xnu-1504.7.4.tar.gz

[apple/xnu.git] / bsd / vfs / vfs_vnops.c

/*
 * Copyright (c) 2000-2008 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
/*
 * Copyright (c) 1982, 1986, 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 *
 *      @(#)vfs_vnops.c 8.14 (Berkeley) 6/15/95
 *
 */
/*
 * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */

#include <sys/param.h>
#include <sys/types.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/file_internal.h>
#include <sys/stat.h>
#include <sys/proc_internal.h>
#include <sys/kauth.h>
#include <sys/mount_internal.h>
#include <sys/namei.h>
#include <sys/vnode_internal.h>
#include <sys/ioctl.h>
#include <sys/tty.h>
/* Temporary workaround for ubc.h until <rdar://4714366 is resolved */
#define ubc_setcred ubc_setcred_deprecated
#include <sys/ubc.h>
#undef ubc_setcred
int     ubc_setcred(struct vnode *, struct proc *);
#include <sys/conf.h>
#include <sys/disk.h>
#include <sys/fsevents.h>
#include <sys/kdebug.h>
#include <sys/xattr.h>
#include <sys/ubc_internal.h>
#include <sys/uio_internal.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>

#include <vm/vm_kern.h>
#include <vm/vm_map.h>

#include <miscfs/specfs/specdev.h>
#include <miscfs/fifofs/fifo.h>

#if CONFIG_MACF
#include <security/mac_framework.h>
#endif


static int vn_closefile(struct fileglob *fp, vfs_context_t ctx);
static int vn_ioctl(struct fileproc *fp, u_long com, caddr_t data,
                        vfs_context_t ctx);
static int vn_read(struct fileproc *fp, struct uio *uio, int flags,
                        vfs_context_t ctx);
static int vn_write(struct fileproc *fp, struct uio *uio, int flags,
                        vfs_context_t ctx);
static int vn_select( struct fileproc *fp, int which, void * wql,
                        vfs_context_t ctx);
static int vn_kqfilt_add(struct fileproc *fp, struct knote *kn,
                        vfs_context_t ctx);
static void filt_vndetach(struct knote *kn);
static int filt_vnode(struct knote *kn, long hint);
#if 0
static int vn_kqfilt_remove(struct vnode *vp, uintptr_t ident,
                        vfs_context_t ctx);
#endif

struct  fileops vnops =
        { vn_read, vn_write, vn_ioctl, vn_select, vn_closefile, vn_kqfilt_add, NULL };

struct  filterops vnode_filtops = { 
        .f_isfd = 1, 
        .f_attach = NULL, 
        .f_detach = filt_vndetach, 
        .f_event = filt_vnode
};

/*
 * Common code for vnode open operations.
 * Check permissions, and call the VNOP_OPEN or VNOP_CREATE routine.
 *
 * XXX the profusion of interfaces here is probably a bad thing.
 */
int
vn_open(struct nameidata *ndp, int fmode, int cmode)
{
        return(vn_open_modflags(ndp, &fmode, cmode));
}

int
vn_open_modflags(struct nameidata *ndp, int *fmodep, int cmode)
{
        struct vnode_attr va;

        VATTR_INIT(&va);
        VATTR_SET(&va, va_mode, cmode);
        
        return(vn_open_auth(ndp, fmodep, &va));
}

/*
 * Open a file with authorization, updating the contents of the structures
 * pointed to by ndp, fmodep, and vap as necessary to perform the requested
 * operation.  This function is used for both opens of existing files, and
 * creation of new files.
 *
 * Parameters:  ndp                     The nami data pointer describing the
 *                                      file
 *              fmodep                  A pointer to an int containg the mode
 *                                      information to be used for the open
 *              vap                     A pointer to the vnode attribute
 *                                      descriptor to be used for the open
 *
 * Indirect:    *                       Contents of the data structures pointed
 *                                      to by the parameters are modified as
 *                                      necessary to the requested operation.
 *
 * Returns:     0                       Success
 *              !0                      errno value
 *
 * Notes:       The kauth_filesec_t in 'vap', if any, is in host byte order.
 *
 *              The contents of '*ndp' will be modified, based on the other
 *              arguments to this function, and to return file and directory
 *              data necessary to satisfy the requested operation.
 *
 *              If the file does not exist and we are creating it, then the
 *              O_TRUNC flag will be cleared in '*fmodep' to indicate to the
 *              caller that the file was not truncated.
 *
 *              If the file exists and the O_EXCL flag was not specified, then
 *              the O_CREAT flag will be cleared in '*fmodep' to indicate to
 *              the caller that the existing file was merely opened rather
 *              than created.
 *
 *              The contents of '*vap' will be modified as necessary to
 *              complete the operation, including setting of supported
 *              attribute, clearing of fields containing unsupported attributes
 *              in the request, if the request proceeds without them, etc..
 *
 * XXX:         This function is too complicated in actings on its arguments
 *
 * XXX:         We should enummerate the possible errno values here, and where
 *              in the code they originated.
 */
int
vn_open_auth(struct nameidata *ndp, int *fmodep, struct vnode_attr *vap)
{
        struct vnode *vp;
        struct vnode *dvp;
        vfs_context_t ctx = ndp->ni_cnd.cn_context;
        int error;
        int fmode;
        uint32_t origcnflags;
        kauth_action_t action;

again:
        vp = NULL;
        dvp = NULL;
        fmode = *fmodep;
        origcnflags = ndp->ni_cnd.cn_flags;
        if (fmode & O_CREAT) {
                if ( (fmode & O_DIRECTORY) ) {
                        error = EINVAL;
                        goto out;
                }
                ndp->ni_cnd.cn_nameiop = CREATE;
                /* Inherit USEDVP, vnode_open() supported flags only */
                ndp->ni_cnd.cn_flags &= (USEDVP | NOCROSSMOUNT | DOWHITEOUT);
                ndp->ni_cnd.cn_flags |= LOCKPARENT | LOCKLEAF | AUDITVNPATH1;
#if NAMEDRSRCFORK
                /* open calls are allowed for resource forks. */
                ndp->ni_cnd.cn_flags |= CN_ALLOWRSRCFORK;
#endif
                if ((fmode & O_EXCL) == 0 && (fmode & O_NOFOLLOW) == 0 && (origcnflags & FOLLOW) != 0)
                        ndp->ni_cnd.cn_flags |= FOLLOW;
                if ( (error = namei(ndp)) )
                        goto out;
                dvp = ndp->ni_dvp;
                vp = ndp->ni_vp;

