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("$FreeBSD$");
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
168 /*
169 * At this point, lvp is locked and will be unlocked by the lookup.
170 * On successful return, *uvpp will be locked
171 */
172 #ifdef MAC
173 error = mac_check_vnode_lookup(td->td_ucred, lvp, &cn);
174 if (error == 0)
175 #endif
176 error = VOP_LOOKUP(lvp, uvpp, &cn);
177 if (error) {
178 vput(lvp);
179 *lvpp = NULL;
180 *uvpp = NULL;
181 return error;
182 }
183 uvp = *uvpp;
184
185 /* If we don't care about the pathname, we're done */
186 if (bufp == NULL) {
187 vrele(lvp);
188 *lvpp = NULL;
189 return 0;
190 }
191
192 fileno = va.va_fileid;
193
194 dirbuflen = DIRBLKSIZ;
195 if (dirbuflen < va.va_blocksize)
196 dirbuflen = va.va_blocksize;
197 dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
198
199 #if 0
200 unionread:
201 #endif
202 off = 0;
203 do {
204 /* call VOP_READDIR of parent */
205 iov.iov_base = dirbuf;
206 iov.iov_len = dirbuflen;
207
208 uio.uio_iov = &iov;
209 uio.uio_iovcnt = 1;
210 uio.uio_offset = off;
211 uio.uio_resid = dirbuflen;
212 uio.uio_segflg = UIO_SYSSPACE;
213 uio.uio_rw = UIO_READ;
214 uio.uio_td = td;
215
216 eofflag = 0;
217
218 #ifdef MAC
219 error = mac_check_vnode_readdir(td->td_ucred, uvp);
220 if (error == 0)
221 #endif /* MAC */
222 error = VOP_READDIR(uvp, &uio, td->td_ucred, &eofflag,
223 0, 0);
224
225 off = uio.uio_offset;
226
227 /*
228 * Try again if NFS tosses its cookies.
229 * XXX this can still loop forever if the directory is busted
230 * such that the second or subsequent page of it always
231 * returns EINVAL
232 */
233 if ((error == EINVAL) && (tries < 3)) {
234 off = 0;
235 tries++;
236 continue; /* once more, with feeling */
237 }
238
239 if (!error) {
240 char *cpos;
241 struct dirent *dp;
242
243 cpos = dirbuf;
244 tries = 0;
245
246 /* scan directory page looking for matching vnode */
247 for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
248 dp = (struct dirent *) cpos;
249 reclen = dp->d_reclen;
250
251 /* check for malformed directory.. */
252 if (reclen < DIRENT_MINSIZE) {
253 error = EINVAL;
254 goto out;
255 }
256 /*
257 * XXX should perhaps do VOP_LOOKUP to
258 * check that we got back to the right place,
259 * but getting the locking games for that
260 * right would be heinous.
261 */
262 if ((dp->d_type != DT_WHT) &&
263 (dp->d_fileno == fileno)) {
264 char *bp = *bpp;
265 bp -= dp->d_namlen;
266
267 if (bp <= bufp) {
268 error = ERANGE;
269 goto out;
270 }
271 bcopy(dp->d_name, bp, dp->d_namlen);
272 error = 0;
273 *bpp = bp;
274 goto out;
275 }
276 cpos += reclen;
277 }
278 }
279 } while (!eofflag);
280 error = ENOENT;
281
282 out:
283 vrele(lvp);
284 *lvpp = NULL;
285 free(dirbuf, M_TEMP);
286 return error;
287 }
288
289
290 /*
291 * common routine shared by sys___getcwd() and linux_vn_isunder()
292 */
293
294 #define GETCWD_CHECK_ACCESS 0x0001
295
296 static int
297 linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, td)
298 struct vnode *lvp;
299 struct vnode *rvp;
300 char **bpp;
301 char *bufp;
302 int limit;
303 int flags;
304 struct thread *td;
305 {
306 struct filedesc *fdp = td->td_proc->p_fd;
307 struct vnode *uvp = NULL;
308 char *bp = NULL;
309 int error;
310 int perms = VEXEC;
311
312 if (rvp == NULL) {
313 rvp = fdp->fd_rdir;
314 if (rvp == NULL)
315 rvp = rootvnode;
316 }
317
318 VREF(rvp);
319 VREF(lvp);
320
321 /*
322 * Error handling invariant:
323 * Before a `goto out':
324 * lvp is either NULL, or locked and held.
