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 #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/parser.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_readpage(struct file *file, struct page *page) 103 { 104 struct inode *inode = page->mapping->host; 105 loff_t offset, size; 106 unsigned long fillsize, pos; 107 void *buf; 108 int ret; 109 110 buf = kmap(page); 111 if (!buf) 112 return -ENOMEM; 113 114 /* 32 bit warning -- but not for us :) */ 115 offset = page_offset(page); 116 size = i_size_read(inode); 117 fillsize = 0; 118 ret = 0; 119 if (offset < size) { 120 size -= offset; 121 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size; 122 123 pos = ROMFS_I(inode)->i_dataoffset + offset; 124 125 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize); 126 if (ret < 0) { 127 SetPageError(page); 128 fillsize = 0; 129 ret = -EIO; 130 } 131 } 132 133 if (fillsize < PAGE_SIZE) 134 memset(buf + fillsize, 0, PAGE_SIZE - fillsize); 135 if (ret == 0) 136 SetPageUptodate(page); 137 138 flush_dcache_page(page); 139 kunmap(page); 140 unlock_page(page); 141 return ret; 142 } 143 144 static const struct address_space_operations romfs_aops = { 145 .readpage = romfs_readpage 146 }; 147 148 /* 149 * read the entries from a directory 150 */ 151 static int romfs_readdir(struct file *file, struct dir_context *ctx) 152 { 153 struct inode *i = file_inode(file); 154 struct romfs_inode ri; 155 unsigned long offset, maxoff; 156 int j, ino, nextfh; 157 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */ 158 int ret; 159 160 maxoff = romfs_maxsize(i->i_sb); 161 162 offset = ctx->pos; 163 if (!offset) { 164 offset = i->i_ino & ROMFH_MASK; 165 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE); 166 if (ret < 0) 167 goto out; 168 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 169 } 170 171 /* Not really failsafe, but we are read-only... */ 172 for (;;) { 173 if (!offset || offset >= maxoff) { 174 offset = maxoff; 175 ctx->pos = offset; 176 goto out; 177 } 178 ctx->pos = offset; 179 180 /* Fetch inode info */ 181 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE); 182 if (ret < 0) 183 goto out; 184 185 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE, 186 sizeof(fsname) - 1); 187 if (j < 0) 188 goto out; 189 190 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j); 191 if (ret < 0) 192 goto out; 193 fsname[j] = '\0'; 194 195 ino = offset; 196 nextfh = be32_to_cpu(ri.next); 197 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD) 198 ino = be32_to_cpu(ri.spec); 199 if (!dir_emit(ctx, fsname, j, ino, 200 romfs_dtype_table[nextfh & ROMFH_TYPE])) 201 goto out; 202 203 offset = nextfh & ROMFH_MASK; 204 } 205 out: 206 return 0; 207 } 208 209 /* 210 * look up an entry in a directory 211 */ 212 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry, 213 unsigned int flags) 214 { 215 unsigned long offset, maxoff; 216 struct inode *inode; 217 struct romfs_inode ri; 218 const char *name; /* got from dentry */ 219 int len, ret; 220 221 offset = dir->i_ino & ROMFH_MASK; 222 ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE); 223 if (ret < 0) 224 goto error; 225 226 /* search all the file entries in the list starting from the one 227 * pointed to by the directory's special data */ 228 maxoff = romfs_maxsize(dir->i_sb); 229 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 230 231 name = dentry->d_name.name; 232 len = dentry->d_name.len; 233 234 for (;;) { 235 if (!offset || offset >= maxoff) 236 goto out0; 237 238 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri)); 239 if (ret < 0) 240 goto error; 241 242 /* try to match the first 16 bytes of