1 /* Block- or MTD-based romfs 2 * 3 * Copyright © 2007 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells (dhowells@redhat.com) 5 * 6 * Derived from: ROMFS file system, Linux implementation 7 * 8 * Copyright © 1997-1999 Janos Farkas <chexum@shadow.banki.hu> 9 * 10 * Using parts of the minix filesystem 11 * Copyright © 1991, 1992 Linus Torvalds 12 * 13 * and parts of the affs filesystem additionally 14 * Copyright © 1993 Ray Burr 15 * Copyright © 1996 Hans-Joachim Widmaier 16 * 17 * Changes 18 * Changed for 2.1.19 modules 19 * Jan 1997 Initial release 20 * Jun 1997 2.1.43+ changes 21 * Proper page locking in readpage 22 * Changed to work with 2.1.45+ fs 23 * Jul 1997 Fixed follow_link 24 * 2.1.47 25 * lookup shouldn't return -ENOENT 26 * from Horst von Brand: 27 * fail on wrong checksum 28 * double unlock_super was possible 29 * correct namelen for statfs 30 * spotted by Bill Hawes: 31 * readlink shouldn't iput() 32 * Jun 1998 2.1.106 from Avery Pennarun: glibc scandir() 33 * exposed a problem in readdir 34 * 2.1.107 code-freeze spellchecker run 35 * Aug 1998 2.1.118+ VFS changes 36 * Sep 1998 2.1.122 another VFS change (follow_link) 37 * Apr 1999 2.2.7 no more EBADF checking in 38 * lookup/readdir, use ERR_PTR 39 * Jun 1999 2.3.6 d_alloc_root use changed 40 * 2.3.9 clean up usage of ENOENT/negative 41 * dentries in lookup 42 * clean up page flags setting 43 * (error, uptodate, locking) in 44 * in readpage 45 * use init_special_inode for 46 * fifos/sockets (and streamline) in 47 * read_inode, fix _ops table order 48 * Aug 1999 2.3.16 __initfunc() => __init change 49 * Oct 1999 2.3.24 page->owner hack obsoleted 50 * Nov 1999 2.3.27 2.3.25+ page->offset => index change 51 * 52 * 53 * This program is free software; you can redistribute it and/or 54 * modify it under the terms of the GNU General Public Licence 55 * as published by the Free Software Foundation; either version 56 * 2 of the Licence, or (at your option) any later version. 57 */ 58 59 #include <linux/module.h> 60 #include <linux/string.h> 61 #include <linux/fs.h> 62 #include <linux/time.h> 63 #include <linux/slab.h> 64 #include <linux/init.h> 65 #include <linux/blkdev.h> 66 #include <linux/parser.h> 67 #include <linux/mount.h> 68 #include <linux/namei.h> 69 #include <linux/statfs.h> 70 #include <linux/mtd/super.h> 71 #include <linux/ctype.h> 72 #include <linux/highmem.h> 73 #include <linux/pagemap.h> 74 #include <linux/uaccess.h> 75 #include "internal.h" 76 77 static struct kmem_cache *romfs_inode_cachep; 78 79 static const umode_t romfs_modemap[8] = { 80 0, /* hard link */ 81 S_IFDIR | 0644, /* directory */ 82 S_IFREG | 0644, /* regular file */ 83 S_IFLNK | 0777, /* symlink */ 84 S_IFBLK | 0600, /* blockdev */ 85 S_IFCHR | 0600, /* chardev */ 86 S_IFSOCK | 0644, /* socket */ 87 S_IFIFO | 0644 /* FIFO */ 88 }; 89 90 static const unsigned char romfs_dtype_table[] = { 91 DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO 92 }; 93 94 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos); 95 96 /* 97 * read a page worth of data from the image 98 */ 99 static int romfs_readpage(struct file *file, struct page *page) 100 { 101 struct inode *inode = page->mapping->host; 102 loff_t offset, size; 103 unsigned long fillsize, pos; 104 void *buf; 105 int ret; 106 107 buf = kmap(page); 108 if (!buf) 109 return -ENOMEM; 110 111 /* 32 bit warning -- but not for us :) */ 112 offset = page_offset(page); 113 size = i_size_read(inode); 114 fillsize = 0; 115 ret = 0; 116 if (offset < size) { 117 size -= offset; 118 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size; 119 120 pos = ROMFS_I(inode)->i_dataoffset + offset; 121 122 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize); 123 if (ret < 0) { 124 SetPageError(page); 125 fillsize = 0; 126 ret = -EIO; 127 } 128 } 129 130 if (fillsize < PAGE_SIZE) 131 memset(buf + fillsize, 0, PAGE_SIZE - fillsize); 132 if (ret == 0) 133 SetPageUptodate(page); 134 135 flush_dcache_page(page); 136 kunmap(page); 137 unlock_page(page); 138 return ret; 139 } 140 141 static const struct address_space_operations romfs_aops = { 142 .readpage = romfs_readpage 143 }; 144 145 /* 146 * read the entries from a directory 147 */ 148 static int romfs_readdir(struct file *file, struct dir_context *ctx) 149 { 150 struct inode *i = file_inode(file); 151 struct romfs_inode ri; 152 unsigned long offset, maxoff; 153 int j, ino, nextfh; 154 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */ 155 int ret; 156 157 maxoff = romfs_maxsize(i->i_sb); 158 159 offset = ctx->pos; 160 if (!offset) { 161 offset = i->i_ino & ROMFH_MASK; 162 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE); 163 if (ret < 0) 164 goto out; 165 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 166 } 167 168 /* Not really failsafe, but we are read-only... */ 169 for (;;) { 170 if (!offset || offset >= maxoff) { 171 offset = maxoff; 172 ctx->pos = offset; 173 goto out; 174 } 175 ctx->pos = offset; 176 177 /* Fetch inode info */ 178 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE); 179 if (ret < 0) 180 goto out; 181 182 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE, 183 sizeof(fsname) - 1); 184 if (j < 0) 185 goto out; 186 187 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j); 188 if (ret < 0) 189 goto out; 190 fsname[j] = '\0'; 191 192 ino = offset; 193 nextfh = be32_to_cpu(ri.next); 194 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD) 195 ino = be32_to_cpu(ri.spec); 196 if (!dir_emit(ctx, fsname, j, ino, 197 romfs_dtype_table[nextfh & ROMFH_TYPE])) 198 goto out; 199 200 offset = nextfh & ROMFH_MASK; 201 } 202 out: 203 return 0; 204 } 205 206 /* 207 * look up an entry in a directory 208 */ 209 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry, 210 unsigned int flags) 211 { 212 unsigned long offset, maxoff; 213 struct inode *inode; 214 struct romfs_inode ri; 215 const char *name; /* got from dentry */ 216 int len, ret; 217 218 offset = dir->i_ino & ROMFH_MASK; 219 ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE); 220 if (ret < 0) 221 goto error; 222 223 /* search all the file entries in the list starting from the one 224 * pointed to by the directory's special data */ 225 maxoff = romfs_maxsize(dir->i_sb); 226 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 227 228 name = dentry->d_name.name; 229 len = dentry->d_name.len; 230 231 for (;;) { 232 if (!offset || offset >= maxoff) 233 goto out0; 234 235 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri)); 236 if (ret < 0) 237 goto error; 238 239 /* try to match the first 16 bytes of name */ 240 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name, 241 len); 242 if (ret < 0) 243 goto error; 244 if (ret == 1) 245 break; 246 247 /* next entry */ 248 offset = be32_to_cpu(ri.next) & ROMFH_MASK; 249 } 250 251 /* Hard