Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/compat/linux/linux_getcwd.c
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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/5.2/sys/compat/linux/linux_getcwd.c 122861 2003-11-17 18:57:20Z rwatson $"); 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 <machine/../linux/linux.h> 63 #include <machine/../linux/linux_proto.h> 64 #include <compat/linux/linux_util.h> 65 66 static int 67 linux_getcwd_scandir(struct vnode **, struct vnode **, 68 char **, char *, struct thread *); 69 static int 70 linux_getcwd_common(struct vnode *, struct vnode *, 71 char **, char *, int, int, struct thread *); 72 73 #define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4) 74 75 /* 76 * Vnode variable naming conventions in this file: 77 * 78 * rvp: the current root we're aiming towards. 79 * lvp, *lvpp: the "lower" vnode 80 * uvp, *uvpp: the "upper" vnode. 81 * 82 * Since all the vnodes we're dealing with are directories, and the 83 * lookups are going *up* in the filesystem rather than *down*, the 84 * usual "pvp" (parent) or "dvp" (directory) naming conventions are 85 * too confusing. 86 */ 87 88 /* 89 * XXX Will infinite loop in certain cases if a directory read reliably 90 * returns EINVAL on last block. 91 * XXX is EINVAL the right thing to return if a directory is malformed? 92 */ 93 94 /* 95 * XXX Untested vs. mount -o union; probably does the wrong thing. 96 */ 97 98 /* 99 * Find parent vnode of *lvpp, return in *uvpp 100 * 101 * If we care about the name, scan it looking for name of directory 102 * entry pointing at lvp. 103 * 104 * Place the name in the buffer which starts at bufp, immediately 105 * before *bpp, and move bpp backwards to point at the start of it. 106 * 107 * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed 108 * On exit, *uvpp is either NULL or is a locked vnode reference. 109 */ 110 static int 111 linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, td) 112 struct vnode **lvpp; 113 struct vnode **uvpp; 114 char **bpp; 115 char *bufp; 116 struct thread *td; 117 { 118 int error = 0; 119 int eofflag; 120 off_t off; 121 int tries; 122 struct uio uio; 123 struct iovec iov; 124 char *dirbuf = NULL; 125 int dirbuflen; 126 ino_t fileno; 127 struct vattr va; 128 struct vnode *uvp = NULL; 129 struct vnode *lvp = *lvpp; 130 struct componentname cn; 131 int len, reclen; 132 tries = 0; 133 134 /* 135 * If we want the filename, get some info we need while the 136 * current directory is still locked. 137 */ 138 if (bufp != NULL) { 139 error = VOP_GETATTR(lvp, &va, td->td_ucred, td); 140 if (error) { 141 vput(lvp); 142 *lvpp = NULL; 143 *uvpp = NULL; 144 return error; 145 } 146 } 147 148 /* 149 * Ok, we have to do it the hard way.. 150 * Next, get parent vnode using lookup of .. 151 */ 152 cn.cn_nameiop = LOOKUP; 153 cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY; 154 cn.cn_thread = td; 155 cn.cn_cred = td->td_ucred; 156 cn.cn_pnbuf = NULL; 157 cn.cn_nameptr = ".."; 158 cn.cn_namelen = 2; 159 cn.cn_consume = 0; 160 161 /* 162 * At this point, lvp is locked and will be unlocked by the lookup. 