contents.c

   1 /*
   2  * Copyright (C) 2010 The Android Open Source Project
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *      http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <sys/stat.h>
  18 #include <string.h>
  19 #include <stdio.h>
  20
  21 #ifdef HAVE_ANDROID_OS
  22 #include <linux/capability.h>
  23 #else
  24 #include <private/android_filesystem_capability.h>
  25 #endif
  26
  27 #define XATTR_SELINUX_SUFFIX "selinux"
  28 #define XATTR_CAPS_SUFFIX "capability"
  29
  30 #include "ext4_utils.h"
  31 #include "make_ext4fs.h"
  32 #include "allocate.h"
  33 #include "contents.h"
  34 #include "extent.h"
  35 #include "indirect.h"
  36
  37 #ifdef USE_MINGW
  38 #define S_IFLNK 0  /* used by make_link, not needed under mingw */
  39 #endif
  40
  41 static struct block_allocation* saved_allocation_head = NULL;
  42
  43 struct block_allocation* get_saved_allocation_chain() {
  44         return saved_allocation_head;
  45 }
  46
  47 static u32 dentry_size(u32 entries, struct dentry *dentries)
  48 {
  49         u32 len = 24;
  50         unsigned int i;
  51         unsigned int dentry_len;
  52
  53         for (i = 0; i < entries; i++) {
  54                 dentry_len = 8 + EXT4_ALIGN(strlen(dentries[i].filename), 4);
  55                 if (len % info.block_size + dentry_len > info.block_size)
  56                         len += info.block_size - (len % info.block_size);
  57                 len += dentry_len;
  58         }
  59
  60         return len;
  61 }
  62
  63 static struct ext4_dir_entry_2 *add_dentry(u8 *data, u32 *offset,
  64                 struct ext4_dir_entry_2 *prev, u32 inode, const char *name,
  65                 u8 file_type)
  66 {
  67         u8 name_len = strlen(name);
  68         u16 rec_len = 8 + EXT4_ALIGN(name_len, 4);
  69         struct ext4_dir_entry_2 *dentry;
  70
  71         u32 start_block = *offset / info.block_size;
  72         u32 end_block = (*offset + rec_len - 1) / info.block_size;
  73         if (start_block != end_block) {
  74                 /* Adding this dentry will cross a block boundary, so pad the previous
  75                    dentry to the block boundary */
  76                 if (!prev)
  77                         critical_error("no prev");
  78                 prev->rec_len += end_block * info.block_size - *offset;
  79                 *offset = end_block * info.block_size;
  80         }
  81
  82         dentry = (struct ext4_dir_entry_2 *)(data + *offset);
  83         dentry->inode = inode;
  84         dentry->rec_len = rec_len;
  85         dentry->name_len = name_len;
  86         dentry->file_type = file_type;
  87         memcpy(dentry->name, name, name_len);
  88
  89         *offset += rec_len;
  90         return dentry;
  91 }
  92
  93 /* Creates a directory structure for an array of directory entries, dentries,
  94    and stores the location of the structure in an inode.  The new inode's
  95    .. link is set to dir_inode_num.  Stores the location of the inode number
  96    of each directory entry into dentries[i].inode, to be filled in later
  97    when the inode for the entry is allocated.  Returns the inode number of the
  98    new directory */
  99 u32 make_directory(u32 dir_inode_num, u32 entries, struct dentry *dentries,
 100         u32 dirs)
 101 {
 102         struct ext4_inode *inode;
 103         u32 blocks;
 104         u32 len;
 105         u32 offset = 0;
 106         u32 inode_num;
 107         u8 *data;
 108         unsigned int i;
 109         struct ext4_dir_entry_2 *dentry;
 110
 111         blocks = DIV_ROUND_UP(dentry_size(entries, dentries), info.block_size);
 112         len = blocks * info.block_size;
 113
 114         if (dir_inode_num) {
 115                 inode_num = allocate_inode(info);
 116         } else {
 117                 dir_inode_num = EXT4_ROOT_INO;
 118                 inode_num = EXT4_ROOT_INO;
 119         }
 120
 121         if (inode_num == EXT4_ALLOCATE_FAILED) {
 122                 error("failed to allocate inode\n");
 123                 return EXT4_ALLOCATE_FAILED;
 124         }
 125
 126         add_directory(inode_num);
 127
 128         inode = get_inode(inode_num);
 129         if (inode == NULL) {
 130                 error("failed to get inode %u", inode_num);
 131                 return EXT4_ALLOCATE_FAILED;
 132         }
 133
 134         data = inode_allocate_data_extents(inode, len, len);
 135         if (data == NULL) {
 136                 error("failed to allocate %u extents", len);
