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(mapping, blocknr + i, NULL); 184 /* synchronous error? */ 185 if (IS_ERR(page)) 186 page = NULL; 187 } 188 pages[i] = page; 189 } 190 191 for (i = 0; i < BLKS_PER_BUF; i++) { 192 struct page *page = pages[i]; 193 if (page) { 194 wait_on_page_locked(page); 195 if (!PageUptodate(page)) { 196 /* asynchronous error */ 197 page_cache_release(page); 198 pages[i] = NULL; 199 } 200 } 201 } 202 203 buffer = next_buffer; 204 next_buffer = NEXT_BUFFER(buffer); 205 buffer_blocknr[buffer] = blocknr; 206 buffer_dev[buffer] = sb; 207 208 data = read_buffers[buffer]; 209 for (i = 0; i < BLKS_PER_BUF; i++) { 210 struct page *page = pages[i]; 211 if (page) { 212 memcpy(data, kmap(page), PAGE_CACHE_SIZE); 213 kunmap(page); 214 page_cache_release(page); 215 } else 216 memset(data, 0, PAGE_CACHE_SIZE); 217 data += PAGE_CACHE_SIZE; 218 } 219 return read_buffers[buffer] + offset; 220 } 221 222 static void cramfs_put_super(struct super_block *sb) 223 { 224 kfree(sb->s_fs_info); 225 sb->s_fs_info = NULL; 226 } 227 228 static int cramfs_remount(struct super_block *sb, int *flags, char *data) 229 { 230 *flags |= MS_RDONLY; 231 return 0; 232 } 233 234 static int cramfs_fill_super(struct super_block *sb, void *data, int silent) 235 { 236 int i; 237 struct cramfs_super super; 238 unsigned long root_offset; 239 struct cramfs_sb_info *sbi; 240 struct inode *root; 241 242 sb->s_flags |= MS_RDONLY; 243 244 sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL); 245 if (!sbi) 246 return -ENOMEM; 247 sb->s_fs_info = sbi; 248 249 /* Invalidate the read buffers on mount: think disk change.. */ 250 mutex_lock(&read_mutex); 251 for (i = 0; i < READ_BUFFERS; i++) 252 buffer_blocknr[i] = -1; 253 254 /* Read the first block and get the superblock from it */ 255 memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super)); 256 mutex_unlock(&read_mutex); 257 258 /* Do sanity checks on the superblock */ 259 if (super.magic != CRAMFS_MAGIC) { 260 /* check at 512 byte offset */ 261 mutex_lock(&read_mutex); 262 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super)); 263 mutex_unlock(&read_mutex); 264 if (super.magic != CRAMFS_MAGIC) { 265 if (!silent) 266 printk(KERN_ERR "cramfs: wrong magic\n"); 267 goto out; 268 } 269 } 270 271 /* get feature flags first */ 272 if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) { 273 printk(KERN_ERR "cramfs: unsupported filesystem features\n"); 274 goto out; 275 } 276 277 /* Check that the root inode is in a sane state */ 278 if (!S_ISDIR(super.root.mode)) { 279 printk(KERN_ERR "cramfs: root is not a directory\n"); 280 goto out; 281 } 282 root_offset = super.root.offset << 2; 283 if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) { 284 sbi->size=super.size; 285 sbi->blocks=super.fsid.blocks; 286 sbi->files=super.fsid.files; 287 } else { 288 sbi->size=1<<28; 289 sbi->blocks=0; 290 sbi->files=0; 291 } 292 sbi->magic=super.magic; 293 sbi->flags=super.flags; 294 if (root_offset == 0) 295 printk(KERN_INFO "cramfs: empty filesystem"); 296 else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) && 297 ((root_offset != sizeof(struct cramfs_super)) && 298 (root_offset != 512 + sizeof(struct cramfs_super)))) 299 { 300 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset); 301 goto out; 302 } 303 304 /* Set it all up.. */ 305 sb->s_op = &cramfs_ops; 306 root = get_cramfs_inode(sb, &super.root); 307 if (!root) 308 goto out; 309 sb->s_root = d_alloc_root(root); 310 if (!sb->s_root) { 311 iput(root); 312 goto out; 313 } 314 return 0; 315 out: 316 kfree(sbi); 317 sb->s_fs_info = NULL; 318 return -EINVAL; 319 } 320 321 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf) 322 { 323 struct super_block *sb = dentry->d_sb; 324 325 buf->f_type = CRAMFS_MAGIC; 326 buf->f_bsize = PAGE_CACHE_SIZE; 327 buf->f_blocks = CRAMFS_SB(sb)->blocks; 328 buf->f_bfree = 0; 329 buf->f_bavail = 0; 330 buf->f_files = CRAMFS_SB(sb)->files; 331 buf->f_ffree = 0; 332 buf->f_namelen = CRAMFS_MAXPATHLEN; 333 return 0; 334 } 335 336 /* 337 * Read a cramfs directory entry. 338 */ 339 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir) 340 { 341 struct inode *inode = filp->f_path.dentry->d_inode; 342 struct super_block *sb = inode->i_sb; 343 char *buf; 344 unsigned int offset; 345 int copied; 346 347 /* Offset within the thing. */ 348 offset = filp->f_pos; 349 if (offset >= inode->i_size) 350 return 0; 351 /* Directory entries are always 4-byte aligned */ 352 if (offset & 3) 353 return -EINVAL; 354 355 buf = kmalloc(256, GFP_KERNEL); 356 if (!buf) 357 return -ENOMEM; 358 359 copied = 0; 360 while (offset < inode->i_size) { 361 struct cramfs_inode *de; 362 unsigned long nextoffset; 363 char *name; 364 ino_t ino; 365 mode_t mode; 366 int namelen, error; 367 368 mutex_lock(&read_mutex); 369 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256); 370 name = (char *)(de+1); 371 372 /* 373 * Namelengths on disk are shifted by two 374 * and the name padded out to 4-byte boundaries 375 * with zeroes. 