xref: /titanic_41/usr/src/lib/libc/port/gen/nftw.c (revision 40e5e17b3361b3eea56a9723071c406894a20b78)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 #pragma ident	"%Z%%M%	%I%	%E% SMI"
28 
29 /*	Copyright (c) 1988 AT&T	*/
30 /*	  All Rights Reserved  	*/
31 
32 
33 /*
34  *	nftw - new file tree walk
35  *
36  *	int nftw(char *path, int (*fn)(), int depth, int flags);
37  *
38  *	Derived from System V ftw() by David Korn
39  *
40  *	nftw visits each file and directory in the tree starting at
41  *	path. It uses the generic directory reading library so it works
42  *	for any file system type.  The flags field is used to specify:
43  *		FTW_PHYS  Physical walk, does not follow symbolic links
44  *			  Otherwise, nftw will follow links but will not
45  *			  walk down any path the crosses itself.
46  *		FTW_MOUNT The walk will not cross a mount point.
47  *		FTW_DEPTH All subdirectories will be visited before the
48  *			  directory itself.
49  *		FTW_CHDIR The walk will change to each directory before
50  *			  reading it.  This is faster but core dumps
51  *			  may not get generated.
52  *
53  *	The following flags are private, and are used by the find
54  *	utility:
55  *		FTW_ANYERR Call the callback function and return
56  *			   FTW_NS on any stat failure, not just
57  *			   lack of permission.
58  *		FTW_HOPTION Use stat the first time the walk
59  *			    function is called, regardless of
60  *			    whether or not FTW_PHYS is specified.
61  *		FTW_NOLOOP Allow find utility to detect infinite loops created
62  *			   by both symbolic and hard linked directories.
63  *
64  *	fn is called with four arguments at each file and directory.
65  *	The first argument is the pathname of the object, the second
66  *	is a pointer to the stat buffer and the third is an integer
67  *	giving additional information as follows:
68  *
69  *		FTW_F	The object is a file.
70  *		FTW_D	The object is a directory.
71  *		FTW_DP	The object is a directory and subdirectories
72  *			have been visited.
73  *		FTW_SL	The object is a symbolic link.
74  *		FTW_SLN The object is a symbolic link pointing at a
75  *		        non-existing file.
76  *		FTW_DNR	The object is a directory that cannot be read.
77  *			fn will not be called for any of its descendants.
78  *		FTW_NS	Stat failed on the object because of lack of
79  *			appropriate permission. The stat buffer passed to fn
80  *			is undefined.  Stat failure for any reason is
81  *			considered an error and nftw will return -1.
82  *	The following value is private, and is used by the find utility:
83  *		FTW_DL	An infinite loop has been detected.
84  *	The fourth argument is a struct FTW* which contains the depth
85  *	and the offset into pathname to the base name.
86  *	If fn returns nonzero, nftw returns this value to its caller.
87  *
88  *	depth limits the number of open directories that ftw uses
89  *	before it starts recycling file descriptors.  In general,
90  *	a file descriptor is used for each level.  When FTW_CHDIR isn't set,
91  *	in order to descend to arbitrary depths, nftw requires 2 file
92  *	descriptors to be open during the call to openat(), therefore if
93  *	the depth argument is less than 2 nftw will not use openat(), and
94  *	it will fail with ENAMETOOLONG if it descends to a directory that
95  *	exceeds PATH_MAX.
