1 /* $OpenBSD: linux_getcwd.c,v 1.2 2001/05/16 12:50:21 ho Exp $ */
2 /* $NetBSD: vfs_getcwd.c,v 1.3.2.3 1999/07/11 10:24:09 sommerfeld Exp $ */
3 /*-
4 * Copyright (c) 1999 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Bill Sommerfeld.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the NetBSD
21 * Foundation, Inc. and its contributors.
22 * 4. Neither the name of The NetBSD Foundation nor the names of its
23 * contributors may be used to endorse or promote products derived
24 * from this software without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36 * POSSIBILITY OF SUCH DAMAGE.
37 */
38
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD: releng/6.0/sys/compat/linux/linux_getcwd.c 147854 2005-07-09 12:34:49Z jhb $");
41
42 #include "opt_compat.h"
43 #include "opt_mac.h"
44
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/namei.h>
48 #include <sys/filedesc.h>
49 #include <sys/kernel.h>
50 #include <sys/file.h>
51 #include <sys/stat.h>
52 #include <sys/syscallsubr.h>
53 #include <sys/vnode.h>
54 #include <sys/mount.h>
55 #include <sys/proc.h>
56 #include <sys/uio.h>
57 #include <sys/mac.h>
58 #include <sys/malloc.h>
59 #include <sys/dirent.h>
60 #include <ufs/ufs/dir.h> /* XXX only for DIRBLKSIZ */
61
62 #include "opt_compat.h"
63
64 #ifdef COMPAT_LINUX32
65 #include <machine/../linux32/linux.h>
66 #include <machine/../linux32/linux32_proto.h>
67 #else
68 #include <machine/../linux/linux.h>
69 #include <machine/../linux/linux_proto.h>
70 #endif
71 #include <compat/linux/linux_util.h>
72
73 static int
74 linux_getcwd_scandir(struct vnode **, struct vnode **,
75 char **, char *, struct thread *);
76 static int
77 linux_getcwd_common(struct vnode *, struct vnode *,
78 char **, char *, int, int, struct thread *);
79
80 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
81
82 /*
83 * Vnode variable naming conventions in this file:
84 *
85 * rvp: the current root we're aiming towards.
86 * lvp, *lvpp: the "lower" vnode
87 * uvp, *uvpp: the "upper" vnode.
88 *
89 * Since all the vnodes we're dealing with are directories, and the
90 * lookups are going *up* in the filesystem rather than *down*, the
91 * usual "pvp" (parent) or "dvp" (directory) naming conventions are
92 * too confusing.
93 */
94
95 /*
96 * XXX Will infinite loop in certain cases if a directory read reliably
97 * returns EINVAL on last block.
98 * XXX is EINVAL the right thing to return if a directory is malformed?
99 */
100
101 /*
102 * XXX Untested vs. mount -o union; probably does the wrong thing.
103 */
104
105 /*
106 * Find parent vnode of *lvpp, return in *uvpp
107 *
108 * If we care about the name, scan it looking for name of directory
109 * entry pointing at lvp.
110 *
111 * Place the name in the buffer which starts at bufp, immediately
112 * before *bpp, and move bpp backwards to point at the start of it.
113 *
114 * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed
115 * On exit, *uvpp is either NULL or is a locked vnode reference.
116 */
117 static int
118 linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, td)
119 struct vnode **lvpp;
120 struct vnode **uvpp;
121 char **bpp;
122 char *bufp;
123 struct thread *td;
124 {
125 int error = 0;
126 int eofflag;
127 off_t off;
128 int tries;
129 struct uio uio;
130 struct iovec iov;
131 char *dirbuf = NULL;
132 int dirbuflen;
133 ino_t fileno;
134 struct vattr va;
135 struct vnode *uvp = NULL;
136 struct vnode *lvp = *lvpp;
137 struct componentname cn;
138 int len, reclen;
139 tries = 0;
140
141 /*
142 * If we want the filename, get some info we need while the
143 * current directory is still locked.
144 */
145 if (bufp != NULL) {
146 error = VOP_GETATTR(lvp, &va, td->td_ucred, td);
147 if (error) {
148 vput(lvp);
149 *lvpp = NULL;
150 *uvpp = NULL;
151 return error;
152 }
153 }
154
155 /*
156 * Ok, we have to do it the hard way..
157 * Next, get parent vnode using lookup of ..
