xref: /kernel/linux/linux-5.10/fs/romfs/super.c (revision 8c2ecf20) 
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#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_readpage(struct file *file, struct page *page)
103{
104	struct inode *inode = page->mapping->host;
105	loff_t offset, size;
106	unsigned long fillsize, pos;
107	void *buf;
108	int ret;
109
110	buf = kmap(page);
111	if (!buf)
112		return -ENOMEM;
113
114	/* 32 bit warning -- but not for us :) */
115	offset = page_offset(page);
116	size = i_size_read(inode);
117	fillsize = 0;
118	ret = 0;
119	if (offset < size) {
120		size -= offset;
121		fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
122
123		pos = ROMFS_I(inode)->i_dataoffset + offset;
124
125		ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
126		if (ret < 0) {
127			SetPageError(page);
128			fillsize = 0;
129			ret = -EIO;
130		}
131	}
132
133	if (fillsize < PAGE_SIZE)
134		memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
135	if (ret == 0)
136		SetPageUptodate(page);
137
138	flush_dcache_page(page);
139	kunmap(page);
140	unlock_page(page);
141	return ret;
142}
143
144static const struct address_space_operations romfs_aops = {
145	.readpage	= romfs_readpage
146};
147
148/*
149 * read the entries from a directory
150 */
151static int romfs_readdir(struct file *file, struct dir_context *ctx)
152{
153	struct inode *i = file_inode(file);
154	struct romfs_inode ri;
155	unsigned long offset, maxoff;
156	int j, ino, nextfh;
157	char fsname[ROMFS_MAXFN];	/* XXX dynamic? */
158	int ret;
159
160	maxoff = romfs_maxsize(i->i_sb);
161
162	offset = ctx->pos;
163	if (!offset) {
164		offset = i->i_ino & ROMFH_MASK;
165		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
166		if (ret < 0)
167			goto out;
168		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
169	}
170
171	/* Not really failsafe, but we are read-only... */
172	for (;;) {
173		if (!offset || offset >= maxoff) {
174			offset = maxoff;
175			ctx->pos = offset;
176			goto out;
177		}
178		ctx->pos = offset;
179
180		/* Fetch inode info */
181		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
182		if (ret < 0)
183			goto out;
184
185		j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
186				      sizeof(fsname) - 1);
187		if (j < 0)
188			goto out;
189
190		ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
191		if (ret < 0)
192			goto out;
193		fsname[j] = '\0';
194
195		ino = offset;
196		nextfh = be32_to_cpu(ri.next);
197		if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
198			ino = be32_to_cpu(ri.spec);
199		if (!dir_emit(ctx, fsname, j, ino,
200			    romfs_dtype_table[nextfh & ROMFH_TYPE]))
201			goto out;
202
203		offset = nextfh & ROMFH_MASK;
204	}
205out:
206	return 0;
207}
208
209/*
210 * look up an entry in a directory
211 */
212static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
213				   unsigned int flags)
214{
215	unsigned long offset, maxoff;
216	struct inode *inode = NULL;
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			break;
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			/* Hard link handling */
249			if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
250				offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
251			inode = romfs_iget(dir->i_sb, offset);
252			break;
253		}
254
255		/* next entry */
256		offset = be32_to_cpu(ri.next) & ROMFH_MASK;
257	}
258
259	return d_splice_alias(inode, dentry);
260error:
261	return ERR_PTR(ret);
262}
263
264static const struct file_operations romfs_dir_operations = {
265	.read		= generic_read_dir,
266	.iterate_shared	= romfs_readdir,
267	.llseek		= generic_file_llseek,
268};
269
270static const struct inode_operations romfs_dir_inode_operations = {
271	.lookup		= romfs_lookup,
272};
273
274/*
275 * get a romfs inode based on its position in the image (which doubles as the
276 * inode number)
277 */
278static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
279{
280	struct romfs_inode_info *inode;
281	struct romfs_inode ri;
282	struct inode *i;
283	unsigned long nlen;
284	unsigned nextfh;
285	int ret;
286	umode_t mode;
287
288	/* we might have to traverse a chain of "hard link" file entries to get
289	 * to the actual file */
290	for (;;) {
291		ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
292		if (ret < 0)
293			goto error;
294
295		/* XXX: do romfs_checksum here too (with name) */
296
297		nextfh = be32_to_cpu(ri.next);
298		if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
299			break;
300