                /* not found, create */
                if (vp == NULL) {
                        /* must have attributes for a new file */
                        if (vap == NULL) {
                                error = EINVAL;
                                goto badcreate;
                        }

                        VATTR_SET(vap, va_type, VREG);
#if CONFIG_MACF
                        error = mac_vnode_check_create(ctx,
                            dvp, &ndp->ni_cnd, vap);
                        if (error)
                                goto badcreate;
#endif /* MAC */

                        /* authorize before creating */
                        if ((error = vnode_authorize(dvp, NULL, KAUTH_VNODE_ADD_FILE, ctx)) != 0)
                                goto badcreate;

                        if (fmode & O_EXCL)
                                vap->va_vaflags |= VA_EXCLUSIVE;
#if NAMEDRSRCFORK
                        if (ndp->ni_cnd.cn_flags & CN_WANTSRSRCFORK) {
                                if ((error = vnode_makenamedstream(dvp, &ndp->ni_vp, XATTR_RESOURCEFORK_NAME, 0, ctx)) != 0)
                                        goto badcreate;
                        } else
#endif
                        if ((error = vn_create(dvp, &ndp->ni_vp, &ndp->ni_cnd, vap, 0, ctx)) != 0)
                                goto badcreate;
                        
                        vp = ndp->ni_vp;

                        if (vp) {
                                int     update_flags = 0;

                                // Make sure the name & parent pointers are hooked up
                                if (vp->v_name == NULL)
                                        update_flags |= VNODE_UPDATE_NAME;
                                if (vp->v_parent == NULLVP)
                                        update_flags |= VNODE_UPDATE_PARENT;

                                if (update_flags)
                                        vnode_update_identity(vp, dvp, ndp->ni_cnd.cn_nameptr, ndp->ni_cnd.cn_namelen, ndp->ni_cnd.cn_hash, update_flags);

#if CONFIG_FSE
                                if (need_fsevent(FSE_CREATE_FILE, vp)) {
                                        vnode_put(dvp);
                                        dvp = NULL;
                                        add_fsevent(FSE_CREATE_FILE, ctx,
                                                    FSE_ARG_VNODE, vp,
                                                    FSE_ARG_DONE);
                                }
#endif

                        }
                        /*
                         * nameidone has to happen before we vnode_put(dvp)
                         * and clear the ni_dvp field, since it may need
                         * to release the fs_nodelock on the dvp
                         */
badcreate:
                        nameidone(ndp);
                        ndp->ni_dvp = NULL;

                        if (dvp) {
                                vnode_put(dvp);
                        }

                        if (error) {
                                /*
                                 * Check for a creation or unlink race.
                                 */
                                if (((error == EEXIST) && !(fmode & O_EXCL)) ||
                                           ((error == ENOENT) && (fmode & O_CREAT))){
                                        goto again;
                                }
                                goto bad;
                        }
                        fmode &= ~O_TRUNC;
                } else {
                        nameidone(ndp);
                        ndp->ni_dvp = NULL;
                        vnode_put(dvp);

                        if (fmode & O_EXCL) {
                                error = EEXIST;
                                goto bad;
                        }
                        fmode &= ~O_CREAT;
                }
        } else {
                ndp->ni_cnd.cn_nameiop = LOOKUP;
                /* Inherit USEDVP, vnode_open() supported flags only */
                ndp->ni_cnd.cn_flags &= (USEDVP | NOCROSSMOUNT | DOWHITEOUT);
                ndp->ni_cnd.cn_flags |= FOLLOW | LOCKLEAF | AUDITVNPATH1;
#if NAMEDRSRCFORK
                /* open calls are allowed for resource forks. */
                ndp->ni_cnd.cn_flags |= CN_ALLOWRSRCFORK;
#endif
                /* preserve NOFOLLOW from vnode_open() */
                if (fmode & O_NOFOLLOW || fmode & O_SYMLINK || (origcnflags & FOLLOW) == 0) {
                    ndp->ni_cnd.cn_flags &= ~FOLLOW;
                }

                if ( (error = namei(ndp)) )
                        goto out;
                vp = ndp->ni_vp;
                nameidone(ndp);
                ndp->ni_dvp = NULL;

                if ( (fmode & O_DIRECTORY) && vp->v_type != VDIR ) {
                        error = ENOTDIR;
                        goto bad;
                }
        }

        if (vp->v_type == VSOCK && vp->v_tag != VT_FDESC) {
                error = EOPNOTSUPP;     /* Operation not supported on socket */
                goto bad;
        }

        if (vp->v_type == VLNK && (fmode & O_NOFOLLOW) != 0) {
                error = ELOOP;  /* O_NOFOLLOW was specified and the target is a symbolic link */
                goto bad;
        }

        /* authorize open of an existing file */
        if ((fmode & O_CREAT) == 0) {

                /* disallow write operations on directories */
                if (vnode_isdir(vp) && (fmode & (FWRITE | O_TRUNC))) {
                        error = EISDIR;
                        goto bad;
                }

#if CONFIG_MACF
                error = mac_vnode_check_open(ctx, vp, fmode);
                if (error)
                        goto bad;
#endif

                /* compute action to be authorized */
                action = 0;
                if (fmode & FREAD) {
                        action |= KAUTH_VNODE_READ_DATA;
                }
                if (fmode & (FWRITE | O_TRUNC)) {
                        /*
                         * If we are writing, appending, and not truncating,
                         * indicate that we are appending so that if the
                         * UF_APPEND or SF_APPEND bits are set, we do not deny
                         * the open.
                         */
                        if ((fmode & O_APPEND) && !(fmode & O_TRUNC)) {
                                action |= KAUTH_VNODE_APPEND_DATA;
                        } else {
                        action |= KAUTH_VNODE_WRITE_DATA;
                        }
                }
                if ((error = vnode_authorize(vp, NULL, action, ctx)) != 0)
                        goto bad;
                

