xref: /src/sys/kern/kern_descrip.c

/*	$NetBSD: kern_descrip.c,v 1.72.2.4 2001/08/24 00:11:26 nathanw 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)kern_descrip.c	8.8 (Berkeley) 2/14/95
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/vnode.h>
#include <sys/lwp.h>
#include <sys/proc.h>
#include <sys/file.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/fcntl.h>
#include <sys/malloc.h>
#include <sys/pool.h>
#include <sys/syslog.h>
#include <sys/unistd.h>
#include <sys/resourcevar.h>
#include <sys/conf.h>

#include <sys/mount.h>
#include <sys/syscallargs.h>

/*
 * Descriptor management.
 */
struct filelist	filehead;	/* head of list of open files */
int		nfiles;		/* actual number of open files */
struct pool	file_pool;	/* memory pool for file structures */
struct pool	cwdi_pool;	/* memory pool for cwdinfo structures */
struct pool	filedesc0_pool;	/* memory pool for filedesc0 structures */

static __inline void	fd_used(struct filedesc *, int);
static __inline void	fd_unused(struct filedesc *, int);
int			finishdup(struct proc *, int, int, register_t *);
int			fcntl_forfs(int, struct proc *, int, void *);

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

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

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

	if (fd < fdp->fd_freefile)
		fdp->fd_freefile = fd;
#ifdef DIAGNOSTIC
	if (fd > fdp->fd_lastfile)
		panic("fd_unused: fd_lastfile inconsistent");
#endif
	if (fd == fdp->fd_lastfile) {
		do {
			fd--;
		} while (fd >= 0 && fdp->fd_ofiles[fd] == NULL);
		fdp->fd_lastfile = fd;
	}
}

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

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

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

	return (fp);
}

/*
 * System calls on descriptors.
 */

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

	p = l->l_proc;
	fdp = p->p_fd;
	old = SCARG(uap, fd);

 restart:
	if ((fp = fd_getfile(fdp, old)) == NULL)
		return (EBADF);

	FILE_USE(fp);

	if ((error = fdalloc(p, 0, &new)) != 0) {
		if (error == ENOSPC) {
			fdexpand(p);
			FILE_UNUSE(fp, p);
			goto restart;
		}
		FILE_UNUSE(fp, p);
		return (error);
	}

	/* finishdup() will unuse the descriptors for us */
	return (finishdup(p, old, new, retval));
}

/*
 * Duplicate a file descriptor to a particular value.
 */
/* ARGSUSED */
int
sys_dup2(struct lwp *l, void *v, register_t *retval)
{
	struct sys_dup2_args /* {
		syscallarg(int)	from;
		syscallarg(int)	to;
	} */ *uap = v;
	struct file	*fp;
	struct filedesc	*fdp;
	struct proc	*p;
	int		old, new, i, error;

	p = l->l_proc;
	fdp = p->p_fd;
	old = SCARG(uap, from);
	new = SCARG(uap, to);

 restart:
	if ((fp = fd_getfile(fdp, old)) == NULL)
		return (EBADF);

	if ((u_int)new >= p->p_rlimit[RLIMIT_NOFILE].rlim_cur ||
	    (u_int)new >= maxfiles)
		return (EBADF);

	if (old == new) {
		*retval = new;
		return (0);
	}

	FILE_USE(fp);

	if (new >= fdp->fd_nfiles) {
		if ((error = fdalloc(p, new, &i)) != 0) {
			if (error == ENOSPC) {
				fdexpand(p);
				FILE_UNUSE(fp, p);
				goto restart;
			}
			FILE_UNUSE(fp, p);
			return (error);
		}
		if (new != i)
			panic("dup2: fdalloc");
	}

	/*
	 * finishdup() will close the file that's in the `new'
	 * slot, if there's one there.
	 */

	/* finishdup() will unuse the descriptors for us */
	return (finishdup(p, old, new, retval));
}

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

	p = l->l_proc;
	fd = SCARG(uap, fd);
	fdp = p->p_fd;
	error = 0;
	flg = F_POSIX;

