aboutsummaryrefslogtreecommitdiffstats
path: root/fs/romfs/inode.c
blob: 1e712cc1693bd5bfcb0ea3d7583c3b275e150d2b (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
/*
 * ROMFS file system, Linux implementation
 *
 * Copyright (C) 1997-1999  Janos Farkas <chexum@shadow.banki.hu>
 *
 * Using parts of the minix filesystem
 * Copyright (C) 1991, 1992  Linus Torvalds
 *
 * and parts of the affs filesystem additionally
 * Copyright (C) 1993  Ray Burr
 * Copyright (C) 1996  Hans-Joachim Widmaier
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 * 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
 */

/* todo:
 *	- see Documentation/filesystems/romfs.txt
 *	- use allocated, not stack memory for file names?
 *	- considering write access...
 *	- network (tftp) files?
 *	- merge back some _op tables
 */

/*
 * Sorry about some optimizations and for some goto's.  I just wanted
 * to squeeze some more bytes out of this code.. :)
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/romfs_fs.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
#include <linux/buffer_head.h>
#include <linux/vfs.h>

#include <asm/uaccess.h>

struct romfs_inode_info {
	unsigned long i_metasize;	/* size of non-data area */
	unsigned long i_dataoffset;	/* from the start of fs */
	struct inode vfs_inode;
};

/* instead of private superblock data */
static inline unsigned long romfs_maxsize(struct super_block *sb)
{
	return (unsigned long)sb->s_fs_info;
}

static inline struct romfs_inode_info *ROMFS_I(struct inode *inode)
{
	return list_entry(inode, struct romfs_inode_info, vfs_inode);
}

static __u32
romfs_checksum(void *data, int size)
{
	__u32 sum;
	__be32 *ptr;

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

static struct super_operations romfs_ops;

static int romfs_fill_super(struct super_block *s, void *data, int silent)
{
	struct buffer_head *bh;
	struct romfs_super_block *rsb;
	struct inode *root;
	int sz;

	/* I would parse the options here, but there are none.. :) */

	sb_set_blocksize(s, ROMBSIZE);
	s->s_maxbytes = 0xFFFFFFFF;

	bh = sb_bread(s, 0);
	if (!bh) {
		/* XXX merge with other printk? */
                printk ("romfs: unable to read superblock\n");
		goto outnobh;
	}

	rsb = (struct romfs_super_block *)bh->b_data;
	sz = be32_to_cpu(rsb->size);
	if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1
	   || sz < ROMFH_SIZE) {
		if (!silent)
			printk ("VFS: Can't find a romfs filesystem on dev "
				"%s.\n", s->s_id);
		goto out;
	}
	if (romfs_checksum(rsb, min_t(int, sz, 512))) {
		printk ("romfs: bad initial checksum on dev "
			"%s.\n", s->s_id);
		goto out;
	}

	s->s_magic = ROMFS_MAGIC;
	s->s_fs_info = (void *)(long)sz;

	s->s_flags |= MS_RDONLY;

	/* Find the start of the fs */
	sz = (ROMFH_SIZE +
	      strnlen(rsb->name, ROMFS_MAXFN) + 1 + ROMFH_PAD)
	     & ROMFH_MASK;

	s->s_op	= &romfs_ops;
	root = iget(s, sz);
	if (!root)
		goto out;

	s->s_root = d_alloc_root(root);
	if (!s->s_root)
		goto outiput;

	brelse(bh);
	return 0;

outiput:
	iput(root);
out:
	brelse(bh);
outnobh:
	return -EINVAL;
}

/* That's simple too. */

static int
romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	buf->f_type = ROMFS_MAGIC;
	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_namelen = ROMFS_MAXFN;
	return 0;
}

/* some helper routines */

static int
romfs_strnlen(struct inode *i, unsigned long offset, unsigned long count)
{
	struct buffer_head *bh;
	unsigned long avail, maxsize, res;

	maxsize = romfs_maxsize(i->i_sb);
	if (offset >= maxsize)
		return -1;

	/* strnlen is almost always valid */
	if (count > maxsize || offset+count > maxsize)
		count = maxsize-offset;

	bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
	if (!bh)
		return -1;		/* error */

	avail = ROMBSIZE - (offset & ROMBMASK);
	maxsize = min_t(unsigned long, count, avail);
	res = strnlen(((char *)bh->b_data)+(offset&ROMBMASK), maxsize);
	brelse(bh);

	if (res < maxsize)
		return res;		/* found all of it */

	while (res < count) {
		offset += maxsize;

		bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
		if (!bh)
			return -1;
		maxsize = min_t(unsigned long, count - res, ROMBSIZE);
		avail = strnlen(bh->b_data, maxsize);
		res += avail;
		brelse(bh);
		if (avail < maxsize)
			return res;
	}
	return res;
}

static int
romfs_copyfrom(struct inode *i, void *dest, unsigned long offset, unsigned long count)
{
	struct buffer_head *bh;
	unsigned long avail, maxsize, res;

