libsysio/src/namei.c

   1 /*
   2  *    This Cplant(TM) source code is the property of Sandia National
   3  *    Laboratories.
   4  *
   5  *    This Cplant(TM) source code is copyrighted by Sandia National
   6  *    Laboratories.
   7  *
   8  *    The redistribution of this Cplant(TM) source code is subject to the
   9  *    terms of the GNU Lesser General Public License
  10  *    (see cit/LGPL or http://www.gnu.org/licenses/lgpl.html)
  11  *
  12  *    Cplant(TM) Copyright 1998-2003 Sandia Corporation.
  13  *    Under the terms of Contract DE-AC04-94AL85000, there is a non-exclusive
  14  *    license for use of this work by or on behalf of the US Government.
  15  *    Export of this program may require a license from the United States
  16  *    Government.
  17  */
  18
  19 /*
  20  * This library is free software; you can redistribute it and/or
  21  * modify it under the terms of the GNU Lesser General Public
  22  * License as published by the Free Software Foundation; either
  23  * version 2.1 of the License, or (at your option) any later version.
  24  *
  25  * This library is distributed in the hope that it will be useful,
  26  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  27  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  28  * Lesser General Public License for more details.
  29  *
  30  * You should have received a copy of the GNU Lesser General Public
  31  * License along with this library; if not, write to the Free Software
  32  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  33  *
  34  * Questions or comments about this library should be sent to:
  35  *
  36  * Lee Ward
  37  * Sandia National Laboratories, New Mexico
  38  * P.O. Box 5800
  39  * Albuquerque, NM 87185-1110
  40  *
  41  * lee@sandia.gov
  42  */
  43
  44 #if defined(AUTOMOUNT_FILE_NAME) && defined(__linux__)
  45 #define _BSD_SOURCE
  46 #endif
  47
  48 #include <stdlib.h>
  49 #include <string.h>
  50 #include <errno.h>
  51 #include <assert.h>
  52 #include <unistd.h>
  53 #include <sys/param.h>
  54 #include <sys/types.h>
  55 #include <sys/stat.h>
  56 #include <sys/queue.h>
  57
  58 #include "sysio.h"
  59 #include "mount.h"
  60 #include "inode.h"
  61
  62 /*
  63  * Parse next component in path.
  64  */
  65 #ifndef AUTOMOUNT_FILE_NAME
  66 static
  67 #endif
  68 void
  69 _sysio_next_component(const char *path, struct qstr *name)
  70 {
  71         while (*path == PATH_SEPARATOR)
  72                 path++;
  73         name->name = path;
  74         name->len = 0;
  75         name->hashval = 0;
  76         while (*path && *path != PATH_SEPARATOR) {
  77                 name->hashval =
  78                     37 * name->hashval + *path++;
  79                 name->len++;
  80         }
  81 }
  82
  83 /*
  84  * Given parent, look up component.
  85  */
  86 static int
  87 lookup(struct pnode *parent,
  88        struct qstr *name,
  89        struct pnode **pnop,
  90        struct intent *intnt,
  91        const char *path)
  92 {
  93         int     err;
  94         struct pnode *pno;
  95
  96         if (!parent->p_base->pb_ino)
  97                 return -ENOTDIR;
  98
  99         err = _sysio_permitted(parent->p_base->pb_ino, X_OK);
 100         if (err)
 101                 return err;
 102
 103         /*
 104          * Short-circuit `.' and `..'; We don't cache those.
 105          */
 106         pno = NULL;
 107         if (name->len == 1 && name->name[0] == '.')
 108                 pno = parent;
 109         else if (name->len == 2 && name->name[0] == '.' && name->name[1] == '.')
 110                 pno = parent->p_parent;
 111         if (pno)
 112                 P_REF(pno);
 113         else {
 114                 /*
 115                  * Get cache entry then.
 116                  */
 117                 err = _sysio_p_find_alias(parent, name, &pno);
 118                 if (err)
 119                         return err;
 120         }
 121
 122         /*
 123          * While covered, move to the covering node.
