fs/xfs/xfs_attr_list.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (c) 2000-2005 Silicon Graphics, Inc.
   4  * Copyright (c) 2013 Red Hat, Inc.
   5  * All Rights Reserved.
   6  */
   7 #include "xfs.h"
   8 #include "xfs_fs.h"
   9 #include "xfs_shared.h"
  10 #include "xfs_format.h"
  11 #include "xfs_log_format.h"
  12 #include "xfs_trans_resv.h"
  13 #include "xfs_mount.h"
  14 #include "xfs_da_format.h"
  15 #include "xfs_inode.h"
  16 #include "xfs_trans.h"
  17 #include "xfs_bmap.h"
  18 #include "xfs_attr.h"
  19 #include "xfs_attr_sf.h"
  20 #include "xfs_attr_leaf.h"
  21 #include "xfs_error.h"
  22 #include "xfs_trace.h"
  23 #include "xfs_dir2.h"
  24
  25 STATIC int
  26 xfs_attr_shortform_compare(const void *a, const void *b)
  27 {
  28         xfs_attr_sf_sort_t *sa, *sb;
  29
  30         sa = (xfs_attr_sf_sort_t *)a;
  31         sb = (xfs_attr_sf_sort_t *)b;
  32         if (sa->hash < sb->hash) {
  33                 return -1;
  34         } else if (sa->hash > sb->hash) {
  35                 return 1;
  36         } else {
  37                 return sa->entno - sb->entno;
  38         }
  39 }
  40
  41 #define XFS_ISRESET_CURSOR(cursor) \
  42         (!((cursor)->initted) && !((cursor)->hashval) && \
  43          !((cursor)->blkno) && !((cursor)->offset))
  44 /*
  45  * Copy out entries of shortform attribute lists for attr_list().
  46  * Shortform attribute lists are not stored in hashval sorted order.
  47  * If the output buffer is not large enough to hold them all, then we
  48  * we have to calculate each entries' hashvalue and sort them before
  49  * we can begin returning them to the user.
  50  */
  51 static int
  52 xfs_attr_shortform_list(
  53         struct xfs_attr_list_context    *context)
  54 {
  55         struct attrlist_cursor_kern     *cursor;
  56         struct xfs_attr_sf_sort         *sbuf, *sbp;
  57         struct xfs_attr_shortform       *sf;
  58         struct xfs_attr_sf_entry        *sfe;
  59         struct xfs_inode                *dp;
  60         int                             sbsize, nsbuf, count, i;
  61         int                             error = 0;
  62
  63         ASSERT(context != NULL);
  64         dp = context->dp;
  65         ASSERT(dp != NULL);
  66         ASSERT(dp->i_afp != NULL);
  67         sf = (xfs_attr_shortform_t *)dp->i_afp->if_u1.if_data;
  68         ASSERT(sf != NULL);
  69         if (!sf->hdr.count)
  70                 return 0;
  71         cursor = context->cursor;
  72         ASSERT(cursor != NULL);
  73
  74         trace_xfs_attr_list_sf(context);
  75
  76         /*
  77          * If the buffer is large enough and the cursor is at the start,
  78          * do not bother with sorting since we will return everything in
  79          * one buffer and another call using the cursor won't need to be
  80          * made.
  81          * Note the generous fudge factor of 16 overhead bytes per entry.
  82          * If bufsize is zero then put_listent must be a search function
  83          * and can just scan through what we have.
  84          */
  85         if (context->bufsize == 0 ||
  86             (XFS_ISRESET_CURSOR(cursor) &&
  87              (dp->i_afp->if_bytes + sf->hdr.count * 16) < context->bufsize)) {
  88                 for (i = 0, sfe = &sf->list[0]; i < sf->hdr.count; i++) {
  89                         if (XFS_IS_CORRUPT(context->dp->i_mount,
  90                                            !xfs_attr_namecheck(sfe->nameval,
  91                                                                sfe->namelen)))
  92                                 return -EFSCORRUPTED;
  93                         context->put_listent(context,
  94                                              sfe->flags,
  95                                              sfe->nameval,
  96                                              (int)sfe->namelen,
  97                                              (int)sfe->valuelen);
  98                         /*
  99                          * Either search callback finished early or
 100                          * didn't fit it all in the buffer after all.
