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 #include <linux/module.h> 15 #include <linux/fs.h> 16 #include <linux/pagemap.h> 17 #include <linux/init.h> 18 #include <linux/string.h> 19 #include <linux/blkdev.h> 20 #include <linux/cramfs_fs.h> 21 #include <linux/slab.h> 22 #include <linux/cramfs_fs_sb.h> 23 #include <linux/buffer_head.h> 24 #include <linux/vfs.h> 25 #include <linux/mutex.h> 26 27 #include <asm/uaccess.h> 28 29 static const struct super_operations cramfs_ops; 30 static const struct inode_operations cramfs_dir_inode_operations; 31 static const struct file_operations cramfs_directory_operations; 32 static const struct address_space_operations cramfs_aops; 33 34 static DEFINE_MUTEX(read_mutex); 35 36 37 /* These two macros may change in future, to provide better st_ino 38 semantics. */ 39 #define CRAMINO(x) (((x)->offset && (x)->size)?(x)->offset<<2:1) 40 #define OFFSET(x) ((x)->i_ino) 41 42 43 static int cramfs_iget5_test(struct inode *inode, void *opaque) 44 { 45 struct cramfs_inode *cramfs_inode = opaque; 46 return inode->i_ino == CRAMINO(cramfs_inode) && inode->i_ino != 1; 47 } 48 49 static int cramfs_iget5_set(struct inode *inode, void *opaque) 50 { 51 struct cramfs_inode *cramfs_inode = opaque; 52 inode->i_ino = CRAMINO(cramfs_inode); 53 return 0; 54 } 55 56 static struct inode *get_cramfs_inode(struct super_block *sb, 57 struct cramfs_inode * cramfs_inode) 58 { 59 struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode), 60 cramfs_iget5_test, cramfs_iget5_set, 61 cramfs_inode); 62 static struct timespec zerotime; 63 64 if (inode && (inode->i_state & I_NEW)) { 65 inode->i_mode = cramfs_inode->mode; 66 inode->i_uid = cramfs_inode->uid; 67 inode->i_size = cramfs_inode->size; 68 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1; 69 inode->i_gid = cramfs_inode->gid; 70 /* Struct copy intentional */ 71 inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime; 72 /* inode->i_nlink is left 1 - arguably wrong for directories, 73 but it's the best we can do without reading the directory 74 contents. 1 yields the right result in GNU find, even 75 without -noleaf option. */ 76 if (S_ISREG(inode->i_mode)) { 77 inode->i_fop = &generic_ro_fops; 78 inode->i_data.a_ops = &cramfs_aops; 79 } else if (S_ISDIR(inode->i_mode)) { 80 inode->i_op = &cramfs_dir_inode_operations; 81 inode->i_fop = &cramfs_directory_operations; 82 } else if (S_ISLNK(inode->i_mode)) { 83 inode->i_op = &page_symlink_inode_operations; 84 inode->i_data.a_ops = &cramfs_aops; 85 } else { 86 init_special_inode(inode, inode->i_mode, 87 old_decode_dev(cramfs_inode->size)); 88 } 89 unlock_new_inode(inode); 90 } 91 return inode; 92 } 93 94 static void cramfs_drop_inode(struct inode *inode) 95 { 96 if (inode->i_ino == 1) 97 generic_delete_inode(inode); 98 else 99 generic_drop_inode(inode); 100 } 101 102 /* 103 * We have our own block cache: don't fill up the buffer cache 104 * with the rom-image, because the way the filesystem is set 105 * up the accesses should be fairly regular and cached in the 106 * page cache and dentry tree anyway.. 107 * 108 * This also acts as a way to guarantee contiguous areas of up to 109 * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to 110 * worry about end-of-buffer issues even when decompressing a full 111 * page cache. 112 */ 113 #define READ_BUFFERS (2) 114 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */ 115 #define NEXT_BUFFER(_ix) ((_ix) ^ 1) 116 117 /* 118 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed" 119 * data that takes up more space than the original and with unlucky 120 * alignment. 