                //
                // if the vnode is tagged VOPENEVT and the current process
                // has the P_CHECKOPENEVT flag set, then we or in the O_EVTONLY
                // flag to the open mode so that this open won't count against
                // the vnode when carbon delete() does a vnode_isinuse() to see
                // if a file is currently in use.  this allows spotlight
                // importers to not interfere with carbon apps that depend on
                // the no-delete-if-busy semantics of carbon delete().
                //
                if ((vp->v_flag & VOPENEVT) && (current_proc()->p_flag & P_CHECKOPENEVT)) {
                    fmode |= O_EVTONLY;
                }

        }

        if ( (error = VNOP_OPEN(vp, fmode, ctx)) ) {
                goto bad;
        }
        if ( (error = vnode_ref_ext(vp, fmode)) ) {
                goto bad2;
        }

        /* call out to allow 3rd party notification of open. 
         * Ignore result of kauth_authorize_fileop call.
         */
        kauth_authorize_fileop(vfs_context_ucred(ctx), KAUTH_FILEOP_OPEN, 
                                                   (uintptr_t)vp, 0);

        *fmodep = fmode;
        return (0);
bad2:
        VNOP_CLOSE(vp, fmode, ctx);
bad:
        ndp->ni_vp = NULL;
        if (vp) {
#if NAMEDRSRCFORK
                /* Aggressively recycle shadow files if we error'd out during open() */
                if ((vnode_isnamedstream(vp)) &&
                        (vp->v_parent != NULLVP) && 
                        (vnode_isshadow(vp))) {
                                vnode_recycle(vp);
                }
#endif
                vnode_put(vp);
                /*
                 * Check for a race against unlink.  We had a vnode
                 * but according to vnode_authorize or VNOP_OPEN it
                 * no longer exists.
                 *
                 * EREDRIVEOPEN: means that we were hit by the tty allocation race.
                 */
                if (((error == ENOENT) && (*fmodep & O_CREAT)) || (error == EREDRIVEOPEN)) {
                        goto again;
                }
        }
out:
        return (error);
}

#if vn_access_DEPRECATED
/*
 * Authorize an action against a vnode.  This has been the canonical way to
 * ensure that the credential/process/etc. referenced by a vfs_context
 * is granted the rights called out in 'mode' against the vnode 'vp'.
 *
 * Unfortunately, the use of VREAD/VWRITE/VEXEC makes it very difficult
 * to add support for more rights.  As such, this interface will be deprecated
 * and callers will use vnode_authorize instead.
 */
int
vn_access(vnode_t vp, int mode, vfs_context_t context)
{
        kauth_action_t  action;
  
        action = 0;
        if (mode & VREAD)
                action |= KAUTH_VNODE_READ_DATA;
        if (mode & VWRITE)
                action |= KAUTH_VNODE_WRITE_DATA;
        if (mode & VEXEC)
                action |= KAUTH_VNODE_EXECUTE;
  
        return(vnode_authorize(vp, NULL, action, context));
}
#endif  /* vn_access_DEPRECATED */

/*
 * Vnode close call
 */
int
vn_close(struct vnode *vp, int flags, vfs_context_t ctx)
{
        int error;

#if CONFIG_FSE
        if (flags & FWASWRITTEN) {
                if (need_fsevent(FSE_CONTENT_MODIFIED, vp)) {
                        add_fsevent(FSE_CONTENT_MODIFIED, ctx,
                                    FSE_ARG_VNODE, vp,
                                    FSE_ARG_DONE);
                }
        }
#endif

#if NAMEDRSRCFORK
        /* Sync data from resource fork shadow file if needed. */
        if ((vp->v_flag & VISNAMEDSTREAM) && 
            (vp->v_parent != NULLVP) &&
            vnode_isshadow(vp)) {
                if (flags & FWASWRITTEN) {
                        (void) vnode_flushnamedstream(vp->v_parent, vp, ctx);
                }
        }
#endif
        
        /* work around for foxhound */
        if (vnode_isspec(vp))
                (void)vnode_rele_ext(vp, flags, 0);

        error = VNOP_CLOSE(vp, flags, ctx);

        if (!vnode_isspec(vp))
                (void)vnode_rele_ext(vp, flags, 0);
        
        return (error);
}

static int
vn_read_swapfile(
        struct vnode    *vp,
        uio_t           uio)
{
        int     error;
        off_t   swap_count, this_count;
        off_t   file_end, read_end;
        off_t   prev_resid;
        char    *my_swap_page;

        /*
         * Reading from a swap file will get you zeroes.
         */

        my_swap_page = NULL;
        error = 0;
        swap_count = uio_resid(uio);

        file_end = ubc_getsize(vp);
        read_end = uio->uio_offset + uio_resid(uio);
        if (uio->uio_offset >= file_end) {
                /* uio starts after end of file: nothing to read */
                swap_count = 0;
        } else if (read_end > file_end) {
                /* uio extends beyond end of file: stop before that */
                swap_count -= (read_end - file_end);
        }

        while (swap_count > 0) {
                if (my_swap_page == NULL) {
                        MALLOC(my_swap_page, char *, PAGE_SIZE,
                               M_TEMP, M_WAITOK);
                        memset(my_swap_page, '\0', PAGE_SIZE);
                        /* add an end-of-line to keep line counters happy */
                        my_swap_page[PAGE_SIZE-1] = '\n';
                }
                this_count = swap_count;
                if (this_count > PAGE_SIZE) {
                        this_count = PAGE_SIZE;
                }

                prev_resid = uio_resid(uio);
                error = uiomove((caddr_t) my_swap_page,
                                this_count,
                                uio);
                if (error) {
                        break;
                }
                swap_count -= (prev_resid - uio_resid(uio));
        }
        if (my_swap_page != NULL) {
                FREE(my_swap_page, M_TEMP);
                my_swap_page = NULL;
        }

        return error;
}
/*
 * Package up an I/O request on a vnode into a uio and do it.
 */
int
vn_rdwr(
        enum uio_rw rw,
        struct vnode *vp,
        caddr_t base,
        int len,
        off_t offset,
        enum uio_seg segflg,
        int ioflg,
        kauth_cred_t cred,
        int *aresid,
        proc_t p)
{
        int64_t resid;
        int result;
        
        result = vn_rdwr_64(rw,
                        vp,
                        (uint64_t)(uintptr_t)base,
                        (int64_t)len,
                        offset,
                        segflg,
                        ioflg,
                        cred,
                        &resid,
                        p);

