dup_args /* {
                syscallarg(int) fd;
        } */ *uap = v;
        struct filedesc *fdp = p->p_fd;
        int old = SCARG(uap, fd);
        struct file *fp;
        int new;
        int error;

restart:
        if ((fp = fd_getfile(fdp, old)) == NULL)
                return (EBADF);
        fdplock(fdp);
        if ((error = fdalloc(p, 0, &new)) != 0) {
                if (error == ENOSPC) {
                        fdexpand(p);
                        fdpunlock(fdp);
                        FRELE(fp, p);
                        goto restart;
                }
                fdpunlock(fdp);
                FRELE(fp, p);
                return (error);
        }
        /* No need for FRELE(), finishdup() uses current ref. */
        return (finishdup(p, fp, old, new, retval, 0));
}

/*
 * Duplicate a file descriptor to a particular value.
 */
int
sys_dup2(struct proc *p, void *v, register_t *retval)
{
        struct sys_dup2_args /* {
                syscallarg(int) from;
                syscallarg(int) to;
        } */ *uap = v;

        return (dodup3(p, SCARG(uap, from), SCARG(uap, to), 0, retval));
}

int
sys_dup3(struct proc *p, void *v, register_t *retval)
{
        struct sys_dup3_args /* {
                syscallarg(int) from;
                syscallarg(int) to;
                syscallarg(int) flags;
        } */ *uap = v;

        if (SCARG(uap, from) == SCARG(uap, to))
                return (EINVAL);
        if (SCARG(uap, flags) & ~(O_CLOEXEC | O_CLOFORK))
                return (EINVAL);
        return (dodup3(p, SCARG(uap, from), SCARG(uap, to),
            SCARG(uap, flags), retval));
}

int
dodup3(struct proc *p, int old, int new, int flags, register_t *retval)
{
        struct filedesc *fdp = p->p_fd;
        struct file *fp;
        int dupflags, error, i;

restart:
        if ((fp = fd_getfile(fdp, old)) == NULL)
                return (EBADF);
        if (old == new) {
                /*
                 * NOTE! This doesn't clear the close-on-exec flag. This might
                 * or might not be the intended behavior from the start, but
                 * this is what everyone else does.
                 */
                *retval = new;
                FRELE(fp, p);
                return (0);
        }
        if ((u_int)new >= lim_cur(RLIMIT_NOFILE) ||
            (u_int)new >= atomic_load_int(&maxfiles)) {
                FRELE(fp, p);
                return (EBADF);
        }
        fdplock(fdp);
        if (new >= fdp->fd_nfiles) {
                if ((error = fdalloc(p, new, &i)) != 0) {
                        if (error == ENOSPC) {
                                fdexpand(p);
                                fdpunlock(fdp);
                                FRELE(fp, p);
                                goto restart;
                        }
                        fdpunlock(fdp);
                        FRELE(fp, p);
                        return (error);
                }
                if (new != i)
                        panic("dup2: fdalloc");
                fd_unused(fdp, new);
        }

        dupflags = DUPF_DUP2;
        if (flags & O_CLOEXEC)
                dupflags |= DUPF_CLOEXEC;
        if (flags & O_CLOFORK)
                dupflags |= DUPF_CLOFORK;

        /* No need for FRELE(), finishdup() uses current ref. */
        return (finishdup(p, fp, old, new, retval, dupflags));
}

/*
 * The file control system call.
 */
int
sys_fcntl(struct proc *p, void *v, register_t *retval)
{
        struct sys_fcntl_args /* {
                syscallarg(int) fd;
                syscallarg(int) cmd;
                syscallarg(void *) arg;
        } */ *uap = v;
        int fd = SCARG(uap, fd);
        struct filedesc *fdp = p->p_fd;
        struct file *fp;
        struct vnode *vp;
        int i, prev, tmp, newmin, flg = F_POSIX;
        struct flock fl;
        int error = 0;

        error = pledge_fcntl(p, SCARG(uap, cmd));
        if (error)
                return (error);

restart:
        if ((fp = fd_getfile(fdp, fd)) == NULL)
                return (EBADF);
        switch (SCARG(uap, cmd)) {

        case F_DUPFD:
        case F_DUPFD_CLOEXEC:
        case F_DUPFD_CLOFORK:
                newmin = (long)SCARG(uap, arg);
                if ((u_int)newmin >= lim_cur(RLIMIT_NOFILE) ||
                    (u_int)newmin >= atomic_load_int(&maxfiles)) {
                        error = EINVAL;
                        break;
                }
                fdplock(fdp);
                if ((error = fdalloc(p, newmin, &i)) != 0) {
                        if (error == ENOSPC) {
                                fdexpand(p);
                                fdpunlock(fdp);
                                FRELE(fp, p);
                                goto restart;
                        }
                        fdpunlock(fdp);
                        FRELE(fp, p);
                } else {
                        int dupflags = 0;

