FreeBSD/Linux Kernel Cross Reference
sys/fs/fdescfs/fdesc_vnops.c

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * Copyright (c) 1992, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code is derived from software donated to Berkeley by
      * Jan-Simon Pendry.
      *
     * 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.
     *
     *      @(#)fdesc_vnops.c       8.9 (Berkeley) 1/21/94
     *
     * $FreeBSD$
     */
    
    /*
     * /dev/fd Filesystem
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/capsicum.h>
    #include <sys/conf.h>
    #include <sys/dirent.h>
    #include <sys/filedesc.h>
    #include <sys/kernel.h> /* boottime */
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/malloc.h>
    #include <sys/file.h>   /* Must come after sys/malloc.h */
    #include <sys/mount.h>
    #include <sys/namei.h>
    #include <sys/proc.h>
    #include <sys/stat.h>
    #include <sys/syscallsubr.h>
    #include <sys/unistd.h>
    #include <sys/vnode.h>
    
    #include <fs/fdescfs/fdesc.h>
    
    #define NFDCACHE 4
    #define FD_NHASH(ix) \
            (&fdhashtbl[(ix) & fdhash])
    static LIST_HEAD(fdhashhead, fdescnode) *fdhashtbl;
    static u_long fdhash;
    
    struct mtx fdesc_hashmtx;
    
    static vop_getattr_t    fdesc_getattr;
    static vop_lookup_t     fdesc_lookup;
    static vop_open_t       fdesc_open;
    static vop_pathconf_t   fdesc_pathconf;
    static vop_readdir_t    fdesc_readdir;
    static vop_readlink_t   fdesc_readlink;
    static vop_reclaim_t    fdesc_reclaim;
    static vop_setattr_t    fdesc_setattr;
    
    static struct vop_vector fdesc_vnodeops = {
            .vop_default =          &default_vnodeops,
    
            .vop_access =           VOP_NULL,
            .vop_getattr =          fdesc_getattr,
            .vop_lookup =           fdesc_lookup,
            .vop_open =             fdesc_open,
            .vop_pathconf =         fdesc_pathconf,
            .vop_readdir =          fdesc_readdir,
            .vop_readlink =         fdesc_readlink,
            .vop_reclaim =          fdesc_reclaim,
            .vop_setattr =          fdesc_setattr,
    };
    VFS_VOP_VECTOR_REGISTER(fdesc_vnodeops);
    
    static void fdesc_insmntque_dtr(struct vnode *, void *);
    static void fdesc_remove_entry(struct fdescnode *);
    
    /*
    * Initialise cache headers
    */
   int
   fdesc_init(struct vfsconf *vfsp)
   {
   
           mtx_init(&fdesc_hashmtx, "fdescfs_hash", NULL, MTX_DEF);
           fdhashtbl = hashinit(NFDCACHE, M_CACHE, &fdhash);
           return (0);
   }
   
   /*
    * Uninit ready for unload.
    */
   int
   fdesc_uninit(struct vfsconf *vfsp)
   {
   
           hashdestroy(fdhashtbl, M_CACHE, fdhash);
           mtx_destroy(&fdesc_hashmtx);
           return (0);
   }
   
   /*
    * If allocating vnode fails, call this.
    */
   static void
   fdesc_insmntque_dtr(struct vnode *vp, void *arg)
   {
   
           vgone(vp);
           vput(vp);
   }
   
   /*
    * Remove an entry from the hash if it exists.
    */
   static void
   fdesc_remove_entry(struct fdescnode *fd)
   {
           struct fdhashhead *fc;
           struct fdescnode *fd2;
   
           fc = FD_NHASH(fd->fd_ix);
           mtx_lock(&fdesc_hashmtx);
           LIST_FOREACH(fd2, fc, fd_hash) {
                   if (fd == fd2) {
                           LIST_REMOVE(fd, fd_hash);
                           break;
                   }
           }
           mtx_unlock(&fdesc_hashmtx);
   }
   
   int
   fdesc_allocvp(fdntype ftype, unsigned fd_fd, int ix, struct mount *mp,
       struct vnode **vpp)
   {
           struct fdescmount *fmp;
           struct fdhashhead *fc;
           struct fdescnode *fd, *fd2;
           struct vnode *vp, *vp2;
           struct thread *td;
           int error;
   
           td = curthread;
           fc = FD_NHASH(ix);
   loop:
           mtx_lock(&fdesc_hashmtx);
           /*
            * If a forced unmount is progressing, we need to drop it. The flags are
            * protected by the hashmtx.
            */
           fmp = mp->mnt_data;
           if (fmp == NULL || fmp->flags & FMNT_UNMOUNTF) {
                   mtx_unlock(&fdesc_hashmtx);
                   return (-1);
           }
   
