/*      $NetBSD: adlookup.c,v 1.22 2022/08/06 18:26:41 andvar Exp $     */

/*
* Copyright (c) 1994 Christian E. Hopps
* Copyright (c) 1996 Matthias Scheler
* 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. All advertising materials mentioning features or use of this software
*    must display the following acknowledgement:
*      This product includes software developed by Christian E. Hopps.
* 4. The name of the author may not be used to endorse or promote products
*    derived from this software without specific prior written permission
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: adlookup.c,v 1.22 2022/08/06 18:26:41 andvar Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/vnode.h>
#include <sys/namei.h>
#include <sys/mount.h>
#include <sys/time.h>
#include <sys/queue.h>
#include <fs/adosfs/adosfs.h>

#ifdef ADOSFS_EXACTMATCH
#define strmatch(s1, l1, s2, l2, i) \
   ((l1) == (l2) && memcmp((s1), (s2), (l1)) == 0)
#else
#define strmatch(s1, l1, s2, l2, i) \
   ((l1) == (l2) && adoscaseequ((s1), (s2), (l1), (i)))
#endif

/*
* adosfs lookup. enters with:
* pvp (parent vnode) referenced and locked.
* exit with:
*      target vp referenced and locked.
*      parent pvp locked.
* special cases:
*      pvp == vp, just ref pvp, pvp already holds a ref and lock from
*          caller, this will not occur with RENAME or CREATE.
*/
int
adosfs_lookup(void *v)
{
       struct vop_lookup_v2_args /* {
               struct vnode *a_dvp;
               struct vnode **a_vpp;
               struct componentname *a_cnp;
       } */ *sp = v;
       int nameiop, last, flags, error, nocache, i;
       struct componentname *cnp;
       struct vnode **vpp;     /* place to store result */
       struct anode *ap;       /* anode to find */
       struct vnode *vdp;      /* vnode of search dir */
       struct anode *adp;      /* anode of search dir */
       kauth_cred_t ucp;       /* lookup credentials */
       u_long bn, plen, hval;
       const u_char *pelt;

#ifdef ADOSFS_DIAGNOSTIC
       advopprint(sp);
#endif
       cnp = sp->a_cnp;
       vdp = sp->a_dvp;
       adp = VTOA(vdp);
       vpp = sp->a_vpp;
       *vpp = NULL;
       ucp = cnp->cn_cred;
       nameiop = cnp->cn_nameiop;
       flags = cnp->cn_flags;
       last = flags & ISLASTCN;
       pelt = (const u_char *)cnp->cn_nameptr;
       plen = cnp->cn_namelen;
       nocache = 0;

       /*
        * Check accessibility of directory.
        */
       if ((error = VOP_ACCESS(vdp, VEXEC, ucp)) != 0)
               return (error);

       if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) &&
           (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
               return (EROFS);

       /*
        * Before tediously performing a linear scan of the directory,
        * check the name cache to see if the directory/name pair
        * we are looking for is known already.
        */
       if (cache_lookup(vdp, cnp->cn_nameptr, cnp->cn_namelen,
                        cnp->cn_nameiop, cnp->cn_flags, NULL, vpp)) {
               return *vpp == NULLVP ? ENOENT : 0;
       }

       /*
        * fake a '.'
        */
       if (plen == 1 && pelt[0] == '.') {
               /* see special cases in prologue. */
               *vpp = vdp;
               goto found;
       }
       /*
        * fake a ".."
        */
       if (flags & ISDOTDOT) {
               if (vdp->v_type == VDIR && (vdp->v_vflag & VV_ROOT))
                       panic("adosfs .. attempted through root");
               /*
                * cannot get `..' while `vdp' is locked
                * e.g. procA holds lock on `..' and waits for `vdp'
                * we wait for `..' and hold lock on `vdp'. deadlock.
                * because `vdp' may have been achieved through symlink
                * fancy detection code that decreases the race
                * window size is not reasonably possible.
                *
                * basically unlock the parent, try and lock the child (..)
                * if that fails relock the parent (ignoring error) and
                * fail.  Otherwise we have the child (..), attempt to
                * relock the parent.  If that fails unlock the child (..)
                * and fail. Otherwise we have succeded.
                *
                */
               VOP_UNLOCK(vdp); /* race */
               error = VFS_VGET(vdp->v_mount, (ino_t)adp->pblock,
                   LK_EXCLUSIVE, vpp);
               vn_lock(vdp, LK_EXCLUSIVE | LK_RETRY);
               if (error) {
                       *vpp = NULL;
                       return (error);
               }
               goto found_lockdone;
       }

