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38 * @(#)vfs_lookup.c 8.4 (Berkeley) 2/16/94
39 * $FreeBSD: src/sys/kern/vfs_lookup.c,v 1.38.2.3 2001/08/31 19:36:49 dillon Exp $
40 * $DragonFly: src/sys/kern/vfs_lookup.c,v 1.13 2004/07/29 20:34:09 dillon Exp $
43 #include "opt_ktrace.h"
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/kernel.h>
48 #include <sys/vnode.h>
49 #include <sys/mount.h>
50 #include <sys/filedesc.h>
52 #include <sys/namei.h>
53 #include <sys/sysctl.h>
56 #include <sys/ktrace.h>
59 #include <vm/vm_zone.h>
61 static int varsym_enable = 0;
62 SYSCTL_INT(_vfs, OID_AUTO, varsym_enable, CTLFLAG_RW, &varsym_enable, 0,
63 "Enable Variant Symlinks");
66 * Convert a pathname into a pointer to a locked inode.
68 * The CNP_FOLLOW flag is set when symbolic links are to be followed
69 * when they occur at the end of the name translation process.
70 * Symbolic links are always followed for all other pathname
71 * components other than the last.
73 * The segflg defines whether the name is to be copied from user
74 * space or kernel space.
76 * Overall outline of namei:
79 * get starting directory
80 * while (!done && !error) {
81 * call lookup to search path.
82 * if symbolic link, massage name in buffer and continue
85 * NOTE: when namei() is called from a pure thread the system rootvnode
86 * will be used as a basis for the search.
89 namei(struct nameidata *ndp)
91 struct filedesc *fdp; /* pointer to file descriptor state */
92 char *cp; /* pointer into pathname argument */
93 struct vnode *dp; /* the directory we are searching */
94 struct iovec aiov; /* uio for reading symbolic links */
97 struct componentname *cnp = &ndp->ni_cnd;
100 KKASSERT(ndp->ni_cnd.cn_td != NULL);
101 p = cnp->cn_td->td_proc;
103 KKASSERT(ndp->ni_segflg == UIO_SYSSPACE);
104 printf("namei() from non-process\n");
107 KKASSERT(cnp->cn_cred == p->p_ucred); /* YYY */
110 KASSERT(cnp->cn_cred, ("namei: bad cred/proc"));
111 KASSERT((cnp->cn_nameiop & (~NAMEI_OPMASK)) == 0,
112 ("namei: nameiop contaminated with flags"));
113 KASSERT((cnp->cn_flags & NAMEI_OPMASK) == 0,
114 ("namei: flags contaminated with nameiops"));
117 * Get a buffer for the name to be translated, and copy the
118 * name into the buffer.
120 if ((cnp->cn_flags & CNP_HASBUF) == 0)
121 cnp->cn_pnbuf = zalloc(namei_zone);
122 if (ndp->ni_segflg == UIO_SYSSPACE)
123 error = copystr(ndp->ni_dirp, cnp->cn_pnbuf,
124 MAXPATHLEN, (size_t *)&ndp->ni_pathlen);
126 error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf,
127 MAXPATHLEN, (size_t *)&ndp->ni_pathlen);
130 * Don't allow empty pathnames.
131 * POSIX.1 requirement: "" is not a vaild file name.
133 if (!error && *cnp->cn_pnbuf == '\0')
137 zfree(namei_zone, cnp->cn_pnbuf);
143 if (KTRPOINT(cnp->cn_td, KTR_NAMEI))
144 ktrnamei(cnp->cn_td->td_proc->p_tracep, cnp->cn_pnbuf);
148 * Get starting point for the translation.
151 ndp->ni_rootdir = fdp->fd_rdir;
152 ndp->ni_topdir = fdp->fd_jdir;
155 ndp->ni_rootdir = rootvnode;
156 ndp->ni_topdir = rootvnode;
162 * Check if root directory should replace current directory.
163 * Done at start of translation and after symbolic link.