 101                          */
 102                         if (context->seen_enough)
 103                                 break;
 104                         sfe = XFS_ATTR_SF_NEXTENTRY(sfe);
 105                 }
 106                 trace_xfs_attr_list_sf_all(context);
 107                 return 0;
 108         }
 109
 110         /* do no more for a search callback */
 111         if (context->bufsize == 0)
 112                 return 0;
 113
 114         /*
 115          * It didn't all fit, so we have to sort everything on hashval.
 116          */
 117         sbsize = sf->hdr.count * sizeof(*sbuf);
 118         sbp = sbuf = kmem_alloc(sbsize, KM_NOFS);
 119
 120         /*
 121          * Scan the attribute list for the rest of the entries, storing
 122          * the relevant info from only those that match into a buffer.
 123          */
 124         nsbuf = 0;
 125         for (i = 0, sfe = &sf->list[0]; i < sf->hdr.count; i++) {
 126                 if (unlikely(
 127                     ((char *)sfe < (char *)sf) ||
 128                     ((char *)sfe >= ((char *)sf + dp->i_afp->if_bytes)))) {
 129                         XFS_CORRUPTION_ERROR("xfs_attr_shortform_list",
 130                                              XFS_ERRLEVEL_LOW,
 131                                              context->dp->i_mount, sfe,
 132                                              sizeof(*sfe));
 133                         kmem_free(sbuf);
 134                         return -EFSCORRUPTED;
 135                 }
 136
 137                 sbp->entno = i;
 138                 sbp->hash = xfs_da_hashname(sfe->nameval, sfe->namelen);
 139                 sbp->name = sfe->nameval;
 140                 sbp->namelen = sfe->namelen;
 141                 /* These are bytes, and both on-disk, don't endian-flip */
 142                 sbp->valuelen = sfe->valuelen;
 143                 sbp->flags = sfe->flags;
 144                 sfe = XFS_ATTR_SF_NEXTENTRY(sfe);
 145                 sbp++;
 146                 nsbuf++;
 147         }
 148
 149         /*
 150          * Sort the entries on hash then entno.
 151          */
 152         xfs_sort(sbuf, nsbuf, sizeof(*sbuf), xfs_attr_shortform_compare);
 153
 154         /*
 155          * Re-find our place IN THE SORTED LIST.
 156          */
 157         count = 0;
 158         cursor->initted = 1;
 159         cursor->blkno = 0;
 160         for (sbp = sbuf, i = 0; i < nsbuf; i++, sbp++) {
 161                 if (sbp->hash == cursor->hashval) {
 162                         if (cursor->offset == count) {
 163                                 break;
 164                         }
 165                         count++;
 166                 } else if (sbp->hash > cursor->hashval) {
 167                         break;
 168                 }
 169         }
 170         if (i == nsbuf)
 171                 goto out;
 172
 173         /*
 174          * Loop putting entries into the user buffer.
 175          */
 176         for ( ; i < nsbuf; i++, sbp++) {
 177                 if (cursor->hashval != sbp->hash) {
 178                         cursor->hashval = sbp->hash;
 179                         cursor->offset = 0;
 180                 }
 181                 if (XFS_IS_CORRUPT(context->dp->i_mount,
 182                                    !xfs_attr_namecheck(sbp->name,
 183                                                        sbp->namelen))) {
 184                         error = -EFSCORRUPTED;
 185                         goto out;
 186                 }
 187                 context->put_listent(context,
 188                                      sbp->flags,
 189                                      sbp->name,
 190                                      sbp->namelen,
 191                                      sbp->valuelen);
 192                 if (context->seen_enough)
 193                         break;
 194                 cursor->offset++;
 195         }
 196 out:
 197         kmem_free(sbuf);
 198         return error;
 199 }
 200
 201 /*
 202  * We didn't find the block & hash mentioned in the cursor state, so
 203  * walk down the attr btree looking for the hash.
