linux_getcwd.c revision 133816
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: head/sys/compat/linux/linux_getcwd.c 133816 2004-08-16 07:28:16Z tjr $"); 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#if !COMPAT_LINUX32 65#include <machine/../linux/linux.h> 66#include <machine/../linux/linux_proto.h> 67#else 68#include <machine/../linux32/linux.h> 69#include <machine/../linux32/linux32_proto.h> 70#endif 71#include <compat/linux/linux_util.h> 72 73static int 74linux_getcwd_scandir(struct vnode **, struct vnode **, 75 char **, char *, struct thread *); 76static int 77linux_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 */ 117static int 118linux_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 200unionread: 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 282out: 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 296static int 297linux_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 408out: 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 427int 428linux_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 } 477out: 478 free(path, M_TEMP); 479 return (error); 480} 481 482