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 struct super_operations cramfs_ops; 31 static 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_blksize = PAGE_CACHE_SIZE; 77 inode->i_gid = cramfs_inode->gid; 78 /* Struct copy intentional */ 79 inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime; 80 inode->i_ino = CRAMINO(cramfs_inode); 81 /* inode->i_nlink is left 1 - arguably wrong for directories, 82 but it's the best we can do without reading the directory 83 contents. 1 yields the right result in GNU find, even 84 without -noleaf option. */ 85 if (S_ISREG(inode->i_mode)) { 86 inode->i_fop = &generic_ro_fops; 87 inode->i_data.a_ops = &cramfs_aops; 88 } else if (S_ISDIR(inode->i_mode)) { 89 inode->i_op = &cramfs_dir_inode_operations; 90 inode->i_fop = &cramfs_directory_operations; 91 } else if (S_ISLNK(inode->i_mode)) { 92 inode->i_op = &page_symlink_inode_operations; 93 inode->i_data.a_ops = &cramfs_aops; 94 } else { 95 inode->i_size = 0; 96 inode->i_blocks = 0; 97 init_special_inode(inode, inode->i_mode, 98 old_decode_dev(cramfs_inode->size)); 99 } 100 return 0; 101 } 102 103 static struct inode *get_cramfs_inode(struct super_block *sb, 104 struct cramfs_inode * cramfs_inode) 105 { 106 struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode), 107 cramfs_iget5_test, cramfs_iget5_set, 108 cramfs_inode); 109 if (inode && (inode->i_state & I_NEW)) { 110 unlock_new_inode(inode); 111 } 112 return inode; 113 } 114 115 /* 116 * We have our own block cache: don't fill up the buffer cache 117 * with the rom-image, because the way the filesystem is set 118 * up the accesses should be fairly regular and cached in the 119 * page cache and dentry tree anyway.. 120 * 121 * This also acts as a way to guarantee contiguous areas of up to 122 * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to 123 * worry about end-of-buffer issues even when decompressing a full 124 * page cache. 125 */ 126 #define READ_BUFFERS (2) 127 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */ 128 #define NEXT_BUFFER(_ix) ((_ix) ^ 1) 129 130 /* 131 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed" 132 * data that takes up more space than the original and with unlucky 133 * alignment. 134 */ 135 #define BLKS_PER_BUF_SHIFT (2) 136 #define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT) 137 #define BUFFER_SIZE (BLKS_PER_BUF*PAGE_CACHE_SIZE) 138 139 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE]; 140 static unsigned buffer_blocknr[READ_BUFFERS]; 141 static struct super_block * buffer_dev[READ_BUFFERS]; 142 static int next_buffer; 143 144 /* 145 * Returns a pointer to a buffer containing at least LEN bytes of 146 * filesystem starting at byte offset OFFSET into the filesystem. 147 */ 148 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len) 149 { 150 struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping; 151 struct page *pages[BLKS_PER_BUF]; 152 unsigned i, blocknr, buffer, unread; 153 unsigned long devsize; 154 char *data; 155 156 if (!len) 157 return NULL; 158 blocknr = offset >> PAGE_CACHE_SHIFT; 159 offset &= PAGE_CACHE_SIZE - 1; 160 161 /* Check if an existing buffer already has the data.. */ 162 for (i = 0; i < READ_BUFFERS; i++) { 163 unsigned int blk_offset; 164 165 if (buffer_dev[i] != sb) 166 continue; 167 if (blocknr < buffer_blocknr[i]) 168 continue; 169 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT; 170 blk_offset += offset; 171 if (blk_offset + len > BUFFER_SIZE) 172 continue; 173 return read_buffers[i] + blk_offset; 174 } 175 176 devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT; 