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  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1990, 1993
    5  *      The Regents of the University of California.  All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Neither the name of the University nor the names of its contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  *
   31  *      @(#)filedesc.h  8.1 (Berkeley) 6/2/93
   32  * $FreeBSD: stable/12/sys/sys/filedesc.h 332657 2018-04-17 18:07:40Z jhb $
   33  */
   34 
   35 #ifndef _SYS_FILEDESC_H_
   36 #define _SYS_FILEDESC_H_
   37 
   38 #include <sys/caprights.h>
   39 #include <sys/queue.h>
   40 #include <sys/event.h>
   41 #include <sys/lock.h>
   42 #include <sys/priority.h>
   43 #include <sys/seq.h>
   44 #include <sys/sx.h>
   45 
   46 #include <machine/_limits.h>
   47 
   48 struct filecaps {
   49         cap_rights_t     fc_rights;     /* per-descriptor capability rights */
   50         u_long          *fc_ioctls;     /* per-descriptor allowed ioctls */
   51         int16_t          fc_nioctls;    /* fc_ioctls array size */
   52         uint32_t         fc_fcntls;     /* per-descriptor allowed fcntls */
   53 };
   54 
   55 struct filedescent {
   56         struct file     *fde_file;      /* file structure for open file */
   57         struct filecaps  fde_caps;      /* per-descriptor rights */
   58         uint8_t          fde_flags;     /* per-process open file flags */
   59         seq_t            fde_seq;       /* keep file and caps in sync */
   60 };
   61 #define fde_rights      fde_caps.fc_rights
   62 #define fde_fcntls      fde_caps.fc_fcntls
   63 #define fde_ioctls      fde_caps.fc_ioctls
   64 #define fde_nioctls     fde_caps.fc_nioctls
   65 #define fde_change_size (offsetof(struct filedescent, fde_seq))
   66 
   67 struct fdescenttbl {
   68         int     fdt_nfiles;             /* number of open files allocated */
   69         struct  filedescent fdt_ofiles[0];      /* open files */
   70 };
   71 #define fd_seq(fdt, fd) (&(fdt)->fdt_ofiles[(fd)].fde_seq)
   72 
   73 /*
   74  * This structure is used for the management of descriptors.  It may be
   75  * shared by multiple processes.
   76  */
   77 #define NDSLOTTYPE      u_long
   78 
   79 struct filedesc {
   80         struct  fdescenttbl *fd_files;  /* open files table */
   81         struct  vnode *fd_cdir;         /* current directory */
   82         struct  vnode *fd_rdir;         /* root directory */
   83         struct  vnode *fd_jdir;         /* jail root directory */
   84         NDSLOTTYPE *fd_map;             /* bitmap of free fds */
   85         int     fd_lastfile;            /* high-water mark of fd_ofiles */
   86         int     fd_freefile;            /* approx. next free file */
   87         u_short fd_cmask;               /* mask for file creation */
   88         int     fd_refcnt;              /* thread reference count */
   89         int     fd_holdcnt;             /* hold count on structure + mutex */
   90         struct  sx fd_sx;               /* protects members of this struct */
   91         struct  kqlist fd_kqlist;       /* list of kqueues on this filedesc */
   92         int     fd_holdleaderscount;    /* block fdfree() for shared close() */
   93         int     fd_holdleaderswakeup;   /* fdfree() needs wakeup */
   94 };
   95 
   96 /*
   97  * Structure to keep track of (process leader, struct fildedesc) tuples.
   98  * Each process has a pointer to such a structure when detailed tracking
   99  * is needed, e.g., when rfork(RFPROC | RFMEM) causes a file descriptor
  100  * table to be shared by processes having different "p_leader" pointers
  101  * and thus distinct POSIX style locks.
  102  *
  103  * fdl_refcount and fdl_holdcount are protected by struct filedesc mtx.
  104  */
  105 struct filedesc_to_leader {
  106         int             fdl_refcount;   /* references from struct proc */
  107         int             fdl_holdcount;  /* temporary hold during closef */
  108         int             fdl_wakeup;     /* fdfree() waits on closef() */
  109         struct proc     *fdl_leader;    /* owner of POSIX locks */
  110         /* Circular list: */
  111         struct filedesc_to_leader *fdl_prev;
  112         struct filedesc_to_leader *fdl_next;
  113 };
  114 #define fd_nfiles       fd_files->fdt_nfiles
  115 #define fd_ofiles       fd_files->fdt_ofiles
  116 
  117 /*
  118  * Per-process open flags.
