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

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * 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
     * $FreeBSD$
     */
    
    #ifndef _SYS_FILEDESC_H_
    #define _SYS_FILEDESC_H_
    
    #include <sys/types.h>
    #include <sys/caprights.h>
    #include <sys/queue.h>
    #include <sys/event.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/priority.h>
    #include <sys/seqc.h>
    #include <sys/sx.h>
    #include <sys/_smr.h>
    #include <sys/smr_types.h>
    
    #include <machine/_limits.h>
    
    struct filecaps {
            cap_rights_t     fc_rights;     /* per-descriptor capability rights */
            u_long          *fc_ioctls;     /* per-descriptor allowed ioctls */
            int16_t          fc_nioctls;    /* fc_ioctls array size */
            uint32_t         fc_fcntls;     /* per-descriptor allowed fcntls */
    };
    
    struct filedescent {
            struct file     *fde_file;      /* file structure for open file */
            struct filecaps  fde_caps;      /* per-descriptor rights */
            uint8_t          fde_flags;     /* per-process open file flags */
            seqc_t           fde_seqc;      /* keep file and caps in sync */
    };
    #define fde_rights      fde_caps.fc_rights
    #define fde_fcntls      fde_caps.fc_fcntls
    #define fde_ioctls      fde_caps.fc_ioctls
    #define fde_nioctls     fde_caps.fc_nioctls
    
    #ifdef _KERNEL
    static inline void
    fde_copy(struct filedescent *from, struct filedescent *to)
    {
    
            to->fde_file = from->fde_file;
            to->fde_caps = from->fde_caps;
            to->fde_flags = from->fde_flags;
    }
    #endif
    
    struct fdescenttbl {
            int     fdt_nfiles;             /* number of open files allocated */
            struct  filedescent fdt_ofiles[0];      /* open files */
    };
    #define fd_seqc(fdt, fd)        (&(fdt)->fdt_ofiles[(fd)].fde_seqc)
    
    #define NDSLOTTYPE      u_long
    
    /*
     * This struct is copy-on-write and allocated from an SMR zone.
     * All fields are constant after initialization apart from the reference count.
     *
     * Check pwd_* routines for usage.
     */
    struct pwd {
            u_int           pwd_refcount;
            struct  vnode   *pwd_cdir;      /* current directory */
            struct  vnode   *pwd_rdir;      /* root directory */
            struct  vnode   *pwd_jdir;      /* jail root directory */
   };
   typedef SMR_POINTER(struct pwd *) smrpwd_t;
   
   struct pwddesc {
           struct mtx      pd_lock;        /* protects members of this struct */
           smrpwd_t        pd_pwd;         /* directories */
           u_int           pd_refcount;
           u_short         pd_cmask;       /* mask for file creation */
   };
   
   /*
    * This structure is used for the management of descriptors.  It may be
    * shared by multiple processes.
    */
   struct filedesc {
           struct  fdescenttbl *fd_files;  /* open files table */
           NDSLOTTYPE *fd_map;             /* bitmap of free fds */
           int     fd_freefile;            /* approx. next free file */
           int     fd_refcnt;              /* thread reference count */
           int     fd_holdcnt;             /* hold count on structure + mutex */
           struct  sx fd_sx;               /* 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 */
   };
   
   /*
    * 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;
   };
   #define fd_nfiles       fd_files->fdt_nfiles
   #define fd_ofiles       fd_files->fdt_ofiles
   
   /*
    * Per-process open flags.
    */
   #define UF_EXCLOSE      0x01            /* auto-close on exec */
   
   #ifdef _KERNEL
   
   /* Lock a paths descriptor table. */
   #define PWDDESC_LOCK(pdp)       (&(pdp)->pd_lock)
   #define PWDDESC_LOCK_INIT(pdp) \
       mtx_init(PWDDESC_LOCK(pdp), "pwddesc", NULL, MTX_DEF)
   #define PWDDESC_LOCK_DESTROY(pdp)       mtx_destroy(PWDDESC_LOCK(pdp))
   #define PWDDESC_XLOCK(pdp)      mtx_lock(PWDDESC_LOCK(pdp))
   #define PWDDESC_XUNLOCK(pdp)    mtx_unlock(PWDDESC_LOCK(pdp))
   #define PWDDESC_LOCK_ASSERT(pdp, what) \
       mtx_assert(PWDDESC_LOCK(pdp), (what))
   #define PWDDESC_ASSERT_XLOCKED(pdp) \
       PWDDESC_LOCK_ASSERT((pdp), MA_OWNED)
   #define PWDDESC_ASSERT_UNLOCKED(pdp) \
       PWDDESC_LOCK_ASSERT((pdp), MA_NOTOWNED)
   
