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 "internal.h" 78 79 static struct kmem_cache *romfs_inode_cachep; 80 81 static const umode_t romfs_modemap[8] = { 82 0, /* hard link */ 83 S_IFDIR | 0644, /* directory */ 84 S_IFREG | 0644, /* regular file */ 85 S_IFLNK | 0777, /* symlink */ 86 S_IFBLK | 0600, /* blockdev */ 87 S_IFCHR | 0600, /* chardev */ 88 S_IFSOCK | 0644, /* socket */ 89 S_IFIFO | 0644 /* FIFO */ 90 }; 91 92 static const unsigned char romfs_dtype_table[] = { 93 DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO 94 }; 95 96 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos); 97 98 /* 99 * read a page worth of data from the image 100 */ 101 static int romfs_readpage(struct file *file, struct page *page) 102 { 103 struct inode *inode = page->mapping->host; 104 loff_t offset, size; 105 unsigned long fillsize, pos; 106 void *buf; 107 int ret; 108 109 buf = kmap(page); 110 if (!buf) 111 return -ENOMEM; 112 113 /* 32 bit warning -- but not for us :) */ 114 offset = page_offset(page); 115 size = i_size_read(inode); 116 fillsize = 0; 117 ret = 0; 118 if (offset < size) { 119 size -= offset; 120 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size; 121 122 pos = ROMFS_I(inode)->i_dataoffset + offset; 123 124 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize); 125 if (ret < 0) { 126 SetPageError(page); 127 fillsize = 0; 128 ret = -EIO; 129 } 130 } 131 132 if (fillsize < PAGE_SIZE) 133 memset(buf + fillsize, 0, PAGE_SIZE - fillsize); 134 if (ret == 0) 135 SetPageUptodate(page); 136 137 flush_dcache_page(page); 138 kunmap(page); 139 unlock_page(page); 140 return ret; 141 } 142 143 static const struct address_space_operations romfs_aops = { 144 .readpage = romfs_readpage 145 }; 146 147 /* 148 * read the entries from a directory 149 */ 150 static int romfs_readdir(struct file *file, struct dir_context *ctx) 151 { 152 struct inode *i = file_inode(file); 153 struct romfs_inode ri; 154 unsigned long offset, maxoff; 155 int j, ino, nextfh; 156 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */ 157 int ret; 158 159 maxoff = romfs_maxsize(i->i_sb); 160 161 offset = ctx->pos; 162 if (!offset) { 163 offset = i->i_ino & ROMFH_MASK; 164 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE); 165 if (ret < 0) 166 goto out; 167 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 168 } 169 170 /* Not really failsafe, but we are read-only... */ 171 for (;;) { 172 if (!offset || offset >= maxoff) { 173 offset = maxoff; 174 ctx->pos = offset; 175 goto out; 176 } 177 ctx->pos = offset; 178 179 /* Fetch inode info */ 180 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE); 181 if (ret < 0) 182 goto out; 183 184 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE, 185 sizeof(fsname) - 1); 186 if (j < 0) 187 goto out; 188 189 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j); 190 if (ret < 0) 191 goto out; 192 fsname[j] = '\0'; 193 194 ino = offset; 195 nextfh = be32_to_cpu(ri.next); 196 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD) 197 ino = be32_to_cpu(ri.spec); 198 if (!dir_emit(ctx, fsname, j, ino, 199 romfs_dtype_table[nextfh & ROMFH_TYPE])) 200 goto out; 201 202 offset = nextfh & ROMFH_MASK; 203 } 204 out: 205 return 0; 206 } 207 208 /* 209 * look up an entry in a directory 210 */ 211 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry, 212 unsigned int flags) 213 { 214 unsigned long offset, maxoff; 215 struct inode *inode; 216 struct romfs_inode ri; 217 const char *name; /* got from dentry */ 218 int len, ret; 219 220 offset = dir->i_ino & ROMFH_MASK; 221 ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE); 