                        if (SCARG(uap, cmd) == F_DUPFD_CLOEXEC)
                                dupflags |= DUPF_CLOEXEC;
                        if (SCARG(uap, cmd) == F_DUPFD_CLOFORK)
                                dupflags |= DUPF_CLOFORK;

                        /* No need for FRELE(), finishdup() uses current ref. */
                        error = finishdup(p, fp, fd, i, retval, dupflags);
                }
                return (error);

        case F_GETFD:
                fdplock(fdp);
                *retval = (fdp->fd_ofileflags[fd] & UF_EXCLOSE   ? FD_CLOEXEC : 0)
                        | (fdp->fd_ofileflags[fd] & UF_FORKCLOSE ? FD_CLOFORK : 0);
                fdpunlock(fdp);
                break;

        case F_SETFD:
                fdplock(fdp);
                i = ((long)SCARG(uap, arg) & FD_CLOEXEC ? UF_EXCLOSE   : 0) |
                    ((long)SCARG(uap, arg) & FD_CLOFORK ? UF_FORKCLOSE : 0);
                fdp->fd_ofileflags[fd] = (fdp->fd_ofileflags[fd] &
                    ~(UF_EXCLOSE | UF_FORKCLOSE)) | i;
                fdpunlock(fdp);
                break;

        case F_GETFL:
                *retval = OFLAGS(fp->f_flag);
                break;

        case F_ISATTY:
                vp = fp->f_data;
                if (fp->f_type == DTYPE_VNODE && (vp->v_flag & VISTTY))
                        *retval = 1;
                else {
                        *retval = 0;
                        error = ENOTTY;
                }
                break;

        case F_SETFL:
                do {
                        tmp = prev = fp->f_flag;
                        tmp &= ~FCNTLFLAGS;
                        tmp |= FFLAGS((long)SCARG(uap, arg)) & FCNTLFLAGS;
                } while (atomic_cas_uint(&fp->f_flag, prev, tmp) != prev);
                tmp = fp->f_flag & FASYNC;
                error = (*fp->f_ops->fo_ioctl)(fp, FIOASYNC, (caddr_t)&tmp, p);
                break;

        case F_GETOWN:
                tmp = 0;
                error = (*fp->f_ops->fo_ioctl)
                        (fp, FIOGETOWN, (caddr_t)&tmp, p);
                *retval = tmp;
                break;

        case F_SETOWN:
                tmp = (long)SCARG(uap, arg);
                error = ((*fp->f_ops->fo_ioctl)
                        (fp, FIOSETOWN, (caddr_t)&tmp, p));
                break;

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

        case F_SETLK:
                error = pledge_flock(p);
                if (error != 0)
                        break;

                if (fp->f_type != DTYPE_VNODE) {
                        error = EINVAL;
                        break;
                }
                vp = fp->f_data;
                /* Copy in the lock structure */
                error = copyin((caddr_t)SCARG(uap, arg), (caddr_t)&fl,
                    sizeof (fl));
                if (error)
                        break;
#ifdef KTRACE
                if (KTRPOINT(p, KTR_STRUCT))
                        ktrflock(p, &fl);
#endif
                if (fl.l_whence == SEEK_CUR) {
                        off_t offset = foffset(fp);

                        if (fl.l_start == 0 && fl.l_len < 0) {
                                /* lockf(3) compliance hack */
                                fl.l_len = -fl.l_len;
                                fl.l_start = offset - fl.l_len;
                        } else
                                fl.l_start += offset;
                }
                switch (fl.l_type) {

                case F_RDLCK:
                        if ((fp->f_flag & FREAD) == 0) {
                                error = EBADF;
                                goto out;
                        }
                        atomic_setbits_int(&fdp->fd_flags, FD_ADVLOCK);
                        error = VOP_ADVLOCK(vp, fdp, F_SETLK, &fl, flg);
                        break;

                case F_WRLCK:
                        if ((fp->f_flag & FWRITE) == 0) {
                                error = EBADF;
                                goto out;
                        }
                        atomic_setbits_int(&fdp->fd_flags, FD_ADVLOCK);
                        error = VOP_ADVLOCK(vp, fdp, F_SETLK, &fl, flg);
                        break;

                case F_UNLCK:
                        error = VOP_ADVLOCK(vp, fdp, F_UNLCK, &fl, F_POSIX);
                        goto out;

                default:
                        error = EINVAL;
                        goto out;
                }