        /* "resid" should be bounded above by "len," which is an int */
        if (aresid != NULL) {
                *aresid = resid;
        }

        return result;
}


int
vn_rdwr_64(
        enum uio_rw rw,
        struct vnode *vp,
        uint64_t base,
        int64_t len,
        off_t offset,
        enum uio_seg segflg,
        int ioflg,
        kauth_cred_t cred,
        int64_t *aresid,
        proc_t p)
{
        uio_t auio;
        int spacetype;
        struct vfs_context context;
        int error=0;
        char uio_buf[ UIO_SIZEOF(1) ];

        context.vc_thread = current_thread();
        context.vc_ucred = cred;

        if (UIO_SEG_IS_USER_SPACE(segflg)) {
                spacetype = proc_is64bit(p) ? UIO_USERSPACE64 : UIO_USERSPACE32;
        }
        else {
                spacetype = UIO_SYSSPACE;
        }
        auio = uio_createwithbuffer(1, offset, spacetype, rw, 
                                                                  &uio_buf[0], sizeof(uio_buf));
        uio_addiov(auio, base, len);

#if CONFIG_MACF
        /* XXXMAC
         *      IO_NOAUTH should be re-examined.
         *      Likely that mediation should be performed in caller.
         */
        if ((ioflg & IO_NOAUTH) == 0) {
        /* passed cred is fp->f_cred */
                if (rw == UIO_READ)
                        error = mac_vnode_check_read(&context, cred, vp);
                else
                        error = mac_vnode_check_write(&context, cred, vp);
        }
#endif

        if (error == 0) {
                if (rw == UIO_READ) {
                        if (vnode_isswap(vp)) {
                                error = vn_read_swapfile(vp, auio);
                        } else {
                                error = VNOP_READ(vp, auio, ioflg, &context);
                        }
                } else {
                        error = VNOP_WRITE(vp, auio, ioflg, &context);
                }
        }

        if (aresid)
                *aresid = uio_resid(auio);
        else
                if (uio_resid(auio) && error == 0)
                        error = EIO;
        return (error);
}

/*
 * File table vnode read routine.
 */
static int
vn_read(struct fileproc *fp, struct uio *uio, int flags, vfs_context_t ctx)
{
        struct vnode *vp;
        int error, ioflag;
        off_t count;

        vp = (struct vnode *)fp->f_fglob->fg_data;
        if ( (error = vnode_getwithref(vp)) ) {
                return(error);
        }

#if CONFIG_MACF
        error = mac_vnode_check_read(ctx, vfs_context_ucred(ctx), vp);
        if (error) {
                (void)vnode_put(vp);
                return (error);
        }
#endif

        ioflag = 0;
        if (fp->f_fglob->fg_flag & FNONBLOCK)
                ioflag |= IO_NDELAY;
        if ((fp->f_fglob->fg_flag & FNOCACHE) || vnode_isnocache(vp))
                ioflag |= IO_NOCACHE;
        if (fp->f_fglob->fg_flag & FNORDAHEAD)
                ioflag |= IO_RAOFF;

        if ((flags & FOF_OFFSET) == 0)
                uio->uio_offset = fp->f_fglob->fg_offset;
        count = uio_resid(uio);

        if (vnode_isswap(vp)) {
                /* special case for swap files */
                error = vn_read_swapfile(vp, uio);
        } else {
                error = VNOP_READ(vp, uio, ioflag, ctx);
        }
        if ((flags & FOF_OFFSET) == 0)
                fp->f_fglob->fg_offset += count - uio_resid(uio);

        (void)vnode_put(vp);
        return (error);
}


/*
 * File table vnode write routine.
 */
static int
vn_write(struct fileproc *fp, struct uio *uio, int flags, vfs_context_t ctx)
{
        struct vnode *vp;
        int error, ioflag;
        off_t count;
        int clippedsize = 0;
        int partialwrite=0;
        int residcount, oldcount;
        proc_t p = vfs_context_proc(ctx);

        count = 0;
        vp = (struct vnode *)fp->f_fglob->fg_data;
        if ( (error = vnode_getwithref(vp)) ) {
                return(error);
        }

#if CONFIG_MACF
        error = mac_vnode_check_write(ctx, vfs_context_ucred(ctx), vp);
        if (error) {
                (void)vnode_put(vp);
                return (error);
        }
#endif

        ioflag = IO_UNIT;
        if (vp->v_type == VREG && (fp->f_fglob->fg_flag & O_APPEND))
                ioflag |= IO_APPEND;
        if (fp->f_fglob->fg_flag & FNONBLOCK)
                ioflag |= IO_NDELAY;
        if ((fp->f_fglob->fg_flag & FNOCACHE) || vnode_isnocache(vp))
                ioflag |= IO_NOCACHE;
        /*
         * Treat synchronous mounts and O_FSYNC on the fd as equivalent.
         *
         * XXX We treat O_DSYNC as O_FSYNC for now, since we can not delay
         * XXX the non-essential metadata without some additional VFS work;
         * XXX the intent at this point is to plumb the interface for it.
         */
        if ((fp->f_fglob->fg_flag & (O_FSYNC|O_DSYNC)) ||
                (vp->v_mount && (vp->v_mount->mnt_flag & MNT_SYNCHRONOUS))) {
                ioflag |= IO_SYNC;
        }