           LIST_FOREACH(fd, fc, fd_hash) {
                   if (fd->fd_ix == ix && fd->fd_vnode->v_mount == mp) {
                           /* Get reference to vnode in case it's being free'd */
                           vp = fd->fd_vnode;
                           VI_LOCK(vp);
                           mtx_unlock(&fdesc_hashmtx);
                           if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK))
                                   goto loop;
                           *vpp = vp;
                           return (0);
                   }
           }
           mtx_unlock(&fdesc_hashmtx);
   
           fd = malloc(sizeof(struct fdescnode), M_TEMP, M_WAITOK);
   
           error = getnewvnode("fdescfs", mp, &fdesc_vnodeops, &vp);
           if (error) {
                   free(fd, M_TEMP);
                   return (error);
           }
           vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
           vp->v_data = fd;
           fd->fd_vnode = vp;
           fd->fd_type = ftype;
           fd->fd_fd = fd_fd;
           fd->fd_ix = ix;
           if (ftype == Fdesc && fmp->flags & FMNT_LINRDLNKF)
                   vp->v_vflag |= VV_READLINK;
           error = insmntque1(vp, mp, fdesc_insmntque_dtr, NULL);
           if (error != 0) {
                   *vpp = NULLVP;
                   return (error);
           }
   
           /* Make sure that someone didn't beat us when inserting the vnode. */
           mtx_lock(&fdesc_hashmtx);
           /*
            * If a forced unmount is progressing, we need to drop it. The flags are
            * protected by the hashmtx.
            */
           fmp = mp->mnt_data;
           if (fmp == NULL || fmp->flags & FMNT_UNMOUNTF) {
                   mtx_unlock(&fdesc_hashmtx);
                   vgone(vp);
                   vput(vp);
                   *vpp = NULLVP;
                   return (-1);
           }
   
           LIST_FOREACH(fd2, fc, fd_hash) {
                   if (fd2->fd_ix == ix && fd2->fd_vnode->v_mount == mp) {
                           /* Get reference to vnode in case it's being free'd */
                           vp2 = fd2->fd_vnode;
                           VI_LOCK(vp2);
                           mtx_unlock(&fdesc_hashmtx);
                           error = vget(vp2, LK_EXCLUSIVE | LK_INTERLOCK);
                           /* Someone beat us, dec use count and wait for reclaim */
                           vgone(vp);
                           vput(vp);
                           /* If we didn't get it, return no vnode. */
                           if (error)
                                   vp2 = NULLVP;
                           *vpp = vp2;
                           return (error);
                   }
           }
   
           /* If we came here, we can insert it safely. */
           LIST_INSERT_HEAD(fc, fd, fd_hash);
           mtx_unlock(&fdesc_hashmtx);
           *vpp = vp;
           return (0);
   }
   
   struct fdesc_get_ino_args {
           fdntype ftype;
           unsigned fd_fd;
           int ix;
           struct file *fp;
           struct thread *td;
   };
   
   static int
   fdesc_get_ino_alloc(struct mount *mp, void *arg, int lkflags,
       struct vnode **rvp)
   {
           struct fdesc_get_ino_args *a;
           struct fdescmount *fdm;
           struct vnode *vp;
           int error;
   
           a = arg;
           fdm = VFSTOFDESC(mp);
           if ((fdm->flags & FMNT_NODUP) != 0 && a->fp->f_type == DTYPE_VNODE) {
                   vp = a->fp->f_vnode;
                   vget(vp, lkflags | LK_RETRY);
                   *rvp = vp;
                   error = 0;
           } else {
                   error = fdesc_allocvp(a->ftype, a->fd_fd, a->ix, mp, rvp);
           }
           fdrop(a->fp, a->td);
           return (error);
   }
   
