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#include <linux/module.h>
60#include <linux/string.h>
61#include <linux/fs.h>
62#include <linux/time.h>
63#include <linux/slab.h>
64#include <linux/init.h>
65#include <linux/blkdev.h>
66#include <linux/parser.h>
67#include <linux/mount.h>
68#include <linux/namei.h>
69#include <linux/statfs.h>
70#include <linux/mtd/super.h>
71#include <linux/ctype.h>
72#include <linux/highmem.h>
73#include <linux/pagemap.h>
74#include <linux/uaccess.h>
75#include "internal.h"
76
77static struct kmem_cache *romfs_inode_cachep;
78
79static const umode_t romfs_modemap[8] = {
80	0,			/* hard link */
81	S_IFDIR  | 0644,	/* directory */
82	S_IFREG  | 0644,	/* regular file */
83	S_IFLNK  | 0777,	/* symlink */
84	S_IFBLK  | 0600,	/* blockdev */
85	S_IFCHR  | 0600,	/* chardev */
86	S_IFSOCK | 0644,	/* socket */
87	S_IFIFO  | 0644		/* FIFO */
88};
89
90static const unsigned char romfs_dtype_table[] = {
91	DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
92};
93
94static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
95
96/*
97 * read a page worth of data from the image
98 */
99static int romfs_readpage(struct file *file, struct page *page)
100{
101	struct inode *inode = page->mapping->host;
102	loff_t offset, size;
103	unsigned long fillsize, pos;
104	void *buf;
105	int ret;
106
107	buf = kmap(page);
108	if (!buf)
109		return -ENOMEM;
110
111	/* 32 bit warning -- but not for us :) */
112	offset = page_offset(page);
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			SetPageError(page);
125			fillsize = 0;
126			ret = -EIO;
127		}
128	}
129
130	if (fillsize < PAGE_SIZE)
131		memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
132	if (ret == 0)
133		SetPageUptodate(page);
134
135	flush_dcache_page(page);
136	kunmap(page);
137	unlock_page(page);
138	return ret;
139}
140
141static const struct address_space_operations romfs_aops = {
142	.readpage	= romfs_readpage
143};
144
145/*
146 * read the entries from a directory
147 */
148static int romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
149{
150	struct inode *i = filp->f_dentry->d_inode;
151	struct romfs_inode ri;
152	unsigned long offset, maxoff;
153	int j, ino, nextfh;
154	int stored = 0;
155	char fsname[ROMFS_MAXFN];
156	int ret;
157
158	maxoff = romfs_maxsize(i->i_sb);
159
160	offset = filp->f_pos;
161	if (!offset) {
162		offset = i->i_ino & ROMFH_MASK;
163		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
164		if (ret < 0)
165			goto out;
166		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
167	}
168
169	/* Not really failsafe, but we are read-only... */
170	for (;;) {
171		if (!offset || offset >= maxoff) {
172			offset = maxoff;
173			filp->f_pos = offset;
174			goto out;
175		}
176		filp->f_pos = offset;
177
178		/* Fetch inode info */
179		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
180		if (ret < 0)
181			goto out;
182
183		j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
184				      sizeof(fsname) - 1);
185		if (j < 0)
186			goto out;
187
188		ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
189		if (ret < 0)
190			goto out;
191		fsname[j] = '\0';
192
193		ino = offset;
194		nextfh = be32_to_cpu(ri.next);
195		if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
196			ino = be32_to_cpu(ri.spec);
197		if (filldir(dirent, fsname, j, offset, ino,
198			    romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0)
199			goto out;
200
201		stored++;
202		offset = nextfh & ROMFH_MASK;
203	}
204
205out:
206	return stored;
207}
208
209/*
210 * look up an entry in a directory
211 */
212static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
213				   struct nameidata *nd)
214{
215	unsigned long offset, maxoff;
216	struct inode *inode;
217	struct romfs_inode ri;
218	const char *name;		/* got from dentry */
219	int len, ret;
220
221	offset = dir->i_ino & ROMFH_MASK;
222	ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
223	if (ret < 0)
224		goto error;
225
226	/* search all the file entries in the list starting from the one
227	 * pointed to by the directory's special data */
228	maxoff = romfs_maxsize(dir->i_sb);
229	offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
230
231	name = dentry->d_name.name;
232	len = dentry->d_name.len;
233
234	for (;;) {
235		if (!offset || offset >= maxoff)
236			goto out0;
237
238		ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
239		if (ret < 0)
240			goto error;
241
242		/* try to match the first 16 bytes of name */
243		ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
244				       len);
245		if (ret < 0)
246			goto error;
247		if (ret == 1)
248			break;
249
250		/* next entry */
251		offset = be32_to_cpu(ri.next) & ROMFH_MASK;
252	}
253
254	/* Hard link handling */
255	if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
256		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
257
258	inode = romfs_iget(dir->i_sb, offset);
259	if (IS_ERR(inode)) {
260		ret = PTR_ERR(inode);
261		goto error;
262	}
263	goto outi;
264
265	/*
266	 * it's a bit funky, _lookup needs to return an error code
267	 * (negative) or a NULL, both as a dentry.  ENOENT should not
268	 * be returned, instead we need to create a negative dentry by
269	 * d_add(dentry, NULL); and return 0 as no error.