name */ 243 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name, 244 len); 245 if (ret < 0) 246 goto error; 247 if (ret == 1) 248 break; 249 250 /* next entry */ 251 offset = be32_to_cpu(ri.next) & ROMFH_MASK; 252 } 253 254 /* Hard link handling */ 255 if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD) 256 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 257 258 inode = romfs_iget(dir->i_sb, offset); 259 if (IS_ERR(inode)) { 260 ret = PTR_ERR(inode); 261 goto error; 262 } 263 goto outi; 264 265 /* 266 * it's a bit funky, _lookup needs to return an error code 267 * (negative) or a NULL, both as a dentry. ENOENT should not 268 * be returned, instead we need to create a negative dentry by 269 * d_add(dentry, NULL); and return 0 as no error. 270 * (Although as I see, it only matters on writable file 271 * systems). 272 */ 273 out0: 274 inode = NULL; 275 outi: 276 d_add(dentry, inode); 277 ret = 0; 278 error: 279 return ERR_PTR(ret); 280 } 281 282 static const struct file_operations romfs_dir_operations = { 283 .read = generic_read_dir, 284 .iterate_shared = romfs_readdir, 285 .llseek = generic_file_llseek, 286 }; 287 288 static const struct inode_operations romfs_dir_inode_operations = { 289 .lookup = romfs_lookup, 290 }; 291 292 /* 293 * get a romfs inode based on its position in the image (which doubles as the 294 * inode number) 295 */ 296 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos) 297 { 298 struct romfs_inode_info *inode; 299 struct romfs_inode ri; 300 struct inode *i; 301 unsigned long nlen; 302 unsigned nextfh; 303 int ret; 304 umode_t mode; 305 306 /* we might have to traverse a chain of "hard link" file entries to get 307 * to the actual file */ 308 for (;;) { 309 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri)); 310 if (ret < 0) 311 goto error; 312 313 /* XXX: do romfs_checksum here too (with name) */ 314 315 nextfh = be32_to_cpu(ri.next); 316 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD) 317 break; 318 319 pos = be32_to_cpu(ri.spec) & ROMFH_MASK; 320 } 321 322 /* determine the length of the filename */ 323 nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN); 324 if (IS_ERR_VALUE(nlen)) 325 goto eio; 326 327 /* get an inode for this image position */ 328 i = iget_locked(sb, pos); 329 if (!i) 330 return ERR_PTR(-ENOMEM); 331 332 if (!(i->i_state & I_NEW)) 333 return i; 334 335 /* precalculate the data offset */ 336 inode = ROMFS_I(i); 337 inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK; 338 inode->i_dataoffset = pos + inode->i_metasize; 339 340 set_nlink(i, 1); /* Hard to decide.. */ 341 i->i_size = be32_to_cpu(ri.size); 342 i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0; 343 i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0; 344 345 /* set up mode and ops */ 346 mode = romfs_modemap[nextfh & ROMFH_TYPE]; 347 348 switch (nextfh & ROMFH_TYPE) { 349 case ROMFH_DIR: 350 i->i_size = ROMFS_I(i)->i_metasize; 351 i->i_op = &romfs_dir_inode_operations; 352 i->i_fop = &romfs_dir_operations; 353 if (nextfh & ROMFH_EXEC) 354 mode |= S_IXUGO; 355 break; 356 case ROMFH_REG: 357 i->i_fop = &romfs_ro_fops; 358 i->i_data.a_ops = &romfs_aops; 359 if (nextfh & ROMFH_EXEC) 360 mode |= S_IXUGO; 361 break; 362 case ROMFH_SYM: 363 i->i_op = &page_symlink_inode_operations; 364 inode_nohighmem(i); 365 i->i_data.a_ops = &romfs_aops; 366 mode |= S_IRWXUGO; 367 break; 368 default: 369 /* depending on MBZ for sock/fifos */ 370 nextfh = be32_to_cpu(ri.spec); 371 init_special_inode(i, mode, MKDEV(nextfh >> 16, 372 nextfh & 0xffff)); 373 break; 374 } 375 376 i->i_mode = mode; 377 378 unlock_new_inode(i); 379 return i; 