165 cnp->cn_nameptr = cnp->cn_pnbuf;
166 if (*(cnp->cn_nameptr) == '/') {
168 while (*(cnp->cn_nameptr) == '/') {
172 dp = ndp->ni_rootdir;
175 ndp->ni_startdir = dp;
178 zfree(namei_zone, cnp->cn_pnbuf);
182 * Check for symbolic link
184 if ((cnp->cn_flags & CNP_ISSYMLINK) == 0) {
185 if ((cnp->cn_flags & (CNP_SAVENAME | CNP_SAVESTART)) == 0)
186 zfree(namei_zone, cnp->cn_pnbuf);
188 cnp->cn_flags |= CNP_HASBUF;
190 if (vn_canvmio(ndp->ni_vp) == TRUE &&
191 (cnp->cn_nameiop != NAMEI_DELETE) &&
192 ((cnp->cn_flags & (CNP_NOOBJ|CNP_LOCKLEAF)) ==
194 vfs_object_create(ndp->ni_vp, ndp->ni_cnd.cn_td);
198 if ((cnp->cn_flags & CNP_LOCKPARENT) && ndp->ni_pathlen == 1)
199 VOP_UNLOCK(ndp->ni_dvp, NULL, 0, cnp->cn_td);
200 if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
204 if (ndp->ni_pathlen > 1)
205 cp = zalloc(namei_zone);
209 aiov.iov_len = MAXPATHLEN;
210 auio.uio_iov = &aiov;
213 auio.uio_rw = UIO_READ;
214 auio.uio_segflg = UIO_SYSSPACE;
216 auio.uio_resid = MAXPATHLEN;
217 error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred);
219 if (ndp->ni_pathlen > 1)
220 zfree(namei_zone, cp);
223 linklen = MAXPATHLEN - auio.uio_resid;
225 if (ndp->ni_pathlen > 1)
226 zfree(namei_zone, cp);
231 linklen = varsymreplace(cp, linklen, MAXPATHLEN);
233 if (ndp->ni_pathlen > 1)
234 zfree(namei_zone, cp);
235 error = ENAMETOOLONG;
239 if (linklen + ndp->ni_pathlen >= MAXPATHLEN) {
240 if (ndp->ni_pathlen > 1)
241 zfree(namei_zone, cp);
242 error = ENAMETOOLONG;
245 if (ndp->ni_pathlen > 1) {
246 bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen);
247 zfree(namei_zone, cnp->cn_pnbuf);
250 cnp->cn_pnbuf[linklen] = '\0';
252 ndp->ni_pathlen += linklen;
256 zfree(namei_zone, cnp->cn_pnbuf);
265 * This is a very central and rather complicated routine.
267 * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
268 * The starting directory is taken from ni_startdir. The pathname is
269 * descended until done, or a symbolic link is encountered. The variable
270 * ni_more is clear if the path is completed; it is set to one if a
271 * symbolic link needing interpretation is encountered.
273 * The flag argument is NAMEI_LOOKUP, CREATE, RENAME, or DELETE depending on
274 * whether the name is to be looked up, created, renamed, or deleted.
275 * When CREATE, RENAME, or DELETE is specified, information usable in
276 * creating, renaming, or deleting a directory entry may be calculated.
277 * If flag has LOCKPARENT or'ed into it, the parent directory is returned
278 * locked. If flag has WANTPARENT or'ed into it, the parent directory is
279 * returned unlocked. Otherwise the parent directory is not returned. If
280 * the target of the pathname exists and LOCKLEAF is or'ed into the flag
281 * the target is returned locked, otherwise it is returned unlocked.
282 * When creating or renaming and LOCKPARENT is specified, the target may not
283 * be ".". When deleting and LOCKPARENT is specified, the target may be ".".
285 * Overall outline of lookup:
288 * identify next component of name at ndp->ni_ptr
289 * handle degenerate case where name is null string
290 * if .. and crossing mount points and on mounted filesys, find parent
291 * call VOP_LOOKUP routine for next component name
292 * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
293 * component vnode returned in ni_vp (if it exists), locked.
294 * if result vnode is mounted on and crossing mount points,
295 * find mounted on vnode
296 * if more components of name, do next level at dirloop
297 * return the answer in ni_vp, locked if LOCKLEAF set
298 * if LOCKPARENT set, return locked parent in ni_dvp
299 * if WANTPARENT set, return unlocked parent in ni_dvp
302 lookup(struct nameidata *ndp)
304 char *cp; /* pointer into pathname argument */
305 struct vnode *dp = NULL; /* the directory we are searching */
306 struct vnode *tdp; /* saved dp */
307 struct mount *mp; /* mount table entry */
308 int docache; /* == 0 do not cache last component */
309 int wantparent; /* 1 => wantparent or lockparent flag */
310 int rdonly; /* lookup read-only flag bit */
313 int dpunlocked = 0; /* dp has already been unlocked */
314 struct componentname *cnp = &ndp->ni_cnd;
315 struct thread *td = cnp->cn_td;
318 * Setup: break out flag bits into variables.