 137                 return EXT4_ALLOCATE_FAILED;
 138         }
 139
 140         inode->i_mode = S_IFDIR;
 141         inode->i_links_count = dirs + 2;
 142         inode->i_flags |= aux_info.default_i_flags;
 143
 144         dentry = NULL;
 145
 146         dentry = add_dentry(data, &offset, NULL, inode_num, ".", EXT4_FT_DIR);
 147         if (!dentry) {
 148                 error("failed to add . directory");
 149                 return EXT4_ALLOCATE_FAILED;
 150         }
 151
 152         dentry = add_dentry(data, &offset, dentry, dir_inode_num, "..", EXT4_FT_DIR);
 153         if (!dentry) {
 154                 error("failed to add .. directory");
 155                 return EXT4_ALLOCATE_FAILED;
 156         }
 157
 158         for (i = 0; i < entries; i++) {
 159                 dentry = add_dentry(data, &offset, dentry, 0,
 160                                 dentries[i].filename, dentries[i].file_type);
 161                 if (offset > len || (offset == len && i != entries - 1))
 162                         critical_error("internal error: dentry for %s ends at %d, past %d\n",
 163                                 dentries[i].filename, offset, len);
 164                 dentries[i].inode = &dentry->inode;
 165                 if (!dentry) {
 166                         error("failed to add directory");
 167                         return EXT4_ALLOCATE_FAILED;
 168                 }
 169         }
 170
 171         /* pad the last dentry out to the end of the block */
 172         dentry->rec_len += len - offset;
 173
 174         return inode_num;
 175 }
 176
 177 /* Creates a file on disk.  Returns the inode number of the new file */
 178 u32 make_file(const char *filename, u64 len)
 179 {
 180         struct ext4_inode *inode;
 181         u32 inode_num;
 182
 183         inode_num = allocate_inode(info);
 184         if (inode_num == EXT4_ALLOCATE_FAILED) {
 185                 error("failed to allocate inode\n");
 186                 return EXT4_ALLOCATE_FAILED;
 187         }
 188
 189         inode = get_inode(inode_num);
 190         if (inode == NULL) {
 191                 error("failed to get inode %u", inode_num);
 192                 return EXT4_ALLOCATE_FAILED;
 193         }
 194
 195         if (len > 0) {
 196                 struct block_allocation* alloc = inode_allocate_file_extents(inode, len, filename);
 197                 if (alloc) {
 198                         alloc->filename = strdup(filename);
 199                         alloc->next = saved_allocation_head;
 200                         saved_allocation_head = alloc;
 201                 }
 202         }
 203
 204         inode->i_mode = S_IFREG;
 205         inode->i_links_count = 1;
 206         inode->i_flags |= aux_info.default_i_flags;
 207
 208         return inode_num;
 209 }
 210
 211 /* Creates a file on disk.  Returns the inode number of the new file */
 212 u32 make_link(const char *link)
 213 {
 214         struct ext4_inode *inode;
 215         u32 inode_num;
 216         u32 len = strlen(link);
 217
 218         inode_num = allocate_inode(info);
 219         if (inode_num == EXT4_ALLOCATE_FAILED) {
 220                 error("failed to allocate inode\n");
 221                 return EXT4_ALLOCATE_FAILED;
 222         }
 223
 224         inode = get_inode(inode_num);
 225         if (inode == NULL) {
 226                 error("failed to get inode %u", inode_num);
 227                 return EXT4_ALLOCATE_FAILED;
 228         }
 229
 230         inode->i_mode = S_IFLNK;
 231         inode->i_links_count = 1;
 232         inode->i_flags |= aux_info.default_i_flags;
 233         inode->i_size_lo = len;
 234
 235         if (len + 1 <= sizeof(inode->i_block)) {
 236                 /* Fast symlink */
 237                 memcpy((char*)inode->i_block, link, len);
 238         } else {
 239                 u8 *data = inode_allocate_data_indirect(inode, info.block_size, info.block_size);
 240                 memcpy(data, link, len);
 241                 inode->i_blocks_lo = info.block_size / 512;
 242         }
 243
 244         return inode_num;
 245 }
 246
 247 int inode_set_permissions(u32 inode_num, u16 mode, u16 uid, u16 gid, u32 mtime)
 248 {
 249         struct ext4_inode *inode = get_inode(inode_num);
 250
 251         if (!inode)
 252                 return -1;
 253
 254         inode->i_mode |= mode;
 255         inode->i_uid = uid;
 256         inode->i_gid = gid;
 257         inode->i_mtime = mtime;
 258         inode->i_atime = mtime;
 259         inode->i_ctime = mtime;
 260
