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 <asm/semaphore.h> 26 27 #include <asm/uaccess.h> 28 29 static struct super_operations cramfs_ops; 30 static struct inode_operations cramfs_dir_inode_operations; 31 static struct file_operations cramfs_directory_operations; 32 static struct address_space_operations cramfs_aops; 33 34 static DECLARE_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_blksize = PAGE_CACHE_SIZE; 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_cache_page(mapping, blocknr + i, 184 (filler_t *)mapping->a_ops->readpage, 185 NULL); 186 /* synchronous error? */ 187 if (IS_ERR(page)) 188 page = NULL; 189 } 190 pages[i] = page; 191 } 192 193 for (i = 0; i < BLKS_PER_BUF; i++) { 194 struct page *page = pages[i]; 195 if (page) { 196 wait_on_page_locked(page); 197 if (!PageUptodate(page)) { 198 /* asynchronous error */ 199 page_cache_release(page); 200 pages[i] = NULL; 201 } 202 } 203 } 204 205 buffer = next_buffer; 206 next_buffer = NEXT_BUFFER(buffer); 207 buffer_blocknr[buffer] = blocknr; 208 buffer_dev[buffer] = sb; 209 210 data = read_buffers[buffer]; 211 for (i = 0; i < BLKS_PER_BUF; i++) { 212 struct page *page = pages[i]; 213 if (page) { 214 memcpy(data, kmap(page), PAGE_CACHE_SIZE); 215 kunmap(page); 216 page_cache_release(page); 217 } else 218 memset(data, 0, PAGE_CACHE_SIZE); 219 data += PAGE_CACHE_SIZE; 220 } 221 return read_buffers[buffer] + offset; 222 } 223 224 static void cramfs_put_super(struct super_block *sb) 225 { 226 kfree(sb->s_fs_info); 227 sb->s_fs_info = NULL; 228 } 229 230 static int cramfs_remount(struct super_block *sb, int *flags, char *data) 231 { 232 *flags |= MS_RDONLY; 233 return 0; 234 } 235 236 static int cramfs_fill_super(struct super_block *sb, void *data, int silent) 237 { 238 int i; 239 struct cramfs_super super; 240 unsigned long root_offset; 241 struct cramfs_sb_info *sbi; 242 struct inode *root; 243 244 sb->s_flags |= MS_RDONLY; 245 246 sbi = kmalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL); 247 if (!sbi) 248 return -ENOMEM; 249 sb->s_fs_info = sbi; 250 memset(sbi, 0, sizeof(struct cramfs_sb_info)); 251 252 /* Invalidate the read buffers on mount: think disk change.. */ 253 down(&read_mutex); 254 for (i = 0; i < READ_BUFFERS; i++) 255 buffer_blocknr[i] = -1; 256 257 /* Read the first block and get the superblock from it */ 258 memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super)); 259 up(&read_mutex); 260 261 /* Do sanity checks on the superblock */ 262 if (super.magic != CRAMFS_MAGIC) { 263 /* check at 512 byte offset */ 264 down(&read_mutex); 265 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super)); 266 up(&read_mutex); 267 if (super.magic != CRAMFS_MAGIC) { 268 if (!silent) 269 printk(KERN_ERR "cramfs: wrong magic\n"); 270 goto out; 271 } 272 } 273 274 /* get feature flags first */ 275 if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) { 276 printk(KERN_ERR "cramfs: unsupported filesystem features\n"); 277 goto out; 278 } 279 280 /* Check that the root inode is in a sane state */ 281 if (!S_ISDIR(super.root.mode)) { 282 printk(KERN_ERR "cramfs: root is not a directory\n"); 283 goto out; 284 } 285 root_offset = super.root.offset << 2; 286 if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) { 287 sbi->size=super.size; 288 sbi->blocks=super.fsid.blocks; 289 sbi->files=super.fsid.files; 290 } else { 291 sbi->size=1<<28; 292 sbi->blocks=0; 293 sbi->files=0; 294 } 295 sbi->magic=super.magic; 296 sbi->flags=super.flags; 297 if (root_offset == 0) 298 printk(KERN_INFO "cramfs: empty filesystem"); 299 else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) && 300 ((root_offset != sizeof(struct cramfs_super)) && 301 (root_offset != 512 + sizeof(struct cramfs_super)))) 302 { 303 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset); 304 goto out; 305 } 306 307 /* Set it all up.. */ 308 sb->s_op = &cramfs_ops; 309 root = get_cramfs_inode(sb, &super.root); 310 if (!root) 311 goto out; 312 sb->s_root = d_alloc_root(root); 313 if (!sb->s_root) { 314 iput(root); 315 goto out; 316 } 317 return 0; 318 out: 319 kfree(sbi); 320 sb->s_fs_info = NULL; 321 return -EINVAL; 322 } 323 324 static int cramfs_statfs(struct super_block *sb, struct kstatfs *buf) 325 { 326 buf->f_type = CRAMFS_MAGIC; 327 buf->f_bsize = PAGE_CACHE_SIZE; 328 buf->f_blocks = CRAMFS_SB(sb)->blocks; 329 buf->f_bfree = 0; 330 buf->f_bavail = 0; 331 buf->f_files = CRAMFS_SB(sb)->files; 332 buf->f_ffree = 0; 333 buf->f_namelen = CRAMFS_MAXPATHLEN; 334 return 0; 335 } 336 337 /* 338 * Read a cramfs directory entry. 