320 wantparent = cnp->cn_flags & (CNP_LOCKPARENT | CNP_WANTPARENT);
321 docache = (cnp->cn_flags & CNP_NOCACHE) ^ CNP_NOCACHE;
322 if (cnp->cn_nameiop == NAMEI_DELETE ||
323 (wantparent && cnp->cn_nameiop != NAMEI_CREATE &&
324 cnp->cn_nameiop != NAMEI_LOOKUP))
326 rdonly = cnp->cn_flags & CNP_RDONLY;
328 cnp->cn_flags &= ~CNP_ISSYMLINK;
329 dp = ndp->ni_startdir;
330 ndp->ni_startdir = NULLVP;
331 vn_lock(dp, NULL, LK_EXCLUSIVE | LK_RETRY, td);
335 * Search a new directory.
337 * The last component of the filename is left accessible via
338 * cnp->cn_nameptr for callers that need the name. Callers needing
339 * the name set the CNP_SAVENAME flag. When done, they assume
340 * responsibility for freeing the pathname buffer.
343 for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++)
345 cnp->cn_namelen = cp - cnp->cn_nameptr;
346 if (cnp->cn_namelen > NAME_MAX) {
347 error = ENAMETOOLONG;
350 #ifdef NAMEI_DIAGNOSTIC
353 printf("{%s}: ", cnp->cn_nameptr);
356 ndp->ni_pathlen -= cnp->cn_namelen;
360 * Replace multiple slashes by a single slash and trailing slashes
361 * by a null. This must be done before VOP_LOOKUP() because some
362 * fs's don't know about trailing slashes. Remember if there were
363 * trailing slashes to handle symlinks, existing non-directories
364 * and non-existing files that won't be directories specially later.
367 while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) {
372 *ndp->ni_next = '\0'; /* XXX for direnter() ... */
377 cnp->cn_flags |= CNP_MAKEENTRY;
378 if (*cp == '\0' && docache == 0)
379 cnp->cn_flags &= ~CNP_MAKEENTRY;
380 if (cnp->cn_namelen == 2 &&
381 cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
382 cnp->cn_flags |= CNP_ISDOTDOT;
384 cnp->cn_flags &= ~CNP_ISDOTDOT;
385 if (*ndp->ni_next == 0)
386 cnp->cn_flags |= CNP_ISLASTCN;
388 cnp->cn_flags &= ~CNP_ISLASTCN;
392 * Check for degenerate name (e.g. / or "")
393 * which is a way of talking about a directory,
394 * e.g. like "/." or ".".
396 if (cnp->cn_nameptr[0] == '\0') {
397 if (dp->v_type != VDIR) {
401 if (cnp->cn_nameiop != NAMEI_LOOKUP) {
410 if (!(cnp->cn_flags & (CNP_LOCKPARENT | CNP_LOCKLEAF)))
411 VOP_UNLOCK(dp, NULL, 0, cnp->cn_td);
412 /* XXX This should probably move to the top of function. */
413 if (cnp->cn_flags & CNP_SAVESTART)
414 panic("lookup: CNP_SAVESTART");
419 * Handle "..": two special cases.
420 * 1. If at root directory (e.g. after chroot)
421 * or at absolute root directory
422 * then ignore it so can't get out.
423 * 2. If this vnode is the root of a mounted
424 * filesystem, then replace it with the
425 * vnode which was mounted on so we take the
426 * .. in the other file system.
427 * 3. If the vnode is the top directory of
428 * the jail or chroot, don't let them out.
430 if (cnp->cn_flags & CNP_ISDOTDOT) {
432 if (dp == ndp->ni_rootdir ||
433 dp == ndp->ni_topdir ||
440 if ((dp->v_flag & VROOT) == 0 ||
441 (cnp->cn_flags & CNP_NOCROSSMOUNT))
443 if (dp->v_mount == NULL) { /* forced unmount */
448 dp = dp->v_mount->mnt_vnodecovered;
451 vn_lock(dp, NULL, LK_EXCLUSIVE | LK_RETRY, td);
456 * We now have a segment name to search for, and a directory to search.
