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 read_folio 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 read_folio 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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 60 61 #include <linux/module.h> 62 #include <linux/string.h> 63 #include <linux/fs.h> 64 #include <linux/time.h> 65 #include <linux/slab.h> 66 #include <linux/init.h> 67 #include <linux/blkdev.h> 68 #include <linux/fs_context.h> 69 #include <linux/mount.h> 70 #include <linux/namei.h> 71 #include <linux/statfs.h> 72 #include <linux/mtd/super.h> 73 #include <linux/ctype.h> 74 #include <linux/highmem.h> 75 #include <linux/pagemap.h> 76 #include <linux/uaccess.h> 77 #include <linux/major.h> 78 #include "internal.h" 79 80 static struct kmem_cache *romfs_inode_cachep; 81 82 static const umode_t romfs_modemap[8] = { 83 0, /* hard link */ 84 S_IFDIR | 0644, /* directory */ 85 S_IFREG | 0644, /* regular file */ 86 S_IFLNK | 0777, /* symlink */ 87 S_IFBLK | 0600, /* blockdev */ 88 S_IFCHR | 0600, /* chardev */ 89 S_IFSOCK | 0644, /* socket */ 90 S_IFIFO | 0644 /* FIFO */ 91 }; 92 93 static const unsigned char romfs_dtype_table[] = { 94 DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO 95 }; 96 97 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos); 98 99 /* 100 * read a page worth of data from the image 101 */ 102 static int romfs_read_folio(struct file *file, struct folio *folio) 103 { 104 struct inode *inode = folio->mapping->host; 105 loff_t offset, size; 106 unsigned long fillsize, pos; 107 void *buf; 108 int ret; 109 110 buf = kmap_local_folio(folio, 0); 111 112 offset = folio_pos(folio); 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 fillsize = 0; 125 ret = -EIO; 126 } 127 } 128 129 buf = folio_zero_tail(folio, fillsize, buf + fillsize); 130 kunmap_local(buf); 131 folio_end_read(folio, ret == 0); 132 return ret; 133 } 134 135 static const struct address_space_operations romfs_aops = { 136 .read_folio = romfs_read_folio 137 }; 138 139 /* 140 * read the entries from a directory 141 */ 142 static int romfs_readdir(struct file *file, struct dir_context *ctx) 143 { 144 struct inode *i = file_inode(file); 145 struct romfs_inode ri; 146 unsigned long offset, maxoff; 147 int j, ino, nextfh; 148 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */ 149 int ret; 150 151 maxoff = romfs_maxsize(i->i_sb); 152 153 offset = ctx->pos; 154 if (!offset) { 155 offset = i->i_ino & ROMFH_MASK; 156 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE); 157 if (ret < 0) 158 goto out; 159 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 160 } 161 162 /* Not really failsafe, but we are read-only... */ 163 for (;;) { 164 if (!offset || offset >= maxoff) { 165 offset = maxoff; 166 ctx->pos = offset; 167 goto out; 168 } 169 ctx->pos = offset; 170 171 /* Fetch inode info */ 172 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE); 173 if (ret < 0) 174 goto out; 175 176 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE, 177 sizeof(fsname) - 1); 178 if (j < 0) 179 goto out; 180 181 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j); 182 if (ret < 0) 183 goto out; 184 fsname[j] = '\0'; 185 186 ino = offset; 187 nextfh = be32_to_cpu(ri.next); 188 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD) 189 ino = be32_to_cpu(ri.spec); 190 if (!dir_emit(ctx, fsname, j, ino, 191 romfs_dtype_table[nextfh & ROMFH_TYPE])) 192 goto out; 193 194 offset = nextfh & ROMFH_MASK; 195 } 196 out: 197 return 0; 198 } 199 200 /* 201 * look up an entry in a directory 202 */ 203 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry, 204 unsigned int flags) 205 { 206 unsigned long offset, maxoff; 207 struct inode *inode = NULL; 208 struct romfs_inode ri; 