380 381 eio: 382 ret = -EIO; 383 error: 384 pr_err("read error for inode 0x%lx\n", pos); 385 return ERR_PTR(ret); 386 } 387 388 /* 389 * allocate a new inode 390 */ 391 static struct inode *romfs_alloc_inode(struct super_block *sb) 392 { 393 struct romfs_inode_info *inode; 394 395 inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL); 396 return inode ? &inode->vfs_inode : NULL; 397 } 398 399 /* 400 * return a spent inode to the slab cache 401 */ 402 static void romfs_i_callback(struct rcu_head *head) 403 { 404 struct inode *inode = container_of(head, struct inode, i_rcu); 405 406 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode)); 407 } 408 409 static void romfs_destroy_inode(struct inode *inode) 410 { 411 call_rcu(&inode->i_rcu, romfs_i_callback); 412 } 413 414 /* 415 * get filesystem statistics 416 */ 417 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf) 418 { 419 struct super_block *sb = dentry->d_sb; 420 u64 id = 0; 421 422 /* When calling huge_encode_dev(), 423 * use sb->s_bdev->bd_dev when, 424 * - CONFIG_ROMFS_ON_BLOCK defined 425 * use sb->s_dev when, 426 * - CONFIG_ROMFS_ON_BLOCK undefined and 427 * - CONFIG_ROMFS_ON_MTD defined 428 * leave id as 0 when, 429 * - CONFIG_ROMFS_ON_BLOCK undefined and 430 * - CONFIG_ROMFS_ON_MTD undefined 431 */ 432 if (sb->s_bdev) 433 id = huge_encode_dev(sb->s_bdev->bd_dev); 434 else if (sb->s_dev) 435 id = huge_encode_dev(sb->s_dev); 436 437 buf->f_type = ROMFS_MAGIC; 438 buf->f_namelen = ROMFS_MAXFN; 439 buf->f_bsize = ROMBSIZE; 440 buf->f_bfree = buf->f_bavail = buf->f_ffree; 441 buf->f_blocks = 442 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS; 443 buf->f_fsid.val[0] = (u32)id; 444 buf->f_fsid.val[1] = (u32)(id >> 32); 445 return 0; 446 } 447 448 /* 449 * remounting must involve read-only 450 */ 451 static int romfs_remount(struct super_block *sb, int *flags, char *data) 452 { 453 sync_filesystem(sb); 454 *flags |= MS_RDONLY; 455 return 0; 456 } 457 458 static const struct super_operations romfs_super_ops = { 459 .alloc_inode = romfs_alloc_inode, 460 .destroy_inode = romfs_destroy_inode, 461 .statfs = romfs_statfs, 462 .remount_fs = romfs_remount, 463 }; 464 465 /* 466 * checksum check on part of a romfs filesystem 467 */ 468 static __u32 romfs_checksum(const void *data, int size) 469 { 470 const __be32 *ptr = data; 471 __u32 sum; 472 473 sum = 0; 474 size >>= 2; 475 while (size > 0) { 476 sum += be32_to_cpu(*ptr++); 477 size--; 478 } 479 return sum; 480 } 481 482 /* 483 * fill in the superblock 484 */ 485 static int romfs_fill_super(struct super_block *sb, void *data, int silent) 486 { 487 struct romfs_super_block *rsb; 488 struct inode *root; 489 unsigned long pos, img_size; 490 const char *storage; 491 size_t len; 492 int ret; 493 494 #ifdef CONFIG_BLOCK 495 if (!sb->s_mtd) { 496 sb_set_blocksize(sb, ROMBSIZE); 497 } else { 498 sb->s_blocksize = ROMBSIZE; 499 sb->s_blocksize_bits = blksize_bits(ROMBSIZE); 500 } 501 #endif 502 503 sb->s_maxbytes = 0xFFFFFFFF; 504 sb->s_magic = ROMFS_MAGIC; 505 sb->s_flags |= MS_RDONLY | MS_NOATIME; 506 sb->s_op = &romfs_super_ops; 507 508 #ifdef CONFIG_ROMFS_ON_MTD 509 /* Use same dev ID from the underlying mtdblock device */ 510 if (sb->s_mtd) 511 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index); 512 #endif 513 /* read the image superblock and check it */ 514 rsb = kmalloc(512, GFP_KERNEL); 515 if (!rsb) 516 return -ENOMEM; 517 518 sb->s_fs_info = (void *) 512; 519 ret = romfs_dev_read(sb, 0, rsb, 512); 520 if (ret < 0) 521 goto error_rsb; 522 523 img_size = be32_to_cpu(rsb->size); 524 525 if (sb->s_mtd && img_size > sb->s_mtd->size) 526 goto error_rsb_inval; 527 528 sb->s_fs_info = (void *) img_size; 529 530 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 || 531 img_size < ROMFH_SIZE) { 532 if (!silent) 533 pr_warn("VFS: Can't find a romfs filesystem on dev %s.