linux_getcwd.c revision 83366 
1/* $FreeBSD: head/sys/compat/linux/linux_getcwd.c 83366 2001-09-12 08:38:13Z julian $ */
2/* $OpenBSD: linux_getcwd.c,v 1.2 2001/05/16 12:50:21 ho Exp $ */
3/* $NetBSD: vfs_getcwd.c,v 1.3.2.3 1999/07/11 10:24:09 sommerfeld Exp $ */
4
5/*-
6 * Copyright (c) 1999 The NetBSD Foundation, Inc.
7 * All rights reserved.
8 *
9 * This code is derived from software contributed to The NetBSD Foundation
10 * by Bill Sommerfeld.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 *    notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 *    notice, this list of conditions and the following disclaimer in the
19 *    documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 *    must display the following acknowledgement:
22 *        This product includes software developed by the NetBSD
23 *        Foundation, Inc. and its contributors.
24 * 4. Neither the name of The NetBSD Foundation nor the names of its
25 *    contributors may be used to endorse or promote products derived
26 *    from this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
29 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
30 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
31 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
32 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
34 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
35 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
36 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
37 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
38 * POSSIBILITY OF SUCH DAMAGE.
39 */
40#include "opt_compat.h"
41
42#include <sys/param.h>
43#include <sys/systm.h>
44#include <sys/sysproto.h>
45#include <sys/namei.h>
46#include <sys/filedesc.h>
47#include <sys/kernel.h>
48#include <sys/file.h>
49#include <sys/stat.h>
50#include <sys/vnode.h>
51#include <sys/mount.h>
52#include <sys/proc.h>
53#include <sys/uio.h>
54#include <sys/malloc.h>
55#include <sys/dirent.h>
56#include <ufs/ufs/dir.h>	/* XXX only for DIRBLKSIZ */
57
58#include <machine/../linux/linux.h>
59#include <machine/../linux/linux_proto.h>
60#include <compat/linux/linux_util.h>
61
62static int
63linux_getcwd_scandir __P((struct vnode **, struct vnode **,
64    char **, char *, struct thread *));
65static int
66linux_getcwd_common __P((struct vnode *, struct vnode *,
67		   char **, char *, int, int, struct thread *));
68
69#define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
70
71/*
72 * Vnode variable naming conventions in this file:
73 *
74 * rvp: the current root we're aiming towards.
75 * lvp, *lvpp: the "lower" vnode
76 * uvp, *uvpp: the "upper" vnode.
77 *
78 * Since all the vnodes we're dealing with are directories, and the
79 * lookups are going *up* in the filesystem rather than *down*, the
80 * usual "pvp" (parent) or "dvp" (directory) naming conventions are
81 * too confusing.
82 */
83
84/*
85 * XXX Will infinite loop in certain cases if a directory read reliably
86 *	returns EINVAL on last block.
87 * XXX is EINVAL the right thing to return if a directory is malformed?
88 */
89
90/*
91 * XXX Untested vs. mount -o union; probably does the wrong thing.
92 */
93
94/*
95 * Find parent vnode of *lvpp, return in *uvpp
96 *
97 * If we care about the name, scan it looking for name of directory
98 * entry pointing at lvp.
99 *
100 * Place the name in the buffer which starts at bufp, immediately
101 * before *bpp, and move bpp backwards to point at the start of it.
102 *
103 * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed
104 * On exit, *uvpp is either NULL or is a locked vnode reference.
105 */
106static int
107linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, td)
108	struct vnode **lvpp;
109	struct vnode **uvpp;
110	char **bpp;
111	char *bufp;
112	struct thread *td;
113{
114	int     error = 0;
115	int     eofflag;
116	off_t   off;
117	int     tries;
118	struct uio uio;
119	struct iovec iov;
120	char   *dirbuf = NULL;
121	int	dirbuflen;
122	ino_t   fileno;
123	struct vattr va;
124	struct vnode *uvp = NULL;
125	struct vnode *lvp = *lvpp;
126	struct componentname cn;
127	int len, reclen;
128	tries = 0;
129
130	/*
131	 * If we want the filename, get some info we need while the
132	 * current directory is still locked.
133	 */
134	if (bufp != NULL) {
135		error = VOP_GETATTR(lvp, &va, td->td_proc->p_ucred, td);
136		if (error) {
137			vput(lvp);
138			*lvpp = NULL;
139			*uvpp = NULL;
140			return error;
141		}
142	}
143
144	/*
145	 * Ok, we have to do it the hard way..