376 */ 377 namelen = de->namelen << 2; 378 memcpy(buf, name, namelen); 379 ino = CRAMINO(de); 380 mode = de->mode; 381 mutex_unlock(&read_mutex); 382 nextoffset = offset + sizeof(*de) + namelen; 383 for (;;) { 384 if (!namelen) { 385 kfree(buf); 386 return -EIO; 387 } 388 if (buf[namelen-1]) 389 break; 390 namelen--; 391 } 392 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12); 393 if (error) 394 break; 395 396 offset = nextoffset; 397 filp->f_pos = offset; 398 copied++; 399 } 400 kfree(buf); 401 return 0; 402 } 403 404 /* 405 * Lookup and fill in the inode data.. 406 */ 407 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) 408 { 409 unsigned int offset = 0; 410 int sorted; 411 412 mutex_lock(&read_mutex); 413 sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS; 414 while (offset < dir->i_size) { 415 struct cramfs_inode *de; 416 char *name; 417 int namelen, retval; 418 419 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256); 420 name = (char *)(de+1); 421 422 /* Try to take advantage of sorted directories */ 423 if (sorted && (dentry->d_name.name[0] < name[0])) 424 break; 425 426 namelen = de->namelen << 2; 427 offset += sizeof(*de) + namelen; 428 429 /* Quick check that the name is roughly the right length */ 430 if (((dentry->d_name.len + 3) & ~3) != namelen) 431 continue; 432 433 for (;;) { 434 if (!namelen) { 435 mutex_unlock(&read_mutex); 436 return ERR_PTR(-EIO); 437 } 438 if (name[namelen-1]) 439 break; 440 namelen--; 441 } 442 if (namelen != dentry->d_name.len) 443 continue; 444 retval = memcmp(dentry->d_name.name, name, namelen); 445 if (retval > 0) 446 continue; 447 if (!retval) { 448 struct cramfs_inode entry = *de; 449 mutex_unlock(&read_mutex); 450 d_add(dentry, get_cramfs_inode(dir->i_sb, &entry)); 451 return NULL; 452 } 453 /* else (retval < 0) */ 454 if (sorted) 455 break; 456 } 457 mutex_unlock(&read_mutex); 458 d_add(dentry, NULL); 459 return NULL; 460 } 461 462 static int cramfs_readpage(struct file *file, struct page * page) 463 { 464 struct inode *inode = page->mapping->host; 465 u32 maxblock, bytes_filled; 466 void *pgdata; 467 468 maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 469 bytes_filled = 0; 470 if (page->index < maxblock) { 471 struct super_block *sb = inode->i_sb; 472 u32 blkptr_offset = OFFSET(inode) + page->index*4; 473 u32 start_offset, compr_len; 474 475 start_offset = OFFSET(inode) + maxblock*4; 476 mutex_lock(&read_mutex); 477 if (page->index) 478 start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4); 479 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset); 480 mutex_unlock(&read_mutex); 481 pgdata = kmap(page); 482 if (compr_len == 0) 483 ; /* hole */ 484 else if (compr_len > (PAGE_CACHE_SIZE << 1)) 485 printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len); 486 else { 487 mutex_lock(&read_mutex); 488 bytes_filled = cramfs_uncompress_block(pgdata, 489 PAGE_CACHE_SIZE, 490 cramfs_read(sb, start_offset, compr_len), 491 compr_len); 492 mutex_unlock(&read_mutex); 493 } 494 } else 495 pgdata = kmap(page); 496 memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled); 497 kunmap(page); 498 flush_dcache_page(page); 499 SetPageUptodate(page); 500 unlock_page(page); 501 return 0; 502 } 503 504 static const struct address_space_operations cramfs_aops = { 505 .readpage = cramfs_readpage 506 }; 507 508 /* 509 * Our operations: 510 */ 511 512 /* 513 * A directory can only readdir 514 */ 515 static const struct file_operations cramfs_directory_operations = { 516 .llseek = generic_file_llseek, 517 .read = generic_read_dir, 518 .readdir = cramfs_readdir, 519 }; 520 521 static const struct inode_operations cramfs_dir_inode_operations = { 522 .lookup = cramfs_lookup, 523 }; 524 525 static const struct super_operations cramfs_ops = { 526 .put_super = cramfs_put_super, 527 .remount_fs = cramfs_remount, 528 .statfs = cramfs_statfs, 529 }; 530 531 static int cramfs_get_sb(struct file_system_type *fs_type, 532 int flags, const char *dev_name, void *data, struct vfsmount *mnt) 533 { 534 return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super, 535 mnt); 536 } 537 538 static struct file_system_type cramfs_fs_type = { 539 .owner = THIS_MODULE, 540 .name = "cramfs", 541 .get_sb = cramfs_get_sb, 542 .kill_sb = kill_block_super, 543 .fs_flags = FS_REQUIRES_DEV, 544 }; 545 546 static int __init init_cramfs_fs(void) 547 { 548 int rv; 549 550 rv = cramfs_uncompress_init(); 551 if (rv < 0) 552 return rv; 553 rv = register_filesystem(&cramfs_fs_type); 554 if (rv < 0) 555 cramfs_uncompress_exit(); 556 return rv; 557 } 558 559 static void __exit exit_cramfs_fs(void) 560 { 561 cramfs_uncompress_exit(); 562 unregister_filesystem(&cramfs_fs_type); 563 } 564 565 module_init(init_cramfs_fs) 566 module_exit(exit_cramfs_fs) 567 MODULE_LICENSE("GPL"); 568