   /*
    * vp is the current namei directory
    * ndp is the name to locate in that directory...
    */
   static int
   fdesc_lookup(struct vop_lookup_args *ap)
   {
           struct vnode **vpp = ap->a_vpp;
           struct vnode *dvp = ap->a_dvp;
           struct componentname *cnp = ap->a_cnp;
           char *pname = cnp->cn_nameptr;
           struct thread *td = cnp->cn_thread;
           struct file *fp;
           struct fdesc_get_ino_args arg;
           int nlen = cnp->cn_namelen;
           u_int fd, fd1;
           int error;
           struct vnode *fvp;
   
           if ((cnp->cn_flags & ISLASTCN) &&
               (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
                   error = EROFS;
                   goto bad;
           }
   
           if (cnp->cn_namelen == 1 && *pname == '.') {
                   *vpp = dvp;
                   VREF(dvp);
                   return (0);
           }
   
           if (VTOFDESC(dvp)->fd_type != Froot) {
                   error = ENOTDIR;
                   goto bad;
           }
   
           fd = 0;
           /* the only time a leading 0 is acceptable is if it's "" */
           if (*pname == '' && nlen != 1) {
                   error = ENOENT;
                   goto bad;
           }
           while (nlen--) {
                   if (*pname < '' || *pname > '9') {
                           error = ENOENT;
                           goto bad;
                   }
                   fd1 = 10 * fd + *pname++ - '';
                   if (fd1 < fd) {
                           error = ENOENT;
                           goto bad;
                   }
                   fd = fd1;
           }
   
           /*
            * No rights to check since 'fp' isn't actually used.
            */
           if ((error = fget(td, fd, &cap_no_rights, &fp)) != 0)
                   goto bad;
   
           /* Check if we're looking up ourselves. */
           if (VTOFDESC(dvp)->fd_ix == FD_DESC + fd) {
                   /*
                    * In case we're holding the last reference to the file, the dvp
                    * will be re-acquired.
                    */
                   vhold(dvp);
                   VOP_UNLOCK(dvp);
                   fdrop(fp, td);
   
                   /* Re-aquire the lock afterwards. */
                   vn_lock(dvp, LK_RETRY | LK_EXCLUSIVE);
                   vdrop(dvp);
                   fvp = dvp;
                   if (VN_IS_DOOMED(dvp))
                           error = ENOENT;
           } else {
                   /*
                    * Unlock our root node (dvp) when doing this, since we might
                    * deadlock since the vnode might be locked by another thread
                    * and the root vnode lock will be obtained afterwards (in case
                    * we're looking up the fd of the root vnode), which will be the
                    * opposite lock order. Vhold the root vnode first so we don't
                    * lose it.
                    */
                   arg.ftype = Fdesc;
                   arg.fd_fd = fd;
                   arg.ix = FD_DESC + fd;
                   arg.fp = fp;
                   arg.td = td;
                   error = vn_vget_ino_gen(dvp, fdesc_get_ino_alloc, &arg,
                       LK_EXCLUSIVE, &fvp);
           }
   
           if (error)
                   goto bad;
           *vpp = fvp;
           return (0);
   
   bad:
           *vpp = NULL;
           return (error);
   }
   
   static int
   fdesc_open(struct vop_open_args *ap)
   {
           struct vnode *vp = ap->a_vp;
   
           if (VTOFDESC(vp)->fd_type == Froot)
                   return (0);
   
           /*
            * XXX Kludge: set td->td_proc->p_dupfd to contain the value of the file
            * descriptor being sought for duplication. The error return ensures
            * that the vnode for this device will be released by vn_open. Open
            * will detect this special error and take the actions in dupfdopen.
            * Other callers of vn_open or VOP_OPEN will simply report the
            * error.
            */
           ap->a_td->td_dupfd = VTOFDESC(vp)->fd_fd;       /* XXX */
           return (ENODEV);
   }
   
   static int
   fdesc_pathconf(struct vop_pathconf_args *ap)
   {
           struct vnode *vp = ap->a_vp;
           int error;
   