96  *
97  */
98 
99 #include <sys/feature_tests.h>
100 
101 #if !defined(_LP64) && _FILE_OFFSET_BITS == 64
102 #pragma weak nftw64 = _nftw64
103 #define	_nftw		_nftw64
104 #define	fstat64		_fstat64
105 #define	fstatat64	_fstatat64
106 #define	lstat64		_lstat64
107 #define	openat64	_openat64
108 #define	readdir64	_readdir64
109 #define	stat64		_stat64
110 #else
111 #pragma weak nftw = _nftw
112 #define	fstat		_fstat
113 #define	fstatat		_fstatat
114 #define	lstat		_lstat
115 #define	openat		_openat
116 #define	readdir		_readdir
117 #define	stat		_stat
118 #endif /* !_LP64 && _FILE_OFFSET_BITS == 64 */
119 
120 #define	chdir		_chdir
121 #define	close		_close
122 #define	closedir	_closedir
123 #define	fchdir		_fchdir
124 #define	fdopendir	_fdopendir
125 #define	fprintf		_fprintf
126 #define	getcwd		_getcwd
127 #define	opendir		_opendir
128 #define	seekdir		_seekdir
129 #define	strdup		_strdup
130 #define	strerror	_strerror
131 #define	strtok_r	_strtok_r
132 #define	telldir		_telldir
133 
134 #include "lint.h"
135 #include <mtlib.h>
136 #include <sys/types.h>
137 #include <sys/stat.h>
138 #include <dirent.h>
139 #include <errno.h>
140 #include <limits.h>
141 #include <ftw.h>
142 #include <stdlib.h>
143 #include <string.h>
144 #include <unistd.h>
145 #include <thread.h>
146 #include <synch.h>
147 #include <stdio.h>
148 #include <strings.h>
149 #include <fcntl.h>
150 
151 #ifndef PATH_MAX
152 #define	PATH_MAX	1023
153 #endif
154 
155 /*
156  * Local variables (used to be static local).
157  * Putting them into a structure that is passed
158  * around makes nftw() MT-safe with no locking required.
159  */
160 struct Save {
161 	struct Save *last;
162 	DIR	*fd;
163 	char	*comp;
164 	long	here;
165 	dev_t	dev;
166 	ino_t	inode;
167 };
168 
169 struct Var {
170 	char	*home;
171 	size_t	len;
172 	char	*fullpath;
173 	char	*tmppath;
174 	int	curflags;
175 	dev_t	cur_mount;
176 	struct FTW state;
177 	int	walklevel;
178 	int	(*statf)(const char *, struct stat *, struct Save *);
179 	int	(*savedstatf)(const char *, struct stat *, struct Save *);
180 	DIR	*(*opendirf)(const char *);
181 };
182 
183 static int oldclose(struct Save *);
184 static int cdlstat(const char *, struct stat *, struct Save *);
185 static int cdstat(const char *, struct stat *, struct Save *);
186 static int nocdlstat(const char *, struct stat *, struct Save *);
187 static int nocdstat(const char *, struct stat *, struct Save *);
188 static DIR *cdopendir(const char *);
189 static DIR *nocdopendir(const char *);
190 static const char *get_unrooted(const char *);
191 
192 /*
193  * This is the recursive walker.
194  */
195 static int
196 walk(char *component,
197     int (*fn)(const char *, const struct stat *, int, struct FTW *),
198     int depth, struct Save *last, struct Var *vp)
199 {
200 	struct stat statb;
201 	char *p, *tmp;
202 	int type;
203 	char *comp;
204 	struct dirent *dir;
205 	char *q;
206 	int rc = 0;
207 	int val = -1;
208 	int cdval = -1;
209 	int oldbase;
210 	int skip;
211 	struct Save this;
212 	size_t base_comp, base_component, base_this_comp, base_last_comp;
213 	size_t base_fullpath, base_tmppath;
214 
215 	this.last = last;
216 	this.fd = 0;
217 	if ((vp->curflags & FTW_CHDIR) && last)
218 		comp = last->comp;
219 	else
220 		comp = vp->tmppath;
221 
222 	if (vp->savedstatf == NULL)
223 		vp->savedstatf = vp->statf;
224 
225 	if ((vp->walklevel++ == 0) && (vp->curflags & FTW_HOPTION)) {
226 		if (((vp->curflags & FTW_CHDIR) == 0) && (depth >= 2)) {
227 			vp->statf = nocdstat;
228 		} else {
229 			vp->statf = cdstat;
230 		}
231 	} else {
232 		vp->statf = vp->savedstatf;
233 	}
234 
235 	/*
236 	 * Determine the type of the component.