 204  */
 205 STATIC int
 206 xfs_attr_node_list_lookup(
 207         struct xfs_attr_list_context    *context,
 208         struct attrlist_cursor_kern     *cursor,
 209         struct xfs_buf                  **pbp)
 210 {
 211         struct xfs_da3_icnode_hdr       nodehdr;
 212         struct xfs_da_intnode           *node;
 213         struct xfs_da_node_entry        *btree;
 214         struct xfs_inode                *dp = context->dp;
 215         struct xfs_mount                *mp = dp->i_mount;
 216         struct xfs_trans                *tp = context->tp;
 217         struct xfs_buf                  *bp;
 218         int                             i;
 219         int                             error = 0;
 220         unsigned int                    expected_level = 0;
 221         uint16_t                        magic;
 222
 223         ASSERT(*pbp == NULL);
 224         cursor->blkno = 0;
 225         for (;;) {
 226                 error = xfs_da3_node_read(tp, dp, cursor->blkno, &bp,
 227                                 XFS_ATTR_FORK);
 228                 if (error)
 229                         return error;
 230                 node = bp->b_addr;
 231                 magic = be16_to_cpu(node->hdr.info.magic);
 232                 if (magic == XFS_ATTR_LEAF_MAGIC ||
 233                     magic == XFS_ATTR3_LEAF_MAGIC)
 234                         break;
 235                 if (magic != XFS_DA_NODE_MAGIC &&
 236                     magic != XFS_DA3_NODE_MAGIC) {
 237                         XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp,
 238                                         node, sizeof(*node));
 239                         goto out_corruptbuf;
 240                 }
 241
 242                 xfs_da3_node_hdr_from_disk(mp, &nodehdr, node);
 243
 244                 /* Tree taller than we can handle; bail out! */
 245                 if (nodehdr.level >= XFS_DA_NODE_MAXDEPTH)
 246                         goto out_corruptbuf;
 247
 248                 /* Check the level from the root node. */
 249                 if (cursor->blkno == 0)
 250                         expected_level = nodehdr.level - 1;
 251                 else if (expected_level != nodehdr.level)
 252                         goto out_corruptbuf;
 253                 else
 254                         expected_level--;
 255
 256                 btree = nodehdr.btree;
 257                 for (i = 0; i < nodehdr.count; btree++, i++) {
 258                         if (cursor->hashval <= be32_to_cpu(btree->hashval)) {
 259                                 cursor->blkno = be32_to_cpu(btree->before);
 260                                 trace_xfs_attr_list_node_descend(context,
 261                                                 btree);
 262                                 break;
 263                         }
 264                 }
 265                 xfs_trans_brelse(tp, bp);
 266
 267                 if (i == nodehdr.count)
 268                         return 0;
 269
 270                 /* We can't point back to the root. */
 271                 if (XFS_IS_CORRUPT(mp, cursor->blkno == 0))
 272                         return -EFSCORRUPTED;
 273         }
 274
 275         if (expected_level != 0)
 276                 goto out_corruptbuf;
 277
 278         *pbp = bp;
 279         return 0;
 280
 281 out_corruptbuf:
 282         xfs_buf_corruption_error(bp);
 283         xfs_trans_brelse(tp, bp);
 284         return -EFSCORRUPTED;
 285 }
 286
 287 STATIC int
 288 xfs_attr_node_list(
 289         struct xfs_attr_list_context    *context)
 290 {
 291         struct xfs_attr3_icleaf_hdr     leafhdr;
 292         struct attrlist_cursor_kern     *cursor;
 293         struct xfs_attr_leafblock       *leaf;
 294         struct xfs_da_intnode           *node;
 295         struct xfs_buf                  *bp;
 296         struct xfs_inode                *dp = context->dp;
 297         struct xfs_mount                *mp = dp->i_mount;
 298         int                             error = 0;
 299
 300         trace_xfs_attr_node_list(context);
 301
 302         cursor = context->cursor;
 303         cursor->initted = 1;
 304
 305         /*
 306          * Do all sorts of validation on the passed-in cursor structure.
 307          * If anything is amiss, ignore the cursor and look up the hashval
 308          * starting from the btree root.