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

	FILE_USE(fp);

	cmd = SCARG(uap, cmd);
	if ((cmd & F_FSCTL)) {
		error = fcntl_forfs(fd, p, cmd, SCARG(uap, arg));
		goto out;
	}

	switch (cmd) {

	case F_DUPFD:
		newmin = (long)SCARG(uap, arg);
		if ((u_int)newmin >= p->p_rlimit[RLIMIT_NOFILE].rlim_cur ||
		    (u_int)newmin >= maxfiles) {
			error = EINVAL;
			goto out;
		}
		if ((error = fdalloc(p, newmin, &i)) != 0) {
			if (error == ENOSPC) {
				fdexpand(p);
				FILE_UNUSE(fp, p);
				goto restart;
			}
			goto out;
		}

		/* finishdup() will unuse the descriptors for us */
		return (finishdup(p, fd, i, retval));

	case F_GETFD:
		*retval = fdp->fd_ofileflags[fd] & UF_EXCLOSE ? 1 : 0;
		break;

	case F_SETFD:
		if ((long)SCARG(uap, arg) & 1)
			fdp->fd_ofileflags[fd] |= UF_EXCLOSE;
		else
			fdp->fd_ofileflags[fd] &= ~UF_EXCLOSE;
		break;

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

	case F_SETFL:
		tmp = FFLAGS((long)SCARG(uap, arg)) & FCNTLFLAGS;
		error = (*fp->f_ops->fo_fcntl)(fp, F_SETFL, (caddr_t)&tmp, p);
		if (error)
			goto out;
		fp->f_flag &= ~FCNTLFLAGS;
		fp->f_flag |= tmp;
		tmp = fp->f_flag & FNONBLOCK;
		error = (*fp->f_ops->fo_ioctl)(fp, FIONBIO, (caddr_t)&tmp, p);
		if (error)
			goto out;
		tmp = fp->f_flag & FASYNC;
		error = (*fp->f_ops->fo_ioctl)(fp, FIOASYNC, (caddr_t)&tmp, p);
		if (error == 0)
			goto out;
		fp->f_flag &= ~FNONBLOCK;
		tmp = 0;
		(void) (*fp->f_ops->fo_ioctl)(fp, FIONBIO, (caddr_t)&tmp, p);
		break;

	case F_GETOWN:
		if (fp->f_type == DTYPE_SOCKET) {
			*retval = ((struct socket *)fp->f_data)->so_pgid;
			goto out;
		}
		error = (*fp->f_ops->fo_ioctl)
			(fp, TIOCGPGRP, (caddr_t)retval, p);
		*retval = -*retval;
		break;

	case F_SETOWN:
		if (fp->f_type == DTYPE_SOCKET) {
			((struct socket *)fp->f_data)->so_pgid =
			    (long)SCARG(uap, arg);
			goto out;
		}
		if ((long)SCARG(uap, arg) <= 0) {
			tmp = (-(long)SCARG(uap, arg));
		} else {
			struct proc *p1 = pfind((long)SCARG(uap, arg));
			if (p1 == 0) {
				error = ESRCH;
				goto out;
			}
			tmp = (long)p1->p_pgrp->pg_id;
		}
		error = (*fp->f_ops->fo_ioctl)
		    (fp, TIOCSPGRP, (caddr_t)&tmp, p);
		break;

	case F_SETLKW:
		flg |= F_WAIT;
		/* Fall into F_SETLK */

	case F_SETLK:
		if (fp->f_type != DTYPE_VNODE) {
			error = EINVAL;
			goto out;
		}
		vp = (struct vnode *)fp->f_data;
		/* Copy in the lock structure */
		error = copyin((caddr_t)SCARG(uap, arg), (caddr_t)&fl,
		    sizeof(fl));
		if (error)
			goto out;
		if (fl.l_whence == SEEK_CUR)
			fl.l_start += fp->f_offset;
		switch (fl.l_type) {
		case F_RDLCK:
			if ((fp->f_flag & FREAD) == 0) {
				error = EBADF;
				goto out;
			}
			p->p_flag |= P_ADVLOCK;
			error = VOP_ADVLOCK(vp, (caddr_t)p, F_SETLK, &fl, flg);
			goto out;

		case F_WRLCK:
			if ((fp->f_flag & FWRITE) == 0) {
				error = EBADF;
				goto out;
			}
			p->p_flag |= P_ADVLOCK;
			error = VOP_ADVLOCK(vp, (caddr_t)p, F_SETLK, &fl, flg);
			goto out;

