Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/fs/fdescfs/fdesc_vnops.c
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1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1992, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software donated to Berkeley by 8 * Jan-Simon Pendry. 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. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)fdesc_vnops.c 8.9 (Berkeley) 1/21/94 35 * 36 * $FreeBSD$ 37 */ 38 39 /* 40 * /dev/fd Filesystem 41 */ 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/capsicum.h> 46 #include <sys/conf.h> 47 #include <sys/dirent.h> 48 #include <sys/filedesc.h> 49 #include <sys/kernel.h> /* boottime */ 50 #include <sys/lock.h> 51 #include <sys/mutex.h> 52 #include <sys/malloc.h> 53 #include <sys/file.h> /* Must come after sys/malloc.h */ 54 #include <sys/mount.h> 55 #include <sys/namei.h> 56 #include <sys/proc.h> 57 #include <sys/stat.h> 58 #include <sys/syscallsubr.h> 59 #include <sys/unistd.h> 60 #include <sys/vnode.h> 61 62 #include <fs/fdescfs/fdesc.h> 63 64 #define NFDCACHE 4 65 #define FD_NHASH(ix) \ 66 (&fdhashtbl[(ix) & fdhash]) 67 static LIST_HEAD(fdhashhead, fdescnode) *fdhashtbl; 68 static u_long fdhash; 69 70 struct mtx fdesc_hashmtx; 71 72 static vop_getattr_t fdesc_getattr; 73 static vop_lookup_t fdesc_lookup; 74 static vop_open_t fdesc_open; 75 static vop_pathconf_t fdesc_pathconf; 76 static vop_readdir_t fdesc_readdir; 77 static vop_readlink_t fdesc_readlink; 78 static vop_reclaim_t fdesc_reclaim; 79 static vop_setattr_t fdesc_setattr; 80 81 static struct vop_vector fdesc_vnodeops = { 82 .vop_default = &default_vnodeops, 83 84 .vop_access = VOP_NULL, 85 .vop_getattr = fdesc_getattr, 86 .vop_lookup = fdesc_lookup, 87 .vop_open = fdesc_open, 88 .vop_pathconf = fdesc_pathconf, 89 .vop_readdir = fdesc_readdir, 90 .vop_readlink = fdesc_readlink, 91 .vop_reclaim = fdesc_reclaim, 92 .vop_setattr = fdesc_setattr, 93 }; 94 95 static void fdesc_insmntque_dtr(struct vnode *, void *); 96 static void fdesc_remove_entry(struct fdescnode *); 97 98 /* 99 * Initialise cache headers 100 */ 101 int 102 fdesc_init(struct vfsconf *vfsp) 103 { 104 105 mtx_init(&fdesc_hashmtx, "fdescfs_hash", NULL, MTX_DEF); 106 fdhashtbl = hashinit(NFDCACHE, M_CACHE, &fdhash); 107 return (0); 108 } 109 110 /* 111 * Uninit ready for unload. 112 */ 113 int 114 fdesc_uninit(struct vfsconf *vfsp) 115 { 116 117 hashdestroy(fdhashtbl, M_CACHE, fdhash); 118 mtx_destroy(&fdesc_hashmtx); 119 return (0); 120 } 121 122 /* 123 * If allocating vnode fails, call this. 124 */ 125 static void 126 fdesc_insmntque_dtr(struct vnode *vp, void *arg) 127 { 128 129 vgone(vp); 130 vput(vp); 131 } 132 133 /* 134 * Remove an entry from the hash if it exists. 