summaryrefslogtreecommitdiffstats
path: root/fs/romfs/super.c
blob: c32006ea3d88197e9b77dc115e63805d9a296493 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
/* Block- or MTD-based romfs
 *
 * Copyright © 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * Derived from: ROMFS file system, Linux implementation
 *
 * Copyright © 1997-1999  Janos Farkas <chexum@shadow.banki.hu>
 *
 * Using parts of the minix filesystem
 * Copyright © 1991, 1992  Linus Torvalds
 *
 * and parts of the affs filesystem additionally
 * Copyright © 1993  Ray Burr
 * Copyright © 1996  Hans-Joachim Widmaier
 *
 * Changes
 *					Changed for 2.1.19 modules
 *	Jan 1997			Initial release
 *	Jun 1997			2.1.43+ changes
 *					Proper page locking in readpage
 *					Changed to work with 2.1.45+ fs
 *	Jul 1997			Fixed follow_link
 *			2.1.47
 *					lookup shouldn't return -ENOENT
 *					from Horst von Brand:
 *					  fail on wrong checksum
 *					  double unlock_super was possible
 *					  correct namelen for statfs
 *					spotted by Bill Hawes:
 *					  readlink shouldn't iput()
 *	Jun 1998	2.1.106		from Avery Pennarun: glibc scandir()
 *					  exposed a problem in readdir
 *			2.1.107		code-freeze spellchecker run
 *	Aug 1998			2.1.118+ VFS changes
 *	Sep 1998	2.1.122		another VFS change (follow_link)
 *	Apr 1999	2.2.7		no more EBADF checking in
 *					  lookup/readdir, use ERR_PTR
 *	Jun 1999	2.3.6		d_alloc_root use changed
 *			2.3.9		clean up usage of ENOENT/negative
 *					  dentries in lookup
 *					clean up page flags setting
 *					  (error, uptodate, locking) in
 *					  in readpage
 *					use init_special_inode for
 *					  fifos/sockets (and streamline) in
 *					  read_inode, fix _ops table order
 *	Aug 1999	2.3.16		__initfunc() => __init change
 *	Oct 1999	2.3.24		page->owner hack obsoleted
 *	Nov 1999	2.3.27		2.3.25+ page->offset => index change
 *
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/parser.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/statfs.h>
#include <linux/mtd/super.h>
#include <linux/ctype.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/uaccess.h>
#include "internal.h"

static struct kmem_cache *romfs_inode_cachep;

static const umode_t romfs_modemap[8] = {
	0,			/* hard link */
	S_IFDIR  | 0644,	/* directory */
	S_IFREG  | 0644,	/* regular file */
	S_IFLNK  | 0777,	/* symlink */
	S_IFBLK  | 0600,	/* blockdev */
	S_IFCHR  | 0600,	/* chardev */
	S_IFSOCK | 0644,	/* socket */
	S_IFIFO  | 0644		/* FIFO */
};

static const unsigned char romfs_dtype_table[] = {
	DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
};

static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);

/*
 * read a page worth of data from the image
 */
static int romfs_readpage(struct file *file, struct page *page)
{
	struct inode *inode = page->mapping->host;
	loff_t offset, size;
	unsigned long fillsize, pos;
	void *buf;
	int ret;

	buf = kmap(page);
	if (!buf)
		return -ENOMEM;

	/* 32 bit warning -- but not for us :) */
	offset = page_offset(page);
	size = i_size_read(inode);
	fillsize = 0;
	ret = 0;
	if (offset < size) {
		size -= offset;
		fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;

		pos = ROMFS_I(inode)->i_dataoffset + offset;

		ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
		if (ret < 0) {
			SetPageError(page);
			fillsize = 0;
			ret = -EIO;
		}
	}

	if (fillsize < PAGE_SIZE)
		memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
	if (ret == 0)
		SetPageUptodate(page);

	flush_dcache_page(page);
	kunmap(page);
	unlock_page(page);
	return ret;
}

static const struct address_space_operations romfs_aops = {
	.readpage	= romfs_readpage
};

