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 */
romfs_read_folio(struct file * file,struct folio * folio)102 static int romfs_read_folio(struct file *file, struct folio *folio)
103 {
104 struct inode *inode = folio->mapping->host;
105 loff_t offset, size;
106 unsigned long fillsize, pos;
107 void *buf;
108 int ret;
109
110 buf = kmap_local_folio(folio, 0);
111
112 offset = folio_pos(folio);
113 size = i_size_read(inode);
114 fillsize = 0;
115 ret = 0;
116 if (offset < size) {
117 size -= offset;
118 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
119
120 pos = ROMFS_I(inode)->i_dataoffset + offset;
121
122 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
123 if (ret < 0) {
124 fillsize = 0;
125 ret = -EIO;
126 }
127 }
128
129 buf = folio_zero_tail(folio, fillsize, buf + fillsize);
130 kunmap_local(buf);
131 folio_end_read(folio, ret == 0);
132 return ret;
133 }
134
135 static const struct address_space_operations romfs_aops = {
136 .read_folio = romfs_read_folio
137 };
138
139 /*
140 * read the entries from a directory
141 */
romfs_readdir(struct file * file,struct dir_context * ctx)142 static int romfs_readdir(struct file *file, struct dir_context *ctx)
143 {
144 struct inode *i = file_inode(file);
145 struct romfs_inode ri;
146 unsigned long offset, maxoff;
147 int j, ino, nextfh;
148 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
149 int ret;
150
151 maxoff = romfs_maxsize(i->i_sb);
152
153 offset = ctx->pos;
154 if (!offset) {
155 offset = i->i_ino & ROMFH_MASK;
156 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
157 if (ret < 0)
158 goto out;
159 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
160 }
161
162 /* Not really failsafe, but we are read-only... */
163 for (;;) {
164 if (!offset || offset >= maxoff) {
165 offset = maxoff;
166 ctx->pos = offset;
167 goto out;
168 }
169 ctx->pos = offset;
170
171 /* Fetch inode info */
172 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
173 if (ret < 0)
174 goto out;
175
176 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
177 sizeof(fsname) - 1);
178 if (j < 0)
179 goto out;
180
181 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
182 if (ret < 0)
183 goto out;
184 fsname[j] = '\0';
185
186 ino = offset;
187 nextfh = be32_to_cpu(ri.next);
188 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
189 ino = be32_to_cpu(ri.spec);
190 if (!dir_emit(ctx, fsname, j, ino,
191 romfs_dtype_table[nextfh & ROMFH_TYPE]))
192 goto out;
193
194 offset = nextfh & ROMFH_MASK;
195 }
196 out:
197 return 0;
198 }
199
200 /*
201 * look up an entry in a directory
202 */
romfs_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)203 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
204 unsigned int flags)
205 {
206 unsigned long offset, maxoff;
207 struct inode *inode = NULL;
208 struct romfs_inode ri;
209 const char *name; /* got from dentry */
210 int len, ret;
211
212 offset = dir->i_ino & ROMFH_MASK;
213 ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
214 if (ret < 0)
215 goto error;
216
217 /* search all the file entries in the list starting from the one
218 * pointed to by the directory's special data */
219 maxoff = romfs_maxsize(dir->i_sb);
220 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
221
222 name = dentry->d_name.name;
223 len = dentry->d_name.len;
224
225 for (;;) {
226 if (!offset || offset >= maxoff)
227 break;
228
229 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
230 if (ret < 0)
231 goto error;
232
233 /* try to match the first 16 bytes of name */
234 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
235 len);
236 if (ret < 0)
237 goto error;
238 if (ret == 1) {
