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 #include <asm/semaphore.h> 27 28 #include <asm/uaccess.h> 29 30 static const struct super_operations cramfs_ops; 31 static const struct inode_operations cramfs_dir_inode_operations; 32 static const struct file_operations cramfs_directory_operations; 33 static const struct address_space_operations cramfs_aops; 34 35 static DEFINE_MUTEX(read_mutex); 36 37 38 /* These two macros may change in future, to provide better st_ino 39 semantics. */ 40 #define CRAMINO(x) (((x)->offset && (x)->size)?(x)->offset<<2:1) 41 #define OFFSET(x) ((x)->i_ino) 42 43 44 static int cramfs_iget5_test(struct inode *inode, void *opaque) 45 { 46 struct cramfs_inode *cramfs_inode = opaque; 47 48 if (inode->i_ino != CRAMINO(cramfs_inode)) 49 return 0; /* does not match */ 50 51 if (inode->i_ino != 1) 52 return 1; 53 54 /* all empty directories, char, block, pipe, and sock, share inode #1 */ 55 56 if ((inode->i_mode != cramfs_inode->mode) || 57 (inode->i_gid != cramfs_inode->gid) || 58 (inode->i_uid != cramfs_inode->uid)) 59 return 0; /* does not match */ 60 61 if ((S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) && 62 (inode->i_rdev != old_decode_dev(cramfs_inode->size))) 63 return 0; /* does not match */ 64 65 return 1; /* matches */ 66 } 67 68 static int cramfs_iget5_set(struct inode *inode, void *opaque) 69 { 70 static struct timespec zerotime; 71 struct cramfs_inode *cramfs_inode = opaque; 72 inode->i_mode = cramfs_inode->mode; 73 inode->i_uid = cramfs_inode->uid; 74 inode->i_size = cramfs_inode->size; 75 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1; 76 inode->i_gid = cramfs_inode->gid; 77 /* Struct copy intentional */ 78 inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime; 79 inode->i_ino = CRAMINO(cramfs_inode); 80 /* inode->i_nlink is left 1 - arguably wrong for directories, 81 but it's the best we can do without reading the directory 82 contents. 1 yields the right result in GNU find, even 83 without -noleaf option. */ 84 if (S_ISREG(inode->i_mode)) { 85 inode->i_fop = &generic_ro_fops; 86 inode->i_data.a_ops = &cramfs_aops; 87 } else if (S_ISDIR(inode->i_mode)) { 88 inode->i_op = &cramfs_dir_inode_operations; 89 inode->i_fop = &cramfs_directory_operations; 90 } else if (S_ISLNK(inode->i_mode)) { 91 inode->i_op = &page_symlink_inode_operations; 92 inode->i_data.a_ops = &cramfs_aops; 93 } else { 94 inode->i_size = 0; 95 inode->i_blocks = 0; 96 init_special_inode(inode, inode->i_mode, 97 old_decode_dev(cramfs_inode->size)); 98 } 99 return 0; 100 } 101 102 static struct inode *get_cramfs_inode(struct super_block *sb, 103 struct cramfs_inode * cramfs_inode) 104 { 105 struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode), 106 cramfs_iget5_test, cramfs_iget5_set, 107 cramfs_inode); 108 if (inode && (inode->i_state & I_NEW)) { 109 unlock_new_inode(inode); 110 } 111 return inode; 112 } 113 114 /* 115 * We have our own block cache: don't fill up the buffer cache 116 * with the rom-image, because the way the filesystem is set 117 * up the accesses should be fairly regular and cached in the 118 * page cache and dentry tree anyway.. 119 * 120 * This also acts as a way to guarantee contiguous areas of up to 121 * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to 122 * worry about end-of-buffer issues even when decompressing a full 123 * page cache. 124 */ 125 #define READ_BUFFERS (2) 126 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */ 127 #define NEXT_BUFFER(_ix) ((_ix) ^ 1) 128 129 /* 130 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed" 131 * data that takes up more space than the original and with unlucky 132 * alignment. 