1 /* $FreeBSD$ */
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
62 static int
63 linux_getcwd_scandir __P((struct vnode **, struct vnode **,
64 char **, char *, struct proc *));
65 static int
66 linux_getcwd_common __P((struct vnode *, struct vnode *,
67 char **, char *, int, int, struct proc *));
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 */
106 static int
107 linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, p)
108 struct vnode **lvpp;
109 struct vnode **uvpp;
110 char **bpp;
111 char *bufp;
112 struct proc *p;
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, p->p_ucred, p);
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_proc = p;
151 cn.cn_cred = p->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
185 unionread:
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_procp = p;
200
201 eofflag = 0;
202
203 error = VOP_READDIR(uvp, &uio, p->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
262 out:
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
276 static int
277 linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, p)
278 struct vnode *lvp;
279 struct vnode *rvp;
280 char **bpp;
281 char *bufp;
282 int limit;
283 int flags;
284 struct proc *p;
285 {
286 struct filedesc *fdp = p->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, p);
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, p->p_ucred, p);
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, p);
365 if (error != 0) {
366 vrele(lvp);
367 lvp = NULL;
368 goto out;
369 }
370 }
371 error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, p);
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
388 out:
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
407 int
408 linux_getcwd(struct proc *p, 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)p->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(p, &bsd);
423 if (!error) {
424 lenused = strlen(bsd.buf) + 1;
425 if (lenused <= args->bufsize) {
426 p->p_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 (p->p_fd->fd_cdir, NULL,
452 &bp, path, len/2, GETCWD_CHECK_ACCESS, p);
453
454 if (error)
455 goto out;
456 lenused = bend - bp;
457 p->p_retval[0] = lenused;
458 /* put the result into user buffer */
459 error = copyout(bp, args->buf, lenused);
460
461 out:
462 free(path, M_TEMP);
463 }
464 return (error);
465 }
466
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