222 if (ret < 0) 223 goto error; 224 225 /* search all the file entries in the list starting from the one 226 * pointed to by the directory's special data */ 227 maxoff = romfs_maxsize(dir->i_sb); 228 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 229 230 name = dentry->d_name.name; 231 len = dentry->d_name.len; 232 233 for (;;) { 234 if (!offset || offset >= maxoff) 235 goto out0; 236 237 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri)); 238 if (ret < 0) 239 goto error; 240 241 /* try to match the first 16 bytes of name */ 242 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name, 243 len); 244 if (ret < 0) 245 goto error; 246 if (ret == 1) 247 break; 248 249 /* next entry */ 250 offset = be32_to_cpu(ri.next) & ROMFH_MASK; 251 } 252 253 /* Hard link handling */ 254 if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD) 255 offset = be32_to_cpu(ri.spec) & ROMFH_MASK; 256 257 inode = romfs_iget(dir->i_sb, offset); 258 if (IS_ERR(inode)) { 259 ret = PTR_ERR(inode); 260 goto error; 261 } 262 goto outi; 263 264 /* 265 * it's a bit funky, _lookup needs to return an error code 266 * (negative) or a NULL, both as a dentry. ENOENT should not 267 * be returned, instead we need to create a negative dentry by 268 * d_add(dentry, NULL); and return 0 as no error. 269 * (Although as I see, it only matters on writable file 270 * systems). 271 */ 272 out0: 273 inode = NULL; 274 outi: 275 d_add(dentry, inode); 276 ret = 0; 277 error: 278 return ERR_PTR(ret); 279 } 280 281 static const struct file_operations romfs_dir_operations = { 282 .read = generic_read_dir, 283 .iterate = romfs_readdir, 284 .llseek = default_llseek, 285 }; 286 287 static const struct inode_operations romfs_dir_inode_operations = { 288 .lookup = romfs_lookup, 289 }; 290 291 /* 292 * get a romfs inode based on its position in the image (which doubles as the 293 * inode number) 294 */ 295 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos) 296 { 297 struct romfs_inode_info *inode; 298 struct romfs_inode ri; 299 struct inode *i; 300 unsigned long nlen; 301 unsigned nextfh; 302 int ret; 303 umode_t mode; 304 305 /* we might have to traverse a chain of "hard link" file entries to get 306 * to the actual file */ 307 for (;;) { 308 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri)); 309 if (ret < 0) 310 goto error; 311 312 /* XXX: do romfs_checksum here too (with name) */ 313 314 nextfh = be32_to_cpu(ri.next); 315 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD) 316 break; 317 318 pos = be32_to_cpu(ri.spec) & ROMFH_MASK; 319 } 320 321 /* determine the length of the filename */ 322 nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN); 323 if (IS_ERR_VALUE(nlen)) 324 goto eio; 325 326 /* get an inode for this image position */ 327 i = iget_locked(sb, pos); 328 if (!i) 329 return ERR_PTR(-ENOMEM); 330 331 if (!(i->i_state & I_NEW)) 332 return i; 333 334 /* precalculate the data offset */ 335 inode = ROMFS_I(i); 336 inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK; 337 inode->i_dataoffset = pos + inode->i_metasize; 338 339 set_nlink(i, 1); /* Hard to decide.. */ 340 i->i_size = be32_to_cpu(ri.size); 341 i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0; 342 i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0; 343 344 /* set up mode and ops */ 345 mode = romfs_modemap[nextfh & ROMFH_TYPE]; 346 347 switch (nextfh & ROMFH_TYPE) { 348 case ROMFH_DIR: 349 i->i_size = ROMFS_I(i)->i_metasize; 350 i->i_op = &romfs_dir_inode_operations; 351 i->i_fop = &romfs_dir_operations; 352 if (nextfh & ROMFH_EXEC) 353 mode |= S_IXUGO; 354 break; 355 case ROMFH_REG: 356 