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 page *page = &folio->page; 105 struct inode *inode = page->mapping->host; 106 loff_t offset, size; 107 unsigned long fillsize, pos; 108 void *buf; 109 int ret; 110 111 buf = kmap(page); 112 if (!buf) 113 return -ENOMEM; 114 115 /* 32 bit warning -- but not for us :) */ 116 offset = page_offset(page); 117 size = i_size_read(inode); 118 fillsize = 0; 119 ret = 0; 120 if (offset < size) { 121 size -= offset; 122 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size; 123 124 pos = ROMFS_I(inode)->i_dataoffset + offset; 125 126 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize); 127 if (ret < 0) { 128 SetPageError(page); 129 fillsize = 0; 130 ret = -EIO; 131 } 132 } 133 134 if (fillsize < PAGE_SIZE) 135 memset(buf + fillsize, 0, PAGE_SIZE - fillsize); 136 if (ret == 0) 137 SetPageUptodate(page); 138 139 flush_dcache_page(page); 140 kunmap(page); 141 unlock_page(page); 142 return ret; 143 } 144 145 static const struct address_space_operations romfs_aops = { 146 .read_folio = romfs_read_folio 147 }; 148 149 /* 150 * read the entries from a directory 151 */ 152 static int romfs_readdir(struct file *file, struct dir_context *ctx) 153 { 154 struct inode *i = file_inode(file); 155 struct romfs_inode ri; 156 unsigned long offset, maxoff; 157 int j, ino, nextfh; 158 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */ 159 int ret; 160 161 maxoff = romfs_maxsize(i->i_sb); 162 163 offset = ctx->pos; 164 if (!offset) { 165 offset = i->i_ino & ROMFH_MASK; 166 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE); 167 if (ret < 0) 168 goto out; 169 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 170 } 171 172 /* Not really failsafe, but we are read-only... */ 173 for (;;) { 174 if (!offset || offset >= maxoff) { 175 offset = maxoff; 176 ctx->pos = offset; 177 goto out; 178 } 179 ctx->pos = offset; 180 181 /* Fetch inode info */ 182 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE); 183 if (ret < 0) 184 goto out; 185 186 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE, 187 sizeof(fsname) - 1); 188 if (j < 0) 189 goto out; 190 191 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j); 192 if (ret < 0) 193 goto out; 194 fsname[j] = '\0'; 195 196 ino = offset; 197 nextfh = be32_to_cpu(ri.next); 198 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD) 199 ino = be32_to_cpu(ri.spec); 200 if (!dir_emit(ctx, fsname, j, ino, 201 romfs_dtype_table[nextfh & ROMFH_TYPE])) 202 goto out; 203 204 offset = nextfh & ROMFH_MASK; 205 } 206 out: 207 return 0; 208 } 209 210 /* 211 * look up an entry in a directory 212 */ 213 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry, 214 unsigned int flags) 215 { 216 unsigned long offset, maxoff; 217 struct inode *inode = NULL; 218 struct romfs_inode ri; 219 const char *name; /* got from dentry */ 220 int len, ret; 221 222 offset = dir->i_ino & ROMFH_MASK; 223 ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE); 224 if (ret < 0) 225 goto error; 226 227 /* search all the file entries in the list starting from the one 228 * pointed to by the directory's special data */ 229 maxoff = romfs_maxsize(dir->i_sb); 230 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 231 232 name = dentry->d_name.name; 233 len = dentry->d_name.len; 234 235 for (;;) { 236 if (!offset || offset >= maxoff) 237 break; 238 239 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri)); 