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[minix3.git] / sys / fs / cd9660 / cd9660_lookup.c

/*      $NetBSD: cd9660_lookup.c,v 1.25 2013/06/23 07:28:36 dholland Exp $      */

/*-
 * Copyright (c) 1989, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley
 * by Pace Willisson (pace@blitz.com).  The Rock Ridge Extension
 * Support code is derived from software contributed to Berkeley
 * by Atsushi Murai (amurai@spec.co.jp).
 *
 * 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.
 *
 *      from: @(#)ufs_lookup.c  7.33 (Berkeley) 5/19/91
 *
 *      @(#)cd9660_lookup.c     8.5 (Berkeley) 5/27/95
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: cd9660_lookup.c,v 1.25 2013/06/23 07:28:36 dholland Exp $");

#include <sys/param.h>
#include <sys/namei.h>
#include <sys/buf.h>
#include <sys/file.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/systm.h>
#include <sys/kauth.h>

#include <fs/cd9660/iso.h>
#include <fs/cd9660/cd9660_extern.h>
#include <fs/cd9660/cd9660_node.h>
#include <fs/cd9660/iso_rrip.h>
#include <fs/cd9660/cd9660_rrip.h>
#include <fs/cd9660/cd9660_mount.h>

struct  nchstats iso_nchstats;

/*
 * Convert a component of a pathname into a pointer to a locked inode.
 * This is a very central and rather complicated routine.
 * If the file system is not maintained in a strict tree hierarchy,
 * this can result in a deadlock situation (see comments in code below).
 *
 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
 * whether the name is to be looked up, created, renamed, or deleted.
 * When CREATE, RENAME, or DELETE is specified, information usable in
 * creating, renaming, or deleting a directory entry may be calculated.
 * If the target of the pathname exists, lookup returns both the target
 * and its parent directory locked.
 * When creating or renaming, the target may * not be ".".
 * When deleting , the target may be "."., but the caller must check
 * to ensure it does an vrele and vput instead of two vputs.
 *
 * Overall outline of ufs_lookup:
 *
 *      check accessibility of directory
 *      look for name in cache, if found, then if at end of path
 *        and deleting or creating, drop it, else return name
 *      search for name in directory, to found or notfound
 * notfound:
 *      if creating, return locked directory, leaving info on available slots
 *      else return error
 * found:
 *      if at end of path and deleting, return information to allow delete
 *      if at end of path and rewriting (RENAME), lock target
 *        inode and return info to allow rewrite
 *      if not at end, add name to cache; if at end and neither creating
 *        nor deleting, add name to cache
 */
int
cd9660_lookup(void *v)
{
        struct vop_lookup_args /* {
                struct vnode *a_dvp;
                struct vnode **a_vpp;
                struct componentname *a_cnp;
        } */ *ap = v;
        struct vnode *vdp;              /* vnode for directory being searched */
        struct iso_node *dp;            /* inode for directory being searched */
        struct iso_mnt *imp;            /* file system that directory is in */
        struct buf *bp;                 /* a buffer of directory entries */
        struct iso_directory_record *ep = NULL;
                                        /* the current directory entry */
        int entryoffsetinblock;         /* offset of ep in bp's buffer */
        int saveoffset = -1;            /* offset of last directory entry in dir */
        int numdirpasses;               /* strategy for directory search */
        doff_t endsearch;               /* offset to end directory search */
        struct vnode *pdp;              /* saved dp during symlink work */
        struct vnode *tdp;              /* returned by cd9660_vget_internal */
        u_long bmask;                   /* block offset mask */
        int error;
        ino_t ino = 0;
        int reclen;
        u_short namelen;
        char altname[ISO_MAXNAMLEN];
        int res;
        int assoc, len;
        const char *name;
        struct vnode **vpp = ap->a_vpp;
        struct componentname *cnp = ap->a_cnp;
        kauth_cred_t cred = cnp->cn_cred;
        int flags;
        int nameiop = cnp->cn_nameiop;

        flags = cnp->cn_flags;

        bp = NULL;
        *vpp = NULL;
        vdp = ap->a_dvp;
        dp = VTOI(vdp);
        imp = dp->i_mnt;

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

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

        /*
         * We now have a segment name to search for, and a directory to search.
         *
         * 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;
        }

        len = cnp->cn_namelen;
        name = cnp->cn_nameptr;
        /*
         * A leading `=' means, we are looking for an associated file
         */
        assoc = (imp->iso_ftype != ISO_FTYPE_RRIP && *name == ASSOCCHAR);
        if (assoc) {
                len--;
                name++;
        }