 309          */
 310         bp = NULL;
 311         if (cursor->blkno > 0) {
 312                 error = xfs_da3_node_read(context->tp, dp, cursor->blkno, &bp,
 313                                 XFS_ATTR_FORK);
 314                 if ((error != 0) && (error != -EFSCORRUPTED))
 315                         return error;
 316                 if (bp) {
 317                         struct xfs_attr_leaf_entry *entries;
 318
 319                         node = bp->b_addr;
 320                         switch (be16_to_cpu(node->hdr.info.magic)) {
 321                         case XFS_DA_NODE_MAGIC:
 322                         case XFS_DA3_NODE_MAGIC:
 323                                 trace_xfs_attr_list_wrong_blk(context);
 324                                 xfs_trans_brelse(context->tp, bp);
 325                                 bp = NULL;
 326                                 break;
 327                         case XFS_ATTR_LEAF_MAGIC:
 328                         case XFS_ATTR3_LEAF_MAGIC:
 329                                 leaf = bp->b_addr;
 330                                 xfs_attr3_leaf_hdr_from_disk(mp->m_attr_geo,
 331                                                              &leafhdr, leaf);
 332                                 entries = xfs_attr3_leaf_entryp(leaf);
 333                                 if (cursor->hashval > be32_to_cpu(
 334                                                 entries[leafhdr.count - 1].hashval)) {
 335                                         trace_xfs_attr_list_wrong_blk(context);
 336                                         xfs_trans_brelse(context->tp, bp);
 337                                         bp = NULL;
 338                                 } else if (cursor->hashval <= be32_to_cpu(
 339                                                 entries[0].hashval)) {
 340                                         trace_xfs_attr_list_wrong_blk(context);
 341                                         xfs_trans_brelse(context->tp, bp);
 342                                         bp = NULL;
 343                                 }
 344                                 break;
 345                         default:
 346                                 trace_xfs_attr_list_wrong_blk(context);
 347                                 xfs_trans_brelse(context->tp, bp);
 348                                 bp = NULL;
 349                         }
 350                 }
 351         }
 352
 353         /*
 354          * We did not find what we expected given the cursor's contents,
 355          * so we start from the top and work down based on the hash value.
 356          * Note that start of node block is same as start of leaf block.
 357          */
 358         if (bp == NULL) {
 359                 error = xfs_attr_node_list_lookup(context, cursor, &bp);
 360                 if (error || !bp)
 361                         return error;
 362         }
 363         ASSERT(bp != NULL);
 364
 365         /*
 366          * Roll upward through the blocks, processing each leaf block in
 367          * order.  As long as there is space in the result buffer, keep
 368          * adding the information.
 369          */
 370         for (;;) {
 371                 leaf = bp->b_addr;
 372                 error = xfs_attr3_leaf_list_int(bp, context);
 373                 if (error)
 374                         break;
 375                 xfs_attr3_leaf_hdr_from_disk(mp->m_attr_geo, &leafhdr, leaf);
 376                 if (context->seen_enough || leafhdr.forw == 0)
 377                         break;
 378                 cursor->blkno = leafhdr.forw;
 379                 xfs_trans_brelse(context->tp, bp);
 380                 error = xfs_attr3_leaf_read(context->tp, dp, cursor->blkno,
 381                                             &bp);
 382                 if (error)
 383                         return error;
 384         }
 385         xfs_trans_brelse(context->tp, bp);
 386         return error;
 387 }
 388
 389 /*
 390  * Copy out attribute list entries for attr_list(), for leaf attribute lists.
 391  */
 392 int
 393 xfs_attr3_leaf_list_int(
 394         struct xfs_buf                  *bp,
 395         struct xfs_attr_list_context    *context)
 396 {
 397         struct attrlist_cursor_kern     *cursor;
 398         struct xfs_attr_leafblock       *leaf;
 399         struct xfs_attr3_icleaf_hdr     ichdr;
 400         struct xfs_attr_leaf_entry      *entries;
 401         struct xfs_attr_leaf_entry      *entry;
 402         int                             i;
 403         struct xfs_mount                *mp = context->dp->i_mount;
 404
 405         trace_xfs_attr_list_leaf(context);
 406
 407         leaf = bp->b_addr;
 408         xfs_attr3_leaf_hdr_from_disk(mp->m_attr_geo, &ichdr, leaf);
 409         entries = xfs_attr3_leaf_entryp(leaf);
 410
 411         cursor = context->cursor;
 412         cursor->initted = 1;
 413
 414         /*
 415          * Re-find our place in the leaf block if this is a new syscall.
 416          */
 417         if (context->resynch) {
 418                 entry = &entries[0];
 419                 for (i = 0; i < ichdr.count; entry++, i++) {
 420                         if (be32_to_cpu(entry->hashval) == cursor->hashval) {
 421                                 if (cursor->offset == context->dupcnt) {
 422                                         context->dupcnt = 0;
 423                                         break;
 424                                 }
 425                                 context->dupcnt++;
 426                         } else if (be32_to_cpu(entry->hashval) >
 427                                         cursor->hashval) {
 428                                 context->dupcnt = 0;
 429                                 break;
 430                         }
 431                 }
 432                 if (i == ichdr.count) {
 433                         trace_xfs_attr_list_notfound(context);
 434                         return 0;
 435                 }
 436         } else {
 437                 entry = &entries[0];
 438                 i = 0;
 439         }
 440         context->resynch = 0;
 441
 442         /*
 443          * We have found our place, start copying out the new attributes.