 124          */
 125         while (pno->p_cover && pno->p_cover != pno) {
 126                 struct pnode *cover;
 127
 128                 cover = pno->p_cover;
 129                 P_REF(cover);
 130                 P_RELE(pno);
 131                 pno = cover;
 132         }
 133
 134         *pnop = pno;
 135
 136         /*
 137          * (Re)validate the pnode.
 138          */
 139         err = _sysio_p_validate(pno, intnt, path);
 140         if (err)
 141                 return err;
 142
 143         return 0;
 144 }
 145
 146 /*
 147  * The meat. Walk an absolute or relative path, looking up each
 148  * component. Various flags in the nameidata argument govern actions
 149  * and return values/state. They are:
 150  *
 151  * ND_NOFOLLOW          symbolic links are not followed
 152  * ND_NEGOK             if terminal/leaf does not exist, return
 153  *                       path node (alias) anyway.
 154  */
 155 int
 156 _sysio_path_walk(struct pnode *parent, struct nameidata *nd)
 157 {
 158         int     err;
 159         const char *path;
 160         struct qstr this, next;
 161         struct inode *ino;
 162
 163         /*
 164          * NULL path?
 165          */
 166         if (!nd->nd_path)
 167                 return -EFAULT;
 168
 169         /*
 170          * Empty path?
 171          */
 172         if (!*nd->nd_path)
 173                 return -ENOENT;
 174
 175         /*
 176          * Leading slash?
 177          */
 178         if (*nd->nd_path == PATH_SEPARATOR) {
 179                 /*
 180                  * Make parent the root of the name space.
 181                  */
 182                 parent = nd->nd_root;
 183         }
 184
 185 #if DEFER_INIT_CWD
 186         if (!parent) {
 187                 const char *icwd;
 188
 189                 if (!_sysio_init_cwd)
 190                         abort();
 191
 192                 /*
 193                  * Finally have to set the curretn working directory. We can
 194                  * not tolerate errors here or else risk leaving the process
 195                  * in a very unexpected location. We abort then unless all goes
 196                  * well.
 197                  */
 198                 icwd = _sysio_init_cwd;
 199                 _sysio_init_cwd = NULL;
 200                 if (_sysio_namei(NULL, icwd, 0, NULL, &parent) != 0 ||
 201                     _sysio_p_chdir(parent) != 0)
 202                         abort();
 203         }
 204 #endif
 205
 206         /*
 207          * (Re)Validate the parent.
 208          */
 209         err = _sysio_p_validate(parent, NULL, NULL);
 210         if (err)
 211                 return err;
 212
 213         /*
 214          * Prime everything for the loop. Will need another reference to the
 215          * initial directory. It'll be dropped later.
 216          */
 217         nd->nd_pno = parent;
 218         P_REF(nd->nd_pno);
 219         _sysio_next_component(nd->nd_path, &next);
 220         path = next.name;
 221         parent = NULL;
 222         err = 0;
 223
 224         /*
 225          * Derecurse the path tree-walk.
 226          */
 227         for (;;) {
 228                 ino = nd->nd_pno->p_base->pb_ino;
 229                 if (S_ISLNK(ino->i_stbuf.st_mode) &&
 230                     (next.len || !(nd->nd_flags & ND_NOFOLLOW))) {
 231                         char    *lpath;
 232                         ssize_t cc;
 233                         struct nameidata nameidata;
 234
 235                         if (nd->nd_slicnt >= MAX_SYMLINK) {
 236                                 err = -ELOOP;
 237                                 break;
 238                         }
 239
 240                         /*
 241                          * Follow symbolic link.
 242                          */
 243                         lpath = malloc(MAXPATHLEN + 1);
 244                         if (!lpath) {
 245                                 err = -ENOMEM;
 246                                 break;
 247                         }
 248                         cc =
 249                             ino->i_ops.inop_readlink(nd->nd_pno,
 250                                                      lpath,
 251                                                      MAXPATHLEN);
 252                         if (cc < 0) {
 253                                 free(lpath);
 254                                 err = (int )cc;
 255                                 break;
 256                         }
 257                         lpath[cc] = '\0';                       /* NUL term */
 258                         /*
 259                          * Handle symbolic links with recursion. Yuck!
