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