link handling */ 252 if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD) 253 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 254 255 inode = romfs_iget(dir->i_sb, offset); 256 if (IS_ERR(inode)) { 257 ret = PTR_ERR(inode); 258 goto error; 259 } 260 goto outi; 261 262 /* 263 * it's a bit funky, _lookup needs to return an error code 264 * (negative) or a NULL, both as a dentry. ENOENT should not 265 * be returned, instead we need to create a negative dentry by 266 * d_add(dentry, NULL); and return 0 as no error. 267 * (Although as I see, it only matters on writable file 268 * systems). 269 */ 270 out0: 271 inode = NULL; 272 outi: 273 d_add(dentry, inode); 274 ret = 0; 275 error: 276 return ERR_PTR(ret); 277 } 278 279 static const struct file_operations romfs_dir_operations = { 280 .read = generic_read_dir, 281 .iterate = romfs_readdir, 282 .llseek = default_llseek, 283 }; 284 285 static const struct inode_operations romfs_dir_inode_operations = { 286 .lookup = romfs_lookup, 287 }; 288 289 /* 290 * get a romfs inode based on its position in the image (which doubles as the 291 * inode number) 292 */ 293 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos) 294 { 295 struct romfs_inode_info *inode; 296 struct romfs_inode ri; 297 struct inode *i; 298 unsigned long nlen; 299 unsigned nextfh; 300 int ret; 301 umode_t mode; 302 303 /* we might have to traverse a chain of "hard link" file entries to get 304 * to the actual file */ 305 for (;;) { 306 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri)); 307 if (ret < 0) 308 goto error; 309 310 /* XXX: do romfs_checksum here too (with name) */ 311 312 nextfh = be32_to_cpu(ri.next); 313 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD) 314 break; 315 316 pos = be32_to_cpu(ri.spec) & ROMFH_MASK; 317 } 318 319 /* determine the length of the filename */ 320 nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN); 321 if (IS_ERR_VALUE(nlen)) 322 goto eio; 323 324 /* get an inode for this image position */ 325 i = iget_locked(sb, pos); 326 if (!i) 327 return ERR_PTR(-ENOMEM); 328 329 if (!(i->i_state & I_NEW)) 330 return i; 331 332 /* precalculate the data offset */ 333 inode = ROMFS_I(i); 334 inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK; 335 inode->i_dataoffset = pos + inode->i_metasize; 336 337 set_nlink(i, 1); /* Hard to decide.. */ 338 i->i_size = be32_to_cpu(ri.size); 339 i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0; 340 i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0; 341 342 /* set up mode and ops */ 343 mode = romfs_modemap[nextfh & ROMFH_TYPE]; 344 345 switch (nextfh & ROMFH_TYPE) { 346 case ROMFH_DIR: 347 i->i_size = ROMFS_I(i)->i_metasize; 348 i->i_op = &romfs_dir_inode_operations; 349 i->i_fop = &romfs_dir_operations; 350 if (nextfh & ROMFH_EXEC) 351 mode |= S_IXUGO; 352 break; 353 case ROMFH_REG: 354 i->i_fop = &romfs_ro_fops; 355 i->i_data.a_ops = &romfs_aops; 356 if (i->i_sb->s_mtd) 357 i->i_data.backing_dev_info = 358 i->i_sb->s_mtd->backing_dev_info; 359 if (nextfh & ROMFH_EXEC) 360 mode |= S_IXUGO; 361 break; 362 case ROMFH_SYM: 363 i->i_op = &page_symlink_inode_operations; 364 i->i_data.a_ops = &romfs_aops; 365 mode |= S_IRWXUGO; 366 break; 367 default: 368 /* depending on MBZ for sock/fifos */ 369 nextfh = be32_to_cpu(ri.spec); 370 init_special_inode(i, mode, MKDEV(nextfh >> 16, 371 nextfh & 0xffff)); 372 break; 373 } 374 375 i->i_mode = mode; 376 377 unlock_new_inode(i); 378 return i; 379 380 eio: 381 ret = -EIO; 382 error: 383 printk(KERN_ERR "ROMFS: read error for inode 0x%lx\n", pos); 384 return ERR_PTR(ret); 385 } 386 387 /* 388 * allocate a new inode 389 */ 390 static struct inode *romfs_alloc_inode(struct super_block *sb) 391 { 392 struct romfs_inode_info *inode; 393 inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL); 394 return inode ? &inode->vfs_inode : NULL; 395 } 396 397 /* 398 * return a spent inode to the slab cache 399 */ 400 static void romfs_i_callback(struct rcu_head *head) 401 { 402 struct inode *inode = container_of(head, struct inode, i_rcu); 403 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode)); 404 } 405 406 static void romfs_destroy_inode(struct inode *inode) 407 { 408 call_rcu(&inode->i_rcu, romfs_i_callback); 409 } 410 411 /* 412 * get filesystem statistics 413 */ 414 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf) 415 { 416 struct super_block *sb = dentry->d_sb; 417 u64 id = huge_encode_dev(sb->s_bdev->bd_dev); 418 419 buf->f_type = ROMFS_MAGIC; 420 buf->f_namelen = ROMFS_MAXFN; 421 buf->f_bsize = ROMBSIZE; 422 buf->f_bfree = buf->f_bavail = buf->f_ffree; 423 buf->f_blocks = 424 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS; 425 buf->f_fsid.val[0] = (u32)id; 426 buf->f_fsid.val[1] = (u32)(id >> 32); 427 return 0; 428 } 429 430 /* 431 * remounting must involve read-only 432 */ 433 static int romfs_remount(struct super_block *sb, int *flags, char *data) 434 { 435 *flags |= MS_RDONLY; 436 return 0; 437 } 438 439 static const struct super_operations romfs_super_ops = { 440 .alloc_inode = romfs_alloc_inode, 441 .destroy_inode = romfs_destroy_inode, 442 .statfs = romfs_statfs, 443 .remount_fs = romfs_remount, 444 }; 445 446 /* 447 * checksum check on part of a romfs filesystem 448 */ 449 static __u32 romfs_checksum(const void *data, int size) 450 { 451 const __be32 *ptr = data; 452 __u32 sum; 453 454 sum = 0; 455 size >>= 2; 456 while (size > 0) { 457 sum += be32_to_cpu(*ptr++); 458 size--; 459 } 460 return sum; 461 } 462 463 /* 464 * fill in the superblock 465 */ 466 static int romfs_fill_super(struct super_block *sb, void *data, int silent) 467 { 468 struct romfs_super_block *rsb; 469 struct inode *root; 470 unsigned long pos, img_size; 471 const char *storage; 472 size_t len; 473 int ret; 474 475 #ifdef CONFIG_BLOCK 476 if (!sb->s_mtd) { 477 sb_set_blocksize(sb, ROMBSIZE); 478 } else { 479 sb->s_blocksize = ROMBSIZE; 480 sb->s_blocksize_bits = blksize_bits(ROMBSIZE); 481 } 482 #endif 483 484 sb->s_maxbytes = 0xFFFFFFFF; 485 sb->s_magic = ROMFS_MAGIC; 486 sb->s_flags |= MS_RDONLY | MS_NOATIME; 487 sb->s_op = &romfs_super_ops; 488 489 /* read the image superblock and check it */ 490 rsb = kmalloc(512, GFP_KERNEL); 491 if (!rsb) 492 return -ENOMEM; 493 494 sb->s_fs_info = (void *) 512; 495 ret = romfs_dev_read(sb, 0, rsb, 512); 496 if (ret < 0) 497 goto error_rsb; 498 499 img_size = be32_to_cpu(rsb->size); 500 501 if (sb->s_mtd && img_size > sb->s_mtd->size) 502 goto error_rsb_inval; 503 504 sb->s_fs_info = (void *) img_size; 505 506 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 || 507 img_size < ROMFH_SIZE) { 508 if (!silent) 509 printk(KERN_WARNING "VFS:" 510 " Can't find a romfs filesystem on dev %s.\n", 511 sb->s_id); 512 goto error_rsb_inval; 513 } 514 515 if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) { 516 printk(KERN_ERR "ROMFS: bad initial checksum on dev %s.