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 (nextfh & ROMFH_EXEC) 359 mode |= S_IXUGO; 360 break; 361 case ROMFH_SYM: 362 i->i_op = &page_symlink_inode_operations; 363 i->i_data.a_ops = &romfs_aops; 364 mode |= S_IRWXUGO; 365 break; 366 default: 367 /* depending on MBZ for sock/fifos */ 368 nextfh = be32_to_cpu(ri.spec); 369 init_special_inode(i, mode, MKDEV(nextfh >> 16, 370 nextfh & 0xffff)); 371 break; 372 } 373 374 i->i_mode = mode; 375 376 unlock_new_inode(i); 377 return i; 378 379 eio: 380 ret = -EIO; 381 error: 382 pr_err("read error for inode 0x%lx\n", pos); 383 return ERR_PTR(ret); 384 } 385 386 /* 387 * allocate a new inode 388 */ 389 static struct inode *romfs_alloc_inode(struct super_block *sb) 390 { 391 struct romfs_inode_info *inode; 392 393 inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL); 394 return inode ? &inode->vfs_inode : NULL; 395 } 396 397 /* 398 * return a spent inode to the slab cache 399 */ 400 static void romfs_i_callback(struct rcu_head *head) 401 { 402 struct inode *inode = container_of(head, struct inode, i_rcu); 403 404 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode)); 405 } 406 407 static void romfs_destroy_inode(struct inode *inode) 408 { 409 call_rcu(&inode->i_rcu, romfs_i_callback); 410 } 411 412 /* 413 * get filesystem statistics 414 */ 415 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf) 416 { 417 struct super_block *sb = dentry->d_sb; 418 u64 id = huge_encode_dev(sb->s_bdev->bd_dev); 419 420 buf->f_type = ROMFS_MAGIC; 421 buf->f_namelen = ROMFS_MAXFN; 422 buf->f_bsize = ROMBSIZE; 423 buf->f_bfree = buf->f_bavail = buf->f_ffree; 424 buf->f_blocks = 425 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS; 426 buf->f_fsid.val[0] = (u32)id; 427 buf->f_fsid.val[1] = (u32)(id >> 32); 428 return 0; 429 } 430 431 /* 432 * remounting must involve read-only 433 */ 434 static int romfs_remount(struct super_block *sb, int *flags, char *data) 435 { 436 sync_filesystem(sb); 437 *flags |= MS_RDONLY; 438 return 0; 439 } 440 441 static const struct super_operations romfs_super_ops = { 442 .alloc_inode = romfs_alloc_inode, 443 .destroy_inode = romfs_destroy_inode, 444 .statfs = romfs_statfs, 445 .remount_fs = romfs_remount, 446 }; 447 448 /* 449 * checksum check on part of a romfs filesystem 450 */ 451 static __u32 romfs_checksum(const void *data, int size) 452 { 453 const __be32 *ptr = data; 454 __u32 sum; 455 456 sum = 0; 457 size >>= 2; 458 while (size > 0) { 459 sum += be32_to_cpu(*ptr++); 460 size--; 461 } 462 return sum; 463 } 464 465 /* 466 * fill in the superblock 467 */ 468 static int romfs_fill_super(struct super_block *sb, void *data, int silent) 469 { 470 struct romfs_super_block *rsb; 471 struct inode *root; 472 unsigned long pos, img_size; 473 const char *storage; 474 size_t len; 475 int ret; 476 477 #ifdef CONFIG_BLOCK 478 if (!sb->s_mtd) { 479 sb_set_blocksize(sb, ROMBSIZE); 480 } else { 481 sb->s_blocksize = ROMBSIZE; 482 sb->s_blocksize_bits = blksize_bits(ROMBSIZE); 483 } 484 #endif 485 486 sb->s_maxbytes = 0xFFFFFFFF; 487 sb->s_magic = ROMFS_MAGIC; 488 sb->s_flags |= MS_RDONLY | MS_NOATIME; 489 sb->s_op = &romfs_super_ops; 490 491 /* read the image superblock and check it */ 492 rsb = kmalloc(512, GFP_KERNEL); 493 if (!rsb) 494 return -ENOMEM; 495 496 sb->s_fs_info = (void *) 512; 497 ret = romfs_dev_read(sb, 0, rsb, 512); 498 if (ret < 0) 499 goto error_rsb; 500 501 img_size = be32_to_cpu(rsb->size); 502 503 if (sb->s_mtd && img_size > sb->s_mtd->size) 504 goto error_rsb_inval; 505 506 sb->s_fs_info = (void *) img_size; 507 508 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 || 509 img_size < ROMFH_SIZE) { 510 if (!silent) 511 pr_warn("VFS: Can't find a romfs filesystem on dev %s.