146	 * Next, get parent vnode using lookup of ..
147	 */
148	cn.cn_nameiop = LOOKUP;
149	cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY;
150	cn.cn_thread = td;
151	cn.cn_cred = td->td_proc->p_ucred;
152	cn.cn_pnbuf = NULL;
153	cn.cn_nameptr = "..";
154	cn.cn_namelen = 2;
155	cn.cn_consume = 0;
156
157	/*
158	 * At this point, lvp is locked and will be unlocked by the lookup.
159	 * On successful return, *uvpp will be locked
160	 */
161	error = VOP_LOOKUP(lvp, uvpp, &cn);
162	if (error) {
163		vput(lvp);
164		*lvpp = NULL;
165		*uvpp = NULL;
166		return error;
167	}
168	uvp = *uvpp;
169
170	/* If we don't care about the pathname, we're done */
171	if (bufp == NULL) {
172		vrele(lvp);
173		*lvpp = NULL;
174		return 0;
175	}
176
177	fileno = va.va_fileid;
178
179	dirbuflen = DIRBLKSIZ;
180	if (dirbuflen < va.va_blocksize)
181		dirbuflen = va.va_blocksize;
182	dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
183
184#if 0
185unionread:
186#endif
187	off = 0;
188	do {
189		/* call VOP_READDIR of parent */
190		iov.iov_base = dirbuf;
191		iov.iov_len = dirbuflen;
192
193		uio.uio_iov = &iov;
194		uio.uio_iovcnt = 1;
195		uio.uio_offset = off;
196		uio.uio_resid = dirbuflen;
197		uio.uio_segflg = UIO_SYSSPACE;
198		uio.uio_rw = UIO_READ;
199		uio.uio_td = td;
200
201		eofflag = 0;
202
203		error = VOP_READDIR(uvp, &uio, td->td_proc->p_ucred, &eofflag, 0, 0);
204
205		off = uio.uio_offset;
206
207		/*
208		 * Try again if NFS tosses its cookies.
209		 * XXX this can still loop forever if the directory is busted
210		 * such that the second or subsequent page of it always
211		 * returns EINVAL
212		 */
213		if ((error == EINVAL) && (tries < 3)) {
214			off = 0;
215			tries++;
216			continue;	/* once more, with feeling */
217		}
218
219		if (!error) {
220			char   *cpos;
221			struct dirent *dp;
222
223			cpos = dirbuf;
224			tries = 0;
225
226			/* scan directory page looking for matching vnode */
227			for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
228				dp = (struct dirent *) cpos;
229				reclen = dp->d_reclen;
230
231				/* check for malformed directory.. */
232				if (reclen < DIRENT_MINSIZE) {
233					error = EINVAL;
234					goto out;
235				}
236				/*
237				 * XXX should perhaps do VOP_LOOKUP to
238				 * check that we got back to the right place,
239				 * but getting the locking games for that
240				 * right would be heinous.
241				 */
242				if ((dp->d_type != DT_WHT) &&
243				    (dp->d_fileno == fileno)) {
244					char *bp = *bpp;
245					bp -= dp->d_namlen;
246
247					if (bp <= bufp) {
248						error = ERANGE;
249						goto out;
250					}
251					bcopy(dp->d_name, bp, dp->d_namlen);
252					error = 0;
253					*bpp = bp;
254					goto out;
255				}
256				cpos += reclen;
257			}
258		}
259	} while (!eofflag);
260	error = ENOENT;
261
262out:
263	vrele(lvp);
264	*lvpp = NULL;
265	free(dirbuf, M_TEMP);
266	return error;
267}
268
269
270/*
271 * common routine shared by sys___getcwd() and linux_vn_isunder()
272 */
273
274#define GETCWD_CHECK_ACCESS 0x0001
275
276static int
277linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, td)
278	struct vnode *lvp;
279	struct vnode *rvp;
280	char **bpp;
281	char *bufp;
282	int limit;
283	int flags;
284	struct thread *td;
285{
286	struct filedesc *fdp = td->td_proc->p_fd;
287	struct vnode *uvp = NULL;
288	char *bp = NULL;
289	int error;
290	int perms = VEXEC;
291
292	if (rvp == NULL) {
293		rvp = fdp->fd_rdir;
294		if (rvp == NULL)
295			rvp = rootvnode;
296	}
297
298	VREF(rvp);
299	VREF(lvp);
300
301	/*
302	 * Error handling invariant:
303	 * Before a `goto out':
304	 *	lvp is either NULL, or locked and held.
305	 *	uvp is either NULL, or locked and held.