        if ((flags & FOF_OFFSET) == 0) {
                uio->uio_offset = fp->f_fglob->fg_offset;
                count = uio_resid(uio);
        }
        if (((flags & FOF_OFFSET) == 0) &&
                vfs_context_proc(ctx) && (vp->v_type == VREG) &&
            (((rlim_t)(uio->uio_offset + uio_resid(uio)) > p->p_rlimit[RLIMIT_FSIZE].rlim_cur) ||
             ((rlim_t)uio_resid(uio) > (p->p_rlimit[RLIMIT_FSIZE].rlim_cur - uio->uio_offset)))) {
                /*
                 * If the requested residual would cause us to go past the
                 * administrative limit, then we need to adjust the residual
                 * down to cause fewer bytes than requested to be written.  If
                 * we can't do that (e.g. the residual is already 1 byte),
                 * then we fail the write with EFBIG.
                 */
                residcount = uio_resid(uio);
                if ((rlim_t)(uio->uio_offset + uio_resid(uio)) > p->p_rlimit[RLIMIT_FSIZE].rlim_cur) {
                        clippedsize =  (uio->uio_offset + uio_resid(uio)) - p->p_rlimit[RLIMIT_FSIZE].rlim_cur;
                } else if ((rlim_t)uio_resid(uio) > (p->p_rlimit[RLIMIT_FSIZE].rlim_cur - uio->uio_offset)) {
                        clippedsize = (p->p_rlimit[RLIMIT_FSIZE].rlim_cur - uio->uio_offset);
                }
                if (clippedsize >= residcount) {
                        psignal(p, SIGXFSZ);
                        vnode_put(vp);
                        return (EFBIG);
                }
                partialwrite = 1;
                uio_setresid(uio, residcount-clippedsize);
        }
        if ((flags & FOF_OFFSET) != 0) {
                /* for pwrite, append should  be ignored */
                ioflag &= ~IO_APPEND;
                if (p && (vp->v_type == VREG) &&
                ((rlim_t)uio->uio_offset  >= p->p_rlimit[RLIMIT_FSIZE].rlim_cur)) {
                psignal(p, SIGXFSZ);
                vnode_put(vp);
                return (EFBIG);
        }
                if (p && (vp->v_type == VREG) &&
                        ((rlim_t)(uio->uio_offset + uio_resid(uio)) > p->p_rlimit[RLIMIT_FSIZE].rlim_cur)) {
                        //Debugger("vn_bwrite:overstepping the bounds");
                        residcount = uio_resid(uio);
                        clippedsize =  (uio->uio_offset + uio_resid(uio)) - p->p_rlimit[RLIMIT_FSIZE].rlim_cur;
                        partialwrite = 1;
                        uio_setresid(uio, residcount-clippedsize);
                }
        }

        error = VNOP_WRITE(vp, uio, ioflag, ctx);

        if (partialwrite) {
                oldcount = uio_resid(uio);
                uio_setresid(uio, oldcount + clippedsize);
        }

        if ((flags & FOF_OFFSET) == 0) {
                if (ioflag & IO_APPEND)
                        fp->f_fglob->fg_offset = uio->uio_offset;
                else
                        fp->f_fglob->fg_offset += count - uio_resid(uio);
        }

        /*
         * Set the credentials on successful writes
         */
        if ((error == 0) && (vp->v_tag == VT_NFS) && (UBCINFOEXISTS(vp))) {
                /* 
                 * When called from aio subsystem, we only have the proc from
                 * which to get the credential, at this point, so use that
                 * instead.  This means aio functions are incompatible with
                 * per-thread credentials (aio operations are proxied).  We
                 * can't easily correct the aio vs. settid race in this case
                 * anyway, so we disallow it.
                 */
                if ((flags & FOF_PCRED) == 0) {
                        ubc_setthreadcred(vp, p, current_thread());
                } else {
                        ubc_setcred(vp, p);
                }
        }
        (void)vnode_put(vp);
        return (error);
}

/*
 * File table vnode stat routine.
 *
 * Returns:     0                       Success
 *              EBADF
 *              ENOMEM
 *      vnode_getattr:???
 */
int
vn_stat_noauth(struct vnode *vp, void *sbptr, kauth_filesec_t *xsec, int isstat64, vfs_context_t ctx)
{
        struct vnode_attr va;
        int error;
        u_short mode;
        kauth_filesec_t fsec;
        struct stat *sb = (struct stat *)0;     /* warning avoidance ; protected by isstat64 */
        struct stat64 * sb64 = (struct stat64 *)0;  /* warning avoidance ; protected by isstat64 */

        if (isstat64 != 0)
                sb64 = (struct stat64 *)sbptr;
        else
                sb = (struct stat *)sbptr;
        memset(&va, 0, sizeof(va));
        VATTR_INIT(&va);
        VATTR_WANTED(&va, va_fsid);
        VATTR_WANTED(&va, va_fileid);
        VATTR_WANTED(&va, va_mode);
        VATTR_WANTED(&va, va_type);
        VATTR_WANTED(&va, va_nlink);
        VATTR_WANTED(&va, va_uid);
        VATTR_WANTED(&va, va_gid);
        VATTR_WANTED(&va, va_rdev);
        VATTR_WANTED(&va, va_data_size);
        VATTR_WANTED(&va, va_access_time);
        VATTR_WANTED(&va, va_modify_time);
        VATTR_WANTED(&va, va_change_time);
        VATTR_WANTED(&va, va_create_time);
        VATTR_WANTED(&va, va_flags);
        VATTR_WANTED(&va, va_gen);
        VATTR_WANTED(&va, va_iosize);
        /* lower layers will synthesise va_total_alloc from va_data_size if required */
        VATTR_WANTED(&va, va_total_alloc);
        if (xsec != NULL) {
                VATTR_WANTED(&va, va_uuuid);
                VATTR_WANTED(&va, va_guuid);
                VATTR_WANTED(&va, va_acl);
        }
        error = vnode_getattr(vp, &va, ctx);
        if (error)
                goto out;
        /*
         * Copy from vattr table
         */
        if (isstat64 != 0) {
                sb64->st_dev = va.va_fsid;
                sb64->st_ino = (ino64_t)va.va_fileid;