177 178 /* Ok, read in BLKS_PER_BUF pages completely first. */ 179 unread = 0; 180 for (i = 0; i < BLKS_PER_BUF; i++) { 181 struct page *page = NULL; 182 183 if (blocknr + i < devsize) { 184 page = read_mapping_page(mapping, blocknr + i, 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 = kmalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL); 246 if (!sbi) 247 return -ENOMEM; 248 sb->s_fs_info = sbi; 249 memset(sbi, 0, sizeof(struct cramfs_sb_info)); 250 251 /* Invalidate the read buffers on mount: think disk change.. */ 252 mutex_lock(&read_mutex); 253 for (i = 0; i < READ_BUFFERS; i++) 254 buffer_blocknr[i] = -1; 255 256 /* Read the first block and get the superblock from it */ 257 memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super)); 258 mutex_unlock(&read_mutex); 259 260 /* Do sanity checks on the superblock */ 261 if (super.magic != CRAMFS_MAGIC) { 262 /* check at 512 byte offset */ 263 mutex_lock(&read_mutex); 264 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super)); 265 mutex_unlock(&read_mutex); 266 if (super.magic != CRAMFS_MAGIC) { 267 if (!silent) 268 printk(KERN_ERR "cramfs: wrong magic\n"); 269 goto out; 270 } 271 } 272 273 /* get feature flags first */ 274 if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) { 275 printk(KERN_ERR "cramfs: unsupported filesystem features\n"); 276 goto out; 277 } 278 279 /* Check that the root inode is in a sane state */ 280 if (!S_ISDIR(super.root.mode)) { 281 printk(KERN_ERR "cramfs: root is not a directory\n"); 282 goto out; 283 } 284 root_offset = super.root.offset << 2; 285 if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) { 286 sbi->size=super.size; 287 sbi->blocks=super.fsid.blocks; 288 sbi->files=super.fsid.files; 289 } else { 290 sbi->size=1<<28; 291 sbi->blocks=0; 292 sbi->files=0; 293 } 294 sbi->magic=super.magic; 295 sbi->flags=super.flags; 296 if (root_offset == 0) 297 printk(KERN_INFO "cramfs: empty filesystem"); 298 else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) && 299 ((root_offset != sizeof(struct cramfs_super)) && 300 (root_offset != 512 + sizeof(struct cramfs_super)))) 301 { 302 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset); 303 goto out; 304 } 305 306 /* Set it all up.. */ 307 sb->s_op = &cramfs_ops; 308 root = get_cramfs_inode(sb, &super.root); 309 if (!root) 310 goto out; 311 sb->s_root = d_alloc_root(root); 312 if (!sb->s_root) { 313 iput(root); 314 goto out; 315 } 316 return 0; 317 out: 318 kfree(sbi); 319 sb->s_fs_info = NULL; 320 return -EINVAL; 321 } 322 323 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf) 324 { 325 struct super_block *sb = dentry->d_sb; 326 327 buf->f_type = CRAMFS_MAGIC; 328 buf->f_bsize = PAGE_CACHE_SIZE; 329 buf->f_blocks = CRAMFS_SB(sb)->blocks; 330 buf->f_bfree = 0; 331 buf->f_bavail = 0; 332 buf->f_files = CRAMFS_SB(sb)->files; 333 buf->f_ffree = 0; 334 buf->f_namelen = CRAMFS_MAXPATHLEN; 335 return 0; 336 } 337 338 /* 339 * Read a cramfs directory entry. 340 */ 341 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir) 342 { 343 struct inode *inode = filp->f_dentry->d_inode; 344 struct super_block *sb = inode->i_sb; 345 char *buf; 346 unsigned int offset; 347 int copied; 348 349 /* Offset within the thing. */ 350 offset = filp->f_pos; 351 if (offset >= inode->i_size) 352 return 0; 353 /* Directory entries are always 4-byte aligned */ 354 if (offset & 3) 355 return -EINVAL; 356 357 buf = kmalloc(256, GFP_KERNEL); 358 if (!buf) 359 return -ENOMEM; 360 361 copied = 0; 362 while (offset < inode->i_size) { 363 struct cramfs_inode *de; 364 unsigned long nextoffset; 365 char *name; 366 ino_t ino; 367 mode_t mode; 368 int namelen, error; 369 370 mutex_lock(&read_mutex); 371 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256); 372 name = (char *)(de+1); 373 374 /* 375 * Namelengths on disk are shifted by two 376 * and the name padded out to 4-byte boundaries 377 * with zeroes. 