1 /* 2 * Compressed rom filesystem for Linux. 3 * 4 * Copyright (C) 1999 Linus Torvalds. 5 * 6 * This file is released under the GPL. 7 */ 8 9 /* 10 * These are the VFS interfaces to the compressed rom filesystem. 11 * The actual compression is based on zlib, see the other files. 12 */ 13 14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 15 16 #include <linux/module.h> 17 #include <linux/fs.h> 18 #include <linux/pagemap.h> 19 #include <linux/init.h> 20 #include <linux/string.h> 21 #include <linux/blkdev.h> 22 #include <linux/slab.h> 23 #include <linux/vfs.h> 24 #include <linux/mutex.h> 25 #include <uapi/linux/cramfs_fs.h> 26 #include <linux/uaccess.h> 27 28 #include "internal.h" 29 30 /* 31 * cramfs super-block data in memory 32 */ 33 struct cramfs_sb_info { 34 unsigned long magic; 35 unsigned long size; 36 unsigned long blocks; 37 unsigned long files; 38 unsigned long flags; 39 }; 40 41 static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb) 42 { 43 return sb->s_fs_info; 44 } 45 46 static const struct super_operations cramfs_ops; 47 static const struct inode_operations cramfs_dir_inode_operations; 48 static const struct file_operations cramfs_directory_operations; 49 static const struct address_space_operations cramfs_aops; 50 51 static DEFINE_MUTEX(read_mutex); 52 53 54 /* These macros may change in future, to provide better st_ino semantics. */ 55 #define OFFSET(x) ((x)->i_ino) 56 57 static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset) 58 { 59 if (!cino->offset) 60 return offset + 1; 61 if (!cino->size) 62 return offset + 1; 63 64 /* 65 * The file mode test fixes buggy mkcramfs implementations where 66 * cramfs_inode->offset is set to a non zero value for entries 67 * which did not contain data, like devices node and fifos. 68 */ 69 switch (cino->mode & S_IFMT) { 70 case S_IFREG: 71 case S_IFDIR: 72 case S_IFLNK: 73 return cino->offset << 2; 74 default: 75 break; 76 } 77 return offset + 1; 78 } 79 80 static struct inode *get_cramfs_inode(struct super_block *sb, 81 const struct cramfs_inode *cramfs_inode, unsigned int offset) 82 { 83 struct inode *inode; 84 static struct timespec zerotime; 85 86 inode = iget_locked(sb, cramino(cramfs_inode, offset)); 87 if (!inode) 88 return ERR_PTR(-ENOMEM); 89 if (!(inode->i_state & I_NEW)) 90 return inode; 91 92 switch (cramfs_inode->mode & S_IFMT) { 93 case S_IFREG: 94 inode->i_fop = &generic_ro_fops; 95 inode->i_data.a_ops = &cramfs_aops; 96 break; 97 case S_IFDIR: 98 inode->i_op = &cramfs_dir_inode_operations; 99 inode->i_fop = &cramfs_directory_operations; 100 break; 101 case S_IFLNK: 102 inode->i_op = &page_symlink_inode_operations; 103 inode_nohighmem(inode); 104 inode->i_data.a_ops = &cramfs_aops; 105 break; 106 default: 107 init_special_inode(inode, cramfs_inode->mode, 108 old_decode_dev(cramfs_inode->size)); 109 } 110 111 inode->i_mode = cramfs_inode->mode; 112 i_uid_write(inode, cramfs_inode->uid); 113 i_gid_write(inode, cramfs_inode->gid); 114 115 /* if the lower 2 bits are zero, the inode contains data */ 116 if (!(inode->i_ino & 3)) { 117 inode->i_size = cramfs_inode->size; 118 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1; 119 } 120 121 /* Struct copy intentional */ 122 inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime; 123 /* inode->i_nlink is left 1 - arguably wrong for directories, 124 but it's the best we can do without reading the directory 125 contents. 1 yields the right result in GNU find, even 126 without -noleaf option. */ 127 128 unlock_new_inode(inode); 129 130 return inode; 131 } 132 133 /* 134 * We have our own block cache: don't fill up the buffer cache 135 * with the rom-image, because the way the filesystem is set 136 * up the accesses should be fairly regular and cached in the 137 * page cache and dentry tree anyway.. 138 * 139 * This also acts as a way to guarantee contiguous areas of up to 140 * BLKS_PER_BUF*PAGE_SIZE, so that the caller doesn't need to 141 * worry about end-of-buffer issues even when decompressing a full 142 * page cache. 