\n", 512 sb->s_id); 513 goto error_rsb_inval; 514 } 515 516 if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) { 517 pr_err("bad initial checksum on dev %s.\n", sb->s_id); 518 goto error_rsb_inval; 519 } 520 521 storage = sb->s_mtd ? "MTD" : "the block layer"; 522 523 len = strnlen(rsb->name, ROMFS_MAXFN); 524 if (!silent) 525 pr_notice("Mounting image '%*.*s' through %s\n", 526 (unsigned) len, (unsigned) len, rsb->name, storage); 527 528 kfree(rsb); 529 rsb = NULL; 530 531 /* find the root directory */ 532 pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK; 533 534 root = romfs_iget(sb, pos); 535 if (IS_ERR(root)) 536 return PTR_ERR(root); 537 538 sb->s_root = d_make_root(root); 539 if (!sb->s_root) 540 return -ENOMEM; 541 542 return 0; 543 544 error_rsb_inval: 545 ret = -EINVAL; 546 error_rsb: 547 kfree(rsb); 548 return ret; 549 } 550 551 /* 552 * get a superblock for mounting 553 */ 554 static struct dentry *romfs_mount(struct file_system_type *fs_type, 555 int flags, const char *dev_name, 556 void *data) 557 { 558 struct dentry *ret = ERR_PTR(-EINVAL); 559 560 #ifdef CONFIG_ROMFS_ON_MTD 561 ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super); 562 #endif 563 #ifdef CONFIG_ROMFS_ON_BLOCK 564 if (ret == ERR_PTR(-EINVAL)) 565 ret = mount_bdev(fs_type, flags, dev_name, data, 566 romfs_fill_super); 567 #endif 568 return ret; 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 #ifdef CONFIG_ROMFS_ON_MTD 577 if (sb->s_mtd) { 578 kill_mtd_super(sb); 579 return; 580 } 581 #endif 582 #ifdef CONFIG_ROMFS_ON_BLOCK 583 if (sb->s_bdev) { 584 kill_block_super(sb); 585 return; 586 } 587 #endif 588 } 589 590 static struct file_system_type romfs_fs_type = { 591 .owner = THIS_MODULE, 592 .name = "romfs", 593 .mount = romfs_mount, 594 .kill_sb = romfs_kill_sb, 595 .fs_flags = FS_REQUIRES_DEV, 596 }; 597 MODULE_ALIAS_FS("romfs"); 598 599 /* 600 * inode storage initialiser 601 */ 602 static void romfs_i_init_once(void *_inode) 603 { 604 struct romfs_inode_info *inode = _inode; 605 606 inode_init_once(&inode->vfs_inode); 607 } 608 609 /* 610 * romfs module initialisation 611 */ 612 static int __init init_romfs_fs(void) 613 { 614 int ret; 615 616 pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n"); 617 618 romfs_inode_cachep = 619 kmem_cache_create("romfs_i", 620 sizeof(struct romfs_inode_info), 0, 621 SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, 622 romfs_i_init_once); 623 624 if (!romfs_inode_cachep) { 625 pr_err("Failed to initialise inode cache\n"); 626 return -ENOMEM; 627 } 628 ret = register_filesystem(&romfs_fs_type); 629 if (ret) { 630 pr_err("Failed to register filesystem\n"); 631 goto error_register; 632 } 633 return 0; 634 635 error_register: 636 kmem_cache_destroy(romfs_inode_cachep); 637 return ret; 638 } 639 640 /* 641 * romfs module removal 642 */ 643 static void __exit exit_romfs_fs(void) 644 { 645 unregister_filesystem(&romfs_fs_type); 646 /* 647 * Make sure all delayed rcu free inodes are flushed before we 648 * destroy cache. 649 */ 650 rcu_barrier(); 651 kmem_cache_destroy(romfs_inode_cachep); 652 } 653 654 module_init(init_romfs_fs); 655 module_exit(exit_romfs_fs); 656 657 MODULE_DESCRIPTION("Direct-MTD Capable RomFS"); 658 MODULE_AUTHOR("Red Hat, Inc."); 659 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */ 660