339 */ 340 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir) 341 { 342 struct inode *inode = filp->f_dentry->d_inode; 343 struct super_block *sb = inode->i_sb; 344 char *buf; 345 unsigned int offset; 346 int copied; 347 348 /* Offset within the thing. */ 349 offset = filp->f_pos; 350 if (offset >= inode->i_size) 351 return 0; 352 /* Directory entries are always 4-byte aligned */ 353 if (offset & 3) 354 return -EINVAL; 355 356 buf = kmalloc(256, GFP_KERNEL); 357 if (!buf) 358 return -ENOMEM; 359 360 copied = 0; 361 while (offset < inode->i_size) { 362 struct cramfs_inode *de; 363 unsigned long nextoffset; 364 char *name; 365 ino_t ino; 366 mode_t mode; 367 int namelen, error; 368 369 down(&read_mutex); 370 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256); 371 name = (char *)(de+1); 372 373 /* 374 * Namelengths on disk are shifted by two 375 * and the name padded out to 4-byte boundaries 376 * with zeroes. 377 */ 378 namelen = de->namelen << 2; 379 memcpy(buf, name, namelen); 380 ino = CRAMINO(de); 381 mode = de->mode; 382 up(&read_mutex); 383 nextoffset = offset + sizeof(*de) + namelen; 384 for (;;) { 385 if (!namelen) { 386 kfree(buf); 387 return -EIO; 388 } 389 if (buf[namelen-1]) 390 break; 391 namelen--; 392 } 393 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12); 394 if (error) 395 break; 396 397 offset = nextoffset; 398 filp->f_pos = offset; 399 copied++; 400 } 401 kfree(buf); 402 return 0; 403 } 404 405 /* 406 * Lookup and fill in the inode data.. 407 */ 408 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) 409 { 410 unsigned int offset = 0; 411 int sorted; 412 413 down(&read_mutex); 414 sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS; 415 while (offset < dir->i_size) { 416 struct cramfs_inode *de; 417 char *name; 418 int namelen, retval; 419 420 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256); 421 name = (char *)(de+1); 422 423 /* Try to take advantage of sorted directories */ 424 if (sorted && (dentry->d_name.name[0] < name[0])) 425 break; 426 427 namelen = de->namelen << 2; 428 offset += sizeof(*de) + namelen; 429 430 /* Quick check that the name is roughly the right length */ 431 if (((dentry->d_name.len + 3) & ~3) != namelen) 432 continue; 433 434 for (;;) { 435 if (!namelen) { 436 up(&read_mutex); 437 return ERR_PTR(-EIO); 438 } 439 if (name[namelen-1]) 440 break; 441 namelen--; 442 } 443 if (namelen != dentry->d_name.len) 444 continue; 445 retval = memcmp(dentry->d_name.name, name, namelen); 446 if (retval > 0) 447 continue; 448 if (!retval) { 449 struct cramfs_inode entry = *de; 450 up(&read_mutex); 451 d_add(dentry, get_cramfs_inode(dir->i_sb, &entry)); 452 return NULL; 453 } 454 /* else (retval < 0) */ 455 if (sorted) 456 break; 457 } 458 up(&read_mutex); 459 d_add(dentry, NULL); 460 return NULL; 461 } 462 463 static int cramfs_readpage(struct file *file, struct page * page) 464 { 465 struct inode *inode = page->mapping->host; 466 u32 maxblock, bytes_filled; 467 void *pgdata; 468 469 maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; 470 bytes_filled = 0; 471 if (page->index < maxblock) { 472 struct super_block *sb = inode->i_sb; 473 u32 blkptr_offset = OFFSET(inode) + page->index*4; 474 u32 start_offset, compr_len; 475 476 start_offset = OFFSET(inode) + maxblock*4; 477 down(&read_mutex); 478 if (page->index) 479 start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4); 480 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset); 481 up(&read_mutex); 482 pgdata = kmap(page); 483 if (compr_len == 0) 484 ; /* hole */ 485 else { 486 down(&read_mutex); 487 bytes_filled = cramfs_uncompress_block(pgdata, 488 PAGE_CACHE_SIZE, 489 cramfs_read(sb, start_offset, compr_len), 490 compr_len); 491 up(&read_mutex); 492 } 493 } else 494 pgdata = kmap(page); 495 memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled); 496 kunmap(page); 497 flush_dcache_page(page); 498 SetPageUptodate(page); 499 unlock_page(page); 500 return 0; 501 } 502 503 static struct address_space_operations cramfs_aops = { 504 .readpage = cramfs_readpage 505 }; 506 507 /* 508 * Our operations: 509 */ 510 511 /* 512 * A directory can only readdir 513 */ 514 static struct file_operations cramfs_directory_operations = { 515 .llseek = generic_file_llseek, 516 .read = generic_read_dir, 517 .readdir = cramfs_readdir, 518 }; 519 520 static struct inode_operations cramfs_dir_inode_operations = { 521 .lookup = cramfs_lookup, 522 }; 523 524 static struct super_operations cramfs_ops = { 525 .put_super = cramfs_put_super, 526 .remount_fs = cramfs_remount, 527 .statfs = cramfs_statfs, 528 }; 529 530 static struct super_block *cramfs_get_sb(struct file_system_type *fs_type, 531 int flags, const char *dev_name, void *data) 532 { 533 return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super); 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 cramfs_uncompress_init(); 547 return register_filesystem(&cramfs_fs_type); 548 } 549 550 static void __exit exit_cramfs_fs(void) 551 { 552 cramfs_uncompress_exit(); 553 unregister_filesystem(&cramfs_fs_type); 554 } 555 556 module_init(init_cramfs_fs) 557 module_exit(exit_cramfs_fs) 558 MODULE_LICENSE("GPL"); 559