143 */ 144 #define READ_BUFFERS (2) 145 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */ 146 #define NEXT_BUFFER(_ix) ((_ix) ^ 1) 147 148 /* 149 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed" 150 * data that takes up more space than the original and with unlucky 151 * alignment. 152 */ 153 #define BLKS_PER_BUF_SHIFT (2) 154 #define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT) 155 #define BUFFER_SIZE (BLKS_PER_BUF*PAGE_SIZE) 156 157 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE]; 158 static unsigned buffer_blocknr[READ_BUFFERS]; 159 static struct super_block *buffer_dev[READ_BUFFERS]; 160 static int next_buffer; 161 162 /* 163 * Returns a pointer to a buffer containing at least LEN bytes of 164 * filesystem starting at byte offset OFFSET into the filesystem. 165 */ 166 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len) 167 { 168 struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping; 169 struct page *pages[BLKS_PER_BUF]; 170 unsigned i, blocknr, buffer; 171 unsigned long devsize; 172 char *data; 173 174 if (!len) 175 return NULL; 176 blocknr = offset >> PAGE_SHIFT; 177 offset &= PAGE_SIZE - 1; 178 179 /* Check if an existing buffer already has the data.. */ 180 for (i = 0; i < READ_BUFFERS; i++) { 181 unsigned int blk_offset; 182 183 if (buffer_dev[i] != sb) 184 continue; 185 if (blocknr < buffer_blocknr[i]) 186 continue; 187 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_SHIFT; 188 blk_offset += offset; 189 if (blk_offset + len > BUFFER_SIZE) 190 continue; 191 return read_buffers[i] + blk_offset; 192 } 193 194 devsize = mapping->host->i_size >> PAGE_SHIFT; 195 196 /* Ok, read in BLKS_PER_BUF pages completely first. */ 197 for (i = 0; i < BLKS_PER_BUF; i++) { 198 struct page *page = NULL; 199 200 if (blocknr + i < devsize) { 201 page = read_mapping_page(mapping, blocknr + i, NULL); 202 /* synchronous error? */ 203 if (IS_ERR(page)) 204 page = NULL; 205 } 206 pages[i] = page; 207 } 208 209 for (i = 0; i < BLKS_PER_BUF; i++) { 210 struct page *page = pages[i]; 211 212 if (page) { 213 wait_on_page_locked(page); 214 if (!PageUptodate(page)) { 215 /* asynchronous error */ 216 put_page(page); 217 pages[i] = NULL; 218 } 219 } 220 } 221 222 buffer = next_buffer; 223 next_buffer = NEXT_BUFFER(buffer); 224 buffer_blocknr[buffer] = blocknr; 225 buffer_dev[buffer] = sb; 226 227 data = read_buffers[buffer]; 228 for (i = 0; i < BLKS_PER_BUF; i++) { 229 struct page *page = pages[i]; 230 231 if (page) { 232 memcpy(data, kmap(page), PAGE_SIZE); 233 kunmap(page); 234 put_page(page); 235 } else 236 memset(data, 0, PAGE_SIZE); 237 data += PAGE_SIZE; 238 } 239 return read_buffers[buffer] + offset; 240 } 241 242 static void cramfs_kill_sb(struct super_block *sb) 243 { 244 struct cramfs_sb_info *sbi = CRAMFS_SB(sb); 245 246 kill_block_super(sb); 247 kfree(sbi); 248 } 249 250 static int cramfs_remount(struct super_block *sb, int *flags, char *data) 251 { 252 sync_filesystem(sb); 253 *flags |= MS_RDONLY; 254 return 0; 255 } 256 257 static int cramfs_fill_super(struct super_block *sb, void *data, int silent) 258 { 259 int i; 260 struct cramfs_super super; 261 unsigned long root_offset; 262 struct cramfs_sb_info *sbi; 263 struct inode *root; 264 265 sb->s_flags |= MS_RDONLY; 266 267 sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL); 268 if (!sbi) 269 return -ENOMEM; 270 sb->s_fs_info = sbi; 271 272 /* Invalidate the read buffers on mount: think disk change.. */ 273 mutex_lock(&read_mutex); 274 for (i = 0; i < READ_BUFFERS; i++) 275 buffer_blocknr[i] = -1; 276 277 /* Read the first block and get the superblock from it */ 278 memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super)); 279 mutex_unlock(&read_mutex); 280 281 /* Do sanity checks on the superblock */ 282 if (super.magic != CRAMFS_MAGIC) { 283 /* check for wrong endianness */ 284 if (super.magic == CRAMFS_MAGIC_WEND) { 285 if (!silent) 286 pr_err("wrong endianness\n"); 287 return -EINVAL; 288 } 289 290 /* check at 512 byte offset */ 291 mutex_lock(&read_mutex); 292 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super)); 