           switch (ap->a_name) {
           case _PC_NAME_MAX:
                   *ap->a_retval = NAME_MAX;
                   return (0);
           case _PC_LINK_MAX:
                   if (VTOFDESC(vp)->fd_type == Froot)
                           *ap->a_retval = 2;
                   else
                           *ap->a_retval = 1;
                   return (0);
           default:
                   if (VTOFDESC(vp)->fd_type == Froot)
                           return (vop_stdpathconf(ap));
                   vref(vp);
                   VOP_UNLOCK(vp);
                   error = kern_fpathconf(curthread, VTOFDESC(vp)->fd_fd,
                       ap->a_name, ap->a_retval);
                   vn_lock(vp, LK_SHARED | LK_RETRY);
                   vunref(vp);
                   return (error);
           }
   }
   
   static int
   fdesc_getattr(struct vop_getattr_args *ap)
   {
           struct vnode *vp = ap->a_vp;
           struct vattr *vap = ap->a_vap;
           struct timeval boottime;
   
           getboottime(&boottime);
           vap->va_mode = S_IRUSR|S_IXUSR|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH;
           vap->va_fileid = VTOFDESC(vp)->fd_ix;
           vap->va_uid = 0;
           vap->va_gid = 0;
           vap->va_blocksize = DEV_BSIZE;
           vap->va_atime.tv_sec = boottime.tv_sec;
           vap->va_atime.tv_nsec = 0;
           vap->va_mtime = vap->va_atime;
           vap->va_ctime = vap->va_mtime;
           vap->va_gen = 0;
           vap->va_flags = 0;
           vap->va_bytes = 0;
           vap->va_filerev = 0;
   
           switch (VTOFDESC(vp)->fd_type) {
           case Froot:
                   vap->va_type = VDIR;
                   vap->va_nlink = 2;
                   vap->va_size = DEV_BSIZE;
                   vap->va_rdev = NODEV;
                   break;
   
           case Fdesc:
                   vap->va_type = (vp->v_vflag & VV_READLINK) == 0 ? VCHR : VLNK;
                   vap->va_nlink = 1;
                   vap->va_size = 0;
                   vap->va_rdev = makedev(0, vap->va_fileid);
                   break;
   
           default:
                   panic("fdesc_getattr");
                   break;
           }
   
           vp->v_type = vap->va_type;
           return (0);
   }
   
   static int
   fdesc_setattr(struct vop_setattr_args *ap)
   {
           struct vattr *vap = ap->a_vap;
           struct vnode *vp;
           struct mount *mp;
           struct file *fp;
           struct thread *td = curthread;
           cap_rights_t rights;
           unsigned fd;
           int error;
   
           /*
            * Can't mess with the root vnode
            */
           if (VTOFDESC(ap->a_vp)->fd_type == Froot)
                   return (EACCES);
   
           fd = VTOFDESC(ap->a_vp)->fd_fd;
   
           /*
            * Allow setattr where there is an underlying vnode.
            * For O_PATH descriptors, disallow truncate.
            */
           if (vap->va_size != VNOVAL) {
                   error = getvnode(td, fd,
                       cap_rights_init_one(&rights, CAP_EXTATTR_SET), &fp);
           } else {
                   error = getvnode_path(td, fd,
                       cap_rights_init_one(&rights, CAP_EXTATTR_SET), &fp);
           }
           if (error) {
                   /*
                    * getvnode() returns EINVAL if the file descriptor is not
                    * backed by a vnode.  Silently drop all changes except
                    * chflags(2) in this case.
                    */
                   if (error == EINVAL) {
                           if (vap->va_flags != VNOVAL)
                                   error = EOPNOTSUPP;
                           else
                                   error = 0;
                   }
                   return (error);
           }
           vp = fp->f_vnode;
           if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) == 0) {
                   vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
                   error = VOP_SETATTR(vp, ap->a_vap, ap->a_cred);
                   VOP_UNLOCK(vp);
                   vn_finished_write(mp);
           }
           fdrop(fp, td);
           return (error);
   }
   