 260                          */
 261                         ND_INIT(&nameidata,
 262                                 (nd->nd_flags | ND_NEGOK),
 263                                 lpath,
 264                                 nd->nd_root,
 265                                 nd->nd_intent);
 266                         nameidata.nd_slicnt = nd->nd_slicnt + 1;
 267                         err =
 268                             _sysio_path_walk(nd->nd_pno->p_parent, &nameidata);
 269                         free(lpath);
 270                         if (err)
 271                                 break;
 272                         P_RELE(nd->nd_pno);
 273                         nd->nd_pno = nameidata.nd_pno;
 274                         ino = nd->nd_pno->p_base->pb_ino;
 275                 }
 276 #ifdef AUTOMOUNT_FILE_NAME
 277                 else if (ino &&
 278                          S_ISDIR(ino->i_stbuf.st_mode) &&
 279                          (nd->nd_pno->p_mount->mnt_flags & MOUNT_F_AUTO) &&
 280                          nd->nd_amcnt < MAX_MOUNT_DEPTH &&
 281                          ino->i_stbuf.st_mode & S_ISUID) {
 282                         struct pnode *pno;
 283
 284                         /*
 285                          * We're committed to a lookup. It's time to see if
 286                          * we're going to do it in an automount-point and
 287                          * arrange the mount if so.
 288                          */
 289                         assert(!nd->nd_pno->p_cover);
 290                         err =
 291                             lookup(nd->nd_pno,
 292                                    &_sysio_mount_file_name,
 293                                    &pno,
 294                                    NULL,
 295                                    NULL);
 296                         if (pno)
 297                                 P_RELE(pno);
 298                         if (!err && _sysio_automount(pno) == 0) {
 299                                 struct pnode *root;
 300
 301                                 /*
 302                                  * All went well. Need to switch
 303                                  * parent pno and ino to the
 304                                  * root of the newly mounted sub-tree.
 305                                  *
 306                                  * NB:
 307                                  * We don't recurseively retry these
 308                                  * things. It's OK to have the new root
 309                                  * be an automount-point but it's going
 310                                  * to take another lookup to accomplish it.
 311                                  * The alternative could get us into an
 312                                  * infinite loop.
 313                                  */
 314                                 root = nd->nd_pno->p_cover;
 315                                 assert(root);
 316                                 P_RELE(nd->nd_pno);
 317                                 nd->nd_pno = root;
 318 #if 0
 319                                 P_REF(nd->nd_pno);
 320 #endif
 321                                 ino = nd->nd_pno->p_base->pb_ino;
 322                                 assert(ino);
 323
 324                                 /*
 325                                  * Must send the intent-path again.
 326                                  */
 327                                 path = nd->nd_path;
 328                                 nd->nd_amcnt++;
 329
 330                                 /*
 331                                  * Must go back top and retry with this
 332                                  * new pnode as parent.
 333                                  */
 334                                 continue;
 335                         }
 336                         err = 0;                        /* it never happened */
 337                 }
 338 #endif
 339
 340                 /*
 341                  * Set up for next component.
 342                  */
 343                 this = next;
 344                 if (path)
 345                         path = this.name;
 346                 if (!this.len)
 347                         break;
 348                 if (!ino) {
 349                         /*
 350                          * Should only be here if final component was
 351                          * target of a symlink.
 352                          */
 353                         nd->nd_path = this.name + this.len;
 354                         err = -ENOENT;
 355                         break;
 356                 }
 357                 nd->nd_path = this.name + this.len;
 358                 _sysio_next_component(nd->nd_path, &next);
 359                 parent = nd->nd_pno;
 360                 nd->nd_pno = NULL;
 361
 362                 /*
 363                  * Parent must be a directory.
 364                  */
 365                 if (ino && !S_ISDIR(ino->i_stbuf.st_mode)) {
 366                         err = -ENOTDIR;
 367                         break;
 368                 }
 369
 370                 /*
 371                  * The extra path arg is passed only on the first lookup in the
 372                  * walk as we cross into each file system, anew. The intent is
 373                  * passed both on the first lookup and when trying to look up
 374                  * the final component -- Of the original path, not on the
 375                  * file system.
 376                  *
 377                  * Confused? Me too and I came up with this weirdness. It's
 378                  * hints to the file system drivers. Read on.