239 /* Hard link handling */
240 if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
241 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
242 inode = romfs_iget(dir->i_sb, offset);
243 break;
244 }
245
246 /* next entry */
247 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
248 }
249
250 return d_splice_alias(inode, dentry);
251 error:
252 return ERR_PTR(ret);
253 }
254
255 static const struct file_operations romfs_dir_operations = {
256 .read = generic_read_dir,
257 .iterate_shared = romfs_readdir,
258 .llseek = generic_file_llseek,
259 };
260
261 static const struct inode_operations romfs_dir_inode_operations = {
262 .lookup = romfs_lookup,
263 };
264
265 /*
266 * get a romfs inode based on its position in the image (which doubles as the
267 * inode number)
268 */
romfs_iget(struct super_block * sb,unsigned long pos)269 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
270 {
271 struct romfs_inode_info *inode;
272 struct romfs_inode ri;
273 struct inode *i;
274 unsigned long nlen;
275 unsigned nextfh;
276 int ret;
277 umode_t mode;
278
279 /* we might have to traverse a chain of "hard link" file entries to get
280 * to the actual file */
281 for (;;) {
282 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
283 if (ret < 0)
284 goto error;
285
286 /* XXX: do romfs_checksum here too (with name) */
287
288 nextfh = be32_to_cpu(ri.next);
289 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
290 break;
291
292 pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
293 }
294
295 /* determine the length of the filename */
296 nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
297 if (IS_ERR_VALUE(nlen))
298 goto eio;
299
300 /* get an inode for this image position */
301 i = iget_locked(sb, pos);
302 if (!i)
303 return ERR_PTR(-ENOMEM);
304
305 if (!(i->i_state & I_NEW))
306 return i;
307
308 /* precalculate the data offset */
309 inode = ROMFS_I(i);
310 inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
311 inode->i_dataoffset = pos + inode->i_metasize;
312
313 set_nlink(i, 1); /* Hard to decide.. */
314 i->i_size = be32_to_cpu(ri.size);
315 inode_set_mtime_to_ts(i,
316 inode_set_atime_to_ts(i, inode_set_ctime(i, 0, 0)));
317
318 /* set up mode and ops */
319 mode = romfs_modemap[nextfh & ROMFH_TYPE];
320
321 switch (nextfh & ROMFH_TYPE) {
322 case ROMFH_DIR:
323 i->i_size = ROMFS_I(i)->i_metasize;
324 i->i_op = &romfs_dir_inode_operations;
325 i->i_fop = &romfs_dir_operations;
326 if (nextfh & ROMFH_EXEC)
327 mode |= S_IXUGO;
328 break;
329 case ROMFH_REG:
330 i->i_fop = &romfs_ro_fops;
331 i->i_data.a_ops = &romfs_aops;
332 if (nextfh & ROMFH_EXEC)
333 mode |= S_IXUGO;
334 break;
335 case ROMFH_SYM:
336 i->i_op = &page_symlink_inode_operations;
337 inode_nohighmem(i);
338 i->i_data.a_ops = &romfs_aops;
339 mode |= S_IRWXUGO;
340 break;
341 default:
342 /* depending on MBZ for sock/fifos */
343 nextfh = be32_to_cpu(ri.spec);
344 init_special_inode(i, mode, MKDEV(nextfh >> 16,
345 nextfh & 0xffff));
346 break;
347 }
348
349 i->i_mode = mode;
350 i->i_blocks = (i->i_size + 511) >> 9;
351
352 unlock_new_inode(i);
353 return i;
354
355 eio:
356 ret = -EIO;
357 error:
358 pr_err("read error for inode 0x%lx\n", pos);
359 return ERR_PTR(ret);
360 }
361
362 /*
363 * allocate a new inode
364 */
romfs_alloc_inode(struct super_block * sb)365 static struct inode *romfs_alloc_inode(struct super_block *sb)
366 {
367 struct romfs_inode_info *inode;
368
369 inode = alloc_inode_sb(sb, romfs_inode_cachep, GFP_KERNEL);
370 return inode ? &inode->vfs_inode : NULL;
371 }
372
373 /*
374 * return a spent inode to the slab cache
375 */