133 */ 134 #define BLKS_PER_BUF_SHIFT (2) 135 #define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT) 136 #define BUFFER_SIZE (BLKS_PER_BUF*PAGE_CACHE_SIZE) 137 138 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE]; 139 static unsigned buffer_blocknr[READ_BUFFERS]; 140 static struct super_block * buffer_dev[READ_BUFFERS]; 141 static int next_buffer; 142 143 /* 144 * Returns a pointer to a buffer containing at least LEN bytes of 145 * filesystem starting at byte offset OFFSET into the filesystem. 146 */ 147 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len) 148 { 149 struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping; 150 struct page *pages[BLKS_PER_BUF]; 151 unsigned i, blocknr, buffer, unread; 152 unsigned long devsize; 153 char *data; 154 155 if (!len) 156 return NULL; 157 blocknr = offset >> PAGE_CACHE_SHIFT; 158 offset &= PAGE_CACHE_SIZE - 1; 159 160 /* Check if an existing buffer already has the data.. */ 161 for (i = 0; i < READ_BUFFERS; i++) { 162 unsigned int blk_offset; 163 164 if (buffer_dev[i] != sb) 165 continue; 166 if (blocknr < buffer_blocknr[i]) 167 continue; 168 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT; 169 blk_offset += offset; 170 if (blk_offset + len > BUFFER_SIZE) 171 continue; 172 return read_buffers[i] + blk_offset; 173 } 174 175 devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT; 176 177 /* Ok, read in BLKS_PER_BUF pages completely first. */ 178 unread = 0; 179 for (i = 0; i < BLKS_PER_BUF; i++) { 180 struct page *page = NULL; 181 182 if (blocknr + i < devsize) { 183 page = read_mapping_page_async(mapping, blocknr + i, 184 NULL); 185 /* synchronous error? */ 186 if (IS_ERR(page)) 187 page = NULL; 188 } 189 pages[i] = page; 190 } 191 192 for (i = 0; i < BLKS_PER_BUF; i++) { 193 struct page *page = pages[i]; 194 if (page) { 195 wait_on_page_locked(page); 196 if (!PageUptodate(page)) { 197 /* asynchronous error */ 198 page_cache_release(page); 199 pages[i] = NULL; 200 } 201 } 202 } 203 204 buffer = next_buffer; 205 next_buffer = NEXT_BUFFER(buffer); 206 buffer_blocknr[buffer] = blocknr; 207 buffer_dev[buffer] = sb; 208 209 data = read_buffers[buffer]; 210 for (i = 0; i < BLKS_PER_BUF; i++) { 211 struct page *page = pages[i]; 212 if (page) { 213 memcpy(data, kmap(page), PAGE_CACHE_SIZE); 214 kunmap(page); 215 page_cache_release(page); 216 } else 217 memset(data, 0, PAGE_CACHE_SIZE); 218 data += PAGE_CACHE_SIZE; 219 } 220 return read_buffers[buffer] + offset; 221 } 222 223 static void cramfs_put_super(struct super_block *sb) 224 { 225 kfree(sb->s_fs_info); 226 sb->s_fs_info = NULL; 227 } 228 229 static int cramfs_remount(struct super_block *sb, int *flags, char *data) 230 { 231 *flags |= MS_RDONLY; 232 return 0; 233 } 234 235 static int cramfs_fill_super(struct super_block *sb, void *data, int silent) 236 { 237 int i; 238 struct cramfs_super super; 239 unsigned long root_offset; 240 struct cramfs_sb_info *sbi; 241 struct inode *root; 242 243 sb->s_flags |= MS_RDONLY; 244 245 sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL); 246 if (!sbi) 247 return -ENOMEM; 248 sb->s_fs_info = sbi; 249 250 /* Invalidate the read buffers on mount: think disk change.. */ 251 mutex_lock(&read_mutex); 252 for (i = 0; i < READ_BUFFERS; i++) 253 buffer_blocknr[i] = -1; 254 255 /* Read the first block and get the superblock from it */ 256 memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super)); 257 mutex_unlock(&read_mutex); 258 259 /* Do sanity checks on the superblock */ 260 if (super.magic != CRAMFS_MAGIC) { 261 /* check for wrong endianess */ 262 if (super.magic == CRAMFS_MAGIC_WEND) { 263 if (!silent) 264 printk(KERN_ERR "cramfs: wrong endianess\n"); 265 goto out; 266 } 267 268 /* check at 512 byte offset */ 269 mutex_lock(&read_mutex); 270 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super)); 271 mutex_unlock(&read_mutex); 272 if (super.magic != CRAMFS_MAGIC) { 273 if (super.magic == CRAMFS_MAGIC_WEND && !silent) 274 printk(KERN_ERR "cramfs: wrong endianess\n"); 275 else if (!silent) 276 printk(KERN_ERR "cramfs: wrong magic\n"); 277 goto out; 278 } 279 } 280 281 /* get feature flags first */ 282 if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) { 283 printk(KERN_ERR "cramfs: unsupported filesystem features\n"); 284 goto out; 285 } 286 287 /* Check that the root inode is in a sane state */ 288 if (!S_ISDIR(super.root.mode)) { 289 printk(KERN_ERR "cramfs: root is not a directory\n"); 290 goto out; 291 } 292 root_offset = super.root.offset << 2; 293 if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) { 294 sbi->size=super.size; 295 sbi->blocks=super.fsid.blocks; 296 sbi->files=super.fsid.files; 297 } else { 298 sbi->size=1<<28; 299 sbi->blocks=0; 300 sbi->files=0; 301 } 302 sbi->magic=super.magic; 303 sbi->flags=super.flags; 304 if (root_offset == 0) 305 printk(KERN_INFO "cramfs: empty filesystem"); 306 else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) && 307 ((root_offset != sizeof(struct cramfs_super)) && 308 (root_offset != 512 + sizeof(struct cramfs_super)))) 309 { 310 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset); 311 goto out; 312 } 313 314 /* Set it all up.. */ 315 sb->s_op = &cramfs_ops; 316 root = get_cramfs_inode(sb, &super.root); 317 if (!root) 318 goto out; 319 sb->s_root = d_alloc_root(root); 320 if (!sb->s_root) { 321 iput(root); 322 goto out; 323 } 324 return 0; 325 out: 326 kfree(sbi); 327 sb->s_fs_info = NULL; 328 return -EINVAL; 329 } 330 331 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf) 332 { 333 struct super_block *sb = dentry->d_sb; 334 335 buf->f_type = CRAMFS_MAGIC; 336 buf->f_bsize = PAGE_CACHE_SIZE; 337 buf->f_blocks = CRAMFS_SB(sb)->blocks; 338 buf->f_bfree = 0; 339 buf->f_bavail = 0; 340 buf->f_files = CRAMFS_SB(sb)->files; 341 buf->f_ffree = 0; 342 buf->f_namelen = CRAMFS_MAXPATHLEN; 343 return 0; 344 } 345 346 /* 347 * Read a cramfs directory entry. 348 */ 349 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir) 350 { 351 struct inode *inode = filp->f_path.dentry->d_inode; 352 struct super_block *sb = inode->i_sb; 353 char *buf; 354 unsigned int offset; 355 int copied; 356 357 /* Offset within the thing. */ 358 offset = filp->f_pos; 359 if (offset >= inode->i_size) 360 return 0; 361 /* Directory entries are always 4-byte aligned */ 362 if (offset & 3) 363 return -EINVAL; 364 365 buf = kmalloc(256, GFP_KERNEL); 366 if (!buf) 367 return -ENOMEM; 368 369 copied = 0; 370 while (offset < inode->i_size) { 371 struct cramfs_inode *de; 372 unsigned long nextoffset; 373 char *name; 374 ino_t ino; 375 mode_t mode; 376 int namelen, error; 377 378 mutex_lock(&read_mutex); 379 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256); 380 name = (char *)(de+1); 381 382 /* 383 * Namelengths on disk are shifted by two 384 * and the name padded out to 4-byte boundaries 385 * with zeroes. 386 */ 387 namelen = de->namelen << 2; 388 memcpy(buf, name, namelen); 389 ino = CRAMINO(de); 390 mode = de->mode; 391 mutex_unlock(&read_mutex); 392 nextoffset = offset + sizeof(*de) + namelen; 393 for (;;) { 394 if (!namelen) { 395 kfree(buf); 396 return -EIO; 397 } 398 if (buf[namelen-1]) 399 break; 400 namelen--; 401 } 402 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12); 403 if (error) 404 break; 405 406 offset = nextoffset; 407 filp->f_pos = offset; 408 copied++; 409 } 410 kfree(buf); 411 return 0; 412 } 413 414 /* 415 * Lookup and fill in the inode data.. 416 */ 417 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) 418 { 419 unsigned int offset = 0; 420 int sorted; 421 422 mutex_lock(&read_mutex); 423 sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS; 424 while (offset < dir->i_size) { 425 struct cramfs_inode *de; 426 char *name; 427 int namelen, retval; 428 429 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256); 430 