378 */ 379 namelen = de->namelen << 2; 380 memcpy(buf, name, namelen); 381 ino = CRAMINO(de); 382 mode = de->mode; 383 mutex_unlock(&read_mutex); 384 nextoffset = offset + sizeof(*de) + namelen; 385 for (;;) { 386 if (!namelen) { 387 kfree(buf); 388 return -EIO; 389 } 390 if (buf[namelen-1]) 391 break; 392 namelen--; 393 } 394 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12); 395 if (error) 396 break; 397 398 offset = nextoffset; 399 filp->f_pos = offset; 400 copied++; 401 } 402 kfree(buf); 403 return 0; 404 } 405 406 /* 407 * Lookup and fill in the inode data.. 408 */ 409 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) 410 { 411 unsigned int offset = 0; 412 int sorted; 413 414 mutex_lock(&read_mutex); 415 sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS; 416 while (offset < dir->i_size) { 417 struct cramfs_inode *de; 418 char *name; 419 int namelen, retval; 420 421 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256); 422 name = (char *)(de+1); 423 424 /* Try to take advantage of sorted directories */ 425 if (sorted && (dentry->d_name.name[0] < name[0])) 426 break; 427 428 namelen = de->namelen << 2; 429 offset += sizeof(*de) + namelen; 430 431 /* Quick check that the name is roughly the right length */ 432 if (((dentry->d_name.len + 3) & ~3) != namelen) 433 continue; 434 435 for (;;) { 436 if (!namelen) { 437 mutex_unlock(&read_mutex); 438 return ERR_PTR(-EIO); 439 } 440 if (name[namelen-1]) 441 break; 442 namelen--; 443 } 444 if (namelen != dentry->d_name.len) 445 continue; 446 retval = memcmp(dentry->d_name.name, name, namelen); 447 if (retval > 0) 448 continue; 449 if (!retval) { 450 struct cramfs_inode entry = *de; 451 mutex_unlock(&read_mutex); 452 d_add(dentry, get_cramfs_inode(dir->i_sb, &entry)); 453 return NULL; 454 } 455 /* else (retval < 0) */ 456 if (sorted) 457 break; 458 } 459 mutex_unlock(&read_mutex); 460 d_add(dentry, NULL); 461 return NULL; 462 } 463 464 static int cramfs_readpage(struct file *file, struct page * page) 465 { 466 struct inode *inode = page->mapping->host; 467 u32 maxblock, bytes_filled; 468 void *pgdata; 469 470 maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 471 bytes_filled = 0; 472 if (page->index < maxblock) { 473 struct super_block *sb = inode->i_sb; 474 u32 blkptr_offset = OFFSET(inode) + page->index*4; 475 u32 start_offset, compr_len; 476 477 start_offset = OFFSET(inode) + maxblock*4; 478 mutex_lock(&read_mutex); 479 if (page->index) 480 start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4); 481 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset); 482 mutex_unlock(&read_mutex); 483 pgdata = kmap(page); 484 if (compr_len == 0) 485 ; /* hole */ 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 struct inode_operations cramfs_dir_inode_operations = { 522 .lookup = cramfs_lookup, 523 }; 524 525 static 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 cramfs_uncompress_init(); 549 return register_filesystem(&cramfs_fs_type); 550 } 551 552 static void __exit exit_cramfs_fs(void) 553 { 554 cramfs_uncompress_exit(); 555 unregister_filesystem(&cramfs_fs_type); 556 } 557 558 module_init(init_cramfs_fs) 559 module_exit(exit_cramfs_fs) 560 MODULE_LICENSE("GPL"); 561