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 #include <private/android_filesystem_capability.h>
  22
  23 #define XATTR_SELINUX_SUFFIX "selinux"
  24 #define XATTR_CAPS_SUFFIX "capability"
  25
  26 #include "ext4_utils.h"
  27 #include "make_ext4fs.h"
  28 #include "allocate.h"
  29 #include "contents.h"
  30 #include "extent.h"
  31 #include "indirect.h"
  32
  33 static struct block_allocation* saved_allocation_head = NULL;
  34
  35 struct block_allocation* get_saved_allocation_chain() {
  36         return saved_allocation_head;
  37 }
  38
  39 static u32 dentry_size(u32 entries, struct dentry *dentries)
  40 {
  41         u32 len = 24;
  42         unsigned int i;
  43         unsigned int dentry_len;
  44
  45         for (i = 0; i < entries; i++) {
  46                 dentry_len = 8 + EXT4_ALIGN(strlen(dentries[i].filename), 4);
  47                 if (len % info.block_size + dentry_len > info.block_size)
  48                         len += info.block_size - (len % info.block_size);
  49                 len += dentry_len;
  50         }
  51
  52         return len;
  53 }
  54
  55 static struct ext4_dir_entry_2 *add_dentry(u8 *data, u32 *offset,
  56                 struct ext4_dir_entry_2 *prev, u32 inode, const char *name,
  57                 u8 file_type)
  58 {
  59         u8 name_len = strlen(name);
  60         u16 rec_len = 8 + EXT4_ALIGN(name_len, 4);
  61         struct ext4_dir_entry_2 *dentry;
  62
  63         u32 start_block = *offset / info.block_size;
  64         u32 end_block = (*offset + rec_len - 1) / info.block_size;
  65         if (start_block != end_block) {
  66                 /* Adding this dentry will cross a block boundary, so pad the previous
  67                    dentry to the block boundary */
  68                 if (!prev)
  69                         critical_error("no prev");
  70                 prev->rec_len += end_block * info.block_size - *offset;
  71                 *offset = end_block * info.block_size;
  72         }
  73
  74         dentry = (struct ext4_dir_entry_2 *)(data + *offset);
  75         dentry->inode = inode;
  76         dentry->rec_len = rec_len;
  77         dentry->name_len = name_len;
  78         dentry->file_type = file_type;
  79         memcpy(dentry->name, name, name_len);
  80
  81         *offset += rec_len;
  82         return dentry;
  83 }
  84
  85 /* Creates a directory structure for an array of directory entries, dentries,
  86    and stores the location of the structure in an inode.  The new inode's
  87    .. link is set to dir_inode_num.  Stores the location of the inode number
  88    of each directory entry into dentries[i].inode, to be filled in later
  89    when the inode for the entry is allocated.  Returns the inode number of the
  90    new directory */
  91 u32 make_directory(u32 dir_inode_num, u32 entries, struct dentry *dentries,
  92         u32 dirs)
  93 {
  94         struct ext4_inode *inode;
  95         u32 blocks;
  96         u32 len;
  97         u32 offset = 0;
  98         u32 inode_num;
  99         u8 *data;
 100         unsigned int i;
 101         struct ext4_dir_entry_2 *dentry;
 102
 103         blocks = DIV_ROUND_UP(dentry_size(entries, dentries), info.block_size);
 104         len = blocks * info.block_size;
 105
 106         if (dir_inode_num) {
 107                 inode_num = allocate_inode(info);
 108         } else {
 109                 dir_inode_num = EXT4_ROOT_INO;
 110                 inode_num = EXT4_ROOT_INO;
 111         }
 112
 113         if (inode_num == EXT4_ALLOCATE_FAILED) {
 114                 error("failed to allocate inode\n");
 115                 return EXT4_ALLOCATE_FAILED;
 116         }
 117
 118         add_directory(inode_num);
 119
 120         inode = get_inode(inode_num);
 121         if (inode == NULL) {
 122                 error("failed to get inode %u", inode_num);
 123                 return EXT4_ALLOCATE_FAILED;
 124         }
 125
 126         data = inode_allocate_data_extents(inode, len, len);
 127         if (data == NULL) {
 128                 error("failed to allocate %u extents", len);
 129                 return EXT4_ALLOCATE_FAILED;
 130         }
 131
 132         inode->i_mode = S_IFDIR;
 133         inode->i_links_count = dirs + 2;
 134         inode->i_flags |= aux_info.default_i_flags;
 135
 136         dentry = NULL;
 137
 138         dentry = add_dentry(data, &offset, NULL, inode_num, ".", EXT4_FT_DIR);
 139         if (!dentry) {
 140                 error("failed to add . directory");
 141                 return EXT4_ALLOCATE_FAILED;
 142         }
 143
 144         dentry = add_dentry(data, &offset, dentry, dir_inode_num, "..", EXT4_FT_DIR);