	maxsize = romfs_maxsize(i->i_sb);
	if (offset >= maxsize || count > maxsize || offset+count>maxsize)
		return -1;

	bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
	if (!bh)
		return -1;		/* error */

	avail = ROMBSIZE - (offset & ROMBMASK);
	maxsize = min_t(unsigned long, count, avail);
	memcpy(dest, ((char *)bh->b_data) + (offset & ROMBMASK), maxsize);
	brelse(bh);

	res = maxsize;			/* all of it */

	while (res < count) {
		offset += maxsize;
		dest += maxsize;

		bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
		if (!bh)
			return -1;
		maxsize = min_t(unsigned long, count - res, ROMBSIZE);
		memcpy(dest, bh->b_data, maxsize);
		brelse(bh);
		res += maxsize;
	}
	return res;
}

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

static int
romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
	struct inode *i = filp->f_path.dentry->d_inode;
	struct romfs_inode ri;
	unsigned long offset, maxoff;
	int j, ino, nextfh;
	int stored = 0;
	char fsname[ROMFS_MAXFN];	/* XXX dynamic? */

	lock_kernel();

	maxoff = romfs_maxsize(i->i_sb);

	offset = filp->f_pos;
	if (!offset) {
		offset = i->i_ino & ROMFH_MASK;
		if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 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;
			filp->f_pos = offset;
			goto out;
		}
		filp->f_pos = offset;

		/* Fetch inode info */
		if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
			goto out;

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

		fsname[j]=0;
		romfs_copyfrom(i, fsname, offset+ROMFH_SIZE, j);

		ino = offset;
		nextfh = be32_to_cpu(ri.next);
		if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
			ino = be32_to_cpu(ri.spec);
		if (filldir(dirent, fsname, j, offset, ino,
			    romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0) {
			goto out;
		}
		stored++;
		offset = nextfh & ROMFH_MASK;
	}
out:
	unlock_kernel();
	return stored;
}

static struct dentry *
romfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
	unsigned long offset, maxoff;
	int fslen, res;
	struct inode *inode;
	char fsname[ROMFS_MAXFN];	/* XXX dynamic? */
	struct romfs_inode ri;
	const char *name;		/* got from dentry */
	int len;

	res = -EACCES;			/* placeholder for "no data here" */
	offset = dir->i_ino & ROMFH_MASK;
	lock_kernel();
	if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
		goto out;

	maxoff = romfs_maxsize(dir->i_sb);
	offset = be32_to_cpu(ri.spec) & ROMFH_MASK;

	/* OK, now find the file whose name is in "dentry" in the
	 * directory specified by "dir".  */

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

	for(;;) {
		if (!offset || offset >= maxoff)
			goto out0;
		if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
			goto out;

		/* try to match the first 16 bytes of name */
		fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, ROMFH_SIZE);
		if (len < ROMFH_SIZE) {
			if (len == fslen) {
				/* both are shorter, and same size */
				romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
				if (strncmp (name, fsname, len) == 0)
					break;
			}
		} else if (fslen >= ROMFH_SIZE) {
			/* both are longer; XXX optimize max size */
			fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, sizeof(fsname)-1);
			if (len == fslen) {
				romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
				if (strncmp(name, fsname, len) == 0)
					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;

	if ((inode = iget(dir->i_sb, offset)))
		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:	res = 0;
	d_add (dentry, inode);

out:	unlock_kernel();
	return ERR_PTR(res);
}

/*
 * Ok, we do readpage, to be able to execute programs.  Unfortunately,
 * we can't use bmap, since we may have looser alignments.
 */

static int
romfs_readpage(struct file *file, struct page * page)
{
	struct inode *inode = page->mapping->host;
	loff_t offset, avail, readlen;
	void *buf;
	int result = -EIO;

	page_cache_get(page);
	lock_kernel();
	buf = kmap(page);
	if (!buf)
		goto err_out;

	/* 32 bit warning -- but not for us :) */
	offset = page_offset(page);
	if (offset < i_size_read(inode)) {
		avail = inode->i_size-offset;
		readlen = min_t(unsigned long, avail, PAGE_SIZE);
		if (romfs_copyfrom(inode, buf, ROMFS_I(inode)->i_dataoffset+offset, readlen) == readlen) {
			if (readlen < PAGE_SIZE) {
				memset(buf + readlen,0,PAGE_SIZE-readlen);
			}
			SetPageUptodate(page);
			result = 0;
		}
	}
	if (result) {
		memset(buf, 0, PAGE_SIZE);
		SetPageError(page);
	}
	flush_dcache_page(page);

	unlock_page(page);

	kunmap(page);
err_out:
	page_cache_release(page);
	unlock_kernel();

	return result;
}

/* Mapping from our types to the kernel */

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

static const struct file_operations romfs_dir_operations = {
	.read		= generic_read_dir,
	.readdir	= romfs_readdir,
};

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

static mode_t romfs_modemap[] =
{
	0, S_IFDIR+0644, S_IFREG+0644, S_IFLNK+0777,
	S_IFBLK+0600, S_IFCHR+0600, S_IFSOCK+0644, S_IFIFO+0644
};

static void
romfs_read_inode(struct inode *i)
{
	int nextfh, ino;
	struct romfs_inode ri;

	ino = i->i_ino & ROMFH_MASK;
	i->i_mode = 0;

	/* Loop for finding the real hard link */
	for(;;) {
		if (romfs_copyfrom(i, &ri, ino, ROMFH_SIZE) <= 0) {
			printk("romfs: read error for inode 0x%x\n", ino);
			return;
		}
		/* XXX: do romfs_checksum here too (with name) */

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

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

	i->i_nlink = 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;
	i->i_uid = i->i_gid = 0;

        /* Precalculate the data offset */
        ino = romfs_strnlen(i, ino+ROMFH_SIZE, ROMFS_MAXFN);
        if (ino >= 0)
                ino = ((ROMFH_SIZE+ino+1+ROMFH_PAD)&ROMFH_MASK);
        else
                ino = 0;

        ROMFS_I(i)->i_metasize = ino;
        ROMFS_I(i)->i_dataoffset = ino+(i->i_ino&ROMFH_MASK);

        /* Compute permissions */
        ino = romfs_modemap[nextfh & ROMFH_TYPE];
	/* only "normal" files have ops */
	switch (nextfh & ROMFH_TYPE) {
		case 1:
			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)
				ino |= S_IXUGO;
			i->i_mode = ino;
			break;
		case 2:
			i->i_fop = &generic_ro_fops;
			i->i_data.a_ops = &romfs_aops;
			if (nextfh & ROMFH_EXEC)
				ino |= S_IXUGO;
			i->i_mode = ino;
			break;
		case 3:
			i->i_op = &page_symlink_inode_operations;
			i->i_data.a_ops = &romfs_aops;
			i->i_mode = ino | S_IRWXUGO;
			break;
		default:
			/* depending on MBZ for sock/fifos */
			nextfh = be32_to_cpu(ri.spec);
			init_special_inode(i, ino,
					MKDEV(nextfh>>16,nextfh&0xffff));
	}
}

static struct kmem_cache * romfs_inode_cachep;

static struct inode *romfs_alloc_inode(struct super_block *sb)
{
	struct romfs_inode_info *ei;
	ei = (struct romfs_inode_info *)kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
	if (!ei)
		return NULL;
	return &ei->vfs_inode;
}

static void romfs_destroy_inode(struct inode *inode)
{
	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
}

static void init_once(void * foo, struct kmem_cache * cachep, unsigned long flags)
{
	struct romfs_inode_info *ei = (struct romfs_inode_info *) foo;

	if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
	    SLAB_CTOR_CONSTRUCTOR)
		inode_init_once(&ei->vfs_inode);
}
 
static int init_inodecache(void)
{
	romfs_inode_cachep = kmem_cache_create("romfs_inode_cache",
					     sizeof(struct romfs_inode_info),
					     0, (SLAB_RECLAIM_ACCOUNT|
						SLAB_MEM_SPREAD),
					     init_once, NULL);
	if (romfs_inode_cachep == NULL)
		return -ENOMEM;
	return 0;
}

static void destroy_inodecache(void)
{
	kmem_cache_destroy(romfs_inode_cachep);
}

static int romfs_remount(struct super_block *sb, int *flags, char *data)
{
	*flags |= MS_RDONLY;
	return 0;
}

static struct super_operations romfs_ops = {
	.alloc_inode	= romfs_alloc_inode,
	.destroy_inode	= romfs_destroy_inode,
	.read_inode	= romfs_read_inode,
	.statfs		= romfs_statfs,
	.remount_fs	= romfs_remount,
};

static int romfs_get_sb(struct file_system_type *fs_type,
	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
	return get_sb_bdev(fs_type, flags, dev_name, data, romfs_fill_super,
			   mnt);
}

static struct file_system_type romfs_fs_type = {
	.owner		= THIS_MODULE,
	.name		= "romfs",
	.get_sb		= romfs_get_sb,
	.kill_sb	= kill_block_super,
	.fs_flags	= FS_REQUIRES_DEV,
};

static int __init init_romfs_fs(void)
{
	int err = init_inodecache();
	if (err)
		goto out1;
        err = register_filesystem(&romfs_fs_type);
	if (err)
		goto out;
	return 0;
out:
	destroy_inodecache();
out1:
	return err;
}

static void __exit exit_romfs_fs(void)
{
	unregister_filesystem(&romfs_fs_type);
	destroy_inodecache();
}

/* Yes, works even as a module... :) */

module_init(init_romfs_fs)
module_exit(exit_romfs_fs)
MODULE_LICENSE("GPL");