 261         return 0;
 262 }
 263
 264 /*
 265  * Returns the amount of free space available in the specified
 266  * xattr region
 267  */
 268 static size_t xattr_free_space(struct ext4_xattr_entry *entry, char *end)
 269 {
 270         while(!IS_LAST_ENTRY(entry) && (((char *) entry) < end)) {
 271                 end   -= EXT4_XATTR_SIZE(le32_to_cpu(entry->e_value_size));
 272                 entry  = EXT4_XATTR_NEXT(entry);
 273         }
 274
 275         if (((char *) entry) > end) {
 276                 error("unexpected read beyond end of xattr space");
 277                 return 0;
 278         }
 279
 280         return end - ((char *) entry);
 281 }
 282
 283 /*
 284  * Returns a pointer to the free space immediately after the
 285  * last xattr element
 286  */
 287 static struct ext4_xattr_entry* xattr_get_last(struct ext4_xattr_entry *entry)
 288 {
 289         for (; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
 290                 // skip entry
 291         }
 292         return entry;
 293 }
 294
 295 /*
 296  * assert that the elements in the ext4 xattr section are in sorted order
 297  *
 298  * The ext4 filesystem requires extended attributes to be sorted when
 299  * they're not stored in the inode. The kernel ext4 code uses the following
 300  * sorting algorithm:
 301  *
 302  * 1) First sort extended attributes by their name_index. For example,
 303  *    EXT4_XATTR_INDEX_USER (1) comes before EXT4_XATTR_INDEX_SECURITY (6).
 304  * 2) If the name_indexes are equal, then sorting is based on the length
 305  *    of the name. For example, XATTR_SELINUX_SUFFIX ("selinux") comes before
 306  *    XATTR_CAPS_SUFFIX ("capability") because "selinux" is shorter than "capability"
 307  * 3) If the name_index and name_length are equal, then memcmp() is used to determine
 308  *    which name comes first. For example, "selinux" would come before "yelinux".
 309  *
 310  * This method is intended to implement the sorting function defined in
 311  * the Linux kernel file fs/ext4/xattr.c function ext4_xattr_find_entry().
 312  */
 313 static void xattr_assert_sane(struct ext4_xattr_entry *entry)
 314 {
 315         for( ; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
 316                 struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(entry);
 317                 if (IS_LAST_ENTRY(next)) {
 318                         return;
 319                 }
 320
 321                 int cmp = next->e_name_index - entry->e_name_index;
 322                 if (cmp == 0)
 323                         cmp = next->e_name_len - entry->e_name_len;
 324                 if (cmp == 0)
 325                         cmp = memcmp(next->e_name, entry->e_name, next->e_name_len);
 326                 if (cmp < 0) {
 327                         error("BUG: extended attributes are not sorted\n");
 328                         return;
 329                 }
 330                 if (cmp == 0) {
 331                         error("BUG: duplicate extended attributes detected\n");
 332                         return;
 333                 }
 334         }
 335 }
 336
 337 #define NAME_HASH_SHIFT 5
 338 #define VALUE_HASH_SHIFT 16
 339
 340 static void ext4_xattr_hash_entry(struct ext4_xattr_header *header,
 341                 struct ext4_xattr_entry *entry)
 342 {
 343         u32 hash = 0;
 344         char *name = entry->e_name;
 345         int n;
 346
 347         for (n = 0; n < entry->e_name_len; n++) {
 348                 hash = (hash << NAME_HASH_SHIFT) ^
 349                         (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
 350                         *name++;
 351         }
 352
 353         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
 354                 u32 *value = (u32 *)((char *)header +
 355                         le16_to_cpu(entry->e_value_offs));
 356                 for (n = (le32_to_cpu(entry->e_value_size) +
 357                         EXT4_XATTR_ROUND) >> EXT4_XATTR_PAD_BITS; n; n--) {
 358                         hash = (hash << VALUE_HASH_SHIFT) ^
 359                                 (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
 360                                 le32_to_cpu(*value++);
 361                 }
 362         }
 363         entry->e_hash = cpu_to_le32(hash);
 364 }
 365
 366 #undef NAME_HASH_SHIFT
 367 #undef VALUE_HASH_SHIFT
 368
 369 static struct ext4_xattr_entry* xattr_addto_range(
 370                 void *block_start,
 371                 void *block_end,
 372                 struct ext4_xattr_entry *first,