   #define PWDDESC_XLOCKED_LOAD_PWD(pdp)   ({                                      \
           struct pwddesc *_pdp = (pdp);                                           \
           struct pwd *_pwd;                                                       \
           _pwd = smr_serialized_load(&(_pdp)->pd_pwd,                             \
               (PWDDESC_ASSERT_XLOCKED(_pdp), true));                              \
           _pwd;                                                                   \
   })
   
   /* Lock a file descriptor table. */
   #define FILEDESC_LOCK_INIT(fdp) sx_init(&(fdp)->fd_sx, "filedesc structure")
   #define FILEDESC_LOCK_DESTROY(fdp)      sx_destroy(&(fdp)->fd_sx)
   #define FILEDESC_LOCK(fdp)      (&(fdp)->fd_sx)
   #define FILEDESC_XLOCK(fdp)     sx_xlock(&(fdp)->fd_sx)
   #define FILEDESC_XUNLOCK(fdp)   sx_xunlock(&(fdp)->fd_sx)
   #define FILEDESC_SLOCK(fdp)     sx_slock(&(fdp)->fd_sx)
   #define FILEDESC_SUNLOCK(fdp)   sx_sunlock(&(fdp)->fd_sx)
   
   #define FILEDESC_LOCK_ASSERT(fdp)       sx_assert(&(fdp)->fd_sx, SX_LOCKED | \
                                               SX_NOTRECURSED)
   #define FILEDESC_XLOCK_ASSERT(fdp)      sx_assert(&(fdp)->fd_sx, SX_XLOCKED | \
                                               SX_NOTRECURSED)
   #define FILEDESC_UNLOCK_ASSERT(fdp)     sx_assert(&(fdp)->fd_sx, SX_UNLOCKED)
   
   #define FILEDESC_IS_ONLY_USER(fdp)      ({                                      \
           struct filedesc *_fdp = (fdp);                                          \
           MPASS(curproc->p_fd == _fdp);                                           \
           (curproc->p_numthreads == 1 && refcount_load(&_fdp->fd_refcnt) == 1);   \
   })
   
   #else
   
   /*
    * Accessor for libkvm et al.
    */
   #define PWDDESC_KVM_LOAD_PWD(pdp)       ({                                      \
           struct pwddesc *_pdp = (pdp);                                           \
           struct pwd *_pwd;                                                       \
           _pwd = smr_kvm_load(&(_pdp)->pd_pwd);                                   \
           _pwd;                                                                   \
   })
   
   #endif
   
   #ifdef _KERNEL
   
   /* Operation types for kern_dup(). */
   enum {
           FDDUP_NORMAL,           /* dup() behavior. */
           FDDUP_FCNTL,            /* fcntl()-style errors. */
           FDDUP_FIXED,            /* Force fixed allocation. */
           FDDUP_LASTMODE,
   };
   
   /* Flags for kern_dup(). */
   #define FDDUP_FLAG_CLOEXEC      0x1     /* Atomically set UF_EXCLOSE. */
   
   /* For backward compatibility. */
   #define falloc(td, resultfp, resultfd, flags) \
           falloc_caps(td, resultfp, resultfd, flags, NULL)
   
   struct mount;
   struct thread;
   
   static __inline void
   filecaps_init(struct filecaps *fcaps)
   {
   
           bzero(fcaps, sizeof(*fcaps));
           fcaps->fc_nioctls = -1;
   }
   bool    filecaps_copy(const struct filecaps *src, struct filecaps *dst,
               bool locked);
   void    filecaps_move(struct filecaps *src, struct filecaps *dst);
   void    filecaps_free(struct filecaps *fcaps);
   