121 */ 122 #define BLKS_PER_BUF_SHIFT (2) 123 #define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT) 124 #define BUFFER_SIZE (BLKS_PER_BUF*PAGE_CACHE_SIZE) 125 126 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE]; 127 static unsigned buffer_blocknr[READ_BUFFERS]; 128 static struct super_block * buffer_dev[READ_BUFFERS]; 129 static int next_buffer; 130 131 /* 132 * Returns a pointer to a buffer containing at least LEN bytes of 133 * filesystem starting at byte offset OFFSET into the filesystem. 134 */ 135 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len) 136 { 137 struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping; 138 struct page *pages[BLKS_PER_BUF]; 139 unsigned i, blocknr, buffer; 140 unsigned long devsize; 141 char *data; 142 143 if (!len) 144 return NULL; 145 blocknr = offset >> PAGE_CACHE_SHIFT; 146 offset &= PAGE_CACHE_SIZE - 1; 147 148 /* Check if an existing buffer already has the data.. */ 149 for (i = 0; i < READ_BUFFERS; i++) { 150 unsigned int blk_offset; 151 152 if (buffer_dev[i] != sb) 153 continue; 154 if (blocknr < buffer_blocknr[i]) 155 continue; 156 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT; 157 blk_offset += offset; 158 if (blk_offset + len > BUFFER_SIZE) 159 continue; 160 return read_buffers[i] + blk_offset; 161 } 162 163 devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT; 164 165 /* Ok, read in BLKS_PER_BUF pages completely first. */ 166 for (i = 0; i < BLKS_PER_BUF; i++) { 167 struct page *page = NULL; 168 169 if (blocknr + i < devsize) { 170 page = read_mapping_page_async(mapping, blocknr + i, 171 NULL); 172 /* synchronous error? */ 173 if (IS_ERR(page)) 174 page = NULL; 175 } 176 pages[i] = page; 177 } 178 179 for (i = 0; i < BLKS_PER_BUF; i++) { 180 struct page *page = pages[i]; 181 if (page) { 182 wait_on_page_locked(page); 183 if (!PageUptodate(page)) { 184 /* asynchronous error */ 185 page_cache_release(page); 186 pages[i] = NULL; 187 } 188 } 189 } 190 191 buffer = next_buffer; 192 next_buffer = NEXT_BUFFER(buffer); 193 buffer_blocknr[buffer] = blocknr; 194 buffer_dev[buffer] = sb; 195 196 data = read_buffers[buffer]; 197 for (i = 0; i < BLKS_PER_BUF; i++) { 198 struct page *page = pages[i]; 199 if (page) { 200 memcpy(data, kmap(page), PAGE_CACHE_SIZE); 201 kunmap(page); 202 page_cache_release(page); 203 } else 204 memset(data, 0, PAGE_CACHE_SIZE); 205 data += PAGE_CACHE_SIZE; 206 } 207 return read_buffers[buffer] + offset; 208 } 209 210 static void cramfs_put_super(struct super_block *sb) 211 { 212 kfree(sb->s_fs_info); 213 sb->s_fs_info = NULL; 214 } 215 216 static int cramfs_remount(struct super_block *sb, int *flags, char *data) 217 { 218 *flags |= MS_RDONLY; 219 return 0; 220 } 221 222 static int cramfs_fill_super(struct super_block *sb, void *data, int silent) 223 { 224 int i; 225 struct cramfs_super super; 226 unsigned long root_offset; 227 struct cramfs_sb_info *sbi; 228 struct inode *root; 229 230 sb->s_flags |= MS_RDONLY; 231 232 sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL); 233 if (!sbi) 234 return -ENOMEM; 235 sb->s_fs_info = sbi; 236 237 /* Invalidate the read buffers on mount: think disk change.. */ 238 mutex_lock(&read_mutex); 239 for (i = 0; i < READ_BUFFERS; i++) 240 buffer_blocknr[i] = -1; 241 242 /* Read the first block and get the superblock from it */ 243 memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super)); 244 mutex_unlock(&read_mutex); 245 246 /* Do sanity checks on the superblock */ 247 if (super.magic != CRAMFS_MAGIC) { 248 /* check for wrong endianess */ 249 if (super.magic == CRAMFS_MAGIC_WEND) { 250 if (!silent) 251 printk(KERN_ERR "cramfs: wrong endianess\n"); 252 goto out; 253 } 254 255 /* check at 512 byte offset */ 256 mutex_lock(&read_mutex); 257 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super)); 258 mutex_unlock(&read_mutex); 259 if (super.magic != CRAMFS_MAGIC) { 260 if (super.magic == CRAMFS_MAGIC_WEND && !silent) 261 printk(KERN_ERR "cramfs: wrong endianess\n"); 262 else if (!silent) 263 printk(KERN_ERR "cramfs: wrong magic\n"); 264 goto out; 265 } 266 } 267 268 /* get feature flags first */ 269 if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) { 270 printk(KERN_ERR "cramfs: unsupported filesystem features\n"); 271 goto out; 272 } 273 274 /* Check that the root inode is in a sane state */ 275 if (!S_ISDIR(super.root.mode)) { 276 printk(KERN_ERR "cramfs: root is not a directory\n"); 277 goto out; 278 } 279 root_offset = super.root.offset << 2; 280 if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) { 281 sbi->size=super.size; 282 sbi->blocks=super.fsid.blocks; 283 sbi->files=super.fsid.files; 284 } else { 285 sbi->size=1<<28; 286 sbi->blocks=0; 287 sbi->files=0; 288 } 289 sbi->magic=super.magic; 290 sbi->flags=super.flags; 291 if (root_offset == 0) 292 printk(KERN_INFO "cramfs: empty filesystem"); 293 else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) && 294 ((root_offset != sizeof(struct cramfs_super)) && 295 (root_offset != 512 + sizeof(struct cramfs_super)))) 296 { 297 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset); 298 goto out; 299 } 300 301 /* Set it all up.. */ 302 sb->s_op = &cramfs_ops; 303 root = get_cramfs_inode(sb, &super.root); 304 if (!root) 305 goto out; 306 sb->s_root = d_alloc_root(root); 307 if (!sb->s_root) { 308 iput(root); 309 goto out; 310 } 311 return 0; 312 out: 313 kfree(sbi); 314 sb->s_fs_info = NULL; 315 return -EINVAL; 316 } 317 318 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf) 319 { 320 struct super_block *sb = dentry->d_sb; 321 322 buf->f_type = CRAMFS_MAGIC; 323 buf->f_bsize = PAGE_CACHE_SIZE; 324 buf->f_blocks = CRAMFS_SB(sb)->blocks; 325 buf->f_bfree = 0; 326 buf->f_bavail = 0; 327 buf->f_files = CRAMFS_SB(sb)->files; 328 buf->f_ffree = 0; 329 buf->f_namelen = CRAMFS_MAXPATHLEN; 330 return 0; 331 } 332 333 /* 334 * Read a cramfs directory entry. 335 */ 336 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir) 337 { 338 struct inode *inode = filp->f_path.dentry->d_inode; 339 struct super_block *sb = inode->i_sb; 340 char *buf; 341 unsigned int offset; 342 int copied; 343 344 /* Offset within the thing. */ 345 offset = filp->f_pos; 346 if (offset >= inode->i_size) 347 return 0; 348 /* Directory entries are always 4-byte aligned */ 349 if (offset & 3) 350 return -EINVAL; 351 352 buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL); 353 if (!buf) 354 return -ENOMEM; 355 356 copied = 0; 357 while (offset < inode->i_size) { 358 struct cramfs_inode *de; 359 unsigned long nextoffset; 360 char *name; 361 ino_t ino; 362 mode_t mode; 363 int namelen, error; 364 365 mutex_lock(&read_mutex); 366 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN); 367 name = (char *)(de+1); 368 369 /* 370 * Namelengths on disk are shifted by two 371 * and the name padded out to 4-byte boundaries 372 * with zeroes. 373 */ 374 namelen = de->namelen << 2; 375 memcpy(buf, name, namelen); 376 ino = CRAMINO(de); 377 mode = de->mode; 378 mutex_unlock(&read_mutex); 379 nextoffset = offset + sizeof(*de) + namelen; 380 for (;;) { 381 if (!namelen) { 382 kfree(buf); 383 return -EIO; 384 } 385 if (buf[namelen-1]) 386 break; 387 namelen--; 388 } 389 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12); 390 if (error) 391 break; 392 393 offset = nextoffset; 394 filp->f_pos = offset; 395 copied++; 396 } 397 kfree(buf); 398 return 0; 399 } 400 401 /* 402 * Lookup and fill in the inode data.. 403 */ 404 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) 405 { 406 unsigned int offset = 0; 407 int sorted; 408 409 mutex_lock(&read_mutex); 410 sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS; 411 while (offset < dir->i_size) { 412 struct cramfs_inode *de; 413 char *name; 414 int namelen, retval; 415 416 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN); 417 name = (char *)(de+1); 418 419 /* Try to