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
80static struct kmem_cache *romfs_inode_cachep;
81
82static 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
93static 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
97static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
98
99/*
100 * read a page worth of data from the image
101 */
102static int romfs_read_folio(struct file *file, struct folio *folio)
103{
104	struct page *page = &folio->page;
105	struct inode *inode = page->mapping->host;
106	loff_t offset, size;
107	unsigned long fillsize, pos;
108	void *buf;
109	int ret;
110
111	buf = kmap(page);
112	if (!buf)
113		return -ENOMEM;
114
115	/* 32 bit warning -- but not for us :) */
116	offset = page_offset(page);
117	size = i_size_read(inode);
118	fillsize = 0;
119	ret = 0;
120	if (offset < size) {
121		size -= offset;
122		fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
123
124		pos = ROMFS_I(inode)->i_dataoffset + offset;
125
126		ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
127		if (ret < 0) {
128			SetPageError(page);
129			fillsize = 0;
130			ret = -EIO;
131		}
132	}
133
134	if (fillsize < PAGE_SIZE)
135		memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
136	if (ret == 0)
137		SetPageUptodate(page);
138
139	flush_dcache_page(page);
140	kunmap(page);
141	unlock_page(page);
142	return ret;
143}
144
145static const struct address_space_operations romfs_aops = {
146	.read_folio	= romfs_read_folio
147};
148
149/*
150 * read the entries from a directory
151 */
152static int romfs_readdir(struct file *file, struct dir_context *ctx)
153{
154	struct inode *i = file_inode(file);
155	struct romfs_inode ri;
156	unsigned long offset, maxoff;
157	int j, ino, nextfh;
158	char fsname[ROMFS_MAXFN];	/* XXX dynamic? */
159	int ret;
160
161	maxoff = romfs_maxsize(i->i_sb);
162
163	offset = ctx->pos;
164	if (!offset) {
165		offset = i->i_ino & ROMFH_MASK;
166		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
167		if (ret < 0)
168			goto out;
169		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
170	}
171
172	/* Not really failsafe, but we are read-only... */
173	for (;;) {
174		if (!offset || offset >= maxoff) {
175			offset = maxoff;
176			ctx->pos = offset;
177			goto out;
178		}
179		ctx->pos = offset;
180
181		/* Fetch inode info */
182		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
183		if (ret < 0)
184			goto out;
185
186		j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
187				      sizeof(fsname) - 1);
188		if (j < 0)
189			goto out;
190
191		ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
192		if (ret < 0)
193			goto out;
194		fsname[j] = '\0';
195
196		ino = offset;
197		nextfh = be32_to_cpu(ri.next);
198		if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
199			ino = be32_to_cpu(ri.spec);
200		if (!dir_emit(ctx, fsname, j, ino,
201			    romfs_dtype_table[nextfh & ROMFH_TYPE]))
202			goto out;
203
204		offset = nextfh & ROMFH_MASK;
205	}
206out:
207	return 0;
208}
209
210/*
211 * look up an entry in a directory
212 */
213static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
214				   unsigned int flags)
215{
216	unsigned long offset, maxoff;
217	struct inode *inode = NULL;
218	struct romfs_inode ri;
219	const char *name;		/* got from dentry */
220	int len, ret;
221
222	offset = dir->i_ino & ROMFH_MASK;
223	ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
224	if (ret < 0)
225		goto error;
226
227	/* search all the file entries in the list starting from the one
228	 * pointed to by the directory's special data */