 145         if (!dentry) {
 146                 error("failed to add .. directory");
 147                 return EXT4_ALLOCATE_FAILED;
 148         }
 149
 150         for (i = 0; i < entries; i++) {
 151                 dentry = add_dentry(data, &offset, dentry, 0,
 152                                 dentries[i].filename, dentries[i].file_type);
 153                 if (offset > len || (offset == len && i != entries - 1))
 154                         critical_error("internal error: dentry for %s ends at %d, past %d\n",
 155                                 dentries[i].filename, offset, len);
 156                 dentries[i].inode = &dentry->inode;
 157                 if (!dentry) {
 158                         error("failed to add directory");
 159                         return EXT4_ALLOCATE_FAILED;
 160                 }
 161         }
 162
 163         /* pad the last dentry out to the end of the block */
 164         dentry->rec_len += len - offset;
 165
 166         return inode_num;
 167 }
 168
 169 /* Creates a file on disk.  Returns the inode number of the new file */
 170 u32 make_file(const char *filename, u64 len)
 171 {
 172         struct ext4_inode *inode;
 173         u32 inode_num;
 174
 175         inode_num = allocate_inode(info);
 176         if (inode_num == EXT4_ALLOCATE_FAILED) {
 177                 error("failed to allocate inode\n");
 178                 return EXT4_ALLOCATE_FAILED;
 179         }
 180
 181         inode = get_inode(inode_num);
 182         if (inode == NULL) {
 183                 error("failed to get inode %u", inode_num);
 184                 return EXT4_ALLOCATE_FAILED;
 185         }
 186
 187         if (len > 0) {
 188                 struct block_allocation* alloc = inode_allocate_file_extents(inode, len, filename);
 189                 if (alloc) {
 190                         alloc->filename = strdup(filename);
 191                         alloc->next = saved_allocation_head;
 192                         saved_allocation_head = alloc;
 193                 }
 194         }
 195
 196         inode->i_mode = S_IFREG;
 197         inode->i_links_count = 1;
 198         inode->i_flags |= aux_info.default_i_flags;
 199
 200         return inode_num;
 201 }
 202
 203 /* Creates a file on disk.  Returns the inode number of the new file */
 204 u32 make_link(const char *link)
 205 {
 206         struct ext4_inode *inode;
 207         u32 inode_num;
 208         u32 len = strlen(link);
 209
 210         inode_num = allocate_inode(info);
 211         if (inode_num == EXT4_ALLOCATE_FAILED) {
 212                 error("failed to allocate inode\n");
 213                 return EXT4_ALLOCATE_FAILED;
 214         }
 215
 216         inode = get_inode(inode_num);
 217         if (inode == NULL) {
 218                 error("failed to get inode %u", inode_num);
 219                 return EXT4_ALLOCATE_FAILED;
 220         }
 221
 222         inode->i_mode = S_IFLNK;
 223         inode->i_links_count = 1;
 224         inode->i_flags |= aux_info.default_i_flags;
 225         inode->i_size_lo = len;
 226
 227         if (len + 1 <= sizeof(inode->i_block)) {
 228                 /* Fast symlink */
 229                 memcpy((char*)inode->i_block, link, len);
 230         } else {
 231                 u8 *data = inode_allocate_data_indirect(inode, info.block_size, info.block_size);
 232                 memcpy(data, link, len);
 233                 inode->i_blocks_lo = info.block_size / 512;
 234         }
 235
 236         return inode_num;
 237 }
 238
 239 /* Creates a special file on disk.  Returns the inode number of the new file */
 240 u32 make_special(const char *path)
 241 {
 242         struct ext4_inode *inode;
 243         struct stat s;
 244         u32 inode_num;
 245
 246         if (stat(path, &s)) {
 247                 error("failed to stat file\n");
 248                 return EXT4_ALLOCATE_FAILED;
 249         }
 250
 251         inode_num = allocate_inode(info);
 252         if (inode_num == EXT4_ALLOCATE_FAILED) {
 253                 error("failed to allocate inode\n");
 254                 return EXT4_ALLOCATE_FAILED;
 255         }
 256
 257         inode = get_inode(inode_num);
 258         if (inode == NULL) {
 259                 error("failed to get inode %u", inode_num);
 260                 return EXT4_ALLOCATE_FAILED;
 261         }
 262
 263         inode->i_mode = s.st_mode & S_IFMT;
 264         inode->i_links_count = 1;
 265         inode->i_flags |= aux_info.default_i_flags;
 266
 267         ((u8 *)inode->i_block)[0] = major(s.st_rdev);
 268         ((u8 *)inode->i_block)[1] = minor(s.st_rdev);