                if (fd_checkclosed(fdp, fd, fp)) {
                        /*
                         * We have lost the race with close() or dup2();
                         * unlock, pretend that we've won the race and that
                         * lock had been removed by close()
                         */
                        fl.l_whence = SEEK_SET;
                        fl.l_start = 0;
                        fl.l_len = 0;
                        VOP_ADVLOCK(vp, fdp, F_UNLCK, &fl, F_POSIX);
                        fl.l_type = F_UNLCK;
                }
                goto out;


        case F_GETLK:
                error = pledge_flock(p);
                if (error != 0)
                        break;

                if (fp->f_type != DTYPE_VNODE) {
                        error = EINVAL;
                        break;
                }
                vp = fp->f_data;
                /* Copy in the lock structure */
                error = copyin((caddr_t)SCARG(uap, arg), (caddr_t)&fl,
                    sizeof (fl));
                if (error)
                        break;
                if (fl.l_whence == SEEK_CUR) {
                        off_t offset = foffset(fp);

                        if (fl.l_start == 0 && fl.l_len < 0) {
                                /* lockf(3) compliance hack */
                                fl.l_len = -fl.l_len;
                                fl.l_start = offset - fl.l_len;
                        } else
                                fl.l_start += offset;
                }
                if (fl.l_type != F_RDLCK &&
                    fl.l_type != F_WRLCK &&
                    fl.l_type != F_UNLCK &&
                    fl.l_type != 0) {
                        error = EINVAL;
                        break;
                }
                error = VOP_ADVLOCK(vp, fdp, F_GETLK, &fl, F_POSIX);
                if (error)
                        break;
#ifdef KTRACE
                if (KTRPOINT(p, KTR_STRUCT))
                        ktrflock(p, &fl);
#endif
                error = (copyout((caddr_t)&fl, (caddr_t)SCARG(uap, arg),
                    sizeof (fl)));
                break;

        default:
                error = EINVAL;
                break;
        }
out:
        FRELE(fp, p);
        return (error);
}

/*
 * Common code for dup, dup2, and fcntl(F_DUPFD).
 */
int
finishdup(struct proc *p, struct file *fp, int old, int new,
    register_t *retval, int dupflags)
{
        struct file *oldfp;
        struct filedesc *fdp = p->p_fd;
        int error;

        fdpassertlocked(fdp);
        KASSERT(fp->f_iflags & FIF_INSERTED);

        if (fp->f_count >= FDUP_MAX_COUNT) {
                error = EDEADLK;
                goto fail;
        }

        oldfp = fd_getfile(fdp, new);
        if ((dupflags & DUPF_DUP2) && oldfp == NULL) {
                if (fd_inuse(fdp, new)) {
                        error = EBUSY;
                        goto fail;
                }
                fd_used(fdp, new);
        }

        /*
         * Use `fd_fplock' to synchronize with fd_getfile() so that
         * the function no longer creates a new reference to the old file.
         */
        mtx_enter(&fdp->fd_fplock);
        fdp->fd_ofiles[new] = fp;
        mtx_leave(&fdp->fd_fplock);

        fdp->fd_ofileflags[new] = fdp->fd_ofileflags[old] &
            ~(UF_EXCLOSE | UF_FORKCLOSE);
        if (dupflags & DUPF_CLOEXEC)
                fdp->fd_ofileflags[new] |= UF_EXCLOSE;
        if (dupflags & DUPF_CLOFORK)
                fdp->fd_ofileflags[new] |= UF_FORKCLOSE;
        *retval = new;

        if (oldfp != NULL) {
                knote_fdclose(p, new);
                fdpunlock(fdp);
                closef(oldfp, p);
        } else {
                fdpunlock(fdp);
        }

        return (0);

fail:
        fdpunlock(fdp);
        FRELE(fp, p);
        return (error);
}

void
fdinsert(struct filedesc *fdp, int fd, int flags, struct file *fp)
{
        struct file *fq;

        fdpassertlocked(fdp);

        mtx_enter(&fhdlk);
        if ((fp->f_iflags & FIF_INSERTED) == 0) {
                atomic_setbits_int(&fp->f_iflags, FIF_INSERTED);
                if ((fq = fdp->fd_ofiles[0]) != NULL) {
                        LIST_INSERT_AFTER(fq, fp, f_list);
                } else {
                        LIST_INSERT_HEAD(&filehead, fp, f_list);
                }
        }
        mtx_leave(&fhdlk);

        mtx_enter(&fdp->fd_fplock);
        KASSERT(fdp->fd_ofiles[fd] == NULL);
        fdp->fd_ofiles[fd] = fp;
        mtx_leave(&fdp->fd_fplock);

        fdp->fd_ofileflags[fd] |= (flags & (UF_EXCLOSE | UF_FORKCLOSE |
            UF_PLEDGEOPEN));
}

void
fdremove(struct filedesc *fdp, int fd)
{
        fdpassertlocked(fdp);