229	maxoff = romfs_maxsize(dir->i_sb);
230	offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
231
232	name = dentry->d_name.name;
233	len = dentry->d_name.len;
234
235	for (;;) {
236		if (!offset || offset >= maxoff)
237			break;
238
239		ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
240		if (ret < 0)
241			goto error;
242
243		/* try to match the first 16 bytes of name */
244		ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
245				       len);
246		if (ret < 0)
247			goto error;
248		if (ret == 1) {
249			/* Hard link handling */
250			if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
251				offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
252			inode = romfs_iget(dir->i_sb, offset);
253			break;
254		}
255
256		/* next entry */
257		offset = be32_to_cpu(ri.next) & ROMFH_MASK;
258	}
259
260	return d_splice_alias(inode, dentry);
261error:
262	return ERR_PTR(ret);
263}
264
265static const struct file_operations romfs_dir_operations = {
266	.read		= generic_read_dir,
267	.iterate_shared	= romfs_readdir,
268	.llseek		= generic_file_llseek,
269};
270
271static const struct inode_operations romfs_dir_inode_operations = {
272	.lookup		= romfs_lookup,
273};
274
275/*
276 * get a romfs inode based on its position in the image (which doubles as the
277 * inode number)
278 */
279static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
280{
281	struct romfs_inode_info *inode;
282	struct romfs_inode ri;
283	struct inode *i;
284	unsigned long nlen;
285	unsigned nextfh;
286	int ret;
287	umode_t mode;
288
289	/* we might have to traverse a chain of "hard link" file entries to get
290	 * to the actual file */
291	for (;;) {
292		ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
293		if (ret < 0)
294			goto error;
295
296		/* XXX: do romfs_checksum here too (with name) */
297
298		nextfh = be32_to_cpu(ri.next);
299		if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
300			break;
301
302		pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
303	}
304
305	/* determine the length of the filename */
306	nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
307	if (IS_ERR_VALUE(nlen))
308		goto eio;
309
310	/* get an inode for this image position */
311	i = iget_locked(sb, pos);
312	if (!i)
313		return ERR_PTR(-ENOMEM);
314
315	if (!(i->i_state & I_NEW))
316		return i;
317
318	/* precalculate the data offset */
319	inode = ROMFS_I(i);
320	inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
321	inode->i_dataoffset = pos + inode->i_metasize;
322
323	set_nlink(i, 1);		/* Hard to decide.. */
324	i->i_size = be32_to_cpu(ri.size);
325	inode_set_mtime_to_ts(i,
326			      inode_set_atime_to_ts(i, inode_set_ctime(i, 0, 0)));
327
328	/* set up mode and ops */
329	mode = romfs_modemap[nextfh & ROMFH_TYPE];
330
331	switch (nextfh & ROMFH_TYPE) {
332	case ROMFH_DIR:
333		i->i_size = ROMFS_I(i)->i_metasize;
334		i->i_op = &romfs_dir_inode_operations;
335		i->i_fop = &romfs_dir_operations;
336		if (nextfh & ROMFH_EXEC)
337			mode |= S_IXUGO;
338		break;
339	case ROMFH_REG:
340		i->i_fop = &romfs_ro_fops;
341		i->i_data.a_ops = &romfs_aops;
342		if (nextfh & ROMFH_EXEC)
343			mode |= S_IXUGO;
344		break;
345	case ROMFH_SYM:
346		i->i_op = &page_symlink_inode_operations;
347		inode_nohighmem(i);
348		i->i_data.a_ops = &romfs_aops;
349		mode |= S_IRWXUGO;
350		break;
351	default:
352		/* depending on MBZ for sock/fifos */
353		nextfh = be32_to_cpu(ri.spec);
354		init_special_inode(i, mode, MKDEV(nextfh >> 16,
355						  nextfh & 0xffff));
356		break;
357	}
358
359	i->i_mode = mode;