i->i_fop = &romfs_ro_fops; 357 i->i_data.a_ops = &romfs_aops; 358 if (i->i_sb->s_mtd) 359 i->i_data.backing_dev_info = 360 i->i_sb->s_mtd->backing_dev_info; 361 if (nextfh & ROMFH_EXEC) 362 mode |= S_IXUGO; 363 break; 364 case ROMFH_SYM: 365 i->i_op = &page_symlink_inode_operations; 366 i->i_data.a_ops = &romfs_aops; 367 mode |= S_IRWXUGO; 368 break; 369 default: 370 /* depending on MBZ for sock/fifos */ 371 nextfh = be32_to_cpu(ri.spec); 372 init_special_inode(i, mode, MKDEV(nextfh >> 16, 373 nextfh & 0xffff)); 374 break; 375 } 376 377 i->i_mode = mode; 378 379 unlock_new_inode(i); 380 return i; 381 382 eio: 383 ret = -EIO; 384 error: 385 pr_err("read error for inode 0x%lx\n", pos); 386 return ERR_PTR(ret); 387 } 388 389 /* 390 * allocate a new inode 391 */ 392 static struct inode *romfs_alloc_inode(struct super_block *sb) 393 { 394 struct romfs_inode_info *inode; 395 396 inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL); 397 return inode ? &inode->vfs_inode : NULL; 398 } 399 400 /* 401 * return a spent inode to the slab cache 402 */ 403 static void romfs_i_callback(struct rcu_head *head) 404 { 405 struct inode *inode = container_of(head, struct inode, i_rcu); 406 407 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode)); 408 } 409 410 static void romfs_destroy_inode(struct inode *inode) 411 { 412 call_rcu(&inode->i_rcu, romfs_i_callback); 413 } 414 415 /* 416 * get filesystem statistics 417 */ 418 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf) 419 { 420 struct super_block *sb = dentry->d_sb; 421 u64 id = huge_encode_dev(sb->s_bdev->bd_dev); 422 423 buf->f_type = ROMFS_MAGIC; 424 buf->f_namelen = ROMFS_MAXFN; 425 buf->f_bsize = ROMBSIZE; 426 buf->f_bfree = buf->f_bavail = buf->f_ffree; 427 buf->f_blocks = 428 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS; 429 buf->f_fsid.val[0] = (u32)id; 430 buf->f_fsid.val[1] = (u32)(id >> 32); 431 return 0; 432 } 433 434 /* 435 * remounting must involve read-only 436 */ 437 static int romfs_remount(struct super_block *sb, int *flags, char *data) 438 { 439 sync_filesystem(sb); 440 *flags |= MS_RDONLY; 441 return 0; 442 } 443 444 static const struct super_operations romfs_super_ops = { 445 .alloc_inode = romfs_alloc_inode, 446 .destroy_inode = romfs_destroy_inode, 447 .statfs = romfs_statfs, 448 .remount_fs = romfs_remount, 449 }; 450 451 /* 452 * checksum check on part of a romfs filesystem 453 */ 454 static __u32 romfs_checksum(const void *data, int size) 455 { 456 const __be32 *ptr = data; 457 __u32 sum; 458 459 sum = 0; 460 size >>= 2; 461 while (size > 0) { 462 sum += be32_to_cpu(*ptr++); 463 size--; 464 } 465 return sum; 466 } 467 468 /* 469 * fill in the superblock 470 */ 471 static int romfs_fill_super(struct super_block *sb, void *data, int silent) 472 { 473 struct romfs_super_block *rsb; 474 struct inode *root; 475 unsigned long pos, img_size; 476 const char *storage; 477 size_t len; 478 int ret; 479 480 #ifdef CONFIG_BLOCK 481 if (!sb->s_mtd) { 482 sb_set_blocksize(sb, ROMBSIZE); 483 } else { 484 sb->s_blocksize = ROMBSIZE; 485 sb->s_blocksize_bits = blksize_bits(ROMBSIZE); 486 } 487 #endif 488 489 sb->s_maxbytes = 0xFFFFFFFF; 490 sb->s_magic = ROMFS_MAGIC; 491 sb->s_flags |= MS_RDONLY | MS_NOATIME; 492 sb->s_op = &romfs_super_ops; 493 494 /* read the image superblock and check it */ 495 rsb = kmalloc(512, GFP_KERNEL); 496 if (!rsb) 497 return -ENOMEM; 498 499 sb->s_fs_info = (void *) 512; 500 ret = romfs_dev_read(sb, 0, rsb, 512); 501 if (ret < 0) 502 goto error_rsb; 503 504 img_size = be32_to_cpu(rsb->size); 505 506 if (sb->s_mtd && img_size > sb->s_mtd->size) 507 goto error_rsb_inval; 508 509 sb->s_fs_info = (void *) img_size; 510 511 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 || 512 img_size < ROMFH_SIZE) { 513 if (!silent) 514 pr_warn("VFS: Can't find a romfs filesystem on dev %s.