        /*
         * Use `fd_fplock' to synchronize with fd_getfile() so that
         * the function no longer creates a new reference to the file.
         */
        mtx_enter(&fdp->fd_fplock);
        fdp->fd_ofiles[fd] = NULL;
        mtx_leave(&fdp->fd_fplock);

        fdp->fd_ofileflags[fd] = 0;

        fd_unused(fdp, fd);
}

int
fdrelease(struct proc *p, int fd)
{
        struct filedesc *fdp = p->p_fd;
        struct file *fp;

        fdpassertlocked(fdp);

        fp = fd_getfile(fdp, fd);
        if (fp == NULL) {
                fdpunlock(fdp);
                return (EBADF);
        }
        fdremove(fdp, fd);
        knote_fdclose(p, fd);
        fdpunlock(fdp);
        return (closef(fp, p));
}

/*
 * Close a file descriptor.
 */
int
sys_close(struct proc *p, void *v, register_t *retval)
{
        struct sys_close_args /* {
                syscallarg(int) fd;
        } */ *uap = v;
        int fd = SCARG(uap, fd), error;
        struct filedesc *fdp = p->p_fd;

        fdplock(fdp);
        /* fdrelease unlocks fdp. */
        error = fdrelease(p, fd);

        return (error);
}

/*
 * Return status information about a file descriptor.
 */
int
sys_fstat(struct proc *p, void *v, register_t *retval)
{
        struct sys_fstat_args /* {
                syscallarg(int) fd;
                syscallarg(struct stat *) sb;
        } */ *uap = v;
        int fd = SCARG(uap, fd);
        struct filedesc *fdp = p->p_fd;
        struct file *fp;
        struct stat ub;
        int error;

        if ((fp = fd_getfile(fdp, fd)) == NULL)
                return (EBADF);
        error = (*fp->f_ops->fo_stat)(fp, &ub, p);
        FRELE(fp, p);
        if (error == 0) {
                /* 
                 * Don't let non-root see generation numbers
                 * (for NFS security)
                 */
                if (suser(p))
                        ub.st_gen = 0;
                error = copyout((caddr_t)&ub, (caddr_t)SCARG(uap, sb),
                    sizeof (ub));
        }
#ifdef KTRACE
        if (error == 0 && KTRPOINT(p, KTR_STRUCT))
                ktrstat(p, &ub);
#endif
        return (error);
}

/*
 * Return pathconf information about a file descriptor.
 */
int
sys_fpathconf(struct proc *p, void *v, register_t *retval)
{
        struct sys_fpathconf_args /* {
                syscallarg(int) fd;
                syscallarg(int) name;
        } */ *uap = v;
        int fd = SCARG(uap, fd);
        struct filedesc *fdp = p->p_fd;
        struct file *fp;
        struct vnode *vp;
        int error;

        if ((fp = fd_getfile(fdp, fd)) == NULL)
                return (EBADF);
        switch (fp->f_type) {
        case DTYPE_PIPE:
        case DTYPE_SOCKET:
                if (SCARG(uap, name) != _PC_PIPE_BUF) {
                        error = EINVAL;
                        break;
                }
                *retval = PIPE_BUF;
                error = 0;
                break;

        case DTYPE_VNODE:
                vp = fp->f_data;
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                error = VOP_PATHCONF(vp, SCARG(uap, name), retval);
                VOP_UNLOCK(vp);
                break;

        default:
                error = EOPNOTSUPP;
                break;
        }
        FRELE(fp, p);
        return (error);
}

/*
 * Allocate a file descriptor for the process.
 */
int
fdalloc(struct proc *p, int want, int *result)
{
        struct filedesc *fdp = p->p_fd;
        int lim, last, i;
        u_int new, off;

        fdpassertlocked(fdp);

        /*
         * Search for a free descriptor starting at the higher
         * of want or fd_freefile.  If that fails, consider
         * expanding the ofile array.
         */
restart:
        lim = min((int)lim_cur(RLIMIT_NOFILE), atomic_load_int(&maxfiles));
        last = min(fdp->fd_nfiles, lim);
        if ((i = want) < fdp->fd_freefile)
                i = fdp->fd_freefile;
        off = i >> NDENTRYSHIFT;
        new = find_next_zero(fdp->fd_himap, off,
            (last + NDENTRIES - 1) >> NDENTRYSHIFT);
        if (new != -1) {
                i = find_next_zero(&fdp->fd_lomap[new], 
                                   new > off ? 0 : i & NDENTRYMASK,
                                   NDENTRIES);
                if (i == -1) {
                        /*
                         * Free file descriptor in this block was
                         * below want, try again with higher want.
                         */
                        want = (new + 1) << NDENTRYSHIFT;
                        goto restart;
                }
                i += (new << NDENTRYSHIFT);
                if (i < last) {
                        fd_used(fdp, i);
                        if (want <= fdp->fd_freefile)
                                fdp->fd_freefile = i;
                        *result = i;
                        fdp->fd_ofileflags[i] = 0;
                        if (ISSET(p->p_p->ps_flags, PS_PLEDGE))
                                fdp->fd_ofileflags[i] |= UF_PLEDGED;
                        return (0);
                }
        }
        if (fdp->fd_nfiles >= lim)
                return (EMFILE);