270	 * (Although as I see, it only matters on writable file
271	 * systems).
272	 */
273out0:
274	inode = NULL;
275outi:
276	d_add(dentry, inode);
277	ret = 0;
278error:
279	return ERR_PTR(ret);
280}
281
282static const struct file_operations romfs_dir_operations = {
283	.read		= generic_read_dir,
284	.readdir	= romfs_readdir,
285};
286
287static 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 */
295static 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
313		nextfh = be32_to_cpu(ri.next);
314		if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
315			break;
316
317		pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
318	}
319
320	/* determine the length of the filename */
321	nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
322	if (IS_ERR_VALUE(nlen))
323		goto eio;
324
325	/* get an inode for this image position */
326	i = iget_locked(sb, pos);
327	if (!i)
328		return ERR_PTR(-ENOMEM);
329
330	if (!(i->i_state & I_NEW))
331		return i;
332
333	/* precalculate the data offset */
334	inode = ROMFS_I(i);
335	inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
336	inode->i_dataoffset = pos + inode->i_metasize;
337
338	i->i_nlink = 1;		/* Hard to decide.. */
339	i->i_size = be32_to_cpu(ri.size);
340	i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
341	i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
342
343	/* set up mode and ops */
344	mode = romfs_modemap[nextfh & ROMFH_TYPE];
345
346	switch (nextfh & ROMFH_TYPE) {
347	case ROMFH_DIR:
348		i->i_size = ROMFS_I(i)->i_metasize;
349		i->i_op = &romfs_dir_inode_operations;
350		i->i_fop = &romfs_dir_operations;
351		if (nextfh & ROMFH_EXEC)
352			mode |= S_IXUGO;
353		break;
354	case ROMFH_REG:
355		i->i_fop = &romfs_ro_fops;
356		i->i_data.a_ops = &romfs_aops;
357		if (i->i_sb->s_mtd)
358			i->i_data.backing_dev_info =
359				i->i_sb->s_mtd->backing_dev_info;
360		if (nextfh & ROMFH_EXEC)
361			mode |= S_IXUGO;
362		break;
363	case ROMFH_SYM:
364		i->i_op = &page_symlink_inode_operations;
365		i->i_data.a_ops = &romfs_aops;
366		mode |= S_IRWXUGO;
367		break;
368	default:
369		/* depending on MBZ for sock/fifos */
370		nextfh = be32_to_cpu(ri.spec);
371		init_special_inode(i, mode, MKDEV(nextfh >> 16,
372						  nextfh & 0xffff));
373		break;
374	}
375
376	i->i_mode = mode;
377
378	unlock_new_inode(i);
379	return i;
380
381eio:
382	ret = -EIO;
383error:
384	printk(KERN_ERR "ROMFS: read error for inode 0x%lx\n", pos);
385	return ERR_PTR(ret);
386}
387
388/*
389 * allocate a new inode
390 */
391static struct inode *romfs_alloc_inode(struct super_block *sb)
392{
393	struct romfs_inode_info *inode;
394	inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
395	return inode ? &inode->vfs_inode : NULL;
396}
397
398/*
399 * return a spent inode to the slab cache
400 */
401static void romfs_destroy_inode(struct inode *inode)
402{
403	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
404}
405
406/*
407 * get filesystem statistics
408 */
409static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
410{
411	struct super_block *sb = dentry->d_sb;
412	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
413
414	buf->f_type = ROMFS_MAGIC;
415	buf->f_namelen = ROMFS_MAXFN;
416	buf->f_bsize = ROMBSIZE;
417	buf->f_bfree = buf->f_bavail = buf->f_ffree;
418	buf->f_blocks =
419		(romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
420	buf->f_fsid.val[0] = (u32)id;
421	buf->f_fsid.val[1] = (u32)(id >> 32);
422	return 0;
423}
424
425/*
426 * remounting must involve read-only
427 */
428static int romfs_remount(struct super_block *sb, int *flags, char *data)
429{
430	*flags |= MS_RDONLY;
431	return 0;
432}
433
434static const struct super_operations romfs_super_ops = {
435	.alloc_inode	= romfs_alloc_inode,
436	.destroy_inode	= romfs_destroy_inode,
437	.statfs		= romfs_statfs,
438	.remount_fs	= romfs_remount,
439};
440
441/*
442 * checksum check on part of a romfs filesystem
443 */
444static __u32 romfs_checksum(const void *data, int size)
445{
446	const __be32 *ptr = data;
447	__u32 sum;
448
449	sum = 0;
450	size >>= 2;
451	while (size > 0) {
452		sum += be32_to_cpu(*ptr++);
453		size--;
454	}
455	return sum;
456}
457
458/*
459 * fill in the superblock
460 */
461static int romfs_fill_super(struct super_block *sb, void *data, int silent)
462{