237 	 */
238 	if ((*vp->statf)(comp, &statb, last) >= 0) {
239 		if ((statb.st_mode & S_IFMT) == S_IFDIR) {
240 			type = FTW_D;
241 			if (depth <= 1)
242 				(void) oldclose(last);
243 			if ((this.fd = (*vp->opendirf)(comp)) == 0) {
244 				if (errno == EMFILE && oldclose(last) &&
245 				    (this.fd = (*vp->opendirf)(comp)) != 0) {
246 					/*
247 					 * If opendirf fails because there
248 					 * are OPEN_MAX fd in the calling
249 					 * process, and we close the oldest
250 					 * fd, and another opendirf doesn't
251 					 * fail, depth is set to 1.
252 					 */
253 					depth = 1;
254 				} else {
255 					type = FTW_DNR;
256 					goto fail;
257 				}
258 			}
259 			if (statb.st_fstype[0] == 'a' &&
260 			    strcmp(statb.st_fstype, "autofs") == 0) {
261 				/*
262 				 * this dir is on autofs
263 				 */
264 				if (fstat(this.fd->dd_fd, &statb) < 0) {
265 					(void) closedir(this.fd);
266 					type = FTW_NS;
267 					goto fail;
268 				}
269 			}
270 		} else if ((statb.st_mode & S_IFMT) == S_IFLNK) {
271 			type = FTW_SL;
272 		} else {
273 			type = FTW_F;
274 		}
275 	} else if ((vp->curflags & FTW_ANYERR) && errno != ENOENT) {
276 		/*
277 		 * If FTW_ANYERR is specified, then a stat error
278 		 * other than ENOENT automatically results in
279 		 * failure.  This allows the callback function
280 		 * to properly handle ENAMETOOLONG and ELOOP and
281 		 * things of that nature, that would be masked
282 		 * by calling lstat before failing.
283 		 */
284 		type = FTW_NS;
285 		goto fail;
286 	} else {
287 		/*
288 		 * Statf has failed. If stat was used instead of lstat,
289 		 * try using lstat. If lstat doesn't fail, "comp"
290 		 * must be a symbolic link pointing to a non-existent
291 		 * file. Such a symbolic link should be ignored.
292 		 * Also check the file type, if possible, for symbolic
293 		 * link.
294 		 */
295 		if (((vp->statf == cdstat) &&
296 		    (cdlstat(comp, &statb, last) >= 0) &&
297 		    ((statb.st_mode & S_IFMT) == S_IFLNK)) ||
298 		    ((vp->statf == nocdstat) &&
299 		    (nocdlstat(comp, &statb, last) >= 0) &&
300 		    ((statb.st_mode & S_IFMT) == S_IFLNK))) {
301 
302 			/*
303 			 * Ignore bad symbolic link, let "fn"
304 			 * report it.
305 			 */
306 
307 			errno = ENOENT;
308 			type = FTW_SLN;
309 		} else {
310 			type = FTW_NS;
311 	fail:
312 			/*
313 			 * if FTW_ANYERR is set in flags, we call
314 			 * the user function with FTW_NS set, regardless
315 			 * of the reason stat failed.
316 			 */
317 			if (!(vp->curflags & FTW_ANYERR))
318 				if (errno != EACCES)
319 					return (-1);
320 		}
321 	}
322 
323 	/*
324 	 * If the walk is not supposed to cross a mount point,
325 	 * and it did, get ready to return.
326 	 */
327 	if ((vp->curflags & FTW_MOUNT) && type != FTW_NS &&
328 	    statb.st_dev != vp->cur_mount)
329 		goto quit;
330 	vp->state.quit = 0;
331 
332 	/*
333 	 * If current component is not a directory, call user
334 	 * specified function and get ready to return.