   #define UIO_MX _GENERIC_DIRLEN(10) /* number of symbols in INT_MAX printout */
   
   static int
   fdesc_readdir(struct vop_readdir_args *ap)
   {
           struct fdescmount *fmp;
           struct uio *uio = ap->a_uio;
           struct filedesc *fdp;
           struct dirent d;
           struct dirent *dp = &d;
           int error, i, off, fcnt;
   
           if (VTOFDESC(ap->a_vp)->fd_type != Froot)
                   panic("fdesc_readdir: not dir");
   
           fmp = VFSTOFDESC(ap->a_vp->v_mount);
           if (ap->a_ncookies != NULL)
                   *ap->a_ncookies = 0;
   
           off = (int)uio->uio_offset;
           if (off != uio->uio_offset || off < 0 || (u_int)off % UIO_MX != 0 ||
               uio->uio_resid < UIO_MX)
                   return (EINVAL);
           i = (u_int)off / UIO_MX;
           fdp = uio->uio_td->td_proc->p_fd;
           error = 0;
   
           fcnt = i - 2;           /* The first two nodes are `.' and `..' */
   
           FILEDESC_SLOCK(fdp);
           while (i < fdp->fd_nfiles + 2 && uio->uio_resid >= UIO_MX) {
                   bzero((caddr_t)dp, UIO_MX);
                   switch (i) {
                   case 0: /* `.' */
                   case 1: /* `..' */
                           dp->d_fileno = i + FD_ROOT;
                           dp->d_namlen = i + 1;
                           dp->d_reclen = UIO_MX;
                           bcopy("..", dp->d_name, dp->d_namlen);
                           dp->d_type = DT_DIR;
                           dirent_terminate(dp);
                           break;
                   default:
                           if (fdp->fd_ofiles[fcnt].fde_file == NULL)
                                   break;
                           dp->d_namlen = sprintf(dp->d_name, "%d", fcnt);
                           dp->d_reclen = UIO_MX;
                           dp->d_type = (fmp->flags & FMNT_LINRDLNKF) == 0 ?
                               DT_CHR : DT_LNK;
                           dp->d_fileno = i + FD_DESC;
                           dirent_terminate(dp);
                           break;
                   }
                   /* NOTE: d_off is the offset of the *next* entry. */
                   dp->d_off = UIO_MX * (i + 1);
                   if (dp->d_namlen != 0) {
                           /*
                            * And ship to userland
                            */
                           FILEDESC_SUNLOCK(fdp);
                           error = uiomove(dp, UIO_MX, uio);
                           if (error)
                                   goto done;
                           FILEDESC_SLOCK(fdp);
                   }
                   i++;
                   fcnt++;
           }
           FILEDESC_SUNLOCK(fdp);
   
   done:
           uio->uio_offset = i * UIO_MX;
           return (error);
   }
   
   static int
   fdesc_reclaim(struct vop_reclaim_args *ap)
   {
           struct vnode *vp;
           struct fdescnode *fd;
   
           vp = ap->a_vp;
           fd = VTOFDESC(vp);
           fdesc_remove_entry(fd);
           free(vp->v_data, M_TEMP);
           vp->v_data = NULL;
           return (0);
   }
   
   static int
   fdesc_readlink(struct vop_readlink_args *va)
   {
           struct vnode *vp, *vn;
           struct thread *td;
           struct uio *uio;
           struct file *fp;
           char *freepath, *fullpath;
           size_t pathlen;
           int lockflags, fd_fd;
           int error;
   
           freepath = NULL;
           vn = va->a_vp;
           if (VTOFDESC(vn)->fd_type != Fdesc)
                   panic("fdesc_readlink: not fdescfs link");
           fd_fd = ((struct fdescnode *)vn->v_data)->fd_fd;
           lockflags = VOP_ISLOCKED(vn);
           VOP_UNLOCK(vn);
   
           td = curthread;
           error = fget_cap(td, fd_fd, &cap_no_rights, &fp, NULL);
           if (error != 0)
                   goto out;
   
           switch (fp->f_type) {
           case DTYPE_VNODE:
                   vp = fp->f_vnode;
                   error = vn_fullpath(vp, &fullpath, &freepath);
                   break;
           default:
                   fullpath = "anon_inode:[unknown]";
                   break;
           }
           if (error == 0) {
                   uio = va->a_uio;
                   pathlen = strlen(fullpath);
                   error = uiomove(fullpath, pathlen, uio);
           }
           if (freepath != NULL)
                   free(freepath, M_TEMP);
           fdrop(fp, td);
   
   out:
           vn_lock(vn, lockflags | LK_RETRY);
           return (error);
   }

Cache object: edb1c20d645983db6b1089e670b3c916