 379                  *
 380                  * The first lookup will give everything one needs to ready
 381                  * everything for the entire operation before the path is
 382                  * walked. The file system driver knows it's the first lookup
 383                  * in the walk because it has both the path and the intent.
 384                  *
 385                  * Alternatively, one could split the duties; The first lookup
 386                  * can be used to prime the file system inode cache with the
 387                  * interior nodes we'll want in the path-walk. Then, when
 388                  * looking up the last component, ready everything for the
 389                  * operations(s) to come. The file system driver knows it's
 390                  * the last lookup in the walk because it has the intent,
 391                  * again, but without the path.
 392                  *
 393                  * One special case; If we were asked to look up a single
 394                  * component, we treat it as the last component. The file
 395                  * system driver never sees the extra path argument. It should
 396                  * be noted that the driver always has the fully qualified
 397                  * path, on the target file system, available to it for any
 398                  * node it is looking up, including the last, via the base
 399                  * path node and it's ancestor chain.
 400                  */
 401                 err =
 402                     lookup(parent,
 403                            &this,
 404                            &nd->nd_pno,
 405                            (path || !next.len)
 406                              ? nd->nd_intent
 407                              : NULL,
 408                            (path && next.len) ? path : NULL);
 409                 if (err) {
 410                         if (err == -ENOENT &&
 411                             !next.len &&
 412                             (nd->nd_flags & ND_NEGOK))
 413                                 err = 0;
 414                         break;
 415                 }
 416                 path = NULL;                            /* Stop that! */
 417                 if ((parent->p_mount->mnt_fs !=
 418                      nd->nd_pno->p_mount->mnt_fs)) {
 419                         /*
 420                          * Crossed into a new fs. We'll want the next lookup
 421                          * to include the path again.
 422                          */
 423                         path = nd->nd_path;
 424                 }
 425
 426                 /*
 427                  * Release the parent.
 428                  */
 429                 P_RELE(parent);
 430                 parent = NULL;
 431         }
 432
 433         /*
 434          * Trailing separators cause us to break from the loop with
 435          * a parent set but no pnode. Check for that.
 436          */
 437         if (!nd->nd_pno) {
 438                 nd->nd_pno = parent;
 439                 parent = NULL;
 440                 /*
 441                  * Make sure the last processed component was a directory. The
 442                  * trailing slashes are illegal behind anything else.
 443                  */
 444                 if (!(err ||
 445                       S_ISDIR(nd->nd_pno->p_base->pb_ino->i_stbuf.st_mode)))
 446                         err = -ENOTDIR;
 447         }
 448
 449         /*
 450          * Drop reference to parent if set. Either we have a dup of the original
 451          * parent or an intermediate reference.
 452          */
 453         if (parent)
 454                 P_RELE(parent);
 455
 456         /*
 457          * On error, we will want to drop our reference to the current
 458          * path node if at end.
 459          */
 460         if (err && nd->nd_pno) {
 461                 P_RELE(nd->nd_pno);
 462                 nd->nd_pno = NULL;
 463         }
 464
 465         return err;
 466 }
 467
 468 #ifdef CPLANT_YOD
 469 /*
 470  * for backward compatibility w/protocol switch
 471  * remove everything up to the first ':'
 472  * fortran libs prepend cwd to path, so not much choice
 473  */
 474 #define STRIP_PREFIX(p) strchr(p,':') ? strchr(p,':')+1 : p
 475 #else
 476 #define STRIP_PREFIX(p) p
 477 #endif
 478
 479 /*
 480  * Expanded form of the path-walk routine, with the common arguments, builds
 481  * the nameidata bundle and calls path-walk.
 482  */
 483 int
 484 _sysio_namei(struct pnode *parent,
 485              const char *path,
 486              unsigned flags,
 487              struct intent *intnt,
 488              struct pnode **pnop)
 489 {
 490         struct nameidata nameidata;
 491         int     err;
 492
 493         ND_INIT(&nameidata, flags, STRIP_PREFIX(path), _sysio_root, intnt);
 494         err = _sysio_path_walk(parent, &nameidata);
 495         if (!err)
 496                 *pnop = nameidata.nd_pno;
 497         return err;
 498 }