335 	 */
336 	if (type != FTW_D || (vp->curflags & FTW_DEPTH) == 0)
337 		rc = (*fn)(vp->tmppath, &statb, type, &vp->state);
338 	if (rc > 0)
339 		val = rc;
340 	skip = (vp->state.quit & FTW_SKD);
341 	if (rc != 0 || type != FTW_D || (vp->state.quit & FTW_PRUNE))
342 		goto quit;
343 
344 	if (vp->tmppath[0] != '\0' && component[-1] != '/')
345 		*component++ = '/';
346 	*component = 0;
347 	if (vp->curflags & FTW_CHDIR) {
348 		struct stat statb2;
349 
350 		/*
351 		 * Security check (there is a window between
352 		 * (*vp->statf)() and opendir() above).
353 		 */
354 		if ((vp->curflags & FTW_PHYS) &&
355 		    (fstat(this.fd->dd_fd, &statb2) < 0 ||
356 		    statb2.st_ino != statb.st_ino ||
357 		    statb2.st_dev != statb.st_dev)) {
358 			errno = EAGAIN;
359 			rc = -1;
360 			goto quit;
361 		}
362 
363 		if ((cdval = fchdir(this.fd->dd_fd)) >= 0) {
364 			this.comp = component;
365 		} else {
366 			type = FTW_DNR;
367 			rc = (*fn)(vp->tmppath, &statb, type, &vp->state);
368 			goto quit;
369 		}
370 	}
371 
372 	/*
373 	 * If the walk has followed a symbolic link (FTW_PHYS is not set),
374 	 * traverse the walk back to make sure there is not a loop.
375 	 * The find utility (FTW_NOLOOP is set) detects infinite loops
376 	 * in both symbolic and hard linked directories.
377 	 */
378 	if ((vp->curflags & FTW_NOLOOP) ||
379 	    ((vp->curflags & FTW_PHYS) == 0)) {
380 		struct Save *sp = last;
381 		while (sp) {
382 			/*
383 			 * If the same node has already been visited, there
384 			 * is a loop. Get ready to return.
385 			 */
386 			if (sp->dev == statb.st_dev &&
387 			    sp->inode == statb.st_ino) {
388 				if (vp->curflags & FTW_NOLOOP) {
389 					/* private interface for find util */
390 					type = FTW_DL;
391 					goto fail;
392 				}
393 				goto quit;
394 			}
395 			sp = sp->last;
396 		}
397 	}
398 	this.dev = statb.st_dev;
399 	this.inode = statb.st_ino;
400 	oldbase = vp->state.base;
401 	vp->state.base = (int)(component - vp->tmppath);
402 	while (dir = readdir(this.fd)) {
403 		if (dir->d_ino == 0)
404 			continue;
405 		q = dir->d_name;
406 		if (*q == '.') {
407 			if (q[1] == 0)
408 				continue;
409 			else if (q[1] == '.' && q[2] == 0)
410 				continue;
411 		}
412 		if (last != NULL && last->comp != NULL) {
413 			base_last_comp = last->comp - vp->home;
414 		}
415 		base_comp = comp - vp->home;
416 		base_component = component - vp->home;
417 		if ((strlen(q) + strlen(vp->home) + 1) > vp->len) {
418 			/*
419 			 * When the space needed for vp->home has
420 			 * exceeded the amount of space that has
421 			 * been allocated, realloc() more space
422 			 * and adjust pointers to point to the
423 			 * (possibly moved) new block for vp->home
424 			 */
425 			base_this_comp = this.comp - vp->home;
426 			base_fullpath = vp->fullpath - vp->home;
427 			base_tmppath = vp->tmppath - vp->home;
428 			vp->len *= 2;
429 			tmp = (char *)realloc(vp->home, vp->len);
430 			if (tmp == NULL) {
431 				rc = -1;
432 				goto quit;
433 			}
434 			vp->home = tmp;