       /*
        * hash the name and grab the first block in chain
        * then walk the chain. if chain has not been fully
        * walked before, track the count in `tabi'
        */
       hval = adoshash(pelt, plen, adp->ntabent, IS_INTER(adp->amp));
       bn = adp->tab[hval];
       i = uimin(adp->tabi[hval], 0);
       while (bn != 0) {
               if ((error = VFS_VGET(vdp->v_mount, (ino_t)bn,
                   LK_EXCLUSIVE, vpp)) != 0) {
#ifdef ADOSFS_DIAGNOSTIC
                       printf("[aget] %d)", error);
#endif
                       return(error);
               }
               ap = VTOA(*vpp);
               if (i <= 0) {
                       if (--i < adp->tabi[hval])
                               adp->tabi[hval] = i;
                       /*
                        * last header in chain lock count down by
                        * negating it to positive
                        */
                       if (ap->hashf == 0) {
#ifdef DEBUG
                               if (i != adp->tabi[hval])
                                       panic("adlookup: wrong chain count");
#endif
                               adp->tabi[hval] = -adp->tabi[hval];
                       }
               }
               if (strmatch(pelt, plen, ap->name, strlen(ap->name),
                   IS_INTER(adp->amp)))
                       goto found;
               bn = ap->hashf;
               vput(*vpp);
       }
       *vpp = NULL;
       /*
        * not found
        */
       if ((nameiop == CREATE || nameiop == RENAME) && last) {

               if (vdp->v_mount->mnt_flag & MNT_RDONLY)
                       return (EROFS);

               if ((error = VOP_ACCESS(vdp, VWRITE, ucp)) != 0) {
#ifdef ADOSFS_DIAGNOSTIC
                       printf("[VOP_ACCESS] %d)", error);
#endif
                       return (error);
               }
#ifdef ADOSFS_DIAGNOSTIC
               printf("EJUSTRETURN)");
#endif
               return(EJUSTRETURN);
       }
       if (nameiop != CREATE)
               cache_enter(vdp, NULL, cnp->cn_nameptr, cnp->cn_namelen,
                           cnp->cn_flags);
#ifdef ADOSFS_DIAGNOSTIC
       printf("ENOENT)");
#endif
       return(ENOENT);

found:
       if (nameiop == DELETE && last)  {
               if ((error = VOP_ACCESS(vdp, VWRITE, ucp)) != 0) {
                       if (vdp != *vpp)
                               vput(*vpp);
                       *vpp = NULL;
                       return (error);
               }
               nocache = 1;
       }
       if (nameiop == RENAME && last) {
               if (vdp == *vpp)
                       return(EISDIR);
               if ((error = VOP_ACCESS(vdp, VWRITE, ucp)) != 0) {
                       vput(*vpp);
                       *vpp = NULL;
                       return (error);
               }
               nocache = 1;
       }
       if (vdp == *vpp)
               vref(vdp);
found_lockdone:
       if (*vpp != vdp)
               VOP_UNLOCK(*vpp);
       if (nocache == 0)
               cache_enter(vdp, *vpp, cnp->cn_nameptr, cnp->cn_namelen,
                           cnp->cn_flags);

#ifdef ADOSFS_DIAGNOSTIC
       printf("0)\n");
#endif
       return(0);
}

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