  119  */
  120 #define UF_EXCLOSE      0x01            /* auto-close on exec */
  121 
  122 #ifdef _KERNEL
  123 
  124 /* Lock a file descriptor table. */
  125 #define FILEDESC_LOCK_INIT(fdp) sx_init(&(fdp)->fd_sx, "filedesc structure")
  126 #define FILEDESC_LOCK_DESTROY(fdp)      sx_destroy(&(fdp)->fd_sx)
  127 #define FILEDESC_LOCK(fdp)      (&(fdp)->fd_sx)
  128 #define FILEDESC_XLOCK(fdp)     sx_xlock(&(fdp)->fd_sx)
  129 #define FILEDESC_XUNLOCK(fdp)   sx_xunlock(&(fdp)->fd_sx)
  130 #define FILEDESC_SLOCK(fdp)     sx_slock(&(fdp)->fd_sx)
  131 #define FILEDESC_SUNLOCK(fdp)   sx_sunlock(&(fdp)->fd_sx)
  132 
  133 #define FILEDESC_LOCK_ASSERT(fdp)       sx_assert(&(fdp)->fd_sx, SX_LOCKED | \
  134                                             SX_NOTRECURSED)
  135 #define FILEDESC_XLOCK_ASSERT(fdp)      sx_assert(&(fdp)->fd_sx, SX_XLOCKED | \
  136                                             SX_NOTRECURSED)
  137 #define FILEDESC_UNLOCK_ASSERT(fdp)     sx_assert(&(fdp)->fd_sx, SX_UNLOCKED)
  138 
  139 /* Operation types for kern_dup(). */
  140 enum {
  141         FDDUP_NORMAL,           /* dup() behavior. */
  142         FDDUP_FCNTL,            /* fcntl()-style errors. */
  143         FDDUP_FIXED,            /* Force fixed allocation. */
  144         FDDUP_MUSTREPLACE,      /* Target must exist. */
  145         FDDUP_LASTMODE,
  146 };
  147 
  148 /* Flags for kern_dup(). */
  149 #define FDDUP_FLAG_CLOEXEC      0x1     /* Atomically set UF_EXCLOSE. */
  150 
  151 /* For backward compatibility. */
  152 #define falloc(td, resultfp, resultfd, flags) \
  153         falloc_caps(td, resultfp, resultfd, flags, NULL)
  154 
  155 struct thread;
  156 
  157 void    filecaps_init(struct filecaps *fcaps);
  158 bool    filecaps_copy(const struct filecaps *src, struct filecaps *dst,
  159             bool locked);
  160 void    filecaps_move(struct filecaps *src, struct filecaps *dst);
  161 void    filecaps_free(struct filecaps *fcaps);
  162 
  163 int     closef(struct file *fp, struct thread *td);
  164 int     dupfdopen(struct thread *td, struct filedesc *fdp, int dfd, int mode,
  165             int openerror, int *indxp);
  166 int     falloc_caps(struct thread *td, struct file **resultfp, int *resultfd,
  167             int flags, struct filecaps *fcaps);
  168 int     falloc_noinstall(struct thread *td, struct file **resultfp);
  169 void    _finstall(struct filedesc *fdp, struct file *fp, int fd, int flags,
  170             struct filecaps *fcaps);
  171 int     finstall(struct thread *td, struct file *fp, int *resultfd, int flags,
  172             struct filecaps *fcaps);
  173 int     fdalloc(struct thread *td, int minfd, int *result);
  174 int     fdallocn(struct thread *td, int minfd, int *fds, int n);
  175 int     fdcheckstd(struct thread *td);
  176 void    fdclose(struct thread *td, struct file *fp, int idx);
  177 void    fdcloseexec(struct thread *td);
  178 void    fdsetugidsafety(struct thread *td);
  179 struct  filedesc *fdcopy(struct filedesc *fdp);
  180 int     fdcopy_remapped(struct filedesc *fdp, const int *fds, size_t nfds,
  181             struct filedesc **newfdp);
  182 void    fdinstall_remapped(struct thread *td, struct filedesc *fdp);
  183 void    fdunshare(struct thread *td);
  184 void    fdescfree(struct thread *td);
  185 void    fdescfree_remapped(struct filedesc *fdp);
  186 struct  filedesc *fdinit(struct filedesc *fdp, bool prepfiles);
  187 struct  filedesc *fdshare(struct filedesc *fdp);
  188 struct filedesc_to_leader *
  189         filedesc_to_leader_alloc(struct filedesc_to_leader *old,
  190             struct filedesc *fdp, struct proc *leader);
  191 int     getvnode(struct thread *td, int fd, cap_rights_t *rightsp,
  192             struct file **fpp);
  193 void    mountcheckdirs(struct vnode *olddp, struct vnode *newdp);
  194 
  195 int     fget_cap_locked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
  196             struct file **fpp, struct filecaps *havecapsp);
  197 int     fget_cap(struct thread *td, int fd, cap_rights_t *needrightsp,
  198             struct file **fpp, struct filecaps *havecapsp);
  199 
  200 /* Return a referenced file from an unlocked descriptor. */
  201 int     fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
  202             struct file **fpp, seq_t *seqp);
  203 
  204 /* Requires a FILEDESC_{S,X}LOCK held and returns without a ref. */
  205 static __inline struct file *
  206 fget_locked(struct filedesc *fdp, int fd)
  207 {
  208 
  209         FILEDESC_LOCK_ASSERT(fdp);
  210 
  211         if (fd < 0 || fd > fdp->fd_lastfile)
  212                 return (NULL);
  213 
  214         return (fdp->fd_ofiles[fd].fde_file);
  215 }
  216 
  217 static __inline struct filedescent *
  218 fdeget_locked(struct filedesc *fdp, int fd)
  219 {
  220         struct filedescent *fde;
  221 
  222         FILEDESC_LOCK_ASSERT(fdp);
  223 
  224         if (fd < 0 || fd > fdp->fd_lastfile)
  225                 return (NULL);
  226 
  227         fde = &fdp->fd_ofiles[fd];
  228         if (fde->fde_file == NULL)
  229                 return (NULL);
  230 
  231         return (fde);
  232 }
  233 
  234 #ifdef CAPABILITIES
  235 static __inline bool
  236 fd_modified(struct filedesc *fdp, int fd, seq_t seq)
  237 {
  238 
  239         return (!seq_consistent(fd_seq(fdp->fd_files, fd), seq));
  240 }
  241 #endif
  242 
  243 /* cdir/rdir/jdir manipulation functions. */
  244 void    pwd_chdir(struct thread *td, struct vnode *vp);
  245 int     pwd_chroot(struct thread *td, struct vnode *vp);
  246 void    pwd_ensure_dirs(void);
  247 
  248 #endif /* _KERNEL */
  249 
  250 #endif /* !_SYS_FILEDESC_H_ */

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