\n", 517 sb->s_id); 518 goto error_rsb_inval; 519 } 520 521 storage = sb->s_mtd ? "MTD" : "the block layer"; 522 523 len = strnlen(rsb->name, ROMFS_MAXFN); 524 if (!silent) 525 printk(KERN_NOTICE "ROMFS: Mounting image '%*.*s' through %s\n", 526 (unsigned) len, (unsigned) len, rsb->name, storage); 527 528 kfree(rsb); 529 rsb = NULL; 530 531 /* find the root directory */ 532 pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK; 533 534 root = romfs_iget(sb, pos); 535 if (IS_ERR(root)) 536 goto error; 537 538 sb->s_root = d_make_root(root); 539 if (!sb->s_root) 540 goto error; 541 542 return 0; 543 544 error: 545 return -EINVAL; 546 error_rsb_inval: 547 ret = -EINVAL; 548 error_rsb: 549 kfree(rsb); 550 return ret; 551 } 552 553 /* 554 * get a superblock for mounting 555 */ 556 static struct dentry *romfs_mount(struct file_system_type *fs_type, 557 int flags, const char *dev_name, 558 void *data) 559 { 560 struct dentry *ret = ERR_PTR(-EINVAL); 561 562 #ifdef CONFIG_ROMFS_ON_MTD 563 ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super); 564 #endif 565 #ifdef CONFIG_ROMFS_ON_BLOCK 566 if (ret == ERR_PTR(-EINVAL)) 567 ret = mount_bdev(fs_type, flags, dev_name, data, 568 romfs_fill_super); 569 #endif 570 return ret; 571 } 572 573 /* 574 * destroy a romfs superblock in the appropriate manner 575 */ 576 static void romfs_kill_sb(struct super_block *sb) 577 { 578 #ifdef CONFIG_ROMFS_ON_MTD 579 if (sb->s_mtd) { 580 kill_mtd_super(sb); 581 return; 582 } 583 #endif 584 #ifdef CONFIG_ROMFS_ON_BLOCK 585 if (sb->s_bdev) { 586 kill_block_super(sb); 587 return; 588 } 589 #endif 590 } 591 592 static struct file_system_type romfs_fs_type = { 593 .owner = THIS_MODULE, 594 .name = "romfs", 595 .mount = romfs_mount, 596 .kill_sb = romfs_kill_sb, 597 .fs_flags = FS_REQUIRES_DEV, 598 }; 599 MODULE_ALIAS_FS("romfs"); 600 601 /* 602 * inode storage initialiser 603 */ 604 static void romfs_i_init_once(void *_inode) 605 { 606 struct romfs_inode_info *inode = _inode; 607 608 inode_init_once(&inode->vfs_inode); 609 } 610 611 /* 612 * romfs module initialisation 613 */ 614 static int __init init_romfs_fs(void) 615 { 616 int ret; 617 618 printk(KERN_INFO "ROMFS MTD (C) 2007 Red Hat, Inc.\n"); 619 620 romfs_inode_cachep = 621 kmem_cache_create("romfs_i", 622 sizeof(struct romfs_inode_info), 0, 623 SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, 624 romfs_i_init_once); 625 626 if (!romfs_inode_cachep) { 627 printk(KERN_ERR 628 "ROMFS error: Failed to initialise inode cache\n"); 629 return -ENOMEM; 630 } 631 ret = register_filesystem(&romfs_fs_type); 632 if (ret) { 633 printk(KERN_ERR "ROMFS error: Failed to register filesystem\n"); 634 goto error_register; 635 } 636 return 0; 637 638 error_register: 639 kmem_cache_destroy(romfs_inode_cachep); 640 return ret; 641 } 642 643 /* 644 * romfs module removal 645 */ 646 static void __exit exit_romfs_fs(void) 647 { 648 unregister_filesystem(&romfs_fs_type); 649 /* 650 * Make sure all delayed rcu free inodes are flushed before we 651 * destroy cache. 652 */ 653 rcu_barrier(); 654 kmem_cache_destroy(romfs_inode_cachep); 655 } 656 657 module_init(init_romfs_fs); 658 module_exit(exit_romfs_fs); 659 660 MODULE_DESCRIPTION("Direct-MTD Capable RomFS"); 661 MODULE_AUTHOR("Red Hat, Inc."); 662 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */ 663