FreeBSD/Linux Kernel Cross Reference
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.
     * 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: releng/5.3/sys/sys/filedesc.h 136588 2004-10-16 08:43:07Z cvs2svn $
     */
    
    #ifndef _SYS_FILEDESC_H_
    #define _SYS_FILEDESC_H_
    
    #include <sys/queue.h>
    #include <sys/event.h>
    #include <sys/_lock.h>
    #include <sys/_mutex.h>
    
    #include <machine/_limits.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.
     */
    #define NDFILE          20
    #define NDSLOTTYPE      u_long
    #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)
    
    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 */
            NDSLOTTYPE *fd_map;             /* bitmap of free fds */
            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 */
    
            struct  mtx fd_mtx;             /* protects members of this struct */
            struct  kqlist fd_kqlist;       /* list of kqueues on this 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];
            NDSLOTTYPE fd_dmap[NDSLOTS(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 */
   
   /*
    * Storage required per open file descriptor.
    */
   #define OFILESIZE (sizeof(struct file *) + sizeof(char))
   
   #ifdef _KERNEL
   
   /* 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))
   #define FILEDESC_LOCK_DESC      "filedesc structure"
   
   struct thread;
   
   int     closef(struct file *fp, struct thread *td);
   int     dupfdopen(struct thread *td, struct filedesc *fdp, int indx, int dfd,
               int mode, int error);
   int     falloc(struct thread *td, struct file **resultfp, int *resultfd);
   int     fdalloc(struct thread *td, int minfd, int *result);
   int     fdavail(struct thread *td, int n);
   int     fdcheckstd(struct thread *td);
   void    fdcloseexec(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    fdunused(struct filedesc *fdp, int fd);
   void    fdused(struct filedesc *fdp, int fd);
   void    ffree(struct file *fp);
   struct filedesc_to_leader *
           filedesc_to_leader_alloc(struct filedesc_to_leader *old,
               struct filedesc *fdp, struct proc *leader);
   int     getvnode(struct filedesc *fdp, int fd, struct file **fpp);
   void    setugidsafety(struct thread *td);
   
   static __inline struct file *
   fget_locked(struct filedesc *fdp, int fd)
   {
   
           return (fd < 0 || fd >= fdp->fd_nfiles ? NULL : fdp->fd_ofiles[fd]);
   }
   
   extern struct mtx fdesc_mtx;
   
   #endif /* _KERNEL */
   
   #endif /* !_SYS_FILEDESC_H_ */

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