        return (ENOSPC);
}

void
fdexpand(struct proc *p)
{
        struct filedesc *fdp = p->p_fd;
        int nfiles, oldnfiles;
        size_t copylen;
        struct file **newofile, **oldofile;
        char *newofileflags;
        u_int *newhimap, *newlomap;

        fdpassertlocked(fdp);

        oldnfiles = fdp->fd_nfiles;
        oldofile = fdp->fd_ofiles;

        /*
         * No space in current array.
         */
        if (fdp->fd_nfiles < NDEXTENT)
                nfiles = NDEXTENT;
        else
                nfiles = 2 * fdp->fd_nfiles;

        newofile = mallocarray(nfiles, OFILESIZE, M_FILEDESC, M_WAITOK);
        /*
         * Allocate all required chunks before calling free(9) to make
         * sure that ``fd_ofiles'' stays valid if we go to sleep.
         */
        if (NDHISLOTS(nfiles) > NDHISLOTS(fdp->fd_nfiles)) {
                newhimap = mallocarray(NDHISLOTS(nfiles), sizeof(u_int),
                    M_FILEDESC, M_WAITOK);
                newlomap = mallocarray(NDLOSLOTS(nfiles), sizeof(u_int),
                    M_FILEDESC, M_WAITOK);
        }
        newofileflags = (char *) &newofile[nfiles];

        /*
         * Copy the existing ofile and ofileflags arrays
         * and zero the new portion of each array.
         */
        copylen = sizeof(struct file *) * fdp->fd_nfiles;
        memcpy(newofile, fdp->fd_ofiles, copylen);
        memset((char *)newofile + copylen, 0,
            nfiles * sizeof(struct file *) - copylen);
        copylen = sizeof(char) * fdp->fd_nfiles;
        memcpy(newofileflags, fdp->fd_ofileflags, copylen);
        memset(newofileflags + copylen, 0, nfiles * sizeof(char) - copylen);

        if (NDHISLOTS(nfiles) > NDHISLOTS(fdp->fd_nfiles)) {
                copylen = NDHISLOTS(fdp->fd_nfiles) * sizeof(u_int);
                memcpy(newhimap, fdp->fd_himap, copylen);
                memset((char *)newhimap + copylen, 0,
                    NDHISLOTS(nfiles) * sizeof(u_int) - copylen);

                copylen = NDLOSLOTS(fdp->fd_nfiles) * sizeof(u_int);
                memcpy(newlomap, fdp->fd_lomap, copylen);
                memset((char *)newlomap + copylen, 0,
                    NDLOSLOTS(nfiles) * sizeof(u_int) - copylen);

                if (NDHISLOTS(fdp->fd_nfiles) > NDHISLOTS(NDFILE)) {
                        free(fdp->fd_himap, M_FILEDESC,
                            NDHISLOTS(fdp->fd_nfiles) * sizeof(u_int));
                        free(fdp->fd_lomap, M_FILEDESC,
                            NDLOSLOTS(fdp->fd_nfiles) * sizeof(u_int));
                }
                fdp->fd_himap = newhimap;
                fdp->fd_lomap = newlomap;
        }

        mtx_enter(&fdp->fd_fplock);
        fdp->fd_ofiles = newofile;
        mtx_leave(&fdp->fd_fplock);

        fdp->fd_ofileflags = newofileflags;
        fdp->fd_nfiles = nfiles;

        if (oldnfiles > NDFILE)
                free(oldofile, M_FILEDESC, oldnfiles * OFILESIZE);
}

/*
 * Create a new open file structure and allocate
 * a file descriptor for the process that refers to it.
 */
int
falloc(struct proc *p, struct file **resultfp, int *resultfd)
{
        struct file *fp;
        int error, i;

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

        fdpassertlocked(p->p_fd);
restart:
        if ((error = fdalloc(p, 0, &i)) != 0) {
                if (error == ENOSPC) {
                        fdexpand(p);
                        goto restart;
                }
                return (error);
        }

        fp = fnew(p);
        if (fp == NULL) {
                fd_unused(p->p_fd, i);
                return (ENFILE);
        }