306	 */
307
308	error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
309	if (error) {
310		vrele(lvp);
311		lvp = NULL;
312		goto out;
313	}
314	if (bufp)
315		bp = *bpp;
316	/*
317	 * this loop will terminate when one of the following happens:
318	 *	- we hit the root
319	 *	- getdirentries or lookup fails
320	 *	- we run out of space in the buffer.
321	 */
322	if (lvp == rvp) {
323		if (bp)
324			*(--bp) = '/';
325		goto out;
326	}
327	do {
328		if (lvp->v_type != VDIR) {
329			error = ENOTDIR;
330			goto out;
331		}
332
333		/*
334		 * access check here is optional, depending on
335		 * whether or not caller cares.
336		 */
337		if (flags & GETCWD_CHECK_ACCESS) {
338			error = VOP_ACCESS(lvp, perms, td->td_proc->p_ucred, td);
339			if (error)
340				goto out;
341			perms = VEXEC|VREAD;
342		}
343
344		/*
345		 * step up if we're a covered vnode..
346		 */
347		while (lvp->v_flag & VROOT) {
348			struct vnode *tvp;
349
350			if (lvp == rvp)
351				goto out;
352
353			tvp = lvp;
354			lvp = lvp->v_mount->mnt_vnodecovered;
355			vput(tvp);
356			/*
357			 * hodie natus est radici frater
358			 */
359			if (lvp == NULL) {
360				error = ENOENT;
361				goto out;
362			}
363			VREF(lvp);
364			error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
365			if (error != 0) {
366				vrele(lvp);
367				lvp = NULL;
368				goto out;
369			}
370		}
371		error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, td);
372		if (error)
373			goto out;
374#if DIAGNOSTIC
375		if (lvp != NULL)
376			panic("getcwd: oops, forgot to null lvp");
377		if (bufp && (bp <= bufp)) {
378			panic("getcwd: oops, went back too far");
379		}
380#endif
381		if (bp)
382			*(--bp) = '/';
383		lvp = uvp;
384		uvp = NULL;
385		limit--;
386	} while ((lvp != rvp) && (limit > 0));
387
388out:
389	if (bpp)
390		*bpp = bp;
391	if (uvp)
392		vput(uvp);
393	if (lvp)
394		vput(lvp);
395	vrele(rvp);
396	return error;
397}
398
399
400/*
401 * Find pathname of process's current directory.
402 *
403 * Use vfs vnode-to-name reverse cache; if that fails, fall back
404 * to reading directory contents.
405 */
406
407int
408linux_getcwd(struct thread *td, struct linux_getcwd_args *args)
409{
410	struct __getcwd_args bsd;
411	caddr_t sg, bp, bend, path;
412	int error, len, lenused;
413
414#ifdef DEBUG
415	printf("Linux-emul(%ld): getcwd(%p, %ld)\n", (long)td->td_proc->p_pid,
416	       args->buf, args->bufsize);
417#endif
418
419	sg = stackgap_init();
420	bsd.buf = stackgap_alloc(&sg, SPARE_USRSPACE);
421	bsd.buflen = SPARE_USRSPACE;
422	error = __getcwd(td, &bsd);
423	if (!error) {
424		lenused = strlen(bsd.buf) + 1;
425		if (lenused <= args->bufsize) {
426			td->td_retval[0] = lenused;
427			error = copyout(bsd.buf, args->buf, lenused);
428		}
429		else
430			error = ERANGE;
431	} else {
432		len = args->bufsize;
433
434		if (len > MAXPATHLEN*4)
435			len = MAXPATHLEN*4;
436		else if (len < 2)
437			return ERANGE;
438
439		path = (char *)malloc(len, M_TEMP, M_WAITOK);
440
441		bp = &path[len];
442		bend = bp;
443		*(--bp) = '\0';
444
445		/*
446		 * 5th argument here is "max number of vnodes to traverse".
447		 * Since each entry takes up at least 2 bytes in the output buffer,
448		 * limit it to N/2 vnodes for an N byte buffer.
449		 */
450
451		error = linux_getcwd_common (td->td_proc->p_fd->fd_cdir, NULL,
452		    &bp, path, len/2, GETCWD_CHECK_ACCESS, td);
453
454		if (error)
455			goto out;
456		lenused = bend - bp;
457		td->td_retval[0] = lenused;
458		/* put the result into user buffer */
459		error = copyout(bp, args->buf, lenused);
460
461out:
462		free(path, M_TEMP);
463	}
464	return (error);
465}
466
467