209 const char *name; /* got from dentry */ 210 int len, ret; 211 212 offset = dir->i_ino & ROMFH_MASK; 213 ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE); 214 if (ret < 0) 215 goto error; 216 217 /* search all the file entries in the list starting from the one 218 * pointed to by the directory's special data */ 219 maxoff = romfs_maxsize(dir->i_sb); 220 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 221 222 name = dentry->d_name.name; 223 len = dentry->d_name.len; 224 225 for (;;) { 226 if (!offset || offset >= maxoff) 227 break; 228 229 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri)); 230 if (ret < 0) 231 goto error; 232 233 /* try to match the first 16 bytes of name */ 234 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name, 235 len); 236 if (ret < 0) 237 goto error; 238 if (ret == 1) { 239 /* Hard link handling */ 240 if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD) 241 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 242 inode = romfs_iget(dir->i_sb, offset); 243 if (IS_ERR(inode)) 244 return ERR_CAST(inode); 245 break; 246 } 247 248 /* next entry */ 249 offset = be32_to_cpu(ri.next) & ROMFH_MASK; 250 } 251 252 return d_splice_alias(inode, dentry); 253 error: 254 return ERR_PTR(ret); 255 } 256 257 static const struct file_operations romfs_dir_operations = { 258 .read = generic_read_dir, 259 .iterate_shared = romfs_readdir, 260 .llseek = generic_file_llseek, 261 }; 262 263 static const struct inode_operations romfs_dir_inode_operations = { 264 .lookup = romfs_lookup, 265 }; 266 267 #define ROMFS_MAX_HARDLINK_DEPTH 64 268 269 /* 270 * get a romfs inode based on its position in the image (which doubles as the 271 * inode number) 272 */ 273 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos) 274 { 275 struct romfs_inode_info *inode; 276 struct romfs_inode ri; 277 struct inode *i; 278 unsigned long nlen; 279 unsigned nextfh; 280 unsigned int depth = 0; 281 int ret; 282 umode_t mode; 283 284 /* we might have to traverse a chain of "hard link" file entries to get 285 * to the actual file */ 286 for (;;) { 287 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri)); 288 if (ret < 0) 289 goto error; 290 291 /* XXX: do romfs_checksum here too (with name) */ 292 293 nextfh = be32_to_cpu(ri.next); 294 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD) 295 break; 296 297 if (++depth > ROMFS_MAX_HARDLINK_DEPTH) 298 return ERR_PTR(-ELOOP); 299 300 pos = be32_to_cpu(ri.spec) & ROMFH_MASK; 301 } 302 303 /* determine the length of the filename */ 304 nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN); 305 if (IS_ERR_VALUE(nlen)) 306 goto eio; 307 308 /* get an inode for this image position */ 309 i = iget_locked(sb, pos); 310 if (!i) 311 return ERR_PTR(-ENOMEM); 312 313 if (!(inode_state_read_once(i) & I_NEW)) 314 return i; 315 316 /* precalculate the data offset */ 317 inode = ROMFS_I(i); 318 inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK; 319 inode->i_dataoffset = pos + inode->i_metasize; 320 321 set_nlink(i, 1); /* Hard to decide.. */ 322 i->i_size = be32_to_cpu(ri.size); 323 inode_set_mtime_to_ts(i, 324 inode_set_atime_to_ts(i, inode_set_ctime(i, 0, 0))); 325 326 /* set up mode and ops */ 327 mode = romfs_modemap[nextfh & ROMFH_TYPE]; 328 329 switch (nextfh & ROMFH_TYPE) { 330 case ROMFH_DIR: 331 i->i_size = ROMFS_I(i)->i_metasize; 332 i->i_op = &romfs_dir_inode_operations; 333 i->i_fop = &romfs_dir_operations; 334 if (nextfh & ROMFH_EXEC) 335 mode |= S_IXUGO; 336 break; 337 case ROMFH_REG: 338 i->i_fop = &romfs_ro_fops; 339 i->i_data.a_ops = &romfs_aops; 340 if (nextfh & ROMFH_EXEC) 341 mode |= S_IXUGO; 342 break; 343 case ROMFH_SYM: 344 i->i_op = &page_symlink_inode_operations; 345 inode_nohighmem(i); 346 