name = (char *)(de+1); 431 432 /* Try to take advantage of sorted directories */ 433 if (sorted && (dentry->d_name.name[0] < name[0])) 434 break; 435 436 namelen = de->namelen << 2; 437 offset += sizeof(*de) + namelen; 438 439 /* Quick check that the name is roughly the right length */ 440 if (((dentry->d_name.len + 3) & ~3) != namelen) 441 continue; 442 443 for (;;) { 444 if (!namelen) { 445 mutex_unlock(&read_mutex); 446 return ERR_PTR(-EIO); 447 } 448 if (name[namelen-1]) 449 break; 450 namelen--; 451 } 452 if (namelen != dentry->d_name.len) 453 continue; 454 retval = memcmp(dentry->d_name.name, name, namelen); 455 if (retval > 0) 456 continue; 457 if (!retval) { 458 struct cramfs_inode entry = *de; 459 mutex_unlock(&read_mutex); 460 d_add(dentry, get_cramfs_inode(dir->i_sb, &entry)); 461 return NULL; 462 } 463 /* else (retval < 0) */ 464 if (sorted) 465 break; 466 } 467 mutex_unlock(&read_mutex); 468 d_add(dentry, NULL); 469 return NULL; 470 } 471 472 static int cramfs_readpage(struct file *file, struct page * page) 473 { 474 struct inode *inode = page->mapping->host; 475 u32 maxblock, bytes_filled; 476 void *pgdata; 477 478 maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 479 bytes_filled = 0; 480 if (page->index < maxblock) { 481 struct super_block *sb = inode->i_sb; 482 u32 blkptr_offset = OFFSET(inode) + page->index*4; 483 u32 start_offset, compr_len; 484 485 start_offset = OFFSET(inode) + maxblock*4; 486 mutex_lock(&read_mutex); 487 if (page->index) 488 start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4); 489 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset); 490 mutex_unlock(&read_mutex); 491 pgdata = kmap(page); 492 if (compr_len == 0) 493 ; /* hole */ 494 else if (compr_len > (PAGE_CACHE_SIZE << 1)) 495 printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len); 496 else { 497 mutex_lock(&read_mutex); 498 bytes_filled = cramfs_uncompress_block(pgdata, 499 PAGE_CACHE_SIZE, 500 cramfs_read(sb, start_offset, compr_len), 501 compr_len); 502 mutex_unlock(&read_mutex); 503 } 504 } else 505 pgdata = kmap(page); 506 memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled); 507 kunmap(page); 508 flush_dcache_page(page); 509 SetPageUptodate(page); 510 unlock_page(page); 511 return 0; 512 } 513 514 static const struct address_space_operations cramfs_aops = { 515 .readpage = cramfs_readpage 516 }; 517 518 /* 519 * Our operations: 520 */ 521 522 /* 523 * A directory can only readdir 524 */ 525 static const struct file_operations cramfs_directory_operations = { 526 .llseek = generic_file_llseek, 527 .read = generic_read_dir, 528 .readdir = cramfs_readdir, 529 }; 530 531 static const struct inode_operations cramfs_dir_inode_operations = { 532 .lookup = cramfs_lookup, 533 }; 534 535 static const struct super_operations cramfs_ops = { 536 .put_super = cramfs_put_super, 537 .remount_fs = cramfs_remount, 538 .statfs = cramfs_statfs, 539 }; 540 541 static int cramfs_get_sb(struct file_system_type *fs_type, 542 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 543 { 544 return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super, 545 mnt); 546 } 547 548 static struct file_system_type cramfs_fs_type = { 549 .owner = THIS_MODULE, 550 .name = "cramfs", 551 .get_sb = cramfs_get_sb, 552 .kill_sb = kill_block_super, 553 .fs_flags = FS_REQUIRES_DEV, 554 }; 555 556 static int __init init_cramfs_fs(void) 557 { 558 int rv; 559 560 rv = cramfs_uncompress_init(); 561 if (rv < 0) 562 return rv; 563 rv = register_filesystem(&cramfs_fs_type); 564 if (rv < 0) 565 cramfs_uncompress_exit(); 566 return rv; 567 } 568 569 static void __exit exit_cramfs_fs(void) 570 { 571 cramfs_uncompress_exit(); 572 unregister_filesystem(&cramfs_fs_type); 573 } 574 575 module_init(init_cramfs_fs) 576 module_exit(exit_cramfs_fs) 577 MODULE_LICENSE("GPL"); 578