163 * On successful return, *uvpp will be locked 164 */ 165 #ifdef MAC 166 error = mac_check_vnode_lookup(td->td_ucred, lvp, &cn); 167 if (error == 0) 168 #endif 169 error = VOP_LOOKUP(lvp, uvpp, &cn); 170 if (error) { 171 vput(lvp); 172 *lvpp = NULL; 173 *uvpp = NULL; 174 return error; 175 } 176 uvp = *uvpp; 177 178 /* If we don't care about the pathname, we're done */ 179 if (bufp == NULL) { 180 vrele(lvp); 181 *lvpp = NULL; 182 return 0; 183 } 184 185 fileno = va.va_fileid; 186 187 dirbuflen = DIRBLKSIZ; 188 if (dirbuflen < va.va_blocksize) 189 dirbuflen = va.va_blocksize; 190 dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK); 191 192 #if 0 193 unionread: 194 #endif 195 off = 0; 196 do { 197 /* call VOP_READDIR of parent */ 198 iov.iov_base = dirbuf; 199 iov.iov_len = dirbuflen; 200 201 uio.uio_iov = &iov; 202 uio.uio_iovcnt = 1; 203 uio.uio_offset = off; 204 uio.uio_resid = dirbuflen; 205 uio.uio_segflg = UIO_SYSSPACE; 206 uio.uio_rw = UIO_READ; 207 uio.uio_td = td; 208 209 eofflag = 0; 210 211 #ifdef MAC 212 error = mac_check_vnode_readdir(td->td_ucred, uvp); 213 if (error == 0) 214 #endif /* MAC */ 215 error = VOP_READDIR(uvp, &uio, td->td_ucred, &eofflag, 216 0, 0); 217 218 off = uio.uio_offset; 219 220 /* 221 * Try again if NFS tosses its cookies. 222 * XXX this can still loop forever if the directory is busted 223 * such that the second or subsequent page of it always 224 * returns EINVAL 225 */ 226 if ((error == EINVAL) && (tries < 3)) { 227 off = 0; 228 tries++; 229 continue; /* once more, with feeling */ 230 } 231 232 if (!error) { 233 char *cpos; 234 struct dirent *dp; 235 236 cpos = dirbuf; 237 tries = 0; 238 239 /* scan directory page looking for matching vnode */ 240 for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) { 241 dp = (struct dirent *) cpos; 242 reclen = dp->d_reclen; 243 244 /* check for malformed directory.. */ 245 if (reclen < DIRENT_MINSIZE) { 246 error = EINVAL; 247 goto out; 248 } 249 /* 250 * XXX should perhaps do VOP_LOOKUP to 251 * check that we got back to the right place, 252 * but getting the locking games for that 253 * right would be heinous. 254 */ 255 if ((dp->d_type != DT_WHT) && 256 (dp->d_fileno == fileno)) { 257 char *bp = *bpp; 258 bp -= dp->d_namlen; 259 260 if (bp <= bufp) { 261 error = ERANGE; 262 goto out; 263 } 264 bcopy(dp->d_name, bp, dp->d_namlen); 265 error = 0; 266 *bpp = bp; 267 goto out; 268 } 269 cpos += reclen; 270 } 271 } 272 } while (!eofflag); 273 error = ENOENT; 274 275 out: 276 vrele(lvp); 277 *lvpp = NULL; 278 free(dirbuf, M_TEMP); 279 return error; 280 } 281 282 283 /* 284 * common routine shared by sys___getcwd() and linux_vn_isunder() 285 */ 286 287 #define GETCWD_CHECK_ACCESS 0x0001 288 289 static int 290 linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, td) 291 struct vnode *lvp; 292 struct vnode *rvp; 293 char **bpp; 294 char *bufp; 295 int limit; 296 int flags; 297 struct thread *td; 298 { 299 struct filedesc *fdp = td->td_proc->p_fd; 300 struct vnode *uvp = NULL; 301 char *bp = NULL; 302 int error; 303 int perms = VEXEC; 304 305 if (rvp == NULL) { 306 rvp = fdp->fd_rdir; 307 if (rvp == NULL) 308 rvp = rootvnode; 309 } 310 311 VREF(rvp); 312 VREF(lvp); 313 314 /* 315 * Error handling invariant: 316 * Before a `goto out': 317 * lvp is either NULL, or locked and held. 318 * uvp is either NULL, or locked and held. 319 */ 320 321 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td); 322 if (error) { 323 vrele(lvp); 324 lvp = NULL; 325 goto out; 326 } 327 if (bufp) 328 bp = *bpp; 329 /* 330 * this loop will terminate when one of the following happens: 331 * - we hit the root 332 * - getdirentries or lookup fails 333 * - we run out of space in the buffer. 