293 mutex_unlock(&read_mutex); 294 if (super.magic != CRAMFS_MAGIC) { 295 if (super.magic == CRAMFS_MAGIC_WEND && !silent) 296 pr_err("wrong endianness\n"); 297 else if (!silent) 298 pr_err("wrong magic\n"); 299 return -EINVAL; 300 } 301 } 302 303 /* get feature flags first */ 304 if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) { 305 pr_err("unsupported filesystem features\n"); 306 return -EINVAL; 307 } 308 309 /* Check that the root inode is in a sane state */ 310 if (!S_ISDIR(super.root.mode)) { 311 pr_err("root is not a directory\n"); 312 return -EINVAL; 313 } 314 /* correct strange, hard-coded permissions of mkcramfs */ 315 super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH); 316 317 root_offset = super.root.offset << 2; 318 if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) { 319 sbi->size = super.size; 320 sbi->blocks = super.fsid.blocks; 321 sbi->files = super.fsid.files; 322 } else { 323 sbi->size = 1<<28; 324 sbi->blocks = 0; 325 sbi->files = 0; 326 } 327 sbi->magic = super.magic; 328 sbi->flags = super.flags; 329 if (root_offset == 0) 330 pr_info("empty filesystem"); 331 else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) && 332 ((root_offset != sizeof(struct cramfs_super)) && 333 (root_offset != 512 + sizeof(struct cramfs_super)))) 334 { 335 pr_err("bad root offset %lu\n", root_offset); 336 return -EINVAL; 337 } 338 339 /* Set it all up.. */ 340 sb->s_op = &cramfs_ops; 341 root = get_cramfs_inode(sb, &super.root, 0); 342 if (IS_ERR(root)) 343 return PTR_ERR(root); 344 sb->s_root = d_make_root(root); 345 if (!sb->s_root) 346 return -ENOMEM; 347 return 0; 348 } 349 350 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf) 351 { 352 struct super_block *sb = dentry->d_sb; 353 u64 id = huge_encode_dev(sb->s_bdev->bd_dev); 354 355 buf->f_type = CRAMFS_MAGIC; 356 buf->f_bsize = PAGE_SIZE; 357 buf->f_blocks = CRAMFS_SB(sb)->blocks; 358 buf->f_bfree = 0; 359 buf->f_bavail = 0; 360 buf->f_files = CRAMFS_SB(sb)->files; 361 buf->f_ffree = 0; 362 buf->f_fsid.val[0] = (u32)id; 363 buf->f_fsid.val[1] = (u32)(id >> 32); 364 buf->f_namelen = CRAMFS_MAXPATHLEN; 365 return 0; 366 } 367 368 /* 369 * Read a cramfs directory entry. 370 */ 371 static int cramfs_readdir(struct file *file, struct dir_context *ctx) 372 { 373 struct inode *inode = file_inode(file); 374 struct super_block *sb = inode->i_sb; 375 char *buf; 376 unsigned int offset; 377 378 /* Offset within the thing. */ 379 if (ctx->pos >= inode->i_size) 380 return 0; 381 offset = ctx->pos; 382 /* Directory entries are always 4-byte aligned */ 383 if (offset & 3) 384 return -EINVAL; 385 386 buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL); 387 if (!buf) 388 return -ENOMEM; 389 390 while (offset < inode->i_size) { 391 struct cramfs_inode *de; 392 unsigned long nextoffset; 393 char *name; 394 ino_t ino; 395 umode_t mode; 396 int namelen; 397 398 mutex_lock(&read_mutex); 399 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN); 400 name = (char *)(de+1); 401 402 /* 403 * Namelengths on disk are shifted by two 404 * and the name padded out to 4-byte boundaries 405 * with zeroes. 406 */ 407 namelen = de->namelen << 2; 408 memcpy(buf, name, namelen); 409 ino = cramino(de, OFFSET(inode) + offset); 410 mode = de->mode; 411 mutex_unlock(&read_mutex); 412 nextoffset = offset + sizeof(*de) + namelen; 413 for (;;) { 414 if (!namelen) { 415 kfree(buf); 416 return -EIO; 417 } 418 if (buf[namelen-1]) 419 break; 420 namelen--; 421 } 422 if (!dir_emit(ctx, buf, namelen, ino, mode >> 12)) 423 break; 424 425 ctx->pos = offset = nextoffset; 426 } 427 kfree(buf); 428 return 0; 429 } 430 431 /* 432 * Lookup and fill in the inode data.. 433 */ 434 static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags) 435 { 436 unsigned int offset = 0; 437 struct inode *inode = NULL; 438 int sorted; 439 440 mutex_lock(&read_mutex); 441 sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS; 442 while (offset < dir->i_size) { 443 struct cramfs_inode *de; 444 char *name; 445 int namelen, retval; 446 int dir_off = OFFSET(dir) + offset; 447 448 de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN); 449 name = (char *)(de+1); 450 451 /* Try to take advantage of sorted directories */ 452 if (sorted && (dentry->d_name.name[0] < name[0])) 453 break; 454 455 namelen = de->namelen << 2; 456 offset += sizeof(*de) + namelen; 457 458 /* Quick check that the name is roughly the right length */ 459 if (((dentry->d_name.len + 3) & ~3) != namelen) 460 continue; 461 462 for (;;) { 463 if (!namelen) { 464 inode = ERR_PTR(-EIO); 465 goto out; 466 } 467 if (name[namelen-1]) 468 break; 469 namelen--; 470 } 471 if (namelen != dentry->d_name.len) 472 continue; 473 retval = memcmp(dentry->d_name.name, name, namelen); 474 if (retval > 0) 475 continue; 476 if (!retval) { 477 inode = get_cramfs_inode(dir->i_sb, de, dir_off); 478 break; 479 } 480 /* else (retval < 0) */ 481 if (sorted) 482 break; 483 } 484 out: 485 mutex_unlock(&read_mutex); 486 if (IS_ERR(inode)) 487 return ERR_CAST(inode); 488 d_add(dentry, inode); 489 return NULL; 490 } 491 492 static int cramfs_readpage(struct file *file, struct page *page) 493 { 494 struct inode *inode = page->mapping->host; 495 u32 maxblock; 496 int bytes_filled; 497 void *pgdata; 498 499 maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT; 500 bytes_filled = 0; 501 pgdata = kmap(page); 502 503 if (page->index < maxblock) { 504 struct super_block *sb = inode->i_sb; 505 u32 blkptr_offset = OFFSET(inode) + page->index*4; 506 u32 start_offset, compr_len; 507 508 start_offset = OFFSET(inode) + maxblock*4; 509 mutex_lock(&read_mutex); 510 if (page->index) 511 start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 512 4); 513 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - 514 start_offset); 515 mutex_unlock(&read_mutex); 516 517 if (compr_len == 0) 518 ; /* hole */ 519 else if (unlikely(compr_len > (PAGE_SIZE << 1))) { 520 pr_err("bad compressed blocksize %u\n", 521 compr_len); 522 goto err; 523 } else { 524 mutex_lock(&read_mutex); 525 bytes_filled = cramfs_uncompress_block(pgdata, 526 PAGE_SIZE, 527 cramfs_read(sb, start_offset, compr_len), 528 compr_len); 529 mutex_unlock(&read_mutex); 530 if (unlikely(bytes_filled < 0)) 531 goto err; 532 } 533 } 534 535 memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled); 536 flush_dcache_page(page); 537 kunmap(page); 538 SetPageUptodate(page); 539 unlock_page(page); 540 return 0; 541 542 err: 543 kunmap(page); 544 ClearPageUptodate(page); 545 SetPageError(page); 546 unlock_page(page); 547 return 0; 548 } 549 550 static const struct address_space_operations cramfs_aops = { 551 .readpage = cramfs_readpage 552 }; 553 554 /* 555 * Our operations: 556 */ 557 558 /* 559 * A directory can only readdir 560 */ 561 static const struct file_operations cramfs_directory_operations = { 562 .llseek = generic_file_llseek, 563 .read = generic_read_dir, 564 .iterate_shared = cramfs_readdir, 565 }; 566 567 static const struct inode_operations cramfs_dir_inode_operations = { 568 .lookup = cramfs_lookup, 569 }; 570 571 static const struct super_operations cramfs_ops = { 572 .remount_fs = cramfs_remount, 573 .statfs = cramfs_statfs, 574 }; 575 576 static struct dentry *cramfs_mount(struct file_system_type *fs_type, 577 int flags, const char *dev_name, void *data) 578 { 579 return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super); 580 } 581 582 static struct file_system_type cramfs_fs_type = { 583 .owner = THIS_MODULE, 584 .name = "cramfs", 585 .mount = cramfs_mount, 586 .kill_sb = cramfs_kill_sb, 587 .fs_flags = FS_REQUIRES_DEV, 588 }; 589 MODULE_ALIAS_FS("cramfs"); 590 591 static int __init init_cramfs_fs(void) 592 { 593 int rv; 594 595 rv = cramfs_uncompress_init(); 596 if (rv < 0) 597 return rv; 598 rv = register_filesystem(&cramfs_fs_type); 599 if (rv < 0) 600 cramfs_uncompress_exit(); 601 return rv; 602 } 603 604 static void __exit exit_cramfs_fs(void) 605 { 606 cramfs_uncompress_exit(); 607 unregister_filesystem(&cramfs_fs_type); 608 } 609 610 module_init(init_cramfs_fs) 611 module_exit(exit_cramfs_fs) 612 MODULE_LICENSE("GPL"); 613