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

		default:
			error = EINVAL;
			goto out;
		}

	case F_GETLK:
		if (fp->f_type != DTYPE_VNODE) {
			error = EINVAL;
			goto out;
		}
		vp = (struct vnode *)fp->f_data;
		/* Copy in the lock structure */
		error = copyin((caddr_t)SCARG(uap, arg), (caddr_t)&fl,
		    sizeof(fl));
		if (error)
			goto out;
		if (fl.l_whence == SEEK_CUR)
			fl.l_start += fp->f_offset;
		if (fl.l_type != F_RDLCK &&
		    fl.l_type != F_WRLCK &&
		    fl.l_type != F_UNLCK) {
			error = EINVAL;
			goto out;
		}
		error = VOP_ADVLOCK(vp, (caddr_t)p, F_GETLK, &fl, F_POSIX);
		if (error)
			goto out;
		error = copyout((caddr_t)&fl, (caddr_t)SCARG(uap, arg),
		    sizeof(fl));
		break;

	default:
		error = EINVAL;
	}

 out:
	FILE_UNUSE(fp, p);
	return (error);
}

/*
 * Common code for dup, dup2, and fcntl(F_DUPFD).
 */
int
finishdup(struct proc *p, int old, int new, register_t *retval)
{
	struct filedesc	*fdp;
	struct file	*fp, *delfp;

	fdp = p->p_fd;

	/*
	 * If there is a file in the new slot, remember it so we
	 * can close it after we've finished the dup.  We need
	 * to do it after the dup is finished, since closing
	 * the file may block.
	 *
	 * Note: `old' is already used for us.
	 */
	delfp = fdp->fd_ofiles[new];

	fp = fdp->fd_ofiles[old];
	fdp->fd_ofiles[new] = fp;
	fdp->fd_ofileflags[new] = fdp->fd_ofileflags[old] &~ UF_EXCLOSE;
	fp->f_count++;
	/*
	 * Note, don't have to mark it "used" in the table if there
	 * was already a file in the `new' slot.
	 */
	if (delfp == NULL)
		fd_used(fdp, new);
	*retval = new;
	FILE_UNUSE(fp, p);

	if (delfp != NULL) {
		FILE_USE(delfp);
		(void) closef(delfp, p);
	}
	return (0);
}

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

	fdp->fd_ofiles[fd] = NULL;
	fd_unused(fdp, fd);
}

int
fdrelease(struct proc *p, int fd)
{
	struct filedesc	*fdp;
	struct file	**fpp, *fp;

	fdp = p->p_fd;
	fpp = &fdp->fd_ofiles[fd];
	fp = *fpp;
	if (fp == NULL)
		return (EBADF);

	FILE_USE(fp);

	*fpp = NULL;
	fdp->fd_ofileflags[fd] = 0;
	fd_unused(fdp, fd);
	return (closef(fp, p));
}

/*
 * Close a file descriptor.
 */
/* ARGSUSED */
int
sys_close(struct lwp *l, void *v, register_t *retval)
{
	struct sys_close_args /* {
		syscallarg(int)	fd;
	} */ *uap = v;
	int		fd;
	struct filedesc	*fdp;
	struct proc *p;
	struct file	*fp;

	p = l->l_proc;
	fd = SCARG(uap, fd);
	fdp = p->p_fd;

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

	return (fdrelease(p, fd));
}

/*
 * Return status information about a file descriptor.
 */
/* ARGSUSED */
int
sys___fstat13(struct lwp *l, void *v, register_t *retval)
{
	struct sys___fstat13_args /* {
		syscallarg(int)			fd;
		syscallarg(struct stat *)	sb;
	} */ *uap = v;
	int		fd;
	struct filedesc	*fdp;
	struct file	*fp;
	struct proc	*p;
	struct stat	ub;
	int		error;

	p = l->l_proc;
	fd = SCARG(uap, fd);
	fdp = p->p_fd;

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

	FILE_USE(fp);
	error = (*fp->f_ops->fo_stat)(fp, &ub, p);
	FILE_UNUSE(fp, p);

	if (error == 0)
		error = copyout(&ub, SCARG(uap, sb), sizeof(ub));

	return (error);
}

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

	p = l->l_proc;
	fd = SCARG(uap, fd);
	fdp = p->p_fd;
	error = 0;