take advantage of sorted directories */ 420 if (sorted && (dentry->d_name.name[0] < name[0])) 421 break; 422 423 namelen = de->namelen << 2; 424 offset += sizeof(*de) + namelen; 425 426 /* Quick check that the name is roughly the right length */ 427 if (((dentry->d_name.len + 3) & ~3) != namelen) 428 continue; 429 430 for (;;) { 431 if (!namelen) { 432 mutex_unlock(&read_mutex); 433 return ERR_PTR(-EIO); 434 } 435 if (name[namelen-1]) 436 break; 437 namelen--; 438 } 439 if (namelen != dentry->d_name.len) 440 continue; 441 retval = memcmp(dentry->d_name.name, name, namelen); 442 if (retval > 0) 443 continue; 444 if (!retval) { 445 struct cramfs_inode entry = *de; 446 mutex_unlock(&read_mutex); 447 d_add(dentry, get_cramfs_inode(dir->i_sb, &entry)); 448 return NULL; 449 } 450 /* else (retval < 0) */ 451 if (sorted) 452 break; 453 } 454 mutex_unlock(&read_mutex); 455 d_add(dentry, NULL); 456 return NULL; 457 } 458 459 static int cramfs_readpage(struct file *file, struct page * page) 460 { 461 struct inode *inode = page->mapping->host; 462 u32 maxblock, bytes_filled; 463 void *pgdata; 464 465 maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 466 bytes_filled = 0; 467 if (page->index < maxblock) { 468 struct super_block *sb = inode->i_sb; 469 u32 blkptr_offset = OFFSET(inode) + page->index*4; 470 u32 start_offset, compr_len; 471 472 start_offset = OFFSET(inode) + maxblock*4; 473 mutex_lock(&read_mutex); 474 if (page->index) 475 start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4); 476 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset); 477 mutex_unlock(&read_mutex); 478 pgdata = kmap(page); 479 if (compr_len == 0) 480 ; /* hole */ 481 else if (compr_len > (PAGE_CACHE_SIZE << 1)) 482 printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len); 483 else { 484 mutex_lock(&read_mutex); 485 bytes_filled = cramfs_uncompress_block(pgdata, 486 PAGE_CACHE_SIZE, 487 cramfs_read(sb, start_offset, compr_len), 488 compr_len); 489 mutex_unlock(&read_mutex); 490 } 491 } else 492 pgdata = kmap(page); 493 memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled); 494 kunmap(page); 495 flush_dcache_page(page); 496 SetPageUptodate(page); 497 unlock_page(page); 498 return 0; 499 } 500 501 static const struct address_space_operations cramfs_aops = { 502 .readpage = cramfs_readpage 503 }; 504 505 /* 506 * Our operations: 507 */ 508 509 /* 510 * A directory can only readdir 511 */ 512 static const struct file_operations cramfs_directory_operations = { 513 .llseek = generic_file_llseek, 514 .read = generic_read_dir, 515 .readdir = cramfs_readdir, 516 }; 517 518 static const struct inode_operations cramfs_dir_inode_operations = { 519 .lookup = cramfs_lookup, 520 }; 521 522 static const struct super_operations cramfs_ops = { 523 .put_super = cramfs_put_super, 524 .remount_fs = cramfs_remount, 525 .statfs = cramfs_statfs, 526 .drop_inode = cramfs_drop_inode, 527 }; 528 529 static int cramfs_get_sb(struct file_system_type *fs_type, 530 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 531 { 532 return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super, 533 mnt); 534 } 535 536 static struct file_system_type cramfs_fs_type = { 537 .owner = THIS_MODULE, 538 .name = "cramfs", 539 .get_sb = cramfs_get_sb, 540 .kill_sb = kill_block_super, 541 .fs_flags = FS_REQUIRES_DEV, 542 }; 543 544 static int __init init_cramfs_fs(void) 545 { 546 int rv; 547 548 rv = cramfs_uncompress_init(); 549 if (rv < 0) 550 return rv; 551 rv = register_filesystem(&cramfs_fs_type); 552 if (rv < 0) 553 cramfs_uncompress_exit(); 554 return rv; 555 } 556 557 static void __exit exit_cramfs_fs(void) 558 { 559 cramfs_uncompress_exit(); 560 unregister_filesystem(&cramfs_fs_type); 561 } 562 563 module_init(init_cramfs_fs) 564 module_exit(exit_cramfs_fs) 565 MODULE_LICENSE("GPL"); 566