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  * 4. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      @(#)filedesc.h  8.1 (Berkeley) 6/2/93
   30  * $FreeBSD$
   31  */
   32 
   33 #ifndef _SYS_FILEDESC_H_
   34 #define _SYS_FILEDESC_H_
   35 
   36 #include <sys/queue.h>
   37 #include <sys/event.h>
   38 #include <sys/priority.h>
   39 #include <sys/_lock.h>
   40 #include <sys/_mutex.h>
   41 
   42 #include <machine/_limits.h>
   43 
   44 /*
   45  * This structure is used for the management of descriptors.  It may be
   46  * shared by multiple processes.
   47  */
   48 #define NDSLOTTYPE      u_long
   49 
   50 struct filedesc {
   51         struct  file **fd_ofiles;       /* file structures for open files */
   52         char    *fd_ofileflags;         /* per-process open file flags */
   53         struct  vnode *fd_cdir;         /* current directory */
   54         struct  vnode *fd_rdir;         /* root directory */
   55         struct  vnode *fd_jdir;         /* jail root directory */
   56         int     fd_nfiles;              /* number of open files allocated */
   57         NDSLOTTYPE *fd_map;             /* bitmap of free fds */
   58         int     fd_lastfile;            /* high-water mark of fd_ofiles */
   59         int     fd_freefile;            /* approx. next free file */
   60         u_short fd_cmask;               /* mask for file creation */
   61         u_short fd_refcnt;              /* thread reference count */
   62         u_short fd_holdcnt;             /* hold count on structure + mutex */
   63 
   64         struct  mtx fd_mtx;             /* protects members of this struct */
   65         int     fd_locked;              /* long lock flag */
   66         int     fd_wanted;              /* "" */
   67         struct  kqlist fd_kqlist;       /* list of kqueues on this filedesc */
   68         int     fd_holdleaderscount;    /* block fdfree() for shared close() */
   69         int     fd_holdleaderswakeup;   /* fdfree() needs wakeup */
   70 };
   71 
   72 /*
   73  * Structure to keep track of (process leader, struct fildedesc) tuples.
   74  * Each process has a pointer to such a structure when detailed tracking
   75  * is needed, e.g., when rfork(RFPROC | RFMEM) causes a file descriptor
   76  * table to be shared by processes having different "p_leader" pointers
   77  * and thus distinct POSIX style locks.
   78  *
   79  * fdl_refcount and fdl_holdcount are protected by struct filedesc mtx.
   80  */
   81 struct filedesc_to_leader {
   82         int             fdl_refcount;   /* references from struct proc */
   83         int             fdl_holdcount;  /* temporary hold during closef */
   84         int             fdl_wakeup;     /* fdfree() waits on closef() */
   85         struct proc     *fdl_leader;    /* owner of POSIX locks */
   86         /* Circular list: */
   87         struct filedesc_to_leader *fdl_prev;
   88         struct filedesc_to_leader *fdl_next;
   89 };
   90 
   91 /*
   92  * Per-process open flags.