/*
 * read the entries from a directory
 */
static int romfs_readdir(struct file *file, struct dir_context *ctx)
{
	struct inode *i = file_inode(file);
	struct romfs_inode ri;
	unsigned long offset, maxoff;
	int j, ino, nextfh;
	char fsname[ROMFS_MAXFN];	/* XXX dynamic? */
	int ret;

	maxoff = romfs_maxsize(i->i_sb);

	offset = ctx->pos;
	if (!offset) {
		offset = i->i_ino & ROMFH_MASK;
		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
		if (ret < 0)
			goto out;
		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
	}

	/* Not really failsafe, but we are read-only... */
	for (;;) {
		if (!offset || offset >= maxoff) {
			offset = maxoff;
			ctx->pos = offset;
			goto out;
		}
		ctx->pos = offset;

		/* Fetch inode info */
		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
		if (ret < 0)
			goto out;

		j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
				      sizeof(fsname) - 1);
		if (j < 0)
			goto out;

		ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
		if (ret < 0)
			goto out;
		fsname[j] = '\0';

		ino = offset;
		nextfh = be32_to_cpu(ri.next);
		if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
			ino = be32_to_cpu(ri.spec);
		if (!dir_emit(ctx, fsname, j, ino,
			    romfs_dtype_table[nextfh & ROMFH_TYPE]))
			goto out;

		offset = nextfh & ROMFH_MASK;
	}
out:
	return 0;
}

/*
 * look up an entry in a directory
 */
static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
				   unsigned int flags)
{
	unsigned long offset, maxoff;
	struct inode *inode;
	struct romfs_inode ri;
	const char *name;		/* got from dentry */
	int len, ret;

	offset = dir->i_ino & ROMFH_MASK;
	ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
	if (ret < 0)
		goto error;

	/* search all the file entries in the list starting from the one
	 * pointed to by the directory's special data */
	maxoff = romfs_maxsize(dir->i_sb);
	offset = be32_to_cpu(ri.spec) & ROMFH_MASK;

	name = dentry->d_name.name;
	len = dentry->d_name.len;

	for (;;) {
		if (!offset || offset >= maxoff)
			goto out0;

		ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
		if (ret < 0)
			goto error;

		/* try to match the first 16 bytes of name */
		ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
				       len);
		if (ret < 0)
			goto error;
		if (ret == 1)
			break;

		/* next entry */
		offset = be32_to_cpu(ri.next) & ROMFH_MASK;
	}

	/* Hard link handling */
	if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;

	inode = romfs_iget(dir->i_sb, offset);
	if (IS_ERR(inode)) {
		ret = PTR_ERR(inode);
		goto error;
	}
	goto outi;

	/*
	 * it's a bit funky, _lookup needs to return an error code
	 * (negative) or a NULL, both as a dentry.  ENOENT should not
	 * be returned, instead we need to create a negative dentry by
	 * d_add(dentry, NULL); and return 0 as no error.
	 * (Although as I see, it only matters on writable file
	 * systems).
	 */
out0:
	inode = NULL;
outi:
	d_add(dentry, inode);
	ret = 0;
error:
	return ERR_PTR(ret);
}

static const struct file_operations romfs_dir_operations = {
	.read		= generic_read_dir,
	.iterate	= romfs_readdir,
	.llseek		= default_llseek,
};

static const struct inode_operations romfs_dir_inode_operations = {
	.lookup		= romfs_lookup,
};

/*
 * get a romfs inode based on its position in the image (which doubles as the
 * inode number)
 */
static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
{
	struct romfs_inode_info *inode;
	struct romfs_inode ri;
	struct inode *i;
	unsigned long nlen;
	unsigned nextfh;
	int ret;
	umode_t mode;

	/* we might have to traverse a chain of "hard link" file entries to get
	 * to the actual file */
	for (;;) {
		ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
		if (ret < 0)
			goto error;

		/* XXX: do romfs_checksum here too (with name) */

		nextfh = be32_to_cpu(ri.next);
		if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
			break;

		pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
	}

	/* determine the length of the filename */
	nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
	if (IS_ERR_VALUE(nlen))
		goto eio;

	/* get an inode for this image position */
	i = iget_locked(sb, pos);
	if (!i)
		return ERR_PTR(-ENOMEM);

	if (!(i->i_state & I_NEW))
		return i;

	/* precalculate the data offset */
	inode = ROMFS_I(i);
	inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
	inode->i_dataoffset = pos + inode->i_metasize;

	set_nlink(i, 1);		/* Hard to decide.. */
	i->i_size = be32_to_cpu(ri.size);
	i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
	i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;