435 			comp = vp->home + base_comp;
436 			component = vp->home + base_component;
437 			this.comp = vp->home + base_this_comp;
438 			vp->fullpath = vp->home + base_fullpath;
439 			vp->tmppath = vp->home + base_tmppath;
440 			if (last != NULL && last->comp != NULL) {
441 				last->comp = vp->home + base_last_comp;
442 			}
443 		}
444 		p = component;
445 		while (*q != '\0')
446 			*p++ = *q++;
447 		*p = '\0';
448 		vp->state.level++;
449 
450 		/* Call walk() recursively.  */
451 		rc = walk(p, fn, depth-1, &this, vp);
452 		if (last != NULL && last->comp != NULL) {
453 			last->comp = vp->home + base_last_comp;
454 		}
455 		comp = vp->home + base_comp;
456 		component = vp->home + base_component;
457 		vp->state.level--;
458 		if (this.fd == 0) {
459 			*component = 0;
460 			if (vp->curflags & FTW_CHDIR) {
461 				this.fd = opendir(".");
462 			} else {
463 				this.fd = (*vp->opendirf)(comp);
464 			}
465 			if (this.fd == 0) {
466 				rc = -1;
467 				goto quit;
468 			}
469 			seekdir(this.fd, this.here);
470 		}
471 		if (rc != 0) {
472 			if (errno == ENOENT) {
473 				(void) fprintf(stderr, "cannot open %s: %s\n",
474 				    vp->tmppath, strerror(errno));
475 				val = rc;
476 				continue;
477 			}
478 			goto quit;	/* this seems extreme */
479 		}
480 	}
481 	vp->state.base = oldbase;
482 	*--component = 0;
483 	type = FTW_DP;
484 	if ((vp->tmppath[0] != '\0') && (vp->curflags & FTW_DEPTH) && !skip)
485 		rc = (*fn)(vp->tmppath, &statb, type, &vp->state);
486 quit:
487 	if (cdval >= 0 && last) {
488 		/* try to change back to previous directory */
489 		if (last->fd != NULL) {
490 			if (fchdir(last->fd->dd_fd) < 0) {
491 				rc = -1;
492 			}
493 		} else {
494 			if ((cdval = chdir("..")) >= 0) {
495 				if ((*vp->statf)(".", &statb, last) < 0 ||
496 				    statb.st_ino != last->inode ||
497 				    statb.st_dev != last->dev)
498 					cdval = -1;
499 			}
500 			*comp = 0;
501 			if (cdval < 0) {
502 				if (chdir(vp->fullpath) < 0) {
503 					rc = -1;
504 				} else {
505 				    /* Security check */
506 				    if ((vp->curflags & FTW_PHYS) &&
507 					((*vp->statf)(".", &statb, last) < 0 ||
508 					statb.st_ino != last->inode ||
509 					statb.st_dev != last->dev)) {
510 					    errno = EAGAIN;
511 					    rc = -1;
512 				    }
513 				}
514 			}
515 		}
516 	}
517 	if (this.fd)
518 		(void) closedir(this.fd);
519 	if (val > rc)
520 		return (val);
521 	else
522 		return (rc);
523 }
524 
525 int
526 _nftw(const char *path,
527     int (*fn)(const char *, const struct stat *, int, struct FTW *),
528     int depth, int flags)
529 {
530 	struct Var var;
531 	struct stat statb;
532 	int rc = -1;
533 	char *dp;
534 	char *base;
535 	char *endhome;
536 	const char *savepath = path;
537 	int save_errno;
538 
539 	var.walklevel = 0;
540 	var.len = 2*(PATH_MAX+1);
541 	var.home = (char *)malloc(var.len);
542 	if (var.home == NULL)
543 		return (-1);
544 
545 	var.home[0] = 0;
546 
547 	/*
548 	 * If the walk is going to change directory before
549 	 * reading it, save current working directory.
550 	 */
551 	if (flags & FTW_CHDIR) {
552 		if (getcwd(var.home, PATH_MAX+1) == 0) {
553 			free(var.home);
554 			return (-1);
555 		}
556 	}
557 	endhome = dp = var.home + strlen(var.home);
558 	if (*path == '/')
559 		var.fullpath = dp;
560 	else {
561 		*dp++ = '/';
562 		var.fullpath = var.home;
563 	}
564 	var.tmppath =  dp;
565 	base = dp-1;
566 	while (*path) {
567 		*dp = *path;
568 		if (*dp == '/')
569 			base = dp;
570 		dp++, path++;
571 	}
572 	*dp = 0;
573 	var.state.base = (int)(base + 1 - var.tmppath);
574 	if (*path) {
575 		free(var.home);
576 		errno = ENAMETOOLONG;
577 		return (-1);
578 	}
579 	var.curflags = flags;
580 
581 	/*
582 	 * If doing chdir()'s, set var.opendirf to cdopendir.
583 	 * If not doing chdir()'s and if nftw()'s depth arg >= 2,
584 	 * set var.opendirf to nocdopendir.  In order to
585 	 * descend to arbitrary depths without doing chdir()'s, nftw()
586 	 * requires a depth arg >= 2 so that nocdopendir() can use openat()
587 	 * to traverse the directories.  So when not doing
588 	 * chdir()'s if nftw()'s depth arg <= 1, set var.opendirf to
589 	 * cdopendir.
590 	 * If doing a physical walk (not following symbolic link), set
591 	 * var.statf to cdlstat() or nocdlstat(). Otherwise, set var.statf
592 	 * to cdstat() or nocdstat().
593 	 */
594 	if (((flags & FTW_CHDIR) == 0) && (depth >= 2)) {
595 		var.opendirf = nocdopendir;
596 		if (flags & FTW_PHYS)
597 			var.statf = nocdlstat;
598 		else
599 			var.statf = nocdstat;
600 	} else {
601 		var.opendirf = cdopendir;
602 		if (flags & FTW_PHYS)
603 			var.statf = cdlstat;
604 		else
605 			var.statf = cdstat;
606 	}
607 
608 	/*
609 	 * If walk is not going to cross a mount point,
610 	 * save the current mount point.
611 	 */
612 	if (flags & FTW_MOUNT) {
613 		if ((*var.statf)(savepath, &statb, NULL) >= 0)
614 			var.cur_mount = statb.st_dev;
615 		else
616 			goto done;
617 	}
618 	var.state.level = 0;
619 
620 	/*
621 	 * Call walk() which does most of the work.
622 	 * walk() uses errno in a rather obtuse way
623 	 * so we shield any incoming errno.
624 	 */
625 	save_errno = errno;
626 	errno = 0;
627 	var.savedstatf = NULL;
628 	rc = walk(dp, fn, depth, (struct Save *)0, &var);
629 	if (errno == 0)
630 		errno = save_errno;
631 done:
632 	*endhome = 0;
633 	if (flags & FTW_CHDIR)
634 		(void) chdir(var.home);
635 	free(var.home);
636 	return (rc);
637 }
638 
639 /*
640  * Get stat info on path when FTW_CHDIR is set.
641  */
642 /*ARGSUSED1*/
643 static int
644 cdstat(const char *path, struct stat *statp, struct Save *lp) {
645 	return (stat(path, statp));
646 }
647 
648 /*
649  * Get lstat info on path when FTW_CHDIR is set.
650  */
651 /*ARGSUSED1*/
652 static int
653 cdlstat(const char *path, struct stat *statp, struct Save *lp)
654 {
655 	return (lstat(path, statp));
656 }
657 
658 /*
659  * Get stat info on path when FTW_CHDIR is not set.