        /*
         * If there is cached information on a previous search of
         * this directory, pick up where we last left off.
         * We cache only lookups as these are the most common
         * and have the greatest payoff. Caching CREATE has little
         * benefit as it usually must search the entire directory
         * to determine that the entry does not exist. Caching the
         * location of the last DELETE or RENAME has not reduced
         * profiling time and hence has been removed in the interest
         * of simplicity.
         */
        bmask = imp->im_bmask;
        if (nameiop != LOOKUP || dp->i_diroff == 0 ||
            dp->i_diroff > dp->i_size) {
                entryoffsetinblock = 0;
                dp->i_offset = 0;
                numdirpasses = 1;
        } else {
                dp->i_offset = dp->i_diroff;
                if ((entryoffsetinblock = dp->i_offset & bmask) &&
                    (error = cd9660_blkatoff(vdp, (off_t)dp->i_offset, NULL,
                    &bp)))
                                return (error);
                numdirpasses = 2;
                iso_nchstats.ncs_2passes++;
        }
        endsearch = dp->i_size;

searchloop:
        while (dp->i_offset < endsearch) {
                /*
                 * If offset is on a block boundary,
                 * read the next directory block.
                 * Release previous if it exists.
                 */
                if ((dp->i_offset & bmask) == 0) {
                        if (bp != NULL)
                                brelse(bp, 0);
                        error = cd9660_blkatoff(vdp, (off_t)dp->i_offset,
                                             NULL, &bp);
                        if (error)
                                return (error);
                        entryoffsetinblock = 0;
                }
                /*
                 * Get pointer to next entry.
                 */
                KASSERT(bp != NULL);
                ep = (struct iso_directory_record *)
                        ((char *)bp->b_data + entryoffsetinblock);

                reclen = isonum_711(ep->length);
                if (reclen == 0) {
                        /* skip to next block, if any */
                        dp->i_offset =
                            (dp->i_offset & ~bmask) + imp->logical_block_size;
                        continue;
                }

                if (reclen < ISO_DIRECTORY_RECORD_SIZE)
                        /* illegal entry, stop */
                        break;

                if (entryoffsetinblock + reclen > imp->logical_block_size)
                        /* entries are not allowed to cross boundaries */
                        break;

                namelen = isonum_711(ep->name_len);

                if (reclen < ISO_DIRECTORY_RECORD_SIZE + namelen)
                        /* illegal entry, stop */
                        break;

                /*
                 * Check for a name match.
                 */
                switch (imp->iso_ftype) {
                default:
                        if ((!(isonum_711(ep->flags)&4)) == !assoc) {
                                if ((len == 1
                                     && *name == '.')
                                    || (flags & ISDOTDOT)) {
                                        if (namelen == 1
                                            && ep->name[0] == ((flags & ISDOTDOT) ? 1 : 0)) {
                                                /*
                                                 * Save directory entry's inode number and
                                                 * release directory buffer.
                                                 */
                                                dp->i_ino = isodirino(ep, imp);
                                                goto found;
                                        }
                                        if (namelen != 1
                                            || ep->name[0] != 0)
                                                goto notfound;
                                } else if (!(res = isofncmp(name,len,
                                                   ep->name,namelen,
                                                   imp->im_joliet_level))) {
                                        if (isonum_711(ep->flags)&2)
                                                ino = isodirino(ep, imp);
                                        else
                                                ino = dbtob(bp->b_blkno)
                                                        + entryoffsetinblock;
                                        saveoffset = dp->i_offset;
                                } else if (ino)
                                        goto foundino;
#ifdef  NOSORTBUG       /* On some CDs directory entries are not sorted correctly */
                                else if (res < 0)
                                        goto notfound;
                                else if (res > 0 && numdirpasses == 2)
                                        numdirpasses++;
#endif
                        }
                        break;
                case ISO_FTYPE_RRIP:
                        if (isonum_711(ep->flags)&2)
                                ino = isodirino(ep, imp);
                        else
                                ino = dbtob(bp->b_blkno) + entryoffsetinblock;
                        dp->i_ino = ino;
                        cd9660_rrip_getname(ep,altname,&namelen,&dp->i_ino,imp);
                        if (namelen == cnp->cn_namelen) {
                                if (imp->im_flags & ISOFSMNT_RRCASEINS) {
                                        if (strncasecmp(name, altname, namelen) == 0)
                                                goto found;
                                } else {
                                        if (memcmp(name, altname, namelen) == 0)
                                                goto found;
                                }
                        }
                        ino = 0;
                        break;
                }
                dp->i_offset += reclen;
                entryoffsetinblock += reclen;
        }
        if (ino) {
foundino:
                dp->i_ino = ino;
                if (saveoffset != dp->i_offset) {
                        if (cd9660_lblkno(imp, dp->i_offset) !=
                            cd9660_lblkno(imp, saveoffset)) {
                                if (bp != NULL)
                                        brelse(bp, 0);
                                if ((error = cd9660_blkatoff(vdp,
                                            (off_t)saveoffset, NULL, &bp)) != 0)
                                        return (error);
                        }
                        entryoffsetinblock = saveoffset & bmask;
                        ep = (struct iso_directory_record *)
                                ((char *)bp->b_data + entryoffsetinblock);
                        dp->i_offset = saveoffset;
                }
                goto found;
        }
notfound:
        /*
         * If we started in the middle of the directory and failed
         * to find our target, we must check the beginning as well.
         */
        if (numdirpasses == 2) {
                numdirpasses--;
                dp->i_offset = 0;
                endsearch = dp->i_diroff;
                goto searchloop;
        }
        if (bp != NULL)
                brelse(bp, 0);