 373                 int name_index,
 374                 const char *name,
 375                 const void *value,
 376                 size_t value_len)
 377 {
 378         size_t name_len = strlen(name);
 379         if (name_len > 255)
 380                 return NULL;
 381
 382         size_t available_size = xattr_free_space(first, block_end);
 383         size_t needed_size = EXT4_XATTR_LEN(name_len) + EXT4_XATTR_SIZE(value_len);
 384
 385         if (needed_size > available_size)
 386                 return NULL;
 387
 388         struct ext4_xattr_entry *new_entry = xattr_get_last(first);
 389         memset(new_entry, 0, EXT4_XATTR_LEN(name_len));
 390
 391         new_entry->e_name_len = name_len;
 392         new_entry->e_name_index = name_index;
 393         memcpy(new_entry->e_name, name, name_len);
 394         new_entry->e_value_block = 0;
 395         new_entry->e_value_size = cpu_to_le32(value_len);
 396
 397         char *val = (char *) new_entry + available_size - EXT4_XATTR_SIZE(value_len);
 398         size_t e_value_offs = val - (char *) block_start;
 399
 400         new_entry->e_value_offs = cpu_to_le16(e_value_offs);
 401         memset(val, 0, EXT4_XATTR_SIZE(value_len));
 402         memcpy(val, value, value_len);
 403
 404         xattr_assert_sane(first);
 405         return new_entry;
 406 }
 407
 408 static int xattr_addto_inode(struct ext4_inode *inode, int name_index,
 409                 const char *name, const void *value, size_t value_len)
 410 {
 411         struct ext4_xattr_ibody_header *hdr = (struct ext4_xattr_ibody_header *) (inode + 1);
 412         struct ext4_xattr_entry *first = (struct ext4_xattr_entry *) (hdr + 1);
 413         char *block_end = ((char *) inode) + info.inode_size;
 414
 415         struct ext4_xattr_entry *result =
 416                 xattr_addto_range(first, block_end, first, name_index, name, value, value_len);
 417
 418         if (result == NULL)
 419                 return -1;
 420
 421         hdr->h_magic = cpu_to_le32(EXT4_XATTR_MAGIC);
 422         inode->i_extra_isize = cpu_to_le16(sizeof(struct ext4_inode) - EXT4_GOOD_OLD_INODE_SIZE);
 423
 424         return 0;
 425 }
 426
 427 static int xattr_addto_block(struct ext4_inode *inode, int name_index,
 428                 const char *name, const void *value, size_t value_len)
 429 {
 430         struct ext4_xattr_header *header = get_xattr_block_for_inode(inode);
 431         if (!header)
 432                 return -1;
 433
 434         struct ext4_xattr_entry *first = (struct ext4_xattr_entry *) (header + 1);
 435         char *block_end = ((char *) header) + info.block_size;
 436
 437         struct ext4_xattr_entry *result =
 438                 xattr_addto_range(header, block_end, first, name_index, name, value, value_len);
 439
 440         if (result == NULL)
 441                 return -1;
 442
 443         ext4_xattr_hash_entry(header, result);
 444         return 0;
 445 }
 446
 447
 448 static int xattr_add(u32 inode_num, int name_index, const char *name,
 449                 const void *value, size_t value_len)
 450 {
 451         if (!value)
 452                 return 0;
 453
 454         struct ext4_inode *inode = get_inode(inode_num);
 455
 456         if (!inode)
 457                 return -1;
 458
 459         int result = xattr_addto_inode(inode, name_index, name, value, value_len);
 460         if (result != 0) {
 461                 result = xattr_addto_block(inode, name_index, name, value, value_len);
 462         }
 463         return result;
 464 }
 465
 466 int inode_set_selinux(u32 inode_num, const char *secon)
 467 {
 468         if (!secon)
 469                 return 0;
 470
 471         return xattr_add(inode_num, EXT4_XATTR_INDEX_SECURITY,
 472                 XATTR_SELINUX_SUFFIX, secon, strlen(secon) + 1);
 473 }
 474
 475 int inode_set_capabilities(u32 inode_num, uint64_t capabilities) {
 476         if (capabilities == 0)
 477                 return 0;
 478
 479         struct vfs_cap_data cap_data;
 480         memset(&cap_data, 0, sizeof(cap_data));
 481
 482         cap_data.magic_etc = VFS_CAP_REVISION | VFS_CAP_FLAGS_EFFECTIVE;
 483         cap_data.data[0].permitted = (uint32_t) (capabilities & 0xffffffff);
 484         cap_data.data[0].inheritable = 0;
 485         cap_data.data[1].permitted = (uint32_t) (capabilities >> 32);
 486         cap_data.data[1].inheritable = 0;
 487
 488         return xattr_add(inode_num, EXT4_XATTR_INDEX_SECURITY,
 489                 XATTR_CAPS_SUFFIX, &cap_data, sizeof(cap_data));
 490 }