\n", 534 sb->s_id); 535 goto error_rsb_inval; 536 } 537 538 if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) { 539 pr_err("bad initial checksum on dev %s.\n", sb->s_id); 540 goto error_rsb_inval; 541 } 542 543 storage = sb->s_mtd ? "MTD" : "the block layer"; 544 545 len = strnlen(rsb->name, ROMFS_MAXFN); 546 if (!silent) 547 pr_notice("Mounting image '%*.*s' through %s\n", 548 (unsigned) len, (unsigned) len, rsb->name, storage); 549 550 kfree(rsb); 551 rsb = NULL; 552 553 /* find the root directory */ 554 pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK; 555 556 root = romfs_iget(sb, pos); 557 if (IS_ERR(root)) 558 return PTR_ERR(root); 559 560 sb->s_root = d_make_root(root); 561 if (!sb->s_root) 562 return -ENOMEM; 563 564 return 0; 565 566 error_rsb_inval: 567 ret = -EINVAL; 568 error_rsb: 569 kfree(rsb); 570 return ret; 571 } 572 573 /* 574 * get a superblock for mounting 575 */ 576 static struct dentry *romfs_mount(struct file_system_type *fs_type, 577 int flags, const char *dev_name, 578 void *data) 579 { 580 struct dentry *ret = ERR_PTR(-EINVAL); 581 582 #ifdef CONFIG_ROMFS_ON_MTD 583 ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super); 584 #endif 585 #ifdef CONFIG_ROMFS_ON_BLOCK 586 if (ret == ERR_PTR(-EINVAL)) 587 ret = mount_bdev(fs_type, flags, dev_name, data, 588 romfs_fill_super); 589 #endif 590 return ret; 591 } 592 593 /* 594 * destroy a romfs superblock in the appropriate manner 595 */ 596 static void romfs_kill_sb(struct super_block *sb) 597 { 598 #ifdef CONFIG_ROMFS_ON_MTD 599 if (sb->s_mtd) { 600 kill_mtd_super(sb); 601 return; 602 } 603 #endif 604 #ifdef CONFIG_ROMFS_ON_BLOCK 605 if (sb->s_bdev) { 606 kill_block_super(sb); 607 return; 608 } 609 #endif 610 } 611 612 static struct file_system_type romfs_fs_type = { 613 .owner = THIS_MODULE, 614 .name = "romfs", 615 .mount = romfs_mount, 616 .kill_sb = romfs_kill_sb, 617 .fs_flags = FS_REQUIRES_DEV, 618 }; 619 MODULE_ALIAS_FS("romfs"); 620 621 /* 622 * inode storage initialiser 623 */ 624 static void romfs_i_init_once(void *_inode) 625 { 626 struct romfs_inode_info *inode = _inode; 627 628 inode_init_once(&inode->vfs_inode); 629 } 630 631 /* 632 * romfs module initialisation 633 */ 634 static int __init init_romfs_fs(void) 635 { 636 int ret; 637 638 pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n"); 639 640 romfs_inode_cachep = 641 kmem_cache_create("romfs_i", 642 sizeof(struct romfs_inode_info), 0, 643 SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD | 644 SLAB_ACCOUNT, romfs_i_init_once); 645 646 if (!romfs_inode_cachep) { 647 pr_err("Failed to initialise inode cache\n"); 648 return -ENOMEM; 649 } 650 ret = register_filesystem(&romfs_fs_type); 651 if (ret) { 652 pr_err("Failed to register filesystem\n"); 653 goto error_register; 654 } 655 return 0; 656 657 error_register: 658 kmem_cache_destroy(romfs_inode_cachep); 659 return ret; 660 } 661 662 /* 663 * romfs module removal 664 */ 665 static void __exit exit_romfs_fs(void) 666 { 667 unregister_filesystem(&romfs_fs_type); 668 /* 669 * Make sure all delayed rcu free inodes are flushed before we 670 * destroy cache. 671 */ 672 rcu_barrier(); 673 kmem_cache_destroy(romfs_inode_cachep); 674 } 675 676 module_init(init_romfs_fs); 677 module_exit(exit_romfs_fs); 678 679 MODULE_DESCRIPTION("Direct-MTD Capable RomFS"); 680 MODULE_AUTHOR("Red Hat, Inc."); 681 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */ 682