romfs_free_inode(struct inode * inode)376 static void romfs_free_inode(struct inode *inode)
377 {
378 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
379 }
380
381 /*
382 * get filesystem statistics
383 */
romfs_statfs(struct dentry * dentry,struct kstatfs * buf)384 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
385 {
386 struct super_block *sb = dentry->d_sb;
387 u64 id = 0;
388
389 /* When calling huge_encode_dev(),
390 * use sb->s_bdev->bd_dev when,
391 * - CONFIG_ROMFS_ON_BLOCK defined
392 * use sb->s_dev when,
393 * - CONFIG_ROMFS_ON_BLOCK undefined and
394 * - CONFIG_ROMFS_ON_MTD defined
395 * leave id as 0 when,
396 * - CONFIG_ROMFS_ON_BLOCK undefined and
397 * - CONFIG_ROMFS_ON_MTD undefined
398 */
399 if (sb->s_bdev)
400 id = huge_encode_dev(sb->s_bdev->bd_dev);
401 else if (sb->s_dev)
402 id = huge_encode_dev(sb->s_dev);
403
404 buf->f_type = ROMFS_MAGIC;
405 buf->f_namelen = ROMFS_MAXFN;
406 buf->f_bsize = ROMBSIZE;
407 buf->f_bfree = buf->f_bavail = buf->f_ffree;
408 buf->f_blocks =
409 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
410 buf->f_fsid = u64_to_fsid(id);
411 return 0;
412 }
413
414 /*
415 * remounting must involve read-only
416 */
romfs_reconfigure(struct fs_context * fc)417 static int romfs_reconfigure(struct fs_context *fc)
418 {
419 sync_filesystem(fc->root->d_sb);
420 fc->sb_flags |= SB_RDONLY;
421 return 0;
422 }
423
424 static const struct super_operations romfs_super_ops = {
425 .alloc_inode = romfs_alloc_inode,
426 .free_inode = romfs_free_inode,
427 .statfs = romfs_statfs,
428 };
429
430 /*
431 * checksum check on part of a romfs filesystem
432 */
romfs_checksum(const void * data,int size)433 static __u32 romfs_checksum(const void *data, int size)
434 {
435 const __be32 *ptr = data;
436 __u32 sum;
437
438 sum = 0;
439 size >>= 2;
440 while (size > 0) {
441 sum += be32_to_cpu(*ptr++);
442 size--;
443 }
444 return sum;
445 }
446
447 /*
448 * fill in the superblock
449 */
romfs_fill_super(struct super_block * sb,struct fs_context * fc)450 static int romfs_fill_super(struct super_block *sb, struct fs_context *fc)
451 {
452 struct romfs_super_block *rsb;
453 struct inode *root;
454 unsigned long pos, img_size;
455 const char *storage;
456 size_t len;
457 int ret;
458
459 #ifdef CONFIG_BLOCK
460 if (!sb->s_mtd) {
461 sb_set_blocksize(sb, ROMBSIZE);
462 } else {
463 sb->s_blocksize = ROMBSIZE;
464 sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
465 }
466 #endif
467
468 sb->s_maxbytes = 0xFFFFFFFF;
469 sb->s_magic = ROMFS_MAGIC;
470 sb->s_flags |= SB_RDONLY | SB_NOATIME;
471 sb->s_time_min = 0;
472 sb->s_time_max = 0;
473 sb->s_op = &romfs_super_ops;
474
475 #ifdef CONFIG_ROMFS_ON_MTD
476 /* Use same dev ID from the underlying mtdblock device */
477 if (sb->s_mtd)
478 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
479 #endif
480 /* read the image superblock and check it */
481 rsb = kmalloc(512, GFP_KERNEL);
482 if (!rsb)
483 return -ENOMEM;
484
485 sb->s_fs_info = (void *) 512;
486 ret = romfs_dev_read(sb, 0, rsb, 512);
487 if (ret < 0)
488 goto error_rsb;
489
490 img_size = be32_to_cpu(rsb->size);
491
492 if (sb->s_mtd && img_size > sb->s_mtd->size)
493 goto error_rsb_inval;
494
495 sb->s_fs_info = (void *) img_size;
496
497 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
498 img_size < ROMFH_SIZE) {
499 if (!(fc->sb_flags & SB_SILENT))
500 errorf(fc, "VFS: Can't find a romfs filesystem on dev %s.\n",
501 sb->s_id);
502 goto error_rsb_inval;
503 }
504
505 if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
506 pr_err("bad initial checksum on dev %s.\n", sb->s_id);
507 goto error_rsb_inval;
508 }
509
510 storage = sb->s_mtd ? "MTD" : "the block layer";
