vfs_getcwd.c revision 1.19
1 /* $NetBSD: vfs_getcwd.c,v 1.19 2003/06/29 18:43:28 thorpej Exp $ */ 2 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 __KERNEL_RCSID(0, "$NetBSD: vfs_getcwd.c,v 1.19 2003/06/29 18:43:28 thorpej Exp $"); 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/namei.h> 45 #include <sys/filedesc.h> 46 #include <sys/kernel.h> 47 #include <sys/file.h> 48 #include <sys/stat.h> 49 #include <sys/vnode.h> 50 #include <sys/mount.h> 51 #include <sys/proc.h> 52 #include <sys/uio.h> 53 #include <sys/malloc.h> 54 #include <sys/dirent.h> 55 #include <ufs/ufs/dir.h> /* XXX only for DIRBLKSIZ */ 56 57 #include <sys/sa.h> 58 #include <sys/syscallargs.h> 59 60 static int 61 getcwd_scandir __P((struct vnode **, struct vnode **, 62 char **, char *, struct lwp *)); 63 static int 64 getcwd_getcache __P((struct vnode **, struct vnode **, 65 char **, char *, struct lwp *)); 66 67 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4) 68 69 /* 70 * Vnode variable naming conventions in this file: 71 * 72 * rvp: the current root we're aiming towards. 73 * lvp, *lvpp: the "lower" vnode 74 * uvp, *uvpp: the "upper" vnode. 75 * 76 * Since all the vnodes we're dealing with are directories, and the 77 * lookups are going *up* in the filesystem rather than *down*, the 78 * usual "pvp" (parent) or "dvp" (directory) naming conventions are 79 * too confusing. 80 */ 81 82 /* 83 * XXX Will infinite loop in certain cases if a directory read reliably 84 * returns EINVAL on last block. 85 * XXX is EINVAL the right thing to return if a directory is malformed? 86 */ 87 88 /* 89 * XXX Untested vs. mount -o union; probably does the wrong thing. 90 */ 91 92 /* 93 * Find parent vnode of *lvpp, return in *uvpp 94 * 95 * If we care about the name, scan it looking for name of directory 96 * entry pointing at lvp. 97 * 98 * Place the name in the buffer which starts at bufp, immediately 99 * before *bpp, and move bpp backwards to point at the start of it. 100 * 101 * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed 102 * On exit, *uvpp is either NULL or is a locked vnode reference. 103 */ 104 static int 105 getcwd_scandir(lvpp, uvpp, bpp, bufp, l) 106 struct vnode **lvpp; 107 struct vnode **uvpp; 108 char **bpp; 109 char *bufp; 110 struct lwp *l; 111 { 112 int error = 0; 113 int eofflag; 114 off_t off; 115 int tries; 116 struct uio uio; 117 struct iovec iov; 118 char *dirbuf = NULL; 119 int dirbuflen; 120 ino_t fileno; 121 struct vattr va; 122 struct vnode *uvp = NULL; 123 struct vnode *lvp = *lvpp; 124 struct ucred *ucred = l->l_proc->p_ucred; 125 struct componentname cn; 126 int len, reclen; 127 tries = 0; 128 129 /* 130 * If we want the filename, get some info we need while the 131 * current directory is still locked. 132 */ 133 if (bufp != NULL) { 134 error = VOP_GETATTR(lvp, &va, ucred, l); 135 if (error) { 136 vput(lvp); 137 *lvpp = NULL; 138 *uvpp = NULL; 139 return error; 140 } 141 } 142 143 /* 144 * Ok, we have to do it the hard way.. 145 * Next, get parent vnode using lookup of .. 146 */ 147 cn.cn_nameiop = LOOKUP; 148 cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY; 149 cn.cn_lwp = l; 150 cn.cn_cred = ucred; 151 cn.cn_pnbuf = NULL; 152 cn.cn_nameptr = ".."; 153 cn.cn_namelen = 2; 154 cn.cn_hash = 0; 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_lwp = l; 200 201 eofflag = 0; 202 203 error = VOP_READDIR(uvp, &uio, 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 memcpy(bp, dp->d_name, dp->d_namlen); 252 error = 0; 253 *bpp = bp; 254 goto out; 255 } 256 cpos += reclen; 257 } 258 } else 259 goto out; 260 } while (!eofflag); 261 #if 0 262 /* 263 * Deal with mount -o union, which unions only the 264 * root directory of the mount. 