 269
 270         return inode_num;
 271 }
 272
 273 int inode_set_permissions(u32 inode_num, u16 mode, u16 uid, u16 gid, u32 mtime)
 274 {
 275         struct ext4_inode *inode = get_inode(inode_num);
 276
 277         if (!inode)
 278                 return -1;
 279
 280         inode->i_mode |= mode;
 281         inode->i_uid = uid;
 282         inode->i_gid = gid;
 283         inode->i_mtime = mtime;
 284         inode->i_atime = mtime;
 285         inode->i_ctime = mtime;
 286
 287         return 0;
 288 }
 289
 290 /*
 291  * Returns the amount of free space available in the specified
 292  * xattr region
 293  */
 294 static size_t xattr_free_space(struct ext4_xattr_entry *entry, char *end)
 295 {
 296         while(!IS_LAST_ENTRY(entry) && (((char *) entry) < end)) {
 297                 end   -= EXT4_XATTR_SIZE(le32_to_cpu(entry->e_value_size));
 298                 entry  = EXT4_XATTR_NEXT(entry);
 299         }
 300
 301         if (((char *) entry) > end) {
 302                 error("unexpected read beyond end of xattr space");
 303                 return 0;
 304         }
 305
 306         return end - ((char *) entry);
 307 }
 308
 309 /*
 310  * Returns a pointer to the free space immediately after the
 311  * last xattr element
 312  */
 313 static struct ext4_xattr_entry* xattr_get_last(struct ext4_xattr_entry *entry)
 314 {
 315         for (; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
 316                 // skip entry
 317         }
 318         return entry;
 319 }
 320
 321 /*
 322  * assert that the elements in the ext4 xattr section are in sorted order
 323  *
 324  * The ext4 filesystem requires extended attributes to be sorted when
 325  * they're not stored in the inode. The kernel ext4 code uses the following
 326  * sorting algorithm:
 327  *
 328  * 1) First sort extended attributes by their name_index. For example,
 329  *    EXT4_XATTR_INDEX_USER (1) comes before EXT4_XATTR_INDEX_SECURITY (6).
 330  * 2) If the name_indexes are equal, then sorting is based on the length
 331  *    of the name. For example, XATTR_SELINUX_SUFFIX ("selinux") comes before
 332  *    XATTR_CAPS_SUFFIX ("capability") because "selinux" is shorter than "capability"
 333  * 3) If the name_index and name_length are equal, then memcmp() is used to determine
 334  *    which name comes first. For example, "selinux" would come before "yelinux".
 335  *
 336  * This method is intended to implement the sorting function defined in
 337  * the Linux kernel file fs/ext4/xattr.c function ext4_xattr_find_entry().
 338  */
 339 static void xattr_assert_sane(struct ext4_xattr_entry *entry)
 340 {
 341         for( ; !IS_LAST_ENTRY(entry); entry = EXT4_XATTR_NEXT(entry)) {
 342                 struct ext4_xattr_entry *next = EXT4_XATTR_NEXT(entry);
 343                 if (IS_LAST_ENTRY(next)) {
 344                         return;
 345                 }
 346
 347                 int cmp = next->e_name_index - entry->e_name_index;
 348                 if (cmp == 0)
 349                         cmp = next->e_name_len - entry->e_name_len;
 350                 if (cmp == 0)
 351                         cmp = memcmp(next->e_name, entry->e_name, next->e_name_len);
 352                 if (cmp < 0) {
 353                         error("BUG: extended attributes are not sorted\n");
 354                         return;
 355                 }
 356                 if (cmp == 0) {
 357                         error("BUG: duplicate extended attributes detected\n");
 358                         return;
 359                 }
 360         }
 361 }
 362
 363 #define NAME_HASH_SHIFT 5
 364 #define VALUE_HASH_SHIFT 16
 365
 366 static void ext4_xattr_hash_entry(struct ext4_xattr_header *header,
 367                 struct ext4_xattr_entry *entry)
 368 {
 369         u32 hash = 0;
 370         char *name = entry->e_name;
 371         int n;
 372
 373         for (n = 0; n < entry->e_name_len; n++) {
 374                 hash = (hash << NAME_HASH_SHIFT) ^
 375                         (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
 376                         *name++;
 377         }
 378
 379         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
 380                 u32 *value = (u32 *)((char *)header +
 381                         le16_to_cpu(entry->e_value_offs));
 382                 for (n = (le32_to_cpu(entry->e_value_size) +
 383                         EXT4_XATTR_ROUND) >> EXT4_XATTR_PAD_BITS; n; n--) {
 384                         hash = (hash << VALUE_HASH_SHIFT) ^
 385                                 (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