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

	FILE_USE(fp);

	switch (fp->f_type) {

	case DTYPE_SOCKET:
	case DTYPE_PIPE:
		if (SCARG(uap, name) != _PC_PIPE_BUF)
			error = EINVAL;
		else
			*retval = PIPE_BUF;
		break;

	case DTYPE_VNODE:
		vp = (struct vnode *)fp->f_data;
		error = VOP_PATHCONF(vp, SCARG(uap, name), retval);
		break;

	default:
		panic("fpathconf");
	}

	FILE_UNUSE(fp, p);
	return (error);
}

/*
 * Allocate a file descriptor for the process.
 */
int	fdexpanded;		/* XXX: what else uses this? */

int
fdalloc(struct proc *p, int want, int *result)
{
	struct filedesc	*fdp;
	int i, lim, last;

	fdp = p->p_fd;

	/*
	 * Search for a free descriptor starting at the higher
	 * of want or fd_freefile.  If that fails, consider
	 * expanding the ofile array.
	 */
	lim = min((int)p->p_rlimit[RLIMIT_NOFILE].rlim_cur, maxfiles);
	for (;;) {
		last = min(fdp->fd_nfiles, lim);
		if ((i = want) < fdp->fd_freefile)
			i = fdp->fd_freefile;
		for (; i < last; i++) {
			if (fdp->fd_ofiles[i] == NULL) {
				fd_used(fdp, i);
				if (want <= fdp->fd_freefile)
					fdp->fd_freefile = i;
				*result = i;
				return (0);
			}
		}

		/* No space in current array.  Expand? */
		if (fdp->fd_nfiles >= lim)
			return (EMFILE);

		/* Let the caller do it. */
		return (ENOSPC);
	}
}

void
fdexpand(struct proc *p)
{
	struct filedesc	*fdp;
	int		i, nfiles;
	struct file	**newofile;
	char		*newofileflags;

	fdp = p->p_fd;

	if (fdp->fd_nfiles < NDEXTENT)
		nfiles = NDEXTENT;
	else
		nfiles = 2 * fdp->fd_nfiles;
	newofile = malloc(nfiles * OFILESIZE, M_FILEDESC, M_WAITOK);
	newofileflags = (char *) &newofile[nfiles];
	/*
	 * Copy the existing ofile and ofileflags arrays
	 * and zero the new portion of each array.
	 */
	memcpy(newofile, fdp->fd_ofiles,
		(i = sizeof(struct file *) * fdp->fd_nfiles));
	memset((char *)newofile + i, 0,
	    nfiles * sizeof(struct file *) - i);
	memcpy(newofileflags, fdp->fd_ofileflags,
	    (i = sizeof(char) * fdp->fd_nfiles));
	memset(newofileflags + i, 0, nfiles * sizeof(char) - i);
	if (fdp->fd_nfiles > NDFILE)
		free(fdp->fd_ofiles, M_FILEDESC);
	fdp->fd_ofiles = newofile;
	fdp->fd_ofileflags = newofileflags;
	fdp->fd_nfiles = nfiles;
	fdexpanded++;
}

/*
 * Check to see whether n user file descriptors
 * are available to the process p.
 */
int
fdavail(struct proc *p, int n)
{
	struct filedesc	*fdp;
	struct file	**fpp;
	int		i, lim;

	fdp = p->p_fd;
	lim = min((int)p->p_rlimit[RLIMIT_NOFILE].rlim_cur, maxfiles);
	if ((i = lim - fdp->fd_nfiles) > 0 && (n -= i) <= 0)
		return (1);
	fpp = &fdp->fd_ofiles[fdp->fd_freefile];
	for (i = min(lim,fdp->fd_nfiles) - fdp->fd_freefile; --i >= 0; fpp++)
		if (*fpp == NULL && --n <= 0)
			return (1);
	return (0);
}

/*
 * Initialize the data structures necessary for managing files.
 */
void
finit(void)
{

	pool_init(&file_pool, sizeof(struct file), 0, 0, 0, "filepl",
	    0, pool_page_alloc_nointr, pool_page_free_nointr, M_FILE);
	pool_init(&cwdi_pool, sizeof(struct cwdinfo), 0, 0, 0, "cwdipl",
	    0, pool_page_alloc_nointr, pool_page_free_nointr, M_FILEDESC);
	pool_init(&filedesc0_pool, sizeof(struct filedesc0), 0, 0, 0, "fdescpl",
	    0, pool_page_alloc_nointr, pool_page_free_nointr, M_FILEDESC);
}