511
512 len = strnlen(rsb->name, ROMFS_MAXFN);
513 if (!(fc->sb_flags & SB_SILENT))
514 pr_notice("Mounting image '%*.*s' through %s\n",
515 (unsigned) len, (unsigned) len, rsb->name, storage);
516
517 kfree(rsb);
518 rsb = NULL;
519
520 /* find the root directory */
521 pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
522
523 root = romfs_iget(sb, pos);
524 if (IS_ERR(root))
525 return PTR_ERR(root);
526
527 sb->s_root = d_make_root(root);
528 if (!sb->s_root)
529 return -ENOMEM;
530
531 return 0;
532
533 error_rsb_inval:
534 ret = -EINVAL;
535 error_rsb:
536 kfree(rsb);
537 return ret;
538 }
539
540 /*
541 * get a superblock for mounting
542 */
romfs_get_tree(struct fs_context * fc)543 static int romfs_get_tree(struct fs_context *fc)
544 {
545 int ret = -EINVAL;
546
547 #ifdef CONFIG_ROMFS_ON_MTD
548 ret = get_tree_mtd(fc, romfs_fill_super);
549 #endif
550 #ifdef CONFIG_ROMFS_ON_BLOCK
551 if (ret == -EINVAL)
552 ret = get_tree_bdev(fc, romfs_fill_super);
553 #endif
554 return ret;
555 }
556
557 static const struct fs_context_operations romfs_context_ops = {
558 .get_tree = romfs_get_tree,
559 .reconfigure = romfs_reconfigure,
560 };
561
562 /*
563 * Set up the filesystem mount context.
564 */
romfs_init_fs_context(struct fs_context * fc)565 static int romfs_init_fs_context(struct fs_context *fc)
566 {
567 fc->ops = &romfs_context_ops;
568 return 0;
569 }
570
571 /*
572 * destroy a romfs superblock in the appropriate manner
573 */
romfs_kill_sb(struct super_block * sb)574 static void romfs_kill_sb(struct super_block *sb)
575 {
576 generic_shutdown_super(sb);
577
578 #ifdef CONFIG_ROMFS_ON_MTD
579 if (sb->s_mtd) {
580 put_mtd_device(sb->s_mtd);
581 sb->s_mtd = NULL;
582 }
583 #endif
584 #ifdef CONFIG_ROMFS_ON_BLOCK
585 if (sb->s_bdev) {
586 sync_blockdev(sb->s_bdev);
587 bdev_fput(sb->s_bdev_file);
588 }
589 #endif
590 }
591
592 static struct file_system_type romfs_fs_type = {
593 .owner = THIS_MODULE,
594 .name = "romfs",
595 .init_fs_context = romfs_init_fs_context,
596 .kill_sb = romfs_kill_sb,
597 .fs_flags = FS_REQUIRES_DEV,
598 };
599 MODULE_ALIAS_FS("romfs");
600
601 /*
602 * inode storage initialiser
603 */
romfs_i_init_once(void * _inode)604 static void romfs_i_init_once(void *_inode)
605 {
606 struct romfs_inode_info *inode = _inode;
607
608 inode_init_once(&inode->vfs_inode);
609 }
610
611 /*
612 * romfs module initialisation
613 */
init_romfs_fs(void)614 static int __init init_romfs_fs(void)
615 {
616 int ret;
617
618 pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");
619
620 romfs_inode_cachep =
621 kmem_cache_create("romfs_i",
622 sizeof(struct romfs_inode_info), 0,
623 SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT,
624 romfs_i_init_once);
625
626 if (!romfs_inode_cachep) {
627 pr_err("Failed to initialise inode cache\n");
628 return -ENOMEM;
629 }
630 ret = register_filesystem(&romfs_fs_type);
631 if (ret) {
632 pr_err("Failed to register filesystem\n");
633 goto error_register;
634 }
635 return 0;
636
637 error_register:
638 kmem_cache_destroy(romfs_inode_cachep);
639 return ret;
640 }
641
642 /*
643 * romfs module removal
644 */
exit_romfs_fs(void)645 static void __exit exit_romfs_fs(void)
646 {
647 unregister_filesystem(&romfs_fs_type);
648 /*
649 * Make sure all delayed rcu free inodes are flushed before we
650 * destroy cache.
651 */
652 rcu_barrier();
653 kmem_cache_destroy(romfs_inode_cachep);
654 }
655
656 module_init(init_romfs_fs);
657 module_exit(exit_romfs_fs);
658
659 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
660 MODULE_AUTHOR("Red Hat, Inc.");
661 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */
662