135 */ 136 static void 137 fdesc_remove_entry(struct fdescnode *fd) 138 { 139 struct fdhashhead *fc; 140 struct fdescnode *fd2; 141 142 fc = FD_NHASH(fd->fd_ix); 143 mtx_lock(&fdesc_hashmtx); 144 LIST_FOREACH(fd2, fc, fd_hash) { 145 if (fd == fd2) { 146 LIST_REMOVE(fd, fd_hash); 147 break; 148 } 149 } 150 mtx_unlock(&fdesc_hashmtx); 151 } 152 153 int 154 fdesc_allocvp(fdntype ftype, unsigned fd_fd, int ix, struct mount *mp, 155 struct vnode **vpp) 156 { 157 struct fdescmount *fmp; 158 struct fdhashhead *fc; 159 struct fdescnode *fd, *fd2; 160 struct vnode *vp, *vp2; 161 struct thread *td; 162 int error; 163 164 td = curthread; 165 fc = FD_NHASH(ix); 166 loop: 167 mtx_lock(&fdesc_hashmtx); 168 /* 169 * If a forced unmount is progressing, we need to drop it. The flags are 170 * protected by the hashmtx. 171 */ 172 fmp = mp->mnt_data; 173 if (fmp == NULL || fmp->flags & FMNT_UNMOUNTF) { 174 mtx_unlock(&fdesc_hashmtx); 175 return (-1); 176 } 177 178 LIST_FOREACH(fd, fc, fd_hash) { 179 if (fd->fd_ix == ix && fd->fd_vnode->v_mount == mp) { 180 /* Get reference to vnode in case it's being free'd */ 181 vp = fd->fd_vnode; 182 VI_LOCK(vp); 183 mtx_unlock(&fdesc_hashmtx); 184 if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, td)) 185 goto loop; 186 *vpp = vp; 187 return (0); 188 } 189 } 190 mtx_unlock(&fdesc_hashmtx); 191 192 fd = malloc(sizeof(struct fdescnode), M_TEMP, M_WAITOK); 193 194 error = getnewvnode("fdescfs", mp, &fdesc_vnodeops, &vp); 195 if (error) { 196 free(fd, M_TEMP); 197 return (error); 198 } 199 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 200 vp->v_data = fd; 201 fd->fd_vnode = vp; 202 fd->fd_type = ftype; 203 fd->fd_fd = fd_fd; 204 fd->fd_ix = ix; 205 if (ftype == Fdesc && fmp->flags & FMNT_LINRDLNKF) 206 vp->v_vflag |= VV_READLINK; 207 error = insmntque1(vp, mp, fdesc_insmntque_dtr, NULL); 208 if (error != 0) { 209 *vpp = NULLVP; 210 return (error); 211 } 212 213 /* Make sure that someone didn't beat us when inserting the vnode. */ 214 mtx_lock(&fdesc_hashmtx); 215 /* 216 * If a forced unmount is progressing, we need to drop it. The flags are 217 * protected by the hashmtx. 218 */ 219 fmp = mp->mnt_data; 220 if (fmp == NULL || fmp->flags & FMNT_UNMOUNTF) { 221 mtx_unlock(&fdesc_hashmtx); 222 vgone(vp); 223 vput(vp); 224 *vpp = NULLVP; 225 return (-1); 226 } 227 228 LIST_FOREACH(fd2, fc, fd_hash) { 229 if (fd2->fd_ix == ix && fd2->fd_vnode->v_mount == mp) { 230 /* Get reference to vnode in case it's being free'd */ 231 vp2 = fd2->fd_vnode; 232 VI_LOCK(vp2); 233 mtx_unlock(&fdesc_hashmtx); 234 error = vget(vp2, LK_EXCLUSIVE | LK_INTERLOCK, td); 235 /* Someone beat us, dec use count and wait for reclaim */ 236 vgone(vp); 237 vput(vp); 238 /* If we didn't get it, return no vnode. */ 239 if (error) 240 vp2 = NULLVP; 241 *vpp = vp2; 242 return (error); 243 } 244 } 245 246 /* If we came here, we can insert it safely. */ 247 LIST_INSERT_HEAD(fc, fd, fd_hash); 248 mtx_unlock(&fdesc_hashmtx); 249 *vpp = vp; 250 return (0); 251 } 252 253 struct fdesc_get_ino_args { 254 fdntype ftype; 255 unsigned fd_fd; 256 int ix; 257 struct file *fp; 258 struct thread *td; 259 }; 260 261 static int 262 fdesc_get_ino_alloc(struct mount *mp, void *arg, int lkflags, 263 struct vnode **rvp) 264 { 265 struct fdesc_get_ino_args *a; 266 int error; 267 268 a = arg; 269 error = fdesc_allocvp(a->ftype, a->fd_fd, a->ix, mp, rvp); 270 fdrop(a->fp, a->td); 271 return (error); 272 } 273 274 275 /* 276 * vp is the current namei directory 277 * ndp is the name to locate in that directory... 