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

 restart:
	if ((error = fdalloc(p, 0, &i)) != 0) {
		if (error == ENOSPC) {
			fdexpand(p);
			goto restart;
		}
		return (error);
	}
	if (nfiles >= maxfiles) {
		tablefull("file", "increase kern.maxfiles or MAXFILES");
		return (ENFILE);
	}
	/*
	 * Allocate a new file descriptor.
	 * If the process has file descriptor zero open, add to the list
	 * of open files at that point, otherwise put it at the front of
	 * the list of open files.
	 */
	nfiles++;
	fp = pool_get(&file_pool, PR_WAITOK);
	memset(fp, 0, sizeof(struct file));
	fp->f_iflags = FIF_LARVAL;
	if ((fq = p->p_fd->fd_ofiles[0]) != NULL) {
		LIST_INSERT_AFTER(fq, fp, f_list);
	} else {
		LIST_INSERT_HEAD(&filehead, fp, f_list);
	}
	p->p_fd->fd_ofiles[i] = fp;
	fp->f_count = 1;
	fp->f_cred = p->p_ucred;
	crhold(fp->f_cred);
	if (resultfp) {
		FILE_USE(fp);
		*resultfp = fp;
	}
	if (resultfd)
		*resultfd = i;
	return (0);
}

/*
 * Free a file descriptor.
 */
void
ffree(struct file *fp)
{

#ifdef DIAGNOSTIC
	if (fp->f_usecount)
		panic("ffree");
#endif

	LIST_REMOVE(fp, f_list);
	crfree(fp->f_cred);
#ifdef DIAGNOSTIC
	fp->f_count = 0;
#endif
	nfiles--;
	pool_put(&file_pool, fp);
}

/*
 * Create an initial cwdinfo structure, using the same current and root
 * directories as p.
 */
struct cwdinfo *
cwdinit(struct proc *p)
{
	struct cwdinfo *cwdi;

	cwdi = pool_get(&cwdi_pool, PR_WAITOK);

	cwdi->cwdi_cdir = p->p_cwdi->cwdi_cdir;
	if (cwdi->cwdi_cdir)
		VREF(cwdi->cwdi_cdir);
	cwdi->cwdi_rdir = p->p_cwdi->cwdi_rdir;
	if (cwdi->cwdi_rdir)
		VREF(cwdi->cwdi_rdir);
	cwdi->cwdi_cmask =  p->p_cwdi->cwdi_cmask;
	cwdi->cwdi_refcnt = 1;

	return (cwdi);
}

/*
 * Make p2 share p1's cwdinfo.
 */
void
cwdshare(struct proc *p1, struct proc *p2)
{

	p2->p_cwdi = p1->p_cwdi;
	p1->p_cwdi->cwdi_refcnt++;
}

/*
 * Make this process not share its cwdinfo structure, maintaining
 * all cwdinfo state.
 */
void
cwdunshare(struct proc *p)
{
	struct cwdinfo *newcwdi;

	if (p->p_cwdi->cwdi_refcnt == 1)
		return;

	newcwdi = cwdinit(p);
	cwdfree(p);
	p->p_cwdi = newcwdi;
}

/*
 * Release a cwdinfo structure.
 */
void
cwdfree(struct proc *p)
{
	struct cwdinfo *cwdi;

	cwdi = p->p_cwdi;
	if (--cwdi->cwdi_refcnt > 0)
		return;

	p->p_cwdi = NULL;

	vrele(cwdi->cwdi_cdir);
	if (cwdi->cwdi_rdir)
		vrele(cwdi->cwdi_rdir);
	pool_put(&cwdi_pool, cwdi);
}

/*
 * Create an initial filedesc structure, using the same current and root
 * directories as p.
 */
struct filedesc *
fdinit(struct proc *p)
{
	struct filedesc0 *newfdp;

	newfdp = pool_get(&filedesc0_pool, PR_WAITOK);
	memset(newfdp, 0, sizeof(struct filedesc0));

	fdinit1(newfdp);

	return (&newfdp->fd_fd);
}

/*
 * Initialize a file descriptor table.
 */
void
fdinit1(struct filedesc0 *newfdp)
{

	newfdp->fd_fd.fd_refcnt = 1;
	newfdp->fd_fd.fd_ofiles = newfdp->fd_dfiles;
	newfdp->fd_fd.fd_ofileflags = newfdp->fd_dfileflags;
	newfdp->fd_fd.fd_nfiles = NDFILE;
}