240 if (ret < 0) 241 goto error; 242 243 /* try to match the first 16 bytes of name */ 244 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name, 245 len); 246 if (ret < 0) 247 goto error; 248 if (ret == 1) { 249 /* Hard link handling */ 250 if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD) 251 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 252 inode = romfs_iget(dir->i_sb, offset); 253 break; 254 } 255 256 /* next entry */ 257 offset = be32_to_cpu(ri.next) & ROMFH_MASK; 258 } 259 260 return d_splice_alias(inode, dentry); 261 error: 262 return ERR_PTR(ret); 263 } 264 265 static const struct file_operations romfs_dir_operations = { 266 .read = generic_read_dir, 267 .iterate_shared = romfs_readdir, 268 .llseek = generic_file_llseek, 269 }; 270 271 static const struct inode_operations romfs_dir_inode_operations = { 272 .lookup = romfs_lookup, 273 }; 274 275 /* 276 * get a romfs inode based on its position in the image (which doubles as the 277 * inode number) 278 */ 279 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos) 280 { 281 struct romfs_inode_info *inode; 282 struct romfs_inode ri; 283 struct inode *i; 284 unsigned long nlen; 285 unsigned nextfh; 286 int ret; 287 umode_t mode; 288 289 /* we might have to traverse a chain of "hard link" file entries to get 290 * to the actual file */ 291 for (;;) { 292 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri)); 293 if (ret < 0) 294 goto error; 295 296 /* XXX: do romfs_checksum here too (with name) */ 297 298 nextfh = be32_to_cpu(ri.next); 299 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD) 300 break; 301 302 pos = be32_to_cpu(ri.spec) & ROMFH_MASK; 303 } 304 305 /* determine the length of the filename */ 306 nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN); 307 if (IS_ERR_VALUE(nlen)) 308 goto eio; 309 310 /* get an inode for this image position */ 311 i = iget_locked(sb, pos); 312 if (!i) 313 return ERR_PTR(-ENOMEM); 314 315 if (!(i->i_state & I_NEW)) 316 return i; 317 318 /* precalculate the data offset */ 319 inode = ROMFS_I(i); 320 inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK; 321 inode->i_dataoffset = pos + inode->i_metasize; 322 323 set_nlink(i, 1); /* Hard to decide.. */ 324 i->i_size = be32_to_cpu(ri.size); 325 i->i_mtime = i->i_atime = inode_set_ctime(i, 0, 0); 326 327 /* set up mode and ops */ 328 mode = romfs_modemap[nextfh & ROMFH_TYPE]; 329 330 switch (nextfh & ROMFH_TYPE) { 331 case ROMFH_DIR: 332 i->i_size = ROMFS_I(i)->i_metasize; 333 i->i_op = &romfs_dir_inode_operations; 334 i->i_fop = &romfs_dir_operations; 335 if (nextfh & ROMFH_EXEC) 336 mode |= S_IXUGO; 337 break; 338 case ROMFH_REG: 339 i->i_fop = &romfs_ro_fops; 340 i->i_data.a_ops = &romfs_aops; 341 if (nextfh & ROMFH_EXEC) 342 mode |= S_IXUGO; 343 break; 344 case ROMFH_SYM: 345 i->i_op = &page_symlink_inode_operations; 346 inode_nohighmem(i); 347 i->i_data.a_ops = &romfs_aops; 348 mode |= S_IRWXUGO; 349 break; 350 default: 351 /* depending on MBZ for sock/fifos */ 352 nextfh = be32_to_cpu(ri.spec); 353 init_special_inode(i, mode, MKDEV(nextfh >> 16, 354 nextfh & 0xffff)); 355 break; 356 } 357 358 i->i_mode = mode; 359 i->i_blocks = (i->i_size + 511) >> 9; 360 361 unlock_new_inode(i); 362 return i; 363 364 eio: 365 ret = -EIO; 366 error: 367 pr_err("read error for inode 0x%lx\n", pos); 368 return ERR_PTR(ret); 369 } 370 371 /* 