278 */ 279 static int 280 fdesc_lookup(struct vop_lookup_args *ap) 281 { 282 struct vnode **vpp = ap->a_vpp; 283 struct vnode *dvp = ap->a_dvp; 284 struct componentname *cnp = ap->a_cnp; 285 char *pname = cnp->cn_nameptr; 286 struct thread *td = cnp->cn_thread; 287 struct file *fp; 288 struct fdesc_get_ino_args arg; 289 int nlen = cnp->cn_namelen; 290 u_int fd, fd1; 291 int error; 292 struct vnode *fvp; 293 294 if ((cnp->cn_flags & ISLASTCN) && 295 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { 296 error = EROFS; 297 goto bad; 298 } 299 300 if (cnp->cn_namelen == 1 && *pname == '.') { 301 *vpp = dvp; 302 VREF(dvp); 303 return (0); 304 } 305 306 if (VTOFDESC(dvp)->fd_type != Froot) { 307 error = ENOTDIR; 308 goto bad; 309 } 310 311 fd = 0; 312 /* the only time a leading 0 is acceptable is if it's "" */ 313 if (*pname == '' && nlen != 1) { 314 error = ENOENT; 315 goto bad; 316 } 317 while (nlen--) { 318 if (*pname < '' || *pname > '9') { 319 error = ENOENT; 320 goto bad; 321 } 322 fd1 = 10 * fd + *pname++ - ''; 323 if (fd1 < fd) { 324 error = ENOENT; 325 goto bad; 326 } 327 fd = fd1; 328 } 329 330 /* 331 * No rights to check since 'fp' isn't actually used. 332 */ 333 if ((error = fget(td, fd, &cap_no_rights, &fp)) != 0) 334 goto bad; 335 336 /* Check if we're looking up ourselves. */ 337 if (VTOFDESC(dvp)->fd_ix == FD_DESC + fd) { 338 /* 339 * In case we're holding the last reference to the file, the dvp 340 * will be re-acquired. 341 */ 342 vhold(dvp); 343 VOP_UNLOCK(dvp, 0); 344 fdrop(fp, td); 345 346 /* Re-aquire the lock afterwards. */ 347 vn_lock(dvp, LK_RETRY | LK_EXCLUSIVE); 348 vdrop(dvp); 349 fvp = dvp; 350 if ((dvp->v_iflag & VI_DOOMED) != 0) 351 error = ENOENT; 352 } else { 353 /* 354 * Unlock our root node (dvp) when doing this, since we might 355 * deadlock since the vnode might be locked by another thread 356 * and the root vnode lock will be obtained afterwards (in case 357 * we're looking up the fd of the root vnode), which will be the 358 * opposite lock order. Vhold the root vnode first so we don't 359 * lose it. 360 */ 361 arg.ftype = Fdesc; 362 arg.fd_fd = fd; 363 arg.ix = FD_DESC + fd; 364 arg.fp = fp; 365 arg.td = td; 366 error = vn_vget_ino_gen(dvp, fdesc_get_ino_alloc, &arg, 367 LK_EXCLUSIVE, &fvp); 368 } 369 370 if (error) 371 goto bad; 372 *vpp = fvp; 373 return (0); 374 375 bad: 376 *vpp = NULL; 377 return (error); 378 } 379 380 static int 381 fdesc_open(struct vop_open_args *ap) 382 { 383 struct vnode *vp = ap->a_vp; 384 385 if (VTOFDESC(vp)->fd_type == Froot) 386 return (0); 387 388 /* 389 * XXX Kludge: set td->td_proc->p_dupfd to contain the value of the file 390 * descriptor being sought for duplication. The error return ensures 391 * that the vnode for this device will be released by vn_open. Open 392 * will detect this special error and take the actions in dupfdopen. 393 * Other callers of vn_open or VOP_OPEN will simply report the 394 * error. 