/*
 * Make p2 share p1's filedesc structure.
 */
void
fdshare(struct proc *p1, struct proc *p2)
{

	p2->p_fd = p1->p_fd;
	p1->p_fd->fd_refcnt++;
}

/*
 * Make this process not share its filedesc structure, maintaining
 * all file descriptor state.
 */
void
fdunshare(struct proc *p)
{
	struct filedesc *newfd;

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

	newfd = fdcopy(p);
	fdfree(p);
	p->p_fd = newfd;
}

/*
 * Clear a process's fd table.
 */
void
fdclear(struct proc *p)
{
	struct filedesc *newfd;

	newfd = fdinit(p);
	fdfree(p);
	p->p_fd = newfd;
}

/*
 * Copy a filedesc structure.
 */
struct filedesc *
fdcopy(struct proc *p)
{
	struct filedesc	*newfdp, *fdp;
	struct file	**fpp;
	int		i;

	fdp = p->p_fd;
	newfdp = pool_get(&filedesc0_pool, PR_WAITOK);
	memcpy(newfdp, fdp, sizeof(struct filedesc));
	newfdp->fd_refcnt = 1;

	/*
	 * 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 (newfdp->fd_lastfile < NDFILE) {
		newfdp->fd_ofiles = ((struct filedesc0 *) newfdp)->fd_dfiles;
		newfdp->fd_ofileflags =
		    ((struct filedesc0 *) newfdp)->fd_dfileflags;
		i = NDFILE;
	} else {
		/*
		 * Compute the smallest multiple of NDEXTENT needed
		 * for the file descriptors currently in use,
		 * allowing the table to shrink.
		 */
		i = newfdp->fd_nfiles;
		while (i >= 2 * NDEXTENT && i > newfdp->fd_lastfile * 2)
			i /= 2;
		newfdp->fd_ofiles = malloc(i * OFILESIZE, M_FILEDESC, M_WAITOK);
		newfdp->fd_ofileflags = (char *) &newfdp->fd_ofiles[i];
	}
	newfdp->fd_nfiles = i;
	memcpy(newfdp->fd_ofiles, fdp->fd_ofiles, i * sizeof(struct file **));
	memcpy(newfdp->fd_ofileflags, fdp->fd_ofileflags, i * sizeof(char));
	fpp = newfdp->fd_ofiles;
	for (i = newfdp->fd_lastfile; i >= 0; i--, fpp++)
		if (*fpp != NULL)
			(*fpp)->f_count++;
	return (newfdp);
}

/*
 * Release a filedesc structure.
 */
void
fdfree(struct proc *p)
{
	struct filedesc	*fdp;
	struct file	**fpp, *fp;
	int		i;

	fdp = p->p_fd;
	if (--fdp->fd_refcnt > 0)
		return;
	fpp = fdp->fd_ofiles;
	for (i = fdp->fd_lastfile; i >= 0; i--, fpp++) {
		fp = *fpp;
		if (fp != NULL) {
			*fpp = NULL;
			FILE_USE(fp);
			(void) closef(fp, p);
		}
	}
	p->p_fd = NULL;
	if (fdp->fd_nfiles > NDFILE)
		free(fdp->fd_ofiles, M_FILEDESC);
	pool_put(&filedesc0_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.
 *
 * Note: we expect the caller is holding a usecount, and expects us
 * to drop it (the caller thinks the file is going away forever).
 */
int
closef(struct file *fp, struct proc *p)
{
	struct vnode	*vp;
	struct flock	lf;
	int		error;

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

	/*
	 * POSIX record locking dictates that any close releases ALL
	 * locks owned by this process.  This is handled by setting
	 * a flag in the unlock to free ONLY locks obeying POSIX
	 * semantics, and not to free BSD-style file locks.
	 * If the descriptor was in a message, POSIX-style locks
	 * aren't passed with the descriptor.
	 */
	if (p && (p->p_flag & P_ADVLOCK) && fp->f_type == DTYPE_VNODE) {
		lf.l_whence = SEEK_SET;
		lf.l_start = 0;
		lf.l_len = 0;
		lf.l_type = F_UNLCK;
		vp = (struct vnode *)fp->f_data;
		(void) VOP_ADVLOCK(vp, (caddr_t)p, F_UNLCK, &lf, F_POSIX);
	}