i->i_data.a_ops = &romfs_aops; 347 mode |= S_IRWXUGO; 348 break; 349 default: 350 /* depending on MBZ for sock/fifos */ 351 nextfh = be32_to_cpu(ri.spec); 352 init_special_inode(i, mode, MKDEV(nextfh >> 16, 353 nextfh & 0xffff)); 354 break; 355 } 356 357 i->i_mode = mode; 358 i->i_blocks = (i->i_size + 511) >> 9; 359 360 unlock_new_inode(i); 361 return i; 362 363 eio: 364 ret = -EIO; 365 error: 366 pr_err("read error for inode 0x%lx\n", pos); 367 return ERR_PTR(ret); 368 } 369 370 /* 371 * allocate a new inode 372 */ 373 static struct inode *romfs_alloc_inode(struct super_block *sb) 374 { 375 struct romfs_inode_info *inode; 376 377 inode = alloc_inode_sb(sb, romfs_inode_cachep, GFP_KERNEL); 378 return inode ? &inode->vfs_inode : NULL; 379 } 380 381 /* 382 * return a spent inode to the slab cache 383 */ 384 static void romfs_free_inode(struct inode *inode) 385 { 386 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode)); 387 } 388 389 /* 390 * get filesystem statistics 391 */ 392 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf) 393 { 394 struct super_block *sb = dentry->d_sb; 395 u64 id = 0; 396 397 /* When calling huge_encode_dev(), 398 * use sb->s_bdev->bd_dev when, 399 * - CONFIG_ROMFS_ON_BLOCK defined 400 * use sb->s_dev when, 401 * - CONFIG_ROMFS_ON_BLOCK undefined and 402 * - CONFIG_ROMFS_ON_MTD defined 403 * leave id as 0 when, 404 * - CONFIG_ROMFS_ON_BLOCK undefined and 405 * - CONFIG_ROMFS_ON_MTD undefined 406 */ 407 if (sb->s_bdev) 408 id = huge_encode_dev(sb->s_bdev->bd_dev); 409 else if (sb->s_dev) 410 id = huge_encode_dev(sb->s_dev); 411 412 buf->f_type = ROMFS_MAGIC; 413 buf->f_namelen = ROMFS_MAXFN; 414 buf->f_bsize = ROMBSIZE; 415 buf->f_bfree = buf->f_bavail = buf->f_ffree; 416 buf->f_blocks = 417 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS; 418 buf->f_fsid = u64_to_fsid(id); 419 return 0; 420 } 421 422 /* 423 * remounting must involve read-only 424 */ 425 static int romfs_reconfigure(struct fs_context *fc) 426 { 427 sync_filesystem(fc->root->d_sb); 428 fc->sb_flags |= SB_RDONLY; 429 return 0; 430 } 431 432 static const struct super_operations romfs_super_ops = { 433 .alloc_inode = romfs_alloc_inode, 434 .free_inode = romfs_free_inode, 435 .statfs = romfs_statfs, 436 }; 437 438 /* 439 * checksum check on part of a romfs filesystem 440 */ 441 static __u32 romfs_checksum(const void *data, int size) 442 { 443 const __be32 *ptr = data; 444 __u32 sum; 445 446 sum = 0; 447 size >>= 2; 448 while (size > 0) { 449 sum += be32_to_cpu(*ptr++); 450 size--; 451 } 452 return sum; 453 } 454 455 /* 456 * fill in the superblock 457 */ 458 static int romfs_fill_super(struct super_block *sb, struct fs_context *fc) 459 { 460 struct romfs_super_block *rsb; 461 struct inode *root; 462 unsigned long pos, img_size; 463 const char *storage; 464 size_t len; 465 int ret; 466 467 #ifdef CONFIG_BLOCK 468 if (!sb->s_mtd) { 469 if (!sb_set_blocksize(sb, ROMBSIZE)) { 470 errorf(fc, "romfs: unable to set blocksize\n"); 471 return -EINVAL; 472 } 473 } else { 474 sb->s_blocksize = ROMBSIZE; 475 sb->s_blocksize_bits = blksize_bits(ROMBSIZE); 476 } 477 #endif 478 479 sb->s_maxbytes = 0xFFFFFFFF; 480 sb->s_magic = ROMFS_MAGIC; 481 sb->s_flags |= SB_RDONLY | SB_NOATIME; 482 sb->s_time_min = 0; 483 sb->s_time_max = 0; 484 sb->s_op = &romfs_super_ops; 485 486 #ifdef CONFIG_ROMFS_ON_MTD 487 /* Use same dev ID from the underlying mtdblock device */ 488 if (sb->s_mtd) 489 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index); 490 #endif 491 /* read the image superblock and check it */ 492 rsb = kmalloc(512, GFP_KERNEL); 493 if (!rsb) 494 return -ENOMEM; 495 496 sb->s_fs_info = (void *) 512; 497 ret = romfs_dev_read(sb, 0, rsb, 512); 498 if (ret < 0) 499 goto error_rsb; 500 501 img_size = be32_to_cpu(rsb->size); 502 503 if (sb->s_mtd && img_size > sb->s_mtd->size) 504 goto error_rsb_inval; 505 506 sb->s_fs_info = (void *) img_size; 507 508 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 || 509 img_size < ROMFH_SIZE) { 510 if (!