395 */ 396 ap->a_td->td_dupfd = VTOFDESC(vp)->fd_fd; /* XXX */ 397 return (ENODEV); 398 } 399 400 static int 401 fdesc_pathconf(struct vop_pathconf_args *ap) 402 { 403 struct vnode *vp = ap->a_vp; 404 int error; 405 406 switch (ap->a_name) { 407 case _PC_NAME_MAX: 408 *ap->a_retval = NAME_MAX; 409 return (0); 410 case _PC_LINK_MAX: 411 if (VTOFDESC(vp)->fd_type == Froot) 412 *ap->a_retval = 2; 413 else 414 *ap->a_retval = 1; 415 return (0); 416 default: 417 if (VTOFDESC(vp)->fd_type == Froot) 418 return (vop_stdpathconf(ap)); 419 vref(vp); 420 VOP_UNLOCK(vp, 0); 421 error = kern_fpathconf(curthread, VTOFDESC(vp)->fd_fd, 422 ap->a_name, ap->a_retval); 423 vn_lock(vp, LK_SHARED | LK_RETRY); 424 vunref(vp); 425 return (error); 426 } 427 } 428 429 static int 430 fdesc_getattr(struct vop_getattr_args *ap) 431 { 432 struct vnode *vp = ap->a_vp; 433 struct vattr *vap = ap->a_vap; 434 struct timeval boottime; 435 436 getboottime(&boottime); 437 vap->va_mode = S_IRUSR|S_IXUSR|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH; 438 vap->va_fileid = VTOFDESC(vp)->fd_ix; 439 vap->va_uid = 0; 440 vap->va_gid = 0; 441 vap->va_blocksize = DEV_BSIZE; 442 vap->va_atime.tv_sec = boottime.tv_sec; 443 vap->va_atime.tv_nsec = 0; 444 vap->va_mtime = vap->va_atime; 445 vap->va_ctime = vap->va_mtime; 446 vap->va_gen = 0; 447 vap->va_flags = 0; 448 vap->va_bytes = 0; 449 vap->va_filerev = 0; 450 451 switch (VTOFDESC(vp)->fd_type) { 452 case Froot: 453 vap->va_type = VDIR; 454 vap->va_nlink = 2; 455 vap->va_size = DEV_BSIZE; 456 vap->va_rdev = NODEV; 457 break; 458 459 case Fdesc: 460 vap->va_type = (vp->v_vflag & VV_READLINK) == 0 ? VCHR : VLNK; 461 vap->va_nlink = 1; 462 vap->va_size = 0; 463 vap->va_rdev = makedev(0, vap->va_fileid); 464 break; 465 466 default: 467 panic("fdesc_getattr"); 468 break; 469 } 470 471 vp->v_type = vap->va_type; 472 return (0); 473 } 474 475 static int 476 fdesc_setattr(struct vop_setattr_args *ap) 477 { 478 struct vattr *vap = ap->a_vap; 479 struct vnode *vp; 480 struct mount *mp; 481 struct file *fp; 482 struct thread *td = curthread; 483 cap_rights_t rights; 484 unsigned fd; 485 int error; 486 487 /* 488 * Can't mess with the root vnode 489 */ 490 if (VTOFDESC(ap->a_vp)->fd_type == Froot) 491 return (EACCES); 492 493 fd = VTOFDESC(ap->a_vp)->fd_fd; 494 495 /* 496 * Allow setattr where there is an underlying vnode. 497 */ 498 error = getvnode(td, fd, 499 cap_rights_init(&rights, CAP_EXTATTR_SET), &fp); 500 if (error) { 501 /* 502 * getvnode() returns EINVAL if the file descriptor is not 503 * backed by a vnode. Silently drop all changes except 504 * chflags(2) in this case. 505 */ 506 if (error == EINVAL) { 507 if (vap->va_flags != VNOVAL) 508 error = EOPNOTSUPP; 509 else 510 error = 0; 511 } 512 return (error); 513 } 514 vp = fp->f_vnode; 515 if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) == 0) { 516 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 517 error = VOP_SETATTR(vp, ap->a_vap, ap->a_cred); 518 VOP_UNLOCK(vp, 0); 519 vn_finished_write(mp); 520 } 521 fdrop(fp, td); 522 return (error); 523 } 524 525 #define UIO_MX _GENERIC_DIRLEN(10) /* number of symbols in INT_MAX printout */ 526 527 static int 528 fdesc_readdir(struct vop_readdir_args *ap) 529 { 530 struct fdescmount *fmp; 531 struct uio *uio = ap->a_uio; 532 struct filedesc *fdp; 533 struct dirent d; 534 struct dirent *dp = &d; 535 int error, i, off, fcnt; 536 537 if (VTOFDESC(ap->a_vp)->fd_type != Froot) 538 panic("fdesc_readdir: not dir"); 539 540 fmp = VFSTOFDESC(ap->a_vp->v_mount); 541 if (ap->a_ncookies != NULL) 542 *ap->a_ncookies = 0; 543 544 off = (int)uio->uio_offset; 545 if (off != uio->uio_offset || off < 0 || (u_int)off % UIO_MX != 0 || 546 uio->uio_resid < UIO_MX) 547 return (EINVAL); 548 i = (u_int)off / UIO_MX; 549 fdp = uio->uio_td->td_proc->p_fd; 550 error = 0; 551 552 fcnt = i - 2; /* The first two nodes are `.' and `..' */ 553 554 FILEDESC_SLOCK(fdp); 555 while (i < fdp->fd_nfiles + 2 && uio->uio_resid >= UIO_MX) { 556 bzero((caddr_t)dp, UIO_MX); 557 switch (i) { 558 case 0: /* `.' */ 559 case 1: /* `..' */ 560 dp->d_fileno = i + FD_ROOT; 561 dp->d_namlen = i + 1; 562 dp->d_reclen = UIO_MX; 563 bcopy("..", dp->d_name, dp->d_namlen); 564 dp->d_type = DT_DIR; 565 dirent_terminate(dp); 566 break; 567 default: 568 if (fdp->fd_ofiles[fcnt].fde_file == NULL) 569 break; 570 dp->d_namlen = sprintf(dp->d_name, "%d", fcnt); 571 dp->d_reclen = UIO_MX; 572 dp->d_type = (fmp->flags & FMNT_LINRDLNKF) == 0 ? 573 DT_CHR : DT_LNK; 574 dp->d_fileno = i + FD_DESC; 575 dirent_terminate(dp); 576 break; 577 } 578 /* NOTE: d_off is the offset of the *next* entry. */ 579 dp->d_off = UIO_MX * (i + 1); 580 if (dp->d_namlen != 0) { 581 /* 582 * And ship to userland 583 */ 584 FILEDESC_SUNLOCK(fdp); 585 error = uiomove(dp, UIO_MX, uio); 586 if (error) 587 goto done; 588 FILEDESC_SLOCK(fdp); 589 } 590 i++; 591 fcnt++; 592 } 593 FILEDESC_SUNLOCK(fdp); 594 595 done: 596 uio->uio_offset = i * UIO_MX; 597 return (error); 598 } 599 600 static int 601 fdesc_reclaim(struct vop_reclaim_args *ap) 602 { 603 struct vnode *vp; 604 struct fdescnode *fd; 605 606 vp = ap->a_vp; 607 fd = VTOFDESC(vp); 608 fdesc_remove_entry(fd); 609 free(vp->v_data, M_TEMP); 610 vp->v_data = NULL; 611 return (0); 612 } 613 614 static int 615 fdesc_readlink(struct vop_readlink_args *va) 616 { 617 struct vnode *vp, *vn; 618 struct thread *td; 619 struct uio *uio; 620 struct file *fp; 621 char *freepath, *fullpath; 622 size_t pathlen; 623 int lockflags, fd_fd; 624 int error; 625 626 freepath = NULL; 627 vn = va->a_vp; 628 if (VTOFDESC(vn)->fd_type != Fdesc) 629 panic("fdesc_readlink: not fdescfs link"); 630 fd_fd = ((struct fdescnode *)vn->v_data)->fd_fd; 631 lockflags = VOP_ISLOCKED(vn); 632 VOP_UNLOCK(vn, 0); 633 634 td = curthread; 635 error = fget_cap(td, fd_fd, &cap_no_rights, &fp, NULL); 636 if (error != 0) 637 goto out; 638 639 switch (fp->f_type) { 640 case DTYPE_VNODE: 641 vp = fp->f_vnode; 642 error = vn_fullpath(td, vp, &fullpath, &freepath); 643 break; 644 default: 645 fullpath = "anon_inode:[unknown]"; 646 break; 647 } 648 if (error == 0) { 649 uio = va->a_uio; 650 pathlen = strlen(fullpath); 651 error = uiomove(fullpath, pathlen, uio); 652 } 653 if (freepath != NULL) 654 free(freepath, M_TEMP); 655 fdrop(fp, td); 656 657 out: 658 vn_lock(vn, lockflags | LK_RETRY); 659 return (error); 660 }
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