461 cnp->cn_flags &= ~CNP_PDIRUNLOCK;
462 ASSERT_VOP_LOCKED(dp, "lookup");
463 if ((error = VOP_LOOKUP(dp, NCPNULL, &ndp->ni_vp, NCPPNULL, cnp)) != 0) {
464 KASSERT(ndp->ni_vp == NULL, ("leaf should be empty"));
465 #ifdef NAMEI_DIAGNOSTIC
466 printf("not found\n");
468 if ((error == ENOENT) &&
469 (dp->v_flag & VROOT) && (dp->v_mount != NULL) &&
470 (dp->v_mount->mnt_flag & MNT_UNION)) {
472 dp = dp->v_mount->mnt_vnodecovered;
473 if (cnp->cn_flags & CNP_PDIRUNLOCK)
478 vn_lock(dp, NULL, LK_EXCLUSIVE | LK_RETRY, td);
482 if (error != EJUSTRETURN)
485 * If creating and at end of pathname, then can consider
486 * allowing file to be created.
492 if (*cp == '\0' && trailing_slash &&
493 !(cnp->cn_flags & CNP_WILLBEDIR)) {
498 * We return with ni_vp NULL to indicate that the entry
499 * doesn't currently exist, leaving a pointer to the
500 * (possibly locked) directory inode in ndp->ni_dvp.
502 if (cnp->cn_flags & CNP_SAVESTART) {
503 ndp->ni_startdir = ndp->ni_dvp;
504 vref(ndp->ni_startdir);
508 #ifdef NAMEI_DIAGNOSTIC
512 ASSERT_VOP_LOCKED(ndp->ni_vp, "lookup");
515 * Take into account any additional components consumed by
516 * the underlying filesystem.
518 if (cnp->cn_consume > 0) {
519 cnp->cn_nameptr += cnp->cn_consume;
520 ndp->ni_next += cnp->cn_consume;
521 ndp->ni_pathlen -= cnp->cn_consume;
528 * Check to see if the vnode has been mounted on;
529 * if so find the root of the mounted file system.
531 while (dp->v_type == VDIR && (mp = dp->v_mountedhere) &&
532 (cnp->cn_flags & CNP_NOCROSSMOUNT) == 0) {
533 if (vfs_busy(mp, 0, NULL, td))
535 VOP_UNLOCK(dp, NULL, 0, td);
536 error = VFS_ROOT(mp, &tdp);
542 cache_mount(dp, tdp);
544 ndp->ni_vp = dp = tdp;
548 * Check for symbolic link
550 if ((dp->v_type == VLNK) &&
551 ((cnp->cn_flags & CNP_FOLLOW) || trailing_slash ||
552 *ndp->ni_next == '/')) {
553 cnp->cn_flags |= CNP_ISSYMLINK;
554 if (dp->v_mount == NULL) {
555 /* We can't know whether the directory was mounted with
556 * NOSYMFOLLOW, so we can't follow safely. */
560 if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) {
568 * Check for bogus trailing slashes.
570 if (trailing_slash && dp->v_type != VDIR) {
577 * Not a symbolic link. If more pathname,
578 * continue at next component, else return.
580 if (*ndp->ni_next == '/') {
581 cnp->cn_nameptr = ndp->ni_next;
582 while (*cnp->cn_nameptr == '/') {
586 if (ndp->ni_dvp != ndp->ni_vp)
587 ASSERT_VOP_UNLOCKED(ndp->ni_dvp, "lookup");
592 * Disallow directory write attempts on read-only file systems.
595 (cnp->cn_nameiop == NAMEI_DELETE || cnp->cn_nameiop == NAMEI_RENAME)) {
599 if (cnp->cn_flags & CNP_SAVESTART) {
600 ndp->ni_startdir = ndp->ni_dvp;
601 vref(ndp->ni_startdir);
606 if ((cnp->cn_flags & CNP_LOCKLEAF) == 0)
607 VOP_UNLOCK(dp, NULL, 0, td);
611 if ((cnp->cn_flags & (CNP_LOCKPARENT | CNP_PDIRUNLOCK)) == CNP_LOCKPARENT &&
612 *ndp->ni_next == '\0')
613 VOP_UNLOCK(ndp->ni_dvp, NULL, 0, td);
625 * relookup - lookup a path name component
626 * Used by lookup to re-aquire things.