 386                                 le32_to_cpu(*value++);
 387                 }
 388         }
 389         entry->e_hash = cpu_to_le32(hash);
 390 }
 391
 392 #undef NAME_HASH_SHIFT
 393 #undef VALUE_HASH_SHIFT
 394
 395 static struct ext4_xattr_entry* xattr_addto_range(
 396                 void *block_start,
 397                 void *block_end,
 398                 struct ext4_xattr_entry *first,
 399                 int name_index,
 400                 const char *name,
 401                 const void *value,
 402                 size_t value_len)
 403 {
 404         size_t name_len = strlen(name);
 405         if (name_len > 255)
 406                 return NULL;
 407
 408         size_t available_size = xattr_free_space(first, block_end);
 409         size_t needed_size = EXT4_XATTR_LEN(name_len) + EXT4_XATTR_SIZE(value_len);
 410
 411         if (needed_size > available_size)
 412                 return NULL;
 413
 414         struct ext4_xattr_entry *new_entry = xattr_get_last(first);
 415         memset(new_entry, 0, EXT4_XATTR_LEN(name_len));
 416
 417         new_entry->e_name_len = name_len;
 418         new_entry->e_name_index = name_index;
 419         memcpy(new_entry->e_name, name, name_len);
 420         new_entry->e_value_block = 0;
 421         new_entry->e_value_size = cpu_to_le32(value_len);
 422
 423         char *val = (char *) new_entry + available_size - EXT4_XATTR_SIZE(value_len);
 424         size_t e_value_offs = val - (char *) block_start;
 425
 426         new_entry->e_value_offs = cpu_to_le16(e_value_offs);
 427         memset(val, 0, EXT4_XATTR_SIZE(value_len));
 428         memcpy(val, value, value_len);
 429
 430         xattr_assert_sane(first);
 431         return new_entry;
 432 }
 433
 434 static int xattr_addto_inode(struct ext4_inode *inode, int name_index,
 435                 const char *name, const void *value, size_t value_len)
 436 {
 437         struct ext4_xattr_ibody_header *hdr = (struct ext4_xattr_ibody_header *) (inode + 1);
 438         struct ext4_xattr_entry *first = (struct ext4_xattr_entry *) (hdr + 1);
 439         char *block_end = ((char *) inode) + info.inode_size;
 440
 441         struct ext4_xattr_entry *result =
 442                 xattr_addto_range(first, block_end, first, name_index, name, value, value_len);
 443
 444         if (result == NULL)
 445                 return -1;
 446
 447         hdr->h_magic = cpu_to_le32(EXT4_XATTR_MAGIC);
 448         inode->i_extra_isize = cpu_to_le16(sizeof(struct ext4_inode) - EXT4_GOOD_OLD_INODE_SIZE);
 449
 450         return 0;
 451 }
 452
 453 static int xattr_addto_block(struct ext4_inode *inode, int name_index,
 454                 const char *name, const void *value, size_t value_len)
 455 {
 456         struct ext4_xattr_header *header = get_xattr_block_for_inode(inode);
 457         if (!header)
 458                 return -1;
 459
 460         struct ext4_xattr_entry *first = (struct ext4_xattr_entry *) (header + 1);
 461         char *block_end = ((char *) header) + info.block_size;
 462
 463         struct ext4_xattr_entry *result =
 464                 xattr_addto_range(header, block_end, first, name_index, name, value, value_len);
 465
 466         if (result == NULL)
 467                 return -1;
 468
 469         ext4_xattr_hash_entry(header, result);
 470         return 0;
 471 }
 472
 473
 474 static int xattr_add(u32 inode_num, int name_index, const char *name,
 475                 const void *value, size_t value_len)
 476 {
 477         if (!value)
 478                 return 0;
 479
 480         struct ext4_inode *inode = get_inode(inode_num);
 481
 482         if (!inode)
 483                 return -1;
 484
 485         int result = xattr_addto_inode(inode, name_index, name, value, value_len);
 486         if (result != 0) {
 487                 result = xattr_addto_block(inode, name_index, name, value, value_len);
 488         }
 489         return result;
 490 }
 491
 492 int inode_set_capabilities(u32 inode_num, uint64_t capabilities) {
 493         if (capabilities == 0)
 494                 return 0;
 495
 496         struct vfs_cap_data cap_data;
 497         memset(&cap_data, 0, sizeof(cap_data));
 498
 499         cap_data.magic_etc = VFS_CAP_REVISION | VFS_CAP_FLAGS_EFFECTIVE;
 500         cap_data.data[0].permitted = (uint32_t) (capabilities & 0xffffffff);
 501         cap_data.data[0].inheritable = 0;
 502         cap_data.data[1].permitted = (uint32_t) (capabilities >> 32);
 503         cap_data.data[1].inheritable = 0;
 504
 505         return xattr_add(inode_num, EXT4_XATTR_INDEX_SECURITY,
 506                 XATTR_CAPS_SUFFIX, &cap_data, sizeof(cap_data));
 507 }