 444          */
 445         for (; i < ichdr.count; entry++, i++) {
 446                 char *name;
 447                 int namelen, valuelen;
 448
 449                 if (be32_to_cpu(entry->hashval) != cursor->hashval) {
 450                         cursor->hashval = be32_to_cpu(entry->hashval);
 451                         cursor->offset = 0;
 452                 }
 453
 454                 if ((entry->flags & XFS_ATTR_INCOMPLETE) &&
 455                     !(context->flags & ATTR_INCOMPLETE))
 456                         continue;               /* skip incomplete entries */
 457
 458                 if (entry->flags & XFS_ATTR_LOCAL) {
 459                         xfs_attr_leaf_name_local_t *name_loc;
 460
 461                         name_loc = xfs_attr3_leaf_name_local(leaf, i);
 462                         name = name_loc->nameval;
 463                         namelen = name_loc->namelen;
 464                         valuelen = be16_to_cpu(name_loc->valuelen);
 465                 } else {
 466                         xfs_attr_leaf_name_remote_t *name_rmt;
 467
 468                         name_rmt = xfs_attr3_leaf_name_remote(leaf, i);
 469                         name = name_rmt->name;
 470                         namelen = name_rmt->namelen;
 471                         valuelen = be32_to_cpu(name_rmt->valuelen);
 472                 }
 473
 474                 if (XFS_IS_CORRUPT(context->dp->i_mount,
 475                                    !xfs_attr_namecheck(name, namelen)))
 476                         return -EFSCORRUPTED;
 477                 context->put_listent(context, entry->flags,
 478                                               name, namelen, valuelen);
 479                 if (context->seen_enough)
 480                         break;
 481                 cursor->offset++;
 482         }
 483         trace_xfs_attr_list_leaf_end(context);
 484         return 0;
 485 }
 486
 487 /*
 488  * Copy out attribute entries for attr_list(), for leaf attribute lists.
 489  */
 490 STATIC int
 491 xfs_attr_leaf_list(xfs_attr_list_context_t *context)
 492 {
 493         int error;
 494         struct xfs_buf *bp;
 495
 496         trace_xfs_attr_leaf_list(context);
 497
 498         context->cursor->blkno = 0;
 499         error = xfs_attr3_leaf_read(context->tp, context->dp, 0, &bp);
 500         if (error)
 501                 return error;
 502
 503         error = xfs_attr3_leaf_list_int(bp, context);
 504         xfs_trans_brelse(context->tp, bp);
 505         return error;
 506 }
 507
 508 int
 509 xfs_attr_list_int_ilocked(
 510         struct xfs_attr_list_context    *context)
 511 {
 512         struct xfs_inode                *dp = context->dp;
 513
 514         ASSERT(xfs_isilocked(dp, XFS_ILOCK_SHARED | XFS_ILOCK_EXCL));
 515
 516         /*
 517          * Decide on what work routines to call based on the inode size.
 518          */
 519         if (!xfs_inode_hasattr(dp))
 520                 return 0;
 521         else if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL)
 522                 return xfs_attr_shortform_list(context);
 523         else if (xfs_bmap_one_block(dp, XFS_ATTR_FORK))
 524                 return xfs_attr_leaf_list(context);
 525         return xfs_attr_node_list(context);
 526 }
 527
 528 int
 529 xfs_attr_list_int(
 530         xfs_attr_list_context_t *context)
 531 {
 532         int error;
 533         xfs_inode_t *dp = context->dp;
 534         uint            lock_mode;
 535
 536         XFS_STATS_INC(dp->i_mount, xs_attr_list);
 537
 538         if (XFS_FORCED_SHUTDOWN(dp->i_mount))
 539                 return -EIO;
 540
 541         lock_mode = xfs_ilock_attr_map_shared(dp);
 542         error = xfs_attr_list_int_ilocked(context);
 543         xfs_iunlock(dp, lock_mode);
 544         return error;
 545 }
 546
 547 #define ATTR_ENTBASESIZE                /* minimum bytes used by an attr */ \
 548         (((struct attrlist_ent *) 0)->a_name - (char *) 0)
 549 #define ATTR_ENTSIZE(namelen)           /* actual bytes used by an attr */ \
 550         ((ATTR_ENTBASESIZE + (namelen) + 1 + sizeof(uint32_t)-1) \
 551          & ~(sizeof(uint32_t)-1))
 552
 553 /*
 554  * Format an attribute and copy it out to the user's buffer.