629 relookup(dvp, vpp, cnp)
630 struct vnode *dvp, **vpp;
631 struct componentname *cnp;
633 struct thread *td = cnp->cn_td;
634 struct vnode *dp = 0; /* the directory we are searching */
635 int docache; /* == 0 do not cache last component */
636 int wantparent; /* 1 => wantparent or lockparent flag */
637 int rdonly; /* lookup read-only flag bit */
639 #ifdef NAMEI_DIAGNOSTIC
640 int newhash; /* DEBUG: check name hash */
641 char *cp; /* DEBUG: check name ptr/len */
645 * Setup: break out flag bits into variables.
647 wantparent = cnp->cn_flags & (CNP_LOCKPARENT|CNP_WANTPARENT);
648 docache = (cnp->cn_flags & CNP_NOCACHE) ^ CNP_NOCACHE;
649 if (cnp->cn_nameiop == NAMEI_DELETE ||
650 (wantparent && cnp->cn_nameiop != NAMEI_CREATE))
652 rdonly = cnp->cn_flags & CNP_RDONLY;
653 cnp->cn_flags &= ~CNP_ISSYMLINK;
655 vn_lock(dp, NULL, LK_EXCLUSIVE | LK_RETRY, td);
659 * Search a new directory.
661 * The last component of the filename is left accessible via
662 * cnp->cn_nameptr for callers that need the name. Callers needing
663 * the name set the CNP_SAVENAME flag. When done, they assume
664 * responsibility for freeing the pathname buffer.
666 #ifdef NAMEI_DIAGNOSTIC
667 if (cnp->cn_namelen != cp - cnp->cn_nameptr)
668 panic ("relookup: bad len");
670 panic("relookup: not last component");
671 printf("{%s}: ", cnp->cn_nameptr);
675 * Check for degenerate name (e.g. / or "")
676 * which is a way of talking about a directory,
677 * e.g. like "/." or ".".
679 if (cnp->cn_nameptr[0] == '\0') {
680 if (cnp->cn_nameiop != NAMEI_LOOKUP || wantparent) {
684 if (dp->v_type != VDIR) {
688 if (!(cnp->cn_flags & CNP_LOCKLEAF))
689 VOP_UNLOCK(dp, NULL, 0, td);
691 /* XXX This should probably move to the top of function. */
692 if (cnp->cn_flags & CNP_SAVESTART)
693 panic("lookup: CNP_SAVESTART");
697 if (cnp->cn_flags & CNP_ISDOTDOT)
698 panic ("relookup: lookup on dot-dot");
701 * We now have a segment name to search for, and a directory to search.
703 if ((error = VOP_LOOKUP(dp, NCPNULL, vpp, NCPPNULL, cnp)) != 0) {
704 KASSERT(*vpp == NULL, ("leaf should be empty"));
705 if (error != EJUSTRETURN)
708 * If creating and at end of pathname, then can consider
709 * allowing file to be created.
715 /* ASSERT(dvp == ndp->ni_startdir) */
716 if (cnp->cn_flags & CNP_SAVESTART)
719 * We return with ni_vp NULL to indicate that the entry
720 * doesn't currently exist, leaving a pointer to the
721 * (possibly locked) directory inode in ndp->ni_dvp.
728 * Check for symbolic link
730 KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & CNP_FOLLOW),
731 ("relookup: symlink found.\n"));
734 * Disallow directory write attempts on read-only file systems.
737 (cnp->cn_nameiop == NAMEI_DELETE || cnp->cn_nameiop == NAMEI_RENAME)) {
741 /* ASSERT(dvp == ndp->ni_startdir) */
742 if (cnp->cn_flags & CNP_SAVESTART)
748 if (vn_canvmio(dp) == TRUE &&
749 ((cnp->cn_flags & (CNP_NOOBJ|CNP_LOCKLEAF)) == CNP_LOCKLEAF))
750 vfs_object_create(dp, cnp->cn_td);
752 if ((cnp->cn_flags & CNP_LOCKLEAF) == 0)
753 VOP_UNLOCK(dp, NULL, 0, td);
757 if ((cnp->cn_flags & CNP_LOCKPARENT) && (cnp->cn_flags & CNP_ISLASTCN))
758 VOP_UNLOCK(dvp, NULL, 0, td);