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.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0; 326 i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0; 327 328 /* set up mode and ops */ 329 mode = romfs_modemap[nextfh & ROMFH_TYPE]; 330 331 switch (nextfh & ROMFH_TYPE) { 332 case ROMFH_DIR: 333 i->i_size = ROMFS_I(i)->i_metasize; 334 i->i_op = &romfs_dir_inode_operations; 335 i->i_fop = &romfs_dir_operations; 336 if (nextfh & ROMFH_EXEC) 337 mode |= S_IXUGO; 338 break; 339 case ROMFH_REG: 340 i->i_fop = &romfs_ro_fops; 341 i->i_data.a_ops = &romfs_aops; 342 if (nextfh & ROMFH_EXEC) 343 mode |= S_IXUGO; 344 break; 345 case ROMFH_SYM: 346 i->i_op = &page_symlink_inode_operations; 347 inode_nohighmem(i); 348 i->i_data.a_ops = &romfs_aops; 349 mode |= S_IRWXUGO; 350 break; 351 default: 352 /* depending on MBZ for sock/fifos */ 353 nextfh = be32_to_cpu(ri.spec); 354 init_special_inode(i, mode, MKDEV(nextfh >> 16, 355 nextfh & 0xffff)); 356 break; 357 } 358 359 i->i_mode = mode; 360 i->i_blocks = (i->i_size + 511) >> 9; 361 362 unlock_new_inode(i); 363 return i; 364 365 eio: 366 ret = -EIO; 367 error: 368 pr_err("read error for inode 0x%lx\n", pos); 369 return ERR_PTR(ret); 370 } 371 372 /* 373 * allocate a new inode 374 */ 375 static struct inode *romfs_alloc_inode(struct super_block *sb) 376 { 377 struct romfs_inode_info *inode; 378 379 inode = alloc_inode_sb(sb, romfs_inode_cachep, GFP_KERNEL); 380 return inode ? &inode->vfs_inode : NULL; 381 } 382 383 /* 384 * return a spent inode to the slab cache 385 */ 386 static void romfs_free_inode(struct inode *inode) 387 { 388 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode)); 389 } 390 391 /* 392 * get filesystem statistics 393 */ 394 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf) 395 { 396 struct super_block *sb = dentry->d_sb; 397 u64 id = 0; 398 399 /* When calling huge_encode_dev(), 400 * use sb->s_bdev->bd_dev when, 401 * - CONFIG_ROMFS_ON_BLOCK defined 402 * use sb->s_dev when, 403 * - CONFIG_ROMFS_ON_BLOCK undefined and 404 * - CONFIG_ROMFS_ON_MTD defined 405 * leave id as 0 when, 406 * - CONFIG_ROMFS_ON_BLOCK undefined and 407 * - CONFIG_ROMFS_ON_MTD undefined 408 */ 409 if (sb->s_bdev) 410 id = huge_encode_dev(sb->s_bdev->bd_dev); 411 else if (sb->s_dev) 412 id = huge_encode_dev(sb->s_dev); 413 414 buf->f_type = ROMFS_MAGIC; 415 buf->f_namelen = ROMFS_MAXFN; 416 buf->f_bsize = ROMBSIZE; 417 buf->f_bfree = buf->f_bavail = buf->f_ffree; 418 buf->f_blocks = 419 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS; 420 buf->f_fsid = u64_to_fsid(id); 421 return 0; 422 } 423 424 /* 425 * remounting must involve read-only 426 */ 427 static int romfs_reconfigure(struct fs_context *fc) 428 { 429 sync_filesystem(fc->root->d_sb); 430 fc->sb_flags |= SB_RDONLY; 431 return 0; 432 } 433 434 static const struct super_operations romfs_super_ops = { 435 .alloc_inode = romfs_alloc_inode, 436 .free_inode = romfs_free_inode, 437 .statfs = romfs_statfs, 438 }; 439 440 /* 441 * checksum check on part of a romfs filesystem 442 */ 443 static __u32 romfs_checksum(const void *data, int size) 444 { 445 const __be32 *ptr = data; 446 __u32 sum; 447 448 sum = 0; 449 size >>= 2; 450 while (size > 0) { 451 sum += be32_to_cpu(*ptr++); 452 size--; 453 } 454 return sum; 455 } 456 457 /* 458 * fill in the superblock 459 */ 460 static int romfs_fill_super(struct super_block *sb, struct fs_context *fc) 461 { 462 struct romfs_super_block *rsb; 463 struct inode *root; 464 unsigned long pos, img_size; 465 const char *storage; 466 size_t len; 467 int ret; 468 469 #ifdef CONFIG_BLOCK 470 if (!sb->s_mtd) { 471 sb_set_blocksize(sb, ROMBSIZE); 472 } else { 473 sb->s_blocksize = ROMBSIZE; 474 sb->s_blocksize_bits = blksize_bits(ROMBSIZE); 475 } 476 #endif 477 478 sb->s_maxbytes = 0xFFFFFFFF; 479 sb->s_magic = ROMFS_MAGIC; 480 sb->s_flags |= SB_RDONLY | SB_NOATIME; 481 sb->s_time_min = 0; 482 sb->s_time_max = 0; 483 sb->s_op = &romfs_super_ops; 484 485 #ifdef CONFIG_ROMFS_ON_MTD 486 /* Use same dev ID from the underlying mtdblock device */ 487 if (sb->s_mtd) 488 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index); 489 #endif 490 /* read the image superblock and check it */ 491 rsb = kmalloc(512, GFP_KERNEL); 492 if (!rsb) 493 return -ENOMEM; 494 495 sb->s_fs_info = (void *) 512; 496 ret = romfs_dev_read(sb, 0, rsb, 512); 497 if (ret < 0) 498 goto error_rsb; 499 500 img_size = be32_to_cpu(rsb->size); 501 502 if (sb->s_mtd && img_size > sb->s_mtd->size) 503 goto error_rsb_inval; 504 505 sb->s_fs_info = (void *) img_size; 506 507 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 || 508 img_size < ROMFH_SIZE) { 509 if (!