(fc->sb_flags & SB_SILENT)) 511 errorf(fc, "VFS: Can't find a romfs filesystem on dev %s.\n", 512 sb->s_id); 513 goto error_rsb_inval; 514 } 515 516 if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) { 517 pr_err("bad initial checksum on dev %s.\n", 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 (!(fc->sb_flags & SB_SILENT)) 525 pr_notice("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 return PTR_ERR(root); 537 538 sb->s_root = d_make_root(root); 539 if (!sb->s_root) 540 return -ENOMEM; 541 542 return 0; 543 544 error_rsb_inval: 545 ret = -EINVAL; 546 error_rsb: 547 kfree(rsb); 548 return ret; 549 } 550 551 /* 552 * get a superblock for mounting 553 */ 554 static int romfs_get_tree(struct fs_context *fc) 555 { 556 int ret = -EINVAL; 557 558 #ifdef CONFIG_ROMFS_ON_MTD 559 ret = get_tree_mtd(fc, romfs_fill_super); 560 #endif 561 #ifdef CONFIG_ROMFS_ON_BLOCK 562 if (ret == -EINVAL) 563 ret = get_tree_bdev(fc, romfs_fill_super); 564 #endif 565 return ret; 566 } 567 568 static const struct fs_context_operations romfs_context_ops = { 569 .get_tree = romfs_get_tree, 570 .reconfigure = romfs_reconfigure, 571 }; 572 573 /* 574 * Set up the filesystem mount context. 575 */ 576 static int romfs_init_fs_context(struct fs_context *fc) 577 { 578 fc->ops = &romfs_context_ops; 579 return 0; 580 } 581 582 /* 583 * destroy a romfs superblock in the appropriate manner 584 */ 585 static void romfs_kill_sb(struct super_block *sb) 586 { 587 generic_shutdown_super(sb); 588 589 #ifdef CONFIG_ROMFS_ON_MTD 590 if (sb->s_mtd) { 591 put_mtd_device(sb->s_mtd); 592 sb->s_mtd = NULL; 593 } 594 #endif 595 #ifdef CONFIG_ROMFS_ON_BLOCK 596 if (sb->s_bdev) { 597 sync_blockdev(sb->s_bdev); 598 fs_bdev_file_release(sb->s_bdev_file, sb); 599 } 600 #endif 601 } 602 603 static struct file_system_type romfs_fs_type = { 604 .owner = THIS_MODULE, 605 .name = "romfs", 606 .init_fs_context = romfs_init_fs_context, 607 .kill_sb = romfs_kill_sb, 608 .fs_flags = FS_REQUIRES_DEV, 609 }; 610 MODULE_ALIAS_FS("romfs"); 611 612 /* 613 * inode storage initialiser 614 */ 615 static void romfs_i_init_once(void *_inode) 616 { 617 struct romfs_inode_info *inode = _inode; 618 619 inode_init_once(&inode->vfs_inode); 620 } 621 622 /* 623 * romfs module initialisation 624 */ 625 static int __init init_romfs_fs(void) 626 { 627 int ret; 628 629 pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n"); 630 631 romfs_inode_cachep = 632 kmem_cache_create("romfs_i", 633 sizeof(struct romfs_inode_info), 0, 634 SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT, 635 romfs_i_init_once); 636 637 if (!romfs_inode_cachep) { 638 pr_err("Failed to initialise inode cache\n"); 639 return -ENOMEM; 640 } 641 ret = register_filesystem(&romfs_fs_type); 642 if (ret) { 643 pr_err("Failed to register filesystem\n"); 644 goto error_register; 645 } 646 return 0; 647 648 error_register: 649 kmem_cache_destroy(romfs_inode_cachep); 650 return ret; 651 } 652 653 /* 654 * romfs module removal 655 */ 656 static void __exit exit_romfs_fs(void) 657 { 658 unregister_filesystem(&romfs_fs_type); 659 /* 660 * Make sure all delayed rcu free inodes are flushed before we 661 * destroy cache. 662 */ 663 rcu_barrier(); 664 kmem_cache_destroy(romfs_inode_cachep); 665 } 666 667 module_init(init_romfs_fs); 668 module_exit(exit_romfs_fs); 669 670 MODULE_DESCRIPTION("Direct-MTD Capable RomFS"); 671 MODULE_AUTHOR("Red Hat, Inc."); 672 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */ 673