360	i->i_blocks = (i->i_size + 511) >> 9;
361
362	unlock_new_inode(i);
363	return i;
364
365eio:
366	ret = -EIO;
367error:
368	pr_err("read error for inode 0x%lx\n", pos);
369	return ERR_PTR(ret);
370}
371
372/*
373 * allocate a new inode
374 */
375static struct inode *romfs_alloc_inode(struct super_block *sb)
376{
377	struct romfs_inode_info *inode;
378
379	inode = alloc_inode_sb(sb, romfs_inode_cachep, GFP_KERNEL);
380	return inode ? &inode->vfs_inode : NULL;
381}
382
383/*
384 * return a spent inode to the slab cache
385 */
386static void romfs_free_inode(struct inode *inode)
387{
388	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
389}
390
391/*
392 * get filesystem statistics
393 */
394static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
395{
396	struct super_block *sb = dentry->d_sb;
397	u64 id = 0;
398
399	/* When calling huge_encode_dev(),
400	 * use sb->s_bdev->bd_dev when,
401	 *   - CONFIG_ROMFS_ON_BLOCK defined
402	 * use sb->s_dev when,
403	 *   - CONFIG_ROMFS_ON_BLOCK undefined and
404	 *   - CONFIG_ROMFS_ON_MTD defined
405	 * leave id as 0 when,
406	 *   - CONFIG_ROMFS_ON_BLOCK undefined and
407	 *   - CONFIG_ROMFS_ON_MTD undefined
408	 */
409	if (sb->s_bdev)
410		id = huge_encode_dev(sb->s_bdev->bd_dev);
411	else if (sb->s_dev)
412		id = huge_encode_dev(sb->s_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 = u64_to_fsid(id);
421	return 0;
422}
423
424/*
425 * remounting must involve read-only
426 */
427static int romfs_reconfigure(struct fs_context *fc)
428{
429	sync_filesystem(fc->root->d_sb);
430	fc->sb_flags |= SB_RDONLY;
431	return 0;
432}
433
434static const struct super_operations romfs_super_ops = {
435	.alloc_inode	= romfs_alloc_inode,
436	.free_inode	= romfs_free_inode,
437	.statfs		= romfs_statfs,
438};
439
440/*
441 * checksum check on part of a romfs filesystem
442 */
443static __u32 romfs_checksum(const void *data, int size)
444{
445	const __be32 *ptr = data;
446	__u32 sum;
447
448	sum = 0;
449	size >>= 2;
450	while (size > 0) {
451		sum += be32_to_cpu(*ptr++);
452		size--;
453	}
454	return sum;
455}
456
457/*
458 * fill in the superblock
459 */
460static int romfs_fill_super(struct super_block *sb, struct fs_context *fc)
461{
462	struct romfs_super_block *rsb;
463	struct inode *root;
464	unsigned long pos, img_size;
465	const char *storage;
466	size_t len;
467	int ret;
468
469#ifdef CONFIG_BLOCK
470	if (!sb->s_mtd) {
471		sb_set_blocksize(sb, ROMBSIZE);
472	} else {
473		sb->s_blocksize = ROMBSIZE;
474		sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
475	}
476#endif
477
478	sb->s_maxbytes = 0xFFFFFFFF;
479	sb->s_magic = ROMFS_MAGIC;
480	sb->s_flags |= SB_RDONLY | SB_NOATIME;
481	sb->s_time_min = 0;
482	sb->s_time_max = 0;
483	sb->s_op = &romfs_super_ops;
484
485#ifdef CONFIG_ROMFS_ON_MTD
486	/* Use same dev ID from the underlying mtdblock device */
487	if (sb->s_mtd)
488		sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
489#endif
490	/* read the image superblock and check it */
491	rsb = kmalloc(512, GFP_KERNEL);
492	if (!rsb)
493		return -ENOMEM;
494
495	sb->s_fs_info = (void *) 512;
496	ret = romfs_dev_read(sb, 0, rsb, 512);
497	if (ret < 0)
498		goto error_rsb;
499
500	img_size = be32_to_cpu(rsb->size);
501
502	if (sb->s_mtd && img_size > sb->s_mtd->size)
503		goto error_rsb_inval;
504
505	sb->s_fs_info = (void *) img_size;
506
507	if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
508	    img_size < ROMFH_SIZE) {
509		if (!(fc->sb_flags & SB_SILENT))
510			errorf(fc, "VFS: Can't find a romfs filesystem on dev %s.\n",
511			       sb->s_id);