265 */ 266 if ((uvp->v_flag & VROOT) && 267 (uvp->v_mount->mnt_flag & MNT_UNION)) { 268 struct vnode *tvp = uvp; 269 uvp = uvp->v_mount->mnt_vnodecovered; 270 vput(tvp); 271 VREF(uvp); 272 *uvpp = uvp; 273 error = vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY); 274 if (error != 0) { 275 vrele(uvp); 276 *uvpp = uvp = NULL; 277 goto out; 278 } 279 goto unionread; 280 } 281 #endif 282 error = ENOENT; 283 284 out: 285 vrele(lvp); 286 *lvpp = NULL; 287 free(dirbuf, M_TEMP); 288 return error; 289 } 290 291 /* 292 * Look in the vnode-to-name reverse cache to see if 293 * we can find things the easy way. 294 * 295 * XXX vget failure path is untested. 296 * 297 * On entry, *lvpp is a locked vnode reference. 298 * On exit, one of the following is the case: 299 * 0) Both *lvpp and *uvpp are NULL and failure is returned. 300 * 1) *uvpp is NULL, *lvpp remains locked and -1 is returned (cache miss) 301 * 2) *uvpp is a locked vnode reference, *lvpp is vput and NULL'ed 302 * and 0 is returned (cache hit) 303 */ 304 305 static int 306 getcwd_getcache(lvpp, uvpp, bpp, bufp, l) 307 struct vnode **lvpp, **uvpp; 308 char **bpp; 309 char *bufp; 310 struct lwp *l; 311 { 312 struct vnode *lvp, *uvp = NULL; 313 int error; 314 int vpid; 315 316 lvp = *lvpp; 317 318 /* 319 * This returns 0 on a cache hit, -1 on a clean cache miss, 320 * or an errno on other failure. 321 */ 322 error = cache_revlookup(lvp, uvpp, bpp, bufp); 323 if (error) { 324 if (error != -1) { 325 vput(lvp); 326 *lvpp = NULL; 327 *uvpp = NULL; 328 } 329 return error; 330 } 331 uvp = *uvpp; 332 vpid = uvp->v_id; 333 334 /* 335 * Since we're going up, we have to release the current lock 336 * before we take the parent lock. 337 */ 338 339 VOP_UNLOCK(lvp, 0); 340 341 error = vget(uvp, LK_EXCLUSIVE | LK_RETRY); 342 if (error != 0) 343 *uvpp = NULL; 344 /* 345 * Verify that vget succeeded, and check that vnode capability 346 * didn't change while we were waiting for the lock. 347 */ 348 if (error || (vpid != uvp->v_id)) { 349 /* 350 * Oops, we missed. If the vget failed, or the 351 * capability changed, try to get our lock back; if 352 * that works, tell caller to try things the hard way, 353 * otherwise give up. 354 */ 355 if (!error) vput(uvp); 356 *uvpp = NULL; 357 358 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 359 360 if (!error) 361 return -1; 362 } 363 vrele(lvp); 364 *lvpp = NULL; 365 366 return error; 367 } 368 369 /* 370 * common routine shared by sys___getcwd() and vn_isunder() 371 */ 372 373 int 374 getcwd_common (lvp, rvp, bpp, bufp, limit, flags, l) 375 struct vnode *lvp; 376 struct vnode *rvp; 377 char **bpp; 378 char *bufp; 379 int limit; 380 int flags; 381 struct lwp *l; 382 { 383 struct cwdinfo *cwdi = l->l_proc->p_cwdi; 384 struct ucred *ucred = l->l_proc->p_ucred; 385 struct vnode *uvp = NULL; 386 char *bp = NULL; 387 int error; 388 int perms = VEXEC; 389 390 if (rvp == NULL) { 391 rvp = cwdi->cwdi_rdir; 392 if (rvp == NULL) 393 rvp = rootvnode; 394 } 395 396 VREF(rvp); 397 VREF(lvp); 398 399 /* 400 * Error handling invariant: 401 * Before a `goto out': 402 * lvp is either NULL, or locked and held. 403 * uvp is either NULL, or locked and held. 404 */ 405 406 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 407 if (error) { 408 vrele(lvp); 409 lvp = NULL; 410 goto out; 411 } 412 if (bufp) 413 bp = *bpp; 414 /* 415 * this loop will terminate when one of the following happens: 416 * - we hit the root 417 * - getdirentries or lookup fails 418 * - we run out of space in the buffer. 419 */ 420 if (lvp == rvp) { 421 if (bp) 422 *(--bp) = '/'; 423 goto out; 424 } 425 do { 426 if (lvp->v_type != VDIR) { 427 error = ENOTDIR; 428 goto out; 429 } 430 431 /* 432 * access check here is optional, depending on 433 * whether or not caller cares. 