	/*
	 * If WANTCLOSE is set, then the reference count on the file
	 * is 0, but there were multiple users of the file.  This can
	 * happen if a filedesc structure is shared by multiple
	 * processes.
	 */
	if (fp->f_iflags & FIF_WANTCLOSE) {
		/*
		 * Another user of the file is already closing, and is
		 * simply waiting for other users of the file to drain.
		 * Release our usecount, and wake up the closer if it
		 * is the only remaining use.
		 */
#ifdef DIAGNOSTIC
		if (fp->f_count != 0)
			panic("closef: wantclose and count != 0");
		if (fp->f_usecount < 2)
			panic("closef: wantclose and usecount < 2");
#endif
		if (--fp->f_usecount == 1)
			wakeup(&fp->f_usecount);
		return (0);
	} else {
		/*
		 * Decrement the reference count.  If we were not the
		 * last reference, then release our use and just
		 * return.
		 */
		if (--fp->f_count > 0) {
#ifdef DIAGNOSTIC
			if (fp->f_usecount < 1)
				panic("closef: no wantclose and usecount < 1");
#endif
			fp->f_usecount--;
			return (0);
		}
		if (fp->f_count < 0)
			panic("closef: count < 0");
	}

	/*
	 * The reference count is now 0.  However, there may be
	 * multiple potential users of this file.  This can happen
	 * if multiple processes shared a single filedesc structure.
	 *
	 * Notify these potential users that the file is closing.
	 * This will prevent them from adding additional uses to
	 * the file.
	 */
	fp->f_iflags |= FIF_WANTCLOSE;

	/*
	 * We expect the caller to add a use to the file.  So, if we
	 * are the last user, usecount will be 1.  If it is not, we
	 * must wait for the usecount to drain.  When it drains back
	 * to 1, we will be awakened so that we may proceed with the
	 * close.
	 */
#ifdef DIAGNOSTIC
	if (fp->f_usecount < 1)
		panic("closef: usecount < 1");
#endif
	while (fp->f_usecount > 1)
		(void) tsleep(&fp->f_usecount, PRIBIO, "closef", 0);
#ifdef DIAGNOSTIC
	if (fp->f_usecount != 1)
		panic("closef: usecount != 1");
#endif

	if ((fp->f_flag & FHASLOCK) && fp->f_type == DTYPE_VNODE) {
		lf.l_whence = SEEK_SET;
		lf.l_start = 0;
		lf.l_len = 0;
		lf.l_type = F_UNLCK;
		vp = (struct vnode *)fp->f_data;
		(void) VOP_ADVLOCK(vp, (caddr_t)fp, F_UNLCK, &lf, F_FLOCK);
	}
	if (fp->f_ops)
		error = (*fp->f_ops->fo_close)(fp, p);
	else
		error = 0;

	/* Nothing references the file now, drop the final use (us). */
	fp->f_usecount--;

	ffree(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).
 */
/* ARGSUSED */
int
sys_flock(struct lwp *l, void *v, register_t *retval)
{
	struct sys_flock_args /* {
		syscallarg(int)	fd;
		syscallarg(int)	how;
	} */ *uap = v;
	int		fd, how, error;
	struct proc	*p;
	struct filedesc	*fdp;
	struct file	*fp;
	struct vnode	*vp;
	struct flock	lf;

	p = l->l_proc;
	fd = SCARG(uap, fd);
	how = SCARG(uap, how);
	fdp = p->p_fd;
	error = 0;

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

	FILE_USE(fp);

	if (fp->f_type != DTYPE_VNODE) {
		error = EOPNOTSUPP;
		goto out;
	}

	vp = (struct vnode *)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;
		fp->f_flag &= ~FHASLOCK;
		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;
	}
	fp->f_flag |= FHASLOCK;
	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:
	FILE_UNUSE(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.
 */
/* ARGSUSED */
int
filedescopen(dev_t dev, int mode, int type, struct proc *p)
{

	/*
	 * XXX Kludge: set p->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 dfd, int mode, int error)
{
	struct filedesc	*fdp;
	struct file	*wfp, *fp;

	fdp = p->p_fd;
	/*
	 * 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, check for new == old is necessary as
	 * falloc could allocate an already closed to-be-dup'd descriptor
	 * as the new descriptor.
	 */
	fp = fdp->fd_ofiles[indx];

	if ((wfp = fd_getfile(fdp, dfd)) == NULL)
		return (EBADF);

	if (fp == wfp)
		return (EBADF);