 555  * Take care to check values and protect against them changing later,
 556  * we may be reading them directly out of a user buffer.
 557  */
 558 STATIC void
 559 xfs_attr_put_listent(
 560         xfs_attr_list_context_t *context,
 561         int             flags,
 562         unsigned char   *name,
 563         int             namelen,
 564         int             valuelen)
 565 {
 566         struct attrlist *alist = (struct attrlist *)context->alist;
 567         attrlist_ent_t *aep;
 568         int arraytop;
 569
 570         ASSERT(!context->seen_enough);
 571         ASSERT(!(context->flags & ATTR_KERNOVAL));
 572         ASSERT(context->count >= 0);
 573         ASSERT(context->count < (ATTR_MAX_VALUELEN/8));
 574         ASSERT(context->firstu >= sizeof(*alist));
 575         ASSERT(context->firstu <= context->bufsize);
 576
 577         /*
 578          * Only list entries in the right namespace.
 579          */
 580         if (((context->flags & ATTR_SECURE) == 0) !=
 581             ((flags & XFS_ATTR_SECURE) == 0))
 582                 return;
 583         if (((context->flags & ATTR_ROOT) == 0) !=
 584             ((flags & XFS_ATTR_ROOT) == 0))
 585                 return;
 586
 587         arraytop = sizeof(*alist) +
 588                         context->count * sizeof(alist->al_offset[0]);
 589         context->firstu -= ATTR_ENTSIZE(namelen);
 590         if (context->firstu < arraytop) {
 591                 trace_xfs_attr_list_full(context);
 592                 alist->al_more = 1;
 593                 context->seen_enough = 1;
 594                 return;
 595         }
 596
 597         aep = (attrlist_ent_t *)&context->alist[context->firstu];
 598         aep->a_valuelen = valuelen;
 599         memcpy(aep->a_name, name, namelen);
 600         aep->a_name[namelen] = 0;
 601         alist->al_offset[context->count++] = context->firstu;
 602         alist->al_count = context->count;
 603         trace_xfs_attr_list_add(context);
 604         return;
 605 }
 606
 607 /*
 608  * Generate a list of extended attribute names and optionally
 609  * also value lengths.  Positive return value follows the XFS
 610  * convention of being an error, zero or negative return code
 611  * is the length of the buffer returned (negated), indicating
 612  * success.
 613  */
 614 int
 615 xfs_attr_list(
 616         xfs_inode_t     *dp,
 617         char            *buffer,
 618         int             bufsize,
 619         int             flags,
 620         attrlist_cursor_kern_t *cursor)
 621 {
 622         xfs_attr_list_context_t context;
 623         struct attrlist *alist;
 624         int error;
 625
 626         /*
 627          * Validate the cursor.
 628          */
 629         if (cursor->pad1 || cursor->pad2)
 630                 return -EINVAL;
 631         if ((cursor->initted == 0) &&
 632             (cursor->hashval || cursor->blkno || cursor->offset))
 633                 return -EINVAL;
 634
 635         /* Only internal consumers can retrieve incomplete attrs. */
 636         if (flags & ATTR_INCOMPLETE)
 637                 return -EINVAL;
 638
 639         /*
 640          * Check for a properly aligned buffer.
 641          */
 642         if (((long)buffer) & (sizeof(int)-1))
 643                 return -EFAULT;
 644         if (flags & ATTR_KERNOVAL)
 645                 bufsize = 0;
 646
 647         /*
 648          * Initialize the output buffer.
 649          */
 650         memset(&context, 0, sizeof(context));
 651         context.dp = dp;
 652         context.cursor = cursor;
 653         context.resynch = 1;
 654         context.flags = flags;
 655         context.alist = buffer;
 656         context.bufsize = (bufsize & ~(sizeof(int)-1));  /* align */
 657         context.firstu = context.bufsize;
 658         context.put_listent = xfs_attr_put_listent;
 659
 660         alist = (struct attrlist *)context.alist;
 661         alist->al_count = 0;
 662         alist->al_more = 0;
 663         alist->al_offset[0] = context.bufsize;
 664
 665         error = xfs_attr_list_int(&context);
 666         ASSERT(error <= 0);
 667         return error;
 668 }