        FREF(fp);
        *resultfp = fp;
        *resultfd = i;

        return (0);
}

struct file *
fnew(struct proc *p)
{
        struct file *fp;
        int nfiles;

        nfiles = atomic_inc_int_nv(&numfiles);
        if (nfiles > atomic_load_int(&maxfiles)) {
                atomic_dec_int(&numfiles);
                tablefull("file");
                return (NULL);
        }

        fp = pool_get(&file_pool, PR_WAITOK|PR_ZERO);
        /*
         * We need to block interrupts as long as `f_mtx' is being taken
         * with and without the KERNEL_LOCK().
         */
        mtx_init(&fp->f_mtx, IPL_MPFLOOR);
        fp->f_count = 1;
        fp->f_cred = p->p_ucred;
        crhold(fp->f_cred);

        return (fp);
}

/*
 * Build a new filedesc structure.
 */
struct filedesc *
fdinit(void)
{
        struct filedesc0 *newfdp;

        newfdp = pool_get(&fdesc_pool, PR_WAITOK|PR_ZERO);
        rw_init(&newfdp->fd_fd.fd_lock, "fdlock");
        mtx_init(&newfdp->fd_fd.fd_fplock, IPL_MPFLOOR);
        LIST_INIT(&newfdp->fd_fd.fd_kqlist);

        /* Create the file descriptor table. */
        newfdp->fd_fd.fd_refcnt = 1;
        newfdp->fd_fd.fd_cmask = S_IWGRP|S_IWOTH;
        newfdp->fd_fd.fd_ofiles = newfdp->fd_dfiles;
        newfdp->fd_fd.fd_ofileflags = newfdp->fd_dfileflags;
        newfdp->fd_fd.fd_nfiles = NDFILE;
        newfdp->fd_fd.fd_himap = newfdp->fd_dhimap;
        newfdp->fd_fd.fd_lomap = newfdp->fd_dlomap;

        newfdp->fd_fd.fd_freefile = 0;
        newfdp->fd_fd.fd_lastfile = 0;

        return (&newfdp->fd_fd);
}

/*
 * Share a filedesc structure.
 */
struct filedesc *
fdshare(struct process *pr)
{
        pr->ps_fd->fd_refcnt++;
        return (pr->ps_fd);
}

/*
 * Copy a filedesc structure.
 */
struct filedesc *
fdcopy(struct process *pr)
{
        struct filedesc *newfdp, *fdp = pr->ps_fd;
        int i;

        newfdp = fdinit();

        fdplock(fdp);
        if (fdp->fd_cdir) {
                vref(fdp->fd_cdir);
                newfdp->fd_cdir = fdp->fd_cdir;
        }
        if (fdp->fd_rdir) {
                vref(fdp->fd_rdir);
                newfdp->fd_rdir = fdp->fd_rdir;
        }

        /*
         * If the number of open files fits in the internal arrays
         * of the open file structure, use them, otherwise allocate
         * additional memory for the number of descriptors currently
         * in use.
         */
        if (fdp->fd_lastfile >= NDFILE) {
                /*
                 * Compute the smallest multiple of NDEXTENT needed
                 * for the file descriptors currently in use,
                 * allowing the table to shrink.
                 */
                i = fdp->fd_nfiles;
                while (i >= 2 * NDEXTENT && i > fdp->fd_lastfile * 2)
                        i /= 2;
                newfdp->fd_ofiles = mallocarray(i, OFILESIZE, M_FILEDESC,
                    M_WAITOK | M_ZERO);
                newfdp->fd_ofileflags = (char *) &newfdp->fd_ofiles[i];
                newfdp->fd_nfiles = i;
        }
        if (NDHISLOTS(newfdp->fd_nfiles) > NDHISLOTS(NDFILE)) {
                newfdp->fd_himap = mallocarray(NDHISLOTS(newfdp->fd_nfiles),
                    sizeof(u_int), M_FILEDESC, M_WAITOK | M_ZERO);
                newfdp->fd_lomap = mallocarray(NDLOSLOTS(newfdp->fd_nfiles),
                    sizeof(u_int), M_FILEDESC, M_WAITOK | M_ZERO);
        }
        newfdp->fd_freefile = fdp->fd_freefile;
        newfdp->fd_flags = fdp->fd_flags;
        newfdp->fd_cmask = fdp->fd_cmask;

        for (i = 0; i <= fdp->fd_lastfile; i++) {
                struct file *fp = fdp->fd_ofiles[i];

                if (fp != NULL) {
                        int fileflags = fdp->fd_ofileflags[i];
                        /*
                         * If the UF_FORKCLOSE flag is set, skip the fd.
                         * XXX Gruesome hack. If count gets too high, fail
                         * to copy an fd, since fdcopy()'s callers do not
                         * permit it to indicate failure yet.
                         * Meanwhile, kqueue files have to be
                         * tied to the process that opened them to enforce
                         * their internal consistency, so close them here.
                         */
                        if (fp->f_count >= FDUP_MAX_COUNT ||
                            (fileflags & UF_FORKCLOSE) ||
                            fp->f_type == DTYPE_KQUEUE) {
                                if (i < newfdp->fd_freefile)
                                        newfdp->fd_freefile = i;
                                continue;
                        }