        } else {
                sb->st_dev = va.va_fsid;
                sb->st_ino = (ino_t)va.va_fileid;
        }
        mode = va.va_mode;
        switch (vp->v_type) {
        case VREG:
                mode |= S_IFREG;
                break;
        case VDIR:
                mode |= S_IFDIR;
                break;
        case VBLK:
                mode |= S_IFBLK;
                break;
        case VCHR:
                mode |= S_IFCHR;
                break;
        case VLNK:
                mode |= S_IFLNK;
                break;
        case VSOCK:
                mode |= S_IFSOCK;
                break;
        case VFIFO:
                mode |= S_IFIFO;
                break;
        default:
                error = EBADF;
                goto out;
        };
        if (isstat64 != 0) {
                sb64->st_mode = mode;
                sb64->st_nlink = VATTR_IS_SUPPORTED(&va, va_nlink) ? (u_int16_t)va.va_nlink : 1;
                sb64->st_uid = va.va_uid;
                sb64->st_gid = va.va_gid;
                sb64->st_rdev = va.va_rdev;
                sb64->st_size = va.va_data_size;
                sb64->st_atimespec = va.va_access_time;
                sb64->st_mtimespec = va.va_modify_time;
                sb64->st_ctimespec = va.va_change_time;
                sb64->st_birthtimespec = 
                                VATTR_IS_SUPPORTED(&va, va_create_time) ? va.va_create_time : va.va_change_time;
                sb64->st_blksize = va.va_iosize;
                sb64->st_flags = va.va_flags;
                sb64->st_blocks = roundup(va.va_total_alloc, 512) / 512;
        } else {
                sb->st_mode = mode;
                sb->st_nlink = VATTR_IS_SUPPORTED(&va, va_nlink) ? (u_int16_t)va.va_nlink : 1;
                sb->st_uid = va.va_uid;
                sb->st_gid = va.va_gid;
                sb->st_rdev = va.va_rdev;
                sb->st_size = va.va_data_size;
                sb->st_atimespec = va.va_access_time;
                sb->st_mtimespec = va.va_modify_time;
                sb->st_ctimespec = va.va_change_time;
                sb->st_blksize = va.va_iosize;
                sb->st_flags = va.va_flags;
                sb->st_blocks = roundup(va.va_total_alloc, 512) / 512;
        }

        /* if we're interested in exended security data and we got an ACL */
        if (xsec != NULL) {
                if (!VATTR_IS_SUPPORTED(&va, va_acl) &&
                    !VATTR_IS_SUPPORTED(&va, va_uuuid) &&
                    !VATTR_IS_SUPPORTED(&va, va_guuid)) {
                        *xsec = KAUTH_FILESEC_NONE;
                } else {
                
                        if (VATTR_IS_SUPPORTED(&va, va_acl) && (va.va_acl != NULL)) {
                                fsec = kauth_filesec_alloc(va.va_acl->acl_entrycount);
                        } else {
                                fsec = kauth_filesec_alloc(0);
                        }
                        if (fsec == NULL) {
                                error = ENOMEM;
                                goto out;
                        }
                        fsec->fsec_magic = KAUTH_FILESEC_MAGIC;
                        if (VATTR_IS_SUPPORTED(&va, va_uuuid)) {
                                fsec->fsec_owner = va.va_uuuid;
                        } else {
                                fsec->fsec_owner = kauth_null_guid;
                        }
                        if (VATTR_IS_SUPPORTED(&va, va_guuid)) {
                                fsec->fsec_group = va.va_guuid;
                        } else {
                                fsec->fsec_group = kauth_null_guid;
                        }
                        if (VATTR_IS_SUPPORTED(&va, va_acl) && (va.va_acl != NULL)) {
                                bcopy(va.va_acl, &(fsec->fsec_acl), KAUTH_ACL_COPYSIZE(va.va_acl));
                        } else {
                                fsec->fsec_acl.acl_entrycount = KAUTH_FILESEC_NOACL;
                        }
                        *xsec = fsec;
                }
        }
        
        /* Do not give the generation number out to unpriviledged users */
        if (va.va_gen && !vfs_context_issuser(ctx)) {
                if (isstat64 != 0)
                        sb64->st_gen = 0; 
                else
                        sb->st_gen = 0; 
        } else {
                if (isstat64 != 0)
                        sb64->st_gen = va.va_gen; 
                else
                        sb->st_gen = va.va_gen;
        }

        error = 0;
out:
        if (VATTR_IS_SUPPORTED(&va, va_acl) && va.va_acl != NULL)
                kauth_acl_free(va.va_acl);
        return (error);
}

int
vn_stat(struct vnode *vp, void *sb, kauth_filesec_t *xsec, int isstat64, vfs_context_t ctx)
{
        int error;

#if CONFIG_MACF
        error = mac_vnode_check_stat(ctx, NOCRED, vp);
        if (error)
                return (error);
#endif

        /* authorize */
        if ((error = vnode_authorize(vp, NULL, KAUTH_VNODE_READ_ATTRIBUTES | KAUTH_VNODE_READ_SECURITY, ctx)) != 0)
                return(error);

        /* actual stat */
        return(vn_stat_noauth(vp, sb, xsec, isstat64, ctx));
}


/*
 * File table vnode ioctl routine.
 */
static int
vn_ioctl(struct fileproc *fp, u_long com, caddr_t data, vfs_context_t ctx)
{
        struct vnode *vp = ((struct vnode *)fp->f_fglob->fg_data);
        off_t file_size;
        int error;
        struct vnode *ttyvp;
        int funnel_state;
        struct session * sessp;
        
        if ( (error = vnode_getwithref(vp)) ) {
                return(error);
        }

#if CONFIG_MACF
        error = mac_vnode_check_ioctl(ctx, vp, com);
        if (error)
                goto out;
#endif

        switch (vp->v_type) {
        case VREG:
        case VDIR:
                if (com == FIONREAD) {
                        if ((error = vnode_size(vp, &file_size, ctx)) != 0)
                                goto out;
                        *(int *)data = file_size - fp->f_fglob->fg_offset;
                        goto out;
                }
                if (com == FIONBIO || com == FIOASYNC) {        /* XXX */
                        goto out;
                }
                /* fall into ... */

        default:
                error = ENOTTY;
                goto out;

        case VFIFO:
        case VCHR:
        case VBLK:

