The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*
    2  * Copyright (c) 1990, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 3. All advertising materials mentioning features or use of this software
   14  *    must display the following acknowledgement:
   15  *      This product includes software developed by the University of
   16  *      California, Berkeley and its contributors.
   17  * 4. Neither the name of the University nor the names of its contributors
   18  *    may be used to endorse or promote products derived from this software
   19  *    without specific prior written permission.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  *
   33  *      @(#)filedesc.h  8.1 (Berkeley) 6/2/93
   34  * $FreeBSD: releng/5.1/sys/sys/filedesc.h 110906 2003-02-15 05:52:56Z alfred $
   35  */
   36 
   37 #ifndef _SYS_FILEDESC_H_
   38 #define _SYS_FILEDESC_H_
   39 
   40 #include <sys/_lock.h>
   41 #include <sys/_mutex.h>
   42 #include <sys/queue.h>
   43 
   44 /*
   45  * This structure is used for the management of descriptors.  It may be
   46  * shared by multiple processes.
   47  *
   48  * A process is initially started out with NDFILE descriptors stored within
   49  * this structure, selected to be enough for typical applications based on
   50  * the historical limit of 20 open files (and the usage of descriptors by
   51  * shells).  If these descriptors are exhausted, a larger descriptor table
   52  * may be allocated, up to a process' resource limit; the internal arrays
   53  * are then unused.  The initial expansion is set to NDEXTENT; each time
   54  * it runs out, it is doubled until the resource limit is reached. NDEXTENT
   55  * should be selected to be the biggest multiple of OFILESIZE (see below)
   56  * that will fit in a power-of-two sized piece of memory.
   57  */
   58 #define NDFILE          20
   59 #define NDEXTENT        50              /* 250 bytes in 256-byte alloc. */
   60 
   61 struct filedesc {
   62         struct  file **fd_ofiles;       /* file structures for open files */
   63         char    *fd_ofileflags;         /* per-process open file flags */
   64         struct  vnode *fd_cdir;         /* current directory */
   65         struct  vnode *fd_rdir;         /* root directory */
   66         struct  vnode *fd_jdir;         /* jail root directory */
   67         int     fd_nfiles;              /* number of open files allocated */
   68         int     fd_lastfile;            /* high-water mark of fd_ofiles */
   69         int     fd_freefile;            /* approx. next free file */
   70         u_short fd_cmask;               /* mask for file creation */
   71         u_short fd_refcnt;              /* reference count */
   72 
   73         int     fd_knlistsize;          /* size of knlist */
   74         struct  klist *fd_knlist;       /* list of attached knotes */
   75         u_long  fd_knhashmask;          /* size of knhash */
   76         struct  klist *fd_knhash;       /* hash table for attached knotes */
   77         struct mtx      fd_mtx;         /* mtx to protect the members of struct filedesc */
   78 };
   79 
   80 /*
   81  * Basic allocation of descriptors:
   82  * one of the above, plus arrays for NDFILE descriptors.
   83  */
   84 struct filedesc0 {
   85         struct  filedesc fd_fd;
   86         /*
   87          * These arrays are used when the number of open files is
   88          * <= NDFILE, and are then pointed to by the pointers above.
   89          */
   90         struct  file *fd_dfiles[NDFILE];
   91         char    fd_dfileflags[NDFILE];
   92 };
   93 
   94 /*
   95  * Per-process open flags.
   96  */
   97 #define UF_EXCLOSE      0x01            /* auto-close on exec */
   98 #if 0
   99 #define UF_MAPPED       0x02            /* mapped from device */
  100 #endif
  101 
  102 /*
  103  * Storage required per open file descriptor.
  104  */
  105 #define OFILESIZE (sizeof(struct file *) + sizeof(char))
  106 
  107 #ifdef _KERNEL
  108 
  109 #define FILEDESC_LOCK_DESC      "filedesc structure"
  110 
  111 /* Lock a file descriptor table. */
  112 #define FILEDESC_LOCK(fd)       mtx_lock(&(fd)->fd_mtx)
  113 #define FILEDESC_UNLOCK(fd)     mtx_unlock(&(fd)->fd_mtx)
  114 #define FILEDESC_LOCKED(fd)     mtx_owned(&(fd)->fd_mtx)
  115 #define FILEDESC_LOCK_ASSERT(fd, type)  mtx_assert(&(fd)->fd_mtx, (type))
  116 
  117 int     closef(struct file *fp, struct thread *p);
  118 int     dupfdopen(struct thread *td, struct filedesc *fdp, int indx, int dfd,
  119             int mode, int error);
  120 int     falloc(struct thread *p, struct file **resultfp, int *resultfd);
  121 int     fdalloc(struct thread *p, int want, int *result);
  122 int     fdavail(struct thread *td, int n);
  123 void    fdcloseexec(struct thread *td);
  124 int     fdcheckstd(struct thread *td);
  125 struct  filedesc *fdcopy(struct filedesc *fdp);
  126 void    fdfree(struct thread *td);
  127 struct  filedesc *fdinit(struct filedesc *fdp);
  128 struct  filedesc *fdshare(struct filedesc *fdp);
  129 void    ffree(struct file *fp);
  130 static __inline struct file *   fget_locked(struct filedesc *fdp, int fd);
  131 int     getvnode(struct filedesc *fdp, int fd, struct file **fpp);
  132 void    setugidsafety(struct thread *td);
  133 
  134 static __inline struct file *
  135 fget_locked(struct filedesc *fdp, int fd)
  136 {
  137 
  138         /* u_int cast checks for negative descriptors. */
  139         return ((u_int)fd >= (u_int)fdp->fd_nfiles ? NULL : fdp->fd_ofiles[fd]);
  140 }
  141 
  142 extern struct mtx fdesc_mtx;
  143 
  144 #endif /* _KERNEL */
  145 
  146 #endif /* !_SYS_FILEDESC_H_ */

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