301		pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
302	}
303
304	/* determine the length of the filename */
305	nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
306	if (IS_ERR_VALUE(nlen))
307		goto eio;
308
309	/* get an inode for this image position */
310	i = iget_locked(sb, pos);
311	if (!i)
312		return ERR_PTR(-ENOMEM);
313
314	if (!(i->i_state & I_NEW))
315		return i;
316
317	/* precalculate the data offset */
318	inode = ROMFS_I(i);
319	inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
320	inode->i_dataoffset = pos + inode->i_metasize;
321
322	set_nlink(i, 1);		/* Hard to decide.. */
323	i->i_size = be32_to_cpu(ri.size);
324	i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
325	i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
326
327	/* set up mode and ops */
328	mode = romfs_modemap[nextfh & ROMFH_TYPE];
329
330	switch (nextfh & ROMFH_TYPE) {
331	case ROMFH_DIR:
332		i->i_size = ROMFS_I(i)->i_metasize;
333		i->i_op = &romfs_dir_inode_operations;
334		i->i_fop = &romfs_dir_operations;
335		if (nextfh & ROMFH_EXEC)
336			mode |= S_IXUGO;
337		break;
338	case ROMFH_REG:
339		i->i_fop = &romfs_ro_fops;
340		i->i_data.a_ops = &romfs_aops;
341		if (nextfh & ROMFH_EXEC)
342			mode |= S_IXUGO;
343		break;
344	case ROMFH_SYM:
345		i->i_op = &page_symlink_inode_operations;
346		inode_nohighmem(i);
347		i->i_data.a_ops = &romfs_aops;
348		mode |= S_IRWXUGO;
349		break;
350	default:
351		/* depending on MBZ for sock/fifos */
352		nextfh = be32_to_cpu(ri.spec);
353		init_special_inode(i, mode, MKDEV(nextfh >> 16,
354						  nextfh & 0xffff));
355		break;
356	}
357
358	i->i_mode = mode;
359	i->i_blocks = (i->i_size + 511) >> 9;
360
361	unlock_new_inode(i);
362	return i;
363
364eio:
365	ret = -EIO;
366error:
367	pr_err("read error for inode 0x%lx\n", pos);
368	return ERR_PTR(ret);
369}
370
371/*
372 * allocate a new inode
373 */
374static struct inode *romfs_alloc_inode(struct super_block *sb)
375{
376	struct romfs_inode_info *inode;
377
378	inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
379	return inode ? &inode->vfs_inode : NULL;
380}
381
382/*
383 * return a spent inode to the slab cache
384 */
385static void romfs_free_inode(struct inode *inode)
386{
387	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
388}
389
390/*
391 * get filesystem statistics
392 */
393static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
394{
395	struct super_block *sb = dentry->d_sb;
396	u64 id = 0;
397
398	/* When calling huge_encode_dev(),
399	 * use sb->s_bdev->bd_dev when,
400	 *   - CONFIG_ROMFS_ON_BLOCK defined
401	 * use sb->s_dev when,
402	 *   - CONFIG_ROMFS_ON_BLOCK undefined and
403	 *   - CONFIG_ROMFS_ON_MTD defined
404	 * leave id as 0 when,
405	 *   - CONFIG_ROMFS_ON_BLOCK undefined and
406	 *   - CONFIG_ROMFS_ON_MTD undefined
407	 */
408	if (sb->s_bdev)
409		id = huge_encode_dev(sb->s_bdev->bd_dev);
410	else if (sb->s_dev)
411		id = huge_encode_dev(sb->s_dev);
412
413	buf->f_type = ROMFS_MAGIC;
414	buf->f_namelen = ROMFS_MAXFN;
415	buf->f_bsize = ROMBSIZE;
416	buf->f_bfree = buf->f_bavail = buf->f_ffree;
417	buf->f_blocks =
418		(romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
419	buf->f_fsid = u64_to_fsid(id);
420	return 0;
421}
422
423/*
424 * remounting must involve read-only
425 */
426static int romfs_reconfigure(struct fs_context *fc)
427{
428	sync_filesystem(fc->root->d_sb);
429	fc->sb_flags |= SB_RDONLY;
430	return 0;
431}
432
433static const struct super_operations romfs_super_ops = {
434	.alloc_inode	= romfs_alloc_inode,
435	.free_inode	= romfs_free_inode,
436	.statfs		= romfs_statfs,
437};
438
439/*
440 * checksum check on part of a romfs filesystem
441 */
442static __u32 romfs_checksum(const void *data, int size)
443{
444	const __be32 *ptr = data;
445	__u32 sum;
446
447	sum = 0;
448	size >>= 2;
449	while (size > 0) {
450		sum += be32_to_cpu(*ptr++);
451		size--;
452	}
453	return sum;
454}
455
456/*
457 * fill in the superblock
458 */
459static int romfs_fill_super(struct super_block *sb, struct fs_context *fc)
460{
461	struct romfs_super_block *rsb;
462	struct inode *root;
463	unsigned long pos, img_size;
464	const char *storage;
465	size_t len;
466	int ret;
467
468#ifdef CONFIG_BLOCK
469	if (!sb->s_mtd) {
470		sb_set_blocksize(sb, ROMBSIZE);
471	} else {
472		sb->s_blocksize = ROMBSIZE;
473		sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
474	}
475#endif
476
477	sb->s_maxbytes = 0xFFFFFFFF;
478	sb->s_magic = ROMFS_MAGIC;
479	sb->s_flags |= SB_RDONLY | SB_NOATIME;