\n", 515 sb->s_id); 516 goto error_rsb_inval; 517 } 518 519 if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) { 520 pr_err("bad initial checksum on dev %s.\n", sb->s_id); 521 goto error_rsb_inval; 522 } 523 524 storage = sb->s_mtd ? "MTD" : "the block layer"; 525 526 len = strnlen(rsb->name, ROMFS_MAXFN); 527 if (!silent) 528 pr_notice("Mounting image '%*.*s' through %s\n", 529 (unsigned) len, (unsigned) len, rsb->name, storage); 530 531 kfree(rsb); 532 rsb = NULL; 533 534 /* find the root directory */ 535 pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK; 536 537 root = romfs_iget(sb, pos); 538 if (IS_ERR(root)) 539 return PTR_ERR(root); 540 541 sb->s_root = d_make_root(root); 542 if (!sb->s_root) 543 return -ENOMEM; 544 545 return 0; 546 547 error_rsb_inval: 548 ret = -EINVAL; 549 error_rsb: 550 kfree(rsb); 551 return ret; 552 } 553 554 /* 555 * get a superblock for mounting 556 */ 557 static struct dentry *romfs_mount(struct file_system_type *fs_type, 558 int flags, const char *dev_name, 559 void *data) 560 { 561 struct dentry *ret = ERR_PTR(-EINVAL); 562 563 #ifdef CONFIG_ROMFS_ON_MTD 564 ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super); 565 #endif 566 #ifdef CONFIG_ROMFS_ON_BLOCK 567 if (ret == ERR_PTR(-EINVAL)) 568 ret = mount_bdev(fs_type, flags, dev_name, data, 569 romfs_fill_super); 570 #endif 571 return ret; 572 } 573 574 /* 575 * destroy a romfs superblock in the appropriate manner 576 */ 577 static void romfs_kill_sb(struct super_block *sb) 578 { 579 #ifdef CONFIG_ROMFS_ON_MTD 580 if (sb->s_mtd) { 581 kill_mtd_super(sb); 582 return; 583 } 584 #endif 585 #ifdef CONFIG_ROMFS_ON_BLOCK 586 if (sb->s_bdev) { 587 kill_block_super(sb); 588 return; 589 } 590 #endif 591 } 592 593 static struct file_system_type romfs_fs_type = { 594 .owner = THIS_MODULE, 595 .name = "romfs", 596 .mount = romfs_mount, 597 .kill_sb = romfs_kill_sb, 598 .fs_flags = FS_REQUIRES_DEV, 599 }; 600 MODULE_ALIAS_FS("romfs"); 601 602 /* 603 * inode storage initialiser 604 */ 605 static void romfs_i_init_once(void *_inode) 606 { 607 struct romfs_inode_info *inode = _inode; 608 609 inode_init_once(&inode->vfs_inode); 610 } 611 612 /* 613 * romfs module initialisation 614 */ 615 static int __init init_romfs_fs(void) 616 { 617 int ret; 618 619 pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n"); 620 621 romfs_inode_cachep = 622 kmem_cache_create("romfs_i", 623 sizeof(struct romfs_inode_info), 0, 624 SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, 625 romfs_i_init_once); 626 627 if (!romfs_inode_cachep) { 628 pr_err("Failed to initialise inode cache\n"); 629 return -ENOMEM; 630 } 631 ret = register_filesystem(&romfs_fs_type); 632 if (ret) { 633 pr_err("Failed to register filesystem\n"); 634 goto error_register; 635 } 636 return 0; 637 638 error_register: 639 kmem_cache_destroy(romfs_inode_cachep); 640 return ret; 641 } 642 643 /* 644 * romfs module removal 645 */ 646 static void __exit exit_romfs_fs(void) 647 { 648 unregister_filesystem(&romfs_fs_type); 649 /* 650 * Make sure all delayed rcu free inodes are flushed before we 651 * destroy cache. 652 */ 653 rcu_barrier(); 654 kmem_cache_destroy(romfs_inode_cachep); 655 } 656 657 module_init(init_romfs_fs); 658 module_exit(exit_romfs_fs); 659 660 MODULE_DESCRIPTION("Direct-MTD Capable RomFS"); 661 MODULE_AUTHOR("Red Hat, Inc."); 662 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */ 663