	/* set up mode and ops */
	mode = romfs_modemap[nextfh & ROMFH_TYPE];

	switch (nextfh & ROMFH_TYPE) {
	case ROMFH_DIR:
		i->i_size = ROMFS_I(i)->i_metasize;
		i->i_op = &romfs_dir_inode_operations;
		i->i_fop = &romfs_dir_operations;
		if (nextfh & ROMFH_EXEC)
			mode |= S_IXUGO;
		break;
	case ROMFH_REG:
		i->i_fop = &romfs_ro_fops;
		i->i_data.a_ops = &romfs_aops;
		if (i->i_sb->s_mtd)
			i->i_data.backing_dev_info =
				i->i_sb->s_mtd->backing_dev_info;
		if (nextfh & ROMFH_EXEC)
			mode |= S_IXUGO;
		break;
	case ROMFH_SYM:
		i->i_op = &page_symlink_inode_operations;
		i->i_data.a_ops = &romfs_aops;
		mode |= S_IRWXUGO;
		break;
	default:
		/* depending on MBZ for sock/fifos */
		nextfh = be32_to_cpu(ri.spec);
		init_special_inode(i, mode, MKDEV(nextfh >> 16,
						  nextfh & 0xffff));
		break;
	}

	i->i_mode = mode;

	unlock_new_inode(i);
	return i;

eio:
	ret = -EIO;
error:
	pr_err("ROMFS: read error for inode 0x%lx\n", pos);
	return ERR_PTR(ret);
}

/*
 * allocate a new inode
 */
static struct inode *romfs_alloc_inode(struct super_block *sb)
{
	struct romfs_inode_info *inode;
	inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
	return inode ? &inode->vfs_inode : NULL;
}

/*
 * return a spent inode to the slab cache
 */
static void romfs_i_callback(struct rcu_head *head)
{
	struct inode *inode = container_of(head, struct inode, i_rcu);
	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
}

static void romfs_destroy_inode(struct inode *inode)
{
	call_rcu(&inode->i_rcu, romfs_i_callback);
}

/*
 * get filesystem statistics
 */
static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	struct super_block *sb = dentry->d_sb;
	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);

	buf->f_type = ROMFS_MAGIC;
	buf->f_namelen = ROMFS_MAXFN;
	buf->f_bsize = ROMBSIZE;
	buf->f_bfree = buf->f_bavail = buf->f_ffree;
	buf->f_blocks =
		(romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
	buf->f_fsid.val[0] = (u32)id;
	buf->f_fsid.val[1] = (u32)(id >> 32);
	return 0;
}

/*
 * remounting must involve read-only
 */
static int romfs_remount(struct super_block *sb, int *flags, char *data)
{
	sync_filesystem(sb);
	*flags |= MS_RDONLY;
	return 0;
}

static const struct super_operations romfs_super_ops = {
	.alloc_inode	= romfs_alloc_inode,
	.destroy_inode	= romfs_destroy_inode,
	.statfs		= romfs_statfs,
	.remount_fs	= romfs_remount,
};

/*
 * checksum check on part of a romfs filesystem
 */
static __u32 romfs_checksum(const void *data, int size)
{
	const __be32 *ptr = data;
	__u32 sum;

	sum = 0;
	size >>= 2;
	while (size > 0) {
		sum += be32_to_cpu(*ptr++);
		size--;
	}
	return sum;
}

/*
 * fill in the superblock
 */
static int romfs_fill_super(struct super_block *sb, void *data, int silent)
{
	struct romfs_super_block *rsb;
	struct inode *root;
	unsigned long pos, img_size;
	const char *storage;
	size_t len;
	int ret;

#ifdef CONFIG_BLOCK
	if (!sb->s_mtd) {
		sb_set_blocksize(sb, ROMBSIZE);
	} else {
		sb->s_blocksize = ROMBSIZE;
		sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
	}
#endif

	sb->s_maxbytes = 0xFFFFFFFF;
	sb->s_magic = ROMFS_MAGIC;
	sb->s_flags |= MS_RDONLY | MS_NOATIME;
	sb->s_op = &romfs_super_ops;