                        FREF(fp);
                        newfdp->fd_ofiles[i] = fp;
                        newfdp->fd_ofileflags[i] = fileflags;
                        fd_used(newfdp, i);
                }
        }
        fdpunlock(fdp);

        return (newfdp);
}

/*
 * Release a filedesc structure.
 */
void
fdfree(struct proc *p)
{
        struct filedesc *fdp = p->p_fd;
        struct file *fp;
        int fd;

        if (--fdp->fd_refcnt > 0)
                return;
        for (fd = 0; fd <= fdp->fd_lastfile; fd++) {
                fp = fdp->fd_ofiles[fd];
                if (fp != NULL) {
                        fdp->fd_ofiles[fd] = NULL;
                        knote_fdclose(p, fd);
                         /* closef() expects a refcount of 2 */
                        FREF(fp);
                        (void) closef(fp, p);
                }
        }
        p->p_fd = NULL;
        if (fdp->fd_nfiles > NDFILE)
                free(fdp->fd_ofiles, M_FILEDESC, fdp->fd_nfiles * OFILESIZE);
        if (NDHISLOTS(fdp->fd_nfiles) > NDHISLOTS(NDFILE)) {
                free(fdp->fd_himap, M_FILEDESC,
                    NDHISLOTS(fdp->fd_nfiles) * sizeof(u_int));
                free(fdp->fd_lomap, M_FILEDESC,
                    NDLOSLOTS(fdp->fd_nfiles) * sizeof(u_int));
        }
        if (fdp->fd_cdir)
                vrele(fdp->fd_cdir);
        if (fdp->fd_rdir)
                vrele(fdp->fd_rdir);
        KASSERT(atomic_load_int(&fdp->fd_nuserevents) == 0);
        pool_put(&fdesc_pool, fdp);
}

/*
 * Internal form of close.
 * Decrement reference count on file structure.
 * Note: p may be NULL when closing a file
 * that was being passed in a message.
 *
 * The fp must have its usecount bumped and will be FRELEd here.
 */
int
closef(struct file *fp, struct proc *p)
{
        struct filedesc *fdp;

        if (fp == NULL)
                return (0);

        KASSERTMSG(fp->f_count >= 2, "count (%u) < 2", fp->f_count);

        atomic_dec_int(&fp->f_count);

        /*
         * POSIX record locking dictates that any close releases ALL
         * locks owned by this process.  This is handled by setting
         * a flag in the unlock to free ONLY locks obeying POSIX
         * semantics, and not to free BSD-style file locks.
         * If the descriptor was in a message, POSIX-style locks
         * aren't passed with the descriptor.
         */

        if (p && ((fdp = p->p_fd) != NULL) &&
            (fdp->fd_flags & FD_ADVLOCK) &&
            fp->f_type == DTYPE_VNODE) {
                struct vnode *vp = fp->f_data;
                struct flock lf;

                lf.l_whence = SEEK_SET;
                lf.l_start = 0;
                lf.l_len = 0;
                lf.l_type = F_UNLCK;
                (void) VOP_ADVLOCK(vp, fdp, F_UNLCK, &lf, F_POSIX);
        }

        return (FRELE(fp, p));
}

int
fdrop(struct file *fp, struct proc *p)
{
        int error;

        KASSERTMSG(fp->f_count == 0, "count (%u) != 0", fp->f_count);

        mtx_enter(&fhdlk);
        if (fp->f_iflags & FIF_INSERTED)
                LIST_REMOVE(fp, f_list);
        mtx_leave(&fhdlk);

        if (fp->f_ops)
                error = (*fp->f_ops->fo_close)(fp, p);
        else
                error = 0;

        crfree(fp->f_cred);
        atomic_dec_int(&numfiles);
        pool_put(&file_pool, 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).
 */
int
sys_flock(struct proc *p, void *v, register_t *retval)
{
        struct sys_flock_args /* {
                syscallarg(int) fd;
                syscallarg(int) how;
        } */ *uap = v;
        int fd = SCARG(uap, fd);
        int how = SCARG(uap, how);
        struct filedesc *fdp = p->p_fd;
        struct file *fp;
        struct vnode *vp;
        struct flock lf;
        int error;

