freebsd-dev/sys/sys/filedesc.h

/*
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * 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.
 *
 *	@(#)filedesc.h	8.1 (Berkeley) 6/2/93
 * $FreeBSD$
 */

#ifndef _SYS_FILEDESC_H_
#define	_SYS_FILEDESC_H_

#include <sys/_lock.h>
#include <sys/_mutex.h>
#include <sys/queue.h>

/*
 * This structure is used for the management of descriptors.  It may be
 * shared by multiple processes.
 *
 * A process is initially started out with NDFILE descriptors stored within
 * this structure, selected to be enough for typical applications based on
 * the historical limit of 20 open files (and the usage of descriptors by
 * shells).  If these descriptors are exhausted, a larger descriptor table
 * may be allocated, up to a process' resource limit; the internal arrays
 * are then unused.  The initial expansion is set to NDEXTENT; each time
 * it runs out, it is doubled until the resource limit is reached. NDEXTENT
 * should be selected to be the biggest multiple of OFILESIZE (see below)
 * that will fit in a power-of-two sized piece of memory.
 */
#define NDFILE		20
#define NDEXTENT	50		/* 250 bytes in 256-byte alloc. */

struct filedesc {
	struct	file **fd_ofiles;	/* file structures for open files */
	char	*fd_ofileflags;		/* per-process open file flags */
	struct	vnode *fd_cdir;		/* current directory */
	struct	vnode *fd_rdir;		/* root directory */
	struct	vnode *fd_jdir;		/* jail root directory */
	int	fd_nfiles;		/* number of open files allocated */
	int	fd_lastfile;		/* high-water mark of fd_ofiles */
	int	fd_freefile;		/* approx. next free file */
	u_short	fd_cmask;		/* mask for file creation */
	u_short	fd_refcnt;		/* reference count */

	int	fd_knlistsize;		/* size of knlist */
	struct	klist *fd_knlist;	/* list of attached knotes */
	u_long	fd_knhashmask;		/* size of knhash */
	struct	klist *fd_knhash;	/* hash table for attached knotes */
	struct mtx	fd_mtx;		/* mtx to protect the members of struct filedesc */
	int	fd_holdleaderscount;	/* block fdfree() for shared close() */
	int	fd_holdleaderswakeup;	/* fdfree() needs wakeup */
};

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



/*
 * Structure to keep track of (process leader, struct fildedesc) tuples.
 * Each process has a pointer to such a structure when detailed tracking
 * is needed. e.g. when rfork(RFPROC | RFMEM) causes a file descriptor
 * table to be shared by processes having different "p_leader" pointers
 * and thus distinct POSIX style locks.
 *
 * fdl_refcount and fdl_holdcount are protected by struct filedesc mtx.
 */
struct filedesc_to_leader {
	int		fdl_refcount;	/* references from struct proc */
	int		fdl_holdcount;	/* temporary hold during closef */
	int		fdl_wakeup;	/* fdfree() waits on closef() */
	struct proc	*fdl_leader;	/* owner of POSIX locks */
	/* Circular list */
	struct filedesc_to_leader *fdl_prev;
	struct filedesc_to_leader *fdl_next;
};

/*
 * Per-process open flags.
 */
#define	UF_EXCLOSE 	0x01		/* auto-close on exec */
#if 0
#define	UF_MAPPED 	0x02		/* mapped from device */
#endif

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

#ifdef _KERNEL

#define FILEDESC_LOCK_DESC	"filedesc structure"

/* Lock a file descriptor table. */
#define FILEDESC_LOCK(fd)	mtx_lock(&(fd)->fd_mtx)
#define FILEDESC_UNLOCK(fd)	mtx_unlock(&(fd)->fd_mtx)
#define	FILEDESC_LOCKED(fd)	mtx_owned(&(fd)->fd_mtx)
#define	FILEDESC_LOCK_ASSERT(fd, type)	mtx_assert(&(fd)->fd_mtx, (type))

struct thread;

int	closef(struct file *fp, struct thread *p);
int	dupfdopen(struct thread *td, struct filedesc *fdp, int indx, int dfd,
	    int mode, int error);
int	falloc(struct thread *p, struct file **resultfp, int *resultfd);
int	fdalloc(struct thread *p, int want, int *result);
int	fdavail(struct thread *td, int n);
void	fdcloseexec(struct thread *td);
int	fdcheckstd(struct thread *td);
struct	filedesc *fdcopy(struct filedesc *fdp);
void	fdfree(struct thread *td);
struct	filedesc *fdinit(struct filedesc *fdp);
struct	filedesc *fdshare(struct filedesc *fdp);
void	ffree(struct file *fp);
static __inline struct file *	fget_locked(struct filedesc *fdp, int fd);
int	getvnode(struct filedesc *fdp, int fd, struct file **fpp);
void	setugidsafety(struct thread *td);

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


static __inline struct file *
fget_locked(struct filedesc *fdp, int fd)
{

	/* u_int cast checks for negative descriptors. */
	return ((u_int)fd >= (u_int)fdp->fd_nfiles ? NULL : fdp->fd_ofiles[fd]);
}

extern struct mtx fdesc_mtx;

#endif /* _KERNEL */

#endif /* !_SYS_FILEDESC_H_ */