372 * allocate a new inode 373 */ 374 static struct inode *romfs_alloc_inode(struct super_block *sb) 375 { 376 struct romfs_inode_info *inode; 377 378 inode = alloc_inode_sb(sb, romfs_inode_cachep, GFP_KERNEL); 379 return inode ? &inode->vfs_inode : NULL; 380 } 381 382 /* 383 * return a spent inode to the slab cache 384 */ 385 static void romfs_free_inode(struct inode *inode) 386 { 387 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode)); 388 } 389 390 /* 391 * get filesystem statistics 392 */ 393 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf) 394 { 395 struct super_block *sb = dentry->d_sb; 396 u64 id = 0; 397 398 /* When calling huge_encode_dev(), 399 * use sb->s_bdev->bd_dev when, 400 * - CONFIG_ROMFS_ON_BLOCK defined 401 * use sb->s_dev when, 402 * - CONFIG_ROMFS_ON_BLOCK undefined and 403 * - CONFIG_ROMFS_ON_MTD defined 404 * leave id as 0 when, 405 * - CONFIG_ROMFS_ON_BLOCK undefined and 406 * - CONFIG_ROMFS_ON_MTD undefined 407 */ 408 if (sb->s_bdev) 409 id = huge_encode_dev(sb->s_bdev->bd_dev); 410 else if (sb->s_dev) 411 id = huge_encode_dev(sb->s_dev); 412 413 buf->f_type = ROMFS_MAGIC; 414 buf->f_namelen = ROMFS_MAXFN; 415 buf->f_bsize = ROMBSIZE; 416 buf->f_bfree = buf->f_bavail = buf->f_ffree; 417 buf->f_blocks = 418 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS; 419 buf->f_fsid = u64_to_fsid(id); 420 return 0; 421 } 422 423 /* 424 * remounting must involve read-only 425 */ 426 static int romfs_reconfigure(struct fs_context *fc) 427 { 428 sync_filesystem(fc->root->d_sb); 429 fc->sb_flags |= SB_RDONLY; 430 return 0; 431 } 432 433 static const struct super_operations romfs_super_ops = { 434 .alloc_inode = romfs_alloc_inode, 435 .free_inode = romfs_free_inode, 436 .statfs = romfs_statfs, 437 }; 438 439 /* 440 * checksum check on part of a romfs filesystem 441 */ 442 static __u32 romfs_checksum(const void *data, int size) 443 { 444 const __be32 *ptr = data; 445 __u32 sum; 446 447 sum = 0; 448 size >>= 2; 449 while (size > 0) { 450 sum += be32_to_cpu(*ptr++); 451 size--; 452 } 453 return sum; 454 } 455 456 /* 457 * fill in the superblock 458 */ 459 static int romfs_fill_super(struct super_block *sb, struct fs_context *fc) 460 { 461 struct romfs_super_block *rsb; 462 struct inode *root; 463 unsigned long pos, img_size; 464 const char *storage; 465 size_t len; 466 int ret; 467 468 #ifdef CONFIG_BLOCK 469 if (!sb->s_mtd) { 470 sb_set_blocksize(sb, ROMBSIZE); 471 } else { 472 sb->s_blocksize = ROMBSIZE; 473 sb->s_blocksize_bits = blksize_bits(ROMBSIZE); 474 } 475 #endif 476 477 sb->s_maxbytes = 0xFFFFFFFF; 478 sb->s_magic = ROMFS_MAGIC; 479 sb->s_flags |= SB_RDONLY | SB_NOATIME; 480 sb->s_time_min = 0; 481 sb->s_time_max = 0; 482 sb->s_op = &romfs_super_ops; 483 484 #ifdef CONFIG_ROMFS_ON_MTD 485 /* Use same dev ID from the underlying mtdblock device */ 486 if (sb->s_mtd) 487 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index); 488 #endif 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 (!(fc->sb_flags & SB_SILENT)) 509 errorf(fc, "VFS: Can't find a romfs filesystem on dev %s.\n", 510 sb->s_id); 511 goto error_rsb_inval; 512 } 513 514 if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) { 515 pr_err("bad initial checksum on dev %s.\n", sb->s_id); 516 goto error_rsb_inval; 517 } 518 519 storage = sb->s_mtd ? "MTD" : "the block layer"; 520 521 len = strnlen(rsb->name, ROMFS_MAXFN); 522 if (!