                /* Should not be able to set block size from user space */
                if (com == DKIOCSETBLOCKSIZE) {
                        error = EPERM;
                        goto out;
                }

                if (com == FIODTYPE) {
                        if (vp->v_type == VBLK) {
                                if (major(vp->v_rdev) >= nblkdev) {
                                        error = ENXIO;
                                        goto out;
                                }
                                *(int *)data = bdevsw[major(vp->v_rdev)].d_type;

                        } else if (vp->v_type == VCHR) {
                                if (major(vp->v_rdev) >= nchrdev) {
                                        error = ENXIO;
                                        goto out;
                                }
                                *(int *)data = cdevsw[major(vp->v_rdev)].d_type;
                        } else {
                                error = ENOTTY;
                                goto out;
                        }
                        goto out;
                }
                error = VNOP_IOCTL(vp, com, data, fp->f_fglob->fg_flag, ctx);

                if (error == 0 && com == TIOCSCTTY) {
                        vnode_ref(vp);

                        funnel_state = thread_funnel_set(kernel_flock, TRUE);
                        sessp = proc_session(vfs_context_proc(ctx));

                        session_lock(sessp);
                        ttyvp = sessp->s_ttyvp;
                        sessp->s_ttyvp = vp;
                        sessp->s_ttyvid = vnode_vid(vp);
                        session_unlock(sessp);
                        session_rele(sessp);
                        thread_funnel_set(kernel_flock, funnel_state);

                        if (ttyvp)
                                vnode_rele(ttyvp);
                }
        }
out:
        (void)vnode_put(vp);
        return(error);
}

/*
 * File table vnode select routine.
 */
static int
vn_select(struct fileproc *fp, int which, void *wql, __unused vfs_context_t ctx)
{
        int error;
        struct vnode * vp = (struct vnode *)fp->f_fglob->fg_data;
        struct vfs_context context;

        if ( (error = vnode_getwithref(vp)) == 0 ) {
                context.vc_thread = current_thread();
                context.vc_ucred = fp->f_fglob->fg_cred;

#if CONFIG_MACF
                /*
                 * XXX We should use a per thread credential here; minimally,
                 * XXX the process credential should have a persistent
                 * XXX reference on it before being passed in here.
                 */
                error = mac_vnode_check_select(ctx, vp, which);
                if (error == 0)
#endif
                error = VNOP_SELECT(vp, which, fp->f_fglob->fg_flag, wql, ctx);

                (void)vnode_put(vp);
        }
        return(error);
        
}

/*
 * File table vnode close routine.
 */
static int
vn_closefile(struct fileglob *fg, vfs_context_t ctx)
{
        struct vnode *vp = (struct vnode *)fg->fg_data;
        int error;
        struct flock lf;

        if ( (error = vnode_getwithref(vp)) == 0 ) {

                if ((fg->fg_flag & FHASLOCK) && fg->fg_type == DTYPE_VNODE) {
                        lf.l_whence = SEEK_SET;
                        lf.l_start = 0;
                        lf.l_len = 0;
                        lf.l_type = F_UNLCK;

                        (void)VNOP_ADVLOCK(vp, (caddr_t)fg, F_UNLCK, &lf, F_FLOCK, ctx);
                }
                error = vn_close(vp, fg->fg_flag, ctx);

                (void)vnode_put(vp);
        }
        return(error);
}

/*
 * Returns:     0                       Success
 *      VNOP_PATHCONF:???
 */
int
vn_pathconf(vnode_t vp, int name, int32_t *retval, vfs_context_t ctx)
{
        int     error = 0;

        switch(name) {
        case _PC_EXTENDED_SECURITY_NP:
                *retval = vfs_extendedsecurity(vnode_mount(vp)) ? 1 : 0;
                break;
        case _PC_AUTH_OPAQUE_NP:
                *retval = vfs_authopaque(vnode_mount(vp));
                break;
        case _PC_2_SYMLINKS:
                *retval = 1;    /* XXX NOTSUP on MSDOS, etc. */
                break;
        case _PC_ALLOC_SIZE_MIN:
                *retval = 1;    /* XXX lie: 1 byte */
                break;
        case _PC_ASYNC_IO:      /* unistd.h: _POSIX_ASYNCHRONUS_IO */
                *retval = 1;    /* [AIO] option is supported */
                break;
        case _PC_PRIO_IO:       /* unistd.h: _POSIX_PRIORITIZED_IO */
                *retval = 0;    /* [PIO] option is not supported */
                break;
        case _PC_REC_INCR_XFER_SIZE:
                *retval = 4096; /* XXX go from MIN to MAX 4K at a time */
                break;
        case _PC_REC_MIN_XFER_SIZE:
                *retval = 4096; /* XXX recommend 4K minimum reads/writes */
                break;
        case _PC_REC_MAX_XFER_SIZE:
                *retval = 65536; /* XXX recommend 64K maximum reads/writes */
                break;
        case _PC_REC_XFER_ALIGN:
                *retval = 4096; /* XXX recommend page aligned buffers */
                break;
        case _PC_SYMLINK_MAX:
                *retval = 255;  /* Minimum acceptable POSIX value */
                break;
        case _PC_SYNC_IO:       /* unistd.h: _POSIX_SYNCHRONIZED_IO */
                *retval = 0;    /* [SIO] option is not supported */
                break;
        default:
                error = VNOP_PATHCONF(vp, name, retval, ctx);
                break;
        }

        return (error);
}

static int
vn_kqfilt_add(struct fileproc *fp, struct knote *kn, vfs_context_t ctx)
{
        int error;
        struct vnode *vp;
        
        vp = (struct vnode *)fp->f_fglob->fg_data;

        /*
         * Don't attach a knote to a dead vnode.
         */
        if ((error = vget_internal(vp, 0, VNODE_NODEAD)) == 0) {
                switch (kn->kn_filter) {
                        case EVFILT_READ:
                        case EVFILT_WRITE:
                                if (vnode_isfifo(vp)) {
                                        /* We'll only watch FIFOs that use our fifofs */
                                        if (!(vp->v_fifoinfo && vp->v_fifoinfo->fi_readsock)) {
                                                error = ENOTSUP;
                                        }