   93  */
   94 #define UF_EXCLOSE      0x01            /* auto-close on exec */
   95 
   96 #ifdef _KERNEL
   97 
   98 /* Lock a file descriptor table. */
   99 #define FILEDESC_LOCK(fd)                                                               \
  100         do {                                                                            \
  101                 mtx_lock(&(fd)->fd_mtx);                                                \
  102                 (fd)->fd_wanted++;                                                      \
  103                 while ((fd)->fd_locked)                                                 \
  104                         msleep(&(fd)->fd_locked, &(fd)->fd_mtx, PLOCK, "fdesc", 0);     \
  105                 (fd)->fd_locked = 2;                                                    \
  106                 (fd)->fd_wanted--;                                                      \
  107                 mtx_unlock(&(fd)->fd_mtx);                                              \
  108         } while (0);
  109 
  110 #define FILEDESC_UNLOCK(fd)                                                             \
  111         do {                                                                            \
  112                 mtx_lock(&(fd)->fd_mtx);                                                \
  113                 KASSERT((fd)->fd_locked == 2,                                           \
  114                     ("fdesc locking mistake %d should be %d", (fd)->fd_locked, 2));     \
  115                 (fd)->fd_locked = 0;                                                    \
  116                 if ((fd)->fd_wanted)                                                    \
  117                         wakeup(&(fd)->fd_locked);                                       \
  118                 mtx_unlock(&(fd)->fd_mtx);                                              \
  119         } while (0);
  120 
  121 #define FILEDESC_LOCK_FAST(fd)                                                          \
  122         do {                                                                            \
  123                 mtx_lock(&(fd)->fd_mtx);                                                \
  124                 (fd)->fd_wanted++;                                                      \
  125                 while ((fd)->fd_locked)                                                 \
  126                         msleep(&(fd)->fd_locked, &(fd)->fd_mtx, PLOCK, "fdesc", 0);     \
  127                 (fd)->fd_locked = 1;                                                    \
  128                 (fd)->fd_wanted--;                                                      \
  129         } while (0);
  130 
  131 #define FILEDESC_UNLOCK_FAST(fd)                                                        \
  132         do {                                                                            \
  133                 KASSERT((fd)->fd_locked == 1,                                           \
  134                     ("fdesc locking mistake %d should be %d", (fd)->fd_locked, 1));     \
  135                 (fd)->fd_locked = 0;                                                    \
  136                 if ((fd)->fd_wanted)                                                    \
  137                         wakeup(&(fd)->fd_locked);                                       \
  138                 mtx_unlock(&(fd)->fd_mtx);                                              \
  139         } while (0);
  140 
  141 #ifdef INVARIANT_SUPPORT
  142 #define FILEDESC_LOCK_ASSERT(fd, arg)                                                   \
  143         do {                                                                            \
  144                 if ((arg) == MA_OWNED)                                                  \
  145                         KASSERT((fd)->fd_locked != 0, ("fdesc locking mistake"));       \
  146                 else                                                                    \
  147                         KASSERT((fd)->fd_locked == 0, ("fdesc locking mistake"));       \
  148         } while (0);
  149 #else
  150 #define FILEDESC_LOCK_ASSERT(fd, arg)
  151 #endif
  152 
  153 #define FILEDESC_LOCK_DESC      "filedesc structure"
  154 
  155 struct thread;
  156 
  157 int     closef(struct file *fp, struct thread *td);
  158 int     dupfdopen(struct thread *td, struct filedesc *fdp, int indx, int dfd,
  159             int mode, int error);
  160 int     falloc(struct thread *td, struct file **resultfp, int *resultfd);
  161 int     fdalloc(struct thread *td, int minfd, int *result);
  162 int     fdavail(struct thread *td, int n);
  163 int     fdcheckstd(struct thread *td);
  164 void    fdclose(struct filedesc *fdp, struct file *fp, int idx, struct thread *td);
  165 void    fdcloseexec(struct thread *td);
  166 struct  filedesc *fdcopy(struct filedesc *fdp);
  167 void    fdunshare(struct proc *p, struct thread *td);
  168 void    fdfree(struct thread *td);
  169 struct  filedesc *fdinit(struct filedesc *fdp);
  170 struct  filedesc *fdshare(struct filedesc *fdp);
  171 struct filedesc_to_leader *
  172         filedesc_to_leader_alloc(struct filedesc_to_leader *old,
  173             struct filedesc *fdp, struct proc *leader);
  174 int     getvnode(struct filedesc *fdp, int fd, struct file **fpp);
  175 void    mountcheckdirs(struct vnode *olddp, struct vnode *newdp);
  176 void    setugidsafety(struct thread *td);
  177 
  178 static __inline struct file *
  179 fget_locked(struct filedesc *fdp, int fd)
  180 {
  181 
  182         return (fd < 0 || fd >= fdp->fd_nfiles ? NULL : fdp->fd_ofiles[fd]);
  183 }
  184 
  185 #endif /* _KERNEL */
  186 
  187 #endif /* !_SYS_FILEDESC_H_ */

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