660  */
661 static int
662 nocdstat(const char *path, struct stat *statp, struct Save *lp)
663 {
664 	const char *unrootp;
665 
666 	if (lp && lp->fd) {
667 		/* get basename of path */
668 		unrootp = get_unrooted(path);
669 		return (fstatat(lp->fd->dd_fd, unrootp, statp, 0));
670 	} else {
671 		return (stat(path, statp));
672 	}
673 }
674 
675 /*
676  * Get lstat info on path when FTW_CHDIR is not set.
677  */
678 static int
679 nocdlstat(const char *path, struct stat *statp, struct Save *lp)
680 {
681 	const char *unrootp;
682 
683 	if (lp && lp->fd) {
684 		/* get basename of path */
685 		unrootp = get_unrooted(path);
686 		return (fstatat(lp->fd->dd_fd, unrootp, statp,
687 		    AT_SYMLINK_NOFOLLOW));
688 	} else {
689 		return (lstat(path, statp));
690 	}
691 }
692 
693 /*
694  * Open path directory when FTW_CHDIR is set.
695  *
696  */
697 static DIR *
698 cdopendir(const char *path)
699 {
700 	return (opendir(path));
701 }
702 
703 /*
704  * Open path directory when FTW_CHDIR is not set.
705  */
706 static DIR *
707 nocdopendir(const char *path)
708 {
709 	int fd, cfd;
710 	DIR *fdd;
711 	char *dirp, *token, *ptr;
712 
713 	if (((fdd = opendir(path)) == NULL) && (errno == ENAMETOOLONG)) {
714 		if ((dirp = strdup(path)) == NULL) {
715 			errno = ENAMETOOLONG;
716 			return (NULL);
717 		}
718 		if ((token = strtok_r(dirp, "/", &ptr)) != NULL) {
719 		    if ((fd = openat(AT_FDCWD, dirp, O_RDONLY)) < 0) {
720 			(void) free(dirp);
721 			errno = ENAMETOOLONG;
722 			return (NULL);
723 		    }
724 		    while ((token = strtok_r(NULL, "/", &ptr)) != NULL) {
725 			if ((cfd = openat(fd, token, O_RDONLY)) < 0) {
726 			    (void) close(fd);
727 			    (void) free(dirp);
728 			    errno = ENAMETOOLONG;
729 			    return (NULL);
730 			}
731 			(void) close(fd);
732 			fd = cfd;
733 		    }
734 		    (void) free(dirp);
735 		    return (fdopendir(fd));
736 		}
737 		(void) free(dirp);
738 		errno = ENAMETOOLONG;
739 	}
740 	return (fdd);
741 }
742 
743 /* return pointer basename of path, which may contain trailing slashes */
744 static const char *
745 get_unrooted(const char *path)
746 {
747 	const char *ptr;
748 
749 	if (!path || !*path)
750 		return (NULL);
751 
752 	ptr = path + strlen(path);
753 	/* find last char in path before any trailing slashes */
754 	while (ptr != path && *--ptr == '/')
755 		;
756 
757 	if (ptr == path)	/* all slashes */
758 		return (ptr);
759 
760 	while (ptr != path)
761 		if (*--ptr == '/')
762 			return (++ptr);
763 
764 	return (ptr);
765 }
766 
767 /*
768  * close the oldest directory.  It saves the seek offset.
769  * return value is 0 unless it was unable to close any descriptor
770  */
771 
772 static int
773 oldclose(struct Save *sp)
774 {
775 	struct Save *spnext;
776 	while (sp) {
777 		spnext = sp->last;
778 		if (spnext == 0 || spnext->fd == 0)
779 			break;
780 		sp = spnext;
781 	}
782 	if (sp == 0 || sp->fd == 0)
783 		return (0);
784 	sp->here = telldir(sp->fd);
785 	(void) closedir(sp->fd);
786 	sp->fd = 0;
787 	return (1);
788 }
789