463	struct romfs_super_block *rsb;
464	struct inode *root;
465	unsigned long pos, img_size;
466	const char *storage;
467	size_t len;
468	int ret;
469
470#ifdef CONFIG_BLOCK
471	if (!sb->s_mtd) {
472		sb_set_blocksize(sb, ROMBSIZE);
473	} else {
474		sb->s_blocksize = ROMBSIZE;
475		sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
476	}
477#endif
478
479	sb->s_maxbytes = 0xFFFFFFFF;
480	sb->s_magic = ROMFS_MAGIC;
481	sb->s_flags |= MS_RDONLY | MS_NOATIME;
482	sb->s_op = &romfs_super_ops;
483
484	/* read the image superblock and check it */
485	rsb = kmalloc(512, GFP_KERNEL);
486	if (!rsb)
487		return -ENOMEM;
488
489	sb->s_fs_info = (void *) 512;
490	ret = romfs_dev_read(sb, 0, rsb, 512);
491	if (ret < 0)
492		goto error_rsb;
493
494	img_size = be32_to_cpu(rsb->size);
495
496	if (sb->s_mtd && img_size > sb->s_mtd->size)
497		goto error_rsb_inval;
498
499	sb->s_fs_info = (void *) img_size;
500
501	if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
502	    img_size < ROMFH_SIZE) {
503		if (!silent)
504			printk(KERN_WARNING "VFS:"
505			       " Can't find a romfs filesystem on dev %s.\n",
506			       sb->s_id);
507		goto error_rsb_inval;
508	}
509
510	if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
511		printk(KERN_ERR "ROMFS: bad initial checksum on dev %s.\n",
512		       sb->s_id);
513		goto error_rsb_inval;
514	}
515
516	storage = sb->s_mtd ? "MTD" : "the block layer";
517
518	len = strnlen(rsb->name, ROMFS_MAXFN);
519	if (!silent)
520		printk(KERN_NOTICE "ROMFS: Mounting image '%*.*s' through %s\n",
521		       (unsigned) len, (unsigned) len, rsb->name, storage);
522
523	kfree(rsb);
524	rsb = NULL;
525
526	/* find the root directory */
527	pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
528
529	root = romfs_iget(sb, pos);
530	if (IS_ERR(root))
531		goto error;
532
533	sb->s_root = d_alloc_root(root);
534	if (!sb->s_root)
535		goto error_i;
536
537	return 0;
538
539error_i:
540	iput(root);
541error:
542	return -EINVAL;
543error_rsb_inval:
544	ret = -EINVAL;
545error_rsb:
546	kfree(rsb);
547	return ret;
548}
549
550/*
551 * get a superblock for mounting
552 */
553static int romfs_get_sb(struct file_system_type *fs_type,
554			int flags, const char *dev_name,
555			void *data, struct vfsmount *mnt)
556{
557	int ret = -EINVAL;
558
559#ifdef CONFIG_ROMFS_ON_MTD
560	ret = get_sb_mtd(fs_type, flags, dev_name, data, romfs_fill_super,
561			 mnt);
562#endif
563#ifdef CONFIG_ROMFS_ON_BLOCK
564	if (ret == -EINVAL)
565		ret = get_sb_bdev(fs_type, flags, dev_name, data,
566				  romfs_fill_super, mnt);
567#endif
568	return ret;
569}
570
571/*
572 * destroy a romfs superblock in the appropriate manner
573 */
574static 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
590static struct file_system_type romfs_fs_type = {
591	.owner		= THIS_MODULE,
592	.name		= "romfs",
593	.get_sb		= romfs_get_sb,
594	.kill_sb	= romfs_kill_sb,
595	.fs_flags	= FS_REQUIRES_DEV,
596};
597
598/*
599 * inode storage initialiser
600 */
601static void romfs_i_init_once(void *_inode)
602{
603	struct romfs_inode_info *inode = _inode;
604
605	inode_init_once(&inode->vfs_inode);
606}
607
608/*
609 * romfs module initialisation
610 */
611static int __init init_romfs_fs(void)
612{
613	int ret;
614
615	printk(KERN_INFO "ROMFS MTD (C) 2007 Red Hat, Inc.\n");
616
617	romfs_inode_cachep =
618		kmem_cache_create("romfs_i",
619				  sizeof(struct romfs_inode_info), 0,
620				  SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
621				  romfs_i_init_once);
622
623	if (!romfs_inode_cachep) {
624		printk(KERN_ERR
625		       "ROMFS error: Failed to initialise inode cache\n");
626		return -ENOMEM;
627	}
628	ret = register_filesystem(&romfs_fs_type);
629	if (ret) {
630		printk(KERN_ERR "ROMFS error: Failed to register filesystem\n");
631		goto error_register;
632	}
633	return 0;
634
635error_register:
636	kmem_cache_destroy(romfs_inode_cachep);
637	return ret;
638}
639
640/*
641 * romfs module removal
642 */
643static void __exit exit_romfs_fs(void)
644{
645	unregister_filesystem(&romfs_fs_type);
646	kmem_cache_destroy(romfs_inode_cachep);
647}
648
649module_init(init_romfs_fs);
650module_exit(exit_romfs_fs);
651
652MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
653MODULE_AUTHOR("Red Hat, Inc.");
654MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */
655