(fc->sb_flags & SB_SILENT)) 523 pr_notice("Mounting image '%*.*s' through %s\n", 524 (unsigned) len, (unsigned) len, rsb->name, storage); 525 526 kfree(rsb); 527 rsb = NULL; 528 529 /* find the root directory */ 530 pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK; 531 532 root = romfs_iget(sb, pos); 533 if (IS_ERR(root)) 534 return PTR_ERR(root); 535 536 sb->s_root = d_make_root(root); 537 if (!sb->s_root) 538 return -ENOMEM; 539 540 return 0; 541 542 error_rsb_inval: 543 ret = -EINVAL; 544 error_rsb: 545 kfree(rsb); 546 return ret; 547 } 548 549 /* 550 * get a superblock for mounting 551 */ 552 static int romfs_get_tree(struct fs_context *fc) 553 { 554 int ret = -EINVAL; 555 556 #ifdef CONFIG_ROMFS_ON_MTD 557 ret = get_tree_mtd(fc, romfs_fill_super); 558 #endif 559 #ifdef CONFIG_ROMFS_ON_BLOCK 560 if (ret == -EINVAL) 561 ret = get_tree_bdev(fc, romfs_fill_super); 562 #endif 563 return ret; 564 } 565 566 static const struct fs_context_operations romfs_context_ops = { 567 .get_tree = romfs_get_tree, 568 .reconfigure = romfs_reconfigure, 569 }; 570 571 /* 572 * Set up the filesystem mount context. 573 */ 574 static int romfs_init_fs_context(struct fs_context *fc) 575 { 576 fc->ops = &romfs_context_ops; 577 return 0; 578 } 579 580 /* 581 * destroy a romfs superblock in the appropriate manner 582 */ 583 static void romfs_kill_sb(struct super_block *sb) 584 { 585 generic_shutdown_super(sb); 586 587 #ifdef CONFIG_ROMFS_ON_MTD 588 if (sb->s_mtd) { 589 put_mtd_device(sb->s_mtd); 590 sb->s_mtd = NULL; 591 } 592 #endif 593 #ifdef CONFIG_ROMFS_ON_BLOCK 594 if (sb->s_bdev) { 595 sync_blockdev(sb->s_bdev); 596 blkdev_put(sb->s_bdev, sb); 597 } 598 #endif 599 } 600 601 static struct file_system_type romfs_fs_type = { 602 .owner = THIS_MODULE, 603 .name = "romfs", 604 .init_fs_context = romfs_init_fs_context, 605 .kill_sb = romfs_kill_sb, 606 .fs_flags = FS_REQUIRES_DEV, 607 }; 608 MODULE_ALIAS_FS("romfs"); 609 610 /* 611 * inode storage initialiser 612 */ 613 static void romfs_i_init_once(void *_inode) 614 { 615 struct romfs_inode_info *inode = _inode; 616 617 inode_init_once(&inode->vfs_inode); 618 } 619 620 /* 621 * romfs module initialisation 622 */ 623 static int __init init_romfs_fs(void) 624 { 625 int ret; 626 627 pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n"); 628 629 romfs_inode_cachep = 630 kmem_cache_create("romfs_i", 631 sizeof(struct romfs_inode_info), 0, 632 SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD | 633 SLAB_ACCOUNT, romfs_i_init_once); 634 635 if (!romfs_inode_cachep) { 636 pr_err("Failed to initialise inode cache\n"); 637 return -ENOMEM; 638 } 639 ret = register_filesystem(&romfs_fs_type); 640 if (ret) { 641 pr_err("Failed to register filesystem\n"); 642 goto error_register; 643 } 644 return 0; 645 646 error_register: 647 kmem_cache_destroy(romfs_inode_cachep); 648 return ret; 649 } 650 651 /* 652 * romfs module removal 653 */ 654 static void __exit exit_romfs_fs(void) 655 { 656 unregister_filesystem(&romfs_fs_type); 657 /* 658 * Make sure all delayed rcu free inodes are flushed before we 659 * destroy cache. 660 */ 661 rcu_barrier(); 662 kmem_cache_destroy(romfs_inode_cachep); 663 } 664 665 module_init(init_romfs_fs); 666 module_exit(exit_romfs_fs); 667 668 MODULE_DESCRIPTION("Direct-MTD Capable RomFS"); 669 MODULE_AUTHOR("Red Hat, Inc."); 670 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */ 671