   int     closef(struct file *fp, struct thread *td);
   void    closef_nothread(struct file *fp);
   int     descrip_check_write_mp(struct filedesc *fdp, struct mount *mp);
   int     dupfdopen(struct thread *td, struct filedesc *fdp, int dfd, int mode,
               int openerror, int *indxp);
   int     falloc_caps(struct thread *td, struct file **resultfp, int *resultfd,
               int flags, struct filecaps *fcaps);
   void    falloc_abort(struct thread *td, struct file *fp);
   int     _falloc_noinstall(struct thread *td, struct file **resultfp, u_int n);
   #define falloc_noinstall(td, resultfp) _falloc_noinstall(td, resultfp, 1)
   void    _finstall(struct filedesc *fdp, struct file *fp, int fd, int flags,
               struct filecaps *fcaps);
   int     finstall(struct thread *td, struct file *fp, int *resultfd, int flags,
               struct filecaps *fcaps);
   int     finstall_refed(struct thread *td, struct file *fp, int *resultfd, int flags,
               struct filecaps *fcaps);
   int     fdalloc(struct thread *td, int minfd, int *result);
   int     fdallocn(struct thread *td, int minfd, int *fds, int n);
   int     fdcheckstd(struct thread *td);
   void    fdclose(struct thread *td, struct file *fp, int idx);
   void    fdcloseexec(struct thread *td);
   void    fdsetugidsafety(struct thread *td);
   struct  filedesc *fdcopy(struct filedesc *fdp);
   void    fdunshare(struct thread *td);
   void    fdescfree(struct thread *td);
   int     fdlastfile(struct filedesc *fdp);
   int     fdlastfile_single(struct filedesc *fdp);
   struct  filedesc *fdinit(void);
   struct  filedesc *fdshare(struct filedesc *fdp);
   struct filedesc_to_leader *
           filedesc_to_leader_alloc(struct filedesc_to_leader *old,
               struct filedesc *fdp, struct proc *leader);
   struct filedesc_to_leader *
           filedesc_to_leader_share(struct filedesc_to_leader *fdtol,
               struct filedesc *fdp);
   int     getvnode(struct thread *td, int fd, cap_rights_t *rightsp,
               struct file **fpp);
   int     getvnode_path(struct thread *td, int fd, cap_rights_t *rightsp,
               struct file **fpp);
   void    mountcheckdirs(struct vnode *olddp, struct vnode *newdp);
   
   int     fget_cap_noref(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
               struct file **fpp, struct filecaps *havecapsp);
   int     fget_cap(struct thread *td, int fd, cap_rights_t *needrightsp,
               struct file **fpp, struct filecaps *havecapsp);
   /* Return a referenced file from an unlocked descriptor. */
   int     fget_unlocked(struct thread *td, int fd, cap_rights_t *needrightsp,
               struct file **fpp);
   /* Return a file pointer without a ref. FILEDESC_IS_ONLY_USER must be true.  */
   int     fget_only_user(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
               struct file **fpp);
   #define fput_only_user(fdp, fp) ({                                      \
           MPASS(FILEDESC_IS_ONLY_USER(fdp));                              \
           MPASS(refcount_load(&fp->f_count) > 0);                         \
   })
   
   /* Requires a FILEDESC_{S,X}LOCK held and returns without a ref. */
   static __inline struct file *
   fget_noref(struct filedesc *fdp, int fd)
   {
   
           FILEDESC_LOCK_ASSERT(fdp);
   
           if (__predict_false((u_int)fd >= fdp->fd_nfiles))
                   return (NULL);
   
           return (fdp->fd_ofiles[fd].fde_file);
   }
   
   static __inline struct filedescent *
   fdeget_noref(struct filedesc *fdp, int fd)
   {
           struct filedescent *fde;
   
           FILEDESC_LOCK_ASSERT(fdp);
   
           if (__predict_false((u_int)fd >= fdp->fd_nfiles))
                   return (NULL);
   
           fde = &fdp->fd_ofiles[fd];
           if (__predict_false(fde->fde_file == NULL))
                   return (NULL);
   
           return (fde);
   }
   
   #ifdef CAPABILITIES
   static __inline bool
   fd_modified(struct filedesc *fdp, int fd, seqc_t seqc)
   {
   
           return (!seqc_consistent(fd_seqc(fdp->fd_files, fd), seqc));
   }
   #endif
   
   /* cdir/rdir/jdir manipulation functions. */
   struct pwddesc *pdcopy(struct pwddesc *pdp);
   void    pdescfree(struct thread *td);
   struct pwddesc *pdinit(struct pwddesc *pdp, bool keeplock);
   struct pwddesc *pdshare(struct pwddesc *pdp);
   void    pdunshare(struct thread *td);
   
   void    pwd_chdir(struct thread *td, struct vnode *vp);
   int     pwd_chroot(struct thread *td, struct vnode *vp);
   int     pwd_chroot_chdir(struct thread *td, struct vnode *vp);
   void    pwd_ensure_dirs(void);
   void    pwd_set_rootvnode(void);
   
   struct pwd *pwd_hold_pwddesc(struct pwddesc *pdp);
   bool    pwd_hold_smr(struct pwd *pwd);
   struct pwd *pwd_hold_proc(struct proc *p);
   struct pwd *pwd_hold(struct thread *td);
   void    pwd_drop(struct pwd *pwd);
   static inline void
   pwd_set(struct pwddesc *pdp, struct pwd *newpwd)
   {
           smr_serialized_store(&pdp->pd_pwd, newpwd,
               (PWDDESC_ASSERT_XLOCKED(pdp), true));
   }
   #define pwd_get_smr()   vfs_smr_entered_load(&curproc->p_pd->pd_pwd)
   
   #endif /* _KERNEL */
   
   #endif /* !_SYS_FILEDESC_H_ */

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