	FILE_USE(wfp);

	/*
	 * There are two cases of interest here.
	 *
	 * For ENODEV simply dup (dfd) to file descriptor
	 * (indx) and return.
	 *
	 * For ENXIO steal away the file structure from (dfd) and
	 * store it in (indx).  (dfd) is effectively closed by
	 * this operation.
	 *
	 * Any other error code is just returned.
	 */
	switch (error) {
	case ENODEV:
		/*
		 * Check that the mode the file is being opened for is a
		 * subset of the mode of the existing descriptor.
		 */
		if (((mode & (FREAD|FWRITE)) | wfp->f_flag) != wfp->f_flag) {
			FILE_UNUSE(wfp, p);
			return (EACCES);
		}
		fdp->fd_ofiles[indx] = wfp;
		fdp->fd_ofileflags[indx] = fdp->fd_ofileflags[dfd];
		wfp->f_count++;
		fd_used(fdp, indx);
		FILE_UNUSE(wfp, p);
		return (0);

	case ENXIO:
		/*
		 * Steal away the file pointer from dfd, and stuff it into indx.
		 */
		fdp->fd_ofiles[indx] = fdp->fd_ofiles[dfd];
		fdp->fd_ofileflags[indx] = fdp->fd_ofileflags[dfd];
		fdp->fd_ofiles[dfd] = NULL;
		fdp->fd_ofileflags[dfd] = 0;
		/*
		 * Complete the clean up of the filedesc structure by
		 * recomputing the various hints.
		 */
		fd_used(fdp, indx);
		fd_unused(fdp, dfd);
		FILE_UNUSE(wfp, p);
		return (0);

	default:
		FILE_UNUSE(wfp, p);
		return (error);
	}
	/* NOTREACHED */
}

/*
 * fcntl call which is being passed to the file's fs.
 */
int
fcntl_forfs(int fd, struct proc *p, int cmd, void *arg)
{
	struct file	*fp;
	struct filedesc	*fdp;
	int		error;
	u_int		size;
	caddr_t		data, memp;
#define STK_PARAMS	128
	char		stkbuf[STK_PARAMS];

	/* fd's value was validated in sys_fcntl before calling this routine */
	fdp = p->p_fd;
	fp = fdp->fd_ofiles[fd];

	if ((fp->f_flag & (FREAD | FWRITE)) == 0)
		return (EBADF);

	/*
	 * Interpret high order word to find amount of data to be
	 * copied to/from the user's address space.
	 */
	size = (size_t)F_PARAM_LEN(cmd);
	if (size > F_PARAM_MAX)
		return (EINVAL);
	memp = NULL;
	if (size > sizeof(stkbuf)) {
		memp = (caddr_t)malloc((u_long)size, M_IOCTLOPS, M_WAITOK);
		data = memp;
	} else
		data = stkbuf;
	if (cmd & F_FSIN) {
		if (size) {
			error = copyin(arg, data, size);
			if (error) {
				if (memp)
					free(memp, M_IOCTLOPS);
				return (error);
			}
		} else
			*(caddr_t *)data = arg;
	} else if ((cmd & F_FSOUT) && size)
		/*
		 * Zero the buffer so the user always
		 * gets back something deterministic.
		 */
		memset(data, 0, size);
	else if (cmd & F_FSVOID)
		*(caddr_t *)data = arg;


	error = (*fp->f_ops->fo_fcntl)(fp, cmd, data, p);

	/*
	 * Copy any data to user, size was
	 * already set and checked above.
	 */
	if (error == 0 && (cmd & F_FSOUT) && size)
		error = copyout(data, arg, size);
	if (memp)
		free(memp, M_IOCTLOPS);
	return (error);
}

/*
 * Close any files on exec?
 */
void
fdcloseexec(struct proc *p)
{
	struct filedesc	*fdp;
	int		fd;

	fdunshare(p);
	cwdunshare(p);

	fdp = p->p_fd;
	for (fd = 0; fd <= fdp->fd_lastfile; fd++)
		if (fdp->fd_ofileflags[fd] & UF_EXCLOSE)
			(void) fdrelease(p, fd);
}