FreeBSD/Linux Kernel Cross Reference
sys/sys/filedesc.h

     /*      $OpenBSD: filedesc.h,v 1.46 2022/05/12 13:33:09 mvs Exp $       */
     /*      $NetBSD: filedesc.h,v 1.14 1996/04/09 20:55:28 cgd Exp $        */
     
     /*
      * 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. 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
     */
    
    #include <sys/mutex.h>
    #include <sys/rwlock.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. */
    #define NDENTRIES       32              /* 32 fds per entry */
    #define NDENTRYMASK     (NDENTRIES - 1)
    #define NDENTRYSHIFT    5               /* bits per entry */
    #define NDREDUCE(x)     (((x) + NDENTRIES - 1) >> NDENTRYSHIFT)
    #define NDHISLOTS(x)    (NDREDUCE(NDREDUCE(x)))
    #define NDLOSLOTS(x)    (NDHISLOTS(x) << NDENTRYSHIFT)
    
    struct kqueue;
    
    /*
     * Locking:
     *      a       atomic operations
     *      f       fd_lock
     *      f/w     fd_lock when writing
     *      K       kernel lock
     *      m       fd_fplock
     */
    struct filedesc {
            struct  file **fd_ofiles;       /* [f/w,m] file structures for
                                             *     open files */
            char    *fd_ofileflags;         /* [f] per-process open file flags */
            struct  vnode *fd_cdir;         /* [K] current directory */
            struct  vnode *fd_rdir;         /* [K] root directory */
            int     fd_nfiles;              /* [f] number of open files allocated */
            int     fd_openfd;              /* [f] number of files currently open */
            u_int   *fd_himap;              /* [f] each bit points to 32 fds */
            u_int   *fd_lomap;              /* [f] bitmap of free fds */
            int     fd_lastfile;            /* [f] high-water mark of fd_ofiles */
            int     fd_freefile;            /* [f] approx. next free file */
            mode_t  fd_cmask;               /* [f/w] mask for file creation */
            u_int   fd_refcnt;              /* [K] reference count */
            struct rwlock fd_lock;          /* lock for the file descs */
            struct mutex fd_fplock;         /* lock for reading fd_ofiles without
                                             * fd_lock */
            LIST_HEAD(, kqueue) fd_kqlist;  /* [f] kqueues attached to this
                                             *     filedesc */
            int fd_flags;                   /* [a] flags on this filedesc */
    };
    
    /*
     * 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];
           /*
            * There arrays are used when the number of open files is
            * <= 1024, and are then pointed to by the pointers above.
            */
           u_int   fd_dhimap[NDENTRIES >> NDENTRYSHIFT];
           u_int   fd_dlomap[NDENTRIES];
   };
   
   /*
    * Per-process open flags.
    */
   #define UF_EXCLOSE      0x01            /* auto-close on exec */
   #define UF_PLEDGED      0x02            /* open after pledge(2) */
   
   /*
    * Flags on the file descriptor table.
    */
   #define FD_ADVLOCK      0x01            /* May hold a POSIX adv. lock. */
   
   /*
    * Storage required per open file descriptor.
    */
   #define OFILESIZE (sizeof(struct file *) + sizeof(char))
   
   #ifdef _KERNEL
   /*
    * Kernel global variables and routines.
    */
   void    filedesc_init(void);
   int     dupfdopen(struct proc *, int, int);
   int     fdalloc(struct proc *p, int want, int *result);
   void    fdexpand(struct proc *);
   struct  file *fnew(struct proc *_p);
   int     falloc(struct proc *_p, struct file **_rfp, int *_rfd);
   struct  filedesc *fdinit(void);
   struct  filedesc *fdshare(struct process *);
   struct  filedesc *fdcopy(struct process *);
   void    fdfree(struct proc *p);
   int     fdrelease(struct proc *p, int);
   void    fdinsert(struct filedesc *, int, int, struct file *);
   void    fdremove(struct filedesc *, int);
   void    fdcloseexec(struct proc *);
   struct file *fd_iterfile(struct file *, struct proc *);
   struct file *fd_getfile(struct filedesc *, int);
   struct file *fd_getfile_mode(struct filedesc *, int, int);
   int     fd_checkclosed(struct filedesc *, int, struct file *);
   
   int     closef(struct file *, struct proc *);
   int     getsock(struct proc *, int, struct file **);
   
   #define fdplock(fdp)    do { NET_ASSERT_UNLOCKED(); rw_enter_write(&(fdp)->fd_lock); } while (0)
   #define fdpunlock(fdp)  rw_exit_write(&(fdp)->fd_lock)
   #define fdpassertlocked(fdp)    rw_assert_wrlock(&(fdp)->fd_lock)
   #endif

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