434 */ 435 if (flags & GETCWD_CHECK_ACCESS) { 436 error = VOP_ACCESS(lvp, perms, ucred, l); 437 if (error) 438 goto out; 439 perms = VEXEC|VREAD; 440 } 441 442 /* 443 * step up if we're a covered vnode.. 444 */ 445 while (lvp->v_flag & VROOT) { 446 struct vnode *tvp; 447 448 if (lvp == rvp) 449 goto out; 450 451 tvp = lvp; 452 lvp = lvp->v_mount->mnt_vnodecovered; 453 vput(tvp); 454 /* 455 * hodie natus est radici frater 456 */ 457 if (lvp == NULL) { 458 error = ENOENT; 459 goto out; 460 } 461 VREF(lvp); 462 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY); 463 if (error != 0) { 464 vrele(lvp); 465 lvp = NULL; 466 goto out; 467 } 468 } 469 /* 470 * Look in the name cache; if that fails, look in the 471 * directory.. 472 */ 473 error = getcwd_getcache(&lvp, &uvp, &bp, bufp, l); 474 if (error == -1) 475 error = getcwd_scandir(&lvp, &uvp, &bp, bufp, l); 476 if (error) 477 goto out; 478 #if DIAGNOSTIC 479 if (lvp != NULL) 480 panic("getcwd: oops, forgot to null lvp"); 481 if (bufp && (bp <= bufp)) { 482 panic("getcwd: oops, went back too far"); 483 } 484 #endif 485 if (bp) 486 *(--bp) = '/'; 487 lvp = uvp; 488 uvp = NULL; 489 limit--; 490 } while ((lvp != rvp) && (limit > 0)); 491 492 out: 493 if (bpp) 494 *bpp = bp; 495 if (uvp) 496 vput(uvp); 497 if (lvp) 498 vput(lvp); 499 vrele(rvp); 500 return error; 501 } 502 503 /* 504 * Check if one directory can be found inside another in the directory 505 * hierarchy. 506 * 507 * Intended to be used in chroot, chdir, fchdir, etc., to ensure that 508 * chroot() actually means something. 509 */ 510 int 511 vn_isunder(lvp, rvp, l) 512 struct vnode *lvp; 513 struct vnode *rvp; 514 struct lwp *l; 515 { 516 int error; 517 518 error = getcwd_common (lvp, rvp, NULL, NULL, MAXPATHLEN/2, 0, l); 519 520 if (!error) 521 return 1; 522 else 523 return 0; 524 } 525 526 /* 527 * Returns true if proc p1's root directory equal to or under p2's 528 * root directory. 529 * 530 * Intended to be used from ptrace/procfs sorts of things. 531 */ 532 533 int 534 proc_isunder (p1, l2) 535 struct proc *p1; 536 struct lwp *l2; 537 { 538 struct vnode *r1 = p1->p_cwdi->cwdi_rdir; 539 struct vnode *r2 = l2->l_proc->p_cwdi->cwdi_rdir; 540 541 if (r1 == NULL) 542 return (r2 == NULL); 543 else if (r2 == NULL) 544 return 1; 545 else 546 return vn_isunder(r1, r2, l2); 547 } 548 549 /* 550 * Find pathname of process's current directory. 551 * 552 * Use vfs vnode-to-name reverse cache; if that fails, fall back 553 * to reading directory contents. 554 */ 555 556 int 557 sys___getcwd(l, v, retval) 558 struct lwp *l; 559 void *v; 560 register_t *retval; 561 { 562 struct sys___getcwd_args /* { 563 syscallarg(char *) bufp; 564 syscallarg(size_t) length; 565 } */ *uap = v; 566 567 int error; 568 char *path; 569 char *bp, *bend; 570 int len = SCARG(uap, length); 571 int lenused; 572 573 if (len > MAXPATHLEN*4) 574 len = MAXPATHLEN*4; 575 else if (len < 2) 576 return ERANGE; 577 578 path = (char *)malloc(len, M_TEMP, M_WAITOK); 579 if (!path) 580 return ENOMEM; 581 582 bp = &path[len]; 583 bend = bp; 584 *(--bp) = '\0'; 585 586 /* 587 * 5th argument here is "max number of vnodes to traverse". 588 * Since each entry takes up at least 2 bytes in the output buffer, 589 * limit it to N/2 vnodes for an N byte buffer. 590 */ 591 error = getcwd_common (l->l_proc->p_cwdi->cwdi_cdir, NULL, &bp, path, 592 len/2, GETCWD_CHECK_ACCESS, l); 593 594 if (error) 595 goto out; 596 lenused = bend - bp; 597 *retval = lenused; 598 /* put the result into user buffer */ 599 error = copyout(bp, SCARG(uap, bufp), lenused); 600 601 out: 602 free(path, M_TEMP); 603 return error; 604 } 605
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