(fc->sb_flags & SB_SILENT)) 510 errorf(fc, "VFS: 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 pr_err("bad initial checksum on dev %s.\n", sb->s_id); 517 goto error_rsb_inval; 518 } 519 520 storage = sb->s_mtd ? "MTD" : "the block layer"; 521 522 len = strnlen(rsb->name, ROMFS_MAXFN); 523 if (!(fc->sb_flags & SB_SILENT)) 524 pr_notice("Mounting image '%*.*s' through %s\n", 525 (unsigned) len, (unsigned) len, rsb->name, storage); 526 527 kfree(rsb); 528 rsb = NULL; 529 530 /* find the root directory */ 531 pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK; 532 533 root = romfs_iget(sb, pos); 534 if (IS_ERR(root)) 535 return PTR_ERR(root); 536 537 sb->s_root = d_make_root(root); 538 if (!sb->s_root) 539 return -ENOMEM; 540 541 return 0; 542 543 error_rsb_inval: 544 ret = -EINVAL; 545 error_rsb: 546 kfree(rsb); 547 return ret; 548 } 549 550 /* 551 * get a superblock for mounting 552 */ 553 static int romfs_get_tree(struct fs_context *fc) 554 { 555 int ret = -EINVAL; 556 557 #ifdef CONFIG_ROMFS_ON_MTD 558 ret = get_tree_mtd(fc, romfs_fill_super); 559 #endif 560 #ifdef CONFIG_ROMFS_ON_BLOCK 561 if (ret == -EINVAL) 562 ret = get_tree_bdev(fc, romfs_fill_super); 563 #endif 564 return ret; 565 } 566 567 static const struct fs_context_operations romfs_context_ops = { 568 .get_tree = romfs_get_tree, 569 .reconfigure = romfs_reconfigure, 570 }; 571 572 /* 573 * Set up the filesystem mount context. 574 */ 575 static int romfs_init_fs_context(struct fs_context *fc) 576 { 577 fc->ops = &romfs_context_ops; 578 return 0; 579 } 580 581 /* 582 * destroy a romfs superblock in the appropriate manner 583 */ 584 static void romfs_kill_sb(struct super_block *sb) 585 { 586 #ifdef CONFIG_ROMFS_ON_MTD 587 if (sb->s_mtd) { 588 kill_mtd_super(sb); 589 return; 590 } 591 #endif 592 #ifdef CONFIG_ROMFS_ON_BLOCK 593 if (sb->s_bdev) { 594 kill_block_super(sb); 595 return; 596 } 597 #endif 598 } 599 600 static struct file_system_type romfs_fs_type = { 601 .owner = THIS_MODULE, 602 .name = "romfs", 603 .init_fs_context = romfs_init_fs_context, 604 .kill_sb = romfs_kill_sb, 605 .fs_flags = FS_REQUIRES_DEV, 606 }; 607 MODULE_ALIAS_FS("romfs"); 608 609 /* 610 * inode storage initialiser 611 */ 612 static void romfs_i_init_once(void *_inode) 613 { 614 struct romfs_inode_info *inode = _inode; 615 616 inode_init_once(&inode->vfs_inode); 617 } 618 619 /* 620 * romfs module initialisation 621 */ 622 static int __init init_romfs_fs(void) 623 { 624 int ret; 625 626 pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n"); 627 628 romfs_inode_cachep = 629 kmem_cache_create("romfs_i", 630 sizeof(struct romfs_inode_info), 0, 631 SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD | 632 SLAB_ACCOUNT, romfs_i_init_once); 633 634 if (!romfs_inode_cachep) { 635 pr_err("Failed to initialise inode cache\n"); 636 return -ENOMEM; 637 } 638 ret = register_filesystem(&romfs_fs_type); 639 if (ret) { 640 pr_err("Failed to register filesystem\n"); 641 goto error_register; 642 } 643 return 0; 644 645 error_register: 646 kmem_cache_destroy(romfs_inode_cachep); 647 return ret; 648 } 649 650 /* 651 * romfs module removal 652 */ 653 static void __exit exit_romfs_fs(void) 654 { 655 unregister_filesystem(&romfs_fs_type); 656 /* 657 * Make sure all delayed rcu free inodes are flushed before we 658 * destroy cache. 659 */ 660 rcu_barrier(); 661 kmem_cache_destroy(romfs_inode_cachep); 662 } 663 664 module_init(init_romfs_fs); 665 module_exit(exit_romfs_fs); 666 667 MODULE_DESCRIPTION("Direct-MTD Capable RomFS"); 668 MODULE_AUTHOR("Red Hat, Inc."); 669 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */ 670