158 */
159 cn.cn_nameiop = LOOKUP;
160 cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY;
161 cn.cn_thread = td;
162 cn.cn_cred = td->td_ucred;
163 cn.cn_pnbuf = NULL;
164 cn.cn_nameptr = "..";
165 cn.cn_namelen = 2;
166 cn.cn_consume = 0;
167 cn.cn_lkflags = LK_EXCLUSIVE;
168
169 /*
170 * At this point, lvp is locked and will be unlocked by the lookup.
171 * On successful return, *uvpp will be locked
172 */
173 #ifdef MAC
174 error = mac_check_vnode_lookup(td->td_ucred, lvp, &cn);
175 if (error == 0)
176 #endif
177 error = VOP_LOOKUP(lvp, uvpp, &cn);
178 if (error) {
179 vput(lvp);
180 *lvpp = NULL;
181 *uvpp = NULL;
182 return error;
183 }
184 uvp = *uvpp;
185
186 /* If we don't care about the pathname, we're done */
187 if (bufp == NULL) {
188 vput(lvp);
189 *lvpp = NULL;
190 return 0;
191 }
192
193 fileno = va.va_fileid;
194
195 dirbuflen = DIRBLKSIZ;
196 if (dirbuflen < va.va_blocksize)
197 dirbuflen = va.va_blocksize;
198 dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
199
200 #if 0
201 unionread:
202 #endif
203 off = 0;
204 do {
205 /* call VOP_READDIR of parent */
206 iov.iov_base = dirbuf;
207 iov.iov_len = dirbuflen;
208
209 uio.uio_iov = &iov;
210 uio.uio_iovcnt = 1;
211 uio.uio_offset = off;
212 uio.uio_resid = dirbuflen;
213 uio.uio_segflg = UIO_SYSSPACE;
214 uio.uio_rw = UIO_READ;
215 uio.uio_td = td;
216
217 eofflag = 0;
218
219 #ifdef MAC
220 error = mac_check_vnode_readdir(td->td_ucred, uvp);
221 if (error == 0)
222 #endif /* MAC */
223 error = VOP_READDIR(uvp, &uio, td->td_ucred, &eofflag,
224 0, 0);
225
226 off = uio.uio_offset;
227
228 /*
229 * Try again if NFS tosses its cookies.
230 * XXX this can still loop forever if the directory is busted
231 * such that the second or subsequent page of it always
232 * returns EINVAL
233 */
234 if ((error == EINVAL) && (tries < 3)) {
235 off = 0;
236 tries++;
237 continue; /* once more, with feeling */
238 }
239
240 if (!error) {
241 char *cpos;
242 struct dirent *dp;
243
244 cpos = dirbuf;
245 tries = 0;
246
247 /* scan directory page looking for matching vnode */
248 for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
249 dp = (struct dirent *) cpos;
250 reclen = dp->d_reclen;
251
252 /* check for malformed directory.. */
253 if (reclen < DIRENT_MINSIZE) {
254 error = EINVAL;
255 goto out;
256 }
257 /*
258 * XXX should perhaps do VOP_LOOKUP to
259 * check that we got back to the right place,
260 * but getting the locking games for that
261 * right would be heinous.
262 */
263 if ((dp->d_type != DT_WHT) &&
264 (dp->d_fileno == fileno)) {
265 char *bp = *bpp;
266 bp -= dp->d_namlen;
267
268 if (bp <= bufp) {
269 error = ERANGE;
270 goto out;
271 }
272 bcopy(dp->d_name, bp, dp->d_namlen);
273 error = 0;
274 *bpp = bp;
275 goto out;
276 }
277 cpos += reclen;
278 }
279 }
280 } while (!eofflag);
281 error = ENOENT;
282
283 out:
284 vput(lvp);
285 *lvpp = NULL;
286 free(dirbuf, M_TEMP);
287 return error;
288 }
289
290
291 /*
292 * common routine shared by sys___getcwd() and linux_vn_isunder()
293 */
294
295 #define GETCWD_CHECK_ACCESS 0x0001
296
297 static int
298 linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, td)
299 struct vnode *lvp;
300 struct vnode *rvp;
301 char **bpp;
302 char *bufp;
303 int limit;
304 int flags;
305 struct thread *td;
306 {
307 struct filedesc *fdp = td->td_proc->p_fd;
308 struct vnode *uvp = NULL;
309 char *bp = NULL;
310 int error;
311 int perms = VEXEC;
312
313 if (rvp == NULL) {
314 rvp = fdp->fd_rdir;
315 if (rvp == NULL)
316 rvp = rootvnode;
317 }
318
319 VREF(rvp);
320 VREF(lvp);
321
322 /*
323 * Error handling invariant:
324 * Before a `goto out':
325 * lvp is either NULL, or locked and held.