	/* read the image superblock and check it */
	rsb = kmalloc(512, GFP_KERNEL);
	if (!rsb)
		return -ENOMEM;

	sb->s_fs_info = (void *) 512;
	ret = romfs_dev_read(sb, 0, rsb, 512);
	if (ret < 0)
		goto error_rsb;

	img_size = be32_to_cpu(rsb->size);

	if (sb->s_mtd && img_size > sb->s_mtd->size)
		goto error_rsb_inval;

	sb->s_fs_info = (void *) img_size;

	if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
	    img_size < ROMFH_SIZE) {
		if (!silent)
			pr_warn("VFS: Can't find a romfs filesystem on dev %s.\n",
			       sb->s_id);
		goto error_rsb_inval;
	}

	if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
		pr_err("ROMFS: bad initial checksum on dev %s.\n",
		       sb->s_id);
		goto error_rsb_inval;
	}

	storage = sb->s_mtd ? "MTD" : "the block layer";

	len = strnlen(rsb->name, ROMFS_MAXFN);
	if (!silent)
		pr_notice("ROMFS: Mounting image '%*.*s' through %s\n",
		       (unsigned) len, (unsigned) len, rsb->name, storage);

	kfree(rsb);
	rsb = NULL;

	/* find the root directory */
	pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;

	root = romfs_iget(sb, pos);
	if (IS_ERR(root))
		return PTR_ERR(root);

	sb->s_root = d_make_root(root);
	if (!sb->s_root)
		return -ENOMEM;

	return 0;

error_rsb_inval:
	ret = -EINVAL;
error_rsb:
	kfree(rsb);
	return ret;
}

/*
 * get a superblock for mounting
 */
static struct dentry *romfs_mount(struct file_system_type *fs_type,
			int flags, const char *dev_name,
			void *data)
{
	struct dentry *ret = ERR_PTR(-EINVAL);

#ifdef CONFIG_ROMFS_ON_MTD
	ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
#endif
#ifdef CONFIG_ROMFS_ON_BLOCK
	if (ret == ERR_PTR(-EINVAL))
		ret = mount_bdev(fs_type, flags, dev_name, data,
				  romfs_fill_super);
#endif
	return ret;
}

/*
 * destroy a romfs superblock in the appropriate manner
 */
static void romfs_kill_sb(struct super_block *sb)
{
#ifdef CONFIG_ROMFS_ON_MTD
	if (sb->s_mtd) {
		kill_mtd_super(sb);
		return;
	}
#endif
#ifdef CONFIG_ROMFS_ON_BLOCK
	if (sb->s_bdev) {
		kill_block_super(sb);
		return;
	}
#endif
}

static struct file_system_type romfs_fs_type = {
	.owner		= THIS_MODULE,
	.name		= "romfs",
	.mount		= romfs_mount,
	.kill_sb	= romfs_kill_sb,
	.fs_flags	= FS_REQUIRES_DEV,
};
MODULE_ALIAS_FS("romfs");

/*
 * inode storage initialiser
 */
static void romfs_i_init_once(void *_inode)
{
	struct romfs_inode_info *inode = _inode;

	inode_init_once(&inode->vfs_inode);
}

/*
 * romfs module initialisation
 */
static int __init init_romfs_fs(void)
{
	int ret;

	pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");

	romfs_inode_cachep =
		kmem_cache_create("romfs_i",
				  sizeof(struct romfs_inode_info), 0,
				  SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
				  romfs_i_init_once);

	if (!romfs_inode_cachep) {
		pr_err("ROMFS error: Failed to initialise inode cache\n");
		return -ENOMEM;
	}
	ret = register_filesystem(&romfs_fs_type);
	if (ret) {
		pr_err("ROMFS error: Failed to register filesystem\n");
		goto error_register;
	}
	return 0;

error_register:
	kmem_cache_destroy(romfs_inode_cachep);
	return ret;
}

/*
 * romfs module removal
 */
static void __exit exit_romfs_fs(void)
{
	unregister_filesystem(&romfs_fs_type);
	/*
	 * Make sure all delayed rcu free inodes are flushed before we
	 * destroy cache.
	 */
	rcu_barrier();
	kmem_cache_destroy(romfs_inode_cachep);
}

module_init(init_romfs_fs);
module_exit(exit_romfs_fs);

MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
MODULE_AUTHOR("Red Hat, Inc.");
MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */