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 break; 244 } 245 246 /* next entry */ 247 offset = be32_to_cpu(ri.next) & ROMFH_MASK; 248 } 249 250 return d_splice_alias(inode, dentry); 251 error: 252 return ERR_PTR(ret); 253 } 254 255 static const struct file_operations romfs_dir_operations = { 256 .read = generic_read_dir, 257 .iterate_shared = romfs_readdir, 258 .llseek = generic_file_llseek, 259 }; 260 261 static const struct inode_operations romfs_dir_inode_operations = { 262 .lookup = romfs_lookup, 263 }; 264 265 /* 266 * get a romfs inode based on its position in the image (which doubles as the 267 * inode number) 268 */ 269 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos) 270 { 271 struct romfs_inode_info *inode; 272 struct romfs_inode ri; 273 struct inode *i; 274 unsigned long nlen; 275 unsigned nextfh; 276 int ret; 277 umode_t mode; 278 279 /* we might have to traverse a chain of "hard link" file entries to get 280 * to the actual file */ 281 for (;;) { 282 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri)); 283 if (ret < 0) 284 goto error; 285 286 /* XXX: do romfs_checksum here too (with name) */ 287 288 nextfh = be32_to_cpu(ri.next); 289 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD) 290 break; 291 292 pos = be32_to_cpu(ri.spec) & ROMFH_MASK; 293 } 294 295 /* determine the length of the filename */ 296 nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN); 297 if (IS_ERR_VALUE(nlen)) 298 goto eio; 299 300 /* get an inode for this image position */ 301 i = iget_locked(sb, pos); 302 if (!i) 303 return ERR_PTR(-ENOMEM); 304 305 if (!(i->i_state & I_NEW)) 306 return i; 307 308 /* precalculate the data offset */ 309 inode = ROMFS_I(i); 310 inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK; 311 inode->i_dataoffset = pos + inode->i_metasize; 312 313 set_nlink(i, 1); /* Hard to decide.. */ 314 i->i_size = be32_to_cpu(ri.size); 315 inode_set_mtime_to_ts(i, 316 inode_set_atime_to_ts(i, inode_set_ctime(i, 0, 0))); 317 318 /* set up mode and ops */ 319 mode = romfs_modemap[nextfh & ROMFH_TYPE]; 320 321 switch (nextfh & ROMFH_TYPE) { 322 case ROMFH_DIR: 323 i->i_size = ROMFS_I(i)->i_metasize; 324 i->i_op = &romfs_dir_inode_operations; 325 i->i_fop = &romfs_dir_operations; 326 if (nextfh & ROMFH_EXEC) 327 mode |= S_IXUGO; 328 break; 329 case ROMFH_REG: 330 i->i_fop = &romfs_ro_fops; 331 i->i_data.a_ops = &romfs_aops; 332 if (nextfh & ROMFH_EXEC) 333 mode |= S_IXUGO; 334 break; 335 case ROMFH_SYM: 336 i->i_op = &page_symlink_inode_operations; 337 inode_nohighmem(i); 338 i->i_data.a_ops = &romfs_aops; 339 mode |= S_IRWXUGO; 340 break; 341 default: 342 /* depending on MBZ for sock/fifos */ 343 nextfh = be32_to_cpu(ri.spec); 344 init_special_inode(i, mode, MKDEV(nextfh >> 16, 345 nextfh & 0xffff)); 346 break; 347 } 348 349 i->i_mode = mode; 350 i->i_blocks = (i->i_size + 511) >> 9; 351 352 unlock_new_inode(i); 353 return i; 354 355 eio: 356 ret = -EIO; 357 error: 358 pr_err("read error for inode 0x%lx\n", pos); 359 return ERR_PTR(ret); 360 } 361 362 /* 363 * allocate a new inode 364 */ 365 static struct inode *romfs_alloc_inode(struct super_block *sb) 366 { 367 struct romfs_inode_info *inode; 368 369 inode = alloc_inode_sb(sb, romfs_inode_cachep, GFP_KERNEL); 370 return inode ? &inode->vfs_inode : NULL; 371 } 372 373 /* 374 * return a spent inode to the slab cache 375 */ 376 static void romfs_free_inode(struct inode *inode) 377 { 378 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode)); 379 } 380 381 /* 382 * get filesystem statistics 383 */ 384 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf) 385 { 386 struct super_block *sb = dentry->d_sb; 387 u64 id = 0; 388 389 /* When calling huge_encode_dev(), 390 * use sb->s_bdev->bd_dev when, 391 * - CONFIG_ROMFS_ON_BLOCK defined 392 * use sb->s_dev when, 393 * - CONFIG_ROMFS_ON_BLOCK undefined and 394 * - CONFIG_ROMFS_ON_MTD defined 395 * leave id as 0 when, 396 * - CONFIG_ROMFS_ON_BLOCK undefined and 397 * - CONFIG_ROMFS_ON_MTD undefined 398 */ 399 if (sb->s_bdev) 400 id = huge_encode_dev(sb->s_bdev->bd_dev); 401 else if (sb->s_dev) 402 id = huge_encode_dev(sb->s_dev); 403 404 buf->f_type = ROMFS_MAGIC; 405 buf->f_namelen = ROMFS_MAXFN; 406 buf->f_bsize = ROMBSIZE; 407 buf->f_bfree = buf->f_bavail = buf->f_ffree; 408 buf->f_blocks = 409 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS; 410 buf->f_fsid = u64_to_fsid(id); 411 return 0; 412 } 413 414 /* 415 * remounting must involve read-only 416 */ 417 static int romfs_reconfigure(struct fs_context *fc) 418 { 419 sync_filesystem(fc->root->d_sb); 420 fc->sb_flags |= SB_RDONLY; 421 return 0; 422 } 423 424 static const struct super_operations romfs_super_ops = { 425 .alloc_inode = romfs_alloc_inode, 426 .free_inode = romfs_free_inode, 427 .statfs = romfs_statfs, 428 }; 429 430 /* 431 * checksum check on part of a romfs filesystem 432 */ 433 static __u32 romfs_checksum(const void *data, int size) 434 { 435 const __be32 *ptr = data; 436 __u32 sum; 437 438 sum = 0; 439 size >>= 2; 440 while (size > 0) { 441 sum += be32_to_cpu(*ptr++); 442 size--; 443 } 444 return sum; 445 } 446 447 /* 448 * fill in the superblock 449 */ 450 static int romfs_fill_super(struct super_block *sb, struct fs_context *fc) 451 { 452 struct romfs_super_block *rsb; 453 struct inode *root; 454 unsigned long pos, img_size; 455 const char *storage; 456 size_t len; 457 int ret; 458 459 #ifdef CONFIG_BLOCK 460 if (!sb->s_mtd) { 461 sb_set_blocksize(sb, ROMBSIZE); 462 } else { 463 sb->s_blocksize = ROMBSIZE; 464 sb->s_blocksize_bits = blksize_bits(ROMBSIZE); 465 } 466 #endif 467 468 sb->s_maxbytes = 0xFFFFFFFF; 469 sb->s_magic = ROMFS_MAGIC; 470 sb->s_flags |= SB_RDONLY | SB_NOATIME; 471 sb->s_time_min = 0; 472 sb->s_time_max = 0; 473 sb->s_op = &romfs_super_ops; 474 475 #ifdef CONFIG_ROMFS_ON_MTD 476 /* Use same dev ID from the underlying mtdblock device */ 477 if (sb->s_mtd) 478 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index); 479 #endif 480 /* read the image superblock and check it */ 481 rsb = kmalloc(512, GFP_KERNEL); 482 if (!rsb) 483 return -ENOMEM; 484 485 sb->s_fs_info = (void *) 512; 486 ret = romfs_dev_read(sb, 0, rsb, 512); 487 if (ret < 0) 488 goto error_rsb; 489 490 img_size = be32_to_cpu(rsb->size); 491 492 if (sb->s_mtd && img_size > sb->s_mtd->size) 493 goto error_rsb_inval; 494 495 sb->s_fs_info = (void *) img_size; 496 497 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 || 498 img_size < ROMFH_SIZE) { 499 if (!(fc->sb_flags & SB_SILENT)) 500 errorf(fc, "VFS: Can't find a romfs filesystem on dev %s.\n", 501 sb->s_id); 502 goto error_rsb_inval; 503 } 504 505 if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) { 506 pr_err("bad initial checksum on dev %s.\n", sb->s_id); 507 goto error_rsb_inval; 508 } 509 510 storage = sb->s_mtd ? "MTD" : "the block layer"; 511 512 len = strnlen(rsb->name, ROMFS_MAXFN); 513 if (!(fc->sb_flags & SB_SILENT)) 514 pr_notice("Mounting image '%*.*s' through %s\n", 515 (unsigned) len, (unsigned) len, rsb->name, storage); 516 517 kfree(rsb); 518 rsb = NULL; 519 520 /* find the root directory */ 521 pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK; 522 523 root = romfs_iget(sb, pos); 524 if (IS_ERR(root)) 525 return PTR_ERR(root); 526 527 sb->s_root = d_make_root(root); 528 if (!sb->s_root) 529 return -ENOMEM; 530 531 return 0; 532 533 error_rsb_inval: 534 ret = -EINVAL; 535 error_rsb: 536 kfree(rsb); 537 return ret; 538 } 539 540 /* 541 * get a superblock for mounting 542 */ 543 static int romfs_get_tree(struct fs_context *fc) 544 { 545 int ret = -EINVAL; 546 547 #ifdef CONFIG_ROMFS_ON_MTD 548 ret = get_tree_mtd(fc, romfs_fill_super); 549 #endif 550 #ifdef CONFIG_ROMFS_ON_BLOCK 551 if (ret == -EINVAL) 552 ret = get_tree_bdev(fc, romfs_fill_super); 553 #endif 554 return ret; 555 } 556 557 static const struct fs_context_operations romfs_context_ops = { 558 .get_tree = romfs_get_tree, 559 .reconfigure = romfs_reconfigure, 560 }; 561 562 /* 563 * Set up the filesystem mount context. 564 */ 565 static int romfs_init_fs_context(struct fs_context *fc) 566 { 567 fc->ops = &romfs_context_ops; 568 return 0; 569 } 570 571 /* 572 * destroy a romfs superblock in the appropriate manner 573 */ 574 static void romfs_kill_sb(struct super_block *sb) 575 { 576 generic_shutdown_super(sb); 577 578 #ifdef CONFIG_ROMFS_ON_MTD 579 if (sb->s_mtd) { 580 put_mtd_device(sb->s_mtd); 581 sb->s_mtd = NULL; 582 } 583 #endif 584 #ifdef CONFIG_ROMFS_ON_BLOCK 585 if (sb->s_bdev) { 586 sync_blockdev(sb->s_bdev); 587 bdev_fput(sb->s_bdev_file); 588 } 589 #endif 590 } 591 592 static struct file_system_type romfs_fs_type = { 593 .owner = THIS_MODULE, 594 .name = "romfs", 595 .init_fs_context = romfs_init_fs_context, 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 pr_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_ACCOUNT, 624 romfs_i_init_once); 625 626 if (!romfs_inode_cachep) { 627 pr_err("Failed to initialise inode cache\n"); 628 return -ENOMEM; 629 } 630 ret = register_filesystem(&romfs_fs_type); 631 if (ret) { 632 pr_err("Failed to register filesystem\n"); 633 goto error_register; 634 } 635 return 0; 636 637 error_register: 638 kmem_cache_destroy(romfs_inode_cachep); 639 return ret; 640 } 641 642 /* 643 * romfs module removal 644 */ 645 static void __exit exit_romfs_fs(void) 646 { 647 unregister_filesystem(&romfs_fs_type); 648 /* 649 * Make sure all delayed rcu free inodes are flushed before we 650 * destroy cache. 651 */ 652 rcu_barrier(); 653 kmem_cache_destroy(romfs_inode_cachep); 654 } 655 656 module_init(init_romfs_fs); 657 module_exit(exit_romfs_fs); 658 659 MODULE_DESCRIPTION("Direct-MTD Capable RomFS"); 660 MODULE_AUTHOR("Red Hat, Inc."); 661 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */ 662