        if ((fp = fd_getfile(fdp, fd)) == NULL)
                return (EBADF);
        if (fp->f_type != DTYPE_VNODE) {
                error = EOPNOTSUPP;
                goto out;
        }
        vp = fp->f_data;
        lf.l_whence = SEEK_SET;
        lf.l_start = 0;
        lf.l_len = 0;
        if (how & LOCK_UN) {
                lf.l_type = F_UNLCK;
                atomic_clearbits_int(&fp->f_iflags, FIF_HASLOCK);
                error = VOP_ADVLOCK(vp, (caddr_t)fp, F_UNLCK, &lf, F_FLOCK);
                goto out;
        }
        if (how & LOCK_EX)
                lf.l_type = F_WRLCK;
        else if (how & LOCK_SH)
                lf.l_type = F_RDLCK;
        else {
                error = EINVAL;
                goto out;
        }
        atomic_setbits_int(&fp->f_iflags, FIF_HASLOCK);
        if (how & LOCK_NB)
                error = VOP_ADVLOCK(vp, (caddr_t)fp, F_SETLK, &lf, F_FLOCK);
        else
                error = VOP_ADVLOCK(vp, (caddr_t)fp, F_SETLK, &lf, F_FLOCK|F_WAIT);
out:
        FRELE(fp, p);
        return (error);
}

/*
 * 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.
 */
int
filedescopen(dev_t dev, int mode, int type, struct proc *p)
{

        /*
         * XXX Kludge: set curproc->p_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.
         */
        p->p_dupfd = minor(dev);
        return (ENODEV);
}

/*
 * Duplicate the specified descriptor to a free descriptor.
 */
int
dupfdopen(struct proc *p, int indx, int mode)
{
        struct filedesc *fdp = p->p_fd;
        int dupfd = p->p_dupfd;
        struct file *wfp;

        fdpassertlocked(fdp);

        /*
         * Assume that the filename was user-specified; applications do
         * not tend to open /dev/fd/# when they can just call dup()
         */
        if ((p->p_p->ps_flags & (PS_SUGIDEXEC | PS_SUGID))) {
                if (p->p_descfd == 255)
                        return (EPERM);
                if (p->p_descfd != dupfd)
                        return (EPERM);
        }

        /*
         * 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, reject. Note, there is no need to check for new == old
         * because fd_getfile will return NULL if the file at indx is
         * newly created by falloc.
         */
        if ((wfp = fd_getfile(fdp, dupfd)) == NULL)
                return (EBADF);

        /*
         * Check that the mode the file is being opened for is a
         * subset of the mode of the existing descriptor.
         */
        if (((mode & (FREAD|FWRITE)) | wfp->f_flag) != wfp->f_flag) {
                FRELE(wfp, p);
                return (EACCES);
        }
        if (wfp->f_count >= FDUP_MAX_COUNT) {
                FRELE(wfp, p);
                return (EDEADLK);
        }

        KASSERT(wfp->f_iflags & FIF_INSERTED);

        mtx_enter(&fdp->fd_fplock);
        KASSERT(fdp->fd_ofiles[indx] == NULL);
        fdp->fd_ofiles[indx] = wfp;
        mtx_leave(&fdp->fd_fplock);

        fdp->fd_ofileflags[indx] =
            (fdp->fd_ofileflags[indx] & (UF_EXCLOSE | UF_FORKCLOSE)) |
            (fdp->fd_ofileflags[dupfd] & ~(UF_EXCLOSE | UF_FORKCLOSE));

        return (0);
}

/*
 * Doing an exec, so handle fd flags: do close-on-exec and clear
 * pledged and close-on-fork
 */
void
fdprepforexec(struct proc *p)
{
        struct filedesc *fdp = p->p_fd;
        int fd;

        fdplock(fdp);
        for (fd = 0; fd <= fdp->fd_lastfile; fd++) {
                fdp->fd_ofileflags[fd] &= ~(UF_PLEDGED | UF_FORKCLOSE);
                if (fdp->fd_ofileflags[fd] & UF_EXCLOSE) {
                        /* fdrelease() unlocks fdp. */
                        (void) fdrelease(p, fd);
                        fdplock(fdp);
                }
        }
        fdpunlock(fdp);
}

int
sys_closefrom(struct proc *p, void *v, register_t *retval)
{
        struct sys_closefrom_args *uap = v;
        struct filedesc *fdp = p->p_fd;
        u_int startfd, i;

        startfd = SCARG(uap, fd);
        fdplock(fdp);

        if (startfd > fdp->fd_lastfile) {
                fdpunlock(fdp);
                return (EBADF);
        }

        for (i = startfd; i <= fdp->fd_lastfile; i++) {
                /* fdrelease() unlocks fdp. */
                fdrelease(p, i);
                fdplock(fdp);
        }

        fdpunlock(fdp);
        return (0);
}

int
sys_getdtablecount(struct proc *p, void *v, register_t *retval)
{
        *retval = p->p_fd->fd_openfd;
        return (0);
}