325 * uvp is either NULL, or locked and held.
326 */
327
328 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
329 if (error) {
330 vrele(lvp);
331 lvp = NULL;
332 goto out;
333 }
334 if (bufp)
335 bp = *bpp;
336 /*
337 * this loop will terminate when one of the following happens:
338 * - we hit the root
339 * - getdirentries or lookup fails
340 * - we run out of space in the buffer.
341 */
342 if (lvp == rvp) {
343 if (bp)
344 *(--bp) = '/';
345 goto out;
346 }
347 do {
348 if (lvp->v_type != VDIR) {
349 error = ENOTDIR;
350 goto out;
351 }
352
353 /*
354 * access check here is optional, depending on
355 * whether or not caller cares.
356 */
357 if (flags & GETCWD_CHECK_ACCESS) {
358 error = VOP_ACCESS(lvp, perms, td->td_ucred, td);
359 if (error)
360 goto out;
361 perms = VEXEC|VREAD;
362 }
363
364 /*
365 * step up if we're a covered vnode..
366 */
367 while (lvp->v_vflag & VV_ROOT) {
368 struct vnode *tvp;
369
370 if (lvp == rvp)
371 goto out;
372
373 tvp = lvp;
374 lvp = lvp->v_mount->mnt_vnodecovered;
375 vput(tvp);
376 /*
377 * hodie natus est radici frater
378 */
379 if (lvp == NULL) {
380 error = ENOENT;
381 goto out;
382 }
383 VREF(lvp);
384 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td);
385 if (error != 0) {
386 vrele(lvp);
387 lvp = NULL;
388 goto out;
389 }
390 }
391 error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, td);
392 if (error)
393 goto out;
394 #if DIAGNOSTIC
395 if (lvp != NULL)
396 panic("getcwd: oops, forgot to null lvp");
397 if (bufp && (bp <= bufp)) {
398 panic("getcwd: oops, went back too far");
399 }
400 #endif
401 if (bp)
402 *(--bp) = '/';
403 lvp = uvp;
404 uvp = NULL;
405 limit--;
406 } while ((lvp != rvp) && (limit > 0));
407
408 out:
409 if (bpp)
410 *bpp = bp;
411 if (uvp)
412 vput(uvp);
413 if (lvp)
414 vput(lvp);
415 vrele(rvp);
416 return error;
417 }
418
419
420 /*
421 * Find pathname of process's current directory.
422 *
423 * Use vfs vnode-to-name reverse cache; if that fails, fall back
424 * to reading directory contents.
425 */
426
427 int
428 linux_getcwd(struct thread *td, struct linux_getcwd_args *args)
429 {
430 caddr_t bp, bend, path;
431 int error, len, lenused;
432
433 #ifdef DEBUG
434 printf("Linux-emul(%ld): getcwd(%p, %ld)\n", (long)td->td_proc->p_pid,
435 args->buf, (long)args->bufsize);
436 #endif
437
438 len = args->bufsize;
439
440 if (len > MAXPATHLEN*4)
441 len = MAXPATHLEN*4;
442 else if (len < 2)
443 return ERANGE;
444
445 path = (char *)malloc(len, M_TEMP, M_WAITOK);
446
447 error = kern___getcwd(td, path, UIO_SYSSPACE, len);
448 if (!error) {
449 lenused = strlen(path) + 1;
450 if (lenused <= args->bufsize) {
451 td->td_retval[0] = lenused;
452 error = copyout(path, args->buf, lenused);
453 }
454 else
455 error = ERANGE;
456 } else {
457 bp = &path[len];
458 bend = bp;
459 *(--bp) = '\0';
460
461 /*
462 * 5th argument here is "max number of vnodes to traverse".
463 * Since each entry takes up at least 2 bytes in the output buffer,
464 * limit it to N/2 vnodes for an N byte buffer.
465 */
466
467 error = linux_getcwd_common (td->td_proc->p_fd->fd_cdir, NULL,
468 &bp, path, len/2, GETCWD_CHECK_ACCESS, td);
469
470 if (error)
471 goto out;
472 lenused = bend - bp;
473 td->td_retval[0] = lenused;
474 /* put the result into user buffer */
475 error = copyout(bp, args->buf, lenused);
476 }
477 out:
478 free(path, M_TEMP);
479 return (error);
480 }
481
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