        /*
         * Insert name into cache (as non-existent) if appropriate.
         */
        cache_enter(vdp, *vpp, cnp->cn_nameptr, cnp->cn_namelen, cnp->cn_flags);
        return (nameiop == CREATE || nameiop == RENAME) ? EROFS : ENOENT;

found:
        if (numdirpasses == 2)
                iso_nchstats.ncs_pass2++;

        /*
         * Found component in pathname.
         * If the final component of path name, save information
         * in the cache as to where the entry was found.
         */
        if ((flags & ISLASTCN) && nameiop == LOOKUP)
                dp->i_diroff = dp->i_offset;

        /*
         * Step through the translation in the name.  We do not `iput' the
         * directory because we may need it again if a symbolic link
         * is relative to the current directory.  Instead we save it
         * unlocked as "pdp".  We must get the target inode before unlocking
         * the directory to insure that the inode will not be removed
         * before we get it.  We prevent deadlock by always fetching
         * inodes from the root, moving down the directory tree. Thus
         * when following backward pointers ".." we must unlock the
         * parent directory before getting the requested directory.
         * There is a potential race condition here if both the current
         * and parent directories are removed before the `iget' for the
         * inode associated with ".." returns.  We hope that this occurs
         * infrequently since we cannot avoid this race condition without
         * implementing a sophisticated deadlock detection algorithm.
         * Note also that this simple deadlock detection scheme will not
         * work if the file system has any hard links other than ".."
         * that point backwards in the directory structure.
         */
        pdp = vdp;

        /*
         * If ino is different from dp->i_ino,
         * it's a relocated directory.
         */
        brelse(bp, 0);
        if (flags & ISDOTDOT) {
                VOP_UNLOCK(pdp);        /* race to get the inode */
                error = cd9660_vget_internal(vdp->v_mount, dp->i_ino, &tdp,
                                             dp->i_ino != ino, ep);
                vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY);
                if (error)
                        return error;
                *vpp = tdp;
        } else if (dp->i_number == dp->i_ino) {
                vref(vdp);      /* we want ourself, ie "." */
                *vpp = vdp;
        } else {
                error = cd9660_vget_internal(vdp->v_mount, dp->i_ino, &tdp,
                                             dp->i_ino != ino, ep);
                if (error)
                        return (error);
                *vpp = tdp;
        }

        /*
         * Insert name into cache if appropriate.
         */
        cache_enter(vdp, *vpp, cnp->cn_nameptr, cnp->cn_namelen, cnp->cn_flags);
        return 0;
}

/*
 * Return buffer with the contents of block "offset" from the beginning of
 * directory "ip".  If "res" is non-zero, fill it in with a pointer to the
 * remaining space in the directory.
 */
int
cd9660_blkatoff(struct vnode *vp, off_t offset, char **res, struct buf **bpp)
{
        struct iso_node *ip;
        struct iso_mnt *imp;
        struct buf *bp;
        daddr_t lbn;
        int bsize, error;

        ip = VTOI(vp);
        imp = ip->i_mnt;
        lbn = cd9660_lblkno(imp, offset);
        bsize = cd9660_blksize(imp, ip, lbn);

        if ((error = bread(vp, lbn, bsize, NOCRED, 0, &bp)) != 0) {
                *bpp = NULL;
                return (error);
        }
        if (res)
                *res = (char *)bp->b_data + cd9660_blkoff(imp, offset);
        *bpp = bp;
        return (0);
}