334 */ 335 if (lvp == rvp) { 336 if (bp) 337 *(--bp) = '/'; 338 goto out; 339 } 340 do { 341 if (lvp->v_type != VDIR) { 342 error = ENOTDIR; 343 goto out; 344 } 345 346 /* 347 * access check here is optional, depending on 348 * whether or not caller cares. 349 */ 350 if (flags & GETCWD_CHECK_ACCESS) { 351 error = VOP_ACCESS(lvp, perms, td->td_ucred, td); 352 if (error) 353 goto out; 354 perms = VEXEC|VREAD; 355 } 356 357 /* 358 * step up if we're a covered vnode.. 359 */ 360 while (lvp->v_vflag & VV_ROOT) { 361 struct vnode *tvp; 362 363 if (lvp == rvp) 364 goto out; 365 366 tvp = lvp; 367 lvp = lvp->v_mount->mnt_vnodecovered; 368 vput(tvp); 369 /* 370 * hodie natus est radici frater 371 */ 372 if (lvp == NULL) { 373 error = ENOENT; 374 goto out; 375 } 376 VREF(lvp); 377 error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, td); 378 if (error != 0) { 379 vrele(lvp); 380 lvp = NULL; 381 goto out; 382 } 383 } 384 error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, td); 385 if (error) 386 goto out; 387 #if DIAGNOSTIC 388 if (lvp != NULL) 389 panic("getcwd: oops, forgot to null lvp"); 390 if (bufp && (bp <= bufp)) { 391 panic("getcwd: oops, went back too far"); 392 } 393 #endif 394 if (bp) 395 *(--bp) = '/'; 396 lvp = uvp; 397 uvp = NULL; 398 limit--; 399 } while ((lvp != rvp) && (limit > 0)); 400 401 out: 402 if (bpp) 403 *bpp = bp; 404 if (uvp) 405 vput(uvp); 406 if (lvp) 407 vput(lvp); 408 vrele(rvp); 409 return error; 410 } 411 412 413 /* 414 * Find pathname of process's current directory. 415 * 416 * Use vfs vnode-to-name reverse cache; if that fails, fall back 417 * to reading directory contents. 418 */ 419 420 int 421 linux_getcwd(struct thread *td, struct linux_getcwd_args *args) 422 { 423 caddr_t bp, bend, path; 424 int error, len, lenused; 425 426 #ifdef DEBUG 427 printf("Linux-emul(%ld): getcwd(%p, %ld)\n", (long)td->td_proc->p_pid, 428 args->buf, (long)args->bufsize); 429 #endif 430 431 len = args->bufsize; 432 433 if (len > MAXPATHLEN*4) 434 len = MAXPATHLEN*4; 435 else if (len < 2) 436 return ERANGE; 437 438 path = (char *)malloc(len, M_TEMP, M_WAITOK); 439 440 error = kern___getcwd(td, path, UIO_SYSSPACE, len); 441 if (!error) { 442 lenused = strlen(path) + 1; 443 if (lenused <= args->bufsize) { 444 td->td_retval[0] = lenused; 445 error = copyout(path, args->buf, lenused); 446 } 447 else 448 error = ERANGE; 449 } else { 450 bp = &path[len]; 451 bend = bp; 452 *(--bp) = '\0'; 453 454 /* 455 * 5th argument here is "max number of vnodes to traverse". 456 * Since each entry takes up at least 2 bytes in the output buffer, 457 * limit it to N/2 vnodes for an N byte buffer. 458 */ 459 460 error = linux_getcwd_common (td->td_proc->p_fd->fd_cdir, NULL, 461 &bp, path, len/2, GETCWD_CHECK_ACCESS, td); 462 463 if (error) 464 goto out; 465 lenused = bend - bp; 466 td->td_retval[0] = lenused; 467 /* put the result into user buffer */ 468 error = copyout(bp, args->buf, lenused); 469 } 470 out: 471 free(path, M_TEMP); 472 return (error); 473 } 474
Cache object: d5ff0f40e69a5f4c87a12824d8e96aa2
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