326 * uvp is either NULL, or locked and held.
327 */
328
329 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
330 if (error) {
331 vrele(lvp);
332 lvp = NULL;
333 goto out;
334 }
335 if (bufp)
336 bp = *bpp;
337 /*
338 * this loop will terminate when one of the following happens:
339 * - we hit the root
340 * - getdirentries or lookup fails
341 * - we run out of space in the buffer.
342 */
343 if (lvp == rvp) {
344 if (bp)
345 *(--bp) = '/';
346 goto out;
347 }
348 do {
349 if (lvp->v_type != VDIR) {
350 error = ENOTDIR;
351 goto out;
352 }
353
354 /*
355 * access check here is optional, depending on
356 * whether or not caller cares.
357 */
358 if (flags & GETCWD_CHECK_ACCESS) {
359 error = VOP_ACCESS(lvp, perms, td->td_ucred, td);
360 if (error)
361 goto out;
362 perms = VEXEC|VREAD;
363 }
364
365 /*
366 * step up if we're a covered vnode..
367 */
368 while (lvp->v_vflag & VV_ROOT) {
369 struct vnode *tvp;
370
371 if (lvp == rvp)
372 goto out;
373
374 tvp = lvp;
375 lvp = lvp->v_mount->mnt_vnodecovered;
376 vput(tvp);
377 /*
378 * hodie natus est radici frater
379 */
380 if (lvp == NULL) {
381 error = ENOENT;
382 goto out;
383 }
384 VREF(lvp);
385 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
386 if (error != 0) {
387 vrele(lvp);
388 lvp = NULL;
389 goto out;
390 }
391 }
392 error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, td);
393 if (error)
394 goto out;
395 #if DIAGNOSTIC
396 if (lvp != NULL)
397 panic("getcwd: oops, forgot to null lvp");
398 if (bufp && (bp <= bufp)) {
399 panic("getcwd: oops, went back too far");
400 }
401 #endif
402 if (bp)
403 *(--bp) = '/';
404 lvp = uvp;
405 uvp = NULL;
406 limit--;
407 } while ((lvp != rvp) && (limit > 0));
408
409 out:
410 if (bpp)
411 *bpp = bp;
412 if (uvp)
413 vput(uvp);
414 if (lvp)
415 vput(lvp);
416 vrele(rvp);
417 return error;
418 }
419
420
421 /*
422 * Find pathname of process's current directory.
423 *
424 * Use vfs vnode-to-name reverse cache; if that fails, fall back
425 * to reading directory contents.
426 */
427
428 int
429 linux_getcwd(struct thread *td, struct linux_getcwd_args *args)
430 {
431 caddr_t bp, bend, path;
432 int error, len, lenused;
433
434 #ifdef DEBUG
435 printf("Linux-emul(%ld): getcwd(%p, %ld)\n", (long)td->td_proc->p_pid,
436 args->buf, (long)args->bufsize);
437 #endif
438
439 len = args->bufsize;
440
441 if (len > MAXPATHLEN*4)
442 len = MAXPATHLEN*4;
443 else if (len < 2)
444 return ERANGE;
445
446 path = (char *)malloc(len, M_TEMP, M_WAITOK);
447
448 error = kern___getcwd(td, path, UIO_SYSSPACE, len);
449 if (!error) {
450 lenused = strlen(path) + 1;
451 if (lenused <= args->bufsize) {
452 td->td_retval[0] = lenused;
453 error = copyout(path, args->buf, lenused);
454 }
455 else
456 error = ERANGE;
457 } else {
458 bp = &path[len];
459 bend = bp;
460 *(--bp) = '\0';
461
462 /*
463 * 5th argument here is "max number of vnodes to traverse".
464 * Since each entry takes up at least 2 bytes in the output buffer,
465 * limit it to N/2 vnodes for an N byte buffer.
466 */
467
468 mtx_lock(&Giant);
469 error = linux_getcwd_common (td->td_proc->p_fd->fd_cdir, NULL,
470 &bp, path, len/2, GETCWD_CHECK_ACCESS, td);
471 mtx_unlock(&Giant);
472
473 if (error)
474 goto out;
475 lenused = bend - bp;
476 td->td_retval[0] = lenused;
477 /* put the result into user buffer */
478 error = copyout(bp, args->buf, lenused);
479 }
480 out:
481 free(path, M_TEMP);
482 return (error);
483 }
484
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