                                } else if (!vnode_isreg(vp)) {
                                        if (vnode_isspec(vp) && 
                                                        (error = spec_kqfilter(vp, kn)) == 0) {
                                                /* claimed by a special device */
                                                vnode_put(vp);
                                                return 0;
                                        }

                                        error = EINVAL;
                                }
                                break;
                        case EVFILT_VNODE:
                                break;
                        default:
                                error = EINVAL;
                }

                if (error) {
                        vnode_put(vp);
                        return error;
                }

#if CONFIG_MACF
                error = mac_vnode_check_kqfilter(ctx, fp->f_fglob->fg_cred, kn, vp);
                if (error) {
                        vnode_put(vp);
                        return error;
                }
#endif

                kn->kn_hook = (void*)vp;
                kn->kn_hookid = vnode_vid(vp);
                kn->kn_fop = &vnode_filtops;

                vnode_lock(vp);
                KNOTE_ATTACH(&vp->v_knotes, kn);
                vnode_unlock(vp);

                /* Ask the filesystem to provide remove notifications, but ignore failure */
                VNOP_MONITOR(vp, 0, VNODE_MONITOR_BEGIN, (void*) kn,  ctx);

                vnode_put(vp);
        }

        return (error);
}

static void
filt_vndetach(struct knote *kn)
{
        vfs_context_t ctx = vfs_context_current();
        struct vnode *vp; 
        vp = (struct vnode *)kn->kn_hook;
        if (vnode_getwithvid(vp, kn->kn_hookid))
                return;

        vnode_lock(vp);
        KNOTE_DETACH(&vp->v_knotes, kn);
        vnode_unlock(vp);
        
        /* 
         * Tell a (generally networked) filesystem that we're no longer watching 
         * If the FS wants to track contexts, it should still be using the one from
         * the VNODE_MONITOR_BEGIN.
         */
        VNOP_MONITOR(vp, 0, VNODE_MONITOR_END, (void*)kn, ctx);
        vnode_put(vp);
}


/*
 * Used for EVFILT_READ
 *
 * Takes only VFIFO or VREG. vnode is locked.  We handle the "poll" case
 * differently than the regular case for VREG files.  If not in poll(),
 * then we need to know current fileproc offset for VREG.
 */
static intptr_t
vnode_readable_data_count(vnode_t vp, off_t current_offset, int ispoll)
{
        if (vnode_isfifo(vp)) {
                int cnt;
                int err = fifo_charcount(vp, &cnt);
                if (err == 0) {
                        return (intptr_t)cnt;
                } else {
                        return (intptr_t)0;
                }
        } else if (vnode_isreg(vp)) {
                if (ispoll) {
                        return (intptr_t)1;
                }

                off_t amount;
                amount = vp->v_un.vu_ubcinfo->ui_size - current_offset;
                if (amount > (off_t)INTPTR_MAX) {
                        return INTPTR_MAX;
                } else if (amount < (off_t)INTPTR_MIN) {
                        return INTPTR_MIN;
                } else {
                        return (intptr_t)amount;
                } 
        } else {
                panic("Should never have an EVFILT_READ except for reg or fifo.");
                return 0;
        }
}

/*
 * Used for EVFILT_WRITE.  
 *
 * For regular vnodes, we can always write (1).  For named pipes,
 * see how much space there is in the buffer.  Nothing else is covered.
 */
static intptr_t
vnode_writable_space_count(vnode_t vp) 
{
        if (vnode_isfifo(vp)) {
                long spc;
                int err = fifo_freespace(vp, &spc);
                if (err == 0) {
                        return (intptr_t)spc;
                } else {
                        return (intptr_t)0;
                }
        } else if (vnode_isreg(vp)) {
                return (intptr_t)1;
        } else {
                panic("Should never have an EVFILT_READ except for reg or fifo.");
                return 0;
        }
}

/* 
 * Determine whether this knote should be active
 * 
 * This is kind of subtle.  
 *      --First, notice if the vnode has been revoked: in so, override hint
 *      --EVFILT_READ knotes are checked no matter what the hint is
 *      --Other knotes activate based on hint.  
 *      --If hint is revoke, set special flags and activate
 */
static int
filt_vnode(struct knote *kn, long hint)
{
        struct vnode *vp = (struct vnode *)kn->kn_hook;
        int activate = 0;

        if (0 == hint) {
                if ((vnode_getwithvid(vp, kn->kn_hookid) != 0)) {
                        hint = NOTE_REVOKE;
                } else {
                        vnode_put(vp);
                }
        }    

        /* NOTE_REVOKE is special, as it is only sent during vnode reclaim */
        if (NOTE_REVOKE == hint) {
                kn->kn_flags |= (EV_EOF | EV_ONESHOT);
                activate = 1;

                if ((kn->kn_filter == EVFILT_VNODE) && (kn->kn_sfflags & NOTE_REVOKE)) {
                        kn->kn_fflags |= NOTE_REVOKE;
                }
        } else {
                switch(kn->kn_filter) {
                        case EVFILT_READ:
                                kn->kn_data = vnode_readable_data_count(vp, kn->kn_fp->f_fglob->fg_offset, (kn->kn_flags & EV_POLL));

                                if (kn->kn_data != 0) {
                                        activate = 1;
                                }
                                break;
                        case EVFILT_WRITE: 
                                kn->kn_data = vnode_writable_space_count(vp);

                                if (kn->kn_data != 0) {
                                        activate = 1;
                                }
                                break;
                        case EVFILT_VNODE:
                                /* Check events this note matches against the hint */
                                if (kn->kn_sfflags & hint) {
                                        kn->kn_fflags |= hint; /* Set which event occurred */
                                }
                                if (kn->kn_fflags != 0) {
                                        activate = 1;
                                }
                                break;
                        default:
                                panic("Invalid knote filter on a vnode!\n");
                }
        }

        return (activate);
}