512		goto error_rsb_inval;
513	}
514
515	if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
516		pr_err("bad initial checksum on dev %s.\n", sb->s_id);
517		goto error_rsb_inval;
518	}
519
520	storage = sb->s_mtd ? "MTD" : "the block layer";
521
522	len = strnlen(rsb->name, ROMFS_MAXFN);
523	if (!(fc->sb_flags & SB_SILENT))
524		pr_notice("Mounting image '%*.*s' through %s\n",
525			  (unsigned) len, (unsigned) len, rsb->name, storage);
526
527	kfree(rsb);
528	rsb = NULL;
529
530	/* find the root directory */
531	pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
532
533	root = romfs_iget(sb, pos);
534	if (IS_ERR(root))
535		return PTR_ERR(root);
536
537	sb->s_root = d_make_root(root);
538	if (!sb->s_root)
539		return -ENOMEM;
540
541	return 0;
542
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_tree(struct fs_context *fc)
554{
555	int ret = -EINVAL;
556
557#ifdef CONFIG_ROMFS_ON_MTD
558	ret = get_tree_mtd(fc, romfs_fill_super);
559#endif
560#ifdef CONFIG_ROMFS_ON_BLOCK
561	if (ret == -EINVAL)
562		ret = get_tree_bdev(fc, romfs_fill_super);
563#endif
564	return ret;
565}
566
567static const struct fs_context_operations romfs_context_ops = {
568	.get_tree	= romfs_get_tree,
569	.reconfigure	= romfs_reconfigure,
570};
571
572/*
573 * Set up the filesystem mount context.
574 */
575static int romfs_init_fs_context(struct fs_context *fc)
576{
577	fc->ops = &romfs_context_ops;
578	return 0;
579}
580
581/*
582 * destroy a romfs superblock in the appropriate manner
583 */
584static void romfs_kill_sb(struct super_block *sb)
585{
586	generic_shutdown_super(sb);
587
588#ifdef CONFIG_ROMFS_ON_MTD
589	if (sb->s_mtd) {
590		put_mtd_device(sb->s_mtd);
591		sb->s_mtd = NULL;
592	}
593#endif
594#ifdef CONFIG_ROMFS_ON_BLOCK
595	if (sb->s_bdev) {
596		sync_blockdev(sb->s_bdev);
597		bdev_fput(sb->s_bdev_file);
598	}
599#endif
600}
601
602static struct file_system_type romfs_fs_type = {
603	.owner		= THIS_MODULE,
604	.name		= "romfs",
605	.init_fs_context = romfs_init_fs_context,
606	.kill_sb	= romfs_kill_sb,
607	.fs_flags	= FS_REQUIRES_DEV,
608};
609MODULE_ALIAS_FS("romfs");
610
611/*
612 * inode storage initialiser
613 */
614static void romfs_i_init_once(void *_inode)
615{
616	struct romfs_inode_info *inode = _inode;
617
618	inode_init_once(&inode->vfs_inode);
619}
620
621/*
622 * romfs module initialisation
623 */
624static int __init init_romfs_fs(void)
625{
626	int ret;
627
628	pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");
629
630	romfs_inode_cachep =
631		kmem_cache_create("romfs_i",
632				  sizeof(struct romfs_inode_info), 0,
633				  SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT,
634				  romfs_i_init_once);
635
636	if (!romfs_inode_cachep) {
637		pr_err("Failed to initialise inode cache\n");
638		return -ENOMEM;
639	}
640	ret = register_filesystem(&romfs_fs_type);
641	if (ret) {
642		pr_err("Failed to register filesystem\n");
643		goto error_register;
644	}
645	return 0;
646
647error_register:
648	kmem_cache_destroy(romfs_inode_cachep);
649	return ret;
650}
651
652/*
653 * romfs module removal
654 */
655static void __exit exit_romfs_fs(void)
656{
657	unregister_filesystem(&romfs_fs_type);
658	/*
659	 * Make sure all delayed rcu free inodes are flushed before we
660	 * destroy cache.
661	 */
662	rcu_barrier();
663	kmem_cache_destroy(romfs_inode_cachep);
664}
665
666module_init(init_romfs_fs);
667module_exit(exit_romfs_fs);
668
669MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
670MODULE_AUTHOR("Red Hat, Inc.");
671MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */
672