480	sb->s_time_min = 0;
481	sb->s_time_max = 0;
482	sb->s_op = &romfs_super_ops;
483
484#ifdef CONFIG_ROMFS_ON_MTD
485	/* Use same dev ID from the underlying mtdblock device */
486	if (sb->s_mtd)
487		sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
488#endif
489	/* read the image superblock and check it */
490	rsb = kmalloc(512, GFP_KERNEL);
491	if (!rsb)
492		return -ENOMEM;
493
494	sb->s_fs_info = (void *) 512;
495	ret = romfs_dev_read(sb, 0, rsb, 512);
496	if (ret < 0)
497		goto error_rsb;
498
499	img_size = be32_to_cpu(rsb->size);
500
501	if (sb->s_mtd && img_size > sb->s_mtd->size)
502		goto error_rsb_inval;
503
504	sb->s_fs_info = (void *) img_size;
505
506	if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
507	    img_size < ROMFH_SIZE) {
508		if (!(fc->sb_flags & SB_SILENT))
509			errorf(fc, "VFS: Can't find a romfs filesystem on dev %s.\n",
510			       sb->s_id);
511		goto error_rsb_inval;
512	}
513
514	if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
515		pr_err("bad initial checksum on dev %s.\n", sb->s_id);
516		goto error_rsb_inval;
517	}
518
519	storage = sb->s_mtd ? "MTD" : "the block layer";
520
521	len = strnlen(rsb->name, ROMFS_MAXFN);
522	if (!(fc->sb_flags & SB_SILENT))
523		pr_notice("Mounting image '%*.*s' through %s\n",
524			  (unsigned) len, (unsigned) len, rsb->name, storage);
525
526	kfree(rsb);
527	rsb = NULL;
528
529	/* find the root directory */
530	pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
531
532	root = romfs_iget(sb, pos);
533	if (IS_ERR(root))
534		return PTR_ERR(root);
535
536	sb->s_root = d_make_root(root);
537	if (!sb->s_root)
538		return -ENOMEM;
539
540	return 0;
541
542error_rsb_inval:
543	ret = -EINVAL;
544error_rsb:
545	kfree(rsb);
546	return ret;
547}
548
549/*
550 * get a superblock for mounting
551 */
552static int romfs_get_tree(struct fs_context *fc)
553{
554	int ret = -EINVAL;
555
556#ifdef CONFIG_ROMFS_ON_MTD
557	ret = get_tree_mtd(fc, romfs_fill_super);
558#endif
559#ifdef CONFIG_ROMFS_ON_BLOCK
560	if (ret == -EINVAL)
561		ret = get_tree_bdev(fc, romfs_fill_super);
562#endif
563	return ret;
564}
565
566static const struct fs_context_operations romfs_context_ops = {
567	.get_tree	= romfs_get_tree,
568	.reconfigure	= romfs_reconfigure,
569};
570
571/*
572 * Set up the filesystem mount context.
573 */
574static int romfs_init_fs_context(struct fs_context *fc)
575{
576	fc->ops = &romfs_context_ops;
577	return 0;
578}
579
580/*
581 * destroy a romfs superblock in the appropriate manner
582 */
583static void romfs_kill_sb(struct super_block *sb)
584{
585#ifdef CONFIG_ROMFS_ON_MTD
586	if (sb->s_mtd) {
587		kill_mtd_super(sb);
588		return;
589	}
590#endif
591#ifdef CONFIG_ROMFS_ON_BLOCK
592	if (sb->s_bdev) {
593		kill_block_super(sb);
594		return;
595	}
596#endif
597}
598
599static struct file_system_type romfs_fs_type = {
600	.owner		= THIS_MODULE,
601	.name		= "romfs",
602	.init_fs_context = romfs_init_fs_context,
603	.kill_sb	= romfs_kill_sb,
604	.fs_flags	= FS_REQUIRES_DEV,
605};
606MODULE_ALIAS_FS("romfs");
607
608/*
609 * inode storage initialiser
610 */
611static void romfs_i_init_once(void *_inode)
612{
613	struct romfs_inode_info *inode = _inode;
614
615	inode_init_once(&inode->vfs_inode);
616}
617
618/*
619 * romfs module initialisation
620 */
621static int __init init_romfs_fs(void)
622{
623	int ret;
624
625	pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");
626
627	romfs_inode_cachep =
628		kmem_cache_create("romfs_i",
629				  sizeof(struct romfs_inode_info), 0,
630				  SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD |
631				  SLAB_ACCOUNT, romfs_i_init_once);
632
633	if (!romfs_inode_cachep) {
634		pr_err("Failed to initialise inode cache\n");
635		return -ENOMEM;
636	}
637	ret = register_filesystem(&romfs_fs_type);
638	if (ret) {
639		pr_err("Failed to register filesystem\n");
640		goto error_register;
641	}
642	return 0;
643
644error_register:
645	kmem_cache_destroy(romfs_inode_cachep);
646	return ret;
647}
648
649/*
650 * romfs module removal
651 */
652static void __exit exit_romfs_fs(void)
653{
654	unregister_filesystem(&romfs_fs_type);
655	/*
656	 * Make sure all delayed rcu free inodes are flushed before we
657	 * destroy cache.
658	 */
659	rcu_barrier();
660	kmem_cache_destroy(romfs_inode_cachep);
661}
662
663module_init(init_romfs_fs);
664module_exit(exit_romfs_fs);
665
666MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
667MODULE_AUTHOR("Red Hat, Inc.");
668MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */
669